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[Question] [ If all humans (but no other species) just suddenly disappeared, leaving all of their structures standing, how long would it take for an intelligent species as dominant as the humans to evolve? Would the disappearance of humans change anything? [Answer] As sad as it sounds, the safest assumption is **never** (or forever). It has been stated in the comments by @ratchetfreak: The dinosaurs roamed world for million years without developing intelligent society. Or they have been so clever to take all technology with them when leaving Earth, or so unlucky, that the Yucatan asteroid wiped out all technology when it fell down to Earth. But back to reality. If you need to develop intelligent life again, amongst the best candidates are chimpanzees. So you could plausible repeat human evolution again and let chimps evolve to something close to Homo Sapiens. That according to Wikipedia should take [2.3 million years](http://en.wikipedia.org/wiki/Homo_habilis) But You have to ask yourself the most important question: **What defines "intelligent life"?** Is it buildings? You have [termites](http://en.wikipedia.org/wiki/Mound-building_termites) Is it society? Bees, ants, termites. Ask yourself what you want to achieve in your world. Then, being you, I would work backwards from that point: What do I need for *intelligent rats having society like ours*? Is it plausible? If its not, how do I make it sound plausible? (Come on, radioactivity mutation was used so many times that no one is even surprised.) [Answer] There is no way of giving a sensibly supported answer. We have a sample size of one, and we don't know what the requisite steps along the way were. It is quite plausible that many of the steps *have already been achieved* in species such as chimps which share considerable evolutionary history with humans and thus these species would evolve new forms of intelligent life pretty quickly. Alternatively it may be that the conditions that led to humans are so incredibly unique it will never happen again. We really don't know. On the subject of dinosaurs; this is rather misleading because the ground conditions for humans carried on evolving over much longer periods. Based on crude measures of brain size there is good reason to believe that the "typical" mammal is a lot more intelligent that the "typical" dinosaur so it may be that dinosaurs simply didn't have the ground conditions for intelligence to take off. Also, remember that while dinosaurs were - at least - 65 million years less evolved than humans this isn't true of today's life. If I was take a personal guess, I would think that another primate would evolve intelligence within a few tens of million years but there that's little more than a guess. [Answer] Evolution happens on time-scales that are of far greater magnitude than the length of time our current mediums can hold information or any other evidence like buildings. Buildings and landfills break down before intelligence really shows up. CDs are an exemplary back-up medium, yet they only last 20 yrs without degradation. Which means you gain no benefit from an intelligent precursor species over an unintelligent one. Time taken to evolve intelligence is highly variable. Intelligence is not a foregone conclusion. For example, if any of our germ aliens ever end up existing I doubt we would place their evolution to intelligence as anything other than improbable. Humans being gone would only change how the variables in the ecosystem are set. Extinctions from transplanted species probably drops, stable ecosystems have a better shot at staying stable longer, etc. [Answer] Given that Humans are exhausting planetwide limited resources, and otherwise fouling their living space, who says intelligence has yet evolved, whether Humans are present or not. If intelligence equates to avoidance of species extinction perhaps sharks have it, as long as they stay away from Humans. [Answer] It's impossible to answer this question, as others have suggested the process may take millions of years or may not occur at all! Having said that I'll have a go! I'm going to assume for the sake of argument that "intelligence" is about a species using teamwork, plans and tools to work together to succeed rather than simply learned behaviour (which all species display when their parents teach them how to hunt/find food). Evolution does not guarantee intelligence, evolution suggests that the best survivors will flourish but the weaker evolutionary options will be out competed. The only way a species evolves intelligence is if the intelligence gives it an advantage when it comes to survival or reproduction. At some point in our pre-history our ancestors began to outperform other more powerful species because of their intelligence, this gave them an evolutionary edge and allowed our species to flourish. The ancestor to the crocodile gained that edge by growing a ridiculously strong bite, the shark... well (I'll come back to them later). We're actually talking about two sorts of evolution here, genetic evolution (the process of the brain growing bigger and mutations working there way into the population), this take millions of years and cultural evolution (learned behaviour, skills, language, behaviour). This cultural evolution is much faster... from a biological perspective we're not that different from Neanderthals, what has changed is our culture and our education. If you draw similarities between apes and our ancestors the process could be significantly quicker. Neanderthals began agriculture about 8000 years ago, it's possible that you could see a rise of another species (most likely some form of ape) in a similar sort of timescale. However if we're waiting for other species to "catch up" genetically, for example for dogs to evolve to have the mental capacity of some other animal species this process could take millions of years - assuming it happens at all! Which brings us back to the shark, it's commonly believed that the ancestors of the sharks which were around 450 million years ago were very similar to the species of shark we see today. They've had 450 million years where they've never been out evolved and they've never needed to develop intelligence\*! \*I like sharks... from a distance! [Answer] When I think of this topic, the concept of the Singularity comes to mind, of which we are "on the cusp" so to speak. Human beings evolved from lesser species, which evolved from single-celled organisms, which evolved, literally, from molecules, energy, and luck. Looking forward, human beings developed technology, which can be thought of as the next epoch in universal evolution. A whole ton of evolution happened in the first few seconds of the universe, and since then things have slowed down a bit and we've settled on matter and energy as we know it. Then life began to evolve (on our planet, and likely many many many others). Once technology becomes "self sufficient", it really won't matter what happens to human beings. The technology will represent the "level of evolutionary intelligence" that we've achieved. Even today, if human beings became non-existent, some of our technology would continue to operate, and even "advance" to a degree. This will apply even more so as we advance our technology. Similarly to how human beings will continue to "evolve" even if all of the monkeys were to become extinct today (or how we've evolved in the absence of the Dinosaurs). Similarly to how stars and solar systems will still "evolve" if our solar system were to become non-existent today. Similarly to how gravity will still exist regardless of what types of matter our universe consists of... That all being said, the probability of human beings becoming extinct, and "another" species achieving our level of "intelligence" *on this planet* are astronomical. Our planet is lucky enough to have evolved our species; it's a lot to ask that our planet be the one to evolve a species like ours *again*. Although, our planet has an edge, in that it has evolved intelligent life before... Really it's a philosophical issue: do you believe we are alone in the universe, or not? If you think human beings are the "most intelligent" creation of the universe, then our extinction doesn't bode well for the future of intelligent life. If you think the opposite, then it's almost a given that somewhere else, there is a level of intelligence that rivals our own...even today (although "today" is a relative concept in the scale of the universe). [Answer] Actually, the best bet right now to take our place if (or, God forbid--when?) we go extinct would be bonobos, not chimps--they're even more intelligent, more sociable, less aggressive/violent, and yes, a separate species. It has been posited that, eons ago, a troodon--a (theoretically) highly intelligent therapod dinosaur--might have evolved into an intelligent, humanoid creature, if that big rock hadn't dropped out of the sky and wiped them all out. No way to know, of course. Earth has a leg up, in that it's already shown capable of sustaining an astounding diversity of creatures, as well as intelligent life. Still, there's no guarantee that anything would happen: it would require a relatively small population of animals with the right genetic potential to become isolated for even the chance that evolution would occur. But if humans disappeared, and an isolated population of bonobos, say, began to evolve into something else, something more--then my best guess is that the process would take about seven million years (about the time it took for the common ancestor of humans and chimps to evolve into us; we're really the only example we have to work with so far). [Answer] **Around 4300 years ago** From this article on the [BBC](http://www.bbc.com/earth/story/20150818-chimps-living-in-the-stone-age): > > In the rainforests of west Africa, the woodlands of Brazil and the beaches of Thailand, archaeologists have unearthed some truly remarkable stone tools. > > > It's not the workmanship that makes them special. If anything, a casual observer might struggle to even identify them as ancient tools. It's not their antiquity that's exceptional either: they're only about the same age as the Egyptian pyramids. > > > What makes these tools noteworthy is that the hands that held them weren't human. > > > These stone tools were wielded by chimpanzees, capuchins and macaques. The sites where they have been unearthed are the basis of a brand new field of science: primate archaeology. > > > The tools are crude. A chimpanzee or monkey stone hammer is hardly a work of art to rival the beauty of an ancient human hand axe. But that's not the point. These primates have developed a culture that makes routine use of a stone-based technology. **That means they have entered the Stone Age.** > > > More on the article itself. Maybe if we vanished, apes and monkeys would expand into our territories, gaining enough resources to properly develop tool-using traditions without interference from their long-gone hairless cousins. [Answer] Quite a bit of intelligence may develop within a few million years. However, an industrial culture like today may return much slower or not at all, since all easily available resources like copper deposits for early metallurgical experience have been used already. Easily available energy sources are used up as well, and no culture will go from Stone Age to photovoltaics directly. A neo-human population with stone-age culture will not be able to exploit resources that require deep mining the way we do. Domestic animals are another Topic. Some animals like cows have evolved in a way that they may become extinct when mankind would disappear. So the next culture would have no cows to start milk production with. However, other domestic breeds like sheep should most probably remain. [Answer] One factor to consider is how many "puzzles" humans have left around. A lot of animals have been co-evolving with us for millenia, and adapting to the challenges we create for them. For example, we hoard food, but we don't just keep it in open piles, we keep it in pots and packets, and animals that live around us have an incentive to solve these "puzzles" to get to this food. So, arguably, a lot of animals are currently on an evolutionary path that rewards intelligence just by virtue of having us around, in a way that wasn't the case when we were coming up. Obviously if we disappear the supply of new puzzles will stop, but there'll still be an advantage for the animals that can figure out how to use some of the simple mechanisms we leave around. For instance, an animal that can work out how to open a door, has the advantage of having a contained or semi-contained habitat to live in; an animal that can work out how to use a water pump can keep themselves watered while their competitors die of thirst, etc. etc. So, in answer to your question, "how long will it take for a second intelligent species to evolve", my answer would be, probably\* not as long as it took for the first. \*Obvious disclaimer being that it is impossible to talk about any sort of concept of probability for a factor that we only have one point of data for... [Answer] One of the carnivore / omnivore social predators (apes, bears, wolves, etc.) with pack hunting skills and a substitute organ for the "human hand" (like an elephant with trunk) able to manipulate things and tools and enough evolutionary / environmental pressure to adopt or steady change. Considering our rise as a great ape, a million year is my earliest guess. [Answer] If humans would disapear and other land mamals with large brains will remain. You would need the development of another branch like the one it happen 6 million years ago when genus Apes and genus Homo was diferenciated. The question is that you dont know what trigger this development (tool shaping, social structure, communications). What seems to be a fact is that the different species of genus homo achieved a different level of sofictication in tool development control of fire, hunting strategies which were passed to the next). As each new species of homo developed different sizes of brains (even within the same species across hundreds of thousands of years you can see this development) so arround 3 million years ago you can start to talk about stone age technologies or as they are called industries). We find for the case of our closests relative the neantherthal, even having similar brains to us and similar time spands complex societies were not developed (maybe because the gropus were small in size - it is estimated that no more than 100,000 existed at once) for example that when an interglacial period occurred within their existence (125,000 to 115,000 year) ago), they were not able to create agriculture possibly because for most of their existence earth was within a glacia period (adaptation) and due to their small population. While for example at the time of the invention of agriculture the population of homo sapiens was 4 o 6 million individuals so social complexity also seems to play a role. So my guess is between 5 and 15 million years from hominids and possibly hundreds of millions if from other mamals. [Answer] I highly doubt it, and it's all because of the timing. Some other animals have been considered highly intelligent--elephants, dolphins, corvids and New World monkeys. They've all been around for many millions of years longer than humans, so why that shouldn't make them smarter than we is a legitimate question. [Answer] You’ll have to consider the environmental effects that humans vanishing would have as well. No more farming and burning fossil fuels suddenly would end the Anthropocene, but not instantly revert climate change and terraforming. It would take a slightly different path than with us and yes, this may have an effect even on the million-year scale. There would be noone to counter neither erosion nor forestation. Many highways and canals would fade away but some would form the basis for seemingly natural barriers. This, together with preexisting and interdependent geologic and climatic forces (of a much larger scale) would shape the environmental pressures that drive evolution. We don’t know for sure which conditions were mandatory for the genesis of *homo* and later *homo sapiens*, but they happened once (at least) and that means they could happen again, albeit probably in slightly different form, to boost the physical and later psychical limits of another animal within a lot of generations. After the body had evolved and our mind became conscious it didn’t really take us that long to develop society and science. There are certain properties of human body and society that made us so successful. They need not repeat in the same way, but for some species, especially apes or monkey and other mammals, it’s likely that they are beneficial as well and some of them have a head-start. This includes **free hands** to make and wield **tools** (incl. clothes to counter otherwise unsustainable climates later on) which requires **upright gait** if no other flexible, sensible, strong limb was available (like trunk, tail or tongue, but preferably two or more), which like increasing brain/head size makes birth more complicated, dangerous and painful and hence requires strong social groups wherein **language** can develop (maybe again first gestured/signed, then voiced) to coordinate actions and easily pass on knowledge; also a flexible **digestive system** allowing for a variety of diets and thus adapt to many different or changing environments. I don’t think carnivores, e.g. cats and dogs, will ever be pressured enough to evolve that much. It’s more likely omnivores or perhaps herbivores, who can eat fruit not just grass or leaves, will succeed after several hundred-thousand to few million years. Unless the climate changes dramatically, mammals are probably a safer bet than e.g. reptiles, birds or even fish (incl. whales and dolphins), but I wouldn’t rule them out either. Hatching eggs, for instance, could be an advantage – the ability to fly or swim less so. Keep in mind that during recorded history which slowly approaches ten thousand years there have not been observed any significant lapses in freely evolving animals or plants, but those bred and curated by humans have changed a lot. The quickest path to conscious, sentient beings besides us is one paved by us, be it by genetic modification or through advanced technology. That could happen in just hundreds to thousands of years, maybe even in tens, which is several magnitudes less than with undirected evolution. And then there is also the hive mind that maybe also could develop sufficient intelligence to become self-aware. That would take much longer to happen than a second coming of the mammal. By the way, as cities crumbled they slowly became the possible sites of future mines since we already moved and concentrated lots of natural resources there. Some other remnants could also last long enough to be beneficial for a future civilization, even cultural ones. [Answer] To expect just like another humanoid being it may be won't occur at all. But if dominant is the keyword here, maybe in just few years [a population of rats would be exploded](https://www.youtube.com/watch?v=RJA4IW_pkeo). While there will be small to none chance of them evolve to be just like us, they would likely will advance and dominate. Right now they are already everywhere, lurking in the dark side of man made structures globally. When there wasn't any human, leaving our live stock and food unguarded, [they would stepped out and claimed it for themselves](https://www.youtube.com/watch?v=r3RLmErp43k). When there wasn't any of our processed food left, their rapid breeding would sustain themselves a bit longer, made them [cannibalistic](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2211618/) before they expanded to rural areas and eat anything they could. Imagine a cannibalistic enormous half bald sewer rats that roam on post apocalyptic cities, it would cause a mess more than zombies can ever did. [Answer] As others have pointed out, it *might* take a long time -- or never happen at all. We don't have good data. Speculation: If humans suddenly and silently vanished, leaving everything else as is, then we'd have a situation markedly different than evolution to date. Short term, there'd be buildings, relatively non-perishable food, water -- and all sorts of human artifacts, just waiting for a similar species to make use of them. What species are likely to do so? 1. Somewhat intelligent species (primates, some cetaceans) 2. Animals that can manipulate human artifacts and especially tools (primates, elephants) 3. Animals that have seen humans and their artifacts in use -- especially tools and simple weapons -- so any pet species or lab animal, but especially monkeys and chimps. With the humans out of the way, I suspect that a few lucky monkeys and chimps in urban areas would soon be living large on what we'd left for them. Those animal's offspring would have a distinct survival advantage.... Personally, I think that there'd be visible evolution toward man-like intelligence in a hundred generations, so ballpark a thousand years. [Answer] Like the comments have stated, What kind of intelligence are you looking for? But, From my knowledge (as no expert in anything whatsoever), Humans have extremly good cumulative intelligence: as in what is learnt in one generation is passed down onto the next allowing for innovation and improvement over relatively few generations. This is due to the fact that humans only need to see something happen once or twice before they learn how to do it themselves (unlike chimps whom every generation have to learn an ability from scratch all over again). Another factor to consider is what animal they are evolving from. For example, Humans could create and use the tools they did because their evolutionary ancestors had paws (hands) made for gripping. Dolphins on the other hand, whilst they are intelligent and do use tools, have only their mouth to grip onto objects. Therefore if you wish to create a species similar to humans they must not only have the right type of intelligence, but also the means of which to use that intelligence in a manner similar to a human. So to conclude, There are plenty of animals with intelligence near or on par with humanity but overall to create what i think you're looking for you need: A social species (in which social intelligence can grow), cumulative intelligence (where ideas can be spread and improved upon quickly), an environmental pressure which encourages forethought and creativity (such as rapid climate change), and a species with the physical abilities necessary to use, interact and create in a manner similar to humanity. [Answer] Society is more important than intelligence in the evolution of technological adept beings. Everything you know about how the world works is learnt. You might think yourself incredibly clever, but the fact is that what you're thinking at any point is built upon thousands of generations of learning and lost learning. Without an appropriate societal backdrop, learning is lost. If a solitary creature learns something, of what use is that to it's species? None. If it passes it on to it's children and they die [or otherwise fail to engender use] before passing it on in turn, what use is that to the species? None. Learning requires more than just invention. Intelligence is not linear. A human brain is not evolved to nor used to simply think from A to B, a human brain performs multiple simultaneous tasks some of which interfere with or aid the 'A to B' thinking process. We can assume that non-human intelligence will have to operate in a similar fashion, given our experience of various types of system architecture, superior hardware is not the only requirement for a superior system. I bring this up because it's entirely plausible to have a brain with inferior (apparent) hardware to a human that actually can think logically, that could streamline it's own cogitative proces, that cerebral functions were separated more clearly from emotional responses or bodily demands etc etc and thus offer superior results (in at least one sense.) We can hardly say any aspect of our behavior is 'bad' when we are capable of doing anything any animal can do..and better..and what we can do would not have reached this point were it not for some character traits that might seem suboptimal in retrospect.. but.. Imagine an organism that through some quirk of evolution never lied or bore false witness? The time saving! I wouldn't need to check fifteen different scientific papers and still wonder "yeah, but their dept is mostly funded by x or y" Granted it's true that humans to the best of our knowledge are unique in the universe, but it's possible intelligent societies could evolve within just a few thousand years, because as I say it's not about pure native intelligence, but the ability of a species as a whole[or at least in significant groups] to benefit from technology, which in turn then allows the selection process to favor intelligence and better ability to manipulate tools over sheer native survivability. It's a mistake to think one thing happens then another with any kind of finality, evolution is concurrent with life, society evolves with technology, one generation might actually not be as capable as the last, despite the most intelligent reproducing more...etc Look at societies today, there's nothing about flooding, rising sea levels, etc that humanity can't cope with as a species, but local interests and local resources and local planning often simply aren't up to the task, one group ignoring warnings from other localities that they need to work on their irrigation and drainage systems is not a sign that the whole species is flawed..just as if one bee attacks a camper isn't a sign that all bees ought be poisoned. For remnants of human civilization: a dog with a little experience knows the difference between a bush and a fence even if it doesn't watch it being built/growing. People tend to make gates, let's look for a gate. In a society capable of basic tool making this would [clearly] be a massive influence, the differentiation between synthetic & natural allows us to infer purpose, that inference allows us to imagine of what use that construct and it's purpose might be to us. No different to seeing another human using a tool we've never seen before. Granted ofc the purpose might be beyond divination, or billions of man hours might be sunk into talking about how "we do/n't know why the gods built this" but people have shown the ability to do this about storms, particularly big trees, cherry blossoms, etc etc, so it can hardly be called a handicap.. Speaking of dogs..if mankind (and mankind alone) vanished, dogs would obviously spread like wildfire. I'd give them the best chance of dominating every landmass..and given hundreds of millions of them each having their own go at 'society' you might get an intelligent society out of them sometime within say..50k yrs. Ofc I say that coz more bipeds would be boring. [Answer] Case in point, the intelligence of turtles has been steadily increasing for about 210MY, despite setbacks like the K-T event. Its possible that in the absence of humans or a postulated parallel Universe where for whatever reason the Neanderthal/AM human crossbreeding introduced a fatal genetic defect, parasite or virus resulting in extinction in about 61.3MY turtles would have reached the intelligence of dogs. Of course, corvids and small mammals would have reached their zenith long before but its entirely possible that progress could stagnate due to brain size limitations. The brain is more complex than mere size and African Grey parrots seem to be the upper limit (2.3yr old child) ]

[Question] [ Giant Spiders are a traditional element of fantasy worlds. They prey upon most human's primal fears, and are easy to make as evil as possible.  (Note: Not to scale) But are they actually plausible? What kind of environment would be required to sustain a sizable population of giant spiders? What can they eat, and how much of it would be required? Assume: * Fantasy world, ala Middle Earth/Azeroth/etc... * These spiders are social creatures. Most depictions of them in fiction have them ganging together in swarms of at least a dozen. * Sentient creatures are only going to be victims a couple of times before the spiders' territory becomes known and avoided. * Giant spiders, for some biological or environmental reason, exist. [Answer] **Summary**: Yes it would be possible. If the spiders are 40 kg, one deer would feed about 47 spiders for one day. A large forest area could support many spiders. Math note: assume that the word "calorie" actually means kilocal or Cal. I'm going by food calories and not chemistry calories. --- A white-tailed deer weighs about [100 kg](https://en.wikipedia.org/wiki/White-tailed_deer#Size_and_weight) on average. Of that 100 kg, we will assume that about 80 kilos will be eaten by the spider. The "shell" of the deer won't be eaten by the spider, and it is most likely that the spider won't be able to suck the deer dry. 30 grams (1 ounce) of deer meat has about [45 calories](http://www.sparkpeople.com/calories-in.asp?food=deer%20meat) in it. So one deer will approximately have: $80,000/30 \* 45 = 120,000 Cal$ How food a spider needs per day varies widely depending on the lifestyle of the spider and the species, for this post I will use a tarantula as an example. One tarantula owner said that his 200 g tarantula ate roughly [5-50 Cal](https://www.quora.com/How-many-calories-per-day-do-spiders-need-to-live) a day. For the rest of these calculations, I'm going to use 25 calories a day because that's medium range. Let's assume that the giant spiders weigh 40 kg. That's about 200 times the size of a normal tarantula. So $200\*25=5,000$ calories needed a day. That means one deer can feed about 24 spiders for one day. Now spiders can last a long time on one meal, so the spiders wouldn't necessarily eat a deer every day. A spider that large might also need more energy for a better circulatory system or other bodily functions. But even so these spiders could easily survive on the food in a normal forest. A Pennsylvanian forest (with human hunters) has roughly [30 deer per sq. mile](http://www.deerandforests.org/resources/Deer%20Carrying%20Capacity.pdf). A group of twelve spiders would need to have only a couple square-mile territory. Thanks to Shempi and Shisha for noticing math and information errors in this post. --- Now for some fun. MiraAstar asked how dwarves would figure into this. According to a *Lord of the Rings* wiki, average dwarf height is [4' 9''](http://lotr.wikia.com/wiki/Dwarves) (1.4 meters). Dwarf weight was not recorded, but I guessed that a dwarf would have a BMI of roughly 26, due to their tendency to be overweight. This would put the average dwarf at 130 pounds (59 kg). I'm also going to extrapolate the dwarf meat would be about as high energy as pork, which has [229 calories](http://www.livestrong.com/article/339744-how-many-calories-does-meat-have/) per 100 g. Figure that a dwarf is only 70% edible, and you have 41.3 kg of edible meat. $41,300 g \*229 Cal/100 g = 94,577 Cal$. In other words, an average dwarf has about 94,577 calories in him. $94,577/5000 = 18$, so one dwarf could feed about **18 of our 40 kg giant spiders.** --- **Original Post**. The part assumed that spiders only drank the blood of their victims (which is incorrect). Left here because I spent time writing it so I don't want to delete it. Let's do some math: A liter of blood (in a human) has roughly [450 calories](http://www.maynardlifeoutdoors.com/2010/09/calories-in-human-blood_15.html) in it. An average white-tailed male deer weighs around [100 kg](https://en.wikipedia.org/wiki/White-tailed_deer#Size_and_weight). A deer that size has about [six liters](http://www.huntingnet.com/forum/bowhunting/269696-how-much-blood-does-deer-have.html) of blood in it. So $6\*450 = 2700$ calories. That's very rough numbers, but for this question it will do. It's not easy to tell how much a spider will eat, it depends largely on the species and/or the behavior of the spider. This question will assume that the spiders act like a tarantula. I'll also assume that the spiders weigh about 20 kg. That's about 100 times the weight of an average spider. According to one spider owner, a 200 g tarantula eats about [25 calories](https://www.quora.com/How-many-calories-per-day-do-spiders-need-to-live) a day. So $25\*100=2500$, meaning that these massive spiders would eat about one deer a day. In Pennsylvania, there are an average [30 deer per square mile](http://www.deerandforests.org/resources/Deer%20Carrying%20Capacity.pdf). This makes the numbers of deer run pretty low if there are twelve spiders. But with other animals (a bear could probably feed a couple of spiders) and a range of hunting several square miles, then there would be enough feed. Sometimes spiders eat more than that in a day, sometimes less. Most of the numbers in this post are averages. [Answer] As far as dietary requirements go, there's **absolutely no problem** with giant spiders. They'd have essentially the same dietary needs as any other large predator, and so any environment able to support, say, wolves or bears or tigers could also potentially support giant spiders of similar size. (In fact, since spiders are [ectotherms](//en.wikipedia.org/wiki/Ectotherm), they could potentially survive on a sparser and/or less regular food supply than mammalian predators. In that respect, reptilian predators like large snakes or crocodiles might provide a better comparison.) What prevents spiders from growing a big as a bear in real life is not food supply, but difficulties with scaling up the [arthropod](//en.wikipedia.org/wiki/Arthropod) body plan. The [main issues](http://evolution.berkeley.edu/evolibrary/article/_0/constraint_01) appear to be the exoskeleton (and the ensuing need for moulting), as well as oxygen intake: * The bigger the animal, the thicker, even in proportion, its skeleton must be to support its weight. A thicker skeleton is heavier, and thus requires stronger (and thus thicker, and heavier) muscles to move it, which in turn need more skeletal support, and so on. At some point, the skeleton just can't support muscles that would be strong enough to lift it. This is a simple consequence of the [square–cube law](//en.wikipedia.org/wiki/Square-cube_law), and applies equally well to animals with internal skeletons as to those with external ones, but it appears that, at large sizes, an internal skeleton is more efficient at supporting the body, and can therefore support larger body sizes. * Another big issue with arthropod exoskeletons is that they can't grow with the body, but must be shed and replaced by [moulting](//en.wikipedia.org/wiki/Ecdysis). A moulting spider is weak and vulnerable, and the bigger the spider (and thus the thicker the exoskeleton), the longer this "callow" phase lasts. For large tarantulas, like the [Goliath birdeater](//en.wikipedia.org/wiki/Goliath_birdeater), the new exoskeleton can take hours to dry and harden; for a hypothetical bear-sized spider, it would likely take days. During this time, the spider can't move and is essentially helpless. About the only way a giant spider could survive moulting would be to dig a burrow and hide in it, hoping that no opportunistic predator spots it before it's capable of defending itself again. (If the giant spiders were social, they could potentially guard and defend each other while moulting, but this presupposes a very advanced social structure and comes with costs: the spiders that are guarding their moulting pack-mates can't be out and hunting at the same time. Still, if you want to have marginally realistic giant spiders in your fantasy setting, this seems like the way to go.) * For many terrestrial arthropods, such as the insects, the actual size-limiting factor appears to be their (relatively) passive [respiratory system](//en.wikipedia.org/wiki/Respiratory_system_of_insects), which relies on air diffusing directly into the tissues via a network of open-ended tubes called trachea. This works well at small sizes, but scales poorly as the body gets bigger. Some evidence for this hypothesis is provided by fossils of [very large insects](//en.wikipedia.org/wiki/Meganisoptera) from the Paleozoic era, when oxygen levels in the atmosphere were higher than today. Many spiders, however, do have an active oxygen transport system with [book lungs](//en.wikipedia.org/wiki/Book_lung), so they might not be so susceptible to this particular problem. Still, your giant spiders are going to need efficient lungs to absorb oxygen, and an efficient heart to distribute it into their tissues. (The last part is a non-trivial one; the fully divided [double circulatory system](//en.wikipedia.org/wiki/Circulatory_system#Other_animals) in birds and mammals is the result of considerable evolution.) [Answer] First question is, **How large could they get?** Therefore we must know, **how** they grow. Simplified: Insects and Spiders have growth-hormones, just like mammals. But their exoskeleton can't grow with them. They have to change it from time to time, as they get too large for their skeleton. So while growing, the growth-hormones do not increase and at some point the hormone per blood rate will be so low, that they do not grow anymore. This is the time when they change their skin. After they take off their old skin, the growth-hormone production increases and they start to grow again, this is a loop that lasts for their whole life, but decreases more and more over time. [www.iflscience.com/plants-and-animals/why-monstrously-large-insects-and-spiders-dont-exist](http://www.iflscience.com/plants-and-animals/why-monstrously-large-insects-and-spiders-dont-exis) So this tells us that they will grow slower and slower as they get larger. A huge spider (let's say dog-size) must be very old, multiple 1000's of normal spider lifetimes I would guess. But there is another (real(!)) problem: The circulatory system of Spiders works differently than what we know from mammals ! [Image of a spider](https://i.stack.imgur.com/LoNYu.jpg) They do not have a heart like we have, but some kind of tube that pumps the blood from one end of the body to the other. Their organs just "hang" in the blood-soup. This kind of circulatory system is not able to supply a large body with blood due to pressure-problems. There are fossils of bigger insects and spiders, but scientists assume that the air pressure was significantly different than today. So if you want to make big spiders in a realistic environment, you must change either the air pressure or the gravity (which will also lead to lower air pressure). **Second question, what can they eat and how much?** Big Spiders like Tarantulas eat small mammals and birds, when they can get them. Also, many spiders practice cannibalism. So if they can't find easy prey, they will eat their brothers, sisters and parents instead. So a big population will probably not starve completely when prey is low, they will simply eat each other. When prey is plentiful, a single female can lay hundreds and thousands of eggs and push the population back to old size with ease. Essentially, they eat every living thing that they can get down. But they still must be aware of dangerous fights. If they do not have to take a risk, they avoid it. How often they must eat depends on their behavior. Hunting spiders have to eat much more often than web-building species. But both can last long periods with none or low food. The bigger problem is water supply. Because they don't get their liquid from prey, they have to drink. The real spiders in our world do this from waterdrops and puddles. Huge Spiders won't be able to drink waterdrops, so they have to find lakes or something. Therefore I assume that they cannot live in dry caves. [Answer] Spiders don't need to eat that much. In terms of food requirements, giant spiders would be fairly supportable by most environments. As per [Kleiber's Law](http://en.wikipedia.org/wiki/Kleiber's_law): > > For the vast majority of animals, an animal's metabolic rate scales to the ¾ power of the animal's mass. Symbolically: if q0 is the animal's metabolic rate, and M the animal's mass, then Kleiber's law states that q0 ~ M^¾. Thus a cat, having a mass 100 times that of a mouse, will have a metabolism roughly 32 times greater than that of a mouse. > > > The reasoning behind this is that smaller an animal, larger the fraction of their body mass consisting of structure rather than reserve. Structural mass involves maintenance costs, while reserve mass does not; ergo small animals respire faster and need more calories per mass than larger ones. Assuming Kleiber's Law to hold true for these giant spiders, we can calculate their metabolic requirement by comparing it to a "real-life" spider of comparable activity levels, plus caloric requirement of silk production. A *Goliath Bid-Eater*, the largest tarantula species by mass, weighs around 70-80 g on average (though it can grow to be 170 g). According to spider-care websites[[2]](http://www.tarantulaguide.com/tarantulas-food-water-diet/), a diet of 6-8 crickets per week is sufficient for "the larger tarantula species". That's only about 10 Calories a week! By this calculation: > > 70 g spider => 10 Cal / week > > ∴ 70 kg spider => 10 \* (1000^¾) Cal / week ~ 1780 Cal / week. > > > Let's take that number as "Caloric requirement at rest", since a captive Tarantula would have limited activity as compared to a 'wild spider' who would need to actively hunt for prey. For spiders, **a significant source of metabolic cost is also silk-creation.** [[1]](http://academics.holycross.edu/files/biology/CmpBiochmPhys_v57A_p321.pdf). So the more web/silk a giant spider produces, the more calories it will need. Spider silk is light - enough spider silk to go around the world once would only weigh 500 g, but let's say these giant spiders spin proportionally thicker silk, so that the same length of silk weighs a 100 times more. > > **Caloric value of silk** ~ **4500** Cal/g > > > So a 70 kg spider producing just 1 g of silk a day would need an additional caloric intake of *4500 Cal* per day for silk production. Since real spiders eat enough to tide them over for days at a stretch: > > Assuming **70 Kg Spiders** that produce **1 g Silk per day** > > And **100 Kg Deer** that are **80% Consumable** at **[1.5 Cal/g](http://nutritiondata.self.com/facts/lamb-veal-and-game-products/4814/2)** with total **120K Cal** > > => **One (1) Deer** would feed **Four (4) Spiders** for **Seven (7) Days** > > > **ETA:** However, even with a thread 10 times thicker (10 microns => 100 microns) and 100 times heavier than normal spider silk, 1 g of spider silk would be more than 166 m (1.31 g/cc /(0.005 cm \*0.005 cm \*pi)), so it is highly unlikely that even a giant spider would be producing 1 g of silk a day. [Thanks to @Sempie for bringing my attention to this]. So more realistically, unless silk production is significant enough (in terms of width/density/length) to weigh a lot, it would have insignificant calorie cost. Additionally, Spiders often recycle their web silk. If these giant spiders are not expanding territory, they could be eating old silk to 'touch up' their webs, which could eliminate external (non-silk) caloric requirements even more. Hence: > > Assuming **70 Kg Spiders** with negligible Silk production > > And **100 Kg Deer** that are **80% Consumable** at **[1.5 Cal/g](http://nutritiondata.self.com/facts/lamb-veal-and-game-products/4814/2)** with total **120K Cal** > > => **One (1) Deer** would feed **Thirty-Three (33) Spiders** for **Fourteen (14) Days** > > > The paper linked above also gives an equation for activity cost of web building. Total Cost of Web Construction ~ (4.5 \* Weight of Web in mg) + [Weight of Spider in grams \* (2.79 \* Weight of Web in mg)] calories I'm assuming this activity cost gets taken care of by Kleiber's Law, but if it *doesn't*, then the dietary requirements would be: => (4.5 \* 1,000) + [70,000 \* (2.79 \* 1,000)] = 4500 + [70,000 \* 2790] = a whopping and unsustainable 195,304,500 Calories! (An adult African elephant needs around 70,000 Cal per day for comparison) [Answer] The problem is not so much dietary as the two thirds power law. As you scale up a creature, the mass increases as the cube of the size, while areas increase as the square. That means the stress on the cross section of the legs goes up linearly with he size, which is why large creatures have larger legs (proportionate to their body size) than small creatures. Similarly, spiders do not have a circulatory system to move oxygen deep into the body. They depend on diffusion, which works over fraction of an inch distances, but not over many inches. A great essay is ["On Being The Right Size", J. B. S. Haldane](http://irl.cs.ucla.edu/papers/right-size.html) [Answer] The tarantula Aphonopelma anax is on average 6.91 g for males and 15.72 g for females [[1]](https://jeb.biologists.org/content/205/18/2909#T1). According to tarantula care websites, a female Aphonopelma anax should be fed 2 large crickets per week (but they can go months without any food). A fully grown house cricket is 0.34-0.61 g in weight, and is 60% protein, 35% fat and 5% carbs. This makes 1 cricket 1.96-3.5 calories, so a 15.72 g tarantula ideally consumes 3.93-7 calories per week. A 1 kg tarantula would need 88-158 calories per week, 498-886 for a 10 kg spider, and 1955-3483 for a human sized 62 kg spider. A 475 kg spider would need over 9000! A 1.6 kg rabbit has about 6000 calories in it, so nutrition should be the least of your worries, since your giant spider would have difficulty getting enough oxygen and it would have joint problems. ]

[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. In my story a man who works in Military Intel gets early warning that a nuclear attack on his base is inbound. He abandons his post, grabs his wife and kid from on base housing, and books it out of there at 90 miles per hour with 20 minutes to spare. He is 30 miles away from ground zero when the strike happens. This is far enough away that he and his family are 10 miles outside of the air blast radius. The idea is that they continue driving as far as they can before running into clogged roads or running out of gas. My question is, does the EMP stall their car? Does EMP affect cars? I know that EMP is not the magic anti-technology ray that Hollywood makes it out to be, but I don't know what the actual real world effects on a vehicle would be. [Answer] # Depends on the car It also depends on luck, sometimes an EMP will do permanent damage, sometimes it won't. The chances are you'll blow a bunch of fuses at the very least. If you're running a diesel then it'll probably keep going. Not because the electronics are any more robust but because diesel doesn't actually need the glow plugs, it'll run on compression ignition. Depending on which fuses you blow, it may not start again if you stop the engine. If you fry the engine management system it'll run less efficiently, but it'll keep going. I once had a modern diesel running without fuel pumps, without glow plugs, without engine management, and only 3/4 cylinders, diesels keep going. For petrol cars, the more modern and high spec the car, the more damage it's at risk of taking. If you're talking about a new BMW or Mercedes there's a reasonable chance it'll be completely knocked out from permanent damage to delicate electronics and drive by wire systems. Almost nothing you're holding is directly connected to the vehicle control it represents, it all goes through the computer first, even the steering. If you're talking something from the 1970s with minimal electronics and all the refinement of a cart, it may even keep going with a brief cough as it cuts out during the pulse and then bump starts itself from the momentum. --- # Of course you're not the first to consider this issue. The [EMP Commission](http://www.empcommission.org/) (appears legitimate) have [written a report](http://www.empcommission.org/docs/A2473-EMP_Commission-7MB.pdf) that includes considering the damage to vehicles from EMP which implies that there's no real issues. However it should be noted that this report only covers vehicles up to 2002, current high spec vehicles have a far higher level of "drive by wire" computer control. *From page number 115 (pdf page 131)* > > We tested a sample of 37 cars in an EMP simulation laboratory, with automobile vintages ranging from 1986 through 2002. Automobiles of these vintages include extensive electronics and represent a significant fraction of automobiles on the road today. The testing was conducted by exposing running and nonrunning automobiles to sequentially increasing EMP field intensities. If anomalous response (either temporary or permanent) was observed, the testing of that particular automobile was stopped. If no anomalous response was observed, the testing was continued up to the field intensity limits of the simulation capability (approximately 50 kV/m). > > > Automobiles were subjected to EMP environments under both engine turned off and engine turned on conditions. No effects were subsequently observed in those automobiles that were not turned on during EMP exposure. The most serious effect observed on running automobiles was that the motors in three cars stopped at field strengths of approximately 30 kV/m or above. In an actual EMP exposure, these vehicles would glide to a stop and require the driver to restart them. Electronics in the dashboard of one automobile were damaged and required repair. Other effects were relatively minor. Twenty-five automobiles exhibited malfunctions that could be considered only a nuisance (e.g., blinking dashboard lights) and did not require driver intervention to correct. Eight of the 37 cars tested did not exhibit any anomalous response. > > > Based on these test results, we expect few automobile effects at EMP field levels below 25 kV/m. Approximately 10 percent or more of the automobiles exposed to higher field levels may experience serious EMP effects, including engine stall, that require driver intervention to correct. We further expect that at least two out of three automobiles on the road will manifest some nuisance response at these higher field levels. The serious malfunctions could trigger car crashes on U.S. highways; the nuisance malfunctions could exacerbate this condition. The ultimate result of automobile EMP exposure could be triggered crashes that damage many more vehicles than are damaged by the EMP, the consequent loss of life, and multiple injuries. > > > [Answer] One other consideration is the car in the line of sight of the nuclear blast at detonation or not. Estimating a Nuclear Bomb's destructive capacity is a very imprecise science. For example, the Nagasaki device (Fat Man) was theoretically more destructive than the Hiroshima device (Little Boy). In reality, the reverse was observed. This was because Little Boy was detonated over what was an open field with little to stop the destructive forces of the bomb. Fat Man detonated below the mountain tops of a valley, which contained much of the destructive energy of the blast to the valley's sparing the bulk of the city, which could still witness the destruction. The destructive portion of the bomb's blast are light/heat radiation and the over-pressure. In order, you will first see the light, then feel the heat, and then see the overpressure. The former two are near instantaneous. if you are in line of sight, I personally call this the "Simba's Kingdom Fire" because everything that the light touches will burst into flames. The closest known survivor to Hiroshima Ground Zero was in a bank vault at the time of the raid and was not exposed to the light/heat as the rest of the bank became engulfed in an inferno and then blown away. It's distance to GZ was measured in meters. The overpressure will be felt at progressively larger time gaps from ground zero. An air burst is more destructive than a ground burst because there is little to stop this, though the destruction of most of Nagasaki was prevented by obustructions that contained the blast, the affected industrial area was absolutely destroyed. Meanwhile, damage from the light at radiation at Hiroshima could be traced all the way to a grove of trees on a hill overlooking the Jinkaku-ji Temple in Kyoto... a distance of 361.2 km (225 miles) from ground zero. This is true of the EMP as it is line of sight only... it was believed that a full on Soviet nuclear war would start with a very high altitude burst over the continental US... high enough that no target is damaged... but almost every electronic device is put out of commission on the North American Continent. The car may however still survive if something was obstructing line of sight from the blast. Being under a tunnel might give you the chance to get out of the way... the EMP in a full on attack on the US will normally proceed the attack's more destructive capability. A closer to earth air burst will likely be safe if he is safe from the light/fire destruction. [Answer] ## Powertrain: Dumb luck will be the ruling factor It's all going to depend on the luck of the draw and how the hit occurs and how EMP waves bend around local terrain and the metalwork of the particular car. First, remember the powertrain is *already substantially inside a Faraday cage*. The hood is metal, the unibody is metal and so is the engine - this largely wraps the engine package. Nonsense to dismiss: that some cars are "mechanical" and will Just Keep Working. Nosirree. Every modern car is [FADEC](https://en.wikipedia.org/wiki/FADEC). Even the diesels, *remember when [VW cheated the Smog tests](https://www.bbc.com/news/business-34324772) by detecting when the car was on a test stand and detuning the engine during those times*? The only way to do that is with FADEC. All the other builders who were not cheating also required FADEC. **So all modern cars are computer *controlled***. I.E. the computer decides when (i.e. which microseconds) the fuel injector fires, and it does this in real-time on the fly. If the computer gets borked, the car doesn't stay at the last throttle position, **it simply forgets to inject fuel** starting right now, so the engine dies instantly. The days of there being a basically mechanical carb/FI system with computers "only doing trim optimization" started in the 1970s with carburetors, and ended in the early 1990s -- killed off dead in 1996 when OBDII became law. OBDII requires FADEC. But even in 1991 you'd be hard pressed to find a non-FADEC engine, probably in a light truck. Why? It's a darn good technology that makes engines run better, *much* longer, and more powerful too, by enabling *other* performance tech. ## Older automobiles are practically extinct *on the road* The current mix of automobiles found on the highway contain essentially zero pre-FADEC era cars. You might find older trucks without FADEC, the bigger the more likely, but only up to a certain size. California has achieved a practical peace with classic car lovers, based on the following fact: **There aren't enough of them left to make a difference**. No, I mean there are loads. **But they're not daily drivers**. They run so rarely that they don't have a significant impact. Simply put, they're not worth regulating. As an author, that means *if* you prioritize a search for an EMP-proof car, look for well-cared-for but rarely-driven collector cars. *You won't find one in an office parking lot, though*. It'll be in an enthusiast's garage. Or out back up on blocks, but that one won't run. ## Creature comforts: All bets are off Powertrain computers on modern cars are *already* extremely hardened - not against EMP but just against *failing generally*. Some fool shorting an oxygen sensor to 12V, a wiring harness meltdown in transmission control wiring, whatever. That's powertrain. Now modern cars have **a whole second \*tranche** of computers in the carbody, and those don't run the powertrain, they run the human/creature comforts. For instance the left door has 1 power window motor and *Four* power window switches. 14 wires? Not anymore, now it's 2 power/ground wires, and two thin little signal wires, and embedded computers in every door that chat over the signal wires. And in recent years, as you well know, this "body-side" stuff has *exploded* to be *the reason you buy a car* - built in Nav, Siri, Alexa, smartphone integration, your music, Sirius Radio, all the smart-car stuff potentially including the autopilots - some cars *more than 50% of the cost of the car is in this consumer-appeal electronic cruft*. This stuff is all body-side, and there are places where the body is not steel, **but the dash and door panel interiors are not steel at all**. EMP will ignore all that and reflect in unpredictable ways off the parts of the car which are metal, exposing the body-side stuff to a lot of potential damage. So there's a pretty good chance that your engine will work but your speedo will not. Sirius works but ONStar does not, turn signals fail, and you can't roll down your windows. And the A/C won't turn on because the sophisticated comfort control took a hit, that doesn't doom you, but the fan won't run either, *and that dooms you*. Ever drive a car with no fan and no windows in the summer? You cook. It's the same exact physics as dogs and babies dying from being abandoned in the car, except you happen to be moving. However if the blower works, and a smart person could "jumper it so it's hard on" depsite blown electronics, that makes the car interior livable - though if it's a sunny day over 60F, you *will* need quite a bit of hydration, solar load beats you up bad. Actually for best freeway fuel economy you want windows up, A/C off, blower on max. "Windows down" is bad due to aero-drag, and A/C on takes a lot of fuel. [Answer] There are two things to be concerned about, EMP and nuclear radiation. Both will affect the engine. At the distance you are talking about, the mechanical parts of a car are unaffected by nuclear radiation or EMP. The only part of the engine that is affected is the electronics. **EMP** One thing to consider is that the body of most cars is metal and forms a Faraday cage around the engine and all its electronics. The shell of the car will provide a lot of shielding from E-field components of the EMP. If the shell happens to be steel (as in an older car) then it will also provide H-field shielding. For EMP specifically, there is a momentary voltage gradient throughout the space of the car. it can look like a voltage is applied on various points (according to the field gradient in the pulse). Note that the smaller the distance the smaller that voltage will appear. The copper wiring in the car is not directly damaged by radiation or EMP. But it can act as an antenna that can gather energy and put it into circuit cards, where it can do damage. Most modern electronics include ESD protection devices in nearly every microchip. There is also power supply capacitors on each circuit card. All of the power supply capacitors and ESD devices will actually try and locally absorb the EMP. For highly miniaturized electronics (like integrated circuits) the effect can be quite small and won't directly do much damage. Modern CMOS integrated circuits contain opposing pairs of transistors between power and ground. Normally only one of each pair is on. But when exposed to EMP induced voltages both can turn on, causing a short between power and ground, which can destroy the chip. For the most part, the destructive energy that kills electronics exposed to EMP comes not from the radiation itself, but rather from the batteries or AC outlets that power those electronics. Turning off the car and disconnecting the battery will drastically reduce the damage. **NUCLEAR RADIATION:** The fiberglass material that the circuit cards are made from is immune. As well as the copper traces and planes that form the connections in the circuit cards. Ceramic capacitors and film resistors are largely unaffected. The only items that are really affected by nuclear radiation are semiconductors (diodes, transistors, integrated circuits). When particle radiation from an atomic detonation hits semiconductors it causes them to conduct. For diodes, the reverse leakage current increases. For transistors, they can become turned on. Unless the exposure is at a very high does rate, or for a very long time the effects will disappear once the radiation disappears. Modern CMOS integrated circuits contain opposing pairs of transistors between power and ground. Normally only one of each pair is on. But when exposed to radiation both can turn on, causing a short between power and ground, which will destroy the chip. With respect to the radiation, if you simply remove power from the device, then its likely that it may not suffer damage. In general electronics are usually only damaged by nuclear radiation when they have power applied. For the most part, the destructive energy that kills electronics exposed to radiation comes not from the radiation itself, but rather from the batteries or AC outlets that power those electronics. If you knew when the blast was about to happen, then just stop the car, pop the hood, and disconnect the battery. Once the EMP has passed, reconnect the battery and you should be OK. ]

[Question] [ The apocalypse has happened, but humanity survives. People still remember the technology they had, but too many of the people who really understood how it worked and how to make it have died, leading to many modern technologies being lost. The survivors want to rebuild civilization and hope to be able to recover the lost tech in time, but first they have to survive. A lot of medical technology is lost, too, and this is going to be a problem. General knowledge about healthcare (wash your hands, don't sneeze on people, basic germ theory, etc.) isn't lost so we can expect results won't be as bad as in previous centuries, but it's not going to be nearly as good as it is today. If you look at infant and child mortality, it was way higher in the past. [In the 16th and 17th centuries, 60% of all live births would not survive past the age of 16](http://amechanicalart.blogspot.com/2013/09/infant-mortality-then-and-now.html). Combine this with adults who die due to disease, accidents, etc., and it's clear that in order for society to simply survive, you need to have a lot of children being born. As you can imagine, this can easily present a problem for women in society. They'll need to spend a significant amount of their fertile years being pregnant and/or taking care of an infant who still needs to breastfeed. So, as a matter of simple survival the majority of women will need to fulfill a role that, in modern society, is often viewed as being a lesser role. The survivors of the apocalypse want to avoid women becoming second-class citizens in their society. They also know that they are not going to live to see the rebirth of modern society—it will take quite a few generations to rebuild humanity's numbers and recover the lost technologies. **How should the survivors of the apocalypse set up their society and culture in such a way as to prevent women from becoming second-class citizens?** Note that though this is important to the survivors, their first priority is for humanity to survive (second-class > dead). Their next priority is to place humanity on track to recover modern society. They aren't going to put these priorities at risk in order to prevent misogyny—women have won the fight for equality once, they can do it again if they need to. [Answer] You have to look at the situation realistically, and realize that equality is going to become an even more complicated topic than it is today. ### The Reality Civilization - as we know it - is gone. Technology, the great equalizer, is gone. You now live in a world where ***might is right***. If I'm stronger than you I'm in charge, and I take your stuff (maybe even your liberty, dignity, and rights). If you have a gun, you can shoot me, and claim those rights back. But if you don't .... Your biggest problem, right off the bat, is going to be food. A lot of us don't realize how much technological advancements play a role in farming these days - or indeed know anything about farming at all. The short and long of it is that ***farming is hard work*** (I should know: my grandparents are farmers, and I could never do what my grandfather still does at 84). The technology which enabled a couple of people (women, even) to manage a few dozen acres with relative ease has become a thing of the past. If you want to get anything done at this point you're going to need farm animals, tools, and a lot of muscle. This is vital to remember, because it - along with another important fact - helps identify why women were relegated to a secondary role in times gone by. **How it worked** You're a farmer. You need help to plant and harvest your field. Removing rocks, picking weeds, etc. - the joy of low tech farming. That help needs to come from someone capable of doing hard work *quickly*. That, 99% of the time, is going to be a **man**. While the men work the fields the women do the easier jobs. They bring the men water. Cook for them. They watch the children, mend clothes, feed and water the animals, etc. There's 1000 chores on which the survival of the family as a whole will depend, and these will be ***her*** responsibility. They are in no way less important, however it does tend to put her in a *subservient* situation a lot of the time. She feeds the man. Clothes him, etc. An uneducated person might look at this situation and think: *I'm getting all these things done for me, therefore I am in charge*. It's ***only human*** to reach this conclusion. The second important point, and people might not like hearing this one, has to do with re-population and reproduction. Technically, for any civilization to rise they have to put great value on their women (this is a historical fact, not something I made up). As others have pointed out, the bottleneck to population growth are the number of child-bearing women, not the number of men. You'd think this would mean that women would be highly valued. **However**, that's not quite the way it has worked out in the past. The reasons are complex, but can be highlighted by a few examples: A child-bearing woman is valuable in that she can mother children for a family (a man). To him, she is quite valuable. Another, stronger man may desire that woman, kill that man, and take her. This dynamic, which was absolutely universal in olden times (raiding a village, killing the men, the young, and the old and abducting the women). However, this intrinsic value does not empower women - it turns them into objects to be possessed. Another example ties right back in with farming. A woman, though she may mother several healthy children, cannot work and generate food while she is pregnant, and cannot generate much food (not nearly as much as the man) even when she is healthy and able to work all day long. If she were to have to support a couple of children on her own, she would fail, and they would all likely die (in a post-apocalyptic scenario where they have to fend for themselves this is the most likely outcome). It is the man (or men) who would fight off attackers (a little skewed with the advent of modern firearms), work the field, and ensure that the family have a roof over their heads (maybe by building it). The woman, ***while vitally important***, cannot do those things on her own. So now let's assume the worse: the woman dies during childbirth. The man finds another woman, or older child to take care of the home, feed the animals, cook, etc. and keeps doing what he's good at. Feelings aside, the man can keep his family alive. The lone woman will have a very difficult time of it. And thus, in a post-apocalyptic scenario, women become second class citizens. ### How to Preserve Equality What people are going to have to realize is that "equality" is not going to be defined quite the same way that it has come to be defined today. What we should be aiming for is ***equality under the law***, not the complete and utter banishment of sexism, etc. - we, in our modern society, haven't managed to do that yet. The people who survive the apocalypse are going to have little to no chance in that regard. And so, your community of survivors have to make sure to enshrine a Constitution which allows women the right to own property and titles , inherit property and titles (because humanity often falls back on a nobility-type system), and grants them the right to vote. Everything else at that point is window dressing, because this is what grants women real power: ***the ability to influence the economy and the legislation.*** As you yourself have mentioned, young women are going to be spending a lot of their years pregnant. You're going to have to build a group mentality that this is to be desired - simply because you need to repopulate the planet. For this reason you may want to move away from the classic one man, one woman style of marriage and families. A society which raises their children communally spreads a lot of the responsibility around. Men and women might reproduce and own property together, however you should try not to burden one woman with raising an entire brood. Instead, let the community come together, and raise the children in a school setting. This way, a group of women, or older children watch and educate everyone else, which frees up the rest of the women to perform other tasks, such as study medicine, perform tasks in local government, or even help organize the labor parties which the men are a part of. Send some of those women or older children to cook for the men working the fields. Better yet, organize a Cooking Corps, the members of which (women, the older children) cook for *everyone*. Even men can serve a few weeks as cooks in order to see that A) it's not that easy and B) give them some time off from back-breaking field work. Make sure to encourage education. Everyone should be literate. Everyone should know, and respect the law. Everyone should learn a bit about human history, so that they know humanity has something to strive for, not just survive. As far as security goes, train everyone capable of defending the town to use firearms, or whatever weapons you may have available. Defending a fixed position is not very difficult for a woman, or even a teenager to do, as long as they can batten down the hatches and shoot at the enemy. This is important because if an enemy bypasses your defense forces not only will the women and children not be completely vulnerable, but they will also be able to defend themselves from those of their own group who might want to do them harm (a wanna-be rapist, for example). Which brings us to the next point: enforcing the law. People should still be given the benefit of the doubt, and be presumed innocent. However, you will not have room to treat criminals as *nicely* as we do today. A man (or woman) who murders his brother in order to take his property should be hanged. A thief should be publicly flogged (shame is a great future deterrent), but then given medical treatment, and allowed to integrate back into society. Children should be strictly disciplined, and thoroughly educated. Respect for society should be the bed rock on which your new civilization will build. Outsiders, considering what the default state of humanity in post apocalyptic scenarios is, should be treated with distrust, yet slowly allowed to integrate. After all, you will stagnate if you turn them all away, or pick a fight with them. However, competition for resources should not be tolerated, and your group should build the mentality that they should talk softly, yet carry a very large stick indeed. Many of us have become pacifists today, yet that will not be possible in that world. Having to kill someone who tries to kill you, or put down an animal because if you don't eat it *you will die* is something that each of your citizens should be ready to do, for themselves, or for the good of the community. Technology and knowledge should be prized above all else, and sought out relentlessly. Scientific pursuit should be encouraged. Having a high literacy rate will aid you in this pursuit. In time, your community will become a beacon of hope in the the post-apocalyptic wasteland, and with that reputation you will get more recruits, and also attract more enemies who *want what you have*. Be ready to defend your people, stand by your principles, and all will be well. [Answer] # Change General Perspectives And Social Norms The first and foremost thing we would need to do is to change the social norms and general perspective about women's household work. The Soviets had a great method for this. Every woman who had several children and brought them up to be respectful citizens was given the title of [Mother Heroine.](https://en.wikipedia.org/wiki/Mother_Heroine) We would need to introduce this mindset in our society. There is nothing *lesser* in being pregnant and having kids. In fact a woman goes through the door of death to bear a child. It was true even in the past times when healthcare facilities were commonly available. It is more true than ever now, when we have lost that high standard of healthcare. Lacking those high standard facilities, the mortality rate of child bearing mothers is going to be much higher than before. We need to acknowledge the fact that when a woman bears a child, she does it through extreme pain, patience and love. We need to acknowledge that a housewife who raises her children to become active, honorable children of the society is doing one of the noblest jobs there are to do. We need to truly acknowledge the services of women in the society. # Keep Women In Government We have cities and town and we make town committees to collectively make important decisions about collective issues. We need to keep a quota for women in these committees. We also have juries and the legal system. Considering that women in general are not fit for the chair of judge at this time (lack of legal awareness and the general softness of nature), we should give them representation in the public juries. We should also give women representation in our governance system. 20% should be a fair share for higher level decision making seats. We should also try to keep women on seats where they have a lot of public dealing. This would help create a general air of seeing women as having equal honor and value as men. # Facilitate Cottage Industry Cottage industry (creating household items in homes for commercial use) would not only help provide us with daily necessities and accelerate trade, but would also help women to take active part in improving our society. This would also provide them with a positive and meaningful activity to participate in, during free time. [Answer] I don't see the situation as grim as you describe. Most of the modern medical technology is, let's say, on a falling branch of ROI. Most important contributors to children survival are aseptic and antiseptic measures, which are not the rocket science at all. The article you linked emphasizes that > > By 1930 the number of infant deaths had declined dramatically in many countries as the causes of infection came to be understood. Most progress up to this point was due to precautions such as hand washing and sterilization of milk rather than to actual medical advances. > > > So, expect your world to be at the 1930 level in that respect; not bad at all. Even though there are plenty of factors determining the status of women, this particular one should be disregarded. [Answer] Contrary to popular opinion, there is no reason human society is intrinsically misogynistic. If, as you say, your society makes a conscious decision to attempt to avoid that fate, they’re likely to succeed. Let’s run through some particulars. # Physical Force and Equity Societies do not, as a rule, run on physical force. If you have a society that is working relatively smoothly, especially if the society has generally agreed that peaceful coexistence is preferable to continual violence and danger, then you’re not going to need a great deal of violence to get things done. Indeed, violence will quickly come to be indicative of serious problems to be dealt with. The crucial point is that the society must hold the respect of the large majority of its members. Because each of us is individually associated with the collective, crimes against individuals appear, from the perspective of each individual, to be crimes against society as much as against individuals. This nullifies the “not my problem” effect that is so crippling in, for example, much of today’s United States. In essence, the notion of obedience to law—don’t kill, don’t steal, don’t rape, etc.—must rest on mutual social respect rather than on fear of punishment. In real life, we don’t just attack others and steal their stuff, nor does it usually occur to us to do so. This is because we respect the society of which we are members, and we recognize that the same respect is therefore due to other members. The notion that intensive, violent policing is absolutely necessary to prevent people turning into psychopaths is a sick fantasy, albeit a popular one. Most tribal societies do not have police systems at all, for instance. So we can set one point aside: although women will tend, all things being equal, to lose physical fights with men, this has very, very little to do with whether they will be treated as second-class citizens (or worse). # But What About Farming? Look up rice, the world’s most popular crop. Who plants and harvests it? Who maintains it in the paddies? Why… women and children? Huh. Apparently the notion that farming is automatically men’s work is a chauvinistic fantasy too. Now rice is not an ideal crop in all circumstances, but it’s a very good one in many. This is because while the total labor put into it is perhaps higher than with some crops, that labor can be stretched out over long periods of time. In addition, it tolerates a fairly wide climatic range. An interesting effect of a constant-labor crop like this is that children become remarkably valuable in the short term. You can certainly put an 8-year-old to work in the paddies without feeling you’re being cruel. The obvious example is water-cycling. You have a simple pedal mechanism (you can surely scrounge that from the wreckage of your apocalypse, or just build your own like the Chinese have for many, many centuries) with paddles or a water-screw. Put the bottom end in the lower paddy and the top above the upper one. Now pedal. The idea is to move water from the lower to the upper, slowly, in a controlled way, thus mitigating against the constant effects of seepage. Since it turns out that you get better crops the more precisely and constantly you do this, your children become valuable members of your farming society very soon. # Individualism One big concern that tends to come up in these things is an evaluation of what any given person can or cannot do on his or her own. Certain kinds of back-breaking labor seem to require men, because only men have the upper body strength to do it themselves. But this is a nonsense. To begin with farming. Rice, once again, points to another essential issue for your society: collectivism. Everyone gets rice equally. It’s not my paddy, my rice, but our paddies, our rice. But this point expands greatly. In our little town, Frieda makes furniture, Warren does weaving, Delilah is great at dying, and Charles makes cheese. When we sit down to a meal, do we celebrate Charles because he’s the most useful? Well, only if we’re crawling on the floor naked. Otherwise, everyone has contributed. And the same goes for Betty the baker, Sam the sausage-maker, and so on and so forth. This should be obvious. If you have a balanced, planned society, you draw on the skills and talents of each individual. All those abstractions about upper-body-strength and whatnot fail in the face of real life. Charles, for instance, is built like a gorilla… but there was that childhood accident, and he can’t walk without crutches. So do we send him out to do farming because he’s got a penis, or kill him because he’s not “whole,” or do we enjoy the cheese? In fact, almost nothing that has to happen in the village is intrinsically sex-divided. Interestingly, however, some tasks are likely to *become* so. The trick is to avoid this being seen as a matter of superiority on one side or another. Take weaving, let’s say. Anyone can do it—there’s no special strength or whatever involved. But in many communities through the ages, weaving became a female activity. Why? All kinds of local reasons, few if any now recoverable. But once you’ve established a situation like this, it tends to perpetuate itself. In essence, what happens is that a whole bunch of women get together to talk while they work. And they talk about what interests them, of course. And, as everyone knows perfectly well, if you get a bunch of women together to talk about whatever they feel like talking about, the conversation will tend over time to become woman-oriented. I don’t mean that women talk about mothering and menstruation and so forth all the time, only that women and men do tend to have socially-distinct conversation patterns in any given society. From a male perspective, the women may be gossiping or whining or whatever, but then again, from a female perspective the analogous male conversation is a bunch of grunting, fart jokes, and penis-waving. Neither is true—but these conversations do tend to be sex-restrictive. Now once weaving becomes a female activity in this sense, you’re going to see men somewhat disinclined to join, because they feel unwelcome and uncomfortable. (As a side note, I wonder whether your postapocalyptic equal society will be open about those gay men who do feel more comfortable in such social circles, and have them join the weaving.) Meanwhile, there are going to be analogous “male” activities: baking, let’s say. If in our society baking becomes a very masculine, even macho activity, what will happen? Pretty soon, they’ve probably got this whole thing going about how bread is a woman who has to be pressed into shape (or a breast to be fondled, etc.), and sweat, and heat, and columnar phallic ovens, and whatever. Now I choose baking for the simple reason that it does require considerable upper-body strength, it’s hard work, and in many societies the bakers—especially if part of a collective that includes threshing and milling—are male. But also because lots of societies deem any form of cooking intrinsically female. The point should be clear: sex-division with respect to labor is not about intrinsic abilities or the nature of any given task, but about social construction. Provided you want to end up with equity across the sexes, you need to make sure that people value cloth as much as they do bread (and so forth). # Equity and Law I suggest that you start with the assumption that law, in the strong sense, will be a minimal issue in your society. Not only is constant policing not necessary most of the time, but all the complexities of contracts and so forth are irrelevant to your postapocalyptic society. Furthermore, you have a problem working out what sort of law to depend on in the first place. Common law, a la Britain and the US, depends on precedent, which means a vast library of case law. But in your postapocalyptic society, has such a library been preserved well? Who’s maintaining it? Do the people generally trust the lawyers to do this? They don’t trust lawyers now, so why would they in the future? Inquisitorial law, as in France, has the advantage that at least it’s answerable to truth instead of precedent and opinion. And yet, the principal force preventing rampant abuse is very strong hierarchical submission: this court doesn’t abuse its power because the next higher court will crush it brutally if it does. We cannot count on a system like this in our broken world. There are other possibilities, of course, but my point is that *legalism* simply isn’t a good place to begin planning. So what does this mean for women? It means that women must be equal citizens *in actuality* and not merely *in law*. It means, to put that another way, that you can’t build your society by simply trying to legislate the morality you want: you have to build a society that works. # How It Really Works ## On the Farm Women can carry babies on their backs while doing an awful lot of farm work, from planting and harvesting rice to mucking out or feeding livestock. Children over about 6 months do not need continuous breast-feeding: they can eat “solid food” and be topped up with breast-milk whenever convenient. Children who don’t have to breast-feed constantly can be carried or watched by men just as well as by women. As social planners, you’ll want to focus on crops that are long-term sustainable in a number of senses. You don’t want to destroy your fields, certainly, but you also want crops that work well collectively. Rice is an obvious example, but there are many others. Corn is an interesting case: the planting is a brutal couple of days where everyone pitches in, and then there’s harvesting, drying, storage, and so on. But there’s also this weird thing that corn crosses very fast, and the only way to prevent this (or to do it on purpose) in order to keep the best corn for the future is to hand-pollinate. People have been doing this in Mesoamerica for thousands of years. And no, it doesn’t require men: it requires patience, intelligence, and care. Ultimately, your farms will center around collective labor. ## In the Village If you’re planning a society, you must insist that pure individualism is in fact selfishness. Everyone must cooperate in the face of the apocalypse, or all will suffer and die. Tasks can be sex-divided, as noted above, but their worth cannot be constituted in this way. When you find that hunting is considered more valuable than cooking, and hunting is done by men and cooking by women, this tells you that the society is sexist, not that there is any intrinsic connection between these tasks and these sexes, nor that there is any intrinsic superiority of one task over the other. I suggest that you emphasize the village collective is the centerpiece of your society, because it allows for a great deal of planning while granting enormous latitude for local particularities. ## At Home Since any and every task can be apportioned however a society wishes, there is no reason that home life has to be different from this. The first thing to realize is that “home” and “family” are social constructions as much as anything else. There is no reason whatsoever to think that humans naturally live in married couples. Marriage, or anyway preferential bonding, does seem to be enormously more common than other arrangements, but that does not mean that husbands and wives must live together in private spaces. So you have a spectrum. At one end, have the women live together in one kind of longhouse and the men together in another. Couples have private communal spaces they can use for intimacy, physical and otherwise, at will. Life centers around the village, and there are certain spaces in the village that are especially central to communal existence. At the other end, have couples live together in private spaces whose boundaries are impermeable. Your mother-in-law may never, ever come to visit: after the first day, when she comes to inspect to be sure her son isn’t marrying some dreadful hussy, she’s forbidden to enter the marital space. Communal and private life are sharply divided. Humans have existed happily everywhere along this spectrum. No part of it requires or assumes that women are inferior to men. # Conclusion One of the remarkable things about human beings is that they do come up with an amazing variety of different ways of doing things. Another remarkable thing is that they have a strange habit of claiming that their way is the only way because of nature. Pretty much everything you hear about how men or women have to this or that is of this kind: it’s social construction. Ideology, to put it another way. Women get paid less in US society because the society is inequitable, period. There is no other justification. (This doesn’t mean it’s easy to fix, of course.) Women do the cooking in most traditional societies because that worked out to be rather convenient when somebody has to stay home with the kids and somebody has to go out hunting. But this isn’t the way nature is, it’s just how things tend to fall out. If you look at nomadic societies, for instance, you’ll find that this sexual division doesn’t always work thus. And now that the members of your society understand what is and isn’t actually required by physiology, they’re also not bound by traditional assumptions. [Answer] The chief prerequisite for a society that treats women as equals is a society that treats those who are out of power no worse that those who are in power. A society in which the common man and the common woman are both treated as second-class citizens may have equality between them, but I doubt that either would care to defend such a system. I'm not a history major, but it does seem that only in those societies that began to seriously embrace the notion that all men are equal—and by extension, that the government is the servant of the people, and not their master—did the notion that women are equal to men really begin to catch on. And perhaps I am mistaken, but even now it seems that the places where misogynism is still rampant, those in power are permitted to maltreat those who are not in power (both men and women) with relative impunity. [Answer] Equality is a luxury available only to prosperous societies. Only after a society becomes wealthy enough to have warriors defending its walls and officers enforcing its internal laws, does any opportunity for equality arise. Until those minimums are met, each individual will define their own morality and will force their will onto others to the limits of their might. In a post apocalyptic setting, not only women, but non-athletic men, the elderly and anyone in the minority (regardless of gender) will become second-class citizens to the strong; and if firearms are involved, even the strong will be subordinate to the armed. Samuel Colt didn't make all men equal, he put his customers in-charge. So if you want to build a society where women have a fighting chance at equality, teach them from birth how to fight. A trained woman with a long katana is properly equipped to define her own place in your society. [Answer] Need to understand the roots of patriarchy to amswer this. A mysoginstic society is not a natural evolution on its own but nor is it unnatural....during many parts of our own history, in preagricultural times, we were quite likely much closer to an equal society and even possibly matriarchy instead. The thought that mysoginstic culture is an endpoint or even a required step in the process is a bit misguided. (can go further into this point if needed...gods gender is close to 50/50 in horticultural days, in fact its pro feminine many circumstamces. Post agriculture, this shifts to 90% male gods with women regulated to 'wife / property of the male god companion. Of course exceptions exist, but it generally holds up). This first statement here is simply to point out that our patriarchy was formed and no more natural/unnatural than matriarchy or gender equality would be...i think that given the freedom and opportunity, a general population will drift towards equality (speculation on my part, but the point is our social values can and will change, the question becomes can we guide and inspire that change?). This isnt to say this setup isnt ingrained in us....this is 6000 years minimum of patrarchy afterall and only very recently has this been challenged (1793 wollstonecraft is the first of the motion, women finally gaining a vote as recently as 1920). Tis a very deep hole weve dug. Its also equally notable that most men werent people...in modern terms, males in the french republic around 1740 became 'people' in the eyes of their governing body as opposed to property of a monarch. You have perfectly stated the reason women became a second class....child birth and raising the next generation. In particular mortality rates....not just the child, but the mother as well. Stupidly simplified, why train a woman in a skill when there is a chance she will die during childbirth? Sort of wastes the training time, no? Honestly its a brutal conclusion, but the possibilty of your standing army having a childbirth attrition rate isnt easy to deal with. Miscarriage was the other large issue...if you want a women to miscarriage, put her on a horse for an extended period (mongol society values mobility....if women are pregnant and males are on horseback from the age of 4 treasuring their mobility, it doesnt take much to see why men are suddenly in a different societal class). I wouldnt want to know what a life or death battle in a war would for a mother would do to her developing fetus. From a philisophical side, its important to remember that male and female value spheres are going to be different....we are wired a bit differently afterall (our social evolution, its advantageous to have multiple value spheres approaching an issue. Root of our social creativity). One of the flawed approaches that becomes common in equality movements is for women to become equal at the things men value most...its playing the game with a stacked deck, women are not going to succeed in the tasks that have been setup to perpetuate our patriarchy and this route perpetuates patriarchy, not challenge it. The true solution is for society to stop valuing the male value sphere over the female value sphere. Hope that makes sense...but the ultimate solution lies in challenging the image you state in your question, that the majority of people believe raising the children is of lesser value. I got wordy there...but without this background its a bit hard to justify my answer. Specifically your society has to do 2 key things things. 1) medicine. The lower the mortality rate involved in childbearing the better. If for every five women get pregnant atleast 1 should expect not to survive, then you are heavily regulating woman to this childbearing role. This includes reducing miscarriages to as near as zero to reduce the number of tasks they cant do while pregnant. Having tasks availble for women at later stages in pregnancy also helps reduce the impact of pregnancy on their lives. 2) involve men in the child raising process and start challenging the image the child raising is of lesser value. In todays term, parental leave and in particular paternity leave is starting to have an impact here. First, parental leave helps address the image that a job (making money and providing typically within male value sphere) is more important than child raising (typically left to the 'less valuable' female sphere). Paternity leave being extra important here as this is now the male putting aside his male sphere job and giving equal importance on his time to the child bearing 'female value sphere' task and in a small way sayi g that each value sphere is equal. There is a misguided attempt to equate parenthood to a job (cramming the female value sphere into the male one so males can understand its value). Parenthood is not a 'job' in that sense, but it is of equal value to it. When this sense pervades, you will have a society much closer to equal. Of course there are other things that can help, from ensuring women are in governmental positions and equal pay on jobs...but patriarchy will remain as long as something as inheriantly part of womanhood as pregnancy and child raising is a lesser role. Its also important to remeber how quickly we can change as well. Yes, on a single lifetime the change takes forever....but soon youll have a generation thats watched its males tend to child raising and theyll see that it is of equal value....and their children will see it perpetuated once again and by then their grandparent (us) are the last aging relics of the patriarchy. Remeber we have gone through 6000 years of this patriarchy to have it establish to the point that is has. 100 years ago, the majority of women were no more than possessions of their husbands. Even some of the values perpetuated by 1970s tv regarding women seems a world away from where we are now. [Answer] Matriarchal society is your answer - and it was generally possible only in very productive areas (where farming is productive, and female can easily provide for herself and her children), like some Polynesian atolls (hint: a paradise). Otherwise, might makes right, and stronger (= man) will rule. [Answer] First of all, I want to say that I don't think that we've solved this problem yet, in modern, "civilized" society. Others have already pointed out that men and women are not paid equally, certainly favoritism exists within the workplace, even now in 2016 I've heard unbelievable, jaw-dropping misogynistic remarks made by decision-makers-in-power. But my answer to your questions is simple: arm everyone. Pointing a gun and pulling the trigger (like so many activities and occupations!) simply doesn't require male genitalia. In a post-apocalyptic world where might makes right, assuming firearms are available, there's no reason that women couldn't make themselves every bit as powerful as men. Add to this a culture where dueling is permitted/common behavior. Challenge my authority? Disrespect me? Lay a hand on me, uninvited? We fight it out, in front of witnesses. Women could participate in this behavior equally with men. They may even have more incentive than men to become expert in the dueling arts. [Answer] My wife and I have considered this topic often. You have to create a culture in which actions like rape or even sexist words and acts are responded with collective shock and repugnance. It must achieve the level the current US society places on child molesters. We do not know how you would transform our current culture into that one though. But if you had a small enough group of people that agreed to it perhaps it would stick as the community grew. Other options, you could create a culture where women are first class citizens. They are given extra rights and privileges. But this only changes the direction of sexism. A mechanic I have pondered that might work, but still has room for abuse. Set up a legal tradition that every woman once in their lives may accuse a man of rape and have them be punished for it by execution based upon their word alone. Disrespect a woman enough and it could cost you your life. Again room for abuse, but it’s a mechanism that could support the cultural change you wanted. ]

[Question] [ Simply put, what's the expiration date of a computer? The reason I ask is for the sake of a society recovering from some sort of cataclysm and trying to reclaim lost technology. However, I could also see this being useful if there's a cold-case mystery/treasure-hunt that depends on the hard-drive of a computer that once belonged to a key witness. Here's the setup: 1. The computer is disconnected from any electrical grid. (No worries about electrical surges.) 2. The computer is protected from the worst of the weather. (No water or sunlight damage.) 3. The computer is subject to yearly temperature fluctuations. (All climate control is offline.) 4. Before being put into storage, the computer had a fresh operating system of your choice installed, with no unusual backup systems or special care given to it. 5. The computer must be some common variety of desktop computer that is commercially available as of 2014 or earlier. (Sorry Mr. Babbage, no one-offs, plans, or prototypes) 6. The computer must have about a 50% chance of still being able to turn on and retrieve files or run programs, given the proper power supply, at the expiration date. Bonus: If temperature was constant, how much longer would the computer last? For example, if it was in a cave system, an air-conditioned warehouse, or a deep underground vault. [Answer] Are you allowed to perform maintenance before turning it on? For a hard-drive-based computer in storage in a reasonably dry climate, there are two main sources of degradation: loss of electrolyte in the power-supply capacitors, and breakdown of lubricant of various moving parts. If you can re-lubricate the fans and the hard-drive motors, and replace the capacitors, you should be able to get a computer working again several decades after it was last shut down. Over time, the contents of the hard drive will be lost to randomization of the magnetic fields, but this is a very slow process. Solid-state drives introduce a new failure mode: charge loss in the SSD's memory cells. Unlike the above problems, this is irreversible, and depending on the storage technology, may render the computer un-bootable in as little as a year or two. [Answer] The older the better. Modern computers are hard to keep functioning because they are closer to the fundamental limits of the materials. Modern computers tend to have about a 3-5 year lifespan. It could go longer if the computer was not used. There is an *active* community of owners of PDP-11s, some of which are from 1970! If the comparisons of the lifespans of actively used computers is a good metric for how long computers would last when unplugged, the older the better! [Answer] The single biggest issue for the long term dormancy of a computer would be the humidity/moisture. Moisture will allow corrosion and some of the parts don't need much to make them useless. Moisture also allows for the growing of mold etc. which will also damage the machine. Barring that, however, a cool dry place can keep a computer viable for quite a long time. I think someone should figure out what the half life for computers are. Because that appears to me to be a good model to use. [Answer] Right now I have a [1984 year Elektronika\_MK-61 microcomputer](https://en.wikipedia.org/wiki/Elektronika_MK-61) in front of me, and it works perfectly if I turn it on. All these years it was stored in my grandfathers' garage. So, probably the computers can survive few decades in a less than perfect environment. Especially the ones manufactured between 1980 - 1992 years. [Answer] The first thing to go is always your memory... ## Cold storage Cool, dry conditions that preserve a computer at least well enough to prevent corrosion and physical damage are a must. In damp or otherwise corrosive conditions, a computer may not last a year; delicate wiring can very quickly decay, especially if there is no moving air to limit humidity inside the case. Temperature can also play a key role; too wide of a range or too rapid of change can stress physical components. If the computer is in a moderately stable environment, above 50 and below 110 degrees Fahrenheit, it has the best chance of lasting a long time. Sunlight - or even low ambient light - can destroy almost every part of a computer, so it should be stored somewhere out of the light. If a computer isn't stored somewhere cool, dry, dark, and free of vibrations, expect it to last a few years; the worse the conditions, the lower the lifespan. ## Memory, Sweet Memory Regardless of storage medium, duplicate data will mean a much higher chance of being able to boot up successfully. A standard mirrored RAID can extend the lifespan of a drive (assuming it works) by many years. The more duplicates, the higher the chance the data will survive intact, possibly even doubling or tripling the lifespan. * Modern (magnetic) hard drives use tiny magnetic fields on platters. Given the right circumstances, an unpowered magnetic hard drive will last between 2-20 years. At the low end of that range, the drive itself would still function, but the data may be corrupt; by the the end of that range, the lubrication on the drive will have failed, and the motors won't work. Theoretically, given perfect circumstances, the information stored on a hard disk will last for decades, but the drive itself will fail long before that. If the future user is willing to completely dismantle the drive and lubricate the motors, I could see a drive lasting for an additional decade or two. Interestingly, it's very difficult to find any websites describing how long a hard drive would last, unplugged. * Solid state drives would probably fail within a decade. A subsection of SSDs (RAM disks) use RAM with a battery to keep the data fresh; those would fail very quickly. Regardless, the data doesn't seem to last as long as magnetic hard drives, and because of drive fragmentation, it would be much harder to rebuild as well. On the bright side, the drive itself would remain usable much longer, even if the data stored on it were gone; I can't find any good sources, but it looks like an SSD could last over 30 years in the right conditions. * Punch cards last a surprisingly long time. They may not hold much data, but a stack of cardstock punch cards kept in ideal circumstances could last thousands of years! * Magnetic tape has been shown to be perfectly readable in excess of 30 years; as long as the tape itself is undamaged, there is a high chance that data will last many decades. Duplicate data could extend that two or three times. * Floppy disks rarely last 10 years, though I have personal experience with a floppy that worked after almost 15 years - however, other disks in the same box didn't last longer than two or three years. The chances of any given floppy disk working after a decade is quite low. * CDs were initially promised to last hundreds of years, but in reality many disks failed within 5 years; most websites I found list the lifespan of a 'cold storage' CD as about 10 years, though there is a chance that a CD may last longer, as long as the foil backing doesn't degrade. Given the option, I would stick with DVDs. * DVDs, especially high-end, commercially manufactured DVDs, may last 100 years or more; the data is stored differently than CDs, which means that as long as the disk itself doesn't degrade, the data should last a very long time - some sources claim over a thousand years in ideal circumstances. I would expect average media to last about 100 years. * BluRay and other very modern optical storage have similar manufacturer claims of 100-150 years; there isn't as much data on those, but I would guess it is on par with DVDs. * Flash drives, SD cards, and other small, cheap media will likely lose data within 10 years. The better drives may have longer lifespans, but I wouldn't count on it. * Older EEPROM chips should last up to 30 years before the bits decay; some chips are very susceptible to UV light, however, so any sunlight would drastically reduce the life of the chip. * Data stored directly in transistors and diodes (or even wires/resistors) should last nigh-on forever, barring physical decay; instead of using magnetic or electrical charge, they use a physical connection to power or ground to give the 1s and 0s. Obviously, this data would be read only. ## Hardware * Ok, I lied. The first thing to fail is probably the fan on the processor, rather than the storage. For systems with a fan, anyway. The fan is designed to spin all day every day, and without that motion to distribute the lubrication, it will quickly stick. Luckily, most computers will work without a fan... for a little while, at least. * An optical punch card reader could, theoretically, last for thousands of years. It has so few components, and is designed to work with such high tolerances, it may well outlast the computer itself. * Floppy drives need to be thoroughly cleaned after less than a decade. Dust and mold will cover the reading head and reduce even the best floppy drive to a floppy-destroyer. Once clean, however, the drive should last for at least 50 years. * Similarly, magnetic tape readers will need to be carefully cleaned. On the bright side, the tape itself would clean the heads eventually, at the cost of whatever was on that first few feet of tape. Many commercial readers/writers are kept in hermetically sealed cases, which would keep the drive clean. I would expect a tape reader to last for 50-100 years, as long as the components hold out. The motor would need to be lubricated. * Optical drives, especially drives that are normally sealed, will fare much better; solid caps will keep the drive working for 100 years, at least, and probably longer. Unlike sensitive hard drives, the motor on a CD, DVD, or BluRay drive will grind away without lubrication, for a little while at least. If cleaned, I expect an optical reader to last roughly as long as its media - between 50 and 100 years. * Capacitors in the power supply or on the motherboard will likely be the first point of failure there, at around 15 years. The hotter it gets, the lower the lifespan; however, capacitors are fairly easy to replace; as long as the user turning on the computer knows how to fix them, they won't have any effect on the lifespan of the computer. Solid-core capacitors would fix that problem; there are a number of commercially available motherboards with solid caps, however, there are usually not available for power supplies. * The BIOS, as well as various other chips on the motherboard, may become corrupt over time; I would expect modern chips to survive for several decades, and older chips to last even longer. Much older motherboards may use ROMs that are much less prone to corruption, and still older devices would use wires and AND/OR gates as memory, reducing the chance of corruption to almost nothing. ## Conclusion If a modern desktop computer were kept out of direct contact with weather (sunlight, rain, etc.) in an average climate (say, in a garage or shed), I would expect it to last for between 5 and 10 years. If the same computer were buried in a storage container in the desert (controlled climate, no sunlight, no damp), I would guess that it would last up to 20 years. The first thing to fail would probably be the data storage. However, a computer with an SSD could be reinstalled with handy DVD installation disks; some computer could even boot and run from the DVD itself. Without a hard drive to worry about, the same computer would live another 10-20 years. An old, single-board computer with solid-core capacitors, bulky wiring, fewer components in general, and much higher tolerance for noise (due to much slower processor speeds) may last centuries; as long as the chips and wires themselves don't decay, the device should keep working for hundreds of years. Even then, there are still simpler computers that would last even longer. The NES, for example, uses a very basic processor with easy-to-replace components, and boots from a cartridge using a die-cast circuit for data. As long as they clean the contacts on the cartridges, someone could be playing Duck Hunt on an NES a thousand years from now! [Answer] There are *military grade* Notebooks/Laptops out there, prepared for pretty much everything: Water, extreme temperatures etc. Those are of course not only used for the military, but for dusty or wet working environments as well. This specific type of Laptop is called ***Rugged***. As they are sealed I could imagine that they would live for some while. Another option would be microcomputers or development platforms like the Arduino or the RaspberryPi and similars. There are versions out there that are barely bigger than a coin. Of course they are missing a display per default. About conservation: People already tried cooling computers in oils, which seems to work good. Oil isn't only non conductive (at least some sorts), but it also seals stuff perfectly from the environment (water, dust, etc.). [Answer] Another concern here is dust, as it builds up inside the machine (particularly it can affect moving parts in fans and hard drives) if it isn't stored or at least covered. One my old desktops worked fine after being a few years in a very dusty room with no air conditioning, just because it was inside two plastic bags and sealed with some tape. As people have said before, older machines will have better chance of being functional than more modern machines. Built-in obsolescence might play a part on this. If someone puts a cover over the machine, I would assume 7-10 years. If they don't, and the environment is very dusty, I'd say 2-3 years tops. ]

[Question] [ As fas as I know, there isn't a single plant on Earth that (naturally) produces any sort of luminescence. But it is seen in science-fiction worlds, especially Avatar. From an evolutionary point of view, what would be the benefits for a plant from being bioluminescent? [Answer] # Evolution and benefits It is easy to think of evolution as only being about benefits, but in order for something beneficial to be naturally selected it must first arise spontaneously. The fact that plants have not so far evolved bioluminescence does not indicate a lack of benefit. It simply means that they have not stumbled upon a way of doing so. Some bioluminescent organisms do not have any obvious benefit from their light. For some it is apparently a side effect rather than a useful trait - of interest to us but of no consequence to them. For example [bioluminescent fungi](http://en.wikipedia.org/wiki/List_of_bioluminescent_fungi) are sometimes hypothesised to use the light to attract grazers to the fruiting bodies, other times hypothesised to use the light to repel grazers from the mycelium, these apparently contradictory hypotheses seeming somewhat inconclusive. However, the chemical used to produce the luminescence works by being oxidised, which means it acts as an antioxidant. The linked page on bioluminescent fungi mentions research suggesting that the production of the chemical is linked to the metabolism, and that it may provide: > > antioxidant protection against the potentially damaging effects of reactive oxygen species produced during wood decay > > > So the fact that humans are sensitive to the particular light emitted may not be relevant to the benefit it provides as an antioxidant. As octern points out in the comments on this answer, the term for such byproducts independent of natural selection is [spandrel](http://en.wikipedia.org/wiki/Spandrel_%28biology%29). # Glowing plants may not need any benefit If you want to populate a world with glowing plants and ornate patterns of light, they may not necessarily have any benefit from it - it would be perfectly realistic for such plants to arise purely accidentally. The light can arise and persist without need for benefit. Patterns can also arise without need for benefit, as can be seen from the various patterns of leaf veins (here the pattern is beneficial in that it is efficient, but its aesthetic appeal is incidental, not due to any visual benefit). A plant may happen to develop a useful chemical process that has a luminescent chemical as an unused byproduct. This may be more concentrated in the veins, showing up the vein structure in glowing detail through the translucent leaf membrane. Alternatively the luminescent chemical may be a byproduct of producing a hormone. If the hormone stimulates growth then the parts of the plant currently growing fastest will glow brightest, showing the patterns of growth like a textbook picture. If the hormone promotes flower production then it may only be new buds that shine brightly, with a rapidly diminishing glow along the stems leading to them. Some plants produce chemicals in response to damage. If this becomes linked to a luminescent byproduct the result could be leaves which glow faintly when bent or torn, and shine more brightly when crushed or shredded. You can find plenty of examples of benefits of glowing by looking at the examples we know of, and there are doubtless many other possible benefits that could arise that we don't have examples of. However, I wanted to emphasise just how much is possible even without any benefit at all. The rich diversity of life is due to this tendency to branch out and find new forms, even if they are not immediately useful. Sometimes a beneficial trait is only possible because of a series of neutral changes that came before. Sometimes a trait we happen to find useful or beautiful has no benefit at all to the organism we find it in. I find this fact in itself to be beautiful. Going in the opposite direction, a glowing forest scene in a fictional world may be the result of bioluminescent parasites and infections, treated as magical by the inhabitants but actually a sign of poor health of the forest, and not in any way beneficial. # Known benefits of bioluminescence The Wikipedia page for [bioluminescence](http://en.wikipedia.org/wiki/Bioluminescence) lists a number of known benefits for existing organisms. None of these organisms are plants but I will consider some of them for their potential as a hypothetical plant benefit. ### Counterillumination camouflage Some deep sea fish glow underneath so that predators below them cannot sea them against the uniform glow of the light filtering down from the sky. I've been imagining land based plants but there are of course ocean plants. However, they are not present in the deep ocean where the light levels are low enough to make this approach practical, so this benefit is unlikely to apply to plants. ### Mimicry Again, the real world examples are ocean based - predators mimicking much smaller creatures to attract prey, but a land based plant could use bioluminescence to mimic for reasons other than hunting. There are plants that have flowers resembling insects, so that insects trying to mate with the flower inadvertently spread pollen. There are also insects that use bioluminescence to attract a mate. So it would be feasible for a plant that could glow to mimic a glowing insect in order aid pollination. ### Attracting mates In addition to mimicking insects to attract pollinators, glowing could also be beneficial simply to attract pollinators without trickery. Patterns of luminescence could advertise to insects in the same way that colour and smell indicate to insects that nectar is available in existing plants. ### Distraction There are squid that release bioluminescent mixtures instead of ink, using light instead of darkness as distraction and cover. A plant could have leaves that glow when disturbed (perhaps initially evolved as a damage response, but then amplified over the generations as the distraction caused is beneficial). It could be of benefit to small prey animals to have a swaying mess of glowing leaves causing distracting cover when it darts into the undergrowth to evade a predator. Although this is not of direct benefit to the plant, being a common escape route for small animals is likely to lead to the regions around such plants being visited more often by both predators and prey, leading to more defecation with the benefit of increasingly fertile soil. ### Warning Some animals glow to distinguish themselves as poisonous. Plants already use bright colours to make their fruit distinguishable, so that animals can learn which fruit are safe to eat. Glowing fruit could provide a similar benefit, ensuring that the majority of the fruit are eaten by animals that will survive to spread the seeds. Glowing could also be used to indicate ripeness so that unripe fruit is not eaten prematurely. Some plants respond to their leaves being eaten by releasing unpleasant tasting chemicals so that the grazing animals will move on to other plants. Glowing could potentially accompany this unpleasant taste, to highlight when the effect has begun so animals can avoid the plant. Of course all of these warning approaches will only work at night, and as such will likely evolve alongside patterns of colour that perform a similar function during the daylight. ### Predation Predators using bioluminescence are found in the deep ocean, but it is not unfeasible to imagine a bioluminescent insectivorous plant. Similarly to the mimicry of glowing insects for pollination purposes, a pitcher plant, venus flytrap or sundew plant could attract insects using light. This could either be by mimicking an insect to attract a mate, or simply using the glow to attract nocturnal insects like a lamp. ### Illumination The Black Dragonfish lives at ocean depths where red light cannot reach, so red creatures appear black and are practically invisible in the darkness of the depths. By glowing red it can illuminate prey that most other predators cannot see. As an added bonus most creatures at that depth cannot see red light, so the prey is not alerted by the glow. Plants on land live in an environment that allows most wavelengths of light to pass unhindered, and with both day and night light sources that are wide spectrum, so this kind of restriction to one colour is unlikely to give a similar advantage. General illumination may have benefits, simply in bringing increased animal activity and the various associated benefits discussed above. There is the possibility of developing the ability to glow in a colour only visible to some animals, but the probability will be lower as there is much more overlap in light detection in creatures on land. For example, red berries are easily distinguishable from green unripe berries to creatures that can distinguish red from green (such as insects, birds and humans) but to creatures that cannot distinguish red from green (most mammals) the ripe berries do not stand out. However, even creatures that see red and green as the same colour can still see both - they would detect a glow whether in red or green, they just wouldn't be able to tell them apart. An ultraviolet glow would be completely invisible to some creatures (rather than just being an indistinguishable colour). Most mammals cannot see ultraviolet whereas many birds can. Being able to produce a glow that only some creatures can see may have benefits for a plant. For example, being able to make damaged leaves glow may attract the attention of birds or frogs that can eat the insect larvae responsible. The glow may even be visible through the translucent skin of the larvae, so that those that eat the defended plant will glow and be highly visible to predators. This effect may be strongest if the glow is a colour that the larvae cannot see, so that they have no warning and stay out in the open not realising they are suddenly much more visible. [Answer] The simplest answer would be if it attracted bugs. Many flowers have bright colors or attractive smells to get bees and other insects to pollinate them. Maybe in another world bioluminescents helps the plants get fertilized. Along the same lines, bioluminescents could repel predators, either they are light sensitive or the bioluminescent chemical reaction is poisonus or destructive to them. ]

[Question] [ *Radio Thinkers* Creatures that communicate by biological radio pops up in science fiction occasionally and it's a fun idea. However, there are some practical concerns with regards to evolving a radio in a creature's head. I'm looking for a discrete sequence of evolutionary pressures that would encourage a species to develop radio communication without any external tools or equipment. The radio must be embedded in their bodies in order to be considered. **Why would they evolve radios in their heads and what evolutionary steps would get them there?** *Evolutionary Environment* Let's use a cooperative hunter species on an Earth like planet for a start. The planet can have any features you'd like in terms of atmospheric or crust composition, as long as a normal Earth human can survive there without a space suit (ignoring any pathogenic concerns). This is a [science-based](/questions/tagged/science-based "show questions tagged 'science-based'") question so fanciful giant leaps or large amounts of handwaving are discouraged. Note: There is [this question](https://worldbuilding.stackexchange.com/questions/495/how-do-creatures-with-a-hive-mind-communicate) about how a hive-mind might communicate. I believe this question is distinct in that it asks for an evolutionary process instead of just how it might work after evolving. [Answer] As I stated in my answer to the linked question, the evolutionary prerequisites for radio communication is in a species that is able to precipitate a variety of metals in a variety of forms and an environment high in metals. Initially, a precursor species would evolve to use metal to enhance its neural transmission rates as electrical transmission is vastly faster than human nerves' sodium-gate depolarization system, in itself a highly advantageous strategy in evolutionary terms. It is likely that creatures using metal as a nerve conduction rate booster would have found that unshielded nerves would cause radiation detectable not only within a creature's own body, but in other creatures too. As faster nerve conduction is too great an advantage to give up, shielding would have evolved, quite possibly by running nerves through the centres of metal bones, or perhaps by sheathing the individual neurons in metal. However, the possibilities of transmission and detection of EM radiation means that not all metal nerves would have evolved to be completely shielded, some could be partially shielded and be used to detect EM radiation. So, we have evolved creatures that emit RF energy as a by-product of their neural activity. From there, once shielding has evolved to reduce cross-talk between nerve fibres, detection of RF leakage requires more sensitive receiver organs. Along with this, any deliberately unshielded neurons would emit RF energy detectable at greater range. As there is almost always an advantage in being able to communicate at longer distances, the evolution of a stacked pile of depolarising cells (as occurs in electric eels) allows higher transmitter voltages, and hence higher power and range. We then get to the point of bandwidth. EM radiation emission will most likely begin at lower radio frequencies, but it is entirely possible that mechanisms could evolve to increase the frequency of emitted radiation. Since a system of this type could have practically each neuron driving an EM transmitter of a different frequency, high bandwidth can be achieved by rapid changes in signal amplitude and frequency that is allowed by using high-frequency EM radiation, and also by multiplexing - using many frequencies simultaneously. This could ultimately allow an evolved bandwidth many times greater than our own Wi-Fi communication, which could also be somewhat directional. Another argument for higher radio frequencies and microwaves is that smaller antennas are required. Since all this bandwidth is relatively easily achieved in evolutionary terms - simply by duplicating the relevant organs - there is no reason why the beings would not evolve to make use of this bandwidth. Since the highest intelligences of species on earth are found in those creatures with an active social life (and this ability makes for a great social life), the evolution of intelligence is pretty much a given. Considering that a sentient, tool-using species that can communicate via RF at what are probably high bandwidths, it is unlikely that humans could easily develop an interpreter for this alien language, especially given that it would most likely be multiplexed, and both frequency- and amplitude-modulated, as well as rapid and idiosyncratic rather than following any simple grammar as in human-manufactured RF communication. It is far more likely that these creatures - should it occur to them that audio is being used to communicate ideas, a not-unlikely proposition given their inherent ability to share processing - would learn to understand and communicate with humans using human language, given its likely lower bandwidth and complexity. Of course, since we're talking about evolution, an evolutionary feature such as metal-enhanced neurology would have to occur at a very early point in the species' evolutionary history. This means that - thanks to evolutionary divergence - there would most likely be a great number of species on this world which emit RF energy to a greater or lesser extent. We can anticipate that in the groups of creatures with unshielded neurology, the 'noisiness' of their neurons would be a beacon to the RF senses of predators, particularly those who have shielded neurons themselves, and thus have a lower background noise over which they can 'hear' their prey. From this, we can anticipate that these may be easy prey to such predators, and would hence be prone to adopting an [r-strategy](https://en.wikipedia.org/wiki/R/K_selection_theory). Other species would have evolved to communicate via RF to a greater or lesser extent; we can anticipate a wide variety of such creatures occupying multiple niches, though as the communication range of RF is such that it can be anticipated that many would be at least a bit smarter than a terrestrial-equivalent species mainly due to the greater opportunities for social interaction. As to the environment, there is practically a necessity for more metals to be accessible. This does not preclude an oxygen atmosphere, but there may be levels of atmospheric dust containing heavy metals that would have toxic effects on humans not protected by respiratory filters or who eat the local life forms. This would make face mask filters *highly advisable* rather than *essential*, and we could have a human living for quite some time without one before they might start to experience symptoms of heavy metal poisoning. A potential reason for humans to be interested in such a world is that with the biological precipitation of metals, mining metals would be an almost trivial exercise of picking up the carcasses of dead creatures, whether recently dead or fossilised. Some very interesting alloys are likely to have evolved, as is foam-metal which is both light and strong due to its internal voids. [Answer] A complete answer would require a full transceiver, with a means for sending and receiving radio signals. This answer presumes that a receiver evolves first, then later a transmitter, and finally the link is made for social communications. Suppose our planet has birds that have an ability to sense magnetic field, evolved for long range navigation. Further suppose that this bird's prey decides to live near deposits of magnetic ore. Our predator eventually notices that rapidly changing field direction, although disorienting, means something yummy is near. So the birds evolve to enjoy the sensation, and see how quickly they can fly back and forth. Their sensing organ grows, more neurons are dedicated to it, etc. Now suppose some of these birds branch off and become mammals, and some mammals branch off and live underwater, like dolphins, in search of a niche. They evolve an electrical discharge mechanism like eels, to protect themselves from larger predators. Et voilà! One dolphin notices when the others discharge, enjoying the sensation, and joins in. To conserve energy, they gradually boost the frequency to MHz range. Eventually, they develop different modulations to signal danger, satisfaction, food, rhetoric, and ultimately sarcasm. Nothing more remains for these creatures on this world. They leave, saying only "So long, and thanks for all the fish." [Answer] It would be difficult. But I would guess that an organ to sense the radio waves would be first. Like how we see light, to help us navigate more effectively in our environment. So I would think an environment where radio waves are prevalent but not overwhelming and can be used just like sonar. Having an organ more like an ear than an eye for radio wave detection would 'encourage' another organ to generate radio waves, like bats and dolphins use echolocation. However, echolocation really seems more likely to have occurred by generating a sound and getting better and better reception to understand the feedback. In this case having a radio generator. So how do you get a radio generator? All mammals produce infrared radiation and on humans if we could see this we would be able to know much more about each other as we converse. So in a low light environment, instead of our visible light we might shift the more toward infrared. If we could 'see' our body heat patterns we would could learn to control them more into what is being 'said'. Organs might develop that are more a 'mouth' for more direct and form of communication. Slowly shifting both the transmitter and the receptor (though I expect this would begin to require 2 different receptors, one for Infrared and the other for Microwaves, moving on down to radio waves) to different bandwidths maybe for less interference or a way to be 'silent' for prey. [Answer] **Slow and steady growth to radio signals** Monty Wild gave a great answer, but unfortunately there is one thing that is a flight of fancy. The metal nerves. See my comments why they are actually unpractical. This answer is improving on the answer of Monty Wild. *Metal and bones* Most animals that get metals in their body see that most metal ends up in the bones. This is for most harmful, but some creatures like spiders and scorpions use tiny amounts in their claws and teeth to strengthen them. They are arranged singularly though, so no connected weave to make a good transponder. A creature could conceivably increase the amount, trying to store excess as a fixed core inside the bones, like a metal wire. This doesn't need to be much and can be build on the outside of the bones. This will be the start of the antenna. It'll greatly reduce the amount of metal needed compared to metal nerves, making it much more believable. The lesser amount of metal also prevents a lot of difficulty with the creature, as many metals aren't good for animals in larger dosis. They interfere with many normal processes of the body, binding and unbinding important things. *Radio and social* With metal in place, it can resonate thanks to nerves. Especially if they have nodes of Ranvier the electrical signal could jump to the metal a bit, giving it a resonance and a small RF signal. This can be picked up by someone close, probably touching at the start. That means they can feel it, as well as that the interference with the nerve can start signals to the brain. This can be seen as positive, which can lead to evolutionary reinforcement. Just like eyes, this communication can start to develop slowly. The signals are increased with dedicated nerves, stacked like those of electric eels. Together with a straight connection to the brain it'll be the basis from which it can expand to the complexity of communication. First it'll get more range and allow for more feelings, at a very, very rudimentary level, to be transferred. It helps with telling each others location at (really) short distances, helping people not bumping into each other as well. It'll evolve to greater ranges, possibly more tiny antenna for directionality (both for communication as well as feeling the direction someone is present, like your ears can tell the direction of a sound), and attune to more clear signal transfer. This is just a long evolutionary process that increases itself. Like sound replacing sign language, it'll slowly become more important the more range and differentiation they get. Eventually they can transmit emotion and meaning at the same time, clear over distance. *Observations* The RF signals will change with the creatures growth. Young creatures will have shorter antennae than older ones, with likely less powerful nerve cells. That would mean a different band and less range, making it feel like a childrens voice to them. Similarly older people are likely to have bigger antennae, but the age of the nerves could make them "sound" different as well. The creatures can have an "always on" band of RF signals to know exactly where someone is closeby. It is likely only used for short times or intermittently, as it uses a lot of energy to keep it on (you're nit going to talk non-stop), as well as it becomes difficult to understand the signals with many people there (again, the same as talking). The range can be modulated like talking, allowing people to scream or whisper. Talking with RF can be much more efficient, as it can be used two-way at the same time, especially if you have separate receiver antennae, while much more clear on the meanings and feelings. Only problem is processing, as the brain mimics your own thoughts and emotions, meaning the return signals might mix up or can't be processed. The speed and amount of information can be much higher though. Seeing a face also becomes less important, as emotion can be embedded or have it's own frequency. No visual signals needed. This can lead to much better communication, as you don't miss out on many subtleties while not able to see the other. You can continue crawling under your car and talk unaffected for example. [Answer] The visible light band is a special case of the EM Radio Wave spectrum so evolution of vision might be a guide. It started with just detection and seeking the heat from light. So radio evolution would start with just the detection of the magnitude of an existing signal. Creatures have evolved to detect EM waves outside the so called visible frequency band, to detect infrared, some examples are some species of snakes.. Again this likely started as detection of heat. The difference with vision is that any material denser than air blocks infrared. Lenses are important in evolution of vision. Creatures which detect infrared have external sensors on their skin. They can detect presence of infrared but cannot focus it into an image as with the visible light spectrum can be focused with a lense. Further into the radio spectrum, gain from a metal antenna would have the corresponding significance. Birds and bees detect the earth's magnetic field as they fly through it. Motion through a magnetic field produces EM waves. This might also be guidance. You have to consider where the original signal occurred to be detected. Reception would evolve first, because transmission without reception would not have any effect for adaptation. So the transmission has to be present when the creatures first evolved reception. For light and infrared it was heat. It might be motion through a magnetic field. Maybe there is some other natural source of radio transmission. If naturally occuring it might not be a signal interpreted as communication but would just be a constant source of EM waves or pulses. Creatures might evolve to approach to distance themselves in regard to the location of this radio source. [Answer] Pretty straightforward. An amphibious creature that uses multiple electric discharge pulses. Not too useful in air, but as they are sometimes on land the discharges still emit radio waves. Those that develop higher frequency pulses may have a communication advantage assuming they also have electroreception and are a social species. This is similar to another of my ideas where dragons breathe lightning instead of fire. Birds can excrete a type of mucus thingy (thingy is a highly sophisticated technical term) For nest building. So if a bird sized dragon was able to expel a sticky electrically conductive web, that web could act as a letahl taser on small prey and the webbing also catches fire from the pulse of current. Telepathic dragons. That's my best. Initially a water based electric discharge that evolves higher frequency for communication in a social species that is initially amphibious but transitions to dry land or even flying at a later date. Hope this helps. ]

[Question] [ **Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- **Want to improve this question?** Update the question so it can be answered with facts and citations by [editing this post](/posts/118685/edit). Closed 5 years ago. [Improve this question](/posts/118685/edit) I know that RPGs employ eye candy tactics to players of their preferred sex in order to entice the players into the game. Male Wizards are sexy and muscular. Female Wizards are sexy and have big boobs. Aside from that, is there any other practical explanation why some wizards are so hot and sexy when most of their time is spent on studying rather than going to the gym? [Answer] **Glamour is the first spell they learn!** In real life, wizards all look like you would expect - skinny spindly bookish guys, chubby balding bookish guys, unkempt old dudes etc. The first thing they do when they get some magic is get glamoured up, buff and Harlequin romance ready! If you are familiar with the internet, you will understand that the hot sexy female wizards are also actually one of the male types described above. [Answer] ### Breeding One potential mechanism, cribbed shamelessly from [El Goonish Shive](http://www.egscomics.com/index.php?id=1455) is pretty straightforward: Magic is intelligent and has ideas of its own, and it wants to be used. In people with sufficient aptitude, it is so concentrated that it can affect their physiology. Magic is interested in making more people with magical aptitude, so it can be used more. It therefore guides the development of people with that aptitude to make them as sexually appealing as possible in an effort to encourage their successful procreation. Wizards of either sex, therefore, have exaggerated secondary sexual characteristics and an appealing body fat ratio without having to work for it, because magic *wants* them to be good breeding stock. [Answer] **Disguise** We have all the stereotype that a wizard has a long white beard and a pointy hat, and maybe a pair of glasses, while a witch will be a not so nice looking woman, dressed in a black robe and with messy hair. Now, imagine you are walking in a forest and you see a gentleman with a long white beard and pointy hat coming in your direction: you think he is a mage and evaluate your chances of successfully defending yourself should a fight arise. Imagine now that you see a medieval version of Pam Anderson running (with all the bouncing) in your direction: will it inspire you fear or something else? To sum up: in a world where everybody is a potential menace, disguising your true potential and skills is a valuable skill. Mages are known to be dangerous at distance, so having a chance to get close to a potential target is also a valuable tactical advantage. [Answer] **Attracting new practicioners.** Does every basketball player achieve Jordan's success? Do you expect Ronaldo's luck with X brand shaving razor? It sells, so if the Grand Maestre tells you to pick some members for the next fair, you ditch the fat enchanter. No one will join the Alchemist's club if the gal on the stand has pimples and nails-on-chalkboard voice. Pick a sucessfull Spellweaver who has looks and brain, with a passion for the arcane. Then your next year the kids will beg to enroll. More students = more money from the crown. If it brings more money, why not? [Answer] **Practicing magic is a strenuous exercise.** Magic is a powerful force. Summoning and guiding it via gestures is a physical exercise. Learning spells in the library is not all there is to being a wizard. Nearly every Manga uses this to explain the protagonists' hulking bodies. **Being able to control magic is used for selfish means.** Who wouldn't optimize their body in terms of physical appearance, simply if they *could*? [Answer] # Sex magic Seriously. Pick all the forms of magic in the real world and at some point they delve into it. Some are all about it. One of the most known group of practicioners of magic on Earth is the Order Templi Orientis, made famous by Aleister Crowley. Those guys organize their knowledge in degrees, and the higher ones are all about sex magic. They consider masturbatory magic to be the lower form of sex magic, with intercourse based rituals being higher in nature. And you need to be well versed in it these techniques in order to make it to the top of their hierarchy. In a world where magic is a thing and you get power by doing it like mammals do in the Discovery Channel, a sexy body is a tool to obtain ever more power. [Answer] Isn't that obvious? I always marvel at wizards in games, including roleplaying and LARP. They all don't seem to think like real people. Because when you learn something new, you don't change your personality, do you? When you learn a new craft or language or anything, does it change what you want in life? Maybe a little, but not fundamentally. IMHO some of the first things that anyone who more or less suddenly finds himself in possession of magic powers would do is - the same things he would do without, just with magic: * food * shelter * mating The first thing you do, especially in a medieval/fantasy world where hunger is a real thing and most people know how it is to go a day or two without food, is to check how you can use magic to make sure you are never hungry again. The second thing would be to ensure you have a proper roof over your head, preferably with a heat source. Magic flame? Favorite spell! And as soon as you are comfortable and safe, of course your mind turns to "how can I use this new thing to attract members of the opposite sex?". Healing spells, especially if they can restore your teeth, skin, etc. definitely rate high on that scale. If there are spells to shape your body, you will **definitely** use them. The good food and warm shelter from the first steps also helps to get and/or maintain a good body. These things are what biologists call *fitness indicators* and if you can prop them up by magic, you will. Especially if you are a young adult under the influence of hormones. [Answer] Who wants to live forever? Wizards, of course. The only issue is that they have to spend most of their time studying and practicing magic, while other normal people go to the gym and mate other people, but they know that their time will come. After years and years of dedication they finally master some branches of magic and they can have their payback. Given that several enchanters can perform a full shapeshift it's not a big deal to modify their own appearance to meet the current beauty standard. It's not a lazy way, they spent years on their books, and it's way more smart to work out in a library rather than in a gym. A bodybuilder will grow old, a wizard will grow powerfull then, granted intelligence is mandatory to become a wizard, they totally won't spend their time trying to sculpt a mortal, frail, aging body, but they will do their best to increase their power (and therefore their appearance, that can be modified as they wish). There's actually a downside in this behaviour, and it could be a relevant downside especially where there's a high wizard concentration: a wizard will end up mating another wizard, since only another wizard can match his/her beauty. That's a problem because a wizard will recongnize another one and he/she definitely won't to "create a family" with another wizard, and with their power it would be easy to control their fertility. On the other hand the not-wizard people are not that appealinig, except for few really special people. This actually is the reason why, in the end, wizard are so rare: they can have as many one night stand as they wish but they luckily won't have offspring. Ps: since a wizard can modify his appearance and he is intelligent, the "Adone" shape will be used in "commercials" and saturday night but, in order to avoid possbile backfire by gealous ex lovers and/or king's discomfort for the wizard's influence on the queen, when they do their "official" business they will use a "Merlin" shape. They are paid for their wisdom and power, so they are just maximizing their appearance again to have the maximum gain. Aren't they supposed to be really intelligent after all? [Answer] ### They don't have sexy bodies - you just *think* that they have a sexy body This is similar to the [glamour idea from @Willk](https://worldbuilding.stackexchange.com/a/118688/28789), but different in that they don't have an illusion around them. Everyone has a certain magical energy and potential in him. This energy is constantly leaking out. Have you ever thought that someone has this kind of *aura* around them? That's not simply their personal attitude, it's more like magical pheromones. The more magic, the stronger the pheromones that tell you: "This person is *sexy*." Your perception is skewed into *thinking* they are extremely sexy, when in fact they are quite normal, but with an enormous amount of power leaking out of them and telling you that they are exceptional individuals and mating with them would be good for the bloodline, because: magic = power = survival Because of [cognitive dissonance](https://en.wikipedia.org/wiki/Cognitive_dissonance) your brain will then proceed to rationalize why you feel that these ordinary looking individuals are so extremely attractive. And the easiest thing is to overlook everything that doesn't align with the typical characteristics or what society defines to be "sexy" for the average non-magical person. This makes you *think* they have sexy bodies when in fact they don't. This way there is no awkward *morning breakfast* after forgetting to put your glamour back on. It's always on as long as the magical energy is not suppressed by something. But the moment it *is* suppressed the individual will look quite plain compared with the image humans had in mind. This also makes wizards extremely weird for normal people and might help with the perception of them being *different*. While the general view of biology on what defines "sexy" is ingrained into the minds of people there are differences that are defined by society and "sexy" can also differ from individual to individual - which means that different people might desribe wizards slightly different. Simplified: one group of people talks about the upper body, while the rest talks about the lower body of the individual wizard. This leads to people not being able to properly describe the wizard and therefore leads to a *aura of mystery* around these individuals, which increases "traditional sexiness" yet again. They are rare and complicated individuals and nobody is *completely* sure what they look like, but everyone knows they are extremely *sexy* - whatever you think *sexy* means. [Answer] **Mens sana in corpore sano** The manta of wizardry is *mens sana in corpore sano*: the younger wizards wish the attract a partner, the older ones wish to stay alive, all have a direct incentive to stay healthy. Therefore, the first interesting spells studied by wizards, straight out of basics (aka small telekinesis, dust cleaning, ...), are basic body reinforcement spells: * disease purification, * poison purification, * healing, * fat control, * ... Masters know it's important, and know their young students are keen to learn it, so they teach it first and use it to convey the fundamental concepts of magic. As a result, all wizards just know how to maintain a healthy body. Actually, an unhealthy body is a mark of insanity for wizards, and history has proven that those wizards who let their bodies degenerate soon devolve into villains. [Answer] **Inherent "Healing" Ability** Magic is good for the body, and promotes health and well-being in practitioners of both sexes. Minor ailments tend to pass them by, and even major issues will heal completely given time. It could even help them maintain a healthy weight and muscle tone despite lack of exercise. So while they mightn't be super attractive, they do tend to have clear skin, good hair and teeth, be fairly fit and have that air of confidence that comes so naturally to magic-users. [Answer] Magic is sexy! If you're only interested in out-of-world opinions, then the definition of "sexy" comes from our culture, and will need to be tailored to our particular concept of "sexy." However, if you think in-world, if magic is something desirable, any body characteristics or behaviors associated with magic will develop an element of sexyness to them as they become desirable in-world. Whatever magicians have, the opposite sex will want. Related: reading is sexy [](https://i.stack.imgur.com/fwTQ2.jpg) [Answer] Look at The Witcher world, in this world sorceresses look hot while Wizards usually look old and frail even if they are young, they can change their bodies with permanent enchantments and they do it because their clients expects them to be hot for women and old and fragile for men, also the sorceresses tradition usually favors having ugly apprentices so they work hard to master magic so they can change their appearance so they can stop being mocked by others. Also after someone masters magic they lose their means of reproduction so they can fool around all they want without consecuences (also they are unable to catch STD) so being hotter is even better for them. And for wizards not all of them look old, one of the books antagonist is a wizard that looks young and is quite muscular, to the point that it can go 1 on 1 with the protagonist (who is mutant that hunts monsters) without any problem. So maybe the reason in your world both wizards and sorceresses look like super models or porn actresses is because people have that precognition that the best wizards and sorceresses should be hot because the magic to change your own body is hard to master so if one can change its own body means that are truly masters and not lowly apprentices. [Answer] Two reasons, somewhat related. First, wizardry takes energy, some of which (the part that controls the rest) has to come from the wizard's own body. Thus, the more physically fit the wizard is, the easier it is to control magic, and the more powerful the level of magic the wizard can control. So a successful wizard pretty well HAS to be pretty muscular. You might, for instance, think of doing a magic spell as rather like push-starting a car. (Something that those of us who've owned '60s British sports cars¹ are all too familiar with.) Second, part of wizardry involves heightened control over one's own body. One can heal diseases, and within limits shape one's body into a desired form. So while it isn't as simple as waving one's magic wand about, wizardry augments the effects of exercise, so that the wizard gets a buff body with much less gym time than normal folks. PS: WRT female wizards and big boobs², a lot of it is development of the pectoral muscles and the contrast with a trim, muscular waistline, e.g. <https://woman.thenest.com/can-strengthening-chest-muscles-increase-breast-size-7762.html> ¹All hail Lucas, Lord of Darkness! ²It should be noted that not all of us think big boobs are really that sexy. Too much association with Holsteins <https://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Cow_female_black_white.jpg/220px-Cow_female_black_white.jpg> at an impressionable age, I suppose. [Answer] The simple evolution of magic. The most basic needs for humans are food, shelter and sex. Shelter could be anything from finding a dry and out of the wind spot to sleep to making fires to making cloths to building entire houses, and food&sex are similarily large. Why they would look good: * Better food and shelter means indirectly better physical appearance * Having access to magically superior food and shelter will make you more wanted as a mate * Magically improving your physical body has multiple advantages: it helps you survive more, gather more food and build better shelters, helps you recover from dibilitating/ugly wounds and makes you look sexier to the others as you are better adapted to the environment. * As slightly metioned in the previous point, physical body manipulation can be used to heal yourself and others. * another advantage is that you can improve others around you, such as the mate you've chosen or you can help your children be strong, smart and sexy for their futures. Magical manipulation of your physical body would have the most reasons for mages to pursue, so it's likely that if magic were real, physical body magic would be the largest field. [Answer] ## There are two types of wizards - fit ones and dead ones (aka the Rincewind/Harry Dresden style of wizardry) To the general populous, a wizard is a being of unimaginable power. But in the grand scheme of things, wizards are actually fairly low on the totem pole of magical beings. They have just enough power to be attractive as batteries, but not enough to defend themselves from the more powerful beings who want to use them as such. So wizards become very good at running away. And even the average, everyday wizard has got nothing on the research wizards who work in labs. When a chemist says "Oops", everyone with sense ducks behind a desk. When a wizard says "Oops", anyone who's still in the room 5 seconds later is a fool. And the really smart ones have cleared the building. I can't explain the big bosoms, though. [Answer] Perhaps its just that they are **hot and sexy** compared the your typical common dirt farmer. A wizard who knows to cast a spell to purify his drinking water will be worlds more healthy than one who gets theirs from the sewage and parasite infused runoff of the local stream. Commoners might get scarred from the many diseases and poxes they face. For wizards such ailments are unknown. For dirt farmers, toiling under the sun has brutal consequences on their skin, making it cracked and leathery. Wizards stay cool in the shade and have marvelous skin. Ever see the feet of a commoner? All calloused and gross from working the fields with primitive footwear. Wizards have nice sandals and boots. Scraggly and knotted hair? A simple spell will solve that. Mud stains (or worse) on your old clothes? Even an apprentice can keep their colorful silk ropes in top condition. Breasts need a boost... this old concoction the elves told you about will do the trick. And lets not forget bad breadth - a quick wave of the finger and the wizard's breath is now minty fresh. [Answer] Witches and wizards are extremely motivated individuals. They have to be or they wouldn't be any good at magic, because learning magic takes not only great intelligence and memory, but extreme dedication. Most magicians' desires don't end with mastering magic. These narcissists are obsessed with proving their perfection and superiority over weaker people in all ways. Part of this obsession obviously includes obtaining physical superiority. And they are in luck; compared with mastering magic, getting fit is *dead easy*. All they have to do is regularly eat well and exercise, a small task next to the exhausting strain that is practicing magic. [Answer] I think Andrzej Sapkowski of Witcher fame gives one of the best explanations to this. They were not like that, female wizards were generally raised from noble lines. These noble lines found better use for their great looking women. Wizardy didn't improve the nobles situation because they were generally removed from the noble lineage creating their own (or terminating it as it were). So mostly the women chosen for wizardy were in fact ugly. Since this was such a big stigma on the person chosen, more often than not one of the first thing they would do is to improve the situation. [Answer] Genetic correlation. I recall hearing once a theory that the reason different dog breeds have such similar facial structures to each other compared to their shared canine ancestral stock was that they were bred for domestication, and the same genes for that facial structure were involved in tractability. The appearance (or that aspect of it) just sort of came along for the ride. It just so happens that some of the same genes that control attractiveness (e.g. waist-to-hip ratio for women, chest-to-waist ration for men) are also related to magical ability. [Answer] The body needs to be fit to withstand the damage magic may caused, be it from other magicians or their own magic. Some magic systems even include martial arts. If they are supposed to fight against other people they need to be in their best shape. Most magicians also have access to healing magic which can keep their body in good condition. In most settings magic itself alters and enhances bodies of creatures that are infused with it or surrounded by it. That is one of the reasons for their longevity too. [Answer] In "The wheel of time" universe, magic is achieved by channeling an invisible force, not unlike "The Force" in Star Wars. One of the side effects of channeling is that it slows down ageing. Similarly, you can say that magic has rejuvenating properties - the more more you do it, the fitter and better looking you become. [Answer] A lot of good answers, but one that nobody else seems to have gotten to yet: magic runs in families, and magicians have been able to find attractive mates for millennia. Therefore, they all have the genes of their attractive ancestors. [Answer] ### Evolution of sex appeal over physical survival traits (Note: Only works for "magical races") Most species evolve primarily for survival-related traits related to finding food or escaping/fighting off predators - strength, speed, durability, and so forth. In species where life is easy, where food is plentiful and there are no natural predators, sexual selection becomes much more prominent - which is why many island birds (for example) have exaggerated sexual traits, whether visual (the tails of birds of paradise) or otherwise (the impressive booming calls of the kakapo). There is actually some (controversial) evidence that this has occurred in humans; our appearance has become more neotenous (child-like) since prehistoric times, and there are some theories that this is because as we relied less and less on our bodies for survival our sex appeal increased. This may be increasing further since the industrial revolution, though it is still too early to tell. While there is some overlap between physical fitness and sex appeal in humans, it is not quite as direct as many people believe; athletes (especially lifters) do not look like models, and fitness doesn't have a huge effect on the face in any event. Wizards, by virtue of their magic, rely far less on being good at doing stuff physically than non-wizards (especially in a medieval world where most people do a lot of manual labor). Breeding among magical races will therefore place a higher emphasis on sexual traits which will leave its mark on the race over time. ]

[Question] [ John from our future, takes the time-travel bus back in time and steps off in 5th century Europe. He heads for the secret location where travellers are kitted out with authentic clothes, food and currency to keep them alive until they can establish themselves. He has learned enough of the local language to pass for a foreigner. He tells the locals he is from "Nonsylvania" or "far to the North" or such. By time-travel law, he was not allowed to carry any artefact back with him and he didn't. He purchased a return ticket and and can use it by going back to the hideout according to the timetable. He is not allowed to make repeat journeys for any reason. John is an entrepreneur. He left school early to work in a local market. He doesn't have scientific or detailed historical knowledge. There is no way he could invent even electric power. He doesn't know how to make rubber. If he wants to "invent" something that he knows about from his own century, he must do it with ancient tools and technology and get the locals to make it. However John, contrary to all the rules of time-travel, wants to change the ancient world. He settles on one simple invention from later than the 5th century that he can make and sell to build his business. He can employ local crafts people but they can only use their ancient tools. My first thought was scissors but it turns out they were invented around 1500 BC in ancient Egypt. **Question** I then thought of a can-opener (invented around 1810) but then he would have to invent cans. Given that John knows little about metals or where to find them, is it feasible that he could make this "invention" and set up his 5th century worldwide business empire? Can he make cans? If he can't make cans, what can he make? **Assumptions** 1. John has done no research before leaving. He is a businessman not a historian or scientist. His plan is to look around when he gets there and see if they are missing any everyday objects that he knows about. He only has to have a rough idea how to make them and maybe draw a sketch for the local blacksmith to try and emulate. He must rely on local skills, tools and knowledge to do the actual manufacturing. 2. By tool I mean a solid object, e.g. scissors, paperweight, hammer, axe, etc. Remember that John was not allowed to take any artefacts back in time (and didn't). He has to work from memory. Hence he will probably pick something simple but very useful. --- **Detailed timeline of inventions from Wikipedia** <https://en.wikipedia.org/wiki/Timeline_of_historic_inventions> --- **EDIT - in defence of John** NOTE - What follows, superficially looks like story-line but it is actually an explanation of the conditions I set. Without clear conditions a question like this becomes far too open-ended. Many people have queried John's lack of knowledge and research. John does not spend all his time on Worldbuilding, so he does not know about "black powder" and other arcane subjects. He is a man-in-the-street who made good. All his expertise lies in: making money, influencing people, spotting gaps in the market, organising teams to do the things he doesn't have the expertise for, etc. He was moderately rich and successful when he lived in his own century. Thus his skills are fully formed. Now that he can afford time-travel (it's very expensive), he is setting out on the adventure of his life. Instead of being a big fish in a medium-sized pond, he wants to be a big fish in the pond that is 5th century Earth. He didn't do research before starting because he isn't that kind of guy. He enjoys landing on his feet in a new situation and thinking fast. His intention is to spot gaps in the market - at first locally and then more and more widely. He will diversify when necessary and concentrate on efficient manufacturing and distribution - out-competing others when he can, and forming partnerships with them when he can't [Answer] In Europe, the stirrup. They were in use in China by the fifth century, but were unknown in Europe, and give a very significant advantage to cavalry as well as facilitating other uses for ridden horses. The [Wikipedia article](https://en.wikipedia.org/wiki/Stirrup) says: > > Some argue that the stirrup was one of the basic tools used to create > and spread modern civilization, possibly as important as the wheel or > printing press. > > > [Answer] # Hygiene: A powerful battlefield weapon If you really want to get the attention of powerful people, teach them how to keep their soldiers alive when the enemy is dying. Through much of history, diseases have ravaged armies around the world. Even with the improvements of technology made in the next 1,400 years, [two-thirds](http://www.pbs.org/mercy-street/uncover-history/behind-lens/disease/) of fatalities in the US Civil War came from disease. Start teaching a few things like not collecting drinking water downstream of your latrines. Then move on to advanced lessons, like hand washing and properly storing and cooking food. Charge heavily for each lesson. Then train employees to teach these skills and collect fees to have them go to every military unit in the country and explain hygiene. Pros: You don't have to bring anything from the future and you can prevent a lot of human suffering. Cons: You might upset the military balance of power with unknown consequences. [Answer] Since this question has the reality check tag, I'm going to have to point out that people in ancient times weren't stupid. They just lacked the means and the knowledge base. They were far more in tune with is possible with manual labour and handcrafting. So for John, as uneducated as he is and with *no research*, to try and bring back a concept which they were not already aware of, yet have the means to achieve (both technically and economically) seems almost insurmountable to be. A lot of stuff we take for granted now, if it was doable back then was *crazy expensive* and so simply wasn't done. If it's so basic that John is aware of it and they can do it, but they haven't done it, then they either don't need it or they need it but it is too expensive. Even if we put the technical hurdles specific to the product aside, the more challenging hurdle is to make it less expensive (aka feasible). That probably means enabling technologies which are the most challenging of all. You aren't inventing enabling technologies without knowing what you're doing, which John doesn't. The value of the enabling technology would also dwarf the value of any particular product. You're on their turf, doing what they do, with their means, trying to outwit them with no preparation. I'm almost inclined to say it's modern hubris, which might just be up John's alley. So I'm going to present this frame challenge: Are you wanting something that John would actually be believably successful commercializing? Or just something he *thinks* he would be successful at? A laymen bringing back the concept of a steel hammer or lenses might as well be bring back the concept of a computer if he has no idea how to make steel or glass and forge them or grind them in the first place. Ideas are a dime a dozen. [Answer] **I'd honestly go for the printing press**. John doesn't really have to know how to make one, he just has to describe the basic pieces to a craftsman and demonstrate it to the right people. It's utility would be obvious within a highly bureaucratic government structure. It's utility would be obvious to the Church. Plenty of Catholic scholars in that century. Probably some Pagan ones, too. The press doesn't require fancy knowledge or technology to make and can easily be operated by slaves, paid workers, or monks, depending. And eventually, people much more knowledgeable than John will work out the bugs and improve its design. As far as world changing --- that's obvious! More books means higher likelihood of ancient works surviving to the present day. Will eventually mean a surge to the nascent scientific and scholarly explosion of the medieval period. Perhaps, in the hands of the right people, that revolution could be brought forward. We might be seeing proper universities 500 years before they got going in our timeline. We could see the invention of the scientific method much earlier. --- *Address to comments:* * what about paper? They have papyrus and they have vellum and they also have cloth. All of these can be printed on. They'll figure out rag paper soon enough! Or perhaps bark paper. Even regular leather can be printed on. * Ink & metalwork? Do you think they didn't have ink and bronze and even iron in the 5th century AD? Anyway, all John needs to do is demonstrate how letters carved onto blocks of wood can be rearranged to print different words. His audience will take over from there! * all John has to do here is plant the seed. This is why I specified him showing this to the Church: it is within the next three centuries that the Church will be rescuing the Empire from its own decay and bequeathing all the ancient knowledge on to the empires of the future * trust me: if they lack rag paper in John's time, they will figure something out soon enough! Who knows? Maybe the libraries & universities of the 7th century will be founded on books of linen or amate! [Answer] "[Lest darkness fall](https://en.wikipedia.org/wiki/Lest_Darkness_Fall)" protagonist made his first money in 6th century Europe by producing brandy. His revolutionary tool was "[pot still](https://en.wikipedia.org/wiki/Pot_still)" (though I don't know if it qualifies). [Answer] **Basic maths using the Arabic (decimal) number system, basic economic theory and double entry book keeping.** This includes introducing the concept of zero. Basic statistics, compound interest formula's, forecasting, financial analysis and algebra and calculus. As a businessman he should hopefully be numerate and have a high school education or better. He would soon find himself in a senior administrative or teaching post. Better still his knowledge is portable and can't be stolen only learnt. **Amendment:** Forgot to include concepts and formulas used in logistics, project management etc plus currency and commodities hedging etc. **Another amendment;** All the other inventions mentioned in this thread are worthy of development. The problem is the character by default knows about them but cannot (unless otherwise specified) re-invent them himself. So if he were just show up and to try and explain gunpowder or germ theory etc chances are he would be seen as either mad or a witch. BUT- after establishing himself as a mathematical prodigy and gaining peoples trust? *Then* he can start talking about how *other* scholars in his home land had studied these things and describe them in general. **Result?** before you know it experiments and new ideas start being conducted/tried across the land. And all because he's proved his worth first. [Answer] # Lenses John does not knows how to precisely make lenses nor how to shape the glass into the correct form nor the mathematical optical formulas. However, he have some crude ideas of how they work. Also, he knows that it is (a) possible, (b) reachable with the 5th century technology and (c) revolutionary. So, John just need to recruit some loyal people with good skills in glass-making and/or maths. In a few months, with some trial and error, he and his workers would be able to produce glasses for people with no good eyes, spyglasses for soldiers, and also telescopes and microscopes. And this would happen more than a thousand years before than when they were actually invented. With a telescope, astronomers/astrologers would quickly start to use them to observe the skies and soon heliocentrism and gravitation would be figured out, much before than they actually did. With microscopes, the microorganisms would be discovered and would help to make advances in medicine happen much faster. Also, it would also be used in other areas like metallurgy, alchemy and secure communications which would also enable further development in other areas. In fact, lenses already existed in that age, but they were crude and not widely used. What he needs to do is to lead his workers to meticulously produce them in mass with the best quality achievable. And then, he just sells them, a skill that surely any good enterpreneur have. [Answer] Cowlinator [mentions it](https://worldbuilding.stackexchange.com/users/838/cowlinator) but it seems it didn't get much attention. Pasteurization is no small thing to invent! For some strange reason, John can maintain milk for longer than other residents, his milk just won't spoil in a couple of days. There is no need to make **perfect, standardized Pasteurization**. John remembers from school that pasteurization entails heating. Amateurish low-heat warming can definitely get John a couple more days worth of milk. Assuming John has absolutely no idea, I can imagine him practicing by warming his milk for half an hour every day, practicing with the heat levels to avoid boiling it, maybe even wasting much milk in the process. However, as noted in other answers and comments, **what** is no more important than **how**, of course. By setting up some apparatus, mainly for show, to attract the attention, John can definitely start offering to preserve the milk of neighbors. See, everybody observes that John buys more milk than others, while he is rarely seen throwing it away. Little by little, John can perfect the "machinery" (which is simply used to slowly warm milk, of course) et voila! John is the alchemist du-jour, as milk really lasts somewhat longer after he has it flow through his machine. So, John has "invented" a **tool** that can be used to preserve milk. # EDIT As Nosajimiki [notes](https://worldbuilding.stackexchange.com/users/57832/nosajimiki) in a comment, obviously, even pasteurized milk only lasts a couple of hours at room temperature, unless it's quite cold... Unfortunately, John needs to remember that this is most effective in winter times. But as John's profits go up the first winter, he thinks there must be a way to make money during summers too. With time, he concocts a sort of a dripping machine, letting milk drip slowly through a hot furnace-like space. Droplets pass through the heat, drying up, with only the residue reaching the bottom surface (which is not warmed). Week by week, he perfects the layout to ensure adequate travel time for perfect drying. John has invented an arrangement to produce **dehydrated (powdered) milk**! Stored properly, **powdered milk** does actually last unimaginably long compared to the contemporary expectations. [Answer] The invention that would have The most impact if John could get it accepted would be 3 field crop rotation. A 50% increase in farm output would be huge. Persuading farmers to change their ways would be a tough sell though. [Answer] How about a compass? Even without detailed scientific knowledge it should be possible to make one with a bit of experimentation. Lode stones were known in ancient times as were various forms of iron. A bit of experimentation with small fragments / splinters from flattened nails and a lode stone should be able to produce a magnetised pointer. A small marked wooden box would be easy to make and even a small glass cover might be possible. It would be of great use to mariners travelling across the Mediterranean. [Answer] **The wheelbarrow.** This is simple enough that John can understand it and build one using available tools without much enhancement. It seems like wheelbarrows should always have existed, because they're so obvious - but the ancient Romans didn't have them. (They were invented in China in ~ 200 AD but didn't make it to Europe until the 13th century.) But once you see one and use one, their utility is obvious. They have a dramatic impact on small project agricultural and construction productivity, relative to the capital investment required to create one. Raising these two types of productivity at such an early date will dramatically change history as a whole. [Answer] Even on the wikipedia list you provide, there are quite a few inventions that rely on principles so simple that even a layman would probably understand well enough to invent. These include: * The brace (and auger) * The thermometer * The coil spring (assuming ironworking is sufficiently advanced to make wire) * Buttons (and buttonholes) * Eyeglasses/Telescope/Microscope (it might take a layman a long time to get the specifics right, but I think they'd get it eventually) * Barbed wire (assuming ironworking is sufficiently advanced to make wire) * The zipper * The hook-and-loop fastener (a.k.a. Velcro) * Movable type and the printing press * The hot air balloon (and thus flight!) * Reinforced concrete * The Windmill * Banknotes (though it requires people to buy into the idea to be useful) * Medical hygiene * Rudimentary vaccination (such as cowpox/smallpox) * The pasteurization process As well as the general idea for several other basic scientific principles. (E.g. the atomic nature of matter, and the parts of an atom). Which one is the best? I would have to go with **the hot air balloon**. Inventing flight one and a half millennia early just seems so cool... and it would revolutionize exploration, travel, and warfare. [Answer] since others bring invention from other region or just a view century later already, i may as well just jump to the wagon then. heres mine **KITE** its easy to make and quite known for common folk and kid in this era, though i dont know is this true to modern western or specifically to john, you can use leather, cloth, or even use broad leaf as kite not necessary to be made from paper. it can help measure distance, testing wind, lifting men, and signal, or if you near shore you can help fishermen using kite fishing, also help proto benjamin franklin or even your john to proof regarding lightning and electricity theory thing and early air plane invention. **AIR BALOON** already known in china using sky lantern and even made from egg shell, can be use as alternative for kite stuff. **FORK OR OTHER FOOD UTENSILS** most europe people in that times eating using bare hands, this can help hygienic alot especially made of silver, this will be prestigious enough to captivate monarch at least. or john can try chopstick, it can be made from simple wood, precious metal/stone to ivory so it can also captivate monarch, and its quite simple enough and less material require, though need to teach them how to use it to make it a booming, which depend on do john know how to use chopstick or not, this can change european culture as a whole, or at least can make kebab booming earlier, since kebab exist since prehistoric, its meat in stick after all, but not that well used during this period. **PRINTING** like woodblock printing or xylograph and movable clay block press printing no machine required, it use by china and its simple enough, just add paint to the block and press it to the object, can be applied to even stone, and single man is enough to do single printing. **PAPER** ask the carpenter permissions to get the sawdust to get the fiber, asking farmer for their grass, put it into water and mix it, after cleaning it, boil it in water, beat or find something to flattened it until the fiber is thin, dry it, make paper, thats at least the crude way i know, the result is probably not as high grade paper today though, also i may make some mistake there but through trial and error it can be perfected. * and if John come there with his modern clothing, it can also revolutionize clothing or fashion, such as sewing pattern/technique or clothing forms, heck even john way of wrapping clothes to look exotic without any sewing can boom a fashion and change european culture if it captivate the noble or merchant fashionista. * also concrete or cement, it made of water, sand, and gravel. modern people may know this, even though they dont know the correct mixture same as me, though this depend on john knowledge. * oh yeah also if John know how to make wax or clay, he can try make 3d map, akin to 3d printing stuff but more primitive (already a thing in ancient china btw, so basically most modern non electric invention is already an invention or figure out in other regions in the past, and most of it is far before 5th century even, including robot or automaton). * since others says scientific theory is ok, maybe metric system or unified measurements (i dont know the correct english, i hope this is understandable enough regarding what i mean), since europe dont have base or unified measurement in that time or quite inconsistent as far as i know, i believe modern western know it well even without advance educations, though my math suck so i cant say much regarding it. [Answer] Eyeglasses. Glassmaking was millennia old by that point, some experimentation with lens shapes and a bit of uncomplicated metalwork later, and you've started improving vision. The aristocracy and the rich would pay through the nose for better sight as they get older. Similarly, the telescope. The printing press. The screw press was in use by the Romans by the 1st century, so no need to reinvent the wheel there, and the printing press is a relatively simple modification. [Answer] The horse collar. From [Wikipedia](https://en.wikipedia.org/wiki/Horse_collar): > > A horse collar is a part of a horse harness that is used to distribute > the load around a horse's neck and shoulders when pulling a wagon or > plough. The collar often supports and pads a pair of curved metal or > wooden pieces, called hames, to which the traces of the harness are > attached. The collar allows the horse to use its full strength when > pulling, essentially enabling the animal to push forward with its > hindquarters into the collar. If wearing a yoke or a breastcollar, the > horse had to pull with its less-powerful shoulders. The collar had > another advantage over the yoke as it reduced pressure on the horse's > windpipe. > > > From the time of the invention of the horse collar, horses became more > valuable for plowing and pulling. When the horse was harnessed in the > collar, the horse could apply 50% more power to a task in a given time > period than could an ox, due to the horse's greater speed. > Additionally, horses generally have greater endurance than oxen, and > thus can work more hours each day. The importance and value of horses > as a resource for improving agricultural production increased > accordingly. > > > The horse collar was very important to the development of many areas > of the world. Wherever oxen were used and could be replaced with > horses, the use of horses boosted economies, and reduced reliance on > subsistence farming. This allowed people more free time to take on > specialized activities, and consequently to the development of early > industry, education, and the arts in the rise of market-based towns. > > > The horse collar was developed in China in the 4th, possibly 5th century. It was not introduced into Europe until the 12th century. To invent the horse collar in 5th century Europe, John will have to (1) remember roughly what it looked like, (2) realize what problems it solved, (3) obtain a horse, and (4) experiment. He should also interview anyone he can find who has been anywhere near China. [Answer] [The Instant Legolas!](https://www.youtube.com/watch?v=Ovl6_UEIWGY) Joerg Sprave did a lot to try to prove how simple a magazine system (and even a draw assist) can be. It's a bit of complex wood/metal work, but not outside the ability of a hand craft tools. Check out his videos he made as he developed the design. One of the reasons people moved to crossbows and guns is because they're easier to make and easier to train soldiers to use - but they were often poor replacements to a truly well trained bowman. Joerg's invention let's a bowman hold their draw almost effortlessly, he even later strapped a second bow to the front of it as a draw assist desvice to make pulling a heavy bow easier without effecting the strength of the bow. There's another video of someone who made one with hand tools and then let someone who actually shoots heavy bows try it. There was a learning curve, but apparently they thought with some extra time to practice with it it could have made shooting very easy. [Answer] **Semaphore and/or Telegraph** Whatever time you are in, military technology and faster communication are always good. When the Spanish Armada attacked England in 1588, the best system the English had to warn of the attack was to light a series of preconstructed bonfires - faster than a horserider, but a pretty crude (yes/no) message. Land semaphore was invented in 1792 in France and enabled more complex messages to be sent for military and other purposes. Signalling between ships with hand flag semaphore was common up to world war 2. Needle telegraph is also not beyond what could be achieved with 5th century materials. A battery could be constructed from any two dissimilar metals (iron, and copper or lead) and any available mineral or organic acid (vinegar, rancid wine) with sufficient power to deflect a magnetic needle. The issue would be finding enough metal to make wires with. Here's a video on how to make a telegraph (with modern materials) in 6 minutes <https://www.youtube.com/watch?v=1r2eOpkBTOo> [Answer] John is a businessman after all. He might have no scientific skills, so inventing things which also require deep knowledge about chemical/physical processes would not fit his role. Unfortunately it also requires a lot of time and money. There is a lot of trial and error involved. Since neither John nor the blacksmith know how to make new alloys or invent things so that they work, it is not worth the try. In addition, who says that those new invention will sell like crazy and bring him a fortune? Not every inventor got rich within in his lifetime. Often inventions need time to get accepted - and this is even more true the further you go back in time. And more time is needed to 'sell' them to people. Further, you need either a rich patron to pay for the investments or already have some money. So it is too risky and I propose another business method. John should not invent tools, produce them or try to sell 'new' technology. Instead, he should 'invent' what he knows best, e.g.: # Stock market John knows about stocks and how a stock market works in principle. He is also affine with numbers. It is easy for him to evaluate the value of a business (e.g. the local blacksmith) and to calculate the share value. With some money from the priests, leaders or a wealthy trader, he can build up the first stock exchange. # Arabic numerals The [insert whatever numerals are used in your location] are very inconvenient for book keeping and the stock market idea. So John invents the arabic numerals, which he uses every day. This will revolutionize not only mathematics, but will speed up accounting. # Banking - deposition and withdrawal system The first prototype banks were invented around 2000 BC in Assyria, India and Sumeria. So he could also invent new things related to banking, which are not known at this time. Likely it is the deposition and withdrawal system - IMHO its early system was invented by the Templars in the 12th century. With this idea he could increase the safety of merchants and trading routes. # Marketing John could earn some money making extensive advertisements for local businesses. He could design wall posters or invent logos printed on coins. Let him invent the basics of trademarks. So only local businesses are allowed to sell 'special' papyri or bricks, all marked with their logo. # Job market You need skilled people for a certain job? John can help. He can establish a sort of recruiting service in every bigger city. With the 'invention' of CVs and resumes John can always find the best person. # Insurances Everybody needs them. Together with a good marketing strategy John could establish a big insurance company. However, it needs a lot of risk management/analysis and I'm not sure if John knows how to handle that. # Homeopathy? I'm not a fan of it, but John might be. Let him 'invent' a potion which heals every known disease. Paired with his business skills he knows how to market it. He can 'print' advertisements or bribe people to spread the word that this potion can heal everything. [Answer] **John Is Not A Very Smart Man.** John needs to utilize something that already exists! Penicillium, the mold that was discovered to contain a powerful antibiotic, would be an absolute historical game changer. [Answer] I'm going give you a frame challenge here. The fact that John has what I would consider sub-par levels of knowledge of modern technology means he's not really likely to be able to 'invent' anything with earth-shattering ramifications that didn't already exist and just wasn't seen for how useful it was at the time (see steam engines and hot air balloons as canonical examples of this, both were invented in antiquity but neither was recognized for it's utility until early modern history). Let's put this in a slightly different context. How likely is it that a high-school dropout could explain to you how to make something like a mould-board plough? That's about as simple and useful as you can get for tools that hadn't been invented yet (and, were I setting out on a mission like this myself, is actually what I would pick, though I would likely also make the effort to get people to realize that the aeolipile was actually useful rather than just a curiosity) but it's not something almost anybody in modern times who hasn't actually used or made one is likely to be able to tell you how to make. Most other truly 'simple' tools that hadn't been invented yet hadn't been invented because there was no use for them. There's no need for a screwdriver if you don't have screws for example. Essentially, your issue here is that he doesn't have enough knowledge to 'invent' physical tools. In fact, even less tangible stuff like modern business management techniques wouldn't have worked back then (because there just wasn't the population to support it effectively). Based on this, I contend that there is *nothing* he can do other than point out utility of inventions that have already been made but are not seen for how useful they are. [Answer] First, may I just say that, in your story, John not being the type of person to prepare at ALL for his trip back in time makes absolutely no sense. If John is at least smart enough to have been able to make enough money to afford time travel, he should be smart enough to figure out what it is he is going to "invent" before going back if his entire reason for going back is to "invent" something. Someone who's fully-formed skills are "making money, influencing people, spotting gaps in the market, organising teams to do the things he doesn't have the expertise for, etc." is NOT going to go back in time with the sole purpose of "inventing" something that is already around in his own time and not HAVE THAT THING IN MIND. If John were truly that STUPID, he would probably already be dead. That being said, with the limitations of John not being allowed to prepare at all and considering his skill set, my answer to you is: John should "invent" the idea of fractional reserve banking, where one only keeps a fraction of the deposits available in order to loan the rest out and make money on the interest charged on those loans. With his skills of organizing people to do what he cannot coupled with his sole knowledge/expertise being economics learned "from the street", this should suit him to a tea. [Answer] # The map of the world The discovery of the world was very much incomplete from a European perspective in the 5th century. However any ordinary modern person has a much better grasp of how the world map is laid out. John could sell the idea of exploring new (and rich) lands. If he could fund an expedition, the rest is alternate history. [Answer] **Globalism... well kind of** Your best bet would probably not be any singular tool or idea but the knowlede of where to find more knowledge. John remebers that different countries had different ideas at any given time, even though he doesn't exactly know who had what. But his greatest strenght would be that he has a LOT of hindsight. *Some examples:* * Where others see "a black powder that burns quick and stinks" he sees guns, dynamite and so much more. * Where others see just a horse collar, he thinks of quick carriages, drawn by eight horses (eg. post coaches). * He knows what lenses, maths, paper and so much more really are capable of beyond their obvious applications He knows what is possible and the amount of ideas and concepts he has, that are already proven to work, is unrivaled. Most of these may not be doable in that era, but he can already make huge steps in the right direction (or make other people make huge steps) just by spreading this knowledge and nudging people in the right direction. Plus he knows how important it is to properly document each step and make frequent backups of that documentation (especially for the black powder reasearch groups). And even if none of these could possibly be expected to work during his lifetime, he DOES know how countries would benfit from the already existing inventions of other countries. If he is rather attentive, he can travel one country to get a hold of their common knowledge and then travel further to countries like China or Arabia to get a good look at their current level. This might come with huge hurdles, as he would be considered a foreigner in any country and might not get easy access to their knowledge. If he plays it right though, he might end up with some good connections to any country he visits, maybe even with the opportunity to send some bright minds over to learn anything he deems useful with his knowledge of modern times. He would essentially establish the first global corporation ever. **How though?** He might be able to identify himself as some sort of travelling scholar. If he is a foreigner anyway, he might as well be a reputable foreigner. This might actually grant him some boons like becoming the guest of some wealthy people and getting their attention for a little while, which enables him to make connections and find investors/trading partners early on (or at least have a safe place to sleep and eat for a night or three). Plus a scholar would of course seek knowledge. Nothing suspicious about that. This way he can get access to the most promising ideas and inventions from all over the world (or their prototypes anyway) and start spreading them everywhere to make a huge profit off of them. This way you pretty much get all the inventions mentioned here at once. And all of this is possible with "just" entrepreneurship and soft skills. No previous research required. [Answer] The talent of John is to make people do things for him. That's great! Instead of making a part which is then quickly copied, he should introduce some process. Processes normally need to be controlled, that's John's part, and they are less easy to copy from mere observation. Finally, you can cut a process in single task slices so that even the involved never learn all of it. That can be mass production of a part (arrows?), modern organization of a restaurant, shoe making, what you want. The key is, as a business man, he can then kick the concurrence off the market by being cheaper and higher quality at the same time. Being a leader and business man he will certainly be fully capable of dealing with the mafia-like reactions and consequences that were normal at the times. You're setting John into a quite violent time there! [Answer] **The Rocket Stove** Just a few slight modifcations to a traditional brick/steel/clay stove (not needing any additional materials, just a modified shape) drastically increases the burning temperature and fuel efficiency of a stove. One of the things that held back development is the difficulty of smelting and metal working, the effective cost and difficulty of cooking, the expense of fuel, and much more. A Rocket Stove, invented in the 1900's, is pretty much an amusing sidenote of technology today since we have more high-tech solutions of improving our fires such as electric blowers, bellows, space heaters, electric coils, blast furnaces, etc. The rocket stove, had it been invented anytime between 4000 B.C. and 1700 A.D. (the whole range of which had the prerequisite technology), would have drastically revolutionized technological advancement. [Answer] [Aeolipile](https://en.wikipedia.org/wiki/Aeolipile) / Simple steam engine The Aeolipile was made as a curiosity in the first century AD, its essentially a sphere filled with boiling water that has two exhaust pipes that allow the sphere to eject steam and spin the sphere. I think an average person like John would know how to make a really simple steam engine like this and that using more water, more heat and bigger boiler could provide more power which makes it more useful. Once you have a basic steam engine John knows enough history to figure out what comes next, lathe is an obvious first step, make an Aeolipile attach a rod on axis of rotation, skewer something on the rod and now you have a lathe. Power source for an [Archimedes screw](https://en.wikipedia.org/wiki/Archimedes%27_screw) All of a sudden you now have a powerful siege weapon, a self running pump to drain your enemies water supply UP a hill as well as fast water distribution for permanent installs in cities. Grinders for metal work, windless windmills (just called "mills" if you will) for grain, etc... All John needs to know is a steam engine is essentially a kettle with an exhaust pipe and that engines of any kind are really useful. He will simply take seriously and push development what was seen as a mere novelty or curiosity. [Answer] Well, here's two things I can think of off the top of my head. # Germ Theory and Sanitation The Germ Theory was truly *groundbreaking* when it first came out. Before bacteriological causes, every disease was assumed to be caused by either poison or an angry deity. As a result, most "cures" were ineffective, if not harmful (Pliny recommended eating the offending dog's head as a cure fore Rabies). Furthermore, they did almost nothing in the way of sanitation. As a result, introducing the Germ Theory, along with some basic sanitation techniques, would save many lives. Indeed, the "basic sanitation techniques" part probably wouldn't even be necessary - they knew "basic sanitation techniques" in the 5th century (have you ever read [Leviticus?](https://en.wikipedia.org/wiki/Book_of_Leviticus)), they just didn't use them. # Modern Mathematical Notation The ancients were really good at math (many of the theorems and equations you learn in Algebra and PreCalc predate the 5th century). However, actually *doing* the math was a pain, and transferring that knowledge to others was expensive due to the verbosity of their notation. The introduction of modern mathematical notation (Arabic numerals and arithmetic operators being the most important) would make math much easier. While "John" probably couldn't use this to make much money\*, it could probably get him into a monastery (which were just starting to become rich during that period). \* EDIT: On second thought, tutors were paid huge sums back then - it wasn't every day that you could find someone who was both literate and looking for a job. [Answer] # None. There is common misconception that history is linear and things get invented and change the world. It's false. Things get invented, then they fall into obscurity and get reinvented anew. Sometimes they even get forgotten after a period of widespread success, like phalanx formation. John needs the same thing as Beth from 2348 who traveled to today with knowledge how to beat COVID-19 in 3 simple steps: being trusted by powerful and rich people who can make it happen. The thing that an outsider, like a time traveler, can never have. John can't change the ancient world, just like Beth can't stop what's going to happen in early 2021. [Answer] ## Cutlery and plates? Spoons, forks and plates are pretty basic and we use them every single day but nobody thinks "That spoon! I like that spoon! That spoon is great! What would I do without that spoon?" Nobody really appreciates forks, spoons, plates and how important that simple stuff is, because it's something so simple and basic that we think that it's a totally normal everday tool. People ate back then with their hands and put their food on bread cause they didn't had plates and cutlery. Putting a fork in your meat and having clean hands after eating would change a lot. And now imagine how much money you can make with that invention. Change their lifes and throw a spoon in society! [Answer] # The Toothbrush According to Wikipedia: > > The first bristle toothbrush resembling the modern one was found in > China. Used during the Tang Dynasty (619–907), it consisted of hog > bristles. > > > So, if John introduced it to Europe a couple hundred years earlier (and got people to believe it would help them live longer and actually use it), it might change things significantly. ]

[Question] [ So, a group of archeologists from the year 4978 have uncovered something strange. They’ve been searching for the missing link between them and their primordial ancestors, and they seem to have found something interesting. Their was a a large stone, sticking up from the ground. On it were some unintelligible squiggles that read “Here lies Robert Paul Smith 1983-2057” They started digging, and they started finding remains, that looked nearly identical to modern human skeletons. They don’t know it yet, but these future archeologists have just uncovered an ancient human burial ground. It is a modern cemetery to us, but they don’t know that. They can’t read any headstone markings, as they speak a different language. So my question is: In a modern cemetery, what evidence could you find that the skeletons buried in the ground were intelligent? In a cemetery, what evidence could you find that an intelligent, technologically advanced species existed? [Answer] **Medical Devices, Medical Evidence** Some of the skeletons will show obvious signs of recovery from normally fatal illnesses, obvious signs of advanced surgery like titanium pins in healed broken bones, artificial hip joints, dental crowns and fillings, root canals etc etc. They will see that the majority of the skeletons are from individuals who lived to very old ages. This will demonstrate to any future archaeologists that we had a highly organised society with advanced medicine and prolonged intensive care for the ill, which is one of the typical hallmarks for technological advancement. [Answer] What does one normally find in a cemetery? * **Headstones.** Headstones have designs and markings, and chances are, they're going to be at least partially preserved. * **Coffins.** Coffins are [less than 7000 years old](https://en.wikipedia.org/wiki/Coffin#History); some wooden coffins have survived for that long somewhat intact. Modern coffins are often more durable than the early wooden constructs, and are going to last a lot longer. * **The arrangement of graves.** Most of the cemeteries I've seen involve graves laid out in grid-like patterns - which shows deliberate planning on a large scale. Unless there's major seismic activity, there's no way this alignment will change drastically over time. I'd like to note that [claims of burial by *homo neanderthalensis*](https://en.wikipedia.org/wiki/Neanderthal_behavior#Burial_claims) and [*homo naledi*](https://en.wikipedia.org/wiki/Homo_naledi#Deliberate_placement_of_bodies_hypotheses) have been disputed. It is possible that in one or two cases, they buried their dead, but certainly not with the degree of organization that modern human cemeteries exhibit. There does seem to be a divide between prehistoric human burial and modern human burial - namely, that it happens at all! In short, the existence of a planned burial ground itself should be enough to convince the archaeologists that whoever made it was fairly intelligent. [Answer] The headstone is probably more than enough; *we* understand the Ancestors had some sort of conception of death and possibly an afterlife because neolithic and even Neanderthals were buried, often with flowers or rubbed with red ocher or other dyes. A typical modern human burial (at least in the West, as implied by the OP), would have the body preserved with formaldehyde, the skin prepared with makeup, the body dressed in a suit or similar clothing and then laid in a casket made of wood or metal, with metal fittings such as hinges, clasps, carrying handles etc. The casket is lowered in an artificially dug hole (traditionally 6'X4'X6' deep). So the archeologists would discover: A cut headstone, with indecipherable but fairly obviously artificial carvings on it. The stone itself may have marks on it left by mechanical saws used to cut it to size, or the polishing process. The stone is not simply set in the ground, it may be resting on a footer or foundation of some sort. Edit to add, based on some comments, the stone itself is unlikely to be native to the area where it was found, and even badly eroded would be an odd shape and size given the local geology of the region. [](https://i.stack.imgur.com/muTHp.jpg) *A headstone on a base* An obviously dug hole. The earth in the hole does not match the layering of the earth outside of the hole, but seems to have been randomly backfilled. This is even more obvious given the implication by the OP that the entire cemetery site has been buried for two millennia, there are distinct layerings of earth over top of the site as well. [](https://i.stack.imgur.com/4reiE.jpg) *natural layers of soil* The remains of the casket. The wood would leave fairly obvious residue in the ground, and a metal casket would be corroded but may possibly be recognizable depending on the material and conditions of burial. The metal fittings would be fairly obviously artificial as well. Current technologies would allow the archaeologist to date the remains of the wooden casket, and a good guess as to the age of the burial could be made by examining the metal, corrosion and so on. [](https://i.stack.imgur.com/fXyYj.jpg) *A casket showing the multitude of fittings and liner that will become evidence in the ground* The body would likely have decomposed, but there would be interesting residues on the bones from the chemicals used to preserve the body, cosmetics, the decayed clothing and shoe leather, the lining of the casket and so on. It is possible that some of the materials (especially synthetics) night even have been preserved over this time. A skeleton with rayon socks and underwear would be a bit difficult to explain otherwise. So the future archaeologists would not wonder for very long if the burial was "artificial", nor would they be in doubt about the ability of these long ago people to create and use technology. As an aside, considering *we* can read many "dead" languages from civilizations as far back as the Bronze age (Sanskrit, Hittite, Linear B, Egyptian hieroglyphs etc.), it seems a bit strange that they cannot read or decipher *our* languages. A well preserved plaque on the Moon on the side of the Apollo LEM's would provide a great way to begin studying English, for example. [](https://i.stack.imgur.com/Ie1qH.jpg) *LEM plaque. The LEM itself will be recognizable for a quarter billion years, the plaque should be good for a million or so* [Answer] TL;DR Graves at all are a good suggestion, worked stone is a pretty big hint, worked metal is hard to ignore, dismissing plastic would be silly, but finding medical implants would have to be totally suppressed to make a theory of unintelligence plausible. --- Some few other species take interest in their dead so the future people might be forgiven in placing "true intelligence" above some higher bar than just organized dead. Modern graves often have casket liners of metal, plastic or cement, these are obviously worked materials requiring advanced logistics to create. Possibly this could be dismissed as the work of some other group potentially long posthumously. Similarly grave goods like the metal and plastic parts of clothing should survive, and be very clear indications that the site was prepared by an intelligence. Whether that intelligence was the creature in the grave could still be doubted. Objects in the graves intermixed with the remains would much trickier to explain. Fillings in teeth beside unfilled cavities imply advanced care during life because postmortem decoration would presumably get them all. Clearer but rarer; healed surgical wounds especially those involving permanent metal screws or pins would strongly imply contemporary materials and techniques. Nuclear powered pacemakers and other non-natural radiation sources from medical treatment would be a huge giveaway if found, but are rare enough that it might not come up. --- A point was raised that all of this might be true in a pet cemetery as well. The best evidence that the interred are the intelligence might be that the hardware of the coffins and the fasteners for clothes are good fits for human hands. But the actual tool marks on them would likely all be machines. Work related bone growth might also suggest humans occupation. 15th century longbow archers have been identified by skeletal deformities from using heavy bows, possibly back or neck problems from computer hunching or tool marks in bone from industrial accidents or murders could give hints to modern life. [Answer] Jewelry! The first telltale clue of an intelligent being buried in that cemeter would be the jewelry -gold, gemstones...all showing a fine craftmanship. Especially diamonds: producers laser-carve an identification code in the crystals, and that would be the definitive proof that these ancestors were some smart people. Also, it could be of help that in some cemeteries pets and owners are buried together. Studying the remains, these scientists could pinpoint the difference between humans and differently intelligent beings. Also, several skeletons could display prosthetics implants, nails for bones, dental works in gold or ceramic, cardiac bypasses...that's the stuff of some serious technology, when they see the precision in that work. [Answer] ## Metal coffins are dripping with clues for an experienced archaeologist. There's a reason that we talk about the Bronze Age, and the Iron Age. Metallurgy has been constantly developed and refined since the beginning of civilization. Our skill with metal would provide many indications as to exactly how technologically advanced we were. While most of us would picture a wood coffin, metal coffins (in particular stainless steel) are increasingly common. [Stainless steel](https://en.wikipedia.org/wiki/Stainless_steel) was first developed in the 19th century. But a steel coffin is more than just a material. It's a process. **Some clues derived from the [steel coffin manufacturing process](http://www.madehow.com/Volume-4/Coffin.html):** * Flat sheets of steel of uniform thickness are used. * The sheets are welded together. * The coffins are spray-painted. * The lids and handles are attached by screws. All of these point to modern levels of technology and industrialization. In particular the chemical composition of the steel and the paint are going to be very telling. [Answer] In addition to headstones and coffins as mentioned in other answers, many graves will have cremation urns. These can be made out of many materials such as brass, aluminum, steel, and they also have fancy engravings on them: [](https://i.stack.imgur.com/Fdip4.jpg) Urns from 9000 years ago have been found that are still intact. ([source](https://en.wikipedia.org/wiki/Urn#Cremation_urns)) [Answer] # Laser engraved gemstones in jewelry Many dead would be buried with jewelry. Many of the stones would have identifiers lazer etched. Nobody is going to be able to etch something as precisely and small in a low-tech society. [](https://i.stack.imgur.com/HiqVC.jpg) # 3D lazer engraved photos Many people are buried with photos or keepsakes, occasionally they can be things like this: [](https://i.stack.imgur.com/ujMTR.jpg) [](https://i.stack.imgur.com/bYnFY.jpg) Such images would likely last for millions of years if the glass was just sitting underground even if the surface was degraded a little. They would show us to be a species capable of engraving images into the center of glass/crystal blocks (high technology) and the images would show relationships, clothing and other elements of everyday life. # Mobile Phones, watches and electronics. It's not uncommon for people to be buried with a few pieces of personal electronics, some CD's or similar. Particularly when the deceased is younger. These would show silicon chips which no low-tech society would have. # Glass, very perfect glass It's hard to make very flat, very perfect glass. Up until the invention of [float glass](https://en.wikipedia.org/wiki/Float_glass) such glass was impossible to make. Phone screens and even photo frames that people are often buried with would show to be made of very perfect glass and some would show to be far [higher tech materials](https://en.wikipedia.org/wiki/Gorilla_Glass). # The text on the gravestones The text from hundreds of headstones would be an extremely usable corpus for figuring out our number and date system, some common verbs like "died", family terms like mother/father/son/daughter with regular terms to distinguish them like "survived by". The people of the future will not be idiots. Show them enough text in a meaningful context and they'll figure out plenty of elements of our language. [Answer] A cemetery would already reveal that whoever used it had some sort of mental process which was used to elaborate on the death of a relative and, consequently, on the difference between life and death. Something similar happens with elephants, which are known to tribute honors to their deceased peers. Add to this that the content of the graves could contain items which would further hint to some sort of higher capabilities: metal artifacts like golden ring, the stone itself, the coffin, any object buried with the dead. All this inevitably point toward an intelligent species. [Answer] # They already found overwhelming evidence A graveyard and, especially, a headstone is a piece of technology and they should be able to recognize it as such without any question. Being able to read the writing doesn't matter if they can tell that there is writing at all. As far as I know, there are no unintelligent beings on the planet which have graves so finding a grave is itself clear evidence that the people who made the graveyard where intelligent -- the headstone only makes this clearer and having multiple graves in the same area makes it a no-brainer. A graveyard, by Danish standards at least, are always aligned in some sort of grid like structure, with paths between the graves. The graves are almost always dug so that the heads of the dead are facing the same way and the dead are always buried in some sort of casket -- all of these things will be very evident when digging starts, even thousands of years after the cemetery has been abandoned. Whatever else they might find is only useful if they want to assess how advanced the civilization was, but won't really change *if* the people where intelligent or had technology. [Answer] # Mausoleums If the archaeologists can find cemeteries, they should be able to also find mausoleums, which are indisputably built by technological creatures. For instance, if the Taj Mahal got buried by the dust of the ages, uncovering it would reveal finely carved stones from a variety of sources, plus modern pipes, railings, and the like to support fountains, visitors, etc. The adjacent grounds contain toilets, gift shops, and other indications of civilization. A moderately well-sealed private mausoleum should be able to preserve all kinds of high-quality urns and grave effects for a very long time. The craftsmanship and materials would demonstrate that a technological society would have had to build the structure and everything in it. For instance, if they managed to uncover this little gem, there would be no question of technology: <https://gizmodo.com/this-is-probably-the-most-high-tech-cemetery-in-the-wor-1696153589> [](https://i.stack.imgur.com/7TtA8.jpg) [Answer] You can't make conclusions on limited information. There are some very good answers here. But what if the head stone said "Here lies rover 1999 - 2021" and the dog had a [pace maker](https://wagwalking.com/treatment/pacemaker-implantation), they discovered a [pet cemetery](https://en.wikipedia.org/wiki/Pet_cemetery). Do they conclude that rover was intelligent, for the same reason they concluded humans were intelligent? As per the other answers a cemetery can suggest the presence of intelligence, but by itself, can't tell you who had the intelligence. [Answer] Practically everything will point to a technological species. Alloys, especially those that are uniform, require technology as do synthetics. You can find this evidence everywhere. in the order that they would probably find them: **The grounds** There is usually plumbing for watering the grounds. Most modern plumbing is plastic (PVC). Even extruded uniform copper piping will imply a level if industry. **Caskets** They won't have to see the bodies. As has been pointed out, a lot of technology goes into the casket. Even cheap wooden caskets have screws that were made via mass production. **Clothes** Most clothes contain synthetic fabrics. There may be a few people who have all cotton (or whatever) clothes but most have at least some synthetics. Synthetic fabrics don't grow on trees (unless some mad genetic scientist creates the great polyester forest). **Jewelry** As has already been pointed out, modern diamonds have laser etching. Then there are the fake gems. Those would be a dead giveaway (if you forgive the expression) if they looked closely enough. Then there are watches. Even old watches have mechanisms that show a level of tech and before everyone had a clock on their cell phone people wore digital watches. Another dead giveaway. **Medical** Old Tooth fillings show some tech and modern ones are obvious. Medical implants contain alloys that are not simple or producible in quantity without technology. Medical devices contain circuits and circuit boards. Mended bones implies a level of medical knowledge and care for the sick (we look at that in "caveman" bones). [Answer] Answer presumes a typical, large, present-day American/Australian/European cemetery. **Isotopes** Modern-day archaeology uses [isotope analysis](https://en.wikipedia.org/wiki/Isotope_analysis) of bones to figure out what people ate at different stages in their lives, and where that food came from. At a bare minimum, this should tell them that people living in the same area at the same time had very different diets, and probably that much of their food was sourced a long way away from where they were buried. This strongly suggests a technologically advanced society. Isotopic analysis of soil, ice cores, etc. should also tell them that *somebody* detonated a whole bunch of nuclear weapons around 1950-2000, but that's not specific to the cemetery. **Genetics** DNA analysis of bodies in the graveyard may discover the following information: * Genetic relatives are often buried near one another, even when separated by several generations. This implies that these ape-creatures aren't just burying their dead in the next available vacant spot; in some cases they have large family plots, implying some level of organisation. * Genetic diversity within a cemetery is much higher than you would expect from a small insular community, implying a highly mobile population. * The population is fairly monogamous, and characteristics such as size and physical fitness aren't strongly correlated with reproductive success - strongly suggesting a technologically advanced society. * Depending on where the cemetery was, you could deduce the existence of different races who used to be largely separate but have recently (last few hundred years) shown up in the same territories and started interbreeding - but not so much so that the different populations have completely homogenised. Implication: society has recently undergone significant changes that made it much easier for people to move about. * In a US cemetery, examination of mitochondrial DNA and Y-chromosome DNA will indicate that two of these groups are much more closely related along the male line of ancestry than the female line, giving a pretty strong hint that one of these racial groups enslaved another group from a long way away. * In certain genetically distinctive subpopulations, e.g. Ashkenazi Jewish, it might be possible to determine that this subpopulation had a high prevalence of carriers for certain harmful recessive conditions (e.g. cystic fibrosis) but a relatively low rate of marriage between carriers, implying that they had access to premarital DNA screening. However, this would require a large number of bodies to test - probably tens of thousands. **If headstones have survived in legible form** * Because Y chromosomes are passed down the male line, genetic markers on that chromosome correlate strongly with surnames on headstones. This provides a major clue to deciphering headstones, and allows our archaeologists to determine that the species paid attention to male-line descent (further supporting the case for a largely monogamous society). * Comparison to genetics allows identification of typically male vs. female names, and name differences by race. * Comparison of birth/death dates to the approximate ages of those buried, and to their genetic relationship, should be enough to decode the meaning of these dates. This will then imply that these creatures were counting time from a date approximately two thousand years earlier. **What they don't find** Parasites. Pretty much every wild creature and every low-tech society in existence is carrying a significant load of parasites, but there are few or no flea shells and worm eggs among these burials. How did they manage that? [Answer] I think the use of the term “intelligence” is relative. If the signs of intelligence are advanced beyond the level of comprehension of those perceiving them, then those signs may go unnoticed. Also, some signs of intelligence may also be culturally or societally dependent. As such, I think an important aspect of signs of intelligence is how they are perceived. Math and science are universal, so showing examples of mastery in these fields is one way. As an example, the Voyager spacecraft carried a plate with inscriptions showing various mathematical formulas/identities (example: pi), our place in the solar system, and even a Beatles record. Are you looking for signs of intelligence within a certain context? [Answer] To pull inspiration from the original Planet of the Apes series: anything someone would be buried with today. Their skulls could show dental work, especially synthetic fillings, they might have artificial hearts/pacemakers and other implants, there might be jewelry, watches, or glasses present on their person, and, of course, toys. Many people are buried with some form of stuffed animal or toy, often placed there by a child in their family. These are the sorts of clues someone could look at and realize they aren’t just looking at the remains of animals. [Answer] I would like to bring another aspect, somehow inspired by the f[orensic work that was done on Ötzi](https://en.wikipedia.org/wiki/%C3%96tzi#Cause_of_death). ## Cause of death * High speed crash: If they find a large cemetery, they will discover by analyzing skeletons that an important percentage of people died because of high-speed crashes (car crashes, and others ski/plane/... accidents). To travel at high speed implies technology. + Additionally they will see that even more survived such crashes, implying advanced medicine. (But there are already enough answers about medicine) * Bullets hole: Probably will still be recognizable in the skeleton. It's advanced tech again. * Age: Analyze of skeleton will show that many people were old. This implies advanced medicine and hygiene and agriculture tech. ## DNA * If they can retrieve some DNA, they will see that we are pretty mixed. Someone that is born in Australia can die in Europe, ... People from all over the world are having babies together, mixing genes at an unprecedented speed. This implies fast and cheap long distance communication and travel, ... [Answer] 2000 years is long, but a lot of objects would be preserved, see Tutankhamun's grave. The painted murals are still visible, all the pottery and jewels are almost intact. It's different if someone is buried in the directly, but caskets can be fairly resistant. Then, if someone is buried fully clothed like it's common in many countries, and with a watch for example, that would be a clear sign of intelligent life and technological advancement. Even if they were buried in a wooden casket and it completely disappear and their clothes too, there's no way a wristwatch would disappear, it would still be around the wrist of the skeleton, even after 2000 years. ]

[Question] [ It's a well-known fact that attacking or defending from a high ground gives a wide range of advantages over an opponent occupying a lower position. I'm DM-ing a campaign where PCs are about to defend their freshly acquired castle and the village around it from a group of invaders. The village is surrounded by small hills, which obviously leaves them in pretty bad position. I want to create a group of very specific units, excelling at fighting from low ground, so the PC task is going to be to get their help. I know that it'd probably better to set some defenses on the hills and catch the attackers off guard, but what type of unit would be more effective fighting from a low ground, against an enemy shooting and rushing down the hill? What kind of equipment or abilities would it have? Should it be of a specific race? There are no firearms but dwarven engineers exist and they may help with some unconventional gear. The world setting is fantasy, so magic is acceptable to a small degree but very rare. I'm looking for a kind of unit that given an opportunity to pick their position during the battle, would always prefer to be on the low ground to be the most effective. [Answer] The high ground is better because... * you can more easily throw stuff onto the enemy, * you can walk down saving strength, * you can see further, and * in close quarters you stand taller. We need to demolish those bonuses for the attackers, and the accompanying mali for the defenders. Some points (seeing,walking) are already weakend, because the battle site is known, and the defenders do not need to move much anyways. If there was a race of warriors that near perfect natural cover from above, the rest of the main points (throwing, taller) would be weakened. The problem with super-armor is that it encumbers a lot: but this is a plus, it explains why this race is not always winning - they can' t move so well. So now we have warriors formed like mushrooms. They need some martial ability, which either should not require line of sight (say a poisonous gas or spores that is slightly lighter than air) or the armor needs to be transparent (otherwise they have to peek around it, exposing themselves to enemy action). So now we have warrior-mushrooms with poisonous spores and (possibly) a clear-crystal shield-head. If we go with the transparent armor above, we need a way to exploit it: line of sight magic, lasers, basilisk stare, or, my favorite: telepathic links to powerful but dumb-as-bricks airborne creatures. Say, sacks of lifting gas with incendiary bomblets. The mushroom-warriors look up the hillside to the approaching enemy (through their impregnable crystal shield) and compel their floating thralls to release their searing cargo at the right time. So a race of crystal-mushroom warriors with floating, poisonous spores and balloon-bomber thralls. They like getting paid in nitrogen-rich biomass, btw., especially from bovine sources. [Answer] # An army that moves *in* the ground Human warfare has actually been conducted under ground. From the [cave bases in Afghanistan](https://en.wikipedia.org/wiki/Tora_Bora), to [tunnel warfare in Vietnam](https://en.wikipedia.org/wiki/Tunnel_rat), to [mining in The Great War](https://en.wikipedia.org/wiki/Tunnel_warfare#World_War_I). In a fantasy world, where some races live under ground, like for example [Drow](http://forgottenrealms.wikia.com/wiki/Drow) and [Duergar](http://forgottenrealms.wikia.com/wiki/Duergar), relying solely on being on a hill to be safe against attackers would be folly at best. With the victi... eh... defenders, conveniently placing themselves on a hill — with luck a soft earth hill instead of a solid stone hill — undermining their pathetic fortification will be a breeze. Dig out tunnels under the walls and major buildings... blow out the support structures for the tunnels... and watch the whole thing come crumbling down. [Answer] **Mud Hoses** Dwarven engineers create some kind of very big and powerful water/mud hoses. As soon as attackers are charging downhill, they target the hoses against the hillside, to generate a very slippery terrain. You can add spiked traps below or a an elite group of spearmen to deal with the rolling attackers. [Answer] Not necessarily a combat unit: **Sappers**. These are the guys who make castle defenders *very* nervous, just due to the possibility of being there. Now, we do not attack a castle, but defending a valley against an enemy who will be comming down a hillside... How about we treat the hillside like a castle wall, and bring it down when the enemy charges over it? Alot of traps on the way, cave-ins under the feet of the enemy, and you will demoralise your opponents troops! They will not know "Is the path ahead prepared or not?" and slow down by a fair amount. Given enough preparation time, sappers could be the terror on the battlefield. [Answer] In the real world, this is known as a [reverse slope defense](https://en.wikipedia.org/wiki/Reverse_slope_defence). As noted in the Wikipedia article I cite, this is most commonly used by units to reduce the effectiveness of enemy long range or indirect fire, or to set up a sort of ambush on enemy units when they crest the hill. > > when enemy forces are known to have superior long-range direct-fire or indirect-fire weapons, the majority of the defending force can use the hill to limit enemy observation and reduce the effectiveness of said long-range enemy fire. This tactic may even succeed in deceiving the enemy as to the true location and organisation of the main defensive positions. Typically, a smaller unit is still posted on the forward slope to perform observation and delay attackers if the defending force needs to relocate its main body onto the forward slope. Otherwise, when the attacker advances and passes over the top of the hill, they may be ambushed by short-range fire from the defender on the reverse slope > > > Notably, this is only effective for ranged units - you wouldn't see a melee unit setup a reverse slope defense, as being downhill puts melee units at a significant disadvantage. Ranged units can use it great effect in a great many situations, but it's not a tactic that generally applies to one specific type of unit or another; it's a situational tactic. If your opposition outranges you, (say you have a unit of shortbows facing off against longbows, for example) or you're concerned about indirect fire (your opponent has a lot of siege weapons and mages throwing fireballs around), or can't find another way to get an advantage, setting up a reverse slope defense and baiting your opponent into an ambush as they crest the hill might be a good idea. [Answer] If your army was say 80% archers, and the enemy was mainly not, and the low ground can be flooded to make it marshy, you'd **love** to stage the battle on that low ground. While the enemy is out in the open slowly trudging through the muck trying to get to you, your forces are filling them full of arrows. Anyone heavily-armored enough to have any hope of survival out in the open against massed archers is liable to have *extra* problems trudging through the mud (and God help those who slip and fall down in it). Once those melee fighters do manage to get to your forces, they're going to be exhausted. If the other side *does* have some archers, a good trick would be very early on have everyone pack up their bowstrings, then have a druid or mage cause a sudden downpour. That will slacken the enemy bows, making them much less effective than yours. This was the basic setting of the crushing English victories at [Agincourt](https://en.wikipedia.org/wiki/Battle_of_Agincourt#Main_French_assault) and [Crecy](https://en.wikipedia.org/wiki/Battle_of_Cr%C3%A9cy#The_French_attack). Don't get me wrong, your archers would probably *still* also love to be standing up on a nice hill. However, this is a way to get the benefits of a hill, but have it on nice flat ground that cocky knights will be willing to assault you from. [Answer] In a conventional force on force scenario, even combat engineers will have a great deal of difficulty (saps and tunnels can be bombarded from above to collapse them, for example). So don't fight a conventional battle, but rather go 4GW on the enemy: > > Fourth-generation warfare (4GW) uses all available networks -- political, economic, social, and military -- to convince the enemy’s political decision makers that their strategic goals are either unachievable or too costly for the perceived benefit. It is an evolved form of insurgency. Still rooted in the fundamental precept that superior political will, when properly employed, can defeat greater economic and military power, 4GW makes use of society’s networks to carry on its fight. Unlike previous generations of warfare, it does not attempt to win by defeating the enemy’s military forces. Instead, via the networks, it directly attacks the minds of enemy decision makers to destroy the enemy’s political will. Fourth-generation wars are lengthy -- measured in decades rather than months or years. > > > So the attackers sweep down from the hills and find....nothing. The knights and men at arms have fled, leaving only a confused and frightened peasantry. Rumours abound, but when questioned, the peasants have no usable information, only a mass of contradictory stories, many of which sound like nonsense. Unsatisfied, but seeing no real threat, the attackers move into the castle. Men start disappearing at night. Horses are stolen. Raiders come to steal cows and burn crops. Trade caravans are robbed just outside the edge of the territory. Small treasures disappear from the castle (or are sometimes found in entirely different locations from where they were stored). The peasants are in an uproar, and try to crowd into the castle at night for protection. Yet, no matter how rapidly the new lords move, or if they send forces out to piquet the area, they never seem to find anyone. It is as if the night raiders have inside information, or hundreds of eyes watching their every move. The new lords may suspect the peasants may have something to do with this, or the former owners are hidden in the population somehow, but face a quandary: torturing or abusing the peasants for information will only turn them against you, but right now they are already mistrusting the new lords because there is no protection from the night raiders. It is lose/lose either way. Eventually, the new lords will be holed up in the castle, as if they are under siege. The food supplies are running low, morale is shot and lack of water and disease start to take their toll. At this point, your forces can come out of hiding and triumphal reappear to "save" the peasants and finish the siege. After all, the new lords are trapped in the low ground..... [Answer] About the only thing I could think of that might be more effective from low ground would be a shield/spear wall. The shields would be at a better angle to provide more protection from arrows and it would be harder to stop a downhill charge that is met with the spears. The only benefit that they have is that they are defending from a downhill position and not attacking from one. [Answer] The army of... the navy. * If something is higher than the sea level, it's going to become target of more cannons/arrows, and probably WAY lighter than the sea level farer. * On the same level (sea) it'd be level play (heh... ok.) * The lower you are, the easier it's for you to spot the ones above and the harder you are to be found by them. And buoyancy is relatively easy to control (more than gravity, at least). So munitions/attackers won't have a hard time coming hard from below. Like submerged (spiky/explosive) inflatables hitting their faces hits usually stronger than the same mass being pulled by just gravity. So the sea village will look almost normal, but the sea castle should have more guards and higher (lower?) walls on the way down than the way up. Or even better, be all the way down. The sea hills that surround the castle will be no problem. They are called waves, and they will move themselves out of the way, leaving the attacking army surprised and lost because the advantage is gone and the castle just disappeared behind a moving hill. Unless the attackers are surfers, but they are too light armed to pose a challenge to sturdy castle walls, and too cool to bother carrying scuba equipment to even touch the castle if its at the bottom. May be fun. [Answer] **Carbon monoxide / carbon dioxide poisoners** [Carbon monoxide poisoning](https://en.wikipedia.org/wiki/Carbon_monoxide_poisoning) is documented as occurring as far back as 200BC. Carbon dioxide poisoning killed 1746 people and thousands of livestock in one naturally caused incident in 1986 at [Lake Nyos](https://en.wikipedia.org/wiki/Lake_Nyos). In some incidents of volcanic activity it has not been clear which of these gases or others caused the fatalities. It can *only* happen in enclosed spaces or low-lying depressions with minimal air currents, so this is not a defence that can be used on high ground. The danger with these gases is that people often do not realise they are being poisoned until they are too debilitated to remove themselves from the affected area. Dwarven miners can be expected to have learnt about these hazards from their experience underground - mining was the area that high numbers of fatalities inspired research into the causes. So - I propose a small heavily armoured force that: * do not need to breathe (constructs or undead if available) or * that can hold their breath for hours at a time (if there is a race with that ability) or * that have magic / air bottles that will let them breathe normally. Make them obviously equipped with missile weapons only and have them build fortifications that provide cover from missile fire but will not significantly impede a charging army. Evacuate all of the villagers and livestock, then flood the area with CO or CO2 as available. The attacking commander will see a ranged combat opponent with no significant melee capability. Unless he knows the trick, it looks like he is better off charging into close range than undertaking a prolonged archery / siege weapon duel. Once the attacking forces charge in, the defenders just need to fall back before them and all of the attackers will be dead in a few minutes. The possible weakness of this plan in your campaign is the low magic setting. In order for this to be a feasible defence, the defenders must be able to operate in a poisonous gas environment, which requires advanced "dwarven" technology or a racial / magic solution. [Answer] Any army that is facing an attack from the air will likely prefer to fight from ravines and valleys because it will necessarily force their foe to fight on more predictable terms (ie: limited lines of attack) On the other hand, ravines and valleys channel the bomb-blasts and reduce mobility on the part of the defenders, but any fortification that can withstand such weaponry is equally able to do so in the valley/ravine as it is on top of a mountain. So build it low in a place where lines of attack are few and your defences can be properly oriented against the foe. [Answer] # Wildfire! You have a dense forest on the slopes. You can light a fire in the crowns of the trees. These fires are extremely fast moving, and more so on a slope. A tree fire in a flat area can be growing faster than a human, literally running for his life, can flee. Yes, that actually happens. The fire is extreme when it reaches the top of the hill. Like **"you can not imagine"** extreme. No really, you cant. The direction of the strongest blast can change very quickly - if you can control the wind, even a little bit, you have much control for the fire. Now, you want multiple shots! The wood can be separated in independent parts - burning separately. By nature - after landslides, burrowing all trees, or just a part of the hill where no plants can grow - blank rock. It can be man made, like for large high voltage power lines - the company takes very much care that the plants come not near the high voltage lines. Or simply fire breaks - spaces, held free of plants to have fires not cross it. You can have only one shot per section, or sometimes two. But they are strong. Nobody can survive, even with some shelter. The oxygen runs out. So, make sure you light the top of the trees, and good luck! [Answer] **Troops that are good in trench warfare.** Troops that have past successful experience of fighting in trenches when under dire situation will naturally gravitate towards digging-in. Such troops would prefer to conserve energy - as a tactic or out of necessity (low in resources) - by seldom attacking enemy. They would prefer enemy to come to them. Being on low ground can be a clever technique of luring enemy to attack them. In order to cut losses from their enemy's missile weapons *before* the attack they may place their trenches as far away from their enemy's (elevated) position as they can, and/or place some makeshift low wall from whatever is taken out of ground when the trenches were being made. Core tactic of such troops is to convince their enemy that they are at a disadvantage and so is easy to take out, AND cannot be taken out just by throwing missile weapons on them. [Answer] What about an army that specialises in using lighter than air toxins? Or fire? Since these toxins would travel uphill easier than downhill, it would make sense for them to prefer fighting from low ground positions. [Answer] ## You need dwarves from the Giantslayer Clan While these warriors don't necessarily prefer the low ground, they are extremely well-trained in overcoming the disadvantages. They are heavily armored, sure-footed on rough ground, used to attacks from above and their shield wall seems like a cliff-side. No human army can match what the giants throw at them (literally and figuratively). Along with their elite soldiers come the engineers. They specialize in turning the battlefield against the enemy. Traps to hinder movement, smokescreens to limit visibility and effectiveness of ranged weapons and when battle is joined they use flamethrowers to repel cavalry charges. If you're exceptionally lucky, they will be accompanied by a Stormcaller. Hilltops are not a good place to be when the lightning comes and arrows are all but useless when the winds are tearing at you. [Answer] ## A Big Boat The reason you would prefer a low-ground position is that low ground is also where the water is, and if you have a large boat with lots of guns, you want to be able to use it. Especially if it's a smaller town, it might not have a lot of its own firepower, but a warship sailed in on the river from a nearby coast could add it's own powerful arsenal. Maybe its a pirate ship hiding inland temporarily, or a warship that needed to resupply unexpectedly. Either way, getting it on the side of your PCs would provide cannons and an excellent spot to defend from. [Answer] Creatures that have upward angled eyes would prefer to fight from below because they can see better looking up. If their heads were unable to articulate in the downward direction it would drive their evolution towards 'looking up' and create features essential for defending themselves from higher threats. [Answer] Cavalry. Hills aren't easy to plough and are therefore often wooded ... or steep and rocky. Cavalry (especially a formation or unit of cavalry) may prefer flat open ground (e.g. river valley, flood plain, flat fields, roads, etc.). [Answer] If the surrounding hills have trees or other flammable flora, perhaps a specialised fire unit could be positioned at the bottom of the hill where a fire is more likely to spread upwards, towards the attackers. Perhaps the rising smoke might initially obscure the vision of the attackers and prevent them from shooting down accurately (although the smoke might later accumulate in the low village. Could this specialised unit also be experts at fighting in low visibility or poorly oxygenated places, like mine-shafts for example?). Water from the village could be used to douse lower trees/bushes and prevent the fire coming down the hill or spreading amongst the houses. This could lead to further quests if it’s the villager’s hillside crops that end up being sacrificed. [Answer] Two things, make use of knowing how they'll attack and have a reason the Village is in the valley instead of a hilltop. For example: there's a grass that's extremely slippery on the hills, so the villagers avoid it (and perhaps harvest it). Enemies attempting to charge down the hill might break legs, arms and necks even if the defenders dont do anything. The hills are dangerous. Natural gas deposits could create the 'eternal' flame sites we have in the real world. Besides igniting the gas, the natural bouyancy of the gas and the wind could make the valleys the only safe places, with enemies arriving sleepy from lack of oxygen or dead at the bottom after an attack. Other dangers on the hills could be extremely territorial animals like birds or insect swarms that deal with people who disturb their hills. Sarlac pit like animals could live at the bottoms of the hills, or large versions of burrowing spiders or similar that make sure enemies/prey cant stop after the charge and are pulled in to be killed and devoured. [Answer] What you could use are pikemen. If enemy has only/mostly melee, they will have to charge down the hill. And if you ever ran down a hill you know that it is hard to stop. Even if it's matter of being impaled on pike or living. When they charge, then surprise! From shack near hill pikemen emerge and guide, in such formation that there are virtually no spaces in between. Enemy is just impaled! [Answer] Catapults/trebuchets and siege towers.. a castle on hill is still rubble when a big-ass rock smashes it. I'll also borrow this totally asinine weapon and suggest a variant built for a Ballista: [](https://i.stack.imgur.com/xk4X3.jpg) Because you can't defend what no longer exists on this plane! [Answer] Supposedly [elephants struggle to run downhill](http://sharathpandukal.blogspot.com/2012/08/how-to-survive-elephant-attack.html). I'm not 100% sure whether it's to do with how they walk or how their legs work, but if you were attempting to restrict a charge of elephants (or creatures that walked the same and/ or had the same kind of legs as them), a low-ground position might be beneficial to restrict their ability to charge your defensive lines. Of course this is more predicated on what disadvantages an enemy has as opposed to the low-ground working to your own advantages, so it might not be applicable against all enemies. [Answer] You have an Ent-like species of warriors. The hills surrounding your city are made up of loose, shalely material covered by a couple of inches of top soil. When the enemy rushes down these hills thinking they clearly have the upper hand, your special force ents tear in to the hillside causing mini avalanches. The ents are of course also rooted in to terra firma at the base of the hills. Those enemies not buried by the initial slide will be quickly dealt with by large, tree-branch-like arm clubs. [Answer] From Greek mythology, Antaeus was invincible as long as he was touching the earth. Perhaps you could work this hero into your story. [Answer] The army will benefit from being downhill if it uses some kind of reusable missile that can return to them by rolling down the slope after being trown. For example, if the army has a trebuchet-like weapon shooting big round stones, that stones can just roll back to them to be shoot again to the enemy. Of course, the army needs the ability to safely catch a big stone rolling down the slope while the enemy must not have the ability to catch the same stone when landing upon them. Another example would be the mud hoses proposed in Onofre Pouplana's answer. If the mud slides to you, you can collect it and trow it to the enemy again. Please notice that if the army were on the top of the hill, all those missiles will just roll away and you would soon run out of ammunition. [Answer] Camouflaged units have a distinct disadvantage at the tops of hills, where it's easier to see them silhouetted against the sky; they would be a good candidate for a force that preferred to fight on low ground. If they were well-disguised and lying in wait at the bottom of a hill, they'd be able to use ranged attacks to pick off enemy targets with ease at the top of the hill - even though gravity is working against them, the range is short. They'd probably need to be spaced relatively far apart compared with a regular army, though (the camouflage isn't useful if the enemy can just shoot at random patches of ground and have a good chance of scoring a hit), so their overall effectiveness isn't as great - they'd be useful for softening up and demoralising the attackers, and leaving the rest of the fight to a regular army. [Answer] Realistically if you get low or below ground then you'd be in the ocean. Hard to target something like a Russian Sub laying dormant let alone hit one miles deep. With a wide range of missile types including a under water super sonic nuclear torpedo can address most enemy types. 2 Flying drones from below ground nearby would also work. 3 On foot in a fox hole or laying covered with camouflage for a pop up ambush on flatter ground. Didn't read the other answers yet for purity of my answer. I up voted everybody. TKS [Answer] Depending on your time frame and the training of the parties involved,the low ground could indeed be an asset. Viking and early medieval armour consisted mainly of chainmail coat and helmet. The legs were often unguarded or had at least thinner protection than head, torso and arms. Now if your enemy is above you, it's easier to protect your upper body, especially if it's armoured anyway. At the same time you can strike at their legs. Remember that you don't need to kill your enemy to win. Just make sure they can't or won't fight. [Answer] Since it has not been said, a platoon of army tanks. The lowland is some disadvantage to the climber but to the tank, bring anything. Big firing guns make thirsty work of those climbing hills. Clearway over between makes even armour needless, nonetheless, what every sticks and stones and arrows they can hurl will not hurt the tank and by the time they clear over lowland they will be obliterated. ]

[Question] [ Are swords, spears, and arrows that turn slain enemies into pure gold useful, in medieval combat, or are they useless aside from free money? Notes about the weapons: * flesh wounds don't turn people to gold; they need to be killed * it also works on corpses [Answer] Honestly, the best use of this would be to turn corpses (their and yours), waste, and the like into nice safe gold. Campaigning armies in medieval times suffered greatly from disease, and poor hygiene was a major part of that. The fewer dead bodies and other disease-spreading elements you have about, the better off you'll be. [Answer] Assuming they are rare or entirely new, even a single one of these weapons would turn the tide of any war, but it would never see battle. Just follow these simple steps: 1) stab a few cows 2) hire **all** the mercenaries 3) capture whatever important places your mercenaries can reach 4) enjoy your new kingdom This will continue to work until the market becomes flooded with gold, so it's important to never show the weapon to anyone who doesn't understand basic economics. But if its use is well regulated, you can go around hiring massive mercenary items for years. [Answer] Assuming these Midas weapons convert a person into a statue of that person made of solid gold, we are looking at a pretty effective weapon in certain specific circumstances. A person, on average, has a volume of 95 liters. 95 liters of gold weighs just over 1800kg. A typical car weighs about 1500kg for comparison. So these weapons will be extremely effective in situations where the sudden addition of ~1750kg of weight would be catastrophic. Imagine you're laying siege to a castle. You fire some Midas-tipped arrows at the men in the hoardings. Most of the arrows do absolutely nothing, sticking in the wood or bouncing off the stone. But one of them finds its way in one of the arrow loops and hits a defender in the face. He's killed instantly, and suddenly weighs 1800kg. These hoardings are temporary structures built on the walls to provide a wider field of fire. Because they're temporary, they're not that well-built. They certainly aren't made to handle a sudden, localized addition of 1800kg. The floor below him immediately buckles. As he falls, his arms smash the supports out from below him and a ~5-10 meter section of the hoarding collapses. Here's another scenario. You're defending in a siege this time. The enemy tries to use ladders to scale your walls. You equip some of your men with Midas weapons. They kill the man on the top of the ladder. One of two things happens. The ladder might just snap immediately. Or the man may fall backwards, knocking anyone behind him off the ladder, smashing any rung he hits on the way down, and killing anyone he lands on. Now your enemy brings a ram up to the gate. They easily break it down. Your men take their positions in the gatehouse, again equipped with Midas weapons. The first few foes they kill will quickly block the gatehouse; there is no way they move 1800kg statues out of the way, certainly not while your men are there fighting them as well. [Answer] > > Can i make a good use of this magic for medieval war tactics > > > Not really. People are easy to wound, but surprisingly hard to **instantly** kill. > > or its useless aside of free money? > > > All that gold is **heavy** (making it really hard to transport afterwards), and flooding the economy with so much new gold will cause rampant inflation. [Answer] The "Midas" sword is an immensely powerful upgrade to siege engines. For example, a counterweight trebuchet can be used to launch a corpse at a fortification. At the exact moment when the corpse leaves the sling, some mechanism brings the "Midas" sword into contact with the corpse. The 85kg corpse becomes a 1640kg gold projectile (~85kg is the mass of a typical trebuchet projectile). Yes, **free kinetic energy**! For comparision: typical modern day conventional artillery delivers around 1000kg of ordnance per minute. The use of a siege engine with a firmly attached "Midas" sword and an effective combat range of possibly 250m ensures that any "Midas" sword/knife/arrow things will be kept away from the enemy. A "Midas" arrow might, of course, be a single-use device, but if it only injures an enemy, the enemy (or one of his fellows) can grab it and use it against you. That would be about as funny as throwing a hand grenade at an enemy with the safetly still on. Obviously, every alchemist in the kingdom will be researching how to upgrade "Midas" swords to a version which turns corpses into tungsten. Or uranium. I presume one alchemist was successful with plutonium, but he didn't survive his discovery. --- Even without the option to yield "weapon-grade materials", "Midas" devices producing gold isotopes, like $^{201}$Au, might be useful for the more "strategic" purposes. $^{201}$Au has a half-life of around 26 minutes and will turn into $^{201}$Hg via $\beta⁻$ decay. [Answer] Tactically speaking, I don't know that that's particularly helpful. Yes, you would certainly be able to make a wall of golden corpses, and yes, you would definitely be rich after a good slaughter, but it's not a terribly useful magic for weapons. I would think it would get in the way, having a battlefield full of oddly posed golden soldiers, probably with sharp objects sticking out and ready to stab passersby (like you). One thing you might be able to do, if you're dastardly and need a plot twist, is to set up your magic-sword character on the wall of a castle under siege. If the enemy is at the gates and all the defenses are exhausted, your reluctant hero could potentially make the dark hero choice to murder his companion(s) with the sword, chuck the golden corpses into the vats they'd used to boil the oil they presumably already poured down on the invaders, and drench the enemy leader in molten gold, perhaps saving the castle and giving the hero lots to be moody broody hero-y about. That's a *very* specific scenario though. In the realm of psychological tactics, a weapon like that could be huge. Depending on how common magic is in your universe, a weapon that turns the slain into gold could be a massive psychological factor in war. Just imagine coming up to a village, all the buildings torched, everything in ruins, and finding your fallen comrades, forever frozen in their deaths, in gold. You could set up the dead as statues, warning their people of the consequences of challenging you and yours. Then, they have the added conundrum of what to do with their fallen comrades. Do they bury them? Melt them down for coin? How does one cremate a golden statue? And then there's the religious question as well: what happens to one's soul if one is turned to gold? If your enemies are religious, knowing they might be turned to gold could give them pause in considering war. [Answer] ## The exact opposite of free money Gold itself would not be used to back a currency in this world because anyone with a Midas weapon could make more of it too easily. As such silver would likely be the currency of choice, and thus turning enemies into gold would not yield free money. Also, as I will explain turning stuff into gold will actually cause the war to cost more money. ## Trapped in golden armor As mentioned by others as people are struck by these Midas weapons they will turn to gold. Even if it only caused their outer garments that were struck to turn gold this could still pose problems. Gold is a soft metal when compared to other metals, but is heavier than iron. Here are some examples of the kinds of problems: - Plate mail and swords: Become heavier and softer - Leather and cloth armor: Become rigid heavy death traps - Shields: Become too heavy to hold up - Chainmail: Becomes heavy armor with every ring being a weak point which could pull apart With Chain mail if each ring was considered a separate item for purposes of turning into gold, it would likely become the favored armor of choice against Midas weapons. Only the area struck by the weapon would turn and result in only a minor compromise of the armor's strength with each blow from the enemy. ## Scorched earth tactics If enemies in their entirety become gold upon strike this would result in some amount of scorched earth. Any enemy that is converted to gold would mean that their weapons, armor, clothing, food, and other utility items they are carrying would become gold too and thus no longer would be useful for an on going war. This would drive up the cost of war, and with gold not being an acceptable currency would increase the financial burden of the war. ## Unused Midas arrows After World War II bomb removal squads had to go around and find unexploded munitions and carefully remove them. In this field if a bunch of Midas arrows were fired on an enemy unit some of the arrows would have missed their mark and ended up stuck in the ground. All these unused arrows would need to be recovered, lest they accidentally kill one of your own people when someone accidentally steps on the arrow head or a kid pulls one out and pokes someone with it. This would cost time and resources. ## Gold corpses on the field cost money to remove After a battle is over the field will be covered with golden corpses. Burying and burning dead corpses is typically straight forward, but if they are turned to gold then it is going to take more effort to clean it up, which again will cost time and resources. Luckily though a lot of this could be mitigated since craftsman likely would be willing to take the gold as decorative material, but it will take some time for them to haul all that gold out of there. It would mean your cities are decorated in lots of gold or the roads would be made out of gold. ## Other tactic changes With people turning into golden statues on the field would cause changes to combat tactics. First mounted combat would quickly die down. Golden statues would create a dense area of hazards which would make it very challenging for a horse to move quickly through. Second as enemies turn to gold it will cause the battlefield to turn into a maze of golden obstacles. As such the field of combat would quickly expand out as people tried to get out of the more densely packed golden zones and thus a larger area would become the battlefield. Third, enemies will fire Midas arrows back. If I was laying siege to a castle where the archers were firing Midas arrows at me, I would make sure my forces had good cover and were spread out as much as possible. The goal being that as cover was turned to gold Midas arrows that hit it would not activate and with my forces spread out more arrows would hit the ground. I would then have my forces collect those arrows, at which point I would be inclined to return them to sender. [Answer] Flooding the market with vast amount of gold is going to be make gold lose much of its value. First reason not to be fond of using them. Second reason: on a close combat range, it can happen that the killed enemy corpse falls on the fighter at the end of the combat. Removing a 70 kg corpse is difficult. Removing a ton golden corpse with no help is going to be impossible. Also, you don't want to scatter the battlefield with shiny heavy boulders hampering your troops' movements. Therefore the tactical usage you can do of this weapon is simply as cash machine: when you need money, just use a knife or a small blade to kill a small animal and cash a small amount of gold. If it works on wood you can also stab a log. [Answer] A major problem would be cluttering the battlefield. Unless the Midas users are purely on the defensive, gold bodies would cause a lot of trouble for movement. Dead bodies are bad enough, but they're not necessarily slippery and can be kicked or moved without breaking a foot. With gold, kicking a dead arm would be like kicking a boulder, trying to shove aside a body to save a companion would be nearly impossible. Stabbing someone in the chest as they charge you will have you under several hundred pounds of gold. Even if you are fighting defensively, once you get enough gold bodies piled up any attempt at attacking fleeing enemies is gone. It would be impossible to climb over them. It would also make attacking them extremely difficult, but it reduces the choices for the defenders. So these would not be very useful. [Answer] Does it only work on humans? As in, if you jumped on top of a war elephant and plunged the sword into its brain killing it instantly, would the entire elephant turn to solid gold? How fresh does the corpse have to be? Could I go to the local cemetery and turn it into a mining operation? How does the process work? Is it instantaneous? Do I run the risk of having my sword stuck in a gold statue? What happens if I kill someone with my deathblow but the sword gets stuck in a rib or piece of armour then the corpse turns into gold while I'm trying to pull it out? Does the corpse turn into a solid block of gold or only the structural parts of the body? So if a gold corpse was sawed in half could we see gold organs, bone structure, fine gold powder where blood was? That would certainly make transportation easier as it would be easier to make the corpses into smaller parts. I'm assuming too that the body gains weight to match the denser properties of gold though it might be that a person who weighs 75kg is turned into 75kg of gold, not hundreds of kilos. What about wounding someone first? If I cut off an enemy's arm without the injury being fatal and then take his head off, does he still turn to gold? Other than his arm on the ground of course. I do see a big logic flaw in this. If only deathblows work to turn people into gold, but corpses can also be turned, then why fight with such a weapon? Why not just show up after the battle, find a few corpses and there's your gold? You also vastly reduce the risk of dying. It would be better if only the living could be converted as the sword requires living matter to work. If corpses are fine too, then like I said above, you could raid cemeteries for gold resources which seems too convenient. [Answer] There's 16 good answers to this already, but I'd like to throw my ideas into the mix as well. **First, I'd like to dispute the fact that unlimited gold would tank the economy and ruin everything** The most basic guiding principle of any economy is that *Things are worth what people believe them to be worth*. The concept of price changes due to supply and demand is a relatively recent one. Modern humans know to be on guard about the economic effects of obtaining and trading a huge amount of supposedly scarce resources. Pre-industrial humans much less so. The idea that gold would instantly become worthless is one borne off traditional economic assumptions that information is free-flowing and instantaneous, and people have perfect information. In a mediaeval context neither of these things are true. So while, yes, gold would become devalued in the long run, there is *plenty of time in which to exploit man's greed for gold and reap huge economic benefits*. --- **As the king of a small sovereign state with a single Midas sword, this is what I'd do:** Use it for executions. Keep its existence hidden as much as possible, and wrap the process of turning criminals into gold into a ritual with a whole lot of religious mysticism. Use the first 'batches' of person-gold to forge alliances with neighbours and hire mercenaries if the setting allows. Just like the modern diamond trade, you have essentially a monopoly of large amounts of gold and can artificially restrict the supply while trading initially small but slowly increasing amounts of it. Eventually, when my position is secure enough, I will start decorating the city with it. Let it be known far and wide of the Golden City, the new hub of trade, wealth and Philosophy. Once a place is established as the must-go location for trade and pilgrimages, that reputation sustains itself. **Some practical military uses for gold** Gold is almost twice the density of lead. While it is considered a soft metal, a club made from gold is still going to hurt like hell. Furthermore, there was good evidence in ancient treatises that lead projectiles [thrown from slings](https://en.wikipedia.org/wiki/Sling_(weapon)) were especially deadly, owing to the density and lack of air resistance from a small lead sling-bullet. Gold sling-bullets would presumably be even more lethal. If gold can create a military advantage, I say use it! --- I think a 'Midas sword', if used judiciously, sparingly and secretively, could be used to great benefit to the Ruler in the right circumstances. [Answer] ## Psychology Having your fellow soldiers die next to you on the battlefield is already pretty traumatic, but at least it's not too hard to convince yourself they're at peace now, and often to "help them along their way" by burying them or having some other ceremony to dispose of the body (I've seen quite a few examples in fiction where one side asks or both sides agree to be allowed to bury their dead, which is a whole lot less practical here). Now imagine they were to instead be frozen in place while screaming in pain. Are they dead or are they somehow still alive in there, forced to feel that pain and unable to move as long as the statue stands? If they're still alive, is there a way to reverse the "goldification"? Also, imagine the conflicts if one person thinks their thoughts are frozen and they can be brought back somehow, but another thinks they are in a constant state of unbearable pain and leaving them is just prolonging their suffering. What might be even worse would be having to go back to the battlefield tomorrow and seeing them exactly how they died and unable to do anything about it. Not only that, but the battlefield might still be scattered with the dead of the last army who tried to attack you. Additionally, any given soldier getting hit on the battlefield could run around screaming, crying and begging while they slowly turn to gold. This could very well destroy the morale of any enemies you might have. ## More evasion If you turn anything into gold with one touch, that would likely change the battle to focus more on avoiding getting hit. Soldiers would prefer light or even no armour. The enemy might focus more on sneaky tactics instead of facing you on an open battlefield. A few arrows would destroy any tight formation (since it would be kind of difficult to hold a formation around some giant blocks of gold), so the enemy would be more thinly spread (either initially or eventually). Any sort of constructs (catapult, etc.) would get disabled in one touch, so those would be virtually useless. Some of those things might only be good for you if you know how to take advantage of it (assuming the enemy is at least somewhat well-prepared). Although it might create more havoc, confusion and demotivation to mix Midas and regular weapons - focus the Midas weapons on what regular weapons are typically weak against. ## Traps Would the weapon turn liquid (e.g. water) into gold? If yes: Take some enemies charging through ankle-high water. Add one arrow. Get a bunch of enemies who are stuck in place. Although this would be more of a one-off trap. Or launch a giant ball of something very light over your enemies - shoot an arrow at it while it's in mid-air to turn it into a giant ball of death. [Answer] While the use of gold is arguable, I would suggest something more readily convertible to supplies or directly useful such as cattle or iron, it definitely has its uses to turn a body into something solid. **Fast fortifications** Who said the bodies need to be converted at the place they died? You can build castle-like fortifications super-fast and cheap from bodies. If you are evil, friendly bodies will do, either already dead civilian populace from old age/disease or drafted for "building fortifications" (not disclosing the real meaning). This tactic could be used even on battlefield for quick makeshift charge defense or other defensive maneuvers. **Military engineering** The building potential of readily movable solid material is not limited to fortifications. Enemy burned bridges? Build new one within minutes from their bodies! **Artillery** Assuming same process would work for other living creatures, birds more specifically, you could mount powerful artillery strike against enemy positions even in pre-gunpowder era. Either mass released or trained birds (=smart bombs) killed by Midas arrows or some kind of timed mechanism would turn into deadly projectiles. **Naval combat** Few tons of solid gold on board of enemy ships? Sounds quite powerful. Either delivered from your board and converted later or turning part of their crew. [Answer] This would be useful for controlling the battlefield. If you kill enough enemies in the right places, you can build barriers. [Answer] **There are limited tactical implications** Gold is heavy. Turning flesh and bone to gold, by volume, is a local violation of matter conservation. That is useful for making (say) cannonballs - cannons having been invented in the 13th century, they're medieval - and you could also in a pinch use it to create projectiles for catapaults, or similar use in other siege weaponry. It's not very good for building barricades, because it's so soft. **If many Midas weapons exist, gold is cheap** Gold and precious gems were valuable because they were pretty, yes, but also because they were rare. Flowers are also pretty; the one time people kind of sort of used flowers as money was notable for being completely out of control (the tulip bubble). If too many people have these swords, there will be so much gold that it will still be useful - it looks nice, it won't tarnish - but gold won't be *gold* in this world. It will be more like costume jewelry. **If few exist, they are too valuable to risk deploying** On the other hand, let's suppose that there are (say) three of these weapons in the entire world, and forging them is difficult. Then the problem is this: Using these for military purposes means putting them in harm's way. Deploying them to any kind of front means a significant risk that they will fall into enemy hands. This is bad, because gold is still valuable enough that capturing the weapon will be a big boon to your enemies' ability to kick your butt. Therefore you will do better to build your own war chest with the weapon, in a secure place far removed from any battlefield. In fact the exact location of the Midas weapon will probably need to be a secret. It's a big target, those invite raids and thieves. [Answer] I cannot see any world changing event (except, of course, that gold would be officially worthless) but it would have interesting tactical side effect, mostly because of gold high density The density of gold (weight/volume) is almost 20kg/l. Assuming that the volume of the body is unchanged, an average dead body would now weight 1500 kg. ## Sword fight on foot If the poor guy is dead before he hits the ground, you'd better move backward before he crushes you. In a foot battle, this could be used at your advantage as people next and behind a slain enemy are most likely also enemies. A good kick can make the deadly gold statue fall on them. Also, a wall of dead bodies would make a very good defense ## Mounted charge? Imagine the enemy cavalry is rushing at you and you have those magic arrows. If you make an instant kill, the enemy knight is now a large mass of dense metal tumbling amount your lines. Bad, bad idea!!! Even worse if you kill the horse. If you are the guy on the horse, shooting those arrows would be fun, but don't use such a spear. If you're rushing at 20km/h in a soft 70kg mass of flesh that instantaneously turn into a 1400 kg mass of metal, it might hurt you a bit. ## Naval battle LOL [Answer] I'm supposing by "useless" you mean "useless to the story". A lot of the answers here are worried about hyperinflation from production of gold. Actually, used correctly, it could be used to stimulate the local economy, institute development and so increase the wealth of the local lord. But to become that lord... more on that later. Firstly, does the weapon really not need to strike a killing blow to work? That would be more magically consistent, IMO, the transformation being driven by life energy. But given it doesn't, where does the gold come from? The plane of gold? What entities might be concerned or intrigued by chunks of their reality being transferred to another plane? As for conservation of mass, there are various ways to do that, but my preference is that there is a drive from the centre of the slain person's soul, that being drawn back to them, to the surface of their body as each part of them outside-in is replaced by gold-- they become a hollow statue. What's inside the statue? Another plotly question to answer. So, to take over the locale? The main and ongoing difficulty is keeping the secret. If it gets out, others will be after your sword. How one would find people to kill in isolation would depend much upon your character. I think the question is more interesting for a good or (more likely) neutral type. Do they get a job as a healer? A local executioner? But once you have your starting capital, you can expand outwards, for example start a "philanthropic" nursing home for the terminally ill (do they exist in this world?), which also provides for the grieving families. Side effects caused by magical conditions are not covered by this policy. Then you can diversify and reduce the risk from discovery. Get rich in other ways and build power. You have insurance for the time being. [Answer] Forget using the gold as money, you could make your army wildly powerful with a Midas Sword! Stab as many cows as you can and bring along as many smiths as you can grab, because you are about to make a shiny golden army that is better equipped than any the middle ages has seen before. Metal in general is a precious resource especially in that age no matter how useless it becomes as a currency. * wooden spears (a weapon widely used by infantry of that age) get sharp pointy golden tips that make them much more effective. hell wood anything coated in gold becomes way more powerful * need high density projectiles and counter weights to launch at your foes? GOLD! * wheels coated in gold to make them far more durable and able to go much further without repairs * golden bricks to make on the go fortifications and defensive positions for your troops the list goes on about how powerful having an unlimited supply of metal as soon as you need it would be [Answer] **This weapon has so many drawbacks that I arrogantly declare it 100% useless** * Even if there's just one such sword on the battlefield, after 30 minutes of combat you'd have so many metalic, immovable, bodies on the field that you, the user, would be tripping over them to get to the next enemy. A gold corpse can't simply be pushed over, and if you do, it doesn't lay flat in any sense of the word. it would be like filling the battlefield with giant caltrops. * Gold isn't valuable because it's gold. It's valuable because it's RARE (well, that and the fact that it doesn't rust or react with anything, but rare is #1). After each battle the gold market will positively *overflow* with supply, which means the demand drops, which means the price drops, which means gold is utterly worthless. The steel needed to make a good sword would likely become the dominant coin material. * And we'll ignore the fact that the conversion to gold takes X number of seconds and the killing stroke of the blade over or through your opponent takes Y number of seconds and if Y > X then your blade becomes stuck inside a golden corpse and requires a hammer and chisel to get it out. * And last, if not least, is the fact that so long as people *think* gold is valuable, you'll have every arrow, lance, javelin, spear, atl-atl, sling, crossbow, ballista, catapult, shuriken, trebuchet, rock, and pigeon in the country aimed at your chest. So long as they can think of a way to kill you without getting in range of your sword, you're target #1. [Answer] **Yes** it is useless. **You can imagin a midas sword as todays nuclear weapon**. If you are finding nuclear weapons useful for today's war so you do on midas sword on medival era. 1. This kind of weapon can be a reason for consecutive wars from other tribes. So basically you have to hide it somewhere safe and don't show it to anybody. 2. Using it in a war can focus all the army of enemy on getting their hand on the weapon so the midas keeper must be a super warrior to stay alive. 3. The weapon can be a economical power tool so its that much important for a kingdom to not use it as a warfare weapon and putting its ownership on a risk. like todays nuclear weapons. [Answer] They would be extremely useful in terms of financing huge armies. But you would be silly to use such assets in actual battle, or even let people know you had them. It would make you a target for every nation or ambitious warlord. ]

[Question] [ **Closed**. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- **Want to improve this question?** Update the question so it can be answered with facts and citations by [editing this post](/posts/180949/edit). Closed 2 years ago. [Improve this question](/posts/180949/edit) I have a shapeshifting character who isn’t human but pretends to be one, but people who look at them notice something is wrong, but can’t quite place it. What kind of features could I give them that make them look slightly less human? Currently, they are described as having a normal profile and face, if just very sharp and angled with a wide mouth. [Answer] **Uncanny Valley** The uncanny valley is an interesting phenomena discovered by Masahiro Mori, a professor who made realistic robots. Generally, the more something looks like a human face, the more people identify it as resembling a human face, but at a certain point (between 75% and 90%) people stop identifying it as a human face. The reason for this is a psychological one - people notice that the face they're looking at isn't human, but because of how similar it is to human, they can't tell why. Most people, after all, don't know how a human skull looks or what angles are acceptable for cheekbones, or the eye placement or anything of the sort. But the subconscious *does* - it has seen thousands upon thousands of human faces, so it knows something is wrong. This clash between conscious recognition and subconscious rejecting creates the uncanny valley effect - people find the face "uncanny" and get completely creeped out by it. So, to make your humanoid character "look less human", just sink them into the uncanny valley so that everyone who sees them knows that there's something wrong and inhuman about their face, they just can't quite put their finger on it. [Answer] **It doesn't blink.** Unless it knows it is being observed, because a very little kid once asked it why it did not blink. It had not noticed blinking before then. Now it tries to remember to blink if it thinks it is being observed but it is easy to forget if it is concentrating on something else. **Its face does not move** unless the shifter moves it on purpose. Again this is something that it figured out and now incorporates into its mimicry. If it is unaware it lets that part go. **It does not breathe.** Unless it needs air to talk. This one is subtle and the shifter has not figured it out yet. In between utterances it does not take another breath. If it is exercising vigorously it does not increase its respiratory rate. --- All of these things lend themselves to written narrative because as opposed to a subtly different characteristic that is hard to convey with prose, these are all actions (or the lack thereof) which are much easier to convey with prose. [Answer] It’s too perfect. A major breakthrough for animation was the addition of imperfections. Before high resolution texture packs allowed for the addition of skin flaws (and before people realised the flaws were essential) animated characters simply looked fake. Humans simply aren’t perfect, no matter how hard we try there is always asymmetry, blemishes, spots and pores and dimples etc etc etc. Not so your mimic. Their face is perfectly symmetrical. They have no freckles or wrinkles. Their perfectly blond hair is always perfectly done, even after walking through storms. Their fingernails are perfectly manicured and smooth and both eyes are a perfect uniform blue. The overall effect is like someone has tried to paint a human without actually seeing one. And real human seeing such a facsimile will immediately spot it as fake while the mimic will have no idea what it’s doing wrong. After all, everything is perfect, right?? [Answer] ## Invalid wobbles When I watched *Downsizing*, something felt really wrong in the scenes where downsized and regular people were interacting, but it was so hard to put my finger on it. I think it was because subconsciously I expected the fluid mechanics of air, gravity, and so on, to have created differences in motion between large and small people. Different wobbles in clothes and skin, different motion of hair, different difficulty of waving one's hands around. When you move your leg, it doesn't stay the same shape. If you slow down a video, you see that the bone sort of drags the muscle and fat behind it, then they catch up and overshoot, then there's a bit of a wobble before they settle down. This motion pattern is highly dependent on the density and relative position of those tissues. There are also tiny ripples created by air resistance on the skin and skin-hairs, which are dependent on the stiffness and viscosity and density within the skin, coupled with the viscosity and density of the air. The way your cheeks jiggle when you turn your head, the subtle wobbles in your face when you talk and laugh, all depend on the arrangement of things with different densities and viscosities (bone, fat, skin, muscle.) Good shapeshifters would presumably have some sort of skeleton-like internal scaffold to help them be convincing, both with macro motions (like moving limbs) and fine motor skills (because they don't involve a lot of fast movement or air resistance). But it would be unfeasible to emulate a human's internals to enough accuracy to get the waves and wobbles right. If you're up close and see the way their skin undulates your brain will notice that the movements keep violating its expectations. But you couldn't put your finger on it. [Answer] **Clothes and accessories** Their clothes merge with their skin. Only having observed from a distance and out of doors, they don't realise that clothes and accessories are not part of the human. Or, more likely, it's simply too difficult to shape-shift clothing on top of a body - there must be a join somewhere but where? They will be caught if they ever have to undergo any kind of search or medical investigation. Customs officer: Can I have your bag for a moment ma'am? Shapeshifter: Erm ... I'm afraid it's er glued to my hand. I'll have to hold on to it while you look" Customs officer: Not a problem. May we just check your shoes? Shapeshifter: Umm ... Customs officer: Glued? Shape shifter: Yes. [Answer] No eyebrows. I had a friend in high-school who didn't have any eyebrows (there are quite a few reasons people might no longer be able to grow their eyebrows). Whenever he met anyone new and actually took the time to talk with them face to face, there would be a moment when the new person would just stare at his face slightly confused. You could see that they were thinking "There is something off and I just can't place it." and then he would say "I have no eyebrows." And you could see realization slam into the other person's face. "That's it! That's what is off!" Afterwards, the conversation would continue as normal, but that awkward moment would ALWAYS occur when he met anyone new. It isn't really enough to make it clear the character isn't human. After all, many people have conditions where they no longer grow their eyebrows. So you may want to add other traits. But from what I've seen, this is enough to give a moment of "Something is off and I just can't place it." [Answer] They sense the world differently. They see and hear in a different range of light/sound frequencies and amplitudes, they recognize a different set of smells/tastes through quite different sensory organs/mechanisms. For example: * they can only see red as we do, but some more in the near infrared spectrum. They can never get the colors right * they can hear dog-whistle frequencies and are irritated by it * Some of the most delicious food we have is quite disgusting to them (this even happens across human cultures). Have fun exploring how they reflexively react to something they find "disgusting". * They can smell and recognize an object by extending an appendage (which for now looks like a human hand) to within a few centimeters of it. * They hear in infrasonic frequencies, and try to imitate the human heartbeat/blood flow they hear to an abnormal volume that unnerves real humans [Answer] Right now they're giving off vibes to others which could be a trait other humans recognize subconsciously that there isn't something right about your shapeshifter because it's not their species but obviously you want this to be more. Voice - this shapeshifter is impersonating a human their vocal cords might fail or warble or do something they'll have to explain to others as a voice disorder. If you want you can have them claim a real disorder but then have them meet someone who actually has the disorder who knows they're lying or at least uninformed about what they claim to have. This way readers who won't think what your shapeshifter has is true symptoms of whatever you choose to go with. Eyes - they could have collided pupils or a unique tone only to them (like vintage rose) or dusty (insert color) or you could split the color tone of the iris in half you can be complimentary or not or have one eye color split while the other is solid. Skin - they could have patches of harsh skin that patchwork the smooth overall they claim or others assume this to be a skin disorder you can do anything here have rock hard patches or bark looking patches, or else switch skin tones or else give their skin a non-smoothness that pushes up from underneath it people can see something is up they could touch them and feel the under texture but again everyone might assume skin condition. Hair - their eyebrows and hair have streaks of (insert other color here) it's not dyed its a biproduct of the presentation only a few strands have this color like the overall hair is black but streaked with auburn brown the odd is that it's also like this on the eyebrows no one would choose to dye this area in that way. Yes humans would place this again as birth add on or odd dye choice but the point is the shapeshifter knows this isn't as he/she intended it to go. I'd personally go with don't describe the shapeshifter in heightened detail while in the human form. Allow others to imagine what is odd about them it makes it more fun for the reader. [Answer] Imitating the full set of human biochemistry, metabolism and system functions is quite impossible for them. So maybe: * They don't sweat. They vent through pores when overheated. How do they try to hide it? * They smell different due to their biochemistry. How noticeable is it? * They may imitate "eating" something but they do not actually digest it. How do they handle the food they ingested? * They have a different mode of getting rid of their waste products. Does that sit well with human toilets? [Answer] Describe it as "just uncanny" for everyone but a genius. The point about Uncanny Valley from @Halfthawed is really good, but describing it in a cool way is not easy. My suggestion is, make a small character, either very curious, like a child, or very smart and watchful, like a detective. Make this guy realize some of the bits in @Mio's answer, and either narrate him thinking about it by himself or writing somewhere, something like (if it's a detective character): "He doesn't blink nor breaths often enough, when he smiles, just he's mouth changes, even a sinister smile would be less odd. I don't think anyone else realizes those details, but it's clear to anyone that there's something off about him, something... Uncanny, they just can't place it." [Answer] Just as Black Mirror does in the episode "Be Right Back", where a woman replaces her dead boyfriend with a robot, there very subtle things that make him less human, perhaps you could watch the episode and get some inspiration? Things like not needing to: breath, sleep, eat, shower Perhaps go with the approach that "it's weird they never ..." instead of a direct "There's something strange with their face" [Answer] A couple different ideas: They all use the exact same template. Since humans look roughly alike to them they don't recognize how unusual many truely identical humans are. Have them often misgender people by accident, it's generally difficult to recognize gender in other species and English uses gendered words all over the place so it would be difficult to hide the fact you get it wrong a lot. Watch how some mimes can convince you they are carrying something heavy or light. Maybe their mass distribution is off so it always looks a little like they are doing the classic mime leadfoot routine to a degree. When their own mass is different than the body they want to take the form of they just scale it linearly to get the mass to match. so they might have a child's build with an adult height. Or the proportions of a body builder just scaled down evenly. Since human heads are generally of similar size and vary less than weight, scaling everything equally would end up with an odd head size relative to body. Enough to seem a little odd at least. They most definitely will not see the same spectrum range as humans, so they will likely not color match anything properly and if their power changes their skin tone based on their perceptions i'd expect it to be off to some degree. Even if they get a matching base color down, humans are not all one color across their body, for instance they may end up blushing with a blue tinge when they try to replicate it because they are red-blue colorblind. [Answer] You can make it so that they breathe significantly slower, or have no pulse, or don't sweat, or perhaps rarely or never eat or drink. They never get sunburnt or tan, they have no smell, or have seemingly no emotion. Perhaps their ears are shaped differently, or they lack fine details on their skin. [Answer] If you want specific tangible factors regarding the uncanny valley, you should look into videos for animators about animating real people. There's probably a bunch of stuff in there. One thing I remember is something called sub-surface scatter where light penetrates the skin a certain depth and gets scattered back out. I think this is noticeable around your ears. Without it, you don't look quite right. I think it makes you look like wax or plastic if you don't have that. I'm sure there's other stuff but I'm not an animator so I don't know what it is. [Answer] Another possibility could be that their range of joint movement isn't right (i.e., within the norm for humans). Either they're much too stiff for the age that they appear to be, or they move like an old "rubber hose" animation. The head rotating too far is also a horror-genre classic. [Answer] ## People don't see what they don't *want* to see... except when they do. Per @Willik and @YoungJohn's answers, there's actually quite a bit of stuff that you can change before people realize something is non-human. However, I wouldn't stop there. Depending on how the shapeshifter goes about it, he can actually go pretty far into non-human territory by taking advantage of the Somebody Else's Problem Effect. To roughly paraphrase one of the early installments of the webcomic *The Call of Whatever,* > > If humans see a humanoid tentacle being in a trenchcoat and a big hat they'll immediately see through the disguise. **However, if they see a humanoid tentacle being in ratty jeans, a t-shirt and a baseball cap, they'll assume it's a teenager playing a prank.** > > > In other words: if he doesn't try to disguise himself (beyond taking on a humanoid form, of course) people will view him as Somebody Else's Problem, and thus studiously ignore him. Unfortunately for your shapeshifter, this has one major problem: **some people are immune to this effect.** The classic example is children ("Mommy, that man is a skellington!"); however, that's a bit of an overused trope. Instead, you might want to try using Autistic people; one of the common effects of Autism is extreme literal-mindedness. [Answer] I saw someone say something about using Autistic people as a guideline, quick tip: don't do that, it's dehumanizing. Anyways one thing you can do is have their eyes never change shape, like never squinting or never closing, try having them always open wide, or try having their mouth only open in one direction when they speak, so it looks kinda like they're badly lip syncing someone else's words. Maybe try adding a few things into their behavior where they only refer to people using their first or last name, maybe constantly having their head leaning to one side or having their hands never go limp, when people hands go limp they slightly curl forward, so maybe their hands could always be stiff. ]

[Question] [ I'm considering the mechanics of a "shock and awe" scene in my novel which could see an old dam being brought down. The era is equivalent to that of the middle Roman empire, so introducing explosives would be far too convenient and would require altering previous work for the simple logic of conflicts. What was available, or has been used in the past, to undermine the foundations of large structures in minimal time? It's undecided at present how deep the water is on the other side of the dam, and the construction materials. I'm most likely to use the Roman style of architecture ([reference](https://en.wikipedia.org/wiki/List_of_Roman_dams_and_reservoirs)). [Answer] Forts using stone, rock and earth walls as fortifications (and in some cases, still standing !) were often attacked during sieges. Such a wall has much in common with a dam. To breach such a wall you tunnel underneath. It's a well established technique. You dig a tunnel, using normal techniques to prop and seam your tunnel. Then when you've dug enough, you set fire to the supporting structures (or otherwise destroy them) and, the attacker hopes, the subsidence will collapse the wall or (for a siege) damage or weaken it. I gather the tunnels were often (always ?) lined or filled with materials that would burn for an extended period to further weaken the wall above using heat. I see no reason the same principles would not apply to a dam. [Answer] A more devious scheme to bring a dam down: **A secret second dam above the main target dam**. You simply install a second dam above the main dam (as high as possible ideally). You reduce the flow inconspicously so that the main dam manning do not see anything unusual, but slowly the reservoir of your second dam is filling. Now you wait for the perfect time when the second dam reservoir is filled and the main target dam is nearly filled. If the main dam needs only some filling, you can increase the flow from the second dam. Your attack commences with destroying the second dam which is purposefully built for being brought down (you have some pivot support columns which are disengaged). The water rushes down and gets faster and faster, converting the stored potential energy from a higher point to kinetic energy. Friction and obstacles will slow down the water masses to a point, but it will still be very fast. When the water enters the main dam, an effect called the [water hammer](https://en.wikipedia.org/wiki/Water_hammer) comes in effect. The main dam does not allow the moving water masses to continue running, so the moving water causes a sudden pressure increase. The incoming water not only causes water to slosh over, it literally pushes the dam crest apart. Result: catastrophic failure. ADDITION: The original question states that we are on the technological level of the early Roman era, so we should neither expect to have a hydro dam like the Hoover nor a reservoir for a city of million people. It will be more like a dam with the height of metres and the reservoir like a big lake. Still we can compare dynamic with static pressure. The dam need to withstand static pressure, so we can assume we need approximately a pressure with the same order of magnitude to break the dam. \begin{eqnarray\*} \rho & = & density(kg \, m^{-3}) \\ g & = & gravitational \; acceleration = 9.81 \approx 10 \; m \, s^{-2} \\ h & = & height \; m \\ v & = & velocity \; m \, s^{-1} \\ mean \; static \; pressure & = & \frac{1}{2} \, \rho \; g \; h (The \; dam \; holds \; this \; pressure) \\ dynamic \; pressure & = & \frac{1}{2} \; \rho \; v^2 \Rightarrow v \approx \sqrt{10\*h} \end{eqnarray\*} [Moderate flash flood velocity is 2.6 m/s](https://weather.com/safety/floods/news/flash-flooding-vehicle-danger-20140717) and a very fast flashflood is in the range of 26 m/s. A moderate flashflood will be held by a 0.6m dam, a worst case scenario of 26 m/s would give an impressive height of 70 m. But the flash flood water will merge with the still water in the reservoir, so an inelastic collision will occur and the water slows considerably down. So the final velocity of the water will be the ratio $$ r = \frac{flash \; flood \; mass}{reservoir \; mass + flash \; flood \; mass}$$ of the flash flood speed (I also neglected friction and energy dissipation by waves). Result: If the dam is something like 10 m high and the reservoir is big (10-100 times), even the ugliest flashflood will have no pressure effect. Moderate flash floods can be contained even with small dams. On the other hand, if the dam is only a few meters high and the reservoir has not a much bigger capacity (10 times) than the incoming water, an incoming massive flash flood *is* able to forcibly remove the dam. [Answer] Roman type dams were usually buttressed rather than relying purely on their weight to hold the water back, break away the supports and they will fail. Earth dams just need a single point of failure to be induced and the weight of the water will do the rest in short order. Artillery targeting the non water side of either type of dam should be enough to make either type fail fairly quickly, they're not designed to withstand that sort of stress. The Romans were excellent engineers, they would quickly recognise the weakness of a dam and either pull away supports or dig out making a point of failure. [Answer] You can of course excavate under the dam and have it crash for lack of support ("undermining"). This was the routine siege attack against walls and the crash would be quit abrupt. Its feasibility depends on the strength of the foundations and the ease of tunneling through rocks. Romans were quite proficient at that. Depending on the situation, you could perhaps use a *malvoisin* - a high structure built near the dam. Get a heavy stone or iron ball secured to a chain hinged on the dam, raise it with pulleys on the malvoisin, let it fall down and impact the dam. Repeat as needed. Essentially you have built yourself a wrecking ball. [Answer] Make a hole in it. Once there is water flow, the hole will expand. If the hole is low in the dam, the structure above it will collapse. But even if at the top of the dam, it will work its way down over time. You might ask if dams don't already let water through. Sure, this is called a spillway. But spillways receive extra reinforcement so as not to compromise the overall structure. In other words, they are deliberately designed not to wear when water runs through them. If you choose a random portion of the dam (or the ground beside the dam), it won't have that reinforcement. The hole will expand. Making the hole can be as simple as using a pick and shovel. Dams were often simply big earthworks then. You could dig through them. A dam made of mortared stone would be more difficult. You might find it easier to dig near the dam. That would often still be regular earth. The dam might also be buttressed. Then you could remove the buttress by digging around it and removing its support. A buttress near the center of the dam will likely cause the most strain when removed. Note that the water is part of the dam's support. As you remove the water and relieve the pressure, the dam may collapse *into* the water. This is the shock and awe moment, when a small breech turns into total collapse. This is most likely with a buttressed dam. The reason to do this rather than undermine the dam is that undermining requires more digging. Not only do you have to dig through the thickest part of the dam, but you also have to dig down to get there. And with a dam, it's unlikely that you'd be dodging defenders. Unlike a wall, where defenders stand on top and throw things at you. So there's less utility in starting a tunnel away from the wall. Most dam construction in Roman times will be such that it is as easy to dig through the dam as under it. If a mortared stone dam, look to removing its support. This may be easier on the sides than underneath. Let the water do the hard work. You just need to give it a chance to start. I would only see undermining as necessary with a buttress, which is smaller. [Answer] Speaking of tunnels... <https://en.wikipedia.org/wiki/Ruina_montium> > > an ancient Roman mining technique that draws on the principle of Pascal's barrel. Miners would excavate narrow cavities down into a mountain, whereby filling the cavities with water would cause pressures large enough to fragment thick rock walls. > > > [](https://i.stack.imgur.com/sqriP.jpg) Mine tunnel to the center of the damm, as long as possible so that it contains a big quantity of air. Once the tunnel is ready, flood it as fast as possible. The trapped air builds up pressure as the water pushes in, and once it exceeds the tunnel walls resistance it escapes breaking the tunnel walls, effectively acting as the compressed air blast of an explosive's shockwave. Only no explosives needed, just water and air... and look, there's a big damm with water just behind you! How convenient. Additionally, effects from hydrostatic pressure (the higher the water falls, the bigger the force it will do against the walls) add up for extra effect. What the air doesn't blast away, the water force will. [Answer] According to tradition, when Hannibal needed to clear boulders off Alpine paths, he used [fire-setting](https://en.wikipedia.org/wiki/Fire-setting); build a large fire against the rockface, and when it was properly heated, throw a large quantity of cold water (or vinegar, for the acid) on it to cause cracks through thermal shock. This would work well against stone or masonry dams; it's not itself very destructive, but a thin crack all the way through would very quickly widen into a breach. An added bonus is that acetic acid would presumably react with, and weaken, the lime mortar. [Answer] If water could penetrate cavities of the structure and freeze there that would generate large pressure (because water expands when it freezes) that can break rocks. This process is called ice wedging and it occurs in nature. [Answer] Roman concrete used lime mortar, strongly alkali. I don't know if they used it in dams, but it's plausible they might so it's not too far a guess. Alkalis react with acids, which is why modern concrete and cement also come in sulphate (i.e., SO4 ion) resisting versions. Carbonic acid is also an issue. Acids were well within Roman technology, although I'm not sure of the practicalities. But if you could weaken a critical point with acid, or even by just gradually acidifying the water in some static part of the reservoir in contact with the critical mortar, perhaps it would gradually weaken the dam. As a twist, maybe a tunnel would allow the sub-surface part of the dam foundation to be attacked, removing critical support invisibly, and without having to do it slowly to avoid detection, until suddenly......? [Answer] @LSerni is probably right about how the Romans would really do this. If you want some alternate technology within the grasp of the Romans you could destroy it by shaking it at its resonant frequency. Like buildings, dams have resonant frequencies and these are of interest mostly to prevent destruction by earthquakes. <https://en.wikipedia.org/wiki/Mechanical_resonance> Here is an interesting article about a skyscraper that was evacuated because it was shaking. The shaking was caused by 17 people exercising in unison. <http://news.blogs.cnn.com/2011/07/19/scientist-tae-bo-workout-sent-skyscraper-shaking/> Additional reading: Tesla's oscillator, or "earthquake machine" which he claimed could bring down the Empire State Building. <https://en.wikipedia.org/wiki/Tesla%27s_oscillator> I could not find a report of a dam which actually collapsed because of this phenomenon. But as far as the shocking awesomeness, using vibrations to destroy a structure should qualify. You could have people atop it stomping in unison faster or slower as the maestro directs. Could one affix a big piece of metal to a rigid structure and cause the structure to resonate by drawing a bow across the metal? [Answer] My vote goes towards piercing/hammering: Either with a stated wrecking ball (Malvoisin) or with flotsam (in autumn/spring when flow is high, throw a large, somewhat pointed trunk in the river, upstream of the dam...). If it has butresses, undermine these (possibly in a similar way: Chop down the largest tree nearby to fall away from the buttress, but after tying a rope from tree top to buttress -- rope slack on water, to be inconspicuous, so that it suddenly tenses as the falling tree reaches maximum velocity). If you can build your secret dam upstream, even better --- use it to give the flotsam additional speed. This can be part of the plot: The dam(ned) engineers know of the 'secret' dam, and have calculated it to be ineffectual; so it's monitored to an extent and they're very prepared for 'attack day' --- however, they're WRONGLY prepared as in their overconfidence they've overlooked the other legs of the plan: The quickly-tied rope-to-buttress-on-falling-tree, and/or the flotsam-missile. (The flotsam-tree and tree-pulling both have the advantages of being normal jobs as timber is main building material --hence inconspicuous-- and quick versus the secret-dam-building --hence the full attack isn't understood until too late to defend, and it may be difficult to get the people prepared to counterattack (=heavily armed) to adjust to civil-defence jobs (plus, maybe they'll sink in the quagmire from their armour etc). Tunneling under a river doesn't work (you drown, using roman tech), so castle-demolition-analogues won't work I think. [Answer] One possibility - but not sure how to execute it - would be to use steam. Dig a hole, put a sealed metal cylinder with water in it and fire it up. Steam has tremendous power and if there will be enough pressure in the cylinder it would be much like explosion. But someone would need to run some pretty neat equations on cylinder size and water content and I'm not sure you can build one with only blacksmith-level metal craft. Any other way in a short form: not bloody likely. A bit longer answer: unless it's a really small dam, good luck! Long answer: there is a reason why most of the Roman-built dams are still around, with a lot of them still in use. You'd think that engineers who built roads and aqueducts that are around today and are definitely pieces of finest engineering would build a dam that is a simple wall? Yes, there are a few - like subiaco dam, which are like that, but they are exception to the rule. Subiaco especially, as it's said to be built so that Nero had a lake next to his villa. But most of them were lime or concrete (yes, concrete) core, with compacted earth and masonry to protect it against erosion. First of all you can forget catapult or trebuchet. Yes, they would crack the "outer layer", but will be completely ineffective against earth underneath. With limestone or concrete core you can forget burrowing. The only way to break solid Roman dam is with good-old earthworks: spades, picks and shovels. [Answer] I'm not sure if the physics of this hold up, but could you destroy a dam by movement of the water it holds back? I'm thinking you climb up a convenient high, rocky mountain next to the lake above a dam. You carve out a large, round boulder and let it roll down the mountain and into the water. The bow wave from the resulting impact stresses the dam sufficiently to breach it. I guess if you were capable of all that, you might argue you'd be better off rolling the boulder onto or against the dam and have the same effect, although that would require a very conveniently located mountain. [Answer] I think another way to do this would be to block the outflow of the dam, When the dam fills normally it would push water down the overflow. Issues with the overflow can be dangerous. Please see [Oroville Dam](http://www.vox.com/science-and-health/2017/2/13/14598042/oroville-dam-flood-evacuation) had an issue with its overflow. Very dangerous if Dam's have the overflow blocked. [Answer] How to knock down a dam without explosives? Two words: [Miley Cyrus](http://musicreprise.com/wp-content/uploads/2013/10/miley-cyrus-wrecking-ball.jpg) [](https://i.stack.imgur.com/CEL8G.jpg) [Answer] How about a 'solar death ray'? Arguably a whole load of soldiers could spend a day or two polishing the insides of their shields and then hold them in a carefully choreographed way such that they each reflect a small amount of (bright?) sunshine to a single point on the dam. I'm not sure how you'd be able to ensure that every soldier's reflection was on the hot spot, but I guess you might be able to solve that by grouping them and having groups bring their reflections together at the end of the procedure. Even if it didn't work, you'd freak out the dam owners pretty badly. It's been suggested Archimedes did this, although I'm not sure if it's true. Here's one attempt to recreate: <http://web.mit.edu/2.009/www/experiments/deathray/10_ArchimedesResult.html> [Answer] Heat it up, cool it off, heat it up, cool it off, heat it up, cool it off, heat it up, cool it off, heat it up, cool it off. This seems stupid, but I assure you as someone who has some background in engineering if you stress out the material enough like this it will break. you just need to get it really hot and then get it cooled off quickly. I'm pretty sure this happened with a wall either in Egypt or Constantinople - I'm not really sure it was called that when it happened though. This method alone could break a damn by weakening its structure so much that it can no longer hold the load it was supposed to hold, but it would make more sense to use this method to try to weaken the damn before you hit it with a projectile battery. Alternatively if this is too boring, you could just dig a bunch of holes. It's a more cartoonish solution, but it would work in theory. You could also just break all the support structures. The episode of Avatar the Last Airbender where team boomarang breaks the fire nation's drill to stop it from boring into the walled city displays this concept really well actually. [Answer] If you can go near the dam (meaning there is no secrecy involved, no guards, the dam is far from a village, etc. etc.), and if you want a cheap, quick (a few hours total), 100% reliable, 100% risk free method, then it's extremely easy to do. --- Just use dry wood wedges: 1. You need a boat, a bunch of dry wood wedges, hammer and chisel, and a bucket 2. row to the middle of the dam 3. use hammer and chisel to do a few holes -two or three should be enough, and no need to go through the entire dam, just go half the depth of the wedges. 4. Plant the wedges inside the holes 5. Fill the bucket with water and wet the wedges. Keep doing it till you start hearing crack noises coming from the stone 6. Row away 7. Just watch the dam getting teared in pieces. Keep in mind that if you have time or resources you can skip the bucket part and either have a tiny bit of water flowing outside the holes where you put the wedges, or use a bronze tube to move water from the top of the dam to the wedges. But in the end, whatever solution you choose to wet the wedges, you'll get your dam destroyed. And this is not hard science nor something unthinkable in that age, as we (humans being, I mean) have used this exact method since the dawn of humanity to tear apart mountains... [Answer] Try a **ballista** - <https://en.wikipedia.org/wiki/Ballista> > > when it hits a tree or a rock, it pierces it easily. Such is the engine which bears this name, being so called because it shoots with very great force > > > [Answer] Tesla supposedly brought down a building with a device about the size of a shoebox. Supposedly it used resonant vibration to compromise the structure over time - it was also attached to a metal portion of said structure. As you are using the science-based tag, this might be enough to go by. Also, considering the technological feats already accomplished in China, India, and the Americas around that time, it is not too far a stretch. Not to mention that the local neighbors, the Greeks, were building metal clockwork computers around that time. Just bring in an expert (foreigner with a briefcase... or, given the time period, a satchel or similar). Even without using an electrical based device such as Tesla's, anything which produces rhythmic vibrations at the correct frequency would do the trick. A clockwork hammer mechanism might be able to pull it off, and has the advantage of the tech already having been worked out by the neighbors (again, the Greeks). ]

[Question] [ I've got a European medieval-themed world and my focus is everyday life in a small village (population of 300~500 people) in the mountains. I'm trying to stay away from action, adventure, violence, etc. as much as possible, so I want this village to be a remote, quiet place. However, I still want it to see at least some traffic, be it travelers or merchants or whatever, so that the village has significant economic activity. I don't know enough about medieval economics or everyday life to give some concrete numbers, like how many merchants passing per week, but I'm aiming for something high enough to make the village have some significant interaction, yet not too high to make it some economic hub. I'm certain it's possible but wasn't able to come up with a good reason or find a real-life examples myself, so I'd like to seek advice from Stack Exchange. It wouldn't be due to some resources or anything of strategic value because that would get the attention of political and military parties, making my earlier point about remote and quiet moot. There are no powerful religious groups like the church because the people of this world mostly interact with old/wise and powerful animals and call them gods, so no pilgrimage. Tourism and vacation is also difficult because the standard of living isn't high enough for people to have that much free time. Assume nothing magical or supernatural. Those things are difficult to deal with without knowing the full explanation of how they work in my world. And my world doesn't have a lot of supernatural things going on and people haven't started studying the magical laws of nature anyway. That being said, if you have suggestions involving something magical that can explain the situation and also provide some interesting ideas about the events that can happen in or around the village, that would be great. I'm not expecting anyone to solve my problem by directly giving a definite answer. But if anyone knows a lot about how traffic in real-life secluded village worked and explained some factors that can affect it, as well as giving some suggestions that could work in a fantasy setting, I'd be happy to hear about them and hopefully I can figure out a combination or get another idea. If you need me to provide more details, or explain about the lore etc, do let me know. [Answer] **Consider a mountain pass.** In short, you need a small village located on a major road. Possibly, your village is located near (on the only road leading to) a mountain pass. You mentioned the mountainous location, so it fits geographically, and such location will result in quite a bit of traffic (merchants, travellers) passing through. At the same time, the rough terrain will restrict the settlement from becoming a busy town. You might want this pass to be internal (i.e. in a heartland of the country), and away from any borders, and thus without much political/military value, and otherwise unremarkable. [Answer] # The village is on Camino Santiago For centuries in Catholic Medieval Europe, [Santiago de Compostela](https://en.wikipedia.org/wiki/Santiago_de_Compostela), the resting place of St. James the Great (one of the 12 Apostles), was one of the prime pilgrimage destinations of Europe. Because of its location in Galicia, there were only a limited number of ways to get there. Traditionally, the penitent would walk to Santiago on foot to earn absolution from some sin or other. The various paths to Santiago, known as the [Way of Saint James](https://en.wikipedia.org/wiki/Camino_de_Santiago) all generally converged on a few passes through the Pyrenees. [](https://i.stack.imgur.com/BEA44.png) A town in one of these passes would meet your requirements. For example, [Ostabat-Asne](https://en.wikipedia.org/wiki/Ostabat-Asme) in France is on the map above and was the meeting place of major pilgrimage routes from all over central and northern France. However, even today has only about 200 people. You don't have to be the *destination* of a pilgrimage route, you just have to be on the Way. [Answer] Hot springs. The romans kinda invented the idea of the vacation so having something like a hot spring will draw wealthy travelers, even the medieval people recognized the benefits of a hot soak on aches and pains. the mountain setting is perfect for such a spring. If the site is blessed at anypoint or connected to a historical figure it will draw even more as a pilgrimage site. This is where Sir/Saint \_\_\_\_\_ rested before/after his famous \_\_\_\_\_\_. of course a steady flow of money will draw merchants. [Answer] **There are only few ways such a village would see some traffic** * **has some kind of attraction** - a natural wonder or burial site of a prominent religious figure was a good one. Moderation is key here. * **produces some kind of desirable craft good** - in the medieval period it wasn't uncommon for members of a particular trade to collocate and form communities dedicated to the production of certain craft items. Like in Germany there were settlements dedicated to Christmas decorative items. * **Modest agricultural production near a major economy** - If they can produce surplus food within transportation range of a city they see some traffic. Depending on the uniqueness and production capacity can increase/decrease that traffic. **Those methods attract modest traffic, however there are other means that attract far more attention:** * **Production of a strategic resource** - mining * **Strategic Craft** - there were blacksmithing communities both in Europe and China * **Located on a Trade Route** - being a rest stop on the only road between 2 major economies (like a mountain pass) sees a lot of traffic. * **A Major attraction** - having a man made wonder like the colossus or incredibly unique natural wonder or important religious site would bring tons of traffic. [Answer] They live at the a convenient watering place between two towns, just before you start entering the pass: [](https://i.stack.imgur.com/Vyql0.png) I think this fits your requirements: 1. Nothing Magic 2. Nothing strategic (compared to the nearby pass) 3. Nothing Religious 4. Near (or possibly slightly in) mountains You can vary the traffic by varying the desirability of getting from A to B. If they are both big towns, you'd get lots of trade. If they're both small towns, you'd get very little. If town A goes to war with town B, town A's army goes past your villiage and attacks the garrison at the pass. If town B goes to war with town A they go past your town and lay siege. The time between towns is significant. One day will get you from one town to the other, but your town is a nice spot for lunch and a break from journeying. It has a watering spot so you can grab a drink - but you could have done that at many places. But everyone stops here because it's a convenient distance from everywhere, and is either just before or just after the mountains. --- This town is based on [Springs Junction in New Zealand](https://en.wikipedia.org/wiki/Springs_Junction). Springs junction has: 1. A petrol station (a horse-watering-stream) 2. A cafe (a taven) 3. A couple farms (a couple farms) It's four hours from Christchurch and Nelson, so your car's on just over half a tank of gas when you go past. It's a nice place to stop for a leg-stretch and a snack. It's located nearby the Lewis Pass. --- [Answer] **Recurring shipwrecks.** There are some places where weather and shore conditions make for the risk of shipwrecks. Buxton NC can be an example. Cape Hatteras is dangerous. No ships want to stop here but a lot come by and wrecks were common. A community was there to man the lighthouse and also help wrecked sailors / facilitate salvage operations. <https://www.outerbanks.com/buxton.html> > > In history books, however, Buxton is probably most famous for being at > the center of the treacherous Diamond Shoals. Because of the town's > position, located at the veritable "turning point" of Hatteras Island, > a number of sandy shoals jet off the point, shifting daily if not > hourly with new wave patterns and currents... These conditions led to > the shipwreck and destruction of literally hundreds of passing ships > since the 1500s. With sand bars that could change in an instant, and a > shallow coastline that was barely visible from sea, hundreds of ships > fell victim to the Diamond Shoals. > > > With a busy commerce shipping lane off shore, one or two wrecks a year (and subsequent visitors hoping to salvage some cargo) would provide the visitors you are looking for. The thing about this is that there is some action: shipwrecks. But nothing of economic value or strategic value. In your city, almost no-one who goes there is happy about the circumstances that get them there. [Answer] > > a small village (population of 300~500) in the mountains. I'm trying to stay away from action, adventure, violence etc as much as possible, so I want this village to be somewhat secluded (not too much). However I still want it to see at least some traffic. > > > Mountains are by definition secluded. If the village is on the path leading to a mountain pass, it will experience some traffic. The amount of the traffic depends on the importance of the mountain pass. To give you some real world example, consider the Alps passes leading from Austria to Italy: the lowest the pass, the easier it will be and therefore the higher volume of traffic it will attract. Conversely, the higher its altitude, the less attractive it will be, if the people are interested in an easy journey. If instead the people traveling through the pass are more interested in a "quiet" pass (like smugglers) the relative weight of these kind of travelers will be higher. [Answer] It could be set on a path that is much more dangerous than the main trading route, but faster in good weather. If at a high enough elevation, winter storms would isolate it completely, keeping standing population low. During warm seasons the more brave or desperate travelers come through, keeping commerce moving. They may hunt/trap furs during the winter isolation that are harder to acquire. This would motivate traders, but limited supply would prevent the town from growing as a result. [Answer] A well-known artist, craftsman, oracle, healer, sage or wizard lives there - this would attract apprentices, travelers, merchants as well as nobles, all trying to benefit from the resident's skills. Note that they don't necessarily need to be the real thing, but could be a fake, or they could have been mistaken as the real thing. Apprentices would be a given, and travelers would be coming to meet the person, get advice/help, or just see the village because of this resident. Merchants would seek to acquire goods, possibly even completely unrelated ones, as they would fetch higher prices or be otherwise more desirable than normal - compare "rum from a British town" vs "rum from the hometown of the Beatles". None of them would want to stay longer, as the village is removed. Nobles - they would be trying to curry favor from this special individual, as their skills/talents would be very desirable. As with the others, they likely wouldn't want to stay very long due to the removed location - and occupying the village would surely anger the individual, potentially then risking a war with another noble or nation (or several). [Answer] All you need is for your city to be half between two cities, and the 2 cities far enough apart most people would stay there overnight vs doing it all in 1 day. A few bars, hotels, lodging, and etc. Each of those business needs supplies and town folks to make them. Carpenter, blacksmith, and large stables. [Answer] Another possible solution is a remote village near the border of two countries with people that know their way around the mountains and are specialised in contraband. Possibly even with the complacency of/bribing local authorities. Such village would have a steady influx of merchants, possibly thieves, opportunity seekers and rogue warriors. [Answer] It could be on the route to an old pass, that's now closed due to a landslide or earthquake; people now prefer the other pass a mile away (either new because of the earthquake, or it was inferior before because reasons). A few people might have old maps, and the odd one or two might take a detour out of curiosity. Most will stay on the main route. # Main street isn't main street any more ... [Answer] As others mentioned, have the village near a pass. This gives it the traffic you're looking for. My spin on it is to make it really high up in the mountains and it being the only pass for many tens or +100 miles. That means people Have to use it. Putting it high up means there aren't going to be many people that want to stick around (due to the bad weather, bad soil, land/mud/snow slides), but are willing to stay for the high prices they can charge people for food, water, and shelter. Next, make it a military off limits kind of thing. It has great military position, being on the only mountain pass for blah miles, but there is a treaty that makes it completely illegal to occupy the pass. Any military leader (officer, king, ruler, etc.) will be thrown out of their position for sending troops there for any other purpose than using it. Plus, the villagers supremely hate soldiers, so any that stay more than 1-2 days "mysteriously" disappear in the night. The village should be near, but not right at the pass (maybe 1/4 mile away). It's close enough to make the pass very accessible, but not close enough to house an occupying army. This removes some of the positional advantage for a military, since they would need to be right at the pass to make it really secure. Since they would camp out there, they could have mass desertions as well as making it easier for ambushes. [Answer] It could have an important religious shrine or object that members of that religion come to to venerate. Suppose that if the pilgrim performs a ritual at the shrine that some disease or medical condition is cured. You'd have a steady stream of people with that condition or disease showing up to get the cure. [Answer] > > What could make a **secluded** village also have **reasonably high traffic**? > > > *Nothing*, because -- by definition -- your two points are diametrically opposed from one another. <https://www.merriam-webster.com/dictionary/secluded> ``` 1 : **screened or hidden from view** : sequestered a secluded valley 2 : living in seclusion : **solitary** secluded monks ``` Now... if you wanted a **REMOTE** village with reasonably high traffic, then a siting it on an important, but high, mountain pass or making it a pilgrimage are perfect ideas. [Answer] I live in europe and have lived in a lot of small, some remote, villages in four countries. One thing that brings more traffic is markets. In some villages the markets were small, in others large. Remote towns stand a very good chance of having a large weekly or biweekly market where all the farmers, herders, craftsmen around that town will come to sell their things and all the people outside of the remote town in the surrounding areas will come into the village on those days, otherwise buyers are forced to take a lng trip to a city to shop. The situation hasn't changed much in some areas of europe for centuries. [Answer] ***Major Edit*** # Harvesting Long Lived Flowers There are some plants and animals with funny life cycles, some based on prime numbers. If there was a flower that bloomed every 19 years, and that flower that was the only source of a coveted dye (for instance) and only grew in the remote location (maybe because it's also the only place where bees that can pollinate these flowers live), then maybe this would work. During the interludes, between harvests of this flower the village would be isolated, but during the year of harvest, there would be a trade boom. For comparison, see the life cycles of cicadas (13 and 17 year life cycles) and of bamboo (up to a 130 year life cycle, depending on the species). <https://en.wikipedia.org/wiki/Periodical_cicadas#Lifecycle> <https://en.wikipedia.org/wiki/Bamboo#Mass_flowering> [Answer] A secluded village may well have its own micro-culture and customs. Maybe even a microclimate. Those things could mean that the village produces something unique that people will travel to in order to get (merchandise or some celebration or architecture?) or it exports something. Whisky, wine, art… You can control for much in demand that is and so control how much traffic you want your village to have as well as what sort of traffic. [Answer] It could be a tourist destination for youths, like a fun river-rafting place. It could be similar to Vang Vieng, Laos. <https://www.youtube.com/watch?v=8quMliXCIV4> [Answer] Fur trade might be a decent explanation. There's certainly a demand for fur in any pre-industrial economy. Hunting season can very well be defined as late autumn, as you want to harvest the warm winter furs, but not in winter itself. (Up in the mountains where you hunt, it's really too cold in winter) Now the village is small, so there's only a limited amount of clothes production in the village itself. Quite some furs are shipped out before the winter, but not all. Some of the villages spend the winter time producing clothes, and that's why some trade continues. As there's a reasonable amount of traders coming in, the village doesn't need to produce much food, and besides, there's some meat from the hunt. This explains why farming is a small-scale summer activity; not much need to stockpile. [Answer] Maybe the remote village hosts an **annual fair** where merchants come to the village and people from the village and its neighbourhood trade goods they produce for other goods they cannot manufacture themselves. This will produce some traffic at a certain date in the year. There may be regular visits of the ruler of the territory to the village, and the ruler as the supreme judge holds a court in that village. The village may have a palace buildt just for that purpose. [Answer] It's the local venue for stag and hen parties. Of course you wouldn't want to live there ... [Answer] Everyone is mentioning specific locations, but instead, I will give a formula, which may be of more benefit, and is roughly in line with what occurred during the dark ages, and it is one of supportable resources and time. Between any two major areas of habitation (burgeoning cities for example) that have trade or another need of travel, there will be areas that operate as rest-stops (like modern day gas stations), or layovers. Originally, they would have been camp-stops, and become more permanent over time. The key thing (for your example) is the inability for the settlements to be more attractive to settlers, and this is a factor of local resource which should be limited either by the environment or other factors (such as surrounding landowners competing with each other over and preventing any significant utilisation of the area by a third party). The second key thing is time. Over enough time, any permanent location is likely to spread simply by birth numbers, or immigration due to economic possibility, therefore for your scenario, enough time should not have happened for this to occur significantly, or this could be a combination of the two. One of the ways in which the time factor can be limited, was when an alternative transportation route between the two habitation areas was found/discovered/created which made the journey easier or more economical (for instance in Germany many overland hamlets and villages succumbed or stagnated to the introduction of riverboats for good transportation), but for a period of time afterwards, those who could not afford or full utilise the newer methods would still use the old routes. Alternatively, your location could be on the best and quickest route, but suffers from terrible exposure and must endure a terrible winter, when people travel using another route. The above fits many historical settlements, particularly in Europe (less so for the Nomadic peoples of the Middle-East, or the monguls, etc. - where an oasis, or watering point is a better choice. - again this limits the number of people who can live there, but it will allow for good footfall from travellers). In most of the scenarios above, trade is likely to become an important part of the settlements economy, but will be supported by homestead farming, or limited herd grazing etc. Hope that helps! [Answer] It just needs to be the biggest village in the area. I've seen this in modern times. Even a small village of 500 could have a lot of traffic from smaller surrounding villages. Within 20 miles you might have 15 villages all in different directions. Each of them might have a population of around 50. (15 villages \* 50ppl each = 750 ppl). Within 50 miles you may have another 1000 people all in smaller villages than this one. For all these villages the closest alternative village of the same size or larger than this one might be 100 miles away. So this small village of 500 people supports a market of the 500 people that live there plus 1750+ people for which this is the largest village in the area. They all come here to get supplies and then head back home. It's secluded in the sense that it is mostly known only to the people in the surrounding area but still has lots of people coming and going. [Answer] Most of the other answers mention a mountain pass, but this is not necessarily the only possibility: * A ford. Look at the number of times -ford is in place names. If the ford is easy to cross, then much of the traffic would pass through. Sometimes the ford may not be easily passible -- several days after a heavy rain, spring runoff if it's a snowy climate. This gives reason for people to stop some of hte time. * A ferry. See above. * A fuel stop for wood fired steamboats. Boat stops, loads 10 cords and moves on. See Twain's "Life on the Mississippi" Lots of plantations would do this, and while few were 300 people, some were close. * A persistent myth that the El Dorado was near by. This was the last place for outfitting. Since there were no gold trains coming out, it made for a small surge of propspectors each spring, and a smaller surge coming out each fall. * Last water on a desert route. Travelers would want to top up their water, and likely wait an evening and start in the pre-dawn dark and cool. * Meteorlogical conditions that foster extreme fogs. Village is on a hill above the fogs. * Village is a gateway that is open on a regular, but not long basis: E.g. it's open for two hours when the full moon is at zenith. The amount of opening and desireabiity of the other side determines the number of travellers. * The village has a reputation for have unsavory night creatures. (Vampires, werewolves, Igors...) People stop at the town before or after, but never in the town. * Village is not on the main path, but lies a mile off it -- like many small towns bypassed by today's internet. There is a river of traffic a mile away, but only a trickle comes through town. * The path beyond uses a causeway that is only crossable at low tide. [Answer] The village could've indeed been secluded until a sudden and one-time event sparked a stream of traffic? Census, crusade or any other conflict, a disorganized retreat, an exodus. A rather unrelated but specific idea: You could look into the Klondike Gold Rush, maybe there's some nuggets. ]

[Question] [ I have a very large developed (relatively rational) fantasy game world which mostly has medieval technology with some Renaissance technology, and some low-powered magic. In it, when I was much younger, I mapped a great lake with several islands connected by seven *very* long bridges. The map style is rough and large-scale, so their lengths are not necessarily as long as they appear on the map. On the large scale map, the bridges are drawn as if they were 10 - 25 kilometers long. I soon realized these were excessively long (longer than modern bridges), but not before my players learned about them. Rationalizations I invoked to explain / retcon them included: * They may really only be bridging at most 15 kilometers and usually less, due to the real details at smaller scale. * Each bridge shown might actually be a series of many small islands not shown and the bridges could be a series of little islands connected by bridges. * Some or all of them might be wooden floating bridges. * The lake might be quite shallow where the bridges are. * Parts of them may be piled rocks in the shallow water that make a path above the surface. * It may have taken hundreds of years to build them. * The great lake might be a massive caldera from an ancient eruption (it's sort of the right shape) and there could still be a hot spot below. So maybe these bridges are along ridges and/or archipelagos formed along cracks where magma rose up connecting the central island to the edges along three winding but roughly radial paths. There is at least a *reason* for them to have been built: there is a very industrious and clever nation whose capital is on the main central island, and their main source of wealth involves mining in mountains on the islands. The lake provides great defensive and transport benefits. (In hindsight though, they could probably do all right with just ships and ferries.) The bridges do need to be able to bear the weight of horse-drawn wagons, and the marching of armies. Some magic could be used, but the less, the better. Some "ancient artifact" high-tech might be a last-ditch sort of explanation. So my question is, whether anyone can see a plausible reasonable way to explain how these bridges were built and continue to be maintained, using the least excessive, least magical, least post-Renaissance technology feasible? If not, how much should I revise the map details to make the bridge paths be chains of islands linked by smaller bridges and/or ferry routes? Edit: FYI, as requested, below is a very crude map. (I haven't posted the actual map because a major element of the game is about discovering the game world's details.) The numbers by the bridges indicate the rough distances in kilometers that need to be bridged somehow, though possibly by inventing chains of small islands along them. [](https://i.stack.imgur.com/kSJPa.jpg) Edit 2: Changed my mis-use of the word "span" to "bridge" - they just need to cross the distance, often through shallow water, not to engineer impossible single spans through the air. [Answer] ## These aren't long-span bridges, but *causeways* The current record for a single span is just under 2km long, and any single vehicular span over oh, 100 to 200m long is going to require modern truss or suspension bridge technology. However, it has been possible to span far longer distances over water for much longer periods than that, using only pre-Roman era techniques. How? Simple: you mix short spans, achievable using basic masonry arch or timber girder/beam technology, with earthen embankments built out of the lakebed, forming a *causeway* across the lake. For 15km+ stretches, you would have a regular pattern of embanked sections with interspersed spans to provide for waterflow only, using a masonry arch, or both waterflow and navigation, using a single-leaf timber bascule to allow small-ish sailing vessels as well as rowed pleasure craft through. Construction would be gradual, dumping and trampling earth to progressively form the embankment from one shore to the other. Ox-drawn or horse-drawn carts could be used for earth-moving, with the beasts of burden also used to trample and compact the loose earth into an embankment. Large riprap-type boulders and local grasses would be used for slope stabilization along the sides of the embankment in order to keep it from eroding into the lake, while the road atop the embankment could be left as bare earth or paved with cobbles, depending on how sophisticated you want this to be. [Answer] Have a look at Rama's Bridge [here](https://en.wikipedia.org/wiki/Adam%27s_Bridge). It is 48k long and runs between the southern tip of Tamil Naidu and one of the northern islands of Sri Lanka Investigations suggest that a chain of atolls was connected and brought above the water by manual labour. The entire length was above water until the 15th century. Given the right geomorphology and backstory I see no reason your guys could not do the same. The transport economics also works. Barges for bulk low value ores in. Wagons for high value low volume products out. Roads for fast high worth individual transport. Also tolls. If I were running that empire I'd be charging all the market would bear. [Answer] Those bridges are built by connecting together floating rafts or pontoons. They are easy to build and maintain: just chop trees and craft the trunks in the proper shape. Assemble them together, place some anchors along the path. A similar technology was used in Japan to build wooden bridges which could withstand typhoons: during a flood the wooden parts would float away and were kept together by ropes, so that the river was flow was not blocked and the resulting damage to the bridge was minor. [Answer] A deposit of [pumice](https://en.wikipedia.org/wiki/Pumice), a light-weight volcanic rock, near the bridges could help the construction a lot. It's not necessary the volcano exists anymore, the rock could have formed thousands of years ago. Pumice floats on water for a time, making it easy to move even large rocks into place. It will slowly sink when water seeps into its pores, and it could be weighted down with normal rocks. Pumice is also quite easy to cut even with simple hand tools, such as chisels. With medieval level technology, it should be easy to cut out large blocks, float them into place and have horse carts bring paving stones to make a road on top. [Answer] Consider an ancient civilization. In the middle Ages, some of the biggest architectures (aqueducts and bridges) were Roman-built, like the [Alcantara Bridge](https://en.wikipedia.org/wiki/Alc%C3%A1ntara_Bridge). So, in the past history of your world, a big and organized empire left some magnificent relics of its past power, like these bridges. Maybe they were built with the aid of some magic, or just following some very tiny islands, like connecting the dots. To justify their maintenance, together with the extremely sophisticated and long-forgotten techniques of building, there could be something like an alliance between the most important states to keep them working (something like corvees) or even an independent entity that almost religiously dedicates to their preservation [Answer] This lake on which your bridges are built on may have only recently become a lake. What I mean by this is that what if several decades/centuries ago, this lake was only a **canyon/crater** (and has only fairly recently flooded) and these long bridges, as well as the islands, are the only parts of the canyon which were above sea level? These long bridges could have been originally made to cross the canyon and were supported by shorter rises in the canyon's surface, however, they are now submerged, and the 'islands', as well as the 7 old bridges, being the only things that were above the lip of the canyon, are the only things that the water didn't manage to reach. This can also provide a **story element** to your map, as you can hypothesise what *exactly* caused this flood. Hope this helps (or at least makes sense)! [Answer] It being a lake makes the problem somewhat easier from my opinion - any structure in the water would erode much slower then it would in the river or the sea, due to the slower currents. I've looked at the list of longest bridges and dams of the ancient world, and to my surprise, there were actually structures of 2 kilometers in length in both categories. (The longest bridge - <https://en.m.wikipedia.org/wiki/Constantine%27s_Bridge_%28Danube%29?wprov=sfla1>, the longest dam is on the <https://en.m.wikipedia.org/wiki/Lake_of_Homs>). One was built in the second, another in the third century the Romans. So, it means that the construction on this scale is actually possible for a developed pre-industrial civilisation - having the structures only twice as long doesn't stretch the limits of credibility much. What makes I it a problem for me, is a concentration of several huge architectural projects in one place - it should be terribly important for your people, and they should never stop the maintenance. It shouldn't necessarily be bridges. I do not see any rivers entering or leaving your lake, but if we assume the inflow on the south, both southern constructions could be dams, not bridges. Maybe all the southern part of the lake is artificial, flooded for agricultural or military reasons. Gravity dams are surprisingly sturdy, and even if the segments fail, they could be built back. The northern construction could be a bridge - a dam doesn't seem to make sense in that place. And it could be newer then the dams. Shorter segments could be done as Constantine's bridge I've linked above: > > ...a construction with masonry piers and wooden arch bridge and with wooden superstructure. > > > While a longer part may be a pontoon. The bridge is a point of failure, and needs a lot of maintenance. I'm also afraid that one it's destroyed (in a war, for example), your people would find it hard to rebuild it back. [Answer] * **There is a good reason to keep the city on an island in the lake.** The reason may be irrational but still good. "This is were the kings or government have been for centuries, it would put their legitimacy into question to move elsewhere" or "this is where the main temple has been since the founding of the state, the god would be angry if we move it." Consider [Saint Petersburg](https://en.wikipedia.org/wiki/Saint_Petersburg), Russian capital from the early 18th century to 1918, or [Brasilia](https://en.wikipedia.org/wiki/Bras%C3%ADlia), captial of Brasil since 1960. Moving the government may work, or it may not. In your case, it won't work. The traditionalists win. Could have been a close victory, or a clear one. * **Some important people want bridges, not boats.** Perhaps winds almost always blow in one direction, making sailing difficult. Rowboats or galleys are too slow, or the rowers are smelly ruffians, or in the rest of the country a proper noble simply *does* travel on horseback to set him apart from the proles. * **Bridges are feasible.** The lake is not too deep. The ground is suitable for stone piers. There is no rapid flow of water to cause erosion. No ice in winter, either. [Answer] I'm offering this more as storytelling advice than bridge-realism advice, but you can always just leave the origin of these massive bridges a mystery. Tell your players that nobody in the world knows who built the bridges or why. Let them have their theories but never confirm anything either way. Our real world, especially in the time period you mention, was full of mysteries and things that nobody knew, including these in your world will make it feel more realistic than anything you could throw in about bridge construction methods. [Answer] The lake is shallow -- almost a swamp. Three real-world examples of such lakes are the [Tulare Lake](https://www.infogalactic.com/info/Tulare_Lake) basin, the [Everglades](https://www.infogalactic.com/info/Everglades), and the [state of Iowa during flood years](https://www.desmoinesregister.com/story/weather/2018/07/11/iowa-floods-1993-des-moines-ames-register-photos-archive/776821002/). Tulare Lake is named for the reed-like plants that grew in much of its area. If San Francisco Bay, the [Baltic Sea](https://infogalactic.com/info/Ancylus_Lake), and the Persian Gulf were freshwater, they might also be similar lakes. In the eighteenth century, any sensible Englishman could see that it would make sense to build roads across the lake, as requested in the original post. They were even willing to pay taxes to do so. But no sensible Englishman could figure out a way to do it. Fortunately, England had plenty of rascals. One of them was [Blind Jack of Knaresborough](https://www.infogalactic.com/info/Blind_Jack_of_Knaresborough), who literally couldn't see why it was impossible. He figured out that the answer was to "float the road" on a base of bundles of either straw or heather and gorse. He would fit right in to a fantasy game world; you could have legends about him. (For that matter, our world has a man who was made a saint for [daring to build a bridge](https://www.catholic.org/saints/saint.php?saint_id=46043).) [Answer] **Want to improve this post?** Provide detailed answers to this question, including citations and an explanation of why your answer is correct. Answers without enough detail may be edited or deleted. There are places in the real world where roots of rubber fig trees have been trained across rivers and woven together to grow sturdy footbridges. Wikipedia: [Living Root Bridges][1] I imagine to extend something like this to the island would be a lot easier if support pillars are allowable, but with enough time, and a plant whose roots do well underwater, you could grow those too. Perhaps an ancient culture made the supports by floating large tree trunks to the front of the bridge, and weighting one end of them down. Then your roots could be trained around the tree trunks and into the lake bed. Over time perhaps either roots or fallen trees might become petrified under certain conditions. Wikipedia: [Petrified wood][1] Even if not petrified, the roots could plausibly last a long time, giving you a lot of freedom regarding when the culture that built them thrived. [Answer] The [Lake Pontchartrain Causeway](https://en.wikipedia.org/wiki/Lake_Pontchartrain_Causeway) is 38 km long. Interstate and train bridges have also be built in a similar fashion. [](https://i.stack.imgur.com/viaID.jpg) An Interstate highway and train tracks running over the same shallow lake. [](https://i.stack.imgur.com/nq80A.jpg) And another bridge ("only" seven miles) built in the same manner. [](https://i.stack.imgur.com/dxjVN.jpg) [Answer] To add to the excellent answers already given: your "lake" is marshy and swampy and quite seasonally variable, to the point where barges are not economically viable for year round transport. Your roads and bridges are engineered to remain passible in flood stage, drought stage, and everything in between. As an alternative, you can hamper boats with something like water hyacinth. <https://fishbio.com/field-notes/the-fish-report/green-tunnels-of-invasive-weeds> The key in my mind is not in making such long bridges technologically possible, but in crippling water traffic until road traffic is economically superior. [Answer] The ancient empire who lived there believed that water was the source of all life, and water is the after life. Their despots built huge tombs *over the water* in order to experience the best after life. The further from shore, the more impressive the tomb. Over generations, the despots built chains of tombs, connected by bridges. Each pillar the resting place of yet another great leader. When this bridge of tombs crossed a span of water, its surface was turned into a transportation link. And a new chain of tombs where started elsewhere. Eventually the island civilization linked to the mainland, and thus started the golden age. It spread and conquered and brought back slaves and riches. More tomb-bridges where built, fanning out from the central island. Some petered out in the water; others reached another island, and continued bridging to the land. But all things come to an end. This empire fell, its core finally torn out by invading hordes who used the very bridges that built the empire to destroy it. The bridges fell under neglect. Over time, pieces collapsed. Others where cleared out to make navigational passages. It was 200 years ago that the new civilization started the rebuilding project. Built on the ruins of old, a huge project finished a span all the way to the mainland. From the wealth that flowed over that bridge, the others where repaired and made more mighty than before. These bridges are wonders of the world. People travel from the far and wide to see these structures. On the Day of the Dead, huge festivals of colour and flame occur on them, as remnants of the ancient religion that caused them to be built echo through time. A famous poet is known to have said that they can finally die now that she has done the dance to death on the bridges of the lake people. It sounds better in the original language. --- TL;DR - the original bridges where ridiculous projects of manual labour by an ancient, wealthy, despotic civilization. Thousands upon thousands of dead slaves built the bones; a mixture of causeways and bridges. The original "bones" took many centuries to built -- maybe even a millennia. The current bridges are built on these ancient bones, and are wonders of the world. Both the original "bones" and the current bridges are independently awe inspiring. The "bones" themselves will have many myths about how and why they where constructed. In at least one of them, something like the giant's causeway between Scotland and Ireland may be visible (an ancient lava flow was submerged by the land falling); visible by huge hexagon-shaped rock pillars on the surface, and isthmus on both sides going out into the water. Make that isthmus a bit longer, and you'll have the seeds of the claim that the current bridges are the *3rd generation* of them. First, the giants built the bridges. Then it was struck down. Then, the ancients built on top of the ruins of the giant bridge. Today, the modern people built on top of the ancient's bridges. [Answer] Simple answer: objects on the map are not to scale. It's rather an artist impression of the world than an navigator's map. Lord of the rings featured such maps. You can hand-wave these details away in this manner and not have to add intricate details to the history of that world that may entangle you in a web of side-effects of the new explanations. [Answer] If you make your central island the old capital of a long gone empire, then your island sits at the centre of an important crossroad. The empire is long gone, but it influenced settlement patterns and the roads that radiate out from your island are important trade routes between major towns. This is reason enough to keep such routes open. Consider the founders of the empire settled the upland region where the island now is for safety. There was fertile land on high ground surrounded by marshes cut with streams for clean water. As the civilisation rose to power they drained the marshes by damming the sources (no rivers on your map but there must be some due to the mountains and perhaps also underground water pushing up from somewhere). This provided more farmland and also created deeper areas of water where fish stocks could be managed and water generated power for mills, industry etc. They'd already been putting down bridges to link the raised areas to create military roads which also pleased the merchants as the road toll was cheaper than taking a barge. Towards the end of this civilisation money was poured into keeping the roads functioning which further bankrupted them but as the old dams gave way the raised roads were kept going. By this time the ability to repair let along build dams had been lost but something simple like putting down piles and keeping the road above the encroaching water was endlessly copied over the centuries until the present day. Parts of the old capital suffered plague or somesuch and people abandoned those areas, that's why the roads through them were allowed to be submerged by the lake creating islands barely inhabited and why the coasts of those regions are more heavily forested. It may even be that the last major invasion of the area came from that direction so it was allowed to fall into ruin and form a more difficult path for future invaders from that direction. [Answer] Consider Venice... it was built in a (shallow) lagoon by driving wooden piles (tree trunks) into the mud of the lagoon and infilling with 'stuff' that have lasted many centuries. Those were done pre-industrial. Consider the sort of walkways people still build out into the shallow waters of lakes to boat docks... drive wooden piles into the mud of the lake shore and fix plank or log 'lintels' across the tops of them... providing perfectly safe walkways that span many metres across the water. Make a hybrid construction... run walkways (they could be wide enough to take a horse and cart...) to 'islands' built at convenient places... use the islands to build ramps from the close to water walkways up to a height that allows water craft to pass under them and run a simple lintel between two such islands to make a high-level bridge. Repeat as necessary... to cover whatever distance you want to cover. You can easily get a 5m long tree trunk that can span supported at both ends... so you could have passages 4m wide and several meters high for shipping to go under. Choose the right wood it will last decades if not centuries. ]

[Question] [ I'm trying to engineer a scenario where a nation wipes out another's home solar system by vaporizing it into a cloud of gas nearly instantly and it engineers a huge controversy over how it happened and would cause extreme chaos within the galaxy over the war crime. What realistic(ish) theoretical weapon could achieve this effect? EDIT: By vaporizing a solar system I meant turn the whole thing to a cloud of gas or plasma... [Answer] **A Jupiter-sized mass of antimatter** Based on some quick Googling: * If 1 kg of antimatter came into contact with 1 kg of ordinary matter, they would annihilate with 1.8 × 1017 joules of energy. * Jupiter has a mass of around 1.9 × 1027 kg * A supernova can release as much as 1044 joules of energy. Based on these numbers, if you sent a lump of antimatter with the mass of Jupiter on a collision course with the sun, it would annihilate with 3.4 x 1044 joules of energy, or more energy than three supernovae. This should be more than enough to vaporize the entire solar system, and probably a few neighboring systems as well. [Answer] Solar systems are big and hard to vaporize. Fortunately, when we're trying to do so, we can basically ignore all the planets and moons. On a relative scale, planets are easy to vaporize when compared to vaporizing the star at the center of the system. What's difficult about this is that a star has a lot of gravity. The gravitational binding energy of the Sun is $2.276\cdot10^{41} J$. That's a lot of energy, that that's what you'd need to convert a nice tidy ball of fusion supplies and byproducts into something more resembling an expanding cloud of gas. For that, we turn to one of my favorite Wikipedia pages: [Orders of Magnitude (energy)](https://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)) How much energy? Canyon Runner mentions in a comment that you could accomplish it with a [Gamma Ray Burst](https://en.wikipedia.org/wiki/Gamma-ray_burst), which has $5\cdot10^{43} J$. If about 1% of the energy of the burst went into your star, that would be enough to add the kinetic energy needed to break the binding energy of the star. How realistic? Well, let's just say that [wikipedia](https://en.wikipedia.org/wiki/Vela_(satellite)) includes the phrasing "... gamma-ray bursts (GRBs), [which are] now recognised as the most violent events in the universe." These are not small events. Or you could just set off a supernova next to it. That outputs $10^{44} J$ (aka 1 foe). 1/10th of 1% of a supernova would be enough to do the trick. However, we do have to question whether the process of hauling a large star nearby and then somehow causing it to go nova qualifies as instantaneous. In all senses, you will find whatever weapon that gets used will *not* be realistic(ish). The weapon has to emit that much energy, and its simply hard to make devices that have energies on those scales. But if you like, you can use that wikipedia page to see what sorts of events might be applicable. One of them might be "realistic(ish)" within the scope of your story. As for the rest of the galaxy, war crimes may be difficult to level against a foe so dangerous that they wield this kind of power on a whim. [Answer] In terms of technological weapons with a sort of realistic hand wave, you could build a [Dyson swarm](https://www.youtube.com/watch?v=HlmKejRSVd8) around a star and use it to power a [Nicoll-Dyson beam](https://www.youtube.com/watch?v=RjtFnWh53z0). [](https://i.stack.imgur.com/HpLEL.jpg) *Nicoll-Dyson beam in operation* The energy of the beam would be sufficient to vapourize the planets and small bodies orbiting the star, and if focused on the star for a sufficient length of time, could provide enough energy to essentially "evaporate" the star as well. It is also possible to accelerate the rate of fusion reactions by dumping energy into the star, and essentially creating a flare star or perhaps even a false Nova, energized from without. The downside of this is the beam propagates at the speed of light. A Nicoll-Dyson beam launched from [Tabby's star](https://www.nextbigfuture.com/2016/02/physics-phd-reader-of-nextbigfuture.html) today would vapourize the Earth in @1700 years from now. The energy could also be used indirectly to propel a swarm of [RKKV's](https://infogalactic.com/info/Relativistic_kill_vehicle) at the Solar system, with each one capable of adjusting its flight path to impact a target, or if no target was available to strike the star. From a political POV, it s difficult to imagine what sorts of conflicts would last literally tens of thousands of years (know where the enemy is, locate the target, fire the beam, wait for the effects to be known i.e. another 1700 years to see the results on the Solar System, then relay, re-aim and fire again.....). And of course, since space is 3 dimensional, you are shooting at one planet while their allies off the plane of the ecliptic are shooting at you from a totally different direction... [Answer] In *[Children of The Lens](http://gutenberg.ca/ebooks/smithee-childrenofthelens/smithee-childrenofthelens-00-h.html)* by E.E. Smith (1950), The Galactic Patrol fired a planet from another universe at the target star. In the other universe, the vector of the planet was greater than our speed of light. This sheerly fabulous handwave allows the attack to contain as much energy as you wish, for it to be a complete surprise, and for the speed of light in our universe to be effectively irrelevant for the attack. Here's what happened: > > *"What happened? Even after the fact none of the observers knew; nor did any except the L3's ever find out. The fuses of all the recorder > and analyzer circuits blew at once. Needles jumped instantly to > maximum and wrapped themselves around their stops. Charts and > ultra-photographic films showed only straight or curved lines running > from the origin to and through the limits in zero time."* > > > *"Ploor's sun became a super-nova. How deeply the intruding thing penetrated, how much of the sun's mass exploded, never was and perhaps > never will be determined. The violence of the explosion was such, > however, that Klovian astronomers reported--a few years later--that it > was radiating energy at the rate of some five hundred and fifty > million suns."* > > > Of course, this attack was also the penultimate battle of the war - no defense against such an attack was conceivable, so the Galactic Patrol had to finish the war within days after first use - before their enemy discerned the principles used, engineered the mechanisms, and began using this game-changer themselves. [Answer] You will need a portal gun:  ... Or any other thing capable of building stable wormholes on demand. One mouth ot the hole goes on a planet in the solar system you wish to cook. The other gets sent towards [TON 618](https://en.wikipedia.org/wiki/TON_618). TON 618 is a black hole with a mass estimated at 66 billion times that of the sun. At that tonnage, the notion of margin of error becomes ridiculous. Anyway, one of Tony's most striking features is its accretion disc. Its temperature is in the order of dozens of millions of K. Yes, millions.  Compare with the Sun's surface temperature of ~5,770 K. To give you an idea of how hot that is... I'll just quote the wiki: > > The surrounding galaxy is not visible from Earth, because the quasar itself outshines it. With an absolute magnitude of −30.7, it shines with a luminosity of 4×1040 watts, or as brilliantly as 140 trillion Suns, making it one of the brightest objects in the Universe. > > > So there you have it. Once the mouths of the portals/wormhole connect the target solar system to TON 618's accretion disc, you get an expletive amount of energy coming towards the target, as well as enough gravity to shred the star into pieces. [Answer] **A controlled False Vacuum over the area** This is not supposed to be possible, but let's admit that your engineers invented a weapon capable of *producing a false vacuum*, and *control its expansion*. Basically, a way to erase from existence a part of the universe cleanly and in the most horrible way possible. This would cause controversy. Why ? For the same reason that, in today's world, people fear that an uncontrolled black hole would suddenly *pop* from a scientific experience and **delete Earth**. Imagine that your mass weapon of destruction *fails*, and the false vacuum continues his way through the designated area. That would be *really* bad for the WHOLE universe. But also for another reason : *because the area where the weapon has have been used is empty afterward*. Which means it has some impact on the other galaxies around ! Imagine all the orbits changing, or the trajectory of comets taking different destination. The calculations of all your galactic empire become obsolete, and they have to be done again. Here is a cool video that explains it further: <https://www.youtube.com/watch?v=ijFm6DxNVyI> [Answer] Your rogue space nation might be wise to consider nano-disassemblers. These could be manufactured relatively cheaply and could be smuggled (or launched) into the target system relatively easily. Though the effect wouldn't be instant, it would accelerate as the nano-disassemblers produced more of themselves from the matter present in the star system. Though the entire system wouldn't be reduced to gas, the targeted planets and other objects would be reduced to dust. The nano-disassemblers could be programmed to shut off after a calculated time, or perhaps even to dive toward the sun to clean up the evidence. Or if the nano-disassemblers don't shut off, there's a horrible booby trap waiting for anyone foolish enough to investigate. [Answer] You need a way to make the star go novae. A wormhole adding several solar masses to de star or something converting part of the core to antimatter. The resulting blast should vaporise the star system in less than a day. [Answer] As an addendum to the other answers... > > nearly instantly > > > That could be a problem. Using our solar system as an example, Neptune orbits at about 250 light minutes, so you have 3 options: 1. Accept destruction is going to take the propagation time from the centre of the geometric area to furthest object or from the star to its furthest child. So destruction could be a minimum of hours. 2. Use a destruction method that uses multiple distributed and synchronised sources. You'll have to handle relativity issues, but at least you can get that near instant from the right method. Figure one source for the star and one source for each planet you particularly don't like. 3. Use a destruction method that ignores relativity and propagates faster than light. Unfortunately that's pretty unrealistic, so you're definitely in to the realm of science fiction. Something that operates directly on spacetime or "subspace" is probably your best bet. For option 1 my vote's for lobbing some antimatter or a singularity in to the star, depending on how much destruction you need. For option 2 my vote's for a nice Von Neumann grey goo, the nano disassembler approach, or some repurposed mining equipment. For option 3, just grab a nice wormhole generator and see how many event horizons you can pack in to the system, and connect the other ends to somewhere fun like a black hole, some kind of powerful energetic source like an engineered gamma burst or a high speed quasar. A nice combination of gravity and destructive radiation. Even if you don't vaporise it completely, you can probably sterilise the system and detonate the star. Certainly the result of something like that would cause you plenty of chaos even if the destructive amount is a little less. [Answer] # Try firing a [strangelet bomb](http://www.projectrho.com/public_html/rocket/spacegunexotic.php#id--Strangelet_Bomb) at the star. It won't turn the star itself entirely into a cloud of gas or plasma — there will be a [strange star](https://en.wikipedia.org/wiki/Quark_star) remaining at the center of the ensuing explosion — but the energy released should do the trick for the rest of the solar system. I have no way of actually calculating the energy released, but it should easily be enough to vaporize the entire solar system. Given that any potential drone ship used to deliver the bomb would be obliterated along with the rest of the solar system, the identity of the perpetrator nation would be difficult to determine. The effects of a strangelet bomb will propagate at the speed of light outward from the central star — the solar system is vaporized not by the bomb itself, but by the extremely intense and energetic radiation emitted, which travels at the speed of light. Short of simultaneously bombing different parts of the solar system, this is as close to "nearly instantly" as it is possible to achieve. Of course, the compounding issue for anything that vaporizes a solar system is what will happen to surrounding systems in a few years when the radiation released by the event arrives. If the event is too energetic, it will cause disruption and damage to unintended solar systems nearby, potentially resembling the effects of a [nearby supernova](https://en.wikipedia.org/wiki/Near-Earth_supernova). This may or may not be advisable for the perpetrator nation, depending on whether they or their allies occupy any nearby systems. [Answer] Do you know the difference between matter and antimatter? No. Well, now that you got ultra violet secret 3 security clearance... it is simply the direction of the 4th level quantum spin. Energy content is the same. This is very relevant because - you know the work we did with artificial wormholes and hyperjumps? The dead ends. Happens if you create a hyperfield with a very small calibration error, it can invert the 4th level quantum spin on all matter within it. Takes little energy and depending how you set it up, it converts up to nearly 199% of the matter in it's range into antimatter. And yes, this can be weaponized. The warhead is actually quite small - you dont really need to get into hyperjump level energy levels. And you just need to keep the field up for a nanosecond. The biggest joke is that if you want to build a star buster, the shielding to get the warhead into the core of the sun is like 100% as heavy as the warhead. How you think we got rid of the rebels in UAX-249? That sudden sun eruption was... not exactly unexpected given that we are now short one sunbuster projectile. Get the idea? Matter and Antimatter have the same energy level, so come up with some technobabble and voila, free matter to antimatter conversion. Possibly in a large scale. Which makes this anything, from a posibly solar busting projectile to actually free energy - the old problem that antimatter is NOT an energy source (because you need to generate it first,something star trek never cleared up). I used that many many years ago in a SF role playing campaign. Very slow FTL (unless you used up ridiculous amounts of fuel, very ineconomic, or antimatter, very expensive), but there was this military secret that... if you just manipulated a hyperdrive a little, you could acutally make free antimatter. Ultimate WMD. Use a lot more energy and a lot more complex system and you got a 99.999% conversion in a way that you could actually syphon off the antimatter - for use in military starships. How did noone realize it? Well, they imported it from a black ops company they ran (which supposedly had those huge close to the star antimatter generation plants) - and used all the budget saved for not exactly official purposes ;) [Answer] If somebody repurposed an Alcubierre drive to send a black hole into a solar system, that would effectively accomplish the same. Plus, if you make alcubierre drives ubiquitous, this possibility is demonstrated to the whole galaxy's population, who could readily do the same, which makes controversy much bigger than the fate of just one system. As far as vaporization goes, you could use the same mechanism to move the black hole away later, leaving bare space in its wake. If you did it fast enough, it would look like one huge projectile passed through and vaporized it, achieving (at least in appearance) the same effect as having a single weapon vaporize it all. And if you're looking to leave no trace, you *have* to put everything behind an event horizon somehow, due to the conservations of mass and energy. Other than sending it faster-than-light beyond the observable universe, a black hole is the only way to achieve true tracelessness. [Answer] Your scientists and engineers have developed a material that can (temporarily; it doesn't need to be that long) withstand the temperatures in the star. Make a (or more) large missile out of it, with a magnetic containment field full of antimatter. Once the outer shell melts and the anti-matter is exposed... *BLAMMO*!! [Answer] **Kinectic projectile** There's literally not a limit to the amount of energy you can put into one. It just asymptotically approaches the speed of light as you add more energy. Just keep going until it's enough to destroy the star. The star shrapnel will take care of everything else. Be warned that, at near the speed of light, collisions with tiny objects can seriously dent or destroy your projectile. Even individual atoms in the way may be a problem. Better to send a handful of projectiles to be sure. [Answer] One possible method would be artificial wormholes. It wasn't specified how much of the target solar system had to be obliterated. Was it just the area containing the planets, or all the way out to the outer comets halfway to the closest stars? If you could generate an artificial wormhole with a mouth a few billion miles wide just ahead of the solar system as it orbits the galactic center, the solar system will enter the mouth of the wormhole and exit from the other mouth of the wormhole far, far away and unable to bother you. Unfortunately, since the orbital speed of the solar system will be just a few hundred kilometers per Earth second and there are only about 31,000,000 seconds in an Earth year, it might take several years for the target solar system to completely fall into the wormhole mouth. So you may have to give the mouth of the wormhole a very fast velocity toward the target solar system in order to envelope it in weeks or days. Or you will have to create many, possibly hundreds, of different artificial wormholes at once and position their mouths much closer to the orbiting planets, moons, dwarf planets, etc. to make them enter the wormhole mouths in minutes, hours, or days. Another technique would be to create wormhole mouths that are only ten, twenty, or thirty percent as wide as the planets and moons they are formed in front of. So the wormhole mouths will transport cylinders of matter from the onrushing planets to distant regions of space, leaving the spherical planets and moons with missing cylinders through their centers if the wormhole mouths are positioned correctly. Spherical planets and moons are spherical because their gravity is stronger than the strength of their materials and pulls them into a spherical shape. So if the centers of the planets and moons are removed, the matter in their outer layers will no longer be supported and will fall inward toward the mathematical centers of the planets and moons. And when the tremendous masses of matter falling at great speeds collide with each other in the central regions of the hollowed out bodies, the collisions should be many orders of magnitude greater than the greatest asteroid impacts in Earth's history. I guess that most of those astronomical bodies will be totally turned into plasma by the energy released by those collapses, plasma that might be moving fast enough to escape from the gravity of the former bodies. Type II supernovas are caused by core collapses in massive stars. So forming a wormhole mouth in front of a moving ordinary star that transports a cylinder shaped section out of the star should cause the star to collapse. That should result in a much, much smaller version of type II supernova. But of course even a tiny insignificant fraction of a type II supernova should be a very devastating event that further ensures the vaporization of all the remaining matter in that solar system and will probably heat up all that plasma to escape velocity. Then, of course, shut off all of the artificial wormholes so no evidence remains. [Answer] You could destroy all life within a system if you could create a gamma ray burst of sufficient intensity. Normally gamma ray bursts occur when stars collapse to form neutron stars or black holes - for example the infall of material into a black hole drives a pair of relativistic jets out along the rotational axis. This can occur when two stars spiral into each other to become an object with too much mass to remain a normal star, and must collapse to degenerate matter or a singularity. Gamma ray bursts are really one of the most deadly phenomena in the universe, and even though one would not notice much change in the appearance of the earth, it would destroy all life and possibly strip off a lot of the atmosphere. Gamma ray bursts are kind of the galactic scale EMP weapons. Gamma ray bursts also can be beamed long distances in one specific direction in a narrow jet. You can imagine purposely using this to focus on a particular star system. However energetically it takes major cataclysms to create them, e.g. formation of black holes. [Answer] Vibrational energy, and a lot of it! If we're talking about a solar system roughly the size of our own, with the intended effect being effectively crumbling it into gas and dust, the best I can think of would be a local and extraordinarily strong tidal pull from a passing body. This would have to be extremely massive, like a pair of orbiting neutron stars or black holes. The vibration felt by the entire system as they moved in and out of phase could easily crumble any solid matter within it, particularly if the orbit was at an extreme speed. One such system, PSR J1311-3430 (a millisecond pulsar), completes a full orbit every 93 minutes. When both stars are in alignment with the system, it would feel the pull of all present mass at once; whereas when 90° out of alignment, a decent portion of the pull from each star would be canceled by the other. Of course, actually getting your hands on the requisite mass and transporting a couple of neutron stars is no small feat; but it should be doable with some canon scifi technology. Wormholes, mass effects, and such; maybe even some kind of 100 AU wide pulsating artificial gravity beam. In any case, after only a couple of hours (maybe substantially less), nothing living would be left in that system, and as a warcrime-worthy bonus it would likely be an extremely painful death; after a day it would be complete chaos and gaseous debris. [Answer] **Time dilation device.** I lifted this scifi concept from Stargate. It works for your purposes and offers narrative possibilities too. <http://stargate.wikia.com/wiki/Time_dilation_device> > > The Time dilation device was a device of Asgard design, conceived to > artificially change the normal passage of time... Within the bubble, > time could be slowed down by a factor of ten to the fourth power. This > means that one year within the time dilation field would be 10,000 > years for everyone else ... During the Asgard-Replicator war, the > Asgard summoned the Replicators to the planet Hala and trapped them in > a time dilation field... However, the Replicators managed to stop the > time-dilation device and used it to increase time for themselves, > thriving and replicating many thousands of times. > > > Time moved faster inside the bubble once the Replicators reverse engineered it. In your scenario this is what is used against the solar system. Time moves much faster in the bubble. When the bubble turns off, quintillions of years have passed inside. All that remains is a gas and loose elementary particles - a solar system dying the heat death at the end of time. The detectives can figure out what happened by first realizing that not only has there not been an explosion, absolutely nothing is radioactive in this system any more. They then find evidence of [proton decay](https://en.wikipedia.org/wiki/Proton_decay) - something which should not happen in our universe for a long time yet. They realize that all the matter in the system is extremely old. The perpetrators of the event counter that no crime has been committed - from the standpoint within the time dilation field, the worlds went on as normal, and all inhabitants, and their descendants, and their civilizations, and the stars their plants orbited lived out their natural lives. The Outer Limits twist: within the time dilation field, some of the inhabitants figured out what was going on. They could not turn off the time dilation field they were in but they could duplicate a smaller one and esconce themselves inside, slowing the passage of time within to nothing. When the big fast field turns off, the small inner field (later in the story) turns off too. They emerge. They have had hundreds of thousands of their years to improve their technology before turning on their inner field. These beings are very different from who lived there before. [Answer] The Lost Fleet series deals with this somewhat, (spoilers): > > A hyper gate collapse could theoretically result in a super-nova like energy > release and annihilate the system. Hyper gates have an extreme amount of energy > held in tension, and a chaotic release would be devastating. > > > [Answer] Stellar [muon](https://en.wikipedia.org/wiki/Muon) bomb. [Muon catalyzed fusion](https://en.wikipedia.org/wiki/Muon_catalysed_fusion) allows meaningful rates of fusion of deuterium-tritium at room temperature (and lower). Stars are hot enough and dense enough to fuse "normal" hydrogen. (Citation needed?) At room temperature, muons increase the rate of proton-deuteron fusion [about 38](https://en.wikipedia.org/wiki/Muon_catalysed_fusion#cite_note-20) orders of magnitude. One might be concerned that there is very little molecular hydrogen in stars. This is both true and false. In Sol, the [largest fraction of (fluorescent) molecular hydrogen](http://solar.physics.montana.edu/jaeggli/pubs/jaeggli_LWS_2014.pdf) occurs in the chromosphere, around 150 km above the top of the photosphere. The number density exceeds $10^{13} \,\mathrm{cm}^{-3}$ in a 200 km thick layer over the entire surface of the Sol. (ibid., p. 4. See also the pretty pictures in fig. 2 of an [associated paper](https://arxiv.org/pdf/1802.03779.pdf) showing the complicated distribution of molecular hydrogen in the chromosphere.) The total number of $H\_2$ molecules *known* to be "on the surface of the sun" is $$ 6 \times 10^{12} \,\mathrm{km}^2 \cdot 200 \,\mathrm{km} \cdot 10^{15} \frac{\mathrm{cm}^3}{\mathrm{km}^3} \cdot 10^{13} \,\mathrm{cm}^{-3} \approx 10^{42} \text{.} $$ (There are about $10^{63}$ atoms in the sun, so this number isn't wildly too big, a good thing to check for such unfamiliarly big numbers. The "real" number of hydrogen molecules could easily be 1000-times larger.) These hydrogen molecules have roughly the mass of Mars's moon Phobos. So even if you were to fuse all of it at once, although the CME would be quite spectacular, the star would hardly notice. Something that is not known is what muons would do to the [metallic hydrogen phase](https://www.nature.com/articles/nature16164) at the core of stars. It is plausible that muons would cause the lattice spacing of the molecules to decrease substantially, catalyzing fusion in a manner similar to that at room temperature but, instead of a single muon catalyzing fusion of the two members of a single molecule, a single muon would accelerate fusion over an entire delocalized region of the metal. That is, a sufficiently intense beam of near-light-speed (muon half-life is 2.2 microseconds in their comoving frame) muons could cause the portion of the core they reach to engage in fusion about $10^{30}$-times faster (or more, possibly much more than the $10^{38}$-times for room temperature fusion). The mass of the core is about one-third the mass of Sol, roughly $10^{63}$ hydrogen masses. If you could saturate the entire core, you could induce the Sun to perform all the of the rest of its lifetime hydrogen burning in a few femtoseconds. Typical numbers for the power of the sun are around $10^{26} \,\mathrm{W}$. Increasing by $30$ orders of magnitude for $1 \,\mathrm{fs}$ gives $10^{41} \,\mathrm{J}$, the [gravitational binding energy of the sun](https://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)#Over_1024_J). So, this process is releasing about the right amount of energy. (I'm not convinced one needs to *actually* impart escape velocity to all particles. Even one-tenth on average would produce a nebula that would persist for a very long time on human scales.) This would also dump about $10^{15} \mathrm{J}/\mathrm{m}^2$ of energy on the Earth, about the energy of $1 \,\mathrm{Mt}$ of TNT per square meter. The presented cross-section of the Earth is about $10^{13} \,\mathrm{m}^2$, so the initial flash would only carry about $0.1\%$ of the [gravitational binding energy of Earth](https://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)#Over_1024_J). (However, the rather large uptick in solar wind will ablate the remainder rather quickly.) To be clear, this process is roughly the least energetic process to achieve your stated goal. Only exciting a few percent of the core or only exciting a beam or narrow cone through the star will not produce the desired effect. Each muon has rest mass of $100 \,\mathrm{MeV}/c^2$ and it is likely we need more than $10^{50}$ of them if they are imparted with zero velocity relative to the star. (At room temperature, each can participate in 100-1000 fusions before being captured by an alpha -- at core densities, this number should be higher and delocalization should make it higher still. Until someone builds a high intensity muon gun and fires it at a working fusion reactor, we don't any of these numbers.) However, to excite the entire core at once, we postulated relativistic muons. Determining the effect of the heating coming from stopping all those muons exceeds my stamina for this problem, but suffice to say that each muon dumps a few $100 \,\mathrm{MeV}/c$ of momentum when it is captured, which is a few thousand times the activation energy for fusion in the core. So it would be reasonable to describe this as a heat gun which instantly completes stellar fusion. Equivalently, we could reduce the flux of muons by up to 3 orders of magnitude and still get the desired effect. This still necessitates converting about $10^{-10}$ Sol masses (about $10^{20} \,\mathrm{kg}$) to energy 100% efficiently. This is roughly the [mass of a rock having a $300 \,\mathrm{km}$ diameter](https://en.wikipedia.org/wiki/List_of_Solar_System_objects_by_size#From_200_to_400_km) (roughly the [mass of $200$ Death Stars](https://www.quora.com/If-the-Death-Star-is-the-size-of-a-small-moon-does-it-have-its-own-gravitational-pull-If-so-how-do-the-imperials-combat-it-while-having-the-decks-laid-out-horizontally)). What is not known and could make this process *much* easier: muons are easily produced by the decay of charged pions, pions are easily produced by hadron-hadron collisions (i.e., fusion), the rate of pion production depends on the energy of the fusion reactions, which we can now control by the intensity of our relativistic muons. So, can we arrange for our muon catalyzed stellar fusion to produce copious quantities of muons? If so, we could use a *much smaller* rock and/or a more realistic muon production efficiency. [Answer] Everyone here is answering your question quite litteraly offering you weapon concepts, which is great. Now if what you want is the destruction (regardless pieces left floating in space) you could take this problem in a different and more simple way. If you know a little about Newton's laws one of them could help you : **Newton's law of universal gravitation**. [](https://i.stack.imgur.com/ShvHY.png) This law states that a particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. Now to speak in simple terms, if earth (for exemple) stopped rotating around the sun, it would (fast enough for us to be unable to notice), crush into the it because of the attraction between them. That's where I wanted to drag your attention. If you could stop (or at least highly slow down) planets rotation around the sun they would crush into the it and get destroyed. [This article](http://bigthink.com/ideafeed/what-would-happen-if-the-earth-stopped-its-orbit-around-the-sun) explains stuff about the orbiting of the earth around the sun and the consequences if it stopped. [Answer] A few other answers have suggested dropping a black hole into the Sun. This would trivially certainly destroy the Sun by consuming it, but there's another, much more spectacular, mechanism at play. And that is [accretion](https://en.wikipedia.org/wiki/Accretion_disk). When matter falls into a black hole, it won't fall straight in unless aimed *incredibly* precisely. Instead, an object dropped into a black hole will more often be shredded by the black hole's tidal forces, then form into a disk of gas orbiting the black hole. The gas's angular momentum keeps it from falling inward right away, but it can bleed off that angular momentum by knocking into particles orbiting just a bit farther outward, transferring momentum and letting the inner edge of the disk creep ever closer to the event horizon. This whole turbulent momentum-exchange process produces heat- a *lot* of heat. There's a lot of potential energy stored in a mass suspended above a black hole, after all, and when the mass falls in, that energy has to go somewhere. In fact, an accretion disk can covert [around 10% to over 40%](https://en.wikipedia.org/wiki/Accretion_disk#Manifestations) of the mass of the infalling matter into energy that can radiate away from the hole- far more than the 0.7% attainable by nuclear fusion. Imagine that- a weapon capable of converting 10% of the sun's mass into energy. If Jupiter's mass-energy is comparable to a supernova, then 10% of the sun's... is just insane. Now, there are a few caveats here. For one thing, it's not instantaneous. Black holes can only consume matter at a certain rate. The accretion disk emits radiation, and that radiation [exerts a force](https://en.wikipedia.org/wiki/Radiation_pressure) on any matter that it hits, pushing it away. When that force equals the force of gravity pulling matter inward, they balance out- and the hole can't eat any faster. Some matter will continue to slip in, as that's powers the radiation pressure; but the rest of the star will be kept out. This is called the [Eddington limit](https://en.wikipedia.org/wiki/Eddington_luminosity). It increases linearly with the mass of the black hole, which means that bigger black holes can eat faster. And since black holes grow by eating, a black hole dropped into a star will grow exponentially until there's nothing left for it to consume. So you could kick-start the process by using a large black hole, or use a small black hole and let it act as a sort of apocalyptic time bomb. Over time, the star would grow brighter, larger, and redder as the black hole outstrips the thermonuclear reaction in its core (which will happen around when the hole has absorbed about 0.1% of the star's mass), until the rate at which the hole's consuming matter exceeds the rate at which that matter can heat up and expand, whereupon the star will become smaller, hotter, and ever more luminous until there's nothing left to shield the rest of the solar system from being scoured clean by the incredibly intense radiation from the accretion disk. And I have absolutely no idea over what sort of time scale this would take place. I've made a couple of attempts at the math, but I'm fairly sure I messed it up somewhere. Another caveat is that much of that radiation may be directed directly out of the plane of the solar system. We might wind up essentially creating a [gamma-ray burst](https://en.wikipedia.org/wiki/Gamma-ray_burst). Sometimes, when massive stars collapse into black holes, much of the energy of the supernova is directed into two narrow beams of gamma rays perpendicular to the accretion disk. The same thing might happen when a black hole fully consumes a smaller star, depending on how quickly the star is spinning. The third caveat is that this won't fully vaporize the solar system- there will for sure be a stellar-mass black hole left behind, and perhaps also some planets. I have no idea whether or not they could survive this kind of event, although their biospheres almost certainly wouldn't. And if the biospheres somehow did survive the blast, there would be no sun afterwards, and the planets would freeze. [Answer] I'm going to go for something that's real and might be possible with current technology. You put a space telescope in orbit around the solar system you want to destroy. The space telescope looks closely at all the stars around. When you see the light of some stars shift because a [primordial black hole](https://en.wikipedia.org/wiki/Primordial_black_hole) is between you and the that star, you can [figure out the distance and location of that primordial black hole](http://www.astronomy.com/news/2018/02/the-search-for-primordial-black-holes-continues). Then, you fly your space telescope close to the black hole. When the space telescope starts to be sucked in by the black hole, its engines turn on and pull away from it. The black hole is slowly being pulled in the direction of the space telescope. Over time, you can [pull the black hole](https://www.livescience.com/53627-hawking-proposes-mini-black-hole-power-source.html) in a trajectory that causes it to eventually hit the sun of the solar system you want to destroy. Once the black hole is attracted by the sun's gravity, it should start to move toward the sun faster and faster. It might take a few weeks, but it's a sneak attack that nobody expects. Although this is a bit of a stretch as far as really being possible, it makes for good science fiction. [Answer] I assume you have FTL. Create a microscopic black hole on a ship that is in hyperspace right before it drops out of it, right in the middle of the star. Due to radiation pressure and extreme temperatures it generates, it might be enough to send star's matter flying into the planets, causing them to turn into molten pieces of rocks. [Answer] Use iron to make the star die. Iron is unique--when it's created, it begins the countdown to the star's death. With hydrogen, helium, lithium, etc., the star can still use nuclear fusion to create higher and higher numbers of elements. Iron, however, absorbs the energy of the impact. But it won't fuse into heavier elements, so it decreases the fusion of the star. A star's life is marked by a balance between gravity and fusion. If fusion decreases, gravity wins, the star collapses and then . . . A: Goes super/hypernova. B: Blows off its outer layer and fizzles. C: Goes supernova and then collapses into a black hole (note: only for massive stars.) You'd need a lot of iron to do it that quickly, but a planet- or two's worth would probably work. [Answer] ## [Kugelblitz](https://curiosity.com/topics/kugelblitz-the-theoretical-black-hole-made-of-light-curiosity/) all the bodies that you want to destroy. A kuelblitz is a [black hole](https://en.wikipedia.org/wiki/Black_hole) made by focusing light on a specific location in space. When enough light is focused on a specific point, it collapses into a black hole proportionate in size to the amount of energy used to create it. Several incomprehensibly powerful lasers could be directed at the different astral bodies in the solar system designated for destruction. When the lasers converge on the planets and so on that are being targeted, a black hole will form and consume the body. This could be done for every body, turning the solar system into a black hole system. ]

[Question] [ **Edit:** this is not a dupe because the other question asks for an everchanging maze that is built with pre-historic technology and that is impervious to engineering (i.e.: immune to drilling). Mine allows for backtracking until reset must be built with current methods, and involves no magic/alien technology to protect it against heavy machinery. Roguelikes are videogames in which the player must navigate through a procedurally generated network of rooms (and possibly tunnels) to reach the end of the game. Popular examples include Diablo, The Binding of Isaac, and Rogue itself. # Goal To build an underground labyrinth that changes its internal configuration based on a procedural generation algorhitm, which can be reset at will by the maintaining staff (the time it takes to reset is irrelevant). The maze may reuse rooms, but it should be statistically unlikely (< 0.00001% chance) to have the very same network twice. # Constraints Technology level should be what we expect to achieve by 2030. Arbitrary goals for the labyrinth measures are 0.5 km2 per level, for a total of six levels. Disregard/handwave away how the labyrinth is going to be staffed or populated. Suppose no expenditure limits. Finally, the deadliness and level of challenge of the labyrinth are not part of the question. The goal is to determine the engineering feasibility of the changing labyrinth, and only that. # Motivation Suppose a villain has played very hard games such as Rogue and concluded that those are nearly impossible to finish, so they think that hiding in such a dungeon will make them harder to defeat. Alternatively, some TV channel may be one upping the reality show business, or a theme park may be trying this as an attraction (in which cases the traps would not be deadly and the monsters would not harm the guests). [Answer] Well, you can go the operable wall way: [](https://i.stack.imgur.com/QoMA5.jpg) police use this [Tactical Training Grid](https://lotusdoors.co.nz/news/160/Lotus_Tactical_Training_Grid_Vic_Pol_Facility) to construct distinct scenarios to train policemen. I think you can do the same but with automatized walls in a grid, that moves and deploy according to the desired pattern. To compose the maze i suspect a lot of movements will be required, so this in action could be like a giant 2-d rubik. The trickiest part will be the connection between floors, but you can place a lot of doortraps closed and concealed and only open one per level. All the other stuff (chests, furniture, staricases, fountains, etc) can be placed by robotic Forklifts. [Answer] # Thick floors with hydraulic pillars Given a grid made up of 30 to 50cm square pillars, each with an independent hydraulic piston and controller allowing it to either act as a full height pillar, even to the point of acting as stairs to the room above, or sit flush with the "floor", everything else is software. You'd need to define regions on each level that are always open space to allow for removable panels for the stairs to the lower level, but these regions aren't necessarily always available to the adventurer, they can just never be walls or stairs to the higher level. While crude, and slightly limiting in where you can put the level changes, it will fulfill your basic requirements. *It also leaves open the option of crushing your intruder against the ceiling if he gets too close/boring* [Answer] If reset time (and cost!) are not relevant, just tear it down and rebuild from scratch on every iteration. You can procedurally generate the blueprints by computer just like the actual games, perhaps using one of the games as-is. [Answer] You should check out the movie Cube: <https://www.imdb.com/title/tt0123755/> The maze keep changing, with almost infinite possible combinations. In a sense it's a rogue like maze. It consist of many rooms that are shaped like cubes with different sets of traps (some with no traps at all). Each room has six hatches that leads to other cube like rooms. The structure is basically i gigantic cube, made off smaller cubes. **Spoiller alert** - As the time passes by, the rooms move, like a sliding puzzle, modifying completely the structure of the maze. **how to build it** The fictional Cube device in the film was conceived by David W. Pravica, a mathematician. It consists of an outer cubical shell (the sarcophagus) and the inner cube. One side of the outer shell is 434 feet long. The inner cube consists of 26x26x26 =17,576 cubical rooms (minus an unknown amount of rooms to allow for movement, as shown in the film), each having a sidelength of 15.5 feet. There is a space of 15.5 feet between the cube and the shell. Each room is labelled with three identification numbers, for example, 517 478 565. These numbers encode the starting coordinates of the room and the x, y, and z coordinates are the sums of the digits of the first, second, and third number respectively. The numbers also determine the movement of the room and the subsequent positions are obtained by cyclically subtracting the digits from one another. The resulting numbers are then successively added to the starting numbers. [Answer] # VR We’ve already made huge gains in VR in the last few years. By 2030, the medium will be considerably more mature. For both the TV channel and the theme park, that should be more than good enough. As for the super villain, security through obscurity is terrible. Shame on them. [Answer] The TV show version is easy. There, contestants are following rules, so any of the modular room design patterns in the other answer apply. Anyone who tries to break through a wall they aren't supposed to break through gets penalized. The evil villain case is a different story. If you're filling the room with deadly traps and monsters, the heroes assaulting your lair are *not* going to play by your rules. They'll break through walls, go over boundaries, and do whatever it takes to get to you. As such, you are going to want much stronger materials. Typically you would do a lot of work in concrete, which is hard to demolish and rebuild. You would likely need to be refurbishing one or two rooms at a time, and adjust your maze such that that is useful. Indeed, one small change was enough in [The Matrix](https://www.youtube.com/watch?v=nZTcqbsapIo). However, you mention 2030 tech, and that's terribly convenient because I just saw a video of [a robot that can hang drywall itself](https://www.youtube.com/watch?v=XJcBfy5NhTk). A lot can happen in 12 years, and it may be reasonable for 2030 robots to hang steel plate, and bolt it or even weld it in place. A steel plate can be cut down, given effort, but it is decidedly not easy, so it could be a reasonable basis for your mutable labyrinth lair. Of course, we all know labyrinths wont be the same without David Bowie. RIP [](https://i.stack.imgur.com/VzxF1.jpg) [Answer] # Gigantic 3D printer 1. Build an empty underground structure which will be no more than a gigantic 3D printer. 2. Fill the first 10 cm of your cube with sand. 3. Let your gigantic laser (or any very hot beam) melt the sand to created 10 cm height “glass” walls following your maze pattern. This can be archived thanks to rails fixed to the ceiling, allowing the laser to move freely. 4. Add another 10 cm of sand and repeat the process… 5. Once the whole cube is printed, removed the un-melted sand and there you go, you have a 3D maze : [](https://i.stack.imgur.com/HraGA.jpg) The process in [video](https://www.youtube.com/watch?time_continue=17&v=IIlosHwpU4g). # But don't do it with sand ! Of course, removing the un-melted sand will not be easy if you have a true maze with lots of levels and dead ends and removing the whole structure when the maze will have to be reset will also be difficult, but here is the solution. Don’t do it with sand but with **microbeads of a special polymer** that melt when exposed to very hight temperature and then harden when cooled. Then, to remove the un-melted microbeads, just flood the cube with a **selective solvent** that will dissolve un-melted microbeads, but not the hardened walls which will have changed of molecular structure during the hardening step. Then... Flush it by opening some bung ! And when you want to reset the whole thing ? Just turn the heat on and let your structure melt... # Other option If you don't want to have problem with flame-thrower-equiped-adventurer (Thank M.Herzkamp), you can harden your microbeam polymer with UV light and reset your whole maze with solvent specificaly designed for the hardened polymer. Of course, keep the polymer and solvent formulae secret in a very strong vault in your base ! [Answer] I don't see any particular problem here from what you've said so far. You want a six story building (or 5 stories and a basement) with no load-bearing interior walls. You can have load-bearing posts or pillars. You want movable walls for the interior. You might settle for two stairwells and block off every other level on each of them, so you have to get from one to the other. That's easy and cheap, though you could use, say, ladders anywhere you're willing to open up the floors. You didn't specify that you want the interior walls to be resistant to maces and battering rams. Getting robots to do the work is trivial in theory. .5 square kilometer. say a building that's 1 kilometer by 500 meters. About 3300 feet by 1650. 500,000 square meters. The Boeing Everett factory is 400,000 square meters, maybe 10 floors. Close. There are various other great big buildings. So this isn't completely unprecedented. There are various commercial solutions for the actual walls, here's one of them. [movable walls](http://www.jmlproductsanddesign.com/MovableWallPictureGallery.htm) [Answer] You could do it nowadays if you really wanted to. Consider a square room with 4 walls, a roof and floor. Above each room, is a secondary room where a winch and motor are attached to each of the walls. Given a command, each of the walls could be lifted, creating an opening and a new passage way. This way you can create your maze structure fairly easily, and it can be maintained by people walking over the roofs of the modular rooms. [](https://i.stack.imgur.com/6kW24.png) The next key point is set pieces. These are rooms that are designed to be different from your standard passages and contain fixed puzzles. You can change the way your victims travel to each set piece, and you can also move the set pieces yourself. How? Overhanging crane system. If you've ever seen videos of Airplane construction, you will notice that large parts of the planes are moved using a warehouse wide crane system. You lower it the crane down. Attach it to the modular square rooms you want to remove and off they go. Then simply lower a set piece into the game and open up the corresponding passage ways on the modular rooms outside. And there you go... a changing and customizable maze Edit: To get multiple levels, you would use a special set piece in fixed locations that would cover altleast 6-7 stories. It could be an elevator, a pit or a long stair case. You have the original Level they are on (1), the overhead for the changing walls (1), overhead for dangling set pieces/rooms (2-3), Room for the crane (1-2), the next level (1). You could combine these with rooms that spin to disorientate your victims. [Answer] **This shouldn't be an issue even today** (*aside from being horribly expensive.*) Take inspiration from Minecraft, and use a grid structure of "blocks". I'd use 3 "floors", and just fake the floor traversal. Because you're not getting to kill me (the villain) just because you managed to traverse 6 floors... * **Bottom floor** is essentially just hydraulics and cable management to lift the various blocks up/down to create the room and passages. It can even include pitfalls by going further down than the rest of the floors. The randomness is just an algorithm, they do that already in the various rogue-like games. * **Middle floor** is the maze itself where the people get lost. The floor traversal could be a winding stair that just slowly move up/down as the people traverse it, giving the impression of changing floors while the rest of the maze re-arranges itself. * **Top floor** is all your traps, monsters and goodies being shuffled around by warehouse robots, then dropped down in the respective rooms by a hatch in the ceiling. Simple enough. Upon re-arranging the maze, the stuff is pushed back up again by the rising floors. [Answer] Other answers have focused on the mechanisms of how to have a changing maze. I'm going to answer your other question: how many rooms you need so that there's less than a one in ten million chance a randomly generated maze repeats? Surprisingly few. For the number of rooms you need, where people going through the maze do not enter the same room twice, you need a [self-avoiding rook walk](http://mathworld.wolfram.com/Self-AvoidingWalk.html). Here's an example for a 2x2 and 3x3 array of rooms. Think of the rooms as occurring at the intersections of the lines. The entrance is in one corner of the array, exit in the opposite corner. So in the top row, in the 2x2, there's only 2 ways to get form start in one corner to finish in the other. In the 3x3 array of rooms, there's 12. [](https://i.stack.imgur.com/R4Uj7.gif) * In a 4x4 array: 184 possible paths. * In a 5x5 array: 8,512 possible paths. * In a 6x6 array: 1,262,816 possible paths. * In a 7x7 array: 575,780,564 possible paths. * In an 8x8 array, a chessboard: 789,360,053,252 (yes, over 789 *billion* possible routes). You certainly don't need multiple floors, and you don't need to reuse rooms on a given single run through. (Numbers from [here](http://oeis.org/A007764)) Now, the thing is that the rooms certainly don't have to be identical, only that a given room is only connected to between 2 and 4 other rooms at most, depending on where it falls on the array network (and how many doors you allow to be open). So some might be small rooms, some long tunnels, whatever. There is a downside to that: suppose the starting position is in the southwest corner. Someone entering your maze will know, if they've been through it before, there's only two possible rooms that come next, one to the north, or one to the east. If the path is to the north, they'll know that in the next room they can only go either north again or east. If enough groups make it through and compare maps they made, they could probably figure out the general concept of your maze. However, that wouldn't necessarily do them any good. Look again at the possible paths through the 3x3 network. They might know there's only 9 rooms, but they wouldn't know which of the 12 possible routes they'll end up on. They might need to only go through 5 rooms. Or they might have to go through all 9 to reach the end. For an 8x8 network of rooms, it would be a horror show. They start off, they don't know if they're going to be fighting traps and whatever in only 15 rooms, the minimum, or 64. With mapping, they might might have a good idea how many rooms they have left near the end of the run, but still... And if you do only *two* floors, so two 8x8s on top of each other, with ladders connecting rooms so they might have to go up or down a level, and not knowing how many times... So: an 8 x 8 network array of rooms, on each of two floors. Each room has between 2 and 4 doors, depending where it is in the network, and a trapdoor either on the ceiling or floor, depending what floor you are on, but only two doors/trapdoors can be opened: the one you use to enter the room, and the one you use to leave. Not only won't they know what you might have set up in a given room to deal with, they won't know if they'll only face 15 rooms (shortest route, single floor) or have to go through all 128 of them. And to add even *more* fun, why assume they start and end on the corners? Consider the entrance to the maze itself consists of a long, winding tunnel which makes it difficult to determine how far they've traveled, when it suddenly comes an an abrupt end with a door. The only thing is, the end of the tunnel is moveable like an airport bridge, so when they open the door, they don't know what room on the west side of the maze they're entering. It might might be any one of the rooms on the west side. And imagine that the exit consists of a long tunnel that wraps around the other three sides on both floors, that any given room on the north, east, or south sides might have the exit door. Now that screws up their mapping again because if they end up in one of those room, they don't know if the next door is the way out, or if they're going to be turned around and sent deeper into the network. Another thing about thinking of it this way is that it doesn't have to be procedurally generated: for your 8x8 array of rooms, the computer can be programmed with all 789 billion possible routes; despite the number of routes, each can be coded easily, for example NNEESWSEENN... (describing what door in each room opens to the next). When a run is ready to go, the computer randomly selects one of the paths and it's ready to go and flagged so that it's not included in the next random selection. This also allows you to set up "difficulty". Coded like I suggested, it's trivial to tell the computer "select one of the routes that has between 15 and 23 rooms" or "select one of the routes that's between 50 and 64 rooms", giving you difficulty levels through shorter or longer possible mazes. By the time you get through 789 billion combinations, it's pretty safe to assume that someone who's been through once is never going to see the same route again, no matter how much of a human lifetime they keep running it. Fun times, fun times. [Answer] Trivially a grid or cube of e.g. shipping containers, with doors between every one -- so each cube has 6 doors (4 walls, top, and bottom). If you offset the lines of rectangular containers (so the front of one container is adjacent to the back of the one next to it), then 2 doors on each of the long walls, so eight doors per container. What makes it configurable is just that the doors are locked electronically (and networked) -- so maintenance staff can press a button to reconfigure which doors are locked and which aren't. [Answer] Roguelike games consist of lots of rooms. It’s the random nature of the rooms’ connections and contents which gives it the random maze feature. So you don't have to build a massive building with no load-bearing walls. You can pre-build lots of identical rooms in a grid, in a number of sizes. So working with a 10m base grid, you'd have rooms such as 10x10m, 10x20m, 20x20m, 40x40m... (larger rooms will be a little larger than 2x because of the wall thickness). Doors would be in the middle of each standard grid wall (so a 20m wall would have 2 doors at 5 and 15m). Yes, the position of the smaller/larger rooms would be fixed, but given the ability to rearrange the connections inside, your maze qualities are preserved. With foreknowledge of a previous run, users might know that the next room will be larger or smaller, but that doesn't really give them much advantage. You then have automatable doors – you could do a fancy thing retracting into the ceiling, but sliding would be sufficient. You can then change routes through the grid of indistinguishable rooms. Some rooms can be left empty, to serve as corridors. Contents for the rooms can be delivered either via a service floor above, or more simply by sliding all the doors open whilst you rearrange the maze, giving you a wonderfully accessible area for an army of robot forklifts or similar to drive through. You can build your walls and doors out of something nice and solid like re-enforced concrete to prevent damage, particularly if you're having more lethal activities inside it. You can build your levels above each other. Stairs can easily be deployed where you want them as a movable set of steps to a trapdoor in the ceiling. You can have a number of pre-set locations with doors to the floor above; on a 0.5km2 level you could have a hundred or more, and with only 2 open (one up, one down), knowing the potential locations of the stairs provides users with very little help. Similarly with any traps that require installation into ceilings/walls/floors. Provided the rate of them being active is very low, knowing that there's the potential for one in a location is not useful – in rogue, any step is potentially a trap, but knowing this provides no help. A service floor between each level (and at the top&bottom) would be sensible – this would allow you to route power cables, etc. You'll also need substantial air-con; you could probably use small impassable ventilation grilles between rooms, so that air can pass even when the doors are shut, and some clever design could use passive techniques to encourage airflow. This should be entirely buildable with current technology, though the army of robotic forklifts might need some work to make them reliable; that's likely to be the hardest part. The cost would be fairly high, but it's hard to imagine it'd be beyond the pocket of someone like Musk – the issue is that to build an investment of that size, you'd need a plan to make returns on it, and it's hard to see how it could make a meaningful ROI. Trying to get an estimate of costs is hard. The largest building by floor area is the Boeing Everett Factory at 0.4km2. I don't know the cost to build it, but they built it to deliver a 525m USD contract; assuming they had a healthy profit margin and that the bulk of the costs were to build the planes, we can surmise it cost probably no more than 50m USD. Obviously a multi-floor building is more expensive, but normal height ceilings and smaller rooms should make it a lot cheaper. So you're looking in the region perhaps of $500m? It's worth noticing that the Boeing building has lots of its own support infrastructure, including canteens and a fire department. You'll need to add in that kind of stuff too. And a lot of staff; they'll need to be fed etc. I'd recommend a 'staff room' for monsters at regular intervals, particularly if you need to administer first-aid also. Or you could give monsters passes so that they can open doors and take a direct route in/out as long as the adventurers aren't too near. [Answer] You can get the same general result easier if you think about it in a slightly different way. The rooms in your maze are normal, static rooms. The *connections* between them, however, aren't. The simplest example would be to imagine a tower with one room per floor. Floors are accessed via an elevator (fully automated, no accessible controls). When you leave a room, you get in the elevator with no idea where it will take you. You can visit rooms in any order, perhaps visiting some rooms more than once or not at all. Rooms can be reset and re-stocked while they're idle. The end result is a completely unpredictable experience, even if the rooms themselves are mostly static. You don't *need* a fancy automated elevator system for this. Connecting rooms via stairwells/hallways/lobbies with heavy access doors and remotely-controllable locks would also work. You'd likely want some kind of signage or signal light to direct your victim hero to the next open door, to avoid the hassle of having to check a hundred doors just to find the one that's unlocked. I did something similar back in the late 90's when working a haunted house that was built in an old office complex. We would adjust the flow by opening or blocking doors while visitors were in a room, allowing us to dynamically route traffic flow based on which rooms were ready and which were still resetting. We did it manually (so no fancy technology needed), but you can make it as high-tech as you want. I was very surprised at how well this technique could turn what was originally a bland set of rooms along two parallel hallways into something that felt like a sprawling, disorienting maze. Change up the décor a bit while the victim is in a room and it's even hard to detect that you're walking through the same hallway again. For the theme park angle, this also makes it easy to dynamically adjust the difficulty by swapping out difficult rooms for easier ones and adjusting the number of rooms required to finish. For enhanced replayability, you can have hidden puzzles that change the room sequence when solved. An attraction that follows an overarching plot could thus have multiple endings. [Answer] Moving walls that are also mirrors. Something like this [](https://i.stack.imgur.com/6nWdt.jpg) But on system like this [](https://i.stack.imgur.com/4tgiC.jpg) Add the fact that you can gave 3 floors with such system and you're set for all Bruce's Lee's that may want to hunt you. Just remember to invest in those cured, hard to broke mirrors. 7 years of bad luck for each. [Answer] Thing is, you have plenty of time to prepare, because procedural generation is not random (at least in this case). You can map an arbitrarily large part of the labyrinth before it's actually built or used. Assuming we have a set of 10 type of rooms, a dozen or so of every variety, all ten are in some nice shape to be tileable (note: we don't need the mathematically significant concept of covering the full plane), and you can build whatever your want with simple cranes right now. With a moving platform you can even keep the "player" in the center of your arena all the time, so you don't run out of place. I don't see any engineering problems with it. You want the generation to be more fine/detailed, less blocky? [Answer] Pop up walls. Consider a piece of graph paper. Each block has 4 sides. Each of those sides is a pop up wall. The hoisting (pop up) device maintains the integrity of the wall, so you don't need rails in the maze space (you could use rails beneath the floor). The walls would hoist using wheels/rollers, and then pins would secure them in place. There will necessarily be gaps between the walls. If this is a problem, the walls could have pop out edges that expand when the wall is raised to cover the gaps. You can make the walls out of any stiff material you could hoist (metal, wood, cloth flats). You might have a select set of panels that are actually doors. [Answer] People have already given a lot of good answers on the how to do a procedural maze in real life. My answer is more about "do you really need procedural generation" ? I think one of the most important part in a roguelike is the permadeath. That's why I don't think that Diablo can be defined as a roguelike and why it isn't really relevant to talk about roguelike in real life. We are already living in a permadeath world. If your maze kill people when they fail, you don't need to change it everytime, dead people don't try again nor talk. It's only useful if they don't die and just get flushed to the start or if it is a TV show and people can see other tries before going in. But in case of TV show, you could decide that the broadcasting is done when every participant already tried. You film the whole season in one go and you have a year to change the maze manually. ]

[Question] [ I was reading [a World Anvil article](https://www.worldanvil.com/w/dohma-ArchdiAngelo/a/frostkin-article) which has a world that experiences world wide seasonal changes. Specifically quoting the article, > > During the month of Frimense, the Frostkin thrive, as the whole world descends into 49 days of winter. However, as the month of Igmense arrives, . . . > > > Is it even remotely possible for an entire planet to experience world-wide seasons on such a short and regular pattern? [Answer] In theory, the answer is actually yes. However, unlike our own planet, whose seasons are created through tilt, the planet in question would have to have an elliptical orbit that brought it closer to its sun during certain parts of the year and further away during other parts of the year. The regularity of the orbit would create stable season times. This would likely have some unexpected effects on both the stability of the planet in question(Tidal effects from the sun would be weird), and the ecology of it, but it is certainly possible. Popular Science has an article on a similar subject, here: <https://www.popularmechanics.com/space/solar-system/a27956/what-are-seasons-like-on-other-planets/> I believe that your planet would have seasons akin to Pluto's, but on a shorter time scale. [Answer] An even simpler explanation is simply for there to be no land in one hemisphere of the planet. If it’s summer in the southern hemisphere, then no one will care that it’s winter in the northern hemisphere if there is no land and therefore no people. Seasons will be stated as affecting the whole planet even if it’s not technically true. They might affect a few long-distance shipping routes, but nothing else. [Answer] An alternate explanation would be a [binary star system](https://en.wikipedia.org/wiki/Star_system#Binary). While the two stars orbit eachother, they get closer and further away from the planet, producing more and less heat. This allows for seasons of equal length, while an elliptical orbit would have a short warm season, and a longer cold season, as the orbital velocity of the planet is greatest at its perihelion and slowest at its aphelion. [Wikipedia](https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems) also has some notes on the habitability of such systems. In short, they may be habitable depending on many factors. [Answer] First it needs to be noted, that for the entire planet to have same season it needs to have its rotational axis be perpendicular to its orbital plane. As for how it can have changing seasons there're a couple ways: 1. Previously mentioned in one of the answers elliptic orbit. For earth-like seasonal difference the furthest point should be maybe 1.4 times further from the sun than closest. Problem with it is planet moves faster the closer it is to the sun, so the "summer" would be somewhat shorter than "winter". One of the comments mentioned, that it's possible to have each season twice in one rotation, but orbital mechanics doesn't work like that. Sun is always in the focal point of the orbital ellipse. Also shorter seasons (winter is 49 days) would mean shorter year, which means faster rotation and closer orbit. For reference, Mercury has a 90 day year, so for such a planet to be habitable, it will need a different class of star. *As a perk, the color of the sun might have minor Doppler shift, becoming slightly greener in spring and redder in autumn, because planet moves towards/away from it.* 2. [Variable star](https://en.wikipedia.org/wiki/Variable_star) can be an easier explanation, albeit not as fun. They're very flexible, as their period can be anywhere from hours to years. And they're different from pulsars, which have periods in milliseconds. [Answer] Here's a solution that doesn't require elliptical orbits, super fast planets or unusual stellar bodies for the sun. Giant dust cloud. How giant you ask? Imagine that during the formation of the solar system something went horribly wrong and instead of Mercury and Venus forming as is, they instead tried to form one planet but ended up breaking apart in to dust cloud orbiting the Sun. Spread out enough to not clump under gravity but dense enough to cause a noticeable drop in solar radiation when it's between the Earth and the Sun. Maybe something similar in density to Saturn's rings but spread over a wider area? Place it at a bit of an angle from the Earth's orbital plane so that the ring can be consistent density all the way round but still produce a variable masking. Might require fudging the numbers a little to get a reasonable set of values, but it's not the most ridiculous stellar formation I've ever heard of. I suspect the main hurdle would turn out to be solar wind and flares disrupting the structure, but maybe there's a way round that with composition hacks? Plus, how bad ass would that look :p [Answer] I have tried to imagine a way that a planet's seasons might be self-generated and self-regulating through dynamics on the surface, either of weather or of plant life. I'm not quite there, though, but here are some ideas: * deciduous trees in the worldwide forest have white leaves; when the foliage peaks in summer, it increases the planet's albedo, reflecting sunlight into space, and beginning a cooling phase * as it gets cooler, winter begins, these trees drop their leaves, exposing the shorter evergreen trees, which are dark and absorb sunlight, beginning a warming cycle The problem with this idea is that *snow* is white, so if there's a lot of snow, that would increase albedo and create a positive feedback loop where the "cold gets colder" and summer doesn't come again. Can anyone suggest a way to improve my idea? ]

[Question] [ We've got this criminal who likes to interrogate people via Russian Roulette. While his captive watches, he empties an unremarkable-looking 6-chamber revolver, re-inserts a single bullet, spins the cylinder and slams it closed, then points it at the captive's face. Then he asks his questions, pulling the trigger each time he's unsatisfied by the interogatee's reply. Because he does not re-spin the cylinder between trigger-pulls, the chances increase each time that the next chamber will hold the bullet. Thus, each successive question conveys more threat than the last. Our criminal knows this, and wants to maximize the number of questions he can ask. He also wants to give himself the option to end each interrogation *without* killing his captive. So, what he think he needs is a special pistol that somehow guarantees that the cylinder will slam into position such that the bullet is in position farthest from the firing position. What he needs: * it should not be obvious to onlookers that this pistol is unusual in any way; ideally, it would pass casual inspection by a civilian who knows what Hollywood knows about guns * if the pistol has a real bullet in every chamber, it must be capable of firing each like a normal pistol, because this is the same gun he uses as his regular sidearm * he must be able to perform his prep ceremony, because it's a key part of the intimidation, and he enjoys doing it * the pistol must really fire the bullet when it comes around -- he often *does* execute the captive using this weapon, and he doesn't want his goons to know the game is rigged so their own reactions don't give the game away * must be doable for no more than $100,000 US * setting is real-world 1990s; no magic, no aliens, no capes, no super-tech I'm not married to the idea that the cylinder has exactly 6 cylinders. I need to understand the details of your idea clearly enough that I can describe them in the story when it comes time to reveal to the reader how this criminal arranged this, including what kinds of tradespeople he needed to hire (and, later, murder). --- Post-selection update to address a persistent topic in the comments. Using blanks is unacceptable for an obvious reason: firing a blank makes a detonation sound that every observer will notice. Firing a blank is *not indistinguishable* from pulling the trigger when the chamber is empty. [Answer] # Magnets A simple pair of magnets on the cylinder is enough to give it a vastly favored resting position, and also allows verification of the preparation. The frame gets one magnet on the top strap, and one chamber gets a magnet inset on the corresponding position of the chamber. This chamber is also marked on the back, so that it is well known which chamber is the rigged one. To preserve the gun's function long-term, the cylinder is not slammed in but loaded the proper way. Now, our operator was careful with the choice of a revolver or did a minor modification: This revolver, when put in half cock, allows to spin the cylinder. This is actually pretty simple: if the hammer moves back and the trigger tilts *just* a little, the block many revolvers have will get out of the way. Now only the hand that makes the revolver spin in the first place pushes the cylinder a little bit and it can spin in one direction. The hand getting pushed back by the wedges on the back of the cylinder makes the sound. While free-spinning, whenever the magnets pass over one another, the magnets will slow the chamber down extra. For added dramatic effect, after the spinning, our handler might keep the gun at halfcock and rotate the cylinder by pressing it against his forearm a little. By turning the freely spinnable cylinder by hand, the attraction between the magnets will make that chamber that they want to line up at the top noticeable, allowing them to verifiably get the revolver rigged for the questioning. The cartridge is now in the top chamber. At the first pull of the trigger (for which in some models the hammer needs to be lowered from halfcock to the rebound position first) or by going into full cock by drawing back the hammer, the cylinder rotates by one position. Since the top chamber ("6") was loaded, now the first chamber to be fired presents itself as an empty chamber, lines up with the barrel and hammer, and the handler will dryfire the revolver 5 times from chambers 1 to 5 before chamber 6 will go off. [Answer] # Two Identical Guns: Your criminal has a matched set. One is pre-loaded to be only in the last chamber OR just empty (and concealed out of sight of the victim). The criminal does his whole show, steps behind the victim, does a quick swap for the identical gun, and then plays Russian Roulette. Only there's no danger of accidentally killing the victim, and even after 6 shots, they're still available to torture later. OR play Russian roulette with the original spun gun for bonus questions. This also opens up possibilities for head games. "Answer truthfully and I'll play the next round. Lie or don't, and you play." It suggests an almost Joker-esque kind of crazy that really makes you look disbalanced. But since the game is rigged, why not? [Answer] **Skill and Practice** Your criminal has spent hundreds of hours spinning the cylinder, slamming it in, and then checking which chamber the bullet is in without a victim present. After all that practice, he is able to spin the cylinder with the same force, and stop it at the same moment each time, ensuring that the bullet is always in the same chamber. Of course, if the pistol is replaced with a different one, or it isn't kept well maintained, his muscle memory will be off and he'll be back to square one. [Answer] ## A safety and a fake cylinder Keeping the "only the last shot fires" part simple, we can use a hammer-blocking safety with a subtle switch that can be changed at will by the criminal, allowing any shot to be the "live" shot. A hammer blocking safety will also allow the gun to "fire" while on safe, as the hammer will be released, giving the distinctive click, but will not impact the round and fire the weapon. [](https://i.stack.imgur.com/kP7Mk.png) (Image from <https://projects.nfstc.org>) To allow the ritual of emptying the gun, a cylinder with stacked rounds could be used. An outer circle of rounds (which can never actually be fired as they don't line up with the firing pin, but look great when emptied out for show) and a smaller inner circle of live rounds (which all remain loaded) could be hidden by the body of the gun. A real (but extreme, rather than subtle) example of a multi-layered cylinder (in this version, they are all functional and visible, rather than one layer being entirely for show and one being functional but concealed): [](https://i.stack.imgur.com/PNPoB.png) (Image from <http://www.douglas-self.com/>) This should allow the ritual with as many "live" rounds as the criminal desires, while keeping a fully loaded and ready to fire weapon at hand just in case they're interrupted mid interrogation. [Answer] it's possible to arrange for the cylinder to always stop on the same chamber when spun, perhaps some hidden centrifugal mechanism that regulates the speed and activates a stopper when the speed gets low enough. this technology should be possible by a competent watchmaker-gunsmith at technology levels well before 1990s. $10,000 is an entry-level Rolex so it should come in under budget too. If this chamber is marked in some inconspicuous way then it can be carefully loaded with the single round. [Answer] **Heavy Bullet. Freely Spinning Cylinder.** [](https://i.stack.imgur.com/hxomF.gif) Your victim has watched a lot of Hollywood movies. They know you can spin the cylinder of the revolver after you load it. It goes round and around and goes click click whirrrr. . . and means you are now at the end of Act 2 and ready to start shooting baddies. So when the baddy loads one bullet, closes the cylinder and menacingly spins the cylinder, the victim is terrified. [You cannot do this with a real gun.](https://www.youtube.com/embed/3QkY6TuJrkM?start=275&end=300) They are designed that way on purpose for safety. However the baddie is not worried about safety. He has modified the gun so it is possible. Last night he has opened it up and sandpapered down the safety cylinder or housing so it can spin and go whirrrr click click click. They have also filled up one of the chambers with a lump of lead. With a free spinning barrel they can decide where the heavy bullet goes by whipping the wrist in the opposite direction. They put the heavy bullet in the last place and the real bullet in the second to last place. The downside here is you only get five shots and not six. After using five shots you have to switch to threatening the victim with something more painful like a chair leg. This is not the end of the world, since you would rather not kill them with the revolver, and it is better for the mooks if you beat them to death the old fashioned way. Also the "heavy gun" or the "five shot revolver" could be a clue somewhere else in the plot. It would also be a good story twist if the reader doesn't know about this trope, but half way through the plot the investigators point out real guns don't work that way. Or maybe in the final scene the baddie accidentally fires his "lead bullet" and something bad happens. [Answer] A simple rolling pin which stops the cylinder when it catches the bullet. You have a cylinder that can spin when the weapon is closed when the safety is on. You spin the cylinder once more when the weapon is closed. When closed a tiny rolling pin moves outwards and gives resistance to the bullet each time it passes. The cylinder axle also has a resistance, but the time it takes to slow the cylinder to a stop is less than the resistance the pin needs to finally stop the bullet. This ensures the bullet is always in the same position. For extra "fun" you can let the victim spin the cylinder a couple of times when you want to buy yourself more questions, or to quickly ramp up the interrogation. You quickly aim and pull the trigger at the knees and hands, then respin it. Why is this a better option than spinning with the gun open and then closing it? Because the victim might assume that the user is simply skilled and can time it. With a closed cylinder and letting the victim spin it you take that away and it looks more random. Although I would add multiple rolling pins which you can activate or not when the gun is open. That way you can stop the bullet at any position, and your fellows wont be wondering why the gun always fires at exactly the last shot each time. [Answer] Add a hammer block safety. Revolvers such as the [Heritage Rough Rider single shot revolver .22lr](https://heritagemfg.com/small-bore/6-shot-rough-rider/137-6-5-rough-rider-22-lr-22-wmr-black-standard-stag) come with a hammer block safety. By engaging the safety, the trigger still releases the hammer but it never hits the firing pin because a bar is in the way (thus the name, hammer block safety). This would let the character use as many "fake" shots as they would like. I use this mechanism when introducing people to shooting as it lets me get them all set up and then flip the safety off. That extra margin of safety is really nice when working with people who are brand new. As a suggestion, if you live in the US or other area where personal ownership of firearms is legal, you can probably find someone who would be willing to take you shooting with these types of revolvers to give you a greater idea of how they work. If interested, reach out to a local gun store or two to see what options are available. They will probably be able to get you set up with someone who has some experience introducing people to firearms. [Answer] ## Noise Maker As part of the pre-interrogation ritual, the killer loads the bullet, and then manually cycles the cylinder until the bullet is in the last chamber. Now he pretends to spin the cylinder, while activating a hi-fidelity audio recording of a cylinder spinning. The cylinder would only spin for a second or two, so if he is theatrical enough with his hand motions, he can have the gun moving for the duration of the playback, and his victim will never see the gun clearly enough to realize it was a recording. This could be even easier if the lighting is set up appropriately - e.g. a dark room with a bright light aimed towards the victim. [Answer] Modify the barrel, mark a chamber. The cylinder can have an open ring (a groove) on the surface, but near one chamber there is a stop. Near the trigger, the holder can press up a small pin into the open groove, so the freely spinning cylinder moves, but it hits the stop and ... stops. Let go of the pin, so the cylinder can move freely again. But now the same chamber is always at the top, and the bullet (in the chamber marked with an inconspicuous scratch) is next to it. You can let the person watch you spin the cylinder faster than they can see, and watch you make a show of stopping it with your hand, without even looking. But you stop it by raising that secret pin (or lever) the moment before your hand hits the cylinder; they won't even notice that, if the cylinder is concealed by your hand. With practice, it looks like you can spin the cylinder and land in exactly the same place every time. PS You can also put in a check: Another little scratch on the outside visible surface of the cylinder, which will also always be in the same place if the cylinder stopped correctly. Just to prevent accidents. [Answer] ### A fake bullet It never goes off, so it doesn't matter which chamber it's in. And if in the end you really want to execute the guy, just open it up again and add a real bullet. [Answer] **Mark the cylinder.** Your baddie just puts a subtle mark on the cylinder corresponding to a specific firing position--some kind of mark that could be felt would be best, maybe something that would look accidental like a nick/scratch. Then he loads the bullet in a specific place in relation to the mark, spins the cylinder, and before slamming it closed he spins it a bit more until he can feel the mark is lined up correctly. Now you know exactly where your bullet is in relation to the rest of the gun, so you can do a bunch of tricks depending on how you offset it when loading. For example, you can load the bullet 3 cylinders offset and have one of your confederates pretend to be another prisoner--ask them a question two times and have them "break" and tell you on the third time, then say something menacing like "Let's see how lucky you just were." and fire the third time at a wall--bang! Then you turn to the guy you really want to interrogate, do the whole loading trick again, and say, "So, how lucky do *you* feel?" (Or a more bloody version where the first person you interrogate is another actual prisoner who you don't care about and you make it so they actually get the bullet after only one or two tries.) If your criminal has other skills like card sharping or other slight of hand tricks then this fits in particularly well. [Answer] 1. Sheer gunslinging mastery means they can spin the barrel so that the live chamber always lands where they want. 2. There is a subtle method that prevents the firing pin from striking the bullet when held a particular way. Could be the barrel gets off center enough that the strike misses the primer, a slide to change the trajectory of the firing pin so it does the same, or a small bar with a gap in it to allow the firing pin through when desired but block it otherwise. 3. Similar to above but the gun is modified so the barrel always catches on a particular chamber so that the bullet can be put in whichever order is wanted. A particularly clever manipulator might make it stop on a fixed barrel when spun one way but not the other so they can prove the gun is 'fair' beforehand. 4. The chambers on the sides are blocked from view from the front but not from the back, after all the one being interrogated is the only one who needs to have that info hidden. This does have the disadvantage of only letting you know when the bullet will fire, no choice on how many questions beforehand. [Answer] So you're looking at the following scene, based on your premise: * Victim tied to a chair * Table in front of the victim * Criminal in chair across from table * Criminal unloads revolver on table * Criminal picks one unloaded round, places one in cylinder, spins it, closes cylinder, points it at victim's face while both are still seated * At no time does the gun leave the victim's view Several things here, and I'm combining several comments: this setup prevents any easy gun switching or fake noisemakers and thus is more menacing. It also means the victim has a clear view of the firearm, and we have to assume the victim retains a clear head and is capable of noticing things. First problem: with the majority of revolvers, it's possible to see from the front if something is in a cylinder. The only ones you can't see is the one right under the hammer (ie, in firing position) and its opposite, hidden by the frame. If the light is right, and it's a short barrel, you might even be able to see the bullet down the barrel. To make this simple, the first thing you want to do is make sure that any light is, coming from *behind* the criminal (or above and behind), so you've got a bright light in the prisoner's eyes, making it impossible to see the fine details on the gun clearly. That should eliminate the problem of being able to see where the bullet is. You also make sure that the light is arranged so that when the prisoner is looking down at the table, they aren't forced to squint and thus can clearly see everything that's happening. That's important for the trick. You also want a dark, non reflective table top. You've already stated the cylinder is spun when in the loading position, which is good, and then moved into firing position. So, you use a simple trick that requires a very slight modification to the gun. Have an index notch at the rear of the cylinder. Something small that would be hard to see from the front, even if you didn't have a bright light shining in your eyes. Human fingertips are extremely sensitive and can detect very small imperfections, so your index notch doesn't have to be very big. Open the gun and dump the bullets, concealing the index notch, and load the bullet into the chamber in relation to the index which is the one you want to use. Looking down to load the bullet would be natural, so there'd be nothing suspicious to make sure you have the right one. Then, while looking at your victim menacingly, spin the cylinder until you can feel the index notch under the thumb of your left hand (assuming you are a righty and the cylinder swings out to the left). If you have to spin it a few times to get it, that's fine, just makes it more "random". Then, still not looking at the gun, as your left hand swings the cylinder closed, the index notch allows you to determine the cylinder orientation, and thus where the bullet is, namely the last chamber that would come under the hammer, whatever it is depending on the type of gun. As you swing it closed, again, without looking, you subtly rotate the cylinder into the proper position. And you're good to go. When you raise the gun and point at at the prisoner's face, now they're looking into the light, and the shadows on the gun make nearly impossible for them to see the cylinders, and thus where the bullet is. After every trigger pull, you lower the gun and turn it slightly so they can't see the ends of the cylinders. This again conceals the location of the bullet, but also gets their eyes out of the bright light (unless they have nerves of steel, their eyes will naturally follow the gun), so the next time you raise the gun again, they're again partially blinded as their eyes try to adjust from looking at the dark table top. It's all a slight of hand magic trick where the only thing special you need is the very slightly modified gun, which anyone could do with something as simple as a file. [Answer] ***Monte Carlo Simulation*** A variation on @tristan's Don't rig it, predict it. Keep all variables the same: bullet, position, force of spin, temperature in the room, humidity... Rerun the exercise as many times as possible (read in the millions) checking the position of the round. Plot the position of the round using a pie chart. Just be sure the amount of lubricant and replacement parts are from the same manufacturer and of sufficient quality before placing it against the head. But, then again with a sufficiently precise scale an equipment you could account for the variability here too. <https://en.m.wikipedia.org/wiki/Monte_Carlo_method> ]

[Question] [ Assume there is a resource that allows for rapid regeneration of body parts and termination (magical deletion) of foreign objects in the body upon usage. Let's say it is scarce enough that you can't give it to everyone, so it's still valuable. The resource doesn't stay in the system and is a one time thing where upon usage all current wounds and injuries are healed and foreign objects removed. If you take it with no wounds, it will just do nothing and break down into useless components. You have to give it to your soldiers because it's a huge morale boost. If you give it to a more accountable group like the team medic, the injured might die before they can be administered the resource. Also, the team medic can still conspire with the soldiers. What's stopping them from faking mortal injuries and reporting that it was used, then selling it later. You can't really keep them under close supervision, nor can you reasonably punish them for claiming to have used it even if it's suspicious because the injury is already gone. You can't even ask for proof because, if it really was a mortal injury, they wouldn't have time to record any. I have considered testing for blood but even that can be faked. Would the military just have to look the other way? Or would they target the selling of these resources instead, setting up stings to catch embezzlement that way? [Answer] ## Miliary Court and Spot Checks This is the boring answer, but that's how it is handled in basically every army. Soldiers have to account for their equipment. If something is used or lost, they need to report it. Depending on the scarcity and importance of the missing item, you might drag them in front of a military court which judges about the proper use. Discipline is upheld by appointing judges from outside the current company/regiment, and occasional spot checks help you find the criminals. Current examples would include weapons and ammunition. If it is found that you are missing either, you will most likely get jail time for not reporting it, and even more trouble when you cannot explain where they went. (Your comrades will rat on you because they are rewarded for doing so, and because they will get jail time it they are found to be helping you.) Military court of course does not prevent soldiers from trying to stash away your resource during battles. However, spot checks do. If anyone is found with much more resource than they are supposed to have, they will get high sentences. By the way, this would make for an interesting plot device: A group of soldiers conspire to bury all their resources on the battlefield and retrieve it when the war is over. A farmer's boy finds it after the war and is now suddenly rich. Meanwhile, the remaining soldiers (most died during the war) battle each other in order to find it and get rich alone. [Answer] # Tattoo the soldiers. That awful old "SPQR" thing, maybe... it doesn't really matter, except you might need to do two or more widely spaced areas. *IF* they give themselves a dose, all the tattoos disappear, and you give them another dose. If the dose disappears and the markings don't, then they will have some explaining to do. Note this does not depend on the structure or intactness of the army. The effective meaning of the tattoo is *"this soldier is custodian of a dose of super serum"* and if any unit of the army picks him up, they can start asking where it is. Of course, it's still *war* and vials do get shattered, so this is not a perfect barrier. Also, I'm assuming you allow the soldiers to take a goodbye dose when they're finished, as a variant on a VA hospital program to heal any chronic damage they suffered. [Answer] Option 1: **Make the healing unit a subdermal implant**. That way it is always available to the soldier. It cannot be (easily) stolen or sold. The very act of implantation leaves a small scar, which use of the unit will heal: positive proof of usage. A soldier could even have more than one of these, if the mission justifies it. Handy if, for example, the left arm on which the implant is mounted gets blown off. Option 2: **Make possession and/or trading in the unit a capital offense**. This is simple lawmaking. Each unit has a serial number. Anyone found in possession of a unit, other than the soldier it was issued to, is immediately sentences to death. After a nice torture session to make sure where they got the unit from. If a soldier sold their unit, they get arrested under the same charges. Both arrest and execution is publicly listed, of course, for the deterrent value. You won't catch *all* the blackmarketed units, of course, but you should make the illicit trade in them such a scary topic that the volume of trade diminishes to near zero. [Answer] The device has two effects: the short term one is what you describe, the healing of wounds and so on, while the long term one is a terrific death induced by uncontrolled cellular proliferation, something like a cancer but much more quick. You have an antidote for the long term effect and, while you want the device to be readily usable for the cases of emergency, providing the antidote can be done with relative calm in authorized army hospitals under strict surveillance. The antidote, if taken alone, it's also lethal, because it dramatically slows down cellular replication. You make sure that whoever gets the device is duly informed of the risks and consequences using the device without the antidote and the antidote without the device, and then show them the educational movie about Private Joe, who tried to cheat the system by selling the device and reporting its usage to heal his wounds: who bought the device died of the boosted cancer and Joe died after being given the antidote. [Answer] This needs a tight supply chain with constant checks that do not have a chance to get discovered by the enemy. A bad example: every vial is GPS tagged and records when it is used. Enemies can pick up on this. A better example: each vial is tagged with a very very short-ranged RFID chip inside a small armored case (cant have a grenade destroy the contents just when you need it because you were just hit by a grenade). These cases are given to their users shortly before the soldier might enter battle, and the RFID chip is linked to a few receivers on the soldier's armor. The case is fastened to the armor, so it doesnt accidentally fall off (children's carseats have similar systems). Should the case be removed and the vial not used within a minute then the vial and the case will send a signal to the base about it not being used. The armor will log the incident just in case the vial and case cannot get the signal through. If all of these fail because the armor is "damaged" then an incident investigation will determine if there was foul play, which would be likely if the soldier is still alive but both the armored casing and armor are damaged so much that all backups are destroyed. For extra security measures the wearer might as well have some electronics. A helmet camera, microphones and camera at the back to log potential thieves or other foul play would be relatively easy and probably worthwhile if you have a limited high-value resource like this. This would ensure that its almost always clear where the vial is. Someone is responsible when you give them the case, you can log what happens to the case and if the case is gone while no logs remain the owner is held responsible (and their team-mates might be held accountable too, they might have to carry the case on their body should something happen to the carrier). As for who should carry this: medics and squad leaders should be the primary recipients. If you are hit hard enough that you might die before the medic gets there you will likely be in shock or otherwise incapacitated and unable to administer the substance anyway. Additionally you want people with medical knowledge to apply the substance. They will know if a wound is life-threatening enough to require the vial or not. You dont want a panicked soldier with little background knowledge to apply it to himself or his buddy randomly. Additionally the medics and leaders are already people with a higher responsibility and better able to judge when and where its needed. [Answer] ## Hearts and minds Anywhere your soldiers are deployed you also set up clinics that give the stuff away for free to anyone who shows up in need. That kills off the black market and gives the soldiers no incentive to try selling the stuff. You would of course be pumping anyone who comes into the clinic for intel, and checking for enemy combatants, but that's all secondary. ## Economic differences Pay your soldiers well enough that any money the local black market could provide is a drop in the ocean compared to the combat bonus they already get, and it's not worth the court martial for getting caught. [Answer] **The resource won't work on anyone who hasn't received a compatible "enabler".** The enabler could be another resource, artifically even more scarce, to be administered in highly-controlled conditions, e.g. when enlisting into the military. So, the stolen resource won't work on anyone who is not a (former) member. If practical, the enablers, and their corresponding resources, could be rotated on some overlapping basis so that a "green enabler" is administered years 1230 to 1240, "green resource" is produced over the years 1230 to 1235 and gradually phased out, "blue enabler" is administered years 1235 to 1245 etc. [Answer] **What counts as a foreign object?** I have a tooth filling, is that a foreign object? What about a hip replacement? Do you want to heal every soldier’s pimples every time they take the drug? Of course not. That is why every soldier is scanned and issued kits that only remove things that are foreign objects to their bodies. **Other people are foreign objects** You need to clean up your lungs and have a pacemaker? Well, unless the soldier who sold it to you also had a pace maker you can say good bye to the pace maker. Good news, excessive fat may also be considered a foreign object, just don’t let the vaporized sludge hit you on the way out. A female soldier gave a nice guy her medicine? Well, that female soldier didn’t have all of a man’s body parts. If you are lucky, the device will cauterize it and let you sing soprano for the rest of your life. No one will buy or sell these kits if they realize they are about as lethal as whatever they are trying to cure. [Answer] First: resource needs to find who is soldier and who is not. Second: resource needs to know how to rebuild lost parts of body. Both can be done by DNA analysis. If you imprint soldier's DNA to resource then this resource can be used only on this soldier. You can have problem with twins and clones. Resource can be programed or reprogramed in army med center or in research facility. Need big, couple ton of equipment to do that. DNA imprinting removes probability of soldier selling resource. But do not bother with that. Bigger problem is the production line where brand new resource can be taken without you noticing. If you want to prevent the selling resource you need to control all programming devices. [Answer] Package the drug in a reasonably air-tight vial. Adulterate it with a compound that spoils within a couple of minutes after exposure to air. So one can open the vial and drink the content, but one cannot open the vial and pour the content into another container. Then require each soldier to return the empty vial if it is used. AFAIK soldiers are trained to hook morphine or atropine syringes to the pocket flap of the patient, to prevent multiple doses. This would be a similar principle. You would still have the problem of lost and damaged kit, but that needs to be handled much like a lost weapon or pair of boots -- report to a superior, tell the story, and if it isn't credible there will be consequences ... [Answer] **Give the resource to a soldier only before war** Give the resource to a soldier when he is going for war because he could be wounded during war and he knows that this resource is the only thing that could save his life. So he will not sell it to jeopardize his life for some money. **Soldiers fight for a passion** A soldier is ready to sacrifice his life only for a passion or sentiment (nation, country, religion, king, land, ideology etc.). If his passion is strong, he will consider selling it as a sin or betrayal. **Biometric** Make the resource as soldier specific by using some biometric such as fingerprint, eye image, DNA etc. **Etch soldier info on the resource** If resource is found in the black market, it could be traced who sold it. [Answer] I think you hit the nail on the head with the last part of your question: “Or would they target the selling of these resources instead, setting up stings to catch embezzlement that way?” That would probably be the best way of cracking down on embezzlement. The only other idea I can think of is perhaps the medicine leaves a small discoloration of the skin around where the wound was (or some other distinctive mark or symptom) for a few weeks, or something like that. That way it proves the soldier actually used it. [Answer] The simplest solution is that when being used, the device takes a tissue sample of the person on whom it is used, and must be retained by the patient or the person who used it. If it is small enough, it should simply remain attached to the patient. You can also give each one an unique serial number (placed in such a way that to remove or deface the serial will destroy the utility of the item), and log the soldier to whom it was issued. That soldier is then responsible for that piece of gear, and if it is found... *elsewhere* where it shouldn't be, the serial number will allow it to be traced to the soldier who should have been in charge of it. The only excuse should be that the soldier was dead. Make the soldiers aware that if they can't prove who the device was used upon, *they have to pay for it*, unless there is other evidence, such as body-cam video. [Answer] ### Your Money Ain't My Money One relatively simple way to do this that has historical precedence is to set up a dual economy within your sphere of action. You pay your soldiers with short lived Military Money and you set up a parallel Civilian Money system for the locals. Civilians have no access to the Military money and soldiers can't use Civilian money. MASH dealt with this pretty well in a couple of episodes. Every now and then there'd be an exchange day where soldiers and ordinary folk alike would have to turn in their old cash for new. Since civilians can't turn in military cash and soldiers can't turn in civilian cash, it all becomes useless. Likewise, all the old cash that doesn't get turned in becomes useless for everyone, so it can't even be saved or used later. Impose a (reasonable) limit on the amount of cash that a soldier can exchange, taking into account her pay grade and some allowances for looting and gambling and you'll close the biggest gaps. [Answer] ## Frame Challenge: Bureaucracy Prefers Embezzlement Why would you want to stop soldiers from embezzling the drug? Or rather, why would the person in charge of inventory control want to stop it? As a General or Logistics officer, it's not your money paying for the drug, but it is your responsibility to make sure you have enough of it. You are rationed a certain amount, and that is all you get. But here's the thing: The vials are a drug which means they expire. If in a single expiration period General Tightwade's battalion consumes 100/500 vials, and General Snuffy's battalion consumed all 500 that he was issued. Then next ration cycle the government will only issue General Tightwade 200 and General Snuffy gets 800 because the bean counters of the army will try to match supply with demand to waist as little as possible. The problem is that both battalions only used 100 vials, but General Snuffy let his men embezzle all of the excess. Now General Snuffy receives extra rations so that he is prepaired for a major battle, and General Tightwade is screwed if he takes heavy casualties. So whatever anti-embezzlement practices they put in place to make the bean counters happy will be intentionally easy to circumvent or just plain ignored by the people who are supposed to enforce them. Example: A solider walks in with a scrapped knee and says he is mortally wounded. The doctor who does not want to be short on meds next quarter signs the "mortal injury" paperwork saying he was thrown from a moving vehicle or something, hands over the drug, and the solider can do with it what he wants. [Answer] Have it contain a serialized bio-marker. Something harmless for the user and something it ignores in minute quantities, but something that is left behind and possibly breaks down eventually. Then just take a blood sample and check the right marker is present with right or explainable serial number. [Answer] ## The resource is automatically administered by an implant. Every soldier gets a one-shot life-saving implant that monitors the soldier's vital signs and administers the resource when needed. (You may add more methods to trigger it manually to make sure it could also be used for something that does not remove enough vital signs, like a missing arm.) Extracting the implant would not only leave a scar, it would also trigger spraying the resource into thin air as soon as the vital signs are missing (where it would instantly degrade). Administering the resource as intended would remove the implant without trace. This also removes the scenario of using your own dose for someone else, as every soldier has their own "extra life" implant. For easy implanting, you could design the implant to be swallowed, then it would attach itself inside the stomach. [Answer] ## The super-duper-medical resource is actually applied before combat. Be it a pill or a shot, the soldiers are given this resource in base, before any fight o conflict. This is obviously under strict supervision and control. The resource can be in their system for a long time, but it is innactive and doesn't do anything on itself. Once they're injured, they need to take a second pill or shot, which is the catalyst that activates the resource that immediatly heals them, and dissapears from their body. Once they're back in the base, they take this resource again and are given another catalyst to have ready for the next combat. This way, two things are needed to activate the healing effect, and one doesn't work without the other. This also allows a soldier to apply his/her catalyst to a combat partner and save its life if needed. [Answer] **Have the soldiers buy the device, rather than be given it.** This is by no means unheard of; in feudal times, officers typically bought their own equipment. In the modern day, you could imagine this being a paycheck deduction! If it's important to "give" them away, then perhaps the *first* pill/device is given free, but then any replacement pill/device has a cost. This is also not uncommon even in the modern day - most places I have worked at, if you lose your employee provided badge or gear, you pay for it through a payroll deduction. [Answer] **You collect uniquely-labeled empty containers and check the state of containers at regular intervals.** So, every morning, or whatever else the opportunity, everyone presents their containers. Every one of them is either with or without the resource. Those without the resource are recorded and sent for destruction. Those missing are investigated. This sort of prevents illegal handling of own containers. **You RFID the containers.** There are periodic scans for RFID, especially if noticiable number of containers are missing. Any found container which is not expected to be found is investigated. This sort of prevents illegal handling of others' containers. Of course, the resource should not be readily field-removable from the container without either using it or destroying it, and the RFID label should not be removable without destroing both the container and the resource theresin, but probably this could be engineered. [Answer] The resource in question has an extremely short shelf life. Your military has a stockpile of the raw form of this miracle substance, which is not particularly useful. You processes/refine the substance on location and issue it to soldiers on their way out the door to the front lines. Within 36 hours there will be a noticeable loss in potency, and after a week all measurable effects are gone. Soldiers won't try to stockpile it because it will become useless before they can sell it. There's still a small window of time in which it could still reasonably be sold, but there's no practical way to do that since it's only issued to soldiers en route to combat. You'd have to desert your post and find a fence, but in a time of war deserters can be executed. In the event of an unexpectedly swift victory, soldiers are instructed to use any remaining supplies to treat any remaining wounded. Using your leftover substance would be substantially cheaper and more effective than traditional medical care. Selling or withholding your leftovers when a POW or civilian needs them is considered cruel treatment of a non-combatant and is a war crime under the Geneva convention. The only time a soldier could sell their leftovers without a real risk of life imprisonment (your enemy will take every opportunity to rat you out) is if there were no wounded to treat, and in that case there would be no customers for it. The weak point is the refining equipment and process. You need to be able to keep that secret and tightly controlled. Militaries are already good at doing that, though. They regularly deal with classified intelligence and equipment and have extensive procedures for clearance and access control. [Answer] **Metal Neck Collar** Economically, you don't have to prevent all loss, just most loss. Make the collar hard enough to remove that most people won't try. The collar can be designed to ruin the drug in a failed attempt to remove it. Make the collar small enough that it is unlikely (it doesn't have to be 100%) to be significantly damaged by accident. The number of people willing to risk significant cuts or burns to their neck to remove the collar are small and the cuts and burns pretty much tell everyone what happened. **Bone Fusion** Build the drug into a metal injector that you then fuse to a bone (the skull is good since there is very little flesh in the way). You could put it on the forehead where everyone could see it and it wouldn't get in the way much. Since the bone fusion would be seen as a foreign object, the injector would be ejected upon use. Anyone with a hole in their forehead that wasn't healed would be very suspicious. This has the added advantage that it explains anime forehead jewels. [Answer] The same way you do with anything disposable. ## You only put the material in specially made hard to fake syringes, on report of usage soldiers must return the used syringe or be charged the cost of the material. You can also use proof of tampering devises, to make it even harder. Then of course you have the penalty, the same one you use on supply staff if they sell material, theft of military materials generally carries a court martial and prison time. So it hard to sell and high risk, plus your putting your compatriots at risk, this minimizes incentives to even try. Selling the resource would also be heavily punished since it is a limited resource stealing it is the same as putting soldiers at risk. [Answer] As a more distopian version, your government also makes a **fake drugs which looks exactly the same** as the real miracle drug given to soldiers, and distributes them (preferably also by people in military uniforms) in the black market (preferably ones used by political dissidents, but whatever). The **fake drugs has horrible / lethal side effects**. Then you make sure you give it enough media coverage how some people are buying counterfeit drugs on black market and suffer the consequences, but assure the military that of course they're being provided with real miracle drug. Afterwards, very few people would be willing to pay to pay a lot to acquire a something which may as likely be horrible poison, as it is to be miracle cure. Thus, soldiers would be hard pressed to sell it to anyone. So, basically, treat illegal consumers the way software drivers already treat possibly counterfeit hardware - [by destroying it](https://diydrones.com/profiles/blogs/warning-ftdi-drivers-are-killing-fake-chips) (yeah there is a difference between destroying property and destroying life, but remember that black market people are the enemy of the state by definition - so killing them is no different than killing enemy soldiers) --- Alternatively, technological and economy progress. Humanity has abandoned such a silly archaic 20th-century ideas like pieces of paper for money -- as well as bank accounts, credit cards and similar obsolete ideas. **Your wallet is now cryptocurrency identified by your DNA signature**. You pay with your fingertip (or retina scan or your chakra emissions or whatever biomarker which is unique to you only). All transactions you ever made are thus visible on government blockchain. And Government knows everything what you bought and what you sold (which comes in handy when they tax you too - no more tax evasions for regular people). And if blockchain shows you tried to sell that-which-should-not-be-sold, it's court-martial for you. [Answer] Use implanted chips to stop the equipment working unless the soldier is present, or genetic markers as permanent indicators of ownership. It might be only in Hollywood that ex-Soviet nukes are for sale on the black market but pretty-much everything up to that level is, yet surely that's only a problem on a backward world like ours; not where your built world has a resource that allows for rapid regeneration of body parts and termination of foreign objects in the body upon usage, why would it be difficult to Then, if "magical deletion" is allowed, why not magical tracking of ownership? [Answer] # Why don't soldiers sell their ammunition? This seems like a no-brainer. Soldiers in war don't sell their ammunition to strangers in the war zone because (a) they might *need* their ammunition and (b) the buyer might very well be buying it for the enemy. A contributing factor is that in the real world, there isn't necessarily an infinite supply of ammunition at the base, and anything you use up might not be replaced. The same factors would be at work with your soldiers. They know that the super-medicine is in limited supply, might be necessary to save their own lives, and could be used against them by enemies. They will learn to take care of it or be punished for violations. [Answer] Do you actually want it to be impossible for soldiers to sell them, or do you want interesting consequences for when it happens? If the latter, then how about: Give each dose a unique serial number, and record which serial number was given to each soldier. Then, set a bounty for contraband doses that is worth more than anyone would actually pay a soldier for their dose. This can set up all sorts of interesting plot points. What if a soldier *gives* their dose to a civilian who appears to desperately need it, but then they turn around and rat the soldier out? If a civilian from an enemy state gets their hand on some contraband, would they try to turn it in to the issuing state, and would they still get the bounty? Would it turn into a bidding war between the soldiers and the bounty issuers until the civilians revolted? There are all sorts of fun possibilities! ]

[Question] [ So I have a concept in mind for a future dystopian world. The world: * Technology exists on par with modern technology. * This technology is not widespread; in fact, it is quite rare. * Most humans do not know how to create the tech that exists and are only occasionally aware with how to fix things. * Normally available tech has devolved to a more mechanical state, sorta steam-punk-esque. * Most humans live in walled cities. There isn't really government beyond a small regional scale. The largest would probably be the size of Rhode Island. * Small caliber fire arms are available, though not widely. One of the cities is going to attack the other. One of the primary resources at their disposal are small mammals (anything from the mouse up to say a badger). They have available a catapult or two and want to launch animals into the city to cause mayhem before they attack in full. This city retains some pre-whatevertheapocalypsewas technology in the form of a modern communication network and several automated perimeter turrets (effective range is around 100 yards). The turrets would decimate the attackers trying to breach the walls. * **I am not looking for** the standard, launch a dead carcass or two and allow disease to spread * I want the animals to arrive in the city ALIVE. * Well...not all the critters have to make it in alive...it is expected that some percentage will not make it. **How would you deliver the critters via catapult?** * Please include delivery methods (methods must include a catapult) for both small (mice) and large (american or honey badger) mammals. More care should be taken in the delivery of the badgers...they are harder to find and train. **What critters (anything mammalian in the size range mentioned) would most effectively destroy/disable/diminish the effectiveness of the communications and defense networks?** * Minimal training of the critters is allowed. [Answer] **Squirrels** Working IT for several years, I have learned that if any rodent will mess with Comms, it's a squirrel. They are the triple threat: breed quickly with nesting, climb all man-made structures with ease, and seem to hunt out power/comms lines. I have treated cases of squirrel problems that include the following: * Squirrel chewing through backup generator power lines until frying itself alive, but also shorting and disabling the line. * Chewing through fiber optic switch cable because rodents seem to enjoy the taste * Chewing through copper wire buried too shallow in ground * Chewing sleeving off for nest material and causing shorts and downing comm lines In all the above cases, multiple hours were used up trying to isolate the issue and hours more repairing it, since most of these cable failures require running completely new lines. The squirrels could be trained to target wires with [Skinner Boxes](https://en.wikipedia.org/wiki/Operant_conditioning_chamber) that have a trigger buried in wires or sleeving that, when chewed, rewards the squirrel. Bonus points of there's a little speaker near the wire that generates coil wine to simulate high-power lines and transformers. Given enough of these boxes and the high breeding rate of squirrels, these anti-wire squirrels could be churned out in large numbers. So definitely launch the badgers, as they will end up being distractions to hide the more nefarious squirrels, which will run and hide, then seek out the wires that they are conditioned to hunt expecting reward. EDIT: In fact, if you manage to land a few new the turrets themselves, you may even end up with a scenario where they are directly disabled, opening defensive holes for the main forces to walk up to without harassment. [Answer] This question is absurd and ridiculous --luckily I double majored in absurd and ridiculous at the school of Mad Science and Multiple Apocalypses (no relation) Let us begin with the turret systems. Auto turrets are pretty neat, they're coldhearted killing machines, able to pump round after round into any relatively human shaped object in their field of view. Get close to them and you're dog meat. But they ain't smart. That's kind of their glory, just stand em up and they shoot everything to hell. Long as they've got power and bullets they're good to go. So riddle me this, what's the second most important thing in the apocalypse? Besides booze, booze doesn't count, that's like zeroth. That'd be bullets Bob. Bullets. Here's where my mouse-man holograms come in. I mean mice, really they're just mice. But they have these nifty collars. The red gem is [artificial ruby around some radioactive waste](https://en.wikipedia.org/wiki/Diamond_battery). Every now and then the charge builds up enough to cast a man shaped hologram. Suddenly, MAN! And the turrets are all like- PEW PEW PEW. Mouse is terrified and scurries. Rinse and repeat. Drop a couple hundred of these little darlings into the killing field and you waste a goodly portion of the turret's ammo. Or if you're impatient, do it during the assault. Every bullet through a hologram is a bullet not fired at your screaming horde. Next comes the hard part. Communications. I think we need a two part attack here. Insanity mosquitos to target the meaty ends of the comms systems --and here's the glorious part. Radio interference bats. These little collars with the green gems are sapphire batteries constantly transmitting the bat's echolocation sounds on or enemy's communication channel. The beauty of it is that it's imperfect, signal strength is inversely proportionate to the square of the-- lost you. Never mind. The radios work fine one minute, bat zips in to eat one of the insanity mosquitos attacking the operators and BAM- garbled mess. Radio clears back up and some sort of insane ranting comes through (OH MY GOD MY EYES ARE MELTING). If anyone gets wise to the insanity mosquitos they'll welcome the bats. If anyone suspects the bats --well they can start popping off their guns willy-nilly not sure that's a problem for us. [Answer] Of the three major types of weapons most people think of as catapults, only the Trebuchet seems truly suitable for your mission. Tension weapons (giant bows) or torsion catapults generally have high acceleration over a short period of time, and would likely kill or injure animals being fired from them. Watching a high speed film of an arrow as it comes off the bow shows the [shaft flexing wildly](https://www.youtube.com/watch?v=O7zewtuUM_0) as the energy of the bow is being transferred to the arrow. Ancient and medieval bowyers were also aware of the flexing forces in crossbows, which explains the short, thick shafts of a crossbow bolt or quarrel. Counterpoise weapons like a trebuchet release their energy over a longer time frame, providing slower, more uniform accelerations. The best modern illustration is watching the ever entertaining "[Pumpkin Chucking](https://www.youtube.com/watch?v=qC6RJxFEMfY)" contests, where mad home engineers compete to hurl a pumpkin the longest distance. Shots are disqualified if the pumpkin disintegrates while being thrown, so there is a definite limit to the amount of acceleration a trebuchet delivers. Medieval engineers were pretty good at building large and powerful trebuchets, and some modern reproductions can [fling cars](https://www.youtube.com/watch?v=CyCJ69GU974). Engines like the "[War Wolf](https://www.youtube.com/watch?v=RN18I-RBVm4)" fired giant stone projectiles into walls to bring them down and ranges measured in hundreds of metres were recorded for larger ones. More modern trebuchets have added ideas like "[Floating arms](https://www.youtube.com/watch?v=FJ-B-rrXlF0)" or using a "[spiral](https://www.youtube.com/watch?v=PKA2eUneyj4)" to increase the leverage of the weight providing the counterpoise, so if your engineers were "pumpkin chuckers" before the apocalypse, then building large and powerful trebuchets should not be an issue. As for delivering the cargo, filling a wooden box with straw and packing the animal "cargo" inside should provide protection from launch, in flight and on landing, with the wooden box breaking apart and the straw cushioning the impact so the animals can be released. Edit to add: the reproduction of the War Wolf has the announcer mention that beehives were sometimes shot over walls. A Hornets nest would be even better in terms of releasing angry insects...... [Answer] You want the [Raspberry Crazy Ant](https://en.wikipedia.org/wiki/Rasberry_crazy_ant). Granted, they aren't mammalian, and they're very small, but that actually helps you a lot. Ants aren't injured when they impact at their terminal velocity. Most of them should survive whatever kinetic delivery system you come up with, be it catapult, trebuchet, ballista, balloons shot down by arrows, whatever. They'll be hard to kill once they're established. As an added irritant, they'll sting anyone they come into contact with just as any other ant would. As for why you want the crazy ant *specifically,* that's because they're drawn to [electrical equipment.](https://en.wikipedia.org/wiki/Rasberry_crazy_ant#Attraction_to_electrical_equipment) They get into walls and start chewing through the insulation around wires. Pump enough of them into a city and they'll start clogging all of the electrical comms and defense systems. [Answer] ## It's all Hamburger without Protection What we know is that your forces cannot come within 100 yards/150 feet (91.4m) of the fence. Because the fence was built for defensive purposes it seems safe to assume it is at least 12 feet (3.7m) tall. To launch something that far and still have it clear that height, you are probably looking at a flight path that takes the object up a height of around 150ft (~45m). The long/short here is that dropping around 150ft without protection is a very bad idea, not even counting the horizontal velocity impacts. While some small percentage of animals may live, they would likely be very unhappy about it. ## Protection is Tricky - Very Tricky In a world that has regressed to a state where the use of catapults is common, rocket brakes (retrorockets) and similarly advanced braking methods are out of the question. In fact, we are only very recently beginning to have what most would consider real success with them - and that is on a very small scale and only when designed and implemented by dedicated organizations like NASA. At best, if you want the animals to survive you are probably looking at crates and parachutes. Parachutes are actually possible, I would think, given that they were [tested on animals](https://en.wikipedia.org/wiki/Louis-S%C3%A9bastien_Lenormand) by the first man to use a parachute himself successfully by the 1750's. So it seems ridiculous, but with a padded crate and some inspiration from modern parachutes (perhaps diagrammed somewhere?), it seems like it would be possible to launch some small animals. ## How do the Animals Escape their Crates? The good news, I think, is that any animal that has been catapulted would want to leave their crate at the earliest opportunity - so all they would need is a hole. It may take a number of seconds or even minutes for them to leave however, given that they are likely to be disoriented and possibly concussed from the launch. For sufficiently small animals like mice, ensure that the parachutes deploy late enough or provide sufficiently little protection that the crates smash on impact. Many mice will be killed or maimed, but a good number could escape through the resulting holes. For larger animals like honey badgers there are probably ways to engineer a crate to open on impact rather than launch. Openings made of more fragile materials and latches come to mind. I think though that these types of crates are likely to be very prone to staying closed. I think that estimating 50% of the crates would remain closed after landing (or kill/incapacitate the animal inside) would be fair. ## Animals to Throw The biggest problem I see is that unless you have many dozens of catapults set up (which I imagine the citizens would notice and try to stop), large animals are not going to be very effective. Although a badger is a mean SOB, they can be killed pretty easily by two men with a pitchfork and a machete - particularly if the badger is disoriented on landing. It is also incredibly easy to throw a sack over a large box, which could be used to catch the badger and beat it to death. I can personally verify that both of these methods are used today on farms and that, though exciting, they are not particularly complicated maneuvers that any physically fit adult could accomplish. That leaves small animals. The problem is that small animals are pretty much useless, unless they are ridden with disease or lice. **So I would strongly recommend diseased and/or lice-ridden rats.** Even if you catch them, you yourself may catch something you don't want. Sure, head shaving and frequent bathing will help, but the long-term effects would be extremely demoralizing. [Answer] **Small - Mice or Rats** These are pretty quick animals so will be hard for the city defenders to catch/kill. They are pretty smart and will eat any food they find.They are also very good at surviving falls so are quite likely to survive landing, mice are more likely than a rat but rats will do more damage. With some training a swarm of mice or rats could be taught to go straight to the stores for food supplies which they would quite rapidly devour. They could also be trained to leave their waste in water supplies potentially poisoning the inhabitants. The main way they can help in terms of your question is that rodents have been observed chewing wood and wires so with training to encourage this behaviour they could destroy power supplies, pylons, and power flows in the city. With power supplies disrupted there would be no way to recharge communication devices and no lights at night making it easier to sneak in. It may also turn off the automated turrets which would be a big boost. To deliver them all that is needed is to reduce the power of a catapult so it fires them quite gently as close to straight up as will still carry them over the wall. Fill this catapult with mice and you get a lot of mice per shot. **Medium - cats (preferably feral cats)** They famously always land on their feet so landing shouldn't be a problem. Once they're in the city they can run around and start scratching/biting anyone they meet. Cat bites can easily become infected and so could cause many defenders to get ill, they probably won't die but it would put them temporarily out of action. The cats would also provide a decent distraction for any other attacks as well. Although you might need to train them not to eat the mice. I would suggest launching the cats in a similar flight path t the mice but only one cat per shot. Good luck loading the feral cat into a catapult. **Bigger than Cat- Not really worth the effort of firing them** You could try launching badgers or moles, or even rabbits, to try and undermine the foundations of the defences but the amount of effort you would have to go to training them and equipping them with parachutes which would make them easy to spot and kill as they fall in. [Answer] **Human infants.** ``` These small animals have numerous advantages: ``` 1. Human instincts will prevent their immediate slaughter. 2. Although some planning on the year-scale is required for replacements, humans seem to always be working on new stock. 3. They require significant food/water resources, making a siege more effective. 4. They commit sonic warfare when not paid attention to. Distraction that is nearly impossible to ignore. 5. They require no training at all. 6. They are mobile as soon as possible, crawling into restricted areas without caring about any rules. 7. They instinctively break and disassemble anything they can get their pudgy little hands on. 8. They can easily be infected with numerous diseases with *guaranteed* transmissibility to the local populace. These diseases would not need to be fatal, even having a bad head cold during a war would be effective. 9. Even if they do not cause harm immediately, they will eventually grow up into adult humans. The local populace would increase, causing overpopulation of the walled (and thus limited capacity) city. **Delivery Method.** Some form of woven plant-material based basket with padding/swaddling cloths. 1. Effective at cushioning the payload in a trebuchet-launched parachute landing. 2. Cheap to manufacture. 3. The cloths, attached to the basket, would prevent separation of payload from the landing basket. 4. Could contain reconnaissance gear, or secondary weaponry with a timer to go off some time after landing. [Answer] Expanding upon Tmartin's answer: He did a fine job of showing that the squirrel is the animal of choice for this mission. However, the question also asked about delivery. A catapult is not the right choice here, you are going to have an awful lot of g force at launch. Rather, your launcher should be a trebuchet. Since it launches via counterweight rather than tension there's no huge acceleration spike. Furthermore, you don't want to just pile squirrels on it. First, there will be a lot of hard landings that result in dead squirrels and also your range will be severely limited. The same high drag that protects a falling squirrel also limits how far you can throw one. Instead, lets make some squirrel holders. Take a string and tie it to the squirrel--this needs to be something they can chew through reasonably quickly. Now, take a piece of paper and wrap the squirrel's face so it can't chew. The string is wrapped around this paper but not tied. The string is then tied to a larger piece of paper. This paper is wrapped around the squirrel and a decently heavy stone. A ribbon is fastened to the paper and wrapped around this whole thing, not tied and some ribbon is left loose. A bunch of these are piled on the trebuchet in a stone-down orientation. You can have only one layer. When launched the wind grabs the loose end of the ribbon and starts unwinding things. Once the paper starts to unwind the stone falls free, the paper causes a lot of drag and rest of the assembly quickly unwraps. While the squirrel might be a bit dizzy from the unwinding the rotation quickly stops once it's fully unwound. The squirrel won't like being tethered and will quickly chew off the string. Experimentation (dead squirrels will suffice) will tell you exactly how big and long to make the various parts to ensure it opens as late in the flight as possible to get maximum range. While a piece of paper edge on at first glance doesn't look like much of a parachute it's a lot more effective than one would think. Back in my model rocketry days we recovered a lot of light rockets with a strip of crepe paper rather than a parachute. For light enough rockets it was the method of choice because it was basically impervious to malfunctions other than a failure of the tether itself. [Answer] **Timeframes are going to be medium or long term in all cases** Animals need time to do their sabotage work, so its assumed that they will have a few months to a year to soften up the city and disable their comms/defenses. This time will be very different based on whether the enemy city gets alerted from day 1 (so they realize the danger and move quickly to annihilate it) or not. As such, your launch should be done when its nightfall, foggy, overcast etc.; and if you need to use packing materials get those that won't be easily identified as such (e.g. jute bags similar to what are commonly used in the city). **Are the slums within the city or is it only a well-developed area for nobles?** Most animals will need breeding areas which means that having dingy unmaintained sections are crucial for their prosperity. Of course, if the city has a now-unused underground (storm drains etc.) that could work perfectly even if the above ground is patrolled and cleaned regularly. **Match attackers according to the infrastructure** *Communication antennas and turret receivers are the only shiny things around* - you can use flying attackers like magpies which like to collect shiny objects. *Comms use large parabolic dishes* - Get species that love to nest in such areas and/or cover them up in some way (pigeons perhaps). Bonus if the 'turrets' are shaped like statues so the pigeons give them a nice whitewash coating. *Exposed wires are a weak point* - use rats, squirrels etc. that like to chew on them. *Only person who can operate comms has a peanut allergy and is a dog lover* - throw a friendly poodle drenched in powdered peanut residue near his house. Throwing in rodents will end up with a lot of frayed wires, ropes, cloth covers etc. as the animals have a need to gnaw often. **Need short term disruption?** Mainly use mammals as a distraction for the people who would otherwise maintain the turrets or comms. If the weaponry is sufficiently weak, you can just chuck a few leopards to kill people and cause small scale chaos. [Answer] For delivery method, I'd use a cage with a time delayed parachute that could be launched over the wall, release the chute, and then open the cage when it lands. As to the animal, I'd start with rats and other rodents around the food stores. If disease is allowed, rabid animals could be used, or possibly plague carriers, but if not then the attacking army should use underfed puppies as the second wave. Puppies are useless and don't have much meat, but they eat a lot. So the enemy would have to decide between watching the dogs starve (and possibly turn feral), killing and/or eating them, or waste resources feeding them. Any of those options would hurt moral in the city. Edit: Maybe not as good as squirrels, but my friends pet rabbit has done some damage chewing on power cables and the like, so that may be an alternative. [Answer] **Which animal?** [Helper Monkeys](https://en.wikipedia.org/wiki/Service_animal#Helper_monkey) These are small, intelligent and trainable. Sure, squirrels ***might event*** gnaw through some cables. And bat bombs ***might*** land just right. You can even train some of the animals which have been suggested so far, but only a higher intelligence can be guaranteed to destroy the comms network (and small monkeys beat babies hands down, any day :-). Helper monkeys are already known (and meet your modern day tech requirement :-), and are within the specified size parameter. **How to get them in there?** As per previous suggestions: catapult (with or without parachutes), hot air balloons, etc. ***BUT***, monkeys are natural born climbers. Have them scale the walls. **What about the turrets?** We are sending in quire small animals. A fraction of a size of people. If the gun turrets were manned by humans, they would have a very difficult time tracking and targeting such small, mobile animals. That would waste ammo which might have later been used against your attackers when the comms are disabled. In fact, you specify ***automatic*** gun turrets. Such things are generally designed with a human target size in mind; you do ***not*** want them going off every time a bunny rabbit nibbles some grass outside the city walls. It is extremely probably that our monkey could saunter casually up to the walls without the automated guns even registering their presence. [](https://i.stack.imgur.com/vtkoc.jpg) I have a cunning plan ... [Answer] **Skunks** would be the best critter. Getting sprayed by a skunk disables one ability to think clearly, your eyes water uncontrollably, and many people vomit. Inhabitants will chaotically flee the city. But, I'm not sure after how long the city will be inhabitable again. Catapult a pod full of tranquilized skunks. Attach a parachute to the skunk pod. Luckily, skunks are very aggressive as well. [Answer] Its gotta be the bat bomb. <https://en.wikipedia.org/wiki/Bat_bomb> Lightly packed in a barrel that will crack on landing the bats will leave and take up residence in the city, then explode and set things on fire. If timed incendiary devices are unavailable consider the method of Samson, Father of Small Mammal Warfare. From the Book of Judges /3And Samson said to them, “This time I shall be innocent in regard to the Philistines, when I do them harm.” 4So Samson went and caught 300 foxes and took torches. And he turned them tail to tail and put a torch between each pair of tails. 5And when he had set fire to the torches, he let the foxes go into the standing grain of the Philistines and set fire to the stacked grain and the standing grain, as well as the olive orchards. / [Answer] **How would you deliver the critters via catapult?** I'm not sure squirrels need a parachute. I've seen (and heard) one fall 60 feet onto asphalt and walk or limp away, poor dear. Though cats tend to survive too, they're injured ([Can cats survive a fall from any height?](https://skeptics.stackexchange.com/questions/3430/can-cats-survive-a-fall-from-any-height) on Skeptics.SE). Mice might be alright ([Small Animal Terminal Velocity](https://physics.stackexchange.com/q/109467/3773) on Physics.SE). [This answer](https://physics.stackexchange.com/a/259451/3773) claims that a parachute will work with a cat. Insects might be fine if they're of any use to you. A badger is only 2 or 3 times the weight of a cat, so maybe the same ballpark (i.e. a parachute is feasible). A badger isn't built for jumping (and landing from a jump) like a cat is, though. Deciding when to deploy the parachute after launch is key. You may want to use a clockwork timer with a mechanical release mechanism ]

[Question] [ A bit of context first, this question is inspired by the famous North Korean pilot [No Kum-sok](https://en.wikipedia.org/wiki/No_Kum-sok), and his defection to the United States during the Korean war. A quick summary, he breaks formation, flies to a South Korean air-force base, and lands successfully, despite landing at the wrong end and nearly colliding with an F-86 in the process. No Kum-sok successfully defects, but it seems as if he ended up just getting lucky, as the base radar happened to be down on his approach. So at this point the question becomes, what would happen if in a similar situation, the details were more ***dire***, and what could he do to improve his odds of survival? A Federation pilot grows tired of how things are going and decides to defect to the Empire. He is flying a state of the art air superiority fighter jet (**2018**). Less than an hour before, his squadron was engaged in a dogfight where in a strange fluke his radio was destroyed but left his aircraft completely sound functionally. He manages to break formation and contact with all other aircraft. At this point he is committed, and his only option is to head south to the Imperial AFB using his on-board navigation systems. A few details to hammer out: * The plane still has more than half of it's fuel remaining, so he can afford to loiter or use his AB's if necessary. * The plane also has most of its armament remaining in both bullets and missiles, as well as countermeasures. * Due to the damage, the plane is entirely incapable of communicating in the normal sense of radio/phone. * The Imperial base is not far, but is **well defended and patrolled**, with dozens of active and passive missile systems that can strike from tens of miles away, as well as missile equipped fighters. * The Imperials would happily welcome a defector, ***especially*** one with the air-frame he's piloting, but do not even remotely find it **likely** that this will happen. * The Defector only knows the most basic words in the Imperial's language: "Yes, No, Ok" * The ejection seat has also jammed, making a bail out impossible What strategy(s) could the Defector employ that would keep him alive long enough so that he could even attempt to convince them of his intentions? [Answer] **Land and wait** Don't go anywhere near a place that has the capability of bringing you down. You'll be detected flying in their airspace soon enough, you don't need to go to their military base. Simply land your airplane on an empty highway or similar location where you'll be able to land without causing major damage, get out, wave a white flag around and hold your hands up when the police arrives. The military and a translator will be called in soon enough when the police wants to figure out what to do with a warplane and an enemy pilot who seems to have surrendered without a fight. [Answer] Cross into hostile airspace, but don't go *towards* anything. Keep on a level course, away from anything that could be construed as a strategic target. Set the [transponder](https://en.wikipedia.org/wiki/Transponder_(aeronautics)) to whatever the most visible setting is; if it's a modern Mode 3, set its ident to 7600 ("distress - lost communications"), or to an equivalent military code. Disarm the craft as completely as possible; anything that can be done in terms of jettisoning munitions, deactivating ECW, etc. should all be done, preferably where it can be seen by the enemy, but not close enough to be interpreted as an attack. The low threat (one plane, in a region devoid of any obvious targets) should keep you not-shot-down for the longest possible time. Your best-case scenario is that a fighter (or more likely several) is dispatched to intercept - in the general aviation sense, *not* the military sense - the anomalous plane. At this point there are standard protocols that the two pilots can use to communicate visually using just the movements of their plane, which would be sufficient for the hostile plane to guide you down to a landing zone, and for you to signal your intent to follow those instructions. My guess is that you'd get sent down to a civil airfield of some description (just in case it *is* a trap) and there'd be plenty of police on hand. [Answer] ## Vulnerability The defector knows that the flight pattern of one wanting to attack is going to be evasive and attempt to avoid retaliation. The defector also doesn't want to be mistaken for a kamikaze. To communicate that his intentions are not to attack or self-destruct, he deliberately slows down the plane to minimum flying speed and directly towards an anti-air cannon. It is a desperate move, but if he doesn't open fire or speed up, the cannon could easily blast it out of the sky, putting the control entirely in the hands of the Imperials. ## Assume the position He puts down his landing gear right away. Fighters don't do this during combat because it creates drag, but again, the purpose is to defect, not to attack. ## Communication His wing lights can be turned on and off and can be used as a crude form of communication. The actual message is not too important, just the intent to communicate should imply that the intent is not to attack. Should it be feasible, the lights could express Morse code communicating the intention to defect directly. ## Conclusion Would the Imperials blast a single fighter out of the sky which deliberately puts itself in harms way, lowering landing gear, and with light signals? Maybe. It is a risky endeavor to be sure. However, the ball is left to the Imperials to decide if it is worthwhile to take the risk. There is always the possibility of a bomb on board, and a kamikaze fighter might employ such tactics to get close enough to inflict true damage. Perhaps they don't believe a defection is *likely*, though after seeing these signs, they have to at least have doubts in their mind about it being an attack. [Answer] 1) Fuel permitting, put the gear down. That's a clear indication of non-hostile intent and in general will disable the aircraft's weaponry. If you don't have the fuel to reach the intended target keep it up until intercepted. 2) Unlike what some other posters say, do not jettison ordinance. Having your external stores gone says nothing, but if you jettison once enemy fighters show up that's the equivalent of dropping your gun--a sign of surrender. 3) Head for the smallest civilian airport with an adequate runway, stay well away from anything important while doing so. 4) Pilots have hand signals for radio-out conditions. Exactly obey whatever the intercepting pilots direct you to do unless that is impossible. [Answer] Before i start... This is all guess work, i'm not a qualified pilot... let alone a fighter pilot. Fly close enough that he doesn't get shot down, but enough that the imperial forces would send a squadron of fighters out to investigate. often a single aircraft is a sign of something odd, (i'm assuming he's not being chased by the federation) Imperial squadron would fly out, perhaps engage perhaps not. if the pilot was within visual range of the Imperial fighters, he could do many things to show he was no threat. activating his landing lights etc he could get there attention, flashing them on and off or attempting morse code. even flashing code for now constantly could be enough he could release all his bombs and missiles without firing them, they would fall to the ground (hopefully not in a crowded area) the imperial fighters would be able to see he can't attack them. Another common friendly signal is to wave his wings, all of these are signs that the plane in question is not normal, and any experienced pilot would not see this and think, *"Thats odd... oh well, better kill him and get back for breakfast"* they'd be reporting it back to base and their officer would probably suggests having it follow an imperial aircraft into landing, while the other imperials would flank it ready to shoot as soon as the pilot did something aggressive. [Answer] I think it would be very difficult to defect in this manner in an active warzone, after engaging in a dogfight. No Kum-suk was defecting after a ceasefire had been declared but your pilot will be doing so when combat is still ongoing, his travelling towards the Imperial AFB will look a lot like an intruder mission. Without the capability of radio communication and due to the language barrier they will be unable to persuade the Imperial forces of their intention to defect it's likely they will engage the pilot as a hostile before they can get too close to the airbase. Given missle defenses they can engage at range without observing the aircraft so attempts to visually give clues to the intent to defect will be of limited success. Even with a radio to communicate his intention to defect they would treat it with suspicion sending up escort aircraft, asking him to jettison munitions etc. [Answer] This is actually easier then it seems. Contrary to popular media military bodies don't fire the guns and send out missiles at every little thing. Keep in mind that, minus a device like a transponder radar can only see something not rather that something is friendly or not. So what you would do is. * Fly slowly, and at a decent radar height, say 10,000. * If you can manage to drop your landing gear, lower flaps, whatever. Now you may not be able to, (if you're going to fast for example) but with gear and flaps down, you're not going far and you're certainly not attacking anything. * Wobble your wings left and right. That's the pretty much "everyone" signal for I see you (search and rescue). * Don't fly in a straight line, but in S turns. If you see an airport do a "2-minute turn" holding pattern. Again massively common. Both the S turns and the holding pattern is very common before landing and should make it clear. * When you get told to do something via lights or hand signals or plane movements, then do it. * If you can manage, keep your speed below 250 KIAS, not great, but most airspace in many countries (though far from universal) one of the main things you have to do is stay below 250KIAS when below 10,000 feet. Doing this is a clear indication you mean to go down and not up. * Finally, if your transponder has a mode-c, doink with your altimeter so that your "altitude" goes down. The normal altimeter may not be able to fake all the way down to 0, but it can do an impressive range, and that gets sent with the transponder signal. So the radar watcher will see an altitude that goes from 10,000 feet to 0 feet, even if your plane doesn't move like that. [Answer] I suggest you start learning how to say "I defect", "I surrender", "here's a gift for you" and "please don't shoot". If you can only say yes and no, if you can't communicate your defection in their language, you might as well stay at home that day. --- This is a time of war, and you are an enemy aricraft approaching a major strategic location in a war zone. You will get shot down from across the horizon. So firstly avoid AAA coverage. Your briefing should have included intelligence on that. They wouldn't send you to your death without intel, planes are too expensive to be gambled like that. Your second consideration is that a plane loaded with fuel and missiles causes collateral damages when crashing. They might take the risk shooting you down above an air base, they might not. Depends on the base commander's mood really. They will shoot you above a desert or an empty field. However, if you flew above a population center, it would make the decision to shoot you down a bit more difficult. In any case, they'll scramble fighters to intercept (because remember, you aren't within AAA range). You won't have much time to make contact, so you better do it quick. Assuming you have no radio or other wireless comm options, you still have good old visual communication. You might fliddle with your jet's lights, or use a flashlight from your cockpit. The latter would make it really obvious that it is an attempt at communication rather than a technical issue with your plane's electrics. Use Morse code to send a single, short, unequivocal message: SOS. Your next messages might be "defection", "no kill" or "I follow you". Keep it short, keep it to the point. To increase your chances, you'll need to make yourself less threatening. Drop your missiles in a lake or an empty field. Shut down all your weapon systems and countermeasures. Pull the landing gear down. Flap your wings. Anything that makes it look like you aren't interested in combat. --- From that point on, you are a POW. You might get preferential treatment if you are willing to give up information which they can't interrogate you for (at least, according to Geneva Conventions), but don't expect champagne and caviar. You are still an enemy combattant. I would suggest you strike a deal on paper and ask for a legal representation. Make it clear you want to cooperate but you also want guarantees they won't throw you in a dungeon once you've outlived your usefulness, or worst send you back in a prisoner exchange. ]

[Question] [ Humans like to explore and seem to have an almost instinctual need to expand. After spreading throughout the solar system and even into the Oort Cloud they decided that humanity should follow the robot probes out into the galaxy. Without FTL, but having discovered a form of artificial gravity and having experience creating space habitats, they create a number of generation ships. These massive structures are initially given a population and crew of 30,000, with room to expand to 50,000, and each one has all the tools and manufacturing capabilities to make more generation ships and space habitats, along with the ability to terraform a planet. Strapping on a few large meteors with ice, minerals and other things they may need in an emergency, these ships slowly make their way to the nearest solar system. Slow being a little less than half the speed of light, thanks to getting a very large boost as they start their journey. Once there, they get to work making comfortable habitats for the now increased and cramped population using the resources of the system. They spend several decades there, creating a working system of habitats and making any repairs that are needed on the generation ships. After a century or two, the generation ships, possibly a few new ones as well, get crewed by people who want to travel and move onto the next solar system to do the same thing all over again. Eventually the fleet splits into two and each one does the same thing, eventually splitting again, and again and again. If they find a planet that looks like it can be terraformed, a planet with no life, or only the most basic of bacteria which is wiped out, they get to work making the planet livable for the people who want to have a sky over their head. Any planet with multicellular life is carefully studied by probes, but left otherwise alone because the risk of contamination, allergies, etc, are too great for the ships, and terraforming them will destroy the ecosystem. Is this a realistic way to colonize and explore the universe? [Answer] > > Slow being a little less than half the speed of light, thanks to getting a very large boost as they start their journey. > > > # Slow down there! **literally.** At that speed it's not really a generation ship since you can get to many other stars within the original crews lifetime. And there are hazards to going that fast. Lets assume the ship is, say, 10X the mass of the worlds largest supertanker, that's very conservative for the numbers you talk about but it's a number to work with. ## How do you slow down at all? At 0.5 c that ship would have 7.197×10^25 joules of kinetic energy you'd need to get rid of if you want to slow down. That's about 1800 times as much energy as the energy from entire worlds fossile fuel reserves. You need some kind of fuel and some plan for slowing down. ## Hitting things in your path If there's something the size and mass of a sugar cube in your path it hits the front of your ship with the energy of the nuclear bomb dropped on Hiroshima with all the energy pretty well focused to rip through any sane quantity of armor. And that's not the only problem. ## The atoms between the stars using the figures for a cold neutral interstellar medium from wikipedia: 20—50 atoms/cm3 So let's go with 25 atoms/cm3 25000000 atoms per cubic meter. Lets imagine the ship is a nice neat cylinder. We can treat the volume of space that the ship passes through as a cylinder with a cross section equal to that of the front of the ship. Now lets look at how much it hits while traveling, say, 10 light years. Treat it as a cylinder 10 light years long with the diameter of the ship, again, lets guesstimate that the ship has a radius of 100 meters. This lets us estimate the total number of (almost all hydrogen) atoms in the path of the ship, lets assume they all hit and there's no shockwave effects: 946073047258080000000 π m^3 (cubic meters) Multiply by 25000000 atoms per cubic meter. mass of (946073047258080000000 \* π \*25000000 ) hydrogen atoms = 124.4 kilograms so over the course of 10 light years it will impact with 124.4 kg kilograms of gas atoms. For simplicity I'm assuming all hydrogen. Those atoms are hitting at .5c so the front of your ship (assuming it's a big round shield with radius 100m). kinetic energy of 124.4 kilograms at .5c is 1.73×10^18 joules I'm going to ignore time dilation because it's hard and I need to maintain my sanity. so at .5 C it takes us 20 years to travel those 10 light years So lets convert that into the energy of the gas hitting the front of the ship each hour. 1/24 (1/365 (1/20×1.73×10^18 J (joules))) = 9.8748×10^12 joules/h = 2.743 GW h (gigawatt hours) per hour has to cope with 2.743 GW hours worth of energy hitting it every hour. It's like having a large nuclear power plant at the front of your ship producing heat. you have no way of getting rid of that much heat with your ship in a vacuum and it will be melting your heat shield. **So just slow down** It's really common for writers to throw around large fractions of light speed but without magitech shields there's massive practical problems with going that fast at all. At those speeds the fine mist of interstellar gas is enough to cook an astronaut to death just from being outside the ship unshielded and enough to destroy any shielding made of matter within a short time. Since your ships are generation ships anyway you almost certainly want to slow your ships down to something sane like 0.05 C (or probably even lower if your crew want to continue to live) At least then you have some chance of stopping and some chance of surviving if you hit some grains of sand in deep space. # EDIT: Putting more ice or rock on the front of the ship does not help. Lets imagine that we put a cylinder of solid ice 100 meters thick at the front of the ship as a shield. it's an idea, I'll give you that, but lets work out how long it's likely to last at 0.5C .... cylinder | radius 100 meters, height 100 meters = 3.14159×10^6 cubic meters That's 3,141,590 cubic meters of ice, millions of cubic meters of ice. Wolfram alpha gives a helpful table for this Phase change energies for 3.14159×106 m3 of water from 25 °C: ``` energy required to heat to boiling point | 9.85×10^11 kJ (kilojoules) energy required to convert to vapor | 7.01×10^12 kJ (kilojoules) energy required to heat to boiling point and convert to vapor | 8×10^12 kJ (kilojoules) energy released from cooling to freezing point | 3.28×10^11 kJ (kilojoules) energy released from converting to solid | 1.05×10^12 kJ (kilojoules) energy released from cooling to freezing point and converting to solid | 1.38×10^12 kJ (kilojoules) ``` It's annoying that it calculates from 25 degrees C but the energy released from cooling and energy needed to heat can just be added together. Practically speaking I'm being very very forgiving by assuming that the energy needed is the same as at sea level. To melt that much ice we could need 1.05×10^15 J (joules) To turn that much ice into steam we would need about 7.01×10^15 J (joules) Unfortunately the front of our ship would be receiving 1.975×10^13 J (joules) every hour while traveling at 0.5 C from impacts with the fine mist of atoms in interstellar space. From there's it's just a matter of multiplying. it would shield you for a little while.... Within 5 days your 3 million cubic meters of ice has melted. after 34 days your ice has all turned into steam. **But what if we use something stronger than ice!** Lets imagine that instead of 3 million cubic meters of ice we make that shield out of 3 million cubic meters of solid iron! It takes 6.11×10^15 J to melt 3 million cubic meters of solid iron. Within 26 days enough energy has hit the front of your ship to melt 3 million cubic meters of iron. This is not exactly how long your shield will last, some energy will be radiated away, some will be lost to cooking your crew and iron may ablate in a less simplistic manner but it's a rough ballpark figure. At 0.5 C shields are not enough. Asteroids traveling at 0.5 C would melt and turn into a gas in short order. I cannot stress enough how poor natural intuition is when it comes to the rigors put on anything traveling at large fractions of the speed of light. [Answer] > > Is this a realistic way to colonize and explore the universe? > > > No. Apart from problems with generational ships, which you'll find discussed on Worldbuilding SE in other questions, there is a fundamental flaw in the reasoning: > > they get to work making the planet livable for the people who want to have a sky over their head > > > The people you have described have, for hundreds of generations, been a space-dwelling people. Planets may be interesting to *you*, but they're just grubby, messy places with restrictions like not having easy access to space (which is, in fact, home!) and gravity defined by something you can't change, whereas your ship-dwellers (presumably) have some form of pseudo-gravity but can also get to zero-gee (and maybe all points between) easily. As they have and can manage resources without needing a planet, all they need rocks for is to build more homes (i.e. more ships). And they can get those rocks easily without bothering with dirt and bacteria-infested planets that they have to clean first. Nope, they're going to expand all right, but they're going to do it in space. Rocks? Who needs 'em. :-) And if you have the tech to build generation ships like you describe, you have the tech to make them from (for example) asteroids. You have the tech to make a sky for yourself (and what a sky - something that's controlled and *safe* and familiar). For you, the sky could well be that the world curves over your head in a giant cylinder. Actual sky as we know it would be unnerving - you've never seen it and for hundreds of generations no one has written a song with our version of the sky in it. No, planets are, to a space dweller, completely pointless. What would they do with planets? Visit them. Planets are nice places to park, maybe, giving you an interesting view and access to, well, nothing you don't already have in space for these guys. You can explore planets and maybe some people (the dedicated scientists or the crazy people) will want to stay down there for extended periods, but live there?!?!?!? No way! And you've grown up used to the idea of living in a sealed, controlled environment with a stable population. The biggest problem that ship will face is convincing anyone to get off! Even if they reach a destination and need repairs, they'll find a way to do that from space, extracting materials from easier to access sources (small moons, asteroids, etc. ) and not by doing anything crazy like *landing*. Every solar system is indeed an opportunity to expand, but you could do an awful lot of expansion in space without ever getting lumped on something as yucky as a planet. These guys won't leave home and home is space. The minority (and presumably there will be some weirdos like this) who want to live on a planet and become "pioneers" (imagine the derision that would be said with by people who travel anywhere they want in space!), might set up colonies, but these will be villages with bare essentials and just enough equipment to keep them going. You're not going to waste resources on these nutcases if you and your people have been thrifty and efficient space dwellers for a hundred generations. Think about a hundred generations. What were your ancestors doing and where and how did they live a hundred generations ago? Do you know? Do you care? Would you consider *their* way of life anything you want *now*? Your science (even in a generation ship) has advanced and it will be focused on the needs and desires of space dwellers. You won't even *care* about the intentions of the people who sent your ancient ancestors into space. You're a space dweller. And proud of it! No "Rock Clingers" on this ship. :-) [Answer] > > Is this a realistic way to colonize and explore the universe? > > > Sure it is, this is the same process used by Polynesians to colonise the Pacific Islands. They had boats with everything they would need and would find a place, build. Then a few generations later when population pressure mounts they would split and some would go looking for another Island group. Your idea is the same just scaled up. [Answer] Sure, everything seems fine. Except ( and this is my Opinion ) > > If they find a planet that looks like it can be terraformed, a planet with no life, or only the most basic of bacteria which is wiped out, they get to work making the planet livable for the people who want to have a sky over their head. > > > Once you realize it will take hundreds of years, aboard a "generation" ship that is custom built to sustain the population for that time, you will realize that it's unlikely they would want to settle on a rock. Especially if they have to terraform it. Often times the most efficient engines have very poor thrust to weight ratios. It's very possible to build an engine perfectly suited to travel in space that has no utility lifting weight out of a deep gravity well. Given this, and the fact that they are now perfectly comfortable living in their "tin can" remember without FTL it's going to take dozens or hundreds of years to travel to even the closest stars. Even going to the nearest stars to earth will take (@0.5c) anywhere from 8-20 years depending on how fast you can accelerate. After spending 20 years in a perfectly controlled environment why start over. There are no elements on a planet that are not more easily acquired in orbit (if all your infrastructure is in orbit). The only thing unique would be the life on that planet which may or may not be poisonous. Even if it's not, would you ruin the biosphere just to dig up metal you can get by the ton other places? At most you may want to observe and do research on this new life. See if it's compatible with your life, etc. This could take centuries and the risk ... well, you could introduce some virus or bacteria that wipes your whole population out. In short, once you have generational ships, there is no reason to settle on a planet. In fact, it costs more energy to do so. In more likelihood, they will set up an orbital habitat, with some production capability. Maybe drag an asteroid into orbit. And then send science teams down to the planet to research every so often. [Answer] In the early 1600's one hundred people settled in Jamestown. Those 100 people came form a population of 4 million UK subjects. If a colony ship has a population of 50,000, there are very poor odds that you would have enough people willing to start a colony on another planet. But suppose the population of the Earth is eight billion people. Now you'd have a pool of 200,000 colonists. You select 50,000 of those people and put them on the generation ship in suspended animation. The generation ship is then crewed with 30,000 people to run and maintain the ship and watch over the sleeping colonists. This becomes a sleeper/seeder colony ship hybrid. A potential dark twist on this idea is the Australia solution. If a person on the generation ship commits some terrible crime, instead of execution, that person is put into suspended animation, and dumped onto the colony world. Note: My answer was based on the other answers where the colony ship takes decades to reach the next solar system. [Answer] Yes, except the part where you state > > If they find a planet that looks like it can be terraformed, a planet with no life, or only the most basic of bacteria which is wiped out, they get to work making the planet livable for the people who want to have a sky over their head. Any planets with multicellular life is carefully studied by probes, but left otherwise alone because the risk of contamination, allergies, etc, are too great for the ships, and terraforming them will destroy the ecosystem. > > > Reasons: 1. Based on the reconstructed history of life on our planet, the stage which for you is OK to use is a small fraction of the total time where life is possible. This reduces the likelihood of ending on a planet, and people in cramped spaces get easily angry... 2. Based on the history of human colonization, efforts to preserve the hosting environment/populations arise centuries after the colonization has been made. Again, people in cramped spaces get easily angry, and anybody will have an hard time explaining 50000 people that they have to stay in their glass bubble surrounded by deep and hostile space a few more centuries for the sake of preserving the slimy pink mossy blob which covers that nice planet few hundreds kilometers away. [Answer] > > Is this a realistic way to colonize and explore the universe? > > > ## Yes Considering the preconditions you have given, which basically say that you are not interested in *technological* problems at all, surely it is a realistic way! It's your story. You have to find problems (like pointed out in many of the other answers, for example, "why would they *want* to live on a planet") and solve them for your version of humanity. Solving those problems would be the point of interest of your novel. E.g., the argument that people who have lived in space for 100 generations see no point to settle on a planet could be resolved this way: assume that the spaceship technology is barely fun enough to keep everyone from suiciding. No heroic extra-vehicular activities in race boats for fun; no action-packed alien missions, nothing of that sort. Just boringly slogging along. Maybe they *don't* regularly play with gravity, no "free fall sex" escapades or anything of that sort. Maybe there does *not* develop a sense of infinite freedom in space (which there is nothing of, for us, right now). They have no limitless space available to them personally, but just a clunky, degrading, half-lit, stale-air metal can in which they are constantly reminded of death on the other side of the wall. Maybe, to make those generation ships work, they need very strict hierarchies/duties to keep them afloat at all; and part of the incentive to go down to the planet is that small, like-minded groups can go to vastly separated regions to do their own thing. Maybe they bring along pictures/books/films of the earth which turn into some half-religious planet cult; being allowed to live on a planet could from the beginning be made out to be the highest climax of everyone's life. Finally, think about how great of an adventure space is for us today; you can be pretty sure that lots of boys and girls fantasize of spending some time on even our limited versions of space travel/space stations. After 100 generations, maybe in your world, it is simply reversed - boys and girls are just *bored to death* by their spaceship and really looking forward to adventures on a planet. And so on. Whatever reason anyone of us could think about to make it unlikely that your plan works, gives you a reason to make your story interesting. [Answer] Yes, it's realistic. There are a few problems that many of the respondents have overlooked. 1. machines break. These star ships might need to last thousands of years. Think of how worn down the pyramids are - these ships have to run for *twice as long*. Granted, there's no pesky atmosphere to deal with, but you've still got problems with lubrication, for example. After 5,000 years, your elevators might break down. This would be no big deal in a community of billions, but even with sci-fi level fabrication and automation techniques, there will be some issues that cannot be fixed without a shipyard. If there's no ship yard, that means stopping and building one. Which leads us into the next problem: 2. 50,000 is not enough people for specialization of labor to work properly. When they have to stop and fix something, they are going to have to check the wiki, and hope that the problem was something we anticipated 10,000 years ago. Even if every person on the ship works and studies, maybe they won't know how to fix the ship. Maybe they will have to build a new one. Could you build a new pyramid? What if you also had to build the crane you'd use to make the pyramid? 3. Dictator-ships. Ships 'aint democracies. They have captains and strict rules - even cruise ships have big long lists of do's and don'ts. How long would you like to live on a cruise ship before you wanted off? What if you want 4 kids? Or what if you don't like the weird-ass religion that your ancestors made up on the journey? What if you've got some recessive gene that the captain has decided to purge? To conclude: Only a tiny fraction of people ever get *on* colony ships, but when the time comes, they *always* get off. [Answer] # The Journey In 2 Halves We already have an 'artificial gravity' per your requirement, which also sets the time to arrival; acceleration at ~1g. For the first half of the journey you accelerate, then you turn it around and decelerate for the remainder. Per relativity, this will feel exactly like being in a 1g environment on a planet. There is a neat derivation of the time to arrival via this mode for various destinations [on this page](http://math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html), with the result that it would take no more than 30 years to get anywhere you have the data to bother exploring, even popping to the next galaxy. Note that in the Earth frame it would take you a lot longer to get there, but time dilation being what it is, that doesn't matter to the skyfarer. # Generational attitudes, settlers and mariners Some of the other answers assume people would prefer to stay in space, on the assumption they are there for many generations, and it's hard to get out of the gravity well and leave a planet if you land on it. If it's just 1 generation then I suspect a large fraction of the population would be keen to start their life on the planet; these settlers would see the destination as their opportunity, mirroring those who journeyed to settle the Americas. # We generational mariners But the gravity well is deep, so it would make sense for a number to remain on the ship in a wide orbit and pick a new location to head for. These mariners would never land, carrying on to the next planet. After a few generations there would be essentially some who had been on the ship for generations, had never wanted to settle on a planet. If they had a good stock of varied genetic material (e.g. a basic sperm bank) to maintain a decent gene pool, there is no real human limitation on this approach. I would wonder, however, whether some such ships would stop bothering with planets. Perhaps there would be reverse-Moana figures who sought to revive the idea of settling when they discover the ship's origins. # Moon-miners One reason not to just forever flit through the stars is the need for physical resources; reserves of water and minerals which can replenish the exploring ship. It would make sense to harvest some such resources at each system where a settler-division happens; either by sending the settlers down with a rocket which could return material, or more likely by mining smaller moons. This mining stage could easily take a number of years to construct the equipment, refine the material and return the extracts and equipment back to the ship. During this long goodbye, perhaps some of the mariners would change their mind and opt to settle. # Colonial control A key part of the settlement of the Americas was the need to control the settlers; in this instance, the home planet would want to know the settlers weren't going to return to destroy them. There is a tension here; on one hand the colony ship experiences less time than Earth; only decades could pass for them while centuries pass on Earth, so Earth can expect to have superior technology. But, this fact would make the settlers defensive; more people from Earth would likely arrive every few decades, bringing new technology, new diseases, new threats and new opportunities. I think there is an argument for the possibility that the government licensing the explorers to leave Earth with such a ship would require that the settlers were compelled to plant some kind of doomsday device on their new planet to ensure their future cooperation, and obviate the need to impose an external threat. # The Overtakers Consider a ship heading to its second destination planet; subjectively 50 years have passed, but from Earth's perspective several centuries have done. A more recent ship has overtaken the first, by not stopping at the first planet, and thus when the first ship arrives it finds the planet already settled by a century-old settlement. Do they settle, but elsewhere on the planet? Or do they carry on to another planet where they could be even further behind? Newer technologies would inevitably also permit later departures to arrive earlier; better g-suits, genomic adjustments, cryo, take your pick. What is the protocol? What are the rules, thousands of light-years into uncaring space? # The First Man For A Hundred Years Earlier I mentioned an onboard sperm bank as an easy way to ensure a wide gene pool, which has an interesting side-effect: The more fertile men on board, the more the gene pool is narrowed (donor eggs would require a surrogate, so the men would most likely reproduce with the women on board). So the longer you plan to live in space, the fewer men you want on board on a purely pragmatic level. Potent men begin an immediate biological countdown. This could easily lead in some instances to entirely female crews; where perhaps they have had to change destination a few times, and it is safer for the onboard society to just have female offspring for a while. Eventually, perhaps, a boy would be born by accident or by design. Alternatively, a larger male population could exist if the destination is assured but be required to leave on the landing raft, so that the onward exploration could continue unimpeded. # Dreamers Some of the descendants of the settling ships would inevitably dream of the stars, of the people who continued on. With the passage of time some would build their own rockets and starships to follow the mariners, and with the joys of time dilation they could actually meet some of these historical figures, for whom proper time seeps only slowly into the margins of their existence. [Answer] There are a few realism flaws. First, 50% of the speed of light is insanely fast for a macroscopic object. Second, taking only a few centuries to create new generation ships. Slow them down to 1% or even 0.1% of the speed of light. Spend many 1000s of years expanding over a new system. You'll still colonize the galaxy in the blink of a cosmic eye. The current most practical form of interstellar colonization looks like star wisps -- ridiculously light von Neumann probes launched using a type-2 civilization's power output. Possibly coming to a stop using huge mirrors and lasers fired from the source system. The huge investment and tiny payload (traveling at a very small fraction of c, as the interstellar medium is quite dense at fast speeds) then has to be able to replicate itself in the target system and industrialize it. It can carry data with it (uploaded consciousnesses possibly included, or entire biospheres of data) and when industrialization is well underway can deploy this data; or, if civilizations are sufficiently long-lived, it can build an antenna and get it beamed after the fact. If it takes a probe 10 years to produce a duplicate and the probe weighs 2 grams, converting 0.01% of the solar system's mass into probes is 2E23 kg or E27 probes, which is 27/3\*10 = 90 doublings, or just under 1 thousand years. At that point, the system is going to be close to a type-2 civilization and would be capable of launching another star wisp at a small fraction of c. It might also be able to catch a colony ship traveling at a small fraction of c. A type 2 civilization has E26 watts of power. 1 year of output is E33 J. At 1% C, kinetic energy is $$E\_k = mc^2(\frac{1}{\sqrt{1-\frac{v^2}{c^2}}} -1)$$ $$E\_k = mc^2(\frac{1}{\sqrt{1-0.01^2}} -1)$$ $$E\_k = (.00005) mc^2$$ or 1 part in 20,000 of the mass-energy of the target. This means we can speed up or stop 2E20 kg over a period of 1 year if we have 100% efficiency. Ceres is E21 kg. So a type 2 civilization can launch something roughly the size of Ceres at 1% of the speed of light, and another type 2 civilization can stop it at the other side, assuming they can deliver the momentum over a distance of 1% of 1 light year. 5% of the speed of light makes this: $$E\_k = mc^2(\frac{1}{\sqrt{1-0.05^2}} -1)$$ $$E\_k = (.00125) mc^2$$ 30 times more energy for the same mass. It also makes the distance you have to project the energy 5 times further and hence 25 times harder (tyranny of inverse-square). At 50% of the speed of light $$E\_k = mc^2(\frac{1}{\sqrt{1-0.5^2}} -1)$$ $$E\_k = (.15) mc^2$$ 120 times more energy than 5%, and 10 times further energy projection (which is 100 times harder). --- The reason why the star wisp has to be as small as possible is that most of the mass you'll launch will be in the form of mirrors and lenses and light sails. You need to brake, which means you need momentum in the opposite direction. You shoot off lenses/and mirrors, then reflect light from your launch laser *back* onto the star wisp's light sail. These mirrors are pushed further out (and never stop), but you can get a tiny star wisp to stop with ridiculous energy expenditure over "short" interstellar distances. [Answer] > > getting a very large boost as they start their journey. > > > This is an issue. When travelling in space slowing down and speeding up are more or less the same problem. There is pretty much negligible friction to slow you down again. So if there is some special "boost" that it gets from its home system that put it over its maximum natural speed, how it going to stop? It makes most sense to accelerate continuously for the first half of the journey, then decelerate for the second half. [Answer] Dr Bob Enzmann wrote extensively about this sort of thing. He is still around.look him up. Reasons for wanting off the ship: Vast open spaces. as Much population as you can handle. and the 2 word answer? Soylent Green! [Answer] Look at Larry Niven's Outsiders - they lived a little bit like this. There are technological issues as well as social issues with the whole concept, but most of them come from an extremely limited, anthropomorphic point of view. Just because humans, in our current state of development, could not maintain such a society, nor handle the technological challenges, does not make it an absolute impossibility. In fact, much good sci-fi comes from exactly that kind of projection. "IF" we were able to overcome such-and-such a technological or social obstacle, what would be the fallout? [Answer] You're real problem is between the statements "don't have FTL" and "do have artificial gravity." Real linear artificial gravity violates F=ma "equal and opposite reaction" and once you've done that, the speed of light changes from a speed limit to a curio. Chances are the next problem of getting all your energy back into a usable form when you hit [The Big Red Stop Button](https://www.youtube.com/watch?v=ygE01sOhzz0) (lever) will be solved too. [Answer] I would drop the notion that your technology includes artificial gravity (beyond spinning) and engines that can get you to half the speed of light. Which as many point out limits time for the generations and leads to the problem of hitting stuff. I would assume that a spinning cylinder of a decent size with the interior designed to provide space, light and "nature" with the center axis being a source of light and "rain" and your vessel has decks below (outside of the inner space) that provide space for farming, then industrial tools, then storage and lastly the outermost deck would be flooded with water not only to protect the occupants from cosmic radiation, but also to make certain that the ship has enough water to make it across the vast expanse of interstellar space. I would increase crew/passenger size to 100,000 with an expected expansion to 300,000. I would also consider that the on board time between stars is about the same as the remainder lifespan of a 20-something first generation person. 50 to 60 years seems reasonable thus you would have grandparents who remember green hills, blue skies and a horizon that bent down instead of up. 10% light speed tops makes a reasonable on board trip time. I'd go with something along ion engines, low thrust that continues for a very long time. Instead of turning the ship you would have thrusters that would point bow-ward at an angle, thus your deceleration time would need to be longer than your acceleration time. This way you can use both ice(s) plow/shield and a Bussard Ram Scoop collector to provide more fuel. Ion thrusts are weak - [5.4 Newtons of thrust](https://www.space.com/38444-mars-thruster-design-breaks-records.html) is the latest and most powerful ion engine. One can [convert newtons to gravity](https://sciencing.com/convert-newtons-gforce-8720337.html)... But I'm not doing it here. I can pretty much tell you that you would be pulling .01 g which would hardly be felt and the spinning craft would have a greater force on people than the continual thrust. Your ship could get up to a decent velocity given lots of time, but a half the speed of light will bring way too many other technical questions to mind as previously explored. 300,000 colonist/terraformer/ship builders arriving in a stellar system is a good start. One could argue that the ship is feeling crowded by this time so passengers and crew would be hungry for more space. And humans are real good at making new humans so 20-40 years at this new star system, given enough space, humans could be at the half million mark plus. They would need to stay in that system long enough to make enough humans to fill two ships... plus leave behind enough colonists to make a new world, make more ships - what ever direction they want. figure another three generations of time (say 60 years) and 1.5 kids per parent - magically the human population is at or slightly above one million. To give you an idea of how fast humans can make more humans, just look at population growth from 1900 (1 billion humans) to 2000 (7 billion humans). So yes, your basic idea makes sense. Humans making more humans, the desire to find new fresh untouched worlds to explore. Perhaps groups of like minded people are off to make their own worlds by their own rules... As for size. [Rendezvous with Rama](https://en.wikipedia.org/wiki/Rendezvous_with_Rama) might be helpful. Not only with size, but with interior design to handle space travel. ]

[Question] [ How could a fortress that could hold around 5000 people with the technology available in medieval Western Europe (1200-1300) be built into a mountain? The fortress would be designed so it remains entirely hidden from anyone casually walking by the mountain, and preferably even those walking on the mountain, yet would still be easy to defend if discovered? Assume that food and water are not major problems, an underground stream provides water and fish, and there are large storerooms, although ways to acquire additional food would help improve the quality of an answer. [Answer] Consider the real world underground city of Derinkuyu in Turkey They stumbled on a simple solution, a giant stone disc in a groove for a door. Easy to move and brace from the wide interior room but impossible to move from the narrow entrance passage. The narrow bendy entrance made it nearly impossible to break through from the outside without spending weeks or months at it. (literally, hammer and chisel in which time those inside could reinforce the entrance.) the entrance tunnel is so narrow you are not getting more than one attackers at a time. Add a few well-placed holes to drop boiling oil or poke a spear through and it could be defended for as long as the defenders food held out. Note the interior of the city is actually quite spacious. [](https://i.stack.imgur.com/HkxvA.jpg) Hiding the entrances are easy because they are so small, about the size of a normal house door. The city had several such entrances. see the beginning Mormacil's answer for a great idea about using line of sight angles to help hide them, but because of their size even a well placed bush or boulder can hide them from sight. [Answer] From walking by casually? Easy. If you assume it needs to remain hidden from the valley below, you just need to place any entrances, windows, etc., behind a curve. [](https://i.stack.imgur.com/kh2Jo.jpg) I think your biggest issue by far is the population of 5000. That's a lot of people to feed and hydrate. But we're ignoring that problem for the most part I read. So, before we design the fortress itself: The way to win a siege is by exhausting the supplies of the enemy. Either the besieger gives up because they run out of supplies, food or gold. Or 'they're defeated by a relief force. The besieged loses when their supplies run out and not really in any other way. Except for maybe disease. So what you want is endless supplies for your defenders. When you don't rely on outside supplies, the siege can go on indefinitely. The only way the enemy can beat you then is tearing down your walls. Being inside a mountain is a clear advantage here. Your walls are hard to tear down if they're literally the mountainside. For a settlement your size you need multiple entrances; you can't manage just one well-hidden entrance. It would need to be too big. No, you need multiple small ones at multiple levels. Something like this. [](https://i.stack.imgur.com/7nsiY.jpg) Gate #2 can easily be reinforced with wooden beams, a metal portcullis, etc. The wooden floor is like a drawbridge. Either that or you simply destroy it if the enemy knocks on Gate #1. The grate will allow you to harass the enemy if they break down Gate #1. Boiling oil, tar, arrows, rocks, etc. Whatever you want and have. That should allow you to hold the gate for a very long time as long as you have the supplies. For increased security, let your gates go up, inside the mountain. Would make resupplying harder as any cart going into your fortress will need to go up, but will make defense easier. ### Light and air Probably the easiest way to take care of this would be having a hollow mountain or a short canyon of some sorts. With enough time this could be artificially made. Maybe even a steep and dead caldera could work. The majority of your rooms would have a connection to this central shaft. It will bring light down, reducing the need for expensive candles. This, of course, leaves a rather prime location to attack from. So around the opening, you erect a wall. No gate, just a tall wall you can only access from the inside. Pictured below a round wall. A star shape would likely be superior as it offers no way to scale a wall without exposing your rear (to a volley on pointy things). [](https://i.stack.imgur.com/nrrKn.jpg) The stone bridge is my idea of the main access point to the walls. In case they fall you cut the ropes of the bridge. What then remains is this thin strip to walk over. On your end, you either make a shield wall or some wooden screens. Behind them you put pikes. Good luck crossing that. Any ropes thrown or shot to aid can be cut down. And crossing such a thin surface while being stabbed with pikes... Further down, of course, it makes sense to construct wooden and rope bridges across the level. This would allow your people to get to the other side relatively fast. Doesn't matter if that's easy to defend if you lost both the wall and the bridge above you're already doomed. [Answer] I wonder that the other answer did not mention the [National Redoubt](https://en.wikipedia.org/wiki/National_Redoubt_(Switzerland)) of the Swiss Army. It is a well-hidden sytem of massive fortifications inside the mountains, so exactly the thing you are planning to implement. Here are e.g. camouflaged crenels of the Euschels fortification: [](https://i.stack.imgur.com/jxSOP.jpg) [Answer] ## Limestone caves Build your fortress in a region already full of caves and passages. Limestone is absolutely ideal for this, since it naturally forms all kinds of caves and other strange structures. Case in point - the [Tsingy de Bemaraha](https://upload.wikimedia.org/wikipedia/commons/e/ec/Tsingy_de_Bemaraha.jpg) in Madagascar. You would conceal the entrances to your fortress in existing, natural caves, and yes, that's 'entrances', plural. If you have a single Great Gate, the enemy can locate it and besiege it. Instead, you'd have a main gate, then several smaller passages leading to outlets all over the mountain. That would allow your forces to sally forth during a siege and harass the enemy's rear and supply lines. Ultimately, the mountain itself is your best defense. It's difficult to campaign in the mountains, and defenders always have an advantage anyway. [Answer] [](https://i.stack.imgur.com/L2zvh.jpg) A huge crater or depression at the top artificial or not would do the trick, build your fortress in it, site your first contact defenses at the rim, could even have a moat easily enough. Then secondary solid defenses would be your fortress. Unseeable from the ground, solid defensive site if attackers climbed up. Assuming the picture is a mountain top, I could imagine a huge fortress instead of the island, perhaps bigger, with terraced agriculture going on all the way around the rims inner slopes and a bit of animal husbandry happening. If it was big enough it could handle 5000 people. An island like Nauru supported 1200 people and it's only 12 miles around and people could only live in a small strip around the edges the whole inland after a few hundred meters was not habitable. Swiss have fish in their mountain lakes. That Island in the middle is probably a volcano plug which is a solid foundation like Castle Rock in Edinburgh. [Answer] **A castle inside a large cave.** Literally, walls indoors. **So for starters you have the main cave entrance.** (*tremble at my mighty ms paint skills*) This would be the main entrance only, a good cave fortress is going to have multiple egress points for flexibility. [](https://i.stack.imgur.com/39hy3.png) --- **Upon walking into the cave you would see this (below):** A 25 foot tall stone wall nestled into a narrow point in a large cavern. * Your cave should allow for no hiding places for attacking forces once they enter the main chamber of the cave. If it naturally does your defenders could carve it out so it is wide open. * Add a dry moat if you wish, though as you mention there is an underground water source so there is no reason it couldn't also be filled with water...and piranhas. [](https://i.stack.imgur.com/Thlx7.png) **Additional Design Notes:** * The rest of the cavern beyond the wall could have open spaces or a warren-like cave network, that's really up to you. Just consider enough space for your 5000 people. * Make the wall tiered so you have multiple platforms from which to rain pointy death upon your enemies. [](https://i.stack.imgur.com/SOAhJ.jpg) * It may be worth considering crevices and cracks in the stone ceiling to allow for natural sunlight to get in once in a while. This would also aid with ventilation which is always a concern underground. **Keeping it a secret:** This is going to be tough. In an ideal situation... * Your defenders would also be masons so they could create the stone structures themselves. Otherwise, you have to bring people in to build it and if it has to be a secret they either have to stay or be killed. * Make it remote. Keeping it off the beaten path will help, ideally, it would exist in a land NOT part of a kingdom that is looking to exert authority over its entire domain...hold outs are annoying to kings. * Camouflage the entrances, make it harder to find. * Avoid unnecessary excursions outside the fortress. This is particularly important if the surrounding area is even sparsely populated...people wandering into a mountain and not coming back is sure to arouse suspicion. Unless there is no one else around it won't stay a secret forever...but if there is no one else around why do you need a secret cave fortress anyway. **Defending it:** So, yes, this place is insanely defensible or at least it is against standard medieval warfare. Men charging into the tunnel to assault the gate would be in a cramped space with nowhere to hide. Attacking it in a standard fashion would be completely suicidal and you'd potentially end up blocking access to attack with your army's corpses. Defenders could also always cave in the main entrance if they wanted to... **Weaknesses:** * Fire, or more importantly smoke. As mentioned above a standard attack would be idiotic, and that's even without Spartans defending it. But smoke could potentially be a huge problem. Why attack a cave when you can just control the entrance and roll burning balls of pitch into the cave and asphyxiate the defenders. * Siege. This place is going to be pretty easy to lay siege to...sure if they can provide food and water for themselves they can last a long time but unless they have access to the outside world they will eventually fall. [Answer] **Facts** Before we delve into designing the fortress, it seems best to remember a few facts about the period itself: * recreational climbing/exploration wasn't a thing, * most people in a medieval era never left their village, the few trappers would follow game, not venture into arid areas for the fun of it, * trips, whether at sea or in the mountains, were slow-going and dangerous; natural disaster, lack of medical knowledge, wild animals (wolves/bears in mountainous areas) made Nature the greatest enemy, it was expected that travelers may run into trouble and possibly never come back, * in the absence of science, suspicions and myths ran the gamut. **Picking a location** A remote location is unlikely to ever be visited; which minimizes the risks of discovery. Thus, just picking a remote location off the main travel roads is already a significant step in the right direction. A seemingly arid location also helps; if there is nothing to gain, no bounty, game or lush fields, then only fools will willingly set up to explore the area. This can be exacerbated if rumors of dark forces, monsters, spirits, etc... scare people away. If nobody ever comes back, such rumors will form without any active intervention: people wish for an explanation, they'll make one if none is readily available. Depending on the nature of your hidden people, they may choose to integrate the unlucky wanderers, bribe them or kill them, to ensure their secret remains secret. **Hiding the location** It is best if, on top of being in a remote area, your location is only accessible with difficulty. I would elect a deeply ensconced valley, cut-off from the world on 3 sides by nigh impassable mountain ranges. Or even the crater of a former volcano. If there are accessible paths, they can be concealed or rendered impassable, at your leisure. Remote, inaccessible, and with nothing to earn in sight: why would anyone go there? Which actually ties in with the fact that you should aim for autarky. Being self-sufficient will mean that your own people have little reasons to wander about. If only a select few (rangers/spies) go out, they can be trained in not leaving obvious trails and concealing their travels. Also, patrols are great to (1) make wanderers go away and (2) warn of incoming threats. Self-sufficiency is actually easy in this case: you have fresh air, pure water and arable land (at least on the volcano). A few trees would not be amiss for construction material/heating, which if you do not pick too high a spot will be easy. Note that most of the times your people should live in the valley/crater itself, not the fortress. This makes life more comfortable. **Designing a fortress** The fortress itself will depend on the location. And how hidden you want it to be. If the location is sufficiently hidden, then the fortress itself can be as blatant as you wish it to be. Obvious locations include: * the island in the middle of the lake (for a crater), * the top of the valley, with its back to the mountain and flat terrain in front for shooting practice, * a cave system. In any case, an approaching enemy will make a good target for archers, making it costly for an assailant to close in. The lake is maybe the worst case for an assailant, especially if the island is hard to land on (naturally, or artificially). In the case of the cave, note that you have no need for big entrances, which is great since those are harder to defend anyway. A man-size entrance can be closed off by rolling a stone from the side (good luck to whoever attempt to break through it). Otherwise, hearses/thick doors with egresses to harass the assailant will do, especially if you have several sets of them. I would recommend putting the food storage inside the fortress itself; this would make it extremely costly and difficult to besiege the fortress, especially as your patrols could harass the enemy, focusing on destroying/spoiling its own food storage in a war of attrition. [Answer] You've likely got enough ideas about defensibility.. [Feeding the 5000 isn't actually so much of an issue. Crater/Extinct volcano has caldera.](https://en.wikipedia.org/wiki/Caldera#/media/File:La_Cumbre_-_ISS.JPG) Look up caldera and crater lakes for some inspiration maybe. Oregon's originally named 'crater lake' has 18.7 cubic km of freshwater..So you have a freshwater lake all to yourself, providing your terrain blocks off access to visitors, thankfully you're the world builder. Now, you don't have to leave that as it is, you've been preparing this bastion for a little while...you could keep part of the interior slopes for growing trees and turn the rest of those slopes into farmland. If you don't like that idea you can give your mountain fortress access to the sea..doesn't have to be navigable, maybe just tunnelled out angled 'wells' into subterranean saltwater basins fed by the sea..aka a grotto or two for supplementary fishing.. And/or your mountain can have an 'internal access only' ravine open to the sky which (obviously) gets rained on and can be used for agriculture Recreational mountain climbing wasn't so much of a thing when people had to work to stay alive. You'd likely be pretty safe from discovery even if you put advertising signs out. [Answer] **Concerning food** Apparently, you need [about 1m²](https://www.thenakedscientists.com/articles/questions/how-much-wheat-make-loaf-bread) to grow the wheat (550 g) for a single loaf of bread. I don’t know about the area requirements of other crops but wheat is pretty energy dense. Those 550 g contain 1925 kcal, so one loaf per defender/inhabitant per day should be enough. For a whole year that’s 1 825 000 loaves for the whole population, using 1003.75 t of wheat and requiring an area of 1.825 km² to grow. **So we are talking about whole valleys (e.g. at least 3 km long, 600 m wide) with arable land here, not just a small mountain meadow.** Even if you don’t plant your own crops you can see that it would require thousands of carts to transport the food to the fortress. Of course, if you only have to feed the population during short sieges it would become easier. However, for 3 months of siege, you’d still need 250 t of wheat. I guess your best bet would be to disguise the fortress (e.g. as a mine) and don’t even try to hide the supply chain. ]

[Question] [ I have a Roleplay setting on the books. It's a constructed pocket universe that the Dragons built to hide from the Great Old Ones; because of its structure, there are *vast* bodies of water, potentially millions of kilometres, of deep, open ocean water without so much as a speck of land. Such expanses are generally considered by those who live on their shores to be effectively infinite since even with a healthy dose of magic the distances involved are just too great. Over millions of kilometres, without any land-based support and resupply, any ship will eventually founder. But what I'm wondering is how narrow an ocean might be and still be effectively infinite to a sail-based maritime civilisation. Human civilisation is rather variable in this world so as the technological benchmark for creating a relevant answer use the height of the [Age of Sail](https://en.wikipedia.org/wiki/Age_of_Sail) and ships like the *[Cutty Sark](https://en.wikipedia.org/wiki/Cutty_Sark)* or possibly a sturdier version of the *[Wyoming](https://en.wikipedia.org/wiki/Wyoming_(schooner))*; iron or steel framed but wooden hulled vessels in the 90-150 metre range with displacements up to 10,000 metric tonnes. My question is what would be the maximum range of such a vessel that was built specifically to go *as far as possible*, and conversely, how large would an ocean have to be to defy effective exploration by such a vessel? Please note that while the world contains [magic](/questions/tagged/magic "show questions tagged 'magic'") I have deliberately left that tag off with the intention of excluding it from consideration within this particular question, with one exception; a ship's crew can use magic to evacuate if they cannot find land so exploration trips can be made to the absolute limits of supply endurance. [Answer] You should read Antonio Pigafetta's journal. He was one of the first sailors to make a voyage around the world, a member of Magellan's crew. They almost died of starvation while crossing the Pacific. In fact, given what he wrote, the width of the Pacific might do for you. Notice that it is not just the width that will make an ocean hard to cross... The Pacific got its name due to a part of it where the weather is so tranquil, sail ships had a hard time going anywhere in feasible time (i.e.: there were winds, but they were too weak). That's what caused many sailors to die from starvation in Magellan's voyage. If your oceans have little to no wind (absence of wind could be explained by magic), or if the winds will never blow towards shores, your sailors may be trapped forever there. Just reduce this effect to cause them to take years to cross it. But remember: humans are quite the explorers. In times of peace, there will always be someone who will gather immense amounts of food in very large fleets and set out to explore. They may even prepare to survive on fish and filtered/magic water only. At some point they will conquer your ocean. [Answer] Wow - so you have a pocket universe, which is great. You can use any topology in a pocket universe, which means you can have an effectively infinite sea within a topological space. For instance, you could use some form of continuous fractal surface - the sea would not have any discontinuities, it would be infinite in it's size, but it would fit within the pocket universe. Yet, and with no difficulty, every point in the sea would be a unique point so that you could provide a pair of coordinates that pinpointed a specific place, and yet even if one was nominally 'next door', one would never ever be able to travel the distance by sea - because the sea journey is infinite. [Answer] Renan has a great answer, but doesn't consider magic. You've said that crews can magic back to safety if need be, so we can take advantage of this to massively increase our range. I'm going to use some assumptions here, but you can alter these assumptions based on your world. ## Assumptions 1. Your exploration fleet is 25 ships. This is based on the size of the fleets the British Navy had during the age of sail. I'm not a historian, so please alter this to fit how many large ships your nation can build for this expedition. 2. You can crew these ships with a barebones crew of 50 men. This is based on Magellan's crew. He started with more than 200 and finished with 18. I'm guessing 50 could crew a ship effectively. 3. These ships can sail the Pacific in 3 months. This is also based on Magellan's trip. 4. Your ship can carry enough supplies to support 150 sailors for 3 months, or 50 for 9 months. This is also extrapolated from Magellan's expedition. 5. The width of the Pacific ocean is 17000km ## The Strategy You will sustain all of your crew members off the supplies of a single ship. When that ship's supplies are depleted, these sailors magic home, and the remaining sailors eat from the next ship, and so on until there is only one ship left. ## The Math Using the numbers from above, if you start with 25 ships, you have 1250 sailors. This math is very much like the Rocket Equation, but I'll do the math by hand for simplicity. If 50 men can survive 9 months, then 1250 men can only survive .36 months. There's no more use for that ship or the men, so they magic back and there's only 1200 men. These 1200 men can survive for .375 months and so on... ``` 1250: .36 1200: .375 1150: .391 1100: .409 1050: .429 1000: .450 950: .474 900: .5 850: .529 800: .563 750: .6 700: .643 650: .692 600: .75 550: .818 500: .9 450: 1 400: 1.125 350: 1.286 300: 1.5 250: 1.8 200: 2.25 150: 3 100: 4.5 50: 9 ``` Now we sum the whole thing and get 34.34 months of sailing for the last ship. If Magellan's ship could go 17000km in 3 months, then this ship could conceivably have traveled 194593km in its 34.34 months. That's with a lot of guesswork, but you can use my method with whatever numbers you have to get numbers you think apply to you. --- Edit: In the comments a number of limitations have been raised - I'm pulling them in to the answer because they're valid concerns. This doesn't take into account the fact that supplies -- even fresh water -- have shelf lives. Spoilage and/or loss to mice, etc., will take a toll. As will ship repairs after any storms, etc. Sailing is not only about supplies. You have to repair the ship sometimes. You need to remove barnacles from the hull periodically, for example, or else the ship will become slower. Sailors of old did so by careening their ships, which can only be done on shallow water. Bottom line: your food may last for years, but if you don't stop here and there every once in a while your ship will deteriorate as fast as if it had been abandoned. Consider that both of these need to be addressed to make this strategy viable. It's my opinion that they can be solved with magic, since your world allows it. Otherwise, you'll have to find a non-magic solution to these problems, which may or may not be possible. [Answer] I propose an alternate approach to a wide sea, and a pleasantly mythological one. The Sea of Worms! At a certain distance from shore, your ocean teems with hardy creatures, the eponymous worms. These little beasties feed on the cellulose of deep-ocean plants, but prefer the warm, upper waters to spend their time in (and who wouldn’t!). A wooden hulled ship sailing through their waters would be akin to you discovering that there’s a tray of donuts passing by while you’re relaxing in a hot tub: a delicious and welcome surprise. They can be a more voracious and numerous version of the Teredo navalis, which has a stupendous effect on submerged wood:  Assuming you have their habitat also be in a doldrum-prone area of the ocean, so they have time to do their wicked work, you have a virtually impassable barrier for wooden hulled ships. [Answer] It seems like most of the answers are assuming the residents of this place have an infallible way to navigate. I put in a comment... > > What are they doing for navigation? It's pretty easy to turn a boat around once it leaves sight of land. Pocket universe doesn't have to contain stars, magnetic is easy to mess with, currents change. Nobody could tell, until they arrived home again. Even if it just has the closest star (like a sun) that's only useful part of the daytime. Heck two continents could be a couple hundred miles or km apart and be unreachable, in effect. > > > ...asking about details. Lacking details, for now, There is a reason that, for most of our history, most boats who returned from their voyages stayed within sight of land. Ignorance, mostly, not know what there was, not knowing how to make sure they got there, belief in magic that didn't actually work. Much of the exploration of the pacific was facilitated by all the islands, as indicated in other answers, from a survival standpoint, and from a navigation standpoint. Take away all land, no stars and and uncertain (unmappable) currents, and you don't need vast distances. If it's overcast at sea, you don't even get the sun much (assuming there is one) This means that if someone knows the secret of traveling the seas, and it's not all that far, some one power can be very powerful indeed. [Answer] Given an infinite amount of time they can just build a bridge to the other side of the ocean. (either a floating one or not) So, it has to be at least as wide as the bridge they can build using their land ressources. [Answer] **At least *14028* square miles if using modern sails in ideal conditions or *7260* miles if you are sailing at the speeds of a *Cutty Sark*** Let's assume the Dragons are scared and Over-engineer to avoid detection and believe that the crew is perfectly optimized with perfect food storage **Crew Size** For a ship like the Wyoming, a crew of at least [thirteen people](http://www.wyomingtalesandtrails.com/sswyoming.html) needed to be working for its operation. **Space** From the wiki, we learn that > > a cargo capacity of 303,621 cubic feet (8,597.6 m3) > > > this means every person gets provisions for (8,597.6/13) -> **661.4 m3 of supplies** **Food and Water** According to [this site](http://healthyeating.sfgate.com/minimum-water-consumption-per-day-9415.html) a sailor will need about **3.7 liters** of water or 125 ounces per day or (0.0037 m3). Common knowledge on the back of any food product will tell us the recommended amount of food is [2000 Calories](https://www.livestrong.com/article/310517-minimum-amount-of-calories-needed-per-day-to-survive/). If we are eating a [balanced diet and proper portions](https://www.everydayhealth.com/diet-nutrition/portion-sizes.aspx) 1. 5 1/2 ounces of lean meat - roughly 1 cup 2. 2 1/2 cups of vegetables 3. 2 cups of fruit 4. 3 cups of low-fat or fat-free milk or the equivalent dairy products 5. 3+ ounces of whole-grain products - roughly 3 cups 10 cups of food or (0.000236588 cups in a meter3) 0.00236588m3 which ensures people consume (0.0037 + 0.00236588)-> 0.00606588m3 of food and water per day. since we have 661.4m3 of room for supplies, we divide by 0.00606588m3 to get around **109036** days of travel before **Speed** How fast can our ship go will determine how big the ocean must be. If we look at the upper limit of current technology, it seems that the fastest we can go is around [64.45 knots or 75.2 miles](https://www.telegraph.co.uk/sailing/2016/04/14/in-pictures-the-eight-fastest-sailboats-in-the-world/) (a world record but seems achievable with magic). Assuming tireless workers, that is (75.2\*24) = **1804.8 miles** in a day that could be traveled For a ship like the *Cutty Sark* -> this should be 20.14mph -> (20.14\*24)-> **483.4 miles** in a day that could be traveled **Total Travel Distance** 1804.8 \* 109036 => **196788172.8 miles** -> before you run out of fuel and need to teleport back outside of pocket realm 483.4 miles \* 109036 => **52703640.96 miles** -> before you run out of fuel and need to teleport back outside of pocket realm square root of 196788172.8 is **14028.1207865** which is the area you would need for modern ideal circumstances square root of 52703640.96 is **7259.72733372** which is the area you would need for operating a sail at the speed of a *Cutty Sark* [Answer] I see some excellent answers using a lot of calculations to derive some potential distance limits. Allow me to propose an alternative possible method. It has been proposed that sudden releases of methane gas from the sea floor can create plumes of water which are markedly less dense than normal water. Should a boat enter these less dense areas, they would immediately sink to the bottom. The disadvantage of this method is the requirement for massive amounts of methane gas, a non-renewable resource short of underwater or under-seafloor fields of cows or other cattle. If magic is on the table, it becomes much easier to have regions of permanently less dense water which would provide a completely impossible to cross barrier for sailing ships, unless one knew the secrets of how these regions were laid out. However, as the question specifically didn't want to use magic as the solution, I mention this only in passing. Note that **magic is NOT required** in order to have these less dense regions. As another alternative one could even postulate giant sea creatures which instinctively target boats and release enough gas into the water to drop them below sea level far enough to fill up, and then naturally sink thereafter. Giant kraken or other aggressive anti-ship sea creatures would also provide a means of preventing any ships from returning or any survivors at all. Place the other coast of your ocean out of visual distance from these less-dense and/or dangerous creature-infested regions, and your ocean can be any distance greater than the minimum distance required to see land from these regions, which according to some internet research is approximately 12 nautical miles (22.2 km; 13.8 mi), give or take depending on your height from sea level. Thus, if you wish these less dense regions (and thus any disappearances) to be out of sight of land, then you would need to place them around 13 nautical miles from the first coast, and the opposite coast another 13 nautical miles. **This gives a minimum possible distance of 26 nautical miles as the most narrow possible ocean.** Note that this assumes a planet approximately the size of Earth. This value will change depending upon magical visual capabilities, size of vessels (notably height of the tallest mast), and actual size of the planet, among other factors. [Answer] **Distance is a function of velocity and time.** Distance is determined by the average windspeed, and the headway your vessel can make in both directions using (or fighting) that wind. For example: Perhaps, given a wind I chose, let's say your vessel can make 7 knots outbound and 1 knot inbound. In other words, the vessel can travel 21 nautical miles *and* return to it's starting point in 24 hours. Time is a function of the crew size and cargo capacity. Let's pretend that one surveying expedition has an extra-small crew of 30 because they don't intend to land (landing is next season's task), and the cargo capacity of the vessel can carry 250 days of food and water for those 30 sailors. 250 days x 21 nautical mile range per day = 5,250 nautical mile range for the entire journey. Of course, **this is an oversimplification**: It assumes excellent navigation skills and precise tools. It assumes a constant wind, no storms, no currents, no doldrums. The crew arrives home with no food or water left...which stinks if they're only, say, two or three days late. Also, a crew of 30 may be too small to keep the ship afloat in a storm and to make repairs afterward. People are clever - fishermen charted the storm seasons and currents long before explorers used that knowledge ranging out into the deep waters in search of adventure. Then you get into staging (like rocket stages): Extra vessels that turn back early, carrying extra supplies for the expedition to boost it's range. [Answer] It would have to actually be infinite. To make crossing it truly impossible? It would have to be infinitely big. Let's say you have a boat that can carry enough supplies to travel X distance. If you instead send 2 boats, then at .5 X, both boats have half supplies. You magic back the crew of one boat, and transfer the supplies across to the other. That boat continues on, X distance - it has now travelled 1.5X. Do it again, adding two more boats to the fleet, and you will be able to get the final boat to 2 X. Every time you double the number of ships in the fleet, you will increase the distance you can travel by .5 X. Which means that a sufficiently determined civilisation is capable of crossing an arbitrarily large ocean. Even if you remove magic, and require the the emptied boats retain enough supplies to return, it's still possible, you just need a lot more boats. [Answer] Infinitely big, or rendered impassable by other means (rough water, etc). While explorers *could* brave the waves in search of adventure, etc, the ones who will really test the limits are those who have no other alternative. The Polynesian migration is one example of the distances this can bridge, given enough time. So when there's a good enough reason to leave (war, resource exhaustion, running out of space, etc), those who can, like those already living off the bounty of the sea, will start to spread out. With appropriately designed ships, and the correct skills, they could live at sea indefinitely. Islands would provide landmarks, and places to put down roots for a generation or so, but eventually they'd expand and at least some would move on. Repeating that cycle long enough will fill any size ocean, unless there are hard limits to expansion: * Impassible currents, though technology will eventually find a way around this * A continent with a firmly established civilization, though this doesn't work with the premise * Hostile and dangerous creatures, though humans will figure out how to eat these eventually, so breeding quickly is a plus * Something which makes navigation unreliable, which is implausible, but effective. Making this work would allow you to make the ocean almost as narrow as you'd like. The root of the problem is finding away to make whatever limitation you decide to use reasonable and consistent. What you don't want is the equivalent of the invisible walls video games were so fond of during the 90's. [Answer] You need to specify some other things. What is the typical weather they will be encountering? Is there going to be regular rain, which can resupply fresh water? Are there marine animals that can be fished and eaten? Do they have technology that can distill fresh water? How is their food preservation? Do they understand concepts like scurvy, so that they understand they not only have to take into account the amount of food, but also the right kind of food necessary? If they do, they could go a very, very long way. To use real-life example, Reid Stowe sailed the *Anne* (a 70 foot schooner, 60 tons) out of sight of land except for departure and return and with no resupply for 1,152 days, and still had an estimated year's worth of food aboard (not counting plants he was actively growing). Assuming an average speed of 12 knots, generally constant favourable winds, and a similar crew to cargo ratio with the capability of gathering freshwater without needing to land, that puts the distance theoretically covered in 4 years as 420,480 nautical miles. If your ship was designed specifically to operate with minimal crew, had generally favourable weather, was well-constructed to not need major overhaul, and things like acquiring fresh water and fresh food (through fishing and/or growing plants) to extend the endurance of the crew, five years would be entirely reasonable. Keeping the average speed to 12 knots (which it won't be, but magic), that gives a potential range of 525,600 nautical miles. Beyond five years I think the issues are that things are going to start breaking that can't be repaired, and the crew is probably going to start going wiggy. [Answer] In a constructed universe, you can cheat in ways that let you have the ocean be *much* smaller. If you have some undersea trench that (by whatever mechanism) pumps water from under the known islands through the core of the world and out the other side, there will be a constant current against any attempts to explore. If there are no winds (or minimal winds) over large stretches of the open ocean (for whatever reason), then you can hit a point where it's simply not possible to make realistic headway against the currents. You might be able to do somewhat better with decks of rowers, but at that point you start running into serious food supply issues. [Answer] If it's a pocket universe, perhaps it doesn't have the usual topology one might expect. So the sea might not be infinite in size, but might somehow "roll around" or "roll up" or have strange interconnections, that prevent a person from travelling from some points in the universe to other points in the universe, while staying within that universe. Or perhaps its metric (the thing that defines distance) isn't constant but shrinks further from the centre so it takes more and more time and effort to travel the next bit of distance. That's your infinite sea - and it will work, whatever time and resources are allowed, as long as travel (magic or not) is restricted to being within locally connected points in that universe. [Answer] They would not live long. They need fresh water to survive, unless they know to harvest rain water or process ocean water in the ship. For all life forms, this does not bode well. Also The vessel would disintegrate without any maintenance, for which land is required. Human hybrids with fish like gills can solve your problem. No need for a ship. ]

[Question] [ In my story I have paleolithic era humans who were contacted by aliens long enough ago for them to have used space travel to spread across many planets. I want them to be able to fly and somewhat maintain spaceships but not produce them. They are, however, still primitive and still live in caves with spears and bows and arrows. What relationship between aliens and early human society could result in this? [Answer] If you look at current autonomous drones, you could probably train your dog to fly them. So with the right automation, a cavemen could easily use a spaceship even without a concept for the stars. They´d just get a touchscreen with destinations to choose from, and upon pressing one, the ship would do the rest. Maintenance is a harder task. Maybe the ship has advanced robots for this also, but needs raw materials to be restocked? The Aliens could use the cavemen as exploration and/or as mining-crews, or to populate space. * Maybe they are themselves not so fertile and numerous to explore fast. * don´t care to spend all of their time in transit so they let the cavemen do the travelling. * want civilizations to spread across multiple planets to have some infrastructure when they travel there in a few 100 or 1000 years, and be received as gods. * Want to harvest the humans in the future. * Retrieve back the ships once they are loaded up with the desired resources by the cavemen [Answer] There is an inherent misunderstanding of the "cave man" concept. It is true that various groups through history have chosen to live in caves, but that is because caves were more convenient and better than other types of shelter for at least part of the year. Today, we have space travel and paleolithic cultures of the same species living side by side on the same planet. People from paleolithic cultures are no less intelligent than those from more technological cultures. In peru, for example, if is possible for your birth family to live a paleolithic lifestyle (more likely hunter gatherer) but yourself to be a brain surgeon. At that point it becomes a preference, often for independence and simple lifestyle. Like the brain surgeon in Arequipa, who visits his family on vacation and uses a stone tipped arrow to fetch a monkey for supper, the crew of the starship are all professionals who strip down and go paleo when on their own time. "Primitive" is a lifestyle choice, not a state of being. [Answer] If you're not stuck on the idea of spaceships, you could always play off the "Stargate" idea. In case you're unaware, Stargate was a sci-fi movie and television series where human explorers used ancient alien devices to travel between worlds. The titular Stargates would, when used properly, form stable wormholes between two Stargates which allow people to simply walk through them and be transported across the galaxy. Despite the fact that the main characters frequently discover human civilizations on other planets, and some of these civilizations are actually quite advanced, there is surprisingly little use of the Stargates by these other cultures. In terms of the show, this was likely done to make the main characters more special in that they are the ones exploring the galaxy. The other cultures can be forgiven for not achieving what the main characters do because there are various factors that make use of the Stargates both challenging and dangerous. And this is where you have the opportunity to do something completely different - by making the "Stargates" in your story *excessively* simple. Perhaps it could just be an alien structure that contains archways that look completely normal, but are actually a tear in space that connects to another world. I think what would make this reasonable for primitive peoples to make use of and not impact their development too much would be to first make the interface extremely simple or even non-existent, and second not have any hostile aliens occupying the planet network. [Answer] Cavemen are to aliens nothing more than goldfishes are to us. We took goldfishes long time ago from the place where they lived free, grew them into our water tanks and sold them around. So now you can have goldfishes in New York, Sydney, Amsterdam, Copenhagen and Monrovia. Apply the same concept to cavemen, and you have cavemen spreading around the galaxy, in places where they would not be able to reach on their own. [Answer] **Space Whales!** They domesticated a species of space-faring animal and use it to hop from planet to planet similar to current nomadic peoples (IE: Native Americans that lived on the great plains or Mongolians living on the Steppes.) OR, they didn't so much "domesticate" as "are parasites on", which would give you some interesting story dynamics such as the organism's immune response trying to kill them, overpopulation ultimately leading to the organism dying, or the organism deciding to leave a planet early before the people could all hop back on. [Answer] Okay I don't know about flying spaceships *and* living in caves but being *flown* in spaceships and living in caves is doable. Automated ships wouldn't require any particular input from the caveman crew/cargo, so they could transport cavemen without seriously contaminating their way of life. In fact if you're talking about a planetary population, or populations, that still live the primitive way then I'd like to point out that if a group of modern humans were scooped up in only what they stand up in and dumped on a hospitable planet elsewhere with zero equipment they'd be living in caves and using stone tools within a few days of arriving too, or they'd be dead. [Answer] Your alien civilization created an advanced AI that is capable of adapting. At first the cavemen were unable to use any alien tech. It looked different from the surroundings. Smooth surfaces, light colors, lights, etc. Naturally they thought of it as a god and started revering it. With time the AI learned the cavemen language. While the AI is not made to advance the cavemen it is not unwilling to help if asked. Eventually the AI controls ships towards stars the cavemen gestured in the sky. as for maintenance: While extremely unlikely the ships might be in need of materials/fuel that can be harvested in some form by hand. Or each ship has some exoskeletons that can be operated by humanoids. The cavemen follow the voice commands of their goddess(AI) to harvest fuel/spare parts as offerings. The amount of exoskeletons is limited and they are holy, so not everyone runs around in one but only the chosen ones. Since they can only maintain and not recreate they are stuck with spears and bows. They live in caves, because the ship is like a holy place. A place where you pray nothing you linger around. They might even be fearful of the AI's voice. Alternatively, the AI is not so benevolent, but it uses the cavemen as a form of tool. It trains them in the most basic knowledge they need and use them as a work force that acan biologically reproduce. That's easy to maintain and can be recreated with basic materials. Some chosen ones are injected nanobots that make them immortal and give the AI full control over their bodies. Those are the leaders and "avatars of the goddess". They are following the AIs plans to do whatever the aliens wanted. This includes traveling to other planets and creating outposts. They live in caves/use bows and spears because it is cheap. Personally I like the "biological tools" explanation more, that would imply that keeping them "stupid" makes them easier to be controlled. Nanobots are expensive after all... [Answer] Might be a cultural thing. Look at [predators](https://en.wikipedia.org/wiki/Predator_(franchise)), for example. They have FTL technology. FTL as we imagine it would require obscene amounts of energy, which could be directed towards comfort and hedonism. Yet they insist on spending their free time hunting animals in forests. Not seldomly they will forego using their high-tech weapons and will use spears. So maybe the humans involved are trained for starship maintenance (though the ship AI's will do the bulk of the maintenance themselves), but they think that by grabing their food by the horns and delivering the killing blow they might commune with nature and expletive. They might buy the ships from the aliens by trading furs, or the ships might be leftovers from a lost alien civilization (and plot twist: the aliens might be humans from the past). --- Alternatively, the ships themselves might be biological in nature. Look at the Zerg from Starcraft. They are even less advanced technologically than neanderthals, yet they are able to fly through space. [Answer] Maybe this all happened so long ago even the smallest traces of society have been wiped over by natural erosion, wind blowing sand, earthquakes, etc. At the peak of our society we did have alien contact as an intervention to the destruction of our own planet by... well, human means. The aliens and humans successfully made their exodus and relocated to a new and better world. Naturally, there are some who decided not to go. Left with a world in ruins, the population of earth gradually died off, leaving only those in the most remote of places. So few, in fact, that encountering another human would almost positively mean they spoke a different language, or killed you on sight to take your supplies. Earth was abandoned in a sea of ash covering the sky. The only living things were subterranean or in sheltered, controlled environments. They exist, but few and far between and nobody left a map for the remnants. If you came across it, it was purely by chance. As it happens, chance didn't happen for centuries. Maybe even millennia. Until the savage humans left touring the waste of a planet happened across a large pit far in the north where there used to be ice. An installation left in abandonment for technical reasons back in the exodus that were too complicated to repair, and so they were abandoned. After all these years left open, with the ice melted and nothing natural to cover the massive installation, a few of the people left on earth happened across a fleet of interstellar vehicles. Unguarded, and open for pillaging. For whatever reason, the issue that caused this installation to be abandoned is no longer a threat. Maybe massive electrical storms, maybe a system failure that triggered a pressure based safety fallback that forced the hanger hatch open 200 years later when the power source died. Who knows? These humans, now long past the concept of societal structure, exist by scavenging what they can from wherever they can since very little grows on the surface anymore. Essentially, cave men. Weapons and ammo are long gone. So they have their primitive weapons to guard them as they carefully approach a fleet of vessels that were prepared for liftoff. Some with doors wide open. Some crushed by environmental failures, but some of them still had enough reserves to power on when motion entered the door ways. GUI was advanced back in the day. Just a simple happenstance of a few hand gestures around the pilot console closed the doors, counted down, and plotted the course for rendesvous A. Several ships made it out. And now we have cave men traveling the stars in a ship they have no choice but to figure out. There's hydroponics. There's water. There's power reserves enough to keep them alive as long as they would naturally live. And to be fair, they are cavemen and savages by way of condition. This doesn't mean they're stupid or cannot speak. They know they have to figure it out. They want to go wherever the ship will take them. So they have a reason to learn the ship while staying calm, preserving their food source, and knowing they have only lived because of their savagery. [Answer] Our aliens used the cavemen the same way flocks of sheeps are used to clear plots of unwanted vegetation: for example to kill other large animals in a number of worlds the aliens are terraforming. The aliens set ships with very easy maintenance and prefixed routes. They are the hyper-subway taking cavemen from their residential cave complexes to their hunting workplaces. [Answer] > > What relationship between aliens and cavemen or caveman society could result in this? > > > A gruelingly intensive few hundred years of education and breeding of only the most intelligent members of multiple tribes. Remember that **20,000 years** ago, man was making primitive cave paintings, and it's taken that long to develop *Cat In The Hat* and `3x^2 - 4x + 5 = 0`. Cramming that into cavemen plucked straight out of the forest is unreasonable. [Answer] They domesticate a space-faring animal, the way that we domesticated horses long ago to travel long distances. [Answer] Made me think of Horizon Zero Down. The story is, basically, an earth populated by cultures that still use bows an spears, but living with auto-sufficient AI left by ancient humans cultures, that wander arround them as fauna. They 'hunt' thoses AI, use the scratch they can gather from them, and when one of those people found a device into ruins, she's able to figure out it's purpose and use it, though nobody taught her. This device provide her informations like topography or weather, that she's able to understand, because it's entirely composed of vocal messages, holograms and such clears user interfaces. After that she use others devices, more complex as she understand the logic of the conceptors of those devices [Answer] ## Bring the Command &Control interfaces down to their level Civilizations on a paleolithic level are theorized to know how to do certain things: Hunting, possibly fishing, basic sewing and maybe weaving, shaping of wood and bone and stone, gathering, and navigating by terrain and possibly by stars. Interfaces which replicate these actions would be the easiest to train them on. Logical progressions would be the next step. If a shaman or some other leader enters the "magic hut", settles all his folks in the "magic piles of fur ala beds", and then hops in the "magic canoe" in the "sacred room" and paddles to the next nearest "magic island"... lo and behold, they have just instructed a star ship to go from one star system to another. Mining or other operations might take the form of animal hunts, or hunting for valuable objects. Even communications could be filtered through a "magic window" or some such if translation was needed between various races. Might even be mistaken for various religious ceremonies over time. I imagine that alien devices would be VonNeumann style robotic units capable of self-replication as well as building new infrastructure in new locations, subject to the occasional command from the trained individuals. And, of course, there is always the possibility that any sufficiently advanced form of magic is indistinguishable from technology and they actually figured out a way to pull off interstellar travel without what we recognize as technology or alien intervention. [Answer] Okay, let's play with this concept a bit. "Cavemen" - apart from it being a very racist term, I mean, dude, if I was a Neanderthal I would be seriously offended; don't do that, pls - basically describes people living in conditions similar to the Paleolithic era. It says nothing about the world around them, as other commentators already pointed out: There are Stone Age cultures on Earth right now. But let's say it is a planet where really there are no advanced civilizations. Still, it doesn't mean that there wasn't one in the past, and it was destroyed. But it's also not really post-apo: There's abundance of greenery, the world is flourishing with life, and there's still a lot of self-replicating, self-maintaining technology, powered by renewable energy sources. Only that it's just lying around doing nothing, because there's no one to operate it anymore. But there are cavemen. Descendants of the people who created that technology. They don't remember their history, they know nothing about science, and they treat these technological artifacts as magic and gods. Fortunately for them Graphical User Interfaces of these artifacts were made to be idiot-proof. A shaman of one of the tribes figured out at some point that if you do certain moves, touch screens in right ways in right times - basically, if you perform a ritual correctly - then the artifact will do something useful. This dark, deep knowledge was then passed through generations and developed upon. So, after hundreds of years, shamans of this tribe are actually able to launch a small space shuttle into the orbit and come back alive. And then, with another hundreds of years maybe, if the GUI is really well designed, they will be able to perform magic spell which will put them in a long, cold, sleep and make them travel to other planets, still without knowing what is really going on. [Answer] A variant of *Spherical Regression* as described in Piers Anthony's [*Cluster* series of novels](https://en.wikipedia.org/wiki/Cluster_(novels)) might be helpful. In *Cluster*, colonisation spreads in spheres, outward from the home system (Earth/Sol for the most part, although there other spheres described). Travel outward from the centre takes three forms: * **Teleportation** (or *mattermission*): instant but prohibitively expensive for loads of any size. Mostly only used for data transmission, if I remember correctly. * **Freezer Ships**: cryonically frozen crew on auto-pilot take decades to reach the outer edges. The downside is that half the ships are lost due to failures in the containment units or the ships themselves. * **Lifeships**: slower, safer, but controlled (and, to some extent, repaired) by a living (and reproducing) crew who will go through several generations before reaching their destination. This last form is used for the bulk of a planet's colonisation, at the cost of "technical regression" by the end of the journey. (There is also **Kirlian Transfer** – the ability to transfer a person's aura/soul by a variant of mattermission – but while this is central to the series, and can keep *knowledge* up to date on an outlying planet, it doesn't really affect the process of spherical regression). With slightly contrived, but fairly plausible reasoning, Anthony argues that the combination of technical regression over the long journeys, plus the inability to ship materials often needed to maintain "modern" technology in any quantity mean that the further you go from the centre, the less technology the inhabitants of a planet will use. In the extreme, the inhabitants of *Outworld*, Sol's furthest colony, are palaeolithic, hunting with flint spears but not much else. (For the most part, it's not that they aren't *aware* of higher technology, but being so distant, they aren't able to *maintain the use* of such technology). In *Cluster* (as far as I can remember), the outward-lying colonists no longer have use of the ships that took them there. However, it should be possible to adapt his argument so that while day-to-day technology has regressed, the ships can still be used – perhaps advances in self-repair mean that the ships remain viable for long periods, but the colonists don't have enough technology (or the raw materials to maintain that technology) to use in their everyday lives. I can't remember whether the ability to teleport, or send freezer-/life-ships was discovered "naturally", or kick-started by aliens: as far as spherical regression is concerned, it doesn't really matter. [Answer] Something akin to War of the Worlds, where the aliens took several tribes of humans, and then unknowingly exposed themselves to an (inert to Humans) virus or bacteria that ends up killing the aliens Or have the Cave men attack the aliens, they were overconfident in their tech and the didn't see the cave men as a real threat until it was too late, although this is more of an "Alien Invasion" trope you could easily add into the mix, that the aliens weapons are similar in design to say Stargate, Staff weapons, the tribes men perhaps were unable to figure out how to make the energy weapon fire, but can use it successfully as a staff, they would already have bow and arrow. in terms of the figuring out the ship that is the hard part, if modern humans were shown say: Star Trek's USS Enterprise and found themselves on the bridge, then they could figure out the very basics of flying it from having see enough similar shows even if they hadn't ever seen the show before. however just 50 years ago that probably would have been unlikely, some but not all, 100 years and very few would have, due to fewer and fewer points of reference The primitive tribe would have no basis for understanding that pushing something inside the ship would make the entire ship move, this could be solved by say a holographic training designed for the alien kids (therefore no weapons) system taught them the basics, or maybe the ship is AI controlled, and simply doesn't care who is in charge of the ship, or it simply sees that the aleins gone mean these humans will die so the AI helps them. Modern humans would be able to figure out how to fly an alien ship **IF** the design was for bipedal humanoids, being that the basics for the design of the bridge would *most likely* be similar to something we would except, however we would only be able to build one ourselves if we have the entire resources of earth to do so, not just a single tribe [Answer] No way. A screwdriver like the ones they need to operate to do basic maintenance of the ship is a better weapon than anything the cavemen had. The minimal knowledge needed to fly a spaceship, let alone to maintain, as well as the spacehip itself would provide the cavemen with enough ideas, know-how and materials to improve its civilization level to bronze-age at the very least. Remember: they lived in caves and hunted with crude fire-hardened spears because they didn't know any better, not because they were stupid. Show them a better way and they will learn quickly. [Answer] How should we know what a future technology might even look like? Here's an answer inspired by popular culture - you could describe standing stones on hilltops as ancient star-gate devices which became abandoned by some alien culture and then were appropriated by cavemen to populate different planets... Bonuses - no maintenance or technical skill required, no language skills needed - cavemen and animals could literally get teleported by accident if they are in the right place at the right time - fits in with the landscape so well you wouldn't even suspect it, you could write in a possible connection between summer solstice and some kind of universal GPS. The one thing this doesn't answer is the flying about part. [Answer] The aliens could have trained the primitive humans to maintain the ships, and if the ships in question are well enough engineered, the humans are essentially along for the ride. This reminds me of Arthur C. Clarke's "Rendezvous with Rama" series of books. [Answer] In Terry Pratchett's *Long Earth* humans have the ability to step through dimensions to alternate Earths if they are in the right frame of mind. The ability was discovered by accident, and it is implied that people had been doing it accidentally since paleolithic times. You could use a similar plot device. Maybe staring into a fire in a trance and going to sleep leads to your humans occasionally waking up in a cave somewhere else in the universe. Aliens may have given paleolithic humans a DNA altering virus that allowed them to use their minds to open wormhole tunnels to suitable habitable planets - but over time the exact trigger was forgotten and it now happens rarely if at all. (Maybe all those missing persons presumed murdered triggered this ability) [Answer] If you look at a certain species of cricket or locust like insect (the specific name eludes me, but I will update if I can find it), it is completely capable of being totally frozen and coming back to life when it thaws out. So, if you will pass that it is not totally inconceivable for humans to survive being deeply frozen, I will submit the following as being almost plausible, although, not without issues. A super-large, high speed, near-miss asteroid creates a catastrophic wind and simultaneous gravity anomaly flinging several humans off. Because of the combination of unimaginable wind and the gravity anomaly (near miss with planet Nibiru) the humans are flung out of Earth's gravity, past orbit and out into space. This alone could not get the humans out of the solar system, but it could distribute them within it. Given time their mass would accumulate space dust. It is nearly, nearly, nearly believable until re-entry. Suppose in an intricate and almost fantastical way they accumulate a *lot* of ice (perhaps a lot of water was swept off of the Earth as well?) then perhaps they could survive re-entry to a planet with an extremely thin atmosphere if they landed in water. *Mars*. It is not totally certain that they would be pounded into abysmal dust if landing into water. On Mars they learn to grok and you have the alternate pre-lude to an existing series. [Answer] *Stargate*, biological version: Some alien made a synthetic lifeform. It's method of spreading it's seeds is a stargate. While it does make fruit it's contained within the plant, not available for eating. It grows a bunch of fruit (which is extremely long-lasting) and then builds a stargate around it. If it manages to complete the gate it's last act is to activate it. Unlike the TV show this stargate isn't controllable. All the mass drawn into the gate is flung to random locations but subject to energy balance requirements: 1) The air pressure at both ends of the gate must be similar. 2) The two locations must be at similar depths of the local gravity well. 3) The two locations must be at similar depths of the overall gravity well. Each object drawn in is flung to it's own random location, but "object" is loosely defined--a group of people holding onto each other solidly will be one object for this definition. Some cavemen from Earth were investigating a gate plant when the gate fired and were drawn through. (As the gate triggered they grabbed onto each other in fear, this caused them to be thrown to the same location.) They were in a bad way where they came from (game hunted out, bad weather), they arrived in a new land with good weather and no competition. (Remember, plants and animals can be drawn through also, the galaxy will be colonized by the same sort of life, it will mostly be edible.) Thus was born the legend of the gate plant transporting people to heaven. Over time this has been refined as they have learned how to prod a gate plant that is almost ready to fire. When conditions are bad groups sometimes seek out a gate plant as a method of escape. Note that while the energy balance rules ensure you arrive at a planet with an atmosphere they by no means guarantee it's habitable--most voyages actually result in a very quick death. Since there's no return nobody knows this, though, the legends only tell of the past which inherently is the jumps that worked. [Answer] Why do you need aliens? Your “cavemen” might have once had the technology to get to the planet, but crash-landed, ruining their high-tech toys. A few hundred years later, they would only have mythical remembrance of their technology. Being a caveman isn’t being stupid. If you were stranded on a deserted island, you would become a caveman overnight. [Answer] "Gronk, I'm going to destroy this world with a flood. I want you to build an ark. Get two of every animal...." Then the aliens just transport Gronk's ark. [Answer] I really find it hard to imagine that the caveman of the "paleolithic" age will actually know how to operate something as advanced as a spaceship? As defined [here](https://www.merriam-webster.com/dictionary/Paleolithic) these guys only know how to use rocks, and before we could even go to space, it took us a lot of years to do so. **A LOT**. It seems like most people here agree that someone in that age or era will actually learn how to operate something as advanced as a spaceship without any help whatsoever, and will eventually learn it with just the use of manuals? I'm a computer scientist, I have created systems and I will proudly tell you guys I cannot fly a plane even with a user's manual, I will actually need help from someone to teach me how to fly a plane, and learn from them on how to maintain that plane. Another example can a severely secluded ethnic tribesman who was born and lived for 80 years in the forest, use a **TOUCH SCREEN** cellphone? Now tell me, how in the world can a caveman of "paleolithic" age fly a ship? The most logical reason that comes to my mind is that, the cavemen will be held either as lab rats, carried to other planets by means of "bait", and flown through space through "space cages" so that the aliens can use the cavemen as cattle, reproduction, slaves or research purposes. In this scenario, the aliens are indirectly helping them to fly their own spaceships, but the controls are being used by the aliens, why? for some reason that these guys only knows how to use rocks. Now some of you will say that If these cavemen are taught, then they will know how to use the tools around them right, which is basically right, but the OP actually stated that "`How can paleolithic humans colonise the stars without direct help from aliens and still be primitive?`" and teaching something, is already a direct help. Colonizing is another thing, the cavemen may colonize a planet if left alone since they will eventually reproduce, but to colonize the stars, these humans need to learn from their abductors about the technology which they use, since these aliens technology is more advanced than ours(we can travel in space but up to just what extent right?). It might take them more than a millennium to learn how to use the alien tech for interstellar flights, but that is **IF** they will **not be taught** on how to use them. Again, teaching them, in any way, is a direct way of helping the cavemen. [Answer] I seem to recall a movie and long running television series that was all about this topic... what was it again? Oh, now I remember... [Stargate!](https://en.wikipedia.org/wiki/Stargate) [](https://i.stack.imgur.com/RW5MS.jpg) Who needs ships when you can just walk through a portal? ]

[Question] [ Set in the modern day; fairies are tennis ball sized humanoids with wings residing within the dense rainforest throughout the world. Local human populations consider them to be guardians protecting the sacred forest and its inhabitants. A lot of people have been venturing into the rainforest equipped with digital cameras hoping to snap an image of the elusive being without any success. How do the fairies do it? They are as intelligent as us but never developed electronics or any technology which could pollute or harm the forest. Please use magic sparingly. [Answer] **They paint their wings like giant butterflies** Rainforests house many colorful butteflies, some with wingspans of 4-5 inches. With painted wings and carefully chosen clothes and a bit of bodypaint, fairies can be difficult to tell from real butterflies at a distance of more than a few feet. [](https://i.stack.imgur.com/7pNkI.jpg) [](https://i.stack.imgur.com/iN5Ej.jpg) [](https://i.stack.imgur.com/GPMcH.jpg) [](https://i.stack.imgur.com/uuxbp.jpg) [](https://i.stack.imgur.com/2AmhW.jpg) [](https://i.stack.imgur.com/0wF8V.jpg) [](https://i.stack.imgur.com/MRFwq.jpg) [Answer] **They're not stupid.** They see the humans enter the forest and avoid them. They see the cameras left behind and avoid them. It's hard to photograph something actively avoiding you. [Answer] ## Fairies are just hyper-intelligent butterflies They are have two powers, telepathy and telekinesis. The first lets them Glamour themselves to look like versions of whatever is viewing them. If dogs could talk, they'd tell you that fairies look like very tiny dogs with butterfly wings. This is a defense mechanism as most animals have a "cute" reaction to smaller versions of themselves. Telekinesis, on the other hand, lets them manipulate items that their butterfly legs wouldn't on their own. So why don't cameras take pictures of fairies? They do, it's just that they capture their true form, rather than mental interpretation that we humans see. [Answer] Speaking as one who has been birding in a number of dense rainforest environments, the only way you ever see something that small and fast is if it is not trying to avoid being seen. I'm a big fan of hummingbirds, and realistically you only get to see them around feeders. Otherwise all you get is something whizzing by, impossible to photograph. [](https://i.stack.imgur.com/8Y5CB.jpg) Even birds which make quite a racket are often completely invisible in the canopy. You can spend literally hours looking for something up there and never get a peek. Any fairy with hearing is going to avoid camera-wielding humans without difficulty. Their only problem will be if people know where they feed and wait for them. [Answer] ## Government Conspiracy This one only works if you are also using the Urban Fantasy trope where the government hides the existence of supernatural creatures. Similar to how governments prevent the photocopying of money, when a digital camera captures the picture of a supernatural creature, government mandated object recognition software kicks in and either removes the creature, makes it blurry, or changes it to something else. [Answer] **They're really good at hiding** There's no reason to look for a complex answer when a simple one suffices. Fairies are very attuned to the forest, and can always tell when a clumsy human is bumbling through the forest looking for them, at which point they just hide in places that human unfamiliar with the wood can't find them. [Answer] There are a lot of real-life creatures of this size or larger which are almost impossible to photograph simply because they're very shy. In such an environment you don't need amazing hiding skills, you just go into a bush or under some leaves or up into the canopy and you will be virtually invisible if you don't move. And the noise humans make gives you plenty of time *to* hide with such poor line of sight. That said it's unclear if these creatures in your world are hard to spot, or just hard to photograph? Rapid, erratic flight would make getting a conclusive shot very difficult especially in a forest and they'd be very easily mistaken for birds. [Answer] **They camouflage very well** By leaving for so many years among the trees, their body and wings adapted to be able to camouflage very well, just like some butterfly do : <https://en.wikipedia.org/wiki/Kallima_inachus> Being smarter than butterflies, as you said they have human intelligence, they can make the most of such camouflage. You can also add that they have one of the best hearing in the animal world, be able to hear humans entering the forest way before they could even notice them. [Answer] Well, rainforests are visually "busy" places, like a "Where's Waldo" picture, but mostly in shades of green and brown. So if fairies are green and brown, or dress in all green and brown, and you factor in their small size, they're not likely to be noticed in photos unless they're very close to the camera. To take this a step further, they could develop "stealth" clothing made from spiderwebs and dewdrops, which causes a scattering and refraction of light around them. This would "fuzz" their appearance, making them appear to take on the colours of their surroundings, and also creating indistinct edges for their form/silhouette. Their stealth clothing might actually be a liability in full sunlight, making them glimmer and glint in an otherwise empty sky, but in the speckled lighting under the rainforest's canopy, it would be nearly impossible to distinguish them from their surroundings. [Answer] Fairies are literally less than 3 dimensional, so if they figure out there are cameras or people in the area they just turn sideways enough to disappear. [Answer] Fairies are creatures of the psychic world. While able to interact with the physical world, they do not have an actual physically visible form. Seeing a fairy is a result of their psychic interaction with the visual cortex of a nearby brain, inserting them into the visual information coming in from the eyes. [Answer] # Fairies are really translucent Locals have learned to revere the *voices-in-the-trees* that talk to them and levitate objects and consider them as their protectors, but since they are inherently transparent to most wavelengths, no-one has ever seen or photographed one. If you google "translucent animal" you can find results such as this : [](https://i.stack.imgur.com/fFoFZ.jpg) Now imagine your fairies evolved to take that even a bit further and voilà ! Maybe if they sit still and you focus really hard you can see their outline, but that's it. [Answer] # They can shine so bright that they blind&damage cameras Your question reminded me of cyberpunk-style anti-surveillance wear, in particular a project dubbed [camo-flash](https://ahprojects.com/camoflash/). It boils down to a device that can shine *very* bright, enough to blind the CCD sensors of a camera, in response to a bright light (the flash of a camera). [](https://i.stack.imgur.com/SuZHK.gif) (source: [ahprojects.com](https://ahprojects.com/assets/img/projects/camoflash/anti-paparazzi-clutch.gif)) The fairies could wear cloaks made of e.g. a symbiotic photosensitive/photoemmisive algae displaying this behavior - it's a natural defense mechanism evolved somewhere in fairy world and fairies adapted it. Or their skin could shine at will, and the counter-flash is a [reflex action](https://en.wikipedia.org/wiki/Reflex). If they could focus this light source well enough (up to the point of creating something as powerful as current green handheld lasers), they would be destroying cameras [CCD damage from laser](https://web.archive.org/web/20161221174341/http://www.laserist.org/camera-sensor-damage-thesis.htm) is [not pretty](https://photographybay.com/2011/07/09/warning-keep-your-dslr-away-from-lasers/). After a camera has been damaged, horizontal or vertical lines will appear in any photographs: [](https://i.stack.imgur.com/IEigJ.png) If they can damage (expensive) cameras, that would give those pesky humans a reason to stay home and not try to photograph them. There would be some lucky one able to snap an out-of-focus, my-camera-is-almost-dead photo in extraordinary situations. [Answer] **The shutter sound makes them twitch** Whenever they hear the sound of the shutter, they twitch by reflex (inherited from long ago when they were pray to a clicking snake). The twitch is faster than the shutter speed so that they always move out of the picture. They also hang out in the bright sun, where photographers use shorter exposure time, so there is no time for them to fly back into the picture before the shutter closes. If the exposure time is long enough for them to do that, the picture becomes way to bright to see anything anyway. *Why don't the photographer use a silent camera?* Because they don't know that fairies exist, so they don't know that there would be anything to take a picture of. Only professional photographers journey that far into the forest, and they bring those big expensive cameras where the click sound is part of the user experience. *Wouldn't fairies fly very far if the camera is distant?* The forest is so thick, that if the camera is say twenty meters away, they would end up behind bushes and leafs anyway. If they are so far away that they don't hear the camera, they end up too tiny on the picture for anyone to see them. [Answer] I wanted to expand on a comment made by another user: In the Artemis Fowl series, faeries are a group of HIGHLY advanced subterranean species, employing a combination of magic and technology to stay hidden. Their basic way to hide is their "shield", where they raise their heart rate and start vibrating fast enough to go invisible. They also have 2 varieties of highly advanced technological cloaking devices: Camfoil, either a sheet covered in tiny cameras or a sheet made of diamonds depending on the version, which makes you invisible to normal light; and Stealth Ore, a special metal that is invisible to electrical equipment, including cameras. So you can simply say that all fairies wear special hi-tech clothing that makes them invisible to cameras. [Answer] Fairies branched off from chameleon ancestors and as such, have chameleon-like camouflage abilities. Heightened senses and flight allows them to escape before being caught. [Answer] **Infrared** Fairies are mysterious little creatures made from infrared light which cannot be detected by the human eye, so we can "Never" see them, even though they are around all the time. Digital cameras however can detect infrared. Fairies, being the creative little rascals they are, knows this very well, so they are able to change their light spectrum to a range that is unknown to humans. Therefore we cannot build a camera that can capture their images without knowing the spectrum they shift to. There is an upside however. There is a rumor going around that when a fairy sleeps they are visible to the human eye because they switch of their special lighting features to conserve energy. Problem is, fairies apparently never sleep. [Answer] Fairies are not things existing in reality...they only exist in the perception of the observer...and their actions are actually performed by the person 'seeing' them'. Unique virus/parasite? Oddly intense but transitory psychosis as a result of the former? ]

[Question] [ There is a surprisingly diverse range of handheld weapons for use in combat, beyond the typical gun-related firearms. I'm looking for a cooler way to destroy enemies, and though flamethrowers are interesting, I'd like to not incinerate people, but *liquefy* them. The requirements: * The weapon must be handheld, though relevant support equipment can be carried (e.g. a flamethrower has fuel tanks). * The weapon must turn enemies into . . . well, something rather liquid-y. * The weapon must be built using today's technology. * The weapon must liquefy a person in less than one minute. So, how can I liquefy my enemies? --- I should have explained the backstory here, and the reason why I need this weapon to do what it does. In this particular world, the folks in power want to harvest as much genetic material as possible from the population. Liquefying someone makes it easy to get an arbitrarily large amount of material from a (dead) person, while leaving the rest to be disposed of somehow. Some of the methods here will damage genetic material, certainly. But there will still be *some* material left, so those ideas are fine. [Answer] # Fluoroantimonic acid (HSbF6) gun Fluoroantimonic acid is a colorless super acid (Looks just like water!), even more corrosive than sulfuric acid. Fluoroantimonic acid is 2×10^19 (20 quintillion) times stronger than 100% sulfuric acid. Fluoroantimonic acid has a H0 (Hammett acidity function) value of -31.3. It dissolves glass and many other materials and protonates nearly all organic compounds (such as everything in your body). This acid is stored in PTFE (polytetrafluoroethylene) containers. Basically, the only thing this doesn't melt is teflon. I'm not 100% sure this will satisfy your 1 minute requirement but this stuff is so strong it probably will. In order to weaponize this, we use PTFE to build a watergun - make sure this watergun is VERY well designed. (Teflon coated gloves recommended while using this weapon). It's as simple as that. As an added bonus, since you're building a squirt gun it won't look like a weapon till it's too late. Your enemies will laugh at you when you whip out your watergun until the stream of acid hits them - then you get to watch them burn... and melt... Might I suggest choosing a supersoaker as a frame for the design? You can use carry extra "acid packs" for easy reloading. These acid packs also make for great multipurpose tools - if you need to cut a hole through the roof, draw a circle using the acid and let it do its magic! Alternatively, you can put up buckets of this stuff on top of doors, and wait for your enemies to open the door - classic prank style! Or, acid spray frisbees. Simply have a spinning object that you throw out while you duck behind cover, and let the liquid stored in the center propagate outwards via centrifugal force. Have a timer that's hooked up to a button (maybe .5 second delay) that opens the sides of the disk to allow the liquid through. Carry these like grenades. Reference: <http://chemistry.about.com/od/acids/f/What-Is-The-World-S-Strongest-Superacid.htm> [Answer] This weapon already exists. It's called a **Rocket Propelled Grenade**. There is no way to use acid or lasers to melt a person and their bones in under 60 seconds. The thing about the human body is, it's already mostly liquid, you just need to destroy all the bits holding that liquid in. A rocket propelled grenade (RPG) is a high explosive attached to a rocket. The high explosive will shred, break, and disintegrate all the solid bits of the person you fire it at. They will be, for all intents and purposes, *liquified*. Just because a liquid has been spread over 50 square meters does not mean it is not still a liquid. [Answer] ## **Ultrasonic Gun** It's well known that with the correct frequency applied that sound, and sound alone can shatter a wine glass. These demonstrations are always spectacular, so let's build a weapon on the same principle. **Assumptions** Since we are working with sound, above a certain threshold, a sound wave will just pulverize the target. The CDC lists [10psi of overpressure](http://www.cdc.gov/niosh/docket/archive/pdfs/NIOSH-125/125-ExplosionsandRefugeChambers.pdf) as > > Most people are killed > > > so let's use that as our upper bound for power requirements for this weapon since we want to liquify the person, not instantly pulverize them. Further, we assume that we can overcome the high natural elasticity of skin to cause it to liquify. **Safety Concerns** The OP states that this will be human mounted weapon so safety precautions need to be made to ensure the weapon carrier doesn't get liquified too. While ultrasound is still sound, it is "aim-able" in that pointing the ultrasonic transducer sends sound in that direction and not anywhere else. As long as the weapon bearer isn't "looking down the barrel" then they should be okay. **Power Requirements** The 10psi overpressure threshold set out in the Assumption section is 700 times the [limits of human hearing](https://en.wikipedia.org/wiki/Orders_of_magnitude_(pressure)) (130db). Speakers that generate 110db of sound often require thousands of watts. Granted, the energy from normal speakers is spread across a much wider area than an ultrasonic transducer would but I think that sets a decent lower bound on the power requirements for this this weapon. Given that also don't know the power requirements to achieve destructive resonance in human tissues, the power supply may be asked to provide megawatts of power but since we don't know how much power it takes to liquify human flesh, let's just hand-wave and call it good. Regular speakers just don't have the [power output required](http://www.therichest.com/business/technology/the-10-loudest-speakers-and-subwoofers-in-the-world/) or the directionality that we want, so let's go with ultrasonic transducers. Let us assume that a megawatt class ultrasonic transducer can be created and matched to adequate heat dissipation tech. **Frequency Requirements** There is [no one frequency](http://www.ncbi.nlm.nih.gov/pubmed/8176050) that the human body resonates at, or perhaps there is but the power requirements to do so amount to getting hit by the blast wave of high explosives. At a minimum, you only need to know two frequencies: muscle and skin to count as "liquifying the target". Muscle alone will just make the target fallover. Skin alone just make the target look naked. This leaves the horrifying prospect that the brain are still intact but the target's body is liquifying. If the nerve endings are still functional then.....Death shortly follows but looking down to watch your body turning to liquid.....that's nightmare fuel. Killing someone may not be as effective as just maiming them by liquifying their skin. Wounded soldiers take significantly more resources to treat/transport than a dead soldier. **Time for Effect** I have no numbers but I think the effects would happen very quickly, just a few seconds. This makes it an effective battlefield weapon because you can't expect a target to stay still for a minute or so. **Weapon Design** Since an ultrasonic transducer by definition emits sound at greater than 20Khz, we will need a second transducer to use interference to generate the target frequency. Both transducers can be fitted to a gun-like mount linked to the power supply backpack. Heat dissipation from the power source and the transducers will be important considerations. Add a control to allow the weapon carrier to select a target frequency with some presets for skin, bone, etc. However, access to the raw frequency permits the carrier to experiment with finding the frequency for stone or metal. [Answer] Pesky door-to-door salesmen keep calling? Can't get those neighbours to stop asking for sugar? Really not looking to join a religion right now? For dealing with all your unwanted guests we present the "blend-o-matic" 2020: [](https://i.stack.imgur.com/atjVX.png) No, not like that, like this: [](https://i.stack.imgur.com/1h35Q.jpg) Your unwanted guests will drop through the carefully disguised trapdoor and be liquidized before you know it. The environmentally friendly option to dispose of unwanted callers, you can fertilize your roses with the remains! Ok, I admit - that's not hand held. The idea just popped into my head though. :) [Answer] **Bolas made of C4** [](https://i.stack.imgur.com/rNBqu.png) Pull the detonator pin, throw it so it wraps around the enemy, and watch as they are turned into a fine mist. As an added bonus you can kill or injure anyone close to the target. [Answer] If you don't need to go to far into immediate hard science, but more fiction (you question has no science tag): **Nanobot Swarm Weapons** To liquify you enemy you need to destroy enough tissue, which is basically liquid filled (cells are mostly liquids surrounded by a membrane). If you manage to do this, your enemy will be "melting". Therefore carry a weapon releasing a swarm of millions of microscopic nanobots destroying your enemy's tissue. The nanobots could be powered by your launcher, or refill their energy by partly digesting the broken tissue. After a successful attack or a predefined time, the nanobots could disassemble to avoid any further harm. Depending on what effect you desire, the nanobots could work on soft tissue only (skin and flesh), or be more rigorous (skin, flesh and bones). If you like, you could even give them some swarm intelligence: Harm only the one I pointed my weapon at, harm only enemies,... Speed and looks of your launcher are pretty arbitrary, you could choose here whatever you like... Disintegrating a body in subsecond scale or over hours, launching your nanobots from a pistol, a trap or a bottle - everything might work. [Answer] The best chemical I could find for the job comes from an [answer on Chemistry.SE](https://chemistry.stackexchange.com/a/4915/16432) by @KeithS *(emphasis mine)* > > The standard body-dissolving chemical is lye aka **sodium hydroxide**. The main source is drain clog remover, because most drain clogs are formed by hair and other bio-gunk that accumulates naturally when humans shower, exfoliate etc. It works, even though the body's overall chemistry is slightly to the basic side of neutral (about 7.35-7.4), because the hydroxide anion is a strong proton acceptor. That means that it **strips hydrogen atoms off of organic molecules to form water (alkaline hydrolysis, aka saponification)**, and as a result, those organic molecules are turned into simpler molecules with lower melting points (triglycerides are turned into fatty acids, saturated fats are dehydrogenated to form unsaturated fats, alkanes become alcohols, etc). Sodium hydroxide is also a ready source of the sodium ion; sodium salts are always water-soluble (at least I can't think of a single one that isn't). **The resulting compounds are thus either liquids or water-soluble alcohols and salts, which flush down the drain.** What's left is the brittle, insoluble calcium "shell" of the skeleton; if hydrolyzed by sodium hydroxide, the resulting calcium hydroxide ("slaked lime") won't dissolve completely but is relatively easy to clean up. > > > Further research into [Alkaline hydrolysis](https://en.wikipedia.org/wiki/Alkaline_hydrolysis_(death_custom)) seems to indicate that it could dissolve a body in the matter of hours. However, I don't believe it could be made into some sort of hand-sized weapon that works within that timeframe. This is because the body is immersed in the chemical, pressurized, and heated. --- Unless your handheld weapons can somehow create pressurized, heated fields of space around your targets and then introduce a bunch of sodium hydroxide into the field - you probably won't be able to rely on chemicals alone to turn your enemies to goo. [Answer] If the point of the exercise is to extract genetic material from the resulting pool of human, then most, or all, of the chemical attacks listed here will be of little use. In the process of turning your human into a pool of liquid you will have destroyed most of the genetic material contained in said human. Your best solutions are going to be mechanical, or possibly biological, in nature. None of the mechanical options, except nanobot swarms or sound waves are going to be hand held and any biological, i.e. viral/bacterial/prion, are going to take way more than a minute. [Answer] Railgun. There's no better proof that organic matter has a high water content than watching high-speed film of bullets entering fruit. The fruit literally explodes. All that's needed to do the same to a human is to up the energy and the rate of fire. The movie *Elysium* does this when the main character gets ahold of a "Chemrail" rifle (the name likely referring to some hybrid of chemical and magrail propulsion of the projectile). The weapon, firing hypersonic 20mm bullets, disintegrates one of the bad guys from the other side of a bulkhead wall of the space station. Such a weapon would likely need augmented strength to control its recoil, either using a ground anchor (bipod/tripod) or a powered exoskeleton as was used in Elysium. In a fictional universe that would be an easy handwave, as would the fact that the real world doesn't have a man-portable railgun (current technology is working toward a weapon that could fit inside a naval cruiser hull). [Answer] I propose using a device that will produce an extremely strong magnetic field. Fields in excess of $10^5$ Tesla ($10^9$ Gauss) [will instantly kill people](http://solomon.as.utexas.edu/magnetar.html#Strong_Magnetic_Fields): > > Fields in excess of $10^9$ Gauss, however, would be instantly lethal. Such fields strongly distort atoms, compressing atomic electron clouds into cigar shapes, with the long axis aligned with the field, thus rendering the chemistry of life impossible. > > > People killed in this way will have become one big liquid mess, because most of the body consist of water while everything is kept in place using the larger molecules which are not stable and prone to falling apart outside of living organisms. [Answer] I can think of two ways off the top of my head. 1. a large injection of the active piece in spider venom that liquefies the preys insides so it can suck them out like a slurpy. (after adding in the 1 minute time frame this one is much less likely) 2. A sound wave weapon that can breakdown bonds in the body. Some frequencies might resonate with bones, shattering them. High frequencies can disrupt a lot of things in the human body. Might even be able to make your brains run out your ears. Distance would need to be fairly close for best application. Too close and too much power and they might explode like a water balloon (a hotdog in a microwave), and you might get some on you... [Answer] Here's a couple of potentials: **1: Large doses of radiation** Ok, this is pushing the definitions of 'liquefy' and will actually very quickly move into the realms of 'just burn them to death', but a suitably epic dose of radiation (We're talking obscene levels of radiation here. Sort of the 'stand next to a solar flare while touching the sun' levels) will basically cause enough massive damage to an opponents cells that they're reduced to a molten goop. Of course that same epic dose of radiation will cause all sorts of other havoc, notably setting fire to the goop. Oh, and it'll effectively be a 1 shot. **2: Disease** Good for large populations, bad for easily controllable. A couple of vials of engineered, airborne flesh eating virus will reduce a city to bones and goo in short order. Not particularly 'cool' though. More 'icky' **3: Sound** It's only even vaguely possible with some physical science handwaving, but extremely high frequency, high amplitude, very well designed directional speakers could potentially cause the kind of massive trauma injuries usually seen in car crashes. IE: your kidneys turn to soup, but you don't realise it until a little bit later. Could lead to interesting consequences in the case of a headshot, but I'm not sure you could get the design down small enough to be considered handheld. Some examples of this are already used in a crowd-control capacity (obviously without the soup-making) **4: Acid** I feel this is a bit cliché, but an acid (or alkali) thrower could cause some very nasty liquification. Side effects include but aren't limited to: Spontaneous valve malfunction, noxious vapours, spontaneous combustion when exposed to other elements, and worst of all: splashback. Goo(d) hunting! [Answer] Liquefying the bones is a problem without corrosive chemicals and they would take time to eat through the body. I suggest a powerful laser. It auto-detects the shape of the victim and scans back and forth creating incredibly thin slices. For a fraction of a second the victim will continue to stand upright as though not sliced. However the body's own enzymes will immediately start to digest all tissues (a form of [apoptosis](http://www.indepthinfo.com/biology/apoptosis.htm)) . The body will slump and form a pool on the ground. There may be some solids left but they will be very finely sliced like a specimen for a microscope slide and so have little strength. [Answer] You don't ask for science in your tags. I suggest a very powerful vacuum cleaner. You suck the enemy through a small nozzle and collect them in the extra-large waterproof bag. To avoid the nozzle getting clogged you must force them at gunpoint to remove all clothing before being sucked. Unfortunately the bones would remain and would have to be dissolved in acid. [Answer] I think the fastest way to reduce a human to a liquidy mess would be to pop them like a balloon. A gun firing a high-pressure hose containing any flowing liquid would do it, but perhaps the liquid of choice would be the Fluoroantimonic acid mentioned in another answer - dissolve the insides of your enemy in the few seconds they are expanding. Just remember to wear protective clothing - it's gonna be messy. [Answer] ## Lasers It is simple. You carry around huge lasers. Sure, it will first turn them to ash, but then you melt\* the ash, and know you enemy is liquified. --- \*For some reason, I couldnn't find what its melting point was. [Answer] Give aging prop-comic Gallagher a call and he can bring you a...*SLEDGE-O-MATIC* Ok, he's gonna have to call the factory for an oversized, mech-mounted one, but one shot from huge hammer should pretty much liquify anything it hits on it's way to the ground. Bones will get shattered into bits and everything else is pulped. no chemicals or heat to destroy genetic material. If it's big enough to require a mech, it's not technically handheld, but it would be in the hands of a mech...so I could make a (feeble) argument for it's validity In all honesty, mechanical means of rendering a human down to liquid are going to be faster than chemical methods ]

[Question] [ The United States (as well as many other countries) is covered in a vast network of tubes: [](https://i.stack.imgur.com/ceSpI.png) These tubes vary greatly in diameter. Some could hardly fit a baseball, while others are large enough to comfortably fit a prone human. [](https://i.stack.imgur.com/dFVrA.jpg) [](https://i.stack.imgur.com/XGkFS.jpg) In a future world of renewable energy, where this natural gas infrastructure is no longer needed for fuel transportation, how could these tubes be repurposed? If your proposal requires pipelines to have a certain diameter, please take into consideration how prevalent that pipe size is when explaining the reach and impact it would have. I have used the United States as an example in this question, but if you are more familiar with the natural gas infrastructure of another country you should feel free to use that country as part of your answer instead. For bonus points\*, include a consideration of contaminants that linger inside these pipes (likely not food-safe, for example), and how that might impact your proposal. \*Disclaimer: not actually worth extra stackexchange points. [Answer] They can used for [underground power and communication lines](https://en.wikipedia.org/wiki/Undergrounding), as a replacement for [overhead lines](https://en.wikipedia.org/wiki/File:Cigognes_Vladeni_Roumanie.jpg). The reason why overhead lines are still prevalent in America is due to the initial cost of installing the lines underground and the sheer number of lines needed for the sparse rural areas covering most of the US. However, if the power companies had available pipes across the country to simply snake the power lines through then the installation costs should be significantly lower. Having underground lines would lower the number of outages due to not being affected by strong wind, falling branches, or drunk drivers, so the power companies would likely support it. It would also improve the view of most areas due to no longer having [interconnected monoliths](https://en.wikipedia.org/wiki/Overhead_power_line#/media/File:Stromtrasse_bei_Mannheim-Seckenheim.jpg) cutting across the landscape, so environmental groups would likely back it as well. [Answer] It is actually a trick question, in a fully renewable energy economy natural gas pipelines will continue to transfer natural gas produced from renewable sources. Natural gas normally comes from fossil fuel sources, but at its most basic it is methane which can be renewably generated from the decomposition of organic material (such as food wastes or other organic garbage). There are a number of operating biogas producers using large scale digesters (often common for waste processing plants or dairies) which mostly use the gas on-site. In a post fossil fuel world it may make economic sense to have larger scale processing centers and use existing pipelines to distribute the gas for usage. [Answer] It's unlikely that they would be repurposed. Since natural gas is the least carbon-emitting of the fossil fuels, it's likely to continue to be used for longer than coal, and its use is likely to tail off over a period of fifty years or more. The key thing here is that pipelines don't stay in good shape without maintenance and as natural gas usage ramps down (and remember it hasn't even peaked yet) it's likely that the system will be abandoned a bit at a time when the cost of operation and maintenance exceeds the value of using it. The long-distance pipelines have significant redundancy and as production drops, the redundancy will decrease as specific pipelines can no longer earn their keep and are abandoned. The local distribution system has no redundancy, so as usage declines a section of pipes serving a part of a city will earn less and less and at some point it will be more economical to transition the last uses to whatever the new power sources are and stop maintaining the pipes. (Paragraph added based on questions below) The process will be gradual. As usage of natural gas decreases and the cost of extraction *increases*, people will move to other power sources and the industry will become less and less profitable. The companies will react by cutting costs, including maintenance (which will suffer for years before a pipeline is abandoned.) Another way to cut costs is to cut off local delivery networks that are no longer profitable and to drop entirely redundant long-distance pipelines which are no longer needed. A section needing expensive maintenance or replacement will be an especial trigger to abandon it. The whole system will slowly shrink and in general, the parts which get abandoned will be older and in need of repair. It's *possible* that the pipes will be dug up and recovered for raw materials. That's plausible enough, but depends on fiddly legal details (the gas company owns right-of-way access rights, but who has the right to dig across your property to pull up the pipes?) and on relative costs compared with other sources. But the bottom line is that the pipeline system is likely to be in pretty rickety shape by the time it's all abandoned and not likely to be useful for very much. [Answer] ## Many misinformed Answers here ## People should actually read the references they have quoted. Not an answer, just a point of view from a Natural Gas / Petroleum Engineer The answers about pipelines will still be used for 'biofuels', 'biogas', 'landfill gas', 'Hydrogern' storing CO2 etc are very misinformed. Those Wikipedia pages are misinformed as well, they are 'theoretically true' The truth is, compressing is expensive. These pipelines have utility for Natural Gas since NG is extracted from deep, high pressure high temperature wells (HPHT wells), a natural high pressure is provided by the reservoir, which let's us humans to use/transport the gas at a reasonable cost. The cost of compressing increases exponentially as the difference between input and output pressure rises, compressors increase the pressure from 10-20bar (natural) to 30-100bar for long distance transmission only. These gaseous mixtures do not have the natural pressure that NG has, an oil company could compress a gas from 15bar to 30bar; for lower initial pressure than that, the owner would rather burn it (flaring), than find a use for it. In Fact, any gas is useless for commercial applications if it has no pressure. To think these pipelines can be used for used biofuels is naive, it's like traveling on an Autobahn with a bicycle. Answers here are talking about compressing any gas like it's free. As someone who has been around pipelines and gases all my life, I would say the accepted answer is plausible. [](https://i.stack.imgur.com/H6oFq.jpg) This is from one of those studies that answerers here just saw the title of, read the conclusion. [](https://i.stack.imgur.com/f6Tf0.jpg) ## EDIT There is a lot of discussion on using alternate energy careers and fuels in these pipelines, ignoring the thermodynamics and mechanics of such operations. Hence, I am posting a few sentences from my favorite undergrad book (Mccabe-Smith-Harriot 5th Ed, Page 204) to make a few things clear about why these pipelines, are natural gas pipelines. > > \*The theoretical head developed by a centrifugal pump (context: any pressure head increasing device), depends on the impeller speed, the > radius of impeller and the velocity of the fluid leaving the impeller. > If these factors are constant, the **developed head is same for fluids > of all densities and is same for liquids and gases. The increase in > pressure, however, is the product of the developed head and the fluid > density.** If a pump develops a head of 100 ft and is full of water, > the increase in pressure is 100\*62.3/144 = 2.9 atm. If the the pump is > full of **air at ordinary density** the pressure increase is about > 0.007atm.\* > > > Natural gas is at a high pressure naturally, rising up due to its own pressure from thousands of feet under the earth. It also has a higher density due to high pressure ([see here](http://www.unitrove.com/engineering/tools/gas/natural-gas-density)). Hence, the pressure difference created by a compressor on such an input is large. Once you lose pressure of Natural Gas, it is effectively wasted (because the cost of compressing is high), hence flared (unless the volume is very large). So when the answers above discuss biogas, landfill gas, biofuels, hydrogen, CO2 to use in these magnificently long and large diameter pipelines; it's naive, because there are **no known high pressure, significant volume sources** of these gases. And unfortunately, it also exhibits an ignorance of the properties of these alternate fuels that are being promoted. **These fuels are compressed to burn**, and not transport at the scale at which a country requires. Compressed air is used in many industrial operations, but not as a primary energy carrier. You don't want to put in more energy, than you get to use later. Using these pipelines for such purposes is not the way forward. These gases may be mixed with natural gas for transport, but that is also silly; because you manufactured the gas after investing in separation processes, and then you mix it back with another gas to transport. Plus, the question implies scenarios when we run out of natural gas. On a side note, I do not think the Earth running out of natural gas anytime soon. These are actual pressures in pipelines. In a gas distribution network, notice entry point is high, Those are big pipelines where most of the pipeline money went. The city is just the delivery point, a tiny part of the network. [](https://i.stack.imgur.com/SPoer.jpg) [Answer] If you are going to use them, the only thing I can think of is a vacuüm train. Although it's likely not using a "full" vacuüm but a low-density air environment as the pipes wouldn't be able to handle full vacuüm in all likelihood. What you do is place a small maglev train in them for transport of goods. The lowered air pressure means lower air resistance. The speed and relative silent operation allow you to unburden a portion of the normal tracks and roads. [Answer] ## It's already been done. And its being done a LOT. [Williams Brothers](https://en.wikipedia.org/wiki/Williams_Companies) was a pipeline company founded in 1908. A lot of the nations natural gas pipelines in place had been placed by them. In the 1970's they diversified into several companies, one of them a communications division. This division would use pipelines that had been decommissioned to pull fiber optic cable through the unused lines. You can read in the Wikipedia article how they built a nationwide fiber optic network TWICE. They sold the first one to LDDS (which became Worldcom, then MCI). The second continued to be owned by Williams Communications until they went bankrupt in 2001, where it was acquired by Level 3 communications. Technology has advanced for having [both through the same line](https://www.lightwaveonline.com/articles/print/volume-19/issue-7/news/live-gas-lines-to-carry-energy-and-information-53447552.html) concurrently. It is now common practice to pull at least one fiber optic cable through natural gas pipelines that is used (at least) to [monitor](https://www.prnewswire.com/news-releases/socalgas-to-use-fiber-optic-technology-to-monitor-pipelines-in-real-time-300389053.html) the pipeline. [Answer] To add to Josh King's excellent answer - ## We'll still need natural gas for plastics. In the US, natural gas is one of the main feedstocks for plastics, beating out coal and oil as the primary source for carbon polymers. <https://www.alleghenyfront.org/this-is-exactly-how-natural-gas-gets-turned-into-plastics/> <https://extension.psu.edu/how-plastic-is-made-from-natural-gas> Even if we get to the point where 100% of our plastics are recycled, continued population growth means the market for plastics will outpace the supply of recycled materials. In addition, replacing metals and woods with plastics as products made from those materials wear down will reduce the environmental impact of mining and forestry. And plastics are used for ***a lot*** of things that people consider critical infrastructure. If you watch the videos below, you'll notice that the American Plastics Council focuses on biotech, but it's actually in many things that your day-to-day life depends on. <https://www.youtube.com/watch?v=rE70FAEOX-M> <https://www.youtube.com/watch?v=l2Yh_y7Wlbk> <https://www.youtube.com/watch?v=viTtllRFYsc> [Answer] ### You would still use them. It's a post-fossil economy but that doesn't mean that natural gas produced in factories -[biogas](https://en.wikipedia.org/wiki/Biogas)- (like [landfill gas from waste](https://en.wikipedia.org/wiki/Landfill_gas) or some kind of algae process of biofuel that if you want I can explain more) wouldn't be used. Natural gas would still be a good energy source, and if it's produced from organic compound it won't increase the net value of CO2 in the atmosphere. Also, natural gas isn't the only energetic gas, you can still send hydrogen produced artificially with water electrolysis (break water in H2 and O2 that I can also explain) and send it with the pipelines (note that hydrogen made with electrolysis is only an [energy vector/carrier](https://en.wikipedia.org/wiki/Energy_carrier) because it doesn't have net energy gain, if you look that read [biohydrogen](https://en.wikipedia.org/wiki/Biohydrogen)). Finally, I don't know if it's possible to send liquid on that pipelines, but you could send some [biofuels](https://en.wikipedia.org/wiki/Biofuel). [Answer] **Compressed Air Energy Storage** You post fossile fuel economy would need some energy storage. One way to achieve this is [compressed air energy storage](https://en.wikipedia.org/wiki/Compressed_air_energy_storage): Compress air using solar or wind power, expand it through turbines at a later time to regain some of the energy. The pipelines not only connect points, they themselves also provide a certain volume to work with. The system would look like this: * Places near large pipeline terminals that are well suited for wind or solar power generation compress air into the pipelines * This process also creates heat, which will either go to waste or be used in co-located industrial processes or even district heating (though I doubt many compressor sites will be situated in residential areas) * At gas terminals, generators with expanders supply electrical power as needed * This requires heat, this is could supplied by some renewable source (biogas?) * Alternatively, the cooling gases go through when expanding is used in a co-located industry * Gas storage tanks, caverns etc. can also be used I think you can't give a roundtrip efficiency of such a CAES system without accounting for energy use at co-located industry. Something between 50% and 70% could be achievable. That's the thing about a post fossile economy: You have to treat energy (in any form - heat, cold, electricity ...) as if it's worth something. That means energy flows will be more closely coupled. There are of course headaches: * Air needs to travel from compression sites to expander sites. Depending on air volume, there will be pressure losses (=energy losses) along the way. This will effectivly limit how much power can be transmitted like this. * Flushing the natural gas from the pipelines will be interesting: Normally you'd flush a pipe from one end with an inert gas like N$\_2$ until the natural gas level on the escaping end is safe (Gas on this end will be used until to diluted, then flared, then vented). For flushing the whole pipeline system, cheaper inert gases would have to be used. CO$\_2$ maybe (but from what source?) or sometimes water could be used. I'd expect the refurbishing of a gas pipe network to compressed energy storage to employ a generation of engineers & tecnicians. [Answer] **Use them as a minable resource.** The Romans built a quite extensive network of aquaeducts. After the fall of the Roman empire, they met all kinds of fates, from continued use to being dismanteled. The is one Roman aquaeduct in present day Germany, the [Eifel Aquaeduct](https://en.wikipedia.org/wiki/Eifel_Aqueduct#The_aqueduct_as_a_stone_quarry), which was used as a stone quarry. Note, even the limestone deposit within the aqueduct was used. Depending on the setting of your post fossil-fuel world, gas pipelines could make for a useful "natural" resource. Think, of modern day [low background steel](https://en.wikipedia.org/wiki/Low-background_steel), which is a similarly artificial "natural" resource, which is mined for its special properties. [Answer] For the larger pipes, I can see them being re-purposed for long distance shipping of time sensitive items, or just less than 1 day shipping across the country. Shipping companies might use automated skate boards, luge, bobsleds, etc. to whip through these pipes carrying 1 or more packages. Packages that can be delivered without the need of long-haul semis, being thrown on an airplane, or couriers could reduce the time to cross mountains or areas with few roads. Shipping this way probably wouldn't eliminate current shipping methods, but could act as a supplementary method for super fast delivery. However, a break in a pipe, a mechanical failure on a delivery system, or a host of other things could cause massive problems, due to not being able to easily access the tubes for maintenance and clearing blockages. An accidental breakage due to someone digging in the wrong spot or an earthquake could cause all kinds of issues as well. This idea would assume that the inside of the pipes are (for the most part) seamless, otherwise very smooth, and without quick dips or bumps. [Answer] **Compressed Hydrogen Gas** Electrical energy can be stored as chemical energy by electrolyzing water. The hydrogen can be [transmitted in pipes](https://en.m.wikipedia.org/wiki/Hydrogen_pipeline_transport) the same way as natural gas. The major problem is that [hydrogen damages metals](https://en.m.wikipedia.org/wiki/Hydrogen_damage), and the [mitigations add cost](https://www.nist.gov/news-events/news/2015/07/nist-calculates-high-cost-hydrogen-pipelines-shows-how-reduce-it). It's conceivable that existing pipelines could be [retrofitted with protective liners](http://www.aegion.com/capabilities/hdpe-pipe-lining). [Answer] The obvious answer is a massive bagpipe, which the US military could use to globally coordinate ship and troop movements. Such nation-spanning pipes should be able to produce sound heard all the way across both flanking oceans. If the military by then has better ways of communicating, then I believe storks could use the pipes as a more efficient way of delivering babies. Flying through the air carrying a squirming child has historically been error prone. If enough pipes are available, storks could just put the babies in pipes and then use air pressure to push babies to destinations. I think this might decrease the total number of storks required to do baby delivery, which is good since most bird species have been declining. Final alternative, pipes could be used for secret storage. By capping one end, people could whisper secrets into the open end... the secrets would then be contained. Passwords, aliases, hideouts-- any secret a person doesn't want to accidentally share could be stored in a nationwide series of secret storage tunnels. By timing the echo length of the pipeline -- which could be days for really long pipes -- people would have timestamps for when to stop by to recover their secret, with an option to whisper it again. People could encrypt it by speaking in their preferred animal language, in case they miss their timestamp. As people outside the same family rarely speak the same animal tongue (no one outside my clan so far as I know speaks bottlenose dolphin, for example), that would protect from most accidental hearings. [Answer] They could be converted to a renewable fuel source. Josh King mentioned renewable sources of natural gas, and Spencer Joplin mentioned hydrogen, although most natural-gas pipelines would need to be replaced to carry hydrogen anyway. Other strong possibilities are [methanol](https://en.wikipedia.org/wiki/Methanol_economy), which replaces gasoline and can be synthesized by hydrogenation of captured carbon dioxide using hydrogen produced from renewable energy and water; dimethyl ether, a gas which can be produced through dehydration of methanol and can replace either propane or diesel (in redesigned engines); and ethanol, which is more dangerous to store and transport than methanol but can easily be produced from plants in a carbon-neutral, renewable way. These would not use the last mile of pipe leading to people’s homes, but the accepted answer of running power lines and fiber through them could. ]

[Question] [ I am currently writing/hard-core procrastinating on a fantasy novel that includes a race known as Orthaks. Basically an amended version of Orcs, they range from seven to nine feet tall, weigh between four to six hundred pounds, and are significantly stronger than a human. My question, then, is what are some realistic battle tactics that the race of men could use in order to not be completely dominated by this foe? I know relatively little about ancient battle tactics, but have already discarded a Greek hoplite-style phalanx or a Roman style advance, as the strength disparity would seem to render these useless. Cavalry also would seem to have less effect than normal, as the Orthaks can run at speeds approaching that of a horse, and their great weight makes a direct assault less devastating than normal. My primary answer to this currently is archers, used to prevent the enemy from reaching them at all, but I wonder if any melee style fighting could be used here. As far as the weapons and tactics of the Orthaks, they have little tactical knowledge besides perhaps a basic pincer movement, and usually just charge in a mad rush. Their weaponry is not advanced beyond basic swords, axes, clubs, etc. They wear very little to no armor, but have tough hides resistant to swords or light bows, but something like an English longbow with a bodkin arrow would have little trouble penetrating. To reiterate and clarify, I'm looking for some sort of ancient battle tactic that would give a more technologically and tactically advanced race such as men an edge over a significantly more physically advanced race such as Orthaks. This could also be at least partially applied to men fighting trolls, the Urgals from Inheritance, the Wargals from Rangers Apprentice, Orcs from Tolkien, etc. A race such as this is fairly standard for a fantasy world, although Orthaks are larger and stronger than most of these other examples. Edit: It was brought to my attention by @JGreenwell that information regarding the topography of the battlefield would be helpful. This takes place in a large, relatively flat, open grassland. Also, I am happy with the answers that have suggested blocks of pikemen with archers in the rear, this seems to solve many of the problems I was concerned about. [Answer] ## I think you have unfairly disregarded the Phalanx Whilst other answers are correct about focusing on ranged weaponry and fortifications, they are primarily defensive measures. You need to be able to take to the field and push the enemy away, because focusing only on defence merely delays your defeat. However your Orthaks sound like they have a lot in common with cavalry. They are large, powerful and move quickly, thus having a lot of momentum in a charge and frightening close-quarters capability. But, armies have had to deal with cavalry since antiquity. Imagine charging towards this: [](https://i.stack.imgur.com/fQotMm.jpg) (Image credit to Liliane and Fred Funcken, [source](https://www.abebooks.com/9780130462923/Arms-Uniforms-Age-Chivalry-Part-0130462926/plp). Kudos to @ASGM for finding this) This is a swiss pike square (*Gevierthaufen*), the medieval equivalent of a Macedonian/Greek phalanx. Those pikes could be up to 20 feet (6 meters) long. Before you can get within sword range of the first rank, you have to get past three ranks worth of pikes, all stabbing you repeatedly. If your Orthak is charging into this hedgehog of doom, then that just makes it easier, because his own momentum will skewer him. Thus, when your kingdoms of men must take the fight to the Orthak, they will deploy large blocks of pikemen and slowly advance across the field, cutting down any Orthak who try and get into melee whislt archers shoot the ones who hang back. [Answer] I wonder, how long can your Orthaks sustain their horse-speed running. In my opinion that would be a bigger problem then increased weight and strength. First thing first, I wouldn't discount the cavalry charge so readily. A mounted knight with horse and armor would weight 1200-1500 pounds at the very least, twice as much as a heaviest Orthak. Given a long lance, a knight may also have an advantage in range. The cavalry charge should be supported by the rest of the army though, since for all intents and purposes you are charging another troop of cavalry. The same consideration concerns the infantry troops. Orthaks are *fast*. You do not want to put your archers in the field against them unprotected. It wouldn't take the monsters long to charge the archers and gobble them up. In fact, I would propose that you need to use infantry in combined-arms troops, something similar to Spanish Tercio. Even if your humans don't have firearms to make a proper 'pike and ball' troop, you can combine pikemen with archers or crossbowmen. I would repeat, humans should treat it as if Orthak army consists solely from light cavalry. They are scary fast, they can inflict a lot of damage, but they can be bogged down fighting pikemen, whereupon they are a good target for archers and/or a flanking charge by heavy cavalry. If your army commander aspires to Caesar-like fame, there are tricks and traps you can use. Orthak seem to be heavy for bipedals, with a lot of pressure on the feet. Caultrops and other similar traps that target the feet would be effective. If your commander doesn't have cavalry or doesn't plan to use it in the battle, he can even divert a river on the battlefield, to literally bog the Orthak army down. Another factor that can play against your Orthaks is their appetite. Being as big and fast as you describe them, they would need a lot of food. Scorched earth strategy should work against them. Disease and starvation were always a bigger threat to the army then direct battlefield confrontation. Harrying tactics would do little against Orthaks, again due to their natural speed. Although it may be possible to provoke smaller groups to split away from the main army and to lure them to the prepared positions. In short, it seems to me that if humans overcome the initial fear and surprise and translate Orthak army into familiar terms - 'barbarous light cavalry with little tactical and strategic insight' - they may win, using the appropriate tactics (anti-cavalry combined arms for infantry and flanking charge for their own cavalry) and strategy. [Answer] The logical way to face an opponent who is superior at melee battle is to avoid melee at any costs. Fortification and ranged weapons would be key to winning. Skirmish / scout attacks would be the preferred method of engagement. Building good defensive structure like forts would be very important. You would want to invest a lot of resources developing ranged weapons like catapults, crossbows or even canons. It doesn't really matter if you are 9 feet and 600 pounds when you face a fortress full of archers and canons firing at you. As you mentioned, the Orthaks are not very advanced so they would not be able to mount attacks with siege weapons. So you would let them come to you, let them crash and burn on your castles. Also since the Orthaks don't seem very intelligent, you could strategically mount skirmish attacks on their supply lines/iron mines/farms while they are attacking elsewhere, gradually destroying their economy. Once their economy is so badly destroyed that they can't even forge weapons you have basically won the war. [Answer] I would recommend using something like a Boar Spear or Bear Spear in a Roman-style shield wall (multiple ranks.) These weapons are very long, and have crosspieces just behind the head in order to keep a furious animal as far away from the user as possible, while still bleeding them to death. Because these Orthaks are slightly smarter than the average bear, I would make the spears barbed to inflict additional damage if they back off instead of berserking onward. If your opponent acts like a wild animal, treat them like one. Metal should be used to reinforce the front bit of the spear to make it a bit harder to destroy. The battle line would probably have a line of men equipped with something like the Roman scutum - a shield that provides good coverage against anything thrown. Behind them would be spearmen. In order to actually stop a charging Orthak, the spears need to be different lengths. You want the Orthak to hit all the spears at the same time, and you want each spearman bracing the spear against the ground and their foot. This is, of course, only a frontline intended to stop charges into melee. Behind them will be some sort of ranged attacker, probably archers, to whittle down enemy numbers and force them to either charge or retreat. [Answer] Scorched earth. A being that big consumes much more energy than a human. Make it impossible for the to forage and pick up food when campaigning and they are doomed. C.f., the Mongols: one of the reasons they got stuck at the border of continental Europe was the lack of steppe where they could feed their horses (Europe at the time had much more, and dense, than today, forest). [Answer] Ever heard of [David and Goliath](https://en.wikipedia.org/wiki/Goliath)? > > Goliath (/ɡəˈlaɪəθ/ gə-LY-əth) is described in the biblical Book of Samuel as a Philistine giant defeated by the young David in single combat. The story signified Saul's unfitness to rule, as Saul himself should have fought for Israel. > > > The phrase "David and Goliath" has taken on a more popular meaning, denoting an underdog situation, a contest where a smaller, weaker opponent faces a much bigger, stronger adversary. > > > On a more modern version, look at how the Vietcong fought their war against the US. * Avoid direct and traditional fight * Wear the enemy down, morally and physically, with a constant usage of hit and run tactics * Play dirty: scatter [booby traps](https://en.wikipedia.org/wiki/Booby_trap) wherever you can > > A booby trap is a device or setup that is intended to kill, harm, or surprise a person or animal, unknowingly triggered by the presence or actions of the victim. As the word trap implies, they sometimes have some form of bait designed to lure the victim towards it. [...] Lethal booby traps are often used in warfare, particularly guerrilla warfare, > > > [Answer] I think the Mongols would have the right type of force to defeat an enemy like you describe. Their forces were almost entirely mounted archers and lancers (they did pick up other technologies from conquered enemies later i.e. siege craft. Their composite bows were famous for their power and their ability to fire accurately from horseback. I'm sure a volley of arrows from these would be enough to slow a massed charge of creatures like you describe. Tactically the Mongols tried to pin their enemy in place with their archers so they could be flanked and charged by the lancers. The lancers spear range should be longer than the reach of their enemy allowing them to hit their foe hard before retreating while the enemy is still shocked. Which brings me on to the final reason I think this is a good comparison. The Mongol's were highly trained, well organised and well led. They could perform difficult horse back manoeuvres during battle. They were masters of flanking and the feigned retreat, both of which would probably be excellent tactics against a foe of brute strength but relatively low intelligence. [Answer] The enemies major traits are speed, strength, size, low intelligence and weight. All of these can be turned against them or at least made useless. As far as speed and strength goes, I totally agree with [this answer](https://worldbuilding.stackexchange.com/a/148658/29956) and won't reiterate that all over. Thus remain size and weight. Size can be fairly easily turned into a disadvantage. First of all with increased size comes slower movement, which limits your opponents to devastating blows while taking any option for faster fighting-styles. Guerilla-warfare would be absolutely deadly against them. A dagger in the back of the knee and you've turned a rampaging giant into a mostly immobile weapon-swinging opponent that is completely defenseless on it's rear side. Ropes should also work for on the battlefield to achieve the same purpose without the need to get close to them. Just tangle them up and you've got a package of panicking rage that can easily be finished off. Next they will most likely use weapons that are appropriate for their size. So probably a 5 feet long sword (?) or something similarly large. These weapons surely could be devastating on open fields, if it's impossible to keep them at sufficient distance. On the other hand if the battle takes place in a forest, both the wielder and his weapons will be limited to little movement. A historical example of this tactic would be the [battle of the Teutoburg forest](https://en.wikipedia.org/wiki/Battle_of_the_Teutoburg_Forest), in which the Romans suffered a complete defeat against the Germans. Due to their size in combination with their mental capabilities, they will be limited to fast attacks thanks to lacking logistic options on one side and a strong consumption of resources on the other hand. This offers several advantages to humans: withstanding long enough (most likely not that long), will deprive the Orthaks of resources required to continue the war. The possibility to wait longer increases the chance of being able to decide where battles will take place (the enemy **must** move or give up, humans don't have that limitation to the same extent). Their weight can be turned against the Orthaks in quite a few ways. Lure them into swamps and watch them sink into the mud. Construct your bridges in a manner that allows humans to use them, but make them weak enough to give in under the weight of a few Orthaks. Construct booby-traps that only prime when a sufficient weight rests on them. Use their momentum against them. If they are charging, changing direction will become a fairly complex task. [Drive them off a cliff](https://en.wikipedia.org/wiki/Bison_hunting#Native_American_plains_bison_hunting) and you might even wipe out a complete army, with no loss on your own side, if done correctly. Last but not least, what makes armies so strong isn't only the equipment, but also discipline and order. A killing-frenzy may be a good tool for a short attack consisting solely of charging and slaughtering. As long as the frenzy goes on your opponents may not care so much about losses among their troops. Get them to stop, the frenzy wears off and any loss will make quite a different impression. If the guy next to you in the line suddenly gets his head ripped off by a large projectile that makes quite some impression. A properly trained army may withstand such incidents, but in a group of untrained people this will definitely cause chaos. Retreating will also most likely be a major danger for the Orthaks, since it will most likely happen unordered, leading to extreme losses, if your humans manage to use the situation to their advantage. To summarize: * Use phalanxes of spears and heavy artillery, where applicable * Restrict their mobility by terrain, weapons, traps or any other means you could think of * The strategic limitations of the Ortharks especially in terms of duration of any military campaign offers ways to both weaken them and device better strategies for oneself. * Booby trap battlefields and routes the enemy-army will take * Impressive deaths (impressive like the impact of a [ballista](https://en.wikipedia.org/wiki/Ballista)-projectile going straight through an Orthark) to demoralize them. While Ortharks seem to be far superior, they are actually extremely weak except for a few specific scenarios that can easily be avoided. EDIT: [Greek fire](https://en.wikipedia.org/wiki/Greek_fire) shot by catapults or used in booby traps should also lead to some quite impressive effects among the Ortharks. Be prepared to get out of the resulting chaos though, as a group of inextinguishable Ortharks will most likely turn against anything it sees and wreck havoc. Useful as long as they only turn against each other, but definitely nothing one would like to get themselves into. [Answer] The "*(r)ealistic, logical way for men with medieval-era weaponry to compete with much larger and physically stronger foes*" is to not fight on terrain which is favorable to the much larger and physically stronger foes. "*To reiterate and clarify, I'm looking for some sort of ancient battle tactic that would give a more technologically and tactically advanced race such as men an edge over a significantly more physically advanced race*". Since "*(t)his takes place in a large, relatively flat, open grassland*", the "ancient battle tactic" is to **not** fight there. Run away and find somewhere else to fight. [Answer] Another anti-cavalry tactic that your heroes can apply here is to choose and prepare the battlefield. Big and heavy foes might sink in swamps, would have trouble fording rivers, and could be tricked into charging into spikes or pits dug into the ground. The *cheval de frise* was a defense that remained in use into the twentieth century. You say that the battle is taking place on a flat plain, but there still might be time to prepare hazards and fortifications that would stop a charge. [Answer] I really can't help you with battle tactics; however, if this was life I would tell you that they couldn't win by any sort of battle. The sheer size of the orthaks would make it extremely unlikely that they could be overtaken in battle. I believe they should look for alternative methods, e.g., * Poisoning the drinking water or food supply. * Setting fire to their homes after stealthily watching their sleeping and rising habits, to see how and when would work best to set fires and trap them inside of their homes. * Setting traps is another. This would seem the rather safer plan of attack to me. If it had to be a battle, then still, watching them for a while to see if you can take them down in smaller groups would definitely be a plus. If worst came to worst and a battle had to be fought, a well-thought out attack plan and a resignation that you had to fight to the death for your fellow soldiers is really the only thing left. Some things are worse than death. [Answer] You have a big and exceedingly strong enemy, but why would that mean he automatically wins? First, let's look at physiological traits. Their size means they'll overheat faster, their strength likely comes from using high strength muscle types that sacrifice endurance for strength, meaning they tire quickly. So humans would try to maneuver as long as possible and once battle is joined keep the fight going as long as possible. The human death toll early on would be high, but quickly drop as the Orthaks overheat and tire out. (You can find more on this in my answer here: [Realistic fantasy Orcs](https://worldbuilding.stackexchange.com/questions/109572/realistic-fantasy-orcs).) Your sizeable enemies also take up space. So for each Orthak in a line there could be multiple humans against him. This makes the age-old Phalanx very good against Orthaks, who would severely injure and kill themselves if they charged one similar to hoe cavalry will injure and kill themselves if they charged a phalanx that had their spears out and supported by the ground. Technology will also help. Crossbows lack the range of the good old English bow, but at close ranges they do have the penetration power. Orthaks are large and easy targets that will quickly go down after a few volleys. Also accidental hits to vital areas like the eyes would take down a very large threat. More technology could even the odds. Ballistas, onagers, catapults could all give a firepower that will kill orthaks before the fight ever begins, which could morally discourage them to continue the fight for long. Since Orthaks are probably brutal and warlike you don't have to chase them, you can simply dig in and wait. They'll happily run into a fortified area of stakes and ditches. Also these Orthaks are simple minded from what you've told us. Baiting them shouldn't be too hard. Use horsemen to distract them, they could fire arrows or charge with lances. Sometimes they break off a charge, sometimes they would slam their lance into their adversary. This way the Orthaks would likely try and engage the horsemen, or at least waste time preparing for the horsemen to attack after which things like ballistas could fire another shot. It also serves to tire out the Orthaks. [Answer] Perhaps you should have asked this of my keno instructor, who was maybe an inch or two over 5 feet tall :-) Size, in and of itself, is not an overwhelming factor: speed and agility are equally important. So your smaller humans, if well-trained (which it appears your Orthaks aren't) can generally keep out of the way of their larger but slower opponents. You might consider the few professional basketball players who are close to 8' tall. Despite playing in a sport where height gives a definite advantage, they don't dominate the sport or give their teams an overwhelming advantage. [Answer] I would say that size really does matter at all in a battle. But if Sun Tzu would be alive today and reading your questions, I think he would laugh at the problem and say, "Oh! It's very easy!" (It's not me laughing, it's Sun Tzu) If you haven't heard of Sun Tzu, he's a Chinese philosopher-general who wrote the famous book "The Art of War". In his book, he lays 13 Chapters dedicated on how to fight successfully, not bloodily. Regarding your question, if I would be the general of the human race in your story facing the Orthaks in a battle, I would apply the principles that Sun Tzu laid in the Art of War. For him, war is not battle of sizes, weapons, and numbers. It is a combination of the Weather, Terrain, Resources, Morale, and Backing of the People. He himself experienced fighting a force of 400,000 men of the enemy state when he had only 30,000 men in his hand. And he won the war, with little casualties. I recommend you to read the Art of War if you wanted to have a hero in your story who is skilled in tactics and battle manuevres. Good luck on your story! [Answer] [Heavy Cavalry](https://en.wikipedia.org/wiki/Heavy_cavalry) the Orthaks run as a fast as horses right? That is to your advantage if you're charging straight at them charging at you, it's an impact energy boost when you put a 12 foot lance in their chest. Being on horse back also erases their height advantage, or most of it. The really great thing is that because of their large size they're less able to "receive a charge" than humans because they can't pack together as tightly either laterally or in formation depth; that means they can't present a pike wall or similar to stall a charge of heavy horse. It's true that if heavy horse get into a melee with these brutes they're in trouble but heavy horse that get bogged down in melees with heavy infantry are *always* in trouble. [Horse Archers](https://en.wikipedia.org/wiki/Mounted_archery) are also a possible option, they can stay out of reach and fire repeated volleys, if the Orthaks chase them that's all to the good the [Parthian Shot](https://en.wikipedia.org/wiki/Parthian_shot) is easier with a foe who can more or less keep up with you. [Answer] The men have trained their hunting falcons for battle duty. Clouds of falcons land on the orcs heads and pull their eyes out. [Answer] Building on [Lisa Rainer’s answer](https://worldbuilding.stackexchange.com/q/148641/20215#148708): passive weapons; i.e., booby-traps. Pick a location that’s secure for the moment (i.e., no Orthaks in sight).  Dig pits, put spikes (maybe poisoned) in the bottom, and cover them.  Then go find some Orthaks, yell “Nyah nayh!” at them, and then run around the pits and watch gleefully as the Orthaks run straight at you and fall in. Also, you might want to look for information on “asymmetric warfare”. [Answer] I noticed that although weather was mentioned, no situational solutions were provided utilizing specific conditions. Say perhaps it is windy, while probably unreliable, I suggest looking at using some kind of kite or small glider similar to the Saqqara Bird. These could be fitted with Greek Fire, or some kind of primitive explosive. Another (admittedly outlandish) idea utilizing kites, would be to use some kind of Ben Franklinesque device attached to a crossbow. I know it sounds silly, but check out rocket triggered lightning for a better idea of what I'm proposing. All of this would greatly depend on how you have developed your human generals/leaders. If they are sufficiently ingenious and out of the box, the technology does exist and the strategy might be feasible. On another note, perhaps grenadiers could make a difference if they fit into your universe. Grenades themselves have been around since the 15th century, so while not ancient, aren't decidedly modern. [Answer] The guys you are describing sound like the typical barbarian enemy of Rome but tougher. If they have tough hides then they are no different than a tall human wearing hardened leather which the Romans were built to fight. <https://www.youtube.com/watch?v=7-cS_ptYF9I> Remember most battles were not fights to the death. The Romans had good discipline so they didn't break much but most of their enemies wanted to charge in, overwhelm the Romans, then live to tell the tale. Many battles that the Romans fought went something like "two sides meet, Romans throw waves of Pilum at the enemy, they get into a melee battle, they are not doing too well against the Romans, the enemy doesn't want to die anymore so the charge dies and they retreat with about 10-15% losses". With your Orthaks they would be giant and easy to hit ranged targets but hard to hit in melee combat. I would have a front line with 1-2 shield bearers with short spears designed to attack their ligaments and finish off fallen Orthaks. Outfit them with Pilum too. Behind that I would have 16ft spears stabbing at their chest, face,, and just generally being scary. Behind them I would have dedicated Pilum throwers since they are so nice, tall, and easy to hit. Behind that crossbow men to take full advantage of their range. I'd bring Ballesta too so anything that gives you trouble can be skewered. If you can inflict enough damage early on then you can demoralize an enemy that otherwise has a numbers advantage. The absolute best tactic would be the Hun strategy of run around them in circles on horses, avoiding all melee combat, and pelt them with arrows till they stop moving but that makes for a boring story. Is there anything they are allergic to or that can weaken them that can be mass produced and ranged weapons can be dipped in? If you know little about ancient battle tactics then these three channels will get you into ancient era warfare and show you how to make a realistic world: <https://www.youtube.com/channel/UCv_vLHiWVBh_FR9vbeuiY-A> <https://www.youtube.com/channel/UCMmaBzfCCwZ2KqaBJjkj0fw> <https://www.youtube.com/channel/UCwO-UgquohXwoe7f0e6lMnw> Could probably copy and paste some tactics and only historians would be able to tell. [Answer] There are a lot of good answers here, to put it simply, do not engage in melee combat. This is a summary, plus bits from my own mind: * Train everyone in the use of ranged weapons * Train their stamina to outmaneuver the Orthaks. You wanted it to be impossible to outrun them, so don't, just dodge. It will take a **lot** of energy and stamina for these big creatures to stop or slow down enough to change direction. They will tire out quickly and become exponentially easier to deal with. Split them up in battle, don't let them form groups that can gang up and kill soldiers trying to dodge them * Invest in making your raged weapons bigger and more powerful * Invest in making your soldiers better with them * Build heavily fortified positions, the Orthaks seem too dumb to siege * "the Orthaks can run at speeds approaching that of a horse", but not matching *or* exceeding it. **So just ride horses** and you can outrun the Orthaks indefinitely. Shoot bows from the horses. Not even a single casualty Their physical advantage is simply not enough alone to guarantee them victory, and additionally you've added a handicap by making them not very intelligent creatures. In fact, **they'd** be lucky not to be the dominated ones. **However**, despite specifically saying that you are looking for a tactical advantage for the humans, if you are keen on forcing this melee conflict to happen the answers you are looking for are # [Shock Troops](https://en.wikipedia.org/wiki/Shock_troops) and [Ninjas](https://en.wikipedia.org/wiki/Ninja) ## Shock Troops Shock troops are frontline soldiers, they are better trained and better equipped than normal soldiers. The way I would use them is to form squads of an arbitrary size, say 5. These men would be the biggest and strongest around with heavy armor, heavier than equivalent plate armor; weighing at least 80lbs. They would carry battleaxes or perhaps poleaxes rather than swords, swords are meant for humans; our meat cuts easily. You'd want and need the extra force that comes with a heavy axe to cut through tough flesh. The tactic I would use is send out fast units, the fastest horses and an unarmored, or lightly armored rider, meant to harass and piss off the advancing vanguard by filling them with arrows. They will charge and the light cavalry will retreat and spread out to split them up. At this point the shock troops will rush in and gang up on the individual or small groups of Orthraks and simply overrun them with muscles and steel ## Ninjas I don't think I need to explain what ninjas are. The tactic is maybe an hour before daybreak, you send them in to silently kill as many as possible. When day breaks, they will flee. During the main battle you will hope that the ninjas killed enough that the archer forces can dispatch the rest ]

[Question] [ This short story, which I've already written, is set in the FAR, FAR FUTURE, where a robotic space probe is exploring as much of the known universe as it can, despite its AI not knowing if its creators--humanity--still exists as a species. The exact number it has calculated to be slightly over a billion years since it first departed Earth. Currently, could a robotic, humanoid space probe (a successor to the Voyager 1) be able to last 1 billion years or longer out in space, as long as it doesn't take on any external damage? If so, I'm curious what kind of materials don't deteriorate over time? [Answer] ## Nope! (but you can still make this story work!) So the short answer is no - * the power source would run out * the physical hardware of the computer, thrusters, etc. would degrade * high energy particles and high-speed dust collisions would slowly convert the spacecraft into a ball of metal and rock 50 years is probably about the limit of what is achievable right now, and a billion years is just too, too much longer than that to be reasonable. **BUT** What if it doesn't have to "last" that long at all? [Von Neumann Probes](https://en.wikipedia.org/wiki/Self-replicating_spacecraft) have been the stuff of sci-fi for decades. Have your spaceship stop in various systems, harvest new materials, repair itself, and move on. It's basically a gigantic factory, flying through space stuffed to the gills with spare parts. The nice bonus for a short story is that now your AI can ponder if it has become "life" given that it grows, experiences the universe, and perhaps even procreates. How does this affect its relationship with the long lost human race? [Answer] ## Yes. Relativity is on the robot's side. Using the Time Dilation Equation, $$ t = \cfrac{t\_0}{\sqrt{1-\cfrac{v^2}{c^2}}} $$ where $t$ is time seen by stationary observer, $v$ is velocity, $t\_0$ is time in rest frame, and $c$ is speed of light (≈ 2.998 × 108 m/s). And if we apply the following values: $ t = 1\,000\,000\,000 $ $ v = 0.999999999999999 c $ We'll get a dilated distance of ~44.70. So that means that if you make the robot accelerate to 99.9999999999999% of the speed of light and make it travel for 44.7 years (or 391570 hours) from its point of view, roughly a billion years will have passed for a stationary observer. 45 years seems to be a reasonable amount of time to keep a particularly sturdy robot operational. (Disclaimer: The method to accelerate the robot to 0.999999999999999 *c* is left to the OP's discretion.) Credits: [Wolfram Alpha](https://www.wolframalpha.com/input/?i=time%20dilation%20at%20.9999c&assumption=%7B%22FS%22%7D%20-%3E%20%7B%7B%22TimeDilationRelativistic%22,%20%22t%22%7D,%20%7B%22TimeDilationRelativistic%22,%20%22to%22%7D%7D&assumption=%22FSelect%22%20-%3E%20%7B%7B%22TimeDilationRelativistic%22%7D,%20%22dflt%22%7D&assumption=%7B%22F%22,%20%22TimeDilationRelativistic%22,%20%22to%22%7D%20-%3E%2250%20years%22), [Time Dilation Calculator](http://www.emc2-explained.info/Dilation-Calc/#.XH72b4hKjzQ) [Answer] I have to agree with others: self-repair is your only hope. Everything wears out, given enough time. You may want to see how other authors have addressed this. Robert Silverberg thought it could be done, in *Across a Billion Years*, but I don't recall that he specified how. James Hogan pointed out how self-repairing AIs might go wrong in *Code of the Lifemaker*. Meanwhile, Robert Moore Williams wrote in "Robots' Return" of a future so far that Man had become a myth among the robots. [Answer] The [Centennial light](https://en.wikipedia.org/wiki/Centennial_Light) is the world's longest-lasting light bulb, burning since 1901. Electronic and/or electromechanical devices have been in use for less than that, but none of them has shown a lifetime longer than a few decades. > > Currently, could a robotic, humanoid space probe (a successor to the Voyager 1) be able to last 1 billion years or longer out in space, as long as it doesn't take on any external damage? > > > Even if this device took no damage, which is already a far-fetched assumption, considering how "nice" space is (high energy photons and particles, strong magnetic fields), we have no power source which can supply energy at an appreciable level for such a long time span. The only thing which has been able to self sustain for a billion years has been life as a whole, but it doesn't stand up in the environment of space. [Answer] **Have your robot based on crystals.** <https://www.bbc.com/news/science-environment-26324968> [](https://i.stack.imgur.com/2QQJK.jpg) > > A tiny 4.4-billion-year-old crystal has been confirmed as the oldest > fragment of Earth's crust. > > > The zircon was found in sandstone in the Jack Hills region of Western > Australia. > > > Scientists dated the crystal by studying its uranium and lead atoms. > The former decays into the latter very slowly over time and can be > used like a clock. > > > Your robot uses solid state electronics based on zircon crystals. These are durable on Earth for billions of years and so with a modicum of shielding should do for your spacefarer. Extremities, probes and other moving apparati will probably be manufactured new for each solar system visited but the main program of the robot and its memory will be as immortal crystals. [Answer] Your biggest problem is going to be entropy and redundancy. Entropy pretty much guarantees that anything, given enough time, will gp through molecular changes from the original. Atoms will migrate through the material, any exposed surface will diminish through vapor pressure, 'pure' substances will always become less pure, and after a billion years you will not have anything at the atomic level close to what you started with. So systems will have to be redundant to the extreme. Then, you have quantum effects. Quantum tunneling and indeterminacy. How do you prevent this from happening in critical systems? And, of course, there is radioactive decay. Elements change in physical properties as they go through such basic changes as emitting radiation. So is a billion years enough time for all of these things to affect critical systems? With today's level of technology, absolutely a certainty. No robotic system that we build will last a billion years. Consider recent history. As humans endeavored to reduce the size of computer chips, the first pentium processors began to suffer terminal illnesses. Turns out, the copper traces were so thin (atoms wide), that as high frequency electrons flowed through them and coursed around sharp corners, the electrons 'shortened' their path by rounding the corners into curved ones, and they began to short out on the traces beside them. Just the act of sending an electrical current through a copper wire is enough to cause it to change shape. So any computer chip microprocessor today is extremely unlikely to be operational in a billion years. It will be one huge mass of electrical shorts and cross signals. At most, it is extremely unlikely that any pentium processor in continuous use will last a hundred years without the circuits degrading enough to produce just random garbage in the data. Even twenty year old chips can no longer be relied upon in critical applications. And yes, that means any ICBM made more than twenty years ago, the electronics of which have not been replaced, should no longer be considered reliable enough to target and perform properly. ('Dang, it hit New York? It was supposed to be aimed for Moscow!!!!') [Answer] We have no good evidence for or against the possibility of any kind of machine remaining operable on those time-scales. That said, ## Probably, but not by accident. I'm going to ignore the various more creative options (on the one extreme, a completely passive porous rock that "explores" by absorbing stellar ions as it passes near each star) (on the other extreme, a dwarf-planet engineered to "naturally" evolve extremely specific kinds of life when warmed by a star) and focus on machines that are recognizably analogous to probes humans have already launched into space. ### In general, simpler devices will function longer. A probe designed for a 100-year mission, or even a 1k-year mission, would not still work after 1G-years, because its designers would have had no reason to make the kinds of compromises to the probes *capabilities* that would have been needed. For example, they would have wanted a smarter AI (requiring silicon transistors or similar electronics that [degrade naturally on extreme timescales](https://www.quora.com/How-long-do-transistors-last)), more sensitive cameras (which would be more easily burnt out), or more powerful thrusters (which would have their own problems, and would add stress to all the other components). ### A machine that was still operating after 1Gy would be simple to the point of idiocy. * A camera? How about a single directional photo-sensor. We'll just sweep it across the sky to build a picture. We can refract the input and adjust the lens a little to get color. * On-board power? How about a 100m sphere of [$^{40}\mathsf{K}$](https://en.wikipedia.org/wiki/Potassium-40). [This person's estimates suggest it might work](https://www.wired.com/2013/02/could-you-build-a-banana-powered-generator/) * Thrusters? How about we adjust a big electromagnet against the magnetic field of the nearest star. Might work if we plan our trajectory a millennia in advance and aren't too picky about where we're going. * An AI? [Willk's answer](https://worldbuilding.stackexchange.com/a/140774/58141) is ok, but the electronics will *still* need to be over-built by a factor of a thousand. "Solid state" electronics *do* have moving parts: The electrons move back and forth, smashing into atoms. The atomic lattice jiggles around; defects form, heal, and move. Dopants diffuse. I think you can have a computer, maybe even an "AI", but it will be physically large, dumb as bricks by it's maker's standards, and *slow*. * Landing gear? Tools for making spare parts? **NO! Absolutely not! This probe will *never* come within 30AU of a star, and will *prioritize* avoiding any close passes with any objects or phenomena.** Even in principal, is it possible for a machine to last a *billion* years? I still think it is. Consider the surface of [Ultima Thule](https://en.wikipedia.org/wiki/(486958)_2014_MU69#Formation). As long as the probe stays well away from all the excitement of inner solar-systems, space is a nice relaxed place to pass the eons. [Answer] Sure it can. **Every** critical system must exist in multiple copies and the robot must be capable of manufacturing replacement parts when it finds accessible raw material (say, an asteroid that it can land on.) You can make a robot with any desired mean time to failure by application of sufficient redundancy. In the extremes your "robot" is really a swarm, anyone of which can rebuild the whole swarm if need be. The robot spends a lot of time checking it's data for errors and repairing corruption from other copies or from error-correcting codes. A swarm approach actually makes repair easier as it means you can go with total replacement on some suitable timescale, thus avoiding headaches caused by transmutation-induced weakening of parts and the slow evaporation that happens to everything. [Answer] The chances for a modern day space probe to survive for 1 gyr and be anything but a metalrich asteroid are quite slim. How slim exactly depends on its speed and that it doesn't run into any big debris out there. While debris are rare and space is quite empty there is always a chance for bad luck. Speed and time are the factors here. If you plot a smart course with several solar flybys a few percent of lightspeed are on the table. Needless to say that this makes collisions way worse as Ekin = 0.5 \* m \* v^2. Even a few atoms might degrade the probe significantly at high speeds. Of course lower speeds could help, yet I assume you want the probe to get somewhere within 1 gyr. I'm not an expert on radiation induced material fatigue. Your probe will most likely suffer mostly from cosmic rays, but especially during solar flybys charged particle radiation will be an issue. Assume that the material will wither away over the eons. Your worst issue on the radiation front will be the breakdown of computers though. Look up the design of computers on mars rovers like opportunity for example. Less probable yet more intriguing story whise is data corruption. The mission (given more complex ai and some freedom to take decisions) statement might be "explore milky-way"; have some freak data corruption turn a r into a d and you have "explode milky-way". (Not very probable but an ai will do anything as long as it gets the reward circuit tickling). So the answer is no. BUT there might be a solution, albeit one using slightly future technologies. Don't aim for longevity, aim for maintenance. Pick a big (maybe 10 to 100 m diameter), metalrich asteroid and turn the whole thing into a probe. Reinforce it structurally to get meters of radiation and impact shielding. Have huge databanks and really smart or slavishly dumb, yet specialised AI. Most importantly you need manufactories capable of producing anything on the asteriod probe and redundancies for every system. For power you could employ a number of technologies. Nuclear reactors, (fusion or antimatter if available), radioisotope generators with an isotpe with a long (the desired mission time) half live, or solar panels during stellar flybys (you want to keep doing those as they counteract drag or slow you down if the system is interesting) (keep in mind that you can manufacture solar panels once you approach a system so the won't degrade). Generally beeing really conservative about using power will be helpfull as well. Let the probe hibernate during inter system flights and let it do the repair and exploration near stars where there is free energy and something to do. Now you might wonder how to move such a kiloton behemoth to interstellar velocities, yet thats not so hard. Huge lightsails, laser thermal rockets, nuclear rockets or even ion drives will move it eventually. Then you simply need to plot a very smart flyby course arround moons planets and suns and you might cruise of at a not insignificant portion of lightspeed. Astronomer Paul Birch once said that one could theoretically throw a pebble into the asteroid belt and end up crashing mars into the sun. Now even such a maintenance probe will run out of some resource (energy, ejection mass or raw materials) eventually or might degrade from collisions. (Come to think of it manufacturing, a huge thin mirror arround the probe when in a system seems highly beneficial. Use it as a high resolution telescope to scout out the system and the route ahead and use it as a solar sail to save ejection mass to get into an optimal gravity assist.) It is very conceivable that such a probe might survive for a billion years. PS:Check out this video, it deals with constructing a spaceship for similar ammounts of time. <https://youtu.be/25ODAzr6Bbw> [Answer] > > Currently, could a robotic, humanoid space probe (a successor to the Voyager 1) be able to last 1 billion years or longer out in space, as long as it doesn't take on any external damage? > > > If you want a "real science" answer: **No** Most people won't know this, so publish your story anyway - I'd read it. Many people know that "Transistors don't have moving parts," but then wrongly believe that implies: "so they never fail." ## If you're interested in the science: Transistors built 50+ years ago are likely still working fine today if they were cared for properly, and may be expected to work without issue for 1,000 years in the future (maximum life approx 10,000 years). Let's ignore the additional problems of traveling through space for even a century - as most of those (radiation/power/propulsion) are insurmountable given today's knowledge. A probe that is 'smart' enough to be called AI would likely be based on current technologies. Modern chips have very very small transistors with very very small connectors. Part of the reason that integrated circuit voltages have gone down is that the smaller the "wires" the more troubles you have, like [electromigration](https://www.sciencedirect.com/topics/materials-science/electromigration) (as the device is used, current flowing through the circuit causes the metal to actually move around which can form opens or shorts in your circuit). As transistors get smaller, you see problems that weren't even known recently such as Hot-carrier injection (where the switching characteristics of the transistor can be permanently changed). A good read is "[Transistor Aging](https://spectrum.ieee.org/semiconductors/processors/transistor-aging/0)" in IEEE. The article's focus is how to test transistors, but you'll learn some stuff related to your question if you read through it. It contains on of the better descriptions of Hot-carrier injection that I've encountered: > > "Over time, charge carriers... with a little more energy than the average, will stray out of the conductive channel between the source and drain and get trapped in the insulating dielectric. This process, called hot-carrier injection, eventually builds up electric charge within the dielectric layer, increasing the voltage needed to turn the transistor on. As this threshold voltage increases, the transistor switches more and more slowly." > > > A **slowing of switching** (your probe's computer computes slower) and a **need for increased voltage** (your probe's power consumption increases over time) spell doom for a "real science" answer to a space probe that lasts a *million* years. I will restate my opinion that your stories *do not* need to be completely based in 'real science' to be enjoyed. [Answer] Interesting question; this timeline will probably cause your craft to encouter issues never before seen. You will need some sort of material that is not easily affected by radiation. Perhaps Tungsten would be a good material for your craft's shielding? Tungsten is the densest metal on the planet. Also, we currently struggle with computer memory degradation for long term storage, our best and most stable storage devices currently are, oddly enough, clay pots and magnetic tape. Crystal based memory has shown good potentiality for overcoming those challenges. [Superman style crystal memory storage. Think of the Fortress of Solitude.](https://www.computerworld.com/article/3034260/superman-memory-crystals-could-store-data-for-billions-of-years.html) > > Researchers at the University of Southampton have discovered a way to store data in five dimensions on nanostructure glass that can survive for billions of years. > > > The storage method enables up to 360TB of capacity on a disc about one-inch in diameter that can withstand temperatures of up to 1,000 degrees Celsius and has a virtually unlimited lifetime at room temperature (13.8 billion years at 190 Celsius). > > > "As a very stable and safe form of portable memory, the technology could be highly useful for organizations with big archives, such as national archives, museums and libraries, to preserve their information and records," the researchers said. > > > The technology has already allowed major documents from human history such as the Universal Declaration of Human Rights (UDHR), Newton's Opticks, the Magna Carta and the Kings James Bible, to be saved as digital copies "that could survive the human race," the researchers said. > > > ]

[Question] [ In my fictional universe there are two galactic civilizations that have never interacted until recently and thus have developed different cultures, science, etc. From a technological standpoint, one of the civilizations is similar to Halo's UNSC and is on the "Right" side of the map while the other is similar to star wars and is "Left" on a map. Both have faster-than-light travel, but the left side of the galaxy has more advanced ones. What prevented them from ever interacting is a "natural" barrier of dead worlds making the trips longer and more risky with the lack of any ports/refuelling stations. There was ***never*** a unified galactic government that just split and forgot the other. And these dead worlds have no possibility to hold life at all. **So my question is: would the dead world divide realistically stop the two civilizations from ever meeting just enough so that two galactic civilizations develop differently?** [Answer] **You need more than dead. You need dead and weird.** Interstellar spaces are huge. Ships need to be able to traverse these distances. The fact that there are clumps of matter - "dead worlds" - in between that are not useful to these ships should make no difference. It is like the fact that there are some empty office buildings on my route home. Who cares? You can't pull over for lunch at a star or a black hole either. Also, even if they did need to pull over from time to time, I cannot imagine why they would need a life filled world. These ships don't burn wood. If they need dilithium crystals or something they go where those things are. You need a barrier that is not just lifeless and useless, because presumably lifeless and useless is most of everywhere. The barrier needs to pose some existential threat to the ships that want to get near it - something active that poses a hazard. And it needs to be a unique hazard - these spacefarers will know about radiation, know about asteroid fields, know about gravity wells. It needs to be something that does not occur in their territories and that is hard to study and understand. **I propose that you have spacetime itself be unpredictable within the dead zone**. The fabric of space is full of holes and the laws of physics do not reliably apply. Weird stuff happens. This is also why these civilizations are not aware of one another - electromagnetic radiation does not reliably traverse the dead zone, and what does get across is changed and different once it does. When they finally do get in touch it is because someone took the long way around and found out what was on the other side. The long way around is still a barrier but at least you know what and when you are when you finally finish it. [Answer] This is basically a variant of [Willk's answer](https://worldbuilding.stackexchange.com/a/157920/11879) (it needs to be "dead and weird"). You specifically mention Star Wars technology, and I happen to know Star Wars uses "[hyperspace](https://starwars.fandom.com/wiki/Hyperspace/Legends)" for its faster-than-light drives. A quick Google search confirms that Halo uses "[slipspace](https://halo.fandom.com/wiki/Shaw-Fujikawa_Translight_Engine)", which is basically the same thing. In both cases, they rely on jumping from normal space into some parallel dimension that has different physics, traveling through that dimension to a point that's linked to the normal space destination, then jumping back into normal space. **Instead of making barriers in normal space, put the barrier in hyper/slip space. This makes it a lot easier for a science-savvy reader to accept.** The Star Wars universe explicitly states that navigating hyperspace is extremely dangerous, and most of the modern hyperspace routes were actually discovered by an ancient civilization using unknown methods. It's fairly rare for people to discover new hyperspace routes to new places. (To be fair, this is a really nonsense explanation based on some notion that there's a giant asteroid to avoid every three miles or so, but the concept works if we make the dangers related to hyperspace itself instead of "gravity shadows" from normal space.) With Halo, it [appears that](https://halo.fandom.com/wiki/Slipstream_Space#Travel_Times) slipspace has no direct correlation to normal space in terms of distance and direction. So you can't just hop in, go northwest five hours, and hop out. The tangled mess of slipspace means you have to find a route, then hope it gets you there faster than normal, and the shortest distance is probably not a straight line. With both of these concepts, it's not hard to imagine there's simply never been a reliable path between your Halo civilization and your Star Wars civilization. Until now . . . [Answer] Yes, but it will depend heavily on the values of each civilization. A pragmatic society will only visit solar systems they expect to be worth the return on investment based on what they already know. They will do years of analysis for hazardous solar activity, scan for signs of existing civilizations, search for promising exoworlds, and send unmanned probes, all before they ever risk sending a ship on a mission to any star system. They will be very selective as to where they go just to be good and sure it is safe and profitable; so, they will rule out the dead zone quickly and go the other way. However, a more idealistic civilization will care more about exploration for exploration sake. They will be intrigued by these dead worlds. They will want to chart each one just to see if there are new kinds of life there that they could have never predicted with their current understandings of science. They will want to know, "what is on the other side". Such civilizations are much more willing to risk a multi-billion dollar ship and the lives of all it's crew exploring worlds that are not expected to have a measurable return on investment. **[EDIT]** Bases on the OP's revisions, I'd say a UNSC type civilization might be contained by such a barrier, but not a Star Wars one. UNSC ships travel at an average of 2.625 light years per day making a trip across the galaxy take about 110 years. As such something like the gap between 2 spiral arms might be a daunting 6-12 year expedition. In contrast, StarWars FTL tech is thousands of times faster with ships being able to cross the entire Galaxy in less than 2 weeks. Such a civilization would even find the gaps between entire galaxies trivial to cross; so, there are not going to be any meaningful natural barriers for them. If one of your civilizations is to be convinced not to cross a natural barrier, you need to make sure their FTL is too slow for it to be practical. This means you will also need to address how big these empires are vs how fast they can fly. If you constrict their FLT speeds to less than 10 ly/day, then forming any sort of unified society that spans more than 1000-2000 light years is unlikely. If you want larger civilizations, you could always make a natural shortcut between two VERY distant civilizations in the form of a wormhole or trans-dimensional rift. In this case, the "barrier" may be billions of lightyears, or the very fabric of reality, and it is only the discovery of a singular hard to find anomaly that makes transit possible. [Answer] Yes this is a realistic possibility. If Earth ever develops a probe that can travel long distances. You can bet we will pick a target where we think life exists, probably the direction that involves passing the most candidates as possible. If we find life, that will probably be where we focus all our efforts. So for your galactic civilizations, you just need something more interesting in a different direction as to distract both civilizations from ever meeting each other. --Edit New edits to the question somewhat invalidate my answer. [Answer] # Black Hole Drives If you have an interstellar *civilization*, presumably travel between stars is somewhat fast (i.e., weeks to months, rather than decades to centuries). None of the technologies we have today are remotely suitable for such interstellar travel. Nor have you stated how hard-science you want your drive technology to be. But if you want somewhat realistic physics, then your best bet is a "[black hole drive](https://en.wikipedia.org/wiki/Black_hole_starship)". A black hole gives you near-perfect conversion of matter to energy, if you are able to harness it. You literally just let matter fall into the BH, and as it does, tidal forces pull it apart and release gamma rays and other energy, which is how we "see" BHs today. Obviously, if your BH is too big, then it is hard to move, making it a terrible ship drive. And if it's too small, then it will *evaporate* too quickly, turning into a massive bomb that will annihilate your ship (and a bunch of stuff around it for quite a distance!). So it turns out that there's a "Goldilocks" size which gives you decent power but portable mass. # It Hungers The problem with a black hole drive is that the BH needs to be fairly small to be reasonably movable. And the smaller a BH is, the faster it evaporates. As mentioned earlier, you *don't* want that to happen! So you need to constantly feed it mass, to maintain its size within an ideal range. This means you need a steady source of "fuel". Fortunately, they aren't picky about what you feed them, but there is no way to "turn it off." Your hand-wavium works if you make the drives + fuel load only big enough to travel between "adjacent" stars. After all, your average velocity will depend on your mass and thrust, and at some point, adding more fuel will increase the trip time to unacceptable levels. Thus, the ships need to stop at planetary systems simply to bring more fuel mass onboard. # Custom Fuel/Shielding Although a black hole doesn't care what you toss into it, *how you harness* its energy matters a great deal. Also, the BH itself is microscopic (much smaller than an atomic nucleus), so just directing fuel into it may be a [non-trivial matter](https://arxiv.org/pdf/0908.1803.pdf) all by itself (pun intended). One problem is that Hawking radiation from a subatomic black hole (SBH) is expected to be hot...very hot...like, gamma-ray hot. And gamma rays are so energetic they are not easy to harness. Just making an adequate shield so that the crew are not fried is a serious engineering problem. However, it may be possible to create a "gamma scintillator" which "down-converts" the gamma photons to UV range or lower. However, gamma rays are so energetic that they are going to eventually degrade/destroy your shielding anyway via [photodisintegration and photofission](https://en.wikipedia.org/wiki/Gamma_ray#Matter_interaction). So, there's two possibilities for requiring special refueling facilities: 1) The fuel itself needs to have certain properties amenable to focusing and control, and 2) the gamma shield probably needs to be replaced at regular intervals. Since 2) strongly favors heavy (high Z) elements, this is exactly the kind of thing you would want to visit a rocky planet for. Since your ship needs to be as small and light as possible to maximize useful cargo mass, it can't carry a full shield manufacturing facility that can just drop onto a deserted planet and manufacture new shielding for you. # Living Planets Both your civilizations may prefer living planets if they are predicated on the idea that life will spontaneously form on any planet with the basic necessary ingredients: liquid water, thick atmosphere, magnetosphere, abundant carbon, nitrogen, iron, etc. Thus, a planet with no life is lacking one or more of the essentials, and becomes unattractive for colonization, even for just a refueling station. You can hand-wave this a bit more if you argue that the shield manufacturing process requires nano-machining which is best done organically, by engineered bacteria/protista, which, in turn, requires massive quantities of water to operate at scale. So even though it may be *technologically possible* to build a refueling station on a dead world, it is *economically infeasible*. Good luck! [Answer] **No** Refueling stations for spaceships will be in space. Too much fuel is lost going up and down a gravity well. A dead world is perfectly fine and might be a good source of fuel making material. Even empty space is fine as long as fuel haulers keep it restocked. An asteroid belt could also work. A refueling station can be anywhere but preferably near fuel making materials. There is already a barrier and that is the vast distances between stars (and more for galaxies) which is more plausible. [Answer] What if the fuel had the following properties? It's possible all of these together would be too large of a contrivance, though. * The fuel must be created/refined on an industrialized planet, preventing the fuel from being gathered in-situ by general-purpose craft. This could be explained by: needing access to a planetary core; requiring a natural gravity well to refine; the processing being extremely time consuming or energy consuming; any other excuse that would prevent it from being created on a "dead" world. * The fuel is unstable in its raw form and while it could be lifted into orbit of a planet, it cannot be transported by "hyperspace". Therefore to create a fuel depot away from the production facility, it would need to be transported in "normal" space. * The raw form of the fuel is transformed in some way when it interfaces with the craft's engine into an "active" state. Once a ship is fuelled with it, the "active" fuel cannot be transferred to another ship. Perhaps the fuel partially enters "hyperspace" itself during this activation, bridging conventional space and hyperspace. This could explain both why the raw form is incompatible with hyperspace, and the active form is inaccessible to be moved to another ship easily. At this point general-purpose spacecraft will be forced to stop at a habitable planet to refuel, which would cause these interstellar "badlands" to be inaccessible without extraordinary effort. You would have to decide how to limit the effective range of a spacecraft between refuels. Perhaps the fuel, once activated, decays over a relatively short amount of time, like a radioactive substance. This would strongly favour short missions between inhabited worlds, since you would only need small fuel storage and little fuel would decay in transit. Longer trips would require geometrically larger fuel storage, since it would be expected that a vast majority of the fuel would decay over the length of the trip. These large storage mechanisms could be bulky, expensive, vulnerable to attack or inherently unsafe. [Answer] Is there any particular reason why you need both civilizations to be part of the same galaxy? Because if not, then by far the simplest solution is to put them in different galaxies at opposite ends of the universe, and then have someone discover a wormhole if you ever need them to interact. No need to introduce weird regions within a galaxy so expansive that ships can't go around it (which is hard to do, because space is huge). [Answer] # Precursor Sub-Space Gray Goo accident If the worlds are just "dead" that's not going to be enough to stop FTL travel, you need something in subspace/hyperspace/slipspace that is a serious threat. Enter the first [Type III](https://en.wikipedia.org/wiki/Kardashev_scale) alien species. Their empire literally spanned the galaxy, yet for cultural reasons they stuck to a narrow (galacticly speaking) band splitting the galaxy in half. Millennia before either of the now dominate species had discovered fire, a group of precursor scientists went too far. Exactly what technology they used for FTL travel is not known, and probably never will be. However while trying to improve it they accidentally created a memetic-nano-virus that propagated through both normal space and subspace, flattening and expanding it, so that effectively it was the same space-time shape as normal space, rendering any sort of FTL travel or communication ineffective through out the "wall." Even more unfortunate, this alteration of the underlying physics of the region also bent normal space-time, rendering the rules of physics just slightly off. Within the region, technology behaves inexplicably. Electricity tends to be unreliable with the current spiking or waning without warning. Similarly radiation wavelength fluctuates like light through a crystal, making even radio/laser communication unreliable. Structural properties of chemical compounds (including metals) change slightly causing space ships to bend, fold or tear apart when their components suddenly stop being able to withstand the normal stresses they're put under. Worst of all, even protein folding is affected, meaning any biological creatures in the area begin to exhibit mutations (and not the fun X-Men kind) and cellular damage, which progresses faster the deeper into the zone that you travel. Ultimately this isn't TOO hard to circumnavigate, all you have to do is go up and over (or down below) the "wall" by exiting the galaxy and then come back in on the other side. Of course you have to know the wall is even there to know to go around it. And of course (until convenient for your story) no one has tried to go around, because mostly the brave or foolish explorers just try and go through and are never heard from again. FTL probes sent through will eventually come out the other side (if they don't run out of power first) but since they're effectively reduce to a "real" velocity even in subspace it'll take them thousands of years or more to get across the "wall." This last could be a good first contact, as somehow a probe finally comes out the other side, detects the other civ, and pops back into normal space. [Answer] Probably not. Galactic civilizations require a lot of time to develop. If you have a growing civilization that grows in the span of 100.000 years then the light of their activity has also reached 100.000 lightyears of space. A quick google search of the first 3 Galaxies show them anywhere between 30.000 to 100.000 lightyears in size. So at the very least these civilizations know of each other and have attempted long-range communication at the very least. And expanding across the stars even with FTL takes a lot of time. You are better off saying these are in seperate Galaxies and the space between them has gotten smaller or the technology good enough to travel between them. [Answer] Yes, potentially. If all we require is two civilizations separated by distance within the same galaxy, then we can say they evolved separately in opposite spiral arms. The planets in the middle of the galaxy aren't just dead, they're contaminated. This could be because of a terrible ancient galactic war, or some natural phenomenon (like colliding supermassive blackholes) that released a vast amount of deadly radiation. So while there's nothing stopping a ship from flying across the galaxy to visit the other civilization, communication is too slow for any kind of unity, and expansion into the dead-world zone is almost impossible. My question would be, how fast do you want space travel to be in this universe? We could have a galactic civilization 2,000 light years in extent, and a 100,000 light-year gap between it and its rival. If ships travel at a constant speed in hyperspace, we could say it takes 20 days to cross 2,000 light years, and 1,000 days to cross 100,000 light years. [Answer] Space ship plague. It's extremely contagious and slowly destroys space ships or vital space ship parts. There's some microscopic life form LF capable of surviving in space which makes a meal of space ship materials. Once a space ship has been infected, the LF steadily eats away at it, but slowly enough that you might not even realize you're infected until you've reached another planet. And the LF reproduces and spreads rapidly while it does this, so any ships coming into contact with an infected one, even someone trying to leave the infected ship in a space suit, all become infected. LF is not readily detectable when it is simply sitting in space and doesn't spread quickly on it's own, but LF was originally spread by some other civilization who had unregulated travel...which is a cautionary tale for current civilizations. As you can see, LF is very much not popular, to the point where the whole area was interdicted and any ship even remotely suspected of having come from that area is destroyed immediately (including any occupants). There may be pockets of safe space, but no one is willing to try and find out. Even the boundaries are not well defined, anything not definitely safe is considered dangerous. All exploration proceeds in the opposite direction. [Answer] Yes, if they regularly need resources for travel and those “dead worlds” (or simply empty space) don’t provide them. Maybe their faster-than-light drives have to be refueled regularly and it’s impossible to carry more than a certain amount of fuel (because it goes critical or something like that). The dead worlds were harvested by an ancient civilization until nothing useful remained. [Answer] **Yes, but....** A barrier of dead worlds would only work if there are better prospects in another direction. Also, the worlds need to be both dead and useless. Why try to build a town in a desert when there is a river nearby? If there's nothing useful in the barrier then curiosity will only take people so far. Remember that they can make habitats where ever the cost of doing so is less than the value of the resources they can mine and bring back. Also, if you have people use to living on space habitats, dead worlds are just navigation hazards while trying to get at those valuable asteroids. So, make the center be the location of a former empire (or empires) and the area is so mined out and used up that there's nothing worth bothering with there. [Answer] Yes; Taking the book '2321' as inspiration: We do not know that small isolated biospheres/technospheres are possible. Physics-minded people imagine that it's possible to construct mechanical system with <0.001% of the mass of Earth that can support a human for 100 years, but that might not be true. Life is messy in ways that we don't really understand. It's totally possible that mechanical solutions to biological problems produce new biological problems that require new mechanical solutions, etc. And the more mechanical fixes you take with you, the bigger you are. The bigger you are the slower you go. The slower you go the more time for n-order bio problems to creep in. That would create a X light year limit. You'd need to stop at a compatible bio world to restabilize a ship every X-light years. and it could take millennia make two bio worlds compatible (and only a few centuries for them to drift apart). This would make the growth of a civilization very, very slow. Maybe a dozen orders of magnitude slower than its ships. It matters how fast your FTL is, but a bio barrier buffered by life-incompatible worlds could absolutely prevent contact. [Answer] Desert doesn't stop humans, and never has. If there are no refueling stations, one side or the other or both will build them. If there is **anything at all** someone will figure out how to turn it into fuel or some other raw material. At the very least you have these convenient fusion reactors aka suns. A large dead zone won't stop anyone, because it simply won't be large enough. Unless you somehow limit your civilizations to very small hops (and neither of the examples you mentioned do that), then a couple empty stops won't be an issue. If nothing else works, they'll just send tankers alongside the fleet. You could have a really large really empty zone, like the gulf between the galaxies. That's not so easy to cross anymore. Or, as other answers have already explained, you need something more than just "empty". [Answer] A third civilisation occupies the space between these empires. This empire prevented any travel across the area of galactic space which was sandwiched between the two civilisations in question. Due to their xenophobic attitude leading to one or both their neighbours wiping them out, or some internal strife that has changed their attitude. The end result is that they are no longer a major player or have allowed travel (civil or military) across their space and hence allowing the two civilisations to now directly interact with each other. This does mean that the two major powers were aware of the existence of each other at a high level and government leaders may have interacted with each other, but they are completely new to ordinary citizens. Or alternatively, the galaxy has two spiral arms. The two major civilisations started out in the ends of these spiral arms and are now, after 100k years making their way along the spirals to the galactic centre, where they have encountered each other for the first time. Again, unless there is some major interference that prevents electromagnetic/radio waves they are probably aware of each other's existence due to long-range communications or signals, but this is the first time they are meeting/interacting with each other directly. [Answer] I think the nature of their FTL drive makes a big difference. How far can they go between stops? And now much choice do they have about where to go? With decent range and a drive that lets you go basically anywhere it would be pretty hard to have a viable barrier. However, some SF drives are only fixed point-to-point, your fuel cost is based mostly on the number of jumps, not the distance you go. If your cost per jump is high you can't go very many jumps. Furthermore, a "dead" world isn't a meaningful barrier--you can still mine a planet, you can still scoop a gas giant. The delta-v costs of doing so are small compared to what it would cost to get there in a convenient time. Instead, consider what happens if a gas giant spirals in. (Consider all the hot jupiters we have been finding.) You could end up with a star without much of anything orbiting it. A few of those could be a substantial barrier. Also, if you're using a point-to-point drive there might not be a suitable path. I'm thinking of the *Antares* series by Michael McCollum. (Antares Dawn/Antares Passage/Antares Victory.) Point-to-point, the density of jump points is low. Humanity and some very hostile aliens each have their own network of stars and are unaware of each other's existence--until Antares goes boom and disrupts the connections, leaving multiple points of contact. [Answer] You need more than dead. You need deadly. I submit that the planets that form your "dead worlds barrier" are all highly radioactive, or poisonous in some way. You brought up Halo, so maybe something like the Flood is on every one of those planets. I don't know what could irradiate so many worlds over so large an area, but maybe that could be part of your story (multiple massive supernovas?). Also, there could be some kind of limitation to the engines in your story. The combination of that limit and the deadliness of the worlds might do the trick. ]

[Question] [ As a plot device I need some kind of conjecture that is used in lot proofs and widely assumed true. Something like many papers in computer science start with "Assuming P != NP ...". In my story for dramatic purposes my heroine disproves it. It doesn't matter how, or is it plausible in real world, I just need a lot of esteemed work and many careers in tatters. The story is basically about a complicated proof, and those who could understand it due to working in same or nearby fields must choose between the truth or their prestige. I would prefer something from pure math, so the damage would be contained to academia. Breaking cryptography would make three letter agencies very interested. Anything related to relativity and or quantum mechanics would gain too much attention. [Answer] The [Riemann hypothesis](https://en.wikipedia.org/wiki/Riemann_hypothesis) is what you're looking for. Basically everyone in number theory assumes it to be true (although no one can prove it). Variants of it have been proven in other settings. Many results, including entire theories of math, are conditional on its truth; these would all collapse if it was shown to be false. The discovery of even one nontrivial zero off the critical line would wildly throw off widely-accepted heuristics concerning the random-like behavior of primes. **Addendum** Your plot idea isn't actually new. The ancient Pythagoreans embraced the doctrine that whole numbers were the basis for all things in the universe. For Greek geometry, this meant that all lengths and volumes should be ratios of whole numbers (i.e. $\frac{p}{q}$ where $p$ and $q$ are integers). It turns out that $\sqrt{2}$ cannot be expressed in this way (i.e. the diagonal of a square of side length 1). This completely demolished the Pythagorean worldview from its very foundations. The first person to discover this was a Pythagorean around 500 BC who caused a great scandal among his peers by the revelation. Surviving sources tell us that he perished at sea as punishment from the gods for his impiety. Legend has it that his colleagues may have given the gods some help by throwing him overboard. [Answer] This definitely wouldn't work in pure math, as there's nothing so "destructive" you could prove that wouldn't make you a celebrity among mathematicians. Finding a contradiction in ZFC would get you a Fields medal. Disproving the Riemann hypothesis would get you a Fields medal *and* a million dollars. There would never be any question about *whether* to publish, only how quickly to do so. Now, if one wants to get a little silly, a world where P = NP and NP has efficient algorithms is one very unfriendly to mathematicians. In such a world, proof finding (that thing mathematicians pride themselves on) is no more difficult than proof verifying (that thing that mathematicians spent a lot of effort to get machines to do for them), so they'd mostly be either out of jobs or monitoring the automatic proof-finding machines. Perhaps this would be a reason mathematicians wouldn't want to publish such a result, as making your entire job redundant is widely considered a bad career move. Though, since that result also solves a huge number of practical problems, breaks all public-key cryptography wide open, and wins you a million dollars, I can't imagine it staying secret for long. [Answer] The following statement is unproven but widely assumed to be false: **e+π is rational**. A rational number is a number you can write as a fraction. For instance "0.25" is rational because it can be written as "1/4". "7" can be written as "7/1", "14/2" or whatever. We are absolutely sure that π and e are *not* rational, but mathematicians only *assume* that this goes for the expressions "e+π", "π^π" and "e^e". Nobody has ever proven it. The "damage" dealt is more subtle than say, proving "P=NP": If it was proven that the above sum is in fact rational, it would *not* unravel loads of previously watertight theorems. It would however unravel the mathematicians! It flies in the face of the intuition of everyone in the field. An intuition they rely on to guide them towards new results. It undercuts their belief that they "know math", because they "know" that the above sum is irrational in the same sense that they "know" the sun will rise tomorrow. Idea courtesy of mathematician Alon Amit. See [1](https://www.quora.com/For-mathematicians-What-would-be-the-most-surprising-new-finding),[2](https://www.quora.com/Would-it-be-very-interesting-if-e-pi-was-proven-rational),[3](https://qr.ae/TWLuTf) [Answer] A very well known conjecture (hopefully anybody with a CS degree would recall this, for example) is that there does not exist an efficient algorithm to take the [discrete logarithm](https://en.wikipedia.org/wiki/Discrete_logarithm), in the most general case. This fact is sometimes used in cryptopgraphy. There are enough cases in which it *is* computationally tractable that it is plausible, at least, that your character could have with found an algorithm that covers many commonly used cases, or just solved it completely. [Answer] I find it hard to believe that a proof or disproof of any mathematical statement could cause "many careers in tatters". * **If professional mathematicians around the world all made the same mistake, it hardly reflects poorly on any individual mathematician.** Moreover, when a mathematician makes a significant mistake, it almost always is for some non-trivial reason, and the disproof is highly interesting. E.g. Euler's conjecture relating to orthogonal Latin squares ([Wikipedia](https://en.wikipedia.org/wiki/Graeco-Latin_square)) is still studied hundreds of years later, despite it being wrong in every single case Euler did not prove himself (i.e., he couldn't have been more wrong). * If someone disproves e.g. the Riemann Hypothesis, the likely result would undoubtedly be intense mathematical interest in the Riemann Hypothesis. Mathematicians studying the Riemann Hypothesis would likely have a massive boost to their careers as people update their theorems with the new knowledge. If you want a plausible scenario where a disproof of a theorem could result on some egg on mathematician's faces, I suggest the [Classification of finite simple groups](https://en.wikipedia.org/wiki/Classification_of_finite_simple_groups). This theorem is proved, but the proof is so long that it's plausible it contains an error somewhere. Again though, it's not going to destroy anyone's career. But I think there's a better idea... ### Automated theorem proving If you want mathematicians to "choose between the truth or their prestige", **I recommend looking into [automated theorem proving](https://en.wikipedia.org/wiki/Automated_theorem_proving)**, i.e., computers automatically generating proofs. In fact, the computer can be used to make conjectures, and subsequently prove them too. Mathematicians instinctively hate "proofs by computer" and consider them inferior because they don't give human intuition. Thus it's within the realm of plausibility that mathematicians don't want to accept the truth. As proof of concept, see for example the drama surrounding the computer proof of the [Four Color Theorem](https://en.wikipedia.org/wiki/Four_color_theorem). > > This result was finally obtained by Appel and Haken (1977), who constructed a computer-assisted proof that four colors were sufficient. However, because part of the proof consisted of an exhaustive analysis of many discrete cases by a computer, some mathematicians do not accept it. ([Mathworld](http://mathworld.wolfram.com/Four-ColorTheorem.html)) > > > It is within reason that "what a mathematician does" changes radically because of some brilliant ideas in the area of automated theorem proving: many mathematicians are quickly rendered obsolete, replaced by automation (like factory workers previously). [Answer] [Peano Arithmetic](https://en.wikipedia.org/wiki/Peano_axioms#Consistency) (PA) is a very elementary theory of arithmetic. By Gödel's theorems, if it is consistent then it can't be proved to be consistent using methods which can be formalized in the theory itself. Nevertheless, it can be and has been proved to be consistent in stronger theories, so much so that the most mathematicians would regard the consistency of PA as an known result. There are some dissident mathematicians known as [ultrafinitists](https://en.wikipedia.org/wiki/Ultrafinitism) who regard the notion of actually infinite sets as nonsensical. One of the best known was the Princeton mathematician [Edward Nelson](https://en.wikipedia.org/wiki/Edward_Nelson). Somewhat famously, he once claimed to have found a proof that PA was inconsistent. An error was found in the proof and Nelson retracted the claim. He died just a few years later. If your heroine fixes the error in Nelson's proof and shows that PA is inconsistent, the effect would be profound. It would call the coherence of much of pure mathematics into question. Most working mathematicians regard ultrafisitism as a hobbled approach to mathematics, so a result that suggests that ultrafinitism is actually true would be viewed as a hobbling result. (I hedge a bit because, narrowly speaking, a proof that PA is inconsistent is just that. By itself, it wouldn't prove that the ultrafinitist views on the foundations of mathematics are correct). [Answer] That large number factoring is computationally expensive. If You find a way to factor large numbers in a quick way, You've broken most of the encryption used in the world. This means no more banks wiring money to other banks, no more secure websites, no software validation, digital signatures are out... Basically assymetric cryptography as we know it is dead. [Answer] The requirements for such a thing are: 1. Appears to very be strongly correct allowing it to have worked its way into many things, but... 2. the kinks have not been entirely ironed out, which leaves room for it to be disproven. There are three (technically four) candidates I can think of: 1. The Riemann Hypothesis, because because many other proofs are contingent upon it being true. 2. Theory of Relativity and Quantum Mechanics. Discovering the appropriate discrepancies would indicate that we aren't just missing a piece in our understanding of things, but that our understanding is fundamentally wrong. 3. Evolution might be included in this but it's tougher to disprove because it's inherently obfuscated due to deep time which leaves lots of gaps to fill in while also having much of the physically available evidence support it. You could only really disprove it at this point by having a perfect record of deep time. [Answer] Seems like there’s a lot of room in data compression theory. If you were to disprove the minimum space needed to store information (I.e. find a way for two bits to encode all the values zero through five) then you’d change a lot of fields. Data storage and communication would be revolutionized, obviously. But since so much of quantum mechanics is about information entropy, I suspect such a math breakthrough would lead us to some novel material science discoveries. Depending upon how the physical expression of the mathematical compression was expressed, we might have a something-from-nothing energy generator. [Answer] How about going the other way? Proving that PI is 3.1415... instead of [3.2](https://en.wikipedia.org/wiki/Indiana_Pi_Bill) or [4.](https://www.khanacademy.org/math/math-for-fun-and-glory/vi-hart/pi-tau/v/rhapsody-on-the-proof-of-pi-4) You can cook up convincing enough proof that PI=4 for the average joe, and then everyone in academia remain silent because of the ridicule if they go against established truth. Though that has some implications beyond academia, as other industries rely on it. ]

[Question] [ We have a fleet of sub-light speed [generation ships](https://en.wikipedia.org/wiki/Generation_ship) and associated engineering devices/ships. Their original world can no longer support their species, and they must move to survive. The fleet of course cannot support its inhabitants forever. There is therefore a need to populate a new, self sufficient, home world. [](https://i.stack.imgur.com/SAWlK.jpg) [Image Source](http://www.mouthshut.com/hollywood-movies/After-Earth-Photos-Trailers-925666710) The only feasibly reachable planetary system they've identified is very much like our own Solar System, but there's no Earth, no Mars, no Venus - just a wide gap where the [Goldilocks zone](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone) is. For the sake of simplicity, I'll call these planets after their Earth solar-system equivalents. There's a larger asteroid belt, but it's close to the Jupiter whose gravitational forces has prevented the formation of a planet. What would it take to create a new home planet out of the resources available in the other planets and whatever engineering the fleet has brought with them? This should be earth-like, capable of sustaining a breathable atmosphere and plant-life to support life as we know it. **Salient facts:** *Population of the generation-ships* - One million homo sapiens equivalents. There is an ark of breeding stock for plants and animals. *Resources* - We make the assumption that these people understand the mechanics of doing what they want and have brought some necessary equipment - some of the ships are modular in construction so that engines/power generators/whatever else can be separated and combined/used in different ways. *Limit of resources* - the fleet can support the species for the next 1,500 years (counting from when they reach their new home system). I couldn't find any questions that actually built a world, so I'm hoping that we can make this one work. **Scope Guidance** So, I'm looking for a high scale plan with some time estimates for each stage and roughly what would be involved for each stage. Alternative solutions are also welcome. The end result should be a self-sufficient environment which would support and nurture this species until they decide to kill each other off or otherwise ruin yet another world.... [Answer] Well, Difficulty considerations aside, if you took a lot of asteroids and merged them together into an earth-mass planet, it would be entirely molten just from the gravitational binding energy. You'd need a few million years minimum just to get a stable crust, then you'd have to deliver water and volatiles.. Then, once all this had settled down, oxygenate the atmosphere. So no, unless you have quite incredible technology levels. We could do it with human+ tech now, but the time requirements would be huge; millions of years for gradually shifting asteroid orbits and then dealing wit the results of the engineered collisions. *Much* easier would be hollowing out asteroids, spinning them up for interior gravity and turning them into habitats. This would still require a huge amount of work - not least making them strong enough to hold together, but could be squeezed into 1000 years. It's also a much more efficient use of mass. [Answer] What would it take? Answer: Nothing. They're already living in it. If there's a Goldilocks zone, they can park their Space Ark there. That basically sorts out their energy requirements forever, and they can mine asteroids. There's no reason they can't live in their Space Ark indefinitely. But more likely, like any family, they're going to start wanting to build extensions on their house as their family gets bigger... Andrew Dodds's answer is perfectly correct - they can built habitats out of asteroids. Hollowing them out is probably not going to be successful, because space debris tends to be fairly porous, but at the very least it'll provide the raw materials for making concrete. (Not the kind with limestone, of course, but as the Romans proved, there are other ways of skinning that particular cat.) The various metals and silicates in the asteroids can also be processed for other raw materials, and water-rich asteroids will start building up atmosphere and terraforming in those habitats. The best part with this is that it's evolutionary. You start with the Space Ark ship, and over time it'll accrete more and more habitats attached to it. What you'll end up with won't be an "Earth" as such, it'll be more of a 3D zero-gravity rabbit warren. [Answer] **No, you cannot build a world in 1000 years** As already mentioned by Andrew Dodds, the time span you have at your hands is orders of magnitude less than what is simply required by a newly formed planet to cool off and get stabilized in its orbit. Of course we are talking about moving asteroids from their orbit and combining/colliding them together to form a planet in the habitable zone. Here are some of the major concerns. There are many, many more, but I am confining myself to only the primary ones here. 1. **Moving mile-wide and larger asteroids out of orbit is *extremely* difficult** Yes, it is. With a density of no more than 3 g/cm$^3$, (normal for metal/rock mixture) an asteroid of diameter 1 km would have a mass of 1.57 x 10$^{12}$ kg (i.e. 3 billion tons). Asteroids in the asteroid belt have a speed of more or less [25 km/s](https://i.stack.imgur.com/fMILQ.jpg). One asteroid of 1 km diameter would have momentum equal to 3.92 x 10$^{16}$ kgm/s. It is going to *slightly* hard for you (the people in the spaceships) to change the direction of motion of hundreds of millions of asteroids of this much size twice. Once changing their direction towards the central star (to bring them inwards into the goldillocks belt) and then, at tangential direction (to put them into orbit around the sun and stop them from going on and falling into the sun). I haven't done the detailed math, but I can tell you already it will be practically impossible to meet the energy requirements for this, unless you are using antimatter engines and have tens of thousands of tons of antimatter available to you. 2. **It takes really long time at conventional rocket speeds to move things at interplanetary scale** A one-way journey from Earth to Mars takes [150 days](http://www.universetoday.com/14841/how-long-does-it-take-to-get-to-mars/) (shorter estimate). And that is when you have everything planned and a *lot* of fuel at your disposal. For pulling in individual asteroids one by one from the asteroid belt to NEO distance, you would require at least 5 years for each round trip. Travelling to the asteroid, attaching to it and then travelling back to NEO. If you work on individual asteroids one by one (and I see no other method, even theoretical, at current technological levels), it will take you a couple million years at least just to bring in the chunks together in the same NEO orbit, let alone combining them to form a planet! 3. **You need the right materials. And lots of them** Earth has a large content of silicates and metallic minerals. The sodium content of our planet alone is astounding. Then there is a **lot** of iron and nickel, too. Beyond the freeze line, a lot of the asteroids are made of *ices* (frozen carbon dioxide, ammonia, methane etc). Bringing them closer to the sun into the goldillocks zone will quickly melt and then boil them away, removing all hopes of incorporating them into your dream-Earth. While water is available in more than excess quantities throughout the galaxy, the correct ratios of rock, water and ferromagnetic metals (for the core) is far too difficult to find or create. If you pick up asteroids randomly, you would probably end up with a terrestrial planet with a too high metallic content. 4. **The cooling will take tens of millions of years** That has already been discussed by Andrew Dodds, so I will not get into the details here. It should be sufficient to say that your newly formed planet will take orders of magnitude more time to just cool off, than what you have available at your hands. 5. **And the other little issues…** Like oceans formation… the right chemical mix in the oceans… setting up the water cycle… setting up the atmosphere with correct composition and thickness… continent formation… setting up and maintaining the orbital tilt… finding and capturing the right sized moon (of course you wouldn't want to go the giant impact path)… **To Sum It Up** …it means something to say that our Earth is 4.56 billion years old. [Answer] **Build a [fusion candle](https://worldbuilding.stackexchange.com/questions/36732/fusion-candle-getting-earth-to-jupiter).** You have a large gas giant? Perfect, you have a world mover with its own reaction mass/power supply. I assume this gas giant has a few largish moons? If not, move it around the system to capture some other suitable planet. Forget the asteroids, they contribute nothing of value, at least concerning raw mass. ([Wikipedia](https://en.wikipedia.org/wiki/Asteroid_belt): "The total mass of the asteroid belt is approximately 4% that of the Moon.") Maybe use a quick sweep with your gas giant to clear it. Once you have your mobile gas giant with one or more nice rocky satellites, move the assemblage in a cozy orbit and start to terraform the moons. If you did it just right, those icy asteroids you swiped earlier, or maybe a saturnian ring, can provide the water for your oceans. The biggest hurdle is your time plan. I don't know how long the astroengineering will take, but 1000 years isn't even enough to build habitable biospheres from scratch. You'll really want to start (while all the big moving goes on) by constructing closed ecologies to resettle your tribe, with mining and farming, which will extend the time left to you. No need to restrict yourself to an all-or-nothing / ship-or-planet choice. [Answer] I would like to post an answer which expands on Andrew Dodds' excellent post. The colonists, upon arrival, would most likely not WANT to settle on a planet. 1) **They have lived their whole lives in space** and that's probably true of their parents and grandparents as well. People accustomed for generations to living aboard ship will likely view the lifestyle of living on a planet as akin to how most of us would view the Amish. I'm sure they are generally happy with their lifestyle, but I'm not going to do it myself. ("You grow your crops in DIRT? Actual dirt? And you eat real animals? And you go outside and expose yourself directly to the raw environment?") 2) **Asteroids (or space stations built from them) can easily be moved**, eventually forming a Dyson swarm. This is much more efficient and a Dyson swarm is largely the standard model nowadays for a K-2 civilization. 3) **There is a LOT more living space.** A planet can support a few billion inhabitants, a Dyson swarm can support trillions. 4) **Asteroid mining is better than planetary mining**. The reason we don't do it now is because of how hard it is to get there, and minor lifestyle inconveniences like not being able to breathe. But if you already are there, and have the equipment to survive, the resources available are far greater than what we have on Earth. 5) **Earth-size planets have inconveniently large gravity wells**, hampering space travel. These colonists are likely to want to continue to travel in space and constructing a massive gravity well just so you can climb up and down it is not helpful at all. 6) **The colonists may have genetically engineered themselves** to adapt to the space environment, for example adding radiation resistance or tolerance for low gravity. Regardless of cultural and lifestyle issues, they might find an actual planet not especially welcoming biologically, or at least not more so than their regular space environment. 7) **Energy availability on a planet is bad**. You have three plausible choices for energy: solar, fusion, and fission, and all of them favor asteroids or space stations. Solar collection is optimized by constructing a Dyson swarm, for maximum collection area. Fusion power requires lots of volatiles (likely hydrogen), which will be most easily found in either cometary ice or, secondarily, the atmospheres of gas giants, depending on how good your rockets are and how much mass the gas giants have. This requires lots of travel to the outer, or at least middle, solar system to collect it. The low gravity of asteroids simplifies the launching and landing (as well as less energy and time needed for travel due to starting farther away from the star in the first place). Finally, fission power requires lots of uranium, which needs to be mined, and mining is easier on the asteroids. And if you're using fission, disposing of the radioactive waste is a lot easier if you can just toss it out into space (although I would expect colonists at this technology level to be quite a bit better at recycling, or at least concentrating, the stuff than we are). 8) **Planets have pollution problems** that you just don't have on space stations. While simply throwing waste overboard is not necessarily suitable in general (because it is still in your orbit and sooner or later it will come around again and might hit you) you can recycle what you can and easily move most of your really troublesome garbage into a non-intersecting orbit. If some disaster contaminates an entire habitat, you can just build a replacement. Actually there would probably be so many habitats that the civilization as a whole would barely even notice a Chernobyl or Fukushima. 9) **Politics are easier** when you have millions of more or less independent but cooperating habitats. When your only practical choices for war are "we will stop trading with you" and "we will blow up your habitat, killing everyone" it is more advantageous to just pack up and move away or ignore neighbors you dislike, discouraging violence and war. It also means everyone can find a political system that suits them personally. I think it's unlikely that everyone in the colony fleet will want the same political system. Some might want a libertarian utopia, a communist utopia, a socialist utopia, a military dictatorship utopia, or any other form of utopia they can think of, and all of these systems, including many I can't think of, will likely exist. "Asteroidica, love it or leave it" becomes a real option and people can move to any of the thousands or millions of competing political and social systems. I think interstellar colonists will be more interested in the number, variety, and positioning of asteroids in a target star system rather than caring about planets at all, with the possible exception of small gas giants for hydrogen collection. For further insights I recommend Isaac Arthur's excellent Youtube series, including an episode that specifically talks about this issue: [Life in a Space Colony, ep3: Early Interstellar Colonies](https://www.youtube.com/watch?v=6VBCxWcAPXw) [Answer] We need an approximation of their technology level. Suppose the trip took 1500 years. The ships are the size of US aircraft carriers. And the distance was about 20 light years. The ship would then be travelling at 0.013c, which is pretty fast. We'll use Newtonian energy approximations (it is relatively accurate at 1% c) and we get roughly 0.5% of the mass of the ship is kinetic energy. An aircraft carrier is about 100 kilotonnes. So the KE of the ship is 5e22 J, or 1e23 if you count coming to a stop at the end. Slightly more if you want constant accelleration (as that leads to a top speed 2x higher; this is reasonable to not assume, as at 0.01c the interstellar medium isn't frictionless). Plowing through the interstellar medium is another issue. At 0.01 c each square meter of the ship impacts 158 micrograms of hydrogen/year. Over the 1500 year journey, that sums to 237 milligrams. A cylindrical aircraft carrier has a cross section of 5000 m^2, so that comes to about 1 kg of hydrogen. In comparison to the ship mass that is trivial; thus the interstellar medium is mainly dangerous as it is a form of hard radiation. In comparison, the binding energy of Earth is about 1E32. The big problem with assembling a planet is dissipating that binding energy. The binding energy of an earth-sized planet is enough to send 1 billion supercarrier sized generation ships to nearby stars. So the task you have for the ship is 1 K-type civilization higher in effort than the ship itself. Another way to look at it is that it would take a K-2 type civilization 6 years to process enough energy to disassemble or assemble a reasonable tempurature earth-like planet. And if you are anywhere near a K-2 type civilization, why do you want a planet? But we can approach it that way. Assume these generation ships where sent from a K-1 type civilization. The trip might have begun with the plan to aim for somewhere else, or get resupply or something, but a solar-system wide war that ended badly for everyone wiped out the civilization behind them. Over the 1500 years, they managed to avoid a similar conflict, and developed technology sufficient to reach a K-2 level of civilization; they just are missing a star. They arrive in the destination solar system, and they release von neumann machines. These first disassemble small bodies and reproduce, gathering raw materials. This provides them with an industrial base. Huge solar collectors are built to lift more mass out of gravity wells and build yet more solar collectors. Matter is fuzed and transmuted on large scales. Low atomic matter is sucked out of gas giants using ridiculous technologies (fusion candles whose only purpose is to shoot gas up the gravity gradient? Orbital fountains? Vacuum energy pumps?) Computronium is produced and a Matrioshka brain is constructed to aid in further technological development. The star starts to go dark. Only as they approach a full K-2 civilization does the "lets build an Earth" project start. A full K-2 civilization would take 6 years to pull this off; either they efficiently wait until they are a K-2 civilization (or beyond using exotic technology), or they do it slowly before hand (you know, for practice). Regardless of which they do, if they approach K-2 exponentially almost all of the work will be done when they are almost-K-2. A 1% K-2 civilization requires 600 odd years to build an Earth. Of course, the technology level required makes the 1500 year limit a bit of a joke; this civilization has mostly moved out of physical bodies by this point. The building of the duplicate Earth might be a thank you to the ancestors, and a nature reserve for them and a biosphere. Pretty expensive even for a K-2 civilization however. [Answer] Well, I have to ask... > > The fleet of course cannot support its inhabitants forever > > > ...why not? We don't quite have the tech to keep people alive in a fully technological environment indefinitely yet, but we're getting there - and if that technology would be an absolute prerequisite for a generation ship. So honestly, if you have generation ships, why would you need to anchor yourselves to a planet? A planet is a nice place for a species to grow up, but ultimately there's a lot of wasted mass and wasted space that we just can't use, and we're stuck at the bottom of a pretty steep gravity well. A planet, ultimately, could be seen as a dangerously unstable place to live. You can't move it if there's a big rock coming, you can't use the vast majority of its mass, and you can't control its climate. Rather than trying to build a planet, think instead of staying aboard the fleet and just using the resources available in the solar system. Any raw material you can think of can be got from asteroids or gas giants. If you need more living room, consider building [asteroid terreria](https://en.wikipedia.org/wiki/Terrarium_(space_habitat)) and living inside them. [Answer] I don't know if it can be done in 1000 yrs, but it seem unlikely. Here are some ideas to help. First, you need to get a large dense enough group of rock into an earth like orbit. It has to be large enough for gravity to pull in debris from the asteroid belt(well maybe that is too much) and surrounding space. From what I have learned the planet will start auto-rounding at a round 100mi in diameter with the right density core. If you could add a significant layer of water, perhaps you could float an island like structure on it. The water would cool the incoming debris, and allow it to more gradually fall into the center of the planet. There would be giant waves from underneath as the planet rounds itself, but the water would still buffer them. Hopefully, your island like structure, can move like a ship at sea. As long as it has enough engine power to move of the way of giant waves you could start living on them. Also growing food on the tops decks of the ship(s)/island(s). After that timing is going to be a critical issue. You need enough debris to fall into to eventually create a usable land mass, but not so much that the impacts evaporate or blast the water into space. If you don't have gravity assisting you, and you have to actually move 1000's or 10,000's of asteroids manually the project will probably fail. If you can nudge enough asteroids into our new earth's gravity well it improves your chance of success. All of your ships will have to be nudging debris causing it to change trajectory to our planet. You will have debris which contains or even mostly water so you don't have to make it all yourself. The key is having enough land to settle people, but not enough mass to pull in the entire asteroid belt. While pulling in the asteroid belt would certainly create a planet, it would never cool fast enough to live on in a 1000yrs. [Answer] Hypothetically you could probably do it... The first thing you'd have to do is get an iron nickel ball that is roughly 1200 km thick. That's not that hard since you could farm it from just about anywhere in the solar system. You set up a massive magnetic spinner thing, then you wrap that with liquid iron-nickel that is has been heated to a very high temperature till the radius is about 3500 km. Again. This shouldn't be very hard because there should be plenty of iron-nickel in any solar system all over the place in fairly easy to get places... The problem is the mantle and crust which can easily be made, but it's more the getting the proper balance of materials, but in a thousand years that shouldn't be a problem. You just continue heating as you poor the liquid resources onto the planet and then when you get to the right radius you stop heating, poor a layer of silicates more or less over the mantle and build up the continents and such as you like. The biggest issues is getting the materials hot enough. The giant magnet thing might seem like a problem, but you're building a planet. if you're doing that you can build something like giant magnet thing. The second issue is the proper material balance... Lastly there is the terra forming which may make you run into a problem, not in the atmosphere. THat'd be easy, since you're already moving massive resources it's hardly an issue to dump a bit more. The hard part is that dirt is not soil so once you have it all there you have to do a lot of working on making and spreading soil. If people worked diligently it probably could be done, but more than likely they wouldn't. They'd get to "good enough" and stop, which would slow the process down a lot and then it becomes a probably not, but it can probably be done ignoring human laziness. And while all this is possible hypothetically, it would be a huge amount of work for and you'd be wasting resources and time to do something that is largely just a show of power and not a "needing this for living on" situation. But whether it can be done or not isn't really an issue so much as if a civ could, they'd not do this. If they have the tech to move the resources to make a planet then they could have done it to their homeworld. If it's their star that is the issue they could simply move the planet. If it's the magneto sphere dying then they can charge it back up. So you see, the tech needed to do this wouldn't make a whole lot of sense. [Answer] If the gas giant is on the smallish side and within the Goldilocks Zone, your ark ship could build very large microwaves (or some other suitable electromagnetic wave machine...eg giant lasers) to [photoevaporate](https://en.wikipedia.org/wiki/Photoevaporation) the lighter elements (H, He, Li, etc). This should hopefully leave you with the rocky core and the heavier gases (O, N, At, CO2, etc). It'll still be a tad bit warm, but less so than the amount of heat generated by fusing asteroids together. [Answer] If the gas giant has at least one moon that is suitable for terraforming, an artificial sun can be built which supplies the energy needs. This will work only if the moon receives less energy than optimal. If there is a different moon that receives more energy than needed, then a megastructure that covers the moon needs to be built. The purpose of the megastructure is to reduce the intensity of the energy from the star. Another option is to build a ring world. Similar to the rings in the Halo game. A seemingly good option will be to build a [Globus Cassus](https://en.wikipedia.org/wiki/Globus_Cassus). [Answer] **O'Neill Cylinders** - Just going to paste the answer Assumption the Gas Giant or Moons or both can supply enough "gas" to create an atmosphere. One distinct (my opinion) benefit here is we know how to make bigger rocks into smaller rocks :) Ok, as each habitat is constructed it decreases the stress placed on the Generation Ship(s) and with logistical planning may be capable of reducing demand on Ships Stores (build a food/water producing habitat first?). It is believed that a single O’Neill cylinder could house several Million people. <http://www.nss.org/settlement/space/oneillcylinder.htm> Assuming the Gas Giant has the required gas’s for creating an Earth Atmosphere, then the colonist may want to construct a ship that can “dip through” the Gas Giant's atmosphere and “Scoop and Compress” the gas. It is equally reasonable to assume there are comets or other sources for acquiring the components of an atmosphere as well as the regolith for soil. The only Time estimate I have is for the 2nd Island and that is 2 years (L5 Society). So I feel it is reasonable to assume the 3rd Island can be built in less than 100 years. The following is extracted from <https://en.wikipedia.org/wiki/O>'Neill\_cylinder **The Island Three design**, better known as the O'Neill cylinder, consists of two counter-rotating cylinders, each five miles (8 km) in diameter, and capable of scaling up to twenty miles (32 km) long. Each cylinder has six equal-area stripes that run the length of the cylinder; three are transparent windows, three are habitable "land" surfaces. Furthermore, an outer agricultural ring, 10 miles (16 km) in radius, rotates at a different speed to support farming. The habitat's industrial manufacturing block is located in the middle, to allow for minimized gravity for some manufacturing processes. A NASA lunar base concept with a mass driver (the long structure that extends toward the horizon that is a part of the plan to build O'Neill Cylinders). *Substitute Asteroids, Moons etc* To save the immense cost of rocketing the materials from Earth, these habitats would be built with materials launched into space from the Moon with a magnetic mass driver. **Design** **Artificial gravity** The cylinders rotate to provide artificial gravity on their inner surface. At the radius described by O'Neill, the habitats would have to rotate about twenty-eight times an hour to simulate a standard Earth gravity. Research on human factors in rotating reference frames indicate that, at such low rotation speeds, few people would experience motion sickness due to coriolis forces acting on the inner ear. People would, however, be able to detect spinward and anti-spinward directions by turning their heads, and any dropped items would appear to be deflected by a few centimetres. The central axis of the habitat would be a zero-gravity region, and it was envisaged that recreational facilities could be located there. **Atmosphere and radiation** The habitat was planned to have oxygen at partial pressures roughly similar to terrestrial air, 20% of the Earth's sea-level air pressure. Nitrogen would also be included to add a further 30% of the Earth's pressure. This half-pressure atmosphere would save gas and reduce the needed strength and thickness of the habitat walls. At this scale, the air within the cylinder and the shell of the cylinder provide adequate shielding against cosmic rays. The internal volume of an O'Neill cylinder is great enough to support its own small weather systems, which may be manipulated by altering the internal atmospheric composition or the amount of reflected sunlight. **Sunlight** Large mirrors are hinged at the back of each stripe of window. The unhinged edge of the windows points toward the Sun. The purpose of the mirrors is to reflect sunlight into the cylinders through the windows. Night is simulated by opening the mirrors, letting the window view empty space; this also permits heat to radiate to space. During the day, the reflected Sun appears to move as the mirrors move, creating a natural progression of Sun angles. Although not visible to the naked eye, the Sun's image might be observed to rotate due to the cylinder's rotation. The light reflected from the mirrors is polarized, which might confuse pollinating bees. To permit light to enter the habitat, large windows run the length of the cylinder. These would not be single panes, but would be made up of many small sections, to prevent catastrophic damage, and so the aluminum or steel window frames can take most of the stresses of the air pressure of the habitat. Occasionally a meteorite might break one of these panes. This would cause some loss of the atmosphere, but calculations showed that this would not be an emergency, due to the very large volume of the habitat. **Attitude control** The habitat and its mirrors must be perpetually aimed at the Sun to collect solar energy and light the habitat's interior. O'Neill and his students carefully worked out a method of continuously turning the colony 360 degrees per orbit without using rockets (which would shed reaction mass). First, the pair of habitats can be rolled by operating the cylinders as momentum wheels. If one habitat's rotation is slightly off, the two cylinders will rotate about each other. Once the plane formed by the two axes of rotation is perpendicular in the roll axis to the orbit, then the pair of cylinders can be yawed to aim at the Sun by exerting a force between the two sunward bearings. Pushing the cylinders away from each other will cause both cylinders to gyroscopically precess, and the system will yaw in one direction, while pushing them towards each other will cause yaw in the other direction. The counter-rotating habitats have no net gyroscopic effect, and so this slight precession can continue throughout the habitat's orbit, keeping it aimed at the Sun. ]

[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. I am writing a setting for a role-playing game. In it an alchemist has finally found a way to create gold from lesser metals. Like his former historical models the alchemist is so jubilant over his discovery that he seems to ignore that his "gold"...well, it really *looks like* gold and seems to be metallic, but some things like density, conductivity, malleability are absent. In short: It is *not* gold. What I need is a substance which could have been mixed by an alchemist and is as gold-like as possible. May contain heavy metals or poisonous substances, the alchemist may be...a little affected. The well-known pyrite is the soft-option, I do not find it particularly compelling as gold ersatz. ADDITION: Some additions to the proposed solutions * We are talking about a fantasy world with mediaeval technology level. All metals with a comparable density level are out of the question: tantalum, tungsten und uranium are out of the question, their necessary production conditions make them nearly impossible to produce. Platin metals which have an even higher density are even rarer than gold. * For the same reason radioactive decay or nano clusters are out of the question. It takes high technology levels to produce that result and the cost is astronomical. * Mixing gold in small parts does not work. In fact the experience with gold alloys shows that at least 75% volume per cent is necessary to get the given color. Best solutions so far are brass alloys: * Nordic gold: Looks definitely like gold and is a metal. Composition: 89% copper, 5% aluminium, 5% zinc, and 1% tin. *Problem: Aluminium cannot be produced because it needs high-powered electrolysis and rhyolite which is not available at this time.* * Another very gold-like metallic alloy suggested by a friend is [gold tombac or red arsenic tombac](https://en.wikipedia.org/wiki/Tombac). Composition: Gold tombac >85% copper and zinc Red arsenic tombac: 98% copper and 2% arsenic * Lead iodine: Looks like gold powder. *For those who would like to know how characters can test gold*: The metal workers and also the alchemists knew since ancient times that [heating and melting gold](https://en.wikipedia.org/wiki/Cupellation) was a very good method to test purity because normal alloys are separating. Another old method is the stroke test: Move both gold and the unknown metal over a stone and compare the results. Sounds crude, but is very, very good to detect fake gold. Density measurement is another option: Get real gold and a probe of the unknown metal with the same weight. Fill a container with water and drop the gold into it, so that the gold is completely submerged; mark the water level. If the unknown metal is gold, it will have the same level, if not, the water stands perceptibly higher. ANOTHER CLARIFICATION: Many people have wondered or could not believe that alchemists which are capable to create new stuff are not able to admit that it is not gold. It sounds strange, **but it is in fact true.** In "Alchemy: The Philosophers's Stone" from Allison Coudert it is explicitly mentioned in the chapter about transmutation that alchemists believed in several forms of gold. Geber said that gold is created from most subtle mercury substance and some pure, red, fixed sulphur substance which gives gold its color. Like the sulphur has different tones of red, so must have gold different shades of yellow. Chen Yin, a chinese alchemist, mentioned that the gold created from transmutation incarnates so many chemical ingredients that is superior than natural gold. Some of them *drank* actually tin (IV) sulfide as "liquid gold". It is also mentioned that the alchemists stayed away from practical metal workers because they felt grandiose. Allowing to test their gold sounded like a sacrilege. There were also many, many stories about witnessed transmutations (Johann Konrad Richthausen, Wenzel Seiler und Nicolas Flamel. Yes, the guy from Harry Potter did exist in reality). So alchemists were easy prey to delusions of grandeur, their environment (mercury etc.) did not help exactly. [Answer] **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. **Nordic gold** might serve your purposes. It is an alloy which was developed for the Swedish 10 kronors coin. 89% copper, 5% aluminium, 5% zinc, and 1% tin It clearly isn't gold but does look more like it than iron pyrite. It is clearly metallic while pyrite is too crystalline. You can adjust the percentages here to realistically say that you found something that is even closer in color. [Answer] > > What I need is a substance which could have been mixed by an alchemist and is as gold-like as possible. > > > **How about gold itself?** Bear with me, here: While there are a lot of things that look *kinda* like gold, nothing quite looks as good as the real thing (as pointed out in Cort Ammon's most excellent answer). So, why not use the real thing and have your alchemist accidentally stumble across [gold plating](https://en.wikipedia.org/wiki/Gold_plating), which of course is simply the process whereby relatively very small amounts of gold are deposited onto the surface of an object made of a different substance, ideally with a similar density. How could he do this with typical medieval kit (i.e., without readily available electricity)? According to [this paper](http://link.springer.com/article/10.1007%2FBF03354479) in JOM, researchers were able to replicate the results of pre-Columbian smiths in Northern Peru using an electrochemical reaction by dissolving gold into an aqueous solution of NaCl + KNO3 + KAl(SO4)2 · 12H2O, achieving gold plating onto copper. The chemicals would have been readily available minerals to a medieval (al)chemist, consisting of ordinary salt, [saltpeter](https://en.wikipedia.org/wiki/Potassium_nitrate), and [potassium alum](https://en.wikipedia.org/wiki/Potassium_alum). In fact, they are all naturally-occurring. Alchemists I've seen in fiction tend to use hilariously complex apparatus, have spent many years [sniffing mercury vapours](https://en.wikipedia.org/wiki/Mercury_poisoning), and have weathered many, many failed attempts in search of that elusive ? ⟶ Au formula. It wouldn't be hard to imagine an alchemist cracking open a dusty tome that suggests they need small amounts of the target element as a catalyst to start the reaction. Trembling in anticipation, they add in a pinch of gold dust into the above solution, and soon their entire hunk of metal appears to be pure gold! Of course the gold plating would be discovered it as soon as anyone scratched it hard enough, but I think that's the intent, right? Something that is initially very convincing, but doesn't survive scrutiny. You specified "it's not gold", and while this would have a very small amount of gold in it, it's still 99.9% "not gold", which I hope satisfies the spirit of your criteria. [Answer] **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. When I was younger, as part of a science summer camp we made pennies turn to gold. I don't know what the bar will be for "looks like gold," but it seemed like a good starting point for me. The process was: * Start with copper pennies (not the zinc filled ones we have today) * Zinc plate them (which makes them look silver) * Heat them over a Bunsen burner until the zinc and copper meld into brass (which looks "gold" to a bunch of kids) [](https://i.stack.imgur.com/ggOMQ.jpg) [](https://i.stack.imgur.com/GPEuD.png) [Answer] **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. A way to do this would be to allow "success". Our friend has actually found a way to fission Lead into Gold. In particular Lead-206 into [Gold-198](https://en.wikipedia.org/wiki/Isotopes_of_gold), via the chain -alpha-> Mercury-202 -alpha-> Platinum-198 -beta-minus->, the latter isotope having a half life of 3 days. That's a long time for something to be chemically gold before decaying to (mostly) Mercury. Alternatively, Gold-195 has a half-life of 186 days, but mostly decays to Platinum, which may not count as "failure". ## Edit: Useful tables of decay products and sources: Lead-204 is naturally occurring in the absence of [uranium](https://en.wikipedia.org/wiki/Uranium_series#Uranium_series), [actinium](https://en.wikipedia.org/wiki/Uranium_series#Actinium_series), and [thorium](https://en.wikipedia.org/wiki/Uranium_series#Thorium_series) decay chains. Lead-206, -207, and -208 are products of those chains, respectively. Those four variants of lead are "stable". * Lead-204 -alpha-> Mercury-200 with half-life >10^20 years * Lead-206 -alpha-> Mercury-202 with half-life >10^21 years * Lead-207 -alpha-> Mercury-203 with half-life >10^21 years * Lead-208 -alpha-> Mercury-204 with half-life >10^21 years Thallium-203 and -205 are stable. * Thallium-203 -alpha-> Gold-199 with unknown half-life Mercury-196, -198, -199, -200, -201, -202, -204 are stable. * Mercury-198 -alpha-> Platinum-194 with unknown half-life * Mercury-200 -alpha-> Platinum-196 with unknown half-life * Mercury-202 -alpha-> Platinum-198 with unknown half-life * Mercury-203 -beta-minus-> Thallium-203 with 47 day half-life * Mercury-204 -alpha-> Platinum-200 or -double-beta-minus-> Lead-204 with unknown branching fraction and unknown half-life. Platinum-192, -194, -195, -196, -198 are stable. All of these decay via alpha emission to various Osmium isotopes. * Platinum-198 may also twice beta-minus to Mercury-198 with a half-life >10^14 years. Gold-198 is the intermediate in the above Platinum-198 twice beta-minus chain. It has a half-life of 2.7 days. * Gold-199 -beta-minus-> Mercury-198 with half-life 3 days The above give decay chains from Lead-206 and Lead-207 to Gold-199. The only hard science problem here is encouraging these various alpha emissions so our friend's reaction doesn't take many, many times longer than the current age of the universe. I recommend [Fly Amanita](http://www.uesp.net/wiki/Skyrim:Fly_Amanita). (Not really.) [Answer] You can try a reaction between potassium iodide and lead nitrate; the resulting lead iodine will be [visually somewhat similar to gold powder](https://www.youtube.com/watch?feature=player_embedded&v=TRq9hnOGvaE). It involves the usual trope of turning lead into gold, and as it is a lead salt, it is poisonous. It is also not a metal, so, unlike brass, nordic gold, or other copper alloys, it has no metallic properties such as malleability, electrical/thermical conductivity, etc. If your alchemist is minimally competent, he will know this isn't actually gold, but he may deceive himself that it presents a step in the right direction... or he may (try to) deceive others, as long as he doesn't allow them to examine it more closely. [Answer] Based on [an article](http://phys.org/news/2015-09-golden-silver-nanoparticle-gold.html) scientists have discovered that a specially crafter silver structure can look, act and behave exactly like a gold-based structure. > > The entire negatively charged, silver-based complex ion has the chemical formula [Ag25(SPhMe2)18]-. > Although a few other silver nanoclusters have been synthesized in recent years, this is the first silver nanocluster that has a matching analogue in gold: [Au25(SPhMe2)18]- has previously been reported. Besides both nanoclusters having 25 metal atoms and 18 ligands, they also both have all of their atoms and electrons arranged in almost exactly the same way. > In their study, the researchers performed tests demonstrating that the silver and gold nanoclusters have very similar optical properties. Typically, silver nanoclusters are brown or red in color, but this one looks just like gold because it emits light at almost the same wavelength (around 675 nm) as gold. The golden color can be explained by the fact that both nanoclusters have virtually identical crystal structures. > > > Note that this doesn't say that the molecule based on silver atoms behaves like gold, it just says that the structure behaves similarly to a particular gold molecule structure, but which includes some of the properties gold has. [Answer] **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. What about [Brass](https://en.wikipedia.org/wiki/Brass)? I think it actually was discovered by alchemists that thought they finally found gold. [Answer] I see you have an accepted answer already, but I think you'll still find this useful. I did an experiment in my high school chemistry class where we turned pennies into "gold" using a few chemicals. These chemicals are readily available now, I don't know how easy they would be to extract and purify in those times. That'd require further research. [But the basic experiment (full steps at this link)](http://www.sciencecompany.com/Turn-Copper-Pennies-Into-Silver-and-Gold-Pennies.aspx) was simple. You had to get zinc lumps, water, and zinc sulfate solution mixed in a beaker and bring to a boil. This will cause the pennies to turn from a copper color to silver. Remove the pennies from that solution, and heat them (either directly in a flame or just placed on a hot enough surface), and they'll form a brass alloy coloring. I know this can stay for years, as I did this experiment in 2008, and I cleaned out my room last week (October 2016) and that penny is still gold. Keep in mind that modern pennies are a very thin layer of copper over zinc. So this, along with a little bit of speculative history, gives me an idea of how you might be able to fool many people into thinking you have gold. You need your lead of course, then the zinc and zinc sulfate as mentioned in the last paragraph, a little bit of copper, and a [Baghdad battery](https://en.wikipedia.org/wiki/Baghdad_Battery). I did a bit of googling and it is kind of conflicting, but it might be possible to electroplate copper onto lead. A chemist would need to tell you more about that, as I am not one. But on the Baghdad Battery link above, the tv show Mythbusters made a few replicas and proved it was possible to electroplate some metals in copper, at least in small quantities. And the batteries themselves are ancient, so they can be constructed for sure. If you can get the copper onto the surface of your lead object using the batteries, and then run it through the experiment in the first paragraph, you could conceivably form a brass shell around it convincing enough to fool most people into thinking it was gold. With the added benefit of the [density of lead](https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=density%20of%20lead) being kinda close to the [density of gold](https://www.google.com/search?q=density%20of%20gold&oq=density%20of%20gold&aqs=chrome.0.0l6.2159j0j7&sourceid=chrome&ie=UTF-8) (at least close enough to fool someone who hasn't spent much time around gold), since it would still be mostly lead anyway, you could make "gold" coins from lead and fool all but the most sensitive measurements available at that time. [Answer] **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. How much are we confined to medieval chemistry? If not - gold, but an unstable isotope would have quite interesting properties storywise; turning into lesser metals over time, emitting deadly radiation ... Perhaps you could even make a cursed ring out of it, possessing the ring-bearer slowly? Getting unstable gold in the first place is a bit hard, but if you can get high-energy particles into your story, it would be quite possible making from lesser metals. See Wikipedia - [Synthesis of precious metals](https://en.wikipedia.org/wiki/Synthesis_of_precious_metals) [Answer] **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. Note that ever since ancient Greece, measuring density by combined weight and volume displaced has been well known ("eureka!"), as has plating/leaf application, so producing something that survives even basic testing and still seems to be gold is more difficult than it might seem. There are also some other tests. Fake alchemists often used a small amount of real gold to "prove" they were on the right track and just needed more time (and investment) to scale up the process. I actually like the idea of someone scamming a legitimate alchemist, though it would have to be one who didn't know the usual cheats. ]

[Question] [ I have a moment in my story where the main character comes across a planet with "solid" swamps. Let me explain. Basically, there are creatures here that can swim through the ground like it was some very thin liquid, however, when any other organism comes in contact with the substance, it's like walking on solid ground. This creature would be relatively large (around the size of a killer Whale) and prey on the other species that find themselves in the middle of these plots of solid alien swampland. What are the possible organs, adaptations, and behaviors a creature like this would possess, along with what type of substance would exhibit this ability? [Answer] Edit: I've incorporated some of the suggestions from the comments I'm not sure how possible this would be in real life, but as you've not used science-based or hard science tags I think this should be believable enough. What you're looking for is a [Non-Newtonian Fluid](https://en.wikipedia.org/wiki/Non-Newtonian_fluid). The most famous of these is probably corn starch in water (or custard, which often amounts to the same thing) which is a liquid but if enough pressure is applied to it it becomes solid and can be walked on, if you do it right. Now that's not quite what you are looking for, you want your unwary prey not to realize they are in a 'swamp' of sorts so needing to walk in a specific way is out of the question. So here's where we start to play with things. We make the Non-Newtonian Fluid (let's call them NNFs for short) a lot thicker, so that instead of requiring careful high pressure movements to make it solid instead it's solid most of the time but if you move slowly and gently enough through it behaves like a liquid. Edit: Apparently this is possible even without any handwaving, what we need is called a shear thinning fluid - the faster you try to move it, the easier it is to do so. Thanks to [Agent\_L](https://worldbuilding.stackexchange.com/questions/88816/creature-that-swims-in-the-solid-ground/88821?noredirect=1#comment263575_88821) and [Aliden](https://worldbuilding.stackexchange.com/questions/88816/creature-that-swims-in-the-solid-ground/88821?noredirect=1#comment263631_88821) in the comments According to this [website](http://www.discovery.com/tv-shows/mythbusters/about-this-show/swimming-in-syrup/) it is possible to swim in an NNF, and in fact it's easier the bigger you are. That suits us fine as you want a fairly large creature. So lets look at the creature itself now. It needs to be making slow and gentle movements to maintain the liquidity of the NNF so it's not likely to be a chasing predator. Ambush seems much more likely and sensible. So we want a creature that waits under the surface for it's prey to walk over head before springing up. As pointed out by [anaximander](https://worldbuilding.stackexchange.com/questions/88816/creature-that-swims-in-the-solid-ground/88821?noredirect=1#comment263560_88821) in the comments springing should work fine, even if it causes the NNF to solidify a large and strong enough creature should have no problem bursting through a thin layer of solid ground. Waiting for prey to walk over head isn't the best strategy though, you want to lure your prey over. Conveniently your creature also probably needs some kind of snorkel like device to breathe (I'm not sure gills would be effective in an NNF) and we can combine that with a luring mechanism, something that rises up and sits above the ground (in fact maybe it grabs the prey and drags them down, which might be easier than springing up through the NNF). The first thing that comes to mind is an Angler Fish, one of these beasties: [](https://i.stack.imgur.com/CrO5z.jpg) Other options suggested in the comments include; A [snapping turtle](https://www.natgeocreative.com/comp/05/058/417383.jpg) like creature (suggested by [Dent7777](https://worldbuilding.stackexchange.com/questions/88816/creature-that-swims-in-the-solid-ground/88821?noredirect=1#comment263614_88821)) - In real life snapping turtles already use a lure to hunt. Our creature would be a vastly scaled up version whose head was heavily camouflaged and disguised with a lure that sat inside it's open mouth. The head would sit above ground and wait for prey to enter the mouth before swallowing it. A creature whose large mouth rises up to envelop it's prey and swallow them whole (as suggested by [Andrew Cheong](https://worldbuilding.stackexchange.com/questions/88816/creature-that-swims-in-the-solid-ground/88821?noredirect=1#comment263734_88821)). I would imagine in this instance the creature would probably be snake like (indeed a Dune style sand worm, as mentioned in other answers, would fit the bill). [Answer] I would suggest a creature that can create enough vibrations around it to make sand behave like liquid. <https://youtu.be/zjgURBIqJ6s?t=2m15s> Then it would be relatively easy for it to move through because the sand will auto vibrate away when pushed against. Explanation of the mechanics: > > Soil liquefaction describes a phenomenon whereby a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid. > > > The phenomenon is most often observed in saturated, loose (low density or uncompacted), sandy soils. This is because a loose sand has a tendency to compress when a load is applied; dense sands by contrast tend to expand in volume or 'dilate'. If the soil is saturated by water, a condition that often exists when the soil is below the ground water table or sea level, then water fills the gaps between soil grains ('pore spaces'). In response to the soil compressing, this water increases in pressure and attempts to flow out from the soil to zones of low pressure (usually upward towards the ground surface). However, if the loading is rapidly applied and large enough, or is repeated many times (e.g. earthquake shaking, storm wave loading) such that it does not flow out in time before the next cycle of load is applied, the water pressures may build to an extent where they exceed the contact stresses between the grains of soil that keep them in contact with each other. These contacts between grains are the means by which the weight from buildings and overlying soil layers are transferred from the ground surface to layers of soil or rock at greater depths. This loss of soil structure causes it to lose all of its strength (the ability to transfer shear stress) and it may be observed to flow like a liquid (hence 'liquefaction'). > > > A state of 'soil liquefaction' occurs when the effective stress of soil is reduced to essentially zero, which corresponds to a complete loss of shear strength. This may be initiated by either monotonic loading (e.g. single sudden occurrence of a change in stress – examples include an increase in load on an embankment or sudden loss of toe support) or cyclic loading (e.g. repeated change in stress condition – examples include wave loading or earthquake shaking). In both cases a soil in a saturated loose state, and one which may generate significant pore water pressure on a change in load are the most likely to liquefy. This is because a loose soil has the tendency to compress when sheared, generating large excess porewater pressure as load is transferred from the soil skeleton to adjacent pore water during undrained loading. As pore water pressure rises a progressive loss of strength of the soil occurs as effective stress is reduced. It is more likely to occur in sandy or non-plastic silty soils, but may in rare cases occur in gravels and clays (see quick clay). > > > Source <https://en.wikipedia.org/wiki/Soil_liquefaction> As to what organs that creature should possess, I'd look at the crocodile, and expand that <https://gizmodo.com/im-amazed-by-what-happens-during-this-alligators-mating-1713932794> Crocodiles produce strong infrasound waves that sends water around them flying away. > > The bellowing cycle of an American alligator. Starting with head and tail lifted in the so-called 'head oblique tail arched' (HOTA) position, and riding high in the water on inflated lungs, the animal sinks into the water as air is expelled through the larynx to create the bellow. Resonance driven by the sound produced makes the water dance from the flanks and then from the dorsum when it submerges towards the end of the event. > > > <https://books.google.nl/books?id=iGYlBgAAQBAJ&pg=PA1925&lpg=PA1925&dq=how+do+crocodiles+produce+infrasound&source=bl&ots=RiHVYBGrTk&sig=_qRV4B_8ltCbkS-53FB3ybdo6qM&hl=nl&sa=X&ved=0ahUKEwixjZeP6djVAhUEb1AKHciuBTk4ChDoAQgrMAE#v=onepage&q=how%20do%20crocodiles%20produce%20infrasound&f=false> [Answer] The sandworm from Dune immediately popped into mind as the kind of creature you are looking for. Perhaps you can derive some inspiration from it. A description of its **physiology** from Wikipedia: Sandworms are animals similar in appearance to colossal terrestrial annelids and in other ways to the lamprey. They are cylindrical worm-like creatures with a fearsome array of crystalline teeth that are used primarily for rasping rocks and sand. During his first close encounter with a sandworm in Dune, Paul Atreides notes, "Its mouth was some eighty meters in diameter ... crystal teeth with the curved shape of crysknives glinting around the rim ... the bellows breath of cinnamon, subtle aldehydes ... acids ..." <https://en.wikipedia.org/wiki/Sandworm_(Dune)> From another question: <https://scifi.stackexchange.com/questions/3620/in-the-dune-universe-how-do-the-sandworms-enlarge-the-desert> [](https://i.stack.imgur.com/tyCeI.jpg) [Answer] The "swamps" are actually the bodies of massive fungal colonies. They developed a complex symbiotic relationship with small animals that would forage for food and then could be transported in an organic polymer matrix, sort of like the cytoskeletal transport networks in our own cells. This progressed over time to allow larger and larger creatures to interact with the network by releasing enzymes and signalling molecules to activate the network and break the polymer. These signals then swiftly degrade after the animal passes through (thanks to enzymes released by the fungus itself) and the polymer reforms. I'm imagining it started with a relationship sort of like sea anenomes and clownfish, where the fungus provides protection (you can duck back inside to get away from predators) and the animals provide grooming/foraging services. The larger creatures are predators that evolved the ability to biochemically 'hack' the interface and therefore gain access to the prey that would try to hide. The larger animal has become essentially a parasite. [Answer] It's probably easier to define an environment first and then work on a creature that fits into it. So I'm going to advocate for a [peat bog](https://en.wikipedia.org/wiki/Bog), it's basically solid but, when healthy, it's so saturated that it can act like a liquid, especially if you add some localised energy in the form of vibration. So what kind of creature swims through essentially solid peat? An Orca is actually a pretty good shape for this environment but I'd go a little thinner and longer with extended trilateral fins along most of the body, the fins ripple for added speed as well as angling for steering. It's going to use [echolocation](https://en.wikipedia.org/wiki/Animal_echolocation) same as a dolphin except it's going to be a much more powerful vibration emitted from the whole body, this is going to create a [liquefaction](https://en.wikipedia.org/wiki/Liquefaction) pocket around the beast allowing it to swim unimpeded. The liquid bubble around our "Land Whale" also serves another function, where it hits the surface the bog surface is going to go from solid but soggy to something the with the properties of tar sucking down prey. This creature could probably survive as a filter feeder and have gills but I think it's more interesting as an air breathing predator. I also like the idea of them hunting in pods like Orca or Dolphins so you'd see them breaching as a pod the way [cetacea](https://en.wikipedia.org/wiki/Cetacea) do in Earth's oceans. [Answer] You can turn rocks to liquid, if you have enough heat and not afraid of it - melt it. There was [a project](http://www.pravdareport.com/science/tech/07-05-2003/2734-nuclear-0/) for getting rid of nuclear fuel waste - put a lot of it in a big ball made of tungsten. Then heat from fission would heat it up to 3000K(at some sources number 1200C is mentioned, seems a bit low) which is below melting point of tungsten so it stays solid but way above melting point for most of rocks. Also, tungsten is more dense than most of the rocks, so it would sink and bury nuclear waste in the mantle. Make this ball alive somehow and make it less dense so that it would not sink and you have it. [Answer] Another option that comes to mind is that the creature is *incredibly dense*, like neutron star material levels dense. So while such a thing wouldn't be possible in the real world, you might be able to get away with it in sci-fi. By having your critter be so incredibly dense, things that are solid to us as humans would behave like fluids to this creature. Its body would literally just push dirty and rock aside like it was nothing, because relatively speaking, it is. [Answer] In League of Legends there's a champion called Rek'sai. She's a voidborn (an alien from a different realm) and can 'swin' in the ground. She makes the ground vibrate enough to move freely through solid terrain but she also creates portals to travel faster. She's more like a cricket mole but she moves like a shark in the ground. She's a feared monster in Shurima's desert who can eat expeditions like nothing: <https://www.youtube.com/watch?v=OcB-FreSnG8> [](https://i.stack.imgur.com/8aJdl.jpg) She's massive, enough to eat camels with one bite About the organs: * The creatures should lack of eyes. Eyes would be a huge disadvantage when you're swimming through solid terrains * Have an exceptionall smell/hearing * Almost grills **OR** a blowhole to breath outside, this means they would have massive lungs. * They must emite constant sound waves (like a purr to disperse the solid materials and swim freely) * They mostly feel vibrations rather than sounds, since they're underground [Answer] A somewhat different approach: make creates that [“glitch”](https://en.wikipedia.org/wiki/Glitch) through the solid ground. They don’t swim, per se; rather, they propel themselves forward by jerkily disappearing and reappearing (displacing whatever solid was in their place). A (very hand-wavy) basis in solid science would be [quantum tunnelling](https://en.wikipedia.org/wiki/Quantum_tunnelling): you creatures have evolved a way of generating a coherent quantum field to be able to appear as a [macroscopic quantum object](https://en.wikipedia.org/wiki/Macroscopic_quantum_phenomena), and to control the probability and direction of tunnelling their whole mass through the surrounding solid. (Even more hand-wavy would be to rely on the creatures creating localised, temporary wormholes or some other form of teleportation.) [Answer] If you ever saw a [mole dig himself into soft ground,](https://youtu.be/XCMQbE0BHyw) swimming is not that far away. [Answer] This question instantly reminded me of [Hugh Howey's Halfway Home](https://www.goodreads.com/book/show/8428985-half-way-home). In the story, there are tunnel boring wormlike creatures who (if my memory serves me correctly) have an ability to absorb the materials they come into contact with - and then defectate them out the back end turning it into piles of diamonds/gold or something in the process! Kind of questionable science, but potentially acheivable if the creature possesed some attributes of molecular nanotechnology (the [Gray Goo](https://en.wikipedia.org/wiki/Grey_goo) springs to mind here!) [Answer] What about something like a giant, but thin amoeba? It would push it's 'membrane' forward in a sharp point, then flow into it from behind, forcing the membrane outward. If it were moving through sand or loose soil, it may leave a trail visible from the surface, but if it were more of a liquidy material it should flow around and fill in the gap behind. Not sure how fast it would move, but it's your world... ]

[Question] [ We all love the apocalypse, except for those that are actually in it and often apocalypse media, especially zombie apocalypses, show a complete collapse of any form of government. I find this unlikely, that America; the most powerful nation on Earth, would collapse so easily. While it is believable that the government as it is known could collapse, the higher government such as the President who would likely be evacuated or put in the bunker. But what if there is **nowhere** to evacuate? What happens when the bunker's supplies run out? They need a location that can support the President as well as the other higher ups in the government while still being dependable. If a zombie apocalypse were to occur, with hyper-active runner zombies loose in the world, where would the president be evacuated to? Starting assumptions and constraints: * The zombies will be fast, akin to 28 Days Later's runners * The refuge should be able to achieve self-sufficiency during or shortly after the apocalypse * Zombieness is transferred by bites only [Answer] Why would you want to *hide* the President? That concept makes sense if there is an attack by an intelligent adversary who wants to target the chain of command. In this case, it sounds as if you want to *defend* him while maintaining his ability to communicate. * A nuclear-powered aircraft carrier? * [Mount Weather](https://en.wikipedia.org/wiki/Mount_Weather_Emergency_Operations_Center) or a similar site that was in the contingency plans, so people can find him? [Answer] **Fort Knox** Contrary to popular belief, Fort Knox is not just the location where the gold is stored. That title goes to the United States Bullion Depository. Fort Knox is actually a 109,000 acre army post, home to over twelve thousand people, the Bullion vault and even a high school. Imagine an army base and a town made beautiful love under the moonlight, Fort Knox was the baby. The vault itself (which would likely be transformed into the new base of operations for America) is defended 24 hours a day by CCTV cameras, motion sensors and even minefields. Even if for some reason all there were not, you would still need to scale a electric fence crowned with razor wire, blast through thick granite walls and somehow open the 24 ton vault door. The Fort Knox Base is so secure that it is synonymous with security in modern culture. Wind and solar power would be feasible in such an area and would livestock and wells. With your thousands of soldiers (give or take) scavenging would be simpler than going for groceries. All the soldier likely care about is their family, so by allowing their family to stay there, you will have a reliable super army (at least in post apocalypse terms). If any bandit group looks at Fort Knox, the new capital, and manages to destroy it, they deserve it. Thirty thousand troops are currently stationed at Fort Knox and even assuming an 80% abandonment rate, that leaves six thousand soldiers. Not much in the modern world, but enormous in the apocalypse. [Answer] **[Cheyenne Mountain Complex for NORAD](https://en.wikipedia.org/wiki/Cheyenne_Mountain_Complex#Facilities)** It contains a deeply embedded military structure 610 m under a granite mountain with 25 ton blast doors. It has been built to withstand any possible attack, including nukes and biological/chemical weapons. All system for electricity, power etc. are redundant and designed for utmost stability. The mountain contains a spring which gives enough water and gigantic reservoirs for diesel, food etc. [Answer] Any of the numerous war time bunkers built to do just that. Zombies are not getting into a bunker designed to stop bombs and chemical attacks. Check out The Greenbrier, a hotel which famously has a huge bunker complex underneath it. There is even a VR tour of the bunker, see [here](http://www.pbs.org/wgbh/amex/bomb/sfeature/floorplan.html). [Answer] Ohio-class submarine. Those are both nuclear powered, *and* carry ballistic missiles with hydrogen bomb warheads (in the apocalypse h-bombs can come in handy). All the air and water can come from ocean water that is as deep as the sub can dive. Have it filled with food and use a skeleton crew. (Near) endless supply of pure air, water, propulsion, and electricity. You could even put it under a polar icecap. [Answer] **The White House** Sorry to burst the zombie bubble with some realism, but a mob of unarmed suicidal half-corpses would pose no threat to heavily armed security forces, specially if backed up by the army. Most zombie scenarios would end rather quickly as makeshift obstructions are used to funnel the horde, and reliable vehicle mounted weapons mow them down effortlessly. As an example, placing a gun emplacements on or around the White House would be enough to mow down any and all zombies stuck trying to get past the fence (which stands to reason would be reinforced). And I'll guess the real world White House is well guarded enough to handle such a situation until the army arrives, even if the outbreak began in Washington D.C. itself. *Edit:* For further zombie outbreak de-hyping, read this: [Cracked: 7 Scientific Reasons a Zombie Outbreak Would Fail (Quickly)](http://www.cracked.com/article_18683_7-scientific-reasons-zombie-outbreak-would-fail-quickly.html) [Answer] A cold mountain top bunker. Melted snow, all the water you can drink. You would need food storage no matter what. The zombies would all freeze to death before they got there. Zombies don't bother with coats or much clothing for that matter so cold would do them in. Also if you could arrange a bunker near a volcano, the lava would make short work of them. Only the most athletic zombies could swim to in island even a few miles off shore. The ocean is very cold also. My personal favorite, the Moon. Start sending supplies up now. The surface has ice and therefore water. Water can be split into hydrogen and oxygen for fuel and breathing. If you had a structurally sound greenhouse you could even grow food. Another boring answer, the International Space Station. Middle of **Death Valley**, I believe it is in Arizona. The zombies will all die from heat stroke, long before they reach the bunker. [Answer] If you want to base your story in reality, I'd look for places that they would actually put the president in. For Example the Air force bunker in Cheyenne Mountain (as Thorsten S. mentioned) or even in an Airplane (Airforce One) or a helicopter Marine One. It just has to be as inacsessible as possible. Even a Remote Island as Hawaii would be good shelter. Also Alaska is pretty hard to terrain to move forward by foot (Zombies) and has a smaler population (smaller thread, easier to defend) would buy the President some time. Area 51 would also be an easy to defend place, that you could use. As a Tipp check out the known places, where they hide the Presidents in such situations (ex. 9.11) You should put him in a hard to access remote area. And move him as far away from a city as possible. Because that is the most dangerius place in a zombie apocalypse. To me, Cheyenne Mountain comes to mind first and would be a pretty good solution (at least for the beginning), because they have water and food supplies for a pretty long time. from there you can asses the situation and move to a permanent place. The ISS would also be a good place to hide, however if the zombies manage to get on there, or someone carries the virus up there, there is almost no chance to defend that terrain (no guns and if you had them, you couldn't shoot them). So I wouldn't suggest that. (only if you know that no one carries anything contaminated for shure). [Answer] ## [Mount Weather Emergency Operations Center](https://en.wikipedia.org/wiki/Mount_Weather_Emergency_Operations_Center) That's where current continuity-of-government plans will relocate high command in the event of a national disaster. Exact details about the facilities there are, unsurprisingly, classified; however it is known that the site has large stockpiles of food, water, and medical supplies, and access to powerful communications equipment, both via hardline and radio broadcast antennas. It's likely, of course, that Mount Weather would be a key target in the event of a deliberate attack on the United States; but for a zombie outbreak, it's absolutely where the President would go. She would likely travel to the site aboard either a [VC-25](https://en.wikipedia.org/wiki/Boeing_VC-25) (the aircraft most commonly used as Air Force One) or, if necessary, an [E4](https://en.wikipedia.org/wiki/Boeing_E-4). Both aircraft are designed and equipped to operate as mobile command posts and broadcast centers, though the E4 is somewhat more capable in this regard. [Answer] The answer will depend on the spread of zombies, which itself might be largely a function of where the outbreak started and the incubation time for the zombie disease (in addition to their speed and stamina - fast and very long in this case). If the President is to be effective on any level they will have to be accompanied by a sizeable number of staff and military personnel and keeping them fed and watered would likely be a major challenge. You also have to factor in how long the outbreak will last - in the short term secure bunkers could be employed for many months, but if the outbreak goes on longer it may be preferable/necessary to move elsewhere. A list of possible longer term homes for the US president, in rough order of preference, might be: * Stay in DC (i.e. if the outbreak is confined outside the Continental US). * An unaffected US territory (e.g. Hawaii - though there may be issues avoiding famine given Hawaii currently imports most of its food). * An unaffected friendly country, preferably one with a substantial US military presence, e.g. Germany, Japan, South Korea. * An unaffected non-friendly country, who may let the president in if they are accompanied by a decent sized military force * If government has broken down world-wide then those places that are physically isolated (by sea, desert, etc) and have little contact with the rest of the world are most likely to remain unaffected. These places are generally out of contact with the rest of the world for a reason - they can't support many people (e.g. small Pacific islands). However, there are a few places that are (a little) more viable, if not particularly hospitable. One of the sparsely populated/uninhabited Patagonian islands, e.g. Isla Wellington might be a good shout. It generally does not get too cold (which would make Alaska, Nunavut or Siberia difficult) and a combination of seafood and planted potatoes could feed a decent number of people. [Answer] ## Island Always the answer for any zombie apocalypse. * No need to defend assuming that the zombies do not swim. * Easy to control in and out flows of people => quarantines * Contains everything needed. Simply the best answer always. No matter the case, an island will be cozy; there is no need to fight at all. US has a lot of nice islands at Hawaii. ]

[Question] [ **World Rules:** * Travelers are able to move at the speed of light without disruption of their lives. Time passes "normally" for them. They think, breathe, love, cry, and steer the ship as if they were merely crossing the Atlantic. * Whatever allows the ship to travel at the speed of light, it does not distort the traveler's view of the rest of the universe. There is no "warp bubble" or "bending of spacetime" to get in the way of what they see. (**Edit:** I think this is what's getting in some people's way. I don't mean that physics is suspended. I mean that any effects caused by the ship's method of getting to V=*c* should not be considered as part of your answer.) **Premise:** After a probably notable amount of time, the intragalactic cruise liner *Prinzessin Victoria Luise II* has, for the first time, achieved what was previously believed to be impossible: the ship is traveling at 100% *c*, or exactly at the speed of light. Little Victoria Luise, who understandably believes the ship is named after her, breathlessly looks out the viewing port. She's excited to be among the first to look at the universe from the perspective of a photon of light. With wide eyes and an imagination filled with the hope of angels and the fear of dragons, she sees... *What?* **Question:** What, really, would Victoria Luise see outside that view port? * Victoria Luise is looking out a [starboard](https://i.pinimg.com/originals/37/3a/58/373a5877811f1d2aef49d7abd60bb677.jpg) view port. * The trip is at least 20 light years long and there are stars near (relatively) and far out the view port. --- **Edit:** Several commenters are getting bogged down in the backstory. An observer traveling at the speed of light looking perpendicular to the transit vector would see what? If you believe *how* the observer got to the speed of light affects that question, then you need to explain why. It is certainly true that Victoria experienced no time while traveling at the speed of light (from the perspective of a photon, it arrives at its destination instantaneously regardless of distance traveled). *However,* while traveling across the distance photons impacted physically on Victoria's eyes. So, what did she see? [Answer] I have painstakingly assembled a highly realistic 3d rendering using advanced relativistic raytracing and plausible geometry and position for nearby stars. Here's a render of the view to starboard: [](https://i.stack.imgur.com/bMY6f.png) I'm sure you can appreciate the thousands of hours of computing time that went into this. --- Less facetious answer: Leaving aside the issues of whether there's any time for your observers to experience stuff in, lets look at the boring relativistic things. Here's a thing that Einstein cobbled together using some of Lorenz's work, describing relativistic aberration. $$\cos \theta\_o=\frac{\cos \theta\_s-\frac{v}{c}}{1-\frac{v}{c} \cos \theta\_s} \,$$ This is the effect by which things in space (that are effectively stationary background objects, relatively-speaking) around you appear to be warped to bring light sources together into a region in front of you, centred on your direction of travel. $\theta\_s$ is the angle between your direction of travel and the direction of travel of the photon shooting at you. $\theta\_o$ is the observed angle of the incoming photon's trajectory The exact reason for this is kinda hard to articulate in simple terms (but related to the fact that light always seens to be travelling at lightspeed for an observer, regardless of what sublight-speed they may be travelling at), but you can reasonably take it on trust that those two gentlemen knew what they were talking about. This means that as your velocity approaches the speed of light, your entire view gets concentrated into one tiny spot in front of you. You can see that the equation simply resolves to 0 when you reach lightspeed. There's nothing to see to the side. That image above? Totally plausible for an ultrarelativistic traveller. Here's another thing: relativistic length contraction. $$L =L\_{0}\sqrt{1-v^{2}/c^{2}}$$ Here, $L$ is the length of the ship as observed by some "stationary" observer, and $L\_0$ is the actual length of the ship. You'll note that from the point of view of this observer, an object passing at lightspeed *has no length*. If I shoot a laser at a passing C-ship, how can I hit a side window, when it has no side? I can still hit the front, but that's about it. I'm *fairly* certain that this is another way of stating the same sort of thing described as relativistic aberration above. Someone who actually knows relativity, rather than just trying to bluff confidently, feel free to correct me... [Answer] On a ship traveling at exactly *c*, Victoria wouldn't have any time to see any stars -- for her, the ship would arrive at its destination instantaneously due to time dilation. Sorry for the slightly lame answer... [Answer] Let's throw the whole relativistic discussion out the window and just work on the assumption that the ship is doing "something" in such a way that after one second, it is one light second along it's path. The view outside is incredibly boring. Let's assume I am standing there looking out the window, the view takes up 60 degrees of my vision so that means a star which crosses my view starts 60 degrees from my left and ends 60 degrees from my right. Here's a diagram: [](https://i.stack.imgur.com/t4vdm.png) Let's assume my path is the bottom line, does this look familiar? It's an Equilateral triangle. So if the star starts and ends one light year away, then my path is one light year, which means, at light speed, it took one year for the star to cross my window. Space is really empty so most stars are even farther away than that. You can walk up to your window, draw little dots on it where the stars are, go about your day, come back and nothing would have moved. Looking out the window is boring in terms of natural objects, but maybe there's traffic outside, other ships to watch, but that's up for you to write. [Answer] There is a [game](http://gamelab.mit.edu/games/a-slower-speed-of-light/) (made by/with physicists from MIT some years ago) that models the player approaching the speed of light. This leads to multiple effects on vision: * Doppler effect: red- and blue-shifting of visible light, and the shifting of infrared and ultraviolet light into the visible spectrum * Searchlight effect: increased brightness in the direction of travel * Time dilation: differences in the perceived passage of time from the player and the outside world * Lorentz transformation: warping of space at near-light speeds * Runtime effect: the ability to see objects as they were in the past, due to the travel time of light I don't understand the physics behind this well enough to do more than copy pasting what the game description lists, but as far as I remember the game includes further explanations (and you can of course use the names of these effects to look for more details). [Answer] Yalls' universe is so ***boring!!*** Naturally, what little Victoria Luise *actually* sees from the view port (one could have hoped she'd discover this wonder from the starboard side smoking lounge, but one supposes that's for adults only, and not small girls!) is far more interesting than mere science can describe! A wonder indeed for the eyes and a feast for the imagination. And how lucky she is to experience it first hand! First, it's important to understand that bits of Light travel along their appointed paths, wavewise, very quickly. Like the velocipedes Miss Victoria Luise is used to seeing speeding along in her home city. Because she is a well to do little girl, her accustomed mode of transport is a sedan chair carried along by two amiable fellows of the household staff. So, she's used to seeing the electro-telegram boys with their curious flashing devices strapped to their backs whizzing by at such a rate that she can scarcely make out their House liveries, to say nothing of the contents of the e-tels they're carrying. And like the velocipede riding boys of home, she knows from her physioastrological studies that Light moves even faster than the fastest velocipede, faster than the great tram-ships that ply the oceans and faster than the fastest of electro-trains that can bring one from the kaiser's busy parliamentary capital of The Hague all the way to the Oriental Empire's capital at Peking overnight! Second, it's important to understand that these bits of Light are travelling in all directions all the time. It's just like the traffic whizzing through, around, over and under St. Wyziwygus's Circus downtown. At first glance, all seems a bizarre chaos of velocipedes, electro-trams and pedestrians. They're all moving in every conceivable direction and all just as fast as they can. Apart from the poor walkers, who appear to be slothily trudging along among a whizzing cloud of faster traffic. But now little Miss Victoria Luise has gotten herself upon the proverbial velocipede and she can now see Light for what it truly is! ### The View Aft Looking aft, as the *Prinzessin* accelerated towards her magic velocity, she'll see what appears to be a fuzzy wave approach the grand Ship. Due to the amazing properties of the view port itself, she can just make out the lines of Light, breaking like dolphins on the ocean, at the Edge of the luminal breakwater. What she can not see from her vantage, and this is a shame, is that the Edge surrounds *Prinzessin* entirely and demarcates that place where the mighty engines have brought the ship up abreast of the Light cast off from the Sun some hours ago while the crew were easing her up to cruising velocity. The Edge looks fuzzy because it is not possible to maintain *perfect velocity*. For some fractions of a moment, *Prinzessin* might be travelling just shy of or just more than 1 luminal; thus there will be moments when she eases ahead of the light from Sun and some moments where that light catches her up and passes by, which causes a bit of haze to surround the vessel back towards the engineering department. Adding to the haze of the Edge, of course, is orthogonally travelling Light, that is moving perpendicular to their course. As *Prinzessin* whizzes by those pathways, the Light appears to sort of bunch up, mixing and separating in wonderful bands of colours and hues that compress at the interface of the Edge. A spacebow that travels with the Ship and would appear much like a glory or rainbow surrounding an airship. Perhaps just at the edge of her perspective, she might get a glimpse of the Void! This is a spectacular phenomenon that can really only be appreciated when the Ship travels just slightly faster than 1 luminal for a short time. If the engineers can provide such a mighty burst of speed, Victoria Luise will notice that she is suddenly *failing to see* the Edge. As *Prinzessin* overtakes the Sun's ever older Light, that Light which they were just flying abreast of has now disappeared behind the vessel's wake and, being slower than the Ship, is now invisible. As the *Prinzessin* slows again, the Light will rapidly overtake and that part of the universe will again become visible. But the change will not be so fast that it is not noticeable! Victoria Luise will actually be able to see the Front as it careens forward like a cavalry charge overtaking its lead horse. The sizzle of photons as they overtake the Ship will form a brilliant and electrically exciting spectacle! ### The View to Starboard Luckily for little Miss Victoria Luise, her viewing port allows her to see quite a bit of interesting external infrastructure of the great Ship. From this vantage, she can tell when *Prinzessin* is charging forth towards 1 luminal. For there is a bright beacon light some distance below her port which illuminates some of the vanes of the great Scoops that draw in interstitial matter for the powerful engines. As the Ship moves faster, she can see the leading edge of the beacon's light. As with the Front of Light coming in from the Sun, so it is with the lesser lights of the beacons: as the Ship catches up to them, she can see the effects of the photons dancing at the edge, beyond which there is no light. As *Prinzessin* gains speed, the Front wavers and churns, its bright hues alive with squillions of photons bunching up in the wave; until at last, the Ship passes into superluminality and Front dissipates, and all the Light is sucked from beacons and disappears into the Void! ### The View Fore Peering towards the front of *Prinzessin* as she plies the interstitial main, little Miss Victoria Luise will be in the view of her life! For there she may see all the stars familiar from her astrology lessons, but their colours shift and waver, now bluing and now redding in an exciting arc of lights emanating from the bow of the great Ship! Here is a the light fantastic, the mad tarantella of ancient photons dashing in from the depths of space beyond her comfortable world, and like two madly careening velocipede boys passing in the streets of the city, Victoria Luise can catch no more than a searing blur as those bits of Light careen screaming through the Bow Arc and pass like a burst of sudden lightning out of sight into the Void beyond *Prinzessin*. [Answer] She will see a flash of white, and then she will be permanently blinded. Because: > > It is certainly true that Victoria experienced no time while traveling at the speed of light. > > > For practical purposes, the trip is instantaneous. That means all photons that impact on the kid's retinas do so at the same time. The longer the distance travelled, the greater the amount of photons caught. For even just a light second, she is going to collect an awful lot of radiation. Even if you filter X-rays, UV... There is still much more in a light second trip than what you would get from a strong laser pointer. To find out the damage: find out how much light she would be getting in her eyes if she were travelling at regular interstellar speeds (i.e.: the sun's orbital speed around the galaxy, 200km/s). Multiply that luminosity by the distance travelled, since her retinas will cover that much area in zero time. Next time keep the spawn away from the windows. [Answer] ***Horizontal Stripes.*** Your question explicitly states that in your universe no spacetime distortion or whatever happens, so the answers based on theoretical physics are altogether wrong. They are, with some exceptions such as frequency shift (which is very much provable, and observable), mostly unprovable speculations in our universe, too -- but they're *by definition* wrong in the universe you depict. So what you would see is the same kind of horizontal stripes that you see in a high-speed train, only much darker. Very distant things being somewhat less blurry than closer things (though due to your ship moving *very* fast, things would have to be *very* far away). **Why?** Because, well, your eyes still have the same basic properties as they have in our universe (unless you say they don't). While the eye tries hard to re-fixate ("saccade") when stuff is moving, there is a limit to what those poor little muscles can do (plus, your neurons are not infinitely fast). Which is approximately an angular speed of 720° per second, maximum. If the exterior moves too fast (or rather, is stationary and *you* move), the eye becomes unable to re-fixate. That's the blurry view outside a high-speed train. By itself, our eyes are extremely susceptible to motion blur. Every photoreceptor is, more or less, even the fastest camera chip. Biological eyes, however, which involve a complicated G-protein coupled signal pathway going off, are prone to motion blur or "afterlighting" in particular. Why would your view be much darker? Well, you move so fast that the larger amount of light moves backwards, the "sideways" component of any light ray, or photon, being smaller than usual. Thus, everything will be "darker". Since light coming from the front will travel at *twice* the speed of light, and light coming from the back will be "standing still", your blurred stripes would be lighter (flashing white) towards the front, and darker towards the rear. [Answer] Frame challenge: ## We don't know, and may never know As per our current understanding of physics, objects with mass can not be accelerated to the speed of light. As such, there are no images to confirm or deny any of our speculations, and there may never be. It may be physically impossible to take a photograph at the speed of light as we may never find a way to accelerate objects with mass to 100% the speed of light. This means we would never have a point of reference to compare Victoria Luise's experience to. Little Victoria Luise would experience something indescribable, it would be like trying to explain colour to someone who was blind, or love to someone who could not feel, or life to someone who could not experience death. She would see something beyond what words could explain as currently we are blind, we can not see through her eyes to experience what she has experienced – mere words would not be enough to explain it, you would need to see it, to feel it, to be in the presence of it, to have any idea of what she has seen. And I think that is something truly magical, how this little girl would have seen something that she, and only she, would ever know. [Answer] Moving at exactly the speed of light means that no time at all passes inside the ship for the entire duration of traveling at the speed of light. All the light that impacts the ship during that duration hence hits the ship in literally no time at all, meaning that the surface is subjected to light impact of literally infinite energy density. Each photon and atom impacting on the front would also have infinite energy. I can't imagine any material able to stand up to that, much less any human eye trying to view it (even if there was any time to view it, which there isn't). Another issue is that your ship would have literally infinite mass. At the moment it hits the speed of light, all objects in the universe would start moving towards it with infinite acceleration, reaching near-light speed in an instant. The universe would start collapsing on itself. This acceleration would be delayed until the gravity wave reaches the stars and galaxies, but the effect would be instantaneous from that moment, no matter the distance. Even if you use hand-waving metaphysics to bypass the mass/gravity problem (which might be necessary to reach light speed), you still have the problem of impacting photons and atoms. One way to get around all this: Convert your entire starship to light, which per definition travels at light speed, have it received by a large dish, which then converts the light back into solid matter. In this case, however, there would be no view, as the passengers would experience no time at all for the journey. [Answer] A disclaimer. I'm an EE, not an astrophysicist. My own answer is coming from the "[... but I stayed at a Holiday Inn last night!](https://www.youtube.com/watch?v=8dOHEw8izno)" perspective. And I rank my own understanding low enough (hence the reason for asking the question) that Holiday Inn could legitimately be considered an accredited source of doctoral degrees. Fair warning, let's begin. **T=0!** Many of the answers and comments pointed out that Victoria's actual time spend looking at the stars while at light speed is zero. They're absolutely correct. To be fair, I did not explain events along an axis of time. Everybody's right, Victoria couldn't walk up to the window while the ship was traveling at the speed of light. So, the Captain announces that the ship will hit lightspeed "soon" and everybody should get to a window. Victoria arrives at the window while V<*c*, experiences V=*c,* and then V<*c.* What's left in her eyes includes everything that happened while V=*c* even if her brain can't process it until V<*c.* However, some of the answers/comments seem to think that ~~time~~ action has stopped for Victoria (and the incoming photons) while V=*c.* Nothing could be further from the truth. She experienced every millimeter of the voyage while traveling at the speed of light. So did all those photons out in space. Relativity doesn't mean everything stops, it means *everything happens simultaneously and instantly.* All those photons... striking poor Victoria's eyes at the same moment. @Renan's answer points out the most likely outcome. But there are complications, some brought out in one answer, others in another. Let's walk through it one step at a time. First, some charts showing time, distance, and velocity. [](https://i.stack.imgur.com/LehPk.png) The figure on the left shows us velocity vs. distance. Distance is involved. Victoria's time may not advance, but the distance is being covered. So my question could have been asked (and perhaps should have been asked), "from some point D0 when V=*c* until some point D1 when V≠*c,* what did Victoria experience from her brain's visual perspective?" (Even that might have been closed. Relativity can make one's head hurt something awful. So can paintings by Picasso. It's probably all the same problem.) The figure in the middle shows us Te or the "time experienced by Victoria" vs. distance. Yeah... I didn't mark D0 and D1 on the charts, but they're the points along D where V=*c* begin and end. From the perspective of a stationary observer, time experienced by Victoria (Te) slows down while approaching and leaving V=*c.* The figure on the right shows (\*ahem\*) what Victoria experienced from our point of view, from Victoria's point of view (people will point out how nasty that description is. Yeah. I get it.). Or Te vs T. Time for Victoria (even though she doesn't perceive it) slows to zero then picks up again. (BTW, this is commonly misinterpreted as time travel. It isn't. Frankly, it's not much different from perfect cyronics. But that's another discussion. Probably one involving Buck Rogers.) My point is, everything that occurs during the transit between D0 and D1 is experienced by Victoria in one magical (and massive) instantaneous burst. *But what happens?* This is where Doppler, Lorentz, Einstein, a bunch of other folks, and a bunch of people on this site (all smarter than myself) all chip in to create a lovely soup. We're going to add effects one effect at a time. Yup, I'm assuming effects are cumulative. They probably aren't, but remember that [spherical horse](https://en.wikipedia.org/wiki/Spherical_cow) (why Wiki has it as a spherical cow I'll never know. It was always a horse in my classes.). Let's start with @Hoyle'sGhost's answer and the doppler effect. let's assume that, looking out the starboard viewport, all you saw was a field of uniform white. That means a lot of photons of all kinds of wavelengths that Victoria's eyes interpret as a smooth, comfortable, field of white. Like this: [](https://i.stack.imgur.com/xhuGp.png) You can edit this answer to see that I really did load a 50x50 pixel white square. It's there. Trust me. As the ship accelerates, photons start shifting. Photons shift red to the left, blue to the right, and the faster we go the more they shift. The important thing to remember is that photons approaching the ship perpendicular to the travel vector *aren't shifted.* You can experience this audibly with a train. When it's right in front of you, it sounds normal. Oh, we're really bookin', so a bunch of these photons are shifted outside what Victoria can see. Maybe something almost certainly not like this: (An astute observer will realize that I have the honking picture upside down. She's looking out the starboard port, which means it should have been blue to the left, red to the right. Rats. It's late, so I'm not going to change it. You'll get the picture.) [](https://i.stack.imgur.com/mmRGA.png) OK. Next we need to deal with @Muuski's and @Damon's answers. One of the most amazing advances in race car video games (occurring back in the 80s, as I recall) was the advent of depth perception: that we perceive objects closer to us to move by more quickly than objects far away. I'm sure there's a fancy word for this effect — I just can't remember it. The reality in our case is that, as @Muuski reminds us, space is really empty and stars are really far away. But we're in a ship traveling at the speed of light across a distance of light years (more faults of my question: no start point and no end point). But even if we were traveling only one or two dozen light years, there are stars that would shift position (perceptually from Victoria's POV, of course) that in the T=0 moment she experiences during V=*c* travel, a line would be drawn by that star's photons across her retina due to the motion of the ship along *D* (see figures above). Of course, the more distant stars would remain dots. And all this is doppler shifted (oh, BTW, I'm ignoring relativistic doppler shifting for the sake of my explanation. Another spherical horse.) So, now we get... [](https://i.stack.imgur.com/RCCNo.png) Which is where Star Trek stopped representing the truth, if any of what they did is true in the first place. Finally, [after an amazing conversation with @StarfishPrime](https://chat.stackexchange.com/rooms/94076/discussion-between-starfish-prime-and-jbh) that I'm pretty sure impressed me a great deal more than it impressed him it seems that some magic happens next. Magic, I say, because when it comes to future light cones, past light cones, lorentz contraction, and the cool math he mentions in his answer, the light's going to shift boward (or forward, but toward the bow, either way). Since precious Victoria is looking our the starboard viewport, I expect it to shift to her left (fool me once...). It will also contract toward a center point, though I'm not convinced completely as she's not looking out the front of the ship (go read that conversation and realize there's a boatload of data that I couldn't access for better understanding. Remember, Holiday Inn...). [](https://i.stack.imgur.com/D5EQo.png) And that brings us back to @Renan's post. All those photons impacting on the ship over all that distance... (yeah, Starfish, I know you don't think this'll happen. The pancake. I'm just not convinced. Future/past cones and stuff.) all while little Victoria sits there, immobilized in time (so to speak) because everything's happening simultaneously at T=0. [](https://i.stack.imgur.com/Ghw66.png) That picture really doesn't do the moment justice. All those bright white, red, and blue spots? *They'd be blinding.* Completely blinding, like looking into a camera flash, but much more precise. So much so that when poor Victoria looks away (V<*c*) to see people around her, it would look something like this: [](https://i.stack.imgur.com/lt3mR.png) The green spots are where the red from the red-shifted light affected her eyes (overstimulating red leaves a green spot in your vision). Likewise, yellow for the blue-shifted light. I'm probably wrong on this one — they'd be black, too, due to the brightness of the flash — but it's possible that you'd get some temporary green and yellow from the weaker (darker) shifts. *Or maybe @Hoyle'sGhost is right and she'd see nothing due to @Renan's answer that the flash would blind her completely. But the above picture is much more fun — and it's what you get when you use spherical horses.* Am I right? HeckifIknow. But the the lawsuit filed by little Victoria Luise's parents against the cruise liner and its captain for not having the brains to close the shutters while the ship was at V=*c* would make a good story. [Answer] If she is looking outside, horizontally, then she would likely see a whole bunch of horizontal lines. If the ship is moving in any sort of arc, then the lines would follow that arc, but that's another problem. Every body in her field of view (assuming she is flying in space where planets are too far away to see) will emit light in a more-or-less spherical manner. This means there is a functionally solid sphere of photons in a radius of (age of the star \* *c*). By intersecting through this sphere with your character's eyes, the eyes are looking at an eye-sized slice of this sphere of light. This goes for every star within her vision. She would only be seeing whatever photons are in that particular point in space. Mileage would vary depending on the thickness of the craft, as it needs time to pass through the ship to her eyes, however any window where her position relative to the bow-side of the window is further than the thickness of the glass would do the trick. An interesting effect is that, if she is looking towards starboard, stars to her left will have their light shifted towards blue and eventually become invisible, while stars to the right will shift towards red, and eventually become invisible. For an indefinitely small period of time, a star in the direct middle of her field of view would appear it's original color. Additionally, due to the shifting outside of the visible spectrum, this band would be incredibly thin, so it would look like French flag confetti in the middle of the window. [Answer] There is no consistent model of reality in which massive particles are moving at light speed and other particles are not, and the two interact. In order for the person on the ship to see the universe, there must be a way to transform their frame of reference continuously into the frame of reference of the emitting light. And there isn't one. You have asked the question "what is the height of a square triangle", without the mathematics to understand that you are asking for a figure to have exactly 3 and exactly 4 sides. The "warp bubble" or "bending of space time" is how physics can generate a continuous transformation of reference frames between the light-speed traveling light-seers and not light-speed traveling light emitters. Physics answers the question of what light you see by tracing what paths the light travels over. With no path, there is no light to see. With no "bending of space time", there is no path. Now, what you could do is try to throw out our current physics. You could talk about worm holes, or equivalently you could have the ship move perpendicular to our 3-space into a hyperplane that has a shorter route to the destination. We could be a simulated reality on some hyper computer, which when you type in the console cheat code the laws of physics change along a path permitting light-speed travel. As you travel, the computer displays some physics-unrelated UI in demonstrating where you are. When you give the halt command, the computer builds a brand new reality in which everyone remembers you being at the source location, but you are at the destination location, in such a way that all sentient beings in the simulation have roughly the same experience and continuity of consciousness. [Answer] In reality, this would be an impossible question to ask. The light behind you would never catch up, and the light in front of you would be blue-shifted so high that it would be like peering into the generator of an x-ray machine. Either way, you'd see nothing. So you have to ask *why* the people can move at the speed of light. Is it because light actually moves faster in your world? Maybe light there truly is instantaneous, in which case you'd see a boring static star field. It wouldn't be as bad as some of the answers suggest it is, however. You know how the sky looks different in the summer and winter? That amount of difference would happen in sixteen minutes. It would be like watching the minute hand on a clock move. Occasionally you'd see something fly by and think, "damn, that could have killed me," but for the most part it would be boring. Except maybe for whatever you were using to deflect things in your path. That's what the big dish on the front of the Enterprise is for. While you're moving at the speed of light, anything in your path is shooting at you at the speed of light. Even at a meaningful percentage of C, you'd be intercepting a huge multiple of the normal particles and light in your path. If light really moved at the same speed, it would look like someone directly in front of you was shooting you with a really powerful laser, and that's just the light. The particles would be like a cosmic particle beam, and you better hope there are no small rocks. So, yea, you need a deflector shield. I imagine it would look like a rainbow umbrella, but that's just in my head. ]

[Question] [ Currently, most, if not, all human languages use sound to communicate. What if, language A, a language much like English in terms of its global dominance and widespread use, on a planet much like ours, used **silence** instead of sound to communicate. If you don't understand, speak the following sentence: *I am speaking a language made of silence.* Instead of listening for sounds, listen for the lack of sounds, rather the **silence** or gap between words (and sometimes these gaps are within words, like the word high-ranking). But you say, "well, don't all words have the same lengths of silence between them when we say them? Wrong. We actually use different types of inflections and different lengths between words to subconsciously express our emotions." Imagine if language A had the same exact grammar and vocabulary as American English. Instead of listening for sounds, speakers of language A listen for silence and thus understand the same ideas in a completely different way. If the length of these gaps were translated into a 60 letter alphabet, and the speakers of language A were a native tribe (about 2500 members) that lived in relative isolation from other humans, how would language A affect their culture? Agreed, human evolution hardwires us to listen for sounds, because when you heard what may have been a hungry lion growling, you'll get away from that place as fast as possible or be eaten. If you listened to silence, you wouldn't really understand anything meaningful and you would probably be eaten. But how would language A affect their culture if they had used language A for over 1500 years (written and spoken)? [Answer] **You can't quite do a language of *only* silence, because you need something to punctuate it**. If I gave you 60 seconds of nothing but silence, you wouldn't have any way to know if I had intended that to be: * A single word, 60 seconds long * Two "words" of 30 seconds each * A "sentence" with words of length 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 seconds respectively (with a 5-second break before or after, which you *also* can't distinguish from the rest) ...or just about anything else. There has to be something to disambiguate where one silence ends and another begins. Most human languages -including, I believe, all languages that use sound at all- use silence to punctuate words and sentences. **You *could*, however, semi-swap the roles played by silence and sound: the silence carries meaning, modified by the sounds that come before and after it**. I'm guessing this is what you intended to do when you spoke of the "tone" of silence. The sounds themselves would likely be limited to monosyllables with tones, since they don't carry meaning in their own right, but that's not a hard necessity. How would a silence-based language affect the culture that spoke it? Since the length of a silence would have to carry greater meaning than the length of a word does in most real languages, that culture would, out of necessity, have to speak somewhat more slowly. Developing a strong sense of rhythm and time would be highly prized, because it would enable people to speak more quickly. But for the most part, I'll leave that speculation to the other answers. It would also confuse the heck out of linguists, who would generally assume that when there is sound, the sound has meaning. They'd probably spend ages trying to figure out what these "words" of one or two sounds actually mean, then move on to assuming some kind of syntactic structure when it turned out that a given sound could mean totally different things based on the words before and after, and so on. **You could have an interesting Eureka moment in your story when a linguist working on this impossible language finally figures out that they should be looking "between the words"**. Which, technically, is actually looking *at* the words, but as a first cut of an oversimplified explanation, it gets the job done. [Answer] It's what they speak on Venus when annoyed, actually. Anyone who has ever had a girlfriend from that planet can testify how utterly, devastatingly effective the language of silence is. > > My dear, are you upset? > > > ... [sullen silence] > > > Is it something I did? > > > ... [Well duh silence] > > > It is, isn't it? > > > ... [Do I really have to say it silence] > > > Was it the way I looked at that girl? > > > ... [Disapproving silence] > > > Was it the comment I made about the jeans making you look fat? > > > ... [Glowering silence] > > > Long story short, 90% of communication is already nonverbal. It may be a bit more challenging with 2 silent partners, but insofar as emotion rather than concrete fact is being conveyed, or the two (non-)communicating parties are British, you should be fine. [Answer] You're going for a language with a single phoneme varied by length (tone? but it's a silence). Problem 1) It's going to be really really slow to say anything like for example, "look out for the lion behind you!" in Morse that would be .-.. --- --- -.- / --- ..- - / ..-. --- .-. / - .... . / .-.. .. --- -. / -... . .... .. -. -.. / -.-- --- ..- Though I'd expect more than two options for duration it's an example of how complex it'll be, especially as Morse effectively uses two phonemes, the beep and the silence, each with two durations. The silences separate letters and words, they're not just the gaps between the dits and dahs. Problem 2) Needing sound to end the silences, it sounds like a very peaceful language initially, but it's still going to be just as noisy. Advantage 1) Being deaf isn't such a massive problem, since everything is timing based sign language is easy for everyone. This sounds like a highly inefficient version of tonal. You'd be better off using the silences as a modifier of meaning rather than the entirety of the meaning. This would allow a much greater density of information while still making the language culturally unintelligible to outsiders and their obsession with sounds. [Answer] If all that matters is the silence, then there's no need for the sounds to be differentiated in any way. I'd suppose speakers of such a language would just grunt to break up the silences. So a sentence would be, like, "Uh ... uh .. uh .... uh . uh ..... uh . uh". Hmm, but how can silence have a "tone"? The only thing I see that could differentiate periods of silence would be their length. So your language would be reduced to deriving meaning from the length of each period of silence. Either the speakers of the language would have to be able to distinguish periods of time very finely, as in, oh, that was 1.24 seconds of silence, that means X, while 1.25 seconds of silence means Y. Or more likely, they'd have a very few lengths of silence, like dots and dashes in morse code, and meaning would be derived from the combination. Frankly it sounds a whole lot less flexible and concise than using silence to break up sound like real-world languages. Not to say that I'm trying to discourage you from using this in a story. But you might want to try to come up with some reason why, for these people (or beings), this is a good idea. Well, I guess for creatures whose physical capabilities are such that they can only make one sound, like all they can do is grunt, then it might make sense: If they can't vary the lengths of the grunts, but they can vary the lengths of the silences, using the latter might actually be more versatile. [Answer] I would expect such a language would have a different effect than you anticipate. Making a typical language which exists in the gaps between words is spectrally inefficient. If the words are not important, then all that matters is the starts and stops (and maybe a final tone to each word). If all of the information is conveyed between the stops, it would be inefficient to waste your time on the words themselves. You'd almost instantly start dropping words, because they had no value in the language. The end result of this would look similar to Morse code. While the content of Morse code is actually in the spaces, we hear the punctuation between them. Each word would be similar to the punctuation at the end of each dot or dash in Morse. Having words would be the equivalent to every single press of a Morse code key being a spoken nonsense word. There's all sorts of issues there. Morse code depends very much on maintaining a clear even timing. If you were interjecting words, you may drop timing while speaking, making it harder to distinguish the value of the space after it. Morse makes it easy, ever click is just that... a click. There's also bandwidth efficiency. [Morse code is slightly more efficient than texting](https://www.youtube.com/watch?v=64tfnG77Nl8). Can you imagine how slow a culture would communicate if they were limited to texting bandwidth? Now if we start to explore atypical parts of language instead, we find some interesting results. It is very clear that, in English, the spacing between words matters. People intentionally pause at different places to transmit meaning. Thus we know *some* information gets transmitted that way, but what information is it? Sure, it might just be "the speaker has chosen to pause, because you can hear the background noise," but sometimes you swear the *way* your mother pauses lets you know whether you can play for another 5 minutes or get your butt inside! One might imagine a language for a people who are very in tune with their environment. Speaking is an efficient form of communication, but what if all you needed to do was modulate the sound around you? What if you had enough of a sense as to what environment noises were out there to weave a story using them. There are wonderful stories of pianists coming up behind a child who is pecking away at Twinkle Twinkle Little Star, and improvising around them to make the child's song seem magical. In this sense, their language would be that of a gate. They either let the sound pass (by being silent), or squelch it (by making noise), depending on if that was the sound they wanted to have the listener hear. In theory this is just Morse code all over again, but there's a twist. What if every single squelch changed the sounds around them. If we speak, the birds in the trees shut up, for fear of a predator. What if their speaking *changed* what the birds chose to say near them. Now they could rely on the birds to speak for them, and merely cultivate their nearby birds to tell the story they want to tell. Sound crazy? Perhaps. But it strongly resembles how the human brain operates. Many of the most visible effects we see in the human brain are inhibition effects, squelching signals. In fact, many systems which need to amplify a signal do so by inhibiting an inhibitor (a double negative, in effect). Maybe there's something to it after all. [Answer] I am not aware of any spoken human languages that I am aware of that use only the silence between words, and ignore the spoken part. For spoken languages, this doesn't make much sense, but is not completely out of the realm of possibility. A language such as this would most likely not be the speaker's primary language. It would most likely have a specialized purpose. There are some existing languages which are similar to your idea. There are several "drum languages" which are used primarily to communicate with people far away. The drums are used very much like Morse code over telegraph lines. [Drums in Communication](https://en.wikipedia.org/wiki/Drums_in_communication) > > In Africa, New Guinea and the tropical America, people have used drum telegraphy to communicate with each other from far away for centuries. When European expeditions came into the jungles to explore the local forest, they were surprised to find that the message of their coming and their intention was carried through the woods a step in advance of their arrival. An African message can be transmitted at the speed of 100 miles in an hour. > > > There are also languages which use whistles, which has many similarities to the type of language you had in mind. [Whistled Language](https://en.wikipedia.org/wiki/Whistled_language) > > Whistled languages differ according to whether the spoken language is tonal or not, with the whistling being either tone or articulation based (or both). > > > Tonal languages are often stripped of articulation, leaving only suprasegmental features such as duration and tone, and when whistled retain the spoken melodic line. Thus whistled tonal languages convey phonemic information solely through tone, length, and, to a lesser extent, stress, and most segmental phonemic distinctions of the spoken language are lost. > > > In non-tonal languages, more of the articulatory features of speech are retained, and the normally timbral variations imparted by the movements of the tongue and soft palate are transformed into pitch variations. Certain consonants can be pronounced while whistling, so as to modify the whistled sound, much as consonants in spoken language modify the vowel sounds adjacent to them. > > > "All whistled languages share one basic characteristic: they function by varying the frequency of a simple wave-form as a function of time, generally with minimal dynamic variations, which is readily understandable since in most cases their only purpose is long-distance communication." > > > Most spoken languages make use of gaps in between words to convey meaning. These gaps are turned into punctuation marks when the language is converted to a written form. These gaps are well documented and the following example shows how they are used (emphasis mine). [Eats, Shoots & Leaves](https://en.wikipedia.org/wiki/Eats,_Shoots_%26_Leaves) > > A panda walks into a café. He orders a sandwich, eats it, then draws a gun and proceeds to fire it at the other patrons. > > > "Why?" asks the confused, surviving waiter amidst the carnage, as the panda makes towards the exit. The panda produces a **badly punctuated** wildlife manual and tosses it over his shoulder. > > > "Well, I'm a panda," he says. "Look it up." > > > The waiter turns to the relevant entry in the manual and, sure enough, finds an explanation. "Panda. Large black-and-white bear-like mammal, native to China. Eats, shoots and leaves." > > > [Answer] Lots of answers have focussed on the troublesome fact that silence appears to have only one dimension: the length of it. But what if the noise that is being interrupted counts? Suppose there is a world where there is a complex continuous background noise, changing at a speed suitable for this purpose. Then when the "gzz" sound comes, I interrupt that with silence (in a manner to be invented by the author :) ) that means one thing. But if I interrupt the "gnah" sound, that means another. And if I hold the silence over the transition between "gnah" and "haggh" that means another etc. This gives you more power/bandwidth to express things, and also hints at various interesting possibilities for what kind of world would have this kind of language... [Answer] Can it be degrees of silence? I'll invent a reason and cause: 1. A species of social animals in an environment without predators. 2. Two lounge valves (for hand-waving reasons) cause them to constantly breathe in and out, with the ability to make a sound. Maybe just a loud murmur? They don't have to be quiet to avoid predators, there are none 3. Evolved this ability for echo location to find food or look inside nuts. Maybe nuts were their primary food source and they used sound to see if the nut was full/rotten/hollow to measure the effort/reward for using energy to open it. 4. Food's scarce, constantly making noise to find food. 5. Making sound is basically the default setting 6. It's more effort to them to halt sound making than to make it 7. Civilization evolved with food producing technology, but evolution doesn't necessarily just de-evolve two valves and a constant sound machine for no reason. The constant sound began to be used in social contexts instead 8. No/less sounds from fellow aliens grabs their attention more than lots of sound, because it represents someone who can't breath, find food well, is sick, wants attention by performing abnormal behaviour Wheter degrees of silence or just a binary sound/no sound + space is the formula for speech is up to you, this story fits both. Silence as a cultural/social function could lead to lots of interesting things. A field of dead soldiers is terrifying - it's completely silent like thousands of souls "screaming" from the terror they witnessed in their last hours. They are apt at working and concentrating in loud environments. The default state of affairs in a city would sound like a full orchestra in a janitor's closet to us [Answer] It seems very unlikely that a species would use a language like this naturally - a language of sound-and-silence is basically a binary language, which means that it's purely semantic whether you want to call it a language of sound or of silence. However, there is one place where this idea has merit: subtext or a secret code. The plain meaning of the conversation is in the sounds, just like our own languages, but the length of the spaces between the words could encode an entirely separate message in binary code. A person could have two completely different conversations at the same time, provided their brains could handle the additional processing. [Answer] From an information-theoretic perspective, this would fail. That's because the language uses a unary encoding (the length of the silence). The unary encoding could carry a binary encoding on top of it, which would make it basically equivalent to Morse code. But in general, a unary encoding is exponentially less efficient than a binary or higher encoding. That's because the digits required to write a number N is proportional to N (it's exactly N). But the digits required to write a number N in base r (with r > 1) is only log\_r N. It's the difference between being able to write the number 1000 on a piece of paper or not. In unary, you would write one thousand scratch marks one after the other. Any creature which used a more complex encoding would be able to transmit information much faster, which would offer an enormous benefit to the creatures trying to communicate in unary. In fact, human language, despite its redundancies, is very efficient. It roughly uses a Huffman encoding for the length of words (common words are short, with infrequently used words being long). Also, using the silence instead of the sound is quite wasteful of the available degrees of freedom. Almost every creature that can make a sound can vary the pitch or amplitude under control. So failing to use these dimensions is an unnecessary handicap. I can't think of a single creature which uses sound to communicate, but fails to use amplitude and frequency to carry information. [Answer] Natural language has happened to use voiceless stops, see the tenuis <https://en.wikipedia.org/wiki/Tenuis_consonant> However, all communication needs signaling elements. If you try to make a language all of silence, your virtual reality might have little appeal: silence is not a signal. ]

[Question] [ I, Lord Leopold Borthwell, have recently encountered a series of most damnable conundrums that all seem to stem from a single problem: flight. You see, caer can merely fly over any walls that would keep a normal human out. This leads to many complications in the seemingly-simple business of keeping people where they belong. Three specific situations have all provided unique variations of this quandary. **First**, my personal estate in the Suncliff district of New Kalston has had a series of lowborn interlopers. I've seen caer children snatching fruit from my garden and flying away before the guards catch them, salesmen merely flying past the gates designed to keep their sort out, and one winged tramp discovered sleeping under a tree in my yard. What's more, I've heard reports of sneak thieves dropping onto rooftops and creeping in through upper-floor windows late at night, hidden in darkness and the night-time fogs of this country. How do I keep these unwelcome visitors away? (In fact, I'd be interested in solutions that keep the riffraff out of this part of the city altogether- perhaps I could suggest them to the constabulary.) **Second**, a business venture of mine (a sort of permanent fair, or "park of amusements"), has been having problems with caer flying into the park rather than paying their admission fee. This problem is somewhat more difficult to solve than that of my house, since it is a much larger area, and furthermore my caer parkgoers must be able to fly about within the park, so solutions that affect all flying people, or rely on individual recognition, are unacceptable. **Third**, I maintain a much larger country estate well outside the city, and my groundskeepers have been discovering evidence of interlopers there as well. This situation regards a tract of land much too large to be actively guarded. Some general information to help when solving this problem is as follows. First, caer fly using wings, and are not particularly subtle- a twenty-foot wingspan is difficult to miss, though this changes at night when the mist comes in. They are fast as well, so chasing them down is difficult (though not impossible). While caer do have a detestable habit of letting themselves into places they are unwelcome, there are those of higher standing among their ranks, and I do not wish to employ any solution that would prevent *all* flight within, into, or out of these locations- I do occasionally have caer guests who dislike walking everywhere, and I must admit a winged messenger is a great convenience I would not readily deny myself. I would also like to solve these problems with a minimum of effort and expense. Therefore, ridiculous numbers of guards and newfangled technological marvels such as this 'electricity' nonsense are right out. Oh, and no ghastly nets. I won't live in a birdcage. [Answer] Hire Caer guards. If they are cheap, hire plenty of them. If they are expensive, hire one or two squads of them and use cheap lookouts. (riff raff, children, low grade guards,...). Once the lookouts spot caer flying somewhere they do not belong, the Caer patrol goes after them and beats them up. Do not kill them, beat them up and let them go back to tell others about what happened. Give it some time and most Caer will not bother your estates and business ventures anymore. [Answer] **With Guns.** A handful of guards with guns should suffice. You see, flying through the sky possesses a singular disadvantage that sneaking on land does not - namely, there's no cover whatsoever. A raised guard tower will have a clear view of the sky, and a human can see miles away - except the effective range here is the gun. And guns have a pretty long range - you mention 'newfangled electricity' so we're discussing the late 1800s-early 1900s here, meaning that accurate and long range rifles *do* exist. (I'd recommend a M1903 Springfield Rifle, a bolt-action rifle with an effective range of a kilometer, and a maximum range of 5 kilometers.) I suppose there's a non-lethal option with net guns or something. But just winging the flying pests should send them flying, and let's face it, they're lowborn peasants. Fog and moonless nights will pose a problem, but it's a double-edge - you see, if you can't see them because visibility is blocked, they can't see you. And flying with visibility blocked is basically a death sentence - there's a reason why the only ones who do it are nocturnal birds who can see in the dark. [Answer] May I suggest decorating the roofs of your buildings with sculptures featuring many upward-pointing things? Gargoyles are *so* last year, statues of spearmen, starbursts, spires and stegosaurs should be the mode du jour. If the caer can't land on the roof you've won half that battle. If it is possible to hire caer to work as guards they could simply fly above points of interest and use their existing combat techniques, much as your landlocked guards do. If they don't use weapons now may I suggest archery or javelins. Care should of course be taken that persons on the ground are not inconvenienced by themselves being pierced. You may also care to consider tethered balloons, inhabited or not, and using hot air or hydrogen as you see fit. While less maneuverable than a flying creature, they have the advantage of being able to stay aloft for long periods in one place. Caer on the balloons would be able to launch from them when something exciting happens, although landing may be more difficult. Defending the balloons against military attack will be hard, but against common criminals the full force of the law can be applied. Few will want to escalate from trespass to attacking the ruler! To address your specific concerns: Keeping riffraff out of grounds and estates should require a balloon or two, preferably with an observer or caer guard to discourage interlopers. Catch one and punish it "pour encourager les autres". Children too young for punishment can simply be returned to their keepers and those advised that they will be held responsible for future problems. The amusement park is slightly more complex, as suggested by my esteemed collegue a marker or token to be worn at all times by legitimate guests is the obvious answer. Failing that monitoring the permeter may be necesary, and using the existing civil systems for chasing and chastising miscreants applied when they disobey the perimeter crossing requirements. Aerial patrols of a much larger estate could be performed using non-tethered balloons in good weather, but may I suggest that if at all possible an arrangement be made with a caer group that they apply their social restrictions on your behalf in exchange for something that they value. Since you have caer residents in good standing within your domain this should surely be possible? [Answer] Dealing with caer while not employing them to police their own is going to be an interesting problem. Fences, that you suggest are designed to keep them out, fundamentally aren't designed to keep them out, they're designed to keep humans and other land dwelling large creatures out. 1. **The townhouse**: This is best dealt with by guard dogs or equivalent, since you have flying people, some sort of flying guard dog would be entirely appropriate. Along with a decent security system to keep them out of your property, securing upstairs windows etc, losing a few apples to children sneaking onto the property is entirely appropriate for the context. Children being chased off by the gardener/housekeeper is entirely appropriate. 2. **The fairground**: The problem here is solved with a change of business model, you're approaching it as an amusement park with an entry fee and then free access to rides, if you change to the model to fairground with no universal entry fee but rather a fee to get onto each ride the whole problem goes away. 3. **The country estate**: You have poachers, what you need are gamekeepers. Whether these gamekeepers are human or caer, they should have guns (or equivalent), and dogs (or equivalent). Their primary role is to look after the game on your estate, a fundamental aspect of that is to keep poachers, trespassers and other undesirables from disturbing said game. You say you have [huge tracts of land](https://www.youtube.com/watch?v=GPX-mW4l1rU), which can't be actively monitored, but you also have access to caer, who can actively monitor said tracts of land. Now of course if you decline to employ them then you have a problem, I would advise holding your nose while taking advantage of this resource. Privilege historically meant [private law](https://www.etymonline.com/word/privilege), in terms of large private estates it effectively means that the law that applies on the estate is the law as applied by the owner rather than the law of the nation. If you wish to keep this riffraff off your lands then you will have to employ the people to do so, to enforce the law of your own land. After all, this is why you avoid paying taxes. (A xenophobic "keep them where they belong" attitude tied to paranoia about criminal classes is always an entertaining trait in rich people.) [Answer] The wingspan is large, use that. 20 feet of wingspan means any "net" that is smaller can make it very hard to get to where you want. So instead of netting you just place festive lines with flags that are spaced about 10 feet from each other over sensitive area's. The Caer can still easily reach the location by just landing away from the area and walking underneath but that is part of its charm as your Cear guests and messengers can land and reach you easily without suffering the indignity of an accidentally failed landing on top of you. To put some more emphasis on my latest edit: social rules can also be very powerful. Most people will not randomly cross a fence or low wall even though it will not really stop anyone who wants to cross it. So these flagline area's function like fences and the punishment for being under one without permission could be anything from a reprimand by the owner to getting thrown in a cell. Any Cear caught underneath these lines is in a sensitive area and needs good reason to be there. If not you can arrest them, they cant fly straight up so its easy to catch. It would be easy to teach the population that when you are beneath such lines you are at risk of being arrested for tresspassing or whatever transgression they can commit there. The flags on the lines can easily help identify your stuff and what its supposed to do for you besides being handy for festive things, and also be used generally to guide Cear to places they do want to go to like the local tavern. To better catch Cear the guards all get slings and/or blunted arrows to shoot at their opponents. Flying is hard when you are large and a blunt force hits you, causing a likely crash by the Cear making it possible to catch Cear before they walk out from under the lines and take off. Listeners could be employed to detect Cear on the premises day and night. Something with a 20 foot wingspan and weighing more than 20kg is going to be loud when flying (I assume, correct me if I'm wrong). So if you hear the signature sound of landing your high-placed listeners can tell ready guards that something is up. Naturally whenever they can the listeners will also just look besides listen. Flag signals held by these listeners can warn off Cear who fly near sensitive area's and communicate with nearby guards as to the location of a Cear. Naturally with half the population being Cear and you already using them as messengers a part of your guard will be Cear that can fly and catch Cear that manage to avoid the ground guards. [Answer] Crows. Lots of crows. Crows are family birds, and any flock you see is a couple of parents and their children. They are already territorial, which means they're vicious blighters that will attack targets relentlessly. They are smart (smarter than dogs by a good measure), and could easily be trained to attack people who flew to get into an area and keep harassing them until they left. (Without attacking people who entered on foot.) And if you feed them, they can be your loyal friends, and will happily use that food to produce an even bigger flock of flying guards. [Answer] My good sire, AS your esteemed advisor, would be my honour and obligation to dispense some tidbits of information that your mind occupied with more stately affairs may have overlooked. Make them fly. A lot. With weights. Come the season of war, when we meet those detestable claimants who trheaten our glorius New Kalston, if our troops are used to fly all the time with weights, why, we will have the advante carrying supplies. Have those scoundrels who scurry at night, wait for them with a cadre of guards and offer them a proposition. Become your ears or lose their hands. What better way than to catch a thief than having your own agents. Come war, they could be invaluable scouts, moving in the night. For the tramp sleeping in the tree, we could make a company of ladies of high class. Same offer, working for your Lordship. A fair with a theatre is common. Now you would make the duchess green with envy if your tehatre displays Cherubs while hers is lacking. That alongside the scoundrels could be our ears to the ground. Much is to be gained by a cunning mind, and a Lord of your pedigree has the cunning in spades. This is my advice sire. [Answer] Even in our traditional 2d world, walls weren't always practical, like around the kings forest. A penalty of death for hunting on the kings lands solved the problem (and was probably not even stringently enforced). In a world where many people have always been able to move freely in 3 dimensions, walls may have never even been a thing. My guess is that many generations ago the flying people were hunted to near extinction because many were perceived as thieves (and other annoying habits--perverts?). their solution has been to enforce a strict moral code within themselves. Any caught using their flight to do something illegal are quickly dealt with (to death?) by their own community--theft is now virtually unheard of and the winged people are thought of as extremely virtuous. Nobody ever thinks to protect their property from them, it would be pointless and somewhat insulting. [Answer] Surely there are multiple solutions. Install **bird spikes** on and around your estates, on roof tops, trees and fences and any place that offers hidden landing ground. Employ caers to locate spots that are less obvious. Have them painted according to their surrounding if you want the spikes to look less intimidating, and in case you want to keep the looks of your estates historically correct, or paint them bright if you want to achieve the opposite. [](https://i.stack.imgur.com/bvBtf.jpg) Use **bracelets of different colour** in your amusement park. To avoid copied bracelets use a different colour each day. I'd also suggest that the park in itself is publicly available and therefor attracts even more visitors who come for the atmosphere and stay for a snack, or even join a spontaneous ride. Only the use of attractions themselves would be costly, as well as the various food stands. Everyone is invited, and you might even make money out of the previous intruders. [](https://i.stack.imgur.com/O9jlW.jpg) Also, make intruders **uncomfortable to return** if they got caught. If the law forbids any physical damage of others, like [clipping their wings](https://en.wikipedia.org/wiki/Wing_clipping), despite their lawlessness, have a professional illustrator draw their face and shame them publicly. [](https://i.stack.imgur.com/zfLdA.jpg) Generally; **reduce obvious attractions** on your estates that you don't want stolen and **scare potential intruders** with fierce, armed guards. [Answer] > > What's more, I've heard reports of sneak thieves dropping onto rooftops and creeping in through upper-floor windows late at night, hidden in darkness and the night-time fogs of this country > > > **HOW ARE YOU STILL ALIVE?!** To solve the first problem, you can start by closing the windows, all of which have proper locks, right? If you've cut corners there, then you have my permission to die. If anyone comes in uninvited, just have a (preferably flying) "bouncer" to "show them out". As for the garden, use nets. You only stated you don't want to live under one. One problem with the question, however, is that the existence of an entire (sub-(?))species would precede the building of the estate. So, it could have been, from the very start, be built as a panopticon, more precisely, in accordance with some of the panopticon's design principles. I might add more here later. ## Securing large areas is impossible. Even if you have patrols, [there can always be a hole somewhere](https://www.thoughtco.com/intruder-enters-queen-elizabeths-bedroom-1779399) (and that's without flight and has happened multiple times), an overlooked detail, especially at night. It's only improved slightly with flying patrols. So one should concentrate on securing the the most valuable assets. If the patrols do catch the interloopers, you can have them first tell how they broke in, then clean up any mess (like seriously, what were they doing there?), regardless whether they caused it or not. It's sorta unjust, but isn't as sociopathic as the rest of the suggestions, saves money and is addressing the problem directly. Note: [Being rich doesn't make you](https://en.wikipedia.org/wiki/Elizabeth_B%C3%A1thory) [immune to being lynched/persecuted](https://www.history.com/this-day-in-history/a-torture-chamber-is-uncovered-by-arson) [Answer] > > While caer do have a detestable habit of letting themselves into places they are unwelcome, there are those of higher standing among their ranks, and I do not wish to employ any solution that would prevent all flight within, into, or out of these locations- I do occasionally have caer guests who dislike walking everywhere, and I must admit a winged messenger is a great convenience I would not readily deny myself. > > > If crime stems from unique abilities, the perpetrators of those crimes need unique punishments. [Wing clipping](https://en.wikipedia.org/wiki/Wing_clipping) is a well known procedure for ensuring winged creatures behave in a more down to earth manner. Of course, whatever procedure is necessary to ensure a caer never flies again, it does not have to be performed on every member of that race, that would be barbaric. However, those of a lesser social standing that continuously resort to using their abilities for criminal purposes, or perhaps can even be suspected of doing so in the future, need to be made an example of. By making examples, you will underline without any doubt what winged flight really is: a privilege. [Answer] Perhaps the solution is far more simpler than we have expected. Don't keep them out rather keep them in a honeypot. You could make traps with something so attractive to them (honey is what does it for humans) that they have no choice just to fly into it. Then they can be trapped and thus cannot go on property near the location. I wish you fair well with your endeavors. [Answer] **Dire Consequences** See Amazon's Carnival Row. If caught flying in an illegal way, clip their wings such that they will never fly again. It does require a mostly bigoted society for people to be okay with it though. After a few wing clippings, interloper numbers should drop pretty steeply. [Answer] If I may recommend a large glass sphere. Surely a gentleman as well-off as yourself could develop a dome made of a clear material to cover the affected areas. This would also allow yout to control the temperature and moisture in the chosen areas to a tee. ]

[Question] [ Man, I really have to find a way to stop getting into logic dead-ends. So, in the story I’m writing, there’s this country that developed big bad war machines that run on steam engines. The way they work or if they make sense or not is irrelevant. These war machines brought military superiority to the said country and made them conquer pretty much every other country except one because this one has magic (specifically, [this](https://worldbuilding.stackexchange.com/questions/68362/what-kind-of-spells-would-magicians-cast-in-combat-if-the-fuel-to-magic-is-very) kind of magic). Now, I need for the sake of logic that the aforementioned big bad war machine bearing country still uses sword, shield and pike infantry and heavy cavalry. Or to be clearer, I need a country that has steam engine technology to not have discovered gunpowder yet. **Obs.:** By "gunpowder" I mean *"projectile propulsion system that would effectively (including cost-wise) replace swords, shields, pikes and heavy cavalry".* I did my research. According to [source](https://en.wikipedia.org/wiki/Gunpowder), gunpowder was first used in the military by China in 1126, while the first steam engine used to actually move a big vehicle (locomotive) was only applied in 1804 ([source](https://en.wikipedia.org/wiki/Steam_engine)). That’s 678 years. Is that plausible that a civilization based on our own would not discover something that important for more than 500 years? Can I have a plausible excuse? Please assume: * This country is cold, harsh, and very military based. The same can be said about its people; * They can’t use magic because reasons. Even if they have the fuel mentioned in the linked question, it just doesn’t work; * Steam engines are the only advanced technology they have. No electricity or the likes. Also, note that they having discovered gunpowder but being unable to apply it in the military is also a solution (obviously with a plausible enough explanation). --- **EDIT:** Lack of interest in chemistry is out of question. There is no way a military force that big is not actively and extensively researching chemistry. Also, little edit in the body of the question. --- **UPDATE:** Thanks for all the answers. I'll go with a mix of @Jeutnarg and @PaulTIKI's answers, as those were the ones that gave the most useful solutions *to my specific world*, and @Graham's comment. [Answer] Yes, and you can do it even in a world where people create gunpowder and recognize its usefulness. In fact, your world *should naturally evolve that way*. The existence of your type of magic gives military technology reason to prioritize projectile defense over melee defense, and this would only increase the more prevalent and powerful magic is, since your magic lends itself towards projectile attacks. Why would you wear expensive, bulky plate armor when your enemy can just shoot a metal spike through you from a mile away? No, you need something that conceals or can deflect projectiles, not something that makes you highly visible and slower. How does anti-projectile armor make it so people don't use gunpowder in war? You may already have guessed, but let's examine why Europe adopted guns to find out more. Guns started really showing up in Europe in the late 15th century. Here's what armor looked like [scroll down to look at cavalry](http://www.medievalwarfare.info/armour.htm) at that time. You may notice that these heavy knights look almost invincible. That's because they darn near were invincible, only succumbing to specialized weaponry or after being knocked to the ground, and trying to do that was a good way to get yourself killed. ***That armor*** is the reason that guns were adopted. Guns were the **only** weapon that could take down these heavy knights reliably and at a distance (period crossbows were not sufficient to penetrate quality plate). The single, crucial advantage of armor penetration compensated for the slow rate of fire, cumbersome nature, and expense of gunpowder weaponry. Without that initial advantage, guns will never be adopted at all and so will not advance to become useful - at least, not for thousands of years. And now you're about to say something about cannons - cannons are fine. OP explicitly stated that their goal is to keep "swords, shields, pikes and heavy cavalry" as viable options on the battlefield. Cannons don't replace those things, so we're in the clear. [Answer] # Yes You're in luck, the first steam engine was actually invented in the 1st Century AD a good 1000 years ahead of gunpowder. The [Aeolipile](https://en.wikipedia.org/wiki/Aeolipile) is technically a steam engine, what's required is for the people of the time to see its potential rather than dismiss it as a toy. > > Heron (c. 10–70 AD) takes a more practical approach, in that he gives instructions how to make one: > > > № 50. The Steam-Engine. > [](https://i.stack.imgur.com/SUn07.jpg) > > > PLACE a cauldron over a fire: a ball shall revolve on a pivot. A fire is lighted under a cauldron, A B, (fig. 50), containing water, and covered at the mouth by the lid C D; with this the bent tube E F G communicates, the extremity of the tube being fitted into a hollow ball, H K. Opposite to the extremity G place a pivot, L M, resting on the lid C D; and let the ball contain two bent pipes, communicating with it at the opposite extremities of a diameter, and bent in opposite directions, the bends being at right angles and across the lines F G, L M. As the cauldron gets hot it will be found that the steam, entering the ball through E F G, passes out through the bent tubes towards the lid, and causes the ball to revolve, as in the case of the dancing figures. > > > # How could this be viable? Luckily most of the required technologies were already in use. The water wheel has been in use for several hundred years. Gears were known to the man who first described the Aeolipile, [Hero of Alexandria](https://en.wikipedia.org/wiki/Hero_of_Alexandria), who also described a wind wheel operating an organ. It's not unreasonable to suggest that he could have invented a steam engine based on a combination of these technologies, if only to do something basic like running an Archimedes' screw. Consider reading Hero's [Pneumatica](http://himedo.net/TheHopkinThomasProject/TimeLine/Wales/Steam/URochesterCollection/Hero/index-2.html), especially his descriptions of machines for [Temple Doors opened by Fire on an Altar](http://himedo.net/TheHopkinThomasProject/TimeLine/Wales/Steam/URochesterCollection/Hero/section37.html). He may not have invented the steam engine but he was most of the way there. If his interests had leaned that way, I'm sure he could have done it. [Answer] Absolutely. The exact chemicals required for gunpowder and the ratios in which to put them, not to mention the various other advances in gunpowder technology that made it so fearsome, can easily be not discovered. Gunpowder is the combination of seemingly unrelated elements, where steam power is the natural evolution of the thought 'gases take up more room when they're hotter'. A scarcity of any of the key components would certainly lead to people not putting sulphur and potassium nitrate together before the advent of steam power, and similarly anything that would lead to steam power being more popular earlier (the success of the [aeolipile](https://en.wikipedia.org/wiki/Aeolipile), for example) would lead to more people focusing on steam power as the means to military success over trying to further refine various chemicals into a destructive force. The thing you will have to watch out for is sufficiently clever people deciding to use compressed steam or a [steam gun](https://en.wikipedia.org/wiki/Steam_cannon) as a weapons system in it's own right. Or maybe that would be good for you. Who knows? [Answer] No. The answer to your title question is "yes", there is nothing about black powder specifically that makes it inevitable that it would be discovered before steam power. But your full question is a very different one, with a different answer. It isn't really feasible feasible for steam engines to be developed without gun-like weapons also being developed. The simple reason is that the same principles used in a steam engine can be used in a projectile weapon: a [steam cannon](http://web.mit.edu/2.009/www//experiments/steamCannon/ArchimedesSteamCannon.html). In fact, such a weapon is considerably simpler than a steam engine and designs of such weapons predate any usable steam engine. Steam guns were never used in warfare because by the time the technology was made to manufacture them in usable numbers and quality, easier-to-use gunpowder was available. But if gunpowder were not available, steam guns would have been a natural outgrowth of the much more complicated steam engine development. It is true that Heron made a very early steam-powered device long before gunpowder or steam guns existed. However, this device wan not a practical way to use steam to power machinery. It produced far too little power to do anything useful for a feasible amount of water and fuel. The machinery to get useful work out of steam is much, much, much more complicated. [Answer] Well, simple gunpowder could be delayed by making elemental sulfur (sometimes called flowers of sulfur) hard to find. Also, keep in mind that it was a pretty long time from when gunpowder was developed to when it was used to propel a lump of metal down a tube with the intent of killing something. Steam power exceeding chemical propellant is very possible. In addition, Melee weapons were in wide scale use all the way up until the Late 1800s so that preference could keep on. Steam Cannon aren't very hard to envision. The same with steam machine guns and so on. They would, out of necessity, be at the very least cart mounted weapons. The advantage of gunpowder as a propellant is that it carries a lot of energy for a very small amount of mass and volume. To get similar results from steam would require a very bulky, dangerous, and above all, slooooowwww machinery. For anything less than a cannon, you'd be better off with crossbowmen (cheaper and faster to engage and reload) Your end result would be Steam powered cannon replacing weapons like catapults and trebuchets, but with the bulk of the fighting being carried out by melee weapons. Archers would still be in demand. You could, in theory, even have gunpowder weapons at this time, but with sulfur being so hard to find they would be prohibitively expensive. Pistols would be the purview of kings. In this world you could even up the Steampunk ante by adding a Nicola Tesla type genius to the mix and have prototype electrical weapons. I like the idea behind this world. Keep it up! [Answer] Basic steam engines are ancient. Making good steam engines was blocked by metallurgy and manufacturing tolerances. Engineering was also important, but nothing could be done without the materials and manufacturing tolerances required. Once you have viable machines, incentive to make better metals and tighter tolerance machining is made, together with the power to make the machines that permit those very things. In effect, this is the core of an industrial revolution; a feedback loop of technology making technology better, and incentives to follow the loop upwards. Gunpowder was also ancient, but it wasn't very practical. The problem is that a good cannon or gun requires strong metals and exact machining tolerances. These two requirements may seem similar. The very things that let you make a strong boiler an pistons is the thing that lets you make a cannon or rifle. Whichever version of gunpowder isn't that important. You just need to make a reasonably stable yet reasonably high energy self-combusting mixture of stuff, and a way to light it on fire. Similarly, boiling water is easy. The hard part is turning that into something useful. Barring trees that grow steam engines, the technological underpinnings of steam technology and guns are too similar for them reasonably diverge too much. [Answer] They might not have gunpowder but they definitely want stem-powered trebuchet to hurl rock long-distance (when they are beyond reach of pikes of their opponents). [Answer] Development is often driven by need and opportunity. if your country had an abundance of steam power everywhere (like at Yellowstone) then people might start figuring out how to use it before fire (Heck, it might delay fire's invention since you could cook and be kept warm by steam). I could see picking a particular vent and jamming rocks into it so that pressure would build until the rock came flying out at speed. Weaponizing that wouldn't be a stretch if such holes were abundant. At that point you might use wood/fire and even coal just to make your steam-ballistics portable because you are so familiar with the way the steam engines and weapons of war work--you might ignore other technology paths altogether for a time. Currently our power generation--from coal to nuclear--all rely heavily on steam technology, it's still THE primary method to convert heat to movement (Wind is the other big one I can think of right now). It might just turn out that there are undiscovered steam solutions to some of our existing problem that are better than our current solutions but we never found them because a portable heat source was harder to deal with than electricity/explosive force. If you could dig a hole anywhere and pour water in and have it turn to steam I'm pretty sure that would be the core of nearly all the machines in the world. Another way this could happen--suppose your civilization evolved on a highly radioactive world and was therefore immune to it. If you could find rocks hot enough to make water boil for an extended period of time, why would you ever need another power source? But as far as I know you'd need steam to convert that heat into movement (There is probably a way to convert it straight to electricity though, but that might be considered more of a gimmick or toy--just like we'd consider a small steam engine a toy) [Answer] Of course. Steam energy requires fossil fuel and water . Gunpowder is made with sulfur, charcoal, and potassium nitrate (saltpeter). Steam energy was technically used as soon as steam could be used to rotate something (in wood for example). Sources of steam can be natural. [Answer] In elaboration to Separatrix's answer, the development of Steam engines would come with some careful consideration of the Aeolipile. Instead of answering how would it be done, I would like to discuss *why* someone would want to develop steam-powered machines instead of gunpowder. **Speed** While not all steam machines were fast or on rails, there have been innovations in steam power that gave steam vehicles such as the [Double steam car](https://en.wikipedia.org/wiki/Doble_steam_car) which boasted 1500 mile range without refuel and 0 to 60 in 15 seconds. If I were a military tactician, such as the Huns, I would like to arrive to arrive with a large force for a surprise attack. **Capacity** To carry your [fancy war machines](https://en.wikipedia.org/wiki/Helepolis) by horse would mean to struggle at every point whenever you have to carry them over a hill and arriving late to the party every time. Steam powered machines would solve the issue of running low in supplies as a single steam vehicle(4) would carry more than several horses. **Intimidation** While OP has not provided many details about the time era where his empire is located, I am assuming that it is between the Medieval era and the early Renaissance era. Most people of the time would be promptly frightened by an incoming iron beasts and the heavy clanging of metal. I would avoid ancient tanks of war(3) though. [Answer] As mentioned by Separatrix, basic steam engine was discovered quite some time before black powder. There is commonly accepted opinion among historians, that it's further development was stymied by wide availability and chipnes of slave labour. Make it unavailable or very expensive, and you've got incentive to develop steam technology, and it is worth mentioning that antiquety possessed very advanced theoretical and practical knowledge in mechanics, as evident <https://en.m.wikipedia.org/wiki/Antikythera_mechanism> Compared to Greeks and romans, your country would need better knowledge of metallurgy, though. [Answer] Depending on how you are developing your world, you can make small tweaks to chemistry and nerf gunpowder. (For example, in Zelazny's [The Guns of Avalon](https://en.wikipedia.org/wiki/The_Guns_of_Avalon "The Guns of Avalon"), the protagonist, knowing of Earth gunpowder, finds with great effort an obscure substance that functions the same way in Amber. If he had not been exposed to gunpowder weapons on Earth he would not have seen the practical use of the explosive substance.) [Answer] Actually it is possible that most planets in our universe invented gunpowder after steam engines(or at least some of them). :) Without chemical industry humans would not be able to obtain nitrate if not for a quirk of biochemistry. First our organisms produce some urea, then microorganisms oxidise it to nitrid acid, then it reacts with potassium carbonate and we get potassium nitrate. Energy is produced while urea is oxidized (that's why microorganisms do it). If vertebrates learned how to oxidize it by themselves, saving a little energy, then producing potassium nitrate would be impossible until chemistry gets at least to the level of 19th century(most likely middle-end of 19th century). [Answer] Yes, steam engines could be invented before gunpowder but it doesn't matter much because steam guns would be invented, too. When you have steam engines you have boilers, cylinders and pistons, it's straightforward to take a long cylinder, leave it open at one end let steam throw the piston to the enemy. The only reason steam guns saw only little use in our timeline was that gunpowder and other explosives are more efficient for most purposes, but in a world without explosives steam tanks and steam war boats wouldn't lack steam guns. The steam-powered trebuchet proposed by Peter Masiar are likely adaptations of early steam machines - like the Newcomen engine - therefore you could expect steam-powered artillery even with the most primitive steam engines. [Answer] The question if wrong. We know that people had steam engines long before gunpowder. Apart from mentioned Aeolipile Hero created steam engine that could open doors. The question you should ask is: **WHY?** Why would they need to use steam engine in warmachines? To build steam powered tank? The amount of resources needed to build such thing would equal hundreds if not thousands of armour and weapons for soldiers. Not to mention the time needed to construct one tank versus time needed to build war chariot. Think that using steam engine in mines, agriculture or to strengthen the economy would bring better fruits for the country. Better mining means more resources and faster creation of standard weapons. So easy calculation would tell anyone that using steam engines as a weapon would be useless. ]

[Question] [ For the purposes of this question, let's *ignore* the causality issues of time travel itself. Suppose our hero, or an accomplice of our hero, has invented a time travelling apparatus. It works like this: a person steps into a chamber, sets some controls, and initiates a jump through time. The apparatus then transports *itself and anything inside it* to the designated time. It is powered by a set of handwavium-unobtainium-based power cells that provide enough power to sustain a small number of time jumps between recharge cycles. To keep this from becoming a too-easy *deus ex machina*, I want this apparatus to be able to transport through time but to be forced to consistently appear in the same location on Earth at the target time. That is, if you start at Brandenburger Tor, Berlin, Germany on midnight, New Year, and go half a year plus twelve hours into the past, you end up at Brandenburger Tor, Berlin, Germany at noon in the height of summer. *In other words,* it somehow works in such a way that we can (and indeed are forced to) disregard the Earth's own rotation, the Earth's orbital movement around the Sun, the Sun's orbital movement in the Milky Way, and so on, but we *cannot* instruct it to move geographically to another location as part of the time jump. There is no need for the apparatus to function at all further away from the surface of the Earth than some small distance, say 1 km or so (to allow for high-rise buildings). How could I possibly explain the fact that **the apparatus after transporting through time appears in the same geographical location,** as explained above? The explanation absolutely does not have to meet strict scientific criteria (we're throwing those out already with time travel in the first place), but it'd be nice if it doesn't break suspension of disbelief too badly. The time jumps will be on the order of hundreds of years or less, so geological stability should not be a major concern and might even provide an interesting obstruction to our hero. (Thanks [Pavel Janicek](https://worldbuilding.stackexchange.com/users/2071/pavel-janicek) for mentioning this issue.) [Answer] The time travel machine could be tied to the Earth and its **gravity**. So as it moves forward/backwards in time it also follows the rotation of the Earth (and all other movement of the Universe). Simply put the gravity of the Earth ensures that the time machine ends up at the same place as before. The Earth basically pulls along the machine as the machine travels through time. This might need some more thought put into it, but this is the basics of the idea that sprung into mind. [Answer] What if the constraint is that the machine can only navigate to a time that it's been in....bear with me here, there's more to it. Now obviously the passengers haven't been to the time in question, so clearly not all of the machine has to have been to the time in question. Thus this constraint boils down "the machine travels through time following the time path of a core component". Similarly the core component was something that your protagonist built, so being aware of the constraint the component would have been designed to key off something with a known timeline inserted in it. What you now have is a time navigation engine that allows you to move relative to any item inserted into it. So you chip off a piece of masonry from the Brandenburger Tor, insert the chunk into the navigation engine and now can move through time with the same relative location to the Brandenburger Tor for as long as that chip was part of it. Try to move to before the chip existed and you drop out of the time stream requiring you to scavenge around for another item you can reference from. This allows you to easily make short jumps, longer jumps require vandalising historical monuments and really long jumps become downright scary if you key off something like a cobblestone from the road that could still have been in it's current form but on a river bed thousands of years ago... [Answer] I'm glad that you mentioned storytelling in your question because it allows me to address it sideways, as a writer, rather than head-on in the role of amateur speculative physicist. There are many ways to handle your time-machine's odd geographic fixation. One method would be explain it away using any of the other fine answers on this page. A second method would be to hand-wave it away, leaving both your time-travelers and your readers in the dark as to why the machine acts that way. My personal preference would be to wrap it in humor... "You may have noticed that my time machine never leaves Berlin. That is one of my favorite features! It wasn't easy to make it work like that, but I finally figured it out." The aging professor smiled at his guests, obviously expecting their praise. Confused, his guests gaped back at him mutely. "I don't understand, Doc." Little Sally broke the tense silence. "Your machine can jump across the centuries, but it can't take us up to Hamburg. Why is that a good thing?" "Wait till you've grown up a little, My Dear." He patted the child's shoulder fondly. "Someday you will learn that globe-trotting is overrated. Dorothy was right all along. There is no place like home." [Answer] Very similar to [Xathien's Answer](https://worldbuilding.stackexchange.com/a/12666/2052), but more explicit. After going to bed at night and waking up in the morning, you are not surprised to find yourself in the same location, even though you have travelled roughly 8 hours into the future. Sure it took you 8 hours to get there, but what do you want for nothing? Along the same lines, when your machine travels 20 years into the past, it actually passes through every moment in between now and then, it just does it quickly. The same laws of momentum apply as you would expect had you simply built a box, waited 20 years, and played a film of it in reverse at high speed. Perhaps there is even some previously unknown sense that all creatures have which makes them unconsciously avoid the space your machine takes in transit. A bare patch of ground where nothing grows, concrete poured beneath it but all the machinery involved just off to the side, interior room space for a while, but the building was destroyed in a fire or war, etc. [Answer] From a conservation of energy point-of-view, you *don't* need to explain why it appears in the same location. Any movement within Earth's gravity well requires a change in energy. Regardless of the time aspect, any geographical movement requires an energy change - firstly energy is put in to accelerate the device, and then to decelerate it again energy must be taken out. Up or down is easy to visualise a change in energy, so consider this: Imagine the device is on the trailing edge of the Earth, and it jumps a moment into the future. An Earth-bound observer would see it disappear, and then re-appear a moment later. If it re-appeared at the exact same point *in space* (relative to the sun, for ease of visualisation), The Earth would have moved on and the device would appear to have gained altitude, now "trailing" above the Earth. It has therefore gained gravitational potential energy. From where did that new potential energy come? Going into orbit takes shedloads of energy, so this device can't simply be used to bypass that - there's no such thing as a free lunch! Similarly, if it were in orbit on the *leading* side of Earth, and jumped momentarily into the future, it would now be closer to Earth, and would need to shed that gravitational potential energy that it just lost. That energy could be converted it to heat (yikes!), or as gained velocity, so now it's hot and suddenly hurtling through space, towards the Earth! The only sensible solution when traveling through time then is for this device to maintain a constant position *relative to the Earth's gravitional well* (actually the whole universe's, which is obviously dominated by Earth's when near Earth). If it were moving, things get slightly more complicated, but not by much: A jump into the future would cause the device to appear in the place where it *would* have been, had it not 'jumped'. Again from a conservation of energy (and momentum) point-of-view, the device couldn't instantaneously decelerate to a stop a the instant of jumping, so that it could reappear at the same place. If the device were travelling 100mph and jumped forward one hour, *it would re-appear 100 miles away*. It must be treated as if it never jumped during that hour. (Now you have a plot device to travel through walls - travel *at* the wall, and jump seconds into the future. Now you're through the wall! [Answer] So there are two issues: **1) Orbital movement.** You can actually ignore this. We usually model the Earth as moving through space because it makes sense and the math is easier, but there's no such thing as "objective" spacetime or movement. It is perfectly valid to state that for your purposes the Time Machine is the center of the universe, and that the Earth doesn't move at all. **2) Rotation.** Unfortunately we can't ignore the Earth's rotation. So what you could do instead is force the device to only work in 1-day increments (down to [Planck Time](http://en.wikipedia.org/wiki/Planck_time)), so that when you go back you're in the same physical location. This would be a restriction your inventor places on the device though, rather than a fundamental requirement. If you wanted to you could transfer to any other longitude on your latitude, it's just that you'd often end up underground or up in the air. [Answer] To expand on the existing answers, in particular [Niffler’s](https://worldbuilding.stackexchange.com/a/12623/308), I suggest the machine to adhere to the following rules: * When travelling forward through time, it keeps its existing momentum. For example, if we ignore orbital motion for a second and the time machine is on a train and travelles 30 s into the future, it arrives at almost exactly the same spot where it would have been at the same time, if it had not travelled through time. When the machine travels backward through time, the momentum gets reversed in analogy. * When travelling through time, the machine is affected by gravity like a regular object but not by the other forces (because it would interact with other objects in a noticeable and possibly harmful manner otherwise). Thus, in the above example, the machine would actually start falling down since it is not hold back by the ground anymore (which is actually not what you want, I will address this in a minute). The above rules sum up the main forces that apply to planets, stars and similar. So, if you built your time machine around the whole earth, it would do exactly what you wish. However, as your time machine is not that big, it would start falling through the earth as soon as it begins time travelling, go through the core with high speed and emerge on the other side, slowing down such that it reaches its maximum height just at the surface (not accounting for geographical height), and then repeats all over in an oscillatory way (see picture below, also see [gravity train](http://en.wikipedia.org/wiki/Gravity_train)). Apart from that it would follow the Earth’s motion through space, as it is attracted by the Sun, the Milky Way and other celestial bodies just the same way as the earth.  Now, here are some ideas of addressing the issue of falling through the earth: * The machine is in a [geostationary orbit](http://en.wikipedia.org/wiki/Geostationary_orbit). Here only gravity is needed to keep it in place. Obviously, this would require all the trouble of getting into and out of a geostationary orbit. * The machine is capable of weakening the influence it experiences by gravitation such that it can make its starting point a geostationary orbit. Note that this would require a selective weakening of the Earth’s gravitational forces, as the time machine needs to experience the same gravitational forces from the sun to follow the earths orbit. This in turn can be achieved by making this feature directional, i.e., the machine attenuates the gravitation it experiences from the direction of the Earth but keeps everything else the same (this in turn requires a continuous adjustment due to the constant change of the Earth’s and Sun’s relative position with respect to the time machine). * The machine only stops travelling through time, when its at the top of its oscillation through the Earth’s core. It may arrive anywhere though. Alternatively, you handwave the Earth’s rotational motion away and say that the machine always oscillates between the same two points. In this case it can emerge exactly where it started (and on the other side of the planet, ignoring geographical height), but only every 84 minutes (when it’s at the height of its oscillation). [Answer] One approach would be to have a device whose exterior travels linearly through time in the same fashion as anything else, but which allows items to enter at one time and leave at another. Under such a scenario, if someone enters a time machine at one location and transports himself ten years into the future, and during that time someone else moved the time machine to a different location, then the time traveler would find himself in the latter location. This approach would allow travel forward or backward in time, but only to places the machine either had been or would be. The movie *Primer* used this concept and took it a little further with a time machine that only transported things back in time, and required the travel parameters be set "in advance" (if I remember correctly, transporting from midnight Jan 1 2014 to midnight Jan 1 2013 would have required that the machine be configured, prior to Jan 1 2013, so that at Jan 1 2013 it would contain whatever was in it on Jan 1 2014). Note that either the restrictive approach from *Primer* or a more general approach given above would avoid some time-machine paradoxes surrounding "bootstrapping", since there's no way that time travel under such rules could be used to facilitate the construction of the first time machine (since such construction would represent the earliest time to which anyone could return). [Answer] The device [latches onto the Earth magnetic field](http://en.wikipedia.org/wiki/Flux_pinning) and uses [quantum entanglement with nearby particles](http://en.wikipedia.org/wiki/Quantum_entanglement) as buoys - [more info](http://www.livescience.com/28550-how-quantum-entanglement-works-infographic.html) - [still more info](http://blogs.scientificamerican.com/observations/2012/08/09/quantum-teleportation-achieved-over-record-distances/). So the device travels through time by locking onto the magnetic field of the nearby area, and by seeding the area with quantum locked particles. As it moves through time, it follows Earth because it is pinned to the magnetic field, and burns the locked particles to do measurements regularly. Once it runs out of quantum locked particles, it has to exit time travel. Also the amount of particles required increases exponentially with the distance in the T dimension. It could add to the story, because seeding these quantum locked particles (it seeds one particle of the pair, and keeps the other) costs a great deal of energy, so the farther the jump, the more particles it need. Also since the quantum locked particles share properties, they also travel to the past around the machine. If the enemies can find the location of the machine, they could jeopardize the jump by undoing the locked status on the seeded particles, cutting the jump short. This also explains why it can only jump a century or so at a time: the magnetic field shifts slowly, but do shift, and the whole battery would have to be used in order to jump farther. [Answer] Sidestep the issue: The device could be some kind of field generator - that way, it wouldn't even need to move in time, never mind space - just enter the field and exit at a different time. There's even been actual science talking about this possibility - though you're limited to when the machine was powered on. Which could cause tension for a forward moving traveller - what if the machine broke after they'd arrived in the future. (No such worries going backwards - you know the machine was powered all the back - unless you stuff up the timeline somehow). From what I remember about the theory for this device - it would use magnetic fields to bend light waves round into a circle with a diameter smaller than the wavelength of light. It would somehow twist space-time so you could "walk" along time within the circle. You can travel as far back or forward as the device has power. [Answer] *Question as posed at time of answer: How can I explain that a time travelling apparatus moves itself through time but appears in the same location?* *Example: if you start at Brandenburger Tor, Berlin, Germany on midnight, New Year, and go half a year plus twelve hours into the future, you end up at Brandenburger Tor, Berlin, Germany at noon in the height of summer.* Simplest answer: Explain that the apparatus stands still (i.e. is as permanently fixed as the Brandenburger Tor itself).  While this simplified answer may be a little different from what the questioner intended, consideration of this rather simple method of time travel while retaining constant position with respect to a position on the Earth's surface should not be ignored from some consideration. Perhaps, at the very least, it has some *component* that is permanently installed like a building, and the machines simply moves into [temporal] alignment with that component that can open to reveal the traveling compartment, a little like an elevator moving through a "permanent" elevator shaft with doors on each floor, which is never in all of those spatial positions at the same moment (just like your machine isn't at all times with range simultaneously, as the Tor is). See also T.A. Barron's book [The Ancient One](https://books.google.com/books?id=qRUuAAAAQBAJ) for another description of a tree-based time machine with some analogy to what you're looking for. [Answer] My first inclination is somewhat akin to Mindwin's answer, but with an explanation that might be a bit easier to grasp for the layperson: The idea goes: Travelling through time is actually relatively easy, if you don't mind ending up anywhere in the universe when you get there. Controlling *where* you end up is actually the difficult thing, and due to Relativity, there's really no such thing as an absolute position, so the only way to make sure you can do that consistently is by "anchoring" your relative spatial position and orientation to surrounding (non time-travelling) masses so that you always end up in the same position and orientation to them as you started. An obvious way to do this would be to design the device such that it is intrinsically tied to all surrounding particles, but the anchor-strength decreases with distance (perhaps an inverse-square relationship, similar to EM/gravity). Thus all particles in the entire planet would participate in the positioning, and the end result would be a consistent position/orientation always relative to the position on Earth, regardless of how the Earth has moved over time. Arguably, you might run into trouble with this due to the substantial motion of convection currents under the Earth's surface meaning that a substantial amount of the Earth's mass doesn't really stay static over time, though (it would definitely be easier on a planet without a molten core). An alternative to avoid that would be to have it anchored to certain key masses carefully chosen by its creator(s) (for example, several spots of the Earth's mantle chosen from particularly geologically stable areas). (This could also potentially be an explanation for why the machine might need to be in a particular place on the Earth to work properly, if that's useful to the story) If you need one, this could also be an explanation for limited temporal range: The anchored masses inevitably will move a bit over time relative to each other, so the positioning mechanism would need to account for that with some fuzziness/averaging/etc over all the associated subatomic particles. Beyond a certain time, the discrepancies might become too much to manage and it would not be able to consistently resolve a landing position due to "drift" of the anchor material within the planet. [Answer] Poor idea which jumped out right now and I have to put it down: The time machine actually works only on **time** scale of our space-time continuum. Which means that while your engine bends time, it does not bend any space. But *hard* thing is, that in that case you would end up somewhere else because of all the rotation of our belowed planet Earth. So, you could explain it by loads of time-travelling cycles: The machine itself makes sure it ends up on the same place by travelling small amount of time in every step. Say, every millisecond, you travel 10 milliseconds in time. So in 100 milliseconds, you travelled one second in 100 time travel jumps. **EDIT** Idea of my second though is to adjust your position in every micro-time-jump. So, you do *move* in space, but in all, you moved about one millimeter, so you end up on *almost same* place as you started. If the time machine is relatively huge, then one millimeter in space can be considered as *same place* [Answer] Let me tell you a bit from the secret technicians manual of your device, but don't tell anyone, I am not supposed to do that. Since Einstein we know that everything is tied to gather, we call it space time. Maybe from some vacation space trips you also know that behind a black holes apparent horizon time and space coordinates are swapped. Anyways, your device basically works the following way (for simplicity we assume only one time dimension). It scans it surroundings and determines the properties of a sample set of 4 dimensional space time coordinates around it. Then it establishes a 4 dimensional sphere of the size of time distance you want to travel, intersects it with the destination direction and on the remaining circle it searches for the best matching space properties. It does that for each sample, and in the end choses the sample set with the best match and performs a space time folding into that set. The reason here is to save energy; for each of those points the energy required grows in a complex but more than linear way. This all has multiple consequences (read: plot devices): * For smaller time differences, the space difference can be bigger, meaning you could end up at a fairly different location that just looks alike (e.g. a chinese replication of the brandenburger tor; those things grew fairly popular after they copied a whole schwarzwald village). Check your lock accuracy settings. * For bigger time differences the space differences should not be too big, otherwise it would fail to acquire a lock. This is why you can adjust the space reading parameter; it will require more energy (i.e. less subsequent jumps with one charge) but allows the geological properties to dominate, instead of the man made objects around you. * In the end it imposes a limit on the time you can jump; depending on the edition you have (each year they are more energy efficient) you could jump only a couple of hundred years, or even millenia. Jumping back to the dinosaurs would probably require you to scan the whole earth (I doubt that even the newest editions have charge left to do the jump back though). [Answer] To expand somewhat on [Niffler's answer](https://worldbuilding.stackexchange.com/a/12623/8266): What if we had our apparatus obey more than just gravity? Let's assume that time is a 4th dimension that our apparatus can now travel through without deconstructing itself. The earth is rotating the opposite direction, but because we still have 3-dimensional forces acting on us, we stick to the earth, conserve momentum, etc. Thus, as we move backward in time, we simply let gravity and friction carry us around in the same place. This presents us with a few interesting problems -- what happens when we run into things that were already there? Since we're traveling 4th-dimensionally (and a little bit in the other 3 dimensions), we could say that we'll actually *collide* with things. The faster we travel, the harder we would hit objects. This could be taken into account in the construction of the device -- a super-strong hull that would let it plow through trees in the forest that used to be in this location, or the resiliency that would let it be deflected slightly. If we want to further enforce the no-movement rule, perhaps the device needs to be anchored deeply into bedrock that is known to exist in roughly the same place/state for the past 100 years, for safety. Otherwise we risk self-destruction. Not to mention, we're pushing existing air out of our way wherever we go, so our device's design should account for some extreme heat. A physicist could likely come up with two dozen types of radiation you'd encounter because of this, too. These problems could provide some interesting narrative. If you travel too fast, you may damage your craft, or maybe you've bounced around over the course of a few kilometers (and a hundred years). Maybe the navigator has time-based maps and knows when they need to slow down their 4th-dimensional travel to avoid the rapids, as it were. Perhaps when they arrive at their destination, they cause a grass wildfire because of all the heat they've picked up. Things like these could provide some realistic considerations for your hero and/or sidekick while keeping them rooted to (roughly) the same spot. [Answer] You could use the same-time principal. Essentially everything that has ever happened or will ever happen is happening NOW. Since some of us are not given to a full understanding of this, you would need to preface your description of the timeline. What we conceive of us the past, the present, and the future is only based on our "view" of the timeline right NOW. Your time machine would be able to calibrate its position in the NOW and in the NOW your want to visit. Since it is physically located where it is, it can see all of the activities of every-NOW for its location. So if the user of the time machine moved from their NOW to another NOW, let's use the forest idea, the time machine would alter its view of the NOW to the NOW the user requested and could alert the user that the new NOW would place them inside a tree and that the user should select a safer NOW, or the machine could give a warning that the user can choose to override and force the machine to follow the NOW of the request regardless of personal/property damage. This approach could provide some second tier direction for your characters as mentioned earlier, or provide some humorous outcomes as mentioned earlier. However you write it, according to this principal, you are writing it NOW, I am reading it NOW, and I am discussing the reading of it with my book club NOW....Good Book by the way. Have fun NOW! [Answer] Honestly, if the concern is people getting caught up in facts, why not take a relative approach. Say that while the machine travels through time it keeps its position relative to some ambiguous constant, such as the 'center' of the earth. Because it's relative, this negates anything that effects both the planet and the machine as far as displacement in space goes. By leaving 'center of the earth' ambiguous, you also don't over-explain, preventing prospective details which are immediately disputable. *edit*: To further explain, anything situated relatively keeps it's position and state to the object it is related with in that manner. Therefore, any force that acts on both equally is negated. By binding it to an ambiguous location (such as the 'center' of Earth, as mentioned above), as opposed to a force or absolute location(s) you avoid concerns such as deterioration, natural disasters shifting mountains (as used in another example), and other external stimuli. So long as you, of course, presume that its ability to stay put relative to whatever the fixed point is is stronger than any external forces acting directly on it whilst it travels. [Answer] How about a variation on benz001's answer: Lets make a time travel machine that's limited to a time road. It can no more go cross country than a train can. You build the time "road"--it's just a platform to anyone observing it from a spacelike dimension but a timelike observer sees the road. Note that travel is limited to the time in which the machine exists (both forward and backwards.) Off the top of my head I come up with Asimov's *The End of Eternity* and Robert Forward's *Timemaster*. (The latter is especially interesting as he was a hard SF guy--there's a couple of handwaves to set the whole thing up but otherwise he stays solidly in the science realm other than the biology of the aliens--and his biology never was up to his physics) as fictional examples of what I'm talking about. There was also a time communicator (a road for a few particles) in the Cheela novels (*Dragon's Egg*/*Starquake*) but it was pretty much off screen. [Answer] Depending on the feeling (serious and gritty vs a little ridiculous) you could use the Anthropic Principle. Lets assume there are a (near) infinite number of universes. When you time travel, you create a new near infinite number of universes, in which the time travel machine appears in a different position in each one. Now, lets assume that disapearing from one place and reappearing in another place involves an infinite impulse (scientific term, rate of change of force), as it is done over a literally 0 length of time. The impulse invovled in this would kill the time traveller. So an infinite number of universes are created, but there is only one in which the time traveler survives. You, as the author, cannot be blamed for choosing to tell the story of the universe where the time traveler survived. And the time traveler, using the anthropic principle, should not question the fact that they are infinitely lucky to be the one time traveler duplicate to survive. If they didn't survive, they wouldn't be there to question how lucky they are. [Answer] The appartus has the exact same momentum of the earths orbit around the sun, the spin of the earth. Just like everything else on it does. But it is very weird for something to suddenly dissapear? It might be better to use a firth dimension to "avoid" time alltogether. (If I lift my beer can from the table it will not "exist" on the table anymore. But it can "suddenly" reappear on it. The table cannot move up and down but the beer can - can move up an down. If we move the table sideways - and the beer can move up (it will keep the tables given side momentum), and drop back in the same position. (It dosent matter wether the table was still or not). If earth is the table and your apparatus is the beer can - the apparatus have the momentum of all four dimensions, but "dissapears" in a fifth dimsenion - and come back in the excact same way - beacuse it will still have the momentum of all the other 4 dimensions. An x cordinate does only effect the x cordinate. If y is added - the x motion remains. [Answer] I would suggest working on the theory that your machine is moving through space-time, rather than just time. Perhaps you're tied into the current gravity well, as mentioned earlier? Another avenue to explore is that if I stand still for 5 minutes, I don't move relative to the Earth, so why should I move just because I'm moving through time more quickly? What causes me to move with the Earth when travelling at 'normal' time and why should that not change when moving more quickly? [Answer] I think you already have answered your question: 1. The time travelling machine should 'land' near enough to the Earth surface in order not to kill its temponauts. It is, give or take, 1 meter. 2. The Earth, Sun and Galaxy move constantly. Ergo, to make sure nobody is killed in the process, the time machine is built so that it actually stays at the same place. Just in case. Warning: Discussion below is in sci-fi mode. So the machine works like this: 0. Observe the local curvature of the space-time continuum, Earth, Moon and Sun velocities, etc. 1. Make a small jump back for a day or even less. Let say, it is easier to calculate. You CAN move through space, but dare not use this option save for spatial trajectory adjustments. 3. Observe what is the difference between where you have landed and where you should have, then loop to point 0, unless you have reached your goal. By the way, trajectory adjustments in 3 dimensions is how spacecraft works these days. You can perform the calculations, but after 10 years in space solar wind alone can move the probe too far away its trajectory. So, you adjust. Calculations and jumps are performed in 1 MS, so a jump of 1000 years should take about 6 minutes. And you can definitely enjoy the view. [Answer] I would go along the idea that device is *only* bending time, thus it still abides by the other positional axis's while time traveling thus is keeps the same position on Earth as if it had just gone unused for 100 years. To explain people not seeing it before or after, I would go with the idea that nature (through a yet to be explained mechanic) does not allow you to alter the primary timeline. Thus anytime you travel through time, a separate timeline instance is spawned specific for those involved in the time travel. On the primary timeline you would disappear and you would "pop into existence" in the instanced time line. Allowing any entity to alter the primary timeline is far too reckless and eliminates paradox's. You might also explain that time is nullified while making this jump between timelines, thus that's what keeps the passengers from aging... [Answer] Is it a time transporter or a time teleporter? If it's a time transporter, i.e. it can move through time like just another dimension, then your solution is simple as the capsule can just rest in one place as it moves through time. To the outside observer it will appear that time inside is very slow, standing still or moving in reverse depending on the direction you're traveling. If it's a time teleporter, like the DeLorean in Back To The Future, i.e. it disappears from one point in time and reappears in another, then the explanation is more complex but still doable. Like all teleporters, it needs to lock on to the coordinates at the destination in order to reconstitute the capsule. Coordinates need an origin and axes, so there's no reason why you can't use something like the centre of the Earth and the magnetic poles. You can even work in some laws of physics which state it's easier to lock onto the same spacial coordinates that you left. Maybe there's a "temporal field" that persists between the source and destination. The real question though is, do you need to explain this? I mean sure you'll get some smart-arses snorting this fact in an attempt to show off their knowledge that the Earth moves, but I'd argue it adds little to the integrity of the concept. Remember, Time Travel isn't an exact science in real life. This is just one of possibly hundreds of equally, if not more difficult details of the overall question, which is, how the hell can you make an object travel through time? In other words, unless you also happen to be writing a companion book on the science of how time travel works, this is just one more issue that the inventor just happened to come across, worked on, and overcame, no different from, "How did you obtain the unobtanium?", "How did you keep the tachyon pulses from losing their polarity at sub-luminal velocities?", "How did you prevent gamma rays from the sun from altering the spin of the ion pulse strings in the flux capitor?", etc. I think a brief hand-wave is enough in any time travel story unless this is the main focus of it. [Answer] Having quickly scanned the answers, I haven't noticed the simplest one: don't explain it! I'm assuming your book will be read by average people, not people with physics PhDs. I never thought of the issues of space time until this question mentioned it. It's a basic accepted tenet of time travel that your machine stays in the same place relative to the earth, isn't it? I never noticed an explanation in H.G. Wells' The Time Machine. [Answer] Simple variation: The time machine follows the same world line as a normal piece of matter would. If you left the TM not-turned-on for a hundred years, where does it wind up? An explicit version that satisfies this naturally is yhe non-Wellsian idea that the exterior of the TM is still seen and felt in normal space. To an outside observer, it appears to be a stasis container. *but*, it can work in reverse, which is **still** exactly like a stasis container in that the internal state is the same at both past and future endpoints; it's just causalty that is reversed surrounding its creation. You could get creative about how the machine+contents appears out of nothing if travelling backwards. Or, to keep it following (only) the gravity, further stipulate that you need to operate it *in orbit*, not on the surface. It doesn't get dragged along by the spinning earth any more than a satellite does. While "in transit" it behaves as a microscopic black hole, as far as the outside world is concerned. Or, if you don't want to be able to detect it at all, say that it behaves as a particle of infinitecimal (but not zero) mass that has no interactions with anything other than gravity. [Answer] This doesn't have to be complicated. Since Jules Verne, moving through time rather than space has been a thing. **As a Safety Feature** It's only geared mainly to move through time, not space, but it does have a mechanism in place which "scans" the area it will be before it materializes, so that you do not end up inside a wall or something--call it a safety feature. **Because moving through time is not the same as space. Set things on fire if they try** Further, moving through space is a different kind of travel, and you may only have room for so much. Also, it may malfunction if you try to move it through space instead of time--it's just not what it does. It's a specialized piece of equipment. The TARDIS from Doctor Who famously does both, however, in both the new series and the old one, it's not good at actually navigating space without also navigating through time. It's actually trickier to manage and can lead to things being on fire. You can do the same with yours, but make it more restrictive. **Exploitation of a local time anomaly not present elsewhere.** Also--maybe the time travel has something to do with the locality. That is, there's a particular time rift or anomaly in that geographic location which is being exploited. [Answer] I like to think of time travel kind of like the way we look at the orbits of electrons around a nucleus, and the act of trading positions with an electron in a position 3 dimensionally observable as ahead of, or behind the trading electron. Might sound lame, but that's the way my brain works :) [Answer] Since time is just one more dimension in the whole string theory tangled mess, you can just say that as you travel along the time string, you also shift in the space strings\*, which keeps you in the same place physically. Another would be that since we're in a gravity well, we're pulled along even in the time stream. \* Just a word picture, I realize that is not how string theory is believed to work. ]

[Question] [ **Santa's1 been taken to court!** Kids in the United States have complained that they're getting too much coal and the class-action lawyers heard their cries for redress! Obedient to a summons from the Superior Court of California, San Fransisco,2 Santa is facing charges of not treating children with moral equity. Obviously, there are more nice children in America than he thinks! But in the 2020 legal environment, in the eye of at least half the public nationally, the definition of moral fortitude has become... somewhat... flexible.3 **Question:** What legal defense could Santa's attorneys use to defend his authority to decide who's naughty and who's nice? * The case is being judged using California state law. * Federal law and circuit court law may be used to establish precedent. * Santa is being charged with unlawfully withholding at least $40 million in anticipated welfare disbursements in the State of California. * If a legal defense cannot be found, the reindeer and sleigh go up for auction. Santa's entire future is riding on this defense. --- 1 *In times past we've allowed sillier-than-usual [Santa questions](https://worldbuilding.stackexchange.com/questions/tagged/santa-claus) during the Christmas season. I honestly don't know if we're still doing that. We have some precedent historically and [this comment from Monica](https://worldbuilding.meta.stackexchange.com/a/5726/40609) some years back. If the mods/community think the time for Santa questions has passed, let me know and I'll delete the question.* 2 *Which Santa responded to by traveling to San Fransisco in traditional style: his sleigh and eight reindeer. There are, of course, only eight reindeer. That nonsense invented by Robert L. May in 1939 about a red-nosed ninth reindeer has caused Santa no end of trouble. An outstanding trademark infringement case against May's estate is outstanding because Santa's been forced to follow up in every individual supreme court world-wide — and most of them think the case is superfluous.* 3 *NOTE: If you believe I'm poking fun at just one aspect of the U.S. Political System, you're entirely wrong. I'm poking fun at the ENTIRE U.S. Political System. I once called it our National Circus complete with Donkeys and Elephants, Clowns and Ringmasters. I'm still of that opinion. Besides, if you're inclined to down vote an answer simply because you disagree with it's political alignment or leanings — you might have both missed the point of this question and the point of asking fun questions at Christmas.* [Answer] Case dropped for two reasons. There is no law enforcing Santa to give anyone anything therefore anything of value is a gift that is given to anyone nice. Second reason for dropping the case is that it's not Santa's obligation to describe the value of the gift to the recipient. For some, a broken guitar is worth nothing. For others it's worth 52 thousand pounds because it was broken by Pete Townsend. The coal is not only worth its BTU in weight but also the type of energy it can be turned into and therefore any other taxes and deductions it came with it. Or as a Vintage paper holder, natural black soap, folk song inspiration, Nobel water filter, jewellery. Also the package might say COAL but the content is toffee. <https://www.fortnumandmason.com/christmas-coal-250g> [Answer] I may be wrong here, but I don’t think this case would ever make it to a court. Santa is a private entity. Any expectation of gifts being given is just that: an expectation. There is no written contract to say Santa must give any gifts to anyone, and the vast resources Santa has at his disposal are his to employ however he chooses. Sure, we can disagree with his methods for choosing who to give money to, but this is no more a matter for the legal system than Jimmy being angry Old Aunt Ethel wrote him out of the will because of what he said to Darlene. Any good lawyer will get this case immediately dismissed. Now, if you really want a court case: get the IRS involved. Santa gets those toys from somewhere, but he apparently neither spends nor accepts money? Yeah right. I smell a money laundering scheme, or at the very least tax avoidance. Just imagine the revenue that isn’t being collected... [Answer] ### The gift of coal includes carbon credits for burning it. After the passing of [Assembly bill 32](https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=200520060AB32) carbon credits are required to offset coal burning in the state of California. Santa is of course, familiar with all local laws and regulations. Santa has gifted the carbon credits as well with the coal, allowing the children to burn it for warmth this winter without further costs or legal consequence. This value when included in the gift calculation adds significant value to the coal, offsetting the coals value such that is now equivalent to the median gift value. --- ### Or - in the current economy - coal is a symbol of hope and far more valuable than a trinket Given 11% unemployment and the [eviction moratorium ending on Dec 31st](https://www.marketwatch.com/story/cdc-issues-nationwide-eviction-ban-through-the-end-of-the-year-in-an-effort-to-control-coronavirus-2020-09-01) about to throw a million Californians out on the cold winter streets, any decent defence attorney Santa hires could argue that to a homeless or soon-to-be-homeless person a method of remaining warm over winter is a superior gift than some trinket - giving children coal could save their lives. There's a historical precedent here - Santa, the Easter bunny, and a few US air force pilots teamed up and delivered 12,941 tonnes of coal in 24 hours to West Berlin in 1949. That coal saved the lives of thousands of people and brought hope to hundreds of thousands more. Santa delivering coal to the soon-to-be-homeless Californians would be a beacon of hope to hundreds of thousands of destitute Californians whose lives have been ruined with a year of hell - wildfires, pandemic, dust storms, depression, race riots, and whatever surprise 2020 has left for the grand finale. Let the children keep their beacon of hope that 2021 will be slightly better. [Answer] In the matter of Pickles et. al. v. Kringle, this court finds for the defense. Kris Kringle (aka Santa Claus, aka Saint Nicholas, aka Father Christmas) established a verbal contract with Ms. Pickles and similar plaintiffs that established that in order to receive desirable presents, that the plaintiffs must behave in a manner that he characterizes as "Nice" and not in a manner that is "Naughty". Mr. Claus additionally took time audit his list on two separate occasions in the calendar year, at great personal cost given the sheer scale of evaluating every single human child of the 7.5 billion members of the human race. While the terms may be overly broad [Defenses' evidence A: Document titled "Santa Claus is coming to town"], Mr. Claus further stipulates that the the criteria of determination for the nice and naughty list are his sole determination, though it is generally assumed that the plain language meaning applies. Certain "naughty" behaviors are described, as the contract explains that children must take caution to avoid behaviors such as "crying" or "pouting" and that while the child has surrendered a good amount of privacy rights to Mr. Kringle, he does have ample documentation to know if someone has been "bad or good" and implores one to be good. We can therefor find that Santa has more than sufficiently meant the burden of proof to make claim that the plaintiffs were in fact "Naughty" and not "Nice." As such, the plaintiffs violated the terms of the verbal agreement with Mr. Kringle, thus the desirable gift(s) were rightfully denied from them. While there has been considerable scrutiny over the contract applying to children who were unable to sign such a document, the burden to be Good and Nice for a year at length is not difficult for the children to meet, and while many recipients of favorable Christmas gifts may have underperformed their quoted estimates to Santa, Santa still was quite lenient and managed to produce the desired gift. Mr. Claus' stated gain in this is that children the world over learn how to treat others with respectful and dignified behavior. Often in our lives, those who do good things are rarely celebrated or discussed. Mr. Kringle is a rare exception to this, who positively rewards behavior that while difficult is what one should aspire to do. We next move on to equity of the gift of coal left for the plaintiffs and whether it is equitable. We must first examine whether the plaintiffs, had they received their desired gifts, would have equal value in those gifts. Of a sampling, we look at the list of Johnny, Susie, and Nelly, who want a pair of skates, a dolly, and a storybook respectively. These are reflective of different goals and pursuits and entertainment of the children. Perhaps Johnny has goals of playing for the NHL or winning a winter Olympics gold medal, while Susie wishes to be a mother and is practicing her maternal skills. Nelly, who openly states that she thinks "dollies are follies" has may have academic pursuits or desires to have a career as a writer. Obviously the gifts are all of different values on the open market if bought new but they are equal in that that they all three bring their recipient happiness, which, we cite Mastercard ex parte, is truly priceless. One can no more put a price on the thrill of a child finding the perfect gift under the Christmas Tree on Christmas Morning than one can count all the stars in the sky... in fact, the emotion is so pure and concentrated, those who are noted to be in exceptionally high spirits are often figuratively likened to children in this magical of moments. We now look at the gift of coal, a commodity traded on the market for energy and having a high value both due to the difficulty in procuring it and the many uses coal has in both the warmth it can bring and the price it can fetch in resale to help offset economic hardship. The plaintiffs do not argue that the coal was given unequally beyond that any amount, in the slightest, is too much. Through this lack of argument, not only are they showing that they would value the happiness of a new toy of their desire over the economic value of coal, but they fail to acknowledge that even while they failed to satisfy their end of the contract, Mr. Kringle did still give them something of some value when he was not obligated to follow up with his part of the bargain at all. Even though, through their own fault, they had a less than desired outcome from the contract, Mr. Kringle still sought to leave them with a gift that could be put to good use. Rather than offering the coal to help keep their families warm or selling the coal to bring in some income to help their families fed and clothed during the harsh winter season (for those south of the equator, they could at least offer it come winter time in six months), which would in this court's opinion be true acts of goodness that Mr. Kringle ought consider in his next audit of lists, they instead chose to bring legal proceedings against a man who has given so much for a payment of so little. Christmas is a time where we are all reminded that a little kindness is an investment that will always have a large payout. The court of law enjoins people to do what they must by the laws we have written. But this court is humbled by the knowledge that no law can be created to enjoin people to do what they need not do, but still want to. One does not need a law saying to do good to others, but we have many saying do not do bad to others. This court was not set up to tell the generous to give more than they have, but to bring justice to those wronged by the greed of others. Mr. Kringle is perhaps the most generous person in the world. For a small deposit of milk and cookies (and carrots for the reindeer) and a promise to do the good things you should already be doing, he gives so much more. For those who fail to meet their obligations, he still gives something that can be useful for those who desire to change for the better. This court finds in favor of the defense. It is so ordered. [Answer] **There is no defense for his behaviour: Santa will not need to be taken to trial, as the only court that really matters in 2020 is the Court of Public Opinion, but he will be thoroughly excoriated:** 1. The forces of wokedom will ensure that the story gets properly spun on all the usual social networks: the twats over over on Twitter will find their knickers in a bind; the emptyheads over on Facebook will rage; flash mobs will descend on every public place where Christmas decorations are to be found, seeking only wanton destruction; 2. The forces of cancel culture will eradicate or rewrite whatever is left: Youtube will bring down any video that mentions Christmas, Santa, Reindeer, Rudolph, Elves, etc; Twitter and Facebook will likewise label such posts as misleading or without evidence and will mark them for removal; Google will send all legitimate references to Santa to page 578 of 666 searches, in preference of less relevant search results; 3. Left wing pressure groups will force all Santa positive media to be removed from public airwaves on the claim that Santa's unfairness is rooted in colonial exploitation, enslavement of non-human sophont beings, homophobia, racism, intolerance, and connexions with the kiddie porn industry (after all, he knows when they're asleep, and he knows when they're awake!); 4. Low information gift shoppers will be subtly guided away from all reference to Christmas and Santa Claus and the entire season will become a santised, Santa-free shopping spree; 5. Hollywood Important People and Social Media Influencers will combine forces to excoriate Santa for his unfair treatment of children and will socially crucify anyone who supports his agenda by seeking to impose their outmoded (traditional American) or unacceptable (Christian) or senseless (common sense) moral views on everyone else; 6. Behind the scenes, various social pressure groups, most likely "led" by charismatic Swedish children, will work with Santa's representative Elves to hammer out some kind of deal that will result in a "refreshing of Santa's brand and image". Gone will be all but the slightest and merest of hints of good morals: sure, there's that whole "naughty & nice" motif, but movies have proven beyond all reasonable doubt that naughty children are really quite good!; Santa will be forced to reorient his whole operation to offer a wider variety of presents to ALL children, regardless of their goodness, obedience status, or relative niceness & naughtitude. The result will be a fairer, more equitable, less sectarian holiday season! [Answer] **Naughty kids are not a protected class.** Santa is free to discriminate against them under freedom of association. ... unless someone can prove a disparate impact on some protected class. [Answer] ## The final plea of Santa Claus The attorneys plead that as these are gifts and not sales, Santa effectively counts as a charity, and charities cannot be held accountable for the value or quality of their gifts to recipients. Santa makes an impassioned plea that everything he has ever given is a gift, and was only meant to make the world a better place and show children the value of being good. The prosecution in turn argues that Santa never registered as a charity in the state, he is effectively functioning as a state-level entity, and so the gifts are considered 'welfare' under California law, ipso facto. Santa ultimately loses the case, and is ordered to pay the $40 million. Everybody's sad, newspaper headlines declare the end of Santa Claus and Christmas. The sleigh and reindeer are held for auction to repay his debt. Santa leaves, embarrassed and disgraced. ## Why does this help? One naughty child who had been the angry and self-entitled 'front face' of the prosecution's legal campaign sees the result of what they've done, and is really sad about it. They immediately launch a social media campaign to gather together all of the coal Santa has left other naughty kids and use it to buy Santa's assets at auction at the full $40 million. When Santa arrives home to the North Pole, he finds all his possessions gift-wrapped beneath a giant Christmas Tree beside his house. The child orders their legal team to draw up a contract binding in California state law between Santa and all children, declaring that from this day forward, Santa shall have full authority and impunity in future distribution of presents to children in the state. [Answer] The case rests on the suggestion that the value of the gift is the face value according to some or other metric (e-Bay perhaps as lots of Christmas gifts probbly end up there unless carefully chosen.) That is rather like saying that the value of a school teachers work product is the cost of the pencil and paper on which tests and essays are written rather than the exercise of professional judgement in the supply of educatioal services. Santa is exercising professional judgment in the field of moral improvement. The value of his services is in the evaluation in-the-round of a childs behaviour and the delivery of motivational feedback. The nominal value of Santa's direct gift giving is usally small, though as a highly qualified gift-giving consultant Santa also offers advice to parents on appropriate gifts that reflect their social-economic circumstances to maximise the incentive effect on children) As such the case has no merit. (As Santa's lawyer I must insist the plaintiffs cease and desist from continuing to slander my client's pre-eminent reputation in gift-giving or further action may be taken to defend it) [Answer] Santa's gifts are private charity and not government welfare, unless he provides welfare on the behalf of the US government which doesn't seem likely as he has been delivering gifts before the invention of the modern welfare state. In fact, according to Internal Revenue Code section 501(c)(3), Santa's organization may qualify as a charitable organization and qualify for tax-exemption, provided his organization does not benefit private interests or get involved politically. [Answer] ### Santa is the ruler of his tiny nation-state. As a head of state, he is immune to prosecution. The case is dismissed with prejudice. Santa rules over his tiny enclave on Lapland. Santa's relationship with the Finnish government is very like the one between the Pope and Italia. They have de-facto sovereignty but use several services from the host nation. <https://en.wikipedia.org/wiki/Immunity_from_prosecution_(international_law)> This is the legal basis that allows Santa to enter most countries without a Visa and without fear of being prosecuted for trespassing and other territorial violations. Let's not mention the heavy surveillance Santa keeps on kids everywhere. Has any court served Santa with a subpoena to release the location of kidnapped or missing children? Of course not. Santa is immune to subpoenas. Since delivering Christmas gifts is a job for Santa, the head of his micro-state, Santa is free from prosecution for any criminal or civil offenses that are committed during the execution of said tasks. He visited the court just to show up. After filing his briefs, he bellowed his trademark belly chortles, earmarked all the kids in the class-action lawsuit and their lawyers as naughty, and went back home. [Answer] ## The Naughty Kids can't sue him, but the Nice Kids Probably Could Santa has the right to distribute gifts based on moral considerations all he wants, but this is not the only anomaly in his gift giving practices. The analytics of his gift giving actually show that the presents he is giving out are not equally valuable based on the race of the children he is giving them to: In California, the average total value of Christmas Presents received by race are about as follows: * Black: \$159 * Hispanic: \$198 * White: \$272 * Asian: \$335 ## Why is this Illigal The Unruh Civil Rights Act, states that "all citizens are entitled to the full and equal accommodations in all business establishments" *Rotary International v. Rotary Club of Duarte* deemed that an entity is a business establishment for purposes of the Unruh Civil Rights Act if it is "truly public" meaning it by policy interacts with persons who are not its members *O'Connor v. Village Green Owners Assn.* deemed that Nonprofits are to be treated as "business establishments" under the Unruh Civil Rights Act. So even if Santa is a registered non-profit in the State of California, he is still legally required to give the same access to resources based on race, gender, nationality, religion, and sexual orientation. Because Santa gives gifts to children who have not opted into membership with his gift giving organization he is liable under the Unruh Civil Rights Act which would probably result in him losing his public non-profit status and be converted to a taxable corporation where he would be liable for back taxes and have to pay whatever reparations the court decides on to the children of minorities. Based on California's racial demographics, the average citizen received \$87.30 less worth of gifts than the average Asian citizen which could easily result in reparations of about 3.5 billion dollars from 2019 alone. That said, I don't think his reindeer and sleigh could be put up for auction since corporate lawsuits can not punitively confiscate specific resources from an organization. Instead, Santa would have a separate settlement hearing after the lawsuit where a method of paying back any debts would be decided. The most likely outcome here is that Santa would be given several years to come up with funds to reimburse damages. ## But He'd Probably Get Away with It Even if it is Illegal... All this said, Santa is a foreign national leader. Since he is not a US citizen, the only way to enforce this lawsuit is if the North Pole has an extradition agreement with the United States that allows Santa to be sued to begin with. Secondly, since Santa IS a foreign despot, he can revoke an extradition agreement (if one exists) before the case ever makes it to court. The only way that California could maybe cause Santa any economic burden is through a trade embargo or deportation. If Santa relies on Silicon Valley in any way for all of his electronic toys, an embargo could be a huge blow. But state courts do not have the authority to do that. The US constitution makes foreign trade relations the sole domain of the Presidency; so, holding Santa accountable for discrimination would have to be done through very different channels than a lawsuit. And deportation is no big deal since he never intended to stay there anyway. [Answer] I'm not legally savvy, but how can a class-action lawsuit originating in the United States be made against an entity that exists outside of the US? Even if the North Pole were a nation, and even if the North Pole were a member state of the United Nations, I don't think any international laws would be broken here, so this case couldn't even be taken to the World Court or anything. [Answer] Santa rolled his eyes and phoned the children's parents... Horrified, the parents cancelled the lawsuit and grounded the children. Bummed out were the lawyers who thought they could've made big bucks out of that case. ]

[Question] [ (We're talking about a pre-industrial society here) Obviously there are many cities in important positions for trade, either because they control an important strait (Danish Sound, Bosphorus), an Isthmus (Panama, Suez) or are in good places for sea-land transfer because the ocean reaches far inland (Venice, Genoa). * Are these cities getting rich because they actually demand tolls (and since they are so important or convenient everybody uses them and happily pays) or because the merchants that travel through just happen to leave a lot of money in the taverns and brothels and simply boost the local economy? * Do cities that do not require ships to actually dock there (i.e. cities that control straits like Constantinople, Helsingør / Helsingborg, Gibraltar) have any economic benefits other than collecting tolls? * Is travel by land actually so much more expensive than by sea that even slightly less optimal cities already couldn't compete? E.g. Ravenna instead of Venice when you want to trade with Germany (only looking at the position, not the political context)? [Answer] The short answer is trade. The larger answer is that the act of trading develops and requires a range of secondary and tertiary activities which are themselves economically significant. Consider, the trader needs a place to exchange money, bed down for the night, feed his caravan and all the men who ride with him (or the ships crew if a port). Cargos need to be offloaded and stored, or taken from the warehouse and reloaded. The animals need care and feeding, or the ship will need repairs and supplies. The sailors or caravan riders will also want some entertainment after a long trip, so places for drinking, gambling and wenching are all going to be an important part of the local economy. The lord of the region will need to supply some sort of law or authority so merchants don't get cheated (too badly) and want to return, and protection from raiders and pirates who want to steal the merchant's goods, so a military force and some sort of court system will be supplied. All these people need to eat, and a large crafts and services industry will also be needed to provide for the needs of everyone from the farmers who supply the food to the merchants who want nice bunting to drape over their trade stalls and give them the appearance of prosperity. So the trading city will develop a large demand for a wide variety of goods and services, and entrepreneurial people will be coming from all over to supply these demands (or skim off the top). [Answer] The thing that makes trading cities rich is the trading part. Think of it as a spider web. The outer area connects to other areas but together to other side resources have to go towards the center. All resources are going towards this trade center and as a result the trade center has all the resources coming to it and is able to use all of them where whereas the outer areas can't. Furthermore, the center, the trading city, is the shortest distance between most points and as a result it's the fastest, safest, and cheapest route. If it decides to do something that blocks one side from trading with the other side, if the two sides wish to continue trading they have to travel a slower, longer, more dangerous, and as a result more expensive route. This is why trading cities are rich and powerful. [Answer] It is culture, not geography, that makes a trading city powerful. A short history of Rennaisance Italy can be plenty constructive. Cities with excellent harbors and local resources like Naples or Taranto were much less of a trading city that cities built on a steep hillside (Genoa) or in a malarial swamp (Venice). Pisa was a port city that was surpassed as the leading city of Tuscany by an inaccessible city up in the hills, Florence. The single thing that is most important for making a trading city successful is freedom from government appropriation. Where a successful trading city of the late middle ages came under the rule of a strong monarch who could confiscate merchant's money as taxes (Naples, Palermo, and Barcelona under Aragon, the Champagne fair cities, Bordeaux and Toulouse under France), that city declined while those cities ruled by weaker monarchial/episcopal rule or republics became more prominent (Venice, Genoa, Florence, Augsburg, Nuremburg, Cologne, Frankfurt, Antwerp (in the County of Brabant, which was only ever half ruled by the dukes of Burgundy and Austria). With safety from confiscation, merchants are free to invest their wealth in generating returns. This is something that no one else was doing in the early modern period. Wealth that accumulated to the noble class was spent on wars or prestige (gold trimmed clothes, fancy feasts, Michelangelo, things like that). Wealth that accumulated to the Merchant class was re-invested. Since only a few of these merchants were doing the trade building, there were profits aplenty, especially considering that the nobles, far from being competition, were pouring money into the Merchant's coffers. Merchants in countries with stronger monarchies would be subject to repeated confiscations. This was done through the parliments of the time, such as the Estates General in France and the various Cortes in Spain. England's parliment, on the other hand, had a richer tradition of opposing the Monarch as was not so pliant. So merchants in wealthy but confiscatory nations like France and Spain would invest their wealth in places where it was safer, and merchants from places where wealth was safer did a lot of the business in rich monarchies. Examples of this are the Fuggers and Welsers from Augsburg in Austria/Spain, the Dorias from Genoa in Spain, and various Florentine bankers like the Medici for France and the Pope. This explains why the income of the Dukes of Milan in the early 1400s was equivalent to that of the Kings of France, who had probably 50 times as many subjects. Liquid capital gravitates to places where it can be invested, and in an Rennaisance/Late Medeival setting, those places are merchant republics and Imperial Free Cities and Hanseatic Leagues and such. Also worth a note, this really isn't restricted to pre-industrial societies. Look at the explosive growth of city states like Hong Kong and Singapore in the modern world. Nation states are the rule in the first world, but I suspect that an independent city state of San Francisco or Manhatten would be fabulously wealthy, even more so than now. The information economy and financial sectors and the income inequality that they cause would make being a city state more viable than ever. [Answer] All excellent answers so far but I think the question everyone's been answering is "why do trade cities form?" rather than "what makes trade cities rich?". To understand how trade cities become rich you need to understand the nature of trade and the difference between worth and value. Merchants buy goods for their trade value which is lower than their actual worth, this is what enables merchants to sell their goods for a profit. This isn't really as unfair as it sounds, the farmer's time is better spent farming, the blacksmith's time is better spent blacksmithing, for them the merchant makes selling their goods quick and easy. Conversely when the farmer needs new tools and the blacksmith wants to buy groceries they could buy these things from each other but the merchant is more conveniently located and has a variety of goods ready to sell. So when both buying and selling the merchant is making a profit which makes trade towns/cities a sort of fiscal gravity well. Thus the more productive the surrounding area and the easier it is to transport goods to and from the town/city the more wealth will gravitate towards it and the faster it will do so. [Answer] Answering only the third part of the question: > > Is travel by land actually so much more expensive than by sea that even slightly less optimal cities already couldn't compete? > > > For bulk goods? Absolutely. Even small boats can carry tens or hundreds of tons of cargo. *Cutty Sark* had a capacity of 1,700 tons according to Wikipedia. In the modern era, "Panamax" ships might carry 50,000 tons. By comparison, horse-drawn vehicles can manage a few tons maximum, and that's only on good flat roads at low speeds. And you need at least one driver per wagon. Not to mention the expense of horses. (Think of a four horsepower lawnmower engine. Now imagine it trying to pull a load uphill.) So pretty much all agricultural trade (which is most trade in the pre-modern era) would be by water. Not necessarily on the open sea, quite a lot of it would be by river barges or coastal cutters. This is why, when engineering developed, it was considered economical to deploy hundreds of men to cut great level channels across the countryside for barges to travel: canals! This is also why so much European pre-modern settlement was on rivers, coasts or both. A large landlocked city would have issues moving enough food in on a daily basis until the invention of the railway - at which point London (and other already large cities) *explode* in population. I suspect neither Ravenna nor Venice would be trading overland with Germany - the Alps are in the way! It would probably be far easier to ship to Hamburg than to cross the Alps. [Answer] Several different factors which "encourage" business at ports: * When ships were powered by oars and sails, ports were a necessity. A galley, even with sail assists, could only stay at sea for a few days. * A sailing ship could be held up at a straits for weeks by adverse winds. Look at the history of the word [embayed](http://www.merriam-webster.com/dictionary/embayed). One old meaning was a ship held in a bay by adverse winds. * In medieval times rules might give a port [staple rights](https://en.wikipedia.org/wiki/Staple_right) which forced traders to enter port and unload their goods. [Answer] Trade and services accompanied with it make the citizens rich and the city taxes them. * Merchant buy and sell with profit; the larger market, the smaller profit but the more opportunities for trade; * Craftsmen buy materials and sell goods; the larger market, the better supply and the bigger demand; * Innkeepers offer services for profit; the larger market, the more customers. All the reasons above have slight positive feedback and al the people pay taxes. The cities have usually better prices than their "customers" so that they can develop a force (army) to protect their interests. [Answer] Four other things to consider amongst all the good answers already: One has been touched on briefly, and that's **quality institutions**. It's a big area of research in sociology, political science and economics, whether a good economy leads to good institutions or good institutions lead to a good economy. Most research I'm aware of suggests that good institutions tend to come first, though it's by no means a "closed" issue. [Here](http://economics.mit.edu/files/4123) is one seminal economic paper on the issue. Particularly in ancient times, good institutions were few and far between. Enforcing contracts, legal protections, and so on, are things that, once they arise, lead to all sorts of other opportunities. In other words, once a city has good institutions it becomes a good place for trade, but *also* a good place for all sorts of economic activity beyond trade. In this case, **trade is not necessarily what leads to a city becoming wealthy; both trade and wealth are instead *consequences* of good institutions.** This might help explain why some port cities were wealthier than others, or why some got rich and others didn't. The second is related to trade, and that's [comparative advantage](https://en.wikipedia.org/wiki/Comparative_advantage). It's covered in any introductory economics course, but in short it's the idea that if city/country/region A is better at producing (for example) guns than they are butter, and B is better at producing butter than guns, each can specialize in what they're best at and trade, **making both A and B better off than either could be alone**. This holds true even if A has an *absolute* advantage; that is, they're better at producing both guns and butter than B is. Another trade benefit is **skill transfers**. Ports are easier to travel to from far away than non-ports, and people often come along with goods when trade is opened up. Particularly in the pre-industrialization (and especially in the pre-internet) age, there could be huge disparities in skills across geographic regions. Therefore, people then often bring unique skills with them as they travel to and through the ports. This leads to obvious benefits. And one final benefit a trading hub might experience is **variety**. This is the root of [New Trade Theory](http://www.sciencedirect.com/science/article/pii/0022199679900175), the area Paul Krugamn won his Nobel for. The simple part of it that may be relevant here is that people care about cost, but they also love variety. No place in the ancient world would have variety like a trading port. Thus it becomes an extremely attractive place to be, and naturally the people with resources are the ones who can afford to move to such places. [Answer] ***I'm going to say that everyone is so far is basically wrong, especially the accepted answer.*** Been studying this exact question of late, focusing on Venice and Golden Age of the Netherlands which also coincided with a 80 year long war to the knife war of independence against the Habsburg Spain. What's really interesting is that trading cities grow not only rich, but militarily powerful vastly out of scale with their populations as well as ***ALWAYS*** becomes the centers of arts, sciences, law, religious freedom and evolving human rights in their eras and regions. Both Venice and the Netherlands started out with vast resources of... mud, murderous neighbors and a sea that liked to try vacation in the mountains occasionally. It was material that made them wealthy, it was human capital. Meritocracy and voluntary association...that's what makes them rich. The key factor in trade is the trader has to leave his own political jurisdiction, where he can pull the old, "Don't you know who my daddy is?" bit and instead travel far away where no one give a bleep who or what the trader is. Long distance travel, especially sea travel is crucial. Separates daddies boys from the orphaned but skilled. Either someone can captain a ship way over the horizon, puzzle out the language and customs, negotiate a deal and then make it back home with a profit... ….or they can't. If they can't, they drop out of the game. Even back home, the powerful find it increasingly difficult to use privilege to get their way because again, far away strangers, the sea and deserts don't care just because you come from a nobel family with lots of patronage and any of the three will kill you if you make a slip. Pretty soon a meritocratic class of traders, artisans and technicians (like skilled sailors) become vitally import. This in turn causes a relative decentralization of political power, which leads to more meritocratic promotion, more social cohesion and overall better decision making. Investment becomes utterly voluntary as well. Resources flow those who have proven they get the job done whether that means long distance trading, building dykes or waging a private guerre de course against a world superpower that is literally minting most of the money in the world. People learn to bribe, weeddle, cajole but they can never force. In the end, it is empirical success that chooses projects, products and the people who manage them. Now, compare the same process in the competitors of the Netherlands or Venice. Leadership selection? Mostly by birth rank, then patronage, then bullying or outright threats. Project selection? Almost entirely political with the focus on image of the leadership that anything else because, surprise, its all paid for by money extracted literally at knife point. If things implode, well the king is not going to get blamed is he? It is the development of vast human capital on all levels that makes trading cities rich and powerful. They can literally start with nothing, Venice certainly did, but using proven merit to advance individuals and interest and by preferring voluntary association and consensus, they became staggeringly rich and powerful. But it's not just trading cities. Every sudden Empire in history, Athens, Rome, Ghengis Kahn, the early Muslim etc all also grew orders of magnitude more powerful than than their competitors merely by using merit selection. Athens was forced into democracy and merit selection by the pressure of the Persians. Rome by the Kings and the Gauls. Ghengis Kahn rose from two-bit eternally feuding step nomad riding deranged shetland ponies to the Emperor of a 6th of the Earth's surface, when he killed his best childhood friend so he could implement leadership selection by merit. Mohammad and the first few generations of his successors, managed the same trick, allowing a bunch of desert raiders to wipe out the Persian and conquer half of Christendom, India and Eastern Africa. Merit, empirically selected, is all it takes. Doesn't take resources of any kind, doesn't take a large population, doesn't take good luck. Just merit selection. Merit lets a people turn literal mud and flood into wealth and empire. Of course, in the end that very wealth and power does them end. Succeeding generations take everything for granted, forget merit and start playing the usual games of protection, privilege and patronage. People get ahead by gaming the system, sucking and threatening. It's still going on. Bonus points if you chart the rise and fall of different economic zones in the US and correlate them with particular strongly anti-mericratic organizations and political ideologies. [Answer] There are two types of trade: commerce (exchange) and profession (crafts). When we talk about trading cities in a pre-industrial-revolution setting, most likely the "trading" is about guilds, small industries and the like. So the riches of trading cities come from having lines of production adding value to many sorts of base, often cheap materials. The finished goods are then sold (by trading/commerce) abroad, and also used locally: as there is little/no transport expenditure, the citizens have access to cheaper finished goods and so enjoy a higher standard of living, when we compare with other less industrious cities. [Answer] I'm glad you asked this question. Ricardo discovered the concept of [Comparative Advantage](https://en.wikipedia.org/wiki/Comparative_advantage). Cities, regions, and even individual people all have advantages and by trading they are better off overall. Here is some game theory to prove how cities can both be better with trade: <http://www.youtube.com/watch?v=NdHsqTEW9Xc> And this one shows how even if your city has an absolute advantage in everything, you are still better off trading: <http://www.youtube.com/watch?v=AF9nJuOaGJ0> [Answer] I don't believe I seen the value added commodity. Trade cities get large amounts of raw material but by packing, adding ingredients, or from say changing ore to iron you really generate a lot of economic activity. ]

[Question] [ A spaceship is a very expensive thing to own and maintain. But what's more, this is a spaceship that can sustain high-g burns for long stretches of time, like in The Expanse verse. So this means that if it accelerates in one direction at about a month, it reaches a significant portion of the speed of light. And since it's now a very massive thing going relativistic, *Very Bad Things* will happen if a planet happens to be in its way. As in "*continental* devastation and up from there" levels of bad. And even without that, a spaceship with such an engine is a weapon even if it doesn't try to ram a planet - if your target is another spaceship or station you can just fly up close, turn around and melt it with your exhaust plume. Given all that, without any additional measures, no sane government will allow individuals to own such weapons of mass destruction, even if those individuals would be rich enough to afford to own a spaceship. Every spaceship would be state-owned (Or at the very least corporation-owned), and every spaceship that would deviate from its carefully preplanned course without warning should be annihilated on the spot in case it was hijacked to become a suicidal RKKV. **Can there be something that would allow classic private space opera spaceships to be plausible despite the aforementioned consequences of them not requiring years to cross interplanetary space?** [Answer] # We already manage this today, with airplanes. Airplanes can cause immense damage to places if they ram into them, as 9/11 proved. We prevent them from causing damage in other ways. 1. Near countries you have defined routes you need to fly. Planets and stations would have similar ideas. They'd ping you at a certain distance and tell you to lock in x route if you wanted to come in. If you instead burnt to move at relativistic speeds, they'd shoot you down. If you just fly in at really slow speeds they'd watch you like a hawk, but not shoot you down. 2. Everything is tracked. We have radio waves and other stuff scanning everything for rogue planes. Space is even easier to track people in, and at relativistic speeds you generate so much heat you'll be spotted from a solar system away. 3. The world is big. Most planes that crash crash somewhere harmless, because most of the planet is sea, and there's nothing human there. Space is even bigger. If someone does a burn to your planet and you blast them just do a small course correction and they'll fly off into space to never be heard of again. None of these issues mean individuals shouldn't own vehicles. It's not like terrorists can't make corporations. Every vehicle would be carefully monitored. [Answer] Lets break this down a bit. > > So this means that if it accelerates in one direction at about a month, it reaches a significant portion of the speed of light > > > There are a number of assumptions here. Being able to sustain high-G burns is one thing, but reaching a significant percentage of the speed of light is very definitely another. The first problem is the tyranny of the [rocket equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation), and the second is [propulsive efficiency](https://en.wikipedia.org/wiki/Propulsive_efficiency). The first tells us that in order to reach very high speeds without needing implausible amount of fuel and reaction mass, you need a rocket with a very high exhaust velocity, and the second tells us that the efficiency of a rocket travelling below its own exhaust velocity is significantly diminished. What can we work out from this? Well, if you want to be travelling at relativistic speeds, you're going to need antimatter, and you're going to need a *lot* of it. Fusion just isn't energy-dense enough, and fusion rockets don't have nearly enough exhaust velocity. This means that the problem you have is not just one of relativistic projectiles whizzing into your inhabited worlds, but the idea that you would allow anyone to put enough antimatter in one place to *crack a hole in the crust of Earth*. Here's the solution to your problem: **don't let anyone wander around with hundreds of tonnes of antimatter**. Antimatter production is very hard, requiring large amounts of energy, and the only way to do it economically is using huge solar arrays in the inner solar system. It cannot be produced in the required volumes surreptitiously. *That's* where security and state controls will be. Literally no-one is going to want to be hanging around next to large quantities of the stuff, because the risks are just too high. Nobody really needs an in-system ship that can reach relativistic speeds, and so no-one will ever be issued with enough antimatter to get them to those speeds. Hell, with any sensible system, people would get either micro or even *nano* grams of antimatter or *none at all*. Now there's no danger of anyone sustaining multiple-G burns for a month, because they'll be out of fuel in a couple of days at most. --- > > a significant portion of the speed of light > > > Space is big, but we know well enough that it isn't empty. Space in our solar system is so not-empty that you can [see its not-emptiness with the naked eye](https://en.wikipedia.org/wiki/Zodiacal_light), if conditions are right. You may be trucking along at several tenths of the speed of light cackling about how much of a hole you're going to leave on Mars, or whatever, and there's a reasonable chance you're going to hit a sand grain and it is going to make a very ugly hole in the front of your ship, which will probably already be partially stripped away by impacts of dust and gas. It is dangerous *to the ship* to try and fly around interplanetary space at these speeds. Consider that there may not be any viable protection against this kind of damage, and it might even be fatal. Also consider that any interception technique can really very easily use your own velocity against you. Speaking of which, --- > > sustain high-g burns for long stretches of time... it accelerates in one direction at about a month > > > Now, if you've followed my guidelines above, no-one will ever be able to travel at relativistic speed within a solar system, because it would be stupid and dangerous and probably obscenely expensive as well. But what if they tried? Well, if the aforementioned rocket has an exhaust speed that's a significant chunk of lightspeed (and it needs to) and it is accelerating at several gravities, then you're going to be able to see its exhaust jet from the Oort cloud. It needs an engine power of ~45 megawatts per kilo to manage a single measly G with an exhaust velocity of .3c (the effective exhaust velocity of a [beam-core antimatter rocket](https://en.wikipedia.org/wiki/Antimatter_rocket#Pure_antimatter_rocket:_direct_use_of_reaction_products)). A thousand tonne ship would therefore need a thrust power of a little under half a petawatt. But wait! Antimatter rockets of this kind release something like 60% of their annihilation energy as gamma rays, so your total power is going to be more like 1.6PW. This will be obvious to everyone, everywhere in the solar system with a line of sight. And lightspeed being what it is, it'll be visible long before you get up to relativistic velocities. And you know what will happen next. Project Rho mentions the phrase "loudness, lawyers and lasers" and what you could expect for braking space traffic control laws. If you ignore the demands, and the legal threats, then what happens next is that you will be promptly destroyed. There are a whole range of ways to do this, but suffice to say that if you can accelerate your ship to silly speeds then there will be purpose-built relativistic interception systems that will reduce you to a cloud of plasma before you can say "*I wonder what's generating all those gamma rays*" --- To summarise, then: * You won't be able to get to up dangerous speeds, even if you wanted to. * Even if you could, everyone will notice well in advance of any collision, and you'll be vaporised. Now, there are various ways of getting around a solar system promptly that don't necessarily require everyone to drive relativistic kinetic kill vehicles and carry planet-cracking amounts of antimatter. Feel free to ask a separate question about them, because this answer is already too long. [Answer] Control on the ownership won't do anything in the direction of mitigating the possible damages caused by a wrongly controlled spaceship. Let's make a comparison with general aviation: a commercial airplane goes fast enough and has enough fuel on board to make some serious damage when impacting somewhere. Do you need some examples? * The airplanes which were hijacked on 9/11 were not individually owned, yet they caused enormous damages. * The airplane involved in the Germanwings flight 9525 was not individually owned, yet it caused substantial causalties. * The airplane involved in Malaysian Airlines flight 370 was not individually owned, yet it disappeared with all the lives of the passengers Unless you have a way to enforce state control also on piloting such a ship (and good luck managing the anti-inertials or the no-turn-leftist), the control of such devices will always be in the physical hands of 1 person. Drawing a parallel again with general aviation, one can increase safety and preventive measures to reduce the chances that whatever might go wrong ends up in going badly wrong, but as long as you need a human to give commands to it, that human will be the point of failure for incidents, not the owner. [Answer] ## No, it won't be safe.. **Maintaining law in deep space: dream on** Forget police in open space, it won't happen. You can't enter a space ship and arrest the crew. When a mad man or a terrorist in a space ship wants to crash a planet, he can attempt that. The ship can approach from anywhere, at some point in time.. Earth needs early warning system and it has to act *very quickly.* There is *no way* any government can prevent the approach. **Energy** The mass of the asteroid that killed the dinosaurs was [1,400 megaton](https://www.google.com/search?client=firefox-b-d&q=asteroid%20dinosaurs%20weight), arriving [arriving at 30 km/sec](https://www.google.com/search?client=firefox-b-d&q=asteroid%20dinosaurs%20velocity%20impact). Suppose, the ship comes in at 1/3 speed of light, which is 100.000 km/sec. Kinetic energy is [](https://i.stack.imgur.com/ogmvx.png) Square speed !! Fillin the numbers, you'd get 25,000,000 times the impact energy, when the ship would have the asteroid mass. That is improbable.. Divide this by 25,000,000 and you'll get the same energy.. with a mass of 1400/25 is **56 tons** for the ship. That seems a lot, but a [space shuttle fully loaded](https://www.google.com/search?client=firefox-b-d&q=space%20shuttle%20weight) is 2000 tons. A space ship impacting on earth with 1/3 speed of light will be a mass extinction event. **It will be an expensive gamble** Near speed of light velocities are quite unsafe, there is a lot of particles, dust and small asteroids in stellar space. The perpetrator would be very stupid going full speed anywhere near a planet, with crew inside the ship. A collision, even a small collision, can destroy the ship. The ship needs to be abandoned well before impact. Whether the ship will actually reach the planet surface is *uncertain*. The ship is much smaller than the asteroid, a relevant part burns up in the upper atmosphere.. it could disintegrate before it reaches Earth surface. But the real mad man will accept that risk. They will loose their ship anyway. **Let Hubble save us** The planet is highly developed, with thousands of satellites, space stations, space military.. The space ship will travel fast, it will approach in a straight line. This makes the path of the ship very predictable. Suppose the ship is detected near Saturn coming in, there will be 1.2 billion divided by 100,000 km/h is 12,000 seconds to act. That is over 3 hours. Earth could attempt to block the incoming ship, by maneuvering satellites and space stations in its path. There's an old telescope named Hubble, size of a bus, weighing 24 tons. That will stop the ship ! The explosion will affect the stratosphere, lots of debris will reach the surface, causing havoc.. a complete hemisphere of Ozon protection could disappear. Nasty, but not deadly, or extinction level. **More advanced defense** The above scenario is current technology level. When a mad man can build (or buy) a ship like this, Earth's defense will be more advanced than it is now. Defense against incoming, unmanned space ships will be similar to current defense systems against missiles. Suppose the terrorists will leave the ship when it's traveling 100,000 km/sec past L2. From that point, Earth will have 10-12 seconds to intercept. This could be easily feasible, with advanced space defense technology. [Answer] A smart wall around inhabited planets, space stations, etc. Obviously at just a high G burn it takes quite some time to get to relativistic speeds; and once you do, it is nearly impossible to steer because the high-G is no match for the built up momentum. So we are traveling in a virtually straight line, like it or not. And that makes our attack projectile wonderfully predictable, far ahead of time. That same high G burn with an AI can be a part of a million large steel sacrificial shields (iron is embarrassingly common in space). These sacrificial shields each have an AI controller as an independent member of a swarming AI (like bees or ants). They are defensive, and position themselves with shifting coverage a million miles from the planet/station, with many able to quickly fly into the path of any approaching relativistic object. So the object must plow through thousands of these thick steel shields long before it reaches the planet, or if it is a station, giving the station the time to move itself. In the meantime, the shields themselves can be tasked with reproducing themselves; a few hundred square yards of focused sunlight can make a great smelting forge to refine asteroids into materials, to build new sacrificial shields. These can orbit the sun; like the asteroid belt, and vigilantly monitor the surrounding space. Give them some advanced telescopic detection equipment so they can detect such approaching relativistic objects months in advance. --- The Obvious Alternative: **Ditch the Planet.** I think it was the "Belters" in The Expanse. After a three or four generations, everybody lives in space, nobody is homesick for the open planet, wildlife, "nature", etc. The notion of fixed buildings that cannot move seems stupid to them; sitting duck targets. Like arming yourself with a knife against a cannon. They are all perfectly content living in their low-gravity rotating ships; that is how they were born and raised for generations, and they just don't share their ancestors love of "Earth"; just like I don't share the Roman citizen's love of watching gladiators fight to the death. Nobody ever feels the urge to have an open sky overhead or open plain before them. That feels dangerous and uncertain to them, they **like** walls and ceilings, they **hate** the open randomness of uncontrolled "nature." Bugs? Who the hell wants **bugs?** Ditto for **wild**life, who's stupid idea is that? Watching them behind glass in a zoo is one thing, but you don't just walk into a cage with them. Earth is quickly just their forgotten cradle; they are hunter-gatherers once more, searching for resources, gold and platinum and other relatively rare metals they require to build new ships and expand their swarm. Because as long as we are mortal, love, sex, kids and family will always be a big part of people's lives. Besides, they can get plenty of planty nature on their giant (movable) hydroponic garden ships. Flowers, trees and all. Because that is still a pretty efficient way to convert CO2, H2O, organic waste and sunlight into tasty food and oxygen. With sufficient warning of some incoming relativistic projectile, the swarm of ships all just disconnect and step aside, open a hole in the path and let the bullet pass, then regroup and reconnect after it passes. Got a lot of relativistic bullets? Disperse! Nobody gets hit. [Answer] **Defence Networks** High value systems all have a defensive sensor & interceptor matrix surrounding and permeating them. Anything coming in too hot would find that a small interceptor has been placed into their path. The network is designed to defend against aggression from other governmental entities, but they're more than happy to blow up individuals that get any crazy ideas too. [Answer] **Navigations limitations** Onboard navigations computers are mandatory for most ships in most settings, mostly because humans are generally too dumb or too prone to mistakes for manual navigations to be permitted(the usual in-setting reason). All you need to do is to make Suicide Tactics & Relativistic Instant Kill Logics Prevention so integral to navigations programming that it will be fundamentally impossible to point your ship directly at an object and accelerate toward it at Relativistic Speeds without the entire system literally preventing you from doing so. Could even have navigation systems be supplied by a governmental entity, allowing you to enforce the fact that most if not all nav systems have prevention measures in place, with those who are exceptions being either governmental in origin anyway(allowing you to control it and sanction scorched earth policies for hopeless situations(essentially nuke-equivalents in space), or saction self-destruct protocols in case of take-over), or entirely reprogrammed from the ground up by a non-governmental entity(which most people would rather not do for in-setting reasons) Now, this will drastically affect flight times, because STRIKLP will prevent you from fully making use of a ship's potential speeds. Not to worry though, you can still go at RS if you won't be at RS when you arrive at your destination, allowing the ship to slow down to safer speeds as it approaches its destination. This will also make docking safer, because you can't go fast enough for the ship to impact with the dock mechanisms due to your max speed always being an amount equal to how quickly your automatic break systems can slow you down over a period of time. The only time the nav systems will fail with this is if something unexpected happens such as an asteroid or another ship suddenly coming into the flight path of the ship, which is going to be a risk ship owners will have to take if they don't want to fly along routes that are the equivalent of space 'highways' where everyone travels in the same direction at more or less the same speeds. [Answer] Here's one more idea: Already with airplanes they are pretty damn difficult to control. Pilot training is pretty lengthy and expensive. It only gets worse for spaceships. Currently we rely on large ground crews and careful monitoring of EVEYRTHING by many radars and sensors just to get it into orbit safely. So how do you get privately owned soap-opera spaceships that can be safely piloted AT ALL then? The answer - advanced AI. Basically people won't be in control of the spaceship AT ALL. They'll just tell the AI where they want to go and it will take them there. And the AI systems are where all the safety measures are. An AI is very difficult and expensive to develop, so it will be only done by large corporations, which themselves will have heavy regulatory oversight. Of course, one might just try to disable or modify the AI and take the direct control of the ship. Which will then trigger additional safety systems. If you disable those too, then the next level of safety systems are external - upon approach to a planet (or anything of value, really), a communication channel is established and the AI needs to authorize itself. If it doesn't, then Red Alert is triggered with all the consequences. There are alternative protocols for when you have a malfunctioning transmitter, for example, but they all involve *flying very slowly*. If a spacecraft is approaching fast and silent - it's KABOOM TIME! [Answer] I just realized another issue with this premise: the spaceship is actually the smallest one of your problems. Energy doesn't come from nowhere. As noted in other answers, if you can get your ship to come in close to lightspeed, it will deliver enough energy to wipe out the planet. So where did this energy come from? Obviously the spaceship has some sort of energy source that has enough energy in it to do this kind of devastation. So ditch the ship and just blow up your power source if you want to do incalculable damage. [Answer] # Computers Currently computers already dictate a lot in normal transportation. Different profiles in your car allow certain amounts of acceleration, help apply breaks, ABS and more. This is true for many years on all cars, not just the hyper modern ones where you can play angry birds while the car stays in the lane. A spaceship is a little bit more complex. Just to navigate a 3d space correctly you need more subtle maneuvers in many directions than a human can provide. Computers are already taking over these tasks today and this is expected to be fully done with computers. The interstellar medium is vastly empty, but efficient and safe travel still relies on on time minute adjustments. You need computers to calculate and execute this. In the end all navigation will be done by computers. If you want to use them at all, you need to accept the limitations build in the computers so you can't ram into a planet or something. You'll simply be locked out from such maneuvers. Computers will most likely write their own code at that point, making (digital) hacking something that can only be done by computers. Writing your own code also means changing code on the fly. Any attempt to break it will be detected and thwarted, requiring a processor that is stronger than the ship to have a reasonable (within a lifetime) chance to succeed. The effort and funds required are so high it'll deter most. Social and moral wven more. The chance of someone wanting to do it long enough, having the means and lucky enough to break through the security will be low enough to be acceptable. [Answer] Psychology may be the better answer, restrict the direct control rather than ownership etc.... Ownership doesn't matter if the crew can be trusted not to use the ship as a WMD. Screen those who get to crew spaceships, especially your officer class, starting when they're toddlers. Ongoing evaluation and conditioning of potential candidates then continues for a couple of decades before they ever set foot on the deck on their potentially deadly new home. Biometric control locks mean only professional spacers carefully conditioned to take their own lives rather than endanger others can run spaceships. Think the [Suk school doctors](https://dune.fandom.com/wiki/Suk_Doctor) from *[Dune](https://en.wikipedia.org/wiki/Dune_(novel))* only ships' pilots instead of physicians. No system is ever going to be perfect though, the odd crewman is still going to be subject to an unpredictable psychotic episode or have a warped pathology that goes unnoticed until it is too late. Hijacking by sufficiently sophisticated agencies cannot be ruled out regardless of the safety precautions taken either. [Answer] # Vigilance ... and manners ... and cheap aerographite spheres Planets have more resources than individuals. They use these resources in what you might say is a substantial extension to the asteroid defense modern space forces dream about. * A network of **gravitational wave observatories** detect the movement and acceleration of all masses in the system. No heavy fast-moving ship goes unnoticed, period. * A network of **neutrino observatories** monitors nuclear reactions in the system. No large mass of radioactive material goes unnoticed. Even ten miles below ground, a nuclear weapon (or propulsion mechanism) is as visible as if it were out on your front yard. * A network of **listening posts** is embedded in the heliopause, monitoring faint disturbances in the electromagnetic vibrations of the stationary solar wind. Any large vessel or astronomical object will be heard at the moment it penetrates the system. * A network of **visual observatories** watches the maneuvers of ordinary space traffic. The manners of space flight may include any number of customs regarding shipping lanes, but there is a more fundamental rule: **No spacecraft shall take on a trajectory that cannot be stopped, nor any trajectory which can rapidly be changed to become unstoppable**. There are countless [spheres of aerographite](https://www.centauri-dreams.org/2020/07/27/aerographite-an-advance-in-sail-materials-with-deep-space-implications/) arranged in [negatively refractive](https://phys.org/news/2022-01-nano-architected-material-refracts-important-photonic.html) structures, standing guard all over the system, as part of a collaborative federated network of self-defense, which can use the Sun's rays to accelerate quickly and for free, which can change their trajectory merely by expanding or constricting their metamaterial networks a little in one direction or another. They will softly pound any uncontrolled or wrongly controlled spacecraft away from an undesired (i.e. unstoppable) trajectory. The catch is that they will start doing this as soon as the ship starts such a trajectory, wherever that is. Another catch is that the operator risks receiving a bill for the spheres if and when he tries to reenter the world of legitimate commerce. If it only takes a moment to make a ship crash into a major station or ecological surface, then that is an undesired trajectory. However, if the ship merely crosses such a crash course, with hours to go during which it can be battered into a different course, then there is no need to initiate such measures (yet). We're not looking so much at the delta-vee here (the amount of propellant needed) as the delta-a (the average intensity of acceleration needed to decide whether a collision occurs). However, the network will inevitably involve *some* human decision making, since a large stockpile of antimatter could evade all the precautions above, and human decisions would need to be made by its risks. [Answer] ## Exotic Space-Drive Reaction drives are so last century. The new hotness is Space-Drives. A fantastical new technology which allows high-efficiency inertia-less motion by < technobabble >Leveraging exotic matter's interactions with spacetime curvature< /technobabble > The catch is that this has a strong negative interaction with gravity. Essentially, gravity acts as a braking force on your fundamental engine components (all that degenerate/exotic matter does interesting extra-dimensional things that don't act intuitively in our normal space) No problem in open space between planets, where the solar system is topologically fairly flat, but when you get close to a planet, the Drive experiences something analogous to drag. Deep gravity wells are basically a mudpit. The drive can't gain "traction" and will generally be slowed to a halt. The faster you hit the gravity-well, the harder the braking force and the more energy you'll need to pump into the system to overcome it. If you want to operate within the hill-sphere of a planet (for earth, that's about 1.5 million km across, which is many times further than the distance to the moon) you'll need a lot more power to keep moving, and this power rises more or less exponentially the closer you get to a planet. Conventional reaction-drives are needed to lift things into high orbit, and within the hill-sphere, the Space Drive is very low efficiency. Not really a problem with the huge resources of nuclear fusion and/or anti-matter reactors behind it, but you can't get much acceleration out of it close to home. Once you're beyond the moon though, drive-efficiency shoots up and you can reach serious fractions of C quite quickly, allowing a privately owned spacecraft to reach other planets in a matter of hours. Slowing down and reaching orbit at the other end is as simple as "grav-braking". Allowing the exotic matter used in operating the drive to act as a Space-Brake and capture the ship into a high orbit where conventional thrusters can take over Of course, the drive itself has a major impact on fuel-consumption. The braking effect can't be turned off. So the typical practice for larger craft would be to use shuttle-type craft for low-orbit/landing-craft and keep the main ship in high orbit. Smaller ships (with less exotic matter to slow them down) would be able to retain most of their efficiency as long as they have the power-generation to operate the drive near a planet. So there's a sweet-spot of power-to-weight where a ship can operate reasonably effectively near planets, puttering around between lagrange space-stations. A spacecraft using a Space Drive is functionally travelling "uphill" to get to a planet or indeed towards the inner solar system at all. And so the use of a starship as a relativistic Kinetic-kill weapon is impractical in the extreme. You *could* feasibly use a starship in open space to act as a launching platform for a dumb RKKV. Simply accelerating up to substantial fractions of the speed of light and dropping the projectile before either decelerating or allowing the hill-sphere of the solar-system/planet to slow you down. But then you're a bright shining energetic beacon doing something incredibly obvious and recognisably an attack. And so your projectile can in principle be detected and intercepted by any other starship (they merely need to match velocities, clamp onto the projectile and then stay that way, using their engines as a brake as the projectile enters the target hill-sphere) TLDR: The upshot is that a spacecraft attempting to perform a RKKV Suicide attack hits the planet's hill-sphere and the interaction between its exotic-matter space-drive and the planet's gravitational hill-sphere acts a bit like a bullet-proof vest, or perhaps oobleck. Robbing the spacecraft of its relative velocity proportionally and ensuring a spacecraft can never achieve the velocities required to be dangerous to a planet while near said planet. [Answer] **No spaceships can go at relativistic speeds** Spaceships themselves cannot reach relativistic speeds. However, there is a network of "jump gates" that lets them dock to the jump gate, which ferries them at the relativistic speed needed. Also, spacecraft use "conventional" reaction drives, like fusion. Also, there are delta-v limits in place, prohibiting spacecraft with above a certain amount of delta-v from being owned unless a permit is had(only well-checked, rich individuals or corporations can own one). Also, spacecraft are mainly launched by the space station, which has a fleet of support "bugs" that help maneuver spacecraft and are a service. Also, delta-v is locked, and only in emergencies, the extra delta-v can be accessed. [Answer] Let's define "significant portion of the speed of light" to be $0.01c$. Why? Well, if I do that, I can hand-wave away a bunch of the relativistic behaviors that I have to worry about at higher speeds. Also, it turns out that a 1g burn gets you to 1% of the speed of light in about 340 days. Why 1g? Well, obviously a 10g ship could get to those speeds in a month, but that could be something solvable. Sustained 10g may simply be something that you ban (perhaps limiting fuel capacity). 1g is, after all, what they sustained in the Expanse. First off, how far do you have to go? a one-way trip at 1g of 340 days, using $x=\frac 1 2 a t^2$ shows us a travel distance of $4\cdot10^{12} \text{km}$. Now, consider good old Pluto. Its orbit is roughly $6 \cdot 10^{9}\text{km}$. So you're looking at traveling from a distance 1000x times further than Pluto. It's actually a good chunk of the way to the Oort cloud. You have to travel pretty far. I point this out because we don't have to worry about "insider threats." Anyone remotely close to being in a reasonable shipping lane isn't going to be able to get to these speeds, even if their ship is capable of it. And this means we can look outward. In the expanse, the governments all had sensor networks. They can look for things. If an angry $0.01c$ freighter is something they are concerned with, they'll be looking for it. And it turns out objects traveling at these speeds are hot. I tried to find out how hot, but it was hard to find numbers. Most of the [interesting numbers](https://www.scirp.org/html/1-8301750_23913.htm) were for faster speeds... but they were worried about melting the nosecone. So I'd expect that the object is shedding IR radiation at a rather high rate. You're not stealthy at those speeds. So the government is going to be ready for you. And they don't really need to stop you. You're not a giant asteroid whose fragmented components will cause planetwide panic. You're a small freighter. If they do something to disrupt you, its unlikely you'll be able to keep targeting wherever you're going. And disrupting you will not be that hard. At $0.01c$, you are the bullet. They just need to put something in your way and you will be a sad panda. (Incidentally, the linked article suggests that about 50% of the speed of light is the limit for a custom designed craft. Faster than that, and the radiation caused by plowing through interstellar hydrogen kills the crew. The effects would be worse in the thicker "atmosphere" of the solar system). Also interesting is that, in near-light space travel, thrust is far less important than ISP. The [expanse engines](https://expanse.fandom.com/wiki/Epstein_Drive) have an ISP of about 1.1 million seconds, which corresponds to an exhaust velocity of 11,000km/s. By the [rocket equation](https://www.omnicalculator.com/physics/ideal-rocket-equation) we can see that if you want to get to 0.01c, you can only have a payload mass that's about 3% the whole rocket. If you want to get faster, its gets harder. Also interesting, the [Rocinante][4] apparently had about 10 hours of fuel at 5g. A 5g 340 day trip is going to be a lot of fuel! [4] [http://toughsf.blogspot.com/2019/10/the-expanses-epstein-drive.html?m=1#:~:text=The%20250%20ton%20Rocinante%20needs,30.75%20tons%20of%20fusion%20fuel](http://toughsf.blogspot.com/2019/10/the-expanses-epstein-drive.html?m=1#:%7E:text=The%20250%20ton%20Rocinante%20needs,30.75%20tons%20of%20fusion%20fuel). [Answer] # Space Caltrops Lots of other answers here have lots of science-y answers for how to solve this problem, but in a "classic space opera" as mentioned in the question, science can be hand-waved in order to make the story more fun. Assuming you can get a ship to light speed, and assuming you can do so without being detected, how would you defend against it? **Space Caltrops** [Caltrops](https://en.wikipedia.org/wiki/Caltrop) are sharp bits of metal which prevent people or animals from walking (quickly) through an area. You have to walk slowly and carefully to avoid getting a nail in your foot. Space caltrops can be small, ball-bearing sized objects which are put into (random, intentionally unknown) orbit somewhere well outside of the region you want to protect, perhaps at a similar distance to the [Kuiper Belt](https://en.wikipedia.org/wiki/Kuiper_belt). Any ship which tries to enter the star system at relativistic speeds will most1 certainly crash into one of the space caltrops. The damage to the ship from hitting even a small object would be catastrophic as described in other answers and would annihilate the ship. Since the annihilation happens at Kuiper belt-equivalent orbit, your planets wouldn't be at risk of harm from any resulting energy or solid matter fallout. Assuming your planetary system follows a traditional model of being mostly-planar, you would only need enough space caltrops to form a deep enough dish to cover the eccentricities of your system, which for most systems would be far less than a complete sphere. Your system is safe from attack from "above" and "below" because anyone piloting a relativistic vessel won't be able to do more than minor course corrections, so they would not be able to plot an elaborate2 course and attack from the "top" or "bottom" of your planetary system3. Finally, to allow wanted vessels through, you could either allow them to enter slowly and safely push through your curtain of caltrops, or you could define some tunnel-like entry point which could be navigated at safe speeds. --- 1Plot device, someone invents a ship which can safely calculate the route of the caltrops and *does* destroy a planet, causing mass panic. 2Hopefully nobody flies out of the galactic plane and comes at you from a different direction! Maybe that's not possible due to lack of fuel, space dragons, etc. 3Assuming your system itself isn't eccentric with respect to the plane of the galaxy, otherwise you would need to build a full sphere! [Answer] ## Non-Newtonian Drives can be Relatively Safe The problem with most planet killer ships is that they rely on Newtonian Physics, but actually reaching near light speeds using Newtonian Physics is next to impossible due to the sheer amount of energy required and devastating result of hitting tiny specs of dust at near light speeds. Instead, many space operas overcome this problem by creating engines that rely on manipulating space-time instead of kinetic energy. Look at the equation E=MC^2. Current technology only knows how to manipulate E (energy) and M (mass) while leaving C (speed of light) a constant, but physics will work very differently for a future civilization that can manipulate M and C instead. If you have an engine that could manipulate M and C while leaving E alone, you could make a ship travel much faster without adding any actual kinetic energy to the system. So if you have a 10,000 kg private yacht flying along at 3km/sec, and you were drop its mass to 0.1 g and raise its "speed of light" to 10,000C, your ship would then be moving at 0.1C relative to normal matter. However, since the kinetic energy has not changed, if such a ship were to ram a planet, it would only result in a 45GJ impact... which would give you a blast radius of about 150 meters. Enough to level a few city blocks perhaps, but not nearly enough to threaten anyone on a planetary scale... Besides, good luck aiming a 0.1C ship accurately enough to hit your target. More likely than not your terrorist ship would just hit the Ocean, wilderness, or maybe wipe out some farm land. [This related answer](https://worldbuilding.stackexchange.com/a/223185/57832) goes into more detail about how matter interacting at different Speeds of Light would work. Another way of manipulating spacetime would be to use wormholes to take shortcuts through space. These work along the same principle because your ship never exceeds normal Newtonian speeds to cover greater distances. [Answer] Edit: removed speculation about FTL **No, there is nothing that could offset the risk sufficiently.** Spaceships impacting a planet at speeds close to the speed of light (say, 0.9c) would obliterate the *whole planet*. As in, the planet would mostly cease to exist as a roughly sphere-shaped rock. Each such ship is capable of killing *billions of people* and destroying the infrastructure of a whole planet. A planet dwelling civilization must require every last bit of risk reduction. In that regard, allowing privately owned/controlled ships is *absurdly* risky. Although this could answer the Fermi Paradox: at some point, every civilization finds a way to easily reach relativistic speeds for their space ships. And without fail someone takes a drunken joy ride and blows up their home planet. [Answer] You would want multiple layers of defense. In other words: "All of the above" referring to the other posts. Note that there are two kinds of space ships, planet hoppers and STAR ships. Planet hoppers don't have the fuel or engines to do a lot of damage. Mind you, they can still recreate 9/11, but since they don't go at relativistic speed they are easier to defend against. Star ships is where the danger is. First rule of star ship travel, a computer flies the ship. The computer makes sure everything is safe. This computer is *NOT* running an AI. It is a running fairly stupid program that is dedicated to avoid collisions. AIs can not be trusted any more than other sapients. Hacking this computer might be possible, but will get you permanently grounded. Second rule of star ship travel is nobody aims straight at a planet, space station or other important fixed object. You aim slightly to the side. Yes, this adds some weeks to your travel time, but on the plus side you won't be shot down. Aiming straight at a planet is a war crime. It doesn't matter if you are in control and avoid the collision. The act of aiming is in itself enough to put you in an early grave. To get into interstellar space, even as a passenger, you have to pass psychological screening. If a shrink says that you are the type who might blow up a planet to watch the pretty sparks, you are grounded for life. Even with all this in place, we still want a physical defense. As other have said, just putting any small object in the path of the ship will turn it into a cloud of debris. You want to do this far enough away from the planet that most of this cloud misses it. By the way, you want to have well established shipping lanes that are kept clean of random small objects. Detection can be a problem, but in soft SF you can just say "long range scanners" and get away with it. Detectors and defenses are likely to be much better at old well established planets like Earth than at newer colonies. ]

[Question] [ A variety of Earth species have hard, more or less rigid shells covering parts of or their entire bodies as a defense against predators. These work to a varying degree depending on the specific predator's hunting style, but they don't really present much difficulty to human firearms. Ignore for a second the pesky issue of exactly which gradual steps would lead up to something like this; let's just say that whatever evolutionary pressure is needed is present in the creature's environment. Here, *I am interested in the observable end result, not really how we got there.* (Though if you can give a brief description of how we got there, I won't vote your answer down for that reason.) * Could a creature reasonably evolve something resembling a bullet-proof vest, as a part of its own body (that is, one or more layers that, taken together, are resistant to penetration by bullets), without invoking magic? * If it could, then what would that "vest" be like? (More specific questions to get you started: What would be the properties of the material that makes up it? How would it appear if you were to touch it? Given these properties, could it help the individual in some other way? What would be its weaknesses?) I'm looking for something that hopefully significantly reduces the risk of death from a (not necessarily point blank or perfect aim, but hit) round fired from a real world circa 1850-1900 human firearm that would be managable and usable by a single human with appropriate training. [Answer] Well, we have several animals that are semi-bullet proof. There are many stories where bullets ricochet of the skulls of bears, even little black bears. Grizzlies have lots of stories where a bullet just pisses them off. Some of the black powder muzzle-loaders could barely break the hide, especially when they were thick with fat to absorb the impact. Elephants have a gun named after them because they had to make one with enough umph to kill it. Though certain well placed shots of lesser guns can make killing shots, though they may take days to a week to do the final kill. Other large animals have similar resistance. Now here's a small animal that has more protection than expected. [A 9mm ricocheted off and hit someone else](http://fox6now.com/2015/04/14/man-accidentally-shoots-mother-in-law-after-bullet-ricochets-off-armadillo/). (actually it was his mother-in-law) so he might have been practicing that one! EDT: For those who keep downvoting this answer, I'll be more specific. The Grizzly bear is bulletproof to quite a few firearms, between it's thick hide and layers of fat, it's body can stop many small arms rounds. Many can't even penetrate the hide, much less all the fat underneath. This is one of the major parts of body armor, prevent/reduce penetration by spreading out the impact over a larger surface area. Most of the personal firearms in the requested time frame would have a hard time with grizzlies. Even today's high powered rifles can ricochet of the skull. So if we already have animals that are effectively wearing bulletproof armor, then the answer is "YES" to an evolved bulletproof vest. [Answer] ## Sure -- if their biology allows them to generate long chains of polymers. Modern bulletproof vests *(without hard ceramic plate inserts)* are made of **multiple layers of tightly woven synthetic fibers** called [aramids](https://en.wikipedia.org/wiki/Aramid) -- aromatic polyamides. They derive their strength from having multiple chemical bonds along the polymer chain, which are oriented along the axis of the fiber when it is drawn out. Some vests have their layers of fabric additionally **coated in a resin**. It should be noted that while such materials will stop bullets from penetrating, the force of the impact will often leave a "dent" below them *(they're tested on clay dummies)* -- which, in a real-world scenario, can often result in internal injuries like a broken rib or heavy bruising. [](https://i.stack.imgur.com/nrUe3m.jpg) **Silk** is a well-known example of a naturally occurring polyamide, renowned for its tensile strength. [Experiments with multiple layers of silk serving as bullet-resistant garments](https://en.wikipedia.org/wiki/Bulletproof_vest#Industrial_era) were done in the late 19th century, and they had some success in stopping low-velocity rounds. The most plausible construction I can think of would be for your creature to use **spinnerets** to encase themselves repeatedly in a **cocoon**, precisely woven in a **geometric pattern found in nature**, and finally setting the layers together with an **excreted resin** *(possibly spread manually over & into the layers)*. The damage done to this material is not "spot"-repairable -- the integrity of the fibers and the weave are compromised -- so your creature would have to discard the entirety of the damaged layer via shedding, and rebuild fresh ones. All of these characteristics point to some sort of **insect biology** -- convenient, as it's estimated they're [80% of the world's species](http://www.si.edu/Encyclopedia_SI/nmnh/buginfo/bugnos.htm) *(900,000+ different kinds)* so there's plenty of room for such unusual evolutionary exploration while maintaining a reasonable suspension of disbelief. [Answer] The short answer is **No**. The long answer is ***define bulletproof***. Soldiers wanted protection from bullets, so we developed bullet proof vests, and kevlar helmets. Then we wanted the ability to kill *enemy soldiers* wearing bullet proof vests, so we developed armor-piercing rounds. When the army wanted to improve the survivability of their troops - armor wearing or not - they started moving them in light-armored transports instead of trucks. So the people who wanted to kill soldiers in light-armored vehicles developed better weaponry to do so, etc. What I'm getting at here is that a creature may very well survive being shot by one caliber weapon, only to be defeated by a hunter with a bigger gun. And we can build bigger, better guns much faster than some animal could evolve better armor. That doesn't mean that a creature couldn't shrug off *some* damage, from *some* weapons. Try killing a rhino or an elephant with a .22 rifle. But humanity has significantly stronger weapons than that at our disposal. > > **Funny (sort of) Story**: In WW2 the standard issue Russian pistol was a .22 caliber. An alarming number of times the bullet fired from this pistol would fail to penetrate the standard issue German winter coat. So the Russians upgraded to a .22 Magnum. The Germans didn't "upgrade" their coats. > > > [Answer] **Yes - well, maybe.** [Abalone armor is pretty tough.](http://www.livescience.com/3800-abalone-armor-toughest-stuff-theoretically.html)1 While not bulletproof, they're certainly strong, and comparable to some body armor designs currently used by humans (see [Lin & Meyers (2005)](http://www.sciencedirect.com/science/article/pii/S0921509304008809)). Their shells are made from interlocking tiles of calcium carbonate, reminiscent of certain tiled arrangements for bulletproof vests (the ones made of ceramic). However, the tiles are arranged irregularly, in a way that makes it harder to penetrate them. They're bound together with a coating of protein "glue". Abalone armor could be mimicked to create new types of bulletproof vests, or the creatures could develop a stronger version of it. So, I think that some sort of bulletproof armor is possible, if it is based on a system like this. I'm aware that there's an ongoing debate in the paleontological community as to whether the armor of ankylosaurs and related dinosaurs was bulletproof. As far as I know, the evidence does not support or destroy the hypothesis that it was. --- 1 An [abalone](https://en.wikipedia.org/wiki/Abalone) is a member of a family of sea snails. [Answer] In *theory* it would be possible for a creature to develop bullet proof armor for a fixed caliber round. However, in *practice* it's not very likely. Nature will typically use a variety of short term strategies when dealing with high mortality: * Go extinct: see buffalo. If you kill them faster than they can evolve. * Reproduce faster. They generate more offspring than you remove by shooting them. Typically only an option for smaller animals, or animals that start small (like fish). * Increase aggressivion: offense is the best defense. They kill/disable you before you kill them. * Increase fear: you can't kill them if they run away fast enough. * Camouflage: you can't kill what you can't find. Only once we get to long term survival, will evolution have time enough to work it's magic. Even then it may not take an obvious direction: * blood clotting and scarring evolved as a strategy to deal with wounds * some animals can auto-amputate limbs and often even regrow them * some animals have distributed neural systems (probably not possible for animals with a larger brain) [Answer] I'm going to answer based on the assumption that the question is essentially asking: > > Could an animal evolve biologically at pace fast enough to outpace technological evolution? > > > As several have pointed out, many animals *were* bullet "proof" at one point in history, only to be trumped by technological advances in firearms that render what protection they had useless against the increasingly improving technology. So, in the context of the real world, I believe the answer is **no, as biological evolution is simply slower than human invention**. Going back to even cavemen era, humans were able to hunt animals much larger than themselves quite successfully. One could argue that if it *were* possible, animals such as Elephants or American Bison would have already figured it out. :) However, there's one major exception to the above logic that I can think of: bacteria. Granted, we're not talking about bullets here, as fighting bacteria with bullets is rather impractical. But if we consider the invention of anti-biotics as a medical "magic bullet" the above argument changes, as bacteria *has* been able to evolve faster than our technology. We humans are in a constant battle trying to fight bacteria as they, quite literally, *do* evolve anti-biotic resistances faster than we can wipe them out. [Answer] # A: Absolutely However, the main complication is minimum size. As others have implied, larger animals have a natural advantage over smaller animals, because all of their tissues are bigger, and must naturally be tougher to hold the animal together (as well as survive the normal bumps and scrapes that animals generally encounter). This is why you can't really hunt bears or elephants or buffalo with your typical 9mm street gat that you would use against hood thugs (with moderate effectiveness, no less). Contrary to AndreiROM's answer, humans cannot simply build guns that kill arbitrarily tough targets. Man-portable weapons have an effective upper bound on size and firepower. At some point, the weapon either becomes too heavy for a single person to carry, or the recoil becomes too great for a human to safely fire the weapon. For instance, one of most powerful rifles in the world today is the modern .50 caliber sniper rifle, like the [Barret M82](https://en.wikipedia.org/wiki/Barrett_M82). Although the M107 is intended to be a shoulder-fired alternative, the fact of the matter is that most pictures of either rifle being operated involve the use of a bipod. This tells you that the weapon is pretty close to the edge of what should be considered "man-portable". Already, the M82 creates so much recoil that a [muzzle brake](https://en.wikipedia.org/wiki/Muzzle_brake) is essentially required for safe operation. And yet, the muzzle brake itself increases the sound exposed to the shooter to well above safe hearing levels, requiring the use of ear protection. # Lethal Ballistics Most guns today are designed to kill animals, humans, or vehicles. Humans are pretty soft targets, so we can ignore those for now. Vehicles are hard targets, but they do not have good protection of vital organs, because that would make them heavier, more expensive, and difficult to maintain. Most animals which are hunted are smaller than moose. So the guns we have today are designed to kill animals that size or smaller. What many non-hunters probably do not know is that it is easy to wound an animal without killing it. Shooting an animal from a bad angle or just grazing it has a good chance of missing vital organs. In this case, the animal has [decent odds](http://www.huntingnet.com/forum/northeast/170377-can-deer-survive-gun-shot-wound.html) of survival, assuming it isn't tracked down and killed. Designing a lethal gun/round is trickier than it might seem. You actually don't want a bullet to just fly through your target at high speed, because if it doesn't create a large exit wound and it doesn't hit vital organs, the target has a good chance of surviving. See this [excellent article](http://www.rathcoombe.net/sci-tech/ballistics/myths.html) on the considerations involved. # Summary If the animal can get big enough, its size alone will produce a thick hide which will allow it to shrug off smaller rounds. I would hazard a guess that a brontosaurus would be pretty safe from most rounds being fired in 1850, except for lucky shots to vulnerable areas. But, supposing that you had a gun which could penetrate the hide easily, there is no guarantee that the bullet could reach vital organs or inflict sufficient damage to kill the animal. Humans are not knife-proof in the sense of having a hide so thick it can stop a blade, but the majority of knife attacks are not fatal. I agree with Nathan that if the animal has a shaped carapace which tended to deflect projectiles, then it could significantly reduce or eliminate the lethality of many rounds. Although you did not request a plausible evolutionary pathway to such a creature, it is not inconceivable to have an environment with regular ballistic hazards, from rocks being spewed by geologically active events (volcanoes, geysers, etc.) to predators that use a kind of high-speed attack to kill targets (think perhaps a hawk-like bird that uses its beak like a spear). Also, armor against bullets would generally be effective as armor against teeth, which is why creatures like the Ankylosaurus would exist in the first place. [Answer] I think it may be a mistake to ignore the environment to a larger degree. Life has evolved to handle immense pressures and temperatures, but not bullets - because there are no bullets in nature. If however, the environment contained objects with bullet-like potential, a very long slow evolution could indeed yield such results. The what could be anything from 'unobtainum' micro-meteors raining down on the planet every few days (from comet-trails composed of such a material), through to a common defence mechanism of other life-forms on the planet. (Plants that have evolved to "shoot" spines using chemical reactions). The latter plants is in my opinion a better option, as an evolutionary "arms race" would occur between armoured-animals, and the plant-guns. Many answers have centred on rapid-evolution, and I will state that I am certainly not. Evolution is rarely rapid in anything short of geological time-scales. @cobaltduck mentioned in the comments Spider-Silk, and this is a very good option. [Spider-Silk Body armour is a possibility!](http://news.discovery.com/tech/gear-and-gadgets/body-armor-spider-silk-121015.htm), Spiders obviously do not weave fibres, though they may cocoon prey. However given millions (if not billions) of years in an environment that demanded it, it could be very possible for a species to evolve specialised cells that lay strands of Spider-silk like material beneath the hardened skin/scales. Another option that springs to mind is the [Dragon Skin Body-Armour](https://en.wikipedia.org/wiki/Dragon_Skin), using ceramic plates this man-made armour can stop AK-47 rounds at close range. While "baking" ceramics with strong composites is a intensive process for technology, Nature could (and would) find short cuts, depositing layers of material with specialised cells. Again, I place my favour on this second option - while it has already been stated there is no such thing as "bullet-proof", Ceramic plates are pretty-damn close in modern warfare, Modern combat armour often includes such plates, capable of stopping most rounds (short of armour piercing). Specificity the gamer's [Favourite the .50 calibre.](https://www.youtube.com/watch?v=RGhIfTAcOgI) Good technical research for this topic would be the [Cells involved in Bone Creation, Osteoblasts and osteocytes](https://depts.washington.edu/bonebio/bonAbout/bonecells.html) these cells constantly dissolve bone-calcites and place fresh layers. [Answer] Something with thick scales or bony plates could shrug off small to medium caliber rounds, especially if they are at range or glancing. A thick hide can stop a lot of rounds. The problem is that's the period where [elephant guns](https://en.wikipedia.org/wiki/Elephant_gun) were being developed, so a normal thick hide isn't going to do the trick. If the creature had really hard, thick scales, then you'd have a lot more chance of stopping the round. The scales could be made of [keratin](https://en.wikipedia.org/wiki/Keratin), which is a what fingernails and lot of animal horns are made of, and if it was thick enough it could do the trick. [Answer] There's no such thing as bullet *proof*, only variations on bullet *resistance*. The answer to your question comes in the form of a poem. [THE HIPPOPOTAMUS](http://www.blueridgejournal.com/poems/hb-bad.htm) > > I shoot the Hippopotamus > > with bullets made of platinum, > > Because if I use leaden ones > > his hide is sure to flatten 'em. > > > Conveniently the author of this lived at the time in question. On a more serious note, you'll also want to look at the [elephant gun](https://en.wikipedia.org/wiki/Elephant_gun) and the fairly obvious reasons for its existence. Evolution works much more slowly than weapon design, so while early weapons might not be powerful enough to punch through the hide of a large animal, the animal is not going to be able to evolve fast enough to counter the speed at which weapons are designed. In other words, no. An animal may initially be bullet proof, but it's not going to remain that way for long. [Answer] It could be plausible if you had crocodilians that had evolved stronger & thicker scaly structures in key areas. They could have really strong hides supporting very hard scales, which would be big enough & positioned in a sort of array resembling some of those modern angular stealth surfaces, so that their 3D structure would encourage rounds to glance off from one surface to the other transferring momentum thru several deflections (especially helpful w/ the high caliber rounds I think were popular in your time period). These scales could grow in a way that developed internal tension, making them extremely strong & hard like [prince rupert's drops](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjOyIrZha3KAhUB12MKHY1CBLgQtwIIHDAA&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3Dxe-f4gokRBs&usg=AFQjCNH8-9IASCWTWk8-q0oAS9zNtT4j5g&sig2=eJM2J7aOvnTj8mkch1xJWQ&bvm=bv.112064104,d.cGc). And they could have thicker skulls, & extra skeletal support for all their armor Plus, keep in mind that crocodilians present a very narrow profile w/ their more vulnerable underbelly protected against gunfire by water or mud most of the time, so they'd be extremely well protected if they developed any kind of bullet-resistant scale structures IRL, there's not been enough time/advantage for this to have evolved, but your world could include some feature to push it along. A significant body of water in a warm climate w/ gravel beaches & frequent tornadoes might be enough [Answer] As far as i know, big Galapagos turtles' armors are bulletproof - as Darwin mentioned in `Origin of Species`. [](https://i.stack.imgur.com/ip7FX.jpg) [Answer] **Want to improve this post?** Provide detailed answers to this question, including citations and an explanation of why your answer is correct. Answers without enough detail may be edited or deleted. Considering this is fictional perhaps there's leeway for a creature from say 67million years ago. [Ankylosaurus](https://en.wikipedia.org/wiki/Ankylosaurus) ]

[Question] [ Traditionally, a Cyclops has one eye, as well as some other aliens in fiction. My question is simple: Would there be **any situations**, Earth-like or otherwise, where a creature would benefit from having only one eye? As far as I know, creatures with eyes on earth all have more than one. This question is not a duplicate of [Anatomically correct Cyclops](https://worldbuilding.stackexchange.com/questions/30163/anatomically-correct-cyclops) as this question focuses on all kinds of creatures, not only primates. Also the other question needs an Earth-like environment, something this question specifically does not require. Answers to this question would not necessarily be applicable to the other. [Answer] As a rule, evolution favors simplicity over complexity when additional complexity does not add anything useful. Creatures that live for many generations in environments without light (such as cave salamanders and fish) often lose their eyes entirely; one fewer structure to expend energy growing or sustaining, one fewer opening for parasites to invade. The hard part is figuring out a case where vision is still useful, but two eyes are not. The advantages to having two eyes over one are: 1. Depth perception (if the eyes are positioned close together, typical for predators) 2. Peripheral vision (if the eyes are positioned far apart, typical for prey) 3. Redundancy in case one eye is lost So if you can think of a creature that would have no use for depth perception or peripheral vision, and the danger of eye-invading parasites is more significant than the danger of having an eye poked out and losing vision entirely, but vision conveys enough benefit that having an eye is better than having no eyes, then such a creature will indeed benefit from having a single eye. One possible circumstance I can think of is if the light is too dim or the environment too cloudy to see anything clearly anyway, but detecting shifts in light or dark is still helpful (recognizing day/night cycles or the shadow of an approaching predator). Such a creature would probably have a simple eye or eyespot akin to those of simple animals like worms, rather than the complex, human-like one cyclopes are generally depicted with. Another interesting possibility is if the creature originally had two eyes, but started using those eyes for separate functions to the point where one eye turned into something completely different. Chameleons, for instance, usually use one eye to watch where they are going and another to keep watch on prey. What if this distinction further developed to the point where one eye moved to the bottom of the head and the other eye moved to the top, and further still until the two eyes hardly even resembled each other? Then, if its descendant lost the use for one of its specialized eyes, it might lose that eye and wind up with only the other. It would probably have a very hard time competing with its binocular counterparts, but if it lived on an island with no competition it might survive. [Answer] There certainly *are* benefits to having two eyes, as listed by Chris G in his answer: stereoscopic vision, redundancy, wide field of vision. Nonetheless it is not necessary for there to be any benefit of one eye over multiple eyes for a creature to evolve only one eye. Evolution occurs when natural variations among a population have a differential effect on how successful the animals or people are at reproducing. But natural selection can only "work" with what it's presented with by natural variation. And what natural variation (mostly mutation) throws up is a matter of chance. Here on earth it seems that the common ancestor of insects, fish, mammals, birds, etc. happened to be bilaterally symmetrical and hence all these creatures now have two eyes. Something about that common ancestor caused its genes to be successful, but that something wasn't necessarily anything to do with its having two ["eyespots"](https://en.wikipedia.org/wiki/Evolution_of_the_eye) (the photo-receptive patches that later evolved into eyes) - and wasn't even necessarily anything to do with its bilateral symmetry. It could even have been a quality that was evolutionarily favourable *then* but has since become ["evolutionary baggage"](https://en.wikipedia.org/wiki/Evolutionary_baggage) or disappeared entirely. But one can easily envisage that evolution went differently on another planet, or in an alternative timeline of this one. A creature happened to be born there with a quality (never mind what) that causes extraordinary evolutionary success, but as it happens this creature has a body shape which only has one location where the chance occurrence of a patch of light-sensitive cells can provide it with immediate advantage. When populations are small, chance plays a bigger role. This creature's genes spread rapidly and "corner the market" on most evolutionary niches. Two-eyed creatures never get started. A less dramatic possibility is one-eyed creatures coexisting with two-eyed creatures but evolving along a separate branch where some other advantage (which always means local, immediate advantage) was so great that the disadvantage of only one eye didn't matter. Evolution only has to be "good enough". We know stereoscopic vision isn't all-conquering. Some creatures on earth have evolved poor vision when their ancestors had better vision, some have no eyes at all. We also know that redundancy isn't the be-all and end-all. We'd be safer with two hearts but we have only one. [Answer] In very narrow tunnels, when species develop more like Worms then Vertebrate and light is introduced late into the development. When you have a species that creates tunnels that it maintains. And if this species and all others in its biosphere don't come near light, ever, they will not develop eyes (at first) because being photo-sensitive is of no advantage. Now, by chance, some bio luminescent species start colonizing this tunnels. The situation changes and any form of vision will be favorable versus no vision. So some species (including our worms) happen to develop photo-sensitive cells on their skin. If they happen to cluster on the front facing side and start to build some form of eyeball that would be favorable to two eyes. 1. Its better then no eye because seeing whats in front of you is helpful in non-collapsing tunnels. 2. Having two eyes is of no advantage because there is no depth to be perceived anyway, the tunnels are narrow and windy. And two eyes mean two places of infection. Also worms (unlike many other species) are "round" not "symmetrical". The value of the left vs. right or up vs. down is sero (until they develop an eye, then mouth-half and eye-half of the front facing side will start to be distinguishable, maybe. Also, as non-symmetrical species their genes don't favor even numbered things over odd number of things (as do a lot of species that have eyes on earth). You still have a lot of problems for this biosphere (where does the energy come from, for example, no light means no sun. No sun is bad. But maybe on the cooling surface of hot plamebo?), but it would be possible. [Answer] No reason at all, and I assume the only reason we generally have 2 eyes is for either wide field vision (in the case of prey) or distance-determining vision (in the case of predators). However, in an imaginary world, there's no reason some other form of determining your location would appear instead of a passive light sensor. Take dolphins or bats and their echo-location senses. It could be possible a species would develop in (perhaps gloomy conditions) where a light-emitting sense would be more useful than a passive light-detecting sense: a species that would flash a light and detect the results using a single eye, maybe the light emission is more directed (to avoid detection from predators) and so multiple detecting sensors would not be useful. So you can have sharks with lasers on their heads! [Answer] **I'm going to say no** Unless you have one HUGE eye, it will highly impractical for you to see 90 degrees or more without leaving your eye highly exposed to damage. With a single eye, there are no redundant systems or back-ups if it gets damaged. --- Eyes have evolved to help with specific functions. Two eyes in front help with depth perception and with hunting/targeting prey. Eyes on the side allow for more vision of surroundings. Less depth perception and more sensing movement and trying to avoid death. One eye has the significant downside of no real benefit. There are very few animals that have a single eye, and the ones I have found are nearly microscopic, and i don't think this would evolve into anything larger, even on an alien planet. --- In order for a species to evolve to have only one eye, either they would have a system that functions as sight for them, thus making the single eye enough supplementary vision, or a single eye would have to present an advantage over dual eyes. I can't find any theories where a single eye is more beneficial, so that leaves the redundant systems idea. One option is for the creature to have an "eye" that's just a photo-receptor to determine time of day for defense purposes. They can navigate using other senses, such as echolocation, sensing water pressure, sensing earth tremors, or smell (such a with bats, some fish, and moles). --- I'm also a bit new to this reality check thing, so if you want sources or anything I can provide some, but this is all based upon some knowledge from my biology classes and some quick google searches for examples. [Answer] You can have depth perception with a single lens if you have the sensing cells arranged at sub-wavelength steps, giving a [light-field camera](https://en.wikipedia.org/wiki/Light-field_camera). Although obviously more complicated than the ordinary eye, structures at such scale are not biologically impossible ( e.g iridescent scales on butterfly wings ). There is an advantage of such optical systems are 'good for imaging fast moving objects where auto focus may not work well', so if your Cyclops hunts something moving faster than conventional eyes can focus, then such eyes could evolve, and having evolved having two of them is unnecessary. [Answer] In a water environment, if vision is only required for orientation 'which way is up?' or when to rise to/migrate from the surface for predation purposes. I suppose these factors may also apply to something that lives just under the soil surface, if particular wavelengths can penetrate some way through the medium. ETA: these are evolutionary reasons why a single eye might develop in the first place, which has to be the start point for any consideration of why there is just one eye. To take this further, additional complexity might develop to introduce rod/cone equivalents in concentric rings at the back of the eye which - with a fixed focus lens - would provided distance measurement and direction identification. This addresses why the binary eye system wouldn't be needed. And if the lens is faceted, as in a fly's eye, then it could become even more efficient. ETA2: And some reasons why it could become more efficient than two eyes? Well, if the lens protrudes from the body surface (and is sufficiently robust - would need either: (a) tough tegument, (b) tough eyelids, (c) ability to retract/extend) could provide greater range of coverage up to 180 degrees all-round with a fish-eye lens. Without eyelids or retract/extend then there would be no need for the development of muscles to even move the eye, and all processing would be done by the brain. [Answer] The real question is : "What is an eye ?" Are we talking of human-like eye ? A fly has very different "eyes" than most of the other animals. > > Compound eyes are made up of thousands of individual visual receptors, > called ommatidia. Each ommatidium is a functioning eye in itself, and > thousands of them together create a broad field of vision for the fly > (<http://animals.mom.me/flies-see-out-compound-eye-5361.html>) > > > They can *see* different things : > > houseflies have the ability to see polarized light, but humans cannot > differentiate between polarized and unpolarized light. Polarized light > is light in which the waves travel only in one plane. > > > A fly need this 360° vision to survive because, well, it's just a fly.. And the fly's eye has many disadvantages, but I used it as an example, your creature can have a different type of eye. We need two eyes for for depth perception because they are quite simple. What if there was two or four pupils in the same eye ? The now extinct [Trilobite](https://en.wikipedia.org/wiki/Trilobite#Eyes) is an interesting one : > > Trilobite eyes were typically compound, with each lens being an > elongated prism. The number of lenses in such an eye varied: some > trilobites had only one, while some had thousands of lenses in a > single eye. > > > [Answer] If we consider an "eye" to be a single biological structure which has the purpose of encoding an image of the world such that its owner can perceive and act within that world based on the image, then this can cover a broad range of sensory organs. There can be good reasons why an organism - even one that relies heavily on vision - might evolve to have only one "eye" rather than two or more, provided that the organism has the right *type* of eye. If we consider the human eye, it has a single lens that focuses light onto an area of photosensitive cells, giving two-dimensional perception. If we consider an insect's compound eye it is made up of many [ommatidia](https://en.wikipedia.org/wiki/Ommatidium), each of which represents one or seven pixels in the insect's field of view. Now consider something in between these two types of eye. If we have a compound eye made up of many subunits that are more like a human eye - each subunit having a lens that focuses light onto an area containing many photosensitive cells, then each subunit would form is own image with a fair amount of detail. By combining the images obtained from all the adjacent subunits, each of which would be pointing in a slightly different direction, and is also slightly offset from its neighbours, we get an optical array that is similar to that found in a [light-field camera](https://en.wikipedia.org/wiki/Light-field_camera). This means that unlike both human and insect eyes, depth perception does not require two or more structures, but only one. By placing an array of eye subunits on part of the organism's body, potentially forming a spherical structure, the organism could gain a 360° 3D view of its surroundings that is in-focus at any range. The organism could house processing structures within the eye's structure, and pass a processed image to its brain. While made up of multiple subunits, each of which could be an eye, the structure operates as a whole. This form of eye has the advantage that the organism has equally good vision in all directions at all distances simultaneously, and gains a true 3D concept of its environment. Unlike human eyes, there is no delay for focusing or tracking. This would be of advantage to a creature that could be attacked from any direction by quick airborne and land-based enemies. However, this form of light-field eye would most likely suffer from the problem that it has a lower resolution, sacrificing perception of fine detail for broad coverage at any range, unless the organism has a particularly large portion of its brain devoted to visual processing. Now, to address the original question: Would it be more advantageous to have only one of these light-field eyes, or more advantageous to have more than one? The answer would be that under most circumstances it would be advantageous to have only one. Each light-field eye would require a significant amount of processing power, and each spherical light-field eye could have a field of view that, if placed at the top of the organism's body, would cover the organism's entire surroundings with the exception of into the structure supporting the eye. If there were two, they would require additional processing structures with their associated metabolic costs, they could conceivable obstruct each-other's field of view, and they would be unlikely to provide much advantage, as each alone produces a 3D image that is in-focus at any range. Under such circumstances, an organism with only one 360° light-field eye that covers all potential avenues of attack would have a metabolic advantage over an organism with more than one, hence favouring cyclopia. There is the issue that the eye would lack redundancy, however if the organism's predators are a sufficient threat that being captured is typically fatal, this would tend to favour the system with the lowest metabolic cost. Additionally, since the light-field eye is made up of many subunits, some subunits could be lost without greatly degrading the acuity of the eye as a whole, unless several adjacent subunits were lost. An evolved light-field eye would be quite similar to the [Lytro Immerge](https://www.lytro.com/immerge) camera, though could cover the area directly overhead in a way that the Immerge doesn't appear to do. [Answer] Following with the answer that indicates that evolving two eyes is not a given. My suggestion would be that the first time an eye evolved in this environment, it happen to be an structure that provided 360 degrees vision. For example, a medusa like creature for which skin cells also are photosensitive, so the skin and eye are the same organ. [Answer] The perceived frequency would matter. Visible light is roughly around 500nm; if a species evolved to be able to view lower frequency, longer wavelength electromagnetic radiation, presumably they would need a larger lens and focal length, and hence a larger eye. If the eye needs to be large enough, the benefit of having a second eye might not outweigh the expense. This would perhaps enable seeing into the far infrared, or maybe even into the microwave or radio spectrum. There would be a large biological cost, but I could imagine benefits from that as well. [Answer] Aside from theoretical speculations, looking at evolution it appears that once a species has evolved two eyes, it is unlikely to go back to one. Even in animals like the [flounder](https://en.wikipedia.org/wiki/Flounder), the useless eye moves to a useful location rather than disappearing. For species where general light-awareness is useful, but eyes are not, there is no need for a (relatively complex) eye to evolve at all. Simple light-sensitivity of the skin (or parts of it) would serve the same purpose for a much reduced evolutionary cost. [Answer] This may be a possible scenario: Protection of the eye is more important a) stereoscopic vision is not particularly important in their environment for some reason, for example if they don't have to do much hunting or fighting and most of their food comes from plants which could be easily identified and foraged. Perhaps they have good passive defenses (like a Hedgehog's spikes or just really tough armour) which discourages predators. Or perhaps the evolution of their brain could never get the hang of processing it. b) the eye could perceive EM frequencies that penetrate objects that would be opaque to us. (e.g. they have X-ray vision) and their environment has a lot of waves of these frequencies flying around. They'll need it because... c) protection of the eye is so important that it's buried deep within their tough and thick skull and only have a single aperture into the skull to see through. Perhaps they are vulnerable to sand-storms or small flying pests. (Though as has been pointed out, redundancy is good protection too, maybe in their environment, it's not as good). Trying to peer through a narrow hole would not be much good for an eye, but they get their peripheral vision (albeit not as clear but still useful to a limited degree) from (b) above. They have limited vision *through* their skull. This hole is the only point of entry to the inside of the skull that doesn't go through bone, so having just a single one (and therefore a single eye) makes all of the contents of the skull easier to protect. [Answer] **The key here is not whether 1 eye benefits the creature, but whether 2 eyes do.** Evolution tends to favor simplicity, and thus the most efficient use of resources given. Now if the species in question evolved 2 eyes, there's nothing you can really do. But if before your species evolved eyes, they went into an area where depth perception doesn't matter, like a cave, then another eye would be nothing more than another part that can get damaged. So, using the logic of evolution 1 eye would be equally matched with 2, if not favored. [Answer] In [Sundiver](https://en.wikipedia.org/wiki/Sundiver), **spoiler alert**, The species evolved with only one eye but had the ability to both use and emit coherent light. That is, project holograms and sense phase and direction of incoming light, which was a return from his own emitted pulses. That is, the being has something more like high-def lidar than a camera. [Answer] You'd have to be in an environment in which having two eyes is a liability instead of an asset, so that evolution would favor creatures with a single eye. Some ideas: * A world in which light is so bright that creatures must use the blind spot of their eye and create an eclipse-like effect in order to look at something. * A world full of things and creatures emitting coherent (laser-like) beams of light. Catching more than one at a time could be too cumbersome or require too much cognitive processing to be worth it evolutionary. * Conversely, a world in which light is bright and washing everything away, so that information is only conveyed in variations in ambient light. * A non-Euclidean world in which light takes such convoluted paths that having two eyes / viewpoints is more troubling than helpful. * Creatures that live in one-dimensional bright environments, like intestinal parasites of a bio-luminescent creature or optic fiber network dwellers. [Answer] There is that old saying; in the last of the blind, the one eyed man is king. If you are talking about an "Earth Like" planet, the scenario where a creature with a single eye would have an advantage. They would have an advantage over all creatures with no eyes. I suspect the main evolutionary reason that we (and pretty much all creatures on this planet) have two eyes is that the bulk of living things on our planet exhibit bilateral symmetry. That is to say we, butterflies, pigs, fish, pretty much everything, are essentially have a creature that's mirrored down the middle. On a planet where creatures are not created with bilateral symmetry, it would be more likely to see a creature with a single eye 1. evolving and 2. having an advantage (assuming everything else didn't have a functioning eye, maybe they just had a few light sensitive cells). [Answer] If an organism is simple enough then it may not be able to afford a second eye. *Cyclops bicuspidatus* exists on Earth and is an example of this. ]

[Question] [ In most science fiction where humans are simulated or uploaded onto computers, the humans are simulated with perfect fidelity. But this seems unlikely-- humans are very expensive to run. In Robin Hanson's *Age of Em*, humans that are too poor to run at full speed are just slowed down; probably the only reason that they aren't "lossily compressed" instead is that in that universe, we haven't made advances in neuroscience and must treat stored minds as black boxes. In a world with the following: * Abundant but finite computing power * Trillions of simulated humans * A value system that looks favorably on lossy compression of human thought, or the elimination of particularly expensive modules, to make room for more people * The scientific understanding to do this what mental faculties of the average person would *actually* be compressed/eliminated? Since computers are trillions of times more efficient than humans at arithmetic, imagine removing the ability for humans to do arithmetic, replacing that functionality with a software library. Or depowering parts of the brain related to social interaction when one is alone. There are surely better candidates. I'm especially interested in examples that result in interesting negative changes to subjective experience, that are plausible based on current scientific evidence. [Related question on Biology.SE](https://biology.stackexchange.com/q/93366/57397) [Answer] **Lag.** The world seems really fast. and sometimes you.... .... because you are sharing the server with so ..... .... [Answer] In point of fact, what you are positing is exactly what the human mind/brain does. The circulatory system, as efficient as it is, can only provide the brain with part of the total energy it needs. To accommodate the deficit, the brain diverts blood flow to areas of the brain that are active. This is the principle of [MRI scanning](https://en.wikipedia.org/wiki/Functional_magnetic_resonance_imaging). This is most evident in sleep, where major functions of the brain are shut down, and brain energy requirements are low. It is also the reason why someone might have to call your name several times, before they 'get your attention'. Our brain has a very efficient central control system to monitor attention and priority brain functioning. It is akin to your AI using a control monitor level that 'loads' specific programs to do specific tasks into 'main memory' in order to execute them. Most computer hard drives might be full of hundreds of programs, or apps, that do various tasks, but your computer or smart phone only loads and executes a select few. It is not just computing power that is a limitation, but data and program storage power as well. On the other hand, the body has several processors that run specific programs continuously, independent of the brain's control. Such things as breathing and heart beat, homeostasis, and balance. So to do modern computers. The printer, screen, remote keyboard, all have processors that run independently of the main CPU, to off-load sub-tasks. The computer CPU, for instance, does not move the cursor around, that is done by the graphics processor. So, basically, anything in the human and the human simulator can be shut down under certain conditions, provided essential services are off-loaded and you have an independent always-functioning control processor. When I am listening to music, I close my eyes. When I am reading, I shut down attention to hearing. When I am sleeping, I shut down mechanisms for maintaining balance. When I am daydreaming, I shut down both hearing and seeing. In point of fact when I meditate, I pretty much shut down everything. Except (unless I am in a coma) the central background monitoring system - the one that brings me awake at a sudden noise - and the autonomic processors and sub-systems (my liver still processes stuff, for instance). Given the size of humans, and thus the availability of data storage space everywhere, including spaces in the feet, torso, and so on, I suspect that future computer-humans will store most of their functionality into programs that are brought up to the main processor as needed. Just as in parallel distributed processing, the trick will be in the system monitor program being able to load the programs as necessary. And given what we have done with cloud systems, I suspect a lot of routines will be offloaded into cloud systems, sort of like the chrome books today. [Answer] You're going to run into two problems trying to idle or compress brain systems. ## Evolution Has Already Favored a Lean System Our brains use heuristic shortcuts, as well as a task manager which itself idles and brings into activity different subsystems. This is to minimize energy costs; there's a finite number of of thoughts you can manage on a handful of nuts and berries or a mouthful of animal flesh. It is for this cause that people are bad at the sort of "brute force" computing that machines do, though people often falsely attribute this to us just not being very smart. Beating nature tends to be more difficult than people anticipate. But what about the subsystems we don't need because we're in a simulation? ## The Brain Has a Habit of Sprawling Into Its Own Subsystems! Close your eyes and picture the last thing you ate. If someone was doing a brain scan as you did that, your visual processing center just lit up (and maybe another system or two). Even profoundly blind and/or deaf people end up using the unoccupied sense-processing real estate, for other tasks. If you eliminated "unused" regions of the brain, there may be unanticipated consequences for basic function. Did that one guy use his visual center to help him find the right word? Idling that subsystem just gave him aphasia. Plus, he can't perform visual abstraction tasks anymore. And that autistic lady who wasn't even good at recognizing faces (different, dedicated subsystem)? She is no longer able to quickly distinguish between images of different bacteria! And your blind mathematician has suddenly lost his mathematical intuition. Worse than that, when systems fail, the brain rewires itself, so forcing subsystems to shut down will have permanent structural implications as the remaining structures change and adapt to losses, even if those losses were intended to be temporary. [Answer] **Where Am I?** If you're exploiting brains to work symbolically rather than in an actual environment — that is to say, walking around in a virtual world and doing things isn't too important for the people organizing this so much as getting the thoughts they need — you can probably (in the vague science-fiction sense, not the one that I can back up with evidence) get rid of most of the functionality of the brain stem and cerebellum. You don't need a heartbeat, you don't need to feel pain, you don't need to know where your hands are. If the people in charge didn't even need to give their emulated friends images to work with, and are planning on using the brainpower for purely abstract reasoning, with some risk, your hypothetical neuroscientists might be able to work outward from there, shutting off sensory processing in the occipital and parietal lobes. The results would be far more unnerving than just being a "brain in a vat"; these people would lose track of where they were, not know whether or not they had bodies, and wouldn't understand what vision or touch could provide for them. But you could still feed them conceptual data and get responses back, like querying some server, assuming there are things you need to poll these minds on that you couldn't just get from computers. [Answer] **Compress individual viewpoints and knowledge.** A common design principle for software engineering is to not repeat yourself, and this would be useful in your scenario. Instead of individuals having their own opinions on a subject, which are all pretty similar to their peers anyway, the individuals could simply be subscribed to a common "ism". For example, not everyone needs a highly personal and unique reasoning around the story of creation. So, just assign one of 'n' creation myths to that person, which is the closest match to their previous belief. As another example, for those not actively interested in politics, just assign them the generic democrat, republican, anarchist belief pattern, and do away with the tiny individual details. They will all have the exact same responses to political questioning. This is a highly efficient type of lossy compression which can be applied to tastes in music, food, childhood memories, sexual fantasies, and so on. The trick is to make people more generic, more identical, and reduce the differences between them as you recycle the resources. It allows people to retain their depth and complexity, as its not the thought processes but the diversity of opinion which gets compressed. The simulation computers respond to Trumps latest tweet once, calculate the result, and all the Trump supporters think exactly alike on the matter. I myself am not particularly interested in nature, and being able to identify individual birds, leaves and animal droppings. So just assign "generic city dweller" module to me to cover that area. If i do take a nature walk I'll recognize a couple of common plants and birds, but I would have to really look carefully to spot that my knowledge of this is *exactly* the same as some other city dweller. That is the lossy compression at work. Naturally, upper class individuals could emerge, where they acquire more computing resources to simulate more unique and individual nuanced versions of one or more areas or opinions. In such a situation, it would be a luxury item to have a custom personality that stands out from the generic masses. [Answer] **I think you're examining the wrong thing. It's much easier to simulate a human mind than it is to simulate a universe the human mind observes.** [Humans - particularly young humans - have eyes and brains capable of pretty high FPS](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2826883/). And when you throw in the fact that eyes don't just detect in 'frames', but have a sensitivity that is continual/blurring (aka, your eyes detect a bright light for longer than the photons are actually hitting it.) Realistically, you're going to have to simulate whatever the eye is looking at with very high frame rate. ... and that's combined with a very high degree of precision. [The total megapixel size of your area of focus (ignoring the peripheral vision) is up to 15 megapixels.](https://www.discovery.com/science/mexapixels-in-human-eye) That's twice the area of a 4k display. Then you come to the lighting/visuals itself. Video games have come a long way, but there hasn't been one produced that is indistinguishable from reality. And finally... the physics of the universe the human is experiencing. How detailed of elements are you simulating? If they hold a mound of sawdust in their hand and blow on it, are you simulating every particle? If they walk along the beach, is each particle of sand simulated? Are the particles displaced by their footprints kept? What about when it's raining - are you simulating each water droplet and how its water molecules interact with each grain of sand? When they boil a pot of water to make pasta, are you tracking each individual steam molecule so you know whether or where it condenses? [For what it's worth... we're still at a point where we're bragging about simulating a *single molecule*.](https://www.sciencemag.org/news/2017/09/quantum-computer-simulates-largest-molecule-yet-sparking-hope-future-drug-discoveries) Whereas... [we're actually taking stabs at being able to simulate the human brain already.](https://www.humanbrainproject.eu/en/science/overview/) I think you'll find that it's not "de-rez'ing parts of a brain" so much as its "de-rez'ing parts of the universe". Nobody's at the beach? Don't track the sand particles, and regenerate/extrapolate once someone enters the scene. Only one person at the park? Don't simulate each individual grass blade, and use a simulated effect for everything more than 50 meters away. Etc. [Answer] That kinda depends on what the simulation is like. Not a complete answer, but if the mind is uploaded, then there are a whole host of things that need not be done, I think. Like controlling the heartbeat and breathing and digestion and various reflexive responses, etc. All the subconscious stuff. No point in calculating things related to body control when there is no body to control. So if your simulation involves a brain floating in "nothingness" then you can pretty much shut down all senses and balance control and what not else. The remaining few senses that are used for communication can be wired more directly and thus require less processing. [Answer] # You're drunk - go home With insufficient computing power your 'brain' struggles with fine motor control, your speech becomes slurred and you become clumsy. Your reactions slow down as each computation takes longer. Your decision making becomes worse as you have less processing power to make good choices. Without the high level processing the world feels calmer, no more micro-calculations buzzing through your mind; the edges of objects get blurred, which is frankly a blessing having been looking at the world in ultra-high definition all week and noticing individual specs of dust on objects all around the room. At the extreme end you are immersed in a world of block-colours, soothing noises and a base feeling of happiness. Imagine going to the pub, but they 'pay' you to drink! People in this world love spend a Friday night on low-power, so they can switch off, relax and hangout with friends. No-one remembers much the next morning. Addiction is still a problem, underclockers mumble at you on street corners. "Got some credits? I've got this job lined up tomorrow, but I need enough credits to process well. Help a guy out. Get me get back on my feet". Their friend nearby is slumped against a wall in a 33MHz trance. [Answer] **Slow** A "kind" society might just slow down the overall computing speed of any individual process (person) and their experienced world to the point that it seems normal to them, but is maybe 1/60th speed to an outside observer. [Answer] Avoid it with limiting abilities and emotions, by providing an "in-life shop". You want to feel love? Pay for it, loads. You want to have a good sense of orientation, that's not for free obviously. Maybe you even can earn money, by voluntary shut down a ability of you basic set your are provided with by law. Shut down an arm for cash. All perks, abilities and so on cost money, and there are many. Most people only can afford a few of them, keeping the system requirement low. Only the few rich ones, can afford a high system load. This keeps the system usage in bounds. ]

[Question] [ I have a community with great knowledge but limited resources so bows are preferenced over guns. Is there any reason why their warriors would carry "English" long bows instead of modern style compound bows? Mainly looking for tactical excuses. [Answer] **Compound Bows** *Pros* * Easier to use * Average user can shoot further * More accurate without practice * Smaller & lighter *Cons* * Complex & slow construction * Suffers wear & tear faster * Suffers from the environment faster * Requires laminate wood, fiberglass, or carbon fiber to take full advantage * Though few consider it, the pullies can be jammed (think "mud") * Though few consider it, natural wood arrows are often too soft for the power behind the bow. **Longbows** *Pros* * Easy to manufacture * Easy to maintain * Effective without lamination/fiberglass/carbon fiber * Highly effective with natural wood arrows * Withstands weather well * Has no moving parts to get gummed up *Cons* * Bulky * Longer training curve * Shorter range * Less power [Answer] from <https://en.wikipedia.org/wiki/Compound_bow> > > Warranties for compound bows do not cover "dry loosing", and it's not > unusual for numerous parts, especially the limbs and riser, to be > damaged or destroyed after even a single dry loosing. If a string or > cable breaks when the bow has been drawn this will have a similar > damaging effect on the limbs. > > > If a string breaks on your longbow you can string it back up in seconds, with the several dry strings you carry. No doubt archers in wars over the millennia with non-technologically advanced bows did this all the time. If you break a string in similar circumstances on a compound bow you will be very lucky to be able to repair it in the field. At best a hunting trip cut short. At worst you will shortly be parrying sword strokes with your worthless bow. The broken string and destroyed bow is one example - compound bows are full of other fiddly parts like (several) pulley wheels with ballbearings which can get grit lodged in them and render the bow useless. Longbows are much simpler and more robust. [Answer] The most obvious reason is the ease of manufacture. With the right wood and a knife, you can whittle a bow. Building a compound bow requires metal working tools. If a community has limited resources, it may not have the tools to build a compound bow. If a community had the tools to build a compound bow, they would build crossbows instead. They are easier to use and don't require the training and practice of a bow to be proficient. The most obvious tactical reasons to use a bow over a gun is that a bow is mostly silent and you have a chance to recover and reuse your arrows. If push came to shove, you could even make your own crude arrows if you ran out. [Answer] You said so yourself: They have limited resources. Even though compound bows are not thought for warfare, but rather for competition or, at best, hunting, they are still far superior to longbows in terms of raw power. However, they are not only harder to manufacture: they're more expensive too. If you're already making a compound bow, you're short from a gun almost just by the powder, and it isn't really justifiable over even a crossbow - which is much more low-cost in terms of maintenance and can be used with much less training - either. A longbow is a logical choice only if you need something that balances fire-power and resource usage. [Answer] I'm actually going to look at three basic possible kinds of bow, longbows, composites (made from laminated layers of materials with different compressive properties), and compounds made from modern composite materials like carbon fibre or Fiberglas. Rate and cost of manufacture, as people have mentioned composite or compound bows are expensive and time consuming to make, if you leave a composite bow to cure by itself, rather than using an oven to force-dry the glues, then it takes years to be usable. Modern compounds just can't *be* manufactured below a certain limit you can't make the material let alone the finished object. Hot climate, in a dry climate old-school bone/horn, wood, and sinew composite bows can last a lifetime, they usually don't but they can, but they tend to de-laminate when exposed to damp air for extended periods, compounds are the opposite, the sun is NOT your friend if you have a modern compound bow the resins and artificial fibres they are constructed from degrade when exposed to UV. Longbows don't suffer from either of these issues, they're a good all weather weapon. Ease of use and efficiency of fire, compound and composite bows are only superior for horse archery; you need more room to fire either one in an infantry formation than with Longbows, not a lot more with composites (quite a bit more for compounds) but when it comes to stopping a charge with an arrow storm density and rate of fire are key. Composite and compound bows require a different, longer, draw to generate the same power so rate of fire is marginally reduced. They also both have less "snap" so per pound of draw so a released arrow goes slightly slower, shorter range, less stopping power. Other issues; compounds and composites are easier to draw at a given draw weight for an untrained archer. Compound bows allow you to "hold the draw" while you aim making them more accurate at the cost of firing rate. Both of these make the weapons easier to use than a longbow but don't necessarily improve combat performance, you don't need "pip the ace" accuracy against massed targets for example. ]

[Question] [ I'm thinking about vampires, as we commonly see vampires who are hundreds (in some cases thousands of years old). In some depictions they appear old fashioned, in others they appear to be as up to date as "normal people". If someone (for whatever reason) stopped aging alongside their peers and remained physically the same as they were when they were thirty (so no ill effects from old age on their mind). Would they be able to continue to learn and keep up with modern times or is it more likely would they find the new societies and technologies overwhelming? Would it come down to personality? Or might it depend on the age they were when they were turned? [Answer] As a **Transylvanian native** with a strong affinity to dark offices, I believe I can shed some light on your question. Since I'm typing this on a computer, it should be obvious that at least some of us are up to date in technology, so have kept up with the times. If I were to engage in introspection, I'd say that **my memories of the distant past recede as a function of the distance in time and the emotional importance I attach to them**. So participating in my [nephew Vlad's](http://en.wikipedia.org/wiki/Vlad_the_Impaler) games with the delicious Turkish forces in the 1450s was so much fun that I rememeber it all as if it were yesterday, but much of the 16th century is a blur (partially due to a recurring bout of madness that century, probably triggered by [something I ate](http://en.wikipedia.org/wiki/Syphilis).) Now in modern times, you'd be surprised by how many of us have servitors working for the Red Cross and other blood-banks, looking out for good rare vintages. It's all very civilized, aside from some reckless youngsters messing about in the more troubled regions of the world. Now due to our telomere relengthening (dis?)order our bodies are essentially stuck around the biological age of 5-35 (it is a long-known fact among us that most bites over 35 don't 'take' very well, for some reason, probably too much gunk in the genecode, while the few attempts to turn people under 5 also seem to universally fail, probably due to the weak immune systems) So most of us have the brain plasticity and energy levels of a young adult, with our superior, uh, persuasion abilities, and centuries of refining learning techniques, building memory palaces and mnemonic systems to boot. Why, if you looked at Fortune 500 companies and hedge funds, you couldn't swing a garlic wreath without ... uh, perhaps I should not talk too much about that. --- Now, am I **old-fashioned?** In some ways, perhaps. I hold many views that are out of place, not all due to my nature. But **you'll never notice them**, **unless I want you to** do so. Why on Earth would I wear 18th century clothing? I may speak with a slight accent, but I **am** foreign, just like so many others. I may sometimes seem young for my age, but I do move from city to city every decade or two for a change of scenery, so not many people notice. As to my ability to drop my old ways and embrace the new, once you've done it twenty times or so, it gets easier. In fact, you get struck with a certain impatience and wanderlust once in place for too long... You'll see, if we come for you. [Answer] As we age, the amount of memory we have available doesn't really increase, which is why experiential time seems to accelerate as we get older- we are trying to pack more events into the same amount of memory. For your long-lived vampires this potentially presents a serious problem, but it also opens up some interesting doors. * Spirit memory - there is some other type of memory belonging to the vampire side of the creature, which allows them to recall greater spans of time in greater detail. This would probably have the side effect of making them a genius by human standards as intelligence is in large part a function of memory. * Limited memory, requiring records - I rather prefer this one, they can remember the equivalent of a long human lifespan, but beyond that recollections are very hazy, or long term memory is strong but the short to medium term is weak. One could make an interesting plot point of their need to maintain a journal to retain their own identity, with those who don't perhaps forgetting themselves and gradually turning feral while those who do live in fear of their journals being discovered either by humans or by other vampires who could use it for leverage or create their own power by adjusting another vampire's written memories. * Refreshed memory - periodically the vampire must choose to give up most of their memories to create new space, but also resulting in them becoming something akin to a new person. This would give them great capacity to adjust to new cultures but also may mean that they move in "jumps" so they become a little set in their ways after a refresh- fitting in great in the 1930s, but a little out of their depth by the 70s and so on. [Answer] I would think that if you lived a very long time, but didn't become old and tired, the main enemy would be boredom (and, of course outliving loved ones and avoiding detection). And the best antidote to boredom would be to have new experiences, challenges and to continue learning. This leads to "keeping up with the times" being a natural thing for such a being to want to do. [Answer] Much like most humans, this will probably depend on the individual. Some elderly folks seem to keep up rather well, they adapt to new technology, they enjoy new music, they try new foods, and so on... They enjoy variety and find interest in the new. Others cling to "the good old days", modern times seem somehow corrupt and lacking compared to their rose colored version of their youth. Much like how members of "The Greatest Generation" looked back on the Great Depression and World War II "you know people had moral fiber back then... hardworking, dependable" or how the "Baby Boomers" look back at the swinging 60's "remember when sex was safe and motorcycles were dangerous?" I would guess that you would find the same diversity in vampires. Some would miss the good old days, when hiding the leftovers from dinner was as easy as tossing them on the [plague cart](https://www.youtube.com/watch?v=grbSQ6O6kbs). While others would probably enjoy the [modern urban subcultures](http://en.wikipedia.org/wiki/Vampire_lifestyle) where vampires could hide out in the open. [Answer] **There are two obvious directions to approach this problem: either continuously add information storage matter, continuously improve the storage efficiency of the information, or continuously optimize the useful information.** The first option is certainly cheating. Eventually we'd have giant heads wobbling on our thin little necks. However, for some creatures, this is a valid approach. Consider if the internet was alive. Its approach to continuing to learn is to keep adding harddrives all along its nodes. The second option is less cheating. If we could gzip the information in our heads, we could compress it better. Unlike the first option, I consider it a fair direction to explore because in theory we could learn new compression algorithms, so it would make sense that you could keep growing this way. The third option is where things get interesting. Consider that we don't *have* to remember everything. Most humans do fine, even though we don't remember much from when we were 2. We kept the parts that were useful (walking is awesome, we should keep doing that), but we generally forgot all of the memories. They weren't very helpful anyways (unless you found a way to puke on your mom's favorite dress without getting her angry... that will be a useful skill in those upcoming frat days). The trick is that we collect a large amount of information, not knowing if it's actually useful or not. Eventually some of it condenses into smaller nuggets which have long term potential, and we keep those. We don't really need to know the exact wind speed or time of day when we fell off the bike and skinned our knees. The part that was really useful was the fact that bikes are not 100% stable. Sometimes we *do* remember the whole event "like it was yesterday," but even that word choice should suggest that that is the exception not the rule. There are unlimited ways you can go about this, but some of them are simple, so it makes sense to look at them before exploring the real creativity that is human existence. One simple approach is time-boxing. Your creature could decide "I remember the last 100 years worth of events, and after that I forget." This approach is nice because it's easy. However, it removes one of the major advantages to living a long time: the ability to collect experience. Pretty soon our creature would forget WWII, and would be on the same footing as any individual from the modern era who never went through it. The next step along that line is repeated time-boxing. In this solution, the unusually long lived being "forgets" everything it knows, and then lives out a normal existence until some trigger "wakes it up." In then processes everything in that life, assimilates it, and then does the process over again. This pattern is common in science fiction as a "solution to getting bored," ensuring each life is as new and exciting as the last. As long as the trigger invokes your full capacity before you get yourself, in trouble, you're safe. Also interesting is that this process can be recursive. Eventually you could "fill up" the larger mind, and then you're stuck. But if that lifespan is also time-boxed, it could pass that information on to a longer lived one. Consider saving half of your mind for "the long existence," that you wake up to at the end of each "forgetful" lifetime. The other half is allocated to life. You could then divide this half mind in half again, devoting one part to "the middle existence," and one to "the short existence" of a lifetime. This path guarantees that your longest existence has complete unfettered control over at least half of your resources at all times, while the rest of the resources cycle useful information up towards it. Of course, this pattern has a catch. It is remarkably hard to start. You have to hold back a remarkably large amount of your mental resources as you walk the earth using a fraction of your brain. The rest is slowly filled... very slowly. If you get in trouble during a "short" life, you won't have a whole lot of experience saved up because you chose to live such a small existence (using only a fraction of your mind for each life). So let's flip it around. Lets use as much mind as we possibly can at all times. That's much more effective while we are young. When our "life" is full, we'll split our mind into two bins, half for holding onto "old" memories, and half for making "new" memories. We then fill the "new" memories bucket again, until it's full, and grab the juicy bits to keep in the "old bucket." Eventually the old bucket gets full. Here's where we change it up. In the previous approach, we had subdivided the "new" bucket, so our brain for holding onto new memories got smaller and smaller as we tried to live longer and longer, leading to thinner and thinner lives. In this approach, we subdivide the old bucket. We now have 1/2 of our brain devoted to "new life," 1/4 devoted to "middle life," and 1/4 devoted to "all life." When we subdivide again, we end up with 1/2 new, 1/4 middle, 1/8 older, and 1/8 "all the rest." Each time we divide this way, we keep half of our brain for new experiences, so life continues to be new and exciting, every time we live it. Now lets take this to the extreme. Buckets are nice, but nature loves continuous processes. If we stretch ourselves out to be *reaaaaly* old, we start to see a really strong exponential pattern form, 1/2, 1/4, 1/8, 1/16... Mathematics has a continuous version of this, the exponential curve: a\*e^-kt. Time to cook with some real gas. Let's make a model for our memories. We're going to show a pattern for compressing memories. Let's make a Y axis be "amount of our mind we're using for this data" and X axis be "how old the data is." Draw an exponential curve in the first quadrant (above and to the right of the axes). The unknown of the world appears in the negative X axis. This is the data which we cannot know because it is "-12 days old," i.e. 12 days in the future. As we move through the world, these unknown values move to the right, towards "0 days old." This is the only point where we can interact with the world, and experience it. We can't experience things that happened in the past, we can only remember them. So we can measure the size of our life experience by how much of the world fits below the exponential curve at X=0 (now). The more that fits under the curve, the more of our mind we've devoted to being in the present. From here on out, the data is no longer experience, it's simply memories. Data moves to the right, becoming older. As it does, the exponential curve clamps down, forcing us to compress the data. We analyze the data, and pick the "most useful" bits to keep going along. Maybe we don't need the full 1080p version of someone throwing a water balloon full of shaving cream at us... maybe the 320x200 youtube video will do. Maybe we realize that all 5 of our Engineering courses actually only taught us one thing, in different ways (differential equations), and that we can remember them all in much less space if we refactor them to all use the same space. Eventually the oldest parts of us remember the most important little details. Perhaps it's a religion. Perhaps it's a thing that drives us to be alive. A long lived creature can modify the exponential they use to store data. However, generally speaking they have finite resources. They can't simply say "give me a larger 'a' term so I can live more of life to the fullest." There's a tradeoff between 'a' and 'k.' The more of life you experience, the faster you have to compress it to stay under the bounding limit of the curve. The less of life you live, the more you can drag out that compression process, giving more fidelity to the older memories, and decreasing the risk of compressing out something you needed. --- So those are the easy versions, which have nice clean shapes. There is a final one that I will write down, which builds off of the exponential. In the exponential memory described above, the march of time was relentless, crushing memories and hopes and dreams alike. It doesn't account for us remembering important events like our wedding night for years afterwards like it was just yesterday. Change up the X axis. It is no longer "time," but "subjective time." The more subjective time has passed, the more compressed an idea is. Other than that, very little changes. The world still meets us at x=0 where we experience the world. However, let's let the process of remembering be a bit more chaotic. Lets let ideas go in both directions: getting compressed as before, and getting 'inflated,' doing our best to reconstitute the original memory from the compressed version. Now we can explain how we remember our wedding night: if we let a memory float in the wide open space near X=0, we can keep its full beauty alive. We simply never let it get compressed. Of course, this forces us to compress the rest of our life faster (making our life a bit thinner), but maybe it gives us purpose. Of course, all good things must come to an end. Under the pressure of all of the incomming experiences, the memory ebbs and flows, compressing and decompressing ever so slightly. Eventually, the memory starts to fade, and we are forced to let time take its course, compressing the memory so we can still hold onto it. This model should be sufficient for your long lived creature to learn. They live the balance: compressing memories as little as possible to keep them beautiful, but compressing them enough to avoid clogging their mind and stopping them from learning and experiencing. As long as they do a good job of this balance, there is no reason they cannot live for as long as they please, and learn the entire time. However, if they ever get "caught in the past," they could clog their mind and miss out on key opportunities to learn. [Answer] I think it comes down to personality and personal tastes/interests. I do have a certain amount of first-hand experience to draw on (though perhaps not as much as Serban Tanasa does :-)). It's certainly possible to keep up with current culture, if sufficiently motivated - as for instance by the need to blend into society, or (in my case) earn a living. On the flip side (see, an antique cultural reference slipping in there!), it can be hard to find a reason to bother, unless there is some inherent interest or benefit. So for example, I find it much easier to understand Shakespeare's English than the patois of contemporary urban culture, work at the bleeding edge of tech but don't see the appeal of Facebook & Twitter, and so on. And tend to irk my friends by sending text messages that are written in full sentences, correctly spelled & punctuated. [Answer] It would come down to specifics, such as: * What is causing them not to age, and what are the relevant side-effects. As you noticed, even within vampire stories, the nature of the cause and effects vary a lot. * What are the mental habits of the person in question. Some people might get quite stuck in various ways, while others would not, and one person might change in this respect depending on what they were experiencing and how they were taking care of themselves or not during these many decades or centuries. * What are their other habits and experiences during this time? Are they abusing drugs or alcohol? Are they experiencing trauma? Are they focusing single-mindedly on some isolative pursuit? Are they fascinated by sociology and always mingling with new people? Do they travel? Are they suffering from various serious illnesses? Exposed to radiation? I think all sorts of possibilities are out there, depending on the answers to these and other questions. For a mundane baseline, I think people tend to pile up mental habits and unconsciously become more and more creatures of habit rather than remaining curious and conscious and developing. I also think that's not necessary unless and until they get stuck in habits, dissociation, or other problems which can interfere with awareness and mental health. If the habit angle sounds interesting, you might check out the easy read *The Habit Loop*, which I think offers some relevant perspectives and also has good insights into breaking addictions and how to be effective etc. [Answer] For a detailed look on this concept I highly advise watching the [movie "The man from Earth"](http://www.imdb.com/title/tt0756683/). This is exactly about what you asked, the story and the views of a man who was born in 14.000 years ago in the upper paleolithic and survived until modern days looking like thirty-something. Of course, he met some interesting people in the past and did a few interesting things. Or did he? [Answer] I have been thinking about this recently and come up with this idea: (not only) **Brain regeneration** - as your brain cells die out, new ones do born. So by mass, your brain remains the same, but it limits your ability to remember something in the past. If you play a little with it, you could have long living being which can remember up to 120 years into past in the same way as we, normal puny humans do. That would allow such being to learn and stay in the game. [Answer] There is evidence that certain skills are best learned at a certain age. Take [languages](https://linguistics.stackexchange.com/questions/1280/evidence-for-age-cutoff-in-foreign-accent-acquistion), for example. Some tastes are acquired early, too. Think back to the music you heard in your teens, or beauty standards from those days. Sure, the vampire can learn new skills and forget old ones. But the bygone era never quite goes away. [Answer] What is the molecular mechanism by which your long lived being stops aging? Memory depends on creating new neural connections in the brain, or reinforcing existing ones by routing information through them more frequently, making them "stronger". If your age-stop prevents this from happening, then learning will cease too. If this mechanism is still intact, there is nothing to physiologically prevent your being from going along with the times. Note that the example of "skills better learned early" doesn't apply here. This is a developmental question, a child's brain is organised differently from an adults, this is why when you learn a language at 5, the knowledge of it is different from having learned it at 35. But once the brain has been fully developed (this seems to happen in your mid-20s), the mechanisms used for learning are settled. So a language learned at 35 is not memorized differently than a language learned at 45 or 55, even though it's different from doing it at 5. I have never read a story which describes the exact physiological change to vampire's bodies down to biochemistry signaling pathways and changes to the cell functions such as a different metabolism or changed reaction to neurotransmitters (good luck writing such a story *and* finding somebody willing to read it!). The problem is that, from a biological point of view, an "undead" state does not exist. A being either has to be alive - which means that it can move, eat, make sounds, and build memories, but also ages, because all these processes introduce wear and tear to the cells - or be dead, such that all its memory functions have ceased. **Any explanation of undead vampires will have to introduce a point where it says "it's magic", and depending on where the author decided to place this point (cell processes continue but aging is magically removed, vs cell processes cease but the vampire is magically still animate), learning will be possible or not.** Also note that everybody grows more conservative with age, learning less and relying more on skills and knowledge learned previously. This surely has both psychological and physiological components (physiological: the neural pathways for some skills are way too well established after decades, psychological: it's tiring to learn new things all the time). As we have never observed century-old creatures capable of communicating abstract thoughts to us, we don't know how the process will continue after a certain age, especially if the usual age-related cognitive decline does not happen. It could be that old vampires resist learning new stuff for much the same reasons that sweet old ladies resist learning how to do online banking and run to the bank office instead, even when their brain is capable of do the learning. There is no way to answer if this would happen, at least not until we have understood how the brain learns. If you are writing your own story, pick continued learning or increasing resistance (with linear, progressive or sigmoid progress) depending on what works better with your plot, both are plausible. [Answer] I believe, the answer is yes, they can manage to cope up with the modern times, but not without problems. Human brain does not work the same as a static flash disc; it does not “fill up” and require more space. A memory might be a visual image, a smell, taste or a pain; but usually it is also associated with other inputs. A smell might remind your ex, a picture of a pizza can make you hungry; seeing blood might bring up memories of war and cause panic attacks and nightmares. There is also a [theory](http://www.themarysue.com/memory-distortion-in-brain/) that each time you remember something, you remember the last time you have remembered it. So, it fades over time and worse, it is distorted. People who live through accidents might remember the event vaguely or may not remember them at all. So, the memories are going to be very unreliable. He is going to have problems of distinguishing memories with old dreams, or even day-dreamings. He might decide to keep a diary. So, if you think a memory as a connection of brain cells, the brain does not fill up. It overrides the old connections; imagine a smell, a sound is associated with many more events and people. As a consequence, I believe they can adapt to the modern world, but living that long is going to have some consequences, like, they are going to have a lot of dejavus. They are going to hear sounds and experience tastes, that remind them of something, but most of the time, it will be impossible to find out what it is. They are also going to react to the world differently, I had a friend who had experienced poisoning on a pesticide treated ship; he developed allergy to machine oil and several other chemicals, associated with the machines. So, their bodies are going to develop some unusual and unexpected behaviours. So, I believe they are going to be weird people, probably a little bit crazy as well. But yes, they can still learn new things and live among us ]

[Question] [ In fictional media that revolves around police, SWAT, or agents from some three-letter-agency, it's common that before they go somewhere, they have their tech-genius go though some database and instantly pull up plans of the building that they're going to so they can make a breaching plan or whatever. Assume a modern country and an urban setting. Questions: * Do these building blueprint databases exist? * If yes, how good is their coverage and accuracy? If no, do people need to go rifling through paper filing cabinets or something? * Do groups like SWAT always look at blueprints before they go somewhere or do they frequently 'go in blind'? [Answer] ## Yes. Building Plans are generally available for buildings back to the early 1900's. I am an architect and we regularly work on extensions and renovations to commercial, institutional and residential projects throughout the world. We regularly request and receive these building plans every day as a part of our work. All buildings when built since the early 1900's up until today require government approval before proceeding. In the early days, this is just a hand drawn plan and elevation sent to a central authority which is stamped and filed. Today, it is detailed construction and service plans submitted electronically. All local governments would have records for all buildings in their jurisdiction. Many I know of actually have active programs to convert old paper plans into new file formats suitable for downloading. There are only 2 instances where building plans are not available: * If records were lost. A council I know of burnt down, and all their records were lost so any renovations required surveys of the existing building as a requirement. * If the building was illegally built, or altered after the plan was lodged. This happens, but not substantially as many governments have major fines for unapproved building. The format it is in depends on the buildings age. Here are the formats you can expect: * 1910 - 1950's: Pencil-drawn floor plans and elevations with sporadic notes but no detail. * 1950's - 1970's: Pen-drafted floor plans, elevations and sections with only marginally more detail. * 1970's - 1990's: Pen-drafted floor plans, elevations and sections with construction details and specifications * 1990's - 2010's: Computer drafted fully detailed construction drawings, service drawings, structural and any reports required for approval * 2010's - 2020's: Computer 3D models (on major projects), BIM Modelling (Service drawings integrated with Architectural in 3D), detailed specifications and schedules, and any reports. Feel free to contact your local government - they are normally very helpful. [Answer] 1: yes these databases do exist, but when I went to check on one all they had available were hardcopies, digital might be available but not on any PC with internet you have to physically go there. When you check one you need to pay a fee (about 50 euro's at the time) to look at it and weren't allowed to take copies (if I recall correctly you could get copies with express permission of the owners but leaking the information was a crime). It was in Europe though and it could vary from country to country. I wouldn't be surprised if 3-letter agencies have copies of buildings of interests digitally in their databases but not from every building. 2: accuracy will vary greatly. The building I checked upon was a monumental building that had to be exactly like the blueprints. After a large fire had ravaged most of the building's inner structure it had to be rebuild, and a few exceptions had been allowed during the rebuild to improve the building. These adaptations (and a few off-the-books adaptations) were not visible as no new blueprint was given. Most buildings wont submit a new blueprint for every change they make, and for non-monumental buildings its even less strict as far as I could tell. Its likely that SWAT teams, who get relatively little time to nip down to whatever repository that country has to get blueprints, will use digital versions made by whoever tried to show it off during a sale or finding a new tenant. But these blueprints would be a guideline, as the occupants could have done their own work that hasn't been added to the blueprints or like with my apartment the given blueprint was from a neighbouring apartment that had everything mirrored. Its quite a shock to find that out once you walk into the apartment. [Answer] I work for a Fire Service in the United Kingdom, we are [required by law](https://www.legislation.gov.uk/ukpga/2004/21/section/7) to inspect all local structures that could pose a risk if an incident were to occur there. This is usually any industrial complex, school, office, shopping centre, dormitory etc. Individual homes are not included. As part of the inspection we collect floor plans, details regarding hazardous machinery, dangerous chemicals, gas and water shut-off valves, location of spare keys, contact details for important personnel or anything that would be useful to know. The quality of these floor plans is typically very good, they are large PDF or CAD files that you can zoom in and out of to get more or less detail. This isn't always the case though, there are some buildings that no floor plans exist. All of this information is available to the Firefighters in a digital format on a computer placed on the passenger side of the fire appliance, there is also a printer in there if they want to make paper copies. I don't know if the police do the same but it's entirely possible, it's also not unlikely they would make use of our information if Firefighters and Police are present on the same incident. *Fun fact, because this is a requirement of Section 7, Subsection 2, Part d of the Fire and Rescue Act, we call these files "7(2)d Risk Files"* [Answer] **Generally the owners of buildings have blueprints.** Large commercial premises (office blocks/malls/factories etc ) retain detailed plans for maintenance and insurance purposes. Depending on the type of building (e.g. chemical plant) there may be a legal requirement that emergency services also have copies. There may or may not be a central registry available in the particular state or city concerned with *current* detailed internal plans but they will have the plans submitted when building approval was granted plus copies of any major changes made since then that required approval. As a rule BTW (at least in my jurisdiction) it's common for the purchasers of private homes to receive a copy of the original architects plans along with the deeds etc. Again any historic extension, alterations etc that required official approval may also be included. The body corporate of apartments and/or the property manager will also have plans for maintenance and insurance purposes. Again the approving local authority may also have a copy of the file/digitized. Note: depending on the circumstances it is possible (but highly unlikely) that the occupiers of a premises have made illegal internal alterations *without* the approval of the landlord or (if they own it) the responsible local authority. Whether or not these records are digitized will vary, increasingly central record offices are but older building records may not be. Residential plans held by private citizens? Probably not. [Answer] **This is absolutely feasible if your world has Eastern Bloc-style mass-produced buildings.** These blueprints may even be publicly available. A good example may be many republics of the USSR. Due to the devastation laid by the WW2, a lot of post-War buildings were built in series. The idea was not unlike British "tower blocks" but featured some key differences. Republican (state-owned) architectural bureaus designed series of blueprints (updating them or making new ones when better materials or new ideas become available), and the number of houses built from each blueprint could reach hundreds or even thousands. This allowed to rapidly provide housing and infrastructure for people left homeless after the war, and afterwards, industrially-built housing kind of stuck as a tradition, especially after the advent of rapid-assembly panel housing (e.g. *Panelák* in former Czechoslovakia, *Khruschyovka* and *Brezhnevka* in Russia). Further generations of builders were taught how to work with such housing in universities of architecture and civil engineering, with the approximate plans becoming sort of common knowledge. Such copy-paste projects were used for apartment buildings and many kinds of civilian infrastructure such as schools, supermarkets, theaters, clinics, and others. Today, the schematics for most of these building series are not only available on the Internet, but also have been assembled into public online databases. [Answer] # Blueprints exist but generally not en route to an emergency The computer systems shown in these shows is called Computer Aided Dispatch (CAD). CAD is a big deal in emergency services. A well-funded city can have computers in every police car, ambulance, and fire department vehicle. CAD provides up-to-date information to every unit responding to an emergency. Despite all the information available via CAD, I've never seen a computer showing a blueprint. Your question made me curious so I dug into it. Here's [the only reference I found](https://www.policeone.com/police-products/police-technology/software/cad/articles/how-interacts-cad-cloud-solution-helps-departments-share-everything-VORhMAOXEInG2vXs/) to blueprints from a CAD vendor (emphasis mine): > > The InterAct system also allows pre-populated choices for location, > code, etc. This can be programmed as an auto-fill or a drop-down box. > An agency can add any kind of information into the system, including > warnings, prior incidents, and resident information such as medical > needs or the location of a fire key. **A building blueprint could also** > **be added.** > > > So vendors are thinking about the ability to add blueprints to dispatch systems for buildings of special interest. Thinking more broadly, there are databases of building designs in some cities. Builders have to submit designs for approval, and some cities have started to gather those designs into one centralized place for public review. The vast majority of SWAT missions are planned well in advance, so there's plenty of time to review building plans if they are relevant. [Answer] The availability of public records is already answered well by others so I will focus just on: > > ... If no, do people need to go rifling through paper filing cabinets or something? > > > Strictly speaking this is not necessary anymore since the technology exists to map the entire inside of a building from the outside using WiFi emitters. While it has not been widely adopted yet, A special operations urban combat unit could use WiFi mounted drones to build a blueprint of any building before going inside. It's not exactly as covert as rifling through paper filing cabinets, but if you had an emergency situation such as a hostage standoff, it would give you some "blue prints" to go off of pretty quickly. <https://www.youtube.com/watch?v=THu3ZvAHI9A> [Answer] With todays technology- you could in theory- generate blueprints from sratch. First there are drones, that can lidar-scan through windows. Then there are WiFi-Nodes, which can work as 3D Scanners through walls. ]

[Question] [ Supposed we have a ship travelling at the speed of light, or very close to it, or over. A second ship is travelling behind it at the same speed. The second ship wishes to communicate something to the first ship, but they can't transmit radio waves or even fire lasers at the ship in front, as that would violate general relativity. Is there any way for them to communicate without overtaking the ship (assuming they could) and sending messages downstream? [Answer] It is impossible for the ship to travel at the speed of light, it can at best travel close to the speed of light. The difference matters. There is nothing really stopping two ships travelling at a speed arbitrarily close to c from communicating with lasers or radio. It will take the laser the same time to travel the distance as it would if you travelled at some other speed. The speed relative to some outside objects is irrelevant. In this case the relative speed is zero so there won't even be Doppler shift or weird relativistic effects. [Answer] With real physics, yes, they can communicate. Both ships must be travelling under the speed of light, and so any light wave (or radio data) sent from one to the other travels at the speed of light, **even from the point of view of the first ship!** This means that if you have two ships travelling on a straight line at 0.99c 300.000Km apart one from the other, the communication would be perfectly normal with just a delay of 1 second. In this case, the ships are **not moving** one with respect the other. If you go for Faster Than Light travel, you are on science-fiction domain, and the same means you use to have FTL engines can be used to have FTL communications. [Answer] If the ships really are travelling *at* the speed of light, using known physics (which *is* possible, sort of — see below), then they *cannot* communicate. The reason for this is [time dilation](//en.wikipedia.org/wiki/Time_dilation): the closer to the speed of light the ship moves, the slower its [proper time](//en.wikipedia.org/wiki/Proper_time) passes. At the limit of a ship moving at the speed of light, *no* proper time passes for it — from the perspective of the passengers, they arrive at their destination immediately after embarking on their journey. Thus, there will be no time for the passengers to send or receive any messages, *or to do anything else*, during the journey. So, how can we make a ship travel at the speed of light using known physics? Well, according to the theory of relativity, only massless particles like photons can reach the speed of light, so we'll have to make the ship (and anything it carries) *out of* light (or some other massless particles, but light really is the most convenient). In practice, such a "ship" would be more like a Star Trek transporter than anything one would normally describe as a spaceship: at the departure station, using Sufficiently Advanced Science™, the passengers will be converted into a pulse of light, which is beamed at a distant receiver that reverses the process. As far as the passengers are concerned, the process resembles instantaneous teleportation, although, of course, a year of (coordinate) time will actually have passed for every light year so travelled. Of course, this process would be a lot more convenient if the "passengers" were already encoded into easily transmissible information — that is, if they were either AIs, or humans (or other originally biological creatures) somehow "uploaded" into software. In fact, if you want to transmit beings with physical bodies this way, the easiest way would be to first scan into a software emulation, transmit the software, and then, if desired, rebuild new bodies for them at the destination. (Hey, I didn't say it would be *easy* — just easier than the alternatives.) Or, of course, you can postulate some new physics (or exotic edge cases of current physics theories, such as stable wormholes) that allow faster-than-light travel. In that case, however, you're pretty much free to assume anything you want about how in-flight communications would work (or not work, as it might be). For the specific case of wormhole travel, a reasonably plausible assumption would be that ships travelling through the *same* wormhole could communicate just like in normal space (after all, a wormhole *is* normal space, just with a weird geometry), but any signals sent from inside one wormhole to another would have to take a detour through the wormhole mouth(s). [Answer] The important thing to realize here is that velocity is always relative to a certain frame of reference. There is no such thing as absolute velocity. (This is basically what the "Relativity" in "General Relativity" is referring to) Imagine two astronauts floating in a vast, completely empty region of deep space. There are no stars visible to them (or whatever equipment they may have) there are no little hydrogen atoms flitting around, there is nothing but the two of them and infinite blackness. If the distance between them is shrinking at a rate of 10 meters per second, then how could you say which one of them is moving and which one is not? You can't. The question itself is flawed. If the astronauts don't know much about these things, this is probably how they would answer if you asked them their opinions: * Astronaut A: I am clearly stationary and Astronaut B is moving toward me at ten meters per second. * Astronaut B: No way, I'm the stationary one and Astronaut A is moving toward me! They are both right. To them, they are stationary and the things around them are moving. This is true for anything, even a spaceship moving away from Earth at relativistic (very, very high) speed. To the passengers on the ship, the situation is reversed: it appears that they are stationary and Earth is moving away from them at relativistic speeds. In the astronaut example, there are only two frames of references we can use, astronaut A's or astronaut B's. There is no one else there whose opinion we can ask. What that really means is that there is no other frame of reference from which to answer the question. You might ask "well, how fast are they moving relative to point Z somewhere between them?" but remember, this is completely empty space. There is nothing at point Z. Empty space does not move, nor is it stationary. It doesn't exist, so of course you cannot speak of where it is. Now here's something only God knows about the situation: the two astronauts are in a distant region of space which, due to the expansion of the universe, is moving away from Earth faster than the speed of light. Thus both astronauts are moving away from Earth faster than the speed of light. But this doesn't matter as long as the astronauts just want to shine lights at each other or poke each other or whatever they do to communicate. Eventually they will collide with one another, just as communications between two spaceships will collide with one another (if the spaceships are moving more slowly than the speed of light relative to one another). If they want to communicate with Earth, that's an entirely different matter, and then the velocity relative to Earth would come into play (in this scenario, Earth is beyond the "Hubble Volume" so indeed, they would not be able to communicate with Earth). [Answer] Relative to each other, the two ships are stationary. Any transmission from the trailing ship will arrive at the leading ship, the same as if the two were stationary. You can think about it this way: Consider the earth, with the moon orbiting around it. If you shine a laser from the moon to a receiving station on Earth, the light will propagate towards the Earth at light speed, taking about 1.25 seconds to arrive. Because the speed of the moon revolving around Earth is very low compared to the speed of light, there is virtually no time dilation. Now, think of your two spacecraft traveling at 0.999999c past the Earth-moon system, with craft A in front of craft B by the same 1.25 light seconds. The time dilation between the spacecraft and Earth-moon is 707 (see <http://www.1728.org/reltivty.htm>), which means that if you transmit from either ship to the Earth, or from the Earth to the ships, the sound and video on your transmission will have to be sped up or slowed down by a factor of 707 in order to be intelligible. BUT, between the two ships, the *relative* speed is zero. Signals traveling from ship A to ship B will propagate at the speed of light *relative to ship A*, so, the transmission from A to B will take 1.25 seconds to arrive, but there will be no time dilation between the two spaceships. [Answer] Current physics answers no. The only potential answer to this that currently exists is found in the domain of Quantum Entanglement...a concept used by games like 'mass effect 3' that has some basis within Quantum physics is a potential option here as 'information' could potentially travel well past the speed of light. It's a weird topic to research as there's a ton of articles claiming to 'debunk' (that's a great term) followed by articles debunking the debunk (which I believe makes it just bunk), and debunking the debunked bunk debunking?...in any case, it's important to remember that this is theory, and disputed theory at that. The brief explanation is pair particles have opposite spins, but you don't know which spin either of them have (infact, it doesn't have a spin until it's measured). By measuring the spin of one, you cause the other one to take the opposite spin...and that other one can be (theoretically) light years away, yet still take the opposite spin of the one just measured instantaneously (please realize this explanation is the equivalent of attempting to explain Schrodingers cat in 2 sentences). The idea that 'information' can travel beyond the speed of light would solve this communication dilemma. [Answer] If two ships were traveling at the same speed at under the speed of light, and away from the Earth, they would communicate normally. They really might not even know they are traveling that fast. For instance, we could be traveling that fast right now and we'd never know it. Now, assume there is a third ship that is traveling so fast the first two ships think it is traveling at nearly the speed of light away from them. Now, a fourth ship traveling at what the third ship thinks is nearly the speed of light faster than the third ship.. and so on until you reach what could only be described as warp 100. From the perspective of the Earth, all the ships are traveling at just under the speed of light and will all arrive at their destination at very close to the same time. Let's just say people of the Earth think it took two years for the ships to arrive at their destination. From the perspective of the ships, the fastest ship might arrive in what it thinks is a couple of seconds. The slowest ship might think it took a year. And, every ship in between thinks it took a different amount of time. So, on the question of communication, each ship would communicate with the other ships in the same way, using some form of the electromagnetic or visual spectrum. There will be a shift or stretching in the wavelength and data rate between ships. So, their communications equipment will need to be capable of handling the shift. If both ships are traveling at the same direction and speed, they will communicate normally no matter what their speed. However, when traveling close to the speed of light, time shifts exponentially. If one ship were traveling slightly faster than the other ship, they would see huge temporal differences in their own perception of time. The temporal differences between ships will cause a Doppler shift between the frequency of transmission and the frequency received. One ship may be transmitting on 2.45 Ghz. The other ship may need to receive on all frequencies (2.2Ghz, 1.9Ghz, 5Mhz, etc.) depending on the degree of the Doppler shift. When returning the transmission, one ship will transmit on 2.45Gz. The other ship would receive on some other frequency (5Ghz, 20Ghz, etc.). The question also asked what if one ship were traveling faster than the speed of light. A ship can never accelerate itself to or beyond the speed of light. Temporal changes due to Relativity will cause the person driving the ship to think they are chasing a carrot. The faster they go, the more temporal change, and they'll always think light travels at the speed of light faster than they do. However, if something is caught in the grip of a Gravity Well which compresses Space/Time beyond the limits of the speed of light, it would be as if they were traveling faster than the speed of light. In this case, the temporal shift approaches or becomes infinity. Any transmission coming from the ship would have infinitely low hertz. If the transmission could escape the gravity well, it would take an infinity to receive the entire transmission. [Answer] So long as the two ships are travelling at the same speed and slower than C (even by a tiny amount), there are no problems. Becasue time slows down as you speed up, a radio signal travelling at C, 0.1 m/s faster than the ship, might take a month to reach the ship in front from the POV of a stationary observer, but to the people inside the second ship, it will seem instantaneous, because they are thnking 'slowly', Similiarly, any hardware emmitting or decoding the signal will be operating 'slowly', so the message will have the correct bitrate. [Answer] Telepathy! Thought has no mass and would therefore take no time to travel so communication would be instant. I know light is made of photons and that this means light has no mass as photons are stated as having no mass. Photons do however have a relative mass. [Answer] Surprised nobody thought Orson Scott Card was correct with Enders Game. I know it's a science fiction book, but since all of the answers seem to be under the assumption that current physics is 100% correct I figured I might go outside of the box (fringe science?!). I think the theory is called supersymmetry which I guess could turn what we know upside down? I'm not sure why people are saying faster than light is impossible though. There are particles that travel much faster than light, neutrinos being one of them. I think knowing that there is something that is faster gives hope that FTL (Faster Than Light) travel could be possible. If it is possible, proving supersymmetry and possibly string theory correct, I'm going to have to go with Orson Cards solution and say the Ansible. Near instant communication across any distance, thanks to what seems to be described as a device that takes advantage of quantum mechanics or string theory to transmit communications. The movie was horrible. [Answer] Here's my 50 cents.. If a ship travelling at lightspeed would be able to reach a ship in front of it, its transmitted radio signal would have to be capable of travelling faster than the ship itself through the same medium (vacuum). In other words, the radio signal must travel faster than light. This by definition is impossible. Nothing travels faster than light. Even if the ship would be travelling slightly slower than a radiosignal trough the same medium, the relative frequency of the radiosignal as percieved by the ship in front of it would have such a low frequency that it would be impossible to decode, or would take significant time as it arrives with high delay. Hence, it is not possible to communicate forward when travelling at lightspeed. Backwards is a totally different ballgame. Even though the radio signal has an absolute speed of 0, its relative frequency as perceived by the ship behind it is still at lightspeed, and still intact. I believe optical gyroscopes are entirely built around this principle. Meaning, built around the certainty that nothing can travel fast than light, even when the light-emitting device itself has an offset speed. ]

[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 3 years ago. [Improve this question](/posts/191988/edit) The problem: My time travelling hero has travelled from the present, back to 14th century France (think 100 years war) to retrieve the mcguffin, a manuscript. He cannot take any physical objects back (or forwards) with him through time and so in order to have the manuscript in the present day he needs to store it safely for 700 years. He needs to find somewhere that the manuscript won't: * rot, * be stolen, * get burned, * be destroyed by revolutionaries, * be moved, * be prematurely discovered by archaeologists, * be eaten by weevils. So the question is: What material (14th century European tech) should the manuscript be made out of and where would it be safe for 7 centuries? [In response to questions... The manuscript takes up about the same volume as a modern ream of A4 paper] [The manuscript should remain undiscovered by anyone other than the time traveller] [The information on the document is only valuable if it comes from a provably original manuscript, not a copy] [Answer] There are a few challenges one needs to meet to solve this problem. First, creating a book in the 14th century was an expensive undertaking. All of the pieces -- the writing material, the ink, the process of writing the document -- had to be done by hand by skilled workers. I don't remember the costs offhand -- although I believe they have been calculated -- but it would require a lot of money. (Can your time traveler bring with him several pounds of gold to pay for these expenses?) Second, there are two different strategies in preserving an object like this: one is passive, the other active. Each has its strengths & weaknesses. The passive requires finding a spot that would be secure for 700 years. Its strength is security thru obscurity: by being hid, no one would know about it before you wanted it to be revealed. Its weakness is that if something happens to the object -- an accident, theft, damage due to age -- there is no way to right the wrong. Your time traveler could secure this object in a durable container, & place it in a remote location. The choices would either be somewhere dry (e.g. the Sahara or Arabian Deserts), or cold & wet (e.g. in the permafrost of Siberia or North America). Such places would have a stable environment, & the materials of the manuscript would not deteriorate. (Keeping paper or parchment soaked in an anaerobic environment & frozen will preserve it. That's how written documents found near Hadrian's Wall dating from AD 100 survived.) The problem with either option is for your time traveler to get to those remote locations in the 14th century. Once accomplished, then there is the challenge of marking the location the manuscript is secreted so it can be found when he returns to the present. The active would be to entrust this to a family that guard it for that time. The strength here is that there would always be someone to respond in case something happened to the object: repair it if there was an accident or damage from age, protect it from theft, etc. The weakness is that, well, families tend to die out. A certain percentage of couples have no children; another will have only female children, & women had fewer rights for that time. And all it takes is for one irresponsible jerk to come into his inheritance for the object to be destroyed. Your time traveler could identify a family that is known to have survived down to modern times, which would prevent some of this. But then you encounter the problem others have pointed out above -- since your time traveler has effected the time line simply by going back in time, you have no guarantee this family will actually survive down to modern times. These solutions have been provided as a thought experiment. To actually implement any of them would require more thought & some careful research. (Or settling on an oddball solution, such as sealing the manuscript in a metal box welded shut & depositing it in the [Cairo Geniza](https://en.wikipedia.org/wiki/Cairo_Geniza). Or have your time traveler create the [Voynich Manuscript](https://en.wikipedia.org/wiki/Voynich_manuscript), thus knowing the key that decodes this mysterious document.) [Answer] @DrMcCleod they did this in the book "The Rise and Fall of DODO", it's actually a really interesting bit of the story where they plan this. The constraints are fairly similar to yours in that the traveler arrives naked. They solve it by "re-visiting" the same place and making friends who help them to source enough money to pay a cooper to hide the first printed manuscript in America in a barrel. They dig the barrel under a rock that they know is present and undisturbed in the future (because they're already there). You can tell from the re-use of casks and barrels nowadays that coopers were good enough then to make barrels etc. that last hundreds of years. [Answer] First off, put it on vellum. This is, indeed, very expensive compared to all other papers since it requires sheepskin, but where, say, papyrus decays after a century barring rare conditions to preserve it and needs very fancy handling, vellum is so tough the graduate students regularly get to handle original documents with no more precautions than gloves. Second off, he should (in the future) thoroughly investigate an obscure library for safety. Didn't get burned in the French Revolution, etc. Check it out for corners where things are not investigated often, too. Pick a library and a corner in it. [Answer] # Carve it in stone Yes it will be a bit of a schlepp to carve out 500 pages of text, but that's quite doable. The text need not be super-precise, gravestone-marker class engraving. Simple chisel marks on stone will suffice quite well. Then, bury the stone in an easily found spot, for future unearthing. Deep enough to be away from treeroots, farmer's ploughs, and definitely deep enough not to be scavenged into some stone wall. As the material is stone, you need take *no* precautions for preserving it from decay, other than a covering of earth. No mere animal or natural disaster will possibly affect it in a 700 year timespan. (assuming you don't put it in a riverbed, or something equally daft) Just be sure to use a natural formation as landmark, to find your stash again. Human artifacts like roads,walls or buildings, and transient natural features like trees, or rivers, may all move around so as to lose your spot. --- If , as has been argued in the comments, your time traveling does not actually change history, and you can 100% rely upon knowledge of what does remain preserved over 700 years and what not. 1. Research carefully for the location you will use to store your manuscript. Make your exact decision to use that location. Select a location that contains an unknown 70-year-old manuscript in perfect condition. 2. travel back in time. Put your manuscript there, and return. You do not have to worry about protecting it from rot, or fire, or theft, because you already *know* that location was preserved perfectly for 700 years. 3. retrieve your manuscript from your chosen location. p.s. you can skip step (2) Because, you have firmly decided that that is where you will put the manuscript back in time. And time travel cannot alter the future, therefore the manuscript must already be in that location before you depart. If you make it so timetravel cannot change history, then you can perfectly fake timetravel just by planning to do it, and paradox the whole need for a time-machine out of existence. [Answer] # Start a cult Building on @llywrch's "active preservation" answer, instead of a single family devoted to the preservation of the document, recruit multiple people and charge them with both the preservation of the document and the recruitment of the next generation of 'true believers'. If you inform them of the true importance of their task, the contents and purpose of the document could sound magical to people lacking 700 years of context, and they (perhaps rightly?) infer that they are defending against the destruction of the world some distant time in the future, which would give them the motivation to see it through. [Answer] Hide it in the walls of the Notre Dame cathedral while it's under construction. At the start of the 100 Years War the cathedral is mostly built but not quite finished. The other answers about vellum are great. Bribe the masons to hollow out a space in the bottom of a large stone brick, and hide your leather-bound vellum codex inside. Don't put it in a statue, a bunch of those are going to be smashed up by revolutionaries later. This may require some research to make sure that bricks from that section of wall weren't moved in later renovations, and don't put it too close to the roof, because the roof will catch fire later. In 2019, when the roof of the cathedral collapses due to fire damage, you can bribe the construction workers cleaning up the debris to "discover" your book. [Answer] **Hiding it away is the (relatively) easy part.** First, the physical manuscript itself. The only real concern insofar as preservation goes is to stash your manuscript someplace cool and dry. A manuscript made with typical 14th century materials will survive just fine if it's kept away from detrimental conditions. No need to do anything special to the usual types of parchment or ink you'd find in use throughout the Middle Ages. (I'm unclear on whether your time traveller is going to retrieve an existing document, or create a new one themself and leave it behind, but it shouldn't matter either way.) Second, finding a good spot. There are many places that have been sealed for 700 years. Before your time traveller goes back in time, have them identify some buildings they're confident haven't undergone any renovations or experienced any structural damage since they were built, where they might be able to stash the manuscript. The walls of a church or a crypt might be good candidates. **Now, the hard part.** Finally, you state: > > The information on the document is only valuable if it comes from a provably original manuscript, not a copy > > > It's not really possible to do this in a way that leaves absolutely no doubt. (How would you prove today that a handwritten letter is not a copy of another handwritten letter?) If you need the manuscript to appear contemporary to the 14th century, then here's some things to keep in mind to increase the chances that future paleographers will determine that the document is original and authentic: 1. Use a contemporary language (e.g., don't write in a dialect no one was speaking there in the 14th century). Follow local spelling conventions, etc. 2. Write using a contemporary script. 3. Be careful not to make any mistakes of any kind that might be interpreted as scribal copying errors. The experts will be able to tell that the writting was produced centuries earlier, and can estimate the antiquity of the materials used. But there might be questions as to just how long ago it was written. Someone could conceivably argue that the writing was made more recently that the 14th century using 14th century materials. [Answer] **Use a grave site** Grave sites are great because they often have a date on them indicating when they were created. So someone in modern times could look at a grave site and say that its been there since the 1400s. Also, for the most part, people leave them alone. Find a grave site, which you are sure still exists in modern times. This could be the burial tomb of a famous person, king, or just some ordinary guys grave that you are sure will still be there. Dig it up and put your manuscript in the coffin, inside of a glass jar with a sealed top. Dig up the grave in the future. [Answer] ## Put It Beyond the Reach of Mankind Just beyond Monaco or Cannes on the east coast, or further out in the Bay of Biscay on the west coast. In these regions the sea floor is more than 3 kilometers below the surface. It was not until the [1980s discovery of the Titanic](https://en.wikipedia.org/wiki/Wreck_of_the_Titanic) that human technology had developed sufficiently to explore and retrieve anything from these depths. **Process :** you can place your manuscript inside a sea chest. With the aid of some oarsmen to get you out to depth, you can dump your manuscript to the bottom. **Fabrication :** put your manuscript in a glass box filled with oil and sealed with wax. Wax and glass seals have worked up to depths of several hundred feet, and by eliminating all air inside the container you significantly reduce the material strength required to avoid implosion. Maybe add one more layer of protection by entombing the wax-sealed box in [waterproof cement](https://en.wikipedia.org/wiki/Roman_concrete). Fill the rest of the sea chest with cork and rocks. You want the chest to be able to take on water (so that it doesn't implode as well), but also slow the descent to the bottom, so that the box doesn't crack up after a 3 kilometer fall. Ideally, you'll design for it to hit the bottom at no more than 3 to 4 km per hour. **Recovery :** now your box is out of the range of humankind from the 1300s to the 1980s (most of the 700 years). Now you'll need to recover it. If your time-traveller can be on the boat that sent your manuscript to the bottom, he or she can pick good landmarks, choose an easy direction of travel (sunrise or sunset on a particular day of the year -- that can be re-computed in the future), and well estimate distance. You'd be much better equipped for recovery than most treasure hunters. Recovery won't be trivial -- you'd still need to spend a not-inconsiderable sum of cash to get subs down to depth looking for your box. [](https://i.stack.imgur.com/c8l9t.jpg) [Answer] Find a famous building (a cathedral or palace) that is being built in the 14th century and still exists. This building must have a tile floor in some rooms. Get access to the process of installing the tiles. Either as someone overseeing the installation, or as one of the workers. Inscribe the information on the bottom of the tiles. This might be during the night when no one is around, or while the tiles are in storage. Or possibly you are the tile manufacturer, and make sure you sell for the best price. The tiles get installed in the building. In the future, pry up the tiles and read the info. [Answer] **Hide safely in distant place and inside disinfected contained.** To preserve an manuscript from dangers of disasters, bacteria, fungi, animals and man, find a place which is free of them in desired time period, as Atakama desert, hidden chambers of Egiptian pyramids, Anarctica, or Greenland ice sheet, Crystal Cave of Giants in Naica, Mexico. There is more chance to survive of such valuable documents in any form if properly hidden. There would be good idea also to encapsulate it inside a clay container with mummification specifics to. Such containers in Egipt preserve i.e cats with inscriptions written on papyrus. "A thought is stronger than object". So it can be another, completely opposite way to preserve such manuscript from being damaged. Make it saint and valuable religion object. Such will be handled by special holy law. [Answer] Hide it in plain sight by [Voynich](https://en.wikipedia.org/wiki/Voynich_manuscript)ing it. Encode your information in a mystery language, and in apparently meaningless diagrams of plants, on vellum. Pass it to a collector. Interest in what the manuscript could possible mean will keep it in circulation, with many copies made and even put online once the modern age is reached making it easy to access when you need it. [Answer] ### Carve it onto clay tablets. The ancient Babylonian cuniform written language was carved onto clay tablets; whenever they needed to erase an existing tablet, they would just re-wet the clay and reuse it to make a new tablet with. However, when their cities were burned down, many of these tablets became baked clay and survived thousands of years to be discovered by archaeologists. As a result, if your protagonist copies the contents of the manuscript onto clay tablets and then bakes them into a kiln, they will become fired pottery that would easily survive 700 years buried in the ground. It would also be a lot cheaper than some of the more complex options endorsed by some of the other answers, because everyone used pottery back then, so contacting a medieval potter about producing these sort of clay tablets should be entirely doable and perhaps even relatively affordable. [Answer] This is a variation of [PcMan's answer](https://worldbuilding.stackexchange.com/a/192008/21222). # Paint it in stone Create a PC font that uses drawings of animals instead of roman characters. For example, a deer could be the letter 'd', and an ox could be the letter 'o'. Or you could make it so that each character represents an idea such as in japanese Kanji or old summer to be able to put a lot of text in less characters. Then paint it on a cave wall. People have found drawings in caves that seem to have been painted thousands of years old[citation needed], so it's feasible to make one to last just a few centuries. ]

[Question] [ I want my story to be science-based. I want there to be technical jargon that goes over most people's heads (the average Joe shouldn't question it). But I keep running into a problem... I'll come up with an idea that I think is great for my story. I'll even do some basic research and then say "this is why it works" and come up with an explanation that I deem plausible. Unfortunately, then I'll later learn that my idea is **literally scientifically impossible** for one or more reasons, like in [this](https://worldbuilding.stackexchange.com/questions/156075/stabilizing-synchronized-orbit) [this](https://worldbuilding.stackexchange.com/questions/156814/is-it-possible-for-a-universally-executable-virus-to-be-written-in-binary) [this](https://worldbuilding.stackexchange.com/questions/156546/giant-periodic-geysers) [this](https://worldbuilding.stackexchange.com/questions/157910/what-technology-is-needed-to-virtually-simulate-everything) [this](https://worldbuilding.stackexchange.com/questions/157527/can-a-planets-electromagnetic-field-be-strong-enough-for-wireless-electricity) [this](https://worldbuilding.stackexchange.com/questions/157822/what-should-the-size-of-these-secret-superhuman-organizations-be) [this](https://worldbuilding.stackexchange.com/questions/156361/can-someone-help-me-determine-plate-divisions) [this](https://worldbuilding.stackexchange.com/questions/158526/what-would-the-health-effects-of-a-giant-proportionally-scaled-human-be) [this](https://worldbuilding.stackexchange.com/questions/157897/is-my-historical-world-domination-reasonable) and [this](https://worldbuilding.stackexchange.com/questions/160027/can-a-robotic-eyeball-be-created-that-perfectly-replicates-human-vision) question. (and that's not counting the many questions I haven't asked here yet) This leads to the following conundrum: I have already become attached to my idea, or incorporated it into my world in some way. And yet I still want it to sound scientifically plausible to most people reading my story. --- What kind of steps should I take to resolve all of these issues? More specifically: ### How can I break down the task of resolving science-based issues into manageable chunks? Here's how I'm making this not too broad or primarily opinion-based: * I want a list of steps from people that have faced this problem before, breaking down the task of "fixing my world" in a manageable way * I don't want any opinions. Use examples, tell me how you have actually resolved these issues before. I don't want "maybe you could do this" answers, I want "Having run into this problem before, here are some steps that might help you and many others with this" answers. * Be detailed. Describe your approach to the problem so that not just I understand it, but other people who find this question can understand it too. * Please don't use "scrap your idea completely" in an answer. The best answer will: * Have the most detail * Be intuitively or easily understood (should not require follow-up comments asking for clarification) * Be considered helpful (has upvotes) * Bonus points for explaining how to avoid the issue altogether in addition to how to fix issues that already exist I believe that this question and its answers will be very relevant and helpful to a vast number of people on this site. --- Please use [this helpful answer](https://worldbuilding.stackexchange.com/a/48/68902) to the very well-received and helpful question [How can I break down the task of creating a world into manageable chunks?](https://worldbuilding.stackexchange.com/questions/2/how-can-i-break-down-the-task-of-creating-a-world-into-manageable-chunks) as an example of what I am looking for. Note: If there are any issues with this question, please let me know how I can make it more answerable. [Answer] **Step 1: Decide how scientific you want to be** There are three general levels of science fiction. 'Soft', 'medium', and 'hard'. Soft science fiction is science fictiong that doesn't even want to try and justifies everything with either new materials that aren't explained or new fields of science that aren't explained. A great example of something which is purely soft sci-fi is Star Wars - there's no part of it which makes sense, and lot of what is done (like the 'etheric rudder' that fighters use to maneuver against the vacuum of space) gets handwaved or a brief explanation at best. This is the type of science fictions that invokes Clarke's Third Law ('Sufficiently advanced technology is indistinguishable from magic') the most. (*cough* The Force *cough*) 'Medium' is when the author uses justifications and real science, but will occasionally violate something in takes a degree to notice. Take Asimov's robots, for instance. They have positronic brains - positrons being antimatter. How? Well, when Asimov first started writing them, he just said that they would figure out effective magnetic methods to keep them contained and effective ways of generating them. That's fine, but we've got no way to do that now - so it's medium. Something which sounds plausible, but can't be done with current tech. Alternatively, consider Asimov's odd element thiotimoline - it's a fictional compound, but Asimov's written entire papers on it's use and properties, so the readers with sufficient knowledge can easily figure out the rules without the writer constantly pulling things out from thing air. 'Hard' science fiction violates *no known rules of science*. This is something like 'The Martian'. In a hard science fiction story, everything is considered and applied by the author. The 'science fiction' in the title is just two separate components, really - it's a story about real science, but the science happens to be fiction. Now, it should be noted that these, in general, are guidelines. More than that, no story really focuses itself on any one aspect. A story which has a mostly hard approach which encounters a brief jolt of medium sci-fi makes for a great story setting. Rather, these are approaches to solving a problem. When you encounter something that you need to do i.e. 'Humanity-killing virus', 'Space travel', 'beam weapons', 'giant robots'. Decide what works best for your story - if you're writing a mostly soft sci-fi, using a hard sci-fi approach to a problem is very problematic - it'll leave your readers wondering why the rules were only applied there. Same with the reverse. Middle sci-fi can be applied to both, but take note of the tones involved as well - it can be just as jarring if not worth if implemented incorrectly. **Step 2: Decide whether you'll sacrifice story elements to the mechanic** Science is reality, not fiction. When you're writing a story, it's important to note that sometimes what you want and what's possible can't coincide. At that point, you're going to be forced to make a choice - do I keep story element X in, or do I obey science law Y? And remember, you're story is fiction. It's not reality, no one expects in to be. Shaving a little off the rules is fine. But violating them does cross a line - not necessarily a bad line! Star Trek wouldn't be exciting without the ability to warp, would it? But it does cross a line, so you need to say to yourself, whenever you have a problem 'Can I still have a good story without it, or is it so important that I'd be willing to handwave things for it?' Because, by deciding that, it helps your mindset in solving the problem. This is *after* you set the baseline for the level of sci-fi, because it's important to first establish the rules you'll be using, then break them. This is allowed - rules exist to be broken in literature. And even in sci-fi, it's allowed. There's very good sci-fi that introduces a plot point which ducks the genre. Sticking to the rules will just create something that everyone expects, so you're allowed to subvert them occasionally, it's not something good writers *can* do, it's something good writers *must* do. But on the flip side, if all you do is violate the rules, then you wind up with a hot mess that doesn't make sense. **Step 3: See how other people solve the problem** This is also to set a baseline. We know how hard FTL is, and we know all the problems with wormholes, and hyperspace, and colony ships, etc. etc. But it's a convention with science fiction these days - so it's OK. Same thing with time travel. Since the early days of sci-fi (literally, HG Wells) time travel plots have existed. And people are fine with it, so long as the rules are set up. (Or not! Dr. Who rules for time travel are all over the place, but the Dr. Who universe runs on soft sci-fi, so it's OK.) Seeing how other people solve the problem will give you a good idea of how to do it yourself. **Step 4: Research. Research. Research. Then solve it.** Now that you have your approach, you've decided what rules you're going to allow yourself to break, and you know how other people might do it, it's time. Run the numbers. Read the books. Look up the articles. Talk to an expert. Figure out what you can and can't do with the problem, and then once you've done that, solve it. It shouldn't be too hard, after all that. You'll know all the components, and simply fit them together. Part of the research process can also be asking other people how they would do it - that's why this site exists. (And also why we've got tags, like 'magic', 'science-fiction', 'hard science', 'reality-check', etc.) **Step 5: Present it to someone who isn't versed in the stuff** (Skip this step if you're writing hard sci-fi.) Most important part. Remember, you're telling a story here, not writing a paper. Take a friend / relative / acquaintance / internet writing group (I use the latter). Then write up the story with your solution - it doesn't need to be the whole story, just demonstrate how you solved it and give it to them. (Or just explain it verbally.) Take note of their reaction - were you too technical in your approach? That can happen - you know how to do something so you go overboard in explaining. In that case, just dial it down. It might sound weird, but occasionally I write something, do a few hours research to check if it's plausible, and then just keep it in. Sometimes it's enough to know that the problem simply can be solved and doesn't need you to go into specifics. Other times, you might get a reverse problem - you check something, figure it out, and then have your characters solve a problem. The reader says 'Hold on. That's not how X works." And that's when you realize something - you explained it from the perspective of someone who's spent a week researching things, and you skipped a few steps, starting from 'We insert DNA into frogs' and end with 'And then all the world's lilypads turn to gold'. Sure, it makes sense to you. But does it make sense to everyone? And then sometimes they'll say 'Well, why didn't you solve it like this?' And then you realize that you know you can't because of principle Y, but they don't know principle Y. And not only that, your different solution won't work anyway because of little known principle Z, but you decided that it wasn't worth rewriting a quarter of the plot because of it. Then you simply say 'That's right. It should be solved like that'. Because, after all, part of solving a problem in a sci-fi story is the *story* element. [Answer] Just as with your previous questions, I'm going to provide an answer that is unlike what you wanted or expected, but which I think is what you need to hear. Take, for example, this question: [Interstellar war tactics with no FTL capabilities?](https://worldbuilding.stackexchange.com/q/159742/21222) The author wishes to use quantum entanglement to allow for FTL communication. Quantum entanglement cannot be used for FTL communication, for reasons better left for a post in physics.SE. Nevertheless, it doesn't take a PhD in quantum mechanics to understand why, and this is something which a regular person can parse with 10 minutes of googling. A lot of sci-fi works do require FTL communication, though. So they use another technology, [the ansible](https://en.wikipedia.org/wiki/Ansible). It was invented by Ursula K. Le Guin in *Rocannon's World*, use again successfully in *The Left Hand of Darkness*, and then copied by so many other authors. So how does the ansible work? In the wise words of the late Sir Pratchett, *Sodomy non sapiens* ("buggered if I know"). Its usage in sci-fi is a real life application of another technology, one coined by Douglas Adams and called the SEP field, a.k.a. clarkean magic: it is a technology so advanced, that for us 21st century people the technology is for all practical purposes actual magic. If you are going to be scientific in a novel, explain the science that you understand, and **handwave** the one that you don't. Joe Haldeman wrote *The Forever War*, a seminal work in sci-fi, in which he nailed everything involving relativity. There is a part about societies operating on hive minds which he completely pulled from thin air though, but which nevertheless was awesome. Let's take this approach to non-sci-fi literature and see how it works. This is from Stan Lee's autobiography: [](https://i.stack.imgur.com/xHFdV.jpg) If you are hit in the face with a gamma bomb, you are more likely to become a cloud of plasma than to become a superstrong green monster. Does it make you enjoy the Hulk less because of that? So don't aim to be pedantic. Fiction is not about being correct, it is about creating an emotional connection with the audience (this is repeated more than 100 times in *Writing Fiction For Dummies*). [Answer] Don't sweat it. You don't need to be rigorous, you just need to be plausible. Some things on your list, yes I would eliminate as they are written. (I skimmed...) E.g. Plate tectonics -- look at plate boundaries, ring of fire, subduction zones, mid oceanic ridges and mountain ranges now on earth, file off the serial numbers. E.g. A moon at the L1 point won't work naturally. So either you have an un-natural way of doing it, or you put the moon in a long period orbit around it's primary, or you put it in the L2 stable point, which may make it way too far away. Another technique is to leave it as a mystery. Visitors comment, "That shouldn't be stable. Why is it stable? Not solved until volume 4.... Larry Niven ran into this with Ring World. Someone at MIT figured out that the ring world was unstable. The repercussions of that gave us 3 more Ringworld books. Really large people is one I would just discard -- or you have to work out the modifications to make it work. There are certain problems that even Robinson Crusoe faced: \* Food \* Clothing \* Shelter Once you have more than a few dozen people, you have some degree of specialization. An old geezer, crippled while mastodon hunting is really good at knapping flint spear points. A crone knows all the herb lore. As the numbers increase you need some form of economy. Can still be barter and trade, but it has an established place, and often established values. You have social problems to solve: * How to treat rule breakers? * how to get a mate? * how to provide for children? * how to deal with the old? A world builder should read some survey books on anthropology. If there is any form of trade, you need to understand some degree of economics. Both macro and micro. Let's look at an example: Anne McCaffrey's Pern books: Even with high strength boron skeletons it stretches plausibility to have a flying creature big enough to carry a person. Pern has other problems to trap the world builder: Over and over you get numeric issues: E.g.: How large is a hold? How much land is farmed? Is this enough people to support a craft? What is the ratio of dragon riders to other people? How much do dragons eat? Is this a reasonable surplus for holds to tithe? You have Gathers -- Fairs. There seems to be some degree of money, 'Marks'. But it's not clear how an ordinary person gets them. These things -- mostly "TheyDidTheMath" problems on Reddit -- contribute more to the failure of worlds to be convincing to me. Threadfall is episodic falling in bands 4 hours long with separations of 22 hours at peak. But a given fall is normally handled by on Weyr -- 300 dragons. If a dragon can fly at 5,000 feet, the horizon is 86 miles away. Can humans see a stream of thread that far away? This is more important than the dynamics of a planet that is spinning fast enough to spin off thread spores, but not spin off it's atmosphere. We're asked to accept that an eccentric orbit can bring two planets close enough to scatter spores from one to the other for a 50 year period of time, and that the source planet doesn't run out of matter. And what do threads eat when they are at home? We know a burst of dragon fire can destroy a clump of thread. If a dragon flies at 30 mph, that's about 50 feet per second. So a 2 second flame would do a 100 foot clump. How far away can we see a 100 foot something and be sure it's there. The moon is 1/2 degree across. It's bright against dark. No problem. Suppose we go down to 1/10 of that. 1/20 of a degree. About 1/1200 of a radian. So you can see something about 1000 times it's size away. So 100 feet \* 1000 = 100,000 feet -- about 20 miles. This 'feels' about right in line with sailors calling out the visibility of land, or ships. This puts a 40 mile diameter circle in view. Consider a weather patrol, where you jump 20 miles forward and scan, 20 forward and scan... How long does it take to patrol the entire planet? Ok, you're a wingmaster of the U.S. You have 1000 x 3000 mile rectangle to patrol It's 150 hops wide by 50 hops tall. To cover it once at 20 mile visibility takes 7500 hops. Probably want to do it right, so you do it 3 times, with staggered positions. 22,500 hops. 12 dragons. 1900 hops per dragon. *Between* costs 6 seconds. A good careful look 24 seconds. 2 jumps a minute. 950 minutes. 16 hours. Double that for Canada. Double again for Russia. This sort of exercise doesn't even make into the book, but it shows why some land would be ignored. A world builder can make good use of a spreadsheet to make his models of how his world works. --- ***General Rule: Don't invent your world from whole cloth. Seek out parallels and learn how they work. File off the serial numbers and claim as your own.*** If you are going to have wars, you need to understand warfare. If it's a medieval tech world, read up on ancient warfare. There's actually a journal for it and a podcast. While called ancient warfare, it covers up to the common use of firearms. If you're stuck try the history subreddit on reddit.com or the history stackexchange. But read up on medieval culture, and the feudal system. Ken Follet does a nice job of capturing the complex of rights and duties in his novel "Pillars of the Earth" One example of someone who got it wrong is David Weber's Honorverse. While they have the spatial equivalent of naval warfare, he never really uses the notion of commerce raiding. Naval warfare from 1800 on had a huge component of interdicting trade. Destroyers were originally made to be fast commerce raiders and were only later adapted to anti-submarine warfare. [Answer] ## It doesn't have to be rigorous, it just needs to be plausible and consistent. First you have to decide how hard your sci-fi is going to be, the harder it is the more rigorous it has to be and the more research you are going to have to do, at a certain point you reach diminishing returns because you can't know enough (literally, no one human can keep up with everything in even a single field of science) and at a certain point you are inventing and engineering technology not writing. **The most successful sci-fi writers don't say how it works they just make the technology plausible and consistent.** **What do I mean by consistent**, that just means you have to have rules for your technology and stick to it. Best way is to start vague than get more specific as the stories continue. but have the basic rules in your head from day one. A good example would be Larry Niven in his writing FTL technology exists it has a few rules (only sapient creatures can steer them because FTL steering relies on psychic technology, if you use a hyperdrive in a gravity well you disappear from the universe, permanently, etc. characters know these rules and have to work within in them. The physics of how they work is never explained and most character would not be expected to know how they work anyway. His stories are full of such technology and it always has known rules, X can do A but not B. **He doesn't tell you how his technology works** not in any detail his FTL tech is only ever described as it moves the ship into hyperspace and out that's the entire explanation, but he does tell you the rules for it. These rules also help shape your stories, drone ships and FTL missiles don't exist because FTL need a brain to steer. This starts to mirror how a [hard magic system](https://www.youtube.com/watch?v=iMJQb5bGu_g) has to be written. Asimov is another example, he doesn't tell you how his robots work just the rules they have. His stories often explore the full implications of those rules. Your story takes a nose dive when you violate your rules, the latest *Star Wars* is an example, for a long time light-sabers were fantastical weapons, we don't know how they work but we do know they cut solid steel and lop off limbs and heads easily and are incredibly dangerous, getting cut without is debilitating to deadly. we are not told the rules we are shown the rules (they don't have to be explicitly stated). Then all of a sudden, because it is a main character, getting cut from neck to crotch with one is something you can walk off, and it drags the audience out of the story because the rules they know get tossed out the window. the suspension of disbelief is shattered not because we know light-sabers can't exist (they can't) but because the rules are not consistent. It also helps that there technology is very advanced, if someone in a WW2 story was pulling out light-sabers it would be a bigger disconnect, I will get to this in "plausible". **What does it mean to be plausible**. This is a more grey are, here is were your scientific knowledge comes in, you do need some rigor in your work, you technology has to be believable. The first step in this is often don't try to use existing terms make up new ones, Asimov had positronic brains, a nonsense term, if he has called them vacuum tube brains many people would hit cognitive dissonance because vacuum tubes are known technology with known limitations, so often making up new technology is easier than meshing existing technology. Godzilla is popular despite being completely impossible, how do they handle rigor, they don't for this one thing, the closest they come is saying the monsters are nuclear powered. Of course you are still going to need laymen levels of rigor, your average person knows you can't have hollow planets or flying people without technology or at least wings. but even this can be violated if you do it once and and obviously Godzilla being the example, Godzillas violation of the normal rules is what makes the story, and people in the universe acknowledge science as they know it is being violated. What gets writers in trouble is when they start violating these laymen levels of understanding for no good reason, when it neither serves the plot nor adds anything to the story. Violate laymen rigor too hard and it pulls you out of the story. And the more often you do this the more often you risk this effect, do it enough and a bad response is guaranteed. Lets try two examples, "signs" and "gremlins" alien life harmed/transformed by water. We will ignore the problem with life being made of water, because people didn't hate gremlins but did signs, why. two problems choice and intelligence. Earth is mostly covered in water and water frequently falls from the sky, so aliens adversely effected by water don't want to be here. In gremlins Gizmo don't have a choice about being here (we aren't even given an origin), Gizmo and the gremlins are also shown to not be that bright, inventive but primitive. Meanwhile the signs aliens are intelligent enough to build spaceships yet would choose to come to Earth, naked no less. Even for a laymen there is no good reason for what they are shown to be an intelligent creature to come to earth just based on our everyday experience with earth and thinking creatures. Worse while the water thing is central to the plot to gremlins in signs it is presented as a twist, which means the story expressly did not need it to stand. Another example is *Jurassic Park*, getting dinosaur DNA from mosquitoes is probably impossible, but it is sufficiently plausible if you are not a paleontologist. At the time it was written it would have even been plausible (plausible enough with a lot of luck and money) to paleontologists. Even a reasonably scientifically literate laymen could not really pull apart the story yet it is still wrong, but it was believable enough to not interfere with reading/watching the story. As an aside I can't recommend enough extra credits review of the the [history of sci-fi](https://www.youtube.com/playlist?list=PLhyKYa0YJ_5AuEhpcGAo4ngmSDKuFgZZx) writing, the series alone may help you a lot by seeing what other authors did or did not do and how they hold up, especially after episode 26 when you get to modern sci-fi writers where the public starts being scientifically literate and hard sci fi starts becoming popular. Lastly use this site, but don't ask how can I make this work scientifically, ask how can I make this plausible with the least amount of handwavium. [Answer] ## Start from the mechanism I'm a devout adherent to [Sanderson's Laws of Magic](https://coppermind.net/wiki/Sanderson%27s_Laws_of_Magic), named after fantasy author Brandon Sanderson. All three of these principles are much easier to achieve if you start by defining *the thing you want to change* about the physics, geography, geology or whatever, of our universe to get your fantasy universe, and then work forward from that to determine what the consequences would be. That way you get 'for free' a pseudo-logically (and pseudo-scientifically) consistent universe that readers can 'explore' in their own minds at the same time as exploring your story. Of course your determination of what you're going to change will be influenced by the sort of world you want to create, the cart before the horse to an extent. It may take some experimentation to find a change that produces a set of consequences that you're happy with, adding the fantasy elements you want to introduce without adding too many elements that you don't. In far too many cases, the unwanted elements include things like "everybody is dead", or "life could no longer exist", or "that person would immediately be imprisoned/enslaved/killed", and you have to go back and tweak things again. But that, to my mind, is a fun part of the worldbuilding process. ## Some examples 1) If you wanted to write a story about [building-sized mecha battling giant monsters](https://tvtropes.org/pmwiki/pmwiki.php/Film/PacificRim), you might start (as those screenwriters did) with the change "there is an underwater portal to another dimension where the physics is compatible with the creation of building-sized alien animals, inhabited by a race of aliens with locust-like destructive tendencies and the mega-(bio-)engineering capabilities to create such animals and set them on earth". If you followed this process, however, you would develop the consequence "we would nuke them", followed by "we would nuke them again", followed by "we would nuke the rock formations *around* the breach to bury it in kilometers of rubble" and you would realise that your worldbuilding needed a lot more work. 2) The wonderful madness of Terry Pratchett's Diskworld series (everything from the flat-earth-held-up-by-four-elephants-standing-on-the-back-of-a-tortoise geography to the speed-of-dark and the entire magic system, and everything in between) is based on one fundamental premise: "the laws of physics are as a typical human would expect them to be", ie they match common sense. The craziness comes from the fact that Pratchett *embraced* all of the insane consequences of such a change and either played them for laughs or used them to parody the more 'boring' real-world equivalents. 3) To take your [world-domination-in-Sel question](https://worldbuilding.stackexchange.com/questions/157897/is-my-historical-world-domination-reasonable), you basically proposed the change "take Medieval Europe with a few standard geopolitical twists, there is an extremely savvy national leader" and asked if the consequences would play out to the world that you were looking to create. All I did in my answer there was to work it through, conclude that it probably wouldn't, but go back and tweak the mechanism slightly into one that I thought would play out closer to your desired outcome. ## How to implement this approach There are two questioning steps you need to work through with this approach, assuming that you start with a vague sense of the world you want to end up with. The first is to ask "what mechanism might cause this effect", and then having specified the mechanism, you have to ask "what consequences does this mechanism have" and check that you get back to the place you want to be. You're right that questions of the first form are often closed for being too broad or opinion-based, because the answers are often "you need to change too many things and everyone dies" or "there are 1001 ways, choose one". If you can hit the sweet spot in the middle you can get some good questions - the whole "Anatomically Correct" series is a good example. The second part again can be too broad, but if you focus the question on a particular 'area' of consequences - "how does change X affect people's ability to Y" or "does the existence of X mean Y is (im)possible", you can again get some interesting questions. [Answer] ## There is no royal road *"How can I break down the task of resolving science-based issues into manageable chunks?"* There is really only one way to do it: learn how the world works, so that *you know more about how the world works than your readers do.* ("Readers" can be watchers, listeners, players and so on. The people to whom you are telling the story.) Note that the goal is not to accumulate more knowledge than most people, but simply to accumulate more knowledge than your target audience; and to use that knowledge to create a world that your audience believes. [It is said](https://en.wikiquote.org/wiki/Euclid) that once upon a time the king of Egypt, Ptolemy something or other, asked [Euclid](https://en.wikipedia.org/wiki/Euclid) how to approach learning geometry faster, so that he could balance his desire for knowledge with the performance of his kingly duties; Euclid answered back that there was no royal road to geometry. This means that the general approach involves the following steps: 1. Have an idea for a story. This is the hardest part, and most people cannot do it. Your questions show that you are imaginative and able to come up with plenty of story ideas, so you are already way ahead. 2. Identify your audience. It is one thing to tell a story to a small child (Disney), another to tell a story to a pre-teen (Star Wars), yet another to tell it to a teen-ager (Star Trek) and yet another to tell it to an adult. In a story for small children the only requirement is plot consistency (i.e., don't forget who killed the dragon); in a story for pre-teens the world must make sense on the individual scale, but large scale consistency is irrelevant; in a story for teen-agers the world should make sense on human scale, because teen-agers have already figured out what makes people tick; but in a story for adults the world should be fully self-consistent, period. This is all about levels of consistency, of which more below. 3. Explain what you must in order to get the desired level of world consistency, *but not more*. This is important. Nobody is ever interested in more detail than it's needed for the story to work. When you read a story where there *seems* to be more detail that what is strictly needed, and yet you find yourself enjoying the story, you will soon realize that the apparently spurious details had actually a very good reason to be there; maybe they set up a larger story arc; maybe their purpose is ornamental; maybe they are actually comments on some aspect of the plot, or of the characters, which you have missed on first pass; but, if they do not detract from the enjoyment of the story it always means that they have a reason which you can find. Sometimes it is even the case that when you actually examine the apparently useless details you will realize that *you have completely missed the real story*, and that you need to go back and re-evaluate everything. To summarize, assuming that you have already created or acquired a basic story idea, the next step is to identify the required level of consistency: * Is this a story for small children? Then only simple plot consistency is needed. Think *Little Red Riding Hood*, *Sleeping Beauty* and so on. Everything goes, as long as you keep track of who said what and who did what. * Is this a story for pre-teens? Then plot consistency is needed, and *in addition* the world must make sense on an individual's level. Physics can be twisted in any shape, as long as on an individual's scale things work as they really do. Star ships the size of a family car can go faster than light? Sure! A pre-teen knows that car-sized objects can travel fast from place to place, so this does not violate their assumptions. A tiny device hidden in a robot projects the three-dimensional moving talking picture of a pricess? Sure, but you need to explain that this is *advanced technology*. Pre-teens know that there is technology to have moving talking images, so this is a simple extension from their point of view. * Is this a story for teen-agers? Then plot consistency is needed, the world must make sense on an individual's level, and *in addition* the world must make sense on human scales. No car-sized star ships. No light sabers. But *big* star ships? Sure! We have seen our rockets go to Mars and Jupiter and Saturn, and the story is *in the future!* Teen-agers expect that the crew of the *Enterprise* has to eat, so you need to explain where the food comes from; but they don't yet fully appreciate macro-economy, so you *do not* need to explain why the Federation exists and why it is expending a lot of effort and resources in maintaining a manned Star Fleet. * Is this a story for adults? Then plot consistency is needed, the world must make sense on an individual's level, the world must make sense on human scales, and *in addition* the world must be fully self-consistent. The key part here is *self*-consistent. The world of the story does not have to be consistent with the real world; it must be consistent with itself. This is why science-fiction and fantasy stories are possible: readers are perfectly willing to accept any self-consistent world; but they rebel and leave bad reviews if they feel that they were cheated and the world of the story breaks self-consistency. And here we come to the gist of your question: how to resolve science-based issues. What you need to do is to establish what *science-based issues* are there in the first place, and then learn enough about them so that you know how to address them. The point being that you do not need and you do not want to place all the aspects of your world in the science-based bucket. Remember that all you need is a self-consistent world. *Some* aspects of the fictional world are how they are because they are how they are, and that's it. Only the remaining aspects of the fictional world can go into the science-based bucket. ## Examples * Taylor Anderson's [*Destroyermen*](https://en.wikipedia.org/wiki/Destroyermen), an entertaining parallel-world adventure series of novels, following the crew of an American *[Wickes](https://en.wikipedia.org/wiki/Wickes_class_destroyer)*-class destroyer which is displaced to a parallel timeline during the [Second Battle of the Java Sea](https://en.wikipedia.org/wiki/Second_Battle_of_the_Java_Sea) (March 1942); in that parallel timeline Earth is inhabited by two native sentient species, the warlike reptilian Grik and the relatively peaceful Lemurians, plus the humans brought there by several timeline-displacement events. Besides the expected military fantasy, it includes at least two rather cute and well-thought cross-species romances. The time displacement and sentient reptiles are *not* science-based issues. They just are. But the rest of the world presents plenty of science-based issues, and they are quite deftly solved. How does the crew of the the (real historical) [USS *Walker* (DD-163)](https://en.wikipedia.org/wiki/USS_Walker_(DD-163)) acquire fuel for their ship? How would a reptile which lacks lips pronounce English words? How to our WW2-era American crewmen adapt to life in a society of shapely Lemurians? How does an r-selected species which has a juvenile non-sentient life stage develop a functional society? *Those* are issues which need to be resolved consistently. * David Drake and Eric Flint's [*Belisarius*](https://en.wikipedia.org/wiki/Belisarius_series), an alternate history military SF adventure, featuring an evil AI sent back from the future to organize an Indian Empire and take over the world, and a good (but much less powerful) AI sent to the Roman Empire of Justinian and Theodora to help the real historical general [Flavius Belisarius](https://en.wikipedia.org/wiki/Belisarius) to fight against the forces of evil. The two AIs are *not* science-based issues. They just are. Moreover, to make for an interesting plot, the good AI is weak, small, and the only superpower it has is to be able to speak telepathically to Belisarius himself. (Actually, to speak telepathically to one person, selected by a process similar to imprinting; it was lucky that the person who found it did not keep it for himself but gave it to Belisarius.) No long-distance vision, no weapons, no teleportation. This sets up an entertaining conflict, in which Aide (the good AI) and Belisarius must co-operate closely if they are to be successful against the existential threat. Plenty of science-based questions remain to be solved, because the rest of the world must still work as the real world does. How to set in motion an arms race in the 6th century Eastern Roman empire? How to resolve the real historical rift between the mainline orthodoxy and the monophysite heresy which risked splitting the Empire? How to acquire a naval power in the Indian ocean? How to fight a successful war in Mesopotamia against a large invasion force, complete with reasonably good logistics and crude gunpowder artillery? * David Weber's [*Honorverse*](https://en.wikipedia.org/wiki/Honorverse), a sprawling and *very tightly* plotted space opera / military SF series, set in a world where two kinds of FTL travel *and* one kind of FTL communications are available. Again, the FTL travel (by means of wormholes and / or Warshawski sails) and FTL communications (by means of grav pulses) just are. They are, they are not explained in any serious way, and nobody cares. But the rest of the world has to be consistent; battles must make sense (the series has been called "missile porn" for the loving detail in which battle tactics are presented), the economic base must make sense (albeit with a massive right-wing "neoconservative" bent, but hey, it's consistent), people must act like people actually act, and so on. This is a good example of following through with the not-real-world aspects of the fictional world. Medical science is very advanced, so that most people can have any injury repaired by regeneration; but what happens to those few on whom this doesn't work? How does society treat them? How do they perceive themselves? Humans are friends with a race of sentient telepathic cats. How does a society of telepaths view non-telepathic humans? What happens when a member of a telepathic race loses this ability? In a world where technology by and large has solved all basic necessities of life, can there be dictatorship and perceived poverty? (Yes, and yes.) How can human society thrive on a poisonous planet? (With difficulty and compromise.) And so on. (Ah, and did I mention that it is *tightly* plotted?) * John Scalzi's [*Old Man's War*](https://en.wikipedia.org/wiki/Old_Man%27s_War) series is a very good example of how well can a good, thoroughly verisimilar story be set in a most fantastic world. Since the first book of this series was published in the 21st century I will avoid any spoilers, but know that it features bionic enhancements, resurrection, AI implants and so on -- and yet it remains self-consistent, and keeps the characters profoundly realistic. Now we shouldn't assume that this approach of building a self-consistent world by merging the real world with one or two or three unexplainable fantastic elements is new; it is not new, it is three thousand years old. Think of Homer's [*Iliad*](https://en.wikipedia.org/wiki/Iliad), which can be seen as the sort of military SF a genius would write in the 9th (or 8th, or 7th, we don't know) century before the common era. There are gods who intervene directly and personally in human affairs; the notoriously quarrelsome Greeks are united under a common leadership against an external foe; some of the characters have superpowers: this is just how it is, Homer does not explain where the gods come from, or how come that Greece has a paramount king. But the rest of the world is thoroughly self-consistent and realistic: in the end, the Iliad is an exemplary story about the power of love and friendship and the dire consequences of a serious managerial mistake. [Answer] > > I want my story to be science-based. I want there to be technical jargon that goes over most people's heads (the average Joe shouldn't question it). > > > Why? I ask this not to discourage you or to be pedantic, but rather because I think your answer to that question will guide you in your next steps. I don't think there's a single right answer to the conundrum you're describing—how to make an idea you're attached to scientifically plausible—but rather a variety of solutions that get you to different places. After all, having a story be strongly grounded in known science doesn't make it good or bad, it just puts some constraints on the story that make some things harder and other things easier. You'll want to do different things depending on why you want those constraints in place, if you really do want them at all. If you just think it would be cool to take existing scientific information and synthesize new, plausible ideas from it, just for the sake of doing that, you might consider becoming a scientist, rather than a science fiction writer. After all, that's a significant part of the work of a scientist. But scientists spend years and years in school before they're even capable of doing original research, and even then they specialize in a very particular region of science as opposed to science in general. If it's that hard for a professional scientist, it's going to be all but impossible for a fiction writer, as it sounds like you've gotten a feel for via your other questions. So, as a fiction writer, I think being rigorously attached to grounding your writing in known science basically means you can't propose any new scientific ideas—you can only work with what we already have. This closes some doors (like most far-future stories) and opens others (like thought-provoking commentary on current technology). I don't think the ideas you've been proposing really fit into this approach, so maybe you're not interested in doing things this way. If you want an example to follow, though, Neal Stephenson's [*Cryptonomicon*](https://www.harpercollins.com/9780380788620/cryptonomicon/) is a good point of reference. There is some fictionalized technology, but it's abstract things like operating systems, cryptographic schemes, etc. that largely stick to what was known to be possible at the time. Of course, that means the furthest the book's timeline goes is the late 1990s, but the book is able to explore themes around the flow of information in a precise, complex manner that's found it an enthusiastic audience among computer geeks and the like. Of course, in order to do things this way, you have to have pretty strong knowledge of what the existing state-of-the-art is in your field of interest. It doesn't really work to come up with an idea and then try to work backwards from it to a justification; you need to pick a subject and get a good comprehensive grounding in it, then come up with ideas based on what you've learned. Science and technology subjects are too complex and interconnected to approach ad-hoc if you really want to base your writing in them. You can look at recent issues of journals, conference presentations, etc. if you want to get an idea of what the state-of-the-art looks like in a given field. If what you find goes over your head, take classes, read textbooks, make friends with people in the field, practice, etc. until you have a good enough grounding to kind of grok what's going on at the field's cutting edge. You don't need to know as much as a professional, but you need to have a decent idea of what the professionals think about and are concerned with. Otherwise, people are going to think your writing is silly, poke holes in it, etc. if you present it as totally based in fact. Many of the renowned hard sci-fi authors have formal scientific training—Asimov had a PhD in chemistry, Clarke had a B.S. in physics and math, Stephenson himself has a B.A. in geography with a physics minor that he picked [to get as much time on the university mainframe as possible](https://www.electricinca.com/56/stephenson/bio.htm), etc. Now, as I said before, I'm not really sure you want to do things this way. The ideas you've been proposing in your other questions read as pretty fantastic to me and also not really based in a strong technical grounding in the subjects they touch on. There's nothing wrong with that from the perspective of writing fiction in general, but I think it does conflict with your stated desire to strongly base your ideas in known science. If you want to come up with cool ideas first and then figure out a scientific basis for them afterwards without knowing the relevant science very well, you're going to get frustrated if you don't do some hand-waving at some point. If all you want is some fancy-sounding technobabble to justify elements of your setting, the sort of stuff an "average Joe wouldn't question", you don't need to know any science for that at all. If you want to give your technobabble a kind of "scientific sheen", look over some recent papers in whatever field is relevant and lift some cool-sounding jargon from them to use. You don't even need to know what the jargon actually means in the field in question; it's purely aesthetic at this point. Of course, I'm not really sure why you even need to give this sort of justification for your sci-fi tech—it runs the risk of putting your readers to sleep if you spend more than a few words on it. On the upside, you don't have to worry about checking your ideas for scientific plausibility. The kind of stories that work that way aren't really interested in a deep exploration of a scientific topic anyway, of course. They're usually more interested in the stuff "regular" literature is—social relationships, people's thoughts and feelings, culture, etc. If that's what you really want to write about, and your sci-fi setting is just a means to give that stuff an interesting structure, I wouldn't worry too much about the scientific grounding for your world. It won't matter anyway—no one's going to read your writing for its scientific content, and any paragraphs dedicated to it are just going to feel like a distraction from your characters and plot. It's worth remembering that many of the science fiction writers most beloved by intellectuals, including of the scientific variety, hardly concern themselves with the nitty-gritty technical details of science and technology at all. One of my closest friends is a professional physicist; when it comes to sci-fi, they like writers like Stanislaw Lem and Ursula Le Guin. Those writers give really interesting food for thought, and they pick the elements of their settings not for their scientific bona-fides but rather to be maximally interesting. For instance, my friend once lent me a copy of Lem's [*The Cyberiad*](https://www.penguin.co.uk/books/256/256135/the-cyberiad/9780141394596.html), which is wildly fantastic but chock-full of funny paradoxes and mind games that are great fun for anyone with a philosophical bent. I don't want to spoil any of the stories, so suffice to say that they play all sorts of entertaining ditties on ideas like simulation, identity, worth, entropy, computation, and the like. In service of this, plot elements are introduced like square-shaped stars and medieval kingdoms in tiny boxes that would never pass as scientifically plausible, and yet managed to delight my scientist friend (and myself). In turn, I once lent them Le Guin's [*The Dispossesed*](https://www.harpercollins.com/9780061054884/the-dispossessed/), which has a rather poetic take on the process of developing a physical theory; consider this quote: > > He looked at the book the older man held out: a thin book, bound in green, the > Circle of Life on the cover. He took it and looked at the title page: > “A Critique of Atro’s Infinite Sequency Hypothesis.” It was his essay, > Atro’s acknowledgement and defense, and his reply. It had all been > translated or retranslated into Pravic, and printed by the PDC presses > in Abbenay. There were two authors’ names: Sabul, Shevek. > > > Sabul craned > his neck over the copy Shevek held, and gloated. His growl became > throaty and chuckling. “We’ve finished Atro. Finished him, the damned > profiteer! Now let them try to talk about ‘puerile imprecision’!” > Sabul had nursed ten years’ resentment against the Physics Review of > leu Eun University, which had referred to his theoretical work as > “crippled by provincialism and the puerile imprecision with which > Odonian dogma infects every area of thought.” ‘They’ll see who’s > provincial now!” he said, grinning. In nearly a year’s acquaintance > Shevek could not recall having seen him smile. > > > There's no "real physics" in this at all in terms of the scientific content, but it has an interesting take on academic politics that both fits the themes of its setting and might have some familiar elements for any scientist who's ever worked in academia. This kind of sci-fi writing is perhaps more likely to appeal to practicing physicists than hard sci-fi—after all, they spend plenty of time reading actual physics, but whitepapers and textbooks are unlikely to touch very deeply on the social experience of being a scientist, which a novel is better positioned to take on. Of course, the core question of *The Dispossessed* is, maybe, "What sort of cultural difficulties might bedevil an anarchist planet?", which contemporary science has hardly anything to say to us about at all, but is an intriguing and ambitious question for a science fiction author to tackle. [Answer] For the bonus points: "I want there to be technical jargon that goes over most people's heads." To avoid the problems this causes, just don't do it. There is always someones head you just can't reach over, and almost all your readers will know a bit more then about something then you do, at which point your jargon risks becoming BS that will date and grate. Does the jargon actually help progress your plot or is it there for decoration or word count reasons? ]

[Question] [ I'm working on a story set roughly 2 million years in the future involving future archeologists discovering evidence of a nuclear war and ensuing winter wiping out humanity. What sort of clues would survive for that long? [Answer] The archeological evidence would be the presence of [long lived fission products](https://en.wikipedia.org/wiki/Long-lived_fission_product) or [activated material from neutrons of fusion bombs](https://en.wikipedia.org/wiki/Neutron_activation). Ice cores from Antarctica (if the ice is not melted for global warming) or sediments would not only contain traces of the mentioned substances, but indicate exceptionally high levels of ash in the air only to be found in supervolcano eruptions and temperature proxies would indicate very cold climate. [Answer] ## It Depends It depends on the technology level of your futuristic society. If they already know about radiation and can detect it, then some radioactive isotopes will still remain. If they do not have advanced technology, then they will have to rely on digging up [layers of soot/ash from the nuclear winter](https://en.wikipedia.org/wiki/Nuclear_winter#Mechanism), or discovering vitrified remains. ## Radioactive Isotopes Nuclear fission creates many radioactive elements. Each has it's own lifespan (measured in [half-lifes](https://en.wikipedia.org/wiki/Half-life) it is constantly radiating ionized parts of itself off (that's why they are called "radioactive") and becoming other elements, some still radioactive and some stable. Only a few of them would still remain after 2 million years: [](https://i.stack.imgur.com/0T3Rv.jpg) Generally speaking, [after 20 half-lives, radioactive isotopes have only negligible activity.](http://www.radiationanswers.org/radiation-questions-answers/radiation-basics.html) So, depending on the technology level of your futuristic society, they might be able to detect some of these remaining radioactive isotopes, even tiny trace amounts. ## Soot Layers Nuclear winter is produced by large having so much soot in the atmosphere that sunlight cannot warm the earth enough and winter-like conditions set in. Over time, this soot will eventually precipitate out of the atmosphere and end up as layers in the geological record. ## Vitrified Remains However, some of the most obvious clues would be vitrified materials. These could be detected by even a stone age society. However, without knowledge of nuclear heat, they might not understand the significance of vitrification. Nuclear weapons produce extreme heat in ways not found in any other natural phenomena normally on earth. One such process is vitrification of stone and other materials. There is a current example today--[in Scotland, some 60 stone forts supposedly have vitrified walls](https://skeptoid.com/episodes/4326): > > For over 250 years, archaeologists studying ancient Scottish ruins have reported a type of construction said to defy explanation. About sixty of these rough stone wall enclosures have been found throughout Scotland, and even a few scattered across mainland Europe. Most are prehistoric. Called vitrified forts, they're notable for a unique and surprising feature. The rocks that make up the walls were originally stacked dry, with no mortar; but have been fused together into a solid surface through a process called vitrification, the transformation into glass. How can rock be melted into glass using prehistoric technology? Some say that it can't because the temperatures required to do it are far too high, and that the only plausible explanation is an ancient atomic blast. > > > Regardless of what vitrified these forts, they still offer clues as to what vitrified remains might be like. So, vitrified structures, particularly ones still obviously man-made, would be very significant clues. [Answer] The first thing is that archaeologists in the future *will* know we were here, and that we had some pretty sophisticated tech, because we'll get fossil plastic imprints. Fossil shells are commonplace throughout the geological record. We have enough plastic junk around that some of it will be lost in mud pits. Over years that plastic bottle or whatever will degrade, but it will leave its imprint in the same way as the shell of an ammonite. They probably won't know exactly what it was or what it was made of, but they'll know it wasn't simply metal or wood (because that would corrode too fast). Evidence of a nuclear war - that's a lot harder. The fallout from a nuclear war isn't likely to last longer than a few decades, and whilst that's probably enough to kill off humanity, it's barely a flicker geologically. The meteorite which killed the dinosaurs (hypothetically; it's still only the best theory so far) may have been the largest planetary disaster so far, but the only evidence we have is a hole in the ground and a thin layer of iridium in the strata. There's ash in the strata too, but there's good evidence for much of that coming from the Deccan Traps. We have absolutely zero direct evidence of any global ecological effects from the meteorite, even though best guess from sophisticated models of impact effects and climate is that it caused a few years of nuclear winter, but that's not direct evidence. All we know is that dinosaurs were alive at some point on one side of these events and dead at some point on the other side, within a margin of tens of thousand years either way. The simple fact is that evidence of global events doesn't survive. If there's no good evidence on Earth, how's about elsewhere? Satellites and space junk generally are all going to have either fallen to Earth or drifted off, so that's out. That leaves one good place for evidence - the Moon. We can reasonably assume that our archaeologists are a curious species, and if their tech is hot enough to be looking for evidence of previous civilisations and nuclear war, they've probably made their own first steps into space. In that case it simply isn't possible that they haven't seen the Apollo remnants on the Moon, which will still be there for millions of years. The Apollo missions won't say anything about a nuclear war, of course. But since this is your world, you could suppose that someone sent a one-way rocket to the Moon containing a decent library and some kind of self-learning language course so they can read it, and carved a big sign on the surface to say "look at this!" This library would naturally include details of how we killed ourselves, partly just for their information, and partly as an example of what not to do as a civilisation. I could see Richard Branson and Elon Musk setting this up together, and a few dozen astronauts heading off on a one-way mission as heroes whose names will be legendary for some future civilisation. [Answer] # Fossil Evidence There are millions of bits of dinosaurs, and around 10,000 "full" dinosaur fossils. Dinosaurs lasted for about 160 million years, and died off about 65 million years ago. In terms of biomass, I'll assume humans are about as dominant as dinosaurs (all of them together) are. Dinosaurs left 1 artifact every 160 years on the planet (and one "full" specimin every 16000 years). So a full human skeleton is unlikely to be found by this future civilization. Bits of human skeleton are likely to be found. I suspect industrial civilization artifacts far outnumber us in volume and count. Buildings are huge, our garbage is everywhere. So I suspect they'll get fossil evidence of the strange thing we build (buildings, cars, plastic bottles). Both of these would show up around about the same time as our civilization discovered and understood dinosaurs. # Geological Evidence of War There are two kinds of geological evidence. The first is the direct blast effects of the nukes. Spread all over the world at the same strata will be nuclear-fuzed glass, both from direct blast and from erosion/ejecta. These will be similar to comet/asteroid impacts that we have geological evidence of. This layer will also have a large number of strange isotopes. A concentration of moderately unstable isotopes of medium-long length will be spread over the planet, and concentrated in this layer. These won't match anything else in nature really; unlike the dinosaur-killer, whose isotope mix matches other asteroids, it will be a mystery for a while where this mix comes from. Only when they themselves discover radioactive decay, nuclear transmutation, and nuclear chain reactions/bombs will those isotope mixes start to make more and more sense. Some larger bombs may even leave craters large enough to last millions of years, depending on what kind of bombs are in fashion at the time. Such lakes would have large amounts of the nuclear glass in them. Connecting said nuclear glass to an ancient intelligent civilization will be tricky. # Geological Evidence of Civilization Beyond actual artifacts, humans move a lot of dirt. We have reshaped the world. Over 2 million years an average of 100 feet of material is stripped off (and replaced) over the world; humans have, on average, done about 1 to 10 feet over the time we have been on this planet (usually moving it somewhere else). While it may not be visible everywhere, it may be visible some places. A project we do (roadworks, canals, pyramids, etc) that reshapes the landscape may be buried by erosion from elsewhere, and unearthed either by natural processes or by digging by the later civilization. Recognizing it as being caused by a particular civilization may be challenging, but the layer of ash, dead plant material, and glaciation evidence directly above that strange layer may draw attention to it. A nuclear war is likely to wipe out cities. Any cities spared by such a war would be a decent concentration of metals, as we have spent centuries mining metals and concentrating them in our cities. Some may be ground to dust by glaciers, with the dust deposits being mined; but somewhat intact cities could draw economic activity, and induce curiosity. [Answer] There could also be geologic evidence in the form of shatter cones (<https://en.wikipedia.org/wiki/Shatter_cone>). They are typically indicators of meteorite impacts but they can also be formed by a nuclear explosion. [Answer] Most of the other answers focused on the Archaeology of physical artifacts, but what about the archaeology of humans and society? So for example, your archaeologists themselves came from somewhere. We trace our own human timeline back hundreds of thousands of years and can say things about early humans. Do people in your future society wonder what their own origins are? What kinds of traditions and mythology do they have? Do they have any "Great Flood/Great Fire/Long Winter" myths, especially ones that have striking similarities in very different cultural contexts? What about regional languages? Are there any commonalities in language that are difficult to explain other than there might have been a global civilization long ago? Obviously there were survivors of the war from eons ago. What kind of stories and rituals did they pass down from generation to generation that have lost their obvious meaning over time but still retain potent symbolism that might point to a great disaster? None of this would be direct evidence for a nuclear war per se, but combined with some physical artifacts might lead a canny investigator down the right path. [Answer] ## Nuclear fallout will be around for an long, long time Nuclear fallout (note: "nuclear fallout" usually refers to *radioactive* fallout. I will be using a slightly different meaning due to the context of the question). will be detectable until earth is destroyed - if geology allows. I am no expert in formation of rock sediments or the spread of nuclear fallout, so I will assume that nuclear fallout will be preserved in relatively clear strata in e.g. sandstone. If so, any civilization with a relatively basic understanding of nuclear physics will be able to see that there was a big release of fissile material (uranium-235 and plutonium-239), along with products from fission processes. An atomic bomb works through a chain reaction in which a lot of either uranium-235 or plutonium-239 fusions (there are a few other choices of isotopes which might be technically possible to use, but they seldom are) . However, not all of the bomb material will be spent; a significant fraction will be released as fallout. This means that a bomb will spread isotopes from three different groups: 1. Unspent [fissile material](https://en.wikipedia.org/wiki/Fissile_material) 2. [Decay products](https://en.wikipedia.org/wiki/Decay_product) from fission processes 3. Activated material from surroundings (e.g. bomb casing, air, soil) We can ignore the last category for our purposes here: the other two will provide clearer evidence. ## Unspent fissile material The unspent fissile material will be either uranium-235 or plutonium-239. Uranium-235 has a half-life of over 700 million years. Thus, virtually all of it will still be around after the two million years in the question. This will be an excellent clue for the archaeologist: not only will it show that someone spread a lot of expensive, highly enriched uranium over the planet, it will also give them a good estimate of *when*, as you can analyse the amount of decay products from the [decay chain](https://en.wikipedia.org/wiki/Decay_chain) to see how long since this took place. Plutonium-239 has a much shorter half-life, only 24000 years. This means that after two million years, it will be gone. However, it will not have disappeared entirely, but have also turned into uranium-235. This will mess with the time-span analysis of above somewhat, and introduce an uncertainty of about 100 000 years. ## Fission products Nuclear fission creates a range of different nuclides. In general, these are short-lived and unstable, but they will also generate daughter nuclides that are stable. The archaeologist will thus find a mixture of different isotopes, in proportions that does not occur naturally, in the same layers as the above uranium. This will clearly show that not only has someone spread a lot of uranium-235, but also a lot of fission products. The theory that would best explain this is an all-out nuclear war: 1. Large-scale nuclear disasters are unlikely. They would also release a lot of uranium-238, which would also be detectable. One could postulate a civilization which has reactors that only runs on highly enriched uranium, but that would be an extreme expense without any clear benefit. 2. Large-scale deployment of dirty bombs is even less likely, for similar reasons: they would tend to leave a lot of fission products, but there is no reason for there to be a lot of uranium-235 and no uranium-238. A smart archaeologist (or rather: a team of different specialists) would thus not only be able to figure out that a nuclear war had taken place, but also roughly when it had. This will even be possible as long as there is geological strata generated during the war around to analyse. [Answer] ## Layers of Sediment These will tell the story. Huge layer of radioactive ash, followed by changes in temperature and a massive extinction event. This would be indicated by an increase in the amount of fossils discovered to come from the exact same period of time followed by no fossils... This includes plants which point to features of climate change when combined with other evidence. I remember seeing a program where they were talking about evidence of a meteorite hitting the earth showing the same signs as a **massive** nuclear explosion however without any radioactive isotopes. I would look up the archaeological evidence surrounding extinction events such as the meteorite from Cretaceous–Paleogene and also Permian–Triassic if you're talking about all life being wiped out. FYI no expert but I think evidence from Ice would either not go back far enough or would be warped in some way to be nearly useless for [>2 million years](https://www.sciencedaily.com/releases/2013/11/131105081228.htm). [Answer] # Anything that was already in the ground when it happened This is a very broad question... but there will be a few very conspicuous things to find. First there is the question about finding remains of the civilization. Will they do that? Yes, they will... because we have so many underground structures made of things like concrete. Since they are in the ground they will be protected from the initial destruction and have a good chance of withstanding erosion. They will notice that the fall was very sudden, if nothing else from **gravestones and tombs**. They will find that the numbers on these burial sits gradually increase and that they become more and more frequent. And then all of a sudden: stop... nothing else. They will be able to pin the event by year and probably even month. It is another thing to match that year to any kind of calendar as *they* know it though. They may find traces of the nuclear war but what they will find first is the traces of other ecological disasters. Oil spills, chemical contamination, heavy metal releases, nuclear plant meltdowns. If humans very suddenly go away, and the infrastructure is destroyed by weapons of mass destruction, then these things will happen and make patches of the planet quite inhospitable. That will leave very clear marks, and many chemicals, not to mention elements like heavy metals, have no half-life but exist forever. As was stated elsewhere... the best place to find a clear time-line of events is most likely the Antarctic ice. There will be sudden layer of all kind of very "foreign" substances that do not exist elsewhere in the layers. Sooth, fission products from the weapon, chemicals of other sorts. And after that, there will be a steady decline as these things are washed out of the atmosphere by precipitation. And after that even the traces of civilization that existed before the calamity will cease to exist in the ice. [Answer] How about looking about some of our remains on the moon or mars? We can still make out footsteps in the dust after 50 years. While weather, bacteria and other movements will deteriorate most of what we have on earth, we have quite a few rovers and landers on the moon. The moon doesn't have volcanoes or big earthquakes, it is also lacking vegetation. There is no water or oxygen to rust away the materials either. All you have to worry about is small floating dust and radiation from space, and since I am neither a physicist nor an archaeologist I cannot comment on that. [Answer] How about the generation after million years is smart enough to design a spacecraft that travels multiple times faster than the light. and they go farther to capture today's light. They can come back at the speed they want and actually see everything that as if it is live. just a thought. If this light capturing sounds interesting you can build the story further on your own. [Answer] Take a look at the short story [No Connection](https://en.wikipedia.org/wiki/No_Connection), by Asimov. Spoilers ahead. The future Archaeologists just discovered isotope dating and are having a lot of progress. But the results on all artifacts from a few sites are wildly implausible. Off the charts implausible. These sites are also very, very rich in human fossils. Towards the end, it's very heavily implied that these sites are our nuked cities, and that the dating is being garbled by the residual radiation from the bombs. [Answer] A lot of people have mentioned the half-life idea, but nobody has specifically mentioned Cesium 135. It has a half-life of around 2.3 million years and is produced in a fission reaction (I've called it "Humanities longest lasting gift to the Earth" in a previous post). A dust layer with higher concentrations of cesium 135 should be recognizable. [Answer] Although not directly related to nuclear war, given the difficulty in finding ANY evidence of a 2million year old civilization I just want to point out the one obvious remenant. Satellites in higher orbits, well clear of our atmosphere, will likely still be in orbit after 2 million years, even if solar wind and micro debris impacts have scoured their surfaces severely. Some of these satellites would be visible to the naked eye. [Answer] You would need radioactive isotopes that will last beyond 2,000,000 years. In the [list of the half-lives of radioactive isotopes](https://en.wikipedia.org/wiki/List_of_radioactive_isotopes_by_half-life#1012_seconds) this would be the substances with half-lives around 10^12 seconds since 2 million years is about 6.3072x10^12 seconds. You probably need to find an isotope that's part of the decay chain of whatever radioactive material was used to set off the nuclear war in your story. ]

[Question] [ My current project features a contemporary scientist who is convinced that some sort of spacetime anomaly occurred in a tiny rural Yorkshire, U.K. community circa-1850; he believes a dilapidated old manor-house may have simply *appeared* on the outskirts of said community, with the locals being mimetically reprogrammed to remember it having existed for decades prior. There's a lot more, of course, but further details are (probably) irrelevant to my question: could there be any subtle, inconclusive geological evidence of this event which my scientist could latch onto? I know so little about the field in question that I struggled to parse out how to even ask this at all, so apologies in advance to any geologists out there. (NOTE: I know Yorkshire is a big place, but I haven't settled on a more precise location for all this. That decision may well depend on what kind of answers, if any, I get for this question.) [Answer] **There is no evidence of construction in the soil surrounding the house.** A Georgian mansion would have been built on site by craftsmen. They would have done much of their work on the land surrounding the house. Generally some evidence of this work would remain buried in the soil - cut bits of wood, broken tiles, etc. Also there would probably be an area next to the house with evidence of excavation where the basement was dug and soil heaped up then later smoothed out. There would be a layer of topsoil buried under a layer of subsoil. For this house, a Yorkshire field which had apparently been farmed since prehistoric times extends right up to the house edge, undisturbed. That is not hard proof that the house appeared. Maybe the builders were exceptionally thorough in cleaning up, or the landscapers who followed them were. Maybe forward thinking landscapers / gardeners reserved the topsoil so as not to bury it under less fertile subsoil (as I wish had been done for my house). There are other reasonable explanations. My failure to exhume any evidence of construction does not mean none exists - maybe I did not look that hard because finding anything would pop my fanciful hypothesis. But perhaps on digging down along the basement wall, your professor finds a ancient buried standing stone. It has a recently cut edge flush up against the basement stones. That might be more meaningful... [Answer] * Isotope ratios in the building materials. The clay in the tiles is *not from here*, possibly *not from this Earth*. Unless it has been mixed by people who could not possibly have known what they're disguising. * Cesspits with stuff at the bottom which does not belong -- pollen from other areas, the wrong style of pottery shards, etc. * Ancient relics in the ground (Roman foundations or pipes) which are sliced in half with awesome accuracy. Part is here, part is missing. [Answer] The [rocks beneath your house](http://www.bgs.ac.uk/enquiries/rocks_beneath.html) could be different to the surrounding local rocks if your house has moved location as well as time. If the HouseRocks are actually similar to the LocalRocks this would help hinder your scientist's claims. If the HouseRocks are different but reasonably logical, it could still be argued that it was a local inclusion or some such. [Occam's Razor](https://en.m.wikipedia.org/wiki/Occam%27s_razor) insists we take the fewest assumptions. Ie a natural but rare/unheard of geological feature/s is more likely than the *obsurd* spacetime theory (disclaimer, I love spacetime theories). I think the best bet is **local subsidence.** Houses, especially older houses, subside over time. The ground around the heavy house sinks causing the house to crack and lean to the side etc. Both the land itself as well as the house have tell-tale discernable signs that there is subsidence (as much as homeowners looking to sell would like to hide it, experienced homebuyers and home surveyors can always tell, as evidenced by many different [Subsidence Insurance](https://www.axa.co.uk/insurance/personal/home/tips-and-guides/spotting-the-signs-of-subsidence/) websites, where I got the image from). [](https://i.stack.imgur.com/DBilZ.jpg) When your House arrives, it could have signs of pre-existing subsidence damage and repair on it. The previously unoccupied land around it will have no evidence of subsidence. No deformation, no sinking etc. So how did the old house get damaged? Some could argue that the garden-land has been covered in a new layer of flat earth in a gardening revamp. However, if you would do a geological survey of the earth directly undeneath the house, and even on the sides, you would see no deformation in the stratigraphy. Using either ground cores or possibly some fancy satellite geological survey. It will certainly be an oddity, and yet no-one 'sane' will want to the state unequivocally that "this subsidence oddity"=spacetime anomoly. Not if they want to keep their jobs and reputation. Good luck to your protagonist :) [Answer] Here are some suggestions. All the land in a tiny Yorkshire village would be owned by someone in 1850. The manor house would have appeared on a plot of land owned by someone. Or maybe on the border of two or more plots of land. Maybe the landowner(s) were hypnotized by space aliens or whatever to believe the house had been there for decades or centuries. But the plot of land would have been described from time to time in various legal documents. And if those documents didn't describe any manor house there until 1850, that would indicate the building wasn't there when those earlier documents were written. If the tiny Yorkshire village was inhabited in the middle ages, it was probably part of a manor, and very probably only one manor, since it is specified as tiny. Thus there was probably one and only one medieval manor house in or near the tiny village. The medieval manor house or its ruins might still be visible, on a plot of land. And the history of that plot of land could be traced back to the times of the medieval manor. It is very probable that the location of the original medieval manor house, and any replacements that might have been built by later lords of the manor, would be known. Thus people would know that the 1850 house was an extra manor house, even if they had been hypnotized or something to believe that it had been there for a long time. The owner of the land where the manor house appeared would have believed it was his property, and might have moved into it. And if he and his family weren't rich enough to build such a manor house, they might not have been rich enough to maintain it, thus explaining its dilapidated condition in 2018. If the manor house had the style of a historic English manor house, it would be easy to guess the approximate era when it appeared to have been built. Since the owners of that property in that era didn't build a mansion on the property, they probably couldn't afford to build a mansion. Thus people who think that the manor house was built long before 1850 would have a mystery on their hands, and there might be many local theories about ill gotten wealth financing the supposed building of the manor house. Some answers speculated the manor house came from outer space. If so, it shouldn't look like any known style of English manor house. If not, there would be no extraterrestrial evidence connected with it. If some land for a distance around the manor house was transported with it, there could be evidence in that land. But maybe only the actual building was transported to the village and every thing outside the foundations was already there. I can imagine the building materializing with its foundations above the ground and falling a few feet to the ground, thus establishing its dilapidated condition post 1850. Thus the foundations are likely to have crushed some plants of various types beneath them. Possibly excavation of the foundations will indicate that there are dead bushes, etc. beneath them. A dead and dried up bush may have its roots outside or inside the foundation and branches crushed under foundation stones, and may be radiocarbon dated to c. 1850. There could be remnants of wooden fences, for example, under foundation stones, and dated by dendrochronology or radiocarbon dating to, say, 1845, while wooden rafters in the manor house are dated to, say, 1645. Low-background steel is steel made before the atomic age beginning in 1945, and thus is useful for many purposes. Making steel uses a lot of air, and since 1945 the air has been contaminated with radioactive fallout. Checking the radioactivity of steel objects is a good way to determine when they were made. Of course steel made 1850 and earlier wouldn't have any radioactivity to test, unless it was made in the future or some other planet, etc. But a manor house made in 1850 or earlier wouldn't have any steel parts except for knives in the kitchen or swords and armor. But that is an example of the kind of tests that could be made. Possibly the rocks in the foundation might be more radioactive than they should be, and contain higher proportions of a radioactive isotopes than similar rocks on Earth do, because they possibly were quarried in a younger solar system where there has been much less decay of radio isotopes. [Answer] You, as the author, need to know three things before that question can be answered: 1. What is the nature of the appearance; 2. What type of ground is the manor on; and 3. Where did the manor really come from. The reason you need to know those three things is because then it can be determined what clues there would be to find. Think of it like writing a murder mystery; you, as the author, have to know who did it and how they did it so you know what clues there would be for the detective to find. Same principle. **1. Nature of the Appearance** How did the building appear: is it the building itself, or did a volume of ground get displaced along with the structure, replacing what was there previously? How big was it? If the building appeared atop existing ground, then there will be minimal disturbance below that would wave an obvious warning flag and the clues would be correspondingly small. If the disturbed ground is limited to the building's foundations and slightly around it, then the clues are going to be slightly more significant, but easily overlooked. If the the manor appeared because, as in the Ring of Fire example, a larger volume of material around and underneath was swapped out, clues will much larger and easier to find. **2. Type of Ground** The second factor is type of ground the existed there previously. A manor that is purely on top of a rock outcropping isn't going to leave a lot of clues indicating it doesn't belong there. If the local ground was glacial till and the ground that came with the manor also came from glacial till, then again a geologist could notice clues but they'd have to have a reason to look more carefully than normal. On the other hand, a manor built on solid rock (that arrived with the manor) that looks different from the solid rock around it would be very noticeable. **3. Where did it really come from** This links to both above; you have to know where the manor came from and what came with it, if anything, in order to know what it interacts with the ground where it appeared, and thus what clues it generates. If you can provide the answer to those three questions than a geologist, such as myself, could tell you what clues there would be, and how obvious they were, for a geologist to figure out something was odd. Without that information, the question can't be answered. All the existing answers here as I type this have been based on assumptions the poster have made and are dependent on the scenario they've postulated individually, not what you've provided. They aren't universal answers applicable in all circumstances because they can't be. [Answer] This scenario arises almost exactly in Eric Flint's *Ring of Fire* series. The American city of Grantville is hit by a n-dimensional construct called an *Assiti shard*, and swapped with an identical sphere four hundred years in Earth's past in the German region of Thuringia. All sorts of geological formations are cut in two (this is actually, I think, a blooper in the book - Grantville has mirror-finish rock formations on two "sides" of the circle, but in modern America there are no corresponding signs and almost nobody suspects a thing) - rocks, seams of coal, underground water tables, everything. So first question: to which depth does the anomaly go? Deeper anomalies leave more significant traces (in their geometry if nothing else). Then, what is the geologist looking for? (And what *was* he looking for when he stumbled upon the house?) He might be e.g. investigating something like the [Devil's Arrows](https://en.wikipedia.org/wiki/Devil%27s_Arrows) - maybe he has a semi-crackpot theory on the Arrows having been erected along *ley lines* or something, and is checking the geomagnetic field in search of some buried Arrows which he just knows must be there. If he succeeds, this will support his theory (and, depending on what this will in turn reveal about early inhabitants and their culture, it might be even be a large splash than just finding evidence of prehistoric dwellings). It turns out that his theory is partly correct - *ley lines* do exist, and they were used by someone in the past to travel between the worlds. The locals happened to notice the characteristic shimmering of the air above the lines, called them "paths of the Gods", and placed menhirs at the crossings. And just where such a menhir *did* exist in the past, recently a manor house has been planted. But of course there is no trace of the manor house actually ever having been *built*, or of the land deeds, or of anything else. So the geologist's plan to excavate in the house's grounds and look for traces of Paleolithic inhabitation is thwarted. Yet during this research, he's discovered a more modern mystery -the House that Should Not Exist. Soil composition is wrong, and attempts to carbon date the trees all fail. More expensive isotope tests yield even stranger results - not only is the 14C ratio off, *several other isotopes* are present in ratios that make no sense for Earth. Even *stable* isotopes: where the Earth has been born of a class-IIa supernova remnant, the nuclear ratios in the samples are more consistent with a much rarer, helium-depleted class-Ic stellar residue. This could be believable of a few pebbles with the right chemical composition to possibly be what remained of an interstellar meteorite - a tiny, remote cousin of ['Oumuamua](https://en.wikipedia.org/wiki/%CA%BBOumuamua); not of a whole *field* with house included. By carefully measuring the weathering of surface stones, the geologist is able to pinpoint the likely beginning of Earth exposure to about 1850. But this is *one* interpretation. Another possibility is that the area has been contaminated with the appropriate mix of neutron-activated substances - which could be conceivable if one were to assume that some waste material from the early days of the *Dungeness B* nuclear reactor had somehow found its way to this remote spot. The skeptics can easily point out that while several isotopes corroborate the geologist's thesis of different stellar origin, other isotopes do not (the error margin is quite great anyway), and some ratios are much closer to those expected of specific nuclear wastes. Also, chemical analyses strongly imply that the soil might at least partly come from elsewhere - it has been mixed with contaminated soil. The readings from the house come from a half century exposure to contamination. Available data support both theories. So, the Government and possible obscure industrial interests also enter into the already significant mess; while the geologist's instincts tell him that the soil was never disturbed - how could it have come "in part" from *elsewhere*? [Answer] As far as I can see, the best way to have a subtle anomaly in spacetime itself is to have space have a non-zero [curvature](https://en.wikipedia.org/wiki/Curvature). An easy way to detect non-zero curvature is that triangles drawn with straight lines have angles that [don't add up to 180 degrees](https://plus.maths.org/content/mathematical-mysteries-strange-geometries). Your characters could find triangles consistently adding up to 179 degrees, for instance. Edit: Interestingly, you mentioned a 1850's setting. Riemannian geometry was invented in 1853. To make this scenario more geological, you could have the discrepancy noted when a group of mapmakers are surveying local hills, mountains, and other geometrical figures and keep making 'mistakes' in their calculations that they cannot rectify. As per the comments, I've just now posted a [related question](https://physics.stackexchange.com/q/403973/194657) on Physics.SE. Edit 2: They answered! Apparently the acceleration would be fairly small, but building materials could be deformed as they move around. [Answer] A simple addition -- a line of ornamental trees that almost line up with the property. Three trees near the property are from the original manor location, and have an age of about 400 years. The other trees, slightly out of line with the old trees but nicely lined up with the landscape and roads, date to 1851. [Answer] Soil type, some soils evolve very different characteristics over time, in particular certain silt loams [podsolise](https://en.wikipedia.org/wiki/Podsolisation) in wet climates creating distinctive structural elements ultimately including a deep iron pan and perched water table. These soils often start out as reasonably well draining but as the silt breaks down, due to repeated wetting and drying cycles, clays form which impede drainage consequential changes in plant cover raise soil water acidity, the acid breaks down the clays and mobilises Iron that migrates deeper into the soil column and precipitates to block drainage altogether. This process takes a long time in human terms but can be relatively rapid geologically speaking. The soil around the house may exhibit a small but crucial difference in how far along this evolution it is. This certainly wouldn't be conclusive, natural variations in the process rate could explain it away, except for the sharp border zone showing a clear delineation between the two zones; that would be harder to explain. ]

[Question] [ If humans didn't exist, what species would populate the earth? Would an animal gain human-like intelligence if humans weren't here? What animal would gain dominance? [Answer] **The Raccoons** Originally a North-American species, it has dexterious hands and thumbs, can stand upright not unlike a meerkat, is an omnivore, good at problem solving and has a complex social life. These are all traits that have been proposed as crucial for the development of Homo Sapiens. Without human existence, present-day North America is full of large herbivores, with descendants of mammoths traversing the arctic from Scandinavia through Siberia and Canada. The Raccoons spread north and live on a mixture of scavenging on large prey and hunting down smaller or weaker prey in packs. Without human interference, the next glacial period arrives when it should and allow the Racoons to cross the Bering Strait. From there they spread rapidly throughout Asia and Europe. In Europe they become a terrible invasive species, decimating birds, amphibians and other mammals just as they have done to a lesser extent in real-world Europe today. A line of Racoons radiate out on open grass-land, either in central Eurasia or Africa and develop a truly upright posture, to better survey the land for prey and predators. This frees up their already dexterious hands and sets off a feedback-cycle between tool-use, more dexterious hands, brain development and hunting techniques. One sunny day, a million years from now, a young inquisitive racoon is left back in camp while her family hunts. Out of curiosity or boredom, she grabs a piece of flint and slams it against a rock laying in the dry grass...   [Answer] Simplified, social behavior in animals demands more brain power for memory, communication, and interactions. *Who is the leader?* *Is Jack watching for enemies?* *Bob is mad at me for stealing his food.* As early hominids evolved to keep track of many members of their 'tribe,' they evolved ever-larger brains to cope with the demand. However, social behavior alone isn't a guarantee to evolving a dominant position on the planet. There are many social animals which are quite intelligent, but obviously have not achieved the same status as humans. Intelligence can be a naturally selected trait for solving problems, and ultimately survival. There are [many theories](http://en.wikipedia.org/wiki/Evolution_of_human_intelligence) on how human intelligence came to be. If humans' ancestors had not existed, it's possible a different type of hominid would have risen up—literally—to take our place. [Some theories](http://www.pbs.org/wgbh/nova/evolution/what-evidence-suggests.html) of human intelligence link bipedalism, at least in part, to our success. Perhaps one of the "most intelligent" animals on the planet would have found a niche without humans present, and evolved even greater intelligence, becoming dominant. The list frequently changes, but among them are: * Dolphins * Elephants * Parrots * Crows * Dogs Perhaps it would take another few hundred million years for dolphins to become what you would consider dominant. *(Perhaps that is happening anyway!)* If humans had not evolved, it's possible *no* other animal would ever evolve human-like intelligence. It's difficult to say if humans' presence has somehow had an effect that caused another species' intelligence to cease being a favored attribute in natural selection. Perhaps instead, we are a *catalyst* for hastening the rise of a smarter species than ourselves. It may be only millennia, you see, before all the dog training we've taken part in, becomes our undoing. [Answer] In terms of non-great ape animals (which I assume is *not* what you want, since they will basically just evolve into something that is, well, more or less like humans, probably… unless you're going for a *Planet of the Apes*-type vibe) I believe that African grey parrots are probably the closest in terms of having the “full package” towards intelligence, including a decent ability to manipulate their surroundings with their talons, with the added benefit that they can also fly! They're not quite there in terms of being able to use tools, but in terms of everything else, they're close to being “sapience-ready,” I think. The other contender, often overlooked in my opinion, is the cuttlefish. They have a surprising number of highly-advanced mental capacities, especially considering that invertebrates are often thought of as being universally far less sophisticated or “less evolved” than vertebrates, and they have their tentacles that they can use to pick things up and move them around… plus, if you go with the cuttlefish, you can have them evolve into a Cthulhu-like or Illithid-type race, which is a cool trope, I think! There are lots of different theories about what aspects of a creature push it more towards overall “intelligence,” as we would probably define it in a worldbuilding context. Social behaviors and ability to manipulate one's surroundings are two of the most important ones, I believe. [Answer] Insects are sometimes viewed as currently dominant taxonomic group. They may have social behavior, hierarchies, bees can communicate each other the location and build relatively complex structures like honeycomb. These families may be superior to human families as they consist of big number of adult, fully capable individuals, not just of two adults and children who cannot do much. The only problem is the small size (so limited size of the brain), but say [Hercules beetle](http://en.wikipedia.org/wiki/Hercules_beetle) may be 17 cm long so the brain need not be very small. Titan beetle is slightly shorter but has more massive body. The problem is probably that social insects are not as big as these beetles. Also, it may possible to have distributed brain built from brains of multiple individuals, using sound or electromagnetic waves to communicate. A bee brain contains about [950 000](https://faculty.washington.edu/chudler/facts.html) neurons, human has about 100 billion. 105 000 bees would be required to have the same number of neural cells. That much can easily live in just two hives standing nearby ([60 000](http://www.hivesforlives.com/beesandhoney/beegeneralfacts.html) per hive) - fully realistic. It may be only a question of time before the nature hits that opportunity. [Answer] By the definition given here: <http://www.biology-online.org/dictionary/Dominant_species>, any species' "dominance" is only relative to a specified environment. A variety of animals could be considered dominant to us in their natural habitats - though if we instead define "dominance" by our ability to dominate/subdue/kill other species in their natural habitats (this seems to be the definition used by the OP and most replies here), and thus dominate those habitats that we are not native to - then I would argue that there would not be a dominant species other than us. If we humans were out of the picture, I don't know if any other species would exhibit our "will to dominate all life". on such a scale that we could consider them to be the globally dominant species. Other species tend to stay in their own habitats, and are not likely to be able to adapt or survive outside of them. Such dominance as we have achieved would certainly not be gained by another species quickly (much evolution and learning would be required), so while an interesting question to consider, I doubt we'd ever come close to guessing the species that would evolve to our level first. Who knows, maybe a bacteria would begin wiping out enough of the life on the planet such that it would become the dominant life form by overall biomass, overall prevalence, and kill-count. [Answer] I'm surprised nobody has yet mentioned rats. Just to piggyback on the reasoning of other answers, rats are social, intelligent w/problem solving skills, dextrous, and omniverous. When working together, much like we think primitive humans did, they can overcome a predator, and bring down prey larger than themselves. [Answer] Lots of neat answers here, but I would propose.. Troodude! OK, I got that from a kids show, I don't even remember which one. It talks about a possible evolutionary progression from a particular Dinosaur called the Troodon. The [Troodon](https://en.wikipedia.org/wiki/Troodon) was a small therapod, possibly omnivorous. It was often put forward as an unusually [smart dinosaur](https://www.thoughtco.com/things-to-know-troodon-1093803) The smart dinosaur theory puts forward that if they had survived the KT event, they would by know have evolved human level intelligence. The reasoning for this is that their brain in relation to body mass was unusually high. They had binocular vision based on eye placement. Their tooth shape suggests they may have been opportunistic omnivores. Their forelimbs could have easily turned into "hands" with manipulative digits. More fanciful interpretations depict something that looks kind of like a sleestak from "Land of the Lost" Who knows, If that little guy could have survived the KT, he may have eaten our most distant ancestors and supplanted us that way. [Answer] To slightly change the question, could an earth-like planet with slightly altered geographical/geo-historical features, themselves based on slightly different chemistry and thus climate and land-altering features, have a different dominant species? Moreover, if this species also evolved abstract science faster than we on earth and they sent astronauts to observe earth, what would this species and its proxies and assistants be? (I.e., human/dog/horse complex on earth) I changed the question because I think a species like the **feline**, which clearly dominates every predatory food chain it has co-evolved with, is given short shrift on your list. Especially since otherwise worthless cats - we certainly don't breed, protect, pamper and give medical attention to cats anymore because of their rat-killing ability, in fact, that aspect of feline behavior is looked at with disgust by most modern "western" humans - are now the fastest growing mammal population worldwide, even surpassing racoons, which several of your contributors rightly pegged as another possibility. To get to the point: a species that can enlist a species superior in some respects (let's say on their planets apelike creatures also developed spoken language) to work for them can't be counted out entirely. The ability to coerce or trick another species into helping them in very a one-sided relationship may be a better indication of evolutionary success than mere "intelligence", whatever that generalized concept means pragmatically. Also, many niche species on earth that are not well known have developed fingers and even thumbs much like ours - certain rain forest tree frogs, for example. And the tentacles of intelligent octopi or other cephalopods could easily be surrogates for hands. And the whole question of language implying a need for writing is also erroneous. Animals IMO can have as sophisticated a nonverbal language, based as mammals and birds clearly must be on visual images - mandalas, icons, emogees, whatever in human terms - and they could transmit knowledge and information via that language in many ways besides with fingers and thumbs. They could have, as I indicated, if they ever needed a written language, have adopted hominid pets to do it for them, the way we adopted wolves for hunting help and horses and oxen for hard work. ( My cat forced me to write this. Actually I think dolphins are the best choi ... [Answer] I see several answers for this, so I'll list them off. \*If only humans are taken out of the picture, then I believe it would be another hominid species, like Neanderthals, who would not have had to deal with competition from Homo Sapiens. \*If by humans you mean homonids, I believe that cephalopods would dominate the sea and either avians or felines would have dominated the land. Then, depending on how fast their intelligence grew after naturally dominating their habitats, it would either be a world of squids, cats, or birds. Or maybe evolution pulls something out of left field and we get talking horses instead. Who knows? [Answer] I think that "dominance" should be defined better, especially because it seems to be direclty linked to intelligence. It's true, we are dominant because of our intelligence but it's worth to underline that we are NOW dominant because of intelligence AND ESPECIALLY TECHNOLOGY. (a physic professor won't be really dominant if left naked in the savannah) We are dominant all around the world because of the same reasons. Dominance and intelligence are not welded together, we evolved a lot because intelligence (our main power) was/is the best tool at that/in this era. We didn't do anything "special", we didn't actually choose to be intelligent rather than strong or poisonous, it happened to be the best option and we came out on top of the food chain. If the earth situation/climate is more or less the current one, and if by dominance we mean superior intelligence/technology, i'd go with primates or racoon as other people already explained. Otherwise, the question is not complete enough to be answered. [Answer] If "dominance" is defined by which kills off the other, then.... Whatever virus, bacterium, or fungus that (largely) kills off humanity. A future gen of a highly deadly virus like Ebola that's evolved to be airborne and thus highly contagious\*; or a highly contagious antibiotic-resistant bacterium. Predicted to happen in the next few centuries. \*we've been lucky that most past microbes have been either deadly or contagious but not both. When one evolves that is both, watch out: see <http://www.businessinsider.com/how-contagious-is-ebola-2014-10> [Answer] If by "dominance" you mean using your own intelligence, strength, mobility etc., then I don't know. But if by "dominance" you mean usurping these abilities of other species if you don't have them yourself, and controlling these abilities of other species to further your own agenda, then the answer is GRASS. What other organism has made itself so valuable to (an)other species that it uses the strength of others to clear forests to give it more living space (all the grain grasses), the intelligence of others to ward off predators/pests and to provide more nourishment (same grain grasses benefitting from pesticides and fertilizer), and even the visual/tactile tastes of others to rip up whatever else was there before and roll sod over it (your good old front lawn)? ]

[Question] [ I'm writing a story that features modified humans that have a very long lifespan/ practically immortality. Immortal characters in fiction aren't exactly rare, but I want to write something more realistic (which might be ironic considering the premise). If we suppose a person wouldn't physically die given extremely long age, what would happen to the brain of the person? Could a person that has lived for thousands of years act as a part of society or would he have trouble with recalling memories and other functions, etc? Edit: I'm assuming that diseases due to immortal nature are not a factor. Though I'm no expert in any of this, so nothing's to say there aren't some diseases that would affect the brain on the long run despite immense recovery capabilities I'd link with immortality. The immortals have stunning recovery capabilities, and are for example capable of regenerating bodily damage almost in an instant, though I'm not exactly sure what this would mean to the brain. [Answer] Neurons are a little bit odd, because [they don't divide and therefore can't reproduce quite like most other cells](https://biology.stackexchange.com/a/21840/9458).1 They can only be produced by [neural stem cells](https://en.wikipedia.org/wiki/Neural_stem_cell), which are active largely in the early stages of an organism's life. In some adult animals, however, neural stem cells are [active in the hippocampus](https://biology.stackexchange.com/a/45166/9458), where they may be instrumental in forming new memories. Without the generation of new neurons here, there could be negative implications for memory storage. You could argue, then, that immortality *with a continuously functioning brain* would require the presence of a large number of neural stem cells. However, it's not quite so simple. While [therapeutic use of neural stem cells](https://en.wikipedia.org/wiki/Neural_stem_cell#Regenerative_therapy_of_the_CNS) has been tried - and has, to some degree, succeeded - replacing large sections of the human brain over time would require extremely delicate procedures, which might have to be developed naturally. In other words, the brain might have to be designed such that this replacement is possible. Without such replacement, then, immortality wouldn't be possible. A person would gradually lose neurons over time - even if they weren't stricken early with a neurodegenerative disease. Their brain cells would quite simply die. It might be like a slow-motion version of [Parkinson's disease](https://en.wikipedia.org/wiki/Parkinson%27s_disease). Memory would begin to fade, as would other brain functions. I've seen many estimates for how fast neurons die, and how fast certain types are made in the hippocampus. For the former, figures vary from [a bit under 10,000 per day](http://www.madsci.org/posts/archives/2002-03/1016223301.Cb.r.html) to [several hundred thousand per day](https://books.google.com/books?id=adeUwgfwdKwC&pg=PA33&lpg=PA33&dq=how+many+neurons+die+each+day&source=bl&ots=Od654yUhI9&sig=oWGq4RLJw9xvKfJOEhXKI4NkLqo&hl=en&sa=X&ved=0ahUKEwjB9qaEve7ZAhUBuVkKHS-1ATw4FBDoAQhgMAk#v=onepage&q=how%20many%20neurons%20die%20each%20day&f=false). For the latter, it seems that [less than 1,000 neurons are produced by the hippocampus each day](https://www.health.harvard.edu/mind-and-mood/can-you-grow-new-brain-cells) - and those usually for memory-related functions. Now, there are [tens of billions of neurons to maybe one hundred billion neurons in the human brain](https://www.nature.com/scitable/blog/brain-metrics/are_there_really_as_many), meaning at the current rate of replication, it would take millions of days to recreate that many neurons at adult production levels. Neurons die at a much greater rate than that. So you'd need one of two solutions: * A substantially lower rate of neuronal death (arguable your best bet). * A substantially higher rate of neuron production *and* the ability to integrate new neurons into the brain. Without this . . . the brain would decay within a relatively short period of time, even without degenerative diseases. [Answer] As I've grown older I've noticed my mind converging on ways of thinking. When I was young the possibilities were open but over time my mind has accumulated a sense of how the world is. This seems a lot like optimizing for your environment by putting blinders on. Maybe that was advantageous in the past in the same way that eating as much salt and carbohydrates as possible was. The problem is that in our world things change, fast. Technology and society change almost every decade and the key to staying agile seems to be about continuously deconstructing what you have learned. An immortal person would need a way to fight against this type of convergence or they would soon, relatively speaking, find themselves in a world that doesn't make sense to them. Actually, you can kind of see this today but if people were immortal I think the issue would be magnified and become much more serious. [Answer] On brain : probably **nothing**. For someone to be practically immortal it is necessary that their body does not degrade over time. That especially includes the brain. It further implies they can recover from inevitable environmental damage, which means they'd have to be functionally eternally young. For brain you can assume they have good memory and learning ability combined with maturity and experience of age. Think a young person who acts much more mature than expected. On consciousness : **more or less unknowable**. People like this would have had lots of time to get to know themselves and develop their own personality. So they would have very strong individual personality and would be unique individuals. Still such strong personalities would probably show as self-confidence and charisma. They might also appear mature and considerate, both pragmatic and principled. They might not be any of those but experience would duplicate the effects. Knowing what causes problems from experience makes you look considerate. Knowing what kinds of solutions will not work makes you look pragmatic. Knowing what compromises you will be happy with or not look much like having principles. And all that will make you look quite mature. They'd generally be calm and stable since they have typically found out the ways of thinking that will work for them. That might come off as being methodical and efficient. Maybe to the point of stubbornness or dogmatism even. [Answer] We know little enough about how the brain works, how aging works, and how the two interact that the answer could be anything you want. Mainly because modifying humans to make them immortal would mean modifying their brains - as others pointed out, we lose neurons throughout our lives and they don't regenerate much. Any kind of immortality would involve some way of compensating for this, which means changing pretty basic aspects of how the brain works. On memories, this neuroscience talk on Youtube points out an interesting difference between young people and older ones: <https://www.youtube.com/watch?v=gdzmNwTLakg> It seems younger people have stronger episodic memories, i.e. memories of specific things, and when asked to recall them they bring a wealth of details to the description. Older people have weaker episodic memories and rely more on semantic memories - when asked to recall something they will bring less detail and talk more about their general knowledge of the world. This is one example of how memory could evolve over time for someone immortal; specific memories would blur into a general sense of what the world is like. But again: the brain would have to work differently for immortality to work. So maybe memory could evolve differently over their lives. There is no theoretical reason why immortals should have worse memory than non-immortals. From a data perspective, if there is a maximum amount of memories a brain can contain, all that means is that the longer an immortal lived, the smaller the proportion of their life they would remember. But that's already true now I think; when I was a child I remembered a lot more about my childhood than I do now, but I also have a lot of memories of my teens and adulthood that I didn't have then. I see no theoretical reason why a thousand-year-old should have fewer memories than a short-lived person. There is also the question of people becoming more rigid or set in their ways as they grow older, but again: is that a consciousness thing, or a brain thing? That is, one can make an argument that as you live longer and accumulate more data about how the world is, you draw conclusions about it and it will be harder to change your mind on those conclusions (it will take at least as much data as that you have already gathered) than is the case with someone who has a lot less data. I.e., we can suppose that getting more rigid in old age is inherent to intelligence itself. But then again, maybe it isn't; maybe it's a consequence of our brain's development over our lifetimes. And maybe it's a bit of both. And brain development would have to be different for us to be immortal; and if it's different, maybe one difference could be to maintain flexibility and openness regardless of age. The same is true of our subjective sense of how fast time flies. Is it inevitable that any conscious being will sense time as a proportion to how much time they've already lived (if that's how our time sense actually works), or is it a property of our brain? Unknown. [Answer] Depending on the way they live and use their brain there will be vast differences. To take the example I mentioned in a comment: look at elves first. Elves are generally depicted as a very social race and while they may act weird when compared to humans or dwarves, there are not so many differences between comparatively long-lived elves and younger ones. If your immortal humans were living in a society that is ruled by strict law and not really inclined to brutality then everything will be fine. They will forget a lot of things as humans normally do, but they will make sure that they will remember important stuff, just like we for example take pictures or write a diary. The normal everyday activities will of course stay in their mind perfectly fine, but there will be more lost if they don't regularly remind themselves of the past. Looking through old books they have written will be a far more normal part of their lives than it is for us - it's important to not forget those that may have died for example, but whom you don't want to forget. Elves are often shown as magically inclined with advanced medical care, which makes them suitable candidates for "immortals", though they are a bit farther from science-based. Looking just at how their society works though is still a valid approach for judging your immortals. If you look at vampires on the other hand you have some depictions that are very close to what you want. Most of the time vampires are depicted as humans that are somehow transformed - be it via magic or a virus - into a vampire. Such a vampire is normally living in solitude - humans are your meals and other vampires would steal your meals or make your meals aware of you, which makes drinking the important parts of them difficult. They are living alone and they are living a brutal life. There is regular violence against what was formerly their own race, there is regular violence trying to protect your free-range humans from other vampires. This leads old vampires to hate other people, vampires and basically everything else - their brains wouldn't physically be altered, but their psyche would transform over the centuries in order to be able to keep up and stay alive. An important part is that they can still perfectly blend in - that's necessary to lure your victims in the next dark alley after all - but they would never really form a *society*. There are sometimes depictions where vampires band together and rule over the land. I am thinking about an Anime right now but will have to look up the name later. Humans are treated as lifestock and a new vampire socitey arises. This perfectly shows that the style of living would influence your immortals. If they have a society that welcomes them the way they are and embraces immortality then they will live a perfectly normal happy life with some minor differences, such as more elaborate diaries and reading to remind you of the past. As the brain wouldn't deteriorate from natural diseases there isn't really anything you would need to fear, except for the loss of some abilities you haven't trained in a few centuries - forgetting how to ride a bike would actually be possible. If your race on the other hand lives in solitutde or undercover the individuals would slowly distance themselves and become less humane - they need to stay up-to-date to blend in and act like normal people, but in reality they are predators only looking for their next meal and survival who would surely forget about their past lives in relatively short order of maybe a few centuries after being transformed. They would remember that they once were human, but nothing more. [Answer] I am quite fond of books by a Russian writer, Alexander Lazarevich, who among other novels, explored technologies for achieving practical immortality and their implications on individuals and society, in "Wish Generator" and somewhat in "Nanotech network" as one of the aspects : <http://technocosm.narod.ru/e/wg_e.htm> Being a sci-fi writer, he leans toward longevity of the conscience - not necessarily confined to the original biological body it was born in. Not necessarily to one body at all (e.g. spawn a copy of yourself - and both are fully yourself, no paradox and conflict of clone/origin - to travel the universe (perhaps in a body that can live in the cold and void or dive into stars), then sync back the impressions of your copies whenever their ways cross again. The technologies and biological basis for what he proposes as initial stages of modularizing the body (and eventually replacing, as it ages) as a carrier of consciousness are already available or will probably emerge in foreseeable decades. Regarding your question, one of his outcomes was that true immortality on scale of many (all) humans can cause them to become very responsible about what they do. There is no more place for "I can do whatever, those who come after me will sort it out" - I will live to be hit by the consequences; even if you're immortal, living forever in a wasteland with no way out is not a good prospect... This will probably boost technologies and space travel as well: "If the Sun burns out in a billion years and swallows the Solar system, this is my personal existential threat, and a problem I have to solve." Quite possibly, the immortal humanity will have to invent ways to travel the galaxy and take the planets (and stars) with them as big comfortable spaceships to fit them all. It can impact the work of memory as well: it is not infinite, so the trick is to remember what is needed, what matters, and to be able to lose the cruft over time. "The perfect memory is not one that remembers everything collected over millennia, but one that is usable and where you can still find the needed memories in reasonable time." [Answer] Fundamentally, if there's way to make someone live for hundreds or thousands of years (or longer), their brain is going to have to function on a biological level, or the person will die. Whatever you do to keep the rest of the cells and systems in the body from breaking around the hundred year mark, you would presumably be able to do for the brain and nervous system as well. Having said that, the big issue you're likely to encounter in the brains of immortal (or long-lived) biological beings for which there isn't a plausible solution is the problem of [neural plasticity](https://en.wikipedia.org/wiki/Neuroplasticity), specifically, what's called [activity-dependent plasticity](https://en.wikipedia.org/wiki/Activity-dependent_plasticity) (or "learning", if you prefer less technical terminology). Because of the way neural networks function at a basic level, they become more rigid over time. Memories and experiences and knowledge are stored in the brain, as are the connections and pathways between them. This has the effect of giving more weight ("a stronger signal") to existing experiences over new ones. (Because there are more old experiences than new ones, of course, and this effect grows stronger over time.) Since neural networks function on a strongest-signal-wins basis, this becomes a problem over time. Past experiences have more weight than new ones, making it harder to integrate new experiences ("learning"). There's many an adage along those lines, such as "can't teach and old dog new tricks" or whatever stereotypical pejorative you want to throw in about old people being cranky and stuck in their ways. It's rooted in the way neural networks function, preferring a large body of historical experience over a smaller number of new experiences. I think current research on neural plasticity pegs 75 as something of a dividing line, but I'm not sure how much of that is due to biological aging, and how much is due to fundamental issues with neural networks in general, but it seems like over a long enough time span, the way neural networks weight new things against their body of existing experience is bound to be a problem. The other issue is that the brain doesn't really scale to the type of time scales you're taking about. Can *you* recall many memories from 10 years ago? 20? I wouldn't say that's a big problem, as people get along just fine with only the vaguest memories of what they experienced years ago, but it will be a more pronounced effect the longer you live. In respect to this question, it means a person who's lived for thousands of years would only have reliable memories of a fraction of a percent of their lifespan, at least with their natural wetware. (There's definitely a sci-fi angle for memory storage implants in there, but the natural state of only being able to recall a tiny fraction of one's life seems weird and unsettling.) So I would suggest that the biggest problem an immortal person would face is that they'd be very limited in what they're able to learn and adapt to after a certain age. They might live 10,000 years and gather new memories, but otherwise, they'll probably be mentally the same person as they were at 75 (or 100 or whatever). [Answer] Going from what we know of [Artificial Neural Networks](https://en.wikipedia.org/wiki/Artificial_neural_network).. The key here is the concept that a given neural network has a finite [information storage capacity](https://www.quora.com/What-is-the-maximum-information-storage-capacity-of-a-neural-network). The exact value does not matter, but what is important is that for an immortal being with a finite (and presumably unchanging) number of neurons, the amount of information store-able is finite. In practice, that means that older memories and concepts will be progressively overwritten by more recent and more frequently accessed ones. In order to be immortal in a practical sense, the above concerns of neural die-off and plasticity would also be addressed (you would just keep the values at age 25, for example). The probable mental effect would be that memories of strong events and concepts would persist for hundreds if not thousands of years, but many intervening events would be lost. Indeed, a 2000-year-old may read documented evidence of what they did as a 1000-year old and have effectively no recollection at all. They might as well be a different person entirely. [Answer] The recent discovery of Telomeres (2009) which preserve genetic information each time a chromosome splits would have implications for the genetic information of an immortal being. If we had no Telomeres, our chromosomes - which hold a cells genetic information - would get smaller and smaller each time they split, eventually leading to nothingness. Telomeres are replenished when we're younger, but As we age, our Telomeres shorten causing the cells to lose genetic information and change. A Telomere works like a password-cracking program in theory, which generates thousands of random numbers and letters per second. So if a chromosome messed up and got smaller, the Telomere would activate and guess each letter in the ACTG strand until the cell started working again. This process isn't perfect, so each time a cell splits there's a roughly 1 in 1000 chance that it mutates, resulting in a different cell, which %99 of the time undergoes apoptosis and dies. But that 0.001% of the time, that cell stays there either because it happens to be overlooked, or it happens to be benign, meaning in an immortal being, his genetic information may slowly change over 1000s of years, meaning his brain cells might start to change, so in said immortal being you may see his personality slowly change, eventually resulting in a completely different person. As far as how this person would fare in society, it would be interesting to see him go from being a a perfectly behaved, law abiding citizen, never a bad thought in his head, to complete lying scumbag capable of manipulating emotions purely for his own selfish gain. Without taking away from HDE's answer: The Neural Stem Cells would still be capable of being damaged and changing. The brain has two main types of neurons, grey matter, used for fast thinking, and white matter, used for slow thinking. With the knowledge that Neural Stem Cells divide and differentiate into these types of cells, it's easy to see how a person could over time become slow in some areas, and fast in others, leading to total personality change. [Answer] The downsides to immortality: Boredom. After a couple of centuries, existence could feel like "I have a thousand channels and nothing to watch." Personally, when asked whether I would rather be a vampire or zombie, I pick zombie. Reason: zombies have a shelf life. Eventually you lose enough parts, you're gone. As an immortal vampire I envision developing a death wish, growing more and more reckless -- or thrill seeking -- until I eventually died of misadventure. Dismay at the immaturity of non-immortals. If the entire society is immortal, dismay at character attributes that you deem unproductive -- and that would build stress like political schisms do. But more so. These would be mental-health issues. Population issues. Even with mortality, birth control, and pollution to slow us down, we traditionally have outbreaks of disease and genocide that cull the human population, but only for a bit. The pressure of ever increasing immortal numbers on the existing territory would be a psychological factor. Unless the birth rate slows, or science + culture decrease it. Strategies: Meditation. Pro-level meditation techniques would help keep the mind fresh, and the attitude positive. Letting go of history / memories. Keeping the basic principles, and ever building on them, would be the path to sanity. Records could be kept -- the way we all bookmark the Egyptian pyramids, and emergence of modern science, and the major wars. Although they would grow less important, and more quaint, as they receded into the past. The same way, when a teenager was trying to convince me I had approved a questionable activity, a friend said, "You don't have to remember any given conversation. You just know what your answer was, is, and would be," you would be less dependent on lists of facts, and more on accretions of your best practices. It would become indistinguishable from acting on instinct. [Answer] The answer depends on the traits of our immortality. I will assume that it means that our bodies are capable of preserving ideal homeostasis indefinitely. Specifically, I will assume that: * Damaged neurons can repair through anything but an [information-theoretic death](https://www.merkle.com/definitions/infodeath.html). * No toxic substances accumulate over time that reduce our mental capacity. * No biological glitches occur when our ~~uptime~~ lifespan becomes excessive. * All other properties of our brains remain unchanged. With this in mind, from a purely neurophysiological point of view, the answer would that we would quickly hit the point where we are not taking in any new information. Memories that we consider permanent may degrade over time (do you think you'll remember yourself as having the same name 600 billion years from now?), and new memories will be formed. An immortal human will become far more *wise* than any mortal counterparts as knowledge gathered throughout their unlimited lifetime makes their understanding of the world around them more *accurate* (but not necessarily more complete, as our memory capacity is limited). Eventually however, a point will come where having a greater knowledge will result in us requiring a higher memory capacity than we currently have, at which case we will hit a plateau. This is assuming of course that we have not used our gathered knowledge to enhance our own mental capacities beyond what they currently are. From a psychological point of view, we will not be much worse off. We will not be eternally bored unless there is nothing to do for eternity. Any emotion we have cannot be amplified beyond our ability to experience it, so at any given moment, even an eternity of hell will be no worse than a decade in hell. We will be emotionally stable most of the time, but the long lifespans means we are more likely to run into situations that cause long-lasting PTSD (how many horrible wars, famines, and tragedies do you think you'd live through if you were born in the 1600s and were still alive today?). Over time, the culture of a human society drifts. This occurs both within and between generations. The elderly today would rarely agree with the opinions and views of their youth. Immortality can thus be thought of nothing more than a society which does not need generations. Languages will change, our moral framework will be vastly different in 100 years than it is now, even if we are the same person. **Overall, we would be more wise and would hold more knowledge, up to a limit. Our culture will drift over time. Other than this, we will remain relatively unchanged.** [Answer] Cracked did a piece on this very topic. The only brain-related issue they discuss is the idea that your perceived flow of time would speed up so much you'd go insane. As you get older, and things are not new and exciting, you pay less attention to things that you're used to. So as you get older, there's less things you're spending time looking at, which is why days seem to pass more quickly. If you're old enough to have literally Seen It All, time would fly past at a rate reserved for trees. Clicky-link - [Why Immortality would be worse than death](http://www.cracked.com/article_18708_5-reasons-immortality-would-be-worse-than-death.html) [Answer] Your skull has a finite size. Even with a future enhanced human, with perhaps a cranium engineered to be somewhat larger, the space is limited. Given the finite space, there is only so much information this human can store in it's head. Even if somehow they have re-engineered the brain to be more efficient in this respect, in terms of both bits per volume and compressing more data per bit, an immortal human will at some point begin to exhaust the available space or permanently forget things, in terms of both memory and learned skills. Let's further hypothesize this human has a cybernetic implant, helping the brain overcome these limits to store information in another location. As the amount of information grows, searching or locating this information will become more difficult. Just getting a computer address location of memory data, collating that data, and recalling relevant information will begin to become an unwieldy process. *The point is, I have to think that memory would be effected after a few centuries.* Maybe sooner. This human would either become very forgetful, or would have a much slower thought process in order to evaluate available data, or would appear absent-minded, where it could remember and use a piece of information in one moment, forget all about it not too long afterwards, and then seem to remember it again later on. If a human like this ever became truly *OLD*, think about pushing all these effects to their extremes. It would possibly resemble forms of dementia or alzheimers. [Answer] Hmm. First of all, if you eliminate degenerative diseases as a cause of death, you still have accidents. You can play with standard actuarial tables and you get an average lifespan of about 1700 years. However you end up with a long tail. Like radioactive decay, people have a half life. I'm not convinced. A better model would be a mix of radioactive substances. The short lived ones decay rapidly. Consider the difference in attitude between a 14 year old boy skiing and his 60 year old grandfather. Us old farts no longer believe in our own immortality, and we tend to be more cautious. This would greatly extend lifespan. As to the memory issue that comes up in other answers. Suppose that we have a well integrated chip memory. With retraining, then much of our brain becomes indexes into the chip memory. This could be a part of the background of your world. People get older, but they get less nimble mentally, and unless they work at it suffer from 'hardening of the neurons' where original thought or even decent decision making becomes increasingly difficult, to the point that some individuals are little more than human flesh automatons. Preventing this takes the same sort of energy and concentration that people spend now trying to look young in their 70s. And there can be considerable quackery connected to these efforts. (Never eat these 5 things and stay sharp) You can have fun if some techniques (Zen meditation, daily treatment with flux capacitors, magic beans....) actually work. Take another step. "Use it or lose it" Suppose stem cell research pays off and your brain is constantly rewiring. You remember well what happened in the last couple of decades, and anything older than that fades. You see this now: Try this as an exercise: Make a chart with a logarithmic scale: This year, 1 year ago. 2 years ago. 4 years ago. 8 years ago. 16 years ago. etc. Now quick as you can jot down incidents. and put them in about the right time frame. Routine stuff melts together much more than other things. I love the crime dramas, "What were you doing on the evening of June 7 2003" For me, the answer to that is, "How the F\*\*\* would I know. I don't remember what I had for supper last night." Suppose that if you don't consciously work at remembering things, you forget. If your life revolves around work, you become an idiot savant about work, to the exclusion of all else. Most people over, say 200 years become less and less human in their outlook, and more and more like specialized AIs One way people try to postpone this: They have a personal camera they wear glued to their forehead. It records their life. An AI processes the daily stream, weeds out the cruft, and indexes the rest. In addition for things that mattered (physio status of emotional indicators: pulse, sweating, respiration) it talks it over with you. Part of your day is spent reviewing events from previous years. Insights: Lois Bujold addresses the organic and the chip memory idea in her Vor universe novel *Memory*. Heinlein visits it in *Time Enough for Love* with the mention of the Libby technique of 'Cascading memory' [Answer] If you assume or want to adhere to relatively realistic biology of the brain (and leverage our ignorance of a lot of things related to it), there are a couple of factors to deal with (and things you can work with): **Cell counts and cell death:** We're assuming the source of immortality effectively defeats cell death from age-related causes (e.g. telomeres being restored via telomerase) and that ongoing radioactive exposure and other environmental factors do NOT in fact result in cancers (the saying is if you live long enough, you will get cancer, no matter what). Your neuron count will largely stay the same once you reach adulthood (barring cell death due to various factors) except for a pool of stem cells that you're left with to expand those mental horizons. Even so, there's a limited pool (if not a very large one) of neurons to maintain everything from skills to memory and your personality. **Synaptic Plasticity and Memory:** With that limited pool, that means that memories, over the years, will likely fade as new ones are made. Neurons can adjust and change connections between themselves to strengthen memories and to change pathways as we live. While most of us, if we get old enough, will likely lose memories and functions due to decay or disease, an immortal would likely not. Instead, they'd just continue to make new memories (and perhaps learn new skills while enhancing existing ones). I would argue, just like most adults don't remember the details of every day of their childhood (just the salient/memorable moments), an immortal will have memories that fade over time, something that might be a saving grace because traumas might have a chance of fading. **Life Experience:** We're all ultimately the culmination not just of our experiences but of the wisdom derived from those experiences. Our presence of mind (namely stemming from our interests in whatever the subject matter might be) defines just how much of those experiences we learn from and retain. If you aren't interested in a subject, you'll rarely retain much except those random facts that somehow got stored likely because something else was tied to it (e.g. environmental memory). And assuming we are focussed and healthy, we can generally accumulate a lot of knowledge...more than we often feel we should be able to. When you talk to a fan who can quote stats across decades of a sport or someone who absolutely loves a topic and knows everything there is to know about it, remember that they also remember large portions of their lives, friends, family, people they hated, foods they loved, places they loved, people they admire, and so on. We store vast amounts of information in these squishy brains. :) I think as you go on, say for a few hundred years or a thousand, you'd find that yes, you'd forget a name, or a face, you'll forget a song or the smell of a certain flower. There might be a mix of sadness associated with that (imagine how someone with dementia or Alzheimer's feels) and wonder (consider just how much knowledge you'll still have at your fingertips though). I could see someone like that, having learned that memories do fade even if it takes 100 years, taking on the same habits mortals take on (keeping photos, mementos, etc.). Meanwhile, there's something to be said about the confidence that stems from having a broad set of knowledge. I figure through just the sheer fact that they have the time for it to happen they'll accumulate a lot of knowledge. They may not be experts but they could piece together associations or bring ideas to a conversation or discussion that most people wouldn't think of simply because they don't have the breadth of knowledge someone like this would have. Just one other thing to consider--something touched upon by some stories involving immortals: there is going to be some emotional scarring that results from seeing all of your family then all of your friends (including newly acquired ones) eventually getting old and dying. It can lead to defense mechanisms (like distancing themselves from mortals) which can definitely affect how they behave as the years go on. Plus, if they're trying to hide from society (e.g. Highlander), that creates a whole slew of stresses but also changes in behavior outside of the norm. The other thing, which is sort of related to the latter part about their interactions with society, is the vampire grampa syndrome. In vampire stories, you often see super old vampires having trouble integrating with modern society. They were just fine with styles from 100 years ago. It's supposedly why they'd take a new victim to help them get up to speed with society and trends. Of course, they also tend to be separated and sequestered from general society so maybe not much of a concern? Hope this helps. [Answer] Given a brain case that does not get any bigger, the brain inside it will have a limit to its capacity. Assuming all cells eventually die, and the only way to keep a brain from shriveling to nothing is if cell death was balanced by replacement (we'll assume an artificially-enhanced natural process), it's reasonable to expect that old connections will eventually disappear as new and different connections are formed. One might extrapolate this to: * Things not actively remembered, or knowledge/skills not actively used/practiced will eventually be lost * New information/skills can always be learned, maybe less efficiently over time, maybe not - if neuron death is offset by increased rate of replacement, the efficiency of learning new things might be maintained * That which defines "who we are", defined by the sum of our experiences, would be stable over the short/medium term, but would be plastic over the very long term. ]

[Question] [ Diamonds are carbon. Plants take in CO2 and use the carbon. Chemically, could the right kind of plant have diamonds for berries, or is there some other limiting factor? [Answer] A plant could produce a diamond chemically by laying down carbon atoms in the right crystalline formation. Heat and pressure are for geological diamonds, they aren't relevant when you're dealing with atoms at a time. There is no reason for them to do this, evolution-wise, but since you're talking about genetic engineering that doesn't matter. Forming diamonds this way would only be limited by how much carbon the plant can get. They could strip hydrogen, oxygen, etc. from any organic compound, but it would probably be much more efficient to feed it carbon directly as either graphite or charcoal. The problem is not with "diamond" but with "berry". From Wikipedia: > > ...a berry is a fleshy fruit produced from a single flower and containing one ovary. > > > Which a diamond definitely is not. But in terms of diamond trees with clusters of jewels, it's possible. [Answer] Quite possibly! Biology has the advantage of being able to micromanage what is going on chemically and mechanically. This often allows life to achieve results that humans currently achieve with huge chambers at incredible temperatures and pressures. With advances in genetic engineering we will become able to leverage this more and more. We can now make synthetic diamonds quite easily using [Chemical vapour deposition](http://en.wikipedia.org/wiki/Chemical_vapor_deposition#Diamond). Although it would be quite difficult for a plant to "handle" gaseous carbon due to its extreme temperature, the plant could instead liberate single carbon atoms at high energy. Of course this would be happening simultaneously all over the surface of the diamond, and the diamond would slowly grow, probably over years. Note that the diamond itself would not be "alive"—it would certainly not have any reproductive capacity. Perhaps living cells could be embedded within it, though. It's possible that the enzymes and/or cells that surround the diamond during its formation would occasionally get trapped within it, particularly with "early prototypes" of the plant. I expect this would manifest as cloudiness of the diamonds. Conceivably such diamonds could become fashionable due to the knowledge that it is caused by living matter trapped inside, at which point genetic engineers might intentionally manipulate the process to create visible patterns within the diamonds. [Answer] Diamonds are considerably more than just carbon. According to [this](http://www.livescience.com/32266-how-are-diamonds-made.html), there are believed to be four steps to the formation of diamonds: 1. Bury carbon dioxide 100 miles into Earth. 2. Heat to about 2,200 degrees Fahrenheit. 3. Squeeze under pressure of 725,000 pounds per square inch. 4. Quickly rush towards Earth’s surface to cool. I'm fairly certain that plants combust a few degrees below 2,200 degrees Fahrenheit. There are a few methods we've managed to produce synthetic diamonds with, but both involve high temperatures. [Answer] Definitely not naturally - for the simple reason this is completely impractical from evolutionary point of view. Diamond requires a lot of energy to form. Even if the process was atom-by-atom, with the biology handily providing easily detached placeholders preventing the surface from oxidation (forming weak bonds with the diamond's carbon, then breaking them and replacing with more carbon atoms making the diamond grow) attaching each new atom would take a lot of energy; energy the plant must obtain on top of maintaining its own growth and life processes. Energy better spent on more useful endeavors like growing taller to outgrow competing plants, or producing more seeds to increase chance of finding fertile soil for them. OTOH artificial species like this would be possible. I doubt it would resemble berry bushes as it would need a massive leaf system to acquire all the needed solar energy and carbon dioxide, a massive root system to provide water and nutrients to the massive leaf system, a "skeleton" to support both, and the diamonds would not be exposed to the air, instead growing inside some fruits that would prevent oxidation and contamination of the growth surface. So - replace your diamond berries with diamond trees :) [Answer] Contrary to some of the answers here, there is no chemical reason why a plant couldn't manufacture diamonds (source: bachelor's degree in chemistry). The individual alkane bonds that make up diamond are nothing special, and living cells make and break that sort of bond all the time. Artificial synthesis techniques work on atoms in bulk, whereas biological systems can synthesize molecules more or less atom-by-atom, and for this reason the constraints that make diamond hard to synthesize by bulk methods are mostly irrelevant to biochemistry. As a very loose analogy, imagine you had a sack of Lego bricks and you wanted to join them all together into a solid block. In bulk chemistry terms this means continually shaking ("heating") and compressing the sack, and the bricks would join together to some extent, because the joined state is more space-efficient ("thermodynamically stable"), but it would take longer than the lifetime of the universe to get to a single solid block, unless you were shaking the bag really, *really* fast. As a living cell, you'd simply open the sack and put the bricks together one by one. Biochemistry isn't magic, and there are thermodynamic costs to working in this organized way. In the above analogy, the living cell first needs to manufacture complicated specialist enzymes to grip and combine Lego bricks, and that background work will require a great deal of energy overall. The difference is, though, the energy isn't expended all at once, so it doesn't necessarily imply high temperatures or pressures. In terms of evolutionary biology, there would need to be a good reason for the plant to evolve this feature (evolution doesn't waste energy). Even then, you could debate whether it's feasible at all in terms of energy landscapes; see e.g. the discussion about evolution and wheels. If it were a genetically engineered feature, the question is not whether it could be done but only how hard it would be. Possibly the answer is "insanely hard", but that's the kind of question you can't answer until someone does it. [Answer] In *A Deepness in the Sky*, Vinge referred casually to strata bearing *diamond [forems](https://www.wikipedia.org/wiki/Foraminifera)*. You might also think about *diatoms* which produce a cell wall of silica, literally glass. I think it's plausible that microorganisms could produce structures of crystalline diamond or carbon fiber, in a variety of manners that real life produces inorganic shells in or around itself. Vinge used forems rather than more familiar diatoms, I think because the *test* (shell) is like a seashell, extruded around the cell. But diatoms produce glass in their cell walls, so you might imagine a mechanism where it is created in a completely enclosed chamber and then the outer skin is disposable leaving the protective shell to face the harsh environment. Others have pointed out that nanotechnology or "life" could plausibility deposit crystals atom by atom, but I think carbon fiber is more realistic: look how carbon fiber is actually manufactured: start with an organic molecule that has a very common carbon hexagon backbone, and then removing all the extra atoms leaving only the carbon hexagons. But I'd like to note that these structures won't be solid rock diamond crystals, but sparse filigree and thin walls, like diatom shells. What might be the use of something like diatomaceous earth that's composed of diamond rather than silica? Obviously abrasives, but could a useful composite material be made? If such a thing existed in nature, technological society would figure out *how* the nanotechnology works inside the cell, and apply the ideas to synthetic processes; or use selective breeding to produce algae that grow long fibers. [Answer] As a follow-up to [knave's answer](https://worldbuilding.stackexchange.com/a/15320/8622), for a diamond-fruit, I'm picturing a walnut-like fruit which has a fleshy outer layer, a hard middle layer, and the living part of the seed in the center. The outer layer would prevent Hydrogen and Oxygen from binding to the Carbon while more layers of Carbon are deposited. A cut in the outer layer could potentially disrupt the carbon-laying process while the fruit is growing. The diamond layer, like a walnut shell, would need a seam; a weak line along which the shell will split when the living inner part sprouts from the seed. The seam must be much weaker than diamond, as no seedling is going to have the ability to punch through even a thin layer of diamond. The shell might grow with [several seams](https://i.stack.imgur.com/RLjTn.jpg) or just one, depending on the plant. It will also need a path for nutrients to enter the inside of the shell, which could be the seam or a hole. Depending on how the shell splits, you may end up with bowl-shaped diamonds...not ideal. The inner part would need enough food for it to grow until the seedling applies enough force to split the shell along its seam. As such, it would probably be close to the size of a walnut, or even as large as a coconut. One potential problem is that while diamond is hard, it is not flexible. Most plant matter *is* flexible because plants are always changing their shape. A diamond fruit would need to grow to its full size *before* it started growing a diamond layer. One last thing. Diamonds are "valuable" because of market manipulation. There are much prettier stones and much rarer stones out there. Their scarcity in the jewel market is manufactured scarcity. Industrial diamonds are valuable because of their hardness, but they are common and can be manufactured already. The cost to develop a plant that grows diamonds would far outweigh the value gained from producing diamonds with plants, for both jewelry and industrial uses. It's more likely that an eccentric billionaire would fund development than that a diamond company would. [Answer] While it wouldn't be a berry I can think of a reason for a diamond to evolve: A plant with diamond needles inside it would be akin to being poisonous but it would be even harder for a creature to evolve resistance. I doubt there is an evolutionary path that leads to this, though. ]

[Question] [ A civilization has a "magic" computer with memory and processing capacities far beyond what our physics says is possible. They decide to run a massive simulation of [Conway's Game of Life](https://en.wikipedia.org/wiki/Conway's_Game_of_Life) with a random "big bang" initial state. The goal is to see if, given enough simulated time steps and a large enough random initial canvas, intelligent life will evolve. But here's the question: even if intelligent life did evolve, how would the simulator civilization know it was there, when all they (or rather, their algorithms) can see is a semi-chaotic pattern of blinking dots? **Edit:** The "life" bit isn't that important; "intelligent non-life" would also work. And the "signs of intelligence" need not be definitive. What sorts of things would scientists (and philosophers) consider when trying to decide if intelligence had arisen? What sorts of debates might they have? --- **Philosophical digression** (trying to provide a substitute for the best of the comments [moved to chat](http://chat.stackexchange.com/rooms/49563/discussion-on-question-by-charles-staats-how-to-tell-if-intelligent-life-has-evo)) *Skeptic:* What is life? What is intelligence? If you will not define these two, your question is unanswerable. [line quoted from user Molot] *Enthusiast:* You don't have to define intelligent life to search for signs of it in astronomy. Why should this be any different? *OP:* Both points are good. Consider why you think other people have minds (as opposed to being mindless automatons). The most relevant response here is that minds have explanatory power: there are certain actions people take -- such as having discussions about the nature of minds -- that would be absurd if they did not, in fact, have minds. If we were searching for alien intelligence, we would look for signs like buildings or [radio message patterns](https://en.wikipedia.org/wiki/Arecibo_message) that can most easily be explained by the existence of an alien civilization. In the same way, we can look for patterns in the Game of Life that -- while not violating the rules -- are virtually impossible to imagine without deliberate design. *Skeptic:* Where to begin? First of all, postulating intelligence cannot possibly add any explanatory power to what we already have. The Game of Life is deterministic and we know all the rules. Second, you can't assume intelligence just because you have an elaborate mechanism for accomplishing a purpose. Many things (like eyes) appear to have been designed for a specific purpose, but were in fact produced by natural selection without any actual intent. *OP:* Let's take these points one at a time. **Explanatory power in a deterministic system:** Consider the laws of statistical mechanics -- most notably entropy. Technically speaking, if you know a physical (Newtonian) system perfectly, the laws of statistical mechanics are completely unnecessary: you can predict exactly where every particle will be after any specified amount of time. But in practice, applying statistical mechanics will allow you to make certain predictions much more cheaply, such as the average velocity of the particles in one particular spot. So statistical mechanics has explanatory power even though in this instance it adds no information. *Enthusiast:* I think your criteria for "explanatory power" is still too stringent. Many explanations have no predictive power whatsoever, even in terms of making cheaper predictions. For instance, if (in real life) we received a radio signal that was the first twenty primes repeated over and over, we would probably postulate an intelligent source even though that explanation doesn't really help us predict anything more cheaply. *OP:* That's true enough. Cheaper prediction is a nice illustration of explanatory power in the face of determinism, but it's not the whole concept. Like many philosophical ideas, "explanatory power" is precise enough to be useful but vague enough that no two people have exactly the same definition. *Skeptic:* How exactly is that useful? *OP:* Let's just agree to disagree on the usefulness of imperfectly defined terms. To be considerate of our readers' time-- *Skeptic* [aside] *That* ship has sailed. *OP:* --let's move on to your second point from earlier. **Designed technology vs evolved organ:** Let's remind ourselves of the earlier exchange: > > *OP:* We can look for patterns in the Game of Life that -- while not violating the rules -- are virtually impossible to imagine without deliberate design. > > > *Skeptic:* You can't assume intelligence just because you have an elaborate mechanism for accomplishing a purpose. Many things (like eyes) appear to have been designed for a specific purpose, but were in fact produced by natural selection without any actual intent. > > > That's fair enough. In our own world, certain kinds of patterns -- such as [projectiles](https://worldbuilding.stackexchange.com/a/2489/16106) or [wheels](https://worldbuilding.stackexchange.com/q/20664/16106) -- seem to be exclusively the domain of designed technology rather than evolution. But even in our own universe these distinctions are hardly intuitive, and spotting them in a completely alien universe like Conway's Game of Life would be all but impossible. Perhaps radial propagation of information might be a sign of designed technology? (In the Game of Life, diagonal, vertical, and horizontal movement are much more natural than movement at any other angle; propagating information in all directions at the same rate could be something highly desirable that would never show up "on its own" (without intent), even through evolution. But who knows?) Another way to think about it is that artifacts designed with intent tend to be good at things that have nothing to do with their own survival. For instance, if we found something in a simulation that appeared to be a program for playing the board game Go exceptionally well, it would certainly be worth publishing as a "sign of intelligence" whether or not the program itself were considered intelligent. Another thing to look for would be advanced communication -- especially concerning mathematics, since that is universal. But it's also possible that things that are difficult to compute in our universe, typically requiring advanced intelligence, can be done comparatively simply in a GoL universe, and vice versa. *Enthusiast:* Perhaps we (or our fictional protagonists) could scan the GoL universe for patterns that obey differential equations! Clearly no differential equations could show up in such a universe without deliberate intent. *OP:* Maybe. But differential equations are so powerful I have a feeling they would work their way in just fine without intelligent help. Anyway, perhaps if we [ask on WorldBuilders.SE](https://worldbuilding.stackexchange.com/q/63118/16106) they'll have some suggestions. [Answer] With a large enough canvas of random data and enough cycles, intelligent life would evolve, assuming the Chuch-Turing thesis. Even weaker than that, assuming the universe is no more than non-deterministic. Rough proof: Conway's game of life is a Turing-complete game. You can create a general purpose computer in it. This computer may require a large initial state and be fragile and slow, but that just increases the size of the initial seed and cycle time before it can exist. This computer is magical, so it can handle both of those issues. In fact, you can have an unbounded number of such computers, running an unbounded number of different programs. Assuming the Church-Turing thesis, at least one such program is intelligent. Assuming the universe is no more than non-deterministic, a NDTM can be simulated in a TM, and a NDTM can thus describe the universe. So given enough space and time and uniformly random initial states, somewhere in the infinite field there will be a turing machine that proceeds to simulate the evolution of every possible universe from an initial big bang with physics like ours. One of these simulated universes would be our universe (without the magical computer, naturally). Our universe appears to contain intelligent life. So that is proof of existence. Now, we should examine what it would take to *find* this intelligent life. The Conway's game of life doesn't *directly* contain it. Rather, it contains a pattern of life that can be interpreted as a computer (actually, unbounded numbers of such patterns, most of which are short lived due to flaws), which simulates a non-determinstic computer, which proceeds to exhastively simulate entire families of universes. No human being or non-magical computer could, if someone pointed out the section of the system that was doing this computation, even interpret it or confirm if that was indeed the section in question. The parts of this machine's state would be literally larger than the entire universe's data capacity. We couldn't even *look* at the part in question. It is so slow that the number of cycles required to describe even the merest fraction of a fraction of a fraction of a ... of a fraction of a ... of a fraction of a fraction of a second of the universe might be a number too large to express in this universe. But that was just an existence proof. In theory, a much smaller system could actually house inteligence. We can look at our universe. One of the possible explanations for our physics is that we are experiencing an inverted platonic wall of shadows. Our physics actually plays out on a 2+1 dimensional boundary of our universe, with the 3+1 dimensional interior of the space being a hologram " "projected" by it. One of the motivations behind this possibility is that there appears to be an information limit in our universe proportional not to volume, but to the surface area of a region! Physicists have created mathematics for toy universes that match this pattern, where there is a N dimensional physics system with a N-1 dimensional system that holographically determines the behavior of the N dimensional system. Such a technique might easily be the easiest way for conways game of life to create a complex enough universe for evolution to occur in. So the 2+1 dimensional game of life might generete a holographic universe where the "interior" perspective of the intelligent beings does not correspond to the 2+1 dimensional "underlying system" that generates the hologram. Stepping back again, even if that doesn't happen and the resulting intelligences do end up living in flatland, they might exist on ridiculous scales. The equivalent to a "cell" of our universe is the Planck length, or a Planck patch. This is about 10^-35 m, or 10^-20 times the size of a Proton. A proton is about 10^-15 m in size. The observable universe is about 10^26 m. ``` -35 -- Planck scale -15 -- Proton scale -10 -- Atomic scale 1 -- our scale 7 -- planetary scale 14 -- Solar system scale 20 -- Galactic scale 26 -- Universe scale ``` If we take jumps of a factor of 10 million per step, we get roughly: ``` -5 -- Planck scale -4 -- ??? -3 -- ??? -2 -- Proton scale -1 -- Atomic scale 0 -- our scale 1 -- planetary scale 2 -- Solar system scale 3 -- Galactic scale 4 -- Universe scale ``` The "cell size" of our universe is ridiculously far away from our scale. Atoms are roughly half way from that to the entire universe. If we assume this is typical, then even in the regions where there is intelligence, figuring out a reasonable model of **physics** that they are experiencing so far away from the rules of Conway's life would be beyond our current skills. They would no more exprience the rules of Conway's cells that we notice the rules of string harmonics when we throw a baseball. [Answer] # Conway's GoL. Conway's Game of Life tend to towards two modes: Extreme chaos and extreme order. (To see this, start a simulation of about a million random pixels and see what happens) Different areas can show different behaviour. In extreme chaos mode every pixel changes seemingly without patterns. In extreme order mode every pixel either is stable or changes in a very short cycle, usually 2 time steps, sometimes 3, very very rarely more than 3. # Life Life would be different. There would be patterns, but they would not be strict. As the life form multiplies, there would be large-scale repetition of approximate patterns. You would recognize life by this: Large number of "cells" that looks more or less the same, and that seems improbable from a local point of view. # The Environment Around these cells would be an environment of the usual chaos and order patches. This environment will be deadly to the life. Simply random changes will kill off the poor innocent little cells. In the beginning these life forms would follow a very simple strategy: Multiply faster than the environment kills them off. # Advanced strategies, "intelligence" Eventually, however, they would become smarter. They would change the environment to be more friendly to them. They would also find ways to recognize each other. They could either compete, to ensure more space for their own children, OR they could cooperate, to tame the environment. Some would *pretend* to cooperate with their neighbours, but secretly preparing to kill them off. Then recognition would become more complex, to see the difference between close relatives that can be trusted and cooperated with, and strangers that has to be fought. The life forms would invent war. At what point should we call them intelligent? That is a matter of definition. I leave that definition up to you. # Looking from the Outside. For the outside observers, all this looks like more and more complex patterns, over larger and larger areas and longer and longer time intervals. I suspect it would be quite clear to the observers why things are happening, this cell attacking that cell, that cell cooperating with that other cell to build a wall and so on. **One indication of intelligence would be that the observers no longer understands what happens.** At first you will have observers going "Oh, so *that* is why it did the odd thing 10000 time steps ago!". Later they will say "I have no idea how they achieved that!". That point is as good as any to say that the life has become intelligent. [Answer] A computer scientist here, I will chime in with my educated guess. You will not find them, unless you have billions of people searching for intelligent behavior in this simulation. Problem is massive, the size of the canvas would be extremely large. I am talking about 10^20 by 10^20 size canvas. The number of atoms in a human body is ~10^28, each atom requires many cells in CGoL. Even if your intelligent beings of automata is much smaller in scale, we are still talking about a pattern that has a size of trillion by trillion. Understanding that this pattern is acting intelligently is a magical task. The interactions at the border of this pattern will be chaotic as well as its internal actions. I think this problem explores this, if we are living in a simulation, it is most likely that our simulator will never understand that we are intelligent and alive. *Factoring in the discussions from the comments:* The size estimates that are done here is for an intelligent system that is not alive. Also the canvas size is not to simulate our universe physics, if you are to do that you will need canvas sizes that are larger than $10^{185}$ cells in the best case. [Answer] Many of the answers here seem to be concerned with whether something like life could develop in a GOL simulation. I will instead begin by assuming that intelligence *could* develop, and try to answer the question "how could we detect it?" by comparing to our own universe. I'll assume we would know it if we saw it, too -- that after a bit of observation, we could tell when cells are working together and making decisions. My conclusion: it would still be **insanely difficult** for outside observers to detect -- it's the biggest game of "Where's Waldo?" I can imagine! To get a sense of scale, if we're trying to compare to our own universe, then we've got to zoom **way** out. The closest thing we have to a quantized length in our universe is the Planck length. So, imagine each GOL cell in this simulation as a single Planck cube. Now, think about the scale when we zoom out to an entire universe. I'm not aware of random Game of Life simulations having been conducted and examined on boards larger than a few thousand by a few thousand -- hardly enough to represent a quark, and hundreds of orders of magnitude smaller than what we're talking about here! But a common pattern to most simulations is that pretty quickly, most of space becomes empty, with scattered cells forming what we can think of like "background radiation." In some areas, there is more complex activity taking place, but these areas are few and far between. Our own universe is structured much the same way, so I can image that a search for intelligence in the simulation would be like a search through our universe. Suppose you had the ability to observe the 100-billion light year sphere of the universe that we can see. Let's even assume you have a computer with enormous memory and processing power to help you. You can look anywhere, zoom in or out, and automate some search algorithms. Would you be able to find the humans? Given enough resources, I imagine you could make a program that filters out the huge portions of space that are mostly empty. What's left would be the galaxies, which you could recursively search for solar systems and planets. The first issue is knowing how far you need to zoom. You don't know how big lifeforms will be -- will they contain thousands of GOL cells? Trillions? More? If you're looking at our entire solar system at once, you won't know humans are here -- you have to know to zoom in on the surface of Earth to see our cities. If you're zoomed in to a molecule, you'd have no idea that it's part of a human cell. You have to know to zoom out to see collections of cells working together. The second issue is that even if you know what scale to look at, there's simply too much to search through. It's estimated that there could be more than a trillion planets in our galaxy alone, and at least 100 billion galaxies in the observable universe. Each of these planets is itself enormous, and would require a close examination to rule out intelligent life (imagine looking at the Earth 50,000 years ago -- if you're going too fast and don't look hard enough, you might not know humans are there!). However you do this, you're not going to be fast enough to process these planets in anything even close to a reasonable amount of time. The only thing I can think of that could help this search would be understanding the laws of physics in the simulated universe. Of course, we know the microscopic rules; they're just the GOL rules. But I mean understanding the rules on a larger scale. How do the cells tend to group together? Let's call these groups particles -- how do the "particles" interact? On what time and distance scales do they affect each other? From there, we can build up the rules of "chemistry" in the simulation. At the opposite end, we could also start looking at a large scale and discover the equivalent of astrophysics. This would take a huge investment of time and research -- humanity's understanding of physics and chemistry was built up over thousands of years, and was aided by our ability to interact with our world. If we had this knowledge, it could potentially help filter out planets faster, just as astronomers do in our own world, based on chemical makeup and environment. But it's still not clear that it would help an outside observer much, since even understanding chemistry and physics in the abstract doesn't help you understand what is and isn't needed for life -- you need some examples of life for that. So I'm left with the conclusion that **even if intelligent life develops in your simulation, unless for some reason it's vastly more common than in our universe, you won't be able to detect it**. [Answer] The search for automated intelligence could resemble the search for extraterrestrial intelligence -- it's all about signals. The search for automated life is similarly simple -- it's all about entropy. The magic computer program could look for regions within the simulation where entropy decreases locally. Those regions may hold life-like constructs. Once those regions are identified, the program could monitor whatever passes between them (gliders, spaceships and so on) and identify those patterns which are complex enough to carry information. This approach is a heuristic, not an algorithm. It certainly won't identify human-level intelligence. Instead, it might find ant-like intelligence, if such a thing evolves within the simulation. The researchers running this simulation have a problem that is the opposite of real-life sciences. In our universe, we struggle to discover what is fundamental to physics. We know how things seem at a human scale, but things like quantum mechanics and string theory are far from intuitive. For the simulation, the researchers know the laws of Conway's Game, but they have no idea what a mind inside the Game might perceive. The fundamentals are obvious, but the emergent structures are unknown. How can you tell the difference between an ant and a person when the things you can directly observe are equivalents to strings and quantum configurations? [Answer] This could be done in a two step approach: 1. Identify possible intelligent system 2. Confirm (or infirm) the presence For step 1, we could consider the application of the causal path entropy [here](http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.168702) > > When following a causal path, entropy is based not on the internal arrangements accessible to a system at any particular time, but rather on the number of arrangements it could pass through on the way to possible future states. > > > The article points to similarities between this observable behaviour and intelligence. The super computer running the simulation could also be programmed to detect those macros effects. For step 2 we could think of a variant of Turing's test. Today it is purely a computer intelligence test of wether a computer can pass as human which limits intelligence to the human intelligence. Once a civilisation has been exposed to more intelligence forms (either biological or not) a more refined test would be available to test those candidates identified in step 1. [Answer] As many others have pointed out, you need a definition of intelligence to be able to answer this question. One possible definition of intelligence for the purposes of this question is an entity that you can communicate with. Whether it is "truly" intelligent in a deep philosophical sense is pretty much irrelevant in this case (see the [Chinese Room Argument](https://en.wikipedia.org/wiki/Chinese_room)). Again, as others have pointed out, GOL is completely 100% deterministic. However, communication means altering the state of a thing externally. In the case of GOL, you would communicate by introducing changes to the system that are against the deterministic rules. The way to test if intelligence has developed as a consequence of some initial conditions is to see how the system reacts to these externally introduced changes. Is it possible to cause a set of changes to which the system responds in a consistent manner? Can we eventually create a language by which we can assign interpretations to outputs? Does the potential intelligence assign its own interpretation to these changes (i.e., does the response to a given input take significantly different forms depending on circumstances, including previous inputs)? [Answer] I'm no scientist but as I understand it there are certain things that you can look for that are otherwise improbable. For instance your simulation might perhaps watch out for movements of dots that are unexpected. Imagine a group of people pushing a big rock up a hill. Normally rocks go down hills or stay where they are. You wouldn't expect one of significant mass to move up a hill. That indicates that something is doing it on purpose. Obviously in this case replace the rock and hills with various patterns. That might not prove that the life is intelligent but I expect you could keep looking for these changes until you have enough or they become complex enough to be considered intelligent. [Answer] The book *Permutation City* by Greg Egan explores this concept exactly; the emergence of an intelligent species from within a 3-dimensional cellular automata, evolved over a large time-span. If you are interested in this question, Egan explores it in-depth over the course of the novel. The prose is suprisngly good for an amateur writer, but the concepts explored and thought experiments involved are fascinating. As mentioned, and similarly to the perspective taken in the book, human observers look for signs of intelligence by observing the symbolic interactions between entities; once they deciphered their "language", the analysis of the complexity and semantics of the language was used to determine whether the species could be considered "intelligent"; i.e. discussing highly abstract concepts, such as mathematics. [Answer] Suppose you have a **HUGE** simulated canvas. Suppose you display an image of it small enough to actually look at. Suppose you observe that the chaos turns into several groups of pixels that each move around, approach others, change direction. Would you consider that "possibly intelligent"? But note that the original rules of the simulation guarantee that solid patterns of significant size cannot form easily and cannot exist for very long. The centers all have too many neighbors to survive. [Answer] Mason Wheeler has the right idea with his answer suggesting that we have to interact with the Game of Life to determine if intelligent life has formed. I wanted to expound upon why. First off, Mołot has the correct question: what is "life" and what is "intelligence?" These are *not* easy questions. These are highly philosophical questions which have been batted around for millennia. If anything, they seem to be becoming harder questions as science pushes the limits of the world. I don't think we're going to answer them here, so instead I would like to pose an ever so slightly altered question which I think we can more likely answer here: > > How can we tell if something has evolved in a Game of Life simulation > that we should treat *as though* it was intelligent life? > > > This question is more answerable because it includes human limits. If a human cannot distinguish a GoL simulation from life, is it not reasonable to start treating it as though it is alive? To get there, we need to be unable to distinguish a part of the simulation from a human. Pesky challenge, really. It's at the heart of the Turing test. At first pass, it's trivial. If it's in the GoL simulation, it's not a human, because it's a pile of bits! Problem solved! Let's all go out and have a cup of tea. Of course, this really isn't fair. How do you know it's just a pile of bits? The answer is that you peered inside the game of life with your sneaky debugger tools and raped its virtual brain. By the time you were done, you could prove beyond a shadow of a doubt that that section of the GoL space was nothing but a pile of bits. How invasive! Perhaps more importantly, we know that we can classify a pile of bits as "not alive" because we can easily create a clone of it, or a hundred clones of it. We know that its' hard to create a clone of Charles, or a clone of your favorite dog. It seems to be a dividing line: things that can be perfectly cloned cannot be called "alive." Dolly's DNA was cloned, so it isn't alive. However, Dolly's "children" are not the same as Dolly. Each developed differently. Each child is a different "living" individual. What if we weakened the rules a bit, and allowed interaction. This means that humans can interact with the GoL space, setting some cells to living and some to dead, against the rules Conway put forth. This introduces a level of unknown into the mix, and creates our first opportunity for confusing the machine with a human. Let's let many humans interact on this same grid in this way, setting bits to 1 or 0. One of them might decide to use this as a communication channel, transmitting data like an old TELNET console. If you came across this bit, you'd notice that it can pass the Turing test, because there's an actual human behind it! While this may be cheating, it confirms that we can communicate with intelligent life using GoL space to do it. To make things more exciting, let's step up the noise. Let's allow humans to make millions of modifications at each cycle. Make a really big grid, and lots of modifications. Many of these modifications may consist of a human feeding this game of life a random number source (such as de-tuned radio waves). Make enough of these modifications in every cylce that it's really not reasonable for any human to track all of these modifications. Now we have an interesting situation. If we see something "intelligent" we can't prove that it was GoL rules evolving an intelligence, but we can't prove it was a human interacting either. We have to accept the unknown nebulous reality that there's merely something out there acting intelligent. We also now know that that intelligence may have power. The intelligence may be someone on the other end, who is offended by what we do, finds us, and does something violent to us. Or maybe they just find our government and raise our taxes. Either way, an "apparent intelligence" found on the GoL field now has the ability to affect our lives. Now we can answer the question of "When is it reasonable to treat something on the GoL grid as though it is alive." We can set some basic criteria: * We cannot reduce it to a deterministic algorithm (defined by a pile of bits). For all we know it may be a deterministic algorithm centered around a *single* random number generator, but we can't reduce it to just a pile of bits and a rule for how to evolve it. * We can communicate with it -- defined as it appears to respond to our interactions in predictable ways, but not so predictable that they could just be a deterministic algorithm. * It can communicate with us -- the entity needs to be able to make changes in the world that we can see and interpret. * It needs to be capable of helping us further our own goals, and it gives us the impression that it can do so better if we classify it as "an intelligent living being." The last criteria is my favorite. It's not a criteria for something believe "alive" or being "intelligent," but it is a criteria for being treated as one. If it appears that classifying it as "intelligent" furthers our own goals, why would we not give it such a classification? [Answer] I was originally having the gut feeling that the rules are too simple to allow for complex patterns to emerge and stay dynamically stable for prolonged periods. But that gut feeling is apparently wrong: [Undecidability](https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life#Undecidability). Building on the statement that a universal turing machine can exists as a GoL pattern, the basic precondition question could something *resembling* life evolve can be answered: Yes. The next precondition question would be, will something that resembles *intelligent* life evolve? I have no basis for the answer, but I will pretend that since humanity *did* evolve from whatever basic life evolved first, it could, and for the sake of the question, it will. So assuming intelligent life exists in that simulation, will they detect and recognize it? Presuming they have infinite processing capability with their *magic computers*, any kind of pattern recognition they could *think of* is feasible to run. On that basis I would presume they will develop the tools necessary to analyze the games state to find cell clusters that show the most basic behaviors of life: self replication, local entrophy reduction and mutation. Once *life* can be identified by these analytical tools, it can be observed specifically and its in the observers judgement if something is considered *intelligent* behavior. The question then can be transformed into something else: Can they really develop the neccessary analytical tools? Their magical computer allows them to answer any question about past, present and future of the GoL, as long as they are able to formulate an analytical way of answering the question. It does however *not* free them of any limitiations they themselves are subject to: Number of scientists working on the problem, limit of their own lifetime and limit of their civilizations time of existence. So it boils down to what abilities in general the experimenting civilization has. Given enough time to analyze, they will find intelligent life in their simulation, if they destroy the simulation or themselves before they found it, then well... Its remarkably similar to the question if *we* will find intelligent life in our universe, really. If it exists and we don't destroy ourselves, we have a good chance of finding it, one day. Thats a big *if* though. [Answer] It could evolve life, so I assume it could even evolve intelligent life, but I don't know if we can know when something is intelligent, so probably we would evolve a sentient life form but we will not be able to recognize it. **Here's the game I played now:** [](https://i.stack.imgur.com/tmvYO.png) In red you can see actually "living" areas, so there's some storm inside those areas and they are actually evolving. This area act just like few living cells because it continue to move and randomly eat or spawn some "still chunk" (areound living areas you see lot of still chunks, that are equiparable to cell foods). Basically this game I'm doing I'm interacting the minimum amount of time to give the life some spread: you will learn quickly that clicking in certain areas will cause the food to just disappear, while clicking in certain areas will make life active for a while. After some time you will find that you find a way to increase number of food, and you see that everytime food amount increase the life will last even longer before eventually coming to a rest: at some point life will continue to spread on its own, meaning there will be a immense space where there are living and still areas, overall food is growing, and living areas are growing too. This is life to me, and after some time maybe this life can become sentient and more autonomous. By the way interacting randomly (and the minimum necessary I now reached this state): [](https://i.stack.imgur.com/WN3E6.png) Which is still continuing to "live" after 10 minutes. It is pretty similiar to real evolution, maybe bits of life evolve and extinguish, but it leaves "traces" that can be eventually be used again if new life evolve again, and slowly a "ecosystem" builds up. [Answer] Has intelligent life evolved in a Game Of Life simulation? # No. It's really that simple. Among other things, intelligence necessarily requires the ability to analyze information and make meaningful choices about it. This can't happen in a purely deterministic system such as Conway's Game of Life. Whether our world truly is nondeterministic, or is simply deterministic at fundamental levels so small that we don't have good models for them yet is a question for philosophers, but intelligent life must be capable of taking actions that appear to an outside observer to be nondeterministic, unpredictable choices. The Game of Life is *perfectly* deterministic; the entirety of the state of each round after the first is 100% predictable from the state of the previous round. Therefore, it is anathema to the evolution of intelligent life, no matter how large of a simulation is being run. [Answer] Intelligent beings would be present right at the start of the simulation, albeit in a non-local form. This follows from the strong AI assumption which says that all computations that renders an intelligence are equivalent; you would have the same consciousness if your brain were replaced by a machine that would simulate your brain perfectly. Suppose then that one could observe by some means that an intelligence has appeared in a CA at time step T. This means that the evolution of the CA from T to T + 1 is such that a local patch of the CA behaves in a way that we would consider to have intelligent presence. This may involve having to consider perturbing that local patch to see if counterfactual initial states at time T is mapped to a corresponding counterfactual state at T + 1 in the right way. What matters is that a local patch has appeared that acts as some program that takes input from its surroundings, processes that in some way leading to some output. The way the output is related to the input defines the program. The intelligence in exactly the state at time T then also exists at earlier or later times T', because the CA rules define a mapping from T' to T and back. So, you can use the CA rules themselves to "see" that the intelligence at time T was already present at the time of the Big Bang. This is also true for us: see [this article](https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time)) on eternalism and [this article](https://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argument) on the Rietdijk–Putnam argument. One can go a step further and argue that running the CA actually doesn't matter. The intelligence would exist anyway; the CA only allows you to see it. The intelligence should be considered as existing in its own universe defined by its own algorithm. [Answer] # Pattern detection Life, in it's basic form, is based around the natural selection of things. What exists today is what survived, either specifically or by replication from yesterday. This thing that survives could be thought of as information: Be it DNA, RNA and so on. When there is no life there is no order, no patterns in the matter that emerge from the chaos repetitively. But life doesn't imply intelligence. What does? ## Mental patterns This is more complex than pattern detection, because it's about finding pattern (or memes) in different hardware (brains). If you see an object with some internal language, and in this language you see those patterns, that may be duplicated in other similar objects, you probably have intelligence. I think it's obvious that this is a necessary condition for intelligence: A thought without some kind of "words" doesn't seem possible. I argue that it's a sufficient condition. There's an ongoing [philosophical debate](https://en.wikipedia.org/wiki/Computational_theory_of_mind) on it, but assuming you don't think intelligence requires any sort of soul, I think this will do. Finding the internal language of the object and translating the patterns to the languages of the other objects is an enormous challenge. It's a challenge to even detect the objects. But luckily the computer are magical :) ]

[Question] [ The gun in question is a normal, reliable and non-specialized .45 revolver. The idealized character is the last descendant of a lineage of carriers of this gun, considered by them legendary. Is it possible that this gun 'survives' (continues to function properly) for thousands of years without rusting or atomic decay, using only the religious zealot-like care of the lineage of carriers? And, assuming that it can 'survive'. Can the ammunition for it be created with used shells of the same gun? Is there a way to craft new shells, without a big apparatus, like in your own home? [Answer] I'm going to address the components of your question in reverse order. > > There is a way to craft new shells, without a big apparatus, like in your own home? > > > Absolutely. [You don't even really need power tools, although they help.](https://www.outdoorhub.com/how-to/2016/05/26/reload-handgun-cartridges/) The question is how LONG you can keep reloading the same brass until it doesn't work anymore. I've seen people state that they've been reloading .45 shells since the '80s without difficulty, as long as you're conservative with not putting more powder in than they were designed for. > > Is it possible that this gun 'survives' (continue to function properly) for thousands of years without rusting or atomic decaying, using only the religious zealot-like care of the lineage of carriers? > > > The real problem is not so much atomic decay and rust, it's usage. A zealously maintained steel weapon surviving completely intact isn't only plausible, [they exist today](https://en.wikipedia.org/wiki/List_of_National_Treasures_of_Japan_(crafts:_swords)#Ancient_swords_(jokot%C5%8D)). There are swords in Japan that are said to be as much as 1500 years old and still basically look new. There are some cases of European swords almost as old that have been found in similar condition. This is particularly true with firearms, since gunpowder puts a lot of force on the structure of the weapon. The biggest problem would be the rifling in the barrel, since there's just no way to keep that from being eroded over time as you use the weapon. There are also precision components like springs and so forth in the trigger mechanism that would be subject to failure over a really long period of time. EDIT: Puppetsock provided a [lovely link](https://www.gungoddess.com/blogs/news/handgun-maintenance-what-should-you-replace-and-when) in the comments that puts some data against this. You're looking at ~5,000 rounds before the springs and so forth need replacement, and 50,000 rounds for the barrel. That sounds like a lot, but a weapon in regular use might see that much usage in just a few generations. **TLDR: For both the ammunition and the weapon itself, it's not how long the weapon is around, it's how often it's fired that's the critical factor.** If your idea is that there's a Navy Colt .45 that spends decades at a time in a gun safe being meticulously maintained and once a generation it's used to ceremonially execute someone, yeah, no problem at all. I have no doubt that some archaeologist in the year 5000 AD is going to run across someone's collection of AR15s in a sealed gun safe that's been buried in a flooded basement for three thousand years, and those guns will be as good as the day they were made. If you're imagining something like the Gunslinger in Stephen King's Dark Tower where's he's putting literally hundreds of rounds through the thing on a regular basis, no way no how. The barrel would be dead in a couple decades, if not sooner. [Answer] > > And, assuming that it can 'survive'. The ammunition for it can be created with used shells of the same gun? There is a way to craft new shells, without a big apparatus, like in your own home? > > > Yes, it can be done and people do reload shells. For example, I have read that the Sioux Indians in the 19th century invented a way to reload shells with loose black powder and homemade bullets, and no doubt that was cheaper than buying loaded shells. There was even an episode of *Death Valley Days* "A Bullet for the Captain" 03 January 1959, with a fictionalized version where a trader is accused of selling ammunition to the Sioux but it is discovered they are reloading shells. <https://www.imdb.com/title/tt0556532/>[1](https://www.imdb.com/title/tt0556532/) So if the 19th century Sioux Indians still basically living in the stone age could invent a way to reload shells, I would assume that your characters could probably find a way to reload used shells with gunpowder and homemade bullets. [Answer] Making new powder,percussion caps,shot and casings is not exceptionally difficult. Old casings can be melted and remade when they get too deformed. Lead is very common for the bullet tips themselves and can be molded using a campfire with the right tools. A common method when out of brass for casings is to use a cardboard casing. To help prevent fouling the barrel you'll want to wrap the lead in paper using lard to make it stick. Overall assuming you don't replace the barrel,spring or need to do repairs you should be fine. You can use either blackpowder or smokeless powder;although blackpowder will be easier to manufacture even if using percussion caps. If the weapon is only used rarely it will need fewer repairs and as a result last much longer. Properly stored and maintained it can easily last a few thousand years. Longer if parts are swapped out repeatedly over time. As is a revolver is a fairly good choice for the situation as they are less prone to mechanical failure. [Answer] According to [Concealed Nation](https://concealednation.org/2017/02/how-long-will-your-handgun-last/), it takes 5-6 years of 1,000 rounds a month (72k-84k rounds) for normal-grade barrels before any difference is noticed. Some high-grade competitive barrels can last for over 100,000 rounds of normal ammunition. Depending on how handy/connected the original owner was, there are apparently some alloys out there that make the normally used steel wet their pants. [This Thread](https://www.m4carbine.net/showthread.php?185269-Superalloy-barrels) talks about super alloy barrels made out of things like 17-4PH or H13, however the main constraint was the price - 2-3 normal barrels could be bought for the same price as one super-alloy barrel, although keep in mind that the design was for military machine guns operating at 350 rpm sustained fire, not standard revolvers. One of the comments mentions that nitriding or chrome-plating would also help extend the life of your barrel. [This Patent](https://patents.google.com/patent/US8333029) contains all the information needed to make an "Extreme duty machine gun barrel," where most of the problems listed in production would only apply to bulk-made parts, not artisan guns (i.e., it is difficult to apply chrome in large production runs, and prevents the barrel from firing at 800 F or higher for prolonged periods of time). Since you have 1) a revolver, and 2) a coveted revolver, going for the longer-life option would help cut down on the number of part replacements. Since the gun is so cared for, none of the other drawbacks would come to pass, so you can go ham with it. ]

[Question] [ I have a race of humanoids with 4 hands. They are on average 7 feet tall and are as dexterous with each of their 4 hands as a human is dexterous with each of their arms. What kinds of weapons would suit these humanoids the best? Tech levels are late medieval, with some magic, but feel free to include super-clock punk ideas if you like. Ranged and melee weapons are both accepted. Besides that, with weapons, it is also important to note their grips and usage styles as well. Would they use 4 one-handed weapons, 2 two-handed weapons, 1 big four-handed weapon, or maybe some sort of other combination? Weapons that immediately come to mind for me are the [Nagamaki](http://en.wikipedia.org/wiki/Nagamaki) and polearms in general, but it would be great to include other weapons instead. META: I also noticed that, to my knowledge, this is the 1000th question in the site. Yay! EDIT 1: Weapons for both personal combat and formation war fighting would be great. EDIT 2: They would be fighting each other, as well as other human(oids) of [varying sizes](https://worldbuilding.stackexchange.com/questions/9507/what-should-architecture-of-an-imperial-capital-be-like-in-order-to-accommodate). Their arms are arranged with 2 arms in the same position as us, and 2 more coming out from under their arms, from their torso. [Answer] If we look at ancient Chinese weaponry, we see that the sky is the limit. There is an unbridled creativity when it comes to weapons. Intentionally avoiding the proper names for things like spears and halberds, here's some descriptions that I am familiar with: * stick * longer stick * shorter stick * stick broken into 2 parts * stick broken into 3 parts (this one was fun) * pointy bit * stick with pointy bit * long piece of stiff-ish string * stick with pointy bit and oxtail whip on the other end * stick with pointy bit and a few other blades attached * long pointy bit (sword) * long pointy bit sharpened on only one side * long pointy bit sharpened on three sides * 9 pointy bits strapped to the end of a rake And those are the less exotic ones. They get even more extreme from there. **They key to finding a good weapon is to understand that the weapon is not just about hurting the enemy, it is about flowing well with your anatomy and your mindset.** A weapon which does not flow with your body is less of a weapon and more of a lever with which your opponent can manipulate you. Many Chinese weapons were designed for people to study them for years before using them in combat. Others, like the sword, could be acceptably effective in a much shorter time. European weapons were usually designed to be very efficient in a short period of time. Anatomy is essential for deciding how to design a weapon. **There is not a weapon today which does not account for the anatomy of the shoulder.** The shoulder is such a special joint that many don't even consider it a fully-fledged joint at all. It's treated more like a few bones strapped together with muscle, a hope, and a prayer. **Your four armed humanoids will have even more complicated shoulder structures.** Weapons they would use would leverage the particular ranges of motion each arm has. As an example, if your lower arms have limited vertical mobility (which would not be surprising), consider a scythe with a sharpened bottom tip and a handle near the end of the blade. When wielded by arms on the same side of the body, it would leverage the lower arm's stronger horizontal strength. However, after a cross-body strike is done, it would be trivial for the humanoid to transfer the scythe to the top arms to use the bottom tip like a spear. Finally, because the scythe is shaped like a right angle, when using it as a spear, there would be a dangling blade near you (bad mojo!). However, it is also in a perfect position for the lower arm to grab the handle on the blade. In this position it is simultanously: * A spear managed by upper arms * A knife in the lower arm (happens to be strapped to a stick) * A lever (using 3 of the 4 hands in their strong directions) * It can turn back into a scythe wielded by upper-arms at any moment if the lower arm imparts momentum into the blade by pushing it in a direction. The latter part is is interesting because this is a motion that is impossible for a 2-armed individual. You need at least 3 arms to hold a spear with 2 hands and a "knife" with a third, and the exact forces the third hand are terribly hard to fake with the shoulder muscles of a 2 handed humanoid (remember I said the shoulder was magic? Your race just found a way to do something without using a shoulder). [Answer] I feel like a major point that is being missed here is that a combatant, unless part of an army where things are issued/standardized has the freedom to choose weapons based on who/what they are facing. So to say physiology would dictate weapon choice is misleading. It adds options but doesn't pigeonhole. That said there are limitations, four arms does not mean that you can be equally effective with double the weapons. Here's why. *THERE IS STILL ONLY ONE **HEAD***. Ahem, anyway, moving on. Here are a few things that **won't work.** * Dual Ranged Weapons: You can only concentrate on one target, and unless targets regularly require two shots to bring down this doesn't make sense. (not to mention you can't aim two bows at the same time.) * Dual Great (two handed) weapons: Given that we have two arms coming out of each side their grips would be the same direction. Imagine holding a baseball bat with two left hands. Because you don't have alternate grip directions at the hand it just can't be as stable. So you would have to grasp each great weapon with one hand from each side, meaning one blade would be under the other and frankly just get in the way. Ok, onto the options that work. I don't feel the need to specify certain weapons sets but more general layout options that seem reasonable. **Defensive Stance** * Two shields (heavy or tower), one weapon (short or long) and the fourth is a free hand or thrown weapon hand. This is sort of the ultimate phalanx soldier, double the shield face, ranged and spear/sword wielding. Very tough to kill when organized. * Ranged defensive. Bow/crossbow with dual shields. This setup can help improve the survivability of archers. **Balanced Stance** * Two shields (kite or lighter), two weapons (not pole-arms). This is of course the utility player or the set-up when you don't know what is coming. This could be two one handed weapons or a one handed with a thrown weapon in the other. **Offensive stance** * The flurry. Four one handed weapons...this could get crazy. All swords, all maces, all axes, a mixture of the three, maybe throw in a flail. The constant barrage that could ensue would be near impossible to defend against. In my mind this is the style that all other styles are attempting to counter. * The big \*\*\* weapon. This is a cool idea and perhaps this finally makes those video game uber weapons realistically useful. While obviously not as agile the utter force brought down by four arms could be devastating. *(This is assuming that your four armed humanoids have evolved to be more sturdy. If the base isn't sturdy the strength of the arm is irrelevant.)* * Polearms. These weapons suffer from the same problem as any other two handed weapon so using two is still impractical. That said with the extra strength and ability to manipulate a weapon that is long, heavy and normally hard to control...you could create some impressive dual ended weapons. This could be a dual bladed sword (naginata) or even a dual halberd. Slashing or blunt weapons make more sense in this style as you'll be going for sweeping strikes rather than targeting a single enemy. * The brawler. No weapons. Two hands to grapple, two hands to pummel. Its like having a friend hold someone down for you...only you don't need a friend. In general a free hand can be very useful in combat. Whether its to lob a grenade weapon, throw dirt in someone's face, or just grab onto them or their gear, never underestimate the value of a free hand in this system. [Answer] As a student of the Italian School of Longsword Fencing, and a student of medieval weapons in general, I would say this: * Extra Arms need not be occupied with weapons. It was common practice to [grapple opponents](https://www.youtube.com/watch?v=E183mRiml7E), even while wielding a longsword. In fact, Fiori de Liberi recommends [pommel-strikes](https://www.youtube.com/watch?v=7eQ0VB68_qk) at close distance. Having extra arms could result in special disarms, or grabbing their sword while attacking with your swords. (And yes, people do grab swords in combat, such as when [half-swording](http://youtu.be/vwuQPfvSSlo)!) * You can cut "with your body," or using your body's momentum. Additional weight in the form of arms can increase already considerable momentum. Four-armed individuals may just decide to use the same weapons that two-armed individuals would, but just benefit from the additional mass. * Extra hands could be used in *mounted fighting* while using a two-handed weapon. You retain your control and have the use of a two-handed weapon! Additionally, you can have hands free to open doors, help others up, etc. * Spear + Shield was considered the best combination **for war**. Obviously, more arms would allow you to hold a longer spear and thicker/larger shield. * Buckler / Dagger + Arming Sword/Messer/Rapier (One-handed swords) was the staple of [**civilian melee** combat](https://www.youtube.com/watch?v=aI-zSSoiWvk). 2 Bucklers and 2 Arming swords could be a good combination. Shields and Bucklers are weapons just as much as swords are. * Crossbows! Load with one set of arms, fire with the other set. It would greatly [increase your fire rate](http://youtu.be/HagCuGXJgUs). * Two weapon fighting is hard, and comes with its own [advantages and disadvantages](http://youtu.be/C2aCr5YfYKE). Four weapons may likely amplify those issues. You also run into problems of having additional arms on a human body. I would mostly be worried about them running into themselves! Their physiology would need to be modified to really get the benefit from those extra arms in combat. [Answer] There are examples to draw on here. There is an obvious one:  The main problem with that example is the execution was with a very 'two-armed' thinking. It's similar to [Kahn only thinking in 2D](http://youtu.be/RbTUTNenvCY). Clearly the style was invented by a person with two arms. The best examples of four arm use I've seen are actually from watching the [Neptunians in Futurama](http://theinfosphere.org/Neptunians). Re-watch Elzar fricassee a Neptunian Slug and you'll see what I mean. Someone clearly thought very hard about having four arms.  As other answers have demonstrated there are a lot of options for filling four weapon/shield slots. The easiest way to determine what would work (and to be able to better describe the fighting in your writing) is to **get a friend to be your second set of arms and try some different mock weapons**. Ideally, you have three friends, then try some mock slow-motion combat between two four armed creatures (or a four-armed creature against one or two two-armed opponents). This would be as much fun as it sounds. [Answer] I think having four hands doesn't mean that you can target multiple enemies at once since our brain could only focus on one specific target. Dual wielding would also means you're an easy target for the enemy's longbowmen My suggestion is: 1. A large-long-two-handed club/poleaxe for strong damage and use the last two hands to wield a large shield 2. More offensive option: no weapon at all, but instead use anything around you and throw it to the enemy 3. Ranged weapon: use a customized ballista / catapult - they need more than two hands to operate, which would be a perfect weapon for a four handed man [Answer] An extra set of hands does not necessarily just double your attacks, and can just as easily limit your options as they get in the way of each other. I would hesitate before considering doing extra things with the extra hands simply from a split-attention standpoint - the pat your head while rubbing your belly problem squared. Archery: the strength for using a bow does not come from the arm, but from using your whole body - unless these creatures are severely hunchbacked because of massive additional back musculature, they cannot get double the power or wield 2 bows to double the rate of fire. Besides, extra muscle would just support a more powerful bow, not 2 weaker bows. While extra arms could allow for slightly more powerful bows (because there would need to be *some* extra musculature for a second pair of functional arms), the greatest benefit would likely be the ability to hold shields while using other weapons. Holding a lightweight shield in the forward-side extra hand could provide some protection from incoming missiles. Melee: the dual-wielding problem with added interference - doubling the number of weapons does not increase your ability to attack. Think about the mechanics of how, exactly, those arms will move in detail, and how will they work around each other. They can get two blades swinging together at the same target, but does this compensate for the restricted movements and possibility of interfering with each other when parried? Getting tangled up with your own weapons would be most unfortunate issue. Perhaps the lower arm holding a buckler might be handy - generally kept close to the body but available in case the opponent gets past your own weapon (a larger shield would likely interfere with the motion of the sword arm). Alternative weapon combinations might be useful - different arms gripping different weapons, such as some sort of hooking weapon to pull against the opposing weapon/shield to create an opening for a stabbing weapon, but more along the lines of one weapon held back out of the way than a sense of a flurry of weapons. Pole weapons are very attractive here - they get power and extra control from the extra arms, without much worry about the arms interfering with each other. 3 hands on a crow's beak while a forth holds a shield/dagger, or possibly held 2 handed, while the leading spare arm holds a shield and the trailing spare arm holds a dagger/hammer, but this is into likely self-interference territory. It might be possible to hold one sword and one shield on each side - this does not imply that they would be functionally like two men in terms of combat effect, but it would definitely be useful if fighting multiple opponents (being able to switch focus onto different targets more easily). How good is their armor? Weaker armor implies the importance of shields, while strong plate armor (think 14th century articulated plate) allows shields to be discarded as a hindrance to focus on armor-penetrating weapons. Are they fighting each other or normal humans? More individually or large battles? Weapons and armor combinations would reflect the threats faced, and that is quite literally an arms race developing different weapons, armor, tactics, and combat styles. [Answer] I could think of several different ways. I could see them using 2 staffs, being able to lay two hands on each. With practice it would make them very dangerous. I could also seem some using four blades like katanas. I think a more common soldier would likely use a combination of swords and shields. Archers I can think of two designs, one would require 2 arms to hold it and two to pull the string, this would be closer to a balista in fire power. The other would be a double bow. two bows joined at the center, two strings and two arrows, though this would really be just weapon of war, though I suppose hunting large animals it could be useful too. Anyone using a polearm would also be able to protect themselves with a shield. The more talented might be able to wield a ranged weapon as well, say a sling or a regular bow. having a sword in one hand a mace in another and a battle ax in a third with a shield in the last would give one the most advantage in a melee fight, but being GOOD with all those weapons takes a lot of training and even there, a certain style might make it hard to put the weapons in different hands. Lots of options but the best for melee is likely best with 2 shields and 1 or 2 preferred weapons. [Answer] I would suggest several things: * Four one-handed swords. What I'm having in mind with this is sort of like General Grievous (Star Wars). And I'm not referring to the spinning hands, rather the ability to do strong one-handed attacks at double the speed and to protect oneself better during flips or fights against multiple enemies. * Dual bows and arrows, however, each bow is used in either the left hands or the right ones. The "lower" hand holds the bow, while the upper draws. Combine that with some nice [forgotten techniques](https://www.youtube.com/watch?v=BEG-ly9tQGk) of holding multiple arrows in the draw hand and putting the arrow on the outer side of the bow and you have yourself walking machine-guns. * One-handeds + shields. This can be quite interesting as you can mix the position of weapon and shield, i.e. lower-right and upper-left have the shields and the other two have the one-handed weapons. This enables a hit with the right hand that is "heavier" as more of the body's mass is put behind it (as it is on the top). Also it enables a sweeping low attach from the left. Attacks that are done in a [backhand](http://en.wikipedia.org/wiki/Backhand) manner will also be protected very well. * One usual combination for a pair of the arms and bare-arms/daggers. This will be very effective against two armed opponents. If their weapons ever get locked, the bare arms/daggers can make quick attacks in order for the opponent to lose their stance. * Nun-chucks. Yep! Swinging like a maniac four of these babies and no-one can hit you. * Two one-handed/one-handed and sheield and a giant two-handed. I imagine two quite effective attacks. A heavy hit at the beginning and a attack with the other hand in order to finish anything that might have been missed and also gives our 4-armed freak time to recover limiting his/her vulnerabilities. Perhaps the lower hands should carry the two-handed weapon in this case. Alternatively, wielding normal weapons with the lower hands and "waiting" for a chance to hit with the upper. This might be used with a spear as well - in a scorpion-like manner. * Throwables. Either only one pair of arms - to keep attackers from the side away, or all fours - a walking machine gun. I find it hard to believe that if their "right" arms are identical, there will be much use of a two-handed in both right arms for example. This will actually limit the movements of the weapons and will give nothing, but strength of direct hit in return. Might be useful in a limited set of situations, but will definitely not be their usual style. [Answer] I think two two-handed weapons would get in the way of each other. Remember also that two handed weapons have shorter range that one handed ones. I don't think this can be answered with certainty (I don't know of anyone with first-hand experience on this hehehe!), but what about a combo: * two blades and a staff * a bow for long range and swords/blades for the person to person combat I think that for person to person combat 4 swords/blades would give you what you need story-wise. [Answer] One of the biggest factors in real-world combat is fighting with the right weapons in the right range. For example, guns are easy to defeat at very close range by an unarmed opponent, but a couple of feet of separation makes them much more effective. Likewise, a knife or short sword at very close range beats a staff or a spear. This is even true in hand-to-hand combat - knees, elbows, and headbutts work at close range, punches and kicks at mid-to-long range. So if I were a four-armed human, I would select weapons that let me fight at close, medium, and long range at all times. If we are talking about melee weapons, that would probably mean a knife, a long sword, and a spear, with a shield for defense against missile weapons. The spear could be wielded with two arms and the sword with another, with the knife on a belt or some other easy-to-access place, since they wouldn't need it unless something had gone very wrong. This would work for formations as well as for one-on-one fights: think of a Roman centuria combined with a Greek phalanx. You combine the effectiveness at close range with the stand-off effectiveness of the spear, and still have full shield protection. If missile weapons are an option, then a sword and shield, plus a bow or crossbow would be good. If guns are allowed, then some sort of automatic weapon for suppressive fire combined with a precision weapon for accurate fire would be ideal. Of course, all of these weapons and tactics have been developed in a world of two-armed people, and so it is likely that other weapons would be created in a world where everyone had four arms. However, one thing that will be the same is that weapons and tactics will have evolved in a series of advancements and counter-advancements, each designed to exploit the limitations of the opposition, and the primary limitation will still be the effective range. [Answer] Medieval? Try a bowman - but instead of having two bows at the same time, you can preoccupy two hands with drawing and firing each arrow, one hand to constantly draw new arrows, and the other hand free. (Maybe it could hold something, like a torch to ignite arrows?) This would make it fire much faster than a normal bow would. [Answer] It appears no one noticed that there is "*some magic*"(Emphasis mine) in the OP's world. This means that magical weapons are possible, and therefore options that would not otherwise be possible. For example, let's say *telekinesis* is possible. In that case, your four-armed warriors would want one of the following setups: 1. If Telekinesis is OPW (Only Possible Through Wands): Upper pair of arms holds a shield, large and rectangular. The ends would have interlocking edges, so they could latch together and become one large shield. That way, if someone fires something at them that they can't stop with telekinesis alone, they can slam their shields together in front of them and hopefully block the brunt of it. If an overhead attack is incoming, they can tilt their shields up and form a pointed "roof" to block that. Alternatively, they could bring that "roof" down, point their wands (see below) backward, and become a flying snowplow of death. The lower pair of arms would likely hold two wands, allowing one to move two objects at once. As stated above, this could also (maybe) allow one to fly by using the wands as propulsion. 2. If Telekinesis Only Requires Line of Sight and Free Hands In this case, telekinetic effects would be invoked through the motion of the hands or arms. The arrangement would be the same, but in a pinch, one could use those hands to punch, grab, or wield weapons. 3. If Telekinesis Only Requires Will and Line of Sight Same arrangement, but a pair of arms are totally free. Granted, it'll be difficult to *use* them when you're focused on something else. The genius of this arrangement is that A) it can be used for any magical setup (staffs, wands, gestures, runes) and B) it allows the four-armed people to defend *and* attack, or do two different kinds of attacks at once. For example, while one arm is using a wand to cast spells, another two arms are blocking and slashing opponents. It's pretty hard for a mage to survive persistent, agile attackers but this one would be able to handle it (I presume). Or perhaps two arms are using shields to block attacks and spells while one wand carves a circle of protection into the ground and the other is firing spells at the enemy. After the circle is forged, the warrior can then put away the wands use one of the weapon arrangements already suggested by those before me, since they only need the wands to A) recreate the circle of protection or B) hit someone with a spell. [Answer] Personally, I'd go for a tower shield on the left, held high and low by the left two arms, a sword on the lower right, and a spear (throwable, if need be) on the upper right. Or the right side might have a chain/hook in the lower right and a sword in the upper right. [Answer] I agree with Pipperchip. A lot of benefit could come from using a spear/shield set up, especially while mounted. My vision of the four armed humanoid looks a lot like [Goro](https://en.wikipedia.org/wiki/Goro_(Mortal_Kombat)) from Mortal Kombat, in the sense that his upper arms are stronger and more dominant than his lower ones, with a wider range of motion. I believe the weapon loadout would be similar to a Hoplite, with a spear and shield being the main weapons, and a small sword as a backup. While advancing, "Goro" would hold the spear with his upper right arm and his lower left one in an underarmed fashion, while his upper left arm handled the shield. The shield itself would have a notch for the spear to lock into, so Goro would be able to free up his lower left arm when stationary. Because Goro could dedicate two arms to the spear when needed, the spear could be longer and handled with more precision and power. His lower right arm would be used to quickly grab the backup sword to stab close combat fighters, or grapple as needed. This would make Goro an incredibly flexible fighter, as he would have range, defence, and a close range option (not to mention the damage a 7 ft four armed humanoid could inflict with just its bare hands). This would translate perfectly to mounted combat as Pipperchip pointed out, as Goro would be able to maintain control of the horse and his weapons at the same time. Alternative weapon options for less warlike scenarios could be a net or bola, or small throwing spears. The lower arms could grab the spears/ammo from his back and "load" his upper arms which do the throwing. [Answer] I would like to look more into the constitution of those beasts. I believe that evolution would have created 4 armed humanoids if only they have a use for it in their early development phase, which probably means they were once living in a 3D environment, using their additional arms to grab branches or rocks. So they will have a pretty good balance and know how tu use 4 arms pretty independently. For dual combat, using at least one lower arm with a pole or a cane as a 3rd leg to withstand a blow should be natural and a good asset for reactivity and mobility. make it a javelin and you can easily add some deadly aspect to dual wielding fights : As I see it, a big dual wielded sword would be managed with the upper arms, a light shield would help protect one lower side, and a javelin on the other side would help to maneuver, can be used aggresively when a blow from the sword is stopped, and if the enemy ever back, you just switch the javelin from the lower arm to the upper arm, and a powerful throw will end him. In closed areas, a short sword and a dagger on the upper arms would be more flexible, and they would be able to block attacks bare handed with the lower arms, use a wall to move, grab the enemy, or even jumping in push up position to get a decisive blow, as they would still be mobile. For group fights, I don't think 4 arms can be as useful in a spear fight, as they won't really be able to use it for balance as they would injure other soldiers standing behind, and attacks will essentially come from the front, so the brute power would be the essential gain. You can still hope to grab the enemy weapons with one of your arms, or throw stuff in the enemy face, or maybe protect yourself from arrows with a light shield, but it will distract you from the enemy spears. For ranged weapons, on the pther side, I think crossbows are really the way to go : equip your soldier with two crossbows, make him aim with two arms, while the others are readying the next one. Shot fired, take the preloaded crossbow, add additional force with a third arm, and prepare to aim. It will drastically increase rate of fire with enough training to make it muscle memory. And as I said in the beginning, having 4 arms mean that they are used to use them all at the same time. Of course I just described a few configurations, but I think what you should be focusing on is the natural abilities of your creatures to use their environnement and balance, which on a flat ground, will result in using a cane to move and react. that can be done with a long pole 2-handed, and some other cose-mid range weapon, and maybe throwable knifes or shuriken, if you want 4-armed ninjas, or some specific pretty long tonfa, which would help you dodge front strike by using your elbow to take support, and then slashing on your sides. Finally, I think that with those specific balance abilities, they won't be able to turn on themselves like whirligig, as they will be affected a lot quicker with diziness, as cats do. [Answer] One shields and two spears and a sword with the sword is held on same side as shield or even a shield with bow. [Answer] What about boxing gloves? Or something more deadly (and serious): fist weapons. Like those on top of [this](http://en.wikipedia.org/wiki/List_of_premodern_combat_weapons) page. [Here](http://listverse.com/2014/06/22/10-rough-and-tumble-fist-weapons/) is another short list with images. ]

[Question] [ Steampunk airships typically use either helium or hydrogen as a source of lift (depending on the specific world). However, the source of the lifting gas is often not fully explained, or frequently even not mentioned at all. **How could a steampunk civilization with limited (although rapidly expanding) understanding of chemistry acquire the large amounts of helium and hydrogen that are required to lift airships?** [Answer] It turns out it's not that hard to make hydrogen gas for an airship, and [you can do it yourself](http://www.rsc.org/learn-chemistry/resource/res00000446/metals-and-acids-experiment?cmpid=CMP00005351). 1. Take some dilute sulphuric acid. 2. Put small pieces of metal in the acid - iron, zinc, and aluminum should all work. 3. Capture the resulting hydrogen gas, and then put it in your airship. This method of hydrogen production [was first specifically used for airships in the 18th century](https://www.chemistryworld.com/opinion/flying-heavier-or-lighter-than-air/6195.article), in a time of technology even less advanced than your steampunk civilization - and at the time, hydrogen was not yet known to exist! It seems quite plausible that they could produce the gas in large quantities. [Answer] Helium was first found in large quantity in gas from oil wells in 1902 and large-scale industrial production for airships started during WW1. This is late, but arguably still within in the steampunk timeframe. Oil and natural gas wells were operating from the mid 19th century and are suitably steampunk technology. [Answer] My guess is that you can't really have a steampunk civilization without having roughly 19th century understanding of chemistry and with that, you're probably home free. As evidence I would like to quote Wikipedia: > > The first gas balloon made its flight in August 1783. Designed by > professor Jacques Charles and Les Frères Robert, it carried no > passengers or cargo. On 1 December 1783 their second hydrogen-filled > balloon made a manned flight piloted by Jacques Charles and > Nicolas-Louis Robert, 10 days after the first manned flight in a > Montgolfier hot air balloon. > > > Extrapolating from this I'd say that it means the lighter than air properties (and the manufacturing/extraction of) hydrogen was known as early as the 18th century. Which coincides nicely with James Watts continuous rotary motion steam engine in time, suggesting that the components of a steampunk style civilization align rather nicely in time. For a history of Hydrogen extraction (And further evidence in the case of lighter-than-air-flight), we can turn to Ebbe Almqvist's "[History of Industrial Gases](https://books.google.se/books?id=t3zZBQAAQBAJ&pg=PT76&lpg=PT76&dq=industrial%20production%20of%20hydrogen%20history&source=bl&ots=W7M4X2xNMA&sig=NWVly5mgN7aq4X3vBtERcovC4_U&hl=sv&sa=X&ved=0ahUKEwiPk8-5v-3WAhXpK5oKHT3oCSYQ6AEIajAH#v=onepage&q=industrial%20production%20of%20hydrogen%20history&f=false)" which states. > > During the 18th century many worked on ideas surrounding the > lighter-than-air principle, but suitable means were not available > until in 1766 Henry Cavendish succeeded in producing hydrogen gas in > pure form (the known as inflammable air), and discovered that it was > 14 times lighter than air. The dream of the century, that of "air > sailing," could now become a reality. > > > In order to produce the gas for the Charles/Robert balloon trip, Almqvist tells us, 500 kilograms of iron and 250 kilograms of sulfuric acid was used. Suggesting, once more, that the industrial production of Hydrogen was well within the limits of late 18th-century chemical science. A more effective and ultimately cheaper way of producing hydrogen is the electrolysis method where you use electricity to split water into hydrogen and oxygen. This is also well within the capacity of most steampunk type civilizations (although it takes us into the 19th century. > > In 1800, Alessandro Volta presented his so-called voltaic pile, the > forerunner of the electric battery. A few weeks later, William > Nicholson and Anthony Carlisle constructed a voltaic battery and > manufactured considerable quantities of oxygen and hydrogen. The > electrolysis method remained expensive until the Belgian Zénobe Gramme > invented the first steam-driven dynamo in 1873. From 1890 on, when > large hydroelectric power stations were built, the method was used on > a large scale wherever cheap hydroelectric power was found. > > > [Answer] Acid and metal reaction was already mentioned, but usually, a cheaper way was used. [Lavoisier Meusnier iron-steam process](https://en.wikipedia.org/wiki/Timeline_of_hydrogen_technologies) was invented in 1784, it generated hydrogen by passing water vapor over a bed of red-hot iron at 600 °C. So only some iron rods and fuel were consumed - no expensive acid required. Union Army Balloon Corps mobile hydrogen generators used acid-metal reaction, so I guess iron-steam generators were too bulky for mobile use. [Answer] *Since I don't see a hard science tag....* Surely we can do better than mundane hydrogen or helium? Even the most ill-educated brute knows that the sky consists of two layers, Aer - the dim, lower part of the sky, and the Aether, the brighter upper part. Using observation we thus know that the brighter, cleaner air is - the higher it rises. So our goal is to cause an airship to rise. Logically this means we must trap cleaner air within the gas bag - so how do we clean the air? Obviously, as educated folks, we know that the purest element is Quintessence - and the studies done by the royal alchemist's guild show that we can create Quintessence and infuse it into the air - transmuting mundane Aer into Aether! The most cost-effective method is, of course, mixing together the transcendent elements Sulphur and Mercury. So we combine them, and using some sort of heating element - I recommend a glass lens focusing sunlight during the day or heated Luminiferous Aether at night to further enhance the heavenly properties of the admixture - burning the impurities out of the Aer and creating Aether - which will lift the airship! Allow for vents at the top of the bag to release the Aether and you can control your descent as well. <https://en.wikipedia.org/wiki/Aether_(classical_element)#Quintessence> <https://en.wikipedia.org/wiki/Air_%28classical_element%29> <https://www.thoughtco.com/alchemical-sulfur-mercury-and-salt-96036> [Answer] ### Mining helium gas If you don't mind doing a little handwaving, you've got two potential sources of helium that I think would both be great. Most commercial helium is extracted from [natural gas deposits that have a high (1-10%) fraction of helium](https://en.wikipedia.org/wiki/Helium_production_in_the_United_States). We build refineries to separate the helium and natural gas. I'm not sure if the typical steampunk world would allow for the mining of hydrocarbons, but oil mining started in the mid 1800's, so that sounds about the right time period. If you want to make it easier on your people then they could find a deposit of nearly pure helium, so it's just a matter of getting it out of the ground. Such deposits have never been found on earth, but that doesn't mean that it is impossible or obviously violates the laws of physics. ### Nuclear Helium Another source of helium is from nuclear reactions. Helium-3 has a number of uses in modern industry and technology, and virtually all Helium-3 used for these purposes is produced [by the decay of tritium](https://en.wikipedia.org/wiki/Helium-3#Industrial_production). Of course tritium itself isn't something you find just lying around (if you did, you could just use the hydrogen as your lifting gas), but it still gives some hints for helium production. Alpha radiation is actually just energetic helium, so any radioactive substance that decays through alpha radiation effectively generates helium gas (which includes Uranium 235). You would need some handwaving, but if you want to get really dangerous then your steampunkers might discover that this strange, cakey, yellow substance produces lightweight gas all on its own. Fortunately for them, it is near impossible to generate a critical nuclear reaction using natural uranium (which is primarily composed of the more stable U-238 nucleus). To get sufficient production of He through alpha decay you may need a less stable element anyway, which is where more handwaving comes in (because less stable elements aren't normally naturally occurring). So this avenue may require more handwaving then you want, or it may be worth a lot of handwaving to mine helium gas from natural nuclear power (and who doesn't want to blow up a steampunk city with an accidental nuclear explosion, right??). ### Water Electrolysis Depending on your level of "technology" you can always have your people produce hydrogen via the [electrolysis of water](https://en.wikipedia.org/wiki/Electrolysis_of_water). You don't need to understand the chemistry for your people to try to do it, and it is so simple that just about everyone has the materials to do it at home. Doing it on an industrial scale and keeping the hydrogen gas separate are a bit trickier of course, but depending on your steampunk world generating hydrogen via electrolysis should be quite doable. If you want to keep the use of electricity simple then you can always come up with some sort of "lightning farm" that uses natural lightning in a stormy environment to split water for hydrogen. That's probably not possible in practice, but this is fiction after all and might be fun for a story. ]

[Question] [ I'm building a world builder out of a SQL database. I'm going to use an implementation of Markov chains to build up lists of 1,000's of names. I'd like those names to have some consistency, so I plan to use various mixtures of real-world names as the input data for the procedure. The intention is not to re-create names that have existed, but rather to use Markovian logic to let SQL notice phonetic/morphological patterns my English-shackled brain can't. I intend to use the worlds I create as backstory for D&D campaigns and also a showcase for my development skills, so the fruits of this labor will be public. For example, the names for culture X are derived from 80% Babylonian and 20% modern Lithuanian. Using a data set of 80 Babylonian names and 20 Lithuanian names will, once fed through the name generator, give me something that is close to historical but hopefully with enough flavor to not sound derivative. Doing this requires large volumes of names sorted by culture. I've been unable to locate such a data source. I'd like something that requires minimal re-formatting, editing, etc. Sites such as [20000-names.com](http://www.20000-names.com/index.htm) are helpful, but I'm hoping to avoid the formatting that comes with them. **Update:** I've published my results so far [on GitHub](https://github.com/ncanderson/SQL-Markov-Name-Generator). For the non-SQL speakers, I hope to have a better interface for this project in the future. For those who can SQL, clone down the repo, run each .sql file, and execute the procedure markov\_Complete. I'm happy to accept pull requests, even if it's just improving the readme. Any conversation specific to the database should happen on GitHub, not here. [Answer] Some time ago (about 2 years) I went looking for a huge [list of names](https://opendata.stackexchange.com/questions/4756/searching-for-lists-of-babynames-containing-huge-10k-amounts-of-unique-name). I wanted to use that list to uniquely name objects in my game-engine without having to resort to using generic uids that are hardly distinguishable. I found help on the excellent [open data stackexchange](https://opendata.stackexchange.com/). Long story short, I present you: <ftp://ftp.heise.de/pub/ct/listings/0717-182.zip> A zip-file containing about 50k human (first) names, classified by gender and popularity in each country. [Answer] A partial answer, combining my comments on the question, plus subsequent finds: 1. For historical names, the Society for Creative Anachronism has an administrative section, the College of Heralds, who maintain lists of registered “SCA Names”. There are rules for authenticity, and they maintain some references for acceptable names. Check their [page on names at the SCA website](http://heraldry.sca.org/names.html). 2. The [Academy of St. Gabriel](https://www.s-gabriel.org/) is an organization separate from the SCA, but who have worked closely with the SCA to assist those who seek a higher level of authenticity for their names or heraldry than the SCA requires. 3. Wikipedia has an entire category of [lists of names](https://en.wikipedia.org/wiki/Category:Lists_of_names), both personal and family, for many cultures. Some of the lists there are of specific types of names within a culture, as well. 4. In addition to the Lists of Names category, Wikipedia has a category [Names by Culture](https://en.wikipedia.org/wiki/Category:Names_by_culture). The pages in this category go into a little more detail about the structure and historical context of the names, rather than just being a simple list. 5. Google, naturally, is your friend. There are innumerable [baby name lists](https://www.google.com/search?q=lists+of+baby+names) out on the web; most will be of *currently* popular names. You can always try to narrow it down by culture or nationality (e.g., [Gujarati baby names](https://www.google.com/search?q=gujarati+baby+names), [Romany baby names](https://www.google.com/search?q=romany+baby+names), etc.). 6. Some countries - and some states in the United States - have restrictions on children’s names. Start with [Wikipedia’s page on naming laws](https://en.wikipedia.org/wiki/Naming_law), or with [this Google search](https://www.google.com/search?q=what+am+i+allowed+to+name+my+baby), and if your worldbuilding is based on the culture of a country/state that has restrictions, check the references and any resources they may direct you to to find the list of approved (or disapproved) names. (This list should by no means be considered either authoritative or exhaustive; as I come across other resources, I will update - and I encourage those with sufficient rep here in Worldbuilders to do the same.) [Answer] I have a different approach for you. Start with an excel column with English words that could be names. For example: Rump Cheek. Next column translate that to Lithuanian via this <https://www.labnol.org/internet/google-translate-for-spreadsheets/10086/> I get "Skruosto Skruostas". Which has a ring to it! Third column is to translate into Babylonian. I used Turkish instead because it is the closest country that uses roman letters I can read. I got "Yanak Yanak". OK, but no Skruosto. Randomly choose by percentage which column you will use. Sometimes translation from language 2 into language 3 will not be the same as from language 1 into language 3. All good. **Downside**: these are not names. Probably. Probably you will not run across Skruosto when you visit Lithuania. I bet it would be a fine nickname. Keep it if you like! **Upsides**: 1: Very fast to do. 2: Names sound great. 3: if any Lithuanians or Turks ever venture into your world they will soil themselves laughing. [Answer] It's fairly certain that by "names" you mean people's names. It is quite unclear whether you mean their "full" names, their surnames, their given names, or what. Names have two purposes, I think: as a form of identification and as a form of address. If we assume the typical Western take on names (given & family) and avoid common issues like name changes (due to coming of age, marriage, etc.), the use of aliases/diminutives (Maria, Masha, Marusya, and Maria Vasilyevna all are for the same person), and the possibility that a person's surname may depend on sex, age, or status (Lord Kelvin = Baron Kelvin = Williams Thomson). (Not only of the person so named but on the relationship, age, sex, and status of the speaker.) So, in your world building perhaps you should also have a couple of choices on selecting among different sets of "rules" as well as the specific character strings to use. The best site I've found is:<http://www.top-100-baby-names-search.com/female-chinese-names.html> which gives 100/100(m/f) names for 19 countries (of course USA & Euro countries also are extensively documented elsewhere.) Copying and pasting those lists into an MS Excel spreadsheet would take about 30 minutes. USA SSA has .zip files for both National and State-by-state first names from ~1915 to current (2016). See <https://www.ssa.gov/oact/babynames/limits.html> Wikipedia maintains a page List of people by nationality which then directs you to various nations' lists. As far as extinct/historical names, I've no wisdom there. [Answer] This won't help with many cultures throughout history, but "pipe rolls" and court records from the Middle Ages are first-hand accounts of the economy, bureaucracy, law and nobility. These are routinely used by historians of every kind - though most online resources are from England - not only to identify names and genealogies, but also the day-to-day lives of historical peoples. You'll find names as (once) common as Piers and Pate and as bizarre as Roger Fuckebythenavele. [Answer] You want [Kate Monk's Onomastikon](https://tekeli.li/onomastikon/). Although it hasn't been updated in 15 years or so, it's still a useful resource. ]

[Question] [ There is an African plain, there are trees, grasses, some seasonal rivers/lakes, and snakes. Upon the plain lives a society of tribesmen (think along the lines of the [Maasai Mara](https://en.wikipedia.org/wiki/Maasai_Mara) people) [](https://l7.alamy.com/zooms/5e1e3bdb36f9477cbb4c5d1f00c5a17b/kenya-narok-district-maasai-men-walk-home-across-the-short-grassy-bfmrj0.jpg) [This image used with permission: Source (Alamy)](http://www.alamy.com/stock-photo/masai-mara-tribe.html) These tribes love life, but hate snakes - they are the embodiment of the evil spirits, they cannot be eaten, they also cannot be killed (life is more treasured than evil is hated). Of course, there's plenty of snakes around. So the question (obviously) is how can the tribesmen get the snakes off the plain? [Answer] # Just ask Moses From [Artapansus of Alexandria](https://en.wikipedia.org/wiki/Artapanus_of_Alexandria) in his History of the Jews: > > Jealousy of Moses' excellent qualities induced Chenephres to send him > with unskilled troops on a military expedition to Ethiopia, where he > won great victories. After having built the city of Hermopolis, he > taught the people the value of the ibis as a protection against the > serpents, making the bird the sacred guardian spirit of the city... > > > # Behold, your savior [](https://i.stack.imgur.com/TbKjq.jpg) # Your people worship the Ibis Not only are [Sacred Ibis](https://en.wikipedia.org/wiki/African_sacred_ibis)' great for keeping around and eating snakes, they are also native to the same plains that the Masai Mara live on, and they are [easy to worship](https://en.wikipedia.org/wiki/Thoth) too! [](https://i.stack.imgur.com/rWMQ1.jpg) [Answer] Why do you have snakes on the plain in the first place? Rodents! So you need to find a way to control the rodent populations. If the snakes have nothing to eat, they won't hang about in large numbers. Introduce species that will eliminate the rodents and the snakes won't have prey. This is why Bast was an Egyptian Goddess. She represented cats, which kept critters out of the grain cribs. Also weasels and ferrets and mongoose might help. The mongoose will also eat the snakes as well. Then the whole killing snakes becomes a circle of life thing. Mammals are going to have an advantage in that they are not as affected by cold. In a culture like you describe, though, I would think the snake might at least be respected because it does help control the rodent population without endangering the food supply. So Sam L Jackson may not be necessary after all. [Answer] > > Kookaburra roams through the plains with glee, eating all the snakes > with a grin is he, laugh, Kookaburra laugh, Kookaburra full your stomach > must be. > > > The humble Kookaburra! <https://en.wikipedia.org/wiki/Kookaburra> A less well known Australian bird who loves to eat snakes and small rodents (solves two suspected problems here!!) My only problem would be that they would usually nest in a tree, so if there are no suitable trees around, we may have to make a hybrid kingfisher-kookaburra breed which would use the habitat of the kingfisher which is small holes in sand-mounds. [Answer] ## Do what any human does and kill them Look at human history, you can likely easily name 5 animals off the top of your head that humanity has hunted to extinction. Unless the animals mass breeds like insects, early man has always had dominion over animal life. If these people truly hated and despised the snakes, to the point that they saw it their religious duty to god to kill them, the snakes wouldn't stand a chance. Humans always win. ]

[Question] [ I hope this isn't too broad. I would like an Earth-like planet for November's [NaNoWriMo](http://nanowrimo.org/) that is just enormous, but plausible. Then I started to get into material composition, proximity to the star, trying to achieve the right densities - well, you get the idea. I'm trying to have 10x the radius of our current Earth, but with similar gravity (ugh) and at least somewhat similar climate and surface conditions; I do not need to have life on this planet, but minerals and liquid water are important to us. Not quite a Jupiter-sized planet, but much larger than ours. Other factors can be modified. [Answer] Because you want a similar temperature and climate to Earth's, your new planet would have to be at approximately the same distance from its sun as Earth is, assuming both solar systems have similar-sized suns. ### For Earth's mean temperature of $15^{\circ}\mathrm C$, the planet would have to be about 1 AU from its sun.  For your planet to possess seasons and be similar in climate to Earth, it would need the same [axial tilt](https://en.wikipedia.org/wiki/Axial_tilt), which is responsible for Earth's seasons. Earth's axial tilt is about $23.45$ degrees, your planet's would have to be similar for similar seasons. Your planet would also need the same day-length so that each part of it will receive the same warming from the sun per day. If the day were longer, your planet might become a bit desert-like, *very* hot in the day, and freezing at night. That doesn't sound promising for life. However, for a massive planet to possess a 24 hour day, the surface would have to be moving much, *much* faster than Earth's: > > Earth's diameter is $12,756$ km, so has a radius of $6,378$ km. > > > Your new planet's radius is 10x larger, so would be $63,780$ km. That means your planet has a circumference of $2 \cdot 63,780\pi$ km, approximately equal to $400,742$ km. > > > For your planet to have a $24$ hour day, the surface would have to spin at $\frac{400742}{24}$ km/h, about $16,698$ km/h, which is pretty fast. (Earth's spin is only $1,673$ km/h.) > > > Your planet would be rotating at about $$ 16,698~\mathrm{km/h} $$ which is pretty darn fast!  Honestly, I was half-hoping that speed of this planet's rotation might be nearer Jupiter's $45,061$ km/h, so that I could talk about extreme weather patterns and phenomena such as the [Great Red Spot](https://en.wikipedia.org/wiki/Atmosphere_of_Jupiter#Great_Red_Spot). Apparently your planet will not be subject to anything near as powerful as Jupiter's hurricanes, but your planet's spin is definitely fast enough to increase the strength of - and therefore devastation caused by - any of its storms. Also, your planet's spin is still slow enough to lead to similar weather systems as on Earth, where winds are constrained to a hemisphere, and Jet Streams will become possible, which will help regulate your planet's climate and keep it more consistent with Earth's.  However, we have yet to face the biggest problem imposed by a massive planet: keeping gravity somewhat similar to Earth's. This is nigh impossible, as we will see after we calculate what density our planet would need: > > Earth's density is $5,540$ kg/m3, and it's volume $1.08321×10^{21}$ m3. > > > Your planet's radius is 10x larger, therefore its volume must be 103x larger. This means that your planet's volume is $1.08321×10^{24}$ m3. > > > Usually, for two objects to have the same gravity, their masses must be the same, but the [inverse square law](https://en.wikipedia.org/wiki/Inverse-square_law#Gravitation) also states gravitational attraction to be inversely proportional to the square of the distance between two objects. > > > Because your planet is 10x larger, anyone on the surface will be 10x further away from its center than they would be from Earth's center on its surface. Using this equality, we can calculate the necessary mass of your planet: > $$ > \mathrm g = \frac{G\cdot M}{r^2} > $$ > Where $\mathrm g$ represents the accelration due to gravity ($\mathrm{m/s^2}$), $G$ the [gravitational constant](https://en.wikipedia.org/wiki/Gravitational_constant) (6.673×10-11 N·(m/kg)2), $M$ the mass of our planet and $r$ the radius of our planet. > > > We can now rearrange and solve for $M$: > $$ > M = \frac{\mathrm g r^2}{G} \\~\\ > M = \frac{9.8 \times 63780000^2}{6.673 \times 10^{-11}}\\~\\ > M \approx 5.974 \times 10^{26} > $$ > > > So, our planet's mass would have to be approximately $5.974 \times 10^{26}$ kg, which looks about right; Earth's mass is about $5.972 \times 10^{24}$ kg, and, for the same gravity, we'd expect our planet to be 100x heavier, which it is! Of course, we are suffering rounding inaccuracies, but so far, so good. > > > Now, we can calculate our planet's target density, using the equality that > $$ > p = \mathrm{M/V} > $$ > where $p$ represents density, $\mathrm M$ mass and $\mathrm V$ volume, we see that: > $$ > p = \frac{5.974×10^{26}}{1.08321×10^{24}} > $$ > so therefore the planet's density must be $551.5$ kg/m3 if you want the same attraction under gravity. > > > Saturn is the least-dense planet in our solar system, with a density of $687$ kg/m3. However, Saturn is a gas giant, composed mainly of Hydrogen and Helium: good luck mining for minerals in a cloud of Hydrogen!  ### Your planet would need a density of $551.5$ kg/m3, 100 kg/m3 less than Saturn's! So, it should be fairly obvious that you will never be able to get exactly the same surface gravity as you do on Earth, but fauna would be able to exist under different gravitational conditions, and, what's more, higher gravity means more pressure, which means minerals will form more readily! There could be some special minerals which only form within the crust of this planet because of its strong gravity, making the planet more valuable!  However, to enable humans to land on this planet, it will be almost impossible to get the gravity weak enough (have you thought of using [exoskeletons](https://en.wikipedia.org/wiki/Powered_exoskeleton) for manned missions on this planet?); the planet would have to be as sparse as possible.  If your planet was composed almost entirely of some really porous [Vesicular rock](https://en.wikipedia.org/wiki/Vesicular_texture), almost like a sponge, it would definitely keep down the density. The same process which forms such rock could also create massive air-pockets, creating a cavernous planet with many underground tunnels and caves on the same scale as [Erebor!](http://lotr.wikia.com/wiki/Lonely_Mountain) ### A cavernous planet, made of porous rock, would remain reasonably sparse. The crust of the planet should be as thick as possible, because a molten mantle and solid core would be more dense than this spacious, cavernous crust. This crust would also need constant renewal, so that collapses don't bring up the density, and to remain, again, more similar to earth. However, tectonic activity would have to be minimal, to prevent metamorphic and denser igneous rocks being formed, so volcanoes would be necessary to keep rejuvenating the surface. Underground lava-flows might be commonplace, where it is still hot enough so that the lava cools slowly into some porous rock. Think about how awesome that could be; a massive, underground cave system where magma seeps up through the floors forming puddles of fiery lava! The one thing we can't change is the presence of a solid, dense core; this is because a nickel/iron core is necessary for a magnetic field, which would protect the planet [as the Earth is.](https://en.wikipedia.org/wiki/Earth%27s_magnetic_field)  The geomagnetic field would protect the planet from solar winds, thus retaining the Atmosphere and ozone layer, protecting inhabitants from radiation which would otherwise be harmful. Also, an atmosphere is generally a handy thing to have if you want life to live on a planet! ### A magnetic field is necessary to protect the planet like earth, so a dense core is also necessary. We can actually calculate the density, and therefore acceleration due to gravity, of our planet: Of course, our planet, possessing a molten mantle, liquid seas, and solid core, would likely be slightly more dense than [Pumice](https://en.wikipedia.org/wiki/Pumice) (a Vesicular rock), but let's just say that Pumice is the most common rock on our planet, and everything else has a similar density. > > The density of Pumice is $641 \mathrm{kg/m^3}$, so our planet's density would also be about $641 \mathrm{kg/m^3}$. > > > The volume of our planet is $\frac43 \pi r^3$, about $1.08321×10^{24}$ m3. > > > Now, using our planet's assumed density and volume, we can plug the values into our density equation: > $$ > p = \mathrm{M/V} \\~\\ > 641 = \frac{\mathrm M}{1.08321×10^{24}} > $$ > Rearranging, we get > $$ > \mathrm M = 641 \times 1.08321×10^{24} > $$ > which is approximately equal to $6.94 \times 10^{26}$ kg. Our planet is pretty heavy! > > > Using this equation (same as before) > $$ > \mathrm g = \frac{G\cdot M}{r^2} > $$ > we can solve for $\mathrm g$, the planet's gravitational acceleration: > $$ > \mathrm g = \frac{(6.673 \times 10^{-11}) \times (6.94 \times 10^{26})}{63780000^2} > $$ > which is approximately $11.38 \mathrm{m/s^2}$. > > > Wait, only $11.38$? That's just $1.16$ Earths! I'm in luck! Well, no, not really, not unless you make some other changes as well: the actual density of your planet would be much greater, as a large proportion of the planet would probably be magma (density: $3100$ kg/m3), and, if the planet is like Earth, a lot of the surface would have to be water (density: $1000$ kg/m3); the planet's mean density would obviously be above Pumice's $641$ kg/m3.  However, if you discover some way of limiting the density of your planet's magma, this would no longer be an obstacle to your 1 Earth goal! Maybe the magma is filled with air, think of [carbonated water](https://en.wikipedia.org/wiki/Carbonated_water), a similar process could have trapped and compressed air within the magma of your planet.  This idea also makes the Vesicular-rock-only surface more likely, as when the lava is released through fissures in the crust (think Volcanoes, etc.), the trapped air within the lava will expand, creating air bubbles. This is like getting the bends when re-surfacing from a deep dive: as pressure is released, compressed nitrogen within one's blood quickly expands into bubbles. And my magma density figures were based on basalt; vesicular lava would have a lower density. ### Earth-like gravity still not too far-fetched an idea. Anyway, that exoskeleton idea still seems pretty cool to me.  [Answer] **Basic Numbers** As it happens (and @TimB) pointed out, we have a planet that very nearly fits your preliminary description - Saturn. Saturn's Stats ``` Diameter ~ 10 Earths Mass ~ 90 Earths Density ~ 620 kg/m^3 - 6/10 as dense as water) Gravity (@1 atm pressure region) ~ 1.07 Temperature (@1 atm pressure region) ~ 134 K -> -139 C -> -165 F ``` In order to have a big planet with low gravity, you need a low density. Saturn has the lowest density of any planet in our solar system. It had to be made almost entirely of hydrogen to accomplish that. It means you'd have to fly to live on that planet. You'd encounter no minerals, metals, few liquids, and certainly no bodies of liquid. In order to not be crushed in the depths of the atmosphere, you would need to fly to survive in Saturn's atmosphere. **Adding Spin** Rotating bodies actually produce an [apparent gravity that varies with latitude](http://en.wikipedia.org/wiki/Gravity_of_Earth#Latitude), as exemplified by the Earth's. On the Earth, this field varies by about 0.3% (~0.029 m/s) due to outward centripetal acceleration and 0.2% (~0.020 m/s) due to difference in the pole vs. equatorial radius. We can use this principal to imagine a planet that meets your needs. Jupiter spins at a rate of 1 rotation per 10 hours. Its equator is about 7% larger than its polar circumference. Planets become unstable and break apart at between 2 & 3 hours per rotation. At around this spin rate, the planet achieves a 100% oblateness (equator is twice as long as the polar circumference). The primordial Earth likely had this appearance shortly after the [Theia Impact Event](http://en.wikipedia.org/wiki/Giant_impact_hypothesis#Theia). Acceleration due to gravity $$ a\_g = \frac{GM\_p}{r^2} $$ Centripetal acceleration due to rotation $$ a\_r = \frac{v^2}{r} $$ Total acceleration is acceleration due to gravity minus centripetal acceleration: $$ a\_T = \frac{GM\_p}{r^2} - \frac{v^2}{r} $$ $ a\_T = 10 \frac{m}{s^2} $ $ G = 6.67 \times 10^{-11} $ $ r = 10 \times r\_{Earth} = 6.378 \times 10^7 $ m $ v\_{rotation} = \frac {C}{t} = \frac {2 \pi 6.378 \times 10^7 m}{2.5 hr \times 3600 \frac {s}{hr}} = \frac {4 \times 10^8 m}{9000 s}= 44527 \frac {m}{s} $ Solve for planet mass $$ \left(10 + \frac{v^2}{r} \right) \times r^2 \div G = M\_{planet} $$ Plug in numbers $$ M\_{planet} = \left(10 + \frac {50211396}{6.378 \times 10^7} \right ) \times 4.07 \times 10^{15} \div 6.67 \times 10^{-11} $$ $$ M\_{planet} = 2.49 \times 10^{27} $$ this is about 420x the mass of Earth. It is also about 1.25x mass of Jupiter. If you approximate the volume of an oblate spheroid as $$ \frac {4 \pi \left (\frac {r\_{polar} + r\_{equat}}{2}\right )^3 }{3} $$ then with a 2:1 equator:pole circumference, this body will have about $7.5^3 = 422 $ times the volume of Earth. That gives this body a density of $$ \rho = \frac {2.49 \times 10^{27}}{4 \div 3 \pi r^3} \rightarrow \rho = \frac {2.49 \times 10^{27}}{1.09 \times 10^{24}} \rightarrow \rho = 2290 \frac {kg}{m^3} $$ This number is 3.5 times the density of Saturn (above) and almost twice that of Jupiter. This planet will be composed of hydrogen gas, water, and a rocky & iron core. It is unlikely to possess solid surface under conditions inhabitants could access them. It is possible that such a planet could have a liquid surface and would appear to simply be a giant water droplet the mass of Jupiter. **Other Fun Facts** Let's compare the acceleration due to gravity and centripetal motion: $$ a\_g = \frac{MG}{r^2} \rightarrow a\_g = 41 \frac{m}{s^2} = 4.2 g $$ $$ a\_r = \frac{v^2}{r} \rightarrow a\_r = 31 \frac{m}{s^2} = 3.2 g $$ Centripetal acceleration helps, however, increasing the equatorial radius helps much more. $$ a\_{g at pole} = \frac{MG}{r^2} \rightarrow a\_g = 163 \frac{m}{s^2} = 16.6 g $$ That's 16.6 $g$ at the poles while you only feel 1 $g$ at the equator. As a rough approximation, your distance between equator and pole with vary according to the sine of the latitude like this: $$ g\_{apparent} = 1 g + sin \left( latitude \right) \times 15.6 g $$ **Other reference information** If you've got the time and interest, this video: [The Surprising State of the Earth after the Moon-Forming Giant Impact](https://www.youtube.com/watch?v=PmhmWs71EMk) provides a lot of information about high spin rate planetary bodies, how they get that way, some simulations, and other information pertinent to your interests. It runs about 1 hour long but I enjoyed it very much and found it highly informative. [Answer] Let me say it outright from the start: you can't get a $10 \times R\_\oplus$ radius world to be inhabitable by anything resembling humans. Before you despair, let me remind you that planetary surface increases with the square of the radius, and Earth is huge to begin with: 510 million square kilometers. So for twice the radius, you get 2.04 **billion** square km, and for three times the radius, you get 4.5 billion square km, nearly 10 times larger! Imagine how different history would have been had the Earth been that large. The larger surface area might mean slower days with longer nights, or perhaps faster orbital rotation. The terror of the night would be prolonged, or storms might be more massive than anything we know here on Earth. The vast oceans would regulate and moderate climate more than on Earth with their vast heat capacity, while waves might build up over the ocean vasts to truly astonishing heights (100m or more). The atmosphere itself would likely be deeper and denser, and given the higher planetary mass, retain more of the primordial gases. **So how do you get such a thing?** The most likely process would be to start from a [Chthonian planet](http://en.wikipedia.org/wiki/Chthonian_planet), have it drift away from the star and rebuild some of the atmosphere from comets and eruptions. [Answer] For temperature and suchlike requirements you just need to orbit at roughly the same distance from the star. The tricky thing here is the gravity, to have 10 times the radius then you either need to make the planet from something much much less dense than earth (which is improbable) or you need to spin the planet really fast. If you spin the planet then it will flatten out into more of a disk shape but the equator could be ten times the radius of earth's and you could still get earth-level gravitational forces everywhere on the planet. The planet would be the same "height" (pole to pole) as earth but much wider. You'd get some very strong weather and Coriolis effects but the apparent gravity would be just fine. [Answer] **Ignore a little bit of science.** In reality, worlds that big have more gravity than Earth. All of the things that have a surface area many times that of Earth, are solid, and have the same gravity, don't occur in nature, and often have significant structural flaws requiring construction of unobtaium in order to remain in one piece. *All of that doesn't mean that you can't write a great story taking place on one.* Niven's *Ringworld* is one such story that takes place on something that probably couldn't exist, and relies on some unobtanium wires to hold things together, but is still widely enjoyed and admired. Your story, for example, could take place on a world that is hollow. A hollow world could quite easily fit all of the criteria that you want, provided that you ignore the fact that hollow worlds can't actually form. You can explain this away with 'aliens made it with super advanced technology,' or 'magic', depending on what type of story you're trying to tell. If you're really feeling creative: aliens created it with magic. Alternately, you don't have to explain it at all. You can have enjoy writing about it and others can have fun reading about it without knowing exactly why or how the world is hollow. Have fun writing! [Answer] The real SFNal way to do this is simply to "pave over" Saturn. A "supra-mundane terraformed world of Saturn" essentially has the atmosphere of Saturn covered over with some material which provides a solid "floor" for people to sand and work on, support buildings and so on. Materials like graphene or a "fabric" woven from Fullerine cables will provide the high strength to weight ratio needed to make this plausible, and while it may seem a bit like standing and working on a trampoline, the reality is the structure will be so vast that most flexing will be damped out and you and I would hardly feel anything. Now the questions of atmosphere and climate will be more difficult to answer. An atmosphere can certainly be added to the outside of the supra-mundane world of Saturn, importing materials from the many moons of Saturn and importing extra nitrogen from the distant moons of Neptune and bodies from the Kuiper belt (if you can cover over Saturn, you can easily import materials from deep space), as well as oceans and soil to support whatever sorts of biospheres you desire. Since you are so far from the Sun, a system of mirrors will be needed in orbit to provide extra illumination. Weather and climate will be very different from that of Earth simply due to the effects of scale, and there will also be lots of variables based on how you compose the atmosphere, the percentage of land to ocean you choose to create and the details of how and where the platoons of mirrors orbit and illuminate the planet, so there will be a lot of handwaving that can be done to meet your needs as a story teller. I would expect that the early period where the atmosphere and biologicals are being added will be marked by violent discontinuities as equilibriums are established and then disrupted, so people living there might not settle on the supra-mundane world unit late in the building and seeding process. Actively moving Saturn into a closer orbit around the Sun is also possible, but the amount of time and energy needed is "astronomical". If a sufficient number of asteroids, comets or similar sized bodies could be sent in looping orbits from the Kruiper belt to pass by Saturn, the planet could transfer some of its orbital energy to these bodies (speeding them up and flinging them from the Solar System) and gradually moving into a closer orbit around the Sun. This will require a lot of planning, as these bodies could crash into planets or spacecraft in the outer system, while as Saturn approaches Jupiter orbit, unexpected effects might arise out of gravitational interactions, resonance orbits between Saturn and the Asteroid belt and even the inner planets. It might be better to stick with mirrors. So maybe our descendants in AD 2500 might be starting a project of this magnitude, it will certainly need a vast amount of resources and the ability to control vast amounts of matter and energy in order to do so. [Answer] An interesting idea would be to have a hollow planet... An old dr.who episode features a pretty awesome plot, where the villains control a giant pirate ship planet that is hollow and can mine other planets by teleporting around them [Answer] Planets don't get much bigger than Jupiter: add more mass and they get denser in proportion, keeping the same radius all the way into brown-dwarf territory. Jupiter is 11 Earth radii, but only 320 Earth masses. 10× across means *1000×* the mass. So why can't you pile up that much rock? Common planetary formation seems to not do that, from the sample we have thus far. But the Universe is large, making improbable things likely *somewhere*. You need a way to collect rock *without* snowballing up all the ice and gas once it gets sizable. Rocky planets form inside the "frost line", but they run out of material. Here's some random ideas: a very large and dusty source cloud forms a blur hypergiant and has lots more "nearby" inside the frost line. Furthermore once the star ignited it ionized and blew off the leftover *gas* leaving dust around longer. More dust arrives from farther regions that are disturbed by other migrating planets and fling half of it inward. The merger of the inner rocky planets doesn't result in the star swollowing it but it's close: it's flung out of the system, and is captured by another star in the same nursery, before the cluster dispurses, so it's not too outrageous to be captured and ot remain rogue. Tidal forces of the close approach can rip off the gas amd ice leaving even more pure rock, which can be topped off after arriving at the new star. You could have a hiarchial binary system with exotic members, like a neutron star. There are pulsar planets...where did they come from? Maybe reformed after the supernova or Chthonian processes. With the long-term instability and past near approaches of the binary suns to the binary exotics, planets may easily get shuffled. A pulsar planet combines with a mundane terestreal planet and icy bodies to form an outer covering of rock, and replaces the terestreal planet around the sunlike star. The believability devises are: * if you want a rare outcome, do a lot of shuffling! * site processes we know about but don't understand yet. * introduce a spectrum of (currently unknown) systems so this is not a *total* outlier. [Answer] This Equation will help you understand why the Earth can not be much larger than it is now and still allow life to stay alive. The upper limit is around 7000 km radius, and even that might be too big as the surface gravity will compress the atmosphere too much, and raise the surface temperature above 150 F. The Rocky Planet Density Equation : Density = (1+Pi) x 10^-1 \* R^3 + (1+sqrt 2) x 10^-1 \* R + 2900 kg/m^3. The best fit is R = 6372.4567 Km producing g = 9.815 m/sec^2 surface gravity. A 7000 km radius produce a 1.19822 g surface gravity. [Answer] ## A cache of negative matter Everything is simple except for making a giant planet with similar gravity to Earth's... so add some unobtanium, which conveniently explains why the planet's minerals are such a valuable resource. Perhaps the planet has a cache of *[negative matter](https://en.wikipedia.org/wiki/Negative_mass)* inside it. This is *not* antimatter, but a hypothetical form of exotic matter that has negative gravity, which repels mass instead of attracting it. Such material is necessary for stable [wormholes](https://en.wikipedia.org/wiki/Wormhole) and [one possible FTL warp drive](https://en.wikipedia.org/wiki/Alcubierre_drive), so if those exist in your universe I would imagine negative matter to also exist, and moreover be very valuable. There are no known particles with negative mass, but they are theoretically possible according to the current understanding of physics. Your planet would have to be almost exactly half normal matter and half negative matter, with only an Earth's-worth of regular matter more. However, it should be reasonably stable; negative matter is still attracted by normal gravity, so you don't have to worry about the planet spontaneously exploding or negative crystals falling into the sky as soon as they are mined. [Answer] Magnetism is "stronger" than gravity, right? So what about an artifical planet with layers of nanite-controled magnetized iron (combined with sort of forcefield) that holds thicker layers of rock, many with air and water on them? The planet is divided like an onion or a spherical sky scraper, many layers have life, perhapse from different planets. Carefull use of nanomachines is how the magnetized mega-structures were made in the first place. ]

[Question] [ I'm considering the following scenario: Over the course of a couple of weeks, a global plague wipes out 99.999% of humanity, leaving just 75,000 people alive. These people are spread out evenly; in every regional and social group, only one in 100,000 survive. That means 14,000 people survive in China, 80 in New York City, and so on. For these people to recreate the world, they would probably want to stick together. A society of 75,000 people is sustainable, since it includes plenty of doctors, engineers, and every other important skill. But if humanity is split up into tiny groups, scattered across the globe, long-term survival is questionable. The question is, how would these people find each other? Global communication media such as the Internet and cellphone networks will shut down, and most survivors won't even be thinking about finding others until the plague is over. There will be a few surviving pilots, but they won't be enough to transport whole populations, let alone decide on where to go. Practically speaking, how will the survivors manage to join together? [Answer] **What made them survive and how long did the plague last?** Answering this question will provide you an answer on "where the people will be when everyone else is dead." For time being, I am going to assume that [Drax'es plan worked](http://en.wikipedia.org/wiki/Moonraker_%28film%29) and thus the answer will be that the plague was quick (almost instant), global (so no remote tribes were left untouched) and you survived simply because there was flaw in the poisonous formula. **But still, random behaves strangely** Even if one in 100 000 survived, it still gives good chance, that both you and your neighbor survived. The first survivors in my "quick poison" imaginations will be the luckiest one - meaning, they stayed alive in big pack of people on relatively small place (within plain sight distance). **What about the dead bodies?** Do not forget, that if *almost everyone* died, there will be *nobody left to burry the bodies*. Even in slower "kill them all" scenario. As the plague progresses, there will be dead people lying on the streets and rotting. So, contrary to popular belief **Big city is the last place you want to go** because you will see a loads of dead people lying on the ground, rotting - and thus polluting the area. Imagine the smell, imagine you wanting to stay here for longer time, because **If you want meet someone, you have to stay here** So, if you survive in this set up and are, for example, in New York, you should * Go to Times Square (because it is most likely possible anyone else will have the same idea) * And keep here a sign noting in which direction you left * Leave city * And find closest farm or self sustainable living [Answer] I think this is a very interesting scenario. If we look at the worldwide **demographics**, one can notice that half of the people on earth live in cities, half of those in cities with more than 500'000 inhabitants. ([UN study](http://www.un.org/en/development/desa/news/population/world-urbanization-prospects-2014.html)) That means that one quarter of the people will find themselves in an area where there's a good chance to meet other people without too much of an effort. For all the others, the most logical step would be to go to the next bigger city to find people. You should consider that not everyone will be able to do this, for various reasons such as them being too young or too old to survive on their own or simply because they live to far from a big settlement and might not have the means to get there. (Think remote islands). Some people might also just not think of it. Now the question is whether all those 75'000 people will eventually meet somewhere common. In my opinion that's very unlikely. It is more likely that there are going to be small settlements scattered near the bigger cities. I would also say that after a while people will probably have to move out of the cities to grow food etc. Once a settlement established, there are methods to **communicate** or reach out to other people with relatively low tech solutions. If you wanted to reach out to individuals you could use radio broadcasting, if you want to communicate with further away places maybe on other continents, you could use morse via radio, or also just broadcast your message via shortwave radio ([This wikipedia page](https://en.wikipedia.org/wiki/International_broadcasting#Shortwave_broadcast) has an image giving an example of distances one can broadcast to in this way). I think staying alive will definitely be the survivors first priority. You might be overestimating the **numbers of specialsts** for instance. Depending on the country, there seems to be between [1 and 4 doctors (with exceptions) per 1000 inhabitants](http://data.worldbank.org/indicator/SH.MED.PHYS.ZS). So even in most developed countries you will need around 250 peoples to have a more or less good chance to have a doctor and even then you might be unlucky and fall on a dentist or a psychiatrist instead of a GP. Even worse for pilots (US: [0.2 out of 1000](http://www.statemaster.com/graph/trn_act_avi_pil_percap-active-aviation-pilots-per-capita)), which should leave you with around 15 professional pilots world wide. Of course those are averages and the numbers will deviate. Another issue would be the **language barrier**. You can see on [this map from wikipedia](https://en.wikipedia.org/wiki/English_language#English_as_a_global_language), that there are many places on the Earth where only very few people speak English. And the same goes for other languages, so if you were to try to bring all those together in one place, most people would probably be unable to speak with each other. The book ["The Stand" by Stephen King](https://en.wikipedia.org/wiki/The_Stand) explores a somewhat similar scenario. [Answer] Do they need to join together? What pressing urge would force them to overcome any hurdles in their way. As you described it, there will be many hurdles. It is very rare for a society to choose a hard route, simply because it's the hard route. Usually they try to find a smoother, easier solution. If I were to let that scenario play out in my head, there would be an initial panic where NOBODY would be foolish enough to interact with anyone. Half of the survivors would probably get shot simply out of fear of being a carrier of the plague still. However, once that initial panic wears off, human society has built in us the basics of how to form small family units again. From those, warring bands can form. From those, tribes. These conglomerations will not occur "just because," but rather they will occur exactly when it becomes beneficial to a group to do so. Because of how few people per acre there are, foraging and farming would be valid solutions, even in New York City or Hong Kong. A small group of people could survive a markedly long time. From there, it would just be a matter of time before these tribes settle down enough to have enough reliable food to start pumping children out (especially since they're good farm helps). Population would begin an exponential rise like bacteria in a virgin petri dish. And then, at some point, they'd start running into each other, and trading stories. I wouldn't rely on technology or a flash in the pan idea to bring people together. A few million years of genetics has given half of our society the ultimate toolkit for reaching out and touching fellow civilizations. We've colonized the globe once, and I see no reason we couldn't simply do it again. Accordingly, I would expect the strongest driver of re-connecting would actually be genetic pressure to avoid any small tribal group from becoming inbred. [Answer] # Amateur Radio Amateur Radio has been practiced since the inception of radio technology. See <http://en.wikipedia.org/wiki/Amateur_radio> for history and common activities. A brief overview of the kinds of things amateurs often do can be found here: <http://www.ve3rhj.net/splitrail/whatdo.htm> Equipment is available on ebay and Amazon. The US National Band Plan can be found here: <http://www.arrl.org/band-plan>. Pay particular attention to the frequencies or ranges called ‘simplex.’ That implies that it is for point to point communications, vs repeater work. The items noted as ‘simplex calling frequencies’ are where other amateurs would monitor when looking to make contact with new people. You would likely benefit from a good quality scanner, in addition to several transceivers in HF, VHF and UHF. If you prepare, you would want to stock 12V auto-type batteries, unless you believe you will be able to scavenge enough samples in the aftermath. Solar and/or mechanical charging equipment is highly advised as well — either in your own collection or knowing where you can scavenge panels and charge controllers. If concerned, I'd recommend beginning the hobby now, so if/when the time comes, you'll have a clue how it all works in practice. [Answer] @Pavel Janicek is right. Random death is not orderly, and random clusters of under or overkill should be expected. Another consideration is what exactly causes high mortality, or low survival rate. **If survival is based on some very rare genetic difference,** death will again be non-random, and some populations (sharing rare difference) would survive **much** better than others. And quite possible that **plague can also affect other mammals/animals.** If so, **piles of dead animal bodies would be not only in cities, but also in rural areas,** and even rural areas would not be healthy/safe. Decomposed animal bodies would poison rural water resources, and because nobody is providing sanitation services, plague survivors might die of other diseases. Also, with so few survivors so widely distributed, **finding local expert speaking needed language** will be very difficult. And transferring this knowledge to new generations would be very hard, because most population will have to **work in low-productivity subsistence farming, with little leisure time.** Big part (20%?) of the survivors would be either too young, too old or in too bad shape to survive by themselves, and would die within weeks without help. Another risk would be that **one of survivors might by dangerous criminal,** or power-hungry psycho. Need of cooperation between survivors is high, but competition for scarce resources would be intense and group cannot risk of allowing non-contributing person to join them. I think **all responses grossly overestimate willingness to cooperate between survivors.** read <http://en.wikipedia.org/wiki/Malevil> . And that group had it good; they were a group of friends with established farm protected by a castle. Survivors would form small groups (tribes) and compete with others for most valuable resources. Mad Max style. With nobody enforce any rules. Wild West. Tribe will be **very selective** to accept new members. **Communication device would be gun**. Hard to argue with. Contacting with new tribe would be rather risky. **Supporting industrial economy requires huge and very specialized human resources.** Lacking these, economy will quickly revert to pre-industrial levels. **With pre-industrial rate of survival.** And pre-industrial rate of progress. No electricity. Surviving machinery will fall apart within few decades, because replacement parts will be not available. After a decade, fuel reserves will be depleted, and no way to drill and distill for more oil. Just FYI this similar scenario happened: Aborigines on Tasmanian Island had less developed stone technology than mainland Australia. Likely reason is that because of small population, groups could not support maintaining even those stone age technologies they brought from Australia. **With small population, any tragic accident has big chance completely eliminating all carriers of some knowledge,** and it is lost. It will be **back to the medieval Dark Ages**. With bicycles and scavenging old buildings, and old knowledge partially preserved, but close to Dark Ages. One good place for survivors would be old castles, fortresses or other protected areas. [Answer] I don't think you need to worry too much about them finding each other because most of your survivors will die, and I think there is almost no chance that the number of survivors will assure the survival of humanity, even if they miraculously find each other. You need a much higher survival rate, which will affect communications and subsequent ability to find each other. Approaching this only from a medical perspective, given your scenario (1 in 100K survive without restriction by genetics, age, location, etc. and loss of electricity/technology), about 12,500 will be aged 9 and under. Those under 5 will die in days from lack of water; those from 5 to 9 might live longer, but will likely die of disease, dehydration, exposure, malnutrition, etc. unless found by adults, so let's be generous and say 200 live and can someday integrate. 6,000 will be elderly (between 65-99) and will be well more than half women. While they will be helpful repositories of knowledge and can do light work, they cannot do too much, and their life expectancy will be dramatically reduced. 12,000 will be 10-19 years old. Most of those will have little skills or resources to stay alive (they will not know how to forage, let alone farm.) They, too, will be subject to disease and dehydration from unsanitary water and conditions (there are an awful lot of decomposing bodies around), and later by exposure. Being generous, let's say about one third will live more than 9 months. that's 4000, with about 2000 females. About 800 will be of reproductive age. The golden number here is 28,000. That's the number of people alive between the ages of 19 and 45 (not inclusive). Half will be women of childbearing age. With the 10-19 year old surviving females, (14,000 plus 800) that leaves 14,800 women to repopulate the earth under adverse conditions. Of these, 2% will never conceive (296) and 10.5% will be unable to conceive after having one child (1,554) Of those who do conceive the first time (14,504), one in 100 will die from each pregnancy (the rate in underdeveloped countries) from postpartum hemorrhage, eclampsia, obstructed labor, and sepsis, (145 women) with the rate being 1 in 16 chance of dying from childbirth in her lifetime. If all the females of childbearing age find males to reproduce with, after the first year of mating (*not* taking into account a spontaneous abortion rate of 20% before the 14th week), ~14000 babies will be born (half girls), 10% of the women will become infertile, and women will continue to die in childbirth: ~12930 women will be left for a second round. Miscarriages will increase due to decreased nutrition. Women will not have a baby per year in even the best of circumstances; the *highest* average number of babies per female in developing nations in the 1980s was 8.3. In the worst of circumstances, it will be much less. In other disasters where a population was forced to become agrarian without technology (e.g. the Cambodia under the Khmer Rouge, after the initial killing of ~3% of the population, close to 25% of the population died in only 4 years (disease, starvation, overwork), and that was in a temperate climate. Your people have to travel to better climates by foot or animal. Think Oregon Trail. Mortality is very significant. A *best* guess scenario might mean the loss of about 3500 women in maybe 5 years, leaving ~9400 women capable of conceiving. So, under *ideal* circumstances of every female mating every year, with the infertility, maternal death (and not even taking into account infant mortality, (which, as in developing nations will be significant), and an overall death rate of 20% in the first 5 years only, you'll be left with too few women and children to come close to repopulation. If they are spread across the globe and must travel to find each other, the numbers shrink to a small fraction of the best case scenario. [Answer] Much of the answer depends on the nature of that plague and the official reaction in the first days and weeks (cf @Jason C). If 99 out of 100 people die in the first week, what will the crumbling governments do? Order everyone to disperse and self-quarantine? Will that order be followed? How long until a guy in a hut in the forest decides that he's really immune, and not just lucky *until now*? Or is it a scenario where the affected people neatly crumble into dust one fine morning, or get beamed up by a passing starship? If 1 in 100,000 wakes up and finds everybody else is just gone, that would be more likely to trigger a search for other survivors. With modern just-in-time delivery systems, cities don't store much in the way of food and other supplies, but remember how few people there are to use the remaining supplies. If most of the deaths come early, the survivors won't have food problems until the last tins start to go bad -- and "best before" dates are rather conservative. To get back to the actual question, I would expect that *some* survivors actively try to find others. If they think it through, they will realize that a random search won't do much good. They'll go to local centers of government or landmarks and leave notes, as @Pavel Janicek pointed out. I think they might stay there a while if the remains of the 99,999 don't make that impossible. Get a car, drive around and honk. [Answer] I agree, amateur, or ham radio is probably the best bet, utilizing skip, but there is no reason for the internet not to still exist. Any IP using solar, or otherwise generated power and bouncing a signal off a satellite can be picked up and transmitted to anyone with compatible receivers, which, face it, there will be lots of, for free. So, what would be required? A working IP, a satellite still in orbit, and they are programmed, they do not just fall down, and a recipient, and yes, satellite phones would work. Other than that, look to carrier pigeons and pony express, lol. [Answer] Depends on details... when power grid fails, that means no power for nuclear plants all around world, and many of them will meltdown because the backup generators ran out of fuel to keep circulating the coolant. (Used fuel generates lots of heat even when sub critical... nuclear plants in US have similar weaknesses to the disaster ones in Japan) So you may have a bunch of nuclear reactors melting down after a few weeks with not enough organisation left to cap them after so still may have to live though a secondary radioactive waste disaster, and good chunk of people who survive the plague may die of cancer. As well, lots of those nuclear plants have lots of spent fuel stored in containers that will eventually sooner or later rust/fail without human maintenance. Similar but smaller problem with some industrial/chemical factories... you can have tanks of hazardous chemicals just sitting there and eventually what holds them fails and they contaminate nearby air or ground. As well, humans may not all cooperate, there can be conflicts over leadership, resources, directions, etc just like now. Anarchy/break down of social order is often nasty business, at least at first. On plus side, resources such as solar panels and chargers, stored food, machines, etc may be plentiful, a smart group could carefully hoard stuff to have nearly modern day living standard for 100+ years even without the know how of building it. Eg horde a large supply of solar panels, when existing ones fail you replace with spares, similar with chargers. Batteries may mostly fail but not so big deal if you only mainly use electrical power when sun is shining... if you have for example 3000 watts of solar panels and inverter you can operate one 15 amp circuit of any sort of electrical appliance. With lots of spare computers, and understanding need one could have access to modern knowledge by accessing replacement computers for 100 years. Possible you would have as result number of villages of 10 to 1000 people forming, and then like our modern world, possibilities of trade, merging, peace or war, etc. The people may not all group together which is both good and bad, on good side it helps avoid every human dying when the government makes bad decisions. Easiest way for such possibly split up groups to talk is short wave radio, but not clear that everyone will want to talk, and not all groups will master it. It is often easier to make a living by salvage and piracy then it is to grow your own food, if you steal someone elses horde of food you have doubled number of years you don't have to grow your own, if you control the guns you can have easy life and others act as your slaves, in contrast the farmers who are have a horde of food, and know how to survive for 100+ years may wish to lie low for risk of being raided by the pirates. [Answer] Most of the answers are telling that you don’t need to focus on how to find each other, because (pick some): * Everybody is going to die * You should try survive instead * If you find someone he/she might try to kill you * You might not be able to speak the same language as the person you found * … But these **are not answering the question**. Let’s accept that there are not problems in this case and address the real question: how to find someone in a mostly deserted world ? * Radio: already some good answers about this. On the bad side, you need power, and someone that is listening on the right channel at the right moment. * Very important: it’s not only about finding someone, it’s also about someone finding you! * Climb some tower or mountain and 1. Start a fire 2. Look for signals (especially at night) * Find a firework shop, take everything in your truck and launch a few of them every night. * Leave traces of your passage: Draw an arrow in the direction you are going, date it, and repeat at every turn you take. If someone sees one of your arrow, even one you left 1 year ago, he/she might be able to trace you up to the place you are now. (Think: painting, arranging stones, …) * Wear flashy clothes * Don’t forget to turn on every loudspeaker you can find, and in general to make as much noise as possible * Release helium balloons with messages * When you stop somewhere, make a smoky fire * Take time to look and listen to signs of someone doing the same. So my strategy would be: travel from one densely populated place to the next one (higher probability of finding someone), leaving arrows and making as much noise on the way as possible. Once you start to gather a small group, divide and set a meeting point planned for a few month in the future. Once the group is too big, settle and send scouts, each time a little bit further. Also I would look for patterns. Maybe the you survived because of luck. But maybe you have something different from the others? Does your family come from a remote alpine valley and have an uncommon gene? Did you participate in a medicine study for which you were inoculated with a later not released vaccine? If you discover a pattern once you found some other survivors, it might help to find even more people. *Let's go to that that alpine valley from where all our ancestors came from guys! Everybody is probably still alive there!* ]

[Question] [ This is a followup question to the question [Wondering what would happen if magic was constrained by Conservation of Energy](https://worldbuilding.stackexchange.com/q/519/74) and it's related to [this post](https://worldbuilding.stackexchange.com/questions/628/explaining-where-energy-comes-from-to-power-magic/664#664). [This question](https://worldbuilding.stackexchange.com/questions/628/explaining-where-energy-comes-from-to-power-magic) asks which sources of energy could feasibly be tapped by magicians, and the answers there compliment the answers below. In this question, I would like to know the specific restrictions on using those energy sources, where the second law of thermodynamics holds1. The second law of thermodynamics [states](http://en.wikipedia.org/wiki/Second_law_of_thermodynamics) that: > > the entropy of an isolated system never decreases, because isolated systems always evolve toward thermodynamic equilibrium, a state with maximum entropy. > > > I will borrow wikipedia's [definition of magic](http://en.wikipedia.org/wiki/Magic_(paranormal)): > > Magic or sorcery is an attempt to understand, experience and influence the world using rituals, symbols, actions, gestures and language. > > > Naturally, this question will focus on the abilities of magic to influence the world. For the present discussion, assume that magic also encompasses superhuman powers. ***Are there clear rules based on science which dictate if a hypothetical magical process, event, trait, or ability would be possible in a world where magic is constrained by the second law of thermodynamics?*** Concrete examples of how one might go about deciding which processes are possible would be very helpful. I would also prefer answers that deal exclusively with Newtonian physics; I think it's going to get a little too complicated if we try and bring in relativistic effects. Also, please assume that the conservation of laws of mass, momentum, and energy also hold. Finally, there should be no reference to other dimensions or other universes to which entropy may be 'dumped'. Any world involving magic is can use this as a workaround to try and explain things, although this is not physical as far as we know. 1 The first law of thermodynamics is another name for the conservation of energy. [Answer] *There's a quick summary at the bottom; read the rest for a better understanding.* ***Spoiler Alert! I discuss characters from The Incredibles and X-Men: First Class with reference to the plot events. You have been warned.*** # Better Evaluation Criteria First of all, it is hard to evaluate the plausibility of a magical process by reasoning whether or not it violates Wikipedia's definition, because that definition applies to an isolated system, and I believe that most magical processes occur in [open systems](http://en.wikipedia.org/wiki/Thermodynamic_system#Open_system) (i.e. mass, energy, and entropy may be exchanged with the environment). An easier way to evaluate second law violations is to question whether a system violates one of two statements, which cover most second law violations. **[Clausius Statement](http://en.wikipedia.org/wiki/Second_law_of_thermodynamics#Clausius_statement)** > > Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time. > > > The first part, `Heat can never pass from a colder to a warmer body`, is eluding to [Fourier's Law](http://en.wikipedia.org/wiki/Thermal_conduction#Fourier.27s_law). We have always observed that heat moves in the direction of the highest temperature gradient, or from warmer regions of a substance to cooler regions. The *spontaneous* movement of heat from cooler matter to warmer matter is widely regarded as impossible. A device which violates the Clausius statement is shown in the figure below.  Modified from "[Deriving Kelvin Statement from Clausius Statement](http://commons.wikimedia.org/wiki/File:Deriving_Kelvin_Statement_from_Clausius_Statement.svg#mediaviewer/File:Deriving_Kelvin_Statement_from_Clausius_Statement.svg)" by Netheril96 - Own work. Licensed under [CC BY-SA 3.0](http://creativecommons.org/licenses/by-sa/3.0 "Creative Commons Attribution-Share Alike 3.0") via [Wikimedia Commons](//commons.wikimedia.org/wiki/). We do have devices that move heat from cool reservoirs to warmer ones; they are called refrigerators, but they require an external work input. That's what the `exception therewith, occuring at the same time.` is referring to. **[Kelvin-Plank Statement](http://en.wikipedia.org/wiki/Kelvin%E2%80%93Planck_statement)** > > it is impossible to devise a cyclically operating device, the sole effect of which is to absorb energy in the form of heat from a single thermal reservoir and to deliver an equivalent amount of work. > > > This statement describes a machine which absorbs energy from a high temperature reservoir (e.g. a boiler), and exports all of that energy as mechanical work (e.g. a [steam turbine](http://en.wikipedia.org/wiki/Steam_turbine)). This is another device which satisfies the first law, but not the second law. To understand why this is an issue consider the figure from wikipedia: [](http://commons.wikimedia.org/wiki/File:Deriving_Kelvin_Statement_from_Clausius_Statement.svg#mediaviewer/File:Deriving_Kelvin_Statement_from_Clausius_Statement.svg) "[Deriving Kelvin Statement from Clausius Statement](http://commons.wikimedia.org/wiki/File:Deriving_Kelvin_Statement_from_Clausius_Statement.svg#mediaviewer/File:Deriving_Kelvin_Statement_from_Clausius_Statement.svg)" by Netheril96 - Own work. Licensed under [CC BY-SA 3.0](http://creativecommons.org/licenses/by-sa/3.0 "Creative Commons Attribution-Share Alike 3.0") via [Wikimedia Commons](//commons.wikimedia.org/wiki/). The imagined engine is the Kelvin-Plank engine on the left, where the mechanical work output powers the refrigerator (Carnot Engine) on the right. The refrigerator does not violate the Clausius statement because it has a work input. But since we don't have any real restrictions on what constitutes a 'device', the combined device (dashed green line) should also be possible. The simplified device is shown in the first figure. This device has a net work input of zero, and at the same time it still moves energy from a cooler reservoir to a warmer one. We can now see that it implies that heat can be moved from a cold reservoir to a warmer one without an external work input, which is impossible. Both of these statements describe machines which violate the second law, and either can be used to evaluate the plausibility of a process1. **We can see that, in general, these statements help us eradicate designs which suggest that heat spontaneously flows from cooler reservoirs to warmer ones.** ## Examples I'm now going to analyze two superhumans from recent movies and use the above statements to decide on whether their powers violate the second law. [Frozone](http://www.writeups.org/fiche.php?id=4986):  ([The Incredibles](http://en.wikipedia.org/wiki/The_Incredibles) - 2004) > > Frozone is a 'Super' from the Incredibles' universe. He utilizes moisture from the air and his own body to freeze parts of the environment. First let's just consider the moisture absorbed from his own body. > > > We can realize pretty quickly that Frozone is just a really efficient and high powered [ice machine](http://home.howstuffworks.com/icemaker2.htm) or ice maker. He extracts heat from a low temperature 'reservoir' (the stream of ice shards coming from his hands) and dumps the heat to the surrounding environment (assuming his body temperature is constant). There is nothing wrong with this; there is just some crazy refrigeration system that is a part of his physiological makeup which allows him to do this. But what about the ability to absorb moisture from the air? It turns out there is a similar form of Fourier's law (heat always flows from hot to cold) that applies to mass transport called [Fick's law](http://en.wikipedia.org/wiki/Fick's_laws_of_diffusion), which dictates that diffusion of a species (e.g. water vapor) in a fluid will always occur in the highest *concentration* gradient. Again, similar to heat transfer, we can't create a device that moves mass from a low concentration reservoir (ambient air) to a high concentration reservoir (Frozone's body) without external energy input. But he can do it so long as he can supply sufficient energy input. **Verdict: Plausible** We know that refrigerators work and dehumidifiers work, so Frozone's ability seems plausible, so long as he can supply the energy required. [Sebastian Shaw](http://en.wikipedia.org/wiki/Sebastian_Shaw_(comics)):  ([X-Men: First Class](http://en.wikipedia.org/wiki/X-Men:_First_Class) 2011) > > Sebastian Shaw is a mutant from the X-Men / Marvel Universe. He has the ability to absorb energy from various sources and release it in alternate forms. For the most part he seems to garner his power from kinetic energy sources, but I'm going to pick on the event towards the end of the movie, where he locks himself in the mirrored nuclear reactor chamber and absorbs the energy from the fuel rods by grabbing hold of them. > > > For this analysis, the nuclear fuel rods can be considered a constant high temperature reservoir. During this scene, he doesn't perspire, suggesting that he isn't losing any heat to the environment, and there's no evidence of significant heat loss by other means. Shaw himself is the 'engine' who is storing energy for later, and as I have seen in other scenes in the movie, he has the ability to use his absorbed energy for kinetic attacks; i.e. he can do mechanical work with the energy. Is this raising any concerns? We have heat engine (Shaw) who is gaining energy from a high temperature reservoir (fuel rods) while dumping a negligible amount of heat to his surroundings (floor and ambient air), where the vast majority of it can be used to do mechanical work. **Verdict: Busted!** Given what we are told about Shaw in *First Class* we can almost certainly conclude that he is behaving as a machine which violates the Kelvin-Plank statement, thereby violating the second law of thermodynamics. ## Other Implications In the last section I talked about the movement of mass as another process which only occurs spontaneously in one direction. There are other forms of transport such as electromagnetic and nuclear are bound by similar restrictions. # Summary **The common thread is the concept of [diffusion](http://en.wikipedia.org/wiki/Diffusion); anything that tends to spread out over time will not spontaneously concentrate in a single place.** Here are some basic questions you can ask yourself to help determine whether your magic obeys the second law of thermodynamics (as the real world does): * *Are there any real world devices which do what this magic is doing?* If so, then your magic is plausible. It might be more powerful and more efficient than any devices humans have invented, but that's acceptable. This is the easiest way to validate the magic. * *Does it Violate the Clausius statement?* Is there a magical rod which always moves heat to one end? Is there a certain wizard who can draw poison from a wound? Can a caster absorb energy by freezing a lake of water? Is there an enchantment which directs airborne viruses into the airways of unfortunate recipients? These are examples of processes which are the reverse of diffusion; they are moving stuff to a desired region of space. They are possible, but they always require an energy input. * *Does the magic violate the Kelvin-Planck statement?* This one is trickier to spot. If the magic uses thermal energy to do some mechanical work or store energy, there just needs to be a lower temperature reservoir where some heat is being dumped, so the process is not 100% efficient. In the example above, if Shaw's hands were sweating a little when he grabbed the nuclear fuel rods, it would show that some heat is being lost to the environment, and for me personally, that would have made the scene more believable. As for how much energy must be dumped, it depends on the process, and that's a more difficult question to answer. Right now I will just say that it shouldn't be insignificant relative to the energy gained from the process. * *Still think there's something unbelievable about the magic?* Post your question on this site! There's a lot of details I've omitted and there might be some very common cases that are worth addressing in a separate thread. 1 Note that the statements are, in fact, equivalent, and any device that violates the Clausius statement also violates the Kelvin-Plank statement. [Answer] The concept of [entropy in thermodynamics](https://en.wikipedia.org/wiki/Entropy) is intimately linked to the concept of energy, therefore I think the answer to this question depends on the answers of a few other questions: 1. Does magic use a separate "magical energy source", or does it just work by redirecting energy flows from existing sources? 2. If a separate energy source (like a "magic field" or similar, that only magicians can tap) is used: Is the magic energy resource work-like (the magician can remove — and possibly even store — energy in it as he wants), or heat-like (the magic reservoir effectively has a temperature, and withdrawing energy from it is limited by that). Let's consider the three cases separately. # Pure energy redirection If the magician doesn't have special magic energy sources, then thermodynamics mostly enters when he affects heat, in which case he actually acts as a [heat engine](https://en.wikipedia.org/wiki/Heat_engine) or [heat pump.](https://en.wikipedia.org/wiki/Heat_pump) Like any heat engine, he would be restricted by the [Carnot efficiency.](https://en.wikipedia.org/wiki/Carnot%27s_theorem_%28thermodynamics%29) Especially, he could not cool anything down without either a cold reservoir where he could direct the heat into, or an energy source he could tap in order to actively cool the object; in this case, he additionally would need to dump the heat *plus the needed work* drawn from that other energy source. If that other energy source is itself heat (which then has to be hotter than the environment), also his harvesting of energy from that heat source is limited by the Carnot efficiency; for example if he's in an uniformly hot place, and any colder place is outside the reach of his magic influence, he cannot harvest the energy in the heat for anything, be it cooling or something else. # Heat-like magic energy source If there's a separate source of magic energy that has the characteristics of a heat reservoir, then of course in principle the same rules apply; except that as long as the environment's temperature doesn't match the "magic temperature" he can use that difference for his magic (if interacting with the magic reservoir is the only way to do magic, this would also mean that if the environment's temperature matches the magic temperature, he would lose all his magic power). In this scenario, the magician could change the general temperature of the environment in the direction of the magic temperature by just letting energy flow between the environment and the magic reservoir. Especially if the magic reservoir is colder than the environment, he could *seemingly* violate the second law by cooling the environment without apparent other change (since ordinary people would have no clue about the magic reservoir). He would also appear to violate energy conservation that way, even if he really doesn't, since the energy flowing to the magic reservoir would be invisible. Of course, he could also turn part of that energy to work, but restricted by the Carnot efficiency; in effect that would mean he'd always deplete the non-magic world of energy whenever he does magic. If the magic temperature is higher than the environment temperature, then just letting energy flow between the environment and the magic environment would heat up the environment. Of course, again he could convert part of the heat drawn from the environment to work, but not completely; any magic would be accompanied with heating up the environment, and using energy which apparently comes from nowhere. If he would want to cool down things, he'd have to use the work extracted for effectively heat pumping, which then again is restricted by Carnot efficiency; cooling down some part of the environment would need heating up another part *much* more (in part to harvest the work from the magic reservoir, and in part from converting the harvested work into heat during the cooling process). Of course if the magic temperature is such that it is sometimes below and sometimes above the environmental temperature, the two cases may apply at different times, and at certain times the magic ability may be completely disabled due to temperature match. I think that would be the most interesting option. # Work-like magic energy source This one is actually quite simple: The magician could tap the magic energy source just like some engine might draw energy from a flywheel. If the magician can only draw energy out of the magic energy reservoir, he would inevitably heat up the world during magic (there may, however, be processes which refill the magic reservoir from normal energy sources). If the magician can also store energy into the reservoir, he could also tap energy sources in the environment to refill it. However, if he taps heat sources, he'd still be bound by the Carnot efficiency. [Answer] I would argue that ***nothing would change*** if "*magic were constrained by the Second Law of Thermodynamics*" because all modern fictional magic systems ***are*** already constrained by the Second Law of Thermodynamics. If they weren't, there wouldn't be a story. Authors just have to be sneaky about how they work it into the magic. The Second Law defines our existence. It drives evolution which in turn lays the foundation of human behavior. By forcing us to expend energy to accomplish anything, it limits the actions we can undertake and forces us to make choices between alternatives. Our intuitive understanding or human behavior and our evaluation of human actions encode a gut understanding of the Second Law even if we know nothing about the math or science of it. A character whose travails a reader can empathize with must wrestle with the Second Law. Characters wholly not subject to the Second Law don't seem powerful, they seem utterly inhuman and ineffably alien. By extension, any fictional world restricted by the Second Law, even in just a part, feels fake and unbelievable. If the world feels fake, the so does the characters. With no strong characters and no reader empathy the story fails. But, the appeal emotional appeal of magic in a story for a reader arrises marvel of seeing the effects of breaking the Second Law. The Second Law restricts and burdens us, we like to fantasize we could escape it (as in the modern search for Free Energy.) Magic fulfills this desire in fiction.Mages create objects "out of thin air," see the future, alter the past, live forever and perform other feats that explicitly violate the Second Law. Arguably, violating the Second Law, is what makes magic, "magic." To have magic in a story, the author must depict explicit violations of the Second Law as readers intuitively understand it. Authors confront a paradoxical story requirements. To create a believable world, the Second Law must be as universal as it is in the real world but to provide surprise, awe, wonder and the emotional appeal of magic for the reader, the magic system must be able to violate the mundane Second Law that readers encounter every moment of their real world existence. The solution is to shift the "cost" of complying with the Second Law ***from physical systems to the characters themselves***. The reader relates to the character's struggles against Second Law limits, not the Second Law's restraint on the inanimate environment. The story will satisfy if the character struggles with limitations that to the reader feel like the limitations imposed by the mundane Second Law. The source of those limitation is largely irrelevant save for stylistic purposes. In magic systems of both traditional cosmologies and in modern fiction, the role of the limitation of the Second Law on the character takes the form of a "price" the character must "pay" to evoke the magic. The price can take any form as long as the character must must struggle to pay it. For example: A mundane car pays one of it's Second Law prices in the form of fuel and provokes no awe or wonder while a car that requires no fuel feels instantly magical to the reader. But a car a car that imposes no cost on the characters using the car, breaks the readers intuitive Second Law model of the world and feels wrong. Often readers describe such magics as shallow, tinny, silly, comical or childish. The appearance of such magics "breaks" the reader's model of the fantasy and yanks them out of their immersion in the story. The author fixes the car's world breaking by imposing a price on its use that the character must struggle to pay. The price serves the function of the limitations imposed by the Second Law in the real world, making the car feel like it belongs in human affairs and thus making the character interacting with the car feel more real as well. The price can take any form as long as it requires the character utilizing the car to expend time and energy in the same way they would have to expend time and energy to obtain fuel for a real car. For example, the character might have to sing a song to the car constantly to induce it to move. While singing the song, the character cannot perform other task. At some point in the story, the need to sing to drive will conflict with some other need or desire and impose a limitation on the character that the reader will intuitively empathize with. The need to sing serves the function of the limitations imposed by the Second Law in the real world. The car now overtly breaks the mundane Second Law and provokes wonder, "look the car moves without fuel!" but still imposes Second Law restrictions ***on the character*** so that the character's conflicts, choices and actions feel human and realistic enough for the reader to empathize with the character. E.g. After a while the novelty of moving the car by singing grows wearing. The character needs to cast a verbal spell at the same time he needs to move and must choose between needed actions. The character grows hoarse. Magical belief systems and modern fictional magical systems have come up with a lot of different types of Second Law mimicking prices. Most magical systems use some combination of prices instead of relying on just one. Below are few off the top of my head. **Violation of Mundane Second Law Causes Problems** The magic breaks the Second Law and appears wondrous but that breaking the Second Law collides negatively with the rest of the story world which still follows the mundane law. The conflict causes the characters to exert mundane time and energy to manage the these side effects. For example, a sword that will cut anything with zero effort appears wondrous but quickly causes negative side effects the character must struggle against precisely because it cuts everything whether the character wants it to cut that thing or not. He must contrive to sheath it or otherwise carry it safely despite the fact that nothing can touch the blade edge. If he drops it, it will bury itself in the ground to the hilt, drop through wooden ship's hull. When wielding the sword, the character cannot strike himself, an ally or an innocent without instantly cutting them. Fumbling the sword could be lethal. The expenditure of mundane time and energy to manage the side effects serves the function of the limitations imposed by the Second Law. **Rarity, Usually with Limited Function:** The magic is very, very rare. Superficially, the magic has no price but it takes an enormous expenditure in time and energy on the part of the character to actually obtain the magic. That expenditure serves the function of the limitations imposed by the Second Law. **Rare Material Components:** Often seen in traditional sympathetic magic. These components are hard to obtain, often unique or specific to a place, object or individual, single use and do nothing more than provide information, the sympathy, to target the spell or give it specific qualities. The difficulty of obtaining the specific material components serves the function of the limitations imposed by the Second Law. **Human sacrifice:** Using humans as a means of enabling spells obviously limits mages owing to humans natural tendency of desiring to avoid being the sacrifice. Sometimes a rare or sacred animal creature or object, something unique and hard to obtain serves as well. The struggle to obtain sacrifices limits the amount of magic the mage can perform and serves the function of the limitations imposed by the Second Law. **Time:** the classic D&D limiter of making mages spend hours every day memorizing spells. Since there are only so many hours in a day, this price limits how much magic a mage can perform per unit of time. The need to trade time, a limited resource, for magic, serves the function of the limitations imposed by the Second Law. **Ephemeral/abstract quantities:** Something abstract and non-material that that has no readily apparent mundane Second Law value but which have some conceptual limited quantity. Parts of one's soul, memories, future potential, life span, mental pain etc are all abstractions but ones without infinite quantity. A mage only has so much soul, so many memories, so much future, so much life span and can only tolerate so much pain. To create a magical effect the mage must decide if the value of the effect warrants the percentage of the abstract quantity he must exchange for it. That need to husband the abstract quantity serves the function of the limitations imposed by the Second Law. **Logical Deal with the Devil:** The mage must bargain with or coerce a magical entity to perform feats which violate the Second Law but the entity will not perform said feats except as strictly required a logical construct in form of a contract or precise instructions. Usually, the entity is actively malicious and seeks to harm or frustrate the mage by exploiting any ambiguity or loophole that mage mistaking leaves in the logical construct. The time it takes to construct the logic, it's unpredictable interpretation by the entity and thus the resulting effects, topped of with the very real danger of the entire process, serve the function of the limitations imposed by the Second Law. (... in the real world it's called programming. Yes, computers are actually malicious, inanimate machines my %$#@!. Just ask any programmer.) **Shamanistic Trading Magic:** In this tradition, common in the world's smaller scale cultures, everything that exist is controlled by a spirit with personality and desires. Shamans can convince the spirit to perform task by trading the spirit something, sometimes an objects, sometimes ephemeral, sometimes getting another spirit to do something. I In may stories, the mage must weave a complex web of trades with many spirits to end up with the particular trade item valued by the one spirit that can do what the shaman wishes done. Often combined with the Logical Deal With The Devil in whole or in part. The complexity of the trades, the time it takes and often the danger of dealing with the spirits, serves the function of the limitations imposed by the Second Law. **Time and/or location restraints:** Classical concept in which magic is only possible when the stars align and/or on certain dates or at specific locations. Often combined with another restraint like Sacrifices. The mage can't just act at any time or place of his choosing. Mundane acts that block access to the location or prevent the mage from evoking the a the stop the magic. The effort of evading interference serves the function of the limitations imposed by the Second Law. **Limited knowledge:** Based in the oldest traditions dating back to Sumerian-Sanskrit Ur magic, which form the roots of most Indo-European magic concepts and the basis for our concept of a "spell." (The most interesting price in my opinion. In this magical system realty is defined by language i.e. specific words, with specific pronunciations and/or spelling/glyphs, within a specific syntax, define reality itself. By speaking/writing/inscribing the correct forms of words in the right syntax directed at the right part of reality, the mage order the addressed part of reality to assume whatever state he wishes. In Ur magic, ***true words are not symbols***, they are reality itself, the only true reality. In Genesis, God commands, "Let their be light" and there is light. This concept of god creating by word alone is of the Sumerian tradition (secularly speaking.) A mage who learns the true name of light as spoke by God can create light at will. In the classic golem story, writing the true word for "life" on the clay golem causes it to adopt the attributes of being alive while altering the name to spell "dead" causes it to lose the attributes of life. Knowing an object's, creature's or individuals true name, the name that marks it as unique in all of realty, gives the mage complete control over it. The Ur magic is the origin of the idea that, "words have power". Today we mean it in terms of the ability to skillful use words to persuade other humans but originally it meant the ability alter reality. The Word of God in the times of the Old Testament was not just moral commands but defined and sometimes altered reality. Humans cannot discover true words on their own. Usually humans learn of them initially only from mystical beings who taught them to humans in the distant past. Overtime the words are forgotten. The mage must struggle to recover and understand them. Since the true words are reality, not symbols, speaking, writing or inscribing the true word in the proper form and syntax instantly alters reality. The true words cannot be communicated directly and openly e.g. "Okay, pupil the true word for 'fire' is Eq Um So...ahhhh! water! water! water!" Neither can they be written e.g. "Chapter 3, Fire. ...ahhhh! water! water! water!" (In Norse Runic magic, the inscribing of the runes creates their effect on the object or place so inscribed. That is were the tradition of runes etched into weapons comes from. Runes where memorized an only actually written when used.) Masters have to instruct apprentices purely by example. The master says the true words and alters reality while the student watches. Then he must try and duplicate the master without further instruction and/or killing himself. Written knowledge of true words must be couched in euphemism and allegory. Mages had to struggle to learn the true words and once they did so, had to devote them solely to memory relying on mnemonic devices to help them remember. Putting the words in rhyme was an obvious memory aid. If a mage died without passing his knowledge on training apprentices by example, then the explicit knowledge of the true word died with him. All the difficulties of preserving, finding, learning to use the true words and names serve the function of the limitations imposed by the Second Law. --- The art of good fantasy world building lays in actively weaving the limitations of Second Law tightly throughout the magic system so that the system feels "real" while disguising it so throughly that the magical effects themselves like wondrous violations to the reader. The reader must experience the wonder of breaking a universal law of our reality but at the same time must empathize with the struggles of the characters against the magic's limitations. The fact that we can ask a question like, "what would magic be like if obeyed the Second Law?" is an indicator of their success in doing so. [Answer] # You would probably get something like Fullmetal Alchemist Fullmetal Alchemist's brand of magic (alchemy) is very explicit about matter/energy never being created or destroyed- referred to as the "Law of Equivalent Exchange". All transmutations which result in a lower entropy or higher energy state must receive energy from somewhere, which in most cases is tectonic energy. Transmutation circles act as a way to channel this energy into reconfiguring the natural elements around them. Mass is meticulously preserved in every normal transmutation throughout the entire series. (Though one scene in the 2003 anime cheats a little with Edward changing his prosthetic arm to different metals, which wouldn't really work due to the different densities of those metals) There are also "philosopher's stones" which appear to sidestep the second law of thermodynamics, but even these are limited. They derive their energy and matter from human life force (Einstein helps us out here with his famous Mass-energy equivalence law) and will stop working as soon as all of the life energy has been consumed. As noted from another answer, storing the energy in a compact form like a philosopher's stone isn't going to work because it would either need to be extremely hot or store the energy in some sort of ethereal form (which is not allowed by your question), but you're still left with a pretty versatile and powerful magic system without philosopher's stones. [Answer] The second law would only be an issue if you tried to use magic in a way which would actually increase entropy, like by splitting temperatures into hot an cold. We can consider conservation of energy a seperate issue. Let's say you want to boil a kettle. Would this increase entropy? Yes! This would make the temperature of the kettle different from the surroundings, since the surroundings would be at the same temperature. Some of the various sollutions to the problem of Maxwell's demon, a device that has a door that opens only for certain types of atoms, and the reconciliation of the problem with the law can offer us some guidence to how magic can be reconciled with entropy. One solution is that the demon's memory increases in entrop, and in a magic system, too, a similar thing could be done where entropy is essentially moved around, so that, rather than just the kettle boiling, you could also melt an ice cube to make there be a bit more order nearby, you could also have the magic automatically mix finely sorted powder, mess up a stick into goo, or run on a sort of entropy fuel like machines run on energy. The entropy would be moved from the kettle's temperature gradient to the stick's mollecular structure, and since this is fictional magic, you can just decide these things, and that's that! ]

[Question] [ I've been working, on and off, on a universe with limited FTL based on the ["one big lie"](http://tvtropes.org/pmwiki/pmwiki.php/Mohs/OneBigLie) principle of sci-fi writing; travel speed averages just a hair over 4 times the speed of light, travel is instantaneous for the ships and crews travelling faster than light. Some time travel is demonstrably possible, ships do occasionally arrive before they leave, but because decisional causality can't be violated you can't do anything interesting with it. But most importantly, to this question, jump times, as measured from a non-FTL reference frame, can be rather variable (Poisson-ish distribution around the expected average with roughly 90% of the ships arriving within plus or minus 10% of their expected transit time on "standard" jumps) some ships will arrive as soon as, or even before, they leave, but never before the decision was made to send them, while others may take several times longer than expected to arrive. **A touch of background to the conflict;** Humanity have been very worried about their weird alien neighbours for some centuries because they think that they could be squashed flat at a moments notice, as such they've sunk enormous resources into a huge battlefleet, all of six fleet carrier class ships, each one capable of pacifying any one system. Their neighbours for their part have concerns of their own, not being able to squash the humans and Humanity having advanced technology in areas that makes the aliens very vulnerable to certain routes of attack. The two are at peace, sort of; the aliens don't let us anywhere near certain installations and otherwise *almost* ignore us. They have no specialised warships but do have vessels that can be used in the role in an emergency that has never come. Oh and a few millennia ago they fought another alien group, their own overlord caste, to extinction and/or exile. **Technical details:** No-one has FTL communications except by courier all intel gathering and ships comms are strictly lightspeed minus processing. So all intelligence gathered will be light speed lagged by the time you get it. In-system big ships are slower than small ones but when it comes to FTL bigger is better for several reasons, not least of all being heat dissipation capability compared to the size of the powerplant for the jump drive. Most populations are planetary but most material extraction and manufacturing is done off-world. **The current conflict;** now the masters are back and our alien neighbours have asked for our help, between us we control a loose cone-like area that at their far frontier is a hundred or so light years across, no-one's sure, there's a small zone that unknowingly overlaps the "masters" self-exile. At a minimum they'd like to create a buffer in that area but ideally they'd like to wipe these guys out for good. The combined fleet is over a dozen fleet carriers, huge FTL capable vessels that are, in the case of the humans, heavily armed and carry large numbers of interplanetary warships, most of which are usually FTL capable in their own right, as cargo. **The question proper:** Given a narrow interstellar battlefront of say 30 Light Years only a few light years deep say 10-15 systems in all and assuming a single strike unit can reliably pacify a given star system, but not a reaction force if one shows up, within days, is the fact that the strike forces' arrivals in the different systems could spread across up to 10 years or so going to hurt their ability to win the war or does a strike dispersion that small make no difference at such a scale? [Answer] This is a fascinating question that will have a substantial impact on your story. I love it! Let's get some basic observations out of the way, which will include some restatement of your limitations. * A group of individual ships launching in tandem always arrive at the same time, but within a +/- 10% variance of when they expected to arrive. * Groups of ships or individual ships not launching in tandem arrive with no guarantee that the other ships won't arrive years apart. Consequently, it's impossible to coordinate attacks between multiple targets. * The "field of battle" is 30x3x3 light years or 270 cubic light years. The amount of physical space this encompasses, compared to the galaxy, is trivial like a grain of sand — but from the perspective of interstellar space ships, it's an inconceivable amount of volume. Massive fleets can be hidden by jumping them into some middle-of-nowhere location. Consequently, battles ***never*** take place in the void (if you were lucky enough to detect their presence, by the time you landed ships there, they'd be long gone after years of R&R). Frankly, who cares if your enemy's fleet is sitting in the middle of nowhere thinking strong negative thoughts about you — you control everything of value, which means you're still building ships.... * This means your battles are taking place at ***resource points.*** A resource point can be anything from a star system to a rogue planet to a "meteor shower" (or, what would be a meteor shower once it hit a planetary atmosphere). Any object or group of objects with a movement vector that is mathematically predictable and has something of value (not to forget that being mathematically predictable is, itself, something of value). * And this all means that a "win" is defined as "I control all the resource points" because there's nowhere else worth going. **Except for one thing... and I'll get to that in a moment...** For the most part, your wars are all about the siege: the process of overcoming the defenses around a resource point and/or holding that resource point. Battles in space will almost always be minimal as only those ships stationed at the resource point can be involved in defense. This begs the question, "how much of that resource point needs to remain to still be of value to anyone?" If the reason a habitable planet is valuable is its mineral makeup, then just nuke it. You don't need its habitability and mining generally takes place underground anyway. (If you can see what I mean....) From this perspective, you don't have a 270 cubic light year front, you have 10-15 siege points. All the rest of it is dead space. **Kind of...** Your first reaction may be, "hey! I can use that nebula as cover! What do you mean no space battles?" Except that it takes years to get there with months-to-years in variability of arrival and if there's nothing useful to be extracted from the nebula then what value is it? Answer: none whatsoever. BUT... You could jump your fleet into the void *near* the target resource point (oh, let's call it "Earth") such that your last FTL jump is a month +/- 3 days. (And this assumes that your variance doesn't grow smaller with jump distance. If it does, that error might be +/- 3 hours.) So "near space" has value as staging areas to ensure the whole fleet is there and coordinated using the very latest intel. In fact, it allows you to *gather* the latest intel because... **You didn't say what your communication was like** And, therefore, I assume you do not have interstellar comms that are faster than your ships. This means that the chance to gather local intel is ***incredibly important*** and near-space battles suddenly become a costly but necessary fact of your war. How do you detect something so small as 1,000 ships of the enemy's line within a light-month of your star? You do have a window of opportunity, because they need at least two months just to send and return reconnaissance. That means if you can find them fast enough, you can land your ships in their midst. Or change your defenses. Or whimper in disbelief that they thought your planet was strategic enough to be controlled. **Like I said, I love this idea** This is the kind of limitation that makes stories really fun. It has a taste of realism while enjoying a bit of fantasy — all the while requiring you to use your imagination to wrap it in an infinite number of plots. Think about it! They can find me within a light-month! Just how far out must I be to be undetectable while I gather intel? Just how fast can I change defenses to obsolete the intel? How much must I bring to both subdue and fortify a resource point? And what if those sneaky bounders left everything behind but a super-nova-causing bomb just waiting for your spies to show up? Cheers! [Answer] The variance of this "Poisson-ish distribution" makes the difference here. "10% of their expected transit time" means that on a 10 year trip, the bulk of the jumping force will be spread over 1-year period. Each jumping ship will be essentially on its own upon arrival. There are two ways to mitigate this issue. 1. Set up a rally point. Establish a rally point just outside target system. this point should be just outside of defenders' scanning abilities (Kuiper belt? Oort cloud?) and should be targeted by jumping ships with precision. Attacking fleet will be regrouping at this rally point until sufficient force is reassembled, and then start the attack on the system. 2. Mother ships. Instead of building a fleet, build one huge ship. It can be a host for smaller fighters and bombers, or some kind of a "Death star". the point is to be able to transfer all of attacking force at once, without spreading out along the way. [Answer] The question can't really be answered without more information! Are the two sides in the war vast interstellar empires or are they relatively small? Are they relatively evenly balanced? You're describing a situation where strength can't ever be concentrated, and that has major consequences. If they're evenly balanced vast empires, all they can do is bleed each other to death -- no battle is more than a pinprick and no assault can me made on the enemy's main strength. If they're small polities or unbalanced enough, a war of attrition can be "won" with the winner almost as devastated as the loser. So the lack of ability to concentrate forces makes a decisive war almost impossible. The optimal strategy may well turn out to be to fortify your systems with enough force to beat off an attack by a single ship -- which is all you are likely to ever see. Fortification is a risky strategy if a whole fleet can pick where to attack and then come after you -- think D-Day -- but not if it must come one ship at a time. For a pretty good analogy, think of the era of fighting sail on Earth, but with the requirement that each ship travels alone and can't predict when it will arrive. No fleet actions are possible. So there are no Trafalgers and the war drags on and on. [Answer] Since there is a statistical variability in when ships arrive, the main effect will be to adjust the fighting platforms to be effective under these conditions. There are several ways to approach this (depending on other conventions you are using in your worldbuilding). If you are a fan of the "Age of Fighting Sail", with individual ships largely alone in a vast ocean of space, you amy choose to emulate the American "44 gun" frigates, such as the [USS Constitution](https://infogalactic.com/info/USS_Constitution). [](https://i.stack.imgur.com/SHIyZ.jpg) *"44 gun" Frigate USS Constitution under weigh* The premise behind the Constitution and her sister ships was to be individually more capable than any comparable European sailing ship of the same class, given the large disparity between the size of the USN and European navies of the day. > > Joshua Humphreys' design was unusual for the time, being long on keel and narrow of beam (width) and mounting very heavy guns. The design called for a diagonal scantling (rib) scheme intended to restrict hogging while giving the ships extremely heavy planking. This design gave the hull a greater strength than a more lightly built frigate. Humphreys' design was based on his realization that the fledgling United States of the period could not match the European states in the size of their navies. This being so, the frigates were designed to be able to overpower any other frigate yet escape from a ship of the line. > > > However, other configurations are possible as well, although what you choose may have more to do with your personal preferences and what worldbuilding conventions you choose to go with. Massive "battleships" capable of carrying gigantic laser batteries or huge railguns capable of firing projectiles at interplanetary velocity (11km/sec+)are an option at on end, while aircraft carrier like ships deploying hundreds of small combat craft are at the other extreme (an old RPG called "[Traveller](http://www.mongoosepublishing.com/rpgs/traveller.html)" split the difference with a "carrier" capable of interstellar jumps carrying "Battle Riders"; warships in their own right). Regardless of what conventions you choose, the key consideration is that ships must be individually capable of dealing with potential enemies *without* support. They must be fast or manoeuvrable enough to be able to accept or decline combat on their terms, and powerful enough to deal destruction to most likely opponents. In some regards this is more similar to an air superiority fighter like the F-22 (and also can be used to describe the difference between ships, the F-22 would represent a combat platform capable of taking the fight to interstellar space, while the home systems would of necessity be protected by more numerous but less capable platforms analogous to F-16's), but since the ships need to operate without support, the naval analogy is much more suitable. So the true issue is to examine how the nature of your FTL system works, and derive the second and third order effects from that. A previous WSE answer looked at some of these aspects: [What shape of a ship would be most effective in real life space combat?](https://worldbuilding.stackexchange.com/questions/107888/what-shape-of-a-ship-would-be-most-effective-in-real-life-space-combat/107962#107962) [Answer] There are many earthbound armed forces that fight under similar conditions. Start with subs. These operated (not sure anymore) with little to no intel, with a mission that is given at the start that may not be viable at the end of a journey, and are/were generally "local only" fighting and recon units. For example, subs may be deployed to a region, but only have the intel available that existed when they left. They get to their destination and have to carry out orders based on their own discretion. They were usually tasked with things like "sink ships in this area" or "fire nukes if they fire first" etc, and would have to decide the best ways to go about it. Another example would be the navies of the earth during the golden age of sail. They would frequently be deployed as a single, or small group of units with a task. They may have intel that existed when they were docked, but once out to sea, they were pretty much on their own. There are several examples of "fleets" of sail ships being deployed to the same region with the same goal, and very little communication between them. You could also use land-based armies prior to the adoption of radio communication. They would be deployed with a goal and a target, but after that, the entire army was kind of a set and forget setup. Attack here! wait for word back of how that objective goes. Generals were given a lot a latitude in most cases to make huge changes to plans and expectations so long as the broader goal was met. It may be unthinkable today where twitter is a source of intelligence gathering, but what you describe is essentially how war worked until very recently. So sending out 6 forces with 6 different goals, and hoping for the best seems reasonable. Once they report back you can send out the next 6. Your war would look more like it did in our history, where goals were more disruption and less about holding land, but you could very easily make it work. Just from your description, I would send out my 6 fleets to attack resource gathering operations. Mostly those that produce fuel, ammo, metals (or whatever ships are made of), and of course water and food if applicable. Also, I would look at some less guarded resources, and try to send at least one fleet there. Something like attacking tobacco fields to disrupt the economy. [Answer] **Small or Single Purpose Vessels are Doomed** **Large Multi Purpose Vessels:** In combat one has to assume that if something can go wrong it will, and then prepare a plan that allows you to succeed even if the very worst happens. In this case each and every single ship arrives by itself spread out over a long time period leaving each and every single vessel launched totally without support or able to give support to another. This means that each and every ship needs to be capable of being completely self-supporting in as close to every way possible as can be manufactured. I am envisioning mother ships with any smaller support vessels they need to have attached to them. These Mother Ships are part factory, part warehouse, part command and control, and equipped with a truly devastating amount of weaponry. **Smaller Battle-Riders** Fighters don't really work in space, were talking about full sized combat vessels that arrive attached to the massive command ship. After it arrives outside the enemy's defensive envelope they detach and form a screen around the command vessel to increase defensive capability and prepare to launch sorties into enemy held territory while recon is gathered. **Drone Swarm Manufacturing** Part of the command vessel's manufacturing capabilities involves creating vast fleets of autonomous drones which will be sent into enemy territory first in attack constellations. They are intended to draw fire from defensive emplacements and locate enemy combat assets and force disposition within the battle space. They are not fighter craft, again, because of physics fighters just don't work in space. These drones are armed, but they are not going to be jinking and dodging and swooping. They are intended to be scattered everywhere from hell to breakfast within the enemy battle space and detect and attack enemy defensive emplacements. These drones will be at least armed with nuclear weaponry and multi-megawatt lasers. If they are destroyed before firing its not a complete loss, the larger vessels watching from afar now know where one more enemy asset is located. If it can detect and fire before being detected and fired upon another chink in the enemies defenses has been opened up. Should any survive they can continue monitoring enemy positions and activity like spy satellites and act as an auxiliary com network if needed. **Assault Begins** After all this has been accomplished the smaller vessels can begin moving into the system to assault enemy forces, exploit gaps in the defenses created by the initial drone activity, and generally make it safe enough for the command vessels to begin moving into the system to finalize the assault and consolidate their hold over the system. Ideally you would have all or most of the command vessels and their assets available to participate, but each command vessel acts as it's own fleet and is capable of independent operations. This is less than ideal however and the goal should always be to coordinate between these battle groups so that they can provide mutual support and cover, and so that reserves can be held in the "rear area" outside of the enemy defensive envelope should the need for reinforcements or to repel a counter attack arise. **Consolidation of Victory** These command vessels are so monumentally powerful, large, and versatile that once a system has been conquered they can act as system defenses if arrayed about the system so that long-term expensive projects like building their own defenses. traditionally forces are most vulnerable when they have recently won an assault, being prepared to defend what you just took is just as important as being able to take it. The automated manufacturing facilities within these ships can begin mass producing the things needed to turn the system into a fully defended staging area for the assault on the next system. These factories can build other automated factories and collect resources to fuel this construction. By the time everything is said and done your ships are repaired, the conquered system is fully defended and you are ready to pass it off to arriving rear echelon defense forces as your newly repaired, refueled, and refitted command ships prepare to jump to the next system and do it all over again. [Answer] There's a potentially vital plot point that you kind of elided...the humans have purpose-built warships which, assuming some technological equivalence, are the superior fighting machines. The friendly aliens have impressive but more general purpose vehicles. It may be best to pair them, either using the same jump or staging action nearby, so that you deliver a premium weapon and are still prepared for any unexpected circumstances you might encounter. The forced interactions would unfold into the story. [Answer] The solution is simple: you build combinable fleets that detach on arrival. Instead of constructing the ships as independent entities, you build them so that the entire fleet attaches into one "whole", performs the jump, and then detaches into its separate parts before mounting the attack. This ensures that the entire force arrives simultaneously. You might even include some parts that simply exist to provide jump capabilities to the rest of the fleet. [Answer] One of the big dangers for a war (for the participants at any rate) like this is that it devolves into a kind of Rocket-Tag. With a huge battle theatre that is mostly empty space, valuable resources and strategically viable locations are going to be at a premium. Add to that the logical consequence of space colonization and you end up with a handful worlds that are the core of a civilization, and several more that are developing colonies (be they singular research stations around a planet or cities with thousands or millions of inhabitants). These core worlds is where a good chunk of the population lives and, more importantly, where the industrial heart of the civilization rests. Naturally, colonies are still valuable and must be defended, but in a scenario like this, the primary goal would be locating the enemy's homeworld or manufacturing base. As long as those remain, with these long travel times, you're going to be doing very little damage of consequence to the other party. Sure, you may destroy a fleet here or there, but with travel times in the range of 10 years, the enemy will have rebuilt that fleet by the time you get to the next system. So a lot of the war would be small scouting fleets or single ships zipping across space with minimal support to find parts of the enemy empire that are valuable enough that crippling or capturing them actually means something. These would need to be ships with FTL capabilities, else your intel will be literally decades or centuries out of date and of such a low resolution as to be practically useless. As a result of how unpredictable FTL travel is, there may be a push for building a large amount of FTL capable scouting drones. This way you can send them all to the same system, have a look around and return, with the hope that some of them return in a matter of days (subjective time), to 'cheat' the time requiredments, as it were. Once a system like this is located, it becomes a race between the aggressor and defender to get as many ships there to either capture or protect the system, turning the war into a series of very low intensity conflicts between scouting ships and picket ships followed by enormous slug-fests between massive fleets over critical resources. Whoever loses their manufacturing base first is the loser of this war. For a good example, look at a typical 4x game where you'll notice that an early resource advantage can rapidly snowball into a huge advantage later. Losing 5% of your annual ship production capability may not seem like a lot, but that means that your enemy will outnumber you by 5% in the first year, likely inflicting heavier casualties, resulting in a larger numerical advantage the next year and so on. For these massive battles around critical locations, there are trade-offs to be made with regards to either bundling your fleet or sending it piecemeal. Bundling them, either by coordinating FTL jumps or using large motherships would concentrate your striking power. However, this has the disadvantage that if you're on the wrong end of the bell-curve with regards to timing, your enemy may have years to evacuate or ready their own fleet. Alternatively, all your ships may map the jump separately hoping some of them can "ride a good FTL current" as it were and arrive before the enemy has the chance to set up additional defenses. Another thing to keep in mind is whether the FTL tech can be weaponized. In theory, if you can speed an object up to 4c, you have an absolutely killer weapon that will likely vaporize a planet if it has sufficient mass. Even if that isn't possible, with the energy output necessary to achieve FTL speeds, there's some fun to be had. It's not inconceivable that once a suitable target is located, the attacker may simply scrounge up several large asteroids, fit them with FTL engines and chuck them at an enemy planet. Jumping a 10-15km diameter asteroid into a planet's gravity well is a pretty good way to cause some major havoc. And because their initial travel is at FTL speeds, there's functionally nothing that can be done to stop them. In terms of command and control, generals are going to have to keep worst-case scenarios in mind and will often be writing orders for soldiers with the idea in mind that they may not arrive until years after the general's retirement, requiring a whole new scale of planning that is profoundly different from what we are familiar with. ]

[Question] [ A class of young gods at Cthulhu University were given a planet to divide between themselves. They are each given an artificially isolated island the size of Ukraine, and must make conditions on that island such that a human population will achieve a fully industrial society, similar to Victorian Britain, in as little time as possible. Let's say within 8640 years. The initial stock is a clan of a thousand hunter-gatherers of sufficient genetic diversity, and they cannot ever travel between islands. Now the catch is that the students cannot interfere in the experiment when it is ongoing; they can only determine the starting situation. The students can determine the shape of the island (though not the area), any life forms or geology on it, any resources in the ground, and so on. They can also set things in motion that will happen at a certain time: e.g., make it so a big volcano will erupt in the year 1500 of the experiment. But they cannot dynamically respond to anything happening in the experiment; they cannot, for example, make the eruption happen as soon as the sailboat is invented. They also cannot provide any technology; the humans must invent everything themselves. So no machines ready to serve their needs, and no books or inscriptions of knowledge (because that would be giving the humans a writing system). Now, the obvious matters such as domesticable animals, iron ore, a fertile river valley surrounded by desert; most students would have thought of these. I am especially interested to hear some non-obvious methods, that would result in a faster technological advancement of the humans. The teacher also rewards creativity, and frowns at constructs that feel too artificial, like pre-domesticated animals that would never evolve that way in the wild, or a chain of little islands, each reachable by a technology that can be found in its natural form on the previous island. For further clarification: making an archipelago rather than a single island is okay - as long as it can still be called an archipelago. Not two islands on other ends of the planet. Having the climate change at a fixed point in time is also okay. [Answer] ## **Diversity and change is the key** For the development of civilization, there are a few key requirements: 1. Challenges to be solved; 2. Conditions for population growth; 3. Multiple cultural centers to foment different ideas. We can create some conditions that ideally suit a civilization at a certain level of development. But once it reaches that level, it would likely stagnate, because there will be little incentive for invention. For example, a "Garden of Eden" would be ideal for hunter-gatherers, but they won't even need agriculture in such a nice place. A fertile valley would be nice for an ancient civilization like Egypt - but they won't develop advanced agriculture or transportation. Thus, we need to create a diverse and preferably changing environment to which humans would need to adapt. Ukraine is about 600K square kilometers big. This is sizeable, but not really enough for our purpose. Of course, we can try to manage. Let's see. First, let's divide this land into **3 or 4 fertile valleys** separated by mountain ranges and plateaus. Each valley should be able to sustain over 10 million population using ancient agriculture. Central plateaus have a distinctively colder climate and initially can't support much population, but with the advent of textiles and better agriculture they could be home to millions as well. The mountain ranges which separate valleys would create dangerous reefs offshore, making sailing along the coast very difficult. Initially, humans will settle in the valleys where they would have **access to grains and animals which can be domesticated**. It shouldn't be long before agriculture is established. From one valley, other valleys can be accessed, but not easily conquered. So a trade between different nations would start, and because the valleys have different resources, it will grow, prompting people to domesticate horses, invent wheel, stirrup, and eventually sailing ships. After sufficient period of time when population centers would boom, a **climate change should shift the equilibrium**. The change should not be too drastic as to make the valleys non-livable, but strong enough to prompt the people to search for solutions. For example, increased rains should make people build dams and levies and move their settlements to different places. Freezing would prompt them to shift to different cultures and make better clothing, and so on. Some valleys would have **abundant copper, tin and zinc**, making it easy to make brass and bronze. Other would lack it, but have **abundant iron ore**. This would make different civilizations trying to keep up with each other in terms of metallurgical development, eventually bringing up iron age. All areas should have a plenty of high quality coal. **War**, unfortunately, looks like the most powerful driver of technological development. For that purpose, separate valleys on this island would always be wary about each other. Because of natural obstacles, bringing up a big army would be difficult, but small scale raids and various hostilities should be common. One nation still can conquer another, but keeping two valleys together as one country should be impossible. Before long, the conquered nation would splinter away, keeping diversity high. Eventually, technology would reach the level of XVI-XVII centuries, allowing for relatively quick and dependable travel between the nations. About the same time, central highlanders, who used to be pushed around by bigger nations, would multiply in numbers and should be able to form a nation of their own. This also means that they would build and maintain good roads through the mountains. After the Renaissance, the coming of the industrial age is only a question of time (and not too much time). [Answer] Ultimately the industrialization in our world occurred because of *trust*, *collaboration*, *economic freedoms*, and *resource availability* Although it may be *theoretically possible* for societies without one or more of these traits to get to a place of industrialization, it is so extremely difficult and unlikely that I wouldn't count on it. What we see with industrialization in countries like North Korea (with very low trust, collaboration, and economic freedoms) is mostly the implementation of industries designed and developed *elsewhere*. In other words, North Korea isn't exactly a powerhouse of innovation. Yet if someone else makes a new type of manufacturing process, they can learn about it and use their strongly hierarchical authorities to force it to be implemented within. Because your gods are not allowed to interfere *in any way* with the societies, you can't know how the humans will evolve *socially*. One of the ways to measure the health of a society is by *trust* and *collaboration*, which (glossing over nuances here) can be seen through things like specialization. For example, if I don't trust you to grow food for me, nor you me to weave clothes for you, then we don't have specialization. We'll both grow our own food and make our own clothes. This kills any hope of innovation or industrialization, *regardless of the resources present*. Simply put, **psychologically speaking**, the conditions in favor of industrialization cannot be encouraged or implemented by your deities because they cannot intervene or leave any knowledge behind. If the humans won't work together then it's not going to happen. Keep in mind that distrust can happen when it's peaceful or violent, when there are natural disasters or no disasters. People are great at screwing over each other, or dominating each other, or manipulating each other. However, **resource wise**, you can create conditions in favor of industrialization. We're talking *a lot* of metal that's easily available, trees that are easy to cut down, fast-growing foods and resources. The more abundant and lower the cost of resources the less likely the humans will hesitate to use and experiment with them. For example, if trees take decades to grow, then cutting one down may seem like a bad idea. If trees grow in days or weeks, then cutting them down isn't a huge cost. If one light of a match or lightning strike can burn a whole forest down, playing with fire is a bad idea. But if fire is (relatively) easy to contain, then go for it. Same with metal, bugs, animals, crops, etc. There's a catch-22 there: if trees grow too fast they may overrun your crops, or vice versa. So you'll need to make the island *as fertile as possible*, and the plants *as easy to grow as possible*, but also prevent them from being overrun. And, of course, make sure that metals like silver and gold are easily found. Make the ground strong but easy to dig, and so on. [Answer] I personally think an Ukraine amount of land is too little because of the reasons discussed in the comments (gimme at least a continent!). That said, here's my best try: * If the question allows it, I would break up the single island into 5 Ireland-sized islands with a few smaller island chains between, and have them on a north-south axis so that they don't suffer from the same plagues and have biological diversity, yet also close enough so that trading, both of goods and diseases, is possible as early as classical antiquity. * All islands would have access to the base metals important in classical antiquity (copper, zinc, iron, lead, etc, maybe in different proportions) and basic domesticated animals (you can have llamas in some islands but sheep in others). All of them would be extremely fertile, because if all you have are 5 Irelands worth of islands, you're gonna have to fit a ton of people in there so that technology progresses. The idea is that you need periods of conflict and outside threat, but not hegemony. As each island reaches a point of being able to centralize and expand their influence to other islands, conflict and outside pressure would give impulse to technology, but distances would make it so that fully conquering and assimilating other islands would be a difficult endeavor for any single culture. Fear of war would exist, but peace and trade would play its important role. [Answer] I thought I would share my own hypothetical situation, to expand on the Andes idea a bit more - if only to bring to attention how unusual their technological development has been. ## The Andes You see, South America is the closest real-life analogue for this hypothetical student project with an 8 millennium deadline. It was settled at between 15 and 11 thousand years BC, and from that moment on there was very little contact with the north. Yes, Panama was technically crossable, and fishing ships made their occasional way around the [Darién Gap](https://en.wikipedia.org/wiki/Dari%C3%A9n_Gap), but it was very much a blockade for cultural and technological ideas. The Andean and Mesoamerican cultural spheres were not aware of each other; there was no Silk Road connecting the two. Roman coins have been found as far as Japan, but nothing of Inca origins have been unearthed anywhere near Tenochtitlan, or vice versa. They might as well be considered separate continents. It commonly stated that this isolation would be a pure detriment for technological, which it would have been to some extent, but it does not the end of the story, for Europe has been settled by modern humans for at least forty thousand years. The Americas achieved all the technology they did, in a quarter of the time. I am going to take the southern half of Peru for the base of my island (which is where the historical cultures in this answer lived), and then make some tweaks to support every stage of civilisation even more than the region did historically. ## Food production [Norte Chico](https://en.wikipedia.org/wiki/Norte_Chico_civilization) is the oldest civilisation in the Americas and, within a rounding error, the oldest in the world (sharing the #1 spot with Sumer). The earliest cities were formed around 3500 BC, so eight to eleven thousand years after the settlement of the continent - but only five thousand years after evidence of the first settlements in the area (dated at 9000 BC). I'm going to be generous to myself, and say that my island could achieve a Norte Chico civilisation around the year 5000 of the experiment, if I do not make any changes. But what if I did? You see, it is indisputable that the ocean was very important to the Norte Chico civilisation. They sailed out to the open sea, slew blue whales (the largest beasts on Earth), and made [stools](https://upload.wikimedia.org/wikipedia/commons/7/74/Caral_-_Caza_-_Ballena.jpg) out of their vertebrae. In the seventies, the scientist Michael Mosely went further; he theorised that the civilisation had maritime origins. He did not just mean that the cities were founded by fishermen, which some theories about the settlement of the Americas already stated, but that fish and other seafood was the main source of subsistence for the entire culture. He theorised that the Norte Chico people did not make extensive use of agriculture at all, unlike any other cradle of civilisation on the planet! Obviously this theory found much opposition in the scientific community, though much like how the equally interesting and unlikely [Phantom time hypothesis](https://en.wikipedia.org/wiki/Phantom_time_hypothesis) forced historians everywhere to challenge their assumptions about the happenings in the Dark Ages (or indeed their very existence), this mad idea coerced many scientists to pay more attention to the Norte Chico civilisation to try to disprove it, which finally granted them some more attention over the more well-researched Inca and Wari empires in the region. Wiseman acknowledged the role of flax as an agriculture product (to make fishnets of), and when further research found that the inland cities were more populous than the coastal ones, his theory became more discredited. Still, it was appearing in scientific literature as late as 2005, so, to put it boldly, if the scientific community seriously considered this idea for thirty years, I think I could have a society based on fish in my little alt history :) So this is the alteration I would make: put some extra reefs and other hotbeds of marine activity in the range of the Norte Chico people. Make it a bay crawling with fish and algae, and increase the size of it. A hunter-gatherer society could quickly become prosperous there and found villages and cities to support a population capable of extracting it all from the sea, much like how population increased in the Indus, Nile and Tigris valleys just to farm all that fertile soil. Slowly, the fishermen would discover how to farm the flax for nets and develop irrigation systems while they're at it. Now, at some point the fish will run out, at which point the budding civilisation should pack their things and move themselves and their knowledge of irrigation to more fertile grounds, which Norte Chico did historically. But in this scenario, I should have moved up their flourishing period at least a thousand years, thanks to the abundance of fish. So I have agriculture in year 4000 of my experiment. This is all I know to write for now. I think I will expand this answer in the future, but as it stands, it should provide some ideas for alternative civilisation budding methods, and the teacher does reward creativity so I should earn some points with this :) [Answer] Russian Sci-Fi strikes again! There is a [short story](https://ru.wikipedia.org/wiki/%D0%9C%D0%B8%D1%81%D1%81%D0%B8%D0%BE%D0%BD%D0%B5%D1%80%D1%8B_(%D0%BF%D0%BE%D0%B2%D0%B5%D1%81%D1%82%D1%8C)) from 1990 about two guys from an advanced civilisation that want Micronesia to be able to fend off European expansion during the Age of Exploration. They artificially divide the nation in two, waging a perpetual (but somewhat ethical and controlled) war against each other – no killings of children, no civilian bombings, etc. There is an old legend that both nations would reunite at the sight of a common enemy. The advanced guys feed both countries suitable technologies and ideas (which differs the setting from the question). Long story short: the Micronesians are using aircraft carriers and have piston engines, powered by spiritus from a palm refinery. When the European caravels with their front-loading cannons are sighted, they are driven off and traced to the port of origin. The latter is then attacked, as the now-technologically inferior Europeans have the resources for which the new Micronesian empire has a better use. --- So, what does it have in common with the question? As sad as it might sound: **war is a great amplifier of an industrial development**. So, your young god might want to create circumstances for a quite ongoing war that should not, however, eradicate the settlements. It also should not end in one of the parties winning too soon. Now, Ukraine has 603,628 km² on land. Split off 242,495 km² for UK – separated with a strait from the main land mass; have around 357,386 km² for something like Germany. Put somewhere the Alps and pull the remaining area in something like Ruhr – or, speaking about Ukraine, – a Donbass and Kuzbass combined. Now, ideally, at some point you'd have some local countries that are fighting each other, an island nation that spends time either fighting itself or provoking the main land countries to fight each other, and a well-isolated country with enough iron ore and coal to kickstart an industrial revolution. [Answer] It has been [suggested](https://medium.com/@MarkKoyama/could-rome-have-had-an-industrial-revolution-4126717370a2) that one thing that held back Rome from having an industrial revolution was the presence of large scale slavery. The ancient Greeks had the basics of the [steam engine](https://en.wikipedia.org/wiki/Aeolipile), and the Romans eventually figured out the value of [standardization](https://www.reddit.com/r/AskHistorians/comments/15gy2z/how_did_ancient_rome_standardize_weapons_and/) for their military supply lines, in the latter parts of the imperial era. Despite reductions in the amount of slavery by that time, they still had a significant (~10%) enslaved population (perhaps not by the standards of the day, but compared to most industrial revolution economies). Why invent machinery if you can just have slaves do all the fabrication? We can also observe that technological development really takes off when there's a class of people who are confident enough in their future to invest in themselves via education, and in research projects to brighten their futures. So, we need to make sure the middle to lower classes are valuable. We also need large populations to get the network effects that produce science. As a result, I'd suggest a predictable boom-bust cycle for crops. Every generation or so, there could be a couple years that produce very little. The goal is to constrain the population to the point where just throwing people at problems is unprofitable, and also to incentivize planning ahead. [Answer] Besides the excellent points about diversity and challenges in other answers, let's not forget about a very important challenge: have a geogoraphy and/or location which guarantees that there is a lot of variation between fertile and infertile time periods. To be able to accumulate, preserve, store, and protect food to last during the less fertile period, people need to organize, build a civilization, and make laws. Take a look at the Middle East (periods of drought, requiring irrigation, water storage, commerce), and Europe/China/Japan, where a few months of winter requires people to both build up a food surplus and to care about heating their homes. In most areas of tropical climate, where the same food sources are available all year round, people remained in hunter-gatherer tribes until fairly recently. Without a need forcing you to build up a surplus for several months (with all the hassle of working more than the others to gather it, and then protecting it once you have it and others don't), there is not much need to organize anything bigger than small tribes. Yes, hunter-gatherers might want to have a small surplus for a case of a bad hunt, but not in the order of magnitude of many months. [Answer] Parrots, thousands of them, parroting preloaded knowledge. No writing system needed. They'll be gone in a century or so, but being available for even a decade will be enough to jump-start things. [Answer] ***Creating shortages is the key.*** People with good hunting grounds don't switch to agriculture. People with steady rainfall don't invent irrigation. People with lots of tin and copper don't invent and improve iron. People with battalions of slaves don't invent the steam engine. People with tons of trees don't invent adobe. People with massive peasant armies don't need to invent the professional army or adapt gunpowder for personal usage. People with plenty of shellac and ivory don't develop plastics. People with lots of whales to hunt don't develop kerosene. **Plagues, famine, natural disasters, etc. will be the shaping tools of your god.** Throw your people into the grinder, just barely giving them enough time to recover and prosper before the next disaster strikes. There will be no dynasties, no Rome, for these your people... only a bitter and constant struggle to survive. Only the invention of industrial tech will give them the ability to finally break this cycle of devastation and triumph over nature itself. Just pick a proper interval of destruction, and you're set. For overall layout, create a few mostly-separate regions so that you can have multiple disaster cycles going simultaneously. Keep them close enough that anybody who makes a big leap in tech can conquer the others and spread it. [Answer] > > must make conditions on that island such that a human population will achieve a fully industrial society, similar to **Victorian Britain**, in as little time as possible. Let's say within 8640 years. The initial stock is a clan of a thousand hunter-gatherers of sufficient genetic diversity, and they cannot ever travel between islands. > > > In the course of actual evolution, humanity went from hunting and gathering to the Industrial Revolution in not that much longer than 8640 years. > > They are each given an artificially isolated island the size of Ukraine > > > That's 2.4x larger than Britain. So... give it the geographic and climactic conditions of Britain. [Answer] This is a little bit of an XY problem. The immediate physical environment matters a lot, but there are in my opinion too many other things at play to be able to focus just on the layout of the island :o) The biggest drivers for development of science, per se, were: 1. Terrain, as mentioned in several other answers and comments, certainly appears to have been a factor, although it's quite hard (for me, anyway) to pin down the reasons for that. However a good mixture of forbidding mountains and fertile valleys does seem to be necessary. The awe provoked by enormous flora, fauna and ... well, *landscape*, to inspire the dreamers, coupled with enough fertility that people have some idle time while still alert enough to notice things, ... 2. The skies were clear enough for both stars and nearby planets to be visible to the naked eye, encouraging both poets and those of a mathematical inclination to wonder *how* and *why*. Throw in the Milky Way too I guess, and the Magellanic Clouds, which also inspired astronomers. Make a few stars explode each century - hopefully bright enough to be noticeable. 3. Thanks to the wonders of the universe, coupled with people devoted to practising peaceful religion and reflection, a monk named Gregor Mendel *noticed* - that word again - the, dare I say it, *beautiful* patterns of nature produced by the mixture of mitosis and meiosis that makes the world go 'round. Anyway, all of these are needed, otherwise people stop dreaming as soon as they can reach everything they can see. Put bright things in the sky, make them do odd enough things to make intelligent life go "Hmmm..."; throw in a *really, really* crazy system of fundamental particles and forces; tweak all the fundamental constants so that one of the most common elements on the planet can be used to build electronics ... It's like stimulating a baby with toys, isn't it? The world is not enough ... [Answer] Put an Old Faithful type geyser or thermal vent that will erupt at consistent intervals forever. This will give them the notion of repetitive, mechanical action, as well as a preexisting steam engine to clone [Answer] They need a good motive. The industrial revolution was a disaster for most people in terms of longevity, quality of life and workers rights. If you already have enough food and shelter, you need a very strong motivation— eg a caste of greedy capitalists - to force the people to give up their rural idyll. Most cultures did not go down this route, even after thousands of years. It’s too early yet to tell, but they may have had the right idea...so maybe you need to present them with a threat or a condition - everyone dying at 30 day - which needs an industrial revolution to overcome. ]

[Question] [ Imagine a race of what we would call 'giants', each of them possibly around 8 to 10 feet (2.40-3.00 meters) tall. What differences would they need compared to us regular humans in order to function? I know that simply up-scaling organs doesn't work as one would expect (Not a biology major, don't hold me on that). And if they could function reasonably well, would there be a way to make them superhumanly tough or strong? Not unreasonably so, just maybe capable of uprooting a tree? [Answer] ## Blood pressure. Changing position would cause larger variations in blood pressure in the head and blood would be packed into legs. I doubt 10ft would be enough to cause huge problems, but adaptations similar to what giraffes have would exist if giants evolved naturally. This would mean larger heart and blood pressure to guarantee blood supply to the brain, valves to reduce blood pressure in the brain and prevent back flow when the head is down and tighter skin in the legs to prevent blood accumulating there. Alternately the circulatory system could have evolved to have pressure control valves for every major area allowing uniform pressure regardless of position. This would also allow giving muscles and lungs higher blood pressure while giving brain and other organs normal pressure. ## Structure Due to weight increasing faster than strength, bones and muscles would have to be proportionally thicker especially at the lower body. Legs would probably have suspensory ligaments at joints. ## Superhuman? Giants would by necessity be muscular in order to avoid issues with legs and spine. Being large and muscular would make them quite strong. Size alone would increase strength by the square of increase in height. Adaptations for increased mass would come on top of that, although possibly simply by weak giants not existing (less variation, not higher average). A giant might (as a guess) be two to three times as strong as a large and strong normal human. Longer limbs would also add leverage and reach. So in melee combat a giant might certainly seem impossible for normal humans to defeat. They would normally get the first strike and should be able to use their overwhelming strength to push aside shields and parries. Longer limbs would also allow using larger bows and arrows, which generally would result in dead opponents as size of the bow allows storing (and releasing) more energy with same pull strength and a larger arrow should be more accurate and have better armor penetration. And of course the giant probably would have higher strength as well. The need for tighter skin for legs could result in the skin being thicker and more tear resistant all over. But I don't see this making much of a difference if weapons are used. Fat and muscle would absorb more damage than with a normal human as there would be more of them, but the difference should not be dramatic. ## Weird scaling effects After some thought I realised that bones and muscles are not the only things that would scale, if the same proportions were retained. Larger eyes would give more light gathering ability for better night vision and resolution would improve as well so that the giants would see as well at their arms length as normal humans at theirs. Sense of scent should also be scaled up. Lung capacity could scale to match the need for oxygen (cubic), but the wind pipe would scale less, so the giants breathing would be much more audible and their voices would be louder. Also since the giants would have more mass generating heat in proportion to skin radiating it, they'd likely use panting for losing excess heat and possibly have a slightly higher body temperature. The strangest question would be with the brains. If the proportions of the head remained the same the brains would be over twice the size of human brains. Considering that humans already have pretty big brains and it is hard to think need for more brain power, the giants heads might be flatter or have thicker bones to reduce brain size. The giants could have much more shock absorbing structures in their head. Potential uses for extra brain mass are relatively easy invent, though. Many animals spend larger proportions of brain for sensory processing. The giants could have large structures for processing visual or scent data. They might have superior memory. On a world with magic the extra capacity could be reserved for magic and make the giants superior mages. [Answer] Their proportions would change slightly, with thicker bones and legs. Generally they would be wider proportionally than humans. They would need a larger heart to keep the blood moving, probably along with adaptations to help prevent blood pooling in the legs. This could include systems similar to the way our leg muscles help lift the blood along with things like stronger veins and arteries. If their bones and muscles were scaled up sufficiently then uprooting a small tree would certainly be possible, Personally I'd look at an elephant for inspiration. Take a look at what feats of strength are possible for an elephant and then design a humanoid with similar proportions and capabilities to the front half of an elephant. I do not expect that scaling up to 10 feet tall would need dramatic changes physiologically speaking, although you are probably approaching the limits of reasonable scaling in humanoids. [Answer] [Robert Wadlow](http://en.wikipedia.org/wiki/Robert_Wadlow), 8' 11" might fit your bill. The picture on wikipedia (below) makes his nearly 6 foot father look diminutive. Of course, his untimely death points out some of the potential problems with such a large body. While the organs scaled up successfully enough, there were other health effects, such as needing leg braces to walk; and I believe I read that the difficulty of pumping blood through his feet helped to hasten the infection that killed him. So maybe not a good characteristic for a successful race, and the cause was probably not a heritable trait (gland/hormone malfunction). But it is a demonstration that such people can (and do, from time to time) exist. Anecdotes describe him being as stronger than most adults at 9 years old and, with no end of his growth expected, he probably would have continued to gain strength and stature until some side effect became fatal. Another [extremely tall man](http://en.wikipedia.org/wiki/Edouard_Beaupre) was able to lift nearly half a ton, so strength seems proportionate to stature (more on that later). But as for a mechanism for an extra tall race, a change in pituitary gland size seems to be enough to dramatically impact the body's growth. Unfortunately such abnormally tall people often die young, as the [wikipedia chart](http://en.wikipedia.org/wiki/List_of_tallest_people#Men) on the subject shows. A short list of health conditions: * [Anklyosis](http://en.wikipedia.org/wiki/Ankylosis) - Rigid joints, possibly resulting in the inability to move the joint * Increased infections, possibly due to circulation problems * Spinal curvature * Tooth problems * Brain hemorrhage and you can find more on [Acromegaly](http://en.wikipedia.org/wiki/Acromegaly). But some people seem to lead [fairly normal lives](http://en.wikipedia.org/wiki/Vaino_Myllyrinne), but with the added benefit of not needed a chair to reach the lightbulb. [](https://i.stack.imgur.com/JfbAa.jpg) (source: [wikimedia.org](https://upload.wikimedia.org/wikipedia/en/5/5c/Robert_Wadlow.jpg)) Now, as far as uprooting trees go, I was surprised to find a study discussing the exact force needed to uproot certain trees. You can find it over at the Finnish forest institute. <http://www.metla.fi/silvafennica/full/sf44/sf444681.pdf> Suffice it to say that uprooting trees is extremely complex, but in general the formula for uprooting Scots Pine stumps in sandy soil is: `F = 6.542 × (D^0.6369 + e^0.041189×D – 1)` (if someone wants to format that better, have at it). F is the forces in thousands of Newtons and D is stump diameter in centimeters. Maybe the formula would be different for trees that have fibrous root systems, though I assume that those would be harder to uproot. So let's take a 5" stump. Plugging the formula into google says that would require about 7000lbs. Given that Edouard Beaupré could lift about 900lbs, 7000 seems to be a bit much. But, for comparison, the Journal of Applied Physiology has an [article](http://jap.physiology.org/content/89/3/1061) discussing weight lifting. They use bench press figures I believe, but they give a formula for computing weight lifted given height: `weight in kilos = 120 * h^2.16` (where h is height in meters). Given this figure, a 6 foot man should be able to lift 975lbs, which is apparently accurate, as a youtube search will show. Comparing records of bench presses to clean and jerk lifts (unscientifically), it seems that lifting limits useful for pulling trees out of the ground would be about 25% lower than the figures given by the formula from the JAP, giving us `90*h^2.16`. So to lift 7000 lbs we'd need someone about 5.2 meters tall (17 feet). A 9' person could, if they were a professional olympic lifter, lift 3/4 ton, but not anywhere near close to our 5" diameter tree. Upshot 1: Trees are wicked hard to uproot. Upshot 2: Formulas are weird. I'm under 6' tall and I know I've uprooted 1cm diameter trees. It was a lot of work, but it's possible. And I can't lift anywhere near 1500 lbs. Upshot 3: if you're only 5 feet tall and you can press 650lbs, you might as well stop trying. Applied physiology says you've arrived. [Answer] For that height range, you don't need to go too far beyond actual humans, e.g. Andre the Giant and the [tallest players in the NBA's history](https://en.wikipedia.org/wiki/List_of_tallest_players_in_National_Basketball_Association_history) ]

[Question] [ For simplicity, lets use our Sun as the star. Next, a dyson sphere is built around it (completely enclosed solid sphere, not a dyson swarm or network, etc.). Handwave how it's built, it's not relevant to the question. Not sure if the diameter of the dyson sphere makes a difference, but in case it does, lets say its inner surface is about 1AU from the Sun. (sorry Earth, you've been replaced). Again, for simplicity, lets assume no other celestial bodies remain inside the sphere (Mercury, Venus, other small bodies, etc., completely used up to build the sphere, or otherwise intentionally removed) Now, the supposed purpose of a dyson sphere is to collect the energy from the star, and put it to good use doing ... something. But shortly after completion of this one, its builders (for whatever reason) flipped the switch from "collect" to "reflect". So instead of collecting the energy from the Sun, it's reflecting most of it back. What about efficiency? Well, silver and can be up to 95% reflective, at least across the visible spectrum. Aluminum comes close at about 90%. I don't have numbers for materials reflecting non-visible spectrum energy, but since we're talking about dyson sphere level technology, lets handwave the composition of the reflective surface, and just say it reflects 90% of all forms of energy that strike the surface. Regardless of what form of energy it is, the surface reflects 90% of it back at the sun. The remaining 10% of the energy, the part not reflected, is absorbed (collected) by the sphere, converted to heat, and then radiated into space on the outside of the Dyson sphere, and has no ill effect on the sphere itself. **Does this cause any changes in the star?** Best answers will include details of changes, if any, and explanations of why they take place, and the time-scales during which the changes manifest themselves. Or, explanations of why no changes take place. [Answer] The star will very slowly reach a new equilibrium. The energy being reflected back will lead to an increase in the star's temperature, starting with the photosphere (which is opaque). The photosphere will become hotter, but there's next to no fusion going on there. The outer layers of the star will swell, and the total energy output will increase (this energy is just the reflected-back energy that gets reflected forward again because of Stefan-Boltzmann's law). Actually I think we can calculate this: the new equilibrium for the photosphere requires that the energy coming in from the Sun's insides is dissipated, *but the dissipation just went down 90%*. So the sun must radiate *ten times as much*, which means [its temperature must increase 1.77 times](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law), to about 11200 K (a blue-white star). Its volume should then approximately double (I'm playing fast and dirty with Clapeyron's [equation for ideal gases](https://en.wikipedia.org/wiki/Ideal_gas_law), ignoring the gravity component altogether), which means its radius should increase roughly by 25%. These two effects are really opposite (when the radiative surface increases, the radiated energy per unit surface must go down, so the temperature also needs to go down. So the final result will be a temperature of less than 11200 K - and a radius increase of less than 25%, but with back-of-the-envelope calculations I am unable to say how to split the difference). The Dyson sphere, meanwhile, is intercepting more and more power, and will ultimately intercept what was, before, the full output of the star (it will still be 10% of the total output, but the total output has gone up by a factor of 10). Slowly, the star will grow and become a strange blue-white demi-giant, while it will take [**hundreds of thousands of years**](https://en.wikipedia.org/wiki/Solar_core#Energy_transfer) for the extra heat to make its way to the star's core below the radiative layer. When that happens, the solar core also will begin to swell (not so much actually), which will reduce its density. As a result, fusion events become less likely, until the power output will decrease, in a self-limiting process. This means that the initial flare-up will be reabsorbed, and the star will grow larger, dimmer and redder, reducing the output being reflected back. This oscillation will be very slow (deca-millennial or slower) and will converge to a dimmer, longer-lived star with a reduced burn rate, but an artificially higher temperature and a spectrum similar to its previous one (it will of course fall outside the Hertzsprung-Russel diagram). I want to say that the star's life will be extended by the same factor of 10 that drives the backreflection, but of course I don't know. [](https://i.stack.imgur.com/g95CO.png) If the back-reflection is raised slowly from 0% to the full 90%, slowly enough that the process never overshoots, then I expect that the star will slowly and linearly progress to the end state, as described by [this paper](https://arxiv.org/pdf/2006.16734.pdf) [3.4] ("*a sufficiently insulating Dyson sphere could put enough energy back into its central star that the star might expand, cool, and dim.*"). I suspect that the final equilibrium will see a marginally swollen core and a ~~white~~yellow-red sub-giant star, its temperature artificially higher, but with the life expectancy of a yellow main-sequence star or even longer. [Answer] This was recently studied and modeled. Link: [here](https://iopscience.iop.org/article/10.3847/1538-4357/ac3421). Excerpt from the Conclusion below, but TLDR is: reflecting a lot back onto a small star makes it bigger, cooler, and hence live longer. Big stars are unaffected. > > Irradiated stars expand and cool. A Dyson sphere may send a fraction of a star's light back toward it, either by direct reflection or thermal reemission. This returning energy can be effectively transported through convective zones but not radiative zones. So, it can have strong impacts on low-mass main-sequence stars with deep convective zones which extend to the surface. It causes them to expand and cool, slowing fusion and increasing main-sequence lifetimes. For higher-mass stars with little to no convective exterior, the returned energy cannot penetrate far into the star and therefore has little effect on the star's structure and evolution, besides some surface heating. > > > [Answer] ### A star is a gas ball, It will expand What will happen to a star being heated? Sane thing as to any star / ideal gas that has increased temperature. It will expand until new equilibrium is met. The time scale will be just a matter of how fast energy transfers between the outer star components. Of concern would be how fast will the non reflected energy heat up the Dyson sphere, and cause the sphere to fail. As to the rest of the system: It will warm up until a failure mode is reached. Few structures can exist at photosphere temperatures. [Answer] **You might extinguish the star.** <https://www.astronomy.ohio-state.edu/ryden.1/ast162_4/notes14.html> > > How does a star's natural thermostat work? Consider what would happen > if you increased the fusion rate in a star's core: > > > -(1) Core temperature increases > > > -(2) Core pressure increase > > > -(3) Core expands > > > -(4) Core density & temperature decrease > > > -(5) Fusion rate decreases > > > In the OP scenario, the star is heated by the sphere. The star will expand and become less dense. Less density means decreased fusion. At a low enough density fusion cannot be sustained. The gas cloud will remain hot and the sphere could keep it hot for a long time. [Answer] ## The star will burn hotter, faster until the Dyson sphere essentially IS a star. For this I will assume the Dyson sphere is sufficiently advanced magic so it can reflect all or most the stars light and particles back and not explode in the a cloud of gas. All or most has essentially the same effect it just changes the degree. So here is how a star works, in the core the heat and pressure is high enough to sustain a fusion reaction but only in the core. that is what is supplying the heat so a stars temperature is controlled by its size, it is a balance between the light pushing out and gravity pushing in. But in your star the star is the same size but way hotter, the interior temperature quickly (millions of years, which is quickly for a star) rises until far more of the stars mass can undergo fusion. this is because there is nowhere else for energy to go, photons just bounce back at the star until all their energy is absorbed. So your star is essentially ALL core, this will burn through its fuel astoundingly fast, your star may only last a few million years before it burns out. but all this heat means photon pressure also makes your star expand, the math is tricky but likely until the Dyson sphere essentially IS the outer surface of the star. Normally something like this only happens to a lesser degree in a supernova, when a star runs out of fuel in its core and collapses, this drastic rise in pressure causes much of the rest of the stars mass (which is mostly stull fusible material) to suddenly undergoes fusion, which produces so much heat and light it blows the star apart, but your star can't explode, the outward pressure is not just countered by gravity but also the reflected light and even reflected particles. This photon pressure will be less than the pressure pushing out but not that much less when you add gravity. You have created a stellar pressure cooker. This is where the amount of reflectivity matters, at a 100% physics breaks down, it is a closed system and sooner or latter all the mass inside gets converted into energy. If it is anything less than 100% the Dyson sphere temperatures rises until it reaches equilibrium. Until it is emitting as much heat as it is absorbing, which means it ranges from hotter than the hottest star to merely as hot as the surface of a blue star depending on reflectivity. Eventually your star runs out of fuel, collapsing, but unlike a normal star it may not have enough fuel left to go supernova, so it may just quietly burndown into a a white dwarf or neutron star\* quietly emitting low energy light for the rest of the lifetime of the universe. * it may turn into a neutron star because although normally a star that size would not form a neutron star, it also blows away most of its mass in the supernova stage, this star does not, ALL of the remaining mass collapses inwards which may be enough. Now if your civilization is clever they build another bigger Dyson sphere around it which will harvest way more energy, albeit for a much shorter amount of time. [Answer] ## Mathematical stellar constructs only exist in mathematics *(NOTE: as indicated in the comments, this is a comment on your design rather than an answer. I put this because your question carries a science-based tag.. the construct you propose cannot exist)* **In a static Dyson sphere, very little light will be reflected onto the star itself** A Dyson sphere has a radius much larger than the star's radius. Rays reflecting back into the star perfectly only exist in mathematics, with a perfectly centered, perfect sphere. A Dyson won't have these properties. Any imperfection in the Dyson's shape will cause rays to go the wrong way and bounce around, loosing 10% at every bounce, eventually releasing 100% of the energy onto your mirrors. That will be the case for a significant portion, when the orbit covered by the Dyson becomes only *slightly* decentric, the focus point will shift away from the star. Agree with Alexander's comment it will get very hot in these mirrors, you'll need a very special material. **You'll need precise surface and orbit control** Imagine a planet-like superstructure in orbit around the sun, which is able to spawn a Webb-quality parabolic mirror with a diameter of about 0.5 AE, in orbit around the sun. You could focus that mirror somewhere, e.g. to do your experiment ("can I blow up my star") or on a moon, to harvest the energy, or onto a far away planet, to raise its temperature. But you'd need propulsion for that, it should be aligned precisely. You can't do these things without a dynamic orbit correction system. **What if a *Dyson swarm* would be built with Webb's mirrors ?** Say the construction would be done and you have the resources and personnel, to blow up your sun safely. You'd use a *Dyson swarm* with Webb quality servo-driven individual mirror segments and very precise control, hanging around the sun, with a diameter of 2AE (hand waive hand waive) The control can compensate for decentering and shape errors. It has to be dynamic. There's no single vertical angle either.. Your Dyson was built as a rotating swarm, so it will flatten out, while it rotates. In any case, the mirror angles are to be adjusted, to compensate for that, you don't have to move the surface, only adjust the mirror angles. All kinds of compensations are needed. The swarm gets deformed, when gas giants orbits are near. Suppose everything can be solved.. **You'd get a heat feedback loop.. you may not need to maintain it for long** I could proceed an attempt to actually answer this question now.. say you would have a sun that gets *a relevant part* of its own energy back. Ok what would happen.. you have a certain helium/hydrogen balance in your sun, that balance will shift, more hydrogen will be burnt by your star and it will get hotter. How long would it take, before the star is "burnt out". In fact you invoke a sliding slope, a feedback loop, because the mirrors keep working. The star is getting hotter and hotter. Inside, the helium is used to build heavier atoms. I can't provide the formulas, but it could be happening quite fast. You'll blow up your sun. [Answer] So, after some quite careful thinking, this is what I come up with. It's a bit boring, but it is what it is. **The luminosity of the star inside the Dyson sphere will increase 10 times**, by becoming bigger and hotter *on the surface*. Thus 10 times more energy will hit the Dyson sphere, **of which 10% escape**, resulting in the same outside luminosity as the sun has now, **matching the almost unchanging energy output in the star's core**, as required by the star's mass to keep gravitational collapse at bay. **The temperature of the *outside* of the Dyson sphere will be approximately the natural temperature at 1 AU, which is 0°F or -18°C** in our solar system currently (Earth surface is warmer only because of the atmosphere), so its luminosity will be in quite cool infrared wavelengths. That's still 200+ Kelvins above the galactic background of course, so should be very visible as a very curious object from far away with an infrared telescope. Inside the sphere, the outer layers of the star would do a lot of what happens in a red giant. That is, **energy the star radiates must increase, which happens by two methods: increased surface area or increased temperature**. Normally a sun mass star will cool when this happens (that's why they become red), but in this case the extra energy is coming from outside, so I'll make an assumption that the surface temperature actually stays about the same. So only surface area increases, by increasing radius. According to [this Wikipedia page](https://en.wikipedia.org/wiki/Red-giant_branch#Properties), The luminosity of Sun-mass star going through its red giant phase can go from 2.2x to 2802x the original luminosity, with corresponding radius increase from 2x to 179x. So, the 10x luminosity needed for us is in the very low end of that range. Doing a quick calculation, **to increase the surface area of a sphere by 10x, we need to increase radius by 3.14x.** So here we see how it doesn't much matter if the temperature stays the same, because if it becomes hotter, the star will be a bit smaller, and if it becomes cooler, the star will be a bit larger, but still small enough to fit inside the sphere. For comparison, 1 Au is about 217 solar radiuses. Additionally, if the Dyson sphere is not a near-perfect sphere, most of the radiation reflected back will actually miss the star in the middle (it's still so very small, radius 3x the original vs Dyson sphere radius is over 200x). Accounting for that the outer layers of the star would actually heat much less, when each extra reflection loses 10% of the energy. But maybe we are to assume, that the 10% loss actually accounts for this effect too. So... Boring result is, the star inside the Dyson Sphere will just expand its outer layers when those are heated by the reflected radiation, until they are big enough to radiate away both the normal energy output of the star, and the extra reflected energy. In a sun-mass star this does not change the evolution of the star significantly, as far as its core is concerned. *As discussed in the comments, the pressure at the center of the star may get less as the star expands, but the expanded portion is basically the atmosphere of the star and very low density, so only a tiny portion of the total mass of the star, so this does not matter*. There is always room for the outer layers to expand as much as is needed, and the core doesn't really care, it'll just keep doing fusion to resist gravity. Of course **any planets left between the Dyson sphere and the star would get quite baked**, and **any star ships traveling inside the sphere would need to be able to travel that close to a luminous star**, which many star ships might not be equipped to do, unless the ship mass does not matter and they can have as much heat shielding and radiators as needed. [Answer] We have a pretty much natural example of what happens if a star is forced to radiate 10 times more heat. It is called **Red giant phase**. The star surface has to radiate more. But it cannot get any hotter, because the surface gravity and the surface temperature of a star are somewhat connected. So the star swells. The surface gravity goes down, so does the surface temperature. The star swells some more and at some point settles. The core loses some of the pressure and some of the nuclear reaction rate, because much of the envelope is now far away and attracted less. But this effect is minor because most of the stellar mass is in the core anyway and it contributes to the pressure much more. p.s. and @Goodies is right, your mirror will have to be impressively precise and even then a great deal of the light will be reflected not to the star, but to another part of the mirror instead. At least, until your star swells enough. ]

[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. For the sake of fixing some image in your mind, imagine you want to practice some sport in a rotating cylinder world: whether it be launching a javelin, strike a tee at the golf club or scoring a 3 points shot on the ball field, some sort of ballistic trajectory will be involved in most of the cases. On Earth we know that, if we neglect the interaction of the object with the air and we are below escape velocity, the trajectory will be an elliptic arc. In a rotating cylinder world I think the apparent gravitation field would be different than on Earth, I even doubt it could be even called a "field". How would that work on a rotating cylinder world? **What are the ballistic trajectories in a ring world?** For the sake of helping the calculation, if needed, assume * a cylindrical world, with 1 km radius, rotating at 0.95 rotation/minute. * neglect drag and aerodynamic effects (Coanda effect, lift, etc.), thus assume the launch is happening in a vacuum * arbitrary direction and velocity of launch + neglect the real gravity due to the cylinder mass Alongside with the mathematical relationships, I would also appreciate a graphical comparison with respect to the Earth case. [Answer] Whenever you're wondering how particles would move in some sort of accelerated reference frame, you have two options: analyze it from an inertial frame or analyze it from the accelerated one. They each have their own strengths and weaknesses. Analysis from an inertial frame requires nothing more than good ol' Newton's laws, but requires you to keep track of some oftentimes confusing coordinate transformations, while using an accelerated frame lets you ditch the transformations but requires you to add new 'fictitious' forces-- in the case of a uniformly rotating frame like this one, these would be the Coriolis and centrifugal forces. The latter approach can be good for getting a rough intuitive idea of what will happen and can be useful in calculations for a trajectory that has no analytical solution. Fortunately, with the constraints you've imposed, there actually exists a relatively simple analytical solution, so we'll analyze this from an inertial perspective. First things first, we need to set up our inertial and accelerated coordinates so that we can relate them and transform our understanding in an inertial frame to one in our accelerated frame. Let's set up our inertial coordinates so that the origin is at the bottom of the cylinder with the z axis pointing radially inward, the y axis tangential to the cylinder wall, and the x axis outward along the axis of the cylinder. The origin and orientation of the inertial coordinates do not change over time. Meanwhile, the accelerated coordinates are denoted by primes, and point in the same direction at $t=0$ but unlike the inertial coordinates, rotate along with the cylinder. Below is a diagram that hopefully makes this clearer: [](https://i.stack.imgur.com/bvZ7Y.png) Here, $\omega$ (technically w in the picture because I couldn't figure out how to get greek letters in my drawings) is the angular velocity of the cylinder and is pointed in the x direction along the cylinder axis. Let $R$ denote the cylinder radius. Now, the conversion between our accelerated and inertial frames is the composition of a translation and a rotation. It's difficult to wrap your head around without fiddling around with it for a bit, so I'll just leave the result: $$\mathbf{x}=A\mathbf{x'+b}$$ Where $\mathbf{x}$ are the inertial coordinates, $\mathbf{x'}$ are the accelerated ones, $$A= \begin{bmatrix} 1 & 0 & 0 \\ 0 & cos(\omega t) & -sin(\omega t) \\ 0 & sin(\omega t) & cos(\omega t) \end{bmatrix}$$ $$\mathbf{b}= \begin{bmatrix} 0 \\ Rsin(\omega t) \\ R(1-cos(\omega t)) \end{bmatrix}$$ Now, the accelerated coordinates are the ones we care about, since they describe how stuff looks from the viewpoint of someone on the cylinder. So, we invert the prior equation to obtain $$\mathbf{x'}=A^{-1}\mathbf{(x-b)}$$ Now the hard part's over. All that's left is to note that a particle will travel in a straight line in the inertial frame, since we are ignoring any gravitational effects. If the initial velocity of the projectile is $(v\_x,v\_y,v\_z)$ as measured *in the accelerated frame*, it is straightforward to show that $$\mathbf{x}= \begin{bmatrix} v\_{x}t \\ (v\_{y}+R\omega)t \\ v\_{z}t \end{bmatrix}$$ By imposing the constraint that at the time of impact, $y^2 + (z-R)^2 = R^2$, we can determine that $$t\_{impact} = \frac{2Rv\_z}{v\_z^2+(v\_y+R\omega)^2}$$ Note that if $v\_y=0$, then in the limit of small $v\_z$ we have $t\_{impact}=(2v\_z)/(R \omega^2)$, which agrees with the prediction of a parabolic trajectory under uniform gravity with an acceleration of $R\omega^2$. When you finally do all of the matrix multiplication, you end up with the parametric equation: $$\mathbf{x'}= \begin{bmatrix} v\_{x}t \\ [(v\_{y}+R\omega)t-Rsin(\omega t)]cos(\omega t) + [v\_{z}t+R(cos(\omega t) -1)]sin(\omega t) \\ -[(v\_{y}+R\omega)t-Rsin(\omega t)]sin(\omega t) + [v\_{z}t+R(cos(\omega t) -1)]cos(\omega t) \\ \end{bmatrix}$$ When I have more time later, I'll add some graphs in here that demonstrate what this looks like for various trajectories, but the general gist is: velocity components that angle along the axis of the cylinder don't have much of an effect on trajectory, while those that are angled along the -y direction can have an immense impact at speeds on the order of 100 m/s given the radius and angular velocity specified in your question. **EDIT: Trajectory Graphs** First things first, it's important to note that what trajectories look like for this problem depend heavily on the initial velocity of the projectile, so I recommend playing around with some graphs yourself to get a more complete understanding-- desmos is a good tool for this. 3D plots of the trajectory are a little busy, so instead I've plotted the projections of the trajectory into the x'z' and y'z' planes. For all plots, the solid blue line is the particle trajectory as seen from the rotating frame, while the dashed red line is the parabolic trajectory expected for a uniform gravitational field of magnitude $R\omega^2$. On the y'z' plane plots, the dotted black line gives the location of the cylinder wall. First things first, what happens if you lob a ball directly upward at about $10 m/s$? Well, in a normal gravitational field, that's easy-- it should go straight up and down. However, in our cylinder world, the Coriolis force will push it in the y' direction. It still goes straight up and down in the x'z' plane, so we will omit that graph because it's boring. You can see that the ball moves about a meter in the y' direction, which probably wouldn't be very noticeable since it's hard to throw something directly upwards anyway.  So, now let's try throwing it a bit harder. It wouldn't be too crazy to throw a ball at $20 m/s$, so let's do that at an angle of 30 degrees with respect to the horizontal in the positive y' direction. We again ignore the x'z' trajectory because it is trivial. We can see that in this scenario, our trajectory still looks parabolic but is noticeably shorter that what we would expect from a uniform gravitational field. [](https://i.stack.imgur.com/Bt7j8.png) If we throw the ball with the same speed and angle but in the -y' direction, the ball instead travels much further than we would expect. [](https://i.stack.imgur.com/3Nb5i.png) If we throw the ball at the same speed but in the x' direction, the projection of the trajectory in the y'z' plane looks exactly the same as it did for when we threw the ball straight up, since the Coriolis force does not act on x' components of velocity. Meanwhile, the x'z' projection looks very similar to a normal ballistic trajectory: [](https://i.stack.imgur.com/dkQPW.png) Let's ratchet things up a notch and get a professional to throw a $40 m/s$ fastball again at 30 degrees from the horizontal in the y' direction. By now, you'd definitely notice something was up-- the ball is only going about half the distance you'd expect: [](https://i.stack.imgur.com/siIQF.png) If you throw it with the same speed but in the -y direction, not only does it go over twice the distance you'd expect, but its trajectory now noticeably deviates from a parabola: [](https://i.stack.imgur.com/hu0nY.png) At this point, we might as well go for broke and get Ryan Winther to hit us a $100 m/s$ golf drive at 6 degrees from the horizontal. If he decides to hit the ball in the -y direction, he's in for an interesting hole: [](https://i.stack.imgur.com/E1OGI.png) This is about the peak for strange deviations to trajectories. If you continue shoot a projectile with greater and greater speeds, it will hit the cylinder so quickly that the accelerated frame will not have time to deviate significantly from the inertial one and so the trajectory will approach a straight line. For instance, if we shoot a railgun directly upwards at $3 km/s$, its trajectory looks like: [](https://i.stack.imgur.com/V0YGk.png) To summarize: things thrown solely in the x' direction will have fairly normal trajectories, as will things thrown in the y' direction at either very small or very large speeds. However, at intermediate speeds on the order of $100 m/s$, projectiles shot in the y' direction will land short an projectiles shot in the -y' direction will go much further than expected. [Answer] This is actually easy to calculate. There is no "gravity", so you just sum your starting velocity with your launch velocity. This makes your launch vector a straight line. Here's what makes it confusing: While someone from space would see a straight line, an observer on an adequately large cylinder world would see an apparently normal ballistics curve. This is because they will move with the projectile starting at the exact speed that was displaced at launch, but as the ring world turns them back into the shot, they will accelerate up towards the projectile as though it were falling toward the ground under the influence of gravity. This phenomenon is comparable to [Einstein's Elevator Thought Experiment](https://www.thegreatcoursesdaily.com/einsteins-experimental-elevator/) whereby the acceleration of gravity and the acceleration of a moving frame of reference are equivalent. **What happens when firing parallel to the rotation of the cylinder.** [](https://i.stack.imgur.com/reLBk.png) **What happens when you fire perpendicular to the cylinder:** [](https://i.stack.imgur.com/JnBab.png) At least this is how it would generally work on a mega structure like a [Ring World](https://en.wikipedia.org/wiki/Ringworld) or even a [Halo Array](https://halo.fandom.com/wiki/Halo_Array). Since you are describing more of a [Stanford Torus](https://en.wikipedia.org/wiki/Stanford_torus), things get a bit weird because the "world" is so small, and the rotation so slow. Here is a JavaScript to calculate exact trajectories: <https://jsfiddle.net/nosajimiki/k98z2h1a/240/> *^Calculator updated to include the effects of gravity caused by a core system's mass.* **Some interesting conclusions based on the calculator are:** 1 - Firing with the rotation has an effect similar to increasing gravity, the projectile will fall faster because you are adding to its angular velocity. A ring with a higher velocity will be less affected by this phenomenon. 2 - Firing away from the rotation causes the object to fall slower up to the point you match the speed of rotation and you lose all "gravity". If you exceed the speed of rotation, your projectile will be able to "fall" again. A ring with a higher velocity will be less affected by this phenomenon. 3 - There is a slight drift in the direction of rotation when firing perpendicular to the ring. This is proportionate to how high your shot goes compared to the radius of your ring. As your shot goes "up" it is also crossing space parallel to the ring, its speed stays the same, but it crosses a larger angle of the ring for its speed making it drift in the direction of the ring's rotation. A shot fired downward from an aircraft drifts in the opposite direction. A ring with a larger radius will be less affected by this phenomenon. 4 - Every sport is affected a little differently . Sports that involve high velocity low angle projectiles such as baseball will be less affected by side-drift; so, they will probably be played perpendicular to the station. Sports with higher arching low velocity balls such as basketball would be less affected by gravity distortion and more affected by side-drift, but probably still be aligned in the perpendicular to prevent one team from having to contend with higher gravity than the other. Less adversarial sports with high angled, fast projectiles like javelin and golf will probably be played in the parallel to the ring with all contestants throwing/driving in the direction of rotation to prevent dangerous low-G and side-drift conditions, and course will be smaller than on Earth since the harder you launch your projectile, the more it must contend with "gravity". Planet sized rings and larger will probably not need special regulations on course and field alignment. 5 - Placing a planet or star in the middle of your megastructure means you need more spin to achieve a desired surface gravity. As your projectile assends, it will try to orbit inside of your ring. If your spin is too low your missile may get into a stable orbit around the system's core mass or crash into it directly. [Answer] As others have noted, outside of the torus the throw is just a straight line. A 1 km world rotating at 0.95 rotations/minute has a velocity of 1.9 pi km / minute, or 100 m/s, or 360 km/h. So you have to add a 360 km/h velocity vector to the vector you throw the Javelin at. In the rotating frame of reference, there are some interesting cases. If you throw it directly counter-rotating at 360 km/h, parallel to the ground, it will appear to *hover* and fly at a fixed speed above the "ground" of the ring. If you throw it direction with the ring at 360 km/h, parallel to the ground, it will fly off at 360 km/h and fall twice as fast as it "should", roughly. This works because when you rotate something 2x as fast, the "gravity" generated also goes up by 2x, and when thrown at 360 km/h + 360 km/h it is emulating the ring spinning twice as fast. If you throw parallel to the ground perpendicular to the direction of rotation, it will fall just as if you dropped it, but also move horizontally as it falls. Throwing up is interesting. For a simple case, imagine you throw it both up and in such a way that in the non-rotating frame of reference, the Javelin is still moving at 360 km/h. This corresponds to the Javelin's arc, instead of being inset by ~1.5 m and then shooting out at 360 km/h perpendicular to the ring (the "drop" case), it instead flies off at an angle from that location. Another fun one to consider is throwing it "backwards" at 360 km/h, then adding some of "hubward" velocity. Outside of the ring, this corresponds to the Javelin moving directly towards the hub. For someone outside the hub, the Javelin floats towards the hub, crosses it, then comes down on the other side facing "backwards". To someone on the ring, the Javelin flies off at 360 km/h. It floats upwards, not falling, but as it gains height it also slows down; it always takes 2 seconds to fly "around" the world, regardless of how high it is, but higher up that "around" is a shorter distance. It reaches the middle. At the middle, it appears to be spinning around its center every 2 seconds. When it passes the middle it appears to be flying *backwards* at increasing speed. Eventually it floats down to human height, where someone could grab the "blunt" end as it flies past at 360 km/h, or let it plow into the ground. The vertical component can be as large as you want here. More generally, horizontal velocity of throws varies with height, and objects rotate strangely with regards to creatures standing on the ring, warping throws away from what you'd expect to see. [Answer] Heh heh. You make me remember my high school geometry classes and polar coordinates. The thing to keep in mind is there is no gravity in this case. The path a projectile takes will just be a straight line while the ring rotates under it. [](https://i.stack.imgur.com/bSp3D.png) So in the coordinates of a person watching from outside the ring the path is the red arrow, and its equations are just this. $$ x(t) = x\_0 + v t $$ $$ y(t) = y\_0 $$ That's just linear motion straight across. But in the rotating coordinates of the ring, the object will move according to the blue line. And that gives you the following. $$ x^\prime = x(t) \cos ( \omega t + d) + y(t) \sin ( \omega t + d) $$ $$ y^\prime = - x(t) \sin ( \omega t + d) + y(t) \cos ( \omega t + d) $$ $d$ is an angle that gets you $y^\prime$ to be zero at $t=0$. That way, in the coordinates of the ring the object starts at the observer standing on the inside of the ring. That's pretty easy to get. $$ \tan d = \frac{y\_0}{ x\_0}$$ $\omega$ is the angular velocity which is just such as to give 0.95 rotation per minute in your example. So that means $\omega$ in "per minute" is the following. $$ \omega = 2 \pi \cdot 0.95 = 5.969 $$ So, you find $x\_0$ and $y\_0$ by symmetry. Rotate things around so the path is horizontal. Then substitute in to get $x^\prime$ and $y^\prime$. And you get the direction of the toss relative to the rotation by changing the sign of $\omega$. [Answer] I want to first apologize to any physicists reading this. Feel free to edit misuse of terms such as speed and velocity, I might use them wrong. Also feel free to skip to the "real fun part". It will give you a sense of how weird throwing stuff may get. # Introduction The most important counter-intuitive thing you need to acknowledge is that the force you feel and mistake for gravity on the ring world is in fact just you moving really fast around the circumference. Think Homer Simpson in his Ball of Death. You stop moving, no more force, just you floating in the space. If you jump, there are no forces acting on you, so you move in a straight line, as all the answers here have correctly pointed out. You also have some initial velocity you got by standing on the rotating ring world and that is why while you jump up or even counter-rotation, you still move rotationward for an observer with your trajectory being a straight line. This is obviously not what you wanted to know because who cares about some high and mighty observers, right? # Balls don't fall back or make spirals When you are on the Earth, jumping direction has almost no significance (Coriolis are negligible). However in your scenario, the rotation has a lot of significance. As H Franklin calculated in his answer, firing a tennis ball at about 100 m/s counter-rotationward would counter-act the initial force and the ball would hang in space for an outside observer and would rotate around the world with the same speed as the world of 0.95 rotations per minute from your point of view. Now if we gave it the same counter-rotation speed but also a slight vertical speed, things would become much more interesting. For your observer, the ball is slowly rising from where you threw it until it hit the world on the opposite side. Now for you, it still files around the world with the 0.95 rotations per minute speed, but also gains altitude at the same time. The trajectory would therefore be a spiral until it hit the center and then spiral again until it hit the ground again. Thing to note here is that it has the same tangential and vertical speed, therefore from your point of view, its horizontal speed (horizontal meaning moving around the circumference, what is horizon anyways?) would decrease as it gained altitude. With this we can already see that elliptical/parabolical approximations of the trajectories don't hold very well but let's continue. # Quick maths Let's make new coordinate system. X will mean the distance you would have to travel on diameter to be directly under the object of interest. Y will mean the distance of the object from the closest point on the circle (i.e. the distance from you if you are standing right underneath it). First we will compute these coordinates for an observer with a given origin, from where the ball was thrown. In our picture that is the point B. The ball always gets the velocity of the rotation (direction of the spin, tangent where we stand, in our case vector BF) and the velocity we give it with our throw. Together it will produce the straight line we discussed for the outside observer with constant speed. We know the speed so we know the standard coordinates at any moment. So the problem is now to translate those coordinates to our knew system. Let's take the point D. I will denote $\phi$ the angle FBD, $r$ the radius AB and $s$ the distance traveled BD. We are interested in $x$ being the length of the arc BE and $y$ as the distance ED. We know that AE has also length $r$, so $y = r - t$ where $t$ is the length of DA. We can calculate $t$ with the law of cosines, i.e. $t^2 = s^2 + r^2 - 2rs \cdot \cos (90^{\circ} - \phi)$ The new x coordinate can be calculated from the angle of BAE denoted $\alpha$ and computed with the law of sines, $\sin \alpha = \frac{\sin ( 90^{\circ} - \phi)\cdot t}{s}$ The last step to have your own experience is to account for your own rotation from the observers point of view. That means adding the distance you travelled due to spin to the x coordinate. # Real fun part ## Throwing balls up Now let's imagine would happen if you were to throw a ball up giving it the same vertical speed as is the speed of spin and for the sake of having nice numbers we'll say that is $1$ and we'll also assume the radius to be $1$. In terms of the last paragraph, $\phi$ would be 45 degrees, the speed of the object would be $\sqrt{2}$. The distance it would have to travel from B to C would also be $\sqrt{2}$, meaning it would fall back down in exactly $1$ time unit. For an outside observer, it would fall exactly one quarter of the circle in the direction of spin, but where would we be in that moment? The spin speed is $1$, which would mean we need $2\pi$ time units to finish one whole rotation and about $1,57$ to finish a quarter. But in the same time the ball we threw vertically landed a quarter of the circle from the point it was thrown, making it seem to us that it fell a bit in front of us. ## Playing catch alone Now for few last points of observation, the ball is traveling in a straight line with constant speed. That means that the higher it gets, the faster it will change the x coordinate, because the closer it is to the center, the faster the tangential speed will become with the same velocity. Now this would allow us to do some neat tricks. Imagine we want to throw a ball and catch it again. We found out already that if you throw it just up, it falls in front of you. So when we combine these two points, you need to throw it up and back a little and as it will rise, it will seem to you that it changed direction and started moving back to you and a bit in front of you in the direction of the spin and after it starts falling, it will change direction once more and fall back to you. If you draw *that* trajectory, that sure as hell is no ellipse. [](https://i.stack.imgur.com/rNcqz.png) [Answer] Okay, first thing's first. Linear speed. You are rotating at 0.95 rotations per minute, with a 1 km radius. 2πr gives us a circumference of 2π km or 6.283185307 km. If you travel 0.95 of that a minute, then your velocity on the ring world is 5.969026042 km per minute, or 358.1415625 km/h. I'll convert that to m/s for all remaining calculation, so that is 99.48376736 m/s (My numbers are long because there has so far been no need for significant figures) Next, let's have a look at the centrifugal acceleration. Now, before you all get up me in the comments, I'll just say I KNOW that there's no such thing as centrifugal force. But technically, the force holding objects down to the ring cannot be called gravity, and to avoid confusion later on, I don't want to call the force holding things down inertia either. So, for the purposes of this question, I'll call it centrifugal force, and if you have a problem about it, you can go cry to Newton. Anyway, the formula for centrifugal acceleration is F = v^2 / r. This means that the force is (99.4837673 m/s)^2 / 1000 m, and the centrifugal acceleration(our planets equivalent to gravity) is about 9.89 m/s^2, or just 0.08 m/s^2 greater than Earths. So if you were blindfolded on this world, you most likely wouldn't notice that you weren't on Earth (unless you fell off). Those are the effects the viewer would notice. So far, I have not seen an answer that addresses the initial speed of the javelin, so I will address that. Once the javelin leaves the hand of the thrower, it is no longer being acted on by the rotation of the ring world. You also said to discount any forces that include the air resistance. This means that once the javelin leaves their hand, the velocity will not change. By definition, the path taken by the javelin is a straight line. However, any object thrown will experience two phenomena. First of all, it has a velocity of 99.483 m/s added to it tangential to the the circle at the point it was thrown. Second of all, while it is in the air, the ring world will be rotating. This leads to some... interesting phenomena. For example, say there is a tennis ball cannon set up to shoot at precisely the same speed as the ring world is rotating in the opposite direction. Due to there not being any air resistance, and no gravity, the tennis ball will seem to leave the cannon, and then it will remain floating until it hits something. Also, something funny. OP mentioned javelins. An Olympic javelin thrower can launch a javelin at a speed approaching 100 km/h. If the thrower somehow throws their javelin straight up, it will take approximately 5.207 seconds to hit the ground. In those same 5.207 seconds, the javelin thrower will travel approximately 518 meters. The javelin hits the ground 550 meters away from the spot where it was thrown, which means if the javelin thrower runs at 6.39 m/s, slightly slower than the average human 100 meter sprint, then there's a chance. Just a chance. That the javelin thrower could be hit by his own javelin. OP, you asked for an examination of the projectile trajectories. The answer is, technically there are none. Any object thrown will travel in a straight line until it hits something on this world. However, the velocity will always have 99.483 m/s added to it in the direction of rotation. And you asked for graphs: [](https://i.stack.imgur.com/B8p00.png) This is the javelin thrower. The vertical arrow represents the speed of his throw, the horizontal arrow represents his speed from the rotation, and the diagonal arrow represents the total velocity [](https://i.stack.imgur.com/TWVtr.png) This is the path taken by the javelin. Thanks for reading! [Answer] **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. I can tell you how best to calculate this, but the formulae are more complicated than I can figure out off hand: You should look at the flight of the (say) javelin in a non-rotating reference system, in which it will not be subjected to any force once it leaves the hand of the thrower (ignoring aerodynamic effects, as you say we should), which means that it travels in a straight line in this reference system. Then you simply have to look at the speed with which the javelin leaves the hand of the thrower (including the rotation speed) and the three-dimensional direction it is thrown, which can be figured (though not easily) from the direction of rotation, the direction of the throw relative to the direction of rotation, and the angle the javelin is thrown 'upwards' from the 'floor' of the cylinder. Once you have the direction, you can calculate where the linear course of the javelin intersects with the cylinder, and the time it takes can be calculated as the ratio between distance and speed. This time, in turn, tells how much the cylinder has rotated since the javelin was thrown. This is fairly uncomplex, but rather complicated, and I am afraid that my spatial geometry is a bit rusty. ]

[Question] [ **This Query is part of the Worldbuilding [Resources Article](https://worldbuilding.stackexchange.com/questions/143606/a-list-of-worldbuilding-resources).** --- From previous questions, I made a nice [mass of land](https://worldbuilding.stackexchange.com/questions/581/creating-a-realistic-world-map-landmass-formation), which was enriched up until the drawing of precise [coastlines](https://worldbuilding.stackexchange.com/questions/21349/creating-a-realistic-world-map-coastlines). But all that nice lands looks a bit empty. In my world, I want to make it alive, and one of the first step, to complete my map is to draw the borders and define the countries. Is there any alternative, to rewriting the whole of history from prehistoric migrations up until the time where the story takes place? For a given country, I could follow the steps indicated in [this question](https://worldbuilding.stackexchange.com/questions/23811/how-do-i-make-the-political-evolution-of-my-world-believable). But if I have a whole continent available? --- Note: > > This is part of a series of questions that tries to break down the process of creating a world from initial creation of the landmass through to erosion, weather patterns, biomes and every other related topics. Please restrict answers to this specific topic rather than branching on into other areas as other subjects will be covered by other questions. > > > These questions all assume an earth-like spherical world in orbit in the habitable band. > > > --- See the other questions in this series here : <http://meta.worldbuilding.stackexchange.com/questions/2594/creating-a-realistic-world-series> [Answer] National borders will follow rivers, mountain ranges, large forests, inland lakes and deserts. Mountain ranges, deserts and large forests will all form buffer zones between nations since these biomes are not well suited to (human) habitation. So you may have two major nations separated by a mountain range, but a minor nations inhabiting the mountains themselves (like the Himalayas). So think of major nations separated by buffer nations with the latter inhabiting buffer zones featuring more challenging habitability. Challenging habitability need not mean its impossible or very difficult to live, merely that the population there will be smaller and have to have special skills to live there. Once these factors have been taken into account, we need to add a second level of fine detail that is based on your worldbuilding the historical linguistics of your world. Decide how ancient peoples in your world migrated, and thus determine the patchwork of distinct language zones in your world. You can then draw more national borders that are based on language that will serve to create border lines in areas that do not feature natural obstacles. To see an excellent example of such an imagined history of migration you could do much worse than look at Tolkien's work on the three ages of middle earth - here (<http://tolkiengateway.net/wiki/Middle-earth>). It covers the creation of elves, men, hobbits and dwarves, and if you scour that site above you will find descriptions of the various migration patterns and how that generated the nations in middle earth at the time of the Lord of the Rings. With specific regard to dutch, it evolved along with various other germanic languages from Low Franconian, which was the language of the Franks. <https://en.wikipedia.org/wiki/Low_Franconian_languages> Then, where you have a single language zone that spans natural obstacles, you can introduce separate dialects/accents of that language. [Answer] It is quite common that borders go along natural features like rivers or mountains (also called "natural borders"). Basically it's a line that naturally is hard to cross. Therefore it's also harder to conquer land beyond that border than if there's no natural border to begin with. Also, if the border is negotiated, those landmarks are easily recognized, and therefore may prevent future disagreement about the position of the border. [Answer] Can't believe I missed this question. **Prep Steps** You need to do these before you really get started, you have some done but I am listing everything for future user reference. 1. You need a map * This map should be geographical down to a regional level (local specifics/peculiarities can and should wait, create them as needed) * Include major bodies of water, rivers, biomes, mountains etc. This should be the satellite image from orbit level of detail. 2. You need a history * Drawing political borders is obviously impossible to do without having some idea of what came before *now* whenever now happens to be in the story. * Like the map this doesn't need to be the nitty gritty. Think of the level of detail you get in elementary education. Egypt, Greek City States, Roman Empire, Byzantium, Medieval, Renaissance...etc etc etc. This should be the broad sweeps of history. Rough out where on the map these major nations/empires covered and overlapped. **Setting the now** 1. Determine a time period. Pick a socio-technical point in time (or create your own, medieval twitter!...ahem anyway) for your *now* to exist. * Technology level helps define the shape of borders. As mentioned in other posts you are, for example, not going to have longitudinal borders during the Roman Empire...and if they could you know the Romans would, everyone knows the Romans loved math. * How much 'open' space is there in your world. For the vast majority of human history much of the world was not part of any political entity, if you're working in the past keep that in mind. **Get to it** Step 1: So between your time period and geographical map you can start plotting obvious places for civilization to start. We all know (or do now) that the earliest civilizations on planet Earth started along rivers. Regular access to fresh, clean water makes life a whole lot easier. You don't need to name these civs or anything like that (though it may be fun to come back and do it later). Step 2: Apply the rough brushes of history you outlined in the preparation steps (you did do the preparation steps right?). Step 3: Once you arrive at *now*, stop. If things look a little too planned out at this point that's perfect. Right where we should be. Step 4: Fine tune your map. * Review major historical events, people disasters (wars, migrations, famines etc) and modify the map appropriately. While you are doing this write down why the changes makes sense while you are doing this, you will never remember why later. This can cause strange squiggles across what looks like an obvious border, or set the border at a certain landmark, for example mountains or a river, or a particular city. This helps give your map more depth. Always keep in mind that borders are fluid and on a planetary scale they change constantly. [Answer] **Political boundaries are geography plus populations** plus as many other things as you want to add. 1. Draw a map of your continent/world/galaxy/universe. Fill in details like terrain, biomes, topography, geology, vulcanology, resources, etc...whatever details you want to include in your story. 2. Make a list of the people's you want to have in your world. Perhaps the benevolent Empire (heh, when are empires ever benevolent?) or a nation of marauding wanderers. Figure out which groups are stronger than the others and *why* they are stronger. Maybe one group has a mobility advantage while another has a great economy. 3. Place your weakest nations/tribes/groups first and give them the largest possible area that seems reasonable for their size. Don't worry, they won't hold this much territory for long. 4. Now drop in your stronger nations. They will naturally push back on the weaker nations, shrinking their territory. Pushback will extend until a natural barrier is reached such as rivers, oceans, or mountain ranges. You may lose a weaker nation or two. Make adjustments to their strengths till they can hold at least a little territory. 5. Go back and make some weird boundaries that can't be explained by one nation being stronger than the other. These small boundary changes give you, the author, an opportunity to inject some political back-history. [Point Roberts](https://en.wikipedia.org/wiki/Point_Roberts,_Washington) on the boundary between Canada and the USA is an example of this kind of political boundary making. Europe is famous for these kinds of boundary shifts. 6. Make a few adjustments to the boundaries to account for resource allocation on the map. Stronger nations will have more resources available to them or very strong trade routes to get those resources. 7. Designate capital cities as meets your needs. Often capitals are centrally located but not always (ex. Moscow or Washington D.C.). **Discussion** Using this method we can retrospectively see why the Mongols gained so much territory as they had a huge mobility advantage over their peers. Every extra "layer" of information added to the map will increase the richness of your world but at the expense of complexity. Add as many layers as you can manage then stop. Just adding terrain, resources and population to your map will be enough for a very rich world. [Answer] # Introduction and assumptions Borders clearly aren’t static; they change over years, decades and centuries as countries grow, shrink, and are born and die. As time passes, they may become vague or disputed. Therefore, I’d argue that you do need to create a somewhat detailed history of a region to properly map out where its borders are at a certain time. However, it should be relatively easy to get a decent idea of where a country’s borders lie when it is first formed, assuming certain conditions hold. I’m going to suggest a way to build a country’s borders from the ground up, starting from a small city-state society with medieval or pre-medieval technology. I want to make a few key assumptions: * Power is somewhat centrally located, preferably in a city or military fortification. This is the most secure part of the state, and it is easier to control land closer to this location than land farther away. * Territory is contiguous; you should be able to travel from any one point to another via land while remaining in the country. * The technology is sufficiently limited such that the above assumptions hold. While naval power may be possible, air travel is not. This should hold for the sort of society we’re talking about, assuming there aren’t significant magical powers. * Neighboring states have relatively similar strengths. I’ll address scenarios where this *isn’t* true more at the end. # Approximation 1: [Voronoi diagrams](https://en.wikipedia.org/wiki/Voronoi_diagram) I’ll hypothesize that the original borders of a city-state, according to what I discussed above, can be approximated by creating a Voronoi diagram. Essentially, given a set of $n$ points (cities) in some two-dimensional space, a Voronoi diagram divides that space up into $n$ regions. The region $r\_i$ contains all the points closer to point (city) $c\_i$. The lines of the diagrams can be interpreted as the borders of these regions. Here’s an example: [](https://en.wikipedia.org/wiki/File:Euclidean_Voronoi_diagram.svg) Image courtesy of Wikipedia user Balu.ertl under [the Creative Commons Attribution-Share Alike 4.0 International license](https://creativecommons.org/licenses/by-sa/4.0/deed.en). Voronoi diagrams have [already been used](http://bigthink.com/strange-maps/657-welcome-to-planet-voronoi-a-capital-place) to model the borders of countries and states; see specifically the work of [Jason Davies](https://www.jasondavies.com/) (images copyrighted, by the way). There are certainly many differences from real-life borders (although in certain parts, like North Africa, things seem to work), but again, this is only a first approximation. For large $n$, creating such a diagram becomes a little complicated. Brute-force searches work but are obviously tedious; more sophisticated methods like [Fortune’s algorithm](https://en.wikipedia.org/wiki/Fortune%27s_algorithm) become useful. For more information, see [Easiest algorithm of Voronoi diagram to implement?](http://stackoverflow.com/q/973094/6535830) and [How do I derive a Voronoi diagram given its point set and its Delaunay triangulation?](http://stackoverflow.com/q/85275/6535830). However, I’d like to deal with a much simpler case, where $n=3$. $n=1$ is obviously trivial, and $n=2$ yields precisely one border - namely, the [perpendicular bisector](http://mathworld.wolfram.com/PerpendicularBisector.html) of the line segment connecting the two cities. However, $n=3$ is a little more interesting, although it is certainly simple to solve. All we need to do is find the one vertex where all three borders coincide. There are several ways in which we can do this, knowing the locations of three cities and *assuming that each one is the center of its own city-state*. We could use one of the above algorithms, if we really wanted, but those can be time-consuming to implement. Alternatively, we could use the fact that any Voronoi vertex is the center of a circle containing three points, and therefore, given three points, we could find the center of that circle. However, I’d like to use what I think is the simplest option: Determine perpendicular bisectors of segments connecting any two cities, and find the point where they intersect. Some assumptions (well, just one, for now): * The three points are not collinear. If they are, then the borders are just parallel lines, and there is no central vertex. ## Mathematics Let’s have a set $C$ of three cities, $(c\_1(x\_1,y\_1),c\_2(x\_2,y\_2),c\_3(x\_3,y\_3))$. We choose to find the segments connecting $c\_1$ and $c\_2$ ($\bar{s\_{12}}$) and $c\_2$ and $c\_3$ ($\bar{s\_{13}}$). Given that the $\bar{s\_{ij}}$ is the set of points equidistant to both $c\_i$ and $c\_j$, we can set $$\sqrt{(x-x\_i)^2+(y-y\_i)^2}=\sqrt{(x-x\_j)^2+(y-y\_j)^2}\tag{1}$$ Simplifying eventually yields the equation $$y=\frac{x\_j-x\_i}{y\_i-y\_j}x+\frac{x\_i^2+y\_i^2-x\_j^2-y\_j^2}{2(y\_i-y\_j)}\tag{2}$$ Clearly, this blows up if $y\_i=y\_j$, but if that’s the case, then the border simply has the equation $$x=\frac{1}{2}(x\_j-x\_i)$$ which is simple enough. We do the above for all three sets of points. To find the vertex, we simply find the point where all three lines intersect, which is simple, as we can do it for any two of the lines. ## Code I wrote a program to do this in Python 3. To simplify things a bit, I’ve assumed that no two cities have the same $y$-coordinate, as that produces a line with infinite slope in $\text{(2)}$. If, for some reason, your setup includes a case like that, simply rotate the coordinate system a little so that all three points have different $y$-coordinates. Here’s an example, with $c\_1=(2,1)$, $c\_2=(9,5)$ and $c\_3=(4,7)$: ``` import numpy as np import matplotlib.pyplot as plt P1 = [2,1] P2 = [9,5] P3 = [4,7] Set = [P1,P2,P3] def dist(point1,point2):     """Returns distance between two points."""     x1 = point1[0]     y1 = point1[1]     x2 = point2[0]     y2 = point2[1]     return np.sqrt((x2 - x1)**2 + (y2 - y1)**2) def perp(point1,point2):     """Returns slope and y-intercept of the perpendicular     bisector of the segment connecting two cities."""     x1 = point1[0]     y1 = point1[1]     x2 = point2[0]     y2 = point2[1]     m = (x2 - x1)/(y1 - y2)     b = (x1**2 + y1**2 - x2**2 - y2**2)/(2*(y1 - y2))     return m,b M1 = perp(P1,P2)[0] B1 = perp(P1,P2)[1] M2 = perp(P1,P3)[0] B2 = perp(P1,P3)[1] def vertex():     """Finds central vertex"""     x = (B1 - B2)/(M2 - M1)     y = M1*x + B1     return x,y   """ This next bit divides each of the lines into a certain number of line segments by adding a number of points onto the lines, and then removes those points in the third city's Voronoi cell. """ for point1 in Set:     for point2 in Set:        if point2 != point1:            N = []            delta = 0.001            for i in range(0,10000):                N.append(i*delta)            M = [perp(point1,point2)[0]*a + perp(point1,point2)[1] for a in N]            Other_point = [a for a in Set if a not in [point1,point2]]            i = 0            while i < len(N):                x = N[i]                y = M[i]                if dist([x,y],point1) > dist([x,y],Other_point[0]):                    N.remove(x)                    M.remove(y)                else:                    i += 1            plt.plot(N,M,'k') for point in Set:     name = 'City at ('+str(point[0])+','+str(point[1])+')'     plt.plot(point[0],point[1],'x',label=name) plt.plot(vertex()[0],vertex()[1],'kx') plt.legend(loc='upper left') plt.title('Voronoi cells of three countries') plt.xlim(0,10) plt.ylim(0,10) plt.show() ``` Here’s the output: [](https://i.stack.imgur.com/O0mnd.png) # Approximation 2: Terrain. Voronoi cells are, I think, a decent approximation. However, they completely ignore the landscape and terrain of the area. For instance, if an edge lies in the middle of a valley surrounded by two high mountain ranges, it seems possible that the border may shift to one of those ranges, as they’re easier to defend. The same thing goes for rivers, cliffs, etc. I’ll assume that the following objects would cause borders to shift: * Rivers * Mountains * Canyons * Large bodies of water I think these objects have been sufficiently justified as limitations (see [celtschk ‘s answer](https://worldbuilding.stackexchange.com/a/23823/627)). ## Mathematics Most of these can be approximated with curves of essentially negligible thickness (lakes and oceans aside). Therefore, let’s say that any landform $L$ can be represented as a curve parameterized by a variable $t$: $$\mathbf{L}=\mathbf{x}\_L(t)=(x\_L(t),y\_L(t)),\quad t\_0\leq t\leq t\_f$$ We can also represent a section of border $B$ as another parameterized curve, given by a parameter $s$: $$\mathbf{B}=\mathbf{x}\_B(s)=(x\_B(s),y\_B(s)),\quad s\_0\leq s\leq s\_f$$ The challenge, then, is to come up with some iterative algorithm that maps $\mathbf{B}\_{n}$ to $\mathbf{B}\_{n+1}$. There are probably many options out there. I chose one of the following form: Divide $\mathbf{B}\_n$ into $N$ points $\{p\_{1,n},p\_{2,n},\cdots,p\_{N,n}\}$. For each $p\_{i,n}(x\_p,y\_p)$, calculate the distance to all points on $\mathbf{L}$ and choose the point on $\mathbf{L}$ that is closest, $l\_{i,n}(x\_l,y\_l)$. Move $p\_{i,n}$ accordingly. I played around with things and decided on a certain formula: $$dx=\frac{x\_l-x\_p}{1+a\cdot\text{dist}(p\_{i,n},l\_{i,n})},\quad dy=\frac{y\_l-y\_p}{1+a\cdot\text{dist}(p\_{i,n},l\_{i,n})}$$ $$x\_{p,n+1}=x\_{p,n}+dx,\quad y\_{p,n+1}=y\_{p,n}+dy$$ where $a$ is some scale factor and $\text{dist}(\mathbf{a},\mathbf{b})$ is the distance between two points $\mathbf{a}$ and $\mathbf{b}$. This can be done as many times as possible. I’ve found that in many cases, even one iteration can be enough. ## Code Here’s my implementation of the above, again written in Python 3. I’ve chosen $a=0.3$: ``` import numpy as np import matplotlib.pyplot as plt scale = 0.3 RiverPath = np.linspace(0,49,1000) def River(t):     x = np.sqrt(t)     y = t*np.exp(-t)     return x,y BorderPath = np.linspace(0,7,1000) def Border(t):     x = t     y = t/4     return x,y def dist(y,x):     """     Returns closest point on the target curve to a given     point on the border.     """     Set = []     for loc in RiverPath:        dx = x - River(loc)[0]        dy = y - River(loc)[1]        distance = np.sqrt(dx**2 + dy**2)        Set.append([distance,loc])     Set = sorted(Set, key=lambda S: S[0])     dR = Set[0][0]     p = Set[0][1]     target = River(p)     return target def move(Q):     """Moves each point on the border curve parameterized by Q."""     X = []     Y = []     for q in Q:        x = Border(q)[0]        y = Border(q)[1]        point = dist(y,x)        point_x = point[0]        point_y = point[1]        mag = np.sqrt((point_x - x)**2 + (point_y - y)**2)        dx = (point_x - x)/(1 + scale*mag)        dy = (point_y - y)/(1 + scale*mag)        X.append(x + dx)        Y.append(y + dy)     return X,Y plt.plot(River(RiverPath)[0],River(RiverPath)[1],'b',label='River') plt.plot(Border(BorderPath)[0],Border(BorderPath)[1],'k',label='Border') plt.plot(move(BorderPath)[0],move(BorderPath)[1],'r') plt.legend(loc='upper left') plt.show() ``` It uses the following parameterizations: $$\mathbf{L}=(\sqrt{t},te^{-t}),\quad0\leq t\leq49,\quad\mathbf{B}\_n=(s,s/4),\quad0\leq s\leq7$$ Here’s the result: [](https://i.stack.imgur.com/fawDn.png) The new border hugs the river near the left, then shifts roughly halfway between the old border and the new border. More iterations might be desirable, but there’s currently something of a balance. The formula for $dx$ and $dy$ could use some improvement, but even though it’s imperfect right now, I do think it’s functional. It can be adapted for multiple perturbing objects (i.e. multiple rivers, mountains, etc.) by calculating all the $dx$s and $dy$s, summing them, and *then* moving the border, not accounting for one landform at a time. You can vary the scale factor if you want, both in general and for specific landmasses. I haven’t yet played around to see how this could affect things. # Where do we go from here? The borders of countries still don’t quite match up with these approximations. I’d argue that part of that is because of modern technology. However, a great deal is due to history. Those mountains over there are supposedly uncrossable . . . until a feud between rival kingdoms necessitates a battle, which ends with one king triumphant, ruler of both. Or maybe that river was considered a fairly good border, until holy relics were found on the other side and suddenly the head priest really wants the site inside the country. At this point, I’d say that [James’ answer](https://worldbuilding.stackexchange.com/a/37086/627) becomes invaluable. In the end, it is the people of your world who shape it, often more than you, the god-like figure outside it. You can control that history, of course, but those events can and will change the world. All my suggestions are are simply slightly more detailed slates with which to start building countries. After that, it’s up to you. [Answer] **Don't focus too much on rivers** Rivers can sometimes be used to mark borders (the Rio Grande being one of the famous ones). However, it's almost always the case that the border would be there regardless, and they simply adjusted it to fit the river so it would provide them both with a bit of defense, and spare each country the trouble of constantly having to cross it. Here's a map of medieval Europe: [](https://i.stack.imgur.com/rKjKF.jpg) There are few things to keep in mind looking at this: 1) **Most powerful nations are based *around* a river, not divided by one.** London, Paris, and Rome all have major rivers flowing through them. This provides a major artery of trade, as well as fertile cropland to feed a large population. Over time, the tribes and cities that expand to form kingdoms tend to be ones with large populations. Therefore, most of your kingdoms will have a fertile heartland containing most of the population and usually the capitol. This core territory will then likely hold dominion over a more rugged hinterland with a much smaller population. When two of these kingdoms collide, the border usually changes quite often as they fight each other. Usually the line will settle down somewhere in between the two, usually across rugged or less hospitable land that neither one is that interested in fighting for. If one side was in the midst of conquering, say, a fertile valley, they wouldn't agree to stop and draw a new border until they'd taken the whole thing. The best example of this is Medieval Scotland. The vast majority of Scotland's population lives in the fertile area around Edinburgh, while the Highlands and islands are only lightly populated. In the population map below, notice now the main farming and trading area is packed with people, and formed the core of a kingdom that then expanded outwards. Note that this is a modern map, and the medieval numbers were likely a bit more balanced, albeit with the same general pattern. [](https://i.stack.imgur.com/kOBLW.gif) 2) **The map is filled with dependent kingdoms.** This was also true in Ancient Roman times. Looking at a map of the Roman Empire makes it seem like one big state, but in reality there were lots of dependent kingdoms within it, who had control over internal affairs, but deferred to Rome in everything else. On the Medieval Europe map above, Bohemia, Croatia, and Moravia fall into this category, along with many others. You may or may not want to include this in your setting, but it was a common historical occurrence. These dependent states often existed on the frontiers of their parent empires, contained a distinct ethnic group, and were used as buffer zones against hostile empires. Late-Medieval Croatia fell into this category. They were ruled by the Austro-Hungarian Empire, but held a lot of autonomy, and were used primarily as a buffer against the Ottoman Empire. These borders will often be very defensible, going along rivers and surrounding rugged of mountainous terrain, as these small dependencies would not be able to hold vulnerable, fertile lands against the encroachment of larger forces. 3) **City States are common in areas with large coastlines and rugged terrain.** City states simply rule one large city and the surrounding countryside. These states focus largely on trade and rarely build empires in their immediate neighborhood, instead conquering overseas possessions to expand their trade network. The Greeks used this system in the Classical Age, and the Italians had it for most of the Middle Ages. If your world has a rugged/coastal area with rich trade connections, I suspect it would be full of smaller city states, with small (and somewhat unimportant) borders. 4) **Undefined Borders are common in vast uninhabited areas.** Nobody (except Muammar Qaddafi) cares where a border is drawn across an uninhabited desert. Notice in the Medieval Europe map, how the Eastern European principalities of Kiev, etc, have borders that just sort of fade out into the Steppes. This is common in sparsely populated kingdoms sharing borders with undefined tribal groups. Since the nomadic horsemen will be crossing the border regardless, and the state doesn't have the will or ability to police it, there isn't so much a border as a general understanding that "the stuff over there belongs to them". This also goes for desert borders. Lots of maps of Ancient Egypt show their empire extending out into the Sahara, but it wasn't like you would run into Ancient Egyptian Border Patrol out there. Rather, there was just an understanding that Egypt ruled the Nile Valley, and anybody that came too close would be in trouble. You can draw a defined line for these types of borders, but just know that the reality on the ground would be much more fluid. 5) **Disorganized Tribal Groups rule the frontier.** In the Medieval Europe map, notice the Cumans, Uzes, and Vlachs in the South East, and the Prussians, Selonians, etc, in the North East. In sparsely populated areas, especially those inhabited by nomads, Kingdoms don't really exist. Instead the area is divided among tribes, clans, and other small entities. On maps these are generally marked together as a single ethnic group (like the Cumans), but are not given a color or borders. Instead, the other borders end, and the white area has the names of said ethnic groups, with the location indicating roughly where they were, and the size of the word often indicating the size of each. So, pre-Genghis Khan, the area north of China would be a blank area with the word Mongols written there, along with a few other nomadic groups. Historically, these groups would often unite and conquer their sedentary neighbors, forming new kingdoms who would be conquered in turn a few hundred years later. The Parthian Empire is a good example of this, as a nomadic horse nation who settled down and was later conquered by the Sassanids, another nomadic horse nation (who were then conquered by Arabs, who were then conquered by Mongols, who were then conquered by Afghans, etc). [Answer] Here's what I do when designing a DnD campaign once I have a map: 1. **Look for every place that has something that would make people settle there.** Minimum would be food and water. Any useful features and resources add bonuses. If the land is recently settled, start at one edge. Otherwise figure that people have been over most of the land (except for areas that you don't want them to be). 2. **Make circles (use light pencil).** Once you have the settlements, judge based on how much food and resources they have, how big their influence will be (a compass or a pencil on a string will work). 3. **Since circles are unrealistic, adjust them for the terrain.** If travel is hard, pull it in some and if travel is easy let it out some. Also, if there are natural features (river, cliff, forest edge, desert edge, etc.) near the edge, the edge usually conforms to the natural feature. 4. **Overlaps are zones of conflict.** The border will generally be within that zone of conflict (often following a natural feature). 5. **Assimilation.** If one settlement is completely or mostly within the area of influence, decide if it has already been assimilated into the larger power or not. If it has been assimilated, extend the powers influence in that direction by the strength of the assimilated power. If it has not been assimilated, pull the border back in that area. On the first pass, most will be assimilated. 6. **Decide which borders might be peaceful and which will have conflict.** Neighbors with different resources may be more peaceful toward each other and have trading relationships. Neighbors with similar resources are more likely to come into conflict since they gain less through trade. 7. **Adjust for trade or conflict.** Widen the borders of powers that have trade agreements and narrow the borders of powers that are in conflict. Repeat 4 through 7 as needed. Some powers may be assimilated and some new zones of conflict may occur. If a border shrinks to "free" a smaller settlement, decide if it breaks away (if not, leave a connection to the larger unit). 8. **Fine tune as needed or desired.** 9. **Back Story.** Create as much history describing how things got to the present time as you wish. There are likely many great plot hooks in the evolving map. You are now at the start of the story or campaign. [Answer] How much detail do you need for your story to make sense? As others have noted, national borders tend to run along coastlines, rivers, and mountain ranges. But there are plenty of exceptions, especially when no convenient river or mountain range was available in the general vicinity of where two nations bumped against each other. Sure, you could write a history of the world up to this point to explain how your borders came to be. But is that necessary? If in a story a writer says, "Bob was tall and had red hair", he normally doesn't find it necessary to trace Bob's genetic history back to Noah to explain exactly how he came by this traits. If for some reason you need an unusual national border in your story -- if say, country A is on the west side of the ocean and also control a tiny strip on the east side of the ocean, and country B is then east of that strip -- you might need a couple of sentences of explanation of how that came to be. But if the history isn't relevant to the story, even that probably isn't necessary. If I'm reading a story set in a ficitonal world, or in some part of the world where I'm not familiar with the geography, I don't recall ever wondering, "Hey, wait a minute! How come the border between Foobar and Plughland runs through the Fwacbar Valley? Didn't the author say that there's a river near here? Why isn't the river the border? What's the history behind that?" Unless the story is about geography and politics, I doubt such a question would even come to the mind of 99.9% of readers. [Answer] Borders are a tricky subject. Though most will end due to natural terrain, like rivers or mountains, most borders are set by expanding kingdoms, only stopping when they meet resistance from another expanding kingdom. Because of this, there's no real formula per se. However, you don't have to write prehistoric histories. Make one kingdom and have fun with. Think about who their enemies are. What do they produce? Maybe they trade with a neighbouring city. Before you know it, you'll have a flourishing kingdom before you. Good luck! [Answer] Although rivers are mentioned frequently here, the reason we humans have them as borders is due to **transportation** of goods, both to a political region and from it. Most USA citizens do not realize that our States had shooting wars, with people killed, over rights to the water sources and waterways for transporting goods, for irrigation and drinking water. The same goes for natural oceanside ports (or those on big lakes). Water wars (literally wars) are the **primary** reason our map has weird bumps and extensions, water access, for both consumption and travel, is critical. Barges are far and away the cheapest form of transportation for goods; far, **far** cheaper than rail, trucks or horse drawn wagons. Unless a region has a lot of natural lakes, it probably can't grow very much on rainfall alone. Not for agriculture or city life. Find your glaciers or heavy lakes being replenished by rainfall, Trace your rivers through the valleys, rank each river based on how much "good land" it provides access to, how many other rivers it can join (it's network connections), whether it reaches a coast line. You can probably find the "good harbors" based on some surrounding landscape criteria (and how many rivers can reach it). The highest-ranking rivers are borders; those are the ones people fought to keep some other political faction (country, state, whatever) from owning entirely. If those borders produce a country too large, sub-divide it using the highest-ranking river that passes through it, and do that recursively. [Answer] One alternative to generating the entire story, is generate stuff using Markov Chains based at current year heightmap/border earth data. First you get an earth height map that has countries borders. If the pixel of the height map is ocean/border you change its color to A, if its ocean/international land, you change its color B, if its ocean/country land you change its type to C, if its not-ocean/border you change it's color to color D, and if its not-ocean/international land you change to E and if its non-ocean/country land you change to F. Some program will then get this modified heightmap and analyze it creating an probability table: The chance of some tile X being border, "international land" or "country land", based at what specific tile type their 8 neighbors are and based too the tile itself you are generating is ocean or non ocean. With that info in your hand, the world map generator program will get a random tile and discover if it is "country land", "international land" or border based at their 8 neighbor tiles and his own type. After find this tile type it will go for the next one and generate it, and then go for the next one, and next one..... until it generate the entire map. Some important things to make sure this works: 1-You must always generate the not-generated tile with most amount of already generated neighbor tiles, if you don't do that, the world will have some patterns based at how you generated it, as some example generating left to right starting from the first line, create something with an X pattern. 2-The markov chain data must be based at ALL 8 neighbors and must be influenced by the direction of the neighbor tile too. 2.1- An example, If at the top of the ocean tile you are generating there is a ocean/border tile, at the bottom of this tile you are generating there is a ocean/border tile too and you didn't generated the other 6 neighbor tiles but they are all ocean. The "question the program will ask" is something like this: "Assuming this tile is a ocean, the top and bottom tile is ocean/border, and all others are ocean tiles, what is the chance of this tile being a border, what is the chance of this tile being 'international land' and what is the chance of this tile being 'country land'? " Then the program will select its tile type (border, country or international) at random weighted by those probabilities. 2.2-If you don't use this method, most of the time you will have a map that is made entirely out of international area, or made entirely of country area. 3-Points 1 and 2 are based at discoveries I found while trying to map makov chain map. You will find some markov chain map generator ideas at internet that assume the markov chain wont work at generating maps (x pattern or whateaver) because they didnt discovered what caused their problems as assumed the use of markov chain itself was the problem. [Answer] You can use [Geographic Information System](https://www.youtube.com/playlist?list=PLB536E2CAE9CD2EE1) tools to make what you want by creating or using existing data, you can use rasters and vectors staticlly or dynamiclly ]

[Question] [ I am a farmer or perhaps a slightly successful merchant in a medieval world. What types of clothes dye would be available to me? Purple is often discussed but would only be available to the wealthy, but what about blue, yellow, green, red etc? How would these type of dyes be made and what is the likelihood they would be available to me? [Answer] First, let's talk about the base fabrics available during the time, because, why not: * Linen, which came from flax, doesn't take dye quite so well as cotton, which was largely imported from Muslim countries to Europe. The base color for this fabric would be beige, or a grey with a brown tone, seldom would it be bright white. Fine linen was used for the veils and wimples, undergarments, and a wide variety of apparel and household furnishings. Although available to commoners, fine linen wasn't used much in most clothing, except as an accent, or in very specific functions (such as a wimple or chest piece). But there was also an every-day version of it, which was used for gowns and general clothing. Often, it was used as the fabric closest to skin, which you would also see--and ladies would wear an over dress over it. The underdress could be dyed or undyed. Sometimes the overdress was made of linen. The picture below gives you an idea of how the under and overtunic worked, although this picture is likely of more highborn folks, likely wearing classier fabrics. The commoner version would be orange and yellow, most likely. [](https://i.stack.imgur.com/46tST.jpg) * Silk. This stuff was high class and it was illegal for commoners to even wear it. Undyed silk was very rare. And since it was so expensive it got the "first dip." * Hemp. Used in work-a-day fabrics, even more common than linen. Often used for aprons and the like. Most did not bother to dye, but if they did it was to hide stains and it would be dyed brown. * Cotton. This fabric that is rising in popularity during this time because it wrinkles less than linen and takes dye more readily. It starts as a bright white. Mostly grown in warmer areas--Italy, the Middle East, Egypt and imported to Europe. RARER THAN HEMP OR LINEN, but increasingly common by the late Middle Ages. * Wool. The start color can vary widely. Grey, white, brown, black, and even a ruddy red. Studies of medieval textiles and manuscripts determine that about 7% of sheep would be brown or black in color. Wool takes dye fairly well and will result in brighter colors even without an extra step of an ammonia wash. MOST COMMON. * Leather. Extremely common and used for over tunics. The tanning process meant that dying leather was rolled in with curing the leather and brightly dyed leather was definitely more expensive and very, very rare. Colors were limited to green, red, blue, black and brown. With stiffer leather but it was often painted, or "washed over" with a color, sometimes to represent a shield of a house. White leather and bright yellow leather were uncommon in the early period. What you will **NOT find for much of Medieval times is velvet**. I know, this is in every costume EVER for a Medieval lady. But despite Hollywood's portrayal, it was not until early in 14th century that it started to be a big thing--and even then, it was exclusively for high religious, and highest nobility. From 500-1100 there wasn't much in the way of velvet.(Yes there are earlier velvets, but the pinnacle for it is in the Renaissance era. Prior to that it was mainly used to upholster, though there was some use in the 12th century) Once it was introduced widely during this period, it was even less likely for a commoner to have any. There aren't many laws prohibiting wearing it for merchants during medieval times, because, unlike silk, it was harder to get. Further, a lot of what people think of as Medieval fashion is actually more like Renaissance era. This is partially because the real advent of painting and art was in the Renaissance & the clothing depicted showing "Medieval times" was often based on the fabrics and colors available during the time of the Renaissance. 1400-1500 was a real jump forward in fashion. [](https://i.stack.imgur.com/o3At2.jpg) Compare the above, which is really very late Medieval/early Renaissance through Mid-Renaissance, to this image from the 1200s [](https://i.stack.imgur.com/gu5qb.gif) A Lot of depictions of "Medieval" clothing you'll find on the net were rendered far later than the Medieval era, and thus were inaccurate. **Black** > > difficult and expensive to achieve. My reading on the subject does not seem to substantiate this reasoning. Black is documented as being achieved by many different but simple methods, using many different kinds materials, including oak galls, human urine, blackberry leaves, and lime, all of which are inexpensive and readily available all over Europe. [Source.](http://renaissancedancewear.com/fabric_colors_in_the_renaissance.html) > > > A nobleman might actually demand that their black or dark brown woolen cloak not be dyed at all--since they knew dying to be a messy and smelly process. Instead, they would ask for it to be woven from the wool of a dark or completely black sheep, prized for its rarity. **Yellow** Everything from onion skins, to weld, to turmeric, can get you a shade of yellow. Pretty darn common. [](https://i.stack.imgur.com/xRQ51.jpg) **Orange** Surprisingly common. You could take leaves or even peat in order to get orange, without even a secondary process. Sometimes, the first run would get you a brown, but running it through with ammonia could bring out the brightness and the color. **Brown** Tannins can result in this color. Very easy to get. Can also happen in combo with other things. **Blue** Woad is the main source, though there's also the more expensive indigo and the prohibitive lapis lazuli. Far more common than you might think! Woad grew all over and the dye result is very pretty! **Green** > > Better living through chemistry was the motto of the day. For instance, I wanted a green wool and after dyeing a hank first in turmeric and then indigo, I was surprised (and dissappointed) to get brown. I already had brown. Lots of brown. “Toss it into the ammonia bath.” Which I did and instantaneously it turned the most lovely shade of moss green. The batch of wool that I dyed in weld and indigo needed no ammonia bath to turn green. But who would have thought. And now we know why urine was so popular for dyeing fibers. It was the period ammonia and it could work wonders. [(source)](https://medievaltailor.com/research/period-dyes-and-colors/) > > > There are some lichens which can produce a dull green as well, which can be brightened by a dip in woad, maybe in the second bath. **Red** Brazilwood, Madder, and kermes or grana from insects. Kermes, grana and Brazilwood is more expensive. Madder is far more common. You could likely also "fake" red by doing overdyed orange dyes and using urea or other derived chemicals to draw out what you need. Surprisingly common, although most of the poorest commoners wouldn't wear a true red, it would be more brick or orange-looking. **Purple** See red, for your base. Red & blue make purple, so, you don't always have to do something that specifically gets you purple, just mix the two or do a dip in red and a dip in blue. Often illegal for commoners to be able to wear this. There's also a snail that gets you purple. But you gotta crush a lot of them. And often it was specific shades (like the ones you could get from the snails) that were illegal--not that sumptuary laws weren't ignored. Some berries and wines could get you a light color, but that often faded to brown. [This link](http://historicenterprises.com/fabrics-colors-c-100_198_200.html) shows you all the colors, and I see someone has already provided it in the comments. It is a great place to start, for certain. **Things to keep in mind.** Intensity of color and expense of the fabric depended on * Time in the vat (& time is $$) * Which dip! Dye vats could be reused, over and over again. Therefore, your commoner might actually have a light red dress (pink was not so much a thing then & they would have specific words for specific shades). The same is true with blue. The darker or more intense the blue, even if was cheaper, it would be a bit more expensive. So a merchant might say: "Blue so fine! Just the second dip! Second only to the ladies of the castle...." and so on. [Answer] What natural dyes are available and affordable depends mainly on the available plants and animals. For example, in Europe, according to this article: [Natural Dyes – The Top 3 European Dye Plants](http://pioneerthinking.com/crafts/natural-dyes-the-top-3-european-dye-plants "Natural Dyes – The Top 3 European Dye Plants") > > For thousands of years, **the three main European dye plants were, and > still are, woad, weld and madder.** Blue can be extracted from fresh > woad leaves whilst the flower spikes and leaves of weld yield neon > yellow and the fleshy roots of madder produce a brick red. Various > shades of green can be obtained by over-dyeing woad and weld, whilst > purples and browns result from over-dyeing woad and madder and it is > no surprise that weld over-dyed with madder produces orange. **All > these colours are light and wash fast.** > > > (Boldfaced emphasis mine.) Although Woad, Weld and Madder produce (respectively) blue, yellow and red -- the primary colors -- overdyeing with these three does not often produce vivid secondary colors. So the available color palette was limited/muted for most commoners. Here are some examples on wool: [](https://i.stack.imgur.com/Z3z4P.jpg) [](https://i.stack.imgur.com/0O1NN.jpg) [](https://i.stack.imgur.com/WvtGn.jpg) There were certainly other colors, but most of the bright (and colorfast) ones were so expensive that only royalty or the wealthy could afford them. For instance Tyrian Purple and Cochineal/Carmine Red: [Tyrian purple (Wikipedia)](https://en.wikipedia.org/wiki/Tyrian_purple) [Carmine (Wikipedia)](https://en.wikipedia.org/wiki/Carmine) Getting a dye color to stick durably to the fiber is not always a simple matter; additional chemicals were often needed to act as mordants: chemicals, often caustic, that make the fiber take up the coloring chemical(s) and bind them durably to the fiber. [Answer] Common people back then knew a lot about dyeing and the use of mordants. Most farm families would know all the uses for the crops they grew as well as the wild plants local to them. Just red cabbage and yellow onions skins produce a whole rainbow of colors- blue (red cabbage and salt), pink and red(red cabbage and vinegar), purple (just red cabbage), green(cabbage and soda), yellow and brown (onion skin), and orange (onion skin and cabbage plus vinegar). Veg dyes work best on protein based fabrics- like wool which was common among farmers. Linen was also common throughout Europe but doesn't dye as well with plant based dyes as wool. Linen could still produce a less bright colored garment that might be more comfortable and affordable to wear than wool. Dharma Trading has inexpensive linen and other natural fabrics suitable for dyeing and sells natural plant dye sources like madder and woad. Whether or not you feel like dyeing your own fabrics, I think you should pick colors that you like and feel good wearing. Odds are that any colors you pick could have been achieved with what plants were available using just the right process. [Answer] I think it's also important to remember that depending on your social class (or the class of your character) that some fabrics and dyes you were not allowed to have; due to the Sumptuary Laws put in place in the early 14th century. I also found a timeline of these laws, when and where they were put in place if you need them. <https://rosaliegilbert.com/sumptuarylaws.html> [Answer] While there are plenty of artistic representation of the "kinds" of colors you could find about cloths dyes in the medieval period, you'll find a multitude of conflicting information with references from official and documented sources. The reason is simple, color dyes were one of a kind of commodities that could be extremely restricted by laws, availability of the dye materials, distances from the source of where the dyes were produced, etc. There's a LOT of information regarding the history of colors in civilization and the medieval period was one quite rich in it because of the high frequency of changes in both social and/or religious groups. To give an example, at one point, England was all "blue" since the dye (known as "Royal Blue" today) was the more expensive dye back available back then as it was produced from a rare stone only available in the Sahara desert regions. France raised the taxes over any dyes that were ordered by England (as a way of raising its coffers and dropping England coffers) and England switched to the "Royal Red" you find today on many of the UK's stuff as that red came from Spain's naval trade route instead. France was, at one point, all about a certain green (from a stone traded from Silk roads), but ended up with a financial crisis where blue dye merchant from the south boycotted the country's trading routes and forced France to buy their stock(unwanted by their main ex-customer England, by that point). Since it was known as a rare/costy dye and it knew England was grumpy about it, France decided to move from the popular green to the blue (and that's where "Bleu Royal" as "Royal Blue" came to be) to show off. Another example is the fact that certain red color were illegal to be wear in many countries (including France and England) due to its relation to the Christ blood, unless the one who was wearing it was on a some religious quest authorized (closely or remotely) by the Pope. Obviously, royalty used red all the time because they though themselves closer to the Christ (and God), but the famous red cross of the Crusaders was one of those examples where religion decided what color and what patterns is what. Unknown today by those how haven't read about it is the fact that serfs were actually restricted in what color they could wear in public. Because of how a single color could represent someone of higher ground, serfs were restricted to really simple dyes (gray and brown) if any at all, but they could use the natural color any purchasable cloth and leather. Yes, many countries like Rome, France, England, Germany and even Spain, the use of colored cloths by serfs could be punished by an execution in said clothes. To give an idea, England was so pissed against France that it made the act of wearing it's Royal Red color (explained above) to be punishable by death on the spot if wear by anyone except England royalty or its personal personnel in England. As such, wearing that color in France, Germany, Spain and some other countries was also a bad idea because someone with that color would be seen as someone who's under the thumb of England, hence you would end up being arrested and tortured just because you don't have any official documents that you're an envoy or just because someone hated England. The same could happen if you were wearing the specific green (explained above) in France during the green craze without being of some sort of "closely" to the King of France. (Basically, having him personally or indirectly telling you that you should wear green as his vassal or something.) You could be jailed for life (or "until the King decided otherwise" which, unless you had people reminding him, would forget about you) for wearing the same color as what was sought by his highness. Those kind of restriction became loose over time with the evolution of the markets as new commercial roads (or avenues) opened up and foreigners came in while wearing many colors that were never seen before. The restriction came from having colorful clothes being illegal to patterns and/or main colors being illegal. The Royal Blue and Royal Red would have to be least than 1/3 of the cloth surface (like with patterns) for example. So, in many countries, the answer to "What color dyes would be available to the average person in a medieval world" would have been: **Depending on who's the average person.** **If it's a serfs**, only natural color from the material used unless on a religious quest with a remote permission from the Pope to wear a pattern of a certain color. **If a Lord's vassal**, usually natural cloth/leather colors or the colors used by Lord of said Vassal. **If a King's vassal (lord)**, depending on the situation and relation with the King himself, they could be wearing colors during events with others excluding their King, but had to wear their official color (based on their coat of arm) during official event. **If it's a trader with no legal attachment**, he could wear any color, but as mentioned above, the restriction of the areas were relative to its authorities, hence it wasn't rare for them to wear the same colors as serfs while traveling, but wearing more colorful attire where selling near someone of high right like King's vassals or Kings themselves. [Answer] My mum used to do a bit of natural dyeing using native plants and home-spun wool. There are loads of books on dyes you can extract from native English plants, each of the dyes changes depending on the mordant used, but I'm not sure if all the mordants would have been available in medieval times. These are the ones I remember * Purple/Red: Yew bark (highly poisonous) * Red: Madder * Yellow: Onion skin, Ladies Bedstraw * Green: nettle * Blue: woad (very complicated process) [Answer] It looks like you already have an ansswer, but here's mine. Red, from berries/blood of livestock. Green can be gotten from the inner bark/sap of young trees. White from sheep's wool. I don't know much about england, so that's it. Also, all the clothes would be stained/dull colors. ]

[Question] [ Dragons. We know them. We love them. They breathe fire and wreck our towns and plunder our gold. But all that destruction has to get fueled somehow. So naturally, I would assume dragons have to eat (or at the very least have some method of caloric intake.) Let's assume our dragon is a traditional Smaug-style dragon. Big (20 meters long, 5 meters tall lying down), flies, breathes fire (assume the firebreathing is a chemical reaction that does not draw substantially from their caloric requirements), has periods of dormancy in which they will require fewer calories. So let's assume there are four modes for our dragon: * Hibernation - spending weeks or months at a time slumbering on massive piles of gold. * General activity - organizing treasure, holding meetings, holding court, studying/learning magic * Scouting - long periods of sustain flight and gliding, perhaps swooping down occasionally to pick up prey * Combat - short periods of intensive and aggressive flying, swinging, and firebreathing In terms of calories per hour, what kind of caloric intakes are necessary for these different categories of activity? If we can't answer them, what pieces of information are we missing? Feel free to be liberal with your assumptions (for example, when estimating mass), as long as you clearly state where they come from. Also, if any of my givens above seem inappropriate, feel free to change them. I want realistic dragons, here! [Answer] In general, when calculating caloric requirements for animals, we can apply what's known as [Kleiber's law](http://en.wikipedia.org/wiki/Kleiber%27s_law). Kleiber's law states that the food requirements of various animals scale by the mass of the animal to the $\frac{3}{4}$ power. This value is then multiplied by a constant that's dependent on the type of animal. To compute a dragon the size of Smaug's caloric intake, then, we can start by computing his weight. According to [this source](http://www.theonering.net/torwp/2013/05/11/71530-analysis-just-how-big-is-jacksons-smaug/3/), Smaug was around 60 meters long. A tyrannosaurus rex, by comparison, is a little over 12 meters long. Smaug had a long tail, though. (About 2/3rds of his length is tail), while t-rexes look to only be about half tail. If we compute weight based on body length, we'd then have Smaug's 20 meter body compared to about 6 meters for our t-rex. If we assume weight scales with the cube of body length, we can then figure Smaug's weight to be around $\frac{20}{6}^3 = 37$ times the weight of a t-rex. The more bird-like assumptions about dinosaurs put the weight of a t-rex at about 4.5 tonnes. Since Smaug flies, we can assume that his weight is probably similarly proportioned to his mass, perhaps a bit less. Since 37\*9 is 166.5, we'll round down to a respectable 150 tonnes for Smaug. This is comparable to the weight of a blue whale (190 tonnes), which, while only about half as long as our dragon, is significantly more densely built. Now let's apply Kleiber's law. First, let's get some base data on how much animals eat * A 290 gram barn owl needs the eat about [72.9g of small mammals](http://www.pesticides.gov.uk/Resources/CRD/Migrated-Resources/Documents/R/Research_PN0908.pdf) per day. (About 120 kCal) * A 20kg crocodile needs to eat about [2kg of meat](http://www.zutrition.com/crocodile-nutrition-guide/) per week. (About 470 kCal/day) These numbers give us estimates for about how much reptiles that are fairly stationary (our dragons sleep a lot) and flying birds (dragons fly around to catch food) need to eat. We can scale these numbers up to get some estimates on how much our dragons need to eat per day. The data I found is specified per day (or per week) rather than per hour, but we can extrapolate based on the activities of our sample animals what sort of activities these things correspond to. **Bird-like dragons** Our dragons weigh as much as around 500,000 owls. Based on Kleiber's law, they should then eat about 20,000 times as much food, for a total of **2.3 million Calories/day.** Smaug ate ponies in the lord of the rings, so we can say that this is about 8 ponies worth of meat, for comparison. This activity level corresponds to a bird that hunts quite a bit, so this is probably a fair estimate for the activity level of a dragon while scouting or hunting. **Reptile-like dragons** If their caloric requirements are closer to those of crocodiles, they'll need a bit less. A dragon weighs 7500 times more than a 20kg croc, and so should need about 806 times the food as one. This comes out to a mere 380,000 Calories per day, or a bit more than one pony per day. This is more like a dragon that's sitting around snoozing on some gold or schmoozing with other dragons and the odd invisible hobbit. **Final estimate** In summary, if our dragons eat about as much as owls (relative to weight) while they hunt, but only hunt once a week and snooze like crocs the rest of the time, they'll need an average of around **655000 Calories per day**. That's about two ponies per day, so once a week a dragon will need to go out and eat a small herd of them before going back to snooze on its pile of gold. [Answer] Well first I'll point you to [this](https://what-if.xkcd.com/78/), where xkcd has figured out it would take a T-Rex about half an adult human every day ~40,000 calories. Taking that and assuming Smaug is about 4 times the mass of a T-Rex, I would start with General Activity (GA) being about 160,000 calories a day or about 2 adult humans, or four 10 year olds, or half a horse or cow. If it stuffed itself like a snake it could likely hibernate for months maybe years after gorging on a small heard of cattle. I was unable to get a good quote on how long an anaconda can go after a large meal, I have heard of 6 months. Scouting I would double or maybe 2.5 times as much as GA, so a whole horse. Combat I would guess 3+ times GA. Part of the issue is even if the firebreathing is a 'chemical reaction' the dragon still needs to produce the chemicals so it would still use calories to produce or reproduce. Depending on how, this could be a LOT of calories. Unless the dragon collects the chemicals and just stores them, which just doesn't sound like a real great dragon. "Wait I can't find any sulfur! How will I belch fire now!" EDT: I was assuming that since dragons are reptilian, that they would have a similar metabolism as the large carnivorous dinosaurs, just larger. ]

[Question] [ Aquatic races are usually assumed to be stunted in technological development by the inability to create fire or forge metals. But what about doing chemistry at all? The development of chemistry in human history seems to hinge on being able to perform reactions in aqueous solution. That's convenient for us because water is abundant, lots of natural chemistry (including biochemistry) occurs in aqueous solution, and you can store dry materials and get them to react only when you want them to by dissolving them, or by mixing solutions that have been stored in separate containers. Underwater, where your entire "atmosphere" is an aqueous solution, many of those conveniences go away. Storing dry materials is much harder, as is keeping pre-prepared solutions separate, as they are liable to diffuse into your equivalent of "air". However, it seems to me that there are analogs for how we do chemistry that would work under water. After all, we can do a lot chemistry with gasses, which must be carefully stored in sealed containers lest they "dissolve" in our atmosphere. Thus, given the ability to construct suitable containers, an underwater civilization ought to be able to do chemistry with separately-stored aqueous solutions and other miscible liquids just like we do with gasses. Additionally, perhaps they could do chemical reactions in non-aqueous solution--say, by storing "dry" ingredients that get dissolved in oil bubbles to perform reactions. So, am I on the right track there? Despite lacking access to fire, and being entirely enveloped in aqueous solution, could an underwater civilization nevertheless develop significant knowledge of chemistry and chemical engineering technologies? And if so, what might that developmental path end up looking like? [Answer] I think you are on the right track and this is a really fun question. I think the issues you mentioned with things like generating heat are much larger obstacles than doing chemistry in a fluid medium would be. For an aquatic-native race, anyway. I'm going to focus mostly on the last part of your question, "What would their developmental path look like?" **I think their first chemistry would be food related** Without being able to salt and dry things for preservation processes like fermentation could be an early way to store and age food. It's also a heat-free alternative to cooking. Something which produces a thick mucus like a frog's egg or a kelp with non-soluble rubbery sap would probably make a thick enough barrier for your underwater kimchi to thrive. Then you start boring holes in the coral or rock to protect your food while it ages. If you're going to get pottery to work underwater without heat, you'd probably start looking for a chemical reaction to harden/cure it around then. This is a good place to mention that if this is an alien world the flora and fauna are going to be providing a lot of inspiration to the scientists there. Clear, pressure-resistant exoskeletons on large aquatic animals could get you past early glassware, for example. It's also a good place to bring up that the aquatic race you mentioned will likely have very different physical tolerances to humans. How close can they swim to geothermal vents? Maybe heat isn't such a big problem for them after all... **Understanding and manipulating pressure, especially water pressure would be an early development** By your "being entirely enveloped in aqueous solution" we're ruling the surface out entirely, so I'll go ahead and assume we're talking about an icy surfaced moon or something where there just isn't an up after a certain point. So down is the only way to go for our sea people when they want to explore new territory or follow migrating prey. They may not have to deal with breathing underwater but they will still have to withstand pressure and possibly temperature changes. They'll want technologies to help the with that. If it were me I'd cheat and give em a pufferfish that works with a chemical reaction. Eats shells or something and combines it with acid in an organ to inflate super-rapidly, even at depth. Starts floating up like a rocket too. That gives 'em inspiration to develop gas bubble producing technology, even at low temps the gas could be harvested slowly over time. Since all you need is an upside-down vessel containment would be relatively easy so you wouldn't need a lot of complicated tech to make a glove box analogue like Dutch's answer shows. Even without the fancy bubblefish, **there'd be streams of bubbles coming out of their primitive carboys and fermenters.** They could catch those. Being able to harvest and capture gas would be a HUGE leap in buoyancy control. Being able to make cargo weightless would probably be as significant to them as the wheel was to us. **With the right natural resources, a hunting society would discover toxicology early** I am picturing highly-venomous sea snakes which our merfolk capture and milk by forcing their fangs into the meat of snails, then sealing the snail shell with clay. The toxin would be extracted later to facilitate hunting more formidable game. Diffusion and concentration, safe storage and handling would all be necessary studies not just to produce and use these kinds of tools but again exploration as well. Are there underwater lakes or currents saturated with heavy salts? Is there oxygen in them, or are they dead zones? They'd need ways to detect these things, ideally before swimming into them. **I'd be hoping for some form of epoxy or thermoset adhesive as a pretty early development.** Once those start getting off the ground and reliable you get to composite materials (like micarta.) If you can get those composites sophisticated enough you'd find alternative solutions for most of our metal products without ever needing heat. The idea is to try to find a workaround to get our briny buddies to plastics without needing metallurgy. I suppose they do potentially have access to unlimited free pressure... They could get their plastics to set/fuse by sinking them really deep and then reeling them back in. [They could use this same process for ceramics too.](https://www.upi.com/Science_News/2017/02/28/Scientists-forgo-kiln-bake-ceramics-with-pressure/2541488310896/) **Speaking of porcelain, sanitation would probably be pretty crazy for an aquatic society.** Have fun figuring out how the toilets work. Here's my vote: I think there's a big room in the basement of your underwater apartment complex full of whatever gas-producing algae they're using. It's analogous to a water tower on earth, gas flows up a central tube and connects to give you "running gas" instead of "tap water." Also pulls a vacuum as it goes, if you seal it well enough and set up the right valves. So you to use the lavatory you'd flip upside-down, sit on the bubble, do your business, then flush it all out the ceiling. It would be carried out of the building on a gently sloping aeroduct to join the sewers far above the town. Eventually it would get to the wastewater treatment plant where the SERIOUS chemistry would happen. Cause let's be real, for these folks wastewater treatment > fire. Underwater smell and taste are effectively the same sense. If you can *taste* your town's pollution and sewage... well, I'm guessing their perfume game would be on point and the essential oils really would be essential. [Answer] During my PhD years I had to work with some materials which were quite reactive: as soon as they were exposed to oxygen or water they reacted very vigorously with them, leaving the poor student with a damaged sample or, even worse, with a sample which spontaneously took fire. A solution for handling these materials and keep the students alive was to use [glove boxes](https://en.wikipedia.org/wiki/Glovebox) [](https://i.stack.imgur.com/d5H0V.jpg) These boxes are sealed and supplied with dry nitrogen, allowing to handle materials otherwise impossible to handle in free air. There are similar concepts for handling highly radioactive materials. Using a similar concept it is possible to carry on chemistry underwater. But a glove box is something relatively recent, Lavoisier and all the chemists before him didn't have it. However there are examples of reactions which happen even though the environment looks not the right one, for example the digestion of fats/oil carried out in a water solution (essentially droplet chemistry), or the existence of biological cells and all the chemical reactions they execute, which are water based solutions in a different water based solution, with a lipid membrane keeping the two separated (again droplet chemistry). Therefore, yes, if you can manage to create and control droplets you are on the right path to run chemistry in an underwater environment, until you are able to build something like gloveboxes. [Answer] The ease with which information could be obtained would depend on the details of the environment and might be seriously limited. The “easiest” situation would be a civilization based in a shallow sea with access to the materials of the coast and access to the surface. Harder would be a civilization based in a deep sea far from land. And the hardest would be a civilization operating at great depth with no access to the surface or the seabed. At issue would be the availability of material substances to experiment with, suitable support structures and access to a phase boundary (liquid solid – the seabed or liquid gas – the surface). One big unknown is the level of technology. As the development of chemistry and technology are intimately linked, it is hard to know where to start. But that starting point would probably not be similar to ours. One of the first human technologies was fire that would not be the case with an aquatic civilization. Given technology such as glass bottles, electric pumps and such like it would be relatively easy to do all manner of experiments under water. But the problem is glass bottles and electric pumps would themselves be difficult to invent underwater without access to high levels of heat. And the high levels of heat available under water such as from volcanism would probably cook anything that got too close. They might well learn a good deal of physical chemistry from the way gases in bladders behaved at different depths but without appropriate containment vessels it would be extremely difficult. If technology is assumed then it’s possible but that would in a way be cheating as they wouldn’t have that technology. [Answer] OK, slightly left field answer to this one. Assuming you are in an equivalent ocean to Earth's, you're *never* going to need to do your chemistry purely underwater. You have a water surface, you have underwater vents, fish have swim bladders etc. If you are careful you can "harvest" these, with anything waterproof (intestines, etc). You may even be able to find "[gas filled](https://physics.stackexchange.com/questions/13141/can-pockets-of-air-exist-underwater)" caves, though you may struggle to maintain any gas ratios without a fair bit of work. [Answer] Above the surface, we contain liquids and solids in concave vessels, openings pointed up, and tilt them to pour contents. Below the surface, you can contain *gases* in concave vessels, openings pointed *down*, and tilt them to pour contents (at least for non-water-soluble gases; wouldn't work well at all for ammonia, hydrogen halides, or hydrogen sulfide/sulfur oxides). But you can also *drive water out* of such a vessel by *displacing* it with gas. Maintaining a gas-filled environment like that is probably easier than maintaining a vacuum environment on Earth's surface, because there's no pressure differential fighting to overcome it. The big catch is going to be heat, though. Nearly every part of chemistry involves adding heat to substances or removing heat from them, and since water transfers heat much more effectively than air (through conduction, convection, and even vaporization/condensation), thermal management will be a lot more work than it is for us surface-dwellers. Also, fire is a super-convenient heat source, and it's essentially unavailable underwater. Maybe the alchemist class builds their laboratories around thermal vents in the ocean floor...? ]

[Question] [ This question is inspired by the last paragraph of my answer here: [Negating the negative effects of childbearing](https://worldbuilding.stackexchange.com/questions/10055/negating-the-negative-effects-of-childbearing/10058?noredirect=1#comment22856_10058) (A follow up question to this can be found here: [Methods to ensure gene flow in species with seperate sapient and non-sapient lifecycle](https://worldbuilding.stackexchange.com/questions/40451/methods-to-ensure-gene-flow-in-species-with-seperate-sapient-and-non-sapient-lif)) I mentioned a concept for a species which I think would be interesting to explore, but which would require some creativity to have evolve logically. The idea is that the species combines R and K reproduction strategies, having many (hundreds) of young originally, but only investing energy into raising a very small number of them to adulthood as sapient creatures. This is done by imagining that the species start out as non-sapient and only some will later metamorph into full sapience. I'm trying to figure out how such a creature would evolve, if it could happen, and perhaps some of the other biological requirements to make it realistic. for this example imagine a creature that's mating starts out similar to frogs. When two sapient adults reproduce the produce hundreds, or thousands, of eggs which are left unprotected by the parents to develop into a sort of tadpole like creature on their one. These creature are not sapient. These non-sapient 'tadpoles' (they don't have to look like tadpoles, just an analogy) will try to survive on their own and many will die to predators or even competition with siblings quickly in the first few weeks. Eventually the parents will come back to the breeding spot where they left the tadpoles and will pick a small number of the strongest/fittest tadpoles that survived to raise as their children. The few tadpoles that are chosen by the parents (probably only 2-5 in total) will undergo some sort of triggered metamorphosis to start developing more complex brains and begin the growth into true sapience, a growth that would require years of rearing and upbringing (you can't have true sapience without learning almost everything from scratch). Call those that go through the metamorphosis as being in their S phase, for sapient. However, in addition to the few young the parents choose to raise there would be other tadpoles that survived and were not chosen by the parents. Those tadpoles not picked by their parents stay in their original phase without the metamorphosis into sapience, call this phase T for tadpole. Lets say that the unpicked T phase tadpoles will continue to grow and develop without parental support. Those T phase young that survive long enough (and very very few will) eventually develop into full T phase adults and be capable of reproducing on their own. These T phase adults can mate, with both T and S phase adults, to produce young of their own, all while still not being sapient. The idea is to have both R and K reproductive strategies in one species, so I'm imagining the parents put extensive effort into raising the few sapient phase children they choose, and put little or no effort into the remaining T phase children, instead leaving them to strive to survive on their own. Thus the parents benefit from both lots of young with little effort on their part, some of whom may manage to beat the odds and survive to reproduce, and also have a few carefully groomed children they will raise and ensure reach adulthood. They get the benefits of both reproductive strategies. For that matter S phase parents who are not ready to raise children would presumably still mate and simply leave all of their children as T phase without choosing any to raise any to S phase. They get the freedom of choosing rather to favor R or K reproductive strategies based off of their situation (though if not enough choose to raise young as sapient phase your eventually end up with only T phase young). The question is how to make such a species work. My biggest question is how to justify their evolving (the sapient phase being the harder part to justify), and justifying their having an evolutionary niche which causes this to be a stable reproductive strategy (ie they don't split into separate populations or evolve to be entirely S or T phase individuals). Any other suggestions about the physical and evolutionary implications of such a species, or even their evolutionary psychology, is always welcome but isn't required. For the sake of this question lets assume that the creatures are sapient but have not reached the level of culture where they would start to use technology to alter or modify their evolved breeding behavior. For instance they won't yet have excess resources which they could use to take care of T phase children or be domesticating/raising T phase individuals, just letting them run wild. Some things I can already guess are likely for what I have already described, you can skip the below if you want, or argue with any of it... 1. There would have to be a large 'feral' group of T phase creatures. They are capable of breeding and expanding on their own even if they didn't have an influx of young coming from the sapient adults breeding. Many of the current T phase adults are not children of sapient adults, but of mated T phase individuals. 2. Sapient adults must have a significantly higher reproductive success rate then non-sapient adults, to justify the massive energy and expense parents put into them when the parents could be investing in simply having more T phase children. 3. There must be a way for the genetics of the T phase creatures to reenter the gene-pool of the sapient phase adults, otherwise speciation would occur quickly. I'm open to any suggestions for this to happen. The most obvious one that comes to mind is that sapient males that are unable to find sapient females to mate may choose to mate with non-sapient females and raise one or two of those as sapient children as a single father. Likewise sapient females could mate with T phase males, but that seems less likely. Presumably it would be considered preferable to mate with sapient phase adult since they were the pick of the litter as T phase children, and a mate would be able to better judge their biological fitness for producing sapient children if they are also sapient. Any other way to increase the gene flow between the sapient and non-sapient phase would be interesting to know, as I see this being the biggest hurdle in justifying such a mating strategy. 4. They would almost have to have an evolutionary ingrained method of identifying their offspring, by sent, sight, sound whatever, in order to ensure they only pick children that are genetically 'theirs' to raise into sapient. 5. They almost certainly started as R strategy non-sapient creatures, with the sapient phase coming later. Though how you justify a metamorphosis into sapience evolving is the real question. 6. The non-sapient creatures are likely not very intelligent, R strategy animals are usually mostly instinctual and not quick learners. Despite the potential for metamorphosis into more intelligent species this does not mean T phase are all that bright. There likely also smaller for much the same reason. edit: One other complication to this being a stable strategy comes up. How do we keep the sapient males from constantly mating with T phase females and out competing their t phase counterparts? Presumably their sapient is a sufficient advantage as to make it fairly easy to compete with non-sapient males for reproductive rights. Two approaches come to mind. First, that T phase males grow to be physically stronger then their sapient counterparts (possible because they invest less nutrients on brain power). This means it is not as easy for a sapient male to out compete with T male for mating rights. I don't like this as much it seems that a R strategy creature doesn't have any right to grow larger then a K strategy one. More importantly this would make it harder for T and S phase to mate and mating between them have to be at least semi-common for gene-flow reasons. A solution I like better is to imply that males actually have a heavy investment in reproduction, equal to that of females. Perhaps in addition to fertilizing eggs they secrete some sort of nutrient rich substance which provides nutrition for the young during their early development. Thus both males and females have a non-trivial caloric investment in reproducing. They can still reproduce semi-often, perhaps as often as every few months, but both males and females have reason to be selective about mates because both have equally high investments into child production and limited mating opportunities. [Answer] Oh boy, lots of question here! Let me see if I can keep from going on for three pages... So you asked: ### How could they evolve? My first thought is that they started out in a temperate or tropical environment that heavily favors r-selected breeding. Lots of food, great weather, some major predators that like to eat them but the carrying capacity of the environment is never a real limitation on their ability to reproduce like bunnies. Then something Really Bad Happens that destroys some but not all of this environment and makes it inhospitable for everything but the best-adapted life. While it gets most of the proto-critters in that area, it also wipes out their major predators, *and* perhaps introduces some kind of novel resource (a high-energy food, perhaps) that lets any slightly smarter proto-critter that wanders into there occasionally score a huge jackpot in the survival lottery. Now let's make the phase transition between the really nasty wasteland and tropical bunny-town abrupt, but not at all impassible for the proto-critters and their predators. Some of them are going to keep wandering into the wasteland, most of them will die, but the extremity of the environment begins working on them. Proto-critters that survive the wasteland start getting progressively smarter, but can still wander back to the more temperate zone to sow their wild oats and thus keep gene flow going between the populations. I think you could potentially see your S phase crop up among the wasteland-dwellers, in this scenario. They'd still be living in the nastier, more dangerous area in the present day, but they'd go back to the temperate one to breed, since the wasteland will kill off something like 99% of the T phase, versus the more "moderate" 75% that get culled in the temperate zone. This separates the S phase and the T phase out into two separate niches that they can uniquely exploit (T phases reproduce faster, S phases benefit from being less predated upon and having [some resource] out in the wasteland in relative abundance). The ability of S phases to induce T phase development might show up later. This is, of course, a just-so story, but a lot of evolutionary origin stories are. ## Some other stuff In no particular order... 1. You might want to introduce some substance that adult S phases produce that induces transformation in T phases. Think of royal jelly in bees--it's fed to all castes of bee initially, but it causes a transformation into a queen in larvae that are continuously fed it through the mechanism of the protein royalactin. Actually, now that I think about it, this gives another evolutionary option for your critters: They used to be eusocial, but the reproductive caste actually evolved sapience (rather than just getting bigger and progressively more useless and reproducing all the time), while the non-reproductive caste got their gonads back. In this situation, S phases may actually exploit their non-sapient T phases to forage and feed them. Everybody wins. This wouldn't be domestication per se as it would be the exploitation of the old eusocial patterns--even though T phases can now breed on their own, they still have psychology that makes them congregate around a related S phase and share food. 2. Ability to recognize near-kin through scent and other markers (perhaps genetically transmissible behaviors like fixed action patterns) isn't a really crazy idea, and it's already especially pronounced in eusocial species (because it lets them avoid having other individuals cuckoo into their nests--though it's not infallible). So it's completely plausible that S phases are very good at smelling out their own children, and it's also plausible that there are some S phases "working on" (i.e., evolving) a reproductive strategy that lets them cheat and get another S phase pair to raise *their* T phases to sapience. 3. I think your idea of S phases breeding to T phases is actually a pretty good one for continued gene flow. Another option might be that S phases see their T phase grandchildren (great-grandchildren, great-great-great grandchildren), rather than direct offspring, as valid targets to raise into sapience. This works especially well if each S phase has some T phase that naturally congregate around it; they might notice one of their nth-generation descendants is already naturally very clever and decide to uplift it. [Answer] You say they will benefit from both reproductive strategies, but they will also bear the *cost* of both strategies. What justifies the huge up-front investment in producing a horde of offspring, as well as the long-term investment in a few? If sapient members are superior, those who waste less on laying masses of eggs will dominate, eventually reducing the number of offspring to those it could care for into sapience. If non-sapient are at all fit for survival, they will quickly out-breed the sapient since far more non-sapient are produced (and non-sapient cannot produce sapient while sapient still produce primarily non-sapient). You say they are not resource constrained, but why would a species which reproduces so prolifically not rapidly fill up its territory? Eventually they will start competing for the same resources (food, nesting sites, mates), and just the sheer weight of numbers will eventually push the sapient into extinction (even if the sapient are completely superior on an individual basis). If I could offer an alternative - the non-sapient are juveniles who failed to develop fully. Sterile, consuming little (no expensive brains or reproductive organs to feed), but performing some necessary contribution. They could be more brightly colored or noisy to distract predators (leaving the sapient more likely to survive), instinctively perform some useful task (building termite mounds) leaving the breeders to concentrate on breeding or raising young (eusocial behavior), or perhaps a very high rate of mutation just results in a lot of malformed individuals. The sentient adults choose the best of a generation to nurse - the selected ones get fed from parental secretions (only so many nipples to latch on to while the rest go off and tadpole), getting the right hormones to develop what will become the adult organs, while the gonads and brain are effectively vestigial for the non-sapient. This gives you the mixed population without the species divergence problem, or the out-competing problem. [Answer] Here is a possible scenario. 1. The sentience is the result of symbiote/parasite that a large percentage of the host species is genetically immune/resistant to. 2. The host species is prey for a larger pack-hunting carnivore. Point 1 gives the sentient forms a reason to pick their own offspring (or that of another sentient) for "uplift", as most of the general population is not compatible. Leaving a portion of their offspring in the wild will keep the vulnerable genes circulating in the wild, just-in-case. Point 2 gives a reason for the sentient form to deliberately not out compete the non-sentient form, as they can intelligently find a way to avoid/defend against the carnivores, so the non-sentient form is more likely to be preyed upon. This gives a reason for a large non-sentient/sentient population ratio. [Answer] First problem I have with this is the relationship between sapience and parental choice. Explaining this part to me is that hardest part. The reason is, if a parent has to choose which children are 'raised' then how did the first 'raised' parent come about? Chicken and the Egg. Sooo I think you'll need to modify how sapience comes about. Maybe the parents keep the ones who appear to have that certain something? There could be a high death toll (like most animals that reproduce this way, fish, frogs etc.). Maybe for what ever reason the genes are not quite as rigid as ours and so has a much wider range of possible outcomes, lots of chaff with the wheat. The parents would try and shift through and look for the 'best' to save, but others might make it with differing levels of intelligence, some debatable as too their actual sapience. Some could be a Tarzan, missed but develop just fine etc. [Answer] My take on this is that there is an unusual environmental trigger for transformation from T-Phase to S-Phase. It may be so rare that only a few T-Phases encounter it naturally and are transformed, but S-Phases are smart enough to recognise this substance and deliberately administer it. Perhaps they can also cultivate or mine it, whatever it is. Anyway, there would need to be a trade-off in fitness with the T to S transformation. Perhaps this would require the growth of a larger brain, requiring the transforming T to eat more of a particular type of food, and if enough of this food could not be obtained, the transformation might abort or go wrong. Perhaps having a larger brain and no training would lead to inadvisable curiosity that would be more likely to lead to deaths than had the transformation not taken place at all. This would mean that you'd have your necessity for training new S-phase individuals, rather than just selecting them all for brain expansion, and only training those you could handle. [Answer] Assuming T and S phases have similar biology, spawning huge numbers of T phase offspring is going to create pressure on food resources for the S phases and the chosen few who are going to be metamorphosed. Not a significant stumbling block, but something to think about which will effect the social relationship between S and T phase populations. Edit: Oops this is really old, and someone said this already. I like the idea though. Any progress on it? ]

[Question] [ Imagine a roughly medieval world with a feudal government. I want a new disease to show up and spread rapidly which affects the nobility and leaders, but not the peasantry, setting up a situation for the feudal system to be overthrown. The disease should not be magical, should be either fatal or at least highly debilitating, and must affect the nobles and royalty. I'd sort of prefer it to affect solders and possible merchant and clergy class as well, but what I most care about is that the nobles and leaders are affected. Finally, as said, the peasantry should be mostly unaffected, or suffer significantly less drastic symptoms if affected. Former peasants that take on a position of power after the former government collapses shouldn't immediately be set upon by the same disease, whether this is because they continue to maintain whatever cultural or environmental habits inoculated them before they rose to power or the disease has simply run its course and died out due to herd immunity once all the nobles are gone doesn't matter. Ideally the disease has/will manage to continue to move from country to country, destabilizing ruling bodies as it goes. In a perfect world it would move between countries slowly enough for countries to already have heard about and fear (or look forward to, depending on your class...) the disease by the time it reaches them, but this is less important. **Edit:** To make it clear I realize that no disease is exact. While I say the disease should attack nobles and not peasant in reality it will likely kill plenty of peasants and miss some nobles. I want only that, in general, the noble class suffers far worse then the peasant class due to the disease. What kind of disease could behave like this, and what is it about the peasant lifestyle the protects them from it? [Answer] ## Spices Spices were rare, expensive, and prestigious. A powerful merchant class has found a new spice, and its use spreads rapidly because, like all spices, it is light and easy to carry, with much value per ounce. It's also a cumulative poison. Additional rumors that it has magical properties that will bring power to the bearer will cut down on the giving of the scraps to the poor -- at least the scraps containing this spice. If you like, you can specify that it weakens the immune system so that people die of different diseases, making it harder to trace. [Answer] **Proximity to Animals Vaccinates Peasants** Small pox was like this. Milkmaids had exposure to cow pox, so were somewhat immune to the more dangerous small pox. If there were a deadly disease (like small pox) only found in humans, but a less deadly, related, disease was already common in farm animals, the same situation could arise, but with the prior exposure not limited a smaller group such as milkmaids. As peasants interact with animals regularly, they might have some form of immunity to the more dangerous disease which the nobility lack because they do not interact with farm animals. [Answer] ## Gout Known historically as the [disease of kings](https://arthritis-research.biomedcentral.com/articles/10.1186/ar1906), identified by the Egyptians in 2640 BC, and listed in the [Ebers Papyrus](https://en.wikipedia.org/wiki/Ebers_Papyrus) (1500BC). It's basically caused by eating too much rich food over a long period, hence it was a disease of the wealthy, cost of food being a limiting factor to the poor. Nowadays it's a disease of the poor, as the wealthy have access to better nutrition, but that's not under consideration here. For your purposes, your ex-peasants are likely to avoid getting fat as a matter of principle and hence not suffer for the first generation of becoming wealthy. [Answer] ## Create an expensive but toxic fad It was common in the 16th century for especially west-European nobility to paint their faces with substances containing lead, in order to appear as white as possible to distinguish themselves from the peasants, who had to work in the fields under the sun. An example of one of these face whiteners is [Venetian ceruse](https://en.m.wikipedia.org/wiki/Venetian_ceruse), which > > consisted of a lead and vinegar mixture, known to cause hair loss, skin corrosion, muscle paralysis, tooth deterioration, blindness, and premature aging. Venetian ceruse was also reported as a source of lead poisoning. Lye and ammonia, found in other skin whiteners, compounded the toxic effects of lead. Other practices done in the name of skin whitening included washing one's face in urine and ingesting wafers of arsenic. > > [source](https://en.m.wikipedia.org/wiki/Skin_whitening#Europe) > > > People are capable of sacrificing a lot in their attempt to look better, which can be used to your advantage. [Answer] You may want to look into **beriberi** for inspiration! It is a disease caused by a Thiamin (vitamin B1) deficiency, and primarily affected people whose diet consisted of mostly white rice or highly refined carbohydrates. Rice with a lot of bran and hulls (peasant food) still had the vitamin, but the "pristine" rice actually lacked it. There were historical cases in Asia during wartime when a large number of the defending forces were suffering from the disease, yet the prisoners didn't as they had been eating the cheaper, less refined rice. The disease was partially identified when the released prisoners were given white rice and began to suffer the disease too. Today's rice and other cereals are enriched post-processing to prevent this, and you can also get the vitamin from the following: * Pork * Fish * Legumes * Peas * Sunflower seeds * Yogurt However, "Thiamin can be destroyed with high-heat cooking or long cooking times. It also leaches into water and will be lost in any cooking or soaking water that is thrown out." [[1]](https://www.hsph.harvard.edu/nutritionsource/vitamin-b1/) In a setting without modern knowledge of nutrition, **anyone with two coins to rub together would rather eat highly refined and pretty carbohydrates**, while only the poor would have to settle with the unrefined, gritty, crunchy stuff that sticks in your teeth even after cooking. In summary, all you need to do is take a staple food, introduce a suddenly popular and novel way to make it more refined, and have it turn out that a vital nutrient not supplied elsewhere in the diet is now missing. [Answer] The only thing I could think of is if a special commodity that they didn't know was actually poisonous. Similar to the Chinese alchemy elixir poisoning, which claimed the lives of many Chinese emperors from 210 BC to 1735 AD (the elixirs, ironically drunk to obtain Immortality, contained Arsenic and Mercury). So if it was something the nobles and rich consumed but the peasants could not, it could be that was the source of the disease (especially if laws restricted the access to the this commodity so it was illegal for peasants to partake anyway, though again, Nobility does not equate to Wealth and vice versa). Other than that, historically, wealth typically correlated with health, as those with money could afford to pay doctors for better treatments. That said, among European Nobility inbreeding was quite common and put many royals at increased risk for genetic diseases, but this wasn't a common symptomology. The hemophilia that famously brought Rasputin to a position of good graces with the Tsars was known as "The Royal Disease" due to how many royal families in Europe were susceptible to the genetic disease. This would only affect the nobility but not the wealthy non-nobles to such a degree. There is very little in the way of biological illnesses, however, that could affect only a class of people since genetics is not an indicator of wealth. [Answer] ## Target behavior, not genetics There are numerous maladies that are peculiar to the wealthy of that period. Gout and tooth decay come to mind. They figured out that doctors need to wash their hands because the women who could afford hospitals [had a higher risk of dying in child birth](https://theconversation.com/ignaz-semmelweis-the-doctor-who-discovered-the-disease-fighting-power-of-hand-washing-in-1847-135528#:%7E:text=In%20fact%2C%20it%20was%2019th,prevent%20the%20spread%20of%20germs.). You want something contagious, though. Come up with something that thrives unusually well in the world of comfort. #### Immunity through labor Alternatively, consider that milk maids were rarely killed by smallpox because they usually got cowpox first. maybe your world has an effective but expensive method of killing off fleas, and fleas carry something that inoculates people against bubonic plague. #### Immunity through diet [Beriberi is something we don't think about much anymore.](https://www.theatlantic.com/technology/archive/2014/10/how-sick-chickens-and-rice-led-scientists-to-vitamin-b1/381903/) It got worse after the rice-hulling machine was invented. You could readily come up with a disease that hit the wealthy harder because of a favored food processing step that removed an essential vitamin. #### Temperature based outgassing Ok, here's one if you want the death to happen quickly, in a single instance. Let's say that there's a particularly vibrant paint that becomes extremely popular as wallpaper or rugs. The problem is that, when heated, it releases poisonous gas. Nobody notices for maybe a decade, until a heat wave blankets the country. Everybody in the castle dies one day. If you haven't played Plague, Inc. yet, I recommend it. It'll give you a few ideas for pathways of transmission. [Answer] The disease causes a severe allergy to something noble-associated. Everyone has the same two-week course of feeling lousy when they get the disease. Unpleasant, but rarely fatal and soon recovered from. But when the virus has left the body, the antibodies remain. Ever afterwards, if you breathe deep near a hawk's feathers your airway will close in anaphylactic shock: disabling and potentially fatal. For peasants, this is no big deal. Wild hawks avoid humans and tame hawks are only legal for nobles anyway. But for nobles, hunting with tame hawks is a critical part of court life. It'd be political suicide to abstain. How realistic is this? Immunologists disagree on how common virus-triggered allergies are, but they're certainly possible. I think I remember at least one medieval European country had strict rules about which levels of nobility could use which birds in falconry, with peasants permitted none regardless of wealth, but I can't find the link now. [Answer] **Make it a genetic disease.** The disease is passed on through inheritance rather than contagion. I realize this may not fulfill your requirements of a disease that quickly spreads from place to place. But it is the only one guaranteed to affect nobles and royalty only. Because of inbreeding, it can be passed down to nearly the entire next generation of nobles and the very rich. Maybe even some soldiers/merchant/clergy who have had children with nobility. Such was the case with hemophilia in the 19th and 20th centuries: > > Hemophilia has been called a "royal disease". This is because the hemophilia gene was passed from Queen Victoria, who became Queen of England in 1837, to the ruling families of Russia, Spain, and Germany. Queen Victoria's gene for hemophilia was caused by spontaneous mutation. > > > Because nobility often married second/third-degree relatives, hemophilia (a recessive, X-linked trait) was expressed in many of their children. But you can do better. Make the trait dominant. This way it will spread to most, if not all, of their offspring. Plus, princesses are often married off to royalty of neighboring countries in order to strengthen alliances, so the disease could be easily spread. It could be fatal or just highly debilitating depending on your preference. This would make the upper class ripe for a takeover. [Answer] **Scurvy** [](https://i.stack.imgur.com/tyNkK.jpg) The nobles get to choose what they eat. White bread and meat and alcohol for every meal. The nobles are rancid with vitamin deficiency. Eating Plants? Plants! Those green things that grow in excrement!? What do you take me for, a lowly peasant? Leave my manor at once, thy foul reprobate! Down the corridor, fourth door on the left, up the spiral staircase, across the courtyard. . . . The noble diet is a more expensive version of the sailor diet. Sailors were historically plagued by vitamin deficiency that killed them or drove them mad. It took hundreds of years to find the cause. The peasants are perfectly healthy. They eat whatever they can get or grow. Meat is expensive. White bread is throwing out half the grain. The peasants eat brown bread and fruit and vegetables and potatoes and milk and cheese. They eat some meat during the winter but they eat other things too. The nobles are rancid with vitamin deficiency. The peasants are fine. **Edit:** > > I want a new disease to show up and spread rapidly which affects the nobility and leaders, but not the peasantry, setting up a situation for the feudal system to be overthrown. > > > What actually happened was a sudden frost killed all the rosehip plants in the country. Rosehip tea was the sole source of vitamin C for nobles. With that gone they start dropping like flies. They did not notice the correlation because (a) the frost also damaged other crops and (b) a weekly cup of rosehip tea is not missed. [Scurvy Mouth from Science Photo Library](https://www.sciencephoto.com/media/262418/view/mouth-of-person-with-scurvy) [Answer] ## Mad King Disease Whoops! It turns out that imported food (wine, meat, corn) is diseased this year. The wine has lead acetate in it - lead acetate tastes wonderful, btw, very sweet. Maybe the corn has some nasty alkaloids. Gruesomest of all, the meat has prions in it, leading the wealthy and powerful to go mad before they go dead. Peasants are protected from Mad King disease by being far too poor to import anything. ## STIs This year's plague's painful boils are extra painful because of where they grow. Soft tissues in dark places. Male peasants are protected because they don't get to have sex with duchesses. Female peasants are still mostly protected but not 100%. ## Addiction Speaking of imports, all this heroin from India doesn't grow locally. Or maybe it's a snorted drug. Did I mention peasants are too poor to import food? There's no way, none, nada, that Count Junky is sharing his stash with you, villein! [Answer] Chronic Wasting Disease is a prion disease in deer, a food traditionally reserved for nobility. Peasants just got their head chopped off if they hunted deer. But hunts were very big social events for nobility - nobles invited all their friends over. The men could join the hunt, but the big meal afterwards was for the whole family. This would be quite selective - perhaps a few cooks would get killed from scraps, but most peasants would never have eaten deer in their lives. And just to top it off, Chronic Wasting Disease causes difficulty in movement, and loss of fear of humans. The easiest deer to hunt are those that have it. But it takes a decade or two before the prion disease affects the nobles, so the infection can get quite out of hand. [Answer] **As you might imagine, there are no diseases that affect a class of people simply because they're members of that class.** Simplifying a lot, disease is environmental or genetic. An example of an environmental disease that would strike a "class" of people would be [Black Lung Disease](https://www.lung.org/lung-health-diseases/lung-disease-lookup/black-lung), affecting coal workers, often numbered among the working poor class. (But people don't get it because they're among the working poor, but because they work in the mines....) I believe what you want will be genetic, but before I go on, let's make something clear. I'm not talking about a genetic disorder. That would be something like autism. That's not a disease. It's not contagious. *And you need to think about that,* because all diseases are, by definition, contagious. I therefore assume you want something that's *contagious* (acting like a real disease) but that's unlikely to be found in the non-noble classes. Not that it isn't impossible, just that it's *improbable* for some reason that relates to nobility. Ah! That means we're back to *environmental.* There's something about *being noble* that makes one *more susceptible* to this terrifying disease! Let's call it "The Dreaded Gombuu." But before we head over to The Dreaded Gombuu, let's close that discussion about genetics. You need something that raises the odds of a noble dying from the disease considerably. So much so that people notice! They may even call The Dreaded Gombuu "the nobleman's curse!" In short, you need a disease with a *[genetic predisposition to the disease](https://www.cancer.gov/publications/dictionaries/genetics-dictionary/def/genetic-predisposition).* (See also [this](https://medlineplus.gov/genetics/understanding/mutationsanddisorders/predisposition/).) **And you don't necessarily want to explain it. In fact, you don't want to explain it.** I strongly recommend that you not get caught in the trap of explaining the disease or the genetic predisposition. Oh, you might choose a particular disease (e.g., Meningitis) and you may choose how the genetic predisposition came to be (e.g., inbreeding), but if you think about it, people in a roughly medieval world wouldn't understand either one of those things in the first place. What they would be reacting to are *symptoms* and *patterns.* And that's what you need to focus on. That's what would make your story cool: the clues are all there, *but not the answers.* So, if you want a disease that kills someone quickly, [pick one](https://www.news24.com/life/wellness/body/condition-centres/infectious-diseases/news/7-diseases-that-can-kill-you-within-24-hours-20171113)! The only thing that matters is that the symptoms and progression of the disease are good for your story. The top-7 contenders for The Dreaded Gombuu from that link are: 1. Meningitis 2. Flesh eating bug 3. Stroke (not contagious, but has enough environmental factors that the requirement can be ignored — hallelujah for red meat and sugar! Both of which nobles would have access to more than peasants.) 4. Cholera 5. Pneumonic Plague 6. Ebola 7. Dengue haemorrhagic fever But to be honest, it could be the common cold given the medieval era. A great many diseases we believe are irritating inconveniences were deadly back then due to bad hygiene, nutrition, and low understanding of basic medical practices. After that, pick how the genetic predisposition to that disease comes to be. The easy one is inbreeding, but it could also be a "genetic defect" from a particular ancestral bloodline (curse the Abrovonavich family from Transylvania!) or truly environmental as it may be a consequence of babies spending tons of time in the presence of something that only the noble would decorate with. I don't know, like asbestos but not as well known. All you need is something that can believably rationalize the genetic predisposition that can be casually mentioned in the course of a story. ("Margaret was well-known for the distinctive Abrovanavich eyebrows....") And that gives your readers the clues. Clues are good. [Answer] ### Autoimmunity from breast milk Noble ladies can't be expected to breastfeed their babies - they need to attend court, and wear the most fashionable new outfits, and can't be expected to be at the beck and call of screaming infants. Noble babies have wet nurses. Breast milk contains antibodies, which help protect the newborn while their own immune system develops. The antibodies work well when the milk-producer and milk-receiver are genetically similar - mother and child. But when the two are unrelated, there is a response not unlike transplant rejection - the noble child develops an inflammatory autoimmune response (a bit like coeliac disease), grows sickly and over time wastes away. Newborns abandoned in convents often suffer the same fate, depriving religious orders of an important source of new initiates. Not all are affected, though: it was not unusual for poor mothers to deliver in secret and leave the baby with the local monastery, in hope of being hired as a wet nurse for their own child. Why this has just recently started happening is unclear - probably, the immune response to some mild new pathogen that causes an autoimmune cross-reaction, like Epstein-Barr virus triggering multiple sclerosis. Although this disease does not affect adults directly, it soon causes despair and panic among the wealthy classes, who find themselves both personally bereaved and genealogically bereft of heirs. Noblemen start taking peasant concubines, who (if they breastfeed their own babies) have much better chances of producing healthy offspring. Noble ladies are incensed and desperate, and not infrequently vindictive - healthy concubine babies often getting poisoned by the official wife, such that it's impossible to discern the link between breastfeeding and health. The church is torn between pressures to stop such sinful behaviour and accusations of divine retribution. Cults arise promising protection from the new Tenth Plague, or declaring the End of Days. Noble families descend into internecine fights between desperate heirs. Marriages, and marriage alliances, break down. The aristocracy is in tatters. Time for a revolution. [Answer] **Diabetes** Nobles eat noble food. Noble food needs to be well presented, have a superior taste and be expensive! And the foods that have all required components to be noble food are **Pastries** [](https://i.stack.imgur.com/yrg6U.jpg) Sugar was very expensive in Medieval times, so they were only accessible to nobles. Therefore peasants were immune to diabetes. This has happened historically, see [the history of diabetes](https://en.wikipedia.org/wiki/History_of_diabetes). [Answer] Make it that the nobility derived from a recent wave of foreign conquerors that took over the region a few centuries ago. Think Indo-Europeans, Greeks, Romans, Polynesians, Bantu, Vikings, ... The greater the difference between the conquerers ancestral environment and their current environment the better. Either environment should have a selective pressure that created a genetic trait like [**sickle cells**](https://en.m.wikipedia.org/wiki/Sickle_cell_disease). The disease simply exploits this adaptation that is present in one population but not in the other or is mitigated by it. Maybe the disease is actually **malaria**. The locals used to inhabit a malaria region and developed a resistance. The climate shifted and malaria left the region. During this time the current nobility conquered the region. To get a stronger effect, have them set up norms against interbreeding. Look at the Indian caste system or the southern United States for inspiration. Now the climate has shifted again, the old disease returns and the nobility is dying in droves. [Answer] Make it a mystery, and keep it so. Do not *explain* anything. In medieval times, they probably even did not have any means to find out what caused it. All they know is what they saw, and survivors want to ensure it never happens again. It may even be promoted to some kind of religious belief that shall not be questioned. Some people may see it as a punishment from God, and even if not everyone believed so, fear of [painful] death is enough to motivate anyone. The fear might even be more powerful if no one knows the true reason. Maybe the peasants were least affected just because they were last to catch it. Who knows. Everyone [in the world of the story] may have their theories, though, and discussions, even fierce debates about the cause may be just as common as feuds over religion. Anyway, because peasants were those who survived, they just concluded that nobility was a crucial ingredient, and maybe the conclusion was accepted because they hated the noble and blaming them was satisfying. Thus nobility become a thing to avoid, like a taboo. It may even have occurred in the past, cause be long gone, no longer actually capable of affecting anyone, but people are still afraid. Besides, if they found out, they would learn how to avoid it, and nobility would be established again. There may even be a secret society who eg. poison those who gain power, using a rare poison known to only few, making it look like as if it is still going on. They may see themselves as servants of God. And, maybe the belief spreads like religion. Peasants in the neighboring countries turn against the noble, too, to prevent the same happening to them as well, even though it is in fact unnecessary. Even slightest sign of danger would ignite the "purification". Fear is a strong motivator without any factual cause behind it. The aforementioned secret society may be doing their work. [Answer] **Organ Specific Parasite** Only the wealthy are allowed to eat the "jewels" of the pig. The parasite that infests the pig "jewels" encysts itself there in a way that survives the brief cooking stage that's used to prepare the delicacy. The second stage of the parasite's life is to come to maturity in the body of the consumers, lay eggs throughout there body and then die. The maturation process and egg laying lead to massive diarrhea' and thus egg shedding. The castle middens are used to fertilize the fields reserved for the food of the nobility and some of that produce, when semi-rotten ends up in the pig's troughs. It's a virtuous cycle - parasites feeding on parasites! [Answer] There are a number of diet related diseases that attack the wealthy more than the poor. The first one I can think of is gout. This isn't contagious, and it isn't life threatening, but it could give you a starting point. In Asia, poor people were less likely to get beri-beri than wealthier people because they ate brown rice. Brown rice contains more of the vitamin B complex you need, but white rice was considered a delicacy. In Peru, poor people have eaten quinoa for centuries, while wealthier people switched over to rice. So if you could come up with a contagious disease that is deadly enough for you purposes, where the food eaten by the lower class provices some immunity, You get the result you are looking for. Incidentally, in England, the black plague created a labor shortage among farm hands that led to the breakdown of the feudal system of farming, and led to hired farm hands taking over. It doesn't have the characteristics you are looking for, but it was a partial factor in the end of feudalism. [Answer] In the real world, lead poisoning caused problems for people able to afford piped water. Maybe in your world, there's a material that's decorative and very expensive like gold, but toxic, and it's used for plumbing fixtures or tableware in the homes of the very wealthy. [Answer] Perhaps a combination of two things, both eaten. Please note, I am fabricating this out of real world things, but their interaction is not of our world. Potatoes are the staple of the peasants. Potatoes are cheap to grow and thus eaten by peasants and are a staple of their diet. The ruling class, nobles and royalty especially, don't eat potatoes, *because* they are a peasant food. Some of the military and clergy, especially the leadership, have forsaken potatoes as well. Unfortunately, there are a few peasants who also don't eat potatoes, because of a starch intolerance. These few are important. A new land is discovered, uninhabited. A new spice is discovered, that people call pepper. It's amazing. It's useful. It tastes GREAT! Everyone starts using pepper. There is a long lag (and deadly) sickness caused from ingestion of pepper. You guessed it, in all except those who have the starches. No one realizes they have built up a deadly amount of pepper, until all the royals, nobles, leadership and those few peasants who can't eat potatoes, all die. Someone, perhaps the hero, who is intelligent, trained, and able, discovers the key linking all who died together. The hero could possible be an apprentice chemist, who figures out the combination. If the story was to be 'realistic' or just a downer, then his girl/sister/wife/whatever is one of those who could not eat potatoes and dies. If it's to be more of a hero saves everyone (important) in the end, then his girl gets sick, and that was causes him to "figure it all out" and save her. Now, after everyone who was "supposed to die" does, he knows and tells everyone "DON'T ... EAT ... PEPPER!" People stop eating pepper. This last part is maybe needed, if in your story, those peasants who are elevated to royal status stop eating potatoes, because they are royals, and royals don't eat potatoes. They don't die, because the built up toxin from the peppers has all worn off. [Answer] Nobility is all about god-given privilege, social status, noblesee oblige, and most and above all incest. Lots of incest. Because nobles are so few, the genetic variability among them is quite limited. If they refuse to make children with the masses, then even more so. Over time all kinds of conditions related to genes become commonplace among their lineages. One example is King Tut, whose parents were siblings. This kind of relationship was not only common but also encouraged for Egyptian nobles. The [Wikipedia article on Tut](https://en.wikipedia.org/wiki/Tutankhamun#Health_and_death) has this passage: > > it has been theorised that Tutankhamun had gynecomastia, (...) Wilson–Turner X-linked intellectual disability syndrome, Fröhlich syndrome (adiposogenital dystrophy), Klinefelter syndrome, androgen insensitivity syndrome, aromatase excess syndrome (...). > > > Now imagine this guy ❤️❤️❤️❤️ing his own sister, which is also his cousin on the 0th degree, and who would have overlapping conditions. The only reason those guys maintained power was because every so often there would be one whose genetic conditions were limited to a combination of madness and ruthlessness. [Answer] #### Ciguatera like disease An idea taken from the [ciguatera](https://en.wikipedia.org/wiki/Ciguatera_fish_poisoning). A particular species, like might be a deer, is considered a delicacy. The places where it lives are turned into hunting reserves and the game ends mostly in the plates of noble people. These things happened often during the middle ages and in many countries the use lasted until the modern age. One day some merchants coming from a far place by mistake spread the seeds of a plant (or some bacteria) that produces a deadly toxin, but that animal can tolerate it. The toxin accumulates in the tissues and when the animal is eaten it accumulates in the tissues of the people and it takes a while to reach a deadly quantity. When people understand what is the source of the illness is too late. [Answer] **Peasants are the carriers.** Your disease is endemic within the community of peasants who have already contracted it, thus they have accured natural immunity to the disease. However, these peasants still carry the disease with them and are contagious. (But all of the peasants had immunity which is passed on to their offspring, so they will not get the disease again.) Because the nobility will attempt to minimize interaction with peasants (who they believe are beneath them) they will not catch the disease immediately, but once a member of the nobility spends extended time in the presence of a peasant, he might inhale one of the disease's pathogens. Once one member of the nobility gets this, the entire caste would be succeptible. (Because the disease is not based in a specific thing (animals, liquids, air, etc.) the symptoms and outcomes of the disease are all changeable and malleable.) [Answer] **Location, Location, Location** There are a lot of answers, but I noted one answer was missing: *location*. Often cities were built on hills, with the royalty and nobility living at the highest part of the hill, and peasants towards the outskirts, downhill of the rich and famous. Further, peasants were much more likely to sleep on a simple bed on the floor, while the rich slept on elevated beds. And of course, only the rich could afford a second story house. Normally, all those work to the advantage of the rich, but in this case, not so much. For whatever reason - gasses from a volcano, swamp gas, fumes from dead animals, natural gas leaking from a fissure - there are toxins in the air that hang like a pall over the city. The toxins are light enough that they don't fill the lower parts of houses, so the peasants sleeping on the floor aren't affected (and they spend most of their day outdoors, where the air is clearer anyway). The rich, sleeping in their high beds, in the most concentrated parts of the gas, die pretty quickly. This would be *very* fast. One day, everything is fine; that evening, there's an odd smell in the air, and a few peasants complaining about headaches. By the next morning, anyone sleeping in high beds or on second floors are either dead, or quite sick. A few servants living in their master's house would die, but most of the dead would be the rich. The peasants at the lowest outskirts would be fine, because the gas would pass overhead; the lower income shop owners would mostly be fine, as they wouldn't have fancy beds, but the richest merchants and nobility would not fare so well. The process could take a few days, slowly suffocating the rich, accelerating as they stay in bed. And after a few still days, the wind picks up and blows the deadly gas away, so there is nothing stopping the peasants from sleeping in the big, fancy beds of the rich. I realize this isn't a disease as such, but neither the wealthy nor the poor would realize that, and it's effects will be much faster and much more severe compared to diabetes, gout, or even smallpox. [Answer] Inherited susceptibility of invading conquerers. Example: The rulung class of Egypt after Alexander were the Ptolemies. They had no Egyptial ancestry, they were Greek, and they intermarried to preserve their line. So we can imagine your milieu - maybe the whole planet - is ruled by invaders, who came from somewhere else and interbreed exclusively. So if a nasty plague crops up they would be carrying the genes to make it deadly and the rest of the population just gets a rash. Peasants who are by-blows of the aristocracy, and the odd nobleman whose grandma liked a bit of rough provide a few outliers. [Answer] How about modifying an existing disease: Typhus. Vector: Body lice. It was a major issue in cold climates that wore a bunch of clothes, it wasn't nearly the issue in warm climates that didn't. Clothing is a symbol of status, peasants are forbidden to wear it. (They can wear cloaks against the cold, but nothing that conforms to the body.) Typhus does not exist in this land. The zoonotic jump happens, but this is a version that's considerably more deadly and has a long incubation period. It's the warm season so the peasants are naked. The classes you want to kill have clothes and thus lice and catch it. The ones you want to save are naked, they have few if any lice, they survive. (And, no, I'm not being unreasonable in postulating a society where peasants do not wear clothes. The idea of indecent exposure is pretty much modern, clothing used to be expensive, for the poor to be working naked was not strange. I'm only taking reality a bit farther in this scenario.) [Answer] Diabetes, smoking/expensive drugs, hemophilia, genetic disease due to inbreeding.. they just came out with a story about covid saying that if you get a lot of exercise you will not die from it.. ]

[Question] [ Set in a zombie apocalypse world somewhere in Chennai, India. News report shows an estimated 90% of the population here has turned into zombies overnight, soldiers setup a human chain perimeter blockade and a kill order has been given to terminate any trespasser with extreme prejudice. Those infected show aggression and violence even unprovoked, they seem to lose their mind and will even attack family members and friends. They are alert to sounds and study shows they could complete a marathon in 2 hours. A zombie bite is considered to be extremely contagious and any bodily contact must be avoided at all costs! As an escape on foot seems impossible. What kind of land vehicle could the survivors drive to reach safety in the neighboring city from a curious horde of zombies as well as stray bullets from SAF Carbine 9mm 2A1? Retrofit must be realistic and no military vehicles are allowed. I'm thinking of an SUV (fuel type: diesel) and with metal drain grates tied all over the chassis including the windscreen. Would it work or should I hijack an ambulance instead? [Answer] Frankly, I would not bother with cars or trucks. **Use a train!** Any large diesel engine, or several combined, with a snow plow up front. As a bonus, you can add waggons for any goods you may want to carry (such as extreme amounts of ammunition and fuel for your flamethrowers), and most of all you can navigate without a problem: you know in advance where the tracks will lead. The weight of the train will give it all the momentum you need, and I doubt it could be possible for the zeds to stop or even overturn it. This kind of mass will give you enough speed that the zeds will be unable to pursue you. That means, unless they anticipated your move, you will be out of danger as soon as you leave the city, and should not need to prepare for any further hindrance of your escape. [Answer] So it needs to plow through zombies (other things a plus), and hopefully survive stray glancing shots from rifles. Has to be realistic as well, and nothing military. I do believe Myth Busters has a solution to your little problem: a dump truck fitted with a heavy reinforced bumper. [Take a look for yourself](https://youtu.be/U4qZTdMOJBk?t=37):  *From youtube* If your story is set in the northern areas of the world, a snowplow truck could work well. [Answer] May I interest sir in the [Paramount Marauder](http://www.paramountgroup.com/capabilities/land/marauder/). [](https://i.stack.imgur.com/ELeHS.jpg) It can take 10 people, is bomb proof, mine proof and described as the **world's most unstoppable vehicle**. You will get where you want to go! There's also a good infographic for other vehicles! [](https://i.stack.imgur.com/DffV5.jpg) [Original Source](https://www.whocanfixmycar.com/blog/7-vehicles-to-survive-the-end-of-the-world/) [Answer] **Dump Truck with plow or forks** [](https://i.stack.imgur.com/ebjpC.jpg) This will surely plow through any horde of zombies. To fortify the dump truck, I would weld on an exterior wall surrounding the frame of the truck fashioned with sharp objects to cut the zombies, and use run-flat truck tires. With the bed in back, you can install in weapons of your choosing, fuel, supplies and maybe add in a few extra spare tires just in case! And why not have a ladder? In the event your zombie plowing machine breaks down (which it will eventually since you are to plow virtually 90% of the world's population of zombies) and you are surrounded by a horde of zombies, you can use a ladder if the truck broke down near a building to escape. [Answer] None of these other vehicles being posted will be available in Chennai. Also, Indian SUVs are small and the ambulances are quite flimsy. In your situation, your best bet would probably be a large Tata: [](https://i.stack.imgur.com/GXs3L.jpg) Most of the ones on the road at any given moment are roughly 40 tons overweight, so you don't have to worry about anything stopping you. They're made of solid steel, so just keep your head down if shots are fired. Anyone possessing such a weapon in India will be highly trained in its use, so I wouldn't worry too much about stray bullets. I would head north on the Guntur-Chennai freeway. If you can make it to Vijayawada, the Krishna River would make a very defensible natural barrier. [Answer] Combine Harvester[](https://i.stack.imgur.com/IHiO4.jpg) Hoard of zombies? What hoard of zombies you'd say while festering body parts are flying all around. It may need a few modifications to secure the cabin a bit better but other than that you're good to go. [Answer] I think the combine was a decent idea, except that combines aren't really meant to chew through stuff as tough as bones. It would probably work for a while, but I'd have some misgivings about its long-term survival. For roughly the same idea, but considerably heavier duty (not to mention faster) I'd consider the kind of snow-blower used to clear highways and airport runways: [](https://i.stack.imgur.com/P4zT1.png) Or: [](https://i.stack.imgur.com/PYLsm.jpg) To give some numbers: this one (the second) has a 2000 HP engine, and is rated for chewing up and spitting out ten thousand tons of snow zombies per hour. You'd probably want to weld on a few steel plates to act as armor, but required modifications should be pretty minimal. [Answer] Dude! Go big or go home as zombie food! Go with the [BELAZ 75710](http://www.skyscrapercity.com/showthread.php?t=1663257): [](https://i.stack.imgur.com/jnakB.jpg) Definitely want to modify so the front ladders can be raised, but with that height, top speed of 64kmph and the thickness of tires, I think you could make it out pretty safely, unless the zombies were as good with pole vaulting as they are with marathons! Also, you can carry quite a large number of people in one trip. Large-scale mining operations are where these huge dump trucks are used, so if survivors can get to a nearby mining operation, they could commandeer one. If you can afford it, I highly recommend picking one up, just in case. [Answer] I'd go with a bulldozer. You'll need to install extra fuel tanks and weld a protective framework around the tanks and any vulnerable components. You'd wind up with something like the [D9 armored dozer](http://www.military-today.com/engineering/caterpillar_d9.htm). You'd want a certain amount of thought to go into your choice of protective material, and you'd definitely want to make sure you tested all your welds, but other than that I don't see a problem. One of the enduring lessons of military history is that steel is much stronger than flesh. 1/4 plate, especially if angled, should be proof against 9mm. Slow but steady wins the race, and in George Patton's words, "They'll be grease for our treads." [Answer] Why not a monster truck? It won't have a crazy amount of built in cargo space, but why drive through them when you can drive over them? And it'd generally be a decent all terrain vehicle for those ill-maintained post apocalyptic roads. [](https://i.stack.imgur.com/eFk4o.jpg) [Answer] If you're not in a hurry and just want to be sure you can destroy without being stopped i would suggest using an excavator like the Bagger 293 . Would take forever but could move through a whole horde of thousands unhindered, When driving you're very high so they can't get to you, you can plough through them, and if there's no road to where you want to go, you can just dig one anyway! [Answer] [The M4 Dozer (aka Sherman Tank)](https://en.wikipedia.org/wiki/M4_Sherman_variants) There has been many variants to the M4 Sherman tank, the large dozer blade in front with it's massive motor should be able to plow through any mass of zombies. If you get bored with that the T2 Sherman can provide with some fun and carnage, originally designed to trigger mines, but i assume it could be a blast against zombies! [](https://i.stack.imgur.com/B3rdE.jpg) The best part is the Sherman is decommissioned since eons ago and can be found in surplus stocks around the US, (and a few in EU that the us left behind), restored by passionate people. So it is running as if it was new and not impossible to get your hands on. The reason i picked this compared to @WhatRoughBeast 's suggestion with the bulldozer, was i assume that the zombies are unintelligent and would have a hard time opening the hatches. [Answer] Going on the theme of giant airport vehicles, an [Oshkosh Striker 8x8 Firetruck](http://www.oshkoshairport.com/ARFFTrucks/NewStriker/Striker4500) would also work well. You would also have a strong watercannon to shoot if you need it as well as some foam. [](https://i.stack.imgur.com/iLlZF.jpg) However, you might need to armour it a little bit, so some system like the M270's "cockpit" would work on the 8x8. [](https://i.stack.imgur.com/4CwCa.jpg) Anyways, the end product will probably look more or less like [a Stryker IAV](https://en.wikipedia.org/wiki/Stryker) with waterguns. [](https://i.stack.imgur.com/PHBFI.jpg) [Answer] If you consider plowing there are specific scenarios you should adress: 1. You will not move at full speed, probably not faster than walking. So Zs climbing on the vehicle will be a real issue. While weapons might take care of the first 100 on the long run it might be better if the vehicle wouldn't expose parts to climb on. 2. The vehicle needs to push it's way through the horde. So its movement is less driving but more pushing through a gelatinous liquid. It will need serious horsepower. 3. Near visibility will be bad. The odd splatter of blood and gore will cover windows. It would be good to have a way to clean the windows - or get rid of the glas and just have grates for protection. 4. Farer visibility will also be problematic - the horde will cover the ground. Hiding all kinds of obstacles - till you hit them. It might help a lot if one could come up with a way to disperse the horde. Also it is a must that you have somebody elevated over the horde just to navigate. In a regular car you will lose orientation immediatly as view in all directions will be blocked by Zs. 5. The ground will be covered by bodies, gore and stuff. Very easy to get stuck or hide the odd spike that might pierce a tire. Definetly large wheels for slippery ground would be advisable. 6. It may be a risk that the vehicle might topple by a push of the horde - or just an unlucky hole in the ground. Ideally the vehicle would be rather wide and stable. Looking at this I would start by adapting a plot truck. It should fullfill many of the requirements. Just replace the windows by grates and cover the easy to climb parts with flat slippery walls. On the professional side riot control vehicles would be equipped perfectly (they are not considered military - though might be against your intentions). But have look what they build into them for ideas [1](http://jinomotors.com/sub/sub02_01.php?idx=1) [2](http://www.carmor.com/system-division/riot-control-vehicles/) [3](http://www.isbi.us/nyala.htm) All that said - given that Zs mass at one place means there are other places where they are sparse. It would be less effort finding a path around them than upgrading a vehicle. [Answer] Perhaps a gas-turbine powered M1 Abrams would provide the instantaneous power that is necessary to negotiate the apocalypse and provide unrivaled safety to its occupants. The artillery is merely bonus [](https://i.stack.imgur.com/9cHVn.jpg) [Answer] Another possibility could be a [valuables armored car](https://en.m.wikipedia.org/wiki/Armored_car_(valuables)): [](https://i.stack.imgur.com/nzPhE.jpg) Readily available in most cities, but maybe not as good for mass transport of many survivors, or rolling over huge piles of zombies. [Answer] I'd say your first problem is not the zombies, but that ALL the tank stations are....permanently closed. Also a plain tanker will make you a sitting dunk unless it's modified to eat its own payload. So, with the caution NOT to smoke, I gladly steal this finished product to present to you: Mad Max's [***The War Rig***](http://madmax.wikia.com/wiki/Tatra_T815_%22The_War_Rig%22). [](https://i.stack.imgur.com/EkiB3.jpg) There are two left up for grabs after filming ended. You just have to find them. [Answer] The simplest modification you could make to a land vehicle, maybe even a mid-size car, is a cow catcher on front. The real fear is being bogged down by the bodies as obstacles, which could seriously hamper the movement of a small car. The cow catcher would just push whatever's in front of the car to the side, the car hopefully not losing all its momentum. [Answer] A large 6X6 dump truck would be ideal. The body is too thick to be vulnerable to most small arms. The ground clearance and massive tractor tires will easily roll right over any group of zombies. The drivetrain is designed to climb over extremely rough terrain. Unlike the harvester or the bulldozer, it can even get up to a pretty good speed depending on the model. Put a couple manhole covers or whatever steel plate is available over the lower half of some of your windows and roll wherever you want! Bonus: tons of cargo capacity, so you can store food, water, and fuel cans in the back (or boulders, if you really want to). [Answer] Its India. There is only one choice. While its lost its cachet, its basically *the* indian vehicle. While british in origin, its earned its place in history, being the vehicle of choice of politicians, and the standard taxi for many years. [](https://i.stack.imgur.com/KDAoY.jpg) Its the [Hindustan motors ambassador](https://en.wikipedia.org/wiki/Hindustan_Ambassador). I'll carry 6 people through the worst roads India can offer. You would probably want to go for a dual fuel conversion, running off either CNG (so you can scrounge a standard gas cylinder) or petrol. As for armour? Rebar or rebar mesh sounds good, though if you could find yourself a decent workship and have the time. A cow catcher sounds good. I'd think cast iron "dosai kal" or tavas would make improvised bullet proof armour, [Answer] A (somewhat) real world example: [2 families fled from east Germany](http://archives.chicagotribune.com/1962/12/27/page/3/article/8-crash-thru-to-freedom-in-armored-bus), breaking through 3 barriers and surviving machine gun fire, in 1962. Their vehicle was a 20 year old bus built in 1941. [](https://i.stack.imgur.com/MQiru.jpg) (Image source: <http://fotoarchiv-alex-waidmann-berlin.de/s/cc_images/cache_2155731002.jpg>) So you don't really need a high-tech vehicle, which might not be available during a zombie apocalypse anyway. The bus was retrofitted with steel plates and steel tire guards, and a snowplough to clear the nails from the street that they expected to be at the crossing - this should clear through zombies as well. A German source says [the steel plates were made from 9 mm well covers, and the bus had (only) 150 hp](http://www.spiegel.de/einestages/hans-weidner-und-seine-ddr-flucht-im-selbstgebauten-panzerwagen-a-947851.html), Something like this, or better, should be available almost anywhere. [Answer] Lots of going big here. Much Ahab. But zombies are like Moby Dick. No matter what, Moby is bigger. I will go with Starbuck, and take a page from Michonne's playbook. [](https://i.stack.imgur.com/adhpE.jpg) Zombies do not attack other zombies. So: a car with giant gas tank in the trunk. Zombies are tied 2 deep facing out all around. Maybe they have castor wheels nailed to their feet. Also tied sitting on top, and sitting on the hood and sitting in the bed. Windows have one-way sunshades. No armor. No weapons. No radio dang it! I am going to unplug that radio just be sure, because it is going to get boring. We will bring lots of nice quiet books. Nothing to see here. Just a humble heap of zombies, moving down the road with all the other zombies at a steady 2 miles per hour. [Answer] From the real world: [](https://i.stack.imgur.com/7J1z0.jpg) This is what happens when corrupt pen-pushers in the land zoning department decide to make someone's life hell, and it happens to be the wrong someone. He armored a bulldozer with metal plates and just razed a large part of the town. See destruction in video: <https://www.youtube.com/watch?v=5zRsmcIaB1Q> Sturdy, unstoppable, zombie-proof, bulletproof, but probably too slow. [Answer] Can I suggest you take some inspiration out of the Syrian's armored cars? They were made by people strapped for resources and without access to much else then you would find in a common garage. [](https://i.stack.imgur.com/jNa0e.jpg) [Answer] Can I go all sci fi and fantasy here, because I found the perfect vehicle. Bagger 288 ghost rider version. Excellent speed due to the ghost rider! Has a wicked weapon to plow through zombies! Is on fire! Tell me! Who can stop this beast? If no sci fi and fantasy, I think the bagger 288 is still a pretty good vehicle. Just need a few adjustments to build a bunker on top and a fuel truck behind me and we're good for days. ]

[Question] [ **What would cause a nuclear power plant to break down after 2000 years, but not sooner?** The setting is a society in a dark age. Their ancestors were considerably more advanced than earth currently is. The society has been stagnate at close to the tech levels of modern earth since. For the past two millennia, they have maintained the existing power plants, but cannot create new ones. Schematics for everything in the plant mostly still exist, but are written in dead languages spread across ancient computer systems that no one understands well. Now one of the most important plants has broken down. **What part of a power plant could work for 2000 years, but stop at that point?** My initial thought was that the uranium was depleted. But Uranium 238 and 235 have half-lives far too long. Uranium 234 only lasts ~200K years, but that still is too long. Then I considered some mechanical or electronic failure, but it can't be something which would happen in the first few decades, or the plant managers would have a recent record of how to fix it. **Specifics about Power Plant:** The underground plant uses a super material 'durium' that is near indestructible. The ancestors used durium for any non-flexible permanent solid in the plant, such as: -The walls, ceiling, and main structure -The tube holding water that gets boiled and turbine sticking into it -The water cooling tubes The fuel is of some kind or quantity that lasts longer than 2000 years. Bonus points if you can think of a reason why all the power plants would break down over the same century. [Answer] ### Software licencing. Software for your automated maintenance and refuelling robots was under a 999-years licence (similar to common law permanent lease) . After it ran out, the licence was automatically renewed for another 999 years, payment pending. As no payment was received during that time the licence lapsed, and the plant went into a controlled shutdown until all contractual obligations are paid in full. Which would be difficult because the old banking system is now defunct as well. [Answer] Remember Y2K? Software is hard, programmers are human. If you want your readers to know exactly what went wrong, you can babble at length about data types or speculative branching or null references or race conditions. But I propose that if your characters don't know what broke or how to fix it, then maybe your readers shouldn't either. The software has a bug, and the power plant isn't power planting. To keep it vague but dangerous, the problem could be with a safety system. An engineer finds a single screen with the message: > > Error 32801: An unsafe condition was detected and the reactor has been automatically shut down. *Do not attempt to restart the reactor.* > > > [Answer] You don't need any special materials to make a reactor last a long time. The [Gabon natural reactor](https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor) consists of uranium deposits in sandstone. Approximately 2 billion years ago they went critical. This is because U235 has a shorter half life than U238. So 2 billion years ago there was relatively more of it, and it could go critical with natural water moderator. The deposits would operate at a few kilowatts for a short time, perhaps a half hour. Then the water would boil, decreasing moderation. Then the reactor would shut down and cool for about 3 hours. This cycle continued until the fuel was depleted. The sandstone then sat for 2 billion years until it was discovered in the 1970s. This 1/2 hour on 3 hours off cycle continued for between 100 thousand and 1 million years. It was busy [breeding](https://en.wikipedia.org/wiki/Breeder_reactor), so U238 was getting converted to Pu239, which supplied additional fuel. Interestingly, when the reactor finally shutdown due to fuel depletion, the remaining Pu239 eventually alpha decayed into U235, which somewhat masked the depletion of U235 that originally tipped people that something was up in Gabon. This has inspired a lot of designs for nuclear reactors. None has been built as yet. The idea is, you would have a block of stone about 8 or 10 meters on a side. You pump cold water in here and get hot water out there. It breeds new fuel until it goes far enough that it can't usefully do that any more. Depending on the design and the use load, it could in principle be made to last for 2000 years. Though it's far more likely to be designed to last 40 or 50 years in the first design, since that will tend to allow for new designs later. You pump cold water in. If you pump it in at the wrong temperature, high or low, or too fast or too slow, or at too high or low pressure, the reactor just stops. And you get boiling water out. You then run a turbine. So if these things were mass produced in a factory, then shipped all over, they could be coming to the end of their useful life. They were all designed to provide the same power for the same time. Subject to a few of them being used slightly less than the others, they will run out of fuel at about the same time. [Answer] This may not be what you were originally thinking, but perhaps some sort of natural disaster strikes which disables the plant. Even if the structure of the plant is made of an indestructible material, it may be vulnerable to less direct damage such as flooding. For a real life example, we can look at the Fukushima-Daiichi accident which happened in 2011. An earthquake struck off the coast of Japan, and while the earthquake did not damage the structure of the plant, the resulting tsunami from the plant caused flooding of key components which eventually led to a meltdown: > > On detecting the earthquake, the active reactors automatically shut down their fission reactions. Because of the reactor trips and other grid problems, the electricity supply failed, and the reactors' emergency diesel generators automatically started. Critically, they were powering the pumps that circulated coolant through the reactors' cores to remove decay heat, which continues after fission has ceased.[10] The earthquake had generated a 13-15 meter high tsunami that arrived approximately 50 minutes later, which over-topped the plant's seawall, flooding the basements and disabling the emergency generators. The resultant loss-of-coolant accidents led to three nuclear meltdowns, three hydrogen explosions, and the release of radioactive contamination in Units 1, 2 and 3 between 12 and 15 March. ([Wikipedia](https://en.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disaster)) > > > [Answer] # Transmutation of the water Both fission and fusion reactors produce copious quantities of neutrons. In fission reactors, the "fast" neutrons are slowed by moderator so that, ideally, most of the split another fuel nucleus. Fusion reactors (at least current conceptual designs), the neutrons escape the plasma, then thermalize and capture in the surrounding water bath, which produces the heat to run the turbine. A huge engineering concern is that some of those neutrons capture on your structural elements and transmute them, leading to eventual material failure. Your structural elements are all made of durium, so presumably they are immune to neutron degradation. But suppose the designers use a closed-loop water system. The designers probably didn't think thousands of years in advance, and *they* would have known to just replace the water eventually. Over time, the water will transmute, in two potentially harmful ways: ## 1) Hydrogen eventually turns to He-3 The hydrogen in the water will first convert to deuterium, then tritium. Tritium naturally decays to He-3, which will eventually escape the system, unless your durium also contains He better than any material we have. Even if not, you'll eventually convert enough of the water to gas that it won't cover things anymore, and either you overheat (fission) or no longer transfer power (fusion). In fusion's case, this would be a gradual decrease in efficiency, whereas for fission, gradually rising heat could lead to a sudden failure at some point. This is easy to notice if the descendants can view the water volume, and just top it off every now and then, but maybe the close-loop water system is not visible to inspection. ## 2) Buildup of HF Let's say the descendants notice that the water needs topping off every now and then, but don't ever empty the whole tank. The oxygen in the water will eventually capture enough neutrons to become O-19, which decays into F-19. The fluorine will bond with hydrogen to become HF, hydrofluoric acid, which is one of the nastiest substances you can dream of. Eventually the concentration will build up enough to be a relatively high-strength acid. Maybe durium isn't quite indestructible, and HF is one of the few weaknesses. Or some part of the water system is made of something else (e.g. glass or fused silica, like a viewing window). This sort of defect would affect all power plants on similar timescales (assuming the volume of water per power capacity is approximately constant, which seems reasonable), although the point where some component, weakened by the HF, eventually gives way will be variable. [Answer] In Asimov's *Foundation* series, the Empire's nuclear power stations were controlled using vacuum tubes and relays. Out-of-universe, this was because solid-state transistors had not been invented when the story was written. In-universe, this might have been for lack of solid-state transistor technology, or because vacuum tubes and relays are easier to understand, make, and replace than bits of integrated circuits. Vacuum tubes and relays can also be designed to handle much larger currents, voltages, and power flows than integrated circuits. In-universe, the Empire lost the technology to be able to replace even "a single quartz D-tube". If enough of those essentially-glass vacuum tubes were physically smashed, an entire nuclear power station would be rendered out-of-commission. In real life, expensive vacuum tubes have cathodes with a limited life. For example, the travelling wave tubes on weather and communications satellites typically have a design life of 12 or 15 years. The limiting factor is the amount of metal in the cathode. (This does not have to be the limiting factor. Some tubes are predicted to have cathode lives of hundreds of years. But satellite parts have strict mass budgets. Every tenth of a gram counts, so only a modest amount of extra cathode metal is included.) When the tube is operating, the cathode is heated to a high temperature, and the metal slowly evaporates at a very predictable rate. The satellite will need to be decommissioned or replaced before the metal's reservoir runs out. The vacuum tubes in the control system of the original poster's power plant were engineered to have a consistently long life. But eventually the cathodes will run out of metal, and the vacuum tubes will stop working. Many vacuum tubes will have experienced similar times at operating temperature, so that they fail after a similar length of time in all of the power plants. As [gbjbaanb](https://worldbuilding.stackexchange.com/users/2029) pointed out in a comment, the consistently long life does not need to be 2,000 years. "All you need is a box of replacements and instructions of what to do to fit them... after 2,000 years the priest-tech goes to find a new one and discovers the box of spares is empty. And, over the same century - all plants had only a similar number of repalcement parts, so will all fail around the same time, particularly if parts were shared out." This scenario is especially likely if the last vacuum tube factory was asked to make a large number of spares just before it went out of business; this would have both extended the life of the factory by a few years, and made it much more difficult to start a business to replace the factory. In real life, the processes to make cathodes for high-efficiency vacuum tubes are notoriously finicky. It is very easy to accidentally contaminate the cathode material while manufacturing it. This is part of why there are so few companies capable of making space-rated vacuum tubes, and why the number of such companies is decreasing. In the original poster's scenario, the vacuum tube manufacturers could well have been out of business for centuries. A great deal of technology would need to be reinvented to replace the failed vacuum tubes. Or the characters could try to get by with much more primitive vacuum tubes, and risk reliability problems in their nuclear power plants' control systems. For that matter, the original vacuum tubes might be much more space-efficient and energy-efficient. There might not be enough room or available "conditioned" power to install a jury-rigged control system. To get an idea of how much technology might need to be reinvented, Chapter 5 (pages 47 - 102) of [Scott Gilmour](http://www.asgilmourjr.com)'s *[Principles of Traveling Wave Tubes](https://rads.stackoverflow.com/amzn/click/com/0890067201)* provides an overview of "Cathodes", with 30 scientific references. Some of the other chapters discuss "Electron Guns", "Reliability", and methods for modulating / using the outputs from "Electron Guns". [Answer] **Ran out of control medium.** While your reactor fuel may last a really really long time, those reactions are controlled by cadmium, hafnium, enriched boron, salt, or some other neutron absorber. As these materials absorb neutrons from the fuel, their ability to hold "extra" neutrons decreases. It may be that the fuel in question can last much longer, but the designers only engineered the control medium to last 2000 years. Once the control medium becomes too saturated or degraded, it will no longer be able to slow the rate of fission resulting in an eventual critical meltdown. They would all break down at the same time because the amount of control medium was measured out for a 2000 year lifespan as per the national safety regulations for nuclear power plants that were in place when they were designed. [Answer] # BUGS! Not software bugs, but the icky kind that can get into those cracks and start chewing on those high temperature super conductive wires. Once a few electro magnets quench, you can no longer sustain the *fusion* reaction. (Fission reactors won't last half that long) [Answer] Despite the described state being a stagnant society, the people's knowledge and skill would have continued to degrade even very slowly until finally there is no overall concern or ability to maintain the power plants any longer. Why? Because most technology that is dependent upon the power plants would have long since failed. If there was no motivation to re-learn necessary knowledge and skill as a society before now, then their long-lasting apathy has simply turned into contentment with basic life as old technology fades away. A burned out light bulb that is no longer manufactured and costs too much money is never replaced, so they get used to a more natural daylight cycle... which is just an example/metaphor of all the other old tech. Pervasive computing devices like smartphones would have stopped functioning centuries ago. About the only thing left to power would be incandescent bulbs and basic motors. In 2000 years of barely being able to maintain the power plants which were designed for long-term robustness, all of the devices and systems that relied on those power plants were far inferior in terms of material quality and longevity. New electronics would have ceased to be produced due to manufacturing failure long before 2000 years. Satellite systems would have failed, thereby rendering many dependent technologies nonfunctional. Basic maintenance as suggested in the question details is simply not enough to continue manufacturing necessary tech components any more than the nuclear science which has become obsolete. If a society cannot handle nuclear science/engineering, then they can't handle necessary material, quantum-mechanical, atomic, electrical, chemical sciences/engineering for all other tech. Eventually their maintenance would simply be insufficient, especially due to depleted stores of necessary components. If only a small number of individuals had continued their education and maintained books and past knowledge, enough to prevent the deterioration of all the other necessary tech surrounding the plant, then certainly the necessary nuclear-science knowledge would also have been maintained. In summary, **2000 years of stagnation for only maintaining nuclear power simply would not be stable**. Either they would have re-learned necessary skills to maintain and replace it, or it would necessarily fall even further past the ability to maintain it. [Answer] ### Coastal erosion A nuclear power station needs a ***lot*** of water for cooling. Almost all are on the coast for that reason - the warm water returned can't significantly warm up an entire ocean. The problem is that coastal erosion is also a thing. Over 2000 years, the shorelines of much of the world have changed fairly significantly. Locations for power stations are chosen for stability, of course. However a change of currents could easily start to dump extra sand and silt around the power station, and with a not-properly-industrialised society they may well not able to keep the water intakes clear. [Answer] **The AI that instructed the maintenance workers how to repair faults finally developed a fault itself.** Your dark age society could hardly be expected to maintain such an advanced piece of machinery in good working order without assistance, after all. Perhaps the AI was always part of the power plant's design, though it might have originally been only intended to supervise maintenance (to reduce the risk of human error) rather than to be in sole charge of instructing the maintenance teams; or perhaps it was a last-minute effort by a society that already realized it was falling into a dark age. Assuming there was sufficient redundancy in the AI systems, it would even have been able to instruct the maintenance teams how to repair faults in its own systems, as would inevitably have happened many times over the centuries. But sooner or later, there was bound to be a fault in a non-redundant component, or multiple faults that took out too many components too quickly to repair in time. After the AI failed, the power plant itself might continue to run for some time, so long as the only mechanical failures were ones that the maintenance team had encountered before. But eventually something new would go wrong, or society would gradually lose the knowledge of how to perform more than very basic maintenance; once the AI was no longer available, it would likely only take a few generations for this to happen. --- Since you would like the problem to affect all the power plants over a relatively short period, you might wish to suppose that there was only a single AI that was supervising all the surviving power plants. Once it failed, the power plants would start failing, any time between a few years or a few generations later. (In the scenario where the AI was always part of the design, this might have been a cost-saving measure; this would not be unreasonable if it was only meant as an additional precaution against human error rather than as an essential part of the system. In the scenario where the AI was created as the society fell into a dark age, they might have only had the resources to build a single AI. Or perhaps they intended to build several, but society collapsed before any additional AIs could be completed. Or perhaps all but one of the systems were cannibalized in an unsuccessful effort to keep society afloat.) [Answer] The plant, being built by those ancient geniouses of the past, was of course self-repairing. It has small robots (either nano bot or something bigger), that would check the whole plant regularly, immediately fixing any issues and counteracting deterioration. Now those robots cannot (of course) create matter. So they were supplied with stocks of the basic materials, from which they could build anything needed. And those materials, sadly, ran out some centuries ago. Despite from not knowing anymore how to resupply them again, there is the issue that none of the materials can be produced in high enough quality anymore, as so much knowledge was lost. So even if the robots got fed the new supplies, they would reject it, as not suitable for fixing a plant. (I hope you read the foundation by Asimov, if you are interested in long lasting (or not lasting) societies?) [Answer] I suggest you read or watch "City of Ember". It might give you idea. In the movie/book there is a generator, made by "The Builders" (ancestors), that has broken down. Simple reasons: * The generator has lasted for over its expected lifetime, * Lack of knowledge/tools to properly maintain the generator [Answer] **It's a breeder reactor.** Reactors can normally operate continously for periods around a year before refuelling. In most reactors, that is a complex operation taking months, involving handling highly radioactive spent fuel rods, i.e. big headache. Some 1970s reactors (AGRs in the UK) were designed for on-load refuelling, without shutting down, but in practice most of them still shut down to refuel. Trend since then is to move towards reactors with a service life of decades *without* refueling - for instance on submarines where there isn't much room to access the reactor in the first place. So, refuelling is such a huge hassle ... even today ... people avoid it if possible. Now, based on the premise in the question, you could imagine a society perfectly capable of servicing external equipment like steam plant - as the Victorians could - but without the ability to open the core and refuel it. (Indeed, perhaps the core is fully sealed with no designed access). All we need to get there, is a way to fuel the reactor for 2000 years instead of 30. Enter the breeder reactor. Only 0.7% of natural uranium (the U235) is fissile; the remainder (U238) is not. However, during normal operation, some of that U238 is converted into Plutonium, which is also fissile, and by tuning the flow of neutrons, you can control the rate of that conversion. Pu "burns" less efficiently, but it's usable and there are mixed fuel and Pu burning reactors operating today. Thus you can extend the operational life until not only the U235 is gone, but most of the U238 has been converted to Pu, burned, and gone. Fiddle around with the numbers, and you can extend the working life from 30 years (U235) to millenia. For example, if the original fuel was enriched to 1.5% U235 and burned in a fairly neutron-efficient reactor, slow enough to last 30 years, there is about 66 times as much U238 waiting to be converted to Pu. And so on, until after 66 times 30 years, the U238 is exhausted. The reactor simply stops because it has run out of fuel, and society has had enough of refuelling accidents and waste disposal centuries ago. (A real nuclear scientist could nitpick many reasons why this won't work exactly this well in practice. But in principle...) [Answer] The concrete will decay after a couple of millenia, assuming they were able to repair/replace corroded metals. Foundation of the plant and the construct of the dome would irreperably fail. [Answer] Durium lasts for millions of years in normal circumstances... but just a couple of thousand years of hard neutron radiation makes it brittle in the parts closest to the nuclear fuel. <https://en.m.wikipedia.org/wiki/Neutron_embrittlement> Some of the atoms of the unobtainium matrix have been dislocated by high energy neutron collisions, weakening the crystal structure, and the nanotube lattice reinforcing it is riddled with nano-fractures. That durium just isn't as durable as it used to be. Because of this, the structure of the building is still very sound, but that turbine is going to break and the pressure vessel could rupture if you look at it sideways. [Answer] I vote for fuel exhaustion. Just because Uranium has a long half-life doesn't necessarily mean an unreplenished supply would remain sufficiently radioactive over 2000 years to be able to generate enough heat to keep putting out usable power. [Answer] > > My initial thought was that the uranium was depleted. But Uranium 238 and 235 have half-lives far too long. > > > Fuel depletion of a reactor is not based on the half-life of the fuel. Half-life determines how long it takes for spontaneous decay to occur. But a fission reactor does not rely on spontaneous decay. It creates a situation where there are alpha particles and free nucleons bouncing around. (An alpha particle is two protons and a neutron; basically a helium-4 nucleus.) When an alpha particle impacts a uranium atom, it creates a plutonium atom (plutonium has two more protons than uranium). The plutonium atom has a much shorter half-life. Nucleons cause different reactions, but the basic idea is the same. Particle meets fuel and forms a less stable atom. This is why they talk about moving fuel rods in and out. They put the fuel rods inside a lead shield to protect them from the particles bouncing around. They pull them out to expose them to the particles, increasing the chance that they will start a fission reaction. If the reactor is in active use, even if it is less use than that for which the reactor is intended, the reactor can simply run out of fuel eventually. The fission process consumes uranium and produces more stable atoms like lead. Eventually, even if all the fuel rods are out, the process will run out of excess alpha particles, nucleons, and/or fuel. No more energy will be produced. Two thousand years seems like a long time for this, but perhaps the reactor is running well below capacity. Maybe it has only been partially exposing one fuel rod and still generating enough heat to keep things going. It's just done this for so long, it ran out of fuel rods. This would be a rather advanced reactor compared to what we have now. It can apparently run at a much broader range of speeds than they currently do. Perhaps it has been adjusted to be not just baseload power but on demand power. So it can give more or less power as required. Apparently it has only been required to give less for a long time. It's also possible that the reactor was designed to run for thousands of years. It has many more fuel rods than it needed for normal operation. So as they became spent, it could replace them internally, pulling them out of their lead shield. Current fuel rods last about [six years](http://www.msnbc.com/rachel-maddow-show/whats-the-deal-spent-nuclear-fuel) before needing to be replaced. So we can imagine a reactor with around 333 fuel rods lasting for 2000 years if one is used at a time. Or there could be 2000 rods with six used at a time. You might even be able to use fewer rods than that. Because while spent rods are no longer able to work at full capacity, they still produce both radiation and heat. So a hundred spent rods might be almost as good as one new rod. 300 rods might last two thousand years. Finally there just isn't enough heat produced to keep the turbines running. If each power plant is running at minimum capacity for the entire time and they all have the same amount of fuel initially, they could all stop working around the same time. It's unlikely to be the same minute, but the same century seems quite feasible. **TL;DR**: it takes about six years of use per fuel rod to deplete it, not anything related to the half life. [Answer] **A time rollover problem**. There are a number of them known about, besides the well known Y2K problem. You can read about them [here](https://en.wikipedia.org/wiki/Time_formatting_and_storage_bugs) some of them are set to give problems in the time frame you mentioned. ]

[Question] [ In an alternate world of magic, a battleship similar in design to the *Bismarck* is stopped in the middle of the ocean. It was built by a society of Earth humans who moved to this world. All other nation’s technology is approximately from the medieval-renaissance era aided with a slight bit of magic. Now, back to the ship. The massive battleship was dead in the water, probably because it was undergoing maintenance for its steam turbines. On the horizon, a fleet of [*ships of the line*](https://en.wikipedia.org/wiki/Ship_of_the_line) appeared. The fleet noticed the massive grey silhouette in the distance and immediately moved to investigate it. The commander of this fleet saw the otherworlders’ battleship and thought to himself, “*I want to conquer that*.” Obviously, the battleship crew had also spotted the fleet of *ships of the line* as there was a huge number of them.The captain, not wanting to waste ammunition, didn’t immediately obliterate them. Instead, he gave instructions to his crew to only fire at the ships attempting to board them. The fleet of *ships of the line* realized death comes for whoever comes close to the massive steel whale. Instead, they decided to sink it from “afar”. The fleet consists of about 700 vessels, they surround the battleship and broadside it until they run out of ammunition. The strategy of the *ships of the line* is similar to the land based musketeers, i.e. once the first group of *ships of the line* run out of cannonballs, they are replaced by the next batch of ships and so on. The battleship **still** won’t budge, not until its steam turbines are repaired which would probably take several more hours or perhaps even a day. The problem is; the real battleship *Bismarck* also had impenetrable armor. It was still sunk by continued shelling from the battleship *Rodney*, battleship *King George V* and torpedoes from multiple destroyers. Some shells (the *Rodney’s*) did penetrate but most ricocheted off the hull. These ricochets made the hull red hot according to some [sources](https://youtu.be/cV0NNZbj2QI). I was wondering if maybe 24 hours+ of constant cannon fire will do the same. [Answer] Imagine for a moment finding a man in full plate armor — a veritable knight encased head to toe in steel — and ordering a few dozen men to attack him with aluminum baseball bats. What you'd end up with after a couple of hours (assuming the knight just stands there) is a whole lot of exhausted men with bent baseball bats, and a knight whose worst problem is the headache he has from all that ringing. Of course, you could order your men to aim at joints or the neck to damage the knight by pushing his armor against his flesh, but if the knight takes any minimal efforts to defend himself, that's not going to be effective. This is the situation you'd have with a 17th century ship of the line attacking a WWII era battleship. The iron balls of cannon shot are too soft to penetrate steel of any reasonable thickness. It could aim for weak spots: concentrate all its fire at one single point in the hopes of creating a big enough dent to split a welded seam; lob shot down onto the upper deck (where the plating is thinest) trying to damage crew, infrastructure, or maybe hit a magazine. But again, if the battleship does any minimal thing to defend itself, getting close enough to do precision firing would be *extremely* problematic. Honestly, all a battleship of that class needs to do is get its engines running. Even at quarter speed it can out-maneuver any ship of the line, so it could chase them down and run them over, no shots fired. I don't even want to dignify that act with the term 'ramming,' because a battleship would tear through a wooden warship and crush it like a bug. If your battleship crew had any sense, they would put cotton in their ears, raise enough of a defense to keep the wooden ships at bay, and focus all their efforts at regaining mobility. And when *that's* done, the fat lady sings. [Answer] During the War of 1812, the United States frigate *USS Constitution* earned its nickname "Old Ironsides" when cannonballs from *HMS Guerriere* were seen bouncing off its heavy all-wooden live-oak hull rather than penetrating. In the mid-1800s, the introduction of ironclad and iron-hulled warships changed the nature of naval combat so quickly that many ships were obsolete as soon as they were launched. The *HMS Warrior* was an early steam-and-sail ironclad launched in 1860, with 11.4cm of wrought iron over 38cm of teak wood. It also carried 68-pounder guns and 110-pounder breechloading rifles, *much* more powerful weapons than *HMS Guerriere*'s 18- and 32-pounder cannon. Wrought iron is, by armor standards, extremely weak. By the start of the 20th century, 38cm of wrought iron was [considered equivalent](https://en.wikipedia.org/wiki/Ironclad_warship#Armor_and_protection_schemes) to just 14.6cm of the Krupp hardened armor steel available at the time. Now, with another 30 more years of metallurgy behind it, the [*Bismark*](https://en.wikipedia.org/wiki/Bismarck-class_battleship#Armor) was built with an armor belt 22 to 32cm thick, with upper decks, superstructure, and turrets covered with anywhere from 5-12cm thick, plus armor up to 35cm thick protecting its conning tower. You're specifying "late medieval-early renaissance". The famed Spanish Armada attacked England in July 1588, so let's look at that. In the [Battle of Gravelines](https://en.wikipedia.org/wiki/Spanish_Armada#Battle_of_Gravelines), the English fleet attacked the Armada. In order to penetrate the hulls of the Spanish ships, they had to close to ~100 yards before firing their broadsides. They spent *eight hours* blasting away at the outmatched Spanish fleet, and when they finally ran out of ammo that afternoon, five Spanish ships -- out of over 100 -- were lost: four drifting aground and one sinking outright. Many other ships were severely damaged and the Spanish suffered ~20% casualties, but given how long and heavy the English assault was, it's pretty telling. And why were the cannon so underpowered compared to the ships they were used against? Because the preferred tactic at the time *was boarding*. Part of the reason the Spanish were hit so hard in that battle is because they were focused on trying to board while the English were sailing circles around them. So, you have a massive fleet of ships which need to be within shouting distance of their targets to have a chance at penetrating even ships of their own era, against one of the most heavily-armored ships ever built, using armor technology over 300 years more advanced. If they try to get within firing range, it will look identical to the "boarding action" that those ships are designed to perform and that the Bismark is worried about. And the Bismark has the problem that its guns can only depress so far; if it lets an enemy ship get that close, it's actually going to have trouble hitting the hull. So each of those ships will attempt to close within their firing range and promptly receive a couple of 15cm or 10.5cm high-explosive shells at the *Bismark*'s point-blank range (by which I mean like 2km), which will penetrate the hull like it wasn't there and do a gruesome amount of damage to whomever's inside. Using one of the 38cm guns against those ships would probably be considered a crime against humanity. Assuming the fuse on the shell detected the impact on the hull of its target, you'd be hitting a ~40m long wooden ship with an 800 kg high-explosive shell -- "overkill" doesn't begin to describe it. (Just for fun, [this explosion on Mythbusters](https://www.youtube.com/watch?v=4IcHUHRf_S0) is in the ballpark of one of those shells going off. Probably a bit smaller, actually.) As far as heating up the metal -- the reason a blacksmith uses a forge is because hitting metal repeatedly doesn't heat it up at all. The shells that sunk the Bismark were explosive, so that energy is what was heating up the hull. Aside from [heated shot](https://en.wikipedia.org/wiki/Heated_shot), which weren't used aboard ships at that time you specified, cannonballs aren't hot enough to start fires or transfer heat to that degree. The hull might get hot to the touch at the point of impact, but you're talking tons and tons of steel sitting in a giant water bath; that's way to big a heat sink to get to red-hot temperatures through kinetic impact alone. On the other hand, I hope everyone on board the *Bismark* has proper hearing protection! [Answer] After the first dozen ships are destroyed with zero chance of causing even the slightest damage, the rest break off. Unless they are suicidal morons. Seriously, they cannot damage the battleship and they get slaughtered in droves as they slowly approach what, to the battleship is point-blank range. Hell, the Bismarck could probably win with just AA and machine guns. EDIT: Bismarck's AA consisted of 16 105 mm guns in dual mounts, 16 37mm in dual mounts and 20 20mm in dual and quad mounts. I couldn't easy see what machineguns they had on board, but with a crew of over 2,000 I'm guessing they had at least a few dozen Mgs along with a larger number of rifles, sidearms etc. Incendiary AA rounds would be extremely effective against wooden ships with cloth sails and plenty of loose gunpowder. Just fire a few bursts at each one until it brews up; you could probably sweep the deck clear of personnel. For the crews, it would be like sailing into a conveyor-belt of death. I imagine a lot would abandon ship as soon as they saw what was happening. [Answer] Even a [32-lbr. gun](https://en.wikipedia.org/wiki/32-pounder_gun) could do serious damage to the superstructure and deck equipment of the battleship. Aircraft, aircraft catapults, ship's boats, radar and radio antenna, optical rangefinders, they would all be vulnerable to a hit. So unless you make the battleship captain stupid, he should fire back. The Bismarck carried only 864-1,004 rounds for the 38cm guns and approx. 1,260 rounds for the 15cm guns, but there were supposed to be approx. 6,400 105mm rounds and approx. 32,000 rounds of 37mm, and even more 20mm. The 37mm and 20mm anti-aircraft ammunition included incendiary/explosive rounds, which should really inconvenience any wooden-hulled sailing ship with tarred rigging (aka *a fire waiting to happen*). --- *Follow-Up:* There is a debate in the comments about how easy it is to trigger a fire or an ammunition explosion. * I'm not confident that a 20mm or 37mm FlaK could target the magazines. Imagine an autocannon shooting at a largish building, in the hope of hitting a specific room in the sub-basement -- except that you don't know where in the sub-basement that room is. *While the gunner is trying to conserve ammo ...* * A single round of incendiary ammunition may or may not start a fire. Give it a 10% chance of a fire that will not be contained by the crew, and a 10-round burst has a 2-in-3 chance of starting at least one such fire. --- The attack maneuver you propose is also difficult for sailing craft. Sails would be reduced for fighting and speeds could drop to 2 or 3 knots -- call it 5 kph. The effective range of the muzzleloaders would be a few hundred yards, which is dangerously close to the "boarding range" that would definitely cause a reaction. Regarding damage to the main hull from sustained fire, a [third rate](https://en.wikipedia.org/wiki/Royal_Oak-class_ship_of_the_line) ship of the line would fire a broadside of 799 [pounds](https://en.wikipedia.org/wiki/Broadside#As_a_measurement). This compares to 2,048 lbs. for a **single** 16" shell from the HMS Rodney. But given the number of attackers you suggest, there might be repeated hits on the juncture of several armor plates, for instance. [Answer] # Let's look at it objectively: You don't even need a battleship. Let's look at the first iron armored ships and their combat - which included frigates and 2 ironclads. The armament of both the frigates and the ironclads is comparable to somewhat superior to an age of sail ship of the line. [USS Monitor](https://en.wikipedia.org/wiki/USS_Monitor) and [Merrimack/CCS Virginia](https://en.wikipedia.org/wiki/CSS_Virginia) in the [Battle of Hampton Roads](https://en.wikipedia.org/wiki/Battle_of_Hampton_Roads) however showed what a mere *1 inch* of wrought iron armor could do: Virginia got shelled by the Unionists frigates and wooden warships like crazy and suffered **no damage**. Monitor hammered away on Virginia and Virginia on Monitor and **neither** did do any damage to the other, **not even dents at point-bank!** Now, you want to send a Battleship in. This battleship has multiple times the armor of these Ironclads and the ironclads hat better guns than a Ship of the Line! Taking the [Bismarck Armor Scheme](https://www.kbismarck.com/proteccioni.html), the armor is 6.25 inches at the top deck and 12.5 inches of belt armor. Deck is 2 inches, impenetrable, and the whole ship was made from superior steel than the ironclads. The New-York Class has very similar armor and taking the Iowa Scheme, the Armada faces up to 14.5 inches or belt armor. Even the HMS Hood featured 6-12 inches of main belt armor! But what about the superstructure? Well, the superstructure is, out of *necessity* to uphold the structure, made from at *least* half an inch of proper steel, which is roughly equivalent, if not superior, to zhe 1 inch of the wrought iron armor of the USS Monitor! ## Conclusion: No battleship can be even be dented or damaged beyond the finish with Ship of the Line armament. Atop that, the cannonballs only deliver *kinetic* energy, while the Rhodney did shoot both much heavier and much larger ammunition that was either Armor Piercing or High Explosive. Without such large ammunition, heating the armor to any glow is *impossible*. The battleship *at best* looses its paint, and once it can raise steam, it just steams away, turning any ship of the line that is in front into driftwood. Much more likely, the commander would observe the armada, pinpoint the flagship, and then sink that, and the ship of the vice-admiral, with 2 shots using secondary or tertiary armaments. Beheaded, the armada would have to see that there is NO safe area within *miles*. ## What if... Now, let's amp up the ante and replace Bismarck with [Musashi](https://en.wikipedia.org/wiki/Japanese_battleship_Musashi): Captain Kaoru Arima spots the armada on the horizon. He has the fire control radar crew trail in the fleet sailing in a rather close formation. He decides to spend 6 shells per volley, one from each gun of the forward facing main batteries. The barrage of 6 times 46 cm (18.1 in), trailed in with the fire control radar over some minute, is launched with about 6° elevation. We start the battle-clock. T+0:0:15 - The barrage of 6 shells reaches 10.000 meters and is some dozen meters above the waterline. Because he saw wooden ships, Capitan Arima ordered to load [sanshikidan](https://en.wikipedia.org/wiki/San_Shiki_(anti-aircraft_shell)) - combined shrapnel & incendiary anti-aircraft ammunition. The shrapnel is distributed in a 20° Cone from the detonation point, ripping through sailors, sails, and ships, further setting ships and sails ablaze with impunity. The zone of destruction for each shell is about 1 kilometer long and 350 meters wide at the end of the cone - and the 3 guns of each turret are aimed with sightly different points of impact (staggered to be about 500 meters from one another) for a total zone of destruction of twice 44080 m² (8.2 American football fields). ANY ship within these ~16 football fields is practically destroyed, and that at the expense of the most useless ammunition Musashi has abroad! In tight formation, that would be between 25 and 50 ships hit. T+0:00:45 The second barrage is launched, aiming a few degrees more port and starboard. T+0:01:00 second barrage sets another 16.2 football fields ablaze before the enemy fleet even has had the chance to even react by setting any signals. The first ca. 20 ships following up on those already set ablaze run into the floating and burning wrecks as they can't maneuver quick enough, suffering damage. Total number of disabled ships is between 70 and 120 at this point T+0:01:30 Third barrage launched, distance to the armada is still very close to 10 kilometers. T+0:01:45 Third barrage hits. Following my estimate, between 16 and 27 % of the armada has been disabled. If the rate of destruction is kept up, the armada will be wholly ablaze between T+0:08:15 and T+0:12:30. By this time the Armada sailing at 6 knots would have managed to close in towards 8.5 km/7.5 km - or several miles outside of their engagement range. Note that he could have started fire at 25 kilometers and still most likely hit his target, 10 kilometers is *guaranteed hit* area for Musashi (and maximum range for the anti-aircraft ammunition), and anything below about 2500 meters is pretty much *elevation 0* for the main armament. The secondary armament of 15.5 cm guns has a depression angle of -7° and is mounted at about 15 meters above the waterline. It can hit ships at their waterline starting at 122 meters - which is closer than the effective range of the ships of the line, meaning any ship trying to get that close gets immediately sunk, either by an armor-piercing shell cleanly ripping through the boat twice, starting to flood it or by a high explosive load of 50 kg blowing up the ship's hull and the magazines. [Answer] If I was the battleship's commander, as soon as the 700-ship fleet of sailing vessels shows up on the horizon I'm altering my orders. "Only vessels which are closing on our ship are to be targeted. Each of the 105mm gun mounts will be assigned targets in its quadrant of the ship. Any enemy vessel closing to eight kilometers range will be targeted by two rounds of 105mm high explosive and two rounds of 105mm white phosphorus and results observed. If an enemy vessel closes to six kilometers range the 150mm battery on the side of the ship that the targeted enemy vessel is on will open fire, firing in groups of two rounds with time allotted after firing to observe results. If any target closes to five kilometers range it will be engaged by the main battery. Ammunition is to be conserved, and firing on disabled targets is not permitted". In other words - if they stay far enough away to be no threat, we won't shoot at them. It they get too close they'll get a warning shot. If they keep coming we'll hit them with smaller stuff, and escalate as needed. In a rational world, one ship *might* close to seven kilometers, but I expect the results - that the closing ship was set on fire and blown to pieces well beyond the range where the guns of the fleet could even hope to reach the battleship - would be sufficient to dissuade other captains. If for some reason the fleet decided to attack from all directions simultaneously - well, I expect the gun crews on the battleship would be busy for a time, but once there is a wall of burning/destroyed ships around the battleship it'll be tough for any undamaged ship of the fleet to get through. I doubt that any would be able to close to even long cannon shot (roughly 2 km). [Answer] Taking just the energy side of the question: say we're using 36lb (17.6kg, we'll round up to 18kg) guns. These have a muzzle velocity of [~450m/s](https://en.wikipedia.org/wiki/36-pounder_long_gun), apparently. That means that the kinetic energy in each shot no firing is ~1.8MJ. Assume that's all perfectly applied to the ship. The armour of the Bismarck weighed 17.5Mkg, so rather conveniently, that's about 0.1J/kg per shot. Steel has a specific heat of around 420 J/(kg°C), so each shot raises the temperature by at most 0.00024°C, so it needs ~4,200 shots to raise the temperature by one degree. Suppose we've got some uprated monster of a ship with 100 of these on (the largest ships to carry them had 32, plus a bunch of smaller guns). That means that we need 84 broadsides to raise the temperature by one degree. If you've got the ships lined up bowsprit-to-stern and moving at 5kph, assuming that your ships are 200m long (a bit shorter than real ships of this many guns), you can get off 25 broadsides per hour, so it will take a bit over 3 hours and 20 minutes to raise the temperature by one degree. However, the target is also going to be shedding that heat to the surrounding water. If we get it 0.015 degrees above ambient, each square meter of surface is going to be chucking out heat at ~0.67W (using [this](https://www.engineeringtoolbox.com/overall-heat-transfer-coefficient-d_434.html) calculator and doubling it because we're only actually doing half of that transfer). Now, assume every single cannon ball is hitting that same square meter. The total input power is 1.8MJ/shot \* 50shots/broadside \* (25 / 3600)broadsides/second = 0.625W. That is: we'll never raise the temperature enough to measure, even locally, even if every single shot hits the same point. [Answer] Let's rephrase your question: "We have a battleship with hard iron plating being hit with slow lead projectiles. What weight of accumulated projectiles is necessary before the battleship sinks?" Lots. Also, they would better with some occasional chain shot to make a more cohesive mass. [Answer] ## The Bismarck wouldn't put up with it for one second They would use any means to repel the attackers. Remember how the Germans lost the *Graf Spee*. The damage they took in battle was trivial - the British attacks barely dented the armor. However, every battleship has some squishy equipment topside - radio masts, rangefinders, lifeboats, and on the Graf Spee, the **fuel purification system** that pre-processes bunker fuel for use by the diesel engines. This was a bolt-out-of-the-blue [critical hit that doomed the battleship](https://en.m.wikipedia.org/wiki/German_cruiser_Admiral_Graf_Spee#Scuttling). So, you **do not let yourself get beat up**. If a Viking ship is shooting arrows at you, you sink it. If a USCG patrol boat is shooting off its .50 cal at you, you sink it. **You just never know** what is going to happen in war, and you do not give the enemy a chance to get a critical hit. [Answer] In order to deliver damage, a projectile mush have * suitable velocity * suitable hardness Velocity is needed to give enough energy to the impact, and hardness to ensure that the target is damaged. A battle ship contemporary of the Bismark would be able to afford shots with both characteristics. A ship dating centuries before would fail on both sides: soft and slow projectiles would keep hitting the target. I don't have hard number for a more sensible answer, but I think those ships have no chance of making any real damage to the target, unless they manage to consistently hit always the same point, which is practically impossible. [Answer] No, the sailing ships cannot sink the battleship using their cannon. But... Once the battleship is moving again, they could lay partly submerged ropes across the path of the battleship in an attempt to tangle the battleship's rudder. The sailing ships wouldn't know about the propellers unless there was some divination magic that revealed their existence and importance, but if the propellers were adequately entangled then the ship would be immobile until divers are able to clear the props. Note that there is absolutely no need to prevent the propellers from spinning, despite what several people seem to think in comments. If enough debris gets wrapped around the propeller then it stops being a propeller and becomes a spinning pile of trash. Put simply, if water cannot flow through the propeller then it will not provide any thrust for the ship no matter how freely it is able to spin. It should also be noted that the blades of a propeller will absolutely *not* cut through a rope. Despite being called "blades" they are not sharp and exert no cutting force. If a rope gets caught by a spinning the propeller it will simply wrap around the propeller and propeller shaft until it is either completely wrapped up or until the rope catches on something too difficult to move and the tensile strength of the rope is exceeded. If the battleship were to sail over a partially submerged wreck of a recently sunken ship, the sails, rigging ropes and many busted up pieces of wooden masts and spars can get caught on the propeller and wrap around it. This debris will reduce the performance of the propeller and slowing down the ship. If the sailing ships could then keep enough pressure on the battleship that the props could not be cleared, or if any other method can be found that immobilizes the ship, then the battleship's stores of food and fresh water become a very critical factor in which side wins this contest. This scenario does not require the ship's speed to literally be brought to zero. It only requires that the ship's movement be reduced in a manner that will prevent it from reaching a source of fresh water and food. Even if only one propeller is significantly reduced in performance and the other cannot be used at full power otherwise the ship will be moving in circles. The ships of the line don't need to defeat the battleship. They need to defeat the battleship's crew. [Answer] For the Iowa class the citadel has enough reserve buoyancy to keep the ship afloat if the rest of the hull is flooded. The the side armor is 12.1" sloped at -19 degrees.The transverse armor is 11.3" There is no way, no how a cannonball is getting through that. Before the cannonball could even get to that armor it would have to pass through 2" of armor plate that was not even counted as "armor" at the hull. For comparison, the CSS Virginia had a maximum of four inches of armor (not face hardened)that the 11-inch cannon of the USS Monitor could not penetrate at point blank ranges. In the mean time, the Iowa's have 500 rounds per 5-inch gun (10,000 rounds) and 1264 rounds of 16-inch projectiles; any one of which could sink a wooden ship on its own. The 40mm guns could also do hull damage to a wooden ship. The 20mm guns could keep an opponent's heads down low. The effect would be a lot of dents. [Answer] The Bismarck carried supplies for less than 3 months, so that's how long it could sustain the attacks. The canon fire doesn't matter. [Answer] > > he gave instructions to his crew to only fire at the ships attempting to board them. > > > Your commander may not be able to fire at ships which are attempting to board his vessel, at least not using his guns: Battleships are tall and the guns can only be depressed a limited amount. For example, the 20mm Oerlikon guns on an Iowa class battleship could typically be depressed to 15 degrees. I can't find out where those guns were mounted, but the deck is about 50' above the waterline. So a 20mm gun mounted on the deck could not target anything closer than about 180'. If the guns were mounted higher in the superstructure, then the minimum range is larger than that. I didn't get numbers for any of the larger guns, but I would guess that the bigger the gun, the larger its minimum effective range. Battleship were designed to shoot targets that were many miles away. [Answer] Though the question specifically asks about the fire-power exchange of these vessels, there is another important factor that has yet to be mentioned: Freeboard. The freeboard, the distance from the water-line to where you'd want to board, on the Bismark was 18 feet at its lowest, simply due to the size of the ship. (see: <https://www.bismarck-class.dk/technicallayout/generaldetails.html>) While earlier ships designed for boarding had high freeboard to provide a better boarding defense/offense. By the time "ships of the line" were in service, ships became less tall and more elongated. While this difference in elevation is not insurmountable, it is less than encouraging. [Answer] # About 2 weeks: Because the *ungodly* noise of dozens of cannonballs per second pinging off the hull and superstructure of the Bismarck would make enough noise so that no person on board could sleep. 2 Weeks is about the upper bounds for how long a person can stay without sleep before they go completely insane and scuttle their own ship, just to end the infernal din. **Damage to Bismarck**? Possibly some windows. The hull armor was some 220 to 320 mm thick Krupp Cemented Steel, cannonballs hitting that would simply fragment, not leaving even a smudge. The upper desk and superstructure was armored from 50mm to 180mm depending on value and vulnerability. Even the thinnest 50mm Krupp Steel would shrug off a point-blank broadside with no more than minor surface denting under 1mm deep. Windows, Humans, Small firearms that are exposed would be vulnerable. The main cannons, including AA class cannons would be invulnerable. (maybe the 40mm AA cannons could be hurt with a direct hit on the mechanism) **Counter-attack**: Ammo be damned! The Bismarck could likely sink any attacking Ship of the Line with a single burst of AA shells. A [10.5cm flak cannon](https://en.wikipedia.org/wiki/10.5_cm_FlaK_38) would quite possibly sink a wooden ship with ONE round. The Bismarck had SIXTEEN of those, with a total of 12000 rounds of ammunition for them. It also had sixteen [37mm rapid-fire AA guns](https://en.wikipedia.org/wiki/3.7_cm_SK_C/30), with 32000 rounds of ammunition. These would not sink a ship of the line with one shot, but a salvo of 20 rounds would make 20 \* 10cm holes in the wooden ship's hull, and kill a large part of its crew by (wooden) shrapnel. Remember that for the ships-o-line to fire at the battleship, they would need to be **close**. Their cannon are only effective from point-blank out to about 1000m. This is so close to the Bismarck that they might have difficulty aiming the main cannons, due to the artillery tables not including such short ranges!! But the Secondary guns ("only" 15cm guns firing 45kg high-explosive rounds) and the AA batteries and guns would have a jolly old time. Bismarck likely has enough ammo, in total, to sink 10 000 wooden ships of the line. [Answer] I expect a very different outcome here: The armada approaches, the commander of the battleship realizes they're facing a bunch of people who have no idea of the degree of mismatch of the firepower. The captain wishes to preserve ammunition. Thus he will do a variation on the traditional shot across the bow--he will drop one shell into the water in front of the flagship of the armada. I expect the armada would quickly surrender or depart. If they do neither the second round obliterates the flagship. I would be very surprised if anyone else steps up to command an attack. [Answer] I agree with other answers that a barrage of cannonballs would have little effect. However, if you are looking for a story that allows the sailing ships to win, consider ## Stealth boarding at night This scenario would be especially effective if... * The initial battle happens during or near nightfall of a moonless night. * Whatever causes the battleship's engines to fail also knocks out the ship's electrical power, making searchlights and lighting unavailable. * After failing an initial battle, the remaining sailing ships retreat and regroup. They devise a plan to wait a few hours, then rush the battleship with boarding parties. * Expecting the battle to be over, most of the battleship's crew goes to bed for the night. Only a small crew is left on night watch. * Because the sailing ships make practically no sound and there is little natural light, they are able to slip close to the battleship undetected. * Casualties are heavy on both sides, but the sailing ships are able to win by overwhelming the battleship's crew. I'm not claiming that the sailing ships would always win, but if you want a scenario that gives them a chance, here it is. [Answer] The other answers here are fundamentally misunderstanding a very important factor: The opposing force vastly outnumbers the battleship. 700 ships, assuming each ship can bring 30 cannon to bear on the target, is 2100 cannonballs. Assuming one in twenty hits, that's still 105 rounds per salvo slamming into the hull or the deck of the ship. 105 rounds of 36+ lb shot traveling at almost 500 meters per second. Repeated impact stress of that magnitude will slowly shake the ship apart, even if not a single shot penetrates the hull, not to mention anything on deck will absolutely be obliterated by massed cannon fire. To be clear, the conflict still weighs heavily in favor of the bismark here - it's armor is substantial enough to take that beating for a significant amount of time and a single shot from basically any of it's armaments could sink any of those ships. But, it does not have an infinite amount of time to leisurely sit and absorb cannon fire from 700 ships of the line while doing nothing. Eventually, something will start to give, and those ships carried enough ammo to continue firing for many hours. The Bismark will need to fight back. ]

[Question] [ Let's suppose we intercepted a message in an unknown language. We were not able to decipher it, but we were able to decode it. Meaning we know the letters but not the meaning of the words in the text. Assuming the text is sufficiently long, we now know every single letter of this language. Can we say that based on the fact that the language uses just a few letters, it is probably simplistic and hard to use for passing complex thoughts? And if so, can we assume that the civilization using this language is probably primitive? Or more generally, can the number of letters in alphabet suggest how advanced the civilization is? Also, is there a practical limit to how few characters an alphabet can have to allow for some possibility of scientific progress? For example, is it OK to assume that civilization using only 10 letters is capable of space travel? **Edit:** Thanks for all the great answers! My conclusion is, that I can't assume anything about level of civilization based on their language. To address those pointing out to binary encoding of message we use, I'm aware of this and for my question I assumed that the message was decoded from *binary* to actual character representation. In our world it would mean I decoded a binary message and got its ASCII representation. I don't know how the characters look, how they sound or what they mean but I can distinguish between them. Thanks for your answers, I'm not sure which to pick as accepted; they are all great. **EDIT2:** I chose to accept an answer which gave me something to think about but if you are interested in this topic, please read through all the answers as they are all great and some are very in-depth. [Answer] There's practically no correlation between the complexity of a given language and the complexity of the writing system used to represent it. Japanese and Korean are both very complex languages, able to convey a wide range of meaning and context. Yet, Japanese uses thousands of characters to represent it in writing, and Korean uses 24. Also, when talking about alien languages, consider that their writing system could be completely, well, alien. Just as an example, what if it were more like musical notation? Or what if it were something akin to DNA? (Just 4 "letters" to code for any protein) I don't think any knowledgeable person would say that DNA isn't complex because it uses only C, G, A, and T for encoding purposes. [Answer] > > can a number of letters in alphabet suggest how advance the civilization is? > > > There is no correlation between the technological advancement of a civilization and the number of symbols in its alphabet. Do you want some counterexamples? The Roman Empire (and the shepherd founding it) used the same alphabet we use today, yet we are way more advanced then them Some Asian languages use thousands of symbols in their writing (think of Chinese or Japanese), yet the civilization using them are not more advanced than we are. [Answer] ## No. An inverse relation is more likely. * Ancient Egyptian hieroglyphs: around 1000 symbols. * Modern English: 26 symbols + 10 digits + punctuation. * Communication between artificial intelligences: not yet known, but probably will be 2. According to the science of semiotics, [signs](https://en.wikipedia.org/wiki/Sign_(semiotics)) used in the language are arbitrary. They are only loosely related to their meaning. To know if the culture is advanced or not, count meanings in their language, not signs. In an indo-european language, you often can do it by counting words in a complete enough dictionary. But with your aliens we don't even know if they have words or not. So you can't tell what goes into the dictionary, and how large it will be. [Answer] The number of letters merely indicates the cultural representation of [phonemes](https://en.wikipedia.org/wiki/Phoneme). Phonemes tell a bit about what sounds can be made, and which of those sounds a listener might find important. But those say nothing about the concepts transmitted by *groups* of phonemes that we call words, nor the grammar, conjugations, and other shaping tools that provide clarity and context. [Answer] Generally speaking, the more symbols used, the more compact the message can be. The fewer symbols used, the longer the message will have to be. In the introduction to *Teach Yourself Sinhalese*, a book on the [Sinhala language](https://en.wikipedia.org/wiki/Sinhalese_language) (Sinhalese is the old name in English, Sinhala is the new name), it says: > > [...] *One of the very striking and significant features of the Sinhalese language is that when a randomly chosen news item is translated into Sinhalese and several other major languages including English with the same size printed letters, the Sinhalese text will occupy the least printing space in most of the cases, which means the least number of words and letters; and the use of the present infinitive form (see 3.4) to indicate the present tense and the future tense by any grammatical person of any gender or number; and the use of the past infinitive form (see 4.2) to indicate the past tense by any grammatical person of any gender or number.* > > > (emphasis by the author) This is not as amazing as the author makes out. For instance, the word නම (nama, rhymes with the English word "mama") means "name" and is spelt with two letters: න (na) and ම (ma). Hang on, isn't that cheating though? In English we generally use one letter per sound, but in Sinhala they mostly use one letter per two sounds (a consonant and a vowel). So, very roughly, we can say that a Sinhala word will be half as long as the equivalent English word. English and Sinhala are both descended from Proto-Indo-European, so many words are still related, although the majority bare no resemblance to each other any more. However, later in the book is listed the letters commonly used in modern Sinhala, of which there are 24 variants just for the letter ක (ka). The base alphabet without variants is about 60 different letters (the exact number varies by inclusion/exclusion of certain rarer letters). In total, the number of letter variants is somewhere around 400 or higher. Compare this with English, which has just 52 basic letters (26 of each upper and lower case) plus some rarely used ones. One of the first example words in the book is ‌ෆෑන් (fan), a loan word from English. Again, it only uses two letters, this time ෆෑ (fǣ) and න් (n). Note that "n" is the same letter as "na" above, but now it has a little mark to remove the "a" sound. "fa" also has a mark to turn "a" into "ǣ". Some of these marks might look like separate letters to you, but they are more like the accent marks used by many European languages. So Sinhala writing encodes more information per symbol than English does. This is not unique or remarkable: many or most scripts for Indian languages are based on an ancient writing system called Brahmi which had the same consonant+vowel combined letters, and Sinhala script is also based on Brahmi. Consider that you can translate all thoughts into every language. That suggests that all languages and all writing systems are equally advanced, regardless of how many sounds are in the language, or how many symbols are used to write that language down. Often, we communicate more information than strictly necessary for the purpose of redundancy. Compare English simple past tense to simple present tense: * I ate * he ate * I eat * he eats It would be perfectly understandable without the "s" in "eats" (he eat), the same way there is no "s" in the past tense, but it redundantly tells us that the subject is third person singular. In French there can be even greater redundancy: * trois grand**es** chat**tes** noir**es** (three big black [female] cats) We already know from "trois" (three) that it's plural, yet a redundant "s" must be added to each of the other words in that example. In English, the redundant "s" only appears in "cats". The feminine form of "cats" (chattes) has been used, so the two adjectives must also be feminine, marked with an "e". Redundancy helps you catch mistakes, and make sense of the message if part of it is missing or distorted. Removing redundancy simplifies communication, at the expense of a smaller margin of error. For instance, we have many ways of writing the "k" sound. "c", "k", "q" (kw), and "x" (ks). We could simplify our alphabet by only ever using "k" (kat, kettle, kween, boks), but we would lose some information along the way, mostly to do with etymology (the ancestry of words). English has a simpler script than Sinhala, and less grammatical agreement than French, yet English is the lingua franca for business and science these days. In summary, the number of distinct symbols used in a writing system tells you nothing about the complexity of a civilisation. [Answer] You decipher this: 0X00X0XX 0XX0X00X 0XXX00XX 0XXX00XX 00X00000 0XX0XX0X 0XXXX00X 00X00000 0XXX0000 0XXX00X0 0XX0X00X 0XX0XX0X 0XX0X00X 0XXX0X00 0XX0X00X 0XXX0XX0 0XX00X0X 00X00000 0XX000X0 0XXX0X0X 0XXX0X00 0XXX0X00 00X0000X Just two letters. What is this, kisses and hugs? Those freaking primitives. Maybe we should send back a message teaching them about fire, or toilet paper. I do not think one can extrapolate the sophistication of a society from the complexity of their alphabet. The most complex messages our society now produces are produced using an alphabet of 2 symbols. [Answer] When you are conveying information using a sequence of letters from an alphabet with n symbols, what's really happening is that you are sending a large number in base n. The question you're asking is, what's a good n? What are the implications of high or low n? Regardless of how big your alphabet, you must have a good way of distinguishing each letter/digit/symbol from others. The easiest way of ensuring that is to have only 2 digits: That way all you have to do is be sure that the letter you look at isn't the other one. If you have very good resolution transmitter and receiver, then adding more digits will save you bandwidth: You will have to send fewer letters for the same information. So the trade off is bandwidth vs. fidelity. Let's look at the manual case. Since you said alphabet, you must be talking about writing specifically. Having more letters could mean that it's easy for you to write legibly and tell them apart, and/or that you like shorter messages. Maybe your grammar is very long range, say words that go into the 10th paragraph depend on exactly how the first paragraph was written (this would only make sense if it came about when paper was still used, and then became crystallized). Or maybe whatever you use to record the information is very precious. On the other end, using a very small alphabet could be because you like to have a very easy time of telling letters apart. The same logic applies to speech as well, however. Language tends to be a stream of sound units that each have a defined meaning. The number of sounds is analogous to the alphabet size. I would say one easy way would be is if your mouth anatomy is not very versatile, or your hearing isn't very good, you would tend to use fewer sounds. But again, if by the time you get to the end of the sentence you have a problem of forgetting how exactly you worded the beginning, it might help to have a complex syllabary, since then you would have to remember a shorter sequence. Although technically, the amount of information your brain has to hold on to is identical, so it comes down to how exactly you assume memory works: General or specialized (ie. not all kinds of information are equally easy to remember). However, based on the situation on our planet, I would say the above are very minor effects, easily overshadowed by stronger factors. For example, you might almost double the alphabet simply because there happened to be a neighboring culture that had a language with very different letters, and you ended up trading a lot with them so you borrowed many letter as well. Probably brain anatomy has some effect on language architecture, because why wouldn't it, but languages also don't just evolve according to anatomy and stay there. A lot of chaos happens as they interact with each other and the environment. So it would be silly to try and rank species intelligence according to alphabet size. As for level of civilization, that's wholly hopeless. Even if there were some dumb aliens using a binary alphabet, they could be really advanced simply because they've been around for a million years. Or maybe someone gave the tech to them and disappeared, so now they are the most advanced. But even then, any advanced species would probably invent computers long before trying at space travel, and at that point alphabet size becomes mostly irrelevant. [Answer] Written language and spoken language are not the same thing. Writing systems can be complex or simple and they do not say anything about the complexity or simplicity of the language. Writing systems sometimes leave out information about how to speak the words (Hebrew leaves out vowels, most tonal languages leave out tones). The number of sounds a language has may or may not be correlated with the number of letters in the writing system. The number of sounds has zero correlation with the complexity of the grammar. Latin has many times more tenses than English, but English has more complex spelling. What does any of this say about the intellect of the native speakers? Nothing. The answer is absolutely nothing. Ditto for the technological advancement of the speakers. Sometimes people inherit a language. Immigrants learn the language of their new home. This doesn't make them smarter or dumb them down. Their children do not more or less technologically advanced based on what language they speak first, it's based on what they're exposed to. Sometimes languages are needlessly complex (*cough* English *cough*) because they're really an amalgamation of several different languages with a ton of loan words. Doesn't make those civilizations better faster stronger. And some languages have great complexity and intelligent users and they have *no* sounds at all. (And no standard written form either.) The fact that the civilization your question is based on: 1) has written language and 2) can transmit a message, is a pretty damn big clue that they're intelligent people with a decent level of technology. The method used to transmit the message will tell you worlds more about their abilities than the number of letters you managed to decipher (and somehow think are all the symbols used in their writing system). [Answer] No. Look at computers there base level language is binary and all you have is 0 and 1. You don't need anything more complex than that. Then its just about stringing the 1 and 0 together to make a letters, and letter form words. Also computers don't even know or care what words are because they use binary machine code. All programming languages designed for humans get translate back to op-codes before the computer executes them. [Answer] There's other metrics to judge tech level. EG: <https://en.wikipedia.org/wiki/Kardashev_scale> That scale starts pretty grandiose (eg: on the planetary scale). But, generally, to judge tech, you judge it by... a) inputs ... what fuels it b) outputs .. what can it accomplish Lets say we got a message from an alien civilization... \* if it came over radio waves.. we know they're sort of primitive, because radio waves are not that hard to produce. Obviously they're not banging rocks together. \* if it was light pulses, they have some kind of advanced laser device to direct-pulse light at us \* if it was some kind of sub-space radiation (Star Trekky stuff we can't think of yet) then they're even more advanced. Bringing this down another scale... \* you see smoke signals on the horizon.. obviously the person knows how to make fire \* you see flashing light on the horizon... someone has enough tech to shine up an object to reflect light \* you see flashing light at night .. someone has enough tech to make a flashlight \* you get a signal on your radio / walkie-talkie.. someone can broadcast "waves" of some type (radio waves, etc). The assumption of tech goes up and up based on the method of communication.. not what they're communicating. Because the method of communication makes us wonder what input was required (what kind of energy and technology) to create that output. If we really wanted to get high-tech about this, we could run various cultures alphabets through data science / machine learning algorithms along with variables for what kind of technology they have (or even just flagging them as 1st, 2nd, 3rd world countries), and let the computer tell us if there's enough variation to for-sure say that characters in an alphabet does indeed dictate a certain level of technology. (Because essentially the machine learning algorithm would just do pattern matching and statistics to see if there's enough probability to say for sure.) [Answer] **No.** We can see some examples in our present day society. A very simple language would be Coorgi-Cox. [](https://upload.wikimedia.org/wikipedia/commons/0/0d/Coorgi-cox.jpg) However a very complicated language that has tons of symbols would be mandarin Chinese. [](https://i.stack.imgur.com/csmBs.gif) There is no way you can tell how advanced a civilization is just by looking at the number of characters. [Answer] A better way to judge, based solely on these messages, is counting how many distinct words there are. You don't need to know what these words mean, only how many there are. The size of a culture's vocabulary does correlate with how advanced they are. You can't discuss a topic you don't have the words for, after all. [Answer] No is indeed the answer. There is no real relation that can be drawn between the number of glyphs a society has, and its sophistication or tech level. Let's look at written human languages. There lots of variants of writing systems, but there are really two basic kinds of writing systems in common use: Logographic and Phonographic. Logographic systems use glyphs to stand in for words (or phrases). Every different word gets its own glyph. This means in theory you need a different one for each word or concept in the language, which for most languages would number at least in the 10's of thousands at the absolute least. There is one Chinese dictionary with over 100,0000 different glyphs in it. Phonographic systems instead use their glyphs to represent spoken sounds. This has a huge advantage for new learners in that there aren't nearly as many of those. English is on the high side with over 10,000 syllables, but that beats the heck out of its vocabulary of 200,000 words. With the further innovation of splitting tongue positions (vowels) from consonants, we can get that down to something we can represent with only 26 glyphs. Alphabets the world over are roughly this size. In fact, Archeologists can make a pretty good guess at the encoding scheme used by untranslated works just by cataloging the number of glyphs used. That's all it tells us. Not their sophistication, just the kind of scheme they used. The drawback to a phonographic system with their small number of glyphs is that the writing really only tells you what the words *sound like*, not what they mean. You have to rely on spoken language knowledge to get over that final hump. This means Phonographic systems aren't very good for dealing with situations where the two parties can't understand each other's spoken language very well. This is why China with all its different ~~languages~~"dialects" has stuck with a logographic system to the present day. --- Now let's think about aliens. Suppose they, like most humans, decide to go with a phonographic system for encoding their language. How many glyphs would that use? The answer is, **we have no clue**. That would depend on how they vocalize, and what all the various options there are. Without knowing that, we couldn't even begin to guess what their encoding scheme was. A *human* language with 100 glyphs we can fairly confidently place as a (phonographic) syllabary. For an alien, for all we know their vocalization mechanisms are so complex that we are looking at a simplified alphabet. Or more likely, they don't have a tongue at all, and we just simply don't know. [Answer] Ok. Alphabetical symbols is one thing. Decoding them and understanding its meaning either in phonetics or in math is another. Combination of those as a possibility is another. Combination of those with communicational and common understanding between two parties is something else. **Question 1:** If the language uses just a few letters, it is probably simplistic and hard to use for passing complex thoughts? And if so, can we assume that the civilization using this language is probably primitive? *or* Can a number of letters in alphabet suggest how advance the civilization is? If the language can communicate with just a few letters complete thoughts (thoughts are always complex) then yes, for the person who is learning the 10 letters and their combinations with the possible meanings, then one can communicate through that language. The answer is hidden behind the word "combination" which as a symbol can stand alone or in combination with another can create a new symbol. An then the combination of the combined symbols can create a word or a new symbol. If you want to communicate the new symbols there must be logic hidden behind them - common to all as of the rules for making new symbols which have a meaning and thus can be translated to thought. Or we can decide that grammatical symbols can have mathematical representation/understanding as well. Complicated? Not, if you speak Greek. Example: There is a saying in ancient greek which is a prayer of a mother to her son and it is written in simple vowels, and only vowels - 7 of them. "Οία η Ηώ, Ω Υιέ αεί Ει" in capital letters, "ΟΙΑ H ΗΩ, Ω ΥΙΕ ΑΕΙ ΕΙ" translation: "Like the Dawn oh my Son always Be". Here are the 7 vowels of the Greek alphabet: Α, Ε, Η, Ι, Ο, Υ, Ω Here what follows is a combination of vowels in the greek language (Diphthongs) which represent similar vowel sounds but used for different grammatical reasons: ΑΙ, ΟΙ, ΕΙ, ΟΥ, ΥΙ, ΑΥ, ΕΥ, ΗΥ And even though I am not aware if there is a language out there which can create words and sentences with the use of vowels, there is no such a thing as less civilized or more civilized because of that. It describes the plasticity and the logic behind the phonetics and thus it is a language which offers more versatility for the user to create coding. Also, Greek is a language which has accepted few changes in its structure and it is spoken through centuries while people can read ancient greek (not common use as the "koine") and understand the meaning without knowing the meaning of the exact word they read, and that because of its logic behind formation of the words. **Question 2:** Also, is there a practical limit to how little characters can alphabet have to allow for some possibility of scientific progress? For example, is it OK to assume that civilization using only 10 letters is capable of space travel? Because the Greek alphabetical symbols (24) are also mathematical symbols, I believe that it is possible for space travel with ten numbers 0-9 and by the creation of a mathematical language (numerical symbols are universally known) as it allows for unlimited combinations. Thank you for your contribution. It was a good opportunity to express my thoughts on the matter. I hope it was helpful. [Answer] Letters are just a context-sensitive representation of phonemes. There's nothing to suggest an Alien intelligence would communicate with phonemes. But assuming an alien intelligence where to use phonemes (or their analogs in their alien experience), there's nothing to suggest such an intelligence would choose to represent those phonemes. As Larry Niven once postulated: "There exist minds that think as well as you do, but differently." A society might communicate via zeros-and-ones analogs, or by a discrete set of signals: think how cephalopods communicate with their chromatophores. There's nothing that could prevent an alien intelligence from evolving communication with a very limited array of chromatophore changes (say in RGB) with changes flashing rapidly and in multiple locations, each color change (and chromatophore position). We do not need go to further away from Earth. The Rotokas language has only 12 sounds and the smallest alphabet. The Pirahã register used by Pirahã women is supposed to contain only 10 phonemes. Aymara, Quechua, has only 3 vowels. Ubykh has only two vowels, but an insane number of consonants, and the Caucasus region is famous for languages with prodigious sound repertoire. OTH, consider the aliens in "Arrival" who wrote with complex circular logographs with no relation with how they "spoke" (kind of like cool-looking circular QR codes, hahaha.) Anyways, yeah, there's no relation between phoneme/letter repertoire and culture complexity/intelligence. The notion doesn't even need to exist as a requirement for intelligence, unless we limit intelligence to that which we know (which reeks of Anthropocentrism.) [Answer] Ooh, a toothy question, with some good answers already. But I think there's more fat to be chewed here yet. As you've established from other answers, some "alphabets" encode entire word stems in single characters. Others, single phonemes. Others, single bits of information. All of these can encode the same words of the same language. They just work at different "transport layers" (<https://en.wikipedia.org/wiki/OSI_model>). And that's the problem. MEssages, and the alphabets therein, don't come from nothing. You aren't going to get a scientist poring over an "alphabet" without first poring over a whole lot more. Communication is a layered activity, and any scientist will be looking at the communication in terms of those layers. So exploring the layers here may be informative, though the OSI model assumes bidirectional communication, so isn't ideal here. At the bottom layer, we have the physical layer. This is the layer that user @blahblah suggested investigating: the "how the data got to Earth" layer. This is the "carrier", perhaps a radio wave, perhaps a metal plate found in a space ship, perhaps a strip of ferrous metal. Next layer up, we have how that carrier was permuted to have a signal encoded onto it. Radio waves are not, by themselves, any kind of bits, characters, DNA, picture, or anything like that. How did they encode the signal on their carrier? AM? FM? Some other thing? If it was a metal plate, were characters etched into it, scratched, cast, stamped, painted on, glued on...? If it was a ferrous strip, did they reverse the magnetism at set periods in lines and columns (how our magstripes work), or did they arrange the magnetic regions in some other, more complex pattern? All this tells us something about the technology that transmitted it. And how fine are the details? If they vary over multiple seconds, that tells different things than if they vary over nanoseconds. A microfiche slide is at a very different scale than a rune-carved dolmen; GHz radio comms are very different from manual morse code telegraphy; and data density on a modern hard drive platter is very different from that on a credit card strip. This doesn't give an upper bound to their tech level, but it gives a lower one, and also shows how far they hoped their message to go (in general, you speak slower and louder to be heard further away). And what data correction did they have in their protocol? Was it just "if we repeat it enough times, it'll get through"? Or were there checksums and other error correction? Given how they permuted the physical layer, how did they encode the data? Bits, for binary or morse-code type communication? Continuous analog levels, such as we might use for brightness levels in a TV raster image? Unique values, for words or characters? And there can be many levels of encoding of the signal. Perhaps the signal, once decoded, builds raster images of characters. Perhaps the signal has unique values, each one of which maps to a character. Perhaps the signal is a sequence of commands which, when executed correctly, generate the characters. Perhaps it's a bunch of bits or trits that need to be assembled according to some pattern into characters, which in turn need to be gathered into words, which in turn need to be gathered into phrases, which in turn need to be decoded as commands, which in turn need to be... you get the idea. And you see there that the alphabet that was used to encode the words of he phrases of the commands is just another layer of encoding, like all the others. So perhaps, to judge a language, we should look at a level other than the alphabet. Words, perhaps? The size of their vocabulary? But can even that help us? I do not believe so. The highest level I think you can get in language is the statement, command or instruction. "Give me all your money". "It is sunny today". That kinda thing. Most human languages contain an infinite number of these. Now I'm gonna make a logical leap here and say: any language can describe any concept. That's a big idea. You often hear "there's no way in English to say the concept X", where X is something like schadenfreude or whatever. Now, ignoring for the moment the fact that [schadenfreude is totally an English word now](https://www.merriam-webster.com/dictionary/schadenfreude), you'll note that the dictionary entry for it defines the word *in English*. So while in some language there may not be a native term for "blue", you can damn well bet there's a native *phrase* that can be used to describe blue. Let's look at the field of computing. It has been shown that any system which is [Turing complete](https://en.wikipedia.org/wiki/Turing_completeness) can do anything that any other computer can do, including evaluate any arbitrary algorithm. And there is a set of computer languages which have a minimal instruction set, languages such as [brainfuck](https://en.wikipedia.org/wiki/Brainfuck) (8 instructions) and [JSFuck](https://en.wikipedia.org/wiki/JSFuck) (6 instructions). These languages have been shown to be Turing complete. Therefore, any mathematical, logical or algorithmic concept can be imparted using a vocabulary of just 6 instructions. I'm not going to say this is equivalent to a human language, but it distills a truly vast area of human discourse down to 6 commands. Therefore, I'd argue, vocabulary size won't tell you anything either. Even things like whether it complies with [Zipf's Law](https://en.wikipedia.org/wiki/Zipf%27s_law) don't tell you anything like whether it's a constructed or natural language or anything, since that arises from the way the language is used, not from how it was created. So overall, I think that your scientists are going to be focusing on the information they can get from the "metadata", the "how it was done", rather than the actual message itself. Note that until/unless the message has been deciphered, the readers of the message cannot tell that this layer was stolen tech. Perhaps not even then, unless the message explicitly says so. Even then, they have no way of knowing where along the chain of communication layers the "stolen" stuff ends and the "stuff they are doing" starts. Did they steal the radio transmitter? The error correction mechanism? Did they steal the encoding? The alphabet? The language? We have historical examples of all of these on Earth, so we know all are possible. Even if the stolen parts are clearly marked as such, it still tells the scientists information about the societies that the scavenger-culture has access to, so it's still valuable and will still be studied. Not only that, but it tells the scientists about the sending society that they can use the tech, so again, still useful. [Answer] The alphabet *per se* doesn't help you, but the quantity of information they exchange might. Essentially there are deep connections between energy and information. In information theory, we measure information using entropy, a term you might previously have associated purely with the laws of thermodynamics. Where this helps you is that there are theoretical (for now!) lower bounds on the energy required for computation/information processing. Let's assume your protagonists are monitoring the total energy emitted by the alien civilization (thermodynamics again, energy is never created or destroyed, just transformed) as well as reading transmissions: they could then calculate that the aliens are using nearly all their energy for information processing, using computers that function close to the physically-allowed limit (imagine an Earth in which data centers use all resources not absolutely required to keep us humans alive). This would be a little scary because it means the aliens have computers that reach the limit of what is possible in our universe and dedicate nearly their whole economy to running their ultra-efficient data centers. Of course, this doesn't leave much energy for traditional weapons, but you can imagine what they could do with *cyber* weapons! More imaginatively, they are mostly playing some hyper-advanced version of Fortnite, and their strategy - if they even notice you! - will be to let you join their ultra-addictive game, so carefully attuned to your reward system that you'll forget your plans for galactic hegemony and focus on climbing their leaderboard instead. ]

[Question] [ In some alternate history, Europeans never discovered the Americas for one reason or another. Maybe the initial motivations just weren't there, or maybe the visionaries of the day fell ill and died before they could change the western world forever. Obviously this would drastically change European history quite significantly in several ways. However, this had me thinking. What of the Native Americans? If the Europeans never discovered their land as early as they did, would the indigenous people of the Americas have eventually formed their own states? Would the empires of South America eventually reach north to conquer the North American mainland? How about their technology? In the absence of the scientifically-minded Europeans to share their technologies, would the people of the Americas inevitably invent them on their own? [Answer] The native Americans *DID* form their own nation states in south america. The Maya, the Inca, the Aztec, the Pueblo. The idea that the North American natives were all a bunch of stone age subsistence hunter-gatherers exists because something like 90% of them died out from the diseases that swept the continents after the Europeans made their first brief contacts with them on the edges of their civilizations. The stone age tee-pee dwellers we ended up conquering were actually the post-apocalyptic remnant of an originally much larger more complex culture. There is archaeological evidence that they actually were experimenting with copper smelting, and possibly a few in the pacific north west may have even begun tinkering with iron. The reason why these metal artifacts were not listed as crafted by the natives is due to 2 reasons: 1. By the time Europeans were having extended contact with them the methods to produce such items had been lost (again, we were dealing with the last few stragglers left over from an apocalyptic series of plagues). Europeans never witnessed natives crafting metal and thus assumed that meant they had never known how in the first place. 2. Because until recent archaeological digs there was no first hand evidence of metal crafting, historians dismissed any Native American made metal artifacts as something the Europeans must have given to them for trade. Here's an image of some native american daggers that until recently had been dismissed as European made trade goods: [](https://i.stack.imgur.com/AWgWT.jpg) So in summary, they were pretty well on their way to doing exactly what you describe before our diseases put the boots to 90% of their population in what may be the worst and yet also hardly recorded plague in human history. [Answer] Have you been following the news recently? About a week and a half ago, stories such as [Lasers Reveal a Maya Civilization So Dense It Blew Experts’ Minds](https://www.nytimes.com/2018/02/03/world/americas/mayan-city-discovery-laser.html) seemed like they were everywhere. Detailed lidar surveys of northern Guatemala revealed the remains of a massive Mayan settlement consisting of *"about 60,000 homes, palaces, tombs and even highways"*. Based on this new information, they're speculating that the Mayan civilization may have had a population of 10 million people, comparing quite favorably to European nations of the time - and, indeed, to many modern nations. So, yes, it's entirely plausible that the pre-Columbian American people could have developed nation-states, because they actually did just that in the real world. [Answer] The existing answers address the fact that Native American states did exist, with distinct, valuable, vibrant cultures. **Excellent.** The second portion of the OP's question is about technology, large empires, etc. I highly recommend Jared Diamond's "Guns, Germs, and Steel" for anyone interested in this topic. It's basically an extended discussion of why Europe conquered the rest of the world, instead of, say, North America conquering Europe. In terms of the New World, several factors limited the native's ability to develop advanced technology, but the largest was: **Lack of Draft Animals** The llama was the largest native domestic animal, after the extinction of horses, oxen, and others around 10,000 years ago - probably due to over hunting and climate change around the time that the Americas were first settled over the land bridge. This limited civilization in the Americas because they could not harness large, domesticated animals to power their agricultural society. Food supplies were less secure, which limited the size of cities. Since cities are centers of learning and drive innovation this slowed technological advancement in the New World. Lots of other factors, including ease of access to mineral wealth (one could literally pick loose coal off the ground in parts of the UK...) played an important role, but the lack of draft animals was absolutely key. [Answer] The Indians did form nations: The Iroquois, Apache, Comanche, Arapaho, Navajo, etc. Whether they would have eventually invented more advanced technology is a question that is, I think, impossible to answer because it is speculating about a hypothetical. Some Indian nations -- the Aztecs, Inca, and Maya -- had advanced to levels comparable to ancient Egypt and Babylon. But most of the rest were still limited to stone age technology or just the beginnings of metal working. One could debate endlessly why this was so. (And just discussing it is liable to get you accused of racism.) Are Indians genetically indisposed to technology? Was it because of some environmental factors? Did they labor under bad governments or some other social liability? Lack of communication with other cultures to share knowledge? Religions that did not encourage a scientific world view? Just bad luck that they didn't get some crucial geniuses while Europe did? Etc. I'm sure there are a million theories. Depending on what theory you find convincing, you could then discuss what it would take to overcome the problem. Given that historians debate the question, for a fiction story you could pick a theory that makes your story work. [Answer] I highly recommend you read Charles C. Mann's *1491* for insight into the pre-Columbian Americas. This may give you a better idea of how the native civilizations of North, Central, and South America could have progressed. As mentioned before in another answer, the majority was wiped out by disease by the time most Europeans arrived. Even in an alternate history, eventually they will have to meet with the Europeans. So forgive me for not remembering this bit of information correctly (or the terminology), but a reason why they died out so fast was that they didn't have the same amount (or lacked a certain kind) of antibodies or antigens that people in Europe, Asia, and Africa already had as they have been in contact for some time. This makes sense just by looking at a map and seeing how isolated the Americas are from the rest of the world. In an alternate history, maybe the Americans (as in the natives of the Americas) would be advanced enough medically to contain such an epidemic before it wiped them out if they were to eventually come in contact with the Europeans? --- On an entirely different topic in regards to your last question, you asked if they would inevitably invent technologies on their own in the absence of the scientifically-minded Europeans. Well, they did have a their own scientific understanding of the world, just different from the Europeans. Just look at Mayan structures, they would have to have some kind of mathematical understanding, and they even claim to have discovered the concept of zero (on their own). An even earlier civilization than the Mayans were the Olmecs, who cross bred wild cord and a grass, to produce Maize... a genetically modified crop that wouldn't have been made without human intervention (also mentioned in the book above). That food fed a growing population. It would be interesting to think of what other advances they could have made on their own without European intervention. But with the rising popularity of alternative forms of food production cropping up these days, such as Permaculture, (look into Bill Mollison's *Permaculture: A Designer's Manual*), you'll find there is a sophistication of more "tribal" methods of agriculture than the popular form of mono agriculture in the western world. Natives in north America practiced controlled burning of forests, for example. Maybe agricultural methods are a bit of a side step from the science question, but it was just to illustrate that there was a dynamic and sophisticated culture who had a deep understanding of the land they lived on, and one that today we are still learning about. [Answer] Any society would have been in serious trouble when ninety to ninety-five percent of the population died to pandemics right before the foreigners who carried those diseases invaded. There has been a serious academic argument that there were limits to how advanced a society could have existed in the New World, Jared Diamond’s *Guns, Germs and Steel*. It argued that, because going north or south takes you into a different climate zone, and going east or west keeps you in the same one, then taking into account natural barriers like rivers and mountain ranges, the Old World had much larger climate zones. Then, most of the megahauna of the Americas went extinct after the first humans arrived and started hunting and burning. He argues that this made it inevitable that the Native Americans would have fewer domesticated animals, especially no horses, and therefore fewer deadly diseases to infect Europeans with than vice versa, since those often evolve in animal species and then hop over. He also makes arguments about how the Natives who remained hunter-gatherers either couldn’t have become farmers, or actually had before the population collapse and couldn’t sustain it afterwards. (For example, the grain highest in protein they might have farmed gives people hay fever.) He also discusses the distribution of natural resources such as tin and copper to make bronze. If you take this as far as it will go, Europeans were the only people in the history of the world who ever missed an opportunity, and everybody else did the best they could given their geographic bad luck. (A statement I doubt Diamond would literally agree with.) Stephen Jay Gould mocked, for example, the part of the book that suggested that China’s geography caused it to be unified, which prevented it from having the kind of international competition that might have discovered the New World. Paraphrasing: “In the universe where the Chinese colonized North America, wouldn’t we saying, ‘Of course it was inevitable: Europe’s geography left it fragmented into tiny nations like Spain and Portugal that wasted all their energy fighting each other. They never could have had the resources to conquer the New World?’” If you want the Americas to do better post-contact, you do want to explain why the pandemics never happened. If they had some kind of limited contact with people like the Vikings who exposed them to measles, smallpox, influenza and the like but didn’t conquer them, and they had already rebuilt from the first wave of those diseases, that might help explain it. Perhaps New World plants like potatoes and maize were introduced to more parts of the Americas through trade. If the point of divergence is earlier, perhaps more domesticable paleolithic megafauna survived. [Answer] People here have mentioned several large South American indigenous states, and several of the larger I would like to point out the civilization of [Cahokia](https://en.wikipedia.org/wiki/Cahokia), situated near the present-day city of Saint Louis: [](https://i.stack.imgur.com/pWOcJ.jpg) It reached its peak in the 13th century, and goods traded all across North America passed through this city. At its base, the main pyramid is larger than the pyramid of the sun at Teotihuacan, Mexico. It was an impressive city. [Answer] Postulate one additional change besides the lack of Europeans: The immigrants over the Bering Straight did not exterminate the megafauna. Both camels and horses were native in North America. This would have given them two draft animals. (It's not clear to me that domesticating buffalo is out of the question too.) The necessary change would be simple: The domesticated them before eating them all. This radically changes cultures. The plains tribes had a huge cultural expansion once they got horses from the Spanish. At last, a way to hunt buffalo. You have the potential of the interior plains with the equivalent of Mongols and Cossacks. You still have the issues of lethal European diseases. Smallpox, measles were the worst. But your second change: Europe had several bouts with bubonic plague. Suppose that you had another one timed to interrupt the voyages of discovery, and the Europeans are delayed until after the germ theory of disease becomes known. Europeans implement vaccination, and the church, once it had seen the effects of disease in the New World sent missionaries armed with vaccines. An alternate way to delay the Europeans: The Maunder Minimum is longer and deeper than our version of history. This would have eliminated the resources that would have been used to explore. A third way to delay: Suppose that the Muslims didn't lose in Spain, and that for the next several hundred years Europe turns into a mess of Islam states. [Answer] If your doing an alternate history, I would say you could change the whole context by changing the one simple fact of the Atlantic exchange that decimated the native civilizations of the America's. Without most of the natives being wiped out by disease the whole of the "conquest" would of been something much different then it turned out. My thinking is that not only would nations be possible, they would be likely and what the Europeans would be dealing with rather then the isolated groups of survivors that made the Americas a relatively easy conquest. It would resemble something more like our western relations with China and the east in the sense that the west while practicing varying degrees of influence over the area never really conquered them. The civilizations of the Americas would of continued to emerge. Maybe at an accelerated rate with an Atlantic exchange that resulted in an exchange of ideals and technology, rather then death by disease. just a thought. [Answer] At the present time the following political entities are in existence in the USA: Caddo Nation of Oklahoma. Catawba Indian Nation. Cayuga Nation of New York. Cherokee Nation, Oklahoma. Chickasaw Nation, Oklahoma. Choctaw Nation of Oklahoma. Comanche Nation, Oklahoma. Delaware Nation, Oklahoma. Fort McDowell Yavapai Nation, Arizona. Lipay Nation of Santa Ysabel, California. Jicarilla Apache Nation, New Mexico. Kaw Nation, Oklahoma. Navajo Nation, Arizona, New Mexico & Utah. Oneida Nation of New York. Onondaga Nation. Osage Nation. Pawnee Nation of Oklahoma. Penobscot Nation. Pinoleville Pomo Nation, California. Prairie Band Pottawatomie Nation. Sac & Fox Nation of Missouri in Kansas and Nebraska. Sac & Fox Nation, Oklahoma. Santee Sioux Nation, Nebraska. Seminole Nation of Oklahoma. Seneca Nation of Indians. Shinnecock Indian Nation. Sycuan Band of the Kumeyaay Nation. The Muscogee (Creek) Nation. Tohono O'odham Nation of Arizona. Tuscarora Nation. Wyandotte Nation. Yavapai-Apache Nation of the Camp Verde Reservation, Arizona. Yocha Dehe Wintun Nation, California. And this is just a drop in the bucket since all 567 Federally recognized Indian governments in the USA are considered "Domestic Dependent Nations", even if they use tribe, band, community, pueblo, rancheria, or something else in their names. So even with the coming of Europeans, there are over 567 current Indian nations in the USA, even if many of them are very tiny. About 1700 the Iroquois were the overlords of a large region in southern Canada, and the northeastern USA, larger than many present countries. The Comanche, ruled most of the Southern plans of the USA for generations, which is sometimes called "The Comanche Empire". In Mesoamerica there were many city states and kingdoms with active military, diplomatic, and political lives. The Incas in South American founded a vast empire stretching for three thousand miles from North to South. Many Indian cultures used agriculture and many important food plants were first raised and modified and improved by Indians. What was necessary for most of the Indian cultures in North and South American to become civilized was to learn from the civilized cultures in Mesoamerica and South America, and catch up with a few thousand years of advances. Many Indian cultures in North and South America used pure copper, gold, and silver where it could be found. in South America smelting and alloying of metals was practiced. Metals were mostly used decoratively, but there was some use of metal tools in some societies. Metallurgy would have continued to advance and spread from culture to culture for hundreds and thousands of years until all the Indian cultures eventually entered the bronze and iron ages. ]

[Question] [ A few decades ago, a new glorious invention in our huge FTL interstellar empire was created - teleportation tech. A 2 meter cube is technologically put in a "Warp" field at one location and deployed 1 minute later at the destination (if there is a transporter there. If there isn't, it takes 5 minutes). You can teleport anything but heavily radioactive elements like uranium, up to the moon and back. You can also teleport humans and animals. The tech is mostly used in military and spaceships. Except, there's a nasty side effect. In 0.1% of cases ( the actual percentage is a closely guarded secret that only a few people know. Not even all teleport technicians know how high the "number of malfunctions" is) , whatever you teleported doesn't show up. In fact, it gets replaced by a nasty warp creature made of material you teleported (let's call it a "demon") which is actively hostile to human and alien life. If you teleport a human being, it can be replaced with such a creature (which might even look human, at first glance, but is not, with the original human dead) but which has an innate connection to its home dimension, can summon more creatures by fiddling with the teleport and wants to violently kill all humans, because killing humans and aliens gives them an unprecedented high. Once the ship blows up/loses power, the "demons" die too but they are too drugged up to notice by that point. If you teleport 100 kg of pudding, it is replaced with a surprisingly tough shape-shifting demon-possessed pudding golem which tries to do the same. Demons are quite hard to kill and it usually takes explosions and incineration by a fire of at least 300 degrees Celsius to kill one. Or 10 days without nitrogen in the coldness of space, but are otherwise pretty much immortal (they eat and breathe nitrogen and don't die from old age). What would the use of the technology be (how to use it safely) and why would anybody use it? Would you make armored bunker "demon resistant rooms" and put the teleporter in there? Why would anybody use technology which can potentially kill everybody involved, if only in a small % of cases? (somewhat related xkcd: <https://xkcd.com/325/> [](https://i.stack.imgur.com/NwAKB.png) ) My idea was that teleporters were used on space navy ships and that 20 or 30 years ago the space navy might lose a whole ship to a runaway "demon" from teleport incident. That problem is solved today and teleports see somewhat regular use. How was it solved? How often is it used today, 50 years after introduction? [Answer] The teleport "conversion" was solved for military ships by the simple expedient of putting the teleport receiver inside an armored compartment with a large, fast-opening door -- to vacuum. Any received transmission is interrogated in a manner that has been developed to provoke "demons" -- but is reasonably harmless to humans or other legitimate payload -- and if the load is found to have converted, a "panic button" opens the vacuum door and flushes the demon out into space, where it will either (eventually) suffocate or collide with something (a moon, an atmosphere, etc.) at an orbital or higher velocity, vaporizing it. A bigger problem was the loss of teleported personnel; this has made teleportation of living things (especially humans) an emergency-only procedure. I *might* step into a teleporter if the alternative was, say, dying as my ship's power converter overloads (and too little time for escape pods to get to safe distance) -- but I would resign a multi-year commission if there was as much as .01% chance that getting home for a furlough would result in my instantaneous death (or transport to the "demon dimension" which is the same only it hurts more) and that was the only method offered. [Answer] It was weaponized. The military now have the ability to teleport sufficiently large numbers of items to an enemy city (or key military facility, spaceship etc.) to trigger a demon invasion. No need for tricky-to-handle plutonium to destroy the enemy, just teleport them a few thousand packs of, say, Stay-Puft marshmallows. [Answer] In a real emergency, maybe you can convince somebody to hop in, but it should be noted that for all we know getting dumped into the hell dimension is a fate much worse than death. Instead, I suggest we just keep using regular 'ole chemical rockets. But, the teleporter is still really useful here. Assuming the energy cost is paid at the sending end (you indicate that you can send to non-teleporter areas in 5 minutes), instead we make our fuel tanks just big enough to get into orbit. From there, we teleport fuel directly into the combustion chamber (or sufficiently securely designed fuel tanks). This gets us around the Tsiolkovsky rocket equation, and who cares if your rocket fuel is demonic? That stuff is already as nasty as it can get, and is about to be exploded. [Answer] Seems like infinity energy, just teleport some stuff and there are chances you get something that would never die and doesn't need much to survive. Stick that demon into a large hamster wheel facing some people and *BAM*, unstopping energy generator. Just hope the demons doesn't break out. [Answer] All teleported goods and passengers are kept in nitrogen free quarantine for 11 days and observed for signs of extradimensional naughtiness. Either in vacuum, or in a low pressure pure oxygen atmosphere, depending on which is least damaging to the thing you're sending. People can't breathe pure oxygen at Earth sea level pressure, but we can breathe pure oxygen at lower pressure. It's inconvenient, but still more convenient than going further than low Earth orbit in a rocket. Note that many things that are barely flammable in normal air become very flammable in pure oxygen. So on the one hand you may need some extra safety precautions, but on the other hand it will be easier to incinerate that shipment of pudding that got too rowdy. [Answer] Passengers: Its usage will be affected by not doing living things unless absolutely necessary. General anti-demon rules: Teleportation to friendlies is as a rule done towards a receivingpad without the controls to teleport. In case a demon takes posession of the material (say a crate of plasma weapons or something similarily harmless if it came alive) the demon will not have access to a working telepad to call in more. Camera's at the receiving end will alert any technician at a working teleporter and they will go into lockdown and power down all teleporters, also in the event of camera shutdown just to be safe. This limits the potential for demons to call in more and makes it easier to get control of the situation. Further safety measures are that the receiving end can be build to contain any threat. Since the demon likely inherits most of the material properties of the beamed over material you can prepare canisters with a gas, liquid or even put plates of material on the ground that would react violently with the beamed over material when released. If the teleport receiver might get damaged in the process alternatives are in place. A few flamethrowers in the surrounding area for example. Or the teleport receiver is in a room with a room around it where lots of remote/espatier wielded guns, acids and such can be made ready. The teleport receiver could be retracted into the ground and the chamber violently spun while some heavy balls are released to crush whatever luckless thing was inside. A dedicated heavy weapons team with a deployed gun could watch the pad and blow anything remotely not looking like what they were supposed to receive out of the way. The options are pretty much all over the place. Matter creation: In the case that the demon accessing a teleporter does not need to teleport materials to create a demon army you can use this to create matter. Just have a controlled environment where the demons are called into being (say an empty ship without any weapons or engines) and when enough demons are called into being you blow it to pieces and collect the matter. In the case the demon does need matter to create new demons you can limit the amount of loose materials and superfluous things that can be ripped loose and teleported for demon creation. [Answer] The usage would be varied, but I think the primary uses would be for material movement and for special forces. Teleporters would be a fantastic supply chain tool. A way to get a big box of rations or bullets across great distances that cannot be interfered with by opposing forces is a fantastic advantage to the Empire. Create your box of goodies as a small atmospheric re-entry vehicle and pop it into a geosynchronous orbit above where you need it, kind of like the "biscuit bombs" used for re-supply in the south pacific in WWII. If you get a demon instead, it will be in hard vacuum for a while and die. Evil demon problem solved. It could work because there is a very small window for the enemy to destroy the interstellar care package. The next use would be to deploy special forces deep into enemy territory. This works well for a number of reasons. Your special forces will have the primary purpose of popping in, destroying as much as they can and then going to some sort of extraction point to be picked up by manned ship, or another teleporter that was sent as a separate package. If things go off without a problem, nasty things happen to the enemy. If you get demons, nasty things happen to your enemy. Win-Win for the Empire. The problems of people being afraid of the risk of demons is almost not a problem because special forces troops already know they might not make it at the best of times. And if they go to demon territory, they will claim to be ready to give the Devil himself Hell. [Answer] It will not affect development of the technology at all... not until the problem is discovered. This wonderful technology was adopted extremely quickly, and it was only some years later when the first demon came out that people suddenly had to backpedal, scale down use, and retrofit protection devices on existing devices. Total abandonment is not possible because a large segment of the economy already depends on the technology (humans on other planets cannot return, some industries depend heavily on imported ore, food farms have been set up in orbit following ecological disasters and depend on the teleportation to feed Earth). Why this problem was discovered only after so long is the object of intense speculation: did the demons simply discover teleportation later? Maybe the first replacement was a random fluke, and the demons quickly put effort into intercepting as many transmissions as possible once they realized that another civilization was intruding on their domain. This would explain large fluctuations in the percentage of impacted transmissions. [Answer] If you're wanting the teleportation technology to be widely used, then you're going to need to keep some secrets. I'd probably say that the cover is that teleportation causes a low-level of radiation: 1. The schematics of the teleporters are closely-guarded industrial secrets. The utility of the process would generate revenue, giving you a "teleportation lobby" to protect these secrets. 2. The surroundings of the teleporters ave thickly coated "shielding to protect the surroundings from the radiation". In reality, these contain the disposal mechanisms for the teleportation contents. If demon appears, the contents are neatly incinerated and re-skinned. 3. Teleportation operatives are highly vetted and trained (read: brainwashed). No one knows about the contingencies, no one knows about the reality of the "industrial accidents". 4. Teleporters are large. If it's done in bulk, then loss quantities stay the same, but it becomes much more difficult to nail down the specific probability. Sufficiently large teleporters also need much more efficient disposal mechanisms, though. The object of all of this is to keep the public unaware of the downside. You could also have some large-scale "radiation leaks" where the demons were able to escape, and the entire area needed to be cleansed, but these were used to re-enforce the containment measures, and the propaganda about radiation and "reducing exposure". If you wanted, you could also go through what would happen when the secret gets out. The sudden collapse of the industry, aswell as all related containment protocols that they enforced. The section of the population intent on reasoning with the demons, and attempting to exploit them (as some of these posts have been through). [Answer] Put it on jupiter orbit or further and **you can travel back in time**. Why? Well "instant" travel from physics perspective is the speed of causality (=speed of light). You probably know about time dilation - the faster you travel, the slower your time relative to observers in destination. If you traveled somehow at the speed of light, the route would be *instant* from your point of view, even if you traveled hundreds of light years. Now your teleport takes things to destination in 1 minute, if there's a port. But it will never take less than 30 minutes to get to Jupiter by light speed. So your one minute is shorten them lightspeed "instant" travel. You experience even less time than light, which experiences zero time. What exactly happens is speculative, but almost all logical thought routes you can take based on known physics mean that you will travel back in time. (there are other ways than the one I outlined to reach the same conclusions, see the article below) Your teleport does not need to send humans. It may just transfer a very tiny computer or SD card or USB drive and you'll be sending information back in time. If you use micro SD, the resulting random demons should be easy to burn with some laser automatically if they appear on either side of this time-internet. You can use this to know movements of enemy forces before they happen, or to know when the world will end. Everything already happened if you can send information back in time. Also worth reading: <https://www.askamathematician.com/2011/09/q-hyperspace-warp-drives-and-faster-than-light-travel-why-not/> [Answer] **Nested teleporters**. If your teleport goes awry, just teleport the whole room into space. Then go retrieve your teleporter in 12 days. [Answer] In an effort to solve a completely unrelated problem, I put a little something on an Excel sheet. It should be transcribed correctly here (unless it's not). With * $p$, the probability it backfires * $n$, the number of uses * $q$, the probability it backfires at least once within $n$ uses It gives * $q=1-(1-p)^n$ , as I said the probability it backfires at least once within $n$ uses * $n=ln(1-q)/ln(1-p)$ , the number of uses at which there is a probability $q$ that it backfires at least once Assuming $p=0.1\%$, after 100 uses, you have a 10% probability to end with *at least* one pudding monster. After 1000 uses, you're at 66%. After 3000 uses, you're at 95%. Needless to say, you will need a pudding monster defence budget, if you are going to use this device with any sort of regularity. For transporting goods, it would be fairly easy to just isolate the device by putting it in a big oven-like room/building, check arrivals for ravenous monsters and activate the defence system when necessary. This may damage the device, and your insurance premium will be quite high. But it might be cheaper than the cost of exploding rockets or refining unobtainium fuel for spaceships. Decisions, decisions. For transporting humans, a typical Boeing 747-8 seats 467 people according to Wikipedia. So, assuming you transport people one by one (or that the probability to be affected is per person rather than per trip), you have a 37% chance that at least one of your passengers turns into a bloodthirsty creature from hell that may or may not kill the 466 other. You decide if you want to buy that ticket. --- For comparison, [this study](http://publicapps.caa.co.uk/docs/33/CAP%201036%20Global%20Fatal%20Accident%20Review%202002%20to%202011.pdf) on "*worldwide fatal accidents to jet and turboprop aeroplanes above 5,700kg engaged in passenger, cargo and ferry/positioning flights for the ten-year period 2002 to 2011*" (essentially big planes), page 30, gives a fatal accident rate of 0.6 per billion flight, or $0.00006\%$ which can be compared with the device's probability of failing. Taking $p = 0.1\%$ again, that's a difference of 4 orders of magnitude. I chose air travel because it's probably the closest analogue to taking a spaceship to the Moon we have. Also I couldn't find data on fatal accident rate per trip for road transport. [Answer] **There is no real side-effect.**, except for occasional hangover-like symptoms and few broken fragile items. The whole thing is a scam, used to remove unwanted people and steal valuable parcels. [Answer] The **Johnson Rectifier**. Scientist Maria Johnson pulled logs from teleporter machines that caused demon events (many brave people died to gather these logs) and discovered a fluctuation in the quark pump, every time. She invented a quark pump filter and since then, no teleporter equipped with one has had a demon encounter--unless the filter was damaged. [Answer] The answer depends on many details. First, assuming the technology has just been invented, is the percentage of demonization even an accurate number? It is one thing to say "we have to maintain the quux field within a range of 15 angstroms (and we can do it reliably 98% of time), else bad guys are coming out of woodwork on the receiving end" vs "we teleported sandbags 100 times and twice we got monsters". If it is the first case, we could limit the transportation of humans to emergencies and have protocols for demon liquidation on both sides, as described in other answers. As a side note, if possible, there should be 2 one way teleporters instead of a single both ways one, to limit extra summonings. If the percentage of demonic possession is *only calculated from empiric evidence* though, you have no case to even build anything like that with one end on Earth. It is far too dangerous, because the is no telling *what might happen next*. [Answer] Why risk human teleportation at all? Robots have been an effective means of exploring the universe for decades, and still make up the majority of our exploration team - and if a demon *does* manifest from one of these robots, well-armed robots are more than capable of dispatching such a creature, with only the loss of some equipment. Teleportation would then become a frequently used pre-cursor to colonization, with protocols in place to swiftly deal with any demon incursions on the receiving end of the teleport. [Answer] This is not an answer to what the OP asked, but it's something about teletransportation that always bothered me. It may be useful in OP's plot. **Teleportation means death**. Even when no demons are generated, all your matter is disassembled into particles and then vanishes. You die on departure. What is reassembled on the other terminal is a copy of you, that has all your memories and thinks it's you, but it's not - you're dead, that's a clone! Star Trek has even scratched the issue a bit on the TNG episode Second Chances (6x24) where William Riker was copied on a transporter incident. A second Riker was created, who thinks he is the original. But the original failed to be killed, so we ended up with both. This might be used as another "well kept secret" in OP's story. [Answer] Usage: Only if **ABSOLUTELY** necessary. However, if it is necessary to use it, here are a few general safety precautions: * Quarantine in a low-oxygen, nitrogen-free atmosphere. * Seperate quarantine chambers for every living thing. This is because, believe it or not, we actually produce a small amount of nitrogen when we exhale. As a result, the quarantine is pointless if you have >1 living creatures (plants included) in the room. * A "big red button" which throws everything in the quarantine chambers out of the airlock, should demons be detected. * "Site-to-Site" transporting ***ONLY*** if it is a "life or death" situation. I hope these answers solve your problem. *Post Scriptum:* Oh, by the way, I would suggest that you NOT use term "demon" to refer to the aliens, as doing so is *guaranteed* to tick off any Christian / Jewish / Muslim / Hindu readers. [Answer] Every passanger will carry a camera with him. He/she reaches a secured place, hands out the camera through a special compartment to the security team. The team analyzes the recording of the entire teleportation process and searches suspicious activities. The camera is embedded into the passenger's wear, so that it will not draw the demon's attention and appear as an integral part of the process. [Answer] In the comments, I pointed out that teleportation breaks the universe by allowing infinite energy. > > Infinite energy (which breaks a WHOLE lot of universes): Build very tall tower, line a shaft with copper coils. Teleport huge magnets into the top of the tower, then let them drop down the shaft. > > > The relevant parts of the response (in chat, so few people will be bothered to look) are: > > The teleport works by putting something into warp field. > > > It takes quite a bit of energy to put things into warp. There is no magnet big enough and no copper shaft long enough to repay that cost. > > > Doing the math: 2 cubic meters of matter means one can teleport a magnetic cylinder of iron 1.25m tall and 1.25m in diameter. (Cubes might be more efficient, but the cylinder is easier to handle) The volume of that cylinder will be 1.52 cubic meters. That will weigh 12,045kg. The tallest building in the world is the Burj Khalifi at 829.8m. (Lets ignore its basement, despite it being useful space for our linear induction generator.) We can ignore terminal velocity; the mass will be falling so slow that the atmospheric drag won't matter, due to Lenz's Law. Also due to Lenz's Law, (very nearly) the entire amount of kinetic energy will be turned into electricity. Restating to make the point crystal clear: The amount of electricity generated is the same as if the mass had been dropped down a vacuum chamber and we somehow harvest all of the energy of impact. At 829.8m, it will have the same potential energy as if it was impacting at 127.3 m/s (459.11 km/h). Weighing 12,045kg, it will deliver 97,950,421 joules or, to put into more familiar terms, about 27 kilowatt hours. In reality, the mass would be traveling about 5cm/s, so would take about 16,596 seconds, or 4.6 hours to deliver its 98 megajoules, giving it a wattage of 5.6 kilowatts. This, of course, ignores the fact that you have an FTL society. FTL societies are used to making megaprojects, like Dyson swarms. FTL societies understand *very well* the implications of relativity, especially the most basic premise: ***every** speed is relative*. So, why start our magnet at zero velocity relative to the surface of a planet? Why not teleport our magnet to a spot near a grand funnel of copper tubing a couple AU long? Since velocity only matters locally, we can have a zero local velocity of the magnet be equal to 1c relative to our funnel (or vice-versa; our funnel with a zero local velocity will see the magnet traveling at 1c). 12,000 kg of mass traveling at 2,997,925,458 m/s is going to deliver far more joules than traveling at 127 m/s. About 2360000 times more energy, for a total of about 2.3 exajoules. If the teleporters run on anything around 2.3 exajoules, your civilization is completely alien to anything a modern human could understand, just as stone-age humans would be absolutely perplexed by humans using computers, driving cars, and having flushing toilets. Sure, a stone-aged person could adapt (humans have been smart for a very long time), but a person then could never have foreseen the most mundane aspects of our daily lives now. We can not draw any conclusions about the weapons and demon mitigation tactics of a civilization that far advanced, just as 2,000 years ago, we didn't know about firearms, tanks, bombers, battleships, and aircraft carriers. ]

[Question] [ My alien civilization is highly advanced. Their ancestors created wondrous things from medical devices that can cure nearly anything to warships that can defeat nearly any enemy. The problem is they have forgotten how these things were created. They have all lasted for centuries, their inventors long dead, and the current inhabitants can only barely maintain them, and usually with patchwork and improvised solutions that are making the tech less and less effective. **How could a civilization get to the point where they have forgotten the secrets to their own technology?** Edit: (Thanks Morris) This would be as if modern society lost the knowledge on how to create the microchip, or the internal combustion engine, but the items were so durable, it was centuries before they started to break down Edit 2: I'm not thinking of the obvious, like disaster, war, or a crisis that would have caused sudden loss. [Answer] **The Holy Order of Engineers** You can take this more or less literal (keep the religious aspect or divorce this answer from it), but either way it works. Due to an internal power struggle long ago (that possibly developed into a civil war that was stamped out), the Powers That Be determined that equipping the masses with the understanding of how to build or develop weapons of war or other technology that could be leveraged militarily, economically, or politically were dangerous to have in the hands of the masses. And so the Holy Order of Engineers was created. This very closed-mouth and tightly-knit organization was given authority and charge over all higher learning, research, and development that possibly could relate to engineering or R&D, or in many cases, the actual manufacturing (for the technological crown jewels). The Followers of Engineering Ongoing was founded as a sister organization to the Order that was taught how to maintain infrastructure. The Followers were overseen and governed at arm's length by the Order as while the Followers were less dangerous than the Order, they still had the potential of arming the masses with easily exploitable technology. The Order dispatches Inquisitors routinely not only to weed out engineering from the masses, but to check in on the Followers to ensure that anyone too intelligent, creative, ambitious, or otherwise on the path of engineering was either recruited or put to the sword (or mag rail gun, as the case may be) and made an example of. And in this manner your civilization continued for quite some time. Centuries perhaps. But like all great things this came to an end. The governing authorities grew to not trust the Order and their ever increasing influence, or perhaps the Order grew too proud and attempted to rebel. Either way, while the Order understood amazing technologies, they lacked the infrastructure and manpower to defend them. It wasn't long before the Order was all but stamped out, and the last few members of the Order followed their holy code to protect their archives from the masses, and deleted or burned them all. (If in the modern era, the Order probably had designed a magnificent virus that was able to crawl through all their servers and scramble the data irreversibly) The last few members of the Order defected and were folded into the Followers, however these measly few weren't enough to provide understanding of these incredibly advanced technologies besides the insight to deal with perhaps more advanced troubleshooting, and even then not in all cases. And so your civilization limps along, possessing the marvelous technology of the Order, but none of its understanding. [Answer] Their toolset became more and more sophisticated. Their universities and trade schools paid lip service to starting from first principles, but that got more and more perfunctory. For a comparison, take modern software development. Many programmers can do java, or javascript, but people who can *really* write machine code are a tiny minority. I've met young programmers who couldn't explain what a bubblesort is, and why it is usually inferior to quicksort, but superior in a few cases. So expand this into the future. There are plenty of people who can build starships if they have a functioning nanofactory. There are some who can build a nanofactory with nanofac assembly tools. But the people who can build the tools to build the tools to build the tools get fewer and fewer, until their number gets *too* low. [Answer] Consider how far removed, for example, Shakespearean English is from the English we speak today. That's a mere 400 years of linguistic evolution. Now imagine that Shakespeare wrote a technical manual. The language of the forebearers has fallen out of use. No one alive today speaks the ancient tongue. The forebearers left detailed instructions on how to replicate their great machines, but linguistic scholars have tried and failed to make sense of the text. Since the machines never needed to be replaced (until now), the study and advancement of engineering ceased long ago. Apprentices abandoned the field for newer, more exciting opportunities and the knowledge was never passed down. [Answer] So, the simplest answer is a confluence of two factors. **First: A technological 'plateau'.** Your society reached a point where further refinement of the basic fundamentals of their technology came to a halt due to diminishing returns on development. A good example of this is the widespread stagnation of military technology during the interwar periods prior to WW1 and WW2. Nobody cared enough about improving things to bother trying to figure out HOW. A more modern hypothetical example would be the point at which the technology required for a smartphone gets so small and efficient that there's no practical benefit in improving it anymore. Basically, in the absence of new frontiers (either physical or technological), your society loses the incentive to innovate, which means most of the citizens of your civilization have no reason to learn how any of their stuff works, because that information just isn't useful. **Second: Massive automation of manufacturing.** Continuing on the theme above, the only two reasons the living members of your civilization would have to learn how their technology works is either to improve it, repair it, or build more of it. We addressed item one in the first section, this section addresses the other two. In the absence of any need to continually retool their manufacturing to accommodate new advancements, your civilization would naturally tend more and more towards automation of their factories. You put raw materials in, finished goods come out the other side. You have robots to build the goods, you have other robots to repair THOSE robots when they break down. You have MORE robots to repair anything ELSE that breaks. Over time the living members of your civilization who actually know how any of this works become fewer and fewer because their contribution has little or no benefit. Eventually the last living member who understood how to build or repair any of the robots dies, and nobody notices because the robots are doing just fine keeping themselves in working order. This state of affairs could persist for a LONG time without any problems, until civil unrest or disruption of the supply chain of raw materials caused things to start breaking down, and by that point there would be nobody left who knew how to repair or rebuild them. [Answer] # The "death" of AI rulers. [](https://i.stack.imgur.com/qF32g.jpg) Their civilization built powerful artificial minds, for thousands of years those mostly benevolent Minds controlled their civilization, ran their factories, invented their medicines, built their spaceships and designed their devices. They built things to last and built everything with a lot of failsafes and fallbacks. But eventually there was a brief and almost silent civil war between the Minds. During that war a host of computer viruses designed to target Artificial Minds were released by both sides through the civilizations networks and infrastructure. One day the citizens of the civilization woke up to find their rulers dead Their queries addressed to the ruling minds unanswered and everything was left in failsafe mode. They tried to build replacement Minds... but everything in their civilization is suffused with computer viruses designed to find and kill such AI's. So they found themselves surrounded by devices that mostly still worked, even many factories to produce things. But the Minds had never explained how the Magitech really worked, perhaps it was simply beyond the comprehension of normal organic minds. So now they hobble along, flying ships they don't really understand, using devices they may not be able to reproduce. [Answer] Because they are *too* reliable there is no need to manufacture new things and thus no incentive to *remember* how to manufacture them. If the technology is reliable enough it might be inevitable… Your great-great-great-great-grandfather was a fantastic engineer and built all these fantastical devices; star-ships for killing enemies, auto-docs to heal wounds, maid-bots to launder clothes; all of them intended to last for five generations without maintenance. And his daughter became a great warlord with impeccably pressed clothes. Her son became a philosopher king bringing peace to the empire. His daughter became a schrewd business owner, making millions. Her son focused on poetry and wrote heartbreaking sagas. So *your* father was a poet and you inherited star-ships and maid-bot that have received *no* maintenance for generations; they didn't need any but are now approaching the end of their service life. Back when you could buy a new auto-doc, you inherited a nearly new one from your parents. Their children *could* still buy new ones, but they were expensive due to low demand and the family-doc still works as good as new. Another generation and the only way to get a new one is to manufacture it yourself. The knowledge is available, but why bother; it still works and is expected to for the rest of your and your childrens lifetime. By the time you actually *need* a new one the knowledge of how to build one is lost. It doesn't take much, a slight technological plateu so the new version of robo-maid, while *better*, isn't worth skipping movie-night for; a stable population so the total number of widgets required for everyone doesn't grow and of course: ridiculously reliable machines. [Answer] ## Secrecy If your technology is a trade secret, then only a few select people are allowed to know exactly how it's done. In fact, it may be complex enough that some people know how to make some parts of the whole, but no one person knows all the secrets necessary to get from raw ingredients to finished product. The [formula for Coca-Cola](https://en.wikipedia.org/wiki/Coca-Cola_formula) is an example. > > According to the company, only two employees are privy to the complete > formula at any given time and they are not permitted to travel > together. When one dies, the other must choose a successor within the > company and impart the secret to that person. The identity of the two > employees in possession of the secret is itself a secret. > > > It is theoretically possible that some massive disaster could wipe out both people at once, dooming the full formula. Assuming it's not written down in some bank vault or something. [Greek Fire](https://en.wikipedia.org/wiki/Greek_fire) is another example of a trade secret that was lost to time. Any time there is a thing known to only a few people, that lack of redundancy makes it more likely that the knowledge is lost to time. ## State Collapse When Rome fell, Europe lost a great deal of [technology](https://en.wikipedia.org/wiki/Roman_technology). Roman roads, Roman sewer, aqueduct, and other architectural systems were all lost for centuries. During an empire collapse, people stop worrying about major projects or passing down critical but complex skills. Their focus shifts to survival: food, safety, shelter. Everything else becomes "we'll worry about that later," but if the collapse spans a generation, then later becomes centuries. We didn't surpass Roman roads until the 19th century. Rome had better roads between cities at 10 CE than Washington DC had, inside the city, in 1865 CE. ## Political/Religious Censorship If a political, religious, or combined power takes control, they may ban entire segments of technology outright. [Galileo Galilei](https://en.wikipedia.org/wiki/Galileo_Galilei#Controversy_over_heliocentrism) faced censorship for his works on heliocentrism, for example. Those parts of modern technology that involve mass communication or the internet are largely banned in despotic regimes like North Korea. If a society is never allowed to study, learn, expand, or pass down knowledge of a technology, then it will quickly be lost to those people. ## Poor or No Documentation Perhaps the technology is poorly documented or only verbally documented. If all the details are written on paper or papyrus and there aren't enough copies that survive, then the knowledge is lost. Or if all of your critical texts on the subject are digital and there's a massive EMP or other catastrophe that destroys your computers, then that knowledge is gone. Perhaps your survivors can restore some of the knowledge from memory, if they survive and if they can remember enough to matter. But probably not all of it and not in all cases. What separates this from Secrecy, above, is the intent. Secrecy implies a desire to prevent outsiders from learning a skill. Poor Documentation is less about preventing the spread of knowledge and more about the inability to spread that knowledge. Examples of this include many of the ancient monument sites like Stonehenge, where we know it existed, but we simply don't understand all of the reasons why and/or the methods how they were built. Was the construction considered a secret or perhaps a state collapse? Maybe, maybe not. But the lack of permanent record clouds the knowledge, certainly. ## Natural Disaster If all of your knowledge of a specific technology is housed in one geographic location, then a major disaster could destroy all of it. An earthquake or fire could destroy a building, losing everything (and even everyone) it contains. This is less likely to be a sole reason than the above. More likely is that this is the flashpoint that destroys a technology because of the limits placed on it by the above reasons. Secrecy forces a lack of redundancy that then leaves it vulnerable to an earthquake, for example. ## Combination Probably, many technologies that become lost over time will be lost through a combination of things, not just any one thing. We do not know exactly how the [Egyptian Pyramids](https://en.wikipedia.org/wiki/Egyptian_pyramid_construction_techniques) were built. Is that because the engineers were lost during the fall of the Egyptian empire? Or because there were so few engineers? It is difficult to be sure, but probably a combination of secrecy, documentation, and state collapse combined to cause the loss. Or maybe a natural disaster triggers a state collapse. Or Secrecy and/or religious/state censorship combined with a natural disaster destroy all the holders of your knowledge... [Answer] You should look into the lore of Warhammer 40k; which has a similar premise. The natural progression to "faith based engineering" is more of an inevitability. As technology becomes more advanced, there is a bigger body of knowledge that goes into making it (metallurgy, side effect mitigation strategies, cost/performance/reliability optimizations, some hundred (maybe millions) of smaller designs incorporated into the final product). This is starting to give rise to "faith based engineering" (especially in the rapidly growing field of software engineering). Faith based engineering is where you accept something is true without knowing how it works. For example, you might not understand how a smooth nail works, but you do understand that if you ram it into 2 pieces of wood, it will hold them together. (You have only faith/experience that the nail will work as advertised) However without the array of knowledge of why things work, you wouldn't understand that the optimum angle for a nail to hang a picture is different for wood vs ice (ice has far better shear strength vs compressive strength, so you actually want to angle the nail down from the horizontal for optimal strength) And that is just the science of how to use a nail! We have chips, engines, vortex generators, and ignorance guards (safety features). Can you imagine just how large the body of knowledge is you would need to build a computer? Right now, "faith based engineering" isn't a problem (except maybe in software to a degree) because we have people who specialize in each aspect that goes into a final product. So while no one knows completely how everything works, they can each contribute to the final product (and replace parts that are too damaged for the final person to fix themselves). Keywords "for now". "for now" we have enough resources to sustain a population capable of maintaining everything. There is a hard upper limit to the population size we can sustain, and no upper limit for the amount of knowledge that can go into a final product. This means it is almost inevitable that in the process of creating newer and better things, "faith based engineering" has to be relied on more. Especially if AI are adopted into Research and Development that can literal just try millions of things until they find something that works better, with no understanding of why it works. With finite people, and near limitless knowledge, it will become harder and harder to determine what people need to know, what information needs to be preserved and what archives can be safely abandoned. Just normal errors over time, records will be lost, backups accidently+unknowingly wiped, contents misunderstood and misfiled/labeled. Once enough of the base knowledge is lost, and tech becomes sufficiently advanced enough, "faith based engineering" will be the only way to engineer. [Answer] One possible solution is having a wide spread very basic technology that suddenly isn't viable anymore. Say, for instance, this alien society had discovered a room temperature superconductor. It would be used for all wiring in everything, because the ability to not lose power to heat from resistance. But if some fungus/organism developed that could eat or corrode the superconductor, and was spread far and wide before anyone noticed what was happening, or how bad the problem was, then it could cripple all technology that the civilization uses, from power delivery to microprocessors. \* You'd have some people who could figure out how to jerry rig solutions, assuming they could find other conductors, but these people would likely be rare, and located in places with high population density, meaning less food to go around, and all the chaos that implies. Just about any technology that most other technology relies on would work. \* This is a sub plot in the book Ringworld by Larry Niven. [Answer] The case of the Rocketdyne F1 engine that was used on the Apollo lunar missions is a perfect example of how quickly knowledge can be lost. <https://www.youtube.com/watch?v=ovD0aLdRUs0> [Answer] The first thought that came to my mind is that you actually have the answer in your question: **people simply forgot**. With all the other answer that you got, either in combination or additionally under the circumstance that there was no need to produce new products/machines/tools etc. it's a very likely scenario. With technology that can 'heal anything,' I'd also guess that the lifespan of your alien race got extended. Immortality is either impossible or brings other problems with it, like slowly forgetting ones past. Offspring is possible but highly regulated to prevent overpopulation. Production slowed down until it eventually stopped as there was no demand, surplus machines were simply stored away as a backup, now those also start to break down, turns out those machines weren't perfect after all. So over aeons, none of the machines broke down while, like you said, everyone who knew how to build/maintain simply died one way or another. The knowledge slowly degraded as it was not necessary to learn how anything worked, after all the button to start the engine of the spaceship never failed. "What it does exactly? Well *clearly* it's starting the engine, dummy." I would like to see the face of those involved when suddenly it does not start after pressing the button. Another one, even more severe, would be that the knowledge is actually still there. Archived and preserved, even some ancient masters are still alive, although after some millennia they are... let's just say not as bright as they used to be. Many materials required to make/run most of those masterful machines, if not all (nobody is really sure on that) require a rare substance for their production. A substance that as it turns out is not stable, it's half-life period was a subject of controversy according to the remaining writings about it, which does not really help anybody now that it is gone. The original mastermind behind its invention/discovery is long dead and all is scriptures are based on the fact that certain materials exist, materials that simply degraded and broke apart. As nobody adapted to those changes, effectively nobody can recreate the required materials and any alternatives, do work but not as good, some of those are even causing damage to the machines. [Answer] **Outsourcing runaway.** **Beginning** It may be beneficial for the advanced civilization to outsource all manufacturing to some less civilized place like Earth for instance, where work is cheaper, work safety worse, ecology can be more dirty and these locals still have some brains, even if much inferior. Lower level of general civilization may not matter much, as the qualified engineers, first machines and ready designs would come, making the production possible. Later, however, education will start catching up, making outsourcing even more attractive, as cheaper locals will be able to replace larger and larger proportion of the foreign engineers. **Overcoming of the self-correcting market force** Of course, at some point the free market would shift making outsourcing no longer so profitable. However if the government of the pure planet is strong enough, they may intentionally distort the market, by buying some useless nonsense for huge money from the "higher race". They would actually pay this money for the price scissors to stay and the further technology transfer to continue. Of course, the higher race may also notice something going wrong, but the current situation may be useful enough for mighty ones to use they powers for making others to shutdown. **Total transfer of the technology** Eventually all manufacturing may move into that cheap and dirty planet, closing the former factories first, and then also moving the research departments closer to production. Ultimately only the managers may remain in the former place, but also management can be outsourced and is more efficiently when not done through interstellar distances. Hence eventually we get one civilization making everything for another, just on the basis of some agreements signed generations ago, and few very rich representatives of the once-advanced civilization that still benefit a lot from all this. And the advanced race failed to notice that not just they passed over all technology they have to that they thought it is just a planet of slaves - they have lost this technology themselves. [Answer] How can an advanced civilization forget how to manufacture its technology? This problem has resurfaced throughout countless generations. One which stands out is the knowledge of Hero's Engine. It is the first engine known to have existed before Christ. Its simplicity in construction and manufacturing has never been equaled and the information began to proliferate as the internet developed. Still though, it is propagated through hobbyists. Creative Inventive Genius is rarely understood by others at the time it first surfaces. Tesla is one of the most prominent. But, the most advanced example is Gauss. Gauss developed most of the non euclidean geometries, yet he did not publish any of them. In my opinion his reason for this was that, none of the mathematicians in his generation had any interest in His Gordian "Space" knot. To my knowledge none of the formally educated mathematicians following his generation know what he was referring to as lack of necessity. Today it is simply space is defined as empty by Euclid 2000 years ago. Einstein's last publication actually agrees that empty space has no existence, an obvious lack of adequate definition for any theory to qualify as scientific method. Todays physicists have most likely have never been made aware that mathematicians never require scientific method is violated by all theories which they use fail. Some actually have names stating this, such as irrational and imaginary numbers. Gauss did express his doubts regarding the validity of Euclidean geometry. He would state the obvious proof in the simple statement "space can not be proven because it fails the necessity requirement". He conducted discussions enthusiastically and freely with non-professionals who had no formal mathematical training. The main point intended here is, Gauss, Tesla, Fuller and others were aware of and taught the errors of logic being made with mathematics, nobody listened because it was not understood:?( For 2000 years students have been taught Euclid's space did not exist but they could observe it on lines drawn on sand or paper. Our generation has been taught "its a pixel"? See : Gauss' letters to friends, to learn of his discoveries which he did not publish; because he doubted they were correct. In my opinion he was correct in that assumption. [Answer] **The robots needed to be rebooted** This culture turned over more and more of its technological capacity to automated servants. After many generations the machines were infected with a malware that required they be shut down and their memories wiped or replaced. Once brought back online, they forgot how to do many things that they used to do. [Answer] **All-consuming consumerism**, much like what we see in the USA today. Case in point: Who among us actually knows how to make *any* of the things we use? Name even one manufactured item that is entirely within the comprehension of your average Joe how it's made and where the materials can be found and processed to be within spec for assembly. It's rare--even for a dumb rubber band or metal pin! It's pure revelation to many people today that their puffed breakfast cereals are created by rapid expansion of heated, pressurized grains in a vessel similar to a glorified cannon. Quaker Cereals advertised their puffed rice in the 50s as ["the cereal shot from guns"](https://www.youtube.com/watch?v=_bn1IYlKiZk). It's funny, but you can try searching the Internet for videos of how to make puffed rice. Some might contain a handful of technological insights, but it's not uncommon to find videos that only teach you how to *season* it or serve it, etc. Except for a very few who are still in the almost-forgotten food *production* industry and some of their close associates, and a much older generation, it is very hard to find anybody in the U.S. who has a clue how it's made. [Street vendors in China still make it](https://www.youtube.com/watch?v=ZyJoqS__7O0), but with all of our education and sophistication, we're pretty ignorant as a society about very basic things that sustain our everyday lives. This trend is true for very many modern commodities. There are very few farmers and butchers nowadays compared to the overall population, compared to previously. The same is true of manufacturing. Try to find the number of people who know how cheese is made. Were it not for YouTube and some DIY sites, most of this knowledge would be beyond the reach of ordinary people. Even they almost always lack trade secret knowledge, and even the most hardcore backyard enthusiasts have been unable to replicate basic store-shelf items, and so once the inventors are gone, and the equipment and its documentation are sold or fall into disrepair, many lifetimes of discovery and invention are erased. We have this very strange presumption in our society that we are "intelligent" and "advanced" far above our ancestors because we *consume* so many technologically advanced items. However, **it requires very little intelligence to consume high technology. Intelligence is required to create it**. By this ranking, many of our ancestors were far more intelligent than we are on average. We are the ones who boast of the technology that we are beneficiaries of--but this is absurd, because they are the ones who built it, and we are in most cases merely exploiting it. If we forget them (our ancestors and their gifts to us), we lose treasures far too valuable to calculate the loss of. We could use up our electric motors until they all burn out, but who would give us another Michael Faraday? Great discoverers are quite rare. Surprisingly few of us are in the business of creating technology, and even they would be severely handicapped or else out of business altogether if, say, a mining company or a microchip fab went offline forever, or if fossil fuels became outlawed. We are so highly specialized that any one of us at best produces only a tiny sliver of those technologies, and nearly everyone lacks any sort of holistic knowledge about even one manufacturing process and the theories behind it. The man who assembles buildings from steel beams is usually not the man who makes those beams, and man who pours the steel into molds is usually not the man who refined the ore, and the man who refines the ore is usually not the man who mined it, and the man who mines it is usually not the man who found it. So it's an exceedingly precarious stack, because the removal of corporate knowledge about even one of these steps would bring the whole industry and all of its dependencies to their knees almost overnight. The higher the technology, the greater its instability because fewer people are required to have a working knowledge of it in order to support a huge population. The following graphic illustrates this phenomenon: [](https://i.stack.imgur.com/VKHmum.png) As technological value increases, there is naturally an upward shift in occupations, as more and more people become technological middle-men who are powerless without their platform, and fewer and fewer people are required to staff the actual production class. The people who are freed from necessity do not *have* to become idle consumers--they could become highly empowered discoverers--but sad experience indicates that most would rather be passive consumers than active producers once the bare necessity of "every man a producer" is gone. Society becomes top-heavy and laden with consumers, so that all that needs to happen is a gradual erosion of the discovering and producing classes until all that remains to support the populace is thin air and the ticking time bomb of a limited technological or product supply. Think about it: If we need stone age tools to make iron age tools, and iron age tools to make Renaissance tools, and Renaissance tools to make Enlightenment-era tools, and Enlightenment-era tools to make Industrial-age tools, and Industrial-age tools to make space-age tools, and we have forgotten how to make Industrial-age or Renaissance tools, how well off are we, really? Technology is produced in a complicated stack. It is far more vulnerable than we realize. What we have built up is highly unstable and vulnerable to a distributed, targeted attack to excise the knowledge. Most people in the U.S. today could easily be **oblivious** to the removal of knowledge until newly produced broccoli, Playstations and automobile parts become unavailable. We'd be oblivious to the loss of that knowledge because we, ourselves, don't have it. If our population were to be reduced down to a tenth its original size, chances are astronomically high that a very considerable proportion of our knowledge of how to make things would go with the 90%. Even without a targeted or indiscriminate attack against the population's knowledge base, this will actually happen quite naturally the more consumer-oriented we become. If we arrive at a point where only 10,000 people in our entire civilization collectively have the know-how to keep things running, and the remainder are largely so enthused with their toys and gadgets that they have no interest to learn or participate in the process of technology production, then as those 10k people gradually die off, the corporate knowledge is lost irretrievably, and the people ironically become stone-age personalities living in temporary space-age luxury--*temporary* because it was made for them, and not by them. Then it's just a matter of time and use before they fall from the stars and hit rock-bottom. The Pixar movie [Wall-E](https://www.imdb.com/title/tt0910970/) actually paints a pretty plausible case for this kind of degeneracy. What you point out here is not just theoretical; it is an actual plague that is bound to hit us pretty soon--and especially if it is accelerated by warfare, we are in big, big trouble, and it could be many hundreds of years or even thousands before we learn to replicate such basic technologies as refrigeration, combustion engines, microchips, gene sequencing, and so on. It is up to each of us to accumulate and store that technology in such a way that our descendants could re-create it without inordinate difficulty long after we ourselves are gone. [Answer] Our technical advances and production efficiencies have come at a price of increasing specialisation. Only a tiny proportion of the population *really* know how to each critical process work and the corporations they work for jealously gaurd that information for competitive reasons. Then, faced with ever more expensive natural resources on one side and customers who saw little need to upgrade on the other, the manufacturers gradually went out of buisiness. Possiblly there was a war or other disaster to help things along. Sure some stuff was written down and people have a crude idea of how things work, but most of the details on how to make the processes work *well* were either kept in peoples heads or kept on encrypted volumes to protect against corporate espionage and can no longer be read. [Answer] **Market Saturation** Simple economics, supply and demand. If you produce enough of something, the marginal value of the next item you make will become zero. To stop this and keep it viable to produce a product long term, it is necessary for either new customers to exist, or the product to have a limited lifetime. If the product lasts a very long time, the market does not grow, and there is no desire from customers to purchase new instead of used, then the business cannot be sustained. Once the business is unsustainable, production will shut down. Keep production shut down and the knowledge is lost pretty rapidly; ask any business who had to shrink their workforce for a few years how expensive it is to expand again (cyclic businesses like shipbuilding are particularly famous for this). Sure you can write down the methods of how to produce something in a book, but that only preserves the knowledge if the book is preserved. People clean, they throw out things they don't see use of anymore. If you came across a manual on computer punch card storage standards, likelihood is you would't keep it. [Answer] Any given civilization is unlikely to "forget" how to manufacture technology, nor all of it, even if they did. A computer is not the same as an abacus, despite both being essentially "counting machines". A lawnmower is not the same as scissors, despite them both being "cutting machines". If you look at our own civilization, we could, in theory, lose the ability to produce and use digital products, as few people even today (as a percentage) understand how they work, at a fundamental level. But at that same fundamental level, electronic components are extremely simple, as is electricity. Once a civilization reaches a certain threshold, and the tech of that threshold becomes widely available and understood, it is very difficult to lose that knowledge collectively. For example, it is highly unlikely that the people of the world today would ever lose the collective knowledge to exploit steam power, and thus electrical lighting. From there we could re-make certain intuitive leaps and re-invent internal combustion, and from there to nuclear fission, as they are all based on the same principles of pressure, heat, and releasing energy from matter. What would actually likely happen is that a civilization would be knocked back an age or two: i.e. Digital Age to Space Age, or Industrial (losing computers, polymers, plastics and robotics, nuclear power, Modern architecture etc). Industrial to Post Dark ages (following some religious anti-technological sin fever). The greater the gap between age thresholds, the more knowledge would be lost, and likewise, the greater the catastrophe would be required to bring about the fall. Indeed, knocking a civ down by more than a single age would require something singular and devastating (nuclear war/meteor impact with few survivors, and a "winter" following, to kill off the old before they can pass on knowledge). So, to answer your question: In order for a civilization to regress technologically several hundred, or a thousand years, it would require not one, but a series of catastrophic events, usually creating a distrust of technology. It could start with(Year 0): 1. Meteor impact (which science failed to predict or stop) 2. Nuclear war ("Science killed everyone") 3. Robotic uprising.(EMP took them all out but destroyed all of our other tech too) 4. Grey goo scenario (See above) Following this(Year 1-5), people not responsible, or involved in the fall, would start to get angry and ask "why did this happen to us?". Tech state regressed to Industrial age, though space age materials are still in use. No fossil fuels are being produced for vehicles, and so, is running out. Central government is failing to maintain civil order and provide food, water, sanitation and medical supplies. Enter the demagogue. A charismatic, and manipulative cult leader, gathers the support of the angry, and dispossessed, moving across the continent, looking for more followers and taking what resources they can find. Seeing the growing anti-technology sentiment as something exploitable, the cult leader delivers a series of rousing sermons, demanding that all technologists are sinners and "enemies of God", and should be punished. (Year 5-20). The cult spreads due to a common distaste for technology, and intimidation. Book burning is common, and technology is actively sought out and destroyed. With a rise in anti-intellectualism, and the persecution of Intellectuals as a group, they are forced underground, and do not pass on their knowledge which is now seen as "witchcraft". Within 50 years, almost all engineering knowledge is lost. Many people do not teach basic numeracy or literacy, which is now the province of those favored of the Church. History is not taught, expect from the perspective of the church. Centuries of written history are lost within 10 generations (year 50-250), in favor of the teaching of basic skills of survival, such as agriculture, smithery, or fighting. We have now regressed to the middle ages. Places with technology that cannot be easily destroyed are treated as unholy, and avoided by people in general. Like all forbidden things, technology becomes a valued commodity. Modern weapons are still incredibly dangerous, but rarely functional, as the fear of technology ebbs, so does the churches power. People start to actively excavate technology for their own benefit. The age of warlords has begun. (Year 251 - 500) Warlords conquer with automatic weapons instead of Bows, and rule with terror, using the few remaining grenades. Empires rise and fall within a generation or two. Slavery the vanquished is widespread, as forced manual labor is the only way to feed armies. Ammunition is now so scarce as to be virtually non-existent. As guns and explosives are no longer functional, war regresses to swords, bows and armor. By this time, people have forgotten all modern technology, and the purpose of most industrial technology. Within 500 years, over 1000 years of knowledge, history, and technology is lost. Most cities have been reclaimed by nature, and are now dangerous poorly understood ruins, prone to collapse, and inhabited by wild animals. Pick any point in this to base your story. [Answer] As @eigenvalue suggests: it's in a dedicated star system. Choose your mechanism: 1. The manufacture of the items is concentrated in a particular star system. This could be for security reasons, or because of unique resources, or because of manufacturing dangers or byproducts that you want to isolate, or because of plentiful power sources, etc. The system goes -- natural disaster, war, rebellion, etc -- and your ability to manufacture goes. 2. The items are manufactured widely, but the empire restricts design/manufacture of one key piece of technology to a particular system, to maintain control over scattered star systems. This key piece may be the controls (something like Asimov's positronic brains) or power sources or something else. If that system is destroyed or cutoff from the rest of the empire, you can make new devices and transplant the critical pieces -- as long as they last -- but you'll have a continually dwindling supply of functional devices, just as if you couldn't manufacture them at all. It's quite natural to concentrate manufacture. If nothing else, such key technology is power, and the organization that controls it will become the power behind the throne of any empire or federation. In addition to centralizing manufacture, it would be natural to centralize design and training as well. Nothing like physical control to make sure you maintain your power. Plus the efficiencies of a Silicon-Valley-like place. [Answer] New technology replaces old, and is a able to completely take over - and by the time old technology is needed; most information about it is lost, the people who worked with it long dead, and examples of it inoperative or destroyed (hard to re-engineer). As an example, we use computers, microprocessors and microcontrollers *everywhere*. Copymachines (Xerox) are no-longer photostatic, but basically a scanner-printer. Oscilloscopes and television are no-longer analogue signal processing and CRT-tubes, but digital signal processing and LCD-screens. Cameras no longer uses film. Radios are no-longer analogue but digital. Washing-machines and clocks no-longer use complex mechanical control-units, but uses digital circuits and microcontrollers. Cars are now computer-controlled, and no-longer based on mechanics for timing &c. How long it will take before *how* to make something like a mechanical control-unit for a washing-machines is forgotten? Then we have lots of crafts that was past from master to apprentice, that's dying or have been dead for a while. No-one needs it anymore, so how it was done is lost. Just take going from building in stone (like medieval cathedrals), to bricks (Victorian), to concrete (today). Undoubtedly many hard-learned tricks have been lost on the way, especially since masons often were close-knit groups that kept their secrets. If something happened that would destroy our electronics or power-supply, it would be difficult to remember *how* to do stuff with just mechanics - even though it was usual before. [Answer] **Environmental catastrophe leading to kinda-Planet of Apes scenarios** If CO2 level in atmosphere reaches 1000 ppm (parts per million - more than twice of current 400ppm) we would survive but with impaired intelligence. Some studies even place the reduced cognition threshold at 600ppm. Fast scenario: the CO2 level jumps suddenly, in course of few weeks, to over 1000ppm. It can be caused by runaway decomposition of methane clathrates in ocean floor, which can't exist in warm water. Methane then quickly decays to CO2 in atmosphere. There's not enough time to equip many buildings with CO2 scrubbers, humanity's intelligence level plunges and in step with it drops the manufacturing ability. Slow scenario: the CO2 level rises slowly, 600ppm is forecasted to be around 2070. It causes widespread mental disability in children, but which manifests only during puberty. This late onset would mean that whole generation is lost. No matter what precautions are taken, it's too late, whole education system gets badly disrupted and with it goes the manufacturing. [Answer] ## I see 2 clear options: 1) When this technology was created they expected it to last until it was replaced so they only published detailed information on how to repair it. However, it lasted hundreds of years and over time the technology that stored the repair information corrupted and broke until only an insufficient amount of information on how to repair it remained and no one remembered how to create new technology because they had always just used the manuals. 2) Chinese whispers. Everybody is trained by being taught how to make and repair the technology and people specialise to making 1 thing so as generations went on the next era of engineers had a bastardised version of repairs and creation to work with. Multiply this over 10 generations and you get what happened to Damascus steel - Blacksmiths wanted to protect their monopoly on making it so they only taught it through word of mouth and over the centuries they forget how to make it properly. E.g. Alien 1 Learns that to make X you need A1, B1, A2, B2, C1 in that order Over the generations, they think C1 goes after B1 and forget the numbers' importance so end up with A, B, C, A, B and then consider that the same thing will have happened with A, B and C and you can see how the technology is forgotten. ]

[Question] [ I had an idea about a lineage supposedly cursed so that the women only give birth to more women, but I'm thinking that some outside force purposefully mutated/altered their DNA to cause the effect without their knowledge. What mechanism might be used in such a scenario to prevent any male children from being born, or maybe even conceived? [Answer] Its been observed that jet-pilots tend to have more girls than boys. Its even something of an inside joke among aviation types. Its been given some scientific credence lately when it was theorised that higher exposure to cosmic radiation or potentially even the high G-forces could be damaging their Y chromosome. Due to a quirk in chemistry the composition of the Y chromosome is slightly less stable than that of the X chromosome. If exposed to radiation or other environmental contaminants or factors at the right level it can potentially not be a high enough exposure to create full sterility, but will still damage the Y chromosome in the *ahem* "awaiting swimmers." This could greatly increase likleyhood of female offspring. <https://www.upi.com/Archives/1987/12/01/Air-Force-fliers-really-do-have-more-daughters/1667565333200/> Perhaps there is some malign force targeting the men these women are with. It's sinister because trying to figure out why the women are only having daughters probably wouldn't look for a source that's actually targeting their husbands. Could make for a good plot twist. [Answer] Self produced testosterone antibodies. As soon as the male embryo starts producing testosterone, it gets attacked by the mother's antibodies and as a result cannot complete its development. [Answer] This is an extreme case of the so-called [Mother's curse](https://en.wikipedia.org/wiki/Mother's_curse): > > In biology, mother's curse is an evolutionary effect that males inherit deleterious mitochondrial genome (mtDNA) mutations from their mother, while those mutations are beneficial, neutral or less deleterious to females. > > > There are known cases where an mtDNA defect largely or solely affects males of the species (e.g. in humans, [Leber's hereditary optic neuropathy](https://en.wikipedia.org/wiki/Leber%27s_hereditary_optic_neuropathy)). All you need is an mtDNA defect so nasty that it renders male embryos non-viable, rather than merely predisposing them to blindness. This works despite the limitations of mtDNA itself; it is known that, at least in fruit flies, mtDNA polymorphism can affect nuclear (DNA) gene expression in males without affecting females. Even though mtDNA doesn't do a lot on its own, it can turn on or off critical parts of the nuclear DNA, causing male embryos to die, or (for a weirder "solution" to the problem) completely deactivate the Y chromosome, causing them to develop as females. As is, there is a theory that part of the lower life expectancy for men is that there are tons of small mother's curses lying around the human genome; since a mother's curse is harmless to women who have it, and the men who have it aren't responsible for propagating mtDNA, from the mtDNA's point of view, there is very little selective pressure to correct the problem. That said, Mother's curses don't tend to spread much on their own; there is little pressure against them, but neither is there (usually) much pressure that spreads them. A founder effect, combined with exclusionary policies on breeding (no outside women may join the community, but outside men are encouraged to do so) could create this sort of scenario. Alternatively, a mother's curse that is actually beneficial to the women who have it (increased fertility, more efficient metabolism, what have you) might create such a community naturally, but it would be inherently unstable; such strong selective pressure would eventually lead to extinction, as more and more women came to possess a gene that prevented conception of men, leaving few men available for breeding at all. [Answer] This actually happens in insects (and other invertebrates) via the bacterium *Wolbachia*. I suggest you research its male killing effects and borrow from there, [Wikipedia is a decent place to start](https://en.wikipedia.org/wiki/Wolbachia). There's no direct mammal parallel to these effects (that we know of) but it should provide a source of face-valid ideas. In general, genetic effects will work poorly for a lineage, because recombination means that only half of the genes are passed on each time. As a result, it would be diluted as the generations pass rather than persistent. You need a mechanism to explain why this does not happen as well as well as a mechanism to explain how it has its effect. [Answer] Consider: there are conditions that are passed on by [X-linked recessive inheritance](https://en.wikipedia.org/wiki/X-linked_recessive_inheritance). The most famous is haemophilia. Here's how it works: mutation *BadNews* is recessive, and carried on the X chromosome. The mother is a carrier. A daughter would get a healthy X chromosome from the father, and either a healthy or a mutated X chromosome from the mother - she is either unaffected, or a carrier - healthy either way. The son only gets one copy of the X chromosome, from his mother, so he is either healthy, or sick. Now, imagine that mutation *BadNews* is so lethal, that the foetus fails to develop, resulting in a miscarriage. Mutations that are so lethal exist, and they could conceivably be X-linked. It's possible that there is an actual disorder that would fit those requirements. But that still leaves the possibility of a healthy boy, you say. 50% of boys conceived would be healthy, resulting in a 2:1 girl:boy ratio. True. There are several ways you can address that, depending on the way you plan your story. * The family is aware of the condition, and having to resort to IVF for unrelated reasons, pick only female foetuses. (Picking only females is much easier and cheaper than picking healthy males). * A really unlikely but theoretically possible situation: the mother carries not one, but two different X-linked recessive lethal conditions: *BadNews* and *TerribleNews*, one on each X chromosome. The boys get either one and die, the girls get either one + a healthy X chromosome from the father. * The family could have in fact had a healthy son, but with chances being 2:1 in favour of a girl, the dice just fell this way. [Answer] Easiest, biological explanation, spermatozoid with Y chromosome are more vulnerable to acidic pH in women vagina. So a lineage may mean that women living in certain area have that ailment due to environment (lack of sodium and potassium in diet while water used for bathing have acidic pH) A fantasy somewhat setting based on a little of anthropology and old wives tales. In Western Europe there is a saying/belief that when there number of boys birth rise it mean the war is brewing. It's based on the fact that during the war the men are the ones who dies so someone would need to replace them and fill that gap that will be done to population of able men. Marvin Harris in his *Cows, Pigs, Wars, and Witches* explain why A) female cows are untouchable in India (because they give birth to oxes that do all the work and die frequently so one cow can during her life can breed many oxes) b)why native on New Guinea have Men housing and wars (called Keiko) are fought by rising and slaughtering pigs every two-three years (because it's better to kill pig every 3 year than a men who have other purposes and abilities) So back to premise: why there would be no need for boys to be born: 1. Men and women are equal for a long time so there is no need to "save" women from war or hard labour (imagine Amazons) 2. the quality of life is so high that there is no biological need for men to be born (there is no men specific tasks) 3. women decided long time ago they don't need local man and can go wherever they please and mate with whomever they please and their bodies over time adapted to fact that there is no such think as "insufficiency" of men and it's better to breed girls as they can give birth to much more humans than any men will ever do. [Answer] There's some prior art in nature, sadly. If we look at [recurrent miscarriages](https://en.wikipedia.org/wiki/Recurrent_miscarriage), one of the causes is male-specific minor histocompatibility. In this a mother develops an immune response to male-specific antigens, which causes miscarriages. It primarily occurs after giving birth to a first-born boy, who primes the mother's immune system just like how a first bee sting primes the immune system of an allergic individual such that the second is deadly. The result is that we see a dramatic change in sex distribution from the firstborn to the others (which are predominantly girls). If you were to extend this further, you might be able to develop a reason why this effect gets stronger and appears before the firstborn instead of after. The result would be a very strong tendency to miscarry boys. [Answer] You're looking for a line of women who only have daughters, and whose daughters always share this trait. This is doable. What I think may be most reliable way to pull it off requires some hefty genetic engineering, but nothing beyond what current technology is capable of. The trick is to use a [gene drive](https://en.wikipedia.org/wiki/Gene_drive). Pick a spot between two base pairs in an unused location in one of your target's chromosomes (doesn't really matter which one; a body chromosome might give slightly better results than an X chromosome, for reasons I'll explain later), and fabricate a strand of DNA containing the following: * A copy of the nucleotides on one side of the chosen location * A nucleotide sequence encoding the [Cas9 enzyme](https://en.wikipedia.org/wiki/Cas9), which, when given a strand of RNA as a guide, will scan a cell's DNA for a section that matches the RNA guide, and cut the DNA right there * A copy of the base pairs immediately around the chosen location on both sides, which will be transcribed into the guide RNA for the Cas9 * A gene that will cause the cell to self-destruct in the presence of a Y chromosome. Maybe a gene that is inactive by default, but is activated by the protein produced by the [SRY gene](https://en.wikipedia.org/wiki/Testis-determining_factor) (which is located on the Y chromosome and causes maleness), and triggers [programmed cell death](https://en.wikipedia.org/wiki/Apoptosis). Or something like that. It doesn't really matter, as long as the presence of this gene and a Y chromosome in the same cell causes the cell to die * And, finally, a copy of the nucleotides on the other side of the chosen location When this strand of DNA is inserted into a cell, the following happens: * [RNA Polymerase](https://en.wikipedia.org/wiki/RNA_polymerase) enzymes in the cell transcribe the DNA into RNA, and then [ribosomes](https://en.wikipedia.org/wiki/Ribosome) read the RNA and synthesize the Cas9 enzyme * The Cas9 programs itself with the guide RNA, then diffuses its way into the nucleus of the cell * The Cas9 sifts through the cell's DNA until it finds a section that matches the guide RNA- which will be the location chosen earlier * The Cas9 cuts the DNA strand right there * The cell's built-in DNA-repairing mechanisms see that one of the chromosomes has been cut, and looks around in nearby DNA for the same sequences as the cut ends of the chromosome (which would normally be the corresponding point on its paired counterpart) * The DNA-repairing mechanisms find that the original DNA sequence you fabricated and inserted into the cell fits perfectly, and "repair" the chromosome by copying your DNA to fill the gap In effect, you've created a strand of DNA that inserts itself into a predetermined location in a cell's genome, in both members of a chromosome pair. Permanently. Get this into a woman's ovaries (maybe by way of [in vitro fertilization](https://en.wikipedia.org/wiki/In_vitro_fertilisation), maybe after she's grown up by way of an [engineered retrovirus](https://en.wikipedia.org/wiki/Vectors_in_gene_therapy)), and the curse is laid. Whenever a woman carrying this "curse" conceives, the Cas9 will immediately go to work in cutting the appropriate chromosome from the sperm in the same, preselected place, and the zygote's DNA-repair machinery will go to work copying over the "curse" DNA from the egg to fill in the gap, by exactly the same means described above. Thus, a cursed woman's children are guaranteed to carry two copies of the "curse" gene. Then, if the sperm carried a Y chromosome, the self-destruction part of the "curse" will trigger, killing the embryo and causing a miscarriage long before the woman could realize she was pregnant. However, if the sperm did not have a Y chromosome, the self-destruct gene will not trigger, and the woman will bear a viable daughter. I mentioned earlier that it's probably preferable if this "curse" gene inserts itself into a body chromosome, rather than the X chromosome. This is because, if the "curse" is in a body chromosome, all of a "cursed" woman's descendants are guaranteed to carry two copies of the "curse". If, by some fluke, she manages to have a son, the son's children will also inherit the "curse", regardless of their gender, so he too will only have daughters. If, on the other hand, the "curse" was aimed at the X chromosome, the improbable son would only have one copy of the "curse" (because he has only one X chromosome). He would be able to have sons and daughters like any healthy man (because his sons would not inherit his "cursed" X chromosome), and though his daughters would still carry the "curse", his sons would be free of it entirely. Come to think of it, that could actually make for an interesting plot. Whatever. It's up to you. Have fun with it. [Answer] ### Parthenogenesis If the females are genetically modified to use [parthenogenesis](https://en.wikipedia.org/wiki/Parthenogenesis) for reproduction, all their children would be daughters. The daughters would also have very little genetic diversity. They would get all their genetic material from their mothers. There's a fifty percent chance that they would get the same chromosome for any specific instance. Then what that woman became a mother, she would only be able to provide that chromosome. After around six generations or so, all the chromosomes would be doubled in any particular mother. From that point on, the daughters will be essentially clones of their mothers. It's unclear what would trigger reproduction. Would it happen after a fixed period of time? In reaction to (not as a result of) sex? How many daughters would they have? As many (or few) as they wanted? A fixed number? The method of triggering reproduction would probably affect this as well. This would have considerable side effects that may make it unsuitable for your story. For example, * None of the daughters would have fathers genetically. They would get all their genetic material from their mothers. Once the genetic material is all doubled (all twenty-three chromosome pairs are of identical chromosomes), the daughters would be essentially clones of the mothers. * There would be a high number of double recessives appearing, so some lines may not be viable. * Condoms might not prevent pregnancy, which does not require men's genetic material. * Since men are unnecessary for reproduction, they might have an uncommonly high number of single mothers. [Answer] You already got a few methods for filtering out male embryos, but keep in mind that genes have a 50% chance of being inherited (except when the parent is homozygous, but then the next generation is heterozygous). So you need a mechanism that is inherited 100% of the time. If you wanted a male only having male offspring, you could work with the Y chromosome, but for females this is not possible. I can see two ways to achieve this for females: 1) You could work with mitochondrial DNA which is always 100% inherited from the mother, but this limits your options what the genes could do. 2) You need a retro-virus that is somehow transferred from the mother to the embryo. However, infecting the child is not as easy as it may sound (umbilical cord and amniotic fluid are not good infection vectors). The possibilities here depend on the medical knowledge of you characters. Maybe the virus modifies a gene that kills male embryos (see other answers) and is then transferred via breast feeding to the child, but this is not known to the family. [Answer] Sex selective mutations already exist, in mice there is a famous one the R2D2 mutation (yes that is really the name) prevents female offspring (X gamete fail to develop), Since the gene is a Y gene all offspring will carry it. Now I know you want all female but a similar X linked gene that favors only female offspring is completely possible. Such genes are called **SA-zygotic drives** There is a whole [list](https://en.wikipedia.org/wiki/Intragenomic_conflict#True_meiotic_drive) of mechanism by which they can operate. One of my favorite is a pair of linked genes on the X chromosome that produce a toxin and an immunity to said toxin, Any gamete carrying a Y lack the defense against the toxin and dies but the X gametes and the parent cells are fine. [Answer] Climate change is already causing an increase in the relative death rate of male fetuses: <https://www.smithsonianmag.com/smart-news/could-climate-change-affect-number-boys-and-girls-born-180952935/> (Well, maybe not climate change, but some stress factor. More research is ongoing.) Males are just more fragile than females. Invent some toxin that kills 50% of female fetuses and 99.9999% of male fetuses. (I read an SF story once about a future Earth where all the men had died off and women reproduced parthenogenetically; when someone revived a Y chromosome from ancient DNA and showed the adult male to scientists, the protagonist's first thought was "the ugliest woman I have ever seen". But you are not creating an all female society, just a lineage blessed with all daughters.) In your cursed family, babies are rare, precious, and overwhelmingly female. [Answer] I have a crayfish in my aquarium that is a mutation of a common species that originates in Florida. All members of her species are female, clones of the same original crayfish. The mutation ensures that meiosis does not occur, and that the eggs produced grow clones of the original mother. <https://www.nytimes.com/2018/02/05/science/mutant-crayfish-clones-europe.html> [Answer] There is a form of reproduction called [Gynogenesis](http://www.fao.org/docrep/005/b3310e/B3310E20.htm) in which the reproductive process of the female requires sexual intercourse with a male but *none of their genetic material is incorporated into the offspring*. The example I am familiar with is the Amazon Molly, *Poecilia formosa* (also called *Mollienesia formosa*, as in the link above) which reproduces by mating with males one of the co-occurring species such as *P. latipinna* or *P. mexicana* and is thought likely to have original arisen by a hybridisation event between these two species. Because the eggs still undergo meiosis and recombination events occur, daughters are not direct clones of their mothers, which would introduce some variation but also a substantially higher degree of genetic problems as with extreme examples of inbreeding. There would likely also be an increased number of miscarriages from the same problem. Mechanistically this process would require a change to the development of eggs in the oocytes so that they remain diploid - which seems a plausible mutation since it is something that occurs at low rates in most women anyway - and some mechanism to prevent the genetic material from the sperm joining the egg which also seems fairly plausible. Obviously extremely advanced genetic manipulation techniques are required for this and the mutation must be homozygous. Because there is no genetic transfer it gets round the objection from [my other answer](https://worldbuilding.stackexchange.com/questions/114246/plausible-cause-of-a-family-only-giving-birth-to-females/114273#114273) that the mechanism would be diluted by recombination. [Answer] I had a friend in college who was the 6th generation of female only children on her mothers side. Now assuming each woman had only one pregnancy that's 1/64 (2^6) (as was the case for my friend). It depends on how long you want the lineage to be. Having the child at 25 years old means that is 150 years of female-only offspring. Increasing the number of children per mother makes the odds get long very fast. The odds of 2 female children per generation for 6 generations becomes 2^12=1/4096 which again isn't all that unlikely. Now 7th daughter of the 7th daughter of the 7th daughter with all female offspring? Minimum number of females is 22 (only the Mother and Grandmother had 7 daughters each, no other offspring). Maximum number if every female had 7 daughters = 1+7+49+343 = 400. Odds? 1 in 2^399 so at this point you need some biological help. If you allow gene therapy, I like [Someone Else 37](https://worldbuilding.stackexchange.com/a/114338/22861)'s answer based on a gene drive, mainly because it sounds plausible and most stories/worlds don't need 100% achievable today tech. The initial female (Eve) probably needs to be built in a test tube and artificially inseminated rather than delivering the genes with a retrovirus. Alternatively, assuming you do not want external influence over the male father's sperm, you need to make reproduction hostile to either the presence of the Y chromosome or a male foetus. That way the fertilisation of male children is possible but none of them come to term. Ideally they miscarry in the first trimester so it's not as big a deal given quick internet search says between 10 and 25 of *known* pregnancies end in a miscarriage. [Answer] A mutation in mitochondrial DNA that causes the mitochondria to shut down or produce a lethal toxin in the presence of one of the following: * typical male levels of testosterone * Y chromosome (if the mitochondria ever have proximity to it?) * some RNA or protein produced from the Y chromosome Unlike mutations in the mother's own chromosomes, which would not survive as a lineage (as in Galastel's answer), mutations in mitochondrial DNA will remain until they mutate again or the lineage dies off. [Answer] It could be a plan to wipe out all humans. There is a plan to eradicate species of mosquito by genetically altering them to only produce males, (I guess males since males cannot carry malaria. As Humans have twice as many female ancestors as male ancestors a modification to cause all females would be a much better genetic attack than males.). <https://www.nature.com/articles/srep31139> > > Mosquitoes have been genetically modified so they only give birth to males in a new technique that scientists hope could help to wipe out malaria. > The disease is spread by female mosquitoes, which pass on the disease when they bite humans. > But researchers from Imperial College London have now tested a new method that introduces genetically modified mosquitoes to normal Anopheles gambiae mosquito populations, the main carrier of the malaria parasite. > The GM insects had been altered so that they would not produce female offspring. > In the first laboratory tests where the modified mosquitoes were mixed with normal insects, 95% of the eggs laid hatched into males. > > > [Answer] This could (in theory) be down to some behavioural practices passed down, or some genetic abnormalities in ovulation, tubes, etc. In practice these effects aren't hugely significant. <http://www.miriamstoppard.com/advice/healthy-pregnancy/pregnancy-myths-debunked/> "You are more likely to have a boy if you have sex only once during your fertile period and a girl if you have sex more often. True This is based on the fact that female sperm live longer and swim slower than male sperm. If you have sex a few days before you ovulate the longer living and slower female sperm will be waiting for the egg. If you have sex just before ovulation the faster pushier male sperm will win the race. Whatever you do remember that really there is a 50:50 chance of having either a boy or a girl. Focusing on having a healthy baby is more important than its gender." [Answer] Many statistically very improbable situations do occur. Perhaps by chance a woman, and her daughters, granddaughters, great granddaughters, great great granddaughters, etc. only give birth to females. Especially if the women give birth to just a few children each, it will be easy for people to keep track of all the children and notice that they are all female. I once read there was a feudal fief that was inherited by heiresses for about six generations in a row because of lack of surviving male heirs. If you don't want to come up with an explanation for the lack of male children, you could make it happen for just a few generations by the time of your story, long enough for people to notice and speculate that it is caused by a curse. And if your story is a fantasy, perhaps probability changing magic is used in this world and a spell was used to make the probability of having male children zero. [Answer] There is in fact known to be genetic factors that predispose a person to have one or the other. This is part of the species ability to adapt to new conditions, via natural selection. If it were just a simple non-genetic thing, with nothing but pure chance involved, then you'd expect birth gender ratios to be 1:1. But that's not what we see at all. Worldwide, the average gender at birth is about 1.09 boys to girls\*, with the gender differential narrowing as the population ages. What's going on here is that humans are tuned to produce slightly more males to make up for their slightly increased death rate. In countries with long-term skewed gender imbalances (eg: China and India, with strong cultural preferences for male children, and Russia where 3 major wars on their territory in 40 years for a time left the ratio among adults nearly 2:1 female), its been observed that the birth ratios slowly adjusted to compensate. If there's going a shortage of the less numerous gender when it comes time to ..er..produce offspring, that makes the genes of parents who tend to produce more of that gender slightly more likely to get passed on to the next generation than the genes of other parents. That of course in turn implies that there are indeed people who are genetically more likely to have one of the genders than the general population is. So all you have to do is make your family one of those. \* - To be fair, this is probably thrown off by the world's two most populous countries having artificially skewed birth rates. The normal ratio in other countries throwing those two out seems to be more like 1.05. Interestingly, the only country in the world that has more women born than men is a small island nation with a traditionally matrilineal society (so their rate is likely artificial as well). [Answer] I am a fan of [Parthenogenesis](https://en.wikipedia.org/wiki/Parthenogenesis). Parthenogenesis (from the Greek for "virgin birth") is the development of an unfertilised female egg into a viable individual. It is known to occur naturally in some invertebrate species, and is thought to have occurred in some birds and fish. However, there have been no natural cases where a mammal has given birth from an unfertilised egg, and it is likely such an embryo would be unviable. The origin of the orgasm is to trigger the release of an embryo from the ovaries. We don't have that issue - humans have monthly cycles where an egg is released and disposed of. As a basis for your scenario, a mutation could have occurred wherein the women's ovaries do not release an egg, except during orgasm (undoing several hundred generations of evolution), which starts developing on its way to the womb. By the time the spermatozoa reach the egg (assuming a male is present) the embryo will already have polarised, repelling any sperm. Each woman's daughter is her own "clone". In this little scenario, it would be possible for a girl to get pregnant when she starts experimenting with masturbating. Her parents won't believe this is a virgin birth or whatever and some local will be arrested for paedophilia. ]

[Question] [ After receiving answers to [this question](https://worldbuilding.stackexchange.com/questions/156814/is-it-possible-for-a-universally-executable-virus-to-be-written-in-binary), I now know that viruses cannot be written in machine code in such a way that they can universally infect all kinds of systems. Every machine has a unique set of instructions, and processes the zeroes and ones in a different way. Knowing that, I have a follow-up question: **Can a virus be made for a system in a way that acts like an anti-virus?** In other words, this virus would infect computers and instead of causing damage, it would protect the computer from other viruses? If the answer is yes it is possible, could this virus be sophisticated enough to automatically update its virus definitions? Perhaps an advanced deep learning algorithm allows this? Upon trying to research this, I am able to get definitions of anti-virus and definitions of virus, but I haven't had any luck in gaining a good understanding of their possible interchangeability. I know that both of them are software-based, so I'm inclined to say this is possible. Or would such a program be too large? (most viruses are very small in order to avoid detection, as well as attach themselves to emails or other programs) UPDATE: For the sake of this question, the virus could be made using modern technology, or future technology with sophisticated artificial intelligence or advanced compression (to make the virus smaller). [Answer] **That has already happened.** The "[2012 Internet Census](http://census2012.sourceforge.net/paper.html)" (known professionally as the [Carna botnet](https://en.wikipedia.org/wiki/Carna_botnet)) was a virus that infected ~400,000 consumer network hardware devices (like routers or modems) by using default passwords. The author of it eventually gained control over a meaningful percentage of devices in the world, and was able to see internet traffic patterns in realtime from *billions* of devices (at the time, only ~4 billion devices could be visible on the internet, due to technical limitations). While doing this, the author says: > > We noticed at this time that one of the machines already had an unknown binary in the /tmp directory that looked suspicious. A simple strings command used on that binary revealed contents like synflood, ackflood, etc., the usual abuse stuff one would find in malicious botnet binaries. We quickly discovered that this was a bot called Aidra, published only a few days before. > > > The [Aidra botnet](https://www.cyber.nj.gov/threat-profiles/botnet-variants/aidra-botnet) was a botnet created by an Italian hacker, who sold time on it for DDoS attacks (the kind of thing that takes down websites). Aidra is a classic case of a virus, in the sense that you're thinking. It infects devices, and uses them to do bad things. The author of Carna goes on to say: > > Since Aidra was clearly made for malicious actions and we could actually see their Internet scale deployment at that moment, we decided to let our bot [...do some technical things...]. This step was required to block Aidra from exploiting these machines for malicious activity. > > > Resulting in... > > Within one day our binary was deployed to around one hundred thousand devices - enough for our research purposes. We believe Aidra gained a litte[sic] more than half of that amount. The weeks after our initial deployment we were able to build binaries for a few more platforms. We also probed telnet every 24 hours on every IP address. Since many devices restart every few days and needed to be reinstalled again, over time we gained machines that Aidra lost > > > This means, in a nutshell, that the author of the Carna botnet observed the malicious Aidra virus spreading, and decided to choke it out using his own botnet. A virus fighting a virus. Carna won, and Aidra had little impact on the world. [Answer] **Yes it's already happened** See [Welchia Virus](https://en.wikipedia.org/wiki/Welchia)\*, discovered in circulation in early 2003. The Welchia virus downloads itself via the same vulnerability that the Blaster virus used. It then deleted the Blaster virus if found and then installed the patch closing the hole down before spreading to new systems and finally deleting itself. The virus was programmed to self-remove on January 1, 2004, or after 120 days of processing, whichever came first, so it is no longer in circulation. An antivirus virus. \*Technically, it is a worm... a virus needs human interaction to spread on the computer network; a worm can propagate itself. [Answer] # Yes A virus is not a virus because it's *doing bad things* per-se, but because of how it is installed / replicates to other systems. Any computer virus can be modified in such a way where the actions it performs is to block other viruses from being installed or modified on the system. In fact, a virus could be used to simply install anti-virus software on the computers it infects. Another way the virus could achieve protection is by simply revoking root / administrator permissions from any other programs or users except itself, effectively stopping any further software from being installed on the system. [Answer] ## Real computer worms that close vulnerabilities There are historical examples of self-spreading network viruses ("worms") that follow the pattern of: 1. exploit a particular vulnerability; 2. "fix" that vulnerability so that it's not exploitable anymore; 3. (optionally) remove other popular malware that uses the same vulnerability and it's likely to be there. One example like this is [Welchia](https://en.wikipedia.org/wiki/Welchia) which is considered to be mostly benign (though with "side effects") as it removed the Blaster worm which was popular at the time and installed Microsoft patches; there are also other examples of ["anti-worms"](https://en.wikipedia.org/wiki/Anti-worm). In addition, there are commercial botnet systems that are designed to close down vulnerabilities and clean up the system of *other* malware (presumably owned/controlled by competitors) so they do remove some bad things (and protect from future infections) so as to have full access to the system resources for *their* malware. If I recall correctly, some variants of [Mirai](https://en.wikipedia.org/wiki/Mirai_(malware)) were doing this, but it's certainly not unique or novel nor *that* unusual. [Answer] You could design a piece of software that works this way in PRINCIPLE, but in practice it would have some pretty significant limitations. The primary problem is that antivirus software relies very heavily on being able to propagate defensive information on new threats and security flaws to the defended machines more rapidly than a threat can infect them. Most security flaws and viruses require some kind of social engineering component to get a human to do something, so that human rate of engagement can slow a virus' spread enough to allow time for the antivirus to analyse the new threat, develop a defense, and distribute it to all protected machines. Therefore in order to provide a successful defense, your your antivirus-virus (henceforth referred to as AVV), needs to be able to communicate with all instances of itself wherever they are to share information. You can't rely on each instance of AVV learning just from what it's exposed to on that machine. You need EVERY instance of AVV sharing information, and that's a very tricky thing. In order to successfully propagate, AVV needs to stay small. Huge pieces of code like a standard antivirus application are just too huge to infect machines successfully. This means your antivirus functionality can't rely on definitions per se, because that requires a massive database of known threats. Therefore each instance can't maintain its own local information storage either. Your database of learned behavior therefore needs to be distributed across all the instances of AVV throughout. You ALSO need a way for the instances of AVV to be able to understand the differences in environments in the machines they've infected and understand which other instances are sharing those environments so they can preferentially share information. E.g. AVV that infects Apple devices has different threats to defend against than those on Android devices, or Windows 10 versus Windows 8, or servers in older powerplants running on NT 4.0 or something gothic like that. On top of all that, AVV is ALSO going to need to be able to at least partially disable any actual antivirus software that's ALREADY on the machine it's infecting. Having two sets of code trying to protect the same machine at the same time causes LOTS of problems. You may never have had to deal with the fallout from someone trying to use Norton and McAfee at the same time on the same computer, but I have, and it's not pretty. The real problem is this though: In order to do ANY of that stuff, AVV needs to use up a significant chunk of the processing power and bandwidth on every machine it's installed on. This is, by and large, exactly what ALL viruses do and so, from the point of view of the user, your AVV is going to be as much of a problem as many of the more malicious viruses it's defending against. Sure, AVV is using those CPU cycles and gigabits of bandwidth to stop threats instead of sending Russian porno spam everywhere, but the result on the infected machine is often the same. [Answer] Yes. A worm (which is a type of virus) spreads by exploiting a vulnerability replicating itself, but if that worm is also patching that vulnerability as it goes along, it isn't *technically* malicious (it can still have deleterious effects though, such as tying up bandwidth, etc...). For example, in Linux, there have been worms which self-replicate and patch the vulnerability they exploit, preventing more nefarious worms from acting on the vulnerability, which would make them a kind of "white-hat" virus. What makes a program a "virus" or "antivirus" depends on what its ultimate impacts on a system are. A virus spreads and damages infrastructure, an antivirus prevents this. Under a strict definition though, a virus is technically any self-replicating program. It is thus possible to have a self-replicating antivirus which provides immunity to a specific exploit (as in the self-replicating patch-worm example). [Answer] The first ever antivirus software ([Reaper](https://en.wikipedia.org/wiki/Reaper_(program))) was a virus! It was written in 1971 to catch the first ever worm, Creeper. The only way to fully eradicate Creeper was by installing Reaper on all connected PDP-10 mainframes. This was done by having Reaper automatically replicate itself on other machines. [Answer] The short answer is yes. A virus can do whatever it is programmed to do. If you want it to install itself as an anti-virus you can absolutely do that. If you want it to attempt to "infect" other hosts to act as an anti-virus you can use the usual exploits. But why though? if your Anti-Virus Virus is so good at its job that you want to black-hat it to everyone, why wouldn't you make it an open source download instead. Why would you intentionally trigger already installed anti-malware trying to protect them? What do you gain? Overall, it is possible. I just fail to see it being worth it. [Answer] as @eigenvalue mentioned. Stuxnet was one of a kind virus, which was able to target specific windows machines. These specific machines were targeted because these machines were the machines of the Iranian scientists who were at the time working on Nuclear Reactor. The special thing about this virus was that it was spread in the wild and if the machine was not who it was looking for it would just sit there idle. From all the machines in the world it was able to figure out which machine it had to be activated on. In industries and nuclear plants special computers are used called PLC's which are programmed via ladder diagram. Its kind of a drag and drop builder used to program. The virus actually infected the scientist's machine which was connected to the PLC and then changed the ladder diagram and increase the spinning speed of nuclear reactors. Increasing the speed caused resonance which destroyed these reactors, and the virus achieved the desired goal. [Answer] > > Knowing that, I have a follow-up question: Can a virus be made for a > system in a way that acts like an anti-virus? In other words, this > virus would infect computers and instead of causing damage, it would > protect the computer from other viruses? > > > Yes, once a program gets in it can do pretty much whatever it wants. > > If the answer is yes it is possible, could this virus be sophisticated > enough to automatically update its virus definitions? Perhaps an > advanced deep learning algorithm allows this? > > > Yes, and its not even hard. The AI deep learning part is a bit harder, but still doable. A lot of viruses spreading is due to users not updating their systems. Just upload a list of software the computer contains and its version, and download and install the new versions. That and running windows update, apt-get update, zypper dup, or etc for your OS offers a lot of native protection if its ever even used. After that implementing a firewall for the user, or re-configuring windows firewall would raise the bar even higher. automatically sandbox know weak programs like web browsers and mail clients. Download a list of bad IP's and bad behaviors ever day, and doing a black list would offer even more protection. So the hacker uses a CDN (content distribution network), so you have a main distribution point from a website hosted on a cdn, and that pretty much all you need. So the program would have a built-in list of IP or website address, and a preset list of files to download. Said program would wget <http://www.goodvirus.com/files.txt> wget <http://www.goodvirus.com/blacklists.txt> The files.txt would contain a list of files and versions to download. If the version is newer than what you have it download the new version. Your biggest problem and where the AI comes in is problems like specter, melt down, and etc are way hard to detect. Also mitigate has issues, After a few weeks the security will have a patch you can just download and install reboot and your safe. You have to ask yourself how far this virus is going to go. An AI which detects, and implements its own solution is going to have to be way smarter. It will takes years to develop and prefect. However, automated tools from companies already exist, google has sysbotz which throws things at the linux kernel until it breaks. Then said bot compiles a report, and sends it off to the kernel devs for them to fix. More and more of these automated testing platforms are being created and deployed. More and more smarter testing routines are being developed and tested all the time. The bigger problem is the difference between program and virus comes down to user consent. Sure your program forcefully propagates every where, but at the end of the day if your program does nothing bad people will willingly allow or install your virus on their computers. Then it's no longer a virus, but a program. [Answer] A long time ago (2007), someone with a very acute case of the oedipal complex decided that the real problem with IT security was the weak link, i.e.: users. Which was probably the inspiration for this Dilbert strip ([source](https://dilbert.com/strip/2007-11-16)): [](https://i.stack.imgur.com/bfQx3.gif) So he created a program called Disk Knight that replicated over networks, and it completely disabled USB drives. No more infections from obnoxious relatives plugging their virus-ridden usb drives on your machine to send their work to your printer! YAY! Only the dude became such a *persona non grata* that the internet gave him a *damnatio memoriae* punishment. The only thing left over of the whole story are passing mentions on Microsoft and Norton's pages about the functions of Disk Knight, and how its behavior was unacceptable. Other than that, mentions and mentions in forums on how to remove it, usually in languages other than English. So you see, if you can write a program to defend the machines of the layspeople, you can protect them from viruses. But if you are not an expert and you don't know what you're doing, you may cause more harm than good. The proper way is still to make yourself a known force against malwares so as to build trust, and in that way you can cooperate with the community in the fight against evil. Fail to do so, and no matter how good your motives, you'll go down in history as a villain. [Answer] [Stuxnet](https://en.wikipedia.org/wiki/Stuxnet) has the code to remove itself after the given date in the future. ]

[Question] [ Say you have some way of seeing somewhere between a microsecond to 0.1 seconds into the future, *or at least the most likely future*. Is it possible,through something like a flip-book effect or some other illusion, to encode a message only another observer capable of seeing the same distance into the future could also read? Clarifications 1. Doesn't need to be encrypted, just laid out in/on a method or medium that enables only those with 'future-vision' to observe a message unobservable to someone without future-vision. 2. The message must not be able to be revealed through mundane means, such as high-speed video or any kind of atypical photography. 3. The future-sight capable observer can only see into the future or at the present, not both at the same time. 4. It doesn't matter how briefly the message is available for our future-sight capable observers, just that only they can see it. 5. Future-sight does not extend into space beyond the 'eye' of the observer. [Answer] **Sure it is, and we can use modern technology to do it** (NB: This relies on being able to see into the future further than the OP requirement, but if that's an acceptable change in scale, this would work.) So, have you ever heard of an [RSA token](https://en.wikipedia.org/wiki/RSA_SecurID)? These are devices that work on the basis of giving you a passcode that changes every 30 seconds or so; similar to the Steam Authentication codes, which would also work in this case. All you have to do is change the synchronicity of the rotating passcode to be 30 seconds behind - in other words, make the RSA token one cycle backwards, and therefore anyone who types in the passcode displayed gets an error message because it's an old passcode. But, your future seer knows what the passcode *will* be. He or she can see that, types it in and you're done. The passcode is valid, because from the perspective of the user of the tag, it's a future passcode. From the perspective of the authentication server, it's the current one. Of course, this doesn't mean that if you have access to the authentication process directly it can't be subverted, but for normal use it takes an existing technology and applies a secondary layer of security by forcing the user to see the future passcode displayed instead of the current one. Once you use that, it's all just standard encryption processes, albeit with the extant vulnerabilities they incur. [Answer] ## Reaction times Average reaction times for most people are roughly 200 ms for simple responses. If you can see 100 ms into the future, your reaction time is going to be roughly half that. So have something like a "Simon Says" type decoder that requires hitting a sequence of light-up buttons within an extremely short reaction window. Of course, electronics are going to have much faster reaction times than humans, so with advance forewarning, something like this could still be defeated with the right hardware. However, if you can see a bit further into the future (250+ ms or so), you could actually have the buttons to be pressed not light until *after* the response window closes. Hardware responding <1ms after the button lights doesn't help if the valid-press window closed 20ms before it ever lit. [Answer] It's "Heisencoded": your message is only there when no one is looking at it. The more closely you observe it, the less intelligible it becomes. This includes electronic observations. However, people can blink - closing and reopening their eyes in about 0.1 seconds - to make the message momentarily "unobserved". Your temporally-gifted individual can thus use their precognition to, just before their eyes shut, see the message as it will appear once they can no longer see it. Quite why many such messages are mysteriously scrawled next to statuary is often debated - as is the "blue box" and the resident "madman" mentioned therein... [Answer] **This power is completely broken.** Any sort of true futuresight is a form of time travel since you're transmitting data from the future to the past. The precog can not only transmit undetectable messages, he/she can ask any possible question and receive an answer from a possible future self encoded in physical responses that interact with this power. The precog only needs to daisy chain the answer back to when it was asked. For example, the precog at time = 0 wants to know the answer to a yes or no question, the answer is locked 10m into the future for whatever arbitrary reason, and the precog has decided on an encoding of eyes open = yes, eyes closed = no. Precog + 10m sees that the answer is no and closes his/her eyes, followed by precog + 9m59.9s seeing the closed eyes and responding appropriately etc. Once precog t0 has the answer, he/she is no longer obligated to behave in any particular way in the future so the timelines of precog + 10m etc. collapses and there is no message for anyone else to observe. Yes/no is of course an analog to basic binary, so any arbitrary message can be passed back once the precog has decided how to code it. [Answer] "[...] into the future, or at least the most likely future." If less likely futures are game, then this is solvable. Encrypt the message and destroy the key. At the press of a button, generate a random key from true random numbers, and try to decrypt with it. Show an error message if it fails, but do not display the key. The seer will be able to see the vanishingly unlikely future in which the random key guess happens to match the key that was used to encrypt. You could explain it away as saying all the futures where it doesn't get properly decoded "collapse" into one since the outcomes are identical, so it's easier for the precog to see the one where it does get decoded. [Answer] I would place the message in a way that reading it would mean instant death to whoever reaches it (for instance, in the walls of a deeeep pit, just before reaching the bottom or a box filled with poisonous gas). This way, if you can see the future, you could intend on walking that path, read the message just before dying (in the future) and then change your mind and not go into the pit. [Answer] Asimov wrote some stories about a substance, the [thiotimoline](https://en.wikipedia.org/wiki/Thiotimoline), which is so soluble in water that is dissolves before touching the liquid, thus seeing the future. This as a consequence of the substance complex structure, which fold the space time allowing the molecule to see the future. > > In Asimov's writings the endochronicity of thiotimoline is explained by the fact that in the thiotimoline molecule, there is at least one carbon atom such that, while two of the carbon's four chemical bonds lie in normal space and time, one of the bonds projects into the future and another into the past. Thiotimoline is derived from the bark of the (fictitious) shrub Rosacea karlsbadensis rugo, and the thiotimoline molecule includes at least fourteen hydroxy groups, two amino groups, and one sulfonic acid group, and possibly one nitro compound group as well. The nature of the hydrocarbon nucleus is unknown, although it seems in part to be an aromatic hydrocarbon. > > > In The Micropsychiatric Applications of Thiotimoline Asimov explains that > > the rationale for thiotimoline's behaviour: namely that the chemical bonds in the compound's structural formula are so starved of space that some are forced into the time dimension. According to the second article, thiotimoline's time of solubility varies depending on the determination of the person adding the water. > > > If you use thiotimoline like a sort of invisible ink to cover the text you want to protect, you can remove it only with the right determination, since *thiotimoline's time of solubility varies depending on the determination of the person adding the water*. In this case is the substance to see the future, not the observer. [Answer] If you had a perfect laser (aka doesn't disperse over any distance, not actually possible but still) you could just shine it on a distant object (or mirror) and encode the message in it. The only way to read it while in transit in space is to intercept it, requiring FTL or similar [Answer] **Use Qubits** The value of quantum bits can only be described by a probability until they are measured, but once they're measured they are determined. Using future sight, observe what the determined value of a quantum bit *would* be. In the present, run the qubits through quantum logic gates that change their value in some predictable way, measure them, then combine the results with the future results from the non-gated observation. The key needed (the non-gated results) came from the future, and was effectively destroyed when you observed them in the present. I believe this depends on how your future sight technology interacts with quantum mechanics. (Also, it's possible I'm overlooking something about how quantum bits works.) [Answer] It may not be quite what you're looking for, but I think there's an argument that someone who can see into the future in an interesting way, ie. one that allows them to act on the information they see to change the future, can decrypt anything. * They look into the future and see themselves trying to decrypt the message with some key * If they see themselves fail, then clearly that key wasn't correct * So, they pick a key at random different to the one they saw themselves fail with, and try that one - quickly enough that the attempted decryption finishes in less time than the interval that they can look forward into the future * Now we've changed the future, the past changes too - they must have seen themselves try the second key, so they wouldn't have picked that one, so they must have picked and tried a different one... * The only way to resolve the situation is when they pick the correct key. Although we can think of this as a time loop eventually broken by picking the correct key, to any observer involved it actually takes no time at all - in our prescient friend's experience, they just see themselves pick the correct key and go with that one. However, it only works probabilistically - if we use the time loop model, we can see that if the chances of them picking the right key at random are significantly less than the chances of them getting hit by a meteorite, that's what's probably going to break the loop first. Or maybe this persons actions are the only thing that vary between 'loops', but there's still the possibility of them fumbling it and not completing the decryption quick enough for past them to have seen the result in time or something. In general, time travel allows us to do arbitrarily complex computations in a fixed amount of time by reading the results of a computational step from the future, doing the next one, and sending the results back to the past. As such, to someone who can send information back in time (or equivalently, see the future), most encryption can be treated as just weak encoding. [Answer] The only thing I can think of would be to use some manner of "invisible ink" whose presence and almost instant evaporarion were both invisible to the naked eye, but the overlapping presense of both simultaneously created a visible hue (so, only someone "flipbook viewing" both the present and the next moment would see it). Of course, the reader would have to have some sort of chemical reaction they initiated to read the message, and so the writer would need to leave some manner of glyph of identifying mark so a potential reader would know a message was there. Otherwise, the ability to see moments into the future would not really provide "secret message" potential, except if they could see multiple possible timelines. Then, the "writer" could build the intent to write something, but decide not to, thus, it would only be visible along the possible future that would never happen. The issues with this are myriad, but the big ones are: 1) it would only be good as a "thieve's cant" for coded dialogue/messages in the moment with bother speaker/writer and listener/reader present. This is because the divergent timeline would only exist up until the decision was made, then be lost to those living on the current timeline forever. 2) your spies would need mich longer spans of time to look into the future in order to catch these messages 3) there is no "secret" to this other than having the ability. Anyone with the ability would quickly become privy to this method. [Answer] One kinda hilarious answer involve quantum mechanics and being able to observe effects "too soon". I mean, I'm not an expert on quantum mechanics, but from what I understand, it's observation that collapses the waveform down. If you did the [double-slit experiment](https://plus.maths.org/content/physics-minute-double-slit-experiment-0), but were able to "see" where the photon would hit before it actually reached the double slit apparatus, I'm not sure the photon would be able to interfere with itself like usual. I have a feeling that a 'precog' looking at the double-slit experiment would *never* see a diffraction pattern, because the "observation" would be occurring before the photon actually got a chance to interfere with itself. **If that's the case? Then the solution is hilariously simple: just have a whole bunch of slits/dots/whatever in a sensitive box that breaks when you open it.** Shine coherent light in one end, and look at the pattern that comes out. If no precogs were around, everyone would just see a mishmash of interference patterns. If a precog was around, it'd instantly change to be dashes/dots/whatever. ***Edit: Delving a bit more into the quantum side of things.*** Basically, everything is a probability wave. How the double-slit experiment works is a photon is beamed at two slits, which it will pass through and arrive at a sensor that measures where the light hit. Intuitively, you'd expect that the photon would have to go through one of the slits and you'd see a 'hit' along two vertical lines. Repeat it over and over, and you'll get a rather weird result: an interference pattern. Basically, the photon is simultaneously going through *both* slits, and interfering as a wave - against *itself*! Now, stage 2 of weirdness. Let's say you rig up something that can detect *which* slit the photon travels through. You then repeat the experiment. Now, though, the interference pattern disappears. That's because your information 'collapses' that wave down. You've 'erased' the possibility that it went through one of the slits, and because of that, the wave can no longer go through both slits and interfere with itself. Stage 3 of weirdness. You use the same rig as Stage 2 - and measure which slit the photon travels through. But... now you *delete* this information before the photon can reach the detector (this is called the Quantum Eraser Experiment.) Now the interference pattern reappears! Why? Because while you measured which slit it went through, you deleted that information - and in effect, restored the possibility that it could have gone through either slit. So, now, the big question: what's the effect of seeing where the photon lands before it goes through the slit or actually lands? *And... ultimately, it's a time travel paradox.* If you observe the photon landing in a way that indicates it went through a specific slit, then you observe something that collapses the waveform down in a way that forces it to go through the specific slit, which in turn prevents an interference pattern from emerging. If you observe the photon landing in a way that indicates an interference pattern, then you observe something that *doesn't* collapse the waveform down in a way that forces a specific slit, which in turn allows the photon to travel through both slits, which allows for the interference pattern. Now, if this was a science site? I'd say, "There's no way to empirically test this; there's no way to answer this." But we're in a worldbuilding site. So you can resolve a time travel paradox however you want. You can say, "So what if they see an interference pattern a bit earlier than the photon actually hits the screen? The photon, being in an interference pattern, doesn't convey information about the waveform that would actually reduce it down." And you can say, "The precog's going to see the photon's final state on the wall based on which slit it went through - because their observation itself is what forces the photon to not interfere with itself." Anyway, in my opinion, the thing that makes this answer so cool is... ultimately, it's taking something so ridiculously unintuitive and complicated and mindbending... and the resulting device is something a child could manufacture. (Well, not the 'can't open/scan' part.) [Answer] If the user sees where something will be, but sees the object/person as it is now, then some tricks would be possible. I'm thinking of a sign changing on the side of a subway car, where the future-vision sees it at the station and can read the sign, but that sign changes before actual arrival, therefore the other people would see whatever is changed to (Community College advertisement, I'm sure). Or they see a person saying something while looking in their direction, but that person is behind a door at the moment, they'll be along shortly. Could be fun and creepy. [Answer] You have to copy a password right before it gets shown on the display. Say you have a small calculator that randomly chooses digits using some on-board entropy device (so actually random, not just pseudo-random). The calculator would flash a digit at a time and to unlock it you must've pressed that digit before it was even generated. Get 10 of these digits right in a row and the calculator reveals the message. Easy if you have future vision of something around 0.2s or near the human reflex limit, impossible if you don't. [Answer] (This answer relies on a 4-dimensional being, capable of "seeing" the past/future, being able to 'look around' 3D objects in the same way that we do 2D lines - even if they don't quite realise that that's what they are doing) Start with 2 layers a special material (Such as e-ink or a liquid crystal) which can change via some mechanism, such as heat or electricity. The top layer (Layer α) can switch, almost instantly, between Opaque and Transparent. The bottom layer (Layer ß) can switch, almost instantly, between "Message" and "No Message". When the Message is Visible on Layer ß, it is completely obscured by Layer α being Opaque. When Layer α is Transparent Layer ß is blank. Because the layers are so tightly fused together, it is impossible to change one without simultaneously changing the other. However, by focusing on the *future* (or, alternatively, on the past) of Layer ß, while Layer α is still transparent, you are able to see the message that it will show when it is obscured. [](https://i.stack.imgur.com/Ixzky.png) [Answer] Stronger encryption schemes like AES512 typically take longer than 0.5-1 seconds to encrypt sth. So just use such a scheme. The future looker already sees the encrypted/decrypted message while the computer is still going. Anyone in the present sees at most an encrypted message (if your computer is that fast). [Answer] The observer would have to convert their prescience into information that no-one else could possess. For example, that person might be able to accurately predict the outcome of a chaotic effect. They would have to repeat their future observations of a period of time long enough to ensure they couldn't have achieved it by chance alone. They would have to add that information to the medium of the message in some way that the message reveals itself only if that information were correct at the instant it were supplied, so the if someone locked in the present were to do it, the information would be out of date by the time it were observed. The best I can come up with is: 1. The message is written on or with some kind of medium. 2. The medium is reveals the message only if the exact inverse of the waveform of cosmic background radiation is supplied (analogous to noise cancelling headphones but for cosmic background radiation) 3. The observer has a firefly-like radiation emitting organ at the wavelength of cosmic background radiation. 4. The observer has evolved its prescience to observe future cosmic background radiation at a moment far enough in the future to exactly match the latency for their brain to transmit the instruction to their radiation emitting organ to emit the inverse waveform. [Answer] Encrypt the message (with modern asymmetric cryptography, but short keys) then destroy the private key. Normal people will only see the message after cracking the code (which involves factorizing a large number), in a few seconds/hours/days/years (depending on the length of the key). People which can see in the future can "guess" what the result of the cracking will be, before it is complete. [Answer] Imagine a Morse code that relies on the viewer looking into the future every 3rd signal. This would allow you to include false signals in the message that would not be observed by the intended target. But in the long run it would only be scrambling a message and I imagine it would be breakable if it was recorded and examined for patterns. I think most messaging done in this way is too limit to be unbreakable, by simply recording it a normal man can observe the whole message out of time. Alternatively if you used the ability as an identifier you can use the cool trick of an elaborate handshake. Anyone with the ability would be able to make a random handshake by seeing what their partner expects of them with enough time to react accordingly. In this way any one can easily and secretly show you that they possess these powers ]

[Question] [ In space-trading games like Escape Velocity, Elite: Dangerous & others, cheap FTL exists, but lags in other advancements results in a playable environment that is politically fractured and not a post-scarcity utopia. Pilots can even manage a profit margin trading mundane materials (like water) just a few tons at a time to space stations in star systems with no terraformed planets. So in a galaxy where stellar neighborhoods can be traversed in hours or minutes, and the demand for moving mundane materials is high, **what constraints probably exist that result in tiny, sometimes chintzy & fragile, spaceships being a favored form of transportation for an average licensed pilot?** Why are large freighters not seen as generally superior? Or, alternatively, why is the volume of space traffic shown in this type of fiction lower than expected? After all, we just mined x-million tons of asteroidal iron and our water usage is through the roof, as we have many thirsty miners in ships not terrifically larger than an 18-wheeler. Some common constraints tend to be that A.I. is not a pervasive technology, so robotic swarms are not usually part of these interpretations, and that atmospheric flight is either impossible or prohibited for most interstellar ships. This means ships can usually only dock on space stations or outposts on airless worlds, which are expensive & time consuming to manufacture & operate, and therefore a trade bottleneck. (these could be perfectly acceptable answers to the question, if they are the only limiting factors) Also worth noting: the FTL drive of Elite: Dangerous' effective range for a single "jump" is inversely proportional to the amount of mass being moved, which presents a hard limit on cargo & theoretical ship size depending on the quality of the drive. Assume this is arbitrary, or that creating increasingly stronger drives isn't insurmountable from a scientific or engineering standpoint. EDIT: I'm sorry I could only choose one answer, many of the below responses offer a lot in unpacking this common feature in near-future FTL universes. Thanks all! [Answer] The ships would be only big enough to meet demand at the destinations. Hauling a planetary sized mega-freighter of materials to Podunk Space Port-1 which only needs a tractor trailer worth of goods is not very efficient. You might ask why goods are mostly transported for final delivery in small trucks and not have the mega cargo ship unload directly to all coastal locations. This type of material management would be just as applicable to FTL transport. If it only takes hours, days, or weeks for a supply ship to show up to deliver goods, you only need to locally stockpile and store enough supplies to last that long. Podunk Space Port can't afford the warehouse space or inventory costs to justify the super-bulk shipments or the infrastructure to support them. It might be cheaper on a per unit basis, but if you only need 10 units buying them in packs of a billion is uneconomical. [Answer] Personal cost might be one. If we're assuming that pilots are owner-operator contractors ferrying materials, odds aren't great that they'd be able to afford massive cargo ships. Even if FTL is "cheap", owning a spaceship of substantial size still requires material and labor costs to build, which people have to pay for. Consider that an 18-wheeler here on Earth costs around $150,000, give or take, and uses a very large version of a relatively basic powertrain (most of them are just huge straight-six turbo diesels). Purchasing something the size of a cruise ship or aircraft carrier is still going to take aircraft-carrier amounts of materials. Added on is that if your massive ship breaks down you have huge downtime where you're making no money until it's repaired, vs a huge fleet of small, inexpensive vehicles that may be able to maintain 80% uptime or better. [Answer] Risk reduction? In many fictional universes space is dangerous and filled with pirates, aliens and alien pirates that want your valuable cargo. If all the cargo is stuffed into a single huge spaceship and it is stolen or destroyed then it's a huge financial loss. If the cargo is distributed among relatively inexpensive independent contractors (and you don't have to pay their life insurance premiums) then perhaps it makes economic sense to use smaller ships since there's a better chance that at least some of the cargo gets to its intended destination. [Answer] 1) Lets look at the Honor Harrington universe (*David Weber*). Normal-space drive performance is inversely related to the size of the ship. In his universe this curve is fairly shallow (it lets small warships run away from bigger ones) lets suppose it's much steeper. Considerable in-space maneuvering is required to use your FTL drive. Your space-warping normal-space drive can produce 100,000g / the cube of the distance to the farthest point on your ship in meters. (Thus it's linear to the volume of space that must be warped.) To use your FTL drive you must be moving at a Lorentz factor of at least 1 (from special relativity--you must have energy of motion as great as your rest mass--.866c) relative to the hyperspace you are going to enter. A courier ship that is 1 meter in radius reaches jump speed 402 seconds after clearing the atmosphere. An explorer in a ship that is 4 meters in radius takes over 7 hours to jump. A small freighter that is 10 meters in radius takes over 4 1/2 days to jump. A large freighter 50 meters in radius takes over 19 months to jump and goes over a light year during that time--in an area of dense stars it might not even use it's FTL drive. 2) Now lets add to this pirates. The space warping is quite unfriendly to locating your targets so long range weapons are impractical. You have to get up close and personal to hit and to actually pack enough punch to defeat things like anti-laser ablation layers you need quite a bit of power--and powerful lasers are big. This makes the best defense be to make your ship smaller than the laser needed to stop you. You will end up with a universe divided between little craft that sprint between stars and some that haul big stuff and have the weaponry to shoot it out with the pirates while plodding between the stars. There will be some intermediate range craft that haul large but urgent cargoes but that's a risky realm to be in. [Answer] Smaller ships are more maneuverable (at least when real-world physics apply at lower than FTL speeds). Lower mass can be moved with less effort/fuel/time. This may not matter during standard travels, but it matters when lifting from orbit. *OR when trying to outrun those space pirates.* [Answer] While this question is tagged with "spaceships" and "space-travel", this essentially a science-fictional question about how FTL travel configured in any fictional world. Since this is about non-relativistic FTL travel, then the author can set whatever worldbuilding rules he or she prefers to institute. For example, the mass limiting rule in *Elite* where the effective jump range is limited by mass of the vessel. One of the simplest rules than can be set to keep FTL ships small is to limit the volume of its drive field. If the field's volume cannot exceed a maximum volume, then ships can be no bigger than that volume. if the maximum volume is a cubic kilometre, you can have big vessels like megafreighter. Make it smaller and you might need with only singleships plying the spaceways. The amount of energy to power a FTL drive might increase exponentially and rapidly too. Especially if it's rate of increase was,say, the fourth power of its mass. The determining factor could the mass of the vessel. Doubling the mass means sixteen times the power to maintain a given FTL speed. By and large, if you play around with factors associated a FTL spacecraft, like mass, power consumption, size of the vessel, hypothetical drag factors in hyperspace or whatever, and as an author you can design whole ensembles of limiting factors to keep FTL ships small. This answer has concentrated on devising the general principles for restricting FTL spaceships to being small. Have devising your own rules! [Answer] # Don't think space ship, think space truck Truckers don't own the whole lorry, only the tractor. A large properly crewed cargo ship is expensive to run, expensive to maintain. A truck is much smaller and cheaper to run. If cargo pods are standardised, then the haulier doesn't need to turn up with a big cargo ship, he just needs a tractor to haul your trailers. Whether you think truck, or think train with a head and tail engine, there's no reason for big ships when the cargo doesn't need an atmosphere. Just an engine with a cockpit and a tow hitch. Perhaps there are vast cargo ships that can take enormous numbers of pods on long runs and the little trucks only do shorter, specialist and express runs, but you don't need the big ships turning up for a mere 50 megatons. Just get a couple of truckers on a regular shuttle run. # It's a mature technology Another factor is availability of the technology. You've said it's cheap and accessible, so treat it like it's cheap and accessible. Early engines were heavy, steam powered, complicated and difficult to maintain. Now everyone has a car. Consider the same cycle, early ships were large, needed vast amounts of bulky fuel and were hard to run and maintain. Now \*everyone\* has a personal runaround to visit their cousins in the next system at weekends and pop down to Stavromula Beta of an evening. Ships are small, cheap and convenient. [Answer] I've already seen people voice two excellent reasons - cost and risk. Another big factor which figures into both the cost and the risk of large-scale trade economies in FTL space-faring civilizations and which is in large part synergetic with risk and cost is liquidity - that is to say, a lack of liquidity in the market tends to arise where conditions are costly and risky, and drainage of liquidity from a market tends to engender higher costs and more risk. It's a vicious economic spiral that is mostly resolved historically by regulating and protecting the market (which sometimes means protecting it from undue intervention) until it is self-sustaining, near as I am aware. In a universe like that of Escape Velocity's, we see in-game that the currency is "universal" because the game wouldn't be "fun" if we had to worry about exchanging currencies at rates which could easily be manipulated by travelers arriving in our own light-cone's past due to FTL (and indeed, the game conveniently ignores the time-traveling effects of FTL travel, breaking physics fundamentally). In real life, however, a galaxy governed by many small states with many competing forms of currency and very little in the way of liquid capital sufficient to build large ventures on their lonesome would have to start with smaller ventures until they could amass enough capital to gain the economies of scale assumed to exist in the OP. Nobody has the money or the raw materials needed to start out big, so everyone goes small. Since nobody trusts each other and going big is very expensive (which multiplies the risk), nobody is really in a position to solve this problem, either. There might even be larger nations in existence somewhere in the galaxy, but if they aren't interested in what the little guys are buying and selling, then they effectively don't exist in the market. Imagine - what position does the United States take in the barter economies of the Amazon forest tribes? None whatsoever, for the most part. Furthermore, high risk and volatile markets lead to a lack of trust in currency because you don't really know if Zanzibar IV (where you foolishly decided to do most of your banking because of its excellently-regulated currency system) are going to be conquered by space vikings who don't honor the Zanzibar Simoleon Credit System because they aren't allowed to redeem it. Fiat money is not going to be favored over coin tied to some form of material redemption. This exacerbates the lack of liquidity further because the only kind of currency worth having on the galactic stage is stuff you can physically back - you're not going to be able to use debt to create wealth more efficiently, and thus investment will have to proceed more slowly. Consider, if you will, a quick instruction on the similar kind of situation which obtained in late middle ages Europe: <https://en.wikipedia.org/wiki/Crisis_of_the_Late_Middle_Ages>. Introduce enough strain on a market and it all comes crashing down, bringing entire nations and peoples with it: > > The European economy entered a vicious circle in which hunger and > chronic, low-level debilitating disease reduced the productivity of > labourers, and so the grain output was reduced, causing grain prices > to increase. Standards of living fell drastically, diets grew more > limited, and Europeans as a whole experienced more health problems. > > > [Answer] Flexibility. Certainly, big ships are more economical if you are sending cargo in bulk and you are not in a hurry. With slightly more crew than the smaller ships, one of the bigger ships can haul the same mass/volume than a complete fleet of small sized ships. But they are so big that they cannot land in most of the planets, so once they get to the destination the transport to/from the planet must be done with smaller, transfer ships. This means that loading/unloading operations will take some time, even if everything is perfect1, while a smaller ship can just land on the planet surface and almost do a "door to door" service. Also, if the regular transfer of goods is small, it does not make sense to keep a full sized cargo ship (with its maintenance and fuel expenses) if it only carries a 10% of its capacity. Additionally, smaller ships may adjust its fuel consumption to the needs of the service. A small ship carrying an express cargo may use greater accelerations (= energy = fuel expenses) if needed, a big ship carrying one express container and 200 low value containers cannot (because it will spend at least 200x more fuel than the smaller ships) So, while the bulk of interstellar transport is done in those behemoths, there is still a need for smaller ships for faster delivery and/or secondary trade routes. 1There is an available slot in a parking orbit, transfer ships are not busy serving other heaby ships, etc. [Answer] ### People are where the common resources are That's pretty much an obvious statement, but there is already quite a lot of metal on earth. If FTL is in humanity's capability, mining the earth's core is not so much out of reach. The space exploration is most likely to be used for scattered, rare things. Note that this wouldn't mean big cargos wouldn't exist. They just wouldn't be the main thing. ### Asteroids are pretty scattered According to [Wikipedia](https://en.wikipedia.org/wiki/Asteroid_belt#Characteristics): > > Contrary to popular imagery, the asteroid belt is mostly empty. The > asteroids are spread over such a large volume that it would be > improbable to reach an asteroid without aiming carefully. > > > A big ship would have to do a lot of stops, mining one asteroid at a time. It could send a lot of smaller mining ships throughout the belt and then make the trip back but in that case *why not send the small ships directly from earth*? If the trip is easy to make, it's the stops that are costly. Small ships can do a lot of mining in parallel. ### The government doesn't want a big mining corporation on its back A big mining corporation can hold a government hostage. That's not something you may want. If in the past, a mining corporation has done that and a great war was provoked from this, then the state may well take extreme measures to avoid that to ever happen again. Of course, it may take care of the mining itself, but it can avoid that job by just ordering mining companies to be really small. [Answer] There's the technical answer, the political answer, and then there's the metagame answer. This thread has some excellent proposed technical answers. As previously pointed out, your FTL may follow scaling laws which favor smaller ships. Also noted is that asteroid mining in particular is a distributed operation which favors a large number of small operators; that leads in turn to a distributed infrastructure of small space stations and depots, which can themselves be served by small freighters. The political answers are so complex I won't try to address them here, other than to paraphrase a line from Alien. When asked why the ship was in such bad repair, the reply was that "It's cheaper to bribe the inspectors than to do the repairs." I guess that's my way of saying that in spite of the advantages of the economies of scale and concentration of skilled talent, sometimes large capital-intensive systems simply don't work out well in practice. Lastly, there's the metagame answer. Since FTL is entirely fictional, any technical or political answer you observe has been crafted to serve a narrative. If you are gaming, then your narrative needs to serve a large number of customers operating alone. Even if you are in an MMORPG, your players are going to favor showing up for a battle in their own ships rather than being assigned a crew position on a larger craft. For purely narrative fiction like books and film, small ships operating independently lend themselves to certain stories and genres; horror, futuristic westerns, and harrowing stories of survival come to mind. I'll bet some of the classic one-man-in-a-spaceship fiction was written in part because the author didn't like writing dialogue. Short stories in particular do not lend themselves to large casts; small spaceships allow the author to introduce a limited cast and a finite setting and then move the narrative along briskly. [Answer] Ok, read all the other answers and didn't see this particular idea, so here goes: Let's decompose "transportation" into: 1. Transporting ourselves (or maybe just our consciousnesses, depending on how our world works), and 2. Transporting everything else - materials/goods/other beings/etc. As far as the utility of transporting "stuff", most successful races would put value on maximizing efficiency, which could be defined as amount of mass transported per unit of "spacetime" (i.e. travel distance and travel time). This metric would become a driver for lots of constraints on ship size (think economies of scale, etc.), and it seems that things would overall tend towards bigger ships. However, consider for a second what a swarm would mean for this - the big, efficient "ships" are really made up of many smaller units working together as a whole (somehow). **Now, the twist:** "personal" transportation - i.e. moving "ourselves", is very different. The human race, and many fictional races, have a strong bias towards personal autonomy and freedom of movement relative to other beings. So we may have a *very* strong incentive for **smaller** craft already, if in many cases we explicitly want to transport only ourselves (or a few beings), not to mention the other benefits mentioned for small craft, like maneuverability, lower costs, less liability (only you are at risk when travelling "by yourself"), etc. Put those two forces together, and it looks an awful lot like a good argument for a swarm-centric model where you have lots of little "personal" craft that consolidate into larger collective units when the efficiencies of bulk transport outweigh the need for personal autonomy. I know swarms have been mentioned. I'm just trying to further explore how likely it might be for a swarm-based transportation model to emerge naturally, which may determine and/or affect many of the *other* constraints on ship size. Just a thought. Great question! [Answer] "Cheap" and "small" are relative terms. On "small"... Think of current day ocean going vessels. The longest ship was about 450 meters (1500 ft); the largest aircraft carrier is around 340 meters (~1000 ft). While the smallest is/was about half of that. Destroyers go from as large as a "small" aircraft carrier (Zumwalt - 170m) to 1/3 of that. On "cheap"... ship prices for destroyers and aircraft carriers can go from 200 million to around 13-14 billion (Gerald Ford class carrier). So, a "small" spaceship could still be a very substantial vessel, but would probably still be expensive enough to make it affordable only to the **super** rich (individuals or corporations). And a large aircraft-carrier sized space-ship would probably only for the well-funded governments, and they do not run trade (at least not in a free market). You could look at cheaper type ocean-going vessels, like tankers or cargo ships, but for space and FTL, you are probably talking complexity and technology at or beyond the level of a military ship (carrier or destroyer). [Answer] Another possible answer lies in looking at existing shipping on Earth and why they are designed the way they are. We have 4 main long distance shipping vehicles: Ocean freighters, cargo planes, trains, and cargo trucks. Of those 4 vehicle types, 3 share a standard shipping container for easily transferring cargo from one vehicle to another. The important considerations for each vehicle type are: **Ocean Freighter** * Water produces high drag. * Having a lot of mass counters the losses of the high drag. * Restricted to water. * Can only deliver to docks. The larger the boat, the fewer the ports that have docks that can support the ship. **Airplane** * High speed. * High fuel consumption. * High cost. * Can only deliver to airports. * The heavier the cargo, the fewer the airports that have long enough runways to support the plane. **Train** * Most fuel efficient. * Engineers typically take turns at the controls (can travel for more than 8 hours without law mandated rest periods). * Slowest overland travel option (if not considering the option of having multiple engineers to keep the train operating around the clock). * Can not share the tracks with other traffic. * High up-front cost to setting up the infrastructure. * Restricted to land. * Can only deliver to stations. **Cargo truck** * Each vehicle typically carries one cargo container; two at most. * Multiple vehicles can share the same road. * Drivers required by law to rest (very long trips take more time than the same distance by train) (yes, I know that there are "sleeper" truck that allow multiple drivers; not all drivers can sleep in a moving vehicle; majority of dispatchers don't want to pay for drivers who are sleeping in the cab) * Restricted to land. * Can deliver to most locations with humans. Taking all of these considerations in account, and working with the "realities" of typical FTL space travel: If there were a region of space with high drag on a ship's FTL drive, it would make sense to make larger vessels like ocean freighters. I haven't heard of any such cases in any stories I've read; space seems to be relatively uniform, even in fiction. These ships will need special spaceports for servicing, though thanks to most things in space sharing the same orbit, transferring all of the individual standard cargo containers from the freighter to local delivery ships would be much faster work than the current cranes of today's ocean freighters. If you've ever disturbed a mother wolf spider with hatchlings on its back, I imagine the cargo containers would disperse in a similar way. If there were a way to inefficiently use energy to produce extraordinarily high speeds, we'll see small, fast, expensive to lease cargo ships. If there were something about the FTL drives that made them work more efficiently if placed in some sort of conditioned space (subspace slipstreams?), we would have space trains. Given the most common description of FTL ships; single-family home sized craft that can zip from system to system in minutes or hours, that can land and take off from atmosphere covered planets without needing to spend 80%+ of their mass as fuel or reaction mass, and craft that really don't need to keep to specially conditioned areas of space or avoid certain areas, this is what most individually piloted space freighters are likely to be. They can go anywhere in any reasonable time, and dock at any port, spacedock (space station based ports), spaceport (planet based launch complex), asteroid mining operation, or space homesteader's front door, and be free to offer their services to any dispatcher in the system, provided they're an owner-operator. *Serenity* and *The Millennium Falcon* were examples of this type of cargo ship, and both crews were owner-operators. [Answer] People and monopolies, firstly humans don't like being crowded, by-and-large we also don't like throngs of other people around us, frontier types who would actually go out into space where people are generally thin on the ground even more so. So spaceships that require more than say a dozen crew are impractical out on the edges of things because of the dominate personalities out on the edge of civilisation. Secondly where there's a lot of profit to be made corporations will monopolise those profits wherever possible. Andre Norton's Freetraders are a good example of the end result of these two ideas, in the core where inhabited worlds are "close" and populations are large the Combines, big interstellar companies, dominate trade with massive freighters but out on the edge the Freetraders run much smaller multipurpose transport ships between isolated new worlds. *Firefly* uses a similar model; on the Rim small scale independent traders can make a buck that isn't available on the Core worlds, not because they're unprofitable but because the profits are all sewn up by larger interests. ]

[Question] [ I have a character in my story (set in 1998) who has been magically altered in three major ways: 1: She cannot be remembered for longer than 60 seconds without continuous exposure to her by one of the five senses. By the time the 60 seconds of not being in her presence are up, all memory of having ever encountered her will completely vanish. 2: Any second-hand direct recreation of her image or voice (photos, videos, tape recordings, etc.; drawings don't count) are impossible to acknowledge. If she's in a group picture, you simply won't notice her. If she's the only person in the picture, you'll think you're looking at a picture with nobody in it. If she makes up most or nearly all of the picture, you won't even be able to recognize you're looking at a picture at all. 3: She can, at any time, transform into an invisible, incorporeal, flying phantom form that can see through walls. She cannot be selective about this, and thus can't "ghost" anything through walls with her, and in fact leaves her clothes completely behind too and has to get new ones wherever she chooses to re-manifest. This, naturally, has made it basically impossible for her to properly participate in human society. She can't get a job, can't go anywhere that requires a photo ID, can't even go anywhere where it would be weird not to recognize someone. My initial idea was that she'd live out of a stolen RV near a small Idaho town, until I discovered I had been grossly overestimating what the internal battery of an RV is capable of powering without being directly plugged in to a power source at an RV campground, which I suspect she wouldn't be able to use without arousing excessive suspicion. This is a problem, because one of the things I want her to be doing in her copious amounts of free time before the plot starts is playing video games, including home console games that she'll obviously need a proper power source to use. So I thought I'd check here if there's a more obvious solution. **Given her above abilities and limitations, what is my heroine's easiest method, legally or otherwise, of securing a source of power with which she can, bare minimum, play video games undisturbed?** [Answer] # People remember account numbers: She's not in as bad of a place as you might think. semi-normal life (and the electricity she needs) is not so far away. Just because you can't remember meeting someone doesn't mean you can't remember them. Letters, notes, and documents are permanent. Email was a thing in 1998 (but not so prevalent), and she could have relationships with folks she didn't meet in person (that they remember). She could talk to people, learn things about them, and then connect with them using those details - all by mail and letters. Your character can get really good at paperwork. She can enter any business or administrative office after hours and mess with the files of anything (as long as the office isn't too chilly). First off, she really needs to find someone who looks a lot like her. Get pictures of this alternate person to use in documents. Identity-theft the crap out of them. She could create an entire alter-ego of the person, or use the image to make a completely new semi-legal entity. People may not remember your character, but they certainly can acknowledge that a hotel log says room 13 is occupied by Jane Dough. If someone goes to room 13 and checks on who is in 13, she tells them to go check the log at the front desk. They'll see 13 is marked as occupied by Jane Dough (probably wondering why they were checking). Similarly, a bank account #3456732 can have money deposited in it by anyone. If a young woman has the bank card, she can fill out the paperwork for a credit card from the bank. If they need a driver's license, they'll find she has one for Jane Dough, the account holder. They don't give a crap about who "Jane Dough" is, or what she looks like; only that she matches. The deed for a house or car can be filed with an agency, and no one looks at it except to fill out forms. If you have the deed, it's yours. * Similarly, she needs a job (assuming she doesn't just steal like crazy, which would be really easy) that has flexible employment in a large bureaucracy. Their records show Jane Dough is an employee, and the work gets done. So what if no one remembers hiring her? Someone punches in every day, and punches out. Admin delivers a check to bank account #3456732. And there's a girl with an ID badge that kind of looks like her but the hair is different. Some jobs pay by how much you produce - so if you log work done, it gets paid for. Do more work, and as long as someone verifies this "Jane Dough" person's work got done, who cares? * She might also manage doing door-to-door sales. If she sells products that she delivers immediately, then people may not recall her, but might have a vague memory of buying a vacuum cleaner that is obviously sitting in their living room. The less reputable version of this is selling stuff out of the back of a van/truck: it might be legitimate or not. * Your mystery woman could also be an outstanding freelance reporter. As long as she can establish a "deep throat" identity (where the editor doesn't know who's providing the articles), she can funnel articles to a newspaper that pays money to her bank account. She could follow people and be immediately forgotten. She ghosts into the police station and reads classified documents or case files, then sneaks out. Even if she's detected, she ghosts away and they just forget. How did she get that exclusive in the New York Times where she reveals secret documents from the Cuban embassy? The most forgettable woman in the world could have a world-famous alias and yet remain perfectly forgettable. An apartment is sub-let by a Jane Dough who always pays her rent. She sure must keep to herself, because she drops off notes to get the sink fixed, but no one can recall seeing her. She's not Jane Dough the famous reporter, is she? Whoever she is, it sounds like she's playing video games. [Answer] **Become a Real Ghost** Other answers work if our hero can still communicate in written form. In that case she can still maintain a job, home, and access to electricity. This answer is in case you want to turn her powers up to eleven, and make even her bank account number subject to the 60-second rule. In that case her best bet is to live in someone else's home and use their electricity. Ideally someone who poses no physical threat for when they run into each other, and who is amenable to things moving around in their house without explanation. The first can be accomplished by a home owner who cannot run or move quickly. The second by them already believing their house is haunted. So she should play the role of a *real* ghost. For example there was once a family family that lost their child son. The family broke up due to the emotional trauma. The mother still lives in the family home, and has entered the delusion that the house is haunted by the spirit of her son. She keeps the room locked and rarely enters. But she often notices her son's spirit has moved things around since last week. Since she has claimed the house is haunted since years before the protagonist moved in, no one believes her now that the house is actually haunted. Additionally, the home-owner has a trick hip, and has installed a stair lift elevator. She mostly lives on the bottom floor and the protagonist mostly lives on the top floor. This makes it easy to avoid the occasional encounter, since the stair lift is very noisy and takes a few moments to reach the top. Enough time to vanish into another room. [Answer] Inspired by Daron's answer, live with someone elderly who has a somewhat shaky memory anyway. Rather than never be seen, you can pop in to the living room and have a nice chat if you want some human company - just tell them you have been sent by the council to help them. Rather than just "stealing" electricity and food from them you can check on their welfare, make sure they've turned the oven out, sit and talk them through those confusing letters from the council or stop them from answering the scammer on the telephone. Sitting with them while they use the phone or call a handyman for example you can easily ask them to add in a couple of extra electrical sockets in the study while they also fix the drip in the tap in the spare bathroom. When the workman comes the elder might not remember exactly why they requested something but there's a good chance they will just accept it. Similarly if you sit with them while they order food from the nearest supermarket you can suggest they get extra, then reappear to help them unpack when it arrives. The outside world just sees a slightly eccentric old lady and forget about her helper after they leave. [Answer] **Theft** She is the perfect thief. She stole the vehicle, why not steal the electricity as well ? Just plug in the console's batteries reloader at the nearest neighbour. Even if the victim sees her, he will forget her presence very quickly, when she vanishes with her magic, or runs away and hides near the house, somewhere.. and try again. She can also easily steal another car. Suppose she would, the owner could even witness the event, no problem. After one minute the owner would remember *someone* stole his vehicle, but he cannot remember what that person looked like. He would be of no help to the police. *(I replaced the text of this answer, thx @E Tam for the remark)* [Answer] Why can't she just use solar panels to get enough power for her games? As for money, she can slip into almost any place--this could be used for good (bugging mob bosses and the like), evil (theft) or in between (espionage.) To use for good: Bug a mob boss. Send an e-mail to the FBI giving the location and frequency--put $50k in such-and-such a place and you'll get another such e-mail. To use for evil: Get a safe deposit box, put tools in it. Go back when it's closed, use those tools to rob other boxes. [Answer] I'm going to assume that she wasn't born this way, since having your parents forget you exist when you're dependent on them for your survival is a little tough. This means she already has a legal identity of some sort. She probably has a bank account, maybe a social security number, driver's licence and so on. She can use these things to get goods and services through the internet, no problems. Doesn't matter if nobody can remember her if they never actually interact with her. Depending on her skills she could also get a job online, without ever having to interact with a real person. Online trading, jobbing sites, whatever. She could hire herself out in a variety of specialist jobs, although most of them are pretty shady. If she used her abilities well she could become one of the most well-known investigative journalists in the world, even though nobody could pick her out of a lineup. If she can build up a reasonable income then she can hire people to do the rest, without ever actually having to meet them. [Answer] Perhaps try to find a friend? Establishing any kind of relationship in this state is hard, but I don't think it's impossible. I think quite a few people would appreciate having a sort-of imaginary friend that actually comes around once in a while - perhaps she should try meeting some science-fiction writer? While people can't remember her, they should believe things that they wrote themselves and that they said, right? So she might come once, tell her story, make the writer write it down, and than say "in order to proove what I said, I'll leave the room now, and come back in 5 minutes. You will experience me as a new person, but I will know the password that you give me now, please write it down for verification". A curious person will be willing to make an experiment, and hopefully will believe the story after a few repetitions. Of course, one day experience, no matter how convincing, may be shrugged as a dream, but show up every day for a week, always remembering some password or secret to authenticate yourself, and with a properly chosen patient you will get a believer, not remembering you specifically, but remembering of your existence (they have written about your existence every day in their diary for a month, right?), and expecting a "new" person showing every day before their door and greeting with "how are you doing, old friend". If she's willing to show naked in front of that person (perhaps picking a female to befriend is preferrable anyway?), a quicker and perhaps more convincing experiment is to simply dissappear in front of the person and appear a short while later - before being forgotten. Oh, actually, there may be people even more interested in meeting her: some doctors and psychiatrists working with people with amnesia and dementia may just want to try having a similar experience. Hopefully no one will go mad from that. Anyway, it's probably not the shortest way to get the electricity, but I think that's an interesting one, and I think there is a lot of place to play with finding loopholes in this memory-vanishing. [Answer] I dont see why she couldnt participate in human society. Yes she cant get photo ID, but photo ID is a gatekeeper. Its not a participation blocker. Three examples: * photo ID is needed to get to work? Not really, its needed to get in the door, past security. Once inside, photo ID isnt needed. Even if someone challenges her for not having it, she can vanish through a wall, and 60 seconds later they wont remember a problem. * But its needed to get a job? Again no, a file record of ID is needed, at HR. But she can visit through the walls, to fake it, as in other answers. * Its needed for a bank account? Again no. She can get her "2 forms of ID" easily, because a utility bill or rent bill is common, she can watch for postal deliveries or letters sent by a homeowner, and slip through a wall to intercept or modify them, and get a bank account with that and some silent file manipulation.... But that aside, what exactly stops her from entering places with electrical cables, and adding a couple of her own to draw on them? That's how I'd do it. [Answer] **Find a translator** So maybe this isnt quite in the spirit (heh) of the character but given: > > She cannot be remembered for longer than 60 seconds without continuous exposure to her by one of the five senses. By the time the 60 seconds of not being in her presence are up, all memory of having ever encountered her will completely vanish. > > > and > > Any second-hand direct recreation of her image or voice (photos, videos, tape recordings, etc.; drawings don't count) are impossible to acknowledge. > > > This doesn't mean people cant remember being **told** about her. A lot of the other answers seem somewhat nefarious or high effort but if she finds a couple of spiritual people she could use one person as a speaker or mouth piece. It doesn't even have to be the same person every time). So a group of people could be aware of her existence around them and even have somewhat convoluted permanent relations with a small group It really depends on how far down the chain of interaction the memories are lost and if a primary interaction with this method removes all previous associated memory (which could be a pretty tragic romance plot) [Answer] I like the idea of making her an actual 'ghost', but if you are willing to bend your second rule a little bit, you can also go the other way and make her participate in society like a normal person. You said that > > Any second-hand direct recreation of her image or voice (photos, videos, tape recordings, etc.; drawings don't count) are impossible to acknowledge > > > but I would change that to > > Any second-hand direct recreation of her image or voice (photos, videos, tape recordings, etc.; drawings don't count) becomes impossible to acknowledge at the same time that the memories from her actual presence vanish (#1). > > > And perhaps expand it a bit to include > > Any recreation of her image or voice matches her current appearance. > > > So she could get her photo taken, get an ID and anyone she will show it to will see that the person in the photograph matches the person in front of them. Even if she leaves her ID lying around, as soon as she disappears from someones memory, they will not recognize her on the photo as per your original rule. The main consequence -- since you said she is not able to take even her clothes with her when she disappears through a wall -- is that if she wants to go somewhere with her ID, she will have to physically carry it there without doing the ghost thing. That may open up new possibilities in your story too (e.g. she really wants to 'fly' through the walls of the secret government base, but she's going to need proof of identity to go into the main control room which means she can't use that ability). [Answer] I'm really quite surprised that no one has thought of using a gas-powered generator. If she can steal an RV, she can steal a generator and a jerry can. Then she can walk up to a gas station, fill up her jerry can, and either sneak off, or provide a big enough distraction to be able to just walk away. A very brief Google search tells me that a generator with a gallon of gas in it (or 4 litres) will run for about 5 hours. Apparently, you're not supposed to run them for more than about 8 hours at a time, so she'd probably need two generators (since she wouldn't need either while she sleeps). [Answer] # Touch is a sense Wait until her hair is longer enough. Cut it. Braid the clippings into string. Dye some of the strings different colors. She trims her grown out fingernails, and the polishes them (as in sands them smooth, not puts on nail polish). Integrate the nail clipping into the string. Make fancy, organic friendship bracelets. Give the bracelets to people to wear. Congratulations, she is now in constant physical contact with the person. Continually stimulating their sense of touch with a piece of her own body. So long as the person doesn't take off the bracelet for more than a minute, they will remember her. [Answer] Electricity can come from an RV park. Hear me out. I currently work at one. And there are residents that we see, and residents that we don't see (because they work night shift or some such). Some people check in after dark. As long as the vehicle slot is paid for by check or money order she can stay in a park. in the 1990s electronic transfer isn't so much a thing, and while it CAN be paid by credit card, in those days this wasn't accepted as payment for rentals as much, depending on the place. You're saying that ID is a problem. But...you fail to see the advantages of being a "ghost." It means you have infinite do-overs to gather information. And that means that you CAN get anything. Including fake IDs with a picture of a girl who kinda looks like you. [Answer] Just steal it the same way lots of people do in real life, hook into a street lamp. She might need to befriend an electrician or you can give her the skills to do it herself. Worst case she may have to move around every now and again if the city keep disconnecting her connection, but as they won't remember her she won't be getting into trouble for it [stealing power](https://nypost.com/2017/08/02/this-homeless-guy-has-found-the-ultimate-power-hack/) ]

[Question] [ Following on from my previous question [here](https://worldbuilding.stackexchange.com/questions/96293/what-methods-might-an-ancient-civilization-take-to-extract-fresh-water-from-grea) concerning the ancient civilization I have called the Androy and their struggle to survive terrible drought conditions on their planet. After years of struggling with having to dig deeper into an aquifer to extract water from underground the Androy encounter an even bigger problem. During routine deepening of the wells they encounter granite. They are at the bottom of the aquifer and within a few years will have to find water from some other source. They are relatively close to the ocean. What techniques can they employ using ancient technology, to extract sufficient fresh water from the ocean to meet their needs? Can they extract as much from the sea than they could from the aquifer? Is it even practical? The geography / geology of the coastline may be configured as you wish. [Answer] You can build a solar still using nothing but pottery tubes, sealed with asphalt or similar. A [single unit (different design)](https://www.youtube.com/watch?v=WhAYbeGEebQ) can produce as much as five liters per day. For continuous production, the main "unit" is a large tube with two tubes inside, the upper one being half open. The upper tube is filled with slowly moving salt water, that evaporates and supplies humid air. The smaller lower tube contains much faster-flowing salt water, and the humid air condenses on its surface (it needs to be glazed), collecting in the low part of the outer tube. This would work a lot better if the upper part of the outer tube was made of glass, but with sufficient surface to dedicate to the project fired clay should work too. A fully-fledged solar still can get you around five liters per square meter per day; assuming the clay is one tenth as efficient, a roof's worth should still (pun not intended) produce water enough for the inhabitants of a two-story building... in the summer. In winter, things might not go so well. Agriculture would require much more water, and I'm not sure it is doable with solar power alone. You might use a slightly different scheme to allow both concentrating sunlight with reflectors and optionally (being careful not to crack the pipes) fire to increase the evaporation rate. To further improve thermal insulation the freshwater pipe could run underground. [](https://i.stack.imgur.com/4Ng8A.jpg) [Answer] **Reverse osmosis.** from Aristotle, [Meteorilogica](http://classics.mit.edu/Aristotle/meteorology.2.ii.html). > > There is more evidence to prove that saltness is due to the admixture > of some substance, besides that which we have adduced. Make a vessel > of wax and put it in the sea, fastening its mouth in such a way as to > prevent any water getting in. Then the water that percolates through > the wax sides of the vessel is sweet, the earthy stuff, the admixture > of which makes the water salt, being separated off as it were by a > filter. It is this stuff which make salt water heavy (it weighs more > than fresh water) and thick. The difference in consistency is such > that ships with the same cargo very nearly sink in a river when they > are quite fit to navigate in the sea. This circumstance has before now > caused loss to shippers freighting their ships in a river. > > > It looks as thought subsequent authors dispute whether this vessel should be wax, or earthenware, or some combination. It also looks as though it was difficult to make this work up until very recently, with modern ceramic technology. But is this necessarily so? The principle laid out by Aristotle is sound: reverse osmosis involves a filter small enough to exclude dissolved ions (here, salt) and pressure enough to drive the fresh water through. [Ceramic reverse osmosis membranes](http://www.waterworld.com/articles/2015/07/ceramic-membranes-trialled-in-singapore-for-seawater-reverse-osmosis-pre-treatment.html) exist. Usually ceramic filters are unglazed ceramic. My scheme for these fictional people: 1. Unglazed ceramic filter pipes. They make these using techniques similar to those invented by the ancient Chinese for making [porcelain](https://en.wikipedia.org/wiki/Porcelain), also a very fine grained ceramic. 2. Hollow wooden cores (or cores of more robust and more permeable ceramic, like terra cotta) are threaded inside, to buttress the ceramic filter pipes against pressure at depth. 3. Filter pipes are lowered to a depth where water pressure will drive seawater through the filter, producing fresh water on the interior via reverse osmosis. This should be in open water - an area with circulating salt water to avoid buildup of concentrated salt brine, which would require higher pressures to desalinate. Perhaps at the end of a jetty? 4. Water is pumped up through these pipes as though from a well. 5. Pipes are periodically raised and scrubbed, to expose new filter surface and reduce fouling. For any interested in back reading on the history of desalination I found this excellent and exhaustive source: [A short history of water desalination](https://www.researchgate.net/profile/Giorgio_Nebbia/publication/301328310_A_short_history_of_water_desalination/links/57a5d1dd08ae3f452932da13/A-short-history-of-water-desalination.pdf) [Answer] You mention that there is an ocean. Therefore, the air has humidity, at least in areas around the coast. Doesn't matter that there's no rainfall - you have humidity. And with a day/night cycle, you get fog and dew. So, I give you [fog catchers](https://en.wikipedia.org/wiki/Fog_collection). Using nothing more than fabric mesh, which even a prehistoric civilisation could master, they'll catch water droplets from the air. No need to dig wells, no need for fancy desalination plants, just weave fine-mesh nets. Your civilisation also needs to look at their agricultural practises. Mulches will radically reduce the need for water. If they can handle deep digging, they can easily enough engineer deep trenches (like several metres deep) to grow plants in, where the trench itself acts as a dew collector and temperature moderator, as with the [Forestiere Underground Gardens](http://www.undergroundgardens.com/). This can potentially give you a unique landscape. Above-ground would be a riot of fabric, most likely with each village using their own colour schemes - but of course no houses above-ground. The trenches will form the "streets" for the villages, and homes will be dug into the rock in the walls of the trenches. The walls of the trenches will be covered with any kind of creeping plant which can provide food, and the floors will contain any other plants which need more space. A few precious locations above-ground may be planted with grain, but the people will mostly have to live off other staple goods - cactus, fruit and root vegetables will probably be their major foods. Trees will be particularly useful, because deep root structures have better access to water. [Answer] Plain old distillation. Now, distillation is *expensive*. It requires huge amounts of energy. So how much they can produce will depend on just how rich they are, and specifically how much energy they can command. If they have oodles and oodles of easily accessible fossil fuels, they might very well be able to produce just as much as they got from an aquifer. The simplest set up would be a solar still. A well-designed industrial-sized solar still, with concentrator mirrors, will produce much more drinkable water than passive evaporation, but you'd need a *lot* of them, over a very wide area to capture enough solar power to make enough water for your whole civilization. The mirrors don't need to be particularly high-tech; in particular, they don't need to be image-forming. Polished brass would be fine. You'd just have to make sure it's well-maintained. Alternatively, you could ditch the mirrors and just spread out the water over a much larger surface area--but that requires building a much larger still, with a much larger transparent roof (basically a greenhouse for water) for letting light in, holding in the heat, and preventing the escape of the vapor. Which may very well end up being a more difficult proposition, not less, especially considering the expense of glass in the ancient world and the technical difficulty of producing large sheets of it. It doesn't need to be optical quality, but still, that's asking a lot. The other option is fire-powered stills. If they have access to fossil fuels, or a large supply of rapidly-regrowing vegetative fuel sources (like, say, a really big bamboo forest), solar concentrators can be replaced with furnaces to heat water for distillation. In theory, such a still could be built entirely out of ceramic pottery, but any amount of metal or glassworking technology they have would be helpful. In any case, note that one of the waste products of the distillation process will be highly concentrated brine--and that's not necessarily a bad thing! Ideally, you'd want to keep up a good flow through your distillery so that you don't build up salt depositions inside (or so that you minimize build up--cleaning the works will be a necessary regular maintenance task regardless), and you can pipe the concentrated brine elsewhere. Don't throw it away, though! Put it into passive evaporation pools, and start manufacturing salt! Salt is an incredibly valuable trade good for ancient civilizations, and they could then start using it to buy supplies fro other civilizations--including fuel, and possibly even aqueduct access to other people's water, if necessary. On top of all that, there are things they can do to reduce their dependence on fresh water. You can, for example, use salt water just fine for evaporative cooling. Additionally, they could try developing saltwater agriculture, as mentioned in Ash's answer, and aquaculture. Sea plants obviously already grow in saltwater just fine, so farming and using seaweeds as a large part of their own diet, as animal feed, or even as fuel for the distillery furnaces, would cut down on how much water they need to distill, as well as eating fish and other seafood to avoid having to spend water on as many domestic land animals. [Answer] I will elaborate on distillation with another solution: [spray desalination](https://www.scientific.net/AMR.512-515.9) First, get some hot air, above 100°C but not too much. You can do this with concentrated solar power using flat mirrors. However a [parabolic trough](https://en.wikipedia.org/wiki/Parabolic_trough) would be a much better option, because one person (ie, child labor) is enough to keep it aligned. The [parabola](http://parabolaonline.tripod.com/history.html) was discovered a very long time ago, mirrors can be polished bronze, and the structure can be built out of wood. The theory to build it would be a bit advanced for the time, but not the construction materials. Now you need to blow some air into the system and heat it up: if this is a coastal area there will be wind, so you can use a sail to funnel the wind into a pipe, or you can use a donkey-powered "windmill" as a blowfan. Then, you would need seawater with enough pressure, so another donkey-powered water wheel, or archimedes' screw to hoist the water into a tank on top of a water tower. Height creates pressure... Now use a spray nozzle to spray the water into the hot air flow. The neat thing about spray evaporation is that a large quantity of droplets have a huge surface area to exchange heat with the air, thus they evaporate very fast. If the water and air flow are just right, you get salt crystals which you can collect and use, and very humid air. The humid air can be cooled with seawater, which condenses the moisture and yields desalinated water. This process is more efficient than plain distillation, although more complex to use, but you also get salt. I'm not sure when spray nozzles were invented, though... [Answer] [Saltgrass](https://en.wikipedia.org/wiki/Distichlis_spicata) has not been mentioned yet. It grows in salty water, and excretes solid salt from it's leaves. Additionally, livestock can graze on it. After much experimentation, the culture follows the following recipe: 1. Excavate a large flat basin that isn't too deep and holds water after a high tide goes back out. 2. Run a flat channel from the basin inland towards the town. 3. Plant saltgrass in the estuary and the channel. 4. Harvest salt from the salt grass. 5. Take sweet water from the point furthest from the ocean. 6. Occasionally harvest and replant the saltgrass and feed livestock with it. 7. Every few years, remove silt from the estuary, re-grade the basin and dredge the channel. The soil from these endeavors will be high in organic content and likely valuable. [Answer] Evaporation, but the yields will be sod all at that level of technology. Alternately they can use [salt-water agriculture](https://www.voanews.com/a/farming-with-salty-water-is-possible/2510044.html) (there's a better example in either Libya or Sudan but I can't find a link) in which salt hardy species like Mangrove are used for biomass fuel production and fodder species with low embodied salt like salt-marsh-grass hay can be used in place of traditional animal feed, some of these species, like [Glasswort](https://en.wikipedia.org/wiki/Glasswort) have a high water content and could serve a duel role (food and water) for some browsing species. I would also suggest that salt hardy animals like the [Camargue](https://en.wikipedia.org/wiki/Camargue) breeds, which can survive year-round without access to truly fresh drinking water, would be a necessity in this situation if people were going to continue to keep livestock. Or you could go big, really really big, landscape engineering scale, the basic technology is not that complex but the large-scale application has never to my knowledge been attempted. It uses the principles of the [solar chimney](https://en.wikipedia.org/wiki/Solar_chimney) but on a grand scale, put a large array of such chimneys along a coastal ridge to suck moist air in off the sea and use equally large [wind harvesters](https://en.wikipedia.org/wiki/Atmospheric_water_generator) to drain the water from that artificial air current, either using a mesh based condenser similar to a fog collector or allowing thermal expansion to do the precipitating within a cooling tower of some kind. The Chileans achieved average yields, from natural fog, of 15,000 litres per day from 94 capture meshes. Creating artificial winds on this scale will not have predictable outcomes so I'm not going to venture an estimate but it could be sufficient to sustain a population big enough to exploit and maintain the system, especially where integrated greenhouse space is used. [Answer] Does the night time temperature fall below freezing at least part of the year? They can freeze distill their water. Get a bunch of salt water. Let it sit out in freezing temperatures. You will then have less salty ice floating in very salty brine. Pull the ice out, drain the brine off somewhere else, melt the ice, repeat. Each time the part that froze will be less salty. [Answer] For potable water ancient civilizations may have relied on filtration - it removes the salt, but leaves the water hard. The "technology" is still used in many Mediterranean countries - usually a large local rock hung in the courtyard, seawater is poured on top in a slight depression, the water percolates through the rock and is drinkable. I'm not sure on the volumes, but it's something I have used. Distillation was also very common on ships, The *Resolution* built in 1770 had "the latest apparatus for distilling fresh water from sea water" – [captaincooksociety.com](http://www.captaincooksociety.com/home/detail/resolution) > > The ‘Ballochmyle’ water filter, circa 1830 a rare colonial Georgian water filter **drip stone**, made of sandstone and wrought iron framework in superb original condition with reservoir at base. > > > [](https://i.stack.imgur.com/Zyynum.jpg) ([source](https://www.antiquesreporter.com.au/index.cfm/lot/482715-the-ballochmyle-water-filter-circa-1830-a-rare-colonial-georgian/)) [Answer] It depends on orography.. They may be able to build a wind trap. General principle is to, somehow, drive hot and humid wind through a relatively cooler cave (possibly rocky). This will cause part of the humidity to precipitate on walls to be brought to underground cistern. A cliff near the sea, possibly facing South, with some shore to build shallow pools would be a great place to build. It might (depending on specifics of prevailing winds) to use something (windmills?) to force air to traverse cave in the right direction. [Answer] A water-cooled greenhouse uses evaporative cooling which, at the same time, provides humidity in the greenhouse. This reduces water consumption. The cooling works equally well with sea water. The humid air may cool enough at night to create condensation. The brine exiting the coolers may be used to produce salt and serve as a raw material for the fertilizer industry. This model has been proposed in the [Sahara forest project](https://www.saharaforestproject.com/seawater-cooled-greenhouses/) [Answer] How much water do we actually need? Modern household in industrial countries use ~150 l/d and person. This is only the smallest part of actual water usage. A more complete number for water usage must include water needed for all industrial processes, watering plants, supplying animals etc. So we look at [virtual water](https://en.wikipedia.org/wiki/Virtual_water) data and the [individual water footprint](https://en.wikipedia.org/wiki/Water_use#Water_footprint_of_individual_consumers). The lower bound appears to be China with 1000m³/a person. I'll go out on a limb and say an ancient civilization needs about a third of that - no industry and I assume reasonably adapted agricultural practices. Also this rounds to 1 m³/d person for everything. Seawater desalination needs stupendous amounts of energy. The most efficient thermal technology, [multi-stage flash distillation](https://en.wikipedia.org/wiki/Multi-stage_flash_distillation), needs 23–27 kWh/m3 of distilled water. Reverse Osmosis used to be half that, but top of class technologies are said ([wikipedia](https://en.wikipedia.org/wiki/Reverse_osmosis), I have my doubts) to be as low as 3 kWh/m3 (this includes energy recovery from brine etc.). I'm not convinced that an ancient civilization can hop to approach these efficiencies, so I'd assume the energy demand to be worse by an order of magnitude. Note that the efficiencies stated above stem from decades of dedicate engineering, on the back of centuries of general engineering. So for the purpose of this answer, I will simply assume that "technological" desalination will not be implemented at scale or as only or main water source. What's left? Your civilization cultures large, artificial [salt marshes](https://en.wikipedia.org/wiki/Salt_marsh). The plants growing there are harvested as fodder, but mostly for their fresh water content. There's [at least one plant](https://en.wikipedia.org/wiki/Spartina) that grows in salty habitats and can be used as fodder, so it's not totally impossible. How to turn grass into water? * Large presses * feed it to milk animals and drink milk * feed it to any animals and drink blood * plant edible, water rich vegetables like (salt toelrant) cucumber. Not that the more water a plant stores, the less yield it will show in a salty environment as plants have to do the work for desalination too! The marshes will be managed inetnesly, they will need to be flushed with lots of excess salty water to remove excess salt. They are also huge: at 1m³/d water means ~1.5 t/d total mass of grass! If we assume 25t/ha a yield (which is unreasonably high, this is grass in modern agriculture (and temperate climate)) every person would need 15ha marshland! At least the working animals won't need extra fodder. This still doesn't look viable to me but is may become viable if ... * you tweak the numbers for water need - maybe find actual usage for desert dwelling people or ancient civs. But make sure to include irrigation & water for animals! * postulate diverse plants that are salt tolerant and have additional uses. Maybe your civ has salt tolerant rice, or can make fibers from salt tolerant cotton or cattails? Cattails also have edible, high starch roots that could double as potatoes? [Answer] They could harvest the juice from some plant, just as we harvest coconut milk and cactus juice. They could drink the milk or blood of some animal that can drink salt water. They could eat the flesh of sea creatures such as mollusks and get moisture that way. Or they could squeeze them in a press if they were plentiful enough. They could do all of these things. In short, they could exploit already-existing biological filters. It would be reasonable to expect that the native flora and fauna had adapted to the conditions and could successfully extract water from the environment. [Answer] What about a large dugout bowl made from the ground just near the edge of a precipice that gravity filters naturally through the soil layers that seeps out the side of the precipice into a collected pool. I was part of a biofiltration project once that prevented toxic asphalt buildup raining off into the vegetation. Our team combated this by layering a series of certain minerals, natural filtration membranes, and arrays of certain toxin-absorbing plants along the natural rain flow channels that fed into the groundwater. The idea behind this being that it filtered heavy metals from the runoff. Perhaps this could be done with salt too, naturally. [Answer] The two most used methods of desalination of ocean water are: \*distillation \*reverse osmosis Either is possible on a large scale where there is a commitment to resources needed. reverse osmosis would likely require support from a fishing industry to provide osmosis membrane materials until research develops suitable replacements. wave pumps established offshore could drastically reduce the pumping energy requirements to make either approach feasible. Parabolic troughs constructed with buoys and supplemented with wave pumps could provide the means for the supply of both energy and unprocessed water. This sort of project might be taken on with little more than a large workforce, determination, and some skill with pottery, ceramics, and glazes. ]

[Question] [ Vampires don't die from old age; They aren't born, and all vampires were humans at some point in their life. After being bitten, a human can turn into a vampire (although the chance is very low, otherwise vampires would run out of food). They're NOT mindless monsters; they have their own personality, memory, and feelings too. It's clear that minds of new vampires aren't "tabula rasa", and they seem to have at the very least some memory and personality of their old selves. This makes it clear that something probably changed in their personality because vampires in general display attitudes that look down on humans (depends on individual vampire, so can vary) such as: 1. "Humans are cattle, vampires are the master race." 2. "It's natural for vampires to attack humans, so there is nothing bad about it." 3. "Humans will die someday anyway, so why bother about their lives?" 4. Radical egoism This is despite them being humans once and still having memory of human life. **How can I explain the radical change in personality when a person has been transformed into a vampire?** [Answer] ### Survivor Bias All vampires who refused their change, and fought against drinking blood, died. Early. As a result, there is a strong survivor bias here: only those vampires who adapted to drink blood are known to society, no matter how small a minority they represent. ### Alternatives to killing It's highly unlikely that a new vampire will immediately kill anyone, especially anyone they *love* or *like*, unless under the effect of a *Frenzy* caused by a lack of control... which would induce guilt and remorse afterwards. Instead, a new vampire is likely to either: * Seek help from loved ones, who could supply blood voluntarily. * Rob blood banks. * "Borrow" blood from involuntary donors, certainly just a sip won't endanger them, right? Those do not involve killing at all. ### Personal Ethics There is a broad swath of choices which do not imply "killing good guys", for a personal definition of "good guys". Remember [Léon: The Professional](https://en.wikiquote.org/wiki/L%C3%A9on:_The_Professional): > > **Mathilda**: Do you "clean" anyone? > > **Léon**: No women, no kids. That's the rules. > > > For Léon, killing women or kids is a firm NO, however he has no compunction killing other men. A racist could justify killing foreigners, a zealot could justify killing non-believers, a would-be-hero could justify killing criminals (The Dark Knight?), ... It's all a matter of personal ethics, really. ### Personality change over time And finally, time. As time wears on, the vampire may very well detach itself from humanity. Their immediate family died a long time ago, their values are antiquated, ... Furthermore, accidents will happen. To preserve their secret, to survive, they may have to violate their personal ethics... a first time, a second time, etc... the guilt will lessen each time, until there is so little guilt left that before they know it they stopped caring much. They still practice their ethics out of habit, but no longer balk at violating their former sacrosanct philosophy. Time, the great eraser, will transform them from super-humans, to monsters. [Answer] The mind and body are less separate than most people seem to think. Changes to body chemistry can *greatly* change how, and even what, we think: * Alcohol is well-known for its disinhibiting effects and also for changing one's perception of what makes an attractive potential partner ("beer goggles"). * I have type 1 diabetes and occasionally become significantly hypoglycemic. At times, this can make it nearly impossible to think about anything other than "Eat! Eat! Eat everything in sight!" as my body tries to raise blood sugar to an acceptable level. * Trans friends have described being fully aware of their taste in potential sexual/romantic partners changing significantly when they started on hormone therapy. * Although I haven't looked into it in any detail, several studies have suggested that changes to gut bacteria can produce significant changes on a person's state of mind. * *"Here we report that, although rats have evolved anti-predator avoidance of areas with signs of cat presence, **T. gondii's manipulation appears to alter the rat's perception of cat predation risk, in some cases turning their innate aversion into an imprudent attraction**. The selectivity of such behavioural changes suggests that **this ubiquitous parasite subtly alters the brain of its intermediate host to enhance predation rate** whilst leaving other behavioural categories and general health intact."* ([Fatal attraction in rats infected with Toxoplasma gondii.](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1690701/), emphasis mine) * Cordyceps fungi compel infected ants to climb to a specific height, clamp on to a leaf stem, and stay there until they die. (Admittedly, this example is a behavior, not necessarily a "thought process" as we normally understand the concept.) Given these phenomena, would it really be that surprising for the biological changes associated with vampiric transformation to alter the subject's perception of "food", "humans", and how those two categories relate to each other? [Answer] Actually I don't think that there is a lot of change of mind involved. Just look at your points: * "Humans are cattle, vampires are the master race." That is something we already do. (Or most of us do) We think that our species is best and that we have the right to use inferior species to our liking. We breed and eat all kind of animals without having a bad conscience. So when you change you species, humans are now a different species than yours, so the same rules apply for humans as for animals. * "It's natural for vampires to attack humans, so there is nothing bad about it." It's natural to eat other species, there is nothing bad about it. * "Humans will die someday anyway, so why bother about their lives?" [Edit: Don't get attached to cattle, you will see it die] Pets have such a limited lifespan. Usually they die way before you. So don't get too attached to your pets. Pretty much the same mindset. [Answer] ## [Rationalization](https://en.wikipedia.org/wiki/Rationalization_(psychology)) > > In psychology and logic, rationalization or rationalisation (also known as making excuses[1]) is a defense mechanism in which controversial behaviors or feelings are justified and explained in a seemingly rational or logical manner to avoid the true explanation, and are made consciously tolerable—or even admirable and superior—by plausible means.[2] It is also an informal fallacy of reasoning.[3] > > > Any vampire that doesn't find a way to rationalize their behavior will die, either by suicide or starvation. No need to come up with strange biological or supernatural explanations - their attitudes are completely normal for human beings in that situation. [Answer] > > Immortality is not living forever, immortality is everyone else dying. - The Doctor > > > It's going to be really hard to maintain your human values when individual humans seem to be such a brief flicker in the passing of time. What does it mean to shorten a human life by a little, they barely exist long enough to register their lives at all. And that's for someone who might have started out fundamentally a good person, people who become vampires aren't necessarily so good in the first place, so it's not so far to fall. [Answer] ## Changes in Brain Chemistry The transformation causes a change in brain-chemistry on a deep level. Empathic feelings which are usually evoked by other humans, are now only evoked by other vampires. This leads to vampires not seeing humans as the same species anymore. They will see other humans like another animal race and will be affected by human suffering no more than by the suffering of a pig. The changes seem to be rooted in the different pheromones, which are produced by vampires. This smell causes vampires to regard other vampires as kin, while humans smell like livestock to them. Other factors are a subtle change in mimics and micro-expressions. A vampire will smile and cry differently than a human. This subtle cues will make a human smile look slightly wrong and "inhuman" to a vampire. Within a short time, the vampire will disassociate with the inhuman figures and cannot help to feel the wrongness in their mimics, gestures, voices and smell. This will lead to traumatic experiences in many vampires suddenly unable to feel connected to their former human peers. These events are not unlike a dissociative episode, which causes severe psychological trauma in the victim. This can lead to highly egoistic and even psychotic behavior. But over time most of the vampires will develop coping mechanisms and seek new bonds within vampire society. [Answer] **Vampires don't die from old age** When a person changes into a vampire, their personality doesn't actually change at all. The only real difference is that they now have a hunger that can only be satisfied by drinking blood. When people think about vampires, we are subject to [suvivorship bias](https://en.wikipedia.org/wiki/Survivorship_bias) - any vampire who refuses to drink blood won't live long, so we only see those that give in to the hunger for blood. Additionally the more bloodthirsty a vampire is, the more people they will go after. Of the vampires that survive, the more ruthless ones are more likely to be encountered. So why do people think that new vampires undergo a massive change in personality? They simply don't understand how someone could go from a normal, average person to the bloodthirsty creature that might hunt people for sport. This leads them to reason that there must be something about the process of becoming a vampire that significantly alters the personality. However, recall what it was like to be a small child. It's rare for children to understand their parents - they say things like "I'll never be old and boring like them". Adults do a better job, but it's still common for them to not understand people who are older than them or those who have lived a significantly different life. What we forget is that vampires don't die from old age. With vampires, we have both of these obstacles to understanding them - not only have they lived far longer than us, they've also lived a significantly different life during that time. The transition from normal person to bloodthirsty monster is gradual, but because vampires do not die from old age most vampires are already old enough to be on the monster side of that transition. [Answer] # Long Term Changes These are the easy ones to explain. Given time, our personalities gradually change. I'm a very different person than I was even 20 years ago, even if many of the key aspects of my personality from back then are still present. Were I to live another 50 years, or 100 years, my personality would doubtless transform further. If my life changed drastically, as becoming a vampire would do, these changes would presumably be accelerated. Not only that, but the parts of my personality that remained constant would have been formed in a society that no longer exists in the same form, and so my personality would diverge not just from the human *I* was, but from the personalities of those humans who were born and raised in these later societies. # Short Term Changes Other answers bring up possible changes in biochemistry, as well as psychological factors such as rationalizations of necessary vampiric behavior, survivorship bias, and the possibility of power corrupting. I would add a variant of that last one: they were already corrupt, but have only recently acquired the power to act on that corruption. > > "Humans are cattle, vampires are the master race." > > > "It's natural for vampires to attack humans, so there is nothing bad about it." > > > "Humans will die someday anyway, so why bother about their lives?" > > > Radical egoism > > > With fairly minor modifications (mainly replacing "vampires" and "humans" with "my group of humans" and "some other group of humans"), none of those ideas are as rare as we might like. What *is* rare is for people to have the power to act on those ideas in a significant way. Many war crimes are simply normal crimes, committed by people who are prevented from doing so during peacetime because the parts of society that would stop them are more powerful than they are. When society no longer holds them in check, their personalities may *appear* to change dramatically, but what has really changed is their power relative to those around them. Vampirism doesn't cause people to become evil. It reveals those who already were. [Answer] They change, but because society makes them. The transition from human to vampire is gradual and horrible. As you crave for blood, people start to notice something is weird about you, and start to push you away. Eventually, they realize what is going own, and you're forced to run away from everything you once called home. As time passes, your human self becomes more and more a memory of the past, destroyed but humans themselves. Some vampires isolate themselves and simply drink blood to survive, while others want vengeance and to bring upon humans what they themselves have suffered. This way, you can explore the spectrum of reactions and experiences the vampires have gone through. [Answer] There is my take on this problem. 1. Natural selection. Vampires who couldn't (or didn't want to) change their attitude toward humans commited suicide or starved to death, while survivors seriously rethought their values and attitudeds. Or found excuses that they themselves try very hard to believe into. 2. During conversion their astral body visits astral plane where they gain spiritual and philosophical insights about life. These insights make them adopt ruthless (toward humans) life philosophy. 3. There was changes in their brain on physical level that turned off their ability to experience affective empathy. They can understand emotions of humans, but they don't feel them. [Answer] **Power Corrupts** Not explicitly stated in the question but by implication of being able to prey on humans and considering them an inferior species it's not unreasonable to think that vampires have a distinct advantage of some kind. New vampires might try to maintain some semblance of their former humanity but gradually come to internalize superiority, perhaps initially they think in terms of leadership or patronage and eventually devolve into disdain as they interact with inferior beings. See the [Stanford Prison Experiment](https://en.wikipedia.org/wiki/Stanford_prison_experiment) for an example. Edit: worth pointing out the experiment has questionable scientific value. There is some indication power correlates with negative traits like [dishonesty](https://www.theatlantic.com/health/archive/2013/07/how-power-corrupts-the-mind/277638/) but of course real life is messy. I'd argue the evidence is sufficient for fiction. [Answer] ## A practical example Think about Lord Elrond in The Lord of the Rings. Pretend like you don't know the story, and I tell you that there is a character who: * Holds grudges over singular mistakes that were made generations ago and actively dismisses the future generations of their ally's plea for help because of it. * Overgeneralizes other races. If one member of the other race makes a mistake, all others are obviously going to do the same. * Prohibits his child from dating someone from another race and living in the conditions of this other race. You wouldn't particularly peg this guy as the good guy, right? What makes Elrond not evil is the fact that he's effectively immortal, which means that Elrond has a **different view** on time-sensitive issues. * Elrond was there when the mistake was made generations ago. To Elrond, that's something that happened in his life. He forgets that humans have had several generations since then and that the descendants of Isildur cannot be blamed for Isildur's mistake. * Elrond did not immediately spring to action when called upon, because he has no sense of urgency. As an immortal being, he wouldn't be particularly bothered about taking 50 years to do something, whereas humans will effectively live their entire lives in that timespan. * Elrond cannot process the idea of fleeting mortality when it affects him. 50 years is the blink of an eye to him. And his daughter has chosen to give up her immortality and will live the rest of her life in the blink of an eye. To a being with a nigh-infinite lifespan, this is the equivalent of Arwen telling Elrond she's going to kill herself in the "near" future. Effectively, Elrond is a parent who will see their child die and thus lashes out emotionally at that prospect (blaming Aragorn for what is Arwen's choice). The point is not to deeply analyze the character of Elrond, but I wanted to show you how a character who is **numb to old age** behaves differently (or with different interest) than a character who does age. --- ## The general approach > > How can I explain the radical change in personality when a person has been transformed into a vampire? > > > In general, a person responds to things that positively/negatively impact them. Often, people do something they don't innately want to do because the benefits outweigh the drawbacks. * A religious person may choose to follow their religion's commandments (even the ones they disagree with) because they want to avoid eternal damnation. * An old man who very quickly breaks his bones will learn to avoid physical activities. Even if he really likes physical activities, he wants to avoid the pain. * A young person can refuse to smoke or partake in unhealthy behavior because they want to elongate their lifespan. But when you take away the punishment, there's no need to still do the thing: * When the religious person finds out there is no eternal damnation (heaven for everyone, or no afterlife for anyone), they may stop complying with commandments they don't agree with. * When the old man get an unbreakable skeleton, he may pick up physical activities again. * When the behavior does not shorten their lifespan, the young person no longer has a reason to avoid the behavior. This can be gradual or immediate, based on the character. A good guy will hold on to their morality, but they may lose sight of it over an extended period of time. A bad guy will almost revel in the opportunity to do the thing they can now freely do. However, you should choose the right response for the right character. Each of your given examples carries a subcontext of the person making this argument: 1. Superiority is a fact we cannot deny and should not avoid. 2. This is how nature works. 3. The long-term goal outweight the short-term goal. 4. No one is more important than me. They are all valid justifications for vampiric behavior, but you can't just give any character any justification (unless you're specifically going for a "you never know what a person is truly like" vibe with your story). Just to oversimplify, you could stereotypically assign these justifications to: 1. A white supremacist 2. A biologist or survival expert 3. A cold and logical person (we come back to Elrond here) 4. A vain politician or celebrity > > This is despite them being humans once and still having memory of human life. > > > I always think back to Sophie. She was a classmate of mine. In class, there were a few advanced students who did not need test revisions (scoring over 90%), but a lot of others did need guidance (scoring under 60%). Because of this, the teacher made a rule that during test revision, those scoring >85% could instead play a board game. Usually, this was the same 5 students. But Sophie was an infrequent addition, she always scored around the 80%-90% mark. * When Sophie scored <85%, she complained that it's unfair for some students to not have to do the same work as her/the rest. She was the one to loudly complain. * When Sophie scored >85% and someone else made that same argument, Sophie responded that *she* clearly didn't need revision and shouldn't be made to do it. Again, Sophie was the only one to take center stage to defend her opinion, the other "passing" students were relatively indifferent to it compared to her. **People's opinion on categories changes when people change categories.** This is normal human behavior, even if an outside observer can plainly see the hypocrisy. Someone who is actively protesting tax cuts for the rich (because they are poor) might, when becoming rich themselves, start arguing that the rich shouldn't need to pay more taxes than other people. Or, a human who advocates enthnically cleansing the world of vampires, may let go of that notion when they themselves become a vampire and possibly start arguing the opposite. This is effectively what Magneto does to Senator Kelly (an anti-mutant political leader) in X-Men: he makes him a mutant, and Kelly changes his rhetoric overnight because he now fears becoming subjected to the system he tried to put in place. [Answer] ## Rejection and Acceptance Although I whole heartily agree with [Dave Sherohman](https://worldbuilding.stackexchange.com/a/139545/8914) that physical changes can have *extreme* impacts on the mind, I want to add an additional source of personality change. When someone becomes a vampire, they will likely be rejected by their community, and then accepted into the vampire community. A change of social circles, along with a change in identity, can *vastly* change someone's behavior. Some examples of this include cults (see Jonestown tragedy), the military (teaches you that you should kill these people), the Nazis (ditto), religions (not necessarily a violent change in this case), or even just migration (migrants often assimilate into the culture they move into, if accepted). If the vampires teach you that killing someone is okay, and you feel a biological urge to eat them, I see no reason you would not eat them. In fact, although a change in brain chemistry definitely can change personality, it is not required. If you make your vampiric narcissism purely a social phenomenon, you could very plausibly have "nice vampires" that were not rejected by their communities, and only feed on cattle. Anywhere in between also works too: for example, maybe some vampires respect humans, but require human blood, resulting in a gentleman's thief type personality. Or maybe their family donates blood to them (in the form of bags so the vampirism does not spread). Or maybe they do not have a physical need for human blood, but a strong psychological urge, that some vampires try to resist. Or maybe human blood is not required at all and is just a vampire society thing, but becoming a jerk automatically happens when you become a vampire either way (for biological reasons that Dave mentioned). [Answer] Since you did not disallow supernatural explanations: In Bram Stokers Dracula, it was implied Vampires where literally damned souls, compelled to walk an unchristian path (Dracula himself was very much at peace with his final death, since his soul was finally set free). That's why vampirism was a curse to. It was kind of like being in Hell, except you were stuck in your corpse, and it didn't matter how you had lived your life. In the same story, vampires aren't very functional as people. Dracula himself was an exception. Every other vampire in the story were mentally much more limited than him, almost as if they had sustained brain damage (or become slaves to a malignant force). Dangerous, but more like how an animal, like a snake or a rabid dog is dangerous. Dracula himself... well in life he was supposed to have been a massive genius with an absolutely brilliant mind. Even then it took him 500 years before he managed to conceive of his grand scheme. That was how long it took him to more or less train his mind back up to something close to what it had been in life. And that was unique as far as vampires went. Every other instance were more or less "Drink blood. Hide from the sun. Repeat." [Answer] Two options come to my mind.: ## Only psychopaths become vampires The psychopaths already have some sort of brain difference that makes them not able to feel empathy. As such they are pretty much predestined to easily adapt to the new role. In fact, they often already believe they are superior to other humans. You can already refer to them as not having feelings (or heart if you prefer more poetic description). ## The blood thirst enforces will of survival This is actually something you may learn from real examples. Consider this [tragedy in Andes](https://en.wikipedia.org/wiki/Uruguayan_Air_Force_Flight_571). Despite moral concerns those who survived turned to eating human flesh. Of course it was about eating the deceased ones, but still in extreme circumstances it might turn you from your normal moral objections. You do not have other food. What do you do then? [Answer] **Change in the philosophical foundations** Our worldview and all of our personal philosophies are based on various foundations, including the fact that we are mortal, and our other biological needs. For example, your perception of mortality might be that you need to leave a mark in the world so that some part of you never dies. But if you're not mortal, your philosophy towards leaving a mark might immediately disappear. You might have reproductive needs that lead you to conclude "I must work on my personality, skills, social value, etc. to improve my chances of reproduction." If your reproductive needs suddenly change, then you might no longer care about these pursuits of self-edification. The vast majority of your actions are governed by fundamental needs, laziness, or need for amusement. If a person's fundamental needs and foundational facts of their existence are suddenly changed, then it has a cascading effect in changing all of their personal philosophies and actions. Immortality would predictably trigger a significant personality change. **Parallels to hunting** I would also conjecture that anyone who hunts / cooks / and eats animals when they aren't forced to would make a good psychological model for a vampire. What life experiences led them to this hobby? Did they tag along with parents for their first hunt? Do head vampires ever take newly converted vampires along for a first hunt, preaching all sorts of philosophy about how killing humans is okay, talking about the sport, and so on (probably only in situations when a head vampire likes the person they converted)? Some fiction writes that vampire victims are only converted when the vampire chooses them to be; whereas the others just die. If you take this approach in your fiction, then this means that there are almost no vampire converts that wouldn't have the direct mentorship of a veteran vampire, and guidance on a first hunt. **Hunger pangs** If vampires don't drink blood, then do they die? If so, then some of them will quickly die, especially if they don't have an instinct to know why they're wasting and dying. Alternatively, it might be the case that no matter how long you go without drinking blood, you never die, the pain just keeps getting worse and worse. If this were the case, then converted vampires would always be forced with the choice between drinking blood, enduring infinite agony, or committing suicide. By the time they reach this extreme crossroads, they might be suffering enough and desperate enough that they would be ready to make extreme moral compromises. Psychologically, this would parallel people who give-in to torture and reveal vital intel, the Tell-Tale Heart short story, people who take unethical jobs out of financial desperation, instances in which depression leads to suicide, instances in which people have turned to cannibalism, and the time that Aron Ralston cut-off his own arm because he was intractably trapped between two boulders. [Answer] # They go somewhat cracked in the head. > > **This thing all things devours: > Birds, beasts, trees, flowers; > Gnaws iron, bites steel; > Grinds hard stones to meal; > Slays king, ruins town, > And beats high mountain down.** > > > In the beginning, all vampires are sane by human standards, respecting regular humans and only eating when absolutely necessary. However, then a few centuries pass. Then a few more. Oh, and did I forget to mention the interminable Sunday afternoons which collectively comprise the "long dark tea-time of the soul"? As the Doctor so eloquently puts it, "Immortality is not living forever, immortality is everyone else dying." After a few centuries not only have they outlived all their friends, they also are unable to gain new ones; people find their outdated customs off-putting. Due to the resulting loneliness, they eventually go somewhat insane. A good example of this is (other than the Doctor, who I already cited) is Bowerick Wowbagger the Infinitely Prolonged, from the Hitchiker's Guide to the Galaxy. Born mortal, he became immortal due to "an unfortunate accident with an irrational particle accelerator, a liquid lunch and a pair of rubber bands." > > "To begin with it was fun; he had a ball, living dangerously, taking risks, cleaning up on long-term investments, and just generally outliving the hell out of everybody." > > > However, then he experienced a couple centuries of Sunday Afternoons. > > "So things began to pall for him. The merry smiles he used to wear at other people's funerals began to fade. He began to despise the Universe in general, and everybody in it in particular." > > > Time erodes at his original [The Wonka](https://tvtropes.org/pmwiki/pmwiki.php/Main/TheWonka) personality, which devolves into a single-minded [Magnificent B-tard](https://tvtropes.org/pmwiki/pmwiki.php/Main/MagnificentBastard) drive to insult everybody in the universe. *In alphabetical order.* [Answer] # People are not rational The rational part of what makes us human is only a small part of the overall experience. Our behavior is controlled by our emotions, which steer us to behave in certain ways. That is, in fact, the *purpose* they serve. Pain and fear exist to protect you, by keeping you out of trouble. # Becoming a vampire warps your mind A game - a very dark and disturbing NSFW horror game, [Song of Saya](https://kotaku.com/saya-no-uta-the-song-of-saya-the-kotaku-review-509012142) - addresses this exact issue. The main character suffers from crippling hallucinations that warp his literal worldview. When he looks at a person, he does not see a person; he sees a Lovecraftian monstrosity. When anyone speaks to him, he hears a warped, Black Speech filter applied over it. This involuntarily fills him with revulsion and disgust towards everyone he meets. Even his own friends. In fairly short order, he can barely stand to be around them anymore. He begins to loathe the thought of seeing or interacting with them. Suffice to say, things do not end well. A nearly irresistible hunger will have similar effects. A vampire looks at a person and sees a three course meal, prepared just the way they like it, by a world famous chef. And they can smell it. Good god, the smell, all around them, constantly, everywhere. It's maddening. And it *never stops*. That's all you need, really. The vampire's personality changes are subtle, but the list of circumstances where it's acceptable to them to feed always grows, and never shrinks, and they're immortal. [Answer] In the [Bible](https://biblehub.com/1_corinthians/13-11.htm) you can read: > > When I was a child, I talked like a child, I thought like a child, I reasoned like a child. When I became a man, I set aside childish ways. > > > Paraphrase it by changing child with human, and man with vampire. > > When I was a human, I talked like a human, I thought like a human, I reasoned like a human. When I became a vampire, I set aside human ways. > > > If you change, also your ways and standards change to match the new status. It's perfectly logical. It's part of the process of change. You don't become a man/woman just because your body changes with puberty, you become such because also your mind changes. Same goes with vampire. Incidentally, the same line of thought is followed by Major Kusanagi in Ghost in the Shell, just applying it to cybernetic bodies, not to vampires. When you grow up/evolve, you change. [Answer] humans eat other humans in desperate situations (los andes's airplane accident for example, there is a movie "survive!" from 1976). if you become a vampire you are not "less moral"or you have a change in your personality, you are still the same but you didnt knew that you would be able to do it, until it happens. you are just another creature that will do what you have to do to survive. ]

[Question] [ The world is going to hell. Global warming, overpopulation, economic crises and other such issues plague humanity. The only logical solution is to summon Hastur, The King in Yellow, an elder god from beyond the void. He will Institute a random genocide across the earth, irrespective of race or creed, killing billions and restoring balance to the planet and making me the savior of the human race. World leaders are more concerned with playing politics than finding real solutions to real world problems, and the liberal fake-news media has ludicrously decried me as " a lunatic with delusions of grandeur", so I have taken the initiative on my own. I have founded a company called C.A.R.C.O.S.S.A which has cornered the market in electronics and computer related equipment. Through nefarious practices, the company has bought out Apple and Microsoft, bringing them under my umbrella corporation. We now have access to billions of loyal customers around the world. The genocide will be completely random and irrespective of race, sex, gender and other such nonsense that the pesky liberals worry about. The Elder god requires worship of its followers in order to weaken the barrier between our realms. I obviously can't tell these people that the purpose of this company was to summon this being, and revealing myself as a cult leader will make people think that I am crazy. What is the best way to get my employees and customers to unknowingly worship a god? [Answer] New EULA for C.A.R.C.O.S.S.A products (previously Microsoft or Apple): > > Apps made available through the App Store are licensed, not sold, to > you. Your license to each App is subject to your prior acceptance of > either this Licensed Application End User License Agreement (“Standard > EULA”), or a custom end user license agreement between you and the > Application Provider (“Custom EULA”), if one is provided. Your license > to any C.A.R.C.O.S.S.A App under this Standard EULA or Custom EULA is > granted by C.A.R.C.O.S.S.A, and your license to any Third Party App > under this Standard EULA or Custom EULA is granted by the Application > Provider of that Third Party App. Any App that is subject to this > Standard EULA is referred to herein as the “Licensed Application.” The > Application Provider or C.A.R.C.O.S.S.A as applicable (“Licensor”) > reserves all rights in and to the Licensed Application not expressly > granted to you under this Standard EULA. > > > a. Scope of License: Licensor grants to you a nontransferable license > to use the Licensed Application on any C.A.R.C.O.S.S.A-branded > products that you own or control and as permitted by the Usage Rules. > The terms of this Standard EULA will govern any content, materials, or > services accessible from or purchased within the Licensed Application > as well as upgrades provided by Licensor that replace or supplement > the original Licensed Application, unless such upgrade is accompanied > by a Custom EULA. > > > b. Consent to Use of Data: You agree that Licensor may collect and use > technical data and related information—including but not limited to > technical information about your device, system and application > software, and peripherals—that is gathered periodically to facilitate > the provision of software updates, product support, and other services > to you (if any) related to the Licensed Application. Your soul now > belongs to Hastur, The King in Yellow. Licensor may use this > information, as long as it is in a form that does not personally > identify you, to improve its products or to provide services or > technologies to you. > > > c. Termination. This Standard EULA is effective until terminated by > you or Licensor. Your rights under this Standard EULA will terminate > automatically if you fail to comply with any of its terms. > > > d. External Services. The Licensed Application may enable access to > Licensor’s and/or third-party services and websites (collectively and > individually, "External Services"). You agree to use the External > Services at your sole risk. Licensor is not responsible for examining > or evaluating the content or accuracy of any third-party External > Services, and shall not be liable for any such third-party External > Services. Data displayed by any Licensed Application or External > Service, including but not limited to financial, medical and location > information, is for general informational purposes only and is not > guaranteed by Licensor or its agents. > > > And thats how you gather a couple billion souls within mere hours. [Answer] There's an app for that. Take advantage of your power over the software industry, specifically the gaming and social-media sectors, and create a trend. Offer meaningless internet points, in-game badges and upgrades and stuff, in exchange for your "character" doing things that advance Hastur's goals. Make it social so it spreads easily. People who run all over the place chasing virtual Pokemons will think nothing of collecting materials to build a virtual temple (or whatever it is your eldritch abomination wants). Use the app to bring your people together and reward them for communal activities -- clicking on the "join prayer session" button is really just the start here. You can influence them to do so much much more and use social pressure to encourage them. In phase two, in-game purchases both fund Hastur's needs in this world and build a stronger investment. People who've actually spent money on the game are more likely to stick with it because of the fallacy of sunk costs. Use that. [Answer] There are a couple of religions, or maybe "religions" in quotation marks, which have become popular as a protests against established religion and the way state and society deal with them: * [Jediism](https://en.wikipedia.org/wiki/Jediism) as a reaction to census questions (by claiming a religion which is apparently nonsense). * The [Flying Spaghetti Monster](https://en.wikipedia.org/wiki/Flying_Spaghetti_Monster) as a reaction to Creationism in schools (by demanding equal time for their creed). In either case, you will find a significant number of people who "go through the motions" of worship. Some might actually believe. So do you have a chance to become the next *meme*? Find a genuine cause. Present your eldritch abomination as a *symbol* for protesting that cause. [Answer] Add it into your tos. A single line, buried deep in a bunch of privacy policies and stuff. Nobody reads them, but by clicking agree they will be worshiping Hastur. And if someone does notice it, what are they going to do? You own the biggest tech companies on earth; is it worth it to not agree after you've already bought the device? [Answer] Hastur should be made into a **logo**. Make a depiction of this being your company logo. Blast it all over TV and the internet. Use it in countless viral memes. Logos are the most widely recognized iconography in the modern world. Pair this logo with an appropriate, brief, slogan, that might be a stylized chant, or acronym. Commission pop artists to make catchy songs about The King in Yellow. [Answer] Create a lag-free, bug-free gaming platform named after the Elder being. Easier said than done, but I guarantee that gamers who are accustomed to their games glitching, crashing and losing their progress everywhere else would be praising its name. They would probably continue praising its name even if they were told the truth. [Answer] The first thing you need to do is define what "worshiping" is. Lets assume for example, that you have a well defined book of **ways to worship Hastur**. If Hastur is gaining his power from these rituals, we should probably assume that the rituals need to be followed very closely or they will have no effect. Let's brainstorm a ritual. Lets assume we can consider a well defined set of dance moves a ritual. Now, take advantage of mass-media to spread your rituals. A great example that @Mixxiphoid pointed out in the comments is Fortnite's dances. These dances have become VERY popular and you can even see Television Show's hosts performing them. How do you make them so popular? You control **social interaction**, by controlling apps used for messaging, ads that are shown etc.. Essentially what you can do is **limit** people's choices for ***trendy*** communication, for example. You could have only emojis that performed these dances, and nothing else. The effects would not be overnight, but they would add up. Another great example of mass-media to propegate a dance is [The Harlem Shake](https://en.wikipedia.org/wiki/Harlem_Shake_(meme)). Millions of people would video themselves performing this dance, and even more would watch the dances being performed, and we should assume that watching and **enjoying** someone else's form of worship can also be interpreted as worship in itself. A great example, is Christians singing along to large christian-rock bands. Now, There are other things as well. Such as **Phrases**. For example, most people in america use "**Jesus Christ**" as an exclimation. `Jesus Christ! That was crazy` In Christianity this is considered a sin, however Hastur could interpret this as praise. This still fits into **controlling social options**, essentially what you should do, is limit peoples options when they communicate electronically, to forms that primarily contain Hastur-praising concepts. Over time you will ingrain these practices into the psychology of men across the globe. [Answer] We need to start from first principles here: * What counts as worship? * How much does each act of worship contribute to breaking down the barrier? * How many kinds of worship must be performed? * Effects of competition? **What counts as worship?** If something as simple as the turn of a prayer wheel counts, all you need to do is stick a prayer to Hastur on everything that spins. Start a company selling a product (fidget spinners, tires, old school hard drives, turntables, disco lights, pottery wheels) and stick the prayer on all of them. Go into turbine maintenance and have your service crew add the prayer to every turbine they service. If you need a full worship service, things get a lot harder. Organized religion is on the wane, so your best bet would be to found some kind of a cult. If short rituals count, consider how they could be baked into things people already do. Maybe stick them into meditation or yoga like health program. Turn them into one of those ridiculous internet challenges or meme (ice bucket challenge, Harlem shake, planking, etc.). **How much does each act of worship contribute to breaking down the barrier?** Examples: prayer wheel (one point), human sacrifice (10 billion points), worship service (100 points), whatever. You just need numbers so you know what to do. Also is there worship decay? Do you need to reach x points within a year? And do older points lose value? This gives you some idea of how much you need to do and how long you have to do it in. **How many kinds of worship must be performed?** Is it enough to just spin the prayer wheel all day long? Or do you have to preach the Gospel of Hastur, spread the yellow sign, sacrifice people/animals/etc, live in a certain way, celebrate certain holidays? The more variety you need, the harder it gets and the more you have to work to integrate worship of Hastur into the culture as a whole rather than sneaking it in on the side. **Effects of competition?** What forces are working against you? Can you make things easier for Hastur if you break down existing religions? Or hamstring cults of different old ones? [Answer] "Your computer requires a security update. Do you authorize this change to your computer?" Clicks "Yes." "In order to verify your authority to approve this change, we will compare your voiceprint with your previously recorded voice samples. Please recite these syllables in your normal speaking voice:" ``` Iä Hastur cf'ayak'vulgtmm, vugtlagln vulgtmm. ``` (This is from August Derleth's "[The Return of Hastur](http://kinginyellow.wikia.com/wiki/The_Return_of_Hastur)", which I can't in good conscience recommend reading. More on the translation of R'lyehian is [here](https://www.yog-sothoth.com/wiki/index.php/R%27lyehian).) Recites nonsense syllables. "Approved. Your update is installing..." I can't help but think that a "What does that *sound like*?!?" button should be floating around -- or that the line should be rendered more nearly phonetically. This can also be used to "augment" any user authentication process. "[recording:] In order to place your call in the correct support queue, please provide a voice sample which we can compare with the one on file. Recite after me..." [Answer] Rather than become a giant corporation you should instead turn to religion. Simply start a new religion that is an extension of another region e.g. Christianity is in part an extension of Judaism and similarly with Islam). Create a series of holidays related to your religion for example Christmas, or Easter and tie them up with pretend dates that fall apart under scrutiny. Now create a bunch of advertisements, catchy jingles and customs that should be performed for during these special days and activities. Soon you will have billions of believers who will spread the faith for you. Imagine if the next jingle bells, or happy birthday was how you expressed your loyalty to an Elder God? Even better create a childrens song, like Twinkle Twinkle Little Star or Incy Wincy Spider or Mary had Little Lamb, sponsor all the schools and provide access to the material for free. Instantly you have millions of child worshipers who have no idea what they are doing and you can push your agenda because your funding all these schools. All they need to do is sing a very small song. [Answer] **Use the internet** Whether it be the latest challenge, or a new meme, the internet seems to be able to get people to obsess over odd things pretty well. You already own the computer companies, try buying out some internet giants. You can manipulate searches so that Hastur appears at the top of anything remotely relevant. Make anything tagged with Hastur move to the top of "what's trending". If people think its popular, many will accept it and it will become popular. [Answer] * Make a personal assistant that requires a short prayer to Hastur to activate. * Virtual reality app which shows a temple to Hastur as its menu. (to access different options, you move your hand in a way that counts as worship to Hastur.) * Release a pop song that includes a prayer to Hastur in it. While people sing it for fun say the prayer * Whenever anything is bought, put in the terms of use something like "by using this product, you forfeit your soul to Hastur." * You're rich. Offer people gift cards if they post videos of them doing a form of worship to Hastur. [Answer] Build a retail store. Think an Apple Store. Of course, you'll offer *most* of your products online, but there will be a few in-store exclusives that can only be bought at said store. Ensure that your shelving has an immense amount of products. No matter how old or irrelevant the item in question is, it receives equal prominence as whatever your new iPhone-equivalent is. Make your filing system as byzantine and complex as possible. You have no separate 'sections' for different types of product, no organization by type, or price, or name. Use something obscure, but still *technically* rational like by the value of every number in its release date added together. Never, under any circumstances, explain this filing system. Finally, and most importantly, build your retail location in the shape of the Yellow Sign. Hopefully, your Pallid Master should see the immense amount of confused and hate-filled souls moving along the outline of His mark, and see it as a fitting tithe. [Answer] Get some maker of jingles to compose an earworm pop song with a summons to Hastur in the chorus. People go around singing "boo boopi doo" and "expialidocious" without questioning it. Why not "iaaa Hastuur, light my fire, burn the world around us"? [Answer] They like it because they're convinced Hastur is going to kill *other* people, not them. Whether you do it explicitly (buy X widgets and receive 500 fhtagn-bucks to spend in the new world order!) or subtlely (I'm going to be the messiah, and a lot of people are going to die. Without clear instructions on how to avoid this fate, they start worshipping out of the notion that intelligent beings don't murder those that are close to them), they see themselves as a righteous force cleansing humanity. Sure, you may have mentioned killing all cheesemongers, and hey, Joe's a cheesemonger, but he's sure you didn't mean him, just the other cheesemongers. [Answer] People worship gods despite absolutely no evidence that prayer working or even evidence of their existence. All your elder god needs to do is something and it would be immediately better than any existing religion and people would flock to it. If your elder god couldn't even be bothered to say "hi", it deserves to be locked out. If your still determined to make it happen despite your god's laziness, you have to use pure charisma to build up your followers. Scientology is a great example of one man with nothing building an entire religion in a very short time. [Answer] # It's all in the marketing ### Phase one, Boy Band. Start with a pop sensation boy band. It doesn't matter if they have any musical talent, so long as they get likes on social media and views on video sites. Their logo is an eldritch symbol, of course. Their concerts are a worship service disguised in perfect costumes and tightly choreographed dance moves. ### Phase two, product placement. The boy band and it's members tap into product placement and branding. Suddenly, people are using a variety of products with their name and logo front and center: breakfast cereals, toothpaste, shampoo and conditioner, energy drinks, clothing lines, jewelry. It's all a fad. But its the MUST-HAVE fad. ### Phase three, the band splits. Everyone gets tired of the band after their second or third album of cookie-cutter music. Once the product purchases begin to fade out, the band splits up. They all start their solo careers to prove they're "real" musicians. During this phase, each of the band's artists adopts a logo that's similar to but different from the original. But more importantly, they branch out into different types of music so they can draw in new fans. ### Phase four, branch out. One of the band members, the most popular one, the bad-boy-image guy, whatever, he decides to found a new social website. Maybe a video service, or a music sharing app, or a social network, or something. Rather than continue making music, he steps out entirely into a new career. One that brings people together. One that puts the eldritch logo on hundreds of thousands of mobile devices around the world. Oh, sure, it's highly derivative content, but that's never stopped anyone before. Maybe another band member starts their own music label. Now dozens of musicians in several genres are all showing the eldritch logo at their concerts and on their album covers, simultaneously! Maybe one starts [making movies](https://en.wikipedia.org/wiki/Rob_Zombie). Now people are watching your logo, not just listening to it. ### Phase five, get the band back together! Once the individual works have reached maximum market saturation, you bring the band back together for a whirlwind tour to coincide with their fresh, new, album. Because they're famous across multiple genres, their fan base has gone up by a factor of 10 or maybe 20 now. Their concerts will be bigger religious events than even the Pope could hope for. [Answer] If you have cornered the computer industry, then you are in a perfect position to turn everyone into Hastur worshipers. The secret lies in the ancient science of [numerology](https://en.wikipedia.org/wiki/Numerology). You see, the universe is sensitive to numbers... Math is the only real language and Hastur, since he is "The Unspeakable One", might be particularly appreciative of worship conducted without speech; a worship composed entirely of numbers. Underneath the text interfaces of every computer is a representative language in which each alphanumeric character is mapped to one or more bytes. There are several different mapping standards, which are (as far as we know) more or less random in their layout. No supernatural though has been applied to choosing which textual character is associated with any given numeric value. That is the aspect of modern computing which you need to change and since you dominate that industry, you are in a perfect position to do that. Announce a new character encoding map and make it the standard in all of your computers and operating systems. Have the mapping be the careful creation of existing hastur worshipers, with every common word in the target human language mapped to a numeric sequence which applies summonsing power upon hastur. Where human knowledge of numerology fails, have the elder gods lend a hand. Make the character encoding map into a diabolical translation tool which turns even the mundane human dialog into powerful summonsing incantations. Now give your creation a catchy name; ASCII for example and use it to build a powerful communication network where people will chat to your god's benefit every hour of every day. Then just wait for the world wide numerical worship accumulates. Until a critical mass of summonsing energy is achieved. Until the threshold opens and the Elder God emerges... ]

[Question] [ My story is set in a small Idaho town called Serpent's Yard, named after the cryptid they believe lives in the lake up in the mountains above the town. The town is built around a river, known as Serpent's Road, that flows out of this lake, which then goes into a waterfall just past the town limits on the other side. An important plot point of the story is that this river has a notoriously strong current that has a penchant for drowning people who fall into it and, crucially, **the bodies are very rarely ever seen again**. I heard this characteristic about other rivers somewhere, but I don't know what aspects of the river might have allowed for that, or if it's even possible for my specific river as I understand it. So I thought I'd check here to see if there are any changes to my setting's geography I need to make in order for this deadly river to be possible. **What needs to be true about my river that makes it difficult to impossible to find the bodies of those who drown in it?** [Answer] **Be very cold.** Cold lakes are said to "rarely give up their dead". The body initially sinks and then the bacterial processes necessary to create the gas that causes the body to float never happens because the water is too cold. Perhaps the river itself is actually something of a deep chasm (essentially a narrow, winding lake), shallow on each side but very deep in the middle. Bodies fall into the chasm, where the water is very cold, and this keeps them down. Could also spice it up and add some deep-water monsters in this chasm. They avoid the surface and normally just eat fish but if a body sinks down, hey, free food. [Answer] Start with what [bodies do when a person drowns and dies](https://slate.com/news-and-politics/2005/09/why-are-bodies-in-the-water-always-facedown.html). Most importantly: > > A cadaver in the water starts to sink as soon as the air in its lungs is replaced with water. Once submerged, the body stays underwater until the bacteria in the gut and chest cavity produce enough gas—methane, hydrogen sulfide, and carbon dioxide—to float it to the surface like a balloon. > > > This is important because the sinking process is where bodies get lost. In lakes where bodies are lost, it's almost always because of underwater debris. Here's [an example](https://weirdnj.com/stories/unexplained-phenomena/round-valley-reservoir-njs-bermuda-triangle/) from Round Valley in NJ > > Over the years, there have been numerous drownings. Storms come up quick and can catch you by surprise. There are still unrecovered bodies in the water. Once in awhile, one will surface, surprisingly, still clothed, as I have seen. When a person drowns in the reservoir, the body will get caught in the underwater trees, brush and structures not leveled when the reservoir was built. Just before I left to a promotion at another park, a victim’s body surfaced after approximately four years. He still had his pants, boots, shirt, ballcap and glasses on! > > > People being lost forever or very nearly, in a body of water is common enough that there are volunteer teams who specifically search for bodies to give loved ones closure. All you really need is a bottom of the river geography that traps the bodies, and you can do that with nearly anything. [Answer] If [I remember correctly](https://www.huffpost.com/entry/yellowstone-hot-springs-death-hot-pot_n_582cf703e4b058ce7aa9258f), not too long ago a man slipped into a thermal pond in Yellowstone. He died because of the high temperature of the water, and before the rescue team was able to reach the place, the body was dissolved by the acidic water. > > Colin Nathaniel Scott, 23, was with his sister, Sable Scott, when he slipped and tumbled into the acidic boiling waters of the Norris Geyser basin on June 7, according to a report released Monday by Yellowstone officials. > > > The brother and sister illegally ventured off the boardwalk near the Pork Chop Geyser when Colin Scott fell in, according to the report. > > > Later that day, rescuers could see portions of Colin Scott’s head with a cross necklace resting on the face and an upper torso in a V-neck shirt, according to the Park Ranger Phil Strehle’s written account. > > > Officials judged Scott to be dead by his severe burns and lack of movement. They were unable to recover the body at the time due to lightning storms and approaching darkness. By the time they returned the next day, the body had dissolved in the boiling waters, according to the report. The only traces were Scott’s wallet and melted flip-flops. > > > Therefore highly acidic waters is one option. The other is that the current is so strong that the bodies are trapped in turbulence underwater and, by hitting the rocks, are slowly chopped to pieces to small to be recognizable. [Answer] Try googling “sinkhole in river”. Depending on the size of the river and the size of the hole, it might go unnoticed. Bodies sink after they drown. They could get washed down the hole to underground caves or an underground river that surfaces somewhere unexpected depending on what your plot requires. [Answer] Trapped at the base of dams or even relatively low waterfalls. It is very hard to perform water rescue for even small dams or water falls, and the bodies are often trapped. This also is risky for natural water. [From dam safety.org](https://damsafety.org/public-safety) > > Many of the most dangerous dams are not the massive concrete structures people often first think of when thinking of dams. Many are low-head dams, also called run-of-the-river dams or "drowning machines". Low-head dams are dams characterized by their low height - usually with a one foot to fifteen foot drop off - that allows water to flow over the top of the dam. Below the surface, the water falling over the dam creates highly aerated, circulating currents that trap people and objects underwater against the face of the dam. These forces are a practically inescapable trap for even the strongest, life jacket clad swimmer or often boats and kayak too. > > > So the circulating currents can keep the bodies trapped long times. Also the tops of waterfalls and dams are slippery... [Answer] The corpse eating part of your river could be a narrow stretch with several underwater caves and features like [the Strid](https://www.snopes.com/fact-check/bolton-strid/) in Yorkshire. > > “Rather than carving a stately way through silt, [The Strid] twists > and turns through flat and overhanging rocks falling over the edge of > a limestone formation,” she said. > > > “Vortices in the flow will trap bodies under the water close to the > bed or the sides, whilst the turbulence will render someone > unconscious very quickly. It’s not a good place to play.” > > > [Source](https://the-yorkshireman.com/the-strid/). [Answer] **Fish** [](https://i.stack.imgur.com/fdfjK.jpg) [source](http://fishindex.blogspot.com/2009/12/goonch-catfish-bagarius-yarrelli-man.html) They are down there. Locals don't fish, but visitors catch some big ones. Visitors hook some bigger things that break the lines. The rumor is that the biggest one only comes up for bodies. The locals call it Angie, because the French missionaries who were the first Europeans in the area called it Anguille; the eel. There are stories about Angie from the Indian times before the French came. Toward the end of the story divers catch sight of Angie. She comes out of a hole in the bottom. But not all the way out. She is not an eel. She is part of something larger. [Answer] You could have a river that nobody *wants* to look in. If there is raw sewage or industrial waste being dumped into the river on a regular basis, nobody will find anything in there, because they don't want to look. Whoever is dumping the harmful waste into the river might not even be breaking the law, depending on the time period and circumstances, but even if it is illegal, it can still happen. [Answer] There are rivers in South America with fish so deadly that pen sized fish actually burrow into the living humans after about one minute and they drown almost immediately. Add to that a feeding frenzy of pirahnas, some crocodiles, and shark-like river fish, all that is left of those that wonder into beyond the safe zone are bones. Also a strange mutant creature might like to drag bodies to the bottom and heap them up under the stones and silt as a kind of hobby. [Answer] There are a couple ways you can approach this in my opinion: are the bodies gone via wildlife or via environment? If it's wildlife - they're eaten by various sized animals. There are places in India where larger fish will eat human remains that have been [put into the rivers](https://www.youtube.com/watch?v=F2Zh3JzfyJU). You also have territorial animals such as hippos that will attack things that threaten their space. From an environmental standpoint, there can be shifts of currents, underwater currents and whirlpools that will pull folks in without warning. This can, and has happened in various rivers in America (check out the Red River for example). Bodies will get sent way downstream, or get caught on underwater rocks / debris and not come up for months at a time. Other than these two, for world building purposes of course, the bodies disappearing could also be a cover up for a much bigger plot. How convenient would it be to have a river that is notorious for removing bodies, when there is someone (or something) that is actually the one doing the removing? Hope this helps! [Answer] **Strong currents** Bodies rise because of the gas build up in the body. However if the body has been smashed into small bits then you cant get a gas build up. So there are strong underwater currents, and lots of rocks that break up a human body into smaller pieces. Possibly there could also be lots of metal waste dumped in the river as well, things like steel pipes, sharp bits of metal etc. These act as additional sources of piercing damage to prevent pockets of gas from forming. [Answer] You could make it so that a specific type of bacteria lives in the lake that 1. prevents anyone from swimming in it and 2. Rapidly consumes and reproduces on the nutrients found in dead bodies. there could also be a a mountain range or higher elevation surrounding it in a humid environment so a permanent layer of fog appears, causing any bodies that do rise to the surface to become hidden by a thick layer of toxic vapor. ]

[Question] [ I've just started out with worldbuilding and got this idea of a state/country that has no need for any armed forces as they don't want to go to war because of religious reasons, and no other state would want to attack them. But during what circumstances could such a state exist? I'm guessing that the state shouldn't have or produce any unique or better resources that no other state already has. But then I'm posed with the problem as to why people should want to stay within this state and not move to another. Geographical accessibility perhaps? I've read that there are countries like Iceland and Andorra without their own military forces, but receiving protection from other countries. That's not what I'm looking to create. I want to create a state without any military defense at all, simply because there is no need for it. The state should neither participate in any military alliance. The state isn't going to be a large one. In relative measures based on europe I'd say the area would be something like Switzerland and the population a bit less than Norway. There is some magic within this world, but none so great that it could protect an entire city from a military attack for example. The same for religion and gods. [Answer] > > they don't want to go to war because of religious reasons > > > I think this is where your answer might lie. This is a country that, if attacked, **cannot and will not fight back**, because their religion forbids it. Attacking them would be the military equivalent of drop-kicking a puppy off a cliff. Yes, you will win easily, and nobody will intervene to stop you. **But every other country in the world is going to treat you like a pariah for it.** There will be international condemnation. Possibly even sanctions. There will *definitely* be protests, from silent marches of solidarity to people burning your country's flag in the streets. You will forever be known, metaphorically-speaking, as "the country that drop-kicked a puppy off a cliff". And so, no sane country would ever, *ever* attack your state-without-a-military, because the damage it would cause to their international reputation is simply not worth it. As for why nobody would intervene in this scenario, I can only think that this would be at the country's own request. A war being fought in their territory on their behalf, is still a war being fought in their territory, and that's still against their religion. [Answer] ## It's a leper colony The pacifistic country is in fact a leper colony where all the ill from the surrounding countries are sent. The land is not worth much and nobody wants to be close to the ill - so no one wants to conquer it. The country is run by monks and/or nuns, who care about the ill, but will never do something like fighting or even defending themselves, let alone doing military service. [Answer] Science fiction author Isaac Asimov wrote an entire series, *Foundation*, on a very similar premise - that a small state with no military strength must find other means to survive against more powerful kingdoms. These ideas come from that series. **The state must have something unique and of great value.** If not natural resources, then perhaps a source or a form of magic unheard of in the rest of the world. The magic/technology doesn't need to overly powerful, nor militaristic, but it should be incredibly useful: * A source of cheap/free energy * Medicine capable of curing the worst diseases and healing the most deadly wounds * Transmutation of common materials into valuable ones (could impact the economy as well) **The asset must be marketable, but not easily replicable.** Perhaps the magic can only be used by highly trained individuals - and only those few individuals trusted by the state can administer it. Perhaps the religion itself can be used to spread influence. Missionaries and prophets can spread the "good news" of their religion, demonstrating "impossible" magical feats only made possible through the "divine power" of the "holy land". Naturally, other states will want this power as well. **Religion, trade, and politics will prevent attacks** Through religious pressure, trade of magical secrets, and careful diplomacy, the state could ward off attacks. * The state could threaten to cut off access to its magical asset if attacked. * The state could claim that its unique knowledge and secrets would be lost forever if attacked. * The state could threaten to align itself with the enemies of its attackers, bolstering *their* military power to the state's advantage. [Answer] 1. Army implies central authority which is interested in organized offense / defense. A country with no central authority capable of assembling, supplying and deploying and army will not have an army. This country has no central authority because it is sparsely populated with nomadic herders and family groups who interact with each other and outsiders via ad hoc and temporary mechanisms. There is not a central government because there is no need and no use. Perhaps there is periodically a [Jirga](https://en.wikipedia.org/wiki/Jirga) where tribal representatives assemble and discuss matters of common interest. If needed, a meeting like this could conclude with the assembly of an army if the participants concluded that would be necessary. 2. Why do the people stay there? Because that is where they are from, and they like it. The things they need are there. They can continue with their way of life. They are not hankering after something which exists in some other country. No central government bosses them around or taxes them. 3. Why does some country with an army not conquer the country? Because the things this country and its people have are not things other countries want - certainly not to the point of fighting for them. The country in question is big. Its people can be fierce when provoked. Trade routes that pass through are controlled and defended by persons interested in maintaining them. Mineral resources are mined and defended by persons interested in those operations. The sparse population of natives are content to continue their own way of life. Consider also that historically, countries did not have armies except when needed. Armies are expensive and dangerous. The founding fathers of the US feared a standing army and this was a big debate at the time. Back up 500 years or more and I think you would find armies were put together by various states on an as needed basis. [Answer] **Have another kind of power** If they are very rich the threat of trade disruptions might be enough to limit the belligerence of neighbors. **Be regionally important** If the religion has a diaspora with non-trivial power in the surrounding countries rulers might not be willing to alienate them. If they are between several mutually hostile powers but in such a strategically bad place that any attempt to fortify would be a disaster it may be the powerful nations know better than to try. **Reserve readiness** If they have the means to create a military overnight they may not need a dedicated permanent force. Like historical English archery or US militias or Eastern mass martial arts practice. "Our form of meditation happens to include techniques for punching kidneys out through the spine." Being very rich could also apply to paying mercenaries at need. **Be one step ahead** With an outstandingly good espionage organization they might not need to kill more than one person at a time. See to it that no leaders intent on bothering the country ever gather enough follower to be a problem. [Answer] Take a look at Costa Rica. Their former president got rid of the military in 1948, though they do still have border patrol and a police force, which aren't quite defensive forces. So not only can a state without a military defense exist, it actually does. link: <https://en.wikipedia.org/wiki/Public_Forces_of_Costa_Rica> [Answer] One possibility is that the country is, e.g., sacred for religious reasons, and attacking it is anathema. Which means that if CountryA attacks, all treaties and commercial liaisons are rendered void, any debts owned to CountryA by anyone can go unpaid, any properties of CountryA's citizens are forfeit everywhere, and attacking, looting and conquering CountryA (a much more juicy target than the 'helpless country') is not only legitimate, but grants you Heaven. Attempting to conquer the Holy Country would be a national suicide unless CountryA is prepared to take on the whole world, or at least the neighbouring nations. You can compare it with the way Aloria defended the Isle of the Winds in Eddings' *Malloreon*: > > it was stopped by a succinct note from the Cherek ambassador to Tol Honeth. > > > *Your Majesty:* > > > *Know that Aloria will permit no attack upon Riva.* > > > *The fleets of Cherek, whose masts rise as thick as the trees of the forest, will fall upon your flotilla, and the legions of Tolnedra will feed the fish from the hook of Arendia to the farthest reaches of the Sea of the Winds.* > > > *The battalions of Drasnia will march south, crushing all in their paths and lay siege to your cities.* > > > *The horsemen of Algaria shall sweep across the mountains and shall lay waste you empire from end to end with fire and sword.* > > > *Know that in the day you attack Riva, will the Alorns make war upon you, and you shall surely perish, and your Empire will be no more.* > > > A different possibility is that the "undefended" country, during the centuries, grew to be arbiter and **banker** of most other nations. Attacking it would guarantee instant economic chaos, and would mean utter ruin for the attacker. Finally (I remember some short novel to that effect), there might be biological reasons. The country's people might have slowly mutated during the centuries, and are now immune to a disease that can be carried by flies and mosquitoes. Ordinarily this is no great threat because the mountains around the country prevent any outbreak, and commerce employs quarantine protocols that allow the goods to flow. But no sane army would ever think of invading the country, especially in some way that leaves unburied corpses around. (Something vaguely similar happens in Bob Shaw's *Wooden Spaceships* series, where the people abandoned on one of two twin planets and believed to have succumbed to the ptertha infection actually survived and became immune - and are now highly contagious, to the point that *talking* to one means death within minutes for a non-immune). [Answer] Your country could be surrounded entirely by another country's territory, as Vatican City is completely surrounded by Italy. Then you basically only have to explain why *one* country wouldn't invade. Possible explanations are that the interior country is a seat of the surrounding country's religion (as in the Vatican/Italy example), or that the surrounding country is generally peaceable, or that the interior country's independence provides a benefit to the surrounding country, such as a tax haven, or a place where gambling is legal (like Indian nations within the USA). If this is to last for centuries or millennia, your country would require a strong sense of its own identity, to avoid being absorbed into the culture of the surrounding nations. Perhaps its sense of identity is so strong that even if it is conquered, its people never really assimilate, and it re-establishes its independence in later eras when the surrounding country is more peaceable. [Answer] [Iceland](https://en.wikipedia.org/wiki/Military_of_Iceland) has only very limited armed forces, which is most probably due to geographical accessiblity. Only during WW 2 and the Cold War the geographical location of Iceland made it important for the Allies. [Answer] You mentioned early in your post a point nobody seems to be covering: geography. Looking through world history, you don't ever have a society that isn't violent, but you do have societies that don't get easily conquered. Ancient Egypt was surrounded by vast swaths of desert, and the only time "invasion" was ever successful was during great political instability. Russia, with its extreme winters, hasn't been successful conquered since 1480. Many of the islands of the South Pacific (Easter Island and Pitcairn for example) are so inaccessible they either hadn't had any inhabitants for hundreds of years, or hadn't had any inhabitants period. What you really need to make a demilitarized people is isolation. If you're not crazy about the idea of an remote island, consider a small cropping of mountains surrounding the peaceful valley, the only oasis in a thousand miles of sand, or in a temperate microclimate in an otherwise polar desert. If you're feeling particularly sci-fi/fantasy, make it a nation that developed underground or in a cave system. Next, you'll want there to be strong defenses. After all, just because they can't kill or attack doesn't mean they can't build walls and gates. Build gates into mountain passes, giant walls, a dome if it's sci-fi enough. There's plenty on non-violent protections you can use. Finally, you'll probably want to scale back the size of your country... or at least what's inhabited. Military and police force didn't use to be differentiated. If a nation has absolutely no military for its entire history, that means the people need to be culturally homogeneous so as not to cause uprisings. Most of the nations today are actually conquered tribes that have, over time, been amalgamated into one country, and the failure to suppress them leads to ruins. That was why the Aztec empire fell to the Spanish, the Roman to the Germanics, why the Mongolians couldn't conquer Japan, why Pakistan is the current mess it is. Even today, countries are too large and too different to keep people with different cultures pleased. There's separatist movements all over. Just in Europe, there's over 100 separatist, succession, and autonomy movements. *That's more than double the actual number of nations in Europe.* Artsakh, Abkhazia, South Ossetia, Transnistria, Kosovo, and Crimea are all technically broken away... and three of those are in the Caucus states, an area smaller than Spain. South Ossetia is only 1500 square miles. Rhode Island is 1200. To have a culture that doesn't suppress one group over another (and, thus, require a military), you need to have a very small area and a small population so that ethnic homogeneity can take over and people treats everyone the same. The same idea of isolationism should come into play here, too. Multiculturalism is great for adding to society's knowledge, but friction between traditions, religions, and immigrant/native classes cause violence. You can see this in England's immigrant population, in Iran 1999, the Tamil/Sri Lankan civil war. I would imagine that this nation would have entirely closed borders to immigration, or at least a very highly selective process. [Answer] If its religion is THE world religion by a large margin or the only one that is possible. Every other country's population would worship the "holy see" or "land"; thus leaders and believers would refrain from entering with "impure intentions" out of respect or even religious / societal fear, especially if it were a taboo ("forbidden city" or "land"). A minority religion probably wouldn't have such strong "defenses" and would need other avenues (see previous answers for examples). [Answer] There are real examples of countries without military forces, apart from the states already mentioned. The Vatican has no military *as they don't want to go to war because of religious reasons*. [Answer] How about Germany and Japan after WW2? No military because they had just lost. They were under control of other states. To this day Japan has never had political will to go to war. Germany did take part in NATO... But not for some years and not until the Russian forces had to leave. [Answer] You ask very broadly > > during what circumstances could such a state exist ? > > > As opposed to other answers, I will not try to elaborate conditions on this particular pacifist state, but rather on the rest of the world. My reasoning start by observing that we live in a world where conquering for its own sake considered good (past conquerors are even frequently still admired). For example when the Romans invaded Gaul, it is arguable that they did not need to conquer it for any reason except the glory of Caesar (Gaul had ressources to offer, but they could be obtained by trading, conquest was not necessary). Conquest was the reason for conquest. In the world you build, this conqueror's mindset is not an obligation. If the population of your world does not have it, launching an invasion require a solid reason, as opposed to needing one *not* to invade. But this raises another question: how to avoid this mindset to appear ? After all the winners write history, and the winners did probably fight in the first place. So here are two possible explanations: # 1. Social norms are radically different to what we are experiencing In western culture personal wealth is seen as desirable and generally implies high social status. However social norms in other culture may differ, for example in traditional Native Americans culture. There high social status is determined by how useful one is to the community. In this context assembling an army to conquer its neighbors may be seen as costing more to the community than it could potentially gives and people may simple refuse to join such project. And to what I know there were no "Native American Kingdoms" or anything of that sort in North America before the European colonisation (raiding on the other side was a thing, probably that the cost/benefit of it was considered better). # 2. Imperial projects resulted in historical trauma If we look back at the history of mankind it looks like (at first glance) that the empire had great achievements, lasting for decades or even century, sometimes bringing stability, fostering the development of art and culture and so on. Look at the Roman Empire, Ancient Egypt, Chinese Empire and other, look great isn't it ? (This may help explain why the figure of conqueror is held in high esteem.) However, we can imagine a world were all attempts to build empires catastrophically failed and only brought disasters to both conquerors and conquered, resulting in a massive trauma. Due to it, everybody may be rather skeptical about the idea of "trying again". --- Note that these examples do not preclude the appearance of states, they may simply be based on either cooperation or soft power rather than on pure military domination. [Answer] **The geopolitical situation values their independence more than their resources** Consider a country between two other larger countries that dislike each other. If one were to invade, the other would be forced to take action, resulting in a costly (for both sides) all out war. A fictional example would be Djelibeybi, in the Terry Pratchett novel 'Pyramids' (Although it is not stated they have no military, certainly either neighbour could crush them easily) Or consider a cold-war era where USA was on the same continent as the USSR. Any state buffering the two would be valued more for being a buffer and preventing war, than for any (relatively minor) territorial gains for the two giant nations surrounding. [Answer] Being a former member of the Air Staff, I have LOTS of ideas. First, would be to make killing "Not an option" either morally or physically. Perhaps body shape? How would two pure energy beings kill each other? Second, other things are more important. Such as a geologically unstable world where rescue is more important than conquest. Third, memory. As the Organians (SP?) in Star Trek forbid the Federation and Klingons to war, another society could simply not let it happen. Eventually, the memory of HOW to fight would go away and there would be no need to exercise such control. Just some ideas... [Answer] Just to add to other great answers: ## A country strategic position is minimum to none If there are no natural resources, location isn't of much help to anyone and the country isn't too large nor too wealthy the benefits of attacking such country do not outweigh the cost of loosing your position internationally so there are high chances that no-one will attack. ## Natural defense exists (can be artificially strengthened) There might be a ring of mountains, rivers, jungle, desert etc that make the country hardly accessible. The cost of attacking such country can be high compared to the benefits of conquering it. The defenses can be enhanced artificially, e.g. there might be some defensive walls in the mountain area that could be otherwise accessed or there is a dam creating an artificial lake to increase the river defensive capabilities. Note, that destroying a dam can be used as a last defense line and does not require military service to use it (this is used twice by Tolkien in Lord of the Rings). ## Passive defense systems It is an extension of the previous point. It is not operated by military but by civilian engineers. It might not be a solution to kill but to scare off and eventually make it more difficult to get to that country. Think of a Chinese Great Wall as a real world example. ## Strong allies A country can have ally treaties with other countries. They can offer some services (religious?) in return for not contributing to the military power of the ally. ## God(s) can counterattack/curse any attacker It does not prevent a possibility to attack the country but it can scare off any potential attacker. Would you nuke an enemy if you know they will nuke you back? If it's god's intervention then the rules of the religion are not broken. [Answer] A country like that would probably be a paradise for organized crime. Suppressing big cartels and gangs while strictly avoiding killing seems just not possible unless you got ideal preconditions. As such, it wouldn't be surprising at all if the state would be more or less controlled by these cartels. How strictly the control they impede upon the country is, is up to you (be it from the shadows, or by blatantly placing themselves as head of the country). Therefore, as long as the cartels are powerful enough and play their cards well, other countries probably wouldn't meddle. Of cause, this situation is a cluster of problems: If the cartels grow overconfident, they might inspire an alliance and an invasion of the country Or if the cartels diminish in power (e.g. due to losses due to infighting), the country would be left in a vulnerable position as well. Not to forget the dichotomy of the appearance of the country (peace loving, friendly inhabitants) and it's shadow-workings, which adds a lot of interesting dynamic. [Answer] Willk is going down the right road I think. Because to have a military (or conduct warfare) you must be sentient. Animals do attack other animals, but do not conduct organized warfare, which is a prerequisite for the creation of a military in the first place. In our case that originates when there is competition for a resource. Central authorities and the need for "something to protect what we have" comes from a civilization attempting to protect something or someone unable to fight such as children, rice fields, elderly, warehouses, etc. Military organizations are unique to one species on one planet. This species has a lousy track record for accepting the "not us" group. If you can make a thing or person that can't fight unable to be harmed (perhaps temporarily incorporeal) nothing could be harmed so no military is necessary. Or you can remove the idea of an enemy with hive mentality that eliminates any concept of enemies or competition there would also not be a need for a military. [Answer] They don't want to go to war for religious reasons, but are they allowed to *defend themselves if attacked*? Consider Switzerland. (I'm probably going to be saying that a lot....) They do not engage in offensive warfare, but pretty much the *entire* adult population is trained in defense, and they have extensive fortifications. As the legend goes, if a invading force shows up that outnumbers the Swiss 2-to-1, the Swiss will "shoot twice and go home". This does not require a formal military. But if that sort of pseudo-military is also off the table.... > > I'm guessing that the state shouldn't have or produce any unique or better resources that no other state already has. > > > That may not be the best guess. If they really have no violent offensive capability at all, you probably want to look at making attacking them a case of mutually assured destruction for whoever does the attacking. That means giving this state *something* that is sufficiently valuable that no other state could afford to permit a third party from gaining control over it. Maybe the pacifist state is, in fact, the sole or primary source of an extremely valuable natural resource; everyone's cool with letting them sit on it, precisely because they are known pacifists, and if anyone else got control of it, they'd take a dominating position in the region. Or maybe the pacifist state (like Switzerland!) occupies a strategically valuable and highly defensible geographic position; again, if anyone else got control of it, other states would be screwed, so they'll fight to keep that from happening. Or maybe (like Switzerland!), the pacifist state is economically powerful, providing secure and impartial banking services, or housing important trading routes / trading centers, etc. Or perhaps (unlike Switzerland!), the pacifist country is not merely religious itself, but represents a "Holy Land" for all of the surrounding countries as well, such that, while other countries are perfectly willing to go to war in general, all of them (or at least enough of them to deter the remainder) are religiously prohibited from fighting *in that land*, just as the pacifist state itself is forbidden from fighting. [Answer] I'm going to get into some Shepard Book level of thinking. The Bible has a few words about not killing. Quite Specific... It is, however, a might bit fuzzier on the subject of selling the weapons? Or to put it a better way, you rob banks because that's where the money is. But you don't rob guns stores cause that's where the guns are. Every army that is going to march will need two things. The first and most obvious is weapons. Guns. Ammo. Swords. Things that make other things stop being other things. Now, say your sandwiched between the evil empire and the good empire. And the evil Empire is marching for war with the good empire and you're in the way. If you're the guy who is supplying the evil empire with their weapons, they would not dare go through you... that would not only cut them off from your weapons, but also cause the good empire to come to your own aide, because of the kicking the puppy dog aspect. But, you say, what if the good empire decides you need to be stopped from arming the evil empire... well, if you're arming the good empire as well, they won't have a problem with you because stopping you from selling to both sides cuts them out of their own weapons and gives the edge to the evil empire. This need not be weapons. Intelligence (your priests are very good at infiltration) or resources (an army marches on its stomach) could be so good and so neutral that either side attacking you would invoke defense from their enemies, who are also getting the same benefits. This is how both the U.S. and Switzerland managed to be neutral for much of their history (The U.S. until the cold war had basically stopped caring about old war politics and said they wouldn't get involved so long as the Europeans kept their wars over there). The U.S. has historically enforced neutrality by being oceans away and has never been successfully invaded and occupied. In modern times, they are also the largest exporter of military hardware and give their stuff to some rather nasty places because now they are dependent on our spare parts and if that's not enough to keep them in line, the U.S. has all the receipts. It's nice to know how many of your fighter jets the enemy owns. The Swiss is notoriously surrounded by mountains, making invasions difficult due to the historical need to march. In addition they have carved a niche in both their neutrality making them a great place for hostiles to meet and negotiate safely AND liberal banking laws that have a good deal of accounts from all over the world. You cannot go to war with a bank when they hold your money. Additionally, although you discounted that option, both nations have a fairly liberal and permissive gun culture. The Swiss Militia drafts all males who are in service from age 18-30 at least and are allowed to take their service weapons home and must keep them in working order and at the ready for recall to active duty. The United States is far and away the biggest owner of firearms, with private gun ownership in the States representing just under half of all guns owned world wide! There are 105,000 private guns per 100,000 people in the United States, and many gun owners keep their arms ready for rebellion against their own government, so they have no qualms shooting an invasion force. Both of these attitudes were feared by belligerents. A common joke among the Germans was of a Nazi General meeting a Swiss general and asked him what would happen if I invaded Switzerland with a million men? "Then, I would call all of the Swiss Militia and order them to shoot every single one of your troops." replies the Swiss General. "And what if I bring two million men?" asks the Nazi. "Then I will order them to shoot twice," responds the Swiss. In Japan, Admiral Yamamoto was quite vocal in his opposition to war with the United States and once described an invasion as impossible because the Americans would not sign terms unless he took the White House and "there is a gun behind every blade of grass." [Answer] Make their religion one that is only practiced there. That will motivate most people to stay there. Make absolute pacifism a core tenet. Make another core tenet that submission to anyone not of that religion a mortal sin. If someone invades, everyone just starts killing themselves and burning their stuff to save their own souls. Then probably make them isolated by geography. Anyone who wanted to invade would be faced with an distant land where all you would get would be scorched earth with no one to work it. Plus, probably pretty demoralizing for your soldiers. [Answer] No natural resources, The only value of this land is the people, who will not work for a foreign oppressor. What little farm land and mines there are, are difficult to mine for the skilled natives but near impossible for outsiders. The location of the treasury is a well kept secret which will be lost if they kill king. [Answer] **University State** The country could have a high concentration of the most prestigious universities in the world. They offer free, high quality education to the children of political, religious, and economic leaders from around the world. (But everyone else has to pay) Giving free education to the children of world leaders offers them two advantages; prestige and security. The security comes in a soft form and a hard form. The soft security comes from the emotional connection leaders have with the country from their time as students there. The hard form is that the children of the world leaders could go from free beneficiaries of the system to hostages at the drop of a hat. To strengthen this hold, the nation has very strict laws controlling weapons - for the "safety and security" of it's citizens, and guests within the country. They also do not allow any students to have their own security, but supply VIP students with neutral bodyguards. So long as the weapons control in the nation is good, these need not be heavily armed, but could carry "ceremonial" weapons (ceremonial weapons can still be deadly!). Why do nations send their children to be voluntary hostages of this state? * The quality of education really is beyond compare (they can after all afford to attract and retain the best academics from around the world by offering great salaries, and great status). * The nation really is politically neutral; they would never dream of harming the students (unless first attacked). * The nation is effective at keeping students safe; combining effective control of weapons, and high levels of surveillance. This need not be a Utopian vision. The people of the nation might not have political freedom, and the lives of workers and poorer students could be very different from the experience of the rich celebrities and the glossy brochures. [Answer] Even though an answer has been accepted, no one mentioned an interesting one: * Evolution / Eugenics The country itself may not be terribly valuable, but the people *are*. These people, isolated from other societies, have been lucky enough to strike on certain genes that allow them to be absolute savants in a particular area (such as technology.) Attacking them means killing off the smarts that are probably currently developing your nation for you. Annexing them means possibly turning them hostile (and the last thing you want is a bunch of p.o.'d smarties you just assimilated that are capable of controlling your economy/technological/etc future.) So, due to the mutual [x] benefits you gain by their mere existence as savants and the fact that the people are worth far more than the land, it only makes sense to let them do their thing and reap the benefits. [Answer] You made a mistake in your assumptions, and that is blocking you from the simple answer. When considering that the area has nothing of interest to anyone that would cause others to invade, you ask "why people should want to stay within this state and not move to another" and essentially dismiss that idea. ## People living in that area is more common than you think In fact I know some of them personally. People leave areas that have lots of resources and move to areas with less all the time, and there are various reasons. Usually the reasons involve people who dislike the current social construct: they dislike or disagree with the religion, or dislike the oppression, or hate the "rat-race" (that's a common modern one), or they just don't like the big city. Often these people leave civilization in small groups, or even alone. I just read an article yesterday about a Japanese man who hated the rat-race so he just abandoned the Japanese mainland and went to a small island in the Pacific where he lived for more than 30 years. Others have done the same in the past. ## But you want a nation, not just a hermit or a few families... You need more people so you can call it a country. Well, some entire families leave civilization and move out into the middle of nowhere to get away from it all; it's actually fairly common. Sometimes groups of families do this, and sometimes groups of people come together to be "independent together," especially if they share ideals. All you need is for *lots* of groups of families to leave an area, and there are 101 reasons they could be leaving, and if there is a controversial political thing going on that generation then they might all be leaving for the same reason (ie: unified ideals). These groups of people could be 10 to 100 each and could coalesce into a larger unified group out in the boonies, so now you have 1000s of people out there with a unified cause. Fast forward a few generations, assuming a reasonable growth rate and that some people leave to go back to "normal" society, and now you could have your small nation of tens of thousands of individuals all having a like-minded reason for being in a less pleasant area. Now if only we knew what that "like-minded reason" was... oh wait, what if they had a pacifist religion that insisted on zero violence of any kind? That might work. Oh yeah, that's what you said you wanted. ;) ## Bio Because of how these people came to be, they are likely to enjoy their privacy, peace, and quiet. They are likely to avoid dense cities, so their nation might not have any. These people are likely spread out in a way that means there are no actual cities to conquer - yet another reason there is no point in invading them. These people are likely to mostly fend for themselves. They probably do a bit of bartering, but they likely grow a lot of their own food with very primitive methods. They might not be very well nourished, and if they have no large, strong, strapping young lads, combined with their independent spirit, they may make awful slaves, so nobody bothers to abduct them despite them being an easy target. At least not usually. Perhaps they do get attacked sometimes. Maybe some of them are killed from time to time, and maybe a few slaves are taken from among them occasionally. Aside from being easy targets, there is not really any other reason to attack them, so these attacks or slave abductions aren't stopped (because pacifist) and would be an infrequent thing that these people hate. This would not ruin the country because of its infrequency. Now there is a lot of flavor to go with it. ]

[Question] [ I am thinking about having multiple races in my story but I also want them to have relationship (Love/Mating). For the moment lets go with generic types, Humans, Elfs, Dwarfs and Orcs. How could these species remain as they are without them mixing to the point where they are just one species? FYI - Each species can mate with each other and have their own offspring with little to no trouble *Just to let people know who read this, all of the answers in this post could have been accepted however the one that was accepted was just a better fit to the question. I recommend you read them all as each person gives a great answer* [Answer] Some quick thoughts for you: * **Social Taboo**: yes, they *could* mate with each other, but that's not socially acceptable. If this taboo is strong enough, it'll result in species differentiation. (Um, I mean "maintain a pure breed..."). I think (American) society is [much more accepting than it used to be](https://en.wikipedia.org/wiki/Interracial_marriage_in_the_United_States) for this sort of thing. Courting between races may be illegal in some societies. Maybe some of these societies even hunt or kill mix-race individuals! * **The Mating Ritual**: There are some birds whose [courtship displays](https://en.wikipedia.org/wiki/Courtship_display) are the reasons they do not interbreed, though they theoretically could. Orcs males could, for instance, try to impress females by smelling like a rotten elk corpse while wrestling a bear. Even though it sounds like fun, it may only do the trick for the orc ladies, but not the other ladies. (To change the race we're picking on: an elf courtships display may involve some very long-winded poem, which the humans find initially very interesting, but then boring due to it's length.) * **Ideals of Beauty**: it could be that these races simply [don't think the other ones are pretty](https://www.youtube.com/watch?v=Xrp0zJZu0a4). Their genetics/society paint the picture of an attractive female as one of their own race, so interbreeding doesn't happen simply because the other races are *not attractive.* Maybe elves just find all other races too... meaty. Dwarves may generally think the other races are too tall and anorexic. Or green. Obviously, these ideals can quickly change, so it's not a sure-fire way to prevent interbreeding. * **Lifestyle Issues**: Would you marry and have children with someone who is guaranteed to live only half your life? Such is the issue with long-lived elves. You could marry a dwarf/human/orc, but have fun raising your kids *and* taking care of an elderly spouse while in your prime. Oh, Sir Dwarf wants to marry a human? They need more oxygen than you, and have no appreciation for gems or masonry. [They can't even see in the dark](http://www.d20pfsrd.com/races/core-races/dwarf#TOC-Senses-Racial-Traits)! If these races have unique, and very appreciable adaptations to certain tasks, marrying outside the race can severely impact the "quality-of-life" for the spouses. (Consider [milk drinking](https://www.youtube.com/watch?v=ecZbhf96W9k) in real-life humans for a much milder analog.) * *From Martin Carney:* **Isolation/Geography:** This one is straight from the causes of [speciation checklist](https://en.wikipedia.org/wiki/Speciation), but these groups can maintain their breed simply be having geographic barriers which prevent the flow of individuals. Something like the European Alps, the Atlantic ocean, or the Sahara Desert would do quite nicely for tool-using, adventurous, and occasionally promiscuous hominids. It's silly for someone to travel to a distant land for a mate when there is a great selection *right here*. Once the geographic barrier is overcome, this does not guarantee the purity of breeds. (Well, unless it's sympatric speciation...) [Answer] I would think along the lines of [Ligers](https://en.wikipedia.org/wiki/Liger), [Mules](https://en.wikipedia.org/wiki/Mule) and other mixed species mating. They produce offspring but their offspring are infertile. The number of "ligers" in general population would be unlikely to reach large numbers due to inter-species cultural differences and possibly more importantly, inter-species attraction. I can't see myself going for a lady Orc for example.. In these conditions the "ligers" would be quite rare, and as a result almost undoubtedly suffer from social stigmatisation and possible persecution (directly and for the parents). [Answer] Evolution should already ensure that species will not want to mate with other species often. This is due to a principle of [Koinophilia](https://en.wikipedia.org/wiki/Koinophilia). On the most basic level The odds of a hybrid species being healthier then non-hybrid is unlikely and thus we all have an instinctual aversion to mating with someone from another species because it's likely our children would be less fit then if we had a child with someone of the same species. Actually avoiding mating with another species is a specific example of a more general principle. We will instinctual avoid mating with anyone that looks abnormal compared to the average for our species, it just happens another species usually looks pretty abnormal compared to our own. People that look substantially different usually had mutations and, despite mutations being mandatory for evolution, most mutations were detrimental. Thus we institutionally learned to avoid anyone that looks significantly different from the norm because the odds are they have a mutation that would harm any child we had with them. This effect is a major part of how distinct species came about a all! The lack of more numerous hybrid sub-species in present day, or in the fossil records, is often refereed to as Darwin's Dilemma, he couldn't figure out why individual species existed at all, he would have expected a whole gambit of intermediate stages between species to exist due to multiple levels of hybridization. He listed this confusion, that distinct species came about when it was possible for species to interbreed, as a potential argument against his evolutionary theory in fact, it wasn't until a little later the Koinophillia was recognized as the cause for distinct species. Once two groups of animals looked distinct enough they would avoid mating with each other, allowing them to evolve and diverge further over time into clearly distinct and separate species. The point being that preventing hybrids from diluting your prue-bred genepool isn't much of a problem, evolution would have already instilled instincts that prevent this, if it hadn't you wouldn't have distinct species. After all when's the last time you heard anyone say they thought that chimp was HOT? If tomorrow all great apes were able to produce hybrids with humans, and the hybrids were healthy & sapient, would you be attracted to a gorilla? I think the thought of producing a child with an ape would feel wrong, even revolting, to many people, *that* is koinophillia, and it's how your species would feel about inter species relationships as well. The harder part to justify is actual the presence of a non-trivial number of hybrids in your world despite the evolutionary instincts to avoid this. Still, this may not be a big problem, humans focus on thinking/learning has resulted in less focus on instincts and thus it's a bit more excusable that humanoids violate the usual koinophillia instinct then many other species are prone to. Plus, it may be that hybrids set off the "koinophillia' radar even more then each distinct species, making the hybrid struggle to find mates even if produced. Basically a degree of hybridization which is low enough will still be sustainable, particularly if hybrid species rarely find people interested in having children with them. I should stress, this koinophillia does not require overt racism or hatred between the species. koinophilia is purely instinctual affect on mate choice, not view on species as a whole, and even the most open minded of humans still show signs of instinctual Koinophillia! It doesn't require one to believe one species is somehow less important then them, or to believe that a species or hybrid species is wrong. However, one may simply happen to find one women attractive, on an instinctual level, and another not attractive; just as someone may be attracted to blond hair over red in women (in fact, koinophilia almost certainly plays a role in hair color preference....) From a story perspective imagine someone saying "she is nice and all, but I just can't deal with scales" or "The gnomes are so small, Id feel like I'm dating a child" or "I just prefer red heads, not tentical hair". basically the overt physical differences will feel 'off' to a different species and unattractive to most people, without their recognizing the cause is koinophilia. They may still respect and get along well with another species, just as someone may love their dog or a zoo warden may grow to respect apes in their care, they just won't find them attractive on a sexual or romantic level as often. [Answer] how about dominant genes? with dominant genes one race would be so dominant that the influence of the other race is practically negligible. for your example i would suggest the following pairing results: * an human-elf couple has human children * a human-orc couple has orc children * a human-dwarf couple has human children * a dwarf-elf couple has dwarf children * a dwarf-orc couple has orc children * an elf-orc couple has orc children orcs are very ugly, so whoever they mate with, the outcome is always an orc. elves can't have elf children from a mixed couple. that is not a problem because elves live very long, so they don't need to have many children in order to preserve their race. compared to other races humans have a short lifespan so they need more chances at getting human children to preserve their race. this can be changed around to suit the setting. aren't orcs and elves closely related? an orc-elf pairing could also produce elves. [Answer] You have two simple options: 1) Total genetic incompatibility. They just can't reproduce. They're physically compatible, the bit that sticks out on one, fits in the hole on the other, but that's as far as it goes. You're breeding horses with cows, nothing is going to happen. 2) Partial genetic incompatibility. The mule, hinny, zedonk or any zebroid, tigon, liger etc. They can have one generation of crossbreed, but that's the end of the line, the cross breed children are almost always infertile (there are occasional exceptions). Then you get into the more complex options: 1) They're genetically compatible but not physically compatible. Think of the great dane and the chihuahua. Technically they're fully genetically compatible, but can you imagine the one mating with the other? 2) Social taboo. The relationship is acceptable but having children in it isn't. 3) It's already happened. Humans are what you get if you cross a dwarf with an elf. 4) Weirder incompatibility. Elves actually reproduce like seahorses. It's the male who carries the baby. The "penis" is actually the female reproductive organ and she plants the egg in the male. So the physical compatibility cross species is actually male-male female-female not male-female. [Answer] the race of the child is always that of the mother. the idea is that the race-specific genes are simply not compatible and are ignored when the genes are combined. also the womb is only capable of growing a child of its own race so any other outcome would result in a miscarriage. [Answer] Not a reproductive barrier, but ... **Half-breeds are swiftly killed by fanatics.** Have a powerful organization which hates half breeds. As in, tracks-them-down-and-murder-them-in-cold-blood "hates". They probably have some sort of ideological/religious idea about "the purity of the races", so they're willing to sink a lot of effort into finding and killing half breeds. The authorities are either in league with the organization, or tacitly turn a blind eye to their activities. (Perhaps not all authorities, but enough such that they have a safe refuge from which to operate.) This means they can work with near impunity across most of the world. Mixed-species individuals certainly can survive - possibly for quite a long time - but it requires an extensive level of diligence, willingness to move often (and/or live out in the middle of nowhere), and a fair amount of luck. This is especially true if half-orcs (etc.) have a distinctive appearance; the moment they walk into a town of any size, someone from the local branch of the organization will notice them, trail them, and attempt to cut their throat or poison their drink. Depending on zealotry, this can go even further. You may be a prosperous and well regarded citizen, but if it eventually comes out that your great-great-grandfather was an elf, chances are that pretty soon your family home is going to burn down while you and your children are locked inside. This, of course, is ripe for abuse due to false rumors, but *"better that an innocent person should die pure, than suffer a mutt to live"*. (... as I said, fanatics.) [Answer] To keep it realistic, you don't really need to get all elaborate . . . unless you want too. Realistically, the reason human races remained separated was primarily geography. There may have been a lot of foreigners in different lands, but the vast bulk of the people of any given race were surrounded exclusively by people of the same given race . . . unless you're talking about individual kingdoms in a given area as a race, in which case, they all usually mixed together, which is why the variations between peoples of any given continent and especially country isn't very much, and usually takes several years, even decades to finally distinguish the subtle differences between them. But there is a difference between each country's people, often between areas of the same country. So even though there was a lot of inter-breeding between them, it still wasn't significant enough to eliminate or avoid development of subtle differences. And again, that's primarily because of geography. Now, there are some people who avoid mixing on purpose, but they don't make a significant difference in the overall race they belong too. And usually, it's not racially-specific, but rather class-specific or religion-specific, meaning mixing can occur even with them, but typically only if it is acceptable by society for a person of their place and position to do so. And some societies didn't care as much as others about racial differences as they did about religious or class differences [Answer] The planet could get its own revenge for interbreeding. Every time a child is produced that is the product of two breeds, one close relative to each parent will die on or shortly after the child's birth. And abortion always kills the mother, also, as the fetus and the mother are interdependent on each other for life from conception until the child's first breath. The first breath could be called something cool like the o'er-weaning. [Answer] I'm thinking something along the lines of the children having health problems or 'defects'. This could discourage a lot of people from having hybrid (for lack of a better term) kids. If there are size differences between the species', it could end up killing the parent during birth. Say, and I know these aren't the species' you mentioned, but if a dwarf and a giant were to have a child together it would most likely kill the carrier and/or the child. even without any social taboo, this would deter a lot of couples from reproducing. And as others mentioned, social taboos or even laws preventing it could be a huge factor too. Anything from gossiping to refusing to legally recognize a hybrid as part of the family. Perhaps the parents could be disowned from their family, or they aren't allowed to get a birth certificate or legal id for the child, or the doctors and nurses might kill the child shortly after birth. The last one would probably result in a large number of home births, which brings some different struggles. Finding an accepting midwife or doula, for one thing. There are probably some sympathizers out there though, and mixed-species couples might be able to get a surrogate or sperm donation from one of these sympathizers. Legally, the child wouldn't belong to the couple (depending on the amount of discrimination in the law) and there could still be some social rejection, but it could avoid some legal problems down the road. I hope this helped, please tell me if you need me to reword anything. ]

[Question] [ In a given fantasy world, I need a deadly (yet not magical) gas that will naturally pool in low depressions and valleys. The level of magic is not high, so I'd like it to be an actual chemical that an astute reader/player might be able to identify. Ideally, it should be mostly opaque in large quantities and deadly to any unprotected living creature. Does such a substance exist? Can it? [Answer] During WW1 chemical warfare was used to break the deadlock at the ocidental front, with cruel consequences but little to no true military value. The simplest gas used was Chlorine, that accumulated in pools and was quite deadly (and quite horrible as a weapon). I believe this one or any of the other gases used in WW1 might work as you want. Phosgene is a alternative but does not produce the thick, greenish cloud that chlorine generates. Below is a chlorine release, photo is B&W, but the cloud color is greenish (green + white).  [Answer] Ok, I misunderstood the question, you want nasty, *seeable* stuff. The natural part is a bit problematic. Here we go: * **Nitrogen dioxide** Brownish stuff which is caused by burning which is a major air pollutant and has this sharp, biting odor. Poisonous, of course . To be exact, the atmospheric nitrogen is bonding with oxgen, first causing nitrogen monoxide which reduces himself to nitrogen dioxide. It reacts with water to nitric acid (exactly, that bad stuff) and nitric acid forms again cloud of nitrogen dioxide. Problem is, natural occurence is quite out of the line...you need too many of this stuff to form pools of nitric acid. So old mining industry or waste disposal are possible settings. * **Chlorine** Has already been mentioned, but here is also the problem how it is generated. The best bet is salt (NaCl) which is reduced by acid to form chlorine. * **Acid clouds** The most common acids like sulphuric acid and hydrochloric acid are creating fumes which are aerosols of small droplets like fog. They are not so much deadly because I cannot imagine that someone will try to enter this stuff, it is definitely a barrier. For history here the old given invisible stuff: * **Carbon dioxide** Yes, the thing used in soft drinks is also naturally occuring, but poisonous in higher concentrations. It is one feared component building up in silos or wine cellars and killing more people than all other gases. There is no protection (gas masks do not work: you need an oxygen supply). At one time 1700 people were killed by the [Nyos Lake](https://en.wikipedia.org/wiki/Lake_Nyos). * **Hydrogen sulfide** While transparent, it cannot be ignored because it smells like rotten eggs (That is in fact the reason because rotten eggs produce hydrogen sulfide). It is not only very poisonous, but also flammable and explosive. It is created naturally in swamps and sewers. * **Sulfur dioxide** Is created when burning sulfur which can be found in nature as native element. It is colorless, very toxic, but smells like a currently lighted match. * **Ethane** Is besides methane the component of natural gas. While methane is lighter than air, ethane is heavier, colorless, odorless and poisonous in higher concentrations. [Answer] Another possibility is Bromine. It's denser than air, so it will pool nicely, and has the literary advantage that it's *red*, with all the symbolism that entails. It's toxic at high concentration, but it also stinks, so it's hard to ignore and hard to imagine anyone getting killed inadvertently, as opposed to silent killers like CO2. [Answer] You actually have quite a few choices. Given your parameters, * **Argon (Ar):** It’s a naturally occurring gas on Earth (it comes from the radioactive decay of a few other elements that naturally occur) and our senses can’t detect it (it’s tasteless, odorless, and invisible). It’s not really a poison in and of itself, but it replaces oxygen in low-lying areas and becomes an asphyxiation risk. * **Chlorine (Cl):** This is a bit more noticeable: argon suffocates you while you breathe normally, while chlorine causes a much more painful reaction. The gas becomes hydrochloric acid when it contacts water, and burns. Inhaling it causes an instant crippling effect and probably gives you the most visually appalling death you can think of. It does have a color and trace amounts of it become detectable. * **Natural Gas (CH4 & others):** This is actually completely scentless (the odor we recognize so well is added so we can ... well, recognize it so well). Methane (CH4) in particular can work here, though combustion might be a hazard. Inhaling it in large quantities for a short period of time cripples a human body and sets in motion a wide array of lung issues. As much as anything, it replaces oxygen in the air (or outright consumes it) and reduces what our bodies can take in. * **Hydrogen Sulfide (H2S):** This is an odd choice, but it gives you the colorless but horrible smell option. This is the rotten egg scent many of us are aware of, though it should be noted that it deadens the senses and is harder to detect than you might think. It would rather quickly discolor any copper the person might be carrying or using. It doesn’t take much: 500 part per million will completely nuetralize the sense of smell and 800 ppm will cause death within 5 minutes (and an uncomfortable one at that). * **Carbon Tetrachloride (CCl4):** This would be an interesting idea, though it’s a bit lighter and isn’t as likely to pool without a source. It has a slightly sweet smell, but is otherwise pretty undetectable in a mediveal world. It’s a horrible toxin to the liver, will place people into comas, goes after our central nervous system, and causes symptoms of depression. The deadening of the nervous system can also dissociate yourself from your body. * **Sulfur Hexafloride (SF6):** This one could be fun: it’s odorless, colorless, and not very detectable until we get to sound. It has the opposite effect to helium, lowering ones voice by several octaves (the give away that you are in it is that everyone’s voice goes lower). It’s not really toxic in and of itself: most of the death risk is from displacing oxygen and not leaving enough behind for our uses. It’s also a functioning anesthetic, just below nitrous oxide (laughing gas) in its effectiveness There’s a pretty good array. You could probably be picky between severity and speed of reaction on the one side and color, scent, and taste on the other. If there were specific parameters that you were interested in, we could probably tailor the gas for you a bit better. Everything listed above is decently commonplace on our globe and is explainable. [Answer] My first thought is Carbon Dioxide. It doesn't seem that deadly, but it is! (...assuming one breathes oxygen). It has been known to pool into depressions and valleys (typically after a volcanic 'burp' or when deep water saturated with CO2 has been agitated by a distant earthquake or something). [Answer] NO2 or nitrogen dioxide is toxic, heavier than air and visible (opaque) in high concentrations as your question asked. It is reactive with organic materials (life) as it is an excellent oxidizing agent. Also forms a strong acid on reaction with water (nitric acid), and ozone on reaction with volatile organics in the presence of heat and light. [Wikipedia on NO2](https://en.wikipedia.org/wiki/Nitrogen_dioxide) [EPA on health effects of NO2](http://www.epa.gov/airquality/nitrogenoxides/health.html) [Answer] Anhydrous ammonia, when subjected to moisture in air, forms a [ground-clinging cold fog](https://www.youtube.com/watch?v=sNkdAs1e7Cw) that rolls away from the point of dispersion and is quite noxious. It is also easier than almost anything else to make, and the final reaction after the fact tends to make the grass a little greener. Are there bonus points for being eco friendly? Oh, and it's explosive. [Answer] ***This is a real story about a lot of people dying.*** [Lake Nyos](http://en.wikipedia.org/wiki/Lake_Nyos) is in a volcanically active area of Cameroon. It sits over a pool of magma, which leaks carbon dioxide gas into the lake. The gas dissolves in the water, but the lake becomes supersaturated. That means that any sudden disturbance of the water (caused by a small earthquake or landslide, for example, which is not unlikely in a volcanic region), can cause it to suddenly release a *lot* of gas. A massive cloud of carbon dioxide pouring down a hillside can kill a lot of people. Wikipedia says, > > On August 21, 1986, a limnic eruption occurred at Lake Nyos which triggered the sudden release of about 100,000 - 300,000 tons (some other sources state as much as 1.6 million tons) of CO2; this cloud rose at nearly 100 kilometres per hour (62 mph). The gas spilled over the northern lip of the lake into a valley running roughly east-west from Cha to Subum, and then rushed down two valleys branching off it to the north, displacing all the air and suffocating some 1,700 people within 25 kilometres (16 mi) of the lake, mostly rural villagers, as well as 3,500 livestock. The worst affected villages were Cha, Nyos, and Subum. Scientists concluded from evidence that a 100 m (330 ft) fountain of water and foam formed at the surface of the lake. The huge amount of water rising suddenly caused much turbulence in the water, spawning a wave of at least 25 metres (82 ft) that would scour the shore of one side. > > > Carbon dioxide, being about 1.5 times as dense as air, caused the cloud to “hug” the ground and descend down the valleys, where various villages were located. The mass was about 50 metres (160 ft) thick and it travelled downward at a rate of 20–50 kilometres per hour (12–31 mph). For roughly 23 kilometres (14 mi) the cloud remained condensed and dangerous, suffocating many of the people sleeping in Nyos, Kam, Cha, and Subum. About 4,000 inhabitants fled the area, and many of these developed respiratory problems, lesions, and paralysis as a result of the gases. > > > If you want coloured gas, you’ll need to use something other than carbon dioxide. However, do check whether the gas is water-soluble. If it is, a lake over a vent can cause a natural way for a lot of gas to gradually build up over a long time and then be suddenly, unpredictably released. [Answer] There exist completely naturally occurring gases which satisfy the criteria. I remember that in the Transylvanian mountains there are locations where sanua-like buildings are built upon [such places](http://en.wikipedia.org/wiki/Mofetta), where the gases have the following properties: * heavier than air, doesn't mix with air. * considered healthy to the bones, joints, etc., good against arthritis and similar illnesses. * heavily toxic. One breath can easily kill you. You can check the level of the gas with a cigarette lighter or a matchstick. If you lower the flame below the level of the gas, it goes out completely. The gas is completely invisible, and feels a little warm. If you carefully enter the "sauna" and sit down, you can be almost neck-deep in the gas, and completely safe. [Tourist guide quote](http://transylvaniantravel.ro/en/prg/9/5/lake-st-ann-mohos), emphasis added: > > What is a mofette? Usually tourists don’t know the meaning but you > have to know that this is one of the many advantages that Sekler land > has. It’s a special bath without water. The gas is coming out of the > earth and as it gets into the blood-stream through the skin it starts > its healing process. These gases come up from the result of post > activity of the volcano and they are present in many places all over > Sekler land. The types of gases are **usually carbon dioxide and > sulphur**. It is good for circulation problems, blood-pressure problems > and for motorical problems. Of cause you need to have a few day > treatment if you want any results. The mofette can be very dangerous > too. Breathing in these gases can be fatal. We have to be careful, do > not bend under the gas sign line and do not mix up with sudden > movements. > > > [Answer] # [Radon](http://en.wikipedia.org/wiki/Radon) Radon is a very heavy radioactive gas. It is naturally present in low concentrations almost everywhere in the world airs and in underground waters, but it is very hard to obtain in large quantities and will decay pretty quickly in a few days (isotope 222, the most long-lived, has a semi-life of a few less than 4 days), so you will need some way to replenish it. But, anyway, it surely do what you want: * Tends to pool down on depressions and lower areas where it can't escape, like underground rooms, basements and mines. In fact, Radon is the heaviest naturally-occurring gas. * In large quantities might suffocate creatures by displacing oxygen. Even if you can handle that, or if the concentration is not so high but still many times higher than natural level, its intense radioactivity will kill any unprotected living creature. If some creature survives the exposure, it still is very likely to die from cancer some time later. * Even when 222Rn decays to 218Po in less than 4 days, then that also decays in a few more than 3 minutes to 214Pb that decays in 27 minutes to 214Bi, which decays in 20 minutes to 214Po, which decays in some microseconds to 210Pb which in 22 years became 210Bi, which in five days become 210Po, which in 138 days becomes the finally stable 206Pb. The result is that your radon gas will quickly fill up with highly radioactive, heavy and toxic metallic dust. Further, that dust will tend to stick to surfaces and be dissolved in liquids, making it very hard to remove the radioactivity even if all the Radon gas is ventilated away. * It would be almost invisible. Being a noble gas, Radon is tasteless and odorless. It is also colorless. However the mostly Lead (with a bit of Polunium and Bismuth) dust will not be, making it somewhat noticeable as a (likely gray, but not sure) smog. The smog will probably be very thin because Lead dust do not tend to be suspended in the air for long time and will soon accumulate in the ground. If there are some strong air currents in the place that do not disperse/leak the gas away, but do not allows the dust to settle down, then the smog will become quite noticeable. * Even if the gas is invisible and the smog normally almost invisible (if you do not prevents the dust from setting down), an astute reader/player might still be able to identify it by the accumulating Lead-rich dust. Then, after identifying it, the player will die due to the radioactivity in a few minutes. You don't need to make the gas opaque and visible for it being noticeable, the accumulated/accumulating dust might be enough. * Even most of digital machines, like smartphones and computers, are very likely to malfunction and glitch in such environment if not properly shielded from the radiaction. * Unaware normal people will likely not understand what is horribly wrong with the place/places where the Radon is. For them, it will looks like some sort of terribly strong evil magical curse. [Answer] I think ozone might serve. It is roughly 50% heavier than air and is known to collect in basins like Los Angeles. Most people will recognize the chemical by smell and they probably know that it is poisonous. Ozone itself is a pale blue, however lethal concentrations are far far below what would be considered opaque. It would be visible in the form of smog when combining with organic molecules in the atmosphere. Sometimes smog can be rather opaque. If you had the right combination of organics naturally in your atmosphere, the smog could be the opaque component though it's the ozone that kills. [Answer] Many welders have been killed by Argon Gas suffocation...As it pools in low areas especially in concrete foundations where it cannot escape... EDT: Argon is an inert shielding gas meaning when it is used for welding it shields the molten metal from exterior gases such as oxygen...It is used in Metal Inert Gas welding or MIG welding. It is odorless unless an odor is added such as garlic or onion fragrance. It is clear and it kills indiscriminately by starving the subject of oxygen death occurs relatively quickly usually under 3 min [Answer] Carbon Dioxide. We have valleys with this on earth, they are called *Mazuku*, and have been responsible for deaths of humans, wildlife and lifestock both in recent history (e.g. Lake Nyos in the 1980s or smaller incidents like Mammoth Mountain, California in 2006) and in the more distant past (perhaps the reason that the Messel Pit in Germany has so many fossils is such an event happened there). It's not visible though, but that could be solved by a visible effect being part of the world building. If you really need to be able to see it, I'd go with high concentrations of chlorine, though note that it's likely to be poisonous in much lower concentrations than make it visible, so your characters can't just walk up to the smoky yellow-green clouds unaffected. [Answer] My I ask why it has to be opaque? If it's so characters can recognize it, consider that seeing the gas is not the only way to recognize the existence of a deadly gas. Seeing the effects it has on others is a key way we do so in the real world. I ask/say the above because the first thing that came to mind was Sarin. It is heavier than air as you request, it's quite deadly, and the effects on living things is recognizable to a learned observer. It is everything you seek except the opacity. I would venture to say Sarin is a *better* killer due to its transparency; you don't know it's coming until you or someone close to you can't breathe anymore, at which point you're pretty much screwed. If you're in the U.S., "60 Minutes" had a story on Sarin just two days ago. Go watch it. [Answer] Nitrogen. It is deadly if it pools in a low place. Before you know it, you pass out and die. Nitrogen is odorless and colorless. It is used to flush explosive gasses from pressure vessels and other containers used in industry. Sometimes a worker will go into the container to perform repairs to the vessel. He gets lightheaded, faints, then dies very quickly. There are cases where others go in to save the worker, and they die, too. The rule is, when you see a worker who is down and you don't know why, you don breathing gear. Nitrogen is slightly lighter than air (which is itself 70% nitrogen) but I think it could be what you're looking for. [Answer] I seems to me that chlorine gas on lower elevations would lead to highly acidic rain rendering the higher elevations uninhabitable as well so you'd probably want something that doesn't combine with water with such enthusiasm. Inert gases are probably the better option even though they have an annoying tendency to be transparent. And it doesn't really matter which inert gas it is since the effects and appearance would be all the same [Answer] All gases mix completely with all other gases. At least we haven't yet found a pair that act like oil and water. So it will need to be regenerated somehow or it will diffuse away, especially if exposed to wind or other currents. ]

[Question] [ [Asian Giant Hornets](https://en.wikipedia.org/wiki/Asian_giant_hornet) are particularly vicious and deliver a dose of neurotoxin to its victims. Generally an average of [59 stings](https://en.wikipedia.org/wiki/Asian_giant_hornet#Effects_of_venom_on_humans) are sufficient to kill a healthy non-allergic man Given a suitable evil empire and access to scientific minds, how would it be possible to engineer a breed of hornets that can be lethal with a single sting? Ideally, the engineered hornets should be self-sustaining in that subsequent generations should be as deadly as the first. Assume a technology level of "near future" (50 years or so in the future) and a very limited adherence to any sense of ethics. [Answer] Sure why not. There are plenty of toxins out there that are lethal in small amounts. We're already getting pretty good at targeted genetic engineering using techniques such as [CRISPR](https://en.wikipedia.org/wiki/CRISPR). Given 50 years of technological advancement we should be able to figure out how to engineer wasps to have a more lethal sting. All you'd need to do is work your genetic magic on the queen of a hive and check the results. Pick an animal with the your desired venom (I'd recommend applying the rule of cool), isolate the genes that produce that venom, splice it into your wasps, and work out the kinks. It should be noted that stings are common amongst professional beekeepers even with protective gear. With wasps being much more aggressive there is a significant risk of personal harm from hive maintenance during the engineering process. [Answer] So two ways I can see. The first is simple selective breeding. Get lots of hornets and sample their venom. Take the ones with the most potent venom and cross breed their lines. In the next generation find the ones with the most potent venom, and cross breed their lines. Continue for 50 years. Having a short maturation period means that you will get a lot of generations quickly, which will speed up the process when compared to other selective breeding programs, such as horses and dogs and seedless watermelon. The second is genetic engineering. Splice in genes for more poisonous venom, such as cobra or other dangerous snakes. **Edit: Bonus third.** Give up on the venom and inject something else. The most deadly insect in the world is not venomous. It's the mosquito, which transfers a malarial parasite when it bites. Engineer a parasite (or nano machine?) that lives in the wasps venom sack and destroys the victim from the inside when transferred by sting. It has a couple added bonuses: 1. When the insects eventually escape the lab, they won't take the attack vector with them, and so it won't become a plague. 2. The normal venom in the sting will act as a decoy. You get stung by a hornet, and start having a bad reaction. So you inject an epipen, maybe an antivenom if something can be developed, and the victim might not die. But if there is a secondary attack vector then they start counteracting the venom, but not the real problem. **Edit 2: Diet** So another possibility might be to find something that would build up in their systems and cause its venom to be more toxic. The Monarch Butterfly Caterpillar is a tasty treat for birds, which the caterpillar finds objectionable. So it feasts on a diet of milkweed, in order to sequester cardenolides in its body, making the caterpillar toxic to anything that would eat it. Through trial and error, find a chemical that won't kill the wasp outright, but is toxic to humans and can build up in its venom gland. This would bring an added punch to the wasps sting. The last two options of course go against the new `Ideally, the engineered hornets should be self-sustaining in that subsequent generations should be as deadly as the first` edit, as they would potentially work with any wasp, but not be carried on genetically if/when the wasps escape (which I kind of suspect is the intended result?) [Answer] ## Researchers notes **Abstract**: Find way to terrorize people for our dark overlord-to-be. Lest we lose our research grant. So we, and our families, will not be used as test subjects by other researchers. *Our new intern had an idea with hornets.* So now we are going to take an already aggressive and slightly sadistic species and improve on that. **Test 1: Failure** we made the Hornets (v1.1) more aggressive and we made sure the venom was both more painful and lethal. We had to terminate this first, promising, attempt when our new intern was stung at least 73 times by our Hornets (v1.1). Reviewing the monitor tapes makes it clear that the upgrades work. But he was also allergic, so it seems. Alas, all available Hornets (v1.1) died in the accident due to being crushed. On the bright side, we have a new intern opening. **Test 2: Failure** this time we only fiddled with the venom in the tail of the Hornets (v1.2). We were able to "borrow" a [saw-scaled viper](http://phenomena.nationalgeographic.com/2016/04/19/why-some-snakebites-are-so-destructive/) from our colleagues in the next lab. We only had to change the venom glands a bit, and it worked. All tests with lab animals, from mice to dogs, worked quite well. But one of the downsides is the rotting of flesh. And our Hornets (v1.2) digestive system was not fast enough, or robust enough, to handle rotting flesh. By the time we figured that out the queen had died. In lighter news, the new intern seems quick on her feet, she loves to dance. **Test 3: Failure** [Box Jellyfish](https://en.wikipedia.org/wiki/Box_jellyfish) nettles work well. And we were even further along than Hornets (v1.2) in testing. Even the digestive problems were solved. Only, tragedy struck on the weekend of "Fear our Overlords", where all senior staff were at home with their families to pay due homage to this festivity. Our new intern decided to take the test one step further and introduce her pet crow to the experiment. Reviewing the tapes we conclude that the crow was scared by the noise the Hornets (v1.3) made. This, in turn, distracted our intern while working with the Hornets (v1.3) and she was stung 3 times. We estimate that one sting has enough venom to kill 10 fully grown men. But the dying process was longer then expected. Still looks extremely painful *(and is hard to watch, we liked her)*. But with her death, her crow went nuts and killed all the Hornets (v1.3). It, too, died in the process. **Test 4: Success** As a stretching of our capabilities we used [inland taipan](https://en.wikipedia.org/wiki/Inland_taipan) as the source species for this test. We also decided to made our Hornets (v1.4) slightly more aggressive, so a single bird will not end our experiment this time. All tests went well. *As a side note, our new intern seems a bit nervous.* **Presentation:** Tomorrow our dear dark overlord-to-be will be visiting the research center to decide on the grant for next year. We feel quite confident in our presentation and Hornets (v1.4). **Grant Status: Denied.** After the speedy yet painful death of our beloved dark overlord-to-be by Hornets (v1.4) during a botched presentation at our #13 science lab, this project has been terminated. *Status of the researchers of this project is unknown. Rumor has it they have fled to our ethereal rival, the Knights of the Neon Disco Suits. Their intern has been given over as a test subject for other groups. Long live our future dark overlord.* [Answer] Firstly, How dare you? Secondly, I'm not sure which toxins would fit best with those awful demonic entities, but whatever you find, make sure it will be compatible with the hornets' physiology. Wasps and hornets are carnivorous, so they can't afford to be poisoned by the very poison they used to kill their food. Then, breed a queen with the poison gene, and she'll make a new hive to devastate the world. Congrats on creating the worst apocalypse ever. ...have I mentioned I have an immense phobia of wasps and hornets? Also, HOW DARE YOU!? *(Just joking, I'm sure you're very awesome and that this'll be an awesome bit for your world. I just saw this, and thought I'd give my two cents on this.)* [Answer] Genetically engineer them to produce [Botulinum toxin](https://en.wikipedia.org/wiki/Botulinum_toxin) as their venom or make them capable of developing a symbiotic relationship with the bacteria that produces it. [Answer] Hornets (F/A-18) have *already* been engineered to kill a human with a single sting! I think engineering hornets to want to nest in cars and swarm when cars are at speed on freeways would be effective. While I respect the (hopefully benign) curiosity of the person asking the question, and generally like the spirit of helping people solve hypothetical problems, let's at least say, for the record, and for the benefit of future readers who the least bit uncertain about the ethical disposition of this concept: "This line of thinking is totally evil!" (Hey, a bag of peanuts has an allergen warning, "contains peanuts", and a box of Wheaties cereal or Wheat Thins cautions, "contains wheat". So, let us say this concept "contains evil", shall we? LOL!) [Answer] **Rabies!** Ok, I'm just riding on a lot of other peoples coat-tails here, but rabies, if unchecked, still has nearly a 50% mortality rate. So, Tweak rabies a little bit and introduce it via your preferred method into the venom sacks of the Angry Angry wasps. As a bonus, you would have something ready made for attack bats or guard raccoons. Just be aware that in World War Z, the zombie bug was called African rabies, so you might be wise to be sure your strain of super rabies doesn't cause a zombie problem. [Answer] They need some poison, what kills us, but doesn't kill them. Some symbiotic virus would be also possible. For example, AIDS (HIV) virus could be relatively easily modified to make it transmittable by hornets. Note, genetical modifications are mostly not advantageous in the raw nature. It is because the Nature also makes a continuous "genetical modification", it is the evolution. These hornets will be probably weaker in the nature as the common ones, and thus they will slowly (or quickly) disappear. Multiple genetical engineering would be needed, to provide for them also advantages. Fortunately, there are already possibilities for that. For example, existing hornet subspecies could be crossed, or somewhere not existing, but more virulent species could be inserted into new regions. Here is an [example](https://www.dailykos.com/story/2015/12/31/1463677/-Some-reports-indicate-the-Giant-Asian-Hornet-is-already-nesting-down-in-the-U-S-A). If they would be genetically engineered hornets to distribute aids, it would be a problem. --- * Extension: I named AIDS only because it was first, for human surely deadly virus what came to my mind. Some other virus, or some poison, may be better. Or, maybe, even the virus could be genetically engineered to be a harmless symbiont in the hornet (or even needed for their survival), but giving faster death for us. [Answer] At risk of being ignored for yet another toxin/antitoxin pair: 1) Splice ricin into the venom genes so that hornets produce ricin in their venom. 2) Overwrite the hornet's ribosome genes with ribosome genes from the same species of fungus castor plant from which you took the ricin gene. 3) Tinker with activation sequence of the ribosome gene so it still works. Muhahaha. There's no antitoxin for ricin. My apologies I have no actual data on ricin fatal dosage I just know the fatal dose is low because it is low of all toxins in that class. My guess is this one is very dangerous because Wikipedia chose to omit any numbers on the actual toxin and only the number of beans involved. [Answer] Genetically change the poison to cone snail poison and a hornet will be able to kill a human with one sting. [Answer] There are a bunch of reasonable answers to this question. And then there's nanobots. Go with nanobots. It's more fun. Have such devices move from one hornet to the next when they reproduce and wait in the hornets venom sacks - I have no idea how hornets work - till it stings something. Then make the stinging thing trigger a thing that activates the nanobots and tells them to seek out human cells, use them to reproduce, and kill them about an hour or two after the sting so the nanobots have had time to travel around the body. This should prevent humans from just cutting the stung bit off. Now all you have to do is train hornets to hate humans and you're good. You could probably achieve all of this with a parasite or a virus if you wanted to. Zombie lore has to deal with this sort of thing a lot. Believe it or not zombies are the og of things that kill only humans for semi-believable reasons. You could probably just use a lot of the same reasoning here. Radiation could also work since animals in general have been shown to be able to adapt to stupid levels of radiation in Chernobyl. [Answer] > > Assume a technology level of "near future" (50 years or so in the future) and a very limited adherence to any sense of ethics. > > > * Pick the least-painful wasp species available. * Modify its poison glands to produce a [lipo-soluble](https://en.wikipedia.org/wiki/Lipophilicity) coated [aerogel-like](https://en.wikipedia.org/wiki/Aerogel) folded structure. Adjust coating to survive a few seconds inside the human body. * Modify the sting itself to work like a [jet injector](https://en.wikipedia.org/wiki/Jet_injector), in order to guarantee that it'll reach the circulatory system; * Engineer its behavior to target the likely placement of large blood vessels. Let's assume an original, folded density of 12g/cm³ to unfolded 3-4 mg/cm³ after coating removal - that means it gains roughly 3,500 times its original size. Due to [friability](https://en.wikipedia.org/wiki/Friability) the structure isn't stable, so it'll shatter like glass instantly once free of the coating - but not before leaving a 5-20cm radius hole where there was only a tiny needle just a few seconds ago. If it happens inside the heart... oh well! [Answer] Well, you did not say, how fast they should kill... So already now it is easily possible to drug a hornet with a virus or bacteria that will kill a human (see how deadly ticks can be). The drugging can happend through spraying a liquid with a bacteria over the hornet. [Answer] Modifying the toxins produced by hornets to make them more toxic is a simple matter of genetics. Their venom is a variant on what spiders or reptiles use. Producing venom is very resource intensive for predators. That’s why the last defense of snakes or spiders is a venomous bite. Generally they hiss, run away or use some other method to warn they do not wish to be bothered or consumed. The same defense strategy applies to giant hornets here on earth. Their first line of defense is defensive posture, then a bite. The last line of defense is a sting. When they go marauding and attack a hive, their strategy is to bite the heads off other hornets, which removes the opposing threat. This is how they destroy another hive. But this attack, which might be very painful, is not enough to kill a human. Giant hornets on earth are scavengers. But what will these hornets eat in this new world? Would they still be scavengers? Would they hunt down quarry, inflict a bite that disables and kills the prey so the hive can feed? If you borrow the killing technique of the Komodo Dragon, another scavenger which has no venom, but it’s saliva is full of bacteria which can kill through septicemia. Although with the dragon, it’s not important where the prey dies because they are on an island. But if the hornets attacked prey in a swarm, perhaps their bite and their sting could disable and kill prey for the hive to use as a food source. Imagine a one-minute deadly attack that leaves the flesh edible to other hornets because the virulent bacteria does not harm their digestive system, but disables prey. That’s a hornet I’d stay clear of at all costs. ]