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so neil ’ s got a sample of sodium . sodium is a very reactive metal , it is stored under an oil to stop air or moisture getting on it - stop it oxidising , stop it reacting - and as you can see it is a very soft metal , so he is going to put his knife in and withdraw the lump of sodium , so there is about 2 kilos of sodium here , it 's a really quite large rod . so we are going to cut a small sample of the sodium and we are going to see if we can explore some of its chemistry . sodium is again a light metal , rather like lithium and it has a , a melting point about 96 degrees . so the sodium is a very , very shiny metal and as you can see as neil cuts some off , you can see the quite nice shiny material . it ’ s really quite beautiful . reacts very , very quickly with air and also with water , you form the oxide layer which is the white , or the hydroxide is the white crust on the outside . and many of you will know that if you drop sodium into water it reacts almost explosively . so we are going to go outside now , go get some even bigger reactions , with the alkali metals . this is a dog bowl which is stoneware , it is very hard , not likely to break , unless i drop it on my toes . this is sodium , the metal that we cut a minute ago and you can see there is quite a substantial amount of the sodium , and we are going to pop it into the water and see what we can do with the reaction . ok ? so here we have a bowl full of water and maybe , oh , a gram of sodium ? so let ’ s see what happens , see what this reaction ’ s like . so it is reacting really , really quite quickly and really violently with the water , and you can see it is fizzing around and it is generating lots and lots of hydrogen gas . and see now the heat from the reaction is burning away all of that hydrogen which is generating and you can see the orange sodium flame . that was um ? that was good that is a bit of , a chunk of molten sodium has come out of there mate . so , let ’ s burn that . oh , it ’ s on your camera . oh it is too ! sodium chloride is transparent through infrared light and so here we have got a sheet of sodium chloride that has been stuck on to a glass vessel so that you can have infrared light going through it . now this is a broken one , which my students have broken . is that bit , have you got a , we need a needle neil , or a pair of tweezers . so you can see here that these windows have been broken but you can see an interesting aspect of sodium chloride that when it breaks it forms cracks that form at right angles . why is that ? this is related to the structure of the atoms inside the crystal which are arranged in a sort of cubic arrangement . i have also got quite a nice crystal of sodium chloride over here which i don ’ t know if you can see has been turned into a table lamp . and if you switch it on it lights up . so this is just a mass of natural sodium chloride from under the ground somewhere , probably in cheshire or somewhere else like this where they have large underground salt mines , deposits . ok so we have got another lump of sodium , and you can see it ’ s really nice and shiny . ok ? so we are going to pop that into that big bucket of water . see what the chemical reaction is , ok ? so here we go ! so you can see again , see the orange sodium spectrum as the sodium is getting excited as the hydrogen is burning all that heat . whoa ! exciting ! that is brilliant . that is much better . so sodium and water , excellent reaction . that was great . i like sodium , because its symbol na was the nickname that my mother whose name was ena used to use when she was a child , she was known as na , so whenever i see sodium in the formula , i sort of feel a sort of warm motherly feeling from this .

so neil ’ s got a sample of sodium . sodium is a very reactive metal , it is stored under an oil to stop air or moisture getting on it - stop it oxidising , stop it reacting - and as you can see it is a very soft metal , so he is going to put his knife in and withdraw the lump of sodium , so there is about 2 kilos of sodium here , it 's a really quite large rod .

sodium is a shiny material , but on the surface of the sample we can observe a white crust . what is this crust ?

to human eyes , the world at night is a formless canvas of grey . many nocturnal animals , on the other hand , experience a rich and varied world bursting with details , shapes , and colors . what is it , then , that separates moths from men ? moths and many other nocturnal animals see at night because their eyes are adapted to compensate for the lack of light . all eyes , whether nocturnal or not , depend on photoreceptors in the retina to detect light particles , known as photons . photoreceptors then report information about these photons to other cells in the retina and brain . the brain sifts through that information and uses it to build up an image of the environment the eye perceives . the brighter the light is , the more photons hit the eye . on a sunny day , upwards of 100 million times more photons are available to the eye than on a cloudy , moonless night . photons are n't just less numerous in darkness , but they also hit the eye in a less reliable way . this means the information that photoreceptors collect will vary over time , as will the quality of the image . in darkness , trying to detect the sparse scattering of randomly arriving photons is too difficult for the eyes of most daytime animals . but for night creatures , it 's just a matter of adaptation . one of these adaptations is size . take the tarsier , whose eyeballs are each as big as its brain , giving it the biggest eyes compared to head size of all mammals . if humans had the same brain to eye ratio , our eyes would be the size of grapefruits . the tarsier 's enlarged orbs have n't evolved to make it cuter , however , but to gather as much light as possible . bigger eyes can have larger openings , called pupils , and larger lenses , allowing for more light to be focused on the receptors . while tarsiers scan the nocturnal scene with their enormous peepers , cats use gleaming eyes to do the same . cats ' eyes get their shine from a structure called the tapetum lucidum that sits behind the photoreceptors . this structure is made from layers of mirror-like cells containing crystals that send incoming light bouncing back towards the photoreceptors and out of the eye . this results in an eerie glow , and it also gives the photoreceptors a second chance to detect photons . in fact , this system has inspired the artificial cats ' eyes we use on our roads . toads , on the other hand , have adapted to take it slow . they can form an image even when just a single photon hits each photoreceptor per second . they accomplish this with photoreceptors that are more than 25 times slower than human ones . this means toads can collect photons for up to four seconds , allowing them to gather many more than our eyes do at each visual time interval . the downside is that this causes toads to react very slowly because they 're only receiving an updated image every four seconds . fortunately , they 're accustomed to targeting sluggish prey . meanwhile , the night is also buzzing with insects , such as hawk moths , which can see their favorite flowers in color , even on a starlit night . they achieve this by a surprising move - getting rid of details in their visual perception . information from neighboring photoreceptors is grouped in their brains , so the photon catch of each group is higher compared to individual receptors . however , grouping photoreceptors loses details in the image , as fine details require a fine grid of photoreceptors , each detecting photons from one small point in space . the trick is to balance the need for photons with the loss of detail to still find their flowers . whether eyes are slow , enormous , shiny , or coarse , it 's the combination of these biological adaptations that gives nocturnal animals their unique visual powers . imagine what it might be like to witness through their eyes the world that wakes up when the sun goes down .

while tarsiers scan the nocturnal scene with their enormous peepers , cats use gleaming eyes to do the same . cats ' eyes get their shine from a structure called the tapetum lucidum that sits behind the photoreceptors . this structure is made from layers of mirror-like cells containing crystals that send incoming light bouncing back towards the photoreceptors and out of the eye .

what is a tapetum lucidum ?

would you rather be bitten by a venomous snake or touch a poisonous frog ? wait , what 's the difference between poison and venom , anyway ? let 's say you have the misfortune to be bitten by a venomous rattlesnake . when it bites you , the snake will eject venom from little sacks behind its eyes , through its hollow fangs and into your flesh . that venom will then travel through your bloodstream and all over your body . in most cases , snake venom contains neurotoxins , proteins that can do all sorts of nasty stuff like make your muscles fire uncontrollably , burst your blood cells , and make you go completely numb . but you might get lucky ! snakes do n't always decide you 're worth wasting venom on . in fact , between 20 and 80 % of snake bites are so-called `` dry bites , '' where the snake is just trying to send a message without actually killing you . you see , venom takes energy and resources for the snake to make , and they do n't want to waste it on a warning shot . when it comes to poison , on the other hand , there 's no warning shot . if you pick up a poisonous dart frog to admire its beautiful colors , you 've already gotten deadly poison all over your hands . as it seeps into your skin and travels through your blood , the poison starts to interfere with your nerves , preventing your muscles from contracting . if the frog 's poison reaches your heart , it can cause it to stop . the distinction between venom and poison is purely in the method of delivery . poison has to be inhaled , ingested , or absorbed . venom has to be injected into a wound . chemically , venoms and poisons are both considered toxins , so a snake bite is venomous . a poison dart frog is poisonous . brown recluse spiders are venomous . lionfish and pufferfish are poisonous . and some compounds can be poisons in one animal and venoms in another . tetrodotoxin , a chemical 10,000 times more toxic than cyanide , is found in pufferfish , where it makes them poisonous . it 's also found in the deadly blue-ringed octopus , where it 's a venom delivered by bite . some animals can even be both poisonous and venomous . take the asian tiger snake , for example . not only does it have venom in its fangs but it also absorbs the toxins from the poisonous toads it eats , and then secretes those toxins from special glands on its neck , rendering it poisonous , too . scientists are constantly finding new animals that employ toxins in weird , interesting ways . recently , researchers discovered the very first venomous crustacean . out of 70,000 species of crustaceans , only this one little remipede is venomous . speleonectes tulumensis has figured out how to create a cocktail of toxins that it delivers through its tiny fangs . scientists are n't totally sure how this venom works yet , but they think that it causes the unwitting victims ' neurons to fire over and over and over again until it becomes paralyzed . then , the little remipede closes in , dissolving away the exoskeleton of its prey and sucking out the juices . but poisons and venoms are n't always all bad . for thousands of years , humans have looked for ways to harness the power of these toxic compounds for good . today , we have all sorts of medicines that come from toxins . the poison from cone snails is used as a painkiller . many poisonous plants have been used to treat everything from malaria to irregular heartbeats . and scorpion venom might one day be used to treat heart disease . so , what should you do if something bites or poisons you ? do n't try any of the things you 've seen on the internet or in movies ! do n't try to capture and kill the animal that bit you , and do n't use a tourniquet or knife on your wound . most importantly , do n't panic ! stay calm , and seek medical attention . treatment will mostly depend on what species you encountered . but if you forget the distinction between poison and venom , and tell the parademics that you were poisoned by a viper , they 'll probably forgive you and treat you anyway .

today , we have all sorts of medicines that come from toxins . the poison from cone snails is used as a painkiller . many poisonous plants have been used to treat everything from malaria to irregular heartbeats .

the poison from cone snails is used as a ________ .

where does all this stuff come from ? this rock ? that cow ? your heart ? not the things themselves , mind you , but what they 're made of : the atoms that are the fabric of all things . to answer that question , we look to the law of conservation of mass . this law says take an isolated system defined by a boundary that matter and energy can not cross . inside this system , mass , a.k.a . matter and energy , can neither be created nor destroyed . the universe , to the best of our knowledge , is an isolated system . but before we get to that , let 's look at a much smaller and simpler one . here we have six carbon atoms , 12 hydrogen atoms , and 18 oxygen atoms . with a little energy , our molecules can really get moving . these atoms can bond together to form familiar molecules . here 's water , and here 's carbon dioxide . we ca n't create or destroy mass . we 're stuck with what we 've got , so what can we do ? ah , they have a mind of their own . let 's see . they 've formed more carbon dioxide and water , six of each . add a little energy , and we can get them to reshuffle themselves to a simple sugar , and some oxygen gas . our atoms are all accounted for : 6 carbon , 12 hydrogen , and 18 oxygen . the energy we applied is now stored in the bonds between atoms . we can rerelease that energy by breaking that sugar back into water and carbon dioxide , and still , same atoms . let 's put a few of our atoms aside and try something a little more explosive . this here is methane , most commonly associated with cow flatulence , but also used for rocket fuel . if we add some oxygen and a little bit of energy , like you might get from a lit match , it combusts into carbon dioxide , water and even more energy . notice our methane started with four hydrogen , and at the end we still have four hydrogen captured in two water molecules . for a grand finale , here 's propane , another combustible gas . we add oxygen , light it up , and boom . more water and carbon dioxide . this time we get three co2s because the propane molecule started with three carbon atoms , and they have nowhere else to go . there are many other reactions we can model with this small set of atoms , and the law of conservation of mass always holds true . whatever matter and energy go into a chemical reaction are present and accounted for when it 's complete . so if mass ca n't be created or destroyed , where did these atoms come from in the first place ? let 's turn back the clock and see . further , further , further , too far . okay , there it is . the big bang . our hydrogen formed from a high-energy soup of particles in the three minutes that followed the birth of our universe . eventually , clusters of atoms accumulated and formed stars . within these stars , nuclear reactions fused light elements , such as hydrogen and helium , to form heavier elements , such as carbon and oxygen . at first glance , these reactions may look like they 're breaking the law because they release an astounding amount of energy , seemingly out of nowhere . however , thanks to einstein 's famous equation , we know that energy is equivalent to mass . it turns out that the total mass of the starting atoms is very slightly more than the mass of the products , and that loss of mass perfectly corresponds to the gain in energy , which radiates out from the star as light , heat and energetic particles . eventually , this star went supernova and scattered its elements across space . long story short , they found each other and atoms from other supernovas , formed the earth , and 4.6 billion years later got scooped up to play their parts in our little isolated system . but they 're not nearly as interesting as the atoms that came together to form you , or that cow , or this rock . and that is why , as carl sagan famously told us , we are all made of star stuff .

matter and energy , can neither be created nor destroyed . the universe , to the best of our knowledge , is an isolated system . but before we get to that , let 's look at a much smaller and simpler one .

explain why the universe must be an isolated system to obey the law of conservation of mass .

conventional wisdom about diets , including government health recommendations , seems to change all the time . and yet , ads routinely come about claiming to have the answer about what we should eat . so how do we distinguish what 's actually healthy from what advertisers just want us to believe is good for us ? marketing takes advantage of the desire to drop weight fast , and be stronger , slimmer , and brighter . and in the big picture , diet plans promising dramatic results , known as fad diets , are just what they seem : too good to be true . so where do diet fads even come from ? while the ancient greeks and romans rallied behind large-scale health regimens centuries earlier , this phenomenon began in earnest in the victorian era with crazes like the vinegar diet and the banting diet . since then , diets have advised us all sorts of things : to excessively chew , to not chew at all , to swallow a grapefruit per meal , non-stop cabbage soup , even consumption of arsenic , or tapeworms . if the idea of diet crazes has withstood history , could this mean that they work ? in the short term , the answer is often yes . low-carbohydrate plans , like the popular atkins or south beach diets , have an initial diuretic effect . sodium is lost until the body can balance itself out , and temporary fluid weight loss may occur . with other high-protein diets , you might lose weight at first since by restricting your food choices , you are dropping your overall calorie intake . but your body then lowers its metabolic rate to adjust to the shift , lessening the diet 's effect over time and resulting in a quick reversal if the diet is abandoned . so while these diets may be alluring early on , they do n't guarantee long-term benefits for your health and weight . a few simple guidelines , though , can help differentiate between a diet that is beneficial in maintaining long-term health , and one that only offers temporary weight changes . here 's the first tipoff : if a diet focuses on intensely cutting back calories or on cutting out entire food groups , like fat , sugar , or carbohydrates , chances are it 's a fad diet . and another red flag is ritual , when the diet in question instructs you to only eat specific foods , prescribed combinations , or to opt for particular food substitutes , like drinks , bars , or powders . the truth is shedding pounds in the long run simply does n't have a quick-fix solution . not all diet crazes tout weight loss . what about claims of superfoods , cleanses , and other body-boosting solutions ? marketing emphasizes the allure of products associated with ancient and remote cultures to create a sense of mysticism for consumers . while so-called superfoods , like blueberries or açaí , do add a powerful punch of nutrients , their super transformative qualities are largely exaggeration . they are healthy additions to a balanced diet , yet often , they 're marketed as part of sugary drinks or cereals , in which case the negative properties outweight the benefits . cleanses , too , may be great in moderation since they can assist with jumpstarting weight loss and can increase the number of fresh fruits and vegetables consumed daily . scientifically speaking , though , they 've not yet been shown to have either a long-term benefit or to detox the body any better than the natural mechanisms already in place . everywhere we look , we 're offered solutions to how we can look better , feel fitter , and generally get ahead . food is no exception , but advice on what we should eat is best left to the doctors and nutritionists who are aware of our individual circumstances . diets and food fads are n't inherently wrong . circumstantially , they might even be right , just not for everyone all of the time .

in the short term , the answer is often yes . low-carbohydrate plans , like the popular atkins or south beach diets , have an initial diuretic effect . sodium is lost until the body can balance itself out , and temporary fluid weight loss may occur .

how do low-carbohydrate diets cause initial weight loss ?

sea turtles are miraculous . first , they 've been around since the late jurassic , roughly 150 million years ago . cohorts of the dinosaurs , sea turtles have survived through the challenges of eons , existing still today , where many others have ended their evolutionary run . second , throughout the centuries and up till today , every living adult sea turtle has overcome the odds , existing as a consequence of chance , skill , and capability . the gauntlet each sea turtle faces in the course of its lifetime goes thus : first , deposited as a clutch of leathery , ping-pong ball-sized eggs into a nesting pit dug by its mother high on the beach , of the 50 to 200 eggs laid , roughly 20 percent will never hatch . roughly a month and a half after having been laid , the surviving eggs hatch , and the young turtles , each small enough to fit in the palm of your hand , squirm to the surface , emerging from the sand en masse , and making their desperate dash for the sea . along the way , debris , pitfalls , crabs , gulls , raccoons , and other threats will claim roughly 50 percent of those who rose from the sand . for those that actually reach the surf , they trade one set of threats for another , as they first face the repelling force of the waves , and then find a whole new host of predators awaiting them : various fish , dolphins , sharks , and sea birds , as the young turtles come to the surface for air . for their first few days of life , should they count themselves amongst the living , the vulnerable turtles swim frantically forward . ultimately , they will often look to settle in a patch of flotsam , preferably a patch of floating seaweed . now for the next several months , they will seek to avoid those that would eat them , find that which they might eat themselves , and not fall to the pressures of challenging weather or unfortunate currents . in this phase , roughly 50 percent of those who reach the surf will perish . ultimately , with the passage of years , the survivors will increase in size , from that of a dinner plate at year one to that of a dinner table , in the case of one species at least , the leatherback , a decade or so later . with size comes some measure of protection . the only truly worrisome predators now are some of the larger shark species -- bulls , tigers , and whites -- and the occasional killer whale . at approximately two decades of age , the survivors will be old enough themselves to breed , and continue the cycle which their very existence heralds . of those that began as eggs on a distant beach , now less than 10 percent remain , at least , those were the odds prior to significant human interference . over the past century , and in particular in the last several decades , human endeavors , from beach development to plastic refuse to poaching , long lines , nets , and even noxious chemicals , including oil , have upped the ante for sea turtles , causing their survival rate to drop to around one percent or less , from each nesting cycle . it is this added human pressure which has pushed each of the eight sea turtle species into either a threatened or endangered state . for while they have evolved to overcome a host of obstacles , the most recent has arisen so quickly and at such scale that the species find themselves overwhelmed . so let 's quickly recap this cycle of odds . using a hypothetical nesting season , for females may nest multiple times in a single year , of 1,000 eggs , for sake of ease . 1000 eggs laid . 800 hatch . 400 make it to the water . 200 progress toward adulthood . 20 survive to breeding age -- that is , without human interference . two survive to breeding age with human interference . so a breeding adult sea turtle is the very embodiment of a long shot . it is the exception , not the rule . a jackpot . it is , in a very real sense , a miracle .

of those that began as eggs on a distant beach , now less than 10 percent remain , at least , those were the odds prior to significant human interference . over the past century , and in particular in the last several decades , human endeavors , from beach development to plastic refuse to poaching , long lines , nets , and even noxious chemicals , including oil , have upped the ante for sea turtles , causing their survival rate to drop to around one percent or less , from each nesting cycle . it is this added human pressure which has pushed each of the eight sea turtle species into either a threatened or endangered state . for while they have evolved to overcome a host of obstacles , the most recent has arisen so quickly and at such scale that the species find themselves overwhelmed .

human influence on sea turtle populations has caused their survival rate to drop to nearly 1 % from each nesting cycle . what factor contributes to this decline ?

translator : andrea mcdonough reviewer : jessica ruby in the 11th and 12th centuries , most english commoners were illiterate . since they had no way to learn the bible , the clergy came up with an inventive solution : they 'd create plays out of certain bible stories so even people who could n't read could learn them . these were called mystery plays because they revealed the mystery of god 's word . at about the same time , the clergy also developed plays about the saints of the church , called miracle plays . in the beginning , the clergy members acted out bible stories on the steps outside the cathedral . the audience reacted so well that soon they needed to move out to the street around the town square . by building moving carts to put on each play and by lining up one after the other , they could put on cycles of stories , which would take the viewer from genesis to revelation . these movable carts , called pageants , looked like huge boxes on wheels . each was two stories tall . the bottom story was curtained off and was used for costumes , props , and dressing . the top platform was the stage for the performance . spectators assembled in various corners of the town , and the pageant would move around in the cycle until the villagers had seen the entire series . soon , the plays required more actors than the clergy could supply . so , by the 13th century , different guilds were asked to be responsible for acting out different parts of the cycle . the assignments were meant to reflect the guilds ' professions . for example , the carpenter 's guild might put on the story of noah 's ark , and the baker 's guild might put on the last supper . can you imagine what might happen to the story if the butcher 's guild put on the crucifixion of christ ? yes , without the clergy , the plays soon started changing from their true bible stories . by the end of the 14th century , a new form of drama , called the morality play , had evolved . faith , truth , charity , and good deeds all became characters on the stage . and , at the same time , the opposite virtues of falsehood , covetousness , worldly flesh , and the devil became the antagonists . the morality plays were allegorical stories in which these characters battled for the control of the soul . audiences loved the immoral characters , and spectators were encouraged to interact with the actors . throwing rotten food and even getting into scuffles with other spectators became very common . the character of the devil often would roam through the crowds and pull unsuspecting watchers into a hell that was depicted as a dragon 's mouth . the virtuous biblical stories had morphed into crude and sometimes comic stories . the clergy intended to teach against immorality . how ironic , then , that the morality plays actually encouraged vices as more popular than virtues . by the mid-15th century , the church started to outlaw these performances . town charters required that any theater must be built outside the city wall . one of the first theaters was built like a larger version of a pageant , with tiers of gallery seating encircling a grassy area in front of the stage . sound familiar ? a young william shakespeare developed his craft here at the theater that was eventually renamed the globe . the medieval morality play had led to renaissance playwrights who were inspired by the inner struggles and the conscience of man . and that , in essence , is how drama emerged as a literary art form .

by the mid-15th century , the church started to outlaw these performances . town charters required that any theater must be built outside the city wall . one of the first theaters was built like a larger version of a pageant , with tiers of gallery seating encircling a grassy area in front of the stage .

what were the reasons the drama had to be taken outside the city wall ?

imagine you 're asked to invent something new . it could be whatever you want made from anything you choose in any shape or size . that kind of creative freedom sounds so liberating , does n't it ? or does it ? if you 're like most people , you 'd probably be paralyzed by this task . without more guidance , where would you even begin ? as it turns out , boundless freedom is n't always helpful . in reality , any project is restricted by many factors , such as the cost , what materials you have at your disposal , and unbreakable laws of physics . these factors are called creative constraints , and they 're the requirements and limitations we have to address in order to accomplish a goal . creative constraints apply across professions , to architects and artists , writers , engineers , and scientists . in many fields , constraints play a special role as drivers of discovery and invention . during the scientific process in particular , constraints are an essential part of experimental design . for instance , a scientist studying a new virus would consider , `` how can i use the tools and techniques at hand to create an experiment that tells me how this virus infects the body 's cells ? and what are the limits of my knowledge that prevent me from understanding this new viral pathway ? '' in engineering , constraints have us apply our scientific discoveries to invent something new and useful . take , for example , the landers viking 1 and 2 , which relied on thrusters to arrive safely on the surface of mars . the problem ? those thrusters left foreign chemicals on the ground , contaminating soil samples . so a new constraint was introduced . how can we land a probe on mars without introducing chemicals from earth ? the next pathfinder mission used an airbag system to allow the rover to bounce and roll to a halt without burning contaminating fuel . years later , we wanted to send a much larger rover : curiosity . however , it was too large for the airbag design , so another constraint was defined . how can we land a large rover while still keeping rocket fuel away from the martian soil ? in response , engineers had a wild idea . they designed a skycrane . similar to the claw machine at toy stores , it would lower the rover from high above the surface . with each invention , the engineers demonstrated an essential habit of scientific thinking - that solutions must recognize the limitations of current technology in order to advance it . sometimes this progress is iterative , as in , `` how can i make a better parachute to land my rover ? '' and sometimes , it 's innovative , like how to reach our goal when the best possible parachute is n't going to work . in both cases , the constraints guide decision-making to ensure we reach each objective . here 's another mars problem yet to be solved . say we want to send astronauts who will need water . they 'd rely on a filtration system that keeps the water very clean and enables 100 % recovery . those are some pretty tough constraints , and we may not have the technology for it now . but in the process of trying to meet these objectives , we might discover other applications of any inventions that result . building an innovative water filtration system could provide a solution for farmers working in drought-stricken regions , or a way to clean municipal water in polluted cities . in fact , many scientific advances have occurred when serendipitous failures in one field address the constraints of another . when scientist alexander fleming mistakenly contaminated a petri dish in the lab , it led to the discovery of the first antibiotic , penicillin . the same is true of synthetic dye , plastic , and gunpowder . all were created mistakenly , but went on to address the constraints of other problems . understanding constraints guides scientific progress , and what 's true in science is also true in many other fields . constraints are n't the boundaries of creativity , but the foundation of it .

those are some pretty tough constraints , and we may not have the technology for it now . but in the process of trying to meet these objectives , we might discover other applications of any inventions that result . building an innovative water filtration system could provide a solution for farmers working in drought-stricken regions , or a way to clean municipal water in polluted cities .

all of the following inventions were discovered accidentally except :

in 1978 , louise brown became the world 's first baby to be born by in vitro fertilization , or ivf . her birth revolutionized the field of reproductive medicine . given that approximately one in eight heterosexual couples has difficulty conceiving , and that homosexual couples and single parents often need clinical help to make a baby , the demand for ivf has been growing . ivf is so common , that more than 5 million babies have been born through this technology . ivf works by mimicking the brilliant design of sexual reproduction . in order to understand ivf , we first need to take a look at the natural process of baby making . believe it or not , it all starts in the brain . roughly fifteen days before fertilization can happen , the anterior pituitary gland secretes follicle stimulating hormone , fsh , which ripens a handful of follicles of the ovary that then release estrogen . each follicle contains one egg , and on average , only one follicle becomes fully mature . as it grows and continues to release estrogen , this hormone not only helps coordinate growth and preparation of the uterus , it also communicates to the brain how well the follicle is developing . when the estrogen level is high enough , the anterior pituitary releases a surge of luteinizing hormone , lh , which triggers ovulation and causes the follicle to rupture and release the egg . once the egg leaves the ovary , it is directed into the fallopian tube by the finger-like fimbriae . if the egg is not fertilized by sperm within 24 hours , the unfertilized egg will die , and the entire system will reset itself , preparing to create a new egg and uterine lining the following month . the egg is the largest cell in the body and is protected by a thick , extracellular shell of sugar and protein called the zona pellucida . the zona thwarts the entry and fusion of more than one sperm , the smallest cell in the body . it takes a man two to three months to make sperm , and the process constantly renews . each ejaculation during sexual intercourse releases more than 100 million sperm . but only 100 or so will ultimately make it to the proximity of the egg , and only one will successfully penetrate through the armor of the zona pellucida . upon successful fertilization , the zygote immediately begins developing into an embryo , and takes about three days to reach the uterus . there , it requires another three or so days to implant firmly into the endometrium , the inner lining of the uterus . once implanted , the cells that are to become the placenta secrete a hormone that signals to the ovulated follicle that there is a pregnancy in the uterus . this helps rescue that follicle , now called the corpus luteum , from degenerating as it normally would do in that stage of the menstrual cycle . the corpus luteum is responsible for producing the progesterone required to maintain the pregnancy until six to seven weeks of gestation , when the placenta develops and takes over , until the baby is born approximately 40 weeks later . now , how do you make a baby in a lab ? in patients undergoing ivf , fsh is administered at levels that are higher than naturally occuring to cause a controlled overstimulation of the ovaries so that they ultimately produce multiple eggs . the eggs are then retrieved just before ovulation would occur , while the woman is under anesthesia , through an aspirating needle that is guided by ultrasound . most sperm samples are produced by masturbation . in the laboratory , the identified eggs are stripped of surrounding cells and prepared for fertilization in a petri dish . fertilization can occur by one of two techniques . in the first , the eggs are incubated with thousands of sperm and fertilization occurs naturally over a few hours . the second technique maximizes certainty of fertilization by using a needle to place a single sperm inside the egg . this is particularly useful when there is a problem with the quality of the sperm . after fertilization , embryos can be further screened for genetic suitability , frozen for later attempted pregnancies , or delivered into the woman 's uterus via catheter . common convention is to transfer the embryo three days after fertilization , when the embryo has eight cells , or on day five , when the embryo is called a blastocyst , and has hundreds of cells . if the woman 's eggs are of poor quality due to age or toxic exposures , or have been removed due to cancer , donor eggs may be used . in the case that the intended mother has a problematic uterus , or lacks one , another woman , called the gestational carrier or surrogate , can use her uterus to carry the pregnancy . to increase the odds of success , which are as high as 40 % for a woman younger than 35 , doctors sometimes transfer multiple embryos at once , which is why ivf results in twins and triplets more often than natural pregnancies . however , most clinics seek to minimize the chances of multiple pregnancies , as they are riskier for mothers and babies . millions of babies , like louise brown , have been born from ivf and have had normal , healthy lives . the long-term health consequences of ovarian stimulation with ivf medicines are less clear , though so far , ivf seems safe for women . because of better genetic testing , delayed childbearing , increased accessibility and diminishing cost , it 's not inconceivable that artificial baby making via ivf and related techniques could outpace natural reproduction in years to come .

in the laboratory , the identified eggs are stripped of surrounding cells and prepared for fertilization in a petri dish . fertilization can occur by one of two techniques . in the first , the eggs are incubated with thousands of sperm and fertilization occurs naturally over a few hours . the second technique maximizes certainty of fertilization by using a needle to place a single sperm inside the egg . this is particularly useful when there is a problem with the quality of the sperm .

when the male partner has poor sperm quality , _____ is used to assist in fertilization of the egg .

for the microscopic lab worm , c. elegans life equates to just a few short weeks on earth . compare that with the tortoise , which can age to more than 100 years . mice and rats reach the end of their lives after just four years , while for the bowhead whale , earth 's longest-lived mammal , death can come after 200 . like most living things , the vast majority of animals gradually degenerate after reaching sexual maturity in the process known as aging . but what does it really mean to age ? the drivers behind this process are varied and complicated , but aging is ultimately caused by cell death and dysfunction . when we 're young , we constantly regenerate cells in order to replace dead and dying ones . but as we age , this process slows down . in addition , older cells do n't perform their functions as well as young ones . that makes our bodies go into a decline , which eventually results in disease and death . but if that 's consistently true , why the huge variance in aging patterns and lifespan within the animal kingdom ? the answer lies in several factors , including environment and body size . these can place powerful evolutionary pressures on animals to adapt , which in turn makes the aging process different across species . consider the cold depths of the atlantic and arctic seas , where greenland sharks can live to over 400 years , and the arctic clam known as the quahog can live up to 500 . perhaps the most impressive of these ocean-dwelling ancients is the antarctic glass sponge , which can survive over 10,000 years in frigid waters . in cold environments like these , heartbeats and metabolic rates slow down . researchers theorize that this also causes a slowing of the aging process . in this way , the environment shapes longevity . when it comes to size , it 's often , but not always , the case that larger species have a longer lifespan than smaller ones . for instance , an elephant or whale will live much longer than a mouse , rat , or vole , which in turn have years on flies and worms . some small animals , like worms and flies , are also limited by the mechanics of their cell division . they 're mostly made up of cells that ca n't divide and be replaced when damaged , so their bodies expire more quickly . and size is a powerful evolutionary driver in animals . smaller creatures are more prone to predators . a mouse , for instance , can hardly expect to survive more than a year in the wild . so , it has evolved to grow and reproduce more rapidly , like an evolutionary defense mechanism against its shorter lifespan . larger animals , by contrast , are better at fending off predators , and so they have the luxury of time to grow to large sizes and reproduce multiple times during their lives . exceptions to the size rule include bats , birds , moles , and turtles , but in each case , these animals have other adaptations that allow them to escape predators . but there are still cases where animals with similar defining features , like size and habitat , age at completely different rates . in these cases , genetic differences , like how each organism 's cells respond to threats , often account for the discrepancies in longevity . so it 's the combination of all these factors playing out to differing degrees in different animals that explains the variability we see in the animal kingdom . so what about us ? humans currently have an average life expectancy of 71 years , meaning that we 're not even close to being the longest living inhabitants on earth . but we are very good at increasing our life expectancy . in the early 1900s , humans only lived an average of 50 years . since then , we 've learned to adapt by managing many of the factors that cause deaths , like environmental exposure and nutrition . this , and other increases in life expectancy make us possibly the only species on earth to take control over our natural fate .

these can place powerful evolutionary pressures on animals to adapt , which in turn makes the aging process different across species . consider the cold depths of the atlantic and arctic seas , where greenland sharks can live to over 400 years , and the arctic clam known as the quahog can live up to 500 . perhaps the most impressive of these ocean-dwelling ancients is the antarctic glass sponge , which can survive over 10,000 years in frigid waters .

how long have arctic glass sponges been estimated to live ?

[ music ] science is coming . [ music ] the game of thrones universe is one of the most brilliantly complex and utterly frustrating fictional universes ever created . but it is a fictional universe , and the only rule of a fictional universe is that it is self-consistent . it does n't have to agree with our science , or logic , or even our commonly agreed-upon moral code that says killing people is not a good thing . there is only one god in that universe , and his name is gurm . but despite that , many things in game of thrones can be linked to the real , actual world , drawing inspiration as if through the thirsty roots of a weirwood tree . many of these connections are interpreted by fans , but some have been verified by the bearded one himself . there are the many competing religious philosophies , the many , many , many similarities to real-life historical characters or the fact that they look like us ? but we are not going to be talking about those ... here 's where i would give you a spoilers warning , but . . . come on . you clicked on this . spoilers are coming . why are the seasons so crazy ? in the game of thrones universe winters and summers are known to last years at a time and apparently show up when they damn well please . we know that the summer/winter cycle normally averages around 5 or 6 years apiece , and as the story begins the most recent summer has stretched to nearly ten years . on earth , seasons are caused by our axial tilt leaning one side of earth toward or away from the sun during our annual trip around it , but george 's world is n't so predictable . the maesters of the citadel are the geeks of westeros , who are supposed to calculate when the next polar doom will arrive . westeros is n't an industrial society , but the architecture , metallurgy , and medicine we see in the known world suggests that these guys are a fairly scientific bunch . many theories have attempted to explain the reason for these seasons , but most of them collapse faster than a greyjoy 's loyalty . we know that the westeros-ian world has a moon , and that it used to have two . maybe their moon is n't as large as ours so the planet 's axis , unstabilized by lunar gravity , wobbles like a broken top . but , according to astronomers , moons do n't stabilize planets , rather a moonless planet should spin more evenly than one with a moon . then what if its orbit , instead of a nearly circular ellipse , like ours , was extremely elongated ? well that does n't work either . while it could cause extreme seasons , they 'd still show up on a regular schedule . even complex combinations of orbital stretches and wobbles , like earth 's milankovitch cycles , could be predicted by any society that knows basic algebra . well , then maybe it 's tugged on by the gravity of a neighboring planet , or its sun has a variable output . george r.r . martin did write his first novel about a planet falling away from its parent star . it 's most likely that the game of thrones planet . . . it needs a name . planet hodor ! lives in a very strange solar system , around a pair of stars . last april , a group of graduate students from johns hopkins university published a paper showing that if the world of game of thrones was subject to the complex dynamics of three celestial bodies orbiting each other , predicting a planet 's seasons would be impossible . this has interesting implications for tatooine . . ? of course , it could also be due to magic , which is cheating . and what about that world anyway ? at the amazing planetary science blog generation anthropocene , miles traer and mike osborne have constructed a detailed geologic history of westeros stretching back more than 500 million years into the fictional past . they determined that , since the north is cold enough to maintain a wall of ice , which we 'll come back to , year-round , it must be near this planet 's arctic circle , and since the south is warm enough to be covered by deserts , which primarily exist near earth 's 30th parallel that planet hodor has a radius of 4,297 miles or about 10 % wider than earth . we know that the first men crossed into westeros on a land bridge near dorne , and like africa and south america , the coastlines of westeros and essos seem to fit like puzzle pieces . they were probably unzipped beginning 25 million years ago by a spreading rift , like the one in the middle of our atlantic ocean . and 40 million years ago , westeros was likely covered by a huge ice sheet , which retreated as glaciers , cutting the great valleys south of winterfell and the riverlands between harrenhal and the twins . the description of the jagged black mountains sounds a lot like our own rocky mountains , which were born around 60-80 million years ago . this would also mark the birth of the mountains of the moon and the high westerlands , as north and south westeros smashed together just like the fault beneath the himalayas . that violent uplift is what exposed all that lannister gold from its origin deep within the crust . that era also would have borne the iron islands . . . but we have a different iron to talk about . valyrian steel was an alloy forged in the ancient empire of the valyrians , lighter and stronger than regular steel , and whose secrets were lost during the great doom , when volcanoes torched valyria , and its dragons , into charcoal . that valyrian steel was forged with dragon fire , which is not actually a thing , but it 's almost certainly a reference to damscus steel , an ancient steel alloy developed in india around 300 bc . like valyrian steel , the secrets of its forgery were lost to history forever . speaking of dragon fire . . . what if dragons could exist ? how could a living thing breathe flames ? my buddy kyle hill came up with an interesting theory . like the tiny bombardier beetle , dragons could secrete reactive `` hypergolic '' chemicals that , when mixed , react violently and shoot out of an orifice like rocket fuel . and if dragons chewed on certain rocks and metals , which i imagine are like cupcakes to them , they could coat their teeth in minerals , creating a spark with rows of deadly knife-like flint and steel . unfortunately , our idea of a fire-breathing flying dragon is about to come crashing back down to earth , because physics . as bran stark found out the hard way , gravity seems to work in westeros just like it does here . and that means the mother of dragons ' kids are grounded . the largest bird that ever lived was the giant teratorn , with a wingspan of 7 meters . not big enough . dragons are probably more like pterosaurs . but even the largest of those , quetzalcoatlus , maxed out at 11 meters from wingtip to wingtip and 250 kg . but daenarys ' dragons are bigger than that by the time they hit puberty , and dragon lore says they never stop growing . even with a pterosaur 's hollow bones , ability to gallop on all fours to take off and huge stretchy wings , even hodor could figure out that the dragons do n't work . unless , yeah . . . magic . the wall ? wo n't work . a sheer cliff of solid ice stacked 700 feet tall would melt at the bottom under its own weight and would fall apart unless it was sloped wildfire ? works . `` greek fire '' was an ancient precursor to napalm made from petroleum , sulfur , saltpeter and was the most potent weapon of its time . add a little trimethyl borate , and you 've got a flaming death that 's ready for st. patrick 's day . milk of poppy ? works . our opiate drugs from morphine to vicodin to even heroin are all derived from the poppy plant . dire wolf ? works . the extinct canis dirus was the largest wolf to ever exist , covering north and south america , thousands have been found in the la brea tar pits alone . of course , the universe of game of thrones would live . . . or die . . . just fine whether or not it agrees with our science . but by combining the two , as raymond chandler said , the truth of art keeps science from becoming inhuman , and the truth of science keeps art from becoming ridiculous what do you think ? does bringing science into a fantasy story kill the wonder like a guest at the red wedding ? or does it help the fictional world . . . truly `` exist '' in our own ? i think it makes the story richer than a lannister . let me know what you think in the comments . and remember , a hanson always pay their debts . subscribe , and i will pay you back with a new video every week . valar morcurious .

we know that the summer/winter cycle normally averages around 5 or 6 years apiece , and as the story begins the most recent summer has stretched to nearly ten years . on earth , seasons are caused by our axial tilt leaning one side of earth toward or away from the sun during our annual trip around it , but george 's world is n't so predictable . the maesters of the citadel are the geeks of westeros , who are supposed to calculate when the next polar doom will arrive .

on earth , what causes our seasons to change ?

space : it 's where things happen . time : it 's when things happen . we can measure where things are and when things take place , but in modern physics , we realize when and where are actually part of the same question . because when it comes to understanding the universe , we need to replace three-dimensional space plus time with a single concept : four-dimensional space-time . we 'll explore and explain space-time in this series of animations . animations ? yeah . well , we 're not very animated are we ? sure we are ! look , i can go from here to here . whoa ! how 'd you get from here to there ? how fast did you go ? did you run ? walk ? did you even go in a straight line ? ah ! to answer that , you 'll need to make our cartoon physics look more like physics physics . you 'll need more panels . more panels , please ! okay , in each panel , andrew 's in a slightly different place . so i can see each one records where andrew is at a different time . that 's great . but it would be easier to see what 's going on if we could cut out all the hundreds of panels and stack them up like a flip book . right , now let 's flip through the book so that we can see one panel after another getting through 24 in every second . see ! i told you it was an animation . now you can see me walking along . drawing all those panels and putting them into a flip book is just one way of recording the way i 'm moving . it 's how animation , or even movies , work . as it turns out , at my walking speed , it takes two seconds to get past each fence post , and they 're spaced four meters apart . so we can calculate my velocity -- how fast i 'm moving through space - - is two meters per second . but i could 've worked that out from the panels without flipping through them . from the edge of the flip book , you can see all of the copies of the fence posts and all of the copies of andrew and he 's in a slightly different place in each one . now we can predict everything that will happen to andrew when we flip through 24 pages every second , including his speed of motion , just by looking . no need to flip through at all . the edge of this flip book is known as a space-time diagram of andrew 's journey through , you guessed it , space and time . we call the line that represents andrew 's journey his world line . if i jog instead of walking , i might be able to get past a fence post every second . he 's not very athletic . anyway , when we look at this new flip book from the edge , we can do the same analysis as before . the world line for andrew jogging is more tilted over than the world line for andrew walking . we can tell he 's going twice as fast as before without flipping the panels . but here 's the clever bit . in physics , it 's always good to view things from other perspectives . after all , the laws of physics should be the same for everyone or no one will obey them . so let 's rethink our cartoon and have the camera follow andrew jogging along as the fence posts approach and pass behind him . still viewing it as a flip book of panels , we do n't need to redraw anything . we simply move all of the cutout frames slightly until andrew 's tilted world line becomes completely vertical . to see why , let 's flip it . yes , now i 'm stationery , just jogging on the spot , in the center of the panel . on the edge of the flip book , my world line was going straight upwards . the fence posts are coming past me . it 's now their world lines that are tilted . this rearrangement of the panels is known as a galilean transformation , and it lets us analyze physics from someeone else 's perspective . in this case , mine . after all , it 's always good to see things from other points of view , especially when the viewers are moving at different speeds . so long as the speeds are n't too high . if you 're a cosmic ray moving at the speed of light , our flip book of your point of view falls apart . to stop that from happening , we 'll have to glue panels together . instead of a stack of separate panels , we 'll need a solid block of space-time , which we 'll come to in the next animation .

you 'll need more panels . more panels , please ! okay , in each panel , andrew 's in a slightly different place .

to create a flipbook from a stack of panels such that the camera follows a moving object we must :

what is the shape of a molecule ? well , a molecule is mostly empty space . almost all of its mass is concentrated in the extremely dense nuclei of its atoms . and its electrons , which determine how the atoms are bonded to each other , are more like clouds of negative charge than individual , discrete particles . so , a molecule does n't have a shape in the same way that , for example , a statue has a shape . but for every molecule , there 's at least one way to arrange the nuclei and electrons so as to maximize the attraction of opposite charges and minimize the repulsion of like charges . now , let 's assume that the only electrons that matter to a molecule 's shape are the outermost ones from each participating atom . and let 's also assume that the electron clouds in between atoms , in other words , a molecule 's bonds , are shaped kind of like sausages . remember that nuclei are positively charged and electrons are negatively charged , and if all of a molecule 's nuclei were bunched up together or all of its electrons were bunched up together , they would just repel each other and fly apart , and that does n't help anyone . in 1776 , alessandro volta , decades before he would eventually invent batteries , discovered methane . now , the chemical formula of methane is ch4 . and this formula tells us that every molecule of methane is made up of one carbon and four hydrogen atoms , but it does n't tell us what 's bonded to what or how they atoms are arranged in 3d space . from their electron configurations , we know that carbon can bond with up to four other atoms and that each hydrogen can only bond with one other atom . so , we can guess that the carbon should be the central atom bonded to all the hydrogens . now , each bond represents the sharing of two electrons and we draw each shared pair of electrons as a line . so , now we have a flat representation of this molecule , but how would it look in three dimensions ? we can reasonably say that because each of these bonds is a region of negative electric charge and like charges repel each other , the most favorable configuration of atoms would maximize the distance between bonds . and to get all the bonds as far away from each other as possible , the optimal shape is this . this is called a tetrahedron . now , depending on the different atoms involved , you can actually get lots of different shapes . ammonia , or nh3 , is shaped like a pyramid . carbon dioxide , or co2 , is a straight line . water , h2o , is bent like your elbow would be bent . and chlorine trifluoride , or clf3 , is shaped like the letter t. remember that what we 've been doing here is expanding on our model of atoms and electrons to build up to 3d shapes . we 'd have to do experiments to figure out if these molecules actually do have the shapes we predict . spoiler alert : most of the do , but some of them do n't . now , shapes get more complicated as you increase the number of atoms . all the examples we just talked about had one obviously central atom , but most molecules , from relatively small pharmaceuticals all the way up to long polymers like dna or proteins , do n't . the key thing to remember is that bonded atoms will arrange themselves to maximize the attraction between opposite charges and minimize the repulsion between like charges . some molecules even have two or more stable arrangements of atoms , and we can actually get really cool chemistry from the switches between those configurations , even when the composition of that molecule , that 's to say the number and identity of its atoms , has not changed at all .

so , now we have a flat representation of this molecule , but how would it look in three dimensions ? we can reasonably say that because each of these bonds is a region of negative electric charge and like charges repel each other , the most favorable configuration of atoms would maximize the distance between bonds . and to get all the bonds as far away from each other as possible , the optimal shape is this .

phosphorus pentafluoride ( pf5 ) consists of a central phosphorus atom bonded to five fluorine atoms . you know that ch4 is tetrahedral . what arrangement of the fluorine atoms around phosphorus would maximize the distance between all five p—f bonds ?

you 're facing a giant bowl of energy packed carbon crunchies . one spoonful . two . three . soon , you 're powered up by the energy surge that comes from your meal . but how did that energy get into your bowl ? energy exists in the form of sugars made by the plant your cereal came from , like wheat or corn . as you can see , carbon is the chemical backbone , and plants get their fix of it in the form of carbon dioxide , co2 , from the air that we all breath . but how does a plant 's energy factory , housed in the stroma of the chloroplast , turn a one carbon gas , like co2 , into a six carbon solid , like glucose ? if you 're thinking photosynthesis , you 're right . but photosynthesis is divided into two steps . the first , which stores energy from the sun in the form of adenosine triphosphate , or atp . and the second , the calvin cycle , that captures carbon and turns it into sugar . this second phase represents one of nature 's most sustainable production lines . and so with that , welcome to world 's most miniscule factory . the starting materials ? a mix of co2 molecules from the air , and preassembled molecules called ribulose biphosphate , or rubp , each containing five carbons . the initiator ? an industrious enzyme named rubisco that welds one carbon atom from a co2 molecule with the rubp chain to build an initial six carbon sequence . that rapidly splits into two shorter chains containing three carbons each and called phosphoglycerates , or pgas , for short . enter atp , and another chemical called nicotinamide adenine dinucleotide phosphate , or just nadph . atp , working like a lubricant , delivers energy , while nadph affixes one hydrogen to each of the pga chains , changing them into molecules called glyceraldehyde 3 phosphates , or g3ps . glucose needs six carbons to form , made from two molecules of g3p , which incidentally have six carbons between them . so , sugar has just been manufactured , right ? not quite . the calvin cycle works like a sustainable production line , meaning that those original rubps that kicked things off at the start , need to be recreated by reusing materials within the cycle now . but each rubp needs five carbons and manufacturing glucose takes a whole six . something does n't add up . the answer lies in one phenomenal fact . while we 've been focusing on this single production line , five others have been happening at the same time . with six conveyor belts moving in unison , there is n't just one carbon that gets soldered to one rubp chain , but six carbons soldered to six rubps . that creates 12 g3p chains instead of just two , meaning that all together , 36 carbons exist : the precise number needed to manufacture sugar , and rebuild those rubps . of the 12 g3ps pooled together , two are siphoned off to form that energy rich six carbon glucose chain . the one fueling you via your breakfast . success ! but back on the manufacturing line , the byproducts of this sugar production are swiftly assembled to recreate those six rubps . that requires 30 carbons , the exact number contained by the remaining 10 g3ps . now a molecular mix and match occurs . two of the g3ps are welded together forming a six carbon sequence . by adding a third g3p , a nine carbon chain is built . the first rubp , made up of five carbons , is cast from this , leaving four carbons behind . but there 's no wastage here . those are soldered to a fourth g3p molecule , making a seven carbon chain . added to a fifth g3p molecule , a ten carbon chain is created , enough now to craft two more rubps . with three full rubps recreated from five of the ten g3ps , simply duplicating this process will renew the six rubp chains needed to restart the cycle again . so the calvin cycle generates the precise number of elements and processes required to keep this biochemical production line turning endlessly . and it 's just one of the 100s of cycles present in nature . why so many ? because if biological production processes were linear , they would n't be nearly as efficient or successful at using energy to manufacture the materials that nature relies upon , like sugar . cycles create vital feedback loops that repeatedly reuse and rebuild ingredients crafting as much as possible out of the planet 's available resources . such as that sugar , built using raw sunlight and carbon converted in plant factories to become the energy that powers you and keeps the cycles revolving in your own life .

so the calvin cycle generates the precise number of elements and processes required to keep this biochemical production line turning endlessly . and it 's just one of the 100s of cycles present in nature . why so many ?

cycles are beneficial in living systems because :

tens of millions of years ago , a force of nature set two giant masses on an unavoidable collision course that would change the face of the earth and spell life or death for thousands of species . the force of nature was plate tectonics , and the bodies were north and south america . and even though they were hurdling towards each other at an underwhelming 2.5 cm per year , their collision actually did have massive biological reprocussions by causing one of the greatest episodes of biological migration in earth 's history : the great american biotic interchange . our story begins 65 million years ago , the beginning of the age of mammals , when what is now north and south america were continents separated by a marine connection between the pacific and atlantic oceans . during this time , south america was the home of fauna that included armored glyptodonts as large as compact cars , giant ground sloths weighing more than a ton , opossums , monkeys , and carnivorous terror birds . north america had its own species , such as horses , bears , and saber-toothed cats . over 20 million years , the shifting of the farallon and caribbean plates produced the central america volcanic arc , a peninsula connected to north america , with only a very narrow seaway separating it from south america . as these plates continued to surf the earth 's magma layer far beneath the pacific ocean floor , the caribbean plate migrated eastward , and about 15 million years ago , south america finally collided with this central american arc . this gradually closed the water connection between the pacific and the caribbean , creating a land bridge , which connected north america to south america . terrestrial organisms could now cross between the two continents , and from the fossil records , it 's evident that different waves of their dispersals took place . even though plants do n't physically move , they are easily dispersed by wind and waves , so they migrated first , along with a few species of birds . they were followed by some freshwater fishes and amphibians , and finally , various mammals began to traverse the bridge . from south america , mammals like ground sloths and glyptodonts were widly distributed in north america . moreover , many south american tropical mammals , like monkeys and bats , colonized the forests of central america , and are very abundant today . south american predator marsupials went extinct 3 million years ago , at which point north american predators , such as cats , bears and foxes , migrated south and occupied the ecological space left behind . horses , llamas , tapirs , cougars , saber-toothed cats , gomphotheres , and later humans also headed south across the land bridge . but what happened on land is only half the story . what had been one giant ocean was now two , creating differences in temperature and salinity for the two bodies of water . the isthmus also became a barrier for many marine organisms , like mollusks , crustaceans , foraminifera , bryozoans , and fish , and separated the populations of many marine species . it also allowed the establishment of the thermohaline circulation , a global water conveyor belt , which transports warm water across the atlantic , and influences the climate of the east coast of north america , the west coast of europe , and many other areas . it 's a challenge to track all of the ways the collision of the americas changed the world , but it 's safe to say that the ripples of the great american biotic interchange have propagated through the history of life on the planet , and that of mankind . what if these species had n't gone extinct , or if there were no monkeys in central america , or jaguars in south america ? what if the thermohaline circulation was n't flowing ? would the east coast of north america be much colder ? it all goes to show some of the most impactful transformations of our planet are n't the explosive ones that happen in an instant , but the ones that crawl towards irreversible change . we are the product of history .

the isthmus also became a barrier for many marine organisms , like mollusks , crustaceans , foraminifera , bryozoans , and fish , and separated the populations of many marine species . it also allowed the establishment of the thermohaline circulation , a global water conveyor belt , which transports warm water across the atlantic , and influences the climate of the east coast of north america , the west coast of europe , and many other areas . it 's a challenge to track all of the ways the collision of the americas changed the world , but it 's safe to say that the ripples of the great american biotic interchange have propagated through the history of life on the planet , and that of mankind .

the ocean circulation influences the climate in many areas of the world . what is the relationship between the warm waters of the caribbean and the climate in the east coast of north america and the west coast of europe ?

humans have done a pretty good job of exploring the earth thus far , climbing mountains and crossing continents and planting our flags all over the place in the name of science . but one part of the world that has remained pretty mysterious to us also happens to cover more than 70 % of its surface : the ocean . yes , we ’ ve sailed across it plenty of times . and drilled for oil in it . and managed to create reality shows about fishing in it . but , from glowing oceans to massive deep-sea creatures , and underwater ecosystems with thousands of undiscovered , basically-alien species -- we still have a lot to learn about it . probably more than any place on earth , the ocean is full of fascinating stuff that we just don ’ t know . not yet . [ music playing ] number one : what ’ s the ocean floor like ? fact is , we still don ’ t know exactly what the ocean floor looks like in most places . the national oceanic and atmospheric administration says that 95 % of the ocean 's bottom remains unseen by humans . as a result , we have a way better picture of the surfaces of other planets than we do of most of the seafloor . in 2014 , a team of scientists created a map of the seafloor using data from satellites equipped with special sensors called radar altimeters . these instruments could precisely measure the distance from the satellite to the surface of the ocean below . essentially , any large mountains or canyons on the ocean floor have a slight gravitational effect on the ocean surface , creating bumps and dips , respectively . these variations are of course too subtle to be detected by human eyes , but they can be measured by these ultra-precise satellite altimeters -- and , after adjusting for the effect of waves and tides , tell scientists what ’ s on the seafloor . this map spans the entire ocean floor , which is awesome , and we ’ re all glad that it exists , but it only has a resolution of about 5 kilometers , which is pretty low . by comparison , most of the surface of mars , venus , and the moon have been mapped to resolutions of 100 meters or less . so , if we want to know what ’ s going on down there and really explore the ocean , detecting life , specific mineral formations , or wrecks , we ’ re gon na need a better map . number two : what ’ s under the seafloor ? ok , probably thinking that you know what ’ s down there : rock . yes . but not just rock . in 2015 , scientists reported that they had drilled down about 2 and a half kilometers below the seafloor off the coast of japan , and discovered living microbes . there were only about 10 to 10,000 microorganisms in a cubic centimeter of sediment that they studied , compared to like billions that you ’ d find in the same amount of dirt from your garden . but still : there 's life down there , even in the intense heat and pressure many kilometers below where the ocean stops . and the genomes of these under-sea microbes showed that they were actually more similar to the kind you ’ d find in forest soil , rather than the ones in seafloor sediments . so it ’ s possible that these microbes are descendants of terrestrial ones from 20 million years ago , that just adapted when their habitat began to get buried way beneath the ocean . so , who knows what other kinds of life could exist in deep marine sediments , or what they could tell us about what life on earth used to be like ? number three : brine pools . we ’ ve all seen lakes and rivers on land , but what about lakes that are … underwater ? sounds a little bit unreal , like maybe it ’ s from a sponge bob episode but these features actually exist -- pockets of seawater that have a different composition than the surrounding ocean : because they ’ re super salty . they ’ re known as brine pools , and they seem to have formed when layers of salt from evaporated oceans millions of years ago got buried under layers of sediment . seawater can reach these deposits and mix with the salt , forming a dense brine that flows out of the seafloor , sometimes filled with oils or methane gas . some brine pools , like those found deep in the gulf of mexico , are four times as salty as the ocean water around it . and the brine is so dense that submersibles can even “ float ” on top of it , like a boat on a lake . all of this salt makes brine pools lethal to larger animals . but colonies of halophilic -- or salt-loving -- microorganisms can flourish there , usually in much higher concentrations than the nearby normal seawater . some pools are even lined with mussels that have symbiotic bacteria in their gills , which use the methane in the brine to make energy for the mussels . but there ’ s a ton that we don ’ t know about these weird underwater salt lakes -- like how brine pools can be so different from each other -- and why some have mussels and others don ’ t -- and even how many there are ! number four : milky seas . also known as mareel , this is a phenomenon in which thousands of square kilometers of the ocean ’ s surface glow a brilliant whitish-blue . it lasts for such a short time , and there have been so few recorded sightings , that these glowing seas were thought to be a myth made up by crazy sailors… … until 2005 -- when a group of researchers was studying satellite pictures of a swath of the indian ocean from 1995 . these pictures showed an area of about 15,000 kilometers-square , around the size of connecticut , glowing for 3 nights . it was the first scientific evidence of the phenomenon , but the glowing waters are still not very well understood . some have suggested that the glow is caused by a mass of tiny dinoflagellates called noctiluca scintillans known as “ sea sparkles ” for the way they glow when disturbed . these protists are what cause the picturesque glittering waves along coastlines in some parts of the world . but the 2005 study found that it was “ unlikely , if not impossible ” that the short-lived glowing of dinoflagellates was what scientists had been seeing from space . the prevailing theory these days is that milky seas are caused by massive colonies of bioluminescent bacteria that are growing on top of an algal bloom . but we ’ re still not sure how or why these ephemeral masses of bacteria gather , glow , and disappear . number five : the 52 hertz whale . you ’ d think we would know a lot about whales . i mean , they ’ re big , and we have their skeletons , and we can observe their migratory patterns . but one thing we still have a lot more to learn about is their songs -- from why some whales make them , to how an animal without vocal cords … or lips … manages to make song-like sounds . and then there ’ s this question -- what whale is producing the 52 hertz song , and why ? this whale song was first noted by a technician on december 7th , 1992 in the northeast pacific ocean . it sounded like a blue whale , but blue whale cries usually are somewhere between 15 and 20 hertz in pitch . so , blue whales in the pacific typically sound like this : [ blue whale cry playing ] but this whale song , played at the same speed , sounded like this : [ 52 hertz song playing ] this high-pitch noise seemed to be unique to one animal -- a whale that became known as 52 blue . this raises a lot of questions , and we have to know more about whales to be able to answer some of them , like , why does this one whale sound different ? and can others even hear it ? and if they can hear it , do they understand ? some people latched onto to the idea that 52 blue is a lonely whale crying out to others that might not hear it or wouldn ’ t call back . but several scientists have rejected this lonely narrative , and think that other whales may be able to understand its call , even if they can ’ t make that call themselves . also , 52 blue seems to migrate independently from any other whales . but its migratory patterns do look kind of like those of blue whales -- scientists have been tracking it up and down the north pacific from alaska to mexico for years now . so some researchers think it might have some malformation that has changed how it sings , or maybe it ’ s even a hybrid between a blue whale and another species . whether or not it ’ s a lonely whale , 52 blue is an oddity that people seem to love . number six : upsweep . now , ocean sounds are practically their own field of study , noaa has been monitoring acoustics in the ocean for decades now . instead of microphones , which are used to collect sound in air , noaa uses hydrophones to record underwater sounds . mostly , these hydrophones are used to listen to the ambient sound of the ocean , to see how humans might interfere with it , and to listen for things like earthquakes and whale calls . and sometimes , they record things that are hard to explain , at least for a while . in 1997 , for example , there was what was known as the bloop , an extremely loud , low-frequency sound heard by hydrophones some 5,000 kilometers apart . oceanographers recently determined that it was the result of an icequake -- the cracking and collapse of glaciers into the ocean , in this case on the coast of antarctica . but there ’ s another mystery sound from the ocean , known as upsweep . recorded in august 1991 , it sounds like a repeating “ boop ” that picks up at the end -- sweeping up -- kind of like the “ red alert ” sound effect you hear on spaceships in sci-fi movies . but instead of trying to describe it , i could just play it for you . [ boop playing ] since 1991 , this sound has been heard regularly in the pacific ocean , and it seems to be seasonal , usually becoming more common in spring and fall . researchers have tracked the sound to a part of the pacific that has lots of volcanic and seismic activity , which seem to be important clues . but according to noaa , “ the origin of the sound is unresolved. ” number seven : why are deep-sea creatures so huge ? from the kraken to sea dragons , all of our favorite mythical sea monsters are gigantic . and the fact is , in real life , many deep-sea creatures are unusually huge . this phenomenon is called deep-sea gigantism . but what drives it is … you guessed it ! … unknown ! in the deep sea , and especially near the polar oceans , some animals seem to get really huge -- like colossal squids , giant isopods , and japanese spider crabs . scientists aren ’ t sure why , but they do have some guesses . there ’ s bergmann ’ s rule , for example , which suggests that temperature may influence gigantism . this might be because larger animals have less surface area relative to volume , so they radiate less heat based on their mass and stay warmer in colder climates . and then there ’ s klieber ’ s law , which states that more massive animals generally have lower metabolic rates -- and therefore need less high-quality food -- - to survive . still other theories suggest that gigantism may help organisms resist increased pressure of the deep sea . but we don ’ t really have conclusive biological reasons why these giant creatures exist . so , the ocean is just full o ’ mysteries , maybe because it ’ s so huge and dark and deep . but just so you know that we ’ re not hyping you -- we ’ re not saying that these 7 topics are things that science can ’ t explain . instead , you should just think of them as reminders of how much we still have to learn about the ocean . as our technology improves , and our access to the ocean takes us to new depths , we ’ ll be able to see and hear and sample more stuff than we ever have before . so in time , these puzzles will be solved , and new creatures will be discovered , and our understanding of our planet , and the life on it , will be that much … deeper . thank you for watching this scishow list show , and thanks especially to all of our patrons on patreon who make this show possible . if you want to help us keep making shows like this , you can go to patreon.com/scishow­ . and don ’ t forget to go to youtube.com/scishow and subscribe !

all of this salt makes brine pools lethal to larger animals . but colonies of halophilic -- or salt-loving -- microorganisms can flourish there , usually in much higher concentrations than the nearby normal seawater . some pools are even lined with mussels that have symbiotic bacteria in their gills , which use the methane in the brine to make energy for the mussels .

what does halophilic mean ?

for as far back as we can trace our existence , humans have been fascinated with death and resurrection . nearly every religion in the world has some interpretation of them , and from our earliest myths to the latest cinematic blockbusters , the dead keep coming back . but is resurrection really possible ? and what is the actual difference between a living creature and a dead body , anyway ? to understand what death is , we need to understand what life is . one ancient theory was an idea called vitalism , which claimed that living things were unique because they were filled with a special substance , or energy , that was the essence of life . whether it was called qi , lifeblood , or humors , the belief in such an essence was common throughout the world , and still persists in the stories of creatures who can somehow drain life from others , or some form of magical sources that can replenish it . vitalism began to fade in the western world following the scientific revolution in the 17th century . rené descartes advanced the notion that the human body was essentially no different from any other machine , brought to life by a divinely created soul located in the brain 's pineal gland . and in 1907 , dr. duncan mcdougall even claimed that the soul had mass , weighing patients immediately before and after death in an attempt to prove it . though his experiments were discredited , much like the rest of vitalism , traces of his theory still come up in popular culture . but where do all these discredited theories leave us ? what we now know is that life is not contained in some magical substance or spark , but within the ongoing biological processes themselves . and to understand these processes , we need to zoom down to the level of our individual cells . inside each of these cells , chemical reactions are constantly occurring , powered by the glucose and oxygen that our bodies convert into the energy-carrying molecule known as atp . cells use this energy for everything from repair to growth to reproduction . not only does it take a lot of energy to make the necessary molecules , but it takes even more to get them where they need to be . the universal phenomenon of entropy means that molecules will tend towards diffusing randomly , moving from areas of high concentration to low concentration , or even breaking apart into smaller molecules and atoms . so cells must constantly keep entropy in check by using energy to maintain their molecules in the very complicated formations necessary for biological functions to occur . the breaking down of these arrangements when the entire cell succumbs to entropy is what eventually results in death . this is the reason organisms ca n't be simply sparked back to life once they 've already died . we can pump air into someone 's lungs , but it wo n't do much good if the many other processes involved in the respiratory cycle are no longer functioning . similarly , the electric shock from a defibrillator does n't jump-start an inanimate heart , but resynchronizes the muscle cells in an abnormally beating heart so they regain their normal rhythm . this can prevent a person from dying , but it wo n't raise a dead body , or a monster sewn together from dead bodies . so it would seem that all our various medical miracles can delay or prevent death but not reverse it . but that 's not as simple as it sounds because constant advancements in technology and medicine have resulted in diagnoses such as coma , describing potentially reversible conditions , under which people would have previously been considered dead . in the future , the point of no return may be pushed even further . some animals are known to extend their lifespans or survive extreme conditions by slowing down their biological processes to the point where they are virtually paused . and research into cryonics hopes to achieve the same by freezing dying people and reviving them later when newer technology is able to help them . see , if the cells are frozen , there 's very little molecular movement , and diffusion practically stops . even if all of a person 's cellular processes had already broken down , this could still conceivably be reversed by a swarm of nanobots , moving all the molecules back to their proper positions , and injecting all of the cells with atp at the same time , presumably causing the body to simply pick up where it left off . so if we think of life not as some magical spark , but a state of incredibly complex , self-perpetuating organization , death is just the process of increasing entropy that destroys this fragile balance . and the point at which someone is completely dead turns out not to be a fixed constant , but simply a matter of how much of this entropy we 're currently capable of reversing .

so cells must constantly keep entropy in check by using energy to maintain their molecules in the very complicated formations necessary for biological functions to occur . the breaking down of these arrangements when the entire cell succumbs to entropy is what eventually results in death . this is the reason organisms ca n't be simply sparked back to life once they 've already died .

you can reboot a cell phone by simply putting in a new battery . why does that work in a solid-state device like a cell phone , but not in a living cell ?

translator : andrea mcdonough reviewer : bedirhan cinar i 'm going to take you on a journey into some hidden worlds inside your own body using the scanning electron microscope . these microscopes use a beam of electrons to illuminate things that are too small to be seen by the photons of visible light . and to put this in context , if you mentally divide one tiny millimeter into a thousand parts , each one of those parts is a micrometer , or micron for short . if you then divide one micron into another thousand parts , each one of those is a nanometer . and it 's nanometers and microns that are the domain of the scanning electron microscope . so , let 's start with something on the body that we can measure at about 100 microns wide , and that would be a human hair , which now you can see is covered with scales , just like all of our hairs , and in fact , just like all mammal hairs . we 're going to plunge into the body now , and we 've landed in the thyroid gland . here we 're looking at proteins that are being secreted into a storage chamber where they are going to develop into the mature thyroid hormones before being released into the body . and at this point you might be wondering if these colors are real . the answer is no . electron images only happen in black and white . i often colorize my images for various reasons , but i do n't change the structures , so the strucutres that you 're seeing are all exactly as they were when i photographed them in the microscope . we 're going to take a detour and zoom in on the heart muscle now . and the heart muscle has this curious structure that 's kind of like corrugated cardboard . that 's what allows the heart to expand and contract as it 's beating . let 's go look at a lung with pneumonia . here we 've got a white blood cell poking around in an air sac , looking for something to clean out like a little vacuum cleaner . this is your immune systems at work . so what are the kinds of things that we do n't want to be breathing , besides bacteria and viruses ? well , we all know to stay away from asbestos and now we can see why . this is a close-up view of the mineral that asbestos is made from , and now you can see that it 's composed of many tiny , fine little needles . each one of those needles is a single crystal . and in this picture , they 're begininng to pry apart and tangle up into a spiky mess , not for breathing . what else might we want to avoid breathing ? well , how about diesel fuel ? we 're looking here at the particles of diesel soot , and these are extraordinarily tiny . in fact , each one of these little particles is only about 50 nanometers wide . we 'll go and look at some blood now . we 've got a collection of nice , fat , happy , healthy red blood cells , but they 're all tangled up in a network of fibers . this is how the body makes a blood clot . and so , it surrounds a group of red blood cells and other cells , and traps them so the blood ca n't flow . we 've got two more blood cells here , but they 're not normal like the ones in the blood clot image . these are distorted . you can see that they 're curling up and beginning to grow what 's going to become spikes . these are sickle cells and these are what cause the condition of sickle cell amenia . we 've gone into the mouth now and we 've landed on dental plague , which you can see is covered with bacteria , and in fact dental plague is host to about 1,000 different species of bacteria . lovely to think about . and now we are on to other teeth . we 're on the surfaces of the , or the internal surfaces of the teeth themselves . the smaller one is a baby tooth that had just fallen out of the mouth of a young friend of mine , and i want to call your attention to the little holes . those little holes are the tops of a whole network of tiny little tubes that circulate nourishing fluids inside your teeth . and we can see those tubes a little better in the larger picture because some of them are in cross-section . but in fact , this larger picture is showing you a portion of a tusk , which you may know is simply a great big , elongated tooth , so you would expect to see the same features between your teeth and a tusk . but that larger tusk picture is also rough by comparison to the young baby tooth . that 's because it 's many , many thousands of years old . it 's also partly fossilized . and , between these two pictures , now you can see how your teeth relate to the tusk of an ice age mammoth . we 're shooting up north now into the brain , and we can see these pink cells down at the bottom . those are the neurons of memory . and i 'm going to leave you with this picture because i know you 're going to take a lot of happy memories away from your exciting day at ted and now you can visualize where those memories are being stored in your own brain . thank you .

but in fact , this larger picture is showing you a portion of a tusk , which you may know is simply a great big , elongated tooth , so you would expect to see the same features between your teeth and a tusk . but that larger tusk picture is also rough by comparison to the young baby tooth . that 's because it 's many , many thousands of years old .

a human tooth has much in common with the tusk of an ancient mammoth .

translator : andrea mcdonough reviewer : jessica ruby the healthy liver cell divides only when it 's stressed . the healthy hair cell divides frequently . and the cancer cell divides even more frequently and recklessly . `` the first draft that i saw was , like , four days before it was supposed to go online or something like that , and i had n't heard , you know i had n't heard , so , i was like , 'hey , guys , just wondering if you need me for anything ? ' you know ? and so she floods my inbox with emails , being like , 'yes , we actually need you for a bunch of stuff ! ' and it was great . like , when i first saw it , i mean , you immediately get the whole natural versus unnatural technique . '' `` not good for you ? '' `` right , yes , there you go , good for you and not good for you . seeing that , actually , was really cool because , i mean , i had no idea . writing the script , you have no idea what it 's going to turn out like in the end . but you get this , like , intuitive feel of 'okay , like , yeah , i get why this is a cancer cell , and i get why this is a healthy cell . ' and , actually , i showed it to , i showed an early draft to the professor with whom i was fact-checking the script who is a cancer researcher at mit , and he said that it was one of the best visualizations of cancer cells that he 'd ever seen . so , that was really cool to hear as well . '' `` when you get a script , do you make a storyboard or not ? '' `` i guess it depends on the method that we use to produce the piece because , for example , things that would definitely be character-heavy , like 'ladder of inference ' , we worked with a storyboard from beginning to end because we were dealing with character animation . and something like that is much different than stop-motion , for example . but , also , i mean biljana and i have also worked together for , like , nearly ten years or something absurd so we do n't need as much of a , you know , a piece of paper to tell us what to do , whereas , if i were working with someone new , then i would really want to work with a storyboard , but we kind of trust each other . '' `` so , you , like , finish ... ... each other 's sentences . '' `` we can try that again . '' `` no , we definitely should n't use that , it 's too cheesy . '' `` so , there was a part in the video where we had to represent how the cells reproduce and how chemotherapy affects it . and it became quite complicated for me to visualize , so i actually had to ask you to draw little doodles for me to actually explain that . how was that for you ? how was that experience ? '' `` i mean , it was pretty difficult for me to visualize , too , so , it was interesting . doing the storyboard actually helped me clarify in my head , like , how it actually works because when you have to explain something to someone else , with anything , obviously , you have to , like , really figure it out yourself . and , then , when you have to draw it , that requires you to take an extra level of abstraction and figure out , like , okay , like , what are the parts of this drawing that are really important ? what do i have to show clearly , and how do i show it ? and , so , doing that on a legal pad , which is , i think , how i ended up sending it to you guys , taking a picture of myself on camera , really helped , you know , me understand the crucial , and that 's the crucial part of why chemotherapy actually works . so , it was a really interesting experience . '' `` yeah , we actually started that on a , we had a whiteboard , and i was trying to figure out that process . i think we started at the beginning from cell division and multiplying and , you know , chemotherapy working . but then it became so crazy that i had to pull back and start from the end and go in a different direction . so , that became quite a challenge , too , figuring it out . '' `` we ended up using the visual that you gave us on the storyboard , which is really cool to have that sort of collaboration with the educator with whom you 're working . '' `` and i ca n't draw , so that should be noted . it was a very rough storyboard . '' `` it was good enough . '' `` good enough ! ''

translator : andrea mcdonough reviewer : jessica ruby the healthy liver cell divides only when it 's stressed . the healthy hair cell divides frequently .

which is not a step to creating at ted-ed lesson ?

today , more than half of all people in the world live in an urban area . by mid-century , this will increase to 70 % . but as recently as 100 years ago , only two out of ten people lived in a city , and before that , it was even less . how have we reached such a high degree of urbanization , and what does it mean for our future ? in the earliest days of human history , humans were hunter-gatherers , often moving from place to place in search of food . but about 10,000 years ago , our ancestors began to learn the secrets of selective breeding and early agricultural techniques . for the first time , people could raise food rather than search for it , and this led to the development of semi-permanent villages for the first time in history . `` why only semi-permanent ? '' you might ask . well , at first , the villages still had to relocate every few years as the soil became depleted . it was only with the advent of techniques like irrigation and soil tilling about 5,000 years ago that people could rely on a steady and long-term supply of food , making permanent settlements possible . and with the food surpluses that these techniques produced , it was no longer necessary for everyone to farm . this allowed the development of other specialized trades , and , by extension , cities . with cities now producing surplus food , as well as tools , crafts , and other goods , there was now the possibility of commerce and interaction over longer distances . and as trade flourished , so did technologies that facilitated it , like carts , ships , roads , and ports . of course , these things required even more labor to build and maintain , so more people were drawn from the countryside to the cities as more jobs and opportunities became available . if you think modern cities are overcrowded , you may be surprised to learn that some cities in 2000 b.c . had population densities nearly twice as high as that of shanghai or calcutta . one reason for this was that transportation was not widely available , so everything had to be within walking distance , including the few sources of clean water that existed then . and the land area of the city was further restricted by the need for walls to defend against attacks . the roman empire was able to develop infrastructure to overcome these limitations , but other than that , modern cities as we know them , did n't really get their start until the industrial revolution , when new technology deployed on a mass scale allowed cities to expand and integrate further , establishing police , fire , and sanitation departments , as well as road networks , and later electricity distribution . so , what is the future of cities ? global population is currently more than 7 billion and is predicted to top out around 10 billion . most of this growth will occur in the urban areas of the world 's poorest countries . so , how will cities need to change to accommodate this growth ? first , the world will need to seek ways to provide adequate food , sanitation , and education for all people . second , growth will need to happen in a way that does not damage the land that provides us with the goods and services that support the human population . food production might move to vertical farms and skyscrapers , rooftop gardens , or vacant lots in city centers , while power will increasingly come from multiple sources of renewable energy . instead of single-family homes , more residences will be built vertically . we may see buildings that contain everything that people need for their daily life , as well as a smaller , self-sufficient cities focused on local and sustainable production . the future of cities is diverse , malleable , and creative , no longer built around a single industry , but reflecting an increasingly connected and global world .

and with the food surpluses that these techniques produced , it was no longer necessary for everyone to farm . this allowed the development of other specialized trades , and , by extension , cities . with cities now producing surplus food , as well as tools , crafts , and other goods , there was now the possibility of commerce and interaction over longer distances . and as trade flourished , so did technologies that facilitated it , like carts , ships , roads , and ports .

reliable food supplies allowed humans the luxury of free time , which provided the opportunity to produce items for trade . describe how the production of goods contributed to the growth of cities .

how many times does the chorus repeat in your favorite song ? and , take a moment to think , how many times have you listened to it ? chances are you 've heard that chorus repeated dozens , if not hundreds , of times , and it 's not just popular songs in the west that repeat a lot . repetition is a feature that music from cultures around the world tends to share . so , why does music rely so heavily on repetition ? one part of the answer come from what psychologists call the mere-exposure effect . in short , people tend to prefer things they 've been exposed to before . for example , a song comes on the radio that we do n't particularly like , but then we hear the song at the grocery store , at the movie theater and again on the street corner . soon , we are tapping to the beat , singing the words , even downloading the track . this mere-exposure effect does n't just work for songs . it also works for everything from shapes to super bowl ads . so , what makes repetition so uniquely prevalent in music ? to investigate , psychologists asked people to listen to musical compositions that avoided exact repetition . they heard excerpts from these pieces in either their original form , or in a version that had been digitally altered to include repetition . although the original versions had been composed by some of the most respected 20th century composers , and the repetitive versions had been assembled by brute force audio editing , people rated the repetitive versions as more enjoyable , more interesting and more likely to have been composed by a human artist . musical repetition is deeply compelling . think about the muppets classic , `` mahna mahna . '' if you 've heard it before , it 's almost impossible after i sing , `` mahna mahna , '' not to respond , `` do doo do do do . '' repetition connects each bit of music irresistibly to the next bit of music that follows it . so when you hear a few notes , you 're already imagining what 's coming next . your mind is unconsciously singing along , and without noticing , you might start humming out loud . recent studies have shown that when people hear a segment of music repeated , they are more likely to move or tap along to it . repetition invites us into music as imagined participants , rather than as passive listeners . research has also shown that listeners shift their attention across musical repetitions , focusing on different aspects of the sound on each new listen . you might notice the melody of a phrase the first time , but when it 's repeated , your attention shifts to how the guitarist bends a pitch . this also occurs in language , with something called semantic satiation . repeating a word like atlas ad nauseam can make you stop thinking about what the word means , and instead focus on the sounds : the odd way the `` l '' follows the `` t. '' in this way , repetition can open up new worlds of sound not accessible on first hearing . the `` l '' following the `` t '' might not be aesthetically relevant to `` atlas , '' but the guitarist pitch bending might be of critical expressive importance . the speech to song illusion captures how simply repeating a sentence a number of times shifts listeners attention to the pitch and temporal aspects of the sound , so that the repeated spoken language actually begins to sound like it is being sung . a similar effect happens with random sequences of sound . people will rate random sequences they 've heard on repeated loop as more musical than a random sequence they 've only heard once . repetition gives rise to a kind of orientation to sound that we think of as distinctively musical , where we 're listening along with the sound , engaging imaginatively with the note about to happen . this mode of listening ties in with our susceptibility to musical ear worms , where segments of music burrow into our head , and play again and again , as if stuck on repeat . critics are often embarrassed by music 's repetitiveness , finding it childish or regressive , but repetition , far from an embarrassment , is actually a key feature that gives rise to the kind of experience we think about as musical .

if you 've heard it before , it 's almost impossible after i sing , `` mahna mahna , '' not to respond , `` do doo do do do . '' repetition connects each bit of music irresistibly to the next bit of music that follows it . so when you hear a few notes , you 're already imagining what 's coming next .

what can repetition illuminate about the difference between music and language ?

have you ever seen a big , red `` no running '' sign at a public pool ? for the most part , the pace on the deck reflects this statement . but while the sign accurately describes the patrons ' movements , is n't it true that people are walking because the sign tells them no running ? so , is this sign portraying the pool 's environment , or is it doing something else , something more powerful ? the difference between a statement that describes and one that commands is an idea developed by british linguist j. l. austin . he defines this distinction as two separate parts of speech : constatives and performatives . constatives are sentences that describe something as true or false , and performatives are sentences that denote an action . in other words , a constative is , and a performative does . to help us distinguish these two parts of speech , let 's start by examining constatives around the park outside the pool . the first sign we encounter says , `` the park closes at 6 p.m. '' after checking with a friendly park official that the park does , indeed , close at 6 , we can confirm that this statement is a true constative . nearby , there 's a man on a bench with a newspaper , and the headline reads , `` heatwave ! '' however , the sky is cloudy and it feels quite chilly . today 's headline is a false constative as it has proven to be incorrect . before the rain starts to fall , let 's throw away our can of soda at the blue trash bin that says , `` recycle . '' it 's a performative . performatives are sentences that are meant to inspire actions . rather than conveying a message , it acts upon the world , it does something . in this case , the performative of `` recycle '' is requesting people to put their trash into the proper receptacle . words not only bring about actions , sometimes words themselves are actions . this is what is known as speech acts . these actions include , but are not limited to , ordering , promising , apologizing , warning , sentencing , christening , and even marrying . take a look at the wedding near the gazebo . the couple says the words , `` i do . '' the speech act here are the words , `` i do . '' these words cause them to marry one another . `` i do '' has acted upon them and profoundly changed their world . however , performatives depend on context and reception . these are known as felicity conditions . imagine if the mayor showed up to the wedding and said , `` by the power vested in me as mayor of the city , i name this gazebo 'the mayor 's pizza palace . ' '' his words would be a speech act by which he named the gazebo . and because he 's the mayor , the gazebo would be known by its new name . but if someone who is n't the mayor , just a normal passerby , decides to name the gazebo after her favorite cat , the chances are the name would not change . felicity conditions are the rules under which the performative can be enacted . these are fairly logical . the performative should have proper authority , it should be understood , it should be clear , and it should be able to be executed . if the performative does n't meet these conditions , then it does n't have the power to denote action . but just because a performative meets its conditions and is clearly stated , does n't mean that it 's implicitly followed . back at the pool , a rowdy group of teenagers races to the high dive . `` no running '' does not seem to have power over them , and they 'll have to face the consequences of breaking this performative . they may even have to force out some performatives of their own , such as apologizing to the life guard and promising to never run again . maybe the life guard will respond with another performative , sentencing them to be banished from the pool for the rest of the day . after all , these teenagers must learn to respect the power of words .

so , is this sign portraying the pool 's environment , or is it doing something else , something more powerful ? the difference between a statement that describes and one that commands is an idea developed by british linguist j. l. austin . he defines this distinction as two separate parts of speech : constatives and performatives . constatives are sentences that describe something as true or false , and performatives are sentences that denote an action .

which is not one of the parts of speech defined by austin ?

all animals communicate . crabs wave their claws at each other to signal that they 're healthy and ready to mate . cuttlefish use pigmented skin cells called chromatophores to create patterns on their skin that act as camouflage or warnings to rivals . honeybees perform complex dances to let other bees know the location and quality of a food source . all of these animals have impressive communication systems , but do they have language ? to answer that question , we can look at four specific qualities that are often associated with language : discreteness , grammar , productivity , and displacement . discreteness means that there is a set of individual units , such as sounds or words , that can be combined to communicate new ideas , like a set of refrigerator poetry magnets you can rearrange to create different phrases . grammar provides a system of rules that tells you how to combine those individual units . productivity is the ability to use language to create an infinite number of messages . and displacement is the ability to talk about things that are n't right in front of you , such as past , future , or fictional events . so , does animal communication exhibit any of these qualities ? for crabs and cuttlefish , the answer is no . they do n't combine their signals in creative ways . those signals also do n't have to be in a grammatical order , and they only communicate current conditions , like , `` i am healthy , '' or `` i am poisonous . '' but some animals actually do display some of these properties . bees use the moves , angle , duration , and intensity of their waggle dance to describe the location and richness of a food source . that source is outside the hive , so they exhibit the property of displacement . they share that language trait with prairie dogs , which live in towns of thousands , and are hunted by coyotes , hawks , badgers , snakes , and humans . their alarms calls indicate the predator 's size , shape , speed , and , even for human predators , what the person is wearing and if he 's carrying a gun . great apes , like chimps and gorillas , are great communicators , too . some have even learned a modified sign language . a chimpanzee named washoe demonstrated discreteness by combining multiple signs into original phrases , like , `` please open . hurry . '' coco , a female gorilla who understands more than 1000 signs , and around 2000 words of spoken english referred to a beloved kitten that had died . in doing so , she displayed displacement , though it 's worth noting that the apes in both of these examples were using a human communication system , not one that appeared naturally in the wild . there are many other examples of sophisticated animal communication , such as in dolphins , which use whistles to identify age , location , names , and gender . they can also understand some grammar in a gestural language researchers use to communicate with them . however , grammar is not seen in the dolphin 's natural communication . while these communication systems may have some of the qualities of language we 've identified , none display all four . even washoe and coco 's impressive abilities are still outpaced by the language skills of most three-year-old humans . and animals ' topics of conversation are usually limited . bees talk about food , prairie dogs talk about predators , and crabs talk about themselves . human language stands alone due to the powerful combination of grammar and productivity , on top of discreteness and displacement . the human brain can take a finite number of elements and create an infinite number of messages . we can craft and understand complex sentences , as well as words that have never been spoken before . we can use language to communicate about an endless range of subjects , talk about imaginary things , and even lie . research continues to reveal more and more about animal communication . it may turn out that human language and animal communication are n't entirely different but exist on a continuum . after all , we are all animals .

honeybees perform complex dances to let other bees know the location and quality of a food source . all of these animals have impressive communication systems , but do they have language ? to answer that question , we can look at four specific qualities that are often associated with language : discreteness , grammar , productivity , and displacement .

why should humans continue to research the communication systems of animals ? what might we learn ?

what makes a good horror story ? sure , you could throw in some hideous monsters , fountains of blood , and things jumping out from every corner , but as classic horror author h.p . lovecraft wrote , `` the oldest and strongest kind of fear is fear of the unknown . '' and writers harness that fear not by revealing horrors , but by leaving the audience hanging in anticipation of them . that is , in a state of suspense . the most familiar examples of suspense come from horror films and mystery novels . what 's inside the haunted mansion ? which of the dinner guests is the murderer ? but suspense exists beyond these genres . will the hero save the day ? will the couple get together in the end ? and what is the dark secret that causes the main character so much pain ? the key to suspense is that it sets up a question , or several , that the audience hopes to get an answer to and delays that answer while maintaining their interest and keeping them guessing . so what are some techniques you can use to achieve this in your own writing ? limit the point of view . instead of an omniscient narrator who can see and relay everything that happens , tell the story from the perspective of the characters . they may start off knowing just as little as the audience does , and as they learn more , so do we . classic novels , like `` dracula , '' for example , are told through letters and diary entries where characters relate what they 've experienced and fear what 's to come . next , choose the right setting and imagery . old mansions or castles with winding halls and secret passageways suggest that disturbing things are being concealed . nighttime , fog , and storms all play similar roles in limiting visibility and restricting characters ' movements . that 's why victorian london is such a popular setting . and even ordinary places and objects can be made sinister as in the gothic novel `` rebecca '' where the flowers at the protagonist 's new home are described as blood red . three : play with style and form . you can build suspense by carefully paying attention not just to what happens but how it 's conveyed and paced . edgar allan poe conveys the mental state of the narrator in `` the tell-tale heart '' with fragmented sentences that break off suddenly . and other short declarative sentences in the story create a mix of breathless speed and weighty pauses . on the screen , alfred hitchcock 's cinematography is known for its use of extended silences and shots of staircases to create a feeling of discomfort . four : use dramatic irony . you ca n't just keep the audience in the dark forever . sometimes , suspense is best served by revealing key parts of the big secret to the audience but not to the characters . this is a technique known as dramatic irony , where the mystery becomes not what will happen but when and how the characters will learn . in the classic play `` oedipus rex , '' the title character is unaware that he has killed his own father and married his mother . but the audience knows , and watching oedipus gradually learn the truth provides the story with its agonizing climax . and finally , the cliffhanger . beware of overusing this one . some consider it a cheap and easy trick , but it 's hard to deny its effectiveness . this is where a chapter , episode , volume , or season cuts off right before something crucial is revealed , or in the midst of a dangerous situation with a slim chance of hope . the wait , whether moments or years , makes us imagine possibilities about what could happen next , building extra suspense . the awful thing is almost always averted , creating a sense of closure and emotional release . but that does n't stop us from worrying and wondering the next time the protagonists face near-certain disaster .

what makes a good horror story ? sure , you could throw in some hideous monsters , fountains of blood , and things jumping out from every corner , but as classic horror author h.p . lovecraft wrote , `` the oldest and strongest kind of fear is fear of the unknown . '' and writers harness that fear not by revealing horrors , but by leaving the audience hanging in anticipation of them .

what did classic horror author h.p . lovecraft say creates the strongest kind of fear in a horror story ?

many generations have felt they 've reached the pinnacle of technological advancement , yet look back 100 years , and the technologies we take for granted today would seem like impossible magic . so will there be a point where we reach an actual limit of technological progress ? and if so , are we anywhere near that limit now ? half a century ago , russian astronomer nikolai kardashev was asking similar questions when he came up with a way to measure technological progress , even when we have no idea exactly what it might look like . anything we do in the future will require energy , so kardashev 's scale classifies potential civilizations , whether alien civilizations out there in the universe or our own , into three levels based on energy consumption . the tiny amount of energy we currently consume pales next to what we leave untapped . a type i , or planetary civilization , can access all the energy resources of its home planet . in our case , this is the 174,000 terawatts earth receives from the sun . we currently only harness about 15 terawatts of it , mostly by burning solar energy stored in fossil fuels . to approach becoming a type i civilization , we would need to capture solar energy more directly and efficiently by covering the planet with solar panels . based on the most optimistic models , we might get there within just four centuries . what would be next ? well , the earth only gets a sliver of the sun 's energy , while the rest of its 400 yottawatts is wasted in dead space . but a type ii , or stellar civilization , would make the most of its home star 's energy . instead of installing solar panels around a planet , a type ii civilization would install them directly orbiting its star , forming a theoretical structure called a dyson sphere . and the third step ? a type iii civilization would harness all the energy of its home galaxy . but we can also think of progress in the opposite way . how small can we go ? to that end , british cosmologist john barrow classified civilizations by the size of objects they control . that ranges from mechanical structures at our own scale , to the building blocks of our own biology , down to unlocking atoms themselves . we 've currently touched the atomic level , though our control remains limited . but we potentially could go much smaller in the future . to get a sense of the extent to which that 's true , the observable universe is 26 orders of magnitude larger than a human body . that means if you zoomed out by a factor of ten 26 times , you 'd be at the scale of the universe . but to reach the minimum length scale , known as the planck length , you would need to zoom in 35 times . as physicist richard feynman once said , `` there 's plenty of room at the bottom . '' instead of one or the other , it 's likely that our civilization will continue to develop along both kardashev and barrow scales . precision on a smaller scale lets us use energy more efficiently and unlocks new energy sources , like nuclear fusion , or even antimatter . and this increased energy lets us expand and build on a larger scale . a truly advanced civilization , then , would harness both stellar energy and subatomic technologies . but these predictions were n't made just for us humans . they double as a possible means of detecting intelligent life in the universe . if we find a dyson sphere around a distant star , that 's a pretty compelling sign of life . or , what if , instead of a structure that passively soaked up all the star 's energy , like a plant , an alien civilization built one that actively sucked the energy out of the star like a hummingbird . frighteningly enough , we 've observed super dense celestial bodies about the size of a planet that drain energy out of a much bigger star . it would be much too premature to conclude that this is evidence of life in the universe . there are also explanations for these observations that do n't involve alien life forms . but that does n't stop us from asking , `` what if ? ''

instead of one or the other , it 's likely that our civilization will continue to develop along both kardashev and barrow scales . precision on a smaller scale lets us use energy more efficiently and unlocks new energy sources , like nuclear fusion , or even antimatter . and this increased energy lets us expand and build on a larger scale .

what other ways than energy and control of small scale technologies could be used to measure technological progress universally ?

some superheroes can grow to the size of a building at will . that 's very intimidating ! but a scientist must ask where the extra material is coming from . the law of conservation of mass implies that mass can neither be created nor destroyed , which means that our hero 's mass will not change just because his size changes . for instance , when we bake a fluffy sponge cake , even though the resulting delicious treat is much bigger in size than the cake batter that went into the oven , the weight of the cake batter should still equal the weight of the cake plus the moisture that has evaporated . in a chemical equation , molecules rearrange to make new compounds , but all the components should still be accounted for . when our hero expands from 6 feet tall to 18 feet tall , his height triples . galileo 's square cube law says his weight will be 27 - 3 times 3 times 3 equals 27 - times his regular weight since he has to expand in all three dimensions . so , when our superhero transforms into a giant , we are dealing with two possibilities . our hero towering at 18 feet still only weighs 200 pounds , the original weight in this human form . now , option two , our hero weighs 5,400 pounds - 200 pounds times 27 equals 5,400 pounds - when he is 18 feet tall , which means he also weighs 5,400 pounds when he is 6 feet tall . nobody can get in the same elevator with him without the alarm going off . now , option two seems a little more scientifically plausible , but it begs the question , how does he ever walk through the park without sinking into the ground since the pressure he is exerting on the soil is calculated by his mass divided by the area of the bottom of his feet ? and what kind of super socks and super shoes is he putting on his feet to withstand all the friction that results from dragging his 5,400 pound body against the road when he runs ? and can he even run ? and i wo n't even ask how he finds pants flexible enough to withstand the expansion . now , let 's explore the density of the two options mentioned above . density is defined as mass divided by volume . the human body is made out of bones and flesh , which has a relatively set density . in option one , if the hero weighs 200 pounds all the time , then he would be bones and flesh at normal size . when he expands to a bigger size while still weighing 200 pounds , he essentially turns himself into a giant , fluffy teddy bear . in option two , if the hero weighs 5,400 pounds all the time , then he would be bones and flesh at 18 feet with 5,400 pounds of weight supported by two legs . the weight would be exerted on the leg bones at different angles as he moves . bones , while hard , are not malleable , meaning they do not bend , so they break easily . the tendons would also be at risk of tearing . tall buildings stay standing because they have steel frames and do not run and jump around in the jungle . our hero , on the other hand , one landing at a bad angle and he 's down . assuming his bodily function is the same as any mammal 's , his heart would need to pump a large amount of blood throughout his body to provide enough oxygen for him to move 5,400 pounds of body weight around . this would take tremendous energy , which he would need to provide by consuming 27 times 3,000 calories of food every day . now , that is roughly 150 big macs . 27 times 3,000 calculated equals 81,000 calculated slash 550 calories equals 147 . he would n't have time to fight crime because he would be eating all the time and working a 9-to-5 job in order to afford all the food he eats . and what about superheroes who can turn their bodies into rocks or sand ? well , everything on earth is made out of elements . and what defines each element is the number of protons in the nucleus . that is how our periodic table is organized . hydrogen has one proton , helium , two protons , lithium , three protons , and so on . the primary component of the most common form of sand is silicon dioxide . meanwhile , the human body consists of 65 % oxygen , 18 % carbon , 10 % hydrogen , and 7 % of various other elements including 0.002 % of silicon . in a chemical reaction , the elements recombine to make new compounds . so , where is he getting all this silicon necessary to make the sand ? sure , we can alter elements by nuclear fusion or nuclear fission . however , nuclear fusion requires so much heat , the only natural occurrence of this process is in stars . in order to utilize fusion in a short amount of time , the temperature of the area needs to be hotter than the sun . every innocent bystander will be burned to a crisp . rapid nuclear fission is not any better since it often results in many radioactive particles . our hero would become a walking , talking nuclear power plant , ultimately harming every person he tries to save . and do you really want the heat of the sun or a radioactive nuclear plant inside of your body ? now , which superpower physics lesson will you explore next ? shifting body size and content , super speed , flight , super strength , immortality , and invisibility .

in option two , if the hero weighs 5,400 pounds all the time , then he would be bones and flesh at 18 feet with 5,400 pounds of weight supported by two legs . the weight would be exerted on the leg bones at different angles as he moves . bones , while hard , are not malleable , meaning they do not bend , so they break easily . the tendons would also be at risk of tearing .

bones are not malleable , which means they

will winning the lottery make you happier ? imagine winning a multi-million dollar lottery tomorrow . if you 're like many of us , you 'd be ecstatic , unable to believe your good luck . but would that joy still be there a few years later ? maybe not . a famous study of 22 lottery winners showed that months after winning , their average reported levels of happiness had increased no more than that of a control group who had n't won the lottery . some were actually unhappier than they had been before winning . and later studies have confirmed that our emotional well-being , how often and how intensely we feel things like joy , sorrow , anxiety , or anger , do n't seem to improve with wealth or status beyond a certain point . this has to do with a phenomenon known as hedonic adaptation , or the hedonic treadmill . it describes our tendency to adapt to new situations to maintain a stable emotional equilibrium . when it comes to feeling happy , most of us seem to have a base level that stays more or less constant throughout our existence . of course , the novelty of better food , superior vacations , and more beautiful homes can at first make you feel like you 're walking on air , but as you get used to those things , you revert to your default emotional state . that might sound pretty gloomy , but hedonic adaptation makes us less emotionally sensitive to any kind of change , including negative ones . the study with the lottery winners also looked at people who had suffered an accident that left them paralyzed . when asked several months after their accidents how happy they were , they reported levels of happiness approaching their original baseline . so while the hedonic treadmill may inhibit our enjoyment of positive changes , it seems to also enable our resilience in recovering from adversity . there are other reasons that winning the lottery may not make us happier in the long run . it can be difficult to manage large sums of money , and some lottery winners wind up spending or losing it all quickly . it can also be socially isolating . some winners experience a deluge of unwelcome requests for money , so they wind up cutting themselves off from others . and wealth may actually make us meaner . in one study , participants played a rigged game of monopoly where the experimenters made some players rich quickly . the wealthy players started patronizing the poorer players and hogging the snacks they were meant to share . but just because a huge influx of cash is n't guaranteed to bring joy into your life does n't mean that money can never make us happier . findings show that we adapt to extrinsic and material things , like a new car or a bigger house , much faster than we do to novel experiences , like visiting a new place or learning a new skill . so by that reasoning , the more you spend money on experiences rather than things , the happier you 'd be . and there 's another way to turn your money into happiness : spend it on other people . in one study , participants were given some money and were either asked to spend it on themselves or on someone else . later that evening , researchers called up these participants and asked them how happy they were . the happiness levels of those who had spent the money on others were significantly greater than that of those who had spent it on themselves . and that seems to be true around the world . another study examined the generosity of over 200,000 people from 136 countries . in over 90 % of these countries , people who donated tended to be happier than those who did n't . but this may all be easier said than done . let 's say a million dollars falls into your lap tomorrow . what do you do with it ?

findings show that we adapt to extrinsic and material things , like a new car or a bigger house , much faster than we do to novel experiences , like visiting a new place or learning a new skill . so by that reasoning , the more you spend money on experiences rather than things , the happier you 'd be . and there 's another way to turn your money into happiness : spend it on other people .

the more you spend money on ___________ the happier you will be .

hi i 'm john green , this is crash course literature , and today we 're gon na talk about this lady , emily dickinson . by the way we do n't have a book today cause she 's on my nook . emily dickinson was a great 19th century american poet who- mr. green ! mr. green ! i already know everything about her : she was a recluse and you can sing all of her poems to the tune of `` i 'd like to buy the world a coke '' , like : [ sings ] `` because i could not stop for death , he kindly stopped for me '' ' - stop , me from the past , you can not sing ! fortunately , your inability to sing does insulate us from copyright claims , because i , for one , did not recognize that as `` if i could buy the world a coke . '' also , dickinson 's meter is more complicated than you 're making it out to be , but yes , you could sing most of her poems to `` if i could buy the world a coke '' , also , `` yellow rose of texas '' . more importantly , these poems have a lot to say about the relationship between death and life , between faith and doubt , between the power of god and the power of individuals , so let 's focus on that , because it actually might change your life and stuff . [ theme music ] so joyce carol oats once called emily dickinson `` the most paradoxical of poets , the very poet of paradox '' , and this can really frustrate students and literary critics alike , particularly when dickinson seems to contradict herself within a single poem . take , for example , this bit of light verse . ''faith ' is a fine invention when gentlemen can see - but microscopes are prudent in an emergency '' . so this seems like a pretty pro-science , anti-religion poem right ? i mean , faith is put in quotation marks and called an invention . but she also implies the possibility of a different and valuable kind of sight , only available to some people at some times , `` when '' gentlemen `` can '' see . and this is where is becomes important to look at how dickinson , for lack of a better phrase , `` sees '' sight . dickinson often imagines seeing as a sort of power , so much so that seeing , not just literal sight , but also the ability to witness and observe and understand , becomes the central expression of the self . like her famous poem that begins `` i heard a fly buzz when i died '' ends with the line `` i could not see to see '' associating the lack of sight , with death itself . dickinson also often played with the fact that this `` i '' and this `` eye '' sound the same . her poem beginning , `` before i got my eye put out '' is about death , for instance , not just monocularizaton . in that poem , she clearly associates sight not just with the power to observe but ownership . she writes , `` but were it told to me , today , that i might have the sky for mine , i tell you that my heart would split , for size of me - the meadows - mine - the mountains - mine - '' . of course in 19th century america , the idea that an eye , possibly a female eye , could own the mountains , the meadows , and the sky was a little bit radical . i mean , all the stuff was supposed to be under the control of god , not any human being who could see it . all this is made even more complex and interesting by the fact that dickinson 's poems sounded like hymns , and throughout her life you can see her faith waxing and waning in her poetry . in short , i do n't think you can make easy conclusions about microscopes and faith in dickinson 's poetry , but that 's precisely what 's so important about it . dickinson 's work reflects a conflicted american world view . i mean , we 're a nation of exceptional individuals who believe that we control our success and our happiness , but we are also more likely to profess a belief in an omnipotent god than people in any other industrialized nation . all right , i know you guys want all the creepy , macabre details of dickinson 's biography so let 's go to the thought bubble . so , emily dickinson was born in 1830 to a prominent family . her father because a us congressman , and lived her whole life in massachusetts . she was haunted , by what she called , the menace of death throughout her life . although , then again , who is n't ? between 1858 and 1865 , dickinson wrote nearly 800 poems , but she also became increasingly confined to her home in those years , and eventually , rarely left her room . she usually talked to visitors from the other side of a closed door , and did n't even leave her room when her father 's funeral took place downstairs . dickinson published few than a dozen poems in her lifetime . in fact , no one knew that she 'd been nearly so prolific until her sister discovered more than 1800 poems after emily 's death in 1886 . dickinson was considered an eccentric in amherst , and known locally for only wearing white when she was spotted outside the home . in fact , her only surviving article of clothing is a white cotton dress . this image of a pale wraith clad all in white is a symbol of the reclusive , brilliant poet , but it 's worth noting that for dickinson , white was not the color of innocence , or purity , or ghosts . it was the color of passion and intensity . `` dare you see a soul at the white heat ? then crouch within the door , '' she once wrote . she called red , the color most associate with passion , `` fire 's common tint . '' for dickinson , the real , true rich life of a soul even if it was physically sheltered burned white hot . thanks thought bubble . oh , it 's time for the open letter ? an open letter to the color white . but , first let 's see what 's in the secret compartment today . oh , it 's a dalek . stan , more flagrant pandering to the whovians . dear white , you are a complicated and symbolic -- ah ! dalek ! they 're not very bright . so , white you 're often associated with purity , like wedding dresses . you can symbolize heaven , or the creepy infinite nowhere where parts of harry potter , and all of crash course humanities take place . but , many 19th century writers inverted those associations . like , melville 's famous great white wall of whale , that terrifying blankness of nature . and to dickinson , white , you were the color of passion and intensity . this reminds us that our symbolic relationships are n't fixed . we are creating them as we go , communally . i mean , other than daleks , which are universally terrifying no matter what color they come in . best wishes , john green . okay , let 's take a close look at a poem we 've already mentioned , sometimes called poem 465 , and sometimes known by its first line `` i heard a fly buzz when i died , '' . speaking of which , here in the studio we 've had a genuine plague of flies in the last few weeks . i mean , in the lights up there , there are thousands of fly carcasses . okay , let 's out aside the fly carcasses , and read a poem together about flies . i heard a fly buzz - when i died - the stillness in the room was like the stillness in the air - between the heaves of storm - the eyes around - had wrung them dry - and breaths were gathering firm for that last onset - when the king be witnessed - in the room - i willed my keepsakes - signed away what portion of me be assignable - and then it was there interposed a fly - with blue - uncertain - stumbling buzz - between the light - and me - and then the windows failed - and then i could not see to see - okay , first let 's talk about the dashes . some critics think that dickinson 's use of dashes as punctuation is just eccentric handwriting , or else an accident . i mean , they point out that dickinson also similar dashes , for instance , in her cake recipes . others argue that the use of dashes are a typographical attempt to symbolize the way the mind works , or that the dash is used as a punctuation stronger than a comma but weaker than a period . regardless though , the appearance of a dash at the end of this poem at the moment of death is a very interesting choice . so , in this poem the speaker is dying , or i guess , has died in a still room surrounded by loved ones . a will is signed , and then the fly with a `` blue - uncertain - stumbling buzz - '' comes between the light and the speaker . this makes it so the narrator can not see to see , and by now you know what happens in dickinson poems when people ca n't see . they 're dead . so , dickinson was just a smidge obsessed with death , which means she got to imagine death in a lot of different ways : as a suitor , as a gentle guide , but here death is a buzzing fly . so , everyone in the room is waiting for the arrival of `` the king '' , which before elvis took over the title in 1958 was a reference to god . but , instead of the quiet , peaceful arrival of god they 're expecting it 's a dirty little fly with `` uncertain stumbling buzz '' that gets between the narrator and the light . so , this poem features dickinson at her most formal . the lines are very iambic ( john speaks rhythmically ) : `` i heard a fly buzz when i died the stillness in the room , '' , and they alternate between tetrameter , four feet , and trimeter , three feet . the rhyme scheme throughout the poem is abcb , which means that the first line ends with one sound , the second line with yet another , the third line with another still , and then the fourth line rhymes with the second line . but , dickinson employs her famous slant rhymes here . like in the first stanza , `` room '' is matched with `` storm '' . in the second , `` be '' with `` fly '' . these words sort of , almost rhyme like `` room '' and `` storm '' both end in /m/ sounds . `` be '' and `` fly both end in hard vowel sounds , but they do n't rhyme . this discomforting lack of closure is a hallmark of dickinson 's poetry , also of most of my romantic relationships . only in the final stanza , when death comes do we get a full rhyme . `` me '' , the eye , is rhymed with `` see '' the thing the eye can no longer do . so , is this a peaceful death ? hardly . i mean , the stillness in the room is broken by the buzzing fly , and yet with that final full rhyme , dickinson offers us a bit of peace and closure that we did n't get in the first two stanzas . to return to an old theme , even though we live in an image drenched culture , this is a good reminder that language is made out of words , and it might sound like over reading to you to say that a full rhyme brings peace . but , i 'm remind of the story of mozart 's children playing a series of unfinished scales in order to taunt their father , who would eventually have to go to the piano and finish them . poetry is n't just a series of images . it 's rhythmic and it 's metric , and we crave the closure of a good rhyme at the end of a poem . that 's why sonnets end with couplets . dickinson gives us that closure , and the she gives us a jose saramago-ine dash . the poet of paradox , still haunting us . thanks for watching our crash course literature mini series . next week , we begin a year of learning about us history together . [ libertage ] [ explosions and patriotic guitar riffs ] now begins the complaining by non-americans that we 're shallow and self-interested and call ourselves americans , even though in fact , this is america . but even my friends , if you do n't live here the history of the united states matters to you because we are always meddling in your affairs . thanks for watching . see you next week . crash course is produced and directed by stan miller . our script supervisor is meredith danko . the associate producer is danica johnson , and the show is written by me . every week instead of cursing , i 've used the name of writers i like . that tradition is ending , but a new one will begin next week . if you have questions about today 's video , you can ask them down there in comments , and be answered by our team of literature professionals including stan 's mom . thanks for watching , and as we say in my hometown , `` do n't forget to be awesome ! ''

like , melville 's famous great white wall of whale , that terrifying blankness of nature . and to dickinson , white , you were the color of passion and intensity . this reminds us that our symbolic relationships are n't fixed .

why do you think dickinson only wore white ?

without water , a human can only survive for about 100 hours . but there 's a creature so resilient that it can go without it for decades . this one millimeter animal can survive both the hottest and coldest environments on earth , and can even withstand high levels of radiation . this is the tardigrade , and it 's one of the toughest creatures on earth , even if it does look more like a chubby , eight-legged gummy bear . most organisms need water to survive . water allows metabolism to occur , which is the process that drives all the biochemical reactions that take place in cells . but creatures like the tardigrade , also known as the water bear , get around this restriction with a process called anhydrobiosis , from the greek meaning life without water . and however extraordinary , tardigrades are n't alone . bacteria , single-celled organisms called archaea , plants , and even other animals can all survive drying up . for many tardigrades , this requires that they go through something called a tun state . they curl up into a ball , pulling their head and eight legs inside their body and wait until water returns . it 's thought that as water becomes scarce and tardigrades enter their tun state , they start synthesize special molecules , which fill the tardigrade 's cells to replace lost water by forming a matrix . components of the cells that are sensitive to dryness , like dna , proteins , and membranes , get trapped in this matrix . it 's thought that this keeps these molecules locked in position to stop them from unfolding , breaking apart , or fusing together . once the organism is rehydrated , the matrix dissolves , leaving behind undamaged , functional cells . beyond dryness , tardigrades can also tolerate other extreme stresses : being frozen , heated up past the boiling point of water , high levels of radiation , and even the vacuum of outer space . this has led to some erroneous speculation that tardigrades are extraterrestrial beings . while that 's fun to think about , scientific evidence places their origin firmly on earth where they 've evolved over time . in fact , this earthly evolution has given rise to over 1100 known species of tardigrades and there are probably many others yet to be discovered . and because tardigrades are so hardy , they exist just about everywhere . they live on every continent , including antarctica . and they 're in diverse biomes including deserts , ice sheets , the sea , fresh water , rainforests , and the highest mountain peaks . but you can find tardigrades in the most ordinary places , too , like moss or lichen found in yards , parks , and forests . all you need to find them is a little patience and a microscope . scientists are now to trying to find out whether tardigrades use the tun state , their anti-drying technique , to survive other stresses . if we can understand how they , and other creatures , stabilize their sensitive biological molecules , perhaps we could apply this knowledge to help us stabilize vaccines , or to develop stress-tolerant crops that can cope with earth 's changing climate . and by studying how tardigrades survive prolonged exposure to the vacuum of outer space , scientists can generate clues about the environmental limits of life and how to safeguard astronauts . in the process , tardigrades could even help us answer a critical question : could life survive on planets much less hospitable than our own ?

but creatures like the tardigrade , also known as the water bear , get around this restriction with a process called anhydrobiosis , from the greek meaning life without water . and however extraordinary , tardigrades are n't alone . bacteria , single-celled organisms called archaea , plants , and even other animals can all survive drying up .

how is it thought that tardigrades protect their cellular components when they dry out ?

translator : andrea mcdonough reviewer : jessica ruby we are constantly asked for our opinions . which team do you think will win the super bowl ? who wore it better on the red carpet ? who are you going to vote for for mayor ? public opinion polls are everywhere . important decision makers in american government have long relied on public opinion polls throughout elections and important legislation . the problem is public opinion is n't easy to track and , often times , is n't even right . in 1948 , the < i > chicago daily tribune < /i > ran a now famous headline : `` dewey defeats truman , '' they cried in big , bold , black and white letters . the problem is that dewey had n't defeated truman . the < i > tribune < /i > had relied on polls to come to their conclusion . whoops ! this happens all the time because public opinion polls are either inaccurate or misleading . so , why are they wrong ? and why do we keep using them ? first , let 's start with an important term : sample . a sample is the group of people that respond to questions during a public opinion poll . a poll 's quality rests largely on its sample , and a sample can be bad in a few key ways . it can be too small , too narrow , or the poll itself can be too difficult . polls that are too small are bad for obvious reasons . and while you ca n't possibly ask every single person in america for their opinion , the more people you ask , the more accurate your prediction . polls that are too narrow , that only ask a certain type of person a question , are bad , too . consider a poll about whether or not the potato is the best vegetable in america . if you only asked people in idaho , where the state food is the potato , chances are that you would get a much different answer than if you asked people in the state of new mexico , where the state vegetable is beans . getting the right kind of diversity in your sample means making sure that your sample has a range of ages , races , genders , and geographic regions , just to name a few . finally , polls that are too hard ca n't tell you much either . if you 're asking people for their opinions on things about which they have no prior knowledge , the results will be pointless . you 're better off shaking a magic 8 ball . it 's not just the people you 're asking that can cause bias , though . the person doing the asking is part of the problem , too . that 's called interviewer bias . interviewer bias is all about the effect that the person asking the questions has on the sample . humans generally do n't like confrontation . people worry that their answers may make them look bad . therefore , we find that people tend to give socially desirable responses , not necessarily their honest opinions , because they do n't want to come across as heartless , racist , or bigoted . and the way we word our questions matters too . when polls purposely sway the answers one way or the other , it 's called a push poll because it pushes people to answer a certain way . `` would you vote for candidate smith ? '' is a perfectly normal question . `` would you vote for candidate smith if you knew that he robs senior citizens ? '' is a push poll . so , if polls are open to all sorts of manipulation and inaccuracies , why are they still so prevalent ? despite their flaws , public opinion polls provide us with some sense of the thoughts and moods of large groups of people . they offer politicians the chance to pass legislation they think a majority of americans will support . they help fashionistas on tv know which star wore the dress better on the red carpet . finally , they make us , the people who get polled , feel as though our voice has been heard . so , next time you get a phone call asking your opinion , or if you see a poll online , take some time to think about who is asking and why they 're asking . then , take that poll , and its results , with a grain of salt or a potato .

first , let 's start with an important term : sample . a sample is the group of people that respond to questions during a public opinion poll . a poll 's quality rests largely on its sample , and a sample can be bad in a few key ways .

what is the word for the group of people that respond to questions during a public opinion poll ?

modern computers are revolutionizing our lives , performing tasks unimaginable only decades ago . this was made possible by a long series of innovations , but there 's one foundational invention that almost everything else relies upon : the transistor . so what is that , and how does such a device enable all the amazing things computers can do ? well , at their core , all computers are just what the name implies , machines that perform mathematical operations . the earliest computers were manual counting devices , like the abacus , while later ones used mechanical parts . what made them computers was having a way to represent numbers and a system for manipulating them . electronic computers work the same way , but instead of physical arrangements , the numbers are represented by electric voltages . most such computers use a type of math called boolean logic that has only two possible values , the logical conditions true and false , denoted by binary digits one and zero . they are represented by high and low voltages . equations are implemented via logic gate circuits that produce an output of one or zero based on whether the inputs satisfy a certain logical statement . these circuits perform three fundamental logical operations , conjunction , disjunction , and negation . the way conjunction works is an `` and gate '' provides a high-voltage output only if it receives two high-voltage inputs , and the other gates work by similar principles . circuits can be combined to perform complex operations , like addition and subtraction . and computer programs consist of instructions for electronically performing these operations . this kind of system needs a reliable and accurate method for controlling electric current . early electronic computers , like the eniac , used a device called the vacuum tube . its early form , the diode , consisted of two electrodes in an evacuated glass container . applying a voltage to the cathode makes it heat up and release electrons . if the anode is at a slightly higher positive potential , the electrons are attracted to it , completing the circuit . this unidirectional current flow could be controlled by varying the voltage to the cathode , which makes it release more or less electrons . the next stage was the triode , which uses a third electrode called the grid . this is a wire screen between the cathode and anode through which electrons could pass . varying its voltage makes it either repel or attract the electrons emitted by the cathode , thus , enabling fast current-switching . the ability to amplify signals also made the triode crucial for radio and long distance communication . but despite these advancements , vacuum tubes were unreliable and bulky . with 18,000 triodes , eniac was nearly the size of a tennis court and weighed 30 tons . tubes failed every other day , and in one hour , it consumed the amount of electricity used by 15 homes in a day . the solution was the transistor . instead of electrodes , it uses a semiconductor , like silicon treated with different elements to create an electron-emitting n-type , and an electron absorbing p-type . these are arranged in three alternating layers with a terminal at each . the emitter , the base , and the collector . in this typical npn transistor , due to certain phenomena at the p-n interface , a special region called a p-n junction forms between the emitter and base . it only conducts electricity when a voltage exceeding a certain threshold is applied . otherwise , it remains switched off . in this way , small variations in the input voltage can be used to quickly switch between high and low-output currents . the advantage of the transistor lies in its efficiency and compactness . because they do n't require heating , they 're more durable and use less power . eniac 's functionality can now be surpassed by a single fingernail-sized microchip containing billions of transistors . at trillions of calculations per second , today 's computers may seem like they 're performing miracles , but underneath it all , each individual operation is still as simple as the flick of a switch .

what made them computers was having a way to represent numbers and a system for manipulating them . electronic computers work the same way , but instead of physical arrangements , the numbers are represented by electric voltages . most such computers use a type of math called boolean logic that has only two possible values , the logical conditions true and false , denoted by binary digits one and zero .

how are numbers represented in a modern computer ?

look at your hand . how do you know it 's really yours ? it seems obvious , unless you 've experienced the rubber hand illusion . in this experiment , a dummy hand is placed in front of you and your real hand is hidden behind a screen . both are simultaneously stroked with a paint brush . no matter how much you remind yourself the dummy hand is n't yours , you eventually start to feel like it is , and inevitably flinch when it 's threatened with a knife . that may just be a temporary trick , but it speaks to a larger truth : our bodies , the physical , biological parts of us , and our minds , the thinking , conscious aspects , have a complicated , tangled relationship . which one primarily defines you or your self ? are you a physical body that only experiences thoughts and emotions as a result of biochemical interactions in the brain ? that would be a body with a mind . or is there some non-physical part of you that 's pulling the strings but could live outside of your biological body ? that would be a mind with a body . that takes us to an old question of whether the body and mind are two separate things . in a famous thought experiment , 16th-century philosopher rené descartes pointed out that even if all our physical sensations were just a hallucinatory dream , our mind and thoughts would still be there . that , for him , was the ultimate proof of our existence . and it led him to conclude that the conscious mind is something separate from the material body that forms the core of our identity . the notion of a non-physical consciousness echoes the belief of many religions in an immaterial soul for which the body is only a temporary shell . if we accept this , another problem emerges . how can a non-physical mind have any interaction with the physical body ? if the mind has no shape , weight , or motion , how can it move your muscles ? or if we assume it can , why can your mind only move your body and not others ? some thinkers have found creative ways to get around this dilemma . for example , the french priest and philosopher nicolas malebranche claimed that when we think about reaching for a fork , it 's actually god who moves our hand . another priest philosopher named george berkeley concluded that the material world is an illusion , existing only as mental perceptions . this question of mind versus body is n't just the domain of philosophers . with the development of psychology and neuroscience , scientists have weighed in , as well . many modern scientists reject the idea that there 's any distinction between the mind and body . neuroscience suggests that our bodies , along with their physical senses , are deeply integrated with the activity in our brains to form what we call consciousness . from the day we 're born , our mental development is formed through our body 's interaction with the external world . every sight , sound , and touch create new maps and representations in the brain that eventually become responsible for regulating our experience of self . and we have other senses , besides the typical five , such as the sense of balance and a sense of the relative location of our body parts . the rubber hand illusion , and similar virtual reality experiments , show that our senses can easily mislead us in our judgment of self . they also suggest that our bodies and external sensations are inseparable from our subjective consciousness . if this is true , then perhaps descartes ' experiment was mistaken from the start . after all , if we close our eyes in a silent room , the feeling of having a body is n't something we can just imagine away . this question of mind and body becomes particularly interesting at a time when we 're considering future technologies , such as neural prosthetics and wearable robots that could become extended parts of our bodies . or the slightly more radical idea of mind uploading , which dangles the possibility of immortal life without a body by transferring a human consciousness into a computer . if the body is deeply mapped in the brain , then by extending our sense of self to new wearable devices , our brains may eventually adapt to a restructured version with new sensory representations . or perhaps uploading our consciousness into a computer might not even be possible unless we can also simulate a body capable of delivering physical sensations . the idea that our bodies are part of our consciousness and vice versa also is n't new . it 's found extensively in buddhist thought , as well as the writings of philosophers from heidegger to aristotle . but for now , we 're still left with the open question of what exactly our self is . are we a mind equipped with a physical body as descartes suggested ? or a complex organism that 's gained consciousness over millions of years of evolution thanks to a bigger brain and more neurons than our distant ancestors ? or something else entirely that no one 's yet dreamt up ?

how do you know it 's really yours ? it seems obvious , unless you 've experienced the rubber hand illusion . in this experiment , a dummy hand is placed in front of you and your real hand is hidden behind a screen . both are simultaneously stroked with a paint brush .

in the rubber hand illusion , the dummy hand feels like the viewer ’ s real hand because of the synchronization between two sensory inputs from both hands . what are those two sensory inputs ?

if insects suddenly morphed into large beings , and decided to wage war on us , there 's no doubt that humans would lose . we 'd simply be crushed by their sheer numbers . there are an estimated 10 quintillion individual insects on earth . that 's a one followed by 19 zeroes . so , compared with our population of about 7 billion , these invertebrates outnumber us by more than a billion to one . their astounding numbers exist at the species level , as well . there are more than 60,000 vertebrate species on the planet . but the class of insects contains a million known species , and many others that have n't been classified . in fact , these critters make up approximately 75 % of all animals on earth . so , what 's their secret to success ? insect abundance comes down to many things that together make them some of the most adaptable and resilient creatures , beginning with their impressive ability to breed . many species can produce hundreds of offspring within their lifetimes . most offspring will die , but more than enough will survive into adulthood to reproduce . offspring also mature very rapidly , so the cycle of reproduction resumes quickly , and can occur over and over again in a short time . these numbers mean that as a class , insects harbor a tremendous amount of genetic diversity . the different species contain a wealth of genetic data that give them the necessary adaptations they need to thrive in a range of environments across the planet . even some of the most extreme environments are in bounds ; flat bark beetles can live at -40 degrees fahrenheit , sahara desert ants can venture out when surface temperatures exceed 155 degrees , and some bumblebees can survive 18,000 feet above sea level . insect exoskeletons also work like body armor , protecting insects against the outside world and helping them cope with habitats that other creatures ca n't . even their small size , which we might see as a disadvantage , is something they use to their benefit . because most species are so tiny , millions of insects can inhabit a small space and make use of all the available resources within it . this means they can occupy hundreds of different niches across ecosystems . some insects survive by eating the roots , stems , leaves , seeds , pollen , and nectar of specific plants . others , like wasps , make use of live insects by paralyzing the victims and laying their eggs inside so that when the hatchlings emerge , they can eat their way out and get nourishment . mosquitos and biting flies feed on blood , taking advantage of this unusual resource to ensure their survival . and a whole bunch of other insects have built a niche around feces . flies lay their eggs there , and some beetles even build large balls out of animal dung , which they eat and use as accommodation for their eggs . and then there 's the insects ' mighty power of metamorphosis . this trait not only transforms insects , but also helps them maximize the available resources in an ecosystem . take butterflies . in their larval caterpillar form , they chomp hungrily through leaves at a rapid rate to help them grow and spin cocoons . but when they emerge as butterflies , these insects feed only on flower nectar . metamorphosis means the larvae and adults of one species will never compete for the same resource , so they successfully share an ecological niche without limiting their own success . this process is so efficient that an incredible 86 % of insect species undergo complete metamorphosis . we 're big and they 're small , so it 's easy to forget that these critters are moving in their millions all around us , all the time . but examine almost any patch of ground , and you 're sure to find them there . their numbers are immense , and their success is unmatched . we may have to accept that it 's insects , not us , that are the true conquerors of the planet .

this means they can occupy hundreds of different niches across ecosystems . some insects survive by eating the roots , stems , leaves , seeds , pollen , and nectar of specific plants . others , like wasps , make use of live insects by paralyzing the victims and laying their eggs inside so that when the hatchlings emerge , they can eat their way out and get nourishment . mosquitos and biting flies feed on blood , taking advantage of this unusual resource to ensure their survival .

what kinds of foods do insects eat ?

on october 4 , 1957 , the world watched in awe and fear as the soviet union launched sputnik , the world 's first man-made satellite , into space . this little metal ball , smaller than two feet in diameter , launched a space race between the u.s. and u.s.s.r. that would last for eighteen years and change the world as we know it . sputnik was actually not the first piece of human technology to enter space . that superlative goes to the v-2 rocket used by germany in missile attacks against allied cities as a last-ditch effort in the final years of world war ii . it was n't very effective , but , at the end of the war , both the u.s. and u.s.s.r. had captured the technology and the scientists that had developed it and began using them for their own projects . and by august 1957 , the soviet 's successfully tested the first intercontinental ballistic missile , the r-7 , the same rocket that would be used to launch sputnik two months later . so , the scary thing about sputnik was not the orbiting ball itself , but the fact that the same technology could be used to launch a nuclear warhead at any city . not wanting to fall too far behind , president eisenhower ordered the navy to speed up its own project and launch a satellite as soon as possible . so , on december 6 , 1957 , excited people across the nation tuned in to watch the live broadcast as the vanguard tv3 satellite took off and crashed to the ground two seconds later . the vanguard failure was a huge embarassment for the united states . newspapers printed headlines like , `` flopnik '' and `` kaputnik . '' and a soviet delegate at the u.n. mockingly suggested that the u.s. should receive foreign aid for developing nations . fortunately , the army had been working on their own parallel project , the explorer , which was successfully launched in january 1958 , but the u.s. had barely managed to catch up before they were surpassed again as yuri gargarin became the first man in space in april 1961 . almost a year passed and several more soviet astronauts completed their missions before project mercury succeeded in making john glenn the first american in orbit in february 1962 . by this time , president kennedy had realized that simply catching up to each soviet advance a few months later was n't going to cut it . the u.s. had to do something first , and in may 1961 , a month after gargarin 's flight , he announced the goal of putting a man on the moon by the end of the 1960s . they succeeded in this through the apollo program with neil armstrong taking his famous step on july 20 , 1969 . with both countries ' next turning their attention to orbital space stations , there 's no telling how much longer the space race could have gone on . but because of improving relations negotiated by soviet premier leonid breshnev and u.s. president nixon , the u.s.s.r. and u.s. moved toward cooperation rather than competition . the successful joint mission , known as apollo-soyuz , in which an american apollo spacecraft docked with a soviet soyuz craft and the two crews met , shook hands , and exchanged gifts , marked the end of the space race in 1975 . so , in the end , what was the point of this whole space race ? was it just a massive waste of time ? two major superpowers trying to outdo each other by pursuing symbolic projects that were both dangerous and expensive , using resources that could have been better spent elsewhere ? well , sure , sort of , but the biggest benefits of the space program had nothing to do with one country beating another . during the space race , funding for research and education , in general , increased dramatically , leading to many advances that may not have otherwise been made . many nasa technologies developed for space are now widely used in civilian life , from memory foam in mattresses to freeze-dried food , to leds in cancer treatment . and , of course , the satellites that we rely on for our gps and mobile phone signals would not have been there without the space program . all of which goes to show that the rewards of scientific research and advancement are often far more vast than even the people pursuing them can imagine .

two major superpowers trying to outdo each other by pursuing symbolic projects that were both dangerous and expensive , using resources that could have been better spent elsewhere ? well , sure , sort of , but the biggest benefits of the space program had nothing to do with one country beating another . during the space race , funding for research and education , in general , increased dramatically , leading to many advances that may not have otherwise been made .

which one of these advancements is not directly related to the space program ?

acids and bases are everywhere . they 're used to make foods , soaps and detergents , fertilizers , explosives , dyes , plastics , pesticides , even paper . our stomachs are very acidic . our blood is slightly basic . our proteins are made up of amino acids , and the letters in our genetic code , those as , ts , cs , and gs , are all bases . you were probably taught how acids and bases behave on the molecular level . you were probably never taught that a long time ago , like ancient greek ago , before anyone knew about atoms or molecules , acids and bases were defined by how they behaved . acids tasted sour and corroded metal . bases felt slippery and could somehow counteract acids . when molecules dissolved in water interact , they are exchanging two main currencies with their surroundings : protons , also known as hydrogen ions , and electrons . depending on how a molecule is composed or shaped , it may be willing to donate or accept either protons or electrons with some other community member . and some molecules are far more aggressive than others when it comes to donating or accepting either currency . remember that protons are positively charged and electrons are negatively charged . so , if a molecule is willing to give up a proton , that 's not too different from it being willing to accept an electron -- either way it 's becoming more negatively charged . other molecules are willing to accept a proton or give up an electron . these are becoming more positively charged . some substances are so aggressive about donating their protons that when they get a chance , all of the molecules in a sample will dump a proton , sometimes more than one , to the surrounding water molecules . we call these strong acids . meanwhile , some compounds are so ready to accept a proton that they wo n't wait around , they 'll just rip one off water , which usually has two protons but is generous enough to hang out with just one . we call these strong bases . other acids and bases are not so strong . they may donate just a few of their protons to water or accept just a few protons from water , but most of their molecules stay exactly the same . if left alone in water , they 'll reach some equilibrium point where maybe only one out of a hundred or one out of ten thousand of their molecules has exchanged currency with water . as you might guess , we label these acids and bases weak , but in the common sense of the word , they 're not weak . the vinegar in your salad dressing that you can smell from across the room , that is a weak acid . the ammonia you spray on glass for a streak-free shine , that is a weak base . so , it does n't take much to be an active player in the chemical economy . most acid-base chemistry takes place in water , which can act as either an acid or a base , accepting deposits and enabling withdrawals like a 24-hour molecular atm . and when a proton-deposit customer , that 's an acid , and a proton-withdrawal customer , the base , shop at the same time , their net effect on water 's account may cancel out , and we call this neutralization . now , certain molecules can behave as acids or bases without water , but that 's another story . let 's end by saluting water as the resilient and fair banker for acids and bases . it 's always open for business , does n't charge interest , and will never foreclose on your molecules , which is more than i can say for [ bleep ] . waah-waah .

so , it does n't take much to be an active player in the chemical economy . most acid-base chemistry takes place in water , which can act as either an acid or a base , accepting deposits and enabling withdrawals like a 24-hour molecular atm . and when a proton-deposit customer , that 's an acid , and a proton-withdrawal customer , the base , shop at the same time , their net effect on water 's account may cancel out , and we call this neutralization .

two important characteristics of acids and bases are : ( 1 ) strength and ( 2 ) concentration . we talked about strength in the video , but not concentration . what is the difference between a strong acid and a weak acid ? vinegar is about 5 % acetic acid . is this a measure of its strength or concentration ? if you were given the choice between drinking a solution of 0.1 % hydrochloric acid ( a strong acid ) to 70 % acetic acid ( a weak acid ) , which would you choose and why ? is there any additional information you ’ d need to answer this question ? ( note : don ’ t drink things that aren ’ t meant to be drunk . this is purely a thought experiment . )

remember the time you fell off your bike or bumped your head on a sharp corner ? childhood injuries are things we 'd often like to forget , but our bodies often carry the memories in the form of scars . so what are these unwanted souvenirs and why do we keep them for so long after that unintended vacation to the emergency room ? the most common place we see scars are on our skin , a patch that looks slightly different from the normal skin around it . often , this is considered an unfortunate disfigurement , while other times , deliberate scarification has been used in both traditional and modern cultures , to mark a rite of passage or simply for aesthetic decoration . but the difference is n't only cosmetic . when we look at healthy skin tissue under a microscope , we see the cells that perform various functions connected by an extracellular matrix , or ecm . this is composed of structural proteins , like collagen , secreted by specialized fibroblast cells . well-arranged ecm allows for transportation of nutrients , cell-to-cell communication , and cell adhesion . but when a deep wound occurs , this arrangement is disrupted . during the process of wound healing , collagen is redeposited at the wound site , but instead of the basket-weave formation found in healthy tissue , the new ecm is aligned in a single direction , impeding inter-cell processes , and reducing durability and elasticity . to make matters worse , the healed tissue contains a higher proportion of ecm than before , reducing its overall function . in the skin , the overabundance of collagen interferes with its original functions , like producing sweat , controlling body temperature and even growing hair . the scar tissue is fragile , sensitive to changes in temperature and sensation , and should be kept in moist environments to maximize healing . this presence of excessive fibrous connective tissue in an organ is known as fibrosis , and if that term sounds familiar , it 's because our skin is not the only organ vulnerable to scarring . cystic fibrosis is a genetic disorder that causes scarring of the pancreas , while pulmonary fibrosis is a scarring of the lungs , resulting in shortness of breath . scarring of the heart and the buildup of ecm following a heart attack can inhibit its beating , leading to further heart problems . what 's common to all these conditions is that although it retains some of the original functions , the scar tissue formed after a wound is inferior to the native tissue it replaces . however , there is hope . medical researchers are now studying what causes fibroblast cells to secrete excessive amounts of collagen and how we can recruit the body 's other cells in regenerating and repopulating the damaged tissue . by learning how to better control wound healing and the formation of scar tissue , we can utilize the multi-billion-dollar budgets currently used to address the aftermath of wounding in a much more efficient manner , and help millions of people live better and healthier lives . but until then , at least some of our scars can help us remember to avoid the sorts of things that cause them .

this presence of excessive fibrous connective tissue in an organ is known as fibrosis , and if that term sounds familiar , it 's because our skin is not the only organ vulnerable to scarring . cystic fibrosis is a genetic disorder that causes scarring of the pancreas , while pulmonary fibrosis is a scarring of the lungs , resulting in shortness of breath . scarring of the heart and the buildup of ecm following a heart attack can inhibit its beating , leading to further heart problems .

what is the medical term for scarring in the lungs resulting in shortness of breath ?

as a wildfire rages through the grasslands , three lions and three wildebeest flee for their lives . to escape the inferno , they must cross over to the left bank of a crocodile-infested river . fortunately , there happens to be a raft nearby . it can carry up to two animals at a time , and needs as least one lion or wildebeest on board to row it across the river . there 's just one problem . if the lions ever outnumber the wildebeest on either side of the river , even for a moment , their instincts will kick in , and the results wo n't be pretty . that includes the animals in the boat when it 's on a given side of the river . what 's the fastest way for all six animals to get across without the lions stopping for dinner ? pause here if you want to figure it out for yourself . answer in : 3 answer in : 2 answer in : 1 if you feel stuck on a problem like this , try listing all the decisions you can make at each point , and the consequences each choice leads to . for instance , there are five options for who goes across first : one wildebeest , one lion , two wildebeest , two lions , or one of each . if one animal goes alone , it 'll just have to come straight back . and if two wildebeest cross first , the remaining one will immediately get eaten . so those options are all out . sending two lions , or one of each animal , can actually both lead to solutions in the same number of moves . for the sake of time , we 'll focus on the second one . one of each animal crosses . now , if the wildebeest stays and the lion returns , there will be three lions on the right bank . bad news for the two remaining wildebeest . so we need to have the lion stay on the left bank and the wildebeest go back to the right . now we have the same five options , but with one lion already on the left bank . if two wildebeest go , the one that stays will get eaten , and if one of each animal goes , the wildebeest on the raft will be outnumbered as soon as it reaches the other side . so that 's a dead end , which means that at the third crossing , only the two lions can go . one gets dropped off , leaving two lions on the left bank . the third lion takes the raft back to the right bank where the wildebeest are waiting . what now ? well , since we 've got two lions waiting on the left bank , the only option is for two wildebeest to cross . next , there 's no sense in two wildebeest going back , since that just reverses the last step . and if two lions go back , they 'll outnumber the wildebeest on the right bank . so one lion and one wildebeest take the raft back leaving us with one of each animal on the left bank and two of each on the right . again , there 's no point in sending the lion-wildebeest pair back , so the next trip should be either a pair of lions or a pair of wildebeest . if the lions go , they 'd eat the wildebeest on the left , so they stay , and the two wildebeest cross instead . now we 're quite close because the wildebeest are all where they need to be with safety in numbers . all that 's left is for that one lion to raft back and bring his fellow lions over one by one . that makes eleven trips total , the smallest number needed to get everyone across safely . the solution that involves sending both lions on the first step works similarly , and also takes eleven crossings . the six animals escape unharmed from the fire just in time and begin their new lives across the river . of course , now that the danger 's passed , it remains to be seen how long their unlikely alliance will last .

so that 's a dead end , which means that at the third crossing , only the two lions can go . one gets dropped off , leaving two lions on the left bank . the third lion takes the raft back to the right bank where the wildebeest are waiting .

assuming the correct scenario in question 2 , what animal gets dropped off on the left side of the river ?

here 's what has to happen for pregnancy to occur after sexual intercourse . sperm must swim up the vagina , through the cervical opening , upwards through the uterus , and into one of the two fallopian tubes . if an egg , released during that month 's ovulation , is in the tube , one sperm has a chance to fertilize it . contraceptives are designed to prevent this process , and they work in three basic ways . they block the sperm , disable sperm before they reach the uterus , or suppress ovulation . block is the simplest . male and female condoms prevent sperm from coming into contact with the vaginal space . that barrier is also why they , unlike other contraceptive methods , are able to prevent transmission of certain sexually transmitted diseases . meanwhile , the diaphragm , cervical cap , and sponge work by being placed over the cervix , barricading the entrance to the uterus . these contraceptives are sometimes called barrier methods and can be used with spermicides , an example of the second category , disable . a spermicide is a chemical that immobilizes and destroys sperm . today 's spermicides come as foam , cream , jelly , suppositories , and even a thin piece of translucent film that dissolves in the vagina . these products can be inserted directly into the vagina before intercourse , or can be combined with block methods , like a diaphragm or condom , for added proection . the third category for preventing pregnancy works by suppressing the action of an egg maturing in the ovary . if there is n't an egg available in the fallopian tube , there 's nothing for sperm to fertilize . hormonal contraceptives , including the pill , the patch , the depo shot , and the vaginal ring all release synthetic versions of various combinations of progesterone and estrogen . this hormone cocktail suppresses ovulation , keeping the immature egg safely sequestered in the ovary . synthetic progesterone also has a block trick up its sleeve . it makes cervical mucus too thick and sticky for sperm to swim through easily . there are other contraceptives that use multiple approaches at the same time . for example , many iuds , or intrauterine devices , contain synthetic hormones which suppress ovulation . some also contain copper , which disable sperm while also making egg implantation in the uterus difficult . block , disable , or suppress : is one strategy better than the other ? there are differences , but a lot of it has to do with how convenient and easy it is to use each contraceptive correctly . for example , male condoms would be about 98 % effective if everyone used them perfectly . that 98 % means if 100 couples correctly used condoms for a year , two women would get pregnant . but not everyone uses them correctly , so they 're only 82 % effective in practice . other methods , like the patch and pill , are 99 % effective when they 're used perfectly . but in practice , that 's 91 % . spermicide is only 85 % effective , even with perfect usage , and just 71 % effective with typical usage . another important consideration in the choice of contraceptives are side effects , which almost exclusively affect women rather than men . hormonal methods in particular can cause symptoms like headaches , nausea , and high blood pressure , but they vary from woman to woman . that 's why these methods require a prescription from a doctor . the choice of contraceptive method is a personal one , and what works best for you now may change later . scientists also continue to research new methods , such as a male pill that would prevent sperm production . in the meantime , there are quite a few options to block sperm , disable them , or suppress eggs and keep them out of reach .

there are other contraceptives that use multiple approaches at the same time . for example , many iuds , or intrauterine devices , contain synthetic hormones which suppress ovulation . some also contain copper , which disable sperm while also making egg implantation in the uterus difficult .

methods of contraception can be placed into how many categories according to their general action ?

( music ) esteemed members of the jury , i submit the following words for immediate and violent execution and extraction from our vocabularies , to be locked away forever , if you would prefer . these words i present to you are `` good '' and `` bad . '' these words have served as treacherous liars for eternity . these two words have worked in tandem to produce vague and bland sentences that have crippled the creativity of humanity . these two deceptively tiny words stifle real description and honest communication . look at them , just sitting there on this page , all smug and satisfied with their work . how dare they ? you serve no purpose in our world , and we must rid ourselves of your influence . we must replace these two words with the truth , with phrases that include adequate and sincere adjectives . i 'll offer you `` radiant , '' `` stupefying , '' `` awful , '' `` gut-wrenching . '' these choices create clarity and depth . `` good '' and `` bad '' only provide gray vagueness . we must demand color ! we should even use winding similes and metaphors , where appropriate . we have to do whatever we can and should to make our real sentiments known . `` good '' and `` bad '' will no longer be our go-to words that we rely on when we are too afraid or too languid to express our real thoughts . ladies and gentlemen of the jury , i implore you to deliver a verdict of guilty and send these words to their rightful fate . now imagine a world without these two words . imagine a world where real description is required , digging further into our vocabulary than just a monosyllabic effort to get away with not being honest , impactful , creative . how does my hair look ? good . what is that ? a dull attempt not to be honest ? perhaps my hair looks like a hideous mess of tangles and bald spots . yet someone does not want to be honest , and offers the quick fix `` good , '' to try and mask the truth and send me hurling into the evening with a plop of disorganized tresses . this will not do . perhaps my hair looks like an amazing glossy sculpture that frames my face perfectly , and lends an air of magic to the night . well , `` good '' just does n't cut it . i wo n't take any more of this formless , lifeless description . i will not take these lies , and neither should you . a doctor asks you how you feel . `` i feel bad . '' heresy ! the doctor , based on this paltry report , could conclude that you have brain cancer or the flu or rabies . you owe it to yourself and the possible misdiagnosis of your life to be honest about exactly how you feel . `` i feel like a herd of wombats has taken up in my chest . '' a-ha ! there we have it . an accurate description . now the doctor has some real evidence to work with in order to assist you . we have become addicted to the numbness that `` good '' and `` bad '' have created . we have become linguistic slobs , churning out `` good '' and `` bad '' wherever we are too lazy to allow our minds to communicate with creativity and specification . you look good , you sound bad , this tastes good , the weather looks bad . lie after lie , repeating this verbal gray , this sloshy mush , this fuzzy picture that reflects no real truth . replace them with grittier , exact terms that have been buried in our lexis , waiting to see daylight . no longer does the weather look good or bad , the weather looks ominous or exhilarating . nothing tastes good or bad . it tastes like pillows of sparkles or old shoe and dung . no more of sounding good or bad . you sound like lilting baby laughter or ogres marching to war . dear god , you do not look good or bad . you look like a feathery angel or a morose faun . today , you look at these two words , `` good '' and `` bad , '' examine them closely . because behind their seemingly unassuming visages reside two deceitful offerings that smother the truth . these words are liars . these words must be stopped . remove them from our language so that honesty can return to our communication . ladies and gentlemen , if i say to you that you have been a good jury , you will take the compliment , make your decision and go on about your day . but if i say to you that you are an honorable jury , and that i hope your unshakeable determination to better the vocabulary of humanity will result in finding `` good '' and `` bad '' guilty , you will recognize the ingenuity of this argument and find `` good '' and `` bad '' guilty . ( music )

how does my hair look ? good . what is that ?

revise and rewrite the following passage by utilizing superior replacements for the terms good and bad . it was a good day . the sunlight felt good on her legs that had been sheltered under jeans all year . the beach and the ocean smelled good . she let all the good sounds soak into her soul . she was determined to make this as good a vacation as her grandmother had ever had .

food does n't last . in days , sometimes hours , bread goes moldy , apple slices turn brown , and bacteria multiply in mayonnaise . but you can find all of these foods out on the shelf at the grocery store , hopefully unspoiled , thanks to preservatives . but what exactly are preservatives ? how do they help keep food edible and are they safe ? there are two major factors that cause food to go bad : microbes and oxidation . microbes like bacteria and fungi invade food and feed off its nutrients . some of these can cause diseases , like listeria and botulism . others just turn edibles into a smelly , slimy , moldy mess . meanwhile , oxidation is a chemical change in the food 's molecules caused by enzymes or free radicals which turn fats rancid and brown produce , like apples and potatoes . preservatives can prevent both types of deterioration . before the invention of artificial refrigeration , fungi and bacteria could run rampant in food . so we found ways to create an inhospitable environment for microbes . for example , making the food more acidic unravels enzymes that microbes need to survive . and some types of bacteria can actually help . for thousands of years , people preserved food using bacteria that produce lactic acid . the acid turns perishable vegetables and milk into longer lasting foods , like sauerkraut in europe , kimchi in korea , and yogurt in the middle east . these cultured foods also populate your digestive track with beneficial microbes . many synthetic preservatives are also acids . benzoic acid in salad dressing , sorbic acid in cheese , and propionic acid in baked goods . are they safe ? some studies suggest that benzoates , related to benzoic acid , contribute to hyperactive behavior . but the results are n't conclusive . otherwise , these acids seem to be perfectly safe . another antimicrobial strategy is to add a lot of sugar , like in jam , or salt , like in salted meats . sugar and salt hold on to water that microbes need to grow and actually suck moisture out of any cells that may be hanging around , thus destroying them . of course , too much sugar and salt can increase your risk of heart disease , diabetes , and high blood pressure , so these preservatives are best in moderation . antimicrobial nitrates and nitrites , often found in cured meats , ward off the bacteria that cause botulism , but they may cause other health problems . some studies linking cured meats to cancer have suggested that these preservatives may be the culprit . meanwhile , antioxidant preservatives prevent the chemical changes that can give food an off-flavor or color . smoke has been used to preserve food for millennia because some of the aromatic compounds in wood smoke are antioxidants . combining smoking with salting was an effective way of preserving meat before refrigeration . for antioxidant activity without a smoky flavor , there are compounds like bht and tocopherol , better known as vitamin e. like the compounds in smoke , these sop up free radicals and stave off rancid flavors that can develop in foods like oils , cheese , and cereal . other antioxidants like citric acid and ascorbic acid help cut produce keep its color by thwarting the enzyme that causes browning . some compounds like sulfites can multitask . they 're both antimicrobials and antioxidants . sulfites may cause allergy symptoms in some people , but most antioxidant preservatives are generally recognized as safe . so should you be worried about preservatives ? well , they 're usually near the end of the ingredients list because they 're used in very small amounts determined by the fda to be safe . nevertheless , some consumers and companies are trying to find alternatives . packaging tricks , like reducing the oxygen around the food can help , but without some kind of chemical assistance , there are very few foods that can stay shelf stable for long .

some compounds like sulfites can multitask . they 're both antimicrobials and antioxidants . sulfites may cause allergy symptoms in some people , but most antioxidant preservatives are generally recognized as safe .

which of the following is/are not antioxidants ?

now and then i think of what i learned in high school like ap bio and british literature is that igneous or metamorphic ? i do n't need to write a nine bic and i 'll admit i do n't know shit about millard fillmore why did i have to learn this stuff ? it is never common -- had they never used it for nothing ? why did we have to read the scarlet letter ? puritans are boring even when one is a slut there 's actually one thing i still know eli whitney he invented the cotton gin definitely do not need that , though now it 's just a study that i used to know now it 's just a study that i used to know now and then i think of all the things i 've taught you every handout with a far side cartoon apropo you do n't want to live that way forgetting every word i say you said you 'd never let it go i guess mnemonic devices just were n't enough for you though you really freaking pissed me off i worked so hard to teach you something , now you do n't know nothing what does the comment symbolize ? or anything beyond the first three digits of pi and what about sohcahtoa or asexual reproduction of a protozoa i guess you did n't need that though now it 's just a study that you used to know a study i used to know now it 's just a study that you used to know i used to know a study

now and then i think of what i learned in high school like ap bio and british literature is that igneous or metamorphic ? i do n't need to write a nine bic and i 'll admit i do n't know shit about millard fillmore why did i have to learn this stuff ? it is never common -- had they never used it for nothing ?

personal question : malcolm gladwell talks about how it takes many hours of practice to learn proficiency and become an expert in anything . in his book , outliers , he quotes neurologist daniel levitin as saying `` the emerging picture from such studies is that 10,000 hours of practice is required to achieve the level of mastery associated with being a world-class expert—in anything. ” if expertise is based on the time we 've practiced something , what have you spent considerable time practicing ? what else do you want to develop expertise in ? what do you need in order to start ?

imagine if half the people in your neighborhood , your city , or even your whole country were wiped out . it might sound like something out of an apocalyptic horror film , but it actually happened in the 14th century during a disease outbreak known as the black death . spreading from china through asia , the middle east , africa and europe , the devastating epidemic destroyed as much as 1/5 of the world 's population , killing nearly 50 % of europeans in just four years . one of the most fascinating and puzzling things abut the black death is that the illness itself was not a new phenomenon but one that has affected humans for centuries . dna analysis of bone and tooth samples from this period , as well as an earlier epidemic known as the plague of justinian in 541 ce , has revealed that both were caused by yersinia pestis , the same bacterium that causes bubonic plague today . what this means is that the same disease caused by the same pathogen can behave and spread very differently throughout history . even before the use of antibiotics , the deadliest oubreaks in modern times , such as the ones that occurred in early 20th century india , killed no more than 3 % of the population . modern instances of plague also tend to remain localized , or travel slowly , as they are spread by rodent fleas . but the medieval black death , which spread like wildfire , was most likely communicated directly from one person to another . and because genetic comparisons of ancient to modern strains of yersinia pestis have not revealed any significantly functional genetic differences , the key to why the earlier outbreak was so much deadlier must lie not in the parasite but the host . for about 300 years during the high middle ages , a warmer climate and agricultural improvements had led to explosive population growth throughout europe . but with so many new mouths to feed , the end of this warm period spelled disaster . high fertility rates combined with reduced harvest , meant the land could no longer support its population , while the abundant supply of labor kept wages low . as a result , most europeans in the early 14th century experienced a steady decline in living standards , marked by famine , poverty and poor health , leaving them vulnerable to infection . and indeed , the skeletal remains of black death victims found in london show telltale signs of malnutrition and prior illness . the destruction caused by the black death changed humanity in two important ways . on a societal level , the rapid loss of population led to important changes in europe 's economic conditions . with more food to go around , as well as more land and better pay for the surviving farmers and workers , people began to eat better and live longer as studies of london cemeteries have shown . higher living standards also brought an increase in social mobility , weakening feudalism , and eventually leading to political reforms . but the plague also had an important biological impact . the sudden death of so many of the most frail and vulnerable people left behind a population with a significantly different gene pool , including genes that may have helped survivors resist the disease . and because such mutations often confer immunities to multiple pathogens that work in similar ways , research to discover the genetic consequences of the black death has the potential to be hugely beneficial . today , the threat of an epidemic on the scale of the black death has been largely eliminated thanks to antibiotics . but the bubonic plague continues to kill a few thousand people worldwide every year , and the recent emergence of a drug-resistant strain threatens the return of darker times . learning more about the causes and effects of the black death is important , not just for understanding how our world has been shaped by the past . it may also help save us from a similar nightmare in the future .

modern instances of plague also tend to remain localized , or travel slowly , as they are spread by rodent fleas . but the medieval black death , which spread like wildfire , was most likely communicated directly from one person to another . and because genetic comparisons of ancient to modern strains of yersinia pestis have not revealed any significantly functional genetic differences , the key to why the earlier outbreak was so much deadlier must lie not in the parasite but the host .

how was the black death likely spread ?

the presidency of the united states of america is often said to be one of the most powerful positions in the world . but of all the u.s. presidents accused of misusing that power , only one has left office as a result . does richard nixon deserve to be remembered for more than the scandal that ended his presidency ? find out as we put this disgraced president 's legacy on trial in history vs. richard nixon . `` order , order . now , who 's the defendant today , some kind of crook ? '' `` cough . no , your honor . this is richard milhous nixon , the 37th president of the united states , who served from 1969 to 1974 . '' `` hold on . that 's a weird number of years for a president to serve . '' `` well , you see , president nixon resigned for the good of the nation and was pardoned by president ford , who took over after him . '' `` he resigned because he was about to be impeached , and he did n't want the full extent of his crimes exposed . '' `` and what were these crimes ? '' `` your honor , the watergate scandal was one of the grossest abuses of presidential power in history . nixon 's men broke into the democratic national committee headquarters to wiretap the offices and dig up dirt on opponents for the reelection campaign . '' `` cough it was established that the president did not order this burglary . '' `` but as soon as he learned of it , he did everything to cover it up , while lying about it for months . '' `` uh , yes , but it was for the good of the country . he did so much during his time in office and could have done so much more without a scandal jeopardizing his accomplishments . '' `` uh , accomplishments ? '' `` yes , your honor . did you know it was president nixon who proposed the creation of the environmental protection agency , and signed the national environmental policy act into law ? not to mention the endangered species act , marine mammal protection act , expansion of the clean air act . '' `` sounds pretty progressive of him . '' `` progressive ? hardly . nixon 's presidential campaign courted southern voters through fear and resentment of the civil rights movement . '' `` speaking of civil rights , the prosecution may be surprised to learn that he signed the title ix amendment , banning gender-based discrimination in education , and ensured that desegregation of schools occurred peacefully , and he lowered the voting age to 18 , so that students could vote . '' `` he did n't have much concern for students after four were shot by the national guard at kent state . instead , he called them bums for protesting the vietnam war , a war he had campaigned on ending . '' `` but he did end it . '' `` he ended it two years after taking office . meanwhile , his campaign had sabotaged the previous president 's peace talks , urging the south vietnamese government to hold out for supposedly better terms , which , i might add , did n't materialize . so , he protracted the war for four years , in which 20,000 more u.s. troops , and over a million more vietnamese , died for nothing . '' `` hmm , a presidential candidate interfering in foreign negotiations -- is n't that treason ? '' `` it is , your honor , a clear violation of the logan act of 1799 . '' `` uh , i think we 're forgetting president nixon 's many foreign policy achievements . it was he who normalized ties with china , forging economic ties that continue today . '' `` are we so sure that 's a good thing ? and do n't forget his support of the coup in chile that replaced the democratically-elected president allende with a brutal military dictator . '' `` it was part of the fight against communism . '' `` were n't tyranny and violence the reasons we opposed communism to begin with ? or was it just fear of the lower class rising up against the rich ? '' `` president nixon could n't have predicted the violence of pinochet 's regime , and being anti-communist did n't mean neglecting the poor . he proposed a guaranteed basic income for all american families , still a radical concept today . and he even pushed for comprehensive healthcare reform , just the kind that passed 40 years later . '' `` i 'm still confused about this burglary business . was he a crook or not ? '' `` your honor , president nixon may have violated a law or two , but what was the real harm compared to all he accomplished while in office ? '' `` the harm was to democracy itself . the whole point of the ideals nixon claimed to promote abroad is that leaders are accountable to the people , and when they hold themselves above the law for whatever reason , those ideals are undermined . '' `` and if you do n't hold people accountable to the law , i 'll be out of a job . '' many politicians have compromised some principles to achieve results , but law-breaking and cover-ups threaten the very fabric the nation is built on . those who do so may find their entire legacy tainted when history is put on trial .

`` it is , your honor , a clear violation of the logan act of 1799 . '' `` uh , i think we 're forgetting president nixon 's many foreign policy achievements . it was he who normalized ties with china , forging economic ties that continue today . '' `` are we so sure that 's a good thing ?

which of the following was not one of nixon 's economic initiatives ?

in the early hours of august 13 , 1961 , east german construction workers flanked by soldiers and police began tearing up streets and erecting barriers throughout the city of berlin and its surroundings . this night marked the beginning of one of history 's most infamous dividing lines , the berlin wall . construction on the wall continued for the next decade as it cut through neighborhoods , separated families , and divided not just germany , but the world . to understand how we got to this point , we have to go back to world war ii . america , britain , and france joined forces with the soviet union against the axis powers . after they defeated nazi germany , each of the victorious nations occupied part of the country . the division was meant to be temporary , but the former allies found themselves at odds over their visions for post-war europe . while western powers promoted liberal market economies , the soviet union sought to surround itself with obedient communist nations , including a weakened germany . as their relations deteriorated , the federal republic of germany was formed in the west while the soviets established the german democratic republic in the east . the soviet satellite countries restricted western trade and movement , so a virtually impassable border formed . it became known as the iron curtain . in the former german capital of berlin , things were particularly complicated . although the city lay fully within the east german territory of the gdr , the post-war agreement gave the allies joint administration . so america , britain , and france created a democratic enclave in berlin 's western districts . while east germans were officially banned from leaving the country , in berlin , it was simply a matter of walking , or riding a subway , streetcar or bus , to the western half , then traveling on to west germany or beyond . this open border posed a problem for the east german leadership . they had staked a claim to represent the communist resistance against hitler and portrayed western germany as a continuation of the nazi regime . while the u.s. and its allies poured money into west germany 's reconstruction , the soviet union extracted resources from the east as war reparations , making its planned economy even less competitive . life in east germany passed under the watchful eye of the stasi , the secret police whose wiretaps and informants monitored citizens for any hint of disloyalty . while there was free health care and education in the east , the west boasted higher salaries , more consumer goods , and greater personal freedom . by 1961 , about 3.5 million people , nearly 20 % of the east german population , had left , including many young professionals . to prevent further losses , east germany decided to close the border , and that 's where the berlin wall came in . extending for 43 kilometers through berlin , and a further 112 through east germany , the initial barrier consisted of barbed wire and mesh fencing . some berliners escaped by jumping over the wire or leaving from windows , but as the wall expanded , this became more difficult . by 1965 , 106 kilometers of 3.6-meter-high concrete barricades had been added topped with a smooth pipe to prevent climbing . over the coming years , the barrier was strengthened with spike strips , guard dogs , and even landmines , along with 302 watchtowers and 20 bunkers . a parallel fence in the rear set off a 100-meter area called the death strip . there , all buildings were demolished and the ground covered with sand to provide a clear line of sight for the hundreds of guards ordered to shoot anyone attempting to cross . nevertheless , nearly 5,000 people in total managed to flee east germany between 1961 and 1989 . some were diplomats or athletes who defected while abroad , but others were ordinary citizens who dug tunnels , swam across canals , flew hot air balloons , or even crashed a stolen tank through the wall . yet the risk was great . over 138 people died while attempting escape . some shot in full view of west germans powerless to help them . the wall stabilized east germany 's economy by preventing its work force from leaving , but tarnished its reputation , becoming a global symbol of communist repression . as part of reconciliation with the east , the basic treaty of 1972 recognized east germany pragmatically while west germany retained its hope for eventual reunification . although the eastern regime gradually allowed family visits , it tried to discourage people from exercising these rights with an arduous bureaucratic process and high fees . nonetheless , it was still overwhelmed by applications . by the end of the 1980 's , the liberalization of other eastern bloc regimes caused mass demonstrations for free travel and demands for democracy . on the evening of november 9 , 1989 , east germany tried to defuse tension by making travel permits easier to obtain . but the announcement brought thousands of east berliners to the border crossing points in the wall , forcing the surprised guards to open the gates immediately . rejoicing crowds poured into west berlin as people from both sides danced atop the wall . and others began to demolish it with whatever tools they could find . although the border guards initially tried to maintain order , it was soon clear that the years of division were at an end . after four decades , germany was officially reunified in october 1990 . and the soviet union fell soon after . today , parts of the wall still stand as a reminder that any barriers we put up to impede freedom , we can also break down .

some shot in full view of west germans powerless to help them . the wall stabilized east germany 's economy by preventing its work force from leaving , but tarnished its reputation , becoming a global symbol of communist repression . as part of reconciliation with the east , the basic treaty of 1972 recognized east germany pragmatically while west germany retained its hope for eventual reunification .

how did the wall shore up the east german government in the short run and why did it become a symbol of communist repression in the long run ?

if humans could fly , without tools and machines , how fast do you think we would go ? as of 2012 , the world record for fastest short-distance sprint speed is roughly 27 miles per hour . running speed depends on how much force is exerted by the runner 's legs , and according to newton 's second law of motion , force is the product of mass times acceleration . and newton 's third law states that for every action , there is an equal and opposite reaction . so , that means running requires having a ground to push off from , and the ground pushes back against the runner 's foot . so , flying would actually be more similar to swimming . michael phelps is currently the fastest human in water and the most decorated olympian of all time . guess how fast he swims ? the answer may surprise you . his fastest recorded speed is less than 5 miles per hour . a child on the ground can easily outrun michael phelps in water , but why is that ? well , let 's go back to newton 's third law of motion . when we run , we move forward by pushing against the ground with our feet and the ground pushes back , propelling us forward . the ground is solid . by definition , it means the particles are essentially locked into place and must push back instead of getting out of the way , but water is liquid and flows easily . when we move our limbs to push back against the water , a part of the water molecules can just slide past one another instead of pushing back . now , let 's think about flying . air has a lot more free space for particles to move past one another , so even more of our energy would be wasted . we would need to push a lot of air backwards in order to move forward . astronauts move around in shuttles in zero gravity when they 're in outer space by pulling on handles installed on the ceiling walls and floors of the shuttle . now , imagine you were given the ability to float . how would you move around in the middle of the street ? well , you would n't get very far by swimming in air , would you ? nah , i do n't think so ! now , assuming you were granted the ability to float and the speed to move around efficiently , let 's discuss the height of your flight . according to the ideal gas law , p-v n-r-t , pressure and temperature has a positive correlation , meaning they increase and decrease together . this is because the air expands in volume with less pressure , so the molecules have more room to wander around without colliding into each other and creating heat . since the atmospheric pressure is a lot lower in high altitudes , it would be freezing cold if you were flying above the clouds . you 'd need to wrap yourself up to keep your core body temperature above 95 degrees fahrenheit , otherwise you 'd start shivering violently , gradually becoming mentally confused and eventually drop out of the sky due to loss of muscle control from hypothermia ! now , the ideal gas law implies that as the pressure decreases , gas volume increases . so , if you were to fly straight up too quickly , the inert gas in your body would rapidly expand the way soda fizzes up when shaken . the phenomenon is called `` the bends , '' decompression sickness , or `` divers disease '' since deep sea scuba divers experience this when they come up too quickly . this results in pain , paralysis , or death , depending on how foamy your blood becomes . okay , well , let 's say you want to fly just a few meters above the ground where you can still see the road signs and breath oxygen with ease . you 'll still need goggles and a helmet to protect you from birds , insects , street signs , electrical wires , and other flying humans , including flying cops ready to hand you a ticket if you do n't follow the flying rules , buddy . now remember , if you have a collision mid-air that knocks you unconscious , you would experience free fall until you hit the ground . without society or the laws of physics , flying would be a totally awesome ability to have . but , even if we could all just float around a few feet above the ground and only moving at a snail 's pace , i 'm telling you , it 's still a cool ability that i 'd want , would n't you ? yeah , i thought so . now , which superpower physics lesson will you explore next ? shifting body size and content , super speed , flight , super strength , immortality , and invisibility .

this is because the air expands in volume with less pressure , so the molecules have more room to wander around without colliding into each other and creating heat . since the atmospheric pressure is a lot lower in high altitudes , it would be freezing cold if you were flying above the clouds . you 'd need to wrap yourself up to keep your core body temperature above 95 degrees fahrenheit , otherwise you 'd start shivering violently , gradually becoming mentally confused and eventually drop out of the sky due to loss of muscle control from hypothermia !

please compare and contrast the air in extremely high and low altitudes in as many ways as you can .

commas are tricky things , especially when subordinates and conjunctions are involved . if you can remember a few basic rules , a simple law of physics , and some common scenarios , you will be able to use commas correctly . i like to think of the different parts of our sentence as characters . let 's meet a few of them : the tiny conjunctions , the mighty subordinates , and the clever comma . conjunctions are small and nimble . they are words that connect clauses , words , and phrases . you can easily remember the conjunctions by remembering the acronym fanboys . the conjunctions are for , and , nor , but , or , yet , so . because they 're so small , more often than not , they require the help of a comma but not always . subordinates , on the other hand , are the wwe heavyweight champions of sentences . they are words that connect two unequal things , dependent and independent clauses . subordinates make it very clear what is being prioritized in a sentence . commonly used subordinates are although , because , before , however , unless , and even though . because subordinates are all about power , they can do a lot of heavy lifting by themselves . but , of course , sometimes even the strongest among us needs some help from our clever friends . because our clever comma is so nice , she often roams her neighborhood looking for some community service to do . today , as soon as she leaves her house , she sees a subordinate lifting the weight of two complete sentences , one on each arm . bartheleme loves engaging in political debate even though he usually loses . the comma asks the subordinate if he needs help . well , we know that subordinates are the wwe heavyweight champions of sentences . they can easily hold the weight of these two complete sentences because they are distributed evenly on both arms . so , when the comma asks if it can help , the subordinate is appalled at the idea of needing assistance . no thanks , maybe next time ! so , the comma continues on . soon , she seems a couple of subordinates attempting to lift the weight of sentences directly in front of themselves . even though bartheleme loves to sing , he never sings in front of others . the comma asks the subordinates if they need help . they might not want to admit it , but this time the subordinates do need help . complete sentences weigh quite a bit . simple physics tells us that it 's easier to balance heavy objects if the weight is evenly distributed . so , while the subordinates are quite capable of balancing two complete sentences when carrying the weight on both sides , they 're having trouble picking just one up . the comma rushes over to help the struggling subordinates , but how will she help ? when subordinates begin sentences , the comma will place herself directly after the first thought or complete sentence . after helping the subordinates , our comma heroine continues on and spots a conjunction holding the weight of two complete sentences . bartheleme was accepted into the university of chicago , and he is on the waitlist for stanford university . the comma asks the conjunction if he needs help . of course he does ! hurry ! the comma rushes and places itself before the conjunction . fanboys are n't as militant as subordinates . for this reason , the commas do n't have to fall in line behind the fanboys . fanboys are courteous creatures . they allow the comma to go ahead of them . helping others is hard work ! on her way home , our comma sees a conjunction holding up the weight of a complete sentence and a fragment sentence . bartheleme is going to major in molecular biology or interpretive dance . the now-exhausted comma asks the conjunction if he needs help lifting the items . this is one of the rare occassions where a conjunction does n't need the help of a comma . the conjunction assures the comma that help is n't needed , which is good for the comma because by now , all it wants to do is go home and rest up for another day of vigilant sentence constructing .

on her way home , our comma sees a conjunction holding up the weight of a complete sentence and a fragment sentence . bartheleme is going to major in molecular biology or interpretive dance . the now-exhausted comma asks the conjunction if he needs help lifting the items .

i want harold to show me how to dance but i ’ m afraid to ask him .

o polônio foi outro elemento descoberto por madame curie , a madame curie ela polonesa , mas fez boa parte da pesquisa , se não toda , em paris . polônio é um nome por causa da polônia polônio é um elemento que tem sido não muito importante , até a invenção da bomba atômica , e o polônio tornou-se um material absolutamente crucial pq é usado , ou foi usado , como um gatilho no centro da bomba atômica original . uma das dificuldades é que tem uma meia-vida muito curta . se vc tem um pedaço de polônio , metade dele decai em 138 dias se vc mantém por muito tempo , ele se vai , ou quase todo se vai , e portanto , no início da produção de bombas atômicas , das de hiroshima e nagasaki , o fator limitante na produção de bombas era a produção de polônio para o gatilho . em vez do enriquecimento de urânio ou plutônio , que eram usados para as bombas . bem recentemente o polônio teve uma nova notoriedade , pq foi usado neste caso trágico de envenenamento . no qual uma grande dose de polônio foi dado a um infeliz cidadão russo , que visitava a inglaterra . e ainda não está claro de onde veio o polônio . mas é um material bem pouco comum . e difícil para alguém comum encontrar . se for ingerido , pq decai muito rápido , a radioatividade pode causar todo tipo de efeitos desagradáveis . e , novamente , é provavelmente venenoso ele mesmo . traduzido por prof. dr. luís brudna

o polônio foi outro elemento descoberto por madame curie , a madame curie ela polonesa , mas fez boa parte da pesquisa , se não toda , em paris . polônio é um nome por causa da polônia polônio é um elemento que tem sido não muito importante , até a invenção da bomba atômica , e o polônio tornou-se um material absolutamente crucial pq é usado , ou foi usado , como um gatilho no centro da bomba atômica original .

when did marie and pierre curie discover the element polonium ?

before he turned physics upside down , a young albert einstein supposedly showed off his genius by devising a complex riddle involving this list of clues . can you resist tackling a brain teaser written by one of the smartest people in history ? let 's give it a shot . the world 's rarest fish has been stolen from the city aquarium . the police have followed the scent to a street with five identical looking houses . but they ca n't search all the houses at once , and if they pick the wrong one , the thief will know they 're on his trail . it 's up to you , the city 's best detective , to solve the case . when you arrive on the scene , the police tell you what they know . one : each house 's owner is of a different nationality , drinks a different beverage , and smokes a different type of cigar . two : each house 's interior walls are painted a different color . three : each house contains a different animal , one of which is the fish . after a few hours of expert sleuthing , you gather some clues . it may look like a lot of information , but there 's a clear logical path to the solution . solving the puzzle will be a lot like sudoku , so you may find it helpful to organize your information in a grid , like this . pause the video on the following screen to examine your clues and solve the riddle . answer in : 3 2 1 to start , you fill in the information from clues eight and nine . immediately , you also realize that since the norwegian is at the end of the street , there 's only one house next to him , which must be the one with the blue walls in clue fourteen . clue five says the green-walled house 's owner drinks coffee . it ca n't be the center house since you already know its owner drinks milk , but it also ca n't be the second house , which you know has blue walls . and since clue four says the green-walled house must be directly to the left of the white-walled one , it ca n't be the first or fifth house either . the only place left for the green-walled house with the coffee drinker is the fourth spot , meaning the white-walled house is the fifth . clue one gives you a nationality and a color . since the only column missing both these values is the center one , this must be the brit 's red-walled home . now that the only unassigned wall color is yellow , this must be applied to the first house , where clue seven says the dunhill smoker lives . and clue eleven tells you that the owner of the horse is next door , which can only be the second house . the next step is to figure out what the norwegian in the first house drinks . it ca n't be tea , clue three tells you that 's the dane . as per clue twelve , it ca n't be root beer since that person smokes bluemaster , and since you already assigned milk and coffee , it must be water . from clue fifteen , you know that the norwegian 's neighbor , who can only be in the second house , smokes blends . now that the only spot in the grid without a cigar and a drink is in the fifth column , that must be the home of the person in clue twelve . and since this leaves only the second house without a drink , the tea-drinking dane must live there . the fourth house is now the only one missing a nationality and a cigar brand , so the prince-smoking german from clue thirteen must live there . through elimination , you can conclude that the brit smokes pall mall and the swede lives in the fifth house , while clue six and clue two tell you that these two have a bird and a dog , respectively . clue ten tells you that the cat owner lives next to the blend-smoking dane , putting him in the first house . now with only one spot left on the grid , you know that the german in the green-walled house must be the culprit . you and the police burst into the house , catching the thief fish-handed . while that explanation was straightforward , solving puzzles like this often involves false starts and dead ends . part of the trick is to use the process of elimination and lots of trial and error to hone in on the right pieces , and the more logic puzzles you solve , the better your intuition will be for when and where there 's enough information to make your deductions . and did young einstein really write this puzzle ? probably not . there 's no evidence he did , and some of the brands mentioned are too recent . but the logic here is not so different from what you 'd use to solve equations with multiple variables , even those describing the nature of the universe .

three : each house contains a different animal , one of which is the fish . after a few hours of expert sleuthing , you gather some clues . it may look like a lot of information , but there 's a clear logical path to the solution .

which pair of clues below did not require any logic at all ?

muhammad ali spent years training to become the greatest boxer the world had ever seen , but only moments to create the shortest poem . ali captivated harvard 's graduating class in 1975 with his message of unity and friendship . when he finished , the audience wanted more . they wanted a poem . ali delivered what is considered the shortest poem ever . `` me , we . '' or is it `` me , weeee '' ? no one 's really sure . regardless , if these two words are a poem , then what exactly makes a poem a poem ? poets themselves have struggled with this question , often using metaphors to approximate a definition . is a poem a little machine ? a firework ? an echo ? a dream ? poetry generally has certain recognizable characteristics . one - poems emphasize language 's musical qualities . this can be achieved through rhyme , rhythm , and meter , from the sonnets of shakepeare , to the odes of confucius , to the sanskrit vedas . two - poems use condensed language , like literature with all the water wrung out of it . three - poems often feature intense feelings , from rumi 's spiritual poetry to pablo neruda 's `` ode to an onion . '' poetry , like art itself , has a way of challenging simple definitions . while the rhythmic patterns of the earliest poems were a way to remember stories even before the advent of writing , a poem does n't need to be lyrical . reinhard döhl 's “ apfel ” and eugen gomringer 's `` silencio '' toe the line between visual art and poetry . meanwhile , e.e . cummings wrote poems whose shapes were as important as the words themselves , in this case amplifying the sad loneliness of a single leaf falling through space . if the visual nature of poetry faded into the background , perhaps we 'd be left with music , and that 's an area that people love to debate . are songs poems ? many do n't regard songwriters as poets in a literary sense , but lyrics from artists like paul simon , bob dylan , and tupac shakur often hold up even without the music . in rap , poet elements like rhyme , rhythm , and imagery are inseparable from the form . take this lyric from the notorious b.i.g . `` i can hear sweat trickling down your cheek your heartbeat sound like sasquatch feet thundering , shaking the concrete . '' so far , all the examples we 've seen have had line breaks . we can even imagine the two words of ali 's poem organizing in the air - me , we . poetry has a shape that we can usually recognize . its line breaks help readers navigate the rhythms of a poem . but what if those line breaks disappeared ? would it lose its essence as a poem ? maybe not . enter the prose poem . prose poems use vivid images and wordplay but are formatted like paragraphs . when we look at poetry less as a form and more as a concept , we can see the poetic all around us : spiritual hymns , the speeches of orators like martin luther king , jr. , jfk , and winston churchill , and surprising places like social media . in 2010 , journalist joanna smith tweeted updates from the earthquake in haiti . `` was in b-room getting dressed when heard my name . tremor . ran outside through sliding door . all still now . safe . roosters crowing . '' smith uses language in a way that is powerful , direct , and filled with vivid images . compare her language to a haiku , the ancient japanese poetic form that emphasizes bursts of brief intensity with just three lines of five , seven , and five syllables . the waters of poetry run wide and deep . poetry has evolved over time , and perhaps now more than ever , the line between poetry , prose , song , and visual art has blurred . however , one thing has not changed . the word poetry actually began in verb form , coming from the ancient greek poiesis , which means to create . poets , like craftsman , still work with the raw materials of the world to forge new understandings and comment on what it is to be human in a way only humans can . dartmouth researchers tested this idea by asking robots to pen poetry . a panel of judges sorted through stacks of sonnets to see if they could distinguish those made by man and machine . you may be happy to know that while scientists have successfully used artificial intelligence in manufacturing , medicine , and even journalism , poetry is a different story . the robots were caught red-handed 100 % of the time .

poets , like craftsman , still work with the raw materials of the world to forge new understandings and comment on what it is to be human in a way only humans can . dartmouth researchers tested this idea by asking robots to pen poetry . a panel of judges sorted through stacks of sonnets to see if they could distinguish those made by man and machine .

what does the dartmouth study mentioned in the video suggest about the nature of poetry ? were you surprised by the results of the study ?

this is the bop . the bop is a type of social dance . dance is a language , and social dance is an expression that emerges from a community . a social dance is n't choreographed by any one person . it ca n't be traced to any one moment . each dance has steps that everyone can agree on , but it 's about the individual and their creative identity . because of that , social dances bubble up , they change , and they spread like wildfire . they are as old as our remembered history . in african-american social dances , we see over 200 years of how african and african-american traditions influenced our history . the present always contains the past . and the past shapes who we are and who we will be . ( clapping ) the juba dance was born from enslaved africans ' experience on the plantation . brought to the americas , stripped of a common spoken language , this dance was a way for enslaved africans to remember where they 're from . it may have looked something like this . slapping thighs , shuffling feet and patting hands : this was how they got around the slave owners ' ban on drumming , improvising complex rhythms just like ancestors did with drums in haiti or in the yoruba communities of west africa . it was about keeping cultural traditions alive and retaining a sense of inner freedom under captivity . it was the same subversive spirit that created this dance : the cakewalk , a dance that parodied the mannerisms of southern high society -- a way for the enslaved to throw shade at the masters . the crazy thing about this dance is that the cakewalk was performed for the masters , who never suspected they were being made fun of . now you might recognize this one . 1920s -- the charleston . the charleston was all about improvisation and musicality , making its way into lindy hop , swing dancing and even the kid n play , originally called the funky charleston . started by a tight-knit black community near charleston , south carolina , the charleston permeated dance halls where young women suddenly had the freedom to kick their heels and move their legs . now , social dance is about community and connection ; if you knew the steps , it meant you belonged to a group . but what if it becomes a worldwide craze ? enter the twist . it 's no surprise that the twist can be traced back to the 19th century , brought to america from the congo during slavery . but in the late '50s , right before the civil rights movement , the twist is popularized by chubby checker and dick clark . suddenly , everybody 's doing the twist : white teenagers , kids in latin america , making its way into songs and movies . through social dance , the boundaries between groups become blurred . the story continues in the 1980s and '90s . along with the emergence of hip-hop , african-american social dance took on even more visibility , borrowing from its long past , shaping culture and being shaped by it . today , these dances continue to evolve , grow and spread . why do we dance ? to move , to let loose , to express . why do we dance together ? to heal , to remember , to say : `` we speak a common language . we exist and we are free . ''

but what if it becomes a worldwide craze ? enter the twist . it 's no surprise that the twist can be traced back to the 19th century , brought to america from the congo during slavery .

watch the twist , the jerk , and the monkey . wordless communication is being shared between the participants . in your opinion , what is being “ said ” or conveyed ?

in 1996 , 56 volunteers took part in a study to test a new painkiller called trivaricaine . on each subject , one index finger was covered in the new painkiller while the other remained untouched . then , both were squeezed in painful clamps . the subjects reported that the treated finger hurt less than the untreated one . this should n't be surprising , except trivaricaine was n't actually a painkiller , just a fake concotion with no pain-easing properties at all . what made the students so sure this dummy drug had worked ? the answer lies in the placebo effect , an unexplained phenomenon wherein drugs , treatments , and therapies that are n't supposed to have an effect , and are often fake , miraculously make people feel better . doctors have used the term placebo since the 1700s when they realized the power of fake drugs to improve people 's symptoms . these were administered when proper drugs were n't available , or if someone imagined they were ill . in fact , the word placebo means `` i shall please '' in latin , hinting at a history of placating troubled patients . placebos had to mimic the real treatments in order to be convincing , so they took the form of sugar pills , water-filled injections , and even sham surgeries . soon , doctors realized that duping people in this way had another use : in clinical trials . by the 1950s , researchers were using placebos as a standard tool to test new treatments . to evaluate a new drug , for instance , half the patients in a trial might receive the real pill . the other half would get a placebo that looked the same . since patients would n't know whether they 'd received the real thing or a dud , the results would n't be biased , researchers believed . then , if the new drug showed a significant benefit compared to the placebo , it was proved effective . nowadays , it 's less common to use placebos this way because of ethical concerns . if it 's possible to compare a new drug against an older version , or another existing drug , that 's preferable to simply giving someone no treatment at all , especially if they have a serious ailment . in these cases , placebos are often used as a control to fine-tune the trial so that the effects of the new versus the old or alternative drug can be precisely compared . but of course , we know the placebos exert their own influence , too . thanks to the placebo effect , patients have experienced relief from a range of ailments , including heart problems , asthma , and severe pain , even though all they 'd received was a fake drug or sham surgery . we 're still trying to understand how . some believe that instead of being real , the placebo effect is merely confused with other factors , like patients trying to please doctors by falsely reporting improvements . on the other hand , researchers think that if a person believes a fake treatment is real , their expectations of recovery actually do trigger physiological factors that improve their symptoms . placebos seem to be capable of causing measurable change in blood pressure , heart rate , and the release of pain-reducing chemicals , like endorphins . that explains why subjects in pain studies often say placebos ease their discomfort . placebos may even reduce levels of stress hormones , like adrenaline , which can slow the harmful effects of an ailment . so should n't we celebrate the placebo 's bizarre benefits ? not necessarily . if somebody believes a fake treatment has cured them , they may miss out on drugs or therapies that are proven to work . plus , the positive effects may fade over time , and often do . placebos also cloud clinical results , making scientists even more motivated to discover how they wield such power over us . despite everything we know about the human body , there are still some strange and enduring mysteries , like the placebo effect . so what other undiscovered marvels might we contain ? it 's easy to investigate the world around us and forget that one of its most fascinating subjects lies right behind our eyes .

these were administered when proper drugs were n't available , or if someone imagined they were ill . in fact , the word placebo means `` i shall please '' in latin , hinting at a history of placating troubled patients . placebos had to mimic the real treatments in order to be convincing , so they took the form of sugar pills , water-filled injections , and even sham surgeries .

the term placebo ’ comes from latin , and means :

[ music ] this episode is supported by prudential [ music ] with more than 7 billion people on earth and one car for every six of us , traffic is bad just about everywhere . [ honking ] last year , american drivers wasted nearly a million collective years staring at each other ’ s tail-lights . the average driver in london has it the worst , spending more than four days a year in gridlock . `` there 's big ben , kids ! parliament ! '' but earth is home to another great commuter , whose populations number in the trillions , and they don ’ t get stuck in traffic . an army ant ’ s day is a lot like ours . set off in the morning alongside thousands of our neighbors , moving out and back in neat little lines so we can provide for our brood… i mean family . crowding , bottlenecks , slowpokes , ants face the same traffic challenges we do . but they don ’ t get in traffic jams , which is why scientists are looking to them for solutions to human traffic . in a perfect world cars could pack in bumper to bumper and drive at that magic speed , but we ’ re not perfect . one wrong tap on the gas or brakes , and oh come on ! get moving ! when speed and density hit a tipping point , jams are inevitable . yet in the ant world , traffic jams don ’ t happen , even when things get crowded . the easiest solution to an overcrowded road is to make it bigger . but ants can ’ t just cut trails as wide as they want . wider roads take time and energy to maintain , and the pheromones that mark them become weaker . instead , ants get organized . it might not look like it , but there ’ s lanes here . ants headed back to the colony loaded up with food use the center lane , while outbound ants stay to the edges . why three lanes and not two , like our roads ? when two ants are on a collision course , eventually one ’ s got ta give . the loaded inbound ants are less maneuverable , so the empty-handed ant almost always turns first , half the time to either side . and voila : three lanes , no crashes , no traffic jams . if you think you ’ re so different from an army ant , pay attention next time you ’ re in a busy crosswalk . we naturally form similar lanes in crowds , mindless individuals contributing to a larger pattern . but put us behind the wheel , and this happens . [ honking ] there ’ s a simple reason we hate traffic . because we hate waiting in line . queueing up plays weird tricks on our brains ’ sense of time . occupied time feels shorter than unoccupied time . this is why people listen to the radio , or play that license plate game . and it ’ s the same reason supermarkets put magazines in the checkout lines . ever been late for a big meeting and felt like the universe is standing in your way ? anxiety makes waits seem longer . ever been in a traffic jam with no obvious cause ? the worst . uncertain or unexplained waits are longer than known or explained waits . but traffic engineers have learned that simple information signs can change how we experience delays . but more than anything else , we hate unfair waits . you see a sign that says “ lane closed ahead ” , so you get over with plenty of time to spare , only to see some jerk zip past you and get over at the last second . what… you can ’ t wait like the rest of us , mr. hurrypants ? quick side note . gon na let you in on a little secret . traffic researchers have found that late merging is actually better . if everyone drives up to the bottleneck and goes one-by-one like a zipper , traffic moves up to 15 % faster . we use both lanes at max capacity , no one gets cheated , everyone wins ! the more you know . and where were we ? oh yeah . our innate sense of “ what ’ s fair ” leads to the biggest psychological illusion that we experience on the road . why does traffic always move faster in the other lane ? well , spoilers first : it doesn ’ t . let ’ s say two cars enter your standard stop-and-go traffic jam side by side . let ’ s count the time each one spends passing versus getting passed . one driver zips past a few cars in the other lane , only to stop and wait and watch other cars pass . and then go ! woo hoo ! and then wait . even if the two cars cross some invisible finish line together , the same way they started , each driver will feel like they spent more time being passed than passing , because they did . our brains pay more attention to the losses than the gains . all of this points to the real problem with traffic . our ego . human drivers care about minimizing their travel time and don ’ t give two honks about what other drivers want . driving slower may be faster for everyone else , but it ’ s not faster for me ! i don ’ t care if we all get where we ’ re going at the same time , i don ’ t like being passed ! when leaf-cutter ants get stuck on a twig behind a heavily-loaded slowpoke , do they honk and yell bad ant words ? no ! they simply slow down and march behind the ant returning with the goods , because that ’ s what ’ s best for the group . worker ants are all related and working toward the same goal , the good of the colony . that ’ s the cooperative genetic programming that underlies their awesome traffic systems . the fact that we have big , complicated brains is the very reason that we get stuck in traffic and ants don ’ t . we think of traffic as something that happens to us rather than admitting we are the problem . ants are essentially tiny machines with simple programming . put them on a trail with a few rules , allow individuals to communicate and interact with each other , and voila , you ’ ve got complex traffic networks running at near-maximum efficiency . sound familiar ? it should ! that ’ s basically what we ’ ll get when we stop letting our egos drive and put traffic in the hands of a network of self-driving cars optimized to serve the collective good . sure , sentient machines may enslave humanity , but at least they ’ ll cut down on our commute ! but that ’ s a video for another day . stay curious . thanks to prudential for sponsoring this episode . saving a little more today , even just one percent more of your annual income , can go a long way toward building a better retirement tomorrow . let 's do a math equation . say a 25 year-old that earns $ 40,000 a year is planning on retiring at 70. if they save an additional 1 % of their salary by deducting $ 33 from their monthly paycheck and earn 6 % compounding interest , they could increase their retirement savings by about $ 97,944 . you can go to raceforretirement.com for more information .

our innate sense of “ what ’ s fair ” leads to the biggest psychological illusion that we experience on the road . why does traffic always move faster in the other lane ? well , spoilers first : it doesn ’ t .

when one lane of traffic shuts down , which of the two following options moves traffic along at a faster rate ?

every four seconds , someone is diagnosed with alzheimer 's disease . it 's the most common cause of dementia , affecting over 40 million people worldwide , and yet finding a cure is something that still eludes researchers today . dr. alois alzheimer , a german psychiatrist , first described the symptoms in 1901 when he noticed that a particular hospital patient had some peculiar problems , including difficulty sleeping , disturbed memory , drastic mood changes , and increasing confusion . when the patient passed away , alzheimer was able to do an autopsy and test his idea that perhaps her symptoms were caused by irregularities in the brain 's structure . what he found beneath the microscope were visible differences in brain tissue in the form of misfolded proteins called plaques , and neurofibrillary tangles . those plaques and tangles work together to break down the brain 's structure . plaques arise when another protein in the fatty membrane surrounding nerve cells gets sliced up by a particular enzyme , resulting in beta-amyloid proteins , which are sticky and have a tendency to clump together . that clumping is what forms the things we know as plaques . these clumps block signaling and , therefore , communication between cells , and also seem to trigger immune reactions that cause the destruction of disabled nerve cells . in alzheimer 's disease , neurofibrillary tangles are built from a protein known as tau . the brain 's nerve cells contain a network of tubes that act like a highway for food molecules among other things . usually , the tau protein ensures that these tubes are straight , allowing molecules to pass through freely . but in alzheimer 's disease , the protein collapses into twisted strands or tangles , making the tubes disintegrate , obstructing nutrients from reaching the nerve cell and leading to cell death . the destructive pairing of plaques and tangles starts in a region called the hippocampus , which is responsible for forming memories . that 's why short-term memory loss is usually the first symptom of alzheimer 's . the proteins then progressively invade other parts of the brain , creating unique changes that signal various stages of the disease . at the front of the brain , the proteins destroy the ability to process logical thoughts . next , they shift to the region that controls emotions , resulting in erratic mood changes . at the top of the brain , they cause paranoia and hallucinations , and once they reach the brain 's rear , the plaques and tangles work together to erase the mind 's deepest memories . eventually the control centers governing heart rate and breathing are overpowered as well resulting in death . the immensely destructive nature of this disease has inspired many researchers to look for a cure but currently they 're focused on slowing its progression . one temporary treatment helps reduce the break down of acetylcholine , an important chemical messenger in the brain which is decreased in alzheimer 's patients due to the death of the nerve cells that make it . another possible solution is a vaccine that trains the body 's immune system to attack beta-amyloid plaques before they can form clumps . but we still need to find an actual cure . alzheimer 's disease was discovered more than a century ago , and yet still it is not well understood . perhaps one day we 'll grasp the exact mechanisms at work behind this threat and a solution will be unearthed .

every four seconds , someone is diagnosed with alzheimer 's disease . it 's the most common cause of dementia , affecting over 40 million people worldwide , and yet finding a cure is something that still eludes researchers today .

which is a symptom of alzheimer ’ s disease ?

calcium is the third element in group two on the periodic table . it ’ s really very common . we find it all over the world in all sorts of minerals . so for example you can have bones , this is a pelvis of a sheep , i found it when i was walking one day , you can see the legs go in there and there . in here we have some calcium turnings . we ’ re storing them in our glove box . this glove box here is a contraption full of nitrogen , it ’ s dry nitrogen so that we can keep our calcium away from oxygen and away from moisture as well , because obviously what we don ’ t want is when we get our nice very reactive calcium surface we don ’ t want it to tarnish from oxides too quickly before we can react it with things . so what we have here inside the bottle are turnings of calcium . calcium is quite hard compared to sort of the heavier group two elements , so strontium and barium , so it ’ s harder to file . bones are made from calcium phosphate mixed with some organic material as well and they ’ re very strong because of the structure within the bones . there are all sorts of shells of molluscs and the like where they use calcium carbonate from the sea water , getting the calcium out , reacting with carbon dioxide and making their shells . and because shells are made out of calcium carbonate , which dissolves in acid , people are quite worried about the effects of global warming . not the heating up but when the c02 dissolves into the sea it makes it more acid , so in principle shells could start dissolving and some molluscs may not be able to survive because they just can ’ t make their shells . if i just pour them out so you can see . calcium looks metallic than the calcium metal itself because of the way the electrons behave in the solid . in fact it is because it is a very good electrical conductor but the compounds are all white , because calcium has no free electrons that can go from one energy level to another in the way you can say with copper . so copper sulphate is a beautiful blue colour , calcium sulphate is white , and it ’ s actually colourless , so if you see a big crystal of calcium sulphate it just looks like glass . but the white is caused by very small crystals which scatter the light , just in the same way that any sort of white powder will scatter light , flour for example or talcum powder , anything like that . calcium compounds themselves are actually mostly white , but calcium metal itself , as you can see we ’ ve got tarnished parts but also there are some shiny bits where it ’ s untarnished . so you ’ re actually seeing the metal the lustre of the metal there as well . calcium carbonate dissolves in water saturated with c02 to make calcium bicarbonate which is more soluble . and so you can get water , so called hard water , that has quite high levels of calcium . and when this percolates through the ground and comes to a cave it can then crystallise out and you can get hanging down pillars of calcium carbonate , which are called stalactites . and you can have pillars growing from the floor called stalagmites . this is a stalagmite from turkey . one of my friends called hugh was really naughty . he knew i was interested in minerals and he broke this off from a cave in turkey about 45 years ago and brought it and gave it to me so i was really pleased . and you can see the outside looks quite blobby , and inside you can see there are nice crystals of calcium carbonate because it has grown very , very slowly and so it can crystalise . and sometimes these stalagmites and stalactites can grow really big . and more recently , in the last few years , people have found huge crystals of calcium sulphate under the ground . some of you may have seen pictures of caves in mexico where there are crystals big enough you can actually walk along them . so there is no danger that calcium will ever run out , it ’ s the basis of cements and concretes , or one of the bases because then you need other elements like iron and silica to make the concrete itself , but calcium is one of the principle components . we ’ re going to take calcium chloride , put it in a flame and do a flame test and see if we can see the colour of the calcium in the flame . so as i said before about calcium compounds , calcium compounds are often white , and here is a white calcium compound . so i ’ m going to put it in the flame and see if we get any colour . oh hello , that looks quite red doesn ’ t it ? brick red is the classic calcium colour . bit orangey to me , might be a bit of sodium in there , or something like that . that was our calcium flame test . the reason that you don ’ t find lumps of calcium metal lying around , the way you do with copper or gold , is that metallic calcium is very reactive , reacts with water very quickly . magnesium doesn ’ t react because it has a layer of oxide on the surface , so surprisingly magnesium is not nearly as reactive as calcium . you can use magnesium , or its alloys , for the wheels on your car , go round really fast because they ’ re light . you couldn ’ t have calcium wheels in your car , well you could , but the first time it rained your whole car would go up in flames . this again what we ’ ve got is our calcium chloride , hydrated calcium chloride . we ’ ve got a bunch of it on this spatula . i ’ ll put it in the flame so that you can see that it ’ s burning with a brick red flame which is characteristic of calcium . it ’ s kind of a bit orangey to me as well actually , might be a bit of sodium or something in there . got anymore in there ? a little bit . many people see calcium as a very english element , unlike strontium which was discovered in scotland , because of the white cliffs of dover , the gateway for many people when they first come to england . they ’ re made of calcium carbonate . and so this white colour of chalk is very characteristic and all over the southern part of england you find large amounts of chalk , which in the north of england they tend to be limestone , which is also calcium carbonate but a slightly different variety of calcium carbonate so it ’ s a yellow or honey colour because of the impurities of iron or some other element that ’ s in it . well you need calcium for all sorts of processes in the body and of course to build up your bones . particularly , say in the case of pregnant women , they need to have calcium for the bones of the developing baby . but as people get older the calcium can come out of their bones and make them very fragile , this is why elderly people sometimes break their hips and break their bones so easily . so drinking milk and eating other sources of calcium are good because it helps you replenish your bones and keep a reasonable level of calcium .

a little bit . many people see calcium as a very english element , unlike strontium which was discovered in scotland , because of the white cliffs of dover , the gateway for many people when they first come to england . they ’ re made of calcium carbonate .

why did the professor say that many people see calcium as a very “ english element ” ?

what do fans of atmospheric post-punk music have in common with ancient barbarians ? not much . so why are both known as goths ? is it a weird coincidence or a deeper connection stretching across the centuries ? the story begins in ancient rome . as the roman empire expanded , it faced raids and invasions from the semi-nomadic populations along its borders . among the most powerful were a germanic people known as goths who were composed of two tribal groups , the visigoths and ostrogoths . while some of the germanic tribes remained rome 's enemies , the empire incorporated others into the imperial army . as the roman empire split in two , these tribal armies played larger roles in its defense and internal power struggles . in the 5th century , a mercenary revolt lead by a soldier named odoacer captured rome and deposed the western emperor . odoacer and his ostrogoth successor theoderic technically remained under the eastern emperor 's authority and maintained roman traditions . but the western empire would never be united again . its dominions fragmented into kingdoms ruled by goths and other germanic tribes who assimilated into local cultures , though many of their names still mark the map . this was the end of the classical period and the beginning of what many call the dark ages . although roman culture was never fully lost , its influence declined and new art styles arose focused on religious symbolism and allegory rather than proportion and realism . this shift extended to architecture with the construction of the abbey of saint denis in france in 1137 . pointed arches , flying buttresses , and large windows made the structure more skeletal and ornate . that emphasized its open , luminous interior rather than the sturdy walls and columns of classical buildings . over the next few centuries , this became a model for cathedrals throughout europe . but fashions change . with the italian renaissance 's renewed admiration for ancient greece and rome , the more recent style began to seem crude and inferior in comparison . writing in his 1550 book , `` lives of the artists , '' giorgio vasari was the first to describe it as gothic , a derogatory reference to the barbarians thought to have destroyed classical civilization . the name stuck , and soon came to describe the medieval period overall , with its associations of darkness , superstition , and simplicity . but time marched on , as did what was considered fashionable . in the 1700s , a period called the enlightenment came about , which valued scientific reason above all else . reacting against that , romantic authors like goethe and byron sought idealized visions of a past of natural landscapes and mysterious spiritual forces . here , the word gothic was repurposed again to describe a literary genre that emerged as a darker strain of romanticism . the term was first applied by horace walpole to his own 1764 novel , `` the castle of otranto '' as a reference to the plot and general atmosphere . many of the novel 's elements became genre staples inspiring classics and the countless movies they spawned . the gothic label belonged to literature and film until the 1970s when a new musical scene emerged . taking cues from artists like the doors and the velvet underground , british post-punk groups , like joy division , bauhaus , and the cure , combined gloomy lyrics and punk dissonance with imagery inspired by the victorian era , classic horror , and androgynous glam fashion . by the early 1980s , similar bands were consistently described as gothic rock by the music press , and the stye 's popularity brought it out of dimly lit clubs to major labels and mtv . and today , despite occasional negative media attention and stereotypes , gothic music and fashion continue as a strong underground phenomenon . they 've also branched into sub-genres , such as cybergoth , gothabilly , gothic metal , and even steampunk . the history of the word gothic is embedded in thousands of years worth of countercultural movements , from invading outsiders becoming kings to towering spires replacing solid columns to artists finding beauty in darkness . each step has seen a revolution of sorts and a tendency for civilization to reach into its past to reshape its present .

although roman culture was never fully lost , its influence declined and new art styles arose focused on religious symbolism and allegory rather than proportion and realism . this shift extended to architecture with the construction of the abbey of saint denis in france in 1137 . pointed arches , flying buttresses , and large windows made the structure more skeletal and ornate .

the abbey of st. denis was built in 1137 in :

`` war and peace , '' a tome , a slog , the sort of book you should n't read in bed because if you fall asleep , it could give you a concussion , right ? only partly . `` war and peace '' is a long book , sure , but it 's also a thrilling examination of history , populated with some of the deepest , most realistic characters you 'll find anywhere . and if its length intimidates you , just image how poor tolstoy felt . in 1863 , he set out to write a short novel about a political dissident returning from exile in siberia . five years later , he had produced a 1,200 page epic featuring love stories , battlefields , bankruptcies , firing squads , religious visions , the burning of moscow , and a semi-domesticated bear , but no exile and no political dissidents . here 's how it happened . tolstoy , a volcanic soul , was born to a famously eccentric aristocratic family in 1828 . by the time he was 30 , he had already dropped out of kazan university , gambled away the family fortune , joined the army , written memoirs , and rejected the literary establishment to travel europe . he then settled into yasnaya polyana , his ancestral mansion , to write about the return of the decembrists , a band of well-born revolutionaries pardoned in 1856 after 30 years in exile . but , tolstoy thought , how could he tell the story of the decembrists return from exile without telling the story of 1825 , when they revolted against the conservative tsar nicholas i ? and how could he do that without telling the story of 1812 , when napoleon 's disastrous invasion of russia helped trigger the authoritarianism the decembrists were rebelling against ? and how could he tell the story of 1812 without talking about 1805 , when the russians first learned of the threat napoleon posed after their defeat at the battle of austerlitz ? so tolstoy began writing , both about the big events of history and the small lives that inhabit those events . he focused on aristocrats , the class he knew best . the book only occasionally touches on the lives of the vast majority of the russian population , who were peasants , or even serfs , farmers bound to serve the owners of the land on which they lived . `` war and peace '' opens on the eve of war between france and russia . aristocrats at a cocktail party fret about the looming violence , but then change the topic to those things aristocrats always seem to care about : money , sex , and death . this first scene is indicative of the way the book bounces between the political and personal over an ever-widening canvas . there are no main characters in `` war and peace . '' instead , readers enter a vast interlocking web of relationships and questions . will the hapless and illegitimate son of a count marry a beautiful but conniving princess ? will his only friend survive the battlefields of austria ? and what about that nice young girl falling in love with both men at once ? real historical figures mix and mingle with all these fictional folk , napoleon appears several times , and even one of tolstoy 's ancestors plays a background part . but while the characters and their psychologies are gripping , tolstoy is not afraid to interrupt the narrative to pose insightful questions about history . why do wars start ? what are good battlefield tactics ? do nations rise and fall on the actions of so-called great men like napoleon , or are there larger cultural and economic forces at play ? these extended digressions are part of what make `` war and peace '' so panoramic in scope . but for some 19th century critics , this meant `` war and peace '' barely felt like a novel at all . it was a `` large , loose , baggy monster , '' in the words of henry james . tolstoy , in fact , agreed . to him , novels were a western european form . russian writers had to write differently because russian people lived differently . `` what is 'war and peace ' ? '' he asked . `` it is not a novel . still less an epic poem . still less a historical chronicle . 'war and peace ' is what the author wanted and was able to express in the form in which it was expressed . '' it is , in other words , the sum total of tolstoy 's imaginative powers , and nothing less . by the time `` war and peace '' ends , tolstoy has brought his characters to the year 1820 , 36 years before the events he originally hoped to write about . in trying to understand his own times , he had become immersed in the years piled up behind him . the result is a grand interrogation into history , culture , philosophy , psychology , and the human response to war .

russian writers had to write differently because russian people lived differently . `` what is 'war and peace ' ? '' he asked .

tolstoy originally thought `` war and peace '' would be a book about :

translator : andrea mcdonough reviewer : bedirhan cinar so i work on trying to understand how the universe works at the very basic level , the most basic level we can find . so , when you try in your everyday life to try and work out how something works , what you 're actually doing is you 're looking for what i call hidden structures . for example , you take something like your cell phone , your smart phone , it 's a complicated object , and you might wonder how it works . well , what you can do is go in and actually take it apart . you 'll void the warranty , but that 's ok. and you 'll go in and what you 'll find is that it 's made of tiny little electronic components . and those electronic components are actually moving around a certain kind of particle that we know that 's called the electron , and that 's where the name `` electronics '' comes from . so if you know the actual rules of how to put those things together , you can actually make your smart phone or you could make various other electronic devices as well . so , there are people like myself who , actually for a living , try and do this sort of thing not just for , say , a cell phone or its components , but asking what , say , your hand is made of , or the chair you 're sitting in , or the planet earth , the sun , the stars , the entire universe . and so , using various kinds of instruments and observations and experiments , we 've been able to probe deeper and deeper over the years , and we now know that the matter that we 're made of and that we see around us is actually made of tiny little elementary particles . and elementary particles interact with each other via the forces of nature , but we 've also discovered that those forces of nature themselves actually operate by exchanging elementary particles as well . they 're actually particles of force that are exchanged by the particles of matter . and you may have heard this year that there was big news , a major announcement in this story , the large hadron collider , the lhc , a huge experiment in europe , has actually uncovered a higgs boson , and that particle 's job is to interact with the various elementary particles and give them the masses that we observe . so , this exciting picture is analogous to the one i showed you for the cell phone . we have the components and we have the rules of particle theory , as it 's called , by which these all operate and give rise to the various things . now , we actually think that we 've only just scratched the surface of finding this quantum world , the hidden structure of our world . let me give you three examples of the puzzles we 're still working on . so , what i did is i gathered the particles up into the patterns that they tend to form , but we do n't know where those patterns come from . we know how to describe the particles , but we do n't know where the patterns come from . when you see patterns in science , you look for a hidden structure , so that 's one of the things . also , we now know that there 's a huge amount more matter out there than just the things that i was just talking about . that stuff is called dark matter . we do n't know what it is , and we 'd like to be able to get it and experiment with it and figure out what it is . and then , the other thing i 'd like to talk about is the fact that the force of gravity , perhaps the most familiar force we know , when you get down to the quantum level , it actually does n't operate according to those rules of particle theory . so , given that gravity is actually about the shape of space and time as einstein taught us , we , in working out what the quantum story of gravity is , which we call quantum gravity , we hope to get to groups of questions like , are there particles of space and time itself and how do they fit together ? what are the rules ? so , this leads us to things like studying where it all began , 13.7 billion years ago , the big bang . we know matter and energy as we understand it was created , but also , space and time itself . so those are the sorts of things we study in this quest . also , we have things that are around us today , such as black holes , which are very important clues . they 're actually holes in space that we 'd like to understand . also , the newly discovered dark energy , which is the tendency of space all through the universe to accelerate its expansion . so scientists are working on these kinds of things , trying to understand what we think is now the case that there 's not just hidden structures of matter and energy , but also space and time . so the question is , what are the rules ? and there are many approaches to this , and one of them is one you may have heard of , called string theory . and so it is one of many approaches and we do n't know if it 's right yet , we 're not finished developing the theory , but it 's given us some really exciting , tantalizing hints . i 'd like to tell you about a few of them . so , one of them is simply that you take away the idea of looking for a tiny quantum particle , you look instead for an extended object , a string , which can vibrate . and it actually gives you some exciting opportunities because , for example , it would say if we 've missed that hidden structure by not looking closely enough , we would n't realize that many different kinds of particles are just different vibrations of the same string , which is a really exciting possibility and a huge simplification . so that 's one of the ideas . the other thing that 's really exciting about string theory is that one of those particles it describes is actually the missing quantum of gravity that we have been trying to understand . and then the other thing is that strings actually , instead of one wanting just to move in the dimensions , the three space dimensions that we are familiar with , actually seem to want to move in higher dimensions . so we have this idea , then , what would it mean for our world , if this were anything to do with our world , and we do n't know that yet ? here 's a way that our world would arise from that . you would have our world , and then one of the hidden structures would be hidden chunks in space time that are not visible , those extra dimensions . and then the various particles that we see in the world would come from being vibrations of strings and those patterns we saw that we ca n't explain come from the fact that the strings can probe and feel the shape of those internal dimensions . so , one of the things , then , is can we actually test this ? this is a lovely idea , but how do we confront this with real experiments and observations because we 're doing science here ? and that 's the hard thing . we think that the energy you need to probe the tiny-enough scales to see the strings if they 're there , is more than we can hope to get any time soon . but what we can do is we can look for the consequences of those hidden structures , we can look for how those things show up in physics that we can get access to . so , that 's why we study things like dark matter , black holes , dark energy , and we also look at remnants of the early universe , the cosmic microwave background that satellites . and , importantly , we look for clues from the various kinds of particle physics experiments , like the lhc . so , one last thing , then , is a new thing that 's been going on . string theory may turn out to be useful in other areas of physics . there are new kinds of experiments that start out , say , with our friend the electron , and actually show that in certain circumstances , the electrons interact in a way that give you completely new , weird kinds of behavior . and there are models that show that string theory 's actually the best way . in some circumstances , using the rules of string theory , you can actually explain that sort of behavior . so this gives us an exciting possibility , there 's real experiments you can do with these electrons that will help us shape the rules for what string theory is . and you might go , `` well , ok , that 's going to give us maybe some fancy new kind of electronics that we can make a better cell phone with . '' but , what i 'm saying that those rules may actually be the same rules we 're looking for to see if string theory can help us with these bigger questions . so , at the end of the day , the hidden structures of the universe we 're looking for , may , one day , be right under our noses . thank you .

translator : andrea mcdonough reviewer : bedirhan cinar so i work on trying to understand how the universe works at the very basic level , the most basic level we can find . so , when you try in your everyday life to try and work out how something works , what you 're actually doing is you 're looking for what i call hidden structures . for example , you take something like your cell phone , your smart phone , it 's a complicated object , and you might wonder how it works .

when you try in your every day life to figure out how something works , you are looking for what clifford johnson calls ____________ .

translator : andrea mcdonough reviewer : jessica ruby how do you get from point a to point b ? why not spice it up with homemade special effects ? a film is simply a series of images played in sequence to create the illusion of motion . if you manipulate those images , crazy things can happen . we used a tablet and one of the many stop motion apps out there . how do you get from point a to point b ? we started off by taking a bunch of pictures of celeste in place . then , just like stop motion animation , the character is moved just a bit before the next picture is taken , which , in this case , creates a sliding effect . here we use the oldest trick in the book . by alternating between photos of celeste on-screen and off-screen , we 've made her childhood dream of teleportation a reality . with a little creativity , there are a million ways you can used homemade special effects to make something as simple as getting from point a to point b much more fun . if you 're at a loss for ideas , try finding inspiration in your surroundings , like the refrigerator and your coat rack . you can even try incorporating everyday objects from around your house , like , say , umbrellas or binder clips . wherever there is an object , there is an opportunity to make it come to life . when humans are used in stop motion animation , that 's called pixilation , a term coined in the mid-twentieth century , well before the word pixel was a part of our vocabulary . but these sorts of special effects are as old as the art of film making , and thanks to today 's technologies , can be reproduced in your very own kitchen . moving an object from point a to point b is a fundamental principle of animation . to learn more about the process and the tools we used , visit the `` dig deeper '' section on ed.ted.com .

why not spice it up with homemade special effects ? a film is simply a series of images played in sequence to create the illusion of motion . if you manipulate those images , crazy things can happen .

in the video `` fly there , ” what type of sequence of images creates the illusion of flying ?

good morning . how are you ? ( laughter ) it 's been great , has n't it ? i 've been blown away by the whole thing . in fact , i 'm leaving . ( laughter ) there have been three themes running through the conference which are relevant to what i want to talk about . one is the extraordinary evidence of human creativity in all of the presentations that we 've had and in all of the people here . just the variety of it and the range of it . the second is that it 's put us in a place where we have no idea what 's going to happen , in terms of the future . no idea how this may play out . i have an interest in education . actually , what i find is everybody has an interest in education . do n't you ? i find this very interesting . if you 're at a dinner party , and you say you work in education -- actually , you 're not often at dinner parties , frankly . ( laughter ) if you work in education , you 're not asked . ( laughter ) and you 're never asked back , curiously . that 's strange to me . but if you are , and you say to somebody , you know , they say , `` what do you do ? '' and you say you work in education , you can see the blood run from their face . they 're like , `` oh my god , '' you know , `` why me ? '' ( laughter ) `` my one night out all week . '' ( laughter ) but if you ask about their education , they pin you to the wall . because it 's one of those things that goes deep with people , am i right ? like religion , and money and other things . so i have a big interest in education , and i think we all do . we have a huge vested interest in it , partly because it 's education that 's meant to take us into this future that we ca n't grasp . if you think of it , children starting school this year will be retiring in 2065 . nobody has a clue , despite all the expertise that 's been on parade for the past four days , what the world will look like in five years ' time . and yet we 're meant to be educating them for it . so the unpredictability , i think , is extraordinary . and the third part of this is that we 've all agreed , nonetheless , on the really extraordinary capacities that children have -- their capacities for innovation . i mean , sirena last night was a marvel , was n't she ? just seeing what she could do . and she 's exceptional , but i think she 's not , so to speak , exceptional in the whole of childhood . what you have there is a person of extraordinary dedication who found a talent . and my contention is , all kids have tremendous talents . and we squander them , pretty ruthlessly . so i want to talk about education and i want to talk about creativity . my contention is that creativity now is as important in education as literacy , and we should treat it with the same status . ( applause ) thank you . ( applause ) that was it , by the way . thank you very much . ( laughter ) so , 15 minutes left . ( laughter ) well , i was born ... no . ( laughter ) i heard a great story recently -- i love telling it -- of a little girl who was in a drawing lesson . she was six , and she was at the back , drawing , and the teacher said this girl hardly ever paid attention , and in this drawing lesson , she did . the teacher was fascinated . she went over to her , and she said , `` what are you drawing ? '' and the girl said , `` i 'm drawing a picture of god . '' and the teacher said , `` but nobody knows what god looks like . '' and the girl said , `` they will , in a minute . '' ( laughter ) when my son was four in england -- actually , he was four everywhere , to be honest . ( laughter ) if we 're being strict about it , wherever he went , he was four that year . he was in the nativity play . do you remember the story ? ( laughter ) no , it was big , it was a big story . mel gibson did the sequel , you may have seen it . ( laughter ) `` nativity ii . '' but james got the part of joseph , which we were thrilled about . we considered this to be one of the lead parts . we had the place crammed full of agents in t-shirts : `` james robinson is joseph ! '' ( laughter ) he did n't have to speak , but you know the bit where the three kings come in ? they come in bearing gifts , gold , frankincense and myrrh . this really happened . we were sitting there and i think they just went out of sequence , because we talked to the little boy afterward and we said , `` you ok with that ? '' and he said , `` yeah , why ? was that wrong ? '' they just switched . the three boys came in , four-year-olds with tea towels on their heads , and they put these boxes down , and the first boy said , `` i bring you gold . '' and the second boy said , `` i bring you myrrh . '' and the third boy said , `` frank sent this . '' ( laughter ) what these things have in common is that kids will take a chance . if they do n't know , they 'll have a go . am i right ? they 're not frightened of being wrong . i do n't mean to say that being wrong is the same thing as being creative . what we do know is , if you 're not prepared to be wrong , you 'll never come up with anything original -- if you 're not prepared to be wrong . and by the time they get to be adults , most kids have lost that capacity . they have become frightened of being wrong . and we run our companies like this . we stigmatize mistakes . and we 're now running national education systems where mistakes are the worst thing you can make . and the result is that we are educating people out of their creative capacities . picasso once said this , he said that all children are born artists . the problem is to remain an artist as we grow up . i believe this passionately , that we do n't grow into creativity , we grow out of it . or rather , we get educated out of it . so why is this ? i lived in stratford-on-avon until about five years ago . in fact , we moved from stratford to los angeles . so you can imagine what a seamless transition that was . ( laughter ) actually , we lived in a place called snitterfield , just outside stratford , which is where shakespeare 's father was born . are you struck by a new thought ? i was . you do n't think of shakespeare having a father , do you ? do you ? because you do n't think of shakespeare being a child , do you ? shakespeare being seven ? i never thought of it . i mean , he was seven at some point . he was in somebody 's english class , was n't he ? ( laughter ) how annoying would that be ? ( laughter ) `` must try harder . '' ( laughter ) being sent to bed by his dad , you know , to shakespeare , `` go to bed , now ! and put the pencil down . '' ( laughter ) `` and stop speaking like that . '' ( laughter ) `` it 's confusing everybody . '' ( laughter ) anyway , we moved from stratford to los angeles , and i just want to say a word about the transition . my son did n't want to come . i 've got two kids ; he 's 21 now , my daughter 's 16 . he did n't want to come to los angeles . he loved it , but he had a girlfriend in england . this was the love of his life , sarah . he 'd known her for a month . ( laughter ) mind you , they 'd had their fourth anniversary , because it 's a long time when you 're 16 . he was really upset on the plane , he said , `` i 'll never find another girl like sarah . '' and we were rather pleased about that , frankly -- ( laughter ) because she was the main reason we were leaving the country . ( laughter ) but something strikes you when you move to america and travel around the world : every education system on earth has the same hierarchy of subjects . every one . does n't matter where you go . you 'd think it would be otherwise , but it is n't . at the top are mathematics and languages , then the humanities , and at the bottom are the arts . everywhere on earth . and in pretty much every system too , there 's a hierarchy within the arts . art and music are normally given a higher status in schools than drama and dance . there is n't an education system on the planet that teaches dance everyday to children the way we teach them mathematics . why ? why not ? i think this is rather important . i think math is very important , but so is dance . children dance all the time if they 're allowed to , we all do . we all have bodies , do n't we ? did i miss a meeting ? ( laughter ) truthfully , what happens is , as children grow up , we start to educate them progressively from the waist up . and then we focus on their heads . and slightly to one side . if you were to visit education , as an alien , and say `` what 's it for , public education ? '' i think you 'd have to conclude , if you look at the output , who really succeeds by this , who does everything that they should , who gets all the brownie points , who are the winners -- i think you 'd have to conclude the whole purpose of public education throughout the world is to produce university professors . is n't it ? they 're the people who come out the top . and i used to be one , so there . ( laughter ) and i like university professors , but you know , we should n't hold them up as the high-water mark of all human achievement . they 're just a form of life , another form of life . but they 're rather curious , and i say this out of affection for them . there 's something curious about professors in my experience -- not all of them , but typically , they live in their heads . they live up there , and slightly to one side . they 're disembodied , you know , in a kind of literal way . they look upon their body as a form of transport for their heads . ( laughter ) do n't they ? it 's a way of getting their head to meetings . ( laughter ) if you want real evidence of out-of-body experiences , get yourself along to a residential conference of senior academics , and pop into the discotheque on the final night . ( laughter ) and there , you will see it . grown men and women writhing uncontrollably , off the beat . ( laughter ) waiting until it ends so they can go home and write a paper about it . ( laughter ) our education system is predicated on the idea of academic ability . and there 's a reason . around the world , there were no public systems of education , really , before the 19th century . they all came into being to meet the needs of industrialism . so the hierarchy is rooted on two ideas . number one , that the most useful subjects for work are at the top . so you were probably steered benignly away from things at school when you were a kid , things you liked , on the grounds that you would never get a job doing that . is that right ? do n't do music , you 're not going to be a musician ; do n't do art , you wo n't be an artist . benign advice -- now , profoundly mistaken . the whole world is engulfed in a revolution . and the second is academic ability , which has really come to dominate our view of intelligence , because the universities designed the system in their image . if you think of it , the whole system of public education around the world is a protracted process of university entrance . and the consequence is that many highly-talented , brilliant , creative people think they 're not , because the thing they were good at at school was n't valued , or was actually stigmatized . and i think we ca n't afford to go on that way . in the next 30 years , according to unesco , more people worldwide will be graduating through education than since the beginning of history . more people , and it 's the combination of all the things we 've talked about -- technology and its transformation effect on work , and demography and the huge explosion in population . suddenly , degrees are n't worth anything . is n't that true ? when i was a student , if you had a degree , you had a job . if you did n't have a job , it 's because you did n't want one . and i did n't want one , frankly . ( laughter ) but now kids with degrees are often heading home to carry on playing video games , because you need an ma where the previous job required a ba , and now you need a phd for the other . it 's a process of academic inflation . and it indicates the whole structure of education is shifting beneath our feet . we need to radically rethink our view of intelligence . we know three things about intelligence . one , it 's diverse . we think about the world in all the ways that we experience it . we think visually , we think in sound , we think kinesthetically . we think in abstract terms , we think in movement . secondly , intelligence is dynamic . if you look at the interactions of a human brain , as we heard yesterday from a number of presentations , intelligence is wonderfully interactive . the brain is n't divided into compartments . in fact , creativity -- which i define as the process of having original ideas that have value -- more often than not comes about through the interaction of different disciplinary ways of seeing things . by the way , there 's a shaft of nerves that joins the two halves of the brain called the corpus callosum . it 's thicker in women . following off from helen yesterday , this is probably why women are better at multi-tasking . because you are , are n't you ? there 's a raft of research , but i know it from my personal life . if my wife is cooking a meal at home -- which is not often , thankfully . ( laughter ) no , she 's good at some things , but if she 's cooking , she 's dealing with people on the phone , she 's talking to the kids , she 's painting the ceiling , she 's doing open-heart surgery over here . if i 'm cooking , the door is shut , the kids are out , the phone 's on the hook , if she comes in i get annoyed . i say , `` terry , please , i 'm trying to fry an egg in here . '' ( laughter ) `` give me a break . '' ( laughter ) actually , do you know that old philosophical thing , if a tree falls in a forest and nobody hears it , did it happen ? remember that old chestnut ? i saw a great t-shirt recently , which said , `` if a man speaks his mind in a forest , and no woman hears him , is he still wrong ? '' ( laughter ) and the third thing about intelligence is , it 's distinct . i 'm doing a new book at the moment called `` epiphany , '' which is based on a series of interviews with people about how they discovered their talent . i 'm fascinated by how people got to be there . it 's really prompted by a conversation i had with a wonderful woman who maybe most people have never heard of , gillian lynne . have you heard of her ? some have . she 's a choreographer , and everybody knows her work . she did `` cats '' and `` phantom of the opera . '' she 's wonderful . i used to be on the board of the royal ballet , as you can see . anyway , gillian and i had lunch one day and i said , `` how did you get to be a dancer ? '' it was interesting . when she was at school , she was really hopeless . and the school , in the '30s , wrote to her parents and said , `` we think gillian has a learning disorder . '' she could n't concentrate ; she was fidgeting . i think now they 'd say she had adhd . would n't you ? but this was the 1930s , and adhd had n't been invented at this point . it was n't an available condition . ( laughter ) people were n't aware they could have that . ( laughter ) anyway , she went to see this specialist . so , this oak-paneled room , and she was there with her mother , and she was led and sat on this chair at the end , and she sat on her hands for 20 minutes while this man talked to her mother about the problems gillian was having at school . because she was disturbing people ; her homework was always late ; and so on , little kid of eight . in the end , the doctor went and sat next to gillian , and said , `` i 've listened to all these things your mother 's told me , i need to speak to her privately . wait here . we 'll be back ; we wo n't be very long , '' and they went and left her . but as they went out of the room , he turned on the radio that was sitting on his desk . and when they got out , he said to her mother , `` just stand and watch her . '' and the minute they left the room , she was on her feet , moving to the music . and they watched for a few minutes and he turned to her mother and said , `` mrs. lynne , gillian is n't sick ; she 's a dancer . take her to a dance school . '' i said , `` what happened ? '' she said , `` she did . i ca n't tell you how wonderful it was . we walked in this room and it was full of people like me . people who could n't sit still . people who had to move to think . '' who had to move to think . they did ballet , they did tap , jazz ; they did modern ; they did contemporary . she was eventually auditioned for the royal ballet school ; she became a soloist ; she had a wonderful career at the royal ballet . she eventually graduated from the royal ballet school , founded the gillian lynne dance company , met andrew lloyd webber . she 's been responsible for some of the most successful musical theater productions in history , she 's given pleasure to millions , and she 's a multi-millionaire . somebody else might have put her on medication and told her to calm down . ( applause ) what i think it comes to is this : al gore spoke the other night about ecology and the revolution that was triggered by rachel carson . i believe our only hope for the future is to adopt a new conception of human ecology , one in which we start to reconstitute our conception of the richness of human capacity . our education system has mined our minds in the way that we strip-mine the earth : for a particular commodity . and for the future , it wo n't serve us . we have to rethink the fundamental principles on which we 're educating our children . there was a wonderful quote by jonas salk , who said , `` if all the insects were to disappear from the earth , within 50 years all life on earth would end . if all human beings disappeared from the earth , within 50 years all forms of life would flourish . '' and he 's right . what ted celebrates is the gift of the human imagination . we have to be careful now that we use this gift wisely and that we avert some of the scenarios that we 've talked about . and the only way we 'll do it is by seeing our creative capacities for the richness they are and seeing our children for the hope that they are . and our task is to educate their whole being , so they can face this future . by the way -- we may not see this future , but they will . and our job is to help them make something of it . thank you very much . ( applause )

the problem is to remain an artist as we grow up . i believe this passionately , that we do n't grow into creativity , we grow out of it . or rather , we get educated out of it .

what do you think sir ken means when he says that we do n't grow into creativity , we grow out of it ?

how 's this for a strange idea : a day off from work in honor of work itself ? actually , that is what labor day , celebrated in the united states and canada on the first monday of every september , is all about . the first american labor day was celebrated in new york city on september 5th , 1882 , as thousands of workers and their families came to union square for a day in the park . it was not a national holiday but had been organized by a union to honor workers and their hard efforts with a rare day of rest , halfway between july 4th and thanksgiving . there were picnics and a parade , but there were also protests . the workers had gathered , not just to rest and celebrate , but to demand fair wages , the end of child labor , and the right to organize into unions . during the period known as the industrial revolution , many jobs were difficult , dirty and dangerous . people worked for twelve hours , six days a week , without fringe benefits , such as vacations , health care and pensions , and if you were young , chances are you were doing manual labor instead of your abcs and fractions . children as young as ten worked in some of the most hazardous places , like coal mines or factories filled with boiling vats or dangerous machines . trying to win better pay , shorter hours and safer conditions workers had begun to form labor unions in america and canada , but the companies they worked for often fought hard to keep unions out and to supress strikes . at times , this led to violent battles between workers and business owners with the owners often backed up by the police , or even the military . in the following years , the idea of labor day caught on in america with official celebrations reaching 30 states . but then came the violent haymarket square riot of 1886 , which led to the deaths of several policemen and workers in chicago and the execution of four union leaders . after that , many labor and political groups around the world had begun to mark haymarket square on may 1st , which became known as international workers ' day . in 1894 , president grover cleveland signed the law making labor day a federal holiday in america , only days after he had sent 12,000 soldiers to end a violent railroad strike that resulted in the death of several people . the original september date was kept , partly to avoid the more radical associations of may 1st . canada also created its labor day in 1894 . but , in spite of this new holiday , it would be a long time before the changes that workers wanted became a reality . in 1938 , during the great depression that left millions without jobs , president franklin d. roosevelt signed a law calling for an eight-hour work day , a five-day work week , and an end to child labor , some of the first federal protections for american workers . as america and canada celebrate labor day , most of the two countries ' children enjoy a day off from school . but it is important to remember that there was a time that everyday was a labor day for children in america and canada , and unfortunately , the same fact remains true for millions of children around the world today .

the original september date was kept , partly to avoid the more radical associations of may 1st . canada also created its labor day in 1894 . but , in spite of this new holiday , it would be a long time before the changes that workers wanted became a reality .

list three changes that happened as a result of labor day .

why is it so difficult to cure cancer ? we 've harnessed electricity , sequenced the human genome , and eradicated small pox . but after billions of dollars in research , we have n't found a solution for a disease that affects more than 14 million people and their families at any given time . cancer arises as normal cells accumulate mutations . most of the time , cells can detect mutations or dna damage and either fix them or self destruct . however , some mutations allow cancerous cells to grow unchecked and invade nearby tissues , or even metastasize to distant organs . cancers become almost incurable once they metastasize . and cancer is incredibly complex . it 's not just one disease . there are more than 100 different types and we do n't have a magic bullet that can cure all of them . for most cancers , treatments usually include a combination of surgery to remove tumors and radiation and chemotherapy to kill any cancerous cells left behind . hormone therapies , immunotherapy , and targeted treatments tailored for a specific type of cancer are sometimes used , too . in many cases , these treatments are effective and the patient becomes cancer-free . but they 're very far from 100 % effective 100 % of the time . so what would we have to do to find cures for all the different forms of cancer ? we 're beginning to understand a few of the problems scientists would have to solve . first of all , we need new , better ways of studying cancer . most cancer treatments are developed using cell lines grown in labs from cultures of human tumors . these cultured cells have given us critical insights about cancer genetics and biology , but they lack much of the complexity of a tumor in an actual living organism . it 's frequently the case that new drugs , which work on these lab-grown cells , will fail in clinical trials with real patients . one of the complexities of aggressive tumors is that they can have multiple populations of slightly different cancerous cells . over time , distinct genetic mutations accumulate in cells in different parts of the tumor , giving rise to unique subclones . for example , aggressive brain tumors called glioblastomas can have as many as six different subclones in a single patient . this is called clonal heterogeneity , and it makes treatment difficult because a drug that works on one subclone may have no effect on another . here 's another challenge . a tumor is a dynamic interconnected ecosystem where cancer cells constantly communicate with each other and with healthy cells nearby . they can induce normal cells to form blood vessels that feed the tumor and remove waste products . they can also interact with the immune system to actually suppress its function , keeping it from recognizing or destroying the cancer . if we could learn how to shut down these lines of communication , we 'd have a better shot at vanquishing a tumor permanently . additionally , mounting evidence suggests we 'll need to figure out how to eradicate cancer stem cells . these are rare but seem to have special properties that make them resistant to chemotherapy and radiation . in theory , even if the rest of the tumor shrinks beyond detection during treatment , a single residual cancer stem cell could seed the growth of a new tumor . figuring out how to target these stubborn cells might help prevent cancers from coming back . even if we solved those problems , we might face new ones . cancer cells are masters of adaptation , adjusting their molecular and cellular characteristics to survive under stress . when they 're bombarded by radiation or chemotherapy , some cancer cells can effectively switch on protective shields against whatever 's attacking them by changing their gene expression . malignant cancers are complex systems that constantly evolve and adapt . to defeat them , we need to find experimental systems that match their complexity , and monitoring and treatment options that can adjust as the cancer changes . but the good news is we 're making progress . even with all we do n't know , the average mortality rate for most kinds of cancer has dropped significantly since the 1970s and is still falling . we 're learning more every day , and each new piece of information gives us one more tool to add to our arsenal .

here 's another challenge . a tumor is a dynamic interconnected ecosystem where cancer cells constantly communicate with each other and with healthy cells nearby . they can induce normal cells to form blood vessels that feed the tumor and remove waste products . they can also interact with the immune system to actually suppress its function , keeping it from recognizing or destroying the cancer .

mutation in cells always results in cancerous cells . true or false ?

( electronic instrumental music ) ( tape rewinding ) - [ sally ] ever been to disneyland ? that was definitely an e ticket . - [ voiceover ] shuttle control houston . that was mission specialist sally ride comparing her flight to disneyland . - [ sally ] i wish that there had been another woman on my flight . i wish that two of us had gone up together . i think it would have been a lot easier . - [ gloria ] it ’ s tough being the first , but you ’ ve done it with incredible grace . you also have the only job in the world that everybody understands . ( laughing ) - [ sally ] my father , i think , was so grateful when i became an astronaut because he did not understand astrophysicist . he couldn ’ t relate to that at all , but astronaut was something he felt he understood . - [ gloria ] but you could see people all over the world connecting with what you were doing . - [ sally ] roughly half the people in the world would love to be astronauts , would give anything to trade places with you , and the other half just can ’ t understand why in the world you would do something that stupid . ( upbeat instrumental music ) - [ gloria ] you don ’ t have 20-20 vision , can you become an astronaut candidate ? i always thought that was a big disabling factor . - [ sally ] i think it used to be . now as long as it ’ s correctable to 20-20 , it ’ s okay . so you ’ d probably qualify . ( laughing ) ( upbeat instrumental music ) i didn ’ t have any dreams about being an astronaut at all and i don ’ t understand that because as soon as the opportunity was open to me , i jumped at it . and i instantly realized that that was what i really wanted to do . i took all the science classes that i could all the way through junior high school and into high school . i went to a girls ’ school that really didn ’ t have a strong science program at all when i was there . at the time it was a classic school for girls , with a good tennis team and a good english teacher and essentially no math past eleventh grade and no physics and no chemistry . - [ gloria ] i ’ m curious about the reception that you got inside nasa . what kind of thing happened to you ? - [ sally ] really the only bad moments in our training involved the press . the press was an added pressure on the flight for me and whereas nasa appeared to be very enlightened about flying women astronauts , the press didn ’ t appear to be . the things that they were concerned with were not the same things that i was concerned with . - [ gloria ] for instance , the bathroom facilities . - [ sally ] the bathroom facilities . - [ gloria ] how much did you get asked that ? - [ sally ] just about every interview i got asked that . everybody wanted to know about what kind of makeup i was taking up . they didn ’ t care about how well-prepared i was to operate the arm or deploy communications satellites . - [ gloria ] did nasa try to prepare you for the press and the pressure ? - [ sally ] unfortunately , no , they don ’ t . you know , in my case , they took a graduate student in physics who had spent her life in the basement of a physics department with oscilloscopes and suddenly put me in front of the press . ( upbeat instrumental music ) - [ gloria ] what do you suppose are the dumbest kinds of questions you ’ ve been asked to date ? - [ sally ] without a doubt , i think the worst question that i have gotten was whether i cried when we got malfunctions in the simulator . ( laughing ) no . - [ gloria ] that surpassed even the one about whether you ’ re going to wear a bra or not . did somebody really ask you that ? - [ sally ] no . the press , i think , decided that that was a good question for someone to have asked me and for me to have answered but i never got that question . - [ gloria ] and they made you up quite a good response . something about `` in a state of weightlessness `` it doesn ’ t matter , '' or something like that ? - [ sally ] yeah , it was something like that . - [ gloria ] they made up this whole thing ? - [ sally ] yeah , i was never asked that question . ( upbeat instrumental music ) - [ gloria ] what about your feelings during the launch ? was there any time that the enormity of what was going on came over you ? - [ sally ] the moment of the launch , when the engines actually ignited and the solid rockets lit , everyone on the crew was , for a few seconds , just overcome with what was about to happen to us . but a year of training is a long time . a year of sitting in simulators and being told exactly what ’ s going to happen . and you hear the sounds and you feel the vibrations . and they prepare you very well and it worked . we were able to overcome being overcome and do the things that we were supposed to do . - [ gloria ] just watching there at the launch , there were people with tears streaming down their faces , people i never would have expected and yet they were all very moved by , i guess , the human audacity of it . - [ sally ] i think that to imagine , when you see the long trail of flame , and then to imagine that there are really people inside that , that ’ s really something . inside , of course , you don ’ t see the long trail of flame and what you ’ re feeling is really more of an exhilaration . - [ gloria ] well , there are lots of people looking up there feeling proud , not only of you up there but also on the ground . thank you . - [ sally ] thank you . ( inspirational instrumental music ) - [ voiceover ] this special episode of blank on blank is made possible by squarespace . squarespace is a easy way to create a website , blog or online store for you and your ideas . try squarespace at squarespace.com/blankonblank for a special offer . ( upbeat instrumental music ) - [ gloria ] what do you think it might be like in 2001 , in fact ? what ’ s possible for us ? - [ sally ] well , 2001 is a long ways in the future to speculate on , but probably the next step after the space shuttle is gon na be to be a space station . i would foresee a space station as being not just something that is orbiting the earth and used for experimentation or whatever , but would also be used as a launching platform back to the moon or to mars . and i think both of those are inevitable . i ’ m sure we ’ ll go back to the moon and i ’ m sure it ’ s only a matter of time before we send people to mars . - [ gloria ] do you have any speculation about how long it might be perhaps before there are such things as peopled space colonies ? - [ sally ] i ’ d guess that probably by the year 2000 there will be . i think that we ’ ll have a space station by the end of this decade . - [ gloria ] on which it would be possible to live for long periods of time ? - [ sally ] yes . ( upbeat instrumental music ) - [ voiceover ] this episode was also supported by the alfred p. sloan foundation . enhancing public understanding of science , technology and economic performance . more information on sloan at sloan.org . ( upbeat instrumental music ) ( tape rewinding ) subtitles by the amara.org community

- [ voiceover ] shuttle control houston . that was mission specialist sally ride comparing her flight to disneyland . - [ sally ] i wish that there had been another woman on my flight . i wish that two of us had gone up together .

sally ride says she wishes there had been another woman on her mission and that they could have been `` the first '' together . what do you imagine the benefits would be of sharing the responsibility of breaking new ground ?

is teleportation possible ? could a baseball transform into something like a radio wave , travel through buildings , bounce around corners , and change back into a baseball ? oddly enough , thanks to quantum mechanics , the answer might actually be yes . sort of . here 's the trick . the baseball itself could n't be sent by radio , but all the information about it could . in quantum physics , atoms and electrons are interpreted as a collection of distinct properties , for example , position , momentum , and intrinsic spin . the values of these properties configure the particle , giving it a quantum state identity . if two electrons have the same quantum state , they 're identical . in a literal sense , our baseball is defined by a collective quantum state resulting from its many atoms . if this quantum state information could be read in boston and sent around the world , atoms for the same chemical elements could have this information imprinted on them in bangalore and be carefully directed to assemble , becoming the exact same baseball . there 's a wrinkle though . quantum states are n't so easy to measure . the uncertainty principle in quantum physics implies the position and momentum of a particle ca n't be measured at the same time . the simplest way to measure the exact position of an electron requires scattering a particle of light , a photon , from it , and collecting the light in a microscope . but that scattering changes the momentum of the electron in an unpredictable way . we lose all previous information about momentum . in a sense , quantum information is fragile . measuring the information changes it . so how can we transmit something we 're not permitted to fully read without destroying it ? the answer can be found in the strange phenomena of quantum entanglement . entanglement is an old mystery from the early days of quantum physics and it 's still not entirely understood . entangling the spin of two electrons results in an influence that transcends distance . measuring the spin of the first electron determines what spin will measure for the second , whether the two particles are a mile or a light year apart . somehow , information about the first electron 's quantum state , called a qubit of data , influences its partner without transmission across the intervening space . einstein and his colleagues called this strange communcation spooky action at a distance . while it does seem that entanglement between two particles helps transfer a qubit instantaneously across the space between them , there 's a catch . this interaction must begin locally . the two electrons must be entangled in close proximity before one of them is transported to a new site . by itself , quantum entanglement is n't teleportation . to complete the teleport , we need a digital message to help interpret the qubit at the receiving end . two bits of data created by measuring the first particle . these digital bits must be transmitted by a classical channel that 's limited by the speed of light , radio , microwaves , or perhaps fiberoptics . when we measure a particle for this digital message , we destroy its quantum information , which means the baseball must disappear from boston for it to teleport to bangalore . thanks to the uncertainty principle , teleportation transfers the information about the baseball between the two cities and never duplicates it . so in principle , we could teleport objects , even people , but at present , it seems unlikely we can measure the quantum states of the trillion trillion or more atoms in large objects and then recreate them elsewhere . the complexity of this task and the energy needed is astronomical . for now , we can reliably teleport single electrons and atoms , which may lead to super-secured data encryption for future quantum computers . the philosophical implications of quantum teleportation are subtle . a teleported object does n't exactly transport across space like tangible matter , nor does it exactly transmit across space , like intangible information . it seems to do a little of both . quantum physics gives us a strange new vision for all the matter in our universe as collections of fragile information . and quantum teleportation reveals new ways to influence this fragility . and remember , never say never . in a little over a century , mankind has advanced from an uncertain new understanding of the behavior of electrons at the atomic scale to reliably teleporting them across a room . what new technical mastery of such phenomena might we have in 1,000 , or even 10,000 years ? only time and space will tell .

the two electrons must be entangled in close proximity before one of them is transported to a new site . by itself , quantum entanglement is n't teleportation . to complete the teleport , we need a digital message to help interpret the qubit at the receiving end .

in addition to entanglement , what else is needed to complete a quantum teleport ?

what would you say is the most important discovery made in the past few centuries ? is it the computer ? the car ? electricity ? or maybe the discovery of the atom ? i would argue that it is this chemical reaction : a nitrogen gas molecule plus three hydrogen gas molecules gets you two ammonia gas molecules . this is the haber process of binding nitrogen molecules in the air to hydrogen molecules , or turning air into fertilizer . without this reaction , farmers would be capable of producing enough food for only 4 billion people ; our current population is just over 7 billion people . so , without the haber process , over 3 billion people would be without food . you see , nitrogen in the form of nitrate , no3 , is an essential nutrient for plants to survive . as crops grow , they consume the nitrogen , removing it from the soil . the nitrogen can be replenished through long , natural fertilization processes like decaying animals , but humans want to grow food much faster than that . now , here 's the frustrating part : 78 % of the air is composed of nitrogen , but crops ca n't just take nitrogen from the air because it contains very strong triple bonds , which crops can not break . what haber did basically was figure out a way to take this nitrogen in the air and put it into the ground . in 1908 , the german chemist fritz haber developed a chemical method for utilizing the vast supply of nitrogen in the air . haber found a method which took the nitrogen in the air and bonded it to hydrogen to form ammonia . ammonia can then be injected into the soil , where it is quickly converted into nitrate . but if haber 's process was going to be used to feed the world , he would need to find a way to create a lot of this ammonia quickly and easily . in order to understand how haber accomplished this feat , we need to know something about chemical equilibrium . chemical equilibrium can be achieved when you have a reaction in a closed container . for example , let 's say you put hydrogen and nitrogen into a closed container and allow them to react . in the beginning of the experiment , we have a lot of nitrogen and hydrogen , so the formation of ammonia proceeds at a high speed . but as the hydrogen and nitrogen react and get used up , the reaction slows down because there is less nitrogen and hydrogen in the container . eventually , the ammonia molecules reach a point where they start to decompose back into the nitrogen and hydrogen . after a while , the two reactions , creating and breaking down ammonia , will reach the same speed . when these speeds are equal , we say the reaction has reached equilibrium . this might sound good , but it 's not when what you want is to just create a ton of ammonia . haber does n't want the ammonia to break down at all , but if you simply leave the reaction in a closed container , that 's what will happen . here 's where henry le chatelier , a french chemist , can help . what he found was that if you take a system in equilibrium and you add something to it , like , say , nitrogen , the system will work to get back to equilibrium again . le chatelier also found that if you increase the amount of pressure on a system , the system tries to work to return to the pressure it had . it 's like being in a crowded room . the more molecules there are , the more pressure there is . if we look back at our equation , we see that on the left-hand side , there are four molecules on the left and just two on the right . so , if we want the room to be less crowded , and therefore have less pressure , the system will start combining nitrogen and hydrogen to make the more compact ammonia molecules . haber realized that in order to make large amounts of ammonia , he would have to create a machine that would continually add nitrogen and hydrogen while also increasing the pressure on the equilibrium system , which is exactly what he did . today , ammonia is one of the most produced chemical compounds in the world . roughly 131 million metric tons are produced a year , which is about 290 billion pounds of ammonia . that 's about the mass of 30 million african elephants , weighing roughly 10,000 pounds each . 80 % of this ammonia is used in fertilizer production , while the rest is used in industrial and household cleaners and to produce other nitrogen compounds , such as nitric acid . recent studies have found that half of the nitrogen from these fertilizers is not assimilated by plants . consequently , the nitrogen is found as a volatile chemical compound in the earth 's water supplies and atmosphere , severely damaging our environment . of course , haber did not foresee this problem when he introduced his invention . following his pioneering vision , scientists today are looking for a new haber process of the 21st century , which will reach the same level of aid without the dangerous consequences .

the nitrogen can be replenished through long , natural fertilization processes like decaying animals , but humans want to grow food much faster than that . now , here 's the frustrating part : 78 % of the air is composed of nitrogen , but crops ca n't just take nitrogen from the air because it contains very strong triple bonds , which crops can not break . what haber did basically was figure out a way to take this nitrogen in the air and put it into the ground .

what element is most important for growing crops ?

far beneath the palace of the treacherous king minos , in the damp darkness of an inescapable labryinth , a horrific beast stalks the endless corridors of its prison , enraged with a bloodlust so intense that its deafening roar shakes the earth . it is easy to see why the minotaur myth has a long history of being disregarded as pure fiction . however , there 's a good chance that the minotaur and other monsters and gods were created by our early ancestors to rationalize the terrifying things that they saw in the natural world but did not understand . and while we ca n't explain every aspect of their stories , there may be some actual science that reveals itself when we dissect them for clues . so , as far as we know , there have never been human-bull hybrids . but the earliest material written about the minotaur does n't even mention its physical form . so that 's probably not the key part of the story . what the different tellings do agree upon , however , is that the beast lives underground , and when it bellows , it causes tremendous problems . the various myths are also specific in stating that genius inventor daedalus , carved out the labyrinth beneath the island of crete . archeological attempts to find the fabled maze have come up empty handed . but crete itself has yielded the most valuable clue of all in the form of seismic activity . crete sits on a piece of continental crust called the aegean block , and has a bit of oceanic crust known as the nubian block sliding right beneath it . this sort of geologic feature , called a subduction zone , is common all over the world and results in lots of earthquakes . however , in crete the situation is particularly volatile as the nubian block is attached to the massive buoyant continental crust that is africa . when the nubian block moves , it does not go down nearly as easily or as steeply as oceanic crust does in most other subduction zones . instead , it violently and abruptly forces sections of the mediterranean upwards in an event called uplift , and crete is in uplift central . in the year 2014 , crete had more than 1300 earthquakes of magnitude 2.0 or higher . by comparison , in the same period of time , southern california , a much larger area , experienced a mere 255 earthquakes . of course , we do n't have detailed seismic records from the days of king minos , but we do know from fossil records and geologic evidence that crete has experienced serious uplift events that sometimes exceeded 30 feet in a single moment . contrast this for a moment with the island of hawaii , where earthquakes and volcanic activity were tightly woven to legends surrounding pele , a goddess both fiery and fair . like the minotaur , her myths included tales of destruction , but they also contained elements of dance and creation . so why did hawaii end up with pele and crete end up with the minotaur ? the difference likely comes down to the lava that followed many of hawaii 's worst earthquakes . the lava on hawaii is made of basalt , which once cooled , is highly fertile . within a couple of decades of terrible eruptions , islanders would have seen vibrant green life thriving on new peninsulas made of lava . so it makes sense that the mythology captured this by portraying pele as creator as well as a destroyer . as for the people of crete , their earthquakes brought only destruction and barren lands , so perhaps for them the unnatural and deadly minotaur was born . the connections between mythical stories and the geology of the regions where they originated teach us that mythology and science are actually two sides of the same coin . both are rooted in explaining and understanding the world . the key difference is that where mythology uses gods , monsters and magic , science uses measurements , records and experiments .

instead , it violently and abruptly forces sections of the mediterranean upwards in an event called uplift , and crete is in uplift central . in the year 2014 , crete had more than 1300 earthquakes of magnitude 2.0 or higher . by comparison , in the same period of time , southern california , a much larger area , experienced a mere 255 earthquakes .

roughly how many more earthquakes did crete experience in 2014 than all of southern california ?

it begins with a bit of discomfort and soon becomes a pressing sensation that 's impossible to ignore . finally , it 's all you can think about , and out of sheer desperation , you go on a hunt for a bathroom until `` ahh . '' humans should urinate at least four to six times a day , but occasionally , the pressures of modern life forces us to clench and hold it in . how bad is this habit , and how long can our bodies withstand it ? the answers lie in the workings of the bladder , an oval pouch that sits inside the pelvis . surrounding this structure are several other organs that together make up the whole urinary system . two kidneys , two ureters , two urethral sphincters , and a urethra . constantly trickling down from the kidneys is the yellowish liquid known as urine . the kidneys make urine from a mix of water and the body 's waste products , funneling the unwanted fluid into two muscular tubes called ureters . these carry it downward into the hollow organ known as the bladder . this organ 's muscular wall is made of tissue called detrusor muscle which relaxes as the bladder fills allowing it to inflate like a balloon . as the bladder gets full , the detrusor contracts . the internal urethral sphincter automatically and involuntarily opens , and the urine is released . whooshing downwards , the fluid enters the urethra and stops short at the external urethral sphincter . this works like a tap . when you want to delay urinating , you keep the sphincter closed . when you want to release it , you can voluntarily open the flood gates . but how do you sense your bladder 's fullness so you know when to pee ? inside the layers of detrusor muscles are millions of stretch receptors that get triggered as the bladder fills . they send signals along your nerves to the sacral region in your spinal cord . a reflex signal travels back to your bladder , making the detrusor muscle contract slightly and increasing the bladder 's pressure so you 're aware that it 's filling up . simultaneously , the internal urethral sphincter opens . this is called the micturition reflex . the brain can counter it if it 's not a good time to urinate by sending another signal to contract the external urethral sphincter . with about 150 to 200 milliliters of urine inside of it , the bladder 's muscular wall is stretched enough for you to sense that there 's urine within . at about 400 to 500 milliliters , the pressure becomes uncomfortable . the bladder can go on stretching , but only to a point . above 1,000 milliliters , it may burst . most people would lose bladder control before this happens , but in very rare cases , such as when as a person ca n't sense the need to urinate , the pouch can rupture painfully requiring surgery to fix . but under normal circumstances , your decision to urinate stops the brain 's signal to the external urethral sphincter , causing it to relax and the bladder to empty . the external urethral sphincter is one of the muscles of the pelvic floor , and it provides support to the urethra and bladder neck . it 's lucky we have these pelvic floor muscles because placing pressure on the system by coughing , sneezing , laughing , or jumping could cause bladder leakage . instead , the pelvic floor muscles keep the region sealed until you 're ready to go . but holding it in for too long , forcing out your urine too fast , or urinating without proper physical support may over time weaken or overwork that muscular sling . that can lead to an overactive pelvic floor , bladder pain , urgency , or urinary incontinence . so in the interest of long-term health , it 's not a great habit to hold your pee . but in the short term , at least , your body and brain have got you covered , so you can conveniently choose your moment of sweet release .

simultaneously , the internal urethral sphincter opens . this is called the micturition reflex . the brain can counter it if it 's not a good time to urinate by sending another signal to contract the external urethral sphincter .

if a person had a spinal cord injury , what could happen to the micturition reflex and what issues could this person face ?

cloudy climate change : how clouds affect earth 's temperature . earth 's average surface temperature has warmed by .8 celsius since 1750 . when carbon dioxide concentrations in the atmosphere have doubled , which is expected before the end of the 21st century , researchers project global temperatures will have risen by 1.5 to 4.5 degrees celsius . if the increase is near the low end , 1.5 celsius , then we 're already halfway there , and we should be more able to adapt with some regions becoming drier and less productive , but others becoming warmer , wetter and more productive . on the other hand , a rise of 4.5 degrees celsius would be similar in magnitude to the warming that 's occurred since the last glacial maximum 22,000 years ago , when most of north america was under an ice sheet two kilometers thick . so that would represent a dramatic change of climate . so it 's vitally important for scientists to predict the change in temperature with as much precision as possible so that society can plan for the future . the present range of uncertainty is simply too large to be confident of how best to respond to climate change . but this estimate of 1.5 to 4.5 celsius for a doubling of carbon dioxide has n't changed in 35 years . why have n't we been able to narrow it down ? the answer is that we do n't yet understand aerosols and clouds well enough . but a new experiment at cern is tackling the problem . in order to predict how the temperature will change , scientists need to know something called earth 's climate sensitivity , the temperature change in response to a radiative forcing . a radiative forcing is a temporary imbalance between the energy received from the sun and the energy radiated back out to space , like the imbalance caused by an increase of greenhouse gases . to correct the imbalance , earth warms up or cools down . we can determine earth 's climate sensitivity from the experiment that we 've already performed in the industrial age since 1750 and then use this number to determine how much more it will warm for various projected radiative forcings in the 21st century . to do this , we need to know two things : first , the global temperature rise since 1750 , and second , the radiative forcing of the present day climate relative to the pre-industrial climate . for the radiative forcings , we know that human activities have increased greenhouse gases in the atmosphere , which have warmed the planet . but our activities have at the same time increased the amount of aerosol particles in clouds , which have cooled the planet . pre-industrial greenhouse gas concentrations are well measured from bubbles trapped in ice cores obtained in greenland and antarctica . so the greenhouse gas forcings are precisely known . but we have no way of directly measuring how cloudy it was in 1750 . and that 's the main source of uncertainty in earth 's climate sensitivity . to understand pre-industrial cloudiness , we must use computer models that reliably simulate the processes responsible for forming aerosols in clouds . now to most people , aerosols are the thing that make your hair stick , but that 's only one type of aerosol . atmospheric aerosols are tiny liquid or solid particles suspended in the air . they are either primary , from dust , sea spray salt or burning biomass , or secondary , formed by gas to particle conversion in the atmosphere , also known as particle nucleation . aerosols are everywhere in the atmosphere , and they can block out the sun in polluted urban environments , or bathe distant mountains in a blue haze . more importantly , a cloud droplet can not form without an aerosol particle seed . so without aerosol particles , there 'd be no clouds , and without clouds , there 'd be no fresh water . the climate would be much hotter , and there would be no life . so we owe our existence to aerosol particles . however , despite their importance , how aerosol particles form in the atmosphere and their effect on clouds are poorly understood . even the vapors responsible for aerosol particle formation are not well established because they 're present in only minute amounts , near one molecule per million million molecules of air . this lack of understanding is the main reason for the large uncertainty in climate sensitivity , and the corresponding wide range of future climate projections . however , an experiment underway at cern , named , perhaps unsurprisingly , `` cloud '' has managed to build a steel vessel that 's large enough and has a low enough contamination , that aerosol formation can , for the first time , be measured under tightly controlled atmospheric conditions in the laboratory . in its first five years of operation , cloud has identified the vapors responsible for aerosol particle formation in the atmosphere , which include sulfuric acid , ammonia , amines , and biogenic vapors from trees . using an ionizing particle beam from the cern proton synchrotron , cloud is also investigating if galactic cosmic rays enhance the formation of aerosols in clouds . this has been suggested as a possible unaccounted natural climate forcing agent since the flux of cosmic rays raining down on the atmosphere varies with solar activity . so cloud is addressing two big questions : firstly , how cloudy was the pre-industrial climate ? and , hence , how much have clouds changed due to human activities ? that knowledge will help sharpen climate projections in the 21st century . and secondly , could the puzzling observations of solar climate variability in the pre-industrial climate be explained by an influence of galactic cosmic rays on clouds ? ambitious but realistic goals when your head 's in the clouds .

cloudy climate change : how clouds affect earth 's temperature . earth 's average surface temperature has warmed by .8 celsius since 1750 . when carbon dioxide concentrations in the atmosphere have doubled , which is expected before the end of the 21st century , researchers project global temperatures will have risen by 1.5 to 4.5 degrees celsius . if the increase is near the low end , 1.5 celsius , then we 're already halfway there , and we should be more able to adapt with some regions becoming drier and less productive , but others becoming warmer , wetter and more productive .

a certain climate model calculates a climate sensitivity of 0.8 celsius per watt/m2 . ( 1 watt/m2 = 1 watt per square metre ; a candle is about 40 watt so 1 watt/m2 is equivalent to the energy of one candle spread over 40 square metres . ) what global temperature rise is predicted by this model for a doubling of carbon dioxide in the atmosphere ( radiative forcing = 3.7 watt/m2 ) , which is a level that may be reached during the second half of the 21st century ?

living with her family high above the ground in the northern tropical forests of colombia , you will find shakira , a cotton-top tamarin with a penchant for conversation . say , `` hola ! '' though you may not realize it , this one pound monkey communicates in a highly sophisticated language of 38 distinct calls based on variations of chirps and whistles . the response she just gave is known as a `` b chirp '' , a call often directed at humans . to appreciate the complexities of shakira 's language , let 's learn a few chirps and whistles , then examine how their combinations form grammatically structured sequences . the chirp shakira used to greet us comes from a class of calls known as single frequency modulated syllables . this class is made up of short duration calls , or chirps , and long duration calls , like screams and squeals . researchers have determined that there are eight different types of chirps categorized by stem upsweep , duration , peak frequency , and frequency change . in addition , each chirp has its own unique meaning . for example , shakira 's `` c chirp '' is used when she is approaching food , where as her `` d chirp '' is only used when she has the food in hand . single whistles also exhibit a unique intention with each call and just as there are eight different chirps , there are five different whistles . based on frequency modulation , single whistles are subdivided into four categories : squeaks , initially modulated whistles , terminally modulated whistles , and flat whistles . the language 's quality of unique intention is wonderfully exemplified by the category of initially modulated whistles . these whistles change based on the proximity of shakira to other members of her family . if shakira is greater than .6 meters from her family , she 'll sound a large initally modulated whistle . but if she 's less than .6 meters from her family , she 'll sound a small initially modulated whistle . now that we 've learned a few chirps and whistles , shakira wants to show off by taking you through a quick day in her life with these calls . while heading towards a feeding tree for her first meal of the day , she says , ( monkey noise ) , a call most often used in relaxed investigations . however , suddenly she spots the shadow of a hawk . `` e chirp '' for alarm . this call alerts her family to the presence of this predator , and shakira jumps to the safety of an inner branch . the coast seems clear , so shakira makes her way towards her dad . wait , wait . who is that ? ah , it 's her younger brother , carlos . cotton-top tamarins often squeal during play wrestling . uh-oh . he 's playing a little too roughly , and shakira screams , alerting her parents to help her . her dad makes his way towards the ball of rolling fur and her brother stops . shakira shakes herself and scratches herself to get the hair on her head back in place . then shakira spots another group of unfamiliar tamarins and hears their normal long call . she turns to her family . ( monkey noise ) did you catch that ? first there was a chirp , then a whistle . this is what 's known as a combination vocalization , a phrase that contains both a chirp and a whistle . these are two calls strung together to convey a message . the combination of these two elements alerts her family to the presence of another group , the `` f chirp '' , and the distance they are away , the normal long call whistle . in other words , shakira just said a sentence . her simple demonstration is just the tip of the iceberg . she 's got trills , chatters , multiple whistle calls , more combination vocalizations , even twitters . yet sadly enough , we may not get to hear everything she has to say . mixed in with chirping sonatas from high above is the constant thud of a machete chopping trees . shakira 's habitat in colombia is being cut down , piece by piece , and if we do n't work to protect the critically endangered cotton-top tamarin , it will become extinct in our lifetime . if the chirp from one tamarin to the next has proven to be more than just idle chit chat , imagine what else we have left to discover . imagine what else shakira can tell us .

her simple demonstration is just the tip of the iceberg . she 's got trills , chatters , multiple whistle calls , more combination vocalizations , even twitters . yet sadly enough , we may not get to hear everything she has to say .

vocalizations are characterized by the following :

for most of us , two degrees celsius is a tiny difference in temperature , not even enough to make you crack a window . but scientists have warned that as co2 levels in the atmosphere rise , an increase in the earth 's temperature by even this amount can lead to catastrophic effects all over the world . how can such a small measurable change in one factor lead to massive and unpredictable changes in other factors ? the answer lies in the concept of a mathematical tipping point , which we can understand through the familiar game of billiards . the basic rule of billiard motion is that a ball will go straight until it hits a wall , then bounce off at an angle equal to its incoming angle . for simplicity 's sake , we 'll assume that there is no friction , so balls can keep moving indefinitely . and to simplify the situation further , let 's look at what happens with only one ball on a perfectly circular table . as the ball is struck and begins to move according to the rules , it follows a neat star-shaped pattern . if we start the ball at different locations , or strike it at different angles , some details of the pattern change , but its overall form remains the same . with a few test runs , and some basic mathematical modeling , we can even predict a ball 's path before it starts moving , simply based on its starting conditions . but what would happen if we made a minor change in the table 's shape by pulling it apart a bit , and inserting two small straight edges along the top and bottom ? we can see that as the ball bounces off the flat sides , it begins to move all over the table . the ball is still obeying the same rules of billiard motion , but the resulting movement no longer follows any recognizable pattern . with only a small change to the constraints under which the system operates , we have shifted the billiard motion from behaving in a stable and predictable fashion , to fluctuating wildly , thus creating what mathematicians call chaotic motion . inserting the straight edges into the table acts as a tipping point , switching the systems behavior from one type of behavior ( regular ) , to another type of behavior ( chaotic ) . so what implications does this simple example have for the much more complicated reality of the earth 's climate ? we can think of the shape of the table as being analogous to the co2 level and earth 's average temperature : constraints that impact the system 's performance in the form of the ball 's motion or the climate 's behavior . during the past 10,000 years , the fairly constant co2 atmospheric concentration of 270 parts per million kept the climate within a self-stabilizing pattern , fairly regular and hospitable to human life . but with co2 levels now at 400 parts per million , and predicted to rise to between 500 and 800 parts per million over the coming century , we may reach a tipping point where even a small additional change in the global average temperature would have the same effect as changing the shape of the table , leading to a dangerous shift in the climate 's behavior , with more extreme and intense weather events , less predictability , and most importantly , less hospitably to human life . the hypothetical models that mathematicians study in detail may not always look like actual situations , but they can provide a framework and a way of thinking that can be applied to help understand the more complex problems of the real world . in this case , understanding how slight changes in the constraints impacting a system can have massive impacts gives us a greater appreciation for predicting the dangers that we can not immediately percieve with our own senses . because once the results do become visible , it may already be too late .

for most of us , two degrees celsius is a tiny difference in temperature , not even enough to make you crack a window . but scientists have warned that as co2 levels in the atmosphere rise , an increase in the earth 's temperature by even this amount can lead to catastrophic effects all over the world . how can such a small measurable change in one factor lead to massive and unpredictable changes in other factors ? the answer lies in the concept of a mathematical tipping point , which we can understand through the familiar game of billiards . the basic rule of billiard motion is that a ball will go straight until it hits a wall , then bounce off at an angle equal to its incoming angle .

create a visual representation of what is meant by a tipping point . include carbon dioxide levels , temperature and the results of these changes .

the biggest kidney stone on record weighed more than a kilogram and was 17 centimeters in diameter . the patient did n't actually swallow a stone the size of a coconut . kidney stones form inside the body , but unfortunately , they 're extremely painful to get out . a kidney stone is a hard mass of crystals that can form in the kidneys , ureters , bladder , or urethra . urine contains compounds that consist of calcium , sodium , potassium , oxalate , uric acid , and phosphate . if the levels of these particles get too high , or if urine becomes too acidic or basic , the particles can clump together and crystallize . unless the problem is addressed , the crystals will gradually grow over a few weeks , months , or even years , forming a detectable stone . calcium oxalate is the most common type of crystal to form this way , and accounts for about 80 % of kidney stones . less common kidney stones are made of calcium phosphate , or uric acid . a slightly different type of stone made of the minerals magnesium ammonium phosphate , or struvite , can be caused by bacterial infection . and even rarer stones can result from genetic disorders or certain medications . a kidney stone can go undetected until it starts to move . when a stone travels through the kidney and into the ureter , its sharp edges scratch the walls of the urinary tract . nerve endings embedded in this tissue transmit excruciating pain signals through the nervous system . and the scratches can send blood flowing into the urine . this can be accompanied by symptoms of nausea , vomiting , and a burning sensation while urinating . if a stone gets big enough to actually block the flow of urine , it can create an infection , or back flow , and damage the kidneys themselves . but most kidney stones do n't become this serious , or even require invasive treatment . masses less than five millimeters in diameter will usually pass out of the body on their own . a doctor will often simply recommend drinking large amounts of water to help speed the process along , and maybe taking some pain killers . if the stone is slightly larger , medications like alpha blockers can help by relaxing the muscles in the ureter and making it easier for the stone to get through . another medication called potassium citrate can help dissolve the stones by creating a less acidic urine . for medium-sized stones up to about ten millimeters , one option is pulverizing them with soundwaves . extracorporeal shock wave lithotripsy uses high-intensity pulses of focused ultrasonic energy aimed directly at the stone . the pulses create vibrations inside the stone itself and small bubbles jostle it . these combined forces crush the stone into smaller pieces that can pass out of the body more easily . but zapping a stone with sound does n't work as well if it 's simply too big . so sometimes , more invasive treatments are necessary . a rigid tube called a stent can be placed in the ureter to expand it . optical fibers can deliver laser pulses to break up the stone . stones can also be surgically removed through an incision in the patient 's back or groin . what about just avoiding kidney stones in the first place ? for people prone to them , their doctor may recommend drinking plenty of water , which dilutes the calcium oxalate and other compounds that eventually build up into painful stones . foods like potato chips , spinach , rhubarb , and beets are high in oxalate , so doctors might advise limiting them . even though calcium is often found in stones , calcium in foods and beverages can actually help by binding to oxalate in the digestive tract before it can be absorbed and reach the kidneys . if you do end up with a kidney stone , you 're not alone . data suggests that rates are rising , but that world record probably wo n't be broken any time soon .

unless the problem is addressed , the crystals will gradually grow over a few weeks , months , or even years , forming a detectable stone . calcium oxalate is the most common type of crystal to form this way , and accounts for about 80 % of kidney stones . less common kidney stones are made of calcium phosphate , or uric acid . a slightly different type of stone made of the minerals magnesium ammonium phosphate , or struvite , can be caused by bacterial infection .

what is the most common composition of kidney stones ?

when you picture a spaceship , you probably think of something like this , or this , or maybe this . what do they all have in common ? among other things , they 're huge because they have to carry people , fuel , and all sorts of supplies , scientific instruments , and , in rare cases , planet-killing lasers . but the next real-world generation of spacecraft may be much , much smaller . we 're talking fit-inside-your-pocket tiny . imagine sending a swarm of these microspacecraft out into the galaxy . they could explore distant stars and planets by carrying sophisticated electronic sensors that would measure everything from temperature to cosmic rays . you could deploy thousands of them for the cost of a single space shuttle mission , exponentially increasing the amount of data we could collect about the universe . and they 're individually expendable , meaning that we could send them into environments that are too risky for a billion dollar rocket or probe . several hundred small spacecraft are already orbiting the earth , taking pictures of outer space , and collecting data on things , like the behavior of bacteria in the earth 's atmosphere and magnetic signals that could help predict earthquakes . but imagine how much more we could learn if they could fly beyond earth 's orbit . that 's exactly what organizations , like nasa , want to do : send microspacecraft to scout habitable planets and describe astronomical phenomena we ca n't study from earth . but something so small ca n't carry a large engine or tons of fuel , so how would such a vessel propel itself ? for microspacecraft , it turns out , you need micropropulsion . on really small scales , some of the familiar rules of physics do n't apply , in particular , everyday newtonian mechanics break down , and forces that are normally negligible become powerful . those forces include surface tension and capillary action , the phenomena that govern other small things . micropropulsion systems can harness these forces to power spacecraft . one example of how this might work is called microfluidic electrospray propulsion . it 's a type of ion thruster , which means that it shoots out charged particles to generate momentum . one model being developed at nasa 's jet propulsion laboratory is only a couple centimeters on each side . here 's how it works . that postage-stamp sized metal plate is studded with a hundred skinny needles and coated with a metal that has a low melting point , like indium . a metal grid sits above the needles , and an electric field is set up between the grid and the plate . when the plate is heated , the indium melts and capillary action draws the liquid metal up the needles . the electric field tugs the molten metal upwards , while surface tension pulls it back , causing the indium to deform into a cone . the small radius of the tips of the needles makes it possible for the electric field to overcome the surface tension , and when that happens , positively charged ions shoot off at speeds of tens of kilometers per second . that stream of ions propels the spacecraft in the opposite direction , thanks to newton 's third law . and while each ion is an extremely small particle , the combined force of so many of them pushing away from the craft is enough to generate significant acceleration . and unlike the exhaust that pours out of a rocket engine , this stream is much smaller and far more fuel efficient , which makes it better suited for long deep-space missions . these micropropulsion systems have n't been fully tested yet , but some scientists think that they will provide enough thrust to break small craft out of earth 's orbit . in fact , they 're predicting that thousands of microspacecraft will be launched in the next ten years to gather data that today we can only dream about . and that is micro-rocket science .

for microspacecraft , it turns out , you need micropropulsion . on really small scales , some of the familiar rules of physics do n't apply , in particular , everyday newtonian mechanics break down , and forces that are normally negligible become powerful . those forces include surface tension and capillary action , the phenomena that govern other small things .

which type of normally negligible forces become powerful at a small scale ?

sometimes when a fish is reeled up to the surface it will appear inflated , with its eyes bulging out of their sockets and its stomach projecting out of its mouth , as if its been blown up like a balloon . this type of bodily damage , caused by rapid changes in pressure , is called barotrauma . under the sea , pressure increases by 14.7 pounds per square inch for every 33 foot increase in depth . so , take the yelloweye rockfish , which can live as deep as 1800 feet , where there 's over 800 pounds of pressure on every square inch . that 's equivalent to the weight of a polar bear balancing on a quarter . now , boyle 's gas law states that the volume of a gas is inversely related to pressure . so , any air-filled spaces , like a rockfish 's swim bladder , or human lungs , will compress as they descend deeper and expand as they ascend . after a fish bites a fisherman 's hook and is quickly reeled up to the surface , the air in its swim bladder begins to expand . its rapid expansion actually forces the fish 's stomach out of its mouth , while the increased internal pressure pushes its eyes out of their sockets , a condition called exophthalmia . sometimes rockfish eyes will even have a crystallized appearance from corneal emphysemas , little gas bubbles that build up inside the cornea . thankfully , a scuba diver does n't have a closed swim bladder to worry about . a diver can regulate pressure in her lungs by breathing out as she ascends , but must be wary of other laws of physics that are at play under the sea . henry 's law states that the amount of a gas that dissolves in a liquid is proportional to its partial pressure . the air a diver breathes is 78 % nitrogen . at a higher pressure under the sea , the nitrogen from the air in a scuba tank diffuses into a diver 's tissues in greater concentrations than it would on land . if the diver ascends too quickly , this built up nitrogen can come out of solution and form microbubbles in her tissues , blood and joints , causing decompression sickness , aka the bends . this is similar to the fizz of carbon dioxide coming out of your soda . gas comes out of solution when the pressure 's released . but for a diver , the bubbles cause severe pain and sometimes even death . divers avoid falling victim to the bends by rising slowly and taking breaks along the way , called decompression stops , so the gas has time to diffuse back out of their tissues and to be released through their breath . just as a diver needs decompression , for a fish to recover , it needs recompression , which can be accomplished by putting it back in the sea . but that does n't mean that fish should just be tossed overboard . an inflated body will float and get scooped up by a hungry sea lion or pecked at by seagulls . there 's a common myth that piercing its stomach with a needle will let air escape , allowing the fish to swim back down on its own . but that is one balloon that should n't be popped . to return a fish properly to its habitat , fisherman can use a descending device instead to lower it on a fishing line and release it at the right depth . as it heads home and recompression reduces gas volume , its eyes can return to their sockets and heal , and its stomach can move back into place . this fish will live to see another day , once more free to swim , eat , reproduce and replenish the population .

that 's equivalent to the weight of a polar bear balancing on a quarter . now , boyle 's gas law states that the volume of a gas is inversely related to pressure . so , any air-filled spaces , like a rockfish 's swim bladder , or human lungs , will compress as they descend deeper and expand as they ascend .

what does boyle 's gas law state ?

astronomers have discovered thousands of planets orbiting stars other than the sun . they come in all sizes , at different orbital distances from their stars . the closest of them are trillions of miles away , and even the largest are just fuzzy patches in the fields of high-powered telescopes . but if one of these planets is close in size to the earth and orbits not too close and too far away from its parent star , it could be rocky and warm enough to have oceans and perhaps life . astronomers discover these potentially habitable planets , and their eyes get big and wide . could one of these distant worlds carry the building blocks of life ? or even a living , breathing , civilization ? is the question , `` are we alone in the universe ? '' about to be answered ? but wait . maybe we should ask a different question first . should we try to find out if we 're alone in the universe ? if we do find the atmospheric fingerprints of life on one of these small , distant worlds , should we try to contact any beings who may live there ? is that wise ? three decades ago , nasa decided the answer was yes . voyager 1 and 2 were launched in 1977 to explore the giant planets in the solar system . each spacecraft carried a golden phonograph record , a time capsule of sorts that included clues and messages meant to convey the story of human civilization . the contents of these gold-plated copper disks were chosen by a committee chaired by american astronomer and author carl sagan . they included over 100 images , and a range of sounds from the natural world : ocean waves , thunder , the sounds of birds and whales . the records also included music from many different time periods and cultures , greetings in 55 languages , and messages from the president of the united states , and the un secretary general . they also included a map . each golden record displays the location of our solar system with respect to fourteen pulsars . their precise , unique frequencies were indicated so that intelligent , extraterrestrial lifeforms could use them to find the earth . many years later , renowned physicist stephen hawking said that it was a mistake to give an alien species a roadmap to our planet . hawking suspected that any extraterrestrial life probably was n't any more complex than microbes , but he warned that if an advanced alien species did visit earth , it could be as catastrophic as christopher columbus 's arrival was for the native americans . meanwhile , the golden records continue their journeys . in 1990 , both voyager spacecraft passed beyond the orbit of pluto . voyager 1 entered interstellar space in 2012 , and will reach the nearest stellar system in 40,000 years . if either spacecraft is discovered by extraterrestrial life , there 's a possibility that they could decipher the clues from the golden record and one day reach our planet . that 's particularly true if theirs is a much more technologically advanced civilization . that life could be benevolent , as we would hope to be if humans are one day able to achieve interstellar travel . or it could be hostile . searching for planets that might have life means staring into a great abyss . we 'll likely have no clear knowledge of the evolutionary stage , sentience , character , or intentions of the first form of life we discover . so it 's a risk to turn our eyes outwards . we risk our very way of life . but it may be a greater risk not to look , to deny the very pioneering spirits that help shape our own species . we are all born curious about the world and the universe . pursuing that curiosity is one of humankind 's greatest achievements . perhaps there is room to push the frontiers of science , provided that we cradle alongside our fervor another of humankind 's greatest assets : hope .

that 's particularly true if theirs is a much more technologically advanced civilization . that life could be benevolent , as we would hope to be if humans are one day able to achieve interstellar travel . or it could be hostile .

while the search for life elsewhere in the universe is uncertain , humans have always been ______ , so not satisfying the quest for discovery would go against our very nature .

translator : tom carter reviewer : bedirhan cinar ( stories from the sea : how life came to land ) life for my kind was n't always this way . there was a time when no animals lived on land . all life was in the ocean . the ocean 's where all of us animals got our start , more than half a billion years ago , this is where all animal body types -- or phyla , as scientists call them -- first evolved . you know , there are more than 30 animal phyla , but only a handful of major ones had what it took to do something completely daring : step out of the ocean , and on to dry land . so , which of these land-dwelling phyla first invaded the land ? was it me and my mollusc friends , with our amazing mantles and single foot ? perhaps the chordate crowd , with their notochords , segmented muscles and big bony skeletons . or maybe those lowly annelid worms , with their powerful ringed bodies . or did the arthropods first make landfall , with their little flexible suits of armor -- their exoskeleton ? ah , yes . the arthropods . from crustaceans to millipedes , spiders to insects , the arthropods outnumber all animals on land . so what 's their secret ? their exoskeleton is key , but here 's the real kicker : jointed appendages . they 're like little living swiss army knives : antennae , multiple mouth parts , an obscene number of legs , if you ask me . there 's one group of arthropods -- the insects -- that really rule the land . three body parts , six legs , and an annoying tendency to take over . sure , they have to molt to grow , but that does n't seem to pose a problem . the insects even invented the first wings , and conquered the skies . ah , well . so what if arthropods were the first to reach land and invent flight , a hundred million years before the rest of us ? so what if they pollinate crops around the world , and make up 75 % of all land animal species ? and that for every single human , there 's 200 million of them ? sure , those leggy arthropods may still be in the lead when it comes to conquering land , but we still rule in the sea . there are more species of molluscs in the ocean than any other animal phylum . we 're just getting started up here on land . besides , the seas are rising . just give us some time . who knows who 'll end up ruling this ocean planet ?

you know , there are more than 30 animal phyla , but only a handful of major ones had what it took to do something completely daring : step out of the ocean , and on to dry land . so , which of these land-dwelling phyla first invaded the land ? was it me and my mollusc friends , with our amazing mantles and single foot ?

other lesser-known animal phyla have also invaded land but for the most part remain tethered to moist habitats . who are these other phyla and what features have enabled them to make the leap ?

in the summer of 1976 , a mysterious epidemic suddenly struck two central african towns , killing the majority of its victims . medical researchers suspected the deadly marburg virus to be the culprit . but what they saw in microscope images was an entirely new pathogen , which would be named after the nearby ebola river . like yellow fever or dengue , the disease caused by the ebola virus is a severe type of hemorrhagic fever . it begins by attacking the immune system 's cells and neutralizing its responses , allowing the virus to proliferate . starting anywhere from two to twenty days after contraction , initial symptoms like high temperature , aching , and sore throat resemble those of a typical flu , but quickly escalate to vomiting , rashes , and diarrhea . and as the virus spreads , it invades the lymph nodes and vital organs , such as kidneys and liver , causing them to lose function . but the virus itself is not what kills ebola victims . instead , the mounting cell deaths trigger an immune system overload , known as a cytokine storm , an explosion of immune responses that damages blood vessels , causing both internal and external bleeding . the excessive fluid loss and resulting complications can be fatal within six to sixteen days of the first symptoms , though proper care and rehydration therapy can significantly reduce mortality rates in patients . fortunately , while ebola is highly virulent , several factors limit its contagiousness . unlike viruses that proliferate through small , airborne particles , ebola only exists in bodily fluids , such as saliva , blood , mucus , vomit , or feces . in order to spread , these must be transmitted from an infected person into another 's body through passageways such as the eyes , mouth , or nose . and because the disease 's severity increases directly along with the viral load , even an infected person is unlikely to be contagious until they have begun to show symptoms . while ebola has been shown to survive on surfaces for several hours , and transmission through sneezing or coughing is theoretically possible , virtually all known cases of contraction have been through direct contact with the severely ill , with the greatest risk posed to medical workers and friends or relatives of the victims . this is why , despite its horrifying effects , ebola has been far less deadly overall than more common infections , such as measles , malaria , or even influenza . once an outbreak has been contained , the virus does not exist in the human population until the next outbreak begins . but while this is undoubtedly a good thing , it also makes ebola difficult to study . scientists believe fruit bats to be its natural carriers , but just how it is transmitted to humans remains unknown . furthermore , many of the countries where ebola outbreaks occur suffer from poor infrastructure and sanitation , which enables the disease to spread . and the poverty of these regions , combined with the relatively low amount of overall cases means there is little economic incentive for drug companies to invest in research . though some experimental medicines have shown promise , and governments are funding development of a vaccine , as of 2014 , the only widespread and effective solutions to an ebola outbreak remain isolation , sanitation , and information .

and as the virus spreads , it invades the lymph nodes and vital organs , such as kidneys and liver , causing them to lose function . but the virus itself is not what kills ebola victims . instead , the mounting cell deaths trigger an immune system overload , known as a cytokine storm , an explosion of immune responses that damages blood vessels , causing both internal and external bleeding .

what is the best treatment currently available for the ebola virus ?

so molybdenum is an element which is essential to life and most organisms beginning with you and me and going down to bacteria have enzymes that contain molybdenum . one of the most important enzymes is so called nitrogenase which is an enzyme that will turn nitrogen into ammonia , and nitrogenase is found in various bacteria that live in the roots of plants like beans . so the beans , via these bacteria , can absorb nitrogen into the atmosphere and turn it into a form that we can digest and we need that nitrogen so that we can make the proteins in our body . so without molybdenum nothing could live .

so the beans , via these bacteria , can absorb nitrogen into the atmosphere and turn it into a form that we can digest and we need that nitrogen so that we can make the proteins in our body . so without molybdenum nothing could live .

molybdenum has a high melting point , but this is not the highest in the periodic table . what is the melting point of molybdenum ?

to survive in this high pressured , crazy world most of us have to become highly adept at self-criticism . we learn how to tell ourselves off for our failures and for not working hard or smart enough . but so good are we at this that we 're sometimes in danger of falling prey to an excessive form of self-criticism what we might call self-flagellation a rather dangerous state which just ushers in depression and under-performance . we might simply lose the will to get out of bed . for those moments , we need a corrective . we need to carve out time for an emotional state of which many of us are profoundly suspicious . self-compassion . we 're suspicious because that sounds horribly close to self-pity but because depression and self-hatred are serious enemies of a good life , we need to appreciate the role of self-care in a good , ambitious and fruitful life . to this end we can perform what we 've called a , `` self-compassion exercise '' a structured meditation , lasting 15 minutes or so lying in bed , or perhaps a bath turn over a sequence of thoughts that interrupt and correct the flow of your worse self-accusations . for a time adopt an entire kindly perspective on your setbacks the self compassion exercise goes like this : we 're so in love with success we fail to notice the scale of the challenges we routinely set ourselves . there is nothing remotely normal about what we 've tried to achieve . we 've failed , but given the mountain we were trying to climb , the conclusion does n't have to be that we 're simply flawless . we have tricky family histories , we all do . there were things which happened to us at the hands of others which can help to explain some of our current troubles . we 're not entirely sane or well , but none of us are . we were n't well set up to carry out certain tasks it is n't wholly our fault in the here and now . from the media , you 'd think everyone was rich and famous and successful . but in reality , undramatic , quiet failure is by a huge margin the statistical norm . we should n't tear ourselves apart for not managing to be to what were in truth , awesome odds . tough , self-critical people do n't allow themselves the indulgence of believing in luck . they take responsibility for everything . they think winners make their own luck but they do n't for the most part . luck is a genuine feature of existence we 're robbing ourselves of fair concilation by believing that we 're entirely in control , and therefore entirely to blame when we crash . you are not only your achievements . status and material success are one bit of you . but there are others as well , those who loved you in childhood knew this , and in their best moments helped you to feel it . rehearse the internalized voices of all those who have been kind to you . bathe in the memory of a laugh independent of achievement . it seems it will never end that 's not the truth it 's just how a crisis feels . you need to reduce expectations to zero for a time . take each new hour as it comes , and without being banal , what you need most of all , is some rest .

we need to carve out time for an emotional state of which many of us are profoundly suspicious . self-compassion . we 're suspicious because that sounds horribly close to self-pity but because depression and self-hatred are serious enemies of a good life , we need to appreciate the role of self-care in a good , ambitious and fruitful life .

we often think that when it comes to our goals , there is only success and failure . this exercise in self-compassion encourages us to take a closer look at the scale of our goals . to what end ?

translator : andrea mcdonough reviewer : bedirhan cinar nearly every one of your science classes starts off with the scientific method . you recognize this ? ask a question , form a hypothesis , perform an experiment , collect data , draw conclusions , and then memorize a bunch of facts . this is really boring ! science is not a simple recipe in a cookbook , and learning is not memorizing facts for tests . yet , that is exactly what we do . we have to change this ! we have to look at how curiosity can ultimately benefit society by looking towards tomorrow , by going through a path from involvement to imagination to invention to innovation . and i 'd like to illustrate this by telling you the real story about how we discovered how geckos stick . first you need to get involved . you need to do curiosity-driven research yourself . we know that learning by being an active researcher is the best way to learn . imagine being in my lab and trying to discover how geckos stick . `` here is one of our subjects . this is a crested gecko . we are going to put the gecko on glass and we 're going to use a high speed camera that can capture up to 1,000 pictures in one second . there he goes . ok , record it . there 's the animal 's toes . '' `` so how do their feet stick and unstick so quickly ? '' how < i > do < /i > they do this ? we wonder , it 's kind of crazy , right ? it 's hard to believe . well it turns out , it was already known that the geckos have hairy toes , and those hairs are really small compared to your hair , and the little tips at the end are even smaller . well , my student tanya , who is not much older than some of you when she did this , a sophomore undergraduate , tried to figure this out , and we told that her that in order to do this , you 'd have to measure the force of a single hair . though we kind of only did this jokingly because these hairs are so small , we did n't think it was possible . but tanya did n't know that , and she went on to build the simplest , most beautiful measurement device ever . here it is : she took one of those tiny little hairs and put it on to a probe , and then she began pushing it into the metal beam . now she was very frustrated for months - it did n't stick . but she had figured out she had to orient it just like the gecko grabs on , and then it worked ! and there 's the little split ends grabbing the beam in that little window . and then she did something magical : for the first time ever , she measured the force of a single gecko hair that allowed her to discover a completely new way to stick to something , something no human has ever known before . they have hairy little toes , huge numbers of hairs , and each hair has the worst case of split ends possible , 100 to 1,000 nano-tips that an animal has on one hair , and 2 billion total , and they do n't stick by glue , or by suction , or by velcro . it was discovered that they stick by inter-molecular forces alone , by van der waals forces , and you 'll learn this in chemistry and physics , if you take it . it 's unbelievable ! it 's a whole new way of thinking about making an adhesive ! well , this is n't the end of the story , there are still mysteries . why are the gecko 's feet looking like this ? they have bizarre toes and we do n't know why . if you go into a museum and look at each gecko species , you see they have all different hairs , different lengths , and thicknesses , and patterns . why ? i do n't know ! but you should come to berkeley and help me figure this out . it 's just about right , so , apply . but it 's a mystery . there is even more stuff that is unknown . this tarantula also has hairs and can stick this way , too , but recently it was found that they also can secrete silk from their feet , not just their behind , like you know they do . and even more recently , my graduate student ann showed that all spiders can secrete glue , and we know nothing about this glue except it was around way before this guy , millions of years before . so do n't stop at the discovery , next imagine the possible uses for society . here is the first human supported by a gecko-inspired adhesive . this is my former graduate student , kellar autumn , who is professor at lewis and clark , offering his second born child for the test . and she 's a very good sport about it ! now imagine all the things you could make from this , not only adhesives , but products in sports , and biomedicine , technology , robotics , toys , automotive , fashion , clothes , and yes , even hair pieces . i swear to you , we got a call from michael jackson 's hairdresser about hair pieces before he passed away . who would have guessed from studying geckos ? ! ? next , invent a game-changing technology , device , or product . like my engineering colleague at berkeley , ron fearing , did when he made one of the first synthetic , self-cleaning dry adhesives after the simplest version that you see in animals . believe it or not , right now , because of this work , you can make your own synthetic gecko nano-tape by nano-molding with just a few parts , and here 's the recipe that we can give you . it 's been incredible since we made this discovery of all the papers and the work and the different ways to make it , it 's emerging into a billion dollar industry . and who would have imagined that it started because we were curious about how geckos can run up walls . next you need to innovate , create a business that ultimately benefits society . did you know that there are 6 million people per year that have chronic wounds , 2 million develop an infection , and infections account for 100,000 hospital deaths ? imagine if you could build a company that could produce a gecko-inspired band-aid that would remove the pain and suffering . just a simple invention . if you look at the last three great earthquakes , over 700,000 people were trapped and lost their lives . imagine the company that made a search-and-rescue robot inspired from a gecko that could move anywhere and quickly find individuals that have been trapped , that sometimes survive as long as two weeks . there is a gecko-inspired robot , stickybot , from the stanford group , that can grab on to any surface . now we ran our own , for ted , mini bio-inspired design challenge to get you to think about these kinds of products . we have a winner . here 's the winner . the winner came up with this design called stickyseat . really clever . it 's a seat that is not only comfortable , but it aids a seat belt , if you were in an accident , in terms of keeping your seat and moving . this is brilliant ! we did n't think about this , although we might think about patenting it now , but there is a winner for this , and the winner , and you ca n't , you ca n't make up something like this , the winner 's name is harry . where 's harry ? harry , come here , we have a prize for you . where 's harry ? harry ! come here ! we have a crested gecko for you that has very cool hairs on it . congratulations for harry ! excellent job ! so do n't worry , if you missed out on this , it 's ok because we are doing another design challenge working with the san diego zoo . they 're developing a best ideas project in san diego , but it 's going to go national . and i 'll leave you with a fact that you should keep being curious because curiosity-based research leads to the biggest benefits , as we showed you in our example , and you < i > can < /i > make a difference < i > now < /i > because like tanya , you do n't know what ca n't be done . thank you .

first you need to get involved . you need to do curiosity-driven research yourself . we know that learning by being an active researcher is the best way to learn .

do you think animal research is important ? how far should we go in using animals in our research labs ?

translator : andrea mcdonough reviewer : jessica ruby the ancient greeks had a great idea : the universe is simple . in their minds , all you needed to make it were four elements : earth , air , fire , and water . as theories go , it 's a beautiful one . it has simplicity and elegance . it says that by combining the four basic elements in different ways , you could produce all the wonderful diversity of the universe . earth and fire , for example , give you things that are dry . air and water , things that are wet . but as theories go , it had a problem . it did n't predict anything that could be measured , and measurement is the basis of experimental science . worse still , the theory was wrong . but the greeks were great scientists of the mind and in the 5th century b.c. , leucippus of miletus came up with one of the most enduring scientific ideas ever . everything we see is made up of tiny , indivisible bits of stuff called atoms . this theory is simple and elegant , and it has the advantage over the earth , air , fire , and water theory of being right . centuries of scientific thought and experimentation have established that the real elements , things like hydrogen , carbon , and iron , can be broken down into atoms . in leucippus 's theory , the atom is the smallest , indivisible bit of stuff that 's still recognizable as hydrogen , carbon , or iron . the only thing wrong with leucippus 's idea is that atoms are , in fact , divisible . furthermore , his atoms idea turns out to explain just a small part of what the universe is made of . what appears to be the ordinary stuff of the universe is , in fact , quite rare . leucippus 's atoms , and the things they 're made of , actually make up only about 5 % of what we know to be there . physicists know the rest of the universe , 95 % of it , as the dark universe , made of dark matter and dark energy . how do we know this ? well , we know because we look at things and we see them . that might seem rather simplistic , but it 's actually quite profound . all the stuff that 's made of atoms is visible . light bounces off it , and we can see it . when we look out into space , we see stars and galaxies . some of them , like the one we live in , are beautiful , spiral shapes , spinning gracefully through space . when scientists first measured the motion of groups of galaxies in the 1930 's and weighed the amount of matter they contained , they were in for a surprise . they found that there 's not enough visible stuff in those groups to hold them together . later measurements of individual galaxies confirmed this puzzling result . there 's simply not enough visible stuff in galaxies to provide enough gravity to hold them together . from what we can see , they ought to fly apart , but they do n't . so there must be stuff there that we ca n't see . we call that stuff dark matter . the best evidence for dark matter today comes from measurements of something called the cosmic microwave background , the afterglow of the big bang , but that 's another story . all of the evidence we have says that dark matter is there and it accounts for much of the stuff in those beautiful spiral galaxies that fill the heavens . so where does that leave us ? we 've long known that the heavens do not revolve around us and that we 're residents of a fairly ordinary planet , orbiting a fairly ordinary star , in the spiral arm of a fairly ordinary galaxy . the discovery of dark matter took us one step further away from the center of things . it told us that the stuff we 're made of is only a small fraction of what makes up the universe . but there was more to come . early this century , scientists studying the outer reaches of the universe confirmed that not only is everything moving apart from everything else , as you would expect in a universe that began in hot , dense big bang , but that the universe 's expansion also seems to be accelerating . what 's that about ? either there is some kind of energy pushing this acceleration , just like you provide energy to accelerate a car , or gravity does not behave exactly as we think . most scientists think it 's the former , that there 's some kind of energy driving the acceleration , and they called it < i > dark energy < /i > . today 's best measurements allow us to work out just how much of the universe is dark . it looks as if dark energy makes up about 68 % of the universe and dark matter about 27 % , leaving just 5 % for us and everything else we can actually see . so what 's the dark stuff made of ? we do n't know , but there 's one theory , called < i > supersymmetry < /i > , that could explain some of it . supersymmetry , or susy for short , predicts a whole range of new particles , some of which could make up the dark matter . if we found evidence for susy , we could go from understanding 5 % of our universe , the things we can actually see , to around a third . not bad for a day 's work . dark energy would probably be harder to understand , but there are some speculative theories out there that might point the way . among them are theories that go back to that first great idea of the ancient greeks , the idea that we began with several minutes ago , the idea that the universe must be simple . these theories predict that there is just a single element from which all the universe 's wonderful diversity stems , a vibrating string . the idea is that all the particles we know today are just different harmonics on the string . unfortunately , string theories today are , as yet , untestable . but , with so much of the universe waiting to be explored , the stakes are high . does all of this make you feel small ? it should n't . instead , you should marvel in the fact that , as far as we know , you are a member of the only species in the universe able even to begin to grasp its wonders , and you 're living at the right time to see our understanding explode .

but there was more to come . early this century , scientists studying the outer reaches of the universe confirmed that not only is everything moving apart from everything else , as you would expect in a universe that began in hot , dense big bang , but that the universe 's expansion also seems to be accelerating . what 's that about ?

give possible explanations for why the universe is expanding .

the human eye is an amazing mechanism , able to detect anywhere from a few photons to direct sunlight , or switch focus from the screen in front of you to the distant horizon in a third of a second . in fact , the structures required for such incredible flexibility were once considered so complex that charles darwin himself acknowledged that the idea of there having evolved seemed absurd in the highest possible degree . and yet , that is exactly what happened , starting more than 500 million years ago . the story of the human eye begins with a simple light spot , such as the one found in single-celled organisms , like euglena . this is a cluster of light-sensitive proteins linked to the organism 's flagellum , activating when it finds light and , therefore , food . a more complex version of this light spot can be found in the flat worm , planaria . being cupped , rather than flat , enables it to better sense the direction of the incoming light . among its other uses , this ability allows an organism to seek out shade and hide from predators . over the millenia , as such light cups grew deeper in some organisms , the opening at the front grew smaller . the result was a pinhole effect , which increased resolution dramatically , reducing distortion by only allowing a thin beam of light into the eye . the nautilus , an ancestor of the octopus , uses this pinhole eye for improved resolution and directional sensing . although the pinhole eye allows for simple images , the key step towards the eye as we know it is a lens . this is thought to have evolved through transparent cells covering the opening to prevent infection , allowing the inside of the eye to fill with fluid that optimizes light sensitivity and processing . crystalline proteins forming at the surface created a structure that proved useful in focusing light at a single point on the retina . it is this lens that is the key to the eye 's adaptability , changing its curvature to adapt to near and far vision . this structure of the pinhole camera with a lens served as the basis for what would eventually evolve into the human eye . further refinements would include a colored ring , called the iris , that controls the amount of light entering the eye , a tough white outer layer , known as the sclera , to maintain its structure , and tear glands that secrete a protective film . but equally important was the accompanying evolution of the brain , with its expansion of the visual cortex to process the sharper and more colorful images it was receiving . we now know that far from being an ideal masterpiece of design , our eye bares traces of its step by step evolution . for example , the human retina is inverted , with light-detecting cells facing away from the eye opening . this results in a blind spot , where the optic nerve must pierce the retina to reach the photosensitive layer in the back . the similar looking eyes of cephalopods , which evolved independently , have a front-facing retina , allowing them to see without a blind spot . other creatures ' eyes display different adaptations . anableps , the so called four-eyed fish , have eyes divided in two sections for looking above and under water , perfect for spotting both predators and prey . cats , classically nighttime hunters , have evolved with a reflective layer maximizing the amount of light the eye can detect , granting them excellent night vision , as well as their signature glow . these are just a few examples of the huge diversity of eyes in the animal kingdom . so if you could design an eye , would you do it any differently ? this question is n't as strange as it might sound . today , doctors and scientists are looking at different eye structures to help design biomechanical implants for the vision impaired . and in the not so distant future , the machines built with the precision and flexibilty of the human eye may even enable it to surpass its own evolution .

the human eye is an amazing mechanism , able to detect anywhere from a few photons to direct sunlight , or switch focus from the screen in front of you to the distant horizon in a third of a second . in fact , the structures required for such incredible flexibility were once considered so complex that charles darwin himself acknowledged that the idea of there having evolved seemed absurd in the highest possible degree . and yet , that is exactly what happened , starting more than 500 million years ago .

who is quoted to have said that the evolution of the human eye appears `` absurd in the highest possible degree '' ?

translator : andrea mcdonough reviewer : jessica ruby nowadays , we take curiosity for granted . we believe that if we put in the hard work , we might one day stand before the pyramids , discover a new species of flower , or even go to the moon . but , in the 18th and 19th century , female eyes gazed out windows at a world they were unlikely to ever explore . life for women in the time of queen victoria was largely relegated to house chores and gossip . and , although they devoured books on exotic travel , most would never would leave the places in which they were born . however , there were a few victorian women , who , through privilege , endurance , and not taking `` no '' for an answer , did set sail for wilder shores . in 1860 , marianne north , an amateur gardener and painter , crossed the ocean to america with letters of introduction , an easel , and a love of flowers . she went on to travel to jamaica , peru , japan , india , australia . in fact , she went to every continent except antarctica in pursuit of new flowers to paint . `` i was overwhelmed with the amount of subjects to be painted , '' she wrote . `` the hills were marvelously blue , piled one over the other beyond them . i never saw such abundance of pure color . '' with no planes or automobiles and rarely a paved street , north rode donkeys , scaled cliffs , and crossed swamps to reach the plants she wanted . and all this in the customary dress of her day , floor-length gowns . as photography had not yet been perfected , marianne 's paintings gave botanists back in europe their first glimpses of some of the world 's most unusual plants , like the giant pitcher plant of borneo , the african torch lily , and the many other species named for her as she was the first european to catalog them in the wild . meanwhile , back in london , miss mary kingsley was the sheltered daughter of a traveling doctor who loved hearing her father 's tales of native customs in africa . midway through writing a book on the subject , her father fell ill and died . so , kingsley decided she would finish the book for him . peers of her father advised her not to go , showing her maps of tropical diseases , but she went anyhow , landing in modern-day sierra leone in 1896 with two large suitcases and a phrase book . traveling into the jungle , she was able to confirm the existence of a then-mythical creature , the gorilla . she recalls fighting with crocodiles , being caught in a tornado , and tickling a hippopotamus with her umbrella so that he 'd leave the side of her canoe . falling into a spiky pit , she was saved from harm by her thick petticoat . `` a good snake properly cooked is one of the best meals one gets out here , '' she wrote . think indiana jones was resourceful ? kingsley could out-survive him any day ! but when it comes to breaking rules , perhaps no female traveler was as daring as alexandra david-neel . alexandra , who had studied eastern religions at home in france , wanted desperately to prove herself to parisian scholars of the day , all of whom were men . she decided the only way to be taken seriously was to visit the fabled city of lhasa in the mountains of tibet . `` people will have to say , 'this woman lived among the things she 's talking about . she touched them and she saw them alive , ' '' she wrote . when she arrived at the border from india , she was forbidden to cross . so , she disguised herself as a tibetan man . dressed in a yak fur coat and a necklace of carved skulls , she hiked through the barren himilayas all the way to lhasa , where she was subsequently arrested . she learned that the harder the journey , the better the story , and went on to write many books on tibetan religion , which not only made a splash back in paris but remain important today . these brave women , and others like them , went all over the world to prove that the desire to see for oneself not only changes the course of human knowledge , it changes the very idea of what is possible . they used the power of curiosity to try and understand the viewpoints and peculiarities of other places , perhaps because they , themselves , were seen as so unusual in their own societies . but their journeys revealed to them something more than the ways of foreign lands , they revealed something only they , themselves , could find : a sense of their own self .

and all this in the customary dress of her day , floor-length gowns . as photography had not yet been perfected , marianne 's paintings gave botanists back in europe their first glimpses of some of the world 's most unusual plants , like the giant pitcher plant of borneo , the african torch lily , and the many other species named for her as she was the first european to catalog them in the wild . meanwhile , back in london , miss mary kingsley was the sheltered daughter of a traveling doctor who loved hearing her father 's tales of native customs in africa .

aside from their beauty , why were marianne north ’ s paintings so useful to scientists back in europe ?

most of us think of the sun as our friend . it helps plants grow , keeps us warm , and who does n't love to lie on the beach on a sunny day ? but for all of it 's good qualities , the sun can also be harmful in large amounts . that 's why we invented sunscreen . the purpose of sunscreen is to shield the body from the sun 's ultraviolet rays , which have several harmful effects , including sunburn , aging , and skin cancer promotion . these rays are separated by their different wave lengths , into types such as uva and uvb , which exert a variety of effects in the skin due to the absorption patterns of chromophores , the parts of the molecules responsible for their color . the primary two chromophores are hemoglobin , found in our red blood cells , and melanin , which gives our skin its pigment . we know that uvb rays cause the skin to burn . the role of uva rays is less well understood and appears to have an effect on our tanning response , carcinogenesis , and aging . so , how does the sunscreen protect us from these rays ? there are two basic types of sunscreen , physical and chemical blockers . physical blockers , like zinc oxide or titanium dioxide , reflect the sun 's rays by acting as a physical barrier . if you 've seen lifeguards with noses covered in white , then you know what this looks like . the same ingredients are primary components of diaper creams , where the goal is also to create a physical barrier . historically , they have n't always been easy to apply and were conspicuously visible on the skin , but new formulations have made this less of an issue . chemical blockers , on the other hand , absorb the sun 's rays . they deteriorate more quickly than physical sunscreens because their ability to absorb the sun diminishes . generally , these are more transparent when rubbed on the skin , but some people develop allergric reactions to some of the chemicals . regardless of the type of sunscreen , all are subjected to testing to determine their sunburn protection factor , or spf . this is essentially a measure of the protection that the sunscreen will provide from uvb rays before one begins to burn . but even if you do n't burn , you still need to use sunscreen because unless you live in a cave , you 're not immune to the effects of the sun . it is true that darker skinned people and those who tan easily have more built-in protection from sunburns , but they are still vulnerable to the effects of uva . children under the age of six months , on the other hand , should have almost no sun exposure as their protective mechanisms are not fully functioning , and their skin is more likely to absorb any sunscreen that is applied . wearing sunscreen helps protect against the development of all three types of skin cancer : basal cell carcinoma , squamous cell carcinoma , and melanoma . on a daily basis , the dna in your cells is developing mutations and errors that are generally handled by machinery within your cells , but ultraviolet rays from the sun lead to mutations that the cell may not be able to overcome , leading to uncontrolled growth and eventual skin cancer . the scariest thing about this is that usually you ca n't even see it happening until its too late . but if these concrete risks to your health are not enough to convince you to use sunscreen , there are aesthetic reasons as well . along with cigarette smoking , sun damage is the leading cause of premature aging . photoaging from chronic sun exposure leads to a loss of elasticity in the skin , in other words , making it look saggy . take a look at this truck driver who 's left side was chronically exposed to the sun and notice the difference . this is an important point . car windows block uvb , the burn rays , but not uva , the aging rays . it is recommended to use sunscreen daily , but you should pay special attention before prolonged sun exposure or when at the beach or among snow since the reflectivity of water and ice amplifies the sun 's rays . for these cases , apply about an ounce fifteen to thirty minutes before you go out and once again soon after you get outside . after that , you should reapply it every two to three hours , especially after swimming or sweating . otherwise you should wear protective clothing with ultraviolet protection factor , or upf . stay in shaded areas , such as under trees or an umbrella , and avoid the sun at the peak hours of 10 a.m. to 4 p.m. and what 's the best kind of sunscreen ? everyone will have their preference , but look for the following things : broad spectra , spf of at least 30 , and water-resistant . a light moisturizer with spf 30 should be good for daily use . take note if you decide to use a spray . they take several coats to effectively cover your skin , like painting a wall with a spray can versus a paint brush . so , enjoy the sun , but enjoy it with sunscreen .

these rays are separated by their different wave lengths , into types such as uva and uvb , which exert a variety of effects in the skin due to the absorption patterns of chromophores , the parts of the molecules responsible for their color . the primary two chromophores are hemoglobin , found in our red blood cells , and melanin , which gives our skin its pigment . we know that uvb rays cause the skin to burn .

in addition to hemoglobin , the other primary chromophore in the skin is :

jean-paul sartre made thinking and philosophy glamorous . he was born in paris in 1905 . his father , a navy captain , died when he was a baby – and he grew up extremely close to his mother until she remarried , much to his regret , when he was twelve . sartre spent most of his life in paris , where he often went to cafes on the left bank . he had a strabismus , a wandering eye , and wore distinctive , heavy glasses . he was very short ( five feet three inches ) and frequently described himself as ugly . by the 60 ’ s sartre was a household name in both europe and the united states , and so was his chosen philosophy , existentialism . sartre is famous principally for his book being and nothingness ( 1943 ) , which enhanced his reputation not so much because people could understand his ideas but because they could n't quite . existentialism was built around a number of key insights : one : things are weirder than we think sartre is acutely attentive to moments when the world reveals itself as far stranger and more uncanny than we normally admit ; moments when the logic we ascribe to it day-to-day becomes unavailable , showing things to be highly contingent and even absurd and frightening . sartre ’ s first novel – nausea , published in 1938 – is full of evocations of such moments . at one point , the hero , roquentin , a 30-year-old writer living in a fictional french seaside town , is on a tram . he puts his hand on the seat , but then pulls it back rapidly . instead of being the most basic and obvious piece of design , scarcely worth a moment ’ s notice , the seat promptly strikes him as deeply strange ; the word ‘ seat ’ comes loose from its moorings , the object it refers to shines forth in all its primordial oddity , as if he ’ s never seen one before . roquentin has to force himself to remember that this thing beside him is something for people to sit on . for a terrifying moment , roquentin has peered into what sartre calls the ‘ absurdity of the world. ’ such a moment goes to the heart of sartre ’ s philosophy . to be sartrean is to be aware of existence as it is when it has been stripped of any of the prejudices and stabilising assumptions lent to us by our day-to-day routines . we can try out a sartrean perspective on many aspects of our own lives . think of what you know as ‘ the evening meal with your partner ’ . under such a description , it all seems fairly logical , but a sartrean would strip away the surface normality to show the radical strangeness lurking beneath . dinner really means that : when your part of the planet has spun away from the energy of a distant hydrogen and helium explosion , you slide your knees under strips of a chopped-up tree and put sections of dead animals and plants in your mouth and chew , while next to you , another mammal whose genitals you sometimes touch is doing the same . two : we are free such weird moments are certainly disorienting and rather scary , but sartre wants to draw our attention to them for one central reason : because of their liberating dimensions . life is a lot odder than we think , but it ’ s also as a consequence far richer in possibilities . things don ’ t have to be quite the way they are . in the course of fully realising our freedom , we will come up against what sartre calls the ‘ angoisse ’ or ‘ anguish ’ of existence . everything is ( terrifyingly ) possible because nothing has any pre-ordained , god-given sense or purpose . humans are just making it up as they go along , and are free to cast aside the shackles at any moment . three : we shouldn ’ t live in ‘ bad faith ’ sartre gave a term to the phenomenon of living without taking freedom properly on board . he called it bad faith . we are in bad faith whenever we tell ourselves that things have to be a certain way and shut our eyes to other options . it is bad faith to insist that we have to do a particular kind of work or live with a specific person or make our home in a given place . the most famous description of ‘ bad faith ’ comes in being and nothingness , when sartre notices a waiter who strikes him as overly devoted to his role , as if he were first and foremost a waiter rather than a free human being . his movement is quick and forward , a little too precise , a little too rapid . he comes towards the patrons with a step that is a little too quick . he bends forward a little too eagerly : his voice , his eyes express an interest a little too solicitous for the order of the customer… ’ the man ( he was probably modelled on someone in saint-germain ’ s café de flore ) has convinced himself that he is essentially , necessarily a waiter rather than a free creature who could be a jazz pianist or a fisherman on a north sea trawler . four : we 're free to dismantle capitalism . the one factor that most discourages people from experiencing themselves as free is money . most of us will shut down a range of possible options ( moving abroad , trying out a new career , leaving a partner ) by saying , ‘ that ’ s if i didn ’ t have to worry about money . ' this passivity in the face of money enraged sartre at a political level . he thought of capitalism as a giant machine designed to create a sense of necessity which doesn ’ t in fact exist in reality : it makes us tell ourselves we have to work a certain number of hours , buy a particular product or service , and so on . but in this , there is only the denial of freedom – and a refusal to take as seriously as we should the possibility of living in other ways . it was because of these views that sartre had a life long interest in marxism . marxism seemed in theory to allow people to explore their freedom , by reducing the role played in their lives by material considerations . sartre took part in many protests in the streets of paris in the 60s . arrested yet again in 1968 , president charles de gaulle had him pardoned , saying , “ you don ’ t arrest voltaire. ” sartre also visited fidel castro and che guevara and admired them both deeply . as a result of these connections and his radical politics , the fbi kept a large file on sartre trying to deduce what his suspicious philosophy might really mean . sartre is inspiring in his insistence that things do not have to be the way they are . he is hugely alive to our unfulfilled potential , as individuals and as a species . he urges us to accept the fluidity of existence and to create new institutions , habits , outlooks and ideas . the admission that life doesn ’ t have some preordained logic and is not inherently meaningful can be a source of immense relief when we feel oppressed by the weight of tradition and the status quo .

existentialism was built around a number of key insights : one : things are weirder than we think sartre is acutely attentive to moments when the world reveals itself as far stranger and more uncanny than we normally admit ; moments when the logic we ascribe to it day-to-day becomes unavailable , showing things to be highly contingent and even absurd and frightening . sartre ’ s first novel – nausea , published in 1938 – is full of evocations of such moments . at one point , the hero , roquentin , a 30-year-old writer living in a fictional french seaside town , is on a tram .

what is the name of sartre 's first novel ?

you probably know that all stuff is made up of atoms and that an atom is a really , really , really , really tiny particle . every atom has a core , which is made up of at least one positively charged particle called a proton , and in most cases , some number of neutral particles called neutrons . that core is surrounded by negatively charged particles called electrons . the identity of an atom is determined only by the number of protons in its nucleus . hydrogen is hydrogen because it has just one proton , carbon is carbon because it has six , gold is gold because it has 79 , and so on . indulge me in a momentary tangent . how do we know about atomic structure ? we ca n't see protons , neutrons , or electrons . so , we do a bunch of experiments and develop a model for what we think is there . then we do some more experiments and see if they agree with the model . if they do , great . if they do n't , it might be time for a new model . we 've had lots of very different models for atoms since democritus in 400 bc , and there will almost certainly be many more to come . okay , tangent over . the cores of atoms tend to stick together , but electrons are free to move , and this is why chemists love electrons . if we could marry them , we probably would . but electrons are weird . they appear to behave either as particles , like little baseballs , or as waves , like water waves , depending on the experiment that we perform . one of the weirdest things about electrons is that we ca n't exactly say where they are . it 's not that we do n't have the equipment , it 's that this uncertainty is part of our model of the electron . so , we ca n't pinpoint them , fine . but we can say there 's a certain probability of finding an electron in a given space around the nucleus . and that means that we can ask the following question : if we drew a shape around the nucleus such that we would be 95 % sure of finding a given electron within that shape , what would it look like ? here are a few of these shapes . chemists call them orbitals , and what each one looks like depends on , among other things , how much energy it has . the more energy an orbital has , the farther most of its density is from the nucleus . by they way , why did we pick 95 % and not 100 % ? well , that 's another quirk of our model of the electron . past a certain distance from the nucleus , the probability of finding an electron starts to decrease more or less exponentially , which means that while it will approach zero , it 'll never actually hit zero . so , in every atom , there is some small , but non-zero , probability that for a very , very short period of time , one of its electrons is at the other end of the known universe . but mostly electrons stay close to their nucleus as clouds of negative charged density that shift and move with time . how electrons from one atom interact with electrons from another determines almost everything . atoms can give up their electrons , surrendering them to other atoms , or they can share electrons . and the dynamics of this social network are what make chemistry interesting . from plain old rocks to the beautiful complexity of life , the nature of everything we see , hear , smell , taste , touch , and even feel is determined at the atomic level .

by they way , why did we pick 95 % and not 100 % ? well , that 's another quirk of our model of the electron . past a certain distance from the nucleus , the probability of finding an electron starts to decrease more or less exponentially , which means that while it will approach zero , it 'll never actually hit zero .

at about 3:02 , an atom of lithium loses an electron to an atom of fluorine . is this a chemical reaction ? why or why not ? why are there “ + ” and “ - ” signs on the elements after the electron is transferred ?

what is consciousness ? can an artificial machine really think ? does the mind just consist of neurons in the brain , or is there some intangible spark at its core ? for many , these have been vital considerations for the future of artificial intelligence . but british computer scientist alan turing decided to disregard all these questions in favor of a much simpler one : can a computer talk like a human ? this question led to an idea for measuring aritificial intelligence that would famously come to be known as the turing test . in the 1950 paper , `` computing machinery and intelligence , '' turing proposed the following game . a human judge has a text conversation with unseen players and evaluates their responses . to pass the test , a computer must be able to replace one of the players without substantially changing the results . in other words , a computer would be considered intelligent if its conversation could n't be easily distinguished from a human 's . turing predicted that by the year 2000 , machines with 100 megabytes of memory would be able to easily pass his test . but he may have jumped the gun . even though today 's computers have far more memory than that , few have succeeded , and those that have done well focused more on finding clever ways to fool judges than using overwhelming computing power . though it was never subjected to a real test , the first program with some claim to success was called eliza . with only a fairly short and simple script , it managed to mislead many people by mimicking a psychologist , encouraging them to talk more and reflecting their own questions back at them . another early script parry took the opposite approach by imitating a paranoid schizophrenic who kept steering the conversation back to his own preprogrammed obsessions . their success in fooling people highlighted one weakness of the test . humans regularly attribute intelligence to a whole range of things that are not actually intelligent . nonetheless , annual competitions like the loebner prize , have made the test more formal with judges knowing ahead of time that some of their conversation partners are machines . but while the quality has improved , many chatbot programmers have used similar strategies to eliza and parry . 1997 's winner catherine could carry on amazingly focused and intelligent conversation , but mostly if the judge wanted to talk about bill clinton . and the more recent winner eugene goostman was given the persona of a 13-year-old ukrainian boy , so judges interpreted its nonsequiturs and awkward grammar as language and culture barriers . meanwhile , other programs like cleverbot have taken a different approach by statistically analyzing huge databases of real conversations to determine the best responses . some also store memories of previous conversations in order to improve over time . but while cleverbot 's individual responses can sound incredibly human , its lack of a consistent personality and inability to deal with brand new topics are a dead giveaway . who in turing 's day could have predicted that today 's computers would be able to pilot spacecraft , perform delicate surgeries , and solve massive equations , but still struggle with the most basic small talk ? human language turns out to be an amazingly complex phenomenon that ca n't be captured by even the largest dictionary . chatbots can be baffled by simple pauses , like `` umm ... '' or questions with no correct answer . and a simple conversational sentence , like , `` i took the juice out of the fridge and gave it to him , but forgot to check the date , '' requires a wealth of underlying knowledge and intuition to parse . it turns out that simulating a human conversation takes more than just increasing memory and processing power , and as we get closer to turing 's goal , we may have to deal with all those big questions about consciousness after all .

even though today 's computers have far more memory than that , few have succeeded , and those that have done well focused more on finding clever ways to fool judges than using overwhelming computing power . though it was never subjected to a real test , the first program with some claim to success was called eliza . with only a fairly short and simple script , it managed to mislead many people by mimicking a psychologist , encouraging them to talk more and reflecting their own questions back at them .

what was the name of the first program claimed to have passed the turing test ?

translator : andrea mcdonough reviewer : jessica ruby we are constantly asked for our opinions . which team do you think will win the super bowl ? who wore it better on the red carpet ? who are you going to vote for for mayor ? public opinion polls are everywhere . important decision makers in american government have long relied on public opinion polls throughout elections and important legislation . the problem is public opinion is n't easy to track and , often times , is n't even right . in 1948 , the < i > chicago daily tribune < /i > ran a now famous headline : `` dewey defeats truman , '' they cried in big , bold , black and white letters . the problem is that dewey had n't defeated truman . the < i > tribune < /i > had relied on polls to come to their conclusion . whoops ! this happens all the time because public opinion polls are either inaccurate or misleading . so , why are they wrong ? and why do we keep using them ? first , let 's start with an important term : sample . a sample is the group of people that respond to questions during a public opinion poll . a poll 's quality rests largely on its sample , and a sample can be bad in a few key ways . it can be too small , too narrow , or the poll itself can be too difficult . polls that are too small are bad for obvious reasons . and while you ca n't possibly ask every single person in america for their opinion , the more people you ask , the more accurate your prediction . polls that are too narrow , that only ask a certain type of person a question , are bad , too . consider a poll about whether or not the potato is the best vegetable in america . if you only asked people in idaho , where the state food is the potato , chances are that you would get a much different answer than if you asked people in the state of new mexico , where the state vegetable is beans . getting the right kind of diversity in your sample means making sure that your sample has a range of ages , races , genders , and geographic regions , just to name a few . finally , polls that are too hard ca n't tell you much either . if you 're asking people for their opinions on things about which they have no prior knowledge , the results will be pointless . you 're better off shaking a magic 8 ball . it 's not just the people you 're asking that can cause bias , though . the person doing the asking is part of the problem , too . that 's called interviewer bias . interviewer bias is all about the effect that the person asking the questions has on the sample . humans generally do n't like confrontation . people worry that their answers may make them look bad . therefore , we find that people tend to give socially desirable responses , not necessarily their honest opinions , because they do n't want to come across as heartless , racist , or bigoted . and the way we word our questions matters too . when polls purposely sway the answers one way or the other , it 's called a push poll because it pushes people to answer a certain way . `` would you vote for candidate smith ? '' is a perfectly normal question . `` would you vote for candidate smith if you knew that he robs senior citizens ? '' is a push poll . so , if polls are open to all sorts of manipulation and inaccuracies , why are they still so prevalent ? despite their flaws , public opinion polls provide us with some sense of the thoughts and moods of large groups of people . they offer politicians the chance to pass legislation they think a majority of americans will support . they help fashionistas on tv know which star wore the dress better on the red carpet . finally , they make us , the people who get polled , feel as though our voice has been heard . so , next time you get a phone call asking your opinion , or if you see a poll online , take some time to think about who is asking and why they 're asking . then , take that poll , and its results , with a grain of salt or a potato .

who are you going to vote for for mayor ? public opinion polls are everywhere . important decision makers in american government have long relied on public opinion polls throughout elections and important legislation .

what effect do you think public opinion polls have of members of congress when it is time for them to vote on laws ?

when we think of classic works of art , the most common setting we imagine them in is a museum . but what we often forget is that much of this art was not produced with a museum setting in mind . what happens to an artwork when it 's taken out of its originally intended context ? take the example of michelangelo 's statue of david , depicting the boy hero who slew the giant philistine , goliath , armed with only his courage and his slingshot . when michelangelo began carving a block of pure white marble to communicate this famous biblical story , the city of florence intended to place the finished product atop their grand cathedral . not only would the 17 foot tall statue be easily visible at this height , but its placement alongside 11 other statues of old testament heroes towering over onlookers would have a powerful religious significance , forcing the viewer to stare in awe towards the heavens . but by the time michelangelo had finished the work , in 1504 , the plans for the other statues had fallen through , and the city realized that lifting such a large sculpture to the roof would be more difficult than they had thought . furthermore , the statue was so detailed and lifelike , down to the bulging veins in david 's arm and the determination on his face , that it seemed a shame to hide it so far from the viewer . a council of politicians and artists convened to decide on a new location for the statue . ultimately voting to place it in front of the palazzo della signoria , the town hall and home of the new republican government . this new location transformed the statue 's meaning . the medici family , who for generations had ruled the city through their control of banking , had recently been exiled , and florence now saw itself as a free city , threatened on all sides by wealthy and powerful rivals . david , now the symbol of heroic resistance against overwhelming odds , was placed with his intense stare , now a look of stern warning , focused directly towards rome , the home of cardinal giovanni de medici . though the statue itself had not been altered , its placement changed nearly every aspect of it from a religious to a political significance . though a replica of david still appears at the palazzo , the original statue was moved in 1873 to the galleria dell'accademia , where it remains today . in the orderly , quiet environment of the museum , alongside numerous half-finished michelangelo sculptures , overt religious and political interpretations fall away , giving way to detached contemplation of michelangelo 's artistic and technical skill . but even here , the astute viewer may notice that david 's head and hand appear disproportionately large , a reminder that they were made to be viewed from below . so , not only does context change the meaning and interpretation of an artwork throughout its history , sometimes it can make that history resurface in the most unexpected ways .

what happens to an artwork when it 's taken out of its originally intended context ? take the example of michelangelo 's statue of david , depicting the boy hero who slew the giant philistine , goliath , armed with only his courage and his slingshot . when michelangelo began carving a block of pure white marble to communicate this famous biblical story , the city of florence intended to place the finished product atop their grand cathedral .

when was michelangelo ’ s statue of david debuted ?

have you ever had someone try to explain something to you a dozen times with no luck – but , then , when you see a picture , the idea finally clicks ? if that sounds familiar , maybe you might consider yourself a visual learner . or , if reading or listening does the trick , maybe you feel like you ’ re a verbal learner . we call these labels learning styles , but is there /really/ a way to categorize different types of students ? well , it actually seems like /multiple/ presentation formats , especially if one of them is visual , help most people learn . when psychologists and educators test for learning styles , they ’ re trying to figure out whether these are inherent traits that affect how well students learn , instead of just a preference . usually , they start by giving a survey to figure out what style a student favors , like visual or verbal learning . then , they try to teach the students something with a specific presentation style , like using visual aids , and do a follow-up test to see how much they learned . that way , the researchers can see if the self-identified verbal learners really learned better when the information was just spoken aloud , for example . but , according to a 2008 review , only /one/ study that followed this design found that students actually learned best with their preferred style… and it had some pretty big flaws . the researchers excluded two-thirds of the original participants because they did n't seem to have /any/ clear learning style from the survey at the beginning . plus , they removed outliers from the data if they thought they were “ extreme , ” without defining exactly what that meant . and , they did n't even report the actual test scores in the final paper . so ... it doesn ’ t really seem like learning styles are an inherent trait that we all have . but , that does n't mean that all students will do amazingly if they just spend all their time reading from a textbook . instead , /most people/ seem to learn better if they ’ re taught in several ways – especially if one is visual . in one study , researchers tested whether students remembered lists of words better if they heard them , saw them , or both . and everyone seemed to do better if they got to see the words in print , even the self-identified auditory learners . that preference did n't seem to matter . similar studies tested whether students learned basic physics and chemistry concepts better by reading plain text or viewing pictures , too . and everyone did better with the help of pictures . so the question of whether or not you 're a visual learner could best be answered with : `` well , yeah , kinda . but so are most people . '' thanks for asking , and thanks especially to all of our patrons on patreon who keep these answers coming . if you ’ d like to submit questions to be answered , or get some videos a few days early , go to patreon.com/scishow . and don ’ t forget to go to youtube.com/scishow and subscribe !

well , it actually seems like /multiple/ presentation formats , especially if one of them is visual , help most people learn . when psychologists and educators test for learning styles , they ’ re trying to figure out whether these are inherent traits that affect how well students learn , instead of just a preference . usually , they start by giving a survey to figure out what style a student favors , like visual or verbal learning .

what is the distinction researchers test for when trying to assess learning styles ?

translator : andrea mcdonough reviewer : bedirhan cinar the development and spread of railroads across the united states brought a wave of changes to american life . during the railroad boom , thousands of jobs were created , new towns were born , trade increased , transportation was faster , and the overall landscape of the nation transformed . but , perhaps the most interesting change of all is the least known : the establishment of standard time . today , we know if it is 6:28 a.m. in los angeles , it is 9:28 a.m. in new york , 2:28 p.m. in london , 5:28 p.m. in moscow , and 10:28 p.m in tokyo . no matter where you are , the minute and second are the exact same . but , before the railroads , there was no need for a national or global clock , and each town kept its own local time . so when it was 12 noon in chicago , it was 12:07 p.m. in indianapolis , 11:50 a.m. in st. louis , and 11:27 a.m. in omaha . this worked just fine when the only modes of travel were horses or steamboats , but it became incredibly problematic when railroads came along . how can you keep a train schedule when each town has its own time ? and how do you prevent collisions or accidents on the tracks if train conductors are using different clocks ? it does n't really make sense to leave a station at 12:14 p.m. , travel for 22 minutes , and arrive at 12:31 p.m . in order to eliminate that confusion , the railroads of the united states and canada instituted standard time zones on november 18 , 1883 at noon . it allowed the railroad companies to operate more effectively and reduce deadly accidents . the american public , however , was not so quick to embrace this new change , as many cities continued to use their own local time . resistance was so strong that , in some towns , clocks would show both the local time and the railway time . imagine this conversation : `` pardon me , sir . do you have the time ? '' `` why yes , which do you need ? it 's 12:13 local time and 12:16 railway time . '' ultimately , the logic of keeping a standard time prevailed , and the united states government made time zones a matter of law with the standard time act of march 19 , 1918 . since then , there have been numerous changes to the time zones , but the concept of standard time has remained . but , the united states was actually not the first to develop standard time . the first company to implement the use of standard time was the great western railway in 1840 in britain , and by 1847 , most british railways were using greenwich mean time , or g.m.t . the british government made it official on august 2 , 1880 with the statutes , or definition of time , act . but , while britain may have been the first to establish standard time , it is asia and the islands of the south pacific that enjoyed the first hour of each new day . the international date line passes through the pacific ocean on the opposite side of the earth from the prime meridian in greenwich where , thanks to trains , standard time was first used . trains have evolved over the years and remain a prominent form of transportation and trade throughout the world . and , from the new york city subways to the freight trains traveling across the great plains , to the trolleys in san francisco , they all know exactly what time it is . and , thanks to them , we do too !

the british government made it official on august 2 , 1880 with the statutes , or definition of time , act . but , while britain may have been the first to establish standard time , it is asia and the islands of the south pacific that enjoyed the first hour of each new day . the international date line passes through the pacific ocean on the opposite side of the earth from the prime meridian in greenwich where , thanks to trains , standard time was first used .

what area of the world enjoys the first hour of the day ?

translator : jessica ruby reviewer : caroline cristal they 're long and slithery , and they 're not very colorful . but they do have a strange beauty of their own . their sinuous , nocturnal movements through the water are mesmerizing to watch . and though they may resemble underwater snakes , eels are , in fact , a very interesting type of fish . there are several things about eels that make them unique besides their elongated shape and limbless bodies . for one thing , eels have the ability to breathe through their skin . some can even leave the water and move over land for short periods . and , unlike most migratory fish , such as salmon , which spawn in fresh water but live their adult lives in salt water , eels of the genus anguilla migrate in the opposite direction , spawning and breeding in oceans and seas , while spending most of their intervening time in fresh water . if we were to take one such fresh water eel and follow its life story , it would be born in the middle of the north atlantic ocean , about a thousand miles east of bermuda . this area , called the sargasso sea , forms the western part of a subtropical gyre , a giant whirlpool in the middle of the ocean . our eel , let 's call it eli , would begin as one of ten to twenty million tiny eggs , carried by a female eel , hatching into a transparent leaf-shaped thing that looks nothing like an adult eel . eli starts to drift in ocean currents , predominantly the gulf stream towards either europe or north america , depending on its particular species . upon reaching the coast , eli is about two inches long , looking more eely but still transparent , known at this stage as a glass eel . but within a couple of days in fresh water , eli 's skin becomes pigmented a brownish-black , now looking more like that of an adult eel . you might notice that we have n't mentioned anything about eli 's gender yet . that 's because this is only determined once an eel enters fresh water , though nobody is sure exactly how that happens . most of the eels that stay in the estuaries and brackish water become males , while those that go upstream become females , growing up to two to three times bigger than their future mates . in this case , it turns out that eli was actually short for elaine . as a female eel , elaine will be quite solitary for most of her life in the stream , eating whatever falls in the water : grasshoppers , crickets , small fish , insect larvae , frogs , baby birds , almost anything she can get her mouth around . and she will grow quite big , up to four feet long and weighing as much as thirteen pounds . we do n't know exactly how fresh water eels know when it 's time to return to the ocean , but something calls to them . and their fall migration is one of the largest unseen migrations on the planet . as elaine leaves fresh water for the ocean , she undergoes a shocking metamorphosis . her eyes enlarge by about ten times , her skin gets thicker , and her fins get larger . these are most likely adaptations for their upcoming ocean travel , and elaine seamlessly makes the transition from fresh to salt water , which would be toxic for most other fish . once elaine leaves the mouth of the fresh water streams , she will disappear completely from human view . no one has witnessed , or been able to follow , an adult eel on their migration , nor do we know how deep they spawn . but it 's assumed that they can follow some signs that they can detect , such as a thermal barrier between ocean currents or a salinity front , in order to return to the same area of the ocean where they were born . because we do n't even know exactly what happens during an eel 's migration , we can only imagine what the actual breeding looks like . but the common hypothesis is that elaine and thousands , or hundreds of thousands , of other eels gather in large , intertwined masses and release their eggs and sperm in a giant orgy known as panmixia . a couple of days after the eggs are laid , they hatch , and the cycle begins again . and because we 've never seen the adult eels returning up the fresh water rivers , we must assume that , having completed their long and roundabout journey , these amazing and mysterious creatures finally die there , in the same place where they were born . goodbye , elaine ! it was a pleasure knowing you .

this area , called the sargasso sea , forms the western part of a subtropical gyre , a giant whirlpool in the middle of the ocean . our eel , let 's call it eli , would begin as one of ten to twenty million tiny eggs , carried by a female eel , hatching into a transparent leaf-shaped thing that looks nothing like an adult eel . eli starts to drift in ocean currents , predominantly the gulf stream towards either europe or north america , depending on its particular species .

how do you think global climate change could possibly affect eel migration in the sea and freshwater ?

translator : andrea mcdonough reviewer : bedirhan cinar by now , i 'm sure you know that in just about anything you do in life , you need numbers . in particular , though , some fields do n't just need a few numbers , they need lots of them . how do you keep track of all those numbers ? well , mathematicians dating back as early as ancient china came up with a way to represent arrays of many numbers at once . nowadays we call such an array a `` matrix , '' and many of them hanging out together , `` matrices '' . matrices are everywhere . they are all around us , even now in this very room . sorry , let 's get back on track . matrices really are everywhere , though . they are used in business , economics , cryptography , physics , electronics , and computer graphics . one reason matrices are so cool is that we can pack so much information into them and then turn a huge series of different problems into one single problem . so , to use matrices , we need to learn how they work . it turns out , you can treat matrices just like regular numbers . you can add them , subtract them , even multiply them . you ca n't divide them , but that 's a rabbit hole of its own . adding matrices is pretty simple . all you have to do is add the corresponding entries in the order they come . so the first entries get added together , the second entries , the third , all the way down . of course , your matrices have to be the same size , but that 's pretty intuitive anyway . you can also multiply the whole matrix by a number , called a scalar . just multiply every entry by that number . but wait , there 's more ! you can actually multiply one matrix by another matrix . it 's not like adding them , though , where you do it entry by entry . it 's more unique and pretty cool once you get the hang of it . here 's how it works . let 's say you have two matrices . let 's make them both two by two , meaning two rows by two columns . write the first matrix to the left and the second matrix goes next to it and translated up a bit , kind of like we are making a table . the product we get when we multiply the matrices together will go right between them . we 'll also draw some gridlines to help us along . now , look at the first row of the first matrix and the first column of the second matrix . see how there 's two numbers in each ? multiply the first number in the row by the first number in the column : 1 times 2 is 2 . now do the next ones : 3 times 3 is 9 . now add them up : 2 plus 9 is 11 . let 's put that number in the top-left position so that it matches up with the rows and columns we used to get it . see how that works ? you can do the same thing to get the other entries . -4 plus 0 is -4 . 4 plus -3 is 1 . -8 plus 0 is -8 . so , here 's your answer . not all that bad , is it ? there 's one catch , though . just like with addition , your matrices have to be the right size . look at these two matrices . 2 times 8 is 16 . 3 times 4 is 12 . 3 times wait a minute , there are no more rows in the second matrix . we ran out of room . so , these matrices ca n't be multiplied . the number of columns in the first matrix has to be the same as the number of rows in the second matrix . as long as you 're careful to match up your dimensions right , though , it 's pretty easy . understanding matrix multiplication is just the beginning , by the way . there 's so much you can do with them . for example , let 's say you want to encrypt a secret message . let 's say it 's `` math rules '' . though , why anybody would want to keep this a secret is beyond me . letting numbers stand for letters , you can put the numbers in a matrix and then an encryption key in another . multiply them together and you 've got a new encoded matrix . the only way to decode the new matrix and read the message is to have the key , that second matrix . there 's even a branch of mathematics that uses matrices constantly , called linear algebra . if you ever get a chance to study linear algebra , do it , it 's pretty awesome . but just remember , once you know how to use matrices , you can do pretty much anything .

matrices really are everywhere , though . they are used in business , economics , cryptography , physics , electronics , and computer graphics . one reason matrices are so cool is that we can pack so much information into them and then turn a huge series of different problems into one single problem .

matrices are used in all of the following fields : business , economics , cryptography , physics , electronics , and computer graphics .

thinking of getting a tattoo ? decorating your birthday suit would add another personal story to a history of tattoos stretching back at least 8000 years . tattooed mummies from around the world attest to the universality of body modification across the millennia , and to the fact that you really were stuck with it forever if your civilization never got around to inventing laser removal . a mummy from the chinchorro culture in pre-incan peru has a mustache tattooed on his upper lip . ötzi , mummified iceman of the alps , has patterned charcoal tats along his spine , behind his knee and around his ankles , which might be from an early sort of acupuncture . the mummy of amunet , a priestess in middle kingdom egypt , features tattoos thought to symbolize sexuality and fertility . even older than the mummies , figurines of seemingly tattooed people , and tools possibly used for tattooing date back tens of thousands of years . tattoos do n't have one historical origin point that we know of , but why do we english speakers call them all tattoos ? the word is an anglophonic modification of `` tatao , '' a polynesian word used in tahiti , where english captain james cook landed in 1769 and encountered heavily tattooed men and women . stories of cook 's findings and the tattoos his crew acquired cemented our usage of `` tattoo '' over previous words like `` scarring , '' `` painting , '' and `` staining , '' and sparked a craze in victorian english high society . we might think of victorians having victorian attitudes about such a risque thing , and you can find such sentiments , and even bans , on tattooing throughout history . but while publicly some brits looked down their noses at tattoos , behind closed doors and away from their noses , lots of people had them . reputedly , queen victoria had a tiger fighting a python , and tattoos became very popular among cook 's fellow soldiers , who used them to note their travels . you crossed the atlantic ? get an anchor . been south of the equator ? time for your turtle tat . but westerners sported tattoos long before meeting the samoans and maori of the south pacific . crusaders got the jerusalem cross so if they died in battle , they 'd get a christian burial . roman soldiers on hadrian 's wall had military tattoos and called the picts beyond it `` picts , '' for the pictures painted on them . there 's also a long tradition of people being tattooed unwillingly . greeks and romans tattooed slaves and mercenaries to discourage escape and desertion . criminals in japan were tattooed as such as far back as the 7th century . most infamously , the nazis tattooed numbers on the chest or arms of jews and other prisoners at the auschwitz concentration camp in order to identify stripped corpses . but tattoos forced on prisoners and outcasts can be redefined as people take ownership of that status or history . primo levi survived auschwitz and wore short sleeves to germany after the war to remind people of the crime his number represented . today , some holocaust survivors ' descendants have their relatives numbers ' tattooed on their arms . the torah has rules against tattoos , but what if you want to make indelible what you feel should never be forgotten ? and those criminals and outcasts of japan , where tattooing was eventually outlawed from the mid-19th century to just after world war ii , added decoration to their penal tattoos , with designs borrowed from woodblock prints , popular literature and mythical spirtual iconography . yakuza gangs viewed their outsider tattoos as signs of lifelong loyalty and courage . after all , they lasted forever and it really hurt to get them . for the maori , those tattoos were an accepted mainstream tradition . if you shied away from the excruciating chiseling in of your moko design , your unfinished tattoo marked your cowardice . today , unless you go the traditional route , your tattoo artist will probably use a tattoo machine based on the one patented by samuel o'reilly in 1891 , itself based on thomas edison 's stencil machine from 1876 . but with the incredibly broad history of tattoos giving you so many options , what are you going to get ? this is a bold-lined expression of who you are , or you want to appear to be . as the naturalist aboard cook 's ship said of the tataoed tahitians , `` everyone is marked , thus in different parts of his body , according maybe to his humor or different circumstances of his life . '' maybe your particular humor and circumstances suggest getting a symbol of cultural heritage , a sign of spirituality , sexual energy , or good old-fashioned avant-garde defiance . a reminder of a great accomplishment , or of how you think it would look cool if hulk hogan rode a rhino . it 's your expression , your body , so it 's your call . just two rules : you have to find a tattooist who wo n't be ashamed to draw your idea , and when in doubt , you can never go wrong with `` mom . ''

thinking of getting a tattoo ? decorating your birthday suit would add another personal story to a history of tattoos stretching back at least 8000 years .

what differentiates a tattoo from other means of self-expression ?

every chicken was once an egg , every oak tree an acorn , every frog a tadpole . the patch of mold on that old piece of bread in the back of your fridge , not so long ago that was one , solitary cell . even you were once but a gleam in your parents ' eyes . all these organisms share the same basic goal : to perpetuate their own existence . all lifeforms that we 've discovered so far stay alive by using basically the same rules , materials , and machinery . imagine a factory full of robots . these robots have two missions : one , keep the factory running , and two , when the time is right , set up an entirely new factory . to do those things , they need assembly instructions , raw materials , plenty of energy , a few rules about when to work normally , when to work quickly , or when to stop , and some exchange currencies because even robots need to get paid . each factory has a high security office with blueprints for all the possible factory configurations and complete sets of instructions to make all the different types of robots a factory could ever need . special robots photocopy these instructions and send them off to help make the building blocks of more robots . their colleagues assemble those parts into still more robots , which are transported to the right location in the factory and given the tools they need to start working . every robot draws energy from the central power plant , a giant furnace that can burn regular fuel but also scrap materials if not enough regular fuel is available . certain zones in the factory have harsher working conditions , so these areas are walled off . but the robots inside can at least communicate with the rest of the factory through specialized portals embedded directly into the walls . and as you 've probably figured out , what we 're describing here is a cell . the high security office is the nucleus . it stores the blueprints and instructions as deoxyribonucleic acid , or dna . the photocopied instructions are rna . the robots themselves are mostly proteins built from amino acids , but they 'll often use special tools that are , or are derived from , vitamins and minerals . the walls between factory zones and around the factory itself are mostly made up of lipids , a.k.a . fats . in most organisms , the primary fuel source are sugars , but in a pinch , fats and proteins can be broken down and burned in the furnace as well . the portals are membrane proteins which allow very specific materials and information to pass through the walls at the right times . many interactions between robot proteins require some kind of push , think robot minimum wage . a few small but crucial forms of money are transferred between proteins to provide this push . electrons , protons , oxygen , and phosphate groups are the main chemical currencies , and they 're kept in small molecular wallets or larger tote bags to keep them safe . this is biochemistry , the study of how every part of the factory interacts to keep your life running smoothly in the face of extreme challenges . maybe there 's too much fuel ; your body will store the excess as glycogen or fat . maybe there 's not enough ; your body will use up those energy reserves . maybe a virus or bacteria tries to invade ; your body will mobilize the immune system . maybe you touched something hot or sharp ; your nerves will let you know so you can stop . maybe it 's time to create a new cell or a new person . amazingly , oak trees , chickens , frogs , and , yes , even you share so many of the same basic robot and factory designs that biochemists can learn a lot about all of them all at the same time .

the portals are membrane proteins which allow very specific materials and information to pass through the walls at the right times . many interactions between robot proteins require some kind of push , think robot minimum wage . a few small but crucial forms of money are transferred between proteins to provide this push .

you might already know that cells evolve from one generation to another . random mutations in the dna of a cell can cause certain proteins to function differently than before . mutations ensure genetic diversity across a particular species and can help that species survive when it ’ s faced with environmental pressures . how would you extend the robot/factory analogy to accommodate this new information ?

so my name is kakani katija , and i 'm a bioengineer . i study marine organisms in their natural environment . and what i want to point out , and at least you can see this in this visualization , is that the ocean environment is a dynamic place . what you 're seeing are the kinds of currents , as well as the whirls , that are left behind in the ocean because of tides or because of winds . and imagine a marine organism as living in this environment , and they 're trying to undergo their entire lives while dealing with currents like these . but what i also want to point out is that small organisms also create small fluid motions , as well . and it 's these fluid motions that i study . and we can think about them like being footprints . so this is my dog kieran , and take a look at her footprints . footprints provide a lot of information . not only do they tell us what kind of organism left them , they might also tell us something about when that organism was there , but also what kind of behavior , were they running or were they walking ? and so terrestrial organisms , like my cute dog kieran , might be leaving footprints behind in dirt or in sand , but marine organisms leave footprints in the form of what we call wake structures , or hydrodynamic signatures , in fluid . now imagine , it 's really hard to see these kinds of structures because fluid is transparent . however , if we add something to the fluid , we get a completely different picture . and you can see that these footprints that marine organisms create are just dynamic . they are constantly changing . and marine organisms also have the ability to sense these signatures . they can also inform decisions , like whether or not they want to continue following a signature like this to find a mate or to find food , or maybe avoid these signatures to avoid being eaten . so imagine the ability to be able to not only see or visualize these kinds of signatures , but to also measure them . this is the engineering side of what i do . and so what i 've done is i actually took a laboratory technique and miniaturized it and basically shrunk it down into the use of underwater housings to make a device that a single scuba diver can use . and so a single scuba diver can go anywhere from the surface to 40 meters , or 120 feet deep , to measure the hydrodynamic signatures that organisms create . before i begin , i want to immerse you into what these kinds of measurements require . so in order to work , we actually dive at night , and this is because we 're trying to minimize any interactions between the laser and sunlight and we 're diving in complete darkness because we do not want to scare away the organisms we 're trying to study . and then once we find the organisms we 're interested in , we turn on a green laser . and this green laser is actually illuminating a sheet of fluid , and in that fluid , it 's reflecting off of particles that are found everywhere in the ocean . and so as an animal swims through this laser sheet , you can see these particles are moving over time , and so we actually risk our lives to get this kind of data . what you 're going to see is that on the left these two particles images that shows the displacement of fluid over time , and using that data , you can actually extract what the velocity of that fluid is , and that 's indicated by the vector plots that you see in the middle . and then we can use that data to answer a variety of different questions , not only to understand the rotational sense of that fluid , which you see on the right , but also estimate something about energetics , or the kinds of forces that act on these organisms or on the fluid , and also evaluate swimming and feeding performance . we 've used this technique on a variety of different organisms , but remember , there 's an issue here . we 're only able to study organisms that a scuba diver can reach . and so before i finish , i want to tell you what the next frontier is in terms of these kinds of measurements . and with collaborators at monterey bay aquarium research institute , we 're developing instrumentation to go on remotely opperated vehicles so we can study organisms anywhere from the surface down to 4000 meters , or two and a half miles . and so we can answer really interesting questions about this organism , this is a larvacean , that creates a feeding current and forces fluids through their mucus house and extracts nutrients . and then this animal , this is a siphonophore , and they can get to lengths about half the size of a football field . and they 're able to swim vertically in the ocean by just creating jet propulsion . and then finally we can answer these questions about how swarming organisms , like krill , are able to affect mixing on larger scales . and this is actually one of the most interesting results so far that we 've collected using the scuba diving device in that organisms , especially when they 're moving in mass , are able to generate mixing at levels that are equivalent to some other physical processes that are associated with winds and tides . but before i finish , i want to leave you all with a question because i think it 's important to keep in mind that technologies today that we take for granted started somewhere . it was inspired from something . so imagine scientists and engineers were inspired by birds to create airplanes . and something we take for granted , flying from san francisco to new york , is something that was inspired by an organism . and as we 're developing these new technologies to understand marine organisms , what we want to do is answer this question : how will marine organisms inspire us ? will they allow us to develop new underwater technologies , like underwater vehicles that look like a jellyfish ? i think it 's a really exciting time in ocean exploration because now we have the tools available to answer this kind of question , and with the help of you guys at some point , you can apply these tools to answer this kind of question and also develop technologies of the future . thank you .

but what i also want to point out is that small organisms also create small fluid motions , as well . and it 's these fluid motions that i study . and we can think about them like being footprints .

what components are required for particle image velocimetry ( piv ; the fluid measurement technique discussed here ) ?

deep inside yale university 's beinecke rare book and manuscript library lies the only copy of a 240-page tome . recently carbon dated to around 1420 , its vellum pages features looping handwriting and hand-drawn images seemingly stolen from a dream . real and imaginary plants , floating castles , bathing women , astrology diagrams , zodiac rings , and suns and moons with faces accompany the text . this 24x16 centimeter book is called the voynich manuscript , and its one of history 's biggest unsolved mysteries . the reason why ? no one can figure out what it says . the name comes from wilfrid voynich , a polish bookseller who came across the document at a jesuit college in italy in 1912 . he was puzzled . who wrote it ? where was it made ? what do these bizarre words and vibrant drawings represent ? what secrets do its pages contain ? he purchased the manuscript from the cash-strapped priest at the college , and eventually brought it to the u.s. , where experts have continued to puzzle over it for more than a century . cryptologists say the writing has all the characteristics of a real language , just one that no one 's ever seen before . what makes it seem real is that in actual languages , letters and groups of letters appear with consistent frequencies , and the language in the voynich manuscript has patterns you would n't find from a random letter generator . other than that , we know little more than what we can see . the letters are varied in style and height . some are borrowed from other scripts , but many are unique . the taller letters have been named gallows characters . the manuscript is highly decorated throughout with scroll-like embellishments . it appears to be written by two or more hands , with the painting done by yet another party . over the years , three main theories about the manuscript 's text have emerged . the first is that it 's written in cypher , a secret code deliberately designed to hide secret meaning . the second is that the document is a hoax written in gibberish to make money off a gullible buyer . some speculate the author was a medieval con man . others , that it was voynich himself . the third theory is that the manuscript is written in an actual language , but in an unknown script . perhaps medieval scholars were attempting to create an alphabet for a language that was spoken but not yet written . in that case , the voynich manuscript might be like the rongorongo script invented on easter island , now unreadable after the culture that made it collapsed . though no one can read the voynich manuscript , that has n't stopped people from guessing what it might say . those who believe the manuscript was an attempt to create a new form of written language speculate that it might be an encyclopedia containing the knowledge of the culture that produced it . others believe it was written by the 13th century philosopher roger bacon , who attempted to understand the universal laws of grammar , or in the 16th century by the elizabethan mystic john dee , who practiced alchemy and divination . more fringe theories that the book was written by a coven of italian witches , or even by martians . after 100 years of frustration , scientists have recently shed a little light on the mystery . the first breakthrough was the carbon dating . also , contemporary historians have traced the provenance of the manuscript back through rome and prague to as early as 1612 , when it was perhaps passed from holy roman emperor rudolf ii to his physician , jacobus sinapius . in addition to these historical breakthroughs , linguistic researchers recently proposed the provisional identification of a few of the manuscript 's words . could the letters beside these seven stars spell tauran , a name for taurus , a constellation that includes the seven stars called the pleiades ? could this word be centaurun for the centaurea plant in the picture ? perhaps , but progress is slow . if we can crack its code , what might we find ? the dream journal of a 15th-century illustrator ? a bunch of nonsense ? or the lost knowledge of a forgotten culture ? what do you think it is ?

perhaps medieval scholars were attempting to create an alphabet for a language that was spoken but not yet written . in that case , the voynich manuscript might be like the rongorongo script invented on easter island , now unreadable after the culture that made it collapsed . though no one can read the voynich manuscript , that has n't stopped people from guessing what it might say .

the script used in the voynich manuscript contains :

have you ever heard the sound of frogs calling at night ? for hundreds of millions of years , this croaking lullaby has filled the nighttime air . but recent studies suggest that these frogs are in danger of playing their final note . over the past few decades , amphibian populations have been rapidly disappearing worldwide . nearly one-third of the world 's amphibian species are endanger of extinction , and over 100 species have already disappeared . but do n't worry , there 's still hope . before we get into how to save the frogs , let 's start by taking a look at why they 're disappearing and why it 's important to keep them around . habitat destruction is the number one problem for frog populations around the world . there are seven billion humans on the planet , and we compete with frogs for habitat . we build cities , suburbs , and farms on top of frog habitat and chop forests and drain the wetlands that serve as home for numerous amphibian populations . climate change alters precipitation levels , drying up ponds , streams , and cloud forests . as the earth 's human population continues to grow , so will the threats amphibians face . there are a variety of other factors contributing to the frogs ' decline . over-harvesting for the pet and food trade results in millions of frogs being taken out of the wild each year . invasive species , such as non-native trout and crawfish , eat native frogs . humans are facilitating the spread of infectious diseases by shipping over 100 million amphibians around the world each year for use as food , pets , bait , and in laboratories and zoos , with few regulations or quarantines . one of these diseases , chytridiomycosis , has driven stream-dwelling amphibian populations to extinction in africa , australia , europe , and north , central , and south america . on top of all these problems , we add hundreds of millions of kilograms of pesticides to our ecosystems each year . and these chemicals are easily absorbed through amphibians ' permeable skin , causing immunosuppression , or a weakened immune system , and developmental deformities . okay , so why are these little green guys worth keeping around ? frogs are important for a multitude of reasons . they 're an integral part of the food web , eating flies , ticks , mosquitoes , and other disease vectors , thus , protecting us against malaria , dengue fever , and other illnesses . tadpoles keep waterways clean by feeding on algae , reducing the demand on our community 's filtration systems and keeping our cost of water low . frogs serve as a source of food for birds , fish , snakes , dragonflies , and even monkeys . when frogs disappear , the food web is disturbed , and other animals can disappear as well . amphibians are also extremely important in human medicine . over ten percent of the nobel prizes in physiology and medicine have gone to researchers whose work depended on amphibians . some of the antimicrobial peptides on frog skin can kill hiv , some act as pain killers , and others serve as natural mosquito repellents . many discoveries await us if we can save the frogs , but when a frog species disappears , so does any promise it holds for improving human health . fortunately , there are lots of ways you can help , and the best place to start is by improving your ecological footprint and day-to-day actions . the next time you listen to that nighttime lullaby , do n't think of it as just another background noise , hear it as a call for help , sung in perfect croaking harmony .

many discoveries await us if we can save the frogs , but when a frog species disappears , so does any promise it holds for improving human health . fortunately , there are lots of ways you can help , and the best place to start is by improving your ecological footprint and day-to-day actions . the next time you listen to that nighttime lullaby , do n't think of it as just another background noise , hear it as a call for help , sung in perfect croaking harmony .

a person ’ s ecological footprint is the total impact that person has on the planet . what are some ways that your daily habits may affect the environment ? what are some simple changes you can make to be more environmentally friendly ?

among the great poets of literary history , certain names like homer , shakespeare , milton , and whitman are instantly recognizable . however , there 's an early 20th century great french poet whose name you may not know : guillaume apollinaire . he was a close friend and collaborator of artists like picasso , rousseau , and chagall . he coined the term surrealism , and he was even suspected of stealing the mona lisa in 1911 . during his short lifetime , he created poetry that combined text and image in a way that seemingly predicted an artistic revolution to come . in the late 19th and early 20th century paris , the low-rent districts of montmartre and montparnasse were home to every kind of starving artist . it was all they could afford . these painters , writers , and intellectuals , united in their artistic passion and counterculture beliefs , made up france 's bohemian subculture . and their works of art , literature , and intellect would shake up the world . at the turn of the 20th century , within this dynamic scene , art critic , poet , and champion of the avant-garde , guillaume apollinaire was a well-known fixture . as an art critic , apollinaire explained the cubist and surrealist movements to the world , and rose to the defense of many young artists in the face of what was often a xenophobic and narrow-minded public . as a poet , apollinaire was passionate about all forms of art and a connoisseur of medieval literature , especially calligraphy and illuminated initials . as a visionary , apollinaire saw a gap between two artistic institutions . on one side was the popular , highly lauded traditional art forms of the time . on the other , the forms of artistic expression made possible through surrealism , cubism , and new inventions , like the cinema and the phonograph . within that divide , through the creation of his most important contribution to poetry , the calligram , guillaume apollinaire built a bridge . apollinaire created the calligram as a poem picture , a written portrait , a thoughts drawing , and he used it to express his modernism and his desire to push poetry beyond the normal bounds of text and verse and into the 20th century . some of his calligrams are funny , like the `` lettre-océan . '' some of them are dedicated to his young dead friends , like `` la colombe poignardée et le jet d'eau . '' some of them are the expression of an emotional moment , as is `` il pleut '' : `` it 's raining women 's voices as if they had died even in memory , and it 's raining you as well , marvellous encounters of my life , o little drops . those rearing clouds begin to neigh a whole universe of auricular cities . listen if it rains while regret and disdain weep to an ancient music . listen to the bonds fall off which hold you above and below . '' each calligram is intended to allow readers to unchain themselves from the regular experience of poetry , and feel and see something new . `` lettre-océan '' is first an image to be seen before even the words are read . text-only elements combine with words in shapes and forms . two circular forms , one locked in a square , the other , morph beyond the page in the shape of a spiral . together they create a picture that hints towards cubism . then on closer reading of the text , the descriptive words within suggest the image of an aerial view of the eiffel tower . they give tribute to electromagnetic waves of the telegraph , a new form of communication at the time . undoubtedly , the deeply layered artistic expressions in apollinaire 's calligrams are not just a brilliant display of poetic prowess from a master of the form . each calligram itself is also a snapshot in time , encapsulating the passion , the excitement , and the anticipation of all the bohemian artists of paris , including apollinaire , most of whom are well ahead of their time , and with their innovative work , eagerly grasping for the future .

among the great poets of literary history , certain names like homer , shakespeare , milton , and whitman are instantly recognizable . however , there 's an early 20th century great french poet whose name you may not know : guillaume apollinaire . he was a close friend and collaborator of artists like picasso , rousseau , and chagall .

guillaume apollinaire was close to a young painter by the name of :

each time you take a step , 200 muscles work in unison to lift your foot , propel it forward , and set it down . it 's just one of the many thousands of tasks performed by the muscular system . this network of over 650 muscles covers the body and is the reason we can blink , smile , run , jump , and stand upright . it 's even responsible for the heart 's dependable thump . first , what exactly is the muscular system ? it 's made up of three main muscle types : skeletal muscle , which attaches via tendons to our bones , cardiac muscle , which is only found in the heart , and smooth muscle , which lines the blood vessels and certain organs , like the intestine and uterus . all three types are made up of muscle cells , also known as fibers , bundled tightly together . these bundles receive signals from the nervous system that contract the fibers , which in turn generates force and motion . this produces almost all the movements we make . some of the only parts of the body whose motions are n't governed by the muscular system are sperm cells , the hair-like cilia in our airways , and certain white blood cells . muscle contraction can be split into three main types . the first two , shortening muscle fibers and lengthening them , generate opposing forces . so the biceps will shorten while the triceps will lengthen or relax , pulling up the arm and making it bend at the elbow . this allows us to , say , pick up a book , or if the muscle relationship is reversed , put it down . this complementary partnership exists throughout the muscular system . the third type of contraction creates a stabilizing force . in these cases , the muscle fibers do n't change in length , but instead keep the muscles rigid . this allows us to grip a mug of coffee or lean against a wall . it also maintains our posture by holding us upright . skeletal muscles form the bulk of the muscular system , make up about 30-40 % of the body 's weight , and generate most of its motion . some muscles are familiar to us , like the pectorals and the biceps . others may be less so , like the buccinator , a muscle that attaches your cheek to your teeth , or the body 's tiniest skeletal muscle , a one-millimeter-long tissue fragment called the stapedius that 's nestled deep inside the ear . wherever they occur , skeletal muscles are connected to the somatic nervous system , which gives us almost complete control over their movements . this muscle group also contains two types of muscle fibers to refine our motions even further , slow-twitch and fast-twitch . fast-twitch fibers react instantly when triggered but quickly use up their energy and tire out . slow-twitch fibers , on the other hand , are endurance cells . they react and use energy slowly so they can work for longer periods . a sprinter will accumulate more fast-twitch muscles in her legs through continuous practice , enabling her to quickly , if briefly , pick up the pace , whereas back muscles contain more slow-twitch muscles to maintain your posture all day . unlike the skeletal muscles , the body 's cardiac and smooth muscles are managed by the autonomic nervous system beyond our direct control . that makes your heart thump roughly 3 billion times over the course of your life , which supplies the body with blood and oxygen . autonomic control also contracts and relaxes smooth muscle in a rhythmic cycle . that pumps blood through the smooth internal walls of blood vessels , enables the intestine to constrict and push food through the digestive system , and allows the uterus to contract when a person is giving birth . as muscles work , they also use energy and produce an important byproduct , heat . in fact , muscle provides about 85 % of your warmth , which the heart and blood vessels then spread evenly across the body via the blood . without that , we could n't maintain the temperature necessary for our survival . the muscular system may be largely invisible to us , but it leaves its mark on almost everything we do , whether it 's the blink of an eye or a race to the finish line .

wherever they occur , skeletal muscles are connected to the somatic nervous system , which gives us almost complete control over their movements . this muscle group also contains two types of muscle fibers to refine our motions even further , slow-twitch and fast-twitch . fast-twitch fibers react instantly when triggered but quickly use up their energy and tire out .

fast twitch muscle cells :

`` all men are created equal and they are endowed with the rights to life , liberty and the pursuit of happiness . '' not so fast , mr. jefferson ! these words from the declaration of independence , and the facts behind them , are well known . in june of 1776 , a little more than a year after the war against england began with the shots fired at lexington and concord , the continental congress was meeting in philadelphia to discuss american independence . after long debates , a resolution of independence was approved on july 2 , 1776 . america was free ! and men like john adams thought we would celebrate that date forever . but it was two days later that the gentlemen in congress voted to adopt the declaration of independence , largely written by thomas jefferson , offering all the reasons why the country should be free . more than 235 years later , we celebrate that day as america 's birthday . but there are some pieces of the story you may not know . first of all , thomas jefferson gets the credit for writing the declaration , but five men had been given the job to come up with a document explaining why america should be independent : robert livingston , roger sherman , benjamin franklin and john adams were all named first . and it was adams who suggested that the young , and little known , thomas jefferson join them because they needed a man from the influential virginia delegation , and adams thought jefferson was a much better writer than he was . second , though jefferson never used footnotes , or credited his sources , some of his memorable words and phrases were borrowed from other writers and slightly tweaked . then , franklin and adams offered a few suggestions . but the most important change came after the declaration was turned over to the full congress . for two days , a very unhappy thomas jefferson sat and fumed while his words were picked over . in the end , the congress made a few , minor word changes , and one big deletion . in the long list of charges that jefferson made against the king of england , the author of the declaration had included the idea that george the third was responsible for the slave trade , and was preventing america from ending slavery . that was not only untrue , but congress wanted no mention of slavery in the nation 's founding document . the reference was cut out before the declaration was approved and sent to the printer . but it leaves open the hard question : how could the men , who were about to sign a document , celebrating liberty and equality , accept a system in which some people owned others ? it is a question that would eventually bring the nation to civil war and one we can still ask today .

`` all men are created equal and they are endowed with the rights to life , liberty and the pursuit of happiness . '' not so fast , mr. jefferson ! these words from the declaration of independence , and the facts behind them , are well known .

as the lesson points out , jefferson used the work of other writers . who were some of the important men who influenced jefferson ’ s ideas ?

studies have shown that taking vitamins is good for your health and bad for your health . that newly discovered herb can improve your memory or destroy your liver . headlines proclaim a promising new cancer treatment and never mention it again . on a daily basis , we are bombarded with attention-grabbing news , backed up by scientific studies , but what are these studies ? how are they performed ? and how do we know whether they 're reliable ? when it comes to dietary or medical information , the first thing to remember is that while studies on animals or individual cells can point the way towards further research , the only way to know how something will affect humans is through a study involving human subjects . and when it comes to human studies , the scientific gold standard is the randomized clinical trial , or rct . the key to rcts is that the subjects are randomly assigned to their study groups . they are often blinded to make them more rigorous . this process attempts to ensure that the only difference between the groups is the one the researchers are attempting to study . for example , when testing a new headache medication , a large pool of people with headaches would be randomly divided into two groups , one receiving the medication and another receiving a placebo . with proper randomization , the only significant overall difference between the two groups will be whether or not they received the medication , rather than other differences that could affect results . randomized clinical trials are incredible tools , and , in fact , the us food and drug administration often requires at least two to be conducted before a new drug can be marketed . but the problem is that an rct is not possible in many cases , either because it 's not practical or would require too many volunteers . in such cases , scientists use an epidemiological study , which simply observes people going about their usual behavior , rather than randomly assigning active participants to control invariable groups . let 's say we wanted to study whether an herbal ingredient on the market causes nausea . rather than deliberately giving people something that might make them nauseated , we would find those who already take the ingredient in their everyday lives . this group is called the cohort . we would also need a comparison group of people who do not have exposure to the ingredient . and we would then compare statistics . if the rate of nausea is higher in the herbal cohort , it suggests an association between the herbal supplement and nausea . epidemiological studies are great tools to study the health effects of almost anything , without directly interfering in people 's lives or assigning them to potentially dangerous exposures . so , why ca n't we rely on these studies to establish causal relationships between substances and their effects on health ? the problem is that even the best conducted epidemiological studies have inherent flaws . precisely because the test subjects are not randomly assigned to their groups . for example , if the cohort in our herbal study consisted of people who took the supplement for health reasons , they may have already had higher rates of nausea than the other people in the sample . or the cohort group could 've been composed of people who shop at health food stores and have different diets or better access to healthcare . these factors that can affect results , in addition to the factor being studied , are known as confounding variables . these two major pitfalls , combined with more general dangers , such as conflicts of interest or selective use of data , can make the findings of any particular epidemiological study suspect , and a good study must go out of its way to prove that its authors have taken steps to eliminate these types of errors . but even when this has been done , the very nature of epidemiological studies , which examine differences between preexisting groups , rather than deliberately inducing changes within the same individuals , means that a single study can only demonstrate a correlation between a substance and a health outcome , rather than a true cause and effect relationship . at the end of the day , epidemiological studies have served as excellent guides to public health , alerting us to critical health hazards , such as smoking , asbestos , lead , and many more . but these were demonstrated through multiple , well-conducted epidemiological studies , all pointing in the same direction . so , the next time you see a headline about a new miracle cure or the terrible danger posed by an everyday substance , try to learn more about the original study and the limitations inherent in any epidemiological study or clinical trial before jumping to conclusions .

so , why ca n't we rely on these studies to establish causal relationships between substances and their effects on health ? the problem is that even the best conducted epidemiological studies have inherent flaws . precisely because the test subjects are not randomly assigned to their groups .

rcts can not always be conducted in humans due to :