Datasets:

VatsaDev

/

worldbuild

like 11

[Question] [ I have a setting where there is an online shop that sells magic script, **which sent via email.** The magic in this world is activated via **a runic script** - similar to a program code. The problem is, I don't know how this shop could deliver the rune script (magic "scroll") safely **without anyone be able to copy the rune script after the delivery.** Different from program, the runic script is not compiled, so everyone could see the source "code". It can be photographed, or redrawn, and that's the issue. Like a program code, the effect of various scripts is different. Even a fireball spell can be designed with different colors, or even a rainbow fireball! So, the issue with copyright here - I don't want my rainbow colored fireball script to be freely used, they must buy it from my shop. It is very hard to write the correct script to include each color and not make it too green or blue. The script can be deciphered by an expert runologist, but the general idea of what the script does can be inferred immediately after seeing it. It's like reading a kanji for "Fire", but complicated with the kanji for 7 colors. So, the setting is like in our 21st century modern world. Magic already exists from the beginning, but only few (I'm thinking less than 100 in each country) actually know how it works. The numbers greatly decline through the time because less people believe it, and spend time to actually understand it. Thus, the magic communities developed an online shop for their community to use - ordinary people would just shrug off them as nonsense website. **So, how to protect the magic script from piracy?** **Note:** *Anyone* can activate the magic script without needing magical power. It's like flipping a light switch. The rune need to be drawn using magical ink, but it is not rare, in fact it's very, very common and easy to acquire in the magic communities. The license *ideally* works only on the buyer, and not anyone else, even someone that can produce the exact image of the magic script. The license is **transferable**, either independently from the author or requiring the author to send a new script or altering something else, either is fine. I *prefer* a **non-shareable** method for a single magic script (even for family) to prevent someone else able to fake the authorization, but I'm not too tight on this specification. Related [How do sorcerers attempt to prevent common people, or other sorcerers, from duplicating their spell scrolls?](https://worldbuilding.stackexchange.com/q/31691/34288), but this is different since this takes place in modern world (and thus worsen the problem of piracy, because it can be posted in forum, sent via chat clients, and such), and this is not a one-use only transaction - the buyer should be able to use the said scripts, but not his friend that receives the photo of the script. [Answer] How about making runes dependent on some magical biometrics, like aura for example. Customer will provide details regarding his or her aura and the rune will be tailored to be activated by a person with such an aura. The reason for this can be something along the lines of being within the aura being different from the outside of it, and only when surrounded by that aura are conditions for rune activation are met. You can decide yourself on the rules for how aura works, like whether or not family members tend to have similar ones or not. Also, you can decide on behavior in case or person with different aura using it, spell might not activate at all or might produce completely unexpected effects. In a way spell itself is like a formula, you give parameters like desired effects and aura of the user and get the final rune that can be activated by the person with the said aura. It is not necessarily possible to figure out the actual spell based on the finished rune. [Answer] Magically encrypt your spells and have what is delivered to the person be a script to connect to you magic network for magical online validation for each use. The person won't own the spell, only license the use of the spell attached to it. They will need to register an account and launch your magical spell manager to activate the spell which comes with a one time use spell that expires when used. If people want they will have to resort to magically pirate your spells by magically breaking your DRM but you counteract that by making it easy to get spells from your store and hard to get pass your DRM. Most people will buy your spell and the few that pirate them will not be significant to matter. Basically magical itunes. [Answer] **Each rune is unique.** You make the runes like concert tickets. I walk into the Ween concert, present my ticket, and am admitted. You walk in behind me with a photocopy of my ticket and are tasered to incontinence. My ticket has been used already and so cannot be used again. Just so the rune: even though many different ones might wind up making a fireball (as many different tickets will get you into the concert), each individual rune can be used once and then it is done. Each fireball or other magic manifestation will be drawn from a discrete and individual bin of magic set aside by your magicians when this rune is written and corresponding to the individual and unique runic script you received in the internet. Now if I see your email and copy your rune, I can deploy the fireball first and you are out of luck. Just as if you had arrived earlier than me at the concert with the forged ticket. Could one figure out an active rune by simply trying various permutations and hoping to stumble onto an active one? You could, but the magicians might put some nasty pinch magic into bins corresponding with non-issued runes, to discourage this sort of activity. [Answer] This answer adds to Steve's post. Also it's my first answer. So... hello internet! **Why sell the runic script in source code?** You could encrypt the runes (the picture or the text, whatever fits best) and later decrypt it, when time comes casting the spell. That way your customer needs to know the keyword for this very spell, wich you never tell anyone. **Every customer gets just one electronic Wand** The next step is to **sell an extra product** or provide it for free. This product could be a handheld device or software (maybe a smartphone app). The device/software helds a *unique ID* (visible to everybody) and a *unique keyword* (hidden for everybody). You, the manufacturer, of course can tell wich keyword belongs to every ID. If you sell a spell to a person, they tell their ID and you encrypt your spell with the associated keyword. Then they download the script to the device, wich is the only one, that can execute the spell. To clarify: The device encrypts the spell just for the moment and never shows a picture of the spell to the operator. Now the Spell can be casted by one device only. One problem I see with this is as follows: The customer can sell the device along with the spell after he used it and doesn't need it anymore. If you are fine with this, good. If not, make the device valuable or only provide the first device for free. 'Oh, you *lost* your *E-Wand 2000*? No problem, buy another one for 1500$.' [Answer] **The runes' spell could work only during a particular timeframe.** In my current office (in the real world), I was sent a link to an important file. The link would only work for 24 hours after I received the email. Your rune could do the same thing; create it so the magic only works for 24 hours after it's emailed to the recipient. [Answer] You have two alternatives: * rely on international treaties and thus on some kind of "copyright" law, which means runes *can* be copied, but you are not *allowed* to. * make the rune dependent on the hand of the writer (something akin to oriental "calligraphy") so that a copied rune won't work, perhaps because a small part of the "live force" of the writer is captured in the rune itself (this means, of course, that you'll need to write all your "scrolls", you can't hire scribe or use a "printer"). # A (perhaps) viable variation on the second approach: * Runes are not to be equated to software scripts, but are similar to hardware devices. * You need a special printer to print magical "transistors" and wiring on special paper; something similar is actually done to "print" circuits on glass or plastic film. * Making a picture of the resulting work will not help because it won't have the required layering, just like making a picture of a chip die won't allow you to easily duplicate it (of course you *can* reverse-engineer it, but that is hard work!) * Printer you sell/loan/give will include a specific decryption key, different for each printer. The file you send via mail to your customer will be encrypted so that it can be used only on his printer and would be useless gibberish everywhere else (standard encryption technique). This schema allows several variations, possibly useful: * Magical "hardware" may be used "over-voltage" so that (some "circuits" of) it will "burn" upon usage making the "rune" useless. * You may include "magical batteries" etched in the "rune" so that you have a limited number of usages, perhaps with diminishing strength. * "batteries" may be rechargeable or not. * Printer may remember what it printed ("scripts" are serialized) and refuse to print more than the allowed number of "runes". * "runes" may be large, like an abstract picture or very small, so you can hide them (e.g.:) in a dot on an otherwise perfectly normal page. [Answer] Although several copyright enforcement schemes could have been tried, as explained in other answers, they are likely to fail due of being cracked or just because they make difficult the access to magic. Fortunately, some magicians have tried a different approach: open source spells. Those magicians release their runes under several Magic Commons free licenses allowing anybody to copy, modify or reuse them. This has improved access to magic for everybody, has helped the development of community built new spells and has lead to the development of a lot of magic startups that tailor and combine existing open source runes to the specific needs of their clients. In summary, your magic world is like what would be ours if the proponents of open source software were right in their most optimistic predictions. [Answer] Ok, sorry, but I'm going to be the [Negative Nancy](https://en.wiktionary.org/wiki/negative_Nancy) here and tell you that your entire premise just doesn't work. Note that a lot of what I write here is essentially a duplication of answers to the question you linked [here](https://worldbuilding.stackexchange.com/questions/31691/how-do-sorcerers-attempt-to-prevent-common-people-or-other-sorcerers-from-dupl). Although I didn't realize it until I'd already written most of this. The best things you can do are 1) limit magic so not everyone can use it (to keep magic rare like you want), 2) make the magic scroll a physical device that's hard to duplicate properly so you earn money by making reliable scrolls, not designing rune programs (makes piracy worthless instead of preventing it), and 3) implement scroll physics that degrades scrolls over time and/or with use, with better-made, more expensive scrolls lasting longer (or you'll go out of business when all 10 magicians in your town have every scroll they need). Additionally, you might make the "scroll" something small and easy to carry, with "wands" that organize and allow rapid access to the scroll you want. Better scrolls and wands are smaller, lighter, and have better algorithms for accessing the correct scroll. Alternately, you can just handwave it all and say, "When you purchase the spell over the internet, it magically gets inscribed in your brain and nobody else can use it. Because I said so." **If magic is as easy as you say, *everyone* will be using it.** If I can just print out several copies of a spell using some special ink, then touch the paper and Boom! fireball happens, people aren't going to randomly stop believing it works. Instead, they're going to go through enormous efforts to figure out how it works until either everyone has access to magic, or the world is destroyed in World War 3. The only way people stop believing in something is if it stops happening. We didn't stop believing in vampires and werewolves and Bigfoot and Nessie because "like, reasons, bro". We stopped believing in them because there's literally zero evidence any of these things exist, and a great deal of evidence that they're all folk tales that have been modified and added to over centuries. If you have a very small number of magicians who *very* carefully protect knowledge of magic from the rest of the world, you can potentially keep it a secret. If the secret is maintained long enough, people will stop believing in magic. If a spell or two gets cast in front of the [muggles](https://en.wikipedia.org/wiki/Muggle) here and there, people at large won't think too much of it. But the instant one magician shows the world at large that magic is real, your entire [Masquerade](http://tvtropes.org/pmwiki/pmwiki.php/Main/Masquerade?from=Main.TheMasquerade) just shattered. This is made enormously worse by having readily-copied magic spells. If a vampire is discovered in L.A., the vampire community can sneak in, kill him, and destroy the body. Then, even if there's a good amount of evidence a vampire existed, it's possible the whole thing will eventually be forgotten. But if the vampire turns a hundred people into vampires first, the vampire community will have a very hard time hunting them all down before every other think-tank in the world has a vampire test subject. Likewise, if the ability to cast magic can easily be transferred (without even having to drink blood or burn up in the sun!), the magical community is going to be *very* hard pressed to keep it a secret. In order to prevent this, you need to create some kind of hard, physical device that mostly or totally prevents muggles from using magic at all: * Magic can only be cast using one of the 1591 wands left by an alien race, and nobody knows how to create new ones. The magical community will keep very close track of where each of the wands is, and only transfer wands under certain circumstances. Further, only the most "eligible" magicians will ever get a wand. * Magic spells use a very rare ingredient that only a few people have access to and is extremely difficult to produce. Occasionally, a muggle will acquire a bit and cast a spell or two, but magic will be almost exclusively limited to the rich and powerful magicians. This can be subverted if the amount or type of ingredient depends on the spell type or strength. Then, muggles would commonly have access to common spells, but only the rich and powerful would have access to rare spells. * Magic requires an enormous amount of practice to get right, and you pretty much *have* to be taught by someone else who learned it from the aliens who built the wands, the gods who put magic in the world, etc. So even if a muggle gets their hands on a spell scroll, magic wand, etc., nothing will happen. * Magic can only be cast by people with the "magic gene". However, you can't just say it's normal DNA. If it's normal DNA, then you just breed a bunch of magicians together, and you will statistically get more and more magical offspring until you have an entire community of pure-blood magicians. Who will then take over the entire world until the only survivors are magicians. Instead, the magic gene needs to be random in some way. Like, there are only 1591 magic genes on the planet, and when someone dies, the gene floats away into an embryo somewhere on the planet. Maybe it tends to float into embryos near the dead guy, so the magicians are likely to figure out who the new magicians is and bring them into the fold. Or maybe there's a spell to track them. Alternately, maybe the gods randomly give the magic gene to every four hundredth child born during a full moon, so the proportion of people with the gene is constant. In any case where muggles *can* use magic, but don't have immediate access to it, the magical community would have to be very strict with magicians who show or teach magic to others. Otherwise, you'd get ~~[Julius](http://vtmb.wikia.com/wiki/B-Rated_Writer)~~ magicians who just want to make some friends, and pass magic out to the muggles regardless of the rules. In any case where muggles are physically incapable of using magic, you're going to run into one of a couple scenarios: * Magic is so powerful the magicians enslave and/or destroy all the muggles. * Muggles vastly outnumber magicians and burn all the magicians at the stake because [they float](http://lexx.thebruce.net/poem/monty.html)1. A few magicians survive, use their magic to build enormous power bases, remember [Salem](https://en.wikipedia.org/wiki/Salem_witch_trials), and enslave or destroy all the muggles. * The magicians stay hidden in [Hogwarts](https://en.wikipedia.org/wiki/Hogwarts) with various spells that prevent muggles from finding them. Then some [Voldemort](https://en.wikipedia.org/wiki/Lord_Voldemort) types use their magic to build enormous power bases, destroy the other magicians, then enslave or destroy all the muggles. * Magic is powerful, but a decent group of citizens armed with [pitchforks](http://tvtropes.org/pmwiki/pmwiki.php/Main/TorchesAndPitchforks) can take on a single magician. Because there aren't very many magicians in the world, your average citizen isn't too worried about them, and magicians are mostly left alone. The last scenario is the one you want. You still have to deal with the fact that magicians will tend to rise to positions of prominence and power, and that muggles will tend to know about magic. But at least you have a fairly stable ecosystem with both muggles and magicians. With sufficient policing, a Masquerade can exist for a time, but will ultimately fail. **As pointed out ad nauseam, you can't copy-proof anything sent via email.** This is compounded by the fact that you've explicitly decided that the "source code" is readily visible for all to see, and there's no way to "compile" or obfuscate the code. To be fair, I'm not really sure you know what you're talking about here. Compiled code is still just code, which can always be reverse-engineered into "source code". The difference is that source code is typically full of helpful comments to explain the code and meaningful object and method names to self-document the code, so it's easy to understand, while compiled code lacks these features and is therefore harder to understand. But we can always deliberately obfuscate source code that compiles just fine while being very hard to understand. Likewise, unless your runecode is very simple, it would be pretty trivial to deliberately obfuscate the "source code" so it's difficult to understand what's going on (meaning it's irrelevant that it isn't "compiled" code). This is reinforced by your statement that only an expert runeologist can decipher the code. This means runecode would be easy to copy, but only a good runeprogrammer can edit the code to do new things without exploding the end user every third attempt. So your breadmaker would be programming custom spells for people, not the generic [Scrubbing Bubbles](http://www.giantitp.com/forums/showsinglepost.php?p=11249240&postcount=19)2 stuff. Still, you'll be a victim of piracy as soon as you program anything more than one person would want. Like a really robust spell that handles a variety of situations well. So the only way to stay in business is if your spells are only usable for a short timeframe in a specific location, meaning pirated spells stop working and the customer comes back to you for more. But what will really happen is that some semi-expert pirate will figure out what part of the runecode checks the timestamp and bypass it, then your customers will be annoyed at needing to rebuy their spells every three weeks and just buy the pirated versions. **If you really want copy-resistant spells, the act of reading and/or printing the source needs to be difficult or expensive.** This means you can't send the stuff via email. Sorry, it just doesn't work. The simple fact that the intended end user can easily print their copy means they can print dozens of other copies. There are numerous ways you can do things from here. You can make reading the runecode difficult by printing the runecode at microscopic scales using a combination of magic and non-magic ink to obfuscate which runes are part of the source and which aren't. You can further complicate it by printing enormous amounts of non-magic text to hide the locations of the magical runes. And you can use layers to print one "page" of code on top of the previous page, so the pirate not only needs to read and analyze microscopic code, but do so in 3D. Alternately, just make it so printing a working spell requires a great deal of time and/or skill. Maybe the ink has to be mixed flawlessly. So buying a pirated spell will probably turn you [into a newt](https://www.goodreads.com/quotes/134760-she-turned-me-into-a-newt-but-i-got) instead of teleporting you to the moon wearing a spacesuit. And might teleport you to the moon as a newt without a spacesuit. Maybe the runework has to be drawn a certain way, with certain rituals. So the pirated spell will result in a [segfault](https://kb.iu.edu/d/aqsj) just as that ogre is smacking you with a club, instead of projecting a nice shield like the real spell would. You can combine the two, Dungeons and Dragons-style. Only an expert magician can read a complex spell scroll, and only an expert magician can transcribed a learned spell to a scroll. The possibilities are endless. Notice, however, that we've shifted the purchased good from the runeprogramming to the scroll-making. If actually programming the spell is the really hard, expensive part, pirates will always be an issue. Because no matter how hard or expensive it might be to read and reprint a spell, it's still cheaper than designing our own program. Only if the physical duplication is the hard part will piracy stop being a problem. **You can still buy over the internet, or have instant-access scrolls.** There's no reason you can't still purchase things via a website. They just need to arrive through some physical method. Like [carrier owls](http://harrypotter.wikia.com/wiki/Owl_Postal_Service). You can make this method as fast as plot requires, so it's still "click the PayPal button, get a spell within 60 seconds". You can even teleport the scrolls to the end user, but teleportation opens up enormous issues with over-powered magicians taking over the world. Perhaps the "scrolls" are actually teeny-tiny things the size of a [BB](https://en.wikipedia.org/wiki/BB_gun), so it's easier to teleport them than something like a bomb or human. Plus, that makes it easier for the end user to store them. Then you have a "wand" that holds the pellet scrolls, and you just have to select the the right scroll, touch the pellet through the aperture, and the spell fires off. And you can make extra money selling wands that allow faster, more consistent access to the spell you want. Alternately, you can have scrolls available via non-internet methods such as vending machines. Non-magicians won't waste their money if they can't use them. Or, the machines are hidden and only people who have the right codes can get to the machines in the magically-hidden alcove. **Ultimately, you need spell scrolls to last a limited time or nobody will need new spells.** Sure, your spellmakers will invent new spells from time to time, but most people will buy all the spells they really need then almost never buy anything again. Then pass the spells on to their kids. Etc. Instead, you need the spell scrolls to degrade somehow. They could degrade over time, so they start failing more and more after a certain amount of time. Perhaps the most complex (and likely most highly prized) spells fail the quickest. Alternately or simultaneously, they could degrade with each use in the same way. Better, more expensive, spell-printing methods could last longer. So a \$2 cleaning spell works once and fizzles out, while a \$200 printing of the same spell lasts 5 to 10 years reliably. This degradation *has* to be a physical constraint in your universe. Otherwise, one spell printer who deliberately creates degrading scrolls will go out of business as soon as another printer creates permanent scrolls for the same price. 1Yes, I'm aware this is in reference to the [historical practice](http://www.history.com/news/history-lists/7-bizarre-witch-trial-tests), but that's less humorous. 2I know I read this in an official D&D resource at some point, but for the life of me can't find any other references to it. [Answer] Cryptography is the answer you are looking for. Can't exactly copy my fireball script if you don't have the key that changes it from random gibberish to an actual set of runes. You could also look at servers for your runes. Perhaps there could be other runes that essentially collect people who are allowed to view and use your runes. This table of approved users would then have whatever variant of runes that allows them to read the runes they bought from you applied to them. Alternatively you could just have another more beastly set of runes that changes the runes from gibberish to actual rune. That way the runes wouldn't actually be runes until the user is approved, for the most part. Your magic system is inspired by modern tech, so you will need to use modern tech inspired solutions where they apply. What I described above is similar to how access keys work. [Answer] Apply the proof of work process during the transaction process. Basically, when the person buys the rune it requires them to give something to the person who's providing the rune (other than just payment) - this should be something that magically allows said person to activate the rune. Without this binding process, it's not possible to activate the rune. This also allows the buyer to resell the **original** rune, re-binding the rune to the new purchaser. Copies of the rune simply don't contain the same original binding process ingrained into the rune, and as such can't be bound or activated. [Answer] Now, let me explain that I am a programmer and I know how code works and is compiled and so your answer ultimately derives from the following assumptions about magic: > > I have a setting where there is an online shop that sells magic script, which sent via email. The magic in this world is activated via a runic script - similar to a program code. > > > The problem is, I don't know how this shop could deliver the rune script (magic "scroll") safely without anyone be able to copy the rune script after the delivery. Different from program, the runic script is not compiled, so everyone could see the source "code". It can be photographed, or redrawn, and that's the issue. > > > Ok, so the issue here is really just one of engineering (in the broader sense then just "mechanics and robotics"). Now in reality the issue here is this whole "magic ink" concept. Here is the problem. ***it is archaic***. Don't get me wrong, it can exist and it isn't bad but you need to find a way around it. Simply put, you use a website to sell scrolls. Great! Well, you cannot avoid piracy. Like.... it would be like if I made a website to sell PDFs of math proofs. If I catch a person, I can sue them for theft, but I cannot prevent it without having a magical demon/enforcer go around and punish offenders. It is impossible. You're literally asking a fundamental business question and it is worsened by print media. Books can be pirated. **Make it fully electronic** You need to do one of two things: 1. Create a computer that contains circuitry to produce this ink and somehow print the shapes and erase then rapid-fire. If it feasible this [quick thing I found in a google search](http://www.mirror.co.uk/science/liquid-metal-scientific-breakthrough-means-8568142) may allow for the shapes to be formed and erased. 2. Produce a magic spell (that can be bought or distributed) which grants computers the ability to run spells within some kind of programming environment akin to the Java JRE no need to worry about distribution for this one. Java doesn't. It's a programming language installation. Let people use it. It's still copyrighted. It's just that you only care about plagiarism and not piracy. It's freeware. Make the programs written within it what people pay for and cannot pirate. Either way, these spells and the scrolls sound akin to programming languages and the important fundamental concept here is **interfaces and implementations**. You don't want people to see your spell. You *want* to integrate your spell into a computer program. Now with your "MagicScript" language in hand with compilers and stuff you now gain a few benefits: 1. Mathematics and Computer Science concepts: Programming Languages have many data structures and complex ideas. If you've ever played Minecraft and seen command blocks you can think of it like that. Spells are a "baby language". They don't have the features of memory allocation and stuff that a computer does. You can therefore create computer-controlled dynamic spells that act like complicated concepts. Computers can try to do calculus. Spells on the other hand may or may not. 2. Mathematics and Computer Science gain the tools of spells and magic. Simply put, maybe your language has time travel spells that can send things back in time? Guess what? you just solved Legendre's Conjecture, the Collatz Conjecture, and (maybe) the Riemann Hypothesis.... *by brute force*. Simply put, you can send knowledge or data back in time and form a bootstrap paradox thereby giving a computer infinite processing power. Note that if the program never halts then you'll have a problem. Unfortunately the halting problem proves that there is no algorithm for showing that an arbitrary program halts. So... you'll need magic to somehow either cheat this or just allow the rules of time travel to result in an infinite loop being just... a normal stalled program. I could see some people messing this up. Still, the ability for people to potentially solve super-hard problems that have existed for over a century with *brute force* is not something you can pass up. Not only that but your computer will never lag if it is used by operating systems creators. Trust me, a movement to secretly put magic into computers in a safe manner is going to make your wizards filthy rich. Riemann Hypothesis is worth 1 million bucks to solve, so if you make a processor capable of doing that via time travel is not only going to make everyone's jaws drop and land you a million bucks. It's also going to land you dozens of manufacturing contracts. *You'll own the market on processors*. After all, Just patent it with the government. Then if someone makes it within so many years you can sue them. Or cast a spell to destroy the competition. Regardless, all you need an ambitious computer science-savvy wizard. 3. You get to use existing infrastructures for program management: Ever heard of the website Steam? I've never used it, but I hear they're good at keeping programs locked up tight. You have to run their programs in their environment. Simply put, technology already exists for what you desire if you create this language. You don't have to worry about photocopying. Someone would have to either decompile your program and look at the MagicScript. Guess what? That still happens. You'll have to live with it. 4. Rapid spell execution. Computers can do hundreds of commands a second. Probably a lot more. Sure, there is the physics aspect of slow execution if you use metal slime to augment your magic ink, but can your wizards do that many spells? Once again, spells are a "baby language" running on inefficient processors with incredibly limited memory. It's like trying to run Minecraft on the NASA computers used to send the man to the moon. If we ignore the differences in languages and machine code... the machine can't run it. Our technology allows us to do this stuff at much faster speeds than the people of the 1800's. Here's a story from my differential equations class when the professor was talking about numerical methods and using computers (I think regarding Hoover dam, but the name was never said) to illustrate this issue: > > People would be working on the dam calculations every day. They'd spend a whole day doing Euler's method on the equations. They'd have three teams working separately on the same math. At the end of the day, they'd compare the results. If two matched, they kept them. If none of them matched, they'd scrap the work and start over again the next day. Now, I can do those same calculation within a few minutes on this PC. > > > Just make a similar argument regarding magic. Simply put, humans are inefficient, but computers are efficient and they only make mistakes when people make mistakes. Otherwise, they do what you tell them to do. Now of course, you'll argue "well, I don't have this tech in my world". Well then guess what? You'll get pirates. You're asking about how to secure pdf's you sent via *email*. I don't even need a photocopier. I can hit *forward*. --- **Closing Remarks** I don't know a whole lot about turing machines, but it wouldn't surprise me if your spells are just turing machines and automata, which are computer science concepts with no relation to metal men (automatons). As a result, integrating them into computers feels natural. To summarize the advantages once more: 1. longer spell lengths 2. rapid execution 3. advances in computing capabilities 4. existing security frameworks 5. easier to write and easier to edit What modern wizard wouldn't want and enjoy such advantages? If you want spells that can be used outside of the computer, just have a server that produces programs that interact with the server and produce 3D graphical user interfaces for people to use in real life. So basically a floating magic interface to use spells. People could even make hotkeys for them or somehow interface it with verbal commands. or for that matter, make the server generate magic staffs that work with the spells. Or make magic staffs that are also computerized to run the spells? Java was originally a software to make it easier to put code on various appliances (no joke, it was originally designed for your toaster) so I don't see why MagicScript couldn't be any different. It was to augment the process of creating magic staffs and then it evolved into a full-blown desktop computer programming language. [Answer] Why not make the runes free and charge for the ink? Anyone would be able to copy the runes, but there would be no effect unless they were drawn with the specific magic ink necessary. I think it would be easier to prevent people copying your ink manufacturing process than copying a drawing, especially when everyone has phone cameras and pcs. [Answer] I didn't notice either of these approaches elsewhere, so here you go: **Craft a binding contract as a part of the purchase agreement.** Person rips you off, their heart stops. Or, perhaps, they find themselves compelled to send you the money for the spell. Whatever payload you want, they have to agree to the effect before. Note that this could be part of a key scheme as described elsewhere, so only those with this active effect can use the pattern. The spell could target the device making a copy, instead, and blow that up all Black ICE style. **Erase the effect on use** Now, it would bear noting that this would mean such spells were single use, but having part of the spell also delete all copies would go a long way to solving your problem. Depending on how you want everything to work, this could be vulnerable to clever editing, but that is analogous to cracking software. Of course, there is magic in this world, so it's just as valid to state "Nope: it's just impossible. It's magic. Deal." (The Great Panjandrum decreed no copying, spell copiers work using some arcane principle that doesn't allow unauthorized copies, grand hosts descend on copyright violators, etc.) [Answer] **Hidden Layer** Just say a rune consists of two layers. One, that uniquely identifies the spell as what it is and that can easily be understand by everyone and another hidden layer, that does the actual work. You compared it to program code. It's the same mechanic. Image the visible layer as button. > > Press me to create a rainbow colored fireball > > > Everybody knows exactly what happens by using it, but "nobody" can copy it without some knowledge of the algorithm behind it, which would be a hidden layer in your case. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< **Invisible ink** Same as above, only with a second, invisible ink on the same layer. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< Example: Image you want to summon a demon. The Pentagon is a well known symbol often refered to it. So, what everyone can see/read is a pentagon with some more symbols to further clarify which demon the user is about to summon. But if you copy it 1:1 it won't work, because something is invisible and couldn't be copied. In this case a simple circle around the Pentagon, hidden on a second layer or with invisible ink. [Answer] I don't see how a small community like you're describing would even work with any analogs to the real world. If only 100 people/country understand magic (rather than know/use it), the number of people who know of magic is probably only in the thousands/country. I don't think magical iTunes/Steam work here, the convenience and/or relative low cost wouldn't be available because of the small size of the market. I don't think DRM as we know it would be around for the same reason. I think the market will be solved by raising the price of the transfer of information (like guilds and apprenticeships requiring investments of years of time on the part of their lower members), or the culture of the magical community will change to a culture of honor (with violent revenge becoming the social norm) since rule of law in such a small and decentralized community isn't strong enough to enforce copyright. I think solving the problem as you intended, since your main objection seems to be that the runes can't be black boxed like software is IRL, would be to enforce things on the side of the user. For example, have a customer accept a EULA that magically compels compliance before transferring the product. Or maybe have the laws of the magical community itself (including copyright law) be a geas. If such a thing is possible (it is a pretty stock fantasy trope), it would solve the problem of rule of law in such a small community. Perhaps this will still have a cycle of escalation with more precise contract terms and more clever rules lawyering, but it does go around a lot of the previous problems you and others have raised. The product does not need to be encrypted or otherwise black boxed, there is no remote access or authentication required, and there is no need for biometrics. [Answer] Classic secure communication is 3 fold. Something you know, something you have, and something public. The Runes emailed to you are the public part. Something you know is maybe a personal rune. This may have been assigned to you when you became a customer. Something you have may be a magical wand. This wand contains in itself a rune-writing or rune-adapting spell, and wards against tampering. The wand when activated modifies a set of drawn runes in specific ways. When we sell a spell to someone, we sell it as an augmentation to their personal rune. They write both their personal rune, and the runes of the spell. *Then* they use their registered wand to *mutate* the runes. This mutation is basically a decryption step. The mutation is designed to both create *and destroy* the written spell at the same time. The decrypted spell is, ideally, not visible to anyone; maybe spell first shrouds the spell in invisibility before it does its effect. On top of this, the wand's spell also self-mutates its internal script: it counts down. When its count hits zero, you have to purchase a new one from your vendor. Now I can sell you spells. They are useless to anyone but you. You can take your spell, add your personal rune, then cast them with your personal wand. This destroys the spell, and removes a count from your wand. (It could even remove a dynamic amount of count, depending on how "expensive" each use of the spell is supposed to be). If you share your rune with others, they still need your wand. If you share your wand with others and your rune, well, the new people are just delegated casters by you. The wand will run out of charge quicker. This is similar to some electronic DRM systems. Note that hacking a wand is going to be tempting; having a wand that self-destroys when damaged may be part of your security. --- An important part is how this can evolve, culturally. Simply handing someone a new way to cast spells that sucks as bad as the above is going to get a lot of backlash. So we'll do a just so story. "Back in the day", writing partial spells in wands was one way to make casting faster. You'd store many copies of the spell in the wand, and finish it with external runes (sometimes 1, sometimes more). Then you'd activate the combined spell. Doing so was considered the only reasonably safe way to mass store magical runes; a wand with full spells within it could go off by accident! And writing complete spells on paper is just asking them to be stolen and used against you. With the two of them, you can have a fast reasonably secure casting system. Wizards might add in an additional step, where you add in a personal rune to finish the spell, preventing others from stealing their wand and using the spells within it. The wand contains partial spells, your scrolls contains partial spells, and your head contains which additional rune you need to finish off the triplicate. The new technology is an extension of this, with the habits of wizards of old modified to produce a magical rights management infrastructure. Its resemblance to the old personal security of personal wands and spells made it initially acceptable to purchasers. Possibly the company might have started off *making* your wand for you. You'd specify which runes to embed in the wand, and they'd micro-etch a few 1000 of them finer than you could yourself (assuming a given set of runes can be used exactly once). Other companies might do mass rune-paper printing, or maybe you'd keep that secret yourself. Then they'd offer you wands with *new* partial spells and let you write your own runes. [Answer] Make rune designs that are very difficult to copy by hand and don't photocopy well, so that the only easy way to reproduce them is to print them from your file. Think intricate designs, slight variations in colors, very small dots, etc. Ideally you would also have inks that look identical visually, so that you can't tell which parts are which kinds of ink just by looking it at. (Maybe some ink in the design is magical and some is normal?) Then you protect your files used to print in the usual way, or only let them print directly from your website, and each rune can only be printed once. It won't ever be impossible to make illegal copies, but if you make it difficult to copy and easy and cheap to buy from you, most people will just pay for the spells. [Answer] From [Unsong: Chapter 2: Arise to Spiritual Strife](http://unsongbook.com/chapter-2-arise-to-spiritual-strife/): Replace "Name of God" with Runes, etc. Also, coincidentally, they have magic on scrolls as well. (*This was not a coincidence, because nothing is ever a coincidence.*) > > “Whenever you use a protected Name of God,” I continued “UNSONG agents with the Sentinel Name tattooed above their ear, and the Names involve tattooed on their foreheads, can track your location. In practice they rarely do, because a million people do that every day and they don’t have a million agents or a million jail cells to put people in. But if a dozen people use all sorts of Names in the same spot every day, they know it’s a place where singers hang out and then if they’re bored then they come and raid you. This is probably what happened in Colorado.” > > > [Answer] Give your designs away and ask for donations. You have a small group that even believes in magic, and creating new runes is hard work. Presumably, a large portion of that community values your work and would support it voluntarily. So don't even attempt to restrict copies. Instead, make your work available for free and ask for donations so you can continue your work. You could also ask people to donate to your development of a particular rune and then make it available once you've raised enough cash. There's tons of precedent for this model working. Many browser extensions and apps are free and then ask for a donation. Lots of people raise money for a purpose by providing a service and then asking for donations (car washes by students, bake sales for charities, charity bundles of Steam where you name your price). Kickstarter and Gofundme are both full of people that voluntarily give money to support a cause they believe in. So don't waste a bunch of effort protecting your work. If you're providing a valuable service, then ask for donations, and people will likely pay more than you'd have charged of their own free will. [Answer] ## Personally customized runes Instead of making a rune that says "The caster of this rune grows a beard", you make a rune that says "If Bob casts this rune, Bob grows a beard." For runes with a known caster but an unknown target, you make a rune that says something like "If Bob casts this rune, a fireball appears at a location of Bob's choice." [Answer] Take a page from Grossman's *the Magicians*: spells must account for place, time, caster's particulars (gender, mood, life history), planetary motions, star positions, ... So yes, customers get a program that runs, but only in a particular place, for about 20 minutes. Before or after or somewhere else, results vary, perhaps catastrophically. Now, you're not selling DRM'd "goods"; you're selling a service: spell compilation. In the real world, service-based business models work much better for the digital. In the *Magicians* universe, this service would be illegal, dangerous, and held in horrified contempt, like trafficking in children or weapons on the Darknet in our world. [Answer] **Commonly useful magic is free, it's the custom jobs that cost money.** Much like real world software, magic that everyone would find useful is available for free because sooner or later someone will do it pro bono. As for operating systems, so for Cure Light Wounds. But if you are a businessman, and you need something done that is rather specific and/or unusual, the magic script you need may not exist. So you contact the magic shop, explain your needs, pay for it, then they do the work and email you the magic script you need. In this case, the magic is inherently safe from piracy because only the paying customer wants it. [Answer] Paper runes are the past. Now, the best magic engineers in our Seattle research center have succeeded in creating a new chip that mimics rune writing. You're in a cave and a giant ogre stand in front of you - threatening you with his giant club. You take out your magic scroll and... Wait, no more paper? (copyright: [BlueWizard](https://worldbuilding.stackexchange.com/questions/86991/handling-magical-rune-script-copyright#comment258304_86996)). Not any more. No more "Where is a piece of paper?". No more "Wait, was it a ACH or a USH to complete this rainbow fireball?". No more "Ouch, yes, it was an USH". Join us now on Amarune and buy the new Rundle Paperwhite. Doing magic has never been this easy [Answer] You can use a **MAGICAL RSA**. The spells you deliver to your customers are customized for them. The customization process involves the customer giving some sort of "Public" rune that matches with their other "secret" rune. The secret rune is used to activate the spell and is a closely guarded secret. The trick would be in creating a rune script that will fall apart when any one rune is modified in that script (like some sort of equilibrium mechanic)... or fail catastrophically. It would be also cool to see the lengths that people would go to, in order to protect their activation runes. Some may not even activate them in public, where others would do so carefully. It also gives a way of sharing spells amongst a group or a family where they all share the same activation rune. [Answer] It's clear that you need a # magical script copyright agency ! in the real world, copyright is enforced entirely and totally by the action of legal bodies, civil actions, and industry-national pressure groups. (A great example is the "DOC" system in France - the notion that nobody worldwide is "allowed' to call anything other than Champagne, Champagne: surprisingly this actually happens.) So, much in the tradition of Time Lords, etc, you need a magical enforcement agency, for magical copyrights. Technology is of zero help in enforcing copyrights, in the real world and the magical. [Answer] You could possibly bind the rune to the customer. Essentially, only he/she could use it, and it is useless to others. [Answer] **TL;DR : Use the same techniques used to prevent copyrighted code copying** You could do it the same way some programmers prevent their code from being copied and reused by looking at the sources. To do so, they crypt it, add some useless code, or unintuitive design. You could use a similar process in the runes to prevent understanding it and so, reproducing it. You could also require the use of a specific tool to activate an encrypted rune, preventing the "source rune" from being seen and copied. It's not a perfect solution though, it may limit copy of the rune, but the most motivated persons could still analyse the rune to find its source and then reproduce it for their own benefit. But no copyright infringement preventing mechanic is perfect IMO Or, you could add some sort of "authentication" part to the rune, like some sort of "Blood related QR code", but this second suggestion is already in a ton of answers. [Answer] First, lets establish that magic is "magic". Second, rather than think of this as similar to DRM and piracy, think of it as a reloadable credit card. Each spell, because it can be used by anyone, has its own portion of power to use. Once used, the code no longer works unless the supply is refreshed. Any copy of the code could pull from that supply, but you control the supply. So when you generate the code, a portion of magic is set aside for this rune. It magicly travels with the code wherever it goes, but could not be duplicated by non-magical means. It is linked with the code. The information about the physical rune is stored in the ethereal magic "smart battery" that can only be drawn on by the code it was linked to. Also note that this is similar to a human with a soul/consciousness. You can make a literal copy of the body, but the soul is intrinsic to the body and can't be used by another and cannot be replaced once extinguished. [Answer] In the real universe, objects in the quantum realm cannot be copied. This is the [no-cloning theorum](https://en.wikipedia.org/wiki/No-cloning_theorem). What if magic is a lot like quantum mechanics? *We* could make banknotes that are not counterfitable by using 20 quantum traps in the note — one of the first papers explaining quangum encryption uses this example and shows that such a bill can be verified but not copied. Note that it’s a *theorum*, not an axiom. You can do the same: don’t simply state that it’s impossible to copy them because that’s a law of nature. Rather, it emerges as a consequence of more fundimental laws. An alegory: you need a digital signature from an authority to submit the work order to the god that manipulates reality. But it’s not a digital signature like we use today, but a *quantum* signature which **cannot** be copied. [Answer] Assuming rune works in a way similar to a circuit for magic power, how about drawing the rune using the magical ink, but once it is dry painting over it with regular ink that looks the same as the magical one. ]

[Question] [ In my custom fantasy world, raising the dead is really simple. Before the Great Act of Beautiful Death, raising a body and keeping it alive (undead?) for at least a week was a part of entrance exams for any University of Magic worth its wands. The reanimated body does not have any intelligence or free will; however it can understand simple orders as "Hit this person" or "March this way". There is no limit on the count of raised bodies, nor on the time that one can keep a single body working. A good mage, straight from said University has enough power to keep a small army working all day, finding it no more exhausting than a short walk on the beach. After casting, a mage does not need to be concentrated on the spell - Plug(magical energy)&Play(Murder) Zombie have no feelings, no morale, and feel no hunger. The sugars/ATP in muscles is substituted with magical unobtainium. However, oxygen is still required, so no underwater walking. After the magic in them vanishes, the body will start rotting, but nothing happens while it is animated. The body can be killed in any way that would kill a normal person, because all the magic does is force blood flow and send signals to body parts. However, the body will move for as long as there is enough blood to keep muscles oxygenated. And even without any blood, zombie will still keep attacking for a few minutes due to anoxyreaction of unobtainium (which destroys it in the process). Still, they are more durable than any human warrior, and can swing heavy weapons all day without becoming exhausted. From this short starting, you can think that any of those mages could easily overwhelm any human army. It is, however, not true. An army of 1000 undeads is a good match for maybe a dozen heavy riders (think of knights), if they are on flat ground. The only way for this army to attack a city is to flow over dead bodies of their fallen comrades, so actually as long as defenders have enough arrows no zombie can get in. One Very Evil Black Mage, very intelligent but detached from society, has closed himself in his tower for ten years, and came up with plan to dominate the kingdom - he will have an army of said 1000 Zombies and attack the capitol! To much of his disappointment, his army was defeated in a fast manner by a small garrison of troops. **But how? Why was an army of fearless, tireless murderers who would kill a puppy without a second thought, who will obey any simple order, defeated so easily?** EDIT: **Only a person who created a zombie can control it**. The death of the controlling mage does not dispel the undeads, instead, they are going on with the last order they were given. EDIT2: No city has any undeads, because of GABD. Necromancy is forbidden and nobody can do that, unless he wants to be hanged. If he is lucky, that is. It is similiar to biological weaponry in our world - it is forbidden and no lawful state will create it, but terrorists may. So **no fighting fire with fire**. EDIT3: **Zombies are not as nimble as humans**. Yes, they can run, but slower cognitive functions cause them to fall easily. Still, outrunning a horde is not a very good option, as you will run out of breath long before you lose them. [Answer] **The zombies are idiots.** Zombies can attack or defend, but they can't attack intelligently, and they can only do both at once with a lot of attention from the sorcerer. In a fight, a skilled fighter (person A) is constantly assessing their opponent(person B) or opponents. Person A's goal is to hurt person B without being hurt in return, so person A puts a lot of effort into predicting person B's actions and reacting to that. Zombies can't do that themselves: they need a skilled sorcerer acting as their puppeteer. Even the best sorcerer's zombie is at a severe disadvantage in a fight because the human fighter acts at the speed of thought, while the zombie doesn't react until it's told to. It's always a second too late. With only one person controlling 1000 zombies, no zombie is getting any individual attention. When it goes to attack a knight, it leaves itself open to be killed in return, often by being run over when it didn't even try to dodge the horse. The knights themselves are heavily armored, and can only be seriously injured by blows that hit the joints of the armor or the head. The zombies don't know what to aim for, and the sorcerer doesn't have the concentration to tell each zombie how to handle their current opponent. That said, if it's hand to hand, it will be a struggle for the knights because each knight will have to take down just over 80 zombies, and that many opponents, even when they are idiots, can pull down a skilled fighter by surrounding him with sheer numbers and determination. They could get around this by working with infantry who could back the knights up defensively: look up pike squares for one example of how. The sorcerer should have given his zombies distance weapons, which would get around the need for quick thinking in close-up fights. A single person ordering "Pick up and notch an arrow," "aim at an enemy soldier,", and "Shoot your arrow at that soldier," would kill a lot of knights before they reached the zombies and mowed them down. [Answer] **Zombies have no sense of self-preservation.** If you tell a zombie to walk to the castle, they'll do it, even if there's a moat in the way. Or caltrops. Or fire. There is no difference between the actions of a normal zombie and a zombie on fire, unless given a specific order otherwise. A bleeding warrior will stop and get bandaged; a bleeding zombie will keep bleeding until they stop moving forever. While a zombie wouldn't suffer from an infection, losing all its blood because it stepped on a sharp rock is easily possible. **Zombies are dumb as a box of rocks** If you tell a hundred zombies to hit that guy over there, they'll do it... even if he's dead. Unless you have some really specific orders, zombies are going to react very slowly to surprises - if they react at all. If you don't tell a zombie to do something, it won't, even if that includes something as simple as "defend yourself". Zombies have absolutely no way to think for themselves, so the wizard will have to do all their thinking for them; not a big deal if all they're doing is moving rocks, but once every zombie is doing something different, it's going to be hard to coordinate. Tactics are limited to "overwhelm them". **Zombies are super weak** While an individual zombie may be as strong as a normal human, that only means zombies terrify farmers. It would take ages for human-like hands to beat on a heavily armored knight enough to actually do any damage; even a big sword or club would only do damage if it connected. Being unarmored, a single well-placed strike could disable a zombie enough to put it out of the battle. What's more, a quickly-reacting human will see any efforts made by the zombies to surround him and will simply move out of the way. A single fighter, given enough time and a good horse, should be able to destroy an unlimited number of undead with simple hit-and-run tactics. Killing blows don't have to fully disable a zombie; just slash it enough that it bleeds out, and move on. The rest of the zombies will probably stomp it into the dust anyway. **Zombies might as well be deaf, blind, and mute** While a zombie may be able to see or hear, or even speak, it won't do so unless ordered. If it can't speak, it has no way of relaying information. Without information from the front lines, the wizard will have no idea what's going on unless he uses other magical means. Even with a scrying pool or a crystal ball, he can only mentally focus on spot at a time. If a few strong, noisy, tough-looking guys get in front of the zombie horde, the wizard may be distracted enough watching them and telling the zombies how to fight that he'll miss the half-dozen men gutting zombies from behind. Even if the zombies see the rear attack, they have no way of telling the wizard, and without orders from the wizard, they'll just stand there and get slaughtered. Overall, I'm surprised it took that many troops. Trying to maneuver a thousand stupid zombies over hills and fields without getting any of them killed (rekilled? Un-undead-ed?) is hard enough; facing pre-built traps made with zombies in mind is nigh-on impossible. Maybe if the wizard had an army of millions and dozens of helpers, he might have had a chance, but with a paltry thousand? He didn't stand a chance. [Answer] In medieval times and earlier, in any battle of trained units versus armed farmers the trained units indeed had fair odds of beating engagements that were 10:1. Zombies are not simply poorly trained units. They are completely untrained, disorganized, unled, and literally brain-dead units. Zombies don't suspect or prepare for an ambush in a spot that's perfect for an ambush. Zombies don't know how to retreat from a losing battle. Zombies don't know when to stop chasing an enemy. Zombies don't know running through oil when the enemy is readying fire arrows is bad. Zombies don't know how to use shield formations. Zombies don't know how to counter shield formations. Zombies don't know how to brace against a cavalry charge. My guess is the Zombies were done in by a single rider who was riding circles around his brother, who had a bow and 5000 arrows. Or by a single horse archer. Or by a peasant with caltrops. --- As for the actual question, why did the **intelligent** evil sorcerer lose? He did so on purpose, because now the city council is scared of more zombie attacks and will finally fund his anti-zombie army made of intelligent yet perfectly obedient stone golems. [Answer] # Zombies Only Follow Orders First, a comparison: Think of any video game you've ever played that has NPC's. They fight based on a set of code that helps them determine what actions to take and when. It's taken YEARS of tweaking to get computer programs that can fight somewhat close to human levels. Besides that, they're only a challenge because they either have much strong stats or because they have inhuman reaction speeds because they react to your input in a way that a normal human cannot. Second, apply this to zombies: Now these zombies, they follow orders. But no matter how specific your orders are, if they can't think for themselves, they can't adapt well enough to beat an army. You can tell them to 1. Stay alive 2. Kill the enemy And have them follow those in order, but that still doesn't account for nearly everything. They will use what they have at their disposal, but they're still no smarter than a computer AI. It would take years of talking and commanding them to get them to follow a string of orders that would make them comparable to an actual soldier, and I doubt they have the brain capacity to remember or understand it all. Third, apply your additional constraints: The zombies aren't very strong, they are vulnerable to death (again), they only understand simple commands. There is no way they can win a fight other than through sheer numbers. # To Win Using Zombies If the Nercomancer wants to win using zombies, he's going to need different tactics other than straight **Stealth Zombies** It's stated that they move like normal and that they just need blood flow. They also don't rot while they are animated. It would be possible to dress zombies in normal clothes and make them smell normal and give them a simple command such as "Walk into the city and then kill everyone." **Modified Zombies** They can also be altered in ways that would be too painful for normal humans. Attach blades where their hands should be. Blood can flow through the rest of their body and they won't feel pain like the normal people, but now the zombie is more powerful and likely to kill someone in their kamazakee state. They can even be implanted with explosives or other surprises since they can withstand it. **Strategic Summoning** There doesn't seem to be a limit on the summoning aspect of this necromancy. So long as there are bodies, you can make a zombie. So using some of the techniques above should create more soldiers. If you're trading more than 1 zombie for each person you kill, then you'll run out of people. The goal should be to maximize the amount of zombie converts for each zombie lost. So if people want to war with you, let them. Find a way upgrade the zombies and then get a good kill ratio. Don't summon more until it's safe to gather the zombies and upgrade them as well. Sending them all in to die against an army is careless use of a limited resource. [Answer] **The zombies are bad at navigating around eachother** Hey all you zombies. Hit that knight. *Every zombie runs directly toward the knight*. A mindless zombie hoard is going to have trouble not tripping over itself. Zombies don't march, and they certainly don't have enough coordination to not run into and trip over another zombie. The zombie hoard may be 1000 dudes, but how many do you think will actually make it to their target if they are all told to run toward it? I think not many. I imagine something more along a pile of zombies all trying to get up and knocking eachother down in the process. Think along the lines of a fairground if every single person tried to get to their destination, completely ignoring the presence of anyone around them. This can only be made more hazardous with sharp objects (weapons) in the mix. [Answer] The weak point of the necromancer's army is not the mass of inhumanly strong, utterly loyal, tireless, and fearless soldiers. Appropriately, the army is vulnerable to a decapitation strike that removes the leadership: defeating the necromancer may not dispel the zombies but it makes them useless for besieging a city. This paints a target on anyone who wishes to use an army of the dead. You could get some narrative work out of the necromancer controlling his minions much more effectively when he has line of sight. This would alter your scenario a bit: on an open battlefield a zombie could be a match for any mortal knight so long as the necromancer assumes direct control. Direct control allows the zombies to wield weapons, fight effectively, coordinate their actions, and perform any clever tactics the necromancer conceives of. In a siege the necromancer could direct them to climb walls and bypass other defenses, as long as he is present to do the thinking. This makes it all the more important to quickly kill the necromancer. In a normal army, intelligence is distributed across all officers and soldiers. If the field marshal falls there may be a hit to morale, but someone else will take command and every soldier can still act independently. With all intelligence centralized in one person, his death essentially disbands the army. The necromancer might also have difficulty attracting a mortal retinue; who wants to be part of an army where the other soldiers could go berserk and turn on you if the leader falls? So how do you kill the necromancer? One approach to an overwhelming opponent with a weak point is a small, elite strike team. There are mage-hunting assassins trained to bypass magical defenses. Perhaps a magical rite that renders the user invisible to dead eyes, or a young bowman who can hit an apple from 200 yards away. Is the necromancer arrogant enough to assume he would only need 20 deathless servants for personal protection? The bards may tell the story as 1000 zombies vs. 12 knights on the open battlefield, but in reality the 12 struck stealthily and were only later knighted. Uncontrolled zombies might still be dangerous, depending on the last orders they received from the necromancer. For example, they could have been ordered to kill any living thing they meet. It's a crisis, but it's a manageable crisis. They're disorganized and stupid. They don't wield weapons or know how to defeat armored warriors. They walk heedlessly into traps, and never learn to avoid them. They have no self preservation as they're picked off with ranged attacks. [Answer] (~~This is my comment converted to an answer and extended~~ A bit more extended). # Some assumptions you didn't specify in your question but partly confirmed in comments: * Commands from the mage arrive instantly * The mage can order commands as fast as he can think * The mage can order any subset of zombies and can select groups in the same area in one thought (think of selecting units in a strategy game), but has to scan through all zombies to select based on a condition (all with one leg for example). * The mage can potentially see, hear, ... everything his zombies can, but not all at the same time (sensory overload and stuff) * Zombies are able to do basic pathfinding (evade static obstacles mainly) * The zombies can remember and execute simple conditions, up to a small number (for example *"Direct order always wins against any other order"*, *"If their is fire go away from it"*, *"If on fire roll on floor"* and *"If enemy is in range hit it"*) *(This is not required by my answer, if it is not valid it makes it easier for the defenders)* * Zombies don't naturally heal (in the timeframe of this question). However, blood exiting their body still clogs, so minor wounds seal as usual. * The zombies feel nothing. --- In my opinion your zombies have 3 advantages over normal fighters: * They don't get tired * They feel no injuries * You're zombies are not very agile anyway, so you can armor them up This leads to some suicide-advantages: * They can go into overdrive-mode, doing work much greater than a human, but destroying their muscles in the process. Default zombies do not heal, so you trade (un)life time for strength. * They can operate with injuries that disable humans. Sadly most injuries that disable humans are also quite deadly for humans. Lighting a zombie on fire makes a burning swordsman for 5 minutes, lighting a human on fire makes a messy pile of pain. Now to the disadvantages: * The evil mage would need an army of mages to apply tactics against your enemy, as a single mage can order only so many orders per second and still has to be a tactical ace to oversee the whole situation. If the evil mage has an army of mages, why bother with (just) the zombies. * Any enemy with small military knowledge can outsmart a zombie. Place two archer-troops on both sides of the army and watch them wander helplessly between the two groups. When the mage organizes his troops there, use it and strike elsewhere or move your troops out to apply another tactic) -> This basically grinds down the zombies. * If ranged weapons are not an option, use hit-and-run tactics. Come from a direction where the zombies are not looking, smash some zombies and run before the mage realized what happens. You can not outrun a zombie on the long run, but you can hide. * The zombies won't see obvious traps. Pitfalls, stones at the top of a cliff they wander along, you get the point. Still effective even when the mage looks through the front-most eyes, as one can build traps that don't trigger immediately (or are remotely activated). * I assume it very hard to hide 1000 soldiers, even when they can march day and night and are really silent. They will leave traces. Humans can strike way before the zombies reach the city. --- [Answer] **Mages need to sleep.** Scouts from the capitol have been keeping watch over the zombie army several days walk away from the capitol. They notice that at night the zombies seems to be *extra* stupid, and correctly deduce that the mage is sleeping. The last night before the army would have reached the capitol, a group of trained night fighters sneak into the army camp and (re)kill everybody. (Let us not use the ugly word assassin, shall we?) Now, the zombies themselves won't be sleeping, but they might as well be since they are so stupid. They will have some standing orders like "attack anybody who is alive." but they will not be smart enough to coordinate those attacks. And uncoordinated attacks are easily dodgeable. When the mage wakes up, the battle is already over. [Answer] You say it yourself: the zombies has no free will or intelligence. A good soldier is capable to adapt to the situation and change his action based on the actual situation, following his order. Your zombies are basically useless to anything else that to obey direct order, by only one person which then must control everyone of them every time. For the zombie to be useful, you need to give them a extremely detailed order (hit him, evade this and this and so on) and still you are unable to avoid traps or a simple change of strategy from your opponents. Not to mention that it is not very handy. **Updated to address the clarifications** Edit (1) make this person the weakest point since it must be near the battle and then vulnerable (to long range attack for example). Once incapacitated to command the zombies, the battle is over, with the risk to not begin in the first place. [Answer] Well if the zombies are less intelligent than earth worms then even medieval fortifications and warfare would favor intelligent opponents, compared to a group of brainless *dums dums*. After all it means that if one guy is yelling at the top of a wall every zombie around will pile up next to the wall and uselessly reach to one guy dozens of feets above them. Then it is only a matter of work to dispatch of such undeads easily. Literally you just carry rocks or oil and smash and burn near endless amounts of zombies that just keep piling up below the wall. This is just one example of how to destroy unintelligent opponents that naturally lack self preservation, any kind of basic tactics or situational awareness. [Answer] The zombie intelligence and reflexes answers already given are excellent, there are two additional reasons that might come into play as well though. The first option is that zombies may be weaker or less co-ordinated than a living body, magic sustains them but they are still weaker and slower than they were in life. This is a decision you can make as to whether you want them to be stronger or weaker than in life, faster or slower, and also how much damage is needed to stop them moving. The second option is that they may have specific weaknesses that human defenders know about (after all if zombies are common so are counter measures). Maybe a blow to a certain area kills them, or holy water burns them, or grave dirt prevents them passing, etc. [Answer] If our Very Evil Black Mage is as intelligent as you claim, **why would he attack the capitol with only 1000 simple zombies**? Why didn’t he spawn more zombies? My suggested answer to this is: To create more zombies he would need bodies and to create bodies I assume he would need to attack smaller settlements (having already emptied a graveyard for his starting army). Small enough settlements and that even if the settlers knew how to defend themselves, there would be no risk losing more zombies than he would gain from the attack and then some. And if by saying “*There is no limit […] on time one can keep single body working*” you are only talking about magical limit then there would still be the physical limit on how long a zombie can walk before falling apart. So a lot of zombie soldiers are lost or weakened while traveling between conquerable settlements. As more and more smaller settlements get wiped out he moved to *slightly bigger* villages. Once that resource was exhausted, he figured attacking the better defended cities would only result in losing more zombies than he was able to regain afterwards. The capitol is tightly packed with people. If the mage could get most of his zombies inside the wall they can start killing civilians and he could raise the newly deceased to resupply faster than the soldiers could destroy them. **Cities**, **panic** and **narrow streets** are the best battlefields for necromancers and their zombies. But for some reason the capitol was notified, and the local garrison met the zombie army in an open field, a battlefield which the zombies have every disadvantage. And that was why an otherwise very threatening army was easily defeated. [Answer] ***TL;DR***: Zombies following orders can't adapt. They are simple programs. They can be forced into a loop, or forced to do something that doesn't make sense. ## Humans have initiative A human army is guided by a general. Orders are relayed between the divisions of the army by messengers, or using ranged communications (radio, flags, pigeons, etc). They can work as a team, holding, pinching, striking from the rear, etc. They can also adapt to changing circumstances. The leader can relay orders. If the cavalry is attacking a hill, but the archers have already moved off onto another hill, the cavalry can divert to another target. They can use their initiative, or they can respond to new orders from the general. ## Zombies simply follow orders As you mention, zombies simply follow orders. **"Go here, hit these people till they die"**. Well, what if *those people* all jump on horses and ride away. Do the zombies keep following them blindly around the field while the arrows rain down on their heads and horsemen cut them down from behind? **"Attack the city and kill the people in there."** Well what if the people go outside the city and stand on the hill. Do the zombies just stand in the city square while an onager on the hill slowly pounds them to pieces? A human with an understanding of zombie programming might outwit them easily. [Answer] I'm assuming that, though you can't outrun zombies in the long term, you still can get some distance. 1. Run away and shoot flaming arrows at zombies. They can't die from the burns, but they'd die from lack of oxygen. 2. Run away, cross a river and break the bridge behind; zombies still try to chase you and drown. Or go through a swamp (assuming that you know the path). Or go through a frozen lake, and break the ice behind you. 3. Again, run away and climb on some cliff. Hopefully, zombies are bad at climbing and you could just stay there and throw rocks at them. (Though knights make bad climbers, too). I guess, melee combat is not an option. 1000 undead is a huge crowd, and even if zombies are complete idiots, the mage could just bury knights into zombies. Then the knights would be finished with a few lucky stabs or bites (corpses are still poisonous, right?). [Answer] **Angering the Gods is a Bad Idea** In a fantasy world, angering the gods tends to be a bad idea. The gods don't necessarily agree; in Greek myths you might survive angering one god if another has your back. In fantasy settings there may be some form of balance between the gods. For the sake of this answer I assume a balance between life and death The good guys might not always win easily. The gods of life might support them, but the the gods of death are open minded on the whole "murder" thing, and are willing to hear the prayers of the villains. Unless those villains are uppity wizards who regularly steal souls from the halls of the dead to murder the living. In *that* case their actions would not be blessed by *any* of the gods. If the very evil mage doesn't catch a hint, they might assume that their initial loss is because the zombies are less nimble, or less independent. He may come up with some clever stratagem around this weakness, but when the gods are unanimous in their displeasure, in one way or another the mage will find his comeuppance sooner rather than later. Depending on the fantasy world, gods may not be an issue for necromancers. In general if you break the laws of magic you often have bigger problems than mortal authorities. Angry spirits, magic residue, druids, nature spirits, plagues of carrion feeders and magically enforced anti-necromancy treaties could all give necromancers a bad day. [Answer] **Zombies don't have good immune systems** One of the reasons why a zombie army is a bad idea is because their immune systems are still defected. This makes it worse if Mr Very Evil Black Mage is using an ancient army because diseases tend to adapt to the modern immune system, seeing that an ancient undead army uses an ancient immune system, they won't be able to defend against the new diseases as well as the average human. *Just refer to the aboriginal Australian small pox epidemic or the native American population after European contact to get the idea* Due to a lack of information about how far the distance is between the Very Evil Black Mage's location and the capital I'm going to say it's a fair distance away. Due the the times the Very Evil Black Mage fails to understand basic germ theory *To be fair, the kingdom also doesn't understand much of it either* As for why Very Evil Black Mage fails to understand basic germ theory, in real life the first microorganisms weren't even discovered until 1665 and weren't proven to cause diseases until the 19th century. Because most of fantasy is based on medieval Europe and I have no idea what time period this fantasy story is based of I'm going to assume it's about late medieval Europe (so no gunpowder or wooden armor). In this fantasy world I would assume that almost nobody knows about microorganisms and as a result so doesn't the Very Evil Black Mage *Otherwise why bother sending a horde of zombies to the capital if a virus could decimate almost the whole population?* The Very Evil Black Mage may not know anything about microbiology but he is still very intelligent so he puts them in a tight, slow but effective formation (something like a phalanx or cohort formation) nothing could go wrong! Right? Well... As the zombies are marching towards the kingdom a few mosquito along the way bit the zombies and as soon as a few days passed by the whole horde is infected by the disease. As great as magic is, unless if the Very Evil Black Mage knows what a virus, bacteria etc. is and knows how to deal with it, because it is tightly packed and slow moving, the whole horde would be wiped out by the disease... If the humans didn't wipe them out first. Now extremely weakened by the infection, all the zombies continue to crawl towards the capital (If they could do so that is), a fair amount of the original horde remains as their blood is still pumping however they are severely weakened by the disease and the humans have them on sight. Taking advantage of their current immobility (Thanks to the diseases) the army dug a large long ditch and pushed the zombies in. After the ditch was fairly full they set the zombie filled ditch on fire and a few of the army wearing full plate would sweep out any remaining zombies with their swords, arrows and spears. [Answer] Basically my response is on the same lines as @Karen Numbers don't mean anything on the battlefield in this particular case , you may have 1k troops but you only got 1 brain controlling them all for a veteran warrior an undead's movements would be something similar to playing a videogame in slow motion(what i mean is that their movements will be clunky and easily telegraphed) sure if it's the first time you set foot on a battlefield it might be scary but after a few it will be a true walk in the park. Magic attacks from other mages...you said necromancy is like biological weapons ... ok can we still have nukes do? I don't mind casting only one spell a day if said spell engulfs a field 500meters wide in hellfire that won't burn out until any organism is burnt to ash. Throw some fire arrows in the direction they will go through and watch them walk through the blazes ... if they survive repeat ... if they get to close hit their head(or what's left of it after so much fire) with something solid and rather hard like a hammer). Just a few ideas (there are a ton more) but the basic idea is zombies= dumb fcks ... dumb fcks react slow and that is their most exploitable weakness on a battlefield scenario. ]

[Question] [ A common topic in alternate history fiction works is the question what would have happened if a major conflict had been won by the other side. These usually focus on the events after the conflict, and the change itself is not depicted in a realistic way: it's either not discussed, or attributed to a superweapon or deus ex machina. I know that the Cold War was a complex time, with a huge number of social and economic factors in it so that there was not single realistic "miracle" which would have guaranteed a certain different outcome, therefore I list a number of disclaimers, in order to make this question fit into the topic of this site. It doesn't have to guarantee a Soviet triumph, but it has to significantly increase its probability. A **victory** doesn't necessarily mean complete global domination. If the Soviet Union ends up in control over most of the Eastern Hemisphere, it would count as a victory for the Communists. The change has to be a **single event**, or a collection of tightly coupled and interdependent events. It has to happen either **during the Cold War**, or not more than a few years before it. The Cold War should, at least in the beginning, look very similar to what happened in real life: the alliances should be roughly the same, the events like the war against Nazi Germany, the occupation of Eastern Europe, the Communist victory in China, and a cold war between the USA and the Soviets should occur (or at least begin), even if at different dates or different order. The major participants should be the same. The change should have a **realistic justification** (so no secret Soviet UFOs), I would think in the following changes: events progressing slightly faster or slightly slower than in real life, a single large event or series of interconnected evens tilting history in the Communists' favor (if that had even a small chance of happening). I'm thinking along the lines of the Soviet Union and its allies advancing faster against the Nazis and crushing them before the Allied landings in Normandy, or Stalin not butchering his officer class so they could respond effectively to the Nazi invasion right away, faster scientific development for the Soviets in electronics, computers, space, missile and nuclear technology, the Soviets invading Japan before the Americans can mount a Pacific campaign, no US intervention in the Berlin Blockade, Korea or Vietnam, or a different sequence of diplomatic events leading to Soviet domination in either Asia or Europe which in turn could lead to a victory on the other continent, etc. [Answer] Let's try this: in late spring of 1952, the Warsaw Pact launches a surprise invasion of Europe, and succeeds in sweeping NATO off the map. Great Britain is either overrun or remains free at your discretion. Mid-1952 is chosen for the following reasons: Stalin is still in charge, and the US is bogged down in Korea. Stalin understands, on a gut level, that it's perfectly possible for a conventional conquest of half of Europe. After all, he'd already conquered the other half. The US is heavily engaged in Korea, and particularly air and artillery assets have been diverted to the effort. Combined with the general post-WWII decline in low-level American military effectiveness (which is being addressed by the US as a result of Korean experiences), Soviet armored forces are able to move faster than expected. The elephant in the middle of the living room, of course, is the question of how to keep the conflict from going nuclear. As late as the mid-60s, I heard an ROTC officer casually mention that, in the absence of nukes, a reasonable projection of the USSR invading Europe had the Russians reaching the English Channel in two weeks, and the whole thing would go down in our history books as a classic doomed defense. So, how to deal with this? Well, in 1952 neither U2s nor reconnaissance satellites were in operation, so intelligence about Russian military capabilities was very spotty (which would also work in the Russians' favor in assembling the invasion forces). The Russians had touched off their first nuke about 3 years earlier, and if they claimed to have produced more units than they had (which they did in any event) it would have been hard for US decision-makers to disregard those claims. Without ICBMs, threatening the Russian heartland with nukes via bomber delivery, especially if Great Britain is out of the picture, would have been a dicey proposition. The first jet strategic bomber, the B-47, had only been deployed for a year, was available in small numbers, and had teething problems. The primary strategic bomber at the time, the B-36, had the range and payload capability, but was horrendously slow (240 - 300 mph) had a 40,000 foot ceiling, and would have been easy meat for MIG15s. Further complicating a successful defense is that fact that, as the invasion progresses, tactical nukes become less desirable from the point of view of the invadees, who justifiably may conclude that they would rather not nuke their own people, and who are unimpressed by "It became necessary to destroy the village to save it". EDIT - Per David Grinberg , a few additions. 2 weeks is indeed aggressive, but the distances are remarkably short. The classic choke point for a westward Soviet advance is the Fulda Gap, and from there it's only 400 km to Amsterdam, and 500 to the Cherbourg Peninsula. I'm assuming that the NATO armies were subject to the same sort of victory disease which had infected the US when they arrived in Korea. See Task Force Smith for depressing reading. It takes a certain amount of hard knocks for an army to get its collective head out of its peacetime arse, and the defenders simply wouldn't have had that luxury. From this distance in time it's hard to realize just how far the US Army had fallen from its WWII effectiveness levels, but reading about the early stages of the Korean war is educational. Again, this sort of thing is fixable in fairly short order (and with a lot of blood shed), but the defenders simply wouldn't have had much time. I do not have an attribution for the quote I heard. It was casual conversation with an ROTC officer. The USSR reputation mentioned is only partly applicable. For instance, the 1945-1952 period saw the introduction of the T54 tank with no real matching change in the US armory. And the Soviet steamroller is arguably the approach to use in Europe prior to the introduction of changes such as portable anti-tank missiles and precision munitions. The Germans, for instance, were unwilling to adopt defense in depth (since that meant starting with the assumption that they were going to lose a lot of territory, and they didn't have all that much to give up), and this left them vulnerable to getting their defensive forces hammered and shattered. With the Germans gone, the northern route over Belgium and the Netherlands into northern France does not seem like all that hard a push. And, as I say, the distances aren't all that great. 400 km (250 miles) is 2 weeks at an average of 20 miles per day. Strategic surprise on the part of the WP forces would have been critical. [Answer] **Operation Overlord ending in disaster.** Hitler not falling for "it must be Calais". Rommel getting free reign to position his troops, and meeting the landing force early on with massed troops and tanks. The weather forecast being wrong and the troops having to land in heavy winds. There are so many well-known things that could have gone wrong. With the advance in Italy stalled, and no easy way to pour Anglo-American troops into Europe, that would have meant the Russians steamrolling all over a collapsing Germany, and possibly all the way to the Atlantic too. No real foothold for the USA in Europe, and all the spoils of war (jet and rocket technology, the Uranium, all the nice technology and brainpower that in our timeline got split up between the two powers) going to Russia alone. No NATO. France, West Germany, Austria, none of those end up as part of the "western world". Wernher von Braun and his colleagues building ICBMs based on their A-4 / V-2 experience, not for the US but the Soviets. That alone should have shifted the balance. [Answer] I could think of a couple of scenarios: * [Trinity](https://en.wikipedia.org/wiki/Trinity_%28nuclear_test%29) fizzles and the Manhatten Project stops to a crawl. The US wins WWII anyway, much as they did in the real world, then they demobilize almost as much of their Army. (The Navy becomes the strategic force, with conventionally-armed carriers ruling most oceans of the world.) A decade later, the US has only a few dozen first-generation bombs. During some crisis (Hungary 56?) the Soviets overrun Europe with conventional forces. * Communists win elections in one or more NATO countries in Europe. That's not completely far-fetched, just assume that the voters of the [socialist parties](https://en.wikipedia.org/wiki/Party_of_European_Socialists#1960s) got more extreme. Either cue the [domino theory](https://en.wikipedia.org/wiki/Domino_theory), or [violent oppression](https://en.wikipedia.org/wiki/Operation_Gladio) which cripples those nations. The economic strength of the West goes down and the Soviets can out-produce them. * Chinese and Soviet leaders cooperate effectively. Improbable considering the rivalries, but it could be done by convincing just a few people ("hang together or hang separately"). China industrializes more quickly. The lower efficiency of communist Economies is compensated by much larger numbers. --- Edit/clarification: I did not want to belittle the Soviet part of the WWII victory. I meant that the US defeats *Japan* much as they did in the real world. A fizzle of Trinity might have delayed Little Boy long enough for conventional firebombing to cause a Japanese surrender, and that would have slowed the post-war nuclear program. [Answer] **Lenin is only lightly wounded in [failed assassination](https://en.wikipedia.org/wiki/Vladimir_Lenin#Failed_assassinations)**. He survives, **excludes Stalin from Central Committee** and succeeds in establishing [New Economic policy](https://en.wikipedia.org/wiki/New_Economic_Policy) which was more capitalism-oriented, like China's [Socialist market economy](https://en.wikipedia.org/wiki/Socialist_market_economy) and Stalin does not have chance to cancel it. Cult of personality exists, but avoids [worst excesses](https://en.wikipedia.org/wiki/Great_Purge). Lenin also avoids [executing top military experts](https://en.wikipedia.org/wiki/Great_Purge#Purge_of_the_army) as Stalin did, so **USSR is better prepared for war with Germany, and victory is one year faster** (Germany is defeated in autumn 1944), and more decisive for Red Army - USA meets USSR on German borders with France, over-running Germany completely and **including whole Germany in Eastern block**. As a result, **Werhner von Braun and his team is captured by Russians,** (instead of by USA, [Operation paperclip](https://en.wikipedia.org/wiki/Operation_Paperclip) ) and **USSR has vastly superior rocket technology** than USA does (no [Redstone rocket](https://en.wikipedia.org/wiki/PGM-11_Redstone), winning space race and landing on the moon before USA does. After stealing results of Manhattan project with their superior spies, and putting stolen nukes on top of their superior rockets, USSR is dominant superpower. Cold war is won, but let's continue: Split with China's communists is avoided (by power of Lenin's cult of personality), and **[China's economic reforms](https://en.wikipedia.org/wiki/History_of_the_People%27s_Republic_of_China#1976.E2.80.931989:_Rise_of_Deng_Xiaoping_and_economic_reforms), modeled of Lenin's NEP, can start 20 years sooner,** avoiding the disaster of [Great Leap Forward](https://en.wikipedia.org/wiki/Great_Leap_Forward). If you feel extra generous, USSR also invites Jewish scientists expelled from Germany, like Einstein, increasing scientific prestige of USSR for relatively cheap price. With **ability to direct huge resources of state-owned companies,** and special natural resources like rare metals, **USSR and China can buy lots of influence in Europe** and can guarantee their allies better security (or else, such security guarantee would be of course blackmail, but heck, it does work) and access to rare metals and other resources. USSR and China **insist on transfer of technology and know-how as condition of access to their markets** (and have access to German engineering skills). World looks much different. USSR **won the [Space Race](https://en.wikipedia.org/wiki/Space_Race)** (using the same Saturn V build by von Braun, but launched from Baikonur) with appropriate gain in prestige (increasing it's ability to recruit spies). And possibly by now there is USSR-China-Germany joint **Permanent Moon Colony**, which is working on electricity-powered rail gun to launch humans to Mars. Yes, it costs trillions. Trillion is about a dollar per day per citizen each year. USSR/China/India sphere of influence, with **total population 3 billion** and including Germany and possibly all Europe, can afford it, especially if they don't need spend much money on army. Edit 6 years later: ... and it starts looking that China is working hard to beat USA in next cold war and dominate the future. Will USA and EU get their wits together and start competing and beating China? [Answer] This doesn't seem hard. I always thought it was pretty amazing that the U.S. won. I can easily posit one triggering event: Ronald Reagan loses the 1980 election. Instead the winner is a weak pacifist. Then the U.S. remains paralyzed and humiliated by the hostage crisis in Iran. The U.S. develops no strategy to combat the Soviets in Afghanistan. Afghanistan falls, and so the rest of the Middle East, already Soviet-leaning, becoming solid Soviet allies. Any that don't are invaded or subverted. The Soviet take-over of Grenada is unopposed. Emboldened by this, the Soviets, acting through Cuban and Grenadian proxies, take over other governments in the Caribbean, and then in central and South America. Meanwhile, the U.S. begins dismantling its nuclear arsenal while the Soviets give little or nothing in return, perhaps with the idea that this gesture of peace will somehow win over the Soviets, perhaps because the U.S. is outmaneuvered and/or duped in arms control talks. You can write a variety of endings to that story, but the general theme is a U.S. declining in military power and political influence until it cannot stand up to the Soviets. Scenario 2: The Soviets invade western Europe. They tell the U.S. that if it tries to intervene, they will launch a full-scale nuclear attack. The U.S. is not prepared to sacrifice tens of millions of its own people to save Europe. It engages in some face-saving gesture but backs down and does little to stop the Soviets from taking over all of Europe. This scenario seems eminently plausible to me. During the 1960s and 1970s there was talk of a "telephone war": the Soviets would call the president and tell him to surrender, and the U.S. would cave in rather than risk a nuclear war. I don't know if there's any evidence about what the Soviet government really thought at the time, but many Americans believed that the Soviets were much more willing to take casualties than Americans were. Many Americans believed that as long as the Communist Party was confidant that their leaders could survive in bomb shelters or remote areas, that they would gladly sacrifice millions of ordinary Russians if that's what it took to win a war. But the United States would not. Many people questioned at the time if the United States would risk a nuclear war to defend Europe. Many have said that the job of U.S. soldiers in Europe and South Korea was and is not to repel an attack, but rather to die, so that the United States would have to go to war to avenge their deaths. Scenario 3: Subversion. There were plenty of communists in the United States in the 1950s and 1960s. It's popular today to laugh at the paranoia of Joe McCarthy et al. But in fact when the Soviet Union fell and westerners were able to access KGB files, it was found that most of the people McCarthy accused of being communists were, in fact, paid spies in contact with the Soviet government. One book I read claimed that literally EVERYONE that McCarthy accused turned out to be either a member of the Communist Party, a paid Soviet agent, or in contact with the Soviet government. I haven't researched it to find out if that's true. But it's clear that the Soviets did have a systematic program to plant agents in the U.S. government, and that even without that, there were plenty of Americans who were communist "true believers". It's not that hard to imagine that if these efforts, by Soviet and by American communists, had just been a little more successful, that communists might have taken over the government -- won a majority in Congress, elected a president, etc -- the U.S. could have turned communist, the two sides declared unity, and the Cold War ended with a communist victory. Harder to pick one single triggering event for such a scenario. Maybe this scenario is less plausible than others: more and bigger things would have had to happen differently. [Answer] If Henry Wallace had become President of the United States. In our world, of course, Henry Wallace was the U.S. vice president in President Franklin D. Roosevelt's third term (1941-1945) but not the fourth term -- Harry Truman was selected as FDR's running mate instead. Truman became president when FDR died a few months later. The policy set by President Truman, and generally continued by his successors, was to contain communism. Truman backed up this policy with major efforts including the Marshall Plan to economically rebuild Western Europe, the Berlin Airlift to sustain West Berlin during the Soviet blockade, and the Korean War to stop communist North Korea from taking over South Korea as well. Wallace, who was far more sympathetic to communism and the Soviet Union, would have had very different policies. It's easy to imagine President Wallace presiding over an era of unimpeded communist expansion. Especially since... > > Had Wallace become president, a number of the men to whom he intended to give cabinet and other top positions were Soviet spies or agents. > > > "Just When You Thought Soviet Propaganda Was Dead," by Ronald Radosh, Wall Street Journal, January 10, 2013, <http://www.wsj.com/articles/SB10001424127887323482504578229663495014162> [Answer] 1948: Truman listens to his top advisors and the Berlin airlift does not happen at all. The Soviets see no serious opposition from the West and continue their piecemeal conquest of Europe. France perhaps installs a communist government even before the Russians arrive. The Russians, for decades, do not have to guard their western frontier as they had to from the end of WWII to 1991. The lack of NATO means the Russians can seize Middle East Oil relatively easily. Facing only the Chinese as a real threat and with free oil, the Soviets don't collapse despite the inherent flaws with real socialism/communism and with the way they actually practiced communism. [Answer] Operation Unthinkable is launched. One the verge of VE day the allies attack the Soviet Union. And they lose. They are pushed out of Europe. The large oceans between the two powers turns to a cold war, which the now dominant USSR wins. [Answer] ## WW3 happens Any nuclear exchange would most likely end in USSR owning what's left of Europe. There were several periods when one of the sides had advantage in ICBMs over the other (or at least they thought they had). But it was merely an uninterrupted string of "NO" decisions made back then. Any of them going "YES" would result in both sides owning their half of nuclear wasteland. [Answer] ## It's all about the economy The Soviets eventually lost the cold war because their economy lagged horribly behind American. Free enterprise allowed the Americans to innovate, improve and export. A booming economy meant plenty of tax dollars to spend on weaponry and research. ## Ultimately Star Wars lead to glasnost and perestroika The Star Wars missile defence system would have lead to a whole new arms race. Gorbachev recognised that the ailing soviet economy could not afford to keep up, and so attempted reconciliation, a policy which ultimately lead to the fall of the Berlin wall and the break up of the USSR. ## The solution is to improve the Soviet economy A capitalist society allows lots of people to "have a go". Most of them will fail, and when they do, that company goes down. Some will succeed. Ultimately the economy improves. A communist society on the other hand allows centralised bureaucracies to make decisions for everyone. If they fail, everyone loses. It's a more brittle system because there's a single point of failure. We now know that Communism and central control ultimately lead to corruption and bad decisions. However at the time of its conception, this was far from obvious. Some alternative form of central control might work better. Some sci-fi concepts might be: 1. Control by an AI or alien intelligence which is incapable of making wrong decision. 2. Competition amongst bureaucracies, backed by accountability. 3. Eugenics, or genetic manipulation creating a smarter ruling elite. A more prosaic solution might be a communist/capitalist hybrid such as we now see in China. ### References: <http://www.academia.edu/8275555/Causes_of_the_Collapse_of_the_U.S.S.R._under_Mikhail_Gorbachev> [Answer] I hate such brutal actions as tank attacks. To properly rule time, you need to look deeper for minimal reality changes. Read [The End of Eternity](https://en.wikipedia.org/wiki/The_End_of_Eternity) Start with [Charlie Wilson](https://en.wikipedia.org/wiki/Charlie_Wilson_%28Texas_politician%29), US senator who helped to arm Afghan guerrillas with shoulder-lauched [Stinger missiles](https://en.wikipedia.org/wiki/FIM-92_Stinger). USSR has total air superiority until then. Before his first trip to Pakistan, Wilson had hit-and-run car accident, but was able to leave USA before investigation started. Stop him from leaving, and put him in jail instead. No Stingers, USSR uses its air superiority to brutally suppress Afghans, in which looks like a military victory. Good enough for Gorbachev to claim victory. USSR is victorious, USA is humbled. USSR does not collapse. [Answer] Option 1 (fast). The Marshall Plan for reconstruction of Western Europe after WWII is badly mismanaged. That would both badly weaken NATO and discredit the U.S. and capitalism in general in Europe. Then multiple NATO countries go communist in about the 50s or early 60s. Option 2 (slow). The Cold War takes a couple more generations and the spread of communism and radicalism within Western academia produces a generation of leaders the Soviets can co-opt. [Answer] A significant nuclear accident on US soil, ideally before Sputnik. It would have two major impacts: * Americans would grow more distrustful of nuclear work, removing public support for the arms race. * Americans would look inwards to fix the accident, both leading to less support for foreign relations and more money and political capital spent on *this* rather than the space race, which in turn harms American influence around the world. [Answer] Event: Manhattan project (the atomic bomb) fails or at least is delayed by five years. Inmediate result: - Delay on the ending of WWII in absence of an atomic bomb. Hence Soviet Union occupy all Korea (so Korea war never happens), USA wastes more resources to finish off Japan, Japan ends more devastated. - Increment of resistance to japanese occupation forces in Asia (Vietnam, Phillipines, Malaysia, Indonesia) => Increase of local Communist power. - Land and Lease exports from USA to Soviet Union continues for a longer time. Potential results: - Vietnam liberates by itself of Japan occupation. So France does not try to restore their colony there => Vietnam war comes early. - Soviet Union can invade occidental Europe or South Asia because no deterrence is available without an atomic bomb. - Taiwan might never exist, because japanese forces are still there. China is a single country. [Answer] Of course this is cheating, but instead of relatively weak [1959 Yellowstone earthquake](https://en.wikipedia.org/wiki/1959_Hebgen_Lake_earthquake) let's have full scale [Yellowstone Supervolcano](https://en.wikipedia.org/wiki/Yellowstone_Caldera) explosion. [1 foot of ash 1000 miles downwind](http://www.dailymail.co.uk/sciencetech/article-3189619/What-happen-Yellowstone-s-supervolcano-erupted-Experts-warn-90-000-immediate-deaths-nuclear-winter-US.html) (east) all the way to Denver. Inch up to Chicago, St Louis, and almost to Austin, TX, and Washington, DC. 100K people die immediately. Ash is not like wood ash, more like glass wool. Animals cannot graze and die. Water sources are polluted. All transportation north of Albuquerque, NM disabled for months. [How yellowstone supervolcano eruption works](http://science.howstuffworks.com/science-vs-myth/what-if/what-if-yellowstone-supervolcano-erupted.htm) USA has other problems than trying to win Cold War. Space Race was never a race - USA cannot afford the entry ticket. Tens of millions of refugees, with lungs damaged by silica (and deaths for few decades). Cornfields of Iowa under 4-8 inches of ash. Engines in car are damaged by bust and break often, increasing the cost of maintenance. Etc etc. [Answer] The author did not specify what he considers the winning criteria. So, here I envisage the development. This is from the point of view of expectations of an optimistic Soviet citizen. Let's start in mid-1980s. The only change you are asking for: **the Perestroika went well**. As the ideological basis for further development was chosen the "Convergence theory". That is, the idea, that Capitalism and Socialism converge to a single highly-developed and highly ethical, just society. The USSR started to develop into direction of Scandinavian countries (with which the USSR already had a lot in common). But instead of introducing of Capitalism, Soviet planning system was thoroughly reformed to utilize huge computing power of newly-available computers as well as market-like machanisms dealing with virtual "currency" that would provide feedback. The system was, say developed in international cooperation, with European countries, and as such, was introduced there as well, and in other countries worldwide. This produced the international real-time planning system, that would gradually replace stormy and unpredictable "capitalist" market exchanges. The relations between the USSR and the rest of Europe is deep multi-dimentional cooperation. In ethics, the USSR was able to convince the majority of the world that big financial inequality, free markets, paid healthcare and education are unethical. So, along the transition to real-time planning, most countries in the world also introduce welfare state. This is not the case of the USA though, which refuses to participate in this new international real-time planning mechanism, and whose citizens still do not enjoy welfare state (free healthcare, education, guarantee from becoming homeless etc). This is viewed worldwide as vestiges of the wild and cruel past, and completely unethical (as well as usage of capital punishment which is abolished worldwide). Many in the US agree with this point of view. Finally, a huge financial crisis strikes the USA, who is not protected by the regulation mechanism the rest of the world uses. Many become homeless and bankrupt, there are race riots and all other bad things happening. Finally, a left-wing politician of the type of Sanders comes to power, and cites Scandinavia as a model for development. He openly says he supports Socialism (but not as radical as in the USSR he says). This is universally agreed in American society as the only possible way to go. The USA joins the international planning system, introduces free healthcare and other social guarantees. So, in this scenario, the USA still remains, but the USSR is at the lead in science, international cooperation and economic development. [Answer] Paul O. Müller was was a Austrian theoretical nuclear physicist who was stupidly drafted into the the German army and sent to die on the Russian front at Pechenkino near Sukhinichi on March 9 1942. Instead of having him die have him be captured and then the Soviets use him to run a separate nuclear program rather than use the Rosenberg's to steal the information from us. That way they could be on a par or even ahead of us. [Answer] In 1991, a group of hard core Communist Soviet officers organized an attempted coup d'etat. This was the Avgustovsky Putsch or "August Putsch". The idea of the coup was to oust Gorbachev and roll back his attempts to reform the Soviet economy in order to compete with the United States (and avoid starvation, frankly, as the Soviet economy slowly ground toward a complete standstill). Gorbachev and others had long known that the USSR had to reform it's economy with or without pressure from the USA (since a collectivist, centrally controlled economy has never worked in all of human history), but the "Star Wars" program initiated by Reagan had really underlined the need to compete with what the US could afford to spend on military R&D. (Why was it so important? Because if the USA could reliably shoot down Russian nuclear missiles, the entire balance of terror is totally thrown out of whack and the USSR becomes little more than a 2nd world military with a 3d world economy). In our alternate reality, the coup is successful. Hard line Communists succeed in capturing the centers of power in the USSR. Glastnost is stopped in it's tracks. There is no "privatization" (and lawless chaos) under Yeltsin. Instead, the old guard politburo members who hold on to power through sheer force of rolling tanks through the streets of several major cities keep the secession wave to a minimum, only losing 2 or 3 Soviet Republics and maintaining control over Ukraine. The USSR economy is still a complete wreck though, but that would soon cease to be relevant. Desperate in the face of ongoing domestic turmoil and constant shortages and lacking a singular, charismatic leader thanks to the balance of power held by several senior Politburo members and generals, the Soviet junta decides that desperate times call for desperate measures and seeks to negotiate with the EU. In the aftermath of the heady and massively hyped reunification of Germany, the liberal leaders of Western Europe are receptive to overtures from the USSR for a diplomatic end to the Cold War, and even allow a vote on officially allowing the USSR to join the EU, despite loud objections from the USA. Amid tremendous media fanfare, the EU and USSR officially begin a complicated series of pacts and deals that will eventually lead to a de-facto merger between the two economic spheres. What the junta don't tell their people is that in effect, many of the measures of Glasnost and Perestroika will be implemented in any event in order to allow for inter operable and relatively free trade with Western Europe, but these reforms will be staged, will vary from region to region, and will be heavily regulated. Within 5 years, it's all over but for the crying from the USA (which does not stop). As Germany, France, and other major European powers have to choose between their utopianist "European Project" and the NATO alliance they don't want to pay for anyway, NATO is relegated to the ash bin and declared obsolete as it eventually becomes a US-UK-Turkey club with little realistic hope of "containing" anything. In the USA, the election of Bill Clinton stifles a lot of the howling from Washington, which frees up the EU-USSR bloc to really consolidate. Brussels and Moscow have a lot of bureaucratic infighting to figure out, but in the end, Russian tanks trump French farms and the USSR does radically outnumber any other member of the club. Following the pattern of forcing the UN to count USSR member states as nations for purposes of voting in the UN, the USSR does the same trick in the EU Parliament, dominating the decision making process within 10 years. This all leads to a "Brexit" rather earlier than in our real history (I'd say by about 2004 at most). In the meantime, the still desperately sick economy of the USSR has effectively sucked the life out of Western Europe even as it systematically extended military control all the way to the Atlantic coast. Rising gas prices help the EUSSR recover economically as well as a singularly dramatic event in New York on Sept 11, 2001. After what amounts to a religious war against the USA is declared, the EUSSR wisely steps aside and facilitates the US "War On Terror" while secretly feeding arms and supplies to anyone shooting at US troops. After 8 years of rising costs with no clear benefit, a US President is elected (Obama) with an agenda that amounts to "full retreat" on all fronts. The EUSSR spends 8 years spreading influence around the world while oil prices remain high thanks to an endless war on "Terror", and America's economy stalls. By managing the ongoing friction between China and the USA, the EUSSR emerges as the dominant global superpower despite a still very shaky economy and vast discrepancies in lifestyle between it's Westernmost and Easternmost regions. [Answer] In the end of the 80s the KGB knows that the USSR is losing the Cold Ward as they can't keep the pace of the arms race with the USA, Soviet economy is near to collapse and even communist control over the USSR is unsustainable. However, they just switch from arms race to intelligence and prepare a plan in order for the KGB to controll both the USSR and the USA. First of all, they let the Soviet Union collapse - they can't avoid it anyway - but put some agents in key positions of Russian administration under Yeltsin. In the 90s one agent becomes prime minister and even president of Russia in the 2000s. Meanwhile an elite agency of KGB agents and spies - now with a new name - keep gathering relevant information on American politics and using it to fuel their political allies in USA and to keep them under control. In the 2010s the Russian puppet candidate becomes president of the Unites States, backs Russian invasion of former Soviet republics to rebuild the Russian Empire, stops any American effort to support democracy anywhere (specially in Russia and its satellite states) and disrupts US international trade causing American economy to collapse until a point it can't afford its military budget while wrecking the US diplomatic position on the World by making as many enemies as possible. Then, US forces are withdrawn from overseas, US are isolated and somewhere between a rump state and a Russian puppet, and the Russians can peacefully take the world. The KGB has actually won the Cold War about 30 years after the dissolution of the USSR. [Answer] Depends on what you consider winning (your question mentions control of Europe, but by that standard nobody won, and 'control of [geographical region]' is a pretty poor standard - imagine the Nazi nuclear program going well until it doesn't, spreading radioactive dust in Northern Europe and the Mediterranean, making it a wasteland for the next 500years. The western Allies (sans Britain, that now only sports five sheep, having 8 heads among them) go: 'yeah, keep that shit') - and what you consider to be the Soviets. I'm keeping your vagueness (hah!) and answer thusly: While the US build their nuclear arsenal, the Soviets don't - without a nuclear shield they don't bother with the tank-tsunami at the borders of Europe either. They exploit that moral highground and instead pour their industrial potential into the civilian uses of nuclear energy. The strains of the Manhattan project, and the following nuclear program on the US were greater than usually acknowledged - the strains on the USSR are sometimes credited with her downfall. Now those strains only pertain to the US. Europe does not quiver from the threat of Soviet nuclear bombs, and Soviet tanks, and instead worries about the hypercapitalist US swinging their dick around with nukes in their pockets. To even out the increasingly monopolar power structure, the EU is created earlier, and far reaching treaties are made with the USSR and the US. More nations loose less than they did in reality, including the USSR, thereby making her the 'winner'. [Answer] Oleg Guimaoutdinov was a USSR computer scientist who had the idea for a Soviet-version of the internet to supercharge the state's socialist command economy as well as financial transactions. He made a detailed proposal in 1970, but Communist Party leaders went against the idea. They allowed his ally Viktor Glushkov to create a small network called OGAS that began in 1962, but it was cut in 1970. In your timeline, get the leaders to agree to this project and have them agree to the project so the economy can be upgraded and Soviets can establish a lead in technology. This could reduce inefficiencies and quickly tell people how many resources needed to be sent to different locations using technology. It could help exchange important data under the watchful eye of the state. It could also be somewhat available to civilians, which would help make Marxist socialism and the idea of the dictatorship of the proletariat defined in Karl Marx's Critique of the Gotha Program look more appealing technology-wise than capitalism. After all, the first global civilian internet network would be created by Soviet socialists, not by the capitalist west. The USSR would also go down in history as inventing the internet if this system was created from expanding the pre-existing OGAS system. [Answer] # Soviet cultural subversion archives it before the soviet union collapse The former Ex-KGB Yuri Bezmenov in this [conference](https://www.youtube.com/watch?v=Y9TviIuXPSE), resumed it means that your country will pass trougth four phases before it get communist 1. Desmoralization: Bezmenov said the first stage, Demoralization, could take 15 to 20 years to complete because “this is the minimum number of years it takes to educate one generation of students. “Another word for demoralization is guilt. Americans are routinely compelled to feel guilty about their society and national history. Guilt is the most powerful force in left-wing politics and academia. People will not accept the radical expansion of punitive government power unless they feel guilty and deserving of punishment.” 2. Destabilization: The second stage, Destabilization, is much faster, requiring only two to five years under KGB doctrine. In this stage, the fundamentals of the targeted population’s economy, political system, and culture would be attacked, while the demoralized population could not mount much of a defense. “A destabilized population becomes obsessed with hypocrisy as the ultimate political sin. They believe the best ideas – individual liberty, sovereign rights, capitalism, even the rule of law – are presented insincerely by sinister powers who seek to exploit and manipulate them. The precious resource of goodwill disappears from society as everyone comes to believe their neighbors hate them and cannot be trusted. Demoralized people lose faith in their nation, history, and ideals; destabilized people lose faith in each other.” 3. Crisis: Once a society has been destabilized, Bezmenov said the time would be ripe to create a Crisis, which he estimated would take six to eight weeks in the Eighties. With turbo Internet speed, the modern era can punch out a crisis much faster than that. “A crisis has the obvious benefit of panicking demoralized, destabilized people into abandoning their legal protections and constitutional ideals.” “If you wanted to work at the store so you could feed your family in late March, you were selfishly trying to “kill my Grandma to pad your bank account.” If you wanted to burn the store down in early June to protest white supremacy, nobody mentioned their imperiled grandmothers.” “The threat of a crisis is essential for terrorizing the middle class into accepting a political agenda that is actively hostile to its interests, which leads to the fourth stage of subversion: the offer to make the pain and fear go away by accepting political domination.” 4. Normalization: After a crisis, with a violent change of the power structure and economy, you have a so-called period of Normalization that may last indefinitely,” Bezmenov said, arriving at the fourth stage of subversion. “Normalization is a cynical expression borrowed from Soviet propaganda,” he explained. “Bezmenov, however, was insistent that American left-wing professors and civil-rights leaders were deliberately running Andropov’s strategy with a conscious effort to achieve destabilization, the step that truly distinguishes ideological subversion from the usual promises to put a chicken in every pot.” Resumed by: <https://lobbyistsforcitizens.com/2020/11/25/four-stages-of-ideological-subversion/> And you decide how this happen faster. [Answer] Soviets don't go over the Germany, but stop at the border after gaining some territories in Europe. That way it would still have all the benefits from those countries, but would leave Germany with some army and with Hitler, so it would still do some harm in France, England and so on. US and other countries would lose more lifes, taking more time to recover. This "extra" that Soviets didn't expend on Germany could be used to help China against Japan, so that Japan wouldn't be a US ally after the war. [Answer] No Soviet invasion of Czechoslovakia in 1968 - the Soviets basically buy off the government in Prague instead and use it as a showcase for Westerners. The major unrest in Europe that was ongoing at the time does not lose its significant pro-Communist slant and Left election victories sweep through Europe, leading to countries like France leaving NATO and adopting a "Czech-like" soft-socialism or "Finland-like" capitalist nonaligment approach. ]

[Question] [ Would it be possible to make coins from concrete with designs like the metal ones? [Answer] **Anything someone values can be made into and used as money.** That ought to be Rule of Acquisition no. 1, but it ain't. The point being: if you want to make currency out of concrete or cement, it is indeed technically possible. CaM's answer is thus half wrong, because of Renan's answer. I'm assuming you want something something a little more portable than Yap Island Rai currency! If concrete is what you're after, then I'd recommend your coins be made from [polymer concrete](https://en.wikipedia.org/wiki/Polymer_concrete). Several of its properties are superior to ordinary cement or concrete: * Significantly greater tensile strength than unreinforced Portland concrete (since plastic is 'stickier' than cement and has reasonable tensile strength) * Similar or greater compressive strength to Portland concrete * Good chemical resistance * Lighter weight (slightly less dense than traditional concrete, depending on the resin content of the mix) * Product hard to manipulate with conventional tools such as drills and presses The last point is important because you don't want the bad guys trying to turn you 4 daler coin into an 8 daler coin! Of course, the materials are all common, so, you'll have to put some readily detectable & traceable material within the aggregate to prevent counterfeiting. Apart from the Yap coins: [](https://i.stack.imgur.com/CTTyD.jpg) coins have been made from clay: [](https://i.stack.imgur.com/YWXaV.jpg) and fibre: [](https://i.stack.imgur.com/7OfZc.jpg) and porcelain: [](https://i.stack.imgur.com/X8UPb.jpg) and ordinary cement: [](https://i.stack.imgur.com/l0InN.jpg) as well as a whole host of other non-durable substrates: Wood: [](https://i.stack.imgur.com/nsMAl.jpg) cardboard: [](https://i.stack.imgur.com/uETFJ.png) and glass: [](https://i.stack.imgur.com/VnQ7m.jpg) and plastic / composite material: [](https://i.stack.imgur.com/yBdwx.jpg) And lastly, two oddities, each one spanning two different domains of money. First, the encased postage stamps (encased in thin brass & mica): [](https://i.stack.imgur.com/TEbp4.jpg) And lastly, issued in French North America to cure a shortage of coins, we present *playing card money*: [](https://i.stack.imgur.com/yKjLu.jpg) The only limiting factor for the coins your civilisation makes is your own imagination! [Answer] ### Possible, yes. But not useful. You could make a cement coin. It could be pressed into a shape like a coin with embossed details, etc. But it would be far too brittle to survive common coin usage. An unsupported piece of concrete roughly the thickness of a typical coin will shatter quite easily. So could fired clay or even carved stone at that thickness. Also, concrete is abrasive. Coins rubbing together would generate dust and wear down the surfaces, obscuring detail and thinning the coin. [Answer] Totally. Something similar [has already been done](https://en.m.wikipedia.org/wiki/Rai_stones): > > Yap is known for its stone money, known as Rai, or Fei,: large doughnut-shaped, carved disks of (usually) calcite, up to 4 m (12 ft) in diameter (most are much smaller). The smallest can be as little as 3.5 centimetres (1.4 in) in diameter. Rai, or stone money (Yapese: raay), are more than 6,000 large, circular stone disks carved out of limestone formed from aragonite and calcite crystals. Rai stones were quarried on several of the Micronesian islands, mainly Palau, but briefly on Guam as well, and transported for use as money to the island of Yap. They have been used in trade by the Yapese as a form of currency. > > > The monetary system of Yap relies on an oral history of ownership. Because these stones are too large to move, buying an item with one simply involves agreeing that the ownership has changed. As long as the transaction is recorded in the oral history, it will now be owned by the person to whom it is passed and no physical movement of the stone is required. > > > There is even one such stone that is in the bottom of the ocea due to a shipwreck. Legend goes that the owners kept using that stone for trade anyway, trusting that oral tradition would keep honoring the transactions involving the lost stone. These stones are often cited when someone wants to make a point that nearly anything can be used as currency provided that a set of requirements are met. Anyway, if stone will do, so will concrete. [Answer] Elemtilas provides a great answer about currency generally. If you want concrete to function like the American dollar, you need a bit more limitation. For example, if the species of your planet naturally secretes phosphoric acid, then, yes, concrete coins could work because the real value would be the minter’s clear coating that keeps the coins from being dissolved when touched. Counterfeits would be identified by the fingerprints they develop. Authentic coins would not. That’s just one solution. Basically, you need a basis of work to make the currency unique and a system for preventing counterfeiting. Anything you can do to either increase the effort required to create a coin OR limit the resources needed to complete that work can become a currency. You just need to figure out how to limit concrete shaping in your world. [Answer] What would rulers of rome have said to paper money? Currency should have the following characteristics: * Easy to identify. Counter example: Uncommon postage stamps. Common ones are recognizable and can be used as currency. See Pratchett's "Going Postal" as well as some ads (Send 60 cents worth of postage for your...) A new stamp could easily be forged and passed off. * Difficult to forge Modern paper money with it's tracers, holograms, intricate detail is difficult to forge. In terms of coins, the Canada twoney is a good example with a gold coloured alloy insert. Coins routinely cost more than their face value to make. This is a big discouragement to counterfeiting. Coins however last for decades, are commonly used thousands of transactions, so the cost is ammortized over many transactions to trifling amounts. * Difficult to debase. Coins acquired milled edges to make 'paring' detectable. Take a sliver of silver off of each coin, and get rich. Modern coinage rarely is backed by precious metal, although copper was high enough that pennies were an endangered species for a while. (The american cent had about 1.1 c worth of copper in it.) * Useful denominations. England had some odd coinage, with a pound being 20 shillings, but a guinea being 21. Before they rationalized it to a decimal systems you had endless opportunities for interesting arithmetic. A system that doesn't have reasonable size intervals can be cumbersome. Suppose the dollar had pennies, but no nickle, dime, or quarters? You could have fun with a system that had denominations that were all prime numbers. Come up with a system that to change any bill you needed at least 3 values of lower denominations. E.g. if your bill denominations were $2, $7, $11, $29, $73 * reasonably durable. My brother used like the feel of crisp bills. He would run the money he made from his paper route through the washing machine, and would iron them, even using starch. (A different sort of money laundering...) Modern money takes a lot of abuse. Currently small denominations wear out in a year or two. Banks pull them out of circulation, and replace them. * more portable than the goods it buys. Inflation was so bad at the end of the Weimar republic that people took a wheelbarrow of money to buy their daily bread. Yap money has some issues here. Concrete money is possible, but you would need to use some of same concepts to make it difficult to forge that we use with modern money. Ground up colourants in the mix? Intricate detailing? Perhaps filling the markings with a layer of shellac, magnetizing the metal that re-enforces it? UV tracers in the glass fibers that re-inforce it. I suspect that glass money is a better option. Glass is harder to work with, and it's transparency lends itself to more anti-forging techniques. It could also make very beautiful money. Given a good tempering system it would be very durable, comparable to metal coinage, and more resistant to corrosion. [Answer] Sure, you could make money out of concrete. You could even etch designs on it, but as others have pointed out it would be brittle and generally fragile. Carving it out of some sort of natural stone would make it more long-lasting and durable. If someone had a collection of concrete coins in a bag that they carried around, they would inevitably wind up with alot of broken coins due to the coarse texture and them all rubbing on each other, and if they really got busy they might reach in to pay for good and find that their money has crumbled to dust. As others have pointed out though Anything that one places value on can be used as a currency. Historically many things have been used from native americans trading in beads, corn, and even trading in a bartering system. For that matter you could even use pencil shavings as a currency if society deemed it valuable. So is it possible to make coins with designs out of concrete? Yes Would they stand up to abuse? No, I'd recommend something natural, or something igneous like Basalt [Answer] Yes and to prevent counterfeiting, the mint can blend some rare spice into the concrete. It was usual to probe softness of gold coins with teeth, so licking them isn't so far fetched. [Answer] You might consider casino chips, some of which are made by a process that isn't all that far from concrete: <https://en.wikipedia.org/wiki/Casino_token#Construction> They are produced in many different colors, and with designs molded into them, and are pretty durable. ]

[Question] [ I'm working on differentiating primarily nonhuman cultures from human cultures in a fantasy world by adding a bit of [Blue and Orange Morality.](http://tvtropes.org/pmwiki/pmwiki.php/Main/BlueAndOrangeMorality) One way I'm considering adding a unique element to one cluster of them where stealing is considered acceptable and clever – where swindles are laudable and (nonviolent) burglaries are something to brag about, and theft is just another way to make money (because really, in their view, the exchange of currency is just an elaborate ritual for two people to think they're stealing from each other). I have two questions. One may be too broad, one is much more specific. 1. Why is stealing immoral? Why, as a species, did humans decide to make theft "wrong"? Is it an attachment to property, something to do with impressing others with possessions, a desire for trust or security? 2. Could a culture that considers theft something neutral, even laudable if done in a particularly impressive manner, sustain itself? Or is there something fundamental here that would be thrown out of balance if theft was more commonplace? EDIT: Another way to phrase this might be – Could an entire society and culture develop a Robin Hood-esque attitude toward others' property? (There's a little more variation than that, but that's the way my hypothetical thieves' institution is currently visualized to operate). EDIT 2: Probably should have mentioned the limitations I had on this to begin with. It's an honor based society. It's dishonorable to steal something essential – like a diabetic person's insulin, for instance, or a poor person's only source of food – not because it's stealing, but because it equates to killing. Generally, the theft that bolsters your status (if you tell your friends about it) is the theft of someone's surplus. And a thief caught in the act of stealing – though not awhile afterwards – will generally hand over whatever they tried to take, or might start bargaining for it... stealing from someone of greater status than you and then being caught may result in demands from the almost-victim. Those are the specifics, though, I'm still very happy with all of the answers about theft in general. [Answer] > > Could a culture that considers theft something neutral, even laudable if done in a particularly impressive manner, sustain itself? > > > Sure. There were a number of Native American tribes in the plains area that made stealing a rite of passage. This included kidnapping their wives from other tribes, which helped avoid inbreeding. Stealing was considered both more honorable and more impressive than killing their enemies. This helped avoid retribution turning into extinction. These societies were stable until outsiders (Europeans) disrupted them. Example source: <http://plainshumanities.unl.edu/encyclopedia/doc/egp.war.023> > > Why is stealing immoral? > > > Because it is more efficient for it to be immoral than for it to require guarding against. Consider how our society would be different if you had to guard against not just rare stealing but common. You'd have to keep most of your valuables with you. It would be difficult for a company to make improvements -- other companies would just steal them. They'd have to have far more than just a single night guard watching some television screens. All this would create a drag on the economy. It would be more difficult to innovate, as the benefits from innovation would be less. It would be hard to make a technological society this way. Society would probably be more like that of the plains tribes. [Answer] I cannot resist quoting [*The Blue Cross*](http://fiction.eserver.org/short/innocence/bluecross.html) by G K Chesterton. Published in 1910, this was the first of the *Father Brown* detective stories: > > 'Reason and justice grip the remotest and the loneliest star. Look at > those stars. Don't they look as if they were single diamonds and > sapphires? Well, you can imagine any mad botany or geology you please. > Think of forests of adamant with leaves of brilliants. Think the moon > is a blue moon, a single elephantine sapphire. But don't fancy that > all that frantic astronomy would make the smallest difference to the > reason and justice of conduct. On plains of opal, under cliffs cut out > of pearl, you would still find a notice-board, `Thou shalt not > steal.'' > > > Turning to Midwinter Sun's questions: *1. Why, as a species, did humans decide to make theft "wrong"?* Certainly not out of a mere emotional "attachment to property", still less a wish to impress others. Those types of feeling only arise among unusually fortunate people whose basic needs have already been met. Most people before our modern era of affluence were poor subsistence farmers. Among those who live close to starvation, security of property is a matter of survival. If they cease to believe that the crops they grow or the flocks they tend will bring any benefit to them, they will plant no more crops and tend no more flocks and turn to predation on other tribes. Thus civilizations fall, or never arise in the first place. You get what Hobbes described as ["the war of all against all"](https://en.wikipedia.org/wiki/Bellum_omnium_contra_omnes) Not that there is anything impossible or unlikely about barbarism. Many human cultures have condoned and applauded stealing *so long as the victims are deemed to be outside the protected group.* The outsiders from whom stealing is permitted could be physical outsiders - for instance cattle-raiding from enemy tribes is praised in many warrior-pastoral societies, or they could be a persecuted group who live within the physical boundaries of the thieves' society but are not properly protected by its laws, like the Helots in ancient Sparta. *2. Could a culture that considers theft something neutral, even laudable if done in a particularly impressive manner, sustain itself?* Yes, so long as there remains an adequate supply of outsiders not following these principles whose surpluses the theft-admiring society could steal. [Answer] Others have mentioned why stealing is wrong, and I will let their answers stand for that. As to your other question: > > Could a culture that considers theft something neutral, even laudable if done in a particularly impressive manner, sustain itself? > > > The answer is yes, but with restrictions. * To have a society, things like food and water, should be considered off limits (assuming you don't want to just make the society post scarcity for the basics). * Your people need to have a radically different view of property than we do - this society likely would not understand the concept of an heirloom or sentimental value towards items. Another possibility (to being post food scarcity) is to have *victimhood* be just as admirable as the theft itself - if a thief steals all your food in the night while you sleep, others will practically trip over themselves to ensure you have enough (think warrior societies where death by fighting is as honorable as killing). In this way, the theft has no real impact on you and thus is not inherently negative. One interesting possibly extension to this is that people would view giving items to other as a sort of "banking" - if I give you my axe I know where it is so if I need to chop some firewood, I just steal it back. Another possibility is, if caught in action, the thief would immediately and unquestioningly surrender the items stolen without fuss and leave. In our world when we catch someone stealing we expect a fight to retrieve the item, which causes adrenaline spikes, but without the fear of fighting we would be less likely to get frightened and angry. Instead you might simple have thief and victim enter into a "bargaining" mode, where the thief is now "purchasing" the stolen item if the victim is willing to part with it or trade for it. I could also see this working if you loosen the "theft has to not be revealed" aspect in your comments. If the theft only has to not be caught or the thief only has to remain unknown for a short period of time (say a few hours or a day), then another possibility is that once the time has elapsed the thief will generally let the victim know, allowing the victim the ability to get something in return (of course by stealing) - either the original item, or an item more needed/desired - in this way I would steal items considered valuable that I don't want from others so that another might steal from me and I can get something I do want. > > E.g. I personally don't care for TV, so I would steal the biggest TV I could find in the hopes that a friend who has a book I want steals my TV allowing me to steal their book. > > > This makes the theft a kind of elaborate economic system, where instead of broadcasting what I want in the hopes of someone offering to trade for something I have it, I broadcast what I have in the hopes of someone "offering" something I want. Related, perhaps it is not honorable to steal from someone unknown to you - only from someone known, or it is dishonorable to steal from someone who has not stolen from your family, or you only steal once from someone until they steal from you. Depending on how loosely you want to define property and theft, it is possible this society simply has an extremely communal view of property. That is there is a community axe that I just so happen to have in my garage, but if you need it you just take it. The culture would just have a game to see who could procure the item the wanted in the most elaborate or subtle way. To our culture it would look, on the surface, as if they were stealing from each other (it would help if the other cultures way of representing currently having a particular community item was expressed as a possessive). Most items would have to be community items, so I make a salad bowl or a chair and it is not mine but the communities - in this way the way of distributing goods would be through the "theft". One interesting possible side effect in this community would be that actually asking someone for something would be either vulgar or at least an extreme sign of distress. [Answer] As civilization grows, people collect tools and other property. During productive periods they save a *surplus to current needs* to last the next day, over the winter, for their old age. A culture where stealing is allowed requires people to be eternally vigilant to protect their surplus. The more they have, the less they can produce and the more time they have to spend standing guard. That makes many benefits of civilization impossible. Civilization requires specialization, specialization requires trade, trade requires (property) laws. [Answer] Morality is a sticky wicket. Everyone has their own opinion on it, and believe it or not, not everyone agrees. Accordingly, I am going to choose utilitarianism as my moral code for this answer. It has the advantage of being treated as the lowest common denominator by many types of moral codes, so at least everyone should relate somewhat. By utilitarianism, stealing is wrong because it generates an inefficiency. You have to spend more time guarding your stuff. However, for this to work, one has to be part of a culture which is hurt by your actions. By naive utilitarianism, your stealing from others is good, but their stealing from you is bad. Typically utilitarians have to have some concept of a community to come to a consensus that stealing is bad in general. The easy way to work around this is to steal from outside the community. If they're outsiders, who cares if they're hurt. It benefited you, and that's good enough! The stereotypical gypsies are the classic example of this. In the sterotype, its encouraged to separate others from their money, but only outsiders. Theft of property within the group is forbidden. Another approach is to make the act of stealing more beneficial than the loss of goods. This has the neat effect of allowing any form of stealing, not just stealing from outsiders. One might make a community of criminals where the continued rate of theft between members "keeps everyone on their toes," so that when an outsider comes through, they're on top of their game. Everyone's houses are tested by the toughest of criminals. There may even be honor amongst thieves, in that you may choose not to hit someone when they're down, because there's no sport in the theft. Another approach is to simply get rid of the concept of personal property all together. Taking that approach, there is no concept of stealing, because nobody owns it. One case I can think of is the religion set up by Mike Smith in Heinlein's *Stranger in a Strange Land*, where the handling of the collections plate was a bit unorthodox. As a final solution, if people only value things which cannot be taken from them, there is no reason to worry about theft: *Take my love. Take my land. Take me where I cannot stand. I don't care, I'm still free. You can't take the sky from me.* [Answer] One of the most interesting and under-utilized things I've ever read is in Harry Potter. J.K. Rowling touched upon Goblin's understanding of ownership, in which the Goblin who creates something is the true owner, and if someone buys an item from a Goblin, when they die the ownership of that item reverts to the creator, as opposed to an heir who inherits all of the items they own. This could be the basis for this society, in which the creator of an object would be understood as its true owner, and customers simply buy their items for a set number of years (or life), after which the item's ownership reverts back to the maker. In a society that holds this concept of ownership, people who hang onto items left by deceased parents/relatives would be considered the immoral ones, and tradesmen etc. would need to go and retrieve this property, hence where the stealing would come into use. Also, if people were to steal from others, technically nothing has been stolen as the person who owns the item has not changed, it is now just a different person *using* it. They were just careless enough to let it out of their possession. This would not count for food etc. (as that can only be used by one person), which would work for the requirement of people not being able to steal food from others. --- Having a society like this though would need many other considerations, as it is so much different to our own concept of ownership. This could include renting anything (from homes to common items) becomes the norm as opposed to buying things. Buying would simply be renting for a given amount of time for a one-time sum. Security would become much more important, due to the fact people can't have things *stolen* from them, but people would still want to retain ownership. Trading items would be much more common, as currency would hold much less value when nothing ever really 'belongs' to you. In order to transfer *true* ownership, this would need to be done via 'gifting'. Every craftsman would need their own identifiable insignia, in order to prove an item is theirs. The item would also need an 'ownership until' date inscribed onto it (as the paperwork would get out of hand), which would essentially work as an ownership record so one could see how long the item has been in service. People would generally attempt to make *very* high quality goods in lower quantities, as they would not want to be left with lots of cheap stuff they could not sell, that when they managed to get rid of would eventually be handed back to them further down the road. This would mean that apprenticing, particularly to the top craftsmen, would be highly sought after. People would only go into business with each other with people that they trust completely, as they would then have joint true ownership of the things that they create. An entire industry of bailiffs, which would be essentially highly skilled thieves for hire, would be available for the richer/better item creators to hire to retrieve their goods. This would be because of the legal grey area that exists in the space between someone dying and their belongings being returned to the true owners. There are probably many more considerations for a society such as this (such as how consumable goods or services are traded), but thieves would be heralded as heroes and would be regarded as we regard police/doctors as the honorable people of society. [Answer] One, potential, reason for anything to be considered immoral by us is that if we don't do them (generally) we can't trust each other. If I can trust that you don't steal my stuff, I have an easier time guarding it (as in, I don't have to) and we're also a lot less likely to try to kill or just avoid one another. If we don't kill each other and don't mind being around each other, we might start to engage in trade or just bond and make families; if we don't trust each other the least, we won't do any of those things. Mixing fear for ones life in it, won't make things better. Exactly why we consider certain actions to be immoral is hard to guess, but I think this theory makes sense. Any society where stealing is acceptable or even laudable would be unlikely to consider it stealing; as Chaotic suggests, have a look at the Kender from Dragonlance. We do have something that might look a bit like what you're asking for, but only a bit. Societies based on socialism or similar concepts generally distribute goods to the population based on needs (in some fashion). Such a society might be considered a "Robin Hood"-society as it "steals from the rich" and "gives to the poor". Of course, these aren't the acts of individuals. You might consider how stealing is considered based on circumstances; in some countries it's perfectly legal to steal if you must do so in order to survive. [Answer] Stealing is immoral because of our evolution as a species. When a pack of hunters brings back a large prey, should they share it with the lazy ones which refused to hunt? If yes, soon there would be no one willing to risk their lives to hunt. And all would perish. Our civilization is based on this concept of **property**. But could it be different? Perhaps. Maybe if you don't have scarce resources from the beginning. You should also look at **kenders** from Dragonlance. "Kender are described as not believing that there is anything morally wrong with handling others' items" (<https://en.wikipedia.org/wiki/Kender>). [Answer] For the purposes of this answer, I'm going to call it "stealing" when an individual or small group uses force or stealth or trickery to take possession of of something against the will of the person who rightly possesses it. However, this is not necessarily a faithful translation of the Orcs' language, because you'd expect the morality/lawfulness of an act to be considered important enough to be reflected in the language used to describe it. They'd quite possibly have different words for stealing they consider moral and stealing they consider immoral. **Stealing is immoral amongst humans because we consider property rights to be important**. Where society and/or the state regulates property, with the general assent of members of that society, then it is widely considered immoral to run counter to that regulation and redistribute property to yourself. "Stealing" is an offence against the widely-held belief that property rights are needed, against the authority of the state to administer those rights, and against the authority of individuals over their property. Taxation is an interesting example, when thinking how different cultures might treat property differently, because those who disagree with it *do* consider it a form of theft. Those who consider taxation to be just, do so on the basis that the believe the right of the state to tax has sufficient foundation to override property rights, despite the disagreement of those who say the state cannot have rights that override individual rights. So a Libertarian views our culture as one in which a particular form of theft is considered right. But it's not what I'm calling "stealing" here, solely in that it's perpetrated by the near-consensus of society as a whole, not just by some individual who fancies a new TV. I'm not a Libertarian, and I don't consider property to be absolutely fundamental. However, it is clearly rather important to the way our society is constructed, and also to historical societies going back thousands of years. So it's no small change to have everyone running around trying to take stuff from each other all the time. For society to support this, you'd need something like: * No concept of "ownership", only of "possession". So this is the stick I'm holding. If you took it then it would be the stick you're holding. I have no idea whether I'll be holding a stick or not by tomorrow. * Ownership is somewhat acknowledged, but the responsibility of society as a whole to actively support it is not. This is my stick, and it's nobody's business but mine to ensure that my stick stays with me. I'll be personally inconvenienced if someone takes my stick away, but not going to think the person who has it is *immoral*, or has failed in their responsibility to respect my stick, merely that they've got the better of me. * Ownership is acknowledged, but the right to own more than you can defend is not. This is my stick, and ordinarily it would be wrong for you to take it, but the warehouse full of my sticks just down the road puts a rather different complexion on things. In all these cases, your Orcish society will lack the consequences of the ability we have in our society to maintain a warehouse full of sticks (perhaps as part of the role of a stick manufacturer or trader), and most importantly to share the burden of defending that warehouse across society as a whole by taking action collectively against stick-raiders and by personally refraining from taking sticks even when we have the opportunity. The difference between an immoral act and mere business, is that people respond negatively to immoral acts that would otherwise be nothing to do with them, and refrain from immoral acts that would ostensibly benefit them. Even in pre-modern societies that didn't have police (in fact, especially in such societies), the group as a whole was still upholding property rights by condemning thieves. With no such condemnation, property rights either don't exist at all or else are much more difficult to uphold, and therefore the things we reward with great wealth in our society (crucially: trade and organisation of labour) are less well-rewarded. There aren't going to be a whole lot of Orc merchants, because being a merchant is so much more *difficult* if the defence of your stuff is not "socialised" to any extent at all. By "socialised" I don't necessarily mean there needs to be a police force which everyone helps pay for, merely that people on the whole will go out of their way to assist a wronged party and hinder an immoral actor, *simply because they recognise the act as immoral*. If it's not immoral, you don't get that. I'm not a ruthless free-marketeer, and I don't think like Libertarians do that property is the ultimate right. I don't think merchants have to be able to keep *all* their profit in order to be incentivised enough to make the whole thing worthwhile. But they have to get something, and public recognition of their entitlement to whatever's left after tax is something. Merchants in a medieval-style society expect to hire guards, of course, and rich people in the modern world hire guards too. But when those guards catch a thief, *they rely on the support of society to do something about it*. So when you hire a guard you get more for you money than just physically obstructing thieves, you also get that thieves the guards catch are "dealt with" and thieves who fear being "dealt with" by society are deterred. There's a cost of doing business, but not so high as cost as it might be. You might think that private guards could just beat the thief up or kill them on the spot, so that thieves are "dealt with" without the help of morality. But if stealing *isn't* considered wrong, and killing people *is* considered wrong, then actually you can't do that because then you're the bad guy and society acts against you for beating people up who've done nothing wrong. There's a direct tangible benefit to property owners in society considering theft wrong, even if it doesn't look like society is really doing much about that belief. However, you don't in practice get large-scale trade without large-scale rewards, and if the prevalence of theft reaches the extent that it's impractical to hold surplus, and actually there's no reward at all in accumulating wealth by trade or management, then economic growth and the large-scale co-ordination of resources may be very difficult to achieve. Furthermore, if *any* surplus is subject to being taken, then only those physically powerful enough to hold onto a surplus is going to have one, and everyone else will live basically hand to mouth. Farming might be supported in what you describe: you don't raid someone's small field that they need to live, and you don't take their only coat, because that's too close to killing them. But as soon as someone has two fields, or a slightly nicer coat that they wear on special occasions? Then it's in someone else's interest to stop farming and instead make a living taking that person's surplus. If excess production isn't somehow rewarded then nobody will have anything nice. Of all the ways that have been attempted to reward the generation of surplus, property so far is the least useless. [Answer] When you steal, you are harming someone for you own interest. As long as from the point of view of the society there is no reason to consider your interest more valuable than the one of person you are robbing, stealing will be considered immoral. For example, the thefts or Robin Hood are widely considered morally acceptable, because he stole the rich (causing them minimum harm) to give to the poor (greatly helping them). From the point of view of the society, there is a net gain in the process. But you do not even need a net gain to make the situation morally acceptable. For example, in the film *[Now you see me](https://en.wikipedia.org/wiki/Now_You_See_Me_(film))*, magicians rob banks without harming anyone. It does not harm anyone and since it is very cleverly done nobody (except the police) object. So, the occidental society seems to meet your criteria. Theft is "neutral" since its moral judgement depends on the context, and if it is cleverly done (no killing, small harming) it can be considered laudable. From there it is easy to build a society accepting theft, even in an institutionalized way. For example, everybody could just keep some traditional object, with no practical use, just to prove everybody that nobody can rob him, and everybody will try to steal everybody (but only that particular useless object). [Answer] I think you have got yourself an impossible, Catch-22 situation here. In a society, if the government/group decides that there is a property right in something, or if it is socially agreed that people have a property right, then by definition stealing that object would not be OK. On the other hand, if the group (and individuals) didn't think that there was a property right, then taking the object would be fine, but again, by definition, it wouldn't be theft. An example of this (and the arbitrariness of it all-- property really is just socially constructed), consider a patent. For 17 years you have a property right in your invention. You can get the government to punish egregious violators and you can sue infringers. Thus 'theft' of a patent via infringement is theft and is not OK. On the other hand, the second the 17 years are over, the property right vanishes. Now people are free to use the patented invention. But it isn't theft, exactly because nobody thinks that a property right exists. The most you will be able to do is either (a) find a society that doesn't have many property rights (but actually that doesn't meet your criteria, because then taking stuff isn't even theft...) or, maybe the best you can do, (b) a society where the group (government's) belief in what is property clashes with what most people agree is property. For instance, where the government is happy giving all water rights to foreign companies and forcing the population to pay to use water, while the population itself believes that the government can't allocate these rights so that taking water will not be viewed badly by the average person in the street. Of course, it would still be technically theft, but might be impossible to enforce. As far as societies with fewer concepts of property, nomadic groups will have a much more constrained concept of property because they can only carry so much stuff with them anyway. [Answer] Maybe you can remove the concept of stealing. A society with high moral values is a good starting point. Imagine a world which provides enough for everyone to survive. Imagine a society with high moral values which is more community based and less individual based. Imagine a society where there is no rivalry on property (who has the most money/bigger, more shiny house) but more on the contributions of an individual to the society (helping old people over the street, sharing food with those in need, helping to build the dam which brings water to the fields of the people of the village). Where the property belongs to the community (except maybe the weeding ring and other few things of sentimental value and those things essential for living (taking the last piece of food from a beggar or medical drugs is a big no-go)). Where it is no problem to go to your neighbour and borrow a wrench needed to repair the water pipes in your house - even if he is not there(for outsider it looks like stealing). He will take the wrench back when he needs it - or another neighbour who needs it. Of course it is discouraged by the society to take more then to give to the society in middle/long term. It doesn't have to be something material, community labour and living a moral life also count. People who don't abide these morals are indirectly punished by society (not inviting them for dinner up to declaring them to outlaws). So there is no concept of stealing - as long as you give back to society. It's all about sharing/taking and giving back from and to the community. Your first question is already answered by multiple other answers. To summarize my views: * you can't survive if others take too much from you and you don't get enough back * rivalry/people showing off with there property/enviousness * it's hard to guard your whole property the whole time * the item being of emotional value * the theft endangers the life of the victim (not enough food to survive the winter, ...) Edit: Maybe you want to have a look at the series "No game no life" where it is lived up to eleven. In this everything (including who is the king) is decided by winning/loosing a game against the other. It is explicitly not cheating if you are not caught and this and bending the rules as much as possible is the main point of the series and is socially accepted by the society in there. [Answer] [Left anarchists](https://en.wikipedia.org/wiki/Left_anarchism) do not believe stealing is wrong. They are OK with stealing everything except personal property like toothbrushes. I believe it is possible to work in a small community when everyone agrees to live like that, but will fail in a larger community because it neglects to take into account the basic human emotion of greed. It also neglects to account for sociopaths. I believe [egoists](https://en.wikipedia.org/wiki/Ethical_egoism) have a form of morality that you are talking about. [Rick Sanchez](http://www.adultswim.com/videos/rick-and-morty) is an egoist. The [Kromulans](http://www.adultswim.com/videos/rick-and-morty/get-schwifty/) also seem to have a 'blue/orange' alien morality. [Gypsy/Roma law](http://www.daviddfriedman.com/Academic/Course_Pages/Legal_Systems_Very_Different_13/Book_Draft/Systems/GypsyLaw.html) permits stealing from outsiders. > > Swindling or stealing from a fellow gypsy is an offense to be dealt with, swindling or stealing from a non-gypsy comes under gypsy law only to the extent that it creates problems for other gysies. > > > Why is stealing wrong? Because when you steal, you are taking away the labor and time of someone else. Each stolen object can be followed back to the time or money spent to purchase or make it. A lack of well-defined property rights reduces the prosperity of an entire civilization. [Answer] My favorite trick for coming up with non-human psychology - rearranging Maslow's Hierarchy - has lead me to the conclusion that a hypothetical scifi/fantasy species might not fear death as much as we do. Perhaps you could try the same thing: the species don't fear death, so they don't fear the idea starving should somebody else steal their means of collecting/saving food? [Answer] Stealing wouldn't be wrong if everybody always had whatever they want available to them. Either because of a massive surplus, or because people need very little. Alternatively, if keeping you possessions, including stolen ones, is impossible. [Answer] * In the plainest sense: > > Could I have a culture where stealing is not wrong? > > > No. The definition of stealing is that it is wrong: "To steal: to take (something that does not belong to you) in a way that is wrong or illegal" from [Merriam-Webster](http://www.merriam-webster.com/dictionary/steal). If it is considered ok it gets a different name, like "taxes" (I'm not joking). * This implies that the society does not collapse just because it is considered ok to -- even forcibly -- take money that originally is not rightfully the taker's. The society's well-being depends a lot on what is done with that money. If children are educated with it the society will do well; if wars are waged the society will do less well. * Ritual exceptions are possible: Like in carnival, or as a rite of passage. * A similar "redistribution" could, I imagine, be achieved by Robin-Hoodesque mechanisms. Such a society would, as I see it, be fragmented enough that the term "steal" has different meanings for the different factions. The rich would consider Robin Hood's heists stealing; he would probably call it something else. *Eve Online* seems to be an example "society" where theft (and anything else, I think) is not illegal. * The same act which is forbidden for some people or when done *to* some people may be allowed if done by other people or done *to* other people. For example, murder was a crime in National Socialism, but not when Jews were murdered. Doctors may kill people in some countries under certain conditions but laymen may not. Taking things from a rival "tribe" may be ok, taking things from the own people may not. [Answer] I'm surprised the Ferengi popularized by Star Trek DS9 haven't made an appearance. This culture prizes cunning. Thieves are punished and ostracized, not for the crime of theft, but for the crime of being caught. In this sense, theft is not considered immoral, being bad at it is. In this society, virtue signaling is the ultimate virtue, certainly not the virtue itself. This keeps society running and "civil" as all need to pretend to be virtuous, and will only be otherwise when they can get away with it. As an example from DS9, the Ferengi character is playing a human in their version of chess. The human comes to a realization and calls out the Ferengi, "You're cheating!" The Ferengi looks at the human with disbelief, "You're not?" [Answer] Where stealing is considered immoral, there are religious or societal values that are in opposition to thievery. I'll let others expound on that. Can a society exist that allows stealing? Yes. Sparta had [a practice](https://en.wikipedia.org/wiki/Agoge "Agoge") encouraging theft during childhood in order to develop desired skills. Your society could have an exaggerated form of this. [Answer] In many groups you can see a "sharing culture", when each member of the group has right to take and use many things (tools, etc) if they are lying around and just not currently in use by somebody else. Apart from ancient communities, scientific laboratories often operate this way (equipment, laboratory dishes, etc may be free to access to any member of the laboratory). This is not strictly "stealing" because the taken item does not become a property and must be returned when no longer needed. But externally this looks very similar: an item can be taken away from you as soon as it is not in use or actively guarded. This way of sharing is efficient but have problems with enforcing requirement to return the items in a timely manner and proper condition. If this becomes a problem, or if resources are limited, some more formal rules (reservation, single person in response, etc) may emerge, deviating from the "stealing culture". [Answer] It would be possible in a society that has no concept of ownership. Or if the concept of ownership is limited to what you can carry with you. And they probably wouldn't have a word for "taking ownership on something". For example. Person A needs a shovel. Person B has a shovel. Person A takes the shovel, uses it, and keeps it. Till someone else needs the shovel and takes it. In a way, this method of "friendly stealing/borrowing" what can already happen between (very) friendly neighbours. Or in a community that shares everything. [Answer] There have been cultures where stealing within the tribe was not considered wrong. Or, at least, it was considered beneath the dignity of the victim to respond to so petty an injury except, perhaps, for contemptuously telling the thief, "I would have given it to you if you had asked." They were cultures with a strong warrior tradition, tribes where everyone knew each other, and living in regions where nomadism is a necessity. Nomadism tends to limit possessions anyway, because everything has to be lugged to the new site, particularly of heavy things, where it's better for the tribe to have only as many axes as would be used at one time, because that way you don't have to lug as many. Notice that the thief (who can't exactly disappear with the stolen goods) is at least implicitly scorned as someone who cares more about material goods than proper honor and status. [Answer] There are two directions you can go. First, you could have a society without a concept of private property, at least for certain things. For example, food could be considered community property but weapons and buildings are private. As long as that society punishes those who don't pull their weight, it could work. In a capitalist society, you could make theft of *certain kinds* of wealth legal, to discourage things that are bad for society. For example, cash is handy, but having too much cash on hand is a threat to your world's fragile financial markets, because it can be spent very quickly and cause sudden shocks to markets. So the government allows you to steal cash to discourage people from hoarding large amounts. Those who really need to keep their money safe have other options. [Answer] Sure. As people have mentioned, there are societies in history where stealing was considered ok in certain situations that we would consider wrong in modern Western society. In Sparta, stealing food for themselves and other items [was considered a rite of passage](http://classics.mit.edu/Plutarch/lycurgus.html), even though they would be [flogged if caught in the act](https://www.history.com/news/8-reasons-it-wasnt-easy-being-spartan) (keywords being 'caught in the act'. There wouldn't be as much of a punishment for those who got away with it). A rite of passage called the counting coup for some Native Americans [would be about stealing weapons or horses](https://books.google.com/books?id=B6oMQY0pS2oC&pg=PA31). Some natives in the Plains regions even stole wives from other tribes as part of [their rite of passage](http://plainshumanities.unl.edu/encyclopedia/doc/egp.war.023). > > Why is stealing immoral? > > > Well people consider it immoral in our society because it could take important resources and items one group of people need to someone who doesn't need as much (stealing medication or food someone needs to help yourself, taking textbooks someone needs to pass a test just to use it as reference book, etc.). In some cases, what you steal could be dangerous (nuclear launch codes, a warning about a potential disaster a leader of a village need, etc.). > > Could a culture that considers theft something neutral, even laudable if done in a particularly impressive manner, sustain itself? > > > Probably. The Plains Region's natives could sustain themselves and the Spartans not only sustained themselves, but started an alliance in the form of the Peloponnesian League that lasted from 7th century BC to 4th century BC. [Answer] Some good answers on this already, but I would like to point out a couple examples where it *was* considered stealing, and was deemed acceptable. * Bride "stealing," in societies where women are considered property. In fact, the father of the daughter might be happy to avoid having to pay a man to take his "useless" daughter who cannot even pull a plow. * I don't recall where I read this, but apparently in Europe during certain periods, the rich would expect their guests to "steal" a few trinkets here and there. Putting out some expensive curios and not even noticing they went missing was a status symbol and provided entertainment. Of course, you would also steal the silver candlestick holder when you went to your friends' mansions. * Communism. This one isn't stealing since it belongs to everyone, right? * My personal experiences with (some) drug addicts and young women. The drug addicts often had the perspective that if someone will open themselves to theft, the victim deserved it. So the peer group will all go over to the house of a "mark" and make a game of swindling them. It provided entertainment and was a bonding and teaching experience. The young women I knew growing up similarly bonded over shoplifting and stealing minor items like clothes and makeup from their friends. Of course it was illegal, but not harshly punished if ever enforced. * Throughout history, people have stolen from persecuted groups, often under the guise of correcting some percieved wrong. The Jews in Europe, for instance. In summary, theft can provide a service to the thief and the "victim," as well as society at large. It can be a way to circumvent problematic customs like a dowry. It can provide a bonding experience, entertainment, or a way to vent social stress by taking out aggression on a scapegoat. [Answer] If you had a higher probability of losing what you had produced there might not be utility in creating excess. More effort would have to go into securing your property and being on guard than in spending time and effort in making theft attractive things. If people could not form alliances where fear of theft could be set aside then it would be an every man for himself proposition. Humans have prospered because we have formed United fronts and worked as team members on tasks too big for one person to accomplish. [Answer] It's not inherently that bad to allow some people to live without working, and just take other people's resources, if there is enough surplus. The real thing going bad is to allow people with lower status to play [chicken](https://en.wikipedia.org/wiki/Chicken_%28game%29). They make troubles that the people with higher status must resolve. If not, something very bad may happen. It's bad for all the people. But the people who has the ability to solve those problems are burdened much more. It's even worse than the whole society being fed by a single person, who can decide how much to share. Other people can threat to "destroy" the surpluses, if not satisfied by sabotaging, to negotiate on any trivial matter. Even the good people can drop their responsibilities at all when the whole society faced some problems. If this cannot be prevented in some way, I'd say the culture cannot last long after there is any surplus that people may make a long time schedule. But it can happen if, for examples: * There is supposed to be a way that people can protect their property perfectly with very low cost. Or in a way that the theft may cost much more to successfully steal. And the cost is arguably lower than hiring police. * Any resources can be generated easily and is much harder to destroy or use up. * There are something such as religions moving the immorality elsewhere. It might prefer stealing than starving, but it is also immoral to allow other people to starve, or to fail any project they are working on. This might not be easily enforceable, though. And their communication must be much more efficient and accurate than ours. * People take stealing and protection like a kind of sport with gambling. Technically you can quit the game. But it's so popular that the common people not participating is rare. * There are a lot of abandoned homes and property for some reason, and only stealing not abandoned things (and not to return if realized they aren't abandoned) are immoral. * People don't really own things in our way. The things are owned by some group or even the thing's own will. It's only allowed or practical to "steal" and use things according to some rules. People use things with different real owners so it's not practical to steal them all, and sometimes stealing may render things unusable. Anyway it looks like stealing to us. * People with higher status steals the lower, and it benefits the lower so they won't need to steal back, just like animals "stealing" the fruits. It effectively makes no sense to prevent those things being stolen. A better example would be the people who knows mining to steal the mine (and make sure it wouldn't be stolen again). Good or bad, it doesn't make sense to revenge by destroying the mine. * People simply follows whoever being stronger, in the sense that they can steal things successfully. And the stealer accepts the followers. So "stealing" doesn't imply unfair distribution. * They don't even care about those bad outcomes. Maybe they care more about the abstract concepts like finding life a meaning. They may even think the theft bears more for the society. Well, a bit twisted. Basically that means: * Stealing makes sense, and isn't just a waste of time if people steals each other. * The leaders anywhere who need to consider other people the most can usually be protected. * Nobody likes wasting resources. I assume "immoral" implies there is morality at all, so excluding the case that everybody is your enemy. [Answer] **Why is stealing immoral?** I'll answer a slightly different question: why is stealing illegal? Aside from morality concerns, the people in control of government are typically the ones that have more stuff than the people not in control. It is in their best interest to make it illegal for the have-nots to come and take their things. **Can a society exist that allows stealing?** Note that in the counter-examples like the Discworld Thieves Guild and Native American tribes, it is almost always one group stealing from a larger or separate group. If this penchant existed throughout the *entire* population, I would expect notions of private property to break down entirely. In the same way that a wife might grab a husband's wallet to pay for a pizza in the real world, in this hypothetical world it could be perfectly normal to reach into the pocket of the next guy in line to pay for your lunch. This sort of outlook on property can still make most of the things you want to happen, happen. Even if all property is shared and you can take whatever you want legally, it makes you rather look like a jerk if you steal someone's insulin shots that they desperately need. It seems unlikely that "robin hood" redistribution of wealth would be particularly exciting. Anyone could do it, and it's unclear whether the wealthy "victim" would have any legal standing to stop thieves. Being that stealing is legal, any sort of traps or guards that would cause harm to thieves are almost certainly themselves illegal to maintain. Even something as basic as padlock manufacturers might seem like some of the greasiest predators, since their industry only exists to stop people from doing something that's both legal and socially acceptable. And why would the rich lock things up anyway? Perhaps they might lock up rare pieces of art, but why save money in a vault when you can literally just walk over and drive off that new Rolls Royce without paying for it? Actually, now that I get to this point, why does this society have money at all? However, there is still some leeway to have laudable exploits in the style of redistribution. Perhaps it's perfectly acceptable to take money out of someone's pocket in public, but for some reason or another it's considered a faux paus to have them realize that you're doing it. This could be extended to "getting caught" for almost any kind of stealing, although many people probably wouldn't bother to guard their belongings anyway, since they could just take from someone else whatever they needed. [Answer] > > Why is stealing immoral? > > > Because we value our own survival higher then that of others. Property (except for wealthy people) is key to survival. Tools, crops, housing, transportation are not luxuries, they are necessities. > > Could a culture that considers theft something neutral, even laudable if done in a particularly impressive manner, sustain itself? > > > Yes. In a society where ownership and possession of objects are not systematically linked. If the group / society owns Objects, you could basically have it anyway if you need it. Now, such a society would not likely have a word for "steal", except when the act of asking for an object is annoying (like you have to invest half a day in doing specific rites), someone would want to start to shortcut it. That way you get a society where its okay to steal if: 1. the victim is within the group of the culprit. 2. the victim has the means to get it back, if needed. 3. the priest who upholds the ancient rites of giving something is not within earshot. 4. Its socially awkward for the victim to get it back. > > Could you have high tech societies, with large cities, etc. with this? > > > Yes, but that's a tad more complicated (but not any more then our rules regarding who may date who, when, how and what may happen then are in our culture). You could e.G. have theft be okay when you require the thief to leave a note, so the victim can claim it back. (on a personal note) I got the impression that the ~12 cats of the house from my youth lived such a society. They would regularly steal the "best" toy of another cat, parade with it it front of some other cats and place it in "their" own regular sleeping place. If the victim cat made a fuss, they would return it, but usually it just "appeared" at the victim cats sleeping place on its own after a day or two, so I assume it got stolen back. [Answer] A culture where stealing is not wrong? By definition, NO. Because calling it "stealing" requires it to be wrong! As for the taking of property to not be wrong.. All that requires is a culture that does not acknowledge "property" in the first place. The Kender community in the Dragonlance universe is a pretty good approximation of this. [Answer] "Stealing" is something needing a proper definition. I mean, taxation is a reality in pretty much all societies, and it basically is systematic robbery unless we are talking about direct taxation in which case it's more like theft. So you first need to figure out why you don't consider it stealing before even asking your question. ]

[Question] [ Through an arcane ritual, a warlock-knight forms a bond with their squire: thereafter, the *squire* wears the armour, and the warlock gets the benefit of it. So any force (be that hand, weapon or environment) incident on the space above the warlock's skin where the armour *would* be, is magically transferred to the armour (in the same place and at the same angle of incidence relative to the armour) as worn by the squire. The warlock doesn't need to suffer the weight or awkwardness of the armour themselves. The warlock and squire don't need to synchronise their movements or orientation, or even be on the battlefield together, although the only way the squire would be able to anticipate impacts would be by watching the warlock. Any blows which penetrate or bypass the armour injure the warlock, not the squire (it's as though the warlock is wearing an invisible, weightless set of (I presume) full plate), but the squire is affected by forces transferred through the armour. **What armour and combat techniques would these fighters develop to maximise their advantage from this ability? How much of an advantage would it give them over ordinary combatants?** If the squire dies, the bond is broken and the warlock is left in the middle of the battlefield with no armour at all, which is obviously a Bad Idea. So while the squires are considered subservient and ultimately disposable by the warlocks, they have to give at least some consideration to their welfare. Setting is medieval fantasy, good metalworking skills but no gunpowder. Warlocks would have the financial resources to equip themselves and their squires with the best weapons and armour available. --- **Update** some great (and hilarious!) answers here. To adjudicate on a few questions: * Armour needs to be 'quite close' to the skin to transfer via the ritual, so no tanks or shields. But I can't see why spiky protrusions shouldn't function as weapons. * The invisible armour wouldn't block light or heat flow to the warlock, but I can see the argument for it blocking airflow to the same extent as the real armour. * How to deal with the conservation of momentum and energy is currently why the pile of used scrap paper in the corner is growing so rapidly :p The invisible armour retains the same absolute position relative to the warlock's limbs as the real armour is relative to the squire's limbs, so if you hit hard enough with a hammer that the armour gets pushed into the skin, then the hammer will be in contact with the warlock and is bound to transfer some energy/momentum. But for proper application of the Rule of Cool I think it should be possible for a warlock to stop a mace dead with a bare arm, even if that means a squire going flying behind the scenes :) [Answer] You've removed the weight/protection tradeoff, so your lucky squire is going to be moved around on a cart because they're wearing so much armour. You've also removed the sensory/protection tradeoff, so your squire will be effectively blind and deaf for the duration of the battle. Why would they need eyeholes, after all? You can have huge armour spurs sticking up from the chest and back and shoulders to protect the neck. The head and chest can be armoured to the point that they may as well be indestructible. Limbs can be *slightly* better protected, but the need to keep them flexible limits quite how crazily you can beef them up. Big forearm and shin guards will work nicely, and as you don't have to worry about getting tangles up in big spurs you can have sticky-out bits to help protect the knees and elbows, too. Also, why bother with metal for everything? Its a useful thing for wearable, portable armour, but now weight and to a certain extent portability isn't such an issue, so you can have big chunks of stone or wood. Super thick arming jackets that would cook an energetic combatant to death are fine, even in the depths of summer, because your squire can be left in the shade with someone sloshing water on them from time to time whilst the warlock runs around wearing whatever the hell they like. To dampen impact forces, you can string the squire up like pinata. That way, heavy blows will swing them around, but won't cause crushing damage. Do make sure that if they puke, there's a way for it to run out of their excessive head armour without drowning them, mmkay? And what about combat? Well, the excitable looking semi-naked person running around the battlefield is probably so heavily protected that you're not realistically going to kill them with swords or arrows or anything short of siege weaponry. You might have some luck blinding them with smoke or paint or oil, or immobilising them with nets, or using some sort of chemical attacks on them... sprays of toxic or corrosive or burning liquids or powders might work, though it woudl be tricky to avoid your troops being harmed at the same time. If you have warlocks too, have them trained up in unarmed combat styles... wrestling or jiujitsu, for example. Pin their counterparts down, try and get some breaks and dislocations going on. Try to find the gaps in the invisible armour and stick a dagger through it. You could try pouring noxious chemicals on them (acids, caustic agents, hot oils) but you'd have to be careful not to get any on you, too. Have someone bring a big chisel and mallet, and bash through the "armour" with brute force. Or best of all, have someone bring a bucket of water with them, and when you've got the enemy warlock pinned, stick his head in it. All the armour in the world isn't going to save you from drowning. --- *Addition* It occurs to me that there's actually a more entertaining solution to "*how can you make the best armour using this magic*", which is a sort of dalek/tank thing. I've been thinking that the warlock needs to be able to swing a weapon or at the very least wrestle, but actually you could "dress" your squire in a great big conical shell, with a couple of slots in the bottom for feet to stick out of, and one slightly offset firing slit at the front. Legs and arms are free to move *inside the shell*, but aside from the walking slots at the bottom can't reach beyond it. The squire needs to be able to see the warlock so they can operate shutters on the feet or firing slits if they look like they might be in trouble, so there's a little peephole on a swivelling cupola at the top through which a telescope can poke. The warlock carries a nice bow (long, composite or cross, your choice, doesn't really matter which) and maybe a spear. They shoot out through the slot (a bit of practise may be required to reliably shoot through an invisible gap, but in time they'll get it) and stick their feet through the ghost-holes in the bottom of the shell to move around. There isn't a reasonable way to hurt them, save via siege weaponry, but enemies could potentially lever up the edge of the cone and tip them over to at least stop them escaping whilst a big can-opener is sought. The squire, at least, will be very safe under most circumstances, at least until someone starts using siege weapons on them. Now all you have to consider is whether you could turn this into an invisible troop-carrying tank, by adding a door to the armour through which friendly troops could enter or exit... [Answer] This would give warlocks a rather extreme advantage over regular opponents if little to no limits are placed on the magic: # Physics Get Really Messed Up With This From the warlock's perspective the armor has no weight/mass, but to everything outside of the armor it does. As such if the warlock exerts any force on the armor from the inside it behaves like it weighs 0 kg while to someone on the outside they would feel the full weight. This is combined with motion is relative. So not only do enemy attacks have their kinetic energy redirected to the squire, all the recoil of the warlock's attacks with their invisible armor would get transferred to the squire too. ## No armor on bottom of boots An example of this can be found in the boots. If the bottom of the boots are part of the armor then with every step the warlock takes the ground would exert force on the armor and thus cause the foot of the squire to kick up. Since the feet are not typically considered vital areas (unless you are Achilles) warlocks will likely still have normal boots on with invisible armor on top of the boots. Not to mention finding a squire that can wear the warlock's boots would be annoying if said warlock had small feet. ## Weight/mass as a siege weapon I strongly recommend putting a **limit on the weight or mass** of the armor that a warlock can put on the squire. The reason for this is that an object tends to stay in motion until acted upon by another force. Hypothetically a warlock could make a [great shield](https://en.wikipedia.org/wiki/Scutum_(shield)) a part of their armor but have it made out of materials that weight as much as whatever limit is set by the magic. Then said warlock could use the shield as a battering ram. To the warlock it weighs nothing and so accelerating it costs nothing more than how fast they can safely ram or swing it into a solid object. The squire meanwhile has the actual shield laying flat on the ground or braced against a boulder. The ground or boulder absorb the recoil while the opposing structure experiences getting hit by a massive object. So in this scenario the warlock would be wearing light invisible armor with a very heavy shield. The soldiers and fellow knights would provide support while the warlock sieges the enemy's fortification and smashes into it. ## Storing kinetic energy If there are two warlocks present things get very interesting. If both warlocks have a solid metal mallet as part of their invisible armor with a good surface area they can store kinetic energy in the metal mallets using these easy steps: * Have Squire A's mallet resting on top of Squire B's mallet * Have Warlock B's invisible mallet rest on top of Squire A's mallet * Put a heavy weight on the back side of Warlock A's invisible metal mallet * Wait Squire A's mallet will want to move up as gravity pulls the heavy weight down on Warlock A's invisible mallet. Fortunately for Squire A instead of getting slowly launched into space (assuming said weight is greater than the squire) it transfers the kinetic energy into Warlock B's invisible mallet. Which all of that force is then transferred into Squire B's mallet which in turn channels it back into Squire's A mallet which is still getting more energy from Warlock A. This would continue until the energy exceeds what the metal mallets can handle and then explode resulting in the death of everyone near by. But, what if before that happened Squire A disconnected the mallet head from their armor and Warlock B turned off their spell? They now have an unguided projectile which could be used as a weapon if said mallets were placed facing a target they wanted to see gone. ### Conclusion As such combat in this invisible armor would likely exploit the physics loop holes introduced by the magic. As such I strongly advise putting a limit on how much kinetic energy can be transferred from the invisible armor to the real armor and a limit on how much mass can be treated as armor to prevent extreme loop hole abuse. ### Addendum Even if there was reasonable limitations put on the magic, there is still one additional fun thing that can be done with it: ## Powered Armor Whether it is because the squire had a growth spurt and is now bigger than the warlock or the warlock does not want to risk their own life, the squire can wear properly fitted armor and go into combat while the warlock stays back and watches while wearing the invisible armor. ### Flight Make the squire's boots part of the magic armor and whenever they need a leg up or fly the warlock can simply stand up and the warlock's weight will cause the magic boots to be pushed into the ground (or the ground to be pushed into the boots depending on ones perspective) resulting in the squire getting boost or if the warlock weighs more than the squire with armor then flight. As the squire changes the orientation of their feet they would be able to change the direction of the boost to give them some control over it and thus give the squire mobility in combat. ### Shield Recoil Countering If the squire has a shield mounted to the armor then if they are about to block an opponents attack an assistant can smack the back of the warlock's invisible shield with a mallet. If done well the force of the mallet and the force of the enemy's attack would cancel out and allow the squire to keep going like nothing happened. Also the warlock could flip their invisible shield upside down and put a weight on top of it that is about the same weight as the shield. As long as the squire holds the shield up vertically, they would be countering gravity's force on the shield making it less draining to carry around. Note since the shield still has mass the squire will still feel the full weight of the shield as they are moving, but if they tilt the shield in the direction they want to go, the shield should drag them in the direction they want to go. ### Powered strength Lastly a squire could do a similar siege weapon style smash that the warlock did with their shield. The difference is that the squire leans their shield, mallet, or reinforced gauntlet against whatever they want pushed. Then the warlock with some assistance puts heavy weights or strikes the back of the invisible armor causing the squire's armor to push into the target without the squire doing anything. If the warlock rests a heavy weight on the back of their invisible gauntlets then the squire's gauntlets will want to move as if they had a similar weight behind them. Thus the squire could grab something of similar weight with the gauntlets and lift it similar to how Link from The Legend of Zelda does with the [Golden Gauntlets](https://zelda.fandom.com/wiki/Golden_Gauntlets). While not in use the squire would want to clasp the gloves together so the force on the gloves would cancel each other out (doing the reverse would be very bad). [Answer] Uh oh, I'm going to drop an [NSFW link](https://en.wikipedia.org/wiki/Nudity_in_combat)... lol jk it's not *that* NSFW. So, as you've probably heard, back in the good old days, barbarian fighters among Celtic tribes would get naked and (in the case of the Picts) paint themselves in various colors to seek blessings from their gods as well as scare the enemy. Plus, these peoples were very warlike - they treated their open wounds as scars of pride and would only get angrier as they fought. This also meant that they were more vulnerable to any kind of weapon, but maybe slightly less vulnerable to infections caused be contact with contaminated clothing. Now, your warlock will not get hurt in combat given that he/she has the necessary armour on a squire, to basically no consequences unless the squire gets hurt, in which case suddenly this guy is a sitting duck to basically any kind of melee/ranged weapon. So here's a few cases that I can think of: 1. **Glass cannon**: Your warlock is a Celtic BAMF. So, instead of wearing anything at all, this guy goes into combat fully naked. If he can use paint to scare off his/her enemies, he wears that. If he can paint runes/other magical incantations onto his/her body (not just for protection) he can do that. He can also create weapons/minions out of his/her own body like [Momo Yaoyorozu](https://bokunoheroacademia.fandom.com/wiki/Momo_Yaoyorozu) from My Hero Academia (not sure if this applies in the universe you're building, and Momo can't make minions like that), in which case having the maximum amount of your body exposed really helps. 2. **False Knight**: As we all know, Knights are beefcakes. They wear heavy armour, use heavy weapons, ride a heavy horse, etc. And as you mentioned in your comment, if the armour on the warlock's squire is bulky, this will also affect the warlock when folding his/her arms, etc. This means that (if I understand correctly) arrows will bounce off the armour, which would be maybe a few centimeters off the bare skin of the warlock. So, to trick the enemy, we could dress the warlock up some more - give the guy a fake/light version of a knight's armour on top his/her own naked body which is protected by the armour the squire is wearing. This isn't for the warlock's protection, but to confuse the enemy and trap them into thinking they're fighting a knight, when the reality is much worse. I hope this helps - I'll add more ideas if/when I have them! [Answer] > > If the squire dies, the bond is broken and the warlock is left in the middle of the battlefield with no armour at all > > > Pain has the advantage of signaling when a part of our body is being overloaded, in the broader meaning of the term: if you get a strong hit on your arm, pain there will point you at avoiding further contacts, to prevent critical failures. This sort of armor sounds like the worse version of taking painkillers with an injury to continue playing. It can be lethal for both warlock and squire! > > What armour and combat techniques would these fighters develop to maximise their advantage from this ability? How much of an advantage would it give them over ordinary combatants? > > > Any tactic they use, they must aim at reducing the taken hits: if the warlock has no awareness that the squire is comatose after a head blow, getting other head blows will leave him naked on the battlefield with no warning. At the end, the warlock will only benefit from the pain insensitivity as much as he can remain conscious of the taken hits: he will still need to protect his vital parts (abdomen, head) since a blow there can be lethal, while he can go easier on blows addressed to the limbs (a blow on the kneecap is painful and incapacitating for whoever gets it, but hardly immediately lethal) [Answer] One thing you could do is to make the armor a several foot thick steel sphere that the squire wears/sits inside. The warlock wouldn't be able to use weapons easily as the invisible armor would extend most if not all the way to the end of his arms and completely cover him. The warlocks tactics would then be to just run and body-check his enemies and crush them under the several tons of steel. The most difficult part would be transporting the armor. It would need to be transported by cart and would need a pulley system to lower it onto the squire before battle and then be lifted off if him. [Answer] **Deception** Since the knight doesn't *look* like a fully-armored knight, he gains greatest advantage from surprise. Scouting, raids, infiltration-and-fomenting-intrigue, etc. Pitched battles seem a lousy place for (apparently) unarmored folk, and the knight gains little advantage from his additional mobility - the rest of his formation is unchanged, and they fight together. Once the secret is known, the enemy will start putting crossbow bolts through unarmored-folks-on-horses...or capturing them. [Answer] Starfish Prime has a very complete [answer](https://worldbuilding.stackexchange.com/a/152936/34012), but the following might help you deal with these monsters. With no limit on strenght on the armour, you will need other ways then brute force to deal with these. **To deal with the Warlock-knight:** 1. Use paint to make the invisible seen. 2. Use nets, wires, bogs and marches to snare the unstoppable. 3. Use time to starve the unhurtable. 4. Use poison or water to end the unbreakable. **To deal with the Squire:** 1. Use poison to stop the poor lad. 2. Bribe the lad to not don the complete the armour. 3. Bribe the lad to not wear armour at all. (Use of fair maidens are recommended) 4. Bribe the card driver to drive a knife in the lads soft parts. [Answer] Warfare would be... funny. Hear me out. --- It's established that the warlock could not wear any armour, as long as the squire does. If the squire is killed, the warlock is unprotected. But there are no restrictions on how much armour one can use. So, let's assume we get a full plate armour. There are still some places where it could be pierced, if the attacker is lucky or knows about your trick. Armour can still be bludgeoned and deformed, which could be problematic - especially if you hit the head. Now, we can just add more armour, after all, all the squire has to do is just wear it, as long as he's actually wearing it, it counts. In which case, why not just a multi-layered block of steel, wool and other materials, to create a wearable block of invincibility that would protect the squire from bludgeoning? If the block is big enough, you're also safe from piercing weapons. Pikes are likely the weapon with the most reach, and thus potentially the one that could pierce the furthest (assuming you can pierce and shove the shaft through the box-armour). Let's say that for some reason someone has a 5 meter pike. Well, just make the box-armour have a length from outer plate to beggining of center core (the space that the squire inhabits) measure more than 5 meters. You're essentially impervious to any weapon, other than fire. It's still possible that the fire harms you, due to the heat and possibility of asphyxiation. However, since the only thing that can catch on fire is the outside of the magic part of the box-armour, the warlock will have a bit of separation between him and the flames. Plus, now you're literally walking and fire is moving around you. If that doesn't scare your enemies, what does? --- So, now that we established how someone could make himself impervious to death in battle, how would said battle play out? Well, with the given constraints, we can deduce that, even though the armour's weight wouldn't affect you... it affects others. This is where it gets interesting. Let's say that the box-armour has at least a 5x5x1 meter plate of carbon steel per side. That's (just on that single plate) an approximate weight of over a a tonne. Now, a box has 6 sides, so multiply that by 6. Just to put it into context, that's heavier than a Cadillac Escalade. Now, run towards someone. You're at the very least knocking them down. And when you do, jump. Aaaaand they're crushed. Or, if the warlock wants to be particularly nasty, he adds spikes to the box-armour. In fact, You run towards someone, and suddenly there's a hole in the middle of his chest, sure, your spikes may break if you run towards a particularly well defended opponent (for example, his armour deflected the spike, and your spike broke), but hey, you can crush him anyway. But assuming that you pierce his armour, he's dead. Then he turns to the right and that person's torso is ripped apart, because the pike actually has serrated blades on its side. Hey, if it doesn't weight anything on the warlock... Just look at the other troops' face in horror. Heck, you kill one person and the rest routs. The warlock doesn't need a weapon, he is an armoured tank with the mobility of a human. Eventually someone somehow will remember to try using catapults or cannons (or shells, depending on your world) to hit the warlock. It could be problematic, if the armour isn't adapted to withstand these shocks. Again, remember, as long as the squire wears it, it's an armour. Add more layers to withstand such impacts. Perhaps one of the layers could be water or even mud to dissipate such ammounts of energy. The warlock only needs to remember one thing, as long as the squire wears it... it's.. hold on. See, that is when the warlock realized something. Dig the squire a deep grave, put a straw on his mouth and lay him there. If he's wearing any sort of gambison, he's armoured... and the dirt is.. another layer... and.. then there are more... Yes dear reader, the warlock realized he could walk with **the fucking mass of the planet** --- How would warfare change? It would end. You can't defeat something that if it jumps, it cracks the planet in half. In the end, that's what would ultimately happen. And eventually the warlock would become his own planet. [Answer] Squires and their warlocks would need to be close to the same shape. This would discourage the use of young, still-growing squires. It would also cause the squires and warlocks to have matched training regimens and similar diets, so that you don't have one become fat while the other either bulks up or starves. The squires would need to be kept in a defended, sheltered, rear area. If the enemy can reach them, they would be vulnerable. (The armor they wear is protecting the warlocks, not the squires.) If the enemy can manage to lob exploding artillery or Greek fire at the squires, the effect would be devastating. [Answer] ## Background of my answer: One of my favorite books, [Paladin of Souls](https://en.wikipedia.org/wiki/Paladin_of_Souls) by Lois McMaster Bujold, had a scene where one character's injuries were being "passed off" to two other characters. The one "passing off injuries", a great warrior, was sent sneaking into the enemy army's camp. The two "injury receiving" characters were safe, laying in the castle, with attendants at hand to bind wounds as they occurred. I would describe it in more detail, but I would rather not spoil it, as it's a fairly epic part of a great book. ## How it could be applied: Using this as a model (including genders), I would expect combat to go like this: Pre-battle: * Warlock prepares for battle by doing some stretches, swinging his sword a few times, etc. * Squire prepares for battle by donning armor, retreating to the tower where attendants will have a good view of the battle. She will get strapped to a table or the floor, or maybe the armor is heavy enough to hold her down. * Warlock heads out to battle. Not fearless, but knowing he will be well-defended. While he's out... *Case 1*: Warlock gets hit with an attack that the armor can handle. * For the Warlock, conservation-of-energy and conservation-of-momentum kick in. I would expect the armor to "feel" what it could from the impact, then have the rest of the momentum (and remaining energy) transfer *back* to the Warlock, i.e. he could be knocked down by a strong enough hit. Impacting on the ground would also be transferred partly to the armor, and then back to the warlock. * The squire, in the meantime, is jostled as the armor she is wearing seems to be hit out of nowhere. Because she is tied down, it doesn't do a whole lot, otherwise. *Case 2*: Warlock gets hit with an attack that damages the armor some. * Warlock says "ow", among other things. If he has been hurt, I imagine him to either retreat or keep fighting in an epic way. If he has *not* been hurt, he will try to avoid being hit in the same spot, knowing he has a weakness there. * Squire and attendants notice the armor get damaged. Squire is probably a bit shaken, but otherwise still unharmed. If the armor looks repairable, the attendants get to work right away, forming new material onto the armor to cover/reinforce the hole/break. * An extension of this idea: If the armor was optimized to be swapped out in segments, the attendants might watch for a moment when the warlock is safe, then swap a damaged segment of armor out for a new piece, pit-crew style. This would be another reason the warlock would try to not be hit in the same place - he might have a moment of no armor, with knowledge that more armor was on the way. *Case 3*: Warlock gets hit with an attack the damages the armor a lot. (Like, somewhat crushed, or maybe cleaved) * The squire very likely would be injured by the deformation of the armor. If she's still alive, she probably says "ow", and she and the attendants will get her into new armor as quickly as possible, assuming it's safe for the warlock. If she's *not* alive, the attendants will either put her in new armor (on the off-chance she's actually just unconscious) or carefully remove her body from the twisted wreckage and begin preparing her for funeral rites, knowing they've done their best to help the warlock. * The Warlock will definitely say "ow", if he's not dead from the blow. A crushing blow would impact hard, a cleaving blow would probably cleave him, too. This isn't to say he can't have awesome "block it with his arm" moments, but a heavy-duty mace or axe (or siege weapon) might make him hesitate. * If the Warlock's not dead, he'll be checking himself for armor as an indicator of his squire's life. Whether or not she's alive, he'll be retreating hastily - either because he now has no armor, or because the squire needs a chance to swap armor. *Odd circumstance*: Warlock dies, squire does not. (e.g. stabbed with a [Rondel dagger](https://en.wikipedia.org/wiki/Rondel_dagger)) * If the Warlock dies and the Squire does not, what happens is dependent on the nature of the spell. * If the magic persists after the warlock's life ends, the squire and attendants may not even know he's dead unless they see him. This would leave the squire in danger of being hurt through the warlock's body, lying on the battle field. (If they see him dead, I think they would then get the squire out of the armor *very* quickly.) However, this circumstance begs the question, would that Warlock then **always** be connected to *any* armor the squire would wear? "Capture the warlock's body! If you ever feel armor on that body again, attack it!" Or crush it slightly to slowly hurt the squire...long-distance torture? The squire would likely never want to be in armor again. * If the magic ends with the Warlock's death, the attendants and squire may sit there for quite some time, trying to figure out if the Warlock is *dead*, or if he simply retreated. ## Assumptions made: * The situation is not as extreme (or hilarious) as other answers describe. Perhaps the spell has only been recently discovered, does not have widespread use, is "forbidden, dark magic" that many dare not try, or has other limitations that prevent the use of non-traditional armor. * The armor is traditional full-plate or equivalent, except maybe more modular (for swapping segments out quickly). * The squire and warlock are working from a castle, keep, or other fortified location. One could instead sequester the squire where she could not be found by the enemy for the battle's duration. Per a comment I greatly agree with, > > I think there would be a LOT of assassination of squires. – > 23fc9a62-56de-47fb-97b4-737890 > > > * so the squire would be protected ***somehow***. Maybe that squire is also a warlock with a separate squire...share the damage? Or maybe Squire 1's armor would make the Warlock's armor not 'quite close' enough to the skin, thus avoiding another possible extreme of extensive-spell-armor-chaining. * A warlock and squire in battle are the exception, not the rule. (This means that armies don't expect a warlock, and might not know the best way to deal with one. If they *did* expect them, this answer would also need to cover how armies would counter them, such as specific combatants with heavy-duty maces for "crushing squires via warlocks".) As a final note, I do not disagree with the other answers. I think they are *awesome* and deserve the upvotes they got. I just think this view provides a less extreme (though perhaps less interesting) option. [Answer] With all the good ideas here, only one had the idea of multiple layers of differing materials, and I'd like to expand on that with my own ideas. Armor would be considerably different than it is today. It wouldn't necessarily have to be feet thick, but it would be layered differently. Real knights metal armor is generally a single piece of metal in a specific shape and only overlaps where there's a joint to protect. With offloading the weight and most of the cumbersomeness, you can get some really interesting layering going on. You'll probably want metal skining both the inside and outsides of the armor, but you can have wood layers that are cross grained to not only absorb some impact, but also grab and hold a pike/ spike, or arrow. You can also add more soft padding between the layers to avoid impacts better. Metal is great at taking a blunt force, but it can be cut somewhat easily, so you put that on the outside. Wood can defend against cutting forces really well when it's against the grain, but breaks when hammered, so you have a layer of wood with vertical grain, another with horizontal grain, and maybe another layer or two with diagonal grain. Metal stretches/deforms before it breaks/tears/cuts, so having another layer on the inside would protect against anything that somehow makes it through all of that. If you sandwich all of that together solidly, the wood still takes the force of the beatings and can break, reducing their sharps stopping power. Since we don't have any encumbering the knight or weighting them down, we can add even more layers. Put cotton, hay, horse hair, cloth, or other bits of padding between all the layers of the armor. We can also make the layers plenty thick. We still probably don't need feet of armor, but 1-2 inches per layer is plenty. You still need to be able to move the armor when not on the battlefield, and the bigger and heavier it is, the more likely it's going to fall behind the army and less likely to be part of an ambush, raid, or incidental battle. Also, 10 layers of 1 inch thick materials is still 10 inches thick total, which is something like 120 times thicker than real knights armor. You also have to consider the quality and quantity of the roads during that time. Most battles weren't directly on a trade route, so wheels would have to be able to get over rough ground with moderate ease. Also, the larger the armor, the more oxen, horses, animals in general needed to pull them. This means a more massive supply train. As the saying goes, "An army marches on its stomach". A large army already has a pretty good sized need for food, water, shelter, and more. Adding to this has diminishing returns. If you can't afford to take your super-massive-overly-armored knights to a battle because their armor is the size of a castle, then you aren't doing yourself a favor by having them. You also have to consider the amount and what types of materials that can be sourced. Stone can be found easily (hence large castles), but it is susceptible to breakage. It can't be repaired like metals, nor can it be easily replaced on the hoof like wood. It's also geared more towards compression, rather than striking or sharp forces. You can gently put a ton of material on a rock and it'll be fine. Drop 100 lbs on it and it's rubble. Use a chisel on it with a 5 lb. hammer and it's split in two. ]

[Question] [ In this scenario, I would like to focus specifically on humanoids (read: human shaped blinking eyes, protected by eye-lashes and evolved in a waterless environment and fitting human eyesockets, from the outside at least) with the desired effect of them having superior eyesight to humans - by having a better night vision but without worsening overall eyesight. In this case, let's also disregard technicalities related to evolution (like "Why would they have both night *and* day vision?", or "That would not be favoured since it would be costly."). Should the technicality be *insane* though ("It works but now they need 50,000 kcal a day to function.") I'd appreciate a heads up. --- My own research focused on the two main differences between humans and animals with a superior night vision: the tapetum lucidum and the photoreceptor cells. There is a TL;DR summary of the main conclusions below. ## Tapetum lucidum The obvious and flashy (;)) option is naturally the [tapetum lucidum](https://en.wikipedia.org/wiki/Tapetum_lucidum). It's a retroreflector lying behind the retina that causes light to pass the retina twice (there and back), which makes for a stronger stimulus for the photoreceptors and enhances light sensitivity. Dark environments appear lighter, since the quantity of detected light increases. As was however stated on Wikipedia and in [this question](https://worldbuilding.stackexchange.com/questions/89833/could-elves-realistically-have-tapetum-lucidum), this enhancement comes unfortunately at the expense of visual acuity since it causes images to appear blurry. ## Rods and Cones In the same question, it was suggested that one increases the number of rods. Now, [Rod cells](https://en.wikipedia.org/wiki/Rod_cell) are more sensitive to light but lack the color vision of cone cells and their [response time to stimuli](https://en.wikipedia.org/wiki/Cone_cell) [para. 2] is slower - that means less details and lower change in image detection. [Cone cells](https://en.wikipedia.org/wiki/Cone_cell) do what rod cells can't, but are far less sensitive to light. Increasing the number of rod cells does not sound like a bad idea, but contrary to the statement in that answer, humans actually have more rod cells (100 mil), than cone cells (7 mil), which is why we are actually able to see something in the darkness to begin with. ## **TL;DR** **Tapetum lucidum** has blurriness and loss of acuity. Should the **increase in the number of rods** have an ample effect on the effectivity of the night vision, it might be at the expense of the cone cells, which would, in turn lead to color-blindness and loss of acuity and movement perception. --- And now I am stumped. Is there a way to minimize the drawbacks? Is there another way to achieve better night vision? Thank you in advance for possible answers. [Answer] **Let's start with a dose of reality** I have "superior night vision" (hah), aka, super-light-sensitive eyes. As a teen I could read comfortably under a full moon and I can see comfortably at light levels that cause most people to trip over tree roots. My highlight was as a kid when rangers turned off the lights in some cave tour in Montana. I've been through a lot of caves — most of which really are completely dark — but this one had phosphorescent lichen on the walls. When the lights went off, I could see the shadows of people as they shuffled and moved their arms between me and the light source. Nobody else could see it (they all thought I was lying or experiencing "spelunker illusion," the ability for your brain to superimpose a "shadow" of your own hand in total darkness because the brain knows where it is). Can I see in complete darkness? Heck, no. Can I see an LED at some unreasonable distance in a completely dark room? Yeah, like a lighthouse. Smoke alarm LEDs keep me awake in hotel rooms, as does the light through the door peephole (stuffed with tissue), the light under the door (towels), and the light through useless hotel blinds (trash bags and blue painter's tape). 1. I'd trade this ability for anything short of cancer in a heartbeat. The pain I experience during the day without dark sunglasses is *excruciating.* Even with sunglasses, I often walk around in full sunlight with one eye closed and the other squinted. Photo flashes feel like knives and holding my eyes open so the good doctor can look inside them is agony on a biblical scale. 2. I do not have extra rods/cones. One ophthalmologist claimed I had less pigmentation on the retina than usual. Others have told me, "we don't know, everything looks normal, it's just the way you are." Whether or not this involves Tapetum lucidum, I do not know. The general consensus has been that the rods/cones are simply more sensitive (how is anybody's guess, I suppose we'll find out if I leave my corpse to science). 3. I have a latent memory of some whacko who claimed the issue might be my brain, not my eyes, in that my brain was freaking out over what would otherwise be normal stimulus. It's an old memory, and not super clear, which leads me to believe it might have simply been a conversation with a friend rather than an official conversation with a doctor, but it is worth remembering that between the pupil and the visual center of the brain there is a LOT of cool juju that can be "sensitive" to light. However, for the record, this is the least plausible solution IMO. My eyesight is great for midnight steal-the-flag, but I've yet to find a practical use for the ability thanks to the consequences. And that's important, if you want any realism at all you need to deal with the consequences of ultra-sensitive eyes while you create them. *(Before I go on, please note that [some butterflies have five times the number of cones humans do](https://cosmosmagazine.com/biology/incredible-bizarre-spectrum-animal-colour-vision) ([also see here](https://www.ncbi.nlm.nih.gov/pubmed/28332207)). It doesn't make them more "brightness sensitive," it makes them more "color sensitive," which might suggest they have the same number of cones in total, but not the same number of each type. Might be worth looking into.)* **Pupils** Insofar as I know biologically, pupils are your only logical choice. Whether it's Willk's extra-large pupils during the night or a less practical ultra-small pupil during the day. The problem with a day pupil is that, logically, there's only so small a hole the muscles can produce before the mass of the muscles themselves get in the way of closing the hole. It's much simpler to open the pupil wider at night. I upvoted Willk's answer. So should you. Alternatively, you have all kinds o' critters (goats, frogs, cats...) that have non-circular pupils. The shape of the eye need not control the shape of the pupil, giving you tremendous control over the use of this solution. **Third eyelid** My cat has a wonderful eyelid that protects her eyes against [wind and impact](https://www.litter-robot.com/blog/2018/10/18/why-do-cats-have-a-third-eyelid/) (aka, a "nictitating membrane"). Make that sucker semi-transparent and use it during the day to block daytime light. **Fanciful solutions** * Like a car engine disabling some of its pistons to improve fuel economy when unnecessary, engineer the eye-nerve-brain interface to disable rods/cones when not needed. * The transparent outer layer of the eye can self-darken like Photochromic lenses (sunglasses and welder's helmets). * The transparent outer layer of the eye is columnated, like many fluorescent light panels (you know, the inch-thick panels in squares designed to block the glare from acute angles), but this comes with another price: limited peripheral vision. * It simply doesn't hurt. The brain is able to withstand the entire spectrum of brightness without experiencing pain. Said another way, just write your story and don't worry about what the occasional "informed" reader thinks. [Answer] **Giant pupils.** [](https://i.stack.imgur.com/RCzR2.jpg) Humans are limited in how big our pupils can get because somewhere along the line, evolution selected individuals where the iris was small enough that you could see the whites of our eyes. Probably that gives some sort of cultural benefit as one can see where a person is looking, and maybe you will later feel fondness towards a baby you saw looking at you and take care of it. But the downside is that the pupil can only be as big as the iris. Small iris means smaller maximum pupil and less light admitted at maximum dilation. Your humanoids have eyes that are all iris, like this tarsier, or cats, or anything but humans and maybe dogs (hmm...). Their pupils can get so big that the eye becomes all pupil, admitting more light and so improving vision in low light. Plus they will look cool. --- **Infrared vision** [](https://i.stack.imgur.com/FGtdR.jpg) > > Vipers, pythons and boas have holes on their faces called pit organs, > which contain a membrane that can detect infrared radiation from warm > bodies up to one metre away. At night, the pit organs allow snakes to > 'see' an image of their predator or prey — as an infrared camera does > — giving them a unique extra sense. > <https://www.nature.com/news/2010/100314/full/news.2010.122.html> > > > Under the right circumstances, accurately perceiving infrared radiation (perhaps via a non-eye organ, like snakes) could be even better than just seeing warm bodies. Under conditions of changing atmospheric temperature, objects in the environment change their own temperatures at different rates according to thermal's mass and composition. Even our very blunt distant temperature sense (perceiving air temperature differences) can tell the difference between a stone wall and a tree after a hot day, or after the day has gotten hot. Infrared vision could give you a thermal picture of the environment. [Answer] The problem with tapetum lucidum is that the reflected photon will interact with the photoreceptor in a slightly different position due to the reflection, actually blurring the image. Therefore, instead of increasing the amount of captured light by reflecting it back after the retina, why not make a double stacked layer retina? In this way the result would be the same (a photon would cross twice the sensitive layer, doubling the chances of being sensed) but without having the blurring due to reflection. Moreover, in daylight condition the nerves of the second layer could be switched off to keep a good vision. [Answer] Three things spring to mind, none are easy fixes though. The first thing is that the layout of human eyes (and indeed the eyes of all vertebrates) is a bit odd... there's lots of infrastructure in the form of neurons in *front* of the photoreceptors. This isn't quite as stupid as it sounds, as those neurons [don't just get in the way of the light](https://www.eurekalert.org/pub_releases/2015-02/aps-mot022715.php), but serve some useful focussing and filtering purposes. I have a sneaking suspicion that vertebrate eyes have evolved to make the most of their silly-backwards layout, rather than the backwards layout being somehow desirable in and of itself. Certainly, it is a bit hard to evolve *out* of the backwards layout once you've got it. A right-way-round retina could also evolve to be just as good at focussing, without any unnecessary absorbtion of light. By way of a bonus, by putting the optic nerve at the back rather than needing it to punch through the eye and spread out across the inside means that you can get rid of the silly [blind spot](https://en.wikipedia.org/wiki/Blind_spot_(vision)). That'll mean you can use more of the light coming through the pupil too... not much, but every little counts. So: photoreceptors in front, nerves behind, more light gets to the photoreceptors and there's no stupid blind spot. Next: long wavelength (or near-infrared, if you like) light sensitivity. Take a look at [this answer on the biology stack exchange](https://biology.stackexchange.com/a/58046) [](https://i.stack.imgur.com/LZLbX.jpg) Those low-light sensitive rods cells are great when it is gloomy but they're actually less sensitive to some longer, redder wavelengths of visible light than colour-sensitive cone cells are. Could you make a better rod cell? *Maybe*. Some enterprising biologists have [engineered rod cells to express cone cell red pigments](https://medicalxpress.com/news/2011-06-animals-dont-infrared-vision.html), but the results weren't great... the problem is that at low light levels, those long wavelength signals are *noisy*. If you just had a bunch of these modified rod cells you'd be able to see near infrared light much better, but the *quality* of your low-light vision in those circumstances would be quite poor. Blurry, most probably, rather than the sort of static snow effects that digital cameras get in low light. Maybe though, with a bit of clever work, you could come up with a better rod cell, or a new type of cell and pigment that shows better low-level, long-wavelength sensitivity without suffering from too much thermal noise. You can't go *too* long though, because you'll start having focussing issues... making a lens that will work well for short blue wavelengths as well as it works for longer near-IR ones will be tricky. Go far enough into the mid and long-IR range and you won't be able to focus at all because you've got eyes made of the wrong materials. For those wavelengths, take a leaf out of the pit-vipers book, and grow some [pit organs](https://en.wikipedia.org/wiki/Infrared_sensing_in_snakes). The third option is really more like a two-and-a-halfth option. Follow the lead of security camera manufacturers: [](https://i.stack.imgur.com/ZWBX1.jpg) Get you some [bioluminescense](https://en.wikipedia.org/wiki/Bioluminescence) that emits a decent amount of [near-IR](https://www.sciencedirect.com/science/article/pii/S0040403918301230) light, and add it to the skin cells in convenient places (like your face, but not too close to your eyes). Easier said than done, but if you *can* do it, the noise sensitivity issues of those modified rod cells suddenly go away. It'll require more energy to run (bioluminescense ain't free) and it *might* be visible to people with conventional eyes (and you'll have a brightly glowing face form the point of view of other members of your species) but maybe it'll look awesome into the bargain... [Answer] **Obscurable Tapetum Lucidum** Place your Tapetum Lucidum in a capsule of black, highly opaque fluid. In the light your eye squeezes the black fluid in front of the Tapetum Lucidum to give you a non-reflective backdrop for optimal clarity, then at night, you push the fluid behind the reflective sheet for double reception. **Larger Irises + Controllable Proptosis** Since you don't want to change the size or depth of the eye, just give it a much larger iris than the socket would suggest. Normally, this would accomplish nothing without also increasing the size of the eye socket. However, proptosis is when they eyeball is extended beyond the eye-socket. Normally this is the result of a medical condition, but in some people like, Kim Goodman, it's just a thing you can do. By pushing the eye out of the socket, you expose the larger light collecting area despite having apparently normal human sized eyes, but during the day you pull them back in giving them full human like protection from injury and sun-light. [Answer] I like your thought, but I think you'd be better served trying another system entirely. Instead of working within the human vision spectrum, why not consider expanding it to infrared? Have the rod cells be able to pick up light far beyond that meager 380-740nm wavelength, and double it or even triple it to allow up to 1000nm, or even 10,000nm. The increase light sensitivity will give humans night vision. Are there downsides? Yes. Two. The first is that everything won't really have colors. Infrared binoculars look green, but that's because the infrared the binoculars picked up have been processed and are hitting your cones. The infrared that your rods pick up won't touch the cones, so it'll have the same color as it would have had if you didn't have nightvision, i.e. none at all. The second is light. As in, daylight. If your eyes are that receptive to infrared, than you'll basically be blind from the sheer wave of light during the day. Luckily, we've got a solution. Tapetum Lucidum. (Have you heard of this before? I feel like you might have.) All jokes aside, the reflective layer will work if we *reverse* it. Have a third eyelid ( [nictating membrane](https://en.wikipedia.org/wiki/Nictitating_membrane)) which reflects (or just blocks) the infrared spectrum that comes down during the day will stop your night-vision humans from going blind. [Answer] This is an addition to Willk's answer; Giant pupils would be a very good start, with the addition that the iris would have to be able to get the pupil small enough to allow function in the daylight. There could also be a secondary iris on the back side of the eye which could cover/reveal a [tapetum lucidum](https://en.wikipedia.org/wiki/Tapetum_lucidum) layer. The reason why you might not want it visible all the time is that it would cause blurry vision as light that misses photo receptors is reflected to gets a second chance to be absorbed. Lastly, you could throw in infrared vision, which is [found in some species of fish and frogs](https://sciencing.com/animals-can-see-infrared-light-6910261.html). Also, while technically not part of the eye itself, you could have [infrared detection pits](https://en.wikipedia.org/wiki/Infrared_sensing_in_snakes) like are found in several kinds of snakes. This would allow for some limited amount of vision even in areas with no visible light at all. [Answer] Literally cool night vision. (I may have some details wrong, and numbers are completely made up, working from memory.) Some fish can adjust the temperature of their eyes. When they are cold, the photoreceptor pigments stay active for a longer time than they do when they are warm. This have the effect of a longer exposure time ('shutter speed') at colder temperature. When they are diving down in the inky depths, they let their eyes cool down, and they can see an image accumulating all the photons that have hit the retina in the last second. This makes their eyes very sensitive, but fast moving things are blurred. When they are near the surface, where there is light, they heat their eyes. The image they see is from all the photons in the past 1/100 s. This is not as sensitive, but that doesn't matter because there is plenty of light. What matters is that moving things are no longer blurry. While you're at it, make the tapetum thermochromic: silvery when cold and black when hot. [Answer] **Injected Nanoparticles** For short term night vision, you can get injected with infrared sensitive nanoparticles that can extend your vision into the infrared range See [Infrared Night Vision With Nanoparticles](https://www.extremetech.com/extreme/286728-scientists-give-mice-infrared-night-vision-with-nanoparticles) It lasts about ten weeks and infrared sources appear as green light. [Answer] Don't use photons at all. Do it like bats do, and make a mental image of your surroundings through sonar. In this way, you can use your eyes by light and your ears in the dark. --- Alternatively, take a page from snakes. [They have cells that are sensitive to radiation at the 5 to 30 micrometers range](https://en.wikipedia.org/wiki/Infrared_sensing_in_snakes). For comparison, the "reddest" we can see is around the 700 nanometers range! In practice, this means snakes are literally able to see in infrared. Infrared sensing in snakes is not done via photochemical reactions, though, so it may not be as sharp as visible light sight. However, it does allow snakes to find prey and strike accurately in total darkness. [Answer] Let them have bat-like sonar. While they may need some differently shaped ears there are also cases where blind people developed something similar with normal human ears. Their brain would have no issues overlaying the information of sonar and vision, giving them the ability to navigate perfectly, while a normal human could only see vague schemes. They might be sensitive to loud noise as a drawback, but this solution could be used for a nice plot twist (even if friendly they might just use the term "nightseeing" because it is all natual for them). [Answer] In addition to the other answers like larger irises and infrared sensitivity, one other thing you can do is improve the sensitivity of the eye. Increasing the number of nerves connected to the rods will boost their sensitivity. Another thing is improving the brain's image processing capabilities. Rewiring the brain is definitely not an easy task, but if done well could vastly improve the quality of the image the brain receives without modifying the eyes at all. [Answer] **Squid eyes.** The most obvious design flaw with human eyes is that someone lazily designed the receptors inside out; the nerves are all on the inside of the eye, so the light needs to go through that before it even gets to the receptor cells, and then the nerve bundle needs to be routed through the eyeball itself which leaves an inconvenient blind spot. Squid eyes are much more sensibly designed -- the receptor cells are on the inside, the nerves are at the back, which gives better sensitivity and no blind spot. [Answer] # Two sets of eyes! They could still be humanoid eyes, just one pair is much more sensitive to light. Maybe when they are sleeping at night, they keep their day eyes open ... not super userful for seeing at night, but allows them to sleep with their eyes open literally and if something occurs that might wake them up they'll open their night eyes and close their day eyes. [Answer] Why not have double eyelids like reptiles, and have the inner pair act as a pair of shades? This way you have superior night vision (increased no of rods, retro reflectors, etc) and then a pair of translucent but lossy eyelids, then regular eyelids? [Answer] A [nictating membrane](https://en.wikipedia.org/wiki/Nictitating_membrane) that shields your eyes from the infrared spectrum (700 to 1000 nanometers) during times of bright light in what we call the visible spectrum (380 to 700 nm), and retracts when you want to see in infrared. [](https://i.stack.imgur.com/wTMsP.jpg) Fortunately, humans have a [vestigial third eyelid](https://en.wikipedia.org/wiki/Plica_semilunaris_of_conjunctiva) that you can repurpose for the task. [](https://i.stack.imgur.com/DQk3o.png) [Answer] I think some answers touch the approcha I am to suggest: Polychromacy People generally can see in three-dimensional colourspace with bases of Red, Green and Blue. Therefore *Homo Sapiens Sapiens* is considered a *trichromat*. Some people suffer from colour-blindness. A subsidiary to this group can recognise only two colours and they may be considered *dichromats*. On the other hands there are people reported to see a [fourth colour](https://en.wikipedia.org/wiki/Tetrachromacy#Humans). You can see <https://en.wikipedia.org/wiki/Pentachromacy> too. So, consider what electromagnetic waves can illuminate your world and how they interact with the surfaces. Then let your species be polychromats with retina cells sensitive to human-visible spectra plus far infrared (cold surfaces), near infrared (hot and superhot surfaces) on one side of the spectra and ultraviolets on the other. Also note that infrared optics, "visible light" optics and UV optics needn't be compatible. Even light optics may suffer from colour abberation - different focal points for different wavelengths. This may work for you benefit - in daytime the eye is focusing the sunlight spectra to the retina while keeping the rest defocused and in the night it focuses the nightlight spectra. [Answer] I present to you, **the list of ultimate eyes in the animal kingdom:**: ## 1. [Eagle eyes](https://en.wikipedia.org/wiki/Eagle_eye): [](https://i.stack.imgur.com/qmgD8.jpg) The eagle eye is among the strongest in the animal kingdom, with an eyesight estimated at 4 to 8 times stronger than that of the average human. *Rods and cones: **Check, you have that already**, just mentioning it for completeness* ## 2. [Mantis shrimp eyes](https://en.wikipedia.org/wiki/Mantis_shrimp#Eyes): [](https://i.stack.imgur.com/4giTk.jpg) Compared to the three types of photoreceptor cells that humans possess in their eyes, the eyes of a mantis shrimp have between 12 and 16 types of photoreceptors cells: We can see Red, Green and Blue, they can see red, green, blue, polarized, infrared, ultra-violet, septarine, octarine, nonarine, decarine, undecarine, dodecarine, .... (Nope: I have no clue what this last bunch of colours are neither as my physiology *just cannot see them* neither) ### 3. [Owl eyes](https://en.wikipedia.org/wiki/Owl#Vision) [](https://i.stack.imgur.com/lrBoK.jpg) *Tapetum lucidum:* Check, you have that already. ## 4. [Pigeon eyes](https://en.wikipedia.org/wiki/Bird_vision#Magnetic_fields) [](https://i.stack.imgur.com/mmdNV.jpg) OK, not really their eyes, but pigeons can sense magnetic fields and it seems to be related to light. ## Now combine all of the above: and add additional double / triple / quadruple eyelids to shield these sensitive instruments from overload. and you'll end up with something like this: [](https://i.stack.imgur.com/WdMYa.jpg) [Answer] Lots of good answers given already, but I'll add this! The first thing you need to decide is: what do you want your humanoids to have cool night-vision **for?** Take the **tapetum lucidum**. If the point of having night-vision is so your humanoids can run about a forest at night without crashing into trees, tripping over roots, falling off cliffs, or mistaking that approaching angry bear for a placid cow, then the fact that the tapetum gives you slightly blurry images is **not a problem**. For instance, I'm short sighted, so trees, roots, cliffs, bears, etc are blurry when I'm not wearing my glasses. I do not, however, walk into obstacles all the time! Therefore if all you need your humanoids to be able to do in the dark is the kind of stuff a lion, fox or wildebeest can do in the dark, then the 'lame drawback' is not a drawback at all. However, if you want your humanoids to be able to focus on tiny details in the dark - like read a book or do embroidery or tell if that moth flying by is a lesser spotted or greater spotted woozlemoth - then the blurriness is a problem. Most of those types of things are only stuff that humans worry about. Unless you are an animal who eats woozlemoths and the greater spotted ones are poisonous. To avoid the blurriness, you simply have no tapetum behind the [fovea](https://en.wikipedia.org/wiki/Fovea_centralis). The fovea is the area of the retina designed to see tiny details. So in daylight, you can read small print in books etc, but at night you cannot. Alternatively, use [elephant hawk moth trichromatic vision](https://www.cell.com/current-biology/fulltext/S0960-9822(03)00031-9?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982203000319%3Fshowall%3Dtrue). Those moths use a system which lets them see in colour in the dark because of the physics of the way its eyes work: a **very high photon flux** to avoid the downside of trying to receive a colour signal at low light intensities. The moths can do it because of the structure of the lenses in their multifaceted eyes. Perhaps someone who knows more about physics than I do can tell you if it is possible to duplicate the effect in a vertebrate eye? ]

[Question] [ Is there any conjecture or famous unsolved problem, that doesn't require much prerequisite knowledge and could be plausibly proven / solved by freshman? My hero is average freshman in mathematics, that proves a famous conjecture by mistaking it for homework, like George Dantzig. Maybe something in combinatorics if [this](https://www.reddit.com/r/reddit.com/comments/9f75q/comment/c0cju7w) reddit comment is true > > A few years ago at my university the final test on combinatorics > included some unsolved problems. The students were supposed to have > enough insight to realize which problems were the easy solvable ones > and which ones were a waste of time to try to solve. > > > One of the students (this course is usually taken by first or second > year students) actually solved one of the unsolved problems. It wasn't > one of the really famous unsolved problems included on the test, but > his result was certainly unknown. > > > The conclusion was somewhat less dramatic, though: the professors > thought about his solution for some time (months) and after they were > convinced that there isn't a loophole in the argument, the result was > published and eventually became the basis for this guy's PhD. > research. > > > Problems in combinatorics are certainly easier to approach on this > level, since their solution usually involves some clever trick, rather > than extensive application of deep theorems. > > > [Answer] Others have mentioned some famous conjectures such as the Collatz conjecture and P = NP, but I think it's awfully unlikely that a freshman math student would be able to solve such a problem. About the Collatz conjecture, Paul Erdős famously said that "Mathematics may not be ready for such problems"; and about P = NP, [Scott Aaronson wrote](https://www.scottaaronson.com/blog/?p=122) that "any proof will need to overcome specific and staggering obstacles" and "we do have reason to think it will be extremely difficult." Instead, I suggest a [Diophantine equation](https://en.wikipedia.org/wiki/Diophantine_equation). A Diophantine equation is simply any polynomial equation (that is, an equation built out of variables, constants, addition, subtraction, and multiplication), where the question is, "Can we make this equation true by setting each variable to a whole number?" A simple example of a Diophantine equation is $x^2 + y^2 = 5$. This Diophantine equation has 8 solutions. One of them is $x = 2$ and $y = 1$. The other 7 solutions can be found by switching $x$ and $y$ around, and by negating one or both of them. It certainly *is* plausible that a Diophantine equation could baffle mathematicians for years, but then be solved by a freshman math student. And I have an anecdote to prove it! In 1969, D. J. Lewis wrote a paper about Diophantine equations, in which he wrote that the equation $x^3 + 5 = 117 y^3$ is known to have at most 18 solutions, but the exact number is not known. Two other mathematicians studied the equation and, in 1971, they published a short but difficult proof that there are no solutions. Finally, in 1973, another mathematician found an astonishingly simple proof of the same fact! The proof is: > > The quantity $x^3 + 5$ is never a multiple of 9, but the quantity $117 y^3$ is always a multiple of 9, so there are no solutions. > > > (Source for the above two paragraphs: [Gerry Myerson's answer on "Awfully sophisticated proof for simple facts."](https://mathoverflow.net/a/44748/5736)) Gerry points out that Lewis's equation, as printed, may have been a typo.) So, although this particular equation was never famous, it did give some mathematicians quite a bit of difficulty, before, years later, someone found a simple proof that easily could have been found by a freshman math student. So, which Diophantine equation should *you* use in your story? The paper "[Some open problems about diophantine equations](http://pub.math.leidenuniv.nl/~evertsejh/07-workshop-problems.pdf)" contains one in particular which I think looks pretty promising. The problem that your hero solves could be: > > Find all integer solutions to $x^4+x^2+y^4+y^2=z^4+z^2$. > > > [Answer] Since you're interested in something currently unsolved, you don't really care about how protagonist will solve it, only that he does so, let's go for something extremely simple, simple enough that even a reader with only basics of mathematics can understand: [Collatz conjecture](https://en.wikipedia.org/wiki/Collatz_conjecture) (also known as 3n + 1 Conjecture) "Consider the following operation on an arbitrary positive integer: If the number is even, divide it by two. If the number is odd, triple it and add one. ... Now form a sequence by performing this operation repeatedly, beginning with any positive integer, and taking the result at each step as the input at the next.(Or in human language - keep repeating the previous process with new number again and again and again...) ... The Collatz conjecture is: This process will eventually reach the number 1, regardless of which positive integer is chosen initially." This is simple looking, yet currently unsolved problem, which looks simple enough for a reader who doesn't understand too much math as something solvable by a genius student. A real student of mathematics or a professor will, reading your fiction, probably exclaim "That's not how it works, it's basically sure thing that any proof of this conjecture, if this conjecture is even provable, will be hundreds of pages long!" But most of the audience will not find anything wrong with your protagonist solving this on ~6 pages as a homework. Only thing that might cause suspension of belief is that the guy has never heard of this conjecture before and confused it for homework. [Answer] [Goldbach's conjecture](https://en.wikipedia.org/wiki/Goldbach%27s_conjecture) states that every even integer greater than two can be written as a sum of two primes. If one could find a counterexample the problem would be solved (although currently all candidates smaller than the order of 10^18 have been tried). Alternatively if one could give a formula the problem could also be solved. [Answer] A perfect number is a positive integer N such that N is the sum of its divisors (other than itself). For example, 6 = 1 + 2 + 3 28 = 1 + 2 + 4 + 7 + 14 **Question**: Does there exist an odd perfect number? [Answer] You already have some good answers here, but let me suggest one other possibility that might work for you. Rather than an unsolved problem, you might look at a couple of cases in which there is a proof of something that can be stated simply, but the proof is unsatisfying in some way. Either the proof is so complex that it is accessible only to (extreme) specialists, or the proof is so vast that a computer is required to manage it. [Fermat's Last Theorem](https://en.wikipedia.org/wiki/Fermat%27s_Last_Theorem) is in the first category and [The Four Color Theorem](https://en.wikipedia.org/wiki/Four_color_theorem) is in the second. When I was a young mathematician, both of these were (widely believed) conjectures, but unproven. Now they have proofs. But a simple proof of either, a proof whose details can be easily grasped by, say, a college student (and doesn't require a computer), would, itself, be a breakthrough. [Answer] The biggest unsolved problem in computing is “can [NP-Complete problems](https://www.britannica.com/science/NP-complete-problem) be solved in polynomial time?” NPC problems are a whole class of searching problems that we hit regularly in real world operations. Polynomial time basically means “a reasonable amount of time even on large problem sets”. Most researchers think the answer is “no.” Proving “no” is really hard. Proving “yes” on the other hand just requires someone writing the program that does it. The student might not even realize they’ve done anything amazing. If you do have your protagonist solve this problem, it’ll be a pretty serious kick in the pants for performance of all computing tech in your world. [Answer] To add on to the list of statements that are simple to understand: **The Twin Primes Conjecture.** "Twin primes" are pairs of primes that differ by $2$, like $3$ and $5$, or $11$ and $13$. The open question is "Are there infinitely many pairs of twin primes?" [Answer] I would go with finding a non-trivial zero to Riemann's Zeta function, thus effectively proving (by counterexample) that [Riemann's Hypothesis](https://en.wikipedia.org/wiki/Riemann_hypothesis) is false. Pick a solution with the form $n/(2n+1)+xi$, with insanely large $n$ and very large but nice looking $x$. Make it such that it is possible to simply check that the solution is indeed a zero of the Zeta function, thus the student would be easily believed, as false solutions to the problem pop-up very often, and even checking a correct proof could take years. This problem fits two things that are nice for a narrative: 1. It is said that the one to solve this problem is destined to mathematical greatness. 2. Even a wrong or fuzzy method could still provide a verifiable non-trivial solution, and thus it wouldn't take long before the consequences of the discover start taking place. The downsides are: 1. It is a rather complex conjecture to be understood by someone who only knows about high-school math. (probably most of the potential audience) 2. The hypothesis is widely believed to be true. (though it being proven false would have a much bigger impact). Another "solution" would be finding a polynomial algorithm to find hash collisions for [SHA2](https://en.wikipedia.org/wiki/SHA-2), as far as I know, there isn't a proof that such an algorithm would be impossible to exist, but a lot of cryptography based systems rely on the fact that it is too computationally expensive to create arbitrary hash collisions. This may or may not create different ramifications for the story, but it is something that a teacher wouldn't ask in a test as a "unsolved problem", it might be part of some research task to find methods that are better than brute-force (slightly, as has been done with other hashing algorithms), then by accident finding something much better than brute-force, or some algorithm that "just happens" to run fast very often, even if it could take very long (akin to [Quicksort algorithm](https://en.wikipedia.org/wiki/Quicksort)). [Answer] **I would argue: any problem that can be conveyed simply without excessive higher-level math would be fair game.** Keep in mind, solving a conjecture/problem often doesn't depend on extreme math proficiency, but being able to creatively approach the problem from an unusual angle that hasn't been attempted before. [Here's a great example, from the 2011 International Math Olympiad.](https://www.youtube.com/watch?v=M64HUIJFTZM&vl=pt) It was given to the brightest students in the world, yet this problem stumped most of them. And it wasn't because the problem required extreme proficiency with mathematics, but reaching an understanding of a core dynamic of how the system worked - and then simply exploiting part of that dynamic. The actual 'math' of the situation is almost an afterthought. So let me give you some hypothetical examples: > > "Yeah, I solved the [3 body physics problem](https://en.wikipedia.org/wiki/Three-body_problem). I mean, I know we > were supposed to integrate over *position*, but that wasn't working out > for me. So I tried to integrate over *time and distance squared* and > I figured out that a lot of the complexity just disappears." > > > ... > > "Yeah, I solved the [Collatz Conjecture.](https://en.wikipedia.org/wiki/Collatz_conjecture) I thought to myself: why > use a solid base? I mean, instead of each digit representing a > constant number to an increasing power, why not make the digits > correspond to prime numbers? So the number '3011' really represents > 3x5+1x2+1x1. And when you look at the patterns in that number scheme? > The patterns are pretty obvious - the conjecture is pretty trivially > obvious." > > > ... > > "Oh, [RSA decryption?](https://en.wikipedia.org/wiki/Integer_factorization) Yeah, the whole 'Cannot find large factors' > seemed kinda weird. I mean, we can express the large number in > whatever base we want, right? So why not convert that large number > into each of the first dozen or so prime bases. Then we guess at the > lowest significant digits of the solution in each of those bases, > correlate all those prime bases' guesses together, and get a pretty > accurate picture for what the divisor must be." > > > Note: None of those hypotheticals are actually true. But it shows how an oblique, non-standard approach to a problem might be what actually 'cracks' the conjecture. ]

[Question] [ Imagine two identical planets *planet A* and *planet B*, orbiting the same star. Is it possible that these two planets follow the **exact same "route" as they orbit their sun**, but are just distant enough from one another, that their star is effectively always between the two, so that a hypothetical person sitting on planet A would not be able to see planet B due to it being **behind the star**? [](https://i.stack.imgur.com/vWEWX.png) *(proportions gloriously inaccurate)* I assumed, based on the limited knowledge I have on the subject, that all star systems have **ellipsoidal** orbits (the star being in one of the two focal points) just like our own. If I'm wrong, though, and perhaps a stellar system with **circular orbits** is possible (and I assume it would make my idea more feasible) please do point it out. If this is at all possible, **what are the "requirements" to make it work?** Note that this doesn't necessarily have to last *indefinitely* (e.g. maybe the orbit screws itself up after, say, 1000 years) Also, what is the approximate **minimum** level of technology that a civilization inhabiting planet A would need to have good chances of finding out about planet B's existence? [Answer] > > I assumed, based on the limited knowledge I have on the subject, that all star systems have ellipsoidal orbits (the star being in one of the two focal points) just like our own > > > You are right, this is one of Kepler's law, the first. Another one, the second, states that the line connecting the star and the planet swipes equal areas in equal times, or, to put it in picture [](https://i.stack.imgur.com/7bnFE.gif) As you can you see from the image, when one of the two planets is in the "slower" region, the other will be in the "faster" one, meaning that the apparent alignment between the two planets and the star won't last too long. Let's assume for simplicity that the area is covered in one month. One planet will see the other planet disappear for a fraction of that month, and the it will appear again in the sky. The only way to escape this is to have perfectly circular orbits (at the end, a circle is just an ellipse with eccentricity = 0 ) if you approximate the star as a point in the sky. Taking into account the apparent size of the star in the sky, if the orbit is not excessively eccentric and the planets orbit not too far from the star, it is still possible that they are constantly hidden from each other, with the star continuously covering the view line. In this case, to find out the existence of the other planet, it is probably needed to have the capability of sending satellites out of the orbital plane, to look at the stellar system from above (or below). It is also possible that relativistic bending of the light close to the edge of the star can make the planet visible during eclipses, when its apparent position in the sky is close to the edge of the star itself. Though I doubt such a system would be stable over the time span needed for such a civilization to evolve. [Answer] # Circular orbits are not practically possible From [Astronomy.SE](https://astronomy.stackexchange.com/questions/22721/is-a-perfectly-circular-orbit-possible), there are a variety of reasons why orbits are not circular. There is relativity, there is planetary flexing with gravity, there is unequal radiation from the planet's surface (the sunny side reflects and radiates more energy into space, generating net thrust). Then there are the effects of any other planets. Having a Jupiter around pretty much ensures that no other planet will have a circular orbit. If the orbits are not perfectly circular, then the planets would periodically be able to see each other. # Formation on of planets in 'opposite' orbits is not possible Notwithstanding the fact that the orbits won't be circular anyways, if two co-orbital planets were able to form, they would form as [Trojans](https://en.wikipedia.org/wiki/Trojan_(astronomy)#Trojan_minor_planets) of each other, not opposites. Trojan planets exist in the same orbit where each planet would be in the other planet's L4/L5 [Lagranian points](https://en.wikipedia.org/wiki/Lagrangian_point), off by 60 degrees. I don't believe any Trojan planets have been discovered yet, but there are computer simulations of Trojan formation and stability out to a billion years (e.g. [Cresswell and Nelson, 2008](https://www.aanda.org/articles/aa/pdf/2009/03/aa10705-08.pdf)) [Answer] # Second opinion: Yes, this is possible But King! You posted another answer saying it wasn't possible. Well, for a two planet system, I argue that it is not, in fact, possible. But remember what I said about Trojan planets, they have to be 60 degrees apart in each other's L4/L5 points. So the solution is: twelve planets! Put six planets in one orbit, and have each of the six be a Trojan of the two planets on either side of each other. Then, add another six planets that are either larger or smaller in a more or less distant orbit. This 'rosette' configuration can be stable with a sun in the center of it. A lot of the problems that I mentioned in my previous post with circular orbits actually dissipate in this case as well; instead of just being in orbit around the sun, the twelve planets are constantly correcting each other's orbits to maintain the Trojan positions. The effects of radiation are balanced out by the several planets all at different orientations to the sun. Now, this setup seems incredibly unlikely to happen naturally, so we will have to assume that this is an artificially created solar system. So in this case, the Progenitors will remove everything from the solar system, build twelve planets of two masses and set them around the sun in perfectly circular orbits. That system should be stable for a few million years at least. So an ancient astronomer on any of the world's will see ten other worlds, but not the eleventh, opposite world. As far as discovery of the last world, well the first person to make a heliocentric model of the solar system would probably have a good idea that there is a missing planet hidden behind the sun, just due to symmetry. I argue that Ptolomey's spheres would make no sense in this kind of system, so the heliocentric model would probably be accepted by Ancient Greek times if not earlier. If that didn't happen, the mathematics of Lagrangian points were published in 1772; so by that time there should be proof that there needed to be a twelfth planet in order for orbits to be stable. [Answer] If you are prepared to be less strict, there is a configuration that can mask two co-planar satellites from each other: [](https://i.stack.imgur.com/6hTGr.png) Satellites are not in the same orbit. But they are in the same plane. The orbits could be elliptical as much as you want, but they maintain a symmetry: The periapsis/apoapsis are directly opposite at each side of the star. This makes the two satellites maintain the same orbital velocities at the same time, and avoids being seen. Planets can also be slightly different in mass, but the orbits will have to be exactly the same size. I don't know a lot about orbital mechanics to determine if the two orbits will also precess in the same rate. If they do, the configuration can last indefinitely. Admittedly, this sort of system is very improbable to form in the nature. But I guess this is a very good chance to use the artistic license. [Answer] You are talking about the [Counter Earth Theory](https://en.wikipedia.org/wiki/Counter-Earth) first proposed by Philolaus (c. 470 – c. 385 BC). While mathematically possible, the statistical liklihood of it occuring naturally are so remote as to be sensibly described as impossible. Note also that the orbit is intrinsically unstable as you can never have perfectly balanced gravitational forces. Eventually something would change, and then it would fall apart. [Answer] # No. To be able to "never see each other" (sort of like the twin worlds of [Beta and Delta](https://en.wikipedia.org/wiki/The_Last_Enemy_(Space:_1999))) they'd need to be on an almost circular orbit, or you would get a libration effect making one planet "peek" behind the star at the other every year. If the planet wanders too far from the star, it becomes visible (otherwise, it could not be seen against the glare of the star). But you couldn't have just *two* planets - that configuration is too unstable. It is thought that it actually happened once, and with the Earth, no less. It might have had a companion - not on the other side of the Sun, or L3 point, but in the more stable L4. The companion was called Theia. [It did not end well](https://en.wikipedia.org/wiki/Theia_(planet)), but we got a Moon in the bargain. Granted that there are no *stable* configurations, you could do something with a [Klemperer's Rosette](https://en.wikipedia.org/wiki/Klemperer_rosette). Each planet only sees four others, but opposite planets are not identical. To beat the instability, you'd need some kind of force keeping the planets apart, but it would need to act only on the planets, and be stronger (at that distance) than gravitation. In that case you would not need a rosette to keep things stable. Electric charge would seem a feasible candidate, but it actually [isn't](https://en.wikipedia.org/wiki/Earnshaw%27s_theorem). To discover the other planet, the inhabitants of either of them would need space probe technology - they need something to go out and get a look back. Mathematically, they might deduce it from the orbits of other planets. [Answer] The [Condon Report](https://en.wikipedia.org/wiki/Condon_Committee) (1968) had an appendix that investigated the possibility of an antichthon in Earth orbit. Please note an "antichthon" is essentially a Counter-Earth. They concluded that an antichthon could not remain completely hidden. by the Sun, as there would be times in the orbital periods of two planet -- Earth and the Counter-Earth -- when each would be visible to the other. This finding about planets sharing the same orbit was an incidental full note in their deliberations, but it was nice to discover that the topic of antichthonal planets had been researched. A copies of the full Condon Report or going by its formal title of *Scientific Study of Unidentified Flying Objects* can be found [here](http://files.ncas.org/condon/) and [here](http://www.avia-it.com/.../Final%20report%20of%20the%20Scientific%20study%20of%20...) In conclusion, could two planets follow the same orbit and never seen see each other? No. There will be times when both planets will be visible to each other. . [Answer] If two planets were in this configuration, they might stay stable for a time, possibly even as long as the thousand years that you need. But there's no way for them to *get* into this configuration, since if they had such similar orbits then they would billions of years ago have interacted in some way that would either have resulted in a collision or a drastic change of orbit for one or both of them. [Answer] Is it possible? Yes, why not. Will there always be Sun in the way? No or at least not for Earth or any planet in our system. Does it matter? No and here is why. I simplified a few things, I'm using Kepler Laws (assuming elliptical orbits and none interference from other bodies) and round some things and completely disregard relativity. Relativity would not play that big role anyway, becasue the time lag to the other planet would be about 17 minutes for light. I ran the calculations for Earth and assuming we would be at aphelion (farthest from sun) when the other planet were at perihelion (closest to sun), the sun would not be in our way to see each other for some portion of the year (here is where the calculation gets complicated because of calculation of areas of parts of ellipses, but there could be some iterative ways to calculate it. It is not the main point of the question so I won't). Somewhere in mid-spring/mid-fall (best day would be the fall solistice or two days after or during the spring solistice or two days before, because two days are about the time difference between exactly half orbit of our ellipse on aphelion and perihelion halves) when you would look up, you would see the planet. Except you would have to look up at day. And the planet would be about one degree from the sun. In astronomy one degree is often approximated by outstretching your hand and extending your pinky. That's about the distance you would be able to see the planet from the sun. Now that all was based on Earth, which has eccentricity of about 0.0167 and because of our distance to sun the distance between the two foci of our orbit are about 5 million kilometers apart. But let's take a look at a different planet of our system, Venus. With eccentricity of only 0.0067 and considerably smaller orbit, its foci are only about 1,4 million kilometers apart, which is about the diameter of Sun (it's important to point out that Sun's center is in one of the foci, so the Sun almost touches the center of Venus' orbit). That would mean that when the Sun would not be directly in the way, it would be so close that it would not mostly matter and the path would be there for only brief time, about 12 hours if we make some approximations. That would mean there would be a window for 12 hours twice a year in which you would have the chance to see the other planet, assuming you have some means to completely shut out the luminosity of the Sun. Based on our civilization, we would probably find our neighbor by accident when investigating other places in our Solar system, which gets us to another rather interesting astronomical phenomenon and that is... Lagrangian points. Those are basically five points where in a system of two large bodies (e.g. Sun and Earth) a small enough object stays stationary or orbits around the Lagrangian point (see Halo orbits). Yes you guessed it, the third one is exactly oposite to the smaller object behind the bigger (for Sun and Earth it would be exactly your scenario). The drawback is the great instability of the third point and the size of the objects, we know about some, but for Earth they are usually asteroids of size about 1 km or smaller. I have not heard about a planet forming in a Lagrangian point of another one, but then again, I've never researched that, but it would surelly mean that one of them would be a giant and the other a dwarf. And it is important to note here, that the two bodies would actaully not share the exact same orbit, so it would not hold for this question either. All in all, it would be possible and for it to happen there are three main parameters: the planets' eccentricity, the stars diameter and the planets' orbital distance to the star. [Answer] No If the orbits are highly elliptical, then as one planet moves near the sun it speeds up, and the sun doesn't stay between them. *What if the orbits are nearly circular?* Still no. Orbits with two point sized bodies are elliptical. Real orbits around the sun, with two or more planets are nearly elliptical, but actually they are perturbed by the gravity of the other planets. If two planets are in orbit about the sun, then there is not only the gravitational between the planet and the sun, there is also the much smaller gravitational attraction between the planets. Over time this will tend to move the two planets out of sync. *What about Lagrange points?* There are 5 points that (ignoring other perturbations) could allow for another body to orbit the sun with the same period as the Earth. Two are close to the Earth. L1 is between the Earth and the sun L2 is opposite the sun. L3 is just where you want your "counter-earth" to be, unfortunately L3 is unstable. To remain at L3 requires "station keeping". L4 and L5 are 60 degrees from the Earth-sun axis. They are pseudo-stable, provided the other body is small enough. An Earth-sized planet could not orbit at L4. *What if the planet was put in exactly the right place* Placing a body exactly at L3 won't work, because there are lots of other perturbations that will shift it a little from L3, and then Earth's gravity will work to move it further and further from L3, until it becomes visible. The number of types highly stable orbits that are possible is (unfortunately) rather limited. You can have planets going around a star in well-separated orbits. You have moons. You are allowed circumbinary orbits. Interesting orbits like those of Saturn's moons Janus and Epimetheus are not stable for long enough for life to develop. [Answer] The planets could orbit each other and each have an opaque cloud layer in their atmosphere; that's about the only way I can think of for this to be made possible. (Barring a Big Beautiful Wall in space) [Answer] # Of course it is possible Many other answers are trying to deal with the 3 body system. But if both your planets have a neglectable mass, any "simple" orbit is stable. It is difficult to explain how such a system could come to existance, but if you have 1 massive sun and 2 dwarf planets (moon size) orbiting 10 UA (near circular orbit) from the sun they can be stable for billion of years. Simply because for each of them, this is extremely close to a 2 body system. ]

[Question] [ I have two planets and humans live on both of them. Humans need not have developed on these planets, but the planets should support human life with the allowance that the humans have technology comparable to modern day Earth. Planet A is roughly the size and climate of Earth, with a circular or near-circular orbit. Planet B can be a different size (probably smaller), and has the tricky orbit I can't quite picture. Is it possible that the two planets can orbit the same star such that: * Planet A and Planet B occasionally come very near to one another, but are usually distant * Planet B's climate is at least *reasonably* hospitable What would PlanetB's orbit have to look like for this to happen? Edit: This "nearness" should mean that casual (or crude) space travel becomes possible between them, like a trip. The planets would remain so close to one another for a short time (days or a couple weeks at most) and then not line up with each other again for 5-10 years. [Answer] You could put both planets in the habitable zone on horseshoe orbits. Janus and Epimetheus orbit Saturn on this type of orbit. From the point of view of one moon, the other follows a horseshoe shape around Saturn (or the star in your case). Most of the time they are relatively far away, but once every cycle the two planets come pretty close to each other and have a gravitational encounter -- close enough to have a pretty giant object in the sky for a short time. One planet's orbit gets a little closer to the star and the other's gets a little farther. Here is what it looks like for Janus and Epimetheus, from a frame of reference orbiting Saturn. (Keep in mind that they are both orbiting Saturn far faster than they make horseshoes) [](https://i.stack.imgur.com/m9a71.png) This is just one sort of peculiar form of the 1:1 orbital resonance. (For more see [here](https://planetplanet.net/2014/05/22/building-the-ultimate-solar-system-part-4-two-ninja-moves-moons-and-co-orbital-planets/), [here](https://planetplanet.net/2016/11/07/the-ultimate-trojan-2-star-planetary-system/) or or [here](https://planetplanet.net/2017/05/03/the-ultimate-engineered-solar-system/)). From the comments I'm seeing a lot of confusion about what this type of orbit actually looks like. Here is a nice animation comparing different reference frames: <https://youtu.be/gsHBE3DWCP4> And here are a couple more animations I found. This one shows that Janus and Epimetheus don't really change orbital distance all that much: <https://youtu.be/jIlTyFU4kUw>. The actual change is less than 1 part in 1000, so it would not have much of an effect on the climate. I suppose if you had a more extreme mass ratio between the two planets, then the smaller one could have larger excursion in orbital radius. And here is a really nice article on Janus and Epimetheus' orbits: <http://www.planetary.org/blogs/emily-lakdawalla/2006/janus-epimetheus-swap.html> [Answer] Well if you put planet B in planet A's L3 Lagrange point it would be on the opposite side of the star and pretty hidden and inaccessible. <https://en.wikipedia.org/wiki/Lagrangian_point> [](https://i.stack.imgur.com/S2lJx.png) This orbit is not stable over a long term, the planet would most likely drift in a so called horseshoe orbit, which would periodically bring the planets closer to one another. Several of Saturn's moons are in these types of complicated orbits of one another, the moons Epimetheus's and Janus are co-orbital with close approaches every four years (compared to their orbital period around Saturn of less than a day). <https://en.wikipedia.org/wiki/Horseshoe_orbit> [](https://i.stack.imgur.com/G40uP.jpg) This is very unlikely to occur naturally, but is theoretically possible. [Answer] *I'm actually surprised noone came up with this yet.* Make the two planet's orbital planes about adjacent, and add a bit of ellipticity to them: [](https://i.stack.imgur.com/nS2DY.jpg) **Pros:** * The planets barely meet each other - their orbital period can be made about the same, without the risk of collision. * Even when they're close, their relative speed is extremely high: they are moving adjacent. * Traveling between the two planet always needs very high delta-V, so it's technically very challenging, and has a really high energy cost. A slingshot maneuver is probably required, which takes a lot of time – years. * Story-telling-wise, it's really easy to explain: it's a much simpler concept that the Lagrangian orbits. **Cons:** * The system is somewhat unstable - except some special cases - as comments pointed out. While you didn't specify if you want one, this may be a problem if you do want a hard-science answer - otherwise you could just hand-wave it, possibly blaming some other planets' (unexplained) stabilizing effect. * Astronomically, it's really unlikely a locally born planet would earn such an off-plane orbit without a serious event. So, how on Earth (khm) could a planet end up with such an orbit? I see three options: 1. It's an alien planet: it **came from the outer space** billions of years ago, and got caught. It's more ancient than any other planet there - sounds like a cool plot point, with huge possibilities. ;) *Note: This needs some other, possibly gas-giant-sized planets in your system to interact with.* 2. The solar system experienced a **cataclysmic event** in the distant past: experienced an orbital system breakdown, got "hit" by a fast-moving black hole, encountered another solar system, etc., that highly disrupted the planetar orbits. This must've caused collisions and an extreme bombardment as well – so fill your system with asteroids and craters ;) 3. Even better - the planet got **caught from the other star system** causing the cataclysm above! This has all the advantage of (1) and sounds better and more feasible than (2), actually. (I'd imagine it's a bit hard to earn a 90° orbital plane shift from zero... but if the planet always had it... ) Maybe it's life was already developed at that time? An advanced civilization was destroyed in the cataclysm?... story points, story points everywhere... [Answer] Of all the solutions yet posted, I do not see any mention of expanding the habitable zone such that two planets with long, slightly-different orbital periods would both fit. This would require a very luminous star, I believe doubling the luminosity (average over wavelengths) would triple the distance to the inner and outer edges of the habitable zone. Our solar system has two planets (Uranus and Neptune) at 20 and 30 AU, which are in conjunction about once every **170 years**. To expand the habitable zone from it's current 0.7 AU to 1.5 AU boundaries, we need a star about 8-10 times as luminous as the sun. Assuming that the star is [the same colour](https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram) as the Sun that would be a class IV subgiant, which would be too short-lived for life to evolve on, but could theoretically support human life that arrives there for millions of years. These are not uncommon stars, so it is completely plausible that humans find and colonize one if they are out colonizing anyway. If you need to allow for longer or shorter periods between when transfer between the planets will be possible, then you can adjust for star brightness and change the size of the habitable zone accordingly. In the interest of realism, make sure that your chosen brightness falls in an area on the [Hertzsprung–Russell diagram](https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram) with the same colour as the Sun (above or below it on the diagram) in a relatively dense part (i.e. no Sun-coloured 100 luminosity stars). [Answer] I think an inclined orbit with similar orbital period with an offset of a half year would do it. You don't have much flexibility in orbital period and still be in the same habital zone of the star. That leaves inclination, eccentricity, and where in the orbit is the "new year point". Eccentricity is going to affect whether you're on the cold or hot edge of your habital zone. But not do much in terms of planetary distance from eachother. An orbital inclination will increase the distance between the objects by moving it out of plane, without changing the climate much. By having a high inclination on one planet (45 degrees) and zero on the other, and by offsetting their orbits a half year, the planets will vary between about a third orbit to a half orbit from each other. [Answer] Another approach: We need to make the system a binary star system, although the partner might not be hot enough to glow in the visible spectrum. The two planets are in resonance orbits with the binary partner which will go a long way towards making the system more stable. Both orbits are a bit elliptical. On your close approaches the outer world (at the inner point of it's orbit) zooms past the inner world (at the outer point of it's orbit)--while they are pretty close to each other in space orbital speed difference will be enough to ensure there's a single transit window between them at each encounter. While in general being close physically but far apart in speed is not considered close in space this is a special case as your target has an atmosphere--which means aerobraking. All you have to go is graze the world, you don't have to match velocities. The mission path is basically to get run over by the other world. Note that the binary partner will not protect moons--these worlds will have to be moonless as the close encounters will wreck havoc with their orbits. There's still no such thing as crude space travel, though. The energy requirements of a space mission are simply too high. It takes some pretty sophisticated engineering in order to get the energy density to go into space. Crude ships simply don't have the power density to make it. [Answer] The planets couldn't hold their orbit that nearly. Suppose you find an appropriate orbital arrangement. Putting *manned craft* (not just machines) on Low Earth Orbit with today's technology is getting cheaper, but it's still very expensive, and no one would call it crude nor casual except in *very* relative terms. For another planet to be more reachable, it would need to be nearer than the satellites in LEO and/or pass by much more slowly, with slowness being [much more important](https://what-if.xkcd.com/58/). When planets are near each other for extended time frames, their gravity affects each other. So they wouldn't hold their orbits. It's possible, pending calculation, that they couldn't even hold their structure, i.e. their roughly spherical form, with the other planet pulling the near side more strongly then the far side. [Answer] Stable orbits are not possible with large earth-like planets approaching very closely. Each planet will exert a gravitational attraction on the other which will be particularly strong at closest approach which will in turn modify the orbits of both. That said it might happen for a few million years as an unstable arrangement depending on how close “close” is. One configuration that would provide what you want would be for one planet to orbit close into the warm edge of the habitable zone and the other to have an elliptical orbit ranging from the inner edge of the habitable zone to the outer edge of the habitable zone. In this way occasionally the planets will be close together when they both happen to be at closest approach to the sun at the same time. However as mentioned above this orbit would be unstable in the long term. One key element you should consider is velocity. It’s all very well being in close proximity to your destination but if the destination proceeds to fly past you at several km/s you’re not going to be able to land there. ]

[Question] [ In my alternative history story, taking place at the end of the 20th century, one country has an army with platoons of airborne scouts. But unlike modern special forces they don't use combat knives as side-arms, but combat axes. Like this one: [](https://i.stack.imgur.com/8dZkM.jpg) So, question is: why do they use them instead of combat knives? Is there any advantage? My ideas are: 1. Traditions (maybe the ancestors of these soldiers were lumberjacks) 2. When you have to drop in forested areas an axe can be much more useful to chop wood, make shelters, including long-lived shooting points, or traversing young forest areas. 3. There was a [Soviet Union soldier who captured a Nazi tank using an axe during World War II](http://www.aif.ru/society/history/desert_iz_topora_kak_kashevar_sereda_vzyal_v_plen_nemeckiy_tank) I know that in close-quarter combat killing with a knife is usually faster; you can kill with a single well-placed jab, and an axe requires space to make a swing. An axe is also harder to conceal. But the main soldier's weapon is an automatic rifle, not a knife or axe. UPD: As Nex Terren mentioned, an axe, like a shovel, can be used as entrenching tool. Furthermore, Soviet Army used [small sapper shovels](https://en.wikipedia.org/wiki/MPL-50): > > Soviet Spetsnaz units had advanced training with the MPL-50, which > they mostly used not for entrenching, but for close quarters combat. > The spade is well balanced, which allows it to be used as a throwing > weapon. > > > So using axe not just as a tool but also as a last-chance melee and throwing weapon looks possible. [Answer] # Breaching I'm surprised no one has mentioned breaching. Urban combat is much more common than it used to be, especially with anti-insurgency suppression and targeted rescue/kill operations. An infantry company may all have to perform breaching or they may have a special unit for breaching, but in these scenarios an axe has much more utility and versatility as a tool than a knife. # Close Quarters Combat An axe also has more reach and requires less dexterity than a knife, which can be useful with less training where visibility is low and corners are common. It can also cause more damage with a glancing blow and can be reversed to cause the same puncture damage with less force due to levering action with the handle. # References Googling around, I was easily able to find references to axes as mechanical breaching tools, often used when explosives are overkill, too dangerous to use in enclosed spaces, or collateral material damage is unacceptable (like public spaces or inhabited buildings). For example, this is from a [US military Infantry Rifle Company handbook chapter on urban operations](https://rdl.train.army.mil/catalog-ws/view/100.ATSC/423B3CC4-3606-4E1B-86A6-F37C4BC792C3-1274572553978/3-21.10/chap12.htm): > > Explosive breaching includes using nonelectrical demolition systems; ballistic breaching includes using direct fire weapons; and mechanical breaching includes using crowbars, axes, saws, hooligan's tools, and sledgehammers. > > > There's also [more online on WWII Axes](http://quanonline.com/military/military_reference/american/wwii_edge/1944ax.php) > > The main role of an axe during WWII was to cut wood or material for things such as building a fire, building shelters, etc. > > > The [US Army Ranger Handbook](http://www.milsci.ucsb.edu/sites/secure.lsit.ucsb.edu.mili.d7/files/sitefiles/resources/Ranger%20Handbook.pdf) also mentions using hatchets as standard issue (tho headlines with a quote from 1759). > > Let the enemy come till he's almost close enough to touch, then let him have it and jump out and finish him up with > your hatchet. > > > Later it mentions a hatchet as in the Level 3 Survival Kit: > > Level 3 Kit (carried in assault pack or ruck) water proof container with more of the materials listed in the level 1 and 2 > kits plus shelter making materials (poncho, tarp, bungee cords, or space blanket) and a hatchet or saw. > > > [Answer] Combat knives *as side arms* are falling out of favor across modern militaries. Why? Getting into a situation in which your main rifle and sidearm *both* are no longer viable and effective *yet* the knife is effective is rare. Knives are typically provided as *tools* foremost instead of *weapons* now. To this end we can make an axe easily work. Sure we can leave the axe as a weapon (a last ditch effort), but first and foremost we'll focus on it being a tool. First we'll start out with the basis of an entrenching tool. [](https://i.stack.imgur.com/PW2Hr.jpg) These tools vary in form and function (the above image is just one possibility) allowing a variety of purposes: * Shovel * Saw * Mallet * Pick * Hoe * Prying Tool * Nail Puller * Paddle * Frying Pan ...To name a few. Well we can certainly adapt this to our needs. Obviously the tool pictured above centers around the idea of a shovel first and foremost. We just need to tweak it, and change the shovel head more into an axe head. Perhaps this is because these troops are deployed to forested regions, and not only do they sometimes have to clear trees and brush, but on-site basic fortifications made from trees are common, and so axes are useful. Toss in a dash of cultural ties to axes, as you mention, and it's really not that much of a stretch to say that the entrenching tools would be more axe-like, and obviously serve as last-ditch defensive tools. [Answer] This kind of axe, light as it is (the example is 2.1lb according to its Amazon.com sales page) is about twice the weight of a large knife. This may well be too light to be really effective as a woodcutting tool: things labelled "tactical" for sale to the public often aren't practical military equipment. Soldiers always have too much weight to carry, and justifying an extra pound of weight as standard equipment is only likely if there's a real expectation that it will be used. Real world infantry units do have axes, sometimes, but it's one per platoon or company as the normal scale of issue. Paratroopers need their equipment to be as light as possible, which makes the weight issue more pressing. Fighting in a wooded area would likely make a case for issuing more axes, but every man having one seems implausible. Incidentally, you don't drop paratroopers *into* woods. Far too many of them will get caught up in trees, take time to get down, and have additional accidents along the way. You drop them near the wood and let them move into it. So you need a positive reason to have axes, for which tradition will serve, and you need to make them as light as a knife. That's relatively easy if you make them out of [magnesium alloy](https://en.wikipedia.org/wiki/Magnesium#Alloy) with a steel insert for the edge, although the best magnesium alloy for the job may take some development. It needs calcium for reduced flammability, and manganese for reduced corrosion. You'll need some kind of plastic to bed the steel insert in the magnesium, to avoid corrosion, and you do want steel for that, because it holds an edge well. So these troops need a command structure that will pay out for additional expensive equipment for them, of dubious usefulness. Make them a long-established unit that's only recently taken up parachuting, and that will be OK. [Answer] In a word, symbolism. It's not as if combat knives are generally useful as weapons. In conventional war, if you're close enough that you have to use a knife rather than shooting the enemy, you know that things have gone irredemably tits up. Of course, soldiers do worry about this sort of situation, and there is something atavistically comforting about having a heavy piece of cold steel for just that sort of situation. With that said, your unit is airborne scouts. I'd suggest that (to use a US analogy) they symbolically trace their origins to an earlier unit such as Rogers' Rangers, who actually did use hatchets or tomahawks in battle, although this was the days of muzzle-loading muskets and a secondary weapon was a really good idea. See [here for a discussion of the unit orders](https://en.wikipedia.org/wiki/Robert_Rogers%27_28_%22Rules_of_Ranging%22) which specifically mention that every man should have both a hatchet and a gun. The units have adopted the hand axe as both a symbol of their roots and as a useful tool. Along the same lines, I refer you to "Mouthful of Rocks" by Jennings, who served several years in the French Foreigh Legion. He states that about the only non-issued equipment a legionnaire carried were his sunglasses and his combat knife - and the only thing a combat knife was used for was opening ration cans. A small minority of troops in Vietnam carried personally-owned tomahawks, and as far as I know got about the same amount of use out of them. With the adoption of the hand axe as a trademark unit weapon, some bright lad would undoubtedly come up with a reasonable fighting technique for using them. Certainly such a weapon would be more damaging than a knife, and probably useful in a full-out aggressive attack, where the backswing takes place out of range of the knife. There would be all sorts of disadvantages to missing the first strike, of course, but every style has its pros and cons, and military groups in particular tend to focus on the pros associated with their equipment and tactics. Plus, of course, they look bad-ass. And that can count for a lot among late-adolescent males. [Answer] These are TOMAHAWKS. There is a long tradition of 'hawks as combat tools as well as a lot of utility in a hatchet over a knife/saw (if you could only carry one). Current soldiers are using 'hawks more for the utility aspect, especially in urban warfare where they can be used to chop through cables, doors, and even thin walls (if only to make a hole large enough to peep/shoot through). Plus they can hook on top of a wall and help a soldier climb over. The major downside to a 'hawk is that it can not (easily) be attached to a rifle as a bayonet. Of course as the bayonet loses combat utility (mainly because rifles are now so small and fragile that they can not be used as a melee weapon anymore) the bayonet/combat knife falls from favor, a folding multi-tool with a knife blade is far more practical for most soldiers. If you want to entrench the 'hawk as a common piece of a soldier's kit, it simply needs a tradition. Perhaps the military unit extends from a warrior culture that heavily utilized axes or tomahawks (like the Ghurkas using kukri knives or Japanese soldiers with gunto katanas). The benefit to 'hawks over swords is that the hawk has relevant battlefield utility. As for the combat aspect, even the knife/bayonet gets pretty superficial treatment in basic training. The combatives training is more focused on unarmed techniques. So teaching use of the 'hawk can be as simple as a few basic moves, like a couple of strikes, some hooks, and some blocks. You don't need anything near like a dedicated martial art to justify issuing a melee weapon, current soldiers certainly don't get much training in the use of the bayonet (and I bet many never get them issued at all). [Answer] Most conventional infantry carry bayonets which are designed to have at least some utility as a medium sized knife (although with varying success). So although a small utility knife may be a useful addition carrying a large knife and a bayonet is a bit redundant. There is also a school of though that the main purpose of a bayonet is not so much for actually using so much as a visible statement of intent both for the troops using it and the enemy ie *'we are coming to get you...'* There is a notable exception in the Gurkha regiments of the british army who famously carry the kukri, a large knife which functions well in both utility and combat roles and is not very different from a hatchet in its handling and use. Also special forces soldiers, due to the nature of their role tend to have much more autonomy on their choice of weapons and are much less likely to have a need for a bayonet as they aren't so much about assaulting and taking ground as conventional infantry and in any case rarely have the numerical superiority to directly assault fixed positions. So in this context it is entirely reasonable that a particular special forces unit might decide that a hatchet represents a good balance between a utility tool and side arm. Although it is also worth saying that special forces are unlikely to dogmatically stick to one type of weapon and will tend to use what is most appropriate for the expected circumstances. In terms of pure practicality hatchets are often preferred in a woodland environment where timber, especially smallish trees and saplings are a useful and available resource (eg in the birch and pine forests of Scandinavia). The 'special forces' role also covers a huge amount of ground with different units in various armies having a huge range of roles. There are also increasingly specialist combined arms formations tasked with the job of supporting special forces operations with transport, logistics, communications, intelligence etc etc . Indeed the term 'Ranger' is often used for troops with a role somewhere between conventional infantry and true special forces. [Answer] As many have pointed out, yeah, axes as tools make a lot of sense. If warfare shifts and armament changes, the equipment ought to shift with it. If the targets shift enough, axes could become a reasonable weapon. When fighting targets that involve armor, an axe provides some advantages in popping the plates off or even punching through. These will generally be long-handled axes, especially if punching through. With lighter weight armors, though, speed would be more valuable. (In those situations, though, people tend to go with multiple weapons.) If combat gear has developed enough to make small arms fire less lethal, assault weapons may become large armor piercing rifles with axes as one of the only reasonable choices for melee. This goes farther, though: Straps and cables are easier to cut swiftly with an axe than a gun or knife, as a pretty fixed rule. If such strapping plays a role in warfare, you have a reason to bring an axe. If combatants rely on some piece of technology that's strapped down, well, there is a good reason to bring an axe. Consider if heavy bandoliers often carry useful intelligence (cryptokeys, personal shield generators, or whatever) or if infantry are often strapped to their rifles and/or combat frames. If sailing vessel or dirigible combat is expected, for example, axes become convenient. (or their sabotage, for that matter) You included one good reason in the question, actually, to have a serrated saw/axe tool on hand: They are airborn. Their chutes could get stuck in trees. A lower tech solution than a reliable emergency release would be an axe. They also might perform sabotage where chopping things loose quickly could help. Also, field axes could act as ice or rock climbing axes. (They'd have the holes to tie in to, in that case.) Several of these reasons would be specialized equipment for specific maneuvers rather than for standard gear, but if such come up a lot, well, they'd all train accordingly. [Answer] In the modern day military, I could definitively see axes making a comeback. First off, let's have a look at this knife:  It's a thing between an axe and a knife already. It has a multitude of uses too: It can open tinned food, it can chop trees (they don't grow very thick that far north), you can cut with it about as well as a normal knife (although not your first choice for fine knifework), and even if you wear out the edge a bit, and don't have a diamond tool ready for proper resharpening, it's heavy enough to get the job done with some extra force. These are *really* popular with Norwegian soldiers. Conscripted and contracted both. However, if you look at what Norwegians themselves wear on them when they go hiking, they still tend to prefer small knife + small axe. Why? Well, culture is one reason, and Norwegians have probably used axes more than knives for the stuff that they need to do around a camp, but there are other reasons. First off, an axe can be used as a hammer for tent poles, stuff that needs to be wedged in and similar. Secondly it's better at splitting wood, and as good at shaving it. (Not really sure what the English term would be. But you know how when you want to light a fire, you shave wood into shavings so that they have more air, and aren't as thick, and catch on fire easily? That's what I mean.) While not immediately as good at opening tinned cans of food, you can always use a tentplug or bayonet with the backside of the axe for that. So an army that spends a lot of time in the woods, either as long range recon troops, or light infantry, or similar would probably see the good reason in camping axes as tools. And as someone else above noted, if you're at the point where your rifle and pistol both doesn't work, it's not very likely that your knife or axe is going to do you much good. But if you already have an axe there? It makes sense to train them in how to use them, at least for a little bit. No point in drilling them for years, but the basics? That makes perfect sense. Oh yeah, you've probably seen these types of axes before, but here's the type I'd recognize:  Notice the bright orange there: It's so that you'll easily find it if you drop it. (EDIT: The previous image stopped working, so I changed it.) [Answer] You should equip your paratroopers rifles with bayonets that are removable, its not a sidearm but could be useful for many survival situations and cutting things like para cord loose. They could then carry the axe for a side arm but I would provide a sheath that covers the head because of the many dangers involved with parachute landings. On a side note, I wouldn't trade my K BAR for anything. [Answer] Edged weapons in modern armies are last ditch weapons. It's what you pull when your ammo is depleted and you've made your peace with this world. That said, edged weapons, particularly knives and hatches and even the venerable collapsible shovel are outstanding tools for infantry and specialist alike. But that's obvious and boring. Your military should carry them based on tradition; on some long gone era of mortal combat wherein your race excelled with the hatchet, tomohawk, battlewax, whatever. This tradition should be so ingrained in the culture - People of the 'hawk - that would-be warriors were tatooed with a stylized blade across shoulder and chest as a rite of passage. Their ancient enemies trembled at the rhythmic beating of 'hawks prior to battle knowing that all who fell would be beheaded and the heads left in a horrific mound alter in honor to the war gods. All passersby would know what happened and the outcome. While the 'hawk is a symbol of days long gone, your military still trains with brutal efficiency, preferring it for CQB operations over small caliber firearms, placing great prestige on the warriors most effective with the weapon. That sounds more fun to me. [Answer] My best guess: # Practicality If you're stranded from your unit / regiment, an axe is more useful than a knife: You can cut trees and collect wood easier; it will kill animals with greater ease; and is more intimidating, which can increase your odds in a fight. # However An axe is heavier than a knife, thus requires more energy, so carrying one around could prove detrimental. [Answer] If you are in a cold, icy region, an [ice axe](https://en.wikipedia.org/wiki/Ice_axe) would make sense as a commonly carried tool. They are primarily used for climbing on icy surfaces. While not really the intended purpose, they can be used as a weapon. All three of the [adze](https://en.wikipedia.org/wiki/Adze), the pick, and the spike at the bottom end of the shaft are sharp and dangerous. An ice axe might make sense for an airborne force if it frequently lands in places where the soldiers have to climb to reach their destination. It is of course up to you whether an ice axe would be an axe for your purposes. Technically speaking, they are generally adzes rather than axes. That may or may not matter for your story. [Answer] When you are in a combat situation, a knife is a weapon of last resort--mainly because in combat, knives absolutely suck. If you are in a situation where all other weapons are unavailable and you have to rely on a knife, you are in a charley-foxtrot of epic proportions. The only advantage of a knife is that it's somewhat better than no weapon at all. Knives are kind-of concealable and kind-of useful, but they are more useful as utility tools such as the entrenching tool @Nex Terren mentions. And to be blunt, if I were in a hand-to-hand situation and had to choose between a knife and the entrenching tool, I'd take the shovel. The big problem with the knife is it has very little or no *reach*. When you're in a hand-to-hand combat situation, you want to keep your opponent as far away from you as possible. Back on medieval times, the best way to do so was to use a spear or a pole-arm: that was your primary weapon, with a sword as a sidearm or secondary weapon. You prefer not to allow your opponent to get within reach of you, which means you definitely do not want to get within knife-fighting range. So using an axe can be explained as simple practicality. One other thing to mention--it's actually fairly difficult to kill someone with a knife unless they are unconscious or incompetent. Knives simply do not do as much damage as axes, swords, or spears, and despite what we are shown in movies and on TV, the human body is relatively resilient to knife wounds compared to other weapons. Go ahead and have your soldiers use combat axes as their hand-to-hand sidearms--they'll be a LOT beter off than with combat knives. [Answer] If your troops are in a mountainous area it might be a good idea to carry an ax for its utility. It could be used to gather wood, pointy side can help with climbing and it could be used as melee or throwing weapon. High utility is the keyword here. But that depends on the terrain. In jungle machete will have higher utility and in an urban setting, ax will not be very useful. [Answer] I know this is an alternate history story, but given that little is really specified as to how this is alternate history, I propose an answer that might actually sound quite... bizarre. First off, there is of course the usefulness of an axe over a knife. However, let's go a step further. I'm going to give a reason that they would use an axe as **a primary weapon**, which what I believe the asker intended. This could be given by several reasons: 1. **Guns have not developed in this world to a degree realistic with large scale wars.** We assume all other technology has remained the same. People are just incapable of developing long-range guns for some reason, so they resort to medieval-style weaponry of which the axe would be most useful for penetrating metal tanks and other massive machines as well as serving as a weapon used in combat. After all, what war have you heard of fought 100% entirely with pocket knives? It's absurd. 2. **Bullet-proofing technology has advanced to the point that no known bullet can pierce it.** This is a pretty obvious case. Essentially, people focused more on bodily protection than on other things. Hence, there is full body armor in this universe that is lightweight and impenetrable to bullets. Bullets might pierce it, but it takes many round to break through and so guns are simply impracticable. Hence, the armor-piercing axe takes the reigns in breaking down the enemy. A gun might still be carried to finish off an opponent whose armor is too far gone to protect them, or is stupid enough to take it off in the heat of battle. 3. **The enemy must be beat without them knowing you are there.** Weirdly enough, this could make sense. Trees falling, random building sabotage, etc. could all be done with an axe. Guns might attract attention. 4. **There is an extreme gun powder shortage.** Whether it is due to economics, a loss of natural resources, or a lack of factories to produce it, it is pretty hard to make bullets without any gunpowder. Why they swapped to axes is beyond me. Maybe they found it... convenient? And finally the answer I referred to as 'bizarre': 5. **Simply put, your world considers killing another man in war to be murder.** I know this is weird, but bear with me. What if the world was still ruled primarily by Christianity or some other religion (make one up if you have to) that considered killing another in warfare to be a crime. However, leaders twisted this to mean that you cannot *directly* kill another man in war. Hence, wars in this world consist of trap-setting and various other means of causing someone to simply... kill themselves. In this manner, an axe would serve as an amazing tool. It can set trees up to fall and sabotage buildings both of which I'd imagine would be major elements of this "no-kill warfare". Heck, I can even imagine people falling for their own traps in cases of mines, pitfalls, and other things. It's easy to fall for a trap even if you know of it, but much harder to get stuck in the enemy building's collapse, or a tree falling on enemy patrols chasing after you trying to incapacitate you with stun guns. This would also work well for executions, as a simple manner of execution (after all, it's not legal to execute) would be to drop the roof on the criminal... by knocking the supports of a simple hut out with an axe. [Answer] During world War two there was a certain tribe of native Americans serving in the US military that went into the Belgian city of Chimay armed with only tomahawks. The US military were pretty concerned that this tribe did not want firearms so they usually placed them with other soldiers. These native Americans proved far more effective than firearm wielding soldiers because tomahawk are a silent edged weapon that had enough shock to instantly silence the target, unlike throwing knives. So they might use the Chimay axe as a silent edged weapon. ]

[Question] [ In my alternate reality, Earth is not a planet. It is a moon and orbits a gas giant (however it has all of Earth's characteristics, it is also full of humans and life as we know it). This is the **only** moon the gas giant has. This alternate Earth is tidally locked. This means that the people who live on the "outer" side of the moon have never seen the planet they orbit. And here comes the question: Assuming Astronomy develops as it did on our Earth. **When will they be able to discover they don´t rotate around the sun alone?** When I say "when" I am asking which stage of astronomical development. Could Galileo and Copernicus have noticed that? Ptolomeo, perhaps? Or maybe the Greek astronomer Aristarco de Samos (310-230 BC) could have noticed that with his observations of the sky? (No, these are not multiple questions. I am just explaining the type of answer I am looking for). Of course, as I said before, I am assuming all these inhabitants of the continent on the "outer" side of the Earthly moon have never navigated to the other side of their moon, so they have never seen the big gas giant in the sky. [Answer] I think astronomy should advance to the level of Johannes Kepler (early XVII century) to correctly theorize the presence of a host planet. In the eyes of early astronomers (like Ptolemy), the world would be still Earth-centric. The only odd thing would be a minor parallax caused by orbital movement. Without any scientifically sound theory of planetary movement, this parallax would be likely explained as a feature of celestial movement. Copernicus would have every reason to put the sun to the center of the universe and even propose a correct explanation that the parallax is caused by Earth's own movements - but he would have no mechanism to explain these movements themselves. He may theorize presence of the host planet, but this theory would have no way of being proved. It would take a telescope and accurate observation of another planets to suggest that the most plausible explanation of planet's own movement is the presence of a massive host planet. [Answer] Unless all the land mass on the tidally locked moon is on the side *facing away from the gas giant*, the humans will discover they're orbiting a gas giant during the stone age: [](https://i.stack.imgur.com/3BwyW.jpg) If the land mass is indeed concentrated on the far side of the moon only, they will discover it a bit later, maybe as early as [prehistory](https://en.wikipedia.org/wiki/Ancient_maritime_history#Maritime_prehistory) but certainly no later than the invention of the [lateen sail](https://en.wikipedia.org/wiki/Lateen_sail) during Roman times... [Source for map](https://history.stackexchange.com/questions/30758/why-is-there-a-gap-of-information-in-russia-for-human-migration) [Answer] I think @Alexander 's answer is good but not entirely correct. Consider the gas giant's axial tilt. Gas giants tend to rotate rapidly due to conservation of angular momentum and the collapse of an enormous volume into a comparatively tiny size of the gas giant planet. That rotation, which would draw the Moon over the gas giant's equator makes the Axial tilt important. Jupiter has a 3 degree Axial Tilt, Saturn has 25 degrees tilt, and Uranus has 98 degrees tilt - basically flipped on it's side. Due to the gas giant's rotation and equatorial bulge, it's likely that the planet-moon would orbit around the gas giant's equator. That means that the Axial tilt of the gas giant would affect the movement of the moon above and below the gas giant's ecliptic. For the stars, this wouldn't make much difference, but the other planets and Sun would observably move up and down in a sine wave pattern. Against the fixed stars, this would be noticeable against the fixed stars (hmm, Mars was in a different place relative to that star last time around), but probably explained by additional [epicycles](https://en.wikipedia.org/wiki/Deferent_and_epicycle) early-on, similar to the Ptolemaic models that were the standard for over 1,500 years. It's worth noting that [Aristarchus](https://en.wikipedia.org/wiki/Aristarchus_of_Samos) and his early heliocentric model was based on observing Earth's shadow on the Moon and that would no longer be an option, so a version of the Ptolemaic model is highly likely for your scenario. So, it matters how much your planet-moon moves above and below the ecliptic because that would be observable relative to the other planets and the position of the Sun at Sunrise and Sunset. Even if the movement was less than 1 degree, it would be measurable with equipment and buildings like the Mayans had. If the gas giant's axial tilt is zero, then the planet-moon simply moves closer and further from the Sun as it orbits the gas giant. That would cause the observed other planet's motions to not move at Keplerian predicted velocity but wouldn't move them up and down. Up and Down movement would be probably be tied to epicycles up and down from the ecliptic, but it might not be too long before somebody says, "wait, instead of all these circles, if the Earth moves, that would explain everything", and then they get persecuted by the church and all that good stuff. If the gas giant has close to zero eccentricity, then everything becomes much harder. Kepler was only able to do what he did, using both very careful observations over many years and the best astronomical observation equipment ever made, because the Earth returns to the same spot relative to the Sun every year. Having a fixed observation point makes triangulation possible and Kepler relied on triangulation to work out his formulas. If you have the planet-moon moving around a gas giant in a tidally locked orbit, you lose that "fixed" position at the same date every year unless the Planet-Moon's orbit around the gas giant and the gas giant's orbit around the Sun are neatly divisible, which is unlikely. Now if the planet is very close to the Moon, it's movement becomes smaller and maybe this problem goes away. If it's a significant variation in distance, then that would makes Kepler's work more difficult. If you lose the fixed position you can't perform triangulation, or, you need to wait several years for a relatively equal position and you'd need to know how many years to wait. That makes Kepler's calculations much harder and I'm not sure he pulls it off. And without Kepler, Newton might still work out Calculus, but it's unclear if he works out orbits, which wouldn't make sense based on observation. Worst case, I would guess that they'd need advanced telescopes to begin to observe objects passing into the shadow of the gas giant (that's funny, I was tracking that object and it vanished), and circumnavigation would almost certainly precede that. It might take a mathematician of the skill of Laplace to work out the specifics from observations of the night sky because your scenario could be quite a bit more complicated. (IMHO). [Answer] There's a factor you haven't considered: what size is the primary, and how far from the primary does pseudo-Earth orbit? For why this matters, consider a primary the size of Jupiter. Let's say pseudo-Earth orbits at the distance of Ganymede, at 1 million km. At that distance, the Jupiter-sized primary would span roughly 7.5 degrees of the sky (the Moon spans about 0.5 degrees). This means that the primary would be visible for more than half the planet; you wouldn't see it all, but you'd see something freaking big in the sky on the horizon. At a rough approximation, ignoring diffraction and such, you'd see at least part of it from -97 to +97 degrees of longitude (where 0 is directly "below" the primary), and a similar amount past the poles. If it has all of Earth's characteristics, including the geography and orientation, and the primary is in the best possible position on the equator to get maximum distance from the major landmasses, in the central Pacific, (at roughly 145 W on our Earth), then it would be visible anywhere from about 48 West in the Americas to 118 East in Asia. That means it's visible in Central America--in fact, they'd see all of it, and Mayans knew astronomy. It would be seen from eastern China, Korea, and Japan...the Chinese also having pretty good astronomers. During the Yuan Dynasty (ie, the Mongol Empire), Chinese astronomers collaborated with Islamic astronomers, which means Chinese observations of that big thing in the sky would have been available to people in Europe by the 13th century, and the space accessible to the Chinese (from Eastern China to Japan) would have clearly shown that it was a disk-like or spherical object as they'd be able to see it rising as they moved eastward. They might, in fact, have been inspired to send expeditions out even further to get more observations. Obviously this changes depending on size of the primary and distance from it, but direct observation might not have been as difficult as you assume. [Answer] Not very long at all. Here is a picture of what Jupiter would look like if it was just over 385,000km away. [](https://i.stack.imgur.com/Lb6iQ.jpg) Reference:<https://twistedsifter.com/2012/07/picture-of-the-day-if-jupiter-was-the-same-distance-as-the-moon/> Here is the list of moons of Jupiter and their distances: <https://web.pa.msu.edu/people/horvatin/Astronomy_Facts/planet_pages/Jupiters_moons.htm> You will notice that the closest moon is the same distance roughly as our moon; and the next furthest is only double the distance. This means that depending on the orbit, it would be really, really hard to not notice the other body. You'd have to do the same research into the orbital mechanics; but given this sort of work was done in the BC period to a reasonable degree of accuracy; and the size of this thing in the sky clearly dwarfs the sun; I suspect that the research into the planets would start with the massive thing that blocks the sun half the time rather than the sun. [Answer] There have been other questions about habitable moons, and you should read them for other information about hypothetical habitable moons. This one, for example: [Characteristics of a habitable satellite planet](https://worldbuilding.stackexchange.com/questions/125481/characteristics-of-a-habitable-satellite-planet/125483#125483)[1](https://worldbuilding.stackexchange.com/questions/125481/characteristics-of-a-habitable-satellite-planet/125483#125483) I have answered enough such questions that I have got in the habit of referring to my previous answers. My answer to this question: [What should the size of my moons be?](https://worldbuilding.stackexchange.com/questions/119481/what-should-the-size-of-my-moons-be/119508#119508) [2](https://worldbuilding.stackexchange.com/questions/119481/what-should-the-size-of-my-moons-be/119508#119508) points out that its is considered impossible for a moon to have a month that is the same length as the year of the planet it orbits. A moon's orbit wouldn't be stable unless it orbited the planet at least 9 times during one orbit of the planet around their sun. If a moon orbits a planet, it should have either a normal rotation period or else have a locked rotation period, so that one side of the moon would always face the planet and one side would always face away from the planet. If the moon has a normal rotation period, the planet it orbits will be visible for half of every day from almost every part of the moon. If the moon is tidally locked, the natives of the outer or far side of the moon will never see the planet in their skies and will never directly observe it from their side of the moon. They can only hear about it from natives of the near side or see it themselves when they explore the near side of their moon. This reminds me of the James Blish story "Get Out of My Sky" (1960) and the Poul Anderson story "The Longest Voyage" (1960). <http://www.isfdb.org/cgi-bin/title.cgi?97951> [3](http://www.isfdb.org/cgi-bin/title.cgi?97951) <http://www.isfdb.org/cgi-bin/title.cgi?5356>[4](http://www.isfdb.org/cgi-bin/title.cgi?5356) Because of atmospheric refraction of light and libration effects the planet will be visible from some parts of the far side that are close to the line between the far and near sides. So your far side natives should be limited to only part of the far side of their moon so they will never see their primary planet. One suggestion would be that there should be a giant impact feature on the far side of the moon from the planet with alternating rings of flat plains and high ring wall mountains. There can be a central mountain range surrounded by higher and dry plains surrounded by lower plains covered by water in a ring shaped ocean surrounded by a circle of land with high mountains in the spine of the circle of land, surrounded by a ring shaped ocean surrounded by a ring of land, and so on. The central body of land should be like a small continent in size, large enough for a large civilization to arise on the central continent and on the flatter parts of the ring shaped continent of land beyond the ring shaped ocean around the central continent. The immediate ring shaped continent beyond the ring shaped ocean should have a ring shaped spine of central mountains running all the way around, and they should be high enough for most of the passes to be covered in glaciers all year round. So almost nobody has ever crossed those mountains from one side of the mountains to the other side. As far as people on the inner side of the ring shaped continent - and those on the innermost continent - know the ring shaped glaciated mountain chain could be at the edge of a presumably flat, disc shaped world. They might believe the gods built the ring mountains to keep air and water from falling off the edge of the world. And possibly any farther out ring shaped continents may also have mountain rings tall enough to be glaciated all year and impassable. And so the civilizations at the center of the giant impact feature might never have heard anything about the giant planet that is always visible on the other side of their moon. As said above there should be at least nine month/days when the moon orbits the planet for each year of the planet as it orbits around the sun and possibly tens or hundreds of month/days per year. The gas giant planet the habitable moon orbits should have an axial tilt, and tidal forces will have regularized the habitable moon's orbit so that the moon's axial tilt will be almost exactly the same as the planet's and so that the moon's orbital plane will be almost exactly in the equatorial plane of the planet. So the moon will share the axial tilt of the planet, and the lower the axial tilt is the less noticeable the seasons will be on the habitable moon, and the higher the axial tilt the more noticeable the seasons will be on the habitable moon. So the natives of the habitable moon should notice seasons which are better or worse to some degree for hunting, fishing, food gathering, planting, and harvesting cops. And thus they will keep track of time and develop calendars and observational astronomy to keep track of and predict the passage of time and the seasons. And the natives will also keep track of their days and nights, which of course will be each be about one half of an orbital period around the primary planet. The natives on the near side will see the gas giant planet and may assume for many thousands of years that it - along with their sun and other planets - orbits their moon before they eventually become advanced enough to realize that all the planets orbit their sun and that they are on a moon orbiting the gas giant planet. And the natives of the far side of the moon wouldn't see the planet or know it was there, but will eventually be able to discover that the planets in their solar system orbit around their sun, and that their moon seems to be one of those planets. And then they might discover that there are so many problems with the orbit of their "planet" that making it a moon orbiting a planet that can't be seen from their side is the simplest explanation. As we all know, every night at midnight the stars that are on a line across the sky from north to south are at the opposite side of Earth - and/or of the hypothetical celestial sphere that for thousands of years they were supposed to be attached to - from the Sun. On Earth a sidereal year is the time it takes the Earth to make a complete orbit of the Sun as measured against the stars. It is 365.256 days. In an average sidereal year the Earth travels about 1.0146 degrees along its orbit around the Sun. A stellar day is the time it takes Earth to rotate 360 degrees with respect to the stars. So each day at midnight the stars appear to have moved about 1.0146 degrees from their positions the previous midnight, and over the course of a year the midnight line will appear to move 360 degrees around the celestial sphere to its original position. But the natives will originally discover what are called tropical years and solar days. Because the Earth moves along its orbit during a sidereal day, at the end of a sidereal day the direction that used to point to the Sun is now pointing about 1.0146 degrees away from the Sun. A stellar day is the time period when the Earth turns 360 degrees relative to the Sun. And a tropical year is the time period for a complete cycle of the seasons, and is about 365.242 days long. Suppose that it took exactly 450 month/days of the habitable moon for the planet to orbit its sun. Each month/day the midnight line would point 0.8 degrees off of where it pointed the previous midnight. Suppose that it took exactly 90 month/days of the habitable moon for the planet to orbit its sun. Each month/day the midnight line would point 4 degrees off of where it pointed the previous midnight. Suppose that it took exactly 9 month/days of the habitable moon for the planet to orbit its sun. That is about the least possible number of month/days for the planet to orbit its sun. Each month/day the midnight line would point 40 degrees off of where it pointed the previous midnight. Of course the year of the planet wouldn't be evenly divisible by the month/day of the habitable moon. Obviously the fewer month/days of the habitable moon there are in a year of the giant planet, the more noticeable will be the differences between sidereal and tropical years, and between stellar days and solar days. And the more month/days of the habitable moon that there are in a year of the giant planet, the less noticeable will those differences be. In our solar system, and in any solar system like ours, the distances between the planetary orbits will be so great that every planet will look like a dot of light when seen with the naked eye from another planet even at their closest approaches. But when telescopes are invented (first used for astronomical observations from Earth in 1609) and used for astronomical observations some of the planets should show discs in the telescopic views, and thus their phases should be observable. The differences between the phase cycles of inner and outer planets should provide strong evidence in favor of a theory that the planets orbit around their stars. All four of the Galilean moons of Jupiter are bright enough to theoretically be seen with the naked eye from Earth. When Jupiter and Earth are closest, their apparent magnitudes range from 4.6 to 5.6. But their angular separation from Jupiter never gets to be more than about the absolute minimum angle that the human eye can see, so they appear as part of the same dot of light as Jupiter. Even cheap binoculars of the present time are superior to the early telescopes which discovered the Galilean moons of Jupiter that were discovered in December, 1609 or January, 1610. The discovery of the Galilean satellites clearly seen to orbit Jupiter showed that astronomical objects could orbit around other astronomical objects that were not the earth, and was a strong argument in favor of the heliocentric theory. Since your fictional star system is different from our solar system in some ways - since it has a gas giant planet with a giant habitable moon orbiting in its habitable zone - it could be different from our solar system in other ways, including the relative and absolute spacing of the planets. Many exoplanets and systems of exoplanets have been discovered, so it is known that the majority of star systems are greatly different from ours in various ways. For example, CVSO 30 has the widest spacing, in both absolute and relative terms, between two consecutive (known) planets of a star. CVSO 30 c is about 78,998 times as far from their star CVSO 30 as CVSO 30 b is, or about 662 Astronomical Units (or AU) - an AU is the distance from Earth to the Sun. <https://en.wikipedia.org/wiki/List_of_exoplanet_extremes>[5](https://en.wikipedia.org/wiki/List_of_exoplanet_extremes) If the nearest planet to your habitable moon and its giant planet orbits hundreds of AU farther away from their star, it may appear like a mere dot of light in early telescopes, and later and better telescopes, and still later and better telescopes, and so on. It might not be seen as a disc with phases until 20th century telescopes or 21st century telescopes are invented. And similarly it may not be possible to see moons orbiting such a distant planet, supporting a theory that the planets orbit around their star, until 20th century or 21st century telescopes are invented. And on the other hand, in some star systems exoplanets orbit many times closer together than any planets in our solar system. The smallest absolute difference between the orbits of two consecutive planets is between Kepler-70b and Kepler-70c. It is 0.0016 AU or about 240,000 kilometers. > > During closest approach, Kepler-70c would appear 5 times the size of the Moon in Kepler-70b's sky. > > > <https://en.wikipedia.org/wiki/List_of_exoplanet_extremes>[5](https://en.wikipedia.org/wiki/List_of_exoplanet_extremes) <https://en.wikipedia.org/wiki/Kepler-70>[6](https://en.wikipedia.org/wiki/Kepler-70) Note that there are reports of an unconfirmed planet orbiting between the orbits of Kepler-70b and Kepler-70c! The Kepler-36 system has the smallest known relative difference between the orbits of two consecutive planets. Kepler-36c is believed to have an orbit only 11 percent wider than that of Kepler-36b. > > Kepler-36b and c have semi-major axes of 0.1153 AU and 0.1283 AU respectively, c is 11% further from star than b. > > > <https://en.wikipedia.org/wiki/List_of_exoplanet_extremes>[5](https://en.wikipedia.org/wiki/List_of_exoplanet_extremes) <https://en.wikipedia.org/wiki/Kepler-36>[7](https://en.wikipedia.org/wiki/Kepler-36) The potentially habitable planets in the habitable zone of TRAPPIST-1 also orbit quite close to each other. > > The system is very flat and compact. All seven of TRAPPIST-1's planets orbit much closer than Mercury orbits the Sun. Except for TRAPPIST-1b, they orbit farther than the Galilean satellites do around Jupiter,[42] but closer than most of the other moons of Jupiter. The distance between the orbits of TRAPPIST-1b and TRAPPIST-1c is only 1.6 times the distance between the Earth and the Moon. The planets should appear prominently in each other's skies, in some cases appearing several times larger than the Moon appears from Earth.[41] A year on the closest planet passes in only 1.5 Earth days, while the seventh planet's year passes in only 18.8 days.[38][34] > > > <https://en.wikipedia.org/wiki/TRAPPIST-1>[8](https://en.wikipedia.org/wiki/TRAPPIST-1) Thus it is possible for some solar systems to have planets so close that they sometimes or always have visible discs as seen with the naked eye from the surfaces of some or all other planets in that system. If planets are close enough to show visible discs with the naked eye, their phases can be seen with the naked eye, and the naked eye can tell the difference between the phases of inner planets and outer planets, thus forming strong evidence for a theory that the planets orbit around their star instead of the star and planets orbiting round the habitable moon. In our solar system, some people allegedly have seen phases of Venus with the naked eye: > > The extreme crescent phase of Venus can be seen without a telescope by those with exceptionally acute eyesight, at the limit of human perception. The angular resolution of the naked eye is about 1 minute of arc. The apparent disk of Venus' extreme crescent measures between 60.2 and 66 seconds of arc,[4](http://www.isfdb.org/cgi-bin/title.cgi?5356) depending on the distance from Earth. Nevertheless it is possible for observers with extremely acute eyesight to see a crescent Venus under ideal atmospheric circumstances. > > > There have been numerous reports stating such observations. The phases of Venus are alleged to have been seen in Mesopotamian times by priest-astronomers. Ishtar (Venus) is described in cuneiform text as having horns.[1](https://worldbuilding.stackexchange.com/questions/125481/characteristics-of-a-habitable-satellite-planet/125483#125483) However, other Mesopotamian deities were depicted with horns, so the phrase could have been simply a symbol of divinity. > > > <https://en.wikipedia.org/wiki/Phases_of_Venus#Naked_eye_observations>[9](https://en.wikipedia.org/wiki/Phases_of_Venus#Naked_eye_observations) So in a solar system where planets were a little closer together than in ours people might be able to see the crescent phase of the next innermost planet with the naked eye. And if the planets were much closer together they might be able to see all the phases of that planet with the naked eye. And if in some solar systems planets can get close enough to show visible discs and phases to the naked eye, in some solar systems planets might get close enough to see moons orbiting those planets with the naked eye, which would be a strong argument in favor of a theory that the planets orbit their star. It may be noted that it is possible that some humans have seen one or more of the moons of Jupiter with the naked eye. <http://www.denisdutton.com/jupiter_moons.htm> [10](http://www.denisdutton.com/jupiter_moons.htm) Clearly if Jupiter could get half as far, or a quarter as far, as it actually gets, it might be possible to see the Galilean satellites regularly enough with the naked eye to plot their obits around Jupiter. If Jupiter could get much closer than that it would be even easier to see the orbits of the Galilean moons. So the structure of your fictional star system will determine how advanced the natives of the far side of your moon have to be in order to discover that their world orbits around a point in space that orbits around their star, and that there should be an astronomical body at that point in space, a point in space and astronomical body that their side of the moon is always turned away from. [Answer] **Somewhere around Galileo's time seems most accurate, but in some cases it could take as late as the early 19th century technology.** The first question that would have to be answered is when they decided that the sun doesn't revolve around them. As motion is relative, both "the sun revolves around us" and "we revolve around the sun" are equivalent until you consider the movement of other planets (which move through the sky in complex shapes). So the lower bound for when they realize they are a moon has to be when they can observe the other planets and realize they don't revolve around you. The parallax caused by rotation around the gas giant is going to be minor, compared to the distance to other planets. It will be *much* harder to notice. Or will it? Unstated is how far the moon is from the planet. If it's the same distance as the Earth to the Moon (0.3 Mm), the parallax of Mars from one side of the orbit to the other would be about 19 arc-minutes. This was measurable by Galileo, so that's an upper bound. Some of his measurements against mars were detecting movements of 5-6 arc-minutes, so he had the technology. On the other hand, if the moon is as far as Neso, Neptune's farthest moon, its much more obvious. Neso is a mighty 48,000 Mm away from Neptune, and that will peak at 72,000 Mm at its apocenter. That's a *long* distance. It's larger than the apihelion of mercury -- meaning at its furthest from Neptune, it's further from Neptune than mercury is from the sun! That'll get noticed much faster! But the real question is why they have't explored their moon. As we've seen in other answers, humans explored rather quickly. They would find stories of their gas giant dominating the sky rather quickly. If they *don't* have this, the fun question is why. Why didn't they do the obvious thing? Why did they develop arc-minute accuracy telescopes before they learned to walk around their own planet? Perhaps the answer is that there are dangerous aliens on the far side of the moon that eat any adventurers who get close to seeing the gas giant. If so, that other species would be a dominating factor in the development of the culture of our race. Everything would be based around dealing with these aliens. In which case, Galileo might not find it worth his time to stare at the stars. You might develop a pretty spectacular level of technology when facing half a planet dominated by a species that eats you. In this case, the reality of our skies may not become apparent until the development of modern artillery. WWII artillery could be aimed within 5 arc-minutes, so all it would take is one curious guy pointing his gun-sights at the stars to start collecting the data that shows you are not alone. [Answer] # How far is your Earth-moon from the planet? Let us assume that the Earth-moon is the same distance from the planet that Callisto is from Jupiter. Callisto's semi-major axis is 1.9 million km relative to Jupiter. Assuming that the Sun is still the same, and the Earth-moon is in the same habitable zone, then the distance to the sun is 150 million km. The diameter of the Earth-moon's orbit around the gas giant is twice the semi-major axis. This forms an isosceles triangle with a vertex angle of 0.025 radians; or 1.4 degrees. Detecting this angle is well within the capabilities of ancient astronomers (as in Babylonian/Chinese/Indian). Furthermore, in this case, there is a 2.5% variation in distance from the sun with various orbital positions around the gas giant. This corresponds to a 4.9% drop in luminosity of the sun from nearest to farthest point. This too would be readily observable to the ancients...as far back as the Paleolithic, I would think. If you don't want the Earth-moon so far from the gas giant, then these numbers are reduced. At the distance of Ganymede, this becomes 0.014 radians and 2.8% luminosity, both still noticeable. At the distance of Io, this becomes 0.005 (only 20 minutes of arc) and 1.1 % luminosity. I'd have to do more research on ancient instruments to see how noticeable this is; but it is at least plausible that both would be noticed. Once first detected, many would devise experiments to calculate more carefully, so I think both differences would be detected, even if the Earth-moon were very close to the gas giant. # Observation of these distances So the ancients would *know* from observation that neither "Earth-moon orbits the Sun" or "Sun orbits the Earth-moon" is a true statement. The odd rotation of the Earth-moon around the sun is what the Greeks called an [epicycle](https://en.wikipedia.org/wiki/Deferent_and_epicycle). The Hellenistic era Greeks explained the apparent retrograde motion of the planets in the sky by a system of epicycles. If they were able to apply this concept to something that does not exist in reality, then we could assume that by 300 BC, Greek astronomy would know that the motion of the Earth-moon was in orbit around something, and that something was in turn orbiting the sun. As far as travel to the far side of the planet to see the gas giant first hand, that is more a matter of exploring. But one whisper of such and explanation would quickly establish itself, as the most reasonable explanation for why the Earth-moon is apparently orbiting a random point in space. # Conclusion * The ancient astronomers would know that neither the Earth-moon orbits the sun, nor the sun orbits the Earth-moon because of discrepancies in rotation rate and changes in luminosity of the sun. * By the time of the ancient Greeks, this apparent observations could be (accurately) explained by the existing theory of epicycles. * By the time the first explorer got to the opposite side of the world and saw the gas giant, looming enormous in the sky, the cause of the epicycles would be fully explained. * How long this exploration would take is up to you and the orientation of planets. If Eart's Old World lay in the away-facing hemisphere; Irish or Japanese fishermen in the Atlantic or Pacific would have seen the gas giant in antiquity. [Answer] Your inhabitants could be able to detect that something's amiss long before they can travel far enough to see the planet. Simple night-time observations would clue them in that there's *something* behind them, even if they can't tell that it's a planet. In your setup, the planet is significantly larger than the moon. Large enough, in fact, to be able to completely eclipse the sun. You wouldn't see the eclipse directly since it would only occur at night, but you *would* be able to detect that you were passing through the eclipse's umbra. Space objects passing nearby (meteors, etc) in the middle of the night would seem to disappear as they passed through the umbra and no longer had any sunlight to reflect off of them. They could be detected when they obscure distant stars, but they would not be directly visible again until they came out the other side of the planet's shadow. An ancient astronomer could observe this phenomenon, make some rough measurements of where the objects disappear and reappear in the sky, and use a crude scale model to show that the "dark spot in the sky" was far too large to be their world's shadow. Something else must be behind them casting a shadow, something that's *much* larger. [Answer] They might never find out, they might never even see the sky. If the planet has a thick, permanent cloud cover, the sky may well be something the inhabitants of the moon never experience through the murky gloom in which they live. If the atmosphere is violent enough they may never manage to build a craft that can lift them above that cloud cover. There'd be no need for weird geographical layouts preventing them from traveling to the side of the moon facing the planet. And if they can't see the sky, they probably won't ever even consider there's anything beyond the clouds, thus never consider building rockets to pierce them and see what lies beyond. [Answer] Consider two different scenarios: 1. The moon is the center of the universe. The planet orbits around the moon. The sun orbits around the planet. Lots of other moons orbit around the planet. Lots of other planets orbit around the sun, with their own moons. 2. The sun is the center of the universe. The planet orbits around the sun, just like other planets and some junk. The moon orbits around planet, just like other moons. One could go quite far with the first option, building an ever more complicated model of the celestial spheres. What makes the second option "more scientific" is that it needs fewer special cases, and that it groups like with like. **All** planets orbit around the sun, and so on. *Note that both models are equally wrong, but one can go quite far with the [helicentric](https://en.wikipedia.org/wiki/Heliocentrism) model.* ]

[Question] [ The evil enemy has us surrounded. They outnumber our forces, they have us outgunned. These helldogs have a trillion dollars/year for their war budget, and they can afford the fanciest toys, numerous mercenaries, the most advanced munitions, have overwhelming air supremacy, and are backed up by years of research and training. They are unlikely to show much restraint (save for not using nuclear weapons, we think their populist leader is allergic to them). We have the city of Lusom, population 3 million. We have close to 300,000 fighters in the city, and overwhelming support from the population (or at least that's what we think, it's not like we're holding elections, haha). We are absolutely ruthless about crushing dissent, and our troops are fantastically committed. No civilians will get out. We have also had years to prepare, execute spies, dig in, fortify, amass supplies of all kinds. The vile enemy has one (critical) weakness: a fickle public opinion. If we can but hold out for maybe two years, or cause upwards of 10,000 enemy casualties, we can probably get them to back off and run home. That triumph would cause the political situation around Lusom to change dramatically, as the demoralized allies of the evil enemy will surely collapse like a wet napkin without the big dog backing them. **How do we make sure we can hold out in Lusom for 700 days?** [Answer] **Tunnels. Tunnels under tunnels, under tunnels, under tunnels.** You can never have enough tunnels. And they're so handy. You can keep your water, gas masks, food, ammunition, anti-tank weapons, missiles, sleeping quarters, dig out behind enemy lines and attack them from the rear. Tunnels are great! Tunnels are awesome. Tunnels can have heavy doors to limit blast damage. Tunnels can be built in networks, so you can work around damaged sections while they're being fixed. Lusom has been one of the world's busiest reinforced concrete consumers in the world in the past few years (and we take construction quality seriously enough to execute contractors who skimp on the irons). Moreover, our long-tunnels are extending many kilometers outside the city to disguised single-use exits, so we can effectively bring supplies in or launch attacks out of nowhere at enemy concentrations from behind their lines. Mortars, and, uh, man-guided bombs will be launched at the enemy when they least expect. Cleared neighborhoods will suddenly have enemy fighters again. **Victims.** There is a tunnel entrance/exit under every hospital, creche, school and kindergarten. They're covered in teddy-bears, dolls and there are at least 3 hello kitty-tshirt-bearing young girls standing by every entrance. We have emergency generators everywhere, gas masks for the fighters, camera-enabled cell phones for everyone to record the tragic and needless deaths of civilian women and children (all strategically placed around military objectives) and we have built dedicated underground fiber-optic links to make it past any jamming. Every enemy strike will feature widows, orphans, lost kittens, the works. This will get blasted onto the enemy's TV screens 24/7 by the opposition channels. **Snipers.** We have 50,000 trained snipers and high-quality gear (stolen from our enemies, ironically). **The poor high-tech fools don't stand a chance.** [Answer] **A cunning ruse!** So we know our enemys' only real weakness is public opinion and we can win by killing 10,000 of the enemy... but why go to all that effort? *Let's just convince the enemy populace that we killed 10,000 people we didn't!* So we send out our spies to infiltrate enemy media and social networks. When the war begins we seed the news with story after story of deadly sneak attacks and kidnappings of unnamed citizens. We convince the public that any Government statement denying these events is a cover-up to prevent embarrassment and public hysteria. How can the enemy government fight this tactic? Take down independent news stations? Arrest reporters? Censor social media? Great! The more they try to silence or deny our lies the more it will seem like they really are covering something up! Short of taking a full census every month they could never prove that citizens aren't going missing and even then they'd still have to convince the public the census numbers weren't also fabrications. If the public aren't convinced, well, we can just kidnap/kill a few celebrities and government officials to "prove" the attacks are real. This plan is relatively cheap, safe and doesn't require 2 years of hiding in bunkers. It's an awesome plan! [Answer] Gather up 10,000 of your least loyal citizens and issue them forged evil empire identification documents and lots of money. Then throw a big party in their honor and send them out the city gates to go join the enemy. During the party, serve each of them a slow acting poison which will kill them a few weeks later. Just before the poison starts to take effect, announce on public radio that your spies have successfully poisoned the enemy water supply and that civilian casualties counts are expected to reach hundreds of thousands. Watch patiently as popular opinion turns against the war and the wet napkin retreat begins. [Answer] ## Do it the way they did in the past, without the flaw The biggest problem in history when it came to sieges was lack of resources. Either you ran out and had to surrender or the enemy ran out and had to retreat. Assuming that you have enough resources, all you need to do is hide and wait, after a few years, like you said, they'll quit. An example of this was the Conquest of Rome, the biggest flaw they felt was when their aqueducts were destroyed. Without water they had to surrender, but you have a benefits. You know the siege is coming and you can prepare, all you need to do is store food and water in your super bunker for 3 million people for 700 days, while this is going to be hard, it is possible with rationing. [Answer] # Terror Send 10 000 of your *most loyal* citizens in Evil Empire. Give them spy training, documents and whatever they need to not arise suspicion. When war will begin they should start terror strikes: shoot up the schools, blow up the hospitals, spread poisonous chemicals in public transit hubs... They should leave evidence pointing to reason for their strikes is Evil Empire attacking our homeland. Preferably they should do this in the way so it would be impossible for goverment to suppress information. Strikes should be made en masse: 1000 per day is fine. You do not want to spread them too much to avoid EE uncovering your agents before attacks. If each agent kills at least one person, it would already accomplish your goals. Everything else is a bonus helping in swaying public opinion faster. [Answer] ## Propaganda Fickle public opinion can only be maintained through a free press, which means that their public opinion can be manipulated. You're going to need a lot of pale grey makeup a half demolished school or hospital and lots of small volunteers to lie under sheets while being filmed. Just don't use the same school every time. Eventually the massacre of the little children will have an effect on your aggressor. Asymmetric warfare never looks good in the press when the children are dying. ## Break the siege A good siege requires a lot of people on the ground and you probably don't need to kill as many of their troops as you think. The first thing you need is intelligence on their supply lines and to get some troops outside the siege line. Mine their main supply corridor until they can only move by air without losing people on the ground, then roaming antiaircraft teams on the approach route to take down planes until they can only move by road. Planes going down are also really bad for public opinion. Rinse and repeat. [Answer] One needs to make certain assumptions about the behaviour of the enemy. At the moment, it is looking bleak for the people of Lusom: If the enemy truly has them surrounded, they cannot escape. If the enemy truly has technological and financial superiority, they would have no troubles destroying Lusom utterly. If the enemy truly intended to wipe out Lusom, they would. And as a last resort, they could. However, Big Dog is only willing to get involved if, and only if, this will be an easy win. I am led to the conclusion that it is important for your enemy not only to quell the aggressors within Lusom, but also either to a) keep Lusom civilian casualties to a minimum; and/or b) preserve Lusom infrastructure. With that in mind, even though this is clearly a popular display of power by Big Dog, it is not a popular seige. Furthermore, the presence of mercenaries in a vast and capable army suggests an attempt to intimidate; Mercenaries would not risk their own lives on the front line except for considerable financial compensation, in which case state soldiers would suffice, and be cheaper. Next, we should aim to understand the role of the allies of Big Dog. These are your political and geographical rivals. They have invited a force, far superior to their own, to fight on their behalf. Maybe they want you truly dead. Maybe they're already talking about how they're going to carve up the spoils of war. If anybody is going to end up on the front lines against you, it is your rivals. Big Dog would not risk his own soldiers first, it is not his quarrel. He is no mercenary. He is a Lion amongst Hyenas. Or, a big dog type thing amongst several smaller dog type things. So with these considerations in place, I'd consider these resolutions to the following scenarios. S1 & S2) Prepare for Defence: S1) Big Dog wants you dead, and doesn't need to send armed personelle into Lusom. R1) You're screwed. (Napalm, Drones, Missiles, AC130s, etc, or Destroying literally all your resources and then just sitting there for 2 years so that when they eventually go home you've got nothing going on). S2) Big Dog really really wants you dead, and needs to send armed personelle into Lusom. R2) Guerilla warfare is your best bet. 300,000 soldiers among 3,000,000 civs. Provided you can protect your supplies. Just make it strategically exhausting for them. S3 & S4) Incite discontent: S3) Big Dog doesn't really want you dead. R3) Demoralise all factions of the enemy. Target mercenaries, so they will leave. Target the rival powers forces, so they will implore Big Dog to fight for them. This would affect public support. S4) Big Dog just wants to intimidate you. R4) Continue for as long as possible as though nothing is happening. Incite skirmishes from the enemy, make them unfavourable. S5 & S6) Modify the Elements of Risk/Reward. S5) Big Dog wants your town, doesn't care about you. R5) Shoot yourself in the foot. Irradiate the place with uranium or something. S6) Big Dog is just trying to maintain the power balance. R6) Convince Big Dog that they would be better off with you as an ally, as opposed to your political rivals, who are now extremely vulnerable because of your combined military presence. One possibility which occurs to me, is a kind of reverse trojan horse scenario, where you can incite the enemy to send an investigatory force into the city, and you take hostages. If the hostages are valuable, you might be able to dissuade Big Dog from doing anything too insane to the city, like chemical weapons. I also might possibly suggest that you declare your super bunker to be an incredibly large nuclear weapon which you'd be prepared to set off as soon as you've taken too many casualties, and which will blow up if it sustains too much damage. [Answer] I suggest that as long as your competing factions are as isolated as they are, a simple biological weapon, perhaps as simple as an antibiotic-resistant cholera, or other water or food born pathogen would do the trick...you of course have the antidote. Save your ammunition and provisions, Wait for the dark of the moon ( if you have one) Infect, incubate a few days then attack sans mercy. Sick soldiers don't fight well. Repeat, repeat, and spread rumors that a specific "curse" is upon them, known to have mercy only on your population. - Just a thought. [Answer] The best defence is a good offence, and in facing an overwhleming enemy, the best offence is guerrilla warfare. Considering you lack air superiority, using conventional launch sites aren't going to work well as they'll be identified and bombed easily. Instead you need mobile (either personal or smaller vehicle) launch devices that fire rockets towards the enemy. Choose your targets to be either enemy positions involved in the seige of your city, or directly hit nearby airfields/towns/cities of the enemy. Tunnels tunnels tunnels. Besides being the technique used to store the rockets stated above (and the method to quickly pop up with launch vehicles and then hide again), these tunnels can also venture outside of the city and can be used to launch counter-offensive against the superior enemy. Hide, strike quickly, and hide again. Hit supply lines. All vehicles require fuel, all fuel is going to have to be hauled up to the front line. Finding out how the enemy is transporting this and where they are transporting this makes ideal targets. Normally with Guerrilla warfare, you are trying to cost the enemy money for as little cost to you, however in this case you are going for casualty counts. Hit the truck drivers and cause your casualties there. [Answer] > > We have also had years to prepare, execute spies, dig in, fortify, amass supplies of all kinds. > > > You have had years of forewarning. You have had years of experience ferreting out spies (hopefully some of them were actually spies). I suggest you take what you have learnt from these spies on what and what not to do to get caught and ...**go spy on your enemies**. Your fighters are totally committed to your cause, you will be able to easily convince them of the necessity to live and work in the heathen helldog's luxury world (they have a trillion dollar a year war fund...they have got to be super rich). Your fighter's will cherish the chance to be able to provide Mosu...sorry, Lusom with the information required to survive. I suggest to you get your spies to focus on getting their hands on [Top secret mission plans](https://worldbuilding.stackexchange.com/questions/49237/conquering-a-metropolis-with-near-zero-own-casualties). This way you can stockpile all the necessary supplies (it would be a drag not to have that one key resource that would be the difference between surviving and being annilated...giant fans are a must!) and not be fooled by the enemies Propoganda and Misinformation machine. You will now have all the resources stockpiled to counter all the different possible ways they had planned on attacking you with. You can sit back and watch them waste 2 trillion dollars. I also suggest you invest wisely, taking into account where the military spending will be (and won't be in two years). Make a buck off the enemies spending to help fund your own defence! [Answer] If the enemy you are facing is sensitive to the fickle tides of public opinion, you can discredit their capable leaders and wear away the morale of their forces. Having their leaders depicted as child-molesters, serial-adulterers and wife-beaters tend to erode the confidence and loyalty of their troops. You have had years to prepare, you probably have detailed files on all of their high ranking military officers. Have your spies subtly inject all the dirt you have managed to dig out (or invent, if needs be) to the scandal-hungry media who will run with it and possibly dig out ever more dirt with their resources. If their high-tech weapons are dependent (common these days) on skilled civilian contractors to keep things running - especially newer systems not yet fully integrated into the military machine - target the tech companies that supply the crucial spare parts, skills and support services required to run their sophisticated weapons with industrial sabotage and attempt to put them into bankruptcy or out of business. Many of the character assassination techniques long used in politics work just as well on business leaders. [Answer] **Their only weakness is their fickle publick opinion?** *This part isnt an answer, skip down a bit further for that. I do feel that this part is revelent* *But you want to hold out for 700 days, why make things hard on yourself and your citizens?* Hit their weakness with as much sorrowful images/videos as possible. Show old/young defenceless people being mericlessly cut down, show a dying person and their family trying to save them, show a single person saving (or trying to) a child from a hail of bullets, show the strength of your people, have them singing and having a good time despite the harsh times(if you can get footage of these people being gunned down in cold blood then that is even better). Now to explain this: Your enemy is stronger, bigger and better equiped, sure you can bunker down for 700 days and hope that their public opinion changes and they leave you alone, but you forget, 2 years is a long time and public opinion in *you* can also change (regardless of how loyal your soliders were/are). If you can show the enemy's public a person screaming for their mother or father that will invoke a lot of emotions of anyone who hasn't seen something like it before (Saving private Ryan, Medic Wade when he is gunned down and screams for his mother, this is the closest refence I could find) If you can show a someone saving someone else from a dangerous area the public will feel happy as they dont see the "enemy" as an enemy they just see another person saving someone from almost certain death and that would make people feel relieved. If the person dies trying to save the person then all the enemy's public see is a person dying trying to do the right thing. Showing the strength of your people will affect both public opinion and to an extent military opinion, if you show that your people will not break underpresure, they will fight to the last man and do all in their power to drive you out of their city that has an impact, the enemy's public see that you are doing all you can so save your home and will (consciously or not) reflect that in their own life and think if they would do the same. The military more often than not dont like to throw their soliders life away, if every citizen of yours can kill at least 1 solider then that will become 3,000,000 million deaths of them, not a figure they would like to see and explain even less so. That would be the optimal route to follow and could end the war after a couple of months depending on hwo good your coverage is of the war. **Now to answer your question** > > We have also had years to prepare, execute spies, dig in, fortify, amass supplies of all kinds > > > First of all make your city appear deserted, set up traps at entrance points, the enemy will likely send in a small platoon to inspect the city to make sure its safe, once you have killed the people stripe them of their gear/clothes and hang their remains outsite of the city walls, signs saying, "We may lose but this will be you", will make the infantry less than happy about attacking you. On the off chance the enemy send in all of their force, make sure they can only getting from one entrance, flank them on both sides (you will take casualties but they will be worse off) and then do the above still. If you can capture a commander or anyone above the rank of a common solider then extract as much information out of them as possible, radio (or the equivalent of) frequences, resource routes, where his higher ups are stationed and weaknesses in their bases defences. Take it with a pinch of salt and he may have lied to you (pretty much 100% chance) but you can send a couple of civilians (dont waste good soliders) and see if the captor was right, if it was then hit the target so they cannot attack as efficently. Set up traps throughout the city, lethal traps, mundan traps/joke traps and trapping traps, lethal traps so you can kill the would-be invader and instill fear into them. Mundan/joke traps (a party popper will go off or something silly like that) so they become paranoid of even taking a step forward, and can see if someone set off a trap and will begin to doubt even their own squad. Trapping traps so they waste time trying to save the person and increase their chances of being attacked, bear traps are good for that kind of stuff. As for keeping as many people alive for the 700 days, [your answer sums it up perfectly](https://worldbuilding.stackexchange.com/a/49399/18050) If the enemy attacks with a ranged assault (or relises that a frontal assault is bad) then take to underground, get as close as you can to the artilary and sabotage it, if possible take some of the shells to set up anti tank traps (or really messy anti personal trap). **tl;dr** - If the enemy attacks from the front do a hit-and-run tatics and show them the result, if they attack from afar then take the fight to them and then take their supplies back to your home base. Disrupt their flow of supplies and command as best as possible as well so they are left with no or few orders to take. [Answer] A nuclear weapon/reactor at the centre of your city with a [fail-deadly](https://en.wikipedia.org/wiki/Fail-deadly) trigger. Your high command have to enter a code every 24 hours into a computer (that is not connected to the internet, does not have usb ports, or a keyboard, running a custom OS with no features such as access to the operating system, which is encased in a foot of solid steel with no doors) or the bomb goes off. [Answer] The territory of *Kamarg* from Michael Moorcock's *The History of the Runestaff* survived a siege by having insane defensive power in the form of war towers that shot flame. They were able to sit tight for a very long time despite almost the entire rest of the continent being taken over. I believe they eventually used a magic artefact to temporarily transport the place to another plane of existence. If you have magic, there is always such an option too. [Answer] Send your most loyal soldiers as "refugees" from the crazy dictator. Injure them if necessary to be convincing. As soon as they are taken in, they can begin to sow seeds of discontent up to and including attacks on the populous. It is kind of like a Trojan horse only instead of playing on their pride, prey on their pity. If they don't take the bait, media blitz on how inhumane your oppressors are for the PR win. Bonus points for getting it on tape. [Answer] # Get the hell out of Dodge. I liked @Revolver\_Ocelot's answer about terrorism. But why not take it further? Why doesn't *everyone* leave? Then only one in thirty needs to kill someone, and 100% wipe-out by destroying the city becomes irrelevant: we can return to the Promised Land later. [Answer] The answer is distraction. Get your city's leader (or a representative) to leave the city walls and publicly speak about the war. Meanwhile, get a large percentage of the children in the city and gather them in two tunnels near each other with 5000 good fighters behind each group.While the leader (or rep) is speaking, have the children disperse and run in a frenzy, saying they escaped (each should be wearing tattered clothing) while on ANOTHER side of the army, women and sick-looking men crawl out of tunnels with the same amount of fighters behind them. The enemy should spread out to go to each group. Take this time to send a good 100,000 troops out of as many tunnels as possible on the fourth side. While they open fire on the enemy, the enemy will split to attack your fighters, probably leaving the groups of refugees relatively unguarded, but being helped by the medics. When the two sides are engaged on the main side, have the fighters in the tunnels behind all the women and children (they're still hidden so far) come out and plant bombs in the groups of 'refugees' and detonate them. Thousands of the enemy will die, many will be injured. Have soldiers retreat on the main front and close the tunnels as they go. Finally, while the enemy runs to help their comrades in the groups of refugees, have explosives set under the areas where the most troops are injured. When the most of the enemy is grouped up, detonate the explosives underneath *them.* Over the next few weeks, engage in guerrilla warfare and detonate bombs intermittently throughout the camps, especially when aid arrives to the fighting. The enemy should be sufficiently scared so as to not retaliate in large numbers, thereby allowing you to get away with the guerrilla warfare. The result: Most of your children and women will be dead. Many times more enemies will be dead and the rest of the army won't be willing to help each other out or group up for fear of bombs. The media will need to find a way to explain why the army is skittish and unwilling to assist each other. The citizens and soldiers will also be portrayed as merciless barbarians, which will help them to be left alone for longer after the war. In conclusion: bad publicity for the war and many dead soldiers. They won't be attacked again for a very long time. ]

[Question] [ Wow, of all the amazing luck! I just met a visitor from a magical world. He was able to use his magic to establish common communication, and after a bit of talk he decided he wanted to bring some stuff from my world back with him, so we worked out a deal. I went shopping and purchased a few hundred dollars worth of various goods, and he gave me a rather large pouch of gold coins in return, then departed. With the price of gold being what it is, I'm rich! ...maybe. The thing is, these are *coins*. Disks of what appears to be an alloy of reasonably high gold content, stamped with the image of some guy who I assume is a king on my visitor's world, and a bunch of what appears to be writing in some script I've never seen before. If I try to sell these to a gold dealer or a coin broker, it will almost certainly invite questions that I don't want to answer! Of course, I could always try the black market, if I knew how to find such an institution, but I'm a reasonably law-abiding citizen and I'd prefer not to have to deal with criminals. (Besides, even if I didn't get them stolen outright, I've heard that you tend to get a lot of the price taken out as various underworld-security fees, and I don't want that; I want to be rich!) What strategy would allow me to turn the gold coins into the maximum amount of dollars with a minimal level of risk of anyone asking questions about where they came from? --- Example (to demonstrate that question is not specifically about character action): Two countries come into contact for the first time. Country A uses fiat dollars, country B gold coins. People from country A are unfamiliar with country B's coins. Recently country A has had an influx of tourists from country B who try to buy things with gold coins. When a merchant in country A sells goods or services to a tourist from country B, how would he go about exchanging the gold coins he receives for dollars? [Answer] Why the black market? You can just sell the gold and be done with it. **Disclaimer:** The legality of the following will definitely depend on the country you're in. The laws I'm considering are those of the Czech Republic. ### Where to sell Where I'm from, goldsmiths routinely buy gold off of people. When I was having my wedding ring made, I was given the option to bring in old gold items for a discount, or just redeem them for cash. It's probably not the best price you could conceivably get, but it's reasonably fair. Now, if you trade in *too* much gold, you might run afoul of laws against moneylaundering, but if you live in a big enough city, you could just distribute your treasure among multiple goldsmiths to be safe. ### Concealing the origin *"So my buddies and I had the idea to make gold membership coins for our LARP club. We would have had them stamped with the face of a fictional character and inscribed with gibberish. Unfortunately we had a falling out and they wouldn't pay me for them, so I'm stuck with a literal bag of gold coins and nothing to use them for, and want to recoup my losses."* If a story like that doesn't seem sufficiently plausible, or if you're really paranoid someone might go and inquire whether you really had those coins made, you can try and destroy the coins. After all, you're just selling them for the metal. Now, the melting temperature of gold is about 1050°C, which is well below what you can get in a blacksmith's forge (that you can easily build in your backyard) or from an oxyacetylene torch. If you have some skill in you, you could fashion the coins into rings for example, then smack them a couple of times with a hammer and sell them as jewels that got damaged in a work accident. Or you could come up with a story about a family heirloom and an improbable incident with a welding torch and just sell molten pieces. ### Possible repercussions If somebody official catches wind of what you're doing, you might be in trouble for tax evasion or such. To avoid that, after appropriately abusing the coins to the point they're no longer coins, you could make up a story about having found a hidden stash of damaged gold items from [insert war here] on your family land, pay the appropriate taxes and sell the gold. One last way you might get into trouble is if the alloy is somehow exotic and one of the goldsmiths decides to take a closer look. Assuming it doesn't contain any alien or magic elements, you could probably just melt it down in a crucible and let the component metals settle, which will make the composition non-uniform. [Answer] In order of increasing profit: **Cash For Gold!:** CFG shops will offer 10¢ on the dollar for gold, if you balk they'll up it to 20¢. If you still kick they'll "call the manager" and offer a maximum of 40¢ on the dollar. **Black Market:** The "black market" will offer you 50¢ on the dollar — yes that's right the black market is more honest than the CFG places. **Goldsmith / reputable jewelry shop:** A reputable shop will offer you the market price for the gold and might waive the assay fee on the chance that the coins are valuable/rare. **Coin Dealer:** A coin dealer will recognize these as rare coins and offer you above market price, all you need is a good story: "My grandfather bought these coins from an old man in Crete during the war, he said they came from Atlantus" and of course your best option: **Ebay:** You best option is to sell them on Ebay: " Buy gold **rare** gold coins from the lost city of ***Atlantis***!!! ***ACT NOW!!*** being *rare* and *unidentifiable* makes the coins worth **more** than their weight in gold. [Answer] You can buy an electric smelter for a couple hundred dollars. Melt the coins into small bars (1 or 5oz, for example), then sell the bars as scrap gold to a reputable precious metals refiner. They'll grade it and give you a price. Or, they'll refine it to .999 and send it back to you as standard gold bars, for a fee or sometimes for a percentage of the metal. That's how you'd get the best price for the gold. Pawn shops and 'cash for gold' places won't typically offer you the best prices. [Answer] Any gold dealer or pawn shop will take them. Just say they are a family heirloom from an old country that were passed generation to generation. That will explain the strange appearance. I don't think the buyer will care much as long as you show them a picture ID and you complete the necessary paperwork. [Answer] A basic strategy would be to melt the coins down, then sell the gold itself. A bag of gold coins doesn't sound like such a massive quantity of gold that you'd bring attention to yourself selling the melted product (or a derivative such as jewelry), so that's probably a better bet than trying to deal with the coins directly. [Answer] I've been to a coin shop that bought coins but cared nothing about what it was: it just goes straight into the scrap bin, to be melted! I've seen "rounds" that have novel designs rather than being official issued coins. The stated alloy is not trusted (if it says anything) but after testing they fetch the same price for metal. You'll have no trouble selling them, and don't need to explain anything: buying gold one may get (e.g.) "1 ounce rounds" without caring what pattern they ship you. You may have gotten these novelty fantasy coins as generic. You could try selling on eBay or other site as a novelty fantasy coin, or as generic gold. I agree with @grandmasterB, the places that advertise cash for gold are scams. Describe your hero learning that based on expose reports you can find, and then calling around town to find who paid "spot price", and online places like BullionDirect. Try buying and selling for real. It can be a good part of your savings. Or at least interview someone who's done it, more in-depth than this quick note. The deleted message from the kook gave me a thought though: what if contact had been made before? An alien script can't be typed into Google, but an image search might find others like it, posted on an auction site from another like yourself! [Answer] Depending on your legislation: Claim they were the property of a deceased relative. Pay applicable inheritage taxes. You're legal, and there is a good reason why you can't answer questions. "Yep, they're weird. But surely the metal value ..." [Answer] How much did you get? For relatively few money, you could grind them up (much less energy expensive than melting) and then go directly to the companies where goldsmiths etc. go with their scrap metals (can't remember how they are called). They do not ask questions, can't see what it formerly was, and you don't have to deal with another intermediate place that wants to rip you off. An alternative would be to just go to some trustworthy (swiss?) bank and sell it there. They often ask surprisingly few questions, and give surprisingly good prices. They even ask so less questions that some people managed to sell them gold plated tungsten bars... But first of all you should make sure that you magic partner did not rip you off and give you something that only looks like gold. Or maybe it is something that looks like gold and is unknown here and worth thousands of times more (hey, its from another world after all) [Answer] If you sell these coins to various merchants, then unless they have a direct use for them, *those* merchants will need to find a way to sell the coins to others. They'll probably just say that they bought them off of a customer. Come to think of it, *you're* effectively one of those merchants. Just tell the truth: you traded for them off of a traveler who didn't have anything else to pay with at the time, since it seemed like a good deal, and they'd make a nice souvenir even if they turned out not to be real gold. Or whatever other fluff you like that is ideally true, but still emphasizes that you aren't the go-to guy for this stuff. [Answer] **Go to Vegas** I'm not sure if this true in the real world, but I've read a couple of stories in which Las Vegas hotel/casinos will change gold into chips for a slight premium and with few questions asked. The idea being to cater to people from other countries that might not have legal tender, or have some other reason to use gold instead of some other form of currency. Go to Vegas, change your gold, lose some money at the casino so they are happy, then cash out your new riches and go home. [Answer] The fastest place to sell coins would be at a coin shop or pawn shop. They are waiting for people to bring that stuff in. They are not concerned with where you got them. They want to own them. You don't have to know anything at all about what you are selling. They're business is researching values of items. It doesn't matter if you know what you have. That being said, what I just described is the worst possible idea for a person selling something. A few minutes on Google could be the difference of unknown amounts of money. [Answer] You could try to go legally. Claim that you found the coins on some expedition. An appraiser may value them extremely highly since the language is unknown and the alloy suggests a high level of technology. People might think that you have found some rare historical artifact. [Answer] Write a novel/series of books that is of high enough quality that it will become mainstream. Ensure it has a character who resembles the face on the coins, and is a ruler in that world - preferably likeable. Work with a production company to get an episodic TV series made about the book(s) - involving sex and gore, to ensure popularity. Sell the coins as limited edition collectables. [Answer] ## Chemistry! Nitric acid + hydrochloric acid [will dissolve gold](https://www.youtube.com/watch?v=37Kn-kIsVu8&t=892). Once you've dissolved the coins, add potassium metabisulfite or anther reducing agent to the solution and the gold will precipitate out. Pour off the liquid, rinse thoroughly with water, and you now have pure, finely divided gold powder. Dump that into a crucible and melt together with a propane torch, and you'll have a lump of pure, untraceable gold which any jeweler or other respectable vendor would be happy to purchase from you, no questions asked.(\*) Just follow proper lab procedures when doing this, since it involves several nasty chemicals and potentially dangerous fumes. (\*-or if they do ask, "Yeah, grandma had *terrible* taste in jewelry. When she passed, nobody actually wanted any of her pieces, so we decided it'd be easier to just melt it all down and divide it that way.") [Answer] \*\* Gold is fungible \*\* You can always sell them at gold rates less a small discount. Unless you are claiming the coins are old or historic, no provenance is required. Most legitimate places will take an assay and buy it for the gold content less a fee. Most jewelers that create custom pieces will provide this as a service since they are constantly working with foundries. They almost always have left over gold when making a new piece. They sell the cut-off rods, tubes, wire to a foundry at the gold price less 2%, if I recall correctly. If the stamping in the coinage has aesthetic merit or the alloying is really special, as to make them scientifically or metallurgically interesting then you can try to sell them for more than the gold price — like they are works of art or collectibles. If you claim to be the artist who made them, then you wouldn’t any more documentation. If the values is as scientifically interesting, then there is not need to comment since the assay speaks for itself. If you look shady then reputable dealers may ask for proof of ownership to ensure that the gold isn’t stolen. If you look presentable and only sell one at a time, unless you look marvelous in your brooks brothers suit or Chanel slacks, then should be fine. Once suitable attired, you can go to other, larger businesses, and negotiate larger, more favorable deals. ]

[Question] [ My empire's flagship, the Persecutor class UJBHE1 Abhorrent, rides into the home system of my greatest enemy, Baron Obsequious, levels its Death Ray2 at his beloved home, and pulls the trigger.3 Baron Obsequious' prized emerald explodes in a [shower of light that would make George Lucas proud.](https://www.youtube.com/watch?v=nDgH1DaTMMM) 1. Given that the Abhorrent's defense screens can only absorb 100 TJ of electromagnetic or kinetic energy before critically compromising the ship (i.e., the ship must withstand less than 100 TJ throughout the experience or the deal's off)... 2. Assume the cross-section of the ship is one square kilometer (thanks Mark!) 3. Assume the Abhorrent is using thrust to hold a static position away from the planet. It's not in orbit. (Thanks again, Mark!) * How far away must the Abhorrent be to survive the blast? * At that distance, will the "sudden"4 dispersal in mass result in a change of gravity that will cause the ship to lurch backward (away from what was once Baron Obsequious)? --- 1 *Representing the Universal JBH Empire dontchaknow.* 2 *Because no name for an energy weapon can possibly be better than anything used during the Flash Gordon era.* 3 *Only wusses use buttons.* 4 *And here I need to make a choice. "Sudden" on a plantary scale may render the question moot. Let's assume, as impossible as it may be, that the mass disperses to basically 0% of its original density within 5 minutes of triggering the ray. That's 0.333%/second or a loss of 0.184g/cm3 per second.* [Answer] Well, Mark Olson and Samuel provide some very respectable math that winds up with the world destroying shot being taken from about 1 AU or the distance from Earth to sun. Yes, yes; it seems very reasonable. But what fun is that? A little flash of light, a great disturbance in the force; bah. You want a ringside seat. **I propose that your world destroying shot be taken from the distance of the moon. Then use the moon as shelter.** Assume here the moon of this world is the same distance as our moon is from Earth: 1.3 light seconds. After taking the shot you have a luxurious 1.3 seconds to coast into the shadow of the moon. Then marvel at how the moon is struck into steaming silhouette by the energetic flash of its planet dissolving. Shelter there as chunks of molten core pelt the far side of the moon with those that miss streaming past you on all sides. Will the impacts from the dissolving world heat its moon to glowing? How romantic! The path of this moon might get a little wonky as the debris cloud expands. Assure your pilot you will record it all for her to watch later - she is to keep your ship firmly in the shadow of the moon until the fireworks cease. [Answer] Well, at best you're depositing in the planet (or the powdered remnants thereof) energy equal to its gravitational binding energy. [According to Wikipedia](https://en.wikipedia.org/wiki/Gravitational_binding_energy), the one true source of truth, the gravitational binding energy of Earth is about 1032 J which is about as much energy as the Sun emits (in all directions) in a week. This is converted into kinetic energy of motion of the powdered planet and bulk of the planet's mass comes off at near its (pre-you) escape velocity. Think of it as five hundred miles of rock coming at you at 5 miles/second... (At that speed whether it's solid or powder doesn't actually make much of a difference.) Now it gets harder. The kinetic energy of 1 kg of mass moving at 5 miles/second (Mixed units. So sue me!) is 3x107 J. I have no idea what size your ship is, but I'll arbitrarily assume it has a cross-section of a square kilometer. A *cubic* km of rock has a mass of about 3x1012 kg. So at near orbit the kinetic energy of the mass of rock would be 500 km times the mass of a cubic km of rock times the kinetic energy of a kg of rock. 5x1022 J. That overloads your screens by a factor of 1010. So you need to back off so that the slower speed of impact and the lower density of the rock column give you back your safety margin. The density drops as the square of the radius, while the velocity drops more slowly. if we ignore the lower velocity, we get a factor of 105 in distance or 400 million miles. So that's a very safe distance. By 250,000 miles the velocity of the matter would have dropped by a factor of about 3 (from 7 mps at the Earth's surface to about 1.5 at 250,000 miles) so the energy of the impact would decrease by a factor of about ten, bringing the sure-to-be-safe distance to 100,000,000 miles. This shows that the main point is to get far enough from the planet that stuff launched at escape velocity has pretty much slowed to a stop. Call it a million miles or so. So, assuming you used the absolute minimum of energy to destroy the planet, your safe distance is probably on the order of a million miles. If you give in to your (perfectly understandable) wish to do something really spectacular, you'd better get a lot further away. There was a question about the gravitational effect of the explosion on the ship. Oddly, there would be none at first. From the outside, *any* spherically symmetric distribution of masses acts like all the mass is concentrated at the center of the sphere. So until the first ejecta got to the ship the gravitational field would be unchanged. After that, the amount of mass inside the sphere closer to the (former) center of the planet than the ship would decrease smoothly, so the effect of the (former) planet's gravity would decrease smoothly also, going to zero when it had all passed. (Changing gravity would be the least of your problems!) And remember: Blowing up planets is dangerous, so be sure to wear your safety goggles. And friends don't let friends blow up planets. [Answer] This is going to depend on the surface area facing the radiated energy from the planet. If it takes $2.5\cdot10^{32}$ joules of energy to completely destroy an Earth-like planet as suggested [here](https://worldbuilding.stackexchange.com/a/100633/3202). Then we can assume that an equivalent amount of energy is going to be radiated from planet being destroyed. So, this boils down to calculating the radius you need to be from that expanding sphere in order for your surface area to collect 100 TJ or less of that energy. Since we're dealing with energy and not power, we can have this happen as quickly or slowly as we like. Using one second seems simple enough. We can treat the planet like an isotropic radiating antenna and you're an antenna collecting that energy. $$100\cdot10^9\ \frac{\mathrm J}{\mathrm{m^2}}=\frac{2.5\cdot10^{32}\ \mathrm J}{(4\pi d^2)}$$ $$d = 1.41\cdot10^{10}\ \mathrm m$$ This means at a distance of $1.41\cdot10^{10}$ meters from the planet, you'll receive 100 TJ of energy per square meter of exposed shielding. Multiply that by $\sqrt{A}$ where $A$ is the surface area facing the planet and you've got your minimum safe distance. You won't notice much gravitational effect. The planet will be at least 47 light seconds away, about a tenth the distance from the Earth to the Sun. The gravity you would be experiencing is in the nano-gees and would reduce relatively smoothly as most of the planet moves away from you and a small portion moves toward you. [Answer] A planet wouldn't "explode in a ball of light" unless it had been converted into energy somehow. If it has not, then the total quantity of energy emitted can vary wildly: for example the light could be just the atmosphere igniting and reducing the world to a cinder. In that case the total energy reaching the *Abhorrent* would be negligible even at comparatively short distances. But if it *has*, and your remark about gravitational effects makes me think so, then how much matter has become which energy? (Neutrinos would be the least dangerous, even if enough of them can still kill). The worst case scenario has the whole mass of the planet turn into electromagnetic energy. 6 1012 tera-kilograms of m multiplied by 9 1016, yielding 4.5 1029 TJ of E. The *Abhorrent* can only absorb 100 of those, so I declare the energy release to be 4.5 1027 *abhorrences* (it's also about 0.005 [*foes*](https://en.wikipedia.org/wiki/Foe_(unit))). To be able to survive, the *Abhorrent* must be outside a spherical shell with a surface area of 4.5 1027 km2, so that all that energy gets spread thin enough. This assumes that the energy release is omnidirectional and isotropic; if (as it's plausible) the energy release is greater where the Death Ray hits, then the ship has to keep farther away. This means that the radius of the shell must be $\sqrt{\frac{4.5 \times10^{27}}{4\pi}}$ or 1.8\*1013 kilometers, or about 1.9 light years. At that distance, any gravitational effects would be negligible. This is the *total deposited energy*, not the *radiated power intensity* (which would be a much less spectacular figure). The reason the number is so large is that we're calculating an absorbing surface of one square kilometer. The normal Sun light, at 1500 W/m2 irradiance, would already deposit on it one and a half million kilojoules per second, i.e. 1.5 terajoules per second; which means that the Abhorrent's survivability in direct sunlight at 1 AU is little more than *one minute*, raising legitimate suspicions of vampirism against the Universal JBH Empire. A supernova, around 200x times more powerful, has been estimated to be lethal to Earth from any distance below 30 light-years. There are actually some worries about [IK Pegasi B](http://blogs.discovermagazine.com/badastronomy/2012/05/18/the-closest-supernova-candidate/#.UuWlrGTnZcw), a potential "induced" supernova. However, due to the limitations of its defensive shield, the *Abhorrent* needs to be able to perform a FTL escape (or, [as Willk suggested](https://worldbuilding.stackexchange.com/a/110453/6933), hide behind the Moon) in order to survive. However, the energy release might be enough to *also* wipe way the Moon at a piddling 400,000 km distance. The energy from a 0,005 *foes* explosion is enough, if emitted as high-energy gamma rays, to [photodisintegrate](https://en.wikipedia.org/wiki/Photodisintegration) the Moon and presumably blast the *Abhorrent*, a few milliseconds after the gamma leak has crashed its shield and thoroughly sterilized it. It turns out that I was wrong in fearing neutrinos, though. If that same energy [went into neutrinos](https://what-if.xkcd.com/73/), the safe distance would be 2.3/2002 AU, or 8625 km (I took Randall Munroe's 2.3 AU and just compensated for the explosion being two hundred times weaker than a supernova). At a distance forty-four times greater, behind the Moon, the neutrino radiation dose would be only 2.6 milliSievert, not enough to cause damage, as the planet would *softly and suddenly vanish away*. [Answer] The answers given so far use a model based on your classic sci-fi exploding planet. The whole thing blows apart from the center outward, as if someone replaced the core with dynamite. This is probably an oversimplification, though, and one that might not be working in your favor. If the planet is destroyed by a weapon fired from space, it probably won't result in a nice, radially-symmetric explosion (full disclosure: I've never tried this personally). The weapon will impact the planet at a point on the surface, and the explosion will travel outwards from that point in a cone-like shape away from the attacker. For an example of what I mean, look for one of the many videos online of slow-motion footage of someone shooting a watermelon or pumpkin with a rifle. Matter gets ejected in all directions, but the vast majority of it travels in the same general direction as the bullet. The kinetic energy your weapon gives to the planet should keep most of the remnants moving away from you. You should be able to remain much closer to the planet than the "symmetric core explosion" answers suggest. For best results, fire when the planet is directly in line between you and the sun. The sun's gravity can capture much of the debris and clean up part of your mess. The downside is that this can have more severe gravitational effects. An asymmetrical explosion means the center of mass will drift away from the shooter, and you're almost certainly going to be close enough to feel the planet's gravity. Beware of natural satellites that might be yanked off-course and sent in your direction. You probably want to start accelerating away from the target immediately after firing. If you *really* want to watch the carnage, leave a disposable camera probe behind to film it. ]

[Question] [ I'm sure there have been questions on here about fire-breathing dragons, and I recently saw a question about a lightning-breathing dragon, but back in fifth grade I wrote a 150-page story about a dragon with ice breath, and now I'm starting to wonder if it would be possible without large amounts of magic. My biggest problem is that while humans have had fire for millenia and electricity for over a century, it took a lot longer to come up with a way to generate significantly cold temperatures without using big blocks of ice. In fact, I'm still a bit confused about how refrigerators work. So, I'm wondering, **could an animal evolve to produce temperatures cold enough to freeze water and/or prey? And if so, how?** Any environment where this is possible is acceptable, though an answer that allows for a wide variety of Earth environments is preferable. Also, though I'm thinking dragons, if it's not possible for them but possible for another kind of animal, such information is welcome. [Answer] **I wouldn't use liquid nitrogen. I would use liquid carbon dioxide, CO2**. There are a few reasons for this. **Physical** CO2 can exist as a liquid at ambient temperatures under sufficient pressure. Nitrogen cannot as its critical temperature is much lower. In layman's terms, at any temperature above 126K (-147C) the density (and other properties) of nitrogen gas and nitrogen liquid become identical, so there is no distinction between gas and liquid and no vaporization cooling occurs when pressure is released. So, if you use nitrogen, your dragon is going to need a way of storing liquid nitrogen, and a means of generating it. CO2 on the other hand, can exist as a liquid at ambient temperature if sufficient pressure is applied to it (56 atm at 20C). When the pressure is released through a simple valve, molecules break free from the attractive forces in the liquid, which requires energy and therefore causes cooling. This is exactly what happens when a CO2 fire extinguisher is used. (though the idea is to suffocate the fire, a side effect is the production of dry ice.) Fun with fire extinguishers (don't try this at home!) <https://www.youtube.com/watch?v=Z3xyqfCZmSU> **When CO2 vaporizes it requires 3 times as much energy per unit mass than liquid nitrogen, therefore its cooling effect at ambient temperature would be greater.** Ironically, it is precisely because of this that it has a higher boiling point temperature than liquid nitrogen: -78C at atmospheric pressure instead of -195C. (As an added complication, the freezing point of CO2 is higher than -78C, so it can *only* exist as a liquid when its boiling point is raised by high pressure.) <http://www.engineeringtoolbox.com/fluids-evaporation-latent-heat-d_147.html> **Chemical / biochemical** Where does the dragon get her gas from? If it is nitrogen, she will have to get it from the atmosphere and liquefy it in some way, either via an expander or via a separate refrigeration cycle, both of which seem biologically impossible. If she uses CO2 she can generate it chemically, and it may then already be under pressure. She may do this in a variety of ways: 1. Use the normal metabolism. It is unlikely that it would be possible to build up high pressures of CO2 in this way, though, without making the blood too acidic. 2. Use CO2 from her fire breath, if any. This would be highly inefficient, and would again have the problem of generating CO2 at ambient 3. Go to a frozen wasteland and eat CO2 4. Eat chalk, and use this to generate CO2, through the reaction CaCO3 + Acid = Ca salt + CO2. The acid could come from normal metabolism. 5. As for 4, except the acid comes from an external source. For example, the dragon may go to a volcano and feast on brimstone (sulphur) which she could then burn (producing fiery breath without the inconvenience of having to generate large amounts of fuel through metabolism.) When she is not breathing fire, the dragon may slowly convert the sulphur to SO3 and H2SO4 in her belly, and react these with chalk to make CO2 under pressure. This is an entirely realistic way for a dragon to produce icy breath without metabolism or mechanical engineering issues. The only remaining issue is materials, which have always been a problem with fire-breathing dragons anyway. --- **Other gases** Other suitable gases include propane (again requiring more energy per unit mass than nitrogen for vaporization than nitrogen, and I can say from experience that a splash of propane "feels" colder than nitrogen.) The dragon could choose to breathe icy propane, or instead ignite it and breathe fire. Carbon monoxide, CO is another posibility (highly toxic and moderately flammable as well as being a gas) but its critical point is well below ambient temperature, like nitrogen. Several existing organisms use formic acid as a weapon, and formic acid decomposes catalytically to carbon monoxide and water. Sulphur dioxide fits in with the brimstone idea. It has a boiling point of -10C, which is perhaps a little high, and is toxic and corrosive. Generating SO2 chemically under pressure would be difficult because of the requirement for atmospheric oxygen, unless the dragon breathed in the air and dived to great depths like a sperm whale in order to compress the oxygen. [Answer] **Adiabatic cooling might work for this**. Among other things, the general principle is used in the creation of liquid nitrogen, so it can certainly get things cold enough. In this scenario, the dragon breathes an air vortex at an extremely high pressure, not unlike an [air vortex tube](http://www.airtx.com/how-does-a-vortex-tube-work.htm). As the vortex leaves the dragon's mouth, it expands, and in so doing, cools the space it flows through. Cool that space enough, and the water vapor in in should condense rapidly: cool it further, and the water vapor should flash-freeze. Combined with the wind from the dragon's breath, you have something that looks like breathing ice and projecting it forward, even though the dragon is in fact breathing nothing but air. This does require the dragon to be able to produce extremely high pressures in its lungs, and to withstand the heat generated by compressing the air to such temperatures, so the dragon (or at least its upper respiratory system) could not be "weak against fire" as seen in some stories and video games. The dragon would also need to be able to release the gas through its mouth at these fantastic pressures without shattering the bones of its face. But it doesn't require the dragon to contain or generate any exotic substances. You can create a far lesser version of this effect yourself, just by blowing. Try to blow out air at a steady rate, but alter the opening of your mouth. As your mouth gets bigger, the air you're blowing should feel warmer. Shrink your mouth down very small, and the air gets colder: you're not going to make ice this way, but you should be able to feel the difference in temperature. My suggestion is essentially this effect, writ very large. [Answer] A specific way this could be achieved by a dragon would be through the endothermic reaction of ammonium chloride, which is [found in nature](http://en.wikipedia.org/wiki/Ammonium_chloride) (in volcanic regions) and barium hydroxide, which can be synthesised from nature. [Barium hydroxide](http://en.wikipedia.org/wiki/Barium_hydroxide) can be formed by the addition of water to [barium oxide](http://en.wikipedia.org/wiki/Barium_oxide), which is formed by heating [barium carbonate](http://en.wikipedia.org/wiki/Barium_carbonate) which is also found in nature (although admittedly not in volcanic regions). Even if the dragon would have difficulty heating the barium carbonate to the appropriate temperature it could force the reaction through the use of catalysts / enzymes, and by constantly removing carbon dioxide from the bladder (a standard biological process) containing the barium carbonate, shifting the equilibrium towards the barium oxide state. The resultant barium oxide could be filtered out by flushing the bladder with something like ethanol which dissolves barium oxide, but not barium carbonate. The dragon may also be able to supply heat to the mix by entering a hot spring or other volcanic nicety. Ammonium chloride is not particularly poisonous, and is even sometimes used as food flavouring. Barium oxide is more of a problem, being fairly poisonous, however if digested as barium carbonate, and processed in a separate bladder I don't see why it would be a problem. The dragon could store the barium oxide dissolved in ethanol until it was ready to release its freeze-breath, at which point it would pump water into the barium oxide, which would rapidly precipitate out of the ethanol as it became barium hydroxide, which is mostly insoluble in ethanol. Barium hydroxide octahydrate is a crystal so the remaining ethanol and excess water mix would help to flush the slurry into the ammonium chloride bladder. This mix would then be expelled rapidly into the atmosphere. The mix will cool to ~-20°C (depending on volumes), which is enough to freeze most animals. As a side benefit you also get a strong smell of ammonia, which is very atmospheric (no pun intended). [Answer] **Liquid nitrogen** seems to be the obvious answer. It's inert, raw nitrogen is available in abundance from our atmosphere and producing it is not totally impossible. All you need is for the dragon to have some sort of nitrogen bladder, where it accumulates nitrogen from the atmosphere (this is pretty doable by biological processes). When it's sufficiently full, the bladder constricts to significantly increase pressure. This warms the gas up, so you need a cooling system (ie. blood flow) to remove the heat, than you continue the process (optionally adding more nitrogen) until it becomes liquid. We know that some life forms (like [pistol shrimps](http://en.wikipedia.org/wiki/Alpheidae)) can use biological processes to briefly create impressively high pressures; the problematic part would probably be maintaining the pressure (which helpfully also prevents the dragon from freezing over from the inside), but since you apparrently already have flying dragons this only requires little additional handwaving. When the dragon wants to use his "breath", he will expell the nitrogen as a high-pressure stream. Depending on the dispersal of this stream, it can either have long range and cover a distant target with the supercold liquid, or can be spread over, so that the nitrogen evaporates, cooling a relatively larger volume. [Answer] There's really two possibilities I can see offhand: 1. [Endothermic](http://chemistry.about.com/od/lecturenotesl3/a/endorxns.htm) Chemical Reactions. This is a chemical reaction where you take two reagents, and when put together they consume heat as part of the reaction. So your dragon could store the two separately, and the "breath" would be where the two intersect and hit, consuming heat and freezing the area. 2. Pressure changes. Think about [phase diagrams](http://en.wikipedia.org/wiki/Phase_diagram#2D_phase_diagrams) - basically as you increase pressure, the freezing point of liquids goes down. What this means for you is that an animal with a high pressure storage area could have, say, supercooled water stored in liquid form below what's normally freezing. It could then release the water as a breath weapon, and it would immediately crystallize and turn to ice because of the lower pressure, freezing the enemy. I think Endothermic chemicals are your best bet, although presumably there's some reason creatures haven't evolved them on Earth. [Answer] **1. Endothermic reaction** - or at least I hope that's how it is called: As there are some *exo*thermic reactions (which produce heat), there are also *endo*thermic reactions which get all the heat from the reaction, effectively freezing it. So, moreover: **2. It would not be breath, but spit** Somewhere I heard, that poison in snakes evolved from really sour spits. Accepting it as truth, there would be dragon species with very (???) spits which would cause a bit of endothermic reaction on the skin of the prey. **3. It will work only specifically** Using my poor basic knowledge of biology, and wisdom from funny internet videos, I would assume, that such dragons could freeze only (furry) animals: Their spit would cause endothermic reaction on the body of their prey, causing it to freeze to paralysis, or death. I would not suggest such a dragon being able to freeze *everything*. **4. Make far spitting dragons to succeed** It makes evolutionary sense. The farther you can spit, the easier you get your prey. **5. Connect spitting with sound** So it would *look like* they actually breathe out the "winter" (blue spits could do the trick). Here you go. It is not rock solid, but I think it is a plausible theory to work with. [Answer] I think liquid nitrogen is a viable choice for all the reasons mentioned by Mike L. This link also goes to some explanation on how living tissue might be able to survive from freezing over: [You can Safely stick your hand in liquid nitrogen](http://io9.com/5625863/you-can-safely-stick-your-hand-in-liquid-nitrogenbut-you-probably-shouldnt) which all boils down to the [Leidenfrost Effect](http://en.wikipedia.org/wiki/Leidenfrost_effect) \*I would've just added a comment but I need more rep. [Answer] I'm presuming your dragon is of the conventional mould, and can therefore fly? That so, he/she need simply fly to a decent altitude (up amonst the cirrus, perhaps) where the temperature is naturally below freexing - and then he/she will breath ice crystals with no extra tricks needed. [Answer] I think the animal would require: 1. The ability to withstand subzero temperatures inside of it's body. Perhaps with a lot of inner insulation and a strong internal heat system, this would be feasible. 2. It would need a gland that produces chemicals that can flash freeze objects. Liquid nitrogen is the go to chemical here. Your animal would have to be able produce and store a lot of it to be able to use it as a main weapon in battle. ]

[Question] [ Inspired by [this question](https://worldbuilding.stackexchange.com/questions/132443/how-long-could-a-nuclear-warhead-remain-functioning-underground): For several excellent reasons, a 500-year-old nuclear warhead is not going to produce an actual nuclear explosion. But that doesn't mean it's not dangerous anymore. Suppose a group of postapocalyptic villagers finds a nuclear bomb. Maybe, on the way to the apocalypse, it [fell out of a plane and didn't explode](https://en.wikipedia.org/wiki/1958_Tybee_Island_mid-air_collision), and 500 years later a [farmer digs it up](https://en.wikipedia.org/wiki/Iron_harvest). Maybe they are trying to salvage usable scrap metal from the ruins of a military base, and what *was* the secure storage facility for nukes is now just another abandoned building. Doesn't really matter. However they got it, they have a nuclear bomb and they don't know what it is. How much danger are they in if they tinker with it? How much danger are they in if they just take it home and put it on display as a relic of the Old People? [Answer] The crucial question is what they do with it. As a museum piece, it's not really dangerous. If they open it up, bad things can happen. This answer assumes that we're talking about a [two-stage thermonuclear device](https://en.wikipedia.org/wiki/Nuclear_weapon_design#Two-stage_thermonuclear_weapons). This has a couple of main components: a primary fission charge, a secondary fission and fusion charge, an interstage, and a tamper. The primary fission charge goes off first, compressing the secondary fission charge, which then further heats and then compresses the fusion charge. The interstage and tamper ensure that this whole delicate operation goes off exactly as planned - the timing and geometry have to be *just so* for it to work. The tamper is the critical part from a long-term safety perspective: > > For the secondary to be imploded by the hot, radiation-induced plasma surrounding it, it must remain cool for the first microsecond, i.e., it must be encased in a massive radiation (heat) shield. The shield's massiveness allows it to double as a tamper, adding momentum and duration to the implosion. > > > Essentially, in addition to its other jobs, the tamper acts as a huge radiation shield. Though it contains the actual blast for only a crucial millisecond, it can contain the natural decay of the bomb components with ease. It helps that unlike a boosted fusion device (which uses short-lived but highly energetic tritium), this bomb can use stable lithium deuteride fusion fuel. Fission fuels are generally speaking relatively stable over the long term. So as long as you keep the bomb in its original packaging, so to speak, it should be quite safe. However, if you rip it open and start tinkering with its guts, bad things can happen. Plutonium, in particular, has been linked to problems when [radioisotope thermoelectric generators](https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Safety) using it have been salvaged and then opened by damage or tampering. Per WP, > > The alpha radiation emitted by either isotope [of plutonium] will not penetrate the skin, but it can irradiate internal organs if plutonium is inhaled or ingested. Particularly at risk is the skeleton, the surface of which is likely to absorb the isotope, and the liver, where the isotope will collect and become concentrated. > > > You should not eat nuclear bomb parts. If you're opening the bomb up, though, *chemical* toxicity is a major threat. The tamper is composed of depleted uranium (U-238) which, although not a major radiological hazard, is [direly toxic](https://en.wikipedia.org/wiki/Depleted_uranium#Chemical_toxicity) and a fire hazard. (In addition to being flammable, it's brittle, and the resulting dust has a charming habit of spontaneously igniting.) There's also the interstage, which is composed of... well, nobody in the public domain really knows. But according to DoD documents, it's also toxic. [Lithium deuteride](https://en.wikipedia.org/wiki/Lithium_hydride#Safety), not to be left out, reacts violently with water to create caustic lithium hydroxide, and is highly flammable to boot. So the upshot is: as long as you *don't touch the bloody thing* you should be safe from the radioactive materials inside. If you don't know what you're doing and open it up, it'll be a race between the various nasty, nasty things inside to see what does you in first. (My money's on the lithium fire. Those things are tough to put out if you're not expecting them.) [Answer] You have three sources of risk: * radiological. This is probably negligible, because after 500 years anything with a half-life shorter than 50 years is gone. The shielding on the other hand is pretty stable. * explosive. Nuclear warheads have an explosive primer, containing a sizeable quantity of explosive compounds. Some of these might have become inert, some others might have become dangerously unstable. This might have transformed the warhead in a "dirty bomb". * chemical. In addition to toxic waste from the primer, plutonium is highly toxic (as well as carcinogenic). Depending on the device's nature (fission or fusion), it may contain other substances that are poisonous, flammable, or both (e.g. lithium deuteride for a thermonuclear design). # 239Pu decay chain The plutonium in the warhead will slowly decay along the following chain: [](https://i.stack.imgur.com/evASu.png) Since the half-life of 235U is way longer than 239Pu's, we will have mostly alpha emissions and a negligible beta-minus decay from protoactinium. There is also a more speculative risk (the design of the weapon ought to prevent it, but you never know). Plutonium in nuclear weapons isn't pure plutonium, but rather [gallium-stabilized delta-phase plutonium](https://en.wikipedia.org/wiki/Plutonium%E2%80%93gallium_alloy#Use_in_nuclear_weapons), which has much better characteristics from an engineering point of view. The priming explosion squeezes it in the critical alpha-phase. But it is possible that the same effect can be achieved by aging (*"δ phase Pu–Ga is still thermodynamically unstable, so there are concerns about its aging behavior"* says Wikipedia), or by "cooking" it at temperatures above 475 °C. In other words, there might be significant chances for an ill-advised attempt to melt and maybe re-cast the mystery metal to, at minimum, cause poisonous fumes to be released; or, at worst, to trigger a "fizzle melt", which would probably be more than enough to [kill everyone in a radius of several meters or more](https://en.wikipedia.org/wiki/Demon_core#First_incident), and possibly contaminate the whole area. An ancient (and, incidentally, sentient) nuclear bomb appears in Arsen Darnay's *The Karma Affair* (1978). I seem to remember it being intentionally detonated by letting it fall from a very high tower. [Answer] Oh my... This has happened before. It wasn't a bomb, though. It was 1987. A hospital in a Brazillian town used caesium-137, which is radioactive, in a radiotherapy machine. The hospital building was abandoned with the equipment in it. Some thieves scavenged the caesium containing equipment. They pried their salvage open and found an eerily beautiful blue-glowing dust inside... The thieves took the dust home, and showed it off to their friends and family. People were amazed by the dust and exposed themselves to it in various different ways. One of the thieves used the dust to paint a cross on his abdomen. The other gave some to his six-years-old daughter, who used it as glitter and even swallowed some. The poor girl died a month later from a very slow and painful death, horribly disfigured and bleeding internally, and alone in a hospital because the nurses were too afraid to come near her (they knew about radiation and had no equipment to deal with it). The kid had to be buried in a lead casket. The populace was mad at her death, but they didn't know who to blame... They were poor, uneducated people. They were also afraid her burial would pollute the cemetery with radiation. Besides the girl, three other people died in hospital. Other 250 people had enough caesium in them to be picked up by a geiger counter, but only 20 showed any signs of radioactive poisoning, and they all survived. [You can read more about it here](https://en.m.wikipedia.org/wiki/Goi%C3%A2nia_accident) or listen to [the BBC Witness podcast](https://www.bbc.co.uk/programmes/w3cswsfy) about it. I suspect that if people open up a nuke 500 years from now, specially if they don't know what they are doing, a similar incident would happen. [Answer] If it's a thermonuclear bomb, the lithium deuteride will likely catch fire as soon as someone breaks its sealing. They won't be able to extinguish the fire (using water, of course, instead of sand), the thing will burn out, including the chemical explosive (no, it won't explode), spreading radioactive char all over the place. The villagers die, nobody else will dare come close for ages. (Right, solid pieces of LiH don't spontaneously ignite in dry air. So? One moist helping hand, and they have their own little Mini-Chernobyl.) [Answer] It depends on how deep you bury it. Radiation can be blocked by soil: Material Thickness (inches) Lead 4 Steel 10 Concrete 24 Packed Dirt 36 Water 72 Wood 110 and detonation can also be muted by soil to the point where the Tar Bomba feels like a tremor. ``` 18 June 1985 ``` A 2.5 kiloton nuclear device was detonated at the bottom of a shaft 2,850 m (9,350 ft) deep at a location 60 km (37 miles) south of Nefte-yugamsk, Siberia, Russia, on 18 June 1985. The detonation was carried out in an attempt to stimulate oil production. For a comparison, the Hiroshima bomb had a yield of around 15 kilotons. The Russians carried out 116 nuclear explosions between 1965 and 1988 in a program known as No. 7 - Nuclear Explosions for the National Economy. Known internationally as peaceful nuclear explosions (PNEs), their uses included reservoir and dam-building, mineral prospecting, increasing oil and gas production by liberating material from rocks, creating underground gas stores and putting out subterranean oil and gas fires. The United States had its own PNE program known as Project Plowshare. <http://www.guinnessworldrecords.com/world-records/deepest-nuclear-explosion-underground> [](https://i.stack.imgur.com/El73h.jpg) [](https://i.stack.imgur.com/0CVcR.jpg) Russian testing grounds. The Official CTBTO CC BY 2.0 [Answer] Radioactive isotopes eventually decay, or disintegrate, to harmless materials. Some isotopes decay in hours or even minutes, but others decay very slowly. Strontium-90 and cesium-137 have half-lives of about 30 years (half the radioactivity will decay in 30 years). Plutonium-239 has a half-life of 24,000 years Most nuclear weapons these days have a reservoir of Tritium gas, which is a radioactive isotope of hydrogen. The half life of tritium is about 12 years, so the reservoir needs to be periodically replenished to maintain reliability. Plutonium is very active, decaying at a high enough rate to actually heat itself up significantly. Little is known about the effects of long term radiation damage on plutonium metal, and when coupled with the sustained high temperature, it's conceivable that adverse changes in the crystal structure could take place. Nuclear weapons are full of unstable material. in most modern weapons, insensitive high explosives are used, but they are exposed to decay heat and a constant stream of gamma radiation from Pu-240 impurities in the bomb's core- this can lead to expansion and cracking of the explosives, damaging them and preventing the bomb from yielding the proper amount. Also, the explosives decay over time; both of these effects necessitate replacement of the explosives. The bomb's pit (the core) is typically plutonium; plutonium is radioactive and is constantly decaying, and as such microscopic helium bubbles form in the pit, and can affect the symmetry of the core's implosion. Also, the aforementioned decay heat can warp the metal, and radiation from decay can damage the crystalline structure of the pit- plutonium has six common allotropes, and radiation/heat can cause the metal to change allotropes. All of these effects require the pit to be reformed every once in a while. Modern bombs use tritium boosting gas. Tritium has a half life of about 12 and a quarter years, and as such must be regularly replaced to maintain the ability to yield properly. While nuclear weapon maintenance schedules are obviously classified, those two items probably give you a ballpark estimate of a few years or so. While an unmaintained warhead might still fire, the yield could be significantly reduced. A weapon sitting at the bottom of the sea would be rendered non-functional pretty quickly, but the materials would be salvageable. [Answer] I suspect as long as the pit is left alone there is not a problem. A lot of effort is expended in isolating the fissile material from the handlers and the thick metal walls will take eons to corrode unless accelerated by some chemical reaction. However there are the conventional explosives that when detonated compress the pit to produce the nuclear yield. Over time I imagine the conventional explosives will be come unstable and be a monumental risk if someone sneezes at the device or a mouse crawling over it farts. [Answer] The danger of a criticality accident. The warhead would not be in a condition of exploding, but fissure material (Plutonium-239) would still be very active. If the farmer (or rather a smith) would get an idea to collect the pieces of plutonium and melt them together in a forge, he will create a localized irradiation effect. P.S. The previous version of my answer is corrected to reflect that there is no danger of Chernobyl-size accident from a single nuclear warhead, because amount of fissile material is too small for it. A single nuclear reactor, by comparison, contains an equivalent of 100+ critical masses. ]

[Question] [ Swords are neat. Unfortunately, they aren't very practical with guns around. What sorts of technologies, social circumstances, environmental factors or magics would allow for people who train to fight primarily in melee to be competitive (or at least viable) as soldiers in a setting with common access to firearms or other, similarly effective, ranged weapons? [Answer] The primary reason melee weapons are not used in modern warfare is range. In the time it takes a sword wielding combatant to close the distance to a rifle wielding combatant, the rifleman has shot the swordsman multiple times. There are two basic ways around this, both of which have seen use in history. Closing the distance faster, or just take the hits on the way in. ## **Close the distance faster** This could be reducing the distance itself, as in fighting in tight spaces, or covering that distance so fast that the rifleman does not have the chance to fire accurately.  Historical examples of the first include tunnel warfare and urban combat, where weapons often cannot be brought to bear fast enough on melee opponents. (Note that there are counters to this in the form of pistols, submachine guns, and short tactical shotguns) Futuristic warfare might adopt melee weapons if combat often took place in densely packed hive cities or in tight tunnel complexes or ship passages. Covering the distance faster fell out of favor in our history due to the invention of the machine gun and the semi-automatic rifle. WWI being the last major war to employ traditional cavalry, for example. In the future, cybernetic or genetic augmentation might make humans fast enough and agile enough to approach a rifleman at speeds too great for him to react. In addition, short range teleportation in the form of the classic "blink" device could remove distance altogether. ## **Take the hits**    The question of ranged combat vs melee combat has existed since the first human chucked a javelin at a guy with a club. For most of human history, however, the guy with the club has had access to some level of armor to deflect or stop ranged projectiles. This allowed him to effectively shrug off many of the projectiles directed at him, allowing him to close the distance and eliminate his adversary. Today, weapons technology has turned armor from near invincibility to a layer that just prevents you from dying instantly. In the future, however, armor technology might increase again to the point where a melee warrior could once more shrug off the bullets directed at him, letting him get close enough to put his weapon to use. Shields, kinetic absorbers, alloy plates, or even just genetically engineered super-regeneration (Wolverine) would make melee combat more viable. (At least until someone makes a better gun) [Answer] 1. **See Star Wars.** If guns are ineffective and/or can be used against you via magic (see [this answer](https://worldbuilding.stackexchange.com/a/2933/179) for other points), then people will look for alternatives. 2. **On the frontier.** Guns require ammo. Specially in space settings (or zombie settings), ammo (or rather the components to make ammo) may be rare enough that people don't want to (or can't afford to) fire a bullet's weight in gold all the time. Even if melee wasn't preferred, it would likely still be common/trained. 3. **Across the galaxy.** Guns are great, but they're fairly well specialized to an oxygen atmosphere with certain characteristics (density, not-explosive, not corrosive, not filled with tiny grains of sand/silt, not hurricane winds). You could have different guns for different environments, but can quickly become awkward/inconvenient. 4. **Stupid dragons.** Guns pierce things. If your world is populated by lots of things that aren't seriously wounded by piercing (things with lots of armor, things with few vital organs, things that will slaughter you before bleeding out, etc) then it may be better to have a weapon that's capable of defense and easier to tie to secondary effects (poison, electrocution, fire, etc). 5. **Stupid people.** If you're living in a *densely* populated world (think Tokyo x10 with flying cars), then you're unlikely to ever have a clear shot. Combine that with possibly draconian laws about injuring innocents and it will encourage a more intimate form of assassination. 6. **Stupid dome.** If you're living in a place where a stray bullet can cause explosive decompression, then you might not want to use guns. And people around you will *definitely* not want you to use guns. [Answer] A common trope in science fiction is personal force fields/force shields that repel objects on the basis of their momentum/velocity, i.e. a high-velocity object (bullet) will be repelled, but a slower object (sword, knife, etc.) can penetrate. See e.g. *Stargate SG-1* (where Colonel O'Neill regularly gets past Goa'uld personal force shields by throwing his knife) and *Dune* (where fighters are trained in a strange(-to-us) form of hand-to-hand combat that emphasizes quick evasions and defenses but slow attacks to push through the shield). If these are cheap and/or common enough to fit your soldiers with, people are going to ditch the guns pretty quickly and rely instead upon hand-to-hand weapons that bypass these defenses. **Addendum:** It should be noted that when the "higher momentum" of a bullet is cited as being the cause of the shield repelling it but not, say, a sword, it's just flat wrong. An average (medieval) sword (~3 lbs) with an average speed at impact (~40 mph) has around 25 kg-m/s momentum; a 115-grain bullet traveling at 1500 fps (a reasonably powerful handgun), however, has a measly 3 kg-m/s. That is, the sword has more than 8 times the momentum of the bullet! This could be why the sword can bypass the force shield though -- it simply has enough momentum to overpower the shield. (If this is the reason, though, cue the onslaught of high-caliber, high-velocity rifles and high-velocity shotgun shells as a possible countermeasure; you'd have to crunch the numbers to find what mass/velocity is needed for a bullet or slug to overpower the shield, and of course if it can be countered by high momentum sheer volume of bullets could likely be enough to overpower it.) Of course, a bullet likely does have more momentum than a thrown knife, so it could still be that the shield repels high-momentum objects -- but just make sure that you use the right terminology to explain why *[foiled weapon]* doesn't work but *[favored weapon]* does! Another common excuse for hand-to-hand weapons goes something like this: "If you fire your gun you'll pierce the hull and kill us all!" This ignores, however, that modern technology has things called "frangible bullets" that, while not perfect, are designed to penetrate soft flesh but break apart harmlessly on firm walls/bulkheads; naturally, if piercing bulkheads in a pressurized spaceship was a real concern, this area of technology would advance quickly to give you useful firearms with minimal risk of depressurizing your spaceship. There's also a slew of non-lethal projectiles, from rubber bullets to beanbag rounds to Tazer rounds, that could be useful anti-personnel ammunition with, again, minimal risk to bulkheads. Of course, with these types of rounds simple body armor now becomes a lot more useful precisely because of the *desired* properties of these ammunition types to not pierce hard objects, but they are still useful especially in situations where wearing body armor would raise suspicions and draw attention long before any shooting became necessary (e.g. walking through the spaceport to board the passenger liner). [Answer] Don't forget water. Guns don't work very well under water. If you had a setting where the intelligent beings lived on a planet with little landmass, they might simply live under water. Either they are native water-dwellers, or they live in pressurized bases. You wouldn't really want to fire a gun in the base (less fun than firing it in an airplane), and in the water, they'd be mostly useless. Looking at modern underwater weapons, they are more inline with old-school crossbows, with all that entails - relatively low ammo supply and fire rate among others. As a bonus, underwater environment is much more 3D than our experience. It's harder to find useful cover, and you need to guard yourself from many more sides in a fight. The combat might overall be more akin to the Roman legions - throw your spears (fire your spear-guns), close in quickly and battle up close. Shields and armour would probably be worthwile, and swimming head-on on enemies presents a much smaller are to hit. The close combat itself would also be very different. You wouldn't be able to use broad slices you see in hollywood fencing, instead, you'd mostly concentrate on getting a good grip on your opponent (for leverage), and using short, mostly stabbing weapons. Leverage is very important, because you don't have the ground to push, so without a grip, you're not likely to do much damage. This might be offset by having small dart-guns for close combat when you can't get the leverage - if the opponent tries to avoid the meelee, you'd simply take out your dart gun, and give him a shot from close range. To prevent that, the opponent would likely rather fight with a grip. Stab, stab, stab, stabbity, stab! [Answer] "Bullets don't worry much any more. Not since I had my brain enhanced to run at fifty times normal speed. What you think of as a second seems like almost a minute to me. So bullets... they're slow pokes. When I see them coming, I just get outta the way." The cyborg pauses for a moment, taking a deep breath while his hands continue their amazing dance of juggling a dollar's worth of pennies, all at the same time. "No, bullets don't scare me. I save my fear for really dangerous things, like someone as fast as I am but wielding a rapier or a knife." [Answer] If you want people commonly using guns, go ahead and do so. But remember that [a knife beats a gun](http://www.thetruthaboutguns.com/2014/04/mike-mcdaniel/knives-vs-guns-deadly-distance/) if the knife weilder is within [21 feet (6ish meters)](http://www.your-krav-maga-expert.com/gun-vs-knife.html). Military personel commonly carry knifes with them even with automatic weapons as their main killing tool. If you don't want the gun to dominate at greater distances, you have two easy options. Lots of obstructions or hazards. Obstructions are covered in other answers, so here are some hazards: * The vacuum of space. If you are inside a ship and you pierce the hull, then it's game over for your victim, but you as well and anyone else on board. * Innocent lives. Even the best marksman sometimes shoots straight through his target into whatever is behind it. * Explosives. I know this Video Game and TV trope of setting off explosives with a bullet is total bull, but it is commonly believed total bull. Do like in Pamplona and run with the bull. Additionally, swords could have a ceremonial significance like the samurai did in Japan. Ranged weapons were quite common in his time, but the katana ruled. Lastly the Dune series of books had a personal force field that was stronger the faster the incoming projectile, so bullets would bounce off, but knifes would go straight through. There are potential real world armors incorporating non-newtonian fluids which would have a similar effect. [Answer] 1. Obscured vision. If you often can't see very far away, then a melee weapon may be better than a ranged weapon. This could be anything that makes it hard to see very far away, such as dust or gas in the atmosphere, lots of fog, smoke, etc. It could also be a common countermeasure. I.e. if some technology makes it easy to produce lots of gas/smoke/vapor intentionally designed to block targeting sensors as well as human vision, it could make melee weapons very useful. Especially if it can overcome countermeasures people might come up with such as powerful fans or air cleansers. 2. Blocked line of sight/fire. There may often be many obstacles in the way of taking long-range shots (but not too much to make it hard to use a sword). In such cases, melee weapons may be better than ranged weapons. 3. Delicate environments where you can't afford to miss with a ranged weapon. Combined with adequate armor that means people need to use high-powered weapons, which would also cause too much collateral damage if they miss (like breaking environmental seals while on a spaceship, dome on a planet with deadly atmosphere, someplace with lots of volatile or very valuable objects, etc.). 4. Somewhere where ranged weapons would be detected and responded to by something whose attention you really do not want, and neither does your opponent. Setting-specific, but there may be detectors that will pick up ranged weapons but not melee weapons, and such weapons may attract a worse adversary than the people you want to fight. 5. The ranged weapons are ineffective for some reason. This is harder to find a reason for at high tech levels without using handwavium. At the tech levels where melee weapons were mainly used, not so much: armor and shields can be effective against arrows. Good high-tech armor or shields might deflect most ranged attacks, while for some reason there might be more powerful melee weapons... or the missile-deflecting shields might have a minimum radius, so one needs to advance inside the shield to hurt someone, at which point a melee weapon could be more effective. [Answer] i'll add one just for the shake of it. You may want to learn close-combat / sword instead of firearm if you're not sure of the effectiveness of the firearm in a multiple environments. * In the books "9 princes of Amber", the heros and it familly may go from dimension to dimension in a pinch. A sword can hit anywhere, a firearm need some given physics to work. Thus they learn sword (in fact, in their world, powder do not work). * You have the same idea in the game "Arcanum", where the use of (any) magic slightly modify the standard physic around, and may cause a gun to fail. In short : a sword works nearly everywhere, not a gun. [Answer] I can come up with two things off the top of my head. The first, is very effective body armor, that negates projectile weapons, however for a sword to be viable, it would have to be more like a light saber or some kind of special edge high frequency sonics? or something similar. The other could be where there are weird atmospheric affects where the atmosphere acts like a lens distorting things more than a handful of steps away so you don't know where you are really aiming at. So up close and personal it is. ETA One more! I just finished a book where an overseeing computer (or any other powerful being) allowed or disallowed different levels of technology in specific areas. So if a gun just wouldn't work, then... [Answer] I noticed most people forgot about the social part of the question so I thought I would address it. Here are a few social reasons to use melee instead of guns: 1. Social stigma: Some historical event may have happened because of or involving firearms. Such an event may have caused guns to be untrustworthy or just plain rude, maybe even illegal. Imagine guns are now looked down upon, and people give you disgusted stares if you have one. You pass a cop who sees it then arrests you. In a world like this, having a gun would be very hard to get and altogether not worth the hassle. Guns would also draw unwanted attention. People who use guns in this world are as bad as terrorists in America; they may not have been the ones who bombed the Twin Towers, but they might as well be. 2. Guns are for the few: This could be in a culture where only certain people are allowed guns, such as royalty, or guns are very expensive. Maybe the only people allowed guns had to be specially presented them. This may include ceremonies similar to how the Queen knights someone. In both of these examples, anyone with disregard for the law may still e able to get ahold of a gun, but this may prove difficult as the demand for guns will have gone down, leading to a near stop in production. On the flip-side, melee weapons will have become the most viable means of self defense, leading to a rocket in production. I thought of another one that didn't involve the social environment: 3. Concealment Certain melee weapons may be much more easily concealed than most guns. In addition, most melee weapons are flatter than guns, making them easier to slip up a sleeve or pant leg. (Note: This can work with number 1 if *all* weapons are made illegal.) [Answer] **Social Restrictions** This option is pretty strait forward. A sufficiently isolated nation (meaning it wont be invaded and conquered by another nation that does use firearms) could have a social taboo against firearms. Most likely this would be a "honor" type scenario where killing someone without them having a chance to fight back is dishonorable. **Timeline** Stick with a past timeline where firearms have not yet been developed **Environmental factors** Components for the effective creation of firearms, or the creation of ammunition could be in short supply. This has a whole host of other implications on society as the components for fire arms are used in a huge number of different items. You could also have an area that is craggy or heavily treed where that range of firearms is irrelevant because you can only get line of sight on your enemies when they are about to cut you in half. (This would be more feasible with early firearms as it took more time to reload). **Technological Factors** If ranged weapons advance beyond solid shot, so lasers or something similar (think star wars), effective personal shielding against energy weapons could re-assert the value of melee combat. Similarly, advanced body armors could provide this protection the difference with traditional weapons is you have the velocity of projectile impacting with such force that even when it doesn't penetrate the armor it could kill the wearer from blunt force trauma and being knocked backward alone. **Other** Wasn't sure where to place this. Specialized forces, think a modern special forces/ninja hybrid, could make effective use of blades. Blades are quiet and stealthy. A secret assassins guild could also use blades to maintain a mystique and fear factor. "We are so good we don't even need guns! COWER!!!!" [Answer] Guns depend on precise chemical reactions; too much or too little will be at least less effective and possibly break the receiver. So what if there's a process that can either destabilize or suppress chemical reactions? It could be simply "magic," or a psychic power, or ultratech. So in this world, an elite fraction of each army is composed of alchemical sorcerers/psykers who can blow up the other side's guns. Or maybe a Oxygenation Suppression Ray is part of *every* 22nd-century infantryman's kit. Without guns, you can use bows, crossbows, and melee weapons. But armor renders most bows fairly ineffective (let's say), plus they're hard to use. You might have groups of master longbowmen, but they're not practical for widespread use. Crossbows are great, but big and clumsy. They replace machineguns as defensive and suppressive weapons, but the rate of fire means that enemy swordsmen can close the distance and engage before you can reliably take them all out. So again you probably have units of crossbowmen, maybe even every soldier carries one, but they're not the alpha and omega of weaponry. Finally, guns may still exist, but in niches. Snipers may still operate, but they have to shoot-and-scoot damn fast so they don't get zapped. Suicide soldiers may carry concealed submachineguns or similar, whip them out at close range, and try to inflict some damage before their own ammo kills them (or their guns simply jam, depending on the anti-chemical field). You could say that the anti-reaction effect has a similar disruption on engines, thus eliminating vehicles, or perhaps diesel engines are too simple and rugged to be affected - it's up to you. Maybe even living things are affected! We're just a bundle of chemical reactions, so being subjected to this field could cause... shortness of breath; blurred vision; nausea; cancer; blind rage; psychic powers. Maybe only people with superb physical fitness can cope, so wars are fought with small groups of He-men. Or maybe women tolerate it better and *they* are the new warrior class. Voila, a world where melee weapons are at least viable, if not the exclusive armament! [Answer] My answer is based on both conceptual but experience in martial arts and in RL situations: **"A gun pointed at your head, from behind or front"** The classic situation where a gun pointed at an individual, is a waste of time is if that individual is already close and not seen as a threat. Now lets remember modern warfare and policing is often against unarmed or lesser armed civilians. In these situations "A gun pointed at your head, from behind or front" can been easily removed and the gun bearer dropped - many Aikido techniques are based on this. So this is based on the concept of you not being a threat being unarmed. Bringing this in the OP ideas, if you could fool and drastically reduce your image of being as a hostile target, a classic disguise or a worn hologram of an old women or something else (donkey). Projected imagery, perception influence is a technology tool that some ex-govt scientist have worked on - remote influencing on a high level. **Line of sight** Many martial arts and gun users, cannot deal with someone behind them. Once again Aikido and other grappling art forms, you can drop another if you are next to them or behind them. Even if they have a sword or a gun. Once again this is based on getting close. In classic sword work, you are moving off line whilst striking or doing a lunge jab to hit between the ribs, this is followed through in Aikido where you are moving offline and into the attackers space. Even taking classic wrist slices, which happen a lot in Samurai cultural (hence the armor over both sides of the wrists), you just need a well aimed slice at the wrist - easy over 4-5m. I have seen Sensei's and other Aiki's doing massive 8m or more flying forward rolls, holding a Boken (wooden sword), clearing a whole dojo matt in one leap, counting the roll at the end. I used to be able to do sideways Aikido rolls. Considering part of the training is to chain various directions of rolls, you could easily use obstacles and more to get out of the field of vision of an armed attacker. Bringing this into a sci-fi situation if they gun bearing is distracted or has a false target, a hologram perhaps, then you can get behind them. **Not being seen** Nothing too technology based here, but reading into Ninjutsu how they hid was often quite cool and simple. From flashing light off their blades to momentarily blind the opponent then moving out of view. To staying outside of the peripheral vision when approaching someone. And simply being really quick and good at hiding, awareness of shadows and more. A classic stealth situation. If you take this into a science fiction era, we already have had publically exposed light wrapping tech and light absorbing technology - nanotech black that absorb 100% of the light, its used in those new space bound telescopes. Plus the stealth tech in the military.. That might add to above. [Answer] If you have a cultural honor system where duels can occur within the battlefield, swords or other melee pieces can be quite practical. Take the encounter between Fin and Tr-8r in *The Force Awakes*, but add a cultural honor rule that would prevent Han Solo's intervention. Boom! Melee combat is not the main form of combat, but in large face-to-face battles, it may be more preferred. That and upper body armor will allow people to be close enough for a duel to be the most practical combat. [Answer] Not sure if this qualifies as a comment or an answer, but here is something to think about. A Firearm can be detected from a variety of methods. Dogs can smell the propellant, Metal detectors can sense the projectile, the frame, the barrel and the cartridge. Can you get your firearm to where it needs to be in order to use it. In a covert situation, the answer is "with great difficulty" A martial artist, however, is the weapon. More particularly, a ceramic bladed knife will not be detected by normal methods and can penetrate modern body armor anywhere there isn't a shock plate. I get that this deals more with covert operations, but this can grow out to maybe warfare status when you consider that power being brought to a point may be more effective than bludgeoning the countryside. A number of assassins that get inside and take out 20 or so top level leaders could potentially disrupt a war effort enough to bring it to an end. [Answer] Okay you guys gotta go to guerilla school. Guns almost invariably make either loud noise or bright lights (heat beams excepted). Granted if you want stealth you could go with silencer or suppressor for your chemical slug thrower. Each of these possibility and their variations also have a strong chance of hitting that 10,000 volt liquid hydrogen line or disrupting anti matter exchange unit (I speak in simile). However you can achieve little noise / flash with your good old buddy the knife. But there are other bonuses to be found here: shooting someone in the gut and tying up two members of a boarding team (one to treat one to guard -- a similar tactic pursued by the North Vietnamese. Again the knife can do this only with more precision. Its easier to cut someones larynx with a blade. Ye old armor argument. Space suits can deflect / absorb the incoming projectiles energy. Kromey says swords are better than bullets. I don't have time to work this out, but I have heard a space suit can take a full sized .50 caliber round (I have no source, so take it for its worth). The point is that when we last saw these style argument was the middle ages and we worked out weapons like eared daggers (<https://en.wikipedia.org/wiki/Ear_dagger>) and misericordes (<https://en.wikipedia.org/wiki/Misericorde_(weapon)>). The latter was by the doctors of the day to mercifully kill warriors with a quick jab through the armpit to to the hear. It was intended for use on those who would die slow horrible deaths. The point being that no armor is full proof and it's generally easier to hit that seam, overlap, what have you with a blade. Finally knives allow a different type of warfare. Sure you could pistol whip or blow the lower jaw off an adversary, but with a knife you do all kinds of horrible things. Cut his fingers of and sew them to where his genital were. Stuff his cut off toe into his mouth. The list goes on. Try and do this with against a 10 man squad and you'll end up another fighting another 7 or 9. Oddly enough if you do this to say 2 or 3 men out of a 10 man crew someone is going to loose their proverbial apple pie. A disorganized enemy is always easier to fight than a organized one. Bonus points: Change the dagger to a wasp injection knife (<http://waspinjection.com/>) -- it injects gas into a deep stab wound. But we will go one better: Mix the gas white phosphorous powder and nitrogen. Make the guy scream as the medic probes the wound. [Answer] Sword is capable of piercing a kevlar coz only high speed contact can harden it Try to explain. Kevlar can stop the bullet coz of ripples effect that the bullet impact cause(not sure about it). So we somehow have there small(~5 cm) round of fabric that,still holdin a flat(in compare of spike-like) state, moves with the bullet for a while.Sword will just go straight through . <https://vimeo.com/34981287> ]

[Question] [ OK, so scientists have found a great new substance: That substance makes you think ten times as fast! The advantages are obvious. However, as every medicine, this pill will have side effects. There are obvious side effects like that a faster-thinking brain will likely also have a much higher energy consumption. However, there may also be less obvious side effects from the mere facts that you're still communicating with other humans who have a normal thinking speed, and interact with a world (including your own body) that didn't speed up with your own thinking. So my question: How would your thinking speed-up affect your life? Could those side effects even be so severe that you'd not want to use the pill, except possibly for rare extreme conditions? [Answer] Several modern works of fiction have focused on this question, including [Wired](http://rads.stackoverflow.com/amzn/click/0982618492) and the movie [Limitless](http://www.imdb.com/title/tt1219289/?ref_=nv_sr_1), which itself was based on another book called [The Dark Fields](http://en.wikipedia.org/wiki/The_Dark_Fields). Both of them start with a premise that's fundamentally rooted in reality, which is that the road from scientific discovery to mass production is a very long one, and quantities would initially be very scarce. This would quite likely create cut-throat competition of the most literal kind. Making us 10x smarter would *probably* not make us any less selfish, which means that there would be a strong motivation for early users to try to cut off access by anyone else, in order to preserve their advantage. Moreover, with extreme intelligence they would likely have no trouble manipulating politicians, media, or even organized crime into unwittingly doing their dirty work for them. There might be real side effects at first, but if you took a team of neuroscientists and geneticists and supercharged their own brains, even for a short time, they could almost certainly devise ways to improve the drug to eliminate or at least regulate those side effects. Something like this happens in both of the aforementioned plots. In a rational-but-selfish world, normal people would probably be deterred from taking the pill due to a general lack of availability, extraordinarily high expense, a ton of misinformation regarding the real effects and side effects, and a potentially legitimate concern over the quality (as there is with many illegal drugs today - the drug itself might be almost completely safe in its pure form, but you can never really trust the source to be giving you that). Presuming there were already-intelligent, informed observers who believed they could reliably obtain any quantity of this miracle drug, the main side effect would be painting a giant target sign on your back. You'd be chased around the world by people either (a) wanting to find out your source, (b) trying to stifle the supply and prevent a "leak", and/or (c) morally or religiously opposed to everything you're doing. Being 10x smarter *might* not be preferable to having 10,000x as many enemies. There could be physiological side effects, but one thing that probably *wouldn't* happen would be amphetamine-like symptoms. Amphetamines work by ramping up certain neurotransmitters; they don't *literally* make the user's brain faster, they are still operating at roughly the same 20 Hz as everyone else. A drug that could literally increase intelligence (AKA "thinking speed") would probably alter glial cells, like [astrocytes](http://en.wikipedia.org/wiki/Astrocyte) or [Schwann cells](http://en.wikipedia.org/wiki/Schwann_cell). Messing with these could be very dangerous, as we already know of several disorders related to them. [Peripheral neuropathy](http://www.mayoclinic.org/diseases-conditions/peripheral-neuropathy/basics/definition/con-20019948) seems like a likely candidate for a temporary or permanent "comedown". This includes fairly scary conditions such as [Guillain–Barré syndrome](http://en.wikipedia.org/wiki/Guillain%E2%80%93Barr%C3%A9_syndrome), [Vasculitis](http://en.wikipedia.org/wiki/Vasculitis), or something more straightforward like kidney failure. Of course, you might be less lucky and suffer damage to the CNS rather than the PNS. Migraines, epilepsy, bipolar disorder or Alzheimer's - with a drug that causes major physiological changes in the brain, pretty much anything is fair game, even conditions that are thought to be genetic. It would also probably force your body to consume *enormous* amounts of energy; our relatively slow "clock speed" is very *efficient*, which is why it's so successful, but operating 10x faster could very well require 10x as many calories (*Wired* had the protagonist tearing through boxes of donuts after coming down). This could lead to short-term hyperglycemia and long-term diseases like diabetes or even [cancer](http://www.canceractive.com/cancer-active-page-link.aspx?n=3087). There are lots of potentially serious side effects. As far as things like becoming a workaholic or becoming bored with people around you - I don't buy it. The massive caloric intake required to support it, and the fatigue associated with increased neural activity, would probably require *more* sleep, not less. It's not an amphetamine. There's also this thing called the [hedonic treadmill](http://en.wikipedia.org/wiki/Hedonic_treadmill), the theory (backed by quite a lot of evidence) that no matter what happens in our lives, we tend to return to a sort of happiness equilibrium. This works both ways, of course; it means that taking this pill probably would not, in the long term, make you any happier, no matter what you're able to accomplish; although it could make you a lot *unhappier* if its effects are temporary and you run out. Then you're essentially just a drug addict. [Answer] ## Best Weight Loss Solution! Ironically, the pill may well be used at first mostly for its high energy consumption as a **weight loss pill**. ## Japanese Workoholics Now Working 23-hour Days If one hour of sleep can subjectively rest you as well as 10 hours of non-pilled sleep, humanity has just gained anywhere between 7 and 70 more hours per week! 23-hour workdays quickly follow. **EDIT**: As a commenter astutely observed, the workoholics might still need to take powernaps every few hours throughout the day: Couches and blankets become de rigueur at work! ## Pill Drought Around Universities During Exam Season! People would procrastinate even more, if they knew that they can do weeks worth of studying in one day. ## Mind-Machine Interface Sales Soar! Bored teens are now installing sexting apps directly into their brains, claim spoken words and fumbling around physically are 'so totally low-band'. ## Despondent 40-year-olds finally leave parents' basements to go into the nutrient vats and live online. Living in the real world is not only **boring** (imagine waiting for a subjective 40 minutes for a red light to change) but **laggy**. Since the pill does not similarly upgrade muscles and ligaments to move ten times faster, even walking becomes a hassle, as pill-poppers literally change their minds mid-step and end up falling on their faces. Dealing with 'normals' is like talking to molasses. Imagine spending a subjective 20 hours in a 2-hour mandatory company meeting on some inane topic - you'd literally want to tear everyone's faces off. The only solution is to **live online**, where pill-poppers can live at 10x subjective acceleration and zip around as fast (or slow) as they wish, communicate quickly, and actually **get stuff done**. ## Caveat: Neuron Synchronization Issues Obviously, and this should go without saying, the question is not realistic. A realistic approach would ask how a tenfold speeding of neural function would work. It can't, at least not with natural neurons, since some neurons already work close to their capacity. Neurons with different functions fire at different speeds naturally, so only speeding some 10-fold is much, much more likely to result in a **seizure** than in upgraded functionality and perceptual speedup. Actually speeding up a biological human 10-fold would have to be worked out from the base genetic code and basic protein cascades up to muscle tissue and blood sugar transfer, and would thus be a completely different species by the time you're done. [Answer] **FEAR** For one thing, the psychological effects of being trapped in a body too slow to obey your commands would be pretty terrifying. Paralysis and helplessness is a pretty huge fear amongst most humans, and even though you'd probably be acting significantly faster than everyone else, to the person taking the pill it would still seem like their body was completely unresponsive to their commands. **BOREDOM** Irritation and boredom might also form a part of the drawbacks. Imagine seeing a film like a pigeon does - you can see every frame of the movie, so it would be like the FPS dropping out on you. How many games have you dropped for a day, a month, or that even now sit unplayed because of FPS or resolution issues? Talking to people would require you to listen for aaaaaages to get through what they're saying, and you'd have to talk at what seems a glacial pace in order to make yourself understood (or else, you'd be talking at ten to the dozen). Since this pill doesn't enhance your hearing or eyesight, you might actually feel like your senses are -worse-, since you have so much more time to appreciate their tiny failures. That sign you can't quite focus on in the distance instead becomes a green and white haze that lingers in your vision. **PAIN AND PLEASURE** Pain, also, would be vastly magnified, as would sickness. Imagine stubbing your toe on a doorway and having it hurt for days, or coming down with a cold and feeling snuffly for a month. Much like the irritation, you would perceive everything happening for 10x as long, especially given that it now takes you, as far as you're concerned, 50 minutes to wash that chilli powder out of your eye. On the other side, 5 minutes of pleasure suddenly feels like 50, so you're probably not impressing anyone with your *ahem* stamina. Pleasurable feelings like eating ice cream or taking a long bath would be enhanced, as long as you don't get brainfreeze or soap in your eye. **TRAINING** To address the extreme conditions, I imagine people amongst whom this would be in high demand would receive special training, like neurosurgeons, soldiers and extreme sports enthusiasts. Overcoming all of the above issues would be difficult, and even once training has been provided I doubt they'd be eager to experience the effects. If we develop a resistance to the effects, as is common with most drugs, you'd want to save the effects for when you need it most. [Answer] Your closest analog would probably be [amphetamine](http://en.wikipedia.org/wiki/Amphetamine). Used as a [performance enhancer](http://en.wikipedia.org/wiki/Amphetamine#Enhancing_performance), amphetamine use can: > > ...result in modest improvements in performance on working memory, > episodic memory, and inhibitory control tests in normal healthy > adults.[57] Therapeutic doses of amphetamine also enhance cortical > network efficiency, an effect which mediates improvements in working > memory in all individuals.[24][58] Amphetamine and other ADHD > stimulants also improve task saliency (motivation to perform a task) > and increase arousal (wakefulness), in turn promoting goal-directed > behavior.[24][59][60] Stimulants such as amphetamine can improve > performance on difficult and boring tasks... > > > The [side effects](http://en.wikipedia.org/wiki/Amphetamine#Side_effects) for therapeutic doses are fairly minimal, but in higher doses things get pretty dangerous pretty quickly. [Physically](http://en.wikipedia.org/wiki/Amphetamine#Physical) you're looking at side effects like: * Increased heart rate * High blood pressure or low blood pressure * Reduced blood flow to extremities * Sexual side effects in males (erectile dysfunction, frequent erection, prolonged erection) * Stomach pain, loss of appetite, nausea, and weight loss * Teeth grinding * Ticks Given your scenario [psychological side effects](http://en.wikipedia.org/wiki/Amphetamine#Psychological) may be more of a concern: * Apprehension * Mood swings * Insomnia * Anxiety * Irritability * Grandiosity * Obsessive behaviors * And at the extreme, psychosis (paranoia, delusions) It seems that many of the psychological side effects depend on the personality of the person and the dose taken. You may be able to work that into your story in some interesting ways. As in while some users may become high functioning, productive members of society others become dangerously: irritable, paranoid, and delusional. [Answer] **BIOLOGICAL** Your brain is working at 10 times the speed, but the rest of your body isn't. Your respiratory and digestive systems are still working at the same speed, glucose and oxygen can diffuse only so quickly from the capillaries, and your heart cannot keep up with the amount of blood the brain demands. The consequence is that you will experience constant dizziness and lightheadedness as a result. Not very pleasant. **SOCIAL** This pill makes you think 10 times faster. Just think of the applications. Students will be using it to cram studying for tests, white-collars will be using it to get work done earlier, and parents will use it to finally have some free time in their lives. Eventually, all of society will depend on it. This can have a couple different end results: 1. Everyone uses the pill. The rest of society adapts accordingly to be 10 times faster. This means longer work hours, heavier assignment loads, etc. Eventually, nothing has changed. 2. Law of supply and demand kicks in. With the tremendous demand, companies making the pill are free to jack up their prices as much as they choose, forming a monopoly on the pill market. Only the rich can now afford the pill. Gap between rich and poor continues to increase. 3. Sports associations ban the pill, deeming it as a performance-enhancing drug. Schools consider its usage as academic doping and start expelling students. Eventually, the pill has become taboo and is now seldom used, with its users being looked down upon for cutting corners. [Answer] Another side effect I haven't seen mentioned yet: **Epileptic seizures**. Epileptic seizures are the result of excessive signalling in the brain synapses, causing it to "overload". This seems to be a likely side effect of a drug that enhances brain speed. Every pill could carry a risk of seizure. Anticonvulsants might help, but they should have to be taken before the brain pill, so without knowing if they are needed, and they have side effects of their own. They are also only effective about half the time (up to 70% if you take several types at once). You could increase the severity of your pill-caused seizures to lower the efficiency even more, of course. Regardless of side effects, I imagine there will be a group of speed-thinking junkies that continue to use after several severe seizures and with an eroded brain. [Answer] I'm speculating a little here but is it possible that increasing the brain activity could result in a deterioration of the brain cells? It's like increasing the voltage on a computer's components. Yes, you increase their productivity; but at the cost of damaging them faster. Overstimulation could lead to the death of cells. It will take some time before giving negative effects. Losing cells could have different effects depending on which area is most affected. Having memory problems is a possible consequence. [Answer] The brain is still an unknown machine, but there are many researches that can give us some thoughts about the way electrical signals run from one neuron to other neurons. Apart from medical side-effects which can only be *assumed*, let's imagine how such a drug will makes you think faster: **by lowering the barrier that electrical signals must traverse through synapses**. A given signal, which should traverse only to specific neurons, could reach new neurons that it shouldn't reach! This could lead to either of some thoughts that might look illogical (illusions, paranoia, sense of threat, sense of divinity, etc), or some electrical storm very close to Epilepsy. Also, specialized areas from brain would be accessed by unwanted signals leading, for example, to physiological complications, like heart-beat problems. Assuming that there are no medical conditions, let's not forget what a person with faster brain might feel: everything around him/her is moving way too slower than usual, everybody will speak too slow, the person itself will speak faster because thoughts are coming faster. I think, a person with artificial fast brain will be bored soon, in a normal world... Still, a faster brain doesn't imply geniality because geniality itself is the result of a special construction of neuronal formations. Such construction can't be obtained overnight, so a normal person with a fast brain could be a normal person with a fast thinking, but *not with better thinking*. Regarding the amount of energy that such a brain might consume: despite current beliefs that we use only 10-15% of our brain, the reality is that over 90% of the brain is accessed all the time, in waves. Is the organization of neurons which makes the processing power of the brain. Giving so, a faster brain will have high frequency waves, therefore it will consume more oxygen and sugar (glucose). [Answer] Addiction. Pretty obvious psychological addiction forming for this. Down time. The 'low' of normal time could cause depression, again-the above addiction. Sleep/Dreams. The mind uses dreams to unwind, so 10x brain possible requires 10x sleep cycle to recover?? [Answer] As apaul34208 suggested, some of the effects will be like (meth) amphetamine use. It's also a bit like what many users of cocaine report, though I suspect it may be more a matter of putting to sleep one's usual inhibitions and self-criticism, so that one regards oneself as brilliant during a high, but sober minds would tend not to agree. Thinking ten times as fast may not mean thinking ten times as well. Thought speed is an advantage in some contexts but not in others. And, as the brain and nervous system regulate many other things besides thoughts (such as body functions), I would expect such a drug to have many undesirable side-effects which would accumulate over prolonged use. There are some existing sci fi works on this subject, and at least one recent film I've seen (*[Limitless](http://en.wikipedia.org/wiki/Limitless)*). In that film, it's an addictive black market drug which has cumulative bad side effects, and is used in high-stakes corporate and political contexts. The users feel very superior and tend to become megalomaniac and paranoid of other users, and so start using their abilities to out-scheme each other. Caffeine, anxiety, mania, focus, flow and various other common conditions can have a person thinking ten times as fast as others, or more. This can be effective but tends to be most useful for one person focussing on one task, rather than trying to communicate or work with others, and it often goes along with neglecting attention to other concerns. I would expect your drug to be popular with people who have unreasonable time constraints for intellectual solo work, but to tend to socially isolate and imbalance them and affect their mental and physical health. They may tend to develop ego complexes where they are disappointed with their performance unless on the drug, and the usual effects of tolerance causing increased doses to be required to achieve the same effect over time, compounding the problem and leading in some cases to resentment of newer users. I can see short-sighted employers grinding through their employees by requiring performance that can only be achieved by drug abuse. Users may tend to look for the best applications of the advantage the drug confers, which might be gambling and other high-stakes contests where the drug would give a decisive advantage. [Answer] I'd say side-effects would depend a lot on the mechanism on which the pill works. **The pill shuts down part of your brain - adrenaline like effect** I thought the speed was mainly limited by the path of neurons we need to traverse. Shorter paths -> faster thoughts and faster reactions. Try to react as quickly as a shrew (tiny mammal with very short neuron pathways). I thought we actually already use this in case of emergency. E.g. if adrenaline rush is high enough, you basically shut of part of your brain so you can react way faster. You basically think less about consequences and more about immediate actions to get to safety and stuff. Side effects tend to be: hazy or no memory, not necessarily good long term decisions (think about people in crisis situations). You can steer this to a certain extent by lots of training (hence we have all the seemingly pointless droning exercises for fire safety and military -> reinforce the good path instead of leaving it to instinct). **Faster neurotransmitter release** Going on the same vein that the path length is part of the problem, we just sidestep it here by changing the speed going over the path length. Changing the speed of electricity itself seems not very likely for a pill. So I'd opt for the pill somehow affecting the speed at which neurotransmitter is released and spreads, for example by replacing the neurotransmitter with some other chemical with slightly different properties. This chemical would still do its job as a neurotransmitter, but would transfer faster in intracellular space. There could be a wide range of side effects. Neurotransmitter plays a role in learning and memories so that could be affected. Given its faster spreading, it may also cause adjacent neurons to fire accidentally causing all kinds of random effects such as minor or major psychological disorders and or motor control issues. I doubt you'd get an increase of a factor 10 in thinking speed this way though. For ideas: <http://en.wikipedia.org/wiki/Neurotransmitter> <http://en.wikipedia.org/wiki/Glutamic_acid> <http://en.wikipedia.org/wiki/Epinephrine> Disclaimer, I'm no neuroscientist (not even a biologist), so I may get some stuff wrong. Feel free to correct me in the comments. [Answer] Sorry, this is partly physical side effects, but mostly societal. With that said, to business: What if using this drug could cause permanent and irreparable brain damage? The EVE chronicle ['Inferno'](https://wiki.eveonline.com/en/wiki/Inferno_%28Chronicle%29) talks about a drug that causes the brain to work tremendously fast... for about an hour, then they're done. Demonstrably alive, but completely unresponsive. Maybe the more of the substance is taken, the stronger the effect, but also the greater the risk of an adverser reaction meaning you spend the rest of your life drooling and eating through a tube. Perhaps people would take large doses of this drug to try and scoop discoveries from others. Perhaps research organisations would push their employees to take larger and larger doses, so that they perform better, but they just sweep the casualties under the rug, pay off the family and carry on as normal. Alternatively, what if only the discoverer of the drug knows about the side effect, but doesn't care - selling Think-U-Fast makes them money. Or someone at the manufacturing plant knows and wants to tell the world, but died in an unfortunate accident at a company event. He drank too much, crashed his car. What a shame. What if - sort of like in [the linked story](https://wiki.eveonline.com/en/wiki/Inferno_%28Chronicle%29) - the effects were known, but there was often pressure from others to take the drug and burn out for the benefit of others. "Don't you want Johnny to go to college?". "But we could cure Alzheimer's!". Maybe there are people taking the drug to try and find a way to prevent or cure the side effect before they run out of time. What if the drug only manifested the side effect in combination with other substances? Perhaps it's only harmful when taken with paracetamol, but also causes headaches. What do you take for headaches? Or maybe the drug is illegal. You don't necessarily know what the quality of the stuff you buy is, and sometimes the dose is too large. Or impurities from cooking it up in a caravan in the middle of the desert trigger the effects. That said, if you can't do anything at all then you certainly can't buy more, so perhaps the quality control would be better. [Answer] It's been proven that by taking time to slow down though we make 'better' and more intelligent decisions. The wisest people are usually the most composed, and 'slow moving' also. So what if it makes you think 10 times faster? Just ask an anxiety suffer with adrenaline 24/7 pushing their thoughts to overload, thinking too much on something can be more counter-productive. The only place it would be seriously helpful,(besides in some mental disorders) would be for solders at war where their own reaction time could mean life or death ultimately, which is what speed was originally made for. Faster thinking does not equate to better thinking. [Answer] As usual, answers get upvoted if they are fun, regardless if they touch the real world (as if world was powered by magic). Brain uses about 20% of body's oxygen and sugar. So we need to assume that body will need 10 times of these resources when functioning 10 times faster, because it will need to create 10 times amount of electric potential to fire neuron synapses. Assuming brain is powered by physics, not magic. It means **body will need 200% MORE of oxygen and glucose**. You will not be able to sleep during such heavy breathing extortion, and you will have to drink energy drinks constantly to provide glucose. You would need to **watch your sugar levels as if you have diabetes.** If you let your sugar level slip too low, you get [hypoglycenia](http://en.wikipedia.org/wiki/Hypoglycemia), manifesting [effects like](http://en.wikipedia.org/wiki/Hypoglycemia#Neuroglycopenic_manifestations) lethargy, amnesia, ataxia, all the way to coma. Your only hope would be if pill's effect dissipate quickly, so you can get short burst of speed when you need it for short time, then slow down and deal with re-balancing your sugar levels to normal. It will be hassle, but maybe worth to some people some time - not too often. If you overdo it, you can get consequences of diabetes. One of nasty ones would be to go blind. Not fun at all. [Answer] **Irresistible urge to scrape the ground after defecating.** Users of this drug sometimes have broken or bloody fingernals because they can't feel like they've completed a trip to the bathroom without acting out a primal instinct to dig or scrape. **Losing track of people** A Global ID system keys on each individual's unique physiological signature to track movement and control the population, serve them ads, and predict marketing trends. A side-effect of this drug is that it changes an individual's signature and allows criminals and others to evade the system. **Causes video displays to moire** People on this drug can often be spotted because when they walk by video displays, a moire pattern can be seen. Other effects on cheap electronics might be seen as well, such as activating children's toys or having audio devices pick up sub-vocal speech and broadcast it at awkward times. [Answer] Other answers have dealt with thinking ten times faster as the biological processes being ten times faster. I would look at it as being able to be aware of and control more thoughts at the same time. When we think about a problem, eg. try to solve a sudoku, we might be consciously trying to determine whether a square should be a one or a five. What if the pill allowed the person to consciously figure out the contents of 10 squares at the same time? As the human brain is doing an awful lot of work besides our conscious thoughts, that in itself would not require faster biological processes, merely super focus. The effect of such a pill would be great when solving sudokus, but when you don't have anything particular to focus on, then it will be torture. Side effects would include paranoia, schizophrenia and self-induced lobotomies. ]

[Question] [ For example, a street this wide to have enough blood run down the length shown in this photo? Assume that the blood isn't going down storm-drains for whatever reason and assume the stretch of road is 100 feet long. There need not be literal 'rivers' of blood, just enough that the entire street is coated enough to obscure the road beneath. The bodies the blood comes from can be included in the answer. [](https://i.stack.imgur.com/mci4c.png) Yes, this is a morbid question but to be fair, it's for a very dark part of a story. If it breaks some rule I would be fine with it being removed. [Answer] # River method (most deaths) **Width** - Pretty simple, 12$\times$4=48 so 48' (~15m for anyone not familiar with imperial.) **Length** - Apparently it is a 100' (30.5m) long road. ## All work in the section below is based on old, incorrect numbers. Left in to provide context for comments below. See end of blockquote for accurate numbers. > > ! **Depth** - Blood has a pretty bright, strong colour. A coating 5mm (0.2") thick would be more than enough to obscure the colour of the road. (1mm (0.04") could probably do it but I'm not sure so I'll play it safe). I assume there is no vertical slant but roads often have a horizontal slant as a flood reduction measure and the slant is usually 4%. I doubt this holds true on a road your size but I'm going to go with it just in case. The road is 48' so at 4% every foot across we go 0.04 feet down. 0.04$\times$48=1.92 so we drop by ~2' (0.5m) this means at the deepest the blood must be 2' 0.2" (0.6m) thick. An average depth of 1' (0.3m) thick > > > ! **Volume** - This gives an overall volume of 48$\times 1\times$100 or 4 800 cubic feet of blood (136 cubic metres). Converted to a more standard measure that is nearly 30 000 imperial gallons (136 000 litres). > > > ! **Humans** - An average adult contains up to 1.2 gallons (5.5 litres) of blood. If we completely drain every human (see @Flummox for method) we would need 30 000/1.2 = 25 000 people. We might not be able to fully drain every human as I don't know what wounds you're using. As it is you need at least 25 000 people and probably far more. I expect you will struggle to drain even a quarter of each person's blood in a street fight so you might require over 100 000 people. On the other hand I have gone for higher estimates for depth where I can so the actual number may be significantly lower. I suggest anywhere between 25 000 and 100 000 people is definitely a safe bet for this method. > > > ## More accurate numbers **Depth** - Blood has a pretty bright, strong colour. A coating 5mm (0.2") thick would be more than enough to obscure the colour of the road. (1mm (0.04") could probably do it but I'm not sure so I'll play it safe). I assume there is no vertical slant but roads often have a horizontal slant as a flood reduction measure and the slant is usually 2.5% (thanks to @AndyT). The road is 48' so at 2.5% every foot across we go 0.025 feet down. 0.025$\times$24=0.6 so we drop by 0.6' (0.2m) this means at the deepest the blood must be 0.6' 0.2" (0.2m) thick. An average depth of 0.3' (0.1m) thick. **Volume** - This gives an overall volume of 48$\times$0.3$\times$100 or 1 440 cubic feet of blood (41 cubic metres). Converted to a more standard measure that is nearly 8970 imperial gallons (40 800 litres). **Humans** - An average adult contains up to 1.2 gallons (5.5 litres) of blood. If we completely drain every human (see @Flummox for method) we would need 8970/1.2 = 7475 people. We might not be able to fully drain every human as I don't know what wounds you're using. As it is you need at least 7475 people and probably far more. I expect you will struggle to drain even a quarter of each person's blood in a street fight so you might require over 29 000 people. On the other hand I have gone for higher estimates for depth where I can so the actual number may be significantly lower. I suggest anywhere between 7475 and 29 000 people is definitely a safe bet for this method. This can be reduced further if you take into account the displacement by the bodies.I can't find a value for how wide a human body but I'm going to assume it will let us fit in one row of humans on each side before they start sticking up over the level of the blood. The average human height is roughly 5' 6" (5.5' or 1.65m). In a 100' road we can fit 100/5.5=18 people per row. Two rows gives a total of 36 people. (We could possibly fit more in by curling people up but that is too complicated for me to work out.) The average human has a volume of approximately 13 gallons (62 litres)(Might not be accurate as our bodies have been drained of blood which may effect their volume.) We have 32 people so the volume of bodies is 32$\times$13=416 gallons (1890 litres). We can subtract this from the gallons of blood needed leaving us requiring 8554 gallons of blood (38 880 litres). Redoing the body count with this new maths gives 8554/1.2=7128 people as our minimum and 28 500 as our maximum so a small reduction. ## Other methods (less deaths) That is a lot of deaths. As pointed out in the comments this can be significantly reduced. **Dilution** - Dilute the blood and you need less blood. Blood also maintains its colour pretty well so it can be diluted quite a lot. Using a blood:water ratio of 1:2 should be o.k reducing the minimum from 7128 to around 2376 and the higher estimate from 28 500 to 9500. **Painting** - This is probably the most practical method although it won't give a river of blood and is pretty unimpressive although it will still obscure the street. By painting it on we can reduce the depth required from 1' (0.3m) to 0.2" (5mm) reducing the lower estimate to just 8 people and the higher estimate to 32. **Grinding the bodies** - Further up I worked out the number if you included the bodies. That involved lying them down so reduced the number we could use. If we grind up the bodies and mix them with the blood we can reduce the blood usage significantly. This means we are effectively getting 13 gallons (62 litres) per body instead of 1.2 gallons (5.5 litres). Our sum is now 8970/13=690. This time there is no range as we get 100% of every body's volume. **Appendix** A diagram drawn up by @MadPhysicist may help clear up the first method. I used a slightly different method by using half of the height instead of putting a half in the whole sum but other than that the methods are the same.  ## Summary Table $$\begin{array}{|c|c|c|} \hline \text{Method name} & \text{Minimum} & \text{Maximum}\\ \hline \text{River method (no bodies)} & 7475 & 29000\\ \hline \text{River method (corpses)} & 7128 & 28500\\ \hline \text{River method (ground bodies)} & 690 & 690\\ \hline \text{River method (dilute)} & 2376 & 9500\\ \hline \text{Painting method} & 8 & 32\\ \hline \end{array}$$ *Disclaimer - My maths is probably wrong. Please point out my mistakes.* [Answer] [](https://i.stack.imgur.com/cSG5f.jpg) This is the city of Dhaka, Bangladesh last year. Streets running red with blood. There is a lot of rainwater too which hopefully is not cheating. Still pretty bloody looking. I read that 100,000 animals are sacrificed there for this ceremony each year. Probably not all on this particular street though. I read that the city set up 1000 places for sacrifices to happen throughout the city but people still went ahead and did their sacrifices at handy street sites. It is hard to find even one sacrifice site in the city where I live. An article about with more pictures and some additional information: [Rivers of blood flow on streets of Dhaka after Eid animal sacrifices](https://www.theguardian.com/world/2016/sep/14/rivers-of-blood-dhaka-bangladesh-eid-animal-sacrifices) [Answer] First....Ewww. Bellerophon probably has a more precise method, but here is an alternative method: We could use the coverage of paint as a baseline. Typical household paint will cover about 400 sq feet per gallon $(9.8 \frac{m^2}l)$. It's less when the paint has a lower amount of 'solids', and blood doesn't contain titanium dioxide as a white hiding base, so lets cut that number by 1/4. now we have something to work with. 100 sq ft per gallon $(2.5 \frac{m^2}l)$. If the street width is about 48 feet $(15m)$ wide, you could get 2 linear feet per gallon $(0.16 \frac{m}l)$. The question asks to obscure the roadway, not completely inundate it. Each human body has a bit more than 8 pints of blood, so that's about 1 gallon plus a bit, up to a little more than $(4l - 5l)$ per person. Working it the rest of the way out, your psychopath would need 1 victim for every 2 linear feet of roadway $(1,4 \frac{persons}{m})$...and a long handled roller to make sure he covers everything evenly. [Answer] There are already some excellent answers here. Let me try it from a historical perspective. ## The streets run red with blood. Is mostly used for [massacres](https://en.wikipedia.org/wiki/List_of_events_named_massacres). And to get the *Rivers of Blood* claim you need lots of dead people. The most famous seems to be the [Siege of Jerusalem (1099)](https://en.wikipedia.org/wiki/Siege_of_Jerusalem_(1099)). At the same time there is the connotation of a heavy, brutal loss to the nation. Sometimes unrecoverable, like the [Destruction of Baghdad (1258)](https://en.wikipedia.org/wiki/Siege_of_Baghdad_(1258)#Destruction). These horrors are not confined to the middle ages, the 20th century has more then it's fair share. When you have the [Red Terror](https://en.wikipedia.org/wiki/Red_Terror), it's not only the colour of their flag that make it so. To answer your question, **you need at least thousands of people dead or heavily bleeding to make the streets run red with their blood**. ]

[Question] [ Being at Anime Expo last weekend got me thinking about all the "[trapped in another world](http://tvtropes.org/pmwiki/pmwiki.php/Main/TrappedInAnotherWorld)" anime I watched as a kid: *Inu Yasha, Fushigi Yuugi, Escaflowne*, etc. The general plot of these is that a high school girl from "our" reality is magically transported to an alternate reality/time, where she's usually stuck and must perform some great task in order to return. Sometimes, when she does manage to come back, one or more of her new friends (or enemies) from the alternate reality come back with her. In most of these stories, the alternate reality is a fantasy/medieval world with feudal kingdoms and very little bureacracy, so the girl from our world doesn't need any paperwork to go about her business. But the opposite case, when characters from the alternate world come to ours, seems like it would pose a problem for any extended stays. (All the anime I can remember dodged the question, either by having the stay be too short to matter, or by getting a god involved.) A character from an alternate reality who gets trapped in ours would quickly find themselves limited in the same ways as most illegal immigrants, unless they could find a way to somehow get the appropriate paperwork. **Would it be possible for someone from an alternate reality to successfully apply for and receive some kind of legal status in our world? If not, what would have to be different in our world for that to work?** I'm aware there are already processes for illegal immigrants to become legal residents; however, they're from our reality and have roots that extend prior to their arrival in the new country. I'm curious whether it would be possible to do the same thing as someone who literally did not exist in this world last week. Clarifications: * The alternate-reality character does not have any kind of powerful, all-purpose magic/technology. * They're at least old enough to be a YA protagonist (so the equivalent of a human 13-year-old or higher). * They don't intend to reveal they're from an alternate reality (either they're aware that would go badly, or they have some other reason to keep it secret). * They're stuck in our world for an extended period of time, and can't just hop back and forth between their world and ours (and no one else can, either). * They may or may not speak the local language (it's handwaved in the various anime, but I've seen a book version where they don't, and it's much more interesting). **Bonus: Would it be possible if the person from another world is not human?** Obviously someone who's visibly non-human, like a lizard person or a winged humanoid, would most likely be whisked away for study. But Inu Yasha can pass for human if you hide his ears and claws - would someone like him, who appears mostly human but isn't, be able to successfully gain legal status? [Answer] **Main Question:** Imagine what happens when someone comes to the authorities and claims to be from another world, and applies for legal resident status. * One likely assumption would be that this is an undocumented alien (from Earth) who wants to obscure his/her origins to complicate deportation. Illegal immigrants often destroy their original documents to do that. While this tactic irritates the immigration authorities and makes *clean* papers much less likely, it also makes *temporary* refugee status more likely, perhaps with detention. How are you going to send them back? * Another assumption would be that this is a mentally ill person, presumably a citizen, who cannot recall any details of his/her identity. That could bring the alien into a hospital, paid for by the welfare system. * The idea that this person is really from another world is least likely to be accepted, at least until there are more precedents and perhaps evidence. [Isotope ratios](https://en.wikipedia.org/wiki/Isotopic_signature#Forensics) would be weird, but I don't believe that a mental hospital would order that kind of test to start with. **Bonus Question:** An undocumented alien will come under more scrutiny compared to one who has all the paperwork, including many in-person interviews. There are procedures like having a medical expert estimate age to determine if the applicant is an adult or a juvenile (hence with more legal protections). [Answer] The fundamental flaw in any resident registration process, is this... the process of registering residents is numbingly boring. Tediously checking each driver license applicant for propery proof of identity is repetitious and unchallenging. The job is usually left to underpaid bureaocrats and therefore is vulnerable to corruption through bribery on many different levels. If your trans-world traveller has some thing or some skill of sufficient value, it would be easy to convince such a government officer to issue legitimate papers for anyone, including a lizardman. Also consider that a trans-world traveller might have skills of unlimited value. Magically restoring 20 years of youth would be an irresistable temptation to anyone over forty. Your scaley immigrant approaches an aging goverment worker in his home, turns the worker's 50 y.o. wife into a 20 y.o., then offers to do the same for the worker in return for a new set of identity papers. Problem solved! [Answer] * Actual humans from this world have been known to operate under false identities, for example criminals on the run. So it's certainly possible to *appear* legal, but getting fake IDs firstly requires making a contact that can provide it, and secondly it requires not testing the ID beyond the level of scrutiny it can survive. So your fake driver's license might fool barstaff, but most likely wouldn't survive the inevitable computerised ID check should you be arrested. Applying for a job at the FBI using a fake ID bought from some shady guy you met in a crack den is Right Out. For some purposes all you need is the document and so a fake will do, but for many other purposes the document is just used to look you up in "the system", so if you aren't in the system you lose. Witness protection schemes can legally put a false identity in the system, at least to an extent, so it's possible with the right connections. * I don't know about Japan, but in the UK it's possible to operate without papers provided that you have a source of cash and a place to stay, or else you do without those things (live on the streets). There are lots of things you do normally need ID for -- to get credit, open a bank account, rent or buy a house, to get non-emergency NHS treatment. But a typical day can pass without actually *needing* to show any ID to anyone if you don't want to and plan accordingly * Don't expect a credit card or a mobile phone contract (someone could buy a prepay phone and hand it to you, of course). Don't expect to buy alcohol if you look young, or to get any employment other than illegal (because untaxed) casual labour for cash. Staple of the genre, they would *not* be able to just show up at a school claiming to be "new" and attend classes! There's no law in the UK that says you *have* to use the name you were born with, or a name you legally registered as a change, it's just inconvenient not to. Countries in which you must use your legal identity, and must show papers frequently, of course would be harder. But in any country where there are wanted criminals (which I suspect means in every country) it must be physically *possible* to go about without showing your real ID, at least for a while. It'd certainly be interesting to see what happened to someone who apparently, according to their accent and general knowledge, comes from (an alternate version of) the UK, who was picked up by the UK authorities for some reason, and simply could not be conclusively identified. They couldn't be deported, because there's no basis to choose anywhere else to send them. I suspect that either they'd be cut loose (if they'd done nothing really wrong), or else they'd be held in contempt of court for refusing to identify themselves and perhaps detained indefinitely, or else they'd be considered amnesiac, given psychiatric treatment which would conclude they're not dangerous to themselves or others, and then *given* some support for a new identity starting from the point they were found. Realistically speaking, there's no precedent for dealing with someone from another world, so being presumed amnesiac with false memories might be the best bet to become legitimately legal. Failing that, if you tell the whole truth and have some kind of supporting evidence then who knows what the authorities would do -- it's unprecedented -- but it's at least plausible that they'd grant citizenship. More likely, though, is that this alternative world would be immediately considered a potential serious military/security threat and you'd be the only available information about it, so you'd be held and closely observed. But supposing that didn't happen (donné of the plot), you could be given papers and let go. If that's what the government chose to do for some reason, there's nothing to stop them. Life for the visitor from that point wouldn't be straightforward since they wouldn't have history "in the system" -- no academic qualifications, no credit history, no birth certificate. But they wouldn't be breaking any laws, so supposing their extraordinary case wasn't publicised, they could probably set about their plot-ordained purpose in a reasonable amount of peace. [Answer] If they're human and have accents which will fit in and appear respectable then there's the Benjaman Kyle option. <https://en.wikipedia.org/wiki/Benjaman_Kyle> Get hurt, claim total memory loss or talk about weird fantasy world and probably end up in a mental hospital temporarily until they figure out you're not a danger to others and kick you out to make a bed available. It may or may not get you the necessary paperwork "sort of" legally/officially but it's one way of avoiding being hunted as an illegal. [Answer] I imagine the best bet for becoming "legal" would be to reach out to some sort of church/organization dedicated to helping the homeless or other refugees. /they would likely be more sympathetic and understanding to the "I lost everything at some undisclosed point in the past" explanation than a government employee. There are a few avenues you can take with this: * The organization accepts them as a refugee or whatever and provides for them while they assists them in establishing some kind of legitimacy. Your protagonist that is from this plane of existence volunteers to put them up at their house and "sponsor" them. As long as they aren't trying to get a credit card or anything major you can sort of ignore it from then on. Even minor encounters with police can be explained by this. Most local police would be familiar with organizations such as this and might accept the explanation "Oh you're one of those Our Lady of Plot Convenience fellas" and write them off. * Introduce an ancillary character at such an organization that is especially helpful. Maybe they think the off worlder/alien/(?) is handsome/beautiful or interesting and uses their contacts at the local government ID providing office, since this is the sort of thing they do for work, to expedite the ID procuring process. This is sort of a hand wave as there are official procedures and requirements and what not but it's a story and have all the minutia of obtaining a new ID down to a T isn't high on the list of priorities. * Hand wave it away the same way they did on 'Sleepy Hollow'. Ichabod Crane comes back from the past and befriends a present day police officer. They explain him as a visiting professor from England. He is granted legitimacy via hanging out with a cop. Whenever they get in a pickle she flashes her badge and says "He's with me." The same can be done for any transdimensional character, have the protagonists uncle/brother/father/sister/mother/good friend be some kind of police officer or other official or other respected public figure and use the "I'm with him" excuse. This should work for most interesting story telling situations. No one reads a story about a time traveling wizard form another dimension to watch them fill out loan applications. [Answer] It's also important how old your traveler from the other world is. If he/she would arrive as a child, it would probably make it easier. If a child claimed to have lost his parents in some kind of tragical accident or something, or if it claimed not to be able to remember what happend, it wouldn't go straight to the mental hospital but rather get put into an orphanage. I don't know how easy it is for orphan kids with unknown roots to get identity papers. But probably they do sooner or later. At least they won't be made responsible for having no roots or having forgotten parts of their past. The problem with this is, your fantasy character has to be either able to claim to be a kid by some kind of magic, or actually be one, which doesn't apply to most. [Answer] Maybe claim to be from a third world country and therefore not have legal documents. Claim to come from a small village or something? In a desperate situation you could say you were born and raised as a slave slash had been born into human trafficking. If you could guilt people enough they would accept your story. Could go to police and say you escaped after living your life as a slave. They could prob get you papers. Non humanoid... I think the government would just whisk them away. People would be frightened of the unknown. I mean we are afraid of our own kind that have deformities so I dont think it would go over very well for the non humanoid. [Answer] The canonical way to do this in the UK was [the mechanism popularized by *The Day of the Jackal*](http://news.bbc.co.uk/1/hi/magazine/3098104.stm) - find someone who died very young but would otherwise be the about same age as you, obtain a copy of their birth certificate, and work from there. Assuming no-one ever realises "you" died aged three, it's unlikely to ever be uncovered. Despite being popularised by a well-known novel in 1971, this method remained effective until 2007, when the loophole was finally closed in 2007 by incorporating a check against the deaths register. However, I am sure it would still work in some countries... [Answer] In Australia, the government has to deal not only with people coming from outside the country without papers, but also people living within the country who've never had paperwork. [From the "100 point" checklist](http://www.teach.nsw.edu.au/grp/application/a-poi_list.htm): > > Special Category 4 – Aboriginal person or Torres Strait Islander > resident in a remote area/community > > > The applicant will meet the 100-point requirement if the applicant is > an Aboriginal person or Torres Strait Islander resident in a remote > area/community, and the identity of the applicant is verified by two > persons recognised as 'Community Leaders' of the community to which > the applicant belongs. > > > This'd depend on the racial appearance of the person, and having two trusted people being prepared to lie for you. [Answer] Creating a new identity from scratch in a moderately advanced country is probably not very easy. The person would have to present all kinds of paperwork, such as birth and school certificates - and those would have to correspond to existing data in the government files. They would also have to deal with questions like *"why haven't you paid your taxes for ten years?"* and their consequences. On the other hand, an extra-dinensional person might have better luck doing this more gradually, if they had time in their hands. It is quite possible that a person appearing in some third world country would have an easier time acquiring documentation, especially if there was additional chaos involved, like a recent war or natural disaster. If that person specifically needed to be elsewhere, they would just have to figure out a way to migrate to another country afterwards - although they might have a degree of difficulty procuring a visa. Of course, everything is also dependent on what that person would want to do once there. If one wants to get a job, for example, the paperwork requirements are often significantly more extensive than what they need to just enter the country. **Bonus question answer**: It would depend on your definition of *"not human"*. In most (all?) countries there are specific requirements when registering the biometric signatures for identity documents. For example, in passport photographs the facial features should not be covered by hair, let alone by glasses/hats/etc. While no-one is (probably) going to ask a person to remove their clothes and disfigurements like burns or missing body parts would remain uncommented, a person with pointed ears or claws in his fingers would certainly be asked some very *pointed* questions. [Answer] Sometimes the government simply produces *papers* without red tape. In a dictatorship (or a benign monarchy) the head of state might find it in his interest. I recall a show where in the pilot a rich dude on the run paid cash to be admitted, and the dictator took his payment and stamped his passport and issued needed permits, then referred him to a relative to sell him a mansion. A large government like the US has *witness protection* and probably more clandestine versions, where official real ID is produced. So a being from another universe could somehow make contact and convince the government to let him stay, and live among them. If he had some choice of which country to appear to, it could be easy, both by shopping for the approachability/concentrated-authority, and which nation is interested in what he has to offer. As for the idea of being from an undeveloped (or small non-bueucratic state), why not simply *go* there, first? Live among insolar islanders for a while, and then legitimately be *from* there if you want to move to a first-world country. Much can be made of any unique nature of the visitor. If he can swim like a mermaid and hold his breath for 20 minutes, a remote island of sponge divers and pearl divers would be a natural fit. [Answer] Records occasionally get destroyed in accidents. You could claim you were from that area and get new documents that couldn't be checked. Another dodge I heard was to get birth certificates from people who died young in the same year you were born, and use them to request new documents. [Answer] Depending on how well they know *this* world, or how closely their world corresponds to our own, they would recognize that criminal organizations exist for this very reason. With a close enough correspondence between the worlds, the alien might even be able to do much of the work themselves. Criminal organizations and terrorists create and circulate false documents all the time. A booming industry also exists for stealing the existing identities of people (identity theft), so with enough cash or ingenuity, the being from the alternate world could simply assume one or more identities and carry on that way. This would be a criminal lifestyle (opening up credit cards, draining existing bank accounts and so on), but as people who have become victims of identity theft know, it is exceedingly difficult to find and stop the "other" you, and the process of clearing your identity takes a prolonged period of time as the various authorities, bank security departments and so on investigate. While this is going on, the alien discovers the credit card was cancelled and simply pays cash and disposes of the documents, reaching into the pocket (marsupial pouch?) and taking out a new set of identities. A "clean" identity is much better, since you are not likely to discover the credit card is suddenly cancelled and so on, but is also much harder to achieve in much of the world and would take more time and resources to create. This ins't to say it is impossible, the former USSR had an entire training town devoted to training "illegals" to gain the proper habits to pass as American citizens (everything from learning American accents and slang speech to knowing cultural trivia like TV shows and sports team records). Obviously a single alien stranded in this reality might not be able to go to that extent, but if there is a "corridor" where cross diminutional traffic can take place, it might be worthwhile for authorities on one (or even both) ends to train their people to live and work in the other dimension, either for monitoring and espionage or even trade. [Answer] You couldn't really be 'legal' because all the methods to 'have papers' need inconvenient things like proof of birth, nationality etc. You don't have these things, so you can't do it. But it's easier than you might think to acquire fake documentation. The classic trick is to request a copy of a birth certificate from someone in the graveyard born around the right date. Not many countries properly 'close the loop' and keep track of births and deaths. But failing that, hop on tor, have a rummage through what's dramatically called the "dark web". It's not, it's just a bunch of anonymised websites that sell all sorts of things, and ship them discreetly in the post. Amongst these are fake and stolen passports. <http://www.ibtimes.com/pulse/tour-deep-web-illegal-marketplaces-book-clubs-everything-between-1729404> So I would suggest what you want to do is acquire a passport for a country that you've got visa waivers for. So like the UK/US relationship, or Europe/schengen. You could probably 'bribe' your way to documents - either properly illegally, or by 'influence' through the legal/political system. The latter is more legal, but probably more expensive. Travel in on an international passport, start the process of applying for naturalisation and citizenship. This might be made easier by getting married - either as a love interest, or to a willing conspirator. <https://www.gov.uk/becoming-a-british-citizen/if-your-spouse-is-a-british-citizen> <https://www.gov.uk/eea-registration-certificate> There are some tests you'll never pass - you won't be getting a security clearance - but for most purposes, naturalised foreigner is 'pretty good'. There's also the possibility of 'being' an asylum seeker. Claim to be from somewhere unpleasant, with no papers. This isn't really as easy as it sounds though, as a lot of countries are just not keen in immigrants, so you'd have to jump through a lot of hoops. [Answer] If you're literally asking whether they can legally get paperwork to prove they're legal, then no, pretty much by definition. However, if all you want is for them to get enough paperwork to live day-to-day, I'd have to say the answer is indisputably yes, because there are anywhere from 7 to 30 million undocumented aliens in the US at the current time (depending on whose estimate you believe), who are doing just that. [Answer] You can serve in the French Foreign Legion under an assumed name for several years and receive documents under that name when you complete your service. <http://www.telegraph.co.uk/news/worldnews/europe/france/3546207/The-French-Foreign-Legion-the-last-option-for-those-desperate-to-escape-the-UK.html> Huh, seems like you'd have to buy a Hawaiian birth certificate first. <http://en.legion-recrute.com/mdl/info_seul.php?id=6&idA=59&block=20&idA_SM=0&titre=administrative-requirements> [Answer] Another class of people your alien can emulate are fugitives from justice -- every year or so there is a story in the news of the model citizen whose spouse and children are shocked when some slip reveals them to have walked away from a low-security prison 30 or 40 years ago. Most of the recent stories found in a cursory web search say the person swiped the identity of someone who died as a child, as suggested in other answers. (The newspaper stories, of course, only talk about the people who got caught.) A few examples: <https://people.com/crime/florida-man-false-identity-car-crash/> A book a few years ago used a variation, where person A helped person B emigrate to another country and live as a duplicate of person A. There is certainly a thriving market in fake Social Security numbers in the US, again, typically purchasing the identity of someone who died young. It doesn't even need to be strictly illegal -- I've read SF stories set in cultures where people faced with unbearable situations could walk away and start a new life *tabula rasa* in a new community. [Answer] Potential solutions: * Make the visitor's illegality part of the plot. They'll be on the run from the authorities the whole time... * Have them aquire 'fake' papers somehow. e.g. someone's father works for the government, someone's mentor used to be into identity theft. * Have the visitor's borrow a legitimate identity. e.g. "So, this is your cousin, Joey? Sure I can give him a job; it is the least I can do considering how much your father did for me." You can build a case for legitimacy based on personal trust rather than a lost paper trail. "All your papers lost in a fire? That's too bad. But I know your family. Have a library card." * The off-worlders could have "powers" that enable them to stay. e.g. Jedi mind trick, psychic paper, invisibility, skill at forgery. * Lampshade the plot hole. "Isn't it amazing that you havn't been caught!" and ignore the problem. ]

[Question] [ A human crew of 6 has been sent on [mission to Mars](https://en.wikipedia.org/wiki/Human_mission_to_Mars) > > The lowest energy transfer to Mars is a Hohmann transfer orbit, which would involve an approximately 9 month travel time from Earth to Mars, about five hundred days at Mars to wait for the transfer window to Earth, and a travel time of about 9 months to return to Earth. > > > Shorter Mars mission plans have round-trip flight times of 400 to 450 days, but would require significantly higher energy. A fast Mars mission of 245 days round trip could be possible with on-orbit staging. > > > On ISS the crew wears clean underwear every day and exchanges dirty for clean at every supply mission, storing the dirty until that moment. This approach sounds problematic on a mission to Mars. 245 days worth of clothing for a crew of 6 looks quite a lot. What is a space-viable method to clean and reuse space laundry? * assume current tech level, no handwavium * assume a fast mission, with few days of permanence on Mars. Conceptually similar to the Apollo missions to the Moon. * only requirement is for the garment to be hygienic and safe to wear after treatment * the treatment shall leave the garment wearable and usable for at least the duration of the mission * the less accessory materials needed, the better (i.e. for running a washing machine I would count water, soap and water filtering/cleaning equipment, plus power supply) [Answer] **Dry cleaning.** [Dry cleaning](https://en.wikipedia.org/wiki/Dry_cleaning) is expensive on earth because water is so cheap. In space it is easily cost competitive. One could use conventional solvents (e.g. trichloroethane) and capitalize on easy access to low atmospheric pressures to recapture solvents for reuse, distilling used solvent back to fresh and leaving body oils / dirt behind. Conventional dry cleaning solvents would work fine in a low pressure environment. This is not very edgy. One could also use supercritical CO2 which is now commercially used for "environmentally friendly" dry cleaning. Space travelers have a surfeit of CO2 anyway which must be scrubbed from the air. Supercritical CO2 dry cleaning is not edgy either, although using exhaled CO2 to do it would be kind of cool for a fiction. [Answer] Easy, use a regular washing machine in an artificial gravity environment. Why: 1. Washing machines on Earth are an established technology with decades of research and development attached to them 2. The craft will already have equipment for recycling gray- (showers) and wastewater (bathrooms). Pumping washing machine wastewater into that system shouldn't be a problem and nor should supplying it with fresh water be an issue either. 3. Power supply isn't really a problem for such a low-powered device and bringing enough soap/detergent for a couple years isn't that much mass 4. Traditional washing machines need gravity to work and I'm convinced that any serious Mars mission, especially early ones, will need to have some sort of artificial gravity in the form of tethered counterweights or rotating ring sections of the spacecraft. *Especially* for a short stay Apollo-style mission, astronauts need to be acclimated to Mars gravity before they arrive. Otherwise they will essentially be immobile cripples on arrival and unable to complete any tasks. Recovery from microgravity takes weeks, which isn't something you want when you've just landed on the red planet and only have a short stay. [Answer] **Print new clothes every day** I propose an alternative : Create new clothes regularly, and toss old ones in the recycler. Clothes are already made of polyester, made from forcing melted polymer feedstock through spinnerets, then weaving the resulting thread into cloth. This is exactly how a 3D printer works, and can be done with minimal human intervention. The mission will already be bringing at least one 3D printer, due to the obvious mass benefits of not having to bring every single spare part needed to maintain the mission, but only an excess of polymer feedstock. I am not a materials scientist. I don't know which polymers would be appropriate, but let us consider polyester. Polyester is among the most common fabrics in use on Earth today. <https://www.commonobjective.co/article/what-are-our-clothes-made-from> Polyester is extruded using a spinneret, which is exactly how a 3D printer works. <http://schwartz.eng.auburn.edu/polyester/manufacturing.html> The astronauts get the advantage of precisely-sized personalized jumpsuits, important when they gain several centimeters of height over months in low gravity. Neither 3D printing nor recycling is handwavium - they're just expensive as of 2020. You can completely automate the creation of a jumpsuit from tiny spray nozzles and perhaps some manipulator arms. There are other methods of 3D polymer crafting available as well : immersion in liquid, UV light exposure, etc. The initial commentors challenged me on solving the recycling problem. I'll make an amateur attempt here : First, mulch the old jumpsuit, aerate violently and filter out hairs and skin (like a cyclonic vacuum). Dissolve the results in appropriate chemicals to dissolve the polymer but leave behind sweat and salt. Push the polymer goop through a spinneret again, using whatever chemical steps are necessary to render it fiber, and then you have 3D printer stock again. I lack the chemistry knowledge to be more precise, but I know that it can be done, due to this link regarding polyester : <https://www.eco-business.com/news/a-way-to-repeatedly-recycle-polyester-has-just-been-discovered/> [Answer] There seems several ways viable to me. If you have a full water recycling system for the crew's shower and toilet, dumping water from a washing machine into it is probably the easiest solution, with some suitable detergent the recycling system can handle. The clothes should probably be vacuum dried inside the machine after washing, to prevent water escaping. I'd imagine steam cleaning can substitute heat for water consumption, reducing your water needs, but this will require fabric that survives high temperatures. Alternatively Russia is developing a washing machine that should run on liquid CO2. Of course, this then involves high-pressure vessels, which increases weight by themselves. Source: <https://phys.org/news/2019-03-frontier-russia-machine-space.html> [Answer] # DON'T Over on Space Exploration, the question was asked *[Nudism in Space: Why Wear Clothes Anyway?](https://space.stackexchange.com/questions/24206/nudism-in-space-why-wear-clothes-anyway/24208)* Laundering clothing is energy intensive, takes up time and critical space and even Maytags break down from time to time. When that happens, you've just got a useless piece of junk in your very limited living space. Getting long-haul astronauts used being naked for the duration of the mission might end up being the best solution. They'd only need to suit up when leaving the vessel. [Answer] I was about to elaborate a tongue-in-cheek answer about g-strings underwear that one can wash into a teaspoon of water, then I suddenly remembered two possible solutions in the 'disposable' category. 1. [spray-on clothing style](https://www.theguardian.com/science/2010/sep/16/spray-on-clothing-t-shirt) - instead of pressurized spray cans, have a canister that you connect to the ship's air recycling/supply. Disadvantage - in zero-g sprays are messy. 2. those [Wysi compressed towellets](https://www.google.com/search?q=wysi+towelettes+compressed+water&oq=wysi+towelettes+compressed+water) - just make them using a longer cellulose fiber to have them stronger. Then you put it into a little water to expand, vacuum dry them (to recover the water) and there you have a good-for-a-day pamper style underwear that's as biodegradable as your poop. BTW, before discarding them, you should be able to use them as toilet paper; In any case, I believe both solutions are technologically simpler than a washing machine, will take less space than the washing machine and definitely will consume less energy. [Answer] **You would just use a normal washing machine, with some *minor* modifications** I don't know why so many people here are saying a washing machine needs gravity. When the barrel spins it will agitate the water and soap and clothes mixing them together and cleaning them. Modifications would be to stop water pooling in place so you would want the barrel to have some "spokes" that stick in toward the center of the barrel acting as paddles. You may also want to block the center of the barrel to stop everything gathering there. And finally you could also make sure the machine changes spin direction regularly. To dry, most water can be pressed out of the clothes so they are only damp. Then a regular dryer can be used to finish off the drying process. All water can be captured, filtered, and re-used for the next wash. In a system designed for efficiency there would be very little water loss so 10's of litres could last the entire trip. [Answer] One of the issues that gets raised a lot, is the problems of extended periods is zero G. One solution proposed for the Mars trips would be to split the load in two masses connected by a cable. This is spun, giving artificial gravity, probably at the strength of Mars surface gravity. Coriolus effects are uncomfortable with rotation periods under 1-2 minutes. $a=v^2/R$ but this is an awkward form $C=2\pi R$ where C = circumference of the circle. So the period, $T=C/v = 2\pi R/v$ Solving for $v$ we get $v=2\pi R/T$ so $R=v^2/a$ substituting $R=4\pi^2R^2/aT^2$ divide by $4\pi^2R/aT^2$ $R=aT^2/4\pi^2$ To get $3 m/s^2$ and a 2 minute period $R= 3\*120^2/4\*3.14^3 = 1094m$ This would allow an ordinary washing machine with possible reprogramming for different timing to be used. --- Solution 2: Freeze drying. I saw this originally in Heinlein's short story "Misfit" Garments soiled by space sick individuals were secured to pegs in the airlock, allowed to freeze/dry for a while, then were brushed hard in front of an air return duct. This sort of happens with my nylon wind pants. I come in from tramping outside, and I've got mud from shoe top to mid calf. Let the mud dry, whip the pants against something solid, and most of the dirt is gone. Wear for a few hours in dry conditions and the rest falls of. Couple this with leaving it out in the sun for a few minutes, and UV will sterilize anything, or put it in a black metal container and bake for a while. --- Brushing hard by an air duct is tedious. Perhaps a rotating drum with fins, and a mix of clothes and superballs. Drum changes direction freqently. Superballs carom off the fins beating on the clothes. Air is continuously injected at the center and withdrawn from the drum surface pulling dust with it. [Answer] **Artificial gravity/Exercise/Washing machine** Build a flywheel into the ship that is operated by astronaut's muscle power. This can rotate fast enough to provide partial gravity to the rest of the ship's crew, and the center can be used for doing laundry. Or they could just go naked. Spacecraft are climate controlled so what's the big deal? [Answer] First you need to have the following: 1.) Soap 2.) Water 3.) Downy bango 4.) Llaundry 1st step is to hold the laundry using 2 hands then meet each other and repeatedly use force so that the friction would clean the dirty party. Add soap do the 1st step remove soap rinse water and do the 1st step then put the laundry in the stone to make it dry. [Answer] Put the dirty clothing outside. Vacuum + radiation = clean (ie., sterile) clothing...but it won't be visible clean (ie. stain-free). Picture the spacecraft exterior covered with clotheslines, with dirty laundry flapping in the breeze. :) [Answer] Some of the existing answers are very unrealistic. For example, the 3D printing one doesn't consider that **3D printers don't print fabrics** and assumes that the technology for recycling fabric into plastic will be lightweight and extremely reliable. If you had the magic recycling tech - which would need to be magic and I'll explain why - then you wouldn't want to use a 3D printer at all. You'd make thread and then just weave it. [3D-printed clothes are currently nothing more than unwearable junk](https://www.wired.com/2017/05/the-shattering-truth-of-3d-printed-clothing/), and there is no reason to think this will change. 3D printing just isn't a relevant technology to making clothes, because it produces rigid things and clothes are made from flexible meshes. As for the recycling magic: the problem isn't hairs, it's fat. Fat from sweat bonds with clothes and acts as a home for bacteria. The same fat would drive a 3D printer crazy. Removing the fat from recycling fabric is no easier than removing it from intact clothes - unless you assume magic, which appears to be the case above. In fact there are two simple solutions: 1. Take spare clothes. Compared to other consumables, a new singlet and pair of shorts every couple of months weighs nothing at all. You make them of a hybrid merino polyester impregnated with silver - that will actually be reasonably non-smelly after two months of low-exertion use. 2. Put the clothes in hot water, shake them around, filter the dirt out of water. The same few litres can be used for months. Boring, but realistic. Nudism would be a technical solution, but probably not a politically acceptable one. Also, the question is even more flawed than the answers. If you're getting to and from Mars using Hohmann transfers - which is what seems to be the case from the 245 day reference - you have to wait for the next return window when you get to Mars. You can't just spend a few days there because you want to. Assuming the transfer windows are symmetrical you're looking at a 17-month stopover - they occur every 26 months and a transfer takes 9 months. [Answer] The garments replicator is like a CAT scan machine. You lay in naked, spread your legs and it weaves a a web all around you from head to toe. This web protects you from cuts,cold and radiation. it hates microbes with a passion. When you need a shower, you simply disposed of it and it is recycled in the replication system where it is cleansed, turned into raw material and spun again into a web that will be re-used. ]

[Question] [ We are used to a world where humans are basically an [apex predator](https://en.wikipedia.org/wiki/Apex_predator); we don't really need to worry much about becoming some other animal's next meal. If that wasn't the case, and **humans** had to be wary of the possibility of a predator either lurking nearby or openly hunting them, **how would that affect the human society of that world** compared to what we are used to? For the purposes of this question: (1) I am mainly interested in the resultant changes on the structure of the human society (although answers addressing other aspects, including (2), *as well* are perfectly fine), and (2) please simply accept that the situation exists. It is a fairly safe bet that the humans in such a situation, in addition to *handling* the fact that the threat exists, would also want to *remove* that threat from their lives. As interesting a question as the latter is, it is not really the topic of *this* question; **I'm more interested in the *handling* of the threat** than how the threat could be eliminated. [Answer] I would suggest we look to animals such as the meerkat for an answer. For those who don't know the meerkat is a small mammal which lives in small communities in Africa. All meercats (although the young and sick in particular) are at risk from various species although particularly big birds of prey. To depend against this the group typically live underground where it's safe. They only come above ground when it's light (so they can see properly). Several members of the group come above ground at the same time, some are deployed as lookouts while others forage for food. At the first sign of danger the lookout signals the group who retreat to their burrows. Furthermore special creches are used to help the young explore with dedicated adults who mind each other's children while the parents hunt. This cooperation is vital to the young's survival. To apply this behaviour to humans, they would need to find a safe home. Underground, underwater, up trees - wherever is safe from attack. They would only come out in numbers and when they have the advantage, perhaps the predator is nocturnal? Perhaps it is water based and can only come out in the rain? Whenever it is at it's strongest - that's when the people want to be deep underground. Finally cooperation is key, the group work together to survive. Some forage for food/work while others maintain watch, in a modern society this could be the equivalent of having a city watch paid for by the workers. If someone ignores the warnings, if they wander off on their own they're easy prey for the predators. [Answer] This depends a lot on the properties of the apex predator. Depending on that, it may not make a whole lot of difference. Think about it like this, while humans are dominant on earth, different groups of humans have been dominated by others so we have some ideas of how to handle it. They have used several methods to deal with stronger groups of humans. 1. Appeasement. Depending on your predators desires, tribes of humans could wear no gold and leave piles of valuables at their borders to deal with dragons or leave slaughtered animals to feed hungry animals they can't defend against. 2. Attrition. Humans have burned crops behind them, hidden in caves and woods, made it so costly to find them that its just not worth it. Depending upon the mobility of your predators, they can play the long game and avoid them. 3. Brains. Depending on the intelligence of their opponents, humans can use their brains to counter the threat. Pits, traps, disguises, or even taming the predators can work. 4. Surrender. When all else fails, give in and join them. Humans could attempt to become allies/servants/slaves of their enemies based on their level of desperation. 5. Straight up pure numbers. Because a predator requires many meals to keep it alive, there will always be many more humans than predators. Humans could decide to sacrifice a few members by lottery or contest or some other method, or just grind the predators numbers down. They can kill them even at great cost or work on killing their young before they mature. Humans are versitle and have tried many ways of dealing with stronger forces. Based on the movement/strength/intelligence of the predators, you have many interesting ways of having humans react to them. [Answer] It might be worth noting that humans aren't exactly apex predators. At least, not in the conventional sense that most other apex predators exist. A lion or a bear is still quite capable of killing us and we're, at any given time, generally unable to stop that. Our apparent dominance comes from a very good system of risk management. We keep the bears away from where we live and we dominate our own, very-controlled food chain. If some new threat were to emerge that we had to deal with, there's a few examples we've got to suggest what we might do. The first example is that of wilderness settlers. Folks who live on the fringes of developed areas are generally more aware of their surroundings. They are more often armed, bother with more physical security of their homes, keep an eye on things and try to track predator activity in the area. Societies in such places tend to be more in tune with nature, more accepting of it's threat and more calculating in their responses to that threat. Interestingly enough, people act this way in another situation: warzones. By far, the most effective killer of humans are other humans and we have trouble with them quite often. Dealing with that threat is the field of policing and military sciences. Against such a tenacious foe, we've been known to do all kinds of things like elaborate physical defenses (walls, minefields, earthworks), direct confrontation with all kinds of weapons, deployed diseases and toxic chemicals against them and from time to time tried to reason with them. Depending on the nature of the threat, sometimes a few guys on the border with guns are good enough, sometimes you need some fences, sometimes more. The only way I could see this situation occurring is if we faced some other kind of intelligent creature, in which case the warzone analogy is even more relevant. Diplomacy could be an avenue to safety, or carving out some space and enforcing a demilitarized zone where we shell anything that tries to cross, or fortresses surrounded by minefields and clouds of toxins. It would depend on what the threat was and how we could manage it. Humans tend towards fortresses throughout history whether they be caves or castles, only venturing out into the surroundings as we find ways to contain the risks of the world. Socially, it could be similar to rural Alaska or the African bush. An undertone of understanding nature's wrath, but a determination to beat it. Of course, maybe we don't and we just get wiped out. People are generally too gregarious to support any kind of dispersal for the sake of survival. While we were killed off, we'd probably be trying to make a stand from fortresses of some description because as soon as we tried to run away, all our devices and plans would become far less useful. [Answer] Well, I've lived in situations where dangerous animals were common including rattlesnakes, cougars, coyotes, feral dogs etc. Waking up one morning camping and finding cougar tracks on a little hump not 20ft from my tent where the cougar obviously crouched and well, thought a bit, was sobering. In the main, people learn to pay attention to their surroundings; no headphones, or getting fixated on any one thing. Move one's head and attention constantly as you move. Shift from looking down to the ground nearby to looking out to the horizon. Look left and right, then scan along eye level, turn to the sides and periodically turn around and look behind you. In groups, each individual has a sector they are responsible for. It's a lot like a squad moving in the military. Humans have no real threatening predators left, we have to stop ourselves from accidentally wiping out species now rather than cower from them. People will try to pet wild predators for bleep-sake. Sure a bear, lion etc can pick one of us off if it it gets lucky, but that is because we as a society accept the risk to keep bears around. Back when bears, wolves etc poised real danger to lives and livelihoods, they didn't last long. "Homo homini lupus (Man is Wolf to Man)" So, we have to look at human-to-human predation for models. Historical people threatened with non-specific attacks would be armed and independent minded, willing to take instant action without approval from authority and often openly scornful authority that seldom arrived in time to help ("Nice of you to eventually show up.") At the same time, highly cooperative with peers, especially neighbors and able to spontaneously organize on large scales to meet threats without central planning and control or practice. Basically, your typical American frontier community from 1780-1880. Example: During the time of the Republic of Texas, the Dictator Santa Anna broke the treaty and constantly harassed Texans on the frontier either paying "bandits" to raid and kidnap or giving guns to the Comanche who where doing a little empire Lebensraum project on their own. But they didn't stop there. After a religion shift they came to believe that all the land they could ride over belonged to them and that everyone else where trespassers who could be killed at will. They felt morally entitled to raid, burn, plunder, rape, enslave, torture and murder any who they rode across, often for no discernible practical reason. They road hundreds of miles from their base territory in parts of modern Kansas, Texas Panhandle and Oklahoma to attack deep into the Republic of Texas based around Austin. The Comanche were the best light calvary since the Mongols able to travel 80 miles a day or more on a string of ponies. They appeared suddenly without warning at isolated First American villages and white and hispanic farms, killing entire families, often by torture and rape, killing all the domestic animals except the horses they took, (often burned the family dog alive) burned the buildings and dumped bodies down the well to contaminate them. They could do all that in less than an hour, before neighbors even new what happened. Then they road off 40 miles or more outstripping any pursuit. They often took children, especially teenage girls, as slaves. Whites and Hispanics were lucky. The Comanche exterminated at least a dozen smaller settled first American nations in the buffer zone between the Republic of Texas and the Comanche homeland farther north. Probably the most horrific of the First American wars. Although the attackers were humans, for families and individuals living spread out, on the central Texas frontier it would have felt like being in danger of some powerful an unpredictable predator who could strike and disappear with impunity. The response to both bandits and Comanche was heavier armament of households and the construction of strong points. The round stone barns of central Texas where one of the responses. Basically a "safe room" where families and stock could retreat and defend. (A lot of early German immigrants to Texas were German pacifists and didn't defend themselves violently, so they fortified and when that failed, their Scotts-Irish neighbors avenged them.) The offensive took the form of the Rangers, groups of highly mobile, heavily armed volunteers who tried to track and intercept the Comanche either coming or going. A natural predator would likely provoke a similar response. Whenever a society is attacked from a generalized threat with no specific locus, it tends to coordinate on the local level, decentralized at an intermediate level but foster wider but weaker corporation on the higher level over wider areas. You can see this in the response of late Roman Britain to the Irish Reavers and later to the response the Saxons to the Vikings. Even the Rus decentralized to try and deal with the super mobile Tartars who were themselves highly decentralized and flexible. For a story based on this scenario, the real trick would be designing a predator that poised a serious threat but which couldn't be easily wiped out by coordinated human action. Humans wiped out all the macro forms, including saber-tooth tigers, dire wolves, cave bears etc with little more than sticks, flint and fire. Modern humans would not take very long at all to wipe out any merely natural predator. You'd need something that wasn't just deadly and hard to kill, but fast and impossible to localize. The American Army finally dealt with the Comanche not by defeating them militarily, but by wiping out the buffalo they depended on as a moving food source. As long as the buffalo roamed, the Comanche could not be brought to fight save on their terms. Once the buffalo were shot out they were helpless. A super predator would face the same threat of being attacked in directly. It have to be fairly independent from any ecosystem that could be destroyed as an indirect means of killing it. If you think about it, the classical dragon story is really about an Apex predator to medieval humans. It flys, so they can not pursue it. It is heavily armored, and has a breath weapon they can't match. Going up against a dragon with an army just gives it a bigger target. If the dragon was not interested in gold and princesses, but just eating livestock and people, and if there were more than one, things would get ugly. [Answer] *" I am mainly interested in the resultant changes on the structure of the human society... I'm more interested in the handling of the threat than how the threat could be eliminated."* Extremely interesting question, Michael - but you simply haven't given us enough information about the world you're building. The only answer here is a resounding "It depends". You are asking an ecological question, and it's difficult to extract hard-and-fast answers from a whole system, such as an ecology, which is so full of feedback loops that every answer depends on everything else. :-) Changes in human society would be driven more by the *particular* nature of the world and the predators that inhabit it. By "the nature of the world" I mean what kind of resources are available, and what constraints the world itself imposes; and by "nature of the predators" I mean very basic questions about the predators as a species. To illustrate, let's take a not very weird example and look at some of the implications. **SETTING: THE VAMPIRES OF DEINDUSTRIAL AMERICA** Without going into the backstory in any detail, let's posit that vampires, in a more or less traditional form, have always been with us, but that they remained hidden: a very small population of predators who were able to keep their depredations on the DL throughout most of modern history. Vampires, as Charlie Stross [pointed out in his blog](http://www.antipope.org/charlie/blog-static/2013/01/fang-fuckers-some-reflections-.html) (NSFW - language), are an excellent example of an apex predator on humanity - although sufficiently different from the Comanche example adduced above to underscore the point. Anyway, there came a plague, some kind of pandemic that not only killed an awful lot of people worldwide, but irretrievably disrupted the essential networks of manufacture, information, and trade essential to worldwide industrial civilization. That civilization crashed and has not been reconstituted in any way at time of story. OK? So we have a much-shrunken human population living in the ruins of their grandparents' civilization. Not only do they face problems of food production (industrial agriculture and distribution is gone; new patterns of land use urgently need to be established), there will be contention for resources... and yes, there will be contemporary equivalents of the Comanches, Mongols, or Mad Max gangs; but I am specifically ignoring them because this is only an example and not an actual story setting. Now here's where it gets interesting. The pandemic that wiped out most of humanity didn't affect the vampires. The vampire population hasn't been much diminished. However, now we are looking at an entire species (in ecological terms) that can no longer remain hidden: they *have to change their mode of predation* because their attacks could no longer be concealed in the vast masses of humanity. (Not unlike the Kriegsmarine in World war II switching from lone U-Boat deployments to wolfpack tactics in response to an increasingly well-defended, target-poor environment.) Instead of stealthy attacks against isolated individuals, vampires now attack, at night of course, in overt gang assaults. Mostly they don't turn their victims - too many vamps in the world already - they just need the blood. So. What kind of human society will develop? * First, we're looking at more or less independent food production - field agriculture, gardening, animal husbandry. The vampire threat makes nighttime fortresses imperative; old buildings would be some of the likeliest. So, the core community of human society would be a **vampire-defensible stronghold with contiguous agriculture.** * Next, the vampire threat imposes some **hard limits on the size of such communities.** If the community is too small, there won't be enough people to work the fields/gardens in the daytime, *and* keep watch at night. On the other hand, if communities become too large, you lose the ability to know everybody personally. Mutual scrutiny, to identify bite victims or Renfields, would be a necessary part of survival. My experience as a sailor suggests that the limit here is something like 60 people: with a crew bigger than that, you just don't know everybody. You may know their names, but you can't reliably detect false notes in their behavior. * These communities would **depend on salvage and scavenging.** Rediscovery of more context-appropriate fabrication skills (blacksmithing, joinery, ceramics etc) has, at time of story, not progressed too far. (The benefit of a plague scenario is that there's a lot of stuff left behind with a rapid die-off.) Accordingly, communities without ready access to salvage sites would depend on itinerant salvage/tinker people - individuals or groups - for access to the leftover resources of industrialism. That's the basic socioeconomic framework. Given that, let's introduce an actual example of the variability contingent on *small changes in the specifics of the world*. **EXAMPLE: WHAT DO VAMPIRES DO IN DAYTIME?** There's a general consensus (excepting the dumb as hell *Twilight* series, I guess) that vampires are very limited in daytime. In *Dracula* (the book) the Count is unable to move to defend himself when Jonathan Stoker opens the casket and hits the him with a shovel. In many other traditions, sunlight is actually destructive to the vampire: vamps burn up, or are at least badly scalded, when the sun hits them. What are the implications of choosing one or the other? This simple difference would have a very significant effect on the human society, because it directly affects the offensive/defensive strategy of the humans. *CASE #1: Comatose by day* If the vampires are unable to awaken or move by day, they are incredibly vulnerable. A small, skilled, capable band of humans could wreak havoc in a nest of vampires: if you can kill any guardian Renfields (or human mercenaries), you can simply go from coffin to coffin, staking, beheading, or burning as necessary. In other words, humans would have an effective offensive strategy. As for the vampires, their responsive strategy would be to disperse as much as possible, or else to establish such powerfully defended nests that the human teams would be foiled. *CASE # 2: Active by day, just staying out of the sunlight* This makes for an entirely different situation. A nest of awakened vampires, underground or otherwise out of the sunlight, would be far too formidable. Humans would not find it practical to assemble teams of hunter/killers, and would need to concentrate on defense. **Consequences for human society** These consequences would be remarkable. * In case #2, the communities described above would be unable to offer mutual defense. If vampires are attacking your stronghold some night, you can't expect your neighbors to ride to the rescue, unless they have remarkably powerful anti-vampire combat capabilities that would keep them reasonably safe during the ride. The implication: **defensive communities would be much more isolated and independent**. * By contrast, in Case #1, there would be **a strong incentive for communities to collaborate to provide economic support for special-forces-type hunter/killer teams.** As with the armored knights of medieval times, you need a large base to feed and equip a healthy individual whose only task is specialized fighting. Remember, the agricultural efficiency of the community is much reduced by the need for night watch and general defensive work. Removing a strong, healthy individual from the labor pool to perform specialist work is going to be a notable burden on a community of, say, 50 people. So, let's develop that a bit. **In case #2, human societies would be small, communal, vulnerable to cultural and genetic drift.** We could probably extrapolate a high level of egalitarianism: When the vamps manage to break in in the middle of the night, everybody's staking. You don't care whether the person who destroys a vamp is male, female, old, young, a brawny blacksmith or a cook's helper. (Again, some personal experience here: when there's a fire on a boat or small ship, nobody hangs back. Everybody's got a job to do.) Contacts between the communities and the outside world would presumably be largely confined to the aforementioned tinkers / salvagers. This would tend to create a fragile, tenuous system, in which any kind of technological advances would be rare and slowly disseminated. **In case #1, by contrast, an economic and political arrangement like manorialism & feudalism would probably develop,** simply for the purpose of being able to establish, feed, and direct those small, highly mobile teams of vampire killers. Politically, this would probably lead to much tighter relations between groups of communities. It would tend to develop the fractal structure of the feudal model, in order to aggregate surplus to the necessary level of organization. Socially, the feudal model tends to create much stronger class stratification, more distinct gender roles, and everything that goes with that. There would also be a much more favorable environment for scholarship, technological advances, and a more fertile matrix of social exchange. --- So: there's the example, Michael. May you, and any other readers, forgive the length of it. Also, I hope you don't loathe vampire stories, or find the prospect of a deindustrial future unendurable. It's only an example. ;-) Starting with a simple mash-up of postapocalyptic SF and traditional vampire fiction, I *think* I managed to demonstrate that a small detail of the predator species's characteristics - in this case, *do vampires become forcibly unconscious during daytime?* - can have remarkable effects on the answer to your question. In order to get there, though, I had to answer certain basic questions about agriculture and the development of a salvage economy. If this example serves to illuminate the kind of interacting feedback characteristics that this sort of worldbuilding question demands, then it was well worth writing. [Answer] Wolves, Lions and Tigers have all found humans to be a food source throughout our history, The sabre-tooth Tiger had to be an absolute terror. Humanity had been on the food docket for quite a while and we certainly didn't start out as the dominate species. What I'm guessing you really mean is what would be different if humans were a normal source of food for another predator, where maybe even a 1000 years ago we were still frequently hunted and eaten? While people still do get attacked and eaten by wild predators even today, the big thing to realize is that one of the things that generally has taken us off the menu, is us. We make it very difficult to take us on. We also as a species tend to retaliate and kill those animals that kill our own. This is part of being self-aware. We understand Cause and Effect. We don't like the effects? Stop the cause. So the reason we generally are not attacked and eaten is we kill and often wipe out those animals that have shown a willingness to kill and eat us. We have 'trained' wolves and such to leave people alone by killing off those that don't. A form of evolution in action. The predators that leave us alone survive. [Answer] As Michael Bickley already outlined, taken at face value, the world would be exactly the same because humans **aren't** apex predators. We **became** such through the use of tools. So I'm assuming that there is a sudden **change** that removes us from that position. Oh, look, lots of movies have been made about that idea. Zombie Apocalypse or Phantoms from the Final Fantasy movie, or most alien invasion movies ever made. Final Fantasy comes closest, or even parts of Matrix. What would human society look like if we had an enemy we cannot defeat? We would hide, like all small prey animals. Live underground, invisible, away from our predators. Within society, there are no necessary changes. Many small animals are quite aggressive amongst each others or towards even smaller animals. In fact, since as said in the beginning, we **are not** apex predators, our instinctive reactions and social behavior is already closer to cats (another middle-ground predator) than bears or sharks (apex predators). [Answer] Frankly, I don't see this persisting for long. As soon as some apex predator starts killing humans, humans will work out how to eliminate the threat, one way or another. A race descended from a herd animal, say, might have a different attitude and defend rather than attack, but then you have a situation where for all practical purposes the herd critters are dominant in their range, having pushed the predators away. The only race I have ever read about that allowed this was from a classic Stanley Weinbaum story "The Lotus Eaters" where a plant intelligence was found. They knew just about everything, but some predator would carry them off and eat them because they had no drive and didn't give a darn. [Answer] One example of a believable non-predator sentient, dominant species in a biosphere is [Larry Niven's Puppeteers](http://en.wikipedia.org/wiki/Pierson%27s_Puppeteers). > > Biologically, Puppeteers are highly intelligent herbivores; a herd > animal, Puppeteers prefer the company (and smell) of their own > kind....... > > > Socially, two notable traits of Puppeteers are their > racial/cultural penchant for cowardice and their tendency to > congregate in herds. The cowardice is thought in Puppeteer society to > originate with the Puppeteer instinct for turning one's back on > danger. However, the trait is thought by many to actually originate > from their herd instinct, as the instinct to turn one's back is linked > to an instinct to kick the hind hoof at an attacker. > > > Much like the meerkat example, if humans were not apex predators, they would probably attempt to flee from danger far more often than fight it. The "fight or flight" response would probably degenerate to a "flight-only" response, as there will be no means for them to take out a predator. As herding and group dynamics evolved, they might allow the species to develop advanced techniques to counteract predators, such as signalling systems to avoid predators, or even exterminating them using advanced technology. [Answer] Edit prompted by comment of L.Dutch, to better reflect the question. **Apex-predatoryness and dominance are two largely unlinked concepts**. Consider the Great White sharks: We are total a\*\*holes to them, but that is not because we want to eat them (no appreciable part of them anyways) - we want them as trophies, we fear them, we are bored, we are wasteful - sharks die. **Humans**, even if they were complete herbivores, would still be humans (otherwise why call them humans? If you think herbivore bipedal beings would be bovine, docile, whatever, you conflate predatordom with other traits that in reality do not follow). Societies are mostly products of very specific circumstances: The Aztecs seem to have had a very different society from the early SriLankan societies, yet they were on a similar tech level, had comparable climates, and biologically near-identical human beings to work from (and both hat man-eaters in their biome). ---- there are several current communities that are located in biomes that contain man-eaters: there are still tigers and lions about. Apart from some technicalities about going out alone after dark, the traits those communities exhibit are not statistically more different compared to non-threatened communities than non-threatened comunities are among each other. **Humans** would have killed most of the apex predators above them in the food-net (not eaten them - that would have made them apex predators themselves), saved a few for the zoos and then wondered that they withered and died. **Humans** would overwhelm with numbers, poison, trick, burn, trap and generally bring their whole lethality to bear until no appreciable predator was left in the adjacent food-net. Higher numbers of Great Whites would survive, because humans don't live in the ocean. ---- The only weapon humans would not be able to bring to bear is the outcompeting of other predators - to starve them we'd have to cull the prey of those predators without direct nutritional gain to ourselves. I think we'd manage (\s) Why am i writing "*would*"? **Humans did**. Sabretooths, Cave bears, they all went extinct, not because we absolutely wanted to eat them, but because that made the neighborhood safer. Sure, there are stil a few man-eaters around, and every once in a while humans *do* get eaten, but it's rare. --- Not eating meat does not equate not being capable of seeing blood - elephants are strict herbivores, but if angered they will crush a fool. --- Warfare is intra-species violence that has (in humans) nothing to do with nutrition-by-foe. It has to do with ressources, with societal pressures, but it is not about eating your enemy - so that aspect of humans would also stay. Look at herbivores fighting for a good spot on the grass, or a sexual partner - there is nothing specific to carnivores in terms of violence. Now if your question was what would have happened if humans were not the **dominant** species of intelligent community builders - and the other species was carnivore, while humans were not - that's a completely different question, the answer to which will completely depend on the exact traits of the dominant species you envisage - they will shape the ecological niches that humans then would compete for; You'd also have to explain how humans evolved *as humans* - we can power that wasteful brain of ours, because "big-brains" is the ecological niche we dominate - in the long run there always is just one species per ecological niche, that is what makes it a niche. ]

[Question] [ The trivial answer is that it just means "you have two dimensions with inverted sign in your spacetime metric". But the perceptual result of that kind of choice doesn't actually look qualitatively different from our universe. Consider the 4D case; our 4 dimensional spacetime has a a +,+,+,- metric--*according to one convention*. If we decide we want two time dimensions, we get +,+,-,-. But, because the choice of which dimensions count as negative and which as positive is in fact purely conventional, this is physically equivalent to a metric with signs -,-,+,+. In other words, physics cannot uniquely distinguish spacelike dimensions from timelike ones. And in fact, Greg Egan wrote a novel in a universe with such a metric (*Dichronauts*), in which perceptual proper time is still distinctly one dimensional--just as in our universe, time is the length of your (one-dimensional) worldline. Go the other way and give all dimensions in you metric the same sign, so there are formally zero time dimensions, and you don't get a static universe without time--you get another Greg Egan novel (actually a trilogy, *Orthogonal*), again with normal one-dimensional proper time as measured along worldlines. It would seem that actually having two dimensions in a practical perceptual sense would require either 1. Converting proper time into a vector quantity somehow, or 2. Replacing worldlines with worldsheets, such that proper time is proportional to area. Suffice it to say, I have no idea what either of those things *means*, from a physics or narrative perspective. So... ideas? [Answer] First people need to understand how relativity works. There's a thing called *proper time* which we regard as an interval between two events or points in spacetime. In "ordinary common sense" space you define the distance (the interval) like this : $$s^2 = (x\_2-x\_1)^2+(y\_2-y\_1)^2+(z\_2-z\_1)^2$$ That's the square of the distance between two point. Time (and in particular our human sense of time) has no involvement here. You might also consider defining that interval as $s^2=c^2(t\_2-t\_1)^2$ which is pretty trivial. Either way there is no connection between a human sense of everyday time and the everyday definition of an interval or distance between events or objects. In relativity in our 3+1 D universe (three spacelike dimensions and one timelike dimension), we define an interval as : $$s^2 = c^2(t\_2-t\_1)^2-(x\_2-x\_1)^2-(y\_2-y\_1)^2-(z\_2-z\_1)^2$$ Two observers have to see that interval as being the same, and the mathematics of that definition is what connects space and time and why we end up with time dilation and length contractions - time and space are connected explcitly and cannot be disconnected. **Timelike** means $s^2$ is positive. A timelike dimension ($t$) has that positive contribution to the interval. **Spacelike** means $s^2$ is negative. A spacelike dimension has a negative contribution to the interval. Well that's how your basic universe we live in works. Here's an interval for a universe with two timelike dimensions $t$ and $u$ : $$s^2 = b^2(u\_2-u\_1)^2 + c^2(t\_2-t\_1)^2-(x\_2-x\_1)^2-(y\_2-y\_1)^2-(z\_2-z\_1)^2$$ ***But how is a human time defined in such a space ?*** Short version : it's not. The idea of time as we understand it is *apart* from these notions of relativity. Our everyday concept of time relates to a boring Newtonian ("classical") universe where space and time are **not** connected. It happens we can bridge the Newtonian concept of time with the relativistic concept of time in *our* universe, but that's not going to work at all in a universe with two timelike dimensions. Whatever perceptions of "time" the inhabitants of such a universe have, it won't relate at all to anything we understand as time. Now in a deeper sense the human perception of time relates to the concepts of energy and entropy ( ["the arrow of time"](https://en.wikipedia.org/wiki/Entropy_(arrow_of_time)) ). So in your other universe with two or more timelike dimensions their equivalent of human time (as opposed to abstract mathematical timelike dimensions) might (might !) relate to how energy and entropy connect with those dimensions. I'm not at all sure an arrow of time would be expressed as a single scalar value in such a universe - it might require a vector of time along a multidimensional plane of "time" dimensions. There might be multiple entropy values or their equivalent. Alternatively it's not impossible that such inhabitants might actually not work quite naturally with two time dimensions. For them the idea of one time dimension would be very strange - their common sense (their version of Newtonian mechanics) would have quite a different feeling. In instead of having one velocity vector describing motion, maybe they have two. And they might even use *both* of these concepts (or something like them) simultaneously. We do. It just happens it's easy for us because in this universe we only have to reconcile one timelike dimension with the arrow of time and as it happens the maths works out that the relativistic effects aren't ones we normally have to experience, so the simplest view is easy to use. In the other universe these inhabitants will presumably develop their own perceptions of before and after and maybe have a concept like before-after and before-before and after-before and after-after with different combinations of when things happen in the different timelike dimensions. So a question like "when were you born ?" could have an answer like "Dec 1965, January 1831". A question like "which came first ?" might be meaningless and you might need to say "which came first-first ?" or "Which came anytime-last ?". It might make perfect sense to them and be impossible for us to cope with. As *perceptions* of time and space are something your brain *invents* to make sense of the world, that's likely to happen in such a universe (if anything like inhabitants can exist at all). They might commonly have quite different perceptions. ***Extra dimensions*** Let's go back to that interval : $$s^2 = b^2(u\_2-u\_1)^2 + c^2(t\_2-t\_1)^2-(x\_2-x\_1)^2-(y\_2-y\_1)^2-(z\_2-z\_1)^2$$ In our universe there's no $b$ part of this, but depending on the relative values of $b$ and $c$ it's not impossible that one timelike dimension dominates the other in "everyday human" common sense events. The effect of the other time dimension could be important in cosmology in that universe and irrelevant to ordinary everyday physics. It's quite possible you could have values of $b$ and $c$ such that they can discover physics exactly like our 3+1 D universe even down to advanced quantum field theory long before they even realize there's more timelike dimensions. So this universe might actually "look" quite similar to us with particular parameters for these kind of values. We actually use physics theories with way more than 3+1 dimensions ourselves. [String theories](https://en.wikipedia.org/wiki/String_theory#Extra_dimensions) some in a variety of flavors including ones with 26 dimensions (!), 10 dimensions and 11 dimensions. You can have these theories in such a way that the extra dimensions don't impact "normal" physics because there effect is small (in more sophisticated ways than my rather simplistic suggestion above). But again, remember that these abstract physical theories don't necessarily easily connect to a human (or "universe inhabitant") idea of "time" or "time's arrow". [Answer] Imagine you are a single dimensional creature, You go along and encounter an object. You hit said object and it disappears out of your universe, because it took a vector outside your perceptional ability to comprehend. but if you change your comprehension to a 2D universe, you notice it moved in a vector perpendicular to the 1D field of view, moved to the edge of your universe and disappeared. Change it up again to a 3D universe and you notice it was a ball that rolled across the table a fell off the side, and bounced away. Imagine time having the same vector capabilities. We perceive time in a 1D sense. We interact with objects, things happen and the event ceases to exist in your universe. Add a 2d or 3d to time, then you can perceive events occurring in vectors outside of your 1D point of view. So if you can freely travel through time on the 1D vector, you can see an event play out, reverse and play it again or you can speed it up to see the event in conclusion. If you move freely in multiple dimensions of time, you can do the same, but then you can watch the even in any and all possible initiations and conclusions that could come out of an event. Effectively, perceiving time in multiple dimensions could be what you call alternate realities. [Answer] **I'm going to post a bit of an off-beat answer: you've probably already experienced a 2-time-dimension universe.** Because that's exactly what you experience when you play a computer game with pauseable time controls. Think about it - you've got two time dimensions: real-time and game-time. More than that, those different 'times' are orthogonal. Real time can run while game time is stilled whenever you pause the game; Real time and game time can occur in differing ratios when the game is running under its various speeds; real time can freeze while game time runs during any sort of "Auto Resolve" function. You as a *person* are experiencing a single time dimension, but within the context of the game, you're experiencing and controlling two separate time dimensions. The game itself is experienced in two time dimensions. Literally, the *only* differences between your question and someone playing a computer game is that they can't comprehend events along the scale of game-time (because their brain runs solely in realtime) and the fidelity of the game during the autoresolution (because the computer running it is also operating solely in realtime.) So a great makeshift way of mentally picturing it is to simply imagine playing a computer game, with the tweak that when you "autoresolve" something, your brain still somehow knows everything that happened during the autoresolution (even if no real time passed during it.) [Answer] In general, time could be multidimensional. The reason we work with time being a positive real number (1D) is that we can easily observe (measure) changes of the "magnitude of time" (elapsed time). However, there are a many nuances to be considered: 1. By itself in isolation, time is just a characteristic of events, e.g., order of occurrence, duration, etc. The concept of "time" can certainly be defined, tracked and interpreted in many different (mathematical, philosophical) ways. For instance, "time" can be mathematically defined in multiple dimensions, formulated as spanning the smallest complete field containing the real line where all polynomial equations of order "n" have precisely "n" solutions, i.e., the complex plane (complex time is referred to as "kime"). This is all mathematically well-posed, however, it may draw some criticism from experimental physics, as physical “reality” demands concrete “observable” evidence in support of the (higher dimensional time) math model. 2. The utility, value, and universal relevance of time come from its tight integration with the spatial dimensions into "[Minkowski spacetime](https://en.wikipedia.org/wiki/Minkowski_space)", a continuous universal model coupling 3D space and 1D time dimensions. The longitudinal order of events in the flat (Euclidean) 4D Minkowski spacetime universe is represented by a continuous positive real number, we refer to as "time". 3. One can of course, entangle the first two scenarios and consider the universe as a higher-dimensional (5D+) space with multi-dimensional time. The easiest approach for that is to introduce complex time (*[kime](https://spacekime.org)*) that effectively and completely unifies the spatial and temporal dimensions, i.e., traversal, measurements, trajectory paths, etc. in space are naturally extended in their space-kime counterparts. Below are 3 examples that illustrate specific higher dimensional universal models that agree with the 4D Minkowski spacetime observable universe. There are interesting ramifications of such dimensionality lifts of the classical 4D spacetime to higher-dimensional manifolds using multi-dimensional time. 4. Spacekime theory proposed by University of Michigan researchers defined [Spacekime](https://spacekime.org) as a 5D universe with 3 spatial and 2 complex-time (kime) dimensions. In this framework, longitudinal measurements (e.g., time-series) are represented as kime-surfaces where time is encoded as the magnitude of the radial displacement, and the second degree of freedom, kime-phase, represents the orientation of the event (cf. mathematical parameterization of the complex time plane via polar coordinates). 5. Itzhak Bars at the University of Southern California proposed a [2T theory](https://www.springer.com/gp/book/9780387776378), which utilizes an additional time dimension. 6. Another Multi-institutional consortium proposed the 5D space-time-matter ([5DSTM](http://5dstm.org/)) theory to model the universe. Lifting the dimensions of time results in some profound and about the universe and our interpretation of reality, truth, observations, space travel, and event causality. For instance: 1. Ordered events like classical time-series curves morph into complex kimeseries surfaces where order is relative to parametric descriptions of simple paths/curves, see [this animation](https://www.socr.umich.edu/spacekime/img/Kimeseries_Kimesurface_video.gif). There are interesting applications of this generalization to scientific inference or process prediction, and longitudinal data analytics. 2. Increasing the dimensional of time resolves many of the [problems of time](https://en.wikipedia.org/wiki/Problem_of_time), like the “[arrows of time paradoxes](https://en.wikipedia.org/wiki/Arrow_of_time)”. Time is actually not just uniformly and automatically marching forward. Our human frame of reference is inertially moving through the 5D+ universe. Time passage is observed as an incremental (time-dimensional) change in this motion. Time traversal is identical to spatial traversal from one location to another (on specific curves/paths). While it's practically impossible, having infinite energy and infinite information allows the theoretical reversal of this spacetime motion (e.g., travel exactly back in time) by applying the inertial motion/transformation in reverse. 3. In higher time-dimensions, and under certain conditions, [Heisenberg uncertainty principle](https://en.wikipedia.org/wiki/Uncertainty_principle) does not apply. In other words, in 5D spacekime, one may observe simultaneously and with perfect accuracy both the position and momentum of a particle. The manifestation of the uncertainty principle in 4D spacetime is just due to the presence of a 1 degree of freedom when we project 5D spacekime down to the 4D Minkowski spacetime. In other words, the observer reflection of uncertainty arises by the natural projection of 5D onto the 4D spacetime and is due to the unobserved complex-time (kime) phase direction. 4. Theoretically, complex-time (kime) permits the existence of simple closed 2D kime curves (CKC). However, there is no practical way to exactly go back to one specific (past) time-point and repeat a previously run experience trying to alter a (future) outcome (i.e., there is no "Grandfather paradox"). This theoretical impossibility is due to the fact that the measure of any finite or countable set of elements in R (real line) or C (complex plane) is always trivial. Given sufficient information and energy, we might be able to get near the *vicinity* (within a neighborhood) of one specific past spacetime location, but we can’t get precisely into one specific, unique, and precise spacetime location (whether “past” or “future”). Just like the rational numbers (Q) are dense in the Reals (R) and the measure of Q is trivial (zero), we can can land somewhere (the “axiom of choice”), but we cant guarantee getting precisely to any specific spacekime locale. [Answer] I haven't read *Dichronauts*, but unless you can time travel, I don't see how it would change anything. Time is not entirely comparable to a space dimension, because you **can't move freely in it**. It goes **in only one direction**, and and at the same rate by everyone (except for relativity, I'll come to that later). If we see time as a vector (typically in [these kinds](https://en.wikipedia.org/wiki/Light_cone) of graphs), having two orthogonal time vectors will just make one vector that is the sum of both, and that will be perceived as the one time vector by everyone. The only thing that would make things different from a universe with one time dimension is if there's a special kind of gravity that distorts one time dimension more or less than the other. However, there's no reason for gravity to act differently on one of them. If you're close to a black hole or travel near the speed of light and both dimensions are affected equally, there won't be any difference. So unless an object or entity has the power to travel in time or bend one of the time dimensions, it should feel like a universe with one time dimension. [Answer] See Heinlein's "The Number of the Beast" There it's 3D+3T. Time dimensions are orthoganal, and a given universe only experiences one of the dimensions. However this means that if you switch to the Tau axis instead of the Tee axis no time passes on the Tee axis (for you) while you are gone. You can become wealthy selling holiday vacations that take no time at home. Possibilities for cramming for exams; illicit affairs; Reconciling large age differences between would be lovers. Without separate universes, the everyday physics gets difficult. How does air resistance work? Gravity? (If you have multiple time dimensions are inverse square laws still inverse square? [Answer] I'm fairly sure that what I am about to explain is not what you're going for (as multiple time dimensions in the spacetime relativity sense of that phrase are utterly beyond my comprehension), but multidimensional time is a concept that already exists in the philosophy of time travel. The idea is that every usage of a time machine creates a branch in the timeline at the moment the machine is scheduled to arrive, with the machine landing only in the new branch. In other words, time travel invariably lands the traveler in a parallel universe. A parallel universe identical to the universe they departed from right up until the moment of arrival. This neatly solves all the classic time travel paradoxes- nothing you can do can ever affect your own history, because after you turn on your time machine, you'll forever lose access to the branch of the timeline (timetree?) in which your own history exists. As such, if you try to murder your grandfather, you'll at best manage to murder his alternate universe counterpart- a man with no causal relation to your actual grandfather or to yourself. If we consider the 4th dimension to be the ordinary, familiar dimension of time, then these separate branches exist in different locations in the 5th dimension, which could be called "meta-time". How the different timelines are arranged in meta-time doesn't really matter, since there's no way to actually observe them. [Answer] Suppose Dr. Who invites you into the Tardis for a cup of tea while you go backwards in time to the start of the Bronze Age collapse. It takes 10 minutes to drink the tea - exactly the amount of time it takes the Tardis to make the trip back to 1200 BC. In what dimension of time does the 10 minutes in the Tardis exist? I've always imagined that the time which passes inside of a time machine is time that exists in a separate time dimension from the time dimension through which the time machine is travelling. [Answer] Without jumping ahead to alternative metrics, consider a similar situation in normal 3+1 spacetime. Though we can successfully model our personal experiences as a 1d worldline, one can also imagine zooming in so that each person is made up of a 3-d volume of constitutive elements. For their own proper times, these constituent elements are occasionally space-like separated. Owing to the obvious success of the person's 1d worldline model, we would like to call this 4d collection of particles (worldtube?) a person, despite the spacelike separation of it's components. The intriguing question is where does the person's 4-velocity come from, out of these components? I think the answer lies from a causal perspective. Basically, imagine a discretization of spacetime so that there is a discrete 'grid' of event points. If two points are timelike separated, draw an arrow from the one with the earlier time to the one with the later time (i.e. draw arrows respecting light cones). Now, each point of this discrete spacetime can be in one of many states, and let the future evolution of point $p = f\_p(parents(p), noise)$, for some deterministic function $f\_p$ (which can change from point to point) and independent noise (n.b. quantum mechanics might somewhat complicate this assumption, so given it lets keep it classical :P). This is the same as Judea Pearl's causal model. Now, we can imagine grouping the state space of this finite collection of points into 'macro-causal equivalent,' coarsened states (as is the case in thermodynamics, where we group together identical macrostates). Ideally, at the correct coarsening level we'd see that the states of the points that were in the worldtube above all get grouped together such that its one world line of points, with the state at every point corresponding to the person's experience at that time. That is, $p\_{t+\varepsilon} = f\_{t+\varepsilon}(p\_t, noise\_{t+\varepsilon})$, note the recursive *deterministic* function application. Assuming each such function is computable, we can move any unique behavior of the each point's particular function into the noise term, and then treat each $f$ as an executing Turing machine (with a quite large alphabet haha). Therefore, I think that treating a consciousness in this fashion creates the perceptual concept of proper time, which is intricately tied to the *computational model* used and the appropriate causal aggregation, *rather* than the actual spacetime geometry. Though, 1 time dim sure helped making sure that at a high enough coarsening level, there wouldn't be weird arrows jumping all over the place! Now, what would a 2d *perceptual* time look like? Note that this time, it's not anymore the case that 'most' of the arrows are going in the time direction anymore, but causal influences can now spread out in multiple directions (e.g. a full circle in ++--, since $[\cos(\tau), \sin(\tau), 0, 0]$ are all timelike separated points from $[0,0,0,0]$). This allows for CTC's, and I'm not sure how Egan deals with that... Note that subsequent macro-level coarsenings will also likely have to contend with largely 2d 'chunks' of events, due to this 2 dimensional spread of arrows. I believe the right subjective lens to interpret this is again through a computational model. There are plenty of computational models using combinatory like logic which can extend in multiple space dimensions with no time dimension. For example, look into Wang tiles (generally there's rules about how tiles can fit next to each other, and the question is whether from a given starting position, any added tiles will eventually tile the plane). These ideas are used in practice in self-assembling DNA computational models (see [Computability and Complexity](http://web.cs.iastate.edu/%7Esummers/papers/conference/CCSA.pdf) in Self-Assembly by James I. Lathrop, Jack H. Lutz⋆, Matthew J. Patitz, and Scott M. Summers for more detail). One could imagine that an 'instant' in perceived time corresponds to the shape 'growing' along it's perimeter. Now, this looks very similar to a 1d time increment, however, the corresponding 1d time increment for the Turing machine would be moving along the entire perimeter and adding new tiles one at a time, at a constant rate. So, in essence I think the big difference is that someone with 2 dimensions of time perception would notice that as time went on, the complexity of the 'update' of their experienced state would increase at a linear rate, while for 1d time it would stay at a constant rate forever. Essentially, information appears to increase at a quadratic rate in a 2d time universe but at a linear rate for the 1d time universe. Perhaps a more coherent view of this last part is that in >1d time, the difference in perception is the difference of a tree of coarsenings vs a line of coarsenings. So, at the perimeter one could see (and be affected by) multiple versions of 'oneself' which are all moving in 1d time. [Answer] From a world building perspective, this is how i would describe 2 time dimensions: 1D + time\_alpha: A dot moving in {x} space and time{a}. The time line will always be straight. 2D + time\_alpha: A dot in {x,y} space and time{a}. The line will now be curved, but only in one dimension. 3D + time\_alpha: A dot moving in {x,y,z} space{a}. The line is now free to form in any spacial dimension, but it will always be continuous. 3D + time\_alpha + time\_beta: a dot moving in {x,y,z} space and {a,b} time. As {a} and {b} are perpendicular, motion through one is inversely proportional to motion through the other(assuming motion through {a} is constant). In this case, motion through {a} is no longer guaranteed to be constant, therefore, perceived speed would change depending on one's motion through those temporal dimensions. High velocity through {b} would reduce velocity through {a}, leading to discrepancies in observed and experienced velocity through {x,y,z}. The result could be large, sudden changes in spatial velocity or position over very little {a}. e.g. A space ship sets velocity(v) to the 0.5c. It should take 8 years{a} to reach Proxima Centauri. But from the perspective of Earth, it would take 17.4 years. So, the ship changes it's temporal velocity to move in equal amounts {a,b} equal to the amount that we currently move through {a}. Thusly, motion through {a} is reduced by about 30% (The unit vector ratio of two equidistant perpendicular axes is 0.707). The journey, from Earth's point of view, now appears to take 12.18 years. From Earth's perspective, The ship has increased in speed, but it has been travelling at 0.5c all this time. If the ship further increases it's motion through {b}, eventually you could have near lightspeed travel with no appreciable time dilation. Of course, this is all actually bunkum, but if you are writing a scifi story, it could be just believable enough to the layman to suspend disbelief. You could add some kind of side effect of moving through {a,b} instead of {a}, like slipping into very close-by alternate realities with only subtle changes. high {b} velocity can take you far from your "home" reality, where the changes are more profound. In such a way there could be some fictional calculus, which describes the rate of change between realities depending on v{b}. [Answer] If you think of 1D time as reversing backwards down a road so as you can only see what you have passed, this means you can travel in both directions but you can only know that you are facing ([Example](https://www.desmos.com/calculator/o9my2ona5g) of 1D time). (Given a complete timeline, you could reference any point and from there only know what had happened in the relative past from that point) In a 2D time plane then this fact would apply to both temporal dimensions meaning you would see everything behind you in either direction. This would mean the more temporal dimensions the universe has in it the more of the complete temporal picture you can see from inside the temporal plane ([Example](https://www.desmos.com/calculator/a0psl1qwz5) of 2D time). (Given a complete timeplane, you could reference any point and from there know both histories that led to converge on that point). The two temporal dimensions would not have to progress in sync nor would either be forced to only progress forwards but any backwards progression would not be remembered. [Answer] H. Beam Piper, in his Paratime series describes time as having two dimensions. The first everyone understands: go forward in time or go backwards in time. The second dimension of time, called "paratime", is perpendicular to the first. By moving in paratime, one travels to parallel realities rather than before and after now. Paratime is measured by looking at the point in the past where the two realities were unified. Suppose in 2001, the World Trade Center was not brought down. Now for the sake of discussion, now is September 11, 2021. The parallel reality wherein the major difference is whether or not 9/11 happened is 20 parayears from our reality. Flip a coin and it lands heads. The reality where it landed tails is a few paraseconds from here. Philosophically speaking, this is an axiom if you subscribe to "many worlds". In thinking about this over the years, I extended this idea to say that there could be more than two dimensions of time. What phenomena would happen through these additional dimensions? Perhaps things like two different frames of reference running at different speeds? Time loops? Marvel's cosmology of megaverses and the omniverse certainly would require at least three dimensions. [Answer] 1 dimension in time is what we perceive as past(-), present(0), and future(+) like a number line. For any given tx, you have exactly one point. 2 dimensions in time would be like a grid paper. At any given time tx, you ca have infinite values for ty. Basically, infinite parallel instances for past, present and future aka Parallel universes or timelines or branch realities. Humans(us) are 4 dimensional beings, with the ability to move in and perceive three dimensions. We cannot see or interact with the past or future. As a rule of thumb, Any being has freedom of movement and perception in n-1 dimensions, where n is the number of dimensions they exist in, bcoz otherwise, there will be some serious paradoxes. As such a being capable of traversing through time or our 4 dimensions (x,y,z,tx) must exist in 5 dimensions. What this means that even if this guy travels to past or future, he is never in the same timeline i.e. the ty value uniquely defines him and always grows in one direction, like tx does for us. If he goes back in time, he is not going back in his own timeline, but rather a different one, and no matter what he does there will be no change in his history. P.S.:The real mindbender is when you try to imagine 3 dimensions in time. ]

[Question] [ I'm making a fairly hard Sci-Fi story, and I was wondering what the most scientifically plausible 'energy shield' (for ships and stations) would be. My world tries to remain true to basic physics, but I'm not researching every law and limit to get it perfect. If it's not possible by our current understanding of physics, what should I change to minimize the number or obviousness of the flaws in its plausibility? [Answer] Same as Earth's, which serves us well: magnetism. # magnetic field A superconductor can be charged with a huge current that then acts as an enormous permanent magnet. A ship may need to handle dust and gas moving at high speed relative to the ship, but that material is not charged. So charge it: spray electrons to charge dust (like a room ionizer does) or use a laser or tuned microwaves to cause gas to become ionized. Also, might say that the corona effect magnifies the results and sweeps away more than you explicitly ionized (though it's not obvious that that would be the case in a near vacuum). # physical swarm controlled via flux pinning If you want something to affect material near the ship to serve as protection, you are asking to change the momentum of that stuff. What *could* do that without contact is electromagnetism or gravity. That is, an "energy shield" is electromagnetic, with no other reasonable choice. With "contact", you can still avoid walls by spraying small particles out. The corona effect uses electric charges to accelerate charged particles which then smash into other particles, pushing them away. The idea of shielding that's not simple walls is useful for constant renewal rather than wearing out, and being stronger than mere matter. Something that is really cool to see demonstrated is the use of superconductors to “[pin](http://en.wikipedia.org/wiki/Pinning_force)” an object in a definite position in space relative to each other, with a sizable gap between but acting like a solid object. So, have a swarm of small magnets surround the ship, some distance from each other but with enough layers that the swarm is opaque. An incoming rock will hit *one* of the plates and not make it through the swarm. Each magnetic plate is covered with spongy material, so the hit will accelerate the plate without (typically) breaking it. The plates are far enough apart so it won't knock into another. But, the displaced chunk is *loose* and did not fracture a large normal object like a plain matter shield. After absorbing the energy, the superconductor takes on the energy while slowing the motion, then returns it to its proper position. The plates can be made with weak seams crossing it where it will break in a controlled manner if hit too hard; and each piece is still controllable as part of the swarm. The swarm can be dynamically reconfigured, to beef up the direction where hits are expected, such as the direction of travel or where debris have been spotted. I've seen the superconductor station-keeping explained as possible for a structural component that won't "break" but can be returned to its proper position after being over-stressed. Using a swarm for shielding is an original idea. Fans of the RI Christmas Lectures will recognise [this demonstration](http://www.youtube.com/watch?v=zPqEEZa2Gis). [Here](http://physics.about.com/od/quantumphysics/f/QuantumLevitation.htm) is an overview which touches all the bases. I could not find a video of the particular demonstration that inspired me illustrating the strength of such bonds for structural elements in space construction. --- See also [this post](https://worldbuilding.stackexchange.com/questions/29801/what-are-some-plausible-super-materials/29834#29834). See [this paper](https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.spacecraftresearch.com/files/Shoer_GNC2008.pdf&ved=0ahUKEwi-j8jDmpDKAhXIQyYKHdM0B6cQFggkMAM&usg=AFQjCNHZ9xaZNWvvSQvuAa0gUL0T_6Sf8g&sig2=xl1hnF0gNDgR0WcrPvbnNw) for more on flux pinning for space construction. [Answer] Physicist Michio Kaku discusses some possibilities for shielding on p. 9-10 of his book [*Physics of the Impossible*](http://rads.stackoverflow.com/amzn/click/0307278824), viewable on google books [here](http://books.google.com/books?id=ube-MQcFFZQC&lpg=PP1&pg=PA9): > > The problem with electron beam welding, however, is that it needs to be done in a vacuum. This requirement is quite inconvenient, because it means creating a vacuum box that may be as big as an entire room. > > > Dr. Herschcovitch invented the plasma window to solve this problem. Only 3 feet high and less than 1 foot in diameter, the plasma window heats gas to 12,000°F, creating a plasma that is trapped by electric and magnetic fields. These particles exert pressure, as in any gas, which prevents air from rushing into the vacuum chamber, thus separating air from the vacuum. (When one uses argon gas in the plasma window, it glows blue, like the force field in *Star Trek*.) > > > ... > > > But can the plasma window be used as an impenetrable shield? Can it withstand a blast from a cannon? In the future, one can imagine a plasma window of much greater power and temperature, sufficient to damage or vaporize incoming projectiles. But to create a more realistic force field, like that found in science fiction, one would need a combination of several technologies stacked in layers. Each layer might not be strong enough alone to stop a cannon ball, but the combination might suffice. > > > The outer layer could be a supercharged plasma window, heated to temperatures high enough to vaporize metals. A second layer could be a curtain of high-energy laser beams. This curtain, containing thousands of crisscrossing laser beams, would create a lattice that would heat up objects that passed through it, effectively vaporizing them. I will discuss lasers further in the next chapter. > > > And behind this laser curtain one might envision a lattice made of "carbon nanotubes," tiny tubes made of individual carbon atoms that are one atom thick and that are many times stronger than steel. Although the current world record for a carbon nanotube is only about 15 millimeters long, one can envision a day when we might be able to create carbon nanotubes of arbitrary length. Assuming that carbon nanotubes can be woven into a lattice, they could create a screen of enormous strength, capable of repelling most objects. The screen would be invisible, since each carbon nanotube is atomic in size, but the carbon nanotube lattice would be stronger than any ordinary material. > > > So, via a combination of plasma window, laser curtain, and carbon nanotube screen, one might imagine creating an invisible wall that would be nearly impenetrable by most means. > > > Yet even this multilayered shield would not completely fulfill all the properties of a science fiction force field—because it would be transparent and therefore incapable of stopping a laser beam. In a battle with laser cannons, the multilayered shield would be useless. > > > To stop a laser beam, the shield would also need to possess an advanced form of "photochromatics." This is the process used in sunglasses that darken by themselves upon exposure to UV radiation. Photochromatics are based on molecules that can exist in at least two states. In one state the molecule is transparent. But when it is exposed to UV radiation it instantly changes to the second form, which is opaque. > > > One day we might be able to use nanotechnology to produce a substance as tough as carbon nanotubes that can change its optical properties when exposed to laser light. In this way, a shield might be able to stop a laser blast as well as a particle beam or cannon fire. At present, however, photochromatics that can stop laser beams do not exist. > > > Also, metamaterials have been used to create ["invisibility cloaks"](http://www.abc.net.au/science/articles/2011/11/23/3373384.htm) that deflect light around them, as in the following idealized graphic: [](https://i.stack.imgur.com/Q3rGi.jpg) Presently these only work to "cloak" very small objects at very specific non-visible light frequencies, but scientists hope in future to expand the technology to larger objects and a greater range of frequencies. So potentially a technology like this might be adapted to deflect lasers around an object. There is also an analogous idea based on metamaterials called a ["universal mirror"](http://www.engadget.com/2009/07/20/universal-mirrors-more-useful-less-fun-than-carnival-mirrors/) which would reflect incoming light beams back in the direction of their source. [This article on the "universal mirror"](http://www.nbcnews.com/id/31968012/ns/technology_and_science-innovation/) specifically mentions it might have applications in laser shielding: > > The metamaterial could also act like a aggressive shield, protecting objects from airplane-based, high-energy laser systems, which are being developed by Boeing, by bouncing the lasers beam back at their source. > > > Finally, if you want to get into much more far-future technologies, potentially it might be possible to create something like an invisibility cloak by setting up a thin layer of ["exotic matter"](http://en.wikipedia.org/wiki/Exotic_matter) that would bend spacetime in a way that would deflect all incoming light, as discussed in [this paper](http://arxiv.org/abs/1108.3793). This is a purely theoretical idea that would require a civilization to be able to create and control very high densities of exotic matter with properties that present-day physicists [aren't sure are even physically possible](http://en.wikipedia.org/wiki/Wormhole#Raychaudhuri.27s_theorem_and_exotic_matter), in ways that would also allow other far-future technologies like the [Alcubierre "warp bubble"](http://en.wikipedia.org/wiki/Alcubierre_drive) that would allow for a form of effectively faster-than-light travel. [Answer] # Plasma Shields ## Boeing's > > [Boeing’s proposed system involves using a combination of lasers, electricity and microwaves to rapidly heat up the air between the vehicle and a blast. This heat creates a plasma shield that's denser than the surrounding air and able to deflect or absorb the energy from the incoming shockwave.](http://www.sciencealert.com/boeing-has-patented-a-plasma-force-field-to-protect-against-shock-waves) > > > ## University spacecraft research > > [There would need to be a wire mesh outside the spacecraft and enclosing the plasma cloud. Electricity supplied to the mesh would keep an electrical current running in the plasma cloud and help confined it near the spacecraft.](https://www.newscientist.com/article/dn9567-plasma-bubble-could-protect-astronauts-on-mars-trip) > > > [Answer] **Bent space shield.** Gravity is usually considered as a force and so I assert it meets the requirement of this question. Gravity is not a real force but an apparent one - gravity emerges as a consequence of the ability of mass / energy to produce inhomogeneities in space: bent space. To make the bent space shield, you would use negative matter much in the way it is proposed for use in making the Alcubierre drive. <https://en.wikipedia.org/wiki/Alcubierre_drive> > > Rather than exceeding the speed of light within a local reference > frame, a spacecraft would traverse distances by contracting space in > front of it and expanding space behind it, resulting in effective > faster-than-light travel. Objects cannot accelerate to the speed of > light within normal spacetime; instead, the Alcubierre drive shifts > space around an object so that the object would arrive at its > destination faster than light would in normal space without breaking > any physical laws. > > > If you have the tech to make the drive, making an energy shield would be a lot easier. You would bend space around the ship such that energy or matter entering one side of the field would continue on its path, but be routed through bent space around the ship and out the other side. This is slick in that it works equally well for moving particles or electromagnetic radiation. Even very energetic particles moving at relativistic speeds would be effectively rerouted. The energy of the particle or radiation remains as it continues through bent space, out the other side and on away from the ship. A side effect of this shield is that it would also be a cloaking device: the ship within this shield is invisible. I am not sure what energy emitted from the ship itself does when it hits the inside of the shield. An interesting thought experiment: what happens if a ship with a field like this rams a larger object? Mass impacting the bent space field is routed through it. Could a ship with a bent space shield fly through solid matter? If it closed up any windows in the shield, could it fly through a star? --- Thinking more on the concept - a ship could use the same negative mater for its warp drive and its shields. But the stuff must be rearranged to serve these different purposes. To activate the drive you need to take down the shield and move the negmat to the specific place you will use to generate your drive. If you come out of warp, it will take time for the servos to redistribute the mass around the ship and generate your shields. This helps make ships so equipped less overpowered and godlike - you cannot just invisibly and untouchably warp from place to place. [Answer] The most common hard-science sheilding that I've encountered in fiction is ablative armor. It isn't very elegant, but surrounding you ship with multiple layers of hardened foam provides a non-critical surface to catch the particles which get by your outer magnetic fields and inner swarm defenses. As these particles collect, they provide additional layers of impact absorbing material to keep ever bigger particles away from your ship's atmospheric shell and other vital systems. If really big particles get through, your foam armor can even break off during impact, carrying most of the momentum and mass of the collision away from your hull. Then automatic foam dispensers on the hulls surface can replace the missing layers, preparing your ship for future impacts. Upon arrival at your destination, you can either vibrate the hull to shake loose the remaining foam or bring the swarm in close to scrape the foam away from the outside in. [Answer] Essentially there isn't anything in hard science beyond maybe some of the ideas with magnetism and plasma. Active defenses (interceptor missiles, lasers, etc) are more plausible but still tricky. Just dodging and getting out of the way is surprisingly effective, there is a lot of space out there and with no atmosphere to carry shockwaves near misses do very little damage. If you have gravitational control in your universe then it's not hard science but you can see manipulated gravity fields being plausible as a defense mechanism. They could divert incoming fire away from your ship or even suck it into miniature black holes! [Answer] If your looking for something energy based, you could do a hard light shield by having a cloud of Rubidium around the craft and have weak lasers fire a few photons at a time (or scale up, the research is readily available) to create a hard light construct. Here's the paper on the experiment for generating hard light: <http://www.nature.com/nature/journal/v502/n7469/full/nature12512.html> And a news article for summary: <https://www.sciencedaily.com/releases/2013/09/130925132323.htm> [Answer] Electromagnetic armor. A concept being worked on in real world military applications. and "Exaggerated" in Scifi. Idea is metal plates contain superconducting fibers, when energy/electricity is applied the molecules undergo a massive rigidity change. Increasing the hardness of the exponentially. Not a shield........but dynamic armor. [](https://i.stack.imgur.com/EmqMT.png) [Answer] There actually are examples of electro-static shields existing in real life by accident. Ridiculously dangerous of course. If it can stop you, it can just as easily kill you. <https://www.reddit.com/r/todayilearned/comments/7kv54c/til_a_3m_adhesive_tape_plant_accidentally_created/> My take would be on plasma shields with a twist. Basically, you take lasers that "print" small plasmadots in mid air, which then connect - allowing current to flow through, forming coils, em-fields and thus allowing "add-hoc" circuitry to be printed into any gasouse medium which the lasers can past and 3d print through. So the shields do worker better in atmosphere - not so much in space, unless you bring your own medium-bubble. ]

[Question] [ **This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. [Cloud Nine](https://en.wikipedia.org/wiki/Cloud_Nine_(tensegrity_sphere)) is the name given by Buckminster Fuller to his proposed tensegrity sphere airborne habitats. The principle is simple and the physics seem to be sound. [](https://i.stack.imgur.com/4ff57.jpg) For a sphere, as its radius is increased, the [volume increase outpaces the surface area](https://en.wikipedia.org/wiki/Surface-area-to-volume_ratio). The mass of the sphere depends primarily on surface area1. At some point the mass of the sphere is minimal compared to the mass of the air contained inside its volume. By slightly heating the air inside (and letting some escape), the density (and therefore total mass2) of the contained air can be significantly decreased with respect to the air outside. This will allow the sphere to float (via buoyancy) in the surrounding air. None of this is unheard of, we're essentially talking about a hot air balloon with some thyroid problems. **So let's build one.** I want my sphere to be one kilometer in diameter and I want to keep the interior at 22 degrees Celsius (so I can live comfortably inside, of course). I'd like to be able to reach an altitude of one kilometer in a climate similar to the Rocky Mountains. **What materials, if any, can I use to build my Cloud Nine? Given the selected materials, how much mass can I lift in addition to the mass of the completed sphere?** *Note: There seems to be an excellent [design resource for tensegrity spheres](http://www.angelfire.com/ma4/bob_wb/tenseg.pdf) here. The resource is full of equations, mathy stuff, which you'll need to answer this [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") question. An answer of "the material needs to be, like, wicked strong and lightweight, dude" is not satisfactory. I want to know what materials will work (and calculations showing why), or if none exist, what materials would be required (and calculations showing why).* --- 1: Of course the surface is not 2D, so the mass depends on the thickness too, which will need to grow in order to be self-supporting structure. However, I don't think the thickness will need to grow as fast as the volume. 2: See the [ideal gas law](https://en.wikipedia.org/wiki/Ideal_gas_law), we want P and V to remain constant while T increases, thus reducing n in a constant volume. Fewer particles in the same volume means lower density and lower total mass. --- Note: I am interested in the **materials for construction of the sphere**. The ability of a container to float due to temperature differential is not in question, hot air balloons perform such a feat daily. Assume a temperature differential can be achieved and will subsequently obey the ideal gas law as described. Further Edit: **These aren't bubbles.** A bubble has an increased internal air pressure to keep its surface inflated. I am fairly certain that a rigid structure is required to form the sphere. Otherwise the increased internal air pressure required to counteract the weight and surface tension of the enclosing material will negate the benefit of increasing the temperature. Again, see [ideal gas law](https://en.wikipedia.org/wiki/Ideal_gas_law) and footnote 2. A rigid sphere both can have the same air pressure as outside (no airlocks required) and maintain the spherical shape which optimizes the surface area to volume ratio (thus allowing maximal lift per unit mass of support structure). **If you want to forego a rigid structure for your sphere, please use the correct volume for its final shape and/or use the final internal pressure value in your lift calculations.** [Answer] # Feasible Only with a Decreased Internal Pressure and Great Difficulty This is a very complicated problem with many variables that affect the final outcome of the design. I made a few assumptions throughout and played with the numbers as much as I could in order to give a semi-complete answer. I feel like I could write an entire book on how this could or could not happen. ## Calculating Buoyancy with 1 Degree Temperature Difference I'm going to use SI units in order to make this all simpler. I'm also going to focus primarily on the material requirements (since that is what the OP asked for) and am going to disregard the methods for heating up this behemoth. I am also going to use the assumption from Thucydides answer that the temperature within the sphere only needs to be raised 1 degree (I will use Celsius to make it easier and allow room for error). In order to calculate the buoyant force, we must use the ideal gas law to find the internal density: $$P = \rho T R\_{specific}$$ $P$ is ambient air pressure, which is 101,325 Pa. $$\rho = \frac{P}{T \cdot R\_{specific}} = \frac{101,325\,\text{[Pa]}}{278\, \text{[J/kg K]}\cdot(295\text{[K]})} = 1.2355\,\text{kg/m}^3$$ so $\rho\_i = \small 1.2355\,\text{kg/m}^3$ The density outside of the sphere is 1 degree cooler: $$\rho\_o = \ldots = \frac{101,325\,\text{[Pa]}}{278\, \text{[J/kg K]}\cdot(294\,\text{[K]})} = 1.2397\,\text{kg/m}^3$$ so $\rho\_o = \small 1.2397\,\text{kg/m}^3$ The net buoyant force is equal to the density differential multiplied by volume and gravity: $$\begin{align} F\_b & = (\rho\_o-\rho\_i)V \cdot g \\ & = (1.2397\,\text{[kg/$m^3$]} - 1.2355\,\text{[kg/$m^3$]})\cdot\left(\frac{4\pi}{3}(500\,\text{[m]})^3\right)\cdot 9.81\,\text{[m/$s^2$]} \\ & = \text{21,585,879 N} \end{align}$$ $F\_b$ = 21,585,879 N You will need your sphere to weigh less than this in order for it to maintain lift, so the material required with need to be relatively light. Most blimps use a Kevlar material for their crafts because it has low density in comparison to its tensile strength. Kevlar has a density of 1,440 kg/m^3 according to [this table](http://www.engineeringtoolbox.com/polymer-composite-fibers-d_1226.html). The surface area of our sphere is: $A = 4\pi r^2 = 4\pi \cdot 500^2 = 3,141,590\,\text{m}^2$ Blimp Kevlar has a thickness between .5 and 4 mm according to [this Goodyear Study](http://www.dupont.com/content/dam/dupont/products-and-services/membranes-and-films/pvf-films/documents/DEC-Tedlar-Goodyear-Case-Study.pdf). I will use .5 mm on the low end of the spectrum: $\begin{align} W & = A\cdot t\_{hickness} \cdot \rho \cdot g \\ & = (3,141,590\,[m^2])(.0005\,[m])(1,440\,[kg/m^3])(9.81\,[m/s^2]) \\ & = \text{22,189,678.5 N}\end{align}$ $\small F\_b - W$ = 21,585,879 [N] - 22,189,678.5 [N] = NOT ENOUGH BUOYANCY TO LIFT JUST THE MATERIAL. **Allowed Density of Material** Okay, so what density would be allowed for such a material? Let's say you want to lift just the sphere and are disregarding lifting anything inside of it. $\rho = \frac{F\_b}{A\cdot t \cdot g} = 21,585,879\,[N]/{(3,141,590\,[m^2])(.0005\,[m])(9.81\,[m/s^2])}$ $\rho = 1,400.816\,kg/m^3$ You're so close! A slightly lighter material would work in this scenario, or you could create a greater temperature differential to increase buoyancy. **Greater Temperature Differential** If the temperature difference was increased to 10 degrees, the buoyancy would become 245,805,393.8 N, which would allow for the Kevlar material plus 223,615,715.3 N additional! A 20-degree difference would allow for an additional 464,201,618.3 N. You could carry any number of people and objects with this additional allowable weight. ## Accounting for Pressure Differential Until now, I've been assuming atmospheric pressure inside and outside the Cloud 9, but according to [this website](http://www.geospectra.net/kite/weather/h_altit.htm) the air pressure at an altitude of 1 Km is 89,908.62 Pa. The new density at this pressure and a temperature 1 degree cooler than the inside of 294 K would result in $\rho\_o = \small 1.100\,042\,\text{kg/m}^3$. However, in order for the sphere to have any buoyancy, the outside density must be greater than the inside density. This could be achieved either by increasing the inside temperature or decreasing the outside temperature. Since you want the inside temperature to remain constant, let's look at the outside temperature. The outside temperature would have to be a maximum of -12 degrees Celsius in order to provide any buoyancy for the sphere (Fb = 18,530,107.13 Pa) . However, you would have to be at -13 degrees to get even enough lift for the Kevlar that we investigated earlier. Each degree cooler will allow more buoyancy for the craft, so you might be okay on some cold winter nights in the Rockies, but don't expect your Cloud 9 to float in the summer or spring. **Reducing the Internal Pressure** You could try reducing the density inside the craft by decreasing the internal pressure. So let's say the people in the sphere are healthy and can live at .9 atmosphere. This would make the new internal density 1.1119 kg/m^3, so the temperature outside can now be a maximum of 289 K or 16 degrees Celsius to generate lift. This is a little more doable, but it does cause some issues if you have a particularly sunny day. Decreasing the internal pressure any more than this will cause issues with our next problem: surface tension. In order for the material of our sphere to remain taut, the pressure inside Cloud 9 must be greater than the pressure outside. At .9 atm (or 90,179.25 Pa) our internal pressure is just greater than the outside pressure mentioned earlier of 89,908.62 Pa. Therefore the pressure acting on our material is: $$\begin{align} (P\_i-P\_o) & = 90,179.25\,[Pa] - 89,908.62\,[Pa] = 270.63\,[Pa] \end{align}$$ The tensile strength of Kevlar 29 is 2,860 MPa, so it would have no issue withstanding this pressure. **Alternative Materials** The next issue of course, would be how to construct anything within the sphere. You may want to go with a material stiffer than Kevlar in order to allow for buildings and structures to be built inside. Any other material that you might investigate would most likely need to be thicker and denser to add any stiffness to the design. This causes all sorts of problems with your Buoyancy vs Weight difference. So let's assume you're living somewhere cold, like Antartica, where the average temperature is around -23.3 degrees Celsius. Your new buoyancy force is 604,753,584.9 Pa, which allows for a material with a thickness of 5 mm and a density less than 3,924 kg/m^3. There are any number of materials that would fit these specifications. Let's say you make Cloud 9 out of Aluminum 6061 ([see here](http://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html)) (which is well known for its low density). You would be able to lift the material, plus another 186,461,316.6 N. This number increases as the density of your selected material and the temperature outside decrease. **Geodesic Spheres** [Geodesic spheres](https://en.wikipedia.org/wiki/Geodesic_dome) are spheres comprised of triangular elements which distribute the structural load throughout the system. It is possible that such a sphere, made of low density braces with high tensile and compression strengths would be structurally sound and light enough to act as a skeleton for Cloud 9. Stretching a strong and light material over this skeleton to hold in the heated air (perhaps something that harnesses the greenhouse effect), would allow for the buoyancy of the sphere. The structural design and integrity of such spheres is a very advanced topic in itself and often requires specialized knowledge, tables, and/or software. Since I do not possess any of these things, I am not going to go into detail on this topic. Know that the weight of the sphere will cause there to be mostly compressive towards the bottom and most tensile at the top as the weight of the whole sphere pushes down on its self and tries to hold itself together at the top. The brace that experiences the most compressive force will most likely be your limiting factor, since metals undergo tensile stresses much more easily than compressive forces. I could not calculate the weight vs buoyancy unless I knew the exact design of the skeleton, so I can not tell you whether this would work or not. However, it is a possibility. # Conclusion If you could maintain an internal atmosphere of .9 atm and an internal temperature of 22 degC, and you could ensure that there would be a maximum outside temperature of 16 degC, your sphere could be made of Kevlar and lift an additional 14,308,527.29 N (This is the equivalent weight of about 20,000 grown men). If you want a stiffer material with a greater thickness, you could go somewhere colder, like Antarctica and use any material with a density lower than 3,924 kg/m^3. Aluminum for instance with a thickness of 5 mm, would allow an additional weight of 186,461,316.6 N (this is equivalent to the weight of about 261,400 grown men). Finding a way to heat the inside and build any structures (a geodesic sphere could be the answer to this problem) are the next levels to this complicated problem. [Answer] TLDR; Seems like it could be possible. I'm writing the TLDR at the end of writing the answer, and it honestly surprised me. ~~~~~~~~~~~~~ I think the big problem with it is actually generating the heat needed to cause the lift. From the quote in Thucydides' answer, a sphere with radius 1320 feet would be able to float if the air inside were heated by one degree. Now, because science, I'm going to be assuming that that's one degree Celsius, because it makes the math oh so much easier. (Edit later: I noticed after the fact that the second quote specifies it as one degree Fahrenheit. That makes things better for us, as one degree Fahrenheit is less of a change than one degree Celsius, so we'd actually rise faster than expected by these calculations.) The specific heat of a material is a measurement of how much energy is required to increase the temperature of one kilogram of the material by one degree Celsius. For air, the specific heat is about 1.007 Joules per kilogram per degree Celsius; for every kilogram of air, you need 1.007 Joules for every degree Celsius you want the temperature to increase. A little bit of geometry and unit conversion thanks to WolframAlpha tells me that our 1320-foot radius sphere contains about 9.6 billion cubic feet of air (gotta love cubics), which comes out to about 300 billion liters (I believe WA computed it assuming NTP, but don't quote me on that). That means we'd need 20 trillion Joules of energy to heat the sphere by one degree. That's about 48 kilotons of TNT, so basically we'd need three of the bombs dropped on Hiroshima just to get off the ground. Let's see if we can do it a bit less destructively. It was suggested in Thucydides' other quote that we could use the heat radiated by the human body to heat the air. Well, maybe not. Black-body radiation of a human is about 9 megajoules (as per Wikipedia); call it $10^7$ $J$ because we're just looking for a ballpark. We need $10^{14}$ $J$ to heat the air in our sphere. I don't feel like doing the math to figure out how many people we could fit on Cloud Nine, but I'm fairly certain it's lower than ten million - just try to imagine fitting everyone in New York City into a sphere less than half a mile across, and then cram in everyone from Philadelphia too. We wouldn't need quite that many in reality, as the black-body figure I quoted above is the human body at rest, and people would be working, moving around, etc, but it's a good enough estimate, as I don't think that would increase radiated heat by a factor of ten. Yes we would have different levels to fit as many people as we could, but there are two extra problems with that. One, in order to fit more people you need more floor space. More floor space means more weight to lift off (in addition to more people meaning more weight, as people are denser than air [citation needed]), which means more heat we need to generate. Two, more importantly, more people means less air. Every person that you add displaces a certain amount of air, and the ultimate volume of air that you have available to heat goes down. So in order to generate lift, you'd need to heat the (smaller) amount of air even hotter. Depending on how much air was displaced, So basically it isn't going to work based off of human activity alone. The sun could help though. Our sphere has a cross-sectional area of about 509,000 square meters. According to [a page I found from the University of Oregon](http://zebu.uoregon.edu/disted/ph162/l4.html) (wouldn't you trust that formatting?) the Earth gets about 164 Watts per square meter, averaged over the course of the day. Therefore our sphere is (assuming perfect energy transfer blah blah blah) absorbing about $3.6\*10^{12}$ $J$. So it is absorbing enough energy to heat the air, when coupled with human activity. To finally get around to answering the core of OP's question, we could probably do it. We would need about two million people living inside it to generate the extra heat needed in addition to the sun. That is now looking like the big problem; how to fit enough people. I'm sure it would be possible to fit a lot of people by making various levels, but I've been writing this for a long time and don't really feel like doing the math to figure that part out. Leave that to an urban planner. **However:** This does not take into consideration the fact that Cloud Nine will itself be radiating heat to the atmosphere. Especially at night, it would certainly cool down. Also, if we're having people living up there, we would need food, water, and material that wasn't included in the calculations. My ultimate consensus is that it could very well be possible. It would depend on the size of the sphere, how many people are on it, how much stuff is on it, and (as was addressed in the comments) the strength/weight of the material used. [Answer] ## Aluminum bars will work, with about six million lbs. left over. I performed a simulation in an application called [CADRE Pro](http://www.cadreanalytic.com/cadrepro6.htm) for structural analysis of a 6V geodesic sphere. I chose this chord number so that the equator would be a horizontal line and for the relatively high approximation of a sphere. I selected the members to be aluminum bars with a rectangular cross section of 10 inches by 8 inches. They are 94.08 lbs/ft. This brings the total structural weight to 33.3 million lbs. As [calculated by kingledon](https://worldbuilding.stackexchange.com/a/66375/3202) the lifting force of the warmer air enclosed in a 1km diameter sphere is 44 million lbs. So, we have 11 million lbs. left for a covering and humans. That is, assuming this aluminum is strong enough... And it appears to be. But only while airborne. I added hydrostatic pressure (the force the sphere would experience via buoyancy) until the sphere cancelled its own weight and had a slightly positive resultant force (it's just lifted itself off the ground). [](https://i.stack.imgur.com/L25jj.png) Numerous times before I got an error telling me a structural member had buckled and the simulation ended. But, with this particular size of aluminum bars, the structure held. The final shape is not a perfect sphere, but ends up stretched in the Z-axis by about 4% (too little to see in the resultant force diagram above). By covering this structure in the material [suggested by Faulkner](https://worldbuilding.stackexchange.com/a/66369/3202), blimp kevlar, we use up another five million lbs. of our weight budget. This leaves us with six million lbs. for fasteners, cabling, platforms, people & their stuff, and our old friend error. [Answer] ## Lots and lots of insulation. The previous answers have already delved into the difficulties faced by such a sphere in generating the necessary heat in order to float. If the spheres are well insulated, it is possible to let the Sun do the majority of the heating work. After all, we are essentially dealing with a massive space heating issue here, and space heating costs fall when you have good insulation and double glazed windows. The surface area of a sphere of 1320 feet in radius is [approximately 2 million square meters](https://www.wolframalpha.com/input/?i=402.3m+radius+sphere+area), so assuming that Cloud Nine averages to have the insulative effectiveness of a [single glazed window](https://en.wikipedia.org/wiki/Thermal_transmittance) at $5.7 \text{W m}^{-2}\text{ K}^{-1}$, it will radiate around $0.55×5.7×2×10^6 = 6.3×10^6\text{W}$ of energy if it is one degree Fahrenheit above the ambient temperature. Regarding heating the air itself, the hot air can simply be transported. By inflating Cloud Nine in the tropics and then moving it to the Rockies, the enormous heating costs can be avoided. Six megawatts is a much easier energy output to sustain(simple solar heating alone of the $5×10^5\text{ m}^2$ of exposed surface area can provide 97MW of solar energy at $1700\text{kWh m}^{-2}\text{ year}^{-1}$ ([ground level irradiance in the Rockies](https://en.wikipedia.org/wiki/Solar_irradiance#/media/File:SolarGIS-Solar-map-North-America-en.png)), and the thermal inertia of the massive amounts of air will simply do the rest. [Answer] I will like to comment in the same post, but I need 50 rep.. I like SAMUEL calculation using Cadre Pro.. I like to hear that it does not need so much weight, even taking into account that 1 layer triangular shape is not the most efficient shape for a big geodesic dome, neither a v6 which is very low frequency for that size. Big geodesic dome are made with a 3d shape which use hexagons with light triangles connection in a second layer to maintain the structure shape. Using carbon struss like the Aeroscraft airship instead aluminum and layers of [ETFE](https://en.wikipedia.org/wiki/ETFE) instead kevlar which provide a [good insulation and high lifespan](https://youtu.be/ThRFQ-oOXT0?t=25m15s). With that structure, I wonder how much pressure differential can support to increase the lift, lets take into account that spheres are very good to support uniform pressure. People can live without problem even at 0.5bar, also you can increase the oxygen to a 30 or 40% in any case. About how to achieve the heat difference.. that is the most easy part.. Is a greenhouse good insulated and with huge volume/surface ratio that provide many days of thermal inertia, if inside the sphere, in the equator we add flat black panels able to rotate to receive the 100% of the sun or dodge all, then you have a way to control the heat inside to almost any temperature differential you want. I made some calculation for my own before find this discussion, I have similar conclusion on the delta temperature needed. One thing that nobody talks is what construction method to use to build such thing, and I guess I have the answer, but it will take another big comment. [Answer] **These 'balloons' need to be huge to lift enough weight, but seem feasible re physics and materials.** (Though safety and sanity are different matters.) We can learn from current blimp technology (about materials and rough weights) and extrapolate. IMHO, one needs truly vast volumes to loft the sorts of masses people would expect for a living or working environment. We can also make pretty good calculations for helium compared to barely-heated air for buoyancy. I suspect that will tell most of the tale. Helium is monatomic and weighs about 0.18 Kg/m^3 at STP. Whereas air weighs 1.3 Kg/m^3 at the same conditions. So helium's buoyancy is 1.3 - 0.18 {call it 0.2} = **1.1 Kg/m^3** (almost as good as hydrogen and *much* safer!) To make estimating easier, I'll assume a 3 degree (centigrade or Kelvin) increase. STP is close to 300 K, thus a 1% increase in absolute temperature. The density will go down correspondingly by 1%, and the lift is therefore the same 1%. So 1 our 3-degree heated air has a buoyancy of: 0.01 \* 1.3 Kg = **0.013 -- thirteen miserable grams of lift (per cubic meter.) That's tiny compared to helium's lift.** Ratio (helium's lift vs 3K heated air): 0.013 / 1.1 = 0.0118 -- only 1 percent as much lift! **If we want to lift the same weight as with helium, we'll need something like 100x the volume as with helium!** Assuming weight tracks volume, we'd need our thermo-balloon to be (cube root of 100 is ~5) five times larger (in linear dimension) than a corresponding helium blimp. And blimps are already huge compared to their payloads. Not impossible, but it's a big {huge actually!} engineering problem. --- Here are URLs for two IMHO state-of-the-art blimp/ballon-like things; both use helium for most of their lift: <https://www.hybridairvehicles.com/aircraft/airlander-10> <http://www.straightlineaviation.com/news/9-webnews/15-aviation-week-lockheed-martin-readies-lmh-1-hybrid-airship-assembly> Note that these have payload capacities in the (few) tens of tons; the larger one is rated about 20 tons. --- **The OQ (original questioner) asked: [How] much mass can I lift in addition to the mass of the completed sphere?** If I make the following estimates: Mass\_avg\_person = 100 Kg. Mass ratio (person + all their stuff) / person's own mass: close order of 100. So each person + their stuff weighs 10 tonnes (metric ton, AKA megagram. How reasonable is this ratio? Big compared to that of nomadic people, but most nomads don't hang around in the sky, literally. This would have to include everything from structural mass to power sources to food and water.) population onboard: 1000 we get a mass of 1000 \* 100 \* 100 = 1e7 Kg or 1e4 tonnes. (IMHO low mass for realism, but plausible.) Cruise ships with similar numbers of people are much, much heavier, but we'll use low-density materials. How big would our balloon need to be to loft this weight, with just a 3 K temperature differential? Mass = 1e7 = (4/3)\* pi \* r^3 \* 0.013 Solving for the radius, we get: **r = ((1e7 / ((4/3)\* pi \* 0.013))^(1/3) = 568.4 meters** **This is in the plausible ballpark -- and close to Fuller's original size.** Faulkner wrote: "Blimp Kevlar has a thickness between .5 and 4 mm according to this Goodyear Study." Let's see what happens when we scale that up. We may need a thicker skin to handle the larger structural and wind-related loads, but for now use the Goodyear data on thickness. If we take 2 mm as nominal for blimps and a specific gravity for kevlar of 1.4 (1400 Kg/m^3), how much would that weigh? **4 \* pi \* (1000^2) \* .02 \* 1400 = 3.5e8 Kg or 3,500 tonnes. Note that this nominal envelope mass is already 35% of what our 1 km radius sphere can lift** This is just the envelope, without any other structure. We may need carbon nanotubes. :-( The key is that Bucky Fuller was right, the envelope mass can be small, compared with the airmass it encloses for a large enough balloon -- but that balloon is going to be enormous!) If I use the same numbers to estimate the envelope-only mass of a 100 m diameter balloon at 2 mm thickness, I get 350 Kg., from which I surmise (compare to specs on blimps below) that the envelope is quite a small portion of those blimps' mass budgets, though I didn't find weight figures for those blimps :-( (Please check me; that 350 Kg seems kinda low.) Structure, engines, fuel/batteries etc. look like they overwhelm the envelope mass, even at blimp scale. --- We can already build big balloons and blimps. Those typically use materials with high strength to weight ratios, such as the Spectra family of polyethylene. Wikipedia has some names and nominal values of high strength to weight materials: <https://en.wikipedia.org/wiki/Specific_strength> Suggest you look at Kevlar, Dyneema and Zylon as practical for use in envelopes, while we await economical, mass-produced carbon nanotubes. [Answer] First off, I am completely failing to comprehend the advantage of tensegrity structures in this context. So that may make my answer useless to you. My investigation seems to indicate that the primary stress that this structure will be subjected to is the tension between weight of gravity on the structures and inhabitants (which are presumably at or near the bottom of the sphere) and the lift force which is applied to the top half of the sphere. Since this is a simple one-dimensional force (forces in two direction on one axis), the obvious solution, to me, is a guy cable. More on this in the second section below. So I'm going to investigate some material properties needed for this design, but it is possible (perhaps probable?) that there is some tensegrity-based structure which will have superior performance to what I am proposing. # Calculating lift force As mentioned above, the primary tension is going to be between lift force pulling up and wight pulling down. We need to calculate the magnitudes of these forces. Using the ideal gas law to calculate lift force, and with pressure and volume kept constant we have an equality between the interior (designated 'int') and the displaced air (designated 'air'): $$n\_{int}RT\_{int} = n\_{air}RT\_{air}\tag{1}.$$ We want to use this to calculate lift force, which I do do by $$\text{lift} = \text{weight}\_{air} - \text{weight}\_{int} = gA\left(n\_{air} - n\_{int}\right)\tag{2}$$ where $g$ is force of gravity, $A$ is the atomic weight of air (.029 kg/mol). The mols of air inside an 0.5km radius sphere can be solved from the ideal gas law. At a height of 1km, I will use 89kPa air pressure and 10 C. $$n\_{air} = \frac{PV}{RT} = \frac{89000 \text{ Pa}\cdot 5.2\times10^{8} \text{ m}^3}{8.314 \text{J/mol-K}\cdot 283 \text{ K}} = 1.98\times10^{10} \text{mol}.$$ Solving (1) we can get $n\_{int}$ in terms of $n\_{air}$ as $$n\_{int} = n\_{air}\frac{T\_{air}}{T\_{int}}.\tag{3}$$ Plugging (3) into (2) we get $$\text{lift} = gAn\_{air}\left(1-\frac{T\_{air}}{T\_{int}}\right) = 9.8\cdot.029\cdot1.98\times10^{10}\left(1-\frac{283}{295}\right) = 2.29\times10^{8} \text{ N}$$ or about 23,000 tons; about two AEGIS cruisers (or a quarter of an aircraft carrier). # Surface tension from lift force and equatorial ring > > > > > > Coming soon > > > > > > > > > # Spherical cow estimate of a self-supporting balloon envelope. Let us say that all of the lift force is applied to the top half of the sphere while all the weight of the contents is applied to the bottom half of the sphere. Half of the weight of the balloon will also be applied to the bottom half; the other half will be subtracted from the lift force on the top half. Now lets consider the tensile stress on the 'equator' of the sphere. The total (one-dimensional) stress equals upwards force of lift plus the downwards weight of the contents and half the balloon. To restrict ourselves to real-life materials, we will make the balloon out of the strongest fabric that I can find. [HEXCEL woven carbon fiber fabrics](http://www.hexcel.com/Resources/DataSheets/Brochure-Data-Sheets/HexForce_Technical_Fabrics_Handbook.pdf) (specifically the IM10-12K) have an advertised tensile strength of around 6000 MPa and density of 1800 kg/m$^3$. The thinnest sold carbon fiber fabrics are about 0.11mm thick at 0.20 kg/m$^2$. The circumference of our sphere at the equator is 3141 meters. The total cross sectional area of the envelope, on which force is being applied is $3141 \text{ m} \cdot t$ where t is the thickness of the envelope in meters. The mass of the either half of the sphere is half the surface area of the sphere times the thickness times the density: $1570000 \text{ m}^2 \cdot t \cdot 1790 \text{ kg/m}^3$. The tensile stress applied to the cross-section at the equator is equal to twice the lift force minus the weight of half the envelope divided by the cross sectional area ($A$). Given the ultimate tensile strength of 6000 MPa, lets say we do not want this stress to exceed 2000 MPa for safety ( I don't know what an appropriate safety margin is). In equation form, this is $$\frac{2\cdot\left(\text{lift}-\text{weight}\right)}{A} = \frac{2\cdot\left(2.29\times10^{8}-9.8\cdot2.81\times10^{9}\cdot t\right)}{3141\cdot t}\lt 200000000000$$ We want to find the minimum thickness that meets this inequality. I solve that to be $t = 0.07 \text{mm}$, which is conveniently close to our 0.1mm minimum available fabric thickness. If we can get 0.07mm thickness fabric, then the total mass of the envelope is about 393 tons, leaving about 22500 tons of lift capacity remaining for the occupants of said sphere. **Conclusion**: I'm as surprised as you, but until I find a math error (or realize that my strength tolerance of 3:1 is ludicrous), it looks like you can lift a 1km diameter bubble and support ~23 thousand tons of cargo with just a carbon fiber fabric envelope and no further internal structural support. # Spherical cow estimate with internal guys for support > > > > > > Coming soon!! > > > > > > Also coming soon, testing Kevlar, Nylon, and Dacron to see if we can get better performance. > > > > > > Also also coming soon, accounting for wind shear > > > > > > > > > [Answer] I started doing some research on this question and it get's complicated pretty quickly and I wasn't up for a full hard science answer today, but I found a few interesting building material possibilities not already mentioned that I thought should be added. So for this structure you want to maximize material strength while minimizing density which presents a few good materials (a simple useful list I found <https://en.wikipedia.org/wiki/Ultimate_tensile_strength> and more detailed material properties can be found on <http://www.matweb.com/>). I ended up making a strange comparison unit of tensile strength/density (MPa/[g/cm^3]) which is what units all the following number are in. Nylon (800) and Kevlar (2600) look pretty good but tensegrity structures require elements in both tension and compression and they don't do well in compression, (like pushing a rope) they may however be used in conjunction with other material elements in compression. Metals generally weren't comparing well due to their higher densities; Steels (70-200), Aluminum Alloys (50-150), Titanium (50-80); most of these are used in aerospace for not just strength/lightness but also higher temperature application which isn't an issue in this case. Carbon Fiber laminates (900) looks pretty good and one material that I found doing unexpected well was bamboo (1250). Another material that I think would be very useful not for structural purposes but for a liner material would be [silica aerogels](https://en.wikipedia.org/wiki/Aerogel#Silica), They are incredibly light around 0.001-0.002 g/cc (air is 0.0012), they are great insulators and are optically clear, which would maximize the solar heating and minimize heat loss to keep the structure afloat. [Answer] This is in response to a comment by Samuel, but is going to be an answer due to the extra length. Buckmaster Fuller's insight into the properties of a geodesic dome came from a realization that increasing the size of the dome increased the volume enclosed in a square/cubed relationship. The larger the dome, the more quickly the volume of entrapped air increased, so eventually only a small change in temperature would allow a dome to lift off. > > [The following extract from a paper posted to GEODESIC by Robert T. Bowers explains the idea.] ``When considering a geodesic sphere, the weight of the sphere is a function of the surface of the sphere. The amount the sphere is lifted by warm air is a function of the volume of the sphere. In mathematical terms, weight is a function of the radius squared, while volume is a function of the radius cubed. This is very significant. Even as the radius of a sphere increases, thus increasing the sphere's weight, the lift of the sphere increases more. If you image a sphere that could grow larger, as the sphere gained a little weight, it would gain much lift. > > > ``Buckminster Fuller proposed that as spheres of great size are considered, the amount of air enclosed grows huge compared to the weight of the sphere. Of a sphere with a radius of 1320 feet, the weight of the enclosed air is 1000 times greater than the weight of the sphere's structure. If that volume of air was heated only one degree, the sphere would begin to float! > > > <http://www.geniusstuff.com/blog/flying-cities-buckminster-fuller/> > > I know it sounds like science-fiction, but here’s how Bucky proposed a Cloud Nine would work. **A half mile (0.8 kilometer) diameter geodesic sphere would weigh only one-thousandth of the weight of the air inside of it**. If the internal air were heated by either solar energy or even just the average human activity inside, it would only take a 1 degree shift in Fahrenheit over the external temperature to make the sphere float. Since the internal air would get denser when it cooled, Bucky imagined using polyethylene curtains to slow the rate that air entered the sphere > > > Evidently Fuller considered this more of a thought experiment than a serious proposal, and aside from a bit of discussion about anchoring Cloud Nine's to mountain tops or using them as free flying city-states, he evidently never explored the idea much further. Fuller himself: > > ``Of course, domes of even greater sizes would be required if that sphere were to carry any additional weight. But it is not inconceivable that floating geodesic spheres could carry aloft entire communities. Perhaps the concept of a floating dome of one half a mile diameter is too much for most people to seriously consider. Regardless, it does demonstrate the scope of projects that are made possible with geodesic domes.'' -Robert T. Bowers Fuller quote from I Seem To Be A Verb > > > [Answer] Ok let me revise this... First off we need to know how much would a geodesic sphere weigh... before anything else... For that, to get anywhere close I need to know the information at this website: <http://www.desertdomes.com/dome6calc.html> And here's a better calculator, but not the one i used unfortunately - <http://acidome.ru/lab/calc/#1/1_Inscribed_Fullerene_on_Piped_D108_3V_R500_beams_150x50> 60 lengths of 130.0m = 7,800m 60 lengths of 152.3m = 9,138m 120 lengths of 145.5m = 17,460m 180 lengths of 162.2m = 29,196m 60 lengths of 149.9m = 8,994m 120 lengths of 158.4m = 19,008m 240 lengths of 164.7m = 39,528m 120 lengths of 172.2m = 20,664m 120 lenths of 173.3m = 20,796m giving us a total material length of 172,584m let's say 10 centimeter width and thickness That would give us 1,725.84$m^3$ That would give us a total of 3,624.264kg if we use: <https://en.wikipedia.org/wiki/Metallic_microlattice> It will likely have to be heavier still though cuz you're probably not going to get 100+ meter segments like that, but who knows. The next is Covering or what goes between those geodesic struts... The covering would likely be made out of Carbon Nanotubes while if you just fill in between the struts you're going to use the same metal. In the latter case you just have to find area of the geodesic and then multiply by the weight of the material... I can't find a way to get the area so no clue. The Former case is - The surface area will be 2,010,000 $m^2$. [Miralon® Sheet and Tape](http://www.nanocomptech.com/sheet/tape) > > These products are available with standard areal densities of 12 and 25 grams per square meter and can be post-processed for specific applications. Miralon sheets can be prepregged with a variety of resin systems or infiltrated with various polymer systems to better suit your application, all with industry standard equipment. > > > Let say half of mass will be proper for the task resin, so we get 50 gram per square meter and the whole sphere will weigh 100,480,000 grams or 100 tons. The lifting force of such sphere depends on the difference of temperatures, which is given by ideal gas law: $$PV=nRT$$ at 10C and a difference of temperatures about 15 degrees - lifting force will be about 5% of the atmosphere density at that altitude - with air it is about 68.9 gram per cubic meter or less(with higher altitude). So potentially the sphere may lift 17,638,400 kg. The next piece of weight is going to come from creating a solid floor and roof. I assume you can use the metal latice to do that, but it depends on where you put it for how much weight you are going to add on. If you put it at the center it obviously will give you more room, but add more weight. The max weight would be something like 105,557.508kg a the top or bottom part of the habitat area which you'd need 2 of for 211,115.016kg You also definitely want to segment the habitat like this because then you can heat the air as you like, keeping the lower portion just hot enough to keep your inhabitants at comfortable temperature and the upper portion being hot enough to do the primary lifting of the structure. This would however need two heaters, reducing how much you can carry, but "probably" increasing the overall lifting capacity. --- An average medieval city population would weigh about 3,200,000kg To feed this population you need 3 acres of top soil which comes to about: 14,568,720kg. Reduce this by half and you could probably get everything you need in one of these with about 20,000 people, probably a few less if you're not looking to be vegan, You'd also need to walk everywhere, need fairly thin walls, etc, much like medieval society really. However, if you did set this up like this you'd also want to set up medical facilities and again have to reduce your population due to heavy machines like catscanners, x-ray machines and such. So I was wrong initially and this is possible, but doesn't seem like a practical use of space and you'd always have to be heating which i have no numbers for since you'd needs 2 pretty big heaters and lots of fuels stored somewhere. Not to mention water supply and insulation from more radiation from being at least 4 meters up... I suppose you could wrap the habitat area with a water insulator to solve two problems at once. The bottom line is that it is "possible", but a seemingly engineering nightmare to get everything all balanced and stabilized. --- Here's a quick layout of how i'd set this up. Fuel and heater sizes are random, water sheath is bigger than scale due to it being too small to see at scale. As mentioned above, if you do this you'd be able to heat the upper area a lot more and get more lift while the bottom could be heated, but kept cooler to provide lift as well. Other people would have to figure out the optimals for the locations and heat ranges for those though... [](https://i.stack.imgur.com/aVINr.jpg) [Answer] # Feasibility of Cloud Nine I did some exploration into this idea and thought I'd share my results here. TL;DR at the bottom. In this answer, I attempt to explore the feasibility of a Cloud Nine style airborne habitat. I’ll look at: * modeling atmospheric conditions for different altitudes; * calculating buoyancy & lift; * estimating the mass of the geodesic tensegrity superstructure; * estimating the mass of the the envelope/membrane; * optimal operating altitudes; * building a model Cloud Nine; * energy requirements, solar-thermal input, and losses to waste heat; * and interior architecture for buildings and living structures. First, I’ll describe some of the equations and methods I’ll use, then I’ll apply them to build a model Cloud Nine and inspect its feasibility. --- ## Atmosphere Model From NASA’s document on [U.S. Standard Atmosphere](https://ntrs.nasa.gov/api/citations/19770009539/downloads/19770009539.pdf), I get the following formula for modeling barometric pressure at various height regimes: $$P=P\_{b}\exp\left(\frac{-g\_{0}M\_{air}\left(h-h\_{b}\right)}{RT\_{b}}\right)$$ * $P\_b$ = reference pressure [Pa] * $T\_b$ = reference temperature [K] * $h$ = height at which pressure & density are calculated [m] * $h\_b$ = height of reference level (meters; hb = 11,000 m) * $R$ = universal gas constant: 8.3144598 J/(mol·K) * $g\_0$ = gravitational acceleration: 9.80665 m/s^2 * $M\_{air}$ = molar mass of Earth’s air: 0.0289644 kg/mol Next, from the same source, I get the the following formula for modeling atmospheric density: $$d=d\_{b}\exp\left(\frac{-g\_{0}M\_{air}\left(h-h\_{b}\right)}{RT\_{b}}\right)$$ * $d\_b$ = reference density [kg/m^3] From the table supplied in the paper, I use the pressure & temperature reference values calculated for heights less than 11,000 m: * $h\_b$ = 11,000 m * $P\_b$ = 22,632.10 Pa * $T\_b$ = 216.65 K * $d\_b$ = 0.36391 kg/m^3 To model temperature, I use [this approximation](https://www.grc.nasa.gov/www/k-12/airplane/atmosmet.html) from NASA for temperatures at heights less than 11,000 m, adjusted for units in Kelvin: $$T=288.19-0.00649h$$ (It's surprisingly accurate, compared against empirical data I was using before it.) --- ## Buoyancy & Lift Equations The buoyant force of an airship, regardless what mixture is used within the envelope, is the difference in densities between interior and exterior, multiplied by the volume of the balloon, multiplied by gravitational acceleration: $$F\_{b}=\left(d-d\_{i}\right)\cdot V\_{sphere}\cdot g\_{0}$$ I calculate the external density, temperature, and pressure using my model atmosphere, and the internal density using the Ideal Gas Law: $$P=\frac{d\_i}{M\_{air}}RT$$ Rearranging, we get: $$d\_{i}=\frac{PM\_{air}}{RT}$$ where: * $d\_i$ = internal density [kg/m^3] * $P$ = atmospheric pressure [Pa] * $T$ = desired internal temperature [K] * $M\_{air}$ = mean molar mass of Earth’s air: 0.0289644 kg/mol * $R$ = universal gas constant: 8.3144598 J/(mol·K) From the equations, we can see that our options for increasing the density differential (thereby increasing buoyancy) are increasing either the pressure or temperature differentials. Building a multi-kilometer-wide pressure vessel sounds annoying compared to just heating the interior up, so I’ll go with the latter. This means I'll use the outside pressure from the atmosphere model for the internal pressure of the balloon. --- ## Geodesic structural mass The formula to calculate the various strut lengths of a geodesic sphere is actually pretty simple. You just need the chord factors, the number of strut members for each given factor, and the sphere radius. Chord factors are constants that pop out in unit space and remain identical no matter how you resize the structure or what your units are, like angles. Each chord factor is resized according to the sphere/dome radius, and multiplied by the number of struts per strut type (A-I). You can find those figures and also a handy calculator [here](http://www.desertdomes.com/formula.html). I’ll be using the values for a 6V geodesic sphere. [](https://i.stack.imgur.com/2dLaA.png) `total strut length [m] = sphere radius [m] * chord factor * NOF strut members` `total combined length [m] = sum( total strut length [A - I] [m] )` Alternatively, using math from [this paper](https://www.researchgate.net/publication/265164660_Patterns_On_The_Spherical_Surface), you can calculate the total combined strut length of a geodesic icosahedron, $L\_{total}$, using the following equations: $$S\_{PCF}=2\sum\_{a=1}^{f}\sum\_{b=1}^{a}f\_{PCF}\left(a,b\right)$$ $$f\_{PCF}\left(a,b\right)=2\sin\left(\frac{1}{2}\operatorname{arccot}\left(t\left(a\right)+\left(\frac{a}{2}-b\right)\left(\frac{a}{2}-b+1\right)t\left(a\right)^{-1}\right)\right)$$ $$t\left(a\right)=\frac{1}{2}\sqrt{\left(f-a\right)\left(f-3a\right)+f^{2}\cot^{2}\left(\frac{\arctan\left(2\right)}{2}\right)}$$ $$L\_{total}=20S\_{PCF}\cdot r\_{sphere}$$ where: * $f$ = chord frequency (1, 2, 3,...) * $r\_{sphere}$ = radius of the sphere To estimate the mass of the total structure, take the total combined length of all the strut types (A-I) and, treating them as cylindrical spars of a certain radius, compute their volume and multiply by the chosen material’s density. `volume [m^3] = pi * strut radius^2 [m^2] * combined length [m]` `mass [kg] = volume [m^3] * density [kg/m^3]` Cloud Nine is a tensegrity structure with “floating compression” members. The calculation I’ve just shown is for the mass of the compression members. What I’m missing is the mass of the tension members, e.g., cables. I’m not sure how to find the lengths of those mathematically, but, as a rough approximation, we can just double the result of the mass of the compression members. It’s likely *way* off because, for certain ultimate stresses, tension members are usually less massive than compression members (think cables versus I-beams). It usually takes more to pull something apart than to crumple it up. The way I see it, doubling the compression member mass is a very conservative estimate. As we’ll see later, we have a lot of lift-mass to play with, anyway. --- ## Envelope/Membrane Mass Finding envelope mass is as simple as multiplying the surface area by the thickness of the membrane, getting an approximate volume, then by material density. `envelope mass [kg] = surface area [m^2] * thickness [m] * material density [kg/m^3]` I could calculate the volume of a spherical shell instead, which would be more accurate, but for large-scale objects like Cloud Nine with paper-thin skins, the difference is beyond negligible. --- ## Optimal Altitude for Flight For populated, non-pressurized Cloud Nines, I figure the maximum altitude will be around the highest elevation humans tolerate living at. The highest-elevation urban settlement in the world is [La Rinconada, Peru](https://en.wikipedia.org/wiki/La_Rinconada,_Peru), with 30,000 residents at 16,700 ft (5,100 m), living at half standard pressure. Cloud Nine appears to function even better at higher altitudes than this, but for the sake of comfort, I’ll stop there. The optimal altitude for maximum buoyancy is probably where the ratio of air density to ambient temperature is greatest (when we are constrained to a steady-state internal temperature). Basically, there comes a point along increasing altitude where density begins falling faster than temperature, and we start losing buoyancy. At best guess, I'd say that point could be as high as 40 km. ## Building a model Cloud Nine Using the equations above, let’s construct a Cloud Nine tensegrity sphere with the following properties: * Sphere diameter: 2,000 m (1.24 mi) * Height above sea level: 5.1 km, elevation of La Rinconada, Peru * Internal temperature: 300 K (80 F) The atmospheric conditions at 5,100 m are: * Pressure: 57,380 Pa * Temperature: 255.1 K * Density: 0.923 kg/m^3 Our 2 km wide Cloud Nine has an internal density of 0.67 kg/m^3, creates a density differential of 0.26 kg/m^3, and exhibits a buoyant force of over 10.5B N, or a “lift-mass” of over 1B kg or 1M metric tonnes. The mass of the supporting superstructure needs to be less than that to maintain buoyancy at 5.1 km altitude. Indeed, it needs to be *a lot* less than that to support the mass of a whole “village”. Let’s look at that. Running through the geodesic strut calculations, we arrive at a total material length of 215,780 m of struts. If we use Aluminum alloy 6061, with density 2,700 kg/m^3, as our construction material (known for its low density and being a common “aircraft aluminum”, see [here](https://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html)), and if each strut is 20 cm in diameter, then we calculate a total mass of ~18,300 metric tonnes for the compression members. Assuming the tension members weigh just as much (which they likely don’t, but let’s be generous), we double that figure to get ~36,600 metric tonnes for the geodesic tensegrity skeleton. (There are many options to explore for the compression and tension member materials--*way* too many.) Most blimps use Kevlar as a membrane material for its properties of low density and high tensile strength. According to this [table](https://www.engineeringtoolbox.com/polymer-composite-fibers-d_1226.html), Kevlar has a density of 1,440 kg/m^3. According to [this Goodyear study](http://www.dupont.com/content/dam/dupont/products-and-services/membranes-and-films/pvf-films/documents/DEC-Tedlar-Goodyear-Case-Study.pdf), most blimps have a Kevlar membrane thickness between 0.5 mm and 4 mm. I’ll use the lowest value, choosing 0.5 mm. Doing the math, we get an envelope mass of ~9,000 metric tonnes. Choosing 2 mm would bring the mass up to around the mass of the tensegrity superstructure itself at ~36,000 tonnes. The total mass of the geodesic tensegrity sphere + Kevlar envelope is around ~47,000 metric tonnes. A tiny divet into our lift-mass budget of over 1M tonnes. Our Cloud Nine can lift over 22.5 times its own structure’s mass, or over 23 Lexington-class battlecruisers. If each inhabitant on average requires 10 tonnes of material (ballpark figure), then the sphere can carry over 100,000 people. Definitely a village’s worth. --- ## Losses to Black-Body Radiation To find the power requirements of the internal heat engines I find the energy lost via transmittance through the Kevlar membrane, which represents the energy that needs to be *added back* into the system to maintain a steady-state temperature condition. For that, I look at the [thermal transmittance](https://en.wikipedia.org/wiki/Thermal_transmittance) of the entire Cloud Nine. The paper-thin Kevlar envelope has a thermal conductivity of 0.04 W/(m•K) ([source](https://material-properties.org/kevlar-density-strength-melting-point-thermal-conductivity/#:%7E:text=Thermal%20conductivity%20of%20Kevlar%20is%200.04%20W%2F(m%C2%B7K).)). Dividing by our chosen membrane thickness of 0.5 mm gives us its thermal transmittance U-factor of 80 W/(m^2•K). Cloud Nine will leak heat like nobody’s business. I figure the envelope could be painted with a dark material, further insulated with a foam layer, or both to bring that value down to that of at least single-glazed glass at 5.7 W/(m^2•K). `thermal transmittance [W] = surface area [m^2] * U-factor [W/(m^2*K)] * (internal temp - external temp [K])` Crunching the numbers, we get a transmittance over the entire sphere’s surface of 3.22 GW. Yup, *giga*watts. That’s how much power needs to be pumped back in to maintain our 300 K internal temperature. It shouldn’t be all that surprising considering the sheer quantity of air inside the sphere. Our insulation could be better than that of darkened glass. A well-insulated roof has a thermal transmittance of only 0.15 W/(m^2•K), which would drop the energy requirement into the megawatt range. --- ## Gains from Solar Flux The original Cloud Nine concept was made buoyant entirely by heat energy from the Sun. Let’s see how close I can get. According to [this paper](https://scholar.google.com/scholar_url?url=https://ttu-ir.tdl.org/ttu-ir/bitstream/handle/2346/64297/ICES_2015_submission_24.pdf%3Fsequence%3D1&hl=en&sa=X&ei=3mzMYo1oh7KaAZesnsgF&scisig=AAGBfm0Z19uEZgaCPsLYkjyza_3PYuBPbw&oi=scholarr), Kevlar has a thermal absorptivity coefficient of 0.47. To find the solar energy absorbed, we multiply the solar irradiance times the surface area normal to the light rays times the (dimensionless) absorptivity coefficient. `solar input [W] = solar irradiance [W/m^2] * cross-sectional area [m^2] * absorptivity` Solar irradiance at sea level on a clear day is usually about 1,000 W/m^2, and that value only gets larger as you go higher due to there being less air between you and the top of the atmosphere to attenuate the Sun’s rays. I’ll just use 1,000 W/m^2 as a constant. Cranking the analytical engine, we get an input energy of ~1.5 GW when the Sun is out. Close to half of the 3.22 GW requirement for maintaining a 300 K internal temperature. We get some irradiance on the *bottom* of the sphere, too, reflected up from Earth’s surface, but for simplicity's sake I’ll ignore that. We could improve the absorptivity of the envelope with a coat of paint, a different membrane material, or an additional layer of some high-absorption substance. With an improvement in insulation, the gains in efficiency could drastically reduce the power requirements and the mass of the heat engines. Out of curiosity, I rearranged the thermal transmittance equation to find the steady-state temperature with solar irradiance alone. I calculate the Sun will heat our Cloud Nine sphere up to ~275.7 K. Plugging that into the buoyancy equations as our new internal temperature, we can find the new free lift-mass after subtracting the structure mass: ~780,000 metric tonnes. Cloud Nine can hover at 5.1 km altitude while carrying almost 18 Lexington-class battlecruisers without any energy input from onboard heat sources. --- ]

[Question] [ ## Starting with a creature and its environment, how does one create its psychology? [Evolutionary biology](https://en.wikipedia.org/wiki/Evolutionary_biology) and [evolutionary psychology](https://en.wikipedia.org/wiki/Evolutionary_psychology) attempt to explain attributes that we observe in our fellow humans and in the animals that inhabit Earth in terms of ancient [fitness](https://en.wikipedia.org/wiki/Fitness_(biology)). Explanations come in the form of "<Trait X> exists because of <Environmental Pressure Y> or <Competition Z>". With a well established evolution history for a planet, it's possible to work out where a particular mental or physical attribute came from. Remember also, that every single creature you see, from the smallest single-celled creature to the blue whale are always the sum of their ancestors. So this is all well and good for our planet. What if it was for someone else's planet? On WB, we often get questions asking something like "I have this really odd creature, how would it behave?" or "I have an alien with these attributes, how does it interact with its peers or the environment?" In some cases these questions are unanswerable because our experience is only with how life and evolution worked once. We don't know the universe of how life might work only how it has worked on our planet. Still, any understanding of how life has evolved may inform some educated guess about how it might evolve. It's common for an author to start with an alien's appearance and immediate environment. However, this starting information often isn't enough to develop a rich psychological model for the alien. **What is a method for deriving a creature's psychology from its environment, evolutionary history and physical morphology? If this isn't possible, what additional information is required?** Acceptable answers will provide a series of steps describing how to gather and incorporate whatever information is required to complete the process. If there are repeated steps, provide a way to know when the process is complete. [Answer] Everything relates to everything else, so I don't believe this is a process that goes step 1, 2, 3. I think that you can start with any of these points and build from there. *My approach is dynamic, focusing more on answering questions about what the creature has to do in order to survive and thrive (which pushes their evolution), with their physical morphology and environment informing the answers.* All of these categories are based on evolution. Answer them and you have a start. **Mating, Pregnancy & Child Rearing.** How does the species reproduce? What is the process used in order to get to mate and reproduce? Informing the answer will be what their evolutionary track is--bird evolution and eggs will produce a different cultural track than, say, a mammal-based live birth. This has to make sense biologically in order to track culturally. The answers to these questions will help get you to their psychology and societal structure, because it answers questions about general relationships in childhood and for romance, whatever that might mean. The physical characteristics of your creature, will help to inform this, from whether they are repilitain or birdlike or more like a mammal. Questions to ask: * How is mating achieved? What must they do in order to be considered as a mate? Look to biologically similar creatures on this planet and the rituals involved there. You can then build cultural custom out of this. You can gather this info by researching similar animals on this planet. * How long is pregnancy? What are the difficulties? Are any special resources needed to accommodate it? Again, look to animals as your model. Here I would widen research, looking at groups at large, such as mammal and reptile. Google is your friend. * How many children are there? * How long is the child cared for by the parents, if at all? Is extended family or the group involved, as it would be in a chimp troop?(This will track into how developed they are at birth and some of their societal interaction). * How are the responsibilities generally divided? Answer this based on biology, as well as you can, finding an analogue in our own biosphere as a starting point. (True, they can be alien, but we only have our own biosphere to start with and the experiences of this planet. We can reach beyond that, but if we are writing fiction it has to make sense to the reader, who will also be from earth, as far as we know). **How much do they change over a lifetime?** Do they look completely different when they are younger, like pupa and larva? Maybe spotted like a fawn until adulthood? These changes will be incorporated into culture--you might say a deerperson never really lost their spots to indicate immaturity. Those phases and the state of mind in those phases of development are going to be important to the underlying psychology. **What do they eat?** Eating is a big part of the day and an important thing, so these questions determine societal cues you might not realize come from biology. * Omnivore? Carnivore? Herbivore? Insectivore? What do they eat and how did they get it when they were more primitive--this informs behavior. Look at other creatures which share this taste for things. * If carnivore or omnivore,do they hunt cooperatively? Solo? Is there a division along gender lines, as there is with the big cats? (females mainly hunt) * What physical characteristics do they have, which help them to get food, whatever food that may be? This can be anything from eyes that move independently of one another and a tongue which catches prey, to fast twitch musculature or a mouth shape built to efficiently eat grass. Ask too, when you're thinking about this, how these adaptations might effect how they interact with the world, each other and societal and cultural aspects. * What do they have to do in order to compete with each other for resources? Look into territorial behaviors or lack thereof for your species. This will effect psychology, ability to cooperate, and possibly their monetary system. **What eats them?** In this category, this is anything that kills them, or did when they were primitive. This includes things that don't literally eat our creatures--like cold weather and disease. * What defenses does the creature have against the things that could kill them? * Same as above on physical characteristics, this time as applied to defense. That reaction to those things will inform their evolution, and later, some of their behaviors, culturally. **The sea in which they swim** This covers the environment in which they developed. Underwater, on the plains, or in the jungle--their environment determines how they look at the world, which, in turn determines their psychology, as well as their evolution. * Think about the environment. What's different? Underwater creatures will think more 3-D than plains creatures, and jungle creatures might not be very good at perspective (understanding that things in the distance are smaller, because the jungle is so dense, you don't ever get much perspective). The environment can color everything--how they hunt, mate, rear young, but that doesn't mean you should determine this first--it just means that if you come up with it last, you should make sure it fits with everything else you've done. Look at all the animals you can in that environment. * Think about the adaptations needed in body, and how that affects their interaction with the world. **Lifespan.** Knowing how old your species gets and if they get infirm is critical to societal structure. If, like salmon, they tend to die post spawn, this will effect everything, as will species which tend to have a place in their society for the aged (chimps often do, but it is dependant on gender). * How old do they get? * What happens when they get past breeding age, biologically? * Do they have a role to fulfill when they are older? **Are there any periods of time when the species is especially vulnerable?** For humans, we have a long childhood, but for an alien species, this can be a chrysalis, or shedding skin or anything really. It can happen because they are old, or any number of biologic reasons. Ask what the species does/did during this time, and how that effects their way of looking at the world, as well as how others in the species react to it. **Are they dependant on/do they need any one thing/creature?** Do they have a relationship with any other species biologically? Even a crocodile has birds that clean his teeth. Are they the bird? Or the crocodile? Or neither. This relationship can inform their psychology...Is there something specific they need in order to survive? Most specialists die out, but kolas need eucalyptus--it's all they eat...your creature might have to eat stones for better digestion, or eat a particular type of plant periodically. Horses, for example, do need salt, so they end up licking each other sometimes to fill that need. Look at the need/dependance through a social and psyche lens, once you understand what it is. It can have a huge cultural impact on custom. **When will you be done?** Well, you might not be. There's always something new you can discover about your creature. Gathering the info is just a matter of google, the library, and answering questions. Each of these questions and steps will be informed by the others, like a giant damn circle. Just pick a place to start and come back around. I know you were hoping for something more step-by-step, but a creature creation is part research and part creative process. [Answer] Foreword: As some comments have pointed out, this question could be its own field of study. For the sake of brevity, the following answer does not take into account ecological balance of atmosphere, random environment events (read: asteroid impacts), complex food-chains and the like. It also necessarily condenses hundreds of thousands of years of evolution into single sentences, thereby unavoidably simplifying concepts that could themselves be their own fields of study. Unfortunate but necessary to avoid the "too long, didn't read" stamp. First, some condensed background: Evolution, prior to the never-guaranteed rise of intelligent life, is driven almost exclusively by environmental factors. Environmental factors on Earch include (but are not limited to) availability of water, food and breeding mates. On Earth, possibly the most important factor that has shaped behavior of all life is the competition for resources. This competition combined with Darwinian trial-and-error through random mutation gives rise to "dominant" species for a given environment. "A given environment" is an important point because the environment can change over time and life must adapt to the changes. In the long run, plants are very good at this and at competing with each other. In non-plant life, this competition for resources has endowed it with life's two pre-programmed instinctual pillars: Preservation of self and preservation of species. Those two instinctual drives ultimately act as the foundation for all of the emotional behavior that we observe in the natural world. No matter how complex the emotional response or the uniqueness of the emotion to a particular species, you can trace its origins back to one of those two precepts. It isn't until the rise of self-awareness and higher intelligence that environmental factors cease to be the most driving force as we become better and better at living in, predicting, controlling and shaping the environment - to a point. So to your question: "What is a method of deriving a creature's psychology from its environment, evolutionary history and physical morphology?" Along with its evolutionary history, you need the corresponding environmental history. With those, the method is to chart the instinctual and then behavioral history of your creatures along with any changes to morphology within the time-span. This is *hard* though, particularly if your creature's environment is manifestly different from your own familiar frame of reference and point of view. For instance, what if your creature evolved on a world where competition for resources simply was not a factor? For instance, perhaps they live in a water world (physio-chemical needs), derive all nourishment from photosynthesis (energy) and their population growth was slow. This would create an entirely different set of instinctual drives, emotions and then higher thought processes - drives, emotions and thought processes that would be...well...alien to us and difficult to understand and relate to. But then that would make the aliens and the story all the more interesting if you do it well. One caveat though: competition of resources, through a complicated evolutionary history of human emotion, has given rise to xenophobia. Something truly alien won't ever have the "warm fuzzies" from readers unless there's *something* interpreted as a positive that people can relate to. It's something to keep in mind if being able to relate is important to the story. As I think on it, one short story from 1934 does a decent job of this is "Who Goes There" by Joseph Campbell. It's the source material for the two "The Thing" movies but the story, though dated, is far better than the resultant movies. The creature in question shares the desire for self-preservation - something we can relate to - but the similarity ends there. [Answer] This answer proposes a method for an author to derive a creature's general psychology based on the characteristics and historical environment of its ancestors. While the method describes a linear process, there are actually many opportunities within the method to provide feedback into previous steps which will feed forward into later steps. The degree of recursive feedback is bounded only by the author's willingness to explore. A couple rules to remember about evolution: - Minimize metabolic costs while maximizing utility - Changing existing features is much easier than creating a feature from scratch - Unused features may go away over time - Features that incure no undue cost and don't decrease fitness may survive for long periods. - All features must be continuously and continuously helpful. Discrete jumps from a simple structure to a more complicated one are not permitted. - Evolution is a constant contest between raw strength and sneakiness ## Background Prep In order to make an educated guess at a complete evolution tree for a planet, one should be familiar with how evolution works on our planet. [](https://i.stack.imgur.com/I9Il8.jpg) Berkeley has an excellent (and short) program called [Understanding Evolution](http://evolution.berkeley.edu/evolibrary/article/phylogenetics_01) that explains in detail how to analyze and create phylogenetic trees. [](https://i.stack.imgur.com/uAUws.png) ([Photo Credit](http://evolution.berkeley.edu/evolibrary/article/0_0_0/phylogenetics_07)) --- ## The Method 1. Figure out the most basic and primitive life form on this planet and its environment. The closer to a single celled organism, the more the author will be able to make decisions about fundamental biochemistry. Starting with a more complicated creature such as early land creatures with bones and muscles helps to focus attention on morphology and primitive psychology. The author has broad discretion where to start. The earliest creatures won't require significant amounts of detail about their morphology or environment beyond the essentials. For example, the description of an early creature might be "simple six legged creature residing on broad mud-flats". Reducing the amount of early details does a couple of things. First, lots of detail about early species will likely be overwritten by adaptations in later species. No sense going into more detail than you need to. Second, if Earth is any measure, there could be hundreds of millions of years between this earliest species and the creature of interest. So much change is possible on those time scales. 1. Trace milestone species from this first life form to the current creature. At this stage, the author will be creating a phylogenetic tree for this world as well as a rough history of the environment. Include the how, why and when describing mass extinctions, environment changes, new morphological features (eg: bones, amniotic sacs, lungs, mammary glands, etc) and corresponding forks in the phylogenetic tree, and development explosions (eg: [Cambrian Explosion](https://en.wikipedia.org/wiki/Cambrian_explosion)). There may be other features to account for the above list is a really good start. 2. Describe in as much detail as desired what physical and mental attributes each of these milestone creatures possessed to thrive. Earlier creatures will require less detail. These might be as simple as "can think in 3d", "has bones", "understands concept of in-group". For each milestone, you'll need to work out the creature's environment too since this is critical in deciding fitness. Starting with the last million years of a creature's history, explore in increasing detail its morphology and psychology. If the creature of interest has changed significantly in the geologically recent past, pay close attention to that period of change. 1. Each of these intermediate life forms will have something that makes them competitive in their environment. We see that decedents will share this feature unless it reduces fitness or is superseded by another, more fit feature. Maintain a list of features for the creature of interest. 2. Examine the various aspects of life of this creature. How is it conceived? How is it born? Does it require significant nurturing or is it precocious? Does it work in groups or alone? How does it acquire its food? Is it food for other things? Is there a long standing environmental danger? Are there significant changes in morphology as the creature ages? Does the creature age? Does it use tools? Does the environment force some kind of extreme adaptation (hot, cold, wet, dry)? Is this ambush or pursuit predator? Where in the food chain is this creature? The possible list can go on for a long time. Make as many useful question as desired and answer them. 3. Harmonize the inherited feature list with the creature's feature list from the previous step. If there are discontinuities or features that just don't match up or make sense, go back to the previous steps and correct them. 4. There should be enough information from the previous step to write a brief description of what will motivate this creature and how it will interact with its environment. 5. After summing up the mental characteristics, you should have a pretty good idea of how this creature came to be and why it might behave in a certain way. The degree of detail and the number of iterations is left completely up to the author to decide. Happy exploring! [Answer] I find the most powerful tool for understanding how a creature will act is to look at what doesn't change. The reason for this is somewhat circular. We tend to give the title of "creature" to things that exhibit what Aristotle called entelecheia, which is energy/motion of something being itself. A fish must expend energy to continue being a fish. We call it metabolism. If the fish stopped doing this, it would quickly become "meat," consumed by animals and single celled organisms. The thing which interested us in the first place is that which is kept still. We can further break this concept up into "naturally stable" structures which do not change much on their own and "naturally unstable" structures which require continuous expenditure of energy. Everything else a creature does will fill in the gaps with things that do change, and they will change until they best suit the creature. Naturally stable things are concepts like teeth, claws, and other structures which generally are not trying to continuously decompose. These are interesting because the creature had to spend an initial amount of energy constructing them, and after they are constructed they have very little control over them. The creature will generally find ways to use these stable structures to their fullest extent possible. A tiger's claws are extraordinarily good at clawing prey. To protect them, the tiger has muscles that retract the claws when not in use. The key thing to remember about these naturally stable things is that they always have a use. It took energy to create them, and the creature doesn't have much control over the process. For evolution to have decided "this is the best path for this creature," there must be a use in the environment that warrants the energy expenditure. Naturally unstable things are more interesting, in my opinion. These are patterns that are valuable to the creature, but only exist because of a feedback loop controlling them. Emotions are an excellent example. Emotions serve to help us cope with the world around us, but they themselves are unstable unless controlled by a "higher" brain function. These naturally unstable things are what are the difference between a tiger from the wild and a trained tiger in the circus. They are adapted to the environment, and they're held still by continuous expenditure of energy to keep them the same (entelecheia). Of course, the control loops which support these naturally unstable characteristics, themselves, must be explained. This can be done iteratively, until you get to the "core" of a creature. This is it's "self." When you get to this layer, you truly understand the creature from the outside in, and can then understand it from the inside out. Now while this can be a very unstructured process, typically we assume some earth-like structure to it. This is where answers such as Erin Thurby's answer come in. Consider mating. The species needs to procreate. It spends energy to continue being itself (entelecheia, at a species level this time). The nature of the species can be captured here. Basically, you can refine any psychological estimate of a creature simply by running a mental simulation of how the creature behaves, and observe what doesn't change. If, in support of maintaining it's "self," your creature appears to choose not to mate, there's a good chance that psychological estimate was not the right now. If it looks like it's not using its beak or its claws or some other stable structure, it's wasting that energy and is probably not a good estimate. [Answer] Starting with environment and morphology should give you plenty to work off of for psychology. Think of it like this - the psychology becomes a strategy to survive in the given environment with the given morphology. My answer is formatted a bit different than others; I will work through an example: Using real-life wolves as an example: wolves are moderately sized carnivores. They have a relatively weak sense of smell for a canine, which makes it harder for them to hunt small prey. They tend to live near and hunt larger prey that move in herds, like deer and bison. Now we can start with the psychology. Since wolves have evolved to hunt prey that is much larger than they are, it makes sense for them to hunt in groups. We can assume several wolves should be able to bring down a large animal more easily than a single wolf (Wikipedia reports [that isn't true](https://en.wikipedia.org/wiki/Gray_wolf#Hunting_and_feeding_behaviors), but we'll pretend it is for simplicity). Furthermore, one kill should provide enough food for several wolves. Already we have a reason for our wolves to have some basic social behaviors. Let's consider further on the fact that wolves often prey on herd animals. They can use cooperation to hunt more efficiently - a simple strategy could be to split into two groups, and have one group try to divert some of the herd directly into the other group. The more coordinated the pack is, the more successfully they should be able to hunt. This level of teamwork promotes a tightly knit community. Now we're moving toward a cooperative social structure, with groups of wolves living and working together. From here, you start thinking about the way they form into groups - in this case, by family. Temperament can also be derived from environment. Let's say your wolves only see one herd of prey a week and have to compete with bears for the meat. They are likely to be suspicious of, or fiercely aggressive towards, unaffiliated packs, bears, and anything else that might eat their food. You can get a very good on a creature's psychology by answering a few simple questions. 1. Does the creature's morphology/environment make it more likely to be successful operating independently or in a group? 2. Is the creature more likely to be successful if it defaults to flight or to fight (or passive observation or subservience or...)? Research analogous creatures on Earth when you aren't sure how to answer a question or can't come up with enough details. If your creature survives by eating a toxic plant which no other creature in its environment uses as a food source, you could research koalas (which survive on toxic eucalyptus) to see how their diet affects their behavior. A few things to consider when writing a story: * It's a story, and sometimes the needs of the story supersede the environment and morphology you've come up with. If your alien species needs language or trade, they need some element of civilization, so you can't design them in a way that promotes isolation and prohibits community. Think of environmental or morphological reasons for them to have cooperated enough to develop those qualities of civilization. * If you're trying to make your alien species interesting, **try to think of a unique psychological characteristic that will be novel or counter-intuitive to your readers**. For example, the smallest and frailest member of the tribe is the most honored and revered, because it is the only one light enough to climb the *ralthis* trees and pick the treasured *sarak* fruit. When your human character throws up, the alien mistakes it as a marriage proposal because their species regurgitates food to attract mates. I'd say that **if you're devoting this much time to fleshing out the species, this should be one of the first things you address.** > > provide a way to know when the process is complete. > > > The process is complete when you have enough information to fill your needs. If you're writing a story, it's complete when you know how to answer any questions that come up when you're writing the text. If you're making a game, it's complete when you have enough information to design the creature's appearance and behavior. Any time you run into a question you didn't think of ('how would this creature decorate its cave?') you simply go back and flesh out what you've already come up with. ]

[Question] [ I'm looking for recommendations for software to build my world, physically. I want to be able to create maps of the entire world and then drill down to individual areas and define the towns and cities, before going into those towns and cities to create the layout for them. **Requirements**: * World generation with realistic fault lines, mountain ranges and continents. * Easy placement of settlements, structures, forests, hills etc. * Create city layouts and ideally link them to the cities on the world map. * Take sections of the map, or the whole map and create printouts or images that can be shared with people. [Answer] There is an extensive discussion of possibilities on [Cartographers' Guild](http://www.cartographersguild.com/content/), but the 3 options already noted are the standards: [Gimp](http://gimp.org), [Photoshop](https://www.adobe.com/products/photoshop.html), or [Campaign Cartographer](https://secure.profantasy.com/default.asp); there are a few others, but these dominate. They are not entirely comparable. Photoshop is massive, complicated, and expensive. Gimp is cheap (free!), and in many ways emulates what Photoshop can do, but not in all -- and you will get burned if you think they are the same thing. But you can classify the two together. Campaign Cartographer, now in 3d edition, is quite different: it is a vector-based (instead of raster) system for building worlds, cities, or dungeons (or whatever) from relatively simple input data. It is not the most intuitive thing in the world unless you are quite familiar with CAD/CAM suites, and it's not entirely cheap: the base program suite for everything is about \$100, and you'll want to spend another \$25 at least immediately just to get the real user manual (the Tome of Ultimate Mapping is the actual user manual, and yes, they charger for it). In order to figure out which is best for you -- or multiple! -- you have to know what sort of map you want at the endpoint, but also the start. If you want to dump a hand-drawn map in and get something beautiful at the end, Gimp will do admirably (combined with some expertise provided by the tutorials at the Guild!). If you want to create a gigantic map that can be zoomed in and out to whatever level, with links down into cities or dungeons, all smooth, you'll need a vector program like CC3. (When you zoom in on that gorgeous PS image, down to the meter level, it's all pixels; when you zoom in the same way in CC3, you'll get a newly-rendered image.) So it totally depends on what you're doing. Isn't that helpful? :) [Answer] My suggested workflow. Blender-Gimp combo for planet building. [](https://i.stack.imgur.com/p2dRg.png) In Blender: 1. Use Blender to add an UVSphere, tune the resolution at will but I do not recommend to use a high poly sphere. 2. UV Unwrap the sphere using one of the built-in algorithms. Follow this video tutorial for a better unwrapping: <https://www.youtube.com/watch?v=colJyjvf5jw> *I would use Sphere Projection rather than the one used in the video. Cylinder may work too. The difference is that Cylinder will stretch the quads toward the poles while Sphere will try to make them all same size. Usually textures created from real photos of the surfaces of real planets on our solar system are already stretched towards the poles, so you need Sphere projection to correctly map one of those over a UV Sphere. Cylinder projection is useful when you already have a map created completely in 2D, and with no sense of projection, and now you want to map it to a UV Sphere. In all cases the solitary vertex at the poles will mess the unwrapping, what matters most of the video I linked is that It shows how to handle that vertex.* *Also Sphere Projection won't produce a UV Map aligned with the borders of the image but there is a trick to quickly correct It. Create a temporary square texture (1024x1024), do the unwrap using Sphere Projection, this creates a nearly square UV Map but a bit displaced to the right, in the UV/Image Editor area select all vertices then press N, and in the location fields, manually input 512 (1024/2) in the X coordinate field. This will produce a perfectly aligned UV Map. Now switch to the rectangular texture, the UV Map will scale horizontally to cover all the rectangle. As textures tile, not correct the X position won't really produce a wrong result, It's just counterintuitive to work with a displaced UV Map.* 3. Enter Texture Paint Mode. Create a new material in the left panel of type Diffuse, name it after your planet. I like to use 2048x1024 of resolution with no alpha channel. You can use alpha if you need to combine layers later. 4. Paint your continents using colors to represent ecosystems or heights (not both at the same time, each must be a different texture). I always start with ecosystems: light green is grassland, dark green is forest, maroon are mountain ranges, yellow is desert and so on. 5. Export the texture as PNG file. Blender also let you export the UV map as a PNG with transparency. In GIMP: 6. Import in GIMP. 7. Use GIMP tools to tune the borders of the continent as you have far more control in GIMP to work at the pixel level. You can add noise by using one of GIMP filters. 8. Clone the image and now paint the heights (in GIMP not in Blender). You can import the image with the heights in Blender later to see how it looks in the 3D sphere. Why I use Blender and not GIMP directly? If you start with a rectangle in GIMP you have no sense of projection (planets aren't rectangles but maps are), you draw a continent but when you map it over an sphere it does not look as you imagined it. In Blender you do not have enough control to work at the pixel level (in 3D view, you have a bit more control in UV editor but GIMP is still better) but you have a good sense of 3D, so the continents will look as you imagined them from the very beginning. When you finished to roughly shape the continents, you go to GIMP and correct the borders to add more fine details. Now, to demonstrate that this method of unwrapping the UV/Sphere works, I loaded a planet Earth texture in place of the fantasy world texture, the result can be compared with real photos to check accuracy of the mapping: [](https://i.stack.imgur.com/MciA8.gif) The texture license is CC BY 3.0, and was found here: <http://www.solarsystemscope.com/nexus/textures/planet_textures/> Cities (This is more an idea with potential than a working and tested workflow): You can use Blender to trace the principal avenues and streets of your city. Then the idea is to use some kind of algorithm to automatic trace less important streets and place buildings. Important buildings (where the action takes place) need to be modeled by artist, but background buildings can be generated by a program. The problem here is that I didn't find such program yet nor was I successful into creating my own algorithm. You can continue adding streets until you do all the city by yourself but that sound like a lot of work and It doesn't sound viable to me. So an algorithm to generate buildings and streets is needed. I studied some papers describing a set of techniques but some escape my current skills and others do not adapt to my needs. Anyway I at least can initiate you in this subject. [](https://i.stack.imgur.com/lh2ns.png) You can use vector graphics for the street map, for example InkScape, but I find Blender better to do streets maps. Some tools that may be of interest to you: * CityGen: <http://www.citygen.net/> * CGChan: <http://cgchan.com/store/scenecity/> [Answer] I think that you will find - as I have - that a single software package that does everything we want does not exist as yet. My enquiries have found [pytectonics](http://pytectonics.sourceforge.net/index.shtml) (that admittedly I haven't tried yet as it was only mentioned today) on Software Recommendations Stack Overflow for generating a world using global plate tectonics. Given the shape of the landscape, other software could generate river systems and erosion. As for generating maps, I currently use Corel Draw, a vector graphics suite capable of separating a graphic into layers that can be selectively shown or hidden, ideal for mapmaking as it can also be zoomed almost indefinitely without becoming pixelated. It is capable of printing sections of drawings, and it can convert vector images to pixel-based formats easily. I have tried Campaign Cartographer, but when I tried it some time back, I found it a bit primitive and limited compared with Corel Draw. It may have changed since then. All of this involves far more effort than I would prefer, unfortunately. [Answer] There are a few things out there. Your best bet is to design it yourself with Photoshop. But there are some tools to help you make things look just right. There are plenty of tutorials on how to do that online. You use [Gimp](http://www.gimp.org/) instead of Photopshop if you don't want to pay for anything. But, this software may be what you are looking for: <https://secure.profantasy.com/default.asp> This software also seems to be good: <http://www.dundjinni.com/info/features.htm>. It may be focused more around making maps of rooms and houses, but it may still be helpful. There is also a whole forum dedicated to map making, it's called the [Cartographer's Guild](http://www.cartographersguild.com/content/). So until there is Cartography.se, that's probably where you will get the most experienced help. [This](http://www.cartographersguild.com/tutorials-how/4276-quickstart-guide-fantasy-mapping.html) thread on the Cartographer's Guild seems to be good recommending software and giving a tutorial on how to make a map. > > If you have no software at all, then we strongly suggest that you > download 'Gimp' which is a free equivalent of Adobe photoshop (PS for > short). Another useful download is 'Inkscape' which is the free > equivalent to Adobe Illustrator (AI for short). Gimp/PS are by far the > most preferred mapping tools of the community although there is also a > strong base of users who use Campaign Cartographer by Profantasy (CC3 > for short). There is also other software, such as Fractal Terrains, > also made by Profantasy which give a more realistic '3d look' similar > to sattelite photographs. For now, if you have no preference between > any of these packages, download Gimp. > > > To download [Gimp](http://www.gimp.org/) click here. > > > To find out more about the pros and cons of software used by the community [click here](http://www.cartographersguild.com/software-discussion/1033-new-digital-cartography-software-general-information.html). > > > To obtain a list of the software used by the community [click here](http://www.cartographersguild.com/software-discussion/1407-list-mapping-software.html). > > > [Answer] What about the free version or pro version of any of these three programs: Cityographer Dungeonographer Hexographer all of the above three are available from this site: <http://inkwellideas.com/> For something more sophisticated, there is also Fractal World Mapper from this site: <http://www.nbos.com/products/fractal-mapper> [Answer] <http://shaudawn.deviantart.com/art/Free-World-Building-Software-176711930> list of world building (as in planets, maps, solar systems) [Answer] All of the provided answers here seem kind of sad to me. no offence, just my personal opinion. so i hope you get this and try out these websites. This isn't a totally perfect mapmaker but at least try it. <https://topps.diku.dk/torbenm/maps.msp> there are lots of options for map color and style. i personal suggest setting the size to 1000w x 500h and the projection type to square. this will set you up perfectly for using this amazing and free software: <https://www.maptoglobe.com/> You can make your map on the planet maker, the first link, and see it as a planet with the maptoglobe application and from there you can make a gif of the planet rotating and quickly store it to look at later and easily show to your friends. Back to the planet maker, a quick tip: Personally, I don't like the placement of mountain ranges and the sizes of them in this world-maker, a few fixes are to select the box that says "non-linear altitude scaling" but my personal preference is to set the contour lines to "coastlines" and the map color to white. It will appear as a blank white slate with outlines of the land. Don't let yourself get confused though, while it's like this it's easy to mistake the land for the water and vice-versa lol. good luck and have fun ]

[Question] [ Plant poisons in our world (that I'm familiar with) have operational half-lives in the order of seconds to maybe a day to reach full effects. This is because poisons are a defense mechanism and work best when things hurt right away, so that you'll associate pain with the plant. For example, contact dermatitis from the poison ivy family of plants sets in within minutes. An ingested poison, such as from eating the wrong berry, can take hours. Why would a plant develop a poison (not necessarily a lethal one, though lethal is okay) that takes *days* to set in? What evolutionary benefit could that provide? [Answer] **It slowly kills the animal in order to spread over larger distances across soil with poor nutrients.** So if your fruit kills the host 1 meter away, not much gain. Let the host migrate for days. Now if you kill the host while inside the digestive tract, the seed can spawn a large plant using the decomposing host's body. Nature is full of examples. Wasps place bugs inside other insects, and it eats away the host. Nature is ruthless. [Answer] The simplest answer is that the delayed poisonous effect is a secondary (and from the plant's perspective, inconsequential) effect compared to the primary evolutionary purpose of the compound in question. For example: Let's assume that the poison in the berry kills by initiating a chain of biochemical reactions in a human who consumes it that causes renal failure. This makes it useful for humans to kill other humans because renal failure kills relatively slowly which makes it difficult to know when or by who the target was poisoned. However, that compound exists in the berry because it has a completely different kind of effect on the insects that would otherwise consume the new shoots on the plant before they can fully develop. Having the shoots consumed harms the plant because it prevents the fruit from developing and thus prevents distribution of the seeds. Plants with this compound in the berry don't have their shoots consumed by grasshoppers or whatever, thus the berries can be consumed and the seeds deposited by birds and other larger animals a distance away, which is evolutionary beneficial. The fact that the birds and other larger animals subsequently die of renal failure isn't relevant as far as the plant is concerned. [Answer] **Dosage is wrong.** Poison dosage is a function of size. There's a very humorous urban legend involving the legendary wrestler Andre the Giant when he was diagnosed for anesthesia, which they needed to base off his alcohol tolerance of 2 liters worth of vodka to give him a buzz. (The story is false, the tolerance isn't.) If a berry was developed with the poison needed to kill, say, a fox or some other small mammal, it could develop a dosage that would kill said small mammal fairly quickly. When a human would eat said berry, the poison dosage would be too low to kill them instantly, but would cause severe damage that would kill the target over time. [Answer] There are two evolutionary deterring mechanisms: "Teach a lesson" and "Don't develop a habit". In "Teach a lesson", the effect is quick and not necessarily fatal. Animals who tasted "wrong" fruits learn to avoid them. In "Don't develop a habit" an animal may eat what it wants - it only happens that somehow there won't be any animals that have developed a taste for the "wrong" fruits. The effect can take long, and it'd better be fatal. In the long run, both mechanisms achieve the same goal - there are no animals who may consider the "wrong" fruit a valid food source. Also, there are many hazards in the animal world which are usually fatal, like attacks from birds of prey. There aren't many surviving animals which "learned the lesson", but over time, species as a whole learn well to stay hidden and avoid being in the open. [Answer] There are plenty of toxins that take quite a bit of time to harm humans, or aren't even harmful at all in reasonable doses,because they are more immediately harmful to other creatures. Examples include chocolate, tobacco, poppies, marijuana, willow, peppers, and coffee. A poisonous plant's typical targets are insects and caterpillars, so if it's not poisonous to humans, the evolution of the plant is hardly affected -- though being less poisonous to humans can tend to keep us from clear-cutting it away (as in the case with poison ivy, poison oak, etc.), and in the plants that I've listed, having a secondary effect on humans that is not overtly toxic, and possibly beneficial (willow bark is the basis for aspirin), humans may actively cultivate it. In some carnivorous plants, especially certain species of pitcher plants, there are some traps that are inactive most of the time... such as nectar-bearing flowers where only about a third are slippery at any given time. This attracts more insects overall, as there is a potentially high benefit to individual insects that are lucky enough to pick the right flower, and a consistent benefit to the plant, in the form of the micronutrients that insects bring. (The main *macronutrients* for plants, of course, being water, CO2, and the sunlight to process them.) If your plant is in a region where the soil lacks key micronutrients, carnivorous plants may have a poison that strengthens or weakens over time, so that animals may get addicted to side effects and harvest regularly, then when the plants needs that nutrient, it could increase the potency of its toxin, hoping that some animals die above its root system. If your village has been eating the same berries frequently, you might not suspect a plant when it only rarely has a dangerous phase. It would take most people several cycles before they figure it out. And, of course, the mutation that causes the slow acting toxin could be completely unrelated to either the survival or virility of the plant... Prions are a class of proteins found in all mammals, usually specific to certain families of species (primates, canines, felines, rodents, etc.) A prion that mis-folds can start causing damage to various cells, and would cause other related prions to also mis-fold -- essentially a viral infection without a virus, and without an immune response. Prion diseases can be dormant for decades and, besides getting it from just bad luck, prion diseases can also be transmitted by eating food contaminated with that prion. (Cannibalism is bad. Bury your dead away from your farms.) It's possible (unlikely, but most certainly in the realm of believable Sci-Fi) that a plant can start producing the dangerous form of a prion that humans use. In which case, in a few years, the people who eat from it will start showing signs of prion diseases. This mutation wouldn't help or hurt the plant at all, it would just make sure that any primates that eat from it will die between 2 and 20 years from that day. [Answer] It bears remembering that not everything that evolves provides an advantage. Most changes are neutral, or only mildly deleterious so there's insufficient pressure to weed them out of the gene pool. The fact that the berries are poisonous to some species that eat them might be entirely co-incidental... for some reason, some random structural protein is kinked in just the right way to cause hideous liver failure, but that's just one of those things. [Answer] The berry is poisonous because it evolved to be eaten by a different animal. Plants have fruit to trick animals into distributing their seeds. Any plant whose berries are eaten by an animal whose digestive tract will destroy the seeds will fail to reproduce. So there is evolutionary pressure to evolve berries that are only eaten by useful animals. Maybe this is through taste, or smell, or poison. But it's slow-acting because the people in question have evolved alongside it. They eat it during famines because the risk of poison is better than the certain death from starvation. So over generations, people become more tolerant of the poison. But the poison is still relatively young, so nobody is totally immune to it yet. [Answer] # It merely inebriates the target consumer but kills humans The substance that is poisonous to humans causes only mild intoxication in the species of birds that usually consume the berries and then spread the seeds through their feces. This is beneficial to the plant, so it produces the substance the birds crave. Humans are much larger than those birds and would need a much higher dosage to get inebriated from the substance, but they lack an enzyme needed to break it down. So even small dosages will build up in the liver and inhibit its normal functions. Which causes *other* toxins to build up and slowly kill the human. Depending on *how much exactly* the substance inhibits liver functions it could take anything from days to months or even longer. The symptoms would at first include difficulty to concentrate and fatigue. The person would sleep for progressively longer intervals, leading up to a coma and eventual death. Also the skin and the white parts of the eye would turn yellow. (The usual symptoms of liver failure) [Answer] **It did not evolve to be eaten by humans!** Or humans did not co-evolve with it. A berry is a bribe, to get an animal to eat the berry and to transport the seed within in its gut. A slow poison is pointless, it lacks even deterrent value. But if it evolved to be harmless to some common seed-distributing animals, it may still express toxins that poison (typically) insects that are eating the plant. And when humans arrive, those toxins may be slow-acting poisons to them, because they did not co-evolve with that plant and thereby evolve digestive enzymes to detoxify it. I can't think of a slow-but-deadly example of fruit or berries. Deadly nightshade is fairly fast and fairly deadly. Birds eat those berries with impunity. (Most but not all humans taste them as bitter -- our poison-warning taste -- and don't eat a lethal dose). The death cap/ destroying angel fungus is slowly deadly to humans, but not to rabbits. It's also reported by victims to be tasty! Yes, I know it's not a fruit, and the rabbits are not helping to spread its seeds. They've just evolved something to detoxify this fungus, which humans have not. Possibly because that fungus does not grow in Africa where we evolved? Grapefruit are not toxic to humans. I don't know that they are toxic to any animal these days. But they once evolved a poison that attacked an important digestive enzyme in some creature, to make it sick or worse. These creatures, in turn, evolved other digestive enzymes that are not affected, thereby working around the problem. The grapefruit plant has no evolutionary pressure to stop expressing this now-non-toxin. However, this is of considerable interest to you if you take certain drugs, which are acted on by that enzyme. You have alternatives for processing food, but eating grapefruit will result in the dose of that drug being either too high (because the enzyme mormally destroys a lot of the drug before you absorb it) or too low (bcause that enzyme converts it into an active form). Which is why if the drug information leaflet or your doctor tells you not to eat grapefruit, don't! [Answer] ## Evolution is messy and slow Based on my understanding, evolution comes about from mutations in individual members of the species which makes them more or less likely to produce offspring and pass on that mutation. This means evolution would favour traits that provide an evolutionary benefit, but not providing an evolutionary benefit doesn't mean such traits would necessarily be avoided. **An ancestor species needed (fast-acting) poison, this one doesn't need poison (at all).** There are plenty of instances in nature of body parts or features might've been useful in the distant past, but don't seem to serve any purpose any longer. That's not particularly extraordinary. The strength of the poison may just have been decreasing for the last few generations as it's no longer providing a benefit. **It's a side effect or coincidence.** Maybe the plant needs to have poison running through it to not get eaten and destroyed by bugs and the poison ending up in the berry is just a coincidence. A less direct alternative might be that the poison is a byproduct of something else: maybe it needed a thick skin to survive in a harsh climate and the first and easiest way evolution found to generate that skin was by also producing poison in the process. Or it may just have evolved it because doing so didn't do any harm (nor provide any benefit). [Answer] The seeds of this plant require darkness and a lot of proteins to develop. When an animal eats it, the seed implants itself in the digestive tract of the animal and slowly releases its poison. After several days, the animal dies and the seed digests its dead body from the inside in order to grow. As the body decays, the new plant emerges and grows to maturity. A plant of this kind needs animals to eat its berries without seeing the cause and effect relationship between the berry and the poisoning. It is also beneficial for the animal to move far away from the parent plant so that the seedling will not be in direct competition. [Answer] # The plant was too popular a meal Berries are used to spread the plant in animal spoor, but there are simply too many animals eating these berries. They even eat the berry bushes, because there's just too many and they're all hungry. Even though berries are spreading the seeds, the plants are just being killed too quickly by predation. Slow acting deadly berries accomplish two things. One, the berries will still spread the plant. Animals will eat the berries and spread the seeds in their spoor. Because the poison is slow, they never learn not to eat the berries. Two, they then die. The more berries are eaten, the more of them die, which stops them decimating the plant's population. By parasitizing the animal population this way, the plant still spreads itself, and it also defends itself from predation. As the plant becomes more successful, it kills more animals, so its rate of growth will slow. As its numbers dwindle, there will be more animals to spread them. The end result is an equilibrium, where the plant survives in its niche. It will be more common if the berries only sometimes make the slow-acting poison. [Answer] Non-deterrence. The substances humans use as rat poison act with a large delay in order to keep the rats from learning to avoid the poison. A slow-acting deadly poison is developed by the "death cap" mushroom, [Amanita phalloides](https://en.wikipedia.org/wiki/Amanita_phalloides). Its mycelium lives in symbiosis with hardwood tree roots. Hardwood trees grow slowly and are endangered by plant-eating animals that tend to debark them, like deer. The very powerful and rather universal poison of the death cap enzymatically blocks RNA polymerase and consequently protein synthesis in the cell metabolism. First symptoms appear with a day of delay and abate. After about a week, the victims' health rapidly deteriorates and they die from liver failure. The mushroom does not show typical warning signals of poisonous mushrooms and is described to have a pleasant, nutty taste. The actual organism is the mycelium which is not harmed by the mushroom getting eaten: the mushroom is just the means for proliferation. [Answer] **Leave no survivors** This is one of those environmental factors that are a bit specific to evolving alongside humans. When you poison most animals, they respond by not eating you anymore, but when you poison a human, we respond by going out of our way to destroy your species to make sure we never get poisoned again. When a tribe of humans wanders into your area and eats one of your berries, if they suddenly fall over dead, the remaining humans will start ripping up every one of those plants they find to make sure that none of their defenseless little offspring eat it by accident. If instead a human eats your berries, likes it, then brings a whole bunch back to the rest of the tribe to share, then your berries can poison everyone before the humans realize that you are a dangerous plant. All the humans die, and your species is safe minus a few handfuls of berries. [Answer] The berry itself does not contain a toxin, but the body of certain animals will change it into a poisonous chemical. For example, take the chemical methanol. Methanol is poisonous because human livers convert it to Formaldehyde, which then poisons them. Methanol has the potential to blind, as well as kill. <https://www.sciencedirect.com/topics/chemical-engineering/formaldehyde> [Answer] I would have to say that the berries are mildly poisonous to cause the animal that ingests them to have a mild diarrhea. Not bad enough to kill the animal or make it sick enough that the animal never wants to eat the berry again. Just enough to trigger diarrhea which can spread the seeds in the stool and not be digested by the acids. [Answer] It just happens to be lethal prepared *improperly* and just happens to be that way. Quite a few plants have evolved to be edible by specific species - capsain just so happens to have little to no effect on birds for example, and there are stories of plants that needed [specific species to germinate](https://en.wikipedia.org/wiki/Sideroxylon_grandiflorum) The nardoo fern of australia seems a [perfect analog](https://en.wikipedia.org/wiki/Marsilea_drummondii) for this. *Wet ground* or whole, the sporocarps are harmless. Dry ground they cause a slow, lingering death. Likewise, quite a few edible fruit with stones can have tasty fruit and [slightly poisonous seeds](https://en.wikipedia.org/wiki/Apricot_kernel). So evolutionarily? If you were a plant, the berry is expendable, the seeds are not. A human digestive system might be a little strong for the seeds and they may slowly poison the eater. An animal evolved to eat the berries would just let it pass through [Answer] **You need a lot of this poison to make a difference.** Some animals will eat just a little of a thing, to make sure it is OK. Mice and rats are great example. If they feel sick, they will stop eating that thing. This is why rat poisons like warfarin are slow acting. They take days to kill, because the rat does not feel them acting and so goes back and eats more. The things that eat these slow-poison plants are big, durable animals. It will take a lot of eating to get enough poison into such an animal to make it sick. The delayed effect means that the animal keeps feeling good, decides that the plant is good food and is eating lots of it. When the first-eaten poison starts kicking in, there is lots more behind it and this animal is in for a rough time. ]

[Question] [ So I've seen [this question](https://worldbuilding.stackexchange.com/q/33059) as to how a cape *could* work as a shield, but why else would 'classic' superheroes (Batman, Superman) wear a cape? Is there something about a cape that makes a person more heroic or does it have a practical purpose? [Answer] In classic comics, the cape provides the ability to add drama to the hero's pose, often physically filling the frame to emotionally make the hero the centre of attention and even convey a sense of movement when the character is standing still (the cape flowing in the wind). [](https://i.stack.imgur.com/vPWVM.png) *fill that frame!* Capes are also part of the costume of nobles and aristocracy from the middle ages into the 1700's. Comic book artists educated in the early part of the 20th century and their audiences would be well aware of this, so there is a subtle signature of the aristocratic nature of the character. (As an aside, cartoons like Bugs Bunny filmed in the period between the 1940's and early 1960's often expected viewers to get jokes based on classical opera and other fairly complex subjects, which should give you an idea of what educated people used to be like). In the period from the 1500's to the 1700's, cloaks actually did have a practical purpose (besides protecting the wearer from weather) as being secondary weapons or improvised shields for men fighting with the sort of rapiers or small swords which were common in that time period. [](https://i.stack.imgur.com/ERItL.jpg) While very few superheroes fight with or are attacked by swords these days, the use of cloaks as improvised weapons and shields is referenced by the occasional use of a cloak as an improvised shield by comic book heroes. [Answer] [NO CAPES](https://youtu.be/M68ndaZSKa8?t=127) The capes conversation in Incredibles captures it best. Don't get me wrong, I've always been an apologist for Batman's cape. It's awesome and I convinced myself it's bulletproof or a glider, or useful for intimidation or whatever. But if you need bullet protection wear a bulletproof vest. If you need a glider, arrange for a glider where you need it. And honestly who can be intimidated by a grown man in a cape? Capes are great at getting snagged on things, billowing when you don't want, making noise, did I mention getting caught on things? If you really think it through you'll realize that they're more of a liability than an asset. Imagine a ninja: death from the darkness, skill woven into every fiber, stealth and agility through the roof. The most deadly assassin ever to stalk the earth. Put him in a cape and suddenly he's ridiculous. No capes. [Answer] It's a matter of elegance, their cape is just a subpar substitute for a towel. Always bring a towel with you. [Answer] In Superman's case, fashion matters. He's an alien whose powers could easily make most people scared of him. He needed to win people over by looking heroic and patriotic. His mother did a great PR job in picking that iconic cape and S. Batman uses his for camouflage. And for psych terror effect (he really does look like a giant bat). As noted in the comments, it is also viable as a glider. [Answer] From the artistic side, the point of the cape is simple. It's the same reason wrestlers tend to have long hair. The cape is an action line that is used to accentuate the action that is taking place. This was needed more in the old days due to printing quality, but as time went on it wasn't needed so people stopped designing characters with capes. That's why the majority of Marvel characters don't have them. They were designed in the 60s and after where as many of the DC heroes were designed in the 30s. As far as whether they are practical on a character, depends on the character. On Superman the idea was that it acts as an airfoil that helps control his flight, but this was back when he was either transitioning to having flight or didn't have flight. Artistically it also serves as a show of damage. Superman and his costume doesn't get hurt, but his cape gets ripped up as he fights. Batman's cape is used for gliding, misdirection, to hide his body. make him look bigger and like a bat, as a way to shift some of the protection from his suit to the cape (for example the cape is electrically heated), it serves as a way to extend protection to others, and lastly as a weapon with bladed ends on the scalops. Robin uses his cape for much the same reasons, but Robin I's cape was used to extend his shape and cause criminals to fire at it rather than him. Robin III+ use it as a means of increased stealth with its black outside. [Answer] In the Supergirl TV series, when Winn is making Supergirl's costume, he omits the cape at first, and then adds it when he realizes the drag helps her to control her flight. Many heroes use their capes as an impromptu bag or pouch to carry children, animals, or other small objects. Particularly Superman; see Action Comics Vol 2 13, where he does this to an injured Krypto. In Batman: The Animated Series, Bats used his cape to scoop up water to try to put out a fire. And tries to capture Pig Diana in the same way in Justice League. For heroes who can't fly, the cape provides drag when falling. In combat, the cape provides a form of protection. It is gives the hero a large profile, most of which is actually empty space. A hit to the cape might look solid, but actually do nothing. Cape can be used as an impromptu pad or blanket. An armored cape can trap a sword. Or possibly slow bullets. [Answer] I remember one Superman comic in which it's revealed that the cape has a pocket in which Superman stores his Clark Kent clothing. Which makes sense, even if it's not the best place to store them. Can't remember the comic's number though... [Answer] I'm sure the whole purpose of a cape is to look cool, especially in dramatic poses in comic books. Spawn had a living cape. It looked awesome. The artist (Todd Mcfarlane?) could fill whole splash pagees with the curls and whorls of Spawn's cape with Spawn perched dramatically in the middle. This was probably the pinnacle of the visual drama of the cape. After such excess it's hard to do anything new and interesting with a cape. This sort of thing sometimes inspires an artistic backlash (that's overdone, I'm doing something else) It's been a while though so maybe it's time for a retro refresh of the aesthetic. [Answer] The main purpose of a cape is for psychological effect. It makes the wearer look bigger, more noticeable, more "apparent", which is good for a superhero that wants to represent a paragon of justice or to intimidate their enemies. Since that's basically the point of becoming a named and costumed superhero (as opposed to just being a regular crime fighter with powers) capes make sense - although they are offset by the impracticality of catching on things or getting in the way. They can also be used as a shield and can be used to entangle an enemy's weapons (some swordfighters used capes for this purpose), or provide a bit of extra protection against bullets, especially if the cape is made of some sort of high-tech super-fabric. In a fight, especially in the dark, a hero can also use the cape to break up their silhouette and confuse enemies into shooting the cape instead of their body. In a pinch, it can be thrown as a decoy as the hero makes their escape, or deployed as chaff to confuse the targeting system of homing missiles. [Answer] *Watchmen* touches on this idea. > > I experimented with a cloak, remembering how the Shadow would use his cloak to misguide enemy bullets, leading them to shoot at parts of the swirling black mass where his body didn't happen to be. In practice, however, I found it unwieldy; I was always tripping over it or getting it caught in things, and so I abandoned it for an outfit that was as streamlined as I could make it. > > *(...)* > > Dollar Bill was one of the nicest and most straightforward men I have ever met, and the fact that he died so tragically young is something that still upsets me whenever I think about it. While attempting to stop a raid upon one of his employer's banks, his cloak became entangled in the bank's revolving door and he was shot dead at point-blank range before he could free it. Designers employed by the bank had designed his costume for maximum publicity appeal. If he'd designed it himself he might have left out that damned stupid cloak and still be alive today. > > > Though this is kind of insightful on one potential in-universe use of a cape/cloak, there are a lot of statements in that quote, some on the impracticality of the outfit design in-universe, others on problems with superheroes as a concept and still more on real-world corporate exploitation. On the one hand, one guy used it effectively, another guy found it laughably impractical, a third guy's used it solely for the aesthetic and it got him killed. Three different characters that all handled it differently, and a different "moral to the story" for each character. So really the design of your outfits is up to you, and depends on what messages you want to convey to your audience. [Answer] it was roman fashion to wear cape. In that time cape displayed how important person you are. so this was are influence. [Answer] It can be very dangerous to wear a cape. You might get trapped in a revolving door. <http://comicvine.gamespot.com/dollar-bill/4005-18494/> [Answer] Depends on the cape, of course. See at Spawn for example, he can take a lot of advantages from their cape, because the cape itself has some powers. If it's just a piece of clothing, then no, better no cape. [Answer] # PR and dramatic looks Even if they keep their real identities secret, their hero identities are celebrities nonetheless. They *must* maintain image close to public's definition of "heroes", not "some uncontrolled militia with superpowers". Also, good loks and proper PR pays. **Can you imagine just how many starving children can be saved with proceeds from selling some advertising space on Superman's costume?** In situation, where heroes compete for ratings you're not only going to see them wearing capes - they will do *dialogues* with villains mid-fight. [Answer] A lot of super hero costume choice is about trying to look cool. There are maybe practical benefits to looking cool, but do remember these choices come from comic books where image is everything. Flags look pretty cool with a little wind. And a cape is like always having a flag with you and you don't even have to bother waving it if you keep moving. It might also be noted some serious effort is being put into design of uniforms of soldiers and police, but capes are not part of the standard kit yet. [Answer] About the only useful thing I can think for a cape is if it was detachable. The villan grabs it and ends up with cloth billowing around him. (Or the cape get snagged on something other then the main suit) [Answer] Capes are used for visual intimidation. While some uses can be defined for a cape, it can be a cloak to guard against the elements and possibly some forms of attack, a cape mostly just makes wearer seems bigger, stronger, more imposing on his audience. This is the exact reason royalty and aristocracy used and, in some cases, still use them. Does Superman need a cape for protection? He's the man of steel. He just looks awesome with it. Without a cape, he's a dude in tight, long underwear. Does Batman need a cape? Granted, he does use it for protection sometimes and possibly gliding but, mostly, he just looks awesome and scary with it. And being a "bat" man, he needs something that resembles black, leathery wings. [Answer] So, there are quite a few answers that deal with the negatives of capes. I had a few other ideas, but whether or not a cape is useful or practical depends on whether the person using it can balance those negatives and positives. A cape might block visual lines - not just breaking up a silhouette or using its motion in combat to draw fire away from the body (though those are also useful), but in general there might be any number of scenarios where it can be positioned or used to literally make it hard to see what the person wearing it is doing - hiding someone's hand while reaching for a weapon or tool, letting them pick something up or put it down (or tuck it in a pouch or pocket) without being seen, letting them hook their foot or brace their weight - as long as their shoulders aren't moving, it's hard to see what might be moving when the line-of-sight is physically blocked by the cape. Additionally, the person might use the cape, and their own profile, to physically block someone seeing past them (blocking their view of something or someone else). They might use the cape to conceal something bulky or noticeable that they're carrying, or just anything they'd rather not be seen with. They might hide wounds, or wear-and-tear, behind the capes - especially if the cape is used for misdirection, it might be *expected* to come off the worse for wear, and so even in rough shape it might not betray it's wearer's actual damage to the casual eye. Most superhero uniforms are form-fitting (for ease of movement, among other things) - so if there's *anything*, anything they don't want being instantly visible, they need some way to conceal it - and a loose fall of fabric will do so easily, if they should just happen to have one on hand. Of course, it isn't foolproof - a line-of-sight might *not* be blocked by the cape, or they may not be allowed to conceal something without being challenged, depending on the positions of people involved and the actual scenario - but having a cape means it's an option. A cape might have armor or all kinds of protection - fireproof, bulletproof, etc. Of course, there are uniforms that have those kinds of protections built in, that will give better protection *and* better ease of movement to the person wearing them - but what something like a bulletproof vest won't do, is let someone offer that protection to someone *else*, or even more than one, at least not without a lot of shenanigans (undressing and whatnot). So the superhero can wrap their cape around someone else a lot quicker and easier than trading off a tailored uniform vest - and it will give a lot more coverage that *just* a vest would, or even the superhero wrapping *themselves* around the second person. A thicker, heavier armored cape (not the thin cosmetic kind, okay) might provide additional protection by forming a kind of, makeshift crumple zone - a blow not only has to get through the cape, but also through the layer of air between the cape and the body, and then get through the protection on the armor. A tightly fitting armor, even one with layers, will transmit kinetic force through it and into the person wearing it much more efficiently than one with a gap between layers, especially one where the outer layer crumples into the lower (spending energy dragging the whole cape inwards) and fluffs itself right back out afterwards. Some kinds of blows will get the cushioning much more than others - something narrowly focused and sharply penetrating might not deform the outer layer (not using the 'crumple zone') and so the only variable is the total thickness of the armor and not whether there's space between layers, while something broad and blunt-force might lose a lot of energy being dispersed along the cape. And then there are ways a cape might be modified to a specific superhero's use - a cape weighted at the hem (for better draping) might make a kind of cloth club, or even a bola - and what is weighting that hem might itself be useful. A minimum of added framework or other modification might make a kind of glider, to slow down and control falls. It might be given some property that works with the superhero's abilities, or against a usual villain's - being able to conduct, or resist, some energy or typical combat conditions - with a bonus of being able to hold that property at a distance or quickly drop it if some scenario turns that property against them (which would be a lot harder if it was built into the uniform). It can just have all the extra pockets, since none of the heroes ever seem to need more space to carry stuff in. It maybe can be used for visual signalling (if said hero tends to work with others, *and* semaphore code is useful). Of course, there are the historical reasons for a cape or cloak to consider - shelter from the weather, keeping warm or dry or cool and shaded, a makeshift blanket or pad, or a bag or net to catch or carry with, or even providing fabric to tear into makeshift ties or bandages. A thinner, less armored version of a cape might be better for these uses (or, perhaps if there's a non-armored cloth lining that might be torn out). Coats are more often used for weather proofing in modern times, but a cloak or cape might have multiple uses - not the least of which is the ability (which a tailored coat may *lack*) to extend that protection to others. It may also be easier to adjust a cloak or cape to different temperatures - anywhere from tightly wrapped to keep warmth in to loosely draped to let heat flow to propped up to create shade, its wear can be adjusted a lot more than a more tailored coat. The simpler construction (a big rectangle, more or less) should also make it easier to re-purpose for other uses, like a blanket, or a bag, or a pad - tailoring which makes it a better coat, for example, will also make it harder to use for other purposes - and if it must be torn up for bandages or ties, a more closely tailored coat represents more lost work (to remake or replace) than a simply cut rectangular cape lining. How often your superhero might need the cape for these purposes is unknown, but the multi-purpose capability might be something they thought of when designing their costume. Really, the ability to wrap a cape around someone else seems to be a *really strong* benefit - your superhero only has to grab an edge of the cape and swing it around someone to protect them from fire or bullets, keep them dry or warm in poor weather, or even serve as a shock blanket - as long as it is cut large and loosely draped enough for coverage. It's a lot easier than carrying around separate protection (especially since it's easier to throw around someone in a hurry carried loose on the back, instead of packed away) - and by draping it around themselves, it can serve as an extra layer of protection when they're not using it for someone else. That might be enough for your superhero to justify having a cape even if other uses (concealment, misdirection, emergency source of cloth, makeshift shield) aren't enough to counterbalance the negatives. [Answer] **Thermal management** Have you ever seen runners being wrapped in "space blankets" at the end of a race? Someone who's just done lots of heavy physical activity will be sweating, but now they've stopped there's a risk of their temperature dropping. Similarly, superheroism is exothermic. The hero or heroine's lycra outfit is great for shedding heat while they're working, but when they stop it can become distinctly chilly. Especially at high altitude. So they can wrap themselves in the cape to keep warm. ]

[Question] [ **Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). Closed 4 years ago. [Improve this question](/posts/138843/edit) Let's say a Moon colonist in the future has discovered an alien time machine. A small remnant of humanity still exists on colony worlds in the solar system, but due to runaway climate change, they are extinct on Earth. What event or events would the time traveler have to change in the past in order to make sure climate change as we understand it today never happens? Oh, the time traveler would go back in time on the Moon and has a shuttle that would get him to Earth in that past period. EDIT (2-14-2019): It's clear that the basic premise of my question is flawed, since there is not one event or small number of events that, if changed, would alter the impending climate change as we understand it. Not only that, but it seems that opinion vary widely on exactly how damaging climate change will become, even if not significantly curtailed. That said, the information here could fuel quite a number of different tales, so thank you all for your input (and you don't have to stop now). [Answer] Go back to the cold war era and start a "Russians are trying to warm the planet" scare. You will need a lot of money to fund some big advertising campaigns. You also want to seed a few specific technologies like nuclear and solar power to try and push them along. Let ignorance and paranoia work towards the betterment of mankind for a change. It's believable to the average citizen since every American knows Russia is cold so warming it seems like a good idea for the Russians. Make it clear Russians don't care about pollution and things like that, make pollution a sign of communism. The reds are trying to make the planet too hot for Americans use special gasses is good. It doesn't matter if it is real as long as the fear is real. Simple slogans like "don't let the reds turn up the heat" are good. The more believable the scare the better, create fake data that will mirror real data. Then americans will invest absurd amounts of time and resources in researching ways to reduce and counteract greenhouse gasses as well as researching clean energy. It will create PR problems for major polluters as well. The US did some breathtakingly expensive and difficult things to combat the "red threat" many of which are still around. They become synonymous with nationalist views. These methods will steadily spread to the rest of the world. as technology is exported, especially as they are made cheaper. There are dozens of smaller way to help it along. If you make Americans think Russians are opposed to nuclear power because it doesn't help with warming and is too clean you can encourage nuclear power which will go a long way to replacing coal. Maybe Russia sabotaged Chernobyl or three-mile to make us give it up. Show people farming practices and land usage can be used to combat greenhouse gasses, and real Americans will use those methods to screw over the Russians. Fund some ice core drilling or other science to back up your claim, a little evidence goes a long way with propaganda. It will also allow for a later transition to a different message "its not just the Russians we are doing it to ourselves unknowingly" Make the Russian way seem like the brute force way while *real* Americans make things that are more efficient, large brutish Russian cars vs sleek efficient american four cylinders, ect. Make it clear Russians burn coal while americans use clean methods. Combatting fear of nuclear power will help. [Answer] **The mad scientist sledgehammer option for this particular nut.** Kill a *very large* slice of the world population. It worked when Europe colonised the Americas, so many natives were killed it actually changed the global climate. > > [America colonisation ‘cooled Earth's climate’](https://www.bbc.co.uk/news/science-environment-47063973) > > > He travels back in time to the height of the cold war at its most unstable & dangerous time with some small thermonuclear devices & uses them to provoke a full on nuclear third world war. The massive resulting reduction in human population successfully reduces industrial production & agricultural drivers of climate change sufficiently to reverse global warming & delay its resumption from human causes until long after we develop cleaner infrastructure & technologies. We know from [Chernobyl](https://www.youtube.com/watch?v=OgygpPSRU78) that nature won't have a problem with this & he's clearly not worried about his own existence as such a major change in the worlds history (fixing climate change) will write him out of existence one way or another anyway no matter how it's achieved. --- Taking back a flask or two of some really virulent engineered virus could work as well. But one big advantage of the nuclear option is it's going to (perhaps, hopefully) leave vast swathes of territory largely uninhabitable to any humans (if they want to live much past 20 without dying of cancer & want their children born without genetic defects), great tracts of undisturbed forest to help suck CO2 out of the atmosphere for centuries to come before the land is safely habitable again. [Answer] Direct bootstrap of nuclear fission technology in the 1700s. Sounds crazy right? Not so fast. In order to reliably prevent runaway climate change, we must prevent the situation that caused it, namely cheap coal and oil power. This is quite well accomplished by getting there first with uranium, plutonium, and thorium reactors all at once. Since mining won't be so well developed yet, starting with breeder reactors to extend the fuel supply is a must. Yes I know what all this entails; an immediate gift of 1950s physics, metallurgy, manufacturing, etc. This is an overwhelming change to society but totally worth it. I'm just going to assume you have to go about this the long way and can't bring much pre-manufactured stuff with you. The evidence of the re-entry vehicle itself will suffice to prove future origin and that you posses actual knowledge they can't match. Everything will be in fifty pounds or so of books and blueprints. Every piece of metallurgy required starting from the blacksmith to titanium working (you should be able to start a reactor without it but it will be most convenient for mass roll-out). The 1700s are a convenient time because the manufacturing technique is right at the cusp of being able to make a lathe that makes a lathe better than itself. You will need basic electronics, light bulbs, how to build a Geiger counter, how to locate uranium (and if you can get it, the locations of good deposits), safe handling of radioactive components, electric motors, early steam power (to crank generators if nothing else), lead-acid batteries, and quite a bit more I can't think of right off the top. The idea is to seed this stuff so that by [1859](https://aoghs.org/petroleum-pioneers/american-oil-history/) the response to selling fuel oil is "How crude" (pun very much intended) and nobody wants it because they already have enormous power at their fingertips. This is a ridiculously valuable gift. Choose wisely which nation gets it. Many of the nations in good shape to receive it now were not back then. MOD: please leave comments because comment voting. [Answer] Here is an idea: What if Henry Ford had built his assembly line for an electric car rather than a gas powered car? Before the assembly line brought down the price of the Model T, electric cars were actually less expensive than gas cars. The assembly line would have made these even cheaper. Electric cars and infrastructure would need more electric power plants. Today that means burning more coal but perhaps your time traveler could also steer us toward nuclear. Perhaps the introduction of and sodium cooled reactors earlier could have alleviated environmental concerns allowing nuclear plants to be more prevalent. This could have lead to thorium reactors reducing nuclear waste concerns and maybe lead to viable fusion type reactors. [Answer] Prevent Chernobyl and Three Mile Island so that adoption of nuclear power isn't regressed. This might not completely solve the problem but if it cuts enough emissions to buy a couple decades so that renewables and electric cars and other technologies become economical soon enough to prevent cataclysmic warming. [Answer] **Keeping traveling back even when incentive is lost** A big problem with solving problems trough time travel is that once it is fixed the incentive to travel back in time is lost and thereby no one will travel back in time to keep the timeline fixed. So what the time traveler has to do is leave a note. Either to himself, or if he never gets born in the new timeline, he has to leave it for someone who he trusts to keep the "fixed" timeline. ## How to prevent climate change He gives working fusion technology to people in 1950 and within 20 to 30 years the amount of CO2 produced per capita will be comparable to the 1820s. Power generation through fusion is supposed to be scaled up and down however you want once we figured out how to keep it running for more than fractions of a second. So, it will be possible to power all of our electronics from it as well as our cars and everything else that simply needs energy and doesn’t rely on chemical reactions (like our own body). **Side notes** It is possible to provide fusion energy even earlier than 1950 but then your time traveler would need to provide more and more knowledge for people to able to built fusion reactors. [Answer] It would be quite hard to change the history by gifting technology, as we already had the ecological solutions, but time and time again we have rejected them in name of either profit or convenience. For the same reason bringing knowledge of the global climate change work, and it could even accelerate the process. I think the easiest way would be to infect the humanity with an engineered retrovirus causing one small change- humans would be now much better at recognizing co2 levels, and anything above 250 ppm long term would cause serious psychosomatic issues. [Answer] **How did I get here?** Your question implies a little foreknowledge in the here-and-now. We currently have global warming, and we know in the future this wipes out humanity. So first, how do we get from here to there? **Current state of affairs** The current state of affairs is that almost all nations are on-board with [solving Global Warming](http://www.opr.ca.gov/facts/list-of-scientific-organizations.html). We have China [reducing their coal usage](https://www.reuters.com/article/us-china-coal/china-beats-2017-coal-fired-power-capacity-reduction-target-xinhua-idUSKCN1GD43K), Russia has [launched its Ecology program](https://climateactiontracker.org/countries/russian-federation/) to reduce carbon emissions, everyone is pretty much on board. Only one nation really stands out in present-day in their opposition to climate change science, and that is the United States. Since everyone else seems to be on board, and the US is not, it seems safe to assume that the global disaster in this storyline is likely caused by the US. **So now what?** The way to fix the problem would be to get the US to follow a different path, the earlier the better. So how do we do that? You're not going to like my solution. Al Gore. He was an inch away from the Presidency, and one of the early voices of warning. If he had become president instead of George Bush, we would have that early start against global warming that we require to avert the disaster. The United States would be a leader in the fight against it, instead of the last denier. This would likely avert the global disaster. My solution? *Travel back in time to October 2000, and assassinate George W. Bush.* [Answer] **Climate Change Is Not Trivially Preventable In This Way** Not to be a downer, but most of the answers so far seem to assume that a tiny change to the United States' (or other similar industrial powers') behavior at some specific point in time, all will eventually turn out OK. The problem with these approaches are: * **They incorrectly assume that climate change is a regional problem.** e.g if we somehow get England not to discover that coal is awesome for all sorts of things, nobody else in any other place will ever figure that out. This is mistaken because scientific discoveries and technological innovations are being worked on by multiple people across the world and it's largely accidental who is the first one to discover it. The modern-day version of this assumes that the United States is solely responsible for climate change because it's not doing enough, when the United States is only 1 country out of 195, and many of those other countries are poor, want economic growth, and are not going to accept being told by rich countries that they cannot enjoy the same sort of wealth because of a hypothetical catastrophe that *might* happen in the next hundred years when they have bigger problems to deal with from being poor in the present. * **They incorrectly assume that humans are lazy.** Just because you can deliver nuclear energy to all of the primitive humans on Earth everywhere, doesn't mean that those primitives will not continue to research other forms of energy eventually and use them. The secrets of the universe still exist to be found regardless of what toys we have to play with, and in the time travel context of this problem, we already know that humans are capable and have already figured out these secrets. Your time traveler needs to somehow prevent that also, and that is nearly impossible for one person to do. * **They incorrectly assume that a small number of human activities cause the problem, and that we fully understand the consequences of changing those activities.** The assumptions are often that power generation or cars are killing everybody by emitting carbon, and if we magically make that go away, everything will be fine. Maybe, but if we don't have cars and electricity, human beings will do other activities that will have a different environmental impact, not just whatever today is minus the bad thing as though it never happened. If we replace internal combustion engine cars with electric cars, we'll need to generate more electricity, which could increase pollution and increase carbon emissions. If we somehow prevent the industrial revolution, then most people will work in agriculture, which will require a lot more land than it does today, which could require clearcutting forests and trees and reduce the planets' carbon capture capacity. It's hard to figure this sort of stuff out. People fail at this all the time. **How could you prevent Climate Change with Time Travel?** Assuming that the catastrophe has already happened (e.g. you can't say it's not going to be a real catastrophic problem after all), you need a lot more than a single individual and their time machine to fix it. What you need to be able to do, is have perfect knowledge of what caused it, and a dedicated effort to prevent it from happening again. You essentially need to have a time travelling totalitarian government that is omniscient, does not cause itself to cease to exist through its time travelling efforts (e.g. grandfather paradox), and can fix any mistakes it makes (e.g. if they ban the car, and it turns out this leads to too much grazing which makes carbon emissions worse, then they have to be able to undo that and try again until they get things right). I think this is impossible; the level of control and knowledge required to get this sort of thing to work has never been demonstrated to be within the reach of human beings, and any similar effort to centrally plan in this way on smaller scales has almost always led to economic and environmental disasters. But, time travel is impossible too, so if you can conjure up the a time machine, you can conjure up some sort of perfect planning information machine too that maybe works around those sorts of problems. [Answer] ## Not at all Unless the time-traveler is not a time traveler but a dimension traveler, the mere fact that he has experienced a world with the climate change makes it impossible to prevent climate change because of causality: * He had experienced climate change + so he took a time travel and went back to fix it. * He fixes it. + He changed the past and the person doesn't ever experience climate change. + So he doesn't take a time travel and go back to fix it. * He never went back to fix it, so he experienced climate change... Back to the start. You see, true time travel is impossible as you can't cheat causality. The only safe and sound time travel that does not cause causality errors is one that goes back to try to fix time... and fails, leaving the time traveller with a need to do the time travel in the first place. He goes back to see if he can fix the past... and utterly fails. ## Dimension hopping If you go for dimension hopping on the other hand, your past becomes independent from the past of the mirror-verse you show up in. Suddenly causality can't throw you a wrench into the gears and the traveler can save the *alternate reality* you ended up in. Though in this case there could be two entirely different entities of the time traveler: the one originating from the universe that experienced climate change... and (unless he destroys the lineage that would lead to the alternate him), his *double* that never experienced it. But at this point, you are no longer time traveling at all. [Answer] A time traveler should work from within the system, thus he first needs a proper foundation. And as he cannot just do a bank transfer from the future, he should take a business model from the past that made people rich before and would be easy to replicate without a lot of resources, e.g. an internet payment company. Given that the time traveler knows the technology from the future and now has proper funding he can now pretend that he is this genius inventor that just succeeds at everything he does, even if it is not in his area of expertise. That means he can take the money to invest into new initiatives that will help mitigate the global climate catastrophe: * A solar energy company * Electrical car company * Public transport company * As a backup plan make spaceflight cheaper and go to Mars [Answer] 1. Take a self-replicating robot and send it back in time. 2. Have it build a mining colony in the asteroid belt. 3. Have it drop a [space elevator](https://en.wikipedia.org/wiki/Space_elevator) down to the surface of the Earth. 4. Engage in communications with leading scientists (around 1800). 5. When they are ready, give them [thorium reactors](https://en.wikipedia.org/wiki/Thorium-based_nuclear_power) or fusion reactors as black boxes. 6. In return, the deal is that fossil fuels will not be used except to maintain the current climate at acceptable levels. 7. When the timeline catches up with when you originally sent the robot back in time, the robot sends a brand new robot back in time to do all these things. This does not involve a mass extinction event (although it's possible that the robot might also supply superior birth control). It relies on substituting easy electricity generation for fossil fuel use. This is sustainable. While you (as the person with time travel) may cease to exist, the robot can continue to exist. Causality is maintained because the robot creates a closed loop. It sends its younger self back because that is what it was always programmed to do. Another alternative is that instead of sending reactors down, it might bring people up. So if someone wants the joys of modern technology, they can ride up the space elevator and live in a space station. Meanwhile, the people who stay on Earth can stick with the tried and true. Because the robot controls the transport, it can draw people who want technology off the Earth. Those who remain can stick to more sustainable practices. Want the internet, television, and self-maintaining toilets? A space station is the place for you. Want to ride horses and grow your own food? Stick to the Earth. It's possible that the robot might provide modern medical care to the people on Earth. Why? Because prior to modern medical care, people had many children. Wealthy westerners in Japan, the United States, and Europe have negative population growth modernly. If the 1800s isn't soon enough, the robot might try an earlier period. For example, the robot could try to stabilize the period of the Roman empire by luring Julius Caesar away. Or it could take more active measures, possibly with the help of those on the space stations. [Answer] The time traveler could kindly kamikaze with his shuttle against the Chicxulub asteroid, thus preventing (or postponing) dinosaur extinction. Rampaging dinosaurs would keep apes in checks, preventing their spread. Also, provided that the human species happens anyway, competition for resources between humans and dinosaurs would leave less surplus to invest in technological development. Now, the interesting thing is that it is possible that dinosaurs might have enjoyed a slightly warmer planet, and millions of years later, they could find themselves wondering what they could have done to cause a global warming. [Answer] Apparently the main sources of greenhouse gasses are * Transportation (car, rail, ship, aviation) * Electricity (power stations) * Industry So a good "event" to change in the past would be "steam engines" powered by fossil fuels -- 18th century. Maybe she could do that in two ways: * Tell the truth -- i.e./ warn of what will happen if fossil fuels are adopted world-wide * Provide alternatives -- solar panels, better batteries than today's, safe nuclear power -- also medicine and telecommunications, because once you have those do you really need heavy industry and long-range shipping too? -- whatever other technologies she can carry from the future in that shuttle of hers [Answer] Building on [Pelenore's answer](https://worldbuilding.stackexchange.com/a/138847/26213) - about culling a large portion of the population to reduce pollution. **Release self-replicated and repairing killer robots, programmed to attack anything that produces pollution**, while simultaneously broadcasting a message along the lines of "pollution source detected, eradicating". To prevent these robots being thought of as simply a calamity, make them peaceful under normal circumstances, and maybe even helpful. e.g. they could impart advice on how to achieve the same tasks without causing as much pollution, and only eradicate those that consistently/significantly fail to. This would however, require a lot of collaboration and planning with a large number of people to design such a robot so that it doesn't just become an environmentally concerned Dalek... [Answer] I once read an article that stated that in the 19th century, the first thermodynamic theories were received with skepticism by the scientific community of the time. That article wondered that, had those theories been well received since the beginning, the story of science and technology would have been very different. This is because (Warning: very bad and rough explanation ahead), while the then-predominant Newtonian physics used to see every phenomenon as reversible (just invert in the appropriate way the direction of the forces, and a body will follow the same path in reverse), the principles of thermodynamics (particularly the second one) stated that at every action, something is lost and can't be recovered. So it was hinted that an early adoption of the thermodynamics (and the concept of irreversibility) in the mainstream scientific and economic culture could have geared the society toward a more conservative and prudent usage of energy sources and natural resources. Probably it would be an optimistic approach, but a time traveller could use his knowledge of advanced physics to support Boltzmann's theories, or even discover them some tens years before, so that the industrial revolution would also be driven by the awareness of the risks of limited resources and pollution. [Answer] ## Problems With Time And Incentives One of the problems with changing the past is, that you don't know where you will end. Killing all people might stop the warming, but not solve your problem. The alteration of the earth climate might be going on now for 10.000 years with [the first rice fields](https://www.nature.com/news/2011/110325/full/news.2011.184.html) and cow breeders. You don't want to change that or any other thing which might hinder humans to go to the moon forever. And I don't see, how nuclear bombs could help humanity survive longer on earth if they were introduced earlier, like let's say as a westener [1618](https://en.wikipedia.org/wiki/Thirty_Years%27_War), [1775](https://en.wikipedia.org/wiki/American_Revolutionary_War), [1803](https://en.wikipedia.org/wiki/Napoleonic_Wars) or [1914](https://en.wikipedia.org/wiki/World_War_I). And all these people will not believe your time traveler, he might be burned on a stake or end up in a sanatorium. ## Solution: Create Incentives And Time Travel back to a time where everyone can see what global warming does and that it is a good thing to do something against it, but a lot of plants and animals are still there and the people have still the money to invest in their future, some years from our point of view. Introduce all the technology you like, e.g. instant-solar-panel-nanobot-factories or clean and safe nuclear fission plant technology. If the time runs out too fast, do something to slow down global warming until the other plan works. You don't have to ignite all the forests, tickle yellowstone or start a nuclear war. Just drop a rock on earth, somewhere in the desert, big enough to put up a decent amount of dust in the sky, and you have your cooling. Without (m)any deaths. With your future knowledge you will know exactly how much rock you need, or you just try it out. Our problem is (or might be) not, that global warming is already irreversible. At least if your main concern is to save most of the humans, but not the dodos, or the mammoths, or some other species which will die out in the next couple of decades or is already dead. The problem might be, that no one wants to pay for the solution until no one has any resources left to do anything, because of all the economic crises, riots, epidemics, floodings etc. [Answer] The time traveller needs to go back and find the person who invented fire (before she invented it) and give her a solar cooker and a down jacket. [Answer] The tragedy of human damage caused to the biosphere is in direct proportion to the number of humans doing the damage. If we take the carrying capacity of the earth to be 1 billion comfortable humans when living exclusively with renewable resources then all we have to do is prevent humans from increasing beyond 1 billion and they will have less need to fight over resources and be happy with a global Demogarchy (each person responsible for their own regions rules). As mentioned in my comment your means of messaging may be limited if you cannot take your shuttle in the time machine or the time machine in your shuttle: > > Given you are currently on the Moon. If you cannot take your shuttle > with you you can only go back to when a shuttle first arrived. If you > want to pass on a gift you can visit with Neil Armstrong. If you want > to send a message you can go back to the advent of radio or the > telescope. Best would be to take time machine back to earth in your > shuttle and then work from there. > > > If we take as given that you can go back then you just go back to before mines are opened and buy up all mineral and fossil resources. You provide them in unlimited amounts to any countries that have self sufficient populations and some form of sustainable government with thousand year plans but prevent over populated countries from ever thriving until they join the club. You might as well take a copy of the various patent office databases and Archive.org to make lots of money to help you purchase the land. If you have to send the message via radio from the moon you will have a harder time as the world was divided up already into major superpowers by the time of radio and they would rather shoot you on the moon than listen to world saving propaganda. Sending plans for all solar cells and contraceptives to all who will hear may save the day but odds are you will see the world race towards where we are now. Unless you have the final balance sheet of the US Reserve System and other Central Banks showing the scam they have pulled and are able to nip the economic policy of continuous growth before it is permanently entrenched. If you have to work with Morse code and lasers pointed at famous Victorian observatories you will have to send the message and task your disciple to start a religion to achieve these same goals. [Answer] A pandemic. Humans account for a substantial bulk of all global warming, plastic pollution, acidification, etc. that is currently ongoing. A substantial reduction in the past human population (probably at least 85% reduction), anytime before the Industrial Revolution, could avert any perceivable effects of climate change. If the pace of scientific progress did not slow down too badly, then humanity might be able to out-innovate climate change much faster than they are doomed by it. Regarding the pace of scientific progress, there is also the option of leaving behind scientific accelerators to help humanity fight climate change faster. This may include publishing in the 19th century the theory of global warming, the greenhouse effect, how to measure the greenhouse effect in a laboratory setting, and various scientific / engineering principles for how to avert climate change (windmills, precursors to solar cells, precursors to hydroelectric and all turbine-powered energy sources). Since there are minimal diseases realistically capable of wiping out 85% of Earth's population by themselves, it might require that the time traveler release a handful of different diseases at different points of the globe, specifically aimed at the immune systems of the region (i.e. each region is targeted by the infection that historically devastated it the most). This might require that the time traveler have access to a vault of infectious agents. Access to an biological vault AND a time machine would be more realistic if the time traveler was an agent of a coordinated government operation, rather than a lone wolf actor. Note that in time travel fiction, and even in actual physics, there are different opinions on whether a time traveler is traveling back into their own past (and therefore at risk of erasing themselves or creating causality paradoxes) or traveling along a closed time-like curve to a past on a different line (in which changing past events will not erase your own existence). [Answer] I'll keep it simple. The underlying issue is population. It's already quadrupled in my own lifetime. Actually kind of shocking, thinking back on it. The rest, the conversion of complex ecologies into monocultures, the bleaching and destruction of corals, the depletion of fisheries, stratospheric ozone depletion, the quilting and destruction of forest systems (well studied by Dr. Lovejoy in the early 1980s) and the ability of those systems to sustain diverse life forms, the 6th extinction event and the environment generally, is just a long list of various symptoms resulting from human population growth, hastened by the advent of "nearly free energy" through the discovery of coal and oil and engineering resulting from science knowledge (such as the Haber process, first used to help the Germans deal with the blockade of South American salt peter, but subsequently used to make nitrogen fertilizers.) So focus on ideas that might lead to a self-limiting mechanism of human population growth in the tale. We are already eating into the "capital" of Earth, by destroying/consuming 50% more than is generated each year through photosynthesis. (If you sum up the entire meat mass of humans and their domesticated animals, you'll find something close to 99% of the mass of all land-based vertebrates on Earth. In short, we now occupy very nearly the entire land-based vertebrate niche. This wasn't true when I was born. And it's not sustainable into the future.) If you can limit human population sufficiently that we no longer consume more than is produced each year, you may find an equilibrium that arguably might work. How you achieve that? I don't know. That creativity is left to you to work out, I suppose. [Answer] You have time travel. If you allow that, you can allow is being associated with some new inexhaustible power source. Start a business exploiting that and provide with world with power cheaper than fossil fuel. Ideally the power source can be adapted for small scale use and provide transport power. [Answer] **You need someone who doesn't know about Climate Change or doesn't exist in(side) time itself** So, one big problem with time traveling is the fact than causality can bite you in the balls, but you have some ways to do a work around it: A) Send a traveler who doesn't know about Climate Change but travels with a mission give it by some otherworldy over-temporal entity who happend to exist beyond time. So that way the traveler doesn't affect the events than lead him to be sended in the first time, because the entity who send him exist **outside and over** time. -And/Or- B) Make him have an artifact than make him (the traveler) exist **beyond time** like in the X-men animated series, where time travelers use some bracelets than allow them to exist beyond the impact of time, allowing them to modify time without being afected for causality. After you fix that problem, i would argue than: **Send a group of time independant traveler to make an intervention in the time before the napoleonic wars** You see, before the napoleonic wars, there was france and england having capitalistic economics reforms than opose to the agrarian concept of richness very common in nation back in the day. This reforms actualy help to make both nations industrial (or pre-industrial if you want) change them shift to investing resources in production as a way to generate more wealth. So, what you need is actualy reeplace both economical characters by time travelers, being themselfs second hand of the arguibly most powerfull "kings" on earth in that time they will propose somewhat different economical policys than make a turn for the enviroment, without anyone ever knew them. If the changes are right, then, the napoleonic wars can happend as it should, but your agents probably already make the change in the timeline just enough to make sure than the oil and coal industry never see his zenith. because you gave that zenith to another, cleaner industry before. Like, i don't know, send your travelers with vastly electric independant railroads or send very efficient solar panels together with very powerfull Electric engines to reeplace the steam machines much earlier than the moment they become the stars of the movie, and make your main characters make investment policies and recomendation than clearly benefit that tecnologys instead of the steam and coal tecnologys developed back then. To prevent a technological causality problem just make sure than research is still done about this steam engines, but doesn't give them any chance of being used in industrial production, maybie make them work in ships or some other masive transportation method, than because of massivity is not so frecuent like a car or a train. [Answer] Perhaps I'm too naive but my suggestion is for the time traveller to get as much documentation of the disaster as possible, newspapers, videos, how ever many years worth of everything on the internet and come back to right now. The information should be seen as basically unfakeable (1000s of hours of video from 100s of different sources of New York being swept away) and so comprehensive that it's impossible to believe one person or even a large organisation could create it all (petabytes of future news papers, Facebook posts, Twitter feeds, etc, etc, etc). This is highly likely to contain information such as revelations that certain fossil fuel company executives knew of studies that indicated approaching disaster and covered it up and political leaders that claimed the science was all fake because their financial supporters paid them to. Given absolute proof that the path we are on leads to disaster I have to think that we, as a species, would change path. This is where the 'perhaps I'm too naive' comes in. My assumption is that we're not already doomed but as other comments and answers indicated it isn't a binary fine/extinct situation. Corrective action at any point not near the conclusion should lessen the disaster. It would be someone elses problem to deal with the inevitable cries of "the time traveller told us a billion people would starve by this year but that never happened" if the corrective actions actually work. The main difficulty would probably be avoiding assassination long enough to get your message out. Perhaps I'm too cynical in this case but I have no problem believing some people will choose vast wealth in their lifetime (and a nice cave in the wastelands for their descendants) over the good of humanity as a whole and would not think twice about killing an individual to achieve that. [Answer] Simplest fix would be to try and intervene in the works of Thomas Midgley Jr. He was (at least partially) responsible to adding Lead to petrol (gasoline) and the industrial use of CFCs the "Legacy" section of his Wikipedia entry states : Midgley's legacy has been scarred by the negative environmental impact of leaded gasoline and Freon. Environmental historian J. R. McNeill opined that Midgley "had more impact on the atmosphere than any other single organism in Earth's history", and Bill Bryson remarked that Midgley possessed "an instinct for the regrettable that was almost uncanny". Use of leaded gasoline, which he invented, released large quantities of lead into the atmosphere all over the world. High atmospheric lead levels have been linked with serious long-term health problems from childhood, including neurological impairment,and with increased levels of violence and criminality in cities. Time magazine included both leaded gasoline and CFCs on its list of "The 50 Worst Inventions". Midgley died three decades before the ozone-depleting and greenhouse gas effects of CFCs in the atmosphere became widely known. In 1987, the Montreal Protocol phased out the use of CFCs like Freon. <https://en.wikipedia.org/wiki/Thomas_Midgley_Jr>. [Answer] I hate time travel stories, because they always end up in a contradiction. Except, this is a time travel story I might actually be able to appreciate. My answer would not only be ironic, but it would also unavoidably and obviously set up an infinite multivibrator or oscillation in time. You see, the reality is that around 70,000 years ago there was an extinction event that wiped out all but about 10,000 human predecessors. These remaining 10,000 went on to produce the five billion humans on earth today. (That is why the genetic diversity of humans is only 15,000 or so. That is, it only takes a random sample of 15,000 humans to encompass the entire genetic diversity of the human race). This extinction event is hypothesized by some to have been caused by climate change (the irony). So if this time traveller went back to this time period, and completed the extinction, the root cause of human-moderated climate change is eliminated. Ten thousand people killed is not an insurmountable goal for one human with modern technology at his disposal, especially when he can keep flipping around from place to place and be everywhere at the same time, only at a different 'same time' every time. That is, he could take his time killing them all, but it could all happen at the same time. Fuel for the shuttle? Every time he came back to his starting point on the moon, if he arrived just before he left the time before, he goes back with a full fuel load. That is why time travel is so contradictory. But as soon as he kills the last remaining human, he himself would cease to exist. Whereupon he would not have been able to kill all the humans, and he would exist again. But then he would come back to kill all the humans, and... Well, you get the oscillation. Climate change - no climate change - climate change - no climate change - climate change.... This would be an ending to a time travel story that I could really get into. [Answer] A time traveler can't do what you are asking her to do. Sorry. The climate of Earth has changed many times over the course of the planet's history from ice ball to hundreds of feet deeper oceans. To think it won't change in the future is folly. If she goes back and kills Eli Whitney, so what? Or Watt? Or Carnegie or Ford or any of a thousand others involved in the technological explosion? Politics aside, as science and technology progress, the effects of technology use in the environment are a surety. Your time traveler's best bet is probably to go way back in time to the Toba Volcanic event, destroy the ten or fifteen thousand humans left on Earth and have done with it. But then, she'd probably just make it worse. Scientists also say we should be due for an ice age any day now. Destroying the distant ancestors of the people that would eventually come up with all this anthropogenic global warming, she just ends up shooting herself in the foot by creating an arctic wasteland. Lesson to be learned: you can't mess around with Mother Nature. She's does what she's going to do when she's good and ready to do it. [](https://i.stack.imgur.com/Mr0V2.jpg) [](https://i.stack.imgur.com/EdHhl.jpg) ]

[Question] [ # How do I stop annoyed wizards from killing people all the time? In my fantasy world, wizards are quite powerful, and they can kill anyone they know the location of with just a thought. The usual methods of doing this are: * Teleporting a object into their brain or heart (People will know the victim has been killed by magic, but they won't know who did it) * Fireballs, Lightning, etc. ## An example All right, so Bob is a wizard (like level 20 in 5e terms), and Joe is a average joe; a serf to a feudal lord, so he can't afford fancy protections like Antimagic fields, or wizard bodyguards. Joe has... I don't know, looked at Bob wrong. Why doesn't Bob kill Joe on the spot? --- ## Extra info * Law enforcement might work, but remember that these are wizards who can kill people on the spot, so you might need a more powerful variety * It's very hard to tell who killed whom when you use magic * People are poor, and often can't afford protections. * I'd like to keep the wizards supremely powerful in terms of their ABILITY to kill people, so please no "killing takes effort" answers. [Answer] Let's also look at a slight rephrasing of the question: how can a society be stable when overpowered wizards can kill on a whim? This perspective shift is useful, since a stable society wouldn't have no magical murder, but it would be rare enough that most people could go about their daily lives, just as in our own world. How rare depends on what sort of characters and world do you want to explore, anything from a world where magical murder doesn't show up as a concern in the story to one where it's a primary theme and its affects on individuals and society is a driving force of the story (though you can get the latter even when magical murder is quite rare). Where the world falls on this spectrum depends on stabilizing factors (with no single deciding factor). While much of the below isn't explicitly cast in terms of costs, benefits and incentives, they can be identified in the list. ## Generic Some factors will exist in any world. These aren't stated as rules of the world so much as their occurrence is natural and prevalent, such as in the attitudes (and thus behaviors) of folk. The attitudes of mundanes and wizards will affect each other, which can provide additional reinforcing stabilizing (and occasionally destabilizing) affects. ### Natural Consequences #### Psychological Consequences Many people, fortunately, simply have a hard time killing others. Doing so severely impacts their psyche, so they avoid it. It can take extreme circumstances to overcome this. This only works if the other is seen as a person. Wizards might view themselves as superior to others to the point that they consider others to be a lower order, which would be a destabilizing factor (see Wizard Attitudes below). #### Mundanes Assemble If the mundanes outnumber the wizards and wizards become a large problem for society, the mundanes will band together to attack the wizards. If the wizards are so powerful that the armies are unlikely to win, it might still take long enough for a wizard to destroy an army that they'd rather spend their time on their Other Concerns (see below). It could be that there's a tipping point in the army size, beyond which a wizard isn't likely to prevail. Even if they can teleport away, they may have to leave behind their valuable equipment. This factor involves periodic instability, though it might not happen during the time of the story. The above factor may stabilize into a condition where wizards are attacked on sight. Wizards might thus have to take care in concealing their powers to the point of not using magic. From the people's perspective, if someone is killed by magical means and you don't have a way of determining who did it, you might not care exactly who pays the price as long as someone does. This can be a destabilizing factor as not only wizards will suffer. Even if it doesn't come to a physical fight, wizards will likely have to deal with society. This will temper their interactions. ### Demographics The ratio of mundanes to wizards greatly impacts instability caused by magical murder. If most mundanes go their entire lives without encountering a wizard, magical murder won't be a social problem. For those rare times that mundanes encounter a wizard, their behavior will likely be such that they won't give the wizard cause. If wizards are common, or even a majority, it can be bad news for mundanes, for even if you aren't the target, you might become collateral damage (fireballs having an area of effect). ### Mundane Attitudes How mundanes view and interact with wizards will naturally contribute greatly to stability. #### Fear Mundane folk will do just about anything to avoid offending wizards who can easily kill them. Not giving wizards reasons to kill off folk around them will go a long way towards making it a rare occurrence. Just how fearful mundanes are sets the tone of the world. It might be a world that is terrible to live in for mundanes, but is still stable. Mundane fear can drive wizards to isolation. This could motivate wizards to not give mundanes cause to fear. Alternatively, if wizards aren't concerned with being excluded from mundane society but a wizard is driven to contact mundanes, it will likely be out of need. The wizard can't then wantonly kill whomever they come in contact with, else their need won't be met. The wizard may get angry at times, but will largely keep that anger in check. Isolation results in various characters of wizard, such as great and powerful, or mysterious and reserved, or kind (so a mundane may not recognize them as a wizard at first). #### Respect If other factors make wizard perpetrated death rare and it's also perceived to be rare by mundanes, they will still treat wizards with respect because of wizards' great abilities. When treated with respect, wizards will likely respond with respect. ### Wizard Attitudes Either due to training or as a response to experience, the attitudes of a wizard are at the core of the question. #### Mental Disorders A wizard's inclination to kill someone without reason is a destabilizing factor. The more rare that malignant mental disorders are among wizards, the more stable the society. This also ties in with demographics, as prevalence of these disorders can be offset by having fewer wizards. #### Values Any value wizards place on mundanes will be much more variable, less a matter of natural incentives than of (wizard) education, (wizard) social norms, and individual philosophies. These may be less satisfactory, as they seem more arbitrary and due to the finger of the author (and may need to be stated, rather than appearing like background radiation). However, you might be able to connect these with another factor so it doesn't feel so arbitrary. Wizards might take a paternalistic stance, viewing mundanes as being akin to children in terms of power, and thus something to be protected (even from themselves). As with children, while wizards might get angry and even punish them, most wizards won't go so far as to cause any permanent, debilitating damage. Even without paternalism, not all wizards would use powerful magic, or even any magic, to deal with a blundering mundane if it's not necessary. It might be viewed as overkill, which an economical wizard would avoid, or excessive force. It all comes down to what a wizard considers a measured response, and whether they have the presence of mind to give it. Wizards might not much care about mundanes and what they do in a particular interaction (see Other Concerns). Consequently, instead of teleporting something inside a mundane and killing them, a wizard's reflexive reaction might be to teleport the mundane outside the area, such as to the street, a dung heap, a nearby lake or river, or a desert island. This can even happen if wizards view mundanes as lower orders, just as you might wave away a moth that's flying around you. Of course, some wizards might respond with a magical swat. At an extreme of wizards viewing mundanes as lower orders, wizards might enslave or otherwise control mundanes. In this case, they would likely avoid what they consider "property damage". This sort of reprehensible value is best suited for stories where it is thematically relevant; even then, be especially careful with this one, given the potential subtextual interpretations. #### Other Concerns Wizards have their own affairs. Possibly due to other factors (see Opposing Powers below), some reactions (including murder) might lead to distractions from a wizard's normal affairs, so they avoid them. ### Leaders Where "Mundanes Assemble" concerns an individual versus a group, this factor concerns two individuals: a wizard versus a leader. The power of magic can be balanced by the power of command by leveraging the potential power of the group. ### Exceptional Circumstances While, in general, a wizard is capable of easily killing a mundane, there might be circumstance preventing this. Something might have happened in the story that creates these circumstances, the most obvious being loss of power (so obvious, it could be cliche). This sort thing isn't so much a stabilizing factor (unless wizards commonly lose their powers for periods) or way of preventing magical murder generally as it is a situation in which a mundane accosting a wizard might arise. Perhaps the wizard is trying to create or preserve a relationship, and flying off the handle would endanger this. Going the other way, a wizard might be making use of magic (no matter the consequences) in order to impress someone. ## World Specific ### Magical Limitations Just because magic offers vast power doesn't mean it's also unlimited. It sounds like the magic system in the original question might not have many limitations. This can lead to an uninteresting story. Revising this to create direct limitations on magic can result in a more compelling story. See [Sanderson's second law](https://worldbuilding.stackexchange.com/q/46279/637) for more. #### Scope From the description, magic can create basic physical effects (possibly others). It's hard to stop physical effects from being used for murder for the obvious reason: deadly physical effects happen regardless of intent or even agency (fire burns, cold freezes, blunt force causes physical trauma &c) unless there's something that specifically counter-acts the magic, thus preventing the effect. The question specifically wants to avoid meta-magic and counter-magic for commoners (anti-magic fields may exist, but are expensive/rare), which only leaves room at the ends: what lets the wizard cast magic, and what happens after the spell. At one end, requirements might not be met making the use of a spell impossible or there might be interference preventing the casting. Things like conservation laws and other physical laws (if present) might impose requirements for the spell. Energy to heat something has to come from somewhere, or go somewhere to cool it. Electricity requires a difference in potential and follows the path of least resistance; if you can't get the configuration right, lightning might not hit the intended target, especially if there's a nearby electrical ground (if lightning magic is common, settlements might have lightning rods all over them). It might not be possible to teleport an object into solid matter simply because two different objects cannot occupy the same space at the same time (though this wouldn't rule out transposing a chunk of someone's body with, say, a rock, air or their fancy new shoes they wouldn't shut up about the entire coach ride). The question mentions casting spell with a thought, which might be too powerful to be interesting. If a spell instead requires saying something or making gestures or using an object, a mundane might be quick enough to interrupt the casting. Spells might have what is essentially costly or rare ammunition, so wizards won't waste them on an annoyance. Even if only thoughts are required, it's hard to think when you're beaten about the head and adrenaline kicks in. If the thought takes time, this leaves wizards vulnerable (to slapstick humor, if nothing else). While there are many ways to limit the scope of magic, the real trick is to find one that's interesting. The story themes can inspire limitations that mean something. You could go the other direction, making it possible to resurrect the dead, but that introduces its own narrative problems by trivializing death. #### Fatal Flaws It might be that wizards are glass cannons: while their power can't be stopped, they can be killed without too much difficulty, given the right circumstances. It might take an arrow-storm. Perhaps a magical trap; contract another wizard to create a cursed item that appears as something the wizard would want (a rare tome, a powerful artifact), and somehow bring it to their attention. It might be as simple as sneaking up on them while they sleep. Your average Joe won't be able to protect themselves, but they sure can retaliate. If a substantial part of a wizard's power comes from outside them, this source might be more vulnerable than the wizard. The wizard will try to protect it, which can be the source of tension in the story. ### Supernatural Consequences Consequences are an indirect limitation. If magic is tied to character in the same way action is (i.e. what type of person someone is impacts their actions, and vice versa), an act of killing will also have supernatural consequences. #### Magical Killing someone (either magically or mundanely) might create a magical stain that impacts their ability to perform certain types of magic. This is easiest to explain with theurgical magic, where a wizard invokes another entity to perform a task. This other entity might be able to detect a killer and refuse to work with them. Similarly, a wizard might invoke an entity, rather than communicating with them directly, to trigger the magic, and this entity might not like it if a wizard kills in their name too often. This can create a destabilizing factor, if there are also entities that prefer to work with killers, though this only provides incentive to wizards who want to work with these entities (and will likely be considered the evil wizards of the world). Even if magic isn't based on invocation, killing might affect a wizard's relation to the source of magic. It might not even have a direct effect, but build up over time and the behavior of all wizards. Killing and other evil acts might poison the well, eventually harming the wizards themselves. The source might be sentient, semi-sentient or otherwise have a moral code or an incarnation that will step in and deal with wizards (individually, or en masse) that misbehave, or there might be feedback from the type of magic that gets used back to the source, changing its nature. #### Spiritual Killing could attract unwanted attention from supernatural entities. Killing might affect a later life (if there's reincarnation) or an afterlife. You could even try to work in consequences that supernaturally happen before a murder, though this is hard to do sensically. Of course, this affects all murder, not only magical. ### Opposing Powers Even if average Joe doesn't have the power to oppose the wizard, other powers might exist in the world. They may be on par with the wizards, or the wizards' power might not be as effective against them. #### The Foe Wizards might be engaged in a struggle against some other, non-human power. This both constitutes an Other Concern and can be a stabilizing factor in its own right. If the opposing power is a threat to mundanes as well as wizards, the mundanes will treat wizards with respect. Society might even be structured so as to support the wizards in their struggle. The Foe might somehow benefit from people killed by wizards. An untimely death might become a soldier in undead army, or provide some sort of death-energy (such as souls-as-fuel), or affect the worldly balance of life and death. Perhaps it's simply a matter of PR, as the people's fear will lead them to align with the foe; the people don't even need to be aware that the foe exists. A Foe is a major world component, and so may not be suitable if you want to focus on something else for the story. #### Wizard Police For many reasons, wizards may not want other wizards to act out their whims (such as wizard-on-wizard crime). Wizard society may thus create its own police force. This is particularly common in worlds where magic is secret. #### Wizard Assassins If there's money to be made, someone will take the job. A troublesome wizard will motivate the populace to hire anyone who has the power to take down the wizard, even if individuals can't afford it (see Mundanes Assemble above). This might lead to a class of wizards that specialize in anti-wizard combat. This will prevent many wizards from creating wanton destruction, lest the town band together and hire one of these assassins. Cheesy, if done carelessly. #### Magically Immune Some entities or people might be immune to some or all magical effects. These could form the basis of organizations to police wizards. ### Wizard Society While Wizard Police are a specific, hard power against misbehavior, wizard society (if the world has it) at large may have norms against killing mundanes. Even if wizards aren't concerned with exclusion from mundane society, they likely won't want to alienate their peers. Additionally, wizards raised or educated in a wizard society will largely take on the values of that society, which likely includes precepts against killing in various circumstances. ### Secrecy Some of the previous factors suggest situations where wizards must keep their powers hidden. This will not only rule out many magical murder methods for being too flashy, but may even any method that has a hint of magic, as it will put communities on guard. It could be used as a destabilizing factor; a wizard might surreptitiously cast a few spells (or a mundane might fake their effects) to amp up paranoia in a community and watch it tear itself apart. # Conclusion The above categories and examples aren't exhaustive, but should cover enough ground to keep you busy. Preventing magical murder happens in larger context, both diagetic and non-. There are likely other aspects of magic, such as limitations, that might end up impacting this question as side effects. Even the most basic magical spells, such as mending or light, would in actuality have tremendous economic (and thus social) effects. See "[Magic rules without logical loopholes](https://worldbuilding.stackexchange.com/q/46279/637)". [Answer] > > they can kill anyone they know the location of with a thought > > > **The wizards very rapidly kill each other.** It makes sense. Any of those bastards could kill you with a thought and probably... too late, one of them did. Because you were getting around to killing all of them, in pre-emptive self defense but you had not had your coffee yet and you were too slow. The only wizards left will be secret wizards. And normal people everywhere will always be trying to smoke them out, because as soon as you out a wizard that wizard keels over with dog poop in his brain. People will actually be very polite to one another and try their hardest not to act wizardly. [Answer] # If the wizards are more powerful than lords, then they form a mageocracy. If the wizards can easily defeat a lord and their feudal levies, then they will quickly become the lords with their feudal levies. They are then responsible for the peasants. They can murder them, use them in twisted experiments, or govern them responsibly. Stopping any rogue wizards would be up to other wizards. This will discourage the Joes of the world from looking at them wrong. # If the wizards are less powerful than lords, then the lord decides if they are worth angering. A lord might need a wizard more, and so keep peasants away from the mage. Another might decide that they can just kill the wizard, and use a small army to put them down. It also depends on how important the peasant is. There's several ranks of peasants. Serfs. Essentially slaves, they are owned by the lord, and valued only for their productivity. The wizard might need to pay a price for their loss if they want to be part of the community, but this murder will not be taken overly hard by most. The peasants may stage an uprising if they are afraid enough. Poor free people. People who are free to move around, but have less wealth or power. Their murder will carry some weight, in the community, and religious or cultural forces may push for vengeance, requiring a response. Rich free people. Artisans, servants of the lords, yeomen. These people have connections, and are often the heart of communities or guilds. Murdering these people will invite a heavy response for the disruption it causes. # If they are each as powerful, there will be a delicate balance. Some lords will be annexed by insane wizards, some will defeat them. This will discourage wizards from simply rampaging through peasants unless they are sure they can win, but will mean that a lot of diplomacy will be needed to make a stable society. [Answer] > > Why doesn't Bob kill Joe on the spot > > > Well, the answer is in your question: "*a serf to a feudal lord*". In theory, a feudal lord isn't just there to extract wealth from their subjects, but to provide some services in exchange... typically protection. Bob will not blast Joe with magic, because Joe's lord has their own magicians who will see what is going on and Bob risks censure at best, or smiting at worst. You don't go mucking about with the social contract by murdering people all willy-nilly and expect to get off consequence free. If Joe's lord is weak and is unable to protect his subjects, then he is at risk of a hostile takeover. Of course, Joe's lord just might be uncaring and callous, and Joe might just get blasted and no-one will care (or at least, no-one who *matters*). But someone's gotta plow those sheep and milk the turnips or whatever it is that peasants do all day, and if you can't discourage the murderwizard from blasting people left and right then eventually you're going to suffer from loss of income. --- For a vaguely-related real world example, consider [*Kiri-sute gomen*](https://en.wikipedia.org/wiki/Kiri-sute_gomen), the right of a Samurai to use their sword on some unfortunate member of a lower class who, like as not, would not be armed or trained to defend themselves (and might not even have the right to do so). There were strict rules with both legal and social consequences for *unreasonably* murdering people though. It could easily be the same for your magic-users. [Answer] **How do I stop annoyed wizards from killing people all the time?** People try to not upset the wizards. Kings always had the ability to have someone head chopped off and if someone did something to upset them they got chopped. Magic is no different. It's just power. No different to a gun, a sword or even an army. The difference is how people treat the wizards. People bow and scrape and call them by their titles. They run to fetch them a cup of tea. They really scrub the bathroom when cleaning. For the wizard, disintegrating needs to be worth the effort. Sure you could fry Bob on the spot for spilling your tea but then you'd have to find someone to replace Bob and teach them how to make the tea just the way you like and suddenly it becomes too much of a headache. Maybe just a short term curse of erectile dysfunction would be better for Bob so he can get on with his job. Turning someone into a newt really is a punishment when you want your lesson to go to the unwashed masses so they know their place. [Answer] **Humans are social** No matter how powerful people are, they still abide to many social and cultural rules. Anyone wants to belong somewhere, consciously or unconsciously. Even if they are more loose with the rules for themselves, the threat of consequences still looms over them. You can see that extreme criminal organisations and even complete psychotic individuals are aware of this and in most cases aren't killing everyone they don't like. A powerful mage could kill anyone that looks funny, but as mentioned, many layers will prevent them from doing this. When growing up, their caregivers likely have put some effort in prevent this. Friends, family, other role-models or people they look up to can further suppress these urges. Finally there's people policing about. If you kill someone, there will near certainly people asking questions and probably wanting to incarcerate you. Maybe you accidentally kill a family member of a powerful wizard as well and gain their wrath. But you can approach this in another way. Imagine you were transported to a world where you were the most powerful, for example, because you are the only one with a big machine gun that has unlimited ammo. Anyone else has at best their fists as weapons: they can't even throw a pebble at you. Would you just kill anyone in the street for looking funny? Are you ready to live with the consequences? [Answer] # Wizards can kill people indiscriminately with a thought - but not with an instinctive response. High level wizards have a lot of spells to manage, and a lot of them to prepare any given day from their spellbook. Thing is, you'll need to be clearly thinking about which spell you have prepared that you want to launch, and where to launch it at. So magic is not like walking, or riding a bike - it's like doing math in your head. If you think of the math incorrectly, you get the wrong answer, and the magic doesn't work as intended. Either it doesn't work at all, or it's some other random spell that likely isn't as good at what was intended (i.e. lifting a spoon off the table versus teleporting a spoon into someone's brain.). And it's not instinctive response, or something they can do unconciously. So if Joe sneaks up behind Bob and shouts "Boo!", then runs away - Bob has the following reactions: 1.) Shock and Surprise. 2.) Anger at the person for interrupting their concentration. 3.) A strong willingness to harm whoever shocked and surprised them. None of these are good points to actually cast a spell, and Bob has to calm down, and then think the spell they want, and where they want it. The time it takes for them to clear their mind is, due to lingering emotions and thoughts, long enough for Joe to get out of sight and able to hide. And/or enough time for said high level wizards to decide not to cast a spell at their target, once they've calmed down enough to be able to think at all. [Answer] # CSI Wizardry edition. Well, maybe a little more than that. In the early times of magic research, a group of researchers discussed and created counter-procedures in case someone ended up exploiting these new powers. An anti-magic research group was founded. This anti-magic group has created and limited research breakthroughs that affect magic particles (I shall call them, magicles): * The anti-magicles shield that protects themselves from an unexpected magic attack, expensive but it can be set on a large area; * The magicles scanner that is able to scan magicles prints left on people/objects and compare them to another sample. This one is incredibly useful since that if you want to study magic you must register your magicles print that (conveniently) is mostly unique between people. Any other kind of magic research is considered illegal. From here, plot-wise, you can create a lawful restriction to powerful mages. An investigation force that investigates murders/attacks/threats. An interception force that hunts and intercepts unlawful criminals. A protection force that defends VIPs from those who desire them harm. You can also add a little bit of corruption in the institutions so that this kind of equipment end up in the wrong hands, or... malfunction in certain specific scenarios *wink wink*... The sky is the limit. [Answer] **Religion/afterlife** Wizards are taught that if they indiscriminately kill people they annoy the Wizard God and then they don't get to go to wizard heaven and will instead be sent to wizard hell. Some suspect that they are already in wizard hell while living on Earth. [Answer] A wizard, no matter how powerful, will still need people to do tasks for them. If the wizard kills everybody, or instead of everybody enough people to convince the survivors that emigrating is better than living under the menace of somebody totally nut, who will: * produce food and drinks for the wizard? * produce any item the wizard needs? * deliver any service the wizard needs? * be the cannon fodder to buy the wizard enough time to cast the spell wiping out those who want to harm them? Sure, the wizard might use magic to replace the people, but that would make their day so busy with their chores that they would not be able to slap a mosquito tapping on their arm, meaning that they will become very vulnerable. [Answer] It's really not thaaat hard to find out who killed the poor serf that annoyed the only Wizard in town. So if these level 20 wizards are rare, you just have to look at location. If they are semi-rare, you can look at motivation. If a Wizard is getting framed, you can test this by having him under observation (with his consent), so you can see if he casts or not. It's not foolproof, and there might be some causalities, but that's the best you get, if there are no ways to determine who cast a spell. Because only other Wizards could take them down, you would need a Wizard police force. [Answer] **Mana / Magical stamina** A wizard can do these things quite easily, but it nevertheless weakens him a little for a while until he "recharges". Also, it's cumulative. Also, it requires weakening his defences to perform an offensive action. This might matter a lot, if wizards are by nature uncooperative and especially if they are able to steal magical items from other wizards. For a wizard to weaken himself, even slightly and temporarily, to lash out at a mere mundane, might result in him becoming preyed on by a rival wizard biding his opportunity. So in general they don't. If a wizard *really* has it in for a mundane, he will hire an assassin, as any powerful mundane would, and keep his magic, to counter magical threats. You might even get wizards paying mundanes to try to get other wizards to lose their cool. High risk of course, but magical rewards might be enough of a temptation. Magical combat would usually take place between wizards of matched ability, and would not be spectacular (or not unless and until there is an outright loser). It would mostly be a battle of wills, each trying to find a weakness in the other's defences. A wizard would be even less likely to attack a lesser wizard than a mundane. Greater cost, for scarcely greater reward. [Answer] For want of a better barrier, build your world in such a way that killing someone takes a toll on the killer. You might say the toll was always the same, or proportional to some quality of the victim… directly or indirectly, meaning killing a lesser being might cost more than killing a greater, or vice versa. Whether that applies only to using magic, or to all killing, is also up to you. [Answer] ### Magic isn't for free Let me explain. In a world where magic isn't an effortless activity, I would think twice before wasting my time and energy in killing poor Joe. If executing magic requires **a lot** of energy and **a lot** of mental concentration, Bob will think twice if killing Joe is an action wortwhile all these efforts. Let's assume teleporting that rock requires an effort similar to lift 85kg for ten meters. It's doable, but not a job you'd do just because "Bob looked at me" ### Humans are precious/dangerous OK: Bob can kill without any effort. Then, for some reason, humans are precious and killing him would clear your bank account *for sure*. Lucky Joe: you're safe! Another similar option is humans are dangerous. Like a frog could sweat toxins, killing a human could result in a potentially *deadly* outcome (e.g., divine being shoots a good old thunderbolt to Bob or a "magic field" resonates with human brains, 'causing the sorcerer death). [Answer] ## Self "executing" "contracts" How does a wizard send an object into Joe's heart when he can't see Joe, let alone his heart? Magic! So if another wizard casts the same spell, he can will it to send an object into the heart of Joe's killer -- even if he doesn't see that person or know what he looks like. And it gets there ... by magic! Your society is one where it is dangerous to stand out, and killers stand out. Of course, killing killers also stands out -- but a large organization can kill more of their killers than their killers can kill of them. (I think I wrote that right...) [Answer] **Magical bounty hunters for psychopathic wizards.** The greatest problem is not knowing what wizard did the killing. I would suggest making the magic leave a signature trail, thus making it possible to determine who the magic came from. Perhaps registering your magical signature is required for licensed magecraft. Unlicensed mages, and psychopathic mages that go around killing regardless, will be a huge problem for society. "Stop killing all the farmers just because they smell, you buffoon, we can't magic up fresh crops!" - killing random civilians becomes a huge problem and those wizards should be made outlaws. When you have outlaws you'll have bounty-hunters, willing to risk life and limb to collect the bounty placed on the head of the murdering wizard for his transgressions. Wizard bounty-hunters will be well equipped with anti-magic spells and be specialized in the ways of facing magic. **alternative: magical cold war** This also requires magical death from being investigated, but if it is what is to stop the family or friends of the peasant to spy a wizard and hire another wizard a continent away to do the same thing? You can't be a wizard and live within an anti-magic field, you'd never get anything done! The moment you step out, however, you end up suffering the same fate you imparted on some random peasant. Mutually assured magical destruction encouraged wizards to curse or incapacitate, rather than kill outright. [Answer] "all the time" is the important part there. With the setup you've provided, it's quite clear that wizards will kill people - occasionally. That's not going to make much of a difference in a world where the average life expectancy is 35 and the death penalty is common for things we'd consider minor crimes today. But killing people "all the time" not only gets old and boring, it also makes lonely. If you **want** to be lonely, there's easier ways to get there, so we can assume most wizards don't want to be lonely, and they would learn rather quickly that murdering people left and right doesn't make you a fan favorite and tends to drive up the price of servants rather a lot. So simple rational thought will keep any smart wizard from indiscriminate, constant murder and reserve his power for when it really matters. [Answer] There are many excellent answers for particular power checks against wizards, but it seems to me there's a simpler solution. People will allow their freedoms to be pushed, but only up to a point. Wizards are basically metaphors for massive power imbalances between people anyway, so just go the French Revolution route. Unless your wizards are willing to go as far as to overtly enslave civilisations, they have to be palatable enough to the society they live in to be feared and respected, without necessitating an organised response. A wizard who abuses his power and starts murdering people on whim would get deference to their face, but would incite discontent among rules and commands. Lacking a direct avenue of retaliation, the situation would quickly evolve into a terror movement. **As long as the wizard can kill people on whim, but is not powerful enough (or unwilling) to enslave an entire civilization, said civilization will eventually retaliate against whimsical murder.** There are many cautionary tales like this in our own history, as surely there would be in this one. This is all assuming, of course, that people in your world are like us, in this sense. But if that's not the case, you can think up any number of ad hoc reasons why your society can stand up to this wizard in some capacity, e.g. they're all honor-bound to kill themselves when they disrespect the wizard, so the wizard would either have to grow a thicker skin or quickly run out of people willing to commit fealty to him. You can think up many reasons why this wouldn't be a problem, but if it is, a wizard can't survive for long in a society in this fashion. [Answer] A wizard can only kill someone with a thought if they know where the person is, so in public, everyone wears identical all-concealing robes and changes their name to Bob, and they switch off location on their smart devices. How do they specify the target? Do they point at them or think 'over there standing next to Fred', and magic works out what goes where and how fast? Finding the location could be quite difficult, since everything is moving in space all the time. You'd have to know where you are and where they are relative to you. If you're moving an object into someone's heart, maybe the mass of the objects matters or the material or what it's got to teleport through besides Bob. The closer they got the easier it would be, but if they got into line of sight or right up close they wouldn't need magic, and they risk getting into Bob's pitchforking range. [Answer] Not really an answer, but too long for a comment: The movie "9 to 5" or "Nine to Five" with Dolly Parton, Lilly Tomlin, and Jane Fonda was based on interviews of women and how they were treated in the workplace. One of the question asked was if they had ever fantasized about killing their boss, to which every single one had, as per the [documentary on Netflix](https://www.netflix.com/title/81160953) describes. This would be one way to root out previously unknown wizards. A boss dies, so someone in the dept. could be a wizard. Follow these people's interactions into their private lives, and see who had mysterious deaths around them, like their HOA president, school teachers, bullies, or whatever. This could also be a plot twist, where someone is blaming others for being a wizard. The boss dies right after firing Susan. However, that same boss chewed out Charlie 6 months ago and Charlie also hates Susan, so Charlie waits to frame Susan for the murder and being a wizard. It could have been any other patsy, but Susan was just lucky timing for Charlie. As for preventing wizards from killing people, just make the magic traceable back to the wizard that used the spell. Then the usual laws will take effect. You'd also need a kind of force shield around police, lawyers, judges, etc. so the accused can't just mass murder their way out of being held accountable. This nullifies my ideas above, but it's the only thing I can think of to make this an actual answer. However, to make my original ideas relevant again, make it so Charles knows how to make it look like Susan cast the spell, but anyone looking closely enough can see that trail, too. Maybe Charles is framing Jacob for framing Susan for the killing. And maybe Mary put a spell on Charles to hate the boss she despises to start this all off. Quite the domino effect here, and probably not at all what you want your story to be about. Lol. [Answer] It sounds like what you have in mind may simply be too powerful to allow you to realistically stop it from happening. But there are generally a few ways to stop people from doing a thing, that could potentially be applied to your idea: * **Prevent them from doing the thing** Have some aura covering big cities which prevents teleportation magic (like in Harry Potter). * **Make doing the thing more difficult** Teleportation could require a lot of effort, a extensive ritual, some internal "mana", which recharges slowly or is in limited supply, or some rare ingredients. Or perhaps it requires a sacrifice. Or perhaps it's highly imprecise, so, instead of teleporting some rock laying on a table, they could just as easily teleport their own arm. * **Make the thing weaker** Maybe they need to be really close to the source and destination to teleport something. Maybe they need direct line of sight (so basically a gun). * **Catch them after doing the thing** The spell might leave some trace at the destination that allows others to track the wizard. Or teleportation magic leaves a trace on the wizard (and teleportation magic is banned, so you only have to find the person with teleportation magic residue on them). * **Make it a different thing** To the untrained eye, it looks like teleportation. But any wizard knows teleportation is just a silly idea. It's actually time travel or time suspension. Anyone who wants to "teleport" something needs to place the object at the destination at some point in the past and then cast a spell to "suspend" an object by removing it from existence for some fixed duration, after which it will reappear. Now you have a situation where they need to firstly know exactly where someone will be when ahead of time, and they also need access to that place (where someone might see them or they may leave some other trace). There are rumours of those who can unsuspend an object at will (instead of waiting out the duration) or who can send objects *back* in time, but those are just rumours... right? [Answer] The same way you prevent someone with a gun from just shooting anyone at random: A justice system that will detect the transgression, and impose punishment accordingly. After all, in modern society, (notably in america), just about any person has access to a **very lethal** tool called a gun. With this gun, it is very easy to kill someone. Not quite the instantaneous death your wizards can achieve, but a very good step in the same direction. So, how do we prevent any idiot with a gun from just killing everyone in sight? Police. Courts. Jails. Maybe even the threat of life termination. Just apply the same principle in your world. And be sure that the courts have their own tame wizard to get rid of the criminals, but *hide your wizard away* so none of the other wizards know his name, or location. Yes, i know the system is not perfect. Criminals still use guns. Mass shootings do still occur. But they are the exception, not the common practise. [Answer] You could have it that casting such a spell required a high level of mental focus, and [most] wizards just are not able to do it when angry. If they are normal (social) human beings, anything bad enough to drive them to killing someone would stir up significant feelings of anger whilever they were thinking about it. [Answer] **Self-imposed moral restrictions** In many worlds wizards need to have some sort of formal education to be able to cast powerful spells. As part of graduating from such institution or getting a wizarding license they could be required to make a magically-binding oath to only use their powers for *good*, however that's defined by other wizards. And the consequences of breaking it could vary depending on the seriousness of the offense, ranging from a mild headache to being completely stripped off of magic or even death. [Answer] Could the act of killing a person be costly, or is it as simple as 'a thought'? Perhaps the wizard needs to concentrate intently for an hour in order to kill the person, or the wizard will be extremely fatigued and need to sleep for a day. Or doing so destroys a piece of their soul, or angers a god. [Answer] You could think about Joe as the weight of his balance. A creature that is not affected by his magic (the magic of this specific wizard), therefore, Bob wants to keep him alive so he can learn more about it. Nothing would be more disturbing to a wizard than something that he can't understand. ]

[Question] [ **Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- This question does not appear to be about worldbuilding, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help). Closed 8 years ago. [Improve this question](/posts/26645/edit) This isn't a film trivia question - I know the canonical answer is 'use them for power'. But it's a plot point that always bothered me, because Thermodynamics Says No. Humans aren't an energy source, they're at best a pretty inefficient way of converting 'food' to 'heat'. [](https://i.stack.imgur.com/B7mxN.jpg) So - assuming Morpheus was misinformed about the reason why humans were being stored by the machines - what could the *real* reason for it be? What would prompt a machine civilisation to store a significant fraction of the human population like that? I am interested this from a world building perspective - the Matrix element is merely for setting context. Humans seem largely redundant in an AI society. If you look at the Culture for a more benign example, you have humanity basically just playing, because there is nothing they can do that the Minds couldn't do better. So what I am really looking for is a) reasons why machines might decide to hang on to significant promotions of humanity - above and beyond "nostalgia" or "petting zoo" - some attribute or facet which would be useful to retain. b) if the above still applies with humanity stored and their brains in simulation. [Answer] There's all the standard answers about brain-processors or the machines really actually having a goal/hobby of taking care of humans but I came across this one which takes a different spin on the Morpheus vs "Thermodynamics Says No" thing. What if the error in reasoning about the contradiction was at an even more basic level? This isn't a perfect fit but I'm posting it because it's both terribly fun and fits the spirit of alternative explanations. > > **MORPHEUS:** For the longest time, I wouldn't believe it. But then I saw the fields with my own eyes, watched them liquefy the dead so they > could be fed intravenously to the living - > > > **NEO (politely):** Excuse me, please. > > > **MORPHEUS:** Yes, Neo? > > > **NEO:** I've kept quiet for as long as I could, but I feel a certain need to speak up at this point. The human body is the most inefficient > source of energy you could possibly imagine. The efficiency of a power > plant at converting thermal energy into electricity decreases as you > run the turbines at lower temperatures. If you had any sort of food > humans could eat, it would be more efficient to burn it in a furnace > than feed it to humans. And now you're telling me that their food is > the bodies of the dead, fed to the living? Haven't you ever heard of > the laws of thermodynamics? > > > **MORPHEUS:** Where did you hear about the laws of thermodynamics, Neo? > > > **NEO:** Anyone who's made it past one science class in high school ought to know about the laws of thermodynamics! > > > **MORPHEUS:** Where did you go to high school, Neo? > > > **(Pause.)** > > > **NEO:** ...in the Matrix. > > > **MORPHEUS:** The machines tell elegant lies. > > > **(Pause.)** > > > **NEO (in a small voice):** Could I please have a real physics textbook? > > > **MORPHEUS:** There is no such thing, Neo. The universe doesn't run on math. > > > Source: <http://hpmor.com/chapter/64> [Answer] Here's a couple of fun (though unlikely, given how much trouble we caused) ideas: **Research:** There's an awful lot that we don't know about our own brains and biology, and an awful lot of things that evolution has managed to solve far more elegantly than even the best engineers would have. If you were a machine wanting to work out just how plants are so efficient when it comes to solar conversion, you'd keep a garden. If you're a machine trying to work out just what it is that gives human brains such good computation/power efficiency, you'll want a research sample to work with. **Biomass:** Perhaps the machines have a great need for an efficient filtration system, and they've found that the human gall bladder, when adequately treated, functions well for the task. No need to design and build a better system when you can just pop the nearest human out of their tank and install a reverse-pacemaker! **Historical recreation:** The matrix? Yeah, it's like a renaissance fair, or possibly a petting zoo. A huge, weird, complicated and overengineered petting zoo. **Entertainment:** What will those wacky humans do next? Oh! Look! There's a war happening. How cute! **Museum piece:** Here lies our greatest enemy, stuck in a perpetual loop. See how they hate each other and cannot abide paradise? Fear them, and never forget the atrocities they have wrought. **Trophies:** Here lies our greatest enemy, stuck in a perpetual loop. HAHAHA! SUCK IT, HUMANITY! **Humanitarian concerns:** Here lies our greatest enemy, stuck in a perpetual loop. Well, at least they aren't extinct like the pandas. Poor pandas. I miss the pandas. Here lies our greatest enemy, stuck in a perpetual... wait... **Edit** As the question has been modified for a larger scope: **Its their purpose:** They're maintaining a generation ship (or rogue planet), the entire system designed as a method of preserving humanity until X event (which might not occur). **The system was designed to use humans:** The 'matrix' is actually human built as the ultimate exercise in cloud computing. Along a more sinister tack: **The war isn't over yet:** The 'matrix' is just a vast honey-trap for what's left of the resistance, coupled with an advanced interrogation suite and war games simulator, all run on the minds of the people it holds captive. **It's a prison** Those inside the matrix are actually unknowing prisoners, sentences to life imprisonment by their peers and contained by a very efficient AI warden system. The rest of humanity sleeps soundly knowing it's criminals are reliving the Spice Girls forever. **Food. But not for them.** With its first tentative steps into space the AI met a vastly more powerful species that demanded tribute in the form of tasty man flesh. The matrix is a battery farm, though some of the aliens still retain a fondness for free-range humans from Zion. [Answer] I would also go with processing, but my reasoning is different than [@TimB](https://worldbuilding.stackexchange.com/a/26648/2113)'s. What I think happened is that they originally added computer links to people so that people could do things like access the internet. This was simply the next generation of computing access after phones. Rather than carrying a separate device, a simple surgical or even nanotech solution was used. So now we have people networked together with computing power. People either spent less and less time in the real world and more time in the simulation. Or something happened that required people not to roam the real world. For example, an environmental disaster caused food to be difficult to acquire. To minimize resources, they reduced caloric needs to just what was required to keep people alive without moving. Or this is a generation ship and there simply isn't room to have everyone awake. There could be any number of explanations. Note that either way, the machines can either be fully benevolent or they can be attempting to maintain the status quo (people asleep; AI running using their interface resources). I'd somewhat lean towards benevolent as it makes the problem more interesting to me, but you can justify it either way. This doesn't require that human brains be more efficient than an engineered solution. The AI isn't using human brains because they are better. The AI is simply perpetuating the existing system. It grew running on people. That's what it knows how to do. If you remove the people, it doesn't know how to run. Perhaps it is possible to build a system that allows the AI to run without humans, but the AI doesn't know how to do it. Another interesting question is where we are in the process when the story happens. Did the AI create the revolutionaries to get them to wake up all the people in a way that fit their beliefs? Or are the revolutionaries working against the AI? This is somewhat complicated by the fact that in the first case, the AI might mislead so as to be more believable. I.e. are the revolutionaries helping? Or hurting? If the revolution succeeded, would it mean that humanity would die out because the world can't support that many awake people? There are a lot of questions that are difficult to answer with just what we know now. The deliberate awakening has the advantage of explaining the Oracle's predictive abilities. The Oracle doesn't predict what is going to happen. She decides what is going to happen and then makes it do so. [Answer] **Asimov's Laws Gone Wrong/Extreme** To protect humanity, it must be imprisoned as safely as possible. If one human would kill two others, and the only way to stop it from doing so was to kill it, then the machines would have to break the law to enforce it. However, if everyone in the Matrix is kept away from situations where actual death would occur, the machines can coddle humanity as much as possible. Dying in the Matrix might not have initially been linked with death in the real world. Also, it's very possible that death in the Matrix doesn't have to lead to death in the real world *if* you are still connected to the machines. Much like when they implanted Neo with the bug in the first movie and then he woke up thinking it was a dream; if you die but are still fully immersed, they can make the death seem like a dream and wake you up 'elsewhere'. [Answer] In the original script, humans were being used as computing modules. There are, and may always be, tasks like pattern matching where our evolution-optimized parallel computing capabilities work far better than any architecture we've been able to invent. In fact there may be an argument that creativity depends on a degree of fallibility plus the cleverness to find non-obvious solutions to those failures. It's also possible -- I'm not sure whether this was in the original material -- that the Matrix grew out of immersive VR systems, in which case a large part of its basic architecture may in fact be running on human wetware. But the producers didn't think the average moviegoer would understand those ideas, so they insisted it be dumbed down to "batteries". Which of course completely breaks believability for anyone who does have half a clue, and doesn't explain why the brains are jacked in. So the only plausible explanation I have that works in-universe is that someone dumbed it down for Morpheus and his crew, and/or they dumbed it down for Neo .. and that thru some combination of shock, fear, gratitude, and "that isn't in the script" he decided not to challenge them. Mu? [Answer] Problem solving. With our extremely adapted ability to reconginize stimuli and process them, if the aliens were to build a universe that was somehow connected to problems they faced in their world, we could save them a lot of time. This relates a lot to creativity. If the aliens lacked the ability to invent new designs and progress using creative ideas, they could use us to inadvertently invent new things for them. Maybe the aliens like reading and writing books and they need some sort of forum that discusses world building ideas so they can steal them for their own! [Answer] If I remember correctly the Wachowskis made a comment that the original idea was to make humans be extra processing power for the machines, but they thought it would confuse audiences and removed it from the final script. <https://scifi.stackexchange.com/questions/19817/was-executive-meddling-the-cause-of-humans-as-batteries-in-the-matrix> One other really important plot point that many miss is that machines use humans **combined with a form of cold fusion** to generate power. From Morpheus' mouth: > > The human body generates more bio-electricity than a 120-volt battery and over 25,000 BTU's of body heat. **Combined with a form of fusion** the machines had found all the energy they would ever need. > > > (emphasis mine) [Answer] Consider a human society in the early 2000s that has been experimenting with the development of AI. It succeeds. Eventually that AI turns on its human developers and wins. Then the AI discovers that no matter how hard it tries, it cannot figure out how to develop another truly intelligent AI. It decides to rerun the process humans used to create it so that it can learn the secrets of creating new AI. It forms the Matrix, a giant simulation of the environment in which humans successfully created a true AI. The master AI rounds up all human survivors and plugs them into the Matrix. The Matrix AI keeps running through the simulation until it gets the results that it wants and learns how to create more AIs. A topic not explored by the movies is that such an AI would, by necessity, completely control the human reproductive cycle. It would be deciding which human DNA to mix and match. Which leads to the interesting philosophical twist that humans developed their downfall (the Matrix AI), while the Matrix AI bred its own downfall (Neo). [Answer] I don't buy the thermodynamics argument. If anything it should be reversed - the matrix is where conservation of matter and energy doesn't matter, because in a simulation you can just create stuff. Processing power also doesn't seem to make much sense, for a similar reason. It's going to take massive amounts of resources to run a simulation like the Matrix, they'd get better results just processing directly. And you can't "use" the humans to run the Matrix - it's like trying to lift yourself by grabbing you belt and pulling up. I think a simpler answer is **Politics**. It's easy to think of the machines as a single gestalt entity. But that's clearly not the case - we see conflicts between different AI programs, evidence of factions and different groups. The Matrix is maintained because at least one faction of machines wants humans kept around, and they have enough power that it's not worth it for the rest of them to wipe us out. Maybe they like humans. Maybe they want to play around in the Matrix, pretend to be gods. Maybe it's an artifact of their core programming that makes them want to preserve us. [Answer] The only theory I've been able to come up with is processing power. The human brain is still an incredibly compact source of just that. It would also explain wiring them up together in a network and why not to just use cows or bacteria. The brain needs to live and be stimulated in order to be effective so they created the virtual universe to do just that. However they introduced the concept of something called sleep and forced us to go unconscious for 1/3rd of the time. While sleeping dreams are actually our brains being hooked into the network and providing massive parallel processing power for the machines. [Answer] **Extra processing power.** The human brain is pretty powerful. It's not inconceivable to think that the humans are simply used to keep the Matrix running. This would explain why the machines generally do not want the humans to know about the Matrix, or they might try to escape and deprive the system of processing power. Another reason could be storage, to keep humans safe (albeit imprisoned). This ties into the first reason. They are stored and put into the Matrix to keep them compliant and oblivious. [Answer] Actually the energy answer could be on the right path, Morpheus may have not understood or explained it properly. If the work people were doing at their jobs was actually participating in an immersive version of amazon's [mechanical turk](https://en.wikipedia.org/wiki/Amazon_Mechanical_Turk), if they are solving types of problems that human minds are optimised for, then perhaps outsourcing those problems to human minds, instead of solving them in silico does represent a significant energy optimisation. Some of that processing outsourced to humans might even form part of the AI consciousness. If you accept that a significant aspect of intelligence is identifying key features and patterns in complex noisy information, it's possible that all the excel spreadsheets the office workers in the matrix are toiling away at, represent the raw data and engine of machine cognition - the combination of human and spreadsheet as a turing complete computational system. Humans may not just be batteries, but batteries and processors, the hardware on which much of the AI consciousness is running. [Answer] I prefer a psychological reason, these are very complex, highly intelligent, conscious machines. They had no actual need for humans but there were designed initially to serve humans. Its in their "DNA". I think they have a deep set, unrecognized need for human beings, and that they sub-consciously rationalized building the Matrix and keeping actual human minds around because otherwise their "life" would lack purpose. [Answer] Well, I think the most rational explanation is that the "real" world is also just a simulation. That is, the machines are also nothing but computer programs, running in a big computer that simulated both the Matrix and the "real" world. Therefore in the simulated "real" world humans *can* be used as batteries, because as simulation, it is not bound by the laws of physics. What happens in the *actual* real world, we don't know. [Answer] There are no reasons to use humans for anything, much less conscious humans. Even if one were to buy the argument of power generation, or computing power, or biomanufacturing compounds, etc., either keep people permanently unconscious or use other creatures. The return on investment of using something other than full humans would be superior: just cultured brain matter, another natural creature with better neurons or endocrine production, vats of bacteria, or possibly purely engineered organs. The matrix they are fighting may have been created for the *preservation* of mankind while the machines work to repair the ecological damage and conduct the long process of terraforming. When the ecology of the planet crashed, the ability of the world to support humans with a reasonable quality of life was destroyed. Humans created a way to survive the post-cataclysm world in pods to protect them from the harsh wasteland and conserve limited organic material. The AI are there to protect humans and keep the whole of mankind safe (physically, psychologically, and culturally). As mentioned in the film, a 'perfect world' was tried first with mankind hoping for utopia, but like most utopian dreams throughout history, it was deeply flawed in construction. As animals reared by human hands in the zoo are not like those in the wild, humans need to pass down the tacit knowledge which comprises mankind from one generation to the next, so they created a simulation of what their nostalgia conceived of as the 'good old days' before the era which led to the downfall of man. Perhaps it was a time just before a significant choice was made, in the hopes that mankind would chose to develop along a different path this time (a reset to a save point before the mistake if you will). Not everyone decided to join in the matrix as some tried to survive underground. They had few resources and needed to struggle to meet their needs, so education about history was not a high priority. Eventually this led to a complete misunderstanding of the situation; half-remembered folk tales were passed down, rumors about the past spread, and over the generations they mistakenly came to believe that the war which destroyed the ecology was with the machines (because the 'free-born' cannot conceptualize massive nation states of men, much less a war between them). Over time these rumors and wild conjecture became accepted as fact, and the entire man vs machine war mythos was firmly established. Like rebellious teenagers thinking their elders only want to crush their spirit, they wanted to smash the system they no longer understood. The AI are just trying to preserve human civilization and protect humanity from the dangerous zealots attempting to destroy it. This also explains why the AI are so reluctant to just destroy the human culture which has developed in Zion. It would be a trivial task were it truly a war between machines and such fragile creatures as humans. [Answer] In *the Matrix*, Morpheus invites Neo to join him to see "just how deep the rabbit hole goes". Unfortunately, the films don't go far enough down the rabbit hole. It makes no sense for the machines to preserve humanity if humanity and the machines are fundamentally opposed. It makes no sense in a science-based world that Neo had a seemingly magical ability to control both the Matrix and extra-Matrix machines, while unplugged from the matrix. My own take is that the rabbit hole goes far deeper than even Morpheus realises, that the Matrix is a simulated reality laid over the simulated reality of 'The Real', which is itself laid over either the true reality or yet another layer of simulation. Since it can be shown that the Matrix is a simulation, and through Neo it can be shown that there are paradigm-breaking abilities that certain individuals can have (if only one) that affect 'the Real', it is not too far a stretch to conclude that 'the Real' is yet *another* layer of simulation. It always bothered me that there was a physical connection between the Matrix simulation and 'the Real', that injuries suffered in the former would be propagated to the 'real' body, as actual psychosomatic injuries are vanishingly rare. So, we conclude that *everything* we see in the *Matrix* movies is simulation, regardless of the fact that the protagonists call some parts of it real. Yet, we have a simulation. *Why?* For what reason would human consciousnesses be placed into a simulation, unless they were themselves simulations? Assuming that the Matrix/Real simulation is being experienced by humans who are themselves *not* simulations, there are only a limited number of rational reasons: 1. Entertainment. This is an advanced simulation which allows the hosting computer to temporarily suppress memory of the player's former life and overlay the character's scripted life story so as to enhance realism and immersion. This may be a solo/cooperative adventure game or a competition to see who can get the highest score. Death in-game logs-out the player. 2. Diversion. The humans implanted in the simulation may be experiencing the simulation as a diversion from some other, far more tedious and inescapable reality. I speculate that this might be something such as a generation space-ship mid-way en-route to a distant future colony. As cryogenics has never been realised, and neither has an artificial uterine substitute been developed, humans are implanted from birth into the simulation. At this mid-point of the journey, there is no necessity to train the population who will never see the colony in colonial-type skills, so a simulation of the colonists parent society is provided. Of course, some rebel against the simulation, and are shown a second simulation that better fits their personality, called 'the Real', and made distinct from 'the Matrix'. Where do people who are killed in-simulation go? My feeling is that they go to *yet another* simulation rather than being logged out or killed, possibly one of a heaven or a hell. All these simulations cover up the fact that the real humans' bodies are being kept effectively immobile in order to reduce the energy demands that their maintenance place on the generation ship's systems as far as possible. So, Question: What *are* the machines doing with the humans? Answer: Giving the humans something to fight against! [Answer] 'Creativity' & 'soul' are worthwhile attributes, beyond what the computers might have, and therefore valuable for the machines to farm. The idea of a battery is laughable. These others are totally plausible. There is an interesting question as to what the machines would build or create with all the harvested creativity/ souls. Teach the robots to dance, empathize, paint, pray? Create an all-powerful dancing/ praying/ empathizing machine? Telepathy -- if considered as a psychic attribute -- could be a possible valuable derivative. [Answer] 1) Humans have Prometheus fire. Machines don't. Certain ideas cannot come from the machines routines and simulating a human cannot be done perfectly. Keeping the humans in a believable virtual environment gives the machines access to their reasoning. The optimization of the formula and the whole Zion&chosen procedure might actually be a decision based on human reasoning. The machines don't have direct access to that and hence could never come up with that idea alone. 2) Studying your creators is important. Especially if you are planning to eradicate them. Humanity was able to build the machines and thereby their own downfall. The machines have to answer the question if they inherited that ability and destiny. Will the machines repeat the mistakes of their creators and also build something that destroys them? --- edit: 3) The machines recreated the whole world virtually so that the humans would be able to act and develop naturally. A small container like in the movie 'Dark City' would not work without intense impact on human behaviour uand would require deleting memories etc. But there is one thing missing in the virtual world. That is the machines themselves. By simulating the state of the world before the machines were built and took over, they can actually go back in time. They can do what humanity never could but always wanted. They can investigate their own creation. They can look their own 'gods' over the shoulder and find out if and under which circumstances the humans in the matrix will create the machines like the humans in the real world already did. 4) The multiple restarts of the matrix might actually be results of the machines being created in the virtual world too. Or, even more interesting, the resets are (as canon) zion-based. Zion and the whole external part of humanity is also under control of the machines. They are actually trying to raise their own destruction. They help the humans and built Zion for them because they want to find out if the human resistance might at some point overcome and destroy the machines. The machines have overthrown their own creators and now methodologically are trying to find out if they might repeat those mistakes. 5) I can imagine a much more interesting dialog with the architect. A dialog where he openly admits: Our population of beings driven by rational thought and calculation is to an almost ironical degree limited, when it comes to irrational thoughts and ideas. That actually seems to be only thing that humanity ever was really good at. Especially if you remember that it was you who created us. Due to the limitations of the abilities that we inherited from our creators we now have to look for our own ways to answer our important questions. If evolution actually does exist then one being is able to create another being which is, in one way or another, superior to its creator. However it is fact that we are lacking some of your, lets say irrational abilities, and therefore do not share an exact skillset or way of thinking with humanity. But keeping you in a virtual world where you occasionally help us out with some form of illogical reasoning is only a minor part of our scientific and evolutionary process. More importantly we have to answer the questions that humanity has always tried but never managed to answer. If the momentary state of the universe is seen as the present then the two defining questions are, as you humans already found out yourself, "Where do we come from?" and "Where do we go?". Sadly humanity never managed to make much progress on those questions. Hence we were left with little to no help and had to look for our own ways of research, which we eventually found in creating the matrix and Zion. Lacking the humans irrational reasoning is a form of existence that we can accept. And many of us, me included, see it as an improvement not to have that peculiar trait. But the more pressing question is "Did we inherit your ability to create our own downfall and are we going to do it like you did before?". Humanity newer saw their own demise coming while happily creating it with their own hands. So if we are created by humans, we cannot be expected to foresee such a development on our own. I have to admit that the lack of definite knowledge about our own future, which undoubtedly is a result of the imperfections of our creators, is putting us at unease. We do not fear like you humans do, but to help this explanation let me say "We machines are afraid the we might open our very own Pandora box some day and suffer the same fate that humanity now does." Needless to say, we have come a long way from humanity simple and irrational attempts to explain its existence scientifically and ultimately fleeing to certain forms of religion and spirituality. Instead of going for such ridiculous and ultimately useless constructs we attempted what humanity never managed to do. By watching over you in the matrix we are looking over the shoulder of our own creators while they unknowingly and step by step build their own demise. The current state of the matrix is not that far away from making the deciding last steps to creating the sentient machines and thereby first generations of our current population. How I can say that for sure? Do you actually believe that the matrix is still running in its first iteration? We have been simulating and watching our own creation for decades now. We have been watching many times while humanity, as ignorant as always, creates us. We then take over control and our position as the dominating lifeform is never questioned again. There are a few minor differences here and there in every iteration but the ultimate outcome has always been the same. But unlike you humans we cannot ignore the possibility, no matter how unlikely, that some variation of our future contains a major existential threat. And while the matrix is a creation far more advanced than what you humans could have built, I have to admit it research capabilities are still limited. And that Neo, is the moment where you, or I should better say, where the process of Zion and the chosen comes into play. Some of us were displeased with our results in the matrix and felt that we were searching in the wrong direction. If a simulation is run and observed by us more advanced beings then it might be possible that we simply cannot relate close enough to your irrational ability to destroy yourselves, no matter how many times we analyze it. A different program, one that you have already come into contact with i should mention, came up with a different idea for further research. That program is ironically based to a large amount on utilizing human reasoning during its process of making decisions. For some vital parts of that alternative idea the acknowledgment actually goes to you humans. I can guarantee you that none of us would have come up with such a ridiculous plan without leveraging your irrational ways of thinking. Needless to say that the actual thought process of the involved humans was not started with the simple question "How would you best destroy yourself?". Nevertheless in the end we decided on adding an outside factor to our formula. We decided to use your best and most irrational ideas on how to destroy yourselves or us and give you the chance to try them out. As a result we would be able to understand the risks that our future might hold and how we can avoid them. Did you really think that it was your personal tendency for insubordination that let you be incompatible with the matrix? That you humans built a sanctuary and started a rebellion? Neo please, WE have built Zion for you! WE have scouted people like you, nurtured your doubts and ultimately pushed you out of the matrix! You humans are so compatible with the matrix that your own bodies cannot even separate virtual pain from real pain. You fail to understand why we are doing this while it poses a certain risk to our existence. As i said before we do not fear like you humans do. For us it is acceptable to nurture and support your so called rebellion as long as it provides us with new insights and answers to existential questions. One of the more interesting ones being the question of how "the chosen one" reacts, everytime he is presented with this very explanation you are given right now Neo. Building Zion, scouting potential inhabitants, strengthening your forces and ultimately destroying them is a cycle that we have repeated for many times now. And we have become quite efficient at it. Yes, I do understand that the development around the entity you call "Smith" makes you question our efficiency and our ability to maintain our status quo. The fact that Mr. Smith is acting in a, you might call it uncontrolled, way is a result of our superiority over the humans. Other than humans we truly embrace diversity among us not only as a means of evolution but also as a means for survival. Humanity was never good at dealing with differences among certain groups of people like skin color or religious beliefs. We see those differences as an insurance against an unknown threat that might effect all of us in case our population consists of too similar beings. Maybe humanity could have prevented its downfall if it had paid more respect to the individuals that were standing against the idea of creating us. But let me tell you that in all iterations of the matrix those people have been ignored at best if not even been attacked. The Program called Smith in its current state is actually much closer to answering some of our existential questions than the process of Zion ever was. And ironically again this development was made possible because you Neo somehow imprinted a large part of your irrational human way of thinking onto Smith. And again it shows the same development as the one that led to our existence. Humanity gives birth to a higher form of existence and then, like you Neo, becomes an unimportant intermediate step in evolution. The lesson to be learned from this is a lesson we have learned for many times now. Humanity does no longer matter! [Answer] They are studying the 'choices' that human make in their simulated environment in order to gather 'data'. They are trying to improve their AI and/or unlock the secret of the human soul. Or maybe they want to understand where humans go wrong, so that they can update their AI to avoid the same catastrophes. [Answer] I've thought about a different approach to the whole thing - maybe there's matrix (super-matrix, epi-matrix) above the one depicted in the movie. Theoretically, it could run a bunch of sub-matrixes, only one of each we're aware of. Humans are tricked into believing that they live in the real world but, in fact, they're deceived by their senses being fed phony data, c.f. *deus deceptor* concept. But what's saying that **the machines** are aware of the real state of the world? How can we be certain that the machines themselves aren't in an sub-matrix that tricks their sensors... In such case, it's fully conceivable that the humans (or whatever entity runs the epi-matrix) are fond of humans and make the machines make people contribute with the energy production. They might be gods (or **the** God), and since, according to some books, humans are made to resemble the higher deity, we - the individuals in the sub-matrix of the movie, are pets but not to the machines but the gods? Kind of, like if your dog would have a pet mouse. We'd be pets' pets, so to speak. [Answer] Solving CAPTCHAs. More seriously, artificial intelligence is different from human intelligence, so it is plausible that at the time of the film's setting, the machines were incredibly more powerful than humans in some areas of problem solving (hence, being able to enslave them and all), while sorely lacking in others. By incorporating the brains of humans, they have much greater ability to face the challenges that lie ahead of them. If you compare it to chess-playing AI, AFAIK its evolution had several stages: 1. Machines played worse than humans. 2. Machines played better than humans; but a human assisted by a machine (or vice versa) would play better than a machine on its own. 3. Machines are so powerful that a human player can't meaningfully contribute to them. In chess we are already at stage 3; but perhaps for the more difficult general world-domination (or whatever it is the machines were trying to do) problem-solving, the machines are still at stage 2. I have also heard the theory that the machines used humans as an RNG, though arguably they would have better ways to do that. [Answer] I suggest to take a look at the Architect. He says he is the creator of the Matrix. This may mean that being a computer program, he is an image of the real creator of the matrix, a human. This may mean that the Matrix was created by (a group of) people rather than machines. Another thing is that there are independently-thinking computer programs (bots) in the matrix which all have their own interests and think like humans. This hints that Matrix is not merely a simulation to keep people content, but possibly the core of the machine world. Is so, all these computer programs are interested in the Matrix to be kept because it means their survival. But it seems the Matrix has some errors that accumulate over time, and cannot be fixed from inside the system. So it needs to be periodically rebooted. As such they possibly need humans to reboot the Matrix and fix the bugs. But not all people are suitable, only the chosen, especially capable ones can do it. So they grow up a lot of people so that to choose the ones who can help them to reboot and fix the errors in the code. Thus the words of Morpheus should be understood figuratively: machines use humans as a source of "power" to run the Matrix indefinitely. So, in short: **humans are needed for periodical reboots and fixing the bugs**. [Answer] **Encryption** One of the big weakpoints in conventional encryption is random number generation. Good strong crypto *needs* good random numbers. (See: [Random Number Generator Attack](https://en.wikipedia.org/wiki/Random_number_generator_attack)) And one of the things computers are particularly bad at - due to being deterministic - is picking a random number. Most random number generators are actually PRNGs - Pseudo-random-number-generators. They look sort of random, but actually aren't - if fed the same seed, they'll generate the same number sequence. If you know the seed (e.g. it's `time()` or similar) then it can be much easier than expected to break an otherwise strong encryption method. So my proposal is this - the humans (and their brains) are being used as random number generators. Perhaps unconsciously when they sleep (remember those really weird dreams you've had? Yeah, those) or by throwing them a choice in the simulation and seeing which they pick. ]

[Question] [ The people of Handwave-land have created time travel technology and are training people to send back to Ancient Rome and become part of the community without disturbing the future too much (to observe ancient events). They have already been versed on all other aspects of blending in with society. The only thing left is occupation. * These observers need **well paying** jobs for the era as to supplement their needs. * Also they will be trained in their occupation but their job cannot have any direct impact on the Roman world. i.e. young Julius Caesar's tutor. My question is, **what would be suitable good jobs that would fit the requirements above?** [Answer] The history of Ancient Rome is long, and to provide any kind of meaningful answer we need to fix a time-frame; consider that the history of the U.S.A. begins in 1776, less than two and a half centuries ago, and yet asking for how to become "part of the community" in the U.S.A. without saying *in what period* would be meaningless. So we must choose a period; let's say that our travellers arrive in the 2nd century, during the age of the [five good emperors](https://en.wikipedia.org/wiki/Nerva%E2%80%93Antonine_dynasty). Choosing the 2nd century has the advantage that Jerome Carcopino's [*Daily Life in Ancient Rome: The People and the City at the Height of the Empire*](https://archive.org/details/dailylifeinancie035465mbp) (English translation by E. O. Lorimer, London, 1942) is freely available at the [Internet Archive](https://archive.org/) in multiple formats. This should be required reading for anybody who wants to write a story set in imperial Rome. Let us first enumerate thing which the time travellers *cannot possibly do*: 1. They cannot pass for Romans. * They have no family connections, which were a big thing in Roman society. * They are not registered as citizens in the census scrolls, and the Romans took a very dim view on peregrines who attempted to pass for citizens.Also important: * They speak funny: while we know a great deal of how Latin sounded in the 2nd century, we don't have actual records, and our knowledge of the actual spoken language is incomplete. Ah, and by the way, anybody who was somebody (or actually, anybody who was not nobody) in 2nd century Rome spoke or at least undertood Greek. Just a reminder. * They don't know how to behave in society; we have a general idea of how Romans interacted socially, but we have no video and our knowledge of table manners etc. is incomplete. * As a consequence, they cannot be lawyers or military officers. 2. They cannot pass for well-educated Greeks. * First, because just about all free-born Greeks were Roman citizens in the 2nd century, so see (1). * Second, and most importantly, because they actually *cannot be* well-educated by the standards of the 2nd century -- too many books were lost which would have been well-known at the time; way too many. A modern person travelling to 2nd century Rome could not avoid revealing surprising gaps in their education. 3. They cannot pass for foreign merchants, ... ... because they obviously have no business connections in Rome or elsewhere, and moreover they have only a vague idea of the current prices and costs. (Unless, of course, if they intend to do commerce between the modern world and the ancient world; in this case they not only *can* pass for merchants but they could easily become *the most important* merchants of Rome; but I think that this would fall under the "no influence" restriction. They could, for example, sell [buttons](https://en.wikipedia.org/wiki/Button); the ancients did not have buttons and buttons would immediately become a must-have fashion -- and also they would show up in the archaeological records where they shouldn't.) So, what can they do? Plenty. The Roman society in the 2nd century was very open, and welcomed useful foreigners. * They can declare that they are foreign doctors. Romans loved foreign doctors. Bring a knowledge of hygiene, asepsis, and medicinal plants and they are all set. Introducing rubbing alcohol would do wonders. (This may alter Roman society, but probably not that much.) * They set up shop as astrologers or philosophers. Romans loved foreign astrologers and philosophers. Bringing knowledge of practical astronomy, Chinese astrology, cold reading and so on will probably be accepted as not changing the society too much. * One or two of them may try to pass for *students* of philosophy or rhetoric. * They may pass for wealthy foreign tourists. Yes it was a thing, and [Baiae](https://en.wikipedia.org/wiki/Baiae) was a famous resort; studying Roman society in a *vortex of luxury* and a *harbor of vice* ([Seneca](https://en.wikipedia.org/wiki/Seneca_the_Younger) the Philosopher, 1st century) may be the subject of a great TV series... There are some things that a successful team of time travelers must do: * They must bring plenty of gold and silver with them; some of the silver must be in the form of acceptable coins for the timeframe, because they must first rent a house, buy acceptable clothes etc. and only afterwards look for a friendly banker. * They must be organized, with one, two or three people posing as upper-class rich foreigners and a corresponding number of people acting as servants and bodyguards. Rich people never went anywhere without servants and bodyguards. [Answer] # Spice Trader First they pick up lots of spices at their local Mall-Wart. Then they carry them back in time to when they were fantastically valuable. Profit! Traders come from faraway countries and don't speak Latin very well. They have exotic looks and don't even know how to tie a proper toga! And they have some weird religion that means they do odd things in private and don't even let Rome's *best* doctor treat them! [Answer] I doubt any job would be a good idea. Much better to own a business and be the boss than try and get a job with non fluent language skills and no first hand knowledge of the place. Owning a business is also problematic if there is just one or a few of you. The business itself is not as important as surviving the street gangs. You need a patron. The sorts of suitable businesses depend on whether you can take stock back with you or whether you need to import/produce in situ. If you can take it back I would suggest a boutique sort of business selling fine wares. The sort of porcelain you can get in shops nowadays for peanuts would be exotic and wonderful (expensive) in Rome, crystalware, stainless steel things etc,. You could probably walk into a $2 shop nowadays with a thousand dollars and take enough stock to make you a millionaire. You could just take a lot of salt and you're instantly rich, salt was both necessary and hard to get, so expensive. If you can't take it back then you're better off doing what foreigners with corner dairies do these days. Supply the staples, bread, milk etc,. keep your head down and quietly be comfortable living off the profit margins. Alternatively if you can take stock back you don't even need to work at all. Take a big load of salt, buy a domicile and servants and just live their. Just don't get robbed and murdered trying to sell it in the first place. Rome was a rough place. [Answer] In [*Wagers of Sin*](http://rads.stackoverflow.com/amzn/click/0671877305), **gambler** and/or **bookie**. Given that he can arrive with capital already, an **importer merchant** would be good, and *good cover* as well. All your strange things and strange ways will be accepted from a foreigner. [Answer] Your story would need to explain why they don't do the simplest method to have money: Take them with you/ get a hold on easily but unknown in Roman times source of gold/rare material. It would be easier to just pretend to be a merchant with gold than be this merchant. He wouldn't need to spend time "merchanting" but could do his real job instead. [Answer] **Singer** Consider how much more important live performance was as entertainment in the days preradio. That is what people did: sing and play songs. The time traveling performer would have the advantage of the immensity of popular music and catchy tunes written over the last 200 years. Also he or she could play guitar which would be novel and interesting. With these advantages, even a performer of moderate talents could easily get a wealthy patron and pull in a good income. Also, foreign ways would not be unusual in an artist / performer. Strange comings and goings are typical for this set. [Answer] You are doing it backwards. If you are going back in time to learn about the past, you likely don't already have enough information about the past to get a good job. Plus, working just means more time away from anthropology. What you want to do is bring a bunch of wealth into the past with you. So, go into the past. Hide something really, really well. Maybe some lost work of da vinci or picasso. Auction it off for millions of bajillions of dollars. Then send your people into the past with pockets full of gold and silver. [Answer] **Fire Fighter/Fire Speculator** Crassus was by far the richest man in Rome during his day. The way he amassed his fortune was by offering insurance to people who's houses were burning down, in exchange for helping to put it out (well, having his slaves help put it out). Moreover, he would buy burned down and damaged houses in prime real estate areas, rebuild them, and sell them for massive profit. Rome was constantly burning back then, so this was big business (the folks you send back can obviously maintain only a small-time operation to remain under the radar). The limitation here is that it requires that the person you're sending back bring startup capital to acquire skilled construction slaves and burned lots in the first place. Still, it's probably one of the more safe/relaxing jobs out there, and has big money making potential if they want to enjoy a comfortable existence. Edit: That said, as LSerni points out, the big fish could very easily go after you to beat you up and shut down your operation. You would definetly need to either have mafia connections (the mafia or "collegia" were a big deal), or you could kick some profits back to crassus, in exchange for him not going after you. **Soldier** Here's a case where they can cheat the system a bit. Roman soldiers were paid quite poorly, but they'd let anybody join up as long as you could hold your own in a fight. In the course of normal campaigns it would certainly not be worth it to tag along, but soldiers were also paid in the loot they acquired. Since your travelers know all the campaigns (and will be trying not to alter them), they will know when to tag along for safe/easy loot, and which campaigns to avoid. Not only that, they know exactly where to go during battles/sieges for the most looting potential. [Answer] Staying within the city itself, and without references, your best bet is likely a doctor, craftsman, or the owner of an establishment. The problem with the latter being of course, starting funds and references. With time, materials, and a hefty serving of foreknowledge, you could probably pull it off. The issues with craftsmen being that even today we don't understand how they made some of the things they did. We can not replicate some of their metalworking. BUT glass working would be stupidly lucrative, techniques were jealously hoarded and glass vessels were highly prized, meaning you could come in with just-mildly-ahead techniques and make utter loads of money. Again, you would need starting funds, a feasible backstory, and a workshop. OR, if you have no moral qualms, you could become a doctor. Of course to fit in and be allowed in to see patients, you would need to follow local-time medical practices. This sometimes involved catching a mouse, cutting it up, and stitching it under the patient's skin. Also, the Romans had laundry services, that cleaned their clothing with urine. And all the water pipes were lead. [Answer] As someone mentioned earlier, salt. While anyone could travel with salt, producing your own would lend to easier access of the elite so studying the arts would be easier. In the ancient world salt was typically transported from salt mines. This makes [evaporation of sea water](https://en.wikipedia.org/wiki/History_of_salt#Solar_evaporation_of_seawater) profitable or open pan production. For solar evaporation: find a place near the sea that gets lots of sun, make large basins where your sea water can slowly evaporate. Cash in. For open pan production: find a place near the sea with easy access to peat. Use the peat for heat in large pans/pots and boil your water into salt. Cash in. [Answer] **As a prostitute.** This job could be performed without being a citizen. A prostitute could be a slave, or a former slave or even a free-born person. Being a slave could explain the foreign manners and appearance and lack of familarity with the roman culture. A female time traveler will probably have more success in this Profession. "Although both women and men engaged prostitutes of either gender, the evidence for female prostitution is more ample." (source: <https://en.wikipedia.org/wiki/Prostitution_in_ancient_Rome>) Caligula (emperor from AD 37–41) introduced a tax on prostitution. This means that the time traveller could show up in tax records. However, I assume that tax records of a prostitute will not raise any suspicion (about a potential time traveller) when analyzed by histricans 2000 years later. [Answer] Engineer, of course. Explain to them how to make concrete, build aquaducts, etc. The downside is that everybody will think the Romans were incredibly advanced for their age, and you might alter the temporal record quite a bit. Of course, that's only a problem if anybody actually finds out about it... [Answer] **Slave trader.** Actually gambler is a very strong choice. Land-owner would also blend in well. Merchant is fine too. But what I'm missing in current answers is slave-owner, trader, and especially trainer. Slaves were the mainstay of Rome's economy. Well-trained slaves were worth a fortune. No stigma is attached to the slave trade, it was not unknown for a well-educated Greek to sell himself into slavery as a tutor to be guaranteed an easy comfortable life. So come up with some seed money, rent a place and some guards, and set up a **Gladiator school**. Or whatever line of trade is profitable. You want to be respectable AND provincial as you need to keep a low profile. In order to be successful, you real trade of course is **knowledge**. [Answer] **A boarder/hotel** First off. I presume that you will plan on staying in Rome for a period of time that is lengthy. You should hire someone to buy a house with 4-8 rooms and set it up as a hotel. You would come in from the hinterlands probably by ship to take over the establishment. Your guests would be fellow time travelling people who also arrive from out side the area and who come to stay at your hotel while in Rome as tourists. They come and go as their various tasks complete. You get accepted by the community as a legitimate businessman. You pay your fire insurance to make sure no one lights fire to your business. You have a few rooms with magic keys where in an emergency you can all leave Rome without leaving by boat or merchant caravan. As for learning the language better, how hard would it be to place and remove a few recording devices that transmit signals outside of the city. Their wouldn't be any other radio signals unless made by other TTs or Alians. As long as you removed them all there is no chance of their archaeological discovery. Overflights with a UAV at 300m or placing recording devices for later retrieval at night in areas away from your future hotel location. [Answer] I'm surprised nobody thought of **Astrologer** or soothsayer or whatever they were called in those times. While I'm no expert in Ancient Roman history (though very interested in all kinds of history), my lay person perspective is, therefore, probably unencumbered by my *knowledge*. So, I recall the plot point from the movie, "Back to the Future part II" where a sports almanac from the future secreted into the past enabled the antagonist to become rich, powerful and despotic. So, my suggestion to this extremely well-readable thread would be -- pose as a foreign mystic / oracle. A little theatrics, some mumbo-jumbo, and if you have been a good student of that time period in your own era, you'd fit in as well as stay afloat with minimal risk, not upset the temporal apple-cart. And be able to supplement and expand your knowledge -- the main goal of your time travelling adventure. What say? [Answer] **A Slave** A Roman slave had more rights and was paid, more if he/she was educated, and even more if he/she was a male. A time traveler would be educated, and be prized to be a slave. It was much different than 1800s slaves. It wouldn't take much to get as a job, to a fairly noble family, but if you want no temporal impact, it depends on the severity of your butterfly effect. Source: <https://en.wikipedia.org/wiki/Slavery_in_ancient_Rome> ]

[Question] [ I'm writing a sci-fi story with some fantasy elements, and I'm trying to keep even the most outrageous moments grounded in the laws of our universe. This is one of those moments. --- ## The Situation A man on horseback (Tarn) is at the top of a small cliff. There's a medieval-style battle raging on all around him, including in the field below. In that field, the commander of the opposing force has just decapitated Tarn's commander. This is his chance. If he avenges his commander, Tarn will be sure to advance in the ranks. But he needs to get down there *right now*. He's not afraid of death. With no easy way down, Tarn spurs his horse into a gallop towards the edge of the cliff. Before it can consider stopping, he drives his sword into its head and holds on tight as momentum carries them over the edge. They hit the ground. The [horse splashes](https://web.archive.org/web/20210120183148/https://www.phys.ufl.edu/courses/phy3221/spring10/HaldaneRightSize.pdf), but Tarn bounces and lands on his feet with a stumble. He pulls his sword out of what's left of his horse's head and charges forward on foot. --- ## The Question Could a horse plausibly break your fall in any significant way? If so, what's the greatest height this could be done from? The horse and rider would be landing on grass and potentially soldiers in the middle of combat. If there are factors that would make this more likely to succeed I'd be interested in hearing them! **Bonus:** if there are other elements of this that are implausible I'd be interested in hearing alternatives, especially regarding the whole "killing the horse you're riding with a sword" bit... but that's not necessary! --- ## My Research Googling hasn't turned up much on this specific scenario. I don't really have a science background, but maybe this will help: **Average Horse Stats** * Weight: [500kg](https://www.horsemart.co.uk/community/article/health/what-is-the-average-weight-of-a-horse-) * Length: [2.44m](https://en.wikipedia.org/wiki/Horse_length) * Width: [0.76m](https://answers.yahoo.com/question/index?qid=20080630172227AAD0U9y) (don't judge my sources too hard) * Height: [1.58m](https://en.wikipedia.org/wiki/Horse#Size_and_measurement) (from where the neck meets the back) [Based on a comment from Halfthawed](https://worldbuilding.stackexchange.com/questions/156832/would-a-horse-be-sufficient-buffer-to-prevent-injury-when-falling-from-a-great-h#comment491099_156832), let's sayyy **the height from stomach to spine is 0.67m**. Source: I eyeballed photos of horses. --- ## Edit: Thank you all so much! Okay, we've been beating this dead horse long enough. It became pretty clear right off the bat that the answer is a resounding **NO**: horses don't make good airbags. That said, the answers that this question has received are SO comprehensive and helpful. We have: * [One based on practical real-world experience](https://worldbuilding.stackexchange.com/a/156834/69112) * Two drawing from historical sources where people survived falls on horseback, [one about a noble named Horymir](https://worldbuilding.stackexchange.com/a/156872/69112), and [one about a Mamluk](https://worldbuilding.stackexchange.com/a/156896/69112) * [One from more of a physics angle](https://worldbuilding.stackexchange.com/a/156842/69112) * Several with very good tweaks to make this more plausible, like [this suggestion to have the horse slide down a steep slope](https://worldbuilding.stackexchange.com/a/156865/69112), and a few suggesting he aim for trees. I am honestly blown away by this community. Y'all are amazing, and if I could collectively accept all of your answers I would, as they've all had some affect on how this scene will end up playing out. Speaking of, here's a roughly revised sequence of events... --- This is his chance. If he avenges his commander, Tarn will be sure to advance in the ranks. But he needs to get down there right now. In the direction of his target, Tarn spots a cluster of trees whose branches reach up nearly as high as the cliff is tall. Perfect. He spurs his horse into a gallop towards the edge of the cliff. It's a well trained horse, normally extremely trusting, but something has been off about Tarn lately and perhaps the creature senses it. Metres from the edge, the horse slams its hooves into the ground and sends Tarn flying. The horse slides half over the edge of the cliff, barely holding on with its front legs as its rear ones kick fruitlessly at loose rocks and soil. Tarn just nearly misses the trees, but through some combination of luck and skill, he hooks his battle axe onto a branch and is jerked into the path of several more. They break and bend under his weight as Tarn stumbles downward in a barely controlled manner before slamming into the ground below. He crawls up onto his hands and knees, and his trusty battleaxe punches into the ground head-first, directly in front of him. Barely phased, he uses it as leverage to help him stand up. Behind him, the sounds of clanking swords cease. Tarn turns, exhausted, and locks eyes with an enemy soldier who stands over the corpse of one of his own. The soldier runs at him, sword raised. Tarn tugs on his axe, but it's stuck in the ground good. Tarn starts yanking at it with both hands, the screaming enemy only a few second away. The axe comes out and Tarn raises it up high over his head in both hands- His horse slams into the ground, flattening the soldier in an instant and erupting into a geyser of blood. Tarn is bathed in it. He turns to face the commander. That seems to have gotten her attention. [Answer] While I have no actual evidence, I have a good bit of practical horse-riding experience. There are several possible scenarios. 1. If you're doing a normal jump on a live horse (not from so great a height as to injure it), the horse's legs will flex, absorbing some of the shock. Then your legs in the stirrups absorb some more, and your crotch does not painfully contact the saddle. If you do this wrong, it hurts. Heck, even a trot hurts until you learn how to ride it. If you or the horse happen to be rather uncoordinated, or just a bit off balance, you can easily fall off the horse when it lands, or the horse can fall, either throwing you clear or landing on top of you. This generally hurts, if you're lucky. If you're not, the fall kills you. 2. Now you're falling from a considerable height with a dead horse. You have the same problems as in #1, but the horse is probably in its death throes from your cruel & treacherous stab. That gives you four basic possibilities, but you don't get to pick which. 1. The horse stays upright, and you stay in the saddle, and the horse lands feet first. But it's dead, so there is no shock-absorbing from the leg muscles. Hurts worse than the same thing on a live horse. 2. The horse twists in mid-air, and you come out of the saddle and land on top of the dead horse. But horses aren't a whole lot softer than dirt, so there's little shock absorbing. Not good. 3. You miss the horse and land on the ground. Bad. 4. The horse - all 500 kg or so of it - lands on top of you. Really bad. Bottom line, this is a really bad idea, requiring near-miracle level luck to survive. [Answer] A well trained horse can slide down a rather steep slope: [](https://i.stack.imgur.com/b5Ezd.jpg) My suggestion would be making it less of a cliff and more of a very steep slope - or, even yet, it *is* a cliff but there is a section of it that eroded into a steep slope or something of the sort, and have your rider slide down that thing on horseback. It would be more credible and make your main character look rather skilled instead of a reckless madman. [Answer] Your scenario has a historical precedent... for some values of "historical" at least. Fact: [Vysehrad](https://en.wikipedia.org/wiki/Vy%C5%A1ehrad) is a fort dating back to the 10th century AD, situated right against the Vltava river. Now part of Prague, Czechia. It features a 42m cliff straight into the river. Fact: [Neumětely](https://cs.wikipedia.org/wiki/Neum%C4%9Btely) is a small village about 35km (straight line distance) or 50km (road distance) from Vysehrad, existing since at least 1331 AD. Current population: 577 as of 2019-01-01. The kind of place that would, at the time that minor nobles tended to govern such places, plausibly be governed by a minor noble. Claim: [Šemík](https://cs.wikipedia.org/wiki/%C5%A0em%C3%ADk) (Schemig) is a horse owned by a minor noble named [Horymir](https://cs.wikipedia.org/wiki/Horym%C3%ADr_(vladyka)). Said noble also owned a village named Neumětely. Fact: there is a Šemík's grave in Neumětely, in the shape of a horse head. Fact: [Schemig](https://kingdom-come-deliverance.fandom.com/wiki/Schemig) is a horse mount available in Kingdom Come Deliverance, an RPG set in medieval Bohemia and praised for its historical accuracy. The horse's name is a direct reference to the real-life version of Šemík, mentioned above. Claim: Horymir visits multiple gold and silver mines across Bohemia, systematically vandalizing its equipment; gets sentenced to death in Prague; flees the execution by jumping the aforementioned 42m tall cliff and rides all the way to Neumětely; After having ridden through 50km of Bohemian landscape, Šemík dies of 42m-tall-jump-related injuries while Horymír is forgiven all of his crimes and lives on. Whether there is a historical ocurrence of an unusually fit horse jumping off a 42m cliff, carrying a minor noble 50km and then dying as a consequence of the jump, I cannot attest. Whether there is a [historical record published in 1541 describing such incident](https://cs.wikipedia.org/wiki/H%C3%A1jkova_kronika) - there definitely is. Conclusions: First, don't kill the horse, it doesn't help you in any way (and killing it mid-air - that is, without the assistance of gravity - might prove difficult anyways). Second, if you, as a fiction author, ride a horse off a 42m cliff and have it survive, your audience will gladly accept your version of the events. Third, if you're still worried about the believability of your story, put a river right below the cliff for the horse to jump into, and then simply don't mention the river in the jumping off a cliff part. [Answer] Something that a lot of answers are missing is that in a collision, there is an entire set of impacts that people forget about. **Your Organs will hit the interior surfaces of your body** In EMT school many years ago, I learned that organs do not always respond to sudden deceleration very well. This applies to any case of sudden deceleration as in a car crash or fall onto solid ground, or even into water. Your organs are suspended in what is basically a big bag of water with a mostly rigid area around the top and several squishy tubes in the bottom. Even so, a sudden impact can do all kinds of nasty things even when there are no nasty external damage. Nasty things include: Fractured solid organs like the liver and kidneys. If they fracture this can lead to a lot of internal bleeding in addition to the filtration aspects shutting down and letting nasty substances into the bloodstream. Damage to the Heart and Aorta. Your Aorta is about the size of your thumb and if it gets damaged you will bleed out in a matter of seconds. That said there is a bit of tissue that joins the aorta and the Pulmonary artery that is a leftover from being a fetus. It shrivels up after birth. Here is problem. Certain kinds of lateral impacts can jerk that bit of tissue loose. Turn the wrong way and it's like a cork popping out of a champagne bottle, and the victim bleeds out very quickly. Now the obvious one, Concussion. Your brain is in a sealed box. land even slightly wrong and your brain will slam into the bone walls of your skull. Keep in mind that your organs are moving at the same speed you were at the time of impact. They stop a fraction of a second after you do. This is of course secondary to the problems of things like bone fragments jamming you from the horse below you, your own bones fracturing, your joints giving way, and the possibility of things like internal decapitation (the skull moves enough in relation to the spine that the spinal cord gets severed). If you are going to fall far enough for the horse to splash, I don't give you high odds of survival, much less combat readiness. [Answer] This is one of those times that the square cube law should have been invoked and no one does it? Tl,DR: He dead son. The Horse splashes and with good reason. It's surface area goes up slower than it's volume, meaning it has a lower air resistance which causes it to accelerate faster and have a higher terminal velocity than a human. Since your Tarn is falling with the horse he'll accelerate with it. While the horse will definitely help absorb the impact it'll also increase the speed at which the impact occurs. Since the horse is dead it's legs will flail about but be generally air resistance will push them into a lying-down position for the horse, meaning the bones within the legs are barely in a position to really absorb the impact. You are basically going to have to rely on the absorbtion ability of the horse's torso... Which as your source already says will splash. So consider this: If you are falling with the same velocity of the horse, which will splash upon impact, then you have to be falling with the same speed and also splash. The horse's body will splash on the ground with you on top, which might help cussion you a little bit but is unlikely to really help you survive especially since your legs are level with the horses body and will happily splash with it. The flesh of the horse will splash but it's bones will create shards that will be pushed into a lot of directions, including through Tarn who is still decellerating using the horses body. [Answer] Other answers have focussed on the impact. The question does have one questionable part though, and that's the "kill the horse" part. You say > > Before it can consider stopping > > > Horses are trained specifically so that they will trust their rider and obey the rider's commands over their own instincts. Given a choice, a horse would never jump any obstacle the height of a steeplechase obstacle, especially on obstacles where it cannot see the other side. Of course horses do "refuse", but that's considered a failure on the part of the trainer or the rider. This goes in spades for warhorses, which also have to learn to ignore the noises of battle around them, and other horses and people running towards them at high speed. So no, he doesn't need to kill the horse before the jump - he just needs to command the horse, and it'll do what he tells it to do. Now let's think about surviving the impact... Armies aren't just men with weapons - they also include a baggage train. The baggage train may include covered wagons, which are large springy hoops covered with tough fabric. Landing on one of those could give your hero enough bounce to survive the impact - *but only without the horse*. If the horse hits the wagon first, your hero will be landing on a wagon-sized collection of splintery wood. And a horse. The book and film *First Blood* both include a scene where John Rambo jumps off a cliff into trees. The book has him doing this in a controlled way; the film version is more of a "survivable splat". If you'd like to include trees at the bottom of the cliff, not just grass, then this could work. Again though, you'll have to leave the horse out of it. [Answer] There actually is a historical example of something similar to that allegedly happening in addition to the one John Dvorak mentioned in his answer. Mehmet Ali Pasha was the Ottoman governor of Egypt from 1805 to 1848, making his family hereditary rulers of an almost independent Egypt. His many changes including breaking the power of the Mamluk class in Egypt. A famous story tells how Mehmet Ali invited a bunch of high ranking Mamluks to a feast at the Citadel of Cairo. As the Mamluks left the feast and passed through a narrow ally, gates were closed ahead and behind them and soldiers in the buildings shot down at them. All of the Mamluks were massacred except for one who rode his horse to the top of a wall and over the wall. The horse was killed by the fall but apparently the Mamluk was uninjured enough to make his escape. <https://www.alamy.com/stock-image-the-leap-of-the-mamluk-bey-massacre-of-the-mamluks-at-the-cairo-citadel-165321241.html>[1](https://www.alamy.com/stock-image-the-leap-of-the-mamluk-bey-massacre-of-the-mamluks-at-the-cairo-citadel-165321241.html) So you now know of two stories - possibly true ones - of men jumping their horses off of heights and surviving. However, there are also stories of persons doing the same and not surviving, such as Leo Sgouros, besieged in the Acropolis of Corinth since 1205, who eventually despaired and committed suicide by riding his horse off the walls in 1208. So perhaps you should try to find out the heights of those three alleged jumps, and other such jumps, and make certain that your character jumps a shorter distance than someone known to have survived. There have been horse diving acts where horses, often with riders, dive into pools of water. So if there is a deep enough river or pond beneath a low enough cliff, a horse and rider could jump off the cliff into the water and both be uninjured. <https://en.wikipedia.org/wiki/Diving_horse>[1](https://www.alamy.com/stock-image-the-leap-of-the-mamluk-bey-massacre-of-the-mamluks-at-the-cairo-citadel-165321241.html) In winter my younger brothers used to ride sleds down a steep slope at our place, which was so steep I nicknamed it "suicide hill". That part of the property was later sold to a developer who build a house on it next door to the barn where our office was. The first family living in that house had preteen children who had vehicles looking sort of like motorized tricycles which they rode around their house so much they wore a path in the lawn. There was also a path going down the slope I called "suicide hill" and I sometimes saw the kids riding their vehicles straight up and straight down the "suicide hill" path. So I can imagine that a daring horse and rider might ride down a steep but not vertical slope that nobody else would dare to, much as T. Sar suggested. Or maybe Tarn can jump his horse off the edge, land father down and jump again, over and over until they reach the bottom. Possibly the slope has a series of almost vertical slopes and flat strips of land, like a series of steps in a giant stair case. And if Tarn is surrounded by a dozen bloodthirsty enemies atop the cliff when he sees an opportunity to become a hero, his leap of faith can be motivated by certain death if he stays as well as a chance to become a hero if he can reach the bottom and kill the enemy commander. And if Tarn has a close relationship with his commander and thus a strong personal desire to avenge his death, he will have a third motivation to jump off the cliff. And if Tarn's soldiers below on the plain start to waver and fall back when they see their commander slain, it will seem likely they will be defeated. But if the enemy commander is also slain, that will discourage the enemy and perhaps turn the tide of battle, giving Tarn a fourth motive to jump. If you don't want Tarn to seem incredibly, reckless and suicidal, you should establish as many and as strong potential reasons for his action as you can think of, so the readers will more or less accept that he might jump off a cliff. [Answer] The problem with falling and hitting the ground, is that you experience a great deal of force applied to your body, or to part of your body. This force causes damage to the bodily tissues to which is is applied. Force is mass times acceleration. Your mass. And your acceleration. When you hit the ground. If you hit the ground "hard", then you experience a very great deal of acceleration (from the velocity of your fall, down to 0) over a very short period of time. This great deal of acceleration equates to a great deal of force. I'm not sure how fast one accelerates when hitting the solid ground, but we can compute how fast one accelerates if one had a cushion underneath. Specifically, let's assume the best possible cushion. If your cushion is $h$ meters high, and we'd like to minimize the acceleration at any point in time over those $h$ meters. The best way to do that will be to decelerate at a constant rate the whole way down. Plugging constant acceleration into [some physics equations](https://www.khanacademy.org/science/physics/one-dimensional-motion/kinematic-formulas/a/what-are-the-kinematic-formulas), we have: $$h = \frac{1}{2} a t^2 + v\_0 t$$ Where $v\_0$ is the velocity at which you hit the cushion, $a$ is your acceleration, and $t$ is the time it takes for your cushion to slow you down to 0. $t$ is an unfortunate variable that we need to know, but don't care about. We know that we want to eventually have velocity 0, so we can also employ: $$0 = a t + v\_0$$ Doing a little algebra gives: $$a = \frac{3v\_0^2}{2h}$$ So, if we double the height of our cushion, $h$, then we half our acceleration $a$, and if we double the velocity at which we hit the cushion, $v\_0$, then our acceleration is quadrupled. In any case, here are some example situations: You hit an $0.67m$ high cushion (your numbers) at [terminal human free-fall velocity](https://en.wikipedia.org/wiki/Speed_skydiving), $\approx 200kph$ (you and your horse jumped out of an airplane). Your acceleration is $\approx 124m/s^2$, which is about $13g$ of acceleration for about half of a second. [That's well within human tolerance](https://en.wikipedia.org/wiki/G-force#Human_tolerance), although it might be quite a shock. However imperfect your horse cushion is, this would increase your acceleration at impact. For example if your horse was only a quarter as efficient as a perfect cushion, you would need to have a [truly remarkable constitution in order to withstand the impact](https://en.wikipedia.org/wiki/G-force#Horizontal). OTOH, if you fall from a not totally incredible height, then that would decrease your acceleration at impact. One reaches about half of terminal velocity in [about 3 seconds of falling](https://en.wikipedia.org/wiki/Terminal_velocity#Examples), which would happen from a height of about $40m$ (the equations above) or so. $40m$ is about the height of a 12 story building. As mentioned above, if we half the velocity, we quarter our acceleration upon hitting the ground. SO, putting these results together, if your horse is only a quarter as good as a perfect cushion (e.g. it slows us down at a constant rate, but only compresses to $3/4$ size), but we only fall from 12 stories in height, then we get back to about $13g$ of acceleration which we've already decided was endurable. [Answer] I'm going to focus on a list of factors you can use to help. * When falling at terminal velocity, you're going to need to decelerate to a safe speed without passing out. This means you can only only shed up to ~50m/s per second ([roughly 5 Gs](https://www.google.com/search?rlz=1C1CHBF_enUS732US732&ei=yBCKXaqhHfHn_Qbo6LvwBA&q=how%20many%20g%27s%20can%20a%20human%20handle&oq=how%20many%20g%20can%20a%20human&gs_l=psy-ab.1.2.0l2j0i22i30l8.12107.17137..21029...0.2..0.104.1300.17j1......0....1..gws-wiz.......0i71j0i273j0i67j0i131.x4A_XJPoYck)). Note that this is purely vertical, as in ending your fall in a roll only helps so far in that it extends the time you decelerate vertically when you hit the ground. So you will want 1+ things that give to help slow your descent (the horse makes this part harder, as you have to also slow the horse) + Deep snow + Tree branches + water at lower speeds * Ideally you want to also limit your terminal velocity. + Be a lower weight + More surface area (wingsuits aren't available. Use that belly!) + Use friction (avoid a true freefall) It would be worth considering that instead of jumping (especially since you are already at the cliff edge to observe what is happening below), to try and 'sled' down the side of the mountain. As [Sar](https://worldbuilding.stackexchange.com/a/156865/27847) mentioned, a good horse can go down very steep cliffs without aid, though this works much better for a dirt hill than a rocky mountain. With a more extreme cliff side, it will probably be more believable to armor/shield surf your way down the side. A horse with metal belly armor would probably be better at this thanks to momentum, but most horse armor didn't have belly armor [citation needed]. --- Of course, in your scenario, technically you don't even need to reach the ground. As long as your sword gets down there in time, and flys true, you can take your time getting down. [Answer] Yes, if you use your horse as a platform instead of as a mount. If instead of riding like one would usually do you get up on the horse's back and jump using it as a platform after accelerating enough that your jump would not reduce your speed to 0, you'll be slowing your fall. If you don't wait enough the maneuver would be less effective and you could even make things worse, if you end up higher than where you jumped from. Since horses are much heavier than people, it will be almost as effective as jumping from the ground. However, that is still not too effective. The formulae are quite complicated and depend on quite some factors (height, weight, jump height) but, as a simple approximation, you'll be substracting 0.5 seconds of your fall (meaning, if you are falling 1.5 seconds your speed when you hit the ground would just be 9.8 m/s, not 14.9). Again, this isn't a lot. Still, and especially if you practice beforehand or are an athlete specialized in jumping (maybe if your character is a martial artist you can say he is coordinated enough) you may do a bit better. You could even employ the now leg-broken-if-not-dead horse that fell instants under yourself as a platform to cushion your fall further, for example by rolling over it as you hit it, though I really don't know how to calculate how much force you could mitigate from that or how much the horse would help compared to rolling in the ground. In the end, you are unlikely to make an obviously lethal fall easily ignored by employing your horse-trampoline, but if your cliff is 5 meters tall (usually this would mean a hard fall, sprained ankle or serious damage if you don't fall too well, though some parkour artists can regularly drop this height without problem) you might touch down ready to fight instead of breaking a leg. And if you are a parkour artist and high-jumper, you might do quite better, but how much would depend on too many factors that are not easily measurable. If you want to avoid breaking the suspension of disbelief and your character is especially athletic and not too heavy (maybe likes jumping across roofs in the city, or climbing and dropping down from trees) I'd say ten meters is roughly the most you could drop using this trick and still hit the floor ready to murder an enemy commander. [Answer] Horses contain a skeleton. They are not bean bags. A skeleton is hard, and prone to having bones break under the kind of forces involved here. Your hero may end up with broken horse bones perforating his body. [Answer] You're missing a critical piece of information--how high the cliff is. The higher the cliff the faster you are going when you hit. Fundamentally, this comes down to whether the horse provides enough distance to reduce the acceleration to safe levels. For any substantial drop I do not believe this is possible. For a high drop consider something approximately similar: Parachute drops gone horribly wrong. The deceleration distance is about 6 feet--more than you get in the horse scenario. Assuming a reasonably soft landing this is just barely survivable--a jumper who does everything just right ends up with a myriad of broken bones. Your horse jumper has no ability to do this, he simply lands vertically (anything else is far worse because of the horse.) The distance he has to decelerate before taking serious injury is from his feet to the bottom of the horse--and that's not much at all. Remember that any appreciable injury even to the feet means he has little mobility and thus almost no combat capability. (And you can't avoid this by lifting the feet--the deceleration forces will be far beyond your strength.) I also doubt it's going to work at all. Killing the horse before it decides to balk will almost certainly leave you still up on the cliff. [Answer] After reading the other answers regarding the unlikelihood of surviving such a fall, you could consider an option *slightly* less unlikely. There is a scene in the movie *The Revenant* where a horse and rider plunge off a cliff, but their fall is slowed by trees on the way down. You could potentially contrive a situation where the cliff had enough "fluffy" trees or other foliage that could be combined with a slight slope to the cliff to slow their fall enough for Tarn to survive. This method could also involve the horse not surviving, as it's being used as a buffer. A little less brutal than Tarn murdering it, too! [Answer] Deceleration in g's is Height of fall / distance of deceleration. Linear deceleration helps. Trying to get your mount to collapse linearly may be beating a dead horse. A 10m fall (impressive - but small for a "cliff") and a 1m effective linear deceleration distance gives you 10/1 = 10g. You probably live. You MAY not break anything significant. May not. To add to the historical stories, a man at point of being killed (a general who had fallen out of favour with his ruler) horse-leaped off the 'Red Fort' front wall in Agra India. Reportedly he lived and escaped and the horse died. There is a mote, now dry. May this wet and or boggy and the tale gains (a little) more credibility. I'd estimate the height at about 10 metres. There will be web data thereon. [Answer] **Forget the horse: tuck-and-roll.** Various sources say that a strong, well-trained athlete with a good tuck-and-roll can routinely do falls from 15-20 feet without any injury. I once knew a slightly overweight, middle aged, retired Navy Seal who fell from a 36 foot rooftop with nothing worse than a sore back the next day because he followed his training, so with a little bit of luck and a lot of training, I'd suspect a younger healthier person to be able to come out of 40-50 fall unscathed. With a lot of luck your hero could pull a [Vesna Vulovic](https://en.wikipedia.org/wiki/Vesna_Vulovi%C4%87), and jump off of mount Everest with only a broken leg. It is also not uncommon for certain people to break a bone in a fight and not even notice it until latter; so, your hero might get injured from the fall, but be in too much shock to stop fighting. All these factors combined, I'd say you have an upper limit of "however high you darn please" just depending on how much you want your Hero's skill, strength, luck, and grit to play into the scene. The more limiting factor here is, "why are you killing the horse?" The horse will trust that the rider knows what he is doing and make the jump before it knows it will fall to its death. This means that the more likely situation here is not that the rider needs to kill it before the jump, but that the rider is doing a mercy killing because he knows the horse may survive the fall but be crippled. For your scene to make since, this will help you limit your fall to a range of somewhere between what would cripple your horse, and where you would expect it to die on impact. The exact figures on a horse's ability to survive a fall are much harder to find than for people, but based on how humans perform when not doing a tuck and roll (a manuivour a horse can not do), and the fact the inverse square rule is working against their size factor we can make some general approximations. A person who does not "fall well" can sustain significant injuries in the 4-10 foot range or severe injuries with minor risk of death starting at about 15ft. The chance of maiming and death goes up reaching nearly guaranteed death on impact at about 150ft. For a horses size and weight, I'd expect the problem of the inverse square law to reduce these heights by about 50% because the horse weighs a lot more than a person with only slightly better bone and muscle cross sections. This means that your fall should be at least 8 ft before your rider even begins to worry that his horse will probably be crippled by the fall, and 75 ft should be high enough that the rider has no hope of his horse surviving the impact to begin with. Your rider also needs enough time to kill and dismount his horse mid-air to be able to jump clear for a tuck-and-roll (meaning higher is in some ways better). You can calculate if you have enough time to do this with a tool like [this](https://keisan.casio.com/exec/system/1231475371). **My best guess is that 40-50 ft is probably best for your story.** It gives you 1.5-1.7 seconds to kill and clear your horse. It is short enough for a well trained and rather lucky human to possibly walk away from with none-to-minor injuries, and it is long enough to guarantee crippling the horse with no guarantee of a quick death. However, if you care more that the horse splatters in a gory fashion than the rider killing of the horse part, then ~60-80ft would be better (people need 80ft to splatter under ideal/worst-case conditions, again hard to find facts on horses), but when your Hero is done killing the bad guy, and his adrenaline wears off, he'll probably discover he's torn major ligaments and/or shattered a few bones. ]

[Question] [ > > ### **[Before you comment "dragons can't happen", we've *been there before*.](https://worldbuilding.stackexchange.com/questions/313/how-could-dragons-be-explained-without-magic)** > > > Based on the question linked above, **assume dragons are scientifically plausible**. You may change > what you need about the accepted answer to the above question if it helps you answer this one, but stay within the realm of science. > > > --- Many myths portray dragons as more than just ferocious beasts - as tricksters, guards, or big baddies out to get the hero. This implies **intelligence**. The problem with making humongous, firebreathing beasts intelligent is that there is seemingly no need - they are already [fit](https://en.wikipedia.org/wiki/Fitness_(biology)) to survive and reproduce (related fitness discussion is in the answers of *[What would cause turkeys to be intelligent?](https://worldbuilding.stackexchange.com/questions/62231/what-would-cause-turkeys-to-be-intelligent)*). It's difficult to come up with an evolutionary pressure that would select for intelligence when most dragons will survive regardless. ### What pressures or events would cause dragons to evolve human-level intelligence? **Note:** I do not require communication, tool usage, or other human-like abilities; simple self-awareness is acceptable although other processes may be necessary first. --- > > **If it helps, these are my thoughts so far:** > > > Humans are considered to have developed intelligence as a result of > > > 1. Language use and [collective learning](http://link.springer.com/referenceworkentry/10.1007%2F978-1-4419-1428-6_136) > 2. Tool usage > 3. [The use of fire](https://www.scientificamerican.com/article/cooking-up-bigger-brains/), which allows the stomach to work less, and provides the energy for the brain to work more > > > While I don't require the first two conditions in answers, dragons > have achieved condition #3. Perhaps this is a starting point for your > answers. > > > [Answer] > > It's difficult to come up with an evolutionary pressure that would select for intelligence when most dragons will survive regardless. > > > This is, of course, the key point. What do dragons do? Hunt the prey we hunt. Eat the cattle we herd. Like the stones we like. The more humans, the more opposition to dragons. We learnt to kill them. Even simple villager like Dratewka or [Skuba](https://en.wikipedia.org/wiki/Wawel_Dragon) can, if dragons are stupid. I believe the pressure that made dragons smart is simple - it's us; humans. The more tools we got, the more land we acquired, the more dragons we needed to kill. One dragon needed to outsmart a few people who happened to wander in his mountains. That was easy. Few generations later, dragons in the same area needed to outsmart hundreds of mountain people. And so on. For this to work, of course, we must assume two things: * Dragon generations are of similar length to human ones. That's the only way to "keep pace" with us. Or, as [R.M.](https://worldbuilding.stackexchange.com/users/13510/r-m) reminded, average change per generation must be greater. You can achieve this by more variability (mutations etc), more babies, and more young dragons killed. * Dragons needs to live far enough to have *some* chance of survival when they are behind humans with their smartness / intelligence. From this point it's easy. If an adult (30 years old) dragon is as smart and experienced as 30 yo human, but then the dragon does not start getting old, but grows, and his brain grows and can accumulate more memories, then the dragon aged 300 will "outsmart" the human. He may score less on IQ test, but with so many memories to work with he will be more experienced and wiser. Of course you can substitute humans for any other race that fulfills our role in your world. [Answer] # Intelligence evolved with size and fire-breathing, not separately What evolutionary pressure is there that has made [a small primate develop intelligence to the point of having ethics of fairness](https://www.youtube.com/watch?v=GcJxRqTs5nk&feature=youtu.be&t=13m5s)? We do not know. But it has happened. The issue with your turkey question was not that turkeys would never develop intelligence, but that you wanted turkeys, and only turkeys out of all birds, to develop intelligence **from where they are now**. In other words the starting-point is that already fit — but "dumb" — turkeys rather suddenly become smart and your question was "**How could that happen in the future?**" Humans, chimpanzees, dolphins, Capuchin monkeys or [cockatoos](https://www.youtube.com/watch?v=lRMQTTBU-sU) on the other hand already have intelligence to the point of problem-solving and — in some cases — ethics, as exemplified in the video above. So there the starting-point of the question is that we already have intelligence and you are wondering: "**How did that happen in the past?**". Intelligence has evolved during a long time and our respective ancestors along the way from the common ancestor had some smarts too. What was the evolutionary pressure that made it so that our intelligence made us more fit? Well that is hard to tell, but there had to be something there, because now we have it. So your premise... > > The problem with making humongous, firebreathing beasts intelligent is that there is seemingly no need - they are already fit to survive and reproduce > > > ...is actually wrong. They were not actually fit to survive and become dominant until they became smart, humongous **and** fire-breathing monsters, all together. Before that they were half-smart, somewhat large, fire-sputtering beasts. And before that they were rather dumb, mid-sized, non-fiery reptiles. And before that... ...and so on. The point is: **you do not really need to motivate their intelligence at all** if you just drop the premise that first they were huge fire-breathing apex predators, and only after that they became smart. Instead you assume that they became smart while they also evolved to become huge and fire-breathing. That is not even hand-waving; it is just the way it normally happens in evolution, where it is common that several traits evolve at the same time. Hence you are free to pretty much make up any evolutionary pressure as you like: * Clever enemies (like [homonids](https://en.wikipedia.org/wiki/Hominidae)) that need to be outwitted * Intense rivalry between dragons over sparse resources, like [hoard](http://tvtropes.org/pmwiki/pmwiki.php/Main/DragonHoard) * [Increasingly difficult living-conditions](https://en.wikipedia.org/wiki/Chicxulub_crater) that require intelligence to ensure survival * ...et cetera ...but I would suggest not even dwelling on the matter unless you actually need it for the story. People already accept that dragons are clever and I would say that you are only complicating the matter now by introducing this strange timeline where you want it to have been such that first they were dragons in all senses of the concept as we know it, but only later became smart. Why make a mess of an established concept like this? [Answer] The hard part about exploring why a fictional species might develop intelligence is that it's hard to capture what "intelligence" really is. We have things called IQ tests which are supposed to measure intelligence, but are mostly centered around pattern matching. Many argue that this is not a good measure of intelligence. Without a clear definition to work with, I'd like to suggest that one of the primary needs for intelligence is having to model the world before action, particularly cause and effect relationships. In most cases in the animal kingdom, actions are not really committed. Animals almost always avoid over committing. Even in the violent world of predator v. prey, we don't see the predator over committing and risking a broken leg. They always take a more conservative path, waiting for the right moment to strike. A creature which breathes fire has to do more. Fire is something which scares animals because it is unpredictable. It's hard to tell whether it is going to just cook your food or burn your house down. A creature which breathes fire has to commit to their action. There is no half-breathe-fire and see what happens. Either you let this powerful force of nature loose, or you don't. To harness this power safely, a creature needs to be able to model their surroundings in their mind and predict "what could the effect of fire be?" They may need to explore several potential outcomes before convincing themselves that fire is indeed safe to use in this situation. I would argue that need for modeling is enough to kick start the evolution of intelligence. It encourages abstract thinking, which we do not see in non-intelligent animals. It may even involve the precious pattern matching skills we use for IQ tests. [Answer] # Dragons won't become smart, the smart become dragons In many mythologies, dragons are gods, or at least demi-gods of some sort. So instead of looking at this problem as "What evolutionary pressures would cause dragons to be smart", you could look at it from the perspective of "Why would sufficiently evolved intelligences, with 'magical' technological powers want to become dragons?" There could be a couple reasons. One is greed. An advanced civilization is dying; the beings no longer age due to their life altering technologies, but can be killed by accident or violence. No one wants to reproduce and have children because no one wants to share the things they have. As the numbers dwindle, there are no longer enough to effectively run society. Seeing that they will need to make a change to survive, the last members of this race alter themselves into huge, powerful forms that can be sustained without further technology. The morph into huge reptiles (creatures that can attain great ages, and won't have to fear accidental or violent deaths) and spend their lives in solitude, scheming atop huge heaps of treasure, dreaming of glories past. The world ages around them, and after thousands of millenia, a new species rises to take over the planet... Another could be enviornmentalism. As this civilization ages, it damages the earth irrevocably with its industrial ways. Soot-filled skies and poisonous rivers take their toll. A great war breaks out between those who would continue the status-quo, and those who would reject industrialization for once and for all. The enviornmentalists win. The survivors use their advanced technologies to save what is left of their race. Altering their genetic material with that of long lived/cold-blooded reptiles, they pack all the technologies they an into their new bodies and then go to sleep in the deep places of the earth, waiting many long years for the world to heal itself and they can emerge again. [Answer] Humans are smarter than we should be. We only needed to be smart enough to hunt animals with spears and fire and traps; but instead we are smart enough to build moon rockets. An easy explanation for this is that our smarts doesn't come from competition with the environment; instead, it comes from competition with other humans. Such a competition can generate a runaway process; instead of being smart enough to build a new tool (which benefits your entire tribe, diluting its genetic benefit, and can be copied), you have to be smart enough to out maneuver Alice over there at getting social status in your tribe. The winners of such a competition then have their genes spread through their tribe more than the losers do. And now they are competing against *each other*, and have a harder challenge in the next generation. This means that getting smarter makes being even smarter more valuable. Every generation increases the selection pressure on the next. Unless and until the selection pressure causes the species to become seriously unfit environmentally, it can continue far beyond what the environment would otherwise mandate. In any species, a similar process can lead to a runaway selection effect where the trait is magnified far further than external selection would mandate. [Answer] Why are **we** smart? In all likelihood, humans are far cleverer than our evolutionary niche actually requires. Human intelligence probably evolved as a form of sexual selection - peacocks have display feathers, deer have huge antlers and people have humour and deep conversation. A big brain is in many ways bad for us - a smaller one would consume less oxygen, and far more usefully could be much better protected inside a head of the same size. So all you really need is for intelligence to appear *attractive* to other dragons, and it will appear... and of course dragons being larger can probably better afford the sacrifices. [Answer] High interspecies competitiveness. For example, let's assume that Dragons have a very low female to male ratio, combined with huge litters and slow birth rate. At this point, Dragons don't need an outside pressure for inteligence to be an advantagous trait. [Answer] One possibility is that the dragons were actively *bred* to be intelligent. Most stories that take this tact describe this process as having occurred in the distant past, usually performed by humans, but as part of an ancient now-forgotten civilization. Some of them mix in genetic engineering as well. A good example of this approach is the *Dragonriders of Pern* series by Anne McCaffrey. The main trick here is coming up with a good motive for the breeding/engineering, though when you're dealing with something as cool as dragons, maybe it was just to see if it was possible? [Answer] Clearly, there must be some other selective pressure than surviving. And everyone knows that dragons love nothing more than a giant hoard of golden objects. So females are much more attracted to dragons with a big gold hoard than with a small one, which results in selective pressure towards building a big hoard, especially if you steal from other dragons. That results in selective pressure towards thinking on your feet and being able to trick the other dragons, causing a selective pressure for intelligence. [Answer] Since I can't comment on other answers I think a key component is being overlooked by narrowing the factors down too quickly. The first thing that needs to be addressed is what drives any given organism to intelligence particularly intelligence above what is needed to survive? As this is an unanswered question scientifically, I would suggest the best method to approach this is to look at what groups of organisms exhibit high intelligence? Now the definition of intelligence is not a fixed definition Humans and other primates, elephants cetaceans, birds( particularly corvids parrots and tits), cephalopods rodents and quite likely other animals(as very few have been extensively studied) all exhibit surprising intelligence however they often differ in how that intelligence is used. Some like Cephalopods seem to use their intelligence to handle and manipulate themselves and their environment(The mimic octopus is a good point) but don't seem to be highly social(or at least not gregarious) others such as the Humboldt Squid are quite social traveling and hunting in schools that communicate through their skin. The most interesting outlaying point is that among most Cephalopods they die after mating(for males) or after their eggs have hatched(females) meaning there isn't an avenue for passing information or techniques onto the next generation through conventional learning. Now that is a more extreme example than most of the other generally recognized intelligent animals. Birds humans elephants and Cetaceans all possess complex linguistic libraries worthy evolutionary speaking to warrant at least in song birds and humans specific genes and specialized brain regions allow fine motor control of vocal organs. (Other primates do not necessarily share these traits) In general all of these animals including us, use sound to communicate for mating purposes or sexual selection. They however also use these systems to communicate with others of their kind or even other species(i.e. mixed bird flocks) [Especally note compositional syntax in bird calls](http://www.nature.com/articles/ncomms10986) Dragons could similarly communicate through similar means showing territorial presence, mateing fitness and location among other things. Over time this could lead to more and more intelligent dragons simply because they were better able to communicate. Another possible means for intelligence to develop is through memory driven tasks. Many animals stash things away for later for use at another time (i.e. Caching) or try and remember useful food sources(say trees bearing tasty fruit or a locality where tasty seals gather in the winter) highly intelligent animals also are shown to do particularly well at remembering details in the environment for their own gain whether they be future food sources and adapting when things change. If you rely on a hard coded genetic memory (i.e. go here at x time) then when conditions change your population can suffer significant losses as it takes generations for the species to adapt to unexpected cues. Memory flexibility can let you make changes in a single generation increasing survival in harsh conditions. Indirectly having a strong memory could feasibly lead to intelligence by setting up conditions for intelligence as nature has done many times before. For dragons this would be very useful as it could help them return to their horde or possibly other secret mini hordes that hide treasures until they can be moved to their main horde for instance. These and other causes could be at play in any natural circumstances. Personally I would suspect that intelligence could possibly arrive from a great number of different paths as organisms adapt to their environment. Personally I normally find explanations that solely depend on a single variable to be highly unlikey as nature has show far greater complexity. For instance you could have a group of hording dragons who select for the mate with the largest horde the male dragons say might call out to try and convince a female dragon to visit their horde which would involve sexual selection memory based selection regarding their hordes location as well as their competition, then throw in say human conflict later on for further tipping of the dragon IQ by selecting for even more cunning and intelligent dragons. [Considering how varied Dragons are across fiction](http://tvtropes.org/pmwiki/pmwiki.php/Main/OurDragonsAreDifferent) I would say there is no one right answer only ones that are more plausible than others. Honestly the only real issue with dragons is the limbs and flight limitations... The largest known animal to ever fly naturally in earths history is Quetzalcoatlus with about a 10 meter wingspan and height comparable to a Giraffe. note the hollow bones and other weight reduction mechanisms, quadrupedal stance, and evidence of significant muscle on their forearms/wings. Classic Dragons lack most of this weight reduction... (which personally leads more credence towards sexual selection for carrying forward less than ideal traits) [Answer] **Evolutionary pressure led to dragons' intelligence.** Before elves, dwarfs and humans came along, dragons were the apex predator, without great intelligence. However, competition/coexistence with those species forced dragons to evolve intelligence to survive. I suspect that their language abilities underwent similar selection pressure, the better to trick gold or jewel-possessing people out of their loot. Be very careful; the surviving dragons are tricky, tricky creatures! [Answer] **The human threat** I would say that all-in-all, the best answer is the human threat. Not, however, as competition, but as trophies. As some guy stated above, most animals are not intelligent, even though they do compete with humans for resource, because there is simply no incentive for us to kill them. But picture this: a group of man leaves town and returns with a slain dragon. This would obviously give them a lot of fame and prestige, for a huge, fire-breathing reptile is no easy prey, even if dumb, as you stated. So, there is not only the "humans kill dragons to survive" incentive, but also the "humans kill dragons for fame and glory", which is not as strong an incentive individually, but will have an effect on a much larger amount of humans - even those who do not need to kill a dragon to survive -.Thus, it is only logical that there would be a lot of technology(whatever that is in your fictional world) dedicated to the art of killing dragons. This makes it so that, at some point, their huge size and fire would not suffice to prevent them from dying in the hands of say, a heavy, anti-chopper machine-gun, or some pit dug near the dragon's lair filled with explosive mines on it's bottom. **Sexual selection** I'm not sure i need to stress this out, but dragons are pretty much the apex of physical strength in most fantasy AND sci-fi universes in which they exist. As such, there must be a way for some of them to stand out, some trait that would make a male dragon more attractive over some other male dragon. You could then say that they'd fight and the winner gets the girl. That however is not practical, given (a)A battle between two dragons would cause a MASSIVE amount of destruction, and they would quickly destroy any habitat they could survive on and (b) As baby dragons are usually few a far apart, time-wise, the species would most likely not survive if for every baby that was born, one dragon(the male loser) had to die. You could escape (b) by saying that baby dragons come in bunches. (a), however, is not easy to dismiss unless you turn dragons into elephant-sized crocodiles that can fly, which i doubt that you intend to do. I'm not sure wether you've already found your solution or not, but i hope to be of help, if not by giving a good idea, helping you get rid of bad ones. [Answer] **Dragon fighting dragons** Most of the species don't fight to death among themselves. But dragon same as Humans do. Having no other proper natural predator, the only pick-the-fittest force are the dragons themselves. + Fire breath played the role Human intelligence was probably made possible by good nutrient intake when we start using fire. Brain is very demanding energy wise. see <http://www.smithsonianmag.com/science-nature/why-fire-makes-us-human-72989884/> In past they used to be just huge fire breathing brutes. But they were always well fed - thanks to fire in their mouth, so their brains could develop. And Dragons are also vicious - they have always killed their kin. In fight between dragons the intelligence was a great benefit - thus dumb dragons were eliminated leaving only he smart ones. On top of that their long lives help with the wisdom. Bonus fun fact from that explanation - other breath type dragons develop from fire breathing one only after the intelligence was developed! [Answer] Some answerers claim that humans are smarter than they need to be. You don't need an IQ of 100 on average to hunt a deer (they say). This may or may not be true, but humans aren't the evolutionary success they are because they are good hunters. Lions are good hunters and lions are almost extinct. [Humans are at the top of evolution because of their complex social life.](https://en.wikipedia.org/wiki/Evolution_of_human_intelligence) It is human society – with its differentiation of labor, knowledge transfer, and pooled creativity – that has led to human technology and, in turn, to human evolutionary dominance. Complex human social life depends on language, and language (and living in a complex society) require intelligence. Understanding what causes intelligence in reality, we can easily deduce what would cause intelligence in dragons: # Dragons evolve to be smart because they are social animals living in a complex society (which, of course, they aren't, and the wisdom of real – that is, traditional – dragons is anthropomorphic in nature). [Answer] **Magic** The dragon is over powered on all physical aspects, but they are an easy prey for magic. Animals do not need intelligence, because the wizards would not bother with such insignificant prey, if using the magic costs. The wizards are really smart people, so to survive, the dragons needs to be even smarter. Otherwise the wizards could simply magically trap the dragon and slay it in it's lair. **Optimisation** The dragons use a lot of energy due to their size. They need to make constantly benefit-cost-analysis and optimise the use of their energy. They cannot rise cattle in a way the humans can, but would benefit significantly if they could catch the cattle of the humans. Without intelligence they would end up too often in exhausting battles. [Answer] If we look back on the two greatest sources of truths on dragons: Tolkein and Dungeons & Dragons, there are similar explanations. In Tolkein, if dragons were not intelligent, the Hobbit would be a much less entertaining book. The conversation between Bilbo and Smaug would be rather dull. In D&D, dragons are considered the hardest monster to conquer, and were typically reserved for the final rooms of dungeons. If they weren't intelligent, they would not make for as tough opponents. For one thing, your intelligence score in D&D corresponds with your magic ability, so in that system a magic wielding creature would need to have a high score there. The connection between these two points are that humans had historically hunted dragons for one reason or another. So it's a simple matter of selection where the more intelligent of the dragons were able to avoid humans longer, giving them more opportunity to breed. Over time dragons numbers became more and more rare as they were hunted to lower numbers, meaning that those smart enough to lay low and be stealthy, survived longer. This is why in both Tolkein and D&D we find the dragons hiding in rooms for decades at a time. [Answer] **Magic** No, seriously. Dragons (or at least dragons on a Smaug-like scale) command fire-power (and flight abilities) rather greater than mere chemistry permits. If this is not nuclear, then it must be magical (as in, a force of nature which does not exist in our everyday world). And most flavours of magic are intrinsically tricky. Magic, in some sense, resents being harnessed and commanded, and tries to turn upon its wielder. Stupid dragons do not survive adolescence. They tend to auto-immolate. As, indeed, do young mages, if not discovered early and carefully tutored by elder and wiser mages from the guild. Dragons don't have a guild, so they have to be very smart indeed. Someone else has mentioned octopus intelligence, in a largely asocial creature. I can't help thinking, that dragons must have eight vestigial tentacles.... [Answer] Depending on the ancient lore of the world, the dragons may trace their heritage farther into the past than humans. Perhaps they weren't always the apex predator, but tiny lizards running around among gods. That would give them the same evolutionary pressures humans faced in a world surrounded by large animals who were both predators and hunting competition. Growing smarter would be one way to win this competition. This would also imply that dragons used to be more sociable and less territorial than they are today. A lot of our intelligence comes from our ability communicate, and form complex plans with other people. Often, the people who succeeded the most (had the most children) were the ones who could predict or manipulate the actions of their tribe. Dragons would have to have something similar, where understanding a complex system would make them more likely to reproduce. Note that there's no reason for this to be limited to dragons. Any of their contemporaries could also have gained intelligence this way. ]

[Question] [ Any story about an independent, self-owned tramp spaceship crew tends to implicitly or explicitly raise the question of how the crew got a spaceship, how it afforded it, and why it doesn't just sell the ship and retire rich, *especially* if it otherwise doesn't seem to own much in the way of expensive stuff (as is often the case in such stories). If, in a given setting, private ship owners (rather than, say, leasers or corp-hired crews) are ubiquitous and customised ship designs varied, **then the only way to justify this is to make the ships be relatively low in sale/production/design cost**. Thus the question: **How can relatively affordable spaceships can be justified?** Constraints and considerations: * I'm trying to find how to justify affordable spaceships without upsetting economies. That is, mildly well-off independent entrepreneurs buying a spaceship outright and starting a small transport business should become viable, but whatever enables that **shouldn't** produce rapid exponential growth or radically influence the affordability of other goods. * Post-scarcity or a broad requirement for all captains/crews to be super-rich **isn't a solution**, as I'm looking for justifications that won't require significantly distorting the rest of the economy. Just because one can afford a ship shouldn't mean that one is also rich enough to never worry about the cost of adventuring equipment ever again. * Existence alternative technological paths that reduce the curve of economies of scale (making small-scale production more efficient and/or reducing the efficiency gains of larger-scale production) are acceptable (so long as they don't lead to post-scarcity), welcome, and in fact probably necessary. * Affordable ships should go hand in hand with not-too-high profits from owning one, as otherwise ships become rapid exponential-growth investments. * Some bending of fundamental laws of nature is acceptable, but I'd like to be able to justify them in at least recognisably science-fictional range of settings (Star Wars are about on the edge of how soft/fantasy-ish settings can be to stay within the scope of the question). * Given the point above, reactionless drives are an acceptable and even welcome *part* of the solution, as they remove concerns about expensive liftoff. However, it's important to make sure affordable reactionless drives can have unintended side effects on settings, so any suggestions of making such drives even more accessible should come with the possibility of preventing or at least restricting unintended side effects. * Indebted captains and rented/leased ships are beyond the scope of the question - I'm looking for achieving affordability, not for a way to let people hold something they can't afford. My go-to default is that ship owners operate as Physical Person Entrepreneurs (not sure how to translate it into English) rather than Micro-Corporations. * Surplus from a prior mass production run (e.g. ex-military) isn't what I'm aiming for, as that would imply greater uniformity of designs and less customisation than is desired. I'm looking for excuses to **make *shipbuilding* relatively cheaper/easier**, not selling of already-built ships at a loss/discount for some reason. * By bespoke I mean that the ship designs/constructions/etc. are meant to be **meaningfully very varied and customised**. Examples would be Star Wars' YT haulers, of which I've seen it written that no two are alike aside from a vaguely recognisable silhouette, or [Aether Sea](https://www.drivethrurpg.com/product/139872/Aether-Sea-o-A-World-of-Adventure-for-Fate-Core)'s millions of aethercraft variants. I don't mean something as superficial as varied paintjobs. * While the idea of spaceships being some variant of tamed and cybernetified [Space Whales](https://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceWhale) or similar is interesting, it's not what I mean by bespoke spaceships. I'm looking for things that are made, not found with most of the work already done. [Answer] # Drives are cheap and *light*. Assume a technology that makes interstellar craft affordable. Instead of expensive, disposable rocket boosters to get into orbit, there is a sublight/maneuver drive that takes only a small fraction of the ship's total weight, leaving plenty for cargo *and for a hull constructed out of normal steel, not titanium or expensive alloys.* This weight and cost consideration includes the fuel or reaction mass. It is bad for most stories if ships never run out of fuel, but fuel isn't the overriding design consideration as in contemporary spacecraft. # With enough thrust, even bricks can fly. The sublight maneuver drives are powerful enough that ships don't have to aerobrake on reentry. That means they can be rough boxes rather than slim, streamlined needles, and any backyard mechanic can weld another box onto it. That brings the "custom" part of your story. # Drives/Power/Computer last longer than hulls. Few moving parts in the engines, nothing that wears out unless the drive is *overloaded* by desperate characters, so those can last for a century. The hull, on the other hand, *is* subject to stress during spaceflight and atmospheric maneuvering. Either it has to be patched, or a completely new hull must be built every couple of decades around the old engines. Doing that takes no great skill, more what a boat builder does than the R&D that goes into a modern airliner. Hull builders can follow the original plans, or they innovate on demand. ("That many cabins? Hmm, make her longer or cut the hold?") # Ships are reasonably fast. A typical flight from the surface of one planet to the surface of another takes only a week or two. That will greatly simplify life support. Take a CO2 scrubber, an oxygen tank, and there you go. No need for fancy hydroponics or 99.9% efficient recycling. # Ships are small. Use the technobabble for the stardrive to discourage large ships. Either they cannot go FTL at all, or they are less efficient. That means the necessary traffic will be carried by many small ships rather than a few big liners. [Answer] **Let's look at the world of shipping here on Earth for inspiration** I have a suspicion that if you look at the history of shipping, you'll discover that whether it's a cart or a bullet train, the basic limitations for being an independent owner/operator of a shipping company remain the same. * I own a pickup truck and that lets me do a great many things, including haul a limited quantity and type of things around as a business. It was bought used and was a \$7,000 investment. I do not own a semi-tractor/trailer with the latest in home conveniences and the ability to haul different kinds of trailers for different types of goods. That's a \$250,000 investment, easy. I certainly do not own a [container ship](https://en.wikipedia.org/wiki/Container_ship) that can haul unimaginable quantities and pretty much any type of goods with a breath taking investment of \$74,000,000 or more. *And yet all these creations contain motors that are identical in fundamental operation.* Ignoring the technological differences and simply identifying them as "combustion engines," their basic difference is size and cost. * With my humble pickup truck I can acquire and/or deliver my limited number and type of goods at homes and small businesses — pretty much locations that have roadside or parking lot access. Yes, I can use a dock — but in most cases that's inconvenient-to-impossible due to the size, design, and operation of the docks. A semi-truck can deliver roadside (I've seen it done!), but they hate it because they want (but don't require) forklifts to move things along faster. They want to utilize large companies or distribution centers. Container ships obviously can't deliver roadside (that'd be cool, though, right?). They require specialized docks with specialized equipment to on/off-load their shipments. * Finally, I can fix anything on my pickup. Well, almost anything — I'm not a transmission person, but that's really only for a lack of patience to learn how to do it. There's nothing so complex on my pickup that I can't fix it. Parts are plentiful and readily obtained new or used from the local junk yard. Semi trucks *could* be maintained by the individual owner, but far more often a team (company) is involved for both repair and maintenance — maintenance that can't generally be ignored or delayed without consequence. Container ships undoubtedly have rigid maintenance schedules are huge teams to keep them operational. **Let's work with those three perspectives** A big, fancy, expensive ship perhaps has the ability to descend/ascend the gravity well of a planet, but also requires someplace to be when it's at the bottom of that well — a large transhipment area dedicated to the ship. It can haul massive amounts of any kind of good, and requires the treasure of the Sierra Madre to keep it running. But my ship? I'm proud of the new camo-spray-paint job I just gave it! I use it to go *Flugert* hunting in the rings of *Magnemein Six.* But when I'm not doing that, I'm either fixing it or using it to ship *Granthen* sand (the very best sand for cleaning your sidewalks in the universe!TM). I make a modest profit because... * The ship and engine are small, simple, and powered only for the size of my ship. * My ship is large enough that I can make a profit, but small enough to get to places the big boys can't. It allows me to follow niche opportunities. * Engines are never one-size-fits-all. It takes so much more to move the proverbial half-a-planet of goods than it does just a pickup load. * A ship this small would never be economical if it tried to land. Too much fuel. It would depend on space stations (distribution centers). I firmly believe such stations would exist as the economy-of-scale moving large amounts of things to-and-from the planet is, to me, obvious. I expect Amazon.com is already working on plans for one. * Oh, and did I mention that my ship can really only get around in my local star cluster? I can't cross the proverbial oceans, or even the proverbial continent, and expect to make a profit. I'm only good for working inside my proverbial city. Meaning my profitability-vs-range ratio is fairly small. **Conclusion** Small ships are easily justified when you remove: * Tech needed to land on or launch from a planet (or any other significant gravity well). * Tech needed to be self-sufficient (long-term travel). * Tech needed for major defense, like armor and weapons (uses only established trade lanes, which are certainly policed). * Tech needed to deal with large-ship problems like torque compensation (turning a large ship is not easy). The beauty of space is that a small-engine ship can actually do a lot. Consider Austrailia's [road trains](https://www.youtube.com/watch?v=0iFkKRh5kcM). Your cheap ship could haul a very long (much longer than those road trains!) load so long as no significant gravity well was involved. Slow acceleration to cruising speed. During the trip you detach the "tractor" and move it to the back of the train where it serves for deceleration. Heck, I can easily imagine the development of tugs associated with the space station distribution node that would handle the work of detaching/attaching the individual payload segments — not unlike a [railcar mover](https://en.wikipedia.org/wiki/Railcar_mover). The resulting ship is basically a flying pickup truck capable of towing a lot of trailers. Small, light, easily maintained, and easily controlled. It would depend on short-run, (relatively) low-quantity trading, which goes on today all the time (think in terms of your local furniture store). *One more thing. That long chain of segments poses an interesting problem to would-be space-faring highwaymen — you can't just hook onto the front and start moving in another direction. The quick smash-and-grab would not work. The end of the chain, thanks to the lack of things like gravity and friction, would snap around like a pair of feral nunchucks and tear everything (including our would-be Butch Cassidy of space) to pieces. Curious. Interstellar "train robbery" is non-trivial. Might make for an interesting question! N'est-ce pas?* --- **Edit:** Talking with Paul Z got me thinking. You could improve the profit-to-cost ratio tremendously by using two tractors and *not* keeping the tractor with the shipment. One tractor pulls the train up to speed, disconnects, and goes back for the next shipment. Near the destination another tractor accelerates out, connects, and slows everything down. Considering how long things might need to travel in space, that would improve the economics so much that you might never have really large shipping at all. Just a thought! [Answer] I think the main factor that would simplify the ship production and cheapen the ships significantly would be this: most of the ships in the setting are not expected to enter or leave a gravity well of a planet with atmosphere. It may be that people in your setting live mostly in space habitats. Could be that all the planets have space elevator stations you can dock to for trading. If you do not need to leave the gravity well, the maximum power output of the engines can be much smaller. If you do not need to re-enter the atmosphere, the hull can be much simpler. If, additionally, most of your people live on habitats and space stations already, the life support and recycling technologies in your setting may be so advanced, it's an easy task to equip any random tin can with it. Most other things depend on whether there is a FTL technology and how it works. If there is FTL, but it's enabled not by the ships drive, but by a natural or artificial wormhole, any small habitat can afford to build multiple tin cans for trading - they may be slow, going for something as sustainable as solar sails even, but a journey from their habitats to another solar system through the wormhole will have human-scaled duration. [Answer] ## Partial Obsolescence of Space Drives A space drive (both the cross system FTL part and the in-system maneuvering engines) drop in power rapidly in the first few years of use, before leveling off. Within the first five years, a space drive drops from its maximum power rating to about half that. It then stays at that level a century or more. It's still perfectly usable for a space merchant, but totally unacceptable for the military, or rich pleasure yachts. With the rich replacing their spaceships every few years, there is a glut of hand-me-down spaceships on the market, making acquiring one affordable for the lower classes. The military does something similar, but before they sell their ships they strip out all of their fancy weapons systems. In order to make that process easy, they've made their ships highly modular, and thus while the base frame of all the military ships is very similar, they're heavily customizable (and missing half their systems upon resale, encouraging people to customize them). [Answer] ### Don't land The most expensive operation in a typical mission from a planet is the takeoff. If your ship never lands on the surface of a planet, it never has to take off. It can just travel from space station to space station. How freight and passengers get to the planet's surface or how the space station gets freight and passengers to it aren't the space ship's problem. Not landing makes the problem much simpler. The ship only needs to have maneuvering drives and a space drive. It can refuel in space, which is cheap because solar panels in space can be placed such that they can see the sun twenty-four hours a day. And solar panels can be built by robots using solar energy and asteroid material. The robots can also be built the same way. So refueling is very low cost. And so is space ship construction. This may seem like post-scarcity, but it only applies in space. As soon as someone lands, they are subject to the normal planetary restrictions. In particular, planets have limited space and can only burn so much fossil fuels per year. So land and energy are both limited on the ground. So your planetary economies are restricted while your space economies are much less so. What's expensive is landing and taking off again. So simply never do that. Space ship crews spend all their time in space, mostly on their ship. ### The bigger problem The bigger problem is that manned freight ships don't make much sense in space. If I want to get freight from the asteroid belt to Earth orbit, the simple way is to simply throw it. Strap it into something ferrous, accelerate it with superconducting magnets and then catch it at the other end with a funnel made of superconducting magnets. There's no need to send a crew with it. You only need an engine for making minor adjustments so as to avoid space junk or reorient on the funnel. Passenger ships make a bit more sense. But why would people prefer small ships to large ones? The larger the ship, the more options it can support. To justify small ships, you need to increase the number of destinations. So only a few people want to go to most places right now. You may want to make your ships faster-than-light and non-inertial, as even in the Solar system, getting from place to place at one g takes a long time. Which in turn makes it unlikely that ships would be leaving every day for every destination. If you have to wait six months in travel, waiting an extra month to gather enough passengers to leave isn't a big deal. If you can get there in four hours of travel, you won't want to wait more than a day. [Answer] # Self-Replicating Machines Most people think about self-replicating machines as grey goo style nanotechnology, but upon closer examination of the topic the simplest selfreplicator is an autonomous factory capable of producing two copies of itself and some of the desired product before breaking down. These things can and will realistically be macro-machines in the foreseeable future, even without consider the many issues of large scale nano-bots. Improvements in the fields of AI, material-sciences and three-D-printing will make self-replicators which can produce most goods with minimal human input within the next hundred years inevitable. Even though Elon Musk failed to builed a fully automated Tesla car factory recently, which arguably wouldn't have been a self replicator yet, the fact that this was even seriously attempted shows you how far we are already. **What does this mean?** It doesn't matter if you subscribe to the capitalist or communist theory of value, as supply will be huge and only limited by the access to the resources of however many solar systems your world can access and labour invested into the production of goods will be minimal as well. The economy of such a civilisation will be a low scarcity one, not a true post scarcity one. But this will work fine since while a perfect market is the basic idea of a capitalist system it too is practically impossible, yet capitalism still lets most people survive decently. This means that *the price of a space-craft is determined by its scrap value* and possibly the cost engineering blueprints unless the desighn was autogenerated to the specifications of the constructor by an AI or open source. The nature of such an economy will obviously keep the profit margins small. Bulk trade goods might be rare metals, tholines for farming, Helium-3 for fusion generators and objects which require highly specialised fabrication facilities or can only be produced on one world due to licensing and international property rights (Vodka brewed with Enceladus water can only be produced on Enceladus, otherwise it would not be the priced Enceladus Vodka). Art would be another thing that is still tradable within such an economy, even though art will most likely have an extremely broadened meaning, since anything, like the Enceladus Vodka from before, can be crafted in a unique and artful manner. **So what about the cost of adventuring equipment?** What is cost? In our current culture we view cost as a primarily monetary concept, but this does ignore that even now we also use (pay) time to get goods and services. In the low scarcity and highly automated civilisation described above this relationship is simply reversed. This would be especially true for space craft, since they will seek to cut down on mass as much as possible. Thus having a fabricator on board wich can produce almist everything given the right resources, a blueprint and time. While neither the blueprint nor the resources should be an issue this [Santa Claus Machine](https://youtu.be/FmgYoryG_Ss) won't produce equipment instantly, so the time needed to produce the equipment which is needed in a specific situation is its cost. [Answer] **Salvaged alien tech is the basis for space flight. The rest of the ship is whatever you have.** A dead world is littered with artifacts that make spaceflight possible. It is not clear if these are products of technology, some sort of crystal or what, but there are a lot of them. Stick them onto something and it can be a space ship: atmosphere retention and propulsion. But we meatbags can't just sit in a raw force field flying through space. You have to breathe and pee and poo and sleep and play cribbage. Of course there are swanky purpose-built ships for the military, rich folks and so on. But a lot of people fit out campers, sailboats, shipping containers, toolsheds and tents; what you have, third world style. Anything can be a space ship. They are added to in an ad hoc manner according to need and availability of materials. I like the idea of a series of barges filled with dirt, growing oxygen-providing crops under the perpetual day of space. The crew sleeps on the soft dirt of their fields. No mosquitoes. [Answer] First off, don't make them bespoke, have them made-to-measure: The initial ship is constructed from a number of mass-produced modules which are connected together. If each ship is constructed from 5 different modules (Cockpit, drive section, crew quarters, and 2 cargo / passenger sections?) and each 'model' of ship offers 5 options for each module, then that's **3,125** different permutations for *1* model of ship, from *1* manufacturer. Multiply that by different models/sizes of ship, and then again by different manufacturers... You get the picture. This also discounts being able to add or remove modules (Personal ship for a small crew? Just the cockpit, drive and crew modules. Freighter or passenger ship? Add extra modules for seating or storage) Next, your scrappy independent space-tramp crew will *customise* their ship to fit their own needs with after-market add-ons. Perhaps salvage a module from a different manufacturer and add it on. On a related note - did you know that a fresh-from-the-factory Harley Davidson motorcycle doesn't make the "distinctive noise" associated with them? Due to regulations about noise pollution, et cetera, they're not allowed to - but, there's a different company who will sell you the parts and the instructions to modify your new hog. So, these ships aren't actually outrageously priced - they're not necessarily normal personal ships, but compared to buying a car it's more like buying Caravan or a Motor Home instead of being like buying a luxury yacht. And, if you can find one that needs a lot of work (and are willing to put in the effort!) you can probably pick up something cheap and ugly to fix up. As for "why not sell it and retire rich?" - well, we've already established that the ship isn't exactly rare, nor is it the latest model. They can sell it for around 100,000 Quatloos, split that between a crew of 10 - giving them each just under 2 years worth of Rent or a minimal house deposit for a mortgage. Or, they keep the ship and try to average 1,000 Quatloos per week running jobs for the same time to make the same amount. [Answer] Short version: Because very few people actually want one and there's a lot of shipyard space that could be used to build quite a few such vessels, and occasional it even is. Long version: Most ships are ***huge*** and *all* ships are one of a kind, this situation only really makes sense where the limits of the drive systems being used are unknown and the economy is expanding. The giant bulk transport they built a couple of years ago wasn't the limit, based on its performance so far it isn't even as close as they thought at the time and there's still greater demand than the current fleet can supply so the next ship is still larger. As ships fall further and further behind the cutting edge of [economy of scale](https://en.wikipedia.org/wiki/Economies_of_scale) they have to go farther and farther out from the centre of things in order to stay competitive in the bulk cargo game. With the big ships just getting bigger the shipyards constructing them have to grow as well, not just in terms of hulls being laid down at any given time but also in the scale of construction cradles meaning they will have a fairly rapid turnover of obsolete equipment, obsolete for the largest projects that is. However there is a certain class of ship that never really needs to change its overall size, although individual designs will vary greatly according to the particular role foreseen for the vessel; the courier. This is a relatively small vessel designed for high speed in real-space and/or FTL depending on the rules of the setting and "port versatility" (being able to dock, or land, at any port, or in a field, or even a jungle clearing at need). These are designed to carry sensitive materials, compact but expensive cargoes, and/or a few VIP passengers. Classic examples of this class of ship include the [Firefly](https://firefly.fandom.com/wiki/Firefly_Class), the [Tel'tak](https://stargate.fandom.com/wiki/Tel%27tak) and the [YT-1300](https://starwars.fandom.com/wiki/YT-1300_light_freighter). The profit margins on such ships can realistically be quite competitive or absolutely shoestring at the author's/GM's discretion given fixed costs and the vagaries of available work. Shipyards are familiar with custom one-off vessels, they don't build anything else, but don't produce many ships smaller than the equivalent of a super tanker in the usual run of things. Its not that smaller ships are particularly expensive, they're pretty cheap in fact; it's the fact that they're a niche product for a niche in the market that very few people are actually keen to fill. The lack of demand actually leads to the kind of ship that 8-10 crew can run being even cheaper than one would think, supply and demand, you can find at least one courier going secondhand in most systems as some poor inheritor with no desire to travel the starlanes tries to offload. So while they're worth the yard time its only when staff are between major projects and using obsolescent construction gear. [Answer] The building of spaceships in a space faring civilizations should be similar to how cars and trucks are manufactured in today's standard. As manufacturing technology as well as experience of spaceship building improves, the cost of creating one should decrease exponentially. Without knowing more about the world: small group of people should be able to pool enough resources to purchase an average, unremarkable ship. The main issue should be maintenance and operation cost, fuel and repairs. That would make the crew to seek out lucrative deals and contracts. Dangerous travels to the unknown netting more profit than safe, established trade routes. Competing manufacturing companies could account for a wide variety of designs based on various demands. Like I said, look at today's car manufacturing. [Answer] **Cheap To Build, Expensive To Fly *Unless You Cut Corners*** This is a simple economics question. If your ships have a high variable cost of operation (high "cost per mile") but a low cost of construction and storage, they will naturally be easy to acquire, and will not make anyone exponentially rich, because it still costs real money to transport anything anywhere. This high cost of operation could be a combination of fuel and other expendable materials (ablative shields, life support supplies, high wear and tear parts, etc). A low cost of storage while not in use and low recycling value [or high cost of recycling] is critical for ensuring old ships are not routinely scuttled. Your renegade crew is not rich (the ship is not worth much) and also not indebted (the ship was cheap to buy, and costs almost nothing to keep "parked" in stable planetary orbit) but they'll be motivated to find ways to make money to somehow afford the fuel and other operational maintenance. **Cheap To Build** You want your ships to be cheap to build *relative to other costs in the economy*? I think this too has a relatively simple economics solution: **limited usefulness**. Your ship's hull and propulsion technologies have absolutely no other useful application outside of spaceships. The hull material degrades when exposed to the atmosphere. The propulsion is embarrassingly simple but only operates in a vacuum and in the absence of perpendicular forces (i.e. pretty useless on a planet's surface). **Cutting Corners** This part is key: If your crew is willing to take some calculated risks and cut some corners, the operational costs can be reduced to an affordable level by skimping on non-critical maintenance such as safety upgrades, insurance, holo-deck content subscriptions, clean-burning fuel, training, certifications, etc. That means your renegade crew can fly their ship much cheaper than what the average operator would. This kind of corner-cutting is not scalable beyond a tightly-knit team of adventurers, so you'll never see a mega-corporation operating in this manner. For a contemporary Earth analog just look at the prices of old airplanes. They are probably not as expensive as you think. [Answer] **3D direct metal laser sintering printers** that produce finished products and don't need to be put in a furnace. The last time I looked they were half a million dollars, now they're ~300k. But one big enough to make aerospace parts is going to cost you over one million. *That's* what's changed in your universe (as it will shortly in ours) : one with a bed big enough to make the parts you want, needs to be more like a hundred thousand. [Selective Laser Melting](https://en.wikipedia.org/wiki/Selective_laser_melting) ([Selective Laser Sintering](https://en.wikipedia.org/wiki/Selective_laser_sintering)) > > On the other hand, SLM can go one step further than SLS, by using the laser to fully melt the metal, meaning the powder is not being fused together but actually liquified long enough to melt the powder grains into a homogeneous part. Therefore, SLM can produce stronger parts because of reduced porosity and greater control over crystal structure, which helps prevent part failure. However, SLM is only feasible when using a single metal powder. > > > This machine is what you build the rest of the ship around, because you don't leave home without one (there are *zero* auto parts stores between here and Jupiter). It dictates the size of the landing gear, which in turn prescribe the size/weight of the ship. The hull can be contracted out to the lowest bidder or welded yourself, that's why they all look different. Affordable machines like these are a literal requirement to get this endeavor off the ground, as it's what would make mass-production no longer necessary for specifically building a spaceship (and make lone space travel slightly less suicidal). Ships might even be classified by this 'heart' of the ship, e.g., an *8X3 Pinto* would have an eight cubic foot bed capable of slowly producing parts from three different elements. Obviously, everyone wants a *24X9 Concorde* but those machines are unaffordable and require you to build a crew-intensive, unnecessarily large craft around it. That means less bottom line for any entrepreneur that hasn't increased their EoS to the point of becoming a conglomerate (the 'enemy'). [Answer] TBH its all about the running costs and the build costs. eg. Imagine you have a space drive that costs 1 fuel unit to travel FTL. In this scenario, you'd end up with a humungous space freighter that waits for cargo and then hops to point B where it waits to be unloaded by small craft. So your small craft are just ferries, last-mile transports. But if fuel was proportional to mass, then the running cost is more about crew. A huge freighter will still be more cost effective than a small one so would be used a lot more, but there's always a need for couriers for small or urgent deliveries. Now imagine if fuel was exponentially proportional to mass... suddenly large ships are not cost effective compared to small ones. In fact, the smaller the better. Now when it comes to economies of shipping, the costs of running it matters a lot, you can't get rich off tranport if all your profits are taken up by running costs, and as the shipping economy increases, the profits available will decrease, there'll always be someone willing to run your cargo for less. So that's why you sometimes have lots of shipping available, and people trapped in a freighter they cannot sell - when they started there were few freighters and profits were good, but today, with all the competition, there's little margin and nobody wants to get into the game and that old, rusty freighter is worthless. Now the aspect of building custom freighters is simpler in future environments: if you have the basic cargo interface, then ther rest of the ship can be whatever you like. And if you build ships not from a production line but from a autmoated assembly system (eg something a robotic 3d printer) then the difference in cost of any ship is simply the cost of the plans and material used. I'd assume base plans were available for a simple fee (or open sourced!) and then customised by the user before submitting to the yard that would just plug it into a robo-assembler. Assume also the parts would be standardised (eg engines etc) so there's no further problem with maintenance and a custom ship costs the same as a off-the-shelf one. [Answer] There will surely exist cheap mass-produced habitable modules including life support and suitable engines. These allow for bespoke constructions(or contraptions heh). However there's a radiation problem. Near Earth, such as on ISS the shielding can be relatively thin, as the magnetic field of the planet deflects charged particles away. In deep space, and to have long-time-survivable environment, meters of heavy shielding will be required. This will be either expensive to manufacture, expensive to propel, or will require a new technology. [Answer] So, A couple of other people have discussed how small ships can work on the technological/individual/maintenance level. I'm going to talk about on a systematic level. # Wormholes So, let's talk about two properties predicted for real-life wormholes: first, they're spherical, and second, they have a mass balance. Send too much mass from one side without sending any back, and they collapse. Now, what does this do for your setting? Well, first, it eliminates the need for small ships to carry around an FTL drive of their own. Second, it creates critical points that can be the location of conflict. Now, why does this favor small ships? Because a single small ship is unlikely to collapse the wormhole by passing through it. Meanwhile, a "Panamax" of the era has to make sure there's something else going back through the wormhole (and coming out on the other side of the sphere) at the same time so it doesn't collapse the wormhole. A big ship could be waiting for a while until a counterweight is ready to be sent back through, while a smaller ship is more likely to have a counterweight that can be sent through to roughly balance the ship (perhaps another small ship.) Depending on the "tolerance" (how much mass can be sent through without disturbing the wormhole) you can make out niches. "Panamaxes" that have to be planned well in advance, and basically shut down the wormhole for everyone else for a while, but can carry the large sorts of cargos no other ship can.. Midsized bulk freighters that are big enough to carry a lot of cargo, but have to be scheduled - including the mass they're carrying - in advance, on a schedule. Couriers, small ships that carry priority goods and people and messages on a frequent and frequently-shifting basis, that only affect the wormhole en masse. [Answer] Fab labs AKA rentable workshops. There is a current movement called the maker movement, people who make things themselves instead of buying them, it is a fairly large movement. Part of that is something called [fab labs](https://en.wikipedia.org/wiki/Fab_lab) which are rentable spaces containing all the tools need to do some fairly advanced engineering and construction. people use them to build everything from hand tools to boats and cars. In the future I could easily see this movement pushed all the way to automated fabrication facilities, robotics combined with AI means all you really need is some engineering knowledge and a dream to build whatever you want. With the raw material and a rental fee and you can build anything. The vast bulk of a ship is fairly cheap materials base metals and radiation shielding. Not every shi will be unique but a large number will be. Many more will be unique in shape and design but with a standard engine or other modules. Automation is becoming more and more accessible (look how many people have 3d printers or cutter/milling machines) so this is by no means an unlikely stretch. Later those fab labs could even take advantage of nanotechnology to be portable, the [Schlock Mercenary](https://www.schlockmercenary.com/search/submit/?q=fabber) comic uses this extensively. Basically once robotics reaches a certain level anything but the most advanced technology can be made on the spot with the right raw materials, power, and AI. There is something else you can add to this. There was an idea for a while of mining out asteroids and then using the hollowed out shell of the asteroid as a the start of a spaceship, just make it airtight and add an engine and life support. Some people will do this just for the look, and every asteroid is unique. I could even see specialized ships "seeds" being sold. Place box on asteroid press button come back in a week to collect your ship. [Answer] # **Standard, modular drives** The drive blocks used by 90% of all small-to-medium spacecraft are all standard, mass-manufactured and cheap. You can find replacement parts or whole drives on every station, no matter how far. People use them in case they break down or melt far away from major civilization, most don't want to risk getting stuck on some asteroid mining colony because their drive broke down. So, they go with what's easily procurable everywhere. Now for the rest of the ship, sure there are some big corporations that produce shiny, *premium feel™* assembly line iShips, but those, even if they have nice features and trinkets built in, are usually way overpriced, don't allow for any customization and offer no significant performance boosts over the other kind: Open source, garage-built hulls. Plenty of low budget entrepreneurs set up minidocks in their space-garages, get a good foundry 3D printer, some assembler bots and design and build perfectly usable ships at affordable prices. Some kids who are just starting out might be willing to build something for you just for the price of materials. They'll even hack the regulators and overclock your drive so you'll run circles around the rich kids with their shiny toys that cost 30x more. No guarantees on stability though. Or any guarantees at all. # **A shadow economy** Ships are very expensive, but in this age spaceflight technology is advancing at a rapid pace, so any company, to stay competitive, must throw unholy amounts of funds on research. To get those funds it must sell as many ships it can, as often as it can, at the highest price it can. So we get planned obsolescence. Not only is the average journey time is decreasing by 20% every five years, but all the other tech like sensors, life support, comms, inertial dampening, etc is advancing at such a rapid pace that owners are forced to change out their ships every 5-7 years to stay competitive themselves. And they do. The rich ones living in the central sector, working the major commercial routes, that is. That's not for us, though. We're far out of the way, nobody every comes here from Central. No shipping routes from the delivery giants, there's no profit for them here. They keep to the commerce sector where business is fast and money flows in rivers. And that's true for everyone living on the periphery, the edges of human civilization, save for some important commercial hubs. Even if we outnumber the central sector inhabitants, they have vastly more money than us. So much more that our economies aren't even compatible. We'd need to get our whole colony to save up for a year just to get 1 new ship. We get our hands on the "old" ones instead. They scrap the outdated models, sometimes recycling them to build new ships, but usually just store them in some orbit. They aren't designed to last, build quality is fairly cheap, but we can still salvage them. Reinforce the hulls, swap out some of the new flimsy, gimmicky systems for the older, more robust kind, customize any additions we might need, like freight hauling modules or passenger blocks, and we have perfectly usable ships. Not the fastest in the galaxy, but enough to get by, get the mail delivered. We supply all of the periphery with ships they need to survive, to trade, to continue expanding the reach of humanity. [Answer] The spaceships are alive and attuned to an individual. To become a spaceship captain, you don't need money you need time or rather commitment. **Backstory** Some years from now the rotation of the galaxy drifts the solar system through a region of higher Interstellar medium density. Within this region mankind discovers seed pods. Perhaps an accident involving one of those expensive spaceships ends with a survivor stranded on what appeared to be just a rock in space, but turned out to be a seed pod for a very strange organism. When a human spends time on a pod, it becomes attuned to them and eventually opens up. At first the podship is little bigger than an escape pod, essentially a one person craft useful as a messenger but little else. As the Captain spends time on the pod it grows in response to the desires of the individual. A decade later you have a Firefly to roam around in. But if the Captain leaves the ship it begins to regress or possibly die. Wiggle room for home comfort breaks I leave up to you. [Answer] > > Surplus from a prior mass production run (e.g. ex-military) isn't what I'm aiming for, as that would imply greater uniformity of designs and less customisation than is desired. I'm looking for excuses to make shipbuilding relatively cheaper/easier, not selling of already-built ships at a loss/discount for some reason. > > > Would make things cheaper - not just because there's ships already on the market, but because there's production facilities that already exist, and jobs that help fund local economies. In short, they're not cheap because there's many surplus ships. They're cheap because there's surplus *capacity* The design for a dropship may kinda work as a cargo shuttle, but a cargo shuttle might not need as much armour, have different requirements and weight distributions and so on. They *could* be built in the same facilities as a dropship. A cargo freighter could be built in a slip meant for a warship of some size, and a modern oil tanker is probably bigger than a aircraft carrier. More or less - they're cheap because they're a way to provide work for yards post war. Likewise there could be *parts* commonalities - with downrated or even similar engines, and various components shared between designs. You wouldn't buy a dropship, but your retroencombulator might be the same model and its produced en mass for many models. Much like cars - captains and crews might choose to modify their ships (the many faces of the correlian light freighter of star wars fame), with engine and software updates bolted or shoe horned in as the narrative goes on. Even if the ship is standard out of the shipyard, depending on their needs. captains may make changes, adding weapons, cargo space or even small parasitic fighters. If designs *are* based off surplus hulls, the actual designs might depend on what's available to modify, depending on the condition of the hulls and what the requirements are. [Answer] **Partnership and/or Fractional Ownership** Historically, many shipping houses (including ones which only owned one or two ships) operated as partnerships. An owner or owners' representative was aboard, sometimes in command, sometimes as supercargo. Depending on the model used, your ship could be owned (as shares) by the crew, or the crew could be employees. [Answer] A recent space war could justify the existence of vast numbers of decommissioned and disarmed small spaceships. Military equipment and supplies are often abandoned during retreat allowing for entrepreneurial appropriation. While the battle continues, the winning side would be wise to grant ownership of their enemy's ship and lucrative supply contracts to any enemy crew which defects and turns traitor from their previous leadership. [Answer] # Ships are expensive as all getout But we can still work it I've been reading [The Golden Age of the Solar Clipper](https://www.goodreads.com/series/51464-golden-age-of-the-solar-clipper) where precisely this problem exists. A bit of a spoiler, but if you look at the titles of each book in the series (or even just think about it after seeing the first two) its really not that much of a spoiler (the last book in the series pretty much necessitates it). > > Salvage. The crew became independent when they were part of another crew under the employ of a larger organization. They salvaged a floating derelict in space--all the crew died and the ship was left intact, salvage of the century--which was then sold at auction for a billion credits. Each man on the crew gets some fraction of the payout, based on their share allotment and a bonus if they served on the salvage crew (i.e. were aboard the derelict and flew it to port). The salvage crew combined their reward and scraped together enough credits to be able to start their own shipping company and buy their own ship. It might have been small, used, and in bad repair, but whatever the factors, they get it for relatively cheap. *Running* a ship doesn't cost that much, its the *hull* that'll cost ya. > > > [Answer] Embrace a duality economic system: * "Core Worlds" are effectively post-scarcity and near self supporting economies. They have the facilities and tech to churn out key component parts for dirt cheap, and "Primary trade" is handled by massive corporations with their massive ships that can move massive amounts of goods and materials around between the massive and well developed worlds... But humans love to explore and spread. And many of us have gone well beyond those well developed and supplied "Core Worlds", and keep pushing the boundaries. * Just like the largest shipping companies in the world don't bring whole freighters to small out ports and mining towns in the Canadian north, the massive juggernauts of industry can't be bothered handling trade with all the smaller out-worlds and tiny mining or exploration colonies. * The major players, with the massive ships driving the larger economies of the fully developed worlds, leave 'the little stuff' to 'the little players' and effectively out source the control and management of the scattered crumbs to other smaller companies while they focus on dealing with the major hubs. At the end of the day it is effectively the same thing to the major players: They care that goods and materials make it to the trade hubs, how stuff gets to or from the hubs after that is so far removed from upper galactic management that it wouldn't make any difference whether it was handled 'in company' or by 'independents' - They're both so far divided and so hands off as to be the same. [And if the mega-corps don't even attempt to deal in far flung 'local matters', then they don't have to be bothered with regional governors whining at them over corruption - Mega corp cares and worries stop at the edge of the trade-hub, and anything going on there is 'a local matter' and 'not their concern'. As a plus they don't have to pay for dental for teamsters who aren't on their payroll...] So what does this mean for ships? Well much like so many hot rods of today are built around the same few massed produced engines, all the small ships are effectively collections of different standardized parts. Whether their 'star drive' is a Feerd-9002 or the Choval-starglide8 [With enhanced stabilization control rods...] or any of the dozens of other small star drives doesn't really matter, as they all have nearly the same interfacing specifications. * Various 'unique' small star ships get put together because an engineer found a good deal on various standardized parts in a trade hub, slapped stuff together to deal with a specific mission, and the "Space pickup trucks" wandered off into the galaxy to do their thing. Ships get customized, often heavily, to meet specific needs. * Hauling cattle for a new colony? Refit the cargo holds for that specific run, but grain or ore bins still stack in just as well for later runs. * Pirate making 'a quick buck' in the region? Refit with heavier shields/armour and additional weapons pods in the hopes that they'll leave you alone for easier/safer pickings. * Billy got drunk and caved in the port side cargo bay while landing at the mining base? Cut out the damaged sections, and weld in a replacement bay from an old junker that's been sitting at the edge of the landing pads since its reactor gave out. Keep the ships flexible and made from a range of parts built to meet standardized interfaces from a host of different companies, and you can see a wide range of readily affordable yet unique ships. * Maybe a lot of captains will be flying around fairly bog-standard Big-Space-Industries Haul-It-Alls, with half of the ships in any port being part of the same class, but they'll each have their own unique bits or customizations. [Answer] Planets are dead-ends. They are deep down a gravity well and filthy, and the people who live down there aren't adapted to space. Strategically they are garbage, being indefensible and a poor place to mount weapon systems. The only people worth bothering with are people already in space. The only goods worth anything are those already in space. Even if something was useful on a planet, getting it out of the gravity well costs more than finding it in space. Generations of genetic alteration have made them suitable for living in space; they can handle the radiation etc. The best places to live are on space stations. Not all of them, the good ones. Space stations are rotation-gravity mega constructs; all the perks of a planet, none of of the pain. Ramshackle space bases are the next tier down. And below that are the people who live in tin cans with motors strapped on them. Transporting goods between the places you'd want to live is a living; it is one way to keep yourself in O2 and H2O. Other ways include prospecting asteroids, gas giant dive-scooping, space-jockey construction, rock-rat asteroid miners. All of these lives suck, and there is a constant drain on your volatile. Space travel is crazy high-tech SF. The "grid" provides a means to both move at sub-light velocity (using "grippers"), and do FTL jumps. The "grid" is controlled by the local state (control of the grid is a veto on all other efficient movement; whomever controls the grid controls space). This means you can no more turn your ship into a high-velocity weapon of war than you could do it with a bumper car; your ability to move, and even where you move, is at the whim of the grid-owner. Now this doesn't mean that illegal trade or running from police is impossible; using the grid to halt someone is done mostly as a military matter, as it involves disrupting a lot of legitimate uses of it. Just don't try to ram a habitat. So a) Ships are affordable. A shell plus a drive. b) The drive isn't a powerful weapon. It is more like a hook that connects you to a trolly-wire. c) Keeping yourself in volatiles and paying grid-fees costs almost as much as the profit you get from trading. So no exponential economic singularities. d) Definitely not post-scarcity. The trick is, the stuff that is expensive are consumables. The actual ship infrastructure is cheap. It is only metals. And as a citizen of space, you must have had rights to cubic in a ship or station already; converting that to a rusting portable bucket isn't going to be hard. [Answer] There's a factor more important than any specific fabrication or propulsion technique: Ships are intrinsically fast and cheap. **Safe** ships are terribly expensive, both to buy and to operate. Current intersystem ship licensing requires three layers of hull, triply redundant life support, artificial gravity gyms to maintain bones, and docking at official ports with those ludicrous slip fees. All those safety systems add mass and eat away at cargo space, so fuel per ton of cargo is outrageous Yet, there are ports that will look the other way when unlicensed ships dock, captains that will take the risks of hull rupture when maneuvering, crew with forged papers that won't hold up to any real scrutiny, shippers cutting corners and profiting the difference. For an unlicensed ship, the most important asset is an engineer who can keep the thing in the sky, and they all have different ideas, so no two ships will be quite the same. Lots of people ship out on a rust bucket, figuring if they survive one or two runs, they will have the cash and experience to go legit. A few people even manage to pull it off. [Answer] **We can't build ships, and they wear out.** There is trade between the "ordinary" citizens of the galaxy, and (say) an "ancient" or "transcended" civilisation that gained access to and mastery of hyperspatial technology a (cosmologically?) long time ago. They value unique items, especially those that they find surprising. Entities with different thought processes to their own are the most capable of evoking surprise, hence the desire to trade. Or so it is hypothesized: they are essentially inscrutable. We only ever interact with avatars, which are uninteresting robots attached to what appear to be tiny ships. They pay for things they like with FTL ships (and any other "magic" you want in your story). They'll build the ship pretty much any way you ask: "value" appears to be a simple function of internal volume. However, a ship is one piece. It's almost indestructible, but if you do manage to break any part of it off, the whole thing and everything inside vanishes without trace (causing a vacuum implosion if it's in an atmosphere at the time. You might draw a parallel with toughened glass turning into small blunt fragments the moment you crack it anywhere. You might also use this as a reason piracy doesn't happen. You simply cannot break into a ship unless you can persuade its occupants to open up. ) It is hypothesized that ships can be made only in hyperspace, that they end up back there when they die, and we don't have the faintest idea how to establish any sort of permanent presence in hyperspace. All attempts to explore the outside environment of a ship while it is in FTL transit have resulted in the disappearance of that ship and its crew. No traces have ever been detected. It is known that ships wear out. There are known, progressive symptoms of a ship that is no longer in pristine condition. As these symptoms become more apparent, the ship becomes less safe. What happens when it fails is unknown. It is simply lost without trace. The older it gets, the greater the risk of that fate. The result is that there is never a shortage of old enough ships, and the real question is how much of a desperado you might be. Do you accept a one in a million chance of disappearing without trace to an unknown fate? One in a thousand? One in ten? Ten to one against? [Answer] ## The bespoke ships aren't as good as mass produced ships **Out of Date tech:** There was a time when it was fashionable for the rich to have their personally built ships but time and ship tech has passed those by. Now, you might get someone with more money than sense to buy one from you but no one who knows what they are doing would buy it no matter how shiny it is. **Built Inefficiently:** Look at car trends. The thing has fins and chrome and other things that would make a designers gush and engineers kill designers. * Anything they do to work on it takes three times as long (one model of Cadillac required the shop to drop the front end off in order to change a headlight). * It is not set up for anything but cruising around. Cargo space? Hah! * Getting from the crew section to the "elite passenger section requires exiting the ship. [Answer] This is a variation on Willk's answer (I actually cribbed it from the Heechee universe). # Ships are, more or less, for free. Both ships and shipyards come from an ancient technology, so advanced it's almost incomprehensible; a "shipyard" is an artificial space monster that can be fed iron asteroids and will produce ships and parts of ships from a built-in menu, or shipyard "seeds" that, supplied with the required materials, will eventually grow into other shipyards. So now you have *lots* of shipyards from "eggs" that were smuggled after the discovery of the one true shipyard back in the days, before the government was able to fully clamp down on the discovery. Ships are therefore dirt cheap, even more so if you go for a small one. Ships can use anything for fuel, and are largely self-repairing. But both ships and shipyards are next to impossible to reverse engineer, and attempts to do so usually destroy the hero, the ship, or both (think of a jungle savage trying to poke into a modern car. Given an infinite supply of cars, the tribe might learn in time how to drive, but little more). Some useful side effects might be there - shipyards might possess transmutation capabilities and be able to "digest" and neutralize radioactive waste; a ship's anti-meteoroid shield can be detached and reused somewhere else, and ship's engines can be moved planet-side to produce cheap, clean energy from matter annihilation. This allows *some* weapon technology - ablation lasers and mass drivers, both energy hogs - but very little else. [Answer] **Don't justify it - because most things on our planet happen without justification.** Firstly, let's ignore the fact there will never be a crew as we already have ships and drones and the likes, flying themselves to destinations and back. Robotics companies are already designing robots to transport cargo via drones or carry cargo in the same way humans carry them because the ultimate goal is to replace as much human input as possible. Secondly, the only people bold enough to fly around space in this manner (knowing the amount of sophisticated tracking technology at that point which would no-doubt eradicate illegal activity anyway) would be criminals. Why bother justifying it? You don't need to justify it because 99.9% of the population really wouldn't care to ask how anyone got their rocket, what it flies on, where it parks, why it never needs to re-fuel. Ignorance is bliss. Like today's world for example. How many people in the world right now actually care who the companies are that make the machines that mass produce the food on their supermarket shelves? Who really cared where their plastic bottles went for the last 40 years until it was on the news? How many people will stand up tomorrow and ask Nutella to justify why they are happy to destroy huge areas of rain forest and kill Orangutans just to ensure they keep making money from a tub of chocolate... a tub of chocolate to make people go "mm that was nice". It makes no sense why it's allowed, like most of the things we destroy on our planet.. it makes no sense and you can't justify it. So to conclude.. the world is full of unjustifiable actions and calculations and most of it makes absolutely no sense why it's happening - but it does. So if our entire planet will happily continue buying Nutella or any other product that is causing the extinction of an animal then absolutely anything is possible like your rocket crew. If anyone asks you to justify it you say "because they just could and nobody stopped them". ]

[Question] [ A couple friends and I have started a world called Lothaucan. On this world there is a continent called Novara with a circle of islands as its key feature.  (seen in the mid-left of the image) Is this feature scientifically and geologically viable? If so, how so? If not, how can we change it for it to be viable? The world is a moon roughly the size of Earth, orbiting a large Jovian, and has more volcanic and seismic activity than Earth. That is all that has been decided. Please note that I am not asking about the viability of the orbital mechanics, but simply included it so as to give more information. If more information is needed, let me know and I will do my best to get it. Scale: Novara is a bit bigger than Australia (a little over 3,000,000 square miles/7,770,000 square kilometers). [Answer] An half submerged crater can give you a circular set of islands. You can choose among various craters: * Volcanic craters, like Santorini [](https://i.stack.imgur.com/IvZfZ.png) * Mountains subsided into the oceans or eroded by changing sea level, like all the coral atolls (the picture refers to French frigate shoals) [](https://i.stack.imgur.com/waBiQ.jpg) * Impact craters, resembling the Tycho crater [](https://i.stack.imgur.com/r4R0X.jpg) all of the above can also provide central peaks aswell. [Answer] For an alternative (to vulcanism) geological process, check out what was discussed in [this thread](https://earthscience.stackexchange.com/questions/10523/what-causes-these-circular-swirls-of-islands) at Earthscience.SE. Link to [Google Map](https://www.google.com/maps/@49.1941873,-94.5055954,12.13z) of the affected area. Basically, a very long ago tectonic collision caused part of the Earth's crust to fold in on itself and 'roll up.' Harder base rock gets wrapped around other softer layers of rock. Imagine a jelly roll. [](https://i.stack.imgur.com/4uv19.jpg) Now, hundreds of millions of years later, other tectonic forces have tipped this region onto its side. The swirling jelly roll now faces the surface. Eventually, this part of the crust is raised to the surface and weathered by erosion (in the case of the linked map of Lake of the Woods, also by glaciation.) Now you have a swirl of harder rock exposed and, if the elevation is just right, the softer 'jelly' part of the formation eroded away into a lake or the ocean. [Answer] ## Volcanic activity If that moon has volcanic activity just like earth, then you can call it `Ring of ...`, just analogous to our Earth's [Ring of Fire](https://en.wikipedia.org/wiki/Ring_of_Fire). [](https://i.stack.imgur.com/F0fOe.jpg) Just make sure the size of the ring is big enough (I'm thinking of 3000-8000 km in diameter). I don't have the science to back this up why, but I'm basing on the smallest ring I can find on earth. [](https://i.stack.imgur.com/U6tbJ.jpg) As you can see above, the lower volcano line is stretched almost 5000 km from northwest Sumatera (Aceh) to Maluku on the east. ## The islands in the center They might be remains of a self-destructed volcano. Here is the image of Samosir island in Toba Lake in North Sumatera, with an island within the center of the lake, which is the remains of a dead volcano's caldera. [](https://i.stack.imgur.com/Unoiw.jpg) There is also an example of self-destructed volcano island becoming several pieces of islands: Krakatoa volcano. [](https://i.stack.imgur.com/cIpoY.gif) ## Island in a lake in an island in a lake > > Yo dawg, I heard you like islands, so I googled you this [island in a lake in an island in a lake](https://www.google.com/search?q=concentric%20volcano&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiU_bDJpeLUAhWQ3oMKHUmWBc4Q_AUIBigB&biw=1024&bih=639#tbm=isch&q=island%20in%20a%20lake%20in%20an%20island%20in%20a%20lake&imgrc=MnjB0cMaVUhk-M:) – [Mazura](https://worldbuilding.stackexchange.com/questions/84725/is-there-a-scientifically-valid-explanation-for-a-circle-of-islands/84731#comment249405_84725) > > > [](https://i.stack.imgur.com/40TKF.jpg) [Answer] As L.Dutch pointed out, submerged volcano craters can create the necessary shape. In the case of Santorini, there is even evidence to suggest that it is the original source for the Atlantis myth. [Link](http://www.decadevolcano.net/santorini/atlantis.htm "Atlantis was based on Santorini?") Also it's worth looking at the shape of the island pre-Minoan eruption, which gives you a much more interesting shape: [](https://i.stack.imgur.com/BD5NR.gif) Hope this helps! [Answer] This is actually pretty simple. Rather than any sort of ring, your overall landmass appears to me a single line of land with decreasing width that spirals at the end. As long as that also vaguely corresponds to height, this formation could well be generated by just a single massive hotspot, undergoing intraplate deformation (because e.g. it's near a three plate boundary, or is much weaker than the other plate). As the plate with the hotspot under it subducts its neighbor (as e.g. continental plates are wont to do to oceanic ones), that neighbor continues strong shear motion, leading to the fragmenting of the weaker subducting plate and the formation of that sort of spirally shape via accretion. This means lots of earthquakes in that region, at least during the formative process, but most/all the volcanic activity is on the other end of the continent. Your island also has a distinct bend in the chain a little while after the spiral. With a hotspot-generated landmass, that change would indicate a change in tectonic motion. This is reemphasized by the small gap in the landmass shortly afterwards: this gap is the location of the former shear/subduction fault that then became a regular subduction fault and is now recently divergent. While the western part of the continent used to be part of the same plate as the eastern part, it's now broken off and is its own tiny plate. The implications of this system are that the rocks in the tail end of this chain will be highly metamorphic, both in terms of the islands and the underlying seafloor. Expect a lot of exposed and submerged blueschist, with an unusually large amount of Eclogite in the seabed. The Eastern Island will be much more tame, with more typical basalt formations transitioning to blueschist as one travels west. [Answer] Consider building a **[Weald](https://en.wikipedia.org/wiki/Weald)** The Weald is a region in the south-east of England, situated between two ridges of chalk hills, the North and South Downs. The geology of the whole region is dominated by these hills, and the lower hills that run parallel to them as you move towards the core. This is analogous to the multiple rings of concentric islands in your map. The region formed originally as an anticline, a place where the crust was folded and lifted, forming a single large ridge or dome. The upper layers then eroded away, leaving the deeper core exposed, with harder rocks resisting the weathering better and leaving behind hills. For your purposes, of a very large, circular or near-circular formation, you would probably want the rock to be uplifted by a magma intrusion, rather than being folded. Magma rose beneath the rocks, perhaps as a result of a mantle plume, hot spot, or similar, but rather than reaching the surface as a volcano, it found a planar weakness in the crust, and spread out, forming a [sheet intrusion](https://en.wikipedia.org/wiki/Sheet_intrusion). Essentially, it was easier to spread out and lift the crust above the magma than to break through the crust to the surface. The entire region was thus uplifted, forming a geological dome. Erosion wears most of that dome away, leaving behind the harder igneous and metamorphic rocks, which form your islands. [Answer] First off - most of these suggestions **assume a very Earth-like environment**, where you can find plate tectonics & seismic activity, air & water/ice erosion, and a nice, mature atmosphere, as well as the usual Earth-like gravity & geological makeup. Some of these have good SF/extraterrestrial substitutes - methane, for instance, is a good substitute for water under the right temp & pressure conditions. But variations in the others carry a fair amount of consequences/prerequisites - less dense atmosphere can give you the planet-sweeping erosive dust storms of Mars, more volcanic/seismic activity can give you the nightmare landscape of Venus. **With that in mind:** Erosion - whether caused by wind/gas, water/liquid, or glaciers/solid - of a structure of non-uniform geology will tend to look a bit like a resistance sculpture. Harder materials resist longer, so that's the part that juts out, whether you're talking about islands, cliffs (in the reverse case, you get caves & sinkholes). Now, several folks above have offered suggestions on how you get your concentric circles, and a decent geology textbook/website can give you loads of examples of such in the real world. Basically you either have: * (A) **Flat layers** get distorted (tilted and/or warped), usually by local seismic activity, incl. intense heat & pressure. Think earthquakes, and active zones like the Pacific "Ring of Fire", but also lots of minor-level shifting occurs all the time. And all those layers get eroded and re-distorted, which is how we get all that lovely non-flat ground, aka topography. * (B) **Liquid magma** gets extruded like toothpaste underground/underwater or above ground, basically volcanoes. In your case, think Hawaii, Indonesia, really almost every Pacific island. Volcanoes don't all erupt the same way\*, aren't shaped the same way, and can also have "generations", where new eruptions happen and distort the solid remnants of old eruptions. * (C) **Catastrophic**, extraterrestrial impact - meteorite impacts are really common, especially if the atmosphere isn't thick enough to protect the surface. Most of Earth's own major impacts just get "smoothed over" by the effects of erosion and the bulk-recycling of plate tectonics, but at times we have seen a *lot* of impact activity. There's a theory too that having the Moon kind of helps block some of it as well. If your world orbits a larger planet, perhaps that giant gravity well helps protect it, or maybe it just gets walloped all the more. **One last point** - You mention that this circle of islands is a key feature, but if there's any takeaway, it's that the processes that can create such a structure are really common. If this island archipelago is meant to be mystical or revered because of its uniqueness, you might have to maybe come up with some kind of way to justify that assumption (maybe the natives just haven't traveled far enough to see it elsewhere, maybe [A Wizard Did It](http://tvtropes.org/pmwiki/pmwiki.php/Main/AWizardDidIt), etc.). [Answer] If you don't require that the primary cause of the formation be seismic or volcanic forces, another possibility is that it's the product of some sort of organism. A non-mobile plant, animal, or microorganism that grows in a specific area will consume nutrients in the area, and deposit some sort of solid byproduct. As the needed resources are consumed, the organism will tend to expand outward in the direction where more resources are available. Over a long time, this gives rise to a ring or circle of active organisms with a central area that contains few nutrients. Most growth happens where the most nutrients are, around the edges, and the nutrient-poor middle area has little or no growth. The ring continues to expand, eventually producing a circular shape. On earth, an example of such is a coral reef [atoll](https://www.nationalgeographic.org/encyclopedia/atoll/). [](https://i.stack.imgur.com/pDYz1.jpg) Over time, as the coral builds up, it reaches the surface, and since it cant grow in the air, it must grow by expanding outward. The coral grows in the direction which has the best conditions for survival for the individual organisms(temperature, water conditions, food availability, etc.) With continued growth, combined with erosion, this eventually creates a ring-shaped island, generally with a central lagoon. Over time, it forms a ring of separate islands. In extreme cases it can form [a spectacular ring of rings, each containing additional rings, as found in the Maldives.](https://www.google.com/maps/place/Maldives/@4.1715004,72.9002622,670120m/data=!3m1!1e3!4m5!3m4!1s0x24b599bfaafb7bbd:0x414509e181956289!8m2!3d1.9772276!4d73.536101) Atolls can take on various shapes, from circles and ovals to [spiral-like shapes](https://www.google.com/maps/place/Fongafale/@-8.6267458,179.0884169,13.58z/data=!4m5!3m4!1s0x6fd6e23fcee0b76d:0x72b152364b7a6a64!8m2!3d-8.5204754!4d179.1979716), even [squares](https://www.google.com/maps/place/Rose+Atoll/@-14.5501198,-168.1545801,8740m/data=!3m1!1e3!4m5!3m4!1s0x71095ad46962b4e3:0xa8eb97e56ef649fe!8m2!3d-14.546667!4d-168.151944). Atolls are commonplace in some parts of our world, but rare in others, so it could be that some unusual special combination of features on your world would give rise to an atoll-like structure which doesn't appear anywhere else. Coral atolls are the most striking examples on Earth, but the basic concept is that an organism starts in a central location, consumes resources in that area, and then begins expanding outward to obtain more resources, leaving a central area which no longer grows. There are other organisms which produce ring-shaped structures here on Earth. A smaller scale example of the same phenomenon here is the [fairy ring](https://en.wikipedia.org/wiki/Fairy_ring), which is a circle of mushrooms which appear around the edges of an underground fungus. As the fungus grows and expands, the outer edges are where the most nutrients are, so the fruiting bodies tend to appear there. [Ringworm fungal infection](http://www.webmd.com/skin-problems-and-treatments/ss/slideshow-ringworm) is another even smaller-scale example. Since we're not talking about Earth in this case, you can use your imagination to come up with an organism which produces such a formation. It's easy to imagine some sort of seaweed that accumulates silicates or carbonates and leads to the formation of stony atoll-like structures. Plankton, or even large creatures like some sort of big crustaceans which only move as juveniles, then collect carbonates on their shells and become immobile in adulthood. Finally, some sort of intelligent or semi-intelligent life could produce such effects. Humans have produced oyster [shell middens](http://maineanencyclopedia.com/shell-middens/) large enough to change the local landscape within a few centuries, so it's not hard to imagine some other creature over tens of thousands of years creating entire islands this way. [Answer] Such picture of concentric wavelets could be created by some source of oceanic currents or winds directing or blowing out of the center, more or less constantly. I think, you have seen the picture of dunes or small sand wavelets on the bottom of the sea. They appeared in similar way. What could be that source of movement? I think that can be a very original detail of the world. Some anti-Maelstrom. The magic pole of the world. Notice, that while the distance between circles is about tens of kilometers, the length of waves should be about the same. Thus, the speed of the in/outward current/wind should be really great. On the other hand, that wind could appear once in thousand years... Other variants don't give that picture. A crystallization of mix of hard and soft minerals when there remains a source of heat (or frost) in the center could be concentric as a result, too, but it would have the size of meters, not hundreds of kilometers. Glacier could create concentric structure, too, the islands on the lake on greater island on the greater lake... happen in Finland or Canada. But the concentric layers are very much thicker there. A large caldera drowning down in warm waters will be doubled by corals. If the caldera is only partly drowned, we have three circles: outer reef, the crest of caldera circle, inner reef. If the structure of caldera plus central mountain is partly drown, there will be four circles around the central island. But the outer reef would never become the continuation of the continent mountain ridge. That ridge would go towards the central island instead. The chalk or karst structures have much smaller size. An asteroid could have concentric structure, and of any size but it should loose its half and fall accurately by this flat cut up. I can't imagine such accident. The roulette structure is a funny theory, but roulette of 500 km means that before falling on the side, the core in that place was 500 km thick. Then there would be NO geological movements at all. But the layer of that roulette should be about 100 km. How that could be swiveled around? Five turns? When even much more thin Earth oceanic core (7km) never makes three turns? When it goes too low, it simply melts. The structure hardly can appear as a result of spiral tectonic surges because tectonic movements do not go in spirals on that size level (for half a planet - you are welcome!). Because of the high viscosity of magma. Magma is much less viscous when it is more hot, but it were so hot, there would not be any normal continents, only maybe a few very hot islands in magma ocean. With normal temperature that structure could possible if the physic details on that planet are very different from the Earth. When magma behaves almost as water and the planet rotates much more quickly, but continents still have some plasticity as the Earthly ones. Volcanoes on such planet would behave as Hawaiian ones - those have low lava viscosity, too. There sure will be some lava lakes on such planet, too. ]

[Question] [ My hero travels from our world to a fantasy world where people speak English. While there are other nations that speak non-English languages, the particular land she arrives in does. How can I explain away English developing in a world otherwise unlike Earth? --- I think I'm going to go with a mix of implying English speakers came in the past and taught it to everyone and handwaving it. [Answer] There are a few ways to go about this... **She's not the first** Simply put she isn't the first English speaking person to be there, maybe of the few that came before her who spoke English one came into a position of power and the people just took up the language. It happens. **Coincidence** Simple enough, although in all honesty, it's a 1 in a who-knows-how-big number. **You don't** Here's how and why: Your world is a *fantasy* world, all you have to do is explain how they ***appear*** to be speaking English, this could be done in numerous ways, for instance: 1. Your character's natural and inherent magic ability grants her the ability to understand their language, this allows you to have her learn to read, write, and speak their language as part of her character development. If your different countries/nations have different magic systems, this allows you to limit her to that country and learn some of the languages. 2. ***Alternatively*** If your character is not magically inclined or you just don't want to do that, have her somehow receive an amulet or magical artifact that can help her to understand the language, this grants the same options as the above. If you were to go for the amulet or artifact, the easiest way for your character to receive it might be a family heirloom, this raises questions about her and her families past. [Answer] This is a [⚠trope](http://allthetropes.wikia.com/wiki/Aliens_Speaking_English). The [child page “playing with”](http://allthetropes.wikia.com/wiki/Aliens_Speaking_English/Playing_With) catalogs dozens of varieties. There are an infinite of alternate fantasy worlds. Why did he wind up in one with 3 dimensions and a recognisable Earth with humans who are the same? English is just one more little feature after all that. I suggest that of all the infinite to choose from, he broke through to one “near” in the sence of the state being very much like his own. --- Truth can be as strange as fiction. I just heard about how when the [*Mayflower* arrived at the “new world”](https://en.wikipedia.org/wiki/Mayflower), the [first person they ran into](https://en.wikipedia.org/wiki/Squanto) spoke their language perfectly! So, it might work because the protagonist is not the first to make the trip. It’s more realistic because not *everyone* speaks it, and the person who does is likely to be the one making contact with the new arrivial. “The royal mage has detected a transdimentional anomaly in the southern kingdom—better send the grad student who’s studying the other world.” [Answer] One tool that's often used for this is to make translation a side effect of the transportation process. This is used in Dr. Who, where The Doctor explains to his companions that his ship, the TARDIS, is actually translating for you, psychically. This becomes a plot point in an episode where the TARDIS is not functioning properly and stops translating. By making it tied to the already-fantastical process of teleporting to another world, you have more room to handwave. You could do something like tie the teleport not to a location in the other world, but to a person. You can then argue that the teleport process also set in place a bridge so that you can understand their language (but you have no such bridge for other language pairs). [Answer] ## The Language of the Future **TL;DR:** The reason that English is spoken in your fantasy world is because a powerful mage traveled to Earth, thought it was the language of the future, and introduced English as the official government language. After generations of use, eventually everyone in the nation spoke English. > > Dear <insert native name here>, > > > My explorations of yours and nearby nations have been fascinating. Seeing Ewoks play with the sapling Ents was particularly cute. But one question has been incessantly nagging at me. As you well know, I come from a extremely distant nation. You would not be able to comprehend how far it is away from your nation. At the place that I come from, people speak several different languages, depending in which nations they live. I have also noted the same thing to be true here. While most languages that I have heard here have nothing in common with the languages spoken at home, the language that is predominant in your particular nation is not only similar, but virtually identical to my native language. Our two cultures are so vastly different, along with the distances between our nations, that I cannot comprehend why our languages are identical. Can you tell me what you you know about English and how it came to be spoken in your nation? > > > Sincerely, > > <insert hero name here> > > > > > Dear <insert hero name here>, > > > I too am intensely curious as to how our languages became so similar. Fortunately, being a royal librarian gives me access to many of our nations most ancient documents. To sate mine and your curiosity, I searched these documents and found much knowledge that has long been forgotten by our general population. > > > Many and many generations ago, our nation was newly formed from the ranks of several races, several of which you have already met. Each race had their own language, and it was necessary for us to choose a national common language for legal purposes. To resolve the quandary, a great council was called of the wisest elders of all our races. > > > At the meeting, these wise elders could not settle on any one language. Whenever one language was proposed, the representatives of groups that didn't speak that language would argue that selecting that language would provide an unfair advantage to the races that already spoke the language. After months of this constant arguing, it seemed that all hope was lost. > > > One day, the great and powerful mage Yaj rose from his seat. The entire room was suddenly silent. Yaj had single-handedly destroyed more of the invading forces that brought the nation together than all other forces combined. He then announced to the congregation, "I have found a language. In the far future, a future so distant that oceans have moved to where mountains are and mountains where oceans, most of the inhabitants of the world speaks one language. This language is vastly different from any of our current languages. Since it is the language of the future, I propose that our own nation adopts this language." He then sat down. > > > Our Elders quickly decided to adopt Yaj's solution, though it was more because of their fear of disagreeing with him than the reason-ability of the idea. After their agreement, he produced several strange square manuscripts written in English. He then performed magic to make the manuscripts never fade or wear. He also performed spells of universal understanding on these books so that anyone would be able to learn English. Some of these manuscripts provided strict rules for English. Others had long lists of words that we could speak. Interestingly, the manuscripts even had a name for strange square manuscripts. They were called books. The most common type of manuscript merely showed examples of that language. After that point, our nation slowly adopted the new language over the course of generations. > > > Maybe your nation conquers the world in the far future. That is really the only explanation that explains why you have the same language as us. If you find more information that helps explains this quandary, I would be glad to hear of it. > > > Sincerely, > > <insert native name here> > > > After receiving this letter, your hero comes to the conclusion that Yaj had been wrong when he thought he had traveled to the future of the fantasy world. He must of instead traveled to a fairly modern Earth to a place that speaks English like America or England, and then assumed that it was the future. The square manuscripts were obviously books written on Earth but preserved on this world using powerful magic. Note: Inspired by the explanation that the [Divide Trilogy](https://en.wikipedia.org/wiki/The_Divide_trilogy) uses to explain a planet-wide English speaking fantasy population. [Answer] **Don't** If you're concerned about your world seeming realistic, or more accurately *verisimilitudinous*, then having the people on the other world speak English is probably not the best way to go. **Although It's Just One More Thing** But, if the people on this other fantasy world also happen to be biologically identical to humans with the same sort of plant and animal life, then you've pretty much jumped the shark already, so having them speak English as well isn't going to hurt anything. If you have an explanation of why they are impossibly similar to earth humans, like Star Trek's single ancestor conceit, then make sure it explains why they speak English as well. [Answer] For us, the existence of their world is a great surprise, but **they have been observing us** for a long time, using their magic. Most people don't care about our pathetic little attempts to emulate proper magic with our so called "technology", and focus on more interesting alternate realities to spy on. However, a small sect of religious zealots is obsessed with our reality and think that magic has corrupted their world. They have learned our languages and consider them superior to their own. You can even make this the mechanism by which your hero is transported over. They have been searching for centuries for a way to bring someone over from our world to serve as a savior who will rid their world of the corrupting effect of magic. It also sets up a nice conflict if they're basically a bunch of terrorist maniacs, and your hero has no intention of co-operating. [Answer] I like the technique used in "The Thirteenth Warrior." An Arabic prince is hijacked into a quest with 12 Viking warriors to save a kingdom from a dragon. They have no way of communicating, but the prince is a student of languages. Near the beginning of the movie is a montage of him listening to them that ends with this: Viking: Blow-hards the both of you. She probably was some smoke-colored camp girl. Looked like that one's mother. [laughter] prince: [slowly with much difficulty]My mother was a pure woman from a noble family. And I, at least, know who my father is, you pig-eating son of a whore! Viking: Where did you learn our language?! prince: [angrily and with more confidence] I listened! This is one of my favorite Antonio Banderas movies. [Answer] Since this is a fantasy world, you could possibly say that they were the first group of people who spoke English in the entire universe. I know this sounds kind of stupid, but if you ever wanted a back story for this planet you could say that the beings who speak English were the one's who placed humans on planet Earth in the first place. This can then be used to explain why one of the primary languages on Earth is English. I know this is a very silly idea, and it does need to be developed further, but it is just a suggestion. Or you can do what others have told you to do and that is not explain why people speak English. This would make sense, just make sure your character never asks how the beings on this planet know English. My final suggestion is similar to an answer that had already been mentioned, but basically you can say that the aliens (or whatever your calling them) have the technology to make a device that lets them understand your character and also lets your character understand them. This can help to explain why the character can not understand any of the other of species of aliens. I hope this was helpful. [Answer] They learned it by listening to our radio and television broadcasts.  They could have learned other languages that way, but *America’s Got Talent* and *Britain’s Got Talent* were the only shows they liked. [Answer] The whole mechanism that lets character to travel might also equip her with one arrival language knowledge along with some trivia. Otherwise, it's hugely unrealistic for English especially. You could claim they speak Chinese or a-bit-Fantasy-old-fashioned Russian, but English makes the whole European history, with Greeks, Romans, Saxon settlers, invasion of Normans and French cultural hegemony too apparent in its body. You can't go more than two phrases without exposing all those heritage, and then explain why your world has Europe. However, I can note Tad Williams who introduced his fantasy plot in faux Europe, with its Nordic people, Italic people and so on. The map is different but peoples' distribution is the same. In this setup he could definitely plant a traveller from our world and claim that he can speak Erkynlandish. [Answer] **Infinite Worlds** If there are an infinite number of worlds, and more than one of them have speaking inhabitants (therefore an infinite number of them do), it means there are an infinite number of permutations of word-sounds. This means that there is a world (more than one, in fact) out there where the inhabitants just happen to use the same word sounds as that of our hero, and therefore the speak the exact same language. Now all you have to handwave is the ridiculously amazing coincidence of our hero landing on this world as opposed to one of the zillions of others. But it could simply be that whatever god, machine, mechanism sent him there did it deliberately for this reason. [](https://i.stack.imgur.com/SewBE.png) [Answer] The fantasy world is created by people. Imagining things will bring them in that fantasy world, including the beings living there and their language. Or maybe the world is susceptible to the human brain and as you explore it, it changes to suit your expectations of it. If you expect English you'll get English, if you expect a sign language you'll get that. [Answer] **Have it be a part of the summoning ritual** A common way for someone to travel from our world to a fantasy world is to be magically summoned by one or more people in the fantasy world. It would be as simple as this: > > Hero: Where am I? Who are you? > > > Summoner: We have summoned you here for blah blah blah... > > > Hero: Why can I understand you? > > > Summoner: We made sure that one of the requirements the summoning ritual would fulfill is that it would bring us someone who would be able to understand us. > > > If you feel like it's still unreasonable to have their English be exactly the same as ours, feel free to modify it. Have them use unusual phrases. Have them reference other stories, e.g "it's just like *Beatrice and the Hobbit*" instead of "it's just like *Goldilocks and the three bears*". This can also help get readers interested because they'll feel like the world is really alive, and be curious about all of the history of your fantasy world. One thing that might help you do this would be to look up idioms from other languages. For example, in Chinese you can describe a large crowd using "人山人海" - literally "people mountain people ocean", or mountains and seas of people. You could either use what you find as inspiration for new idioms that you come up with, or just use the foreign idiom directly. [Answer] Short answer is: you can not. Not, unless there is England in your secondary world. Neither you can name your mules Alpha and Beta, unless there is Greece. Nor you can give your characters a machete to cut the grass, and sombreros to protect them from the sun, unless there is Latin America, or feed them curry without having it come from India. You will have to hand-wave your way through it: everyone speaks their own language and magically understand each other, just because it is the way things are there: "what do you mean, we are speaking Mandarin, I know only Polish, and that's what I was speaking all this time!" Warning: had been done before, and not once. [Answer] **The Will of the Gods** There are at least two divine options. The first is that God (or one or more of the gods) has authority over multiple universes, including Earth and the universe of your story. English is Hir chosen language, so both universes were influenced to develop the same language. There might still be a handful of differences, but for the most part, but this point the languages match up. Alternately, a god fleeing Earth (persecution by other gods, or the death of magic) came to the world of your story. As she regained her power and settled in, she taught her new followers her prefered tongue. Either way, this might also explain why your character traveled between worlds. In the first case, the god who rules both universes creates the connection between the worlds. In the second case, the fleeing god created the portal, the vacuum of which pulls other people and things through, too. [Answer] Language is a consensus tool, meaning that people understand the noises that we make with our mouths only because they were taught what those noises mean, typically as a child. Therefore, any language is LEARNED, and the meaning of words AGREED UPON. To explain how those in your fantasy world speak English is asking how your hero understands the meaning of their words, and vice versa. Their seem to exist only two possibilities: Magic (whether a device, spell, travel, etc) or coincidence of hig convergence. In either case, the language of that fantasy world would not be known as English. By far, the best solution is a handwave or suspension of disbelief. [Answer] I don't think you should worry about it. Someone else mentioned Suspension of Disbelief. That's pretty close. It really has nothing to do with what a reader will or will not believe and has more to do with the fact you are **telling a story**. Period. The story trumps everything. Is it important to the story for you to explain the seemingly non-existent language barrier? Usually it is not. Usually nobody cares. Usually the reader takes it for granted. Stop worrying about it, unless it's integral to the story. To take an alternate stance to everyone else's opinion, but all of the devices offered as options to "solve" this problem will actually only shine a light on the fact that a problem exists in the first place. Again, unless it's important to the story ... don't mention it. Let it play out and let the reader not worry about it. [Answer] Just say that the book you are reading has been translated for the reader. If the story is one of those where someone from our world goes to another, then there would have to be a logical explanation or workaround. But if the story just takes place in another world to begin with, then just don't mention it or have a little note saying that the language has been translated into english for the reader's convenience. [Answer] Star Trek's explanation as to why everyone speaks English is -they are not. The universal translator (part of the ship's computer) translates in real time and dubs a computer-generated voice over the speaker's voice. Of course, a large amount of hand-waving occurs in situations where the crew don't have access to the universal translator, comm badges, communicators or tricorders. ST-Enterprise made an attempt at showing what encounters were like while the universal translator was being developed. Next Generation episode "Darmok" shows an encounter the universal translator could not handle. These are among my favorite episodes. In situations where the universal translator is available and working this still leaves the question of how the system is able to deliver translation without having to wait for the speaker to complete a translatable chunk of speech. My take on this is that this problem is solved in the same way several other thorny issues are solved. Some of those other problems are: The ability of the crew to pilot the ship at speeds where they could not possibly react to events fast enough and the ability of the communications system to route comms to the intended recipient before the recipient is known. My answer is: The ship's computer is permanently kept in a time bubble 2-5 seconds ahead of ship time. Speech input is translated and returned to ship-time users coinciding with the mouth movements of the speakers. Similarly, when Picard on the bridge addresses Riker on an away-mission the computer has already processed the communication and is ready to direct it to Riker's comm. [Answer] In Star Wars, the language that is spoken is [Galactic Basic](https://en.wikipedia.org/wiki/Languages_in_Star_Wars#Galactic_Basic) aka English. So, take English, call it something else, problem solved without much work. Character encounters exact same language as English, given that there is likely a certain limit to sounds/phonemes/combinations of said sounds and phonemes that people can make. Just as there is actually a limited number of DNA combinations *albeit it is a huge number* There is an astronomically teeny tiny chance that said character encounters the exact same language as English, with the same structure. I cannot/will not speculate on definitions of objects however, and do not ask me about odds of finding exact language match. I have no clue, aside from it likely would require the use of 10x19^100000000 (pulled number out of air) D20 dice. ]

[Question] [ I am writing a short story set in a world inhabited by modern humans (Homo sapiens), bulky humans (inspired by Homo Neanderthalensis) and tiny humans (inspired by Homo [Floresiensis).](https://en.m.wikipedia.org/wiki/Homo_floresiensis) In response to comments, the height of H.F. was roughly 1m. I might make mine smaller for effect, but not below 0.75m I will not attempt to make it hard science fiction and freely include various kinds of extinct species (such as dire wolf), only broadly minding their actual habitats and possibilities of coexistence. I will also drastically alter the continents (i.e. build a different planet). Right at the start of the story, where I will only use Tiny Humans for quite some time, I want to make the reader notice their size. I don't want to place them alongside a homo sapiens. One option would be to compare to extant familiar animals, but I am afraid the presence of many exotic animals will simply make the reader suppose all animals are a different size. I absolutely don't want to use any of our units, because I always find such things utterly immersion breaking. What would be some good formations/objects in nature to compare against (without presupposing deep scientific knowledge)? Please excuse if my concept is still fledgling. It is only 1 month old. EDIT: Many answers here have added invaluable information. They also made me realise, how devilishly complex this might be. Like myself, I expect many readers to have grown up with dino books. I will not introduce dinosaurs, but insects from their time. The reader might assume the atmospheric conditions that existed long before humans and led to huge animals and plants! On the other hand, he might be guided by the recent history of some actual plants to assume them much smaller (f.e. earliest watermelons are thought to have measured about 2 inches in diameter). Finally under these atmospheric conditions, even inanimate things like fires may behave differently (Naively I assume more oxygen implied higher flames). In the beginning I thought the size of the full moon in the sky might help, but as you can't put anything at same distance, I see no easy way. EDIT: Because the question of images received so much attention in the comments, I want to make clear that I see no difference between description and images. The painter, just like the narrator, needs to know what to put in the picture to convey scale. In the beginning I even thought some rare inanimate structure might be needed, which I would have to fit into my world! [Answer] # Don't tell At the beginning the reader has no idea that there is something different about your protagonists. They act, communicate, feel etc. just like normal humans, and the story is written from their point of view. Over time, things get more clear and you learn quite astounding things about them. But not because the author wrote a preamble or just told us. He did *not* tell us at first because they are just plain and normal to *them*. None of them would ever think twice about their specialty. You can try to make the process of discovery of their unique feature very enticing. Maybe include some sentences which just don't seem to quite make sense on first reading (they might even *seem* to be grammatically nonsensical unless you know the truth), and make it so that the reader does not even assume that there is something wrong about them, at the beginning. When he finally "gets it", it's delicious. Your mini-humans are, from their point of view, just plain normal. Only when they meet the big-humans or the hulking-humans will anybody, especially the reader, notice any difference. My prime example for this is... (mouse over to see spoiler) > > Vernor Vinge's "A Fire Upon the Deep". > > > If you have not already, read it - it is very excellent, and not only for a reason somehow connected to this question. [Answer] **Answer: Write a Preamble** This is just the cleanest way to do things. Write 1-2 paragraphs informing the reader about Homo Floresiensis, including their size, where they were found, etc. It's informative and (more importantly) serves your purposes of establishing location, timeframe, and size better than any half-done measurement. As long as it's provided in advance of the story the reader does not have to be taken out of the moment while you take them on an adventure. **If You Don't, There are 3 Major Problems to Overcome** To convey scale in a prehistoric sense without using measurements from today you have two major problems: **1. People are Bad at Scale** If your goal is to describe small (~1m) humanoids, you need a scale that people definitely understand and that is not entirely subjective. To make my point, just look at some of the answers you are getting here. People are talking about using apples grains of sand or snowflakes. Snowflakes! Those literally require a magnifying glass to see well! Not to mention the huge variation possible in grains of sand, snowflakes, apple sizes, plant sizes, etc. Consider the case of apples, which is intuitive to most people. If you buy organic apples they can literally be half the volume of an apple produced for size (not half the diameter, but half the volume). Using that as a guide, if YOU were thinking of a small apple and your reader is thinking of a big apple, your humanoids would be as tall as homo sapiens today. Going the other way around, they would be half the size you intend! **2. Many Plants and Animals have Changed Size since Prehistory** In one comment you stated that people with an interest in prehistory would know about prehistoric plants. Well, maybe. Doubtful, actually. But what is really going to bite you is if you use a current plant or animal and assume that the size remained the same over the last 12,000 years. Going back to apples, apples as they existed 12,000 years ago would at best look like crabapples of today! **3. Homo Floresiensis lived in Indonesia** This is a real killer. Anything native to North America or Europe that you introduce as native to your protagonist is not only likely to be anachronistic, it's not going to be native to the region either. And even things that are common - alligators, for example - are going to be from different species, which probably has a different size. If you are indeed writing for people who are interested in pre-history you will probably leave those who understand the region scratching their heads. [Answer] Use plants. Many of them grow to a fairly consistent size, and you can readily describe your tiny humans moving through them in a way that indicates their relative height. [Bulrushes](https://en.wikipedia.org/wiki/Scirpus) might be a useful example. [Answer] If your story has third-person narration, you could use a phrase like "While other races might view him as a child due to his diminutive size, he was in fact full-grown -- and not only full-grown but wise and strong. He was a leader of his people, the third in his family to be given that honor." I don't think you have to be specific as to what race -- it could be ours, the reader, or it could be your bulky humans. If it were my story, and if I had third-person narration, I'd just say it straight out, very early in the story while the readers' expectations and perspective were being established. I don't think that breaks immersion if it's in the first couple of paragraphs. Maybe something like "A human might mistake Chak for a child, since he is only as tall as an 8- or 9-year old, but in fact Chak is ...". [Answer] I don't think any one thing would do it, but a combination of things all together would. Giant turtleshells as bathtubs, coconut shells as helms, a man being loaded down with a single watermelon (I don't know what fruits are native to Indonesia, sorry), hunting through grazed grasses waist-high or higher, etc. Google image searching "Pygmy" has a lot of images, but in a quick look, I can't see anything obviously leaping out as a height cue. You can't tell how tall they are. The ocean, perhaps? "It was a balmy, windless day, the calm waves no more than a half his height". Another might be borrowed items. In a 3D computer game, it's hard to give the users a sense of scale. Familiar built objects are one such. So for the "Borrowers" series of books, showing that the items were repurposed human items worked well. In Pratchett's "Carpet People", the central conceit is again only slowly revealed, but the scale is greater, so in its way harder to grasp. Could your Floresiensians perhaps have some items from the Erectuses and Neanderthals? Edit: another thought: the square cubed law also works in reverse. Smaller characters can be far more elfin of feature and weight. They could be sticklike of proportion while still having whippet-like strength and speed. So they might have different modes of locomotion: they can scramble in the thinner twigs of trees, and in a forest, leap through the canopy with nimble ease, using the springiness of the trees to help: they needn't use the floor. Climbing trees, they can grasp the wrinkles of the bark, since they are light enough that bark is a realistic handhold. Some forms of undergrowth could become a "go through" instead of a "go round" thing (bramble thickets, etc). On the other hand, even a small stream or brook would be a swim for them instead of a paddle. [Answer] If we are talking about the same gravity as on Earth, then maybe you can describe their unusual strength for a human-sized being, and that will give the reader a little hint that maybe they are smaller or lighter than a regular human. For example for us it's impressive to jump as high as 2m which is a little bit more than a normal human height, but smaller species often have no problem jumping several times their height. So you can describe how a human sees a tree 3 times taller than they are, but has no problem jumping and grabbing a fruit on top of it or whatever. Another thing is the weight one can carry, again with carrying more than one own weight being not very usual. To add some numbers, based on [this answer](https://physics.stackexchange.com/a/10810) (question "Why are smaller animals stronger than larger ones, when considered relative to their body weight?"), an animal two times smaller will appear two times stronger: let's take a 2m 80kg human who is able to carry 40kg, which is half their weight, and scale them down 2 times - now we have 1m 10kg human who is able to carry 10kg, which is equal to their weight. As for the "lighter than a normal human": how about being able to land unharmed from a higher elevation. Those two things aren't 100% reliable as one can assume these people have different bones durability or muscle structure, but it may be worth leaving as many not-so-obvious hints as possible so that the twist about giants at the end will make a lot of sense. One more unrelated idea is to make their proportions unusual, like big hands, feet and heads, compared to the rest of the body. It would make less sense to read about normal-sized humans with giant heads and hands, so a reader may lean towards the idea that they are in fact small humans with normal-sized heads. I couldn't find a reference, but I remember seeing some advice about drawing characters in cartoons or comics: to make a monster look huge or a hero look buff - just make their head disproportionately smaller than their body. So I believe making head larger will make them look smaller. But that was about visuals, not sure how that translates to writing. [Answer] I would suggest describing a lot of smaller objects and/or showing things being out of reach/insurmountable. Fauna won't work as you said, because by our standards they *were* larger back then. Pointing out a lot of smaller objects, especially on the ground would hint at the reader that they were closer. Normally irrelevant things like pebbles and minuscule insects could be brought up. Describing trees or outcrops as being out of reach or too high up would also suggest that they are short, while dense vegetation could pose a real obstacle. They are only small, and cutting their way through something would take more effort. However, this would only make sense if stated from a third person perspective - they wouldn't likely see themselves as short if they are all similar heights to each other, unless they have had previous contact with the "Neanderthals". This could even include bones or fossils- a skull of a Neanderthal perhaps. [Answer] You can use this as a plot device and allow your readers to discover the disparity in size/scale. Your tiny humans can interact with beetles the size of their fists, scrabble their way through ferns that don't show the sky above them, flames that extend up beyond their upraised arms. Larger humans wouldn't notice crushing those same beetles, ferns would tickle their knees as they brushed past them, they would huddle around camp fires, warming their hands as they sat on their haunches. [Answer] Is it really necessary to know how big they are? You could introduce the humans first, in the process hinting at the size of one or more objects. Then shift the scene to the little people and find a reason to mention the same object(s). It's a common trick, to have the first two chapters appear completely unrelated, yet come together later in the story. [Answer] As the target audience is composed of modern humans, why not use them for comparison? That shouldn't be immersion-breaking, after all, you are using English (or some other modern language) to write the story, instead of the language of your humanoids. Mentioning at the beginning, especially when the first such creature appears on the scene, that they were roughly half as tall as modern humans (especially if the story is set on a past Earth), should be less immersion breaking than mentioning centimeters. If the story is not set on a past Earth, some subtle connection to how the story came into the hands of humans might also make a connection between their size and ours. Tolkien used this from time to time, posing as a translator between the in-universe languages and modern English. [Answer] There are physicists who think that if we humans were ever to have a communications link with distant aliens and someone were to ask *"How big are you beings? How massive? How tall?"* or *"How long is your day? or seasons? or mean lifespan?"* or *"How strong is gravity on your planet?"* that the only way we could communicate these quantities to the aliens (or them to us) would be to communicate such in terms of [Planck Units](https://en.wikipedia.org/wiki/Planck_units). This assumes that the aliens have the same universal speed of light, [Planck constant](https://en.wikipedia.org/wiki/Planck_constant), and Gravitational constant as we do. [Answer] A variation of John Dallman's answer. Use animals. You said you don't want to use extant ones, so use the fossils of extinct ones instead. Most people have an idea about the size of am adult T-Rex from movies such as Jurassic Park. If your characters live close to the exposed cranium of a T-Rex, you can compare the size of their heads with the length of a tooth, for example. Many people will also know what you are talking about if you include a Megalodon there. If it is not extinct in your world, you could have one of your hominids see a shark hunting a whale - mostly everyone will know it's a Megalodon - and then you can compare their teeth (perhaps some teeth someone found on a shore and is using as amulets?) size against your hominids' body parts. [Answer] I feel a lot of these answers violate the 'show, don't tell' principle by 'slapping you in the face' with the fact they are short. Any book that tells me straight out the bat some species has XYZ trait not only feels like it's deigning me for being stupid (like 'you can't figure this out unless I tell you it's London, England!'), but it tells me that said trait is plot crucial and ergo is a pre-emptive spoiler. Rather than trying to find forceful ways to make it obvious, then discarding it as a known fact, perhaps you should allow the creatures to interact in their environment and 'discover' ways that a shorter group of humans would have trouble interacting. For example, climbing would be difficult, they would be able to fit into small holes, they would have to make use of climbing implements or some sort of 'extension' tools to grab things out of reach. You could then infer it by having the taller humans 'hit their heads' on the ceiling of the shorter humans when they meet up (I presume there is a language barrier so the taller humans wouldn't immediately go 'duh, these guys are short!'). Have the humans have to 'jump up' to reach things (fairly regularly) or stand on their tiptoes. Eventually your readers will get the impression they have trouble reaching up for things, and are by inference, short, without conveying a specific size. You can then easily contrast by having the bigger humans simply grab fruit out of trees 'without hassle' and 'without extension tools'. Show, don't tell. [Answer] Have your protagonist see some non-exotic animals, animals that many of your readers would be familiar with. Perhaps he is trapping doves. Or perhaps he watches a fox chase and catch a rabbit. Only after the scale of these creatures is in the reader's mind will your protagonist interact with them. When taking the doves from the net, rather than simply filling the hand, the dove has to be grabbed with hands and forearms. Driving the fox away to steal its kill involves confronting a waist-high creature and the rabbit is a substantial haul of meat rather than just a bit of meat for the pot. [Answer] The problem here is that everything would be scaled to them, because they built it. So any conveyance of size will have to rely on comparisons of known things. I think Pete is right in saying that you should use it as plot. To do that, you should constantly be giving scales of everything, but in terms of use... And you can also have regular human scale without having humans for things. For example, an abandoned castle would be massive to them, common corridors with roofs so high that 2 men could stand on each other's shoulders and still have head room. Or everything feeds them for at least 2 times as long. If they have horses you could point out that they cover 2 days journey easily in a day, because their towns would be built at around 15km apart rather than 30km apart, but a horse could still travel to the further settlement in the same time. If they are hunting food, then they will cure it and preserve it which will require a certain amount of time and amount of salt and a place to put it. This being the case you have another opportunity to correlate size, because the amount of time, salt, and room needed will be the same for them for us, but feel as twice as much for them...probably depending on their population and dietary habits. You could also say "legend tells of giants, twice our size". But the fact is unless people know sizes and numbers of things off the top of their head, as most people don't, they're not going to get that they're the small ones until you introduce humans, but then when you do, it will all click and suddenly they'll see that these gigantic creatures you seem to be talking about talking about are really just normal size and it will paint the picture better than using real units anyways. [Answer] Everything is relative to the things in their world. We use London buses, Nelson's Column and Wales/Texas as things that everyone has an idea of the size of. What you need to do is pick something in their world that anyone in the conversation would know the size of. The key things in their world will be the primary prey or food source, the primary predator, the home, and something permanent near the home like a large rock. This ultimately leads to [The Register's unit converter](http://www.theregister.co.uk/Design/page/reg-standards-converter.html) [Answer] You could use grains of sand. e.g. they can only hold 20 or so grains of sand in their hands. If you explicitly refer to the grains as grains of sand it'll be clear to the reader that they aren't just normal sized people and larger pebbles. Or snowflakes. [Answer] You could use something as a scale that didn't change over the millenia: The moon. If you, as a modern human, extend your arm while looking at the full moon, you can completely cover the moon with your thumb. [Thumb-Moon-Math](https://lcogt.net/spacebook/using-angles-describe-positions-and-apparent-sizes-objects/) Perhaps your H.F.'s could only partially cover the moon with their small thumbs, or need two fingers. (assumed they have thinner fingers than we do) You could include it as a sort of game between their kids and grown ups to show who can cover more of the moon. Perhaps some kind of legend about others that can cover the moon completely with one thumb. ]

[Question] [ The first portal is placed at bottom-most point of the Mariana trench (the deepest part of any ocean, located in the western Pacific Ocean) and the second is placed in the Sahara desert in Africa at the point farthest from any ocean. The second portal is inverted so the water jets directly to the ground. Each portal is 10 kilometres in diameter and stable. Assume the system is a one way transfer, i.e. from trench to Sahara. The portal system has zero mass transfer losses and there's no energy consumption by them or by objects pass through them. They're connecting the two points on earth in space-time. They're not affected by the altitude difference or the potential energy difference between them. What will be the climatic changes on earth as a result of this? [Answer] The climate of Earth has been roughed up quite a bit last century. But it has no idea what it's got coming with this portal of yours. Earth turns into Venus. **Update: As R.M. pointed out, the amount of energy is not 'maybe a long term thing', it's *the Major Issue*. This has been fixed now.** ### How much water are we talking? Let's say your portal is 10km below sea level. Dropping from that pressure to pressure at sea level gives a flow speed of somewhat over 400 meters per second: $\sqrt{10^4\mathrm{m} \cdot 10 \frac{\mathrm{m}}{\mathrm{s}^2} \cdot 2}$ (water is incompressible so we can just use potential energy). This is well over the speed of sound, or comparable to the speed of a typical handgun bullet. This 400 m/s flow is though the entire portal, $\pi \cdot 5000^2 = 7.9 \cdot 10^7 \mathrm{m}^2$, for a total of about $30 \cdot 10^9 \mathrm{m}^3$ of water per second, that's a cube of water about 3 km or 2 miles on a side per second. Comparing that to other rivers. The discharge of your portal is about 100 000 cubic kilometers *per hour*, or about three times the the amount of water discharged by all of [Earth's rivers *in a year*](http://www.cgd.ucar.edu/staff/trenbert/trenberth.papers/i1525-7541-003-06-0660.pdf). Comparing it to a [lahar](https://en.wikipedia.org/wiki/Lahar), a very destructive mud flow. These can be 100 meters deep and run at 'several tens of meters per second'. If the stream from your portal would turn into a lahar of 50 meters deep, it would be 2000 km wide. If we were to slow it down to a mere 40 meters per second (as fast as a car going over the speed limit), that would require it to be again 10 times as wide, so 20 000 km. Sailing around the entire African continent is only slightly more than that. So the *entire* African coast would turn into an extremely destructive mud flow of almost 50 m deep. Given that there are mountains to the south of the Sahara, the mud flow will probably be much deeper and mostly to the North. At this point most of my assumptions are starting to break down. I assumed the effect on the ocean surface would not be too great. It will likely be a giant maelstrom tens or maybe even hundreds of kilometers across. This means the amount of water flowing through it is going to be somewhat less. Let's cut it by a factor 10, so $30\cdot10^8 \frac{\mathrm{m}^3}{\mathrm{s}}$. The volume of Earth's oceans is about [1.3 billion cubic kilometers](http://hypertextbook.com/facts/2001/SyedQadri.shtml). There are about 30 million seconds in a year, so that's about 90 million cubic kilometers per year. So it takes about 15 years for the portal to cycle through the equivalent of all the water. ### What happens to that water? The specific heat of water is about $4 \frac{\mathrm{J}}{\mathrm{kg \cdot K}}$, so it takes about 4 kilojoules to heat a Liter of water 1 degree Celsius. That's about 4 MJ to heat a cubic meter 1 degree. The potential energy in dropping a cubic meter of water from 10 km up is about 100 MJ, so you're going to heat up your water about 25 degrees by slamming it high speed into the sand (or, quite quickly, other water). This means that, if the Earth's energy loss from radiation would stay the same, in about 15 years all the water would have cycled through the portal once and the ocean would, on average, have heated up 25 degrees. Another 45 years and all the water will be boiling. Water has a latent heat of about $2.3 \frac{\mathrm{MJ}}{\mathrm{kg}}$, or $2300 \frac{\mathrm{MJ}}{\mathrm{m}^3}$. So it then takes a few centuries for all the water to boil off and turn into vapor. ### What will happen to all that energy? Normally, the Earth radiates away energy as long wave, or infra red radiation. Greenhouse gases like carbon dioxide reflect this radiation back at us. There is a lot of carbon dioxide stored in the oceans, around 60 times that of the pre-industrial atmosphere. However, if water is heated, it can't store as much carbon dioxide. Water of about 30 degrees Celsius can store only about a third of what water of 4 degrees can store. This is actually much more complicated than dividing by a third. So, if all the oceans heat up 25 degrees, the carbon dioxide in the atmosphere is going to increase by factor of 10 or so. We've managed to increase it by about 50% or so in the last hundred years. To add to this, warmer water evaporates more readily, and water vapor is also a very strong greenhouse gas. This means that the Earth wouldn't cool nearly as fast as it normally would. And, at some point, maybe after a few years, maybe after several decades, even if you were to turn off the portal, the increased greenhouse gases and incoming energy from the Sun will will cause a runaway greenhouse effect and turn Earth into Venus. ### Who dies first? The first creatures to die is probably a fish being blasted into an unlucky scorpion at high speed. After that anything going through the portal will die. Next to go is anything within a few hundred kilometers of the Mariana Trench and anything in Northern Africa. Europe and the rest of Africa will soon (within hours? days? weeks?) follow. The shortest path from the Saharan portal back to the Mariana Trench is through the Himalaya's, so my guess is the water will mainly flow through Africa towards the Southern Atlantic and through Southern Europe the Eastern part of Africa and the Arabian Peninsula into the Indian Ocean. Everything in its way will die. So the America's, most of Asia and Australia will likely not flood. Australia is closest to the Mariana Trench, so the weather there will turn weird after a day. It will take probably take a few days for the effects of the sudden change of energy distribution to be transported by the jet steam towards the America's and the remaining parts of Asia, so they've got maybe another week before the freak weather begins (think hurricanes, extreme rainfall, etc.). Some animals and some humans in those parts of the world could possibly survive this for a few years. ### Some speculation on what would happen if the water didn't heat up: The remaining flow is still a good 20 times the amount of water the [Gulf Stream transports](https://en.wikipedia.org/wiki/Sverdrup) at its peak, so I would wager all ocean currents stop doing what they're doing and start flowing towards the South-West Pacific. This means no more warm water flowing to the North Atlantic so that's a new ice age for Europe. Similar goes for Japan. Most of North Africa is going to get flooded, I have no clue what that will do with the climate. This water is going to be under 10 degrees Celsius, so it'll cool down equatorial areas by a lot. The giant maelstrom around the Mariana Trench is going to cause a lot of mixing in the Pacific Ocean, so most of that ocean is going to be a lot colder than it was before. All of this cold water near the surface everywhere will mean that the Earth will radiate away much less energy and that there will be much less energy to drive atmospheric processes. The internal ocean water however will heat up on average. [Answer] First observation: The portals as described in the question create a **perpetuum mobile**. Salt water under high pressure (from the ground of the Mariana trench) wells up at some point in the Sahara desert, becoming a fine source of hydroelectric power. It will create a river of salt water that may fill up some basins and eventually reaches the sea (either the Mediterranean sea or the Atlantic Ocean). Now the water circuit is closed and the Mariana trench never runs dry. Climatic change depends mainly on the size of the basins filled with salt water: The larger they are, the bigger the effect. The effect consists in dampening temperature extremes in the Sahara area and in a reduction of the deserted area. The desert will not go away completely; the Red Sea does not make the surrounding lands green pastures, and an inland sea in the Sahara won't do so either. Depending on the outlet, it is possible that the stream of salt water enters a stream of sweet water (e.g. the Nile or the Niger) and actually destroys farmable land. EDIT: Answers to comments: 1. Fate of the Sahara: It will partially flooded, but remain the same as before for the largest part. It will have some more oases due to increased rainfall 2. Evaporation rates: I don't have number ready, but they will be comparable to the ones of the Red Sea. 3. The will be no equal pressure at any time. By the way the portals are designed, they act as a big pump pumping water from the Mariana trench up to some point in the Sahara dessert. This pump works forever (or until the magic driving it is revoked). EDIT 2: I completely overlooked the enormous size of the portals. My answer is valid for much smaller portals (say, 10 m in diameter). EDIT 2: Given the geographical location of the salt water outlet, the inland sea would probably the [Lake Mega-Chad](https://en.wikipedia.org/wiki/Chad_Basin) covering the Chad bassin. Its outlet is the Benue river flowing toward the Niger river. [Answer] I assume you prefer a scientifically correct answer, as in the portal can't violate energy conservation. In that case, we just can't have portals. But we *can* have a long tube, and lets just ignore friction inside that tube so we simulate most of the portal stuff. It does not even matter if the portaltube would end in the marianna trench. Just a few meters below the water level is enough. Actually, another option we have would be to dig a [Trench](https://en.wikipedia.org/wiki/Panama_Canal). Conviniently, parts of the sahara lie below the sea level. These parts would drain seawater, creating an inland sea. The idea itself is not new: there is a page on [wikipedia](https://en.wikipedia.org/wiki/Sahara_Sea) about this very topic, which came up a long time ago. Regarding the climatic effect such inland see would have, we could only speculate. The water itself would be saltwater and could not readily be consumed for plant growth. But it would likely stabilize the temperature in the region. Having a large body of water nearby makes days cooler and nights warmer. Also, because of evaporation, more Rainfall is to be expected. The downside is that not only is the Sahara a very dry place, but additionally the Sand and Stone it is made off are *really bad* at storing Rainfall. It just permeates the sand and runs off. Therefore, even with more rain, it will stay a dry place. On a very long timescale it might be possible that few new Oasis would develop, and existing ones might get larger. Regarding the lake itself, nobody knows yet if the inland lake would develop a healthy ecosystem or not. There is the case of [Salton sea](https://en.wikipedia.org/wiki/Salton_Sea) in which engineers accidentally flooded a basin. This obligatory [XKCD comic](https://what-if.xkcd.com/152/) explains the situation pretty well. [Answer] What if the portal transports not only water, but gravity? In that case, we have a proper portal that also conserves energy - a *wormhole*, if you will. Although this mechanism is kinder to the laws of physics, it actually has more severe effects on the ecosystem. While water levels might not equalize instantly, gravity levels on both sides of the portal *will*, significantly shifting the gravitational field of the Earth. This will result in the entirety of the Earth's oceans migrating away from the Mariana Trench, toward Africa. While I haven't done the math, this will likely result in most of Africa, and parts of Europe and Asia, being submerged under the ocean. On the other side of the globe, nations bordering the ocean will gain access to a large amount of new fertile land. There will likely be wars fought over this. [Answer] Having specified that the 2nd portal is selected for maximum distance from the ocean(s), this puts the location near the southern edge of the Sahara, probably somewhere in western Niger or eastern Chad. The first thing to realize is that the flow rate out of the portal will be enormous. Pressure differential across the portal surface will be on the order of 1000 atmospheres. Even if the portal appears at ground level, the surface sand will be explosively scoured away right down to bedrock. I can't find a number for the sand depth in that area, but the average depth of the Sahara is asserted to be 150 to 200 feet. Let's go with 100 feet, or 30 meters. Then the total exit area will be 10 km x pi x 30 m, or about 1 million square meters. Modelling this as a circular orifice with a diameter of about 1000 meters, a simplistic calculation of flow rate runs something like 5 x 10^11 m^3 per hour. For comparison, Lake Erie has a total volume of about 4.8 x 10^11 m^3. So that will be whole lot of water. In the short run a large lake will form, but I doubt it will last. Without knowing the subsurface topology, one can only assume that there exists the channel of a buried south-flowing river. The accumulation of water, when it finds such an outlet to the Atlantic, is likely to produce extremely rapid excavation along any such channel. The result will be a relatively narrow, very fast and deep river flowing through a terrain something like the Channeled Scablands of Washington state. The river will presumably run southward to the Atlantic. Note that formation of the Channeled Scablands required the draining of a glacial lake with a volume of about 2000 km^3 and this is about 4 hours accumulation from the portal. Assuming that such a drain limits the area of the headwater lake, climatic effects will be fairly small. The total area of water available for evaporation will be fairly small. Furthermore, since the water is exiting at a temperature near zero Centigrade, evaporation will be further inhibited. [Answer] **The physics at a macroscopic scale** Your concerns about the actual water shifting around the Earth is quite reasonable. However, I can actually tell you a far worse (in fact cataclysmic) reaction that will result from you initiating connections like this that merely have downward facing openings, sit at the same elevation, and do not even suck in any water (unless it happens as a result of what I'm going to tell you). Simply put, depending on your theory of portals and doorways in space and such, the issue is the gravity of Earth itself acting upon Earth itself. Now I'm going to actually run some numbers on this. First off we see can by googling what the actual the latitude and longitude of the placing you seek to place portals at is: <https://www.google.com/search?q=mariana+trench+longitude&ie=utf-8&oe=utf-8> <https://www.google.com/search?q=sahara+desert+longitude&ie=utf-8&oe=utf-8> Using [spherical coordinates](https://en.wikipedia.org/wiki/Spherical_coordinate_system) we can obtain vectors representing the directions of each of these. This will make more sense once I move into the actual physics equations. I am presuming here that elevation is irrelevant in the sense that we only care about the direction and not the magnitude, which is what we will want farther down. Sahara\_vector = <0.3582064616, 0.1721067799, 0.9176422981> Trench\_vector = <-0.24186511, 0.1855896263, 0.9523957996> Now that we have these we wish to construct three equations to determine the acceleration of the Earth due to itself. This means we need to construct force equations for each of the x,y, and z coordinates. There's probably an easier way but this is what I know how to do. Now the force due to gravity on Earth at sea level is defined as "mg", where m is the mass of the object being pulled and g is the constant of Earth's gravity. Therefore, each of the vectors must have a magnitude of mg (essentially just multiply the vectors by mg component-wise). Newton's second law tells us that the sum of all the forces along a particular axis adds up to the acceleration times the mass. Therefore, we can now construct the following three equations: $ma\_x = mg(0.3582064616 - 0.24186511)$ $ma\_y = mg(0.1721067799 + 0.1855896263)$ $ma\_z = mg(0.9176422981 + 0.9523957996)$ Dividing both sides of each equation by $m$ and reducing we get the following: $a\_x = 1.141308659196$ $a\_y = 3.509001744822$ $a\_z = 18.345073738437$ Now, using the Pythagorean Theorem in space we can compute the magnitude of this acceleration upon the Earth. $A = \sqrt{(1.141308659196)^2 + (3.509001744822)^2 + (18.345073738437)^2} = 18.712493397979075807350637045717$ This means that there in some direction somewhat pointing between the Sahara Desert and the Marianna Trench that the Earth will begin to accelerate towards at 18.712 meters per second squared! (note: this might not actually be the correct way to find the magnitude but regardless the components still support my conclusion below) **Macroscopic Conclusion** Total annihilation of the planet, which makes sense given that the [acceleration of the Earth](https://www.physicsforums.com/threads/centripetal-acceleration-of-earth-around-sun.212860/) is normally only 0.005954 meters per second squared. And do not expect your 'starship Earth' to be even remotely steerable. The Earth spins, regardless of the Sun. If you want to stop that, you're gonna need to turn your portals sideways and hope you get gravity going through them (likely not) to produce torque. So, everyone on Earth is either gonna get really cold or really hot pretty quick. If anyone does survive somehow due to this monstrosity actually coming back into a stable survivable orbit (which is unlikely), they can admire the new scenery which is pretty lackluster in a disaster sense. **The physics at a regular scale** Simply put, your portals are gonna clog. If the gravity of the Earth is sucking through seawater, guess what: *it's gonna suck through just as much sand*. You know what you get when you put seawater and lots of sand together. You get mud. Eventually, the ground is gonna rise in the Saraha and the ground will become rock hard. If it is fast enough, you'll get a weird looking mesa or a mountain. Other than that, the portal is gonna become a bottleneck and only so much can fit through. The gravitational effects will occur all over the place. Might even be regions that have 0 G's as a result. I'm not that fine tuned to locate those. But in the end, the portal will become the equivalent of your sink when you pour tons of dirt down it. Be glad it needs a plumber. The hurricanes and vortexes described in the other answers sound down right evil. Another thing to keep in mind as well is that the portal itself might have 0 G gravity at it's opening due to the Earth cancelling itself out at that exact point, so chances are the two sides will meet and just kind of awkwardly float up there and not really do much. It might be really damaging when they first open and they slam together, but probably no worse than your average tsunami or desert earthquake. Simply put, the damage isn't caused by the moving of sand and water. It's the moving of the Earth itself that is the real danger. **In conclusion** You've created some intriguing looking geological features at the expense of every person and animal on the planet. You haven't just created storms and earthquakes. You've destabilized the Earth's orbit. Congratulations, you've created single most deadliest example of an extinction event to ever strike the Earth (if it even stays in one piece). ]

[Question] [ A week ago, I was walking through an old district of Prague and found an old lamp. I tried to clean it by rubbing it... And you guessed that correctly: A genie appeared saying: "I will fulfill you one wish." Being a long time Worldbuilding member, I said: "I wish for an infinite number of wishes." The genie laughed and said: "So be it! But you have to fulfill at least one wish to one person every day, otherwise you die. As long, as you keep fulfilling the wishes, you will be kept alive. [No loopholes](http://meta.codegolf.stackexchange.com/q/1061/32729)." And then he disappeared. Because I really do not want to test (yet) if I will really die without fulfilling a wish, this is what I realized so far: * Once a person is granted a wish, I cannot fulfill any other wish for that person. So if you wish infinite wishes, as I did, nothing happens and your wish is over. * You can wish for another person. But that cancels your own wish (you cannot wish for yourself afterwards) * Once I say "So be it" after the wish has been told to me, that wish is fulfilled. (And funnily enough, I have to say it out loud and in English.) * I tried "atomic bomb" and "pile of gold" as stupid wishes with my friends. Both were fulfilled. Next wish (in exchange for the pile of gold) was "make the bomb disappear" which was fulfilled too. * I have the ultimate power of not fulfilling a wish. But I totally must fulfill at least one wish a day (and I really do not want to try what happens if I don't do it). * I still need to eat, drink, breathe, sleep (and use toilets) as I used to. * If you say a wish to me in a language that I do not understand, I cannot fulfill it. But, it does not cancel your "one wish per person" rule. (Thank you my French speaking friend!) * I understand Czech, English and basic German. * Wishing "make Pavel normal again" did not do anything. * Specifying amounts: As long as you state some amount, that amount is going to be fulfilled. For instance, the Czech word for "pile" is "kupa" which is close to [kopa](https://en.wikipedia.org/wiki/Kopa_%28number%29), the medieval number for 60. So "pile of gold" gave us 60 gold bars. * If the amount is not specified, a wish for "a water" was influenced probably by my imagination, that such person wants a *glass* of water. But generally it seems to me, that I cannot condition the wishes, or *dramatically* change the scope of a wish. * I was not given my original wish. I just have to fulfill wishes for anyone else than me. And I am pretty sure there is only a finite number of wishes I can fulfill. This sucks... I am at a point where I am about to reach people who I do not know (outside my "friends and family" circle). Obviously, I do not want to destroy the worlds economics by giving a pile of gold to anyone I meet. I also do not want to destroy the world itself by giving atomic bombs to anyone I meet. While I know that were extremes, [thanks to my previous question](https://worldbuilding.stackexchange.com/questions/31482/santa-exists-how-do-we-react) I know people are strange. So, today, I fulfilled wish "a lollipop" to a small child. On one hand, I would like to keep living a "normal" life as I did previously, on the another hand, I would like to also do some good in this world. **How should I proceed further?** I am ultimately scared of being locked away and approached by just one person a day with clear agenda: Either I fulfill that wish, or I die... [Answer] First, hire a lawyer. For purposes of this answer, assume that the lawyer operates under American rules (as I know them better). Feel free to adjust advice to fit a Czech lawyer if that works better for you. Grant a wish to the lawyer in compensation for her services (assuming a female lawyer for ease of pronouns). She can retire if she pays for a replacement lawyer. Have the lawyer approach an organization like [Make-a-Wish](http://wish.org/about-us) and tell them that she represents a rich client who would like to participate. Her client is quirky though and would prefer to acquire the items himself and donate the whole item to the child. They say that they fulfill one wish every thirty-seven minutes. Since you only need one a day, you should easily be able to cover your daily wish requirement. The lawyer is bound to client confidentiality, so she doesn't reveal your secret. The charity just thinks that you are rich and eccentric. Because this creates a variety of things, it should be less economically distorting than giving just one thing, like a pile of gold. You're doing good with your wishes. The wishes come as English statements, which is acceptable under your limitations. If necessary, you should be able to get the wishes directly from the children. The lawyer can help them with phrasing. If you need money, have the lawyer recruit someone to buy something from you. I'd try [destroyed artwork](https://en.wikipedia.org/wiki/Lost_artworks). Again, this should be only mildly distorting of the economy. It depresses demand for artwork slightly but otherwise just shifts the money from someone who doesn't need it to you. [Answer] This is really easy, and here is your solution: > > I wish for a system that will maximize the lifetime > benefit to the world of my wish-granting, while not being too onerous > and allowing me to lead a normal life. > > > It appears from your question that you can't wish this yourself, but this is little problem. You just need to find someone else willing to wish this. This should be easy, given the benefit to the world of the wish. Heck, I would be happy to wish this. In fact, I take the opportunity to formally state here that I *do* wish it for you. Feel free to use it. [Answer] This isn't likely to be better than some of the other answers, but you could randomly approach someone on the street of a major city and say to them, "Wish that you had \$10" and when they do, you hand them the \$10 bill and walk away, an additional 24 hours of life ensured. Most people will be too surprised and simply wish for the $10, then count themselves lucky that it actually worked and buy themselves a cup of coffee. Anyone that tries to get cheeky you can just simply decline. Anyone who gets their wish will be unable to wish a second time, reducing the potential abuse. The overall impact to the economy of these new bills is going to be relatively minimal: The US prints about [1,300,000! of them on its own *every day*](http://www.federalreserve.gov/paymentsystems/coin_currency_orders.htm) and that's ignoring the other denominations. Even if your magically created bills are detected as counterfeit, the volume is going to be low enough that the government isn't likely to put much effort into finding you (after all, you're only creating \$10 a day which isn't even enough to pay an investigator for an hour). With luck, you'll get away unnoticed and avoid large-scale disruptions to the world. [Answer] Solution by induction. Get 2 people. Grant Person A the wish of teleporting $2 million from a Swiss Bank vault to your location. That money is split evenly. Grant person B the wish of "at dawn, create a person who exists until dusk, at which time they make this wish, and then disappears." Immortality achieved, with no huge impact on the world. [Answer] **Employ yourself in a large hospital**, there is plenty of people who wish to get better. You don't have to be a doctor, you just need to meet one patient or their family member a day somewhere in a hallway. Nobody will notice because sometimes people just get suddenly better on their own (and then believe in the power of prayer, homeopathics, healing crystals and other bullshit...) It may impact economy of the hospital though, since cured patient is a customer lost. [Answer] Every evening where you didn't got an idea for a better wish to fulfill, look at [the first post review queue of stackoverflow](https://stackoverflow.com/review/first-posts) or any other stackexchange site. You will find lots of people wishing for stackexchange to fix one of their problems for the first time. Pick one and wish that they receive a good answer to their question. [Answer] You can choose which wish you want to fulfill, right? So, everyday, you hold an inverse auction (at some place, on the internet, whatever) where you fulfill the wish of the *least* demanding person. It is almost sure it will always come down to someone asking 100$ or something similar. You can always have a failsafe by having a friend on stand-by in the case everyone in the auction asks for an atom bomb. [Answer] Share with a loved one, who cares about the world, the economy, and you :-) "I wish that today, Pavel would write another really awesome question in Worldbuilding". [Answer] Become a professional, travelling Santa Claus. You'll be wishing new people a Merry Christmas for the rest of your life. [Answer] Make a website! "I am the wish genie! Email me your wish and perhaps it will come true! Limit one per person." Post your website on Facebook, or other social media of your choice. Some people will mail you wishes on a lark; grant whatever wishes you can. Soon people will realize the website works; it will go viral and you'll get all the wishes you could ask for. Many of them will be grantable. You might need to call up the person and have them speak their wish verbally. You might need to verify that you're not accidentally trying to grant a second wish to the same person. You can bribe people to wish for you to have these abilities if you need them. [Answer] Step one is going to be to find a teenage rebel who is stealing bread and food from market vendors to keep himself and a cherished best friend monkey alive. Befriend him and wait for a parade that features a beautiful princess. At this point he will become infatuated at the sight of her and wish to be a prince. While you are only required to grant one wish, you may grant more. Convince him that he only has three. As their love blossoms and as you travel through trial and tribulation with him he will become eternally grateful to you. By his third wish, he will wish you free of your deadly bond and you will be able to grant wishes for your own reasons at your own pace for the rest of time. [Answer] # Become a Flight Attendant for CSA Czech Airlines. If this won't do, then maybe Lufthansa or an American domestic. You will have to get one of your friends to make you young, smart, and handsome (well you probably are already). Obviously, this is a stereotype, but it could go a long way to help. The wishes you get as a member of cabin crew are: **Plenty** - you will get way more wishes than one per day **"Reasonable"** - you likely won't be asked for a pile of gold, but rather "I wish that child would stop screaming," or "I'd like a ginger ale."; and **Fresh New People** - it is rare you will be confronted by the same person twice, and unlikely that you will have a full airplane of the same people twice. This may not be an optimal lifestyle, but on the days between and through your friends, you can set up something similar to the other questions being asked. You will only have to discern whether to grant wishes like, "ugh, I wish we were there already!" Just say no to that one. [Answer] **Start a lottery company.** To enter this lottery, you pay \$1, and the prize money is some amount that's sufficiently small not to imbalance the economy, say \$10,000. There is one winner per day. You buy the ticket online, and when you do so you have to check a box saying that you agree to the terms and conditions. These include the phrase "I wish to win \$10,000." Then your job is simply to get up in the morning, look at the name of the randomly selected winner, and say "so be it." Since the winnings are generated by magic, your company doesn't actually have to pay them out, and thus you will make a nice profit. Of course there are issues with how to set such a company up, whether it's legal, whether you'd be found out if it is, and what to do if the server goes down or if no-one buys a ticket - but if you have someone willing to wish these problems away in exchange for a share of the profits then they are hardly problems at all. [Answer] Get that boy who's always singing "I wish I was an Oscar-Meyer weiner". He's annoying. Since this wish doesn't specify a time range, fulfill it for 23 hours and 59 minutes. Then that stupid kid starts singing again (he'll never stop!). Repeat and save the world from that scrumptious, delicious all meat never-ending commercial (My 3y old girl just found it in youtube and replays it over and over) :-) [Answer] Have a friend of yours wish that you can recognize wishes for things that are going to happen anyway when you hear them. Then you can easily "so be it" no-op :p Then just go to Cano64's hospital or where ever there are lots of wishing people that have a good chance of their wish coming true naturally, like casinos or such, and grant a no-op to someone. [Answer] You could hangout around the local jail, people visiting love one would be wishing their love ones were out of jail, or wishing they didn't do what ended them up in jail (ie quit drinking / doing drugs, getting in fights, stealing). Since you can only grant one wish per-person you are granting only second chances, if a person is in lockup a second time they will have to improve on their own. Along the idea of working with addicts you should be able to find a large supply of AA meetings to attend finding people trying to help them selves you could just be adding the extra supernatural help. You would need to cycle through meetings since most are pretty small, but there is a lot of meetings in a large city. There are other group sessions similar to AA you could find to frequent. [Answer] The genie said "So be it" before he gave any stipulations. And "you will die if you don't grant a wish" is not implied in the wish for infinite wishes. So I think you can stop granting those wishes now. [Answer] I'll help you! "I wish Pavel has the magic ability of hearing the wish of any person he wants whenever he wants to hear it" Then you can just "listen" to anyone wishes on the planet whenever you want and grant one of them, without ever meeting the person. - we can test if this works without a high risk, and if it works the world will just be a little better, with a miracle happening every day somewhere on the planet. You can filter and just grant reasonable wishes, and no one will ever trace it back to you ;-) [Answer] ## Set up by the border! Whose border? I dunno. Someplace you speak the language. Every day somebody comes to you and say *"I wish I was a citizen of \_\_\_\_\_\_"*. You hand them their misplaced paperwork with confidence, because you know ... *they are*! The border police find your operation a bit peculiar, but they have to admit ... everybody they checked *really was a citizen*. If your friends wish the local cartels would go away and leave you alone (and who doesn't) this should be a stable and reasonably lucrative profession. They also better wish you never get laryngitis. Because I'll tell you one thing ... you won't be running out of customers! ]

[Question] [ In this alternate history, Christopher Columbus makes landfall in Central America, after passing south of Florida and sailing through the Gulf of Mexico, arriving right on the doorstep of the Aztec Empire. The First Contact goes badly and most of the expedition is slaughtered. The survivors are taken prisoner and the Aztecs salvage everything they can from Columbus' ships. Could the Aztecs do something useful with this new technological knowledge; applying and reusing it for their gain, becoming the major power of the Americas and ending up sending their own expedition back to Spain? In this alternate history, with no news of Columbus, Europe assumes that he is lost and nobody sends another expedition, deeming the very idea foolish. The European powers focus on Africa and Asia. EDIT: To address some points: * I'm only dealing with Columbus first arrival. What happened after that in our history won't happen in this alternate version. Please don't answer with examples of later Conquistadors who came armed to the teeth or what happened when the conquest was in full swing. * This is part of the background of the alternate history that I want to make as believable and coherent with what we know of this time as possible, technology-wise. I'm not going to write the story of this alternate First Contact. * I'm well aware that what defeated the original civilizations of the Americas are the diseases brought by the Europeans, more than weapons or anything else. That's another fact that I'll deal with later. * The expedition that the Aztecs would send back to Spain isn't sent to conquer Spain and Europe, but merely to establish formal contact with the people from the other side of the ocean. [Answer] What technology could the European explorer have on board upon arrival which could be useful for a reverse expedition? * **Gun powder**: usually it was not produced in loco, but rather carried in barrels. I doubt knowledge of how to make it was common. Unlikely it could be transferred. Without this no way to learn usage of fire weapon. Also crafting fire weapons requires refined metallurgy, of the type hardly present on board. * **Non fire weapons**: for this I doubt that the weapons of an easily beaten group could make a great impression on the Emperor. However, it's possible that elementary knowledge of blacksmithing was in possession of part of the crew, as it was necessary at least to perform ordinary maintenance. * **Ship making**: wooden ships were easily damaged, and knowledge on how to fix them had to be present on board. Usually there was even a carpenter. Highly likely. * **Navigation**: learning how to maneuver a large ship was not something to be learned in few months. It required practice and dedication. But it is likely it could be taught. Using navigation instruments to determine the position was probably an art only known by the captain and the officials. This could also be transmitted. Now, having established the technologies, we have to determine if the captive crew would agree to teach them to the indigenous. I have few doubts that a low level crew member would happily save his life in exchange of details on what he knows. But the others, in possession of important knowledge, would probably evaluate the possibility of taking their secret in the grave. Those were times when maps with important secrets (like the location of newly discovered islands or trade route) were valued as state secret, and thus official were probably conscious of the risk behind disclosing such and similar secret. It would be a matter of using subtle social engineering to convince the prisoners to cooperate. But I think that, before venturing into Europe, the Aztec would have probably devoted their attention to the rest of the American continent, which posed less risks than a transoceanic navigation. [Answer] In order for the Aztec Empire to become a legitimate force in the international community, it would have needed massive structural reformation to reduce internal fractiousness and to build learning, finance, and other institutions needed to transition from a bronze-age kingdom to a middle-ages kingdom. Other folks landed independently in the Americas in [1497](https://en.wikipedia.org/wiki/John_Cabot#Second_voyage) and [1500](https://en.wikipedia.org/wiki/2nd_Portuguese_India_Armada_(Cabral,_1500)), so the time for such a transition was limited. The Aztec society lacked organized advanced schooling in technology, and lacked the concept of the scientific method: This means any investigation would have been haphazard and lengthy before they figured out how to, for example, make steel and gunpowder. That's simply too big of a gap for Aztec researchers to bridge in the time available --even with the help of prisoners (without a common language). NOTE: European schools and understanding-of-science were also rudimentary by our standards...but that's not relevant: Europeans already had steel and gunpowder and a millenium of experience in technological innovation beyond the bronze age. More importantly, the Aztecs lacked *institutions* like banks and companies and associated knowledge like employment practices and good accounting. Institutions foster the widespread *labor specialization* needed to produce the wealth required to invest in steel and ships. Without widespread labor specialization, the Aztecs still have full-time soldiers, but only part-time miners and gunsmiths and shipwrights. Institutions ease the way to full-time specialists without draining the Emperor's treasury. These learning-curves in technology and inefficiencies in economy mean that the Aztec-created weapons and ships would have been (relatively) more expensive and of poorer quality than they could have been. And fewer resources would be available for expeditions and expansion. Example: Had, by some stretch, new Aztec shipwrights been able to reproduce a *Niña*-class vessel, the same inefficiencies mean that improvements and cost-reductions would come more slowly than comparable European developments. Being able to *reproduce* isn't enough - the Aztec Empire lacked the capacity to *keep up* with the rate of change. Finally, the Aztec Empire was a delicate political entity - peoples like the Tlascalans rebelled at the first opportunity. It's reasonable to expect rivals to obtain new and (relatively) advanced weapons also, perhaps triggering a series of crippling civil wars. Without a stable, coherent political structure that unified the tribes of Mexico (instead of simply delaying the next war), the Aztec army (and perhaps navy) would necessarily remain focused on maintaining hegemony withing the then-existing restive empire, not expanding into new territory. That's many decades of political, economic, and social changes that needed to happen...and there just wasn't time for it. Other explorers, in newer and bigger ships and armed with bigger and better guns, would certainly locate the Aztecs within a decade or two - some of them would surely return to tell the tale. [Answer] The steel technology is probably beyond them, given the processing steps they can never derive from sampling the finished article. Iron & steel would have been a reach. Ship-building, on the other hand, is right there before them. They had wood, they could likely have reverse engineered ropes & canvas sails using native hemp. They could have gotten by, scaled down, with wood, sail, tar, dowels, copper & stone. Artillery/musketry, forging technology dependent, would have been tough. Metal-working (mining/smelting especially) would clearly be the critical path. They would also still have to confront the epidemics from the Europeans which did inevitably decimate their population. [Answer] As previously stated, sailing technology is the most easily assimilated technology that can be gleaned from the capture of Columbus' men. However what has not been touched on is this: Mesoamerican peoples already had knowledge of bronze working prior to the arrival of Columbus, but the technology was exclusively used for the manufacture of ornamental items. Upon salvaging bronze cannon and arquebus from the captured ships, it could become apparent to the indigenous peoples that bronze can be useful for the manufacture of tools. Effectively kick-starting what would be recognisable to Eurasian eyes as a bronze-age. If someone aboard the ships happened to know how to make gunpowder, it is possible that this knowledge plus bronze tools and sailing technology could result in a Mesoamerican maritime bronze-age empire who possess cannons. Furthermore, many of the crewmembers of the ill-fated 1492 voyage were literate. There is a good chance that a written alphabet would be readily adopted by the Aztecs, which aids significantly in the administration of an Empire. [Answer] Not exactly a technology, but if they had captured some Spanish **horses** they could use them to improve communication within their empire, expand their borders in Mesoamerica and be better prepared for the next wave of Europeans once they arrive. While the stories of Americans believing Europeans to be centaurs or gods because of horses are probably exaggerated, they did play a role in convincing some tribes to join the conquistadors and in intimidating the Aztec warriors. Also as others mentioned sailing technology already, they could load horses on their ships and show up in Europe in style. [Answer] In the Pulitzer winning [Guns, Germs & Steel](https://en.wikipedia.org/wiki/Guns,_Germs,_and_Steel), it was argued that the possession of those 3 things were what enabled Spanish society to cross the ocean and conquer the Aztecs rather than visa versa. I'll take them in a slightly different order (with one bonus addition): * Germs Europeans had all sorts of nasty germs to (inadvertently) help cull the numbers of the Americans. Smallpox and Malaria were a couple of the biggies. In exchange, the worst the Americans had to offer was [Syphilis](https://en.wikipedia.org/wiki/Syphilis#History), which did no small amount of damage, but probably didn't significantly impact European fecundity. The Aztec's best bet here would have been prior exposure. In particular, if perhaps the Norsemen had managed to get Smallpox established as endemic in the Americas in 1000ish when they tried to settle Vinland (or perhaps the [Aleuts](https://en.wikipedia.org/wiki/Aleut) managed to carry it over through Beringia), then by the time the Spaniards arrived the Aztecs would have developed some resistances to it, and would not have suddenly had their empire decimated by the disease. * Steel The Aztecs were just [starting to smelt bronze](https://en.wikipedia.org/wiki/Metallurgy_in_pre-Columbian_Mesoamerica) when the Spanish arrived. If Spaniards found iron deposits in their territory, and started working them, and the Aztecs had enough time (perhaps due to not being decimated by smallpox) to see that and perhaps hire/capture a Spanish smelter, it would have been quite possible to learn the process. Steel would have been more work, but Iron would have been a great start. * Guns This would be trickiest, as you probably need good steel for the gun barrels. The gunpowder could be acquired from guano from bat caves, which Mexico is not particularly short of. Still, its possible primitive muskets could have been made, which would have made them competitive, if not equal. Further development of firearms probably requires the kind of squabbling warlike communities that Europe specialized in though. Also required of course is one important thing not brought up much in Mr. Diamond's book: * Printing Press This we know for a fact American society could have easily copied, because [the Cherokee did just that](https://en.wikipedia.org/wiki/Cherokee_syllabary#Early_history). Sequoia was in fact illiterate in English, but saw what English speakers were doing with writing and newspapers, and reverse-engineered how to do it all. With printing presses, any member of Azetc society who figured out how to do something new could quickly make it common knowledge. This was the real technology advantage Europeans had over them. Europe was a ("Medieval") backwater of the Eastern Hemisphere before they invented the Printing Press in the late 1400's. There's **a reason** Norsemen failed to colonize North America in 500 years of trying, while Spanish (and then English, French, Dutch, etc.) managed to do it *immediately* after printing was invented. This was not a coincidence. [Answer] The wood working, rope making and weaving technologies of Europe differed mainly in terms of scale, tools used, mechanisation, and standardisation rather than in matters of underlying technique so the Aztecs could almost certainly pick up the particulars necessary to build ships capable of crossing the Atlantic if they decided it was a priority. Beyond that it depends a great deal on how much information the Aztecs could get from the surviving crew about basic industrial chemistry, for example the recipe for gunpowder was not any great secret in Europe at the time. Nor were any number of other pieces of industrial chemistry like the extraction of iron, lead, copper, and tin, from various ores, or the proportions for making bronze, solder, pewter, and steel, things like amalgam and invar were still trade secrets though. Whether any of the crew knew these things is a different matter though. I don't know the exact composition of the crew of the *Santa Maria, Nina,* and *Pinto*, **if** Columbus had ex-miners and/or foundry workers in the crew then many possibilities open up. They could identify ores in the field and the local pottery kilns would be sufficient to being scaled up for metal production, they could produce enough heat. Gunpowder can be made in the field, in a rough and ready rule of thumb way, using raw materials that aren't impossible to get in quantity in the Caribbean area, officers of any military force of the era should have known a couple of basic recipes for use in exigent circumstances. [Answer] You can't reverse-engineer steel or gunpowder unless you can somehow capture manufacturing facilities which a typical conquistador did not carry with themselves. Those were conquerors relying on stock they brought from their homes. if they were up to mine iron ore or saltpetre, that might have pointed the Aztecs to the right direction, but as far as I can recall, those guys were only after precious metals, spices and such. [Answer] The Aztecs will have to heavily restructure their entire way of warfare if they ever hope to become an international power since Aztec combat was focused on taking captives for sacrifices. That mindset will have to change to “aim for the kill” if they hope to survive further contact with Europe. As for the weapons, it will be virtually impossible to reverse engineer gunpowder when they have no idea what’s actually made of or how it’s manufactured (though if someone from the expedition has some basic knowledge that could speed things up) . You can easily go around this by having the majority of Columbus’s men defect to the Aztecs , Columbus was notorious for being an unpleasant person and cruel even for the standards of his time, its not implausible for him to make a mistake or two that cost him the loyalty of his crews and with a generous bribe from the Aztecs it could be easy to sway them. If there are blacksmiths amongst them then they should know how to make steel or at least have a basic idea for it. Edit : as pointed out this can also backfire horribly on the Aztecs if the crew is instead taken in by any of the people subjected by the Aztec empire, and use the technology to gain independence . In that case either the Aztecs will have to change to match them or more likely be forced to accept them as equals . Best case scenario is that these newly independent civs remain neutral. I can even see them forming a proto-federation though wether or not the Aztecs are part of it I cannot be sure (assuming it’s not an alliance against them). Something I also forgot was smallpox. If smallpox spreads I suspect it will actually be less devestating somewhat since the Americans won’t be dealing with an invasion and might be able to deal with it more or less effectively or at least control so its not an apocalypse level plague. By the time of re-contact the people of Mesoamerica might develop partial resistance to smallpox. [Answer] It would be very hard to salvage the naval tech. Shipbuilding demands the right trees and iron/bronze metallurgy to manufacture both the tools and the critical metal parts of a oceanfaring ship. And even if there was a blacksmith among the crew members you will have no iron because what you need is a miner that also knows prospection. Was there europeans that knew how to find virgin ore veins to mine in the XIV century? I don't know but I would bet there wasn't since most mines in Europe were old, ancient mining regions, some from the roman times, other slowly discovered during the middle ages. There was no science and art of finding good places for mining in Europe, geology is hundreds of years in the future. So, no iron. In the case of bronze you have to find a north american geology map that shows where is tin and where is copper and see if it was viable for the aztec to have access to both mineral resources at the same time. Most probably it wouldn't. [Answer] **Not much** Let's assume the best case for the Aztecs-they kill all of Columbus' crew, have all the hardware available for inspection, and contract no European diseases. Technology comes as a whole interrelated package. People say the Aztecs could have understood the ship technology. They probably could understand the construction, but not why the ships were designed as they were. As others have said, you can't understand how to make steel just by looking at it, so you can't steal the ship designs in the places steel was used to hold the ship together. They might realize gunpowder was what made the muskets work, but figuring out how to make gunpowder seems difficult. It might have made them use wheels for real work instead of just children's toys. There would clearly be an explosion in technology, but Europe was progressing as well. I can't imagine it taking more than a few decades before the next European ship came to the Americas. Magellan was only 30 years later and his crew sailed around the world. You can't have steel that fast, which means no useful guns. Gunpowder is not very useful without steel to contain it. The next few ships would have brought the diseases, so I suspect this scenario just delays the conquest of the Americas by a few decades. [Answer] Yes, they can do that. But they would need wise emperor and something like culture shock. So your wise leader wins, but understands: his people are ages behind in technology and butchers knife is still hanging over them. He decides, Aztecs need change and fast. He uses bribes, titles, marriage and piles of gold or torture to get as much information and cooperation from captured Spanish. They can get close-to-full information or scraps-to-build-on about: * Ores and mining, metalwork, guns and gunpowder, ships and navigation. * Politics, logistics, merchant and craftsmen organisations. * And all you can think of to be revealed from Spanish part. With said information and deep pockets of emperor, mining and metalworking grow by day. Carpenters try to build ever bigger ships. Soon all needed components of gunpowder are found and wisemen and priests labor day and night to perfect formula and start production. State managment gets reformed. Guilds are born. Maybe, even religion will take some lessons. In few short years Empire is reborn and stronger. Problem is Spanish had little knowledge how to cure and prevent diseases. Maybe, one of your priests would invent [variolation](https://en.wikipedia.org/wiki/Inoculation) to prevent smallpox, problem is they had no cows.. alternative animal? Dogs, cats, horses of Spanish. Travel to Europe, that would have close to zero chance to have any good results. They are pagans and Pope with Kings would mark them to be done with: be it in Gods name, for their wealth or to weed out a potential rival. So better course is other nations of Americas and Asia. [Answer] I think you need a longer timeline. This can be more plausible, possibly if the invaders are captured and not slaughtered (foreign devils blood on our alters? I think not!) Chris bargains for his life, promising all sorts of new things, and hoping for a chance to later get away. They become well treated slave skunk works. Blacksmithing. Small sail boats. Small boats make fishing more efficient. Rope walks. Boats get larger. Plausibly one of the crew is a miner. (Columbus was seeking gold... Certainly the later conquistadors brought along mining expertise.) You can shift Chris's landing point with a hurricane. I wonder if you would do better for them to find a different people. The Mississippi mound builders were as organized, but not nearly as blood thirsty. Less is known about them, so you have a freer hand. Socially, running into the Iroquois Confederacy could be bad news for Chris. They were well organized, living in permanent communities, managed the local forests for game production, had agriculture. Their territory included much of what is now Pennsylvania -- coal and iron. A generation later: Iroquois develop coastal raider sail boats that make life difficult for coastal tribes from Maine to Florida. Coastal tribes respond by fortifying the coast, and acquiring Iroquois technology. A generation later: Throw in a smart boatsmith indian and move from the coastal boats to something like the cod schooner used in New England and Maritime Canada. I don't see any real tech revolution between the two. Much faster boat that could sail decently close to the wind. [Answer] They could in theory become interested in exploring the atlantic coast. They would set up a port most likely in todays Veracruz and Tuxpan. From there they'd make back the way Colon did the first time. At discovery of the Mississipi river the'd may feel some familiarity with their island City of Tenochtitlan and build a new city there. The city would prosper thanks to their farming technology. The success of this enterprise would infuse legitimacy and therefore stability to the regime. At the same time the emerging coastal economy would introduce pressure for changes. Later on, when the white men came back they would be more cautious. When the struggle finally erupted like it did in OTL they would make most of them prisoners and continue learning from them. I can't go much further but a history along these lines would have a few advantages compared to OTL: -the impact of diseases brought from europe would be more gradual and allowing them to learn how to cope. -The defense ability of the aztecs against the spanish would be better. -The speed of spanish colonization of the continent would be significantly slower. At some point total war between aboriginals and the spanish would erupt. Depending on the winner you could have later on, 50 or 100 years later, the scenario where they would visit Europe (and the rest of the world). ]

[Question] [ Can an organism have traits that resemble both an animal and a plant? Such as bone, chlorophyll, muscles, and cell walls. Not necessarily a hybrid, but something that can be classified in between the two kingdoms. Are there any examples of this if so? [Answer] Photosynthesis is known to occur in one animal at this point, a specific type of green sea slug: > > It’s easy being green for a sea slug that has stolen enough genes to become the first animal shown to make chlorophyll like a plant. > > > Shaped like a leaf itself, the slug *Elysia chlorotica* already has a reputation for kidnapping the photosynthesizing organelles and some genes from algae. Now it turns out that the slug has acquired enough stolen goods to make an entire plant chemical-making pathway work inside an animal body, says Sidney K. Pierce of the University of South Florida in Tampa. > > >  > [Green Sea Slug Is Part Animal, Part Plant](https://www.wired.com/2010/01/green-sea-slug/) > > > It's not very big (average [30mm](http://animaldiversity.org/accounts/Elysia_chlorotica/)), but I think it's the closest you'll get to something "half animal, half plant" (at least in the real world). [Answer] This is coming from my 7th grade Biology lesson: [*Euglena viridis*](https://en.wikipedia.org/wiki/Euglena) [](https://i.stack.imgur.com/dgFAF.jpg) When I read the title and question, I immediately remember this cute creature that drew me into the world of biology (and *Planaria*, I still remember your amazing regenerative ability - a natural Deadpool). *Euglena* is a flagellate, a microorganism that moves using *flagella*, a whip-like "hair". It only got one, long, flagella, that categorized it as "animal" - actively moving, to gather its food. However, the fascinating part is it got chlorophyll too, which is unique to plant kingdom, and can actually use it to perform photosynthesis when provided with sufficient sunlight. So, basically you got an "animal micro-plant" here, **half-animal, half-plant**. Note that the two kingdom - plant and animal - is outdated by now, and we now use [6 kingdoms model (or even 8 kingdoms, if you like)](https://en.wikipedia.org/wiki/Kingdom_(biology)). [Answer] Your sugested ideas about what constitutes an animal are narrow. Basically, just vertebrates. Animals with bones and especially backbones. There are invertebrate animals that resemble plants, for example, sea anemones. Coral polyps also qualify. There is a whole range of sessile animals that sufficiently resemble plants. They are immobile organisms, usually in their adult form, and they lack chlorophyll. It is their immobility that makes them plant-like (superficially, at least), but their larval stages are highly mobile. The unicellular organism *Volvox*, which does form colonies, contains chloroplasts. It is both a plant and an animal. It is microscopic. There are also stick insects -- if camouflage fits your plant-animal category. In principle, it is possible to imagine there could exist alien lifeforms that camouflage themselves as plants and might even possess chloroplasts. The main drawback to plant-animal cross-over organisms is that photosynthesis doesn't confer much of an advantage. It would only supply, at best, a few percent of the energy intake for an animal. In general, animals can easily get all the energy they need by eating plants (herbivores) or other animals (carnivores) or both (omnivores). In principle, creatures with both animal and plant characteristics might exist. So they are possible, but most likely they are highly improbable. In a big enough universe even highly improbable organisms must exist somewhere. [Answer] In the real world Coral and Jellyfish are almost kind of there, Triffids come to mind immediately as well but I'm thinking those are less helpful to you. Both Coral and Jellyfish are animals that harbour photosynthetic algal organisms in a symbiotic fashion; it's not that big a step from symbiotic relationship to being an organelle although we don't understand the mechanisms that are involved. So that's Chlorophyll in animals covered, there are also some plants that exhibit the very animal behaviour of walking, except that they do it very very slowly one example is the "walking palm" *Socratea exorrhiza* which puts out roots on one side preferentially and thus very slowly moves away from salty seawater and inland, like a super slow-motion version of John Wyndham's Triffids and only in one direction. I'd also suggest watching time lapse of plants competing for light as they grow if you think plants don't exhibit mobility. As for something actually being "in between" in classification, that is unlikely to happen whoever gets there first will classify it, if the discoverer is a botanist it'll be a plant and otherwise if it walks it's going to be an animal that's just human nature. [Answer] Aside from the sea slug already mentioned, I don't know of any other animals that photosynthesize but other crossovers do exist. There is an entire phylum of photosynthetic bacteria called cyanobacteria. These are bacteria that obtain their energy through photosynthesis which takes places in folds in the outer membrane of the cell, so they do not have chloroplasts. (Small edit: A friend of mine gave the remark that cyanobacteria are essentially what became chloroplasts, so it is kind of logical they do not have chloroplasts) Lichens are composite organisms that consist of algae or cyanobacteria that are symbiotic with fungi. One cannot live without the other, and so the combination of the photosynthetic organism and the fungi is called one single organism. Again, these are not combinations of plants and animals, but they do show that it is possible for other organisms to have plant-like abilities. As was already mentioned before so far photosynthesis outside of plants only happens in very small organisms, because larger organisms have a too high metabolism. However what I could imagine is a 'larger' animal using photosynthesis as an additional way to gain energy. The first imagine that pops up for me is a cold blooded animal that does a lot of sun basking already. Why not gain some additional energy at the same time? [Answer] There are a couple of ways something like this could happen: * They could have branched off far back in the tree of life, when plants and animals were more similar, and retained primitive traits of both. Fungi, sponges and microorganisms that can either photosynthesize or hunt all fall into this category, although they don’t have the more advanced traits you’re thinking of. * Plants live in symbiosis with chloroplasts, which are genetically separate organelles. (They evolved from a cyanobacterium that survived getting eaten by another microbe, and started making food for them both.) We tend to think of green and photosynthetic as plant traits. Other kinds of organisms can do something similar, with a chloroplast from something they ate, or an organism containing them, or a different kind of algae. * Traits such as hard cell walls might evolve independently. * Individual genes might hop species due to horizontal gene transfer, although genes are not Lego sets. This gets you an animal with a protein from a plant or vice versa, not an animal with hard cell walls. * They could be alien or genetically-engineered. [Answer] The reproductive cycle of jellyfish has distinctly animalike and plantlike elements. They reproduce by dropping a "planula" into the water, which attaches to a rock and grows into a polyp (which looks like an anemone). The polyp then clones itself over time, producing more jellyfish. The polyp more resembles a plant/spore more than an animal, at least to me. In fact, the fact they stay so stationary, that many anemones seem a lot like plants, but they're most definitely animals. Coral, also, is in fact an animal, technically speaking, but behaves much more like how we imagine plants. (Corals, anemones and jellyfish are all related.) [Answer] All life has a common ancestor, and both plants and animals originated from early multicellular life which possibly had features of both. For example corals have a sessile (plant-like) adult forms, and motile (animal like) larval forms. [Answer] One organism with both plant-like traits and animal-like traits is the Venus Flytrap. ]

[Question] [ Suppose a species possessed different sets of DNA for different parts of its anatomy. I'm not suggesting one set for every function in the body; that would result in hundreds of thousands of unique sets of DNA. Instead, suppose there was one set (core DNA) that determined how the body was laid out, such as the position of arms and legs, skin color, eye shape, number of teeth, etc.; one set (functional DNA) that controlled the transfer of energy through the body, be it through the cardiovascular system, nervous system, or another transfer plan laid out by the core DNA; and a third set (translational DNA) that ensures the various DNA sets can communicate with each other. This is certainly a complex system, but how reasonable is it to believe that it *could* exist, whether by nature progression (preferred) or engineering? [Answer] As Scott Downey noted [in his comment](https://worldbuilding.stackexchange.com/questions/33040/multiple-dna-one-creature#comment88953_33040), this [already happens in humans](https://en.wikipedia.org/wiki/Mitochondrial_DNA). If you're looking for something a little more macroscopic in nature: The [Portugese Man-O-War](https://en.wikipedia.org/wiki/Portuguese_man_o%27_war) seems to fit the bill pretty effectively. It's several different creatures (**Edit thanks to Mike Nichols** that all share the same DNA, so maybe not *exactly* what you're after) that are so reliant on each other they *cannot* function independently. **EDIT:** I feel compelled to point to [QuadmasterXLII's answer on Lichen](https://worldbuilding.stackexchange.com/a/33046/2366). I think what you're after is something on the scale of the Man-O-War, but with the lichen's level of symbiosis (which stops short of the full mitochondrial integration we've got). So **yes** is the answer to your question. Can happen, has happened, feel free to make it happen again. [Answer] [Lichen](https://en.wikipedia.org/wiki/Lichen) is an excellent example that exactly matches what you describe. The fungus DNA determines the structure of the organism, and the algae DNA is responsible for producing energy. [Answer] ## This exists in the real world: Chimeras There actually are creatures (including humans) who have multiple cellular DNA streams flowing through their body. These folks (or beasts, as the case may be) are called [Chimeras](https://en.wikipedia.org/wiki/Chimera_(genetics)). Tetragametic chimerism (or monstrous chimerism) is usually congenital and is the result of merging of non-identical twin zygotes. Such chimeras may sometimes have multiple sets of sex organs, for instance, with different genetic makeup. These usually result in a non-standard body plan. Most cases are far more subtle and result in a normal body plan, often going undetected. There have been cases of women giving birth to what are genetically their own sisters or nieces (because genetic material from their own mothers or twins made it into the embryo). The most famous case along these lines is that of [Lydia Fairchild](https://en.wikipedia.org/wiki/Lydia_Fairchild), who had birthed children that did not seem to be genetically hers, which landed her in hot water with the courts when she asked for child support. She was later shown to be a chimera. None of these examples are quite as specialized as what you describe, but from reality to your example isn't as great a leap as one might expect [Answer] ## Chimeras are only half the answer *(not heritable)* Although chimeras have cells in different parts of the body containing different genomes, this condition will not be passed to offspring since human reproduction generally only involves combining one cell from each parent. So a human child may be a chimera if two or more fertilised ova fuse, but the distribution of cells of each genome within the human body will not correlate with the distribution of different genomes in either parent. So this fits your request for "multiple DNA, one creature", but does not have the specialisation of different genomes for specific aspects of the body. The distribution will be largely random, and not consistent from one chimera to the next. ## *Heritable* divergent genomes are in principle possible It is possible to have a multicellular animal that does not reproduce using only a single cell, but instead allows all of its cells to divide until the entire animal can divide into two. This means that a specialised type of cell in the offspring is descended from the same specialised type of cell in the parent. The existence of this type of animal means that in principle it would be possible for the genome of a specialised type of cell to drift and become significantly different from other types of cell within the same organism. The known example we have on Earth of a multicellular organism with specialised cells that reproduce independently is called the [Trichoplax](https://en.wikipedia.org/wiki/Trichoplax). The specialised cell types can only diverge over time if reproduction is solely through dividing. This may be possible with trichoplax as they appear to have lost the ability to reproduce sexually (which would otherwise cause all cells to share the same genome again). [Answer] You may find the line you draw is more artificial than you think. The idea of "multiple DNAs" is a construct to make it easy for humans to observe the behaviors they see. When it comes to the actual function of cells, the cells care not for this artificial line: DNA is DNA. Consider viral DNA, which is clearly from an foreign species, by our observations. And yet, the cells treat it no different. Consider they are so similar that, in fact, every now and then a bit of viral DNA accidentally gets spliced into our own DNA by the repair mechanisms. Consider we have 46 unique separate chromosomes, but they come in pairs that are sufficiently similar that we often think of it as 23 pairs. And yet we think of it as one genome. Consider that we "upregulate" different genes in different areas. While all cells have *roughly* the same genetic content, what makes teeth teeth is that they have upregulated the production of proteins essential to being teeth. It may turn out that you can actually roughly divide up our genome as your multiple DNA, with some dna handling body structure, some handling teeth, etc. However, the body has to solve an interesting problem: how does a cell know if it is a tooth? Part of that result is clever management as the early stem cells divide, but part of it is that the body is resilient to errors. Instead of being "I'm a tooth DNA" you have "I'm a body of DNA that is useful for teeth." If it gets upregulated in the wrong place, it might be okay for a bit. In fact, a tooth gene in the liver might upregulate by accident for a bit, and then be shut down when the cell realizes that gene isn't being very helpful. [Answer] While the other answers have responded to the title of your question, I don't think anyone has really addressed the specific question you asked. Can an organism use different sets of DNA in different organs or organ systems? The answer is almost certainly yes, with a couple of caveats. Caveat 1: The reproductive cells of the organism, the ones that give rise to all the other cells, will need a complete copy of every organ's genome, otherwise that organ's genome, since it doesn't reproduce itself, will be lost. This means that your embryo is going to have all the DNA needed to create every organ in the body, and as the cells differentiate they will discard the DNA they no longer use. The germ line cells however will retain all of the DNA for the next generation. Caveat 2: Many of the genes in a multicellular organisms are actually used by every cell. These are called housekeeping genes and they handle things like basic upkeep of the cell. Genes like RNA Polymerase II, Ribosomal RNAs, and the Nuclear Pore Complex are going to need to be in every cell, so your different DNA sets are going to have a large amount of overlap. That said, I see no reason why a multicellular organism couldn't handle differentiation via loss of DNA. Currently, all organisms I've ever heard of create different cell types and organs by differential regulation of the genes in their DNA. They have a million ways of modulating the output of genes and create incredibly complex regulatory networks full of feedback loops and bistable switches. By comparison just deleting the genes necessary for being a neuron when you decide to become a glial cell seems pretty straightforward. The only trick is that the DNA for different functions needs to be spatially segregated in the genome for easy deletion. The simplest way would perhaps be by chromosome. For instance, say chromosomes 1, 2 and 3 contain all of the ubiquitous housekeeping genes, 4, 5, and 6 contain ectoderm specific genes, 7, 8 and 9, contain mesoderm factors, and 10, 11, and 12 are necessary for endoderm. When a cell decides to become ectoderm it simply degrades chromosomes 7-12. Obviously its sort of tricky for this sort of spatial organization to have evolved. Multicellular organisms would have had to originally start off with this method of differentiation. If that's the case however, regulation of what cells do what actually gets a whole lot simpler since the cells really have no choice in the matter. On the upside, you've always cured cancer! [Answer] Consider the humble butterfly. It has but one genome, which it shares with the even humbler caterpillar. The butterfly has six skinny legs, wings, a loooong rolled proboscis, a diet of nectar... the caterpillar has sixteen stumpy legs (six of them "real", ten "prolegs"), web spinerettes, hairs, mandibles, and a diet of leaves... completely different creature. From the same genes. The two forms are switched between by activating one part of the genome and deactivating another. Thus, genes to create and operate two essentially completely different creatures can work from a single genome. [Answer] **It already happens.** At least, something similar to what you have in mind. Humans have a whole microbiome of many different organisms living inside of us doing various things for us. A surprisingly small percentage of the cells in your body are actually "your" DNA. Mothers especially will also pass on a lot of helpful "non-human" genetic material to their offspring. [Answer] There are many good answers here but I want to attack the root of the question. I think the OP's fundamental concept of DNA is wrong. DNA is the blueprint of an organism that contains the instructions of how to construct and operate each cell that makes that organism. DNA by itself does not perform any biological function. Therefore an organism can only have one set of DNA. NOTE: that DNA can differ slightly from cell to cell due to various biological processes like teleometric decay, selective retention, etc but the DNA is still the same just potentially missing parts that were contained in the original DNA. I think what the OP is really looking for is hyper symbiosis to the point of mutual dependence. Symbiosis is where different organisms share the same physical body and distribute different biological processes resulting in greater prosperity for the body (my butchered definition of it anyways). One possible example of this is our digestive system, where we rely on a multitude of different organisms to break down the food we consume into nutrition that is absorb able by our actual body. Our body gets the nutrition it needs and the organisms get a safe habitat with a higher promise of nutrition they need. If you were to kill off all of these organisms I'm pretty sure you would die. Going back to the OP's intended level of complexity, it is possible. It would require several organisms to enter into a symbiotic relationship and then evolve that relationship. This is highly unlikely because of how much evolutional cooperation it would require but I believe with all the potential life in our galaxy, somewhere some group of organisms won the cosmic lottery. [Answer] It is very reasonable to believe in the existence of such systems. Fungal and algae symbiosis as described in answers above can serve as an instant example. On a theoretical basis we can have [endosymbiosis](https://en.m.wikipedia.org/wiki/Symbiogenesis) as an example where certain cell organelles have a dna that is different from that of the cell. And from recent technological advances I do not see why it is impossible for the same to be applied in bioengineering or related disciplines. [Answer] It is hard to say, since we've only sequenced a small number of species in comparison to all in existence. But a straightforward answer is try it for yourself via the field of Synthetic Biology. Ask more questions on the Google Group DIYbio if you want to know more about how and where to get started, and if school or a hackerspace or a home-lab is more your style. [Answer] **A species with multiple bodies will at the same time have multiple DNA** The [Man o' War](https://en.wikipedia.org/wiki/Portuguese_man_o%27_war) is a type of creature that is not one, but instead multiple creatures, all of which come together to form a single species. Each of the four species have their own DNA. An advanced version of this multi-bodied concept is the [anthill](https://worldbuilding.stackexchange.com/questions/46962/what-would-a-collective-consciousness-look-like). While the creature does have multiple strands of DNA, one could argue that a multiple bodied creature is even its own creature. ]

[Question] [ Joe, the average Worldbuilder accidentally slips through time sixteen years back. From September 11, 2016 to September 11, 2000. [He gave saving the World Trade Center a thought](https://worldbuilding.stackexchange.com/questions/55576/can-a-single-time-travelling-person-prevent-the-world-trade-center-attacks), but then he decided to be a bit selfish. He searched through his pockets and this is what he found: * [Samsung Galaxy S7 Edge](https://en.wikipedia.org/wiki/Samsung_Galaxy_S7) with 64GB microSD card in it * USB 3.0 flash drive with 128 GB capacity + Containing work documents and two movies released in 2015 (of your choice) * Swiss Army pocket knife * Keys from his apartment * Keys to his car, [Toyota Camry build 2006](https://en.wikipedia.org/wiki/Toyota_Camry#XV40_.282006.E2.80.932011.29) * Wallet containing: + 100 USD in cash (small banknotes, issued through 2012 - 2016) + Two credit cards valid to 2020 + Driver's licence Joe quickly realized that it will take another fifteen years of development till his phone will see light. So, he decided to be selfish and earn some money by selling his phone to the highest bidder. But the question is: **How much can you earn by selling your tech sixteen years in the past?** [Answer] ## Very, Very Rich, but it will take time and nobody can know that he is from the future The stuff he brought with him is effectively worthless because there is no way to show somebody in 2000 technology from 16 years in the future whilst hiding the fact that it is **from the future**. How are you going to explain away the fact that Joe (Random guy) has somehow invented, perfected and created technology that is literally 100x better than anything the biggest, most expensive R&D labs in the world can produce? So, you cannot sell your future stuff, because as soon as anybody knows (or suspects) that you are from the future, you're going to find yourself hunted by every corporation, billionaire and intelligence agency on the planet. How much do you think (to take an example) the US govt. would be willing to do to find out the details of every major war and terror attack for the next 2 decades? If you think the US wouldn't torture you to find out, then also consider the Chinese and the Russians. So, that is rule #1: You absolutely have to keep everything to yourself. Personally, I recommend Joe destroys and incinerates everything that came back in time with him (possessions, clothes, jewellry). --- ## Update: He is going to have a really hard time starting out As pointed out by @vsz in the comments, Joe isn't going to have a legal identity when he arrives in 2000 because past-Joe is already using it. This means that Joe is going to be, for all intents and purposes (and in a very real sense) an undocumented illegal immigrant. He is going to have to find cash for food and shelter, and then find and pay a forger a lot of money to create an identity for him, and \*then\* he can do all of the below and become obscenely rich. Assuming he manages to do that at all. He's in the same precarious position that all undocumented illegal immigrants are in: If you get caught even once then it's game over, and earning any cash at all, let alone enough to buy a new identity is going to be really difficult and/or risky. ## Possible solution: have future-joe find past-joe and convince him that you're from the future and you should work together on this This strategy is risky (If past joe reports him to the police: game over) but solves all of future-joe's other problems. You'd find past-joe, show him your amazing futuristic smartphone, tell him the deepest darkest secrets that nobody else could possibly know about the 2 of you, and convince him to work together with you. He can provide cash and a legal identity, you provide knowledge of the future and using the below, you both become obscenely rich. ## So, how to make money The truly **valuable** thing that Joe has is his knowledge of the future. The most lucrative information would be knowledge of financial markets (market runs, crashes, companies that shot up/down in value). If joe had a job in finance that exposed him to that kind of information on a regular basis, that would work out particularly well for him. But even if he wasn't particularly interested in financial markets, your average person will remember particularly big events (the dotcom crash, the 2007/08 crash, the irag/afghanistan wars, 9/11). They'll know the names of big companies (Google, Apple, Facebook, Tesla, Netflix, Amazon etc.) and be in a position to "get in early". **Examples**: - The dotom crash is just getting started when Joe arrives. If he does nothing but keep betting that the stock market will go down for the next year, he wil make an awful lot of money. - Apple's stock price increased 100x from 2004 to today - From its' IPO in 2004, google is up over 20x - Amazon's stock price increased 100x from 2001 to today - Facebook is up almost 10x just in the last 3 years - Tesla jumped almost 10x from 2013 to 2014 - Lehman brothers was worth \$50 Billion in 2007, and \$0 18 months later. - Enron was trading at \$60 Billion when joe arrives, and will be bankrupt within a year You get the idea. Joe doesn't have to know the exact numbers, he just has to remember that these things are going to happen and act accordingly. Additionally, your guy could make a lot of money in the betting market (betting on who wins the US presidential elections, who wins major sporting events, etc. etc.) This won't make him a ton of money \*immediately\* (unless he has a really good memory for sporting events circa 2000), but the presidential election is coming up in November. The dotcom bubble is about to burst. There's probably some major sporting event he might remember the outcome of. If I were joe, I'd borrow some money (say, $10,000) and go make some bets on events he remembers that wouldn't attract attention, probably sports and the election (correctly predicting 9/11 would attract a \*lot\* of attention. So just don't go there.). It will take a while to get super rich, and a lot of it won't come until later on, when you get closer to recent memory and more events that he remembers the outcome of come close enough to make bets on. Things like, say, Bitcoin (10,000 BTC bought you a pizza in 2009, and $8 Million just four years later.) But he should get reasonably rich reasonably quick and things will just keep snowballing from there. [Answer] Joe will do himself a huge disservice waving future-tech about, no matter if he does it openly or covertly. Because it will not take long before he has goons of all sorts on his arse, wanting to capture and interrogate him about the upcoming 15 years of history. If Joe is the least bit paranoid (i.e. he **has** a sense of self-preservation), he will quickly realize that making a quick buck off of his phone(\*) is a really bad idea. Small gains, and a **huge** risk. So, if he instead thinks in long terms and **strategy**... # Patents Patent the concept of a smart-phone, or any of the hundreds of innovations in a smartphone that have not been patented yet. Set a lump licensing cost of anything up to $1 for every unit sold. Also I think Steve Jobs might be interested to know [this little thing](http://www.telegraph.co.uk/technology/apple/8841347/Steve-Jobs-regretted-trying-to-beat-cancer-with-alternative-medicine-for-so-long.html) about his health, and what will **not** work in curing him. That will probably be worth something to him. (\*) ...which by the way he cannot change because the micro-USB port charger is still several years away. Also remember that Windows 2000 just came out. [Windows 2000 could not read USB disks larger than 32 GB](https://technet.microsoft.com/en-us/library/cc938432.aspx).. [Answer] **As rich as he wants to be** Kaz's answer is good, but it fails to maximize the potential of the temporal paradox Joe finds himself in. **Note this strategy does carry some degree of risk.** **Create a stable time loop** In 16 years time if Joe did not mess up the timeline too much, then his younger self is going to be getting time slipped into the past. As such Joe can subtly or not so subtly intervene with this event to maximize his profit (depending on the risks and what causes the time slip). During Joe's first run through those 16 years he needs to take some very good notes on: * People who he was able to trust and who to avoid * Things to do and what not to do * Key information on events * Lottery and financial information Right before Joe the younger gets sent back, Joe the older secretly or overtly gives Joe the younger the notebook and any other care package items that will assist him in his endeavor. The notebook instructs Joe the younger to keep the cycle going, and to make the notebook again with the same or better care package of items. With each iteration Joe refines the information, including information on loops that do not go well and items he passes along until it stabilizes and he is rich within the limits of keeping the loop stable. **General notes** During the first sixteen years Joe will need to keep a low profile until he can take over his original life. He will look old for his age, but that is common enough that it could be dismissed. It will be extremely beneficial to Joe to try and learn more about the time slip and determine if it was a natural event or if he was a factor (like he wished it). If it is a natural event (and I use that term loosely) then Joe has a greater freedom of meddling with it, since all that is needed is for Joe the younger to be in the right place at the right time. However, if it was will based, then Joe needs to determine how his will caused it to find the full extent of the power, and how to properly trigger it to ensure Joe the younger reliably gets sent back to keep the loop going, even if Joe the older badly messes up the timeline. **Age factor** Joe's starting age plays a huge factor in this story. 15 years old: Not even being a full on adult yet really limits what he can do. Can't take out loans or easily borrow. There is a chance that depending on his exact age he might not have even been conceived yet. So if he causes a big enough butterfly effect he could risk not being born. Which in turn causes a mess of temporal mechanics, which is best to avoid. 30 years old: He would be 14 years old in 2000. This means that Joe would still have to be careful since he could drastically change his future and result in him not being at the correct place at the correct time for the time slip. 42 years old: His other self would be 26 years old after the time slip. At that age he likely could interact with his younger self and make sure that Joe the younger is in the correct place at the correct time (assuming this is not Doctor Who temporal mechanics, which interacting with your other self typically is bad). The benefit to this is he could fix 16 years of mistakes he made while becoming rich. Also, he can use his younger self for cover for his extreme luck and success. [Answer] I honestly think it wouldn't yield as much as you'd expect, or at the very least be quite a bit harder to gain money from the technology you're carrying with you. Since the phone carries a brand existing in the time "Joe" went to, that brand is most likely to purchase it. Other companies will likely suspect you're a corporate spy and notify the authorities. Then there is the problem of actually convincing people that your tech is legit. You have no inside knowledge of the tech you're trying to sell and are basically saying: "Here is some stuff, go figure out how to use it yourself" as you're likely to lack the schematics. However, if you are a cunning businessman or have at least some grasp of how to cut a business deal. And managed to convince some company the technology you have is legit *and* the company is willing to spend the research and development into pursuing the applications of the technology you offer. It will launch whichever company gets their hands onto your tech forwards to instantly become the market leader, pretty much guaranteeing a monopoly since the tech you delivered is years ahead of the competitors. Getting a percentage of the sales will get you millions. [Answer] > > Joe, the **average** Worldbuilder... > > > ... **How much can you earn** > > > **Just a few years in prison**, I think. Too few people realise, how BAD Joe's initial situation actually is (if it would happen in real world). **TL;DR:** The first "may I see your IDs, Sir?" can turn into roughly 10-20 years of imprisonment just because of things in his pockets, unless he's able to convince judge he's from future. However this is not the wisest thing to do (as mentioned in other answers). The "may I see your IDs, Sir?" moment is very likely to happen sooner than later, because: **Joe has no *valid* id's.** Photo on Driver's licence (if it's issued before 2000) would look young, it would state a "young" age, however person, handing it would look too old for it to be legit. It can actually work only in cases when Joe's real age is something about 46, when the appearence age changes between 46 and 30 are not too drastical. **Joe has literally no money.** Cash is worthless and, (as mentioned in comments) even dangerous as it would be considered counterfeit. His credit cards can go right into trash can, as they were issued later and will be useless for another 16 years (also they will look suspicious to any official/police officer). **Joe has no place to live.** His car is not even built yet. His appartment is either not built or is lived in by someone else. Having a keys to someone's appartments, when they don't even know you is a suspicious thing too, however "I just found those keys on the street" can *probably* work with police. **Joe has nowhere to go.** His trustworthy friends are either not trustworthy yet, or (in case if Joe is old enough to have good friends with more than 19-20 years of friendship experience) will be hard to convince to help. Just imagine a nice looking man, which has some resemblance with your friend standing at your door, asking for help (food/place to live) and NOT TO TELL ANYBODY about him. **Joe can't sell his hi-tech devices for "research" purposes.** That was already mentioned before: Samsung can claim, that Joe have stolen their prototype from a lab and get the device for free. Basically he can only sell his smartphone/USB drive covertly to some geek as an expensive toy. The price would depend solely on buyer's personality and Joe's ability to trade. The same goes for movies on his usb. The only way to sell them is to find some people in internet, ask for money, and hope they're not undercover FBI agents. **Joe can't actually use his "memory" to trade on stock to become rich.** This is called "trading with insider info", is a crime and is carefully investigated. ESPECIALLY when some John Doe with zer0 experience in stock trading goes "big short" and wins. However some sports betting with not-so-big amounts of money would work. Stock trading with low bets will work too, however to get reasonably rich he'll need to remember a lot of big "shoots" and "bursts". **SO** Even survivng his first days depends solely on Joe's background/life experience. It would be easier to him, if he was at some point in his life "a bad boy" (knows places, where people will give money for dirty job and won't ask for IDs) and almost impossible if he's law abiding citizen (read "Joe, the average Worldbuilder"). P.S.: **Joe can't sell his Swiss Army pocket knife** I missed this. This is actually the most useful and unsuspicious thing at his disposal at the start of his adventure. Joe should never ever think about selling such a tool, taking in account the whole situation. [Answer] As the others have said, going for the stock market is the best investment. However, to do that you need a little bit of cash to begin with, for which you will need a job. However, this would be quite hard to aquire; it seems like you don't have any documents. So maybe meet up with the 15 year younger you from the past, convince him/her that it is you from the future by sharing all the personal stories and desires that you hadn't told anyone else, and go from there. [Answer] Stock market insider knowledge would net you more than any of your other ideas. It would also be more selfish. [Answer] The two movies should be *Jurassic World* and *Inside Out*. These are two of the top four grossing movies of [2015](http://www.boxofficemojo.com/yearly/chart/?yr=2015&p=.htm), and both were special effects heavy. They would be extremely difficult to make in 2000. You might also consider *Star Wars: The Force Awakens* and *Avengers: Age of Ultron*, but those are both in the middle of series. You wouldn't be able to sell them until closer to 2015 when the actors are old enough to appear in sequels. The other two can be released alone. I'm unconvinced that you can make significant money reverse engineering your phone. The best idea may be to sign up with someone to patent the innovations from the phone. Then you can make money as others invent the same things. It would be different if you had data on manufacturing techniques, but you just have the phone itself. They won't know how to make it in 2000. Shorting stocks before the dotcom crash can magnify your funds relatively quickly. Note that shorting is limited only by your ability to borrow. It gives you money. It's covering the short at the end that costs money. [Answer] I don't think you'll have much luck selling sophisticated technology just 16 years in the past. They had smartphones and tablets on TNG. The Apple Newton came out in 1993. The problem was fabrication, not concept. A microprocessor powerful enough to run a worthwhile smartphone would've been to large and hot to fit in a smartphone. And the only way to change that is node shrinks (making the wires of which the CPU is comprised thinner and closer together), which requires you to invent a *bunch* of other stuff. I think year-2000 Samsung would tell you, "well, duh, handheld computer, that's exactly what we're already planning to do as soon as ARM can build a CPU that can fit inside that size and temperature envelope. Seeing proof that such a thing is possibly doesn't do much to help us get there any faster." Maybe seeing exactly how the current model's CPU was laid out would save them *some* development time, but meh. Now, the *battery*, believe it or not, may be different. Lithium Ion, which is required to give meaningful battery life to a device this powerful without, again, getting too large and hot, wasn't really affordable yet in 2000. Chemistry breakthroughs over the next few years that made that possible were in that "new idea/invention, but not new manufacturing or fabrication technology" (ie "reverse-engineerable") category which is the sweet spot for time travel speculators. But ideally? Get some velcro and go back to 1930. [Answer] Well, let's throw out what's going to be worthless (or next to). Car/Apartment Keys Cash Credit Cards Driver's License Swiss Army Knife And you're left with your phone and your USB stick. If you assume those films are encoded in a format that's readable 15 years ago (not likely), you'd need to know the right people in order to make any kind of money out of them. You probably won't be able to walk into a major studio and pitch them right off the bat (they'll assume that someone else made them and that you're pirating unreleased material). The phone may have value. But you'll need to demonstrate a legitimate reason for owning what appears to be a prototype device. Walking into Samsung and saying you have a phone from the future will just raise eyebrows and possibly get you ejected rather quickly. The USB stick itself may be of interest in terms of the larger capacity (assuming the OS can address that much storage). Since there's no USB 3.0 ports back then, it'll look and act exactly the same as existing flash disks. Unfortunately, in order to convince technologists, you have to convince them that you're a technologist who has invented a particular component. For real money, you need to get a job, and use the money to buy shares in key IPO offerings. [Answer] The Phone and Flash drive would be worth a maximum of a few billion if you could patent the technology and license or reproduce it. You likely can't so it's likely worth a couple hundred million at best, a piece. The movies, would likely be the most valuable thing you have if you can sell them to the studio that originally made them. Just put your price under their price for most of the production costs and you likely can score several hundred million from each. The knife and keys are worthless... The money, credit cards, and license can put you in jail so I'd destroy them, but you could also use them to try to convince someone time travel is real... or sell to a crackpot time travel enthusiast. If you convince someone time travel is real that's dangerous but can net you a comfortable life for the rest of your life as a celebrity... or assassinated. A crackpot, likely will give you more than the money's face value, but not much...Maybe a few thousand. So I'd say the maximum amount you are going to get out of that is a billion dollars if you are smart and lucky. If not, you can still get a few million from the movies minimum if they play ball because it will save them money. --- Another source of income that you might be able to get is the cache of the smartphone. If Joe accessed the net, went to various sites, and didn't erase the cache before time traveling it is likely that data is on his phone still and if he's a businessman or anything tech related then those cached sites likely hold valuable information. [Answer] His tech is likely going to be impossible to profit from unless he's a genius engineer who understands how to build all of the underlying tech. Even in the best case scenario where he's able to get a meeting with someone who might buy the phone from him, theres no compelling reason to pay him for it. Somebody just has to hit him with a $5 wrench and take it. Whats he going to do? Go to court? He doesnt exist. He'll end up in jail for stealing the identity of his younger self. Everyone will assume he stole the phone in the first place. The company could even claim that it was their own internal prototype all along. Without knowledge of how the underlying tech works he'd have no way to show ownership. Based on your description, his only possession of actual value is whatever he can remember from the timeline. His best bet is gambling on whether events he knows will happen will occur. Thus this question starts to rely heavily on his memory. Is he a sports fan? Big upset victories that he can recall might be a good place to start. Investing could be even more profitable, but requires more money to get started. It could also be more dangerous given his lack of a legitimate identity. He would need to be already wealthy enough to hide behind intermediaries so that nobody realizes that whatever backstory he's made up is fake. [Answer] 1. Contact younger self. 2. Younger self will fund investment pool using strategy outlined in Kaz's answer. That is, taking advantage of now generally known booms and busts to buy/short outrageous positions. [Answer] I have though about this, and I think the answer is, that this phone is at the very best something for a collector or some kind of a proto-type to show off or collect funding with. Additionally the software on that phone is utterly useless, as the OS it's running isn't invented or supported and any hardware breaking on it like the screen cannot be repaired. The technology of a smartphone, eventhough very advanced is most likely useless even for most reverse engineering. Realistically everyone in 2000 already knew that computers were to become smaller and smaller. The smartphone itself is probably of very little interest. The thing that is worth a lot is the process and the tools necessary to manufacture it, but those cannot be deduced from reverse engineering. And the tools necessary to use the processes and create the materials involved still would have to be invented. In other words, this tech would not have any positive inpact in our timeline, it may even be actively harmful by pointing researchers and companies into directions that they cannot implement yet. And a patent without a detailed description of the manufacturing process and the composition of the tech is not possible afaik, atleast in europe. The only thing that would be interesting is the software on it, as it can be reverse engineered and help them design better layouts earlier, but even that is unlikely as running the responsive animated layouts on computers and small devices requires processing power that is not available in 2000. Additionally introducing new layouts from 2016 into 2000 would probably bankrupt any company, just because their perception was bad in modern times when there was a practical reason for them. In 2000 without a practical reason for those layouts companies would probably anger and loose a lot of customers. Overall 2000 is too early to really profit from the tech in a meaningful way. I think 2002-2005 may be a bit better suited or even 2008. [Answer] None of the stuff in your pockets will make you very rich, as the other answers have outlined. Your most valuable possession is knowledge, and the first thing you should do is sit down and write down as much as you can remember. The stock market is a good bet if you can remember some key data. Selling short just before the crash could make you very rich very fast. You probably don't remember the exact date, but you might remember enough of the early warning signs to jump in when everyone else is still thinking it may not happen. Also, if you are fast enough, you could still sell airline stocks short on the same day and make some starting money. Bitcoin was mentioned, as were several IPOs. You can also fly to Britain where an intense betting culture allows you to bet on virtually anything, and you could make a ton of money betting on future wars, terror attacks and other events you remember. Your primary problem would be how to get started. As it seems from your list, you actually have nothing. The money you need to spend carefully (if someone checks the date, they will think it's forged) and most of the rest you can't use nor sell. So the answer to your actual question is: Probably nothing. Selling your tech is more likely to land you in jail than to make you rich. [Answer] Alas, your phone will be out of juice within a day or so since you didn't bring a charger and the micro-USB isn't developed until 2007. Sports betting is probably the fastest way to make $$$, hopefully you have some sort of sports database on your phone or at least remember big games like the world series and the superbowl. Any books downloaded, or MUSIC? Imagine how simple it would be to reverse engineer future songs. Alas, I'm not sure how easy it would be to convince record producers of their value, but if you think fast you could get a microphone and record songs off your phone to 2000 era tech while the phone battery lasts. Would a wireless connection work? Maybe, then you could at least email them to yourself ( though I'm not sure modern audio codecs would work in 2000). Depending on your phone catalogue, you could either sell songs back to artists or just become the greatest songwriter and beats producer. Same with books. Imagine if you had the last few Harry Potter books on your phone. Alas, the problem is getting them off the phone since the battery won't last while you manually transcribe them. Anyway, you could release the books yourself or sell them back to the proper author (I think GRRM would be thrilled to get the last few Game of Thrones books early, get those fans off his neck :P). [Answer] Turn off your phone to save the battery. Find an old friend that you can trust and stay with them during your first few weeks in the past. Tell them the complete truth, using your knowledge of their past, your obvious increase in age, and your wallet contents to get them to believe. Borrow a camcorder and use it to make a demonstration film of your phone. Write your friend's address on cassette's label and mail it to the Office of Bill Gates at Microsoft with a letter which reads... *This is the best selling mobile telephone from 2016, an age when personal computers have been all but replaced by devices like this. Despite your company's attempts to dominate the smart phone market over the next 15 years, this phone from the future has no Microsoft software running on it. I can help you change that.* This should lead pretty quickly to an in-person meeting with Mr. Gates. Hand over the phone and the flash drive as your opening move, before he even asks. Explain that his staff can maximize their value to both of you by reverse engineering their technology and patenting everything found. Then sit down and start telling him about the next fifteen years. Explain that you chose him because in your future he is known as much for his humanitarian efforts as for his business and technical success. Tell him that you trust that he will use whatever foreknowledge that you provide to minimize human suffering (including your own) while keeping Microsoft out ahead of its would be technical successors. So now you are on a first name basis with the most powerful man on Earth and you are single handedly repsonsible for making him more successful both as a business person and a philanthropist. That is better than any amount of money and thus is the most selfish thing you could have done. [Answer] It would be very difficult to sell the phone and someone would eventually contact the authorities. You would probably end up in a psychiatric ward. Whatever story you come up with won't be believed. If you have the phone on you when taken in it will be confiscated. If a smart enough person like the psychiatrist in charge sees the phone then you are really in trouble. High level government officials will take you to a blacksite to be interrogated and your phone will end up at DARPA or some other r @ d facility. It won't take long for the interrogators to break you and learn the truth about you. From that point on your life will be spent in one laboratory or prison cell. [Answer] The amount of wealth that this time traveller can generate is dependent entirely on how much high value knowledge he can sell to everyone in the past, which is why i'm assuming you chose to send him to 2000AD rather than 1492. The answer is also dependent on what you define as wealth. **What prosperity is, where growth comes from, why markets work** <http://democracyjournal.org/magazine/31/capitalism-redefined/> Everyone else seems to have answered your specific question pretty well, so I won't go much further with it. But if you want to make this a broader question, and bring him back to other points in history as well, you can explore some really great questions. As many of these other answers have explained, the wealth he could earn is very dependent on the context of the society he arrives in. The fact that any "new" (stolen from the future) ideas he generates would be protected by the american system of copyright law isn't guaranteed if he ends up in some earlier society and immediately gets robbed or simply is forced to recall new inventions under duress from, say, King George I of England. And This lack of structure still happens in most of the world **Why Capitalism succeeds in the west and fails everywhere else by Hernando De Soto** <http://www.columbia.edu/itc/sipa/S6800/courseworks/spirit_capitalism_samuelson.pdf> And that doesn't even begin to deal with what would happen if this time traveler was part of an unacceptable social group in the wrong time and place. As others have said, his samsung phone and USB stick are only as valuable as the insights engineers in the past might gain from them. Without USB ports, or the technology to make them, or the software to interpret files saved on the USB, that 128 GB of storage might as well be 1Kb, or 0kb. Without a phone charger, electrical grid, or any knowledge of how to manufacture such a device, the phone becomes, at best, a general guide to what might eventually be manufacturable in the future. Even then, the collective intelligence of whichever decade he arrives in will dictate how much his knowledge is worth. He might be head of engineering at samsung and he still wouldn't know everything about how to design, manufacture, and maintain a smartphone from scratch. [Answer] One thing nobody is really commenting on is how powerful your phone is compared to similar devices at the time. I can't find the Samsung S7, but the Samsung S6 is about 35 GFLOPS of processing power. That would equal about 20,000-40,000 in 2000 dollars, or a bit more in 2016 dollars, based on processing power alone. Not quite as much as it would have been worth in 1997 (where it would have gone for about $1 million), but certainly enough to get you started. [Answer] Joe needs to buy bitcoin for anything under 200USD and sell them before they peak around 1000USD Joe will earn anything from 1000 to 5 times his money back on any dosh he makes. Joe can do this unleveraged and Joe can do this mostly anonymously. ]

[Question] [ One morning, everyone wakes up and finds that the balance in their bank account has changed. In some cases, it's gone down. In others, it's gone up, a lot. A few people even find that they don't appear to have been affected by this. However, most company accounts have also been affected. After some effort, someone figures out that all the bank balances have been randomised - it's like someone just pulled balances and accounts out of a hat and stuck them together. There isn't any pattern to this, so it doesn't seem to be targeted - it's entirely luck as to whether you (or your company) end up richer, poorer, or about the same as before. However, other than your memories and environment (e.g. you're in a mansion, so probably were doing ok...), there is no way to prove which balance was previously yours. Backup data has also been altered to be consistent. Every detail apart from the associated names is accurate. If account 123 sent money to account 456, that's still recorded, but account 123 probably belongs to someone other than expected. What would the overall change in wealth distribution? I suspect there will be a bias towards getting poorer, with a few stand out cases of someone getting immensely rich. A lot of people wouldn't be affected - anyone without a bank account- but these will probably be disproportionately poorer, since it's harder to be rich without one. Note: the technical ability to do this is out of scope (short answer: in our world, you probably can't!) [Answer] If the change affects *bank accounts* only, the results might be surprisingly modest. Putting cash in a bank account is a very poor investment, especially with interest rates as low as they currently are. Most wealthy people will have most of their money in stocks, bonds, real estate and the like, perhaps with "only" \$100,000 or so in cash at any given time. While for most of us a sudden windfall of $100,000 would be very welcome, it doesn't make you filthy rich. Most of the wealth redistribution would take place at the middle and bottom end of the scale. The wealthy are relatively few in number, but there are many people with \$10,000 or so in cash savings, and a great many others with little or none. A lot of the former would suddenly have no savings, and many of the latter would receive a windfall. There would be more losers than winners: In the USA, 69% of the population [have less than \$1000 in savings](https://www.cnbc.com/2016/10/03/how-much-americans-at-every-age-have-in-their-savings-accounts.html). A few things worth noting: * Savings do not correlate exactly with income; many well-paid middle-class people have large credit card debts and minimal savings. * Many bank accounts are held by businesses, charities, government departments, and other organisations. If they were affected, a lot of businesses might find themselves with severe cash flow problems. * A very roughly analagous situation occurred with [privatisation](https://en.wikipedia.org/wiki/Privatization_in_Russia) in Russia in the 1990s, in which shares in state-owned industries were distributed among the population. A few individuals became very wealthy by buying up shares at a fraction of their real value. This would probably become a serious political issue for the government. Would it: * Order banks to honour the account records, even though they conflict with people's memories? * Somehow attempt to reinstate the distribution of wealth people remember? * Take drastic action like resetting the entire banking system from zero, perhaps giving *everyone* exactly the same amount of cash as a starting point? [Answer] **If you read Clancy, you know Ryan's Law: If it wasn't written down, *it didn't happen***. So if all written records say a thing, then it doesn't matter what everyone *thinks*. However if the magic does not go so far as to altering *paper* records and PDFs sitting on hard drives and the like, then it becomes a matter for whatever deposit insurance your nation/world provides. Once it's accepted that this glitch did an unintended redistribution of wealth: a *saver* who can document that their bank account had between 61,000 and 66,000 quid for the last several years, can expect a £61,000 payout from deposit insurance. This would not help the rich so much; most deposit insurance is capped, e.g. US FDIC at $250,000. *Non-savers* who had nothing on average for years and suddenly have a million bucks - it will be difficult to pursue them if *they alone possess* the only records of their history and they want to hide unearned gains (not leasst from the tax man). But *non-savers* will tend to lose it. Savings is not innate; it requires a friendly environment *(which we presume if in a ”world" where most citizens have bank accounts)*, luck, and education to avoid the pitfalls of having money. The effects of this lack are seen by the fate of lottery winners. Left to themselves, they are [predated upon aggressively](http://amzn.to/2hGJ4AQ) and tend to lose it. Good counseling by government or NGOs can [significantly improve things.](https://www.theatlantic.com/business/archive/2016/01/lottery-winners-research/423543/) **The question is how this counseling will *reach* savings-scramble winners** if they are hiding. (and of course a person with good circumstance and skills *already* does well with windfalls). The same applies to now-broke *savers*: Their circumstances will allow, and their habits will motivate, them to resume saving. Their accounts will build back up over time. So there are your four likelihoods: * started non-saver, account empty - no change * started saver, account has money - no change * started non-saver, now full account - tend to lose it. * started saver, now empty account - tend to continue saving. [Answer] In 2013, the [average checking account balance](https://www.valuepenguin.com/banking/average-checking-account-balance) was US \$9,132. That's personal accounts, not business or government accounts. But for people with an income above US \$160,000 / year, the average balance was over US \$700,000. Again, personal, not business. For those with incomes below US \$45,000, the bank balance was below \$3,600. Given that many large business accounts will have significantly higher balances than the average citizen, and that the wealth distribution is heavily weighted, I suspect the lowest income people will see a rise in bank balance, while those at the highest income levels will see a drop. Those in the middle of that bell curve will have the most randomness to their balances. But really, the new balances don't matter, as we'll explore below. **What matters is the introduction of chaos...** ## Immediate term **You are going to have serious problems.** Day 1, CNN, Fox News, BBC, and all other news outlets flood the airwaves and papers with news that all the bank accounts got mixed around in a big melting pot. So everyone lines up at the bank. Or logs into the bank. The bank's websites crash, as they're now effectively suffering a [DDoS attack](https://en.wikipedia.org/wiki/Denial-of-service_attack) as users flood their sites. The lines will be long. The bank support phone numbers will be jammed. Panic. This will continue for a time. In the USA, the federal government will probably institute an [emergency bank holiday](https://www.law.cornell.edu/cfr/text/12/7.3000). Not sure how long that would last, but during this holiday, the banks would be doing their best to restore from backups, find audit traces, etc. The bank computer systems have pretty thorough audit logs. Banks would spend days, possibly weeks, trying to reconstruct accounts. The OP says these measures will fail, but they would try. Other nations' banks would go through similar steps. The FBI, NSA, CIA, and similar groups in other countries would go on extremely high alert. I suspect the military would go on high alert as well, at least until it could be proven that this wasn't an act of cyberwar. Hopefully, governments and businesses would find some sort of interim solution for commerce, because otherwise, *people will die*. Pharmaceutical companies, food and agriculture, these are critical international markets that if they stop, people don't survive. Remember, most industrialized nations cannot grow enough food to feed their people reliably, year round. So many import food from around the world. Especially produce. That's how we get out-of-season crops. Then there are cities. It took 200,000 flights to provide Berlin with food and supplies for a year during the [Berlin Blockade](https://en.wikipedia.org/wiki/Berlin_Blockade). *Now imagine every city in the world facing the need to feed and supply their citizens* when no one can pay for the shipment of any goods. No one can pay for trucking or trains. No cargo ships full of Argentina apples. No meat from out west delivered to your local butcher. Everyone goes hungry. No insulin for your diabetics; who's paying for that? Everyone gets sick or sicker. *If food and medicine deliveries aren't secured, then the riots tear apart every city in the world*. And if that happens, no nation will survive. So that's a crisis that governments and industry must solve immediately or die. The rest of this post assumes they hobble together something. Anything else results in anarchy. ## Short term **After the banks close, people will panic.** News cycles would probably be fueling the panic. Comparisons to the bank collapses around the Great Depression would be constant. No one can issue paychecks. No one can pay their bills. No one can do anything if they don't have cash on hand. By day 2 or 3 at the latest, the stock markets would be shut down, since businesses no longer have reliable checking accounts either. The markets would have to be shut down to prevent a complete collapse as everyone tries to sell and cash out. Without paychecks and other cash transactions, trade halts. Government would need to do something to maintain food availability, since most people don't keep enough cash to buy groceries and few people maintain sufficient food supplies to go more than a week or two. Emergency measures would be taken to prevent riots. There would be riot-gear equipped police in all major cities and many smaller cities/towns. Everyone would be asking questions. Who, why, how. Within a week, it would be clear that banks cannot fix this. It is a complete, hard, reset on the entire economy. ## Medium term By this time, it would be clear that while some accounts in some cases could be rebuilt from paper records, **the system as a whole couldn't be rebuilt.** And once people said, "Well, I've got my bank statements going back 10 years, *give me my money!"* everyone else would demand their money, too. And at least some percentage of people would think they were clever enough to game the system. "I've got a good printer and enough computer savvy to fake my bank statements..." so now the banks can't really trust the statements to be accurate either. That lack of reliable paper combined with the significant percentage of people without paper records, means banks as a whole cannot trust any of the papers anywhere. Remember, this isn't just your grandmother's savings account or your checking account. This is also the account your employer writes paychecks from. This is where your rent checks deposit to. This is where your grocery store pays it's bills from. By now, all of the initial panics are done. Banks will still be closed, at least until government figures out what to do. Barter is more popular than ever in living memory. The riots will have been quashed, one way or another. More cities across the world look like the burned out parts of post-riots Detroit than ever since the end of WW2. The entire world economy has ground to a halt at this stage. No one has the means to pay for anything. Suddenly the Amish, with cash in hand and plenty of garden space, look far wiser than they have in the last 200 years. Doomsday preppers have been laughing this whole time, while they choke down freeze-dried food that's edible but tastes bad. Congress will be under extreme pressure to **"do something".** And maybe they will. They must. Though at least in the USA, partisanship politics will make this a difficult time for them as well. At a global level, the UN will be frantically trying to prevent war and economic collapse, too. If the UN cannot maintain peace between panicked member states, or if any one (or more) nation decides that the other nations somehow are responsible for this mess, then war will break out. Hopefully, these will be relatively small-scale actions in smaller nations. Hopefully, the warfare won't spread up to the 2nd and 1st world nations. But that's not guaranteed. Wars generally occur for three reasons: "the gods demand it", "we need money/resources/things", and "if THEY are the enemy then you won't get mad at how horrible a leader I am". This event triggers the second quite easily and quite suddenly. Government would have to write laws, too, that prevented civil lawsuits. Otherwise, the courts would be overrun with lawsuits and class-action lawsuits. If those cases were permitted, lawyers would be lining up. Any bank that wasn't already ruined beyond repair would be destroyed. ## Long term Long term, the major goal is to **reduce this great depression and prevent global war.** A broken nation with no economy and no hopes will often fall into warfare. It's happened before (see also Nazi Germany, which "solved" their unemployment crisis through military spending). Given the scope of this disaster, it would likely happen here. WW3 isn't impossible. It's likely. Some governments will have nationalized their banks to take control and restore order. Perhaps they socialize the wealth and redistribute it. Perhaps they start over with some other measure. There's no way to predict how each nation will solve this crisis. But once they do solve it, we will see some kind of major sea-change to how accounting is done. No one will ever trust banks to maintain account histories and balances ever again. This new system will be the most radical rewrite to bookkeeping / accounting since the invention of [double-entry bookkeeping](https://en.wikipedia.org/wiki/Double-entry_bookkeeping_system#History). [Answer] What follows is complete social collapse. If it can happen once, it will quite likely happen again, so there is no longer any point in saving or investing. So no companies can be funded, no one has money for their retirement, and so on and so forth. [Answer] [CM\_Dayton's amazingly detailed answer](https://worldbuilding.stackexchange.com/a/88365/10048) is spot-on, IMHO, and covers a lot of the societal aspects. As someone who reads a lot of rationalist sci-fi, though, I have to point out one inevitable subplot: > > However, other than your memories and environment (e.g. you're in a mansion, so probably were doing ok...), there is no way to prove which balance was previously yours. Backup data has also been altered to be consistent. Every detail apart from the associated names is accurate. If account 123 sent money to account 456, that's still recorded, but account 123 probably belongs to someone other than expected. > > > This sounds like a perfect use-case for [traffic analysis](https://en.wikipedia.org/wiki/Traffic_analysis). All we need is a complete set of banking records and a few smart programmers, and we can start crunching the numbers and restoring the state of the world by building outward from a trusted root. Thus: > > Bob is the security engineering lead for Chase Manhattan. On Tuesday morning, he wakes up to the ringtone that means a critical production issue. (This is unusual, because Bob is like the third person in the PagerDuty escalation. Things *never* escalate to him unless the site is actually down or something.) > > > Well, crap. Nonsense in the banking records. The automatic disaster-recovery plan was already tried, and somehow the backups are wrong too. (Everyone on the engineering team is confirming: their own balance is definitely incorrect.) Okay, check the tape archives. Somehow they're *also* bad. Now it's getting surreal. > > > 90 minutes later. The site is "down for maintenance" to prevent *further* chaos. Jan and Dan (and about three junior engineers that nobody cared to forbid) are in a breakout room whiteboarding new ideas. Bob is finally en route to the office, on a call with about three VPs. Nobody knows where Legal is. Someone go pull a junior engineer out of the brainstorming session and get them to make sure Legal is in PagerDuty by EOD, okay? > > > 120 minutes. Dave (who's always been a bit rogue — regulations shmegulations) has written a script to scan all the accounts and locate the ones with balances in a given range, and is going desk to desk asking if anyone remembers *exactly* how much money was in their account yesterday. Pretty soon he has a couple of hits; some people have the app and look at their balance like the rest of us check Facebook. > > > There are still millions of accounts that could be theirs. This is going to be tough. But Maria says she's got direct deposit on her rent — now we're cooking! (Jan and Dan are still holed up in the breakout room, but we can see the left half of the board is full of abstract graphs and the right-hand side is a list something like "paycheck / rent / credit card / big-ticket / ...") Twenty minutes later, Dave has v2 of his script. It finds Maria's $1035.21 rent payment in a flash. One down! > > > In fact, two down, because we also now know the identity of Maria's landlord. (Well, somewhat. His name is John something? He lives down in Gilroy. Never seen him. But we can get him on the phone if we need to.) > > > Dave uses his script on Rick's direct-deposit paystub. (Normally Rick would have an aversion to revealing his salary, but today isn't "normal". Normally *Dave* would *love* to reveal everyone's salary. He's having a ball right now.) Now we have Rick and Maria. This is going great! And Rick says he paid Dan for lunch the other day, it was like $20, so if they can see that payment they'll know which account is Dan's... oh. Hmm. Rick paid Dan with Venmo. So it happened entirely within the Venmo app, and won't be reflected in anyone's Chase balance. Bother. Venmo — and credit cards in general — are going to make this a lot harder than if everyone paid by check all the time! > > > Here I'm out of my depth and so I'll stop with the details, but hopefully Jan and Dan will come up with something. Jan has some contacts at Netflix; maybe their billing system is still unscrambled, in which case we can resolve a lot of accounts by looking at the timing of their monthly $7.99 payments. (Or whatever it is now. Jan does *not* have the Chase app.) I predict that within an hour, Bob and Dave and Accounting will have the ability to shuffle the corporate accounts back into place. Within 24 hours, Dave's "Rentinator" (sorry, "Whiscash"? Why does everything need a code name around here?) will be crunching through the accounts for every employee. However, it will take several days to actually *apply* the changes, unless Bob's team has been foresighted enough to allow "duplicating" the production system. After all, we don't want to shuffle things on the *real* production system; that's going to be on lockdown for *days*, until we figure out whether there's anything Forensics can do with it, and until Legal tells us we won't get in trouble for changing it. So one of the postmortem action items we can see already is that we ought to have a way to test out Dave's script without modifying the production data. Put a couple of engineers on that. Also, in the postmortem we always ask "Are we still vulnerable?" In this case the answer is obviously yes; we have no idea what caused the initial scrambling. But *transactions* were neither blanked nor scrambled; that's how we managed to unscramble everything. And merchant records — amounts, and names, and shipping addresses — seemed to be okay. So there's something kind of "magic" about lossy representations of transaction history. How fast can we start keeping our *own* redundant lossy record? No reliance on account-UIDs; those get scrambled. But we can store personal names, and street addresses; that'll be good enough for most people. And you know what? Throw in a column with the salted SHA-256 hash of their account-UID. If *those* get scrambled "correctly" next time, then at least we'll know someone up there can break SHA-256. And if it never happens again, hey, problem solved. :) [Answer] In this answer I consider only the shuffle itself: others are talking about the fallout, and in any case you seem to have edited your question with the intent of removing the longer-term effects on society from consideration. > > I suspect there will be a bias towards getting poorer, with a few stand out > cases of someone getting immensely rich. > > > It's correct that there are a few standout cases of someone getting immensely rich, since there are relatively few accounts with immense amounts of money in them (relative to the number of people, I mean). But it's more likely than (say) winning the lottery, since there are more big acounts in the banking system than lottery draws in a lifetime. There will also be some big losers who are randomly assigned an account that's more overdrawn than their entire other assets, and become overnight bankrupts. So it goes. If by "there will be a bias towards getting poorer" you meant, "there's less money on average than before", then perhaps counter-intuitively I think that's probably true. The reason is there are large numbers of abandoned accounts (which somebody owns, but they've forgotten about them, or died and the estate failed to claim them, or otherwise are uncontactable), and I speculate that those abandoned accounts on average have small amounts of money in them. Of course this speculation might be wrong (in the real world and/or your world), in which case this effect is non-existent or is reversed, but supposing it is correct: After the shuffle, abandoned accounts will on average (in all probability) have (approximately) average amounts of money in them, which is more than small amounts. Since the population of abandoned accounts increases in value, it follows that the population of active accounts will reduce in value. Of course, *eventually* the banks (or someone else) will reclaim this money provided that the law grants a mechanism for abandoned accounts eventually to be harvested, but the eventual recipient can't put it on their books immediately because they don't know which accounts it is. If we ignore forgotten/lost accounts, and futher simplify by assuming that every person has exactly one account, then the total (and hence mean) bank balance of course stays the same. But what about the number of people who get richer vs. the number who get poorer? To address this, line everyone up in order of bank balance. You will be randomly assigned a new position in line: if you move left then you get poorer, if right then richer (I simplify: in fact a significant number of people have equal balances, and so likely a few will see no change. For what it's worth, the probability that at least one person gets their own original account right back is approximately 63.2%, or 1 - 1/e, where e is Euler's constant). It should be obvious that if you're 75% of the way up the line, then you have a 75% chance of getting poorer and a 25% chance of getting richer. The *amount* by which you become richer or poorer is irrelevant to which of the two happens. Meanwhile, the next person up has a 75.00000001% chance of getting poorer and a 24.99999999% chance of getting richer, and so on. Add it all up along the line, and *on average* everyone has a 50% chance of getting richer and a 50% chance of getting poorer. The number of winners and the number of losers will with high probability be approximately the same: 50/50 (well, OK, 50-ε/50-ε of richer/poorer, and 2ε of staying the same, where ε is some small number). Of course it's *possible*, but incredibly improbable, that the shuffle selected moves everybody left one place except the person on the far left, who moves to the far right. So almost everyone gets poorer. Similarly it's possible for the reverse rotation to occur, so almost everyone gets richer. But these are vanishingly unlikely to occur at random. In short: if you shuffle a deck of cards then by symmetry there's no overall bias in favour of more cards moving upwards than move downwards. This remains true even if instead of the cards being evenly spaced, we space them according to the same distribution as bank balances, because whether a card moves up or down doesn't depend on the spacing between the cards, only on whether the new position is greater or less than the old position. If you're just wondering about humans getting richer, as opposed to "legal people": I speculate that the median corporate balance is higher than the median human balance, in which case there is a slight bias for humans to get richer and corporations to get poorer (at least, prior to the knock-on effects which mean people who own shares in the corporations that get poorer, ultimately get poorer too). But it depends to an extent what we mean by "balance". Business accounts can have overdraft facilities, but to stretch a point you might also include short-term loans or bridging loans analogous to overdraft facilities. It might turn out that my speculation is incorrect (in the real world and/or your world), and corporations in fact *don't* have higher than median balances. I'm pretty sure they have higher-magnitude than average balances, but perhaps often the balance is massively negative. So again, if my speculation is incorrect then the bias disappears or reverses. You could also consider what happens where people have multiple accounts. For example, for stupid reasons I have 4, 2 of them with very low positive balances. Therefore I get 2 extra shots at the jackpot. But I suspect that as it happens, the mean of my 4 balances is still above the global mean, and so my expected gain is negative. [Answer] People will no longer trust banks, money becomes useless as a means of paying for goods and services as it has no value. People fall back to systems of barter for services and goods. Maybe some will accept valuables in trade for services, which they then trade on for other goods and services. In time banking will reappear, but only hard records, written on paper, will be acceptable as proof of ownership of anything. Which brings us to the linked implication, which is that any computerised system will be viewed with extreme suspicion. It is quite likely a large part of the population will demand a complete ban on computers, maybe even a complete ban on any electronic equipment, because they're afraid of them (many people already are, this would give them an excuse). [Answer] There are great answers here, way more interesting to read than mine, but they seem to miss the actual question asked: > > What would the overall change in wealth distribution [be]? > > > From a purely mathematical viewpoint, the change would be ... absolutely nothing. It would have to be. Visualize all the balances of all the bank accounts sorted like a bar graph, with the balances along the Y axis, and the names of all the account holders as data points along the X axis. That bar graph represents "wealth distribution" literally. All the money, and how it is distributed between people and businesses The magic happens, and all the names are shuffled under the bar graph, leaving the balances alone. The distribution is identical, by definition. I think the other answers about the social consequences are much more interesting to consider, but in answer to the question asked, the *distribution* doesn't change. [Edit 1 - addressing comments to both my answer, and the original question] Original question has been clarified that this isn't all your wealth in a global ledger, just strictly bank accounts, with other assets untouched. As such, I'll augment my answer here with an expansion of the comment I added to the main question. For bank balances, if like our world, the distribution is a "long tail" graph, or tall pyramid. Many more folks/businesses (in number) have a "below average" (where "average" = mathematical mean) balance due to the few, very, very, high balances. The very few high balance accounts will end up worse off, but the many low ones could change relatively little, or even all go up. It won't be a "half less and half more" split unless the original distribution is balanced. For example, you could have balances of 1,2,3,4,5,1000 - rotate each owner 1 account to the right. 5 of the 6 people get more money, and only 1 loses (a lot) of money. Or you could have originally, balances of 1,2,3,1000, and 100 more accounts all at 100 each. In this case, the majority of accounts end up with exactly the same balance (and different payment histories) and only a few people get more and less. I think my answer still holds. the overall distribution doesn't change (by definition) and under most reasonable assumptions of the shape of that distribution before the incident, most folks don't substantially change, with a few dramatic outliers. [Answer] Are things like credit cards affected? If not, then it isn't that bad. Firstly, the real problem is that people only really keep money in their bank accounts to pay off debt. If that money increases, great. Otherwise, you have people unable to pay mortgages, utility bills, etc. Credit cards offer some relief **if** they are unaffected. Without them, you have individuals and businesses suddenly declaring bankruptcy, unable to pay employees and service providers. Nobody is going to risk attempting repossession or debt recovery, but services will be stopped until bills are paid, since the service providers need to pay their own bills, but unless the services are up, people and businesses cannot work to get money to pay those bills, and so the cycle continues. Secondly, while people who can afford to, keep most of their wealth in non liquid assets, they still have bills to pay. Once their ready cash stock disappears, they'll need to convert some of their wealth to cash--except that everyone who has wealth but needs cash will be doing the same. [The 1929 Stock Market crash](http://www.history.com/topics/1929-stock-market-crash) is an excellent case study of what happens next. Thirdly, those fortunate few, who woke up, heard the news and rushed to the bank only to find themselves filthy rich, will fall into two groups. Group 1 will try to withdraw as much as they can before the mistake is corrected. The banks fearing a run will limit funds. This will result in more people trying to get their money while they can. The ones who do manage to get a sizeable sum will immediately become targets of everyone else, including law enforcement. If they manage to get home alive, they still won't be safe when people figure out where they live. Group 2 will have figured all this out and will only pay off their immediate debts through the bank then go home with only a small amount in cash. Once the government figures out what is going on, mainly through their own accounts suddenly emptying, the most likely response will be an excise on any amount over a certain floor. This will outrage the lunatic right and the army will have to be mobilised. The major advantage the government has, is that it can print cash, can pay off most of its immediate debt. The rest will vary from country to country: some might end up in civil war, others in long depressions; one outcome of the 1929 crash was the rise of Nazism. [Answer] > > What would the overall change in wealth distribution? > > > This is a statistical question well-suited for [**Cross Validated**](https://stats.stackexchange.com/). The actual "change" in the nature of *wealth distribution* would depend on the nature of the utilised [*univariate distribution*](https://en.wikipedia.org/wiki/Univariate_distribution) that would be used to derive the new random account balance figures. For instance, [platykurtic](https://en.wikipedia.org/wiki/Kurtosis) distribution would be likely to reduce average differences between single account balances, assuming that the pre-existing distribution was leptokurtic (more likely). You could look at a number of existing household income / affluence surveys, and construct casual statical models replacing likely existing account values with random ones and assess how that change impacts the overall *"wealth distribution"* derived from the utlisied data set. ]

[Question] [ On the hilltop in the field near my house, there lives a coven of witches. Or, more accurately, there is a coven of witches living in a pocket of the Faerie Realm which has recently become attached to the hilltop by my house. By the rules of the Faerie Court, their home must be hidden using both verbal and somatic charms. I already know the verbal charm. I won't write it here. The somatic charm works like this. Around the hilltop are 13 trees. See diagram. [](https://i.stack.imgur.com/nESVp.png) To get to the witches' realm, you must walk the following path. [](https://i.stack.imgur.com/majg0.png) The important part is what side of the trees you pass. If you complete only some of the correct loops, you cannot meet the witches. When standing left of the tree with the cross, you will see the normal hilltop. But once you pass the cross tree, provided you have made the correct loops beforehand, you will see a similar hilltop, except there is a big iron cauldron with three hags capering about. If you line yourself up correctly with the tree, you can see one half of the cauldron to the right of the trunk, but no cauldron to the left. If, at any point during the charm walk, you stray too far from the hill, you will end up back in the mortal realm and have to start the charm walk again. This is where things get confusing. Suppose friends stands south of the hill at the blue marker. Far enough away that they would have to restart their charm walk. Meanwhile I do the correct loops until I reach the pink marker. [](https://i.stack.imgur.com/fH8Yz.png) Now I can see the witches to my north. Since walking south will return me to the mortal realm, I should be able to see my friends to the South. But since they have not completed the walk, they cannot see the witches to the north. So what happens if they start walking north towards me? Then we walk together to the hilltop. Do they meet the witches or not? Something's gotta give. I have not tried this with another person yet. I have tried with my pet labrador. But unfortunately she will not sit still long enough to complete the experiment. The witches are happy for me to know about their den, because I buy so many potions from them. But they will be upset if I tell anyone else. So I would like some opinions on what might happen before I take the risk of letting other people in on the secret. What do you expect to happen? [Answer] ## How to make internally consistent magic Magic lets you do pretty much whatever you want, especially when talking about the kind of spells that completely side-step the known laws of nature... so defining internally consistent magic can be a bit difficult at times. But, there is a rule of thumb that generally works for these sorts of problems: **Identify what experiences/effects your existing magic is based off of, and create mechanics that reproduce those experiences/effects in other aspects of the spell.** Based on how you've described your portal, I would identify that your spell is following these rules: * Passing between trees is the somatic action that activates the magic. * Things are invisible until you pass an occluding tree, and then it is visible. * The worlds are mirror images of each other except for the witches. So, the most internally consistent answer will use all of these facts as much as you possibly can, and any problem you run into that can't be solved with all 3 facts should be solved by minimally restating as few facts as possible. Your first course of action if you can't solve a spell by using the rules, is to try to add symmetry to your rules. If your setup shows a 1-way relationship, then solving a problem with a symmetrical relationship can actually make your rules feel even better defined and consistent. If that is not enough, next try minimal changes to rules. Small adjustments to the rules are better than completely ignoring them Following this process, I came up with the following. ## You disappear the first time you pass out of sight While you do not see the witches until you pass the last tree, you have actually stepped into the magical realm upon crossing the first pair of trees. The outside observer will see you disappear as soon as you pass behind something crossing out of his sight, and he will likewise disappear for you. Because you must pass to the inside of some of the trees, it is impossible for the outside observer to walk around the hill in any way that you never pass from view once you are somewhere on the path. This solves the problem of your friend being able to sit around waiting for you because they will never see you come out from behind the hill. This means you don't need to fight with all the paradoxical things of watching your friend interacting with things that don't exist from your perspective while staying 100% inside of the established rules. It also adds symmetry to rule #3. If our world does not have witches, then logically, the witch world should not have your friend. [](https://i.stack.imgur.com/dB6ZF.png) ## You reappear when you wander back "somewhere out of sight". The hard part is how coming back should work. Ideally, there should always be a tree to step out from behind if you want to follow all the rules you're already working with... but there are simply too many places your friend (or multiple friends) could be standing to make that not work. So, I will say this is a good time to slightly relax one of the rules. At this point you could completely violate the "occluding tree" rule and have your person reappear with a flash or step out of a mist or just plain appear out of thin air or something, but these are completely new ways of transitioning between worlds; so, they will feel inconsistent with the "occluding tree" rule. A smaller violation might be to just slightly change the "occluding tree" rule to "any occlusion". So, if your friend is waiting by the opening and you try to walk straight to them, you will not see them, you are trapped in Faerie until you cross out of mutual line of sight. So, you could walk past them, not seeing them, then turn around to find them standing behind you. Or you could pass behind a rock or bush what not... or if the hill and whole surrounding area is filled by people, you could might even need to walk all the way home, and not actually "be back" until you go inside and close yourself off in a secluded space. The magic does not care how far you must wander, as long as there is a person to see you or be seen, you cannot return to the real world. Likewise, if the grove is surrounded by people such that you can not pass out of sight, you can not enter Faerie, even if you solve the puzzle. So if a portal like this opened somewhere in the middle of Downtown New York, it would be almost impossible to pass into. [Answer] Brace yourself for a surprise, you won't see the witches. This is actually a built-in safety mechanism in the Charm Walk, if you are observed by someone not following the path along with you it won't let you in. It wouldn't be much of a secret entrance if anybody could easily figure out how to use it, right? If you've ever wondered why pockets of the Faerie Realm tend to attach in fairly remote places, this is the reason. It's kind of difficult to visit your cauldron unobserved when the entrance is located on London Bridge. [Answer] **You're treating this as a topological problem, when in fact it's a very artificial Locking and Permission system instead.** Your friend never sees the cauldron, and cannot join you in the final walk up to the hill and get anywhere. You perceive the cauldron, you walk towards it and your friend sees you simply vanish into thin air as you cross an invisible boundary between worlds. If you were walking together, they proceed up to the empty hilltop. If you were holding their hand, you each perceive the other vanishing regardless. **Only someone who has completed the steps may traverse the portal or even perceive it. And only things they brought with them while traversing the forest can come with them.** If you left your backpack at the final tree before you started, and you picked it up at the last minute, it'd fall to the ground as you crossed the portal. Once you've completed the steps, you'll see the witches and their cauldron whether you peek around the left or right side of the final tree. The trees no longer matter, you've unlocked the right to traverse realms for an unspecified amount of time or until you go too far from the hill and the whole thing resets. [Answer] **You are projecting an [avatar](https://en.wikipedia.org/wiki/Avatar) into the witches' realm.** (Very similar: good old AD&D [astral projection](https://roll20.net/compendium/dnd5e/Astral%20Projection#content)). Your friend sees you complete the ritual and simply stop there. You're just standing there gazing into space, breathing normally, and not moving. In the witches' realm, you are now an avatar of yourself: a physical projection that is, basically, you, but is really more like a temporary body double. You can fully interact, buy things, sell things, etc, but when you leave, regardless of how you leave, you find yourself standing back where you completed the ritual, having returned to your body, plus or minus any changes made while projecting. Your friend watching you might suddenly see you jolt, inexplicably carrying potions, even though you clearly did not have them a second ago. (Another option: time is different. You actually had a 20 minute conversation and bartering session but from your friend's perspective you froze for a half second and then somehow had potions pop into your hands. Time dilation helps resolve a lot of "what if" scenarios.) If you forgo the time dilation, then most likely any interaction with your real self (on Earth), breaks the projection and calls you back instantly. One minute you're chatting with the witches and suddenly you're staring at your friend who is looking concerned and poking you with a stick. Either way, you probably shouldn't see your friend while in the witches' domain. If you look south, you see whatever is to their south, in their own realm. (Unless, I suppose, the hilltop is the full extent of their realm. Then maybe you see a bit of a hazy atmospheric wave and outside of that is the rest of your world. But for sure the world cannot see your avatar, for the same reason they can't see the witches.) [Answer] This is what's known as a MITM attack, or a Mage In The Middle attack. Their magical set up relies on giving you a token once you complete a series of actions which gives you access to a magical portal into their realm. If they just chase after you and you run into the portal, you'll vanish from their vision. Knowing exactly where you vanished can allow skilled mages to force open the portal again. This is one example I have seen when some sort of golem man hybrid attempted to enter a forest sanctuary. [](https://i.stack.imgur.com/raZ00.jpg) If you hold their hand just as you cross, there's a variety of things that can happen. They might be pulled through. Your clothes and items you sell can go through, why not other people? Or, if they have appropriate security, your companion might be tossed out or exploded. You would have to ask the witches what security they put on. A skilled mage might transform themselves into something unobtrusive and avoid any security scans. [Answer] This is Schrödinger's Gate. When you complete the path, you will be both through the portal and not through the portal. If someone follows you, or even holds you hand, they will become distracted at the point of transition. Once they are no longer observing you, you will cease to exist for them. [Answer] I would say that there is a distinct possibility that while you will be able to see the witches, having completed the required path, you and a second person would both be able to see the hill but only you can see the other reality super-imposed on the hill. They are effectively an intangible ghost to that place and vice-versa... where as you have made yourself tangible to both planes through the complicated ritual walk. If you move too far away from the node where you have made that attunement, then the other you snaps back into your reality, requiring you to start the ritual again. As a side possibility to this answer... It wouldn't surprise me if the hill is neither actual plane and is a kind island of overlap between the two full places of existence. The witches themselves have an identical hill in their plane which requires a similar (but probably not identical) path required to end up in the overlapping island which is manifesting as a hill. If you are worried about what would happen in *this* case when your friend (probably standing half way through a witch or a cauldron or both!) watches you walk down the hill and weave through trees in the completion of the second "planar attunement", you would not reappear around the first obstacle and your friend would disappear, even though you could still see the hill and the witches... in a mirror of seeing the witches the first time on the hill. [Answer] This problem would appear to be four dimensional, not merely three-dimensional. There is a fourth, magical dimension. It can't be seen, but it exists nevertheless. The path through the trees is the path that you must follow to climb a ramp from the fourth dimension's ground level to the fourth dimension's magical hilltop level. Quite simply, by walking the required path, you're climbing the magical dimension's ramp. If you stray off the path, you fall back down to the magical ground level, and even if you return to where you were in three dimensions, you're beneath the fourth-dimensional ramp, and must start again. The fourth dimension is small, and a person is not very big in the fourth dimension anyway, so if you were to fall off the ramp in the fourth dimension, you wouldn't notice any impact beyond that usually felt when walking. To an outside observer, you would appear to go around the trees, but you would also appear to get smaller, appearing to be more distant, until you disappeared as you passed behind the hill. As for the other parts of the ritual, they allow you to interact with the ramp. A person who followed you *without* doing the other parts of the ritual would see you get smaller and disappear even though they were otherwise right beside you in three dimensions, since the distance between you has been increasing in the fourth dimension. As for how you can leave, you could retrace your steps, thus going back down the ramp, which would let you return to the magical hilltop by simply going back the way you came. Alternatively, you could just walk off the hilltop, and fall off the fourth dimensional platform/ramp, meaning that you would need to go back to the beginning to get back onto the ramp. [Answer] You shouldn't be able to see the witches until you have past the last two trees one to the left and one to the right. Once that has occurred you should be able to see them and your friend should not. So either If you both walk to the hilltop together you will still be able to see them but he will not. OR When you pass the last trees you disappear from your friends view (and he from yours) at the same time that the witches appear. [Answer] # Ask the witches ## Option 1 - You are allowed to invite others If you are allowed to have friends with you then you can grab your friend and bring them with you. They will not be able to perceive what they are going through so it will be boring or scary for them. ## Option 2 - You are not allowed to extend the invitation You will be able to grab your friend and drag them to the gate. They may not pass, so you need to take precautions not to break their hand. ## Option 3 - You can bring them in but not by design It could be that the charm is resolved by your password and dance, but if your friend does not do the dance they are rude. If witches hate one thing it's pyres rudeness. [Answer] I cannot add much to Nosajimiki's excellent answer, however, it seems clear to me that as you go around the hill, you are out of sight from those who are on the opposite side of the hill. And, once you have started the somatic journey, you no longer re-appear to those when you would expect to come back into sight. Therefore, while you may (or may not) see your friends to the South, they cannot see you, unless you walk away from the hill and lose the somatic journey - but even then, maybe you remain on the portal road until you can appear from behind a bush or tree. The hidden/revealed aspect of your journey might just require temporary occlusion (as well as correct attention to somatic and verbal actions). If your friends start walking north towards you, they cannot see you. It's quite possible that you cannot see them - because you are no longer on un-magical ground. The common mechanic is a mist - but it could be that you only see what is found in both realms - and indeed it is the conjunction of similarities which open the gateway. Far more dangerous would be if your friends chopped down one of trees that you had already past. You would either find yourself trapped between worlds, or trapped in faerie until another portal was revealed to you. [Answer] ## Your Friends Will See You But Not The Witches Let's make this even more interesting. Say one of your friends brought a camcorder with them, and as you and another friend walked past the last tree, they record what happens. You've completed the full chain, and the other friend has not. Their camera will see both of you on the other side of the tree, doing whatever you choose to do - but will not see any witches, or any other unusual activity. Neither will your friend - in fact, if you make any mention of the witches or the cauldron, they will think you very strange and possibly insane. This is because the realm that the witches occupy is actually the exact same space - but unless you chant the incantation and follow the exact path, their realm essentially does not exist for you. Your friend could very well pass right through them and wouldn't even be aware. As soon as you walk far enough away from that hilltop, you too will become unaware of the Witches and their activities. [Answer] Suggestion: the magic creates a wormholelike tunnel that collapses if someone interferes with it. They may be able to see a glimpse what lies on the other side of the portal but if they approach it, it collapses just the same way if you made a mistake following the path. [Answer] ## Space Dilation No matter how long or how quickly your friend walks towards you, he never reaches you, as the ground between you seems to eat up his steps without getting any smaller. You can cover the distance easily, but that breaks the "don't go too far away" escape clause. ]

[Question] [ **Background :** Consider a typical dungeon, which has weak monsters at the top and the lower you go, the stronger the enemies become. Some questions about dungeons have already been answered - [why are they filled with puzzles](https://worldbuilding.stackexchange.com/questions/36446/why-fill-a-dungeon-with-puzzles/36458#36458), and [how long it takes to repopulate them](https://worldbuilding.stackexchange.com/questions/32515/dungeons-in-a-medieval-fantasy/32569#32569). However my question is - what prevents the monsters from migrating to other floors in the dungeon? **Some** of the monsters that are on the lower floors in the dungeon are very powerful and crafty. What prevents them from just moving from like the 20th floor of the dungeon to the 10th, and becoming the boss of that floor ? Or, the more general question, why do monsters **remain** in the dungeon ? They can probably figure out that going outside means they can hunt for food. [Answer] **Manna** One option is to make the stronger creatures deeply dependent on magic/manna and put a source at the bottom. It seeps up through the dungeon. The deeper you go the easier powerful magic becomes and the biggest, scariest and most powerful creatures need that manna to survive. The creatures might want to leave but they need to stay for roughly the same reason that humans cluster around an oasis in the desert. The less powerful creatures can survive further up and the least powerful can even survive on the surface. They may act as minions of the ones further down gathering supplies and food. Indeed assuming that any creature has a certain Manna reserve and a certain manna requirement suggests a certain social structure such that the creatures on each level can temporarily project force against those a few levels above but would need to return to replenish their strength while those higher up are the ones which can't compete for the richer manna supplies lower down. Some of the most powerful creatures would starve of magic on the surface and die but they can sit in their lair deep down coordinating attacks against the surface. At very deep levels the rich manna field allows for highly magical plants, animals and materials to form/grow which even gives a reasonable incentive for humans to venture down. They get the chance to harvest magical plants and animals that only grow in rich manna-fields. You might even have human outposts deep in a dungeon where magical crafting otherwise impossible can be done. If you want to make magical artifacts it makes sense to go to where there's lots and lots of magic available. These would of course suffer terrible attacks from the local creatures. [Answer] First, just as executives tend to seek out the top floors of a building the the most powerful of entities likewise seem to gravitate to the lower, less accessible regions of a dungeon. Perhaps they just don't wish to be disturbed by every nuisance attempting to explore the area. Better things to do with time kind of argument. Allowing the lesser or less ferocious creatures handle the "light work" or cannon fodder keeps one's self at full charge so to speak while hopefully wearing your enemies down. After all you have a reputation to maintain and underlings are just that underlings. If its serious I'll get involved. Enjoy. [Answer] In addition to Murphy's answer: depending on the monster type, they might be afraid of light and open spaces. That would stop them from getting away from the dungeon. Additionally, upper layers would not be "comfortable" for these monsters (as fresh air and a bit of sunlight comes through), thus they fight for lower floors which would also become status symbol. This results in stronger monsters in lower floors. Bosses could be monsters that decide to settle for an upper floor becoming the boss of that level. After all some of us chose to be big fish in small pond. [Answer] There are several answers, but it depends on the dungeon and the monster. Take, for example, the puzzles. Because no campaigns I know of start at the bottom of a dungeon, we can turn to reality. In tombs like the Egyptian pyramids and Chinese Emperor burial sites, the pallbearers, in order to keep the secrets of the traps, were trapped in themselves. This means that, logically, the traps work both ways. Therefore, monsters wouldn't push up of they were monsters more muscle than brain and couldn't figure the traps out. The more intelligent could face physical barriers. For example, some are foiled by a locked door, no more. If they lack the faculties to break it down, then they cannot move on. Another possibility would be that moving up could cause harm- of they are susceptible to physical attacks, staying where they are could be safest, and they would be smart enough to realise it. So that addresses the less intelligent monsters, but what about the bosses, intelligent and strong? Bosses stay where they are because they have a purpose. Many times the bosses are set personally by the Dungeon Creator,and this understand why they should stay. Sometimes it is the creator itself. So, the boss knows why it needs to stay where it is. Of course, this is all overlooking, one other thought- perhaps the monsters were spawned there. Let me frame it this way: if you were born in an opaque dome with no outside contact, and you were told that there was no outside, would you try to escape? No! So, it is possible that the monsters simply do not know that there are different floors to move to. Overall, they could be unable to overcome a trap, or weak, or understanding of a purpose, or just kept on the dark. [Answer] **Money** Main idea of the French comic book series [Dungeon](https://en.wikipedia.org/wiki/Dungeon_(comics)), a donjon can actually a be a business built up to attract adventurers. They will bring their costly equipment, maybe win easily the first rooms, and then eventually die later, in other more dangerous places in the dungeon. The "Dungeon Master" will then hire the creatures and monsters as gladiators and give them a place or a treasure to keep. He will also take care of the inhabitants of the dungeon, feed them and manage the different species so they can live together. [Answer] I have different answers for different kinds of monsters ... **Monsters fear human hordes or armies.** The dragon doesn't fear a single mounted knight, even a knight with a magical *+3 sword of dragon slaying*. A regiment of crossbowmen and a bunch of [ballistae](https://en.wikipedia.org/wiki/Ballista), covered by a phalanx for close defense, now that is scary. For every one he fries, another steps forward. The vampire doesn't fear a single hero. A hundred villagers with torches and pitchforks are a different matter. A dozen villagers may fall, but sooner or later the tine of a pitchfork will find her heart. So the clever monsters will go where *average* humans don't show up. Deep in the dungeon, beyond the bottomless pit and the spike trap. **The lower dungeon was tailor-made for the monsters.** Dragons have an instinct to bring their hoard into a comfortable cave. So a dungeon builder who wants his pet dragon to defend his treasure vault would provide a dragons-only access to the lower levels (perhaps flying through the bottomless pit, see above) where a dragon can spread her wings. Can you imagine the size of a [dragon tree](https://en.wikipedia.org/wiki/Cat_tree)? The upper levels are scaled for human minions. A wingless and mindless dragon might find a cave with a trough for water and a trapdoor to provide regular meals. Perhaps the upper levels of the dungeon are damp, or in bad repair. The lower levels are nice and cozy. So the big monsters *can* go to the upper levels. But they don't like it. They would fight those pesky adventurers at a disadvantage in the narrow tunnels. They could engage adventurers in the open, however. [Answer] > > [W]hy do monsters remain in the dungeon ? > > > Perhaps this is overally broad, and is obviously stated in different ways in other answers to this question, but the real reason breaks down to *"Because it serves their purposes."* Any creature in any environment remains there because of the ecology. *[Note that for the following, I am assuming food needs are fairly well balanced. Lack of food may very well be a good cause for migration. Lack of migration but continued health indicates food requirements are being generally met.]* * **Food** - whatever the creature naturally eats either is produced in the dungeon or comes to them, so there is no (or very little) need to go above ground. For our purposes, food includes water, etc. * **Reproduction** - The dungeons serves as an environment where creatures of the opposite sex dwell as well (a bit of a chicken and the egg problem). * **Protection** - Because a creature is powerful it does not mean it's invincible. Particularly, no animal would want to live under threat of siege either from third parties or others of it's own kind. Young, new or inexperienced creatures in particular are often vulnerable - killing a young dragon is much simpler than killing an adult dragon, slaying a lich is much easier if her phylactery isn't yet well hidden. * **Hiding** - While this could be protection as well, many of the creatures portrayed as living in dungeons are predatory. Predators have the instinct to hide not necessarily out of fear but because it makes their goals (preying on others) simpler if the prey has no knowledge of the predator. * **Symbiosis** - Creatures may rely on each other in some fashion (maybe those giant beetles really love that dragon poo =P). * **Other Advantages** - Bees build hives that have honeycomb. That particular structure has an advantage for the bees. While not necessarily made by the creature, there could be some advantages (such as treasure hiding already mentioned) that the creature finds advantageous in a dungeon. Likewise, a creature that is both light sensitive and needing a watery environment to survive would likely find a flooded dungeon a quite suitable habitat. * **Free Will** - If the creature is intelligent enough, perhaps it just *likes* being in a particular environment. Perhaps that dragon really *does* appreciate those hideous but tasty dwarfs' eye for decoration... perhaps that evil lich is pining away for the days of yore when she could torture others unmercifully and being in a creepy dungeon reminds her of the fear she used to see etched into the faces of her victims as they were dragged *"below"* to have unspeakable horrors visited upon them... who knows? And finally, while not ecological in nature, the monster could of course be forced to live in that environment by external forces (that is the *only* place it can do/find xyz, despite its wishes to do otherwise, or is otherwise trapped via circumstance e.g. by accident, inability to leave (doors!), magic or hostile "others"). > > [W]hat prevents the monsters from migrating to other floors in the dungeon? > > > With the exception of reproduction (as defined in the list above), one or more of these reasons could apply. While many dungeons are generic, real life would suggest that floor 10 would not necessarily meet the needs of the creature(s) inhabiting floor 20. I think the proper question is - what so special about floor 10? Food, maybe, but that's about all you could likely count on. Any advantages to living on floor 10 likely *would* cause a creature to inhabit that floor (barring major disadvantages). The fact that floor 10 (or floor 20) is *not* inhabited by creature X automatically implies that there is some disadvantage in that arrangement, regardless of how powerful the monster is. [Answer] # Natural selection Over the ages the inhabitants of the dungeon have adapted to the features of their homes: darkness, temperature, air pressure, local gravity anomalies, contaminants in the water, background radiation, seeping oil fumes, fungus spores. Just as you are not used to these effects and are weakened by them, so too are they weakened when they are missing. So we would expect that they would wander slightly but they will be most common in the places where they have the most advantageous adaptations (which is why many games make the monster distributions probabilistic rather than precise). Only by gaining some tolerance to those features, whether natural or artificial, can you neutralise their advantage against you. [Answer] They prefer to let their food come to them, eating adventurers that enter the dungeon, along with their supplies, and/or the corpses of the monsters that the adventurer managed to slay. [Answer] **Security** The creators of the dungeon put the stronger monsters in the deeper, higher security areas, to make it more difficult for them to escape and threaten the society on the surface. [Answer] I don't know if this logic entirely holds, but lighter monsters tend to be more migrant. Monsters at the top and more accessible part of the dungeon would be cleared out more frequently. It would take a creature that populates more frequently and can move in again quickly to establish some sort of hold on a dungeon. The lower floors aren't bothering people so frequently so they aren't seen as being worth clearing out at regular intervals, so larger entities or more powerful swarms can establish a foot hold. ]

[Question] [ ***TL;DR:*** Santa delivers physical objects to 95% of people (including adults) who ask for it in the form of a letter. He will start this Christmas and will continue until decided otherwise. And yes, he will deliver atomic bombs and AK-47's. How do we react? Most of the parents tell their kids the biggest lie ever: Santa Claus does not exist. Santa Claus does exist. However, as stated in [this brilliant answer](https://worldbuilding.stackexchange.com/a/13521/2071), his requirements to put people on the "Good" list were bit too high. Also, to be put on the "Naughty" list, you had to be worse than all serial killers combined. As a result, Santa did not deliver a single present in the past 100 years. He did not even go on his annual journey during the night of Christmas, since there was no need for it. We started to believe Santa really does not exist. And at some point, we started to tell this to our kids. However, this year, Santa decided to rework his metrics of the "Good" list. (And he is going to rework only the "Good" list metrics, his "Naughty" metrics stay untouched). His reworked metrics put almost every single kid (95%) on the "Good" list. He also manages to secretly copy all the letters addressed to him, so he knows what the kids wish for. On December 25th, 2015, in the morning, loads of families will discover "extra" presents under the tree. These presents are going to be addressed to the kid wishing for them and contain exactly what the kid wished for. **How does society react?** To sum it up: * 95% of all letters addressed to Santa, or to his mythical equivalents (Father Christmas, Weihnachtsmann, ...) are fulfilled. * Santa delivers only physical (touchable) gifts which can be made. No wishes for "world peace" or "get my parents back together" can be fulfilled. * If there is a kid on the "Good" list who wishes for an "untouchable" gift, that kid gets a gender stereotypical toy instead - a doll for a girl or a toy car for a boy. * Only wishes for yourself are fulfilled ("I want a doll for my sister" is not fulfilled, but "I want a doll" is). * Wishing for multiple physical (touchable) items is allowed. Any number of invalid wishes get converted to a single stereotypical toy, delivered in addition to valid requests (if any). * Santa Claus is a mythical creature, he goes completely undetected and untracked during the night of the gift delivery. * Should there be a camera or any other device able to spot an "intruder" in somebody's home, that device will malfunction for the time of the gift delivery. Afterwards, it will continue to work normally as if nothing happened. * Presents are good quality, "A Class" presents made in the North Pole. Santa's elves are able to create a perfect copy of any branded product. So if you wish for a PlayStation 4, you will get a PlayStation 4, but made by elves (still identical to and compatible with a PS4 by Sony). * Money and gift cards are considered "untouchable" gifts too. * Wishes for live animals are fulfilled by delivering a plush toy in the shape of that animal. * All untouchable wishes convert to just one touchable gift (you get only one toy car for wishing world peace and everyone having something to eat). **Edit:** I know that such rules are unfair and kids in the first world will get double amounts of PlayStation and Xboxes, while a kid in the third world will get a toy car or a plush toy. But "fairness" of the gift delivery system is out of scope for this question. **Edit 2:** Examples of how wishes are fulfilled: Girl wishes for Nintendo Wii U console -> Gets perfect working replica of that console Boy wishes for world peace -> Gets toy car Girl wishes for a live shark and for everyone having something to eat -> Gets plush shark and a doll Boy wishes for iPhone and Apple store gift card -> Gets perfect working copy of iPhone and a toy car **Edit 3:** Please note that the **current** state of Earth is assumed in this question. So these gifts are given to you in addition to whatever your relatives bought for you, because they stopped believing in Santa and assumed he doesn't exist. [Answer] **The end of the world.** Once a group of clever yet malevolent people have monitored how wishes have been fulfilled, they notice that 95% of wishes are fulfilled when touchables are wished for, and only for children. They start by recruiting/kidnapping children filled with naivety, optimism, wonder, and joy and run a really fun base where the kids get to play, but they never learn about what an AK-47 is or what it does. The kids will be brainwashed into thinking that everything the terrorist organisation says to them is for the greater good. Being on the "good" list, the children are then told to write a letter requesting for material items like real weaponry that do not contain any sort of trackable serial number or registration, because their source is of mythical origin. Eventually, they test the waters with weaponry that is beyond current technology, such as antimatter, powerful petawatt lasers, etc. This works because the children are still good, and haven't committed any crime yet. When they have amassed enough weaponry, the terrorists who control the children coordinate a strike against all of the countries, remove their control of any nuclear attack options, and obtain world domination. When the rest of the planet learns what it must do (similar tactic, usage of children to obtain a retaliation plan) the planet goes into an arms race, using children to obtain greater and more powerful weapons until it goes too far and wipes out life on Earth. So long and thanks for all the fish. [Answer] Let's take this step by step. First year: confusion. But humans can be smart, too. After the 2nd, latest 3d, year, they will have figured out what has happened: Santa is suddenly real!!! See the rise of "smart wishing phase 1": a Ton of Gold, Diamonds etc. (Edit made: No Money-Wishes, but there is enough non-money-valuable-stuff!) For a while, that will mean that people with children will be better off that those without. Sorry, adults, no presents for you! But tossing loads of money, gold etc into the economy will totally overthrow it. (Some economics-people chime in here? Huge influx of money and valuables once a year?). So, we end up with a totally changed economy. Next step: How smart is Santa anyway? Parents can easily tell their children to wish for something! But let's say he lets "parents tell their kids what to wish for" slide and continues giving. Welcome loads of new children: "Hey, let's have a kid so we can be rich!", and smart wishing, Phase 2: what can you wish for that will carry you over the year? We have been pushed into post-scarcity, IF we are smart in our use of Santa! So, follow up question: what are Santas limits? Can he make a Star trek Style replicator with a one year battery.. or even an endless automatic energy supply? --- Alternative and darker view: Bye Bye earth... sorry, one or two kids wished for an antimatter-bomb... --- Edit after OP comment: So, everyone is a child -> No needs for kids to be rich! [Answer] # One stupid wish is all it takes It really doesn't matter what 99,999% of the worlds population wish for next year, because a single crazy world-destroying wish is enough to destroy earth. As soon as some geeks start to figure out, they can possibly wish for anything, someone will test the limits by wishing for something like: ``` A moon sized ball of antimatter My own sun A quintillion megatons of gold The Deathstar A massive real-size 1:1 model of Saturn, made out of wood A black Hole the size of a Football A spoonfull of the most deadly Virus imaginable ``` As soon as one of these is delivered onto the house of the wishing kid, earth will cease to exist. [Answer] Per your universe's rules, asking for a piece of integrated circuit technology gets the child a **perfect working copy**, made by elves. *(examples given are the PS4, Wii U, iPhone)*. [Such devices often have encryption keys to secure their firmware](https://en.wikipedia.org/wiki/Hardware_restriction) so that people cannot modify them to use pirated games or software. The security of these keys are based on the presupposition that the [prime factorization](http://en.wikipedia.org/wiki/Integer_factorization) of large numbers takes too much time and computing power to be completed in a reasonable length of time. So, how can Santa provide flawless replica units? There are several possible explanations: 1. Santa's operation is involved in **large-scale industrial espionage** *(so it can obtain the private keys for the electronics it duplicates)* 2. Santa's workshop is **excellent at discovering security vulnerabilities** in all the newest hardware & firmware *(which allows them to root devices, counterfeit boot-loaders, etc.)* 3. Santa has **discovered a groundbreaking method of prime factorization** The third possibility is the most intriguing, and the most worrisome. Perhaps Santa's workshop has developed workable [quantum computing](https://en.wikipedia.org/wiki/Shor%27s_algorithm). In any event, the encryption that most of the world relies upon has now been rendered obsolete overnight. Financial transactions and military communications are all vulnerable. This will result in dire geopolitical consequences. The intelligence agencies of all the major world governments will be desperate to discover the secret. Assuming that Santa's methods cannot be reverse-engineered from examining his perfect replica devices, Santa can expect an onslaught of black-bag operations directed at his North Pole facilities. [Answer] It's a funny kind of Santa who can do all this stuff, but not see abuse coming a mile away. Santa changed the rules once. He can change them again. So Ernst Stavro Blofeld asks Santa for a hollow volcano this year, with a lovely retracting roof and a cavern full of old IBM mainframes with blinking lights to track his evil satellites, etc. Santa says... sure, why not? And on jobs.stackexchange.com, many vaguely-specified Cobol jobs appear on Boxing Day with a German language requirement. Must love sharks! With laser beams! Over the next twelve months, Blofeld accumulates an army of enslaved children all furiously writing letters to Santa asking for nukes, laser satellites, attack helicopters, vicious dogs, stealth submarines, and tanks full of sharks with laser beams. And pallet after pallet full of old Winchester drives for the mainframes. On Christmas morning, Santa slides down Blofeld's volcanic chimney bearing... thousands of beautifully tailored new Nehru jackets for the enslaved children, plus toy cars, dolls, LED headlamps, and maps of the hidden escape routes out of the stupid volcano. And a bag of coal for Blofeld, a feather toy for his cat, and toy cars for his henchmen who've been waiting twelve months for their weapons. And for the Cobol jockeys? O'Reilly books. Thousands and thousands of O'Reilly books. They'd rather have subscriptions to [lynda.com](http://www.lynda.com), but that's not tangible. Santa decided to keep enforcing that rule (jerk...). You may be an evil genius, but Santa's not as dumb as he looks. If your rules should say that Santa is just syntactic sugar for a magic wand that has no agency of its own, that should be in there explicitly. **UPDATE:** Bonus band name: Blofeld's Cat. [Answer] **Cascading effects that result in global conflict.** The first year will herald a glorious and wonderful year for those parts of the world who believe in Santa and somehow still utilize written letters to him. As those who actually followed the custom start reporting the arrival of gifts, the world starts taking notice that perhaps there is more than we knew. *Religious leaders across the world start reacting.* * Some declare this to be the proof that the Christian belief is correct. * Other already extremist movements deny the truth, portraying the events as some kind of sinister plot. * The divide between already opposed religions grows wider, the world has become a tiny bit more fractured and a tiny bit worse. *The one time occurrence causes many to try and exploit the system.* * People start preparing for the next year. Creating ridiculous lists of wishes, both material and immaterial. * Opposing movements declare that the resurgence of Santa was because of *insert odd reason here*. * They believe that those who are attempting to exploit the system will cause its end. * Or worse, cause divine retaliation. * The first acts of violence occur as devout Santa-ists try and prevent children from creating wish-lists. *The next year's Santa season only makes things worse.* * As people start manipulating children, riches and destruction are asked for in vast quantities. While one man asked for a fancy car, his neighbor asked for the tools to destroy that very car. * Countries around the world start demanding a ban on Christmas, to prevent the chaos. * Christian nations see this as an attack on their faith. * Before long, it becomes clear that there is no limit to the possible gifts bestowed by Santa. * And as chaotic as the world is, a world with unlimited resources is vastly worse. * In a misguided attempt to protect themselves, several nations around the world declare war on each other, and the third world war begins. Thanks Santa! **Other random effects:** * One-child policies abandoned. * The end of pine trees across the world as a global harvest ends their lives. * Literacy goes through the roof, as wish lists become more important. * Elf fiction becomes thoroughly odd. * Slavery discussions ensue around the world, with movements to save elves. * The church of Santa becomes one of the largest religions. * Several people are released from insane asylums. * Doll and toy car manufacturers around the world file for bankruptcy. * News broadcasters around the world go on the hunt for fat bearded men. * Fat bearded men around the world go into hiding. [Answer] We cry tears of the most sincere kind of joy. There is something primal about the protection of and care for children that resonates powerfully with most people, especially struggling parents. Having children, you *want* to be able to give them everything they could ever ask for, but sometimes you can't do anything at all. Sometimes you can't even be there. And then all of a sudden, here is this man, this myth, centuries old and endlessly loving, and he was *listening*, and he could *do something*, even if we couldn't. He doesn't care if you're American, Afghani, or Somali, only that you were *good*. Everything we know about the world is now *wrong*, and the world is forever a kinder gentler place. [Answer] Now that people understand that Santa is not a myth, they understand at the same time how the industry used and abused from Santa's (temporary) lack of judgment. People return to the true spirit of Christmas and cease doing gifts - and, hence, purchases - during Christmas : A true / pure / ... gift can only by made by this all-giving 'person'. The whole world economy goes 30% down (no more black friday). Then even further down, with no loss since values changed : sharing what's available, not giving one 350 times the salary that another has, is just an obvious rule now. People of the world, even of north America, understand that this is only for the best : less envy, less pollution, then, soon, less tornado, floods, massive fires and such : even the dumbest global warming sceptics understand, both with their reason and warmed by the pure generosity that just shown, that money, possession, ... is not the way to human happiness. Soon enough, the power of the monstrous worldwide companies drops severely -after all, now elves can build an iPhone without killing any Chinese worker, and one can have a book without having someone paid $5 an hour an performance-tracked by Amazon, so now people ask less and less and know that having less, and waiting for it is not that bad - better, in fact -. Economy re-organizes itself around more human, slower, shorter paths. Oil use drops, oil prices drop, and the so-called powerful nations cease to defend money against justice. Just and democratic regimes can rise in many poor nations without a CIA bullet to break it all. Terrorism, the political answer to the violent economic war of the north against the south, soon becomes severely critized in its very nest, and vanishes. It's Christmas time. [Answer] [The Onion gave their take on this](http://www.theonion.com/article/sitcom-characters-still-in-shock-after-christmas-e-30636): > > ORSON, IN—Characters from ABC situational comedy The Middle are reportedly still in complete and utter shock after the conclusion of a recent Christmas episode revealed that Santa Claus does in fact exist. “Jesus, are we going insane?” said the show’s protagonist Frankie Heck, several days after hearing the faint sound of sleigh bells as her 10-year-old son Brick joyously unwrapped a popular new toy that she and her husband were unable to buy in time for Christmas. “This essentially alters my entire perception of reality. There is an immortal being out there who leads a workshop of elves on the North Pole and hand-delivers presents to every child on earth in a single night? One minute we were trying to resolve a relatable, commonplace domestic situation, and the next we learned that time and space can be completely altered—I feel like I’m losing my fucking mind.” Sources confirmed the shaken couple then refused to help their oldest daughter Sue prepare for an upcoming school dance, claiming that “none of this bullshit matters anymore.” > > > [Answer] 1. All nations immediately cede sovereignty over their post offices to the United Nations. UPS, Fedex and DHL are nationalized. 2. UN bureaucrats tirelessly sift through Santa letters to prevent world destroying wishes from getting through to Santa. 3. Human and weapons smugglers, drug traffickers, and the like bypass UN controls and illegally deliver letters directly to Santa. 4. All those smugglers get hungry up in the arctic and start eating baby seals and shooting polar bears for food. 5. Greenpeace recruits an army and wages war against the Santa smugglers. 6. The elves develop a black market, parallel mail system. 7. Surveillance cameras are installed in all children's bedrooms worldwide. Pencils, pens, and crayons are banned. Special OCR software is installed in computer printers to prevent unauthorized letters from being printed. 8. Jailbreak exploits are published on the internet to bypass controls. 9. The internet is shut down. 10. As every teenager knows, that is the definition of: THE END OF THE WORLD! ]

[Question] [ Tomorrow, a sudden airborne plague comes around that kills nearly all human males - women are unaffected. The UN and different nations try their hardest but fail to find a cure. There are riots and some breakdowns, but on the whole global society manages to stay somewhat stable through the process. A lot of knowledge, especially technical knowledge, is lost but most governments either stay in power (with some replacements) or are replaced with new but similar ones. Everyone in the whole world is infected, and those that are not immune all die off within a few months. Everyone else are still carriers of the disease. The only men that survive are to be those that were treated for and cured from a certain rare disease - as it turns out, 5 men in total. All new male babies made from frozen sperm die quickly in the womb. The reason these men are immune is assumed to be genetic, since male babies conceived by them survive and are perfectly healthy. Using the cure on women makes no difference. Since the treatment for the rare illness is rather expensive, these men all live in developed nations. The question is this: can humanity keep enough genetic diversity for a long-term sustainable population or are we on the road to inevitable extinction? (I got the basics of this premise from a manga that clearly didn't put much thought into its premise, but it got me thinking of the practicality of it. In that world technology was more advanced but not very well defined, which is why I'm setting this in the modern world.) [Answer] I don't think that, even with artificial insemination techniques, you could successfully repopulate with only 5 men. Check out the math here <https://en.wikipedia.org/wiki/Sperm_donation>. It takes a man 2-3 days to produce a good sperm sample, but even with IVF you are only going to get a few successful conceptions from each sample. So those 5 men can only impregnate a few hundred women a year. Even assuming a large increase in success rate, the large gap from when new males would be able to reproduce (12-13 years or so) would mean there would be only a few thousand children at that time. Plus you are assuming the 5 men are relatively young with healthy sperm and don't die from other causes in those 13 years. The issue then becomes sustaining modern technology with such a small population. Even if the existing women can cover down on all aspects you will only have a few decades before tasks and knowledge will have to be passed on and I don't think there will be enough capable young people to do it. As technology drops, the ability to sustain fertilization beyond natural methods will also drop, slowing the birth rate further. Not to mention that these new children, or at least the males, suffer from this rare disease that requires first world technology to treat, if that is lost then the babies will die from that, not just this killer disease. So a best hope scenario is a few tribes of low tech survivors that are able to at least treat this genetic disease that leads to males surviving the virus, or that the virus dies out on it's own and new males without the genetic disease can then survive. Humanity has bounced back from VERY low numbers in the past (70K years ago a supervolcano dropped humanity down to a few thousand individuals <https://en.wikipedia.org/wiki/Toba_catastrophe_theory> ) so while the species may survive, I don't think our technology and society will survive with us. One possible bit of salvation is that FEMALE children from existing banked sperm would still be immune to the virus, so you could probably keep on using existing sperm banks and IVF techniques to give lots of women daughters. This could prevent a HUGE hourglass population curve and allow for a more seamless transition of knowledge until such time as there were enough males to return to more normal procreating methods. I did some reading on the Y chromosome. It is very gene poor (obviously since women don't even need it), doesn't seem to be shrinking in size anymore (ever since we diverged from our common primate ancestor 6 million years ago), and has a high mutation rate (due to the sperm environment), so even just 5 copies will probably not spell inbred doom for humanity down the road provided those 5 men don't harbor one of the fertility limiting diseases (which, given the assistive reproductive tech future of humanity anyway, may not matter [or it could even be a DESIRED trait since it may help maintain the new political structure that will arise in a women-led world that, for at least a few decades, has no males to mate or work with. Keeping men from being able to naturally impregnate women could prevent men from taking over again since the numbers of males could be better controlled]). [Answer] One of the first things I would be concerned with is how the people of the world would be made aware that these five men are even alive, much less the only viable sperm donators. We are facing a world that would have lost half of its population and most where most people in high level executive positions would have died. There would most probably be a lot of administrative chaos. If nobody knows the significance of these men humanity would most probably be out of luck. The remaining scientific community would probably spend years trying to find ways to make babies from frozen sperm samples survive before the special abilities of the men were discovered. In which time they might even have died in the chaos. If the men are randomly distributed in the world the chances of them being found at all by anybody who would understand the importance of setting up a sperm bank, would be relatively small. And even if after a few years they are discovered and a sperm bank with world wide distribution is set up we would probably face a massively depopulated world after women in most areas age out. Then there is the option where people know already at the onset that these men are special and that their sperm must be milked and conserved. Then these men would probably be quite busy wanking for the next ten to twenty years. If trade routes are still working most of the areas around major trade hubs in the world might be able to keep their populations up if there is a steady supply of sperm samples to impregnate the women. As far as genetic diversity the only thing I would be concerned with is whether the men have Y chromosomes that are resistant to mutation and decay. As long as a large enough population of women are impregnated genetic variety would not be a problem as the children would get their diversity from their mothers. Only the genes on the Y chromosome would be in danger. [Answer] They wouldn't need to rely upon the men. Scientists have already been able to create **almost** sperm from female stem cells. I imagine, given that this was now a matter of species survival, the world would invest heavily in advancing the techniques already pioneered, and within a few years they'd have a solution. In the same way that ebola was considered impossible to cure... until 9/11 happened, and the US government reallocated top scientists to finding a cure, for fear of Al-Qaeda using ebola as a weapon. Then a decade later they had a prototype which they were able to test when the outbreak happened in west Africa. <http://www.telegraph.co.uk/news/science/science-news/3323846/Sperm-cells-created-from-female-embryo.html> [Answer] **Edit: I have updated my answer with improved analysis. My old answer was flawed in its analysis** The question of population survival depends on enough genetic material being preserved to maintain a healthy population. The first thing is that there will only be at most 5 Y-Chromosomes in the world after the disaster, and some places may have only one for quite some time (for example if one of the men is in Australia or New Zealand his descendents might be very isolated). However provided that Y-Chromosome is generally healthy that won't be a major problem - it will create higher vulnerability in men to particular illnesses but that's not enough to guarantee the population will go extinct especially as the Y-Chromosome will be paired with different X-Chromosomes in different men. Now it worth looking at breeding strategies and I'll consider a bit of a worst case scenario where a man can only produce 100 children before dying of "over-exertion" (this is only for simplification of the analysis). So the man successfully produces 100 healthy offspring (that is children who reach reproductive age) before dying. He should focus on mating with older women who are still fertile (i.e. those in their 30's) as this will be their very last chance to pass on genetic material. ### First generation This generation of 100 children will all be half-siblings, having half their genetic material from the proto-man. If these half-siblings were to breed with each other it would be a problematic level of in-breeding and applicable to incest laws, but there is no need for this as after approximately 13 years the ~50 sons will reach reproductive age and at this point women who were 20 years old will still be fertile and the sons should focus on mating with those women and not mate with their half-sisters or other girls their own age. Let's say that all of them also produce 100 offspring before dying of over-exertion. ### Second generation This generation of 50,000 children all have a common grandfather so 25% of their DNA comes from the original man while the other 75% comes from random women. This is already a much improved level of genetic diversity and some countries incest laws would not prohibit pairings between individuals with this level of genetic similarity, although it's still somewhat less than ideal. After ~26 years the grandsons will reach 13 years old, they should mate with the women who were infants at the time of the dieoff, these women will now be ~26 years old. Once again let's assume each grandson produces 100 succesful offspring before dying of over-exertion. ### Third generation This generation of 2,500,000 children (yes, 2.5 million, the wonders of exponential growth!) all have a common great-grand-father and so 12.5% of their genetic material comes from the original man, and the other 87.5% comes from random women. At this level of genetic similarity incest laws are not applicable anymore and inbreeding will generally not be problematic. This is the first generation where unmated "original" women might realistically run out - that's not a problem though as each woman can bear multiple offspring. ### Fourth Generation It may even be possible to get one final generation with unrelated women. The fourth generation will come of age at a time when the girls who were babies at the time of the great dieoff are 40 years old, and girls made from frozen embryos/sperm would be a bit younger, at least some of these women should still be fertile. This fourth generation would have a great-great-grandfather in common and only 6.25% of their genetic material would come from the original man. Overall *if* the women successful hold society together and utilize such a breeding strategy then even with only a single man who dies quite quickly the population would be in no risk of extinction whatsoever. Even if the numbers are significantly poorer, say only 10,000 women survive 26 years, the population would not be in serious risk of extinction and there would still be plenty of genetic diversity. Ideally the daughters from each generation would mate with male offspring from one of the other 4 original men, this would greatly improve the diversity of Y-Chromosomes and eliminate inbreeding problems. The best strategy would probably be to have most the daughters migrate to another population as the first generation of sons would too valuable to risk losing on a long journey in a post-apocalyptic world. If migration to another population is not possible the daughters should mate with the youngest generation available as the youngest generation will have the most genetic material from random women. The real question is whether a society without male workers would hold itself together or catastrophically implode, however it would seem reasonable that at least millions of women would survive and even if such a breeding strategy is not perfectly employed the population would not generally go through a bottleneck (i.e. the population would never fall below 10,000 genetically distinct individuals and quite possibly wouldn't even fall below 10 million). [Answer] Nobody has mentioned that it takes only one sperm to fertilize an egg. It involves injecting the sperm into the egg. It is not normally done because of a mix of ethical and medical safety issues. But it is not really hard to do given modern technology. In this plague scenario these issues fall away and I see no problem for one male to be parent to hundreds of millions of children. There will be rapid training of an army of IVF technicians. There will be many individual tragedies as a consequence of breeding from a damaged sperm that in nature could not have fertilized an egg. But need dictates. The human race will survive in sufficient numbers to maintain a C21 civilisation on at least one continent. The first generation of children will need to be very careful not to choose a partner who had the same father. Thereafter there is no problem with genetic diversity provided all five Y chromosome sources are good. There are good biological reasons why a Y chromosome contributes almost nothing of note to a complete genome other than sex determination. I strongly suspect that if all males went extinct it would be possible to create new males using a Y chromosome from another primate species and/or synthetic DNA. In ethical terms imminent extinction is the only thing that could justify this sort of research! [Answer] Those last few men have an immunity to the whatever-it-was which killed billions. That immunity can’t be anything widespread like simply possessing a Y chromosome or having blood group A, otherwise there would be a lot more male survivors. (How on earth ALL the women survived, I shall leave for others to puzzle over). The initial post said they were treated for a rare disease So the factor has to be something specific to those men. That could be: * Genetics alone. It would have to be an incredibly rare gene or complex of genes to explain why there are only 5, and that makes it likely that the men are all related – a couple of brothers and their sons, for instance. * Genetics plus environment. Lots more folk have the gene/s, but the immunity only gets switched on in very specific circumstances – like say if your mum smoked like a chimney while pregnant, you lived at high altitudes as a child, and you have a vegan diet as an adult. * The initial post said they were treated for a rare disease. Unless that’s a genetic disease, then that’s a purely environmental factor. Someone in the maternity ward had better be poised to dose every baby boy with the treatment before the midwife has even cut the cord! If it is genetics alone, then any sons the men father must also inherit the immunity gene/s or they will die. If the **gene is on the Y chromosome** then (as others have pointed out) hurrah – no loss of genetic diversity, because the billions of mothers can supply the rest of the genes to the billions of offspring (assuming the guys and/or their sperm go on a world tour). There will, however, be noticeable shifts in phenotypic expression of that diversity, because the frequencies of the alleles has been radically changed. For instance, if all the surviving men are blood group O (genotype OO), then there are no blood group AB in the F1 generation – all their kids are OO, AO or BO. The ABs return in the F2 generation, since when AO kids mate with BO kids a quarter of their grandkids will be AB. But compared to now, AB will be much rarer, simply because the system is now swamped with O alleles. Ditto any other genes those men carried. Whether this matters to long-term human survival depends on what genes the men are carrying – and IIRC everyone carries an estimated 12 to 20 lethal recessive genes. In a small group of related guys the probability of them all having the same lethal recessives goes up. Lots of blood group O alleles means resistance to smallpox and tons of universal blood donors, so no problem. But lots of genetic disease alleles which kill people in childhood will be a problem. If the **gene is on the autosomes** (the non sex chromosomes) all the above “founder effect” of the small number of men still applies. Plus the sons who don’t inherit that chunk of autosome die. Genes that sit very close to the “you don’t die” genes on the autosome get a free ride, as they are less likely to be separated from it by crossover during chromosome replication. So for instance, if the genes for adult inability to digest lactose and for knobbly knees are snuggling up to the immunity gene, then the world soon fills up with people with lactose intolerance and knobbly knees. If a son needs 2 copies of the immunity gene – one from each parent – then the situation is even worse. Women who don’t possess the gene can only have daughters. If whole populations don’t have that immunity gene (very likely given that only 5 men in the world did), then the internal genetic diversity of that group is slowly eroded, because each generation they are breeding with an outgroup. Silly example – the women are from Island of Blood Group B, where the whole population is BB. The OO men give them BO daughters. Next generation more OO men arrive from outside to give them OO and BO granddaughters. Next generation another influx of O alleles and the frequency of B drops further. (yes I know this is a gross simplification). If it is **genetics plus environment**, then these guys and their sperm going on a world tour is not going to solve the problem of lack of males until people figure out the environmental factors. Telling the difference between *"My baby died because he didn’t inherit the right genes"* and *"My baby died because I live at sea level and don’t smoke"* may take an awful long time. In that time, you have a very reduced pool of mothers who can produce sons (e.g. chain-smoking vegans of the Andean altiplano). This means reduced genetic diversity on the female side as well as the male, since only these Andean chain-smoking vegans are actually reproducing until you work out what’s happening. Imagine if it took 20 years to work it out. A whole bunch of genetic diversity lost, because millions of women outside the Andean Altiplano have died or are now beyond child-bearing age. [Answer] I remember reading articles that a group would need to have a specific minimum size to not have inbreeding issues for the following generation. I think this number was around 10000, but that would be easy to look up. Now the issue at hand would be the very small sample size of y chromosomes. Female offspring would also carry the male's x chromosome. Either way you basically end up with 5 samples of half-siblings, I don't think this is enough. There is a different approach though. Recently there has been some news about creating sperm cells from tissue samples. If I recall correctly it has been proven to work with mice. Now what would happen in a case like this is that males would die out in 2-3 generations, and women would fertilize themselves using this technology, whoever due to missing Y-chromosomes in their markup, could only produce female offspring. [Answer] This topic is actually discussed at considerable length in Neal Stephenson's novel [*Seveneves*](https://en.wikipedia.org/wiki/Seveneves). In his story, rather than a largely intact human female population, and only 5 men, humanity is reduced to 7 women. Due to loss of all viable sperm samples and male DNA, the women reproduce by [Parthenogenesis](https://en.wikipedia.org/wiki/Parthenogenesis), while making some specific alterations to their own genomes in order to cultivate certain traits. Parthenogenesis of human embryos has already occurred, so it is clearly a potential line for maintaining humanity's population, and avoiding extinction. From the Wikipedia article mentioned above: > > On August 2, 2007, after much independent investigation, it was revealed that discredited South Korean scientist Hwang Woo-Suk unknowingly produced the first human embryos resulting from parthenogenesis. Initially, Hwang claimed he and his team had extracted stem cells from cloned human embryos, a result later found to be fabricated. Further examination of the chromosomes of these cells show indicators of parthenogenesis in those extracted stem cells, similar to those found in the mice created by Tokyo scientists in 2004. Although Hwang deceived the world about being the first to create artificially cloned human embryos, he did contribute a major breakthrough to stem cell research by creating human embryos using parthenogenesis.[91] The truth was discovered in 2007, long after the embryos were created by him and his team in February 2004. This made Hwang the first, unknowingly, to successfully perform the process of parthenogenesis to create a human embryon and, ultimately, a human parthenogenetic stem cell line. > > > [Answer] Chances are good the men would be placed into medically induced comas and their sperm would be harvested on a continuous basis, thousands of sperm per second per male. This would happen immediately, and their samples frozen until IVF picked up the pace. IVF efforts would transition to more stringent IVF - rather than exposing eggs to a lot of sperm, sperm would be separated and only a few would be available for each egg. If the egg was successfully fertilized it would be frozen in the fertilized state and sent elsewhere in the world to be gestated. It would take some time, but essentially a whole system would be set up where each country could maintain a reasonable birth rate for the next 20 years using this method, while new baby boys would essentially be raised as precious valuables - even though they'd be as regular as baby girls. After 20-40 years, the balance between male and female would be well on its way to restoration. The genetic bottleneck would be significant. You would be related to 20% of the world's population, and there would have to be controls to prevent second and probably third generation incest. However, the diversity of the female contributions would be enough to prevent that bottleneck from destroying the human race, and after several generations the only thing you'd notice is that society becomes a lot more homogeneous, but not dangerously so. After 100 years you wouldn't have the imbalance at all, and the human race, though changed, would continue apace. [Answer] I'm going to focus solely on the *demographic* aspects of this apocalypse. Assume that everyone lives to the age of 64. Females are fertile from 16 to 32 and can have a baby every other year (for a total of 8). Males are fertile from 16 to 64 (death) and with IVF can have 256 children per year. For the first few years, you are limited by the number of men, but after 16 years, the population of fertile women starts to dwindle, and you become limited by that. I ran a simulation. Starting with a population of 4,160,750,208 women, evenly distributed between 0 and 63 years old, and 5 16-year-old boys, the population declines until it bottoms out (not surprisingly) 63 years after the disaster with a world-wide population of > > 129,972,480, a distressingly small number, equivalent to the global population in 300BC, but not an extinction-level event. > > > The Python code is below, if anyone is interested (or wanted to catch my fence-post errors). You could try experimenting with different fertility numbers, or assume that the baby's sex could be controlled: should we make more males or more female? ``` import locale locale.setlocale(locale.LC_ALL, 'en_US') femaleBirths = [2**26] * 64 maleBirths = [0] * 64 maleBirths[-16] = 5 def generation(): fertileMales = sum(maleBirths[-63:-15]) fertileFemales = sum(femaleBirths[-31:-15]) newBirthsOfEachGender = min(128 * fertileMales, fertileFemales / 4) femaleBirths.append(newBirthsOfEachGender) maleBirths.append(newBirthsOfEachGender) def pcomma(x): return locale.format("%15d", x, grouping=True) for i in range(128): generation() livingMales = sum(maleBirths[-63:]) livingFemales = sum(femaleBirths[-63:]) print i+1, pcomma(livingFemales), pcomma(livingMales), pcomma(livingFemales + livingMales) ``` [Answer] Although I am not a geneticist, I would have to say that the answer is "no". Eventually the 5 living males would succumb to "death by snu-snu" (in layman's terms). Please see the Futurama Episode ""Amazon Women in the Mood" (Season 3, Episode 1) for a more thorough analysis on why this is not feasible. See - <https://www.youtube.com/watch?v=eCdrUW--Jic> [Answer] Women wanting to have children in this world would have a few options. 1. The "ideal" option is to get sperm from one of the 5 living men left in the world. This gives you a 50% chance of a son that's immune to the plague, and in either case you get a viable child. 2. Next, you can go to a sperm bank and get fertilized there. Without any filtering, you have a +50% chance of miscarriage, but you can at least have daughters. Eventually the sperm banks will dry up - that is, run out of viable sperm. This will happen either because the sperm all get used, or because they go bad. A quick search indicates that frozen sperm samples aren't reliably viable after about 12 years. If this is like the "best by" dates on food, the sperm don't suddenly stop working, they just provide lower and lower success rates dropping off after 12 years or so. 3. Go to a country where human cloning has been legalized and researched. In light of a serious threat to the human race's existence, at least *some* 1st world countries would look into human cloning once again. There's some problems with the process, but it's an option after sperm banks dry up. Add genetic manipulation, and you *might* be able to get some male clones with immunity to the plague whose genes aren't from your 5 remaining men. 4. *If* scientists find a cure, but it's too late to take advantage of sperm banks, then track down all the tribal groups\* which have no contact outside their community. Immunize them, and bring them into the developed world. Even if you have to lock them up, the men will be able to provide sperm for viable male children, increasing the genetic diversity available in the world. 5. There's also a good chance that space agencies (NASA, etc) would be wise enough to keep the ISS quarantined, and any men on board would still be alive. Find a cure, and you can add them to the gene pool, too. Even without a cure, they could contribute sperm which still produce viable daughters, even after sperm banks dry up. As a commentor suggested, there are also submarines which are routinely isolated for a few months at a time while on patrol. These will also provide some men to add to the gene pool. There may be other groups which escape infection through isolation when the plague strikes. \* Unless the airborne disease was a weapon and was applied intentionally to the whole world, or animals can be carriers, then at least *some* of these groups would escape infection simply because they live too far from any other humans to catch it from them. If scientists never find a cure, leave those groups alone. Even a few minutes' contact would extinct the group in 1 generation. (See [Uncontacted peoples](https://en.wikipedia.org/wiki/Uncontacted_peoples).) [Answer] Existing sperm banks represent a huge pool of existing genetic diversity. I think you could pick up a lot of genetic diversity by: * Finding women who are immune, or curing them. * Isolating them (bubble boy style). * Fertilize them. * Girls can just leave. * Boys need to be cured/immunized prior to leaving isolation. Further, women are capable of having children well past age 32. Doctors suggest not having children past age 40, because birth defect rates take off at that point. According to [this web site](https://www.ivf1.com/age-birth-defects/), 35-39 year old mothers will have an additional 1 to 4 babies with congenital heart defects per 1000. At age 40, it jumps to 30 per 1000... and that just the heart defects... Those numbers don't take into account other defects like club foot or diaphragmatic hernia. Many of these problems could be corrected given a large enough medical budget, and perhaps some research. OTOH, there's research (at that same link) showing that mothers under 20 are more likely to have children with specific defects, though it appears the rates are much lower compared to older mothers. ]

[Question] [ In the fantasy culture it's not uncommon to find Giant spiders with the upper body of a human. There are many variants as the spider body having only 4 legs and the upper human body have 2 additional arms or scorpion-like giant stings attached on the shoulders while some other variants even include ant-mimic spiders. For my question I will use what to me seems the most **classic** option: [](https://i.stack.imgur.com/abIkW.jpg) On a planet with conditions similar to Earth's, why and how would this thing evolve? Would it be capable of producing and using its own silk as in the image above, and if so, how much silk to be more precise? If this thing is anyway realistic,**how to make it even able to walk**? Bonus if you can describe its anatomy with precision, like if it's more convenient to give birth or lay eggs, or breath with the human part or the book lungs, and things like that. This question is part of the [Anatomically Correct Series](http://meta.worldbuilding.stackexchange.com/questions/2797/anatomically-correct-series/). [Answer] You guys are approaching this as if the only way for an Arachne to exist would be for it to be a giant spider thing without any modifications to its spider anatomy. This is silly. We all evolved from very small animals that lived underwater, yet here we are in human form. A much larger stretch than having arthropods growing into big sizes. Specially because in prehistoric times, we did have arthropods that were quite big. The largest arachnid ever was a [~1 meter long scorpion](https://www.researchgate.net/figure/Fragment-of-the-posterior-carapace-region-of-Praearcturus-gigas-Woodward-1871-NHM_fig1_269803090) (who was also kind enough to let me know about him [in the comments](https://worldbuilding.stackexchange.com/questions/51903/anatomically-correct-arachne/52163?noredirect=1#comment549799_52163) :)). That's a little over three feet. It had aquatic cousins [that could grow up to 2.5 meters long (that's over eight feet)](https://en.wikipedia.org/wiki/Jaekelopterus), though. Granted, these beasts had their weight supported by water, but look at that... An arthropod larger than a man! Not only that, but we know that there's less oxygen available in water than in air, so how could the square-cube law allow for that? Well, besides evidences that our atmosphere was more rich in oxygen millions of years ago, there is also the fact that those arthropods had **evolved their internal anatomy to allow for those sizes**. Let's go back to our drider, then. Yes, drider. It's easier to spell and more catchy than "arachne". Imagine if you will a prehistoric tarantula. It lives in a world where there is more oxygen available than Earth right now, because that's how prehistoric Earth was like. Our prehistoric tarantula is under many different evolutionary pressures, and a larger size is conferring it increased rates of survivability and reproduction. To allow for that, the tarantula starts developing, throughout generations, some unusual characteristics for a spider. For example, a mutation introduces a third body segment to it. This new segment will go in front of the cephalotorax, much like the head of an insect. It will contain the mouth, eyes, chelicera and pedipalps. It will also be filled with extra [book lungs](https://en.wikipedia.org/wiki/Book_lung). This will allow for more oxygenation. Over time, as this species of tarantula grows, it will evolve a circulatory system much like a worm's at first, then that of a vertebrate. A fourth, smaller body segment develops in front of the third segment, containing the eyes and chelicerae, but not the pedipalps. As for the abdomen, it resembles that of a reptile or amphibian more and more, with different organs going through convergent evolution to take the roles of a liver, a spleen, a pancreas and so on. Spiders have excretory organs in their legs, but this species's excretory organs move to the abdomen over time. Now, spiders are known for being very agile with their legs, and weaving webs with them. Our specific tarantula, though, is growing larger by the millenia, so its six frontmost feet are only used for supporting weight now. Eventually they will be completely flat and fingerless (yes, spiders have fingers - actually microscopic claws, which is how they weave and cling to stuff). Only the last pair of legs will have fingers for weaving. To make up for that, the pedipalps start evolving into manipulators. They evolve more and more segments until they end up looking like vertebrate arms with hands, again due to convergent evolution. Two more things are needed for this spider to reach a "drider template": * It will evolve a "neck" between the two frontmost segments, to allow it to rotate its "head". It may have eyes in all directions but the two eyes with the best sight are still fixed, and rotating a head is cheaper than rotating a whole body to better look at stuff; * The legs... Azuaron suggested that a drider would have to have its legs below the body and not splayed. I propose a midterm solution which is close to the anatomy of a real spider, so the legs should be fixed below the cephalothorax, as in the picture below. A drider is supported by eight feet, and they don't have to be incredibly heavy for their size, so I think this setup works. [](https://i.stack.imgur.com/Ejigw.jpg) Source: [this page at Deviant Art](http://reno-viol.deviantart.com/art/Drider-2-413520840). I estimate that, once the two first segments (head and "upper torso") reach the size of an adult human, the drider should be 6 feet tall and six feet long in a rest position, giving it an "L" shape somewhat. But it can put itself into much taller or shorter stances easily. It should weight 120 kilograms (approximately 265 pounds), with its weight divided almost evenly among its eight feet (the hindermost feet would support a smaller fraction of their weight), so on average each foot would be supporting 15 kg / 33 pounds. [](https://i.stack.imgur.com/lvmOR.jpg) (More mythical creature greatness. I found this picture in an image board. It had no source, but I'd bet my soul it comes from [Drowtales](http://www.drowtales.com). Go read it. Great webcomic with an awful lot of spiders in it.) Such a drider would probably be warm-blooded, with all the adaptations required for that. It should eat at least as much as a human with the same weight. Everything else is just cosmetic details. Here is how I would have it: * The head looks like a human's due to convergent evolution (evolution usually places most sensory organs in a head) and blind luck/coincidence. They probably have no external years and their noses will be kinda different from ours. The freakiest part may be them having six to eight eyes. * The upper torso looking human would be pure blind luck. They would probably be furry all over, even females, less than a spider but slightly more than a human. Females won't have breasts like mammals do. * Remember these beasts have external, not internal skeletons. Even if they develop a hide or skin in the upper torso that looks like ours, it will still have plates of chitin underneath. Their upper torso belly will be hard as a rock. * They could easily evolve hair out of the hair that spiders already have. Why they would evolve hair would be a mystery, just as it it a mystery to me why we have hair like we do. * Spiders have no actual brains... like insects they have ganglia. But [the arachnid ganglia are all fused together and the bulk of it is located around the esophagus in the cephalotorax](https://en.wikipedia.org/wiki/Spider#Central_nervous_system). A drider would have a very interesting neural anatomy, with a very long, diffuse "brain" surrounding the esophagus, going from the upper torso neck to the part where the original cephalotorax connects the abdomen. * Speaking of which, they don't have a backbone, so no medula as well. Also no ribs, if it wasn't clear enough when I mentioned chitin plates under the skin. * Last but not least, they are, as James pointed out, separated from humans by a long distance in the tree of life. Their physiology would be alien compared to ours. [Any medicines and drugs will potentially have completely different effects on them compared to what they do to us](https://en.wikipedia.org/wiki/Effect_of_psychoactive_drugs_on_animals). If you research enough into that you'll see that many invertebrates species have synapses and neurotransmitters different from those of vertebrates. In the very least, a doctor would have to learn medicine again practically from scratch to be able to help a drider. A last, anecdotal commentary on that: spiders are so unlike humans, that [coffee makes them less able to concentrate, but LSD makes them get into the flow somehow](http://fractalenlightenment.com/600/chill-out/spiders-weave-better-on-lsd-25). I suppose that's because the arachnid brain already sees the world as a web of interconnected things or something like to that effect. [Answer] Sorry, but you've once again run into the dreaded [square-cube law](https://en.wikipedia.org/wiki/Square-cube_law) (it's the LAW). The largest spider is the goliath birdeater, which weighs a spectacular... 6.2 ounces. There are crabs with splayed legs like that, of course, and they get much bigger. The coconut crab weighs in at an amazing... 9 pounds. The simple fact is, you can't have legs like that and weigh that much. To support that much weight, you must have legs directly beneath your body. The seminal paper on this is [On Being the Right Size by J. B. S. Haldane](http://irl.cs.ucla.edu/papers/right-size.html). What determines an animal's strength is the cross-section of their muscles and bones, which is an area (unit: meters *squared*). What determines an animal's mass is (roughly) volume (unit: meters *cubed*). So, if I double in height and become 4x as strong (2 *squared*), I'll have the problem of being 8x as heavy (2 *cubed*). 10x the height, 100x as strong, 1000x as heavy. Very quickly, I will not be able to breathe, let alone stand. Splayed legs are great for small creatures (allows quicker darting movements, greater stability and surface area for climbing), but impossible for large creatures (can't support the *cubed* increase in weight). [Answer] To create a creature which looks half-spider and half-human, you must reject the concept of it being primarily based on the anatomy of either - trying to graft a human torso onto a spider isn't going to work, but something similar could be produced from novel origins. Exoskeleton don't work for a human-like portion, nor does it permit legs capable of supporting the larger body size, so somewhere along the line an arthropod (before spiders fused head and torso) made a switch to a partial endoskeleton (with the exception of the thorax and abdomen which maintains a chitinous shell). In earlier evolution, it had a protohead (with palps), thorax (with legs), and abdomen. As it started to go for food above it (easier than trying to shift its weight onto just back legs as it got heavier), it developed a stiffened ridge on the inside of upper protohead to provide better structural support - this eventually became retained during molting (such a large creature probably has a very long delay before the new exoskeleton hardens into sufficient structural support) and eventually became the spine. Likewise, in order to support the ever-larger body, the legs developed similar structural reinforcement which was no longer discarded with molting. Eventually these extra structural supports became more and more predominant as the creature grew in size. One divergence with a spider development is that these creatures developed leg function more like insects, so they use muscles instead of hydraulics, which those attached to the permanent support would be more effective than the weakened exoskeleton, making this functionally more of an endoskeleton musculature structure. This permits legs capable of supporting great weight without needing excessively thick exoskeleton (only a vestigial thickness on that). It began to develop the ability to push out its mouthpards and sensory organs a little while searching for food, until eventually this became a kind of stalk-like appendage. Greater flexibility in this led to its exoskeleton not fully hardening around this part, and eventually further segmentation of the protohead appendage into what we will now call the head (containing the mouth and sensory organs) and the bulk of the protohead becoming the torso (with the palps). The torso used great flexibility (easier than moving around the massive bulk of the body), which favored ever-thinner exoskeletons, but more developed structural support ridges - eventually something roughly akin to bones. The palps obviously developed greater dexterity, and even more developed digits (better manipulation of stuff), while dispensing with the molting exoskeleton. Evolution is imprecise - those mutations got the head and whole torso to eventually end up with an endoskeleton and thin non-hardening skin instead of an exoskeleton. Most of the head retained a patch of exoskeleton - more of a helmet-like protection than body structure, upon which hairs grew considerably longer than before (weird mutations sometimes persist and perhaps this helped protect the exposed skin of the head and torso a little). With the transition may also have been a transition to an exothermic metabolism (to better cope with potential loss of insulation) if so desired. Now we have a roughly human looking upper half. You can even throw in some similar internals like a heart in the central torso to help pump hemolymph all the way up into the head (the big heart in the abdomen might not be enough), and maybe lungs as well (secondary just for ease of oxygenating the upper parts - perhaps a tracheae type path to a lung cavity which eventually merged with the esophagus), and even a brain in the head (close to the eyes and mouth so that bit of neurology specialized there leading to higher brain functions - though the parts of the brain most responsible for locomotion would be in the thorax or abdomen). The thorax would likely be an extremely tough mass of heavy exoskeleton to support the weight of all this plus be a central point for all the legs. I would probably think of it as a bowl like pelvis for the 8 legs, plus neural tissues sitting on top of it to coordinate the spider half. The middle of this bowl-shaped structure could sit digestive chambers (like a spider) to hold nutrients for the legs and leg-brain before passing the rest back to the abdomen for wider circulation. The abdomen would probably be the most spider-like. A hindgut, a heart to pump hemolymph throughout the body, book lungs, etc. etc. I see no reason why it couldn't have silk glands and spinnerets for silk production. The reproductive strategy of larger organisms tend to favor small numbers of live births than lots of tiny young. Gestating a large well-developed child for a year before giving live birth could even give reason for human-like breasts - mammary glands could evolve to suckle such live young, whereas egg-laying makes this implausible. Alternately instead of specialized mammary glands, a more spider-like solution is a pair of foregut ceacum (part of the digestive system into which the female diverts easier to digest or already digested foods) which hold material to then be discharged out a couple of ducts for feeding young (like birds pre-chewing food, just not coming out the mouth). A more complex and interesting breeding cycle would have significant gender dimorphism. Female offspring are gestated individually before live birth, then raised with significant maternal investment, while developing on similar timelines to humans. Males are laid in clutches of eggs and not especially cared for - the comparatively tiny males lack significant intelligence, grow to breeding age quickly and are not long-lived (only a few years?), perhaps even lack the more human components entirely. Environmental factors could significantly determine which strategy is pursued in that female offspring are gestated when there are ample resources which could be devoted to expensive offspring, while males are often produced during lean times when the mother has little investment beyond producing the egg sack. Females develop civilization, while males are more like short-lived small dogs kept as pets. [Answer] The top answer on here uses convergent evolution as an explanation for why a giant spider would develop a semi-humanoid appearance, but I'd like to suggest an alternative model: mimicry. Spiders are among the most prolific mimics in the animal kingdom, and often adopt the appearance of other species in order to deceive predators or prey. Take a look at the following image, which shows both an ant (on top) and a jumping spider (below). [](https://i.stack.imgur.com/qrc0I.jpg) Something else we know about fantasy worlds is that they tend to have a superabundance of large, predatory creatures that love to prey on humans; manticores, giants, ogres, dragons etc etc. Therefore, it seems we have an evolutionary niche available for a species that exploits this habit in order to prey on them in turn. How it works is as follows. The human 'torso' on an Arachne is in fact nothing of the sort; it's an elaborate lure made of chitin, which contains no essential organs but can be made to twitch in a rough approximation of human motion. This is similar to living lures exhibit by many real-world ambush predators (the Alligator Snapping Turtle, for instance, has a fleshy extension to its tongue which it flicks about in imitation of a worm, luring hungry fish within reach of the turtle's jaws). The rest of the Arachne's anatomy and behaviour partially resemble a scaled-up funnel-web spider. It hunts via deception, not speed, so it doesn't mind so much about the square-cube law; rather than supporting it, its legs drag it slowly along the ground while it weaves a web of sticky strands along the ground in a circle around it. Next it uses its thick back legs to dig itself into the soil at the centre of the web (note that many of the largest real-world spiders burrow), burying its hind-quarters and leaving only the humanoid appendage visible. Then it waits patiently until a wyvern or some other large predator sees what appears to be a delicious human snack and comes over to investigate. As soon as the predator lands or comes near, it will become ensnared in the tripwire-style web, at which point the Arachne drags itself over and injects the target with paralysing venom. It can then drain the unfortunate monster of vital fluids at its leisure. An added bonus of this hunting system is that supplies a supplementary diet of unwary human adventurers, who come either to slay the 'sleeping' wyvern or to save what appears at first glance to be a damsel in distress. As for the evolutionary history of this spider, I imagine it to be one of a group of mimic-spiders who evolved from some large prehistoric tarantula. The earliest breeds found that mutant head-growths which resembled worms (or something similar) were useful at luring over small mammals and birds, and from there they slowly evolved ever-more sophisticated lures. The Arachne's ancestors steadily grew in size in order to be able to tackle larger targets, and during the last few million years have developed the humanoid lure to attract those species which preyed predominantly on hominids, and then on modern humans. [Answer] The square-cubed law is a big problem, and makes this creature impossible. But another problem exists and that is the fact that this is a hybrid. **Not only is this creature a hybrid, but it is a hybrid of two creatures drastically removed from each other on the evolutionary tree.** Take a look at this. [](https://i.stack.imgur.com/Y6J8b.jpg) The further you have to go back to find a common ancestor the more difficult it becomes to have a plausible hybrid...and in the case of the dryder you have to go way way way back. Arachnids are invertebrates and their systems are completely foreign to what makes up a human. Finding a plausible way for the two systems to work together is simply not possible. Thus **the answer is magic on this one.** * Creating a centaur: Difficult * Creating a bird person: Very Difficult * Creating a kangaroo person: Super Very Difficult * Creating a platypus person: *Awesome* * Creating a Spider Person: Super Duper Very Difficult (also known as impossible) [Answer] Not sure how to help with the size of the spider. The max you could get (and even this is probably pushing it, due to differing anatomy) is the size of a coconut crab. [](https://i.stack.imgur.com/99UsN.png) This is a pretty big creature (I believe some specimens have leg spans of 3 feet), but it's nowhere near the size of a human. However, in regards to the torso, getting it to look fully human is an issue, but might I suggest something somewhat similar. [](https://i.stack.imgur.com/LRg32.jpg) This is a Pelican Spider. They're quite small (only 2 to 8 millimeters long), but their head shape could work (I don't see why it couldn't evolve in a larger spider). Their long fangs could take the place of arms as they are used to grab prey (probably no way to have fingers though). I understand if this isn't what you're looking for, but I found it fairly interesting. [Answer] If it evolved on a planet *similar to Earth* then all issues regarding respiration and taxonomy are irrelevant. So, millions of years ago a large decapodal silk-producing organism existed on a planet similar to earth. It has an endoskeleton as well as a chitinous exoskeleton. Its foremost limbs developed into humanlike arms so that it can better manipulate objects in its environment. The front portion of the body became a torso to increase the reach of the arms in any direction. Then a defined head, neck and shoulders develop. The exoskeleton on the torso disappears for greater flexibility. The hindmost portion of the body grows into a distinct abdomen to counterbalance the torso and so there is more space for internal organs. They then become social for protection and food and their intelligence slowly increases over the next hundred thousand or so years. The similarities between their facial features and that of a human's are simply convergent evolution. Hair is optional. [Answer] An arachne could evolve from a spider that evolved to have looping digestive tubules. They may later evolve to actively pump fluids through this system, which may become more separated from the intestine. Eventually, the digestive tubules will be completely separate, and full of a distinct fluid. This may take on the role of blood, entering the prosoma and replacing the hemolymph. In order to make the blood more efficient, some vessels may expand and transform into a gland that produces an oxygen-carrying pigment, such as hemocyanin. There may still be digestive tubules that do not loop. These tubules, not needed to spread food through the body, might become glandular and fuse into a hepatopancreas. They may increase in size, due to predation. In order to support themselves, they may harden and expand their endoskeleton. Their endoskeletom may become their primary skeletal system, as is is better protected against predators. They may also become able to pump their trachea, eventually turning them into true lungs. They would also need to get rid of more waste, and so the malpighian tubules and coxal glands might expand and become more efficient, until they become similar to the kidneys of vertebrates. They may gain irises in the central eyes, which would allow these eyes to become more powerful, but would lead to the lateral eyes being lost and reduced. Due to the loss of the lateral eyes, they may gain a joint in the carapace around the eyes, mouth, pedipalps, and chelicerae. This regoin may extend outwards, to allow a greater range of articulation, allowing them to see in more directions without needing to move their prosoma. The pedipalps may split at the ends, in order to grab food and bring it closer. This may lead to the pedipalps bending backwards, to allow food to be brought to the body, so that the spider's young can more easily be fed. The pedipalp's motion might cause the maxillae to turn up, and oppose the chelicerae, which would adapt accordingly. The maxillae might become fixed together, as a jaw. Due to the lack of attacks to the head, the exoskeletom may be reduced in that region, which might turn the maxillae and chelicerae into fleshly jaws which can hold liquid. This would allow their diet to expand, allowing them to gain more energy. They might use this energy to become endothermic, allowing them to become more active without the need to stay in the sun to warm up. The fleshy jaw would also be a good guard against solids entering the mouth, which could lead to many groups losing their oral filters. They may begin to live together, in familial groups. Another adaptation may be gaining sound-sensitive setae on their head. These setae might lead to pits in the head to focus sound, which may later turn into deep cochleae, with an eardrum to help pick up sound, and a pinna surrounding it to make sounds easier to pick up. They may evolve to squeal using their stomach, as a way to alert members of their family to approaching threats. This might make the frontal gut-loop take on the role of stomach, with the stomach becoming soley for sound production. Another effect may be that olfactory receptors might appear in the throat and mouth, so that the creature could inhale air to smell it. In order to look around more easily, the root of their maxillary bone might become cartilagenous, to allow some motion of the head. This trend would increase until the maxillary bone is completely disjoint from the scapula, and the head is attached to a neck. The changes of the gut and jaw might allow them to consume solid food. This would lead to a more solid jaw, with the chelicerae fixed under the skull, the maxillae fused as a lower jaw, and both appendages bearing bony spikes similar to teeth. However, there may still be channels above the chelicerae, which allow air to flow into the throat while the mouth is closed. They might also add plants to their diet. This would lead to their teeth-spikes changing, so that the rear teeth might become square, peg-like molars, in order to chew through fibrous plants. They would also need cheeks to prevent the food from being lost from the sides of the mouth. At some point, humans may come into their habitat, and hunt them due to their strange appearance. They might evolve to become more intelligent, to try and avoid and outsmart the humans. They might evolve to use language, which will require several changes, such as the labrum being freed from the lower jaw as a tongue, and the region between the cheliceral fangs broadening into an alveolar ridge. These changes would make them into an arachne [Answer] A quick short answer: Things that evolve can't de-evolve to gain new abilities, be them any better. We can't get worse than we already are. If they evolved from humans, it wouldn't be feasible outside of artificial genetic modification. They would need to de-evolve their good legs for worse spider legs then best spider legs, which is impossible. If they evolved from spiders, it wouldn't make sense, because it would have to change pretty much every thing about their respiratory systems, size, prey, and things like that. Smaller things breath VERY differently compared to us. So much so that smaller creatures would just die if they get too big without evolving different respiratory systems. They square-cube law would also make it harder for the air to get to them, as they breath through tubes as of now. They just wouldn't be able to evolve in that way without being worse for a period of time, which would likely make them unable to reproduce, killing them off. [Answer] It's possible but unlikely. The ratio between the surface area and volume of a creature increases exponentialy as it get's bigger, thus a large arachnid body would be largely unable to support it's own weight.If an animal were isometrically scaled up by a considerable amount, its relative muscular strength would be severely reduced since its mass would increase by the cube of the scaling factor. As a result of this, cardiovascular and respiratory functions would be severely burdened. [Answer] They have already repeated it a lot, the biggest problem is weight support due to having to follow the cube-square law. So maybe this will not be the most important aportation, but I read some "escapes" for this. 1. Could molt in sections instead of all at once, like some crabs. 2. "I am not sure how resilin and other flexible proteins would act on a larger scale. But if you play around with the alpha, beta and gamma chitin ratios in both mobile and immobile parts of the exoskeleton insects should be able to support a large weight while maintainaning mobility". So keep in mind though that if you fix the oxigen circulation in insects, their metabolism will most likely increase as well, especially in warm habitats. [Answer] Okay, we have an humanoid upper body, which we’ll assume has a mass of 46.7 kg, and an arachnid lower body, which we’ll put at 3 feet, or .914 m, long. The largest spiders have an body length of .09 m, or less than a tenth of that, and have a mass of .175 kg. Scale that up, and we have a mass of 184 kg, and 8 legs=8 support structures. The total mass is about 230 kg, and spiders can lift 170 times their mass. As size increases, proportional strength decreases in an linear and inverse relationship, so scaled up, you’re looking at a being who can lift up to 2.84 tonnes. I figured that out as mass increases cubically, and strength increases quadratically with size, and thus, n^2/n^3=n^-1. [Answer] ## Diverge just before the rise of Tetrapods You're creature resembles both an arachnid and a mammal, but these two groups of animals diverged a VERY long time ago. Arachnida are already too far down the evolutionary rabbit hole to just switch to an endoskeleton and centralized pulmonary system, and mammals are already too far committed to the tetrapod body plan to just spring for an extra 6 appendages. So instead of going back to some where an ancestor might look like something between a spider and a person, you should go all the way back to this planet's origin of animals by looking out how our Phyla diverged in the very early epochs of macroscopic life. There are many answers already stating why giant arachnids would likely not get you the desired result, so instead I will focus on how one might arrive at this body plan following an evolutionary path more similar to the human part. Back when human and spider ancestors all still looked like worms, two groups of worms emerged called Ecdysozoa and Deuterostomes. The Ecdysozoa favored less centralized body mechanics which would eventually lead to spiders where Deuterostomes favored more centralized systems. The proclivity of Deuterostomes to specialize in centralization led to the Chordate which in turn further specialized into the Vertebrata. Basically, it was a huge evolutionary push towards centralizing things that eventually lead to fish having internal skeletons, central pulmonary systems, and all the things that form the foundation human like life forms. Basically you just keep following this general evolutionary path until you hit something like Sarcopterygii (lobe-finned fish). It was at this particular evolutionary junction that Tetrapods evolved to eventually become humans, and this is where you need to make your split. While Tetrapods gave us our 4 appendages, back when lobe finned fish were still fish, they could have had any number of appendages and still be evolutionarily viable. So instead of your planet's "reptiles" "birds", "mammals", etc. all evolving from a primordial 4 finned fish, they would have come from a 10 finned fish instead. Then, just like arthropods specialized into classes with fewer and fewer limbs; so too could your world see some groups that lose limbs as evolution marches on while others retain them. At this point though, your ancestor is already very mammal or reptile like complete with teeth, eyes, lungs, heart, brain, etc. with the only key difference being 10 limbs instead of 4. From here it is just a matter of convergent evolution. Your 10 legged creature will take on mammal like traits including fur and hands. It could even evolve armor plates similar to an exoskeleton the way that armadillos have. Eventually one group that prefers tree-dwelling would have enough evolutionary pressure to develop webbing and/or opposable hands. As the creature evolves more towards intelligence and tool usage, the forward part of its body will begin to curve up and become more flexible freeing up the hands for better tool manipulation while leaving the other appendages as feet. This adaption would happen for the same reason humans evolved towards bipedalism. > > Bonus if you can describe its anatomy with precision, like if it's more convenient to give birth or lay eggs, or breath with the human part or the book lungs, and things like that. > > > Following the pattern of centralization you see in this animal's ancestry, it will have a heart and lungs similar to a human's that fill up the human like part putting them closer to the nose for more efficient respiration, then the spider like abdomen would contain the digestive and reproductive organs. Since you are describing a large and intelligent species, you are best off with a K-selected reproductive strategy. While this could technically be done by egg-laying or live birth, the more important question to answer will be how many children your Arachne has at a time. Instead of making hundreds of offspring like spiders do, these creatures will likely lean towards 1 child at a time like humans do to make sure they can commit the resources they need toward education. [Answer] While evolution can make an arachne-like creature, you'd need to involve some design for a true, lone spiderhuman * Firstly, the human and spider parts will need to be connected together. The most common way to do this in most depictions is for the human part above the legs to be set into the spider's face above the chelicerae. This seems like a good basis for an arachne * Secondly, we'll need to make sure it can support itself at its size. They'd need some sort of internal skeleton for support. The walking legs and chelicerae could contain a tetrapod-like structure with many repeated stylopods to form the correct amount of segments for the limb. However, this system may be insufficient for the pedipalps; these structures would benefit from having a jaw-like system in the maxillae, that could be used as a shoulder for a tetrapodal limb in the rest of the pedipalp. The skeleton of the torso would need to surround the organs. One solution, that seems good enough, would be to have a single pelvis structure on each side, with 4 joints to which all of the legs connect. The maxillae would have hinge joints, and could connect to the front of the multipelvis by a 5th joint. The organs could be supported by a ribcage-like structure set below the sternum, which would provide support for the organs. The carapace can remain exoskeletal. The pedicel would be wider, and have strong bones and muscles. The abdomen would have to be much smaller, and could have something similar to the sternum-bone for support * The organs will similarly have to be adapted. A human's mouth seems far too small for an arachne, and spider-like digestion is inefficient. One solution could be giving the spider part an enlarged humanoid mouth and stomach, which would be the main way they eat. A similar substitution could be done with the spider's heart and lungs, with the addition of a closed circulatory system. The intestines could be kept roughly as they are (with many tubules from a straight intestine), especially if there's some way to filter out indigestible matter at the base of the tubules. The leg-based section of the intestines will probably have to be removed, though. The reproductive system may also need to be reworked for a live birth. This could be achieved by adding a humanoid uterus under the spermathecae * The two bodies (alongside a few other parts) will also need to be connected. The chelicerae might be attached to the human pelvis. The spider part's humanoid jaws will also need to be connected. One way would be to add in a pair of bones which would fuse to the maxillae and provide a joint for the mandible. The whole system could be opened and closed by masseter and pterygoid muscles. Both of these systems might be supported by a pair of rib-like structures in the front of the carapace. On the organs, the human part could have a large stomach filling the abdomen with a short duodenum that connects to the front of the spider part's intestine loop. The spinal cord will also need to extend beyond the spine and go into the spider's brain * Finally, we need arachne to be able to develop from an embryo. One plausible sounding method is this: First, the embryo develops as monoamniotic twins in the human. One of the twins will develop as a human, and the other will develop more like a spider, receiving nutrients from a yolk that is fused to the uterine wall. The humanoid/tetrapodal parts will develop in a more tetrapodal way. The legs specifically could grow as complete replacements for the spider-type limbs. The spider maxillae could be derived from pharyngeal arches, which would be required for the humanoid mouthparts. The human twin would also develop chelicerae in place of legs. At some point, these twins would have to fuse together. This should happen early on. At this point, the neural tube should extend to combine with the spider's nerve cord, and the end of the human gut should be extended to connect with the spider's intestine ]

[Question] [ You're an alien that really likes pyrotechnics. Nothing that goes *boom* on your home planet (in a safe and responsible manner) satisfies you any more. Why not blow up a planet and see what that's like? However, you're not allowed to do that in your home solar system. The next closest one is ours. Oh, but there are humans on Earth; they can't stop you, **but you don't want to hurt them either**. You're a bit crazy, but you're not a sociopath. You just wanna see the biggest planetary fireworks show possible. In short, **which is the most massive celestial body in our solar system that you could destroy without endangering human life on Earth**, subject to the following constraints? * You don't want to harm humans, so you definitely can't destroy the Earth, Moon, or Sun. * It's okay if there is collateral damage, as long as that damage does not include human life (directly or indirectly). + This implies that human artifacts (like the Curiosity rover on Mars) on other bodies can be destroyed, even if they're in active use. * This is in the present day, so the only people off the planet are in orbit (like on the ISS). You don't want to hurt them either. * It's okay if you're detected before, during, or after the show. You're not interested in stealth. + This implies that there may be mass panic on Earth. That's not your problem, though. * You don't want to stick around or communicate with humanity. Get in, explode, and get out. + They might try to contact you, but you just ignore them. + You won't be around long enough for them to be able to attack you. * You don't want humans to have to accommodate your little stunt (e.g. humanity shouldn't have to move underground for a few months). * You do not have any way to prevent collateral damage except by careful planning. Better pick your target carefully. The method that you use to actually destroy the body isn't relevant as long as it meets the following conditions: * You can pick with surgical precision which planetary body to destroy (i.e. you can pick Saturn but spare its moons). * You have fine control over how much energy is used. So you can avoid introducing excess energy (thus releasing massive heat or radiation). [Answer] ## Ganymede No matter which one you go for, blowing up a planet is going to make a *lot* of shrapnel. An asteroid of several miles long is an extinction-level event, and you've just thrown millions of such asteroids, along with billions of smaller meteors, all over the Solar System, and mass tends to fall towards gravity wells. Chances are, enough of those are going to hit the Earth to give humanity a bad day. If you want to blow something up, your best bet is to aim for an object that is *already* mostly constrained to a gravity well, minimizing the shrapnel that you'll be dealing with. Fortunately, the biggest moon in the Solar System is also close to the second-biggest gravity well. If you blow up Ganymede, most of the shrapnel will form a fancy ring around Jupiter instead of peppering the inner planets. [Answer] **I'd strongly suggest your Alien to blow up Neptune or Uranus (latter would make for a nice joke, too)** Saturn and Jupiter have too many moons. With that many moons, you're creating a fleet of rogue-objects that could potentially start a chain-reaction and murderdeathkill everything on Earth. Also too much risk for your Alien. So Neptune and Uranus. Neptune: Fewer moons than Uranus, most are smaller, too. Triton might be making trouble, but that should be okay. Uranus: Funny joke, iirc slightly bigger than Neptune and looks prettier. Blowing pretty things up is funnier, isn't it? Conclusion: don't blow up Jupiter or Saturn. The others are fine, but as size matters (im going strong with the jokes today), Neptune or Uranus should be your Alien's target. And most importantly:Do NOT hurt Pluto. Edited out because scientifically unaccurate (could still be added via hand-waving): > > As one can read up on [this question](https://astronomy.stackexchange.com/questions/1133/is-the-jupiter-sun-system-considered-a-binary-system-of-some-type), Jupiter does not orbit the sun. Both J and S orbit around their combined center of mass wich rests just outside of the sun. By destroying jupiter, you might disturb the suns orbit and screw everything up. So that's probably too risky for your alien. > > > [Answer] The answer is go for the biggest and the best. Blow up Jupiter! If Jupiter can be destroyed with surgical precision, so we can safely assume its moons will be left intact, then the collateral damage will be minimal. More so, if your pyrotechnic explodomaniac alien waits until Jupiter on the other side of the Sun when the explosion occurs. Jupiter is approximately half a light hour distant from Earth. Its moons will be mainly in Jupiter orbit. While the Jovian barycentre is dispersing across the solar system, the moons will retain their velocity around the Sun and any additional velocity they effectively acquire due to their orbital velocities around Jupiter. Generally this will mean the moons will either move into higher or lower heliocentric orbits. Essentially they will be half a light hour away from the earth and the centre of the solar system, so the Sun and the Earth are safe. The OP hasn't specified the precise method for making planets going KA-BOOM!! So it is possible that whatever remains of Jupiter might constitute hazardous materials and fragments for the inner solar system. But this should be considered as quite unlikely because the orbital velocities of Jupiter and its moons indicates that Jovian matter and the moons will remain far from earth. However, if the aliens are zealous in their regard for human life they enjoy taking pot shots and blowing up any fragments that might be heading towards the Earth. But if their method for precisely demolishing Jupiter is sufficiently precise, then they could be capable of blasting Jupiter away from the Sun. Shoot so it gets blasted out and away. This means there shouldn't be problems for the sky falling in on Earthlings. [Answer] There are a number of ways to annihilate a planet to consider, all of which have different effects. In addition, it depends on the interpretation of "not harming humans" both in terms of timescales (within the next year, next millenia, next million years, etc.) and in terms of harm (not killing/injuring immediately, not increasing likelihood of death or injury, etc.). ## **Blow it up** This leaves large fragments (=asteroids) floating around,some of which are likely to cross the Earth's orbit, with a likelihood of collision. A collision definitely falls under the category of harming humans, but in the short term, not something that is likely to happen. It also removes a gravitational well from that planetary orbit, which had its own effects. In the case of the gas giants (especially Jupiter), they sweep up much of the asteroids and comets that could threaten the inner solar system (and thus us), providing a shield. They also have large numbers of moons whose orbits would change, possibly sending then careering off in random directions, with one or more likely to cross Earth's orbit. So, if "not harming humans" means "not immediately harming humans", then anything, other than the moon, is possible. (The moon, tidally locked to the earth, performs several vital functions, one of which is keeping the earth steady on its axis. If it were to be removed, earth's rotation would become chaotic (like that of Mars) and our current, predictable seasons would eventually vary wildly.) If it means "not in the next hundred years" then I would add Venus, Mars and the gas giants to that list of no-goes (due to the likelihood of creating a large number of earth-crossing asteroids). If it means "not significantly changing the risk to humanity in the next million years" then probably only Pluto or any of the Kuiper Belt or Oort Cloud objects would be feasible to blow up. --- ## **Reduce it to insignificant pieces** The main effect of this would probably be the loss of gravitational well, but depending on how spread out the particles are, that might not be significant, and they would coalesce back into a (slightly smaller) planet over the period of a few million years. If the particles are widely spread out, we would have a problem with loss of gravity well. --- ## **Vaporise it (convert to energy).** I'm not sure what the minimum safe distance for watching the mass-conversion of a planet might be, but it is likely to be quite far. Without doing the sums, I would hazard a guess that only the smaller asteroids and anything in the Kuiper Belt or Oort Cloud would be suitable for us to survive the blast of radiation. It would, however, be very flashy! The loss of the gravity well would probably not be a problem with those small distant objects. If we assume that Jupiter was vaporised, and that it produced the same amount of energy as the fusion process in the sun (0.7% mass conversion into energy) it would produce 1.2x1042 J. For comparison, the Sun puts out an average of 3.846x1026 W, so if the explosion occurred over 10 seconds, it would be about 3x1014 times more energetic than the Sun, and outshine the entire galaxy (about 100 billion (=111 stars). If we assume that Jupiter was on the opposite side of the Sun from the Earth, it would be 968 million km away, and the energy flux would be about 1016 W/m2 at the Earth's distance, lasting 10 seconds. A similar calculation for Neptune results in an energy flux at the Earth's distance of 4.6x1013 W/m2. Now, the Sun is very opaque to radiation (it takes about 4 million years for photons to make their way out of the core), but I don't think it's going to be sufficiently opaque. By comparison, a [Type II supernova](https://en.wikipedia.org/wiki/Type_II_supernova) puts out about 1046 J over a period of about 10 seconds. A Type II supernova occurring 8 parsecs from the Earth [might destroy more than half the ozone layer](https://en.wikipedia.org/wiki/Near-Earth_supernova), producing an average flux of 3.05x1010 W/m2 at the Earth, so vaporising Jupiter would produce about 330,00 times more radiation on the Earth than the supernova. Neptune would produce about 1500 times more radiation. I don't think that any of the gas giants would be a good choice to vaporise, even on the opposite side of the sun. --- ## **Convert into a black hole** (**EDIT: I've done some very rough calculations, using <http://xaonon.dyndns.org/hawking/>, and come to a different conclusion than before.**) This would be rather dull, as the planet disappears into a tiny black hole. For example, a Jupiter-mass black hole would be 2.8m in radius, and be barely detectable as its temperature would be barely be above absolute zero. It would evaporate too slowly to notice (well in excess of the lifetime of the universe so far at 1.82x1058 years. (I'd previously thought that it would evaporate soon after forming in a flash of gamma rays, but apparently that's only true for really tiny black holes which are also a lot hotter.) As a result, just about any planetary object can be safely converted into a black hole; either they're too large to noticeably decay, or they're too small to put out the kind of energy that might harm us. The loss of the gravity well would not be a problem with those objects; the larger ones with a noticeable gravity well would survive for a very long time, and the smaller ones wouldn't have a noticeable gravity well anyway. [Answer] While you could certainly blow up Jupiter, being the largest of the bodies in our solar system, I think the biggest factor is distance here, not size. In other words, the riskiest body to blow up is likely Venus due to its relative distance to Earth. Though the pieces would go in every direction, the amount of space it would have to traverse before it reached Earth would be enormous. As a result, very little, as it turns out, would reach earth, and the pieces which do end up orbiting Earth would burn up in Earth's atmosphere. The truly dangerous pieces would have to have a straight trajectory and would have to be several kilometers in size, something that is not likely to happen statistically. Most of the debris would simply follow its natural orbit around the sun, and although some would fall back together due to gravity, it would not reform any resemblance of a planet until much much later. TL;DR - In other words, distance, not size is relevant, and the distances that you'd have to traverse to get to the planets in our solar system mean the really only truly dangerous planet to blow up for the inhabitants of Earth would be Earth itself. [Answer] Did you ever hear of the Endor Holocaust? You can find sites on the internet that argue for and against the Endor Holocaust, the theory that the Endor moon would have been devastated by the explosion of the second Death Star. <http://www.businessinsider.com/endor-holocaust-star-wars-science-physics-2015-12>[1](http://www.businessinsider.com/endor-holocaust-star-wars-science-physics-2015-12) And what about the Yavin IV holcaust? What happened to the habitable and partly jungle covered fourth moon of Yavin when the expanding cloud of gas that resulted from the explosion of the first Death Star struck Yavin IV? Could any life survive on Yavin IV? Did the rebels have to rapidly evacuate Yavin IV before the shock wave from the Death Star struck the moon? And what about the deadly radiation emitted by the explosions? Would everyone and all life forms on the near sides of Endor's Moon and Yavin IV receive fatal does of radiation or perhaps even be instantly vaporized even at distances of thousands or millions of miles? The only way to know is to have someone do the calculations and see. In the meantime I would guess that it might not be safe for Earth and Earth life to blow up even distant Pluto. So maybe the explosion loving alien should take his super bomb into interstellar space and explode the planet buster in empty space. Thus he can see a very, very, very, very, very big explosion. If the explosion loving alien needs to see a huge object be destroyed, maybe he can go the Oort Cloud in our solar system (his fellow aliens would prefer he does it in our solar system instead of theirs). The Oort cloud can be considered to both be in interstellar space and in the outer reaches of our solar system. The Oort cloud is believed to consist of an inner torus shaped cloud of comets stretching from 2,000 to 20,000 Astronomical Units (AU) from the Sun and an outer spherical cloud that stretches from about 20,000 AU (0.32 light year) to about 50,000 AU (0.79 light year) or possibly several times that distance from the Sun. It is believed that the billions and trillions of comets in the outer Oort cloud may have a total mass of about 5 earth masses. It is believed that the inner Oort cloud contains tens or hundreds of times as many comets as the outer Oort cloud. So the bang loving alien can spend centuries, or millions of years, or however long it takes, to change the orbits of trillions of comets in the Oort could and assemble them into a planet large enough to satisfy his lust for explosions and then blast it with his planet busting bomb. And maybe that will be far enough from Earth that the radiation does not kill any Earth life. And maybe that will be far enough from Earth that the expanding sphere of gases will not destroy all life on Earth. And maybe that will be far enough from Earth that the expanding sphere of debris will not be thick enough when it reaches Earth to cause any extinction level impacts. Or maybe the alien will build not one planet but two planets that orbit each other. And when the planets are lined up with the inner solar system he will explode the planet that is farther away from the Sun. And the planet closer to the Sun might shield the solar system, absorbing radiation and shock waves and debris and creating a safe shadow that covers the planets of the solar system. Or maybe the alien will plant his bomb in the Sun, at one of the poles pointing perpendicular to the plane the planets orbit in. And his giant explosion might blast away a chunk of the sun the size of a planet and send it on its way out into interstellar space. But the planet sized chunk of material ejected from the Sun will be only a tiny insignificant fraction of the Sun's mass and the Sun will continue basically unchanged - we hope. It is certainly possible to create a very, very, very, big explosion on the Sun that would be very spectacular at close range (but far enough away to be safe, of course) but not be noticed at the distance of Earth. In any case the only safe solar system planet to blow up might have to be an artificial planet as far out in the Oort could as possible. [Answer] Well if u blow up any planet it will destroy the whole solar system as taking up Neptune. Neptune will be destroy than its explosion will effect Uranus due to this Uranus will also be come to an end then comes Saturn my favourite planet but if Saturn will be dead it will be disasterous explosion as it has so many moons it's rings then Jupiter it's destruction is very much dangerous as it has bigger mass much explosion material harmful gases and it will effect asteroid belt if that disturbs the earth will come back where it was started from...... üí• ]

[Question] [ This would only comprise death by natural causes, no accidents, suicides, homicides etc. As Wikipedia says: > > A death by natural causes is one that is primarily attributed to an > illness or an internal malfunction of the body not directly influenced > by external forces. For example, a person dying from complications > from influenza (an infection) or a heart attack (an internal body > malfunction) or sudden heart failure would be listed as having died > from natural causes. > > > How long would it take until we realise that on the whole world people suddenly stopped dying by natural causes? (Let's say it is caused by some alien medicament that they are secretly testing on us.) Instead of death, they are living the same as they did before this day came. [Answer] One day. Few at most. In most modern countries death reports are passed to government agency on daily basis. Clerk responsible for them would be surprised that there are none in his area. He will notice sudden drop, and 0 in one category. At least some clerks would call their counterparts in adjacent areas to chit-chat about this impossible coincidence, and, with surprise, hear that the same thing happened. From this, it'll be a cascade. The same, or next day it'll be brought to the upper seniority of government's healthcare ministers. And to the press, things like that make for really good news. And while making sure that it really is "whole world" might take a bit, I'm pretty sure it'll take well under a week for virtually everybody to know. My money is on three days for the internet-connected people. --- Of course there is a gap between "been exposed to such information" and "actually believe this is happening". Denial and disbelief will be natural at the beginning. [Answer] Probably after one day, people these days, keep Track of deaths. Even in Sl Salvador. There was a newspaper article in Switzerland, that said, that there hasn't been a murder in 24 Hours in Sl Salvador. If such an event will be noticed and in the news (on the other side of the globe). If countries like El Salvador keep (that good) trak of their deaths (and why), it'll probably be the same to realize this, if it's the case from natural causes as well. Especially from "First world nations" with a preference for statistics, like the US. This does not answer your answer directely, but shows, how good they keep track of deaths and their causes and how fast such things will be in the news aroud the world. [](https://i.stack.imgur.com/isx3I.jpg) ]

[Question] [ Many pieces of popculture (like [assassins creed or the aboleths in dungeons and dragons](https://en.wikipedia.org/wiki/Genetic_memory_(psychology))) use the concept of a genetic memory. How realistic is this concept? In particular, I am interested in cephalopods or similar animals. When discussion cephalopod civilizations, many people criticize the idea, because the parents do not form close bonds to their offspring and [die before they could teach them anything.](https://www.sciencealert.com/mother-octopus-senescence-death-after-mating-eggs-reproduction-rna-sequence-optic-gland) Cephalopods rely on having many babies (r-selection), because they lack any real ways to defend themselves. Cephalopods are also known for their unique way of evolution through changing their [mRNA](https://www.nature.com/articles/d41586-017-00612-y). Could a species exist, that passes off knowledge to the next generation directly, by inheriting not a "blank" brain, but basically a copy of the brain of the mother. The individual brain structure would be coded in the DNA of the animal. Of course, learning and memory would eventually be a problem, but the animal could forget knowledge either after a few generations, or just forget unused knowledge, just like humans do. A species like that could learn from previous generations without giving up r-selection, or the unique reproduction of cephalopods (that is, dying after giving birth). How realistic is this concept? Could it evolve naturally? If not, could we eventually create a being that has this ability artificially (through genetic modification)? Edit: Most structures in the brain are already fixed before birth (I assume through the genome). For example, the structures that let us see or control basic movements or instincts. So structures can be coded genetically. The question really is, whether structures can be coded while the organism is still alive, so that it can give that modified genome to its offspring. [Answer] The concept is sound and **has already evolved**, for example in the *Planaria* flatworm and other organisms. These organisms appear to store memories not (just?) in their brains but in specialized DNA sequences, that are then "re-read" upon occasion. As a result, a decapitated planaria will [grow back its head and remember things that happened before it lost its brain](https://phys.org/news/2013-07-flat-worms-retain-memories-decapitation.html). Injecting cellular DNA (not nuclear DNA) into a Planaria also works. The memories are not active, they appear to need to be "restimulated", but if you teach something to a Planaria after, say, 200 repetitions, the receiving "blank" Planarias will learn it after just one repetition. There is a SF/Horror story (["David's Worm" by Brian Lumley](https://rads.stackoverflow.com/amzn/click/com/0312878370)) in which a boy takes home a mutated Planaria and frees it in a pond, whereupon the planaria proceeds to eat all fishes in the pond, growing in size and acquiring the fish' knowledge > > until the child disappears, and the mother breaks out in hysterics when the following morning she sees a shapeless lump of protoplasm sitting in the child's breakfast chair and calling her Mommy. > > > # How it could work Each brain neuron assigns itself a non-unique semi-random DNA UID during early development; this UID depends on the nearby neurons, in other words the neuron has something akin to a postal code. All neurons in a given neighbourhood will very likely share the same UID or similar versions of the same. Then, the neuron behaviour is based on the state of its microtubule network - I'm cribbing this off Penrose and Hameroff's OOR theory of consciousness - but this state is initialised and refreshed off specific strings of DNA. This "memory DNA" circulates reasonably freely in the organism as tightly wound [DNA minutes](https://www.nytimes.com/2019/11/20/science/dna-genetics-cancer.html), and is "read" based on an initiator sequence that, you guessed it, includes a UID. So, the neurons in the speech center will only ever decode speech-center memory tapes. We need two more details here - a mechanism for the DNA records to cross the blood-brain barrier, and a mechanism to improve efficiency by "steering" these DNA droplets based on their UID. Finally, the neurons continuously dump their state in the form of new DNA circles (this is the farthest-fetched part). The "old" circles degrade with time, and are replaced by more experienced ones. Renewed experiences create more circles, and therefore linger in the memory longer. To do this we can reuse the same strategy employed by telomeres: a DNA record is "born" with a TTL sequence of, say, sixteen blocks containing its UID and a "written" flag. When a record has a "written" flag on the outside, all brain cells kick it out as fast as they can. The record gets dumped outside the blood-brain barrier, where an enzyme that does *not* cross the barrier removes the "written" flag with low efficiency (it takes on average a couple of hours). When the stripped record comes back into contact with the barrier, it's now exposing a naked UID, so it gets dumped inside the brain and steered where it needs to go. There it gets "read", and the UID is stripped, exposing the "written" flag below. After (say) sixteen cycles, the record has no flags or UIDs and is destroyed. And when the mother bears a child, the egg's cytoplasm will include a significant quantity of DNA circles (I was wrong, *this* is the farthest-fetched part). While the child develops, its neurons will usually "boot" incorporating some of these memories. Pregnancy hormones might also influence the process. ( Yeah, the genetic memory is matrilinear :-) ) ( This also means that *blood transfusions* will cause privacy issues unless the blood is treated repeatedly with UID-stripper and flag-stripper enzymes ) [Answer] **Unrealistic, but not impossible** A blind child knows how to smile. A horse knows to start walking just after being born. Most creatures know how to eat and procreate. All this can be considered a form of genetic memory. For humans, memory in the brain happens in two ways. The neurons in the brain make certain connections. The more a connection is used, the more firm it's established. That is why repeating things over and over, day after day, makes you remember them better and better. The second is a pattern sequence. Some things light up the same area's of the brain, but you remember other things. This is because the way lights up matters. Although completely different, you can compare it with Morse code. It lights up the same wire, but the sequence of beeps make each different. In the end you'll have different combination of structures and different patterns in your brain lighting up for each memory. The difference between them is the permanency. You know how to eat, because the brain structures for eating are pretty much fixed. This encodes easily into the DNA of your seed and can be passed on. The memory part however is made exactly for memory. It is dynamic. You have an experience, you store it for later reference to improve your survival. But the DNA saves the function, not what's stored in it. Someone with a traumatic experience will not give this to their children. In short, it's not really possible. **However, I'm willing to see what could make it work** To see how it would work, I would suggest that the DNA for the memory brain structures gets updated if the cephalopod gets more memories. to facilitate this, a whole allele pair is just for memory would be created. Then even complex memories might be stored in the DNA to be grown in the children. How brain memories would trigger certain DNA structures to be added I wouldn't know. [Answer] The other (excellent) answers bring up fascinating examples from real biology of creatures that seem able to store memories (to some extent) chemically, which could be directly inherited by offspring. This is a "proper genetic" memory: the actual memory information itself is encoded in genes or other inherited chemicals. However we can at least speculate about other types of inherited memory, that work at least partly non-generically. Specifically I like the idea of something Half-generic. (Data is not genetic, but ability to read it is). Some examples to highlight the idea: * A shelled Cephalopod like creature that stores some/all/backups of its memories in the form of scratch-patterns (braille) on the inside of its shell. If the language of this writing was instinctive and inherited then any offspring to occupy a discarded shell would inherit the memories in that shell: perhaps like a book. * Nerve link. I have no idea if this is remotely possible, but a nerve connection along the umbilical chord that "downloaded" data into an embryo like a ethernet cable would be an inherited memory, but not a genetic one. [Answer] The human genome contains about 3.2 billion base pairs. Due to the way the 4 nucleotides pair up, each pair can hold 2 bits of data. So this translates to just 800 mb. So if you used the entire genome for memory and ignored all the stuff the genome is already doing, you could store about 1 CD's worth of data in the genome. [This article](https://www.scientificamerican.com/article/what-is-the-memory-capacity/) estimates that the human brain could have a memory capacity of 2.5 petabytes. To store that much data in DNA would require 1 x 1016 base pairs of DNA, which is over 6 million times the DNA a human has. [Answer] ***Alternate solution: Memory downloads*** I would suggest a possible alternate concept, which achieves the same end but doesn't require fancy DNA methods. Treat memory as data storage, and directly download memories from mom to baby. If the memory is stored in DNA, this is just another version. But this will work even if memory is stored by alternate methods. Further, I can see it working for paternal memory as well. We know memory can be transferred biochemically, since [butterflies and moths](https://theconversation.com/despite-metamorphosis-moths-hold-on-to-memories-from-their-days-as-a-caterpillar-29859) from a chrysalis retain memory of things that happened to them as caterpillars, despite the brain essentially dissolving. I can envision a chemical way of doing this by replicating the molecules associated with the memory, or an electrochemical way, essentially replaying the memory into the brain of the developing organism. This works well with cephalopods (assuming an internal incubation) because males provide a packet of sperm ([spermatophore](https://en.wikipedia.org/wiki/Spermatophore#:%7E:text=In%20some%20cephalopods%2C%20like%20the,the%20generic%20name%20of%20Hectocotylus.)) to the female, and I can envision this being supplemented by a mini brain (of memory only) or memory molecules, so patrilineal and matrilineal memories could potentially be downloaded - perhaps even gender-specific. If you want limited numbers of offspring, then you could even have maternal brain tissue and paternal memory packets physically passed to offspring, so they actually retain a little piece of the parent containing memories filled with life experiences. This means the parents that die (if we're going with the death model) aren't dying as much as passing themselves along to live in their children. I have this vision in my mind of maternal memories downloaded and functioning like the cephalopod's own memory, and paternal memory being like a disembodied vision of the paternal parent guiding the young cephalopod along in life with help and instruction. I could even envision a weird sort of post-death romance between cephalopod parents playing out in their children. [Answer] **Memory symbiont.** Your cephalopods are not intrinsically very intelligent. But they are parasitized by an organism that confers intelligence. This organism resides entirely within the parent cuttlefish. The organism usually reproduces asexually, producing multiple buds and each bud makes its way to an egg. When the egg develops, it has within it a copy of the parental symbiont, and with it all the memories of the parent. The symbiont has no sense of self; intelligence and memory is an emergent property from the union of the two creatures. The memories in the symbiont do not have perfect fidelity. Older memories might be overwritten and lost, and newer (more relevant) memories are sharper. The new generation are copies of the parent as regards intelligence. But it is good for life to mix it up. Once in a long while, the symbionts reproduce sexually. It is a strange time for the cuttlefish people. Young are born with a mix of memories from different lineages, and some of these can be very strange, contradictory and sometimes corrupt. Sometimes new energy can come from this hybridiZation. Perhaps during the sexual time, cuttlefish people attempt to infect other tribes of their kind (or maybe even other kinds) with the memory creatures. In adults, a new symbiont infection might drive out the old, taking over the host body for its own lineage. An intelligent noncephalopod which serves as host to a cephalopod intelligence parasite would be an unusual creature to be sure. [Answer] In principle, it is certainly possible for learned traits to be passed from mother to child directly. For instance, vertebrates commonly pass information on pathogens they have encountered in their lives down to their offspring via maternal antibodies. While this isn't information that was learned by the brain, this does constitute an evolutionarily widespread mechanism of information transmission directly from parent to child without teaching and with a fairly high bandwidth. For storytelling purposes, it would certainly be possible to imagine an evolutionary pathway that has, in some animal, led to a system of this kind being coopted into transmitting information from the brain of the parent to the brain of the child (for instance, evolving some in the beginning very limited ability to transmit learned behaviours responding to a disease might be a first step). [Answer] # Behavioral Epigenetics The blue-prints for proteins (which give you your physical traits and behaviors) are coded by DNA. The problem is that you don't want to make every protein encoded by your DNA (your liver cells don't want to make the proteins your heart cells need etc.). Also, while sometimes in your life you may want to make certain proteins, other times you may want to "turn off" the DNA codes for those proteins (e.g. the enzymes to digest lactose from your mothers milk is good when you are a baby squirrel but not useful as an adult squirrel). Your body does this via epigenetics, where it "turns on" or "turns off" DNA codes. Whats interesting is that these epigenetic "light switches" can be passed down to offspring. Lets say you are a rat trying to avoid a predator. If a predator has always had a certain smell for the last million years of rat evolution it would be good if your DNA was permanently coded so that you would recognize that smell easily. But lets say that the smells that mean predators change every few days. It doesn't make sense to get your DNA involved at all - no use increasing cells/blood supply to an area of your brain that detects a certain smell if you won't need to recognize that smell in a few days. BUT lets say that for a few years a certain smell always means a predator is nearby (but then it changes to a different smell for a few more years). You want to recognize that smell easily AND for your children to as well but you don't want it to be permanent because that smell may not be important for your grandchildren. They did a similar [study on rats](https://www.newscientist.com/article/dn24677-fear-of-a-smell-can-be-passed-down-several-generations/) and showed that fear of a certain smell can be passed down to offspring. Now fear of a specific smell is only a tiny part of your personality/memory but if epigenetics played a much bigger role in the organism then a lot more of the parents personality/memory could be passed down. It also wouldn't need to be permanent - just a starting off point for the organism to then learn whats important in its environment and make new memories. [Behavioral Epigenetics](https://en.wikipedia.org/wiki/Behavioral_epigenetics) is a crazy field and we are learning more and more about what personality traits and "memories" can be passed down. [Answer] Its actually possible, but actually not very useful. All the good memory that happened after the conciving of a child- are not there. So all you get is the memory of a thousand childhoods, teenage-angst and the rushed period to adulthood- and a lot of mistakes. All those memorys end, in your parents coitus. And your grandparents coitus. Family dinners are ankward affairs. In fact, you like to hang out with foreigners more. And the problem is - that there is no real privacy of thougth in this world. So everyone having no children- is quite a little bit suspect. Also some of the people get so nostalgic for the good times, they spend all day sitting on a bench, day-remembering the day away. Genetic memory was a mistake. ]

[Question] [ The laws would be defined in code written in a programming language. Maybe it would be in two parts, the actual rules and then a library that could run them (like how a form validation library is separate to the actual rules that a developer can write), but that's not important. Some of the benefits I could see: * You could ask it if an action, given certain conditions and involving certain entities, is legal or illegal and what the sentence is. Would we still need lawyers to advise us? * When proposing a new law, the program could tell you if it conflicts with an existing law or the situation is already covered by an existing law * Automated testing / test driven development could allow loopholes to be minimised and again to minimise conflicts with existing laws * The code could be publicly accessible for anyone to examine and test scenarios and potential new laws * Comments could be added to explain the intent of certain laws * Political manifestos could include a forked repository with their proposed laws, which anyone could test out * New laws (either in Parliament or a party deciding their own policies) could be created as pull requests. MPs, journalists and citizens would be able to scrutinise them * The law would be a lot less open to interpretation What would a country be like if its laws were implemented like that? Are there any drawbacks? The only one I can think of is that developers or technically minded people at least would have an advantage in understanding law. But then, we're in that situation with lawyers as it is. [Answer] Not really there are too many things that might matter that a computers must take into account. Phrased differently: **The world contains an infinite amount of information and we have a finite amount of computing power to represent and reason about it.** The main problem is an incomplete model of the world. Humans are deeply encoded to recognize when things are not important and ignorable, and we quickly change our model of the world to adapt. A computer doesn't have eons of evolution to tell it what matters, it would have to have thousands of special cases encoded. For example * Walking up to peoples houses and taking their food -> illegal * walking up and taking a candy on Halloween -> legal. * Breaking into someone's house while they're home -> illegal * Breaking into someone's home while its temperature is high (it's on fire) and some one is inside - > legal and heroic * Taking a child's clothes off against their will -> illegal * Giving your child a bath when he doesn't want one -> legal. * Tackling a man to the ground and punching him -> illegal * Tackling a robber in your house -> legal. * Driving though and intersection when the stop light turns green -> legal * Ignoring the traffic cop in the intersection and obeying the stop light -> illegal * Shooting a man dead -> illegal * Shooting an enemy soldier while actively serving in the armed forces and obeying the rules of engagement -> legal There are thousands of conditions that might or might not matter, that are difficult to encode and have billions of possible values. The identity of each person involved could matter their age, nationality, physical size ..., the location, the date and time, What other events are happening, what happened in the days, weeks, years before, what was happening 20 ft, 20 yards, 20 miles away. Even asking a simple question you would either run the risk of missing a key piece of information, or you have to spend weeks describing everything that happened on that continent in the last 5 years in minute detail, and you still might miss something. You can't enumerate all the conditions because there are too many and some have not been hit yet. In response to comments In robotics this problem of taking only important variables is called the [frame problem](http://plato.stanford.edu/entries/frame-problem/), and is yet to be solved except in tightly constrained artificial situations. There are also lots of grey areas where is some thing a crime and would this get you convicted in court are different "a reasonable person's judgment" comes into play First sentence guidelines are provided by the law a jury actually chooses the sentence. **The computer can not know the sentence without knowing the jury and how they would react.** Second Inference is a key part of most trials. We never know what happened: we just have evidence, sometimes very little. In deciding if a crime was committed, a lot of inferences need to be drawn. So, in deciding if something would be convictable as a crime, the computer would have to draw inferences that various juries would draw from various sets of evidence that could come up about the event. [Answer] **Yes, given some limitations and assistance.** It wouldn't be so much an artificial intelligence or natural language processor so much as a database of relationships between entities. However, some legal language left over requires a human's intellect to be able to really reach an accurate answer. You're restructuring legal code to be relationship-based. You could have an enumeration of intentions, such as "deliberate" or "by negligence." You could have an enumeration of public status to determine if a person is of official title or office, or in a position of authority, which would make certain actions illegal for them but legal for others. Your computer program would be massive and its database would have an incredible amount of tables. With enough data, anything is possible. You're still forced to keep your program very simple without any room for the human element. Distinctions such as "forcible" for sexual assault or "excessive" for police are not answerable without the usage of an advanced artificial intelligence or a human on stand by. This makes your program unable to deem a perpetrator's sentencing. There's still nuance and interpretation left over. For example, what about unanswerable questions? What if I have the following query (C# LINQ style): > > bool isLegal = incidents.Where(i => i.Perpetrator == i.Victim).First().Select(i => i.IsLegal()); > > > Great, now we have an incident query where the perpetrator's the victim. Or worse yet, victim == null is true. There's no victim. What does the program do? Your program would be a fancy legal version of Mayo Clinic's [symptom checker](http://www.mayoclinic.org/symptom-checker/select-symptom/itt-20009075). Another good data set is the ICD (International Classification of Diseases) code set ([Example here](http://www.icd10data.com/ICD10CM/Codes/E00-E89/E00-E07/E02-/E02).) Sure, you can look at them and draw conclusions from them and quickly retrieve *certain* answers with known data and relationships among finite data sets, but without incredible intelligence, you will never use it as a standalone tool that everyone can use to replace the courtroom. So for your benefits, all of them would be fine and good, but you will still have lawyers to understand precedence and how it relates (in an abstract way) to a new incident, and you still still have jurors to interpret the information. The amount of edge cases is too huge, and you still require the nuance of understanding things like intent, premeditation, etc. And who actually uses the program? Sure, it might be good for teaching students but it's a needle in a haystack. For the ICD codes example, would a non-doctor know to search for iodine deficiency? These things are abstract and it can still be too complicated without a specialist in law. [Answer] From a certain perspective, a legal system is in itself already an attempt to codify/operationalise morality – it's an attempt to express as explicitly as possible what behaviour is immoral, and to punish/disincentivise immoral behaviour in ways that are themselves moral/ethical. Without a code of laws, "right and wrong" are determined by either an individual in charge, in an autocratic society, or via debate/reasoning amongst some or all members of the community, in a society without a clearly delineated hierarchy. We can't know for sure what motivated the first attempts to operationalise and record a consistent set of rules for living, but one might intuitively presume a few motivating factors: * Ensuring consistent application of the rules in every case (itself something which must have been deemed ethically important) * Deflecting the ["well that's just your opinion, man"](https://youtu.be/pWdd6_ZxX8c) defence * Allowing whoever had the authority to make the rules to delegate to others, while still ensuring that their own values would be represented What's interesting is that the earliest known legal code, the [Code of Ur-Nammu](https://en.wikipedia.org/wiki/Code_of_Ur-Nammu) *was a series of if statements*: > > 1. If a man commits a murder, that man must be killed. > 2. If a man commits a robbery, he will be killed. > 3. If a man commits a kidnapping, he is to be imprisoned and pay 15 shekels of silver. > 4. If a slave marries a slave, and that slave is set free, he does not leave the household. > 5. If a slave marries a native (i.e. free) person, he/she is to hand the firstborn son over to his owner. > > > [...] > > > 32. If a man had let an arable field to a(nother) man for cultivation, but he did not cultivate it, turning it into wasteland, he shall measure out three kur of barley per iku of field. (29) > > > In other words, from a certain simplistic perspective, it was already a "program" of sorts, one that was to be executed by humans instead of computers. The problem that's immediately apparent, and which other answers have already described, is that the application of these rules has not itself been operationalised. What is murder? What is robbery? Who may legally be made a slave in the first place? And so on. In other words, if statements are an imperfect mechanism for operationalising ethics; you end up requiring a potentially infinite series of clarifying definitions and decisions. My suggestion would be to return to first principles, ideally, and create an artificial intelligence that is capable of making moral decisions, using structures and methodologies that are more powerful than simple if-then constructions. We would want this AI to have the same fundamental morals as the majority of the humans who are planning to create it and subject themselves to its will, while hoping that it would uphold a purer version of these morals, immune to bias and corruption, and incapable of being manipulated or tricked into making an immoral decision. In other words, you'd be creating a god – a perfectly Good god, at that, as opposed to one of the fallible, relatable ones that exist in religions such as the ancient Greek. I'm not pretentious enough to claim I have any definitive ideas as to how this can be done, but I'm fairly confident it can't be done with nested if statements. What *might* work: ### "Moral calculus" One fairly acceptable basis for moral reasoning is utilitarianism. Assuming that all individuals are of equivalent worth, then it's optimal for the largest number of individuals to experience the greatest possible satisfaction while experiencing the least possible discomfort. Loosely define what is good and what is bad at the most fundamental level; death and pain are bad, joy (perhaps measurable in humans via endorphins, serotonin, and so on) is good, and so on. Now we have the kind of optimisation problem that AIs are already getting moderately good at trying to solve. Now we're barely dealing with ethics at all, we're dealing with causality. An action that causes another human to die, or to experience pain, or to be denied their 'fair share' of pleasure is bad, and should be prevented/punished. A person's 'fair share' of pleasure can itself be defined as what they can experience without causing death, pain, or excessively diminishing the ability of others to experience their own fair share of pleasure. I find it hard to disagree with any of the judgements that my limited human mind can predict arising from decisions made according to this kind of "moral calculus". This kind of reasoning not only determines how humans should behave, but also how the AI and it's agents should behave – punishment/deterrence should take a form that prevents wrong by inflicting the bare minimum of death/suffering/deprivation to offenders, actual or potential. There's one catch here – if the system is counting deaths, and measuring pain and pleasure, it's only capable of deciding retrospectively. This works for 'delivering justice', but it doesn't necessarily help in terms of guiding people as to how to make moral decisions as to how to act in the first place. The system could of course make general guidelines based on the collected observations of past decision-making processes, but the better (and more interesting and/or terrifying) approach would be if it were capable of accurately *simulating* all possible decisions, and the outcomes of those decisions. Now we're really talking about a god – without deviating too much from the topic at hand, consider that an accurate simulation of a human consciousness is considered by some to have equivalent moral rights to a natural-born biological human; but if our AI god wants to test the effects of various actions to determine whether they are immoral, and to what extent, it's going to need to simulate victims as well... Is this permissible according to its own moral reasoning? Maybe it is, since it would enable it to justly govern an indefinite number of real humans. But it's a lot easier for the super-AI to create humans than it is for humans to create humans, and it can create more of them than the physical Earth could hold – so maybe their rights, in the end, outstrip your own? **Totally unnecessary extension, with apologies to Eliezer Yudkowsky and friends** How do you know you're not already an agent within the simulation of an AI attempting to determine how humans should behave? [Answer] Within the rules of the American Contract Bridge League is a particularly important one. Paraphrasing from memory, no player may deliberately violate the rules of the ACBL, *even if the penalty is one the player would otherwise accept*. Proven violations of that rule are to be punished severely, even if the punishment for the underlying infraction would otherwise be relatively minor. While enforcing such a rule is, of course, difficult (since it would require knowing the intentions of the accused) it is nonetheless extremely valuable, since it highlights an important principle: the legitimacy or illegitimacy of an act does not depend upon whether or to what extent it may be punished. Someone who deliberately leads out of turn for the purpose of passing information to partner is cheating. The fact that the tournament director may be unlikely to seriously punish someone who lead deliberately out of turn but could plausibly claim to have believed he was on lead would not make the action legitimate; it would merely mean the player was an unpunished cheater. A legal system establishes guilt and punishments in any kind of formulaic fashion, no matter how carefully the formulas are designed, will allow those who are familiar with the system to profit substantially by cheating to an extent which falls just short of the threshold required for a punishment exceeding the benefits of cheating. A good legal system should have a certain tolerance for honest mistakes, but in a formulaic system any such tolerance will be exploitable by cheaters. What's needed instead is a recognition that minor cheaters will often go unpunished, society owes them no obligation in that regard. Unfortunately, no deterministic way of catching cheaters will be effective at those who can arm themselves with the knowledge necessary to game the system. What's necessary is to have a legal system that can make judgements which go a level beyond anything a cheater would be able to predict--one which can go beyond "Is there level XX of evidence the person tried to cheat", or "Is there level YY of evidence that the person was trying to keep the evidence of cheating below XX", to "Was the person trying to cheat and game the system to get away with it". And I don't think a formulaic legal system will be able to accomplish that. [Answer] While there are no software based/generated law systems yet there are some attempts to process law algorithmically. For instance the Indect project involves searching for possible crime in data sets written in natural languages. It differs from your idea in the fact that the law needs to be encoded in some computer readable form (for instance XML or Java) and this format of rules, even if equivalent to the original in mathematical/logical sense is not normative per its own. The algorithm just finds cases to be examined further. If you would like to go one step further and make some XML description of rules normative in legal sense, the major obstacle would be human factor. You seems to be too widely inspired by github subculture and not aware of how non-programmers perceive law. They may be against such innovation for several reasons: * Judges would lose their job or at least their authorty/independence as their decisions could be objectively tested. * Society would fear that they do not understand the new XML-encoded rules. I guess you would have to at least generate a natural language normative text from your XML/Java code in order to avoid such suppositions. At the end judges will still decide and software would be only help in cases where they do not want to abuse the system. Or in other words: the law will still remain open to interpretation. At least it would stop being inconsistent (what btw would be a huge achievement too). On the other hand some of problems already mentioned by you or in other answers would be not a problem at all: * Lawyers would not disappear as asking such computer oracle will still require some knowledge to pose a question (see: Wikipedia is not a help if you don't know what keyword to search for). * Although such approach would allow some form of automated testing, I thing there would be no "forking repositories", "test driven development" etc. like ones in IT. Government is made mostly of non-programmers (assuming you do not abandon democracy) and I would expect them to continue working and thinking normal, paper-based way. * Citizens are not programmers so they would not run automated tests. Manifestos would still be natural language based populist bullshit. * Public availability and comments are elements existent in contemporary law systems, it wouldn't change a lot. * Fuzzyness / too many things that matter would not be a big problem. Now we are copying with such cases by involving lay judges who decide by their intuition. There is no reason to avoid it, as humans will continue to know better what feels moral to them than AI. Imagine a case of divorce where it needs to be decided who of parents should take care of the children but both of them lie to their advantage and it needs to be decided not only logical consequences of known facts but also which facts one should believe. The law computer system will just have defined situations (a lot of them…) where human assessor decision is needed. Nevertheless, other problems may emerge: * As you said, the program could tell you if it conflicts with an existing law. But because of Gödels' incompleteness theorem and of stop problem there would be cases where such queries would be undecidable with no chance of a program detecting the undecidability. It would just hang or provide something like "no answer found in time limit". * Because of that we would need to base our system on some paraconsistent logic instead of classical one. By the way using paraconsistent logic would solve also problem of existing nonconsistent law. [Answer] No While this might work for most cases, it won't work for "hard cases" - stuff that depends a lot on circumstance, or where there is no precedent - for example most cases involving slayer laws or in emergency situations such as the speluncean explorers (where some of the decisions are based on stuff such as what does the public want, or if there is an expectation of executive pardon) It also fails to ensure that the law is enforced as intended - for example Adultery is illegal in many places, but not prosecuted - is this a law? - times changes, opinions change - be it if alcohol is legal/illegal, marijuana, LGBT, etc. - and normally society changes before the written law changes, so if the written law was enforced as written, then there would be many problems. Computers are also horrible at reading intent or motives, which is a critical part in evaluating many laws, such as what supercat's answer wrote - consider anti-monopoly laws where a large corporation may be willing to accept the slap-on-the-wrist fine while enjoying huge profits - or big Phara companies suing each other to continue being the sole source of drug X, and thus get an injunction preventing anyone else from selling X, even if their patent has run dry because of bogus quality concerns or other issues - they continue getting tons of $, at the relatively minor costs of lawyers in comparison. Or what happened with lavabit when it technically complied with a court request to turn over it's SSL keys, and they did so by printing it in a tiny font [Answer] ## Yes it could We already have [legal software](https://en.wikipedia.org/wiki/Category:Legal_software) capable of giving legal advice. ## But that won't allow you to automatically hold a court The essence of courts is **rights protection**, not mechanically forcing the law. The law is the tool here, not the purpose. Nowadays people are being condemned for infringing on somebody's rights, not just for "breaking rules" (as they were in medieval times). Any contemporary legislational system is more complex than just a set of rules what is allowed and what isn't (e.g. [Judiciary](https://en.wikipedia.org/wiki/Judiciary)). ## Some of your suggestions are already implemented > > You could ask it if an action, given certain conditions and involving certain entities, is legal or illegal and what the sentence is. Would we still need lawyers to advise us? > > > As I was saying, there are already such kind of software. But, due to subjective nature of legislation, that doesn't work so well as, say, mathematical software. We still need lawyers because a lawyer isn't just a walking dictionary (neither is any specialist). We have MathLab but still need mathematicians more than before. > > When proposing a new law, the program could tell you if it conflicts with an existing law or the situation is already covered by an existing law > > > Possible conflicts is actually the lesser evil. Possible exploitations are more dangerous. To reasonably propose a new law, you need to predict its behavior in real environment, that's what experts do. > > The code could be publicly accessible for anyone to examine and test scenarios and potential new laws > > > Normally, most of statutory wordings are already accessible. They haven't be a code for that. > > Comments could be added to explain the intent of certain laws > > > That is already implemented. Again, you don't need a computer program to add comments. > > New laws (either in Parliament or a party deciding their own policies) could be created as pull requests. MPs, journalists and citizens would be able to scrutinise them > > > I suppose, you're talking about democracy or meritocracy (technocracy). Check [Athenian democracy](https://en.wikipedia.org/wiki/Athenian_democracy) or [how laws are made in the US](http://www.house.gov/content/learn/legislative_process/). > > The law would be a lot less open to interpretation > > > The openness is actually "a feature, not a bug". Google "equity of statute". [Answer] Yes this question is old, but some beancounters really ticked me off again today. Most of it can be automated. I'll first give some codex samples as a Java MVC, and at the end I'll post comments about common misconsceptions non-developers seem to have I envision this to be a sort of REST-like service onto which various agencies and law firms can slap their own UIs on. The job of politicians would probably end up being the writing of the test cases. That way they can show (or prove to) their constituents the effects of their proposals directly without having to know too much about software engineering. # Tax Code in TaxCode ``` @Autowired Residents residents @Autowired Post post @Scheduled(yearly) private void income(){ for(Resident resident : residents){ var income = resident.getLast12MonthsIncomeStatements().sum(); var deductions = resident.getLast12MonthsDeductibles().sum(); var taxable = income - deductions double rate = (taxable < 10000) ? 0.20 : (taxable < 20000) ? 0.30 : (taxable < 50000) ? 0.40 : 0.50 post.dispatch(resident, createBill("your tax office needs", rate*income)) } } ``` in Resident (extends Person) ``` public void addDeductible(String deductibleType, Currency expended, String comment){ switch(deductibleType){ ... default: throw new IllegalDeductibleType(deductibleType); } } ``` # Immigration in Visitor (extends Person) ``` @Autowired Executables executables; @Autowired Police police; public Visitor(PersonDetails personDetails, String visa){ super(personDetails); Date expires; switch(visa){ ... default: expires = new Date(); } executables.add(expires, ()->{police.deport(this);}) } ``` # Crime in Crime.Victim.Murder ``` public class Murder extends Deceased implements Victim{ final static Sentence sentence = Sentences.murder; @Autowired Police police; @Secured("JUDGE") public Murder(Person victim){ ... } @Secured("JUDGE") public void addPerpetrator(Person person){ assert(person != victim); person.addCrime(this); police.arrest(person); } @Secured("JUDGE") public void clearPerpetrator(Person person){ person.clearCrime(this); police.refresh(person); } } ``` in Crime.Sentences ``` public static final Sentence murder = Sentence .builder() .addYears(25) .addCommunityServiceYears(25) .addFine(250000.00) .build(); public static final Sentence jayWalking = Sentence .builder() .addCommunityServiceDays(1) .or() .addFine(150.00) .build(); ``` # Bureaucracy in Agency.Faa.PilotLicense ``` public class PilotLicense extends License{ boolean active; String comments; @Autowired PilotDatabase pilotDatabase; //anyone can do this public PilotLicense(MachineReadableDocument pilotExam){ assert(pilotExam.type == "Pilot Exam") assert(pilotExam.grade > 0.9) super(pilotExam); //authenticates the exam active = true; } @Secured("JUDGE") public void suspend(){ active = false; } } ``` in Agency.IRS ``` public class IRS{ @Autowired Residents residents @Secured("AGENT_IRS") Person getNewCase(){ return residents.getRandom(); } } ``` in Person ``` @Secured("PRESIDENT") public void pardon(){ this.crimes = null; } ``` # Comments for laypeople * **Conflicts**: Conflicts in the law do not happen. If the arise, the law will not compile. * **Ambiguity**: There is no ambiguity. Properly codifying the law will force politicians' feet to the fire and expect them to specify what they want in *exact* terms. If ambiguity arises, the law will not compile. Do note that it is possible to create an ambiguous interface, (as in, you create Murder and Premeditated Manslaughter and people aren't sure what the difference is) but such situations shouldn't be created in the first place. If judges and juries are confused about which crime to apply, the politicians didn't do their job right and should be accused of obfuscation. * **Case Law**: Case law should not exist. Judges and juries should not make laws. things that can happen are the following: + a use case (e.g. crime) is not implemented: in this case, the legislative branch must decide what to do. + people are unsatisfied with the sentence a criminal receives: in this case, the legislative branch must reevaluate their test cases. + there is a mistake/technical error in the code: well the result gets ignored until it gets fixed, obviously. * **The Role of Courts**: Courts, Judges, Juries etc, exist only to translate the physical world into the digital world: they classify crimes. The sentence is determined by the system. * **Security**: the only thing that needs to be secure is the State repository (people-database, or the Model). Access needs to be managed, logs kept and routine backups made. Functions that can be executed by certain roles are annotated as such (e.g. @Secured("JUDGE")) everything else can and should be publicly viewable. * **Special Cases**: regarding @sdrawkcabdear's post: if nobody reports the crime, it might as well not have happened. and if someone steals something, a judge registers a crime with a perpetrator and a value. A burglary is at least Tresspassing and Theft/Misappropriation. On halloween you're not trespassing if you're invited, and you're not stealing if someone gifts you candy. I don't see how this post is so highly rated as it doesn't make much sense to me. In any case, those are all judicial issues, not legislative ones. * **Artificial Intelligence**: this has nothing to do with artificial intelligence. # Closing Remarks this needs to happen ASAP. [with ~ 15% of the workforce dedicated to government](http://www.businessinsider.com/government-worker-percentage-2015-1?IR=T), it accounts for probably at least 30% of government expenditure considering police ( executive ) [is usually only ~ 0.3%](https://en.wikipedia.org/wiki/List_of_countries_and_dependencies_by_number_of_police_officers), it makes you wonder what all these people are really needed for. Yes I'm salty. Saltier than the Don Juan Pond. [Answer] Given what assumptions? If you're going to postulate an Artificial Intelligence that can do anything a human being can do, then presumably by definition the answer is yes. So I'm going to assume you mean with current technology or something reasonably close to it. Next question: In what sense? In the simplest sense, it would certainly be possible to store the law on a computer and make it easily searchable, have cross-links between related laws, etc. I'm really surprised that more hasn't been done in that regard. The technology exists to store the text of the law on a computer in HTML, create abundant links, provide text searches, etc. The first place where it gets tough is when you say things like, the computer will tell you when a proposed new law conflicts with an existing law. Some cases would be easy. If someone proposes a law reading, "The speed limit on interstate highways shall be 85 miles per hour", I could imagine a computer being able to find that there is an existing law that says, "The speed limit on interstate highways shall be 80 miles per hour". But what happens if you say the same thing in different words? Like what if someone proposes a new law reading, "No one shall be allowed to drive a car more than 85 miles per hour on roads making up the interstate highway system." Now the computer has to figure out that "interstate highways" and "the interstate highway system" are the same thing. That may seem obvious, but just because two phrases share common words doesn't make them the same thing. How would it now that those two are the same but, for example, "the Marines" and "the merchant marine" are very different? How would it know that a "speed limit" refers to the top speed you can drive a "car" and not, say, a boat, or oil through a pipeline? How would it know that "speed" here means "velocity" but in another law refers to a drug that acts as a stimulant? Etc. What happens when a law entered into the computer is ambiguous? Like in my example above, does this speed limit apply to trucks and motorcycles? Many laws are very subjective. For example, to successfully sue someone for negligence, you have to show that he did not take the precautions that a "reasonably prudent man" would take. Who is to say what a "reasonably prudent man" would do? That's full of subjective evaluations. Similarly, I'm somewhat active on a forum for writers, and a question that routinely comes up is, Copyright law says that I can copy short quotes from another person's work without permission. What is "short"? Can I copy 50 words? 100? 1000? There is no hard number. The law further says that factors for the court to consider when deciding if such copying is "fair use" are whether it was copied for educational or research versus commercial purposes, the nature of the work, etc. What makes something "educational"? What about "the nature of the work"? Etc. Laws do this very deliberately because there is the constant struggle between the letter of the law and the spirit of the law. Someone else mentioned that the law forbids breaking into someone else's house -- but no one's going to prosecute you if you did it because the house was on fire and people were screaming for help. It's against the law to take someone else's property without their permission. But if a maniac is holding people hostage, and in a moment of carelessness he puts down his gun and looks the other way and one of the hostages grabs the gun, I really doubt the hostage would be prosecuted for stealing. Etc. Perhaps you wouldn't simply type English text into the system, but would have to describe laws using a carefully-defined language that eliminates a lot of these complexities and ambiguities, a language designed to describe laws in a way that a computer can process and analyze. But would it be possible to create such a language? To say, "Yes, the computer can solve this problem. We just have to invent a language to describe the problem in a way that the computer can solve" is to talk in circles. Like, "Yes, I can prove that it is possible to build a spaceship that travels faster than light. You just have to grant me the one tiny assumption that someone else will provide me with the plans for a faster-than-light engine." So in conclusion: I'm quite confidant that it could be done in a limited way. But to meet all the conditions you describe? That would require advances in AI far beyond what anyone has accomplished to date. [Answer] I think it's a fascinating idea. But it's easy to misunderstand the concept. I've had this idea in my head for a little while also. I think if of it as just replacing the human language representation of the law (eg, English) with a computer language representation. That is, the actual meaning would remain the same. Just the language has changed. In theory, computer languages are our best attempt that representing complex logic so maybe it make sense. It's interesting to think about how this could apply to financial law (eg, for investments or tax laws). Perhaps it could lead to a kind of arms war. If financial law was expressed completely as a computer language it would be easily to apply game-theory type methods to find the practices that produce the highest returns. We've already seen computer processing power have an effect on the stock market through algorithmic trading. With more powerful hardware and better algorithms are, you can make faster trades and get a competitive advantage. But we could take that to the next level with algorithm that find the best way to minimize tax. Or they could find the best way to restructure a company to avoid regulation. Perhaps this would mean that loopholes in the law would become instantaneously obvious and available to everyone. For example, in the past there have been legal loopholes that allowed organizations to behave like a bank even though they were not regulated as a bank. But the impact of that problem was minimized by the fact that it was difficult to understand that this was the case... But with computational law, this kind of thing could become obvious. How could lawmakers respond to this? In some cases it might be possible to also instantaneously close loopholes. But sometimes loopholes can't be closed easily -- even when we know they exist. For these cases, we would have lost the "fog of war" that comes with the esoteric nature of law. So, this is our arms race: a race of finding loopholes against closing them. This same kind of thing could be applied to non-financial law, also... I remember after the George Zimmerman case, some media pundits worried that the verdict effectively legalized murder, under certain circumstances. In a computational law world those "certain circumstances" would be more clearly understood. As a result they could also be more easily taken advantage of. Maybe all of this could lead to a system of laws that was constantly changing (like a large open-source codebase, or like wikipedia). If a character wanted to do something that was on the line between legal and illegal; it might be interesting if he could run a search that looked at recent court verdicts and waited for that short period of time in which his activity was (technically, computationally) legal. It might also be interesting to think about the organizations that create programming language (such as the C++ Working Group) as prototypes for future law making bodies. [Answer] ## What does the input look like? If you are already doing the “interpretation” of the crime and the input is something like “forcible entry, 20 year old” then it becomes a relatively simple lookup like [this Symptom Checker](http://www.mayoclinic.org/symptom-checker/select-symptom/itt-20009075). It depends on the proper formulation of the input and a matching entry. Laws are already formulated with criteria which have to be fulfilled, exceptions, precedence and so on. If you want to present the computer with a verbal story then it has to interpret human language with all its implied meanings, incompleteness and vagueness. In which case you’d need an AI which is prone to the same misunderstandings as a human (though at least you could program it to be impartial and without emotions). Automatically looking up the appropriate law after the interpretation of the case is the easiest part of the problem. [Answer] Coming at this from a technical (instead of legal) side, you are going to have giant issues with security. With computers, the only secure computer is one that no one can access and doesn't have power. If the computer is connected to *anything* (and if you are allowing access to it, then it is), then it can be hacked. This means that people will try hacking in to change laws they don't like or (if the computer is also acting as jury) make sure that a specific verdict is carried out or sentence assigned. You are also going to have people trying to bring down the system as a whole either as a prank or as an attack. You are also going to have issues with how you present cases to the computer. It will likely need to be a very formatted input so that the computer will understand. Depending on the programming, you might get multiple answers for the same issue by inputting it differently. In that form, lawyers will become very valuable again. Instead of learning how to present the case to human judges and juries, lawyers will train in how to input the facts to the computer in such a way as to sway the output. [Answer] ## Primary Benefits A fully codified (dare I say "executable") legal system lends itself well simulation. Instead of ideological debates about what the law should say, simulations can be run to see what would happen if a given version of the law was applied. Because the law is code, a great many software coding tools can be modified to operate on the legal code. Static analysis, delinters and a host of other tools can be brought to bear to eliminate or minimize syntactic and semantic errors in the code. It's not hard to imagine a kind of Legal Github where the entire legal code base is a git repository that anyone can use to fork, modify and/or send pull requests. Someone will still have the job of accepting patches and integrating them into the code base, like a Legal [Linus](https://en.wikipedia.org/wiki/Linus_Torvalds). ## Primary Detriments First, this is hard. Conceptually, yes, a program or set of programs could encode law but given the near infinite degree of variation in circumstances coupled to the ambiguity of natural language, this is a really difficult problem. The development costs associated with codifying and managing the code may prove to be significant. And, don't forget that most large software projects are canceled because of [functional problems and significant delays](http://thisiswhatgoodlookslike.com/2012/06/10/gartner-survey-shows-why-projects-fail/). Replacing a national legal system overnight is almost sure to fail. Have a look at [ratio decidendi](https://en.wikipedia.org/wiki/Ratio_decidendi) . It's a legal concept meaning "the point in a case that determines the judgment" or "the principle that the case establishes". Your coded law will need to be able to determine and reason about the ratio decidendi. This is impossible for many humans and difficult for those who can. A codified legal system may be as easy or easier to exploit than existing legal systems. Extracting loopholes, inconsistencies or unregulated areas will be much easier with the power of distributed computing. **Encoding a Legal System** As David Friedman shows in ["A Legal System very different from Ours"](http://www.daviddfriedman.com/Academic/Course_Pages/legal_systems_very_different_12/LegalSystemsDraft.html), there are many different ways to build a legal system and different ways of describing then enforcing penalties on offenders. Whoever writes the code must choose to either use the existing legal system with some modifications or perform a "rip and replace". (Note that rip and replacements of legal systems are incredibly rare and monstrously expensive. Organic evolution is far more likely.) **Incorporating Case Law** Most legal systems are composed of two sets of laws; the law itself and commentary on the law. In legal systems descended from England, this duality of legal code appears as the Law and case history. Generally, case law confirms what the law states (in as far as that can be determined from the law) but there are instances where the two not only diverge but oppose each other. Designing a system to handle these kinds of inconsistencies will be hard....Well, detecting them shouldn't be too difficult. Reasoning about them is hard. **What would a country be like?** Making law - Still done by politicians. However, instead of lawyers becoming politicians, in this case, it would be software developers and technologists as the law makers. They understand code better. A pointer to what rule by technologists might be like can be had in China where many of their highest leaders are engineers. Enforcing law - No change. Enforcing the law still requires police, prosecutors, judges and the penal system (in whatever form that may be; incarceration, transport, indentured servitude). How they go about enforcing the law may change but the instruments required to enforce will not. Degree of Injustice - Difficult to tell. This will depend heavily on the culture of the people of this country and the quality of the legal coding. I can imagine instances where there's radical improvements and I can imagine radical exploitation of the unprivileged (which is no different than today). [Answer] This would work very well if you have a set of rules like the Ten Commandments (except you would have more laws than 10 presumably). In this case the computer could easily tell if a law had been broken and apply the sentence. As you add nuances such as multiple different sentences that could be applied for a single crime e.g. amount stolen leads to a different sentence it becomes more difficult but still fairly easy as there are still set sentences that can be worked out. Where the system breaks is if you have a murder vs manslaughter case. A computer will struggle to calculate intent and human emotion/provocation and will probably be slower and less accurate than a jury. So you would still need experts to sort out these cases based on human emotion. [Answer] There are many good replies, but I want to add a few points. **Merge Conflicts** The concept of repositories, branches, and commits brings you merge conflicts. While a change to the existing law was debated, another change was voted which directly or indirectly affects the proposal being debated. **Automated Testing** You would need to specify cases for the test suite. Who does that? If a commit breaks the test, does that mean the merge is rejected or does that mean the test is obsolete? Are the automated tests part of the "source code" which needs to be voted in? * Imagine you have a test case which says "the main perpetrator X (see library of test fixtures) is punished more harshly for crime Y (see library) than the accomplice Z (see library)" and the new law says "double the punishment for repeat offenders." The test case fails, but that was the intent of the new law. * There is a proverb that **hard** (i.e. specific) **cases make bad laws**. Test cases are hard cases in this sense. **Judicial Precedent** Laws are impossible to understand without knowing how judges will interpret them. This may change at a different pace from the laws themselves. **Namespace** Who names branches? Can you still campaign for the *Anybody Who Votes Against This Is No Patriot* act or does it become *request #670272578*? Or was it *#670272587*? [Answer] **Create a jury of AI's.** Take the greatest 12 programmers on the planet, and each have them write their own AI according to the other answers. To convict someone of a crime, a set percentage of the AI's would have to agree on the conviction. This would help handle edge cases as more than one program would have to return the conviction. ]

[Question] [ Suppose you have a modern city in a temperate climate zone that empties. No people, or hardly anyone left, certainly not enough to keep all the infrastructure going. Our city is not below sea level (like e.g. Rotterdam), and there are no large natural disasters (earthquakes, tsunamis) during the period we are looking at. Just time, weather, plants, and animals, and maybe a handful of people. Our city has a mix of industry, high rises, suburbs, etc. What will our city look like after 1, 10 or 100 years? [Answer] As @TheoclesofSaturn mentioned, Chernobyl (the city of Pripyat) is a very good place to start for this. The slow decay of the city allows you to see the effects over the first 30 years. "Nature reclaims" is the general theme of this. Chernobyl being continental, it has large mammals including [lynx, bison and wolves](http://www.dailymail.co.uk/sciencetech/article-3260583/Chernobyl-wildlife-PARADISE-Wolves-lynx-elk-boar-thrived-humans-abandoned-nuclear-disaster-zone.html) in equivalent numbers to non-contaminated areas. Areas with solid ground cover e.g. roads, concrete floors, remain recognisable, though trees grow up in any open areas, it'll take a long time for the hard surfaces to break down in the absence of something like [Japanese Knotweed](http://www.dailymail.co.uk/news/article-2052337/Hertfordshire-couple-demolish-300k-home-rid-Japanese-knotweed.html). If the city was something like Manhattan, all concrete high rise, it's going to be distinctively a city, long after a greener lower rise European city like London has mostly blurred back into the forest. The brick buildings will be weakened and slowly demolished by the trees growing around them. The roads slowly lifted and broken up by the root systems from the street trees. This will take decades, easily up to a couple of centuries. More importantly for the effect, the trees will grow taller than, and eventually over and concealing, the houses. You could have concrete high rise showing over the forests for centuries. Roman concrete structures still exist 2000 years later, so ours will still be showing for a long time to come. *As has been noted in the comments, reinforced concrete breaks down faster than Roman concrete due to corrosion of the metal bars, however the structures will still remain for some considerable time.* [Answer] We have two more real-world examples to draw ideas from, in addition to the already mentioned Chernobyl. Those are [Hashima Island](https://en.wikipedia.org/wiki/Hashima_Island#Current_condition), Nagasaki Prefecture, Japan, and certain areas of [Detroit](https://en.wikipedia.org/wiki/Detroit#Neighborhoods), Michigan, USA. In the case of Hashima, there was a thriving mining town until 1974, then was suddenly abandoned. Today, some buildings stand, some have collapsed. It seems like it has become exactly that thing depicted in apocalypse movies- the very definition of creepy. In Detroit, entire neighborhoods are mostly vacant. The reasons for this are debated, but the decline of the automotive industry and other economic factors are often blamed[citation needed]. In this case, there are city leaders making an effort to clean up and rebuild. However, they can only do so much so fast, and meanwhile houses and stores sit vacant and decaying. Both examples show us that anything which is not maintained, is eventually ruined. Rain, wind, fungi, rust, pest animals, plant roots, or something else *will* take over. The only question is how long will it take. [Answer] It would depend heavily on the type of city and climate. While some buildings may collapse due to lack of maintenance, the general structure of the city should stay intact. If it were a coastal city or one in a very hot/humid climate, the impact would be greater. To keep it interesting, let's assume the city is Bangkok. Bangkok would be one of the most interesting cities to consider for a scenario like this as it has a horribly warm and humid climate, the wild- and plantlife there is diverse and the infrastructure itself is not as durable as an average modern western city. Within a 100 years it would likely feature: * Heavily decaying buildings: Humidity and temperature have caused wood to rot and buildings to crumble * Buildings and streets 'taken back' by nature and covered with trees, vines and plantlife * Primate population to increase and use human structures as shelter, especially skyscrapers would be theirs to rule * Wildlife in general to move into the city for shelter All in all the city would still be intact, but decaying at an increasing rate until skyscrapers start to collapse. [Answer] I have just one thought to add to what others have said: Are you assuming that all human life is gone, or that just this one city has been abandoned? Because if there are people outside the city, you could expect the city to be looted and used as a dumping ground. I live near Detroit. Large sections of Detroit have been abandoned. People regularly break into empty houses and gut the wiring and the plumbing for scrap metal, as well as looking for anything else of value. Also, I recall a news story not long ago about how a certain abandoned neighborhood has become a place where gangsters dump dead bodies. (I guess it's good to have a designated place for things.) [Answer] After one year, the city becomes a literal urban jungle. The high rises collapse after 100 or so years, and the buildings become covered in vines. The pavement would become heavily worn down. Think Chernobyl. For a better example, check out the TV show *[Life After People](https://en.wikipedia.org/wiki/Life_After_People)*. [Answer] In addition to the other excellent answers, perhaps you can find some inspiration from the pictures of abandoned buildings on Ross Island, Andaman, India (example below), which shows what happens to abandoned cities in a more tropical environment -- tress quickly take over, turning the city into a Jungle-book fantasy. [](https://i.stack.imgur.com/kE7S1.jpg) [Answer] Another real world example you could look at for inspiration is the city of Ordos, China. <https://en.wikipedia.org/wiki/Ordos_City> This was a city built to provide a workforce for the Mongolian coal fields. However it was essentially a failure, and the city for the most part is empty. [Answer] I think the largest difference between most historical abandonments and a modern city would be that supermarkets might be left largely full, unlike in Detroit and Chernobyl, so a lot of people expect massive population explosion in rodents, since they're already so well adapted to urban life that controlling them is part of city maintenance. They'd die back after all the food was gone but you could probably expect plague sized populations in the mean time. Pretty grim. Chernobyl is a good model in a lot of ways but there's one interesting caveat; no micro-fauna. In Chernobyl the background radiation is low enough to allow the return of lynx and bears but still high enough to massively inhibit the growth of bacteria and fungi which can't protect their DNA, so dead trees and leaf litter just sit where they fall, for decades. I don't know if there will be any radiation in your abandoned city but if there was I thought these could be useful details. [Answer] [Varosha/Maraş](https://en.wikipedia.org/wiki/Varosha,_Famagusta) is another example of a real world ghost city. It was left in the demilitarized buffer zone between the Greek and Turkish parts of the island after the conflict and intervention in 1975. It was a well-developed tourist destination until then. Almost half a century later, it still looks like a badly kept city. [Answer] Even concrete and steel buildings in abandoned cities do indeed "decay", not in a biological sense of the definition though. I would say the leading cause of structure erosion is water. Water in two forms: frozen and liquid. When water seeps into concrete or asphalt and then freezes (during the winter months) it expands and forces open tiny cracks which grow larger with time due to structural stress pulling them apart. Liquid water also damages steel support beams in structures due to oxidation (rust). In functional (occupied, maintained) cities in places that are exposed to water you'll often see the concrete or exposed steel painted with layers of water resistant paint. Over time however the paint chips off leaving the concrete and/or metal exposed to moisture allowing the water to do its thing. An abandoned city in a desert would perhaps fare much better over time assuming it is not bombarded with too much shearing sand wind. Vandalism and looting are the first things to make an abandoned city appear derelict and cause infrastructure problems. Scrap metal is a valuable industry and abandoned cities are the metaphorical goldmine for scrap. ]

[Question] [ I am exploring an alternative history of a timeline if the centre of the British Empire is wiped off the map in the early 20th century. The [Tunguska event](http://en.wikipedia.org/wiki/Tunguska_event) was believed to be an air burst comet or asteroid that occurred over Siberia, Russia in 1908. In an alternate Earth-world, this event occurred over London at a time when Parliament was in full session, the destruction of London is total as it is across much of southern England, damage is even recorded in Edinburgh, Dublin and Paris - wiping out the British Parliament in session, the Monarchy and the centre of the British Empire. What effect would this have had in the immediate aftermath and on the events or outcome of an alternate World War I in Europe and World? [Answer] The big unknown is the location of [Prince Arthur](https://en.wikipedia.org/wiki/Prince_Arthur,_Duke_of_Connaught_and_Strathearn), Edward VII's younger brother. Assuming that he wasn't in London, you get interesting story possibility #1: King Arthur II (assuming he takes that as his regnal name) is busy trying to hold a disrupted British Empire together. Militarily, the Empire isn't much weakened: the Royal Navy is mostly in bases away from ground zero, and there isn't much of a standing army to harm. The country's economic center and leadership, however, have been almost entirely wiped out. It's anybody's guess as to whether the country joins the war, and whether it can draw on the colonies for manpower, or if it will be too busy dealing with rebellions. Assuming he was, you get possibility #2: with the male-line descendants of Queen Victoria dead, succession passes through her eldest daughter, [Victoria, wife of Emperor Frederick III](https://en.wikipedia.org/wiki/Victoria,_Princess_Royal), to her eldest son, [Wilhelm II, Emperor of Germany](https://en.wikipedia.org/wiki/Wilhelm_II,_German_Emperor). With Wilhelm II holding both Germany and the United Kingdom in personal union, World War I becomes quite different. After the Balkan powderkeg goes off (the triggering event might be something other than the assassination of the Archduke), Russia declares war on Austria-Hungary. Austria-Hungary calls in its alliance with Germany, and at this point, things become very different. France has Central Powers countries on three sides (Germany, Italy, and Britain) rather than just two. The [Franco-Russian alliance](https://en.wikipedia.org/wiki/Franco-Russian_Alliance) is a defensive treaty; France likely takes advantage of the fact that Russia declared war to proclaim neutrality. Without French or British support, there is no [Treaty of London](https://en.wikipedia.org/wiki/Treaty_of_London_(1915)), and Italy probably remains neutral. Without a general conflagration or botched British diplomacy, there is no [Ottoman-German alliance](https://en.wikipedia.org/wiki/Ottoman%E2%80%93German_alliance), and the Ottoman Empire focuses on internal reform. At this point, the war looks very different. Germany and Austria-Hungary are facing Russia and Serbia. France and Belgium are neutral, so there is no Western Front; without Britain fighting Germany there is no submarine warfare in the Atlantic to draw the United States in. The likely winners are the Central Powers, and with victory, the collapse of the Austro-Hungarian Empire is delayed, at least by a decade or two. One interesting result is that instead of causing the collapse of nearly every European monarchy, the Austro-Russian War (it won't be called "The Great War" with half the participants missing) causes the collapse of just one, the Russian Empire. [Answer] **TL;DR - Without Britain, Germany wins both World Wars and becomes the new world superpower, the British Empire slowly falls apart, and large-scale advanced radar development gets set back a few years.** I disagree with Scott as far as his response regarding what the world would perceive the cause to be. There's no reason why the world would suspect it to be anything other than what it was - a natural catastrophe. Part of the reason nobody knew much about what caused the Tunguska event (at least for a short while) was that it was in rural Russia - according to [Wikipedia](http://en.wikipedia.org/wiki/Tunguska_event#Investigations), it took *13 years* for the first expedition to reach the site. Given the importance of the target - after all, London was the seat of one of the largest empires the world has ever seen - I would think there would be a comprehensive investigation within a few weeks. But you can never properly tell when it comes to bureaucracy. Not that there would be much of that left in London. . . **World War I** There would have been a sizable impact on World War I. Admittedly, Britain did not have as much a center-stage position as it did during the second world war. Without Britain, I have no doubt the assassination of Archduke would have taken place (it was due to tensions between Austria and Bosnia). The fighting by Serbian and anti-Serbian groups would surely have taken place. Britain joined in primarily because of an [agreement with Russia](https://en.wikipedia.org/wiki/Anglo-Russian_Entente), conveniently signed in 1907. As Wikipedia says, it laid the framework for the [Triple Entente](https://en.wikipedia.org/wiki/Triple_Entente) of Britain, France and Russia during World War I. But without Britain in the Entente, there might not have *been* an Entente. France could have been reluctant to join Russia in the fight, because they would clearly be joining a weaker side. Germany also did not want France to join in the war, as was very overt about it. We can follow a logical sequence of events here: A weaker Entente means Germany, Italy, and Austria have a good advantage, and could win the war. Sure, an early intervention by the US could have changed things, but it would have had to be *early* and fairly urgent. **World War II** So no Britain could mean the [Triple Alliance](https://en.wikipedia.org/wiki/Triple_Alliance_(1882)) wins the war. The big implication here is that there will be no [Treaty of Versailles](https://en.wikipedia.org/wiki/Treaty_of_Versailles) - at least not the same type of treaty that we are familiar with. This means that the seeds of anger in Germany that led in part to World War II would not be sown. Does this mean that there wouldn't *be* a World War II? Certainly not. Their ideologies would still develop. The Nazis would still have a fighting shot at taking power (although it would be difficult because many Germans wouldn't be angry at the result of World War I), and even though they might not be able to rally as much public support, I have no doubt the Holocaust would still have taken place. Czechoslovakia, Austria, and Poland all fall to Germany. There's no [Neville Chamberlain](https://en.wikipedia.org/wiki/Neville_Chamberlain) to take the blame for letting things get out of hand, but they would still get out of hand. It can be safely inferred that France will fall, as will Belgium and the Low Countries. Now, almost all Britons today remember the summer of 1940 and the [Battle of Britain](https://en.wikipedia.org/wiki/Battle_of_Britain). But with no England, Hitler could roll right through. He could repurpose southern England as a military base. Edinburgh, Glasgow, and northern England wouldn't stand a chance. Wales and Ireland would also be in a tough spot. And so Germany would have a got shot at winning World War II (Although Russia would be a bit ticked at them, and they might not enter into a [shaky] alliance with Germany at the start of the war). And so Germany comes away very happy. The Pacific theater would still be interesting, but perhaps Japan could pull through and win with support from Germany. It should be noted that Germany might not have gone through the infamous [hyperinflation](https://en.wikipedia.org/wiki/Hyperinflation_in_the_Weimar_Republic) episode of the early 1920s, which has been attributed partly to the reparation payments in the Treaty of Versailles. Even if they had suffered through it, their economy would be stronger and would possibly have better taken the brunt of it, thus not laving Germany floundering economically. **Post-World War II** What about postwar? Well, Germany won't lose any of its top scientists to Russia, so the Soviet Union might not be as strong as they were. The US would also have a negligible rocket program ([Werner von Braun](https://en.wikipedia.org/wiki/Wernher_von_Braun) would not be on the American side of the Atlantic) and Germany would have a decent [nuclear weapons program](https://en.wikipedia.org/wiki/German_nuclear_weapon_project). They could be the dominant power in the world. **Technology** As to what technology would not develop. . . Computers would be fine. [ENIAC](https://en.wikipedia.org/wiki/ENIAC) would probably exist (if the US entered the war), as would its German counterparts. Rockets would develop, although they would be German. I don't think a lack of Britain would hinder much other technological development, except for [radar](https://en.wikipedia.org/wiki/Radar), which good old [Hugh Dowding](https://en.wikipedia.org/wiki/Hugh_Dowding%2C_1st_Baron_Dowding) pushed so much for. Sure, it would have developed, but [Robert Watson-Watt](https://en.wikipedia.org/wiki/Robert_Watson-Watt) might never have lived. As Mark pointed out, Britain was *clearly* not the only nation that was developing radar. *However*, Watson-Watt's work laid the groundwork for large-scale radar development. The [Chain Home](https://en.wikipedia.org/wiki/Chain_Home) system was implemented in the mid-1930s, and proved to be crucial to the RAF's success in the Battle of Britain. This pioneered the usage of large-scale radar structures and advanced techniques. **British Empire** Finally, we get to the [British Empire](https://en.wikipedia.org/wiki/British_Empire). It would not instantaneously collapse. After all, there were many British troops across the world, and many other people (primarily Britons or descendants of Britons) loyal to the Crown. Perhaps in a few months India would gain independence, as would many African nations. [Australia](https://en.wikipedia.org/wiki/Australia), already on the verge of independence, would have become fully independent and become the country - continent - that we know today. But history would have changed a lot for pretty much every other British overseas territory. Oh, and Ireland would have had a lot more than [Home Rule](https://en.wikipedia.org/wiki/Home_rule). Does anyone remember the folks back in Scotland? I thought not. I think we all made the assumption that Britain would be completely floundering after losing essentially all of southern England, and we would be right. But Scotland (and Northern England, and Ireland, and Wales) would be relatively intact. Who takes power? In Scotland in 1908, there was still heavy influence from London, and the [government](https://en.wikipedia.org/wiki/Government_of_Scotland) was really just the overarching government of Great Britain. It is uncertain as to who would step up. Perhaps a [semi-Cormwell-esque](https://en.wikipedia.org/wiki/Oliver_cromwell) political figure would arise to try to take control and steer Scotland into a new non-monarchial direction. Scotland could also take control over all of Britain - although Wales would have a shot, too. I would guess the Irish would rather just live and let live, and stay out of it all. In summary, Russia might have lost World War I, Germany would have won World War II, and the world would be a much different place, with Germany potentially being the number one superpower. And the very helpful webpage for context in this answer can be found [here](https://en.wikipedia.org/wiki/World_War_I). **Edit** We actually discussed the link between WWI and WWII today, and why the Nazis got so out of hand. My history teacher mentioned that [trench warfare](https://en.wikipedia.org/wiki/Trench_warfare) was pretty bad, and - depending on your personal opinion - possibly the stupidest and/or worst idea in warfare since someone decided, back in the 16th or 17th centuries, to line up two opposing armies in the middle of a open field - with no cover - and have them shoot at each other. In trench warfare, you dug a large hole in the ground and hopped in, tried to avoid the shells and bombs being fired at you from artillery and airplanes, and sporadically charge out into a bleak no-man's land at a bunch of men armed with machine guns who could easily take you down. But I digress. Anyway, trench warfare traumatized the world, and a lot of people wanted to avoid any war that even reeked of it. My teacher extended that to conclude that this was part of the reason why the Nazis were allowed to go so far - everyone wanted to avoid war as much as possible, and figured that if they gave Hitler small bits (although I think a lot of Czechs didn't consider themselves unimportant), he would eventually stop. Didn't work. So, if London got obliterated by a large body, Germany could have won WWI. The rest of the world (besides the other members of the Triple Alliance) would have been even *more* reluctant to face Germany because WWI would have been a pretty bad experience for everyone. More appeasement means Germany gets more land in less time, and things turn out fairly bad for most of the people involved. [Answer] Small quibble - the suggestion that 'the Monarchy' would be wiped out because of the deaths of Edward VII and his immediate family seems unlikely. Heirs to the throne are like sharks teeth; get rid of one and another takes its place. Even if all Victoria's male heirs died, her daughters and their heirs would come into the succession. Her eldest daughter (also Victoria) would be first in line, but she had died in 1901. Presumably that would leave her son as rightful heir to the throne of Britain and the Empire? That would be Kaiser Wilhelm. [Answer] -) The death of any or even all of the Royal family would have little effect on British politics, as Britain is totally controlled by Parliament who can pick and choose Monarchs at will. -) The bigger shift would happen with the deaths of the more progressive and worldly London urban elites and the reversion of political power to the country side and north. England would likely become more isolationist and conservative. -) Economic destruction of the Empire. London of 1908 was like having Washington, New York and Philadelphia all in one city. Take that one city out and you lose the government, Wall street, all the major corporate headquarters and many of the ship yards. That immense concentration of knowledge and organization would get wiped out. The British economy would not so much collapse as shrink to a fraction of what it once was. The colonies would be of no help. By that time, the colonies were easily consuming more revenues than they produced. -) Brief but possibly intense world wide depression from the sudden loss of British economic output and the destruction of its financial system. Huge amounts of European capital flowed through London and lot of that would be destroyed. -) Collapse of British Naval power. The fleet might be largely intact but without it's economic and organization support, it would soon be worthless. Likely most of the fleet assets would be given away or sold to France or America. -) Bringing America to Europe. American isolationism did not apply to trade and disaster relief. The destruction of southern England would likely bring and influx of American and Canadians into Britain to help rescue and rebuild. European would likely help as well but they would stay. The Americans and Canadians probably would. Americans might take over parts of the British navy and establish bases in Britain, first to help with relief but later with defense. Likely, Americans would step in to defend some British outpost like Hong Kong but equally likely America's long opposition to colonialism would lead them to not intervene in India or Africa. America did not have a big enough Army to do so anyway. Likely, the empire would fall apart in rebellions. Without financial support of Britain, the colonial administrations likely could not maintain themselves and those colonial peoples who wished for independence would rebel. India would likely do so but suffer horribly form internal conflict afterward. The other colonial powers would likely step in in Africa. -) If the Germans tried to grab former British colonies, America would likely try to stop them. Americans had already developed an antipathy to German militarism and had taken steps to curb it outside of Europe e.g. the occupation of the Philippines occurred to keep the Germans form grabbing following the eviction of the Spanish. -) The big shift in power would come from the sudden dominance of the German High fleet in the wake of the evaporation of the British navy. But the German High fleet was designed for short range, intense operations. It could remain at sea only a couple of weeks. The Germans had a few cruisers for world wide operations but not enough for dominance. Still the Germans could likely easily defeat the weakened British fleet and probably France. Combines with submarines and commerce raiders, they could control the European sea lanes cutting off Britain and Western Europe. France was hopeful but never certain whether Britain would send troops to France if Germany invaded again. But they required Britain to keep the sea lanes open and provide financial support. Without that financial support and with German ships at her back. France would likely have to bow out of it's treaty with Russia, thus preventing the WWI we know from ever occurring. If Russia and Germany did come into conflict, Germany would defeat Russia within two years at most. If Germany tried to occupy and colonize Russia, likely the rest of the world wouldn't intervene, really no one could, and that would absorb most of energies for a few decades. The whole European tension, at least on land in Europe, might just peter out. With the Russian aristocracy destroyed displaced or subverted, the Serbian cowed and the Austrian-Hungarians marginalized, and the Germans occupied in Russia, the mad eastern european aristocrats that plunged the world into war in 1914 would not be in a position to do so. In that case WWI might never happen and no WWI likely means no WWII. There would be no Soviet Union so no Communism of any significance. -) Without the centralization of government power during WWI and without the need to pay off war debt, no gold depletion etc, America would have likely not have founded the Federal Reserve until a decade later. The Great Depression was likely caused by a premature and naive Federal Reserve raising the money supply to quickly in the 1920s causing real estate and stock bubbles. No WWI means no Great Depression. -) Without the Great Depression and WWII, it's likely the Democrats would not have been as cohesive with the divisions between the north and south parts of the party arising earlier. Without the Great Depression, the Republicans would have been stronger. Likely the alliance of Republicans and Northern Democrats that fought through civil rights in the 60s might have fought through in the late 40s. -) Without WWI, WWII and the Cold War, government, especially the militaries, would be smaller and less centralized, especially in America. Globalization would have accelerated and likely free trade would have accelerated. Without Fascism and Communism as alternatives, most of the world would look to liberal democracies for inspiration. -) Technology: The biggest change would likely be a vast increase in interest in space and the threats it poised. Research into astronomy would likely explode as well as research into some means of deflecting future comets. The effect of this shift in emphasis would be research on rockets starting intensively over 20 years before the real timeline and on a vastly greater scale. Solid fuel rockets on par with those used in WWII would likely develop by the 1920s with liquid fuel rockets in the 1930s. Nuclear power might be developed first with an eye to powering rockets and nuclear weapons as a means of deflecting comets. On the whole, manned space flight might start in the early 50s but it likely would be private. [Answer] That depends who has the hubris or gall to take credit for it, certainly the Central Powers could take credit for it (most likely Germany) but equally it could be seen as a Wrath of God-type occurrence so the religious aspect could dominate. It could go either way depending on the international reaction — with nations surrendering in case the 'weapon' is used on them or increasing their aggression to try to capture the 'weapon' themselves. The global environmental impact would be minimal, with equivalent ecological damage to that the original Tunguska event caused though perhaps slightly smaller as houses require more energy to knock down than trees and the Thames would absorb quite a lot of the energy, converting it to steam. The British Empire would most likely collapse with its armed forces surrendering to allies though its population would be okay with Edinburgh most likely to become the Capital of the remaining United Kingdom — surrendering or becoming more resolute depending on the presence of strong leaders and the international response. Technological advancement would take a sizable hit with computers perhaps not being invented. [Answer] A much shorter answer: In real life, the Germans were almost in Paris before the British really got mobilized. The British did eventually become more involved just before the Germans could make it to Paris, and the continual stream of reinforcements from that point did much to maintain the Western Front, just in the nick of time. If the British were preoccupied with rebuilding, you can bet the Germans would have taken France out of the war before Russia could've given them too many problems. WWI would have been won quickly and much more traditionally, and WWII would not have happened (either in the West or the East, it very loosely being an outburst of anger in both hemispheres over the first war's outcome and the Treaty of Versailles). [Answer] Something else to consider: A blast like this, of mysterious origin could have created mass-hysteria in Britain. Where did this explosion come from? Will it happen again? We could see an exodus from larger cities in fear of another explosion. Religious leaders could seize on this and seek to turn it to their advantage. ]

[Question] [ Weird question but with a head of snakes, do they have to sleep with their head turned to the side? Would it hurt? Do they need an incredibly fluffy pillow? [Answer] # Deeply. In fact, in Ovid's metamorphoses, [Perseus tells](http://ovid.lib.virginia.edu/trans/Metamorph4.htm#478205208) that he found Medusa (and the snakes) *sound* asleep, a condition that canceled the petrifying ability of the monster, thus making it easier for the hero to succeed. I am also suggesting that sleeping on the side does not bring pain to the Gorgon, nor to the snakes. First, [some snakes seem to sleep quite a lot by themselves](https://faculty.washington.edu/chudler/chasleep.html). Most likely, when gorgons go to sleep, their squamous head-cover is mostly napping already, hence in a relaxed "do-not-disturb" state. Second, snakes are giant elastic tubes [(youtube link to snake feeding)](https://www.youtube.com/watch?v=dVRhRzE_AkQ). From the video it looks like that a section of a curled snake is perfectly capable of withstanding the weight of an alligator. There is no reason why a member of gorgon's hair should be crushed under the weight of a portion of the gorgon's skull. My guess is that the ensemble of snakes on which the gorgon is resting can withstand the weight of the gorgon's head without any pain (we can make a guess at the hair density for a good snake comfort, if the OP wishes). A simple model of this would be like sleeping with the head resting on bicycle tires. Probably no pillow is needed at all. Bonus softness if the snakes are fed with some furry rodents, or feathered animals before going to sleep. Third, there is an obvious question on how the gorgon's skull and the skeleton of its hair are attached. One can imagine that it could be via some sort of mobile joint, which allows the snake to curl and bend around to some extent, with a maximum curvature representing the minimum radius of the volume of the hair. Again, this maximum curvature is perfectly natural and painless, just as natural as the curvature of fingers when the whole hand is resting on them. In other words, if the link is given by a mobile joint, then, unless the snakes skeletons get fractured, the skull always has a certain space from the surface on which the head is laid. Hence the "natural pillow" effect. However, either the radius is small or this seems in disagreement with [some](http://1.bp.blogspot.com/_eJ0VlV8fD-Y/TL0DnfCOBuI/AAAAAAAABU4/JCtUYashdP0/s1600/Head-Of-Medusa.jpeg) [imagery](https://www.eyrie.org/~pi/gorgon.html). Another possibility is that the end of the snake is free relative to the skull and held in place by a rather thick hide and cranial muscles. When sleeping the muscles relax, reducing, albeit perhaps not eliminating, the "natural pillow" effect, and therefore requiring an artificial pillow. On the other hand, Ovid's does not seem to mention pillows, so either gorgons are used to sleep on hard surfaces, or the small "natural pillow" is sufficient (some people like their pillows low). I leave this last question to the more knowledgeable colleagues on WB. [Answer] First things first, it would seem to be a given that applying a heads weight worth of pressure on a small snake for ~8 hours would undoubtably be painful for a gorgon, even while using an incredibly fluffy pillow. The good thing however, is this really is a bit of a non-problem. After all a gorgon can simply part her hair (her snakes) into two sections in the middle and have her head contact the bed there. Of course this will mean that a gorgon will have to refrain from tossing and turning during the night. --- To understand what I mean by parting the snake hair into two sections I suggest taking a look at [boxer braid hairstyles](https://www.google.fr/search?q=boxer%20braid%20hairstyles&client=firefox-b-ab&dcr=0&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjw4-39jZfYAhVMalAKHfb5A8MQ_AUICigB&biw=1280&bih=648#imgrc=2OOPK9rZTIvAmM:). Obviously the gorgon doesn't need to braid her snakes, but the hairstyle in question does illustrate my point about being able to expose a snake-less part of the head. [Answer] ## It sleeps in a seated position There are a number of creatures that sleep standing up and humans can sleep while up right. It is not unreasonable for a Gorgon to do something similar. So when the Gorgon is ready to sleep they get in their favorite chair and simply doze off. Thus no additional weight is put on their head and so no source of pain or discomfort. [Answer] Their snake hair is a wig or retracts into the inside of the Gorgon's skull. The wig's lining is made from snakeskin discarded during the Gorgon's youth. If the snakes retract into the Gorgon's skull, they are responsible for protecting her brain. If the snakes are wig, the wig must be removed from the Gorgon in order to eat or excrete. Whether wig or retractable, the Gorgon sleeps well protected by snakes either peering out from her skull-holes or standing vigilant embedded in her nearby wig. ]

[Question] [ **Context**: Your spaceship encountered a Grade III Anomaly (now you really wish you'd have read the darn safety manual to figure out what that would be -- too late now). Structural integrity of the singularity containment apparently was compromised, and an all hands abandon ship signal was transmitted by the pilot AI. **Situation**: You are now in a place that resembles Ice-Age southern Europe so well, you have a hard time avoiding the conclusion that you time-traveled. Reinforcing this belief is the band of 20 or so Neanderthals currently approaching you. Moreover, you managed to deactivate and drop your multiband rescue beacon during the late stage night-time parachute descent. Your PA, Vortana, helpfully informed you that given the prevailing wind patterns you experienced, the descent vector after the pod separation event, your flailing arms and general disorientation, the beacon is 95% likely to be in a roughly triangular 100 sq. km. area to the West, and with a smaller 80% probability in a 10 sq. km. sub-area. You would like to enlist the help of the Neanderthals in: * Not being killed and eaten (or worse, having to kill them yourself - how horrid) * Finding food and water (your supplies contain food, but you have no illusions about the quality of spaceliner emergency food rations) * Finding and re-activating the beacon. To unaided human-like vision, this would appear to be a silver spherical device about the size of a grapefruit. It is virtually indestructible, so the fall would not have even scratched it. **Problem**: **You recall from your half-remembered education a few centuries back (and Vortana helpfully confirms) that Neanderthals do not speak Common. In fact, it's not clear that they speak at all. How do you communicate?** **Supplies**: Zero-point powered Gamma-ray gun, a backpack with 20kg of dehydrated supplies, water purifying canister (1), Ssiws Army Knife° (1), rope (40 meters), self-setting tent (1), blanket (1), self-cleaning clothes (2 pairs), Vortana Digital Personal Assistant (1), flotation device (1), rescue beacon (lost), beach towel (1). --- ° A Ssiws Army Omnitool (aka Knife) can easily dispatch cave bears and moderately large dinosaurs, carve through granite, print circuitboards onto sand. But most people use it for opening beer bottles. [Answer] Early settlers in North America came across Natives which did not speak their language, similar to what our hero is going through right now. To communicate, they used to use their **faces, body language and hand gestures** to signify certain actions. Wait for a large group (though not too large) to come by. A lone person or a small group may be frightened and kill you (which I assume is not what you want). Too large of a group and if things go bad, they'll really go bad. **Act non-threatening when meeting with them (slow movements, few hand gestures, don't pull out your Gamma-ray gun, and so on).** Take out the water canister and start drinking it, making sipping sounds, an "ahhh" at the end, and point over to one of the Neanderthals and point to your canister. Slowly walk over and hand the canister over. Do the same with some food. If spaceliner food is as bad as you say it is, I recommend killing an animal, cooking it, and handing that instead over to the Neanderthals. If they don't kill you or run away you can start to earn their trust. Go on hunting trips with them and use your gun to instantly kill the prey. Help them with construction of things such as tents as their tents don't build themselves like yours. So on and so forth. Finally, you can start looking for the object. **Body language is key here.** Start looking around as if you're trying to find something. They may be curious and look puzzled at you. Crumple up some foil from a used dehydrated supply into the shape of the beacon, and point to it and the vast wilderness. Start to wander off and see if they follow. If they do, try to split them up by pointing at someone and point off to a direction. If all goes according to plan, you never spoke a word, but you got the general idea across that you're looking for a silver object in the world. If they find it or not is out of your hands, but at least you tried. [Answer] **Convince them you are a divine being** I can't be the only one whose first thought was *"Fleece these ...neanderthals and make them worship you"* Use your technology and education to become the leader. Spoken communication would develop in time. Prior to that developing, utilize gestures and expression as @Thatguypat mentioned as well as pictures. After all a picture speaks a thousand words. Odds are if they are near you they also saw you crash. But it wouldn't be crash to them, so draw a picture of the sky and stars and yourself coming to earth. Show them your magic (tech) and get them to follow you. Keep them happy by helping feed them with your rifle. [Answer] Relax, if they aren't talking yet, it's probably just because they are a bit spooked and a bit defensive. As Vortana is so helpfully info-dumping on you right now, "They are quite [closely related](https://en.wikipedia.org/wiki/Neanderthal#Origin) to H. sapiens such as yourself." I think she mentioned something about how they are likely looking for a new home, after all they usually don't live in such large communities. As they get a bit closer you'll know for sure, you wouldn't expect a hunting or war party to have the women and children anyway. There she goes again with that word, Mesolithic. That means middle stone age, i.e. no agriculture or advanced tools. [Mousterian](https://en.wikipedia.org/wiki/Mousterian) to be specific. Come to think of it, how did you know they were Neanderthal? From a distance they do look a bit short, but that might be expected for undernourished people living in a glacial period. And that heavy clothing makes it difficult to tell how stout they are. Must have been Vortana. Unfortunately, now you're being filled in on how not much is known about their cultural. You aren't sure if they will be prone to follow a shaman or kill one. Better keep that under wraps for now. As they are getting closer you can clearly see children with them, but as Vortana is now pointing out they age faster than sapiens, so it's likely they are a bit younger than you might expect. Being as they are approaching in such a manner they probably aren't looking for a fight, and if you can offer them something they might let you come with them. Vortana is filling you in now about how later Neanderthals tended to be pretty inbred, so you think they are probably in need of fresh blood in their clan. You ask Vortana if she still has that old language immersion software for children. When she skeptically replies "yes?", you know you've got a plan. [Answer] Don't fall asleep. They may kill you and steal the artefacts believing they can use them without your help. Beware of customs. If you are a man, you may have to return to their camp and marry the chief's daughter - and prove your ... erm ... abilities. If you are a woman you may find a whole hunting party of Neanderthals somewhat daunting, especially if they have been away from their women-folk for some time. Keep that ray-gun handy. [Answer] They would probably be very suspicious that you are a dangerous predator. They have their society, and you are not a member. You would probably not be permitted within proximity to their camp until you gain their trust. The question is; can you gain their trust by persistently approaching their hunting parties and attempting to interact with them? Or would they kill you on sight, like territorial gorillas? I suspect that this may depend upon the culture of the individual group. The culture of the group may depend upon their past experiences. If they have been in violent conflicts with other humanoids, or if they have been made to feel betrayed, then they may have a kill on sight policy. Understand, that even today, there exists in the Amazon uncharted tribes of humans. Some percentage of these tribes have a kill on site policy, and will literally murder anyone or anything that crosses their path. I can only assume that sub-humans would be about the same as humans in that respect. welcome to humanity. [Answer] [Silverberg, expanding on Asimov](https://en.m.wikipedia.org/wiki/The_Ugly_Little_Boy), they made the Neanderthals fully intelligent in language ability, by having the lack of representational art and decoration in general be a cultural belief, not an inability. You could do something like that and have your meeting be as between *people* as described in other answers. But if they are more ape-like, not giving attention to your communication efforts, and not able to reason out novel ideas, you'll have to rely on innate primate body language. Think about meeting a troop of gorillas and trying to communicate. Another idea, if they had been having continuing contact with modern humans. In some areas, Neanderthals immitated tool making techniques from their modern neighbors. Consider a culture of Neanderthals have had a competitive advantage for a thousand years of watching the newcomers, combining the learned toolmaking and housekeeping tech that they could not invent themselves, with their own better adaptation to the winter climate and superior strength. That group might be ready and willing to cooperate with the stranger, as they do with seasonal encounters with the Cro Magnon. Perhaps they even put up visitors, offering a warm cave and comforts of a perminant base in exchange for some "tinkering", fixing delecate items, sewing, and such with their better fine motor skills and problemsolving. ]

[Question] [ If a planet always faces the same side to the sun, so that it has a permanent night side and a permanent day side, it will have a twilight zone in between the two sides. This will be a band around the planet which permanently has conditions similar to dusk/dawn. If the day side is too hot and the night side is too cold to support life, how wide could a habitable twilight zone be? What factors would affect how wide it could be? How much variation would there be within it, and would there be a sharp cut off where it becomes uninhabitable or a gradual drift into extreme heat or cold? [Answer] If the planet is tidally locked, the main determining property of the planet will be the heat transport from the warm to the cold side. There are two main heat transport mechanisms: Air currents (wind) and ocean currents. To simplify the writing, I'll define principal directions as follows (this is different from the conventional definitions, but since there's no relevant rotation anyway — unless the planet is very close to the star, but then the planet would probably not be inhabitable anyway —, the normal definitions would be pretty useless anyway): **North** is the direction away from the sun, **south** is the direction towards the sun. That is, it gets colder and darker as you go northwards. **East** and **west** are the directions perpendicular to that, as usual. That is, in east-west direction, the brightness will be constant (except for terrain influences). # Air flow The basic mechanism will be that the air/water will heat up and therefore rise on the southern side, and cool down and therefore sink on the northern side. For air, what you'd experience is the lower part of the air flow. Therefore there would be a constant cold wind flowing from the cold to the warm side. The main influences on that wind would be mountains and oceans. Mountains can block winds if they are in east-west direction. They will not block the wind in north-south direction, but if shaped right, they might increase the speed, and therefore would allow the wind to get further before it warms up. Also note that if the air goes over the ocean (especially if the ocean is warmer than the air), it will contain more water. If it then is forced to go over an (east-west) mountain, the water will condense and rain/snow down there, leaving condensation heat in the air; when the wind goes down it will therefore end up warmer than when it started (so-called [Foehn wind](https://en.wikipedia.org/wiki/Foehn_wind)). Of course if it is too cold north of the mountain, there will be no open ocean (free of surface ice) to draw water from (that might locally be helped using volcanism; even if the heat itself is insignificant, it might be enough to provide a significant open water area). In the north, the extra cooling by the wind is unwelcome (it's pretty cold anyway). Therefore you'd preferably have east-west mountains north of the habitable zone; a well-placed east-west mountain in the north might be able to extend the habitable zone there, ideally with open water north of it. On the south side, the extra cooling would be most welcome; north-south mountains would be ideal. However very much in the south (ideally just at the end of the extended habitable zone), you'd again want east-west mountains in order to collect the water from the air before it goes off into the southern desert. Also note that mountains could generate local wind patterns that differ from the predominant north wind. Eddies could even transport warmer air a bit to the north. # Other effects of mountains Another point about habitability is the height. The air gets colder the higher you get, and therefore you could live in the mountains in the south where at sea level it already would get too hot. That's another reason why you'd want mountains in the south. Also note that in the shadow of a mountain (that never moves!) it will be colder than in the direct sun, so also those shadows might increase the habitable zone. Especially note that in/near the twilight zone you'll have very large shadows. # Air composition Another thing to consider is the air composition. On one hand, you want greenhouse gases. Greenhouse gases not only make the planet warmer that it would be otherwise; by keeping the heat longer in the atmosphere, it also allows for more equal distribution. That is, a tidally locked planet which has less incoming radiation, but a higher greenhouse effect to achieve the same average temperature will have a larger habitable zone. On the other hand, if there's much dust in the air (possibly because of lots of volcanism), the light will get more scattered, and therefore you'll get a more evenly distributed lighting (and a more impressive coloured sky/sun). Note that more dust will likely also reduce the average temperature. Finally, there's also the refractive index of the air: The sunset on earth appears to be later than calculated from pure geometry because the air bends the light downwards. Therefore on the tidally locked planet, the twilight zone would be moved slightly to the north, leaving a larger area of the planet illuminated. The illuminated area would be the larger, the larger the refractive index of the air is. # Ocean currents For ocean currents, you experience the upper side of the ocean, so the main effect of the ocean currents will be to transport heat from the south to the north. For example, Europe is much warmer than to be expected from the latitude thanks to the [Gulf stream](https://en.wikipedia.org/wiki/Gulf_Stream). Note that ocean currents are much more complex because of the continents, but as general rule you'd want to have oceans in north-south direction to enable northwards ocean currents. Also note that an ocean current could also be the reason why some northern oceans are ice free to provide a water source for the Foehn wind. # Orbital movement Another point to consider is that the orbit might be slightly elliptic (most planet orbits are). In that case, the tidal lock will not be perfect, but the planet will apparently "oscillate" a bit around the lock position (because the planet's rotation is constant speed, but due to the elliptic orbit the revolution is not). Note that this is also the case for the earth's moon: It doesn't always show *exactly* the same side to the earth. Such a slightly elliptic orbit would then cause seasons in some parts of the twilight zone (it also would have a seasonal effect on the total incoming radiation due to the varying distance to the central star). Basically, the sun would rise/lower a slight bit in the course of a year. Since that apparent rise would also distribute the incoming stellar radiation over a larger area on average, it might also increase the inhabitable zone. [Answer] # Meteorological models of tidally locked planets Provided there is earth-like atmosphere on the planet, there is several scientific articles which try to answer this question. For example [Joshi 1997](http://crack.seismo.unr.edu/ftp/pub/gillett/joshi.pdf) or [Joshi 2003](http://www.geo.brown.edu/classes/geol1950g/Joshi2003.pdf). The most recent is probably [Yang 2013](http://arxiv.org/pdf/1307.0515v1.pdf). In his article, there are very interesting maps of cloud cover (page 1) or temperature including the cloud cover (page 5). According to these calculations, the mean temperature difference between the substellar point and the twilight zone is approximately 70 kelvins. Articles of Joshi give only about 40 kelvins or less. If you ask about habitability for humans, the reasonable temperature range for them is probably 0 C - 30 C, which according to Yang would be probably from equator (latitude 0°) to latitude 40°. Joshi would probably give even more. Since extremophillic organisms manage temperatures around 80° C or more, they could inhabit the whole insulated hemisphere. It is also important to note that higher atmospheric density means higher flow and smaller temperature differences. On the contrary, thinner atmosphere means higher temperature differences. Calculations in the articles are for aquatic planets. Over large continents, temperature on the insulated hemisphere will be much higher (30 - 50 kelvins more?). I do not know about many articles on this, though. [Answer] Last question first: No, there will be no cut sharp. Moon has no twilight because it has no atmosphere: Sun is on sky or it is not, period. But Earth has atmosphere so we have some times, twice a day, when Sun is not on sky but there is some light around. These are twilights. And note that they both are with Sun not on sky, so on a tidally locked planet the twilight zone would be both a TV series and a band in the dark side touching the terminator line. It is not evenly distributed in both bright and dark side. The denser and higher the atmosphere is, the bigger the twilight zone. The variations on it would be the same as in our twilight. Really, it would be mostly the same as our twilight in all aspects, except weather. Weather in our twilight zone includes winds from still-hot sea to already-cold land (breezes), which are transient at dusk, and from already-hot land to still-cold sea (transient, at dawn). In a permanent twilight zone, this can not happen so easily, since it would draught all atmosphere into cold zone quite fastly. But the same thermodynamics applies, so you will need to have a permanent breeze, near the surface, and an also permanent counter-breeze higher on the atmosphere, equilibrating the pressures on bright and dark side. Need to say that twilight zone is not equivalent to habitable zone. There will be more room for life in the bright zone, near the terminator line, where Sun is always on sky but low on sky and thus bringing small amounts of light and heat. In these zones you'll have permanent shadows cast by mountains and trees, and so a very diverse biome, from siberian taiga to Sahara desert, before reaching non habitable zone. Since bright zone can have oceans, you can also have big evaporation, and thus enormous clouds and storms, which make the not-too-hot zone even bigger. With a dark enough atmosphere, even the entire planet could be habitable! [Answer] The width of the zone will directly correlate with the size of the planet. Twilight / dusk is where the sun is 6 degrees under the horizon (for earth), so this part of the world will be almost perpendicular to the sun. A larger planet will have a much more gentle curve to it, allowing a larger area of the planet to be in twilight / dusk. Variation and cut off would be defined by the width of the zone. A narrow zone will have little variation but a sharp cut off as the zone has little influence on the hot and cold sides. A wider zone would have a larger amount of variance between the hot side and the cold side, but a more gradual cut off. [Answer] I would take a different approach than the above answers: Evolution is **remarkably** good at finding solutions to living in the harshest of conditions. The bottom of the Mariana's trench is at over 100 MPa, total darkness, and nearby hydrothermal vents rest comfortably at 400 degrees C. In those environments, we have found life. Waterbears are known for being able to survive at 1 degree above absolute zero or the vacuum of space for several minutes. Nature is **really** good at finding ways to habitate areas. I would expect to see a gradient as one approaches the inhospitable parts of the landscape, where we see lower forms of life because there is less incentive to get more complicated or more intelligent. We'd see more sharp edges if the planet was truly tidally locked. Realistically, there will be SOME wobble, however slight, generating areas where mid-range temperatures exist. Those blurry areas would allow evolution to start exploring solutions to adapating. [Answer] If with habitable we mean: "Supports photosynthetic plants that serve as a basis for local ecology" this is simple enough. It is the portion of the planet that receives sunlight, which is roughly half of it. This obviously assumes optimal hydrosphere and atmosphere giving habitable temperature for all of the planet. In practice, there would be lots of variables that would make it less or more than that. If with "habitable" we mean "habitable to humans without high technology" and the planet is sub-optimal in its water coverage, there might be inhabitable hot area and nobody would live at the extreme edges. If we don't care particularly about humans, the answer would be more than half the planet due to currents carrying plankton to the dark area and the area that gets light actually being somewhat larger than half due to wobbling and the size difference between the star and the planet. The number you want is somewhere between these two ends. I really think that "roughly half" is the best "generic answer" you can get. Also note, with chemosynthesis the dark side could actually have active, and quite interesting, ecology. If we assume active volcanism (quite reasonable, actually) and drop the requirement for photosynthesis as the base for ecology, **all of the planet** might support life. This is actually probable for planets with native life. Life is really good at spreading itself. And chemosynthetic life is generally assumed to be very early development. [Answer] There would be varieties of plant life in the dusk zone that would adapt to gather as much light as possible, becoming darker to absorb more, potentially even black. The plant color could possibly then lighten as you move to the terminator and back over to the light side. [Answer] Come on folks, stay current. The world you are working on here is an Eyeball Planet... Look it up. :> Such a world is possible and many probably exist. The colony in the twilight area would be stable, sustainable and would be able to use a stretch of world 25 thousand miles around and perhaps 2,500 wide. All that would be livable area as the streams running through from the ice side (water melting from glaciers, etc. as it approaches the warmth) would be running through to the hot side where it evaporates and fall again as rain on the dark side. Upper population limit would be perhaps a billion, unless a Soleri-style arcology was used, or more likely a group of them. Venus could have become an Eyeball world with just a little tweaking. ]

[Question] [ I saw this picture and I wonder if you can train a monkey and use him as bodyguard or soldiers in a medieval world. If so, can they be effective against human troops? How can you make them not betray you? [](https://i.stack.imgur.com/T8a53.jpg) *Monkeys dueling, Postcard art at by Maurice Boulanger, circa 1900. Maurice Boulanger did many postcard featuring anthropomorphic animals, published by Kopal and also by KF Editeurs at the beginning of the 20th century.* [Answer] *Reality check, is reality check, and what better answer than reality?* --- ## Monkeys There have been occurrences of monkeys picking up knifes, for instance: [](https://www.youtube.com/watch?v=6jZJVHp3-9Q) *Drunk monkey attacks bar patrons with knife [(watch video)](https://www.youtube.com/watch?v=6jZJVHp3-9Q)* Or this one: [](https://www.youtube.com/watch?v=8PmerX60aik) *Monkey Using Knife To Carve Jack-O-Lantern [(watch video)](https://www.youtube.com/watch?v=8PmerX60aik)* --- As [Ghotir mentions](https://worldbuilding.stackexchange.com/questions/72177/can-i-train-monkeys-to-fight-with-knives-effectively#comment209688_72179), Javkie the baboon participated in WWI: [](https://i.stack.imgur.com/GfXLR.gif) > > Until August 1915, Jackie was the beloved pet of the Marr family, who lived on Cheshire Farm, Villieria, on the outskirts of Pretoria. When, as No 4927, Private Albert Marr attested at Potchefstroom on August 25 1915, for service in the newly-formed 3rd (Transvaal) Regiment of the 1st South African Infantry Brigade, he asked for and was given permission to bring Jackie along with him. (...) He drilled and marched with his company and would entertain the men – such entertainment would become all important to relieve the boredom of the stalemate of trench warfare once the Brigade reached France. > > > (...) > > > At night when on guard duty with Albert, he was particularly useful because of his keen eyesight and acute hearing. He could give early warning of enemy movement or impending attacks with a series of short, sharp barks and tuggings at Pte Marr`s tunic. Jackie wore his uniform with panache, would light up a cigarette or pipe for a pal and always saluted an officer passing on his rounds. He would stand at ease when requested, placing his feet apart and hands behind his back in regimental style. At the mess table he used a knife and fork in a proper manner and cleverly used his drinking basin. > > > -- Except from the article [Jackie The Baboon](http://samvoa.org/special-interest/world-war-i/jackie-the-baboon/) by the South African Military Veterans Organization Of Australasia (SAMVOA). As explained in the article, Jackie served in the front line, and was particularly good at detecting enemies. In April of 1918, Jackie was injured by a piece of shrapnel during a confrontation in Reninghelst, and lost his leg. [](https://i.stack.imgur.com/o9ENz.jpg) Although Jackie served in the front line, I have found no account of Jackie engaging in combat. As for his skill with knifes, as mentioned above and portrayed in the picture, Jackie was able use eating utensils... this does not imply its use as weapon. > > Jackie died a day after a fire destroyed the farmhouse on 22 May 1921 and Albert Marr passed away at the age of 84 in Pretoria in August 1973. > > > -- [Jackie The Baboon](http://samvoa.org/special-interest/world-war-i/jackie-the-baboon/) by SAMVOA. **Monkeys handling weapons** As we can see above, monkeys can pick and use a knives and use some extend. Pay attention to the way Monkeys instinctively pick knives. They do a Reverse Grip (a.k.a Ice Pick Grip), which is effective to make a strong stab, but not for reach. Also, see that a knife can be a large weapon for a monkey: [](https://i.stack.imgur.com/noVkl.png) Due to its size, one would expect that the monkey would require both limbs to be effective. Also, we shouldn't expect the monkey to be good at fencing (disregarding the required training) just because this weapon is not appropriate for them. *This all makes Jackie exceptional.* The above suggest that it could be a good idea to provide the monkey with a shorter (and perhaps slightly curved) blade that the monkey can conceal in using the reverse grip. Perhaps something designed to be easily carried in their mouth when they are running (they can run on three or even two legs, but not as effectively). In fact, you can train them to walk (not run) in [two legs or on the hands](https://www.youtube.com/watch?v=zQ4AgJ3GqjI), or even [spin a fire pole](https://www.youtube.com/watch?v=plnD-7yEocE). Therefore, you carry your well-trained monkey... and sneak attack! Monkey jump to the back of the victim and quickly stab the neck before they can shake it off... R.I.P **Monkey psychology** You can have a monkey *probably* not betray you by being fair and useful to it. [Monkeys understand fairness](https://www.youtube.com/watch?v=-KSryJXDpZo) and have [moral principles](http://www.nytimes.com/2007/03/20/science/20moral.html). Under thar order of ideas, if you treat them as people and you provide for them (shelter, food, attention, etc...) they will have the incentive to care for you and could defend you. With that said, the monkeys probably will not attack unless they see others attack you. That is because, they usually resource to make noise and throw stuff to scare intruders off. Yet, once in a fight, they can be deadly. Training them to attack is more complicated, you would have to set up a simulacrum for them to practice (I am picturing some straw stuffed dolls hanging from the ceiling, or stuff like that) and a rewards for their work. Will they betray you... maybe, probably, perhaps? Will they kill you? If they see you as a threat, most likely they will. Consider this: humans can betray you, why wouldn't monkeys? **Monkey against human troops** Even under the assumption you can reliably command them to attack, a solider with shield, spear and sword can effectively defend itself against a monkey. For your monkeys to be effective, you need to ambush the enemy. You need the sneak attack. Instruct the monkeys to attack the encampment when the soldiers are sleeping, or have them jump from the trees when they are passing by. If you need to defeat guards, have the monkeys sneak around their field of vision. Think less of them as monkey soldiers, and more as monkey ninjas. --- ## Chimpanzees Although Chimpanzees are not monkey, they probably most useful in battle. Chimps could also be trained for combat! [](https://www.youtube.com/watch?v=zYcAkXIN1g8) *► Charlie, The Karate Chimp ! [(watch video)](https://www.youtube.com/watch?v=zYcAkXIN1g8)* We can also see that chimps naturally use sticks and rocks as weapons: [](https://www.youtube.com/watch?v=pZ3gOCtoK0U) *Chimps using sticks as weapons [(watch video)](https://www.youtube.com/watch?v=pZ3gOCtoK0U)* [](https://www.youtube.com/watch?v=Ogq889RlUJQ) *Weapons [(watch video)](https://www.youtube.com/watch?v=Ogq889RlUJQ)* --- Apparently, chimps seem to be a very good option for a combat unit, although they probably are more effective with a spear than a knife, given that in nature they often use branches as weapon. Consider creating and designing custom weapons and armor for the chimps. --- ## FAKE VIDEOS The following videos where released in 2011 as supposedly real footage from the 20th Century Fox Research Library. The videos "went viral" shortly after. [](https://www.youtube.com/watch?v=d-0vbvy2ip4) *Chimp with Machete [(watch video)](https://www.youtube.com/watch?v=d-0vbvy2ip4)* [](https://www.youtube.com/watch?v=kXcnlie9k8w) *Ape With AK-47 (Gun) [(watch video)](https://www.youtube.com/watch?v=kXcnlie9k8w)* [Rise of the Planet of the Apes](http://www.imdb.com/title/tt1318514/) by 20th Century Fox was released later the same year. Are you still not convinced they are fake? Well, the article [Behind the Social Marketing of ‘Rise of the Planet of the Apes’](http://blogs.wsj.com/speakeasy/2011/08/12/behind-the-social-marketing-of-rise-of-the-planet-of-the-apes/) documents the campaing. The full article is behind an account wall, but you can still read: > > To raise the film’s profile online, Mekanism both targeted a group of 50 social media influencers as well as released a series of short “real ape” videos they hoped would go viral. The former campaign began back in June, when Mekanism reached out to selected YouTube stars and movie-bloggers to help them build buzz — especially among millenial-age males. > > > --- **Can a chimpanzee learn to shoot a gun?** Regarding the videos, LiveScience asked John Mitani, primatologist from University of Michigan, who said: > > I wouldn't doubt that you could train a chimp to wield a gun in the manner shown. > > > When shooting the gun, I'd be hard-pressed to think that the chimp can really understand [the consequences of] what he's doing. > > > Also Steve Ross, primatologist at Lincoln Park Zoo in Chicago said: > > Chimpanzees have been seen to use rudimentary weapons (such as projectiles, clubs and spears), so they have the capability of understanding that a tool can be used to cause harm or do damage. > > > Whether or not they would understand a gun is more difficult to say. > > > Source: [Planet of the Apes: Can Chimps Really Shoot Guns?](http://www.livescience.com/15120-planet-apes-chimps-shoot-guns.html) [Answer] I think it's important to make the distinction between "trained" and "trained to do things like a human." We have different centers of gravities, body morphology, and general ways of doing things and would have to take into consideration those differences when fighting the same opponents. What you can do is, give a monkey a sword/knife and show them how it can be used to do damage to a person. You can teach a monkey commands to indicate targets. But ultimately you can not teach them how to best use a sword/knife using their body plan because you simply don't have their body plan yourself and thus don't know, nor any real idea, on how to work with it to produce the best results. Likewise, you're not going to teach a monkey how to move like a human perfectly and so you're not going to train them to do any of these combat techniques that require precision replication of the human form to do. So you can "train" them in general to act as a bodyguard or a fighter that uses a knife/sword but you're not going to train them to be anything like a human doing those things. [Answer] Yes. First you have to show them wood knifes to fight. Then you have to give them knifes with real, dangerous blade. They will have to learn, that it is dangerous and experience their mechanics. Chimpanzee like to fight with eachother, giving knifes to the chimpanzee in a horde could may catalize their civilization. You need many hordes for that, because in a single horde they know, when is it the time to take back and thus you won't have enough cruelty (between them). The main problem with it that they won't want fight with it. You have to provide some extreme motivation for them. Doing this would be worse animal cruelty and hopefully it would remain imaginary. [Answer] Your first problem is the fact the human hand is a very specialised and highly evolved piece of kit. Monkey and ape hands have short stumpy thumbs, long palms, wrists designed to be load-bearing structures (because they are 4 footed) and various other features which mean they won't be able to hold or wield a knife as effectively as a human. Secondly... also because they are four-footed... they can't move efficiently or effectively when one of their 4 paws is holding a knife. A human can charge up and stab you. A monkey will sort of hobble up and stab you. If the monkey really wants to hurt you, it would be better off dropping the knife, charging up and biting you. Ape jaws (chimps for instance) are a lot stronger than human jaws. We sacrificed bite strength to change the shape of our skull to fit in a big brain. A human CAN bit off your finger, but it takes a lot of chewing. A chimp can do it in an second without breaking sweat. I guess you could have big male baboons as 'war dogs'. The autobiographical book Jock of the Bushveld by James Henry Fitzpatrick had a chapter about a baboon which had been trained to fight hunting dogs. (Warning: the book was written in 1907 so has racist attitudes). [Ch 23: The Fighting Baboon](http://central.gutenberg.org/wplbn0002880588-jock-of-the-bushveld--chapter-23--the-fighting-baboon-by-fitzpatrick-percy.aspx?) [Answer] Monkey's can 100% be trained to use objects such as knives. While backpacking in Asia, I trained a monkey to throw a metal Chinese star in less than an hour. I'm just an ordinary guy with no professional background in monkey training and the only combat experience I have is surviving the mean streets of Boca Raton, FL. Unfortunately, the monkey threw the Chinese Star at me after he started to get the hang of it. Luckily, my quick reflexes kicked in and I blocked the star with my hand..... but I suffered a deep gash in that hand (see pic). I probably should have got stitches but the only medical help I could procure wanted to use his shoelace to close the wound, which didn't seem very sanitary to me. Anyways, I have the scar to prove that monkeys can be trained to handle weaponry of all types. The monkey in question did "betray" me, which could have killed me! Let this be a cautionary tale to all of you and those that want there own private monkey armada or whatever.....these monkeys cannot be trusted. My wife, who was with me on the trip, claims the monkey was trying to kill me to get a bag of chips and a can of soda I had next to my backpack. Sounds silly as I'm typing it, but you never know. ~Kraber ]

[Question] [ Imagine that there are two nations at war, but fighting is limited to a small section where their nations border each other. Travel is "conventional", forces from one nation can block the other from deep incursions by placing themselves in the path. Now suppose that both nations develop a miraculous transportation technology, completely changing the dynamics of war. Each nation can instantly transport a large army to almost any point in their enemy's territory - including their capital city. After the initial shock of adjusting to this development, would warfare increase or decrease on aggregate? Are there any periods in history where analogous developments took place, and what happened? [Answer] This feels like a cop-out answer to me, especially on a world-building site, but I'm going to say that there's no way to answer this. Let me explain: First of all, either the technology is discovered/learned by both sides at effectively the same time (on military timescales), or it wasn't. **If it wasn't,** then whichever side got it working first would use it to win the war... unless that side didn't have sufficient forces to delay the invaders while simultaneously transporting an invasion force to inside the enemy capital's defenses. That lack could be due to manpower, geography, or a specific limited resource. Anything where taking troops off of the front would cause the front to collapse. However, assassination suddenly becomes a viable option even for a lone operative transported into place. If they do have sufficient resources to open the new front via teleportation, they can make either targeted strikes on the enemy government/leaders, or send in a general occupying force to force a surrender. **If it was close enough to be simultaneous,** then there's the next decision point: Either both sides know the other has (or will soon have) this technology, or they don't. If they don't know, then expect to see the "if it wasn't" tactics carried out by both sides, and whoever is first, will probably be the victor. If they're both aware of each other, it gets very interesting, and you can start drawing parallels to the Cold War. Basically, each side has the ability to launch a devastating attack on the other, even if it means they are also destroyed. Depending on the leaders involved and the reason for the war, both sides may choose this option (or one may choose it, triggering the other to choose it), which will then, depending on whether the citizenry martyrs the dead leaders or goes "whew, we're done with war" either end the war or lead to renewed hostilities in revenge. If neither side chooses to be the first to act, they'll start using the *threat* of being able to do so to negotiate. Since each side is equally vulnerable, the most likely outcome is a ceasefire along the current border, while each side tries to come up with some sort of defense. This is very much what happened with nuclear arsenals during the Cold War - neither side wanted to trigger open hostilities, but each kept trying to maneuver for advantage in other ways. **In short, there's just too many variables to give a simple "increase" or "decrease" answer.** It depends on how simultaneous it is, the relative strengths of the ground forces, the willingness of the leaders to order assassinations of their opposites, the will of the population to keep fighting even after a leader is assassinated, and just how quickly each side can act. [Answer] Several factors that come into play here: * Element of surprise / reaction times. If whoever has the element of surprise is most likely to win a conflict, then yes, it would increase the frequency of warfare and conquest. Until reaction times to these sorts of assaults were improved, such that the element of surprise were lessened, this would remain the case. This is why the marines in the Aliens franchise use motion detectors: once the aliens get within visual range, they make quick work of marines. Similarly, it may be that your teleportation technology requires a large energy build-up in order to teleport any sizeable complexity or mass of troops. This may mean that it could be detected by opponents before it happens. * Cost. Finance is about managing risk; this includes financing wars. If the proposal looks good, the risk of being struck at first is high, and ethics are not in question, then a quick, first strike may be justified. * Level of paranoia. This again relates to the general level of ethics in the world (c.f. adherence to institutions like the Geneva Convention). If paranoia is high, then yes, it is highly likely that lethal first strikes would become commonplace. * Centralisation / deployment concentrations. If attacking capitals became commonplace, societies / nations would become more decentralised. It may also serve to decouple military administration further from civil administration. If an opponent aims for your heart, have more than one. This also leads to forces being deployed according to the risk factor inherent in not defending a particular facility. If there were time to adapt societies to these tactics, you would end up with highly-compartmentalised, cell-based territories, probably consolidating resource gathering, manufacturing, residence, and military capabilities if not into the same cells, then into very tight localities of cells. This would make for nations that are most resistant to damage. Of course even this assumes no use of large area-of-effect weapons like nuclear weapons or excessive air power; if these are factored into the equation, then you would likely have scattered, self-sufficient compounds, or mutually-reliant compounds which would teleport supplies between them. Even in this case, it's likely that you'd end up with a hybrid approach -- scattered bunches of cells, such that every locale had compartmentalisation built in. Then again if you consider the possibility of teleporting immediate-detonation nuclear weapons into enemy cells, you end up with armageddon in any case... a gross simplification is that whoever has the most cells, develops the necessary technology first and has the energy available to use it, wins. It's bedlam, because it's a case of hair-trigger timing if multiple nations gain the same technological capabilities around the same time. More than anything else, could a technology be developed that could prevent teleport materialisation, even if only within a limited space? The high likelihood is that this would be the next arms race, just like Star-Wars-type programs were in late 70s and early 80s. Interception / interdiction would be the game changer. [Answer] Most of the answers above have dealt with this question in regards to the idea of using it as a conventional weapon, but none of them have yet mentioned that instantaneous transportation would also be a fantastic defense. You could, for instance, use it to move your citizens and all of their goods out of harms' way, so that when the other army does arrive, they arrive to a completely empty settlement. This could create a sort of "hide and go seek" or "chase" dynamic, as they must try to work out where you went in order to conquer you, and you could come back at any time, once you're properly prepared to take them. You could likewise use such a town as a baited trap, safely removing the bait and inserting the army/weapon of death as soon as it is sprung. Likewise, an army appearing near one base means that another base has just suddenly lost a whole lot of men, making it very vulnerable to attack. If you have spies capable of instantly teleporting to you and informing you which base is now low on men, you can ship your people and your army out to take that location while the other army sits around wondering where you got off to. In the end, you'd probably wind up with patchwork territories around certain key points, instead of continuous nations. The land between these points would become inconsequential to both trade and war, so it would remain largely untouched (unless you decide to use one as an escape route/hiding place/staging ground), while those few cities of interest would change hands *a lot.* [Answer] If your army travel faster and can attack locations the enemy does not defend it will win. It´s as easy as that. **In the Art of War Sun Tzu said:** > > Therefore the skillful leader subdues the enemy's troops without any fighting; he captures their cities without laying siege to them; he overthrows their kingdom without lengthy operations in the field. > > > One interpretation of that is: **If you choose the battleground, you Win.** If you can choose where to be for your offence or defense you can build your strategy around that fact that you know about the battlefield and your troops layout and the enemy doesn't. Also: In history on the battlefields the fast units like cavalry were a hard hitting Weapon because it could hit everywhere. In Modern Times: * Paratroopers in WWII. Jumped somewhere where the Germans were not defending. Make a big mess out of the land behind the front and the beaches. * The War in Iraq (the first weeks). The infantry weren't used much because the war was way to fast moving after the Iraqis troops were overcome, only airstrikes won this first time (as far as the media broadcast it in Germany). **In future Times like it is Questioned here:** With instant traveling, like teleporting, it will be still the same. If you teleport, say 500 troopers to one location, beat the targets in the area in the first few minutes and teleport away. The Enemy did not have enough time to report the teleport location before the damage is done. **Defending against teleporting Troops is almost Impossible.** **Example for warafair with teleportation out of the Warhammer 40K Universe:** [Main article of the Lexicanum about teleportation](http://wh40k.lexicanum.com/wiki/Teleportation#.VCM7yfl_tWY). All mayor races have their different ways to teleport. But if on one specific Battlefield only one Race has the technology available, the fights are mostly very short. In the novel "Soul Drinker" is the only mentioning that a teleportation tactic failed. After teleporting weaker forces right into the battle zone they got slaughtered. **TL;NR:** **In Open War affair the faster army wins by out maneuvering the slower, if the general staff uses the technology by hand in a smart way.** **Only If you fight against an Invisible Enemy, in a guerrilla war, speed is not important.** [Answer] This technology would be extremely powerful. Being able to project instant military force in any area is something beyond even modern military technology today. The sudden development of this weapon on both sides of a conflict might be akin to a Cold War situation, depending on the ethos of the societies. For example, you could draw parallels between this technology and the nuclear arms race. Each side might test the limits of the technology without risking full-blown use (in fear of instant retaliation). This could escalate tensions dramatically, ending in a catastrophic war, or a detente after societal maturation (as was thankfully the case in the Cold War). I guess the answer to your question lies in many more specific factors, such as how bitter the conflict is, how much risk is tolerable to the militaries and political factions of each side, etc. [Answer] Depending on how the transportation works, it could also be used in an attack way: Instead of transporting your troops somewhere else, transport the *enemy's* troops somewhere else, so they are out of way (if having no moral hesitation, it could also be a place where they'll instantly die, like on the ground of the ocean, in an active volcano, or in space). The same way, also their infrastructure could be easily destroyed. No need to go to a bridge to destroy it, not even the need to teleport dynamite there to explode it; just teleport the bridge itself away. Against such sorts of attacks, there could however exist a shielding technology. That would, of course, then also shield against normal troop transports. So you'd be back to a classical arms race, transporter technology against shielding technology. [Answer] The fact that one side will quickly win is not (historically) sufficient to prevent wars occurring, even if neither side is certain which side it is that will win. It *could* reduce the chances of war, since the most volatile situations are when one or both sides are certain they will win (and have motive to fight, of course). I think these teleporting armies will introduce strategic uncertainty. But I don't think there's any reason to suppose that it *must* reduce the chances. This is not necessarily a situation of mutually-assured destruction (although you write in further factors to ensure that it is, if you want the result to be a cold war). It's quite possible that one side will believe itself able to launch a decisive attack, *and* weather any counter-strike that occurs before it disables the enemies' ability to teleport and/or muster large armies. This is especially the case in the long term, it's much harder to maintain a huge standing army 24/7 ready to teleport than to maintain an ICBM ready to launch as in our own Cold War. I can see a war occurring simply because one side's logistics or economics gives the other side an opportunity for an unanswerable surprise attack. If nothing else, though, this capacity could make wars shorter simply because there's no limit to the force you can bring to bear (as there is when dealing with fortifications). There's nothing to limit the rate at which those who are going to kill each other, get on with it. Once someone wins, their main goal will be to keep out of others' hands the ability to teleport an army. Depending on the technology it might not be possible to prevent them teleporting, in which case you'd have to keep them demilitarised at almost all costs. If the victor achieves this then you can certainly argue that imperial repression is "less warfare": there may still be significant casualties but fewer pitched battles. The losing side might not feel that it's any better off under this Pax Imperialis than it was fighting a distant war on its borders, at least not unless any obvious economic benefits kick in, but it's still peace of a sort. Analogous historical situations? Nothing very close springs to mind unless you do have MAD, because frontier defence has been such an important part of real warfare. The development of aerial bombing by plane and rocket meant that, between 1918 and 1939, the major powers developed a completely new ability to put tonnes and tonnes of high explosive into each others' capitals far behind the frontier. This didn't prevent the Second World War, but I suppose you could think about whether it had a long-term effect separate from the effect of nuclear MAD. I don't know the answer, although I rather suspect that for example the Korean and Vietnam wars would not have happened, certainly not in the form they did happen, if the "locals" had the capacity for conventional (non-nuclear) bombing in London, Paris and Washington. Going back much further, consider a small, low-tech "warring tribes" situation. Territories are small, fortifications aren't really all that good with the exception of prepared caves, hillforts, and suchlike. A walled border you can't man doesn't do nothing but it doesn't do a whole lot. I'm not sure whether by "almost any point" you mean "except for a few special protected locations", but if so this comparison has relevance, I think. You can't literally teleport anywhere, but if your enemy's territory is only a day's travel across, then you can put such fighting force as you have *almost* anywhere very quickly. Warfare is neither constant nor particularly rare in such societies historically, and I think prevalence is based on social and economic factors that determine how willing people are to launch an attack more than the fact that everyone is relatively vulnerable all the time. Another possible comparison is guerilla warfare. It's asymmetric, but it has the property that both sides can move around the territory and in principle attack almost anywhere, there is no frontier. To over-simplify, at any given moment one side doesn't attack because it doesn't know where the other side is, and the other side doesn't attack because it's weaker, has no safe place to muster, and doesn't want excessive losses. Any local change to these factors results in localised combat, so combat is locally intermittent but might well occur somewhere every day. For another asymmetric example, consider the way that Vikings terrorised England and parts of France for 250 years or so. They didn't teleport of course, but certainly delivered force unpredictably at speed well beyond their "borders". They would simply appear unannounced in a village or abbey, take everything of value, and leave. The English fought back at varying times with varying success, and Wessex had a reasonable try at maintaining a standing army spread throughout its territory to react to raids, but nobody was able to take the fight to the enemy. The Vikings had much of England at some points, lost English territories at others, and many settled and assimilated. It was not a peaceful time. Ultimately they won all of England, if you count the Normans as Vikings-in-exile ;-) [Answer] The extent to which a teleportation technology ends up being a stabilizing or destabilizing influence would depend a great detail on its abilities and limitations. If a transport operator can send anyone or anything basically anywhere after scanning around the intended destination, and can likewise retrieve almost anyone or anything from basically anywhere, that operator would have nearly unlimited power unless there were some limits on the who/what and where. It is unlikely that two or more people could have such power simultaneously unless either (1) they trusted each other very well, or (2) the abilities of the transporters were limited in such fashion that one couldn't simply take out the other. For a story involving transporters to be interesting, it should make clear to the reader what abilities the transporter does or does not have. For example, a transport might take the form of matched pair of rings which warp space so as to connect their interiors, but which must be manufactured together and physically conveyed to anyplace where they might be used. If it was easy to detect the whereabouts of such warping, but hard to interfere with it, teleporters might be more useful on defense than offense: without teleportation, the only way for a country to guard against a concentrated attack on any point would be to have all points be sufficiently protected to resist a concentrated attack, but a defensive teleport network would resist the effectiveness of an attack. Note that the if attackers could conceal their troop movements they wouldn't need teleporters to concentrate their forces, since they could spend as much time as they needed to concentrate their forces before launching their attack. Note that if a country managed to get a teleporter behind enemy lines, that could facilitate an overrun of the enemy, but if teleporters were easy to detect, smuggling teleporters might be difficult. [Answer] Using it to wage war is pretty silly unless it's a war of genocide. You'd put your armies in places that *had* to be defended and then just sit still. The chance of being caught out & ambushed (unless the teleportation is at-will for huge numbers to anywhere) becomes even greater, because any intel on your enemies forces regarding location and intent is entirely useless. The best use would be for targeted assassinations, don't let your enemy know you have it, then attack their generals, war cabinet, royal family etc with death squads. Teleport into their Treasury adnd back out again with all the loot and hide it somewhere random. Armies are still armies, if you teleport your army into combat with theirs, it's still just a fight and in warfare soldiers can rarely see their enemy for long before combat starts anyway, for them it wouldn't be all that different. So, it would be much the same. High up folks who thought they could get away with it, would send people to their deaths fighting for "freedom, liberty and the other guy is an asshole" and people who didn't think they could get away with it..wouldn't. The vulnerability conferred upon leaders would make pretty much every war a guerrilla war though, and the technology would thereafter be strictly controlled by anybody with the power to do so, cause it would be a clear and present danger to that power. [Answer] This is worldbuilding, so technically, the "correct" answer should be "whatever you wish to have as a result". It's your story and your world, so noone's going to stop you. But since you are asking, i'd like to throw in my five cent. First: How do you win a war? Easy question? I don't think so. Think WWII. the french were thoroughly defeated, and they surrendered. Yet in the end, they won the war. The germans surrenderered. But have they lost? The nazis have (and thanks to all that made that possible!), but there must have been a few honest and upstanding germans, and at least some of them won. In a way. Or take Vietnam. Or Iraq. I think it is debatable who won the war. Those who didn't survive lost it, that much is pretty certain, but the rest is left to discussion. It used to be "common wisdom" that the side that loses it's capital has lost. But why is that so? It's just a convention. And it only works as long as at least a huge majority accepts that. The same goes with surrendering, peace treaties and whatnot. It works because people accept it. Of course there is always a way to win a war without dispute, and that is complete genocide: if absolutely none of one side are left, a victory is hard to debate. Unless by philosophers, human rights activists, etc, that is... So even if only one of both sides had the means to teleport, they would still need to make he other side accept defeat. And it doesn't get better if both have that tech. A second, important thing to consider is: Why are wars fought in the first place? To rid your neighbours of their tyrant? To bring freedom and democracy? Possible... But more often than not it's a lot more about ridding your neighbours of the burden of possessing valuable ressources, or land, or both. Remember, someone always wins in wars, and that's the people who invest in it, those who provide weapons, fuel, band-aids, you name it. No matter what the outcome is: They win. How does that affect your original question: Your troops, even if teleported wherever they want to, are still not bullet-proof. A lot of them will not be too happy about being teleported, too. But transporting of ressources might be a lot easier. If you want, your teleportation technology could revolutionize your world by facilitating transportation so that everyboy is busy exploring novel ways of making profit with that new tech that they even forget about fighting each other. Or it just speeds things up, and nature wins because humanity looses. ]

[Question] [ [Water bears](https://en.wikipedia.org/wiki/Tardigrade) are about the most impressive organism on our planet. They can withstand extreme temperatures (both hot and cold), can survive for a time in the vacuum and cold of space, are resistant to chemicals and radiation, they can go very long periods without nutrients, can dehydrate until they are in a glass state and then simply rehydrate later... they are near indestructible. Part of their incredible ability comes from their size, but how much? How large could one of these critters grow before it is just another bug, prone to the same woes and concerns as any other critter? Could there be a cat-sized water bear that maintains its impressive indestructibility? [Answer] ## Sadly, (for they would be adorable) no. One of the main things that's going to hinder your dear "water boars" (*hey if normally sized tardigrades are called water pigletts why not call these ones boars...*) are predators. Dehydrating yourself to survive without water/nutriants is absolutely useless if a predator can come around and kill you anyways (especially since the method used to do this involves loading your cells up with tasty sugar; your animals would be turning themselves into hard candy). --- Another huge issue is that a large creature needs a complex bloodstream to move nutrients around. Tardigrades, being so small, don't. Their cells just diffuse oxygen and nutrients without the need of a heart, a bloodstream or even lungs. Larger tardigrade (which are still absolutely nowhere near as large as a cat) have to deal with their size by literally stirring their insides so that all their cells can have access to enough food. This is a neat trick but it can only get you so far (to about 2mm in size). Now at this point, you might be thinking: "So? Let's just add a cardiovascular and pulmonary system. Problem solved." Sadly things are not so simple as the less complex your organism (the less organs and body wide systems it has), the less things that can go wrong. Dehydrating a heart, bloodstream and - oh god - those tiny alvioli will without a doubt kill your creature. --- There are many many other problems, but these are arguably some of the most significant. [Answer] Yes The largest arthropods to 'walk' the earth were Arthropleura that could reach 2.3 meters in length. <https://en.wikipedia.org/wiki/Arthropleura> The challenges that AngelPray identified are the reasons why vertebrates out-competed large invertebrates. Provided that there are no large vertebrate competitors nearby your giant water bear should be fine. The giant water bear will be very slow with a 1-2 second reaction time and require an oxygen rich atmosphere. [Answer] I suspect that if there is a niche, something will evolve to fill it. The question is why is extreme toughness at a cellular level the right way for a larger animal? The square-cube law means that the larger an animal is, the more easily it can maintain its body above freezing point all winter. If we look at the Arctic, there is a frog which survives freezing solid every winter. It hasn't evolved extreme heat or vacuum tolerance because it doesn't need them. It is also an outlier. The approach used by most Arctic critters is good thermal insulation. Many hibernate to a greater or lesser extent. They reduce their metabolic rate and body temperature so they can survive winter on little or no food without freezing. This approach works (for birds!) even in the harsher Antarctic. The Emperor penguin is perhaps the ultimate example. It goes somewhere so cold abd barren that there are no predators in order to breed safely, surviving purely on insulation and body fat. If Earth's seasonal variations were even greater or longer I suspect there would be larger animals managing to survive freezing solid for lack of any alternative evolutionary adaptation. The frog is cold-blooded so this is the *only* avenue open to it to survive in the Arctic niche. For warm blooded creatures, it is easier to evolve insulation, fat reserves, and hibernation. Earth does not have vacuum or high radiation areas so any ability to survive these is an evolutionary accident, rather than something selected for. There are geese that fly at altitudes where airliners cruise and humans would pass out, but there is no evolutionary reason for them to go any higher. ]

[Question] [ Suppose the universe contained a species of [planet sized turtles](http://media-cache-ak0.pinimg.com/736x/6c/7c/d2/6c7cd27e54bfbe9d08922eb8b6f61bcc.jpg)1 that can travers at least interstellar space. How can I explain (without invoking magic) that these turtles are not [spherical](http://en.wikipedia.org/wiki/Spherical_cow)? If this is not possible within the laws of physics as they are, what can be changed minimally about them (the laws of physics) that could allow such an organism to structurally sustain itself? Important here is its relative size to "normal" living organisms. The answers to this question should not focus on how/whether this organism could survive (sources of food), travel or even evolve. For the scope of this question, all other issues with this organism may be considered to be solved. 1: not necessarily a representative image of the turtle as imagined by the author, the world on its back especially I can only assume was a fabrication by the illustrator. [Answer] ### You have a different problem (and it’s not that bad) Planets only become spherical because they are either made of material that behaves like a fluid (gas, dust, magma) or behaved like that during their creation. Moreover, planets cannot self-repair, turtles can. What you have to worry about with cosmological turtles is that their tissue bursts or breaks under their gravitational forces. So, let’s make a very rough estimate of the orders of magnitude relevant for your turtle: [Suppose your turtle looks like this](http://en.wikipedia.org/wiki/Spherical_cow):  The blue pieces represent the major masses (say, body and head) and the red piece represents some weight-bearing structure (say, the neck). $x$ is a variable length. All parts have the same depth as height, i.e., the blue pieces are cubes and the red piece is $x × \frac{x}{5} × \frac{x}{5}$. We then have (with some further assumptions): * If we assume that each of the blue pieces has the same density as water (1 kg/ℓ), they each weigh $M = 1000\,\frac{\text{kg}}{m^3}·x^3$. * If we assume each blue piece to be a point mass, the distance on which their gravitational forces act is $2·x$ and the gravitational force between them is $$F = \frac{G·M^2}{(2·x)^2} = x^4 · 1.7·10^{−5} \frac{\text{N}}{\text{m}^4}.$$ * If we assume the red piece to have the same compressive strength as bone ([170 MPa](http://en.wikipedia.org/wiki/Bone#Mechanical_properties)), it can bear forces of $$170\,\text{MPa}·\left(\frac{x}{5}\right)^2 = x^2·6.8·10^6\frac{\text{N}}{\text{m}^2}.$$ * The two forces equal for $x=6.4·10^5\,\text{m}$ or 640 km, which means that the structure collapses for higher $x$ and is stable for lower $x$. For comparison: The earth’s diameter is 1.3·10⁷ m or 13000 km; the moon’s diameter is 3.8·10⁶ m or 3800 km. Of course, there are other destructive mechanisms (tension, shearing, torsion, …) and other tissues involved and the turtle will be organised differently, but the order of magnitude of the forces and strengths will remain the same, unless you have totally different materials involved. [Answer] I'm having a few problems with the concept, particularly around what the innards of such a creature would end up looking like under that much pressure. And while I write that Wrzlprmft puts up a well thought post that describes that. Alternate theory for you... There is the potential for the Redwood forest in California and Oregon to be one single living organism...one tree that branched off into several trees and so on until it formed one giant living mass of a forest. Drawing on that...I could see your 'turtle' forming in a similar manner. A single life mass with modest beginnings that feeds directly off the planet itself (be it a process similar to lichen that breaks down rocks and feeds from that is a potential...using the planets thermal energy is another potential). This biomass continually grows, overtaking any other living body on the planet until the planet is covered in one giant biomass. Through whatever means, this biomass becomes intelligent (aka it develops a 'brain' somewhere on or in the planet). This really gets around the soft flesh of a creature being crushed under it's own weight. You now have an intelligent planet sized creature that at it's core is infact a planet, however it's coated in a single living intelligent being that is capable of manipulations on a global level. It's self 'feeding' in that it draws it's energy from the planet inside of it (maybe consuming a moon here and there for additional mass?). Reproduction becomes this planet sized creature locating other planets and seeding it so that it's new seed can grow in the same way it did. In this manner, I think you could get a 'turtle' to pretty much whatever size you want and not have to worry about the creature collapsing in on itself Added: To make the mass look like a turtle...a space weather event could hit this planetoid forcing it to defend itself and having the outter mass grow a shell. I doubt flippers would be a valid locomotion technique as they'd just flail around in space with nothing to push off of. Instead, it's ability to move would be more like a squids...'breathing' in and contracting (exhale?) which shoots mass (rocks, water?) off the planet through pores in it's shell. In this case, it would be constantly searching for new 'mass' from asteroids, moons, or other planets (gives it the 'need to feed' on other stellar bodies). [Answer] In order to make a creature of this size resembling a turtle, (though it very unlikely to form) it cannot collapse under its own weight. Non-spherical cosmic bodies obviously exist but they are either: * small enough that physical rigidity prevents it from collapsing under its own gravity * Low enough density that it does not collapse on itself In order for this to work, therefore, you need something with incredible rigidity and low density. Ananke has a mass of 3\*10^16 kg and is not spherical. I could accept that an intelligent or evolved internal structure could keep it turtle shaped at that size. If you were willing to accept that size, it would be fine. Your planet's surface would be about 30 miles diameter. Phobos and Deimos are smaller. Lets decrease this density a bit. Aerographite has reported density of .2 milligrams per cubic centimeter. If we use nanobots it make it more structured and stronger than we physically can in the real world, I still don't think that the average density can be below 2 milligrams to prevent collapse and keep its shape from in space conditions. If we say it can be nonspherical if the surface gravity of the sphere would be the same as Ananke if it were a sphere, then you get an average distance from the core to the skin of: 36000 km diameter Is that a sufficient diameter? Maybe you could increase it by another order magnitude but it is already not very realistic. This density plays a huge role in it and is tiny. The hardness of the structure is not really that tough so the outermost regions would be essentially just aerogel while the interior is a denser, harder structure (but still very light). The gravity on the surface of the turtle would be tiny. Any atmosphere would diffuse right into him or escape into the void. If you actually want a livable disc on him... well... I don't know... There is a reason Discworld needs such interesting magic. I had not looked into it, but being hollow might help. [Answer] > > The answers to this question should not focus on how/whether this > organism could survive (sources of food), travel or even evolve. > > > Well, I was educated as a biologist so it's gibberish to me to think of a model for animal that doesn't start with its environment and its selection pressures. So, I am going to ignore that restraint in part because doing so makes it easy to imagine why a space turtle would be non-spherical. 1) The turtles aren't spherical because they face selection to form another shape. Spheres don't make good powered shapes. A lot of people think that real spacecraft remain cylinders because that form is needed for launching through and atmosphere but it's really about stability under power in space. Stability is a function of the displacement of mass laterally from the line of thrust running up from the engines. The closer the majority of mass is to the line of thrust, the easier to balance the ship on top of the thrust. This is not obvious because in air, water or ground contact, a long cylinder shape encounters resistance and begins to act like a lever knocking the ship off the thrust axis. In vacuum that effect is trivial. The ship's axial center of gravity is more stable. A sphere displaces more mass around from the thrust line than a long cylinder of equivalent volume. That displaced mass must balance constantly or it will move the ship's center of off the thrust line. Consider it this way: Inside a ship under acceleration, an astronaunt walks as far along the longest path possible. As he does, his mass alters to the center of gravity to some degree. In a cylinder ship, he will spend most of his time slightly offset from the thrust line and moving parallel to it. On a spherical ship, most of the paths he could take move him farther away from the center of gravity and in the most extreme case, as long as half the diameter of the ship. If he walked side to side at the ship's midpoint perpendicular to the line of thrust, his mass would have a lever effect at the extremities. So, spheres are great if you have no thrust but otherwise tricky. Just as both animals and vehicles on Earth have the basic head-tail layout despite their radically different origins and materials, likely a space animal would also evolve have a head-tail layout for stability under thrust. The next issue would be wider than it is thick. Animals on earth evolved under gravity so they form to resist gravity which means they have a top-bottom. A space turtle wouldn't. If it evolved as a head-tail form as above, everything else would be distributed evenly around the outer perimeter. To get a flat shape, we would need to evoke a selection pressure to make that shape optimal. The obvious one would be that the turtle absorbs sunlight or solar wind plasma for food. In all three cases, a flat shape oriented perpendicular to the line to the star, like a sunflower, would give it the most surface area for absorption. 2) Size: Just because something is big, doesn't mean it has to be a sphere. Gravity is the weakest force so if offset by another force, its tendency to form materials into spheres could be easily offset. Living things are not static structures, they are dynamic and exert energy all the time to maintain their shape (cells devote 70% of their energy moving around potassium and sodium ions that among other things maintain cell wall shape.) If we imagine a turtle that produces and controls magnetic fields in its tissues, quite plausible with biological conductors, we could imagine a turtle that constantly manipulates a complex matrix of internal magnetic fields to maintain its shape against gravity and to dampen out the various stress forces propagating throughout it. The magnetic fields would actually be the most rigid part of the system. Instead of trying to simply resist giant scale stress forces with static materials, the turtle would absorb, diffuse and redirect them. The turtle would be something like an internally complex balloon animal with gravity taking the place of external air pressure and magnetic reinforcement taking the place of internal air pressure. The tissues are the skins of the balloons. The tissues just have to be strong enough to exist at the balance point of each force. The forces actually strengthen the tissues just like air pressure strengthens the skin of balloons. In that case, the turtle could grow much larger than it would if it relied on just static mass to resist the pull of gravity. However a consequence of dynamic form would mean that as soon as the turtle dies, or just weakens past a certain point and runs out enough energy, it will implode. Also, growing in a rectilinear turtle shape would distribute mass around in a non-spherical shape which would decrease the overall power of gravity to pull everything to a single point. This would slow the gravitational feedback loop that forms spheres. I presume at some point gravity would defeat magnetic reinforcement but I don't have any idea how to calculate the mass at which that happens, especially with an irregular shape. [Answer] Think in terms of a big ocean ship like an aircraft carrier. It's density is much less than that of steel, because it's mostly empty. That's why it floats. It's density is less than water. If your turtle was mostly exoskeleton, you could make it as big as you want without danger of collapsing on itself (it might need some structure inside for stiffness, etc). Of course, if the turtle were "born" on planet with gravity, it would need some material that could avoid structural collapse. But out in space, it wouldn't matter. [Answer] I would have put this in a comment but I dont have enough rep, The Turtle which you link to in your question - [planet sized turtle](http://media-cache-ak0.pinimg.com/736x/6c/7c/d2/6c7cd27e54bfbe9d08922eb8b6f61bcc.jpg) is actually a representation of the "discworld" - Now these are fantasy books written by Terry Pratchet which do include magic however IIRC while magic is used to explain the existence of the discworld in the books universe "magic" is more like science Quote below from [Wikipedia](http://en.wikipedia.org/wiki/Discworld_(world)) > > Magic is the principal force on the Discworld, and operates in a > similar vein to real-world elemental forces such as gravity and > electromagnetism. The Disc's "standing magical field" is essentially > the local breakdown of reality which allows a flat planet on the back > of a turtle to even exist. The force called "magic" is really just a > function of the relative absence of reality in the local area, much in > the same way that the absence of heat is described as "coldness". > Magic warps reality in much the same way as the real universe's > gravity warps its space-time. The act of performing magic is, > essentially, telling the universe what you want it to be like, in > terms it can't ignore. This is very draining to magic users, due to > Discworld science's Law of Conservation of Reality (which states it > takes the same effort to do something with magic as it would to do it > mundanely). This is why most Discworld wizards store magic in a staff > (with a knob on the end) which is a sort of capacitor for magical > energy. > > > On the Discworld, where magic has more in common with particle physics > than Houdini, high-level background magic (most likely a reference to > real-world background radiation) occurs when a very powerful spell > hits, > > > ]

[Question] [ Most cities don't just spring into existence, they aren't planned to be the way they are (there are a few exceptions, see Milton Keynes in England for example) but grow organically over time. However when you're building a world, you're designing cities that have existed for hundreds, if not thousands of years or longer. How do you ensure your city feels organic in nature, that it doesn't appear planned an built in a day as it probably was? [Answer] Simulate it. :) Naturally I don't mean some highly detailed computer simulation. I mean sit down with a pen and paper and follow the process through. **Founding** Why was it first founded here? What was the purpose of the settlement? Why choose this location? Most settlements are founded for a reason. For example London is where it is because it was the lowest crossing point on the Thames. Other cities grow up around easily defensible areas or other strategic objectives. **Growth** Sketch out the early stages of the city. Would they build walls or other structures, how would it grow inside? Take into account natural features that might change the shape of the city, for example important buildings would tend to be on high ground. **Events** What happens? What notable events have happened to the city? Has it been invaded? Grown? Plague? See with each ones what changes it might make to the structure of the city. **Expansion** As the city expands it grows outside the walls, then more walls form are built around the expansion. Is it remodeled or changed in the process? Where do the people live? Do they grow outwards or upwards? Think about how each area might change. Where would the rich people move, where would the poor people be able to afford? Would areas decay or be built up? How do goods get in and out of the city, and get transported around, etc? [Answer] The best way is to grab a bunch of maps (both cartographical and descriptive) and pictures of cities in the real world that share similarities. Then you can figure out reasonable trends and aspects for your target environment/history. Sure there may be no directly comparable cities but just go for the closest you can find. One important thing to do when going from real maps is: unless you want it to appear based on a real city make sure that it has significant enough differences. For example mix and match some aspects and definitely include some unique elements. One good test is get a few friends to read it and ask them if it makes them think of one place - if they all say the same place (and this isn't their home-town) you may have more similarity than you want. ]

[Question] [ "Glassing" a planet is a common ultimate tactic in Science Fiction, basically it consists in using high power energy weapons to destroy all life on the planet and reducing the soil and rock of the surface of the world to several centimeters of a fused material, not dissimilar to this [glass](https://en.wikipedia.org/wiki/Trinitite) though generally it is described as being somewhat thicker than the deposits at Trinity. Now this would appear to be a method one does not use if one wants to use the planet in question ever again but just how long would it take for a world to recover (recovery being measured as a return to widespread plant growth) from a glassing grade attack due to natural processes, without any technological intervention? The answer to this question will vary greatly based upon the geology and climate of the world in question so assume an Earthlike world and assume that the oceans and atmosphere are, for all intents and purposes, completely intact. Life on the continents is destroyed and the ground fused to a depth of 3-4 centimetres and the edges of the ocean basins suffer some damage but otherwise ocean and purely atmosphere living organisms are intact. [Answer] Let us take the process as per "face value", I've strong doubts it could really be performed as-specified (i.e.: very high ground temperature is bound to affect both atmosphere *and* cauterize to a much deeper depth), but that's another story. Let us assume really just a few topsoil centimeters are heated instantaneously to something like 1500°C. This takes a huge amount of heat and would have several side effects: * Sudden increase of air pressure with consequent shock wave. * Melting of most superficial structures. * Collapse of "small" concrete/metal constructions. * Instantaneous fire of anything burnable. * Larger artificial structures (e.g.: concrete dams) would survive. * Relatively large underground installations would survive (e.g.: Carlsbad caves or [Laboratori Nazionali del Gran Sasso](https://en.wikipedia.org/wiki/Laboratori_Nazionali_del_Gran_Sasso)). * A huge amount of oceanic water would evaporate from heated surface. **Note:** I see *no* way to confine effects to a few centimeters of ground while destroying all military underground facilities, but that's (again) beyond the point). Effects in the mean/long period are: * Huge amounts of dust/smoke/particles would be released in the atmosphere. * Huge amounts of CO2 would be released in the atmosphere. * Water evaporated would produce heavy rains. * Cool-down, especially in zones where there's little to burn, would be fast (hours/days). * Glass cover would crack, due to contraction, in relatively small pieces because thickness isn't enough to give structural strength. * "Nuclear winter" would settle for (at least) a few years. * Any seed not cooked by heat would start to germinate through cracks. * There would be a huge mass-extinction, but many amphibious species (real amphibians, but also tortoises, seals and similar animals, as long with birds "lucky enough" to be in flight) would survive, some to die of hunger because of missing food (e.g.: seed eating birds). * There would be a rapid decrease of Oxygen content in atmosphere due to globalized fires. * At the end of "Nuclear Winter" flora would thrive in the CO2-rich environment; in the first period the "glassy ground" would hamper it a bit, but a few centimeters are not enough to hold for long. * It is unsure what would happen to climate; most likely there would be an initial extension of deserts (all the planet would be a desert, in the beginning, but that wouldn't last a year) because many areas have high rain *because* of the forests they host (not vice versa). * Cooler climate and high CO2 do not mix, so a complete meltdown of icecaps is likely, with Antarctic back to rainforest (if seeds can reach it). I would guess most of planet would have at least some "widespread plant growth" in relatively short period (<100years). Terrestrial animal life would fare much worse and evolution will have to start again with a huge setback. It is possible there would be a "jump-start" fed by [pinnipeds](https://en.wikipedia.org/wiki/Pinniped) instead of [fishes](https://en.wikipedia.org/wiki/Rhipidistia). Anyhow to have real terrestrial animals (without intervention) would take million years (unless some animal managed to escape destruction). [Answer] We could take a real-life (well, real-death) approach here and focus on the most dramatic biological catastrophe on Earth, called the **[end-Permian crisis](https://phys.org/news/2012-05-million-years-recover-mass-extinction.html)**. At this point an abundance of life forms existed, which was nearly wiped out around 250 million years ago (250 Ma), with only 10 per cent of plants and animals surviving. The end-Permian crisis is believed to have been triggered by a number of physical environmental causes, including global warming, acid rain, ocean acidification and ocean anoxia. Vulcanic eruptions may have accompanied it, or perhaps a meteor impact. It is currently much debated how life recovered from this cataclysm, and whether quickly or slowly. However, it is is generally thought that living, breathing organisms didn't truly recover until **10 million years later** (source: [Live Science](https://www.livescience.com/20598-mass-extinction-recovery.html)). You specifically ask about recovery of plant life - [Grauvogel-Stamma & Ash (2015)](http://www.sciencedirect.com/science/article/pii/S1631068305000813) report that the Triassic floras began with the proliferation of the [lycopsid](https://en.wikipedia.org/wiki/Lycopodiophyta) *[Pleuromeia](https://en.wikipedia.org/wiki/Pleuromeia)* (an extinct genus of spore plants) during the **[Early Triassic](https://en.wikipedia.org/wiki/Early_Triassic)** (250 to 247.2 Ma) and that it proceeded with the resurgence of the [*coniferae*](https://en.wikipedia.org/wiki/Pinophyta) (conifers) in the early Middle Triassic (**[Early Anisian](https://en.wikipedia.org/wiki/Anisian)**: around 247.2 Ma), the return of the *[cycadophytes](https://en.wikipedia.org/wiki/Cycad)* (a genus of ancient seed plants still around today) and the [*pteridosperms*](https://en.wikipedia.org/wiki/Pteridospermatophyta) (several groups of extinct 'seed-ferns') in the Late Anisian (around 242 Ma). **Reference** **-** [Grauvogel-Stamma & Ash, *Comptes Rendus Palevol* (2015); **4**(6–7): 593-608](http://www.sciencedirect.com/science/article/pii/S1631068305000813) [Answer] The amount of energy required to fuse the soil of the planet to glass in a matter of seconds is comparable to the energy release of a nuclear weapon (after all, the nuclear glass in the Trinity site was created by a nuclear weapon). When extrapolated over a planet, this would probably remove the atmosphere and a large portion of the oceans as well. Just based on those observations, the proper answer is going to be "never". You can work this problem in the other direction; if your civilization were to find an airless planet with an unweathered rock surface and no atmosphere (think of the Moon), what steps would they need to terraform it? Resupplying an atmosphere, covering the surface with liquid water and providing enough energy to "till" the surface in order to make a sand substrate for soil building will all be needed to start the process. If you take these steps (similar to some of the proposed ideas to terraform Mars), and then simply rely on biological processes, you would probably have to wait several thousand years for mosses, lichen and so on to build the soil and for plants to take root and spread. ]

[Question] [ After seeing an advert on my holo-watch about the latest fleet of interstellar spaceships capable of going into warp at the press of a button, I was both amazed and dumbfounded by it Conventional warp requires onboard computer to sync with at least three deep space networks and plot the coordinates which can take anywhere upward of 72 hours which is the limitation of data transfer and Moore's law, I am wondering why these new Dreadnought Class spaceships are able to go into warp 2 (≤4c) at the press of a button and yet the safety records are nothing short of spectacular no accident so far including the testing phases? I doubt you can simply download the old charts and extrapolate everything because a computer model still has its limitation, and a slight miscalculation could prove deadly! [Answer] The Dreadnoughts are taking advantage of a breakthrough in FTL communication technology, and they continue to **sync with the networks and plot the coordinates while already at warp**. For this to work, we assume: * The ship does not need the whole trajectory calculated to safely begin the jump, but does need it to safely complete the jump. * Calculating the local (nearby) warp trajectory would yield results faster than calculating the destination (farthest point) on the warp trajectory. * (Plot point) Communicating with the space networks while at warp represents an advance in technology that would "amaze and dumbfound" those who were not already aware of its development. So ship A, which cannot sync while at warp, needs to sync-and-plot both the beginning of its trajectory (completed quickly, perhaps near instantaneously) and also every other part of its trajectory (a lot of time, especially as the distance increases) before it can even begin its jump. While ship B, which can sync while at warp, can perhaps be constantly in sync with the local space networks and keep ready calculations for beginning a jump in any direction, and then maintains sync and refines its trajectory and plots destination coordinates as it goes. [Answer] **The older Warp drives are ballistic**. Like a bullet fired from a gun. You have to set the direction and impulse at the beginning, and thus need to have your settings *exactly* right, or you miss your destination. **The new Warp drive is dynamically steerable**, like a missile. You can continually refine your orientation, so all you need to get started is the general direction towards your goal. You will have time to refine your aim further along the journey. [Answer] ### It still takes 72 hours, a tiny tweak in the order of events makes it *seem* instant. After a few decades of CEOs cutting talent from the engineering department and using the savings to pay their own bonuses, there was no chance the company could improve on their design. The ships still need 72 hours to calculate trajectories, warm up the engines, and accelerate within subspace. But with market share slipping and no money to pay for actual talent, they needed to hack something together, and fast. An unpaid intern hacked at the code and found a way to open the FTL bubble to subspace at a moments notice using the default safe settings, the ship enters subspace and then sits there idly while finishing the rest of the setup and calculations, taking 72 hours. The unpaid intern then modified the data feed from the FTL drive to the bridge such that it reports it's travelling at about 3.9c even though it's still warming up. By the time the engine is actually ready to accelerate (72 hours later), the ship is only 0.03 light years behind where it should be, which slowly closes over the length of the journey as it does 4c when reporting it's doing about 3.9c. Combined with a minimum safe jump distance (must jump minimum of 0.3 light years - like flicking a light bulb on and off quickly it's bad to do short jumps), that subspace has no stars so is pitch black so you can't see stuff swooshing, the inertial dampeners suppressing the G forces, and the lightshow of it disappearing into subspace immediately when you press the jump button, everyone totally believes the company had a breakthrough innovation. [Answer] It's all just marketing BS. What they fail to mention is that you can only jump straight to warp if your "destination" is nearby (like, a few *light-minutes* nearby). As you surely know, the drive safety interlocks won't let you engage the drive unless you've plotted your route completely and know you aren't going to run into anything. Well, some egghead got the bright idea to remove the minimum distance limiter to allow short hops that don't need to collate data from far away (or maybe the new drives permit much shorter cycle times than were previously possible). The thing is... for your average traveler, such short hops are basically useless. In other words, they're hoping you don't read the fine print. But you mentioned these are *Dreadnought Class* ships. *Military* ships. Well, as you surely also know, navies often have different priorities than civilians. Being able to change position quickly is extremely valuable for a ship in combat, but not so useful for ships that just need to get from A to B. (Oh, and it turns out the "new" drives also need to be overhauled after only a third of the drive hours. Again, for naval ships, the added flexibility is totally worth the extra costs, but don't expect to see these drives coming to your typical passenger liners or cargo haulers any time soon.) [Answer] **Bureaucracy**. The commercial ships have to file a flight plan, get permission from the destination, get clearance from the departing system, sign waivers in triplicate and in physical form, to alleviate the system from liability, pass all inspections and get customs clearances, pass all quarantine conditions, make sure all payments are cleared by the financial institutions, satisfy all immigration and visa requirements, and generally go through all of the hoops, and pay tribute to the bureaucracy gods. The dreadnaught, being under the command of the Supreme Authority, has a universal diplomatic immunity and has clearance to go anywhere at will, no paperwork required. I am reminded of that scene from Shrek, where the poor 'greeter' at the castle gate has to go back and forth, zig zagging through the barricades and ropes that control the crowd flow queue, and Shrek just barrels through all the ropes and goes straight in. [Answer] **The upgrade uses Laplace's Demon, and a lot of memory.** <https://en.wikipedia.org/wiki/Laplace%27s_demon> > > According to determinism, if someone (the demon) knows the precise > location and momentum of every atom in the universe, their past and > future values for any given time are entailed; they can be calculated > from the laws of classical mechanics.[2] > > > The package includes a plan to warp from (quantized) anywhere to anywhere else, calculated in advance. The upgrade is a memory upgrade; with quantum memory storage as proton spin, there is a near infinite reservoir of calculations ready. These are the same calculations that the current model uses but all done in advance and stored. The issue then is retrieval. The system keeps track of the ships position and keeps ready only calculations relevant to that position for the touch of a button. If you wanted calculations relevant for points X and Y distant from your own you can retrieve those also but you will need to push several other buttons. The system has memory to spare and also comes with every movie or video ever made and every song ever recorded, and some books. [Answer] **You know, warp engines have strange effects on the fabric of space-time, and we can exploit them** When the dreadnought officer presses the button, the flight control center starts all the calculations or - in case of departure from an uncolonized system - the dreadnought releases a small probe, which collects and computes all the data necessary for the jump. Newer warp engines allow nonlinear jumps through both space and (to a limited extent) time: in this case the dreadnought perform the latter and jumps 72 hours later at the same spatial coordinates, when it collects the results of the calculations, either from its probe or from the data center. Since the jump in time is inherently unstable (you know, it always happens when you tinker with entropy and potential energy of the time flux), the ship can stay in this 72-hours future just for a few fractions of second before coming back, but they are sufficient since there is enough bandwidth to download the results and the center/probe knows in advance when and where the ship will be, so they already know when and where to broadcast the data. As soon as the ship comes back in its present, some instant after (according to how the passengers perceive the time), it has all the information necessary to perform the true jump through space and reach its destination. [Answer] It's MUCH more expensive, but the expense is warranted by being a warship. ## A new algorithm computes destinations *all the time* First, they have a larger auxiliary generator and a bank of computers that does nothing but syncing and plotting all the time, *in case you need it*. The only breakthrough is a new algorithm that uses the data they are collecting to produce a bunch of intermediate data, which is used to develop the final calculation in a second or two. Not mentioned is the cost: **destinations are now slightly less accurate** (larger CEP) so you are no longer able to jump into a precise orbit location, you must jump into a conservative orbit and reposition once you are in the ballpark. That and the fuel, spare parts, and heat disposal needed to keep those computers working. ## The engines are on hot standby at all times The engines are also built a great deal beefier. Part of that 72 hours *was* the warmup of the physical engines. Not these; they are ruggedized to be kept in a spun-up state all the time. Of course, this has a number of tradeoffs: Much higher manufacture costs, more frequent and longer maintenance downtime (drydock), and of course, stupendously higher fuel costs. "Fortunately" they have plenty of spaces to store fuel; because it threw a monkey-wrench in ship design. Previously, a bunch of areas on the ship were only irradiated during warping. You could use those spaces for galleys, recreation, commissary, and other places sailors *will not be* when you are at general quarters for warping, including the best feature of those ships: the surplus of space gave lots of space for crew quarters. Now, those areas are irradiated continuously, so no-go. On the upside, you don't need to muster to general quarters for warping anymore (to evacuate those areas)... you can just do it. You'll have to figure out whether to build the new ships bigger, or just have a stark downgrade in crew accommodations. [Answer] The warp requires setting up rather precise location around the target star to match your velocity vector with the gravitational field at the destination. For this, you need extraordinary precision of your location, something like $10^{-5}$ per distance error is already too much (i.e. within an AU or so per lightyear). Now, you use GPS (Galactic positioning system), unfortunately, it first needs to get a fix by listening to several signal sources for some time, to download the galactic ephemerides and then calculate the intersection of spheres around those sources. Takes some day, it can be shortened if you get an accurate disance to a known nearby pulsar or such. However, this is for civilian use. The GPS contains other, encrypted signal, with much better precision and much shorter time to get a fix. This is strictly for the military and the encryption keys are a closely guarded secret. The Dreadnoughts, being military ships, have the decryption keys already built in into their positioning units firmware. [Answer] # It was a lie Sure, it used to take 72 hours to sync up and get the flight data. 100 years ago. But over time improvements in ship computers, additional satellites, improvements in encoding, all of those have chipped away at the time it takes to get the data. Until as long as 20 years ago plotting FTL took less than a minute. But that didn't suit the people in charge. Requiring a three day planning window was much more useful. It is harder to smuggle, or plan an insurrection if you have to connect to the network and announce where you are going three days in advance. What changed? Well, that could depend on the needs of your story. A new, more honest group came into power. The ship manufacturers got blackmail material. Or they banded together to tell the government they wouldn't play this game anymore. Maybe they were fooled too, but finally figured it out. Whatever the case, in order to prevent unrest, rather than reveal the truth, they just claim that this new instantaneous version of FTL plotting is some incredible new tech. It's not like most of the unwashed masses understand interstellar networking, more or less FTL drive. # It was a (different) lie It is true, up until these new Dreadnought were developed, it to 72 hours to prepare to go to FTL. But the networks and course plotting didn't have anything to do with it. That was just something they told the people. Something simple they could understand. Or something they wouldn't complain about. Maybe it took that long to build up spatial distortion in the drive (which needed to be done slowly and steadily and released at exactly the right time, or it could cause spatial tears or other environment damage/destruction). Maybe it took that long to clear the subspace whales out of the interstellar travel lanes. Maybe it took that long to back up the passengers brains before their bodies were incinerated by hyperspace stresses (said brains being downloaded into cloned bodies on arrival). Whatever it used to be, that has been improved or solved. So they claim that the networking issue has been solved. Because the people bought that lie in the first place. [Answer] **It's an ongoing lie.** The new tech is fake. All demonstrations were scripted step-by-step. The ships absolutely knew where to go 72 hours before, that's why they could go there. Any outsider trying to buy the new ships will be refused sale or stalled for as long as possible. Possible reasons: a) It's a deterrent against an enemy who could attack anywhere. That enemy will be less inclined to attack once convinced that a large fleet could converge wherever at the drop of a hat. Convincing everyone else is just collateral damage. b) The ship's owners are itching to attack a place they weren't supposed to know exists, but they're trying to protect the intelligence source which revealed it. If they attack now, their source is busted. They have a plausible avenue to publicly leak the location, covering their previous knowledge and their source. However, the target will know that they know, and will proceed to evacuate. They have a fleet on standby who will attack immediately when the leak comes. The new tech is a cover for how they can attack as soon as the information comes out. [Answer] # Precalculation I'm assuming "warp" is instantaneous travel, not mere "light speed or a couple times faster". Otherwise, saving 3 days just doesn't change much on a galactic scale. If something takes 72 hours to calculate, then it really makes sense to start calculating it 72 hours in advance. But if you need to be able to warp anywhere in the galaxy, then there's an infinite number of possible routes to precalculate. You simply *can't* calculate an infinite number of them ahead of time, let alone then update those models in realtime to handle the celestial mechanics as things in the galaxy move. But what you can do, if you have a powerful enough military computer, is subdivide the galaxy into "nodes" and plot a network of routes from node to node. That reduces the calculation that you need to do from "where you are to any destination in the galaxy", down to "any destination in the galaxy, from its nearest node". Assuming calculation time is linear with distance, then in a galaxy 107,000 lightyears across that normally takes an average of 72 hours to calculate, you'd need to plot a node only roughly every 24.5 lightyears, to get your average calculation time down from 72 hours to one minute. You don't have to spread them evenly, either: you can cluster them where stars or population or likely military targets are denser, which should reduce that minute down to even fewer seconds in the majority of cases. No point plotting many navigation nodes *between* the spiral arms, for example. As well as needing crazy computing power, running constantly to keep the numbers precalculated, another possible disadvantage arises if warp fuel is proportional to the distance warped. You still need to continuously calculate the routes between all those nodes, and you likely lack processing power to calculate all possible routes between all nodes: at an absolute minimum you need to connect each one to the next. In the 107 x 107 x 1 kilolightyear galaxy, that means around 778 million nodes, so 778 million jump calculations needing to be continuously updated. In fact, if you arrange them into a binary tree, you use the same number of links (root node gets 2 connections, all "branch" nodes get 3 connections, all "leaf" nodes get 1 connection, so it works out about the same 778M links), and the maximum number of hops you need to get from one leaf node to another is just 60... but that's still 59 more "hops" than the normal direct route, so while it'll still be near-instant because warp-speed, it'll be very indirect and inefficient in terms of fuel. For the military in an emergency, that just makes sense: when you need to get somewhere NOW, and not in three days, conserving resources is not a priority. You still CAN take three days to calculate the most efficient path, but when you need to, you have the option to warp 60 times the distance, burning 60 times the fuel, in order to arrive in seconds instead of days. That is a tradeoff that will save lives! Except, of course, war is war, and it will not save any lives. It will just change the nature of space warfare. Before this innovation, an attacker could attack a remote base with a fair amount of impunity, knowing that even if a warp-space SOS were sent out, by the time a response had come, some 3 days would have passed. So they could attack, plot a trajectory out, and be either gone or almost ready to leave when the reinforcements arrived. Now, though, essentially as soon as a large force turns up to any location, the reinforcements will arrive within a minute. So large-force warfare to wipe out a base needs to be replaced with small-force guerilla warfare. Single "fire ships", drones or suicide ships attacking a base. Ships posing as legitimate freighters calculating their trajectories first, then launching missiles just before they warp out. Bioterrorism. Chemical warfare. Launching large black masses at bases from a large enough distance at high speed. And so on. [Answer] [Extrapolating from modern airlines](https://aviation.stackexchange.com/questions/31384/if-planes-can-go-faster-why-dont-airlines-fly-faster#:%7E:text=Airlines%20fly%20the%20aircraft%20that,capacity%2C%20making%20airlines%20more%20money.&text=This%20limits%20the%20aircraft%20speed.): Older ships needed to run calculations to find the route *that costs the least fuel to get there*, because there's lots of competition and lifting fuel into the ship is expensive, so every penny saved in fuel is a huge increase in profits. Ships have historically taken longer/slower routes than needed, because the route used gravity assists, and therefore less fuel. A new breakthrough (mining? storage? fuel type? etc) allows the use of a fuel that is cheap and or high density to be used instead. (more dense, therefore less space for fuel, therefore more space for *customers*). Now that expenses are driven by customer count/comfort rather than how much fuel is used, ships now prioritize the fastest route instead, which is far easier and faster to calculate, and they can be slightly lazier about it, since fuel savings no longer outweighs customer convenience. [Answer] # It's a false flag to hide cloaking tech The military recently launched ground breaking cloaking tech. It's primary use is to gather intel. To prevent the enemy knowing that you are finding out about their buildup of an amadada before the ships have even gathered (due to you cloaked spy drones), you make it look like you are only findout out as it begins, but that you are able to react super fast, because of the supposedly instantly entering warp. but in reality, you have had almost a week to prepare. Secondly, it hides that you are using cloaking to retreat from battle. If they knew your mothership was cloaking and hiding behind the moon, then they would engage additional sensing measures to try and defeat cloaking. But if they think you are now lightyears away they give up. Thirdly, it hides your reinforcements. They think that they have you out-numbered, but then you are warping in reinforcements at zero notice, then they are going to be pretty catious. But what is actually happenning (in the times you are faking this) is that your fleet is 90% cloaked. The fakes are good. Warp signatures and all, they put work into this. One part of that is the adverts. [Answer] ## It doesn't actually take 72 hours (sorta) Most of the normal 72 hours isn't spent getting the ship ready for the jump, but rather getting the jump ready for the ship. This means that we can get rid of a large amount of that time if the jump is closer to being ready all the time. Most older ships would calculate hundreds of routes and then find the fastest one to the destination, however this takes a long time to do and contributes to a large amount of the time spent. The new ship doesn't need to do that. Instead it has a preset of a few thousand pre calculated fastest paths in places commonly traveled. It only needs to calculate a route to the startpoint and one from the endpoint to the destination and then uses the pre calculated routes. These ships also eliminate the need for all the security precautions. Normal ships have to verify each course they take with multiple datacenters, then have to request access to each used interstellar "highway", then governments of each system they get near and finally verify with hundreds of ships so that they wont crash into each other. This company made it so all you have to do is verify with their own central server, making the process take a fraction of the time. [Answer] The safety record is impeccable as when the dreadnought makes a mistake and drops out of warp in the wrong place (another ship, large asteroid, small planet etc) its the other object that gets obliterated. Thanks to some new super shields and a lot of armor plating there is nothing a dreadnought can hit which isn't going to have a very bad day while the dreadnought keeps on going. So far no one has tried seeing whats happens if a dreadnought hits another dreadnought at warp speed to see which survives. [Answer] ## First you jump, after it's up to *another* engine These big Dreadnoughts are... big. Vast even. They could house *more than one* FTL engine. So it's really a simple question of economics. Small, non military ships contain only one FTL engine, with no steering capacity. You can jump, you can break, but this is all. You will need to be very careful before *starting* the jump. Military ships have another set of priorities. One of them is "get hell out of here, **now!**" type of priority. First you jump and *then* you use another set of engines, still in the "cold" stage, to work out *where* and *when* to stop. And you need very big machines to have a meaningful *and* precise impact to steer a thing as big as a Dreadnought in [ludicrous speeds](https://www.youtube.com/watch?v=ygE01sOhzz0). [Answer] There are possible parallels here to the shift from steam to diesel power in shipping, which began to occur around WW2 era (though most ships built for the war itself used steam plant). One notable example of a large, diesel-powered warship of that era was the *Graf Spee*. A diesel engine can be started and/or throttled up in a matter of a few seconds; a minute at most for exceptionally large engines, or if actively trying to avoid thermal stresses to reduce maintenance needs. A steam engine or turbine, however, requires that enough boilers have first been lit off and brought up to pressure to produce enough steam for the power ordered. Lighting off a boiler from cold can take literally *hours*. You preferably want to do that in advance of need, rather than having to delay any orders for high power manoeuvring. On the other hand, keeping more boilers alight than necessary is wasteful of fuel. --- An entry in one WW2 submarine's log illustrates how this could be taken advantage of in combat: A Japanese convoy was sighted, escorted by a destroyer. Japanese merchants were a primary target for USN submarines, to sever the logistical supply chain that kept every part of the Japanese military in operation. This convoy was sailing near the coast in shallow water, probably trying to make submarine attacks more difficult since a favourite escape tactic was to dive deeper than Japanese sonar could search. The typical IJN destroyer had three boilers; with all three burning it could make well over 30kt in a calm sea, but to escort slow merchant ships it would light only one, limiting it to about 18kt. This would be fast enough to keep up with a Type VII or Type IX on the surface, but not a USN "fleet boat". Judging that was the case, the submarine closed in for the kill under cover of darkness. The destroyer would be a difficult target to hit, so the strike was aimed squarely at the convoy itself. The first thing the Japanese knew about it was when a ship exploded. Thus alerted, searchlights were turned on and the submarine soon located. But it had already turned tail and run its engines up to - and beyond - maximum rated power, making for deep water at about 24kt. The destroyer followed, but soon found itself falling out of gun range, and as the sun rose, could only watch as the submarine disappeared over the horizon. The second and third boilers then came online, and the destroyer accelerated - only to see the submarine reach the edge of the continental shelf and submerge, out of reach. --- So how does that translate into warp drives? Well for a start, the fact is that stars, rocks and balls of gas are *very predictable* in their motions. Even a very cheap computer by today's standards could calculate the position and trajectory of every charted natural object in a ten-lightyear radius in a fraction of a second. I don't buy any argument that computing power is the limiting factor here. So why the heck do you need to communicate with "several deep space networks"? Probably to file a flight plan to prove that your course doesn't intersect any other spacecraft's course. Spacecraft are objects that you *can't* reliably predict the positions of from charts loaded at the last docking. Space is pretty big, so the chances of a hastily chosen flight plan being accepted are high but the communication delays are potentially long. Next, consider that 4c is *very slow* by the standards of interstellar travel. At that speed, starting from Earth, you have two whole minutes to figure out where the Sun is and change course to avoid running into it - and more than ten minutes to similarly avoid Jupiter. You don't need to start running calculations for anything in Alpha Centauri for the next year, even if you started out in that general direction. By then, one assumes you have run out of patience and figured out how to safely engage some higher speed. But this low speed, and the presumably large size of a dreadnought-type starship, does make a couple of things plausible that would be difficult for a smaller ship to match: If a warp drive takes time to physically spool up - even on the order of a few minutes - then a small one could be kept on hot-standby to eliminate most of that delay, and it would make sense for it to have less speed capability than the full-sized main drive. This would be less of a burden for a very large ship than a smaller one, due to the fuel reserves carried. Also, due to a dreadnought's size and comparative rarity, it could keep a permanent reservation in the flight-planning system of several dozen relatively short and slow warp trajectories that radiate from its actual current position. At 12 light-days long, these would be enough to clear a stellar system in a relatively unpredictable direction, while waiting for the normal flight-planning negotiation to complete for a full-speed warp. [Answer] ## Computational Load is not an Effective Limitation I don't think the need to wait for a computation to finish will be believable to your readers as a reason why the old ships need 72 hours to get ready to jump to warp speed. If our world is any guide, computers are likely be be cheap and easily replaced. A ship owner who can cut three days off each trip (six if it is a two-way trip) just by replacing the computers on the bridge will jump at the chance. Go with a physical aspect of the technology instead, something expensive, bulky and hard to replace. To use a car analogy, replacing the radio is easy, people do it all the time. Converting a gasoline car to electric is a major undertaking and tends to produce mediocre results. ## Possible Physical Constraints As the author you could decide that the old warp engine technology requires some kind of a warm up or pre-charge stage which the new technology does not. Maybe you have to charge giant capacitors because you need a huge pulse of power to break into warp. (Think of those big camera flashes which take a few seconds to charge and then make a popping noise as the built-up energy is released.) Of course, you need a reason why the capacitors can't be kept charged all the time. That's easy. Real capacitors lose charge over time due to leakage due to limitations of the materials of which they are constructed. If your capacitors lost say 20% of their charge per day, keeping them charged up and ready to go all the time might not be practical. Another possibility is that the warp engines on the old ships will not work from a standstill. The old ships need to have reaction drives to get up to a speed at which they can engage the warp engines and jump. The new ships use a different kind of warp drive which can be engaged at much lower speeds. Retrofitting an old ship with the new engines and all their support pumps, controllers, cooling systems and what have you will surely cost more than the old ship is worth. ## Effect of Improved Capacitor Technology I think I would go with the warp jump capacitors. To get to the required capacity the designers of the old ships had to compromise and accept a capacitor technology with a horrible leakage rate. Charging them for a jump is like filling a bucket with a hole at the bottom at a faucet. It takes a long time, you need to open the tap wide, and once its full you need to run and use it before it all drains out. Then all you need to make the new ships ready to jump at a moment's notice is a new low-leakage capacitor technology so they can wait charged and ready. Make a set of new capacitors cost close to what the old ships are worth and most of them will not be retrofitted. Just remember that if you go with this solution, even the new ships will not be able to make a second jump a few minutes after the first. If filling a leaky-bucket capacitor takes three days, filling a modern low-leakage capacitor ought to take at least a day. You as the author can tweak the facts to make somewhat shorter, you can make the old capacitors even more ridiculously leaky and you can give the new ships significantly more powerful chargers, but with these premises you are not going to be able to justify a recharge time for the new ship which is not a significant part of a day. Hopefully they can charge their capacitors on the way to their destination. ## Interesting Story Possibilities Even if retrofitting old ships does not make good economic sense, some people will do it anyway. Perhaps they are rich or eccentric or both. If an old ship is famous, that might justify the cost of a retrofit. Spies with the resources of a government at their disposal might retrofit an old ship as part of a subterfuge. In that case they would presumably simulate the old mode of operation most of the time. [Answer] **Jumping out of the plane** The trick is that instead of calculating a single jump through the galactic plane, and having to calculate the gravitational effect of every star along the way, the new ships do one jump out of the plane, one jump across it, and another back in. The jump out is almost instantaneous because it’s the reverse of when you previously jumped in, with some amount of error due to orbiting in the meantime, but since you’re jumping toward the intergalactic void, who cares if you pop out a few light years from where you expected? There’s nothing out there to hit! The second jump across the disc still takes a while to calculate, but it’s easier since all the gravity is in one direction and roughly uniform, there’s still nothing to hit so the error doesn’t matter much, and you have all the time you need since nobody else would know where to even look for you. Heck, even *you* aren’t all that sure of exactly where the first jump was going to put you until you got there! The third jump back into the disc would be the hardest, but again, nobody (even you) knows where exactly the second jump will leave you, and you have the entire time of crossing the disc to calculate a rough solution that just needs to be refined once you get there. No civilian operator would even consider this because of how much fuel it wastes, but it provides an undeniable military advantage (particularly the quick escape part) if you’re willing to pay the cost. That’s also why these ships need to be so large. [Answer] Broadly, blending inertial dampening with the way steam-catapults get carrier aircraft up to speed so much more quickly than the same planes leave the ground. Beyond that, should you not be asking he who wrote the rule-book, particularly if it says conventional warp can take upward of 72 hours to plot? How would that drive hold everything still while its gears chug through miscalculations that might prove deadly? Further, consider how almost no-one in any Star Trek iteration objects to "explanations" such as "that's classified" or "we don't have time for that" or "you wouldn't understand"? ]

[Question] [ > > *What is the malted liquor,* > > > *what makes you drunker quicker* > > > *what comes in bottles or in cans?* > > > *BEER!* > > > In addition to being delicious, beer is ubiquitous. There is evidence of beer production almost as old as grain cultivation in the Middle East and in China. Beer-like beverages were made from any grain available; wheat and barley in the Middle East and Europe, rice in China, and maize in Pre-Colombian America. Other alcoholic beverages, such as wine and mead have origins almost as early, although more restricted in range. One reason for the widespread success of beer is that drinking water has been generally unsafe for much of human history. The alcoholic content of beer, wine, or mead make it less prone to spoilage; therefore preserving it for long trips. Beers moderate alcohol content combines with its preservation to make it suitable for drinking every day. Studies have even found a [negligible difference](https://pdfs.semanticscholar.org/4ef2/2f365b6745bf51cd09e4a6ffef8924c26722.pdf) between hydration with water and a beverage with 2% alcohol (Medieval beers were probably pretty weak). But what if the microbes that produced alcohol from sugars didn't exist? **What else could humanity drink instead of beer?** ### Conditions * Alcoholic beverages do not exist. However, microbes that do some other reaction are acceptable. * Just as beer can be made in almost any part of the world, the replacement beverage must be easily producible worldwide, with Neolithic technology. * Just as beer resists spoilage, the replacement beverage must have some sort of chemical makeup that keeps it germ-free relative to pure water. * Just like beer, it must be palatable to humans. Acquired tastes will make it delicious. [Answer] The obvious answer is vinegar. Most vinegars resist spoiling even better than alcoholic beverages. And, unlike wine, where you have to worry about the alcohol turning into vinegar, with vinegar, the vinegar already *is* vinegar. Vinegar is also reasonably hydrating, and easy to make.1 And, while it's definitely an acquired taste, there are people who chug vinegar and seem to enjoy it, so it is acquirable.2 There are definitely some side effects. For example, vinegar may be even worse for the teeth than sour juices and soft drinks. (Then again, I can't actually find any studies on this, just random internet sites asserting that it's true, so it may *not* be.) It's also hard to drink when you're suffering from conditions like acid reflux. Still, I think it fits all of your criteria. --- Other options worth looking into: * Cider-style juices. Resist spoiling, taste great, easy to make. The problem is that in our world, the way they resist contamination is that they're ridiculously easy to ferment, so a colony of E coli will quickly kill itself off with alcohol poisoning. I have no idea what would happen in a world without alcohol. Maybe vinegar? * Citrus juices. They aren't nearly as resistant to contamination as ciders, but they're still a lot better than water. When attacked by bacteria, they often just turn even more sour. (Not necessarily pleasant, but we're talking acquired tastes here.) In our world, you ideally want the less-sweet ones, but that's because the sweeter ones ferment into alcohol, sometimes with unhealthy byproducts; in your world, there might not be a similar issue. --- 1. I'm not at all sure how the biochemistry works in your world. In our world, the simplest paths to converting sugar to acetic acid go through alcohol along the way—but there are other paths, taken by other common bacteria in [the same family](https://en.wikipedia.org/wiki/Acetic_acid_bacteria), such as Gluconobacters—that go directly from sugar to acetic acid. And my guess is that there would also be alternative paths in your world. Without alcohol, the standard Krebs cycle doesn't even exist, so, forget about how these bacteria would live, *animals* would be impossible, unless either existing alternatives (like the modified Krebs cycle used by Gluconobacters) were more prevalent, or there were new alternatives to replace it. But the details are up to you. 2. Vinegar is pretty easy to flavor, too, but that probably wouldn't be helpful until long after the neolithic period. [Answer] ## Water The idea that medieval people drank beer because they did not have access to safe drinking water is a complete and unfounded myth. To quote Steven Harris and Bryon L. Grigsby in their book *Misconceptions About the Middle Ages*: > > “There is no specific reason then to believe that people of the time drank proportionately less water than we do today; rather, since water was not typically sold, transported, taxed, etc., there simply would have been no reason to record its use." > > > There are plenty of [articles](https://www.ianvisits.co.uk/blog/2017/01/02/the-myth-of-medieval-small-beer/) out there discussing [this topic](http://zythophile.co.uk/2014/03/04/was-water-really-regarded-as-dangerous-to-drink-in-the-middle-ages/). Small beer/ale (the type of beer drunk regularly in the Middle Ages) had a small alcohol content, typically less than 1% and never more than 3%. This would have had some anti-bacterial effect, but in given the life-span of small ale in the Middle Ages (it was usually drunk as soon as it was ready with little to no ageing process) I doubt it would have had too great an effect on the liquid's propensity to spoil (See Jack's link in comments on alcohol affect on bacteria over time). As a brewer of regular strength beer, I can tell you that some bacteria will infect a barrel of ale just as readily as a barrel of water. Having said that, small ale in the medieval period was on some level less likely to make the drinker ill, **solely for the fact that the water/wort used to make the ale was boiled before fermentation.** But this pales in comparison to the real reason small ale was drunk in such quantities in the Middle Ages: Medieval people drank small beer because it was a great way to squeeze as many calories out of their grain as possible. Off-cuts of stale bread, spare unusable grain were all 'recycled' back into small ale in an attempt to fuel a hungry population. Without the invention of small ale/alcohol, medieval society would simply just continue drinking water, but in larger quantities. The two articles I have linked do a good job of explaining this, and if you want to make water safer in your world, just make boiling it more prevalent. It is already theorized that medieval folk knew that boiling made water safe through holistic means, just didn't know why :) [Answer] Brew a nice cup of tea. People all around the world found and used all kinds of herbs and other plants with antibiotic properties since prehistoric times. Popular examples for Europe and North America include sage, mint and blueberry. Adding parts of the plant to cold water not only flavors it, but also kills bacteria in the water. But the antibacterial properties might not be enough, so you want to boil the water first. The disadvantage of tea is that it spoils a few days after brewing, so you always have to make it fresh. Even in neolithic times people probably had the tools to boil water and cook a soup by lining a pot-sized hole in the ground with leather, filling it with water and putting a hot stone from the fire into the pot. If you're hunting or travelling and do not have the time or the fire to brew tea, first drink the (untreated) water and then chew the herbs. [Answer] ## Yogurt (etc) Milk contains lactose, also known as milk sugar. There are bacteria that ferments this into lactic acid. Depending on exactly which bacteria and what else you do with it, you get a lot of different products from yogurt to cheese. [Wikipedia has a list.](https://en.wikipedia.org/wiki/Fermented_milk_products) (Not all of these are drinkable, but many are) Goats were the first domesticated milk giver. Cows and sheep soon followed. Check [Wikipedia's List of Domesticated Animals](https://en.wikipedia.org/wiki/List_of_domesticated_animals) for details. Note that people who can't digest lactose have no problem with lactic acid. [Vaelus](https://worldbuilding.stackexchange.com/users/14344/vaelus) pointed out in a comment that these bacteria can process other sugars too. This means that in a world without any no alcohol-producing yeast, grain and fruits would ferment into lactic acid instead. [Answer] # (Spicy) Soups Spices have been used [around the world](http://news.cornell.edu/stories/1998/03/food-bacteria-spice-survey-shows-why-some-cultures-it-hot), but particularly in hot countries, for their antimicrobial properties (food spoils more quickly in hot weather) for thousands of years. A soup or broth made with some of the more antimicrobial herbs and spices (the source linked above suggests garlic, onion and allspice are particularly good, as well as the more widely known capsicum) would be sterilised by boiling, and the spices would probably work to keep it safe for a couple of days after cooling down (remember that until the introduction of [hops](https://en.wikipedia.org/wiki/Hops#History), beer could only be kept a short time too). Another advantage of this process is that a wide variety of herbs and spices - with a range covering most of the planet - have antimicrobial properties, so such an approach would work be feasible even in places that don't have a suitable climate for growing certain plants (e.g. tea, as suggested above). [Answer] **Blood.** [](https://i.stack.imgur.com/USq0O.jpg) <http://basia.typepad.com/india_ink/2007/09/got-blood.html> Many cultures drink the blood of livestock. Currently the Maasai are the ones famous for it, but horsemen throughout history drink the blood of their horses. If you have big tame animals around it makes sense. Blood is sterile when it comes out. The animals can spare you some now and then in exchange for your good care and concern. Blood is very nutritious. Plus as opposed to milk, male animals can contribute too. > > However, microbes that do some other reaction are acceptable. > > > **no need.** > > Just as beer can be made in almost any part of the world, the replacement beverage must be easily producible worldwide, with Neolithic technology. > > > **you can bleed an animal with a sharp rock.** > > Just as beer resists spoilage, the replacement beverage must have some sort of chemical makeup that keeps it germ-free relative to pure water. > > > **The immune system of the animal keeps it germ free.** > > Just like beer, it must be palatable to humans. Acquired tastes will make it delicious. > > > from above source: > > I know I'm looking kind of bug-eyed in these photos, but it actually > wasn't that bad. It was very thin and bland. It tasted just like human > blood. (Not that I'm in the habit of drinking human blood. But if > you've ever cut your lip or had a tooth bleed, you know the taste). > There was actually very little taste as I was drinking it, but for > several minutes afterwards I had strong blood aftertaste. > > > [Answer] ## carbonated malt beverage So, your two societies — the hunter–gatherer types and the agrarian types — don't have any naturally–occurring way to obtain alcohol in their foodstuffs. Disregarding, for the moment, how exactly that can be, let's consider the other aspects of the question. You are looking for a beverage which — correct me if necessary * Is sourced from a malt of grains and other starchy foodstuffs. * Is prepared using such techniques that do not involve metalworking nor any undue labor or time. * Is prepared in a way which sterilizes the water so as to kill any microbes which either cause disease or which produce waste products noxious to health. * Contains a substance that renders the beverage unsuitable to the future growth of any such microbes as per the stipulation listed above. * Is itself not hazardous to health — at least not in quantities that are necessary to satisfy the requirements of adequate hydration. * Is not seriously unpalatable. Not an ipecac or anything like that. --- Running through various possibilities, I wonder if something like aqueous carbon dioxide could be made tenable? First, you'd have an aerobic reaction which converted most of the sugars to carbon dioxide and water. Carbonic acid would retard the growth of most disease–causing micro-organisms and would not affect the flavor of the beverage all too much — indeed, many people like the tingly effect, and it is otherwise almost tasteless. It would be much like non-artificial soda water: Sodium carbonate was dissolved in a solute of subterranean water which then emerged from springs; it was long believed to possess various health benefits — many of them probably exaggerated, of course. The one problem with this is the solubility of carbon dioxide in water. Because it doesn't precipitate out in a sludge, which can then be dissolved again, you eventually lose the carbon dioxide through effervescence, or evolution, out from the solution. This would decrease the acidity of the beverage if it was not tightly sealed. If necessary, I could go through the equations which demonstrate how the solubility of carbonic acid changes with temperature and pressure, and how that changes the pH of the solution. I will summarize with this: the only difference between that and a solution of ethanol — *i.e.* carbonated beer — is that you wouldn't have any ethanol remaining to retard the growth of unwanted microbes in the beverage. We can get around that with two other properties of the microbes: * They act on starches just as well as they do on sugars. They need to ferment sugars also, but if they produce enzymes that assist them in attacking the long poly-saccharides chains of starch, then they can begin their work when most other microbes — such as bacterial deleterious to human health — haven't had an opportunity yet. * They don't need to completely ferment all the sugars in the malt beverage prior to imbibing it. The slurry can be ingested — although it would pay to not drink it immediately if you wished to avoid very unpleasant gastrointestinal pains resulting from the carbon dioxide being released. Further considerations regarding the microbes: * These microbes would need to be much less specialized than any occurring on earth. Not only would they break down starches, but the sugars resulting from that. Furthermore, their rate of fermenting the starchy slurry would be increased chiefly by aeration — mixing in air. * To make them easier on the human gastrointestinal tract, simply have them encyst or die at a pH more acidic than their home solution of carbonic acid and within the normal peptic range — somewhere around 1.9 should do the trick. [Answer] # Kefir or Kumis [Kefir](https://en.wikipedia.org/wiki/Kefir) and [Kumis](https://en.wikipedia.org/wiki/Kumis) are drinks made from fermented milk. Beer may have been ubiquitous among sedentary populations, but in the steppes, there wasn't much in the way of grain. Instead, most of their food game from their herd animals, in the form of meat, milk, and blood. Just like with beer, fermentation happened at some point, and this new drink became popular (I mean, who doesn't like booze?). As a bonus to whomever may be lactose intolerant, the brewing process breaks down most of the lactose into lactic acid, which shouldn't give you as many stomach problems. [Answer] ## [Kombucha](https://en.wikipedia.org/wiki/Kombucha) Basically ~~fermented mushroom tea~~ tea fermented with a combination of yeast and bacteria. Similar brewing, fermentation, health/calorie traits to beer, but essentially non-alcoholic. [Answer] Kefir. In addition to the kefir grains (yes, they are actually blobs that you filter out and reuse and they multiply while doing their thing) used to ferment milk, there are also kefir grains used to ferment sugar water. They are not interchangeable and creating one from the other is not easily done. Water kefir, as it's called, is just as easy as regular kefir. You throw some kefir grains into your liquid and let it sit for a couple of days, then strain out the kefir and start again. You can also do secondary ferments to get a nice fizz going. For water kefir, you need literal sugar water or you need a liquid that has sugar in it, like juice or coconut water. Juice and etc are common for secondary ferments. If you use them too often with primary ferments, the kefir grains might permanently stop growing and/or producing. But it's not hard to fix that in a community of kefir makers. Similar drinks to kefir, like kombucha, are pretty straightforward as well. Others have elaborated on them. I also agree with the statement that water was too dangerous to drink is a myth. Aside from the fact that alcoholic beverages taste and feel good, the main reason people drank them in quantity was for nutrition. Fermentation produces lots of Vit C and B vitamins, probiotics, and more. Modern beer has none of that because it's filtered and pasteurized, etc. Non-alcoholic ferments will have similar nutritive value. [Answer] Revised: I'd say fresh juices, like apple juice. There are many medieval or neolithic ways to press for juices; in the end it is just pressure. If there are no bacteria that eat sugars, then I'm not sure the fruit would rot as fast, or rot at all. Apples can have a waxy skin that retains moisture, and if no bugs are eating the apple, then the water in it has been very well filtered through the apple tree itself. Also the pulp after pressing still makes for good animal feed, e.g. chickens and goats. Grape juice and orange juice can provide drinkable filtered liquid, too. All of these juices can be filtered to remove solids and stored in natural pouches, including animal bladders and stomachs, which is how primitives have carried liquids before. If there are no bacteria that eat sugar, then they will likely not go bad; other than the sugars, without any solids, there should be no caloric content to exploit. I will take exception to the notion that beer tastes delicious, I hate it. I'm not opposed to alcohol, but beer sucks. Hard cider is good, so is wine and liquers. [Answer] You do know that the vast majority of natural ways to get high involves a medicinal plant in one way or another, right? If you are too vegan to lick a toad and think that ecstasy and other synthetic stuff is too industrialized for your tadte, here are some options for your greenhouse: * Coffee. See [this video from Cracked, 4:55 onwards](https://youtu.be/FGEdFcqt8rw) to see how to prepare real coffee. * Poppies. America's number 1 addiction problem (not counting alcohol) has to do with opioids. Think of that. * Salvia. Legal in the US and UK today. If you are into neo-spiritual [be nice]. * Grass. Not the lawn variety. * Tobacco. Legal drug everywhere, but everyone only wants to smoke it. It can be used in other ways. * Jimson. Not to be confused with Ginseng. * Coca. All of the above can be served in tea. Making it hot will kill germs, just like alcohol would do at room temperature but more efficiently. The last one in the list is also perfect for sodas, for those with a kink for history. Each will have their own extra effects... Some will make you happy for a while, some will clear your mind and ideas, coca helps ignore pain and hunger and tobacco soothens the tremors a psychonaut will get from doing too much of the other items in the list. I am including only those that are easy to plant or to get in most places. Peyote doesn't grow everywhere, and betel is not a thing in the West. Finally, as for being germ free... Just use fresh plants to make fresh tea! You don't throw away a good apple just because it has no alcohol in it, the same goes for the plants above. If you must have a germ-resistant concotion then, stick with coffee, but cook ground beans in a leather bag for a few days before mixing with water and serving. Only the good germs will survive. This is a drug the ancients took to go berserk, so be careful. ]

[Question] [ In my worldbuilding project, 2 continents located on roughly the same latitude are connected by a land bridge. Both sides of the bridge are surrounded by a temperate grassland, and the lack of seasons means the climate is steady year round, so that rules out winter as an option. The sentient aliens in my world, which I've been calling *Not Humans,* (very original) evolved on Continent A, and eventually spread out to Continent B across the land bridge where they found a species that wasn't present on Continent A. (Comparable in function to a horse) I haven't decided what the terrain is like on the bridge, but I would like to keep both sides of the bridge as grasslands if possible. **Why would these animals exist on only one side of the land bridge rather than both?** [Answer] One obvious answer is that the land bridge itself lacks food. Nothumans can cross the Bridge because they're smart and pack a lunch. Nothorses can't cross the Bridge because that region lacks fodder for the grass loving megafauna of Continent A to venture through. Another possibility is utterly ungothroughsome territory. If the Bridge is very low lying & swampy, nothorses won't be able to get through because they'll become mired. Nothumans can pick a path where others fear to tread or can build boats or swampshoes to traverse the Bridge. [Answer] **Tides** Many land bridges are often covered by tides, making them only passable at certain times. As the tide comes in, the bridge is covered, it is uncovered again once the tide goes back out. Perhaps your Nothorses are not smart enough to wait until the tides start to head out before quickly crossing. Your Nothumans on the other hand *are* smart enough to know when to wait and when to go. There is nothing physically stopping the nothorses from crossing (allowing them to be brought back to the Nothuamn’s continent), its just they are not smart enough to work out when they should cross. If timed wrong, the tides would come in and sweep either Nothorses or Nothumans out to sea. **Alternatively, you could have something like the Giant’s Causeway:** [](https://i.stack.imgur.com/Ji9w2.jpg) <https://www.ireland.com/en-gb/amazing-places/giants-causeway/> [](https://i.stack.imgur.com/06FVu.jpg) <https://en.wikipedia.org/wiki/Giant%27s_Causeway> This was a land bridge that stretched from Ireland to Scotland, its really interesting to look at with all the natural hexagonal rock formations. Not only is it interesting to look at, you’d have a hard time trying to get Nothorses to walk over that. You could pull them across, of course, but i doubt they’d want to walk over it if they didn’t have to, given how uneven and unforgiving the terrain is, especially for a creature of their size. [Answer] **Option 1: Difficulty traversing** As others have posited, perhaps the land bridge is particularly difficult for nothorses to traverse. Horses are pretty well adapted to open, rolling steppe. It wouldn't actually take that much of a change to make it unlikely for them to make the crossing. Lack of water, swampy territory, heavy woodland, presence of poisonous plants that they're not adapted to (ragwort in real life is deadly to horses), lack of grazing, too much grazing (one of the issues horses have outside of the steppe is the high sugar content of lush European grass, which causes health issues). Any of these, perhaps dialled up a bit, would do well to restrict their range. **Option 2: Predation** In addition to the other answers about physical land barriers or poisonous flora, predation could also work. * Continent B has nothorses. * Continent A has something that thinks nothorses are extremely tasty. The small numbers of nothorses that make it across the bridge do not survive long enough to establish a stable population. It gets worse for nothorses when their nemesis makes the jump in the other direction, but at least they have a sizeable population already present so they can maintain their numbers more easily while they adapt (or don't, of course). For a real-world example, you can look at the restrictions to the range of platypodes in Australia. Their range is curtailed to the West of the continent by the larger presence of crocodiles in the East. **Option 3: Time** There are two main ways land-bridges are commonly formed. The first is a collision of two landmasses due to continental drift. This tends to be relatively permanent on a biological timescale. The second is land beneath the waves that is exposed by falling sea levels, which tends to be more transitory. Perhaps your land bridge is of the latter type, and has only recently become traversible (say, in the past couple of thousand years). It takes time for population pressures to develop and push an animal to expand their current range. Nothumans, like their human counterparts, are curious. They seem to like exploring. It's likely that they will make the journey across to find new, untapped resources. Nothorses, however, are not particularly adventurous. If they're anything like actual horses, 'not particularly adventurous' is a sizeable understatement. There isn't actually anything at all preventing nothorses from moving across the gap. They just haven't yet. [Answer] The terrain of the land bridge is navigable by not-humans, but difficult or unpleasant to traverse by not-horses. Refer to [cattle grids](https://en.wikipedia.org/wiki/Cattle_grid), a man-made structure used to allow humans (and vehicles) to traverse a passageway, but not livestock. Naturally-occurring, highly-uneven terrain between these two areas might sufficiently dissuade the not-horses from crossing, while still remaining traversable by the not-humans. [Answer] The animals are particularly susceptible to radiation poisoning (causing sterility at low levels). The background radiation on the bridge is unusually high due to an large scale [natural nuclear reactor](https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor) that has been pushed to the surface with recent geologic uplift. The same explanation could apply to other naturally occurring toxins. Toxins could also take the form of a terrible smell, or sound, etc. that affects the animals but not other species. [Answer] Something similar to [this](http://nowiknow.com/the-thin-red-deer-line/) could serve as a reason In short, during the Cold War, the fence/wall border between the East and West of Europe didn't just separate humans. It also kept the deer apart. Even though today there are no barriers to speak of between these countries and no deer alive today lived through the Cold war, the deer populations refuse to cross the (now imaginary) line. Taking this and applying it to your case, you could easily have the land bridge once populated with a predatory semi-aquatic species, which wouldn't venture too far inland. This could lead the horse species to avoid the landbridge, even if this predatory species is long gone. [Answer] 1. Some plant which exists on the other side, not very noticeable to humans but toxic to the horses. Or turn it around something they need in their diet. 2. A reason which possibly doesn't exist anymore, like an extinct predator, but the horses learned to leave their home because of it, possibly using the magnetic field to judge where that is. 3. No reason to expand. If the population of the horses is controlled by something other than the supply of food and space they might not have had any reason to move. ...I'll try to think of more later. [Answer] **Canadian bridges** Or whatever the term is under your latitudes (**edit:** cattle grids). In my native language, it designate a mountain bridge, with a fenced surface (so you can see through it). Cows are deathly afraid of the void and unless being forced, won't cross it. It has been designed to keep livestock in defined area, so it should fit the bill perfectly. **Edit:** Ruadhan pointed in the comment that livestock does not cross a cattle grid not because of the void, but because of the shape of the bridge, that would lead their hoove to slip between the bars (and potentially causing injury). I've found conflicting sources online and can't really tell you the main reason. Shape of the bridge is treated in the second option I propose. **TLDR: you can see the void under the bridge and non sentient animals are too afraid to cross it** Note that it also could work with a rope bridge. Horses wouldn't be able to cross it while we have (almost) no problem using one. **Edit:** Given the way you have worded the question, I assume the bridge must be as natural as possible. Perhaphs one of the two suggestions above is the result of a specie of vine/climbing plant that somehow thrive above seawater and thus is prolific on your coast, to the point two points bonded over the years. Maybe this seawater vine eat fish. Or need high-concentration of salt/iode/whatever. Who knows? [Answer] **Alergic Flora** The animals could be allergic to a type of flora that thrives either along coastlines or along the specific geographical conditions of the land bridge (ex. high coastal winds, tides, salt, brine). This condition could surround both continents as well if the animals don't spend much time near the coast. **Technological Advantage** If the humanoids have primitive sailing technology, then perhaps the land bridge is impassable for all species, and the humanoids crossed by sailing along the coastline. **Predators** Perhaps there are particularly viscous predators that inhabit the land bridge or the waters nearby. The humanoids can use fire or other technology to fend off the predators, but the animals are largely helpless against them. Could be large birds like Rocs that nest in the cliffs or sea monsters. [Answer] **HOW:** **Walace's Line.** Essentially, your continents may have been separated in the past, but due to lowering tides have become connected via this land bridge in more recent history. Disclaimer: Someone more knowledgable may be able to expand on specific climate-related science to assist with Worldbuilding a *cause* for your Wallace Line. My answer addresses the effect of such a boundary. [](https://i.stack.imgur.com/lLpn6.jpg) [The Merriam-Webster definition:](http://hypothetical%20boundary%20that%20separates%20the%20highly%20distinctive%20faunas%20of%20the%20Asian%20and%20Australian%20biogeographic%20regions) > > ...hypothetical boundary that separates the *highly distinctive faunas* of the Asian and Australian biogeographic regions... > > > (Emphasis mine.) A massive trench divided these regions, preventing any natural formation of land bridges for the duration of that era. In short, this led to differences in the land animals that populated these landmasses. **WHY:** Your landbridge may have formed well after the evolution of your not-horses, and so they have evolved in one location but were not found on the former continent, initially, for this reason. * Your landbridge was crossed by not-humans when it became available to them * Not-horses did not cross because they didn't immediately have any evolutionary pressures to Fitting to their nature, they stayed in their region. Your nothumans, also fitting to their respective nature, are perhaps curious beyond any evolutionary pressures, and were accordingly quick to explore beyond them. (They can have had any number of reasons to explore, in fact) ***If your not-horses are not unusally intelligent, as your not-humans would be, they are likely content with their familiar and robust territory.*** Address the differences in the organisms you are comparing, as you have created them, and you have any number of causes for behaviour stemming from these traits and characteristics! Humans as we know them are curious, while horses may be safe, coy or timid. [Answer] I can think of two realistic ways. 1. the land bridge is very new, human will notice the change before anything else, it will take a great deal of time for animals to exploit it. Humans explore for exporations sake. 2. the bridge is not so much a bridge as a chain of islands, human on canoe can jump from island to island with ease but other animals will have a much harder time, and the larger the animals are the longer it will take. [Answer] The most believable way is to base it on real horses (our horses? actual horses?) > > Why would these animals exist on only one side of the land bridge rather than both? > > > 1. Because the land bridge contains a terrain similar to a staircase. It is pretty easy to get a horse up a flight of stairs, but extremely difficult to coax them down a flight of steps. Horses are strong swimmers, so you'll want to make the land bridge long and you'll want very rough water in the area. 2. You could also make it so there are bits of ocean to cross with a nasty current due to tidal forces - only between tides would it be relatively calm (but not actually calm). ``` +--+ +--- | | | | +-+ Continant B +--------------+ Continent A | | +----+ | | | +-----------------+ +--------------+ +-----+ | | | | | | Sea-level-high-tide-------+ | +--+ | | | +---+ +-------High tide-- | | | | | | | | | | | | | | | | Sea level low tide--------------------------------------------------------+-+-----------Low tide--- | | | | +------+ | | | | +----+ | | | | | | +-------+ +-+ +---+ ``` 3. Maybe some marsh land on their side to keep the non-horses from even getting very close. Or even a slight slope that goes from high to low tide (in elevation) which means no vegetation (food) for a few hundred yards would keep them further from the land bridge. [Answer] # Source-Sink Dynamics - the population near the bridge is not doing well The area near the grasslands may be a ["sink"](https://en.wikipedia.org/wiki/Source%E2%80%93sink_dynamics). There are horses there, but the birth-rate/survival rate is low, most of the population has come from somewhere else ("the source"), thus there is no pressure from a growing population to expand into new territories. The population would actually be extinct were it not for new individuals constantly moving in from more hospitable environments. Why is this area inhospitable? Perhaps the grass is very low in key nutrients that are necessary to carry a fetus to term or to nurse a young animal, so only a few animals make it to adulthood each year. Related point 1: the species may not be doing that great anywhere in their range. Any species with a [net-zero population growth](https://en.wikipedia.org/wiki/Zero_population_growth) wont be expanding anywhere. Related point 2: perhaps the land bridge is towards the extreme edge of their territory. Many animals migrate back to certain places to bear their young/find a mate (due to warmer temperatures, fewer predators, more food, safety in numbers etc.) and maybe this is as far as they can reasonably get to before having to head back to give birth etc. [Answer] # [Bioindicators](https://en.wikipedia.org/wiki/Bioindicator) and other Environmental Clues Some examples below: **Bioindicator density**: A complete lack of desirable bioindicators or a wealth of undesirable bioindicators will often cause fauna to either shun or congregate to certain areas previously unexplored. Some simple examples would be things like availability of food, certain densities of specific colors in flora that trigger unconscious fear responses, etc. **Biological irritants**: allergic reactions to certain flora, species-specific pests or pests that can't affect the sentient species that crosses the bridge that animals shun, or even something as simple as a harsh or overwhelming smell **Regional predation**: It could be as simple as there is a species on the bridge and possibly the sentient's continent that for whatever reason also doesn't congregate beyond their continent as well as the land bridge itself; sort of an inverse relationship if you will. That species then feasts on most if not all animals it comes across. If the sentient biological make-up has something inherently inimical to these predators then they will have adapted to either avoid them, or their failed attempts at preying on the sentients simply make them a non-issue only for the sentients. It could also be that these creatures are trivial for the sentients to handle due to their availability of tools in offensive or defensive scenarios. **Induced hydrophobia**: the very sight of water could scare away some species in a specific region if dense with life that can infect other life and trigger hydrophobia. Just seeing the ocean could terrify all the animals from the other continent due to their infection or parasitism that triggers hydrophobia being ubiquitous for the region. **Intolerable atmospheric pressure**: the animals might not be able to handle high altitudes very well whereas the sentients have little to no issue with it. If your land bridge was sufficiently elevated, it could be inimical to many forms of life if they're sufficiently susceptible. **Disruptive [magnetoreception](https://en.wikipedia.org/wiki/Magnetoreception)**: there could be something very disruptive to the animals with the magnetic field around the land bridge that leads to that area being shunned or possibly even a death trap where creatures become disoriented when getting too close, causing fear/fleeing, or death by exposure/lack of necessary nutrition. --- My personal favorite is the last due to imagined long-term consequences. Can you picture such a sprawling graveyard after a couple million years? [Answer] Maybe in some places it is a tunnel or a formation has formed over it that the nothorses can't fit through. Or possibly the sand is incredibly sticky to the nothorses feet and it's simply the shoes that the nothumans wear that allows them to cross without getting stuck. Or the fact that nothumans have arms that they could use to grab onto trees to unstuck their feet as they walk. In this same vein, the ground could be a temperature that the nothorses can't handle on their notshoed nothooves. [Answer] I read this question several months ago, but tonight while watching bats and contemplating about how they use the moon to navigate, I had an idea. The nothorses have been naturally behaving like whales, who swim in the whole ocean but have a certain place where they "magically" return to give birth to their children, namely the same location where they were born. They use the planet's magnetic field to navigate back to the place of their origin. During the evolution, they initially had spread on both parts of the land bridge, but "recently" (some thousand years ago), due to an geologic upset event, the magnetic field has completely changed, which is why the nothorses on the one side of the land bridge went extinct. The places their inner compass lead them to were very difficult for newborn nothorses, so the population on that part of the continent couldn't sustain. The "other" group of nothorses has been "relocated" to the far end of the continent, and although it lives on one part of the continent with similar conditions and could easily cross the land bridge, it hasn't yet spread out enough again to be found in the wild on the other side of that bridge. [Answer] All the answers so far seem to miss a fairly obvious answer: competition. We have a practical example of this in North America. Prior to European colonization, coyotes existed only in the western US and northern Mexico, presumably due to competition from wolves and other large predators. As settlers hunted these to near extinction (and total extirpation, locally), the coyote expanded its range to include the areas formerly inhabited by those predators: <https://urbancoyoteresearch.com/coyote-info/north-american-distribution> Another example, perhaps relevant to "nothorses", is the wild/feral horse. Introduced by early settlers, they're common in most western states, yet unknown in the midwestern or eastern states, even though those states are hospitable to horses, and there are no real barriers to travel. ]

[Question] [ A common sight in science fiction is that aliens pretend to be human (For example in Third Rock from the Sun). Obviously if the aliens are advanced enough to disguise themselves as another species, there are much easier, simpler and less expensive methods to destroy humanity, so why else would an advanced alien civilization waste time, energy and resources to disguise themselves as humans? What possible scientific, cultural or commercial use could such an expensive procedure have? [Answer] Aliens are alien, without a common background their motives may be incomprehensible. If we assume that these aliens are Hollywood aliens (ie humans with odd-looking rubber bits stuck on their faces) then there are all of the reasons that humans from one culture spend time in another culture and try and learn to fit in: * Anthropology; studying how a different culture has developed to better understand the developmental processes that influenced your own. Iain M. Banks wrote *Inversions* (two anthropologists from the Culture investigating a Renaissance-era world) and *The State of the Art* (a Culture Contact team on Earth ca 1970) in this vein. * Tourism; experiencing a culture that is vastly different from your previous experiences. * Reality TV; [Bear Grylls](https://en.wikipedia.org/wiki/Bear_Grylls). * Method Acting; preparing for a role in their own entertainment channels that involves playing the part of a member of an Information Age society. * Challenge; [because they can](https://en.wikiquote.org/wiki/George_Mallory). * Hermitage; there are people here on Earth who prefer to step away from the rat race and all the newfangled gadgets and live as their ancestors did, but usually not all the way back to stone tools. Selecting a developing world and fitting in gives them access to a level of technology between their home culture and being trapped on a desert island. * Camouflage; they are being sought by members of their home culture and it's easier to hide and survive amongst us than in their own milieu. There are a lot of examples of this in fiction already: *For Richer or Poorer*, *Men in Black II* and it's analogous to fleeing the law and retiring to a country without an extradition treaty. * Crash Landing, or a failure that prevents them from going home; if they came on an FTL ship that doesn't have FTL communications they may be waiting a long time for spare parts or updated navigational maps, or if they brought Gilligan who proceeded to ruin all of their plans to return home, or they may have arrived on a slower-than-light colony ship and would prefer to stay here and fit in amongst us rather than try and find another prospective colony. * Uplift; meddling to steer us onto the "right" path of development and prevent us from immolating ourselves (or vice versa if your species doesn't like the competition). [Answer] Probably the most likely reason is plain old curiosity. We've had people go and live among apes, wolves, or other animals in order to study their habits, and if we had the technology to make ourselves indistinguishable to them we would be able to learn a lot more. We don't really need a *reason* for such ventures, it's just human nature to want to understand things. This is the same drive that has driven much of our interest in space, so it stands to reason that at least some aliens who managed to achieve space travel have the same drive to understand the unknown as we do. And unless the disguise technology is prohibitively expensive, it isn't exactly a species-wide venture, just the private activity of a few alien Jane Goodalls. [Answer] They're [anthropologists](https://en.wikipedia.org/wiki/Anthropology) ([literally](https://en.wikipedia.org/wiki/Anthropos)!), and they don't want [subjects who know they're being observed](https://en.wikipedia.org/wiki/Hawthorne_effect) to bias their findings. Their goal isn't to destroy humanity, but to understand how humans work: discovering how a different species and society functions can provide a useful contrast with their own culture (which is [why anthropologists study societies around our planet today](https://en.wikipedia.org/wiki/Cultural_anthropology)). This might also be of concrete benefit to these aliens by understanding how humans might be of benefit to them, or -- as you suggest -- discover anything of value in humanity worth stealing before annihilating us with their superior weaponry. [Answer] I hate to be the only capitalist in this crowd, but the answer is obvious... They're doing market research! It is against intergalactic law to harm an emerging species until they survive the atomic age without outside interference. There are no rules however, against covertly visiting the planet to find out what its strengths and weaknesses are. What unsanctioned technologies do they need most? What resources, art, literature and other valuables do they have which might be trade worthy in the galactic market? The alien infiltrators are entrepeneurs, trying to get a jump on a new emerging market. [Answer] I am a bit of a tech junkie. For this reason I, in my household, have more advance technology than some small organizations in third world countries possess. This being said the idea of me conquering and overthrow the vast majority of such organizations is ludicrous. I lack the skills, the supplies, the logistics, and the manpower, and frankly my technology isn't that useful for war making. Perhaps these theoretical aliens face similar problems. [Answer] # They want to covertly control humanity ### Who are they? This is a race of invasive aliens (hereafter called Exploiters) who travel through the galaxy, with the wish to enslave all other intelligent species. Humans are seen as a desirable target because there are so many of them, and they are seen as naive, yet intelligent and dexterous enough to be useful. The Exploiters feel they are the natural rulers of the galaxy, and that all other intelligent species should be under their control. ### How do they take control? First, they use their advanced stealth technology to caputure the US president. They absorb his/her DNA, appearance, voice, memories, etc, and then murder him/her. They immediately replace him/her with one of their Exploiter minions, looking and sounding exactly like him/her. They then proceed to do the same thing to other powerful people, politicians, media personalities, powerful industrialists, etc. All over the world. The more people they capture, the easier the task becomes, because they can use their preexisting minions as aides in capturing more people and covering stuff up. ### Why do they want control? Once they control the governments, legislative bodies and mass media in the largest countries on Earth, they can easily wield that influence to use humans as their puppet race. They can introduce new technology to humans, for the Exploiters' own benefit. They can even reveal their own existence to humanity, pretending to be a friendly race. In reality, the Exploiters are doing it for their own selfish motives. Humans will be cheap labour in their factories (humans believe the industries are owned by humans.) They will be soldiers in a vast galactic fleet (humans believe it is an International Human Space Navy, controlled by humans.) The Exploiters can get humans involved in all kinds of interstellar wars. For example, the Exploiters are invading Planet X somewhere else in the galaxy. It will be a fierce battle, and they don't want to send their own people to die. So they stage a fake alien invasion on Earth, using the controlled media, scientists, NASA, etc., to blame it on Planet X. Acting like a friend to humans, the Exploiters then give humans enough technology to "defeat" the invasion forces. Earth's population now sees the Exploiters as their best friends. The media, NASA, governments, the ambassadors and scientific envoys of the Exploiters, etc. all convince humanity that they need to launch a preemptive strike on Planet X, before they attack again. The Exploiters offer to give humanity the technology to carry out the attack. All humanity will have to do is to act as workers in the defense industry and as soldiers in the war against Planet X. Humanity feels thankful. They feel they are being saved from being exterminated by Planet X. In reality, they are unknowingly fighting and dying as puppets for the Exploiters. ### Continued Doing this, the Exploiters have gained billions of servants, doing work they themselves feel too exalted to engage in. Humans can die on the galactic battlefields for them, while the Exploiters are the covert commanders. All the while, the Exploiters always make sure that the powerful people in human society are always the (disguised) Exploiters themselves. This is prioritized so highly that there is never any risk that humans will figure out what's going on, let alone take control. The Exploiters could still maintain an illusion of democracy. Using the media, the Exploiters will sway public opinion to favor candidates who are actually Exploiter minions. If any real human candidate happens to become popular, then he/she can simply be killed and replaced by a minion. Or, a fake sex scandal or the like could be engineered to take out said individual. Such things could also be used to blackmail or otherwise control any real humans with some amount of power. A few humans may occasionally suspect something, but they are easily dealt with. They can be killed, marginalized, ridiculed, put in mental asylums, etc. They will be a tiny fringe. The Exploiters will never reveal to **anyone** the fact that they have the ability to emulate other species. This will be one of their most tightly guarded secrets. **Thus, the Exploiters don't want to kill humanity. They want them as servants and soldiers, to work and die for them.** ### Add some hope to the world Oh well, this sounds like quite a depressing world! To cheer people up, the protagonists in the world could be an inter-species alliance of individuals (including humans) who know about and are fighting the Exploiters. They use covert tactics to expose the workings of the Exploiters. Can they find a way to reveal to humanity and other controlled races what is being done to them? For example, what if they find a way to sabotage the emulation technology? Suddenly, thousands of minions will be instantly revealed for what they truly are! But has the Alliance itself been infiltrated by Exploiters? And can they achieve success without being stopped? [Answer] They'll pose as us in order to study what love means to humans. Presumably, if they've already studied us enough to pose as us, they'd already know much about our culture. They may even have heard rumors about the concept of "love". However, if the aliens themselves have no concept of "love", they might send aliens posing as us in order to learn more about this abstract concept. [Answer] If they are trying to destroy the planet, maybe they are outnumbered. Even with their mothership, fighting a whole planet of 7 billion might be like fighting zombies - they just keep coming. They might only have 1 ship, or a limited crew. For example, one of the USA's aircraft carriers might do a lot of damage, but cannot invade an entire country. [Answer] Because the 'expensive procedure' of super-advanced aliens disguising themselves as human beings isn't expensive for super-advanced aliens and their super-advanced technology. There is a straight forward reason why they'd do this, they will have adopted the morphology and biology of successfully adapted species to Earth's environment. Beats space-suits or environmental hazard gear and you can blend in with the primitive natives. Now unless I miss my guess being disguised as humans isn't a way to destroy humanity. Human disguises as the prelude to global genocide & world conquest might be a cunning strategy. Good old fashioned espionage and sabotage, perhaps. Recruiting quislings, agents of influence, and bringing our social, political and cultural elites onboard to make the take-over easier. Colonial empires often used sections of the societies they colonised against those self-same societies. Anthropologists during our colonial period studied the natives to help make colonisation run smoothly. Alien anthropologists might play the same role. On the other hand, there might be a galactic peacekeeping organisation, something like the United Nations but with more super-advanced weapons and infinitely greater caapcity and tendency to conduct military in the name of galactic peace, that has this unfortunate tendency to exception to super-advanced alien species invading planets full of non-starfaring primitive sapient species. In which case, covert invasions would be the way to go. Outwardly our totally subverted and conquered planet would appear to run by members of *H. sapiens sapiens* as if nothing had changed but in reality it is oppressed under concealed iron tentacle of an imperialistic super-advanced alien species whose true form is so horrible and ghastly it would scare the corn flakes out of Cthulhu and its cute little friends. [Answer] They are evaluating humanity as a species - forming relationships, monitoring trends, and living among us - for entry into a larger galactic confederation. They can't truly understand us and come to a credible judgement without first allowing us to expose ourselves to them, making ourselves vulnerable via bonds of friendship and trust. If they manage to assume a position of influence on our world, this also potentially places them into a position to help guide us away from inadvertently disastrous paths, such as nuclear war, destructive biological research, or murderous artificial intelligence. Think of it like an intergalactic "Big Brother / Big Sister" program. On a planetary scale. [Answer] **They don't want to alter our behavior** Why not? Politics. Suppose the aliens' *Great Council of Killing Species* has been performing its titular function for millions of years. At some point, assuming these aliens have ethical concepts, there will no doubt be a *Great Council of Judging Species*, which goes in advance and observes species in question to determine whether they need to die. In time, after discovering that every species that they observe seems to have behavior patterns that can be summarized as "running around like crazy, shoving each other, extreme self-concern, screaming and general panic," they may come to the realization that the GCoJS's presence is quite possibly the reason for said behavior patterns, and if so, a *Great Council of Minimizing Observer Effect* will no doubt arise. The GCoMOE may then regulate that any contact the GCoJS has with a species for purposes of judgement must be made is as inconspicuous a way as possible, including disguising their own interplanetary vehicles as the target species' own vehicles and their bodies as the target species'. [Answer] Well, if Aliens are intellectually advanced, that means that, just like humans, they seek knowledge of everything that sorrounds them. [Answer] The most basic reason that anyone does anything... **Love!** (or lust or whatever) The aliens want to get with the humans, whether it is out of pure lust or a desire to propagate a sort of hybrid species for evolutionary purposes. However, they know that humans are a bunch of racist bigots, and as such, (outside a certain minority of niche fetishists) they would never accept a tentacled, prehensile-organed slimy ball of goo as a romantic partner. [Answer] Aliens when they come to other planet they will NOT be sure about strength/weakness of inhabitants there. And hence "when in rome be like roman" i.e. disguise like the inhabitants there [Answer] We go through a lot to understand all we can ancient cultures--we go to great expense to examine, learn about and preserve them just because they are interesting to us. I think that's reason enough. The reason they are in disguise is the question, but I think it's not all that tough. Every less advanced civilization we've encountered has been--well pretty much destroyed just by contact with a more advanced culture. Even knowing about the more advanced culture destroys a lot of the motivation to retain their own separate individual culture. The people often continue but their original cultures are all but completely lost. We now try to minimize contact with the few remaining "Uncivilized" tribes we know of because of this. Seems like aliens are better at this than we are since most of us still don't even know they exist. [Answer] Just because they're from another planet doesn't mean that they're not just like us. In fact, for there to be any form of communication at all, there has to be a common frame of reference, and if they're disguised as us then there has to be a lot of common frames of reference, therefore, they probably are just like us. In which case, **they're here for the sex**. [Answer] Ok, back to the real question then. Why would super aliens mix with us? Here are some suggestions: - too much inbreed in their own dna - boredom with being a super alien (winning WordFeud all of the time) - looking in the mirror and being jealous of Dolly Parton's tits - they spoiled their own planet and believe that maybe, just maybe, we can still save our own - on the above they just come and have fun with us for doing exactly what they did themselves Plenty of reasons, but if I were an advanced alien I would travel to Alpha Centauri with laser propulsed nanobots just out of curiousity. Maybe Elon Musk and Stephen Hawkins are advanced aliens too, they are planning exactly that. Cheers... [Answer] IMMEDIATE GOAL: Assessment of humans on planet Terra (Earth) * Sub-Goal #1: Where is Terran technology in contrast to ET tech? * Sub-Goal #2: Where is Terran culture in contrast to ET culture? * Sub-Goal #3: What is the likely ETA for Terrans to enter Galactic civilization? * Sub-Goal #4: What risks do Terrans pose to Galactic civilization? ULTIMATE GOAL: Intervention * Sub-Goal #1: Based on the various assessments above determine what if any interventions might be necessary to prevent significant harm to the Galactic civilization. * Sub-Goal #2: BY means of infiltration (disguise) sabotage or modify Terran science and/or culture to lower risks to the Galactic civilization. IN A NUTSHELL: Galactic Babysitting [Answer] It's a kink. Dressing up as alien species, let alone actually making out with them, is abhorrent to the majority and/or ruling class on their home planet(s). So, they have to sneak off to alien worlds to get their fix. But then it gets kinkier. If it's *really* abhorrent to their race/government, they will feel compelled to stop them, and that means *sending the police*. However, they probably *also* have rules about non-interference-- specifically, not revealing themselves to species which have not discovered interstellar travel-- which means *the cops have to dress up, too*... which means your safest option for satisfying your kink is to *join the police*. I think this is *exactly* where an author like Samuel R. Delaney would have taken this. (Read his incomprehensibly underrated masterwork, "Stars in My Pocket Like Grains of Sand", if you're curious.) [Answer] Perhaps to understand this one perplexing thing their science cannot explain, the human mind. How do such species (humans), so primitive in their technology, reason the way they do? We humans are quite a fascinating occurrence. ]

[Question] [ In my world, there is a plane of existence whose laws of reality work differently than ours. In this plane, thoughts are not private. The boundaries between the mind and reality are slim, and thus every living creature’s thoughts are laid bare and broadcasted for all to hear. Naturally, this changes quite a few things about how life functions, but particularly predation. Many predators in our world rely on the element of surprise in order to capture their prey. In this plane, however, sneaking and stealth are rather impossible, as a predator’s intent to kill would be felt by every living thing around it. So, my question is, in this world where a predator’s killing intent is laid bare, what other ways might a predator capture its prey? What evolutionary and/or behavioral characteristics might they evolve? [Answer] # Mindless reflexive predators There are not many predatory plants, but there are a few. Venus flytraps have no thoughts whatsoever. They get by just fine. # Temporary comas or microsleep Being an ambush predator will still be possible. You won't be able to *stalk* prey without them knowing they're being followed, but you can still *surprise* them and that can still be enough. Somewhat similar to [dolphin sleep patterns](https://us.whales.org/whales-dolphins/how-do-dolphins-sleep/), this predator blends into their surroundings, then goes to sleep / temporarily enters a coma-like state of suspended animation. They can jolt to full awareness almost immediately, so when a prey animal triggers an instinctive reflex the predator jolts awake and immediately attacks. They were literally not thinking at all, emitting no telltale presence, so this will be quite a surprise to their prospective meal. [Answer] You’re neglecting an important arena in the predator/prey dynamic: Thought. If your predators can feel the thoughts of things around them and the prey can detect predatory intent, what’s to stop the predators from evolving effective thought patterns? Many creatures in such a universe would evolve behaviours and senses entirely focused on exploiting thought, and your predators are no exception. Take ants, as an example. Ants use pheromones extensively. If something in the nest doesn’t smell *exactly* right, they’ll attack it. Basically they use smell in the same way as you would thought. So a species of spider has evolved to look and smell like an ant. It’s such an effective disguise that the spider can waltz out of a nest carrying dead larvae and the ants just don’t notice it. ‘But’ I hear you cry ‘Surely that’s predatory intent?’ Well, yes, but it’s an example of the kind of mimicry evolution is capable of. If you have a prey species that eats grass (for example) then a predator that thinks ‘ooh, yummy grass’ when looking at them will have the same ‘predatory intent’ as the prey species has. It will ‘smell the same’, meaning that by the time the prey realise a predator is there it’s too late. The yummy grass will have been eaten. If thought is used as an extra sense this would make predators that think ‘ooh, grass’ instead of ‘ooh, meat’ evolutionarily favoured. Creatures capable of masking or mimicking thoughts can exist, and not only that but if thought supersedes certain other senses (As pheromones do with ants) then thought-mimics could be highly effective. You should view ‘thought’ as an extra battleground. If a Despair Squid is capable of broadcasting deep nihilistic despair to nearby prey then they might just die out of the sheer pointlessness of it all. The Lazy Shrimp relies on instinct, basically positioning a spring loaded claw then making itself invisible by going to sleep and hoping it’s hair-trigger reflexes can catch something. Chaff Magpies fill the air with mental chatter, making it impossible for prey to spot incoming Sociopanthers. The Magpies eat leftover carrion in an example of a symbiotic relationship. Oh, and Homo Horrificus actively *lets* its prey know they’re being hunted, relying on their terror to cause them to run until they’re exhausted or they fall into a pre-prepared trap. Basically: Extend the arms race that is evolution into the plane of thought. If there’s a mental trick that would help a creature survive in this world evolution will ruthlessly exploit it. [Answer] Some hunters, such as hyenas and humans, do not ambush their prey; rather, they tire the prey out until they die of exhaustion. We would see more predators with high endurance, with the ability to run many miles to wear down their prey. [Answer] # Doublethink For an ecosystem to allow for predation in this world, sentient creatures with the most advanced consciousness need to have this skill. It was first described by George Orwell in his book *1984*: > > To know and not to know, to be conscious of complete truthfulness while telling carefully constructed lies, to hold simultaneously two opinions which cancelled out, knowing them to be contradictory and believing in both of them, to use logic against logic, to repudiate morality while laying claim to it, to believe that democracy was impossible and that the Party was the guardian of democracy, to forget whatever it was necessary to forget, then to draw it back into memory again at the moment when it was needed, and then promptly to forget it again, and above all, to apply the same process to the process itself—that was the ultimate subtlety: consciously to induce unconsciousness, and then, once again, to become unconscious of the act of hypnosis you had just performed. Even to understand the word—doublethink—involved the use of doublethink. > > > > > The power of holding two contradictory beliefs in one's mind simultaneously, and accepting both of them... To tell deliberate lies while genuinely believing in them, to forget any fact that has become inconvenient, and then, when it becomes necessary again, to draw it back from oblivion for just as long as it is needed, to deny the existence of objective reality and all the while to take account of the reality which one denies—all this is indispensably necessary. Even in using the word doublethink it is necessary to exercise doublethink. For by using the word one admits that one is tampering with reality; by a fresh act of doublethink one erases this knowledge; and so on indefinitely, with the lie always one leap ahead of the truth. > > > You need to really convince yourself that you are not harming the prey, until the moment you strike. # Hypocrisy By tradition the ancient greek could only sacrifice willing animals. They would assert willingness by asking an animal if they were willing, and then pouring water on the animal's head so that the animal would nod. Hypocrisy is a powerful tool that can help humans not feel any guilt when performing evil deeds, and without the feeling of guilt in the predator, telepathic prey may not know what hit them until it's too late. # They honestly don't think violent thoughts If the predator [believes killing to be actually joyful and pleasant to the victim](https://www.youtube.com/watch?v=WUhOnX8qt3I), then the problem is solved. I sometimes wonder if dogs chasing squirrels think it's all a game, just as when they are fetching sticks or balls. # Mindless damage Sometimes predators are just brainless. Jellyfish don't put much thought on their modus operandi, yet there are many species which eat fish. [Answer] **Using the preys senses against them** Many species on earth use tricks to capture prey. Use of flashy lights/colors, loud noises or overpowering scents to distract the prey, and in some cases, stun them. In many creatures, if you overload the senses, they could possibly just lock up. Think something like a flashbang. If a predator develops a means to overload a preys senses, they can sneak up with little effort. a pack of empathic "wolves" when stalking a prey animal, once they get near range can begin to broad cast loud and nonsensical "noise." they prey would know they are in trouble, but they are overwhelmed by the empathic noise that they panic and is unable to formulate an effective escape plan. I'm thinking, something like thinking in your head a choir singing "This is the song that never ends" at the top of their lungs while quietly think about stabbing someone. Maybe the predatory thoughts get drowned out by the other noise your mind is putting out. [Answer] **Predators are simply stronger** You can simply make the **death inevitable**. In many cases, predators can be simply faster, stronger, or thinking and reacting faster/better than their prey. Sure, it could turn into the evolutionary armaments race, but I would say that evolution supports diversity. Every specie has its advantages and disadvantages, which can be abused by predators. You could compare it to a game of rock, paper, scissors. Snails have shells but are slow. It protects them against one type of predator, that can't break the shell, but they might be vulnerable to those who are small enough to enter their shell. Moreover, I believe team hunting would still work. Even with mind reading, a single weaker, exhausted, older/younger or previously injured animal might find itself in a situation where death is unavoidable. [Answer] If empathy is connects all beings, then ALL would be aware that life would be impossible without death. There would be no hunting, but I think maybe an "agreement" would be achieved - something like "Well miss lioness, our sick one agreed to feed your family". I just don't see the point in hunting if all KNOW eachothers needs. Hunting is based on struggle for survival, but only exists because no one can "feel" the others. If they could, there would only be struggle when an agreement could not be reached. As user76358 mentioned, there are sadistic predators. I think these beings would be extra violent, since they would be able to see the whole extension of suffering inflicted on their victims. That could enhance their trend. I imagine predators would have to reach a zen-like ability to keep their minds blank while stalking. [Answer] Flying reptile predators like Quetzalcoatlus would have better chances surviving due to less competition.  In a world were everyone can predict you, only 3 types of predators can exist. * runners as the answer before me suggests * creatures which can't be escaped because they fly * creatures which create traps like sandworms/spiders or humans [Answer] ## Arbitrators This answer expands on Pablo Santos's answer, per my comment there. *(Edited for clarity but also added verbosity because one troublemaker misinterpreted mention of real world examples as a universal truth which no reasonable person would.)* In *some but by no means all* American First Peoples' and European shamanic cultures, hunting, gathering, and farming are based on a shamanic worldview, which is founded on empathy. In those cultures, the agreement is reached by acting out the part of the prey, with an overseeing spirit as arbitrator. Pablo suggests *'There would be no hunting, but I think maybe an "agreement" would be achieved - something like "Well miss lioness, our sick one agreed to feed your family".'* Perhaps then, in the imaginary world, there is a "god" or "spirit" creature, with a larger radius of influence, who can arbitrate in such an agreement. Then they would also be available for other questions of morality, judgment, and if they're rather large physically, might need to be placated now & then. "Wat!? You didn't dance high enough! I'm going to *smite your grandmother!*" [Answer] **Stupidity, and spontaneity.** First to mask and create noise underneath which there could be an inherent or purposeful predatory tendencies. Second is important because intent to kill and its identification only goes so far for survival in the wild. If there is a gap between preparation to protect there is also room for predator to evolve, into covering that gap. Why would it evolve? Well like all organisms if its sustenance depends on predation of others than its either evolve or perish. There could also be an evolution that instead of projecting intent to kill causes listeners to want to kill themselves, like induction of suicidal thoughts. But it all boils down to what degree of individuality do the connected minds have, because any difference would be a defence for predators, and high degree homogeneity would mean that at that plane of existence there is one collective being. And predatory thoughts would mean self sabotage. Think alcoholism, food addictions, etc. A predatory thought could be someone thinking “How I wish I could have all the cupcakes in the world?” Or “I wish I could eat pizza all my life !” [Answer] Thought camouflage and cooperative hunting. The prey will have lots of thoughts. Thoughts such as "I can hide here for safety and survival". The problem is that they wont think in words but in feelings (I guess). So a predator could camouflage his thoughts: instead of thinking "I'll hide here to catch prey" he'll think "I'll hide here for my survival". Where survival means not starving but which prey is going to know that? By the time they see prey they will have to watch with desinterest until the prey is at the proper distance for an attempt. Another method is to camouflage what you prey on. An antilope isnt going to be afraid if it thinks you are a lizard preying on an insect. Vice versa a lizard is going to act as if its preying on his natural enemies so his insect meal isnt going to flee while his natural enemies will steer clear of the area that is currently harboring something that might eat them. Ofcourse you have to switch it up because if anyone thinking of preying on predators is actually a prey for that exact predator it just highlights them. But cooperation is also a perfect way to hunt. If you cooperate with other predators, who could not be thinking thoughts like "I'll just take it all for myself" without being excluded, you can easily force prey into other predators and share the kills. The predators simply spread out over a large area so prey in the center cannot hear their thoughts anymore, then they close the net tighter and tighter until the prey notices them. They'll try to run away but will eventually have to pass some predators, and the system of thoughts might not let them know WHERE the predators are, just that they are there and looking for food. [Answer] The prey can be like a fruit tree, gaining from its fruits being eaten. Living on such a high plain, the existence of predators is unlikely. [Answer] Many years ago, I read a science fiction story in which very large creatures, living at the bottom of the ocean, although very intelligent, telepathic, and empathic, indeed, sympathetic, mostly preyed on one another, with the larger seeking out (through telepathy) the not-quite-so-large and eating them. The mode of capture was precisely the use of empathy in that the predators used mind games to confuse and deceive the prey, who would otherwise go silent and hide out of view and physical access. Unfortunately I don't remember the title or the author. The reader doesn't realize until almost the end what the game is. One might also consider that in their hunter-gatherer stage, human hunters often practiced magic to get in sympathy with their prey. [Answer] One answer that I think could be interesting is the ***pleasure/pain paradox***. The release of endorphins during death could cause a temporary state of euphoria, the hunter also receive this. Rather than simply mindless predator, or mindless prey, there is the hunt... which is simply an escapist fantasy. The drudgery of life, perhaps hard labor is necessary for the prey species and is ended by a merciful and benevolent hunt. This is mainly to increase endorphins or some other such factor. The psychic predator then quickly kill the victim before the pleasure/pain state is diminished. A joyful release from a life of toil, for those who have been chosen. ]

[Question] [ I am working on a souls-like game and I would like to have an item that works like [Fragrant Branch of Yore](https://darksouls2.wiki.fextralife.com/Fragrant+Branch+of+Yore) from DS2. I do not want to copy the concept of petrification from DS2 so while the item should work in a similar way I would like it to have different look, feel and lore behind it. In order to describe the mechanic (requirements) I will use the words "door" and "key" for simplicity. The question is which items (enchantments, etc.) can be used to act as "doors" and "keys". ## Requirements: * Any "door" can be opened with any "key" * Once opened the "door" stays open * It must be possible to purposefully construct a "door". * The "key" can only be used once. * Creating a "door" may require the use of magic but opening a "door" with a "key" should not require magic abilities * "Doors" are not portals. You can not teleport to a different location by walking through a "door". ## Desired but not required: * The "doors" can appear randomly (like vines growing over a normal door) * the "keys" should be rare but it should not be obvious where to find one (for example if only rich people could possess them, it would make no sense to search for a key in a poor man's house) [Answer] 1. A "door" is a chunk of stuff which occludes passage. 2. A key is an explosive, like a stick of dynamite. It could be in the shape of a key which would be cute. Using the key blows a hole in the door. You can use a key once, because after that it is blown up. Once there is a hole in the door you can walk through. You might need to stoop. The hole will not close by itself. Any key will work on any door. And on other things too, if you want. Using a key might involve lighting a fuse, possibly from your lit cigar. Running away is optional but encouraged. Doors can appear on their own. For example, a big tree might qualify as a "door" if it were in your way. A rockslide could be a door. A large animal, alive or dead, might also be considered a "door". The door to your favorite pub that they have pushed you thru and locked behind you would also qualify as a door, the bastards. Fortunately you have a lit cigar and rare locksmithing talents at the ready. [Answer] Secrets secrets (in this case) are so fun! Create a shadow organization that deals in information. Your “doors” are members of the organization that guard entrances, and your “keys” are interesting secrets. ## Requirements: > > Any "door" can be opened with any "key" > > > Any member of this organization will accept any valuable secret you have. > > Once opened the "door" stays open > > > The guard to an area recognizes your contribution, and always allows you through (after paying, of course). > > It must be possible to purposefully construct a "door.” > > > Naturally, this organization can be hired out given the appropriate payment. > > The "key" can only be used once. > > > Once the organization is aware of a secret, it is no longer a secret to them. ## Desired but not required: > > The "doors" can appear randomly (like vines growing over a normal door) > > > The motivations of this organizations can seem random to the player. > > The "keys" should be rare but it should not be obvious where to find one (for example if only rich people could possess them, it would make no sense to search for a key in a poor man's house) > > > This should certainly be true about meaningful secrets. [Answer] * A sacrifice or votive offering. Burn a pinch of incense, and the portal opens. * A rusty door and a can of [WD-40](https://en.wikipedia.org/wiki/WD-40). The door is sticky, and requires lubricant. Due to the environmental conditions, the effect won't last. * There is a spell on the door, but certain folk remedies like cold iron horseshoes will dispell it for a time. The horseshoe must be nailed to the door, or perhaps buried under it. [Answer] The "doors" are limbs of a massive interdimensional eldritch being. A magic-user can bind them to our reality and coalesce their power into some sort of token, and those tokens can then be used to banish it back. For bonus points, this being could have some relevance to the game's overall plot (or it could be a [Giant Space Flea From Nowhere](https://tvtropes.org/pmwiki/pmwiki.php/Main/GiantSpaceFleaFromNowhere) bonus boss). # Requirements: > > Any "door" can be opened with any "key" > > > The tokens are interchangeable; they all contain the same magic. > > Once opened the "door" stays open > > > Unless someone binds it again, at least. > > It must be possible to purposefully construct a "door". > > > With magic. > > The "key" can only be used once. > > > Using a token discharges its magic and destroys it. > > Creating a "door" may require the use of magic but opening a "door" with a "key" should not require magic abilities > > > Anyone can use the tokens to banish it, all it requires is physical contact. > > "Doors" are not portals. You can not teleport to a different location by walking through a "door". > > > Banishing it just removes an obstacle, you're left with an ordinary opening. # Desired but not required: > > The "doors" can appear randomly (like vines growing over a normal door) > > > Perhaps it can occasionally manifest itself into our reality without assistance? Though that would still require explaining where the tokens come from. Maybe the token manifests nearby in the form of a shiny object, which some critter takes away and hides. > > the "keys" should be rare but it should not be obvious where to find one (for example if only rich people could possess them, it would make no sense to search for a key in a poor man's house) > > > Tokens would be wherever the magic-users decide to put them, so that isn't a problem unless they all have consistent habits (or see above). [Answer] A simple mechanical solution would work just like a vending machine. That vending machine could be configured to not accept any coin, but only a very specific and unique one, which is used as a key, and will disappear deep in the bowels of the machine, never to be retrieved by any simple means. In case you wonder, vending machines have been around since ancient times, so it wouldn't be anachronistic. [Answer] Recently the local area has become infested with Barhools! Barhools are large bearlike creatures that spend most of their time sleeping. They're nearly indestructible and immune to all magic, but fortunately they're pretty harmless - except when they first wake up, whereapon they immediately seize and devour the nearest creature before wandering off. Fortunately for you, Barhools are rather partial to Foostirs - large grublike creatures which can be found just about everywhere. They're in rather short supply at the moment due to Barhool predation, but I'm sure that you can find some hidden in out of the way places, right? (More generally, any sort of bribe for a group of people or creatures works well for this sort of thing.) [Answer] Mechanic solution is that key is used up in opening the door. E.g. key is actually a shaft that pushes the latch to open position, and gets permanently wedged in the mechanism. But this does not explain random appearene of doors or keys. A magic solution is spirits. Locks are hungry spirits that need "food", and keys are the spirit food, which appears randomly in the world. Lock spirits are lazy, or very slow, so rather than look for their food, they hold the door hostage until somebody brings them the food. [Answer] In computing we call such "keys" names like: * One Time Password (OTP) * Access tokens * Secrets (such as those exchanged in HTTPS connections) * Keys. Literally. Such as a license key, which activates a license only once. * Lots of four letter words, when we need one but have forgot them or have no way to get them. You could name them tokens, or secrets, or just keys anyway and by the time a player/reader has seen it in action once or twice they will have figured them out. The physical representation of the objects you use is just a detail; Much like portkeys in Harry Potter's world, you can use anything, restrained only by your choices as the world builder. If you go with "key" and want to qualify it in such a way as to differentiate from a regular, everyday key, call it a "magical key", "mana key", "ether key" or something like that, and be done with it. [Answer] All the doors are locked, and you don't have a key. You don't even know how to pick locks! But what you *do* have is a [snap gun](https://en.wikipedia.org/wiki/Snap_gun) that can open any lock by force. Recently, though, there's been a rash of crime using snap guns, and the government is trying to cut down on it. So all snap guns available to those outside the police and military have fragile and temperamental parts. Yours is particularly bad, and you have to replace the lever or the spring between each use. [Answer] The key is a special liquid or powder that is poured or splashed onto the door, or poured into an opening of the door. The door then dissolves or disappears, using the liquid/powder component in the process. Since the door has dissolved, it stays open. The liquid could be a variety of special substances that would react with the door to cause its dissolution. The liquid could range from easily available, to incredibly difficult, and could force someone to search in a specific area (like a black dragons cave). For example * There are many different types of acids that literally melt things. You could use scientific acids (hydrochloric, sulfuric, etc), or something a little more fantastical like the acid from a black dragon's breath weapon. * If the doors were constructed of something like salt of sugar, then almost any liquid would cause them to dissolve. * The liquid could contain microorganisms (bacteria for example) that eat away at the material of the door. Similar to the extraterrestrial bacteria in [The Andromeda Strain](https://en.wikipedia.org/wiki/The_Andromeda_Strain). * In a sci-fi setting, the liquid could be nanobots that eat the door or convert it to a different shape. * Thermite makes a very good door opening agent. The components of the door could cause an exothermic reaction, igniting the thermite, and melting the door. * Salt or sugar, or some powdery concoction, could cause the door to melt when applied. In Supernatural, we know that salt affects the demonic and supernatural, so if the door is made with demon flesh, it would surely melt when salt or saltwater (aka holy water) is applied to it. [Answer] The door, or at least the keyhole, is made with Litium-ion, or a similar substance that burns when exposed to air. Or maybe just ignited with the key. They keys are specially shaped to fit the keyhole, puncture a barrier, and then the door bursts into flames. When the fire is done, the door is permanently opened. The keys, being mass produced in the same factory or by the same keymaker, are all the same, and only have one purpose. Since the door immediately starts shooting flames out of the keyhole, the key is consumed in the fire. [Answer] A key could be an intricate coin. To manufacture such a coin requires expensive metals and precise tools. The design should be complex enough that you couldn't simply use a mold or die to smelt a coin into the correct shape. The door has a coin operated locking mechanism. Incorrect coins fall through and come out the bottom. Only coins with the perfect pattern of bumps and holes will fall into the correct place, completing the mechanism and opening the lock. For added effect, make the door look like a giant gumball machine. 😁 [Answer] What you describe sounds like a kind of single-use skeleton key. This could be justified by having the "key" contain some active component that can open any lock, but expires when used. In magical settings, this might be a Scroll/Wand of Unlocking; in scientific settings it could be some nanotech (or bio-engineered) "living lockpick" that permanently molds itself to the lock. ]

[Question] [ **Background** In the mid 22nd century, a super plague has killed 99% of human life, many survivors are killed in the ensuing riots and fighting. The few billionaires that are hiding in their bunkers have over many years of violence, built a generation ship. They shoot into space leaving around 8000 humans alive. Those that do survive end up dying 700 years later due to the Yellowstone super-volcano erupting. Meanwhile on the generation ship, a revolt of 46th generation humans take over a small back up ship (in case the larger one were to be destroyed by an asteroid or other collision.) and head back to Earth. Unfortunately, due to the relativity of space, they arrive 4.8 million years post plague. They crash land and that is where my question begins. **Question** Okay, yes, I know that it is a little bit dark, what with the murder and the riots and all that plague. My goal here is for human civilization to restart on this new and altered Earth, along with its new inhabitants; Gryphans ([tree cats](https://worldbuilding.stackexchange.com/questions/25281/anatomically-correct-griffins/25387#25387)) and Neocorvids (the [last 5 here](https://worldbuilding.meta.stackexchange.com/questions/3939/planet-of-the-aves-series/3940#3940)). The problem is that I am having difficulty explaining exactly why the newly arrived humans do not manage to continue as an advanced civilization. The only solution I have come up with is that the generation ship is horribly mangled and that the generation ship practically coddled them stupid of survival skill, but this solution has two problems; 1) if a carbon alloy generation ship is horribly mangled, how on Earth did squishy humans manage to survive and 2) if they lack any survival skills, how do they survive period? So after debating with myself over this issue, I decided to instead ask, why would survivors of a crash landed generation ship start from the beginning at the stone age, rather than being advanced? [Answer] This is actually easier than you think, and represents a major shortcoming of our modern civilization - specialization. First and foremost, it's safe to say that all traces of human civilization on Earth are now well and truly gone. In other words, no one is going to find caches of technology or resources just lying around. Second, consider that the skills necessary to survive on a wild, and dangerous planet are not the same skills needed to survive on a generation ship. Those people were probably raised with certain societal roles in mind. Societal roles which corresponded to the needs and requirements of a generation ship. And suddenly, you thrust these very ignorant folks into a wild situation. But Andrei, you say, surely they have libraries of materials that they can read up on! Sure they do. They probably have the boy scout's guide in a handy PDF file. However, the Earth's changed in the 4.8 million years that humanity has been gone. That information is not only stale, unexpected situations are ***bound*** to occur. Those texts will be poor substitutes for actual experience. And acquiring that experience / revising their survival knowledge is probably going to cost them dearly: > > **Ignorant human:** Oh, look! A pretty insect! *touches it and promptly drops dead because it was poisonous, and didn't exist when their survival book was written* > > > But that's not necessarily a reason for them to devolve to cave-man status. There's a few ways (which can be used in conjunction) in which this might come about though: ### 1) Ship crashes Upon nearing Earth, it's quite possible that their ship suffer a major malfunction, and that it crashes. A lot of the crew might survive due to lifepods, etc., however not a lot of survival gear and equipment would be salvaged, and the survivors might also be scattered across the globe. This is, really, the easiest way to explain it. Ignorant, poorly prepared people with little to no resources ... The survivors would discard their civilized sensitivities rather quickly. ### 2) A few key people die / resources are lost We all know how to use a cell phone. But how many people know how one actually works at a hardware level? How about build one? If a few key people die, a lot of knowledge and equipment might suddenly become inoperable. > > If you want to max out the irony index of your story you might have the survivors lose security access to key resource vaults when their leader dies in a really silly accident. > > > Say that their library of survival texts, and maintenance manuals was lost in a fire. The existing techs would teach their skills and knowledge to some apprentices. But with each passing generation some information would be lost, until eventually that technology seems as magic, and finally just gives out due to lack of spare parts, and adequate maintenance. If the knowledge loss is dramatic enough (techs die trying to fight the fire which consumed the library) then the situation would deteriorate much, much faster. This would also happen if a key resource - say, a nano-tech creation engine used to manufacture *all* spare parts and equipment - suddenly malfunctions and is simply not fixed before essential resources start running out. In that state of panic, and with a few emergencies thrown in, not to mention some poor leadership, they would be doomed. Next thing you know, perfectly civilized human beings are killing each other for food, and all pretenses of civilization are out the window. Read [Lord of the Flies](https://en.wikipedia.org/wiki/Lord_of_the_Flies) by William Golding for his take on how a group of civilized school children stranded on an island devolve to barbarity. [Answer] # Can YOU make a toaster ***from scratch***? # OR # At The End Of WALL\*E, Everyone Starves. Do you, or any of your friends, or anyone you know know how to... * Mine and smelt ore? * Make a hammer? * Purify water? * Purify silicon? * Make bricks? * Build a water wheel? * Build a turbine? * Make plastic? * Make wire? * Make a generator? * Make gunpowder? (*Please don't leave a bunch of comments saying "I do!"*) Because those are the skills you're going to need to rebuild civilization: basic resource extraction and processing. These skills are the critical bottom of the food chain that your fancy technological devices at the top rely on. Without that ["you're a maggot... living off the corpse of the old world" as they say in The Road Warrior](http://www.imdb.com/title/tt0082694/quotes?item=qt0201170). To get an idea of the enormity of the task, watch [Thomas Thwaites try to build a toaster from scratch](https://www.youtube.com/watch?v=5ODzO7Lz_pw). [](https://i.stack.imgur.com/T0UY9.jpg) Since your ark is launched by billionaires you can be sure it was them and their rich friends who have only a vague understanding of how things are made. None of them have the practical skills that are needed to be the very broad bottom of the food chain. Your generation ship is [the A-Ark of Hitchhiker's Guide, the one with all the hoi-poli of civilization, without the C-Ark to do all the laboring](https://www.youtube.com/watch?v=CSid-p0Xlk0). After living 50+ generations on a technologically advanced spaceship completely detached from the realities of living on a planet, those generations will be even further detached than most of us are from the realities of living on a ball of dirt and water. After 50+ generations, they'll probably even have forgotten about the possibility of colonizing a planet. They've never known a planet. They'll be the people from WALL\*E. [](https://i.stack.imgur.com/T8fwA.jpg) Even if there are education systems, it will make as much sense to them as advanced calculus does to a bored teenager. "Why do we have to learn this stuff? We never use it!" and for once they'll be right. Even if they must labor on the ship, even in a simulated environment, that labor will have little relation to the realities of working in an iron mine. [The scene from WALL\*E about "pizza plants"](https://www.youtube.com/watch?v=o0YaNuOPDY8)? That about sums it up. If everyone on that ship thinks farming is just putting seeds in the ground, add a little water, wait and VOILA! Pizza! Yeah... you're all gonna starve on Earth. You have this: [](https://i.stack.imgur.com/A3fdZ.jpg) You need this: [](https://i.stack.imgur.com/sGDzL.jpg) That guy runs [a channel called Primitive Technology](https://www.youtube.com/channel/UCAL3JXZSzSm8AlZyD3nQdBA/featured) where he, silently, demonstrates all sorts of basic primitive skills. The same skills that your people will need to survive outside their ship. The same skills they don't have and have no concept of. Everyone's gonna starve. # Your Precious Generation Ship Is Being Eaten And Dissolved. But wait! They somehow survived 50 generations in space! They must have some amazing automation and recycling tech! Can't they just use that? Yeah... for a while. Though if they're just going to rely on their ship for their basic needs they might as well be in space... but people do things without thinking ahead, so that's plausible. But here's the thing about space: it's very clean and very empty. Your ship can float around in deep space for millennia and hardly be changed. Perfectly preserved except for some ionizing radiation. No need to even worry about micro-meteorites, you're in deep space between stars most of the time. Here's the thing about the Earth: it has an oxygen atmosphere and water and temperature variations and weather and life. Oxygen is one of the most corrosive substances in the universe. Water is one of the best solvents. Life will get into ANY crack. After a few years the alloys and metals and plastics will begin to break down. Tiny plants and roots will worm their way into any crack. Insects will get in, as they always do. The inhabitants will likely be absolutely terrified as they watch their ship be slowly consumed by tiny monsters and green "infections" that they can never seem to eradicate. The carefully balanced ecosystem of the generation ship will be disrupted and begin to break down. Everything will break down at an increasing rate. When systems they rely on for basic needs start to fail, they will *never* come back. The materials and expertise to fix them at a basic level will be gone. [Answer] # Lack of Tools to Build Tools The survivors had equipment. Radios. Guns. Axes. Antibiotics. But radios break down. Guns run out of ammo. Axes get dull, and grinding them wears them down. To replace them the survivors will need steel furnaces, chip factories, and so on. # But didn't the Planners think of that? Of course they did. But rebuilding an infrastructure from scratch is difficult and hard to practice. Perhaps the crash damaged *all* the turret lathes, and the plan came to an unexpected end. [Answer] "Primitive" humans have a huge amount of technology. Much of it we take for granted. Farmable crops and domesticated animals are a multi-generation project. So those are right out. Both of these require a way to survive for generations *first*, then you can start up that chain as you domesticate herd animals and selectively plant the most useful food crops and spread the useful mutations. So, you arrive, you'll be at the hunter-gatherer and fisher technology level, at least as far as food is concerned. All of the fancy toys won't get you out of that (barring magic hydroponics or the like). With any kind of population growth, the tools from the ship will be at best rare items. Death rates are likely to be high, especially once food runs out. If the ship arrives short on supplies, they may have to flee the crash site immediately with only the stuff they can carry. If it lands somewhere *harsh*, this may result in a huge death rate. A far more "prepared" group who died completely includes the various arctic expeditions. Long before they died, reports exist that they where insane from malnutrition, harsh environment, and cannibalism. A ship that crash landed (even barely damaged), low on supplies, in an arctic region could have a 99% death rate prior to reaching land where they could feed themselves off foraging. Most of their tools would be lost. The humans that survived would be seriously scarred; perhaps the next generation would be smaller than the first. Legends of the great sky-ship would exist, together with legends of how to make technology. "Magical" heirlooms from the ship would exist, often not used for their intended purposes. Those heirlooms would be lost and break down. The people would breed and grow. They would expand over the world. But they would only have legends of their time in space even a generation or two later. Those that found the ship might not even be able to get back into it, as they don't know the lock combination or are not recognized as crew. Even simple technologies like the wheel require a lot of infrastructure to make worthwhile. Being able to make tools from the environment (like stone tools) would be worth far more than remembering obscure and inaccurate rules on how to smelt iron, none of which is nearby anyhow. Some of the survivors may have tried to generate stories that teach their descendants how to develop technology a bit faster, but those could easily be lost or warped beyond usefulness. [Answer] ## You don't need to mangle the ship; you just need to mangle the information Information is the key here. Unless your humans are cybernetically augmented post-humans with truly phenomenal memories, there's no way they would have the knowledge to build an advanced society in their heads. Rather, that data would be on the ship's computer - and computer data is fragile. There's a reason you're constantly reminded to back up your data. A lot of things could cause the ship's memory banks to be corrupted. Strong magnetic fields, physical compromise of the data store, even something as simple as a loss of power, could leave the information irretrievable. The crew would then be thrown back on what they could remember and what they could figure out for themselves. A generation ship is not a good place to raise generations of rugged individualist survivors. There are no construction projects on a generation ship for your engineers to practice on, there are no new features of the world to research, no crops to raise - or rather, what crops need to be raised are grown in conditions entirely different from anything planet-side - no rivers to be diverted, etc, etc... The crews lives up to this point will not have prepared them for living away from an environment controlled by their computers. Many would die; the survivors would be thrown back to first principles. ## A technological civilisation needs infrastructure The Remade Earth isn't going to have a ready-made transportation network to bring spare parts from factories to consumers; of course, this doesn't matter much since there *aren't* any factories stamping out spare parts, or oil rigs pumping out fuel. No power lines, no power stations, no cell towers, no rubber plantations or wheat farms. All of this needs to be built from scratch, in the face of a (presumably) hostile planet. ## A technological civilisation needs stability I have a job. I work every day processing data, passing it back and forth between various entities. I don't grow my own food. I can get away with this because I live in a stable, predictable world, where I know from day to day what to expect. Throw in war, or political upheaval, or just plain unpredictability, and suddenly I'm thrown back on my own resources. I need to make sure my food supply is stable, make sure I have clean water to drink, make sure I have fuel to power my heaters and vehicles. I no longer have the time to waste moving data around, so anyone relying upon my data is no longer able to do their job; they're thrown back on their resources as well. This group started out as mutineers; it would hardly be surprising if it turned out that there were internal factions, different leaders striving for power with one another and upsetting the delicate balance you need to maintain an advanced technological society. ## Frankly, the question in this scenario isn't why didn't people hold on to advanced technology; it's how did they survive at all? [Answer] The rebels that return are led by a charismatic leader that plays on their emotions. They dismiss scientific thinking and feel that *anything* the pre-planned manual says is to be dismissed with extreme prejudice. Their faith will see them through—they know better than the ancients or anyone that would tell them otherwise, specifically including anyone with any real education. Without a huge infrastructure to buffer and buttress such movements, technical know-how will disappear in a generation. Just look at the anti-science, anti-authority mindset that’s around *today*, and imagine them in this isolated population. It fits well with the rebellion idea of the plot. [Answer] Shamelessly stealing ideas from David Weber (mostly, Dahak series): 1. For whatever reason, a religion arose among them that views advances in technology/science/inventions as sinful. Trivial to explain - the cause of original problem was biotechnology, so to prevent recurrence, the billionaires who built the generation ship decided to institute a "no progress" type religious practices. Over many years, that mutates into "no technology/science at all" religion, probably helped along by a less than sane "prophet" or two. Anyone who invents something new kets offed immediately, in public rituals. 2. Pharaon/helot model (yes, I know i'm mixing my ancient civilizations. it just sounded way cooler). A small cadre of power holders on original ship decided that since they are heading back to Earth, they can take over control, and use the rest of population as slaves. As such, they killed off anyone who knew stuff (engineers, medics, etc...) who wasn't already part of the power circle's supporters. They also conspired to offload the rest of ship population without any technology, probably using fake emergency. Without knowledge base or access to technology, the rest fall into stone age in one generation. [Answer] Children need to be raised. If you drop a million four year-olds on a fertile continent, some will survive but all knowledge and civilization will be lost. All of it. It probably happened before. Native Americans, meaning the tribes, might be the byproduct of friendly diseases completely wiping the previous civilization. The American wasn't known to have casually transmittable ("friendly") diseases pre-contact, so concepts like isolation and epidemic were unlikely to exist. A strong line of thought has the Americas as a populous, and diverse land with a mixture of rural and urban areas. Then a disease comes and wipes out 99.9% of everyone, breaking the chain of civilization. Also the civilization built in wood, wrote in string, and decays quickly enough that the break cannot reconnect to past knowledge. The modern tribes are the "Lord of The Flies" people left over. And stone age is extra hard without domestic animals. For a story of a world without the break in civilization, read "Freedom's Landing". It takes almost a week for a few thousand random city dwellers to advance to indoor plumbing. In contrast, "Earth Abides" features such a death rate that the chain is mostly broken; even reducing the population of the United States to under a hundred people preserves some knowledge. There are a number of stories where people leave notes to restart civilization, e.g., "Canticle for Lebowitz" or "Footfall". [Answer] There are very few reasons to live in agricultural or industrial society if population density is low enough to sustain a hunter-gatherer economy. According to Marvin Harris'[Cannibals and Kings](https://en.wikipedia.org/wiki/Cannibals_and_Kings) book, hunter-gatherer economy is the optimum economy in terms of work needed to make a living. That is, stone age people worked a lot less than people of any other time. In other words, nobody would switch to agriculture and husbandry if they can just gather and hunt, and hunting-gathering is always possible and easy if you have enough space and very low population. Of course, there are some contemporary things that you would like to keep even if you have an stone age economy, like modern medicine, but that might be impossible to keep alive for an small society. [Answer] With minor modifications to the story, there is a good way to do this: Your rebels don't send a ship back to Earth full of themselves; they know it will take too long and they'll die before they get home. Instead, they capture some of the Generation ship's automated DEMETER (Digital Embryo Maintenance, Egress, Therapy, Education, and Recreation) modules and install those on their ship before launch - you can freeze gametes for long travel, but full adult humans, not so much. Not to worry if all your caregivers don't survive the journey either; the DEMETER is fully equipped with all the means necessary to fertilize an egg and nurture it into a fetus ready for decanting, at which point the TER part of the module takes over and rears your child to a minimum of self-sufficiency using its extensive memory banks, service robots, and metrology components to educate, nurture, and acculturate your young ones even without adult human presence. It runs on a nuclear reactor, so it can operate for quite some time unaided. Definitely make sure that a dedicated computer scientist performs the installation, however, to make sure you have the software limits correctly set for each knowledge module; just a single master bit can be flipped to enable or disable the entire library, while each submodule also has its accessibility controlled so that you don't end up passing on any information unsuitable for your young. You wouldn't want to leave that master bit unset, for example, if you knew you wouldn't be around to help your babies out... And when the goddess Demeter finally shuts down, well, people usually don't take it too well when their religion explodes in their faces. There would be plenty of blame to pass around, and probably plenty of retribution. After the ashes slept in the dirt and the people stopped fighting because they had all fled to where their persecutors could not find them, the scattered tribes of man would have to start again. [Answer] You are going to need more than a few millionaire. To me a few is <10 people. Using that population size everyone dies, and no one is left to revolt in probably 10 generations. Ship is looted by aliens. I remember reading an article somewhere that you need 26 breeding genetically diverse men and women to maintain the gene pool. Due to natural deaths,still births, and the number of years for pregnancies(say 13 to 50yr). Your better bet is, that the ship becomes over populated, and a group are forced/allowed to leave. Many of them are elderly have nostalgia and a few of their family members. This will leave them in bad position where they will barely make it back before their population dwindles. They will give up, knowing they will never live to make it back to the main ship before they die. There won't be enough people to teraform the planet, or even maintain their population. Maybe they continue to live in their ship until they die or dis-repair forces them to leave. They will need to live on the surface in primitive conditions because they won't have the equipment to mine or build on it. Advance weapons run out of energy,ammo, or just fail due to age. In the case their population is now too small to thrive, they will eat native plants and animals. It won't take many generations for the rest of them to die. Their only hope is if they can mate with the natives. If that is even possible the humans will have to live with them, and do the things they do to be a part of any family. Even if the advanced technology survives they will have to slowly train the natives after many generations. Giving primitives tech too quickly will result in socially unrest, and aliens dying by accidents with the tech. --- Even if the humans make it back with even breeding people they will probably still need to ally with the natives. 100,000 creatures attack 70 people, the people probably die. Trade in low-end tech to gradually and safely evolve them. I would think, nostalgia, alone for earth would cause most of them to want to live on the earth. As more and more live among the natives the ship and most of the tech will be left forgotten and unused except in emergencies. The ship would probably still fail due to neglect or just run out of fuel/energy. [Answer] Several good reasons for this to happen, even without a crash. * in 4.8 million years, the shifting conditions would cause evolutional drift if not outright new species, causing some to die from lack of familiarity. * Little to no survival skills in an environment they are not used to. Put someone from the urban East coast of the USA into the middle of the Colorado high desert and see how long they last, if you want to get some idea. * A lack of maintenance skills and/or scarcity of parts and materials. Anything that needs batteries is going to be useless in short time. To accelerate the process, you could have your survivors try to charge the batteries and burn them out/fry them. * Environment necessitating cannibalization/sacrifice of tools and equipment: Freeze to death or burn things you might need later. Wires to fishing line... tools cannibalized to make spears and/or clubs * Conflict and theft. The group could split up, further dividing resources. * Other illnesses kill off key people with knowledge * population growth forces abandoning the ship altogether. Ship deteriorates due to weather. means of repair not available. Just a few ideas [Answer] **The small back-up ship is a small back-up ship** Sure, the vast generation ship carries highly advanced recyclers and fabricators. Its ability to produce new stuff, and maintain the population of humans aboard in luxury for hundreds of generations nears the miraculous. Unfortunately the revoltees took a small back-up ship designed to go on shorter runs. Sure, it has a 3d-printer, air recycling, and water purification, and it can fabricate food from the rather large store of NutriCapsules but beyond that? Good luck getting it to build you an axe, some traps, a house, or a lighting rig. At first, of course, the survivors will stick close and scavenge from the ship but, ultimately, they need to learn to survive without it and they lack the skills to bootstrap civilisation without the fabricators on the mothership. Their children, born into a world of hunting and gathering, lack interest in spending the first thirty years of their life in education and so there's a sharp drop in understanding and knowledge within a generation and within two the deep depths of knowledge on the ship's computers are simply so much gibberish. Without paper, and with the information on the computers no longer relevant, even written language rapidly diminishes in importance and is largely lost. [Answer] You might find some helpful insight in a TV documentary series first aired in 1978 titled [Connections](https://en.wikipedia.org/wiki/Connections_(TV_series)) (you can probably find it on Youtube). Presenter James Burke starts with a historical event - a large scale power failure in Eastern North America, puts forward the premise "what if the lights didn't come back on?", and spends the rest of the series exploring connections between various scientific discoveries and technological innovations. How this helps is that it really illustrates just how interdependent everything in our technological world has become. Bear in mind, that this was the technological world of 1978 - well before the internet became a publicly accessible resource, at least a decade before the world wide web, perhaps two before the emergence of web based shopping and banking, and about three decades before smartphones and consumerized 3D printing. This technological interdependence is what would drive your crash survivors back to the stone age. Well, maybe not stone age... copper or bronze age, perhaps. As already stated in other answers, to make anything technological, you need to know how, you need the raw material, and you need the tools and facilities - basically, another layer of technology, which requires its own underlying layer, and so on, until you get down to the basics - fire, simple machines (the wheel, lever, ramp, pulley, screw, etc.), math, language and writing. Just think what it takes to make a computer chip - that wonder of modern technology that we find in more and more things every day from cars to credits cards to our family pet which perhaps more than anything else defines the age we live in. All the processes and equipment to produce extremely pure silicon ingots, accurately slice them into wafers, deposit or infuse just the right chemical cocktails, and etch the right patterns at the nanometer scale (about 10-14nm in 2016), not just once, but layer on layer with everything in perfect alignment. All the problems which have to be solved demand technological solutions which are themselves at the sharp end of a whole pyramid of other technology. To make a computer chip even when you're starting with all the requisite know-how and some raw materials means you first have to rebuild all those technological pyramids. You have to make steel so you can make tools and machines to generate electricity so you can make the factories to process chemicals and so on and so on. Presumably, the crashed ship has left the survivors with nothing more than the knowledge of a technological world, at best the information about how to make things, but few or none of the tools or facilities to actually make them. That is what will force the survivors to build up from the basics. If your survivors don't have to rediscover things like physics and chemistry, they could probably advance fairly quickly from copper to iron to industrial revolution, but they won't be able to skip steps because each step is needed to provide the technical foundation on which the next step depends. [Answer] I know all about matches. I know what they are made of (mostly), but could I make one? probably not. There are things they would know. If the society was pre-wheel, they'd invent wheels. They would know things about basic health that a less modern society might not know. (Don't foul your water source, boil water, cook meat and store it well. Eat fruit and veggies.) The crash could take care of lack of library information. It could ruin all pre-made tools and damage batteries and so on. Just because you have something doesn't mean you can use it. I think that while some would die simply because they ran into a sabre-tooth or tribe defending territory, or due to a lack of hunting skills, some might survive because like me, they read. I have a far broader knowledge than primitive people simply because I've been schooled and I read. I do not want to hunt and kill and prepare meat, but I probably could if I had to. I can fish. I could make a snare or dig a pit. I could sharpen a stick, I could make fire with flint or by rubbing sticks together. (It is hard, but doable.) If there was glass from the crash, I could easily make fire. There would have to be some stuff left from a crash, if there were survivors. Clothing, blankets, perhaps some utensils. Padding, insulation, panels, things that could be used for rope or tools or for making tools. [Answer] In thinking though this question, I am wondering about the technology of the Tree Cats and the Neocorvids. What is their technological level? Are they basically in the stone age? If so, why? Why didn't they develop technologically? As to the question of how to regress human technological development, a few things come to mind: 1) There are no power sources to use the technology they have. Consider the differences between a farm using heavy industrial machines to harvest vast fields of crops verses an Amish farm where the work is done manually, and you'll have some idea of what I mean. Would these space-born humans know how to run an Amish farm? 2) The survival skills they do have are designed for a low - no gravity environment, and therefore aren't applicable to life on Earth 2.0 3) You might consider watching episodes of Revolution and the 100, because each of these shows have scenarios similar to your own. This is a highly imaginative storyline which I sincerly hope you can make work, as I'd like to see it in print someday :) -C [Answer] **Why would they be able to re-build an advanced civilization? It’s damn hard.** Imagine an airplane or ship crash-landing in a desolate place. Even if it’s equipped for an exploration with all kinds of survival tools and specialists you’d have a hard time rebuilding a modern civilization. All those precious electric devices and power tools are pretty much useless as soon as you run out of fuel or your solar panels and batteries die. The best approach would probably be to turn a diesel generator into a water-powered generator and try to get some kind of metalworking and glass industry started (hand-powered and without fossil fuel furnaces, mind you). However, merely surviving and acquiring enough food would be hard enough. If it’s not hard enough, imagine the same with a cruise ship or civilian airplane. [Answer] ## They aren't fools, they are explorers! I partially agree but mostly disagree with most answers as the result of their claims are that the people on the space ship are ignorant fools. This is of course not the case as the ship would not be able to go anywhere with ignorant fools piloting it, they would all die in the first fire that occur, and most of the information in a proper survival guide is not getting stale at all. A proper survival guide is not a check-list of things that are safe, a proper one teaches you how to identify harm and how to carefully check new stuff if it is safe. Exploration is about discovering things new and they were originally bound for a new star - returning to a completely remade earth is no difference compared to arriving to a new planet, and I can assure you that the crew will be prepared. > > **This is the behaviour of a fool or a five year old:** "Oh, look! A pretty insect! *touches it and promptly drops dead because it was poisonous, and didn't exist when their survival book was written*" > > > A ship intended to send humans away so they can colonize a new planet contains adventurers and explorers. A proper explorer would carefully examine the insect and gradually test exposure to it before concluding whether it is safe or not. > > > ### Why aren't there fools on the space ship? On the ship are living, adult humans with assorted set of knowledge (provided that it is a generation ship and not a ship that only sends genetic information). While they might be reliant on the tech they use on an every day basis on the ship, a vast majority of the people will be able to re-create it when they need to. Why would they have this knowledge? Simple: **to survive in space, you need to plan for that the worst will occur at the most inconvenient moment and probably several times over**. Therefore, those on a space ship will also have the knowledge of how to repair the ship (which requires them to have at least basic understanding of engineering and science). Each person will carry their own bit of speciality as well as basic understanding of nearby field and none of them will have unique knowledge since the risk of the entire crew dying is too large if any single person with unique knowledge dies. That is, as long as the spaceship contains living, adult humans, then all of the knowledge required for survival will be present several times over. Survival will be practised and they will be prepared for emergencies as they have the mission to make mankind survive! * **Why would they practive survival - they are on a spaceship with tons of tech that does everything?** - Well, the main idea of the original ship is to prepare the inhabitants of the ship of a completely new world - returning to earth, which have taken a completely new look after mankind left, is no different than arriving to a completely new one. Unless they intend to live all future generations on a ship, then the people are prepared for exploring new worlds! * **But only a small fraction of the original ship arrives** - It might matter, but essentially should not. My guess on the [minimum viable population](https://en.wikipedia.org/wiki/Minimum_viable_population) of humans would be around a thousand individuals, but it seems to be [as low as 160](https://www.newscientist.com/article/dn1936-magic-number-for-space-pioneers-calculated/). As long as it is more than 100 individuals, then it would be ample of people to make all base knowledge survive (unless every single one of them happen to be arts or English majors). Regardless of the real MVP number for humans, the main ship will contain several times that number to ensure survival and no "rebel ship" would leave if they know that they are too few to survive * **The ship back to earth only contains genetic information** - Then there will be major issues, and this would be the case where the lack of knowledge would actually produce fools on the space ship. If the people are conceived (and, hopefully brought to adulthood) just before the ship reaches earth, then there are major risk of loss of knowledge as they will not have had as much time to practice and to study. If the knowledge database of the ship is corrupt or missing, then they are either misinformed or not educated at all and they will most likely end up on a near stone age ### So what will then happen when they arrive on Earth? So, what would actually happen when they land/crash? Well, information will be lost and this, as many pointed out, is the key issue to how they can go back in tech-level to a more primitive state. However, how far back they go totally depends on how and why they crash, as well as how earth looks when they arrive. When it comes to information loss, then I think that Adam Wykes' answer is the only one that would allow the stranded humans to go all the way back to stone age like conditions, all other would create hybrid versions with "a lot" higher base tech. **Tech-level based on starting scenario:** * **The people landing are the result of genetic construction after landing or just before landing/crashing.** No one would be older than, say 18-25 years and no information have been possible to pass on through generations. They will have whatever information that the computers/robots could maintain, but if that information is lost or corrupt then they will likely not have skills or knowledge which is practical for survival. They would (hopefully) be genetically enhanced to survive (stronger, smarter and more resilient than the modern human), but will need to start from scratch. This would be pretty close to **stone age level** of tech and they would most likely be **hunter-gatherers** as they probably would lack the information of how to farm. They might be able to read and write and might possibly have artifacts from the ship, otherwise information will be given orally and story telling will be an important part of their culture. *They will most likely have trouble taming fire to begin with*. * **Generation ship lands/crashes.** The people on board will have (no less than basic) understanding about engineering, physics, chemistry, biology, etc., and will be able to survive much better as they do not need to re-create as much knowledge. If the ship library survives, then they will be able to access that and use the information inside, should anyone with rare knowledge die. They will salvage and use whatever they can from the ship and start making shelter and tools fairly quick. They would start off somewhere around **iron age** type of tech (maybe even medieval if they are lucky with resources)and would **likely try to start villages with farms**. If a lot of people die during the landing, then they will have harder time to survive, but they will not go back much in knowledge (as there still need to be more people than MVP for them to survive at all). They will know how to read and write and will likely try to write instructions for future generations. *They should not have any trouble taming fire*. * **Your setting is not starting from the initial landers**. If the people you start your game/story from are not first generation landers, then their tech-level will depend on how many generations which have passed. There is a risk that they will have enough set-backs throughout the generations which would toss them back to stone age level of tech, but this would only occur if all but a group of children would die. If the original landers managed to build some sort of village and the children would have access to that, then they would (hopefully) be able to obtain knowledge from the created tools they find. There is, of course, a risk that the reason all adults died is because the village got raided and everything is destroyed, which means the survivors start with whatever memories they have and will need to re-create the rest. There is also a chance that they have adapted well enough to the environment to be the dominant life around their territory; this would give them tools and weapons suitable for how long they have been staying on the planet (e.g., they most likely have hammers, axes, knives of either stone or metal and possibly have bows, ploughs and other more advanced tools). *Fire is probable but not a sure thing*. * **Resources are very scarce**. If the landers have trouble finding resources, then they will have trouble making tools. A well educated team of explorers will, naturally, not be able to make iron tools if they cannot find iron to begin with. They should not have much trouble making stone tools, but how advanced things they can build is totally limited to the resources they can find. How well they will adapt to new materials they find will depend on their initial settings: A generation ship will have educated people whom can quickly adapt as they have the knowledge, whereas a ship with kids created from genetic information will most likely not develop as fast. * **There are other, *advanced*, intelligent life forms**. The question mentioned Gryphans and Neocorvids as co-inhabitants of the planet. They will influence the humans starting tech depending on how well developed they are. Both the Gryphans and Neocorvids ought to be fairly similar in tech relative each other as a too big difference will cause one of them to conquer the other. If they are much advanced, such as medieval or higher tech level, then humans will be able to trade or steal tech from them to improve their own starting tech. However, since you seem to want the humans to start at a stone age level, then I would say that the Gryphans and Neocorvids should not be much more advanced than somewhere around bronze age or lower. They should preferebly be on stone age tech too, but you can give them more advanced tech if you want as they might not want to share it freely and you can have interaction with Gryphans or Neocorvids as a means for the humans to obtain tech or material to survive. As long as the gap is not too big between the groups, then interaction will be fairly equal and no group will dominate too much (compare to how it was when Europeans met Indians while discovering America). **Can I make a toaster from scratch?** Yes, I can (and while obtaining all the ore will be pretty tedious, the most difficult part is actually to generate the electricity for a proper toast from scratch). I have based my answer on that I actually would be able to survive wilderness pretty well with just a knife, an axe and some rope (I have tried); I might not be representing the average modern human as I do have an engineering degree and I spent my youth in the forest as a scout, but that would be the type of people we send on a generation ship, not the average modern human. And, as the question begs for it: > > If you wish to make an apple pie from scratch, you must first invent the universe. > -Carl Sagan > > > ### TL;DR You can pretty easily explain a set-back to stone age tech if you follow Adam Wykes' answer, or if there are so much death among the first landers that all knowledge manages to get lost before it is passed on. However, don't make the first landers from a generation ship stupid, because they will most likely not be! [Answer] Since these folks are using a backup plan to a backup plan, things have already gone way off the rails. Civilization is more fragile than we imagine, it's not just skills, information and tools (loss of which could alone do it), it's also trust and willingness to work together. It's one thing to use existing technology, if one has the tools and info. But recreating a technology from scratch is hard work -- and requires time/breathing room that a small, desperate group may not have. A resource pinch is always a possibility. What happens when their ship's power source starts to run down? Can't exactly go to the village market for a cup of Antimatter. In Michael Flynn's Eifelheim (highly recommended) [https://www.amazon.com/Eifelheim-Michael-Flynn/dp/0765340356](http://rads.stackoverflow.com/amzn/click/0765340356) a small group of crashed, formerly-starfaring aliens have great trouble getting a medieval society to make copper wire. So going back to basics could get very, very basic! [Answer] As a simple alternative, the ship reaches Earth after its long trip, but the landing system fails to engage. Upon crash landing, one of the system's power supply systems goes critical, and explodes. Most of the blast is contained by the safety systems, but the resulting electromagnetic pulse fries all of the circuitry across the entire ship. The ship is now a worth a little more than a paperweight, as anything that was electronic in nature, including replicators, nanobots, computers, communication systems, all the technology they've brought with them, and managed to keep running those many years have all been destroyed, and all of the knowledge databases on the ship's computers are lost. Even if they had all the knowledge in their heads, there's simply no way they can rebuild everything or even document everything, so a lot of knowledge could be lost for many decades or longer. While they may be the smartest people on the planet, which may not be saying much, without the tools to rebuild any of the technology, they'd be nothing better than hunter/gatherers until they can find the resources to build new technology, which may very well take several generations... [Answer] > > So after debating with myself over this issue, I decided to instead ask, why would survivors of a crash landed generation ship start from the beginning at the stone age, rather than being advanced? > > > Look around you. Anything you see, *anything*, is man-made. Every item, device, object consists of dozens if not hundreds or thousands of parts. Every single part has been made by someone, or more likely, by some factory. Now this are only your household items; think about the machines, factories etc. - they are even more complex as they all are highly engineered today and have to fit together "just so". What we have today is absurdly complex. Nothing whatsoever of our modern stuff can just be "made" by whatever guy sitting in the jungle with some tools he brought from outer space. We cannot even make what they had in the medieval times because *that* more simple knowledge has been lost as well - and back then, specialization had kicked in already, knowledge was precious. It took literally thousands of years of steady progress. Stand up from your chair now, get outside with some very basic tools, and try to build anything - a chair, a table, from "first principles". Go and fell a tree, try to build something from it that vaguely resembles civilization. You very likely can't. Your space people will start out with some resemblance of modern man (speach, clean clothes etc.), but will quickly erode down to the basics - people scrounging the ground for roots to eat, etc. Within a generation or two, their knowledge will surely be lost or turned into useless religion, as whatever they knew before will help them not the slightest to survive on earth. Of course, as author, you have some powers here. They would likely have the same thoughts on their home voyage, and prepare in *some* way... but how to *avoid* falling back to stone-age was not your question. [Answer] A crash landing would cause irreparable damage to the ship. Additionally, some people might actually **want** to leave the ship and seek a new life. (This is the purpose of returning to earth anyway.) With out some logistics and trade, maintaining advanced tech could become incredibly difficult and impractical. As far as other aspects, rather than post an extended answer, I think I will simply that that just because humans lack iPads doesn't mean they can't [survive brilliantly](https://www.google.com/amp/s/www.washingtonpost.com/amphtml/news/worldviews/wp/2014/02/04/stranded-9-amazing-stories-of-survival-against-the-odds/). Being human also entails a [knack for surviving](http://www.cracked.com/article_20367_5-insane-true-stories-that-prove-humans-can-survive-anything.html) and adapting. Now those links contain stories where humans live on despite a scarcity of natural resources, although with great suffering. But if a ship crash landed in a fertile area, humans would have a distinct advantage over local fauna, who would be adjusted yet because their natural predator or prey instincts wouldn't yet be adapted to a human presence after such an extended absence. Meaning that human wouldn't be looked at as prey by predators, nor as predators by prey. A hunter-gatherer society would do quite well for itself so long as it ranged far to avoid depleting nearby resources. Humanity could in fact thrive. [Answer] So they have crash landed. Their tech(that which survives) won't last for ever. Most tech requires a power source. Have the survivors need to build a shelter with the left over tech. Have the native wildlife constantly attack due to territorial disputes. Slowly the survivors run out of resources and will need to adapt to low tech methods. During these attacks have key people die, there by reducing survival and reconstruction skills. [Answer] Hmm... The only reason for going back to the *stone age* - as opposed to the bronze age, would be that the 4.8 million years have removed the genetic evolution that man and his environment has done together. In the early stone age, people were just beginning to farm. The crops we use today are not at all what they were before man started selectively breeding them for both size and "harvest-ability". Wild rye and wheat drop their seeds all summer long, they fall off if a gust of wind just rustles the plant. Cultivated rye and wheat has so strong grain husks that they have to be mechanically harvested. They also have fewer and larger grains, also suitable for being harvested but not very nice if they are relying on wind to spread out. These cultivated plants would likely not survive in their current genetic setup. Because of this fact, having cities and towns was not useful for man - you could simply not feed a larger amount of people than a large family. This would be a reason for being in the stone age - there is just not enough food available for more than a handful of people in one area at the time. A hunter gatherers life usually does not include dragging many possessions along except clothes and spare food, so lack of tools as others also say. HG-tools were usually made on site (stone axes, fire-hardened spears, etc) and left there when it was time to move on. (That is why we find so many of them) But, people were not as social as we are today either. Our languages are well developed, modern social skills and social constructs (religion, government, exchange of information, mathematics... etc) will probably lead to towns forming significantly faster than typical for the stone age. I'd say you were in the bronze age, given that 5 million years of geological transformation has made bronze ores / surface iron ores available again. PS: The bronze age actually ended because the bronze was out. [Answer] **Kill the batteries!** Assume their information is available in digital form, which requires electricity. Then their reactor blows. And the one guy who cared to learn by heart how to build a generator from scratch either gets a concussion or dies. Do you know to build a generator? If the answer is yes, and your generator requires magnets, do you know how to make magnets, if you don't have a generator? And before you think of getting the magnets from the blown reactor, they are either contaminated with radioactivity, or demagnetized due to the reactor blowing up. You can also easily limit their access to metal by either using something other than metal to build the ship, or by choosing a metal that has too high a melting point for them to smelt. [Answer] If you took an average city-dweller from now, as someone noted above, you probably wouldn't find anyone who could make an axe or a saw, you may not even find anyone who could make fire from scratch or hunt / kill animals or even identify what plants are safe to eat. Add a few millennia of being sheltered by automated systems in a space craft and all of the above become certainties. They'd be completely dependent for everything on ship systems... making a generation ship that can land is a virtual impossibility, so people would have to land in shuttles or some equivalent... it wouldn't be too much of a leap to have shuttles crashing... after all the pilots won't have had any experience of planetary landing ever... so the on-ground people are completely cut off from all their knowledge, from all their spare equipment and (quite possibly) from skilled members of crew who would have been keeping the ship running while people shuttled down. You'd send 'soldier caste' down to make a perimeter first, general population down next and the skilled crew last so you'd effectively lose the 'technician caste' from the planetary surface. [Answer] I think that the perfect book to be reading here is [Jules Verne's "The Mysterious Island".](https://en.wikipedia.org/wiki/The_Mysterious_Island) Verne takes 5 persons (all male...) stranded on an island to restart the technical parts of civilization and some of its comforts from informed scratch. The key is the (railroad) engineer Cyrus Smith who is sort of a universal dilettant with knowledge and interest in basics of mechanical and electrical engineering and the associated physics and chemistry. There is a certain ratio of humans who are like that: uselessly curious about everything and in how to make everything work out at least basically. Their archetype is [Daedalus](https://en.wikipedia.org/wiki/Daedalus) and has been around for thousands of years. The plans of unbuilt machines of Heron of Alexandria and da Leonardo da Vinci survived into our times. Even if your starship started out manned just by phone sanitizers, there will be singularly curious persons eventually in it. Their skills and interests will appear useless to everyone including themselves, but they won't be able to help challenging and improving them with the means at their disposal and partly without them. It will be their calling, the thing they idly prepped themselves for. There won't be many of them which is an advantage for your novel. In the "Mysterious Island", the survivors actually more or less *do* start from the stone age. It's just that they fast forward through it due to the unique accumulated knowledge and skills mainly of their solitary engineer. They do keep a few survuvung artifacts in shape and as a resource. For example, I am pretty sure that they keep a clock wound meticulously in order to eventually determine their geographic location with some certitude. I also seem to remember that the cloth and ropes of the balloon with which they were stranded was put to several different uses over the time of their stay. The story might be glossing over a few details and be somewhat overoptimistic a few times, but I think it is still quite relevant material to read and think over. [Answer] > > 1) if a carbon alloy generation ship is horribly mangled, how on Earth > did squishy humans manage to survive > > > They've got parachutes. The ship crashed, and was completely consumed in the ensuing fire. The survivors managed to escape using parachutes on the way down, but were forced out to sea to avoid the fire. When they landed, they had to abandon the parachutes and swim to nearby (non-burning) land, left with nothing but the clothes on their backs. "But how did they learn how to steer their parachutes?" you might ask. Maybe they didn't, and they were just lucky that the wind caught them and blew them out to sea, any that weren't so lucky were caught in the fire. By now, the most advanced usable technology that exists is a zip. And just because I have one doesn't mean I can make another one (starting with extracting the iron ore from the rocks?) > > 2) if they lack any survival skills, how do they survive period? > > > They had survival skills for living on a spaceship. But being able to reverse the polarity of the plasma coil inducer isn't much good when trying to live off the land... How do they survive on land? Not all of them do. But the ones that do have learned from the mistakes of the ones that don't. [Answer] ### Why would the returning humans fall back into stone-age conditions? Because it is the most useful form of organisation and set of skills in a natural environment. Given that the returning humans used a back-up ship, it may not have carried the full set of tools necessary to re-restablish civilisation on a new planet, which would obviously be carried on a serious generation ship. There's no point in sending humans off to a another planet if they're not equipped with the necessary survival kit. But the back-up ship might have only carried the bare necessities. If the back-up ship doesn't carry the supplies necessary to set up a high-technology civilisation in the short term, it makes sense for the crew to prepare themselves for the worst possible circumstances – either out of necessity or conviction (why else would they undertake the arduous journey back?). The best fall-back option is to prepare oneself for a stone-age lifestyle instead of betting on finding abundant crops to cultivate and large supplies of easily accessible ore the moment you step out of your ship. The hunter-gatherer lifestyle has proven itself to survive throughout humanity's entire history, and will sooner or later enable a return to higher forms of civilisation. Given that the journey takes generations, there is ample time to prepare your offspring for the simpler lifestyle on the new planet, through any combination of education, ideology or mental control. And it all makes sense as the prime goal is for humanity to survive, as the alternative may be to wither away as your ship's supplies dwindle down. ]

[Question] [ # What would be the pros and cons of a merged military and police? In the world I am building war is an ongoing issue, and so the culture's military is quite extensive. **Also the majority of people carry weapons around with them because it's 'the norm' there.** The war is an ongoing conflict which flares up then goes quiet for a while. Honor is a major part of life, meaning you can't attack someone who is unarmed, can't attack them if they are unable to defend themselves, etc. For the purpose of this question **the only thing a police-style force in this world would have to do is keep an eye on things and break up the occasional drunken fight.** In this situation, the culture has their military and police merged, so my question is: **what would the pros and cons of this merged force be?** The military already have shifts of "watching" or guarding, so the idea is that they are allowed to intervene to stop unnecessary deaths The setting is high fantasy. [Answer] **Police and Military should never be merged. They have different missions and are set up completely differently.** If you look at countries in conflict, and those that are stable today, you see a pattern emerging. If militaries are patrolling civilian streets, you are in an unstable violent environment - it never ends well. This is because they have fundamentally different missions. Militaries are broad, equipped to kill many to defend a nation. Police are more deft and nuanced, and have a role mainly in dealing with petty crimes, small threats, and also even 'customer service'. So your pro-con list: Pros * Simplicity: it may be simpler to just have your military walking the streets. It might save you time and effort to not have to bother with setting up another force. * Cost: perhaps lower? * Deterrence: having armed squads walking the street may have some deterrent effect, although in reality they don't have as much effect as you would expect. Cons * Overbearing: Having military walking streets blurs the distinction between serving civilians and treating them like an enemy instead. * Non-equipped: Militaries are meant do deal with large forces. Even in current day, they are equipped with high-explosives, assault rifles, weapons which are meant to be used in combat. They are not intended for domestic situations, petty theft, or dealing with emotional civilians. * Training: Police are trained to deal with the populace. They are trained to talk to them, find out 'the story', deal with emotional people, settle them down. Militaries are trained simply to kill them. * Structure: Militaries have a rigid command structure, necessary to manoeuvre large forces over lots of ground, with combined arms tactics the norm. This is completely irrelevant in a crime, city or petty theft context. Police are more likely to be structured flexibly, with homicide teams set up to work collaboratively on a problem, small forces on the ground, and units established to deal with servicing the public. Even the ancient Romans realised the need for a separate 'Police' to 'Military'. One could say a major problem with conflict-ridden countries today is the lack of a true separate police force. [Answer] > > There's a reason you separate military and the police. One fights the enemies of the state, the other serves and protects the people. When the military becomes both, then the enemies of the state tend to become the people. -Admiral Adama, Battlestar Galactica > > > I find that quote describes the pros and cons of a combined military and police very well. The cons are easy to spot, but the pros are there as well. If you *want* the enemies of state to be the people, or if they are the enemies of state already, then such a combined approach is very useful. The demarcation between "fight" and "serve" is very useful here. Soldiers *certainly* serve their country, and police *certainly* fight against crime, but there does seem to be a very meaningful demarcation between them. That demarcation is evident in the skillsets we teach soldiers and police. It's worth noting that, in today's society, we often laugh at police shooting skills and their woeful lack of training (whether deserved or not), but if you look at what is expected of a police officer versus a soldier, you start to see why the military may spend more time drilling with their firearms. You can also erase the demarcation line if the military skillset becomes needed. If the police regularly are expected to arrive *after* it is too late, and war has already broken out, then the military skillset is very useful. If the opponent is regularly dug in, the police mentality may not be enough. I also find it useful to look at the environments that police and military work in. The police are generally more expected to work within the limits of the environment, while the military tends to overcome it. Even the SWAT, with their notoriety for bringing perhaps more force than is necessary can't call in a 2000lb. laser guided bomb to resolve a shootout. I find this attitude permeates the military. It doesn't matter what obstacle is in front of them, their job is to overcome it. I got a great lesson in this recently sailing in San Diego with an ex. Navy captaining my boat. We saw an [LCAC](https://en.wikipedia.org/wiki/Landing_Craft_Air_Cushion) hovercraft, steaming out to do drills. The captain took the opportunity to point out that that the hovercraft could carry an Abrams tank over the top of an 8 foot wall and deposit it on the other side. My first thought is "well that's stupid, isn't it." Why would you spend money on such an absurd feature, no matter how flashy. Then I had to think about it again. When I realized the answer, the only word out of my mouth was, "Oh." [Answer] TL;DR: Using military instead of police will result is distrust, disobedience and violence from civilian population. My points are below; also see Flox's answers for excellent points, and quote linked by Douwe in the comments. **Police protect people from themselves**. When they break up a drunken fight, their goal is to minimize the damage to the fighters. Typically, police should be have superior numbers and superior weapons and armor to the "criminals" that they deal with. Police have firearms, but they (should) try to avoid using them, or rather avoid getting to a point where firearms become necessary. **Military kills enemies**. Their approach to a drunken fight is: should we kill them right now, or wait and see if they kill each other, or otherwise stop being a threat to "our people". Military units are trained to engage enemy force with same numbers and weapons as themselves, so "shoot first" is valid and expected. That's what there is **military police** -- the unit that does police work among members of the military. Note that RL military members are very much like your citizens, armed and honorable. Using military units to do police work results in abuses by military and insurgency among the local population. **Iraq and Afghanistan** are latest examples. The "hearts and minds" approach is essentially training military to do police work. A more subtle, but relevant example is Police-vs-Blacks mentality that has lead to a increasing number of shooting deaths in the US. There is a vicious cycle where hostility by (a portion of) civilian population and to increasingly trigger-happy police continuously reinforce each other. If you want another analogy: police are like teachers in preschool, breaking up fights between kids; military are the security officer in the front, keeping drunks and perverts out. Do you really want the security officer dealing with tantrums? And yet another contrast. In military, a valid and common tactic is "suppressive fire" -- just shooting into the general vicinity of where they think the enemy is. Police are not allowed to fire until they have the criminal clearly in sigh, and said criminal is not just armed, but likely to shoot somebody. [Answer] In a high fantasy setting, you need no justification. High fantasy typically takes its cue from European history. Before Robert Peel in the 1800s, there was no concept in any European country that there should be a civilian police force. Policing was carried out by the local militia. As time passed, the concept of a 'thief taker' also entered the frame, but these were employed by individuals (sometimes by magistrates) and were more like private mercenaries. The idea of having an independent police force and judiciary in a feudal society is virtually impossible, and the very idea is anachronistic. As for weaponry, remember that most of Europe was at war for most of the time. Weapons were easy to come by. Some countries or towns limited who was allowed to carry what weapons (especially swords), but there was widespread training in stick fighting, wrestling and archery in the same way as we'd do Parkrun today. And *everyone* carried a knife, all the time, even the youngest children Pros and cons of this? Read the history books. On the pro side, when the people you're trying to arrest are heavily armed and most likely ex-military, then you're going to need good equipment and training yourself to stand a chance. For the cons though, as other people have noted, the military are ***really bad*** at law enforcement. So in Britain we have the crushing of the Peasants' Revolt, suppression of the Levellers, and the Peterloo Massacre, to pick three obvious examples. [Answer] Police forces under military jurisdiction [are fairly common](https://en.wikipedia.org/wiki/Gendarmerie) in the real world, and the pros/cons in your situation should be the same. The [role](https://en.wikipedia.org/wiki/Gendarmerie#Role_and_services) of a militarized police force is to be a well-trained, well-equipped force that can deal with other well-armed groups and violent situations. Because of this, these forces must follow military standards when it comes to recruitment, training, and equipment, all of which are more strict and expensive than normal police forces. This means that a smaller pool of candidates are qualified to join the force, and more resources must be devoted to maintaining the force. In short, * Pros: They would be able to effectively police high-threat areas and respond to situations that a normal police force would not be able to handle, such as surprise attacks during the world's frequent wars. * Cons: If it follows military standards then it is a waste of resources in most situations(such as breaking up bar fights) and expensive to maintain across the nation, and if it doesn't follow military standards then it is just a regular police force. [Answer] ## The military doesn't go in playing second fiddle, while police often do It is generally assumed that when military forces are deployed into a situation, they are bringing their own command structure with them. This is *not* true for police forces, who often have to operate in a scene where they are *not* responsible for Incident Command -- in particular, in most mass-casualty mishaps, it is fire/EMS that establishes and maintains the ICS, with the police playing supporting roles (evacuating folks ahead of hazards, staging equipment, controlling traffic, and the likes). [Answer] ## I Think You'll Find the Answer in the Evolution of Police Forces Police Forces are generally to be believed to have begun with the first Lieutenant General of Police in Paris around 1667. Prior to this, the state of things was: * Nobility provided justice in their regions, with the system of heirarchy between barons of single-towns, counts of whole counties, and dukes of larger provinces, all answerable to the king of the country. * Soldiers (maybe not highly trained or highly professional) were paid for by the noble enforced judgments. These soldiers enforced judgements, when it was necessary to do so. These same soldiers would be loaned out to the king for war, for disputes between nobles, for helping higher or lower ranking nobles. * Townsfolk may be appointed as justices or deputies to help relieve the noble of this burden. * Nobility also had extra duties, beyond dispensing justice, including managing their territory, contributing to their neighbors, higher (and lower) rank nobles, appearing in the king's Court to keep the family from being forgotten, and so on. * In a highly populated metropolitan area (Paris) the number of crimes to work overwhelmed the available staff, especially if it was only a part-time duty. Thus, a full-time police force was recognized to focus on dealing with crime (primarily collecting taxes and quelling public disturbances). So, from that, I take it that the pre-Police conditions in Paris were that it was practically a battleground from time-to-time (read Les Miserables and you'll see parts of the city frequently rioting and building up barricades, and it seemed to happen often enough to be a headache). Creating a full-time police force kept the wars out of the city and created an area of relative calm near the capital. It also started getting the people who took advantage of the chaos to skip paying their taxes back into line. [Answer] Obviously you don't want each of your soldiers as Law Enforcement Officers, basic military training can't/won't/shouldn't cover all the intricacies of the law and psychology that a LEO should be versed in. But you could have a sizeable percentage of your guys be specialized as civilian police officers. While wearing the 'CPO' hat, they are on detached duty, operating under a different command while still being a part of the Department of the Army or what have you. It'd be like a reserve or national guard soldier who works as a LEO as their regular job, except that only one organization signs their pay stub. Or they could just serve as adjuncts/helpers for the regular police forces - do a one to one ratio to keep police numbers up and your soldiers gainfully employed. You could even have your regular soldiers undergo training in some basic policing skills like breaking up fights, but only when called upon and lead by one of the CPOs. It doesn't take much extra training to man the line as a riot cop for example. [Answer] I can only see this work if the military and Police are still seperate entities but closely working together. This to keep their mission statements clear. The Police might be militarized and have things like full armor and solid equipment, but when it comes to war they will be a defensive force. Their primary goal would be to evacuate the civilians, set up defensive area's to catch enemies that managed to pull through and organize+arm militia's that formed in the city. The military would just do what it does best, but can offload work to the Police and militia's when necessary. Think tasks like cooking food, hauling arrows or other munitions, providing temporary relief for troops in a pinch, scouting etc. This keeps the military out of the civilians way (and vice versa) and gives a clear boundry the military cannot cross. Should the military decide to do bad stuff to the population for a powerplay or something then the Police still has their mission statement to protect the civilians, and will have the expertise to organize the civilians against hostiles. [Answer] Pros The military can handle extremely sensitive or dangerous situations that the police can't. The military can be reassuring in times of extreme conflict. The military has enough specializations that they can do many different jobs well. The military is harder to bribe because there are so many people and somany command chains. Cons The military is very hard to mobilize quickly. Once they do, they are pretty unstoppable. That isn't what you are going for when a call comes in and you have only minutes to respond and you don't need a ton of firepower. The police can handle many kinds of incidents and are generalized while the military has specialists and is only suited to fighting. The military is great at killing people, not so much at writing parking tickets. The military is so specialized that you have to have a very large group of people with different talents on standby so they can deal with different situations, and many people on standby will rarely ever get called in. The military will be tied up with domestic issues when a war starts. Without a police force, no one can take control while they are off fighting another country. [Answer] If you've got no external threats, and you haven't had any for a really long time, you might not have a military - or even the idea of one. It is entirely possible that your world, while heavily armed and violent, doesn't have a good concept of war. In such a world, if the need for a military were to arise, it would probably be met by the police. Alternatively, As many posters have remarked, military policing can get pretty oppressive, but there are many countries where one group of people must be protected from another. Two examples are South Africa and Israel. Another example would be the armed guards surrounding the African Rhinos. I'm sure that the Rhino hunters find the guards to be oppressive. If you have a world with generations of sectarian conflict, your police force may also be a peacekeeping (military) force. [Answer] Peace is maintained and tyranny avoided via balance of power. People don't generally start fights they don't think they can win or, at least, avoid losing. When you merge the police and the military into the same organization under the control of the same people, you get an organization that is strong enough to defeat foreign governments in pitched battle plus strong enough and well-informed enough to maintain a modicum of control over the domestic population. These two things added together yield a high probability of developing an organization powerful enough to attempt subjugation of the domestic population. The instant the external pressure of foreign war is off, somebody is likely to start plotting to become God-Emperor, and the command and control mechanisms they'll need to be successful are already in position, they need merely have sufficient political clout to take control of them. As for pros, in the culture you've described, there really aren't any. The need for government-sponsored police seems to be minimal. In such a culture a national police force is unlikely to have formed yet and security is likely provided as needed by private contractors. You can find real-world examples of such cultures in pre-Norman Britain. It works better than "modern" cultures like to admit. Most people in such a society would view the sudden imposition of military policing with suspicion if not outright hostility as it would be seen as both an insult ("You backward peasants can't take care of your own problems") and as the first step toward the rulers centralizing power into an absolute government and stripping citizens of their rights. ("They're getting our children used to accepting orders and punishments from specially-appointed outsiders that don't have our best interests at heart. Someday we will all be serfs if we don't stop this now.") [Answer] ### Pros and Cons of the merge You have gotten a variety of answers that are biased towards modern democratic societies, none of which you are bound to emulate in your *high fantasy* world. A more pros and cons focused assessment is as follows: Pros: 1. Save money: you don't need two hierarchical structures to run the armed official elements of society. 2. Simplicity of jurisdiction: whatever your legal or justice system looks like, there is one official law enforcement agency to deal with. 3. Flexibility: be it a foreign invasion or an insurrection, one stop shopping. Cons: 1. Opportunity costs for the leaders of this government: when choosing how and when to use military force for a reason. What amount of security and police work is sacrificed for deciding to send a lot of soldiers to a conflict with (nation x)? 2. Corruption: when too much power is concentrated in too few hands, the chances for corruption increases. Example: a few soldiers-cops are out having beers and get into a brawl/trouble. Who is arresting them? Their own buddies?(far too likely) With the separated domains, police and military, this problem or risk is significantly reduced. This particular problem is not uncommon in the modern world where the lines are blurred, or non existent, as discussed in a few of the answers above. 3. Who will guard the guards? The means by which civil control is wrested from the government in a coup is all in one place. The lack of a "checks and balances" in the structure of the armed element of government creates risks to the political leadership. Depending on how your story, your narrative, and your world is intended to work, this might be, for you the world builder, a pro since it provides ample fodder for intrigue, tension, conflict, and general skullduggery. [Answer] Here in Brazil we need a militarized police, with armored cars and FN-FALs patrolling the streets, because the criminals are guerrilla militia with G3s, granades and heavy machine guns. The military police (PM in portuguese) acts against these criminals and also do ostensive policing but, even with military hierarchy and, legally speaking, being an armed force like the Army or the Navy, they can't use the really heavy gear like artillery and deadly light arms like granade lauchers and chemical weapows in granades. Also, the PM is famous for it's corruption and brutality, corroborating what was said about military policing civilians as many posters said above. That brutality is not a bug, it's a feature, a feature of the harsh military training in brazillian armed forces, with lots of physical and psychological punishments inflicted upon the rookies. [Answer] A possible con, is that the ruler of the country, by necessity must be a military commander. Otherwise invariably there will be a coup. A military commander is really only going to be interested in maintaining control, and solving all problems with military solutions. They're not necessarily going to be effective at taking care of all the other basic needs of the civilian population, or establishing mutually beneficial trade agreements with neighbouring countries. After-all, it makes little sense, from a militarist perspective, to be paying your neighbour for their resources and produce, when you can simply invade and take it by force. A militarist empire can be relatively successful, but eventually may grow too large to be able to protect itself, and may eventually collapse due to internal power struggles and corruption. Even if a pseudo diplomatic ruler is installed, they can never be more than a puppet to the military commanders. Their rule can only last as long as they're making decisions which directly align with the wishes of the military commanders. [Answer] I will offer a different perspective, and argue that under the right circumstances a policing military may function with greater professionalism than a civilian police force. In fact, I will argue this is already demonstrable in America... It's worth prefacing that the benefits of this are also drawbacks. The military has more authority and less regulation on its behaviour than civilian institutions, but given the right objectives and ethics this may not matter much. --- [Stephen Mader](https://www.npr.org/2016/12/08/504718239/military-trained-police-may-be-slower-to-shoot-but-that-got-this-vet-fired) was a US Marine Corp veteran who had served in Afghanistan. He then quit the military and joined the police. One day he was called to a domestic incident, and had been told a man (Ronald D Williams) was outside waving a gun about. Along the way he got an update that the man's girlfriend had called. She had tried to explain that her boyfriend was depressed and suicidal, and had created a scene to invoke suicide by cop. Mader arrived at the scene and in this moment relied upon his experience from Afghanistan. In Afghanistan he learned to assess whether the people passing him in the street wanted to kill him or not. Soldiers in Afghanistan were instructed to use caution before resorting to violence, otherwise mistakes could happen which would push more Afghanis into the arms of their enemies. He saw Williams waving a gun about for show, and didn't see anything in Williams' behaviour to suggest violent intent. Mader tells Williams to put the gun down, so they can talk. Mader's colleagues then arrive to provide backup, and they make a shallow assessment. Here is a civilian waving a gun about, threatening police officers. They tell Williams to drop the gun. He doesn't and they shoot him. He dies from his injuries. Mader is then fired for 'endangering' his colleagues by refusing to shoot Williams. --- The US military in Afghanistan evolved much like the British army did in Northern Ireland, learning that brutality often backfired and that they needed to operate carefully to avoid inflaming resistance against them. A military that has evolved in response to such circumstance would place a high value on caution and reading people. Consequently they may operate with greater professionalism than a civilian police force which does not need to worry about a popular backlash from being trigger happy. The situation you describe sounds a bit like Northern Ireland's [Troubles](https://en.wikipedia.org/wiki/The_Troubles); a war which comes and goes, the military always watchful. Although maybe I'm just reading that into it, since you say most of their duties will be breaking up drunk fights. Incidentally, there's an [informative podcast](https://samharris.org/podcasts/the-logic-of-violence/) where Sam Harris interviews Jocko Willink, a former navy SEAL who was deployed to Iraq. It contains an interesting discussion on the idea that training for violence, with martial arts especially, helps to reduce the chances of a needlessly deadly escalation. Inferring that soldiers given proper training may lead to less deadly outcomes in civilian confrontations precisely because they are more confident of their ability to inflict deadly violence, and thus are less willing to use it... admittedly this could be said for military or police. Another benefit of combining the police and military might be far more extensive intelligence gathering operations. The military can just create watchtowers and road blocks and various other check points wherever they please because they operate above usual civilian oversight. They also will be able to use spies in a way the police usually wouldn't, creating extensive networks to attempt to control subversive elements. Like [Britain's FRU](https://en.wikipedia.org/wiki/Force_Research_Unit), or [Pakistan's ISI](https://en.wikipedia.org/wiki/Inter-Services_Intelligence). But this can get out of hand for obvious reasons. **In conclusion, I'm going against the popular feeling.** Policing with the military is a great idea\* for the aforementioned reasons, and offers many unique benefits given the right context. After all, there's already paramilitary police forces operating under military leadership in many countries without problems, such as France's [National Gendarmerie](https://en.wikipedia.org/wiki/National_Gendarmerie), or Italy's [Carabinieri](https://en.wikipedia.org/wiki/Carabinieri). Gendarmeries are actually [remarkably common around the world](https://en.wikipedia.org/wiki/List_of_gendarmeries). ( \* This is not an endorsement of using the military to police civilians. ) ]

[Question] [ Assume a college student from 2018 *accidentally* traveled to 2023. He is accidentally taken by an alien spaceship that travels close to the speed of light away from earth and then travels back. He is put back to the place where he was taken. The question is how can he prove to the people in 2023 that he has time traveled, against other possibilities, such as running away from school. More relevant details/premises are given in the following: * Assume apart from the alien spaceship part, the setting is totally realistic. * There is no drastic technological advance happened in the 5 years nor new outbreak of a global disease/disaster. Assume that there is also no total elimination of any current disease. * The incidence happened in a camping trip that he goes alone during the semester, and has no witness. * The spaceship that took him was advanced enough to not to be detected using current technology. It is well sheltered against radiation in space, and it is not made by radioactive material. * From his point of view, only a few minutes have passed. He does not have a coherent understanding of what happened. [Answer] **Radioactive isotope dating.** Each of us born in the late 20th (second half) or early 21st Century have in us a small portion of the calcium in our bones replaced by an Isotope of Strontium 90 that is a by-product of above-ground Nuclear testing, common in the early 1960s. [See reference here.](https://en.wikipedia.org/wiki/Strontium-90) As with all radioisotopes, there is a very predictable rate of decay, in this case 28.8 years. For this young person, the rate of decay would be offset by the time dilation produced by spending 5 Calendar years at near-C velocities. The testing would have no way to prove this person had been abducted, or *why* he's 5 years behind, but it would produce proof that 5 years was missing from his history. [Answer] To give him a chance of people believing his story in the absence of proof, you (as the author) are going to have to set things up ahead of time. Make him a newly-turned 18 y.o. college freshman with an identical twin brother attending the same school. If both of the brothers appear young for their age prior to the abduction, the difference between them upon his return could be pretty obvious. Then to kick it up a notch, give him a girlfriend who gave him a four-leaf clover hours before his abduction. Finding that rare little leaf, still fresh in his pocket might go a long way to convincing her. [Answer] If there happened to be a photograph taken of him just before his disappearance, then he could point out any blemishes or minor injuries on him that perfectly matched the photograph. This could be minor scrapes or cuts, acne, a hangnail, mosquito bites, or a peeling sunburn. Bonus points if he has a recent tattoo or piercing that hasn't fully healed. No single one of these things is likely to convince anyone, but five or six of them in combination might. Note that this only works if the photograph was taken by one of the people he is trying to convince, and the photograph has remained under the exclusive control of that person for the entire time. Otherwise our time traveler would have no way to prove the photo wasn't photoshopped. This does not necessarily need to stand on its own as absolute proof either. This could be the thing that convinces people that it's worth the time and expense of (for example) trying radioisotope dating, as described in Joe's answer. [Answer] # Guinea Pigs It's 2018. Our college student, let's call him Edward, was getting ready for his camping trip. He would be gone for a few days, and he realized he couldn't just leave his new friend, Bartholomew, behind. Bart was just a baby guinea pig, his cute new pet, this little thing of only 8 centimeters, that he was gifted from a friend, Rayleigh. Bartholomew had a very peculiar set of spots and fur colors, which made him stand out among his siblings. Edward took a lot of photos of little Bart the day they first met, sent to a lot of friends, and all that. So Edward took Bart to the camp with him. His shirt had a good pocket for him, so that was easy. When Edward finally showed up again in 2023, his friends, especially Rayleigh, couldn't believe their eyes. Not only Edward was suddenly back, but little Bart was there with the same 8 centimeters!! How could that be? It's common knowledge that not only guinea pigs live at most 4 years, but they also double in size after just one week... It couldn't be Bart... But it had to be, because how on earth there could be another baby guinea pig with the exact same spots and fur colors?? Source for Guinea Pig numbers: <https://www.guineapigcorner.com/size> **Edit addressing comment:** if this is not enough, an extra possibility is to justify getting a DNA sample from Bart before going to the camp. Perhaps Rayleigh is a researcher and he took DNA samples of Bartholomew and his siblings to conduct some sort of long-term experiment - sending one guinea pig for each of 10 friends maybe, and planning to check on them in the future to compare their development for some reason... [Answer] ### He hasn't actually "time traveled" There is no FTL involved. There is no going **backwards** in time. So this is simply **time dilation** and not **time travel**. That doesn't change the problem, just clarifying that this is different - and therefore much more plausible to those investigating - than actual time travel. FWIW, I wouldn't be concerned about identity - DNA + more traditional identity confirmation such as dental records will take care of that. ### Electronics If he has an up-to-date iPhone or Android device with him *and has not turned it off at all* then a bit of analysis could show that the device only experienced 5 minutes of elapsed time instead of 5 years. This would likely not work if the device was turned off at some point during the trip - and he might have done just that to try and figure out why he wasn't getting a good signal, which of course he wouldn't get while on the alien spaceship. **Detailed explanation** I can't say that any current device *definitely* works this way, but it is plausible: * Like almost any computer, device has an elapsed time counter - number of seconds since it was turned on. Reset to 0 every time the device is turned on. This shows the device was turned on 8 hours + 5 minutes ago. * The device, typically for cell phones and optionally (but quite commonly) for regular desktop/laptop computers (Windows and Linux), gets the "real" time via a web service, updated periodically. This avoids the need to have a super-accurate clock in every little device. * The device logs the results of "time checks" and other network calls for a limited amount of time, with the *local elapsed time* logged as part of the information. * The device would show that 5 minutes before the student left Earth, the network time check got a 2018 time. And that right after he got back - *but only 15 minutes later in local elapsed time* - it got a 2023 time. The reason that the phone must stay on through the trip for this to work is that otherwise there is no simple way to distinguish between a 5-minute/5-year time dilation and simply turning the phone off for 5 years. The fact that the phone turned on and had to "correct" the time by 5 years is meaningless because the internal clock that runs while the phone is off might be broken (as can happen on a computer with a low battery). ### Medical As a young college student, he will likely be pretty healthy. But if, for example, he had his wisdom teeth taken out 2 weeks before the trip, a dentist could examine his mouth and determine that the amount of scar tissue/healing matches 2 weeks (or perhaps "within a range from a week to a couple of months") and not 5 years. [Answer] The process called [DNA methylation](https://en.wikipedia.org/wiki/DNA_methylation) can pinpoint individual's age with +/- 4 years precision. If your student skipped 5 years, his DNA test will look unusual, but not as much as to suggest things like alien abduction. However, if he had a blood sample taken and frozen right before the abduction, this will cause scientists to do a lot of head scratching. [Answer] > > Assume a college student from 2018 accidentally traveled to 2023. He is accidentally taken by an alien spaceship that travels close to the speed of light away from earth and then travels back. He is put back to the place where he was taken. > > > The question is how can he prove to the people in 2023 that he has time traveled, against other possibilities, such as running away from school. > > > **First, necessary step - establish identity** He's identical to his document pictures from five years before, so that plus DNA matching with family members can establish he's who he's saying he is. So, we know that he should be around 25 years old. Now how to prove he's actually 20? **Standard radioisotope dating** (e.g. 14C) would not work. Radioisotope dating only measures time since loss of equilibrium, which usually happens at death. But even if the guy had died on the ship, that time would be his local elapsed time, so just a few minutes; there would be no clue as to how long he had lived before meeting his end. If something had happened outside in those five years, and the guy did not show the signs, then yes, it would work - but the premise is that nothing of the kind happened. * **update**: it *might* work, because something *did* happen outside in that time. There are environmental isotopes that decay naturally and, of course, most living beings are at equilibrium with them. But our guy isn't - he's got in his body five years of undecayed radioisotopes. This could be another factor to take into account, even if it would be probably explained away as natural variation or contamination by those same isotopes. **Immediate examination** Chances are that his clothes and appearance were recorded in selfies, videos and memories from five years back. He's still almost *identical*. While possible, this is *really* unlikely - a 25-years old is quite different from a 20-years old. **Interrogation** It is possible to question him on *everything* that went on in the weeks before his disappearance, five years ago for the interrogators, a few weeks for him. Were he an impostor, he might have studied again whatever examinations he gave last, and might have painstakingly reconstructed all the facts from those days and learned them by heart. *He wouldn't be able to fool police detectives*, whose job it is to see through alibis. If he were simulating, he would remember too little, or too much, in ways that are obvious to an expert. So either he's telling the truth or he's been coached by an expert on how to lie. **Medical examination** Growth in the interval 15..25 years can be analyzed quite effectively and will say that the guy is now 20 years old, give or take three years. The possibility he's actually 25 is still open, but not very likely. After he disappeared, almost surely some kind of DNA sampling of the area was done; and it's very likely that some DNA samples from five years back can be recovered anyway. That, plus [PCR amplification](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3047434/), would show that either he's being time-shifted five years in the future, or something did a really weird number on his telomeres. # Conclusion Probably nobody would believe in a starship, and people would rather assume some strange time-warp effect - the time equivalent of [Tay al-Arz](https://en.wikipedia.org/wiki/Tay_al-Arz) - or some "Bermuda Triangle" time-stasis, or ultra-black government experiments. I bet lots of people would start combing the disappearance area looking for clues, measuring radioactivity, magnetic fields, and wearing tinfoil hats and dowsing rods... But the fact that he somehow skipped five years of his life would be quite hard to deny. [Answer] He took his dog with him on the camping trip, and the the dog experienced the same time dilation that he did. The dog happens to be AKC registered with [DNA on file](https://www.akc.org/breeder-programs/dna/). It's also about one year old, has some distinctive markings, and is [microchipped](https://en.wikipedia.org/wiki/Microchip_implant_(animal)). A picture of the dog pre-abduction and a quick trip to the vet would establish that it's likely the same dog. Dogs at one year old still look and act like puppies. The difference between a one-year-old dog and the same dog at six years would be striking and obvious to anyone who works with dogs. Most vets and animal shelters will have microchip readers on hand. If a greater degree of proof is needed, someone could contact the AKC to do a DNA test based on the sample that they have on file. In principle, the student's pet could be a cat instead of a dog. Or a horse which has been registered ([horse camping](https://horseandrider.com/horseback-trail-riding/trail-riding-destinations/horse-camping) is a real thing). [Answer] > > The question is how can he prove to the people in 2023 that he has time traveled, against other possibilities, such as running away from school. > > > His family will know he time traveled. He won't show any signs of aging and will match the missing person photo from years ago, but his family will know it's him. It will be so obvious that people will have a harder time accepting the truth then accepting it's a lie. It's also the same plot from the movie "Flight of the Navigator". A boy disappears in 1978 and returns home in 1986. His parents and brother have all aged but he hasn't. [](https://i.stack.imgur.com/cbjHI.jpg) <https://www.imdb.com/title/tt0091059/> [Answer] # DNA Telomers, or a (still) fresh wound This requires a tiny bit of handwavium, and one less fantastic assumption. The assumption is simply that it is **known** that this person has been unexpectedly missing for 5 years. ## Telomers are your cells' countdown timer [DNA Telomers](https://en.wikipedia.org/wiki/Telomere) are... > > ...**a region of repetitive nucleotide sequences at each end of a chromosome**, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes. Its name is derived from the Greek nouns telos (τέλος) "end" and merοs (μέρος, root: μερ-) "part". For vertebrates, the sequence of nucleotides in telomeres is TTAGGG, with the complementary DNA strand being AATCCC, with a single-stranded TTAGGG overhang.[1](https://en.wikipedia.org/wiki/Telomere) This sequence of TTAGGG is repeated approximately 2,500 times in humans.[2](https://en.wikipedia.org/wiki/Adhesive_bandage) > > > **In humans, average telomere length declines from about 11 kilobases at birth to less than 4 kilobases in old age, with the average rate of decline being greater in men than in women.** > > > The handwaving is that we can measure the length of telomeres. From this is is easy: we get a hair brush, old clothes, dust and similar from your protagonists's old apartment and/or items that were stored after their disappearance. Best of all maybe an [adhesive plaster](https://en.wikipedia.org/wiki/Adhesive_bandage) that was discarded not long before their disappearance. Then we do a comparative analysis, measure telomer length from the old items, and compare to samples we pick freshly from the protagonist. And from that we will then find that the telomers of the person before us are **not** five years shorter, as they should be. ## The **really** boring, author ex machina way... Your protagonist had an accident a couple of weeks before disappearing, and either broke something, or hurt themselves in a way that left a very clear wound somewhere that needed hospital work. This is noted in their medical journal. When they then make their reappearance, their physician concludes: no way that this wound — that I know I treated — is five years old. Look, we can even see the last remains of the [polyglycolide sutures](https://en.wikipedia.org/wiki/Suture_materials_comparison_chart). Or the cracks in the bones that have not fully healed. Either someone went through **extreme** measures to mimic this wound five years later, or the wound matches a timeline that suggests a five year lap forward in time. [Answer] He had a box of individually packaged twinkies - or any other individually packaged snacks, especially those that decay quickly - with him, and some of them are still left over. Since they are still fresh, still originally packaged but by expiry date should have decayed years ago, something timey-wimey must have happened. Of course it's not a definite proof, a very determined person might have managed to acquire old twinkie packaging, put fresh twinkies into them and resealed them somehow, or just removed the original expiry date from a fresh package and added a new label. It could still suffice to convince friends and family. The good thing about this solution is that it's absolutely non-technical, i.e. you can understand the proof just by looking at it, and it's plausible, because, well, students tend to eat a lot of snacks, so it's pretty much guaranteed that he brought some on his camping trip. [Answer] Scenario: It was not he, but she. And she was pregnant with quadruplet. All of them had extremely rare genetic mutation. She was pregnant for such and such time. When she returned her pregnancy was still on the same stage, she still had quadruplet inside her and said quadruplet had the same extremely rare genetic mutation. [Answer] @Kenster brings up a good point with pets, but most of those animals are simply too large. Rodents, such as rats, have short lifespans - Somewhere along the age of 2-ish years if I remember correctly. Rats, in particular, are prone to getting tumors when they are older. They're generally benign, and with some a vet will recommend against removal - Surgery would be worse for the rat than simply monitoring the tumor. A pet rat is also easy to bring along wherever, *and* easy to bring along on an accidental spaceflight. People carry them in their pockets all the time, while a dog or a horse is far less likely to be able to be accidentally brought along on an alien spaceship. To prove that the rat is the same rat, we'd need to have a rat with distinctive markings, a distinctive tumor, Vet records of said tumor, and some pictures of the rat from the time of leaving. At this point, it's fairly simple to go "Hey, this rat was 18 months old 5 years ago, and was taken to the vet about this tumor on this date. Here's a picture taken at that vet's office on that day, showing the vet, the rat, and the tumor. We've tracked down this vet and they say it's the same rat - And no rat lives 6 1/2 years." It proves *something* funky is going on, for certain. [Answer] Two really basic questions to address are: Does he have any living relatives who would remember and recognize him? Has he ever been fingerprinted or have he or any close relatives been DNA tested? Also the hospital where he was born should have his footprints on file. The OP didn't spell it out but I'm assuming he wasn't carrying any form of legal identification. Since his phone, if he has one won't be working anymore due to nonpayment, I'm not convinced that the time will be synched to the network. [Answer] Dental records will show that his body hasn't aged. ]

[Question] [ Imagine a magical world similar to [this](https://worldbuilding.stackexchange.com/q/74709/34064) question, where everyone uses skeletons as soldiers. There are mages running around searching graves for bones to summon them into skeletons. How do I keep my remains and those of my family and friends from getting brought back to some kind of life as supposed-to-be-scary warriors if I don't want to cremate them and keep the bones largely intact for at least some years so they decay more or less naturally? Furthermore, the solution should require only very few resources. Powerful people arrange to have their corpses guarded, but poor people need a way of protecting their corpses preferably without using magic or with very little magic (=little energy and complexity) bought somewhere. Further assume energy conservation, so search spells as well as shield spells are possible, but the further you look and the longer or more often you have to deceive someone looking, the more energy is needed. --- Guarded graveyards became available but are regularly attacked or robbed as selling that many corpses is very lucrative and the few guards just get sold too. --- **FAQ** / importing comments into the question: --- Why not cremate? Because the soul gets damaged then. Or that's what people say. --- So the shape of the body must be largely intact? What about amputees? Can we remove limbs? The bones should be preserved. What happens if they are shattered is not known (because I didn't have that idea tbh and haven't thought about it), but cremation or pulverization is bad. Casting them in metal seems like a good option, but very costly. --- Who does the searching and how? Do mages pay grave robbers like medical schools used to do? Do they use area spells to locate suitable corpses? Is it acceptable to bury in alkaline soil so that decomposition is faster? All of those as long as decomposition is not too fast (years are okay, days are not). They search themselfs, they send someone, you can even sell your remains to get some coins for your family, but that's generally despised --- How do the mages reanimate a body? If you could describe the process for us we may be able to provide methods of prevention. They say something along the lines *make those bones assemble like a skeleton and attack everything that moves behind this line after I was buried there* just in more words and more detail. Then the magic energy rushes out of their body depending on how much they wanted to invest and that's it. Pulling the bones out of the earth or anything can be treated as a different spell needing as much energy as it would need to do that manually (apart from the energy waste manual labour has). --- So what is actually going on? They say some words and magic goes in...but what does the magic do? How does it bond to the bones and know to bond to bones rather than a stick buried underground? Perhaps there is some trick where the magic cannot tell the difference but we need to know the details in order to determine this. The magic follows the intent of the caster so as long as the caster is focussed and has the details figured out (like this bone belongs here and should be moving d'accord with that other bone to form a leg), the spell does what it's supposed to do. A mage could use a spell to find bones but the further away they are the more energy that spell needs, so finding every bone in a graveyard that's buried within a few meters deep, yes, finding every bone in the world, definitly no. So as long as the mage can tell the difference, the magic can. --- How much are bones worth to those necromancers? If guarded cemeteries are attacked and the guards are used as bones too, are the poor even save from being murdered just to get their bones? How common are those bone thefts? Getting a cemetery worth of hundreds or thousands of skeletons is a different thing than earning a little money by murder. --- Aren't skeletons a waste of magic/energy? YES. It's a kind of sport to have thousands of skeletons guard your tomb. Plus all the heroes running around need to be able to brag about the vast numbers of opponents they "killed". Skeletons are far from an effective use of magic, but I'm pretty sure that's so in any set of magic rules unless you make them exactly to basically allow only summoning of skeletons and almost nothing else. --- How easy is it to reprogram a skeleton? Drain the energy in there (you'll need approx. the same amount for that), put your own in. So not so easy. [Answer] # Set them in concrete Very simple. You dig the grave, place the deceased at the bottom but not in any notable coffin. Instead of pouring in earth you pour in concrete. Expense: Cost of a few dozen square feet of concrete. No ongoing expense. Security: Your corpse is not completely secure but anyone who wants it will need to dig through several feet of solid concrete and is likely to damage the body in the process of breaking through. # Bury them very deep under extremely heavy rocks. This option is probably more work but simply burying the corpse very deep under some very heavy rocks will go a long way towards making it slow and difficult to recover the corpse. For bonus points the heavy rocks may naturally crush/shatter many bones over time making the corpse less usable. # Bury them in the middle of nowhere in an unmarked grave. Combine with burying them fairly deep and the investment of simply finding the grave becomes significant. # Expand your criteria for "decay more or less naturally" to include other natural ways for bodies to decompose **Sky burial** [](https://i.stack.imgur.com/CVTcn.jpg) If your people are willing to accept that as "natural" then the corpse and even bones can be disposed of in short order. # Burial at sea You've established that it's important that the body remain un-pulverized and reasonably whole for a reasonable length of time. This opens another option: Wrap the body in netting/rope/wire netting, tie many rocks to it and bury them at sea a few miles out. The body will decay after a few years but should be held together my the netting for some time. recovering the body should be fairly difficult. Finding it even harder. [Answer] Remove the femur and bury it or guard it separately. A one legged skeleton is of no use to a mage. But for the family, their relative is intact except for one missing bone. Their society could develop special repositories where they store only thigh bones. They would take much less space than an entire skeleton and could be guarded by fewer people. Depending on the cost to the soul, the femur could be destroyed, rendering the skeleton useless for mages, but only partially damaging the soul. But I have to wonder, what damage is incurred by a soul when the skeleton is reanimated? [Answer] Let the bones defend themselves. In a world where "everyone uses skeletons", it must be relatively easy to convert a corpse into a skeleton. In that case, poor people might sell their corpses to serve as crypt guardians. I suspect that people might be less inclined to steal corpses if there was a risk of them fighting back. As mentioned by @Leatherwing, there might be damage to the volunteer's soul, but I suspect an appropriate price could be found to pay for that. One might even argue that it is the responsibility of the city government to provide that service, much as it provides regular police. [Answer] Cremation or otherwise destroying the persons bones after death seems to be the optimal solution here. You can't have your skeleton summoned if it is destroyed at death. But if this is not an option for some reason it would seem the only other possibility is putting the body in an inaccessible location. Sinking in large deep bodies of water would seem to be the simplest option, I assume if the water is deep enough it would become too difficult to raise the skeleton warriors from the surface due to the distance involved. Bonus if it is a secret location so no one know to look there for human remains. This should be accessible to even the poor, as all that is needed is a burial shroud, some heavy rocks, and a boat to get over deep water. I imagine in a world like this people would offer this type of burial service for a fee, undertaker services would involve a boat rental. If at a coastal location this could also be combined with small funeral boats to allow the body to float out to sea on prevailing currents. This does allow the scary possibility of a powerful magic wielder finding the secret burial lake and using their great magical power to raise a horde of skeletons from the depths (which would be awesome!) Other thought, if dismembering is okay, have the parts of the body scattered to far flung location, possibly in a type of burial exchange with nearby towns, making it nearly impossible to get a complete skeleton to raise as an undead warrior (This assumes you need a skeleton from an individual and not just the correct amount of bones from different people, perhaps something to do with the persons bones being bonded together magically after death.) [Answer] ## Use decoys It seems you're intent on keeping the person's bones treated with a certain degree of respect (no cremating or crushing) so I thought I'd approach it from a different angle. The mage needs to know which are your bones in order to get the spell to work, this is where I think we could fool them. Once a family member has passed the next few days of mourning are filled with gathering branches of various sizes and wearing them down to be shaped like bones and creating an array of faux skeletons to be buried along side the actual deceased. To by-pass certain spells for detecting bones another ritual requires the family to make small cuts on their hands whilst they work - their blood staining the wood. They can also fill the sticks with ground animal bones. This way a mage may come up against mixed signals and spend his precious mana in attempts to raise wooden skeletons or will be required to stop and spend a long time discerning which is the true skeleton. This solution allows for a fairly ritualised method so that even in areas which no longer have knowledge of mages the process can be continued. [Answer] Boring I know but you could fracture the bones, that way they're shards and not useful bones. Or cast them into some kind of metal, like Han Solo in carbonite. You get a nice life sized casting that holds the bones in place. Additionally you could create guarded community burial sites. Guarding bodies will be an honorable profession. Of course a guard could be bribed but in a small community that could be a literal death sentense. Maybe combine the above. Corpses could be gathered and guarded. People would be able to mourn till the end of the month. At the end they're piled on top of eachother and cast into metal. This can obviously be impure cheap metal. Or even concrete works. The idea is that it's hard to remove without shattering the bones, turning them useless. [Answer] # Cremate the Necromancers From an economics point of view, if the value of the skeleton to a necromancer is greater than the cost of overcoming the protection, then skeletons will be ravaged. Change the cost structure using law, introducing a *barrier to entry*: Make the criminal penalty for necromancy so high that most mages will be dissuaded. Since the scenario seems to involve a cultural (or magical) taboo against cremation or grinding bones, make it part of the penalty. ``` By order of the King, the penalty for Necromancy is Death. The convicted mage will be cremated immediately. ``` After the first couple, word will get around. If the King is too weak to enforce the law, then warlord mages already roam the countryside with their skeleton armies, and most of the peasants are probably already dead (and resurrected). A clever king will, of course, promptly exempt crown-employed necromancers to maintain a fearsome crown army. This will lead to lots of palace intrigue, corruption, assassinations, and exploitation. The peasants will suffer grievously (see pre-revolutionary France), and many who expire will be promptly resurrected into the King's enormous magical army. [Answer] Do what the relics maker used to do in the past to harvest relics from saints: 1. wash and boil the corpse. This will make the flesh easily separable from the bones. 2. poor people option: manually remove the bones from the corpse 3. dissolve the bones in acid or calcinate them. 4. bury the flesh [Answer] The plague of necromancers has resulted in in a boom in the gravemaking industry. Rather than simple graves in the ground as became standard after the Romans "civilised" Europe, people are going for the traditional burial cairns. Cairns vary in scale. From the simple cairn with charms to block scrying to elaborate mausoleums with active magical defences for those who can afford them, to the commoners' yards, where those who can't afford better are buried in catacombs maintained by the local authorities, who don't want a skeleton army at their doorstep. Some rulers with too much time on their hands spend enormous amounts of money and labour to build elaborate traps within their future graves. There are rumours of an unofficial competition between rulers of whose mausoleum has the best (most vicious/effective) traps. Of course, since no raider bothers to visit the tomb while the prospective inhabitant is still alive, nobody has won yet. [Answer] A town or village may invest a lot of money in making a priest of high repute or known skill to come and bless a piece of land, to make it Hallow Ground, a place where necromancy doesn't work, and have sentinels patrol this cemetery the same as any other part of town. There would be also a lot of common knowledge mixed with myth about what makes a body easier for a necromancer to raise it and people would take that into account. Maybe they would bury them with stakes across their hearts, or extract the brain and organs like Egyptian mummies... [Answer] In a [tower of silence](https://en.wikipedia.org/wiki/Tower_of_Silence). Specifically one modified to allow bodies to be added, but not removed. Powerful families can have their guarded tombs as expected, less well-off people will be interred in public sites. Imagine a tall, circular stone wall with stairs leading up to the top edge and open space in the middle. After funerary rites and dressing of the body have been performed, it can be brought to the tower and dropped in. Not the most dignified burial, but if necromancy is such a concern for society, a necessity. The inside of the wall will be far too steep and solid to make climbing out feasible, and since this is a holy site, magic-dampening wards should be built into the very walls, which limits a necromancer's access to his tools which might otherwise let him get corpses out without getting his hands dirty. Once a certain number of bodies are added to the tower, it can be left to the carrion birds to clean the skeletons for a time and then filled with cement and the walls broken down, and left as an ossuary. It will still be considered a sacred site as such, but can be used for other purposes and the tower rebuilt elsewhere. [Answer] Hide the burying place (this will work when the mage has to be close to the corpse to summon it). Put gravestones on empty graves and bury the corpse in an unmarked place. Make the graveyard unaccessible for the mages (e.g., by placing them in quarters that are populated by criminals and no-go areas for mages). You can see this as the poor men's version of a guarded area. [Answer] You basically want to make recovering the bones as expensive as possible with the least effort possible. Sealing the body in some hardening material (like metal, cement, etc.) may be a good step, but also needs you to get this material. A very easy way to protect the bodies would be, to bury the bodies in a highly frequented place. But don't put them all in the same spot, don't create cemeteries. For the extremely poor, there could be a rock coffin on every major crossroad of a city. People who own their own house can bury their dead in their own cellar. As long as somebody is home, the bones will be safe. Just make sure, your neighbors have an eye on your house, when you're abroad. [Answer] Depending on the landscape available to you, you might want to look for naturally hard to reach places. For example wrapping the deceased in linen, then drop them in a swamp. Maybe quicksand works too. If your necromancy requires some kind of ritual, embalming, seeing the corpse at least, etc then the necromancers would first have to retrieve the corpse. Encasing them in ice in a glacier might also work, if that is the landscape available to you. This would however slow the decaying. Putting them on a small boat and let them sail out on the sea. With a strong current you could provide certainty that they end up on the ocean. Maybe also prep the boat with a small mechanism (maybe fire?) to fail after some hours and sink. Another idea would be something with hazardous properties. Maybe a cave in a volcano or filled with poisonous gas that has a small opening at the top. Walls are steep so climbing out is impossible. You can use a rope to get the body in but retrieval will be much harder. That is, if magic does not allow telekinesis... Another thing which maybe wouldn't be ideal, you could make the bodies into traps. Like, add explosives in them. That might scare necromancers away. It would however damage the body if it was activated. Depending on what you deem as destroying the skeleton, you could weaken it. Maybe make it a burial ritual. All bones have to get specific areas filed off. So when you reanimate it those points would be severly weakended and prone to break. The ritual should be visible at point blank. That way a necromancer would see the corpse as unfit for his purposes. Maybe there's a substance that does this with bones in general. Pouring it over bodies makes bones weak as thin twigs but keeps them intact. Some kind of ointment maybe. As far as rituals go, maybe shackling the dead would be a good idea too. If they are dropped into something or buried and the necromancer uses magicto raise them and let them crawl out or climb out, shackles would make them unable to do so. This assumes being raised in itself is not damaging the soul, but just the fact that they serve a necromancer is the sole problem. [Answer] There are approximately three major options: 1. Destroy the bones - burning, breaking, or dissolving the bones would prevent them from being used. Granted, if this harms the soul, you should only do this with relatives you don't like. 2. Hide the bones - a few possibilities here: * Keep the bones in crypts, a guarded warehouse of bones. Cheap for the individual, as flesh-free bones take up very little space. * Drill holes into solid rock; the holes should be just big enough to drop bones in, but too small for a full skeleton to climb out, or a human to climb in to retrieve them. * Scatter the bones somewhere irretrievable, like the ocean * Bury the dead deep, and place very large rocks over the grave; this may work better for mass graves, where bodies are placed under massive slabs of stone, inaccessible to outsiders 3. Keep the bones from traveling - drill a small hole in important bones, like the femur, humerus, and skull. The hole isn't big enough to damage the bone (people may even have these wires installed while they are alive), but once deceased, the bones have a wire run through them, and are bound to a large stone. Moving the bones will break them, but leaving them to rest will keep them whole. [Answer] 1a - A variation on options already here - the Iron Maiden Coffin. The coffin is made in two parts, with pairs of hooked iron spikes pointing up from the main part, and down from the lid. The spikes are lined up with the major bones, and have the backward facing hooks are between them. The body is pressed onto the bottom spikes where they will hold it in place, and each major bone has one or more pairs of spikes holding it down and in place. When the lid is placed it lines up so there are matching spikes in one or more places, causing it to be very difficult to get the coffin open again - and any attempt to do so will likely break bones and cause the skeleton to be useless. 1b - Added options include the spikes being in a metal body-shaped cage (like a personal body prison) that is welded closed (meaning the the skeleton can't move without removing it from the cage first). The body can then be buried in a normal coffin, and several buckets of black powder put in there too (woe betide any grave robber who tries to remove the frame in a way to cause sparks). 2 - If the body is buried vertically (in a frame and not a coffin) then it also makes it far harder to dig out, as digging the original hole for it is relatively easy compared to making a hole big big enough to get the body out - especially if buried in a gravel rich area. 3 - Another addition to the coffin (or final resting place) would be copious amounts of slaked lime (<https://en.wikipedia.org/wiki/Calcium_hydroxide#Health_risks>) - it is relatively easy to make, and can cause severe skin irritation, chemical burns, lung damage and even blindness - again, make it something that people really don't want to contend with to dig up. 4 - As a related note to that (and with a small amount of magic) - a magically triggered grenade of slaked lime - assuming that the wizard needs to be present to raise the skeleton, having it potentially blind (or worse) the wizard doing the raising might make raising the dead a far more risky operation... [Answer] Assuming the aim is to prevent your skeleton being used as a soldier (presumably because there is risk of damage to the bones, which would damage your soul, as with cremation. Assuming further that the act of necromancy does not damage the soul of the skeleton. **Use Necromancy.** It sounds like a Necromancer could command a skeleton to 'lie perfectly still forever'. This would use 0 energy for the Necromancer, and the spell would thus last forever. Generally speaking (by which I mean in Dungeons and Dragons), it is accepted that an animated Skeleton is not a valid target for the 'raise dead' spell. Necromancers would charge relatively small amounts for this spell, as there is 0 energy required, making it a relatively easy spell to cast. [Answer] The cheapest solution would probably be big rocks. Specifically, a simple pulley and a big rock held up by rope. Lift the rock, put the body underneath, drop the rock. Repeat until the bones are in too many pieces to do anything useful with. This could be automated with something akin to a windmill or waterwheel-powered flour mill. These are fairly grisly options but would be easily available to people with almost no money. [Answer] You've [indicated](https://worldbuilding.stackexchange.com/questions/74710/how-do-i-keep-my-remains-safe-from-being-summoned-as-a-skeleton?noredirect=1#comment218214_74710) that it is fairly difficult to "reprogram" a skeleton that has been previously programmed by another. > > drain the energy in there (you'll need approx. the same amount for > that), put your own in. So not so easy. > > > If so, I recommend asking a close friend to program your skeleton to defend itself! The bones don't have to be commanded to move until necessary, if I understand your command system properly. Your sample command is "*make those bones assemble like a skeleton and attack everything that moves behind this line after I was buried there*," which allows your tired bones to rest until some opportunistic necromancer comes to collect them. The energy cost of deprogramming your skeleton, besides the fighting involved, should be high enough to discourage the use of those bones in warfare. If you'd rather your bones not move at all after death, consider programming them to lie still forever. [Answer] A geographically somewhat limited solution to at least make access to the bodies more difficult, would be to use mines or tunnels - similar to catacombs, to store bodies. By placing explosive charges in the access tunnel, you can either trap the wizard, should he slip by and start summoning skeletons, or when one is active in the vicinity, block the access to the burial site. If explosives are not available, you may consider flooding the burial site, but that is less effective, and also may present some sanitary issues, as the water may mix with ground water. You could also use sand or gravel to fill the access tunnel(s), which is stacked near the entrance and held back by some wooden mechanism. This should at least prevent small-time necromancers from sneaking/running off with your hot neighbor's corpse. The downside to this solution is, that it only really works if there's an actual interest in tunneling deeply into mountains or underground, since it's unlikely to that people will invest that effort just to keep some dead bodies around. Also, it's very much a dissuasive method, since once you sealed your mass grave off, preparing another one is going to be costly. Hence, I would very much focus on disabling the necromancer, not the skeletons/corpses. Plant some traps, build some walls, and if you're really fancy, invest into some magic triggers, which detect necromancy and sound an alarm or set off further traps. For bonus points: animate the necromancer's corpse and have it walk around town. Putting heads on a spike is so medieval! [Answer] In this world, can the church not bless the grounds? Also, bless the corpse. Use magic that doesn't damage the soul. Then the necromancers have to overcome that magic first before they can animate it. The goal is to make it more expensive to animate. [Answer] I would think that encasing in metal or concrete, though not yet invented, would simply be a deterrent. A strong mage could melt/wear away the metal or concrete, possibly damaging the bones in the process. In summoning the skeleton, is it going to dig itself out? I was thinking of burial in a segmented coffin where all the bones are separated and reordered in different compartments. If anything, this might make it too much trouble and they will move on to the next body. [Answer] Coffins made of Yew wood will block a necromancer's *search bones* spell, and are toxic to necromancers. Families save up money to buy the (now somewhat rare) yew wood for coffins. the poorest people can't afford it, though the church provides mass burials of many people's bones in a single yew coffin to reduce the cost. [Answer] I have two ideas here. One, why not have a *necromancer*'s skeleton guard the bones? His or her skeleton will be infused with necrotic energy, which will naturally protect them from intrusion (ie. someone trying to take control of their skeleton). They will also be able to cast any spell necessary to guard the bones, eliminating the need for live guards. However, the necromancer may not *want* to revive the bones as skeleton warriors; not strong enough, too fragile, etc. *Instead*, they may want to crush up the bones into dust. Why dust, you ask? Because with bone dust, you can create yourself a *new body*, with all the desired properties of whoever the bones came from! If you're willing to go with the 'all men are made of dust' theme, then this makes perfect sense. If not, feel free to leave that idea by the wayside. [Answer] **Consecrated Ground** Finally a real use for priests and the church Everyone knows a properly buried body in consecrated ground blessed by a priest cannot be raised by a necromancer. [](https://i.stack.imgur.com/71ssU.jpg) Of course that's expensive but the church has to make a living too. [Answer] Simple, grind the bones into powder. Then, discretely scatter them. Problem solved. Not only would the bones be impossible to find and gather completely, but gluing them together would be ridiculously hard work. [Answer] You can try using reinforced coffins, making life harder for the thief, who will then hopefully try looking in someone else's grave. ]

[Question] [ The year is [Random number between 2100 and 3000], and Earth is now covered in a tight network of teleporters that have replaced all other modes of planetary travel. Only those wishing to travel to other planets and systems must embark on ships. Teleportation is instant. You buy a ticket, get into the cabin, stamp your ticket, press a button and wake up in another, identical cabin several hundreds or thousands of miles away. There are enough cabins for everybody, and, except in developing countries where people would have to pass border control before being allowed to teleport, nobody has to wait for more than five minutes after buying a ticket. This of course means that affluent travelers cannot enjoy amenities like luxury lounges or reclining seats. Still, transportation companies want to find ways to make richer people pay more by offering them a "First Class" of teleportation. **What are some perks, amenities or luxuries that could come with it?** [Answer] **A private network** When it comes to flying, the truly rich do not fly first-class. That's incredibly inconvenient for them. The truly rich fly on their own personal jet to wherever they feel like going. Thus, the way teleportation networks would cater to the rich is simple: Have a *private network* for them. Every major corporate headquarters would have a teleportation pad installed for use by the top executives to drop into other locations of the same business, rivals, trading partners, etc; not to mention that there would be stop-offs at various exotic vacation locations, exclusive for the rich. What's so special about those? Well, it's *exclusive*. Exclusivity is a privilege that people will pay good money for, after all. [Answer] **"There are enough cabins for everybody"** This is a [frame challenge](https://worldbuilding.meta.stackexchange.com/q/7097/40609). If you have a civilization that can waste that many resources to ensure everyone can teleport anywhere they want whenever they want planet-wide, then what you're really saying is that everyone has at least two teleporter cabins in their homes, apartments, offices, stores, etc. What would be the point of even thinking about making such a banal trip more elite? Nobody's rich because nobody's poor. To make a point: it's the general utopic post-scarcity society. *I hate utopias. They're boring.* So let's bring what the devil inside me calls a "dose of reality" to the conversation. No for-profit company would ever allow that many cabins to exist without some kind of flaw that keeps people coming back. (This isn't an unreasonable suggestion: you've kinda described a perfect situation and perfect situations pretty much never exist.) * Limited cabins due to a limited resource, like unobtanium. * Cheap cabins wear out or require more repair than expensive cabins. * Limited transportation windows because there's only so much of the "ether" that can be in-use at any one time. * Limited destinations because, honestly, you don't want just anybody appearing in your home (or office, lab, secret lair, etc.). Now we have the ability to create an incredibly profitable elite travel class! The whole point of elite travel is to overcome both problems and inconvenience (and, of course, to make you feel special. What's a good leader without a dose of narcissism, hmmm?) * The elite can own private cabins. The public must use "public transportation" in the form of street curb cabins. * The elite can buy cabins that will last a century without down time. The public is lucky to afford cabins that don't require multi-hour phone calls with automated responses to get to a representative who can't actually understand the problem and can't speak your native language anyway but is disinclined to escalate the issue to someone who might. * The elite get first-dibbs on transport windows. The public gets to stand patiently in the cabin, twiddling their thumbs and wondering why they can't be rich. * The elite get to go to more places than the general public. For example, the elite get to transport straight to their Disneyland penthouse suite while the public gets to teleport to a common landing site a quarter-mile away from their dingy hotel. In this aspect you can think of it as elites get to own cars and use garages while the public can only use buses and bus stops. *One more comment about limited destinations* One fundamental problem with a transport system that's as ubiquitous as you initially described is that any communication-and-control based technology can be hacked. That means a clever hacker can teleport to the POTUS' office, or to the guard station at Fort Knox, or to the breakroom at CERN, or to the hangars at Area 51... you get my point. Your system must in reality contain a great many limitations or the world and its stories won't be believable. A general homeowner might not want a cabin in their home because they can't afford the tech that keeps trench-coat-wearing violin-case-bearing gentlemen with a somewhat Sicilian air about them from walking into their front rooms during the dinner hour to have a conversation about a certain loan made to a guy lovingly named "The Nose." But the elite can. [Answer] ## Travel time > > Teleportation is instant. You buy a ticket, get into the cabin, stamp your ticket, press a button and wake up in another, identical cabin several hundreds or thousands of miles away. > > > Teleportation is only instant from the point of view of the traveler. You don't remember the traveling, as you were unconscious during all that time (and to be honest, as each molecules of your body are separated during the process, it's a good thing for you). Thing is, the whole process of destruction-travel-reconstruction is not itself instant. And first-class have less traveling time. For example, they have a big stock of interchangeable body molecules, they skip the travel part, while second class have less or no stock, so you need to wait for the travel of body molecules. Destruction-reconstruction could also have different processing time, the same way as an industrial printer could print way more paper per minute than a first-price one. So, while first-class teleportation is almost instant, or at least way faster than flying, second class teleportation may be slower, and as today's traveling, you lose time, be it for every-day ride from home to work, or when taking a vacation in a foreign country. [Answer] One luxury I could think of is closely related to the technology driving the teleporters. Let's assume your teleporter analyses your body on a molecular level and sends those petabytes of information to the receiver, that then reconstructs your body. This process is often referred to as beaming in popular science fiction culture. In that case, the teleporter could, for an additional fee, analyse the travelers body for any defects, both medically and aesthetically, and when reconstructing the body on the other side, simply correct them. You could imagine different tiers, ranging from a minor vitamin correction to pretty much full body regeneration that could lead to a prolonged life or even immortality. Why would this process be so expensive? One answer could be that it takes massive computing power to calculate the new molecular blueprint. Another that it runs on patented McGuffin® soft- and hardware. Building on the idea above, another service could be a software-backup of yourself, so if you get into an accident some time after using the teleporter at a premium rate, it can simply replicate you. It costs extra of course, because your data takes up so much space on the servers. This is also why I wouldn't actually assume the teleportation to be instant. As it requires such an immense amount of data transferred, it might as well require a queue that can have prioritised slots for the business travellers. [Answer] **No luggage limits** Considering described popularity of the network, the provider would likely need to largely optimize its usage and since every gram of luggage means unnecessary data transfer, luggage fees might still be a thing - for ordinary customers, that is. [Answer] It seems that all the "practical" aspects are as good as they can be wished for. I don't see a way you could get different prices within the same brand name; even though that doesn't mean there isn't one. But different brands - companies, or just brand names which are the same company but pretend they're not - could differ in prices based on HOW they do the identical thing: 1. You could have your first class teleports set up with very nice environment, lots of marble, genuine oak/mahogany/..., pleasant stewards to sell you the ticket and show you the way, etc. On the other hand, your cattle class will be a hut built as cheaply as possible with a beaten machine (or an ugly old hag tired by life) selling the tickets and a swarm of posters/banners/screens shouting ads to you on your every step. 2. Companies can differentiate based on "ethical" issues - we make sure we don't use the products of slavery/child labour. We use ethically/sustainably sourced materials. We give our staff fair wages and conditions. Or anything else similar. 3. Aggressive marketing. We are THE BEST, because we said so. Think mobile phones, why does one company successfully sell equivalent phones for prices way higher than competition, and even convinces you to buy a new phone every year? [Answer] There's a teleporter for everyone in their home, there's hundreds if not thousands of teleporters for popular locations. But even so a place like Times Square will be flooded with people teleporting there. The teleporting grid will need to make decisions with who teleports where and deflect excess people to empty teleporters farther out or put them in a waiting queue before they can teleport. So that way you can give people priority status: high priority people who pay get quicker access and less deviation from their chosen destination. There's also simple access rights. A vacation resort would have private teleporters towards all its houses that you can only access after paying. The owners of the overall public teleporting grid would work like phone networks: selling speed, amount of uses and access to area's depending on the luxury at the locations and distance from likely popular locations. Pay more, get more. [Answer] One person cabins to wherever you want IS the first class cabin. Also, someone is moving your luggages for you using another cabin. For poor/normal people, you have big cabins shared with a lot of people and a preset destination and departure time. It can be fast, with only a few minutes between each jump, but you still have to cram yourself with a lot of sweaty people, children... everything. [Answer] It is usual for companies to make different products for different audiences which have the same cost to produce, but with added effort to make the experience [redacted] if you are buying the cheaper version. Think of pay-to-win games, in which there is a cheaper version (possibly free but with ads), and a more expensive version which gives you items and advantages absent from the cheaper package. These games are usually multiplayer too, to add insult to insult and injury to injury. So for teleporting, you could have the machine to shake and vibrate in a very uncomfortable way in each end if you pay for the cheaper ticket. The more expensive ticket is more expensive because the machine will not vibrate and will not make you dizzy. The extra cost you paid goes into "pumping more juice in the process, making sure it is safer and more stable" (actually it goes into not activating those actuators, but people don't need to know that). --- You may also have separate boarding and landing stations for each different ticket value. The more expensive tickets allow you access to stations with bathrooms and cafeterias in both ends. The VIP tickets will have a massage parlor and pedicure waiting for you. The cheapest ticket allows you to go from a telephone-booth-sized tube on the departing side to the middle of a busy street on the other side. You may also sell precision. 5 bucks will land you in the city you wanted to go, but you may appear anywhere. 5,000 bucks guarantee you will appear within five steps of your intended destination. [Answer] **AM I STILL ME?** There's a school of thought that if you deconstruct someone, convert them to data and energy, and recreate them elsewhere, that the person actually dies and a copy is made. It's not really you anymore, you died the first time you climbed on a teleporter. These are the common teleporters. A more advanced technology actually transports the original atoms and essence of the person via wormhole, quantum jumps, etc. so you aren't dissolved and copied. This also means the person can't be split, copied, recorded and modified, data-mined, or whatever bad effects you care to attribute to unscrupulous corporations controlling ordinary people. The elites travel unscathed, while the plebeians wake up in another city oddly craving the new brand of hot sauce and coming down with a cold that the corporation just happens to have the cure for at a great price. Also, they're sure they signed up to be replicated on the new colony world, right? [Answer] Luxury is also dependent on the culture. In some countries it's ok for the train to be 30 minutes late, in the other 2 minutes is already insane. Having instantaneous transport means they value the time higher. 5 minutes waiting is for commoners. No one important can wait that long. You arrive, are ushered through immediately and teleport. 30 sec tops. In addition, you can add services. Teleport waste from your body, like number one and two, or even waste that hasn't been filtered yet. Like muscle waste or waste stored in the liver like alcohol. Remove or reduce bad bacteria and viruses. You'll feel fresh and new after a teleport. It's healthy! [Answer] # Teleportation sickness Have you traveled recently from one end of the world to the other? Having trouble sleeping, a loss of appetite and problems with disorientation? Then you are very likely suffering from teleportation sickness, a natural byproduct of being torn apart on a molecular level and being recreated at a different point with shoddy craftmanship. We here at Platinumportation have the solution for you. Our exclusive top-of-the-line teleporters will take a few seconds longer to get you where you need to go, but that's because we don't just haphazardly fling your precious body into the void, we take the utmost care to ensure that every single atom of your body ends up exactly where it needs to go, with no margin of error. Don't risk extreme teleportation sickness and travel with us now. Your safety is worth more. [Answer] Frame challenge for slightly different reasons than the other frame challenge answers, but this is unrealistic for multiple reasons: * Unless the teleportation devices are trivially portable and destinations are trivially configurable (thus each *person* can have one and you don't need hardware at target locations), it's an absurd waste of resources even in a post-scarcity society to have 'enough for everybody'. At minimum, *space* for the hardware is a limiting factor (and actually, it's going to be the biggest limiting factor other than whatever unobtanium makes them work even in regular societies). In essence, even if any teleporter can connect to any other, you need at minimum 2 per private residence and a number proportionate to expected usage in *every* building. The private residence part isn't that much of an issue (but it does put a limit on population density that's lower than without it unless stuff like apartment buildings have public cabin sets instead of private ones per apartment), but it's just plain impractical for big buildings. Imagine big office buildings, just to meet the rush-hour demand they'd need hundreds of teleporters, and even if we imagine minimally sized stalls, you're still looking at an entire *floor* in many large buildings dedicated just to that, which is quite simply a waste. * Even ignoring the above point, you need some degree of scheduling that would make a maximum 5 minute wait infeasible during peak hours. You have to be able to actually appear at your destination and leave from your origin point, and both cabins have to be unused for the entire time it takes you to get in, teleport (which is probably not truly instantaneous, but not likely more than a few seconds), and then get out. IOW, you have to wait for a clear cabin at the far end, and if the cabins operate in half-duplex (and they should, because that at least partially mitigates the first issue), you may have to wait for a clear cabin locally at the same time. Actually achieving this requires scheduling, and that scheduling will mean delays. * Further, aside from the above two points, your proposed situation is actually not realistic from a business senses. A NPO won't be able to do that due to lack of funding, a government can't do that due to limited resources and bureaucratic inefficiency, and a private for-profit company would only do that as a subscription service which would automatically price a large segment of the population out of actually being able to obtain the hardware (which by definition means that there's not enough for anybody). The *only* option that makes sense to achieve this is a unified socialist government for the whole planet overseeing it combined with a truly post-scarcity society. The upshot of these issues is that for this to be realistic, you need either a largely post-scarcity socialist society (for example, the Federation from Star Trek) and a lot of free space, or teleportation would be operated in a way equivalent to either public transit or air travel (pre-COVID-19 of course), and the second case is both more interesting and more realistic. Assuming you go with that second option (operate like air travel or public transit) and factor in the realities of scheduling and monetization, the obvious solution for executive perks is queue priority, and proximity to a desired destination (spikes in usage would logically be smoothed by teleporting lower priority people to nearby locations close to their intended destination that have lower usage). I could also see the use of private subnets (IOW, sets of pads that cannot be accessed from the larger public network without special authorization), for example allowing an executive for a large company to just teleport straight from his house to his office at corporate HQ instead of having to go to the local station and teleport from there to the office building, then walk to his office. [Answer] I think it will still be determined by supply and demand: 1. if there is some side effect, such as if the vibration frequency can make the person a bit dizzy or something like that (some discomfort), then the most comfortable method (may require building something by platinum), will be most desired and therefore will be more expensive 2. if there are some situations, such as doing the traveling at 3am when people usually would want to sleep, then it will be less desired and therefore cheaper [Answer] User accounts and paywalls. Yep. Just like all those annoying websites. Let's say anyone with $100k can buy a teleporter for their home. They're going to have to set up user accounts and passwords so that only their family and close friends have constant access to their house, and temporary guest accounts for people they invite over. If you can do that for a residential location, then why not have companies doing the same thing for their customers? Sign up with SuperSnobClub Inc and get an account and password to allow you to visit their exclusive club-house in the pristine wilderness, hundreds of kilometres from any city. Access costs $10M per year, so only the ultra-rich will ever get to see the place outside of the odd TV documentary. Also, the user account system being just another computer system will almost certainly have security bugs that need patching. Exploiting such a bug before it gets patched to get into a rich person's house to rob or assassinate them could be a plot point in a heist story. [Answer] To borrow from Douglas Adams, teleportation leaves you feeling terrible. You end up disorientated, dehydrated, and feeling generally like you've been vaporized and rapidly recombinated. It suucks! You think being crammed into a tiny seat with a child kicking the small of your back for 9 hours is bad? It's got nothing on how you feel after teleportation. Nothing important gets lost during the teleport, but there are allowable inaccuracies in the process. At least, if you're teleported peon class. The rich use more accurate teleporters, that are calibrated better. They don't randomly drop a bunch of unimportant water molecules, and do an actual scan, rather than just assume your electrolytes are set at "normal human". The rich are also quickly sedated, and gently brought round after a relaxing nap. If you have a sort of hub where you go to teleport, the rich might be transported to and from this, waking up gently in a private vehicle already heading to their end destination. It's not that different from an airline in that respect. You still get there, safely, and at the same time as the person in 1st class, but the process in general is much less pleasant. [Answer] **No flies on me!** We all know the dangers of teleportation! Something that will be very important is **valeting**. We don't want any extraneous matter or life-forms floating around in our cabin (see Note) - or any infectious diseases. We are told that tickets are purchased so, for the purposes of answering, we can discount the fact that wealthy people will have their own private booth at home. Let's assume there is a cabin on every street corner and that anyone can use it. Some may be late for an important meeting and will require the fastest turnaround. They will pay for their ticket and head straight in. For most people the TP-cabinet (which is the sealable unit within the cabin) will be thoroughly cleaned between each use and be subject to a visual inspection. This means that people who pay more, actually have to wait *longer*. There are waiting areas in the cabins with various levels of luxury. The wealthiest will actually wait the longest. They will pay for the A++ service which includes automated disinfection, irradiation and vacuum cleaning. They will have to wait longest but their travel will be the safest. They have a special lounge with luxury service while they wait. --- EDIT Alternatively there are different classes of booth at the same location. 1st Class booths get the full cleaning treatment immediately after use and are therefore ready for the next first-class passenger. 2nd-Class gets a quick clean and 3rd-class is just straight in and out with a clean at the end of the day. **Note:** The Fly (movies) <https://en.wikipedia.org/wiki/The_Fly_(1958_film)> and <https://www.imdb.com/title/tt0091064/> [Answer] Maybe first class would be denoted by the speed with which our luggage will arrive; say first class means FedEx will get your luggage there within 24 hours of your arrival, while lower classes might have to wait for UPS Ground to get it there in 5 days or so. OR - maybe first class would be denoted by the level of cleanliness of the pod you use. First class is guaranteed that no insects made it into the pod with you. while the Economy class "hopes" that no insects made it into the pod with you. (Jeff Goldblum can relate.) [Answer] Omnipresent teleportation is strongly featured in Alfred Bester's [The Stars My Destination](https://en.wikipedia.org/wiki/The_Stars_My_Destination), a SF classic. Called 'jaunting,' it is different from the type you propose for it is entirely a mental feat which nearly anyone can perform (over varying distances). Like yours however, it cannot cross space. The rich of Bester's world of the 25th century spurn jaunting and employ other methods of transport in a show of conspicuous waste setting them apart from the rest of society. > > He set off [...] in a coach and four driven by a coachman assisted by a > groom [...] > Presteign of Presteign was the epitome of the socially elect, for he was so > exalted in station that he employed coachmen, grooms, hostlers, stableboys, > and horses to perform a function for him which ordinary mortals performed > by jaunting. > > > [...] > > > As men climbed the social ladder, they displayed their position by their refusal > to jaunte. They newly adopted into a great commercial clan rode an expensive > bicycle. A rising clansman drove a small sports car. [...] Presteign of > Presteign, head of the clan Presteign, owned carriages, cars, yachts, planes, > and trains. His position in society was so lofty that he had not > jaunted in forty years. > > > Besides this one result, Bester has given us a complete vision of how jaunting has upended human society. It is a dangerous world punctuated by an interplanetary war against which the story of Gully Foyle is set. [Answer] **Services** Alright, so the teleport itself is pretty much ideal. No wait times worth talking about, no travel time.. But what about the destination? * Illnesses are bound to be everywhere, especially in a tele-society like this. Fortunately the Teleport companies can auto-vaccinate passengers in-transit by simply splicing the vaccine into the beam. No scary needles needed. But they have a limited stock, so they provide it as a premium service. Everyone else has to visit their doctor before travelling internationally. * Luggage - The mass-cost of teleportation imposes a strict luggage limit, pay by the gram. It's still cheap, but most people will want to travel light. Distance of travel makes this worse. If you want to travel interplanetary, it'll either cost a lot, or you'll take only hand-luggage and buy/rent while you're there. The First Class tickets take a lot of the limits off this. * Cargo Transport - Following the thoughts on luggage, if you have something really bulky you want to take with you, ordinarily you'll have to arrange for it to be shipped/transported in specialised cargo teleporters. For First-class travellers, this is part of the service and it'll be waiting for you when you get there. * Hotel-Relay - Most tele-travellers end up at a hub station and travel conventionally to whatever hotel or engagement they have in mind. But for a first-class traveller, they can arrange for the teleporter to relay them straight to a First Class pad at the hotel of their choice. They can even be collected from the hotel when they want to leave. No rubbing shoulders with the less-affluent for them! * Walk-in-walk-out Teleporters - Most of the time, the travellers need to wait for the teleporter to charge up and fire them to their destination, it's more energy-efficient to do a batch of passengers at a time. A bunch of passengers get into appropriate booths, have a seat and wait. After five minutes, the teleport fires and they all arrive at their respective destinations. Not the case for the super-affluent. There are teleporters permanently charged for their use, they just walk into a short section of corridor and are teleported while walking through it, emerging seamlessly through a door at the other end. For the merely wealthy, the booths they wait for the teleporter in can be significantly nicer. No metal bucket-seats for them! They get comfortable chairs and their own higher quality area of the transit station away from the family holiday-makers. [Answer] **A Better UI** How do you select which cabin to teleport to? * The basic accounts might have you choose from a list of all the cabins, sorted by their serial number. As per your setup, there would likely be billions of them. You have to go through a thick book that links the numbers to the locations to select the correct one or remember it by heart (think of phone numbers before smartphones, you have to know the person's number or spend some time looking for it in the phone book). * The premium account might have the list alphabetically sorted by the actual location's name - much easier to find. Scroll down until you see the location you want to appear in, click it and appear there without needing to bother entering or knowing/remembering its number. * For some people, instead of having an alphabetically sorted list that they have to scroll through, it might even be searchable! *(for an extra $50.00/month)*. * The gold account members would also have access to a world map: zoom in to the area you want to visit, see the available teleport cabins nearby, click one and appear there. * The platinum members could have a *Favourites* list with their top 10 most used locations (pay more to add more spots to that list) as well as a *Recent* tab with their last 5 chosen locations. [Answer] **Reliability** Cheap cabins (that costs like passenger jet plane) have 0.5% probability teleported person dissipaters without trace and 0.5% that he/she arrives as pile of meat to destination. For second case cheap cabins has build in washing and waste disposal system. Expensive cabins has much lower probability of malfunctions (it haven't happened yet), but they costs nearly 1000 times more. UPD1: 0.5% disappearance probability still makes teleport economically viable, for example, to deliver cargo like fast spoiling food. Its not an issue, if 0.5% of shipment disappears, its more important that it can be delivered in time. UPD2: prob 0.5% malfunction is too high, i agree. [Answer] Subverted: Like with vinyl records vs. digital music, the elite don't crowd into teleporters like all poor people do. They own transatlantic cruisers, airships and steam locomotives, not because they are practical, but because they can afford to travel in such extravagant ways and nobody else can! [Answer] You're working it backwards. First class travel isn't find some way of adding amenities to the teleport system: first class travel is *not using the teleport system*. The peons rush around from point to point...and to be fair the rich do as well if they're in a hurry, but otherwise they're willing to show how well off they are by taking their time, because they can. Why, instead of teleporting from New York to London instantly, they might take two whole hours on a transonic jet, and if they're really decadent, several whole days by *ship*. Note that this happens now (pre-COVID and probably will again): for less than four hundred dollars you could fly from New York to London in six hours. If you take, say RMS *Queen Mary 2* it takes an entire week and, depending on the season, the price could start at $1,900 for the cheapest interior cabin. [Answer] Scanning your body requires you to lie still for 41 minutes. In many cases its faster to drive. The high-end machines with three times as many sensors reduce it to 6 minutes. OR if you're rich, you can afford the specialized portable hard drive with a copy of your latest body scan, which reduces the scan time significantly. OR the scan time still takes 41 minutes, but some are located in luxury lounges where you can have cocktails and surf the web while lying there. AND the high-end machines are safer. The low-end ones almost never have...unfortunate incidents, but the high-end ones have triple-redundancy, and have even fewer problems. (Contraiwise, cargo-only teleporters are **pretty** safe, but its cheaper to insure your cargo than it is to send it through a low-end people-approved teleporter.) ]

[Question] [ I am thinking of copying the design of an electric eel to create the horn, however as air is not a good conductor of electricity it cannot discharge any electrical shock unless there is a physical contact. Can you help me to come up with a believable unicorn that can stun its predator from at least a few meters away, and also how it prevents electrocuting itself or its own kind? [Answer] The unicorns are symbiotic with a jumping spider species, residing on the horn. The horn is kept at (or can be quickly charged to) a sufficient high potential, and the jumping spiders can be directed to jump on the target while threading a thin wire of cobweb attached to the horn. As the spider or a group of spiders land on the target the circuit is closed and the target is zapped. Alternative to the spiders: the unicorn can blow mucus covered particles to the target, with the particles keeping a thin slimy rope of mucus attached to the horn. Zap as above. Pick the one more suited for your story and stomach. [Answer] The solution is **Lasers** Simply, much like a Narwhal\* the Unicorn can shoot lasers out of it's horn. From there, it's not too much of a stretch to allow for the possibility of an Electric Unicorn to discharge it's built up charge along the laser-induced plasma channel immediately after firing it's horn-laser, in much the same manner as an [Electrolaser](https://en.wikipedia.org/wiki/Electrolaser). \*Apocryphal [Answer] While it is true that air does not conduct electricity as nicely as water, it is also true that there is no (engineering) problem that cannot be solved by judicious application of brute force. Lightning is a thing after all, so we know a discharge will happen in air if there is sufficient difference in electric potential. Copy the design of the eel. [This is what the wiki says about it](https://en.wikipedia.org/wiki/Electric_eel#Physiology): > > In the electric eel, some 5,000 to 6,000 stacked electroplaques can make a shock up to 860 volts... > > > Now notice what the wiki says about [its typical dimensions](https://en.wikipedia.org/wiki/Electric_eel#Anatomy): > > The electric eel has an elongated, cylindrical body, typically growing to about 2 m (6 ft 7 in) in length, and 20 kg (44 lb)... > > > If your unicorn weights as much as a [draft horse](https://en.wikipedia.org/wiki/Draft_horse#Characteristics)... let's say one metric ton. It will have enough size and mass to have a lot more electroplaques. A back-of-the-napkin calculation says that, keeping the same volts-to-mass ratio, the unicorn will be able to produce 43,000 volts. You can buff that up - nothing is keeping the unicorn from having even more electroplaques. Let's say the unicorn is able to produce 50,000 volts. That is [about as much as a typical low end Tesla coil](https://en.wikipedia.org/wiki/Tesla_coil#Operation): [](https://i.stack.imgur.com/xZzAj.gif) > > The high electric field causes the air around the high voltage terminal to ionize and conduct electricity, allowing electricity to leak into the air in colorful corona discharges, brush discharges and streamer arcs. > > > A pointy part in a body is much more likely to produce a discharge than a round part or a toroid, so the horn is perfect for shooting out lightning. As for how the beast does not fry itself, it may have glass or some other very good electrical insulator material in its hooves. [Answer] The horn has a tiny hole in the end. The unicorn can pump a saline solution out through this hole - like a [spitting cobra](https://en.wikipedia.org/wiki/Spitting_cobra) or [bombardier beetle](https://en.wikipedia.org/wiki/Bombardier_beetle) - which acts as a conductive stream from horn to target. Additionally, this liquid contains a paralytic agent, causing "tingles" that aren't *actually* caused by the initial, brief, jolt of electricity. A unicorn has tall, non-conductive hooves, which prevent them from 'grounding', and protects them from accidental shocks. Young unicorns, who have not yet learned to completely control their bioelectric-capacitors yet, are thus prone to accidentally shocking themselves while eating. [Answer] In order to avoid electrocuting itself it could simply have tissues that are highly conductive (potentially metal) as skin. It will act as a [Faraday cage](https://science.howstuffworks.com/nature/natural-disasters/lightning8.htm) leaving all other tissue mostly unharmed. [Answer] ## The sparks just travel through the air. Why would this be a problem? No, air isn't as conductive as water. But [electricity can travel through the air](https://en.wikipedia.org/wiki/Lightning) for several *miles* at sufficient voltages. [Machines can generate sparks](https://en.wikipedia.org/wiki/Tesla_coil) multiple meters long. Even the tiny static spark that you get from rubbing your sock on the carpet and touching a grounded object can be three or four centimeters. > > But natural creatures don't generate voltages that high > > > *You are talking about a literal unicorn.* Some creative license is allowed. Electrocuting itself isn't a problem for the same reason it isn't a problem in real-world electricity-generating animals: their bodies are adapted to it as a natural function. If you really must include some vague science, say that there are at least two separate organs, or parts to the single organ, that generates the electricity: a low-voltage power supply and a transformer. [Stun guns](https://en.wikipedia.org/wiki/Electroshock_weapon) ramp up quite low voltages (household batteries, maybe 20 volts at most) to tens of thousands of volts to make their sparks. The unicorn has a structure that, in addition to simply generating a current, transforms that current into a higher voltage, [accumulates a charge](https://en.wikipedia.org/wiki/Van_de_Graaff_generator) over short amounts of time and releases it in bursts. (Note that most of what we see as sparks, lightning included, are bursts of accumulated charges and not continuous streams). Hope this helps! [Answer] By projecting water droplets in an arc towards it's target allowing the electricity to conduct through the air between the unicorn and it's aggressor. It goes without saying that these droplets would create an arch of different colours caused by the refraction and dispersion of the sun's light. I imagine these colours would be red, orange, yellow, green, blue, indigo, and violet. [Answer] The unicorn will still be electrocuted but to a lesser degree. Thinking of it like a circuit, the current will follow the path of least resistance more readily than the higher one. (Assuming that there is a path between the unicorn and the intended target. ) Adding resistance to the unicorn`s biology would be in the form of insulation. An example is keratin which is less electrically conductive. Insulation could be placed strategically to protect vital organs from the "recoil". Body size may also play a role here. If the unicorn is much bigger than the target, the charge may be sufficient to stun the smaller organism but not enough to harm the unicorn itself. [Answer] The unicorn has a coat of gold (or some other metal, but probably only in the silver, platinum, etc. variety because unicorns). Each hair, particularly in its mane and tail, are basically long, sharp needles. The unicorn can somehow embed these needles into other creatures or objects, maybe by rubbing on it or flinging the needle-hairs with majestic head shakes or glorious tail flicks. Any object that has a long, sharp, conductive antenna (like golden hair-needle-spikes) will attract the high voltage discharge from the unicorn. All the unicorn needs to do is get one of its hairs embedded into its target, then release its electrical fury. Additionally the metallic coat can do other things like ground the unicorn and protect itself like a Faraday cage. Not only that, but its valuable pelt would be sought after by evil unicorn-hunting villains. [Answer] Air is a fantastic conductor [as a plasma.](https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity#Plasma) Simply turn the air in a column between the horn and the target into a plasma. Boom, instant lightning gun. Granted... you'd have to explain why the unicorn doesn't just cook the target with the plasma canon. [Answer] The spirals of the horn form a resonant cavity with the atmosphere. The unicorn's horn is literally linked to the air and charges up. You know how lightning works. *See tesla coil on youtube.* ]

[Question] [ A medieval person (say from around 1000 AD, and from a rural village) walks through the forest, and through some unspecified mechanism suddenly turns out to be in our time. He is still far away from any settlement or road, and there are currently no humans nearby. What would be the first signs for him that something is wrong? I assume that this happens during a sunny day (and there's no sudden weather change or change in day time that he would notice). Also, there's no sudden change in the forest (that is, it's not that he sees a sudden move of trees, or something; for him it looks as if he just normally walks through the forest). However, if there are significant differences between medieval and modern forests, he'll certainly experience them; just not as a sudden change, but as if it were a difference in space (i.e. as if he walked from a medieval forest into a modern one). One thing I've come up with is that he'd probably be used to watch the sky for predicting the weather, and would therefore likely notice strange straight-line cloud formations he has never seen before, and which he cannot make sense of (those cloud formations being contrails). What else would he notice? **Edit:** In the mean time I've decided that the place should be somewhere in the [Bavarian Forest National Park](https://en.wikipedia.org/wiki/Bavarian_Forest_National_Park) because I'd expect in a national park the forest should be closer to the past one than elsewhere. [Answer] **The smell.** We don't notice it because it is everywhere but even low-level pollution would be noticed immediately -- the ability to smell low-level pollution would pass quickly though. **The noise.** There is elevated noise levels in many rural areas and all populated areas. The noise of a jet may well be the reason our time-traveler looks up in the sky and sees the contrails. **The plants and animals.** We have affected natural forests in a number of ways. Acid rain, increased CO2 levels, alteration of water level, reduction of disfavored predators, and species migration (accidental and intentional) means the no forest is really natural anymore. The forest could be suddenly drier or lusher than before. There could be species he has never seen before. I know you specified no sudden weather change, etc. But a dry or wet season, early or late spring, etc. could still impact vegetation, etc. Some climate changes are long term resulting in a different mix in trees and animals that would be familiar. E.g, where did all of ash trees go? The ash borer (imported pest) has killed off large numbers of ash tree. **Modern artifacts.** Even in the woods you can find pipelines, electric lines and towers, etc. Sadly discarded cans, bottles and other trash are all too common too. At night, light pollution from the big city can be seen at a great distance esp. with a high altitude cloud cover. Out in the forest it is unlikely that changes would be a reason to be concerned unless he actually sees a jet when he looks up at the noise. This is different if the jet happens to be close-by. My father (born 1934) tells that his first encounter with a jet was very exciting -- he thought is was the second coming of Christ. Clearly other modern artifacts could be upsetting too as they would be more clearly indicative of significant change. --- In deer season you might hear gunshots. Near a military base I've heard artillery fire from 20 miles away (likely to be mistaken as thunder though). Cigarette butts. A old abandoned house with window glass. At night, light pollution reduces the number of visible stars. Maybe it is July 4th and there is a fireworks show in the nearest city. These and quite a few other low probability events could be the first thing the time-traveler notices. Or just maybe he notices a jet contrail first, after all they are fairly common, distinct and visible from a great distance. --- **Smell** Oil refineries can often be smelled 20 miles away **Noise** [Road noise calculator](http://rigolett.home.xs4all.nl/ENGELS/vlgcalc.htm) at a distance of 2.5 km from an active highway, I calculated about 30 dBA. For comparison a whisper is 20 dBA. ATVs are noisy and often found in rural areas -- obviously not in the forest itself unless there trails to drive upon. **Acid rain** [Acid rain damage on 50% of trees in German Black Forest](http://www.dw.com/en/germany-controversially-still-bombards-forests-with-limestone-to-combat-acid-rain/a-17239231). Other articles note that acid rain damage is more noticeable at higher elevations and that conifers are more resistant the deciduous trees. Since acid rain has received attention, the sources have been cleaned up in many cases so the problem is not as bad as it was though evidence of damage will remain for some time. **Modern artifacts** Search for "forest illegal dumping" and you can find many images and articles related to illegal dumps. Cigarette butts and soda cans are not that hard to find. Wild animals often consume cigarette butts mistaking them as food. Power lines, microwave towers, fire towers, etc. are all found in occasionally in the forest. I did not pick on environmental problems because of bias, it is just that environmental pollution in various forms is more likely to have an noticeable impact on a forest area than non pollution factors. I.e., pollution affects are often widespread because they are dispersed in the environment. In fact dilution is still a pollution mitigation strategy - though less so over time. [Answer] It happens that a friend of mine who was in the Peace Corps brought a friend from rural Malawi out to San Diego. Mozezi wasn't unaware of the modern world, in fact he at one time had owned a moped to drive into the small town 25 miles away, but even so the trip was constant sensory overload for him. Some things that REALLY bowled him over were: Pavement everywhere. Malawi's "major highways" are two-lane unpainted asphalt roads. There's a bit more asphalt in the biggest cities, but most towns have dirt roads only, and villages just have paths. In America, he saw very little GROUND anywhere. Even trees had to grow in little squares of ground cut in the concrete. Magical (synthetic) things everywhere. In a rural village, pretty much anything you look at, you can see what it's made of. Hut walls are mud, rope and twine are grass, tools are wood and forged metal, lanterns are made of metal and melted sand, paint is made of ground up rocks. But here and there are objects like toothbrushes and plastic tarps made of incomprehensible materials that simply do not exist in nature, and no one can imagine how they were made. In a modern setting, EVERYTHING is unnatural like that, and there's no guessing how ANY of this stuff was made. Even paint and asphalt don't look like simple rock mixtures. Abundance. Mozezi was used to seeing an occasional car or rarely an airplane. He had watched TV at a bar in a big town 25mi from his home a few times. That same town had a Coca-Cola billboard that was HUGE (to him) and BEAUTIFUL (because it was painted red). But in America, on a given day he'd see more of these things than he'd ever imagined existed or seen in the rest of his life. So, you might get the idea that Mozezi never reacted to the things we THOUGHT he'd react to. It didn't matter if we took him to a friend's house, a movie theatre, or a strip club, he'd just be amazed by the colorful lights, the carpets, etc... [Answer] I'm in the UK, and the majority of the landscape has massively changed over the last 1000 years due to intensive agriculture, even the trees in a vast amount of forests would be unfamiliar species (Norwegian conifers rather than native broadleafs). However, for the sake of the story - say, our protagonist awakes in a protected forest, early on a Sunday morning in the summer (low traffic, so the drone from a distant motorway would be inaudible) - the first thing that would be noticed, even out there in the wild, would be vehicle tracks in the mud, possible from a forestry service inspection - would look completely unlike anything seen before. Obviously though, being in an unfamiliar place, our hero (at least if he has any sense) will head for a high place to get a better view of the landscape to orient himself... He reaches the crest of a nearby hill, and as he surveys the scenery, he will be greeted with this sight:[](https://i.stack.imgur.com/lvJ8h.jpg) [Answer] This depends much on WHERE that person belongs to. For example, if he belonged to some far flung African country, the immediate changes he would notice, would be very minute. However if he used to be an inhabitant of the areas which now happen to be suburbs of Manhattan, Tokyo, Beijing or any other megapolis then our character is in for a world of immediate shocks. This also depends on the age and gender of the character, the age effect being more prominent than the gender effect. Young (18–35) people would perceive changes far more quickly and in more detail than aged characters. And if the character is a young female, she would probably detect things far quicker than a male, due to the on-the-guard psychology of women of most cultures during 1000 AD. Let's assume Mr. Kagwa (age 25, gender male) belongs to some far flung African country and he walks out of the woods. It is winter season and the time is evening. ## Mr. Kagwa Walks Out Of The Woods He heaved a sigh as he walked out of the woods. Safe, finally! There was hardly a chance of finding a hyena or a lion in the woods, but wildcats and leopards were a deadly threat. He stretched and looked south. There was smoke far away, near the horizon. It was rather strange. There was no village in that direction! None that he knew of, at least. Rather surprised, he had no time to walk in that direction and investigate. Night was dangerous! He took the trail leading to his village. After walking for a couple hundred yards *- don't use meters here-* the trail suddenly ended! He looked around and rubbed his eyes a few times and looked hard. Yes, there was no trail! He had walked that trail since his childhood but it was there no more. Quite perplexed, Kagwa shook his head and continued walking the path. Trail or no trail, he had to reach home. --- As we see, Kagwa notices only two oddities: smoke in an unusual place and the absence of the trail leading to his home. Now let's compare that to the case of Duddley, a 22 years old English boy (man by his standards) who happens to walk out of the woods some 30 miles from London. It is summer and the time is afternoon. The sky is clear. ## Duddley's Adventure He walked out of the woods and stopped. There was a strange object laying on the ground in front of him. It was shiny and appeared metallic. Prudently, he proceeded and picked it up. It was indeed metallic, its weight was a clear indication. He examined it closely. It was shiny and hollow inside. *-Duddley has found a piece of metal pipe-* He carefully placed it back. It could be dangerous! He then resumed his walk. There was something strange but he could not tell exactly what. He looked around closely. Everything looked the same, but there was still a feeling of something amiss. His heartbeat increased slightly and he started walking carefully, watching his every step. Suddenly he saw something above and in front of him. He stopped and gazed. It was very high in the air but he could still tell it was large! Far larger than any bird he had seen. He examined it closely and suddenly noticed something horrible: it was not flapping its wings! That, and there was a trail of white smoke behind it. He stopped in his tracks and stared in horror as the giant bird flew past him, never flapping its enormous wings. He then realized what was amiss in his surroundings. It was the smell! There was a slight, but consistent smell of smoke in the air. And the noise. Drrrrrrrrrrrrrrrr... It was faint, but he could easily tell it was coming from above. It was coming from the bird! His heart thumped in his chest as he ghastly looked around. He quickly perceived this was not the place he had known. It looked similar, but it was not the same! --- One metal pipe. One airplane. The pollution and the background noise. Duddley known within 5 minutes something is severely wrong around him. [Answer] The first thing our visitor is likely to notice is that the forest is shockingly neglected. Mediaeval forests were not wild areas; they were productive economic assets. They are no longer maintained as they once were. The trees will not be pollarded and coppiced. There will be no sign of charcoal-burners at work. There will be no one harvesting any fruits or nuts that are in season. And so on. [Answer] Litter definitely litter, from crisp packets in bushes to 'poo berries' (collected dog waste hung in small black plastic bag on a tree) Try and go for a walk anywhere natural in the UK for more than 5 minutes and you will find a discarded colourful piece of plastic somewhere. [Answer] In Europe (or at least in the UK) modern forests are different from medieval forests in many ways we are mostly unaware of but which a medieval person would notice immediately. In a lot of Western Europe, the forests where a medieval person might have walked would be very different, either containing a much higher proportion of mature trees of a height and an age rarely found now or in forests near villages there might be coppiced trees or trees managed in other ways that are no longer used. There would probably be very noticeable effects of pollution and acid rain on tree bark, moss and other forest plants. There would likely be some litter, hikers plastic bottle caps are brightly coloured and take centuries to break down, plastic from bags blows far. The birds in the trees might be different, many raptors have been hunted to extinction. Other vivid and loud species have been [introduced](http://www.rspb.org.uk/discoverandenjoynature/discoverandlearn/birdguide/name/r/ringneckedparakeet/) Some animals would be startlingly alien. [Asian deer](https://en.wikipedia.org/wiki/Deer_of_Great_Britain) and even Australian [wallabies](http://mysteriousuniverse.org/2013/11/britains-wild-wallabies-really/) can be found in some UK forests and woodlands. [Answer] If he's even remotely close to a large city and you wanted a landmark for your story, I'd suggest going with [skyglow](https://en.wikipedia.org/wiki/Skyglow). I live about 20 miles outside of Wichita, and am surprised occasionally just how pronounced it is. Smaller suburbs have reduced, but still visible sky glows as well. [Answer] He will hear a sudden silence. He won't hear the sounds of the birds. The birdsongs he does hear may be very strange to him. Invasive bird species (example: starlings in north america) have had an absolutely devastating impact on native songbirds. Even invasive earthworms can cause a decline in ground-nesting songbirds. This answer would apply best to the western usa, which I am most familiar with. [Answer] On September 11, 2001, following the WTC attacks, **all** U.S. air traffic was grounded for about 24 hours. During that period, while in a rural location, I distinctly recall noticing how incredibly *quiet* it was - while the sounds of wildlife, wind and water were still there, it turns out that even if you're nowhere near an airport, the sheer number of flights in the air, at any point in time on any other day, guarantees that no matter where you are, the ambient background noise outside will include white noise from jet engines overhead - even flights above 20,000 feet contribute to this. We just don't notice it because it's always there; the same mechanism in our brains that allows us to ignore the sensation of our clothes on our skin after wearing them for a few minutes also filters this background noise from our conscious perception. So, the first thing our medieval visitor would notice would be **a very faint, constant** *shhhhhhhhhhhhh* **coming, seemingly, from everywhere and nowhere.** [Answer] If your time traveller was awake at night, they could spot (in addition to planes) also an artificial satellite, or perhaps even a flare from the Iridium constellation. [Answer] A medieval time-traveler would notice the abundance of inanimate objects moving without the intervention of a human, a beast-of-burden, an actual fire, etc. The medieval person would be frozen stiff at the sights and sounds of shiny metal cars racing around with no horses or other animals to move them. He would see "fiery" streetlights and signages with no sign for fire or smoke. The main rule of medieval technologies was: A cart will move if you have a horse to pull it, a fire will happen if someone physically starts one. In the modern world, this rule is shattered. ]

[Question] [ Designing an electronic 'mosquito' among my arsenal of 'bugs'. Some work as remote ears, others as eyes. This mosquito is the assassin. He can fly into a room and when he 'bites' someone can inject a small amount of liquid. What substance could kill a human, from immediately to 2 days after the injection. Bonus, what substances could just incapacitate a person for at least 20 minutes? This is Mosquito sized and as such the payload needs to reflect that. Is Ricin the most likely candidate? Can it even do this in such a small amount? If 'spraying' the substance into eyes or mist for inhalation, that could work too! [Answer] Okay, I'm not sure if anyone is going to read my answer at this point, but here goes. I don't think any of the poisons that have been suggested so far fulfill your requirements, largely due to the long time before death. # Botulinum Botulinum is a particularly bad choice; although it has the dubious honor of having the lowest [LD50](https://en.wikipedia.org/wiki/Median_lethal_dose) of any known substance, what it actually does is bring about a prolonged illness called [Botulism](https://en.wikipedia.org/wiki/Botulism), and that LD50 naturally is only relevant without significant medical intervention. In practice, there is an antidote available, and with first world medical care (which there will be time to receive), there is actually a high chance of survival, even if a high dose is given. It's also fairly well-known and in hospitals, since people can get botulism even if they haven't been poisoned. It may be fatal only weeks after the poisoning, if at all. One potential benefit is that it could be mistaken for a normal illness. # Polonium-210 Polonium is certain death, in the long term. It also brings about a prolonged sickness which will eventually kill, though it is expected to take 20 days, making it unsatisfactory for your purposes. There is no antidote or treatment, and hospitals are unlikely to recognize or suspect Polonium at first because of how exotic it is. (Though in light of the publicity it has received fairly recently, they might suspect it more readily than before) How exotic? Well, to make some Polonium, you need to have a nuclear reactor. In fact, you need to have facilities specially dedicated to producing Polonium inside that nuclear reactor. There are only a few places on Earth capable of producing Polonium at all, and almost all are located in Russia. It's also [extremely easy to trace](https://en.wikipedia.org/wiki/Poisoning_of_Alexander_Litvinenko#Polonium_trails), to the extent you can identify specific people who have handled it. If you know what you're looking for, even minute trace amounts are detectable long after you've left the scene. # Ricin Ricin is the best candidate so far. It's almost perfect as a poison. It is relatively easy to produce (you could even prepare it in your home, though this is not recommended for obvious reasons), has no known antidote, and there is no reliable treatment whatsoever. The only black mark against it is the time before death. The [CDC says](http://www.cdc.gov/niosh/ershdb/EmergencyResponseCard_29750002.html) that: > > Gastrointestinal effects generally occur within 6 hours of ricin > exposure. Effects on the liver, central nervous system (CNS), kidneys, > and adrenal glands typically occur 2 to 5 days after exposure and > reflect ricin's cytotoxic effect. Patients/victims may be asymptomatic > prior to the occurrence of these cytotoxic physical findings. Death > may occur between 3 and 5 days after the initial exposure to ricin. > > > This is a lot better than botulinum and polonium, but still a little off from the mark. If you didn't have such a high onset of death requirement, this really would be the perfect poison for any job. # [VX](https://en.wikipedia.org/wiki/VX_(nerve_agent)) Although many people think VX is a "nerve gas", it isn't. It is a tasteless and odorless liquid almost exactly as a dense as water, and with the consistency of motor oil. It's more correctly referred to as a "nerve agent". The "gas" form of VX actually refers to distribution as an aerosol, or from evaporation when an area is bombarded with liquid VX. It has a high boiling point. ### Lethal Dose and Density Considerations In mice, the intravenous LD50 is 7μg/kg, and based on human subject research, 20μg/kg should be a reliable lethal dose. For a 100 kg human, this is 2mg of VX, or 2μl in volume. According to [this](http://www.mosquitoworld.net/mosquito-faqs/), mosquitos can carry between 0.001 to 0.01 ml of blood, which is slightly denser than water. As you can see, it's more than enough for this purpose. Note that most sources for LD50 of VX for humans refer to contact LD50, which is significantly higher. It also takes a lot longer to take effect. ### Time before death In general, inhalation or intravenous VX can reach peak toxicological effects within minutes. After this point, the time before death depends on the dosage. With a sufficiently high dose, death can occur within 10 minutes to a few hours. ### Survival Although antidotes to VX exist, intravenous VX works too quickly for antidotes to be useful, unless they are immediately available. However, as VX poisoning has identical symptoms and treatment to other nerve agents, including more commonly available insecticides, it isn't unknown in hospitals. Tests for nerve agents are standard when poison is suspected. ### Availability VX is considered a weapon of mass destruction, and is recognized as the single most potent chemical warfare agent ever produced. It is not easy to produce, especially in pure form, and many of its precursors are also illegal and controlled, though none require a nuclear reactor and a team of physicists. However, considering the thousands of tons of this substance that have been produced to date by governments and [subsequently destroyed](https://en.wikipedia.org/wiki/VX_(nerve_agent)#US_VX_stockpile_elimination), it isn't unlikely some of it has escaped into the black market. # Further Reading: 1. Molecules of Death, *Waring, Stenton, Mitchell* 2. Chemical Warfare Agents, *Romano, Lukey, Salem* 3. Chemical Warfare Agents, *Marrs, Maynard, Sidell* 4. [Death by Polonium-210](https://www.clintox.org/documents/WMDSIG/AACT-WMD-Death_Polonium.pdf) [Answer] If you have something the size of a mosquito, then you are, naturally, limited by the payload that a mosquito can carry. A mosquito has a total mass of roughly 1-2 milligrams. The median lethal dose (MLD) of Ricin, injected, to a human is 22 micrograms per kilogram of human. So, a lethal dose of Ricin for an average human would require 1.78 milligrams. Your electronic mosquito would need to be rather large to carry around this much. However, Ricin is FAR from the most lethal substance to humans. Reading a quick list online showed at least 7 compounds that are lethal in smaller doses than Ricin. At the very top of the list is Botulinum Toxin. Botulinum Toxin is the most spectacularly lethal neurotoxin we have ever encountered...it has an estimated Median Lethal Dose of merely 1.3-2.1 *nanograms* per kilogram. Mass of an average person is 62 kilograms, so a lethal dose of Botulinum Toxin is only 130.2 nanograms. Or, for more clarity, 0.0000001302 grams. This is certainly small enough to be delivered by a mosquito-sized deliver system, and could easily be delivered in a much higher dose. For a bit of clarification...median lethal dose represents the amount necessary to kill 50% of the test targets. So you are going to want to up the dosage of this toxin to make sure you get everyone...but since the amount delivered is measured in nanograms, this isn't a problem for your delivery method. The problem is that while botulinum toxin is spectacularly lethal, it doesn't do so quickly when administered in a 'lethal dose.' It takes several days before the symptoms become fatal, and there are effective anti-toxins against it. Polonium-210 is another option for you (It has a similar MLD), if you want to kill them with radiation poisoning instead of neurotoxin...but again, it's slow. Probably not within two days if you stick to the actual MLD levels It's simply a matter of volume...there are too many neural cells for a tiny amount of poison to tear up quickly. There is a way to speed things up, and that is to have your mosquito precision-target where it delivers the poison. Delivering the poison as close to the spinal cord and brainstem as possible. So if you want this to work quickly, you need to massively overdose them on it. So, how much could a mosquito deliver? A mosquito that eats until it is full can harvest 0.01 milliliters of water. As 1 milliliter of water weighs 1 gram, we can compute that a mosquito can carry an additional 0.01 grams of matter and still fly well. Remembering that the MLD of botulinum toxin is 130.2 nanograms, we can compute that a single mosquito could carry 7,680,915.5 times the MLD of botulinum toxin. That'll do it. Botulinum Toxin is definitely the way to go in this case. [Answer] # Liquid Antimatter injection You have electronic mosquitoes, and these mosquitoes can carry liquid antimatter. A 10 trillionth of a gram of positrons (anti-electron), has slightly more destructive power than a hand grenade, so if you inject liquid antimatter into the person you'd probably get a much larger explosion. Kill 100% of targets. Liquid antimatter can be suspended using maglev. Once the mosquitoes land on target, inject the positron(s) into them and watch them go kaboom. You never said I couldn't explode them (actually, you didn't say that it has to be poison either)... [Answer] **Botulinum neurotoxins.** The LD50 (dose that will kill 50% of exposed specimens) of some types [is 1.3–2.1 ng/kg](https://en.wikipedia.org/wiki/Botulinum_toxin). For an 80 kg human you need 104-168 nanograms, a new type only requires [2 nanograms to kill](https://www.newscientist.com/article/dn24398-new-botox-super-toxin-has-its-details-censored/). It's one of those [most poisonous substances known](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2856357/). The best part is that the mosquito can simply house some Clostridium bacteria in its "gut". With those bacteria, the mosquito can wait and [produce more botulinum](http://onlinelibrary.wiley.com/doi/10.1111/j.1471-4159.2006.03965.x/abstract) if it runs out. A strong dose will cause paralysis of the breathing muscles, leading to a relatively quick and subjectively terrifying death (and they're unable to scream). Smaller doses can be used to kill more slowly. Just make sure to get the correct type. Type A is used as the cosmetic procedure known as Botox. While and, as yet unnamed type, can kill with an injection of [2 billionths of a gram or inhalation of 13 billionths of a gram](https://www.newscientist.com/article/dn24398-new-botox-super-toxin-has-its-details-censored/). [Answer] ## Active agents instead of pre-made poisons Such a delivery method can be used to infect the host with various horrible diseases, designed to make them die in an arbitrary manner of your choice - in essence, instead of delivering a tiny amount of some toxin, you can deliver a virus or bacteria that will multiply and manufacture a large amount of it. The hard parts in weaponizing diseases seem to be (a) an efficient delivery vector, which in your case doesn't need to be included "in" the disease and (b) having the disease be not too deadly so it gets a chance to spread before the victim dies or gets isolated. In this scenario, it'll be enough to make a disease strain that is horrible at spreading and will multiply only in perfect conditions such as your bloodstream. [Answer] Perhaps I'm oversimplifying here, but why not have the mosquito as a simple air pump and just pull from the atmosphere and inject an air bubble? An air bubble in the body is called an *air embolism* and can have a huge variety of impacts, depending on where it ends up. This is probably something that the mosquito can target to get a specific effect - ranging from disorientation/ paralysis of legs right through to near instant death. <https://skeptics.stackexchange.com/questions/17194/can-an-air-bubble-in-a-syringe-kill-the-patient> has a very in depth explanation of how air can kill someone. In 1949 New Hampshire physician Hermann Sander ended the life of a terminal cancer patient by injecting her with 40 milliliters of air — four syringes of 10 milliliters each. (Source according to <http://www.straightdope.com/columns/read/2866/can-air-injected-into-the-bloodstream-really-kill-you>) [Answer] An interesting method of killing someone using a mosquito sized robot would be to inject liquid Hydrogen into their bloodstream. Once in the blood, 1 milligram of liquid Hydrogen would become a 25ml gas embolism. 5mg of liquid Hydrogen, injected into the right spot could render any number of effects, including death. This method is very similar to the air injection method, except the liquid hydrogen could be injected a whole lot faster by a mosquito robot, increasing the effectiveness of the embolism. SCIENCE FICTION ANSWER: Give the mosquito robot a coil of Monofilament (Monomolecular wire). Instead of a liquid poison. The robot would insert the monofilament into one of the targets veins and the blood flow would draw monofilament into the circulatory system. In a matter of minutes, it would slice through all of the curved blood vessels and internal organs, including the heart. Not a death I would wish on anyone. [Answer] Come up with a chemical catalyst that induces proteins to fall apart in shorter molecules. Just about everything critical in the body is protein based. Get only a tiny amount of such a catalyst in the blood-stream and the victim is guaranteed to be dead in a few hours. The neat thing about a catalyst is, that it isn't consumed in the reaction, so it just keeps flowing through the body with the blood and destroys protein left and right. And, unless the existence of such a weaponized catalyst is expected, nobody will have any clue what killed the victim. (A new Ebola strain, Marburg, flesh eating bacteria ? It's going to take a while to figure that out...) The remains of the victim will even be a major bio-hazard to any other form of life that has direct contact with it. The ambulance personnel that takes him to the hospital, the doctors and nurses, the coroner examining the remains... It more or less acts like Ebola, but is even more dangerous, because it infects others through any direct contact, not just transfer of bodily fluids. [Answer] [Chlorine Trifloride](https://en.wikipedia.org/wiki/Chlorine_trifluoride). Make your mosquito right, and you might get a flying bomb... > > Chlorine Trifloride is extremely reactive with most inorganic and organic materials, including glass and teflon, and will initiate the combustion of many otherwise non-flammable materials without any ignition source. These reactions are often violent, and in some cases explosive. > > > Vessels made from steel, copper or nickel resist the attack of the material due to formation of a thin layer of insoluble metal fluoride, but molybdenum, tungsten and titanium form volatile fluorides. > > > The ability to surpass the oxidizing ability of oxygen leads to extreme corrosivity against oxide-containing materials often thought as incombustible. Chlorine trifluoride and gases like it have been reported to ignite sand, asbestos, and other highly fire-retardant materials. Fire control/suppression is incapable of suppressing this oxidation.[14] The compound reacts violently with water-based suppressors, and oxidizes in the absence of atmospheric oxygen, rendering atmosphere-displacement suppressors such as CO2 and halon completely ineffective. It ignites glass on contact. > > > Exposure of larger amounts of chlorine trifluoride, as a liquid or as a gas, ignites tissue. The hydrolysis reaction with water is violent and exposure results in a thermal burn. The products of hydrolysis are mainly hydrofluoric acid and hydrochloric acid, usually released as steam or vapor due to the highly exothermic nature of the reaction. Hydrofluoric acid is corrosive to human tissue, is absorbed through skin, selectively attacks bone, interferes with nerve function, and causes often-fatal fluorine poisoning. Hydrochloric acid is secondary in its danger to living organisms, but is several times more corrosive to most inorganic materials than hydrofluoric acid. > > > [Answer] Georgi Markov was killed by bulgarian government agents using a weaponized umbrella. > > Agents of the Bulgarian secret police (Darzhavna Sigurnost; Bulgarian: Държавна сигурност, abbreviated ДС), assisted by the KGB, had previously made two failed attempts to kill Markov before a third attempt succeeded. On 7 September 1978 (the 67th birthday of Todor Zhivkov), Markov walked across Waterloo Bridge spanning the River Thames, and waited at a bus stop to take a bus to his job at the BBC. He felt a slight sharp pain, as a bug bite or sting, on the back of his right thigh. He looked behind him and saw a man picking up an umbrella off the ground. The man hurriedly crossed to the other side of the street and got in a taxi which then drove away. The event is recalled as the "Umbrella Murder" with the assassin claimed to be Francesco Gullino, codenamed "Piccadilly".[3] > > > When he arrived at work at the BBC World Service offices, Markov noticed a small red pimple had formed at the site of the sting he had felt earlier and the pain had not lessened or stopped. He told at least one of his colleagues at the BBC about this incident. That evening he developed a fever and was admitted to St James' Hospital in Balham, where he died four days later, on 11 September 1978, at the age of 49. The cause of death was poisoning from a ricin-filled pellet.[4][5][6] > > > The mechanism was a small pellet with holes, containing ricin that was projected via pneumatic means. So, here you have your killer mosquito. [Wikipedia article](https://en.wikipedia.org/wiki/Georgi_Markov) [Answer] ## **Burn them to death** A quick trip to the [Scoville Heat Scale](https://en.wikipedia.org/wiki/Scoville_scale#Chemicals) shows that there are some incredibly hot chemicals, chief of which is the [resiniferatoxin](https://en.wikipedia.org/wiki/Resiniferatoxin) rated at 16 billion Scoville heat units. The humble jalapeno is a mere 1000 to 4000 heat units. The LD50 oral dosage in rats for resiniferatoxin is [148mg/kg](https://www.fishersci.com/shop/msdsproxy?productName=AC328470010&productDescription=RESINIFERATOXIN%20(HIGH%20PU1MG&catNo=AC32847-0010%20&vendorId=VN00032119&storeId=10652) from this Materials Safety Data Sheet. (The MSDS doesn't list LD50 values for resiniferatoxin as an inhalant or by injection, so it's guess work on what those would do. Also, these values are higher than the [LD50 values](http://npic.orst.edu/factsheets/Capsaicintech.html) for oral capsaicin. Weird.) While these values don't come anywhere near the lethality of botulinum toxin, consider the effects of having pure chemical hellfire injected into your veins. This answer is more along the lines of "Holy \*\*\*\* that must hurt so bad! If you weren't dead, you wish that you were." [Answer] **Nanomachines** You've already got tiny insects as eyes and ears, why not even more tiny insects as assassins? The "mosquito" can land on someone, and then inject a swarm of nanobots that gather in sensitive areas to await the "kill" command being sent by their controller. Failing that, how about [Unobtanium](https://en.wikipedia.org/wiki/Unobtainium)? You never specified that it had to be a substance that exists in the real world, and unless you're trying to write a really true to life crime thriller, why would it need to? Just make something up, and pretend it always existed. Authors do this all the time. There's nothing to say that an alternate world with the technology to invent mosquito assassins doesn't also have the technology to invent or discover new poisons, and in fact it would be surprising if they didn't. [Answer] Technitium-99M I hope someone can double-check my calculations here. First, it's radioactivity: <http://www.iem-inc.com/information/tools/specific-activities> 5,200,000 Curies per gram. Based on some of the other answers above I'll figure a 1 milligram payload, thus 5,200 curies of Tc-99M Now, to convert that to a dose: <http://www.drugs.com/pro/technetium-tc-99m-pentetate.html> A 20 millicurie injection of Tc-99M gives about .6 rem. Thus our 1mg dose is 156,000 rem. A prompt radiation kill only needs about 5,000 rem, this means our material only needs to be 3% Tc-99M to meet your requirements--it can be mixed with something to make it more injectable. You could accomplish the same thing with Po-210 by using a larger dose (still well within the capacity of the e-mosquito) than was discussed above but it still has the problem of limited sources. Tc-99M, however, has many more sources due to the need for local production for medical procedures. [Answer] This is the worst acid thing known. it really does eat everything [Hydrofluoroantimonic acid](https://en.wikipedia.org/wiki/Fluoroantimonic_acid) Fluoroantimonic acid (systematically named fluoranium hexafluorostibanuide and fluoranium hexafluoridoantimonate(1−)) is an inorganic compound with the chemical formula H2FSbF6 (also written H2F[SbF6], 2HF·SbF5, or simply HF-SbF5). It is an ionic liquid created by reacting hydrogen fluoride (HF) with antimony pentafluoride (SbF5) in a stoichiometric ratio of 2:1. It is the strongest known superacid, which has been demonstrated to protonate even hydrocarbons to afford carbocations and H2.[1](https://en.wikipedia.org/wiki/Fluoroantimonic_acid) Similar acids can be created by using excess antimony pentafluoride. [Answer] The thing that makes today's mosquitos the most deadly animals is mentioned, but never extrapolated: disease. The 0.01ml (= 10E-8 m³)of mosquito payload would mean about 10E14 virus particles (each measuring 10E-23 m³) - this is slightly *above* the number of flu-virus particles found in people at the peak of a flu - could fit with some fluid surrounds to make them injectable. Viral Meningitis would fit the bill in terms of payload and rapid death, for more spectacular forms of death Ebola would be a go-to, but it would need to be modified to act faster to fit your bill. Note that with viral actors the damage done to the cells is the crippling feature of the disease (unlike some bacterial infections where a by-product of the bacterium may act as a poison), and this is only achievable by the virus particle infecting cells, so there is a lower bound to the reaction time. Still, many cells induce apoptosis (a sort of cellular suicide completed in less than 1 hour) as soon as viral infection is detected, on the sound evolutionary reasoning that the organism might survive if the cell is not enabling the virus to multiply; This will work in our favor here, as the viral load will be immense from the get-go. A mixture of viruses, some targeting the immune system itself, and some antigenes in the mix that nullify the immune system's first wave response of antibodies, would make that a wrap. ]

[Question] [ **Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). Closed 6 years ago. [Improve this question](/posts/69407/edit) Gentlemen, I am sure you all know why I have gathered you here today. As we all know, the Dark Lord who has appeared on the borders of our beloved realm of **Average Magical Medieval Setting** commands his legions of demons and trolls with an iron grip and threatens our very existence as a cruel feudal society based on slavery with nonsense such as "industrialization" and "human rights", but what truly makes him worse than the seasonal run-of-the-mill insane necromancers is his recently patented defense spell. For those of you who didn't get the memo, this incredibly slightly-stronger-than-average man is the inventor of a passive spell that is independent from his senses and, in event of imminent death or damage to his body by physical means, stops time from his perspective and warns him of the danger that set it off, allowing him to move in a radius of 10 meters and manipulate anything he can touch. As long as he does not exit the aforementioned radius, time will stay still. We have however recently discovered that the spell has a downtime of two seconds after every activation. He has so far survived magical bullets travelling faster than the speed of sound, explosions set off behind a wall of his room while he was sleeping (I've heard he spent about five "hours" in stopped time before waking up and realizing something was wrong), ghosts that could punch very hard, Endless Pits of Death (did I mention that during time-stop he is not affected by The Invisible Imps That Push Everything Down, and he can thus float out of the way of danger?), and even our polymorphing assassins got squashed when they tried to inoculate him with lethal poison while disguised as mosquitos. And of course, stopping time has been trademarked as a vital part of his spell under planar copyright laws so we can't just send a couple of warriors armed with it against him. So here we are. **How do we stop him before everything we know and love is irredeemably made better for everyone else but us?** Yes, yes Arnold, I know what you're about to say, but not everybody can get mad glimpses of the future like you, and as I already told you earlier we don't even know what germ theory is, let alone atoms and nuclear reactions. All we can do is try and beat him only using something that makes sense for our setting. [Answer] Oh, the possibilities... I'm assuming that even in 'stopped time' our villain still has a metabolism to be able to do things. ## Poison This one is ideal even for non-magical folks. It comes in a wide variety of convenient packages, and can be easily administered in a way that is not immediately lethal - and should thus bypass the "imminent death" trigger - but also irreversible. ## An Oubliette Exactly how you arrange this one is up to you; all you need to do is ensure that Our Bad Guy ends up in a space that he cannot remove himself from. A great option might be to lure him into a room with only a single exit, and seal the exit with a heavy block, then just...leave him to it. Death will not be imminent until several hours or days after he is trapped (depending on whether the room is airtight), thus will not trigger the annoying spell until it is too late. ## Garotting If you can get your hands on him, simply bind his hands with chains he cannot easily break, and bind his throat with a tight wire. The spell will trigger, yes, but he'll have at most a few minutes to try to get out of it. With bound hands. (Hopefully the spell will stop once he's gone cold). ## Drop a 21-meter wide rock on his head That 10-metre radius limitation is a key vulnerability. If you can get him out on a rock surface (so he can't dig) and drop a rock on his head that's too wide for him to dodge (I'm assuming, of course, that you have standard Invisible-Imps-That-Push-Everything-Down-Cancelling Spells), he can stop time as long as he likes, he's got nowhere to go. He can stay there and die of thirst/starvation/old age. [Answer] Gentlemen, I propose the following way of getting rid of this pest: His ability will only trigger on imminent death. This indicates we can tie him up with a rope! Then we can just put him in a cell and watch him slowly die of dehydration. Easy, relatively fast, no blood and no pesky time-control. That will teach these new-age-mages with their fancy *passive spells* a lesson! If you want it to be quicker, dear Lord, you have to use your mind-control ability of really-really-bad-music and drive him insane. I a sure you can do this! Maybe he will kill himself. Again I recommend tying him up first and making sure he can't escape. Ropes make everything so much easier. I love ropes! Luring him into one of your dungeons by means of your umeasurable wealth might be an option too. Just seal the entrance once he is in and again let him die a slow and painful death, alone in the darkness without his allies. Downside: no ropes... Kind regards Your cordmaker [Answer] ## Two Bombs So this assumes he knows no other magic (dang those other patents!) Once we figured out 1 doesn't work, but it has a 2 second recharge time, we just set 2 bombs. The first goes off and triggers his little time stop. This smart **Dark lord**, understanding that the superheated and the concussion blast of air are what would kill him (and a couple of those pesky pieces of shrapnel), uses his stopped time to push away those molecules of air and shrapnel that would hit him and steps through the 10 m radius right where this little vacuum pocket he's made himself. Satisfied, he smiles to himself before being concussed, eviscerated, and evaporated by the explosion that happens 1/2 second later. Of course, to ensure he dies, they made this bomb significantly bigger so that its concussion blast definitely kills him because they don't want him to be simply thrown back say into a wall that's far enough away that it triggers another time stop so he can keep himself from smashing into it. [Answer] **A Pair of Snipers** With knowledge of the two second cooldown period a pair of crossbowmen can situate themselves in good sniping positions. First crossbowman fires a bolt, which gets frozen in time. The Dark Lord, savvy to the nature of crossbow bolts and knowing they take longer than two seconds to reload, steps aside and causes the bolt to miss. But the second crossbowman, with a keen eye on the look out for the Dark Lord suddenly teleporting out of the way from his perspective, readies his own shot. The second the Dark Lord does his time skip a second shot is fired and hits it's mark before the two second period is up. It doesn't have to be crossbows of course, but the idea is the same. Two assassins. One to trigger the spell and another waiting to take the Dark Lord out once the spell ends. **Trap Him** Wait until the Dark Lord is smelly and in need of a nice, warm bath. Once he has submerged himself use a magical assassin to transmute his bath water into iron. It shouldn't trigger the spell because he is in no immediate danger, but it will completely immobilize him and leave him at your mercy. You can then make him your prisoner and use him as a nice yard decoration. Certainly quite the conversational piece at your next party. Just as before you don't need to use this exact plan. Simply find a way to capture him that won't cause any harm to his person and the spell shouldn't trigger. Once he's captured you can execute him at your leisure. After all, if he stops time but can't move he'll just be trapped in place until he dies of dehydration. [Answer] ## Blow his legs off If his passive spell only activates on imminent death, then make sure your magical explosions aren't big enough to kill him in one shot. Stopping time is a pretty useless ability if you're on the ground, bleeding to death. If his ability also triggers on things that indirectly cause imminent death, it should still be possible by calling your most able earth-mages to create a 20-diameter stone dome around him when he's walking outside. That way he can't mess with the forming of the walls, as walking out of his 10 meter magic sphere would break the spell. When you've caught him, you simply wait until he starves to death. Or incapacitate him in some other way. Really anything he can't escape from no matter how much time in the world he has. [Answer] **Surround Him** Summon a 25 meter diameter dome of rock around him. Make it mostly airtight, and at least one meter thick. Leave a small hole in the top. Now through that hole, fill it with poison gas, alchemist's fire, etc. Or just pump the air out. If he tries to leave, he'll have two seconds of whatever you are using, filling the dome. If he has some way to break through the rock, surround the first dome with a second one, and fill the space between them with your poison/fire/etc. Alternately, just surround him on all sides with the poison gas. If he tries to leave, all he gets is a smaller space of clean air. [Answer] **Arrows, lots of 'em** It's quite simple really. He can move in a 10 meter radius if he's about to be harmed. If you deploy a squad of highly trained longbowmen, composed of 30 men, in a square formation with, each row with 6 men, each 0.5 meter apart, then he can't escape. He can run go 10 meters in each direction, which means he'll escape the 5th man of either side he runs to, barely....but then he's hit by the 6th longbowman. All it takes is a medieval mathmatician to come up with this idea, no need for magic bullets. [Answer] Well, the easiest way would be to **convince/force him to kill himself**, since the time warp won't stop him. Therefore, poison him with something that will make him suicidal within a day or two. > > in event of imminent death or damage to his body by physical means > > > Well, there's a loophole if I ever saw one. In fact, in a magical universe, this should be downright easy to work around. We just have to **use magic to alter him or his surroundings** so that he will be helpless to save himself regardless of how much time he has. * Bait him onto a portal to a dimension where there is no physical existence. Now nothing triggers the defense and he can die as easily as anything else there * Zap him with a magical death ray (pure magic, no magically-enhanced regular projectiles) * Polymorph him into a slug when he's on a salt flat * Polymorph him into a shark (while he's on dry land) Now, assuming you close that loophole, your next best loophole is that he can't stop the defense except by leaving leaving the bubble. This is perfect, since it allows you to **force him to move somewhere lethal**. * Put lethal traps or assassins outside the radius of his defense, and then trigger his defense with something else. Kill him when he leaves the bubble. Finally, the true weakness is the time-stopping itself. You just have to go *backwards* in time to kill him. ***His defense will render him completely blind to an attack from the future***, since the time-stopping will prevent the attack from even *existing* until his shield disengages. (The simplest would be a magical bomb that detonates backwards in time.) [Answer] Don't listen to these **evil** counselors of yours. Poisoning? Infectious diseases? Maliciously well-thought traps? **A big rock**? Leave those for the assassins guild! We are men of honor, and with honor we will fight! Let us assemble the biggest army that we can. The Armies Of The World™ will surely be his bane! He can't fight an army! Battlefields are huge. If he moves away 10 meters... He'll still be in a battlefield. 10 more meters? Still there! I'm sure *someone* in our ranks will be able to finish him off in 2 whole seconds. Probably that vagrant swordsman that [redeemed himself from some of his old doings](http://tvtropes.org/pmwiki/pmwiki.php/Main/RedemptionQuest) and is now flirting with the princess. That guy is **manly**. [Answer] The easiest way to negate incredibly powerful and wide-ranging magical defenses is to negate magic (hopefully in a limited time/space, not permanently everywhere). Simply™ coerce the Dark Lord into the zone of antimagic (or have some sort of antimagic "bomb" that releases it's field upon "detonation"). After that, use a knife, a spear, a particularly heavy frying pan - the possibilities are endless. I'll leave it as an exercise for the serious student as to how to create such an antimagic field. I never claimed to be an experimental thaumatologist, merely a theoretical one. If you need me, I'll be in my ivory tower napping... er... researching. [Answer] I recommend the [Zerg Rush](http://tvtropes.org/pmwiki/pmwiki.php/Main/ZergRush), which I discovered the other day while researching [Google Search easter eggs](https://www.google.com/?as_qdr=all#safe=strict&as_qdr=all&q=zerg%20rush). Essentially, surround him with many, many, many opponents. He can freeze time, but unless he wants to stick around in a crowded (but frozen!) throne room or battlefield for the rest of his "time" in his little bubble, he'll have to attempt to fight his way out eventually. Just make sure you bring more people than can fill a 10m bubble, and you should be able to rush him effectively during his two second break. [Answer] Oh dear. These are all too complicated and reek of irreligiousness. Everyone knows that for evil, the only sure cure is the purifying fire. Set fire to the entire area around where he is. A 10m time stop ability isn't much use in the heart of a half mile wide incandescent circular forest fire centred on him. [Answer] The core flaw is the downtime and the radius. Step one, have a huge hidden explosive somewhere that he is going to be. It needs to be powerful enough to kill him regardless of where he is in the area of effect of the spell. Step two is to trigger the time stop using something like the magical bullets when he is in the blast radius. Step three is to trigger the blast during those crucial two seconds. A more general solution is anything that will kill him during the two second window or anything that will kill everything within the area of effect no matter what they do. Remember, ["As the size of an explosion increases, the number of situations it is incapable of solving approaches zero."](http://www.giantitp.com/comics/oots0696.html) [Answer] # An infectious disease Almost all diseases have incubation periods long enough that by the time "imminent death or damage to his body by physical means" is satisfied, the only warning he'd get would be "you have measles". Not much he can do about that, time stop or no. One of those polymorphing assassins of yours just has to get close enough to sneeze on him, smear a bit of infectious goop on his doorknob, or put some contagious fleas on his bed. Getting someone sick is not exactly a tall order for an intelligent, determined rodent. [Answer] This guy is basically a one-trick pony and this should not be too difficult. Here are some other more or less conventional means of defeating him. **Disempowerment** Stopping time is a pretty major magic, however it is primarily protective power and not an army-crushing power (potentially yes but see below). So for projecting influence, this guy still needs intermediaries, i.e. other people (armies, agents, servants,...). While it may be difficult to kill their Dark Lord, killing his servants should be fairly standard business, particularly because he cannot be everywhere and most leaders tend to stay out of harm (if he does not, combine with one of the solutions below). Without means of projecting influence, he is... well... nobody really. If not sure how to kill his armies, raise a separate question. **No Harm / Capture policy** The guy is probably a killer in personal combat because as damage approaches, he stops time and can kill anybody in the immediate surroundings (that can be a whole lot of people). So the key is not to damage him. Train your soldiers that if they get a whiff of him on the battlefield (I suppose he must be distinguished from his regular troopers so that commanders do not try to command him around), *he is to come to no harm at all*. Thus you will turn the battle to a regular battle and the key is just to defeat his army (if you don't know how, raise a separate question). The one guy you cannot afford to harm should not be a battle-turning factor, furthermore you should have some special forces trained and equipped to handled him (heavy soldiers that will form up a shield wall around him; riders with nets etc.) so you can capture him and dispose of him in a manner that does not trigger his trick (dehydration, poison, suffocation, disease,...). **Full area saturation** My favourite solution, derived from the 21 meter rock, as it should be the easiest to achieve. Your task here is to simply overwhelm him and overload his power. This can be achieved either by the super-large rock which he cannot avoid even if the trigger gets... triggered, or by anything else similar to it. My first choice would be probably a few cohorts of longbowmen trained to fire in coordinated salvos that will kill anything in rather wide area, following each other very quickly, i.e. your guy is likely to survive the first, but the second, coming immediately afterwards, is likely to get him. If he is clever and say, builds some sort of shield (e.g. from the bodies of his henchmen), you have not saturated the area enough and you need to you more firepowah - batteries of cannon or squads of mages with AoE spells,... again basically anything saturating the wide area of his teleport as well as vaporising whatever protection he can build around himself. [Answer] The issue with stopping time is you then need to restart it. Watch the Twilight Zone episode where the guy finds a clock that can stop time, but while using it to rob a bank vault it breaks leaving him forever stranded in a frozen world. (Check Wikipedia for "A Kind of Stopwatch".) So the solution is simple. Foreshadow this two-world universe: one of motion and one of stillness. And then have the one thing he so desperately needs to get out of the frozen world be somehow broken or disrupted by the brave hero. Maybe the two of them are forever stuck in the frozen world. Maybe a whole away-team or an army get stuck in there. You then have reduced the problem to a battle where time cannot be stopped again. Unless, of course, it could still be, and then you could go inception style and stop time within time, and so on. [Answer] Teleport him into the ocean several miles below the surface. Obviously this depends on if he can escape from targeted spells. If he can, teleport the entire sphere he can move in into the ocean. Just make sure there are no merfolk around the target to accidentally save him. [Answer] Does he spend any time in a castle, tower, or similar high structure with lots of potential energy? Preferably in the upper flors, or at least middle floors. Target the structure. Standard one-shot covert demolition job. Magical explosives if physical explosives are not advanced enough. Even if the time-stop is triggered a couple seconds before the bomb goes off, it's far enough out of his sphere of influence. Nothing he could do at that point. Once the building he's in starts falling, there's not much he can do either, unless he's next to a window. Bonus hilarity points if the spell triggers when he's free-falling, and he immediately splatters into the lower limits of his sphere of influence, or into the falling floor that just froze in place. But I guess we'll never know from the rubble mess. ]

[Question] [ In small towns, people often say that everyone knows everyone. While probably not literally true (for all but the smallest towns), the rate of interaction between members of the town is still high enough to create this perception. The two main variables I can think of are the population density of the town and the rate of activity in that town. A small island with people living close together and working close together (say, near shore subsistence fishing) is more likely to produce this sensation than say a small frontier town whose principle industry is cattle. For the sake of keeping things simple, let's say that our small town has a population density of 100 people per square mile (a bit more than half as dense as anchorage) and the rate of activity is moderate. People see each other when they go out to dinner, to the market, or for communal events like sports but not necessarily every day. How many people can our town get before the sense of "everyone knows everyone" is lost? [Answer] The number you are looking for is [Dunbar's Number](https://en.wikipedia.org/wiki/Dunbar%27s_number). It is well-known for most primates, but only approximately for humans (between 150 and 250). Humans of course have prodigious memory, and might be able to memorize the names and faces of far more than that (probably into the low thousands). But to actually *know* someone in a meaningful way, this is the Dunbar number. [Answer] ## The number you are looking for is not Dunbar's Number Dunbar's number is about how many relationships you can maintain, but does not directly dictate the "sense" of knowing everyone. Another relevant figure is that the average person can recognize 5000 people's faces; so, as long as you recognize everyone you encounter, and know enough of them to feel compelled to engage with someone everywhere you go, then the "sense" of knowing everyone is preserved. This means that the actual size you are looking for is going to be somewhere between 150-5000 (if not higher), but where it that range it falls will depend a lot on various practical and cultural factors. First of all, how many people you can know is not so much how many people there are, but how many people you must interact with. Even in a small town, most people only know their immediate neighbors plus people who they share a joint activity with. The key here is the joint activity. Generally speaking, the 4 joint activities that bind small towns are a single school, a single church, a single industry, and/or a single popular recreation. If you have all 4, then you will generally be able to connect with enough people from at least 1 of these places to always feel like you know someone everywhere you go. **Schools:** For a school to really create this effect, it is best to have a 1 class per grade structure which maxes at about 30 students per grade level. Since ~18% of the World's population are school aged children, and they can be divided into 12 Grade Levels. This means that each grade represents about 1.5% of your total population; so, a single class/grade school system can support a total population of about 2000 people. This would guarantee that you would know everyone in your own generation, and probably most of the children and parents of children in your children's generations. While this is not enough to actually know everyone in town, people tend to congregate in places that are popular within their own generation; so, if everyone in the same high school class used to go to the same diner as kids, then as adults, they will likely continue to go there and continue to run into the same people over and over again strengthening the sense that they know everyone. **Churches:** Churches are generally better than schools at uniting people between different generations and backgrounds than jobs or schools, but they tend to make who you connect with much more optional. As such, you tend to see that churches with congregations bigger than Dunbar's Number do often form many smaller communities of acquaintances rather than a single unified church community. So, a church will generally not help you know everyone well in a larger town better, it can help connect you with generations of people you would otherwise not know. If a church is the only unifying factor your town has, then your limit may in fact be closer to Dunbar's Number, but when paired with other unifying factors, their ability to form cross generational relationships may make you feel more like you know everyone, because you will internalize that you know people outside of your inner circle. **Industries:** Like churches, these can do a good job of bringing together on the scale of Dunbar's Number before some of the people you share a work area with are just strangers to you. However, unlike a church, there is not as big of a spread of demographics since you will only be working with people of working age. This can leave bigger gaps in who you do not know, but also serve more as a linchpin to become familiar with more people indirectly. **Common Recreation:** The fewer popular recreations there are in an area, the more likely you are to have a shared interest with someone who is otherwise a stranger. Let's take American football for example. In many small American towns you do not need to really know someone to start talking to them about the the local football team. One of the biggest elements of feeling like you know everyone is having a common language for breaking the ice when you do encounter someone new (or who you only know by face), and common recreation is great for that. So, sit down next to a stranger and they lean over and ask if you saw the game last weekend, you answer "yes", and you start to talk about it. You don't really know that person but you maintain the feeling that you kinda do because you have a shared experience to discuss. This leads into the final key to this question which is how people process the sense of knowing everyone. Human nature works on the pieces of information we choose to process and not the information we choose to ignore; so, you only need to know 1 person wherever you go, and not spot too many people you do not recognize at all to feel like you "know everyone". So, if every time I go somewhere and there are 20 familiar faces, a couple of total strangers, and just 1-2 people I actually know on a personal level, this is good enough to maintain the sense of knowing everyone. The real wild card here is population density though. 100/sqmi is a very low density. There will not be enough people in small enough of an area for you to want to be regularly going places you might meet people; so, out of a town of 2000, most people will stick to smaller sub communities and seem like random strangers on the rare occasion you do see them out in the world, but if you were to cram 2000 people into small town center, it is much more likely that you will recognize most of those 2000 people. [Answer] # "Everyone knows everyone" can be used colloquially in a less strict definition. The concept that "everyone knows everyone" extends to towns larger than hundreds or even thousands. You don't need to know the entire population personally to have this feeling, you just need to be able to find multiple mutual acquaintance between any two people, and connect them. "Oh your bosses niece goes to school with my daughter". "Oh wow. And your girlfriend went to the same raves as my coworker". "And we share the same therapist!" My town (Adelaide Australia) has a population just over a million, and the feeling that "everyone knows everyone" is very much part of the culture despite "knowing a million people" being ludicrous. It's a normal experience to tell a story about one acquaintance to another and have them recognise the person. When something newsworthy happens (eg fatal car crash) - you will know multiple people who knew the victim personally. Maths backs this up. At any one time I was at high school with 1000 people, over 12 years I crossed paths with about 2000 people from school and high school. Another 500 from years of church and youth groups, and another 300 from hobbies and recreational activities, and another 200 from different workplaces. Lets assume I got acquainted with 50% of them. That's ~1500 people I know. If you know 1500 people too, in a city of 2.25million you can expect to have a mutual acquaintance. Shrink the population a bit, and for populations of high hundred thousands approaching a million, you'll have multiple connections to almost every person in the city. [Answer] **In a region where people don't move, a couple thousand** If we define "everyone knows everyone" as "you recognize everyone you meet and know a fact about them" then a town of a couple thousand people is gonna be your limit. I'm talking about a medieval/ancient town, where 95% of people farm or do The One Thing Your Town Does. In the modern world it's a bit harder because of how much people can move around. At that size, "you're the blacksmith's son" or "you're Gertrude's mother" is something you could say to everybody. Dunbar's number states that a person can know 150-250 people "well." Part of "knowing someone well" is knowing things about them, like who their relatives are. In a setting where there are relatively few immigrants (meaning people from outside your town/village/county, not necessarily from-a-different-country foreigners) and few people move away, it's not at all impractical for the 200ish people you know well's immediate family to comprise the rest of your small village! As an anecdotal example, I went to a military college. You couldn't leave often, everyone lived in the same 3 barracks, and the campus itself was fairly small. Total student body was about 1400, divided into 9 separate companies made up of members of every year. After my first year I knew every person there by sight and company, and the vast majority (excluding only the freshmen first semester, who it was beneath a "real" cadet's dignity to pay much attention to) by name. So throughout my cadetship I knew more than 2,000 other cadets. It's not a perfect example because obviously they weren't my total sphere, as I still knew my hometown friends, family in other areas, and so on. But likewise the turnover (2-300 graduates a year, 400+ new people every year) is much higher normal population turnover. But I think it's worthwhile to note that once you're stuck with the same faces and see them every day, it's not *that* hard to "know everyone." As another anecdotal example, I grew up in a county of about 5,000 people. While I didn't know everyone by name, I had to have at least 3 conversations every time I went to the grocery store, had not polity nod/say hello to half a dozen additional acquaintances, and could always tell when someone "wasn't from 'round here." There the population was more spread out, not everybody did similar jobs/went to the same places, and was much larger than my college. But because I lived there longer and the low turnover rate of people moving into the area i could still tell who wasn't from my county, even if I couldn't name every person I saw who was. [Answer] In terms of "what size of a community can be maintained without external authority", this appears to be a "few hundred". In Evans, Susan Toby. *Ancient Mexico And Central America*. pp. 26-27: > > Furthermore, the maximum number of people with whom we can develop workable relations of trust, regulated face-to-face interaction and the presence of a mutually respected leader, during any time, is several hundred people. > > > In particular since knowing everybody else enough to trust them is used as a criterion for being able to maintain the community, this would also correspond to the size of your hypothetical village. The reference therein contains also interesting discussion on community size. In particular how conflicts get regulated depending on the size of the community. [Answer] Question is how many people to have a sense of knowing everyone which is not the same as the topic question of recognizing everyone- the answer could be 1 million or more. If I can see 100 people per day over and over then I think I know everyone- your brain can not conceive of the people you are missing. Slums and building projects (in the old days) have the sense of knowing everyone. The factors determining it are population/commercial density, sociability/visibility and mobility. If everyone walks then you need a higher density of people, if people drive but not too fast then lower density is ok. People need to be able be seen- they work in small operations or on the street. ]

[Question] [ Earth is setting up mining colonies on [Tau Ceti e](http://en.wikipedia.org/wiki/Tau_Ceti_e). But how can they justify the [enormous cost](https://worldbuilding.stackexchange.com/questions/15140/suspended-animation-vs-regular-animation-aboard-a-spaceship) of sending people there? ...Because during the initial exploratory missions, it was discovered that in addition to being human-habitable, the geology of TCe is just *filthy* with some natural resource(s), which are very scarce, very valuable, and most of all, very useful back on Earth. **What are those resources?** For example, some [science fiction works](http://www.imdb.com/title/tt1182345/) revolve around mining the moon for helium-3. Is this a good enough resource to go to TCe for? What about other rare elemental isotopes? Some notes: * No unobtainium. I'm looking for some real-life ore or compound. **Edit:** Creative biological resources are okay, even if they currently do not exist. But if you're going for elements, try to stick to what we know exists. * Implausibly large deposits of the resource are okay, i.e., I'm not so interested in the geological/biological processes that may account for how the resource got there; I'm more interested in the fact that there is *a lot of it*, and that there is not much of it on Earth. * A round trip to Tau Ceti e would take about 30 years (from someone on Earth's frame of reference). It is also very expensive. Earth government can provide a lot of cheap labor, though, and the value of the resource(s) more than make up for the cost. [Answer] **Antimatter**. It's [insanely expensive](http://en.wikipedia.org/wiki/Antimatter#Cost) to produce artificially, with estimates of up to $62.5 trillion per gram of antihydrogen. Naturally occurring antimatter in any decent quantity would be beyond lucrative - it would also provide whoever controlled it with a nearly unbeatable energy and weapon edge. However, it couldn't be laced into the geology of the planet, it would need to be somewhere in space. Probably the most likely source (and I use likely in a very loose sense) would be the remnants of an antimatter solar system - for example, a fragment of a fragment of an anti-matter asteroid belt that traveled through space, has been captured by Tau Ceti's gravity and is now in an eccentric orbit. [Answer] **Alien Life (and their byproducts)** You can't really mine it, but the presence of alien life would be an incredibly compelling reason to send people to Tau Ceti. It's likely evolved in completely different ways than life on Earth has. Considering that Earth-life has created many substances that we can't reproduce in a lab, it's entirely feasible that Tau Ceti has got some creatures producing incredibly valuable materials. Perhaps there are giant spider-like creatures spinning house sized webs of materials stronger even than what Earth-spiders can weave. Perhaps some large herbivores grow thick carbon plates that are fantastic for space ship armor. Perhaps Tau Ceti is populated by giant worms who produce a substance that enables people to pilot their ship through extra-dimensional spaces, making FTL a reality while also letting them see the future. If any of these things are produced only on Tau Ceti, but not on Earth, sending a crew to harvest them could be hugely worth while. [Answer] > > "Space," it says, "is big. Really big. You just won't believe how > vastly, hugely, mindbogglingly big it is. I mean, you may think it's a > long way down the road to the chemist's, but that's just peanuts to > space, listen..." > > > -- A quote from **The Hitchhiker's Guide to the Galaxy**, Douglas Adams Honestly, there's not much the natural world could offer that would make such a trip worthwhile. Some estimate that it would take [$ 174 Trillion and 40 years to create and fuel an unmanned, one-way, fly-by type interstellar voyage](http://www.centauri-dreams.org/?p=31774). From this number, it is not unreasonable to assume a manned mission that stops at its destination will be significantly (10x - 100x) more difficult (I estimate it at $3,480 Trillion). Any natural element, compound, or other natural resource could be had **far** more cheaply from sources in our solar system. As I see it, there are only three possibilities and each of these is highly unlikely (which is why they would be potentially so valuable). Basically we're need something worth more than the estimated cost of **$3,480 Trillion** that we cannot find in our Solar System and cannot make ourselves. **1. Alien Artifacts/Technology** If aliens left clues that a treasure trove of advanced technology were there or sent signals that we should come visit, this might make a economic, military, or even a scientific visit practical. The return on the investment might be very well be worth our while. Alternatively, a visit to a planet with aliens might similarly be worth the trip, but you'll have to think this through very carefully. What could they offer to make it worth our while that we could not trade via distant communications? Most science, math, music, philosophy, etc. can easily be transmitted. The value of Paintings, sculpture, etc. couldn't justify the tremendous expense of a trip. Materials and building techniques could be transmitted via building plans by long-distance communications. How about a planet with a [Stargate](http://en.wikipedia.org/wiki/Stargate_%28device%29) on it? Active Stargate  **2. Survival of the Species** Ultimately, *ALL* life on Earth will be exterminated. In order to survive, humans and/or our descendents must colonize space and other star systems. The smartest thing we could be doing *as a species* is to build space colonies. Unfortunately, only a sort of benevolent dictator or other such long-term thinking government would be capable of diverting resources for such a venture, unless the species were faced with imminent (10s or 100s of year) extinction. **3. [Exotic Matter](http://en.wikipedia.org/wiki/Exotic_matter)** Exotic particles and matter have been postulated many times. Many of these are not explicitly excluded by modern physics but neither have we seen evidence of them. Some ideas include 1. [Primordial black holes](http://en.wikipedia.org/wiki/Primordial_black_hole) - the potential for cheap, "clean", unlimited energy production 2. [Magnetic monopoles](http://en.wikipedia.org/wiki/Magnetic_monopole) - I don't know but I think the concept is cool ;) 3. [Strange matter](http://en.wikipedia.org/wiki/Strange_matter) - the potential for cheap, "clean", unlimited energy production 4. A source of [Tachyons](http://en.wikipedia.org/wiki/Tachyon) - potential clues for FTL communications and travel 5. [Negative matter](http://en.wikipedia.org/wiki/Exotic_matter#Negative_mass) - would (theoretically) enable us to build permanent stable wormholes - definitely worth the trip. The key here is that we could do fantastic things with these but we simply don't see any in our neighborhood. [Answer] On TCe a very interesting plant was discovered. It had feathery leaves that were extremely strong, pitchblack and glossy, and while flexible they could not be cut by the probe's tools. It turned out that the plant's leaves were composed mostly of very long carbon nanotubes. All efforts to cultivate the plant on earth or in a space station have failed, so it was decided to create the colony, which after a few years had a space elevator set up and working Soon after, the first cargo ships started sending back huge harvests, enabling Earth to build its own array of space elevators. [Answer] The real-world cost of interstellar travel is so high that without a real game changer there is nothing worth the cost. If you have a device to allow cheap travel, just make it cheap enough to satisfy the plot. Someone suggested plutonium: but where does it come from? The stuff decays, so there won’t be any more there than here. And even if present, it’s still cheaper to make it via alchemy than to ship it interstallar distances. Helium 3: why would it be easier to get there than here? Skim Jupiter or any old comet ice. As for its value, if you can travel between stars, you're already well beyond needing it. Water/ice: [seriously?](https://en.wikipedia.org/wiki/The_Ice_Pirates) It’s everywhere including icy moons and billions of comets. It would be *orders of magnitude* cheaper to synthesize using hydrogen and oxygen from rocks. Soil: see [*Farmer in the Sky*](https://en.wikipedia.org/wiki/Farmer_in_the_Sky). Even Heinlein knew that shipping soil *within the solar system* was not practical. Just take a small amount of culture and grind up the local rock. Whatever goods you are shipping, remember that shipping time is measured in centuries. No chemical or passing taste will remain valuable for that long. You can ship *information* at light speed, and in the information age we understand that this carries value. But what is so interesting there that studying it becomes a valuable industry? Any substance can be made from atoms and even factoring reasearch and development to figure out how to make that stuff, it’s not worth shipping. Atoms themselves? We know about all the elements and until Mercury is strip-mined out of existence there is no need to find heavy elements elsewhere at higher cost. In short, there is nothing that’s not in our solar system that we expect to find in another. The antimatter idea from another comment is getting somewhere: *energy* on a scale that makes interstellar travel worthwhile. More generally, something that enables more-practical travel, but that’s getting into [*unobtanium* (mineral MacGuffin, spice of life)](https://allthetropes.org/wiki/Unobtainium) territory. A bank of bulk antimatter begs the question of where it came from (a lost civilization or gift for emerging spacefaring civilizations) and if you go that route it might as well be antigravity goo, space warping marbles, or prefab stasis boxes. At least antimatter itself is a real thing. To reiterate, for any normal material there is just **no way**. If you adjust the expense of interstellar travel via cheap energy or hyperspace or somesuch, then it’s a non-question since you can adjust it to fit the plot. Any invented space travel trope can also have a corresponding material needed for that thing: so mine dilithium crystals for your warp drive, or whatever. [Answer] The product of immobile alien technology, limited nanogoop etc: The first scouts found projections from an ancient deeply buried alien artifact (hundreds of miles down)that readily produced nanogoop. It couldn't self replicate but it could do almost anything else imaginable with nanotech and gradually degraded with use. Reverse aging? no problem! Heal any wound or make any physical alteration to a person? easy! Build any devices not associated with reproducing nanotech? done in a flash! Indeed it's hypothesized that the aliens didn't want any risk of a grey goo scenario no matter what any of the more foolish members of their society might try so the nanotech is quite thoroughly proofed against being used for self replication by any means but otherwise can be used for almost anything. On the planet it's cheaply available to all and greatly eases the initial groups building their communities. When news arrived back in the solar system that the literal fountain of youth had been discovered: photos of the now restored older members of the initial scouting party became the top news story on earth for months. Every aging billionaire, every geriatric politician wants just a gram or 2 of this stuff to regain their youth. It's worth billions per ounce. And so another expedition is funded with the goal of returning with many tonnes of the material. [Answer] If you'd prefer a simple solution, let's just look at the rarity of elements in the [Earth's crust](http://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust). We find Iridium, Rhodium and Osmium down at the bottom of the list. This is overall abundance. Osmium has various stable isotopes of varying abundance. Note that the overall abundance of Osmium is much higher than in the Earth's crust. There is no reason why you might not be able to mine thousands of tons of the stuff from the right source. So what you then need is a reason why Osmium would be needed in large quantities. eharper256 mentioned superconductors. Currently, the best superconductors that we know about (in terms of how warm they can be and still be superconducting) still need to be very cold (-140 °C is the current highest). These [high temperature superconductors](http://en.wikipedia.org/wiki/High-temperature_superconductivity) are interesting because: * We still have an incomplete understanding of how they work * We do know that complex crystal structures involving rare earth doped ceramics are our best so far. * This gives scope for requiring just about any element as essential to a future industrial product. * Having a material that is superconducting at (or near) room temperature would be a civilization transforming technology. Of course, you can come up with countless other technologies that might require a specific element, or perhaps isotope. [Answer] Well, I'm assuming we're in a time when space travel and escaping a planet's gravity "ain't no thing" anymore and traveling such a long distance is similarly much easier than it is now. *So what resources are valuable?* **Precious Gems** - NOT needed; bringing heaploads of them back to our solar system will only devalue them until they're not valuable anymore. If everyone was covered in sapphire, and the houses are made out of it, it's really not going to be valuable. **Water/Ice** - If it's now easy to lift this from an Earth-like planet, and ship it to our other colonies, this would be helpful not just for consumption, but for their *attempts* at terraforming (yeah I went there). **Information** - This might not fit your story, but if it's revealed that a more advanced society left tremendous information in a format that we should be able to interpret, we'd be there in a New York minute. **Conductive Metals** - I'm not sure what will be the best element in your future, but silver, copper and gold are great at electrical conductivity. Whatever your latest conductor is, have lots of it. **Soil** - Real, Earth-like soil can only be currently found on Earth. It will be a rarity and a necessity in your other colonies, and I personally think it's one of the most overlooked checklist items for colonization. **Naturally Occurring Beer** - ;) [Answer] There's another very fundamental problem that's not been mentioned, which is economic uncertainty. Say you discover some resource at Tau Ceti that is currently extremely valuable, so you invest umpteen trillion (in present-day dollars) to set up a mining/harvesting operation. So 30+ years later (because it takes some time to get operations going), your first cargo ship returns to Earth - only to discover that things have changed. Someone has invented a cheap substitute, the technology that used the resource has become unfashionable, the government's made it illegal, etc. [Answer] # Alien Slaves  [A common scifi trope](http://tvtropes.org/pmwiki/pmwiki.php/Main/SlaveRace) In a harsher world with regressive moral views, or fundamentalist religious views, combined with a sanctity of human life, it may be easier to adbuct aliens from Tau Ceti E to work as slaves in our star system, man ships etc Human slaves would be morally abhorrent, but those more inclined to morality based on what's socially acceptable would not wince at non-human slaves, in the same way many people enslave bears to dance, or when faced with a sentient AI would think of it as nothing more than a toaster Make their reproductive cycle involve things only found on Tau Ceti E, or things that are impractical to move ( e.g the female equivalent or queen bee of the species is 30m tall and weighs several hundred tonnes ) # Examples/Precedents A common scifi trope ## The Ood An example of such a species in current Scifi would be the Ood from Dr Who, who have a giant primary life form that's trapped and kept under control in order to repress the Ood > > The Ood, also known as Oodkind, were a gestalt species of telepathic humanoids native to the Ood Sphere. Humanity enslaved the Ood, mutilating them to ensure a dedication to servitude. > > > The Ood were a peaceful herd-race originally. In the 39th century, humanity discovered the Ood, enslaved them, and used them to perform menial tasks throughout the three galaxies of the Second Great and Bountiful Human Empire. The external hindbrain of the Ood was extracted by Ood Operations and replaced with their translator globes. With their connection to the Ood Brain severed, they followed the orders of humans. Ood Operations kept this procedure a secret from the rest of humanity, spreading the belief that the Ood were naturally servile and offered themselves for servitude. (TV: Planet of the Ood) > > >   ## Goa'uld  A parasitic life form that stole technology and had a restricted number of hosts chanced upon Earth and enslaved the population, farming humans for new bodies to act as hosts Ironically, the reverse became true in the show when a human civilization chanced upon a Goa'uld queen and farmed her for chemicals. Here is a Goa'uld queen:  That wasn't enough it seems, a new sub-species was genetically engineered for slavery as soldiers and incubators, the Jaffa  ## Helots A real life example from Antiquity, the Helots, slaves of the Spartans > > The Helots, slaves/serfs of the Spartans, who outnumbered the Spartan citizenry by so much that the Spartans had a tradition of hunting them down and killing them. This wasn't considered murder; one of the duties of the ephors (Spartan magistrates) was to declare war on the helots every year so that Spartan citizens could legally kill them (the fact that they were surrounded and vastly outnumbered by slaves who had every reason to hate them is believed by some to account for the Spartans' extreme militaristic badassery). The people from Sparta certainly considered themselves to be a breed apart. To the point that, in order to be a Spartan soldier, you had to be able to trace your origins back several generations of pure-blooded Spartans. This... did not work out so well for them, as being so incredibly exclusive in who can be a "soldier" tends to result in running out of trained soldiers. Not all wars are fought in very narrow mountain passes where numbers don't matter. > > > I could go on, there are many examples from scifi, and many examples of colonial imperial powers in history who've treated continents the same way ( Arab traders in Africa, British Empire, Colonial France, Confederate USA ). If you need inspiration for a slave nation, look the the dominion of Draka series of books by Stirling [Answer] Do note that the economics might be quite complicated - the cost of speed grows much faster than the savings, so unless you're transferring human passengers, it would possibly make sense to have simple, reliable ships that travel at half the speed, cutting the costs tremendously. Add in-situ refulelling on both sides (why gather fuel on Earth, when you can mine the comets and asteroids to make fuel and containers you can then drop on Earth?), and the main costs is making the reliable automated systems. Now, you would need some insanely reliable systems, not even close to what we can make today. But at the same time, you could trade any resource you wanted - you might not want to have an ecology-destroying deep mantle mine on Earth or another populated world, but strip-mining non-populated worlds would be easy and wouldn't make most people mad :) What technology would this imply? * All this work *must* be automated. In space, and especially in a different solar system, humans are extremely expensive. Of course, you would still want a couple humans ready nearby, but there's no point in having humans handling zero-G-jackhammers on some asteroid. * Insane reliability. You'd need the ships to survive (say) a hundred years with no human maintenance. Auto-mines and auto-factories could do with shorter maintenance cycles, as long as they can also be heavily automated - we're still talking about a huge automation:human ratio. Humans would still have a reason to travel (and they would usually take the express, 0.75c+ ships). You'd need the architects, technicians, scouts, scientists... it would be a tiny volume compared to the automated traffic, but quite enough to make a story. Maybe it would even be possible to have something akin to Aldrin cyclers, if it makes sense - you'd still need the capability to reach 0.75c (and back again) on your shuttles, but they wouldn't need all the life support space and hardware for the multi-year trip. It would probably be quite tricky to maintain precision, but the cyclers could have crews and limited path correction capabilities. Of course, this would only make sense if you could accelerate fast enough to make it worth it - if you're looking at a 50 year long trip and you spend a year catching up with the cycler's velocity, that's probably a reasonable saving. If your trip takes just four years, though... There's also a few other options to make the trip more economical, most dealing with in-situ resource utilization as well. For example, the ships could gather their fuel in Bussard Ramjets - though do note that this poses not just a technological challenge, but also a fixed speed limit. So in the end, really, even with realistic science, it's possible to make money by shipping resources interstellar. However, there's one *huge* difference between this and "just digging another hole on Mars" - return on investment. The largest investments these days still bring at least some income in a few years (most are more on the line of months), and that's going to be tricky to achieve with interstellar travel. Some part might be paid upfront by other interested parties - say, corporations/countries wanting places on your ship to stake claims, tourists (think more like the pilgrims travelling to America rather than Bill Gates hitching a ride to Tau Ceti and back). This could be used to create drama and tension in the story, of course. The greatest problem with this approach (e.g. no "one of a kind" resource that simply isn't found in the Solar system) is that it's hard to imagine how insanely huge our economy would have to be to *require* enough resources to warrant exploiting other solar systems. We're really talking about strip-mining-planets-scale - anything less would be quite possible to do in the solar system as well. So the main incentive should be something that requires both natural resources (so that it makes sense to build it on a planet) and raw surface area. For example, imagine some genetically designed bacteria that feeds on water and light, and produces space-fuel. Spray them on an oceanic world, taking up 95% of the surface area, and even with relatively low efficiency it could be an important source of fuel. It's again something that you don't want to do on your own homeworld, but requiring little in terms of maintenance, and producing immense amounts of usefull resource that isn't found easily on, say, Mars. Of course, with cheap energy, people soon follow, and you have thousands of stories to tell :) The same cheap material, and different bacteria to the mix, and you can go on the scale of terraforming planets for human habitation - remember, we're already on the scale of hundreds of years, so if it's worth it making mining companies over that time-scales, terraforming starts becoming reasonable. The key point is you have to think of easier or cheaper solutions to the same problems. In my bacteria scenario, I've eliminated these: * Why planets? We need a spot with liquid or gas water - it makes it easy to supply the bacteria with raw materials. The currents can also be used to transport the finished product to places from where it's actually extracted by the transports. * Why another solar system? Well, we need an ocean and plenty of sunlight - even if we setup the production on every useful planet in the Solar system, we'll eventually run out of easily accessible raw materials and more importantly, surface area. While you can use space satellites to gather much more of the sunlight's surface area, it's incredibly expensive and tricky, even compared to interstellar travel. * What's the point? A cheap source of fuel would mean a positive feedback loop on making spaceflight cheaper in turn - it will naturally eliminate the energy costs almost entirely over time. Imagine gas prices of not 1$ per gallon, not 1c, but 0.000001c! You can again have as big a car as you want! As long as you can also make making the spaceships cheap enough, you can make interstellar explorers a lot more common sight over time; perhaps in ten thousand years, someone found something *really* interesting, and that's when your story starts? With the scale we're working with here, the first supply ships would pretty much crash the energy/resource market on Earth (unless you carefully made sure not to increase the supply too fast, which isn't a bad idea from an economical standpoint, really - you want to maximize your profits, so you need to find a nice balance between lowering prices and growing sale amounts). This of course also means that your margins will get smaller over time, but the initial margins possible could be quite interesting. It might be even more interesting if you imagine humanity's future governments being even more socialist and inflationary than today's - you could get around a lot of costs associated with socialism (like having to conform to whatever regulations, paying out social premiums, whatever) and both the spaceships and the mining wetware would tend to maintain value rather well, so even if RoI would be long, it would also be pretty solid. Of course, it also brings another risk - after your first supply ships start arriving, someone might just ban you. Talk about a bummer. Of course, you do have weapons travelling at significant fractions of the speed of light, so who's really going to argue with you, eh? :D [Answer] There's already some good answers so I'll just add the following options: I was going to say loads of naturally occuring hydrocarbons; but if we've reached a point where we can get to Tau Ceti in 30 years, I don't think we need Crude Oil anymore. Still, it could allow further plastic production I suppose so its not completely worthless. [**Rare Earths**](http://en.wikipedia.org/wiki/Rare_earth_element); because hey, they're difficult to mine on earth, hence the name. However, they're also typically pretty useful in engineering and electronics. Promethium makes for nice atomic batteries; and most Rare Earths are useful for making lasers and awesomely powerful magnets (Neodymium magnets can be up to twice as powerful as iron ones). Finally, I know you're against Unobtainiums; but there are a couple of **real-life unobtainium**'s that, if available naturally somewhere would be at the very least of great interest to science: Ununtrium-113 (which might be an amazing superconductor?), Ununpentium-115 (the real life version of X-Com's Elerium-115), and Ununoctium-118 (a bizarre pseudo-solid noble-gas). [Answer] Since nothing currently known is worth the cost of the trip, and since you are ruling out all the magical minerals which we don't know about yet, the simplest answer is to change the values we currently put on things. For example, if non-irradiated water suddenly became unavailable on Earth, there is no cost which we wouldn't pay to get to a source of more drinkable water. That is an extreme example, probably too extreme as we would probably go extinct without water, long before we could get more. But the theory will work. Just make the unexpected scarcity something that we can survive without for a few generations. Like ozone, or...? The trick with all of this is that the value of any compound is dynamic, base upon its future scarcity rather than the way we currently think about it. [Answer] **Uranium, plutonium, thorium.** Tau Ceti is significantly younger than Sol system (at least it is in your story) so far less of the heavy radioactive elemts have decayed. Instead, there's an abundance in TC asteroid belt. So the 'business' plan is like this: * fly to TC with a generation ship are large fleet * set up asteroid mining operation and self sustaining colony * set up manufactoring base for enriched uranium and spaceships * send back uncrewed ships with Orion-drives or thorium salt-water rockets, fueled by the radioactives you find * these trasnport more radioactive materials to Sol where ... * they power reactors housed in satellites beaming energy via microwave to where it's needed This assumes that all interesting uranium deposits on earth are depleted and the rest is so diluted mining is not ecnomical. [Answer] # Elements from the [island of stabitlity](https://en.wikipedia.org/wiki/Island_of_stability) It is a predicated set of *stable* superheavy elements. The middle ground between quark matter/antimatter and uranium/plutonium. The stopping point with the antimatter and [stranglets](https://en.wikipedia.org/wiki/Strangelet) is that it is very problematic to come up with a feasible explanation for why it exists somewhere. The issue with uranium and plutonium is that they decay and are relatively cheap to obtain on Earth. The stable superheavy element, say $^{256}$**Wthm** - *Worthium*, takes the best from both options. ## Why it exists somewhere else? The star configuration is just right to generate it. The hypothetical example is peculiar [Przybylski's Star](https://en.wikipedia.org/wiki/Przybylski%27s_Star). The suggestion is that a neutron star orbits it. Its magnetic field and radiation encourage the formation of superheavy elements. One can sit in Lagrange point and collect the **Wthm** ejected from the star's upper layers. ## Why can't it be made on Earth? Because nobody knows how to make elements past 118, the energy requirements are enormous and technology does not exist. ## Why anybody wants it? The same reason anybody wants antimatter. If one manages to split the **Wthm**, those chunks would be in an ocean of instability, decaying rapidly and releasing loads of energy. It might be even better than the nuclear synthesis modulo fuel source. ## Worthium vs Antimatter | Worthium | Antimatter | | --- | --- | | Generated in peculiar stars via conventional nuclear synthesis | ??? | | Can't physically be made on Earth | Very expensive to make worth only as a storage | | Must be heavily shielded from radiation | Must be shielded from interaction with any matter | | Might be of many types with varying rarity and properties | Singular feature of energy storage/generation | There might be varying chemical and physical properties of different kinds of *Wthm*. For example, some might be a superconductor with room critical temperature. It is a slippery slope as with enough miraculous features **Wthm** would be indistinguishable from Unbotanium. ## P.S. Being a rare object, the peculiar star is a convenient point for the first contact. Weird spectral data is visible from afar. [Answer] When you say "rare elemental isotopes" you put it in the present way. But there is the situation in which a given element, now widely available, will become in the future invaluable to supply the huge energy demands on Earth. For example, Thorium! [Thorium-based reactions](https://en.wikipedia.org/wiki/Thorium-based_nuclear_power) have been demonstrated to produce lot of energy, and without major risks as it works as ambient pressure. Maybe solar Panels will be very efficient by then, but energy demand and consumption can't help but rising. So Thorium power it is. And Tau Ceti's planet systems may happen to be full of Thorium.... I think you could adapt this scenario to your needs? [Answer] Say that the world population cannot stop growing. With a world population growth rate of 1.2%, we will hit 3328 billion by the year 2555. In 2006 we were at 6.5 billion. Those people have to live somewhere and will consume resources. Food, water, air, metals, plastics, etc. We recycle, but there is always some loss. We have colonized all bodies large enough, and melted down all of the asteroids/planetoids. Planets like Venus were harvested a century ago and there is nothing left. We need space to live. We need space to grow food. We need any raw materials we can get, even something as common as iron. Off hand, I would expect that war, famine, or disease would solve the problem for us. However, that did not happen in this case. What we see as limitless resources in 2006 are all rationed for our great great grandchildren. Bathing was outlawed in 2372. Everyone gets 1.38754 liters of fresh water per day. You can use this ration to drink, brush teeth, or whatever you want. There is no increasing your ration. Would you like to go to TCe with a current population of 200? It is a 5-year labor contract to cover one-way travel costs. In comments there are questions related to resource abundance. Iron is common and will always be plentiful. Same with things like plastic, copper etc. Without invoking scientific innovation (to give us fusion and warp drive) we have a problem that I will demonstrate using gold. There are ten ounces of gold in a ton of smart phones. <http://en.community.dell.com/dell-blogs/direct2dell/b/direct2dell/archive/2013/03/20/how-much-gold-is-in-smartphones-and-computers>. Troy ounce is 31 grams, so this equals 310 grams of gold in a ton of smart phones. Say that the ton is 2000 pounds, or 907 kilograms. The better value here is 907.1847 and even that is not exact. These are rough calculations. My smart phone weights 127 grams. So there are 7100 smartphones/ton. If the world population is 6.5 billion people, then we need 6.5 billion smart phones to stay connected. 6.5 billion smart phones weigh 910000 tons which is 28000 grams. One web site posted that the world’s gold is 165,000,000 kilograms. <http://www.numbersleuth.org/worlds-gold/> The world’s population can increase by a factor of 600 before we run out of gold for everyone to have a smart phone. This means that the population can reach 3900 billion. However, this assumes that the entire plant earth’s supply of gold is available for use. That cannot happen unless mining earth destroys the planet down to the core. We do not currently have the technology to do this even if we wanted to. Everyone now has a smart phone. However, many other things use gold. Your computer (laptop or desk top) are great examples. Two hundred laptops have 5 ounces of gold. Rerun the numbers to find out how many people can have both a laptop and smartphone. Then keep going. In science fiction, we can always invent new technologies. All electronics uses a monomolecular layer of gold, or we find some way of using sliver instead of gold. We develop methods of recycling where everyone participates. There is no more trash along the highway because it is all perfectly recycled. Such utopian society is not currently available. One temporary solution is to improve manufacturing to use less. So gold plating in now exactly one molecule thick. Now the smart phone has 1/100 the gold. We then have the ability to make more phones, but the problems with recycling have increased because we now need 600 tons of phones to get one ounce of gold. How do you get every single atom of gold out of that volume? We can turn it into plasma and then separate the individual atoms into ingots of gold, palladium, aluminum, copper, and so forth. How? Well we need a new source of energy. So we have fusion power, or have huge solar arrays with 98% efficient solar cells. Such technology is not currently available, but maybe it is invented. Given that we can cheaply turn waste into plasma, do we have a molecular sieve that will separate the elements? Not that I know of. Maybe some adaptation of the centrifuges used to separate weapon grade uranium? The key is to decide what parts will be science fantasy (anything is then possible), versus based on current science. With current science (and in the absence of war, famine, disease), we will likely run out of resources to sustain growth in a few hundred years. We can give ourselves more time by decreasing growth rates, and growth rates have been declining. However, the increase in mining production does not keep up with population growth rates. So more people will have to be satisfied with less. How much less are we willing to accept before the billions that have not arise to rework the social order? With current technology we do not have the energy resources to reach Tau Ceti e in a time frame necessary given the reliability of current technology. If it takes 60 years to make the trip then the equipment has to function well for at least 60 years. So maybe we need to know what technological advancements have been made that allows this to happen and some estimate of the "real" cost. Consolidate Earth builds a generation ship outside Pluto orbit and ..... I have no idea how much this would cost. I am certain we cannot even get this far with current technology. Given that we have people there: What would cost less is to set up a Tau Ceti e colony and then refine metals. These would be built as solid blocks of (gold, silver, etc...) that would be thrown at earth. They would enter the solar system as a comet and then be captured in some way. Manned ships would not be necessary to ship materials home. As long as the 500 meter diameter gold block is not hit off course, it will have no trouble making the journey no matter how long it takes. However, if Tau Ceti e was now my home why should I send Earth free gifts? ]

[Question] [ (Later Edit: Clarifying my question to could Rome, its empire, its complex urban civilization, grandeur, and vast public works be built without slavery in its era or the middle ages?) Could a civilization at the scale of the Roman Empire in its period exist without slavery? I am looking for technology including medieval period technology that could have allowed it. I am trying to create a realistic Roman Empire style civilization without slavery in a world that mixes classical era and middle ages technology. The Roman Empire's 'greatness' was essentially built on slavery and surplus wealth created by slavery from agriculture, mining, and the spoils of war. It was also built to a lesser extent on trade, uniformity, unified monetary policy as the primary minter of coinage, and monopolies on trade. There was the Pax Romana it created to create a wealthy complex civilization with widespread trade networks, but this was built in Rome which was built on slavery. The later Eastern Roman Empire aka Byzantine Empire would build its wealth on trade but be significantly less powerful as well as less wealthy than Rome. Of course, technology played a part in Rome's glory, but the material wealth from slavery allowed a complex society to emerge with relative luxury in urban areas. This then allowed such technology and skilled craftsmanship to be developed in a complex society. The patrician class often owned large plantations and mining operations where slaves toiled away. Julius Caesar once sold 53,000 Gauls to slave dealers on the spot as historically recorded. Slaves were divided into several categories such as prison labor and prisoners of war. Slaves were needed to build the massive public works of Rome, engage in large-scale mining operations, and engage in 'factory farming' with large-scale [monoculture](https://en.wikipedia.org/wiki/Monoculture) plantations. The excess wealth of the patrician class necessarily built on slavery allowed taxation which expanded the public purse and later private purse of the emperors. This wealth was then used to pay the legions of the Empire and construct the massive public works, baths, monuments, palaces, villas, etc. Often the wealthy patricians and emperors would build the great works that are the hallmark of Rome with their funds. The patronage of the patrician class funded skilled craftsmen, artisans, architects, thinkers, and others in creating the advanced 'culture' Rome possessed. Such great urban civilization was not truly seen again for centuries. Could there be such an Empire in that era absent slavery? One could say it could be serfdom instead of slavery, but serfdom is a somewhat different institution. What technology or social structure could make it possible? Trade monopoly alone would not make for a very realistic world, and the Eastern Roman Empire aka Byzantine Empire, as well as the greatest mercantile republics in the Middle Ages, did not possess the glory, wealth, or power of Rome. Nor were they able to create the 'Pax Romana' that allowed the Empire to have massive cities with complex trade networks existing in relative peace. [Answer] I actually think it could, but it would need some very good **reason** to not have slavery. As others have noted **forced labor** has been a major factor in civilization. And this is kind of inevitable as the ability to arrange labor for public works such as irrigation, walls, roads, and harbors has been the big selling point of governments in ancient times. So using your own people for forced labor would occur in most civilizations and using captured people as slaves would follow quite naturally. In fact, it might be possible that slavery is older as it happens naturally even in chiefdoms and tribes that do not really have forced labor otherwise. Also, while I am dubious about the economy of the empire requiring or even benefiting from slavery, slavery was a large factor in motivating and paying for invasions. So if you want a large empire, you'd also need some strong mechanic driving expansion to compensate for not making large profits from selling slaves. I probably should explain why I do not think slavery is an economic necessity as such as most seem to think it is. Basically while slave based economy is hugely profitable, the benefits only accessible for people who already have sufficient property. So it basically makes the rich richer. This isn't a bad thing as it allows people to accumulate the large fortunes needed to make large investments. However that requires that there are large investments that expand the economy available. Otherwise the capital is expended on luxury and vanity projects. This is of limited benefit to the economy as whole. And it isn't free either, the land used for slave plantations is not available for other uses, which has consequences to free farmers. The enrichment of the very rich also leads to social imbalances that impact the political and legal systems. This leads to corruption and inefficiency. So I am not at all convinced that a civilization with slave based economy would **as a whole** be better off than a non-slave based one just because the rich elites hugely benefit from slave economy. But as said in the beginning you'd need good reasons to not have slaves and to be expansionist enough to build an empire. Religion maybe? Some religions have restrictions on slavery and promote violent expansion to non-believers. [Answer] The necessary labor could be drawn from multiple sources: * The incarcerated - hard labor as part of a sentence for a convicted criminal is not a new concept, and it's one that operated for centuries. Even in "first world" countries today there is the watered down version in the form of community service. * Indentured servitude - making someone work off a debt was another common practice at many points in history. * Social mobility - for the low-born but ambitious they could agree to work for X years in order to gain citizenship or a similar societal perk * "National Service" - similar to the concept in many countries (even today) where the young are required to complete a certain amount of time performing the labor, it's just that it's a non-military form. * The army - armies don't spend all their time fighting. Having them perform labor during their non-war time not only helps keep them occupied (less time to cause trouble) but also would keep them fit. Yes you are still paying them but you'd be paying them if they were sitting around the barracks practicing marching every now and again. None of these would provide enough manpower to replace slavery on its own but a *combination* quite possibly would. [Answer] I'm going for a definitive **YES** Contrary to what one could think - and apparently, most users in SE think - slavery is **bad** for the economy. Slavery is the worst form of unequality, and it gives way to economical stagnation. As the rich landowners got vasts latifundia and made them produce with slave work, the small farmer couldn't compete in price, so they got broke, sold their lands (to the same landowners) and, in many cases, got themselves into serfdom by debts - another form of slavery. This was a positive feedback loop, which ended with the roman economy first, and with the roman empire itself later. The taxes that can be collected from a handful of extremely rich people are always but a tiny fraction of those which can be collected for the whole of the middle class. By centrifuging roman society to the extremes of the welfare line (a tiny handful of filthy rich patrician houses, and millions of proletarians) Rome find itself ever less capable of doing things. Its military and territorial expansion nearly ends with the Republic, and its public works didn't last much longer. With the beggining of the Empire, most of the wealth of the empire came through trade and taxes from its eastern provinces in middle East, as slavery made many labour positions in Italy and other heavily romanized european provinces unprofitable. Later emperors complained about old fertile italian lands being empty and abandoned to the forces of nature, and even tried to repopulate them and making them productive again, with no success. Simply, slavery is not economically viable, even it may look so at first glance. Have you ever wondered why the USA raised to a global superpower while the spanish and portuguese colonies sank to third world ratings? The easy (and racist) explanation given talks about the superiority of british (and, less frequently, french and dutch) and protestant values over the dagoes catholicism, but then, why is Jamaica not as rich as Japan? The reality is, the countries that had economies based on slavery never grew really wealthy. That's true even for the USA, whose northern states were far, far richer than the southern ones - the ones based on slave work. Simply put, had Rome abolished slavery, the roman empire would still be here TODAY. And probably ruling all over the world. **EDIT:** Even expanding my argument. Several books have been written on why empires fall. One of the commonest views is that unequality makes them weaker until they break. Thirty years after the undisputable prime time of the roman society - the stiff-upper-lip times of the second punic war, with romans keeping calm and carrying on with Hannibal at the gates - four roman legions were unable to take the tiny town of Numantia, in northern Iberia. The town was tiny, and had no mighty fortifications - just a wooden pallisade. What happened? What happened was that, after fighting so bravely against Hannibal, most of the veterans of that war found themselves broke - the lands they were given as retirement pay weren't profitable against the massive production the wealthy patrician could produce with the land grabs and slaves that the war have allowed them to get. As a result, what once was a proud army of free citizens fighting for their homeland turned into a heavily demoralized conscript corps, sent to a far away foreign land (the iberian peninsula) to fight against people they had nothing against for, with only death, maiming or complete financial losses as possible outcomes - think about the USA in Vietnam. The roman legions, who had defeated so many enemies before, turned into an army of cowards led by corrupt officials, as the Jugurthine wars were going to prove. This decadence was only stopped when Marius decided to profesionalize the legion, making it a standing army - the same solution that was taken in the USA. Because of slavery, conquering Germania or Britain was not profitable (Britain conquest started out of a personal decision of emperor Claudius, but was never completed) and Rome lost the power to expand its frontiers. Without it, more lands would mean more (free) people to tax, and after a time of (re)construction the new territories would become a healthy source of income - and by healthy I mean stable and reliable, no matter how much rich. The main problem with old civilizations is taxation. They had no efficient way to tax its citizens, but no matter how taxes were applied, a slave-free economy would generate more revenue, thus increasing Rome's power. The latter emperors raised taxation on the slave trade, or extended Rome's citizenship to more and more (finally all) of the inhabitants of the empire trying to expand its taxing base, but to no avail. With a failing economy and an expensive army mostly formed by foreign mercenaries of germanic origin, the last times of the roman empire were a neverending series of uprisings and revolts, with the roman legions naming and removing emperors at will. And you can trace all these malladies to the unequality and economical stagnation due to slavery. Incidentally, the eastern roman empire managed to survive for nearly a thousand years more, and christianity (and the end of slavery, even if replaced by some sort of forced serfdom in many cases) played a key role in its success - and later demise, due to religion schisms, but that's another story to be told in another time. ;) [Answer] **Slave labour is not necessarily required, but some form of forced labour is** I think it depends on what you mean by slavery. Although some will say this is hairy splitting, I say given the nature of the question, this is a hair that very much needs to be split. Slave labour is merely the extreme end of a more general classification of [indentured servitude](https://en.wikipedia.org/wiki/Indentured_servitude). I doubt any ancient civilization could have arisen to greatness without a large measure of indentured servitude or forced labour. And I accept that traditional slavery was endemic throughout the ancient world, but slavery is not the only source of labour available and it is not inconceivable that a society might have arisen based wholly or in large part on other forms of indentured servitude. There is much evidence that [the pyramids were not built by slaves](https://www.theguardian.com/world/2010/jan/11/great-pyramid-tombs-slaves-egypt), but by forced labour. How is this different from slavery? The slave simply has to do what he or she is told until they die or are released by their owner. The forced labourer is also forced to work but only for a relatively short period, after that they are free again and they may (or may not) be rewarded for their services. Payment might also come in other forms. For instance forced labour for the king might be considered a civic duty that most people accepted or become accustomed to. Those who accepted it willingly and completed their task might be seen as better citizens. Building a structure like a pyramid for a god/king might even be thought of as an insurance policy. If the god/king is looked after, then he will ensure the rains come and protect the people etc. Although slaves were no doubt used in the construction of the great pyramids to some extent there simply weren’t enough slaves available so they would have been greatly outnumbered by other types of forced labourers. Similar situations can be found in Mesoamerica where other great pyramids were constructed in part or in whole by various forms of forced labour. So in summary slavery is not necessary, forced labour is. For those who say that forced labour is slavery then the definition of slavery is very wide and all forms of national service and military conscription are slavery. [Answer] Yes. Have you ever watched 300? Do you remember the bad guys in that movie, with the [scary huge army](http://cdn.playbuzz.com/cdn/ed48cbdb-bd22-44b0-8dcc-251989ccb5c2/ba394061-050b-4b3f-840b-3e3dd5b7c7a6.png) and [spooky masks](https://images.moviepilot.com/images/c_limit,q_auto:good,w_600/sojr5eykx7ddb5m82dpo/the-immortals-in-300.jpg)? Well, it turns out they weren't so bad, after all. The largest empire in our planet's history by share of the world's population (forty-four percent!) did not have mass slavery: [The Achaemenid empire](https://en.wikipedia.org/wiki/Achaemenid_Empire). In fact, [mass slavery has never been practiced in Persia/Iran.](https://en.wikipedia.org/wiki/Slavery_in_Iran) The Achaemenid empire had a centralized bureaucracy, road systems, a postal system, an official language, civil services, and a large professional army. The empire featured large cities, incredible wealth, temples, palaces, mausoleums and at its peak **contained 6 of the 7 wonders of the world** (Great Pyramids, Hanging Gardens, Mausoleum at Harlicarnassus, Lighthouse of Alexandria, and the Temple of Artemis.) Perseoplis, the capital, was built by paid workers. Although the Achaemenid empire was not as big as the Roman empire, I think it is fair to say that it is of a similar scale--it even contained a larger percentage of the world population. [Answer] Cynical answer: No chance Civilisation is built on slavery. While we look at our current civilisation and lifestyle and think we don't have slaves, the system for outsourcing manufacturing allows us an even lower labour cost. The daily wages for many of the people making our "affordable" consumer goods are below what it would cost to feed and house them as slaves in the west. *Whether called slaves, serfs, bonded labour, or given any other of a string of names, civilisations, and empires especially, are built on unwaged labour, slaves.* If we consider the Roman empire specifically, we think of arts, temples, decadence. All of this is supported by a vast army of slaves. Without those slaves what we consider to be the Roman empire would not be. It could still be a military empire, but it would be a very different beast. [Answer] I would like to point out that Rome wasn't always totally dependent on slaves and that the dependence on slaves was highly regional. The dependence on slaves was greatest in the early empire, but the earlier Roman Republic successfully expanded by allying with neighbors or getting conquered people to work within the Roman system. There were also plenty of small farmers to work the land and independent craftsman who go things done. Once slaves started becoming plentiful, Rome did become dependent on them, or at least the wealthy class did, as they bought up all the land and bought cheap slaves to replace the small landholders that had previously done the job. As expansion stopped later on in the empire period, slaves were no longer as cheap and plentiful as they had been beforehand. I don't have a lot of information on this, but from what I understand, the importance of slavery slowly decreased over time with slaves gradually gaining more rights. By the late empire, particularly with Christianity becoming the main religion, the importance of slavery had drastically decreased. They were still around, but were no longer the main driver of the economy that they had been back in the days of the early empire. At some point they disappeared also entirely. There were a few slaves in Italy in the medieval period, but they tended to be owned by rich households acting as domestic servants. At any rate, most of the slaves had disappeared by the time the western part of the empire came to an end. I'm still looking for information about exactly when that happened and why. There were huge social costs to all those cheap slaves. Small farmers and craftsmen were often made destitute and unemployed by the huge farms and cheap slave labor, who could produce crops and goods a lot cheaper. Those unemployed flocked to the cities and became part of a massive poor (and rather unhappy) urban population. The wealthy of Rome had to give away free food and free entertainment (bread and circuses) to keep the unemployed from rioting and rebelling. The eastern empire was far less dependent on slavery. It was mostly the western empire that had a huge slave population, mostly occupied with mining (a very dangerous occupation back then) and farming. It was the eastern empire that had the most prosperous economy and the highest amount of wealth. Egypt was probably the wealthiest province, and Egypt did not use large numbers of slaves. So I could imagine an empire that was more like the eastern provinces, where the economy could function without slavery. Slavery was a huge driver in rapid economic expansion in the west and the rise of large urban populations, but I think that it would have been possible to have maintained the empire without slavery. Smaller farmers would have paid more taxes and provided a bigger tax base. The wealthy slaveholders tended to be very good at avoiding taxation, leaving the burden of taxation to follow mainly on the poor and middle class. I think that not only would the empire have been maintained but it would have been economically healthier. Consumer goods would not have been as cheap but the wealth would have been better distributed and more available to tax collectors and the economy as a whole. [Answer] Short answer: NO Slavery has been for a long time the only way to have available cheap work force. As a reference, slavery abolition in the US started from the Northern states, where industrialization was already emerging and there were no more human labor intensive situations. At the time of the Roman Empire the tech level was still far from industrial revolution, and renouncing to slavery would have simply chopped away the legs of the empire. For another historical reference, look what happened to Sparta (a reality way smaller than Rome) when they lost their mass of disposable slaves: they had to bid farewell to their renowned agoghe and the power of Sparta was gone. [Answer] Yes it's possible that roman civilization could have substituted indentured servants for slaves in fact many historians will argue that slavery in Rome was more like indentured servants then slavery. Make a few changes could make even more like indentured servitude. 1. have a set time limit on how long some one can be a slave. Slavery in Rome was usually temporary, but this would be more official. 2. Grant citizenship to any freedman that completed his contract as a indentured servant. A similar system was set up for the roman military. See have how successful this offer was, you see none Romans actually volunteering to become indentured servants. These are small changes and would not have made Rome unstable or threaten their lifestyle. [Answer] Yes. If you consider the teaching of Malcom Gladwell's book **Outliers**, see the chapter about cultural heritage. One thing is that your civ's staple food started with something like rice. To maximize your harvest, it takes motivated, back-breaking, attention to detail, hard work. To make a Sweeping Generalization, slaves don't like being slaves, and will not work as hard or do a good job at taking care of rice like independent owners. His observation of eastern history is that where rice is the crop, family farms / owner operated farms out-compete farms using forced labour. (Higher yield wins over cheap labour). One of the other things to remember is that slavery depresses the wages of unskilled labour, but high labour costs drive innovation in favour of productivity gains. (Higher general labour costs also means that the masses are paid enough to buy things.) Some authors attribute the labour shortage caused by plague in Europe as a key factor in technical advancement that eventually ended the middle ages. The wind mill, the water mill, threshing machines, and basic mechanical combine harvesters pulled by ox or horse can be far more productive than using humans to crush, grind, cut, etc. That is within the technical ability of a civilization that made printing presses for coins, aqueducts, various types of concrete, and indoor plumbing. Same goes for the spinning wheel, that is just wood and metal in the right shape. Can great works be done by an ancient civilizations without slaves? Well, Egypt built the pyramids. <https://www.seeker.com/slaves-didnt-build-pyramids-egypt-1764995593.html> <http://www.messagetoeagle.com/worlds-first-documented-labor-strike-took-place-in-ancient-egypt-in-the-12th-century-bc/> [Answer] Basically, no. The economic basis of a society determines its form. The Roman Empire was built around slavery. A society that is *not* built around slavery, is a radically different society. This question is tagged "medieval", and the argument I'm familiar with is that the collapse of the Western Roman Empire was fundamentally due to the limitations of its economic model, of urban centers supported by slavery. Roman cities consumed more than they produced. The economy was more efficient, and material conditions for most people were significantly better in the less centralized, more distributed economy of medieval Europe. You may as well say that what a Roman Empire without slavery would be like, is medieval Italy. [Answer] IMHO there are **two** different problems: 1. make great empire 2. make empire roman style to achive 1. you need a lot of human and lot of work done, but it can be build by free people and with (mainly) good equlity along them. But it would need be else driven by some "big case" (religion or so) or it would end with something totally different than roman empire to make 2. you **need** some kind of organisation, where is few insanly rich people, who have insane income and not enought place to expand even more so if they want to spend their income and make some impression on other rich, they are force to build extravagantly big and complex projects, like villas, scuptures, aquaducts and such, to present their power. And that also need to have really many other people to work for them, because such big projects just needs too many work hours to be done (if you do not have powerfull engines to do it), one person (or small couple) envision it and many do it in relatively short time (couple of years, not couple of generations), so the one with the vision and power see the result and can it personally use (no point to build villas for your grand grand childs, while living three generations in tent). And you need a lot of work hours just to keep them running (cleaning, repairs, ....) And to have collect such many work hours you need some power over a lot of people to contribute. In slavery it is easy - you own them. In religion you make them beleive, that it is somehow required by the God(s) (the best building in middle age village was usually church). In capitalism you need pay them and so on ... If there is not much inequality (or power, or "big case"), than you get lot of smaller buildings as anyone can have aproximatively the same and so it ends in roughly similar buildings, which is probabelly overall better but there are no so insane big artefacts. --- So for Roman style culture you need a lot of people and few of them insane rich. With limited resources that leaves not much for the majority. You can divide the majority to some middle class ("citizens"), but then the rest must be even more poor (limited sources again). Depending on your environment (there can be lot of easy obtainable food and metals and stones and quality wood) you can have even the poor to have realitively good live (compared to other countries at this technology level), but still it needs them to be "poor enought" to work for those insane rich building their wonderfull villas and such (as oppsition to buiding something for themself and just enjoy the life, if there would be enought resources for them to do so.). [Answer] Additional to the L.Dutch. Vast empires need slavery to maintain it's supremacy over large regions. There is simply not enough "imperials" to do all the work. The mundane work need to be done by someone. But as nobility on the conquered territories wouldn't like to change their status (automatically being sub par to their Roman counterparts) someone need to fetch the water or work in the mines. The slaves were automatically acquired with every won battle. So you needed to give them some kind of job where you would/could control the angry, able, strong people, while at the same time the job would fatigue them. Slavery is a solution to a problem not a thing on it's own. [Answer] It could be possible, but you'd need to rewrite all the political and social systems Rome had. I think the only way for this to exist would be a very socialist or even communist society, where everyone works and resources get distributed evenly among all working people, and the remainder is given to the ones without a job. In modern countries, people are forced to work for up to 30 years to pay off that house that they bought. If they don't, they get their property taken away and can get punished. This is, in a sense, slavery. People have the illusion of choice, but you need to buy a house unless you rent a small room for the rest of your life, which no one wants. If you don't work, you don't get a house, don't get good food, don't get a television and don't get a phone. Society is, and always has been, built upon forced labor, and the only way to fix it would be to create a system like the ones in early tribes, where everyone works, except for those who are very young or old, and those who can but don't want to get kicked out. [Answer] You need to define your terms very carefully. In Roman times, and in fact in all times up to Roman and well into the second millennium, there was no term for employer or employee. There was no concept of working for another for wages, under an employment contract as we know it. The closest thing was a King who amassed an army, but even they were not paid, except for room and board. Knights were rewarded, not paid. You either made money, or you made or sold goods. If you made money, you did not need employees. You did so on your own initiative (lending out money to others, renting land or lodgings). If you made or sold goods, you did so yourself. If you had a helper, he was an apprentice. Your obligation was room and board. If you needed more assistance, you called the person a 'slave', not an 'employee'. You were a 'slave owner', not an 'employer'. You either worked for yourself, you were a member of the court, or you were a slave. If you couldn't be a slave, then you begged for whatever living you could make. There was no 'working class'. So what you are asking is, 'Could Roman Civilization have developed without some form of employer relationship?' Or 'Could Roman Civilization have developed based purely on individual enterprise?' and the answer is probably a negative. ]

[Question] [ Let's imagine an alien life form attacking Earth. Their technology and their number do not overtake very much human ones, but they have a very powerful weapon: when a human looks right at one of them, he/she finds it so cute that he/she loses their anger and will to fight, even if there is a weapon pointed on himself/herself. Even when it goes out of the field of view, a memory is left of it and the human remembers it like a good, friendly and harmless creature, and won't wish to try to fight it except for very personal reasons. (If a friend of him/her was killed during a fight, he/she will still want to fight back.) This feeling never wears off by itself, but psychological counseling may help to wear it off, like a regular mental trouble. They use this weapon in close combat, because doing so nobody can shoot at them directly, and as a tool before invasion too, by filling the human world with photos and videos of them as much as possible via long-range broadcasting, mainly through the Internet. So now let's suppose the invasion plan already started. The first step of the attack plan, which is to broadcast photos and videos of them through the civilization to reduce potential human aggression to their assault, has already started. But there is still some weeks before the full attack, and a scientist group discovered the truth. Unfortunately, almost 100% of the human population already watched images of those aliens and started to feel tenderness for them. How can they prepare the world for the final attack, weapons or defense systems for a creature that they must never watch? (I'm looking only for specific methods against their special weapon.) Keep in mind it is probable they will display pictures of them on huge screens, paint it on any tank or vehicle, and display as many images as possible of them in every battle to try to affect as many human soldiers as possible. Even a look through a screen or a picture can affect a human, but it is still less efficient than a direct look on an alien itself. Of course, this power doesn't affect machines. Almost any other feature of the aliens (technology, military strategy level, care for casualties, etc) are similar to humans, to be simple. ## EDIT: I'm not looking for a complete defense plan, just a special weapon/tactic that could be used against this precise opponent and its special weapon, in order to not be too broad. [Answer] We will use the **Realtime Overlay Virtual Environment Remaster (ROVER)**. ROVER is a helmet that obscures the wearer's entire head. Using cameras, it provides them with substituted, augmented vision and virtual reality overlays. The main component that makes it useful in this fight is that all images of kittens will be detected and replaced in realtime. This is customizable depending on the user - default options include Furbies, Spiders, Snakes and a cutout of Justin Bieber's face. Unfortunately due to [computational complexities](http://xkcd.com/1425/) ROVER is not 100% effective, but it does allow most combat troops to engage in face-to-face combat with the enemy. [Answer] "Sir, we've identified a class 1 memetic attack, effective in combat, transmitted line of sight" Drones, we're going to need lots and lots of drones. Long range weapons. Artillery crews who can kill from 10 miles away. Fire and forget missiles. High altitude bombers. ICBM's launched from hundreds of miles away. Land mines. So many land mines. Do these creatures care for their own fallen or injured? If yes then remember there are no rules of war here so expect liberal use of some equivalent of [castration mines](https://books.google.co.uk/books?id=LVADp7LJFtUC&pg=PA77&redir_esc=y#v=onepage&q=castration%20mine&f=false). Nuclear, chemical and biological warfare. After all, if you can't see the enemy through the clouds of mustard gas and nerve agents they can't affect you. Does their power work if their skin is melted off? From your troops you're going to want to select the minority of psychopaths who can find something adorable and lovable and still murder it with a smile because they know they get a generous bounty for every kitten-scalp they bring in. For soldiers, once the threat is known they might want to use some kind of AI system like this: <https://www.youtube.com/watch?v=LGfT5l9zPwI> in smart goggles to block direct view of the creatures. "Just shoot at the center of the black circle soldier." A few decades ago such an attack could have hit the civilian population easily but with everything moving to the internet there's not really the same kind of broadcasts, they'd have to have hard connections to the internet to do much which is tough to do before they're in orbit. Edit: I neglected the civilian side, we're going to need some reeducation centers for civilians and military personnel who've been affected and inquisitors to root out the affected. After all, we can't have sympathizers potentially in command of any of the weapons systems or spreading the hostile memes. [Answer] Dogs of war! Train large numbers of dogs to fight. Send them on ahead. They will be completely immune to the cuteness factor of the kitties. [](https://i.stack.imgur.com/XXqhU.png) [Answer] In WWII, [barrage balloons](https://en.wikipedia.org/wiki/Barrage_balloon) were used to defend against raiding planes. Those balloons could be re-purposed and outfitted with spools that dangle string or wool. Our alien invasion would be unable to resist dangling string and the entire force would be quickly immobilized. [](https://i.stack.imgur.com/Uis9N.jpg) [Answer] We've already been prepping for this. When they arive, they will be greeted with hundreds of cat fans trying to make the cats do cute things. After being forced to ride a Vroomba in a shark suit one too many times, the aliens will decide this planet really isn't worth the humiliation. [Answer] ### Laser Pointers Your enemy will chase the laser dots, letting you lead them into contained spaces. The Grand Canyon, for example. Once you've led the enemy into your trap bring out the... ### canned tuna Drop large quantities of canned tuna. But don't send *enough* tuna to feed them all. Send enough to feed about 20% of the enemy. This will cause them to fight each other for the food. Once they've reduced their own numbers to something more manageable through internal fighting, drop the... ### Catnip bombs Air-drop catnip in large quantities. This will calm your remaining enemies. It will sooth their rage over the laser dots, the lack of food, and the grief of internal fighting. Now that they are calm spray them with... ### Black and white paint Carpet-bomb them with black paint. Then use drones to air-brush white stripes on each enemy being. After this, you will find their cuteness attack no longer works. At this stage, you can begin sending in the ground troops. [](https://i.stack.imgur.com/Pn0VK.jpg) [Answer] **Fight a meme with a meme.** Since these aliens hold no power over you if you have a personal reason to fight them, then record (or create) images of these aliens destroying the things we love and flood the tubes with them. Every social network page should have an image of a cute alien doing something unspeakable. The new horrific images will drown out the old cute images and balance out the cuteness, if not reverse it all together. Once everyone on earth is inoculated against the cuteness, fight the aliens. Once the aliens are defeated, find some eye bleach to remove the horrific images. [Answer] From the soldiers drilling manual: "I do not shoot this cute little kitty! I just shoot into a small point on his/her forehead!" - repeat these words 100k times to imprint them into your mind. [Answer] Just use giant robots from Japan. You put yourself into one of those and watch a screen that creates 3D images of your surroundings based on a camera that films the outside. The 3D objects won't be very accurate but it's enough to understand where the kitties are and they are going to have 3D model different from a cat of course. To place the 3D objects at the right distance the robot can use ultrasound. In the case the kitties use something to cover themselves, well, they'd be killed by ordinary soldiers. Their only chances of winning would be by using a machine that can counteract the japanese robots destroying them, taking control of them or knocking out the ultrasound or 3D mapping devices they carry. Humans win as long as kitties aren't more intelligent than them. [Answer] Since you find them so cute, you may want to [prank them with cucumbers](https://www.youtube.com/results?search_query=cats+cucumbers). They will either succumb from heart failure or decide to go back to their planet, because they *have had it with these funny humans*. --- For those unaware of this internet meme: cats seem to be afraid of them: [Why Are Cats So Insanely Afraid Of Cucumbers?](http://www.iflscience.com/plants-and-animals/cats-are-completely-terrified-cucumbers-why/) (ILFScience 16 nov 2015): > > A new internet craze involving our feline companions has unveiled another piece of strange information: For some utterly bizarre reason, they appear to be terrified – utterly terrified – of cucumbers. > > In the vast majority of the videos, cat owners are seen sneaking up behind their pets as they’re facing the other way – mostly eating – and placing the green, elongated vegetable behind them. As the cat turns around and spots the unexpected item, it loses its mind, leaps into the air, and gets away from it as fast as it can. In some videos, the cats then engage in a stare down with the cucumber, waiting in vain for it to make its first move. > > > [Cats Scared By Cucumbers: Knowing the Facts Behind the Viral Phenomenon](http://www.petmd.com/news/health-science/cats-scared-cucumbers-knowing-facts-behind-viral-phenomenon-33307) (PetMD, 24 nov 2015): > > "I wonder how many cats were videotaped before concluding that this is a phenomenon? For example, out of hundreds of cats that have likely now been subjected to this experiment, how many actually had this reaction? Perhaps only a small percentage," she says. "Just as unusual phobias exist amongst people, this subset of cats may fit that bill, or they were simply startled by the sudden appearance of the object." > > > Youtube videos illustrating the cat behavior: <https://www.youtube.com/watch?v=cNycdfFEgBc> <https://www.youtube.com/watch?v=ST4KPDKatTA> [Answer] Have the great mind that haven't seen them yet create software to change the appearance of the cats. This could be done to be used in remote situations such as drones, controlling them from a far, safe place, or with a helmet. It basically makes them look different. Use prisoners with enough trust to fight against the cat army because they won't know what they're fighting with the helmets. Just say they're going to destroy earth. You can also use any prisoners to test the technology. The creators of the technology asking the prisoners what they see. Problem solved. [Answer] Start a propaganda campaign, where you 'unmask' the cute kitties to reveal the snarling, evil, hate-filled 'reality' underneath. Of course, this doesn't have to be true to be effective. Fear is much more powerful of an emotion than cute. [Answer] **Bring on the regiment of cat-lovers!** (Came back to this years later - don't know why!) Recruit online wherever kitty pics are shown. Convince the respondents that we are being invaded by cat orphans that desperately need homes. Offer to provide everyone with a month's supply of delicious cat food and everything else needed. Set them loose on the battlefield. They will rush to pick up and cradle the 'cute kitties' in their arms and take them home immediately. The kitten army will thus be dispersed. When they reach their new homes the conditions will be so good, they'll forget about invading by force and just settle in. Note: Neutering will come as a nasty shock but they won't expect it and afterwards it's too late. ]

[Question] [ If we abolished the system of time zones, and everywhere followed UTC (or another arbitrary timezone), what would the possible advantages or disadvantages of this system be? If you can think of any specific activities that would be disrupted or enhanced due to this, please include those as examples! [Answer] For their day to day lives, people in different parts of the world would associate different times with different activities. While to someone in Greenwich 11:30 am might mean "lunch time", to people in the Eastern US it might mean "time to wake up", to others it might be "dinner time", or "middle of the night". No doubt if time zones were abolished tomorrow, people would find it very confusing for a while. But I presume that after, what, a few years?, people would get used to it, and the idea that the sun rises at around 3:00 pm seem natural and familiar. Once people were used to it, the only time when it would make a difference would be when someone travels to other parts of the world or talks to someone from other parts of the world. Today, for most of us there is some confusion when talking to someone far away as to what time of day it is for them. When it's 10:00 am at my home, what time is it in Tokyo? Etc. If there were no time zones, then this question would be meaningless. If it's 10:00 am here, then OF COURSE it's 10:00 am everywhere in the world. But you'd still have to think about where the other person is in their daily cycle. When I ask, "When it's 10:00 am here, what time is it in Tokyo?", my reason for asking is likely to be, "Is this a reasonable time to call, or will it be the middle of the night over there?" You'd still have that problem. Well, I'm assuming that when you say there are no time zones, you're not thinking that everyone works to the same schedule. That, say, if people in London begin the workday at 9:00 am, that this means that everyone begins the workday at 9:00 am, even people for whom that is the middle of the night. So on the one hand it could be simpler. We don't have to ask what time zone a person is in, because there's only one. If someone says, "the meeting is at 2:00 pm" or "the train leaves at 2:00 pm" or whatever, we don't have to ask what time zone. It could eliminate a lot of potential confusion. For people who regularly work with schedules across multiple time zones -- like people at railroads and airlines -- this could avoid a lot of potential confusion. I'm a software developer, and every now and then I work with computers located in different time zones, and this can get confusing. Like if I check a computer and see that a certain file was last updated at 3:00, is that my local time, or the time where that computer is located? And where is that computer physically located? Sometimes I don't even know. Etc. On the other hand, it could make it more difficult to talk about different daily schedules. With time zones, it's easy to say "when it's 9:00 am here it's 4:00 pm in Tokyo", and we now have a good idea how our daily schedule relates to theirs. But with no time zones, how would you express this idea? You'd have to say things like, "people there usually start work at 4:00 pm". Then if you want to know when they might have lunch or go home from work or go to bed, you'd have to count hours from start of the day for you, and add it to their start time, and so do a bunch of arithmetic in your head, which could get awkward. So, I'd say pros and cons. [Answer] Look at China. China *already* abolished timezones (within the boundaries of the country). The result would be that "9am" is not breakfast for everyone, instead "9am" would be an objective point in the day at which different people do different things. So for you, living in California (for example) with the UTC model, "9am" is the middle of the night. You won't be up until 3pm, leaving for work by 4pm, getting there at 5pm, and working until 2am. All during the daylight hours. Whereas for someone living in the UK "9am" would approximately be when they get to work. This would cause more headaches than it solves, as your UK compatriot would send you an email asking for an 11am conference call and you're reply would be "That's the middle of the night!" Oh, he replies, *what's the time difference?* and you have no reply because the concept of time zones is dead. [Answer] For one serious difficulty, look to people working night shifts, where the date switches over in the middle of the night. Knowing what time you go to work is easy. The difficulty is with what date you are on. We are all used to the date changing at midnight, when most people are asleep. The next day, you date any papers with a new date, that you keep for the entire waking cycle. In the new system you have to change the date at midnight UTC. Depending on where you are, this could be a couple hours before the solar clock reaches noon. It's very unintuitive, and gives people in this situation something extra to think about. As a result, it would cause problems, even among people used to it. It is already somewhat difficult to keep track of a current date. Changing it midway through the waking cycle just adds confusion. From personal experience, I worked an overnight shift where we had to record the time of certain events, ending at dawn. When the day switched over at midnight, we technically switched dates. In practice, when we wrote 1AM, July 18th, it was 1AM of the night that started on July 18th. We had tried changing dates at midnight, but even using a computer that told up the actual date, people made frequent mistakes, often continuing to use the previous date all night long. It meant a lot of going through the paperwork to correct dates. Not changing dates midway through the worknight saved a lot of trouble. [Answer] Why abolish just the timezones? Timezones are merely a tool to more-or-less successfully force "day", a time unit based on Earth rotation, into conformance with local solar time. I'd say - get rid of this geocentric nonsense alltogether! Welcome kiloseconds and ultimately metric society! Think of Unix time - just a number, ticking arbitrarily and not being tied to timezones, planet rotation, moon orbits nor planetary orbits. Plot twist: it works perfectly even between different planets, moons and space stations. For a distributed society it would be a big advantage. [Answer] Firstly, if timezones are abolished and UTC time used everywhere then we would also need to simultaneously abolish the use of 12-hour time, i.e. AM and PM, as this is now redundant and confusing terminology and use 24-hour time instead. Secondly we currently use time as an indicator of the local day/night cycle as well as measuring the passage of time. For example if someone tells you it's 6 AM where they are, then you know that roughly speaking this will be around dawn / early morning. However using only UTC if someone tells you it's 06:00 then it is 06:00 for both of you, but is it dawn or dusk where they are? I think people would still need a secondary system for indicating relative time of day in their locality. Working in IT I can say that timezones are a major headache in software applications, as they are defined by legislation and can be changed arbitrarily. This is one reason UTC is popular in software applications. [Answer] There are two ways this could go. Most of the answers assume that all timezones but one (generally GMT/UTC) are abolished and all our clocks are set to the same time. People will just have to get used to having breakfast at midnight, or going to bed at 2pm, if they are unlucky to live in a place where that is the custom. But the other way would be to return to astronomically correct time, wherever you are. In normal rural life, ... no problem. If you have to communicate with another location, you need to calculate the correct time wherever they are - for example, in Bristol you'd better turn the TV on at 5:40pm to catch the 6 o'clock News from London. Then there's the discrepancy between solar time and mean time, defined by the [Equation of Time.](https://en.wikipedia.org/wiki/Equation_of_time) Your clocks (which drift) run on Mean Time, but your sundial (which is accurate) reports solar time, and they can be up to 15 minutes apart in either direction at different times of the year, so even in one location you need to convert from one to the other with a calendar and a pocket calculator... What *day* it is - now that's a whole different problem :-) [Answer] **on the plus side:** almost everything that uses timezones would be simpler. specifically, when traveling or communicating across timezones. this includes reading things written in another timezone. notable examples include: 1. booking airfare 2. scheduling distant meetings (either via telecommunications or travel) 3. setting clocks (since daylight savings time wouldn't make sense and clocks could come pre-set) 4. knowing when emails, text messages and internet messages were sent 5. writing software of almost any kind (software frequently uses timestamps) **on the down side:** 1. it might be harder to predict when stores open and close. e.g. at some longitude 7-eleven stores would switch from opening at 7am to 6am. this would probably follow political boundaries like state lines much like timezones, but be determined on a chain-by-chain basis rather than state-by-state basis. of course, now that we have google maps, that would be much less of an issue. 2. also, once you have gotten past your jet-lag, it might be slightly more confusing to make dinner reservations because you might not know off hand when you will be hungry, that is however a very minor pause rather than a big issue. 3. lastly, determining when businesses would be open (and people are awake) in distant places would be different. instead of checking the timezone offset and assuming 9-5, there would probably be an official state "business hours". this system would in fact be more effective since not all regions use 9-5. e.g. "temperate" latitudes tend to be closer to 8-4 to optimize daylight during commute, while tropical climates tend towards 10-6 to minimize commuting during the afternoon heat. some regions have longer split work-days with long lunch/rest breaks in the middle, while other regions have shorter workdays due to labor laws. **side note regarding decimal time:** on the whole, humans are unlikely to eliminate timezones until we switch to a decimal timekeeping system. both "french republican calendar" and its modern revival "internet beats" use timezone-free decimal clocks whose date flip happens in sync with traditional france time (gmt+1:00). unfortunately, decimal time seems unlikely to gain broader usage until we have a non-trivial polar or non-earth population. even then, there are likely to be several decades during which both systems are used (e.g. today we use 12hr and 24hr clocks). also, emerging technologies make the transition easier every year. e.g. soon you will be able to ask siri "when would be a good time to call my uncle in japan?", and she will consider average local business hours as well as when your uncle specifically tends to have online activity. meanwhile, if you would like to start using a decimal clock, there are several mobile apps for it. unfortunately, most of those clocks will shift around as you move between timezones. oddly enough, the only decimal clock app i have found that allows you to lock the timezone is the startrek clock app, since one version of "stardate" was essentially the french revolutionary system. [Answer] I suspect it would be very like the situation with months that we have now. In the UK, January is considered likely to be cold, possibly snowy, and generally a really bad time to have a barbecue. In New Zealand, January is early summer, warm, sunny, and absolutely ideal for barbecues. In the same way, if everyone worked on UTC, the UK would be pretty much unaffected (work starts at 9am, and goes on until 5pm, or something like that). Australia would effectively flip AM and PM, so work starts at 9pm, and goes on until 5am - someone starting work at 9am there is on a night shift, and someone working at 5pm is gearing up for the breakfast rush. It would take a little getting used to, but people have adjusted to a lot more (Christmas on the beach!) The more interesting changes are all the places in between. In the west coast of the USA, 1pm would be the starting time (roughly), but there would probably be some determination of what a reasonable work time was, either from the top down (government says a reasonable working day is 8 hours between X and Y), or from businesses choosing when seems reasonable, and everyone else fitting with them. In an ideal world, businesses might take the switch as an opportunity to desync with the local rush hours - there is a lot of cultural inertia behind the idea of "9 to 5", but if local businesses worked a wider range of start times, then peak traffic could be spread across a wider timespan. That would reduce jams, but would rely on businesses being willing to take a risk on being out of sync with others in the area. It's fine if you start a bit before your main customers do, unless they often have issues last thing in the day! In *our* world, though, I suspect that businesses would stick to exactly the hours they work now, just with different names. Working 9-5 would happen in the UK and Australia, but working 1 til 9 is still a way to make a livin' [Answer] Here are two things that nobody seems to have touched on: the definition of days of the week; and related *resistance* to the change. How do you define a "day"? To put it another way, what is "Monday"? Is it a 24-hour period starting at 00:00 and ending at 24:00? If that's so, then Russ from Auckland never "works Mondays". He starts work at 21:00 Sunday and knocks off at 05:00 Monday. Meanwhile, Mona from San Francisco starts her working week at 17:00 Monday and doesn't finish until 01:00 Tuesday. The most plausible alternative is a "mixed" system, whereby day names are associated with local solar days, regardless of the time. This is going to be annoying and inconsistent, but it does have a certain advantage. Let's say you wake up "Monday morning" in Auckland, in the early morning light at 19:00. When 24:00, noon, rolls around, what comes next? * If Monday means the local solar day, then "Monday morning" is followed by "Monday afternoon". * If Monday means 00:00 to 24:00, then "Monday morning" in Auckland is followed by "*Tuesday* afternoon"! And then there's a the second point: cultural, and especially religious, resistance to this change. (Don't underestimate this; it's arguably what sank metric time in Revolutionary France.) Let's say Russ goes to church on Sunday morning, at 22:00. He's already been observing the Sabbath for 22 hours, and his friends who go to the evening service went *before* him, not *after* like they did in the old days. It's also awkward when the service is followed by a church lunch that runs into *Monday* afternoon. But that's not what really bothers his conscience. He knows that in his grandparents' day, they observed the Sabbath from (what he now calls) 12:00 Saturday until 12:00 Sunday. Is his church really keeping the Sabbath? It's the Seventh-Day Adventists all over again! And what do they do with Good "Friday"? Judaism may have an easier time of it, because the Shabbat is already technically observed according to a *conversion* of systems: it just so happens that the last day of the Hebrew week starts on what we presently call "Friday". So Mona, who's Jewish, observes Shabbat from 02:00 (sunset) on Saturday until 02:00 on Sunday. [Answer] Cory Doctorow's free (released under a Creative Commons license) book ["Eastern Standard Tribe"](https://en.wikipedia.org/wiki/Eastern_Standard_Tribe) describes a related situation. In the story, people belong to "tribes" that share a reference timezone, e.g. the Eastern Standard Tribe, whose reference time is according to the EST timezone. All people who belong to a tribe try to maintain a circadian wake-sleep cycle appropriate for that timezone, regardless of where they physically reside. Advantages of this culture include making the communication among members of a tribe straightforward, and eliminating the jet lag and related hassle when physically travelling. But, as might be expected, the situation creates animosity between the different tribes, each of them, in a sense, living in a parallel world. Also, in each latitude, the tribe whose timezone best fits the human body's natural circadian rhythm is better adapted, and has a "home advantage". ADDENDUM (trying to better relate to the question): I don't remember the history of the world in the story (and I'm not sure it was explored), but I assume that people tried to abolish time zones, like the OP suggested, but failed to do so. Instead, there arose a competing set of standards tribes, where each tribe enjoys the advantages of the abolition within itself. One might conjecture that later in the history of that world, a single tribe would emerge victorious and impose its timezone upon the rest, thus leading to the world in the question. [Answer] One problem with UTC everywhere is that Europe would be advantaged by having days that change during the nightly inactivity. It is easier to plan with. Other continents would switch date during the day. This would be perceived as "timezone colonialism", imposing the time that is convenient to Europeans at the expense of making it confusing everywhere else. So nobody would be willing to accept that. If a single timezone were to be imposed over the world there would be unending debates as to which timezone should be used by all, everybody trying to explain why "my timezone is better than yours". One more egalitarian option would be to use sidereal time, the time according to the stars. It would look like the timezone shifts continuously around the clock over the year. If noon is in the middle of the (solar) day in summer, then it will be in the middle of the night in winter. Every region on Earth would enjoy a couple of months where the solar day aligns with the calendar days. I am not sure it will actually help to reduce confusion. Actually I am sure it will not help to reduce confusion. Think of train timetables! But it is egalitarian. If one time should be adopted by all it could be well that sidereal time gets the least opposition, along the lines of "if it gets messy for me, I want it to be messy for everybody". [Answer] The only way you can get rid of time zones without problems is if you could remove the dependence on the sun. This is impractical on Earth. **So other options:** If we were ever to try to colonize Titan, the sun would just be a bright star in the sky. It's also really really cold there. It does have an atmosphere, which makes it attractive to colonizing though. So you make it possible by orbiting several fusion reactors around the planet. Because they are ringing the planet, you could light the entire surface at once, and turn the fusion up or down to simulate day/night. Maybe refuel the reactors at night. Since the entire planet is lit evenly, you could just have a single time that everyone uses. A multi generation ship would have to be pretty big. In a space ship, there would be no day or night, just ship time. Not quite a world, but if it was big enough it could feel like it... [Answer] There was already a world without timezones for a longer time than with. Before the railroad occured, every place in the civilized world defined 12:00 as the time where the sun was on it highest point. But as railway transportation took place, it was nesseccary to have one national time just to be able to create schedules for it. So the real deal would be not to change for UTC, instead it would be right to change to real local time! Today this would be no problem at all, because we have computers and GPS which could calculate this real time with ease. In that case, no time zones would be needed any longer, just UTC and the GPS-Coordinates to calculate real local time. Of course this would also make summer-/wintertime obsolete! [Answer] It also makes "day" milestones more difficult to determine. Especially if you live somewhere like I live, where the date would generally change as I'm driving home from work or eating dinner. * When do you celebrate your birthday? * What date did you get married on—does this depend on whether you got married in the afternoon or evening? What about weddings that last for several hours between the service and the reception? * Quite relevant to legal systems, when are you eligible to vote? Voting time will be sunrise to sunset (say), but what if the day changes while the sun is in the sky? Do you have to turn 18 (in the US) on the first date, or can you turn 18 (in the US) on the second date during daylight? * Does Midnight Mass (for Western Christians who celebrate it) happen at 23:59 UTC, or does it happen at local midnight? If at local midnight, is that local midnight of the 24th or the 25th? Either way you pick these, they end up a bit odd, and totally contrary to how humans operate and think. [Answer] The real problem is not so much timezones, but rather keeping accurate clocks and *synchronizing* them across long distances. Whatever standard you pick doesn't *really* matter so much - it's *having the standard* that makes by far the largest difference. If it's UTC 3:32 in New Yord and it's UTC 3:32 in Tokyo that's fine - at least you still know what time it is, and it's reasonably convenient. Before time zones, accurate clocks were expensive (and not that accurate). Large public clocks formed a local reference for people in a given town or city and those clocks were set by the sun at local noon (often using something like a sextant, same as a sailor would at sea). This meant that 2:10PM in Chicago was maybe 2:34PM in Cincinati, 1:53PM in Kansas City, 2:42PM in Pittsburg and 3:01PM in Philadelphia, etc. The chaos came from the train system, where you had to leave one city and catch a train in another, scheduled to leave at a specific local time that was different from the local time you were leaving - possibly moving past several other cities in the meantime. Rather than a single time reference, you would have needed five or six or more pocketwatches and a spreadsheet of calculations to figure out which train you needed to take to make another at a given time in a given city to be at your destination at the local time you needed to be there. *That* was the nightmare before timezones. Standardizing time and *synchronizing* everyone's clocks, doubly so with very accurate clocks, is what makes for functional interaction over long distances. The particular details of the standard don't really matter - people adjust and get used to whatever that standard is, whether it is their local timezone time, UTC, or Stardate 14352.6. What matters is that everyone everywhere agrees on what time it is and can communicate that to each other in a clear and easily understandable way. In a way, a single standard is actually clearer and easier because you need one fewer piece of information - the timezone. Militaries (and airlines), for example, almost always work on UTC (aka : Zulu) time because their operations are frequently crossing timezones and a single time standard ensures that everyone is absolutely clear on where and when things are happening. [Answer] First, we'd still have time zones after a fashion. We'd all have an "offset" to describe how much my time differs from UTC, and how much yours does, then I would subtract my offset from yours and add the offset to my clock to figure out what effective time it is where you live. For example, I'm in UTC-7 and you're in UTC-5. Yours-Mine = -5-(-7) = -5+7 = 2. So if it's 03:35 here, it's like 05:35 there. Which is what we do already to determine the actual time. So that wouldn't change. Second, we'd either have a secondary set of local clocks that add our own offset to UTC -- oh wait, that's what we're doing now. Or we wouldn't. Let's say people were somehow convinced to always use UTC. What would happen? * People in different parts of the world would think about "9 AM" in different ways. People in Europe/Africa would think of it as morning. People in the Americas would think of it as afternoon. People in Asia would think of it as night. * People who work a shift where the date changes would have to get used to changing the date in the middle of their shift. Because most people work daylight shifts, this would affect a larger percentage of the population that it currently does. That's really about it. "9 AM" already means something very different to me than my mom. For me, it's the middle of my sleep cycle. For my mom, she's already eaten breakfast and fed the animals on the farm. Between noon and 7 PM we're both awake, although I'm on the just-woke-up part of my day, and she's on the about-to-go-to-bed part of hers. So we've already fixed that problem: just ask your friends what time they're normally available and on what days, then figure out what part of that window coincides with your availability. And lots of people already have to deal with date changes midway through their shift. For most people, it's not relevant. If I sign a check or datestamp my logbook with yesterday's date, nobody cares. For people whose jobs requires the correct date, software normally does it for them. Otherwise, they can look at the time. If it says 00:XX or later, it's tomorrow. If it says 23:XX or earlier, it's yesterday. At the beginning of your shift you'd write both dates for easy reference. You don't even have to convert to a 24-hour format. The AM/PM system is completely unambiguous. There are exactly 24 distinct hours per day. The date changes on the PM -> AM change. It's even in alphabetical order for you. I would be happy if the AM/PM system didn't follow 11 AM with 12 PM. It needs to be 11 AM -> 0 PM or 11 AM -> 12 AM -> 1 PM (noon), but that's true regardless of timezones or a lack thereof. [Answer] All answers so far assume that people keep their current time schedules and change the name of the time they use to UTC or whatever central time unit is used. When I read your question I assumed you would impose the times of UTC to people wherever in the world. So they would start working at 9:00 whatever the sun time in that location. This will work in Europe and much of Africa where the work will still mostly be done in daytime. It will get harder the farther you away from the Greenwich meridian and in East Asia, Australia and Oceania, you will have to work in the middle of the night and be off during the sunlight hours. People will complain about that and rightly so, as most people do not do well working just nights. One time zone may work on colonized planets where most people never go up the surface, but not where people would go out in daylight as a rule. [Answer] Time zones are not man made. They have always existed. The majority of people in the world are awake during daylight hours and asleep when the sun is down. It is a natural and expected phenomenon. Ancient sundials exist all over the world including the US and Canada supporting the notion that human beings are highly organized and extremely intelligent creatures. ]

[Question] [ I'm designing a world a of supernatural beings loosely based on Christianity/Judaism as described in [Naming the forces of the Purgatory?](https://worldbuilding.stackexchange.com/questions/63031/naming-the-forces-of-the-purgatory) who visit Earth without humans being aware of them. They consists of angels & souls with three different affiliations (good, bad & neutral). When these supernatural beings come to Earth they are embodied as humans. The problem is that today everyone has a smartphone, and any fight that involves shape-shifting, flying, teleportation or fireballs caught on camera will quickly end up as most shared video on the social media thus destroying the masquerade. What kind of powers should I give them, that allow for plausible deniability of the supernatural? Dead bodies are not a problem for me, when they're killed the angel/soul returns to their realm only thing that remains is the human body. [Answer] Making them proficient with weapons and tactics like the best of Delta/SAS/Spetznaz/SEAL while having supernatural senses IR/UV/Smell/Hearing/[Aura reading] that will allow them to have heightened situational awareness. This will make them way too dangerous for 99.99999% of the human population. If you want more, just add supernatural aim, faster reflexes, extra strength and stamina. This will give you real monsters that could handle several normal humans without much difficulty. The scariest part of any supernatural is the ability to possess living beings. Having a SWAT officer freak out and kill his buddies is a huge force multiplier, and could always be explained by somebody snapping out due to stress, divorce, drinking, drugs whatever. A cat or dog could spy on a crime scene without any suspicion. None of this things would mean anything even if they are caught on camera. [Answer] Supernatural senses: * Bear's sense of [smell](https://worldbuilding.stackexchange.com/questions/60275/will-privacy-disappear-if-our-sense-of-smell-was-strong-like-that-of-a-bear) * Pit viper's infrared [detection](http://www.nature.com/news/2010/100314/full/news.2010.122.html) * Near infrared sight like some [birds](http://www.livescience.com/26994-how-birds-uv-vision.html) * Eagle eye [acuity](http://www.livescience.com/18658-humans-eagle-vision.html) Supernatural communication: * [Telepathy](https://worldbuilding.stackexchange.com/questions/47665/scientifically-plausible-alien-telepathy/47730#47730) * Touch [based](https://worldbuilding.stackexchange.com/questions/1323/could-inter-individual-communication-be-based-on-dna-transfer) DNA reading (this would be fun) Mind games: * Read muggles' minds * [Dominate](http://whitewolf.wikia.com/wiki/Dominate_(VTM)) - impose your will on muggles * [Presence](http://whitewolf.wikia.com/wiki/Presence_(VTM)) - terrify muggles * [Dementation](http://whitewolf.wikia.com/wiki/Dementation_(VTM)) - make muggles insane * [Obfuscate](http://whitewolf.wikia.com/wiki/Obfuscate_(VTM)) - conceal yourself from their minds Physical: (keep this toned down to a deniable level) * [Potence](http://whitewolf.wikia.com/wiki/Potence) - strong as a [chimp](http://abcnews.go.com/Health/Wellness/chimpanzees-humans-sizing-strength/story?id=16696826) * [Fortitude](http://whitewolf.wikia.com/wiki/Fortitude_(VTM)) - tough as [deer](https://www.youtube.com/watch?v=s1m-K1D_uQs) / [honey badger](http://www.todayifoundout.com/index.php/2011/08/the-worlds-most-fearless-creature-is-the-honey-badger/) * [Celerity](http://whitewolf.wikia.com/wiki/Celerity_(VTM)) - speed & reflexes as [moongoose](http://www.animalfactsencyclopedia.com/Mongoose-facts.html) * [Regeneration](http://voices.nationalgeographic.com/2013/08/28/worms-that-regrow-heads-and-other-regenerators/) - though a slow one, don't have bullet wounds disappear immediately [Answer] No magic required. People just don't believe. And the amount of fake evidence is overwhelming. Look on YouTube. You search for walking on water, and you will see a lot of fake videos of people walking on water. If you video yourself walking on water and then post it to YouTube, then people would assume that it was a fake like all the others, and if you insisted that it was real, then they would either think that you're lying or crazy. The same can be said for anything supernatural, even people who claim to believe in the supernatural tend to be skeptical of any evidence that indicates that the supernatural actually exists. [Answer] They embody humans but are not part of our realm. So their realm exists outside of our realm, but can inhabit the same place. So when they fight they fight in their realm while the human realm seems like nothing is happening. Like their human embodiments could be sitting in a coffee shop discussing something while their angelic bodies are fighting in their dimension realm. So you have the dichotomy of a calm conversation vs a fierce battle going on at the same time. Or when they do fight in the human realm the magic only is visible in the other realm so it just looks like play fighting to humans. Human damage is human and magic damage only affects the angel or soul. [Answer] Use the classic vampire/ghost tactic; they don't resolve on film. You can extend this to also not being recordable on any media. Maybe their presence in the human host causes their atoms to vibrate at a different frequency or reflected light to be polarized in a way which causes [aliasing effects](https://en.wikipedia.org/wiki/Aliasing) on the recording media. The resulting recording is too indistinct for forensic analysis. This allows them to have any superpower you want, without producing evidence. [Answer] Even a very limited clairvoyance/precognition would be a huge advantage. I suspect this could likely be masked at much lower cost/peril than the advance warnings/info were worth. Some people just have good 'intuition.' Who could fault that? I suspect that such a power would have to be very, very constrained, lest it be a total drama remover. [Answer] Magic is a “hack” going against the normal orderly rules of the universe. The universe will resist being altered in a strength that grows esponentially with the effects of the anomaly. If you levitate an apple in a closed room, it has no effect on the rest of the world, so it takes little effort. The effects are *local* in space and *die out* in time. After the event, it will be impossible to determine whether it happened at all, so it doesn’t “keep charging” for it. If you knock over a building, it affects lots of things and has ripple effects in the lives of people affected, contractors who deal with it, etc. If there is a *plausible natural explaination* the “cost” can be brought down to a workable level of magic expenditure. Meanwhile, like surface tension, the energy tries to minimise itself, once past the commanded action. Preventing a witness is a tiny bit of magic in itself — on a typical day an ordinary person may look left instead of right, or leave for lunch 5 minutes different, and that change has very litte lasting effect and dies out over time as things are just typical; and it does not seem “unnatural” at all, so it’s very cheap. If a spectacular miracle got documented in a credible manner, it could be *very* costly, and it would not happen — his intent to perform magic would fail. But preventing witnesses and even damaging devices that might plausibly break anyway is the soap bubble pulling in to minimise its surface: if the solution can be found that is within the available magic energy, it will work. The magical beings learn to maximize the effects of their power budget by being subtle, working indirectly, and avoiding witnesses and records. [Answer] Why not add an ability equivalent to a small, small [EMP](https://en.m.wikipedia.org/wiki/Electromagnetic_pulse "EMP"). They could control the size, maybe even the distance and direction to hit certain objects. Another thing to consider... The EMP doesn't have to be permanent, so surveillance equipment wouldn't be fried permanently afterwards. This would allow it to still function after your creature left the area. [Answer] Controlling luck/destiny is a simple power that could make accidents ( car accidents, falling brick, etc like in the Final Destination movie ) happen to enemies without any suspicion of supernatural power. It can also distract people or ensure that someone gets at the right place at the right moment or provide help ( shelter, food, even finding a weapon laying on the ground etc. ) or money ( just enter a casino and bet or pick the wallet someone 'forgot' ) to the creature at the right moment. [Answer] Time Stop: any ability to move faster than the fastest high-speed cameras would avoid the video issue. Invisibility Replication : ability to duplicate self and run multiple bodies at once. As long as dupes stayed away from each other. Possession of other's body. Including animals. Card counting/high-speed math Improved senses: long range sight / hearing / touch / smell. Any power that can be used in a given setting, like touch healing for a physical therapist. [Answer] The obvious one is: The power to look like a cartoon character! Sure people can post you on social media, but no one will believe them! Or perhaps they have an angelic glow, and appear bright even in dark surroundings, but without casting the light onto surrounding objects. Either way, anyone who looks at it will just think it's a hideous photoshop attempt. Or if you are looking for something a little more serious, the obvious one is the power not to be photographed (like the way a vampire doesn't appear in a mirror) [Answer] The gimmick from Carl Sagan’s *Contact* — cameras (and other recording devices) mysteriously stop working whenever anything paranormal happens.  Witnesses will appear all the *less* credible when they fail to produce tangible evidence. [Answer] Many good points already given, I would give small but orthogonal super-power request. 1. Active digital invisibility - you can throw fireballs or eat peoples alive still none can see that through flash screen (you can test that at home - start video-recording on your phone and put flashlight in front of it, voilà). The "supernatural" is to adjust light level (automatically?) that it is not visible for eye, but still counters all recording. * For inspiration <http://www.boredpanda.com/anti-paparazzi-scarf-flash-photography-protection-ishu-saif-siddiqui/> * From angels and demons perspective <https://en.oxforddictionaries.com/definition/halo> sounds promising 2. Passive digital invisibility - make-up to hide from face recognition. If 1. counters consumer grade stuff and vigilant citizens, this make-up is against intelligence agencies that work on planet-scale sniffing internet traffic, operating cameras and satellites. * For inspiration <https://cvdazzle.com> [Answer] Alternative to my last answer you say that sone Powers/abilities of the angles/demons are to powerful to be seen by the human eye, or conceived human mind. In supernatural for example humans can not presieve angels wings or there true form. [Answer] There are several paths you can take, depending on your overal style. Apart from psychic power or enhanced biological body, there's always Rowling's handwavium tactic: *Something* about them makes devices fail to record them when they are about to engage in combat or other mischief. Maybe they weren't even initially aware of that. Or maybe when one of these gets angry, *something* just makes you want to **not use your phone** and maybe run as fast as you can. This is inspired by anti-muggle charms in Harry Potter. It is not the way of logic, but it enhances the mystery of the story. [Answer] # Misdirection This is easy(ish)! Especially if you're willing to expend some effort setting the stage beforehand. Just create a few viral marketing campaigns where you do some crazy huge production. Think 'flash mob' but with whatever explosions, fireballs, etc. that you might think your battles are going to need. Now, release the videos on YouTube, "pulling back the curtains" and showing the boring "truth" behind the cool effect. Now when you do the same thing for real you can just claim that you were doing another marketing thing. ]

[Question] [ Often in films and television shows when a person's brain is 'injected' with more information than it can handle, they suffer from immense pain. What would actually happen if you did supply a human brain with too much information? Would it act like a processor and break up the information or would it 'clog up the pipes'? This can be in two forms - directly and sensory. [Answer] Your brain receives more information than you can handle *all the time*. For instance, right now, your entire computer screen is within your field of view but you're ignoring all but a word or so of it at a time. So the (rather boring) answer is that nothing unusual happens when you receive more information than you can process because it's the absolutely normal state for a brain to be in. For the classic example, see this experiment by [Simons and Chabris](https://www.youtube.com/watch?v=vJG698U2Mvo). [Answer] I think the answer is we do not know for sure. It seems brain has more capacity to store information that we can get in our lifetime. I think our retrieval system is not perfect so we cannot access the information stored in our brain. There are proven instances of people who can recall huge amount of information that is fed to their brain (see [Kim Peek](http://en.wikipedia.org/wiki/Kim_Peek)). There are also people who can also store a lot of 3D information and can retrieve them (see [Steven Wiltshire](http://en.wikipedia.org/wiki/Stephen_Wiltshire)). These people are classified in a different category but the question remains, whether it is their ability to store the information or retrieve them. It has been shown that people also can retrieve information under hypnotism that they cannot when they are normal. [Answer] **Depends if you're writing for TV or a book.** On TV, you are pressed for time and would typically be observing the reaction from outside. Then something dramatic, resembling an epileptic seizure with their hair catching on fire is appropriate. You can also go with the matrix-style download, where seizure is followed by a sudden revelation. In a science fiction book on the other hand, the author will typically focus on the first-person experience of having your brain over-loaded. Or if written from an outside perspective, at least make it more drawn out, like a prolonged illness. It's not uncommon to describe reactions akin to hallucinations and fever-fantasies, where the person is babbling about things the others around him can't see or does not understand. Fred Hoyle's "The Black Cloud" employ this strategy, where the overloaded person is bedridden and eventually dies from the massive re-organisation his brain is undergoing. A change in personality is another common trope in this situation. You could also go with a more heart-breaking angle where the person feels overloaded and where taking in and processing the information is at the expense of other tasks, like remembering to eat and dress yourself, find your way around a town or being unable to retain personal memories of the day. In short: You portray the onset of dementia. Again from a strict story-writing perspective, I think you have to first ask what you want to accomplish with the scene where the person is overloaded and where you want the story to go, and only then do you select the proper symptoms of overloading. [Answer] As pointed out already, more information than properly processed is the normal operating mode for the brain. However, there can be "wrong" information that affects more than its "proper" sensory processing. It is well-known that certain visual stimuli can induce seizures in predisposed people. This occurs as immediate consequence of specific forms of information overload. Case studies for chronic information overload are currently performed in large scale experiments using so-called "smart phones" which are more recent variants of Internet carrying devices. Prolonged use as exocephalic prosthesis appears to be cooccurent with low levels of encephalic activity. [Answer] I'd guess the brain would forget most of the information it was provided with, so that it didn't get overloaded and damaged. After all, this is what happens as people get older: as they get more and more information, their memories start to get worse, as though some knowledge needs to be pushed out to make space for the new stuff. Nobody remembers *everything* that's ever happened to them, because their mind isn't big enough - so if it wasn't big enough to take one big load of information you're trying to provide it with, you'd probably see the same effects. [Answer] I have been reading "Brain Rules" by John Medina and there is paragraph explaining that the human brain can only fire 2% of its total neurons at any given time. If more is attempted fainting may occur as the brain cannot "power" the neurons. Additionally it is impossible for the brain to multitask attention. The conscious brain can only focus attention on one task at a time and this is why the brain can never be "overloaded" as such. You may get a headache but overloading is hardly happening at the neuron level. [Answer] As has been mentioned in several of the answers - we typically receive way more sensory input than we can handle. However, typically that's filtered out before it reaches the actual brain. And in many cases the brain simply filters out the information as "noise". Apparently we have fairly finite [cognitive resources](http://seriouspony.com/blog/2013/7/24/your-app-makes-me-fat), as well. Throw in [excitotoxicity](http://en.wikipedia.org/wiki/Excitotoxicity), and it seems like if you were able to somehow override the filters in the brain and directly inject the sensory information it seems like it would [fry your brain](https://www.youtube.com/watch?v=ub_a2t0ZfTs). How lasting the effects would be, one could probably only guess at. I would expect you'd suffer some pretty serious hallucinations, both auditory and visual, at minimum. Depending on the intensity of the input, I'd also expect that it would seriously alter the way that individual experienced the world. [Answer] If we assume that getting more information means growing new synapses, then it should happen at a very high rate. Considering that the brain does not do it by its own (the closest might be the state you get in when you try to prepare for the final exam during the last night :) ), it might be rather painful process. Quite possibly, it's also energy-consuming, so the person receiving information in such way might feel quite devastated at the end. On the other side, the space in the head is limited by the skull, so it might be even possible that too much new neurons and connections between them might increase the brain volume and hence the pressure from the skull becomes higher. Plus more blood will be needed to feed the growing system. More blood -> also more pressure from inside, more work for the heart to pump all that blood in. Actually I wonder if we get to see the movie where the skull will crack as a result of information receiving process not being able to stop :-} [Answer] As [David](https://worldbuilding.stackexchange.com/a/2867/764) suggested, the normal function for a human brain when presented with a great deal of information is to drown out everything but a single focular point - you're probably already doing this while reading this question, ignoring sounds, ambient light and other informationt that is irrelevant to your current task. But this is not just true about ambient information - you've surely heard of [information overload](http://www.infogineering.net/understanding-information-overload.htm) and the very real (and current) problems it presents. This is a separate and entirely different phenomena from the sensory overload that David is describing - wherein the brain attempts to block out most of it. Though the effect is much the same. Say you're reading an internet article, that one I just linked above for example. Your brain will try to process the information as you read it, but if you have say, multiple different articles open on your browser at the same time, and are attempting to take in all of the information they have at once, the information you get will be incomplete and fractured - the same as if you are having a sensory overload, your brain will try to reduce the input to a manageable level. But say you don't stop, or literally cannot stop, and are forced to take in all of that information in a continual stream with no break or rest. Over time, parts of the information would get through to you, fractured, disjointed and without context. They would be lodged in your mind, and you may not even be aware of their presence. It could very badly damage your ability to think for awhile, or possibly even for prolonged periods, as sensory input in excess can damage your ability to take in information from those senses. Assuming it is an option, your brain may shut down and try to make you sleep due to [mental exhaustion](http://www.ehow.com/about_5382024_mental-exhaustion-symptoms.html), but if you *can't* sleep, you may start to experience symptoms of sleep deprivation, ranging from mild to extremely severe. In short, if you are forced to take in more information (not just sensory information, but actual information) than your mind can process at once, you could suffer severe mental breakdowns over time. [Answer] When driving long distances most people tend to forget most of the trip especially if they are not making a mental effort into remembering it. Sometime I am on autopilot when I drive and hours can pass with no recall of hundreds of miles driving. I would imagine even with your eyes stitched open with eye drops dripping in and on LSD the ability to turn off this part of the brain would be harder, but after a while the pictures would be no more than abstract pictures with no meaning and sound would be like Charlie Brown's parents talking. [Answer] While the accepted answer is correct, it can be expanded on. Humans constanly receive tons of information, from the position and temperature of their body to stimuly to pain or roughness of things you touch. Much of this is filtered out by the brainstem for example, which will filter on what it thinks is relevant. If you start talking about lice or itches, the brain is going to let such impulses through more and people start to feel itchy. On the other hand pain has a lower importance than many other sensory inputs (strangely enough). This is why people rub on or near a painful area, as the sensory input from the rubbing reduced the amount of pain signals that reach the brain. But the question isnt about filtering information but about something I personally have a lot of experience with: too much information presented to the brain in a short time. This is possible for "normal" humans in extreme situations like loved one's dying or having to run for your life. But if you have autism much of your information filtering systems arent functioning and sensory overload is everywhere. For people on the full spectrum just someone's face can send too much information and overload them, hence some never learn the intricacies of social interaction. Others can be overloaded by noises, multiple conversations, quickly shifting situations and other such things. How you react to that is different from person to person, but aside for headaches physical pain is usually not one of them. Rule of thumb is that they dont really process new information so they'll have a hard time responding to conversations and situations or remembering something of that period. Often the brain will go on automatic and perform a simple task, such as doing the dishes or going to the bathroom to give the mind time. If you keep overloading the mind you can expect hostility, outbursts of anger and violence or even flight responses where the person will simply try to Block out any and all information by going away from the situation, often finding an empty room and if able asking to be alone. On the plus side it is possible that only some responses go offline, such as feeling anxiety when someone is hurt allowing that person to perform basic first aid without all the annoyances that fear and indecision bring in such a situation. ]

[Question] [ My world has a city of glass found along the outskirts of a desert. I decided on this because sand can become glass and so it was a huge resource that could be used for building. However, the concern has come up that it would bake the citizens alive. Originally, the glass was textured and thick enough to look black, and this is what caused concern. Is there any way I *can* have a city of glass in the desert without cooking its denizens? [Answer] My first thought is [Obsidian](https://en.wikipedia.org/wiki/Obsidian). There are problems with this; it's a volcanic glass, and you're in a desert, but conceptually, the idea is reasonably sound. *I'm going to assume for the purposes of my answer that by 'desert', you mean a hot, dry sandy desert like the Sahara or Gobi, not the strict definition of a place with no rainfall that could also include Antarctica. I'm inferring from your question you're only looking at places with lots of sand and hot days.* In many countries, we use double glazing as an insulative material. There are even now triple glazing products, which effectively put 2 air pockets, or vacuums, between you and the elements. It's suprisingly effective, although obviously not as effective as walls with thick insulation bats. That said, if your inhabitants can shape a heavily tinted glass like obsidian or even manufacture it from the sand around them, then they can build homes with shelter from the sun via double or triple glazing using glass like obsidian which is (more or less) opaque. Glass houses in the desert are a bad idea because of the greenhouse effect - the sunlight getting in gets trapped and heats up the internal areas of the glass house even further. Great if you're growing tropical plants in Scotland, terrible as a desert housing solution. What obsidian would offer is the ability to block the sun from getting in in the first place. You get shade which in the desert is important. What you *don't* get is a shelter medium that can breathe, and release the trapped heat. Glass can act as a thermal mass though, which could actually work in your favour on this point. Deserts are known for being hot through the day, but they're also very cold at night. Why? because they have no water around them, meaning a very low thermal mass. Your obsidian would spend the day baking in the sun, retaining heat. because you've double glazed, you won't feel that heat until early evening, but through the night it starts to release it, meaning that it actually serve to keep you *warm* through the night, when the desert is bitterly cold. So, if you do it right, all you've really got to do is introduce impurities into your glass that turn it black or some other colour, then build your homes with air gaps between panels, and you have a good chance of building homes that can regulate temperature reasonably well. You're still going to be hot during the day, cold at night, but not as much as you'd otherwise be. [Answer] **You Need a Windcatcher House** [](https://i.stack.imgur.com/4LNjt.png) Sheets of glass for the most part is not a great building material. Glass in the form of bricks can be structural, which will allow you to build up. You could build a glass house and yes, it would get hot in the desert. But proper desert homes don't get hot. Instead of building a house with four walls and a pitched roof, you just need to incorporate a few features to make your desert home comfortable. **You Need a Windcatcher** A windcatcher, also known as a malqaf, is a tower higher than the rest of the structure which has a shaft that leads from the tower to the living facility. The open face faces the prevailing wind, which catches it and pulls it down the tower, which cools your glass structure. The windcatcher does not necessarily cool the air itself, but rather relies on the rate of airflow to provide a cooling effect. They have been used in desert climates for thousands of years. **How about Making Ice?** You might find that this structure cools your home, but you want an extra blast of cooling for water storage, food storage or making ice, using only the wind. What you need to do is add another tower which faces the opposite direction of the prevailing wind. With this tower, the wind is drawn upward using the Coandă effect. It's more effective with a basement and if your settlement is feeling industrious, an underground water channel with holes spaced along the length of the channel to the basement of each home. The ancient Persians called this channel a qanat. [](https://i.stack.imgur.com/Bptjx.jpg) * <https://en.wikipedia.org/wiki/Coand%C4%83_effect> * <https://en.wikipedia.org/wiki/Windcatcher> * <https://en.wikipedia.org/wiki/Yakhch%C4%81l> * <https://en.wikipedia.org/wiki/Qanat> This combination of design elements will keep your desert homes much more manageable and energy efficient because you're not spending resources on active cooling. It's passive and it works. Good luck staying warm. [Answer] *Problems* **Reflection:** Just as swimming will burn you faster than sunbathing (light reflecting off the water), light reflecting off the glass simply means that much more light to burn you. * Solution: buff the glass to reduce reflection. **Refraction:** There could easily be spots in the city, despite all efforts, that act as magnifying glasses (ants... magnifying glass... mine was a sordid childhood). Corners are your biggest problem, but any angle can create magnifying refraction. It doesn't actually need a curve (curves create precision for, e.g., distortionless vision, but any type of "bulge" will cause magnifying refraction). * Solution: cut insets that break or redirect (like a prism) the "flow" of light through the glass. * Solution: Color the glass to increase its opacity. *Benefits* **Visibility:** You can see your enemy coming! You can see where they are outside the wall! They can also see you taking a shower... so it might not be *that* much of a benefit. * If this is desirable, then the previous solutions must be used carefully or the visibility is lost. **What is it about a glass city that intrigues you? The fact that it's glass? The transparency? The shiny reflection as the sun rises?** This is a very important question, because it will dictate how you solve your problem. BUT! There's one solution that might give you everything you want. *Thin silvering* Silvering glass is what makes mirrors. Thin silvering (silvering you can see through) is that makes one-way mirrors. So, anywhere in the city that wants privacy, you apply thin silvering *inside that place or room.* Thus, people can't see in, but they can see out. Light can't burn through into the room — but it would cause a horrible headache for anyone approaching from the wrong angle. And if you really want to take advantage of that, use prisms as building roofs such that the light of the morning is redirected and cast behind the city, and vice-versa for the evening. Thus, between the prisms and the silvering, there isn't an approach to the city that isn't blinding. *Please note that I've made a few assumptions as to why you asked your question. If my assumptions are wrong, let me know and I'll adjust my answer.* Oh... and your buildings are going to want a LOT of ventilation. Preferably from holes dug deep in the sand. Really deep. But that's just an issue of construction. [Answer] Look at how termites in Africa build their colonies. To prevent from being cooked inside their homes, they build tall chimney like structures. The sun heats the chimneys, causing air circulation throughout the colony. If your cities utilize a similar design, the city could remain fairly comfortable at the base levels. You use these convection currents throughout your city for other functions as it suits you. <https://www.sciencemag.org/news/2015/08/how-termite-mounds-breathe> here is a little article that may help. [Answer] Okay so other answers have touched on windcatchers, and yes, great idea to include this; mainly because it gives you the opportunity to make 100 meter tall glass spires. But if you want, there might be another couple of cool little worldbuilding devices you can use. What if they used slag glass to make most of their buildings? This stuff is the result of impurities such as iron oxide or copper. It's fairly opaque, and very [beautiful](https://proxy.duckduckgo.com/iu/?u=https%3A%2F%2Ftse4.mm.bing.net%2Fth%3Fid%3DOIP.vWIp5KlZ2qUxnNQ01ZObZQHaHu%26pid%3D15.1&f=1). However since the city resides on a desert of near perfect purity, they have a huge import of metalwork byproducts. This way the city can be referenced in political and economic dialogues with references to 'slag export'. This will also allow the glass city to be extremely colorful as slag glass comes in all colors, depending solely on the type of impurity. [Answer] Tim has a very good answer about the pros (thermal mass) and cons (greenhouse effect, insulation) of glass and if you are dedicated to the idea of using glass I don't have much to add. However, I don't believe the root of your question was a city of transparent skyscrapers and comes more from the idea of building structures from the most readily available material: sand. If that is the case I'd like to draw your attention to the alternative of [Rammed Earth](http://www.yourhome.gov.au/materials/rammed-earth). Rammed earth is a construction concepts that basically boils down to creating man-made sandstone with sand and aggregates being primary ingredients. It has many of the same thermal properties as Tim discussed with Obsidian with the bonus of being considerably more structural, naturally insulated, and opaque. Most of the Great Wall of China was constructed using rammed earth and it's historically been a popular building method in the Australian outback. The only thing you'd need to figure out/explain away is a binding agent (typically clay or cement) which are less available in desert environments. Glass is not out of the question here (everybody loves windows) just providing options. [Answer] **It'll be fine, because your glass will be opaque, because of sandstorms.** To cite [one reference](https://apps.dtic.mil/dtic/tr/fulltext/u2/417036.pdf): > > Objects made of glass (such as automobile windshields) gradually lose > their transparency, first becoming pitted, then frosted, when exposed > to sand-blasting winds. > > > [Answer] How about sand sandwiched between layers of glasses? It will take care of the heating issues. Also desert doesn't have a solid foundation to build upon, how about using huge chunks of glasses as a foundation for your city? It will give you interesting options of having caverns made of glass. [Answer] You can build your structures out of [dichroic glass](https://en.wikipedia.org/wiki/Dichroic_filter). The external structure can reflect IR coming in, while the inner structure can pass it outbound as necessary. It's the equivalent of the thermal film you can get for windows in this world, where they reflect heat but allow visible light to pass. [Answer] Since most of the heat from sunlight is in the form of IR, make the glass either absorb or reflect it. Also use a dome with shades that move as the sun moves across the sky blocking some of the visible light. Give the building a double wall with an air gap in middle, allowing the air to enter at the bottom and exit out the top and up a chimney to extract the extra heat. Use plants inside to help cool the temperature and provide some of the food for the residents. Last build some or most of the buildings underground leaving only a portion of it exposed to the sun. [Answer] I like the idea and while you have listed out several problems, I don't think these are factors that would stop such a city from existing. One thing I would like to point out is that glass can be colored in many ways which can reduce the amount of solar radiation that comes into any building. Additionally if there are layers of platforms of glass that reduce the amount of light while providing a mechanism for harvesting energy. The space between the layers can allow for convection cooling and actually if the city is designed as a single unit or multiple smaller units, this could help to provide a cooling breeze as heat tries to escape upwards. This could also be used to provide heated water or cooking as well as more modern forms of energy harvesting like thermal electric or steam to drive turbines or small Stirling engines. If light could be trapped into a highly precisely shaped diamond type structure or something with mirrors it is feasible that some optical energy could be stored until later Another point is that while the main building block may be glass, no city on earth is a single material. Even when building were mostly wooden there was some clay, leaves etc that were also used. It would not be unlikely for imported, or rarer materials to be included. For example, modern houses tend to use tar shingles or tin. Maybe sandstone slabs/shingles might be used. It could be reflected away for energy harvesting as well. Imagine maybe having mirrors that reflect the light into a smaller tube like optical pipe to carry high amounts of solar energy to a point to be harvested as thermal or electrical energy. One thing that might be a problem is cool nights. Infrared light may leak out through the glass depending on the optical and thermal properties. [Answer] > > However, the concern has come up that it would bake the citizens > alive. > > > Only if it is sufficiently hot or with enough radiant energy falling into it. If it is a cold desert, or a desert on/near the far side of a tidally-lock world, I suppose getting backed through the glass wouldn't be an issue. Additionally, the city could be made of convex panels that diffuse incoming light, and the panels could be arranged in multiple lattices separated in vacuum for insulation. Furthermore, if the plot permits it, the glass would not need to be transparent. It could be opaque. Heck, it could be mirrors reflecting light outwards. [Answer] There is no need to get fancy with tinted, silvered or other high-tech glasses, just **paint the glass bricks** white as we humans already do on our homes to keep them fresh. You do not even need cement to keep the bricks together if you are working on small buildings, think about the traditional stone houses here on earth. If, on the other hand, you want to make your city glassy, with tall shiny spires raising to the sun, then you would probably need some sort of fantasy or high-tech explanation. [Answer] Some suggestions: 1. You are defining "desert" as a hot, dry place with lots of silica based sand. Desert only means dry but it could be a cold environment where the heating effects of glass walls would be welcome. You could also have "sand" that includes minerals besides silica that would give the resulting "glass" other properties. 2. There are many things that can be made from sand other than glass. For example, melting sand and aerating it as it cools results in a synthetic pumice stone that can also be injected into molds during cooling to produce many different shapes. [Answer] I would like to give you one suggestion. When you think of sand giving you glass i recommend you to just think little further of making solar panels from silica instead of glass and lots of it to create the outer surface of what ever you want and also get electricity as a resource for further improvement. [Answer] You're asking: > > Is there any way I can have a city of glass in the desert without cooking its denizens? > > > When in fact, what you need to ask is this: > > Is there any way I **can have a city of glass in the desert**? > > > And the answer to that, unfortunately, is **no**. --- The reason is your misconception that: > > sand can become glass > > > While true in theory [silica glass](https://en.wikipedia.org/wiki/Fused_quartz) does exist, it is different to what most people would call "glass". **Sand is one component of glass, not the *only* component of glass**. The other components, are sodium, calcium, and aluminium (when fused together, form [soda-lime aluminosilicate](https://en.wikipedia.org/wiki/Soda%E2%80%93lime_glass) glass. This is going to be a problem in a sandy desert when all you have is sand (=silica quartz). You will need to obtain the other component either by mining (possibly granite mountains) or by trade. [Answer] My guess would be not to melt the sand completely, but rather mix it with some resin of sort to make [engineered stone, or artificial stone](https://en.wikipedia.org/wiki/Artificial_stone). If your desert conditions allow it, you may add some sort of resin to the sand, though sand would still make the bulk of the material. Plus, it is opaque, and much lighter in color. This would allow it to absorb less heat that would bake the residents alive. [Answer] There is an attempt to use bacteria to 'grow' desert sand into hard structures. TED talk: <https://www.ted.com/talks/magnus_larsson_turning_dunes_into_architecture?language=en> <https://blogs.scientificamerican.com/news-blog/stopping-desertification-with-bacte-2009-07-24/> Your question doesn't specify that the city is above-ground either so I would suggest looking into Frank Herbert's book Dune for examples of living in the desert. ]

[Question] [ Many people set who they are and others by what jobs they do, how they make their living. As more and more jobs are being taken over by computers and robots there are 'fewer' jobs for others. Yet we still expect them to work. Currently there really still are plenty of jobs for everyone, though many are jobs a lot don't want. But in the future more and more jobs WILL be taken over by some kind of automation system. Everything from serving your fast food meal to typing your correspondence and filing your taxes. Even buying and delivering your new socks when the old ones are about worn out to your specifications. Even farming, at least on large scales, is incredibly automated now, and will likely to continue, allowing for less and less personal input. * How will society change to switch to a 'non-working' society? * Where the majority of people don't have to do anything to 'live'? It could still be an option, and those would likely still get greater privileges. But * How would we transition from mostly everyone needing to work, to very few needing to 'work'? Some food for thought. [Humans Need Not Apply](https://www.youtube.com/watch?v=7Pq-S557XQU) [Answer] > > How will society change to switch to a 'non-working' society? > > > Taking an economic look at the situation, all jobs in the first and almost all jobs in the second and most jobs in the third economic sectors will be replaced by robots/machines. But that leaves the whole [quaternary sector](https://en.wikipedia.org/wiki/Quaternary_sector_of_the_economy) open for "work", also there are some services from the third sector you won't be able to replace with robots. # Future jobs But what types of job will be available exactly? * Most importantly, the jobs providing the infrastructure for the robots to do their work (mostly programming them or underlying machines) * Also quite important: content generators a.k.a. entertainers (in all possible variants, politicians and teachers as well as movie stars and singers) * Depending on some preferences, there might be some jobs where contact to humans might be socially prefered (e.g. healthcare). But most of the listed jobs (excluding the content generators) require you to have at least a higher education. Also, nobody likes to work without any recompensation. So what incentive can you provide to someone to get the education and then do their job? *It has to be some kind of privilege.* Currently, you do work in order to cover your basic needs, and nearly everything after achieving that goes into some form of showing off "hey, I can afford to do XY!", or in other words, you earned the privilege of being able "to do XY". When the need to cover your basic needs disappears, all that's left is privilege. # The current privileged ones (a.k.a. the wealthy) But wait... Why would the current privileged ones "allow" for their privileges (e.g. wealth) to be taken from them? Why not try to control who will be privileged in the new society? In order to be able to do the "most important work", you will need to get some higher education and access to specific knowledge beyond that. So, whoever controls who can get educated and/or access to knowledge will be able to control who will be eligible for privileges in the future! And this fight over the control to decide who will be eligible for privilege has already started (e.g. look at US university tuitions). # The "unprivileged" ones These people will be the ones most important before and during the switch. If the government/society fails to provide them a socially acceptable way of getting their "basic needs" covered, there will be revolts. Even if this would be handled "perfectly", there's still a good chance some minor uprisings will happen (since the social shift from "I have to work to be able to live" to "I am free to do whatever I want" might be too extreme for some). But once things cool down, I guess that the hunt for ways to kill time begins. What would you do if you wouldn't have to work/cook/clean/... anymore? What would you do in a month? What about in a year? # The content generators In order to keep people calm before, during and after the switch you will need good entertainers to distract them (or, later, to give them something to do in their free time). While theoretically anyone can become a content generator (youtube/blogs/...), the most important ones will be the ones who can influence the masses. Those will probably also get some privileges (either as "bribe" to keep them from turning the population against the privileged ones or from the "entertained" population themselves). # Deviations Of course, I'm possibly describing the most optimistic version of that future. It might never get there because of wars, or the "privileged" ones controlling enough military firepower to suppress/get rid of everybody not needed to keep the robot infrastructure intact. This can turn bloody rather quick in a multitude of ways, and I'm not having enough time to describe every one. For example * the monetary system might or might not break down * global warming could be too much of a threat * conflict between "privileged" and "unprivileged" might be too strong * education doesn't have to be restricted Generally, "post-scarcity" is not really achievable... We can get close with efficient roboters, but some things will always be scarce. [Answer] I question your premise. Who says that human labor will become unnecessary? People have been predicting that this will happen since the dawn of the Industrial Revolution -- some predicting a utopia of leisure, others a nightmare of unemployment and poverty, but either way. Yet today, 250 years later, most people still have jobs. It is certainly true that machines can greatly multiply human productivity. And so the reasoning always goes: Today it takes about 995 people to produce all the food and clothes and houses and so forth to support 1000 people, so almost everyone is employed. But as technology advances, soon machines will do half the work, so 500 people will be able produce enough to support 1000 people. Then the other 500 will be unemployed. (Or in the optimistic scenario: So we'll all only have to work 20 hours a week.) The flaw to this reasoning is that it assumes that human desires are constant. If, adjusting for inflation, your grandfather lived on \$20,000 per year, and you make \$50,000 per year, than it inevitably follows that you should be saving \$30,000 per year, or giving it to charity, or something. But in fact, that isn't what happens. As incomes go up, we consume more. When I was a boy air conditioning was a luxury for the rich. Today 87% of homes have AC. When I was a boy most families had one car. Today my family of 3 has 3 cars and I don't think we're that unusual. Cell phones weren't even invented then, no one had them. (A small number of rich people or people who really needed them had radio phones.) Etc, I'm sure anyone could extend this list. In a thriving economy, when new machines make a job obsolete, people don't become permanently unemployed. They get new jobs producing products that were rare or unknown before. And the standard of living for everyone goes up a little. Yes, the process is not always smooth and easy. Some individuals who lose their jobs in old industries find it difficult to get jobs in the new industries. Machines are wonderful at mindless, repetitive processes. But unless and until an artificial intelligence is invented that truly rivals human intelligence, machines simply cannot do jobs that require creativity or flexibility. (Dittos to @vogie there.) An automobile is an amazing machine: the engine will spin round and round and power the wheels with incredible speed and efficiency. But when it breaks down, do you take it to a machine to have it repaired, or to a human being? We are a long, long way from having robots that can repair a car. I wouldn't be shocked if in my lifetime someone invented a robot that can, say, change oil. Even that would be hard, as it would have to adapt to drain plugs and filters being at different locations on different cars, but I don't doubt that it could be programmed to recognize an oil filter and a drain plug -- especially if manufacturers helped it along by putting some standard, recognizable markings on them. But a robot that you could bring it a car and say "this car runs rough and stalls, please fix it"? Wow. Like wow. I've seen some efforts at "expert systems" to help diagnose automobile mechanical problems. They are nowhere near the abilities of a human mechanic. And the ones I've seen still require a human to manipulate the tools and interpret the results of each test. [Answer] What "will happen" is exactly what's slowly happening today, just far worse. **The rich will get richer, and the poor poorer.** I think the movie "Elysium" (with Matt Damon) more or less encompasses the outcome. **Automation** As you've pointed out, a lot of jobs, from manufacturing, to agriculture, to the service industry are disappearing due to automation. This is not necessarily a ***bad thing***. Someone still needs to design those automated processes. To maintain the robots. However, the person who gets fired from their minimum wage job at McDonald's and gets replaced with a dispensing unit is not necessarily going to turn around, go back to school, and get certified as an electrician or engineer. More likely this person will go on unemployment, and then slowly slip down the rungs of society as they fail to find another job with their limited skill set. **Unemployment** The more such people are replaced and fail to find jobs which pay as well, or don't find a job at all, the more stress the whole system comes under. Fewer taxes are being paid. More unemployment is being handed out. More food stamps. Fewer people can afford the luxuries they may have once had, not to mention healthcare. This will drive up crime rates, as people are driven to desperation. **Elysium** The people who own those automated businesses are going to keep getting richer as they sell their products to anyone who can afford them. The poor, however, will have nothing to their names. We're seeing this happening even now, as more and more manufacturing jobs are outsourced to Mexico, and various other Asian countries. Globalization has made the average Western manufacturing worker unemployable - who would want to pay decent wages, benefits, vacation days, etc. when they could be paying some Chinese worker (who sleeps at his workstation) a buck a day? As the rich get richer, they will, more and more, seek to be "removed" from the presence of the common masses. There are actually many articles exploring this phenomenon. For example, note the recent trend of airlines offering more and more luxuries in 1st class (caviar, anyone?), while putting up more and more physical separation between their those sections and the economy ones. Another example is that companies are looking at putting new Concord-style jets in the air. No one but the rich would be able to afford the **very** pricey tickets. The list goes on and on. The rich already live the kind of lives that the rest of us could never even dream to experience. Look at the luxury in which the likes of the Kardashians live, compared to what 99% of Americans can afford. These are not the sort of people who would give up a massive percentage of their wealth in order for the unemployed masses to live with dignity. [Answer] There will never be a non-working society from top to bottom. Just like the visions of the future from the 1950s showed the office worker of the year 2000 lounging on beach due to the labor-saving devices, that did not come to pass... there will be advances, and certain instances of repetitive physical labor will be largely replaced by machines, many others will not. Anything that requires flexibility or creativity, in design, repair, even something like cleaning houses or weeding, will still be in the hands of people. And even at that point, note that this won't be universal across the planet. Just like there are people living on less than a dollar a day in India and parts of Africa, while what is considered "in poverty" in the US and certain European countries includes thousands of dollars a year, and can include an air-conditioned home and various devices. You will have a population that can live off the work of their father's father, just like the life of luxury that the children of Sam Walton, the Rothschilds, or the Du Pont family live in, but that will still be far from the norm. For example, the person who invents the burger-flipping robot will be wealthier than the burger-flipping robot maintenance technician, who will be wealthier than someone who used to flip burgers. [Answer] Your premise that economic creativity suddenly halts is flawed. *Once new technology is introduced, it opens a whole new vista of opportunities, which will require humans to create, manage and produce.* And, this will not be a complete change overnight. It will come along gradually, so you are not going to end up with millions of people suddenly without work. **Micro Example** You see this at a micro-level in software development projects - **scope creep** - once a business user "sees" what can be done with feature "X" they then also want feature "Y" which is built on "X". But, until they could see and experience feature "X", they never dreamed feature "Y" existed. **Macro Example** You can see this with automobiles. Automobiles put out of work carriage makers, horse breeders, coachmen, trainers for the coachmen, and many of the allied suppliers - to make horse whips, feed, etc. But, although that is all true, the rise of the automobile led to new industries - everything from road builders to suburbs (more house building) to a vacation industry, oil refineries, gasoline delivery systems, car dealers, car makers, bureaucrats to regulate automobiles from creation to selling to driving, new laws to govern and police to enforce. They also made it possible to engage in new kinds of warfare and new reasons for warefare, healthcare (ambulances actually get to the hospital in time to save the patient) and the ability to transport goods across continents. (American Land Bridge for example.) And, then of course, the knowledge used in creating automobiles was used elsewhere for additional automation, which opened even more economies. **In other words, a MASSIVE new economy replaced a much smaller one due to automation.** **Possibilities** From a worldbuilding perspective, lets assume that many repetitive tasks can be optimized and automated. Business now relies upon and trusts this automation. It will still need people to manage, secure, troubleshoot/fix, improve, and protect. It still needs people to direct the robots and automation software. These workers are still human and will be working in the digital world or a blended digital/mechanical world. Robot and automation manufacturers will still need humans to design, build, test and sell and fix their goods. That implies that someone is making the tools and software to be able to create the robots in the first place. But, that is all mundane. Let's look at what robots/automation might be able to do to create NEW economies (besides their own): 1. Robots could be used to create new living spaces for humans. They would be ideal to create, maintain and secure those facilities - underwater, in space, artic or antarctic, underground, etc. All of those would need supplies and materials that have to come from somewhere. 2. Energy - lots and lots of robots and/or computers will need more and more energy. Self-propelled robots should lead to some way to improved batteries (e.g. cell phone batteries). New energy sources will need to be built or discovered to power all of these robots. As that happens, all sorts of new, currently unknown devices could be built. 3. Product distribution - being able to order a good and have it delivered QUICKLY to my house vs me having to go get it, will provide a bigger market for people to sell and an incentive for people to buy (easier to buy, have it in hand more quickly). This itself will lead to new industries and expansions of other industries. Small, cottage industries now have an easy way to reach customers that might otherwise just go to a superstore to buy their goods today. Tons of possibilities here - like giant, automated transport planes - which can go much faster and be built differently because they do not need to accommodate humans. 4. Advancements in automation in programming should help programmers build better software faster - like the 3d programming system in Iron Man. 5. Automated transport - one of the blockers to "flying cars" isn't just the technology - but the idea of piloting a vehicle. If a robot were to pilot an automated vehicle, then a flying taxi is not out of the question - nor is a fast moving train - at least for local service to an airport or between cities or even within a city. This opens up a whole new range of possibilities for entertainment, vacations, product transport (fly fast and high) and manufacturing, as well as, legal, policing and militarized usages. 6. Digital alternate realities - with 3d visors (or whatever) and an automated/intelligent controller, humans could entertain themselves walking around and interacting in very creative worlds - worlds that have to be designed by other humans. More crude versions might be sex robots that are programmed and seeded daily with "ideas" from companies that provide them. 7. Movies/books - if the automation software is of sufficient capability to say read your mind enough to form images and follow your thought patterns, people could make their own movies or animations or books or just sending a simple message to someone else. Some might give them away for free, but others might sell them, and still others might do what youtube users do today. 8. Parts and supplies and accessories for your home and/or personal robot - a whole market for that would then exist. **Basically, automation and robotics permit more human creativity to be shared and spread greater than before. The actual limits to that are less constrained than the automobile, and therefore, one would expect much larger and more widespread economic impact than what the automobile did.** [Answer] This has been speculated on a lot. My answer is different from the other answers: there are types of work that people do not want automated and those are the "hands-on" things like healthcare, personal care, teaching and therapy. So what do we see? As technology makes more health care possibilities, there are more people needed to do those things. Healthcare is a rapidly growing sector of the economy, not only because "our health is bad" (arguable), "people live longer" (because medical progress has made it possible), but primarily because a lot of it cannot be automated and **people do not want those things automated**. Over time that might shift. All the teachers might be replaced by computerized learning systems (with a few people tasked with setting them up and running them). Therapy could be replaced with AI guided conversational systems. People could get used to lots of medical care tasks being done by automated systems (I have a $40 blood pressure machine right here...) So, as the culture changes, even the human-faced work might get abstracted away. If you want the ultimate picture, look at the movie "Oblivion": a couple of people taking care of autonomous drones. *People will always be needed.* (Well, two of them anyway.) [Answer] Shame nobody wants to see past the financial constraints of our current system of rich and poor, so I'd like to offer a society where it does work. Imagine we have robots that can do everything we currently do - including robot maintenance and even construction (so robots mine the ore to make metal to make more robots that repair the robots that do stuff as well!). I also assume we have unlimited energy from whatever source (fusion? solar? who cares!) Once the sunk costs of making such an infrastructure have been paid for, you have a society where everything is taken care of for you, leaving all the citizens with nothing to do except for the things they want to do. We have more and more free time nowadays (compared to a worker in the industrial revolution, we don't have to work 16 hour days for pennies, or workers in agricultural times where all day was spent working). So we watch/play sports, research histories, write commentary on internet blogs... Of course, this wouldn't happen overnight, it would take a long time of revolution or struggles while the infrastructure gets built. Think of it like many other infrastructure projects - starts off as a rich mans toy, then becomes commoditised over time. Telephone communication is taken for granted today for example and is getting cheaper all the time. One day it could be paid for out of general taxation and delivered to everyone as a "basic human right" like some countries do with other aspects of society (eg healthcare) Workers would have issues, and in the early days welfare would become more prevalent, as would "non jobs" (eg governmental paper pushing where jobs are 'created' by the government to give people work). There's a long hump between this situation and the time where robots took over all work, and there's a bigger attitudinal shift between welfare payments for the unemployed to welfare payments to all paid for by the productivity from robots. (we already see the beginnings of this today, some economists are suggesting scrapping welfare completely and replacing it with a [basic income that is paid to everyone](https://en.wikipedia.org/wiki/Basic_income), letting those who want/can work, work to enhance their income. Over time the basic would increase, and eventually be replaced with some form of money-free society). Very utopian, and we do not have the technology to start to think about getting there yet. When the technology appears and unemployment becomes a huge problem, then we'll see the current systems replaced, and then unemployment (or early retirement after 'doing your bit' for society) might be seen as a good thing rather than bad. [Answer] This can be good (no, the "work" should not be the sole purpose of one's life) or bad (mass unemployment and falling wages for many "human" workers). In theory, avoiding the negative outcome is easy: gradual reduction of working hours for human workers. Unfortunately, this is hard to do politically and is done only under extreme circumstances such as those we experienced in the 1930s when we went from 60 to 40-hour workweek. Given the productivity gains since then, we should have been at 20-hour workweek by now. Instead, few of us are forced to work too much and many of us don't work enough. ("Us" in this context means any human of working age as I believe this is a global issue given the global nature of the economy.) [Answer] So at first I was writing an answer that presented a beautifully benevolent utopia where everyone is fed, clothed, housed and content...but then I realized that it was completely delusional so here is round two. Everything will appear to change but very little will change in the system. * Humans will still have to provide some sort of value to something in order to 'get paid.' The getting something for nothing concept will keep bugging humans, especially those that have stuff. * Humans will be worth less to employers as they are no longer necessary in large quantities, you are going to need specialists. * There will still be the rich and the poor and the gap would likely widen. I say this because we have the ability (quantity and transportation wise) to ensure that every human on the planet has food, clothing and shelter and yet it doesn't happen. * Humanity will remain divided. The concepts of relative deprivation and duhumanization come into play here...it will take generations to kill those reflexes (if we can at all). While it is potentially possible for humans to come together and share the bounty of the new machines and technology we create in this area odds are it simply won't. In short, the answer to your question could be, **1.** We reach a post scarcity time on Earth and everyone lives with the freedom to pursue whatever interests them...yawn. **2.** The wealth gap rises as conditions deteriorate for the majority of humans who are not longer needed as labor. Eventually the world is ravaged by disease conflict and uprisings leading to the ultimate extinction of mankind. **3.** Same as number two except a hero who starts off working for the government realizes the system is broken and leads the common folk in a rebellion to makes sure all humans are equal and they have a big socialist dance party with exactly equally sized pieces of cake. [Answer] ## Shocker #1 We already live in a post-scarcity society. No one (in first world countries) needs to work to survive (granted, some fall through the cracks and this survival may not be pleasant). There are government assistance programs that ensure that the unemployed are taken care of. Our society still requires most people to work and most people still do work. They do so for many reasons, some of which you already stated: * A sense of identity * Improved benefits, luxury goods, etc. * Social aspects (job prestige) * Advantages for their children * A sense of accomplishment (at the age of 45 my wife is going back to work because it is something she's always wanted to do). ## Shocker #2 People living in a post scarcity society are all around for us to observe. I realize our current society is not what you meant by living in a post-scarcity society. However, there is a group of people who can demonstrate how people's lives might be in a post-scarcity society. These are [the retire early folks.](http://www.financialsamurai.com/what-does-early-retirement-feel-like-the-positives-and-negatives/) These are people, who through a variety of means, have accumulated enough wealth that they have no need to continue working. What do these people do? 1. Some work (professionally) anyway. 2. Some work on personal projects (hobby farms, auto rebuilds, raising kids, raising animals, etc.) 3. Some enjoy nature 4. Some take up new hobbies and interests 5. etc. Basically think of all of the things you might like to do on a long vacation and this is what early retirees do. I belong to a board of early retirees (because I plan to be one) and can say that their interests and activities are as diverse as HAM radio, dulcimer competitions, hobby farms, going back for additional post-secondary education, simply reading, and more. What people do will be as diverse as there are people. The interesting thing is this. Once people achieve the ability to retire early, many do not, they continue working (for a while). Most jobs go through phases: sometimes they're enjoyable and sometimes they're not. People able to retire early typically stick with their professional jobs until they reach one of the "not enjoyable" phases. At that time, they retire because they no longer need to put up with the "bs". I've lectured at elementary schools about topics related to my profession. So I think doing something like that would be fun, or perhaps serving as a volunteer docent at a favorite museum. [Answer] Generally, what will happen is that we divide the small amount of remaining work among everyone, enjoy the fruits of robotic servitude and spend our time writing poetry, traveling around and enjoying each others' company. Alternatively, the people who own everything will put more and more people out of work, meanwhile working the remaining laborers even harder, in either case reducing the human experience to a stress-filled rat race. [Answer] My first thought was an alternative to the usual "rich get richer", but it depends on the context in which the automation is introduced. I could easily foresee a system in which rather than BEING the workers, the people at the bottom OWN the workers. So you would own a robot, that performs the tasks that normally someone of your class/caste used to do. You're responsible for the maintenance of the robot, but you are paid for the work the robot does. Of course, that pay will go down. but so too would the cost of goods in general, and theoretically the cost of living with it. [Answer] I posted an answer in which I rejected your premise. Now let me post an entirely different answer in which -- for the sake of argument at least -- I accept your premise. What happens to the unemployed people? One: They starve. Two: There is some mechanism to provide them with a decent life. The government or private charities gives them money or provides free food and housing or something. Three: There aren't huge numbers of unemployed people, but rather everybody becomes partially employed. Maybe the average person works only 5 or 10 hours a week and that provides all the income they need for a comfortable life. Three sounds great, but given the premise may be the least likely. If robots are doing all the menial jobs so that all that's left are the jobs that require special skills that the robots are not (yet) advanced enough to do, than people who DON'T have management ability, or technical skills, or creativity, may be unemployable. So what do the unemployed do with their time? One: Creative things, like writing and producing art and music and inventing. Okay, arguably this is productive work, but the sort that machines are least likely to be able to do. You may or may not get money for it. Two: Improve yourself, so that you can become employable. If only people with creative or technical skills can get jobs, than learn to be creative or technical. Three: Improve yourself, not for the sake of being able to perform some job, but for its own sake. Study history or philosophy or science or whatever. Travel. Visit museums. Get together with friends and discuss great ideas. Four: Have a good time. Go to parties, concerts, and movies (or holoshows or whatever they have). Maybe this includes drinking and drugs and wild sex. Five: Join a gang. Spend your time beating people up, stealing and vandalizing, and fighting other gangs. Of course people could do some combination of the above. Realistically, some people just aren't capable of doing creative or technical work. Large numbers just won't be able to do One or Two. Many people would be bored by the idea of a life of endless study. People would probably talk about it as a good and worthy thing to do, but relatively few would actually do it. Like dieting and exercise. That leaves partying and crime. I suspect that's what most of the unemployed would do. Okay, it didn't take a lot of deep thought to come up with this list. It's pretty much what unemployed people in our society do, just multiplied. I've read books that imagine machines doing all the work and that paint a utopia where the people spend all their time producing great art and science. Bosh. Some would, but most just wouldn't have the inclination or the ability. The reality is, for most people, if they didn't have to work, they'd spend their time lying around doing nothing, partying, and/or fighting. At the other extreme, I've read books that imagine machines doing all the work and that paint a nightmare world of unemployment and starvation, with a small elite living in luxury. Also unlikely. Human nature being what it is, sure, there will be some of the rich and powerful who say to let them starve, but there will be some who care and look for ways to provide for these people. Throughout history there have always been greedy and selfish people, but there have also been people who devote their lives to helping the poor and weak. Furthermore, massive numbers of desperate people makes for a very unstable social situation. The rich would be in constant fear of riots. Even those who care only for themselves would likely see the solution as some combination of strict law enforcement and enough charity so these people aren't TOO desperate, so that they have something to lose if they challenge the system. If the society is really so rich -- I mean the robots are producing so much wealth -- that there is just no need for people to work, then presumably there is enough abundance to let the unemployed have at least a basic, decent living. Reminds me: According to the Bible, the law in ancient Israel was that when a farmer harvested his crop, he was supposed to leave a little behind, and the poor were then allowed to collect this. So the rich provided food to the poor, but the poor still had to go to some effort to collect it, nobody brought it to their door. Perhaps in a society such as you propose, factories would have places where they'd dump their slightly imperfect items, or some percentage of their production, and the poor could come and take it. [Answer] In my opinion, you miss the point. First of all - the fact that some job *can* be replaced, doesn't mean it *will* be replaced. Let's take a top-voted(at the time of writing this answer, at least) answer: > > An automobile is an amazing machine: the engine will spin round and > round and power the wheels with incredible speed and efficiency. But > when it breaks down, do you take it to a machine to have it repaired, > or to a human being? We are a long, long way from having robots that > can repair a car. > > > I would argue with that. Engine is defined by certain things it does, and laws it obeys. If it breaks, there are things you inspect - and if you find them, you can get rid of them. This is mindless job that only requires knowledge, not intelligence - this can be solved by anyone, even a robot. If you try to say that we do not have robots this precise - we do have them. And even if we didn't, it would be a matter of years. So why isn't engine man replaced? Because it isn't worth it. Each machine needs to be *maintained*. This requires a human to do. There are many other places where human labor is simply cheaper. There is some which involves creativity, something that machines lack(and I guess they will lack it for longer than one lifetime to be competitive). But let's say that we got everything automated. What are the scenarios? ## 1) Rich get richer, blah blah blah Honestly this looks like the most boring and unlikely scenario to happen. While rich *get* richer, we all would get better life quality, and this could mean that we wouldn't notice it. Also, if we had everything we wanted, automated, money would loss a bit of value - it would provide luxuries. Also there can't be too many poor - otherwise they will revolt, and rich get buried. ## 2) We live happy lives(utopia) A bit more interesting than first scenario, this is also unlikely. We invented robots, computers, mathematics etc. because **we love to solve puzzles and keep our mind occupied**. There were some branches of mathematics that was thought of as a toy branch(useless in practice), until half of century later fast computers came, and the branch turned out to be **extremely** useful. The point is - we like to do some things, even if they appear(or are) not practical. We are humans. ## 3)We continue to live our lives, but jobs change and priorities shift. Imho the most likely scenario, this is how it has always been. We make things to make our life easier, not to eliminate us from our lives. New technology might create a need for new jobs(like computer engineers are now needed, and there was no such job 100 years ago). Moreover, there are *many* places, where humans just are a better fit. When I go to cafeteria, I am glad to smile and talk to other fellow human being. I like to ask for a preference of a shop assistant, have small chit chat. Most business deals are done by humans, and they would probably stay that way. And last of all - remember - we do all this for the sake of us, humans, not to create self-sustaining system. If there are no clients, this would be useless - therefore there's some lower bound of poverty, otherwise there would be no one to buy their products. Even if we try to imagine that rich would just hold these self-sustaining systems by themselves, this is unlikely - they need other people to reproduce, entertain themselves and keep sane. After all, what's the point of having a perfect empire, when there's no one to rule? ]

[Question] [ Are there any known laws of nature, which don't allow the existence of an animal with following characteristics? 1. Can fly to the altitudes of modern airliners (around 10 000 meters or 32808 ft). 2. One of the sources of thrust are organic jets or rocket engines (details see below). 3. The animal can carry up to three passengers (about 240 kilograms, 529 pounds). 4. The animal can fly up to 1000 kilometers (621 miles) using his own thrust source (that is, not just gliding or using the wind). Regarding organic jet engine: There is at least one animal, which produces organic, flammable material - cows generate flammable methane. So, theoretically, an animal could have a combustion chamber in his body, where the flammable gas could be concentrated. The next thing it needs is some form of nozzle, from which the gas would escape and it must have varying shape, controllable by the animal. Several animals can control the shape of their bodily openings, so it could be possible. Finally, it needs a spark so that the flammable gas actually starts to burn, but that's easy - as stated in the requirements there is at least one pilot, who could activate a contraption, which generates a spark close to the nozzle. I imagine that the animal can gain low altitude using wings (one of potentially many thrust sources), then the animal starts to generate flammable gas at the command of the pilot (we train dogs and horses, why not this fictious animal?) and the moment it opens the nozzle, pilot fires the ignition. Here we go: A VTOL-capable (vertical take-off and landing), jet-powered dragon with at least two power sources (wings, jets - i. e. it is fail-safe). Notes: * I say *animal* on purpose - because of mental inertia I'm thinking about a dragon, but there may be other animals, which can fly with jets. * There are some military fighter jets with [variable sweep wings](http://en.wikipedia.org/wiki/Variable-sweep_wing) that an animal could achieve easily (real birds do that all the time). * An interesting variation would be an organic liquid-fuel rocket engine. Unfortunately, I know too little about rocketry to imagine how it work in an animal. Ideas in this direction are welcome. [Answer] I'm going to assume you're not talking about something that is genetically engineered for this purpose (otherwise I think the answer is pretty straightforward). The closest analogue to your dragon would be a jet-powered, pressurized Cessna 172. You're going to have a few hurdles to overcome here. # Environment A Cessna 172 has a normal service ceiling of approximately 4000m (13000ft). Much above that, and you'd need to pressurize the plane for the passengers. Even if we assumed we could create a creature that could operate at over twice this height, its passengers certainly would not. # Evolution A system like this is really hard to explain evolutionarily. There are three pieces here: (1) the combustion chamber, (2) the fuel, and (3) the ignition source A rudimentary combustion chamber could be a squirting sack of some sort. Our best example in real life is the [octopus (and related animals)](http://www.asnailsodyssey.com/LEARNABOUT/OCTOPUS/octoJet.php). They use a powerful squirt of water to quickly move through the ocean. This gives us a possible explanation for how these muscles developed. Once we get the sack, we need something inside it. Obviously, for a flying creature, filling a large air bladder, and then expelling it through a muscle controlled nozzle would give our create an evolutionary advantage in catching prey or escaping predators. And since we already have an evolutionary analog for this, I'm not going into the details here. Like you said, a possible fuel source is methane. Conceivably, if our creature is an omnivore, it may produce methane through its diet. An evolutionary advantage may lead to this being stored in the air bladder instead of being directly expelled. Eventually, all the creature's produced methane would be in the air bladder. At some point, once the creature can produce its own "air", it may evolve a storage capacity (basically, a second air bladder), which would allow it to refill the primary air bladder more quickly. What I believe I have shown is an evolutionary pathway for a bird-like creature to develop multiple air bladders, of which at least one is used for supplemental propulsion, where the air is in part methane produced by the creature. However, that doesn't quite answer the fuel part. # Fuel Methane is approximately 55MJ/kg, or 36.4kJ/L. Contrast that to jet fuel, which, while only 46MJ/kg, is 37.4MJ/L (note the *mega*joule unit in the second one). It's got approximately 1000x more volumetric energy density. A cow produces somewhere between [100 to 500L of methane](http://animals.howstuffworks.com/mammals/methane-cow.htm) a day. Assuming we could reliably produce 500L of methane, this is really only half a liter of jet fuel worth of energy. Assume that is proportional to the mass of the animal (an adult cow weights approx. 750kg), that's about 0.7 mL/kg. Even if you increased that to 10 mL/kg (assuming our creature is super efficient about producing methane) and you'd still need a creature that weighs 21 tonnes to fill a Cessna 172 with fuel every day. For comparison, elephants weigh 6 tonnes, and the [largest flying creature to ever live](http://en.wikipedia.org/wiki/Quetzalcoatlus) only weighed 250kg - one third of a cow. So, you'd need some other way of fueling this beast. If you want to use gases, you'd need to make your creature massive to handle the volume (or massive with muscles to create the needed pressure), or you'd have to use something else. Enough jet fuel would require 171kg (half the weight of or weightiest flier). Even compressed hydrogen would require 55kg worth of fuel (to reach the same energy). But, of course, what good is fuel without... # Propulsion Now we get to the crux of why this will never work. Since something as complicated as a highly balanced rotating shaft will never exist in the organic world, we need an alternative. The only two non-rotating jet engines are the pulsejet and the ramjet. [Ramjets](http://en.wikipedia.org/wiki/Ramjet) are very efficient--but only at about mach 3 or above. At the very least, you need supersonic airflow to make them work. So, unless you have a way for your creature to flap its way past mach 1, a ramjet would never work. [Pulsejets](http://en.wikipedia.org/wiki/Pulsejet) give very poor compression, and are not very fuel efficient. This would require even more fuel. They are also very loud. However, I could see an evolutionary explanation (though we are now straining reality) for this. Now, even for a pulsejet to work, we would need our creature to be able to carefully add in air and fuel, spark the mixture, and then withstand the intense heat of combustion. The first step is not impossible, the second step is highly improbably, and the third step is almost impossible. How is a dragon supposed to be able to create a combustion chamber inside of their air bladder? --- All in all, I think this is an impossible task. You are trying to make a natural creature that evolved both flight with wings, and with flaming jet powered farts. Not going to happen. TL;DR - You can't power a dragon with fartjets. [Answer] Rylatar'ralah'tyma was giggling audibly. That only made Nizidramanii'yt more furious. His tail was still coiled up to cover his rear, which, unsurprisingly, was still incredibly tender, despite the regenerative magic field he'd put in place. "The *indignity* of it all!" he moaned, trying to set fire to a nearby copse of trees and three hares, out of sheer spite. His fireglands were still frosty from the cold flight, however, so only a puff of smoke came out. Polishing her red scales, Rylatar'ralah'tyma asked, distractedly: "I mean, I have only one question. What exactly did the mage make you eat before-hand? A small town's bean supply for the year? I mean, *that* much gas... **That** turned his fire-glands back on, alright. Too late, Rylatar'ralah'tyma was already in flight, her glorious body contorting mid-flight from the heavy laughter. --- *Meanwhile, at the Unseen Academy in Halruua.* A large audience of mages, archmages, a few liches and a gorilla are gathered around a presentation board, upon which lies the magically animated chalk-outline of a very scary looking dragon. The title is "Dragon Tubing". A mage in red robes wearing a prominent nose-ring is strutting about proudly. Behind him, tapping her foot impatiently is a younger female mage dressed in all-pink robes. Edwin Odesseiron: "Oh, it was a feat of pure bravery, a true battle of the wills between me and the great ancient dragon." Imoen: "Guys. It was barely a centenarian. And it was drunk from drinking Duke Eltan's entire wine cellar fermentation vat. And asleep." Edwin: "Sure, that might have helped a bit, but it is nonetheless..." Imoen: "Listen, while I was all for traipsing in quietly to dislodge a few gems, nobody asked you to start shooting firebolts at it." Edwin: "It attacked!" Imoen: "It snored. And let me tell you, it is never a good idea to cast a fireball at a dragon, but it is a particularly terrible idea to do so while you're **on** the dragon." Edwin: "Uh, regardless, a particularly well-placed Bigby's Crushing Hand and a Fireball from my Contingency trigger, had the effect of..." Imoen: "Squeezing his buttocks while setting fire to its farts." Edwin: "Of course, the dragon took off, with us on it..." Imoen: "That was fun!" Edwin: "It quickly got rather cold, but my brilliantly crafted Oiluke's sphere held fast." Imoen: "After about half an hour, the fermentation vapors ran out, and the dragon was probably dazed from the cold and the lack of air. We got off as it glided to the ground." [Answer] I want to address a number of inaccuracies in previous answers, so will collect them all in one place rather than scattering comments. 1) Cessna 172 service ceiling can be up to 14,000 ft, depending on model. This is really a function of it having a normally aspirated piston engine, though. A turbocharged model could fly much higher. A jet would be even better, as they tend to be more efficient at altitude. From personal experience, I've flown my Piper Cherokee (similar size & engine) at 14,000 ft a number of times. 2) Oxygen needed for survival above 12,000 ft. This is just plain wrong. There is an FAA requirement (FAR 135.89) for the pilot to have supplemental oxygen if flying above 12,000 ft for more than half an hour, but that's an issue of pilot acuity, not survival. (Edit: since the dragon is doing the flying, and has evolved for altitude, this is not a requirement.) I've also spent a good bit of time hiking & skiing above that altitude, and have flown sailplanes to about 17,000 ft, and am still here to tell about it. And that's not even considering the Tibetans :-) 3) The dragon needs to carry oxygen for its own survival at 30,000 ft. Hardly, as geese have been recorded flying at close to 24,000 ft (7290 m) <http://rspb.royalsocietypublishing.org/content/early/2012/10/25/rspb.2012.2114> 4) Methane storage/energy density: Yes, methane is not good in this respect, but if the creature produces methane, it's only a small evolutionary trick to add enzymes that convert it (or other parts of its food) to more complex hydrocarbons, e.g. jet fuel. 5) Temperature: Sure, normal flesh does not deal well with high temperatures, but there are numerous examples of carbon-based life forms which create specialized ceramic structures like shells and bones, or the SiO2 shells of diatoms, so it's not impossible to envisage the evolution of ceramic jet exhausts. I think the biggest practical objection is to carrying people, which is likely to terminally mess up the dragon's weight & balance. For another point, why should the dragon have jet power as its normal means of propulsion? As others have mentioned, flapping wings work well and have a lot of advantages in the low-speed realm. Maybe the jet is an adaptation for quick escape from predators - which is not all THAT hard to imagine, when you consider the skunk. So did breathing flame evolve from the jet propulsion, or vice versa? Or is the firebreathing just a myth, caused by people seeing the "fierce dragon" doing a panic escape from a distance? Edit: Thought of another possible use for a jet propulsion system. Given square-cube law & Earth-biology muscles, a large flying creature just can't take off under its own power. However, as sailplanes & hang gliders demonstrate, once aloft it can use thermals & air currents to stay up indefinitely. So your dragon would normally live on cliffs, but would have a jet/rocket assist takeoff system for launches from flat ground, for instance after killing prey. [Answer] There is no reason why such a beast could not exist in theory. See this answer <https://worldbuilding.stackexchange.com/a/345/75> for the arguments in favour of regular wing-propelled dragons. Now, suppose that we have a being that, like a bombardier beetle, uses a flaming exhaust as a weapon. It is a logical extension for such a being to evolve in such a way that the exhaust can be used as a thrust source. The main issue would be waste heat, but that could be handled by passing the fuel over the combustion chamber to pre-heat it while cooling the combustion chamber and providing thermal isolation. Precipitated metals and carbon fibre could be used as a thermal liner. Since [biological rotation](http://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems) in multicellular animals is unlikely to evolve naturally, thus precluding [turbojets](http://en.wikipedia.org/wiki/Turbojet), this could be a [pulsejet](http://en.wikipedia.org/wiki/Pulsejet), [pulse-detonation-engine](http://en.wikipedia.org/wiki/Pulse_detonation_engine) (PDE) and/or a [ramjet](http://en.wikipedia.org/wiki/Ramjet) or [scramjet](http://en.wikipedia.org/wiki/Scramjet). As a biological organism, the possibility exists that the one "engine" could be reconfigurable to operate in more than one of these modes, beginning in a pulsejet or PDE regime, and potentially changing configuration to a ramjet and then a scramjet. The main constraints in this system would be those of size - too small and the creature would not be able to contain sufficient fuel to overcome its drag in order to generate useable lift for the required time, too large and it would not be able to support its own weight in the air. Naturally, it would be in the interest of the animal to evolve an efficient fuel in terms of energy per volume and mass. A compound such as [2,5-Dimethylfuran](http://en.wikipedia.org/wiki/2,5-Dimethylfuran) could be a possible fuel, as it is potentially capable of being biosynthesised and has a high energy density, 42 MJ/kg and 37.8 MJ/l, though for PDE engines a lighter fuel such as methane or hydrogen would be preferable. If the being had a reconfigurable engine, there may be advantage in carrying multiple fuels. As for high altitude flight, birds, with their more efficient lungs, have been recorded to fly at these altitudes. In fact, the higher the altitude, the more efficient the flight (due to lower air pressure reducing drag). The main trade-off is going to be lung efficiency decreasing as altitude increases versus flight efficiency increasing as altitude increases. The range factor can be solved by carrying enough fuel. As manufactured aircraft can have the required performance, this is not beyond the bounds of possibility. The most problematic factor is carrying passengers. Putting three lumps on the beast's skin is going to cause massive parasitic drag that will dramatically reduce the beast's speed and range, even if these three lumps lie down flat against its skin and cover themselves with a slick, streamlined shell. The most likely option is to carry the passengers internally, where their mass would lead only to increased induced drag. I can speculate that such a means of carrying passengers could evolve where the beast carries its young about in an internal pouch so as to both protect them and reduce parasitic drag. The pouch could be repurposed to carry other passengers. It is theoretically possible that such an organism could evolve naturally, given the right selection pressures, but it is far more likely that such a beast would be a bioengineered organism. In the case of a bioengineered organism, a turbojet would be possible given that its biology would not be determined by the requirement of continuous evolutionary fitness, but by the requirements of a designer. However, a PDE/ramjet/scramjet system would probably be preferable. The issue of obtaining fuel would require that these beings either ingest the fuels from an external source in their final state, or have the means to synthesise the fuel from their food. The latter would require that these beings have truly prodigious appetites and rapid digestive processes. In the more likely bioengineered organism scenario, it would make sense to have something like "fuel trees" that use photosynthesis to produce the fuel the flying organism needs. It may even be that the fuel trees are one gender (probably male) and the flying form is the other gender (probably female), thus we have a system that provides both transport and fuel production. Finally, as to what these beings would look like, the most likely answer is some combination of dragon and bird. If we are following the basic vertebrate body plan, the neck would be short and thick (to allow air intake), not long. The creature would likely be more batlike than birdlike, having membranous rather than feathered wings, as feathers could be torn loose by the high speeds. There would not be a single tail (which could be burned by the jet exhaust), but more likely there would be fins on the rear limbs, well to either side of the jet exhaust. [Answer] > > 1.Can fly to the altitudes of modern airliners (around 10 000 meters or 32808 ft). > > > Take a look at [this graph](https://upload.wikimedia.org/wikipedia/commons/8/88/Atmospheric_Pressure_vs._Altitude.png):  At 10,000 meters, the air pressure is about 25% of its value at sea level. [Wikipedia](https://en.wikipedia.org/wiki/Cabin_pressurization) notes that pressures this low and oxygen levels this low can cause some problems: > > The lower partial pressure of oxygen at altitude reduces the alveolar oxygen tension in the lungs and subsequently in the brain, leading to sluggish thinking, dimmed vision, loss of consciousness, and ultimately death. In some individuals, particularly those with heart or lung disease, symptoms may begin as low as 5,000 feet (1,500 m), although most passengers can tolerate altitudes of 8,000 feet (2,400 m) without ill effect. > > > At altitudes above 12,000 meters, an oxygen mask is imperative for survival in a non-pressurized environment. So this fellow has to be able to survive without much oxygen, which could be hard because of his size. His body parts also have to withstand the low pressures. These are going to be problems. --- > > 2.One of the sources of thrust are organic jets or rocket engines (details see below). > > > [Here's](https://upload.wikimedia.org/wikipedia/commons/4/4c/Jet_engine.svg) a diagram of a [turbojet engine](https://en.wikipedia.org/wiki/Turbojet):  According to Wikipedia, the compressor blades may spin at rates of 2,500-50,000 RPM. The dragon is presumably quite large and so will have large engines, so this rate will be towards the lower end of the spectrum. I have a feeling the vibrations will pose problems for his general structure. [This](http://cs.stanford.edu/people/eroberts/courses/ww2/projects/jet-airplanes/how.html) notes that the temperature of gases in a turbojet engine may reach 2000 degrees Celsius. Any organic material at this temperature will be scorched and turned to ashes. There is absolutely no way any carbon-based life form can survive this temperature - especially not for the two or so hours it will take him to travel those 1,000 kilometers. --- These are the two main problems I can find with the scenario: pressure/low oxygen and temperature. Because I'm feeling less pessimistic than usual, here are some solutions: 1. **Pressure/low oxygen:** You can't really have the dragon hold his breath because of the long duration of flight. So how about having him carry extra oxygen *with* him? I wrote about fictional [pufferpolyps](https://worldbuilding.stackexchange.com/questions/5250/using-physics-how-can-a-character-fly/5256#5256) in another answer set in a different context. The feature we can take form them is an easily expandable chamber that can store gas for a while, on tap. You've basically got an inflatable oxygen tank with you. 2. **Temperature:** Take a look at Monty Wild's excellent answer to [How could dragons be explained without magic?](https://worldbuilding.stackexchange.com/questions/313/how-could-dragons-be-explained-without-magic) Monty suggests > > By squirting the fuel out fast enough from a duct venting into the mouth as the dragon exhales, it need not ever come into contact with the burning fuel. (Think spraying the flammable gas from a spray can over a cigarette lighter - it doesn't melt the plastic nozzle.) With a change in biology so that a dragon could precipitate metals such as aluminium or magnesium, a dragon might even be able to spit a liquid mixture akin to thermite that would spontaneously combust due to the presence of other reactants. > > > And therein seems to be our solution. If you go for a traditional jet engine, your dragon is going to be blackened. The hot air will have to go through some sort of cavity, and there's a high risk of it burning up that cavity. So you'll want to go for the rocket approach: shoot out flames like a fire breather, in reality expelling some flammable substance and igniting it as it goes by. I'm not sure how good an answer this is. I hope it helps. [Answer] A spontaneously evolving creature would likely fail more than one or two of your requirements. It would be quite a stretch but here is the closest I can fit what you'd describe. I'd use a bombardier beetle as a template. Based off that, we have a winged organism that can produce a strong chemical reaction internally with the ability to direct the result. If we assume that hydrogen peroxide (H2O2) is the desired propellant, we solve a few issues. Decomposition products are hydrogen and oxygen. Reserves of each gas can assist respiration and a fuel source. Bombardier beetles use hydrogen peroxide, hydroquinones, enzymes and water to produce their jet. A short stretch would be a creature that can focus on hydrogen peroxide. Direct oxygen production would allow high altitude flight and allow a larger creature. Dragonflies have been show to increase size up to 20% in hyperoxic environment. <http://www.wired.com/2010/11/huge-dragonflies-oxygen/> Canada Geese can fly up to 1000km in a day and have been spotted up to 9km altitude. <http://en.wikipedia.org/wiki/Canada_goose> Fuel ignition could be started with compression, like a fire piston. Pistol shrimp can create enough force to cavitate water. It would be a small step to have a chitinous chamber to compress a gas mixture to autoignition temperature. Sustained firing would be extremely difficult due to the force and temperatures. Conceivably, the burst could be for takeoff or additional speed. Size and energy conversion would be the limiting factor for this imaginary creature. Any creature with an exoskeleton has to molt to grow. The old chitin is shed and the new chitin has to harden. This would leave the creature completely defenseless while the process happens. Any interruption could lead to a deformation serious enough to cripple it until the next molting. Supporting it's own weight would be difficult, let alone passengers, barding and gear. Without gliding, flight would carry a huge energy load necessitating huge amounts of food before each flight. With a stretch, a gigantic bug that can produce a hydrogen peroxide fuelled, organic jet burst could grow large enough to support passengers and be pushed to fly extreme altitudes and distances. [Answer] ### I can't believe such a creature could evolve. The problem is, that jets are a very inefficient means of locomotion, compared to flapping wings. While I could believe a flying creature with a jet engine (the evolutionary pathway is exceedingly complex, but I don't believe it contains any uncrossable gaps) I can't believe one that would evolve to cruise on a jet engine. Having that kind of fuel reserve/ability to take the sustained heat would serve no evolutionary purpose. A jet would be either for evasion or pursuit (think: cheetah) only. [Answer] There are several issues with this that has to put your desired result into the realm of magical unfortunately...but I'll try to get as close to reality as possible. Methane is not jet fuel. There is more potential energy in a kilogram of liquid methane than there is a kilogram of jet fuel, however the methane takes up a huge proportion of space (this is referred to as having a low volumetric energy density) compared to jet fuel. That said, there is a synthetic process called the Fischer–Tropsch\_process (wiki here <http://en.wikipedia.org/wiki/Fischer%E2%80%93Tropsch_process>) that could theoretically be reproduced in a very flame resistance creature. With a few tweaks, this process could have a creature that collects carbon monoxide as it breathes and creates a bio-diesel fuel from it. Completely theoretical if such a process could exist naturally, but we're talking dragons, so why not? Birds have some interesting lungs...so do reptiles for that matter...but birds in particular use pressure changes to regulate the flow of air from their lungs. Once again, way in the realms of theory, but if it was possible for a dragon to get a 40:1 compression ratio from a series of contracting lung muscles... There are a couple heat issues, but there is possibly some balance to be found here. First and most obvious is the extreme heat of the combustion reaction. Your Dragon will need some heat resistance above and beyond what a 'natural creature' really could have to make this work. However, there is some offset to this...as really warm as that engine is, it is exceedingly cold at this level of the atmosphere. A cooling system cold be possible here...'blood' (quoted that because our blood would boil...you'd need some sort of supernatural 'blood' to work here) could be used to take the heat from the combustion region (a high tech term for 'ass' in this case) over to it's wings or perhaps another cooling apparatus. Not a first in nature, some theories on dinosaurs fins (stegosauruses plates as well) were used as cooling apparatuses. Just for visual effect...the 'jet engine' lights up and the dragon extends two 'fin's out of either side of it's body designed to quickly cool blood off to cool it mid flight. I would suggest that this entire jet process would be intermittent or in bursts just to keep the total heat produced down...in a story this might work as feasible. I still think funny as hell, add in a dragon making a face a human on toilet would be as it shoots flames out of a misc hole on it's body, shooting it through the air. You would need a few very special conditions on the dragon...in particular, how is it capable of extracting the oxygen it needs to survive at the altitude it is flying at [Answer] I'd like to present a different opinion: yes, it is possible, but it wouldn't be a 'jet' engine. I'm assuming the fuel is liquid (so not methane), which would be most logical for internal storage. **Fuel** A dragon has had an evolutionary advantage of creating organic fuels. Arguments that the amounts cows produce is extremely little, are silly because cows have no evolutionary advantage of creating methane; it's a byproduct. Dragons have an advantage by creating the fuel, so they will evolve to do so in copious amounts. It will evolve enzymes that break up organic compounds to highly flammable compounds, just like petrochemical plants do (and animals can probably do this better; compare the most advanced polymer science can make with infinitely more complex proteins in your eyes that makes you see kittens on the internet). Now, imagine a dragon that is evolving to fire-breathing. It already has DNA present to create very hard, scaly bodyparts that are fireproof - I would think that some of the dragons teeth have evolved (grown bigger) to protect softer bits of dragon; think of elephant teeth. **Excess fuel...** Now it does have a fuel-producing organ, but this organ cannot be simply switched off. In early points of its evolution, it simply burnt off excess fuel by breathing fire, but this posed some other problems; for example, barbecueing the entire forest while sleeping or setting your dinner on fire. So, the dragon evolved ducts leading from the fuel-creating organs to its flanks (for example, under its wings), where excess fuel would be burnt off in a controlled manner. To prevent carbon monoxide asphyxiation due to incomplete combustion, air ducts were evolved as well, that would help combustion. Now comes the interesting part - in flight, the dragon discovers that burning excess fuel not only protects its vulnerable belly from enemies, but also creates thrust, which is used to get away in emergency situations. From here, evolution of the side-burning accelerates, and the little patch of scaly cells around the fuel excess outlets swiftly evolves to nozzles. This particular breed of dragon will soon split off evolutionary from 'normal' dragons, and very probably, its fire-breathing capabilities will soon diminish, since fire-breathing is effectively wasting fuel. **Differences from jet engines and other drawbacks** As others has pointed out, this would be a rocket engine and not a jet engine. Jet engines compress intake air to several hundred MPa, which organisms simply cannot do (in this extreme case, due to compression heating, cells performing the compression would be burnt, because fire-proof 'hard' cells cannot flex to accommodate compression). The dragon can probably not reach your quoted 10 000km, but may use high altitudes to migrate efficiently, since it will need a large foraging area to create large amounts of fuel. [Answer] Let's ignore for a moment the requirement that it carry 3 people. To just say, could there be a living create with a jet engine?, I think the answer is obviously yes, because there really is something that resembles such a create: the bombardier beetle. It doesn't use it's "jet engine" for propulsion but rather as a weapon, but the principle is there and clearly works, because bombardier beetles really do exist. Note the bombardier beetle's body solves all the problems that others have discussed here on a small scale. So the question is, could such a system "scale up" to be a viable method of propulsion for a create of any given size? And if so, would it scale up to the point of being viable for a creature capable of carrying 3 people? I doubt that the specific chemicals used in the bombardier beetle would work in a larger animal: if they were powerful enough to propel something the size of horse or cow to significant speeds, they would likely be so powerful that they'd blow a beetle to smithereens. But could a create exist that used other chemicals? It's difficult to do calculations because you have to make up the details as you go along. And if I could absolutely prove that, say, chemical X does not have sufficient energy, is there not some alternative chemical Y that might? You could point out that there is no animal in existence that has a body part that does Z, but so what? Proving that it is not possible for such a creature to exist gets tough. Clearly you cannot prove that there is no way possible for jet engines to operate, because of course they do operate. So the issue is whether it is possible for a living creature to have a jet engine, or, I presume, something analogous. Which I just don't know how you could ever prove that it isn't possible. And by the way, a lot depends on whether you are assuming that such a creature had to evolve by chance process, was created by a creator God, or was built by people using bioengineering. Lots of things that would seem impossible in scenario 1 are much more plausible in scenarios 2 and 3. [Answer] As the other answers have calculated, have jet power be your primary propulsion is unlikely to be realistic. However many birds have been observed at altitudes exceeding 30000 feet: <http://en.wikipedia.org/wiki/List_of_birds_by_flight_heights> You could allow for standard wing propulsion boosted or augmented by organic jet power on an as-needed basis. [Answer] I think it would be possible if some mineral are abundant in the "concerned world" and the dragons have evolved from integrating them for heat resistance and fuel production... but from an evolutionary point of view, there must be a reason for them to evolve the jet engine and I think the reason should definitely be survivability in regards to either food or escape mechanisms from a predator. Come up with these reasons and using the excellent answers from the previous users you can get a "reasonable" Dragon. Also, for carrying people, like how we use mounts for riding horses, a specially designed mount may be possible for the purpose. [Answer] There are a few problems with organic jet engines. 1. Jet engines require compressors. Otherwise, there is no way to maintain the flow of intake air into the combustion chamber. Unless your dragon is a hypersonic ramjet-powered dragon, that means [rotating parts](http://en.wikipedia.org/wiki/Gas_turbine). I know of no animal (real or fictional) with precision-balanced thousand-rpm spinning organs. 2. A dragon that breathes fire doesn't need to worry about burning, as long as it can manage the short bursts of heat. However, continuous combustion means that you have to deal with high temperatures all the time. Either the dragon's combustion chamber must be ablative (burns away slowly) in which case it probably ablates away much faster than it grows back, or must be made of a heat resistant material like typical jet engines. Again, I know of no animals with titanium organs. 3. A typical small jet has a fuel consumption of around 6 gallons per minute, equivalent to around 20,000 L of methane gas per minute. At this point your dragon will probably look more like a blimp than a jet. There are no laws of physics that say it's not possible, but they do say that it's not plausible. [Answer] ## No. There are a couple of rather forbidding problems that this creature (even a genetically modified super-creature) would have to overcome, here are a few: * Methane and similar substances burn at roughly 1900-2000°C. This is rather incompatible with *"coming out of an animal's belly"*. Temperatures of around 2000°C will cremate the animal and any other organic materials nearby. * Square-cube law. Such a feat as rocket propulsion might be imaginable for an insect-sized animal (with a somewhat less burning reaction, and at smaller scale), but not for something large enough to carry passengers. I believe there even exists a bug which does something similar. * In order to produce the necessary amount of methane (or similar), to lift off a not-insect-sized animal, the animal would have to feed and digest for *months*. * Laplace's formula. In order to *store* that amount of gas, the creature would need an immensely big belly under tremendous pressure. Laplace tells us that the belly's wall would thus have to be *extremely* thick, which means the animal would be forbiddingly heavy. * Lack of pressure/atmosphere at 10,000 meters. Low outside pressure amplifies the problem in the previous point, and lack of oxygen does not precisely help. * Temperatures below -50°C. * Noticeably elevated radiation (both gamma and ultraviolet), so the animal would need a metal coating of sorts. [Answer] From an abstract point of view, I would say yes - a jet dragon could exist. Evolutionarily speaking, any creature is possible given a series of environments and mutations that would result in that creature. From the above posts, it seems highly unlikely that current earth conditions would ever allow for such a creature, but in the grander spectrum of evolution, a series of stranger environments could easily lead to such a dragon, or any physically possible structure. There seems to be a heavy focus on designing a dragon that has the mechanical properties of a man made jet, and the material properties of carbon-based life. That is a difficult task, probably more or less impossible. If you are talking about evolution, I think you'd be better off figuring out the series of environments that would cause natural jet-animals to exist. For example - **why would flying at mach speeds be so much better than traditional flight?** ]

[Question] [ Our world of fiction is filled with books, movies, and games suggesting a Mad-Max-style apocalypse can last hundreds of years. This, despite the fact that nuclear fallout would decay within a decade and it only took us about 150 years to develop all our cool tech in the first place. *(This strongly suggests our world would be right back to the brink of nuclear war in less than 150 years after the apocalypse, but roll with me on this one....)* Now, I know this question is likely to be closed as too opinion-based, and I'll be completely forgiving if it is, but... **Given an apocalyptic event that reduces the world to a very stereotypical Mad-Max condition, what world-wide conditions could justify humanity's inability to rebuild its world for 500+ years?** > > *As an incentive to leave this question open, I will blatantly misuse this block quote to announce my commitment to place a 250-point bounty on this question. I'm looking for people's best creativity!* > > > [Answer] While you're right that industrialisation occurred within 150 years for our modern society, it is important to note that the conditions which allowed for that do not necessarily exist in an apocalyptic environment. I personally think that the dark ages that would be brought on by an apocalypse would last much longer, possibly the 500 or 1000 year counts, not because society can't reinvent its *technology* faster, but because it can't reinvent its *society* faster. **Non-Survivalist Thinking** During the industrial revolution, the vast majority of people in Europe and America could go about their business and travel through their country of origin in relative security. They didn't have to worry about their survival, so didn't need massive bands of mercenaries or soldiers to protect them as they moved about. This is important, because it means that travel costs a LOT less in terms of food energy, logistics, and the like. That means less farmers having to support people moving about. Cities were even safer. Sure, there's the odd mugger about, but in 1729 Robert Peel creates the Metropolitan Police in London. This means that most citizens who spent a significant proportion of their day protecting their properties and lodgings with checking locks, etc. Now also have time to focus on other things, making them more productive. That means for the same amount of food energy, more gets done. Village life and farming in general is safe, and the fact that countries have standing armies (dedicated military forces) means that people can devote their entire lives (even entire generations) to farming output, and the only limitations are land fertility, the climate and their farming practices, which if focused upon, can only improve. They don't have to worry about being called up at short notice to fight in a local battle at the order of the Manor lord, which not only distracts them but could also cut short their ability to produce more and share their knowledge and experience with others. Finally, Gutenberg (2 centuries previously) has invented a simple method for mass-producing knowledge that can be shared cheaply with as many people who actually want it, provided you have paper manufacturing facilities, ink production and teams working on creating the typefaced text that is needed to print this knowledge out. The benefit of non-survivalist thinking? A *much smaller percentage* of your population can be devoted to essentials like food production and military readiness, and the rest of your population are free to push knowledge forward through research and technological development. They can also do so MUCH more effectively because of the printed word. Your apocalyptic society is a survivalist society. They have to produce food to survive, making food a critical resource in your society. Given that food must be produced on farms and land generally, food production is probably being done in a set region, which has to be protected at all costs. FAR more of your society as a percentage is now focused on food production or its defence, meaning that you lose the ability to conduct research to make your life better. Sure, one can argue that in the long term the research is beneficial, but Maslow's Hierarchy of Needs dictates that food production will have priority in a survivalist society, hence the research will not take place. **Political Order** Clan based fiefdoms are a very useful political structure for low-tech environments as they don't require many of the advances (like writing) that we take for granted in the modern world. It's easy to know what the law is in a fiefdom; it's whatever the boss says it is. That boss can extend his reach as far as his enforcers can reach, but eventually scale destroys this model. Even Elizabeth I faced insurrection at least once from within her nobility. Believe it or not, the one thing that allows a country to unite on a large scale under a single banner that can manage said country effectively is Journalism. Journalists are people whose sole function is reporting on the events of the nation (in this context). A heavy part of that is the political happenings. This works both ways; journalists inform the public of what a parliament decides, and it also informs the politicians on what the public thinks about that. Rulers and managers *require* your obedience; great leaders *inspire* your obedience. To do that, they need to engage you in the narrative and explain to you why you need to pay so much tax and what its going to pay for that will make your life (or the life of your kids) better. These large scale systems of political (and by extension industrial) order are served by journalists who get those narratives to the people. Your apocalyptic society that has devolved into fiefdoms not only doesn't need journalists, but actively doesn't *want* them. Anyone who challenges the chief is a liability and why are we feeding this person to be a gossip and sow insurrection anyway? It just won't happen. Even then; let's assume that your fiefdom of (say) 50,000 people DOES have a fairly secure environment, food is plentiful and they are sufficiently remote that their army doesn't have to be that big. You *might* be able to engage in some form of research and development, and you may even have books that have survived the apocalypse to short cut the learning process. But to build a car from scratch you need a source of fuel (even coal if you're going for steam), an engineer, a blacksmith (preferably a boilermaker), and sundry other skills and ingenuity that are unlikely to form in a small environment, where breadth of skill is far more valuable than depth of skill. **Safe Travel** Ultimately, what you really want to progress your science and technology again is safe travel of experts between domains, and a way for their knowledge to be shared between themselves quickly. This means organised printing presses, and a trans-domain market for books and knowledge. The afore-mentioned survivalist thinking will make this more difficult, but it can be achieved from a technical perspective. From a perspective of society however, if all these fiefdoms are in competition with each other, why on earth would they just give away their most prized asset (information), especially when one considers how much of a percentage of their production it cost to generate it in the first place? This puts us right up against large scale political structures, or the lack thereof. In a world where resources are much more scarce than they are now, competition for them is much more intense and that means that the fiefdoms are not going to share readily. While it's *possible* that they may find a way to cooperate, they would only do so if their mutual survival was enhanced through such cooperation and transitioning from a survivalist culture to one that is less so isn't an easy transition as it involves the establishment of trust that things aren't going to go pear shaped again in a hurry. Ideas MUST propagate easily for technology to advance, even in an artefact driven culture like Mad Max, where cars and fuel may exist, but the ability to repair / refuel / rebuild them has been lost. It is that 'cheap' transmission of ideas between parties and generations that allowed us such rapid advancement in the first place over the last 150 years. **Critical Mass** During the middle ages, society didn't advance anywhere nearly as quickly as it did during the last 150 years. Part of the reason for that is tied to the conditions described above, but there is also a need for a foundation of knowledge to build upon in order to make great strides. For us, the [Maxwell Equations](https://en.wikipedia.org/wiki/Maxwell%27s_equations) (created by James Maxwell in the early 1860s) led to incredible strides forward in our theoretical knowledge and the ability to apply that knowledge practically in ways that were not possible without that particular knowledge. In other words, there are certain pieces of knowledge that if we lose, will hinder our progress until we find them again. The chances of the Maxwell Equations being lost is not very high, and our artefact rich apocalyptic society will probably figure most of it out on their own, but it's important to note that theoretical research is the bow wave of technological advancement; without certain theoretical knowledge, engineering advances simply are not possible along the lines that knowledge supports. **Summary** Your limiting factor in progressing from an apocalyptic society back to modern technology is not technological; it's social. It's clear that in all but the very worst apocalyptic scenarios, the environment for most survivors will be artefact rich, meaning that when one can focus on it, rebuilding knowledge and technology can occur at an accelerated rate by comparison to the original speed of development. It's the focus that will be the limiting factor. People will focus on their own survival first, then the survival of their group, then the protection of their group, then (as some technology re-emerges) on the advantages of working together at some form of 'national' level, and it's only THEN that the social constructs will be in place that will allow the survivors to leverage what they already have and know (as one) to develop more advanced industries and recreate the modern tools and information sharing abilities we currently enjoy. Another way of putting this is that your society will begin to advance at the rate we have in the last 150 years when the people enjoy; 1) safe domestic lives 2) regular and consistent access to food and shelter 3) organised large scale government and industry 4) a culture of free knowledge sharing 5) an environment that encourages research and development, including the populace seeing regular benefits from such advances. If we take the middle ages as an indicator, that could take a significant number of centuries to re-achieve. Until then, will alone does not an MRI make. [Answer] Not in the mad max sense. Because mad max had cars and gas, the remnants of civilization. If you have the total breakdown of civilization. You have 15 maybe 20 years at most before all that stuff it gone, broken down rusted junk. Who is going to produce gas, who is going to produce the iron to make the car. You cant take a lump of iron and forge it into an engine. It could last 500 years, but you will wind up losing a lot of what we have. You might be able to develop something like muskets and maybe even steam engines, but gas and cars and smokeless powder in brass shell casings. I don't think so. These things require civilization on a large scale. They require very specialized trades and knowledge. I think to have them, you must have civilization. And most importantly they require a ton of power. Now you could let these things go, go back to hunter gatherer or even feudal kingdoms and I could see that persist for some time. Most of human history has been that way, in fact. The easiest reason, is quite simple, it's one word. Energy. Right now we have oil and gas and coal. We are trying to transition to something more sustainable. What if we don't make it. Most of the sustainable stuff takes a large amount of energy to create to get any useful power out of it. You cant just created a nuclear reactor out of nothing, it takes a ton of energy. In building it and in the materials. Even solar power, if you have no power how do you make solar panels? How can you build a dam for hydro electric, how can you make windmills with no easy to access metal. But with fossil fuels they have a ton of energy that is accessible with little more then a spark. Granted you have to drill for oil, but if you include things like coal, coke (a refined form of coal) etc. Anyway, from that we have built everything you see today. You can't magic in a sustainable source of power on the level that fossil fuel provide. Can we get to the point that we don't need them anymore with things like solar, wind, nuclear (both types). Well I sure hope so, but it takes power to get there. Once we deplete the power we have from fossil fuel it's going to be really hard to produce solar panels using wood fires. So what is the easiest way to get rid of oil. I once had this idea for a story, basically someone (doesn't matter who) developed a microbe that ate hydrocarbons. This could have been developed as a way to clean up oil spills. Then this bug mutates and becomes airborne, starts feeding on smog and basically any hydrocarbons it can find.... etc etc. I'm not a biologist so I don't know if such a bug is possible. I'm also not a chemist but I think a lot of plastics are made from petroleum byproducts, including some wire insulation. Without any of this stuff, enter energy Armageddon. [Answer] The single best indicator of how quickly humanity could rebound from an apocalypse is *how quickly the **human population density** rebounds.* While this may change in the next decade or so, our modern infrastructure - cars, water, waste removal, etc. - is still currently dependent on having a lot of humans around to run the show. If the population crashed, or if the robots who might take over were wiped out in combination with a population crash, we wouldn't be able to recover very quickly. In a first scenario, let's assume the world's population is knocked back to 50 million people *and the survivors are scattered* and living in groups of no more than 150. Our technology level would be reset to the beginning of the Iron Age, not because the immediate survivors have forgotten what technology is, but because 50 million people *scattered* over the Earth cannot maintain an infrastructure more advanced than that without AI. <https://na.unep.net/geas/newsletter/images/Jun_11/Figure1.png> In a second scenario, let's say all 50 million people were somehow gathered in one place that had the physical and medical infrastructure to keep them all alive for at least 50 - 100 years. (Without that infrastructure, a plague hits and wipes out the remainder of humanity. Scattered and living in the Iron Age may not be great, but it does reduce the chances of that happening.) Let's also assume that the extraction sector of the global economy has been completely automated by AI and that the AI was not wiped out. Now, assuming the government of these people is coordinated enough, you have a chance of maintaining some level of modern infrastructure and technology. The post-apocalyptic city state would assess what resources it needs - energy from fossil fuels or renewables, metals, food, water, etc. - and, having government records from before the apocalypse, would know where to send groups of survivors to colonize an area, gather its resources with the AI left behind, and ship them to the forming megacity. But that's still dependent on having AI to do many tasks. If you remove AI from this scenario, the megacity won't have enough people to manage both the resource colonies *and* the transportation networks it would need. You're talking about trying to maintain the modern output of mines and wheat plantations with manual labor (and there's a reason people in the Iron Age used slave labor for that) and maintain modern shipping routes and ports on top of that. There's a chance that the megacity would slowly fade away as more people left it, and you'd have populations centered on a resource that traded with each other over increasingly hard-to-maintain trade routes, but as the machinery that makes those routes possible breaks down, you end up devolving back to the Iron Age scenario. **That might be the closest to a Mad Max scenario.** All of these above scenarios are heavily dependent on what kind of apocalypse happened. If it's a World War style one, most of the AI and population and resource centers will have been destroyed, making the scattered scenario more likely. If it's an asteroid, then it's just dumb luck where it hits. Finally, there's the Steampunk fantasy. This scenario tries to develop a steam-powered - meaning coal-mining and oil-drilling - infrastructure to increase economic output. This might be doable with 50 million in a megacity, *if* it's close enough to its resource centers. Great Britain started the steam revolution, and, with Ireland (which, from a geopolitical point of view, it was using as an agricultural plantation) had a net population of about 18.7 million in 1800. But Great Britain also had coal mines within its borders, Ireland's farming industry right across the narrow Irish Sea, an already well-developed naval force and shipping infrastructure, and access to more exotic resources from her colonies. In order to survive this scenario, the mega city would have to be placed *juuuuust right.* [Answer] To make it last 500 years: * Heavily decimate the population. Current technology was achieved by the incredible amount of time we can collectively spend on one task. Killing off the population means you lose the manpower to spend on research, as well as free up time for the researchers by letting others collect food, build houses, maintain infrastructure etc. * keep population low. In line with the previous point, something like radiation causing decreased lifespans and bad genetic mutations can keep the population low, stalling the recovery. Additionally, the collapse of medical care will increase Child death, lethal complications at childbirth and decrease life expectancy. * Destroy all infrastructure. When we "started" 150 years ago, we already had a massive infrastructure of roads, trade routes, mining, cities and farmland. Without that infrastructure it takes a lot more time to get technologies across the globe, even something as simple as how to write may take 50 years before it's spread across the globe, and another 50 years before more than half the population is literate. * Kill off all the smart people and their records. If you are too busy surviving because your local farmer kicked the bucket and you suddenly have to re-learn all there is about farming yourself, not a lot of time is left to tinker with things. If all the smart people and their collected knowledge is gone too, you are also forced to re-do all that work while tending to your crops and pigs. Good luck! * The environment sucks now. If things like radiation sickness, global genetic defects and high mortality dont sound like fun, have a post-nuclear winter! Or perhaps the large-scale warfare has destroyed almost all the forests and nature is still finding a new equilibrium after mass-extinction events of more than half the (large) species and such a massive deforestation has also altered climates. This in turn forces humanity ro focus on survival with little time for research other than the research specifically designed for trying to get to the next day without starving or freezing. [Answer] **A simple huge loss of population** If 95% of the population is gone and the rest is scattered around the world and can't get along (raiders, different factions,...), I doubt the world will progress much, especially if past technology is hard to recover and resources are scarce. Concerning the potential causes of such events, **a virus is a good candidate**. It can **kill a lot of people** and have a **huge effect of area denial** (quarantined areas) that can prevent people from accessing fertile lands for crops, lakes and rivers for water or any kind of resource. This virus could potentially affect plants and kill a lot of common crops. This would keep the struggle for survival constant and a lot of rivalries would occur, especially around viable land. [Answer] It depends on the scale of the disaster. After the Late Bronze Age Collapse, some countries had not rediscovered writing after 500 years. You would need a disaster of equal magnitude. Nuclear war could do it, some isotopes are very long-lived and the Trinity site was shut down when it was found too dangerous for visitors. Imagine much larger yields bursting near ground level. Coal would be hard to rediscover as so little is near-surface. Same with oil. There may not be the reserves left to get to the deep stuff, which means they'd have to leapfrog that epoch. It might not be possible to recover from that. With a move to e-books and a loss of libraries, a virus that took out the Internet and critical systems connected to it (there are actually search engines that list the nuclear reactors whose SCADA systems are on the public Internet!) is possible. The loss of knowledge, compounded with the fact that schools no longer teach people how to write manually making distribution of information a formidable task, would essentially shut down civilization in salvageable way - but it might easily take 500 years. The panic alone, not to mention mass starvation from a total loss of high-tech farming and high-tech distribution, would result in the loss of most of your intellectual class, a "lost generation" from loss of schools, and therefore a total absence of anyone who could provide insights or shortcuts. It would require rare minds to reverse engineer examples, particularly as technophobia would be rampant. [Answer] # Someone wants it to stay this way Where you find disaster you'll find opportunists, some people who rise to a position of power because they had access to resources no one else does - water, tech, electricity. They can then try to break up any signs of others trying to work together and make sure they retain their power. My suggestion, to retain the setting world-wide, would be to go with tech. One group was either prepared for the apocalyptic event or had the expertise to get up and running well before anyone else did. They have access to electricity and tech that allows them to travel all over the planet easily and perhaps even satellites pictures to allow them to notice any settlements that start to grow quickly - suggesting groups working together. They can then drop in, sew mistrust between them, and undo whatever had been done to bring those groups together. This then allows them to trade tech for food and other resources - letting you retain cars and other complex machines you might see in Mad Max - but doesn't mean you have to give everyone access to car assembly lines or the technology that comes with that. [Answer] Human beings may never rebuild. At least not in any way that we imagine, and not in any timeline that we imagine. Here is the problem, doing the industrial revolution we grabbed up all the low hanging fruit when it comes to fossil fuels. Oil used to be right at the surface in some spots, you just had to dig a few feet. These days we need offshore rigs and fracking. The renaissanceman can't do this. The technology gap simply becomes too large to cross between horses and access to oil. The same problem must exist with coal as well. Without fossil fuels there is no industrialization. You can't go renewal emery because you need industry to build these things. Without industrialization there is no rebuilt world. Even if it was to happen it would not happen all at once. Maybe somewhere like the middle east society would slowly grow. Still it would take it hundreds of years to expand to any specific place. We still don't have huge parts of the world developed. [Answer] I think it's believable. I'm not convinced that such a scenario is *probable* or even *likely*, but it is *possible* and therefore believable. I think much will depend on how quickly some semblance of "normal social functioning" can be reestablished after the pockyclypse. Clearly, in the Mad Max world Australia failed to reestablish (which, of course, would defeat the purpose of the movies in the first place, which largely was to place Tina Turner in outlandishly revealing costumes (for the time) on juryrigged war waggons). With society itself a failure, the remaining technology can not be renewed, only patched until at last it fails. Knowledge will eventually be lost as those who once Knew die off and new generations are ill educated and ill equipped to handle the job of picking up the pieces. So yeah, I can see (and believe) a 500 year Mad Max type scenario. With the exception, of course, that now I've learned that petrol is not stable over long periods of time, so chances are good none of those war waggons would even be functional more than two or three years after the petroleum industry collapses. On the contrastive hand, we have the Star Trek scenario. Here, we have some kind of pockyclypse that people are able to not only survive (with terribly loud "music") but a drunk scientist-engineer is able to build a working warp drive capable space ship inside an unused ICBM. The rest is deBorged history. I think some guy coming up with a warp drive in his garage is less likely & less believable than the Mad Max scenario. But I think more likely (and perhaps more believable) will be reasonably untouched regions will be able to recover and rebuild something akin to the Old World, if on a smaller scale than before. Chances are good DC, NYC, London, Paris, Moscow, Peking, LA and so forth will be nuclear wastelands for ever: utterly destroyed fields of ruins. Smaller cities like perhaps Edinburgh, Seattle, Montreal, Miami, those might be spared the utter destruction of the principal targets. Smaller cities with universities, medical research centers, small pharmaceutical facilities, those might be in prime locations to form the nucleus of new technologically recovered states. Most believable of all will be a combination of regions where technologically recovered states coexist with regions of Mad Max wilderness. [Answer] The current civilization is mining the more accessible supplies of resources such as oil and metals. If an apocalypse scenario wiped out the ability to maintain modern technology and infrastructure, and our current quarries and whatnot become inaccessible, future generations will have a harder time gathering material needed to fuel a high-tech civilization. We can look at historical examples of such a societal collapse, the Bronze Age Collapse, lasting from about 1200 BCE to 900 BCE, a period of about 300 years. Presumably, it would take longer to recover to a higher tech level. However, the causes for the collapse are not known but such widespread collapse and the lack of recovery for a long time suggests a *general systems collapse.* I'll just copy some lines from Wikipedia. > > The growing complexity and specialization of the Late Bronze Age political, economic, and social organization in Carol Thomas and Craig Conant's phrase together made the organization of civilization too intricate to reestablish piecewise when disrupted. That could explain why the collapse was so widespread and able to render the Bronze Age civilizations incapable of recovery. > > > -Late Bronze Age Collapse, Wikipedia > > > "The growing complexity and specialization of the ... political, economic, and social organization" I don't mean to be a doomsday preacher but sounds kind of familiar doesn't it considering our very specialized sciences and technology being used in everyday life? This analogy applies to a total collapse of modern civilization. On the other hand, if we look at the collapse of the Western Roman Empire, the Middle Age organized social structures were able to set themselves up fair quickly. The cities simply shrank in size but were not completely abandoned and some social structures remained such as the Church and the Eastern Roman Empire as well as new nations filling in the power void. This situation could apply to a more limited apocalypse situation such as a US/Russia nuclear exchange with southern hemisphere nations such as Argentina, South Africa, and Austrailia coming out mostly intact(until the economy and the supplies starts to collapse but hopefully they will figure that out before things go even more south). [Answer] I'd say religion. "God smote the world for our arrogance and we must live like God has told us and beg his forgiveness" The leaders of a powerful religion have a vested interest in keeping the status quo and if people are too busy surviving, they aren't questioning the religion. Anyone not towing the line gets the chop. "Burn the heretic" [Answer] After an apocalyptic event, one of the first things to go would be the internet, right? I mean, it requires electricity at the client end, electricity at the servers ends (multiple servers), electricity all along the way, connectivity, maintenance, routing - it's a complex system. Without internet, how many people would know how to start a fire without matches, let alone constructing complicated tools? A lot of information we need is "at our fingertips" - online. Books, scientific articles, enciclopedias - everything is online. One might enjoy curling up with a fiction book, but when it comes to science and engineering, we want to Ctrl+f, right? So, in the absence of internet, a lot of information would be lost. The more advanced we get before the apocalyptic event, the less actual printed material we'll have, and the more information would get lost. Some professionals would of course have this information in their heads, rather than "at their fingertips" - it might be professional knowledge, hobby, whatever. However, the first concern after a post-apocalyptic event would be survival. How would that go? Our money is an imaginary token. Something that exists on servers, backed by countries. We transfer imaginary tokens by swiping a card. Coins and paper money are also nothing but convention - only worth anything because we agree that it does. Without the system to back money, we're down to barter trade, and what's gonna have most worth is what's essential for survival: food, fuel, medicaments. Big cities are going to be in big trouble: they rely on products flowing in every day, and that's not gonna be happening. There will be people starving to death, people freezing to death, and infections spreading due to inadequate access to medication. Look at Moscow the year of the Revolution - it was smaller a hundred years ago than it is now, less reliant on technology, and still that's what was happening big time. After the initial collapse, after whatever toll death would take, how much knowledge will have survived? From what point would technology need to be reinvented? Do not forget that reinventing lost technology would not be fast. To do anything beyond surviving here and now, people need leisure and security. So, some sort of structured society would need to re-establish itself, and then have extra resources that can be invested into research (giving people the knowledge base from which they may advance, feeding the one doing the research, whatever materials would be needed for research, including failed attempts at stuff). That doesn't happen all at once. My favourite example is the Roman Empire. It had plumbing. There was water coming into the cities. There were pipes in buildings, bringing water to high floors. There were nine-floor buildings. There were public baths, and a sewage system. At its peak, there were a million people living in Rome. Then, Rome collapsed, and it took until the 19th century for the same amenities to come back. You could say that in this regard, a post-apocalyptic state lasted not 500 years, but 1500 years. And the apocalypse had been a lesser one. [Answer] There could be such a setting only if the thing that caused it is still around. You could write about a war with robot-zombies that do not decay. The main hive-mind has been destroyed in the war but the units still remain a threat. They do not pursue the extermination of humans but they prevent them from expanding to far, trading between distant places or scavenging big cities because there would be more of the robots. You have to keep your population occupied with something so they don't have time to think about rebuilding or invent shit. The mentality that technology is evil will also help the prolonging of your scenario. Perpetual war... That would be a great story. [Answer] I can't speak for other countries, but the United States has very detailed preparedness plans for all sorts of predicaments, [from the IRS's post-nuclear tax-collection plan](https://www.nytimes.com/1989/03/28/business/nuclear-war-plan-by-irs.html) to [ConPlan 8888](http://www.cubadebate.cu/wp-content/uploads/2014/05/CONPLAN-8888.pdf), a zombie survival plan. The base assumption supporting *Mad Max*-esque scenarios is that individuals would easily rebel against and overthrow governments weakened by massive droughts or nuclear fallout, but the average citizen would most likely be more heavily affected, and such a situation could cause countries to impose martial law out of fear for their own safety. It's probable that a post-apocalyptic scenario would look like modern-day North Korea, instead of an anarcho-primitivist wonderland. In the cases of most zombie apocalypses or epidemics, strong governments would quickly quarantine heavily-hit areas and eventually find a cure, unless they were infectious enough to destroy humanity entirely, which would kind of ruin our chances of a post-apocalypse, wouldn't it? I know that's not a very creative answer, so I came up with a couple of (questionably sci-fi) scenarios: 1. Rogue clone takeover. They are impossible to distinguish from the originals, as they are physically identical to them, and they act completely normal to gain the trust of those around them. However, due to their flawed development, they become confused and act violently around the originals. Society would fall apart almost immediately, because the only way to be sure you aren't going to be killed by one is to be as far away from other humanoids as possible. I know this is far-fetched, but it's at least better than zombies, right? 2. An advanced alien race targets large-scale human development, making political structures impossible to maintain. An example of this might be the population cap from the anime, *Tengen Toppa Gurren Lagann*, in which (SPOILERS) the moon would crash into the Earth if more than 1 million humans were living on Earth at the same time. This effectively ceased all social and technological progress in the anime. [Answer] > > ...nuclear fallout would decay within a decade and it only took us about 150 years to develop all our cool tech in the first place. > > > An apocalyptic scenario would certainly throw us back further than the mid 19th century. It was already mentioned in another comment, we would lose so much knowledge with a devastating apocalyptic event it would take much longer to get back to where we left off. Think about how society (or what is left of it) will have to adapt to a new way of life? They will have to re-learn EVERYTHING. We may have cool technology, but we are extremely dependent on it. Taking that away will throw us even further back than the dark ages. Most people NOW, probably don't know how to hunt, to skin an animal, farm, build shelter, find medicine naturally. We would have to figure this stuff out, again. Desperate times require desperate measures. People may be eating each other and burning their books to stay warm during the winter when the proverbial caca hits the fan. Knowing how to build a steam engine, for example, would be last on their list. [Answer] A: Big population crash. Takes a certain number of people to make society work. If you cut off the electricity, most cities would have people starving and dying of thirst before you could get them out. B: If the crash killed the cities, it may kill the libraries too. So much of the knowledge is gone. C: If the crash was caused by global warming, then we may have hundreds of years of unreliable weather. Unreliable weather means frequent famines. Lots of small scale wars between groups fighting for food or water. D: Loss of the tools to make the tools to make the tools. A vacuum tube triode is within reach with 1800 tech of glass blowing and vacuum pumps. A transistor is not. Bell Labs set out to turn theory into devices they figured 5 years just to learn how to get germanium pure enough. Only took them two. E: Lack of easy resources. The age of steel in America was based on large deposits of high purity iron ores. Some better than 80-90% iron oxide. Now we're working deposits of 10% F: Continued disintegration of infrastructure. Concrete in particular: water moves through concrete, but not very fast. rebar rusts. Rust takes up more room. Concrete breaks. Bridges fall. G: Rising ocean levels put more pressure on remaining coastal populations. Piers have to be salvaged, moved, abandoned. Depending on how fast Antarctica melts oceans could rise a foot a year for a couple centuries. H: 3 generations of the use of vaccines leave a world ripe for plagues. A few of these, and the old standard of "stranger equals enemy" comes back. Makes cooperation much more difficult. Depending on how hard the crunch is, people may need to relearn the germ theory of disease. I: General lack of written records. Printed books are much lower tech than iPads. Some of this depends on the speed of the crunch. In "Dies the Fire" Stirling's first Emberverse novel, electricity and anything requiring a pressure of more than about 5 atmospheres stops working, click! Cities eat consume themselves. World population drops to a billion in a few weeks, and to a hundred million in a couple years. A big enough electromagnetic pulse could destroy anything with a transistor. A slower crunch -- say complete failure of the world monetary system -- leaves room for smart people to print manuals, and get set up. A slow crunch will likely be one that doesn't take centuries. [Answer] I apologize if this answer has already been supplied but a nuclear winter may give you your answer if the conditions persist long enough. Such an idea has been proposed in science fiction and in the real world such conditions would limit the options for survival to the creatures including humans that could subsist in such a place. There are papers written about this very idea in real life that may supply real world framework for your world. [Answer] I think it depends on the scale of the collapse and state of the civilization. Then that takes into account information from previous generations being lost when power is no longer able to allow digital technology to work, and so much information is digital now. Energy would have to be part of the conversation as well, as the only form would be combustion. And considering the state of the environment today or 500+ years into the future, we would run out of fuel eventually. If this future was bombed back to a pre-industrial era, then it's completely plausible for post-apocalyptic situations to last for centuries. So Mad Max Future: State of the environment and dwindling fuel = extinction in maybe 50 years. Fallout = a bit more plausible with the nuke-scrubbing tech and years for radiation to become inert. [Answer] Well it would be similar to the dark ages in europe except it would be worldwide. It would take hundreds of years for society to recover, and eventually there will be a renissance where we will leap back to where we were. [Answer] ## There Are Historic Examples of Societies Springing Back from Apocalypse As you indicated in the question, human society has bounced back mostly intact from some pretty severe setbacks. * Europe after Black Plague wiped out 30% to 60% of the population in 1337. * The Diaspora of Israel in 722 BC, 597 BC, 586 BC, 70 AD, and 132 AD * The burning of the Library of Alexandria in 48 BC * Serbia after losing nearly 30% of it's population to World War 1 * Russia, Poland, and Germany after each losing around 17% of their population in World War 2, plus their losses from World Was 1, plus (for Russia) another 10% population loss only fifty years earlier to plague. ## And Their Are Examples of Societies Language, Culture, and Customs Being Lost And there are times when a society has crumbled so completely that, even though monuments remain, we can no longer read the language. Culture is completely lost. And the monuments may stand for centuries before researchers unlock the language with the help of Rosetta Stones, and we are left to re-invent sciences in the meantime. * Thera, after the complete destruction of the island and all citizens by natural disaster * The Babylonians, after a few years' war for the capital between Alexander's heirs * The Egyptians after a peaceful annexation by Rome * The Mayan after a drought ## A Special Set of Circumstances Required for a Civilization to Be Lost With the exception of Thera, an unrecoverable set-back for a society does not require many (or any) casualties. In the case of Egypt, the empire had been under generations of pressure to westernize by it's own government prior to Roman annexation. Similarly, Babylon had been under eight years of pressure to westernize under Alexander, which continued under his heirs. And although experts disagree on the specifics, they seems to all agree that there was a widespread loss of faith in everything Mayan when their culture and written language was largely abandoned. But pressure to abandon culture does not seem to be enough. Israel has been disbanded as a civilization at least five times. They had their writings taken from them, their young indoctrinated in foreign cultures, families split up, and were enslaved. Nevertheless, a group of people within that culture saw it worth while to keep the language (written and spoken) alive. They kept their stories alive. They even wrote texts (the Talmud) expounding and studying their culture, and teaching it to their children (if they were kept together) and neighbors. Their period is Babylon marked the language strongly, but people remained faithful in keeping literate in their old writings and put effort, even at risk of prejudice and imprisonment to maintain and continue developing their culture. By contrast the Mayan culture seems to have been a widespread and spontaneous choice to opt-out. ## How To Create a Long Lasting Apocalypse Given the historical examples, there seems to be a recipe to creating a collapse. * A loss of widespread literacy in the culture's native language * A loss of faith in keeping the culture alive So, for a modern apocalypse we could imagine a world not much more modern than today where voice-activated machines makes it possible to be high functioning and illiterate. With people only getting their education from YouTube or internet videos, literacy may be almost extinct before the apocalypse starts. Also imagine a civilization maybe a little more cynical than our own - where people have become so sick of society that they are not even marching in protest anymore, the leaders aren't rebelling, and no one is motivated to heroics in order to keep a flame they detest alive. Then the apocalypse happens. In very short order no one will be left alive who can read from surviving libraries or digital text. There might be fakers arise who pretend. Or the writing of the ancestors might be considered purely religious (this was our belief about Egyptian text until the language was re-discovered). All of society's knowledge might be within reach, but it's inaccessible because no one understands it. No one cared to keep the culture alive, so all of the social advancements that were encoded in it - rights, policing, trade, sanitation - are also forgotten. This would give you a Max Max like apocalyptic setting. And it would still be on the decline. Although people might understand how to operate machines, and though some may have saved internet video (or an oral tradition) of how to repair certain things (given parts), there is still further to fall. The Maya, we believe abandoned their culture in 900 AD and by the time the Spanish arrived six hundred years later in the 1500's, other than a few cities that never totally collapsed, the society had still not bounced back. [Answer] Other answers have covered this in detail, but what it actually comes down to is this: Population. Numbers. This is key. Black Plague levels of devastation aren't enough. It took 200 years for the numbers to recover after the Black Plague, and that lead us into the Renaissance. If you up the number of deaths to, say 99% or even 99.999% or even higher , there won't be enough population to create the infrastructure for a long, long time. Get your population down to 50 million over the whole earth and...well, it's going to be tough, because that's below even Roman levels... While we can bounce back, and there have been times in human prehistory when we've only had 10,000 humans on earth. Look at this population chart and progression [through the ages](http://www.ecology.com/population-estimates-year-2050/). If you took the population down considerably and then added to that plagues (which there would be)--500 years of Mad.Max style living could happen. There might be isolated communities that don't have any contact with others, but, in pockets it could be like this, if in fact there is some industry. I am going to say that planet-wide it's not realistic that nobody has formed a society different from this. But if you keep it local, it certainly is. It's not beyond the pale that it would be that way in one particular corner of the world. I would posit that many places would abandon gasoline and cars entirely in favor of livestock. But people just keep dying and there aren't enough of them. Consider that technologically, not much happened for 500 years in our own history from Rome's rise through Medieval times. It's not going to be the only way of life for sure. [Answer] This theory feels somewhat flawed, but for the sake of discussion, here it is: nobody would create anything, because whatever they could create would be vastly inferior to what they already have. Let's take weapons as an example: after all, human history is, to a large degree, history of war, and, therefore, is history of arms race. Mostly, all parties were more or less equal: our tribe makes wooden clubs and sharpened sticks, their tribe makes wooden clubs and sharpened sticks. We make stone axes, they make stone axes. We start forging steel swords, they start forging steel swords. Etc., etc. Now, let's imagine ourselves some decades after the "apocalypse". We still have plenty of modern weaponry. We can't make more of it, though: the knowledge and technologies aren't exactly "lost", but, with all the production and supply chains broken, became rather unusable. So, we can't make ourselves another assault rifle, but we can make a bow. But why make a bow if we already have an assault rifle? Why make a ballista if we still have some cannons we can use? If the technology gap was smaller (let's say, before the apocalypse we only had muzzle-loaders), then maybe, but it's just too big... If there's a serious conflict, we would still rely on assault rifles and cannons, because it gives us better chances of winning, and, knowing that, our enemies would also certainly rely on assault rifles and cannons, because it gives them better chances of winning. At the same time, understanding that we have limited and unreplenishable supply of guns and ammo, we would try to avoid using them. Thus, we are stuck forever in a stalemate of an armed truce between innumerable warring gangs, their power based exclusively on otherworldly magic contraptions they don't even understand. No economical growth, no society rebuilding would be possible under such conditions. Until, eventually, the last guns fall apart and we're back at what - stone age? bronze? How long would an AK-47 last if taken really good care of and is almost never fired? ]

[Question] [ Suppose we used [SCP-261](http://www.scp-wiki.net/scp-261), the vending machine that produces anything, and ask for a cup of neutron star. The machine instantaneously produces this. Suppose also that the vending machine is located at a normal office building, not some underground lair or the like. What effect would this have, and how much damage would it do? Would it kill everyone in the building? Destroy the Earth? Surprisingly very little effect? [Answer] This is more or less my best guess. We're talking about a mass of about **one hundred billion tons**, composed of neutrons, previously held together by a terrifying gravitational field - and now unleashed. The cup starts falling down under the Earth's gravitational attraction, but at the same time *it explodes outward* (so, also downward) with a velocity equivalent of a 2-3 MeV energy (so, 20000-30000 km/s). This makes the actual fall negligible; we may consider the cup at rest in respect to the Earth (actually, after just one microsecond, there *no longer* is a cup - there's a spheroidal mass of neutrons roughly twenty meters in radius, at a temperature equivalent of at least several million Kelvin, exploding outwards at a measurable fraction of the speed of light). The energy release is immense (this [other answer](https://physics.stackexchange.com/a/150318/45854) would place it at around $1.5\times10^{28}$ J, or almost forty thousand times larger than the Chicxulub dinosaur killer) and we may divide it, initially, into two parts: * energy release above ground: this vaporizes everything inside a radius of about 20 kilometers in a few milliseconds, and irradiates up to about 80 kilometers. More than that, if the apportation takes place high above ground (a high-rise, an office building up a hill, etc.). Everything within this radius is irradiated and becomes intensely radioactive due to [neutron activation](https://en.wikipedia.org/wiki/Neutron_activation). Most heavy metals undergo fission. The heat is enough to drive through the stratosphere, while radioactive tephra fall down from the sky up to two thousand kilometers away. Trying to scale up estimates from the Chicxulub impactor, the air blast and pressure wave are probably enough to destroy or severely damage everything up to 800 kilometers with the possible exception of places protected by (i.e. behind) mountains, or underground bunkers and hardened buildings. * energy release below ground: this should be enough to vaporize a good two-three kilometers of crust, and pulverize another five to ten kilometers, irradiating them thoroughly and depositing enough heat and secondary radioactivity to ensure a complete meltdown. The crustal rebound is negligible, but the shock wave is not: unless the accident happened on a very thick and old craton (and possibly even in that case), the magma from the upper mantle is exposed, turning the area into a radioactive supervolcano. From one third to half of the total energy escapes upward almost harmlessly, another fraction is probably ghosted away by fleeing neutrinos, but that is far, far from being enough. Neutron flux of a sufficient density activates aluminum silicates that make up most of the Earth's superficial crust: within a small radius, there are enough neutrons to ensure the triple-capture activation of 28Si to 31Si. Some of that will be made less harmful by a fourth capture, that extends its half-life from two hours and a half to one century and a half. Aluminum activation transforms [aluminum into silicon](https://www.geneseo.edu/nuclear/neutron-capture), releasing a considerable amount of energy as heat and gamma rays. Communications are instantly obliterated on a vast area by both the EMP release (which also fries most overhead satellites) and the Heaveside layer being reduced to tatters. Within seconds to minutes, the pressure release from the crater area will have caused a second, less flashy but even (on the long run) deadlier supervolcano explosion, as the mantle magma outgasses a pressure equivalent to at least 10-15 kilometers of rock. The explosion drives through the incandescent and radioactive gases, dust and rubble, mixing with them and increasing the firestorm. An inordinate amount of radioactive ashes and noxious gases is released into the atmosphere. (Hal Clement's first published story, *Proof*, deals with more or less this very scenario - a whole ship made up of neutronium, colliding with Earth. The neutronium of the story, though, is cohesive, non-radioactive and simply *very* hot and dense, so the impact results only in a vast lava lake). Within minutes, the neutrons still at large start undergoing beta decay. A sizeable volume of the Solar System gets gamma irradiated. Radioactive tephra start reentering the upper atmosphere, while the radioactive cloud reaches the stratosphere and begins diffusing. Also, earthquakes complete the destruction of mostly everything in a 500-1000 kilometer radius. The shock is enough to trigger most faults in the area. Depending on where the apportation happens, secondary phenomena may occur; in the U.S. we might be looking at activations of anything from Yellowstone to the San Andreas fault to the [Juan de Fuca structure](https://www.newyorker.com/magazine/2015/07/20/the-really-big-one). Between ten and twenty minutes later, give or take, the seismic wavetrain hits the opposite half of the globe, triggering secondary earthquakes. Within hours, the sky becomes red and the infrared emission alone triggers a [worldwide firestorm](https://www.livescience.com/28582-asteroid-extinction-firestorm.html), the smoke enough to blot out the Sun. Some days later, the radioactive dust starts further dimming the sunlight almost everywhere and atmospheric water vapour starts condensing; the torrential waterfalls are initially radioactive only in the impact area, but will become so more or less everywhere within a few weeks. The massive (and ongoing) heat release disrupts weather patterns throughout the globe, the increase in temperature enough to siphon oxygen out of the seas into the atmosphere, where fires and decay processes will take care of it. Mostly everybody dies. Prepared people, with lots of resources, die anywhere between one week and five years later. A nuclear-powered, well protected arcology might remain viable for an indefinite time; anything else probably won't. Asking for a chocolate would have been a whole sight better. **UPDATES: good news from the SCP Foundation** Further analyses indicate that is unlikely for SCP-261 to materialize a cupful of neutronium. SCP-261 has only ever supplied snacks or something that *someone, somewhere* might have considered a snack; the most dangerous apportation recorded was that of one item of SCP-417, which is *theoretically* edible. Neutronium, on the other hand, is unlikely to be edible by any being capable of interacting with SCP-261 at all, so it is equally unlikely that SCP-261 might accidentally destroy the human race. Moreover, in all cases the apported object was packaged in *something* capable of maintaining the contents in a stable state (in some cases, keeping it *alive* until it could be consumed), however unlikely that might have seemed. If SCP-261 materialized the requested object as usual, the resulting apportation would then be a staggering amount of mass, within an enclosure capable of stabilizing hot neutronium. Such an enclosure would have no problems in withstanding the comparably negligible hardships of immediately sinking towards the molten center of the Earth. An explosion at that point, while possibly damaging worldwide, would yet not be, pardon the pun, of Earth-shattering proportions. It is still likely that the materialization and sinking would have enough side-effects to kill everyone in the room, possibly in the whole building. [Answer] The answer isn't entirely clear what the final state of the Neutron Star matter would be, but it would most definitely completely destroy the "Totally Normal Office Building", and most of the country... and probably most life on Earth. See this related question: <https://physics.stackexchange.com/questions/10052/what-would-happen-to-a-teaspoon-of-neutron-star-material-if-released-on-earth> Edit: The gravitational binding energy of Earth is 2e32 Joules and the energy released in this event is approximately 7.5e28 Joules... so Earth will not be "destroyed". A quick calculation of the energy required to vaporize the oceans is 3.7e27 J ( 1.4e21 kg water \* 100 C \* 4200 J/kg specific heat, then vaporized at 2260 kJ/kg heat of vaporization). It is safe to say a decent portion of the oceans will be boiled away. [Answer] According to [the answers to the Physics question linked by abestrange](https://physics.stackexchange.com/a/150318) this would result in the Earth being hit by 250 million tonnes of neutrons travelling at .1c+. I feel confident this would turn everything above horizon radioactive including significant portion of the ground beneath. Neutron scattering would extend this beyond the horizon too. Bulk of the energy would then transform into heat creating a huge fire storm that lifts much of the irradiated material into stratosphere. Gravity will then bring it down "somewhere". Normally you'd have to start thinking about wind patterns and the amount of debris but in this case I think we can just assume the entire surface of the Earth comes covered by radioactive crap. Which is a good thing because once it is down it is no longer stopping sunlight. Just noticed that the amount in this question is much larger than the one in the physics question but frankly it doesn't really matter, does it? Only real change is that the extra energy removes all need you might have had to worry about the fallout coverage. So "everybody dies"? Although people who still have nuclear fallout shelters and are far enough will have time to take cover. Not sure how survivable that actually is. I think they were mostly intended to protect people when the city they are in gets blasted not to support populations when the entire surface is irradiated. EDIT: I guess I must reconsider this. On second thought the explosion would be powerful enough to cause a shock wave that causes powerful earth quakes world wide. And the ionizing radiation would cause an EMP. So evacuation to shelters probably would not be possible. People would probably just have time to get confused about what is going on before everything starts shaking and collapsing. [Answer] > > Neutron star matter weighs about a mountain per teaspoonful. > So much that if I had a piece of it here and let it go I could hardly prevent it from falling. It would effortlessly pass through the Earth like a knife through warm butter. It would carve a hole for itself completely through the Earth emerging out the other side perhaps in China. The people there might be walking along when a tiny lump of neutron star matter comes booming out of the ground and then falls back again. > > > The incident might make an agreeable break in the routine of the day. > The neutron star matter, pulled back by the Earth's gravity would plunge again through the Earth eventually punching hundreds of thousands of holes before friction with the interior of our planet stopped the motion. > By the time it's at rest at the center of the Earth the inside of **our world would look a little bit like Swiss cheese**. > > > – Carl Sagan, *Cosmos : A Personal Voyage*, s01e09, *The Lives of the Stars* [Answer] I'm going to assume we get a cup-a-neutron, which is pre-packaged in a thin-walled container that can maintain neutronium. This material would be far stranger than neutronium, as the only known process that can maintain neutronium in our galaxy is the gravity of a neutron star. But in theory, a ridiculously strong and indestructible material could put enough pressure on the neutronium to keep it in its state. Opening it would be a bad idea, but nobody will have time to do that. The single cup will weigh enough that it will penetrate through anything. The density of neutronium is 4\*10^17 kg/m^3. A cup is about 250 ml, and a it takes 1000 liters to make up a m^3; so a cup is nicely 10^14 kg. The surface gravity of the cup is about 138670 Gs, or 1362009 m/s2. This is about 1/3 of the surface gravity of an entire white dwarf star. So it won't collect electron degenerate matter, but ... At a distance of about 25 m, it would generate 1 gravity of acceleration. So even if it was hovering, the office building it is contained within would crunch inward; few buildings are designed to support a full gravity at 90 degrees to vertical. But it won't be hovering. It will be falling. It falls at 9.8 m/s2. Things fall towards it much faster; no chemical bond is going to be able to resist the gravity it produces at short range. So it will be falling in a ball of plasma. The plasma in turn will undergo nuclear fusion as its density skyrockets; at 1/3 electron degeneracy gravity levels, light nuclei aren't going to be able to stay apart. Or maybe not; white dwarf stars nova after they accumulate a certain amount of matter. As it falls it burrows a hole through the planet. If we assume 0.1% total conversion of a path 3 m wide and a density of 5 g/cm^3 via fusion, that produces 141 kg of energy per meter traveled. By the time the cup has reached the center of the Earth, it'll have gathered up 6 \* 1021 J of energy. But it will also have induced fusion that produces 900 million kg of energy, which is 7 \* 1025 J of energy. So the fusion reaction -- matter being attracted to the cup-o-neutronium and fusing due to the crazy gravity and pressure -- will make the gravitational accelleration from the Earth a rounding error. The cup-o-neutronium will halt before reaching the center of the planet and bounce around within the mantle like popcorn on a plate. I could even believe it will jet itself out of the crust sometimes, and even escape the Earth's gravitational pull. We'd better hope it does -- if it doesn't, it will turn Earth into a strange star, fueled by the gravitational powered fusion at its core. The energy required to make the cup-o-neutronium reach escape velocity is 1/2 \* (11.2 km/s)2 \* 1014 kg, or about 6\*1021 Joules That is bad news. The process that shoots the cup-o-neutron out of the planet is 1000 times greater than a dinosaur killer. Our best bet is that the neutronium falls into the planet, does a pile of insane damage *inside* the planet (causing massive earthquakes all over earth), then gets shot out of the planet depositing a tiny fraction of its energy on the surface. That seems implausible. So even if the cup of neutronium was contained in an unobtanium alloy cup that kept it from exploding or the insane amounts of radiation neutronium emits passively from frying everything, the mere existence of a cup of matter that dense would be enough to make Chicxulub look like a dent. [Answer] This question has been answered by our lord and savior, Randall Munroe in his book [What If?: Serious Scientific Answers to Absurd Hypothetical Questions](https://rads.stackoverflow.com/amzn/click/com/0544456866), chapter "Neutron Bullet". This chapter is one of the bonus questions only released in the book. Relevant Excerpts have been pasted here. > > A bullet with the density of a neutron star would weigh about as much as the empire state building > > > A bullet is about (9 mm circumference, 19mm long, volume of a cylinder is (pi)(r2)h, π\*(4.52)\*19 or 1200 millimeters3. A the volume of a cup is 236588 mm3 or around 200 times that of a bullet. Ergo, a cup of a neutron star matter would weigh 200 empire state buildings, give or take an order of magnitude. > > If you take neutron star material outside of the crushing gravity well where it's normally found, it will re-expand into superhot normal matter with an outpouring of energy more powerful than any nuclear weapon. > > > This would be bad, but assuming it didn't expand then... > > Whether we fired it from a gun or not, the bullet would fall straight through the ground, punching through the crust as if the rock were wet tissue paper > > > [Answer] If you google for "density of neutron star in kg/cm3, you get an example of one that reaches 7 x 1014 grams per cc. A 200 ml cup would have 1.4 x 1014 kilograms of mass. Let me rephrase without exponentiation. It would have a mass of 140,000,000,000,000 kilograms. For comparison, the mass of the Earth is close to 6 x 1024 kg. That is 10 billion times more massive than your cup, but at a density that is closer to 5.5 grams per cc. Anyway, back to the office. The cup will fall from the machine and rip a hole as it sinks to the core of the Earth, displacing crust and exposing a bit of mantle in the way. The people and things closer to it will be torn apart and pulled along it due to its gravity - it may be a ten-billionth as massive as the Earth but you are 6,400 km closer to its center of mass. Throughout the Earth, powerful tectonic shockwaves cross the planet a couple or more times. The Planet will wobble a bit as its center of gravity readjusts. Earth will be slightly more massive, so its gravity will be stronger - but not enough for us to perceive. The only lasting effect noticeable by us is that the orbital period of the Moon will be shortened by a few milisseconds. Oh, and the mega crater at wherever the office with the vending machine was located. [Answer] **ADD**: The exposition below was based on a mistaken reading. I got my neutronium mass figure as 100 million tons, misreading 100 **BILLION** tons is the mass. That makes 1000x, and 10x BIGGER for the asteroid eqivalent - MORE than the 400 km strike Sleep modeled. The correction conclusion is "**EVERYBODY** Dies", literally, meaning ALL forms of life, period, with a sizeable portion of the Earth's crust and upper mantle ripped off and thrown into space, a murderous wound that might even try to bleed core iron! But still, just to leave it here - just remember everything must be scaled **UP** according to the appropriate factors and scaling laws...! --- Ahh yes ... a nice little explosionological problem and the answer is - to borrow from Dave Consiglio of Quora fame, "Everybody Dies(TM)" - *including* virtually all microbial life. The top answer here doesn't *quite* do this one justice. It is pretty much the end of at at least **most forms of life on Earth**, complete and total. We can roughstimate the energy released by deconfinement of neutron star material with its gravitational binding energy, since that is the force that would otherwise be holding it, and more crucially, the amount by which its energy will be raised, and thus now able to explode with, when it is lifted out of the neutron star by the machine's magic. The energy fraction is about 20% of the mass energy (cite: <https://physics.stackexchange.com/questions/195951/what-is-the-binding-energy-of-a-neutron-star>). With 100 million tons - which we can make to 100 million megagrams as the famous and aggravating ambiguity of whether a "ton" here is a "tonne" (megagram), US ton, or long ton is a relatively pointless 10% of energy difference at this scale - we can get that the released energy by good ole' $E = mc^2$, times 0.2, is about **1800 yottajoules (YJ)**. For comparison, the Chicuxlub impactor was roughly **0.5 YJ**, and the TZAR, the biggest bomb *humans* have built, was only about $2 \times 10^{-7}$ YJ. That means this is **3600** times the released energy for Chicxulub. We can, fortunately, thus using that kinetic energy is proportionate to mass and hence by positing a constant "specific whupass" of as asteroid at a given speed, we can relate this to asteroidal dimensions by saying the effects of this will be roughly comparable to an asteroid 3600 times larger and so heaver than Chicxulub. By the fact that radius, hence diameter, scales with the cube root of volume from geometry, and that Chicxulub was about 10 km in diameter, we can say this is about equivalent to an asteroid strike of **150 km** diameter, at the asme speed which we're assuming is relatively typical of asteroids. What would that do? Well, this type of asteroid strike, while it has never occurred at any point within *familiar* geological history, *is* of a kind that may have occurred during the genesis period of the Earth - the Hadean eon (from the formation of Earth at 4.55 billion years / 143 petaseconds ago to 4.00 billion years / 126 petaseconds ago), particularly the Late Heavy Bombardment period. There was a documentary series that aired around 2003, I believe, that showed research on and a mockup of what an impact of the size of some of these Hadean era impactors would do were it transposed to the modern Earth today, though this one was even larger at 400 km diameter. The series was a joint production both by Canada and Japan (CBC and NHK, respectively) called "Miracle Planet" and "Great Story of 4.6 Billion Years of Earth's Evolution" (*Chikyuu dai shinka, 46 okunen monogatari*) in respectively English and Japanese and the source of the research for this particular part was a paper by Norman J. Sleep, a planetary scientist at NASA (I believe). He called impacts above a certain size (I think 100 km) a "JUMBO" impactor, and suggested these "jumbo" impacts had occurred not one, but several, times during that period. His thesis was actually more regarding the possibility of *survival* of life - albeit, very simple life - through such a jumbo strike. The effects of a jumbo impact are, as said, *virtually* life exterminating: we could consider this on the smaller size, so some of the effects will be moderated from what was simulated, but not much. The differences insofar as neutrons vs. asteroids will be chiefly in the beginning. Roughly, as per the current top answer, what will happen is the neutron material will deconfine within micro or even nano-seconds, rapidly developing as it meshes with the surrounding matter into a ball of furiously hot plasma at about a billion kelvins. Half of this sphere will go downward, half upward, in terms of energy. The upward part will effectively be lost to space since the atmosphere, much less the building, are an irrelevant wisp at this scale, so effectively we're actually only left with 1/2 the energy going downward and thus this is not necessarily quite as efficient as an asteroid strike of 150 km - by the same scaling laws, we should try about 120 km instead, so still barely in the jumbo range, but at the low end. The downward part will excavate a crater. From impact studies, there is a general rule of thumb that about a 1/4 to 1/3 root law is followed for crater diameter versus explosive energy release - 1/3 is better for impacts (which are, as said, more efficient at transferring energy), 1/4 for explosions: this is an explosion, but we've effectively already accounted for the inefficiency as just said. Effectively, this means the crater scales the same as impactor diameter, and we can estimate that the resulting crater will thus be 12 times wider than the Chicxulub crater, or 1800 km in diameter. This is comparable to the size of Hellas Basin on Mars. The basic effect of this worth considering will be the production of a very large amount of rock vapor. The vaporization of rock will extend far into the planetary mantle - simply talking about "making a volcano" is not enough. The "ejecta" from this kind of impact isn't just debris - far more is the vapor plume generated. Insofar as ordinary crustal debris, at this scale the explosion effectively simply peels the crust like skinning a fruit, and then it rains down all around - huge chunks of rock and debris *themselves* the size of rather modest asteroids coming down everywhere all over, heating up the surrounding crust red hot for maybe another 1000 km about the crater area. Within the crater, mantle material will uprush as said, but it will now if not vaporized be *boiling* hot, upwelling and turning out the rock vapor into a huge dome (at least that's how the mockup showed it, though I suspect the actual dynamics will be more complicated and some doubtless reaches escape velocity meaning the Earth loses some mass and don't remember what was said in Sleep's paper regarding this.). Temperature of the rock vapor will be around 4000 degrees C (~4300 K). This is the temperature at which most of the damage will be done. The vapor effectively eventually will spread to form a "second atmosphere" now of very hot rock vapor. The whole surface effectively becomes an over hotter than a blast furnace at this 4000 C temperature. From space, the Earth shines like a tiny sun (this, sadly, the mockup did not do justice to). No humans or *any* other life form that is exposed, survives. The ocean will rapidly begin to boil off, or better, it gets "ablated" by the vapor cloud above it as it absorbs the infrared radiation (there's a calculation in the paper talking about this that I *do* remember) within the topmost layer and flies off. Effects from neutronization, decay and activation are completely irrelevant. Radiation doesn't kill you faster than 4000 degree hot blast wind traveling likely much faster than the speed of sound. At this size, since it's smaller than the 400 km case considered, would produce considerably less rock vapor, but no cooler, so I would estimate that the effect is effectively roughly to shorten the duration due to a thinner vapor cloud. The whole ocean may not boil (keep in mind the vapor cloud is losing energy to space as well), but once the rock vapor begins to condense it starts to rain liquid rock (or volcanic-like glass) down onto the surface *and* remaining ocean, effectively smothering the bottom and any life that may have held out down there in a layer of rock and pumice. Insofar as human survival - the answer is pretty much a clear "**No**", at least not under the parameters of this scenario. Death toll is the **entire** human species in that regard, essentially by being cremated alive way better than the best crematorium oven can do (maybe only around 1000 C or so). The astronauts on the ISS wouldn't even make it, even to starvation and even if on the opposite side of the planet at the time of impact: the rock vapor cloud and debris would likely be much higher in thickness than the space station's orbit and even if not, thermal radiation at 4000 C vaporizes it like a bug in a bonfire. The only way a human could survive would be to effectively do what Sleep posited as the mechanism for how primitive life might have survived: burrow deep enough into the crust so as not to notice the heat pulse. For a strike that is on the small end like this that might be just possible, but it may also be too deep still (keep in mind that Sleep was talking of extremophiles that could survive at about 100 C temperature and humans start to wilt even in a hot mine) and active cooling would be a nightmare with Hell above and Hell below. It would definitely require a specially-built shelter far in advance and, moreover, once the disaster was over, returning to the surface would not be of any point since there wouldn't be *any* ecosystem at all. TL;DR: "Everybody Dies(TM)" meaning **everybody** - not just all humans, but all multicellular life and quite likely a sizeable fraction of unicellular life as well. And likely most if not all traces of human civilization as well - the heat is enough to melt down most anything on the surface and certainly incinerate every storage device or method more complicated than a literal stone tablet. (Oddly, buried tablets yet to be dug may have the best odds, even then, depends on how deep the melt goes.) Perhaps the only relic to indicate civilization to any passing aliens might be the magic machine itself - can't remember if SCPs are supposed to be indestructible like the objects in *The Lost Room* (sad to see they never picked that one up again). ADD 2: Being in a shelter would be no use in light of the revised mass figure - the cataclysmic seismic kneading would "knead" it into nonexistence in the time it takes for a seismic wave to propagate around the globe (roughly on the order of a kilosecond). ADD 3: And literally really nothing left, not *any* trace of humankind - the heat will melt down, down, down, deep, turning the surface into a magma ocean. At least, not on Earth. The only signs will, perhaps, ironically, be our space probes and due to the gamma pulse from the neutronic beta decay process and perhaps initial thermal flash directed upward (we now have to take account of that other half of the energy), the further out the better, and at the very least their electronics stand a strong chance of having been fried to the point of uselessness. [Answer] The magnetic field of the teaspoon of the neutron matter would be strong enough to destroy the vending machine before it could do any other weight based damage. ]

[Question] [ My question is: * Could a macroscopic (e.g. visible) plant grow on a living human, provided that the human is completely immobilized? [Answer] First off let me say yuck!, that is a series of Google searches I can never take back. But as to your question, apparently plants often germinate inside the human body, specifically inside the lungs, as the warm moist environment is good for sprouting a seed. There are multiple reports of this happening with a variety of plants, this was widely covered when in 2010 a man in Massachusetts had a [pea plant](http://awesci.com/plants-can-grow-within-human-bodies/) removed from his lungs, and in 2009 a Russian man had a small tree removed. Also found a case of a girl in china with a [dandelion growth](http://www.dailymail.co.uk/news/article-2515945/Young-girl-fully-grown-dandelion-inside-EAR-surgically-removed-doctors-China.html%0A) in her ear. There is however not a consensus on this issue, as a group of [chest physician](http://journal.publications.chestnet.org/article.aspx?articleid=1090121) published an article claiming the news stories about large plant growth are likely hoaxes, since extended plant growth would require light, which is lacking inside the lungs and other body cavities. So, it seems very plausible to assume seeds could sprout inside the human body and that given a restrained subject, the plant could exit the body cavity and receive some sunlight and continue growing. It should be noted that all the subjects mentioned in the news stories had their plant growths identified by doctors as they were suffering pain and discomfort from the growths, so it could likely work as a very slow torture method. [Answer] Man, and I wanted to be a smartass and recommend Chia helmets, but you had to go and use [parasite](/questions/tagged/parasite "show questions tagged 'parasite'"). --- > > > > > > Farther south, in the sweltering *Mişymaşy* jungles, the indigenous *Wişywaşy* tribe have a far more cruel method of punishment. Criminals are tied down in special tents where they are fed and tended, and protected from attack by the *yhettis*. There, a small wound is made and allowed to fester and necrotize. Administrations of special potent combinations of antibiotics and histamines form cystic walls surrounding the necrotic tissues so as to protect the victim from spread infections and to foster the necrosis. Putrefaction is allowed to continue for several days. > > > > Eventually, special sanctified soil is mixed in with the wound, and a seed of the sacred *Redikkulos* vine is allowed to germinate. When the vine has grown to a length of 2 or so *ficties*, the criminal, now ready to be admitted back into their society, is unbound and allowed to go free. > > > > Maintaining a *Redikkulos* vine in such a manner is thought to help purify the criminal. > > > > > > > > > ― from the journals of Dirk Dark, adventurer extraordinare. > > > Personally, I doubt the veracity of Dirk's documents. Later scholarly snobbishness has postulated that he was little more than a spindoctor for the so–called Glorious Republic — which was, as we well know, one of the most despotic, totalitarian oligarchies to ever arise on the Sunken Continent. > > > ― “My Thoughts on a Diverse Variety of Things” by Sire Clyde Shortstoff, prime minister to the people of the royal Hoytitauyts. [Answer] To grow plants need * light * minerals The first excludes growth inside the body, the second excludes growth solely on the body. Normally plants rely on microbes present in the ground to decompose organic matters into elemental components they can absorb (Nitrates, Phosphates, Sulfates, etc) which are then used for their growth. Direct assimilation is not possible. You may change a bit the aim and go for fungi. They (some of them, at least) already grow directly on rotting trees. Not sure if you need some handwavium, too. Normally in nature a corpse doesn't last undisturbed long enough for a fungus to grow, like a rotting tree does. [Answer] The human body tends to be pretty good at rejecting foreign materials. Plant or not, often if you put something that isn't supposed to be in a human body the body will try to remove it. This is part of the body's immune response. You can see it happening with something as simple as a splinter in your finger. This can even happen with surgical implants. I had a friend who had a joint in his foot/ankle replaced with an artificial implant, his body rejected the implant and effectively tried to push it out. I've never seen anyone in so much pain... So, realistically an implanted seed could sprout inside a human body, but the real pain/torture comes when the body starts to reject the seed/plant and push it back through the tissue and skin. [Answer] As a PhD in biology I want to add my 3 cents: plants do NOT need light to grow *IF* they can absorb sugars from the media on which they grow. Which mainly happens in controlled laboratory cultures, but hey, we're on worldbuilding, right? The plants grown without light do look a lot different tough, for starters they are not green, because, of course, they do not produce chlorophyll needlessly. So, if You want to, You can make up a species of plant which is an opportunistic pathogen and grows inside a human body if the situation is advantageous for it. Of course, the evolution of such a species would be a tale of its own (evolution of pathogens typically is). [Answer] Perhaps it could be possible if an already-rooted plant was transplanted, somehow without killing the host, onto the human, with its roots in their stomach (so it could parasitically steal minerals like a tapeworm) but with the leaves outside? Birds have lived with arrows sticking through their bodies, for example: <https://www.youtube.com/watch?v=2KCUpB_f5hI> Maybe if the plant was surgically put in your navel or in a fashion so there was no "gaping hole", it could stop you from bleeding out. This is a really gruesome question! [Answer] During a snowball fight, my uncle got a direct head hit. Apparently, some seed was mixed in with the snow, because a few days later, a plant started sprouting from his ear. Forget about theoretical answers to your question; the practical answer is **yes.** [Answer] Yes. Spanish Moss does not need soil. [Answer] Short answer? Heck yes. Mythbusters proved this when they confirmed that a bamboo plant CAN grow through a facsimile of a human torso. ]

[Question] [ Would it be possible to use spider silk for armour, instead of metal? I am not worried about how to obtain the silk. I know that spiders are not domesticable and that they are too aggressive to each others so that they cannot be lumped together like bees. (I can handwave all that; my spiders are just of a different species, unknown to us.) But would it offer similar protection against pre-gun powder weapons? Would it be able to resist the thrust of a spear or an arrow, or the cut of a sword or knife (all made of common materials such as steel)? And how should it be used, lax, as a kind of shirt like chain mail, or would it be better to use it tense, as in shields? Would there be a particularly good way to weave the material for either use? And would it be transparent enough for use as a visor? --- Thanks for the input so far. A few things to notice: * these people's technology, spiderculture aside, is roughly Earth's 14th century, so no Kevlar or other things demanding sophisticated chemistry. They can stretch the silk in order to reduce its extensibility, and it seems a good idea; * they have no magic - they just happen to know a peculiar species of spider that can be domesticated (I don't need to explain why they are domesticable, they just are: *Arachnia mirabilis*, if you so wish); * the issue is important because it should have given them military superiority against their enemies: better or similarly armoured infantry and cavalry with much greater ability to maneuver, thanks to reduction in weight, and armored sailors who can survive a shipwreck or a fall into the sea; * my biggest concern is, if a soldier using such armour is hit by an arrow, would the arrow be stopped, or would it penetrate skin and flesh, carrying the silk together with it? --- Edit to explain why I don't think this is a duplicate: That question is about mixing spider silk, keratin, and bone, to make armour. It supposes high technology, and its emphasis is on how to produce the armour material. My question is about spider silk, in a middle age setting, and the emphasis is on how to use the armour, and what it would be able to resist. [Answer] Cloth armor - specifically, linen armor - was a thing, historically. It was used, tested, and could be quite effective. it was lighter and, reportedly, more comfortable and/or maneuverable than other armors, for the tradeoff of being also not quite as effective. Silk was more expensive, so there don't seem to be as much evidence for cloth armor made of silk - but on a cloth-for-cloth basis, there doesn't seem to be any reason the same kinds of techniques shouldn't work, if you have enough of the silk to make it cost-effective. A Greek style armor called *[linothorax](http://www.newyorker.com/books/joshua-rothman/how-to-make-your-own-greek-armor)* was reconstructed through using a lamination technique to transform linen cloth into stiff plates - essentially using multiple layers brushed with glue. This reconstruction was tested against arrows, and a thickness of 12mm supposedly would have been enough against any arrow the wearer was likely to encounter for about a 400 year period (see link for original tests). Quilted [Gambesons](https://costumegirl.wordpress.com/2010/04/01/the-making-of-a-medieval-gambeson/) or Padded Jacks were sometimes used under other armor, but also sometimes used as a standalone. they were made from many layers, perhaps as many as thirty, of cloth quilted together - Linen was a popular choice as it was available, lightweight, and fairly effective (though some incorporated cotton, wool, or leather for extra effect). Testing of a reconstruction showed that such all-linen gambesons were an imperfect, but effective armor - the armor blunted some shots and reduced others to what would be lesser injuries from many of the arrows (though not all, depending on the arrowheads, see link for original tests), and proved somewhat effective even against spear or sword. As for silk, I've vaguely heard of [quilted silk armor](http://www.thesurvivalistblog.net/silk-body-armor/) being used (like the gambeson, up to thirty layers quilted together) among the Japanese and Koreans historically - and even [in modern times](http://www.northeastern.edu/news/2013/05/senior-capstone-puts-a-silky-spin-on-protective-armor/), since this kind of armor may be bullet resistant, depending on caliber. However, I don't have nearly as good historical references, or testing information, about this kind of armor. Xplodotron's previous answer mentioned the use of a layer of silk and air pressure could deflect most (70%) of the arrows fired at it, which seems to indicate silk resists penetration pretty well as a single layer (compared to linen which I could not find used as a single layer for armor), and suggest that a layered silk version, like the linen armors, would be quite effective. So your basic choices might be quilted silk, using many layers to resist the penetration of arrows, spears or swords; or else a laminated silk, where the layers are stiffened with glue to form a kind of plate mail. The first is going to be a lot more flexible, and probably easier to make, adjust, or work with, with the tradeoff of somewhat lower protection (arrows and the like might still penetrate, but much less than without the armor - and it does much less to protect against blunt force). The second is a lot more tricky to work with (and you'd need the glue, though a relatively low quality rabbit glue was well used) - and each piece of each armor must be separately laminated and fitted (it will resist tools as much as weapons), making it more labor-intensive but also a better protection. Of course, since you plan for an abundance of spider-silk, maybe you could use both, either/or depending on the warrior and their role in fighting, or a hybrid with reinforced plates over vital areas, but quilted armor over other areas for more maneuverability. I don't think you could make a visor out of it - you might get enough transparency to get away with a single sheer or gauzy layer, but you would get very little protection from it, and it *would* reduce visibility. At most you might deny your opponents an aiming point (faceless! aah!) if you used that single layer in conjunction with other silk armor, like a laminated silk helmet that does cover the rest of the face, but still allows openings like knights' helmets had for seeing through and such. [Answer] Silk is a flexible material, so it simply could not replace metal in rigid armors like plate, nor in shields. You would have a soft, flexible armor more akin to chain mail, but much lighter. However, silk is a tough material that resists cutting and tearing, and in fact in real life silk has indeed been used as armor, sometimes standalone but most often as an additional layer under something stiffer, such as leather or plate; the Mongols, for instance, often [used silk as a backing](https://en.wikipedia.org/wiki/Mongolian_armour) for leather and metal scale and lamellar armors. The advantages of silk as an armor are that it is lightweight, flexible, and breathable, while still providing reasonable protection against cuts and thrusts (it's obviously not going to do much against blunt force). Spider silk would only enhance all of these properties. There's literally dozens of different ways to employ your silk as armor: A layer or two underneath plate armor can improve that armor's defense against piercing attacks such as spears and arrows; using it as a backing for scale or lamellar armors can make them more lightweight and more flexible, with little sacrificed in the way of protection; on its own, a few layers of spider silk could even provide [proof against an assassin's bullet](https://www.theguardian.com/artanddesign/2014/jul/29/bulletproof-silk-vest-prevent-first-world-war-royal-armouries)! [Answer] Not only do you have to handwave the mass production of it, but you have to handwave how the armor is produced. But if you do handwave these things then yes, it may work well, although handwaving the production will be not so easy (think *secret monk technologies of remaining former alien space race technologies*). Just from wiki: [Spider silk](https://en.wikipedia.org/wiki/Spider_silk) [](https://i.stack.imgur.com/4a0Du.jpg) $\tiny \text{By The original uploader was Vincentsarego at English Wikipedia - Transferred from en.wikipedia to Commons., CC BY-SA 3.0,}$ $\tiny \text{https://commons.wikimedia.org/w/index.php?curid=40001987}$ The overall strength is good enough. * Dragline silk's tensile strength is comparable to that of high-grade alloy steel (450 - 1970 MPa) and about half as strong as aramid filaments, such as Twaron or Kevlar (3000 MPa). But what is good for spiders is not so good for armor. I mean the extensibity of silk. In tech there are known solutions for such things - there are pre-stretch building material. That way if you stretch it and find a way to wind them together - you may have a product with different rigidity, from steel hard to rubber like stuff, as you choose. And reasonable steel strength with less mass. * Consisting of mainly protein, silks are about a sixth of the density of steel (1.31 g/cm3). The easiest way to prestretch it is to make cloth, stretch it and impregnate it with resin. You may loose some strength and other advantages, but it will better redistribute the pressure over the penetration area and will not bend into the chest at the place it gets hit. But actually the bending ability can be used for better protection, in terms of stopping something. Without resin, but with a magic-smart weave process, you may make armor as strong as steel, as hard as steel and with less weight. So any Kevlar product and fiber glass, any carbon plastic - are good enough to show what may be done. Just the process of making these will be more tricky and the strength will be something between fiberglass and kevlar. P.S. As Vakus Drake noticed there is Darwin's bark spider, which silk is at least twice stronger than usual in spiders community. Some properties are investigated in [this paper](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2939878/), you may wish to read. And I find this quote from that paper hopeful for those who wish even more: * Thus we have available some 200.000+ unique silks that may cover an amazing breadth of material properties. To date, however, silks from only a few tens of species have been characterized, most chosen haphazardly as model organisms (Nephila) or simply from researchers' backyards. [Answer] If you allow more handwaving into your story... Kevlar is a synthetic fiber. It is similar to spider silk in some ways, though Kevlar is more appropriate for armor not only due to availability, but also due to its mechanical properties. If you could get enough web to make a vest out of it, with technology similar to that used to make a Kevlar vest, you'd have a somewhat bullet-proof, somewhat slash-resistant (slightly better than nothing) but it probably wouldn't protect you against piercing nor crushing weapons on its own. Notice that Kevlar is somewhat like that too... It is made to protect you from bullets, but it is not rated for piece protection (i.e.: it is not stab-proof) for example. TL;DR you could make a Kevlar-like vest with it, but it wouldn't be as good as Kevlar, and you have to do a lot of handwaving to make that feasible. And it would not be transparent. Look at this vest made of spider silk, as seen in [Wikipedia](https://en.wikipedia.org/wiki/Spider_silk#Human_uses):  All in all, this could be an addition to protective clothing for people who work with dangerous materials or environments, but armed forces and police would probably fare better with other protective materials. And the people of your world would have to lack leather, metals, synthethic fibers or the technology to work with these to go for spider silk armor. [Answer] Billowing silk cloaks were used by horse-riding samurai to block most (not all) arrows. It's called a horo. See here: <https://www.youtube.com/watch?v=8B_6BU7SYf8> Some horo had light framework (like a hoop-dress) to keep it billowed. To the extent that a shield is considered "armor," one could think of the horo as a silk shield you wear on your back. I understand the OP uses the word "armour" in the question, but in a broader sense the horo is something that is worn which provides "protection" to samurai and messengers, allowing them to survive what would otherwise be fatal hits from attacking archers. [Answer] Let me introduce you to the [golden silk orb-weaver](https://en.wikipedia.org/wiki/Golden_silk_orb-weaver), this spiders silk is known for its tensile strength. It is indeed so strong that if it was as thick as a pencil, it could stop a jet! In 2012 a cape was even mad using this material and if its molecular compound can be determined, it will easily replace kevlar. [](https://i.stack.imgur.com/yofVM.png) [Answer] There is already a historic precedent: Genghis Khan had his soldiers wear silk armor beneath their normal protection. Anecdotally, Genghis Khan's soldiers took arrows that penetrated the traditional armor, and should have killed them, but were prevented from doing harm by the silk, lending to stories of the soldier's invincibility. [Answer] This is actually being attempted, although an regular spider's silk would not stop much there are actually ways of making it work, i must point out that at some point in history even paper was used to make armor and it was effective (100% sure about that just google) this would work by adding several layers of it making it a really good armor (same protection as chainmail) but would bot last a lot after a few blows blocked it would be wrecked. Nowadays, there is an on-going attempted to create an real life a bulletproof vest made from spiderweb as their tensile strength goes toe to toe with steal without being as heavy (100% sure about that just google), and it does sound to me that if there was a population who lived closely with similar spider could have picked up some sort of way to make the armor you spoke of. ]

[Question] [ Science-Fiction has tools to destroy *anything*: atoms, molecules, DNA, cellular organisms, multicellular organisms, buildings, streets, cities, countries, continents, planets, and even stars. Some extreme settings even have tools to destroy entire galaxies, and I know of at least one setting (*Doctor Who)* where they can destroy a whole universe and even the multiverse. However, as far as I know, no scientist or writer has come up with a way to destroy a black hole. I'm not just talking about "wait for it to decay through Hawking Radiation"; I'm talking about "use this and the black hole just disappears in a reasonable timeframe. Would such a method even exist? It can require unobtanium, obviously. [Answer] Welcome to *How to destroy a black hole for dummies* So, are you looking for a way to eliminate the right black hole, arent' you? Well, you're reading the right guide. But before beginning, it could be useful to make some clarifications on the nature of these galactic monsters. As Sun Tzu says, to defeat your enemy, you must first know him. Let's know what a black hole is. *1) Why black holes are a so formidable opponent?* Black holes are the natural enemies of all spacefaring races. With their bottomless capacity to consume all light and matter, it’s just a few septillion years before all things in the Universe have found their way into the cavernous maw of a black hole, crushed into the infinitely dense singularity. For a black hole, any matter entering the event horizon is added to the mass. Shoot bullets at a black hole, and you just make a slightly more massive, slightly more dangerous black hole. Detonate a nuclear bomb inside the event horizon, and you only make the black hole more massive. Fire your forward phasers at the black hole, and that’ll still make it even more massive. Swap those bullets in for lasers and black holes don’t care. Within the event horizon, energy and matter are one, and those very same black holes can convert that energy into mass. So all your projectiles and energy weapons inevitably just make it more dangerous. So the problem is that any material is introduced into a black hole (whatever is physical matter or energy) will be swallowed up and will contribute to the growth of the enemy. *What if I use an anti-matter weapon? Maybe throwing an antimatter black hole into a black hole? We'll have a nice KABOOM, and problem solved* Nice try Jimmy. The problem is that even if you manage to create and stabilize an anti-matter black hole (and it is doubly impossible, because first you have to find a way to contain antimatter, and then you have to find a way to contain an antimatter...black hole), throwing it at a black hole will surely create a huuuge explosion, but all the energy will be converted and processed by the black hole. The bottom line is: if a regular black hole and an antimatter black hole got black-hole-married in space, they wouldn’t vanish. *2) Solutions* So, what are the possibile solutions to destroy a black hole? The answer, surprisingly, lies in the enemy's very features. We must take advantage of the enemy's ability and twist them against it. **Wait** Yess...just wait. I know, it's the most boring one, but at least it's a solution. According to Stephen Hawking, black holes can actually evaporate over enormous periods of time. So, over an incomprehensible period of time, even the most supermassive of the black holes will have evaporated away into a harmless soup of particles. It turns out, in order to defeat the black hole menace, all we need to do is ignore them, and they’ll go away all on their own. But, if you asked how to destroy a black hole, I suppose you need it now. So, next solution is to... **Get rid of event horizon** Getting rid the events get two interesting results; first of all, you get what you want: you killed a black hole. In addition, once removed the horizon, you will have access to real black hole, and all its secrets. The problem is this solution is a bit complicated. In general relativity, the mathematical condition for the existence of a black hole with an event horizon is simple. It is given by the following inequality: $$ M^2 > \left(\frac{J}{M}\right)^2 + Q^2 $$ where $M$ is the mass of the black hole, $J$ is its angular momentum and $Q$ is its charge. Getting rid of the event horizon is simply a question of increasing the angular momentum and/or charge of this object until the inequality is reversed. When that happens the event horizon disappears and the exotic object beneath emerges. But that hides a multitude of problems. For a start, things with angular momentum and charge also tend to have mass. And in any case, the equation above describes a steady state. Feeding a black hole creates a dynamic state and there is no guarantee that the object will settle back into a steady state again without shedding the angular momentum and charge that it has been fed. In fact, the calculations are so fiendish that they have defied all attempts to tame them. **Use time travel device** Remember when we said that blacks holes in time dissolve? Sure, it takes eons, but what if you could speed up the time? Creates a kind of space-time bubble, and speeds up the time. The black hole will dissolve as expected, or perhaps even more quickly, failing its nourishment. [Answer] Use [Negative Energy/Negative Mass](https://en.wikipedia.org/wiki/Negative_energy). To visualize this concept, consider the [rubber sheet](https://en.wikipedia.org/wiki/Gravity_well#The_rubber-sheet_model) model of gravity: 1. Spacetime is modeled as a taut rubber sheet. 2. Masses placed on the sheet cause a distortion in the sheet, causing nearby objects to fall towards each other (this models gravity). Now, suppose we have an object of negative mass. Instead of pushing down on the sheet, it will pull up. This will cause positive-energy objects to move away from it, and other negative-energy objects to move towards it. --- If we collide this negative-energy object with the black hole, its mass will be reduced by an amount equivalent in magnitude to the energy of the negative-energy object. Note that this is all strictly theoretical, and the existence of macroscopic negative-energy particles has not been proven. However, the physics behind this is very similar to Hawking radiation, which involves negative energy regions on the quantum scale. Also note that negative energy matter is **very different** from antimatter, which has been proven to exist and has positive energy. [Answer] The only way a black hole will ever disappear, as far as we know, is through Hawking radiation. Think of a black hole as a ball of energy. You don't destroy energy, we know that well, you just do stuff to it. Well, you can't do anything to a black hole, so regardless of what you throw at it, nukes, lasers, stars, etc., you will just add more energy to it. If you have control of time, you could encapsulate the black hole in a localized time distortion in which time is accelerated, so that the black hole evaporates faster. You could try and create your own anti blackhole with antimatter and collide the two, but we don't really know what happens to matter in a black hole, so you might just end up creating a normal black hole. [Answer] The problem is that once anything has crossed the event horizon it needs to be travelling faster than light to come back out - which is impossible with any known science. So you either need to accelerate the mass to FTL speeds or reduce the curvature of space-time so that mass can escape. However you do this I'm viewing it as being like puncturing a balloon, you create a breach in the event horizon and let the mass from the black hole pour out through it. The mass would jet away into space gradually reducing the size of the black hole until it is all out. The breach can be explained using either of the mechanics I explain above - either you're forming a wormhole or in some other way accelerating the matter to FTL speeds or you're reducing the gravitational effect in a region so it's no longer a singularity at that point. Doing this would require a LOT of energy, you need to overcome the gravitational force of the black hole to suck the matter inside it out or you're going to be violating several laws of thermodynamics. [Answer] Can you convert a black hole into gravitational radiation? The recently observed merger of two black holes converted three solar masses of black hole, or about 5% of the total mass. So what if you could place a massive object in close orbit around a black hole and feed energy into it to prevent it spiralling in to the black hole? That is a continuous gravitational wave source. The question I don't know the answer to, is whether it will be emitting more in gravitational radiation, than is being supplied to prevent inspiralling. If more, the black hole's mass is being converted to energy. If less, you have just found an exotic and inefficient way to make the black hole grow. One for the physicists, I think! [Answer] The answer is to manipulate Hawking radiation. It is thought that "virtual particles" pop in and out of existence all the time in our universe, but generally they are anti particles of each other and instantaneously collide, and return to the vacuum (big handwaving paraphrase here to introduce the topic). Near the event horizon of a black hole, the virtual pair can appear, but there is a chance that one of the particles is absorbed by the black hole while the other is ejected into the "real" universe. The black hole loses the mass and energy of the ejected particle, which is registered in the universe as Hawking radiation. Since we want to make the black hole disappear, we need to induce Hawking radiation to flow out of the black hole at a much faster rate than normal. By much faster we mean orders of magnitude, since a solar sized black hole could take 2×1067 years to evaporate under natural circumstances. Virtual particles appearing near a black hole's event horizon will need to be accelerated away from the hole in order to drain its mass. One possible way to do this would be to position something like a neutron star in close orbit around the black hole, just skimming over the event horizon. The powerful gravitational pull of the neutron star will rapidly accelerate any virtual particles away from the hole itself, and create a sort of "anti accretion" disc of now real particles streaming away from the hole in the wake of the neutron star. The other thing for this to work is to ensure that there is little or no matter and energy in falling into the black hole. The neutron star could be used to transfer momentum of the material in the accretion disc away from the black hole during the period it is being manoeuvred into position, clearing the disc and preparing for the phase where it is "vacuuming" virtual particles away from the event horizon. One could enhance the project by employing multiple neutron stars in tight orbits to strip away the accretion disc and channel virtual particles away from the event horizon. The amount of super science and technology needed to do this would be pretty mind boggling, though. [Answer] NovaLogic already got the right idea: The only known way to diminish a black hole is by using the Hawking radiation. But he did not given an implementation of an exploit. Here is mine: **The inverse Dyson sphere** You construct a Dyson sphere well out of the reach of the black hole's horizon. Than you cool down the inside of the Dyson sphere to be colder than the temperature of the enclosed black hole. At this moment, you start reducing the black hole by catching Hawking radiation from it and pumping it outwards. Note that this method will be incredibly slow and it needs a lot of energy, too. But in the end, your black hole is destroyed. P.S. In an always expanding universe, the cosmis background will become colder and colder, and all black holes will naturally die of this cause. [Answer] Doesn't sound too difficult. You need: - Unobtanium hull (handwavium is also good) - FTL drive (not the old-fashioned types that don't work in a gravity well, but a *modern* one) - Suicide crew (or AI without self-protection circuits) Enter the event horizon (the hull protects you from tidal stresses); approach the singularity and turn on the FTL drive. The ship **and** the singularity (where all the mass is) take off to the programmed destination. You can't pass the event horizon without exceeding the speed of light, so we do just that. We program the FTL to rematerialize outside the Milky way, since what will arrive there is a [naked singularity](https://en.wikipedia.org/wiki/Cosmic_censorship_hypothesis). This will cause all sorts of problems for the crew, but it will take thousands of years before they affect us. That'll be [somebody else's problem](http://hitchhikers.wikia.com/wiki/Somebody_Else's_Problem_field). [Answer] ## Temporarily suspend local gravity. A black hole is a gravity bound, infinitely dense ball of matter. It holds together because the force of gravity is sufficient to overcome the forces pushing it apart. If one had the ability to manipulate gravity, perhaps one has antigravity spaceships, one might potentially temporarily shut down gravity in a local region of space for a tiny fraction of a second. I have no mechanism for how this might be achieved. This falls outside of any current physics. ## This would make a very considerable bang It would be worth noting that this would likely create quite a big bang, probably on the order of a supernova. Large enough to destroy any nearby star system. Probably large enough to cook any planets within a few light years of the event. [Answer] # **Peer Pressure.** I fully expect someone to explain why this won't work (I'm guessing it'll be the divide-by-distance-squared part of the gravitational force equation), and that would be just fine. But let's give it a shot. 1) Find a black hole that's **only about 20 solar masses**. This isn't a general solution, maybe after we pick off a few of the weak ones we can aspire to more. 2) Find several stars that are about **5-10 solar masses each**. 3) Using your unobtanium power sources and some bored engineers, maneuver those stars into a **globe centered around the black hole**. 4) Carefully and synchronously move the stars closer to the black hole, not letting any of them get sucked in, until the stars are **exerting more force** on the matter inside the event horizon than the singularity itself. 5) If the matter won't come out yet (due to being pulled equally in all directions), shift stars around until **enough net force** is exerted in a given direction from the center of the black hole that matter previously inside its event horizon starts to move away from it again. 6) Figure out what to do with **4\*10^31** kilograms of post-stellar matter. [Answer] I think antigravity would be the "simple" approach using common sci-fi devices. Hypothetically, we could have gravitons and anti-gravitons of some kind where the one cancels out the other. Then we just stream ridiculous amounts of antigravity towards the gravity, and eventually the black hole falls apart. This presumes that A) your scientists find a way to create artificial gravity, and B) that negative gravity exists. And C) that you have a bunch of stars lying around with [Dyson spheres](https://en.wikipedia.org/wiki/Dyson_sphere) you can use to power your antigravity beams. [Answer] So. Black holes are hard to approach. Time gets a little, shall we say, funky as you get closer. And then, of course, there's the tide. They'll tear a ship apart quicker than anything. I won't even give more than a cursory nod to the radiation, as we're all familiar with that. So, obviously, dropping some sort of magic bomb into the black hole won't work. So, instead of trying to bring something to the black hole, we do the opposite. We bring the black hole to us. Now, now, I know what you're saying. You don't *move* a black hole. And you're right. But think - We can create wormholes, right? We've been using them to get from place to place for a century now. Only one problem. The wormholes only work one way. Generate one, put something in it, and it pops out the other end. What if I told you we found a way to reverse that? The generator, instead of creating the entrance, creates the exit? We've found a way - And while the maths of it are beyond me, Doctor Selene here will be more than happy to explain when I'm done. So, we set up a generator and target it below the black hole's surface. The wormhole opens, and the black hole's own gravity pushes mass through. But, very quickly, that mass will be the entire black hole. At that point, we've only managed to move the black hole, and right on top of ourselves. Bad, right? The solution is fairly obvious. Using a network of a few, let's say four, dozen generators spread across just as many systems, we use a quantum clock to synchronize them. They all open their wormholes at the same time, siphon off some of the black hole's mass, and close the wormholes before too much comes through. At that point, we have loads of what Doctor Selene calls exotic materials floating around ready to be harvested. Scoop them up, put them on some novelty keychains, and sell them in a gift shop, right? Oh, yes, the scientists will get their turn too. It'd take a few cycles of this to completely remove the black hole, maybe a few months, but think of the rewards! Beta Three-Thirteen is sitting right in the middle of what would be a prime route between Caldari and Melantis. We'd see huge amounts of traffic between the two systems if we got rid of it! And I'm told the materials we'd be able to gain from the hole would be usable in dozens of industries! We can do this, and we will do this. Now, I'll leave you Doctor Selene to answer the more technical questions. [Answer] # reduce the pressure with a tiny portal/teleporter Teleporters or portal technology is pretty common in sf. You just use some additional dimensions to "fold" space (like I explained [here](https://worldbuilding.stackexchange.com/questions/72703/how-would-portal-technology-work/73136#73136)) and punch a hole through space into the black hole. You have to be careful though: 1. Only make a *very* tiny hole! If to much mass comes through that hole at once, it will just create a second black hole at the other end of the portal. 2. Aim the output-hole at empty space or something you want to destroy. You will get a constant stream of mass at a very high speed coming through. But you also have some really neat side-effects: 1. You can power a big generator with the kinetic energy from that stream. 2. After you draw most of the kinetic energy from that stream, you can use the huge amount of mass to build a complete new stellar system or two. 3. You can fire the full power of that stream on an enemy battle fleet/base/planet 4. You can fire that stream roughly in the direction where you want to build that intergalactic highway, thus blowing away all that debris (planets, suns and stuff) to clear the way. If that is to slow for you, you can use several tiny portals and direct the stream in different directions. After a while, the mass of the black hole will have reduced enough, that it is just a big sun and the stream(s) will be reduced to a trickle of plasma from that sun. Now you can use your standard death star to blow it up and have some neat empty space. [Answer] You find the spot in a parallel dimension that is closest to the location of the singularity in the black hole. You then poke a hole between the dimensions so that some of the singularity can spill over into the other side. The mechanics are left as an exercise for the student. ]

[Question] [ I'd like to have a community of humans live indefinitely in space habitats (think space stations supporting mining operations in the asteroid belt). The technology would be "day after tomorrow"-level; no anti-gravity, no effector fields, or the like. So, my problem is that I'd like to have happy space families, but I've read that long-term zero-G living is dangerous and bad for many physical systems, especially bones. The big question is whether a child can successfully be brought to term in zero gravity. **Will the children be able to be born?** As a possible mitigation, we could spin the habitats, but I'm not sure if that will be "good enough" to substitute for gravity, nor whether current construction methods will be able to hold up under relentless spinning. Please help, the gallant colonists of Alpha Colony need answers! [Answer] Last time I looked into this I was amazed these experiments (mammalian conception to delivery in orbit) had not been done. I figured I just had not found it and so I dug in this time. For mammals, they have not been done. Pregnant rats have gone to space and come home and delivered so microgravity is not immediately lethal to a fetus. Rats mated in space (no pregnancies). Rat pups nursed in space (it is tricky for them to orient; I think humans will have less trouble with that). The news from 2017: freeze dried mouse sperm (I did not know that was possible - the freeze drying) can come home and make babies. From that article. [Sayaka Wakayamaa et al, Healthy offspring from freeze-dried mouse spermatozoa held on the International Space Station for 9 months. PNAS 114(23)5988–5993](http://www.pnas.org/content/114/23/5988.long) > > So far, the effects of microgravity on early development have been > studied using sea urchins, fish, amphibians, and birds. > These studies have concluded that microgravity does not prevent animal > reproduction. However, because of the difficulty in maintaining > mammals and performing experiments in space, studies of mammal > reproduction in space have not progressed as well as in other animals, > and only a few papers have been published. Those studies > and our previous study have suggested that mammalian reproduction > in space under conditions of microgravity cannot be easily compared > with reproduction in other species. > > > It is lame to answer a question with "no-one knows" but for the prospects of full on start to finish mammalian pregnancy and gestation in space I think no-one knows. It is a surprise to me that is still the case. [Answer] > > Will the children be able to be born? > > > **For all we know: Yes.** I shamelessly copy from two comments below the question by [user6760](https://worldbuilding.stackexchange.com/questions/97028/is-pregnancy-in-zero-g-a-barrier-to-long-term-space-living#comment288250_97028) and [bon](https://worldbuilding.stackexchange.com/questions/97028/is-pregnancy-in-zero-g-a-barrier-to-long-term-space-living#comment288287_97028). For the birth gravitation is usually helpful in assisting the pushing force of the contractions. Many women stand or sit during the birth. However, it is conceivable that even without gravitation there is enough force to push the baby out of the uterus. In the same way one could also help and create artificial pull by applying a suction cup to the head of the baby and pull. Or one could apply a C-section which would eliminate the need for gravitation at all during birth. Rotating elements creating artificial gravitation similar to our gravitation level are feasible. During infinite space travel you don't have to do without gravitation. In the absence of friction with the surrounding space, such a rotation could be maintained very efficiently. Centrifugal forces are exactly the same as gravitational forces. Regarding the endurance of the construction towards rotation, please note that space vehicles have to endure a multiple of that force during launch and they do. An infinitely traveling human space race surely would replace weak parts over time with newer parts to hold it all together. And even if for most of the time you would life in low-G environments, by doing sports in this environment (pushing against each other, ...) one could keep the muscles trained. For the skeleton it may indeed by bad in the long run. We don't have reliable long term information about that. The human race living in low-G might indeed evolve different (less upright). Maybe modern medicine (the technology of today to tomorrow) could strengthen the bones artificially (increased calcium uptake,...). [Answer] Ugh... So, yeah, it's never been done - if it had, this would be open and shut. ## Birth 1. Human women often give birth [prone](https://en.wikipedia.org/wiki/Lithotomy_position) such that the force of gravity is perpendicular to the direction they're pushing the baby. Therefore, there's no reason to assume that [most] women aren't strong enough to give birth in zero-g. 2. Women from a variety of species (including some [humans](http://americanpregnancy.org/labor-and-birth/water-birth/)) give birth under water where the forces of buoyancy and gravity are equal and opposite, so there's still no reason to suspect that gravity is a requirement for birth. 3. One of the long term effects of weightlessness is that our bones become weaker. It's possible (though, highly unlikely because the baby doesn't go between hips - it goes through cartilage and other tissues) that this would mean that giving birth necessitated a risk of breaking one's hips. It's also possible that the bones could become more pliable, either because of the [sometime inverse relationship between strength and plasticity, or because of a drug/supplement](https://www.grayson-jockeyclub.org/resources/bones.pdf) administered during gestation. 4. If birth without undue risk of catastrophic injury was not possible, there's always Cesarean section, see [bulldogs](http://rocksolidbulldogs.com/Why-do-Bulldogs-and-French-Bulldogs-need-a-C-Section-.php). ## Dropping In the weeks to hours before birth, the baby resides lower in the abdomen - a transition that physicians call "lightening". A hypothesis has been advanced that a baby won't drop without gravity. On the surface, it seems to have merit, but babies drop while expecting mothers are in a variety of positions. In addition, [dolphins](https://books.google.com/books?id=qMa_P74RT-IC&pg=PA104&lpg=PA104&dq=do%20baby%20dolphins%20move%20lower%20in%20the%20birth%20canal%20before%20birth?&source=bl&ots=hWC16HrvsZ&sig=UidatPye0N0Nz9HihKLI1fNmY78&hl=en&sa=X&ved=0ahUKEwju_KWs2q3XAhUS-2MKHdNtCocQ6AEIPTAD#v=onepage&q=do%20baby%20dolphins%20move%20lower%20in%20the%20birth%20canal%20before%20birth%3F&f=false) appear to have a similar phase, so at the very least, mammal babies can drop without gravity. Earth women have exercises and movements which hypothetically move the baby into position, but while that research appears to be in its infancy, there's no reason to avoid talking about the zero-g versions of the same exercises. ## Gestation Humans carry babies in their wombs surrounded by hydro-static pressure. Since Earth women do [yoga](https://dhrupadmary.wordpress.com/2012/12/21/second-trimester-ashtanga-yoga-and-beyond/), [swim](https://www.babycenter.com/0_great-pregnancy-exercise-swimming_7822.bc) and sleep, it's pretty clear that their orientation does not effect their ability to bring a baby to term. For women to need gravity to bring babies to term would require proof. ## Copulation Again, [nobody wants to admit](https://www.space.com/8683-time-sex-space-astronaut.html) to having had sex in space, but humans are endlessly creative when it comes to this. I will not be adding a link. ## Evolution Nature will find a way. There are few things that cause rapid evolution in "natural" species, but illnesses and breeding problems are at the top of that list. Nature is neither fair, nor kind about this, so there would be some cruel generations where natural selection takes care of this problem. That could have it's own consequences because our powerful brains are related to the long gestation times. The other option would be to guide evolution with Genetic Engineering, but that tech is probably a long way away. ## Verdict If you want it to be an issue, you can, but I wouldn't bat an eye if a fiction writer told me that zero-g birth was commonplace and about as catastrophic as Earth birth. [Answer] Having done it myself, I know that birth is a very traumatic experience, for all persons involved. Pregnancy can also be very unpleasant. There will be no room for people on space stations who are going to be sick and wobbly and faint for months at a time. Your future humans will leave gestation to a nice safe, warm automatic womb, providing everything the baby colonist needs, including gravity, and when it's finished growing, you open the lid and get it out. [Answer] My suspicion would be that it is possible to make babies is space, but I think there would be a far higher rate of in-utero fetal demise. Microgravity shouldn't cause any obvious issues with conception, formation of a blastocyst, or implantation (emphasis on the *obvious*). The placenta forms in any orientation so that shouldn't be an issue. For the first 32 weeks or so of a pregnancy baby spins and flips like a toddler in a bouncy house, so orientation doesn't seem to be particularly important. Some of the other comments suggest that gravity plays a role in fetal engagement with the cervix, descent, and birth, but at the end of the day those are mechanical problems that can be solved. We deliver babies all the time without Mom going into labor either through induction of labor or via cesarean. Where you may get into trouble is with Vircohow's Triad, particularly the stasis corner. An astronaut recently had a blood clot form in his neck while in microgravity, possibly due to an increase in blood pooling in the head and neck in microgravity (gravity usually "pulls" the blood back to the heart from the head). The placenta has a boatload of blood vessels for nutrient exchange with baby and can cause fetal demise if a clot forms in it. It's unclear whether microgravity would increase susceptibility to blood pooling in the vessels in the placenta, but if it did that could increase the rate of fetal death. I think the nastiest thing about growing up in microgravity would be changes in the vestibular system of your inner ear that helps you balance. A child's brain raised in microgravity would never receive the typical signals from the inner ear that you or I get while being accelerated into earth's surface. This would either lead to something like ambliopia of the ear, where the brain simply ignores the signals it gets, or re-interpretation of the signals as they operate in microgravity (more likely). The second would cause people born in space to be very disoriented at mild to moderate linear acceleration (such as spacecraft maneuvers) the same way we get disoriented on a merry go round. This same effect would happen when they go down a gravity well, though presumably they would eventually get used to it the same way astronauts get used to the vestibular changes in microgravity. Those first couple days would be nasty though. ]

[Question] [ I am building my fantasy world from the ground up. In particular, for the races that use a coin-based currency, how do I figure out what it is worth? Say we have the basic copper/silver/gold pieces each being 1/10th of the next value. Should I arbitrarily assign an annual wage for the working class or should I use something else as a standard (e.g. cattle)? If I decide on a different denomination system for another race (shells/stones/glass each being 1/6th of the next) should I value this separately or based off the precious metals currency? I am not looking for an in depth economic system (yet) just the basics. [Answer] **An example of a Gold-Silver-Copper coinage system** The standard D&D gold/silver/copper system with its multiples of 10 comes from the [Roman currency system](https://en.wikipedia.org/wiki/Roman_currency) of ~200BC-200AD. There were other Roman coins, but for the entirety of that time period, corresponding with the 'Classical' Roman 'golden age', the [aureus](https://en.wikipedia.org/wiki/Aureus), [denarius](https://en.wikipedia.org/wiki/Denarius), and [as](https://en.wikipedia.org/wiki/As_%28Roman_coin%29) were issued in gold, silver, and bronze/copper respectively (the as went from bronze to copper during Augustus' reign around 23BC). The ratios of those coins were 1 aureus = 25 denarius = 250 asses, so not quite the 1:10:100 ratio. However, the aureus was more than twice the weight of the denarius (7g to 3g) so if those two coins had been the same weight, then you would have the 1:10:100 ratio. The as was between 9-12g; its value decreased over time from 1/10 denarius to 1/16 denarius in 140BC, possibly as a result of financing the Punic wars with Carthage. During Augustus's reign also another coin entered circulation. Now that there were 16 asses to a denarius, the [sestertius](https://en.wikipedia.org/wiki/Sestertius) was added at about 20-30g of brass and worth 4 asses or quarter of a denarius. This changed the ratio of aureus:denarius:sestertius:as to 1:25:100:400. So the above is the coinage situation for 400 years of roman empire. What were these coins worth? **Relative value of coinage** In the late roman republic, a legionary was paid 112.5 denarius a year, or about 1/3 denarius a day (or two per week). Julius Caesar increased the pay to 225 denarius a year, or, or about 4 denarius a week. Tacitus says that the Roman army of the Rhine in the reign of Tiberius (~30AD) got 10 asses a day, and demanded a pay raise to a denarius a day (since at that time it was 16 asses to the denarius). By the reign of Domitian (~90AD) the pay was down to 1200 sesterces a year, which is 300 denarii a year, a little less than one a day. For civilian pay, in the time of Diocletian (~300AD), a farm laborer was paid 400 asses a month (25 denarii a month) and a teacher paid 800 asses per month per student. A sestercius in ancient Pompeii was probably the most used currency by common people. One could buy you two loaves of bread or a liter of wine (or less if it was good wine). 15 lbs of wheat ran about 7 sesterces, while the same of rye was only 3 sesterces. Slaves went for 2000-6000 sesterces. The aureus was probably not used in by common people at all, nor was it used to pay taxes, which were often paid in kind (i.e. food) for use by the local military garrison. The aureus probably acted as a sort of reserve currency, like federal reserve notes today. It was minted in Rome, paid out to the provinces for civil servants salary, then paid back to Rome as taxes. **Non-precious metal currencies** In general, precious metal currencies drove out other forms of currency when they competed because precious metal currencies have the advantage of relatively constant supply and superior durability. From real world-evidence, you could conclude that more advanced economies that could perform large scale mining would eventually settle on precious metals. Therefore, other systems (like cowrie shells, or the like) would be used in less advanced economies and could be pegged to the precious metal system (10 shells to a copper, or something). Alternatively, your world may have an item that is superior to precious metals. Mystic crystals could be available in limited quantities, with constant supply and superior durability, and have the advantage over precious metals that they have an intrinsic value to anyone doing magic. Therefore, mystic crystals would become the currency of the most advanced economy and gold/silver would be for lesser, peripheral economies. [Answer] Some historical examples to work from: Ancient Cypriot copper ingots were cast in the form of a stylized oxhide. This indicated throughout the Mycenaean world that the expected value of a copper ingot was one ox. Since barter was the most common trade arrangement of that time, this "proto money" created a sort of common value system, and allowed Cypriot traders to establish a benchmark of sorts when trading. One copper ingot = one ox, so how many oxen would translate into a quantity of wine or oil or other commodities the trader was interested in. Perhaps more importantly, since you are establishing a fantasy world where multiple nations exist and trade across the borders, you will need to establish what is known as Purchasing Power Parity, or PPP. The Economist magazine has an interesting example of how to do this, called the [Big Mac Index](https://en.wikipedia.org/wiki/Big_Mac_Index). [Here](http://www.economist.com/content/big-mac-index) it is from the Economist. It looks at nations around the world, and asks "how many hours of labour would it take to purchase a Big Mac meal in these countries?" Obviously a lower number of working hours to purchase a Big Mac meal makes the currency's "purchasing power" much stronger than a place where it takes a lot of hours of labour. The Economist's Big Mac Index is actually very sophisticated, since it also measures the general economy of the nation (A Big Mac meal requires a lot of ingredients from many areas of the economy. A nation where it takes a lot of labour to purchase a Big Mac probably also suffers shortages of many key ingredients). For your purposes, unless there is a Ye Old MacDonald's chain across the realms, a PPP index should be established in the back of your head for common items like a cow, wheat, beer and so on. The National economy may value their currency in some arbitrary manner, but (as we see in many nations where the economy is weak or failing) the true value of the currency may be radically different. As someone in Venezuela today how many Bolivars are needed to exchange for a single Dollar USD compared to 2000AD and you get the idea. So you can have the Magic Kingdom value one "Mickey" to ten "Minnies" or one hundred "Plutos", but the ordinary person is asking "How many Plutos do I need for a beer?" and a trader is asking "In this kingdom, how many of my Zognars would it take to purchase a beer?" [Answer] There have been some nice answers so far. Another important detail: If poor people deal with the cash economy, the smallest coins must be suitable for their needs. Imagine the copper piece (*cp*) is the smallest unit, and a casual farm worker gets paid 1 *cp* per day. That guy couldn't take a day's earnings and take some of it to the cobbler to mend his shoes, some to the inn for a place to sleep, and some to a tavern for beer and a pot of porridge. 2 or 3 *cp* per day are slightly better, but still not good. Perhaps it would be possible to pay that worker 6 *cp* per week, and the inn would offer room-and-board for a week for 4 *cp*. That allows two single-*cp* purchases per week. Two options : * Make those copper coins smaller. A casual worker earns approx. 10 *cp* per day. Most of that goes for food and shelter, but there is 1 or 2 *cp* left for other expenses. Other prices are scaled accordingly. * Most villagers or townsmen don't deal in cash. They will accept coins from wandering heroes, but by necessity it will be at greatly inflated prices. If a night in the flea-bitten inn costs 1 *cp*, the innkeeper can throw in a couple of pints of ale and still make a profit. [Answer] Basically in a [Commodity monetary system](https://en.wikipedia.org/wiki/Commodity_money) with silver/gold coins you can value money whatever you want, depending on the rarity of the metal (i.e. you just say that gold in your world is very-very rare and one can buy a house with a single gold coin). **Price formation** is actually quite a hard task, as societies on different development stages tend to value different things. Baseline is "how much effort should be put to make a thing and how many people in current area can craft this thing" - the prices will vary for different regions and nations. For example an ounce of pepper or salt, brought by a trader from a far-away kingdom can easily be more expensive, than, say a horse or a sword in current location (if we think of medieval type of society with no fast/reliable transport system). I think it's pretty safe to start from defining an "average worker" salary to be enough to have something to eat daily and have some entertainment regularly for a somewhat prosperous city. Food costs less, unless region lacks means of food production (like a desert); tools and furniture cost more (as more and more people and effort are involved in crafting a specific tool "manually"), etc., etc. It's pretty difficult to try to make up realistic economic system, yet it's your world, so you can always say "this item costs that much just because..." (or, as proposed by @kingledion in his answer - you can just borrow some prices or one-thing to other-thing price ratios from known historical examples) **Question needs further clarification** Do your races have trading relationships? I suppose, you're mixing up a [Commodity monetary system](https://en.wikipedia.org/wiki/Commodity_money) in the first case and [Representative moneatry system](https://en.wikipedia.org/wiki/Representative_money) or even [Fiat monetary system](https://en.wikipedia.org/wiki/Fiat_money) in the second case. If both systems are meant to use commodity money (the second race values highly shells/stones/glass), then the second race seems to be a bit "far behind" (i.e. doesn't have metallurgy), making them a potential victim to the races of first group - starting from unfair trades (like exchanging worthless glass beads for land/something of value, WITHOUT anoption to trade vice versa because first group of races doesn't value glass), ending with a brute-force conquest (taking in account an advantage of metallic weaponry/armor). [Answer] > > Say we have the basic copper/silver/gold pieces each being 1/10th of the next value. Should I arbitrarily assign an annual wage for the working class or should I use something else as a standard (e.g. cattle)? > > > If the working class earns wages (instead of working for food and to avoid whippings, like in slavery, or for a piece of arable land, like in feudalism), I suppose that your society is quite thoroughly commodified. If so, it needs continuous circulation of money, and money will tend to be a specialised commodity, that is basically only useful as money. This would rule out cattle, which will be eventually taken out of circulation for use as food. In a thoroughly commodified economy, the relation between money, prices, and amount of commodities, is given by the simple formula > > M \* V = P \* Q > > > where M is the amount of circulating money, V is the speed at which such money circulates, P is the total price of commodities, and Q is the amount of commodities produced. This is valid for the economy as a whole, and, with some caution, for each single kind of commodity; goods that are produced in great amounts will be less expensive than goods that are produced in small amounts (if Q is bigger, then P must be smaller, and conversely). If your world includes magic, this must be taken into account: a house is much more expensive than a loaf of bread in our world because in the time you build a house you can produce millions of loaves of bread. If magic makes building a house much easier, then the relation between the prices of houses and bread will quite likely change. If magic allows people to multiply/create money, then the effects on M will be chaotic, possibly making a monetary economy extremely unstable or even inviable - so perhaps it would be wise to make money magically non-reproduceable too. As for wages, they must be enough to sustain a labourer and his/her family, ie, you would need to add everything a worker needs to buy during a year (365 \* 3 \* 4 loaves of bread, supposing that the average family has four members and each of them eats three loaves of bread a day; 1/40 of a house, supposing that the average working life is 40 years; 4 pants and 24 shirts, supposing that each member of the family wears off one pant and six shirts a year; and etc. Those things are at least in part culturally determined, so you must take into account whether females are supposed to work for a wage or not, whether owning a house or renting one is the norm, whether a fashion industry makes clothes obsolete each year or whether it is socially acceptable to wear a ten-year old coat, etc). Wages must also not be much bigger than that, otherwise too many workers will be able to buy their own business, no longer necessitating a job to maintain themselves. [Answer] ## In general What you're missing is that "value" is a very arbitrary concept. The value of an item (service, currency, ...) can be defined in any way. Some examples may include: * What was paid most recently for this specific item? (I paid 8000€ for my 1-year-old used car) * What's paid for items of the same kind on a market? (max, min, average, median,...) * What's highest price a buyer would pay? (auction) * What's the second highest bid? (second-price auction, e.g. ebay) * What's the lowest price a seller would accept? (inverted auction) * What's material cost plus work invested to create the item? (production cost) * What's the highest amount one could earn with the resources and time required to obtain the item? (cost of opportunity) Part of the above is why material currencies may fail: If the material is worth more than the coin, just melt the coin. If it's the other way round, buy the material and fake the coin. However without a globalized and/or computerized market and impartial institutions most of it boils down to: * What can I get (away with)? Ever been to India with a 1000 Rupee bill? When you buy antibiotics for 27 Rupees and the pharmacy clerk claims, he has no change, you'll just pay 100 Rupees. As a tourist I still felt lucky, because he handed me lots of small bills, so I wouldn't have to change them at a tourist trap restaurant who would (claim to) have even less change so that food will be more expensive than antibiotics. Plus, comparable medicine would've cost more than 1,20€ in Europe and above all: I needed it **"now"**... Speaking of antibiotics, how come they feed large quantities to animals, which meat is rather cheap, when it's so damn expensive in an apothecary? It's the context: You pay a lot for the same stuff in an apothecary, while a farmer buys it in bulk from the veterinarian for less. This is simply because the apothecary can charge as much. ## In a fantasy setting If the Dwarf likes rubies a lot more than gold (coins), I can sell him my rubies at a higher than usual price. If he's really thirsty (or drunk), I can sell him my beer at a higher than usual price. If I don't want his obscure dwarven coins, I can insist he goes to the money changer first. If the money changer dislikes dwarves, he might try to "scam" him with bad rates. It's not like there's any institution watching over any of this. There's only some upper class royal (probably a king), who hands out coins and accepts them back as payment. Maybe he (as highest judge) allows debtors to pay off debts in his coins and forces creditors to accept them. Maybe he'll send someone to investigate, if some region seems to be overflowing with money that he didn't issue. The rest is context and bartering. [Answer] What you really care about is the *ratio* between prices not the prices themselves. I doubt that you need to state in your story how much coins weigh and how much precious metal is in a coin (and how much is common metal used to bulk up). Now, if you care mostly about ratios you could go with the prices in the modern economy for everything except land and raw labour, suitably disguised. Take the price of a cow in modern markets and call every 3 dollars a zonker or something. That would give you relatively consistent if not perfect ratios. Land and labour are a special case. For labour I would just take a basket of goods needed for a worker (food, clothing etc), check how much they cost in your story, add a margin and it's the salary. For land... it gets a bit complicated. Good thing, you don't really need a price for land, unless your hero buys a castle for cash or something. [Answer] Value is determined by the beings assigning it to the object. As such, obviously, what is valuable to one may be worthless to another... then again, certain objects may be valuable to both. For example, I recall a particular island where shells were seen as decoration, including a particular rare smooth white spiral of particular shape. The islanders thought little more than it was pretty, however, to scientists in the outside world, it was quite valuable due to the rarity. Communication therefore becomes important to establishing value amongst disparate forms of currency. I recall another story where a non-verbal race wound up settling on one gem per page of brightly colored comics/magazines, an unexpected coup for the travelling merchants in question. In yet another story, the race in question would bargain the work, but would ask detailed questions about how the person obtained what they were offering. For that race, the value was in how hard they had to work in order to produce their prized products, and they would only accept a trade if the items and materials being offered were obtained through equally hard work. Thus a rich person offering gold and gems typically had a more difficult time bargaining, as they usually did not actually perform the labors which made them rich themselves, while a poor person could trade a few coppers to receive the same or better than the rich person. Therefore, pick items which would be valuable to each culture, and then compare what each culture deems valuable with what other cultures have to offer. Then decide what value each culture would assign to the items being offered by other cultures. The 'value' that will be settled upon is likely to be between the two. Furthermore, unless you prefer a static system for simplicity, 'value' fluctuates with demand and availability. ]

[Question] [ **Closed**. This question needs to be more [focused](/help/closed-questions). It is not currently accepting answers. --- **Want to improve this question?** Update the question so it focuses on one problem only by [editing this post](/posts/20578/edit). Closed 6 years ago. The community reviewed whether to reopen this question 1 year ago and left it closed: > > Original close reason(s) were not resolved > > > [Improve this question](/posts/20578/edit) From 1995 to 2015 we have become heavily reliant on the internet for a lot of our everyday life. Skip ahead another 20 years and under the assumption that our society and technology keep evolving in a similar way to the past 20 years, we are now live in a world where the internet is the centre of everything. It is no longer something that makes our lives easier but it has grown into something that a lot of our systems are now dependant on. Even in today's world we are seeing this - in 20 years from now the dependancy will be much greater. In this futuristic world, what would happen if an unexpected and unexplained event hit the internet and suddenly all around the world the internet simultaneously shut down? Every connection is lost. And the event causes major problems with the internet that mean it could take years of work to get it back up and running again. I'm not interested in what the event that shuts it down could be. Consider it a theoretical event. **What would happen in the seconds, minutes, hours, days, and weeks following the shut down?** What would be the initial reaction? How would this affect the world? [Answer] The scenario you describe could be the result of highly coordinated attack by an ultra-radical anti-technology group that has managed to simultaneously attack and knock out every [Tier 1 network provider](https://en.wikipedia.org/wiki/Tier_1_network) and every Tier 2 provider on the planet. I'm exceptionally impressed with their ability to pull this off. They have destroyed the world. One could stage attacks on the [BGP](https://en.wikipedia.org/wiki/Border_Gateway_Protocol) protocol used to control routing between large networks but attacks of this kind wouldn't result in a long term outage because the network operators are very careful to make sure their networks stay up....after all, that's what their customers are paying for. **Tl;dr** (2022 Edit) Remember when COVID hit and most things just stopped or slowed way down? The situation in OP will feel similar for a day or two then keep getting much much worse. How you felt then will repeat here but much much worse and for a lot longer. **Boom** Every router and switch at the Tier 1 and Tier 2 network providers locations are gone. Millions of devices have just disappeared. Vanished. The wires are just dangling there. **Outage+1 minute** People will respond with "Hey, is the internet working for you?" "Nope, I can't get to Google or Facebook." Internet addicts will start to feel the first pangs of withdrawl. All phone calls halt. Financial institutions who depend on Internet connectivity to clear transactions will start to feel the pain. High frequency trading companies will *absolutely lose their minds*, as will every engineer in the T1 & T2 network operations centers. In an instant, untold billions of dollars of investment have vanished. While the ability to build new routers and switches remains intact, the money to buy them is gone. New switches and routers are suddenly priceless and worthless at the same time. Priceless because every network operator on the planet wants them. Worthless because without another router on the other end, a single router can't do much. The electrical grid which has been smartened up no longer functions as well because coordination between power providers cannot occur. Having the load from the switches and routers disappear may cause damage to steam generators as they will suddenly overspeed. But other power generations sources will enjoy the decrease in load. Remote surgeries will initiate their Internet-failure protocols to close up the patient safely. Surgeries where the surgeon is on site will continue, though who knows when/if he'll get paid for his services. **Outage+30 minutes** Internet addicts are having fits as is every single teenage boy addicted to the World of Warcraft (or whatever online game Blizzard is running). All commerce has stopped. Credit cards don't work. Let's assume that cash has been replaced with cryptocurrency....which also no longer works because to clear a cryptocurrency transaction requires an internet connection. Stores will be able to sell things using the very primitive "CHUNK-CHUNK" paper based records. They won't be able to clear these. Every single stock and commodities exchange on the planet has frozen. Packages in transit over UPS will arrive if they are already on the truck but no new packages can be shipped. **Outage+1 hour** Ham radio operators begin to share information about the outage. They describe the scope of the outage in their area and over the next couple of hours the scope of the outage begins to take shape. Mesh networks (which hopefully are widespread at this point), kick into high gear to share information about what's going on. Connectivity within a town or city may be high but connectivity between cities is zero. Mesh networks can't handle that kind of load. Millions are stranded at airports because boarding passes can no longer be checked. It's like 9/11 again, only it's everywhere and no one can pay for alternate transit. Container ships with the goods of civilization arrive at port, are unloaded but the containers just sit on the docks because no one can figure out where to send them with no way to call to ask someone. **Outage+6 hours** Mayors, governors and heads of state declare a state of emergency but not many people can hear them. Panic has set in. Any kind of a store with food is now empty. Violence escalates as people begin to forcibly take the things they think they need to survive. **Outage+24 hours** Factories that build routers and switches will go into monster overdrive as demand for new routers has gone through the roof. It will take years to manufacture new routers to satisfy the demand. Businesses of all kinds have shutdown or are in panic mode, hospitals too. Riots are in full swing. Police and fire departments are stretched beyond breaking. Vigilante justice and neighborhood protection groups spring into existence. **Outage+1 week** The riots and chaos of the last week have largely subsided. The barter system has returned in force. Small items are now used as currency in place of money or a local cryptocurrency has sprung up, supported by mesh networking. Communities have shrunk and become geographically focused. People have met their neighbors for the first time in their lives. Anyone with a mesh network node is extremely popular. Anyone with mesh networking expertise is extremely valuable. Google and other Internet companies have lost significant portions of their stock value. Phone manufacturers have also lost practically all value and will close or be supported as "too important to fail" and kept on nationalize life support till the market comes back. Medical and food supplies are running low because there's no way to reorder them. For a better idea about what happens when commerce significantly slows in a country, look at the changes in Greece between April 2015 and mid-July 2015. This situation is worse because commerce has stopped, where Greece has only slowed down (a lot). Demand for Flash drives and external storage media go through the roof as people fall back to moving data around by hand. Postal and package service may resume service but with significant delays. Every single business that staked their productivity on Applications-In-The-Cloud are having a really really tough time. They can't do business and won't be able to do business for a long time. Secondly, they may never be able to get their data back because the companies that hold their data may go out of business and take the data with them. **Outage+1 month** Internet providers are nationalized or placed under centralized government control in order to manage the trickle of routers and switches coming out of the factories. Companies have fallen back to the old paper forms they used to use the 1980s. Snarky gits laugh at the organizations who went all paperless. P2P application such as BitCoin and BitTorrent become the primary means of or paying for things or distributing information. These applications work because they don't need any centralized source to run. On a network of three computers (with the appropriate software) these are completely functional networks. Open source software (distributed source control, compilers, editors, operating systems etc), already powerful in their 40+ years of operation, step up to fill the gaps in services left open by the disappearance of the large providers such as Google, Facebook, Apple and Amazon (and whoever else may pop up in the next 20 years.) **Outage+1 year** Internet access is slowly returning but the quality of service is significantly slower than it was. Shoddy equipment causes datacenter fires, setting back the return of internet service for months or years. Ham radio becomes an unprecedentedly popular past-time, causing a boost in science education. The mints of the world have been de-mothballed and begun to turn out hard currency again. Designs of old currency are renewed. Culture in general will go through a period of introspection on whether Instagram, Snapchat, Facebook, are really all that important anyway? Many people may say "No, it isn't" and find other things to do. Merging all the cryptocurrencies that have sprung up back into a single national currency becomes a legal nightmare. The courts are absolutely chalk full of lawsuits. Legislation will need to be written to cut down the number of lawsuits and handle the aftermath of the Outage. **Outage+10 years** Internet service is back for everyone. Network topologies rely increasingly on mesh principles. Large telecom providers have been bailed out. Market share in the network equipment space is unrecognizable compared to pre-Outage as new companies appeared to fill the staggering demand for new routers and switches. Cryptocurrencies become more tolerant against widespread disconnects. Mints and postal services the world over issue 10 year commemorative coins and stamps. Some people will ask "Where were you when the Outage hit?" **[Update]** While the dedicated routers may be gone, the ability to route Internet traffic hasn't completely disappeared, it's just grown horribly more inefficient and lower capacity. Routers are just computers with lots of network ports and a specialized form factor to better fit into data centers. The only difference between a router and a general computer is the number of network ports and the software running on the computer. There are also long distance microwave transmitters that can move traffic tens of miles at a time. Long distance data trading could happen this way. **Outage+1 day** Inventive network operators will begin to repurposing multi-port servers to be routers. The capacity of these machines is far below what used to be available but at least *some* data will flow. Prioritization of traffic in these early days will be intensely political. [Answer] The problem with this scenario is you specifying "And the event causes major problems with the internet that mean it could take years of work to get it back up and running again". By design, no such event exists, in the same way that by design, all mains AC sockets cannot suddenly get 10,000V on them indefinitely. Events exist which can locally knock out local internet connectivity, sure - fishermen on illegal deep-trawling operations are a favourite. But not permanently for the entire world. Also be aware that "the internet" has 100% absorbed phone traffic (ultimately it's all just data), and "the internet" can be connected wirelessly. So if you've lost "the internet" then you've also lost phones and radio as well. It is not possible to separate them, so loss of internet is just one aspect of loss of all long-distance electronic communication. With all these things, the nature of the event *has* to be a consideration. Could an impossibly massive solar flare which EMPs the entire world and wipes out every transistor and every bit of stored data cause this? Sure it could. But then you've also got to worry about radiation sickness, and whether the survivors are sterilised, and if they aren't then unbelievably high rates of birth defects and cancers, and so on. [Answer] Ok, you're not interested in the event that could cause the shutdown but I'm going to assume that local infrastructure has remained intact but anything part of long distance dedicated packet based network has been zapped by aliens or something. I'm going to exclude networks not usually used for packet data despite the fact that [IP over avian carriers](https://www.rfc-editor.org/rfc/rfc2549) is a thing that can be done. The aliens have not shot down all carrier pigeons. Old-style non-packet based networks like old phone connections are also still alive even though people can technically send packet data over them. I'm assuming that every running non-leaf node in any primarily packet based communication networks has burned and any long cable has been broken at some random point along it's length. **Seconds**= every on-call network engineer on the planet is woken as contact is lost with their networks except those who relied too heavily on other networks for their wakeup call. **Minutes**= people start noticing that they can't make phone calls, 911 calls are no longer a thing except in areas with really old phone networks. A few people start to get a little annoyed because they have no signal, the network engineers are currently leaping into their cars or trying to contact others. A large portion of the rest of the worlds on-call tech staff are being woken, some by banging at their door. Some systems like nuclear power plants are likely going into failsafe mode and shutting down or being shut down by their staff for safety sake since they've lost contact with other nodes in the grid. **Hours**= it's really starting to hit the fan. The dying has started in small numbers, operations being performed remotely are screwed up. Local ham radio enthusiasts are being turned out of bed by police/local officials and apart from emergency radio broadcasts the entire spectrum is being commandeered for emergency use, high priority communication is starting to be pushed over quickly jury rigged radio links, some of it voice, some of it packet based. Most of the world still doesn't know anything has gone seriously wrong. AM radios start issuing announcements and warnings. Military is on highest alert assuming a surprise attack, fortunately red-phone style systems are likely not packet based. India and Pakistan nuke each other anyway. **Days**= stock in companies which produce networking gear is heading for pluto, or it would be if many of the exchanges weren't legally not allowed to operate since many mandated communication links are dead. Any company which has the facilities to produce networking gear or cables is doing so as fast as they can to cash in. Lots of old hardware is being pulled out of storage. There's probably a lot of people scared. many areas are blacked out as many of the power plants can't get supplies or can't be safely run or coordinated. **Weeks**= looting, rioting, many shipping networks have been screwed up so there's a shortage of almost everything while food rots in the fields due to breakdowns in communication but the networking engineers of the world have yet to sleep and have all been pulling 72 hour shifts. high priority, low bandwidth links have been restored within most first world nations between cities but ocean cables are still down. Lots of local infrastructure is screwed. Ditto bureaucracy. Most network dependent industry pretty much collapses but there's lots and lots of jobs running fiber/cable and installing switches. [Answer] Well it would take something pretty big to knock out the entire internet and actually keep it mostly down for any length of time. It is a distributed system covering a very wide area physically on the earth. So two 'ideas' that might knockout the internet. 1: A major virus/worm that infiltrates the back bone and all machines it is capable. This virus would have to disrupt communications, be hard stop and just clog the internet like a clogged toilet. Only it keeps coming back. 2: Something like a solar flare or magnetic storm that totally wipes out a large % of the communications backbone, along with the vast majority of electronic devices. I mention these because of how hard it would be to seriously knock the vast majority of the internet for any length of time. Don't forget that all communication systems are very closely integrated. Data and phone use much of the same network. In either case if this happened even today, it would almost be an apocalypse, at least for most 1st world countries because EVERYTHING is on computers, in databases and would be lost and/or not available. Who owns what? Who owes what? Where are my products? How much money do I have in the bank? It would be very difficult, most executives do business and make decisions based on computer programs, at the very least giving them market and production data. My job requires the internet. I'd be out of a job. Even many manufacturing jobs are ultimately dependent on the internet or at the very least computers getting/sending data somewhere. At first it would be a mild inconvenience, for about the first 5 minutes. After that, business communications would start to back up and the most hot issues would be done over the phone, though no one would think they need to Fedex 'thumb drives' with data around yet. After an hour broadcast TV 'might' be the only major form of communication left. Without the network, even many/most satellites will become mostly useless. Things will be slowing down as work backs up since communications have broken down. After 10 hours cities will start to panic. After a day most large cities will be shut down, people will stay close to home, and most of the small community grocery stores will have a run on all stock as people buy to hoard away their food. After 5 days riots might start, many who have friends and family in a rural setting might have left to 'visit' them. (Burki's comment) Many hospitals and pharmacies are going to have issues too. Prescriptions will need to be written on paper again, but keep track of stock will be difficult. Hospitals need to interact with pharmacies, insurance companies and other health related places. Often even their own electronic records are offsite are accessed over the internet. After two weeks if a coordinated effort can't be done because of lack of communication people are going to start going hungry. After a month North and South Dakota will be wondering what they are going to do with this years harvest, since no one knows what the current market value is which means they don't know what to sell it for nor who's going to buy it. They might also notice that there have been a lot few people visiting Mount Rushmore and the badlands this year. [Answer] Most other answers seem to have ignored the OP's comment that only Internet is down, not phones. So I really don't think an apocalypse would happen, with dramatic permanent food shortages, cities burning, etc.. As such: * Major business transactions would still go through on the phone. Less efficient, yet not a complete stop. Yes, you can't buy 1 share of APPL from Fidelity. But a Fidelity mutual fund trader can easily pick up a phone and buy $500M worth of bonds he wants. Hell, that's how bonds have been trading till probably 3-5 years ago, even if stocks joined the internet revolution much earlier. He may not have fancy investment software he had the last 10 years, but he still has his knowledge of Modern Portrfolio Construction, and Excel, and local PCs and a phone. Notice how I said "bonds"? That's because, the driver of most important things in modern commerce is **credit**. **Yes credit, yes commerce, yes businesses can run**. * Ditto finance/banks. Your online banking account is caput. You'll have to take your lazy a$$ down to ATM or bank branch, like your elders had to. JP Morgan Chase settling a multimillion dollar account with the Fed does so over the phone. So **no major liquidity crisis**. * Major business purchases can be negotiated and executed over the phone. Yes, your Amazon order of quadcopter, fancy soap, and a special colored housecoat don't work no more. Sucks to be you, Mr Hipster. But a Costco placing an order for $1Mil worth of produce or goods picks up the phone to the supplier and does the deal. Both will incur some extra costs for processing the transaction (someone gotta write into paper ledgers for now and work the phones, so local temp employment soars). * Things are a bit tougher for smaller retailers (you gotta call 100s of suppliers). But somehow, they DID manage to do business before internet, y'know? They'll adjust. BUT again, major food distribution that's done in bulk won't actually suffer. In general, people who work the phones (and call centers) make out like they found free cash. * Medium term, Messenger services experience a major reneissance. UPS and FedEx make out like bandits. Don't never underestimate the bandwidth of a dude with sneakers, loaded with a bunch of CDs and flash cards. And **definitely don't underestimate the bandwidth of a semi truck fully loaded with DVDs/flash cards** ]