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magnesium is one of the lightest elements . it ’ s right at the beginning of the period table and , in fact , it ’ s the first of the light metals that you can actually use . lithium and sodium react violently with water so you can ’ t really use them as a metal and beryllium is fantastically poisonous so unless you are using it in the lab where you can be sure that nobody is going to touch it , it ’ s useless , so magnesium is the lightest metal you can use . so , for example , if you are trying to make mobile phones that are really light , then you can make the frame of the mobile phone out of magnesium . you can use it for laptops . there is a professor in germany , who has promised to send me a laptop frame made of magnesium , but it hasn ’ t arrived yet . so another classroom classic . normally comes along in chemistry lesson number three i guess , time to combust a reactive metal in the air , so the reactive metal we are going to look at is magnesium . the other thing that is good about magnesium is that there is a lot of magnesium about in the world , so it is not an element that is difficult to get . if you look at this periodic table here , which is from barcelona so it is in catalan , the areas of these , each element are approximately the abundance in the world . some of the rarer elements have a slightly bigger squares than they should do so you can read the letters , but you see magnesium here is pretty large , so magnesium and sodium are pretty common , beryllium is much less common , and lithium is even less common than that , so there is lots of magnesium . magnesium is very light , it is very reactive , very pliable metal , it is very nice , it is easily alloyed with things like aluminium and other light metals to make very strong , very robust materials . used in construction , it ’ s used in high-performance components of cars . when i was a child when we got , had indigestion , we were given ‘ milk of magnesia ’ . magnesium oxide in water which came in these really nice blue bottles , sort of white looking liquid , didn ’ t taste very nice , but it was meant to be good for you , i am not sure if it was . it is used in the hulls of ships , you know like , warships , things like that , so incredibly strong , incredibly light but incredibly reactive if you give it enough energy . so we are going to combust it in the oxygen and see what happens . magnesium as you know , burns , and one of the ways that magnesium used to be used was for photographic flashlights , and you use bulbs like these which contain magnesium , inside a bulb filled with oxygen . and for each photograph you had to put this on the top of the camera . so i ’ ve got one here that i have taken out . so , if you look at it , so much heat has been produced by this tiny amount of magnesium , that it has melted the glass . so , let ’ s see what happens when we light it . you can see , really fierce bright white light that classical glow , everyone has seen this in the chemistry lab at school , fantastic reaction . it is one of the few metals which is meant to burn in nitrogen . in theory you can take a piece of magnesium , set fire to it in air so its burning well and then plunge it into nitrogen gas , and it should continue burning . i have tried this experiment lots of times and it ’ s never worked . in fact for 25 years i demonstrated this experiment to my lecture class when i was talking about nitrogen , and every time , it didn ’ t work , and the students thought , the poor professor , he has been made a fool of , it hasn ’ t worked and they didn ’ t know that it never worked and i would have been more surprised if it had done , but it taught them a bit about the chemistry of nitrogen and magnesium . why did you keep doing it if it never worked ? because it is a really good experiment , because it got such a good reaction from the audience . because it went wrong ? yes ! you were playing the fool on purpose ? yes ! so this is magnesium metal , but the magnesium metal here is not the ribbon which we normally see in perhaps , scientific labs or perhaps in school labs , this is a very , very fine powder of magnesium , so what we are going to do in a moment is bring on a really very powerful torch , a gas flame and we are going to see what happens when we sprinkle a little of this material into the flame . magnesium is also very important in all our lives , because magnesium is found in the green pigments in the leaves of all plants , in chlorophyll . chlorophyll is an organic molecule , carbon , hydrogen and nitrogen and in the middle there is an atom of magnesium , and it is chlorophyll which catches the sunlight and transfers it eventually to cause the reaction of carbon dioxide and water to make all the sugars and other things in the plant . if that didn ’ t happen none of us would be alive , because we all rely either directly or indirectly on plants , to give us the energy to live . i don ’ t understand completely the mechanism of photosynthesis , because the energy that is absorbed by one molecule , is transferred to another and another one as it were along a chain , but the magnesium is very important , if you don ’ t have magnesium there it is not nearly as efficient . let ’ s light it again .
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the other thing that is good about magnesium is that there is a lot of magnesium about in the world , so it is not an element that is difficult to get . if you look at this periodic table here , which is from barcelona so it is in catalan , the areas of these , each element are approximately the abundance in the world . some of the rarer elements have a slightly bigger squares than they should do so you can read the letters , but you see magnesium here is pretty large , so magnesium and sodium are pretty common , beryllium is much less common , and lithium is even less common than that , so there is lots of magnesium .
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which property of magnesium is shown on the catalan periodic table that arrived for the professor from barcelona ?
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translator : andrea mcdonough reviewer : jessica ruby so two guys walk into a bar . really ? no , seriously . two guys walk into a bar , an ice cream bar : dave , a physicist working on the large hadron collider at cern , the european laboratory for particle physics , and steve , a blues singer . `` dave , how 's it going ? '' `` steve , good to see you ! '' `` two scoops of chocolate almond for me . '' `` vanilla shake . '' `` hey , i just saw something about the lhc on tv . you guys found bozo in your detector ? '' `` well , not exactly . we found a boson , probably the higgs boson . '' `` what 's that ? '' `` it 's a particle . '' `` do n't you find particles all the time ? '' `` yes , but this one means that the higgs field might really exist . '' `` field ? what field ? '' `` the higgs field . it 's named after peter higgs , although many others contributed to the idea . it is n't a field , like where you grow corn , but a hypothetical , invisible kind of force field that pervades the whole universe . '' `` hmmmm , okay . if it pervades the whole universe , how come i 've never seen it ? that 's a bit strange . '' `` well , actually , it 's not that strange . think of the air around us . we ca n't see it or smell it . well , perhaps in some places we can . but we can detect its presence with sophisticated equipment , like our own bodies . so the fact that we ca n't see something just makes it a bit harder to determine whether its really there or not . '' `` alright , go on . '' `` so , we believe this higgs field is all around us , everywhere in the universe . and what it does is rather special - it gives mass to elementary particles . '' `` what 's an elementary particle ? '' `` an elementary particle is what we call particles that have no structure , they ca n't be divided , they 're the basic building blocks of the universe . '' `` i thought those were atoms . '' `` well , atoms are actually made of smaller components , protons , neutrons , and electrons . while electrons are fundamental particles , neutrons and protons are not . they are made up of other fundamental particles called quarks . '' `` sounds like russian dolls . does it ever end ? '' `` actually , we do n't really know . but our current understanding is called the standard model . in it , there are two types of fundamental particles : the fermions , that make up matter , and the bosons , that carry forces . we often order these particles according to their properties , such as mass . we can measure the masses of the particles , but we never really knew where this mass came from or why they have the masses they do . '' `` so how does this higgs field thing explain mass ? '' `` well , when a particle passes through the higgs field , it interacts and gets mass . the more it interacts , the more mass it has . '' `` ok , i kind of get that , but is it really that important ? i mean , what if there were no higgs field ? '' `` if there were no higgs field , the world would n't exist at all . there would be no stars , no planets , no air , no anything , not even that spoon or the ice cream you 're eating . '' `` oh , that would be bad . okay , but where does this higgs boson fit into things ? '' `` alright , now , you see the cherry in my shake ? '' `` can i have it ? '' `` no , not yet . we have to use it as an analogy first . '' `` oh , right , the cherry 's the higgs boson . '' `` no , not quite . the cherry is a particle moving through the higgs field , the shake . the shake gives the cherry its mass . '' `` i get it . okay , so the molecules of the shake are the higgs bosons ! '' `` well , you 're getting closer . it takes an excitation of the higgs field to produce the higgs boson . so , for example , if i were to add energy by , say , dropping this cherry in the shake , '' `` ah , then the drops that spill on the bar are the higgs bosons . '' `` almost ! the splash itself is the higgs boson . '' `` are you serious ? '' `` well , that 's what quantum mechanics teaches us . in fact , all particles are excitations of fields . '' `` okay , right . well , i kind of see why you like particle physics , it 's quite cool , strange , but cool . '' `` yeah , you could call it a bit strange , it 's not like everyday life . the higgs boson is an excitation of the higgs field . by finding the higgs boson , we know that the higgs field exists . '' `` right . so now you found it , we know this higgs field exists . you must be done . is there anything left of particle physics ? '' `` actually , we 've just begun . it 's a bit like , you know , when columbus thought he had found a new route to india . he 'd , indeed , found something new , but not quite what he was expecting . so , first , we need to make sure that the boson we found is actually the higgs boson . it seems to fit , but we need to measure its properties to be sure . '' `` how 'd you do that ? '' `` take a lot more data . this new boson lives for only a very short time before it breaks down or decays into lighter , more stable particles . by measuring these particles , you learn about the properties of the boson . '' `` and what exactly are you looking for ? '' `` well , the standard model predicts how often and in what ways the higgs boson would decay to the various , lighter particles . so we want to see if the particle we have found is the one predicted by the standard model or if it fits into other possible theoretical models . '' `` and if it fits a different model ? '' `` that would be even more exciting ! in fact , that 's how science advances . we replace old models with new ones if they better explain our observations . '' `` right , so it seems like finding this higgs boson gives a direction for exploration , a bit like that columbus guy heading west . '' `` exactly ! and this is really just the beginning . ''
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what field ? '' `` the higgs field . it 's named after peter higgs , although many others contributed to the idea .
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if the higgs field didn ’ t exist , what would be the consequence for our universe ?
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translator : andrea mcdonough reviewer : jessica ruby the world we live in is made of things , billions and billions of different things , like pickles and pianos and dump trucks and octopi . and even though these things seem totally different , they 're all made of the same stuff , just combined in different ways . to give you an idea of how this combining works , let 's take something apart . let 's start with this bowl of macaroni salad . if you were to reverse a recipe for macaroni salad , you 'll see it 's made by mixing together a bunch of ingredients , like macaroni , mayo , vinegar , vegetables , and mustard . this type of combining is called a mixture . when you make a mixture , you 're combining two or more things together without actually changing the chemical identity of those things . like mud , for example . the soil and water in mud have n't actually changed . they 're still soil and water , you 've just created a mixture of soil and water -- mud . it turns out that macaroni salad is actually a mixture of mixtures because many of the ingredients , like mayo and mustard , are already mixtures themselves , which is nice for us because if we look closely , we 'll the see the three main types of mixtures that exist . the size of the particles in a mixture determines the type of mixture . on one end of the scale is a suspension , like our muddy water example . you get this if you take big chunks of something and mix it with something else so those chunks are just floating around . take runny mustard for example . you 'll see a bunch of little particles like mustard seeds , pepper , allspice , and minced shallots all floating around in a liquid , in this case vinegar with water . this is called a suspension because you 've got particles of one thing suspended in another . now , on the other end of the spectrum is a solution . the particles in this mixture are so small , they are the actual molecules . a solution is sort of like a suspension of molecules where one type of molecule is blended or dissolved with another . vinegar is an example of a solution where the molecules of acetic acid are blended with molecules of water . the chemical properties of the molecules have n't changed , they 're just evenly mixed together now . saltwater and carbonated soda are both examples of solutions where other molecules are dissolved in water . the last type of mixture is called a colloid , which is somewhere between a suspension and a solution . it 's when you take two materials that do n't dissolve and you make the particles so small that they ca n't separate . mayo is what happens when you take oil and water , which do n't mix , and you bind them together , usually with the help of another substance called an emulsifier . in the case of mayo , it 's lecithin , found in eggs . and now you are left with really small globs of oil hanging out with really small droplets of water . whipped cream , hairspray , styrofoam , and jello are all other examples of colloids . so , let 's get back to macaroni salad . you 've call colloids like mayo , suspensions like mustard , and solutions like vinegar , but you 've also got celery , shallots , and all other vegetable chunks that are also part of the salad . these are n't mixtures , really , but we can break them up , just like a tv can be broken up into smaller and smaller complex component parts . in the case of vegetables , if you keep breaking things up , they 'll eventually end with thousands of complex organic molecules , things like atp synthase and rna transcriptase and water . so now , once we 've unblended all the solutions , unmixed all the colloids , separated all the suspensions and taken apart all of our vegetables , we 've reached the end of what we can unmix physically . what we 're left with is a whole bunch of molecules , and these molecules remain chemically the same whether they are by themselves or thrown together in a salad . if you want to separate these guys even further , we need to unmix things chemically , which means we need to start breaking some bonds .
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what we 're left with is a whole bunch of molecules , and these molecules remain chemically the same whether they are by themselves or thrown together in a salad . if you want to separate these guys even further , we need to unmix things chemically , which means we need to start breaking some bonds .
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how do you `` unmix '' things chemically ?
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there 's an organism that changed the world . it caused both the first mass extinction in earth 's history and also paved the way for complex life . how ? by sending the first free oxygen molecules into our atmosphere , and they did all this as single-celled life forms . they 're cyanobacteria , and the story of these simple organisms that do n't even have nuclei or any other organelles is a pivotal chapter in the story of life on earth . earth 's atmosphere was n't always the oxygen-rich mixture we breathe today . 3.5 billion years ago , the atmosphere was mostly nitrogen , carbon dioxide , and methane . almost all oxygen was locked up in molecules like water , not floating around in the air . the oceans were populated by anaerobic microbes . those are simple , unicellular life forms that thrive without oxygen and get energy by scavenging what molecules they find . but somewhere between 2.5 and 3.5 billion years ago , one of these microbial species , probably floating on the surface of the ocean , evolved a new ability : photosynthesis . structures in their cell membrane could harness the energy from sunlight to turn carbon dioxide and water into oxygen gas and sugars , which they could use for energy . those organisms were the ancestors of what we now call cyanobacteria . their bluish color comes from the blue-green pigments that capture the sunlight they need . photosynthesis gave those ancient bacteria a huge advantage over other species . they could now produce their own energy from an almost endless supply of raw ingredients , so their populations exploded and they started polluting the atmosphere with a new waste product : oxygen . at first , the trickle of extra oxygen was soaked up by chemical reactions with iron or decomposing cells , but after a few hundred million years , the cyanobacteria were producing oxygen faster than it could be absorbed , and the gas started building up in the atmosphere . that was a big problem for the rest of earth 's inhabitants . oxygen-rich air was actually toxic to them . the result ? about 2.5 billion years ago was a mass extinction of virtually all life on earth , which barely spared the cyanobacteria . geologists call this the great oxygenation event , or even the oxygen catastrophe . that was n't the only problem . methane had been acting as a potent greenhouse gas that kept the earth warm , but now , the extra oxygen reacted with methane to form carbon dioxide and water , which do n't trap as much heat . the thinner atmospheric blanket caused earth 's first , and possibly longest , ice age , the huronian glaciation . the planet was basically one giant snowball for several hundred million years . eventually , life adjusted . aerobic organisms , which can use oxygen for energy , started sopping up some of the excess gas in the atmosphere . the oxygen concentration rose and fell until eventually it reached the approximate 21 % we have today . and being able to use the chemical energy in oxygen gave organisms the boost they needed to diversify and evolve more complex forms . cyanobacteria had a part to play in that story , too . hundreds of millions of years ago , some other prehistoric microbe swallowed a cyanobacterium whole in a process called endosymbiosis . in doing so , that microbe acquired its own internal photosynthesis factory . this was the ancestor of plant cells . and cyanobacteria became chloroplasts , the organelles that carry out photosynthesis today . cyanobacteria are still around in almost every environment on earth : oceans , fresh water , soil , antarctic rocks , sloth fur . they still pump oxygen into the atmosphere , and they also pull nitrogen out to fertilize the plants they helped create . we would n't recognize life on earth without them . but also thanks to them , we almost did n't have life on earth at all .
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about 2.5 billion years ago was a mass extinction of virtually all life on earth , which barely spared the cyanobacteria . geologists call this the great oxygenation event , or even the oxygen catastrophe . that was n't the only problem .
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the great oxygenation event was caused by a change in oxygen composition in the atmosphere , where the amount of oxygen :
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are you as good at things as you think you are ? how good are you at managing money ? what about reading people 's emotions ? how healthy are you compared to other people you know ? are you better than average at grammar ? knowing how competent we are and how are skill stack up against other people 's is more than a self-esteem boost . it helps us figure out when we can forge ahead on our own decisions and instincts and when we need , instead , to seek out advice . but psychological research suggests that we 're not very good at evaluating ourselves accurately . in fact , we frequently overestimate our own abilities . researchers have a name for this phenomena , the dunning-kruger effect . this effect explains why more than 100 studies have shown that people display illusory superiority . we judge ourselves as better than others to a degree that violates the laws of math . when software engineers at two companies were asked to rate their performance , 32 % of the engineers at one company and 42 % at the other put themselves in the top 5 % . in another study , 88 % of american drivers described themselves as having above average driving skills . these are n't isolated findings . on average , people tend to rate themselves better than most in disciplines ranging from health , leadership skills , ethics , and beyond . what 's particularly interesting is that those with the least ability are often the most likely to overrate their skills to the greatest extent . people measurably poor at logical reasoning , grammar , financial knowledge , math , emotional intelligence , running medical lab tests , and chess all tend to rate their expertise almost as favorably as actual experts do . so who 's most vulnerable to this delusion ? sadly , all of us because we all have pockets of incompetence we do n't recognize . but why ? when psychologists dunning and kruger first described the effect in 1999 , they argued that people lacking knowledge and skill in particular areas suffer a double curse . first , they make mistakes and reach poor decisions . but second , those same knowledge gaps also prevent them from catching their errors . in other words , poor performers lack the very expertise needed to recognize how badly they 're doing . for example , when the researchers studied participants in a college debate tournament , the bottom 25 % of teams in preliminary rounds lost nearly four out of every five matches . but they thought they were winning almost 60 % . without a strong grasp of the rules of debate , the students simply could n't recognize when or how often their arguments broke down . the dunning-kruger effect is n't a question of ego blinding us to our weaknesses . people usually do admit their deficits once they can spot them . in one study , students who had initially done badly on a logic quiz and then took a mini course on logic were quite willing to label their original performances as awful . that may be why people with a moderate amount of experience or expertise often have less confidence in their abilities . they know enough to know that there 's a lot they do n't know . meanwhile , experts tend to be aware of just how knowledgeable they are . but they often make a different mistake : they assume that everyone else is knowledgeable , too . the result is that people , whether they 're inept or highly skilled , are often caught in a bubble of inaccurate self-perception . when they 're unskilled , they ca n't see their own faults . when they 're exceptionally competent , they do n't perceive how unusual their abilities are . so if the dunning-kruger effect is invisible to those experiencing it , what can you do to find out how good you actually are at various things ? first , ask for feedback from other people , and consider it , even if it 's hard to hear . second , and more important , keep learning . the more knowledgeable we become , the less likely we are to have invisible holes in our competence . perhaps it all boils down to that old proverb : when arguing with a fool , first make sure the other person is n't doing the same thing .
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they know enough to know that there 's a lot they do n't know . meanwhile , experts tend to be aware of just how knowledgeable they are . but they often make a different mistake : they assume that everyone else is knowledgeable , too . the result is that people , whether they 're inept or highly skilled , are often caught in a bubble of inaccurate self-perception .
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what mistake do experts make when evaluating their skills ?
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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 .
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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 .
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past a certain distance from the nucleus , the probability of finding an electron starts to decrease more or less exponentially . how would you represent this on a graph ? draw a quick sketch and label the axes . how would you account for the “ past a certain distance from the nucleus ” part of the question in your sketch ?
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can plants talk to each other ? it certainly does n't seem that way . plants do n't have complex sensory or nervous systems like animals do , and they look pretty passive , basking in the sun , and responding instinctively to inputs like light and water . but odd as it sounds , plants can communicate with each other . just like animals , plants produce all kinds of chemical signals in response to their environments , and they can share those signals with each other , especially when they 're under attack . these signals take two routes : through the air , and through the soil . when plant leaves get damaged , whether by hungry insects or an invading lawn mower , they release plumes of volatile chemicals . they 're what 's responsible for the smell of freshly cut grass . certain kinds of plants , like sagebrush and lima beans , are able to pick up on those airborne messages and adjust their own internal chemistry accordingly . in one experiment , sagebrush leaves were deliberately damaged by insects or scissor-wielding scientists . throughout the summer , other branches on the same sagebrush plant got eaten less by insects wandering through , and so did branches on neighboring bushes , suggesting that they had beefed up their anti-insect defenses . even moving the air from above a clipped plant to another one made the second plant more insect-resistant . these airborne cues increase the likelihood of seedling survival , and made adult plants produce more new branches and flowers . but why would a plant warn its neighbors of danger , especially if they 're competing for resources ? well , it might be an accidental consequence of a self-defense mechanism . plants ca n't move information through their bodies as easily as we can , especially if water is scarce . so plants may rely on those airborne chemicals to get messages from one part of a plant to another . nearby plants can eavesdrop on those signals , like overhearing your neighbor sneeze and stocking up on cold medicine . different plants convey those warnings using different chemical languages . individual sagebrush plants in the same meadow release slightly different sets of alarm chemicals . the makeup of that cocktail influences the effectiveness of communication . the more similar two plants ' chemical fingerprints are , the more fluently they can communicate . a plant will be most sensitive to the cues emitted by its own leaves . but because these chemicals seem to be inherited , like human blood types , sagebrush plants communicate more effectively with relatives than with strangers . but sometimes , even other species can benefit . tomato and tobacco plants can both decipher sagebrush warning signals . plants do n't have to rely solely on those airborne broadcasts . signals can travel below the soil surface , too . most plants have a symbiotic relationship with fungi , which colonize the plants ' roots and help them absorb water and nutrients . these fungal filaments form extensive networks that can connect separate plants , creating an underground super highway for chemical messages . when a tomato plant responds to blight by acitvating disease-fighting genes and enzymes , signaling molecules produced by its immune system can travel to a healthy plant and prompt it to turn on its immune system , too . these advance warnings increase the plants chance of survival . bean plants also eavesdrop on each other 's health through these fungal conduits . an aphid investation in one plant triggers its neighbor to ramp up production of compounds that repel aphids and attract aphid-eating wasps . if you think of communication as an exchange of information , then plants seem to be active communicators . they 're sending , receiving , and responding to signals without making a sound , and without brains , noses , dictionaries , or the internet . and if we can learn to speak to them on their terms , we may gain a powerful new tool to protect crops and other valuable species . it all makes you wonder what else are we missing ?
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nearby plants can eavesdrop on those signals , like overhearing your neighbor sneeze and stocking up on cold medicine . different plants convey those warnings using different chemical languages . individual sagebrush plants in the same meadow release slightly different sets of alarm chemicals .
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in what ways are communication systems between plants similar to communication systems between animals ? in what ways are they different ?
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how did adolf hitler , a tyrant who orchestrated one of the largest genocides in human history , rise to power in a democratic country ? the story begins at the end of world war i . with the successful allied advance in 1918 , germany realized the war was unwinnable and signed an armistice ending the fighting . as its imperial government collapsed , civil unrest and worker strikes spread across the nation . fearing a communist revolution , major parties joined to suppress the uprisings , establishing the parliamentary weimar republic . one of the new government 's first tasks was implementing the peace treaty imposed by the allies . in addition to losing over a tenth of its territory and dismantling its army , germany had to accept full responsibility for the war and pay reparations , debilitating its already weakened economy . all this was seen as a humiliation by many nationalists and veterans . they wrongly believed the war could have been won if the army had n't been betrayed by politicians and protesters . for hitler , these views became obsession , and his bigotry and paranoid delusions led him to pin the blame on jews . his words found resonance in a society with many anti-semitic people . by this time , hundreds of thousands of jews had integrated into german society , but many germans continued to perceive them as outsiders . after world war i , jewish success led to ungrounded accusations of subversion and war profiteering . it can not be stressed enough that these conspiracy theories were born out of fear , anger , and bigotry , not fact . nonetheless , hitler found success with them . when he joined a small nationalist political party , his manipulative public speaking launched him into its leadership and drew increasingly larger crowds . combining anti-semitism with populist resentment , the nazis denounced both communism and capitalism as international jewish conspiracies to destroy germany . the nazi party was not initially popular . after they made an unsuccessful attempt at overthrowing the government , the party was banned , and hitler jailed for treason . but upon his release about a year later , he immediately began to rebuild the movement . and then , in 1929 , the great depression happened . it led to american banks withdrawing their loans from germany , and the already struggling german economy collapsed overnight . hitler took advantage of the people 's anger , offering them convenient scapegoats and a promise to restore germany 's former greatness . mainstream parties proved unable to handle the crisis while left-wing opposition was too fragmented by internal squabbles . and so some of the frustrated public flocked to the nazis , increasing their parliamentary votes from under 3 % to over 18 % in just two years . in 1932 , hitler ran for president , losing the election to decorated war hero general von hindenburg . but with 36 % of the vote , hitler had demonstrated the extent of his support . the following year , advisors and business leaders convinced hindenburg to appoint hitler as chancellor , hoping to channel his popularity for their own goals . though the chancellor was only the administrative head of parliament , hitler steadily expanded the power of his position . while his supporters formed paramilitary groups and fought protestors in streets . hitler raised fears of a communist uprising and argued that only he could restore law and order . then in 1933 , a young worker was convicted of setting fire to the parliament building . hitler used the event to convince the government to grant him emergency powers . within a matter of months , freedom of the press was abolished , other parties were disbanded , and anti-jewish laws were passed . many of hitler 's early radical supporters were arrested and executed , along with potential rivals , and when president hindenburg died in august 1934 , it was clear there would be no new election . disturbingly , many of hitler 's early measures did n't require mass repression . his speeches exploited people 's fear and ire to drive their support behind him and the nazi party . meanwhile , businessmen and intellectuals , wanting to be on the right side of public opinion , endorsed hitler . they assured themselves and each other that his more extreme rhetoric was only for show . decades later , hitler 's rise remains a warning of how fragile democratic institutions can be in the face of angry crowds and a leader willing to feed their anger and exploit their fears .
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but upon his release about a year later , he immediately began to rebuild the movement . and then , in 1929 , the great depression happened . it led to american banks withdrawing their loans from germany , and the already struggling german economy collapsed overnight .
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why was germany hit harder by the great depression than any other european nation ?
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thorium itself as a metal is quite frisky and if you heat it in air it burns incredibly intensely . it ’ s also a component of lenses for cameras because when it ’ s mixed in with certain other elements to give you these lenses , it has a very high refractive index and a very low dispersion , which means you get really sharp images ; possibly in the lens that you ’ re filming me with right now .
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thorium itself as a metal is quite frisky and if you heat it in air it burns incredibly intensely . it ’ s also a component of lenses for cameras because when it ’ s mixed in with certain other elements to give you these lenses , it has a very high refractive index and a very low dispersion , which means you get really sharp images ; possibly in the lens that you ’ re filming me with right now .
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of the 30 known isotopes of thorium , which one does not occur naturally ?
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what does the french revolution have to do with the time nasa accidentally crashed a $ 200 million orbiter into the surface of mars ? actually , everything . that crash happened due to an error in converting between two measurement systems , u.s. customary units and their s.i , or metric , equivalence . so what 's the connection to the french revolution ? let 's explain . for the majority of recorded human history , units like the weight of a grain or the length of a hand were n't exact and varied from place to place . and different regions did n't just use varying measurements . they had completely different number systems as well . by the late middle ages , the hindu-arabic decimal system mostly replaced roman numerals and fractions in europe , but efforts by scholars like john wilkins to promote standard decimal-based measures were less successful . with a quarter million different units in france alone , any widespread change would require massive disruption . and in 1789 , that disruption came . the leaders of the french revolution did n't just overthrow the monarchy . they sought to completely transform society according to the rational principles of the enlightenment . when the new government took power , the academy of sciences convened to reform the system of measurements . old standards based on arbitrary authority or local traditions were replaced with mathematical and natural relationships . for example , the meter , from the greek word for measure , was defined as 1/10,000,000 between the equator and north pole . and the new metric system was , in the words of the marquis de condorcet , `` for all people , for all time . '' standardizing measurements had political advantages for the revolutionaries as well . nobles could no longer manipulate local units to extract more rent from commoners , while the government could collect taxes more efficiently . and switching to a new republican calendar with ten-day weeks reduced church power by eliminating sundays . adoption of this new system was n't easy . in fact , it was a bit of a mess . at first , people used new units alongside old ones , and the republican calendar was eventually abandoned . when napoléon bonaparte took power , he allowed small businesses to use traditional measurements redefined in metric terms . but the metric system remained standard for formal use , and it spread across the continent , along with france 's borders . while napoléon 's empire lasted eight years , its legacy endured far longer . some european countries reverted to old measurements upon independence . others realized the value of standardization in an age of international trade . after portugal and the netherlands switched to metric voluntarily , other nations followed , with colonial empires spreading the system around the world . as france 's main rival , britain had resisted revolutionary ideas and retained its traditional units . but over the next two centuries , the british empire slowly transitioned , first approving the metric system as an optional alternative before gradually making it offical . however , this switch came too late for thirteen former colonies that had already gained independence . the united states of america stuck with the english units of its colonial past and today remains one of only three countries which have n't fully embraced the metric system . despite constant initiatives for metrication , many americans consider units like feet and pounds more intuitive . and ironically , some regard the once revolutionary metric system as a symbol of global conformity . nevertheless , the metric system is almost universally used in science and medicine , and it continues to evolve according to its original principles . for a long time , standard units were actually defined by carefully maintained physical prototypes . but thanks to improving technology and precision , these objects with limited access and unreliable longevity are now being replaced with standards based on universal constants , like the speed of light . consistent measurements are such an integral part of our daily lives that it 's hard to appreciate what a major accomplishment for humanity they 've been . and just as it arose from a political revolution , the metric system remains crucial for the scientific revolutions to come .
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and switching to a new republican calendar with ten-day weeks reduced church power by eliminating sundays . adoption of this new system was n't easy . in fact , it was a bit of a mess .
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what historical event was pivotal in the adoption of a unified measurement system ?
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mysteries of vernacular : quarantine , a state , period , or place of strict isolation meant to prevent the spread of disease . in the 14th century , the bubonic plague , later called `` the black death , '' spread across europe with devastating consequences . it 's been estimated that the plague decimated at least one-third of europe 's population . in a vain effort to stave off infection , the italian-speaking port city of ragusa , in what is now croatia , mandated that ships arriving from plague-infested areas remain isolated on the water until it was deemed likely that they were n't carrying a disease . this meant that the entire contents of a ship and all of its passengers were often forced to remain on board for five or six weeks before being let ashore . though the drastic measure was only marginally successful , it was n't long before other port cities followed suit . in 1397 , the official period of isolation imposed on ships and crews was set at forty days . although it did little to protect ports from infection , the directive stuck . from the italian word quaranta , meaning forty , this period of stasis was given the name quarantine . and by the mid 1600s , the word quarantine was being used to describe any place , period , or state of isolation , plague-related or not .
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though the drastic measure was only marginally successful , it was n't long before other port cities followed suit . in 1397 , the official period of isolation imposed on ships and crews was set at forty days . although it did little to protect ports from infection , the directive stuck .
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in 1397 , what was the official period of isolation imposed on ships and crews ?
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the epic poem `` la dragontea '' describes how english explorer sir francis drake sailed across the gulf of venezuela in 1595 . he was aiming for the nearby lake maracaibo , home to a colony of spanish settlers he planned to overthrow . but as drake moved towards the mouth of the lake under cover of darkness , his plot was suddenly and magnificently foiled . huge flashes of lightning illuminated the landscape , exposing the fleet as if it were daytime , which warned the spanish about his approach . lake maracaibo is the stormiest place on the planet . the massive body of water at over 13,000 square kilometers is a place of almost perpetual storming . thunderstorms rage above it for up to 200 days of the year , each earsplitting event lasting for several hours . like everywhere else on earth , lightning at lake maracaibo is the result of opposing electrical charges that steadily build up inside storm clouds . once there 's a large enough difference between charges either within the cloud or between the clouds and the earth below , it forms a spark that becomes a lightning bolt . lightning strikes the earth about 350 million times per year , averaging out to eleven strikes a second . we know that thanks to satellites up in space and sensors on the ground . we can also measure the earth 's lightning density , which is the frequency with which lightning flashes in a square kilometer . knowing where lightning strikes and how often reveals the most lightning-rich places on earth . in the polar regions , there may only be one strike per several square kilometers each year . meanwhile , lightning density at the equator averages out to tens of flashes per square kilometer on account of the sun providing more heat to drive storms . yet nowhere can quite compare with lake maracaibo , where lightning strikes an average 250 times per square kilometer , giving it the highest lightning density of any place on earth . a number of factors converge to create the lake 's seemingly everlasting storms . firstly , lake maracaibo lies just ten degrees north of the equator , so there 's a wealth of solar energy available to fuel the storms . thunderstorms also require a supply of water vapor to feed on , and having the warm waters of the caribbean so close by provides an endless supply . finally , the lake 's southern and western edges are bordered by two massive mountain ranges , and as cool winds surge down these slopes , they force up warm air , destabilizing the atmosphere and causing storm clouds to form . together , these ingredients combine to give rise to the most awe-inspiring thunderstorms on the planet , a true sight to behold . centuries ago , sir francis drake may have cursed the lake 's intense illumination , but today , sailors actually embrace this phenomenon . they call it the maracaibo beacon , and use it as a natural lighthouse to illuminate their path across the seas .
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meanwhile , lightning density at the equator averages out to tens of flashes per square kilometer on account of the sun providing more heat to drive storms . yet nowhere can quite compare with lake maracaibo , where lightning strikes an average 250 times per square kilometer , giving it the highest lightning density of any place on earth . a number of factors converge to create the lake 's seemingly everlasting storms .
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which of these regions has the lowest average lightning density ?
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to someone first encountering the works of william shakespeare , the language may seem strange . but there is a secret to appreciating it . although he was famous for his plays , shakespeare was first and foremost a poet . one of the most important things in shakespeare 's language is his use of stress . not that kind of stress , but the way we emphasize certain syllables in words more than others . we 're so used to doing this that we may not notice it at first . but if you say the word slowly , you can easily identify them . playwright , computer , telephone . poets are very aware of these stresses , having long experimented with the number and order of stressed and unstressed syllables , and combined them in different ways to create rhythm in their poems . like songwriters , poets often express their ideas through a recognizable repetition of these rhythms or poetic meter . and like music , poetry has its own set of terms for describing this . in a line of verse , a foot is a certain number of stressed and unstressed syllables forming a distinct unit , just as a musical measure consists of a certain number of beats . one line of verse is usually made up of several feet . for example , a dactyl is a metrical foot of three syllables with the first stressed , and the second and third unstressed . dactyls can create lines that move swiftly and gather force , as in robert browning 's poem , `` the lost leader . '' `` just for a handful of silver he left us . just for a rib and to stick in his coat . '' another kind of foot is the two-syllable long trochee , a stressed syllable followed by an unstressed one . the trochees in these lines from shakespeare 's `` macbeth '' lend an ominous and spooky tone to the witches ' chant . `` double , double , toil and trouble ; fire burn and cauldron bubble . '' but with shakespeare , it 's all about the iamb . this two-syllable foot is like a reverse trochee , so the first syllable is unstressed and the second is stressed , as in , `` to be , or not to be . '' shakespeare 's favorite meter , in particular , was iambic pentameter , where each line of verse is made up of five two-syllable iambs , for a total of ten syllables . and it 's used for many of shakespeare 's most famous lines : `` shall i compare thee to a summer 's day ? '' `` arise fair sun , and kill the envious moon . '' notice how the iambs cut across both punctuation and word separation . meter is all about sound , not spelling . iambic pentameter may sound technical , but there 's an easy way to remember what it means . the word iamb is pronounced just like the phrase , `` i am . '' now , let 's expand that to a sentence that just happens to be in iambic pentameter . `` i am a pirate with a wooden leg . '' the pirate can only walk in iambs , a living reminder of shakespeare 's favorite meter . iambic pentameter is when he takes ten steps . our pirate friend can even help us remember how to properly mark it if we image the footprints he leaves walking along a deserted island beach : a curve for unstressed syllables , and a shoe outline for stressed ones . `` if music be the food of love , play on . '' of course , most lines of shakespeare 's plays are written in regular prose . but if you read carefully , you 'll notice that shakespeare 's characters turn to poetry , and iambic pentameter in particular , for many of the same reasons that we look to poetry in our own lives . feeling passionate , introspective , or momentous . whether it 's hamlet pondering his existence , or romeo professing his love , the characters switch to iambic pentameter when speaking about their emotions and their place in the world . which leaves just one last question . why did shakespeare choose iambic pentameter for these moments , rather than , say , trochaic hexameter or dactylic tetrameter ? it 's been said that iambic pentameter was easy for his actors to memorize and for the audience to understand because it 's naturally suited to the english language . but there might be another reason . the next time you 're in a heightened emotional situation , like the ones that make shakespeare 's characters burst into verse , put your hand over the left side of your chest . what do you feel ? that 's your heart beating in iambs . da duhm , da duhm , da duhm , da duhm , da duhm . shakespeare 's most poetic lines do n't just talk about matters of the heart . they follow its rhythm .
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in a line of verse , a foot is a certain number of stressed and unstressed syllables forming a distinct unit , just as a musical measure consists of a certain number of beats . one line of verse is usually made up of several feet . for example , a dactyl is a metrical foot of three syllables with the first stressed , and the second and third unstressed .
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review the definitions of “ trochee ” and “ dactyl. ” to which kinds of moods or tones might these types of feet be suited , based on the way they sound in verse ?
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translator : denise rq reviewer : callum downs i just want to start with a little bit of a word of warning and that is my job here tonight it 's to be a little bit of a doctor bring me down . so bear with me for a few minutes , and know that after this , things will get lighter and brighter . let 's start . i know that many of you have heard the traveler 's adage , `` take nothing but pictures , leave nothing but footprints . '' well , i 'm going to say i do n't think that 's either as benign or as simple as it sounds , particularly for those of us in industries who are portraying people in poor countries , in developing countries and portraying the poor . and those of us in those industries are reporters , researchers , and people working for ngos ; i suspect there are a lot of us in those industries in the audience . we are going overseas and bringing back pictures like these : of the utterly distressed , or the displaced , or the hungry , or the child labor , or the exotic . now susan sontag reminds us that photographs in part help define what we have the right to observe , but more importantly , they are an ethics of seeing , and i think right now , is a good time to review our ethics of seeing as our industries of reporting , and research and ngo work are collapsing and changing in part by what it 's been happening in the economy , but it 's making us forge new relationships . and those new relationships have some fuzzy boundaries . i worked at the edge of some of these fuzzy boundaries and i want to share with you some of my observations . my ethics of seeing is informed by 25 years as a reporter covering emerging economies and international relations . i believe in a free and independent press . i believe that journalism is a public good . but it 's getting harder to do that job , in part because of the massive layoffs , because the budgets for international reporting are n't there anymore , new technologies and new platforms begging new content , and there are a lot of new journalisms . there is activist journalism , humanitarian journalism , peace journalism , and we are all looking to cover the important stories of our time . so we are going to ngos and asking them if we can embed in their projects . this is in part because they are doing important work in interesting places . that 's one example here : this is a project i worked on in the blue nile in ethiopia . ngos understand the benefits of having reporters tag along on their team . they need the publicity , they are under tremendous pressure , they are competing in a very crowded market for compassion . so they are also looking to reporters and to hire freelance reporters to help them develop their public relations material and their media material . now , researchers are also under pressure . they 're under pressure to communicate their science outside of the academy . so they 're collaborating with reporters because for many researchers is difficult to write a simple story or a clear story . and the benefit for reporters is that covering field research is some of the best work out there . you not only get to cover science , but you get to meet interesting scientists , like my phd adviser revi sterling ; she 's one of the magic research high tops there . and it was in a discussion with revi that brought us to the edge of the researcher and reporter , that fuzzy boundary . and i said to her , `` i was looking forward to going to developing countries and doing research and covering stories at the same time . '' she said , `` i do n't think so , girlfriend . '' that confusion , mutual confusion , drove us to publish a paper on the conflicting ethics and the contradictory practices of research and reporting . we started with the understanding that researchers and reporters are distant cousins equally story tellers and social analysts . but we do n't see nor portray developing communities the same way . here 's a very classic example : this is somalia 1992 . it could be somalia today . and this is a standard operating procedure for much of the news video and the news pictures that you see , where a group of reporters will be trucked in , escorted to the site of a disaster , they 'll produce their material , take their pictures , get their interviews , and then they will be escorted out . this is decidedly not a research setting . sometimes , we are working on feature stories . this is an image i took of a woman in bhongir village in andhra pradesh in india . she is at a micro-finance meeting . it 's a terrific story . what is important here is that she is identifiable . you can see her face . this also is not a research picture . this is much more representative of a research picture . it 's a research site : you see young women accessing new technologies . it 's more of a time stamp , it 's a documentation of research . i could n't use this for news . it does n't tell enough , and it would n't sell . but then , the differences are even deeper than that . revi and i analyzed some of the mandates that researchers are under , they are under some very strict rules governed by their university research review boards when it comes to content and confidentiality . researchers are mandated to acquire a document of informed consent , while as a reporter , if i hang a microphone on someone , that is consent . and when it comes to creating the story , i 'll fact check as a reporter , but i do n't invite company to create that story . whereas social scientists , researchers , and particularly participatory researchers will often work on constructing the narrative with the community . and when it comes to paying for information , checkbook journalism is roundly discouraged . in part because of the bias it introduces in the kind of information you get . but social scientists understand that people 's time is valuable so they pay them for that time . while journalists are well-placed to convey the beauty of the scientific process - and i would add the ngo process - what about the words ? what happens if a research project is not particularly well designed or an ngo project does n't fulfill its goals ? or the other kind of words ; that happens after dark when the drinks happen . research environments , and reporting , trips and ngos projects are very intimate environments ; you make good friends while you are doing good work , but there is a little bit of johnnie walker journalism after dark and what happens to that line between embedded and inbedded ? what do you do with the odd and odious behavior ? the point is that you 'll want to negotiate in advance what is on the record or off the record . i will turn now to some ngo imagery which will be familiar to some of you in this audience . ( video ) for about 70 cents , you can buy a can of soda . regular or diet . in ethiopia , for just 70 cents a day , you can feed a child like jaamal nourishing meals . for about 70 cents , you can also buy a cup of coffee . in guatemala , for 70 cents a day , you can help a child like vilma get the clothes she needs to attend school . leslie dodson : there is some very common imagery that 's been around for 40 years . that 's part of sally struthers ' famine campaign . some of it is very familiar ; it 's the madonna and child . women and children are very effective in terms of ngo campaigns . we 've been looking at this imagery for a long time , for hundreds and hundreds of years ; the madonna and child . here is [ duccio ] , and here is michelangelo . my concern is : are we one noting the genders in our narratives of poverty in developing communities ? do we have women as victims and are men only the perpetrators ? the guys with the ak 47s or the boys soldiers ? because that does n't leave room for stories like : the man who is selling ice-cream at the refuge camp in southern sudan , where we did a project . or the stories of the men who are working on the bridge over the blue nile . i wonder , are these stories inconvenient to our narratives ? and what about this narrative ? this is a for profit game , and its aim is to make development fun . one question is did they inadvertently make fun of ? another set of questions is what are the rights of these children ? what rights of publicity or privacy do they have ? did they get paid ? should they get paid ? should they share their profit ? this is a for profit game . did they sign talent wavers ? i have to use these when i 'm working with ngos and documentary film makers here in the states . in the states , we take our right to privacy and publicity very seriously . so what is it about getting on a long , whole flight that makes these rights vaporize ? i do n't want to just pick on our friends in the gaming arts , i 'll turn to the graphic arts where we often see these monolithic , homogeneous stories about the great country of africa . but africa is not a country , it 's a continent . it 's 54 countries and thousands and thousands of languages . so my question is is this imagery productive ? or is it reductive ? i know that is popular . we have usaid just launched their campaign `` forward '' -- fwd : famine war and drought . and by looking at it , you 'd think that was happening all the time , all over africa , but this is about what 's happening in the horn of africa . and i 'm still trying to make sense of africa in a piece of wonder bread . i 'm wondering about that . germaine greer has wondered about the same things and she says , `` at breakfast and at dinner , we can sharpen our own appetites with a plentiful dose of the pornography of war , genocide , destitution , and disease . '' she is right . we have sharpened our appetites , but we can also sharpen our insights . it is not always war , insurrection , and disease . this is a picture out of south sudan just a couple of months before the new country was born . i will continue to work as a researcher and a reporter in developing countries , but i do it with an altered ethic of seeing : i ask myself whether my pictures are pandering , whether they contribute to stereotypes , whether the images match the message , and am i complacent , or am i complicit ? thank you ( applause )
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this is a picture out of south sudan just a couple of months before the new country was born . i will continue to work as a researcher and a reporter in developing countries , but i do it with an altered ethic of seeing : i ask myself whether my pictures are pandering , whether they contribute to stereotypes , whether the images match the message , and am i complacent , or am i complicit ? thank you ( applause )
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dodson says she now approaches her work with an “ altered ethic of seeing. ” what kinds of questions is she now asking herself ?
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i 'm changing my tie to an alkali metal tie . you have an alkali metal tie ? it 's a new tie i just got . this one 's a dutch one . i was given it on saturday so here you can see we have the alkali metals ( and where are they ? ) here . and the alkali metals are very reactive . so , we 've seen that lithium does n't react very much but then as you go to sodium and then to potassium and rubidium the violence of the reaction gets more and more and more . in cesium it 's even greater . i do n't know wether the people making this tie were so frightened that they did n't put it on . but in each of these cases the reaction is removing one electron after another , one electron from the outer shell of the atom , and the bigger the atom , the easier it is to remove the electron . and as you go down the periodic table , the size of the atom increases so it 's easier to remove the electron . so francium would almost certainly be even bigger than cesium , because it 's a whole row lower down . and so , that should react with water with enormous violence . but , unfortunately , francium is very radioactive and you ca n't get a nice lump of francium the sort of size that you 'd like to throw in water to make the youtube video of the century . francium was named after france , was discovered by one of madame curie 's pupils in 1939 , five years after madame curie herself died . i always thought it was madame curie herself that discovered it but in fact it was discovered after her death . but its properties would probably be similar to those of cesium if it was not very radioactive . but radioactivity like that makes it very difficult for chemists to study the chemistry in enormous detail . chemical reactions are really quite sensitive to temperature and radioactive materials , as they decay , give out energy so the compounds themselves tend to heat up . a lump of plutonium , which is very radioactive , is really quite warm to touch . and francium , which i think is more radioactive , is probably very warm . so i think the melting point of francium will be lower than that of cesium because the melting points go down the group , and because it will be generating heat , almost certainly francium will be liquid at room temperature . but i 've never seen it . it might well be colored , as well , because cesium is golden colored so i would not be surprised if francium was red . but i have no idea . and i 'm not sure if anybody knows . . . . . . . . . . . . . captions by www.subply.com
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here . and the alkali metals are very reactive . so , we 've seen that lithium does n't react very much but then as you go to sodium and then to potassium and rubidium the violence of the reaction gets more and more and more .
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what is the correct order in increasing atomic radius of alkaline metals ?
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lanthanum is the first element in a series called the ‘ rare earths ’ . they are not terribly rare but never-the-less they are called rare earths and they all have rather similar names so there is quite an amusing little rhyme , mnemonic , that people learn to remember the names which at the first two letters of each word tell you this chemical symbol the elements so this goes ‘ language centres praise ned ’ s promise of small european garden tubs . dinosaurs hobble erotically thrumming yellow lutes ’ , which takes us from lanthanum all the way to lutetium . lanthanum is the largest of the lanthanides . it ’ s a prototype for the lanthanide series and because it is the largest it is the most reactive . it ’ s a strange metal in that you can actually cut it with a knife . so it ’ s not actually that hard . i haven ’ t worked much with lanthanum but one of my students or a russian visitor did some rather interesting experiments with making a compound of lanthanum and copper , so-called lanthanum cuprate , which is quite an interesting catalyst . lanthanum ’ s got quite a few technological uses . it ’ s used in , of all things , lighting in hollywood studios . lanthanum can also be used in hydrogen storage though obviously the hydrogen economy is becoming a very important issue with the energy crisis and so on and so forth ; and it ’ s , in certain circumstances , it ’ s very effective as what we called a hydrogen sponge so it can suck up all of the hydrogen and then hopefully you could use it as a fuel source . but because it ’ s quite heavy it might not be actually that useful in the end , but it ’ s good to know that it can do that .
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it ’ s used in , of all things , lighting in hollywood studios . lanthanum can also be used in hydrogen storage though obviously the hydrogen economy is becoming a very important issue with the energy crisis and so on and so forth ; and it ’ s , in certain circumstances , it ’ s very effective as what we called a hydrogen sponge so it can suck up all of the hydrogen and then hopefully you could use it as a fuel source . but because it ’ s quite heavy it might not be actually that useful in the end , but it ’ s good to know that it can do that .
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how could lanthanum be important in helping to solve the energy crisis ?
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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 .
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ah , it 's her younger brother , carlos . cotton-top tamarins often squeal during play wrestling . uh-oh .
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do cotton-tops learn how to give vocalizations in the appropriate social context ? explain .
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denis diderot left a dungeon outside paris on november 3 , 1749 . he 'd had his writing burned in public before , but this time , he 'd gotten locked up under royal order for an essay about a philosopher 's death bed rejection of god . to free himself , denis promised never to write things like that again . so he got back to work on something a little like that , only way worse , and much bigger . in 1745 , publisher andré le breton had hired diderot to adapt the english cyclopedia , or a universal dictionary of arts and sciences for french subscribers . a broke writer , diderot survived by translating , tutoring , and authoring sermons for priests , and a pornographic novel once . le breton paired him with co-editor jean le rond d'alembert , a math genius found on a church doorstep as a baby . technical dictionaries , like the cyclopedia , were n't new , but no one had attempted one publication covering all knowledge , so they did . the two men organized the french enlightenment 's brightest stars to produce the first encyclopedia , or rational dictionary of the arts , sciences , and crafts . assembling every essential fact and principle in , as it turned out , over 70,000 entries , 20,000,000 words in 35 volumes of text and illustrations created over three decades of researching , writing , arguging , smuggling , backstabbing , law-breaking , and alphabetizing . to organize the work , diderot adapted francis bacon 's `` classification of knowledge '' into a three-part system based on the mind 's approaches to reality : memory , reason , and imagination . he also emphasized the importance of commerce , technology , and crafts , poking around shops to study the tools and techniques of parisian laborers . to spotlight a few of the nearly 150 philosoph contributers , jean jacques rousseau , diderot 's close friend , wrote much of the music section in three months , and was never reimbursed for copy fees . his entry on political economy holds ideas he 'd later develop further in `` the social contract . '' d'alembert wrote the famous preliminary discourse , a key statement of the french enlightenment , championing independent investigative reasoning as the path to progress . louis de jaucourt wrote a quarter of the encyclopedia , 18,000 articles , 5,000,000 words , unpaid . louis once spent 20 years writing a book on anatomy , shipped it to amsterdam to be published uncensored , and the ship sank . voltaire contributed entries , among them history , elegance , and fire . diderot 's entries sometimes exhibit slight bias . in `` political authority , '' he dismantled the divine right of kings . under `` citizen , '' he argued a state was strongest without great disparity in wealth . not surprising from the guy who wrote poetry about mankind strangling its kings with the entrails of a priest . so diderot 's masterpiece was n't a hit with the king or highest priest . upon release of the first two volumes , louie xv banned the whole thing but enjoyed his own copy . pope clement xiii ordered it burned . it was `` dangerous , '' `` reprehensible , '' as well as `` written in french , '' and in `` the most seductive style . '' he declared readers excommunicated and wanted diderot arrested on sight . but diderot kept a step ahead of being shut down , smuggling proofs outside france for publication , and getting help from allies in the french regime , including the king 's mistress , madame de pompadour , and the royal librarian and censor , malesherbes , who tipped diderot off to impending raids , and even hid diderot 's papers at his dad 's house . still , he faced years of difficulty . d'alembert dropped out . rousseau broke off his friendship over a line in a play . worse yet , his publisher secretly edited some proofs to read less radically . the uncensored pages reappeared in russia in 1933 , long after diderot had considered the work finished and died at lunch . the encyclopedia he left behind is many things : a cornerstone of the enlightenment , a testament to france 's crisis of authority , evidence of popular opinions migration from pulpit and pew to cafe , salon , and press . it even has recipes . it 's also irrepressibly human , as you can tell from diderot 's entry about a plant named aguaxima . read it yourself , preferably out loud in a french accent .
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d'alembert wrote the famous preliminary discourse , a key statement of the french enlightenment , championing independent investigative reasoning as the path to progress . louis de jaucourt wrote a quarter of the encyclopedia , 18,000 articles , 5,000,000 words , unpaid . louis once spent 20 years writing a book on anatomy , shipped it to amsterdam to be published uncensored , and the ship sank .
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who didn ’ t contribute to the encyclopedia ?
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why can ’ t i just get on a plane and go from , like , montana to london , in a couple hours ? i just want to experience the thrill of zooming through the sky faster than the speed of sound ? well , if you flew on a concorde jet back before they were grounded -- or you happen to be a fighter pilot -- then you ’ ve probably experienced faster-than-sound travel . and , some companies are looking to make supersonic flight a reality again , with new commercial planes that travel faster than the speed of sound . and someday , you might be able to fly over the atlantic ocean in an hour -- or even less . problem is , most people don ’ t want to fly on a plane that feels like an out-of-control rocket . and there ’ s also the problem of faster-than-sound planes becoming ridiculously hot and unbearably loud . so engineers have some developing to do . on the morning of december 17th , 1903 , orville wright became the first human to successfully pilot an airplane -- a heavier-than-air vehicle that was controlled , powered , and sustained . his flight lasted 12 seconds , and crossed 120 feet of a north carolinian beach -- with an average speed of almost 11 kilometers an hour . by the end of the day , his brother wilbur flew the same airplane for almost a whole minute , with an average speed of almost 16 kilometers an hour . less than a century later , in the 1970s , commercial planes went supersonic -- faster than the speed of sound . a few dozen supersonic planes were in regular service , available in two models , the concorde and the soviet tupolev . but the tupolev only made 55 passenger flights , from 1977 to 1978 . and after a concorde crashed in 2000 , people started to fly on them less . eventually , they just weren ’ t financially worth it anymore , and the planes were retired in 2003 . 13 years later , there still aren ’ t any new commercial faster-than-sound planes . but soon , there might be ! there are just a couple of improvements companies are trying to make first . the main challenge comes from getting past what ’ s known as mach 1 . see , sound usually travels around 1230 kilometers per hour , but that ’ s not a constant number -- it depends on things like the temperature and humidity of the air . so , when it comes to planes , it ’ s easier to talk about speed in mach numbers , which take into account the speed of sound in the particular place where the plane is flying.. mach 1 is just the speed of sound . anything slower than that is called subsonic , and anything faster is called supersonic . but switching from subsonic to supersonic isn ’ t easy , because the plane has to overcome the infamous sound barrier . and that can be a problem , because the sound barrier is sometimes strong enough to tear away at planes , and even send them crashing to the ground . the sound barrier exists because of the way sound waves travel : by compressing and stretching the air they travel through . the compressed air ends up at a higher pressure , and the stretched air has lower pressure . as a plane moves , it produces sound waves that shift the air back and forth , creating areas of lower and higher pressure . but as the plane gets faster , it starts to catch up with those waves . new sound waves start to form on top of the old sound waves , causing huge swings between higher and lower pressure air . those differences in pressure can rattle and shake planes like toys , and there ’ s a real danger of tearing them to pieces . low pressure areas can also lead to drops in temperature , condensing any moisture in the air and forming a visible cloud , sometimes known as a vapor cone . the first plane that could get past the sound barrier was the bell x-1 , built in 1947 . it was designed to absorb 18 times the force of gravity , and modeled after a machine gun bullet . it didn ’ t actually lift off from the ground on the zone , though -- it was dropped from a larger mothership plane , known as the b-29 , so it got a bit of a head start . by the mid-1970s , supersonic planes were ready for commercial use -- with the uk and france designing the concorde , and the soviet union designing the tupolev . the concorde flew passengers from london to new york in about three and a half hours -- about half the time it would take in a plain old subsonic commercial plane . but they only flew that one route , and there ’ s a reason they spent as much time over the water as possible : the painfully disruptive sonic boom . like the sound barrier , sonic booms come from a build-up of compressed sound waves , known as a shock wave . the shock wave heads away from the plane , which you hear as a very loud boom -- so powerful that they ’ re sometimes mistaken for earthquakes . and those sonic booms don ’ t just happen once , like when a plane breaks the sound barrier . they continue throughout the entire supersonic flight . that ’ s because the sound waves keep bunching up behind the plane , then expanding outwards , creating a cone shape known as the mach cone . so wherever the plane flies over land , people hear that incredibly loud boom . so that ’ s why the concorde ’ s supersonic commercial flights only really happened between western europe and eastern north america . if they flew over land , odds are people would not have appreciated the booms . and even though you can ’ t fly on a concorde anymore , you might still be able to fly on a supersonic plane someday . nasa , for example , is looking into how to dampen the effects of the sonic boom . one way to do that might be by moving one , or even two engines above the wings , which would direct shockwaves upwards . so the sonic booms would happen in the sky , rather than on the ground . then there ’ s the concorde 2 , which airbus is working on . the concorde 2 would first fly directly upward , to an altitude of about 30 kilometers . then , the plane would rotate its tail fin in a way that would redirect the shock waves to be horizontal , so you wouldn ’ t feel them as much on the ground . the concorde 2 would be able to accelerate up to mach 4.5 -- and at those speeds , it could take passengers from london to new york in an hour . but maybe that ’ s not enough , what if you want to go faster ? the concorde 2 would be very close to going beyond supersonic , and into an even faster category , known as hypersonic . when people talk about hypersonic speeds , they ’ re generally talking about mach 5 or higher -- more than five times the speed of sound . those speeds get their own category , because that ’ s when the temperature of the plane becomes a bigger issue . the plane is flying through the air so quickly that friction with particles in the air is a real problem , because it makes a lot of heat . at hypersonic speeds , planes need to be able to withstand temperatures over 1000 degrees celsius… but almost all of the more typical metals would melt , or at least become very weak , at temperatures below that . the other challenge is the engine , because a regular jet engine wouldn ’ t work . standard , subsonic planes use large rotating blades to compress incoming air , inject fuel , and then let it burn . propelling them forward . at supersonic speeds , it becomes even easier , because the high speeds already compress the air . in that case , the engine doesn ’ t even need the blades -- that ’ s what ’ s known as a ramjet engine . ram , because the air is just rammed into the engine . at hypersonic speeds , though , this plan doesn ’ t work as well . sure , the air is compressed , but it ’ s moving so fast that there ’ s not enough time for it to combust and actually help move the plane . so hypersonic planes need their own fuel and their own oxygen -- which is what nasa used in the x-15 , the first plane to reach hypersonic speeds . it used a titanium skin to protect itself from the extreme temperatures , and was able to fly at mach 6.72 . it also flew high enough that some of the x-15 test flights are considered space flights . but the x-15 is not the kind of plane that could be used commercially . for one thing , it burned through fuel so fast that it would run out in less than two minutes . also , pilots sometimes experienced 8 times the force of earth ’ s gravity , and most people wouldn ’ t consider that a comfortable business trip . so , until engines became more efficient and practical , commercial hypersonic planes are a long way from reality . and the scramjet might be the answer . scramjet engines work kind of like ramjets do , but they ’ re designed to handle the faster-moving air . in testing , nasa ’ s found that they could work at speeds up to mach 15 , at least in theory . there ’ s one big drawback , though : scramjet engines only work at hypersonic speeds . the x-43a , for example , an unmanned test plane that uses a scramjet , has to be accelerated above mach 5 before it can fly on its own . it ’ s strapped to a booster rocket , which is then loaded onto a subsonic plane . alright , stay with me ... the plane flies up to about 6 kilometers above the ground , then releases the x-43a , along with the rocket , which gets to about 30 kilometers up and to speeds of mach 5 . then the x-43a can start its flight . so , it might be a while before hypersonic planes are a practical way to get across the atlantic . but a future where a trip to the other side of the world involves flying faster than the speed of sound , without painful sonic booms for the people on the ground ? that might not be so far off . thanks for watching this episode of scishow , which was brought to you by our patrons on patreon . thank you patrons on patreon . if you wan na become one of those people , you can go to patreon.com/scishow . and don ’ t forget to go to youtube.com/scishow and subscribe !
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in testing , nasa ’ s found that they could work at speeds up to mach 15 , at least in theory . there ’ s one big drawback , though : scramjet engines only work at hypersonic speeds . the x-43a , for example , an unmanned test plane that uses a scramjet , has to be accelerated above mach 5 before it can fly on its own .
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what is currently the major drawback preventing the scramjet engine from being used for commercial flight ?
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for most of human history , medical workers sought to treat diseases or cure them . the rise of vaccination in the 19th century enhanced the potential to prevent people from contracting illnesses in the first place . but only in recent decades did it become possible to ensure that a particular disease never threatens humanity again . the story of smallpox , the first and , so far , the only disease to be permanently eradicated from the world , shows how disease eradication can happen and why it is so difficult to achieve . smallpox emerged in human populations thousands of years ago as a contagious virus that spread rapidly , primarily through close , face to face contact , causing fever , aches and rashes . it killed up to 30 % of its victims and often left survivors with life-long disfiguring scars . the devastating impact of smallpox was so great that several cultures had religious deities specifically dedicated to it . in the 20th century alone , it is estimated to have killed more than 300 million people worldwide . with the effective deployment of vaccination , the number of cases began to decrease . by seeking out infected individuals , isolating them , and vaccinating their contacts to prevent further transmission , scientists realized that the spread of the disease could be haulted . in fact , because smallpox could only survive in human hosts , vaccinating all of an infected persons ' potential contacts would stop the virus dead in its tracks and eliminate it from that region . once this strategy had succeeded in ridding most industrialized countries from disease , health officials realized that eradicating it worldwide was within reach . but this was not an easy process , proving especially difficult in places suffering from poor infrastructure or civil wars . the eradication effort took decades and involved millions of people working together , from world leaders and international organizations to rural doctors and community workers . in india , one of the last strongholds of the disease , health workers visited every one of the country 's 100 million households to search for cases . through this unprecedented worldwide effort , in which even rival superpowers cooperated , smallpox was finally declared eradicated in 1980 , saving approximately 40 million lives over the following two decades . there were several factors that made smallpox an ideal candidate for eradication . first , humans are essential to the smallpox lifecycle , so breaking the chain of human to human transmission causes the virus to die out . in contrast , many other pathogens , like ebola or the bubonic plague , can survive in animal carriers , while the bacteria that cause tetanus can even live in the soil . secondly , individuals infected with smallpox displayed a characteristic rash , making them easy to identify , even without a lab test . the lack of such practical diagnostic tools for diseases with non-specific symptoms , or that have long incubation periods , such as aids , makes their eradication more difficult . third , the availability of a smallpox vaccine that provided immunity for five to ten years in a single dose meant that there was an effective intervention to stop the virus from spreading . and finally , the initial success of several countries in eliminating the disease within their borders served as a proof of principle for its eradication worldwide . today , the same criteria are applied to determine whether other diseases can be similarly eliminated . and even though smallpox remains the only success story thus far , several other pathogens may be next in line . great progress has been made towards eradicating guinea worm disease simply by use of water filters . and vaccination for polio , which previously disabled hundreds of thousands of people each year is estimated to have prevented 13 million cases of paralysis , and 650,000 deaths since 1988 . with a 99 % drop in infections since the eradication effort began , one final push is all that is needed to ensure that polio will never paralyze another child . disease eradication is one public health effort that benefits all of humanity and challenges us to work together as a global community . beyond eliminating specific diseases , eradication programs benefit local populations by improving health infrastructure . for example , nigeria recently used facilities and personnel from their polio eradication program to effectively control an ebola outbreak . further more , globalization and international travel means that even a single infection anywhere in the world can potentially spread to other regions . by helping to protect others , we help to protect ourselves . disease eradication is the ultimate gift we can give to everyone alive today , as well as all future generations of humanity .
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secondly , individuals infected with smallpox displayed a characteristic rash , making them easy to identify , even without a lab test . the lack of such practical diagnostic tools for diseases with non-specific symptoms , or that have long incubation periods , such as aids , makes their eradication more difficult . third , the availability of a smallpox vaccine that provided immunity for five to ten years in a single dose meant that there was an effective intervention to stop the virus from spreading .
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there have been efforts to eradicate malaria in the past . what makes this task difficult ?
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how fast are you moving right now ? that seems like an easy question . the first tempting answer is , `` i 'm not moving . '' upon further reflection , you realize that maybe the earth 's motion counts . so , a second tempting answer is , `` 19 miles/second around the sun . '' but then you recall learning that the sun moves around the center of the milky way galaxy , and the milky way moves within the local group of galaxies , and the local group moves within the virgo cluster , and the virgo cluster moves within ... `` how fast are you moving ? '' is not an easy question . when mission control tells astronauts how fast they 're going , there 's always an assumed standard of rest . at the start of the voyage , speeds are given relative to the launchpad . but later , when the launchpad is just one more arbritrary place down there on earth 's spinning surface , speeds are given relative to the idealized , non-spinning pinpoint center of earth . on their way to the moon , apollo astronauts had a hard time answering the question , `` how fast are you moving ? '' speed away from earth was one thing , and speed toward the moon was quite another . that 's because the earth and the moon move relative to one another . ah , of course ! speed is a relative quantity . when captain kirk ask lieutenant sulu if the starship enterprise has reached a speed of warp 7 , sulu should reply , `` relative to what , captain ? '' such a sassy reply may get subordinate starfleet officers in trouble , but it is the only good answer to the question , `` how fast are you moving ? '' this is basic relatively talking . not fancy einsteinian relativity , but good old fashioned ( and still correct ) galilean relativity . galileo seems to have been the first person to realize that there is no such thing as an absolute speed . speeds are relative . this means that speeds only have meaning when they are referred to a reference frame . presumably that reference frame is itself at rest . but then we have to ask again , `` at rest relative to what ? '' because even the concept of rest has lost any hint of absolute meaning . speed is relative , and rest is relative . earth 's speed is 19 miles/second relative to the sun . the enterprise 's speed is warp 7 relative to the center of the milky way galaxy . your speed is zero relative to your easy chair . but depending on where you sit , it is hundreds of miles/hour relative to earth 's center . when we furrow a brow and ask , `` but how fast is earth really moving ? '' we imagine spaceship earth plowing through the ocean of space as it orbits the sun . but space is not an ocean . it has no substance as water does . space is not a thing ; space is nothing . space is no thing . you can move between two points in space , say between earth and mars , but you ca n't move through space . there 's nothing to move through . it 's like trying to say how much a hole weighs . a hole weighs exactly nothing because a hole is nothing . it 's a void , and so is space . to move relative to nothing is meaningless . the concepts of speed and of rest have only relative meaning . they are absolutely meaningless . they mean something only with respect to arbitrarily chosen , artificial frames of reference . if , someday , you are buckled into your spaceship , and you see from the side window , say , a space station whizz by at constant speed , there is no way to know which of you is really moving . neither of you is really moving because there is no deep reality about constant speed . constant speed in a straight line has only relative meaning , a kind of relative reality . does this mean that all motion is relative ? no ! some motions have only relative meaning , but some motions have absolute meaning , are absolutely real . for example , constant speed is relative , but change in speed is absolute . calling something absolute in science means that arbitrary standards are not used in its measurement . it is unambiguously measurable . when your spaceship fires its engines , your change in speed is beyond doubt . you feel it in your stomach , and your ship 's sensors can measure it . outside your window , the passing space station may seem to be changing speed , but the beings inside the station will not feel it . and no sensors can measure it . you are really changing speed , and they are really are not . there 's something absolutely real about changes in speed . the same goes for rotation . if your spaceship is spinning , you can feel it , and your ship 's sensors can measure it . the space station outside may seem to be going around you , but it is you who feels queasy , not the folks in the space station . you are really spinning , and they really are not . there 's something absolutely real about rotation . so , some motions are relative , and some are not . there is no deep reality about constant speed , but changes in speed are deeply real , and so are rotations . we have to be thoughtful in our analysis of everyday experience in order to identify what is deeply real . since we can be fooled by perceptions as basic as speed , maybe every perception deserves careful scrutiny . this is what inspired einstein to his incredible insights about the speed of light and forward time travel . knowing how to identify what is deeply real is tough and important work . if a police officer ever pulls you over for speeding and asks , & amp ; amp ; quot ; do you know how fast you were going ? & amp ; amp ; quot ; an insightful , though perhaps unwise , reply would be , `` relative to what ? '' and then , as you sit in the backseat of the police car and feel it accelerate toward jail , you can add , & amp ; amp ; quot ; but some things are absolute ! & amp ; amp ; quot ;
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galileo seems to have been the first person to realize that there is no such thing as an absolute speed . speeds are relative . this means that speeds only have meaning when they are referred to a reference frame .
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will the day ever come when knowing that all speeds are relative is intuitive and does not have to be learned ? what future experiences might help such intuition to develop in early childhood ?
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translator : tom carter reviewer : bedirhan cinar this is the story of an invention that changed the world . imagine a machine that could cut 10 hours of work down to one . a machine so efficient that it would free up people to do other things , kind of like the personal computer . but the machine i 'm going to tell you about did none of this . in fact , it accomplished just the opposite . in the late 1700s , just as america was getting on its feet as a republic under the new u.s constitution , slavery was a tragic american fact of life . george washington and thomas jefferson both became president while owning slaves , knowing that this peculiar institution contradicted the ideals and principles for which they fought a revolution . but both men believed that slavery was going to die out as the 19th century dawned , they were , of course , tragically mistaken . the reason was an invention , a machine they probably told you about in elementary school : mr. eli whitney 's cotton gin . a yale graduate , 28-year-old whitney had come to south carolina to work as a tutor in 1793 . supposedly he was told by some local planters about the difficulty of cleaning cotton . separating the seeds from the cotton lint was tedious and time consuming . working by hand , a slave could clean about a pound of cotton a day . but the industrial revolution was underway , and the demand was increasing . large mills in great britain and new england were hungry for cotton to mass produce cloth . as the story was told , whitney had a `` eureka moment '' and invented the gin , short for engine . the truth is that the cotton gin already existed for centuries in small but inefficient forms . in 1794 , whitney simply improved upon the existing gins and then patented his `` invention '' : a small machine that employed a set of cones that could separate seeds from lint mechanically , as a crank was turned . with it , a single worker could eventually clean from 300 to one thousand pounds of cotton a day . in 1790 , about 3,000 bales of cotton were produced in america each year . a bale was equal to about 500 pounds . by 1801 , with the spread of the cotton gin , cotton production grew to 100 thousand bales a year . after the destructions of the war of 1812 , production reached 400 thousand bales a year . as america was expanding through the land acquired in the louisiana purchase of 1803 , yearly production exploded to four million bales . cotton was king . it exceeded the value of all other american products combined , about three fifths of america 's economic output . but instead of reducing the need for labor , the cotton gin propelled it , as more slaves were needed to plant and harvest king cotton . the cotton gin and the demand of northern and english factories re-charted the course of american slavery . in 1790 , america 's first official census counted nearly 700 thousand slaves . by 1810 , two years after the slave trade was banned in america , the number had shot up to more than one million . during the next 50 years , that number exploded to nearly four million slaves in 1860 , the eve of the civil war . as for whitney , he suffered the fate of many an inventor . despite his patent , other planters easily built copies of his machine , or made improvements of their own . you might say his design was pirated . whitney made very little money from the device that transformed america . but to the bigger picture , and the larger questions . what should we make of the cotton gin ? history has proven that inventions can be double-edged swords . they often carry unintended consequences . the factories of the industrial revolution spurred innovation and an economic boom in america . but they also depended on child labor , and led to tragedies like the triangle shirtwaist fire that killed more than 100 women in 1911 . disposable diapers made life easy for parents , but they killed off diaper delivery services . and do we want landfills overwhelmed by dirty diapers ? and of course , einstein 's extraordinary equation opened a world of possibilities . but what if one of them is hiroshima ?
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with it , a single worker could eventually clean from 300 to one thousand pounds of cotton a day . in 1790 , about 3,000 bales of cotton were produced in america each year . a bale was equal to about 500 pounds .
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before the cotton gin was widely available , the american slave population was 700,000 in 1790. by 1860 , the narrator says , the slave population was :
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what do an ancient greek philosopher and a 19th century quaker have in common with nobel prize-winning scientists ? although they are separated over 2,400 years of history , each of them contributed to answering the eternal question : what is stuff made of ? it was around 440 bce that democritus first proposed that everything in the world was made up of tiny particles surrounded by empty space . and he even speculated that they vary in size and shape depending on the substance they compose . he called these particles `` atomos , '' greek for indivisible . his ideas were opposed by the more popular philosophers of his day . aristotle , for instance , disagreed completely , stating instead that matter was made of four elements : earth , wind , water and fire , and most later scientists followed suit . atoms would remain all but forgotten until 1808 , when a quaker teacher named john dalton sought to challenge aristotelian theory . whereas democritus 's atomism had been purely theoretical , dalton showed that common substances always broke down into the same elements in the same proportions . he concluded that the various compounds were combinations of atoms of different elements , each of a particular size and mass that could neither be created nor destroyed . though he received many honors for his work , as a quaker , dalton lived modestly until the end of his days . atomic theory was now accepted by the scientific community , but the next major advancement would not come until nearly a century later with the physicist j.j. thompson 's 1897 discovery of the electron . in what we might call the chocolate chip cookie model of the atom , he showed atoms as uniformly packed spheres of positive matter filled with negatively charged electrons . thompson won a nobel prize in 1906 for his electron discovery , but his model of the atom did n't stick around long . this was because he happened to have some pretty smart students , including a certain ernest rutherford , who would become known as the father of the nuclear age . while studying the effects of x-rays on gases , rutherford decided to investigate atoms more closely by shooting small , positively charged alpha particles at a sheet of gold foil . under thompson 's model , the atom 's thinly dispersed positive charge would not be enough to deflect the particles in any one place . the effect would have been like a bunch of tennis balls punching through a thin paper screen . but while most of the particles did pass through , some bounced right back , suggesting that the foil was more like a thick net with a very large mesh . rutherford concluded that atoms consisted largely of empty space with just a few electrons , while most of the mass was concentrated in the center , which he termed the nucleus . the alpha particles passed through the gaps but bounced back from the dense , positively charged nucleus . but the atomic theory was n't complete just yet . in 1913 , another of thompson 's students by the name of niels bohr expanded on rutherford 's nuclear model . drawing on earlier work by max planck and albert einstein he stipulated that electrons orbit the nucleus at fixed energies and distances , able to jump from one level to another , but not to exist in the space between . bohr 's planetary model took center stage , but soon , it too encountered some complications . experiments had shown that rather than simply being discrete particles , electrons simultaneously behaved like waves , not being confined to a particular point in space . and in formulating his famous uncertainty principle , werner heisenberg showed it was impossible to determine both the exact position and speed of electrons as they moved around an atom . the idea that electrons can not be pinpointed but exist within a range of possible locations gave rise to the current quantum model of the atom , a fascinating theory with a whole new set of complexities whose implications have yet to be fully grasped . even though our understanding of atoms keeps changing , the basic fact of atoms remains , so let 's celebrate the triumph of atomic theory with some fireworks . as electrons circling an atom shift between energy levels , they absorb or release energy in the form of specific wavelengths of light , resulting in all the marvelous colors we see . and we can imagine democritus watching from somewhere , satisfied that over two millennia later , he turned out to have been right all along .
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experiments had shown that rather than simply being discrete particles , electrons simultaneously behaved like waves , not being confined to a particular point in space . and in formulating his famous uncertainty principle , werner heisenberg showed it was impossible to determine both the exact position and speed of electrons as they moved around an atom . the idea that electrons can not be pinpointed but exist within a range of possible locations gave rise to the current quantum model of the atom , a fascinating theory with a whole new set of complexities whose implications have yet to be fully grasped .
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bohr ’ s “ planetary model ” states that electrons are in specific energy levels or “ orbits ” around the nucleus . explain how this is not possible using heisenberg ’ s uncertainty principle .
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ok so gadolinium is smack-bang in the middle of the 4f series . it ’ s perhaps most famous for the fact that it ’ s used as a contrast reagent in mri machines . so if you need a full body scan , a doctor will come along an inject you with a solution which contains a bit of gadolinium and what it basically does is that it changes the way that molecules , water molecules react in your body when they are scanned and then you can see the contrast between healthy tissue and , perhaps , unhealthy tissue and then that aids the doctors in their assignment . the thing about the lanthanide series is that it ’ s probably the best example of a smooth contraction in size as you move from the left-hand side to the right-hand side and you lose about 25 % of the radius of the atoms as you move from the left to the right and this is called the ‘ lanthanide contraction. ’ this is actually what ’ s responsible for 2nd and 3rd row transition metals having very similar types of chemistry by group even though actually they should be quite different . the 3rd row should be much larger but , because of the ‘ lanthanide contraction ’ , that increase in size is counterbalanced so they actually end up being more- or-less the same size as their 2nd row counterparts . even chemists sometimes wonder how people can get excited about particular parts of chemistry , and the rare earth elements are elements which , those who are not working in the area don ’ t always see why it can be very exciting . so when i was a student i saw an advertisement in the lab where i was working about a lecture about the oxidation states of the rare earth elements , and the relative stability of two of the oxidation states by a chemist called david johnson , who in those days worked for the open university . and , i went to this lecture because i couldn ’ t imagine how anybody could make it interesting , and it was really fascinating ! he was so enthusiastic and so on , by the end , i rushed out really quite excited i went and bought this book which has been sitting on my bookshelf ever since and has been quite useful for teaching some of my students .
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ok so gadolinium is smack-bang in the middle of the 4f series . it ’ s perhaps most famous for the fact that it ’ s used as a contrast reagent in mri machines . so if you need a full body scan , a doctor will come along an inject you with a solution which contains a bit of gadolinium and what it basically does is that it changes the way that molecules , water molecules react in your body when they are scanned and then you can see the contrast between healthy tissue and , perhaps , unhealthy tissue and then that aids the doctors in their assignment .
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gadolinium is famous for its use in magnetic resonance imaging ( mri ) . what is its role in mri ?
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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 .
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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 .
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the 5th century soldier who deposed the western emperor was :
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fish are in trouble . the cod population off canada 's east coast collapsed in the 1990s , intense recreational and commercial fishing has decimated goliath grouper populations in south florida , and most populations of tuna have plummeted by over 50 % , with the southern atlantic bluefin on the verge of extinction . those are just a couple of many examples . overfishing is happening all over the world . how did this happen ? when some people think of fishing , they imagine relaxing in a boat and patiently reeling in the day 's catch . but modern industrial fishing , the kind that stocks our grocery shelves , looks more like warfare . in fact , the technologies they employ were developed for war . radar , sonar , helicopters , and spotter planes are all used to guide factory ships towards dwindling schools of fish . long lines with hundreds of hooks or huge nets round up massive amounts of fish , along with other species , like seabirds , turtles , and dolphins . and fish are hauled up onto giant boats , complete with onboard flash freezing and processing facilities . all of these technologies have enabled us to catch fish at greater depths and farther out at sea than ever before . and as the distance and depth of fishing have expanded , so has the variety of species we target . for example , the patagonian toothfish neither sounds nor looks very appetizing . and fishermen ignored it until the late 1970s . then it was rebranded and marketed to chefs in the u.s. as chilean sea bass , despite the animal actually being a type of cod . soon it was popping up in markets all over the world and is now a delicacy . unfortunately , these deep water fish do n't reproduce until they 're at least ten years old , making them extremely vulnerable to overfishing when the young are caught before they 've had the chance to spawn . consumer taste and prices can also have harmful effects . for example , shark fin soup is considered such a delicacy in china and vietnam that the fin has become the most profitable part of the shark . this leads many fishermen to fill their boats with fins leaving millions of dead sharks behind . the problems are n't unique to toothfish and sharks . almost 31 % of the world 's fish populations are overfished , and another 58 % are fished at the maximum sustainable level . wild fish simply ca n't reproduce as fast as 7 billion people can eat them . fishing also has impacts on broader ecosystems . wild shrimp are typically caught by dragging nets the size of a football field along the ocean bottom , disrupting or destroying seafloor habitats . the catch is often as little as 5 % shrimp . the rest is by-catch , unwanted animals that are thrown back dead . and coastal shrimp farming is n't much better . mangroves are bulldozed to make room for shrimp farms , robbing coastal communities of storm protection and natural water filtration and depriving fish of key nursery habitats . so what does it look like to give fish a break and let them recover ? protection can take many forms . in national waters , governments can set limits about how , when , where , and how much fishing occurs , with restrictions on certain boats and equipment . harmful practices , such as bottom trawling , can be banned altogether , and we can establish marine reserves closed to all fishing to help ecosystems restore themselves . there 's also a role for consumer awareness and boycotts to reduce wasteful practices , like shark finning , and push fishing industries towards more sustainable practices . past interventions have successfully helped depleted fish populations recover . there are many solutions . the best approach for each fishery must be considered based on science , respect for the local communities that rely on the ocean , and for fish as wild animals . and then the rules must be enforced . international collaboration is often needed , too , because fish do n't care about our borders . we need to end overfishing . ecosystems , food security , jobs , economies , and coastal cultures all depend on it .
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fish are in trouble . the cod population off canada 's east coast collapsed in the 1990s , intense recreational and commercial fishing has decimated goliath grouper populations in south florida , and most populations of tuna have plummeted by over 50 % , with the southern atlantic bluefin on the verge of extinction . those are just a couple of many examples .
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by what percent has the amount of tuna decreased globally since 1950 ?
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the earliest known pregnancy test dates back to 1350 bc in ancient egypt . according to the egyptians , all you have to do is urinate on wheat and barley seeds , and wait . if either sprouts , congratulations , you 're pregnant ! and if wheat sprouts faster , it 's a girl , but if barley , it 's a boy . in 1963 , a small study reproduced this test and found that it predicted pregnancy with a respectable 70 % accuracy , though it could n't reliably tell the sex of the baby . scientists hypothesized that the test worked because pregnant women 's urine contains more estrogen , which can promote seed growth . now it 's easy to take this ancient method for granted because modern pregnancy tests give highly accurate results within minutes . so how do they work ? over-the-counter pregnancy tests are all designed to detect one thing : a hormone called hcg . hcg is produced in the earliest stages of pregnancy and starts a game of telephone that tells the body not to shed the inner lining of the uterus that month . as the pregnancy progresses , hcg supports the formation of the placenta , which transfers nutrients from mother to fetus . the test starts when urine is applied to the exposed end of the strip . as the fluid travels up the absorbent fibers , it will cross three separate zones , each with an important task . when the wave hits the first zone , the reaction zone , y-shaped proteins called antibodies will grab onto any hcg . attached to these antibodies is a handy enzyme with the ability to turn on dye molecules , which will be crucial later down the road . then the urine picks up all the ab1 enzymes and carries them to the test zone , which is where the results show up . secured to this zone are more y-shaped antibodies that will also stick to hcg on one of its five binding sites . scientists call this type of test a sandwich assay . if hcg is present , it gets sandwiched between the ab1 enzyme and ab2 , and sticks to the test zone , allowing the attached dye-activating enzyme to do its job and create a visible pattern . if there 's no hcg , the wave of urine and enzymes just passes on by . finally , there 's one last stop to make , the control zone . as in any good experiment , this step confirms that the test is working properly . whether the ab1 enzymes never saw hcg , or they 're extras because zone 1 is overstocked with them , all the unbound ab1 enzymes picked up in zone 1 should end up here and activate more dye . so if no pattern appears , that indicates that the test was faulty . these tests are pretty reliable , but they 're not failproof . for instance , false negatives can occur if concentrations of hcg are n't high enough for detection . after implantation , hcg levels double every two to three days , so it may just be too early to tell . and beverages can dilute the urine sample , which is why doctors recommend taking the test first thing in the morning . on the other hand , false positives can come from other sources of hcg , like ivf injections , ectopic pregnancies , or certain cancers such as uterine cancer or testicular cancer , making it possible for one of these tests to tell a man he 's pregnant . the best way for a woman to find out for sure is at the doctor 's office . the doctors are also looking for hcg , but with tests that are more sensitive and quantitative , which means they can determine the exact level of hcg in your blood . a few minutes can feel like forever when you 're waiting on the results of a pregnancy test . but in that brief time , you 're witnessing the power of the scientific method . that one little stick lets you ask a question , perform a controlled experiment , and then analyze the results to check your original hypothesis . and the best part is you wo n't even have to wait until the next harvest .
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if there 's no hcg , the wave of urine and enzymes just passes on by . finally , there 's one last stop to make , the control zone . as in any good experiment , this step confirms that the test is working properly .
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what happens in the control zone of the test ?
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after witnessing the violent rage shown by babies whenever deprived of an item they considered their own , jean piaget , a founding father of child psychology , observed something profound about human nature . our sense of ownership emerges incredibly early . why are we so clingy ? there 's a well-established phenomenon in psychology known as the endowment effect where we value items much more highly just as soon as we own them . in one famous demonstration , students were given a choice between a coffee mug or a swiss chocolate bar as a reward for helping out with research . half chose the mug , and half chose the chocolate . that is , they seemed to value the two rewards similarly . other students were given a mug first and then a surprise chance to swap it for a chocolate bar , but only 11 % wanted to . yet another group started out with chocolate , and most preferred to keep it rather than swap . in other words , the students nearly always put greater value on whichever reward they started out with . part of this has to do with how quickly we form connections between our sense of self and the things we consider ours . that can even be seen at the neural level . in one experiment , neuroscientists scanned participants ' brains while they allocated various objects either to a basket labeled `` mine , '' or another labeled , `` alex 's . '' when participants subsequently looked at their new things , their brains showed more activity in a region that usually flickers into life whenever we think about ourselves . another reason we 're so fond of our possessions is that from a young age we believe they have a unique essence . psychologists showed us this by using an illusion to convince three to six-year-olds they built a copying machine , a device that could create perfect replicas of any item . when offered a choice between their favorite toy or an apparently exact copy , the majority of the children favored the original . in fact , they were often horrified at the prospect of taking home a copy . this magical thinking about objects is n't something we grow out of . rather it persists into adulthood while becoming ever more elaborate . for example , consider the huge value placed on items that have been owned by celebrities . it 's as if the buyers believed the objects they 'd purchased were somehow imbued with the essence of their former celebrity owners . for similar reasons , many of us are reluctant to part with family heirlooms which help us feel connected to lost loved ones . these beliefs can even alter our perception of the physical world and change our athletic abilities . participants in a recent study were told they were using a golf putter once owned by the champion ben curtis . during the experiment , they perceived the hole as being about a centimeter larger than controlled participants using a standard putter and they sank slightly more putts . although feelings of ownership emerge early in life , culture also plays a part . for example , it was recently discovered that hadza people of northern tanzania who are isolated from modern culture do n't exhibit the endowment effect . that 's possibly because they live in an egalitarian society where almost everything is shared . at the other extreme , sometimes our attachment to our things can go too far . part of the cause of hoarding disorder is an exaggerated sense of responsibility and protectiveness toward one 's belongings . that 's why people with this condition find it so difficult to throw anything away . what remains to be seen today is how the nature of our relationship with our possessions will change with the rise of digital technologies . many have forecast the demise of physical books and music , but for now , at least , this seems premature . perhaps there will always be something uniquely satisfying about holding an object in our hands and calling it our own .
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although feelings of ownership emerge early in life , culture also plays a part . for example , it was recently discovered that hadza people of northern tanzania who are isolated from modern culture do n't exhibit the endowment effect . that 's possibly because they live in an egalitarian society where almost everything is shared .
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the “ endowment effect ” describes our tendency to :
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you know , i had a real rough time in school with add , and i have a phd . i earned a phd , but ... tough to pay attention -- biology , geology , physics , chemistry -- really tough for me . only one thing grabbed my attention , and it 's that planet called earth . but in this picture here , you 'll see that earth is mostly water . that 's the pacific . seventy percent of earth is covered with water . you can say , `` hey , i know earth . i live here . '' you do n't know earth . you do n't know this planet , because most of it 's covered with that -- average depth , two miles . and when you go outside and look up at the empire state building , chrysler building , the average depth of the ocean is 15 of those on top of one another . we 've explored about five percent of what 's in that water . `` explored , '' meaning , for the first time , go peek and see what 's there . so what i want to do today is show you some things about this planet , about the oceans . i want to take you from shallow water down to the deep water , and hopefully , like me , you 'll see some things that get you hooked on exploring planet earth . you know things like corals ; you 've seen plenty of corals , those of you who 've been to the beach , snorkeling , know corals are an amazing place to go -- full of life , some big animals , small animals , some nice , some dangerous , sharks , whales , all that stuff . they need to be protected from humanity . they 're great places . but what you probably do n't know is in the very deep part of the ocean , we have volcanic eruptions . most volcanoes on earth are at the bottom of the sea -- more than 80 percent . and we actually have fire , fire deep inside the ocean , going on right now . all over the world -- in the pacific , the atlantic , the indian ocean . in this place , the ocean floor , the rocks actually turn to liquid . so you actually have waves on the ocean floor . you 'd say nothing could live there , but when we look in detail , even there , in the deepest , darkest places on earth , we find life , which tells us that life really wants to happen . so , pretty amazing stuff . every time we go to the bottom of the sea , we explore with our submarines , with our robots , we see something that 's usually surprising , sometimes it 's startling and sometimes revolutionary . you see that puddle of water sitting there . and all around the water there 's a little cliff , there 's a little white sandy beach . we 'll get closer , you 'll see the beach a little bit better , some of the waves in that water , down there . the thing that 's special about this water is that it 's at the bottom of the gulf of mexico . so you 're sitting inside a submarine , looking out the window at a little pond of water beneath the sea . we see ponds , we see lakes , we see rivers -- in fact , right here is a river at the bottom of the ocean going from the lower left to the upper right . water is actually flowing through there . this totally blew our minds . how can you have this at the bottom ? you 're in the ocean looking at more water . and there 's animals that only live in that water . so , the bottom of the ocean -- i love this map , because it shows in the middle of the ocean , there 's a mountain range . it 's the greatest mountain range on earth , called the mid-ocean ridge -- 50,000 miles long , and we 've hardly had a peek at it . hardly had a peek at it . we find valleys , many thousands of valleys , larger , wider , deeper than the grand canyon . we find , as i said , underwater lakes , rivers , waterfalls . the largest waterfall on the planet is actually under the ocean , up near iceland . all that stuff is in that five percent that we 've explored . so the deal about the ocean is that to explore it , you 've got to have technology . not only technology , but it 's not just dave gallo or one person exploring , it 's a team of people . you 've got to have the talent , the team . you 've got to have the technology . in this case , it 's our ship , atlantis , and the submarine , alvin . inside that submarine -- this is an alvin launch -- there 's three people . they 're being wheeled out onto deck . there 's 47 other people , the teamwork on that ship , making sure that these people are okay . everybody in that submarine is thinking one thing right now : should i have gone to the bathroom one more time ? because you 're in there for 10 hours -- 10 hours in that little sphere . three of you together and nobody is going to be around you . you go into the water and once you hit the water , it 's amazing . there 's a lovely color blue that penetrates right inside you . you do n't hear the surface ship anymore , you hear that pinging of a sonar . if you 've got an iphone you 've got sonar on there -- it 's that same pinging that goes down to the bottom and comes back up . divers check out the sub to make sure the outside is okay , and then they say `` go , '' and down you go to the bottom of the ocean and it 's an amazing trip . so for two and a half hours , you sink down to the bottom . and two hours of it is totally pitch black . we thought that nothing could live inside that world at the bottom of the ocean . and when we look , we find some amazing things . all the way down -- we call it the mid-water -- from the top of the ocean down to the bottom , we find life . whenever we stop and look , we find life . i 'm going to show you some jellies . they 're absolutely some of the coolest creatures on earth . look at that thing , just flailing his arms around . that 's like a little lobster . that one is like all these animals with their mouths hooked together , the colonial animals . some animals are tiny , some can be longer than this stage . just amazing animals . and you ca n't collect them with a net -- we have to go with our cameras and take a look at them . so every time we go , new species of life . the ocean is full of life . and yet the deepest part of the ocean -- when we go to that mountain range , we find hot springs . now we were sure -- because this is poisonous water , because it 's so deep it would crush the titanic the same way you crush an empty cup in your hand -- we were sure there would be no life there at all . instead , we find more life and diversity and density than in the tropical rainforest . so , in one instance , in one peek out the window of the sub , we discover something that revolutionizes the way we think about life on earth ; and that is , you do n't always have to have sunlight to get life going . there 's big animals down there too , some that look familiar . that guy 's called dumbo . i love him . dumbo 's great . this guy -- oh man , i wish i had more footage of this . we 're trying to get an expedition together to go look at this and maybe in a year we 'll have that . go online and look . vampyroteuthis infernalis . the vampire squid . incredibly cool . in the darkness of the deep sea , he 's got glowing tentacles , so if i 'm coming at you like him , i put my arms out in the darkness so all you see are little glowing things over here . meanwhile , i 'm coming at you . when he wants to escape , he 's got these glowing pods on his butt that look like eyes . glowing eyes on his butt . how cool is that ? just an amazing animal . ( laughter ) `` vampire '' squid , because when it gets protective , it pulls this black cape over its whole body , and curls up into a ball . outrageous animal . this ship , `` the ship of dreams '' -- a hundred years ago this coming april , this ship was supposed to show up in new york . it 's the titanic . i co-led an expedition out there last year . we are learning so much about that ship . the titanic is an interesting place for biology , because animals are moving in to live on the titanic . microbes are actually eating the hull of the titanic . that 's where jack was king of the world there on the bow of the titanic . so we 're doing real good . and what 's exciting to me is that we 're making a virtual titanic , so you can sit there at home with your joystick and your headset on , and you can actually explore the titanic for yourself . that 's what we want to do , make these virtual worlds , so it 's not dave gallo or someone else exploring the world ; it 's you . you explore it for yourself . so here 's the bottom line : the oceans are unexplored and i ca n't begin to tell you how important that is , because they 're important to us . seven billion people live on this planet and all of us are impacted by the sea , because the oceans control the air you breathe , the water you drink , the food you eat . all those are controlled in some way by the ocean , and this is a thing that we have n't even explored -- five percent . the thing i want to leave you with is , in that five percent , i showed you some cool stuff . there 's a lot more cool stuff -- every dive we go on in the ocean , we find something new about the sea . so what 's in that other 95 percent ? did we get the exciting stuff or is there more out there ? and i 'm here to tell you that the ocean is full of surprises . there 's a quote i love by marcel proust : `` the true voyage of exploration is not so much in seeking new landscapes , '' which we do , `` but in having new eyes . '' and so i hope today , by showing you some of this , it 's given you some new eyes about this planet , and for the first time , i want you to think about it differently . thank you very much . thank you . ( applause )
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they 're great places . but what you probably do n't know is in the very deep part of the ocean , we have volcanic eruptions . most volcanoes on earth are at the bottom of the sea -- more than 80 percent . and we actually have fire , fire deep inside the ocean , going on right now . all over the world -- in the pacific , the atlantic , the indian ocean .
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80 % of the planet ’ s __________ are at the bottom of the deep ocean :
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bees are very busy little matchmakers . wingmen in every sense of the word . you see , the bees ' side of the whole `` birds and the bees '' business is to help plants find mates and reproduce . in their work as pollinators , honeybees are integral to the production of nearly 1/3 of the food that we eat . and these bees , dutifully helping lonely plants have sex , are n't alone . but rather are part of a very complex network of matchmaking creatures , critical for the pollination of natural ecosystems and crops . plants in many natural ecosystems need help to have sex . like many of us , they 're too busy to find a relationship . they have too much photosynthesis to do , and they ca n't find the time to evolve feet and walk to a singles bar . those places are called meat markets for a reason , because plants ca n't walk . so they need matchmaker pollinators to transport their pollen grains to flowers of the same plant species , and they pay these pollinators with food . today , around 170,000 plant species receive pollination services from more than 200,000 pollinator species . pollinators include many species of bees , butterflies , moths , flies , wasps , beetles , even birds and bats , who together help pollinate many species of trees , shrubs and other flowering plants . in return , flowering plants are an abundant and diverse food source for pollinators . for instance , fossil records suggest bees may have evolved from wasps that gave up hunting after they acquired a taste for nectar . plant pollinator networks are everywhere . ecologists record these networks in the field by observing which pollinators visit which plants , or by analyzing the identity of pollen loads on their bodies . networks , registered in these ways , contain from 20 to 800 species . these networks show a repeated structure , or architecture . pollinators interact with plants in a very heterogenous way . most plants are specialists , they have only one or a few matchmakers . meanwhile , only a few generalist plants hire a diverse team of matchmakers , getting visits from almost all the pollinators of the network . the same occurs with pollinators . most are specialists that feed on only a few plant species , while a few pollinators , including the honeybee usually , are generalists , busily feeding from and matchmaking for almost all the plant species in that ecosystem . what 's interesting is that specialists and generalists across both plants and pollinators , sort themselves out in a particular pattern . most pollinator networks , for which we have data , are nested . in a nested network , specialists tend to interact more with generalists than with other specialists . this is because if you 're a specialist plant , and your only matchmaker also specializes on you as its only food source , you 're each more vulnerable to extinction . so , you 're better off specializing on a generalist pollinator that has other sources of food to ensure its persistence in bad years . the same goes if you 're a specialist pollinator . you 're better off in the long run specializing on a generalist plant that gets pollinated by other species in times when you 're not around to help . finally , in addition to nestedness , the networks are usually modular . this means that the species in a network are compartmentalized into modules of plants and animals that interact more with each other than with species in other modules . think of them like social cliques . a plant or pollinator dying off will effect the species in its module , but those effects will be less severe on the rest of the network . why 's all that important ? because plant pollinator network structure effects the stability of ecosystems . heterogeneous distribution , nestedness and modularity enable networks to better prevent and respond to extinctions . that 's critical because nature is never static . some species may not show up every year . plants flower at different times . pollinators mature on varying schedules . generalist pollinators have to adapt their preferences depending on who 's flowering when . so from one flowering season to the next , the participants and patterns of matchmaking can drastically change . with all those variables , you can understand the importance of generalist pollinators , like bees , to the stability of not only a crop harvest , but the entire network of plants and pollinators we see in nature , and rely on for life . next time you see a bee fly by , remember that it belongs to a complex network of matchmakers critical to the love lives of plants all around you .
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so they need matchmaker pollinators to transport their pollen grains to flowers of the same plant species , and they pay these pollinators with food . today , around 170,000 plant species receive pollination services from more than 200,000 pollinator species . pollinators include many species of bees , butterflies , moths , flies , wasps , beetles , even birds and bats , who together help pollinate many species of trees , shrubs and other flowering plants .
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today , around ________ plant species receive pollination services from more than 200,000 pollinator species .
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we 've all seen movies about terrible insects from outer space or stories of abduction by little green men , but the study of life in the universe , including the possibility of extraterrestrial life , is also a serious , scientific pursuit . astrobiology draws on diverse fields , such as physics , biology , astronomy , and geology , to study how life was formed on earth , how it could form elsewhere , and how we might detect it . many ancient religions described other worlds inhabited by known human beings , but these are more like mythical realms or parallel universes than other planets existing in the same physical world . it is only within the last century that scientists have been able to seriously undertake the search for extraterrestrial life . we know that at the most basic level organisms on earth need three things : liquid water , a source of energy , and organic , carbon-based material . we also know that the earth is just the right distance from the sun , so as not to be either frozen or molten . so , planets within such a habitable range from their own stars may be able to support life . but while we used to think that life could only exist in such earth-like environments , one of the most amazing discoveries of astrobiology has been just how versatile life is . we now know that life can thrive in some of the most extreme environments that 'd be fatal for most known organisms . life is found everywhere , from black smoke of hydrothermal vents in the dark depths of earth 's oceans , to bubbling , hot , acidic springs on the flanks of volcanoes , to high up in the atmosphere . organisms that live in these challenging environments are called extremophiles , and they can survive at extremes of temperature , pressure , and radiation , as well as salinity , acidity , and limited availability of sunlight , water , or oxygen . what is most remarkable about these extremophiles is that they are found thriving in environments that mimic those on alien worlds . one of the most important of these worlds is our red and dusty neighbor , mars . today , astrobiologists are exploring places where life might once have existed on mars using nasa 's curiosity rover . one of these is gale crater , an impact crater created when a meteor hit the surface of mars nearly 3.8 billions years ago . evidence from orbit suggest past traces of water , which means the crater might once have supported life . planets are not the only places astrobiologists are looking at . for example , europa , one of the moons of jupiter , and enceladus and titan , two of saturn 's moons , are all exciting possibilities . although these moons are extremely cold and two are covered in thick ice , there is evidence of liquid oceans beneath the shell . could life be floating around in these oceans , or could it be living around black smoker vents at the bottom ? titan is particularly promising as it has an atmosphere and earth-like lakes , seas , and rivers flowing across the surface . it is very cold , however , too cold for liquid water , so these rivers may instead be flowing with liquid hydrocarbons such as methane and ethane . these are composed of hydrogen , and , more importantly , carbon , which is the basic building block of all life as we know it . so , could life be found in these lakes ? although instruments are being designed to study these distant worlds , it takes many years to build them and even longer to get them where they need to be . in the meantime , astrobiologists work in our own natural laboratory , the earth , to learn about all the weird and wonderful forms of life that can exist and to help us one day answer one of humanity 's oldest questions : are we alone ?
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these are composed of hydrogen , and , more importantly , carbon , which is the basic building block of all life as we know it . so , could life be found in these lakes ? although instruments are being designed to study these distant worlds , it takes many years to build them and even longer to get them where they need to be .
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on which of these are we not searching for life ?
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many elements of traditional japanese culture , such as cuisine and martial arts , are well-known throughout the world . kabuki , a form of classical theater performance , may not be as well understood in the west but has evolved over 400 years to still maintain influence and popularity to this day . the word kabuki is derived from the japanese verb kabuku , meaning out of the ordinary or bizarre . its history began in early 17th century kyoto , where a shrine maiden named izumo no okuni would use the city 's dry kamo riverbed as a stage to perform unusual dances for passerby , who found her daring parodies of buddhist prayers both entertaining and mesmerizing . soon other troops began performing in the same style , and kabuki made history as japan 's first dramatic performance form catering to the common people . by relying on makeup , or keshou , and facial expressions instead of masks and focusing on historical events and everyday life rather than folk tales , kabuki set itself apart from the upper-class dance theater form known as noh and provided a unique commentary on society during the edo period . at first , the dance was practiced only by females and commonly referred to as onna-kabuki . it soon evolved to an ensemble performance and became a regular attraction at tea houses , drawing audiences from all social classes . at this point , onna-kabuki was often risque as geishas performed not only to show off their singing and dancing abilities but also to advertise their bodies to potential clients . a ban by the conservative tokugawa shogunate in 1629 led to the emergence of wakashu-kabuki with young boys as actors . but when this was also banned for similar reasons , there was a transition to yaro-kabuki , performed by men , necessitating elaborate costumes and makeup for those playing female roles , or onnagata . attempts by the government to control kabuki did n't end with bans on the gender or age of performers . the tokugawa military group , or bakufu , was fueled by confucian ideals and often enacted sanctions on costume fabrics , stage weaponry , and the subject matter of the plot . at the same time , kabuki became closely associated with and influenced by bunraku , an elaborate form of puppet theater . due to these influences , the once spontaneous , one-act dance evolved into a structured , five-act play often based on the tenets of confucian philosophy . before 1868 , when the tokugawa shogunate fell and emperor meiji was restored to power , japan had practiced isolation from other countries , or sakoku . and thus , the development of kabuki had mostly been shaped by domestic influences . but even before this period , european artists , such as claude monet , had become interested in and inspired by japanese art , such as woodblock prints , as well as live performance . after 1868 , others such as vincent van gogh and composer claude debussy began to incorporate kabuki influences in their work , while kabuki itself underwent much change and experimentation to adapt to the new modern era . like other traditional art forms , kabuki suffered in popularity in the wake of world war ii . but innovation by artists such as director tetsuji takechi led to a resurgence shortly after . indeed , kabuki was even considered a popular form of entertainment amongst american troops stationed in japan despite initial u.s. censorship of japanese traditions . today , kabuki still lives on as an integral part of japan 's rich cultural heritage , extending its influence beyond the stage to television , film , and anime . the art form pioneered by okuni continues to delight audiences with the actors ' elaborate makeup , extravagant and delicately embroidered costumes , and the unmistakable melodrama of the stories told on stage .
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soon other troops began performing in the same style , and kabuki made history as japan 's first dramatic performance form catering to the common people . by relying on makeup , or keshou , and facial expressions instead of masks and focusing on historical events and everyday life rather than folk tales , kabuki set itself apart from the upper-class dance theater form known as noh and provided a unique commentary on society during the edo period . at first , the dance was practiced only by females and commonly referred to as onna-kabuki .
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what type of stories did kabuki originally focus on , which set it apart from noh dramas ?
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baked or fried , boiled or roasted , as chips or fries . at some point in your life , you 've probably eaten a potato . delicious , for sure , but the fact is potatoes have played a much more significant role in our history than just that of the dietary staple we have come to know and love today . without the potato , our modern civilization might not exist at all . 8,000 years ago in south america , high atop the andes , ancient peruvians were the first to cultivate the potato . containing high levels of proteins and carbohydrates , as well as essential fats , vitamins and minerals , potatoes were the perfect food source to fuel a large incan working class as they built and farmed their terraced fields , mined the rocky mountains , and created the sophisticated civilization of the great incan empire . but considering how vital they were to the incan people , when spanish sailors returning from the andes first brought potatoes to europe , the spuds were duds . europeans simply did n't want to eat what they considered dull and tasteless oddities from a strange new land , too closely related to the deadly nightshade plant belladonna for comfort . so instead of consuming them , they used potatoes as decorative garden plants . more than 200 years would pass before the potato caught on as a major food source throughout europe , though even then , it was predominantly eaten by the lower classes . however , beginning around 1750 , and thanks at least in part to the wide availability of inexpensive and nutritious potatoes , european peasants with greater food security no longer found themselves at the mercy of the regularly occurring grain famines of the time , and so their populations steadily grew . as a result , the british , dutch and german empires rose on the backs of the growing groups of farmers , laborers , and soldiers , thus lifting the west to its place of world dominion . however , not all european countries sprouted empires . after the irish adopted the potato , their population dramatically increased , as did their dependence on the tuber as a major food staple . but then disaster struck . from 1845 to 1852 , potato blight disease ravaged the majority of ireland 's potato crop , leading to the irish potato famine , one of the deadliest famines in world history . over a million irish citizens starved to death , and 2 million more left their homes behind . but of course , this was n't the end for the potato . the crop eventually recovered , and europe 's population , especially the working classes , continued to increase . aided by the influx of irish migrants , europe now had a large , sustainable , and well-fed population who were capable of manning the emerging factories that would bring about our modern world via the industrial revolution . so it 's almost impossible to imagine a world without the potato . would the industrial revolution ever have happened ? would world war ii have been lost by the allies without this easy-to-grow crop that fed the allied troops ? would it even have started ? when you think about it like this , many major milestones in world history can all be at least partially attributed to the simple spud from the peruvian hilltops .
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but then disaster struck . from 1845 to 1852 , potato blight disease ravaged the majority of ireland 's potato crop , leading to the irish potato famine , one of the deadliest famines in world history . over a million irish citizens starved to death , and 2 million more left their homes behind . but of course , this was n't the end for the potato .
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how many irish starved to death during the irish potato famine ?
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an enduring myth says we use only 10 % of our brain , the other 90 % standing idly by for spare capacity . hucksters promised to unlock that hidden potential with methods `` based on neuroscience , '' but all they really unlock is your wallet . two-thirds of the public and nearly half of science teachers mistakenly believe the 10 % myth . in the 1890s , william james , the father of american psychology , said , `` most of us do not meet our mental potential . '' james meant this as a challenge , not an indictment of scant brain usage . but the misunderstanding stuck . also , scientists could n't figure out for a long time the purpose of our massive frontal lobes or broad areas of the parietal lobe . damage did n't cause motor or sensory deficits , so authorities concluded they did n't do anything . for decades , these parts were called silent areas , their function elusive . we 've since learned that they underscore executive and integrative ability , without which , we would hardly be human . they are crucial to abstract reasoning , planning , weighing decisions and flexibly adapting to circumstances . the idea that 9/10 of your brain sits idly by in your skull looks silly when we calculate how the brain uses energy . rodent and canine brains consume 5 % of total body energy . monkey brains use 10 % . an adult human brain , which accounts for only 2 % of the body 's mass , consumes 20 % of daily glucose burned . in children , that figure is 50 % , and in infants , 60 % . this is far more than expected for their relative brain sizes , which scale in proportion to body size . human ones weigh 1.5 kilograms , elephant brains 5 kg , and whale brains 9 kg , yet on a per weight basis , humans pack in more neurons than any other species . this dense packing is what makes us so smart . there is a trade-off between body size and the number of neurons a primate , including us , can sustain . a 25 kg ape has to eat 8 hours a day to uphold a brain with 53 billion neurons . the invention of cooking , one and half million years ago , gave us a huge advantage . cooked food is rendered soft and predigested outside of the body . our guts more easily absorb its energy . cooking frees up time and provides more energy than if we ate food stuffs raw and so we can sustain brains with 86 billion densely packed neurons . 40 % more than the ape . here 's how it works . half the calories a brain burns go towards simply keeping the structure intact by pumping sodium and potassium ions across membranes to maintain an electrical charge . to do this , the brain has to be an energy hog . it consumes an astounding 3.4 x 10^21 atp molecules per minute , atp being the coal of the body 's furnace . the high cost of maintaining resting potentials in all 86 billion neurons means that little energy is left to propel signals down axons and across synapses , the nerve discharges that actually get things done . even if only a tiny percentage of neurons fired in a given region at any one time , the energy burden of generating spikes over the entire brain would be unsustainable . here 's where energy efficiency comes in . letting just a small proportion of cells signal at any one time , known as sparse coding , uses the least energy , but carries the most information . because the small number of signals have thousands of possible paths by which to distribute themselves . a drawback of sparse coding within a huge number of neurons is its cost . worse , if a big proportion of cells never fire , then they are superfluous and evolution should have jettisoned them long ago . the solution is to find the optimum proportion of cells that the brain can have active at once . for maximum efficiency , between 1 % and 16 % of cells should be active at any given moment . this is the energy limit we have to live with in order to be conscious at all . the need to conserve resources is the reason most of the brain 's operations must happen outside of consciousness . it 's why multitasking is a fool 's errand . we simply lack the energy to do two things at once , let alone three or five . when we try , we do each task less well than if we had given it our full attention . the numbers are against us . your brain is already smart and powerful . so powerful that it needs a lot of power to stay powerful . and so smart that it has built in an energy-efficiency plan . so do n't let a fraudulent myth make you guilty about your supposedly lazy brain . guilt would be a waste of energy . after all this , do n't you realize it 's dumb to waste mental energy ? you have billions of power-hungry neurons to maintain . so hop to it !
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because the small number of signals have thousands of possible paths by which to distribute themselves . a drawback of sparse coding within a huge number of neurons is its cost . worse , if a big proportion of cells never fire , then they are superfluous and evolution should have jettisoned them long ago .
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what does “ sparse coding ” of nerve impulses imply ?
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the secrets of the x chromosome . these women are identical twins . they have the same nose , the same hair color , the same eye color . but this one is color blind for green light , and this one is n't . how is that possible ? the answer lies in their genes . for humans , the genetic information that determines our physical traits is stored in 23 pairs of chromosomes in the nucleus of every cell . these chromosomes are made up of proteins and long , coiled strands of dna . segments of dna , called genes , tell the cell to build specific proteins , which control its identity and function . for every chromosome pair , one comes from each biological parent . in 22 of these pairs , the chromosomes contain the same set of genes , but may have different versions of those genes . the differences arrive from mutations , which are changes to the genetic sequence that may have occurred many generations ago . some of those changes have no effect , some cause diseases , and some lead to advantageous adaptations . the result of having two versions of each gene is that you display a combination of your biological parents ' traits . but the 23rd pair is unique , and that 's the secret behind the one color blind twin . this pair , called the x and y chromosomes , influences your biological sex . most women have two x chromosomes while most men have one x and one y . the y chromosome contains genes for male development and fertility . the x chromosome , on the other hand , contains important genes for things other than sex determination or reproduction , like nervous system development , skeletal muscle function , and the receptors in the eyes that detect green light . biological males with an xy chromosome pair only get one copy of all these x chromosome genes , so the human body has evolved to function without duplicates . but that creates a problem for people with two x chromosomes . if both x chromosomes produced proteins , as is normal in other chromosomes , development of the embryo would be completely impaired . the solution is x inactivation . this happens early in development when an embryo with two x chromosomes is just a ball of cells . each cell inactivates one x chromosome . there 's a certain degree of randomness to this process . one cell may inactivate the x chromosome from one parent , and another the chromosome from the other parent . the inactive x shrivels into a clump called a barr body and goes silent . almost none of its genes order proteins to be made . when these early cells divide , each passes on its x inactivation . so some clusters of cells express the maternal x chromosome , while others express the paternal x . if these chromosomes carry different traits , those differences will show up in the cells . this is why calico cats have patches . one x had a gene for orange fur and the other had a gene for black fur . the pattern of the coat reveals which one stayed active where . now we can explain our color blind twin . both sisters inherited one mutant copy of the green receptor gene and one normally functioning copy . the embryo split into twins before x inactivation , so each twin ended up with a different inactivation pattern . in one , the x chromosome with the normal gene was turned off in the cells that eventually became eyes . without those genetic instructions , she now ca n't sense green light and is color blind . disorders that are associated with mutations of x chromosome genes , like color blindness , or hemophilia , are often less severe in individuals with two x chromosomes . that 's because in someone with one normal and one mutant copy of the gene , only some of their cells would be affected by the mutation . this severity of the disorder depends on which x got turned off and where those cells were . on the other hand , all the cells in someone with only one x chromosome can only express the mutant copy of the gene if that 's what they inherited . there are still unresolved questions about x inactivation , like how some genes on the x chromosome escape inactivation and why inactivation is n't always random . what we do know is that this mechanism is one of the many ways that genes alone do n't tell our whole story .
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if both x chromosomes produced proteins , as is normal in other chromosomes , development of the embryo would be completely impaired . the solution is x inactivation . this happens early in development when an embryo with two x chromosomes is just a ball of cells .
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when does the process of x-inactivation occur ?
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imagine yourself standing on a beach , looking out over the ocean , waves crashing against the shore , blue as far as your eyes can see . let it really sink in , the sheer scope and size of it all . now , ask yourself , `` how big is it ? how big is the ocean ? '' first thing , we need to understand that there really is only one ocean , consisting of five component basins that we call the pacific , the atlantic , the indian , the arctic , and the southern . each of these five , while generally referred to as oceans in and of themselves , are really and truly a part of a single , massive body of water , one ocean , which defines the very face of planet earth . the ocean covers roughly 71 % of our planet 's surface , some 360 million square kilometers , an area in excess of the size of 36 u.s.a. 's . it 's such a vast spread , when viewed from space , the ocean is , by far , the dominant feature of our planet . speaking of space , the ocean currently holds over 1.3 billion , that 's billion with a `` b '' , cubic kilometers of water . put another way , that 's enough water to immerse the entire united states under a body of salt water over 132 kilometers tall , a height well beyond the reach of the highest clouds and extending deep into the upper atmosphere . with all that volume , the ocean represents 97 % of earth 's total water content . on top of all that , the ocean contains upwards of 99 % of the world 's biosphere , that is , the spaces and places where life exists . now let that sink in for a second . the immediate world as we know it , indeed the totality of all the living space encompassed by the continents themselves , all of that represents only 1 % of the biosphere . 1 % ! the ocean is everything else . so , the ocean is physically massive . it 's importance to life is practically unparalleled . it also happens to hold the greatest geological features of our planet . quickly , here are four of the most notable . the ocean contains the world 's largest mountain range , the mid-ocean ridge . at roughly 65,000 kilometers long , this underwater range is some 10 times longer than the longest mountain chain found purely on dry land , the andes . beneath the denmark strait exists the world 's largest waterfall . this massive cataract carries roughly 116 times more water per second over its edge than the congo river 's inga falls , the largest waterfall by volume on land . the world 's tallest mountain is actually found in the ocean , hiding in plain sight . while 4200 meters of hawaii 's mauna kea sit above sea level , its sides plummet beneath the waves for another 5800 meters . from its snow-covered top to it 's silt-covered bottom , then , this hawaiian mountain is roughly 10,000 meters in height , dwarfing tiny everest 's paltry peak by well over a kilometer . then , since we 're picking on poor everest , let 's consider the world 's deepest canyon , the challenger deep , existing 11 kilometers below the ocean 's surface , some six times deeper than the grand canyon . that 's deep enough to sink mount everest into and still have over 2.1 kilometers of water sitting atop its newly submerged peak . put another way , the depth of the challenger deep is roughly the same height that commercial airliners travel . so , pretty much however you choose to slice it , the ocean is capital b capital i , capital g , big ! it defines our planet , home to the greatest geological features , comprises the largest living space , and accordingly , is home to the greatest numbers and forms of life on earth . it is practically incomprehensible in scope . but it is not so big , so vast , so extraordinary as to be untouchable . in fact , with roughly 50 % of the world 's population living within 100 kilometers of the coastline and with most of the remainder living close enough to lakes , rivers , or swamps , all of which ultimately lead to the ocean , virtually every single person on the planet has the opportunity to influence the general health and nature of the world ocean . evidence of human influence is seen in every part of the ocean , no matter how deep , no matter how distant . the ocean defines our planet , but , in a very real sense , we define the ocean .
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put another way , that 's enough water to immerse the entire united states under a body of salt water over 132 kilometers tall , a height well beyond the reach of the highest clouds and extending deep into the upper atmosphere . with all that volume , the ocean represents 97 % of earth 's total water content . on top of all that , the ocean contains upwards of 99 % of the world 's biosphere , that is , the spaces and places where life exists .
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the percentage of earth ’ s biosphere that is not encompassed by the ocean is…
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a close encounter with a man-eating giant , a sorceress who turns men into pigs , a long-lost king taking back his throne . on their own , any of these make great stories , but each is just one episode in the `` odyssey , '' a 12,000-line poem spanning years of ancient greek history , myth , and legend . how do we make sense of such a massive text that comes from and tells of a world so far away ? the fact that we can read the `` odyssey '' at all is pretty incredible , as it was composed before the greek alphabet appeared in the 8th century bce . it was made for listeners rather than readers , and was performed by oral poets called rhapsodes . tradition identifies its author as a blind man named homer . but no one definitively knows whether he was real or legendary . the earliest mentions of him occur centuries after his era . and the poems attributed to him seem to have been changed and rearranged many times by multiple authors before finally being written down in their current form . in fact , the word rhapsode means stitching together , as these poets combined existing stories , jokes , myths , and songs into a single narrative . to recite these massive epics live , rhapsodes employed a steady meter , along with mnemonic devices , like repetition of memorized passages or set pieces . these included descriptions of scenery and lists of characters , and helped the rhapsode keep their place in the narrative , just as the chorus or bridge of a song helps us to remember the next verses . because most of the tales were familiar to the audience , it was common to hear the sections of the poem out of order . at some point , the order became set in stone and the story was locked into place as the one we read today . but since the world has changed a bit in the last several thousand years , it helps to have some background before jumping in . the `` odyssey '' itself is a sequel to homer 's other famous epic , the `` iliad , '' which tells the story of the trojan war . if there 's one major theme uniting both poems , it 's this : do not , under any circumstances , incur the wrath of the gods . the greek pantheon is a dangerous mix of divine power and human insecurity , prone to jealousy and grudges of epic proportions . and many of the problems faced by humans in the poems are caused by their hubris , or excessive pride in believing themselves superior to the gods . the desire to please the gods was so great that the ancient greeks traditionally welcomed all strangers into their homes with generosity for fear that the strangers might be gods in disguise . this ancient code of hospitality was called xenia . it involved hosts providing their guests with safety , food , and comfort , and the guests returning the favor with courtesy and gifts if they had them . xenia has a significant role in the `` odyssey , '' where odysseus in his wanderings is the perpetual guest , while in his absence , his clever wife penelope plays non-stop host . the `` odyssey '' recounts all of odysseus 's years of travel , but the narrative begins in medias res in the middle of things . ten years after the trojan war , we find our hero trapped on an island , still far from his native ithaca and the family he has n't seen for 20 years . because he 's angered the sea god poseidon by blinding his son , a cyclops , odysseus 's passage home has been fraught with mishap after mishap . with trouble brewing at home and gods discussing his fate , odysseus begins the account of those missing years to his hosts . one of the most fascinating things about the `` odyssey '' is the gap between how little we know about its time period and the wealth of detail the text itself contains . historians , linguists , and archeologists have spent centuries searching for the ruins of troy and identifying which islands odysseus visited . just like its hero , the 24-book epic has made its own long journey through centuries of myth and history to tell us its incredible story today .
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the desire to please the gods was so great that the ancient greeks traditionally welcomed all strangers into their homes with generosity for fear that the strangers might be gods in disguise . this ancient code of hospitality was called xenia . it involved hosts providing their guests with safety , food , and comfort , and the guests returning the favor with courtesy and gifts if they had them .
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what is xenia ?
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the city sky is , frankly , rather boring . if you look up at the patches of murk between buildings , you might be able to pick out the big dipper , or perhaps , orion 's belt . but hold on . look at that murky patch again and hold our your thumb . how many stars do you think are behind it ? ten , twenty ? guess again . if you looked at that thumbnail-sized patch of sky with the hubble space telescope , instead of points of light , you 'd see smudges . these are n't stars . they 're galaxies , just like our milky way . cities of billions of stars , and more than 1,000 of them are hidden behind your thumb . the universe is bigger than you can see from the city , and even bigger than the starry sky you can see from the countryside . this is the universe as astrophysicists see it , with more stars than all the grains of sand on earth . by staring up at the stars at night , you 've taken part in the oldest science in human history . the study of the heavens is older than navigation , agriculture , perhaps even language itself . yet unlike other sciences , astronomy is purely observational . we can not control the parameters of our experiments from lab benches . our best technology can send man to the moon , and probes to the edge of the solar system . but these distances are vanishingly small compared to the yawning gulfs between stars . so how can we know so much about other galaxies , what they 're made of , how many there are , or that they 're even there at all ? well , we can start with the first thing we see when we look up at night : the stars . what we are trying to learn is their properties . what are they made of ? how hot are they ? how massive ? how old ? how far are they from earth ? and believe it or not , we can learn all of these things simply from the light shining in the sky . we can decipher one kind of stellar message by turning starlight into rainbows . when you look at a rainbow on earth , you 're really looking at light from our sun being scattered through water droplets in the atmosphere into all the different wavelengths that make it up . and we study the light from other stars , we can create rainbows on demand using not water droplets , but other specific instruments that disperse light . when we look at the scattered light from our sun , we see something strange : dark lines in our rainbow . these lines are the characteristic fingerprints of atoms . each type of atom in the solar atmosphere soaks up light at specific wavelengths , and the amount of absorption depends on how many of these atoms there are . so by observing how much light is missing at these characteristic wavelengths , we can tell not only what elements are in the sun 's atmosphere , but even their concentrations . and the same idea can be applied to study other stars . make a spectral rainbow , see what 's missing , and figure out which elements are present . bingo . now you know what stars are made of . but we are n't restricted to just the wavelengths that our eyes perceive . consider radio waves . yes , they can bring the billboard top 100 to your car , but they can also travel almost unimpeded through space . because they 've come so far , radio waves can tell us the very early history of the universe , from just a few thousand years after the big bang . we can also study the infrared light , emitted by colder objects , like the gas and dust clouds in space , and the ultraviolet light from the hot stars recently born from those clouds . studying different wavelengths not only gives us a more complete picture of any single object but also different views of the universe . for this reason , astrophysicists use several different kinds of telescopes covering the spectrum from the infrared to the ultraviolet to the x-ray , from giant radio dishes to giant silver mirrors to space satellites , detecting light that would be otherwise blocked by the earth 's atmosphere . astrophysicists do n't just see the billions of stars among the billions of galaxies in the universe . they hear , feel and sense them through many channels , each revealing a different story . but it all begins with light , the kind we can see and the kind we ca n't . want to know the secrets of the universe ? just follow the light .
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studying different wavelengths not only gives us a more complete picture of any single object but also different views of the universe . for this reason , astrophysicists use several different kinds of telescopes covering the spectrum from the infrared to the ultraviolet to the x-ray , from giant radio dishes to giant silver mirrors to space satellites , detecting light that would be otherwise blocked by the earth 's atmosphere . astrophysicists do n't just see the billions of stars among the billions of galaxies in the universe .
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unlike optical telescopes , almost all x-ray and ultraviolet telescopes are space-based . they are launched above the earth ’ s atmosphere . why do you think these telescopes have to be above the atmosphere ? [ hint : what protects us from the sun ultraviolet radiation ? ]
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what if you could only see one color ? imagine , for instance , that you could only see things that were red and that everything else was completely invisible to you . as it turns out , that 's how you live your life all the time because your eyes can only see a minuscule part of the full spectrum of light . different kinds of light are all around you everyday but are invisible to the human eye , from the radio waves that carry your favorite songs , to the x-rays doctors use to see inside of you , to the microwaves that heat up your food . in order to understand how these can all be light , we 'll need to know a thing or two about what light is . light is electromagnetic radiation that acts like both a wave and a particle . light waves are kind of like waves on the ocean . there are big waves and small waves , waves that crash on the shore one right after the other , and waves that only roll in every so often . the size of a wave is called its wavelength , and how often it comes by is called its frequency . imagine being a boat in that ocean , bobbing up and down as the waves go by . if the waves that day have long wavelengths , they 'll make you bob only so often , or at a low frequency . if the waves , instead , have short wavelengths , they 'll be close together , and you 'll bob up and down much more often , at a high frequency . different kinds of light are all waves , they just have different wavelengths and frequencies . if you know the wavelength or frequency of a wave of light , you can also figure out its energy . long wavelengths have low energies , while short wavelengths have high energies . it 's easy to remember if you think about being in that boat . if you were out sailing on a day with short , choppy waves , you 'd probably be pretty high energy yourself , running around to keep things from falling over . but on a long wavelength sea , you 'd be rolling along , relaxed , low energy . the energy of light tells us how it will interact with matter , for example , the cells of our eyes . when we see , it 's because the energy of light stimulates a receptor in our eye called the retina . our retina are only sensitive to light with a very small range in energy , and so we call that range of light visible light . inside our retina are special receptors called rods and cones . the rods measure brightness , so we know how much light there is . the cones are in charge of what color of light we see because different cones are sensitive to different energies of light . some cones are more excited by light that is long wavelength and low energy , and other cones are more excited by short wavelength , high-energy light . when light hits our eye , the relative amount of energy each cone measures signals our brain to perceive colors . the rainbow we perceive is actually visible light in order of its energy . at one side of the rainbow is low-energy light we see as red , and at the other side is high-energy light we see as blue . if light shines on us that has an energy our retina ca n't measure , we wo n't be able to see it . light that is too short wavelength or high energy gets absorbed by the eye 's surface before it can even get to the retina , and light that is too long wavelength does n't have enough energy to stimulate our retina at all . the only thing that makes one kind of light different from another is its wavelength . radio waves have long wavelengths , while x-rays have short wavelengths . and visible light , the kind you can actually see , is somewhere in between . even though our eyes ca n't detect light outside of the visible range , we can build special detectors that are stimulated by these other wavelengths of light , kind of like digital eyes . with these devices , we can measure the light that is there , even though we ca n't see it ourselves . so , take a step back and think about all of this for a moment . even though they seem different , the warmth you feel from a crackling fire is the same as the sun shining on you on a beautiful day , the same as ultraviolet light you put on sunscreen to protect yourself from , the same thing as your tv , your radio , and your microwave . now , those examples are all things here on earth , things you experience in your everyday life , but here 's something even more amazing . our universe gives off the full spectrum of light , too . when you think of the night sky , you probably think of being able to see the stars shining with your own eyes , but that 's just visible light , which you now know is only a tiny part of the full spectrum . if we had to draw the universe and could only use visible light , it would be like having only one crayon -- pretty sad . to see the universe in its full spectrum , we need to have the right eyes , and that means using special telescopes that can help us see beyond visible light . you 've probably heard of the hubble space telescope and seen its beautiful pictures taken in visible and ultraviolet light . but you might not know that there are 20 space telescopes in orbit , missions that can each see part of the full spectrum of light . with telescopes acting as our virtual eyes , both in space and here on earth , we can see some amazing things . and the coolest thing of all , no matter the wavelength or energy , the light that we see out in the distant universe is the same thing as the light that we can experience and study here on earth . so , since we know the physics of how x-ray , ultraviolet light , or microwaves work here , we can study the light of a distant star or galaxy and know what kinds of things are happening there too . so , as you go about your daily life , think beyond what your eyes can and ca n't see . knowing just a little bit about the natural world can help you perceive the full spectrum around you all the time .
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our retina are only sensitive to light with a very small range in energy , and so we call that range of light visible light . inside our retina are special receptors called rods and cones . the rods measure brightness , so we know how much light there is .
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what are the functions of both rods and cones in your eyes ?
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i ’ ve invited you all here today because i wanted to talk to you about some ugly stereotypes that are going around . i ’ ve been hearing a lot of unfair , unseemly , and unscientific generalizations being made lately . and they mostly have to do with sex . and your hormones . people have a nasty habit of equating “ hormones ” with a particular set of behaviors and conditions , most of which have to do with reproduction , or sexual development , or acts that include what my brother john has referred to as “ skoodilypooping. ” for example , people will say that “ hormones ” are why kevin has zits , and is being all moody , or why hannah , who ’ s three months pregnant , just cried watching a commercial for car insurance -- which , let ’ s be honest , i do that too . now , i ’ m not saying that hormones aren ’ t at the root of sexual attraction , or zits , or occasional bouts of extreme emotion , because they are . that ’ s just not all that they do . not even close . when people talk about “ hormones ” in the contexts that i just mentioned , what really they mean is `` sex hormones . '' but sex hormones are just one kind of hormone that you have coursing through your body right now . in fact , there are at least 50 different types of these chemical messengers at work in your body at this very minute , but only a very few of them have anything at all to do with sex . the truth is , from birth to death , just about every cell and function in your body is under your hormones ’ constant influence . they ’ re floating through your blood , regulating your metabolism , your sleep cycle , your response to stress , and the general and incredibly important overall homeostasis that keeps you not dead . some hormones are just there to make other hormones trigger even more hormones -- in a kind of chemical relay race that biologists refer to , rather elegantly , as “ cascades. ” these hormones run through you no matter what your mood is , or whether you have zits . so the reality is : we ’ re all hormonal ... all of the time . ok , to begin to understand our hormones -- and the endocrine system that produces , releases , and re-absorbs them -- we have to step back and take a broad view . not just by emphasizing that sex hormones aren ’ t the only hormones you have -- but also by looking at how your hormones interact with your other organ systems . because , if anything , your body has two bosses -- two complementary systems that are constantly shouting instructions over each other , to all of your bits and pieces . both your endocrine system and your nervous system are constantly trafficking information around your corpus , gathering intel , making demands , controlling your every move . they just have totally different ways of doing it . your nervous system uses lightning-fast electrochemical action potentials , delivered by an expressway made of neurons to specific cells and organs . but your endocrine system prefers a slower , wider stream of data . it secretes hormones that travel through your blood -- not through neurons -- so they move more slowly , but they also produce widespread effects that last a whole lot longer than an action potential . now , compared to your heart or brain or other , arguably more glamorous organs , your endocrine system ’ s organs and glands are kinda small and lumpy . they ’ re also rogues -- instead of being all nestled together like in your other organ systems , these guys are scattered all over the place , from your brain to your throat , to your kidneys , to your genitals . a gland is a just any structure that makes and secretes a hormone . and the master gland in your body is the pituitary , which produces many hormones that signal other glands -- like the thyroid , parathyroid , adrenal , and pineal glands -- to make their own hormones . the endocrine system also includes a few organs -- like the gonads , the pancreas , and the placenta in pregnant women -- all of which have some other non-hormonal functions and are made up of multiple tissue types . and technically the hypothalamus in your brain is in the endocrine club too , since in addition to all of its busy brain duties , it does produce and release hormones . so , thanks to these glands and organs , you ’ ve got all these hormones diffusing through your blood , doing all sorts of different things , but the thing to remember about them is that a hormone can only trigger a reaction in specific cells -- their so-called target cells -- that have the right receptors for it . so , just like some keys can open many locks , while others only work with one , so too can the hormone-target-cell relationship either be widespread or localized . you ’ re probably gon na want an example of that . so , your thyroid -- at the bottom of your throat -- produces the hormone thyroxine , which stimulates metabolism and binds to receptors in most of the cells in your body . but your pituitary -- which is nestled all comfy under your brain -- produces follicle-stimulating hormone , which helps regulate growth and triggers sexual maturity , and it only targets specific cells in the ovaries and testes . so how do hormones bind to their target cells ? well , chemically , most hormones are either made of amino acids -- including their more complex structures like peptides or proteins -- or they ’ re derived from lipids , like cholesterol . and this is key , because a hormone ’ s chemical structure determines if it ’ s water soluble , like most amino acid-based ones are , or lipid soluble , like steroids are . solubility is important because your cell membranes are made of lipids . that means that water soluble ones can ’ t get across them . so target cells for those kinds of hormones have receptors for them on the outside of their membranes . lipid-soluble hormones , on the other hand , can just basically glide right through that cell membrane , so their receptor sites are inside their target cells . either way , when a target cell is activated , the hormone alters its activity , by either increasing or decreasing some of its functions -- usually with the goal of maintaining your body ’ s homeostasis in one way or another . so , if hormones are keeping your body in balance , what ’ s putting your body out of balance ? i don ’ t know -- could i interest you in some pie ? if you have a couple of nice , generous helpings of strawberry-rhubarb pie -- and just to make things interesting , let ’ s say they ’ re a la mode -- your blood glucose level is gon na go through the roof . and the pancreas regulates your blood sugar by releasing two different hormones -- insulin and glucagon . once you have a belly full of that pie , beta cells in your pancreas release insulin , which helps lower your blood sugar by increasing the rate at which your cells store the sugar either as glycogen or as fat for later use . now , let ’ s say you ’ ve done the opposite : you ’ ve eaten no pie -- you ’ re pie-less -- in fact , you ’ ve eaten nothing for hours . if your blood sugar drops too low , then alpha cells in the pancreas will instead send out glucagon , which helps raise your blood sugar levels , in part by decreasing the storage of sugar in your cells , and triggering their release of glucose back into the blood . lots of different endocrine-related illnesses -- like diabetes or hyperthyroidism -- tend to be the result of either hyper ( too much ) or hypo ( too little ) secretion of certain hormones , which throw your homeostasis off balance . but there are lots of more common -- and less obvious -- ways your hormones can get out of balance , not because of some disorder , but because these signaling chemicals are just caught up in a chain reaction , which can take a while to subside . some hormones just exist to control other hormones , which in turn control still more hormones . so as soon as one starts to trickle out , you can pretty quickly wind up with a cascade on your hands . you ’ ve got a few different hormone cascades going on at any given moment , but one of the big ones -- one that ’ s really worth understanding -- is the hypothalamic-pituitary-adrenal axis , or the hpa axis , because you don ’ t want to have to say that every time . this is a complex series of interactions between three glands that ultimately regulates lots of your body ’ s daily processes , like digestion , sexuality , immune response , and how you handle stress . and it ’ s complex not just because of all the glands involved -- it ’ s also one of the more crucial instances of your endocrine system coordinating with your nervous system . specifically , it ’ s behind that fight-or-flight response that everybody keeps talking about . the hpa axis is essentially the endocrine system ’ s companion to the sympathetic nervous system . the sympathetic system , in times of high stress , does things like speed up your heart rate and direct blood away from the digestive organs and to the muscles . but many of the other effects of the stress response are carried out by your endocrine system . and getting your nervous and endocrine systems to work together in times of crisis is where the hypothalamus comes in . it ’ s the hub of where the two systems meet -- it keeps tabs on what ’ s going on all over your body , analyzing your blood for signs that something might be off . so , let ’ s revisit our fight-or-flight scene from a few lessons ago -- the old burning house scenario . so you ’ re sleeping , dreaming about petting pandas with emma watson or whatever , when the smoke alarm goes off . well , action potentials in your brain trigger neurons in your hypothalamus to release the peptide hormone crh , or corticotropin releasing hormone . the crh makes the very short trip through the bloodstream to the anterior pituitary gland , where , because it ’ s water soluble , it binds to receptors on the outside of its target cells . there , it triggers the release of adrenocorticotropic hormone , or acth . the acth travels -- again through the bloodstream -- to the adrenal cortices of the adrenal glands on top of your kidneys . when the acth binds to receptors on cells in an adrenal cortex , it triggers the release of a frenzy of different freak-out compounds known as glucocorticoid and mineralcorticoid hormones . typically these guys help us deal with day-to-day stress by keeping our blood sugar and blood pressure balanced . but under major stress -- like waking up in a burning building stress -- these hormones , like cortisol , cause the classic fight-or-flight response : ramping up your blood pressure , dumping glucose into your bloodstream , shutting down non-emergency services like your immune system and sperm and egg development . and guess what ? now that all these stress hormones are pulsing through your blood , the hypothalamus back in the brain senses them . and because its job is to monitor and maintain balance whenever possible , it then stops secreting crh , which -- eventually -- causes the other glands to stop secreting their panic hormones . now , because this element of the stress response is hormonal rather than electrical , it comes on more slowly than the nervous system part , and it takes longer to subside , too , as those stress hormones linger in the blood before being broken down by enzymes . so . we ’ re a long way from teenage crushes and zits and crying over commercials at this point , aren ’ t we ? as a life-long owner of hormones , i hope you ’ ll join me in dispelling the stereotypes that surround these powerful and important chemicals , and give them the respect they rightly deserve . today we looked at the endocrine system , and how it uses glands to produce hormones . these hormones are either amino-acid based and water soluble , or steroidal and lipid-soluble , and may target many types of cells or just turn on specific ones . we also touched on hormone cascades , and how the hpa axis effects your stress response . thank you to our headmaster of learning , thomas frank , and to all of our patreon patrons who help make crash course possible through their monthly contributions . if you like crash course and you want to help us keep making free educational content for the whole world , you can go to patreon.com/crashcourse . crash course is filmed in the doctor cheryl c. kinney crash course studio . this episode was written by kathleen yale , edited by blake de pastino , and our consultant is dr. brandon jackson . it was directed by nicholas jenkins , the editor is nicole sweeney , the script supervisor was stefan chin , our sound designer is michael aranda and the graphics team is thought café .
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they ’ re also rogues -- instead of being all nestled together like in your other organ systems , these guys are scattered all over the place , from your brain to your throat , to your kidneys , to your genitals . a gland is a just any structure that makes and secretes a hormone . and the master gland in your body is the pituitary , which produces many hormones that signal other glands -- like the thyroid , parathyroid , adrenal , and pineal glands -- to make their own hormones .
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a ( n ) _____ is any structure that makes and secretes a hormone .
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many elements of traditional japanese culture , such as cuisine and martial arts , are well-known throughout the world . kabuki , a form of classical theater performance , may not be as well understood in the west but has evolved over 400 years to still maintain influence and popularity to this day . the word kabuki is derived from the japanese verb kabuku , meaning out of the ordinary or bizarre . its history began in early 17th century kyoto , where a shrine maiden named izumo no okuni would use the city 's dry kamo riverbed as a stage to perform unusual dances for passerby , who found her daring parodies of buddhist prayers both entertaining and mesmerizing . soon other troops began performing in the same style , and kabuki made history as japan 's first dramatic performance form catering to the common people . by relying on makeup , or keshou , and facial expressions instead of masks and focusing on historical events and everyday life rather than folk tales , kabuki set itself apart from the upper-class dance theater form known as noh and provided a unique commentary on society during the edo period . at first , the dance was practiced only by females and commonly referred to as onna-kabuki . it soon evolved to an ensemble performance and became a regular attraction at tea houses , drawing audiences from all social classes . at this point , onna-kabuki was often risque as geishas performed not only to show off their singing and dancing abilities but also to advertise their bodies to potential clients . a ban by the conservative tokugawa shogunate in 1629 led to the emergence of wakashu-kabuki with young boys as actors . but when this was also banned for similar reasons , there was a transition to yaro-kabuki , performed by men , necessitating elaborate costumes and makeup for those playing female roles , or onnagata . attempts by the government to control kabuki did n't end with bans on the gender or age of performers . the tokugawa military group , or bakufu , was fueled by confucian ideals and often enacted sanctions on costume fabrics , stage weaponry , and the subject matter of the plot . at the same time , kabuki became closely associated with and influenced by bunraku , an elaborate form of puppet theater . due to these influences , the once spontaneous , one-act dance evolved into a structured , five-act play often based on the tenets of confucian philosophy . before 1868 , when the tokugawa shogunate fell and emperor meiji was restored to power , japan had practiced isolation from other countries , or sakoku . and thus , the development of kabuki had mostly been shaped by domestic influences . but even before this period , european artists , such as claude monet , had become interested in and inspired by japanese art , such as woodblock prints , as well as live performance . after 1868 , others such as vincent van gogh and composer claude debussy began to incorporate kabuki influences in their work , while kabuki itself underwent much change and experimentation to adapt to the new modern era . like other traditional art forms , kabuki suffered in popularity in the wake of world war ii . but innovation by artists such as director tetsuji takechi led to a resurgence shortly after . indeed , kabuki was even considered a popular form of entertainment amongst american troops stationed in japan despite initial u.s. censorship of japanese traditions . today , kabuki still lives on as an integral part of japan 's rich cultural heritage , extending its influence beyond the stage to television , film , and anime . the art form pioneered by okuni continues to delight audiences with the actors ' elaborate makeup , extravagant and delicately embroidered costumes , and the unmistakable melodrama of the stories told on stage .
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the tokugawa military group , or bakufu , was fueled by confucian ideals and often enacted sanctions on costume fabrics , stage weaponry , and the subject matter of the plot . at the same time , kabuki became closely associated with and influenced by bunraku , an elaborate form of puppet theater . due to these influences , the once spontaneous , one-act dance evolved into a structured , five-act play often based on the tenets of confucian philosophy .
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the onnagata were introduced into which form of kabuki ?
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one of the most striking properties about life is that it has color . to understand the phenomenon of color , it helps to think about light as a wave . but , before we get to that , let 's talk a little bit about waves in general . imagine you 're sitting on a boat on the ocean watching a cork bob up and down in the water . the first thing you notice about the motion is that it repeats itself . the cork traces the same path over and over again ... up and down , up and down . this repetitive or periodic motion is characteristic of waves . then you notice something else ... using a stopwatch , you measure the time it takes for the piece of cork to go over its highest position down to its lowest and then back up again . suppose this takes two seconds . to use the physics jargon , you 've measured the period of the waves that cork is bobbing on . that is , how long it takes a wave to go through its full range of motion once . the same information can be expressed in a different way by calculating the wave 's frequency . frequency , as the name suggest , tells you how frequent the waves are . that is , how many of them go by in one second . if you know how many seconds one full wave takes , then it 's easy to work out how many waves go by in one second . in this case , since each wave takes 2 seconds , the frequency is 0.5 waves per second . so enough about bobbing corks ... what about light and color ? if light is a wave , then it must have a frequency . right ? well ... yes , it does . and it turns out that we already have a name for the frequency of the light that our eyes detect . it 's called color . that 's right . color is nothing more than a measure of how quickly the light waves are waving . if our eyes were quick enough , we might be able to observe this periodic motion directly , like we can with the cork and the ocean . but the frequency of the light we see is so high , it waves up and down about 400 million million times a second , that we ca n't possibly see it as a wave . but we can tell , by looking at its color , what its frequency is . the lowest frequency light that we can see is red and the highest frequency is purple . in between all the other frequencies form a continous band of color , called the visible spectrum . so , what if you had a yellow pencil sitting on your desk ? well , the sun emits all colors of light , so light of all colors is hitting your pencil . the pencil looks yellow because it reflects yellow light more than it reflects the other colors . what happens to the blue , purple and red light ? they get absorbed and the energy they are carrying is turned into heat . it is similar with objects of other colors . blue things reflect blue light , red things reflect red light and so on . white objects reflect all colors of light , while black things do exactly the opposite and absorb at all frequencies . this - by the way - is why it 's uncomfortable to wear your favorite metallica t-shirt on a sunny day .
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blue things reflect blue light , red things reflect red light and so on . white objects reflect all colors of light , while black things do exactly the opposite and absorb at all frequencies . this - by the way - is why it 's uncomfortable to wear your favorite metallica t-shirt on a sunny day .
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explain ( in your own words ) why it 's better to wear lighter colors ( such as white and pale yellow ) during the summer and better to wear darker colors ( like black and charcoal gray ) in the winter .
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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 .
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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 .
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the cloud experiment is measuring some important unknown physics and chemistry of aerosols and clouds in a large chamber at cern , the european organization for nuclear research . why is it better to do some experiments like these in the laboratory rather than in the real atmosphere ?
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the evolutionary tango of animal genitalia . can you guess what you 're looking at ? if you answered `` duck vagina , '' you 'd be right . although the bird 's outward appearance may not strike you as especially odd , it uses this strange , intricate , cork-screw shaped contraption to reproduce . we see similarly unbelievable genitalia in insects , mammals , reptiles , fish , spiders , and even snails . apparently , no organs evolve faster and into more variable shapes than those involved in procreation . superficially , it makes sense because evolution works via reproduction . when an animal leaves more offspring , its genes will spread . and since genitalia are an animal 's tools for reproduction , any improvement there will have immediate effect . and yet , what 's the point of having such decorative nether regions ? after all , the function of genitalia seems simple . a penis deposits a bit of sperm and a vagina receives it and delivers it to the egg . a pipette-like thingy on the male and a funnel-like gizmo on the female should do just fine for any animal . and yet , that 's not what we see . the penis of a chicken flea , for example , looks nothing like a pipette , more like an exploded grandfather clock . and the vagina of a featherwing beetle resembles something you 'd find in a dr. seuss book . throughout the animal kingdom , genitalia are very complex things , much more complicated than seems necessary for what they 're meant to do . that 's because genitalia do more than just deposit and receive sperm . many male animals also use the penis as courtship device , like crane flies . in some south american species , males have a tiny washboard and scraper on their penis , which produces a song that reverberates throughout the female 's body when they mate . it 's thought that if female crane flies enjoy this unusual serenade , they 'll allow the male to father their offspring . this way , the genes of the most musical penises spread , leading to rapid evolution of insects ' phalluses . similarly , some beetles have two little drumsticks on either side of the penis . during mating , they 'll rub , slap , or tap the female with these . and some hoofed mammals , like rams and bulls , use a whip-like extension on the penis 's left side to create a sensation during mating . but how can females really choose between males if she can only assess them after mating ? this is where the power of female adaptation comes into play . in fact , insemination is different to conception , and the female genitalia exploit this distinction . for instance , in some dung flies , the vagina contains pockets for separating sperm from different males depending on how appealing they were . males using their penises for courtship and females controlling their own sperm management are two reasons why genitalia evolve into such complex shapes . but there are others because genitalia are also where a sexual conflict is played out . a female 's interests are best served if she fertilizes her eggs with the sperm of the best fathers and creates genetic variability amongst her offspring . for a male , on the other hand , this is bad news . for him , it would be best if a female used his sperm to fertilize all of her eggs . so we see cycles of adaptation in an evolutionary arms race to retain control . black widow spiders have a disposable penis tip that breaks off inside the vagina blocking the attempts of his rivals , and bed bug males bypass a female 's genitalia altogether using a syringe-like penis to inject sperm cells directly into her belly . not to be outdone , females have evolved their own countermeasures . in some bed bug species , the females have evolved an entirely new set of genitalia on their right hand flanks where the males usually pierce them . that allows them to maintain the power to filter out unwanted sperm with their genitalia . and duck vaginas are shaped like a clockwise spiral so that when the male inflates his long , counterclockwise coiled penis into her , and she disapproves , all she needs to do is flex her vaginal muscles and the penis just flubs out . so , genitalia differs so much , not just to fascinate us , but because in every species , they 're the result of a furious evolutionary tango of sex that has been going on for millions of years and will continue for millions of years to come .
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that 's because genitalia do more than just deposit and receive sperm . many male animals also use the penis as courtship device , like crane flies . in some south american species , males have a tiny washboard and scraper on their penis , which produces a song that reverberates throughout the female 's body when they mate . it 's thought that if female crane flies enjoy this unusual serenade , they 'll allow the male to father their offspring .
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the penis of some south-american species of crane fly have an unusual feature . what is this ?
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physicists , air traffic controllers , and video game creators all have at least one thing in common : vectors . what exactly are they , and why do they matter ? to answer , we first need to understand scalars . a scalar is a quantity with magnitude . it tells us how much of something there is . the distance between you and a bench , and the volume and temperature of the beverage in your cup are all described by scalars . vector quantities also have a magnitude plus an extra piece of information , direction . to navigate to your bench , you need to know how far away it is and in what direction , not just the distance , but the displacement . what makes vectors special and useful in all sorts of fields is that they do n't change based on perspective but remain invariant to the coordinate system . what does that mean ? let 's say you and a friend are moving your tent . you stand on opposite sides so you 're facing in opposite directions . your friend moves two steps to the right and three steps forward while you move two steps to the left and three steps back . but even though it seems like you 're moving differently , you both end up moving the same distance in the same direction following the same vector . no matter which way you face , or what coordinate system you place over the camp ground , the vector does n't change . let 's use the familiar cartesian coordinate system with its x and y axes . we call these two directions our coordinate basis because they 're used to describe everything we graph . let 's say the tent starts at the origin and ends up over here at point b . the straight arrow connecting the two points is the vector from the origin to b . when your friend thinks about where he has to move , it can be written mathematically as 2x + 3y , or , like this , which is called an array . since you 're facing the other way , your coordinate basis points in opposite directions , which we can call x prime and y prime , and your movement can be written like this , or with this array . if we look at the two arrays , they 're clearly not the same , but an array alone does n't completely describe a vector . each needs a basis to give it context , and when we properly assign them , we see that they are in fact describing the same vector . you can think of elements in the array as individual letters . just as a sequence of letters only becomes a word in the context of a particular language , an array acquires meaning as a vector when assigned a coordinate basis . and just as different words in two languages can convey the same idea , different representations from two bases can describe the same vector . the vector is the essence of what 's being communicated , regardless of the language used to describe it . it turns out that scalars also share this coordinate invariance property . in fact , all quantities with this property are members of a group called tensors . various types of tensors contain different amounts of information . does that mean there 's something that can convey more information than vectors ? absolutely . say you 're designing a video game , and you want to realistically model how water behaves . even if you have forces acting in the same direction with the same magnitude , depending on how they 're oriented , you might see waves or whirls . when force , a vector , is combined with another vector that provides orientation , we have the physical quantity called stress , which is an example of a second order tensor . these tensors are also used outside of video games for all sorts of purposes , including scientific simulations , car designs , and brain imaging . scalars , vectors , and the tensor family present us with a relatively simple way of making sense of complex ideas and interactions , and as such , they 're a prime example of the elegance , beauty , and fundamental usefulness of mathematics .
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no matter which way you face , or what coordinate system you place over the camp ground , the vector does n't change . let 's use the familiar cartesian coordinate system with its x and y axes . we call these two directions our coordinate basis because they 're used to describe everything we graph .
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in the video , we used standard cartesian coordinates , x-hat and y-hat , and rotated those coordinates 180 degrees to get new coordinates , x-prime-hat and y-prime-hat . can you think of another commonly used coordinate system ? what might these coordinates be useful for describing ?
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how many times can you fold a piece of paper ? assume that one had a piece of paper that was very fine , like the kind they typically use to print the bible . in reality , it seems like a piece of silk . to qualify these ideas , let 's say you have a paper that 's one-thousandth of a centimeter in thickness . that is 10 to the power of minus three centimeters , which equals .001 centimeters . let 's also assume that you have a big piece of paper , like a page out of the newspaper . now we begin to fold it in half . how many times do you think it could be folded like that ? and another question : if you could fold the paper over and over , as many times as you wish , say 30 times , what would you imagine the thickness of the paper would be then ? before you move on , i encourage you to actually think about a possible answer to this question . ok. after we have folded the paper once , it is now two thousandths of a centimeter in thickness . if we fold it in half once again , the paper will become four thousandths of a centimeter . with every fold we make , the paper doubles in thickness . and if we continue to fold it again and again , always in half , we would confront the following situation after 10 folds . two to the power of 10 , meaning that you multiply two by itself 10 times , is one thousand and 24 thousandths of a centimeter , which is a little bit over one centimeter . assume we continue folding the paper in half . what will happen then ? if we fold it 17 times , we 'll get a thickness of two to the power of 17 , which is 131 centimeters , and that equals just over four feet . if we were able to fold it 25 times , then we would get two to the power of 25 , which is 33,554 centimeters , just over 1,100 feet . that would make it almost as tall as the empire state building . it 's worthwhile to stop here and reflect for a moment . folding a paper in half , even a paper as fine as that of the bible , 25 times would give us a paper almost a quarter of a mile . what do we learn ? this type of growth is called exponential growth , and as you see , just by folding a paper we can go very far , but very fast too . summarizing , if we fold a paper 25 times , the thickness is almost a quarter of a mile . 30 times , the thickness reaches 6.5 miles , which is about the average height that planes fly . 40 times , the thickness is nearly 7,000 miles , or the average gps satellite 's orbit . 48 times , the thickness is way over one million miles . now , if you think that the distance between the earth and the moon is less than 250,000 miles , then starting with a piece of bible paper and folding it 45 times , we get to the moon . and if we double it one more time , we get back to earth .
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with every fold we make , the paper doubles in thickness . and if we continue to fold it again and again , always in half , we would confront the following situation after 10 folds . two to the power of 10 , meaning that you multiply two by itself 10 times , is one thousand and 24 thousandths of a centimeter , which is a little bit over one centimeter .
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paenza ’ s problem assumes which of the following :
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here at scishow hq we have a little food area for the employees - sometimes there are donuts . sometimes there are nuts . sometimes dried mango . but the one thing that never sticks around and is gone as soon as we can buy it is the wonderful , beautiful , noble banana . unfortunately for us , they may not be around forever . [ intro music ] first , the good : bananas are healthy , packed with nutrition and energy , they fit in your hand and give nice little cues when they 're perfectly ripe , and are easy to peel and eat ; shocking statistic , the banana is wal-mart 's number one selling item . not the potato chip , not coca-cola , not fifty shades of grey , bananas . they appear to be so perfect for human consumption that kirk cameron attempted to use them to prove the existence of god . of course this banana was not created by god , or really even nature . bananas , at least the ones that you see at the store , were created by people . do n't get me wrong , there are wild banana plants - lots of them - they 're native to south and southeast asia , and there are dozens of species and thousands of varieties . they 're just not the ones we eat . some those species , as you might suspect , have seeds , 'cause that 's what fruits are , they 're fleshy bodies containing seeds . so you might wonder , why have you never eaten a banana seed ? well , you have ... kinda . in cultivated bananas the seeds have pretty much stopped existing . if you look closely you can see tiny black specks . those are all that 's left , and they 're not fertile seeds . if you plant them , nothing grows . today 's bananas are sterile mutants . i 'm not trying to be mean , that 's just the truth . unless you were alive in the 1960 's ( hats off to all those older scishow viewers out there ) every banana you have ever eaten was pretty much genetically identical . this is a cavendish , the virtually seedless variety that we all eat today , but it was n't always our banana of choice . until the 1960s , everyone was eating the same banana , it was just a different banana - the gros michel , a bigger , sweeter fruit with thicker skin . you might notice that banana flavored things do n't really taste like bananas . well they do - they taste like the gros michel . the genetic monotony of the gros michel crop was its undoing . a fungicide resistant pathogen called the panama disease began infecting gros michel crop . by the time growers understood how vulnerable their crops were , the gros michel variety was all but extinct . the entire banana industry had to be retooled for the cavendish . since they 're seedless , the only way to reproduce them is to transplant part of the plant stem , and for the last 50 years we 've been good with the cavendish , 'cause it 's more resistant to the panama disease . however somewhat terrifyingly a strain of panama disease that affects the cavendish strain that we all eat has been identified . a global monoculture of genetically identical individuals is a beautiful sight to a pathogen . the fungus only has to figure out how to infect and destroy a single individual , and suddenly there is no diversity to stop it , or even slow it down . that 's led to a lot of scientists worrying about or even predicting the outright demise of the cavendish . this wonderful most popular of fruits might completely cease existence . the good news is we now have a much better understanding of genetics , epidemics , fungi , and pathology . scientists and growers have already taken steps to protect the cavendish . some growers are creating genetically different bananas that might replace the cavendish crop if it fails , while scientists are attempting to genetically engineer cavendish plants with immunity to panama disease . plus we learned a lot from the gros michel debacle . infected fields are quickly being destroyed and new crops are grown from pathogen-free lab-grown plant stock . so thanks to the people who work tirelessly to grow and harvest bananas and bring them to us so that we can offer them inexpensively to our employees , and thanks to the growers and scientists working tirelessly to make sure that they do n't go the way of the gros michel . thanks for watching this episode of scishow , if you have any questions , comments or suggestions for us , you can find us on facebook , twitter or in the comments below , and if you want to continue getting smarter this year at scishow , you can go to youtube.com/scishow and subscribe . [ banana eating noises ] [ music ]
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this wonderful most popular of fruits might completely cease existence . the good news is we now have a much better understanding of genetics , epidemics , fungi , and pathology . scientists and growers have already taken steps to protect the cavendish .
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7. genetics , epidemics , fungi and pathology . use each these words correctly in a sentence .
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here are some images of clusters of galaxies . they 're exactly what they sound like . they are these huge collections of galaxies , bound together by their mutual gravity . so most of the points that you see on the screen are not individual stars , but collections of stars , or galaxies . now , by showing you some of these images , i hope that you will quickly see that galaxy clusters are these beautiful objects , but more than that , i think galaxy clusters are mysterious , they are surprising , and they 're useful . useful as the universe 's most massive laboratories . and as laboratories , to describe galaxy clusters is to describe the experiments that you can do with them . and i think there are four major types , and the first type that i want to describe is probing the very big . so , how big ? well , here is an image of a particular galaxy cluster . it is so massive that the light passing through it is being bent , it 's being distorted by the extreme gravity of this cluster . and , in fact , if you look very carefully you 'll be able to see rings around this cluster . now , to give you a number , this particular galaxy cluster has a mass of over one million billion suns . it 's just mind-boggling how massive these systems can get . but more than their mass , they have this additional feature . they are essentially isolated systems , so if we like , we can think of them as a scaled-down version of the entire universe . and many of the questions that we might have about the universe at large scales , such as , how does gravity work ? might be answered by studying these systems . so that was very big . the second things is very hot . okay , if i take an image of a galaxy cluster , and i subtract away all of the starlight , what i 'm left with is this big , blue blob . this is in false color . it 's actually x-ray light that we 're seeing . and the question is , if it 's not galaxies , what is emitting this light ? the answer is hot gas , million-degree gas -- in fact , it 's plasma . and the reason why it 's so hot goes back to the previous slide . the extreme gravity of these systems is accelerating particles of gas to great speeds , and great speeds means great temperatures . so this is the main idea , but science is a rough draft . there are many basic properties about this plasma that still confuse us , still puzzle us , and still push our understanding of the physics of the very hot . third thing : probing the very small . now , to explain this , i need to tell you a very disturbing fact . most of the universe 's matter is not made up of atoms . you were lied to . most of it is made up of something very , very mysterious , which we call dark matter . dark matter is something that does n't like to interact very much , except through gravity , and of course we would like to learn more about it . if you 're a particle physicist , you want to know what happens when we smash things together . and dark matter is no exception . well , how do we do this ? to answer that question , i 'm going to have to ask another one , which is , what happens when galaxy clusters collide ? here is an image . since galaxy clusters are representative slices of the universe , scaled-down versions . they are mostly made up of dark matter , and that 's what you see in this bluish purple . the red represents the hot gas , and , of course , you can see many galaxies . what 's happened is a particle accelerator at a huge , huge scale . and this is very important , because what it means is that very , very small effects that might be difficult to detect in the lab , might be compounded and compounded into something that we could possibly observe in nature . so , it 's very funny . the reason why galaxy clusters can teach us about dark matter , the reason why galaxy clusters can teach us about the physics of the very small , is precisely because they are so very big . fourth thing : the physics of the very strange . certainly what i 've said so far is crazy . okay , if there 's anything stranger i think it has to be dark energy . if i throw a ball into the air , i expect it to go up . what i do n't expect is that it go up at an ever-increasing rate . similarly , cosmologists understand why the universe is expanding . they do n't understand why it 's expanding at an ever-increasing rate . they give the cause of this accelerated expansion a name , and they call it dark energy . and , again , we want to learn more about it . so , one particular question that we have is , how does dark energy affect the universe at the largest scales ? depending on how strong it is , maybe structure forms faster or slower . well , the problem with the large-scale structure of the universe is that it 's horribly complicated . here is a computer simulation . and we need a way to simplify it . well , i like to think about this using an analogy . if i want to understand the sinking of the titanic , the most important thing to do is not to model the little positions of every single little piece of the boat that broke off . the most important thing to do is to track the two biggest parts . similarly , i can learn a lot about the universe at the largest scales by tracking its biggest pieces and those biggest pieces are clusters of galaxies . so , as i come to a close , you might feel slightly cheated . i mean , i began by talking about how galaxy clusters are useful , and i 've given some reasons , but what is their use really ? well , to answer this , i want to give you a quote by henry ford when he was asked about cars . he had this to say : `` if i had asked people what they wanted , they would have said faster horses . '' today , we as a society are faced with many , many difficult problems . and the solutions to these problems are not obvious . they are not faster horses . they will require an enormous amount of scientific ingenuity . so , yes , we need to focus , yes , we need to concentrate , but we also need to remember that innovation , ingenuity , inspiration -- these things come when we broaden our field of vision when we step back when we zoom out . and i ca n't think of a better way to do this than by studying the universe around us . thanks . ( applause )
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if you 're a particle physicist , you want to know what happens when we smash things together . and dark matter is no exception . well , how do we do this ?
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dark matter is difficult to detect directly because ________ .
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translator : andrea mcdonough reviewer : jessica ruby worst case scenario : zombie apocalypse . how will you survive ? you might be surprised to find out how much geography skills can help you fend off doom . by geography , i mean analyzing the world around you . one geographic concept that could really help you out in a zombie apocalypse is movement . so , first , what moves ? people move , animals move , and , while sometimes slowly , zombies move as well . but that 's not all . goods move , too . goods can be resources , such as food supplies and weapons . people or zombies tend to move these . so , if you see a big pile of zombie supplies where there was n't one before , you 're probably on the trail . ideas also move . ideas can include entertainment , zombie movies , news and information about zombie attacks , and architecture , or how to build a safe shelter . and , second , why do people or zombies move ? when people , animals , or zombies move , it 's called migration . two concepts that affect migration are push and pull factors . push factors will make you want to leave somewhere . pull factors make you want to go to a place . a lack of resources , unstable economy , or high crime rate might be push factors making people want to move . nice weather , a good economy , or lots of resources would be pull factors for lots of people , enticing them to move . while zombies are definitely a push factor for humans , a city full of people would be a pull factor for hungry zombies who want to eat humans . there are some things that make movement easier for people or zombies . waterways and highways can make traveling faster . moving across clear , open space is easier than a tough terrain . and just as land forms can create boundaries that affect movement , so can political boundaries , like a border gate , for example . so , how can you analyze these movement factors to help your chance of survival ? there are three basic steps . one - identify the points or locations to analyze . what are your options ? two - find what connects them . are there highways , waterways , or open land ? and three - find the patterns of movement that happen over that connection . do people or goods move across it ? by comparing relationships between different places , you can see what connections they have . for example , pick two cities . look at the highway connecting them . if people use that highway to commute to work , those cities have a strong relationship . but this other city over here does n't have a direct connection to the other cities . there 's even a river in the way . it does n't have as strong of a relationship . if a zombie outbreak started here , which city would you rather start out in ? where would you flee to ? so , how do you decide where to go in a zombie apocalypse ? do you just run in a random direction ? or do you use your geographic skills to lead your camp of survivors to safety ? if you want to stay alive , it helps to understand how and why we move .
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and just as land forms can create boundaries that affect movement , so can political boundaries , like a border gate , for example . so , how can you analyze these movement factors to help your chance of survival ? there are three basic steps .
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which of the following would most likely help facilitate movement ?
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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 .
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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 .
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experts predict that global population will top out around 10 billion people , with 7 billion of those people living in cities . what are some of the opportunities and challenges that cities will face as the population increases ?
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translator : andrea mcdonough reviewer : bedirhan cinar we all start life as one single cell . then that cell divides and we are two cells , then four , then eight . cells form tissues , tissues form organs , organs form us . these cell divisions , by which we go from a single cell to 100 trillion cells , are called growth . and growth seems like a simple thing because when we think of it , we typically think of someone getting taller or , later in life , wider , but to cells , growth is n't simple . cell division is an intricate chemical dance that 's part individual , part community-driven . and in a neighborhood of 100 trillion cells , some times things go wrong . maybe an individual cell 's set of instructions , or dna , gets a typo , what we call a mutation . most of the time , the cell senses mistakes and shuts itself down , or the system detects a troublemaker and eliminates it . but , enough mutations can bypass the fail-safes , driving the cell to divide recklessly . that one rogue cell becomes two , then four , then eight . at every stage , the incorrect instructions are passed along to the cells ' offspring . weeks , months , or years after that one rogue cell transformed , you might see your doctor about a lump in your breast . difficulty going to the bathroom could reveal a problem in your intestine , prostate , or bladder . or , a routine blood test might count too many white cells or elevated liver enzymes . your doctor delivers the bad news : it 's cancer . from here your strategy will depend on where the cancer is and how far it 's progressed . if the tumor is slow-growing and in one place , surgery might be all you need , if anything . if the tumor is fast-growing or invading nearby tissue , your doctor might recommend radiation or surgery followed by radiation . if the cancer has spread , or if it 's inherently everywhere like a leukemia , your doctor will most likely recommend chemotherapy or a combination of radiation and chemo . radiation and most forms of chemo work by physically shredding the cells ' dna or disrupting the copying machinery . but neither radiation nor chemotherapeutic drugs target only cancer cells . radiation hits whatever you point it at , and your blood stream carries chemo-therapeutics all over your body . so , what happens when different cells get hit ? let 's look at a healthy liver cell , a healthy hair cell , and a cancerous cell . the healthy liver cell divides only when it is stressed ; the healthy hair cell divides frequently ; and the cancer cell divides even more frequently and recklessly . when you take a chemotherapeutic drug , it will hit all of these cells . and remember that the drugs work typically by disrupting cell division . so , every time a cell divides , it opens itself up to attack , and that means the more frequently a cell divides , the more likely the drug is to kill it . so , remember that hair cell ? it divides frequently and is n't a threat . and , there are other frequently dividing cells in your body like skin cells , gut cells , and blood cells . so the list of unpleasant side effects of cancer treatment parallels these tissue types : hair loss , skin rashes , nausea , vomiting , fatigue , weight loss , and pain . that makes sense because these are the cells that get hit the hardest . so , in the end , it is all about growth . cancer hijacks cells ' natural division machinery and forces them to put the pedal to the metal , growing rapidly and recklessly . but , using chemotherapeutic drugs , we take advantage of that aggressiveness , and we turn cancer 's main strength into a weakness .
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cancer hijacks cells ' natural division machinery and forces them to put the pedal to the metal , growing rapidly and recklessly . but , using chemotherapeutic drugs , we take advantage of that aggressiveness , and we turn cancer 's main strength into a weakness .
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there are many actions that you can take to improve your lifestyle and reduce your risk of developing cancer . how can you take an active role in cancer prevention ?
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to understand climate change , think of the game `` tetris . '' for eons , earth has played a version of this game with blocks of carbon . they enter the atmosphere as carbon dioxide gas from volcanoes , decaying plant matter , breathing creatures and the surface of the sea . and they leave the atmosphere when they 're used by plants during photosynthesis , absorbed back into the ocean , or stored in soil and sediment . this game of tetris is called the carbon cycle , and it 's the engine of life on earth . what 's the connection to climate ? well , when that carbon dioxide is in the air , waiting to be reabsorbed , it traps a portion of the sun 's heat , which would otherwise escape to space . that 's why carbon dioxide is called a greenhouse gas . it creates a blanket of warmth , known as the greenhouse effect , that keeps our earth from freezing like mars . the more carbon dioxide blocks hang out in the atmosphere waiting to be cleared , the warmer earth becomes . though the amount of carbon in the atmosphere has varied through ice ages and astroid impacts , over the past 8,000 years the stable climate we know took shape , allowing human civilization to thrive . but about 200 years ago , we began digging up that old carbon that had been stored in the soil . these fossil fuels , coal , oil and natural gas are made from the buried remains of plants and animals that died long before humans evolved . the energy stored inside them was able to power our factories , cars and power plants . but burning these fuels also injected new carbon blocks into earth 's tetris game . at the same time , we cleared forests for agriculture , reducing the earth 's ability to remove the blocks . and since 1750 , the amount of carbon in the atmosophere has increased by 40 % , and shows no sign of slowing . just like in tetris , the more blocks pile up , the harder it becomes to restore stability . the extra carbon dioxide in the atmosphere accelerates the greenhouse effect by trapping more heat near the surface and causing polar ice caps to melt . and the more they melt , the less sunlight they 're able to reflect , making the oceans warm even faster . sea levels rise , coastal populations are threatened with flooding , natural ecosystems are disrupted , and the weather becomes more extreme over time . climate change may effect different people and places in different ways . but , ultimately , it 's a game that we 're all stuck playing . and unlike in tetris , we wo n't get a chance to start over and try again .
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to understand climate change , think of the game `` tetris . '' for eons , earth has played a version of this game with blocks of carbon .
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what are some of the effects of climate change ?
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in 1997 , in a game between france and brazil , a young brazilian player named roberto carlos set up for a 35 meter free kick . with no direct line to the goal , carlos decided to attempt the seemingly impossible . his kick sent the ball flying wide of the players , but just before going out of bounds , it hooked to the left and soared into the goal . according to newton 's first law of motion , an object will move in the same direction and velocity until a force is applied on it . when carlos kicked the ball , he gave it direction and velocity , but what force made the ball swerve and score one of the most magnificent goals in the history of the sport ? the trick was in the spin . carlos placed his kick at the lower right corner of the ball , sending it high and to the right , but also rotating around its axis . the ball started its flight in an apparently direct route , with air flowing on both sides and slowing it down . on one side , the air moved in the opposite direction to the ball 's spin , causing increased pressure , while on the other side , the air moved in the same direction as the spin , creating an area of lower pressure . that difference made the ball curve towards the lower pressure zone . this phenomenon is called the magnus effect . this type of kick , often referred to as a banana kick , is attempted regularly , and it is one of the elements that makes the beautiful game beautiful . but curving the ball with the precision needed to both bend around the wall and back into the goal is difficult . too high and it soars over the goal . too low and it hits the ground before curving . too wide and it never reaches the goal . not wide enough and the defenders intercept it . too slow and it hooks too early , or not at all . too fast and it hooks too late . the same physics make it possible to score another apparently impossible goal , an unassisted corner kick . the magnus effect was first documented by sir isaac newton after he noticed it while playing a game of tennis back in 1670 . it also applies to golf balls , frisbees and baseballs . in every case , the same thing happens . the ball 's spin creates a pressure differential in the surrounding air flow that curves it in the direction of the spin . and here 's a question . could you theoretically kick a ball hard enough to make it boomerang all the way around back to you ? sadly , no . even if the ball did n't disintegrate on impact , or hit any obstacles , as the air slowed it , the angle of its deflection would increase , causing it to spiral into smaller and smaller circles until finally stopping . and just to get that spiral , you 'd have to make the ball spin over 15 times faster than carlos 's immortal kick . so good luck with that .
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that difference made the ball curve towards the lower pressure zone . this phenomenon is called the magnus effect . this type of kick , often referred to as a banana kick , is attempted regularly , and it is one of the elements that makes the beautiful game beautiful .
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who described first the magnus effect ?
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as your country 's top spy , you must infiltrate the headquarters of the evil syndicate , find the secret control panel , and deactivate their death ray . but all you have to go on is the following information picked up by your surveillance team . the headquarters is a massive pyramid with a single room at the top level , two rooms on the next , and so on . the control panel is hidden behind a painting on the highest floor that can satisfy the following conditions : each room has exactly three doors to other rooms on that floor , except the control panel room , which connects to only one , there are no hallways , and you can ignore stairs . unfortunately , you do n't have a floor plan , and you 'll only have enough time to search a single floor before the alarm system reactivates . can you figure out which floor the control room is on ? pause now to solve the riddle yourself . answer in : 3 answer in : 2 answer in : 1 to solve this problem , we need to visualize it . for starters , we know that on the correct floor there 's one room , let 's call it room a , with one door to the control panel room , plus one door to room b , and one to c. so there must be at least four rooms , which we can represent as circles , drawing lines between them for the doorways . but once we connect rooms b and c , there are no other connections possible , so the fourth floor down from the top is out . we know the control panel has to be as high up as possible , so let 's make our way down the pyramid . the fifth highest floor does n't work either . we can figure that out by drawing it , but to be sure we have n't missed any possibilities , here 's another way . every door corresponds to a line in our graph that makes two rooms into neighbors . so in the end , there have to be an even number of neighbors no matter how many connections we make . on the fifth highest floor , to fulfill our starting conditions , we 'd need four rooms with three neighbors each , plus the control panel room with one neighbor , which makes 13 total neighbors . since that 's an odd number , it 's not possible , and , in fact , this also rules out every floor that has an odd number of rooms . so let 's go one more floor down . when we draw out the rooms , low and behold , we can find an arrangement that works like this . incidentally , the study of such visual models that show the connections and relationships between different objects is known as graph theory . in a basic graph , the circles representing the objects are known as nodes , while the connecting lines are called edges . researchers studying such graphs ask questions like , `` how far is this node from that one ? '' `` how many edges does the most popular node have ? '' `` is there a route between these two nodes , and if so , how long is it ? '' graphs like this are often used to map communication networks , but they can represent almost any kind of network , from transport connections within a city and social relationships among people , to chemical interactions between proteins or the spread of an epidemic through different locations . so , armed with these techniques , back to the pyramid . you avoid the guards and security cameras , infiltrate the sixth floor from the top , find the hidden panel , pull some conspicuous levers , and send the death ray crashing into the ocean . now , time to solve the mystery of why your surveillance team always gives you cryptic information . hi everybody . if you liked this riddle , try solving these two .
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so in the end , there have to be an even number of neighbors no matter how many connections we make . on the fifth highest floor , to fulfill our starting conditions , we 'd need four rooms with three neighbors each , plus the control panel room with one neighbor , which makes 13 total neighbors . since that 's an odd number , it 's not possible , and , in fact , this also rules out every floor that has an odd number of rooms . so let 's go one more floor down .
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recall that the hint is that all rooms are connected to three other rooms except one that is connected to only one other room . we see from the solution in the video that a floor containing six rooms is possible and six is the smallest number for which it is possible . would a floor having seven rooms be possible even if not the smallest ?
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as one of the most notorious gangsters in history , al capone presided over a vast and profitable empire of organized crime . when he was finally put on trial , the most he could be convicted of was tax evasion . the nearly $ 100 million a year , that 's 1.4 billion in today 's currency , that capone had earned from illegal gambling , bootlegging , brothels , and extortion , would have served as evidence of his crimes . but the money was nowhere to be found . capone and his associates had hidden it through investments in various businesses whose ultimate ownership could n't be proven , like cash-only laundromats . in fact , those laundromats are part of the reason for the name of this activity , money laundering . money laundering came to be the term for any process that cleans illegally obtained funds of their dirty criminal origins , allowing them to be used within the legal economy . but capone was n't the first to launder money . in fact , this practice is about as old as money itself . merchants hid their riches from tax collecters , and pirates sought to sell their bounty without drawing attention to how they got it . with the recent arrival of virtual currencies , offshore banking , the darknet , and global markets , schemes have become much more complex . although modern money laundering methods vary greatly , most share three basic steps : placement , layering , and integration . placement is where illegally obtained money is converted into assets that seem legitimate . that 's often done by depositing funds into a bank account registered to an anonymous corporation or a professional middleman . this step is where criminals are often most vulnerable to detection since they introduce massive wealth into the financial system seemingly out of nowhere . the second step , layering , involves using multiple transactions to further distance the funds from their origin . this can take the form of transfers between multiple accounts , or the purchase of tradable property , like expensive cars , artwork , and real estate . casinos , where large sums of money change hands every second , are also popular venues for layering . a money launderer may have their gambling balance made available at a casino chain 's locations in other countries , or work with employees to rig games . the last step , integration , allows clean money to re-enter the mainstream economy and to benefit the original criminal . they might invest it into a legal business claiming payment by producing fake invoices , or even start a bogus charity , placing themselves on the board of directors with an exorbitant salary . money laundering itself was n't officially recognized as a federal crime in the united states until 1986 . before that point , the government needed to prosecute a related crime , like tax evasion . from 1986 on , they could confiscate wealth simply by demonstrating that concealment had occurred , which had a positive effect on prosecuting major criminal operations , like drug traffickers . however , a legal shift has raised concerns involving privacy and government surveillance . today , the united nations , national governments , and various nonprofits fight against money laundering , yet the practice continues to play a major role in global crime . and the most high-profile instances of money laundering have involved not just private individuals , but major financial institutions and government officials . no one knows for sure the total amount of money that 's laundered on a yearly basis , but some organizations estimate it to be in the hundreds of billions of dollars .
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with the recent arrival of virtual currencies , offshore banking , the darknet , and global markets , schemes have become much more complex . although modern money laundering methods vary greatly , most share three basic steps : placement , layering , and integration . placement is where illegally obtained money is converted into assets that seem legitimate .
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with the advancement of technology , is it easier to detect money laundering ? please explain .
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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 .
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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 .
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once fluid velocity is measured , what quantities can be calculated ?
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your body is a temple , but it ’ s also a museum of natural history . look closely and you ’ ll see parts that aren ’ t there because you need them but because your animal ancestors did . no longer serving their previous function but not costly enough to have disappeared , these remnants of our deep history only make sense within the framework of evolution by natural selection . with your arm on a flat surface , push your thumb against your pinky and tip your hand slightly up . if you see a raised band in the middle of the wrist , you ’ ve got a vestigial muscle in your forearm . that tendon you see connects to the palmaris longus , a muscle that around 10-15 % of people are missing on one or both of their arms . it doesn ’ t make them any weaker though . there ’ s no difference in grip strength . in fact , it ’ s one of the first tendons that surgeons will take out so they can use it in reconstructive and cosmetic surgeries . you can find the palmaris longus across mammal species , but it ’ s most developed among those that use their forelimbs to move around . in primates , that means the muscle is longer in lemurs and monkeys and shorter in chimps , gorillas , and other apes that don ’ t do a lot of scrambling through trees . it ’ s not the only leftover muscle that we 've got . look at the three that are attached to our outer ear . we can ’ t get much movement out of these muscles , especially compared to some of our mammal relatives who use them to locate the sources of sounds . presumably this would have been quite helpful for early nocturnal mammals . in humans , you can still detect the remnants of this adaptation with electrodes . in one study researchers recorded a spike of activity in the ear muscle cells in response to a sudden sound . not enough to move the ear , but detectable . and you can probably guess the location of the sound based on the results - it came from a speaker to the left of the study subjects . so this is their left ear subconsciously trying ( and failing ) to pivot toward the sound . you can see another futile effort by our vestigial body parts when you get goosebumps . when we ’ re cold , tiny muscles attached to our body hairs contract , pulling the hair upright which causes the surrounding skin to form a bump . for our furry mammal relatives , the raised hair increases the amount of space for insulation , helping them stay warm . birds can do this too . you ’ ve probably seen a puffy pigeon on a cold day . adrenaline is one of the hormones involved in the body ’ s response to cold temperatures , and it ’ s also part of the fight or flight response . so it helps some animals appear larger when they ’ re threatened . and it may be why surprising and emotional turns in music can give some people goosebumps . and then there ’ s our tail . at the end of our spine are a set of fused vertebrae - some people have 3 , some have 5 . we call it the tailbone . it now serves as an anchor for some pelvic muscles but it ’ s also what ’ s left of our ancestors ’ tails . every one of us actually had a tail at one point . when the basic body plan is being laid out at around 4 weeks of gestation , humans embryos closely resemble embryos of other vertebrates . and that includes a tail with 10-12 developing vertebrae . in many other animals it continues to develop into a proper tail . but in humans and other apes , the cells in the tail are programmed to die a few weeks after they appear . vary rarely though , a mutation allows the ancestral blueprint to prevail and a human baby will be born with a true vestigial tail . the most adorable vestigial behavior is the palmar grasp reflex , where infants up until they ’ re about 6 months old have this incredible grasp on whatever you put in their hand . there ’ s a similar reflex for their feet . i wanted to show you this great piece of footage from the 1930s where they demonstrated this behavior . these babies are only 1 month old and you can see that their inner monkey can support their entire weight .
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in fact , it ’ s one of the first tendons that surgeons will take out so they can use it in reconstructive and cosmetic surgeries . you can find the palmaris longus across mammal species , but it ’ s most developed among those that use their forelimbs to move around . in primates , that means the muscle is longer in lemurs and monkeys and shorter in chimps , gorillas , and other apes that don ’ t do a lot of scrambling through trees .
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according to this video , how is the palmaris longus currently most useful ?
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[ 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 .
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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 !
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the biggest difference between human drivers and ant `` drivers '' is that , ants prioritize the good of the colony and human drivers are more concerned with ...
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if someone called you scum , you 'd probably be offended , but scientifically , they might not be far off . have you ever thought about where your food comes from ? you might say it comes from plants , animals , or even fungi , but you 'd probably rather not think about the rotting organisms and poop that feed those plants , animals , and fungi . so really , you and most of the matter in your body are just two or three degrees of separation from things like pond scum . all species in an ecosystem , from the creatures in a coral reef to the fish in a lake to the lions on the savannah , are directly or indirectly nourished by dead stuff . most of the organic matter in our bodies , if we trace it back far enough , comes from co2 and water through photosynthesis . plants use the energy from sunlight to transform carbon dioxide and water from the environment into glucose and oxygen . that glucose is then transformed into more complex organic molecules to form leaves , stems , roots , fruit , and so on . the energy stored in these organic molecules supports the food chains with which we 're familiar . you 've probably seen illustrations like this or this . these green food chains start with living plants at their base . but in real-life terrestrial ecosystems , less than 10 % of plant matter is eaten while it 's still alive . what about the other 90 ? well , just look at the ground on an autumn day . living plants shed dead body parts : fallen leaves , broken branches , and even underground roots . many plants are lucky enough to go their whole lives without being eaten , eventually dying and leaving remains . all of these uneaten , undigested , and dead plant parts , that 90 % of terrestrial plant matter ? that becomes detritus , the base of what we call the brown food chain , which looks more like this . what happens to plants also happens to all other organisms up the food chain : some are eaten alive , but most are eaten only when they 're dead and rotting . and all along this food chain , living things shed organic matter and expel digestive waste before dying and leaving their remains to decay . all that death sounds grim , right ? but it 's not . all detritus is ultimately consumed by microbes and other scavengers , so it actually forms the base of the brown food chain that supports many other organisms , including us . scientists are learning that this detritus is an unexpectedly huge energy source , fueling most natural ecosystems . but the interactions within an ecosystem are even more complex than that . what a food chain really represents is a single pathway of energy flow . and within any ecosystem , many of these flows are linked together to form a rich network of interactions , or food web , with dead matter supporting that network at every step . the resulting food web is so connected that almost every species is no more than two degrees from detritus , even us humans . you probably do n't eat rotting things , poop , or pond scum directly , but your food sources probably do . many animals we eat either feed directly on detritus themselves , like pork , poultry , mushrooms , shellfish , or catfish and other bottom feeders , or they are fed animal by-products . so , if you 're thinking nature is full of waste , you 're right . but one organism 's garbage is another 's gold , and all that rotting dead stuff ultimately provides the energy that nourishes us and most of life on earth , as it passes through the food web . now that 's some food for thought .
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but it 's not . all detritus is ultimately consumed by microbes and other scavengers , so it actually forms the base of the brown food chain that supports many other organisms , including us . scientists are learning that this detritus is an unexpectedly huge energy source , fueling most natural ecosystems . but the interactions within an ecosystem are even more complex than that .
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detritus is defined as ________ .
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think about all the things that need to happen for a human settlement to thrive : obtaining food , building shelter , raising children and more . there needs to be a way to divide resources , organize major efforts and distribute labor efficiently . now imagine having to do this without any sort of planning or higher level communication . welcome to the ant colony . ants have some of the most complex social organization in the animal kingdom , living in structured colonies containing different types of members who perform specific roles . but although this may sound similar to some human societies , this organization does n't arise from any higher level decisions , but is part of a biologically programmed cycle . in many species , all the winged males and winged virgin queens from all the nearby colonies in the population each leave from their different nests and meet at a central place to mate , using pheromones to guide each other to a breeding ground . after mating , the males die off , while females try to establish a new colony . the few that are successful settle down in a suitable spot , lose their wings , and begin laying eggs , selectively fertilizing some using stored sperm they 've saved up from mating . fertilized eggs grow into female workers who care for the queen and her eggs . they will then defend the colony and forage for food , while unfertilized eggs grow into males whose only job is to wait until they are ready to leave the nest and reproduce , beginning the cycle again . so how do worker ants decide what to do and when ? well , they do n't really . although they have no methods of intentional communication , individual ants do interact with one another through touch , sound and chemical signals . these stimuli accomplish many things from serving as an alarm to other ants if one is killed , to signaling when a queen is nearing the end of her reproductive life . but one of the most impressive collective capabilities of an ant colony is to thoroughly and efficiently explore large areas without any predetermined plan . most species of ants have little or no sense of sight and can only smell things in their vicinity . combined with their lack of high level coordination , this would seem to make them terrible explorers , but there is an amazingly simple way that ants maximize their searching efficiency ; by changing their movement patterns based on individual interactions . when two ants meet , they sense each other by touching antennae . if there are many ants in a small area this will happen more often causing them to respond by moving in more convoluted , random paths in order to search more thoroughly . but in a larger area , with less ants , where such meetings happen less often , they can walk in straight lines to cover more ground . while exploring their environment in this way , an ant may come across any number of things , from threats or enemies , to alternate nesting sites . and some species have another capability known as recruitment . when one of these ants happens to find food , it will return with it , marking its path with a chemical scent . other ants will then follow this pheromone trail , renewing it each time they manage to find food and return . once the food in that spot is depleted , the ants stop marking their return . the scent dissipates and ants are no longer attracted to that path . these seemingly crude methods of search and retrieval are , in fact , so useful that they are applied in computer models to obtain optimal solutions from decentralized elements , working randomly and exchanging simple information . this has many theoretical and practical applications , from solving the famous traveling salesman problem , to scheduling computing tasks and optimizing internet searches , to enabling groups of robots to search a minefield or a burning building collectively , without any central control . but you can observe these fascinatingly simple , yet effective , processes directly through some simple experiments , by allowing ants to enter empty spaces of various sizes and paying attention to their behavior . ants may not be able to vote , hold meetings or even make any plans , but we humans may still be able to learn something from the way that such simple creatures are able to function so effectively in such complex ways .
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if there are many ants in a small area this will happen more often causing them to respond by moving in more convoluted , random paths in order to search more thoroughly . but in a larger area , with less ants , where such meetings happen less often , they can walk in straight lines to cover more ground . while exploring their environment in this way , an ant may come across any number of things , from threats or enemies , to alternate nesting sites .
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how should ants move to cover as much area as possible when they are searching ?
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you might think you know a lot about native americans through popular movies , books , and classes in school , but it turns out that a lot of what we think we know about famous native american figures is n't quite right . take sacajawea for example . you probably remember her as a beautiful indian woman who lived an exotic life serving as the all-knowing guide for lewis and clark 's famous expedition , right ? well , that 's not exactly how it happened . not much is known about sacajawea 's early childhood , but we do know that she was born in 1788 into the agaidika tribe of the lemhi shoshone in what is now idaho . in 1800 , when she was about 12 years old , sacajawea and several other girls were kidnapped by a group of hidatsa indians . she was taken as a captive to a hidatsa village in present-day north dakota . then , she was sold to a french canadian fur trapper named toussaint charbonneau . within a year or so , she was pregnant with her first child . soon after she became pregnant , the corps of discovery arrived near the hidatsa villages . captains meriwether lewis and william clark built fort mandan there , and then started interviewing people to help guide them on their perilous expedition . they agreed to hire sacajawea 's husband , charbonneau , with the understanding that his lovely wife would also come along as an interpreter . they figured her very presence would help any encounters with native tribes along the way . as clark noted in his journal , `` a woman with a party of men is a token of peace . '' shortly thereafter , sacajawea gave birth to a little boy named jean baptiste charbonneau . clark called him pompy . she carried pompy on a board strapped to her back as the corps of discovery forged on . besides interpreting the language when lewis and clark encountered indians , sacajawea 's activities as a member of the corps included digging for roots , collecting edible plants , and picking berries . in 1805 , the boat they were riding in was capsized . she dove into the water , recovering all the important papers and supplies that would otherwise have been lost , including the journals and records of lewis and clark . later that year , captain lewis and three men scouted 75 miles ahead of the expedition 's main party , crossing the continental divide . the next day they encountered a group of shishones . not only did they prove to be sacajawea 's band , but their leader , chief cameahwait , turned out to be her very own brother . after five years of separation since her kidnapping as a young girl , sacajawea and cameahwait had an emotional reunion . unfortunately , she quickly had to bid farewell to her beloved brother and continue on with the journey . at one point , the expedition became so difficult and freezing , the group was reduced to eating candles to survive . when temperatures finally became more bearable , sacajawea found , dug , and cooked roots to help the group regain their strength . on the return trip , they encountered an indian wearing a beautiful fur robe . lewis and clark wanted to bring the robe to thomas jefferson as a gift but had nothing to trade for it . so , sacajawea agreed to trade her most precious possession , her beaded belt , for the fur . a little over two years after the expedition began , it was finally over , ending in st. louis . today , we learn about sacajawea in school as a heroic guide , but her life , like most everyone 's , was much more complicated than history books sometimes give her credit for .
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she was taken as a captive to a hidatsa village in present-day north dakota . then , she was sold to a french canadian fur trapper named toussaint charbonneau . within a year or so , she was pregnant with her first child .
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by trade , toussaint charbonneau was a :
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in 1861 , two scientists got into a very brainy argument . specifically , they had opposing ideas of how speech and memory operated within the human brain . ernest aubertin , with his localistic model , argued that a particular region or the brain was devoted to each separate process . pierre gratiolet , on the other hand , argued for the distributed model , where different regions work together to accomplish all of these various functions . the debate they began reverberated throughout the rest of the century , involving some of the greatest scientific minds of the time . aubertin and his localistic model had some big names on his side . in the 17th century , rené descartes had assigned the quality of free will and the human soul to the pineal gland . and in the late 18th century , a young student named franz joseph gall had observed that the best memorizers in his class had the most prominent eyes and decided that this was due to higher development in the adjacent part of the brain . as a physician , gall went on to establish the study of phrenology , which held that strong mental faculties corresponded to highly developed brain regions , observable as bumps in the skull . the widespread popularity of phrenology throughout the early 19th century tipped the scales towards aubertin 's localism . but the problem was that gall had never bothered to scientifically test whether the individual brain maps he had constructed applied to all people . and in the 1840 's , pierre flourens challenged phrenology by selectively destroying parts of animal brains and observing which functions were lost . flourens found that damaging the cortex interfered with judgement or movement in general , but failed to identify any region associated with one specific function , concluding that the cortex carried out brain functions as an entire unit . flourens had scored a victory for gratiolet , but it was not to last . gall 's former student , jean-baptiste bouillaud , challenged flourens ' conclusion , observing that patients with speech disorders all had damage to the frontal lobe . and after paul broca 's 1861 autopsy of a patient who had lost the power to produce speech , but not the power to understand it , revealed highly localized frontal lobe damage , the distributed model seemed doomed . localism took off . in the 1870 's , karl wernicke associated part of the left temporal lobe with speech comprehension . soon after , eduard hitzig and gustav fritsch stimulated a dog 's cortex and discovered a frontal lobe region responsible for muscular movements . building on their work , david ferrier mapped each piece of cortex associated with moving a part of the body . and in 1909 , korbinian brodmann built his own cortex map with 52 separate areas . it appeared that the victory of aubertin 's localistic model was sealed . but neurologist karl wernicke had come up with an interesting idea . he reasoned that since the regions for speech production and comprehension were not adjacent , then injuring the area connecting them might result in a special type of language loss , now known as receptive aphasia . wernicke 's connectionist model helped explain disorders that did n't result from the dysfunction of just one area . modern neuroscience tools reveal a brain more complex than gratiolet , aubertin , or even wernicke imagined . today , the hippocampus is associated with two distinct brain functions : creating memories and processing location in space . we also now measure two kinds of connectivity : anatomical connectivity between two adjoining regions of cortex working together , and functional connectivity between separated regions working together to accomplish one process . a seemingly basic function like vision is actually composed of many smaller functions , with different parts of the cortex representing shape , color and location in space . when certain areas stop functioning , we may recognize an object , but not see it , or vice versa . there are even different kinds of memory for facts and for routines . and remembering something like your first bicycle involves a network of different regions each representing the concept of vehicles , the bicycle 's shape , the sound of the bell , and the emotions associated with that memory . in the end , both gratiolet and aubertin turned out to be right . and we still use both of their models to understand how cognition happens . for example , we can now measure brain activity on such a fine time scale that we can see the individual localized processes that comprise a single act of remembering . but it is the integration of these different processes and regions that creates the coherent memory we experience . the supposedly competing theories prove to be two aspects of a more comprehensive model , which will in turn be revised and refined as our scientific techologies and methods for understanding the brain improve .
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flourens had scored a victory for gratiolet , but it was not to last . gall 's former student , jean-baptiste bouillaud , challenged flourens ' conclusion , observing that patients with speech disorders all had damage to the frontal lobe . and after paul broca 's 1861 autopsy of a patient who had lost the power to produce speech , but not the power to understand it , revealed highly localized frontal lobe damage , the distributed model seemed doomed .
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when broca and bouillaud found brain damage in patients with speech disorders , where was that damage located ?
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light , bright , and cheerful . it 's some of the most familiar of all early 18th century music . it 's been featured in uncounted films and television commercials , but what is it and why does it sound that way ? this is the opening of `` spring '' from `` the four seasons , '' by italian composer antonio vivaldi . `` the four seasons '' are famous in part because they are a delight to the ear . however , even more notable is the fact that they have stories to tell . at the time of their publication in amsterdam in 1725 , they were accompanied by poems describing exactly what feature of that season vivaldi intended to capture in musical terms . in providing specific plot content for instrumental music , vivaldi was generations ahead of his time . if one were to read the poems simultaneously to hearing the music , one would find the poetic scenes synchronizing nicely with the musical imagery . we are told that the birds welcome spring with happy song , and here they are doing exactly that . soon , however , a thunderstorm breaks out . not only is there musical thunder and lightning , there are also more birds , wet , frightened , and unhappy . in `` summer , '' the turtle dove sings her name `` tortorella '' in italian , before a hail storm flattens the fields . `` autumn '' brings eager hunters dashing out in pursuit of their prey . the `` winter '' concerto begins with teeth chattering in the cold before one takes refuge by a crackling fire . then it 's back out into the storm where there 'll be slips and falls on the ice . in these first weeks of winter , the old year is coming to a close , and so does vivaldi 's musical exploration of the seasons . not until the early 19th century would such expressive instrumental program music , as it was known , become popular . by then , larger , more varied ensembles were the rule with woodwinds , brass , and percussion to help tell the tale . but vivaldi pulled it off with just one violin , strings , and a harpsichord . unlike his contemporary bach , vivaldi was n't much interested in complicated fugues . he preferred to offer readily accessible entertainment to his listeners with melodies that pop back up later in a piece to remind us of where we 've been . so the first movement of the `` spring '' concerto begins with a theme for spring and ends with it , too , slightly varied from when it was last heard . it was an inspired way to attract listeners , and vivaldi , considered one of the most electrifying violinists of the early 18th century , understood the value of attracting audiences . such concerts might feature himself as the star violinist . others presented the young musicians of the pietà , a venetian girls ' school where vivaldi was director of music . most of the students were orphans . music training was intended not only as social skills suitable for young ladies but also as potential careers for those who might fail to make good marriages . even in the composer 's own time , vivaldi 's music served as diversion for all , not just for the wealthy aristocrats . 300 years later , it 's an approach that still works , and vivaldi 's music still sounds like trotting horses on the move .
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by then , larger , more varied ensembles were the rule with woodwinds , brass , and percussion to help tell the tale . but vivaldi pulled it off with just one violin , strings , and a harpsichord . unlike his contemporary bach , vivaldi was n't much interested in complicated fugues .
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in what country did vivaldi live ?
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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 .
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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 .
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over what distance is quantum entanglement possible , between two electrons ?
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with every year , machines surpass humans in more and more activities we once thought only we were capable of . today 's computers can beat us in complex board games , transcribe speech in dozens of languages , and instantly identify almost any object . but the robots of tomorrow may go futher by learning to figure out what we 're feeling . and why does that matter ? because if machines and the people who run them can accurately read our emotional states , they may be able to assist us or manipulate us at unprecedented scales . but before we get there , how can something so complex as emotion be converted into mere numbers , the only language machines understand ? essentially the same way our own brains interpret emotions , by learning how to spot them . american psychologist paul ekman identified certain universal emotions whose visual cues are understood the same way across cultures . for example , an image of a smile signals joy to modern urban dwellers and aboriginal tribesmen alike . and according to ekman , anger , disgust , fear , joy , sadness , and surprise are equally recognizable . as it turns out , computers are rapidly getting better at image recognition thanks to machine learning algorithms , such as neural networks . these consist of artificial nodes that mimic our biological neurons by forming connections and exchanging information . to train the network , sample inputs pre-classified into different categories , such as photos marked happy or sad , are fed into the system . the network then learns to classify those samples by adjusting the relative weights assigned to particular features . the more training data it 's given , the better the algorithm becomes at correctly identifying new images . this is similar to our own brains , which learn from previous experiences to shape how new stimuli are processed . recognition algorithms are n't just limited to facial expressions . our emotions manifest in many ways . there 's body language and vocal tone , changes in heart rate , complexion , and skin temperature , or even word frequency and sentence structure in our writing . you might think that training neural networks to recognize these would be a long and complicated task until you realize just how much data is out there , and how quickly modern computers can process it . from social media posts , uploaded photos and videos , and phone recordings , to heat-sensitive security cameras and wearables that monitor physiological signs , the big question is not how to collect enough data , but what we 're going to do with it . there are plenty of beneficial uses for computerized emotion recognition . robots using algorithms to identify facial expressions can help children learn or provide lonely people with a sense of companionship . social media companies are considering using algorithms to help prevent suicides by flagging posts that contain specific words or phrases . and emotion recognition software can help treat mental disorders or even provide people with low-cost automated psychotherapy . despite the potential benefits , the prospect of a massive network automatically scanning our photos , communications , and physiological signs is also quite disturbing . what are the implications for our privacy when such impersonal systems are used by corporations to exploit our emotions through advertising ? and what becomes of our rights if authorities think they can identify the people likely to commit crimes before they even make a conscious decision to act ? robots currently have a long way to go in distinguishing emotional nuances , like irony , and scales of emotions , just how happy or sad someone is . nonetheless , they may eventually be able to accurately read our emotions and respond to them . whether they can empathize with our fear of unwanted intrusion , however , that 's another story .
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this is similar to our own brains , which learn from previous experiences to shape how new stimuli are processed . recognition algorithms are n't just limited to facial expressions . our emotions manifest in many ways .
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emotion recognition algorithms have been around since the 1990s ; why did it take them so long to become mainstream ?
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nothing stuck to mafia boss john gotti who evaded justice for years by bribing and threatening jurors and witnesses . that earned him the name the teflon don after one of the slipperiest materials on earth . teflon was in the spacesuits the apollo crew wore for the moon landing , in pipes and valves used in the manhattan project , and maybe in your kitchen as the nonstick coating on frying pans and cookie sheets . so what is this slippery solid , and why does n't anything stick to it ? teflon is a brand name for polytetrafluoroethylene , or ptfe . it was stumbled upon accidentally in 1938 by a 27-year-old american chemist named roy plunkett while he was trying to develop a non-toxic refrigerant fluid for dupont , a chemicals company . the strange , white substance that formed inside his lab canister was chemically inert , meaning it would n't react with other substances . it also had an extremely low coefficient of friction , making other materials slide right off it . teflon 's properties make it perfect when you need something slippery , chemical resistant , or waterproof , which means it has a lot of applications . it can be found all over the place , as a coating on raincoats , industrial ball bearings , artificial joints , circuit boards , and even the rocky mountains-themed roof of the denver international airport . the incredible properties of ptfe come from its molecular structure . it 's a polymer , meaning it 's made of long chains of repeating units of atoms strung together . a ptfe chain has a backbone of carbon atoms , each of which is attached to two fluorines . the fluorine atoms surround the carbon like armor , spiraling around the chain , and the bond between carbon and fluorine is incredibly tight . like a couple that ignores everyone except each other , carbon and fluorine interact so strongly that the normal , intermolecular forces that help substances stick to each other do n't stand a chance . even the famously adhesive feet of geckos usually ca n't get a grip . but wait ! if ptfe does n't stick to anything , how can it be so firmly attached to something like a pan ? one method involves sandblasting the pan or etching it with chemicals to make it rough . then , a special primer is applied , which acts like glue . its exact composition is a trade secret guarded by each manufacturer . the pan is sprayed with liquid ptfe and heated to around 800 degrees fahrenheit . the layers then solidify into a smooth , slick coating . when you later cook eggs in this ptfe-coated pan , the extra tight carbon-fluorine bonds just ignore the water and fat and protein molecules in the eggs . without those interactions , the food just slides around without sticking . you might wonder if it 's safe to cook in a ptfe-coated pan . the answer is yes , if you 're careful . ptfe is stable at moderate temperatures , like you 'd use to cook eggs or fish , but above 500 degrees fahrenheit , it starts to degrade , and heating it further releases fumes that can make you feel sick . an empty pan can reach 500 degrees fast over high heat , but most kitchens are ventilated well enough to dissipate the fumes . people used to also think that accidentally consuming ptfe that flaked off a scratched pan was bad for you , but the current consensus is that it 's harmless . because ptfe does n't interact with other chemicals very well , it is n't thought to break down inside your body . whether it 's safe to manufacture teflon is another story . dupont and its spin-off company chemours now face lawsuits worth millions of dollars . they 've been accused of polluting the environment for decades and exposing employees and local communities to health risks associated with a toxic chemical called pfoa . that chemical was involved in manufacturing teflon . as for john gotti , in 1992 , the mob boss was finally convicted of five counts of murder , among other charges . that prompted the head of the fbi office in new york city to announce , `` the teflon is gone . the don is covered in velcro , and all the charges stuck . ''
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so what is this slippery solid , and why does n't anything stick to it ? teflon is a brand name for polytetrafluoroethylene , or ptfe . it was stumbled upon accidentally in 1938 by a 27-year-old american chemist named roy plunkett while he was trying to develop a non-toxic refrigerant fluid for dupont , a chemicals company .
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what makes ptfe a.k.a . teflon non-stick ?
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albert einstein . the icon of genius . why ? because he figured out e equals m c squared ? because he did n't like socks ? nope ! because he came up with the most powerful idea in science.. general relativity his masterpiece is now 100 years old . and while the physicists are partying , the rest of us are left wondering what the bleep it ’ s all about ! well here goes . at 26 he figured out nothing less than a new theory of space and time . it led to a nifty way of simplifying physics – by treating space and time as one thing ... spacetime ! but albert was just warming up . he wasn ’ t happy with isaac newton ’ s mysterious force of gravity . naturally , he started work on his own theory . and sure enough , he cracked it . mass causes spacetime to curve ! the natural motion of things is to follow the simplest path through spacetime . but since objects with mass curve spacetime , stuff moves towards the most massive objects . that ’ s what you feel as gravity . it ’ s warped space and time that ’ s keeping your feet on the ground . “ warped space ” might sound too sci-fi to be true . but we can measure the bending of starlight as is passes through the warped space around the sun . warped time sounds even more ridiculous . but take an accurate clock to the top of a building and you ’ ll see it runs slightly quicker than one on the ground ! that ’ s because as you move away from the centre of the planet space and time are less warped . most amazing of all , einstein ’ s theory told us that our universe has a beginning . everything is expanding out from a hot dense origin 13.8 billion years ago . but here ’ s the catch : we ’ ve spotted that the universe is expanding faster than albert ’ s theory predicts . could the old genius be wrong ? to stick with his idea we ’ ve had to invent a made up energy - ‘ dark energy ’ - to account for the speedy expansion . and we ’ ve had to assume there ’ s an exotic form of ‘ dark matter ' we haven ’ t detected yet either . these two unknowns should make up 95 % of the universe – yet we ’ ve never detected them . that ’ s the sort of thing that keeps physicists awake at night . so they ’ re plotting some seriously big experiments to put albert ’ s theory to the ultimate test . for the last 100 years , uncle albert ’ s great theory has passed every test possible . if it succeeds again physicists will party . if they find its limits and it finally fails they ’ ll party too . physicists are funny like that .
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at 26 he figured out nothing less than a new theory of space and time . it led to a nifty way of simplifying physics – by treating space and time as one thing ... spacetime ! but albert was just warming up .
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einstein 's theory of relativity was a way of simplifying physics by ...
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what if electricity could travel forever without being diminished ? what if a computer could run exponentially faster with perfect accuracy ? what technology could those abilities build ? we may be able to find out thanks to the work of the three scientists who won the nobel prize in physics in 2016 . david thouless , duncan haldane , and michael kosterlitz won the award for discovering that even microscopic matter at the smallest scale can exhibit macroscopic properties and phases that are topological . but what does that mean ? first of all , topology is a branch of mathematics that focuses on fundamental properties of objects . topological properties do n't change when an object is gradually stretched or bent . the object has to be torn or attached in new places . a donut and a coffee cup look the same to a topologist because they both have one hole . you could reshape a donut into a coffee cup and it would still have just one . that topological property is stable . on the other hand , a pretzel has three holes . there are no smooth incremental changes that will turn a donut into a pretzel . you 'd have to tear two new holes . for a long time , it was n't clear whether topology was useful for describing the behaviors of subatomic particles . that 's because particles , like electrons and photons , are subject to the strange laws of quantum physics , which involve a great deal of uncertainty that we do n't see at the scale of coffee cups . but the nobel laureates discovered that topological properties do exist at the quantum level . and that discovery may revolutionize materials science , electronic engineering , and computer science . that 's because these properties lend surprising stability and remarkable characteristics to some exotic phases of matter in the delicate quantum world . one example is called a topological insulator . imagine a film of electrons . if a strong enough magnetic field passes through them , each electron will start traveling in a circle , which is called a closed orbit . because the electrons are stuck in these loops , they 're not conducting electricity . but at the edge of the material , the orbits become open , connected , and they all point in the same direction . so electrons can jump from one orbit to the next and travel all the way around the edge . this means that the material conducts electricity around the edge but not in the middle . here 's where topology comes in . this conductivity is n't affected by small changes in the material , like impurities or imperfections . that 's just like how the hole in the coffee cup is n't changed by stretching it out . the edge of such a topological insulator has perfect electron transport : no electrons travel backward , no energy is lost as heat , and the number of conducting pathways can even be controlled . the electronics of the future could be built to use this perfectly efficient electron highway . the topological properties of subatomic particles could also transform quantum computing . quantum computers take advantage of the fact that subatomic particles can be in different states at the same time to store information in something called qubits . these qubits can solve problems exponentially faster than classical digital computers . the problem is that this data is so delicate that interaction with the environment can destroy it . but in some exotic topological phases , the subatomic particles can become protected . in other words , the qubits formed by them ca n't be changed by small or local disturbances . these topological qubits would be more stable , leading to more accurate computation and a better quantum computer . topology was originally studied as a branch of purely abstract mathematics . thanks to the pioneering work of thouless , haldane , and kosterlitz , we now know it can be used to understand the riddles of nature and to revolutionize the future of technologies .
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a donut and a coffee cup look the same to a topologist because they both have one hole . you could reshape a donut into a coffee cup and it would still have just one . that topological property is stable .
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how can we reshape a doughnut into a coffee cup ?
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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 . ''
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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 ?
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what is the modern tattoo machine based on ?
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it 's only been the last few hundreds years or so that western civilization has been putting art in museums , at least museums resembling the public institutions we know today . before this , for most , art served other purposes . what we call fine art today was , in fact , primarily how people experienced an aesthetic dimension of religion . paintings , sculpture , textiles and illuminations were the media of their time , supplying vivid imagery to accompany the stories of the day . in this sense , western art shared a utilitarian purpose with other cultures around the world , some of whose languages incidentally have no word for art . so how do we define what we call art ? generally speaking , what we 're talking about here is work that visually communicates meaning beyond language , either through representation or the arrangement of visual elements in space . evidence of this power of iconography , or ability of images to convey meaning , can be found in abundance if we look at art from the histories of our major world religions . almost all have , at one time or another in their history , gone through some sort of aniconic phase . aniconism prohibits any visual depiction of the divine . this is done in order to avoid idolatry , or confusion between the representation of divinity and divinity itself . keeping it real , so to speak , in the relationship between the individual and the divine . however , this can be a challenge to maintain , given that the urge to visually represent and interpret the world around us is a compulsion difficult to suppress . for example , even today , where the depiction of allah or the prophet muhammad is prohibited , an abstract celebration of the divine can still be found in arabesque patterns of islamic textile design , with masterful flourishes of brushwork and arabic calligraphy , where the words of the prophet assume a dual role as both literature and visual art . likewise , in art from the early periods of christianity and buddhism , the divine presence of the christ and the buddha do not appear in human form but are represented by symbols . in each case , iconographic reference is employed as a form of reverence . anthropomorphic representation , or depiction in human form , eventually became widespread in these religions only centuries later , under the influence of the cultural traditions surrounding them . historically speaking , the public appreciation of visual art in terms other than traditional , religious or social function is a relatively new concept . today , we fetishize the fetish , so to speak . we go to museums to see art from the ages , but our experience of it there is drastically removed from the context in which it was originally intended to be seen . it might be said that the modern viewer lacks the richness of engagement that she has with contemporary art , which has been created relevant to her time and speaks her cultural language . it might also be said that the history of what we call art is a conversation that continues on , as our contemporary present passes into what will be some future generation 's classical past . it 's a conversation that reflects the ideologies , mythologies , belief systems and taboos and so much more of the world in which it was made . but this is not to say that work from another age made to serve a particular function in that time is dead or has nothing to offer the modern viewer . even though in a museum setting works of art from different places and times are presented alongside each other , isolated from their original settings , their juxtaposition has benefits . exhibits are organized by curators , or people who 've made a career out of their ability to recontextualize or remix cultural artifacts in a collective presentation . as viewers , we 're then able to consider the art in terms of a common theme that might not be apparent in a particular work until you see it alongside another , and new meanings can be derived and reflected upon . if we 're so inclined , we might even start to see every work of art as a complementary part of some undefined , unified whole of past human experience , a trail that leads right to our doorstep and continues on with us , open to anyone who wants to explore it .
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almost all have , at one time or another in their history , gone through some sort of aniconic phase . aniconism prohibits any visual depiction of the divine . this is done in order to avoid idolatry , or confusion between the representation of divinity and divinity itself .
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aniconism prohibits any visual depiction of the ________ .
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imagine that day by day , your field of vision becomes slightly smaller , narrowing or dimming until eventually you go completely blind . we tend to think of blindness as something you 're born with , but in fact , with many diseases like retinitis pigmentosa and usher syndrome , blindness can start developing when you 're a kid , or even when you 're an adult . both of these rare genetic diseases affect the retina , the screen at the back of the eye that detects light and helps us see . now imagine if the eye could regenerate itself so that a blind person could see again . to understand if that 's possible , we need to grasp how the retina works and what it has to do with a multitalented creature named the zebrafish . the human retina is made of different layers of cells , with special neurons that live in the back of the eye called rod and cone photoreceptors . photoreceptors convert the light coming into your eye into signals that the brain uses to generate vision . people who have usher syndrome and retinitis pigmentosa experience a steady loss of these photoreceptors until finally that screen in the eye can no longer detect light nor broadcast signals to the brain . unlike most of your body 's cells , photoreceptors do n't divide and multiply . we 're born with all the photoreceptors we 'll ever have , which is why babies have such big eyes for their faces and part of why they 're so cute . but that is n't the case for all animals . take the zebrafish , a master regenerator . it can grow back its skin , bones , heart and retina after they 've been damaged . if photoreceptors in the zebrafish retina are removed or killed by toxins , they just regenerate and rewire themselves to the brain to restore sight . scientists have been investigating this superpower because zebrafish retina are also structured very much like human retina . scientists can even mimic the effects of disorders like usher syndrome or retinitis pigmentosa on the zebrafish eye . this allows them to see how zebrafish go about repairing their retinas so they might use similar tactics to fix human eyes one day , too . so what 's behind the zebrafish 's superpower ? the main players are sets of long cells that stretch across the retina called müller glia . when the photoreceptors are damaged , these cells transform , taking on a new character . they become less like müller cells and more like stem cells , which can turn into any kind of cell . then these long cells divide , producing extras that will eventually grow into new photoreceptors , travel to the back of the eye and rewire themselves into the brain . and now some researchers even think they 've found the key to how this works with the help of one of two chemicals that create activity in the brain called glutamate and aminoadipate . in mouse eyes , these make the müller glia divide and transform into photoreceptors , which then travel to the back of the retina , like they 're replenishing a failing army with new soldiers . but remember , none of this has happened in our retinas yet , so the question is how do we trigger this transformation of the müller glia in the human eye ? how can we fully control this process ? how do photoreceptors rewire themselves into the retina ? and is it even possible to trigger this in humans ? or has this mechanism been lost over time in evolution ? until we tease apart the origins of this ability , retinal regeneration will remain a mysterious superpower of the common zebrafish .
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scientists have been investigating this superpower because zebrafish retina are also structured very much like human retina . scientists can even mimic the effects of disorders like usher syndrome or retinitis pigmentosa on the zebrafish eye . this allows them to see how zebrafish go about repairing their retinas so they might use similar tactics to fix human eyes one day , too .
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retinitis pigmentosa and usher 's syndrome cause patients to slowly become
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okay , i 've got a piece of crystalline bismuth , so you can actually take sort of pellets of bismuth , metal , and heat it up , i 've seen photos of people doing that on their home cookers , their ovens and things , but you can make them in the lab so you get crystals of bismuth out which look like this which is actually really really pretty and there are websites of people who 've made these crystals and they 're selling them for collectors and things which is quite nice . bismuth is interesting because it is the heaviest element that is not radioactive . you can imagine the nucleus , the center of the atom , rather like a drop of water , and if you imagine a drop of water as it gets bigger and bigger it becomes unstable and will usually split into two , and it just happens that bismuth is the largest size that 's not radioactive . - the interesting thing about bismuth actually is that it 's long been regarded , bismuth 209 has long been regarded as the heaviest non-radioactive element , and technically actually that 's not true . it was actually found i think about 5 years ago now , it was actually proven to be an alpha emitter , so it 's actually a radioactive element , that emits alpha particles . - so here is a very old sample of bismuth . this is a bismuth rod and as you can see it 's packed up really quite nicely , but if we open this then we can go in and see what it is in here . let 's see . here if we pull it out carfully . - but actually it 's kind of a little bit pedantic i suppose because the half life of this bismuth 209 they 've found is actually 1.9x10 to the power of 19 years . its half life , that 's the time it takes a kilo of bismuth , for 500 grams of it to decompose to its daughter element which i think is thalium 205 if i 'm right , and so that half life is actually longer than the current age of the universe , so for all intents and purposes , it 's still quite stable and i think they actually call it meta stable . - it is used particularly in an alloy which they call woods metal , which is a very low melting alloy , will even melt in boiling water , and there are endless practical jokes where you can buy woods metal spoons and give it to somebody to stir their tea and it melted in their tea and they look suprised . - bismuth . really old sample from johnson matthey and let 's see if we can find out what the purity is , so it 's 99.9 % , really a quite nice sample of a bismuth rod . - bismuth suprisingly is not very poisonous compared to the fact that led is very poisonous , and so there are some suggestions that we should be exploring more the chemistry of bismuth as a catalist because if it works well then it can be used in chemical processes with much less danger than some of these other materials . - so if we can push it out from this old paper package then you can see it 's packaged really quite nicely , here you can see the bismuth metal itself , bismuth is used in catalysis to attenuate selective reactions so perhaps we might use bismuth with a platinum group metal like paladium or platinum even to make chemistry work even more selectively , it 's a really beautiful element then . really nice , so we 'll pop that back in there nice and safe . - what have you got there , where did that come from ? - i bought it because it 's so pretty , i bought it from a shop , i ca n't remember actually which shop now , but i collect these sorts of things . these very big pretty looking sort of metallic things and crystals and as you can see it 's really nice and irradescent so it 's got a tarnished oxide layer and it shines like all the colors of the rainbow which is really really pretty in my opinion . lovely ! captions by www.subply.com
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- it is used particularly in an alloy which they call woods metal , which is a very low melting alloy , will even melt in boiling water , and there are endless practical jokes where you can buy woods metal spoons and give it to somebody to stir their tea and it melted in their tea and they look suprised . - bismuth . really old sample from johnson matthey and let 's see if we can find out what the purity is , so it 's 99.9 % , really a quite nice sample of a bismuth rod .
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what is the name of the alloy , that is not good for making spoons , which contains bismuth ?
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try to measure a circle . the diameter and radius are easy , they 're just straight lines you can measure with a ruler . but to get the circumference , you 'd need measuring tape or a piece of string , unless there was a better way . now , it 's obvious that a circle 's circumference would get smaller or larger along with its diameter , but the relationship goes further than that . in fact , the ratio between the two , the circumference divided by the diameter , will always be the same number , no matter how big or small the circle gets . historians are n't sure when or how this number was first discovered , but it 's been known in some form for almost 4,000 years . estimates of it appear in the works of ancient greek , babylonian , chinese , and indian mathematicians . and it 's even believed to have been used in building the egyptian pyramids . mathematicians estimated it by inscribing polygons in circles . and by the year 1400 , it had been calculated to as far as ten decimal places . so , when did they finally figure out the exact value instead of just estimating ? actually , never ! you see , the ratio of a circle 's circumference to its diameter is what 's known as an irrational number , one that can never be expressed as a ratio of two whole numbers . you can come close , but no matter how precise the fraction is , it will always be just a tiny bit off . so , to write it out in its decimal form , you 'd have an on-going series of digits starting with 3.14159 and continuing forever ! that 's why , instead of trying to write out an infinite number of digits every time , we just refer to it using the greek letter pi . nowadays , we test the speed of computers by having them calculate pi , and quantum computers have been able to calculate it up to two quadrillion digits . people even compete to see how many digits they can memorize and have set records for remembering over 67,000 of them . but for most scientific uses , you only need the first forty or so . and what are these scientific uses ? well , just about any calculations involving circles , from the volume of a can of soda to the orbits of satellites . and it 's not just circles , either . because it 's also useful in studying curves , pi helps us understand periodic or oscillating systems like clocks , electromagnetic waves , and even music . in statistics , pi is used in the equation to calculate the area under a normal distribution curve , which comes in handy for figuring out distributions of standardized test scores , financial models , or margins of error in scientific results . as if that were n't enough , pi is used in particle physics experiments , such as those using the large hadron collider , not only due to its round shape , but more subtly , because of the orbits in which tiny particles move . scientists have even used pi to prove the illusive notion that light functions as both a particle and an electromagnetic wave , and , perhaps most impressively , to calculate the density of our entire universe , which , by the way , still has infinitely less stuff in it than the total number of digits in pi .
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because it 's also useful in studying curves , pi helps us understand periodic or oscillating systems like clocks , electromagnetic waves , and even music . in statistics , pi is used in the equation to calculate the area under a normal distribution curve , which comes in handy for figuring out distributions of standardized test scores , financial models , or margins of error in scientific results . as if that were n't enough , pi is used in particle physics experiments , such as those using the large hadron collider , not only due to its round shape , but more subtly , because of the orbits in which tiny particles move .
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in ________ , pi is used to calculate the area under a ________ .
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translator : andrea mcdonough reviewer : bedirhan cinar as any current or past geometry student knows , the father of geometry was euclid , a greek mathematician who lived in alexandria , egypt , around 300 b.c.e . euclid is known as the author of a singularly influential work known as `` elements . '' you think your math book is long ? euclid 's `` elements '' is 13 volumes full of just geometry . in `` elements , '' euclid structured and supplemented the work of many mathematicians that came before him , such as pythagoras , eudoxus , hippocrates and others . euclid laid it all out as a logical system of proof built up from a set of definitions , common notions , and his five famous postulates . four of these postulates are very simple and straightforward , two points determine a line , for example . the fifth one , however , is the seed that grows our story . this fifth mysterious postulate is known simply as the parallel postulate . you see , unlike the first four , the fifth postulate is worded in a very convoluted way . euclid 's version states that , `` if a line falls on two other lines so that the measure of the two interior angles on the same side of the transversal add up to less than two right angles , then the lines eventually intersect on that side , and therefore are not parallel . '' wow , that is a mouthful ! here 's the simpler , more familiar version : `` in a plane , through any point not on a given line , only one new line can be drawn that 's parallel to the original one . '' many mathematicians over the centuries tried to prove the parallel postulate from the other four , but were n't able to do so . in the process , they began looking at what would happen logically if the fifth postulate were actually not true . some of the greatest minds in the history of mathematics ask this question , people like ibn al-haytham , omar khayyam , nasir al-din al-tusi , giovanni saccheri , jános bolyai , carl gauss , and nikolai lobachevsky . they all experimented with negating the parallel postulate , only to discover that this gave rise to entire alternative geometries . these geometries became collectively known as non-euclidean geometries . we 'll leave the details of these different geometries for another lesson . the main difference depends on the curvature of the surface upon which the lines are constructed . turns out euclid did not tell us the entire story in `` elements , '' and merely described one possible way to look at the universe . it all depends on the context of what you 're looking at . flat surfaces behave one way , while positively and negatively curved surfaces display very different characteristics . at first these alternative geometries seemed strange , but were soon found to be equally adept at describing the world around us . navigating our planet requires elliptical geometry while the much of the art of m.c . escher displays hyperbolic geometry . albert einstein used non-euclidean geometry as well to describe how space-time becomes warped in the presence of matter , as part of his general theory of relativity . the big mystery is whether euclid had any inkling of the existence of these different geometries when he wrote his postulate . we may never know , but it 's hard to believe he had no idea whatsoever of their nature , being the great intellect that he was and understanding the field as thoroughly as he did . maybe he did know and he wrote the postulate in such a way as to leave curious minds after him to flush out the details . if so , he 's probably pleased . these discoveries could never have been made without gifted , progressive thinkers able to suspend their preconceived notions and think outside of what they 've been taught . we , too , must be willing at times to put aside our preconceived notions and physical experiences and look at the larger picture , or we risk not seeing the rest of the story .
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at first these alternative geometries seemed strange , but were soon found to be equally adept at describing the world around us . navigating our planet requires elliptical geometry while the much of the art of m.c . escher displays hyperbolic geometry . albert einstein used non-euclidean geometry as well to describe how space-time becomes warped in the presence of matter , as part of his general theory of relativity .
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if you are navigating the surface of the earth , then you are using which type of geometry ?
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do you ever struggle to find the perfect description when trying to convey an idea ? like a foggy picture , adjectives and modifiers fail to depict what 's in your mind . illustrators often face a similar challenge , especially when attempting to explain complex and difficult concepts . sometimes the imagery is intangible or way too complicated to explain with a picture . although complex information could be relayed using charts and stats , this could get pretty boring . instead , just like when writing an essay to describe , for example , emotions , illustrators can use visual metaphors to bring to life difficult concepts . just as a written metaphor is a description that relates one object to another , a visual metaphor uses imagery to suggest a particular association or point of similarity . our lesson `` big data '' is a great example of a situation where visual metaphors played a huge role in explaining the concept . what is big data in the first place ? good question ! big data is a huge amount of digital information produced worldwide on a daily basis , challenging us to find solutions for storing , analyzing , and also imagining it visually . quite an elusive concept ! how should we depict this ? let 's take a look at our `` big data '' script . we start with smaller computer servers that branch out into bigger networks to produce data , then even bigger networks and production of even more data . you see where we 're going with this -- an object growing and branching out in many directions and producing something as a result ? does that remind you of something ? just like those computer networks , a tree grows and branches out to produce more leaves each year . and every year , just as the data accumulates and faces us with a challenge to find storage solutions , it gets harder to collect those piles of leaves when they fall off the tree . aha ! there 's our visual metaphor ! okay , so we have the script , audio , and a visual metaphor . the next step in visual development is to design the characters and environments of the animation . to do so , we think of an appropriate and appealing style to illustrate the ideas and help the viewer better understand what they 're hearing . let 's go back to the script and see if we can find any clues there . our story starts in the 1960s when the first computer networks were built . this decade will serve as a good point to make the stylistic choice for our animation as it will allow us to refer to artwork from that era . you may want to start by looking at some art books ( design , illustrations , cartoons , etc . ) from that era and find a style that may our own purpose . look closely , study the material , and try to understand the choices artists of that time made and why . for example , the 1960s minimalist animation style was a significant departure from the cinematic realism that was popular in animated films at the time . the choice to use limited animation techniques was originally made for budgetary reasons , but it became a signature style that influenced many future generations of animators . in this stylistic approach , the simplified characters , flat backgrounds , and angular shapes come together to create new interpretations of reality , which also sounds like a good place to begin visualizing our own big data . well , let 's try an experiment . `` in the 1980s islands of similar networks speaking different dialects sprung up all over europe and the states , making remote access possible but tortuous . '' is this better ? `` in the 1980s islands of similar networks speaking different dialects sprung up all over europe and the states , making remote access possible but tortuous . to make it easy for our physicists across the world to access the ever-expanding big data stored at cern without traveling , the networks needed to be talking with the same language . '' as you probably observed , graphic representations are a great way to capture the interest of your audience . by depicting what you want to present and explain with strong , memorable visuals , you can communicate your idea more effectively . so , now , challenge yourself . think of an abstract concept that can not be explained with simple words . go ahead and try your hand at visually developing that idea .
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aha ! there 's our visual metaphor ! okay , so we have the script , audio , and a visual metaphor .
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what is the visual metaphor the ted-ed animators chose to represent all the computer networks that make up big data ?
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we all know the scene : dorothy closes her eyes , and repeats the good witch 's mantra , `` no coordinates exist like one 's domicile , no coordinates exist like one 's domicile , no coordinates exist like one 's domicile . '' only dorothy does n't say that . she says five one-syllable words , `` there 's no place like home . '' each a word you probably learned in your first year of speaking , each perfectly concise . it 's not that l. frank baum did n't have a thesaurus , it 's that in most cases $ 10 words fail . would aerosmith have had a hit with `` ambulate this direction ? '' probably not . would patrick henry have ignited a revolution by saying , `` provide me with liberty or bestow upon me fatality ? '' unlikely . when it comes to words , bigger is n't always better . ten-dollar words are rendered worthless if they 're not understood . that 's not to say every piece of literature should be written at a fourth-grade reading level , but it is important to know your audience . if you 're a novelist , your audience is probably expecting 300 pages of vivid descriptors . at the very least , they 're expecting you wo n't use the same 50 words to fill those pages . but most of us do n't have the luxury of a captive audience . we 're competing against a whole world of distractions and we 're fighting for space in an attention span that continues to shrink across generations . so get to the point already . variety may be the spice of life , but brevity is its bread and butter . so when it comes to $ 10 words , save your money and buy a scrabble board .
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we 're competing against a whole world of distractions and we 're fighting for space in an attention span that continues to shrink across generations . so get to the point already . variety may be the spice of life , but brevity is its bread and butter .
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which wizard of oz quotation drives the point home ?
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what is reality , knowledge , the meaning of life ? big topics you might tackle figuratively explaining existence as a journey down a road or across an ocean , a climb , a war , a book , a thread , a game , a window of opportunity , or an all-too-short-lived flicker of flame . 2,400 years ago , one of history 's famous thinkers said life is like being chained up in a cave , forced to watch shadows flitting across a stone wall . pretty cheery , right ? that 's actually what plato suggested in his allegory of the cave , found in book vii of `` the republic , '' in which the greek philosopher envisioned the ideal society by examining concepts like justice , truth and beauty . in the allegory , a group of prisoners have been confined in a cavern since birth , with no knowledge of the outside world . they are chained , facing a wall , unable to turn their heads , while a fire behind them gives off a faint light . occasionally , people pass by the fire , carrying figures of animals and other objects that cast shadows on the wall . the prisoners name and classify these illusions , believing they 're perceiving actual entities . suddenly , one prisoner is freed and brought outside for the first time . the sunlight hurts his eyes and he finds the new environment disorienting . when told that the things around him are real , ` while the shadows were mere reflections , he can not believe it . the shadows appeared much clearer to him . but gradually , his eyes adjust until he can look at reflections in the water , at objects directly , and finally at the sun , whose light is the ultimate source of everything he has seen . the prisoner returns to the cave to share his discovery , but he is no longer used to the darkness , and has a hard time seeing the shadows on the wall . the other prisoners think the journey has made him stupid and blind , and violently resist any attempts to free them . plato introduces this passage as an analogy of what it 's like to be a philosopher trying to educate the public . most people are not just comfortable in their ignorance but hostile to anyone who points it out . in fact , the real life socrates was sentenced to death by the athenian government for disrupting the social order , and his student plato spends much of `` the republic '' disparaging athenian democracy , while promoting rule by philosopher kings . with the cave parable , plato may be arguing that the masses are too stubborn and ignorant to govern themselves . but the allegory has captured imaginations for 2,400 years because it can be read in far more ways . importantly , the allegory is connected to the theory of forms , developed in plato 's other dialogues , which holds that like the shadows on the wall , things in the physical world are flawed reflections of ideal forms , such as roundness , or beauty . in this way , the cave leads to many fundamental questions , including the origin of knowledge , the problem of representation , and the nature of reality itself . for theologians , the ideal forms exist in the mind of a creator . for philosophers of language viewing the forms as linguistic concepts , the theory illustrates the problem of grouping concrete things under abstract terms . and others still wonder whether we can really know that the things outside the cave are any more real than the shadows . as we go about our lives , can we be confident in what we think we know ? perhaps one day , a glimmer of light may punch a hole in your most basic assumptions . will you break free to struggle towards the light , even if it costs you your friends and family , or stick with comfortable and familiar illusions ? truth or habit ? light or shadow ? hard choices , but if it 's any consolation , you 're not alone . there are lots of us down here .
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occasionally , people pass by the fire , carrying figures of animals and other objects that cast shadows on the wall . the prisoners name and classify these illusions , believing they 're perceiving actual entities . suddenly , one prisoner is freed and brought outside for the first time .
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how do the prisoners respond to being chained ?
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all year long , researchers at hundreds of hospitals around the world collect samples from flu patients and send them to top virology experts with one goal : to design the vaccine for the next flu season . but why do we need a new one every year ? vaccines for diseases like mumps and rubella offer a lifetime of protection with two shots early in life . what 's so special about the flu ? two factors make the flu a tough target . first , there are more than 100 subtypes of the influenza virus , and the ones in circulation change from season to season . and second , the flu 's genetic code allows it to mutate more quickly than many other viruses . the flu spreads by turning a host 's own cells into viral production factories . when the virus is engulfed by a host cell , it expels its genetic material , which makes its way to the nucleus . there , cellular machinery that normally copies the host 's genes starts replicating viral genes instead , creating more and more copies of the virus . new viruses are repackaged and crammed into the cell until it bursts , sending freshly minted influenza viruses out to infect additional cells . most viruses follow this script . the trick with the flu is that its genetic material is n't dna but a similar compound called rna . and rna viruses can mutate much faster . when cells synthesize dna , a built-in proofreader recognizes and corrects mistakes , but the rna synthesis mechanism does n't have this fail-safe . if errors creep in , they stick around creating new variants of the virus . why is this a problem ? because vaccines depend on recognition . the flu vaccine includes some of the same substances , called antigens , found on the surface of the virus itself . the body identifies those fragments as foreign and responds by producing compounds called antibodies , tailor-made to match the antigens . when a vaccinated person encounters the actual virus , the preprogrammed antibodies help the immune system identify the threat and mobilize quickly to prevent an infection . those antigens are different for every strain of influenza . if vaccination has prepared the immune system for one strain , a different one may still be able to sneak by . even within the same strain of flu , those rapid genetic mutations can change the surface compounds enough that the antibodies may not recognize them . to make things even more complicated , sometimes two different strains combine to create an entirely new hybrid virus . all of this makes vaccinating for the flu like trying to hit a moving transforming target . that 's why scientists are constantly collecting data about which strains are circulating and checking to see how much those strains have mutated from previous years ' versions . twice annually , the world health organization pulls together experts to analyze all that data , holding one meeting for each hemisphere . the scientists determine which strains to include in that season 's vaccine , picking four for the quadrivalent vaccine in use today . in spite of the flu 's evasive maneuvers , in recent years , the group 's predictions have been almost always correct . even when flu strains mutate further , the vaccine is often close enough that a vaccinated person who catches the flu anyway will have a milder and shorter illness than they would otherwise . vaccination also helps protect other people in the community who may not be medically eligible for the shot by preventing those around them from carrying the virus . this is called herd immunity . the flu shot ca n't give you the flu . it contains an inactivated virus that is n't capable of making you sick . you might feel tired and achy after getting it , but that 's not an infection . it 's your normal immune response to the vaccine . some parts of the world use , instead of a shot , an inhaled vaccine that contains a weakened live virus . this is also safe for the vast majority of people . only those with impaired immune systems would be at risk , but they 're typically not given live vaccines . meanwhile , scientists are working to develop a universal flu vaccine that would protect against any strain , even mutated ones . but until then , the hunt for next year 's vaccine is on .
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because vaccines depend on recognition . the flu vaccine includes some of the same substances , called antigens , found on the surface of the virus itself . the body identifies those fragments as foreign and responds by producing compounds called antibodies , tailor-made to match the antigens . when a vaccinated person encounters the actual virus , the preprogrammed antibodies help the immune system identify the threat and mobilize quickly to prevent an infection .
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the flu vaccine includes substances found on the surface of the virus . the body identifies those fragments as foreign , and responds by producing compounds called _______ .
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translator : tom carter reviewer : bedirhan cinar dialogue gives a story color , makes it exciting and moves it forward . romeo : o , wilt thou leave me so unsatisfied ? juliet : what satisfaction canst thou have tonight ? romeo : the exchange of thy love 's faithful vows for mine . without dialogue : ( cricket sounds ) so what goes into writing effective dialogue ? well , there are social skills : making friends , solving conflicts , being pleasant and polite . we wo n't be using any of those today . instead , we 'll be working on -- let 's call them `` anti-social skills . '' if you 're a writer , you may already have a few of these . the first is eavesdropping . if you 're riding a bus and hear an interesting conversation , you could write it all down . of course , when you write fiction , you 're not describing real people , you 're making up characters . but sometimes the words you overhear can give you ideas . `` i did not , '' says one person . `` i saw you , '' the other replies . who might be saying those words ? maybe it 's two kids in a class , and the boy thinks the girl pushed him . maybe it 's a couple , but one of them is a vampire , and the woman vampire saw the man flirting with a zombie . or maybe not . maybe the characters are a teenager and his mother , and they 're supposed to be vegetarians , but the mother saw him eating a burger . so let 's say you 've decided on some characters . this is anti-social skill number two : start pretending they 're real . what are they like ? where are they from ? what music do they listen to ? spend some time with them . if you 're on a bus , think about what they might be doing if they were there too . would they talk on the phone , listen to music , draw pictures , sleep ? what we say depends on who we are . an older person might speak differently than a younger person . someone from the south might speak differently than someone from the north . once you know your characters , you can figure out how they talk . at this stage , it 's helpful to use anti-social skill number three : muttering to yourself . when you speak your character 's words , you can hear whether they sound natural , and fix them if necessary . remember , most people are usually pretty informal when they speak . they use simple language and contractions . so , `` do not attempt to lie to me '' sounds more natural as `` do n't try to lie to me . '' also keep it short . people tend to speak in short bursts , not lengthy speeches . and let the dialogue do the work . ask yourself : do i really need that adverb ? for instance , `` 'your money or your life , ' she said threateningly . '' here , `` threateningly '' is redundant , so you can get rid of it . but if the words and the actions do n't match , an adverb can be helpful . `` 'your money or your life , ' she said lovingly . '' so , to recap : first , eavesdrop . next , pretend imaginary people are real . finally , mutter to yourself , and write it all down . you already have everything you need . this is fictional dialogue , or `` how to hear voices in your head . ''
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at this stage , it 's helpful to use anti-social skill number three : muttering to yourself . when you speak your character 's words , you can hear whether they sound natural , and fix them if necessary . remember , most people are usually pretty informal when they speak .
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a character may speak differently depending on his or her age or geographic region . what are some other factors that may affect the way a character speaks ?
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imagine a brilliant neuroscientist named mary . mary lives in a black and white room , she only reads black and white books , and her screens only display black and white . but even though she has never seen color , mary is an expert in color vision and knows everything ever discovered about its physics and biology . she knows how different wavelengths of light stimulate three types of cone cells in the retina , and she knows how electrical signals travel down the optic nerve into the brain . there , they create patterns of neural activity that correspond to the millions of colors most humans can distinguish . now imagine that one day , mary 's black and white screen malfunctions and an apple appears in color . for the first time , she can experience something that she 's known about for years . does she learn anything new ? is there anything about perceiving color that was n't captured in all her knowledge ? philosopher frank jackson proposed this thought experiment , called mary 's room , in 1982 . he argued that if mary already knew all the physical facts about color vision , and experiencing color still teaches her something new , then mental states , like color perception , ca n't be completely described by physical facts . the mary 's room thought experiment describes what philosophers call the knowledge argument , that there are non-physical properties and knowledge which can only be discovered through conscious experience . the knowledge argument contradicts the theory of physicalism , which says that everything , including mental states , has a physical explanation . to most people hearing mary 's story , it seems intuitively obvious that actually seeing color will be totally different than learning about it . therefore , there must be some quality of color vision that transcends its physical description . the knowledge argument is n't just about color vision . mary 's room uses color vision to represent conscious experience . if physical science ca n't entirely explain color vision , then maybe it ca n't entirely explain other conscious experiences either . for instance , we could know every physical detail about the structure and function of someone else 's brain , but still not understand what it feels like to be that person . these ineffable experiences have properties called qualia , subjective qualities that you ca n't accurately describe or measure . qualia are unique to the person experiencing them , like having an itch , being in love , or feeling bored . physical facts ca n't completely explain mental states like this . philosophers interested in artificial intelligence have used the knowledge argument to theorize that recreating a physical state wo n't necessarily recreate a corresponding mental state . in other words , building a computer which mimicked the function of every single neuron of the human brain wo n't necessarily create a conscious computerized brain . not all philosophers agree that the mary 's room experiment is useful . some argue that her extensive knowledge of color vision would have allowed her to create the same mental state produced by actually seeing the color . the screen malfunction would n't show her anything new . others say that her knowledge was never complete in the first place because it was based only on those physical facts that can be conveyed in words . years after he proposed it , jackson actually reversed his own stance on his thought experiment . he decided that even mary 's experience of seeing red still does correspond to a measurable physical event in the brain , not unknowable qualia beyond physical explanation . but there still is n't a definitive answer to the question of whether mary would learn anything new when she sees the apple . could it be that there are fundamental limits to what we can know about something we ca n't experience ? and would this mean there are certain aspects of the universe that lie permanently beyond our comprehension ? or will science and philosophy allow us to overcome our mind 's limitations ?
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he argued that if mary already knew all the physical facts about color vision , and experiencing color still teaches her something new , then mental states , like color perception , ca n't be completely described by physical facts . the mary 's room thought experiment describes what philosophers call the knowledge argument , that there are non-physical properties and knowledge which can only be discovered through conscious experience . the knowledge argument contradicts the theory of physicalism , which says that everything , including mental states , has a physical explanation .
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which philosophical theory states that there are non-physical properties and knowledge that can only be discovered through conscious experience ?
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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 .
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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 .
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amphibians are important because _____ .
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why are most manhole covers round ? sure , it makes them easy to roll and slide into place in any alignment but there 's another more compelling reason involving a peculiar geometric property of circles and other shapes . imagine a square separating two parallel lines . as it rotates , the lines first push apart , then come back together . but try this with a circle and the lines stay exactly the same distance apart , the diameter of the circle . this makes the circle unlike the square , a mathematical shape called a curve of constant width . another shape with this property is the reuleaux triangle . to create one , start with an equilateral triangle , then make one of the vertices the center of a circle that touches the other two . draw two more circles in the same way , centered on the other two vertices , and there it is , in the space where they all overlap . because reuleaux triangles can rotate between parallel lines without changing their distance , they can work as wheels , provided a little creative engineering . and if you rotate one while rolling its midpoint in a nearly circular path , its perimeter traces out a square with rounded corners , allowing triangular drill bits to carve out square holes . any polygon with an odd number of sides can be used to generate a curve of constant width using the same method we applied earlier , though there are many others that are n't made in this way . for example , if you roll any curve of constant width around another , you 'll make a third one . this collection of pointy curves fascinates mathematicians . they 've given us barbier 's theorem , which says that the perimeter of any curve of constant width , not just a circle , equals pi times the diameter . another theorem tells us that if you had a bunch of curves of constant width with the same width , they would all have the same perimeter , but the reuleaux triangle would have the smallest area . the circle , which is effectively a reuleaux polygon with an infinite number of sides , has the largest . in three dimensions , we can make surfaces of constant width , like the reuleaux tetrahedron , formed by taking a tetrahedron , expanding a sphere from each vertex until it touches the opposite vertices , and throwing everything away except the region where they overlap . surfaces of constant width maintain a constant distance between two parallel planes . so you could throw a bunch of reuleaux tetrahedra on the floor , and slide a board across them as smoothly as if they were marbles . now back to manhole covers . a square manhole cover 's short edge could line up with the wider part of the hole and fall right in . but a curve of constant width wo n't fall in any orientation . usually they 're circular , but keep your eyes open , and you just might come across a reuleaux triangle manhole .
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in three dimensions , we can make surfaces of constant width , like the reuleaux tetrahedron , formed by taking a tetrahedron , expanding a sphere from each vertex until it touches the opposite vertices , and throwing everything away except the region where they overlap . surfaces of constant width maintain a constant distance between two parallel planes . so you could throw a bunch of reuleaux tetrahedra on the floor , and slide a board across them as smoothly as if they were marbles . now back to manhole covers .
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you saw that a collection of reuleaux tetrahedra could be used to slide on ; since they have the same width , the board stays level . name two other three-dimensional solids on which a sliding board would stay level .
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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 .
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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 .
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twenty million years ago , south america had continental faunta :
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translator : tom carter reviewer : bedirhan cinar she 's only a few feet away . the closer he gets , the more nervous he becomes , the budding zit on his nose growing bigger and bigger until it practically eclipses his face . she looks at him hovering nearby , sees the massive zit , and giggles . he slumps away , feeling sick . stress can sure make a mess , and it happens to both teens and adults . but how does it happen ? let 's rewind to before the zit , to before justin even sees his crush . already late for school , justin got to class just in time to hear the teacher say `` pop quiz . '' he had n't done his homework the night before , and felt more unprepared than the ambushed world war ii soldiers he was supposed to write about . a sudden rush of panic swept over his body , leaving him with sweaty palms , a foggy mind and a racing heart . he stumbled out of class in a daze , and ran straight into his all-time crush , spiking up his stress . stress is a general biological response to a potential danger . in primitive caveman terms , stress can make you fight for your life , or run for your life , if , for example , you 're confronted by a hungry saber-tooth tiger . special chemicals called stress hormones run through your body , giving you more oxygen and power to run away from danger or to face it and fight for your life , hence the term `` fight or flight . '' but when you do n't fight , or take flight , you face the plight . when we 're taking final exams , sitting in traffic or pondering pollution , we internalize stress . it all begins in the brain . the hypothalamus , the master controller of your hormones , releases something called corticotropin-releasing hormone . this triggers the pituitary gland , a pea-sized gland found at the base of the brain , to release adrenocorticotropic hormone which then stimulates the adrenal gland sitting on top of the kidneys to release cortisol , the major stress hormone . these natural chemicals are a great help when you need to run away quickly , or do superhuman feats of courage , but when you 're simply sitting , these stress hormones collect in the body and affect your overall health . stress hormones increase inflammation in the body , suppress the immune system , which makes you more susceptible to infection by acne-causing bacteria , and can even increase oil production in the skin . and this is the perfect storm for forming a pimple . cortisol is a major stress hormone involved in making skin cells churn out oily lipids from special glands called sebaceous glands . but when there 's too much of these oily lipids , called sebum , they can plug up the swollen , inflamed pores and trap the pesky , acne-causing bacteria inside , where they set up house and thrive . add a dash of inflammatory neuropeptides released by the nervous system when you 're -- well , nervous -- and angry zits follow . to make matters worse , justin is a boy , meaning he 's got more testosterone than girls . testosterone is another hormone that increases oil production in the skin . so , his already oily skin , together with a boost in oil and inflammation from stress , is the perfect environment for bacteria to swell , swell , swell up into a major zit . so what could 've justin done to avoid the big pimple ? stressful situations are unavoidable . but we can try to change our responses so that we 're not so stressed in the end . and had he been confident in approaching her , she might not have noticed the pimple , or he might not have had one .
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when we 're taking final exams , sitting in traffic or pondering pollution , we internalize stress . it all begins in the brain . the hypothalamus , the master controller of your hormones , releases something called corticotropin-releasing hormone .
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your body has different systems in charge of regulating different processes . the system that controls reactions to stress is called the hypothalamic-pituitary-adrenal ( hpa ) axis . explain the course of events in the hpa axis that ultimately leads to cortisol production starting from the brain . ( video hint : “ stress begins in the brain… ” )
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one of the great things about science is that when scientists make a discovery , it 's not always in a prescribed manner , as in , only in a laboratory under strict settings , with white lab coats and all sorts of neat science gizmos that go , `` beep ! '' in reality , the events and people involved in some of the major scientific discoveries are as weird and varied as they get . my case in point : the weird history of the cell theory . there are three parts to the cell theory . one : all organisms are composed of one or more cells . two : the cell is the basic unit of structure and organization in organisms . and three : all cells come from preexisting cells . to be honest , this all sounds incredibly boring until you dig a little deeper into how the world of microscopic organisms , and this theory came to be . it all started in the early 1600s in the netherlands , where a spectacle maker named zacharias janssen is said to have come up with the first compound microscope , along with the first telescope . both claims are often disputed , as apparently he was n't the only bored guy with a ton of glass lenses to play with at the time . despite this , the microscope soon became a hot item that every naturalist or scientist at the time wanted to play with , making it much like the ipad of its day . one such person was a fellow dutchman by the name of anton van leeuwenhoek , who heard about these microscope doohickeys , and instead of going out and buying one , he decided to make his own . and it was a strange little contraption indeed , as it looked more like a tiny paddle the size of a sunglass lens . if he had stuck two together , it probably would have made a wicked set of sunglasses that you could n't see much out of . anyhoo , once leeuwenhoek had his microscope ready , he went to town , looking at anything and everything he could with them , including the gunk on his teeth . yes , you heard right . he actually discovered bacteria by looking at dental scrapings , which , when you keep in mind that people did n't brush their teeth much -- if at all -- back then , he must have had a lovely bunch of bacteria to look at . when he wrote about his discovery , he did n't call them bacteria , as we know them today . but he called them `` animalcules , '' because they looked like little animals to him . while leeuwenhoek was staring at his teeth gunk , he was also sending letters to a scientific colleague in england , by the name of robert hooke . hooke was a guy who really loved all aspects of science , so he dabbled in a little bit of everything , including physics , chemistry and biology . thus it is hooke who we can thank for the term `` the cell , '' as he was looking at a piece of cork under his microscope , and the little chambers he saw reminded him of cells , or the rooms monks slept in in their monasteries . think college dorm rooms , but without the tvs , computers and really annoying roommates . hooke was something of an underappreciated scientist of his day -- something he brought upon himself , as he made the mistake of locking horns with one of the most famous scientists ever , sir isaac newton . remember when i said hooke dabbled in many different fields ? well , after newton published a groundbreaking book on how planets move due to gravity , hooke made the claim that newton had been inspired by hooke 's work in physics . newton , to say the least , did not like that , which sparked a tense relationship between the two that lasted even after hooke died , as quite a bit of hooke 's research -- as well as his only portrait -- was ... misplaced , due to newton . much of it was rediscovered , thankfully , after newton 's time , but not his portrait , as , sadly , no one knows what robert hooke looked like . fast-forward to the 1800s , where two german scientists discovered something that today we might find rather obvious , but helped tie together what we now know as the cell theory . the first scientist was matthias schleiden , a botanist who liked to study plants under a microscope . from his years of studying different plant species , it finally dawned on him that every single plant he had looked at were all made of cells . at the same time , on the other end of germany was theodor schwann , a scientist who not only studied slides of animal cells under the microscope and got a special type of nerve cell named after him , but also invented rebreathers for firefighters , and had a kickin ' pair of sideburns . after studying animal cells for a while , he , too , came to the conclusion that all animals were made of cells . immediately , he reached out via snail mail , as twitter had yet to be invented , to other scientists working in the same field with schleiden , who got back to him , and the two started working on the beginnings of the cell theory . a bone of contention arose between them . as for the last part of the cell theory -- that cells come from preexisting cells -- schleiden did n't exactly subscribe to that thought , as he swore cells came from free-cell formation , where they just kind of spontaneously crystallized into existence . that 's when another scientist named rudolph virchow , stepped in with research showing that cells did come from other cells , research that was actually -- hmm ... how to put it ? -- `` borrowed without permission '' from a jewish scientist by the name of robert remak , which led to two more feuding scientists . thus , from teeth gunk to torquing off newton , crystallization to schwann cells , the cell theory came to be an important part of biology today . some things we know about science today may seem boring , but how we came to know them is incredibly fascinating . so if something bores you , dig deeper . it 's probably got a really weird story behind it somewhere .
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one of the great things about science is that when scientists make a discovery , it 's not always in a prescribed manner , as in , only in a laboratory under strict settings , with white lab coats and all sorts of neat science gizmos that go , `` beep ! '' in reality , the events and people involved in some of the major scientific discoveries are as weird and varied as they get .
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scientists can only make discoveries in a laboratory with white lab coats and science gizmos that go beep .
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as one of the most notorious gangsters in history , al capone presided over a vast and profitable empire of organized crime . when he was finally put on trial , the most he could be convicted of was tax evasion . the nearly $ 100 million a year , that 's 1.4 billion in today 's currency , that capone had earned from illegal gambling , bootlegging , brothels , and extortion , would have served as evidence of his crimes . but the money was nowhere to be found . capone and his associates had hidden it through investments in various businesses whose ultimate ownership could n't be proven , like cash-only laundromats . in fact , those laundromats are part of the reason for the name of this activity , money laundering . money laundering came to be the term for any process that cleans illegally obtained funds of their dirty criminal origins , allowing them to be used within the legal economy . but capone was n't the first to launder money . in fact , this practice is about as old as money itself . merchants hid their riches from tax collecters , and pirates sought to sell their bounty without drawing attention to how they got it . with the recent arrival of virtual currencies , offshore banking , the darknet , and global markets , schemes have become much more complex . although modern money laundering methods vary greatly , most share three basic steps : placement , layering , and integration . placement is where illegally obtained money is converted into assets that seem legitimate . that 's often done by depositing funds into a bank account registered to an anonymous corporation or a professional middleman . this step is where criminals are often most vulnerable to detection since they introduce massive wealth into the financial system seemingly out of nowhere . the second step , layering , involves using multiple transactions to further distance the funds from their origin . this can take the form of transfers between multiple accounts , or the purchase of tradable property , like expensive cars , artwork , and real estate . casinos , where large sums of money change hands every second , are also popular venues for layering . a money launderer may have their gambling balance made available at a casino chain 's locations in other countries , or work with employees to rig games . the last step , integration , allows clean money to re-enter the mainstream economy and to benefit the original criminal . they might invest it into a legal business claiming payment by producing fake invoices , or even start a bogus charity , placing themselves on the board of directors with an exorbitant salary . money laundering itself was n't officially recognized as a federal crime in the united states until 1986 . before that point , the government needed to prosecute a related crime , like tax evasion . from 1986 on , they could confiscate wealth simply by demonstrating that concealment had occurred , which had a positive effect on prosecuting major criminal operations , like drug traffickers . however , a legal shift has raised concerns involving privacy and government surveillance . today , the united nations , national governments , and various nonprofits fight against money laundering , yet the practice continues to play a major role in global crime . and the most high-profile instances of money laundering have involved not just private individuals , but major financial institutions and government officials . no one knows for sure the total amount of money that 's laundered on a yearly basis , but some organizations estimate it to be in the hundreds of billions of dollars .
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with the recent arrival of virtual currencies , offshore banking , the darknet , and global markets , schemes have become much more complex . although modern money laundering methods vary greatly , most share three basic steps : placement , layering , and integration . placement is where illegally obtained money is converted into assets that seem legitimate .
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criminals have exploited banks in their quest to hide illegal money . what can banks do to better protect themselves from the increasing rise of money laundering ?
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hi , i ’ m john green . this is crash course world history and today we ’ re going to talk about world war ii . finally , a war with some color film ! so , here at crash course we try to make history reasonably entertaining , and fortunately , world war ii was hilarious ... said no one ever . mr. green , mr. green ! is this , like , gon na be one of the unfunny ones where you build to the big melodramatic conclusion about how i have to imagine the world more complexly ? me from the past , as long as you have that eighth rate soup-strainer , i ’ m not even going to acknowledge your existence . [ theme music ] right , so you ’ ve probably heard a lot about world war ii from movies and books , the history channel , before it decided that swamp people were history , the incessant droning of your grandparents , etc . we ’ re not gon na try to give you a detailed synopsis of the war today . instead , we ’ re going to try to give a bit of perspective on how the most destructive war in human history happened , and why it still matters globally . so one of the reasons history classes tend to be really into wars is that they ’ re easy to put on tests . they start on one day and they end on another day . and they ’ re caused by social , political , and economic conditions that can be examined in a multiple choice kind of manner . except , not really . like , when did world war ii start ? in september 1939 , when the nazis invaded poland ? i ’ d say no - it actually started when japan invaded manchuria in 1931 , or at the very latest when the japanese invaded china in 1937 , because they didn ’ t stop fighting until 1945 . then again , you could also argue 1933 , when hitler took power , or 1941 , when america started fighting . it ’ s complicated . but anyway , in china the fighting was very brutal , as exemplified by the infamous rape of nanking , which featured the slaughter of hundreds of thousands of chinese people and is still so controversial today that : 1 . it affects relations between japan & amp ; amp ; china and 2 . even though i have not described it in detail , you can rest assured that there will be angry comments about my use of the word “ slaughter. ” but the world war ii we know the most about from movies and tv is primarily the war in the european theater , the one that adolf hitler started . hitler is the rare individual who really did make history - specifically he made it worse - and if he hadn ’ t existed , it ’ s very unlikely that world war ii would ’ ve ever happened . but he did exist , and after coming to power in 1933 , with the standard revolutionary promises to return the homeland to its former glory , infused with quite a bit of paranoia and anti-semitism , germany saw rapid re-militarization and eventually , inevitably , war . in the beginning , it was characterized by a new style of combat made possible by the mechanized technology of tanks , airplanes , and especially , trucks . this was the blitzkrieg , a devastating tactic combining quick movement of troops , tanks , and massive use of air power to support infantry movements . and in the very early years of the war , it was extremely effective . the nazis were able to roll over poland , norway , denmark , the netherlands , and then all of france , all within about 9 months between the fall of 1939 and the summer of 1940 . so after knocking out most of central europe , the nazis set their sights on great britain , but they didn ’ t invade the island , choosing instead to attack it with massive air strikes . i mean , you look at this poster and think , “ man , the queen wants me to finish my term paper , so i can do it , ” but when this poster was first produced in 1939 , it was to quell terror in the face of bombardment . the battle of britain was a duel between the royal air force and the luftwaffe , and while the raf denied the nazis total control of british airspace , the nazis were still able to bomb great britain over and over again in what ’ s known as the blitz . stan , no . no jokes this time . yes , the blitz . meanwhile , europeans were also fighting each other in north africa . the desert campaigns started in 1940 and lasted through 1942 - this is where british general “ monty ” montgomery outfoxed german general irwin “ the desert fox ” rommel . it ’ s also the place where americans first fought nazis in large numbers . but most importantly , it ’ s where indiana jones discovered the ark of the covenant . okay , let ’ s go to the thought bubble . 1941 was a big year for world war ii . first , the nazis invaded russia , breaking a non-aggression pact that the two powers had signed in 1939 . this hugely escalated the war , and also made allies of the most powerful capitalist countries and the most powerful communist one , an alliance that would stand the test of time and never end ... until like three seconds after the defeat of the nazis . the nazi invasion of russia opened the war up on the so-called eastern front , although if you were russian , it was the western front , and it led to millions of deaths , mostly russian . also , 1941 saw a day that would `` live in infamy '' when the japanese bombed pearl harbor , hoping that such an audacious attack would frighten the united states into staying neutral , which was a pretty stupid gamble because : 1 . the u.s. was already giving massive aid to the allies and was hardly neutral and 2 . the united states is not exactly famed for its pacifism or political neutrality . 1941 also saw japan invading much of southeast asia , which made australia and new zealand understandably nervous . as part of the british commonwealth , they were already involved in the war , but now they could fight the japanese closer to home . and shut up about how i never talk about you australians . i just gave you 1.5 sentences . but by the time the americans and australians started fighting the japanese , it was already a world war . sometimes this meant fighting or starving or being bombed ; other times , it meant production for the war - you don ’ t think of argentina as being a world war ii powerhouse , for instance , but they were vital to the allies , supplying 40 % of british meat during world war ii . thanks , thought bubble . so , not to sound jingoistic , but the entry of the u.s. into the war really did change everything , although i doubt the nazis could ’ ve taken russia regardless . no one conquers russia in the wintertime , unless you are - wait for it - the mongols . okay , we ’ re going to skip most of the big battles of 1942 - like the battle of midway , which effectively ended japan ’ s chance of winning the war - and focus on the battle of stalingrad . the german attack on stalingrad , now known as volgograd because stalin sucks , was one of the bloodiest battles in the history of war , with more than two million dead . the germans began by dropping more than 1,000 tons of bombs on stalingrad , and then the russians responded by “ hugging ” the germans , staying as close to their front lines as possible so that german air support would kill germans and russians alike . this kind of worked , although the germans still took most of the city . but then , a soviet counterattack left the sixth army of the nazis completely cut off . and after that , due partly to hitler ’ s overreaching megalomania and partly to lots of people being scared of him , the sixth army slowly froze and starved to death before finally surrendering . and of the 91,000 axis pows from stalingrad , only about 6,000 ever returned home . stalingrad turned the war in europe and by 1944 , the american strategy of “ island hopping ” in the pacific was taking gis closer and closer to japan . rome was liberated in june by americans and canadians ; and the successful british , canadian , and american d-day invasion of normandy was the beginning of the end for the nazis . oh , it ’ s time for the open letter ? an open letter to canada . but first , let ’ s see what ’ s in the secret compartment today . oh , it ’ s canadian mittens . i wan na thank the canadian crash course fans , who sent us these mittens . canadians are just so nice , stan . like , all we ever do on this show is make fun of them , and they ’ re just like , “ it ’ s so kind of you to mention us . here ’ s some mittens ! ” dear canada , we ’ re not always nice to you here on crash course , but you are awesome . i ’ m pointing , but you can ’ t tell because i ’ m wearing mittens . 45,000 canadians died fighting for the allies in world war ii , which means that , per capita , canada lost more people than the united states . you fought with the royal air force to defend great britain from the beginning of the war and you were there on d-day , successfully invading juno beach . and , as many of you have pointed out in comments , you defeated the united states in the war of 1812 , meaning that , arguably , canada , you are the greater military power . plus , you have lumberjacks , and excellent beer , and hockey , and universal healthcare , and justin bieber . i ’ m jealous ! that 's what it is - i 'm jealous ! best wishes , john green . so , by the end of 1944 , the allies were advancing from the west and the russian red army was advancing from the east and then , the last-ditch german offensive at the battle of the bulge in the winter of 1944-1945 failed . mussolini was executed in april of 1945 . hitler committed suicide at the end of that month . and , on may 8 , 1945 the allies declared victory in europe after germany surrendered unconditionally . three months later , the united states dropped the only two nuclear weapons ever deployed in war , japan surrendered , and world war ii was over . the war had a definite cause : unbridled military expansion by germany , japan , and , to a small extent , italy . now , it ’ s easy to claim that hitler was crazy or evil , and , in fact , he was certainly both , but that doesn ’ t explain the nazis decision to invade russia , and it sure doesn ’ t explain japan ’ s decision to bomb pearl harbor . and there are many possible explanations beyond mere evil ; but the most interesting one , to me , involves food . hitler had a number of reasons for wanting to expand germany ’ s territory , but he often talked about lebensraum or living space for the german people . german agriculture was really inefficiently organized into lots of small farms , and that meant that germany needed a lot of land in order to be self-sufficient in food production . the plan was to take poland , the ukraine , and eastern russia , and then resettle that land with lots of germans , so that it could feed german people . this was called the hunger plan because the plan called for 20 million people to starve to death . many would be the poles , ukrainians , and russians who ’ d previously lived on the land . the rest would be europe ’ s jews , who would be worked to death . six million jews were killed by the nazis , many by starvation , but many through a chillingly planned effort of extermination in death camps . these death camps can be distinguished from concentration camps or labor camps in that their primary purpose was extermination of jews , roma people , communists , homosexuals , disabled people , and others that the nazis deemed unfit . some historians believe that the nazis opened the death camps because the jews weren ’ t dying as fast as the hunger plan had intended . this was a sickening plan , but it made a kind of demented sense . rather than becoming more involved in global trade , as the british had , the germans would feed themselves by taking land and killing the people who ’ d previously lived there . similarly , japan , at the beginning of the war , was suffering from an acute fear of food shortage because its agricultural sector was having trouble keeping up with population growth . and the japanese too , sought to expand their agricultural holdings by , for instance , resettling farmers in korea . so while it ’ s tempting to say that world war ii was about the allies fighting for democratic ideals against the totalitarian militaristic imperialism of the fascist axis powers , it just doesn ’ t hold up to scrutiny . for instance , a hugely important allied power , stalin ’ s soviet union , was , like , the least democratic place , ever . stan just said that was hyperbole , but it ’ s not . stalin ’ s soviet union is tied with all of the other completely undemocratic countries for last place on the democracy scale . it ’ s a big community there , at last place , but they ’ re definitely in there somewhere . and , by far , the biggest imperialists of the war were the british . they couldn ’ t have fed or clothed themselves - or resisted the nazis - without their colonies and commonwealth . so , why is world war ii so important ? well first , it proved the old roman adage homo homini lupus : man is a wolf to man . this is seen most clearly in the holocaust , but all the statistics are staggering . more than a million indian british subjects died , mainly due to famine that could have been avoided if the british had redistributed food . and their failure to do so helped convince indians that the so-called superior civilization of the british was a sham . more than a million vietnamese died , mainly due to famine . 418,000 americans . more than a million noncombatants in both germany and japan . and 20 million people in the soviet union , most of them civilians . these civilians were targeted because they helped sustain the war , mostly through industrial and agricultural production . in a total war , when a nation is at war , not just its army , there is no such thing as a non-military target . from the firebombing of dresden to tokyo to hiroshima , the line between soldier and civilian blurred . and then , of course , there is the holocaust , which horrifies us because the elements of western progress - record-keeping , industrial production , technology - were used to slaughter millions . world war ii saw modern industrial nations , which represented the best of the enlightenment and the scientific revolution , descend into once unimaginable cruelty . and what makes world war ii such a historical watershed is that in its wake , all of us - in the west or otherwise - were forced to question whether western dominance of this planet could , or should , be considered progress . thanks for watching . i ’ ll see you next week . crash course is produced and directed by stan muller . our script supervisor is meredith danko . our associate producer is danica johnson . the show is written by my high school history teacher , raoul meyer , and myself . and our graphics team is thought bubble . last week ’ s phrase of the week was “ an end to history. ” if you want to guess at this week ’ s phrase of the week or suggest future ones , you can do so in comments , where you can also ask questions about today ’ s video that will be answered by our team of historians . if you enjoy crash course , make sure you ’ re subscribed . thanks for watching , and as we say in my hometown , don ’ t forget to be awesome .
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the rest would be europe ’ s jews , who would be worked to death . six million jews were killed by the nazis , many by starvation , but many through a chillingly planned effort of extermination in death camps . these death camps can be distinguished from concentration camps or labor camps in that their primary purpose was extermination of jews , roma people , communists , homosexuals , disabled people , and others that the nazis deemed unfit .
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approximately , how many people were killed during the battle of stalingrad ?
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our planet 's diverse thriving ecosystems may seem like permanent fixtures , but they 're actually vulnerable to collapse . jungles can become deserts , and reefs can become lifeless rocks , even without cataclysmic events , like volcanoes and asteroids . what makes one ecosystem strong and another weak in the face of change ? the answer , to a large extent , is biodiversity . biodiversity is built out of three intertwined features : ecosystem diversity , species diversity , and genetic diversity . the more intertwining there is between these features , the denser and more resilient the weave becomes . take the amazon rainforest , one of the most biodiverse regions on earth due to its complex ecosystems , huge mix of species , and the genetic variety within those species . here are tangled liana vines , which crawl up from the forest floor to the canopy , intertwining with treetops and growing thick wooden stems that support these towering trees . helped along by the vines , trees provide the seeds , fruits and leaves to herbivores , such as the tapir and the agouti , which disperse their seeds throughout the forest so they can grow . leftovers are consumed by the millions of insects that decompose and recycle nutrients to create rich soil . the rainforest is a huge system filled with many smaller systems , like this , each packed with interconnected species . every link provides stability to the next , strengthening biodiversity 's weave . that weave is further reinforced by the genetic diversity within individual species , which allows them to cope with changes . species that lack genetic diversity due to isolation or low population numbers , are much more vulnerable to fluctuations caused by climate change , disease or habitat fragmentation . whenever a species disappears because of its weakened gene pool , a knot is untied and parts of the net disintegrate . so , what if we were to remove one species from the rainforest ? would the system fall apart ? probably not . the volume of species , their genetic diversity , and the complexity of the ecosystems form such rich biodiversity in this forest that one species gap in the weave wo n't cause it to unravel . the forest can stay resilient and recover from change . but that 's not true in every case . in some environments , taking away just one important component can undermine the entire system . take coral reefs , for instance . many organisms in a reef are dependent on the coral . it provides key microhabitats , shelter and breeding grounds for thousand of species of fish , crustaceans and mollusks . corals also form interdependent relationships with fungi and bacteria . the coral itself is a loom that allows the tangled net of biodiversity to be woven . that makes coral a keystone organism , one that many others depend on for their suvival . so what happens when destructive fishing practices , pollution and ocean acidification weaken coral or even kill it altogether ? exactly what you might think . the loss of this keystone species leaves its dependents at a loss , too , threatening the entire fabric of the reef . ecosystem , species and genetic diversity together form the complex tangled weave of biodiversity that is vital for the survival of organisms on earth . we humans are woven into this biodiversity , too . when just a few strands are lost , our own well-being is threatened . cut too many links , and we risk unraveling it all . what the future brings is unpredictable , but biodiversity can give us an insurance policy , earth 's own safety net to safeguard our survival .
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the answer , to a large extent , is biodiversity . biodiversity is built out of three intertwined features : ecosystem diversity , species diversity , and genetic diversity . the more intertwining there is between these features , the denser and more resilient the weave becomes .
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ecosystem diversity , species diversity , genetic diversity all intertwine to create ______ .
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this is a crystal of sugar . if you press on it , it will actually generate its own electricity . how can this simple crystal act like a tiny power source ? because sugar is piezoelectric . piezoelectric materials turn mechanical stress , like pressure , sound waves , and other vibrations into electricity and vice versa . this odd phenomenon was first discovered by the physicist pierre curie and his brother jacques in 1880 . they discovered that if they compressed thin slices of certain crystals , positive and negative charges would appear on opposite faces . this difference in charge , or voltage , meant that the compressed crystal could drive current through a circuit , like a battery . and it worked the other way around , too . running electricity through these crystals made them change shape . both of these results , turning mechanical energy into electrical , and electrical energy into mechanical , were remarkable . but the discovery went uncelebrated for several decades . the first practical application was in sonar instruments used to detect german submarines during world war i. piezoelectric quartz crystals in the sonar 's transmitter vibrated when they were subjected to alternating voltage . that sent ultrasound waves through the water . measuring how long it took these waves to bounce back from an object revealed how far away it was . for the opposite transformation , converting mechanical energy to electrical , consider the lights that turn on when you clap . clapping your hands send sound vibrations through the air and causes the piezo element to bend back and forth . this creates a voltage that can drive enough current to light up the leds , though it 's conventional sources of electricity that keep them on . so what makes a material piezoelectric ? the answer depends on two factors : the materials atomic structure , and how electric charge is distributed within it . many materials are crystalline , meaning they 're made of atoms or ions arranged in an orderly three-dimensional pattern . that pattern has a building block called a unit cell that repeats over and over . in most non-piezoelectric crystalline materials , the atoms in their unit cells are distributed symmetrically around a central point . but some crystalline materials do n't possess a center of symmetry making them candidates for piezoelectricity . let 's look at quartz , a piezoelectric material made of silicon and oxygen . the oxygens have a slight negative charge and silicons have a slight positive , creating a separation of charge , or a dipole along each bond . normally , these dipoles cancel each other out , so there 's no net separation of charge in the unit cell . but if a quartz crystal is squeezed along a certain direction , the atoms shift . because of the resulting asymmetry in charge distribution , the dipoles no longer cancel each other out . the stretched cell ends up with a net negative charge on one side and a net positive on the other . this charge imbalance is repeated all the way through the material , and opposite charges collect on opposite faces of the crystal . this results in a voltage that can drive electricity through a circuit . piezoelectric materials can have different structures . but what they all have in common is unit cells which lack a center of symmetry . and the stronger the compression on piezoelectric materials , the larger the voltage generated . stretch the crystal , instead , and the voltage will switch , making current flow the other way . more materials are piezoelectric than you might think . dna , bone , and silk all have this ability to turn mechanical energy into electrical . scientists have created a variety of synthetic piezoelectric materials and found applications for them in everything from medical imaging to ink jet printers . piezoelectricity is responsible for the rhythmic oscillations of the quartz crystals that keep watches running on time , the speakers of musical birthday cards , and the spark that ignites the gas in some barbecue grill lighters when you flick the switch . and piezoelectric devices may become even more common since electricity is in high demand and mechanical energy is abundant . there are already train stations that use passengers ' footsteps to power the ticket gates and displays and a dance club where piezoelectricity helps power the lights . could basketball players running back and forth power the scoreboard ? or might walking down the street charge your electronic devices ? what 's next for piezoelectricity ?
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but the discovery went uncelebrated for several decades . the first practical application was in sonar instruments used to detect german submarines during world war i. piezoelectric quartz crystals in the sonar 's transmitter vibrated when they were subjected to alternating voltage . that sent ultrasound waves through the water .
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many of us know about the tragedy of the titanic in april of 1912. the sonar technology with piezoelectric quartz crystals was first deployed to detect german submarines during world war i. if only this technology had been available a few years earlier , do you think it could have maybe saved the titanic from the deadly iceberg ?
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the term modern art sounds like it means art that is popular at the moment , but in fact , modern art is a style that originated over 150 years ago , and includes artists that by now have attained classic status , such as picasso , matisse , and gauguin . and what 's even more ironic is that the movement they pioneered , considered revolutionary and even scandalous at the time , was inspired largely by an object of a traditional and ancient design . as far back as the renaissance , the primary european art movements emphasized conventional representation and adherence to classical forms . but that began to change in the late 19th century as artists like van gogh and cézanne expanded the boundaries of painting . soon , a movement arose that sought to create an entirely new style of art , and one way of doing so was to look beyond western civilization . for example , paul gauguin moved to the island of tahiti in the 1890s . there , he found inspiration in the island 's inhabitants , landscape , and culture to create artwork that intertwined european themes and polynesian lore . others looked the cultures of the islamic world , but the most influential inspiration would come from sub-saharan africa . as european empires expanded deeper into the african continent , its artifacts and artworks made their way into the hands of museums and collectors . one such collector was henri matisse , who showed his friend picasso a mask he had acquired made by the dan tribe of the ivory coast . the mask awoke picasso 's curiosity , leading him to visit the trocadéro ethnographic museum in paris in 1907 . founded to house acquisitions from colonial conquests , the museum boasted a collection of african art , with stylized figures and masks made of wood and decorated with simple colors and materials . the visit was a revelation for picasso , who proclaimed that african masks were what painting was all about . at this time , picasso had been working on a painting of five nude women in a style that would later come to be known as cubism . and while three of these ladies show facial features found in ancient iberian art , a nod to picasso 's spanish heritage , the faces of the two on the right closely resemble african masks . created in 1907 after hundreds of sketches and studies , `` les demoiselles d'avignon '' has been considered the first truly 20th century masterpiece , breaking with many previously held notions in art . it was at once aggressive and abstract , distorted yet primal in its raw geometry , a new artistic language with new forms , colors , and meanings . and these avant-garde qualities caused a sensation when the painting was first exhibited almost ten years later . the public was shocked , critics denounced it as immoral , and even picasso 's own friends were simultaneously surprised , offended , and mesmerized at his audacity . more artists soon followed in picasso 's footsteps . constantin brâncuși and amedeo modigliani in paris , as well as the german expressionists , all drew on the aesthetics of african sculptures in their work . others looked to a different continent for their inspiration . british sculptor henry moore based many of his semi-abstract bronze sculptures on a replica of a chacmool , a distinctive reclining statue from the toltec-maya culture . pre-columbian art was also a major influence for josef albers . he created a series of compositions , such as the geometrical series homage to the square , that were inspired by pyramids and local art he encountered on his frequent visits to mexico . inspiration from ancient cultures initiated one of the most revolutionary movements in art history , but were these artists playing the role of explorers or conquistadors , appropriating ideas and profiting from cultures they considered primitive ? questions like this deserve scrutiny , as artists continue to redefine standards . perhaps not too long from now , the bold innovations of modern art will seem like stale orthodoxies , ready to be overturned by a new set of radical trailblazers drawing inspiration from another unlikely source .
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the term modern art sounds like it means art that is popular at the moment , but in fact , modern art is a style that originated over 150 years ago , and includes artists that by now have attained classic status , such as picasso , matisse , and gauguin . and what 's even more ironic is that the movement they pioneered , considered revolutionary and even scandalous at the time , was inspired largely by an object of a traditional and ancient design .
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which artist said “ i do not seek , i find ” ?
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in 1800 , the explorer alexander von humboldt witnessed a swarm of electric eels leap out of the water to defend themselves against oncoming horses . most people thought the story so unusual that humboldt made it up . but fish using electricity is more common than you might think ; and yes , electric eels are a type of fish . underwater , where light is scarce , electrical signals offer ways to communicate , navigate , and find—plus , in rare cases , stun—prey . nearly 350 species of fish have specialized anatomical structures that generate and detect electrical signals . these fish are divided into two groups , depending on how much electricity they produce . scientists call the first group the weakly electric fish . structures near their tails called electric organs produce up to a volt of electricity , about two-thirds as much as a aa battery . how does this work ? the fish 's brain sends a signal through its nervous system to the electric organ , which is filled with stacks of hundreds or thousands of disc-shaped cells called electrocytes . normally , electrocytes pump out sodium and potassium ions to maintain a positive charge outside and negative charge inside . but when the nerve signal arrives at the electrocyte , it prompts the ion gates to open . positively charged ions flow back in . now , one face of the electrocyte is negatively charged outside and positively charged inside . but the far side has the opposite charge pattern . these alternating charges can drive a current , turning the electrocyte into a biological battery . the key to these fish 's powers is that nerve signals are coordinated to arrive at each cell at exactly the same time . that makes the stacks of electrocytes act like thousands of batteries in series . the tiny charges from each one add up to an electrical field that can travel several meters . cells called electroreceptors buried in the skin allow the fish to constantly sense this field and the changes to it caused by the surroundings or other fish . the peter ’ s elephantnose fish , for example , has an elongated chin called a schnauzenorgan that 's riddled in electroreceptors . that allows it to intercept signals from other fish , judge distances , detect the shape and size of nearby objects , and even determine whether a buried insect is dead or alive . but the elephantnose and other weakly electric fish do n't produce enough electricity to attack their prey . that ability belongs to the strongly electric fish , of which there are only a handful of species . the most powerful strongly electric fish is the electric knife fish , more commonly known as the electric eel . three electric organs span almost its entire two-meter body . like the weakly electric fish , the electric eel uses its signals to navigate and communicate , but it reserves its strongest electric discharges for hunting using a two-phased attack that susses out and then incapacitates its prey . first , it emits two or three strong pulses , as much as 600 volts . these stimulate the prey 's muscles , sending it into spasms and generating waves that reveal its hiding place . then , a volley of fast , high-voltage discharges causes even more intense muscle contractions . the electric eel can also curl up so that the electric fields generated at each end of the electric organ overlap . the electrical storm eventually exhausts and immobilizes the prey , and the electric eel can swallow its meal alive . the other two strongly electric fish are the electric catfish , which can unleash 350 volts with an electric organ that occupies most of its torso , and the electric ray , with kidney-shaped electric organs on either side of its head that produce as much as 220 volts . there is one mystery in the world of electric fish : why do n't they electrocute themselves ? it may be that the size of strongly electric fish allows them to withstand their own shocks , or that the current passes out of their bodies too quickly . some scientists think that special proteins may shield the electric organs , but the truth is , this is one mystery science still has n't illuminated .
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that allows it to intercept signals from other fish , judge distances , detect the shape and size of nearby objects , and even determine whether a buried insect is dead or alive . but the elephantnose and other weakly electric fish do n't produce enough electricity to attack their prey . that ability belongs to the strongly electric fish , of which there are only a handful of species .
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electric fish use specialized cells to produce electricity . what are these called ?
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this may look like a neatly arranged stack of numbers , but it 's actually a mathematical treasure trove . indian mathematicians called it the staircase of mount meru . in iran , it 's the khayyam triangle . and in china , it 's yang hui 's triangle . to much of the western world , it 's known as pascal 's triangle after french mathematician blaise pascal , which seems a bit unfair since he was clearly late to the party , but he still had a lot to contribute . so what is it about this that has so intrigued mathematicians the world over ? in short , it 's full of patterns and secrets . first and foremost , there 's the pattern that generates it . start with one and imagine invisible zeros on either side of it . add them together in pairs , and you 'll generate the next row . now , do that again and again . keep going and you 'll wind up with something like this , though really pascal 's triangle goes on infinitely . now , each row corresponds to what 's called the coefficients of a binomial expansion of the form ( x+y ) ^n , where n is the number of the row , and we start counting from zero . so if you make n=2 and expand it , you get ( x^2 ) + 2xy + ( y^2 ) . the coefficients , or numbers in front of the variables , are the same as the numbers in that row of pascal 's triangle . you 'll see the same thing with n=3 , which expands to this . so the triangle is a quick and easy way to look up all of these coefficients . but there 's much more . for example , add up the numbers in each row , and you 'll get successive powers of two . or in a given row , treat each number as part of a decimal expansion . in other words , row two is ( 1x1 ) + ( 2x10 ) + ( 1x100 ) . you get 121 , which is 11^2 . and take a look at what happens when you do the same thing to row six . it adds up to 1,771,561 , which is 11^6 , and so on . there are also geometric applications . look at the diagonals . the first two are n't very interesting : all ones , and then the positive integers , also known as natural numbers . but the numbers in the next diagonal are called the triangular numbers because if you take that many dots , you can stack them into equilateral triangles . the next diagonal has the tetrahedral numbers because similarly , you can stack that many spheres into tetrahedra . or how about this : shade in all of the odd numbers . it does n't look like much when the triangle 's small , but if you add thousands of rows , you get a fractal known as sierpinski 's triangle . this triangle is n't just a mathematical work of art . it 's also quite useful , especially when it comes to probability and calculations in the domain of combinatorics . say you want to have five children , and would like to know the probability of having your dream family of three girls and two boys . in the binomial expansion , that corresponds to girl plus boy to the fifth power . so we look at the row five , where the first number corresponds to five girls , and the last corresponds to five boys . the third number is what we 're looking for . ten out of the sum of all the possibilities in the row . so 10/32 , or 31.25 % . or , if you 're randomly picking a five-player basketball team out of a group of twelve friends , how many possible groups of five are there ? in combinatoric terms , this problem would be phrased as twelve choose five , and could be calculated with this formula , or you could just look at the sixth element of row twelve on the triangle and get your answer . the patterns in pascal 's triangle are a testament to the elegantly interwoven fabric of mathematics . and it 's still revealing fresh secrets to this day . for example , mathematicians recently discovered a way to expand it to these kinds of polynomials . what might we find next ? well , that 's up to you .
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it 's also quite useful , especially when it comes to probability and calculations in the domain of combinatorics . say you want to have five children , and would like to know the probability of having your dream family of three girls and two boys . in the binomial expansion , that corresponds to girl plus boy to the fifth power .
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in tossing a coin three times , ( h+t ) ^3 , the probability of having two heads and one tail is _____ .
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did you know that every time musicians pick up their instruments , there are fireworks going off all over their brain ? on the outside , they may look calm and focused , reading the music and making the precise and practiced movements required . but inside their brains , there 's a party going on . how do we know this ? well , in the last few decades , neuroscientists have made enormous breakthroughs in understanding how our brains work by monitoring them in real time with instruments like fmri and pet scanners . when people are hooked up to these machines , tasks , such as reading or doing math problems , each have corresponding areas of the brain where activity can be observed . but when researchers got the participants to listen to music , they saw fireworks . multiple areas of their brains were lighting up at once , as they processed the sound , took it apart to understand elements like melody and rhythm , and then put it all back together into unified musical experience . and our brains do all this work in the split second between when we first hear the music and when our foot starts to tap along . but when scientists turned from observing the brains of music listeners to those of musicians , the little backyard fireworks became a jubilee . it turns out that while listening to music engages the brain in some pretty interesting activities , playing music is the brain 's equivalent of a full-body workout . the neuroscientists saw multiple areas of the brain light up , simultaneously processing different information in intricate , interrelated , and astonishingly fast sequences . but what is it about making music that sets the brain alight ? the research is still fairly new , but neuroscientists have a pretty good idea . playing a musical instrument engages practically every area of the brain at once , especially the visual , auditory , and motor cortices . as with any other workout , disciplined , structured practice in playing music strengthens those brain functions , allowing us to apply that strength to other activities . the most obvious difference between listening to music and playing it is that the latter requires fine motor skills , which are controlled in both hemispheres of the brain . it also combines the linguistic and mathematical precision , in which the left hemisphere is more involved , with the novel and creative content that the right excels in . for these reasons , playing music has been found to increase the volume and activity in the brain 's corpus callosum , the bridge between the two hemispheres , allowing messages to get across the brain faster and through more diverse routes . this may allow musicians to solve problems more effectively and creatively , in both academic and social settings . because making music also involves crafting and understanding its emotional content and message , musicians often have higher levels of executive function , a category of interlinked tasks that includes planning , strategizing , and attention to detail and requires simultaneous analysis of both cognitive and emotional aspects . this ability also has an impact on how our memory systems work . and , indeed , musicians exhibit enhanced memory functions , creating , storing , and retrieving memories more quickly and efficiently . studies have found that musicians appear to use their highly connected brains to give each memory multiple tags , such as a conceptual tag , an emotional tag , an audio tag , and a contextual tag , like a good internet search engine . how do we know that all these benefits are unique to music , as opposed to , say , sports or painting ? or could it be that people who go into music were already smarter to begin with ? neuroscientists have explored these issues , but so far , they have found that the artistic and aesthetic aspects of learning to play a musical instrument are different from any other activity studied , including other arts . and several randomized studies of participants , who showed the same levels of cognitive function and neural processing at the start , found that those who were exposed to a period of music learning showed enhancement in multiple brain areas , compared to the others . this recent research about the mental benefits of playing music has advanced our understanding of mental function , revealing the inner rhythms and complex interplay that make up the amazing orchestra of our brain .
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the research is still fairly new , but neuroscientists have a pretty good idea . playing a musical instrument engages practically every area of the brain at once , especially the visual , auditory , and motor cortices . as with any other workout , disciplined , structured practice in playing music strengthens those brain functions , allowing us to apply that strength to other activities .
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learning a musical instrument engages which different areas of the brain at the same time ?
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so today we ’ re going to look at bromine . so this is bromine , it ’ s a small sample , about 2 or 3 grammes . bromine is a red liquid . there are not many elements that are actually liquid : caesium , mercury , gallium and bromine . it ’ s this beautiful red colour and it has an unpleasant smell . bromine comes from the greek word bromos which means stench , a really horrible smell . in fact this bromine probably comes from near where i did my degree because in europe , the second , well the largest producer of bromine in europe is the octale company which is based on amlwch on anglesey which is where i went last weekend . so it ’ s a nice sample . we ’ re going to get it out of this bottle now because it ’ s sealed in because it ’ s obviously very , very volatile as a liquid and we ’ re going to cut the glass , get it out and look at its chemistry . thanks neil . bromine is also quite a common element in the world . it is found in sea water as bromide , it ’ s also found particularly in the dead sea between israel and jordan where there are very concentrated solutions of bromide . so you can make bromine just by bubbling chlorine into a solution of bromide like dead sea water and the chlorine displaces the bromine and forms chloride and the bromine just comes out as red fumes which you can catch . so neil ’ s now using a glass knife to open the ampoule and he ’ s going to pour the liquid bromine into this small evaporating dish inside our fume hood . now instantly you can see the vapour of the bromine coming off . you see all those really nice orange fumes which are coming off from the liquid and then they ’ re being drawn away by our fume hood . bromine has a number of uses , it is particularly used in plastics as an additive to try and make them less flammable . if you ’ re watching your videos on a screen which has a plastic surround almost certainly that surround will contain bromine to make it less flammable . bromine itself is strongly oxidising so we thought we ’ d do an oxidation reaction today . and that reaction is to take another element and here we have aluminium , simple aluminium foil , like you wrap your dinner in , and we ’ re now going to put some small amounts of aluminium foil into the bromine liquid . so we put it in and it generally takes a few moments for this reaction to start but as i said , the aluminium is strongly oxidising . it oxidises and generates aluminium tribromide . which is a beautiful nice material but it ’ s a strongly exothermic reaction . so let ’ s see what happens . this may initiate . it is also an unusual element because elements have different isotopes these are the same form of the element but with different numbers of neutrons in the atoms so they weigh different amounts . usually you get one isotope that is very common and another one that is only a small amount . bromine is unusual because it has two isotopes 79 and 81 which have almost equal quantities in nature so that they have approximately 51 % of one and 49 % of the other which is really quite unusual . so here we see the exothermic oxidation and formation of aluminium tribromide . so the reaction is strongly exothermic which means it gives out energy and that energy then evaporates off excess bromine which you can see coming off as a vapour . a wonderful exothermic reaction : very , very fast , very , very rapid forming aluminium tribromide . bromine is quite dangerous but it is less dangerous than chlorine because it ’ s a liquid at room temperature . chlorine is a gas so if you let out chlorine it disperses everywhere . with bromine it is a heavy gas which can disperse rather more slowly . so now as the reaction cools down we can see that the volume of bromine is significantly reduced . reacts with water quite well .
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it ’ s this beautiful red colour and it has an unpleasant smell . bromine comes from the greek word bromos which means stench , a really horrible smell . in fact this bromine probably comes from near where i did my degree because in europe , the second , well the largest producer of bromine in europe is the octale company which is based on amlwch on anglesey which is where i went last weekend .
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as the professor explained , the name bromine comes from the greek “ bromos ” . what property of bromine is represented in its name ?
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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 ? ''
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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 ?
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what is limiting technological progress ?
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it 's easy to forget how vast and deep the ocean really is . about 60 % of it is actually a cold and dark region known as the deep ocean . and it reaches down to 11,000 meters . yet , this remote zone is also one of the greatest habitats on earth , harboring a huge diversity of life , from giant squids and goblin sharks to minuscule animals smaller than a millimeter . how do so many species thrive in this underwater world ? over the decades , intrepid scientists have ventured there to find out . traveling down through the water column , pressure increases and light begins to wane . at 200 meters , photosynthesis stops and temperature decreases from surface temperatures by up to 20 degrees celsius . by 1000 meters , normal sunlight has disappeared altogether . without light , life as we know it seems impossible . that 's why in 1844 , the naturalist edward forbes wrote his azoic theory , azoic , meaning without animals . forbes was sure that nothing could survive below 600 meters on account of the lack of light . of course , the discovery of deep-sea species proved him wrong . what forbes failed to take into account is something called marine snow , which sounds much nicer than it is . marine snow is basically organic matter , things like particles of dead algae , plants , and animals , drifting down into the depths and acting as food for deep-sea animals . largely thanks to that , abundant life forms exist in the darkness , adapting to a harsh reality where only the weird and wonderful can survive . fish with cavernous mouths , spiky teeth jutting from their jaws , and lamp-like structures protruding from their heads , like the anglerfish which entices prey with its misleading glow . several sea creatures have perfected this lightning technique known as bioluminescence , using it to lure prey , distract predators , or attract mates . some creatures use it for camoflauge . in parts of the water column where only faint blue light filters through , animals bioluminesce to match the glow . predators or prey looking up from below are deceived by this camoflauge , unable to see the creatures silhouette . such otherworldly adaptations also arise from the need to locate and snatch up food before it drifts away . some sea animals , like jellyfish , comb jellies and salps can migrate between depths partially because their 90 % water consistency allows them to withstand immense pressure . but they 're the exception . most deep-sea creatures are confined to a narrow range in the water column where nutrients are scarce since the food drifting downwards from the surface rapidly sinks to the sea floor . plunging all the way down , we find more exotic creatures . some take on dwarfism , a trait that transforms them into miniature versions of animals we see closer to the surface . it 's thought that reduced food availability causes the shrinkage . only a tiny fraction of the food produced at the surface reaches the sea floor , so being small gives animals a low energy requirement and an adaptive advantage . and yet , the sea is also the land of giants . here , gargantuan squids can reach 18 meters long . isopods scuttle around the sea floor like enormous wood lice . there are long-limbed japanese spider crabs , and oarfish , whose bodies stretch to 15 meters . this trait is known as gigantism , and it 's something of a mystery . it 's thought that high oxygen levels may drive extreme growth in some species , while the colder temperatures promote longer life spans , giving animals the opportunity to grow massive . many of these exotic sea beasts will never experience sunlight . some will venture up through the water column to feed , and a few will actually break the waves , reminding us at the surface about the incredible survival skills of the ocean 's deepest inhabitants . humans still have an astounding 95 % of the ocean left to explore . so those depths remain a great mystery . what other untold wonders lie far below , and which ones will we discover next ?
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traveling down through the water column , pressure increases and light begins to wane . at 200 meters , photosynthesis stops and temperature decreases from surface temperatures by up to 20 degrees celsius . by 1000 meters , normal sunlight has disappeared altogether .
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at which depth does photosynthesis generally stop ?
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what could octopuses possibly have in common with us ? after all , they do n't have lungs , spines , or even a plural noun we can all agree on . but what they do have is the ability to solve puzzles , learn through observation , and even use tools , just like some other animals we know . and what makes octopus intelligence so amazing is that it comes from a biological structure completely different from ours . the 200 or so species of octopuses are mollusks belonging to the order cephalopoda , greek for head-feet . those heads contain impressively large brains , with a brain to body ratio similar to that of other intelligent animals , and a complex nervous system with about as many neurons as that of a dog . but instead of being centralized in the brain , these 500 million neurons are spread out in a network of interconnected ganglia organized into three basic structures . the central brain only contains about 10 % of the neurons , while the two huge optic lobes contain about 30 % . the other 60 % are in the tentacles , which for humans would be like our arms having minds of their own . this is where things get even more interesting . vertebrates like us have a rigid skeleton to support our bodies , with joints that allow us to move . but not all types of movement are allowed . you ca n't bend your knee backwards , or bend your forearm in the middle , for example . cephalopods , on the other hand , have no bones at all , allowing them to bend their limbs at any point and in any direction . so shaping their tentacles into any one of the virtually limitless number of possible arrangements is unlike anything we are used to . consider a simple task , like grabbing and eating an apple . the human brain contains a neurological map of our body . when you see the apple , your brain 's motor center activates the appropriate muscles , allowing you to reach out with your arm , grab it with your hand , bend your elbow joint , and bring it to your mouth . for an octopus , the process is quite different . rather than a body map , the cephalopod brain has a behavior library . so when an octopus sees food , its brain does n't activate a specific body part , but rather a behavioral response to grab . as the signal travels through the network , the arm neurons pick up the message and jump into action to command the movement . as soon as the arm touches the food , a muscle activation wave travels all the way through the arm to its base , while the arm sends back another wave from the base to the tip . the signals meet halfway between the food and the base of the arm , letting it know to bend at that spot . what all this means is that each of an octopus 's eight arms can essentially think for itself . this gives it amazing flexibility and creativity when facing a new situation or problem , whether its opening a bottle to reach food , escaping through a maze , moving around in a new environment , changing the texture and the color of its skin to blend into the scenery , or even mimicking other creatures to scare away enemies . cephalopods may have evolved complex brains long before our vertebrate relatives . and octopus intelligence is n't just useful for octopuses . their radically different nervous system and autonomously thinking appendages have inspired new research in developing flexible robots made of soft materials . and studying how intelligence can arise along such a divergent evolutionary path can help us understand more about intelligence and consciousness in general . who knows what other forms of intelligent life are possible , or how they process the world around them .
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what could octopuses possibly have in common with us ? after all , they do n't have lungs , spines , or even a plural noun we can all agree on .
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which of the following sentences is incorrect ?
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translator : andrea mcdonough reviewer : bedirhan cinar great weather we 're having ! awesome job ! you 're a tremendous athlete ! compliments , right ? well , maybe . depending on the attitude and tone of voice behind these lines , they very well may be compliments . they may also be , though , pointed and attacking lines . this slight change of attitude behind the lines reveals what we call verbal irony . so when someone says , `` great weather we 're having , '' it is quite possible that the person really means that if the sun is shining , the birds are singing , and the wind is calm . but if the weather is horrible , the clouds are looming , and the wind is a raging tempest , and someone says , `` great weather we 're having , '' he probably does n't actually mean that . he probably means that the weather is horrible , but he has said the opposite . this is verbal irony when the speaker says the opposite of what he means . i know what you 're thinking . is n't this sarcasm , is n't the speaker being sarcastic ? yes . when a speaker says the opposite of what he means , that is verbal irony . when a speaker then goes the step farther to mean the opposite of what he says and seeks to be a little pointed and mean , like he 's making fun of something , then you have sarcasm . take the second example : `` awesome job ! '' someone accomplishing his life-long dream : awesome ! someone winning a sports championship : awesome ! someone rear-ends another car : not awesome . so when the passenger says , `` awesome job ! '' they probably mean the opposite with a hint of poking fun . that is verbal irony and that is sarcastic . `` you 're a talented athlete , '' said to an olympian : authentic , no verbal irony present . said to the klutzy kid tripping into english class and spilling his books and pencil case all over the room , now that is just harsh and verbally ironic because what you said is not what you meant . that is verbal irony . you have said the opposite of what you mean . additionally , since you have the intention of mocking this poor person , you have not only been verbally ironic , but sarcastic as well . beware , though . while all sarcasm fits the definition of verbal irony , not all verbal irony is sarcastic . verbal irony is where what is meant is the opposite of what is said , while sarcasm adds that little punch of attitude . there are times , though , where another layer of meaning can be present without that sarcastic tone . alright , now go out there and find those examples of verbal irony and sarcasm . good luck ! no , seriously , i mean it , good luck . no , no , really , i truly want to wish you luck on this difficult task . ok , ok , sincerely good luck . you can do it ! no verbal irony here .
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said to the klutzy kid tripping into english class and spilling his books and pencil case all over the room , now that is just harsh and verbally ironic because what you said is not what you meant . that is verbal irony . you have said the opposite of what you mean .
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verbal irony occurs :
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`` some are born great , some achieve greatness , and others have greatness thrust upon them '' , quoth william shakespeare . or did he ? some people question whether shakespeare really wrote the works that bear his name , or whether he even existed at all . they speculate that shakespeare was a pseudonym for another writer , or a group of writers . proposed candidates for the real shakespeare include other famous playwrights , politicians and even some prominent women . could it be true that the greatest writer in the english language was as fictional as his plays ? most shakespeare scholars dismiss these theories based on historical and biographical evidence . but there is another way to test whether shakespeare 's famous lines were actually written by someone else . linguistics , the study of language , can tell us a great deal about the way we speak and write by examining syntax , grammar , semantics and vocabulary . and in the late 1800s , a polish philosopher named wincenty lutosławski formalized a method known as stylometry , applying this knowledge to investigate questions of literary authorship . so how does stylometry work ? the idea is that each writer 's style has certain characteristics that remain fairly uniform among individual works . examples of characteristics include average sentence length , the arrangement of words , and even the number of occurrences of a particular word . let 's look at use of the word thee and visualize it as a dimension , or axis . each of shakespeare 's works can be placed on that axis , like a data point , based on the number of occurrences of that word . in statistics , the tightness of these points gives us what is known as the variance , an expected range for our data . but , this is only a single characteristic in a very high-dimensional space . with a clustering tool called principal component analysis , we can reduce the multidimensional space into simple principal components that collectively measure the variance in shakespeare 's works . we can then test the works of our candidates against those principal components . for example , if enough works of francis bacon fall within the shakespearean variance , that would be pretty strong evidence that francis bacon and shakespeare are actually the same person . what did the results show ? well , the stylometrists who carried this out have concluded that shakespeare is none other than shakespeare . the bard is the bard . the pretender 's works just do n't match up with shakespeare 's signature style . however , our intrepid statisticians did find some compelling evidence of collaborations . for instance , one recent study concluded that shakespeare worked with playwright christopher marlowe on `` henry vi , '' parts one and two . shakespeare 's identity is only one of the many problems stylometry can resolve . it can help us determine when a work was written , whether an ancient text is a forgery , whether a student has committed plagiarism , or if that email you just received is of a high priority or spam . and does the timeless poetry of shakespeare 's lines just boil down to numbers and statistics ? not quite . stylometric analysis may reveal what makes shakespeare 's works structurally distinct , but it can not capture the beauty of the sentiments and emotions they express , or why they affect us the way they do . at least , not yet .
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but , this is only a single characteristic in a very high-dimensional space . with a clustering tool called principal component analysis , we can reduce the multidimensional space into simple principal components that collectively measure the variance in shakespeare 's works . we can then test the works of our candidates against those principal components .
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what clustering tool did stylometrists use to collectively measure variance in shakespeare 's works ?
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translator : andrea mcdonough reviewer : bedirhan cinar `` i need a hero ! '' so many people in distress have said this , but why ? what kind of hero do we need and do we even really even need a hero at all ? well , if you look at any piece of literature written for page , script , or stage , the answer is yes ! but , heroes come in all shapes and sizes , depending on what needs to be dealt with . first , you have your epic heroes . epic heroes usually come from a famous family , have super-human strength , are unusually good-looking . they take on challenges that no one else will and succeed . they have great journeys and adventures , some supernatural and some , right here on earth . beowulf does all of this . he travels across the sea with his band of warriors to help another king defeat a supernatural monster that has been terrorizing his kingdom . he defeats the monster and the monster 's mother in an epic battle , and then goes back home and becomes king himself . in his old age , he has one more monster to face , one more threat that he must keep from his people , a dragon . now , being an epic hero , of course he wins , but he is also human , and so he also dies . but he leaves behind stories to inspire others even today . next , we have our tragic heroes . tragic heroes are usually leaders or powerful characters , but the tragic hero is also majorly flawed and that flaw usually leads him down the path to a horrible and tragic death . take the story of oedipus the king , for example . one day , a young man travels to a town called thebes . on the way , he kills a man for not yielding to him on the road in the first documented case of road rage . he also defeats a magical creature and is rewarded by becoming the king of thebes , and thus , marrying their queen . well , that 's not so tragic , right ? wrong ! the queen he just married is actually his birth mother ! oedipus was supposed to have been killed as a child by a servant , but instead he was given to another family . oh , and the man he killed on the road , the previous king of thebes and his dad . so he killed his father and married his mother . now that is quite tragic . not tragic enough for you ? try this one . romeo montague is a guy born into a wealthy family and finds the love of his life at a party , juliet . but , juliet is from a different family that just so happens to hate his family . instead of being patient and working through the family feud , romeo decides he must have his love now , and his impatience leads to bloodshed and death , including his own and juliet 's . moving on to romantic heroes . now these guys might sound like they might have a better love life and chance at happiness , but that 's not always the case . these heroes are emotional and very human . but there is something magical about them . some have a miraculous birth and then are separated from their family . others use enchanted swords or get help from magical beans . they could also reject the expectations of society and adhere to their own code of morality . and in the end , the hero triumphs over evil in an idyllic way , but at great personal , emotional sacrifice . king arthur is a good example of a romantic hero . sure , he became king and married the love of his life , but he was also killed by his son , who was born out of wedlock , and had his wife cheat on him with his best friend . so , although he , too , like beowulf , was a great king , he suffered much more for the greater purpose of society , which makes him more human and relatable to us all . there are different heroes for different situations . sometimes we need the strong warrior to slay the evils of the world . at other times , we need a common person who becomes great so that they can inspire us all to be better . so do we need heroes ? absolutely ! no matter what the time or place , we still need something to believe in . they remind us of the good in each of us , and the need for hope and the importance of knowledge .
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and in the end , the hero triumphs over evil in an idyllic way , but at great personal , emotional sacrifice . king arthur is a good example of a romantic hero . sure , he became king and married the love of his life , but he was also killed by his son , who was born out of wedlock , and had his wife cheat on him with his best friend .
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which of the following characters are an example of a romantic hero ?
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