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translator : andrea mcdonough reviewer : jessica ruby around 1469 , a wealthy money changer commissioned a young painter named sandro botticelli to paint an altar piece . botticelli would , of course , become known as one of the greatest painters of the high renaissance , producing works like `` la primavera '' and `` the birth of venus . '' but , in 1469 , he had not yet earned this reputation . the scene this young artist set out to paint was well-known : the three wise men , or magi , arriving at the birth place of jesus christ . botticelli would aspire to take this common theme and produce an entirely original work , while asserting himself among the most important citizens of florence . many earlier paintings illustrate the magi arriving at a stable , stately manger , fitting for the son of god . the young botticelli , however , chose to place the scene in the dilapidated roman ruin . at the center of this structure , he placed a sturdy rock for mary and jesus to sit high above their visitors . with this decision , botticelli seemed to say christianity will be built on sturdier stuff than rome . botticelli then populated the space with important men from his city . on the right side , he paints the man who paid for this work , gaspare del lama , looking out at the viewer and confidently pointing at himself so that there is no question who is responsible for this masterpiece . though born the son of a barber , del lama amassed a good sum of money through currency exchange in his lifetime . he earned enough money to buy a burial chapel and decorate it with a pretty painting . the three wise men appear at the center of this painting , kneeling to mary and jesus . as models for these important figures , botticelli used members of the important medici family . del lama 's career as a money changer would not have been possible without the help of the powerful medici family , in particular cosimo de ' medici , who appears prominently at mary 's feet . the other wise men can be identified as piero and giovanni de ' medici , cosimo 's two sons . the business of money exchange had dubious ethical and legal associations , so the friendship of this powerful family was important . and the young heir to medici power , lorenzo , could not be omitted from this painting 's composition . he appears to the left of the manger . this painting seems to say the medici legacy , with its many healthy heirs , will be built on sturdier stuff than rome . botticelli then filled the rest of the space with other friends and powerful figures from florence . and , among the florentine elite , the young , confident artist painted himself looking directly at the viewer . botticelli 's presence in this painting illustrates a radical shift in the perception of artists during this time period . botticelli did not view himself as a common craftsman hired for a simple job . he viewed himself as a friend to the powerful families of florence . paintings like `` the adoration of the magi '' reveal much more than a simple retelling of a biblical story . they can tell the story of , among other things , a modestly-born money changer attempting to spend his money virtuously by making a local chapel more beautiful , or the story of an ambitious young painter , elevating the reputation of his craft to stand among the wealthy elite of his city .
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the scene this young artist set out to paint was well-known : the three wise men , or magi , arriving at the birth place of jesus christ . botticelli would aspire to take this common theme and produce an entirely original work , while asserting himself among the most important citizens of florence . many earlier paintings illustrate the magi arriving at a stable , stately manger , fitting for the son of god .
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how does botticelli take a well-known subject and create something original ?
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we are going to try and do an experiment today . it is called the ‘ gallium beating heart ’ . so it is quite a cool experiment , you take some molten gallium and then you submerge it or you put it underneath a layer of sulphuric acid . the sulphuric acid reacts with the gallium to form gallium sulphate and it changes the surface tension , so it all pulls up into a ball and then relaxes and there is this really neat oscillating reaction where you get sulphate on the surface or no sulphate on the surface . so you see big changes in surface tension and the piece of gallium is seen to beat like a heart so we thought we would try that today with a bit of gallium which i am trying to melt in my hand right now . many years ago , a professor bet me a hundred pounds , when a hundred pounds was a lot of money , that the melting point of gallium was lower than that of caesium and i said it was the other way round , but i was not courageous enough to take up the bet or now i would be rich . so this is a small nugget of gallium and as you can see if i tap it on the hot plate it is real metal so now we are going to try and melt it , hopefully in my hand . in my first video about gallium , i said that it was not a very interesting element with not much , many applications and we have had emails from people who were outraged . there is one email from a gentleman in america whose company makes tonnes of gallium salts that have quite important applications and of course gallium is particularly important in new generation of compounds , so-called semi-conductors , that are used in the electronics industry . so if i stand and hold it for long enough , in theory , the temperature should come from my hand , the heat should come from my hand , so it should melt the gallium and then eventually we should have a small amount of liquid . so gallium , you can form an amalgam with this material , with all sorts of different materials like indium and tin . and in fact indium , tin and gallium is used as the material inside many , many thermometers which are used in the medical industry because it is not as toxic as mercury which was traditionally used . you may have heard of mendeleev . he was the guy that sort of conceived or brought together the periodic table and at the time that he did this at about 1870 , gallium hadn ’ t been discovered , so he predicted its chemical and physical properties and he called it eka-aluminium , approximately 5 years after that it was found using a spectroscope . so now we see it is melted , it looks just like a little ball of mercury rolling around on my hand . you can see the thick skin that has developed the surface tension causing it to form such a beautiful bulb . we are going to take out our molten gallium and we are going to put it under a layer of dilute sulphuric acid , about the same strength as battery acid , so now we are going to make the acid . and to do that we are going to dilute concentrated sulphuric acid with water . now it is always important to remember that when you dilute acid you always put acid into water because the reaction can be exothermic and we want to dissipate the heat in the water so that it does not squirt up on our faces . the water was room temperature , but if i hold the measuring cylinder here it is actually very hot , it is maybe 40 , 50 , 60oc . so now before we do our experiment we have got to allow it to cool . we do that by simply running cold water outside the tube . so this is the gallium that we melted on our hand , now let ’ s see what happens when we add the sulphuric acid . wow , did you see that ? i did . what happened ? so the shape of the ball or the lump of gallium has changed , because we ’ ve changed it surface properties , we ’ ve made gallium sulphate on the surface . the surface tension has got higher and it has pulled up into a nice ball , ok . so that ’ s the first step of the beating heart . what we ’ ve seen is the gallium which was relaxed flat on the surface has pulled up really quite sharply and that is the first stage , or the in- beat of the heart , now we ’ ve got to make the heart relax . so what we are going to do is use dichromate . dichromate is a fantastic oxidant and we are going to put a small amount of it in and see what happens . so gallium , i realise now is named after france . it was discovered by a frenchman and its name comes from the old name for france , gaul . so what we are doing in this experiment , we are changing the surface tension of the gallium , so these are the forces that hold the liquid into a ball or allow it to wet and flatten on the surface . so when the gallium is naked , ok ? it ’ s actually quite flat and it wets the surface . but when we put it under sulphuric acid we form gallium sulphate on the surface , this increases the surface tension and then pulls the gallium so it is in a nice proud ball . what we then do is we dribble a small amount of dichromate solution in , which removes the sulphate from the surface and allows the gallium to go flat , and if we add the required amount of dichromate to the amount of acid then we can get the ball to flatten and come back up , flatten and come back up , so it looks like a beating heart . at the moment we are really quite excited at nottingham because steve liddle , my periodic videos colleague , has made a new compound in which he has got an atom of uranium to bond to an atom of gallium and this is exciting because this is the first time that chemists have ever seen a bond between these two atoms . it sort of turns a terracottery colour , it is really a deep orangey brown , it is a bit like brick dust actually . of course they are not naked uranium and naked gallium but each of them have other things bonded to them but it is the first time that anybody has seen a gallium-uranium bond . it was one of those great moments you know , being a chemist is like being on a rollercoaster , you have some days when you wonder why am i doing this ? and you have fantastic days where you totally remember why you are doing this . because it is to be the first , to be the first person who has ever made this particular , you know filling the gap , whatever it is . it is a real thrill when you are the first person to make a compound that does not exist out in the galaxy and space , it has never existed on our planet before but now we have made it for the first time . that ’ s a really good thing to do we are really very excited ! a new union has been formed within the periodic table and it has been done here at nottingham .
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so if i stand and hold it for long enough , in theory , the temperature should come from my hand , the heat should come from my hand , so it should melt the gallium and then eventually we should have a small amount of liquid . so gallium , you can form an amalgam with this material , with all sorts of different materials like indium and tin . and in fact indium , tin and gallium is used as the material inside many , many thermometers which are used in the medical industry because it is not as toxic as mercury which was traditionally used . you may have heard of mendeleev .
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galinstan is an alloy of gallium , indium and tin . why is it used instead of mercury to make clinical thermometers ?
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jean-paul sartre made thinking and philosophy glamorous . he was born in paris in 1905 . his father , a navy captain , died when he was a baby – and he grew up extremely close to his mother until she remarried , much to his regret , when he was twelve . sartre spent most of his life in paris , where he often went to cafes on the left bank . he had a strabismus , a wandering eye , and wore distinctive , heavy glasses . he was very short ( five feet three inches ) and frequently described himself as ugly . by the 60 ’ s sartre was a household name in both europe and the united states , and so was his chosen philosophy , existentialism . sartre is famous principally for his book being and nothingness ( 1943 ) , which enhanced his reputation not so much because people could understand his ideas but because they could n't quite . existentialism was built around a number of key insights : one : things are weirder than we think sartre is acutely attentive to moments when the world reveals itself as far stranger and more uncanny than we normally admit ; moments when the logic we ascribe to it day-to-day becomes unavailable , showing things to be highly contingent and even absurd and frightening . sartre ’ s first novel – nausea , published in 1938 – is full of evocations of such moments . at one point , the hero , roquentin , a 30-year-old writer living in a fictional french seaside town , is on a tram . he puts his hand on the seat , but then pulls it back rapidly . instead of being the most basic and obvious piece of design , scarcely worth a moment ’ s notice , the seat promptly strikes him as deeply strange ; the word ‘ seat ’ comes loose from its moorings , the object it refers to shines forth in all its primordial oddity , as if he ’ s never seen one before . roquentin has to force himself to remember that this thing beside him is something for people to sit on . for a terrifying moment , roquentin has peered into what sartre calls the ‘ absurdity of the world. ’ such a moment goes to the heart of sartre ’ s philosophy . to be sartrean is to be aware of existence as it is when it has been stripped of any of the prejudices and stabilising assumptions lent to us by our day-to-day routines . we can try out a sartrean perspective on many aspects of our own lives . think of what you know as ‘ the evening meal with your partner ’ . under such a description , it all seems fairly logical , but a sartrean would strip away the surface normality to show the radical strangeness lurking beneath . dinner really means that : when your part of the planet has spun away from the energy of a distant hydrogen and helium explosion , you slide your knees under strips of a chopped-up tree and put sections of dead animals and plants in your mouth and chew , while next to you , another mammal whose genitals you sometimes touch is doing the same . two : we are free such weird moments are certainly disorienting and rather scary , but sartre wants to draw our attention to them for one central reason : because of their liberating dimensions . life is a lot odder than we think , but it ’ s also as a consequence far richer in possibilities . things don ’ t have to be quite the way they are . in the course of fully realising our freedom , we will come up against what sartre calls the ‘ angoisse ’ or ‘ anguish ’ of existence . everything is ( terrifyingly ) possible because nothing has any pre-ordained , god-given sense or purpose . humans are just making it up as they go along , and are free to cast aside the shackles at any moment . three : we shouldn ’ t live in ‘ bad faith ’ sartre gave a term to the phenomenon of living without taking freedom properly on board . he called it bad faith . we are in bad faith whenever we tell ourselves that things have to be a certain way and shut our eyes to other options . it is bad faith to insist that we have to do a particular kind of work or live with a specific person or make our home in a given place . the most famous description of ‘ bad faith ’ comes in being and nothingness , when sartre notices a waiter who strikes him as overly devoted to his role , as if he were first and foremost a waiter rather than a free human being . his movement is quick and forward , a little too precise , a little too rapid . he comes towards the patrons with a step that is a little too quick . he bends forward a little too eagerly : his voice , his eyes express an interest a little too solicitous for the order of the customer… ’ the man ( he was probably modelled on someone in saint-germain ’ s café de flore ) has convinced himself that he is essentially , necessarily a waiter rather than a free creature who could be a jazz pianist or a fisherman on a north sea trawler . four : we 're free to dismantle capitalism . the one factor that most discourages people from experiencing themselves as free is money . most of us will shut down a range of possible options ( moving abroad , trying out a new career , leaving a partner ) by saying , ‘ that ’ s if i didn ’ t have to worry about money . ' this passivity in the face of money enraged sartre at a political level . he thought of capitalism as a giant machine designed to create a sense of necessity which doesn ’ t in fact exist in reality : it makes us tell ourselves we have to work a certain number of hours , buy a particular product or service , and so on . but in this , there is only the denial of freedom – and a refusal to take as seriously as we should the possibility of living in other ways . it was because of these views that sartre had a life long interest in marxism . marxism seemed in theory to allow people to explore their freedom , by reducing the role played in their lives by material considerations . sartre took part in many protests in the streets of paris in the 60s . arrested yet again in 1968 , president charles de gaulle had him pardoned , saying , “ you don ’ t arrest voltaire. ” sartre also visited fidel castro and che guevara and admired them both deeply . as a result of these connections and his radical politics , the fbi kept a large file on sartre trying to deduce what his suspicious philosophy might really mean . sartre is inspiring in his insistence that things do not have to be the way they are . he is hugely alive to our unfulfilled potential , as individuals and as a species . he urges us to accept the fluidity of existence and to create new institutions , habits , outlooks and ideas . the admission that life doesn ’ t have some preordained logic and is not inherently meaningful can be a source of immense relief when we feel oppressed by the weight of tradition and the status quo .
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life is a lot odder than we think , but it ’ s also as a consequence far richer in possibilities . things don ’ t have to be quite the way they are . in the course of fully realising our freedom , we will come up against what sartre calls the ‘ angoisse ’ or ‘ anguish ’ of existence .
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how might you look at something in your immediate environment in a sartrean way ?
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we read fiction for many reasons . to be entertained , to find out who done it , to travel to strange , new planets , to be scared , to laugh , to cry , to think , to feel , to be so absorbed that for a while we forget where we are . so , how about writing fiction ? how do you suck your readers into your stories ? with an exciting plot ? maybe . fascinating characters ? probably . beautiful language ? perhaps . `` billie 's legs are noodles . the ends of her hair are poison needles . her tongue is a bristly sponge , and her eyes are bags of bleach . '' did that description almost make you feel as queasy as billie ? we grasp that billie 's legs are n't actually noodles . to billie , they feel as limp as cooked noodles . it 's an implied comparison , a metaphor . so , why not simply write it like this ? `` billie feels nauseated and weak . '' chances are the second description was n't as vivid to you as the first . the point of fiction is to cast a spell , a momentary illusion that you are living in the world of the story . fiction engages the senses , helps us create vivid mental simulacra of the experiences the characters are having . stage and screen engage some of our senses directly . we see and hear the interactions of the characters and the setting . but with prose fiction , all you have is static symbols on a contrasting background . if you describe the story in matter of fact , non-tactile language , the spell risks being a weak one . your reader may not get much beyond interpreting the squiggles . she will understand what billie feels like , but she wo n't feel what billie feels . she 'll be reading , not immersed in the world of the story , discovering the truths of billie 's life at the same time that billie herself does . fiction plays with our senses : taste , smell , touch , hearing , sight , and the sense of motion . it also plays with our ability to abstract and make complex associations . look at the following sentence . `` the world was ghost-quiet , except for the crack of sails and the burbling of water against hull . '' the words , `` quiet , '' `` crack , '' and `` burbling , '' engage the sense of hearing . notice that buckell does n't use the generic word sound . each word he chooses evokes a particular quality of sound . then , like an artist laying on washes of color to give the sense of texture to a painting , he adds anoter layer , motion , `` the crack of sails , '' and touch , `` the burbling of water against hull . '' finally , he gives us an abstract connection by linking the word quiet with the word ghost . not `` quiet as a ghost , '' which would put a distancing layer of simile between the reader and the experience . instead , buckell creates the metaphor `` ghost-quiet '' for an implied , rather than overt , comparison . writers are always told to avoid cliches because there 's very little engagement for the reader in an overused image , such as `` red as a rose . '' but give them , `` love ... began on a beach . it began that day when jacob saw anette in her stewed-cherry dress , '' and their brains engage in the absorbing task of figuring out what a stewed-cherry dress is like . suddenly , they 're on a beach about to fall in love . they 're experiencing the story at both a visceral and a conceptual level , meeting the writer halfway in the imaginative play of creating a dynamic world of the senses . so when you write , use well-chosen words to engage sound , sight , taste , touch , smell , and movement . then create unexpected connotations among your story elements , and set your readers ' brushfire imaginations alight .
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fiction plays with our senses : taste , smell , touch , hearing , sight , and the sense of motion . it also plays with our ability to abstract and make complex associations . look at the following sentence . `` the world was ghost-quiet , except for the crack of sails and the burbling of water against hull . ''
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which of the following represents an abstract connection ?
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have you ever noticed how the full moon looks bigger when it 's near the horizon than when it 's high over head ? if so , you 're not alone . people have wondered about this strange effect since ancient times , and surprisingly , we still do n't have a great explanation , but that 's not for lack of trying . some of the greatest minds in history - aristotle , ptolemy , da vinci , decartes - have all wrestled with this problem and failed to generate an adequate explanation . one of the first ideas suggested was that the image of the moon in the sky really is bigger near the horizon . perhaps the earth 's atmosphere acts like a giant lens , magnifying the moon as it rises and sets . but this explanation does n't cut it . if anything , the refraction of the atmosphere would make the moon look slightly smaller . plus , if you actually measure the size of the visible moon at different positions , it does n't change at all . but then , why does it still seem bigger when it 's rising ? this must be some kind of optical illusion . the question is , which one ? one explanation is the ebbinghaus illusion , where two identical objects look different because of the relative size of the objects they 're surrounded by . here the two center circles are actually the same size . maybe the moon looks bigger near the horizon because it 's next to tiny trees , houses , and towers in the distance . but when the moon is higher up , it 's surrounded by the vast darkness of the night sky and looks tiny by comparison . another possibility is the famous ponzo illusion . if you 've ever tried to draw in perspective , you know that the closer something is to the horizon , the smaller you should draw it . our brain compensates automatically for this by perceiving objects near the horizon as larger than they actually appear . the two yellow lines in this drawing are the same size , but the upper one seems bigger because we interpret it as receding farther into the horizon . so , between ponzo and ebbinghaus , it seems like we 've solved the mystery of the moon illusion , but , unfortunately , there are a few details that complicate things . for one thing , if this was just the ebbinghaus effect , then we would expect the moon illusion to disappear for pilots flying high above the clouds since there would n't be any other smaller objects near the horizon . but in fact , pilots and sailors out on the ocean still claim to see the moon illusion . on the other hand , if it 's just our brain 's autocorrecting the size of objects near the horizon , then we 'd expect the moon illusion to be visible inside a planetarium , where the whole sky , including the horizon , is displayed on a spherical dome overhead . studies have shown , though , that this is not the case . to make matters worse , it seems the moon illusion disappears entirely if you just bend over and look at the moon between your legs . now , this is just getting ridiculous ! one of the most promising explanations today is known as convergence micropsia . our brains judge the distance to objects and their apparent size by the focus of our eyes . when looking at the horizon , your eyes focus far off into the distance so your brain knows you 're looking far away . the moon appears a certain size . your brain thinks it 's far away , which it is , so you naturally conclude the moon must be big . but when looking up at the night sky , there 's nothing for your eyes to focus on , so they default to their rest focus , which is a point just a few meters away . now your brain thinks the moon is much closer than it really is , so you naturally conclude the moon 's not as big as you thought it was . rather than explain why the moon looks so big near the horizon , convergence microspia explains why the moon looks so small when overhead . still not satisfied ? well , frankly , neither are many scientists , so the debate over the moon illusion still rages on and may continue as long as we still see it in the night sky .
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but when the moon is higher up , it 's surrounded by the vast darkness of the night sky and looks tiny by comparison . another possibility is the famous ponzo illusion . if you 've ever tried to draw in perspective , you know that the closer something is to the horizon , the smaller you should draw it .
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which sentence best describes the ebbinghaus illusion ?
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what do charles darwin , michael jordan , and yoda have in common ? they , like many other historical and fictive individuals , are bald , in some cases by their own choice . for centuries , a shining dome has been a symbol of intelligence , but despite this , many balding people still wish their hair would return . scientists have long pondered , `` why do some people lose their hair , and how can we bring it back ? '' the full-headed among us have about 100,000 to 150,000 hairs on our scalps , and scientists have discovered two things about this dense thicket . firstly , the sprouting hair we see is mostly made up of keratin , the protein leftover from dead cells that are forced upwards as new cells grow beneath them . secondly , the structures that drive hair growth are called hair follicles , a network of complex organs that forms before we 're born , and grows hair in an everlasting cycle . this cycle has three main phases . the first is anagen , the growth phase , which up to 90 % of your hair follicles are experiencing right now , causing them to push up hair at a rate of one centimeter per month . anagen can last for two to seven years , depending on your genes . after this productive period , signals within the skin instruct some follicles to enter a new phase known as catagen , or the regressing stage , causing hair follicles to shrink to a fraction of their original length . catagen lasts for about two to three weeks and cuts blood supply to the follicle , creating a club hair , meaning it 's ready to be shed . finally , hairs enter telogen , the resting phase , which lasts for ten to twelve weeks , and affects about 5-15 % of your scalp follicles . during telogen , up to 200 club hairs can be shed in a day , which is quite normal . then , the growth cycle begins anew . but not all heads are hairy , and , in fact , some of them grow increasingly patchy over time in response to bodily changes . 95 % of baldness in men can be attributed to male pattern baldness . baldness is inherited , and in people with this condition , follicles become incredibly sensitive to the effects of dihydrotestosterone , a hormonal product made from testosterone . dht causes shrinkage in these overly sensitive follicles , making hair shorter and wispier . but loss is n't sudden . it happens gradually , along a metric known as the norwood scale , which describes the severity of hair loss . first , hair recedes along the temples , then hair on the crown begins to thin in a circular pattern . at the highest rating on the scale , these balding areas meet and expand dramatically , eventually leaving only a ring of sparse hair around the temples and the back of the head . genetics is n't all that drives hair loss . long periods of stress can release signals that shock follicles and force them into the resting phase prematurely . some women experience this after childbirth . follicles might also lose the ability to go into anagen , the growth phase . people going through chemotherapy treatment temporarily experience this . but while balding may look permanent , scientific investigation has revealed the opposite . below the skin 's surface , the roots that give rise to our hair actually remain alive . using this knowledge , scientists have developed drugs that shorten the resting phase , and force follicles into anagen . other drugs combat male pattern baldness by blocking the conversion of testosterone to dht so that it does n't affect those sensitive follicles . stem cells also play a role in regulating the growth cycle , and so scientists are investigating whether they can manipulate the activity of these cells to encourage follicles to start producing hair again . and in the meantime , while scientists hone their hair-reviving methods , anyone going bald , or considering baldness , can remember that they 're in great company .
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follicles might also lose the ability to go into anagen , the growth phase . people going through chemotherapy treatment temporarily experience this . but while balding may look permanent , scientific investigation has revealed the opposite .
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which describes the correct order of receding hairline in people going bald ?
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translator : andrea mcdonough reviewer : bedirhan cinar you know what the greatest secret of history is ? it 's that history can be changed . and , yeah , yeah , i know , everyone says history ca n't be changed , but it can . and today we 're going to talk about how history is n't just something that goes backwards , history goes forward too . and all those great things that have n't happened yet , that 's history that 's just waiting to be written . so how do you change history ? i 'm going to tell you by sharing with you the three things that i tell my kids every night when i tuck them into bed . it 's true . i stole the idea from a friend of mine who told me what his father used to share with him . every single night , when i tuck my kids into bed , i tell them these three things : dream big , work hard , and stay humble . so let 's look at them all . first , dream big . you know who has the biggest , best dreams of all ? you , young people . you know how old martin luther king , jr. was when he became the leader of the most famous bus boycott in history ? he was 26 . you know how old amelia earhart was when she broke her first world record ? 25 you know how old steve jobs was when he co-founded apple computer ? 21 and you know how old jerry siegel and joe shuster were when they came up with their idea for the greatest superhero of all time , the first one , that they named `` superman '' ? these guys were 17 years old ! two 17-year-old kids created superman . they were n't good looking . ( look at the picture , right ? ) they were n't popular . they had no money , but they were two best friends with one dream . and with just their imaginations , they gave the world superman . and i know , creating superman is a once-in-a-lifetime big dream , so i want to tell you about alexandra scott . she goes by alex . alex was diagnosed with cancer before she was even a year old , and that was the only life she knew : sickness , chemotherapy , and surgery . when she was four , alex asked her parents could she put a lemonade stand in the front yard ? she did n't want to buy anything for herself , she wanted to use the money to give it to doctors to help other kids with cancer . ok , in a single day , alex 's lemonade stand raised $ 2,000 ! but , here 's what i love : soon after that , other lemonade stands started popping up , all with alex 's name on it . eventually , they raised $ 200,000 . and then alex had a new goal . she said let 's raise $ 1,000,000 . on june 12 , 2004 , hundreds of lemonade stands started opening up in every state in the country . ordinary people selling water and sugar and lemons to help kids with cancer . nearly two months later , alex died while her parents were holding her hands . she was 8 years old . but before she died , alex said that next year 's goal should be $ 5,000,000 . today , her dream has raised over $ 45,000,000 and it is still going strong ! one idea , one girl , one big dream . and you know what she said ? this is a direct quote before she died . she said , `` oh , we can do it ! if other people will help me , i think we can do it . i know we can do it ! '' you dream big , i do n't care how old you are , and do n't let anyone tell you otherwise , you will change history . and that leads me to the second thing i tell my kids : work hard . such a simple one , everyone knows this one . work hard . i saw this one for my father and my father died a few months ago . when i was growing up in brooklyn , ok , my father , he worked hard . he had no money , we had , no money growing up . he worked every saturday , every sunday . i watched first-hand every weekend what hard work was . and i saw that the hardest work of all is being resilient when you 're facing failure . when i started writing my first book , my first book got me 24 rejection letters . to be clear , there are only 20 publishers , i got 24 rejection letters , ok ? that means that some people were writing me twice to make sure i got the point . but it was n't until i was writing my ninth book , a book of heroes for my son , that i found my favorite story of working hard through failure . it was a story that a friend told me about the wright brothers . that every time the wright brothers went out to fly their plane , they would bring enough extra materials for multiple crashes . that means for every time they went out , they knew they would fail . and they would crash and rebuild , and crash and rebuild , and that 's why they took off . i love that story . i wanted my son to hear that story , i wanted my daughter to hear that story , i wanted everyone to know that if you dream big and you work hard and you fight failure , you will change history and do what no one on this planet has ever done before . and that leads me to the final thing i tell them : stay humble . here 's the thing : if you invent the world 's first airplane , or superman , or a multi-million dollar lemonade stand , you do n't need to be humble . you can get a tattoo on your face that says , `` i 'm the best ! '' right ? but pay attention here : no one likes a jerk . in fact , the world needs fewer loudmouths , so stay humble ! when thomas jefferson wrote the declaration of independence , you know he never took credit for writing it while he was alive ? it was n't until he died and it was in his obituary that the average american found out that he was the author . that 's humble . so there 's the big secret : dream big , work hard , stay humble . `` wait , '' you 're saying , `` that 's it ? '' `` what , you tell me a bunch of stories and what ? how do i change history ? '' here 's the answer : all history ever is is a bunch of stories , conflicting stories , big stories , little stories , our stories . so how do you change history ? all you got to do is write your story . ok ? no , i 'm serious , this is it . if people think history is a bunch of facts and dates you got to memorize , that 's not what history is at all . history is a selection process , and it chooses every single one of us every single day . the only question is , do you hear the call ? and that leads me to the most important thing i 'm going to tell you here : you will change history . some of you will change it in big ways , affecting millions of people . others of you will do it in more personal ways , helping a family member or someone who needs it . but let me tell you right now , one is not more important than the other . if you help people in mass or one-by-one , that 's how history gets changed , when you take action . but when you start writing your story and you get scared , as we all inevitably do , i want you to know one thing : no one is born a hero . every single person that we talked about today , whether they were a 26 year old preacher , or two 17 year old nerds , or little girl who had cancer , every single one of them had moments where they doubted themselves , like you , like me . they had moments where they worried about school and friendships and would they be accepted by others , like you , like me . they had moments where they worried about loneliness and failure and would they ever succeed , like you , like me . but the best part is , you do n't have to start a multi-million dollar lemonade stand to change the world , all you got to do is help one person , be kind to one person , that 's the answer . it 's my core belief , it is in every story i just told you . i believe ordinary people change the world . i do n't care how much money you have , i do n't care where you go to school , that is all nonsense to me . i believe in regular people and their ability to affect change in this world . i believe in my father , and a 25 year old daredevil named amelia , and a little girl who sells lemonade like nobody 's business . and it 's why i believe in that very first hero we were talking about today , superman . to me , the most important part of the story is n't superman . the most important part of the story is clark kent . and you want to know why ? because we 're all clark kent . we all know what it 's like to be boring and ordinary and wish we could do something incredibly beyond ourselves . but here 's the real news : we all can do something incredibly beyond ourselves . i got 24 rejection letters on my first book , 24 people who told me to give it up , and i do n't look back on the experience and say , `` i was right , and they were wrong , and haha on them . '' what i look back and realize is that every single one of those rejection letters told me to work harder , to dream bigger , and you better believe it , made me more humble , but it also made me want it more than anything . so whatever it is you dream big about , whatever it is you work hard for , do n't let anyone tell you , you 're too young and do n't let anyone tell you no . every life makes history . and every life is a story . thank you .
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and i saw that the hardest work of all is being resilient when you 're facing failure . when i started writing my first book , my first book got me 24 rejection letters . to be clear , there are only 20 publishers , i got 24 rejection letters , ok ?
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how many rejection letters did meltzer receive when he wrote his first book ?
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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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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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which of the following processes generates a new curve of constant width ?
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the thermite reaction which is the reaction of aluminium and iron oxide is used to make iron and because aluminium has much stronger bonds to oxygen than iron that the reaction produces an enormous amount of heat and you can use this for welding pieces of metals together . so this is a thermite mixture , it is a mixture of iron oxide and aluminium powder and we are going to do some redox chemistry and we are going to generate some molten iron which will hopefully stream from the bottom of the flower pot . so here you can see the black particles of the iron oxide and the silver particles are the aluminium powder . so we get some heat on this and we start an instantaneous redox reaction so the aluminium and the iron oxide swap oxygens so the aluminium will become oxidised and the iron will become reduced hopefully we will generate a lot of molten iron which should come from the bottom of the test tube … of the flower pot . alright ! right . now there is a story about students in berkley that some students , or group of students , decided to do a practical joke on a tram of the sort that has one door where you go in and another when you go out . so a big group of students queued onto the tram and got into the front and there were enough of them so they could actually come out at the end at the other door and form a loop so they were just going round and round and round so the tram could not leave because they were just more and more people getting on . we ’ re going to run out of tape . and while they were doing this , other students went down under the tram and set off two thermite reactions and welded the metal wheels of the tram to the steel rails so that when the tram tried to leave , when the students eventually stopped going round and round , it was firmly welded to the tracks and could not move at all . it ’ s gone out . tell us about what is going on mate ! so instantly the thermite reaction starts and you can see that it ’ s so hot that it burnt a whole through the bottom of that terracotta flower pot . but if we go in close now brady , you can see all that really quite nice molten iron . now that is so hot that the iron itself has melted and it has formed this really quite big goo in the bottom on the sand . do you encourage these sorts of practical jokes ? no , no , no , no , no , our students are far more responsible . so as soon as the fire work , or the sparkler , hit the top of the thermite reaction , in the top of here , it started obviously , instantaneous redox reaction . so this is where the metals were fighting for the oxygen , the aluminium won that battle and the aluminium came out of this reaction as aluminium oxide . the iron was reduced and we can see that now in the bottom which is really hot so i am not going to get too close but you can see all of this really , really hot iron . the iron was molten , it dribbled out through the bottom of the flower pot and it is now cooling . it didn ’ t dribble out of the bottom of the flower pot . well it smashed its way out of the flower pot . well you can say that iron is in my blood , it is in your blood as well . it is iron that gives haemoglobin the red pigment in your blood , its red colour . so the reaction we saw was about 5 minutes ago and the iron that was generated is still glowing red hot and you can see it has fused itself to the bottom half of the flower pot , which it broke in its tumultuous step forward . it is an absolutely essential element to life , except for crabs which use copper but you will have to hear about that later . so iron is a really , really abundant metal which is used in lots and lots of structural material , so you get to see lots of pieces of iron around , some of the racking and even in fact some of these pieces of equipment have got high iron content . they have got other elements in them to form alloys like stainless steel . i have an extremely long standing interest in its chemistry and in particular , i made one compound of iron so called iron tetracarbonyl which had 4 groups round it and everybody had expected that it would have a shape like one of these . shaped with tetrahedron like that whereas , in fact , it had a much more irregular shape , the 4 groups were arranged like this , and so every since this , every time i hear the word iron i get quite excited . so this is iron wire , ok , and as you can it is a very small wire . it is 0.2 in diameter and you can see the shiny material underneath is iron that has not undergone oxidation so this is where it has been protected from the oxygen in the air now if we look at the iron at the top we can see that this looks really familiar especially because it looks like some of the rust which we can see at the bottom of some of our cars . so here is some iron oxide on top of the iron . the very first chemical experiment i did the chemical reaction was with iron and i think the same is true for many generations of school children . i heated up iron and sulphur together and made iron sulphide sort of blackish solid but then we put acid on it and got a terrible smell of bad eggs and this was my introduction to chemistry and i really loved it .
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it is 0.2 in diameter and you can see the shiny material underneath is iron that has not undergone oxidation so this is where it has been protected from the oxygen in the air now if we look at the iron at the top we can see that this looks really familiar especially because it looks like some of the rust which we can see at the bottom of some of our cars . so here is some iron oxide on top of the iron . the very first chemical experiment i did the chemical reaction was with iron and i think the same is true for many generations of school children .
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why do you think archaeologists find ancient gold or silver objects more easily than iron ones ?
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what makes a good horror story ? sure , you could throw in some hideous monsters , fountains of blood , and things jumping out from every corner , but as classic horror author h.p . lovecraft wrote , `` the oldest and strongest kind of fear is fear of the unknown . '' and writers harness that fear not by revealing horrors , but by leaving the audience hanging in anticipation of them . that is , in a state of suspense . the most familiar examples of suspense come from horror films and mystery novels . what 's inside the haunted mansion ? which of the dinner guests is the murderer ? but suspense exists beyond these genres . will the hero save the day ? will the couple get together in the end ? and what is the dark secret that causes the main character so much pain ? the key to suspense is that it sets up a question , or several , that the audience hopes to get an answer to and delays that answer while maintaining their interest and keeping them guessing . so what are some techniques you can use to achieve this in your own writing ? limit the point of view . instead of an omniscient narrator who can see and relay everything that happens , tell the story from the perspective of the characters . they may start off knowing just as little as the audience does , and as they learn more , so do we . classic novels , like `` dracula , '' for example , are told through letters and diary entries where characters relate what they 've experienced and fear what 's to come . next , choose the right setting and imagery . old mansions or castles with winding halls and secret passageways suggest that disturbing things are being concealed . nighttime , fog , and storms all play similar roles in limiting visibility and restricting characters ' movements . that 's why victorian london is such a popular setting . and even ordinary places and objects can be made sinister as in the gothic novel `` rebecca '' where the flowers at the protagonist 's new home are described as blood red . three : play with style and form . you can build suspense by carefully paying attention not just to what happens but how it 's conveyed and paced . edgar allan poe conveys the mental state of the narrator in `` the tell-tale heart '' with fragmented sentences that break off suddenly . and other short declarative sentences in the story create a mix of breathless speed and weighty pauses . on the screen , alfred hitchcock 's cinematography is known for its use of extended silences and shots of staircases to create a feeling of discomfort . four : use dramatic irony . you ca n't just keep the audience in the dark forever . sometimes , suspense is best served by revealing key parts of the big secret to the audience but not to the characters . this is a technique known as dramatic irony , where the mystery becomes not what will happen but when and how the characters will learn . in the classic play `` oedipus rex , '' the title character is unaware that he has killed his own father and married his mother . but the audience knows , and watching oedipus gradually learn the truth provides the story with its agonizing climax . and finally , the cliffhanger . beware of overusing this one . some consider it a cheap and easy trick , but it 's hard to deny its effectiveness . this is where a chapter , episode , volume , or season cuts off right before something crucial is revealed , or in the midst of a dangerous situation with a slim chance of hope . the wait , whether moments or years , makes us imagine possibilities about what could happen next , building extra suspense . the awful thing is almost always averted , creating a sense of closure and emotional release . but that does n't stop us from worrying and wondering the next time the protagonists face near-certain disaster .
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and writers harness that fear not by revealing horrors , but by leaving the audience hanging in anticipation of them . that is , in a state of suspense . the most familiar examples of suspense come from horror films and mystery novels . what 's inside the haunted mansion ?
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what techniques does the lesson suggest for creating suspense in fiction ? make a list , and add examples from suspenseful books that you have read . are there any other techniques you would add ?
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¿hablas español ? parlez-vous français ? 你会说中文吗？ if you answered , `` sí , '' `` oui , '' or `` 会 '' and you 're watching this in english , chances are you belong to the world 's bilingual and multilingual majority . and besides having an easier time traveling or watching movies without subtitles , knowing two or more languages means that your brain may actually look and work differently than those of your monolingual friends . so what does it really mean to know a language ? language ability is typically measured in two active parts , speaking and writing , and two passive parts , listening and reading . while a balanced bilingual has near equal abilities across the board in two languages , most bilinguals around the world know and use their languages in varying proportions . and depending on their situation and how they acquired each language , they can be classified into three general types . for example , let 's take gabriella , whose family immigrates to the us from peru when she 's two-years old . as a compound bilingual , gabriella develops two linguistic codes simultaneously , with a single set of concepts , learning both english and spanish as she begins to process the world around her . her teenage brother , on the other hand , might be a coordinate bilingual , working with two sets of concepts , learning english in school , while continuing to speak spanish at home and with friends . finally , gabriella 's parents are likely to be subordinate bilinguals who learn a secondary language by filtering it through their primary language . because all types of bilingual people can become fully proficient in a language regardless of accent or pronunciation , the difference may not be apparent to a casual observer . but recent advances in brain imaging technology have given neurolinguists a glimpse into how specific aspects of language learning affect the bilingual brain . it 's well known that the brain 's left hemisphere is more dominant and analytical in logical processes , while the right hemisphere is more active in emotional and social ones , though this is a matter of degree , not an absolute split . the fact that language involves both types of functions while lateralization develops gradually with age , has lead to the critical period hypothesis . according to this theory , children learn languages more easily because the plasticity of their developing brains lets them use both hemispheres in language acquisition , while in most adults , language is lateralized to one hemisphere , usually the left . if this is true , learning a language in childhood may give you a more holistic grasp of its social and emotional contexts . conversely , recent research showed that people who learned a second language in adulthood exhibit less emotional bias and a more rational approach when confronting problems in the second language than in their native one . but regardless of when you acquire additional languages , being multilingual gives your brain some remarkable advantages . some of these are even visible , such as higher density of the grey matter that contains most of your brain 's neurons and synapses , and more activity in certain regions when engaging a second language . the heightened workout a bilingual brain receives throughout its life can also help delay the onset of diseases , like alzheimer 's and dementia by as much as five years . the idea of major cognitive benefits to bilingualism may seem intuitive now , but it would have surprised earlier experts . before the 1960s , bilingualism was considered a handicap that slowed a child 's development by forcing them to spend too much energy distinguishing between languages , a view based largely on flawed studies . and while a more recent study did show that reaction times and errors increase for some bilingual students in cross-language tests , it also showed that the effort and attention needed to switch between languages triggered more activity in , and potentially strengthened , the dorsolateral prefrontal cortex . this is the part of the brain that plays a large role in executive function , problem solving , switching between tasks , and focusing while filtering out irrelevant information . so , while bilingualism may not necessarily make you smarter , it does make your brain more healthy , complex and actively engaged , and even if you did n't have the good fortune of learning a second language as a child , it 's never too late to do yourself a favor and make the linguistic leap from , `` hello , '' to , `` hola , '' `` bonjour '' or `` 你好 ’ s '' because when it comes to our brains a little exercise can go a long way .
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finally , gabriella 's parents are likely to be subordinate bilinguals who learn a secondary language by filtering it through their primary language . because all types of bilingual people can become fully proficient in a language regardless of accent or pronunciation , the difference may not be apparent to a casual observer . but recent advances in brain imaging technology have given neurolinguists a glimpse into how specific aspects of language learning affect the bilingual brain . it 's well known that the brain 's left hemisphere is more dominant and analytical in logical processes , while the right hemisphere is more active in emotional and social ones , though this is a matter of degree , not an absolute split .
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describe the three types of bilingual - compound bilingual , coordinate bilingual and subordinate bilingual . what are the characteristics of each type ?
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way before the first selfie , the ancient greeks and romans had a myth about someone a little too obsessed with his own image . in one telling , narcissus was a handsome guy wandering the world in search of someone to love . after rejecting a nymph named echo , he caught a glimpse of his own reflection in a river , and fell in love with it . unable to tear himself away , narcissus drowned . a flower marked the spot of where he died , and we call that flower the narcissus . the myth captures the basic idea of narcissism , elevated and sometimes detrimental self-involvement . but it 's not just a personality type that shows up in advice columns . it 's actually a set of traits classified and studied by psychologists . the psychological definition of narcissism is an inflated , grandiose self-image . to varying degrees , narcissists think they 're better looking , smarter , and more important than other people , and that they deserve special treatment . psychologists recognize two forms of narcissism as a personality trait : grandiose and vulnerable narcissism . there 's also narcissistic personality disorder , a more extreme form , which we 'll return to shortly . grandiose narcissism is the most familiar kind , characterized by extroversion , dominance , and attention seeking . grandiose narcissists pursue attention and power , sometimes as politicians , celebrities , or cultural leaders . of course , not everyone who pursues these positions of power is narcissistic . many do it for very positive reasons , like reaching their full potential , or helping make people 's lives better . but narcissistic individuals seek power for the status and attention that goes with it . meanwhile , vulnerable narcissists can be quiet and reserved . they have a strong sense of entitlement , but are easily threatened or slighted . in either case , the dark side of narcissism shows up over the long term . narcissists tend to act selfishly , so narcissistic leaders may make risky or unethical decisions , and narcissistic partners may be dishonest or unfaithful . when their rosy view of themselves is challenged , they can become resentful and aggressive . it 's like a disease where the sufferers feel pretty good , but the people around them suffer . taken to the extreme , this behavior is classified as a psychological disorder called narcissistic personality disorder . it affects one to two percent of the population , more commonly men . it is also a diagnosis reserved for adults . young people , especially children , can be very self-centered , but this might just be a normal part of development . the fifth edition of the american psychiatric association 's diagnostic and statistical manual describes several traits associated with narcissistic personality disorder . they include a grandiose view of oneself , problems with empathy , a sense of entitlement , and a need for admiration or attention . what makes these trait a true personality disorder is that they take over people 's lives and cause significant problems . imagine that instead of caring for your spouse or children , you used them as a source of attention or admiration . or imagine that instead of seeking constructive feedback about your performance , you instead told everyone who tried to help you that they were wrong . so what causes narcissism ? twin studies show a strong genetic component , although we do n't know which genes are involved . but environment matters , too . parents who put their child on a pedestal can foster grandiose narcissism . and cold , controlling parents can contribute to vulnerable narcissism . narcissism also seems to be higher in cultures that value individuality and self-promotion . in the united states , for example , narcissism as a personality trait has been rising since the 1970s , when the communal focus of the 60s gave way to the self-esteem movement and a rise in materialism . more recently , social media has multiplied the possibilities for self-promotion , though it 's worth noting that there 's no clear evidence that social media causes narcissism . rather , it provides narcissists a means to seek social status and attention . so can narcissists improve on those negative traits ? yes ! anything that promotes honest reflection on their own behavior and caring for others , like psychotherapy or practicing compassion towards others , can be helpful . the difficulty is it can be challenging for people with narcissistic personality disorder to keep working at self-betterment . for a narcissist , self-reflection is hard from an unflattering angle .
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to varying degrees , narcissists think they 're better looking , smarter , and more important than other people , and that they deserve special treatment . psychologists recognize two forms of narcissism as a personality trait : grandiose and vulnerable narcissism . there 's also narcissistic personality disorder , a more extreme form , which we 'll return to shortly .
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do you think grandiose narcissism is generally a good or bad trait in individuals ? why or why not ?
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translator : andrea mcdonough reviewer : bedirhan cinar nearly every one of your science classes starts off with the scientific method . you recognize this ? ask a question , form a hypothesis , perform an experiment , collect data , draw conclusions , and then memorize a bunch of facts . this is really boring ! science is not a simple recipe in a cookbook , and learning is not memorizing facts for tests . yet , that is exactly what we do . we have to change this ! we have to look at how curiosity can ultimately benefit society by looking towards tomorrow , by going through a path from involvement to imagination to invention to innovation . and i 'd like to illustrate this by telling you the real story about how we discovered how geckos stick . first you need to get involved . you need to do curiosity-driven research yourself . we know that learning by being an active researcher is the best way to learn . imagine being in my lab and trying to discover how geckos stick . `` here is one of our subjects . this is a crested gecko . we are going to put the gecko on glass and we 're going to use a high speed camera that can capture up to 1,000 pictures in one second . there he goes . ok , record it . there 's the animal 's toes . '' `` so how do their feet stick and unstick so quickly ? '' how < i > do < /i > they do this ? we wonder , it 's kind of crazy , right ? it 's hard to believe . well it turns out , it was already known that the geckos have hairy toes , and those hairs are really small compared to your hair , and the little tips at the end are even smaller . well , my student tanya , who is not much older than some of you when she did this , a sophomore undergraduate , tried to figure this out , and we told that her that in order to do this , you 'd have to measure the force of a single hair . though we kind of only did this jokingly because these hairs are so small , we did n't think it was possible . but tanya did n't know that , and she went on to build the simplest , most beautiful measurement device ever . here it is : she took one of those tiny little hairs and put it on to a probe , and then she began pushing it into the metal beam . now she was very frustrated for months - it did n't stick . but she had figured out she had to orient it just like the gecko grabs on , and then it worked ! and there 's the little split ends grabbing the beam in that little window . and then she did something magical : for the first time ever , she measured the force of a single gecko hair that allowed her to discover a completely new way to stick to something , something no human has ever known before . they have hairy little toes , huge numbers of hairs , and each hair has the worst case of split ends possible , 100 to 1,000 nano-tips that an animal has on one hair , and 2 billion total , and they do n't stick by glue , or by suction , or by velcro . it was discovered that they stick by inter-molecular forces alone , by van der waals forces , and you 'll learn this in chemistry and physics , if you take it . it 's unbelievable ! it 's a whole new way of thinking about making an adhesive ! well , this is n't the end of the story , there are still mysteries . why are the gecko 's feet looking like this ? they have bizarre toes and we do n't know why . if you go into a museum and look at each gecko species , you see they have all different hairs , different lengths , and thicknesses , and patterns . why ? i do n't know ! but you should come to berkeley and help me figure this out . it 's just about right , so , apply . but it 's a mystery . there is even more stuff that is unknown . this tarantula also has hairs and can stick this way , too , but recently it was found that they also can secrete silk from their feet , not just their behind , like you know they do . and even more recently , my graduate student ann showed that all spiders can secrete glue , and we know nothing about this glue except it was around way before this guy , millions of years before . so do n't stop at the discovery , next imagine the possible uses for society . here is the first human supported by a gecko-inspired adhesive . this is my former graduate student , kellar autumn , who is professor at lewis and clark , offering his second born child for the test . and she 's a very good sport about it ! now imagine all the things you could make from this , not only adhesives , but products in sports , and biomedicine , technology , robotics , toys , automotive , fashion , clothes , and yes , even hair pieces . i swear to you , we got a call from michael jackson 's hairdresser about hair pieces before he passed away . who would have guessed from studying geckos ? ! ? next , invent a game-changing technology , device , or product . like my engineering colleague at berkeley , ron fearing , did when he made one of the first synthetic , self-cleaning dry adhesives after the simplest version that you see in animals . believe it or not , right now , because of this work , you can make your own synthetic gecko nano-tape by nano-molding with just a few parts , and here 's the recipe that we can give you . it 's been incredible since we made this discovery of all the papers and the work and the different ways to make it , it 's emerging into a billion dollar industry . and who would have imagined that it started because we were curious about how geckos can run up walls . next you need to innovate , create a business that ultimately benefits society . did you know that there are 6 million people per year that have chronic wounds , 2 million develop an infection , and infections account for 100,000 hospital deaths ? imagine if you could build a company that could produce a gecko-inspired band-aid that would remove the pain and suffering . just a simple invention . if you look at the last three great earthquakes , over 700,000 people were trapped and lost their lives . imagine the company that made a search-and-rescue robot inspired from a gecko that could move anywhere and quickly find individuals that have been trapped , that sometimes survive as long as two weeks . there is a gecko-inspired robot , stickybot , from the stanford group , that can grab on to any surface . now we ran our own , for ted , mini bio-inspired design challenge to get you to think about these kinds of products . we have a winner . here 's the winner . the winner came up with this design called stickyseat . really clever . it 's a seat that is not only comfortable , but it aids a seat belt , if you were in an accident , in terms of keeping your seat and moving . this is brilliant ! we did n't think about this , although we might think about patenting it now , but there is a winner for this , and the winner , and you ca n't , you ca n't make up something like this , the winner 's name is harry . where 's harry ? harry , come here , we have a prize for you . where 's harry ? harry ! come here ! we have a crested gecko for you that has very cool hairs on it . congratulations for harry ! excellent job ! so do n't worry , if you missed out on this , it 's ok because we are doing another design challenge working with the san diego zoo . they 're developing a best ideas project in san diego , but it 's going to go national . and i 'll leave you with a fact that you should keep being curious because curiosity-based research leads to the biggest benefits , as we showed you in our example , and you < i > can < /i > make a difference < i > now < /i > because like tanya , you do n't know what ca n't be done . thank you .
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imagine the company that made a search-and-rescue robot inspired from a gecko that could move anywhere and quickly find individuals that have been trapped , that sometimes survive as long as two weeks . there is a gecko-inspired robot , stickybot , from the stanford group , that can grab on to any surface . now we ran our own , for ted , mini bio-inspired design challenge to get you to think about these kinds of products .
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what is the name of the gecko inspired robot built by the stanford group ?
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translator : tom carter reviewer : bedirhan cinar in society , we have to follow laws that maintain order . did you know all chemical matter follows certain laws as well ? in fact , we can describe those laws by looking at relationships . some easy laws to begin with are the ones that govern the gases . back in 1662 , robert boyle realized that gases had an interesting response when he put them into containers and changed their volume . take an empty bottle and put the cap on it , closing that container . now squeeze your bottle , and what happens ? the pressure inside the bottle increases when the size of the container decreases . you can only crush that container so much until the gases inside push back on your hand . this is called an inverse proportion , and it changes at the same rate for every gas . boyle 's law allows chemists to predict the volume of any gas at any given pressure because the relationship is always the same . in 1780 , jacques charles noticed a different relationship between gases and their temperature . if you 've ever seen a hot-air balloon , you 've seen this law in action . when the ballons are laid out , they 're totally flat . instead of blowing the balloon up like a party balloon , they use a giant flame to heat the air inside that envelope . as the air is heated up , the balloon begins to inflate as the gas volume increases . the hotter the gas becomes , the larger the volume , and that 's charles ' law . notice this law is different from boyle 's . charles ' law is a direct relationship . as the temperature increases , the volume increases as well . the third law is also easily demonstrated . when you 're blowing up party balloons , the volume increases . as you are blowing , you 're forcing more and more gas particles into the balloon from your lungs . this causes the balloon volume to increase . this is avogadro 's law in action . as the number of particles of gas added to a container are increased , the volume will increase as well . if you add too many particles , well , you know what happens next . laws are everywhere , even in the tiniest particles of gas . if you squeeze them , the pressure will increase as the particles are pushed together . low volume means a high pressure because those particles push back . as the temperature increases , gases move away from one another , and the volume increases as well . finally , if you add gas to a closed container , that container 's volume will expand . but be careful not to add too much , because otherwise you could end up with a burst balloon .
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if you add too many particles , well , you know what happens next . laws are everywhere , even in the tiniest particles of gas . if you squeeze them , the pressure will increase as the particles are pushed together .
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can you figure out a way to combine all three gas laws into one expression ? what would you call it ? why would it work conceptually as well as mathematically ?
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when we think of classic works of art , the most common setting we imagine them in is a museum . but what we often forget is that much of this art was not produced with a museum setting in mind . what happens to an artwork when it 's taken out of its originally intended context ? take the example of michelangelo 's statue of david , depicting the boy hero who slew the giant philistine , goliath , armed with only his courage and his slingshot . when michelangelo began carving a block of pure white marble to communicate this famous biblical story , the city of florence intended to place the finished product atop their grand cathedral . not only would the 17 foot tall statue be easily visible at this height , but its placement alongside 11 other statues of old testament heroes towering over onlookers would have a powerful religious significance , forcing the viewer to stare in awe towards the heavens . but by the time michelangelo had finished the work , in 1504 , the plans for the other statues had fallen through , and the city realized that lifting such a large sculpture to the roof would be more difficult than they had thought . furthermore , the statue was so detailed and lifelike , down to the bulging veins in david 's arm and the determination on his face , that it seemed a shame to hide it so far from the viewer . a council of politicians and artists convened to decide on a new location for the statue . ultimately voting to place it in front of the palazzo della signoria , the town hall and home of the new republican government . this new location transformed the statue 's meaning . the medici family , who for generations had ruled the city through their control of banking , had recently been exiled , and florence now saw itself as a free city , threatened on all sides by wealthy and powerful rivals . david , now the symbol of heroic resistance against overwhelming odds , was placed with his intense stare , now a look of stern warning , focused directly towards rome , the home of cardinal giovanni de medici . though the statue itself had not been altered , its placement changed nearly every aspect of it from a religious to a political significance . though a replica of david still appears at the palazzo , the original statue was moved in 1873 to the galleria dell'accademia , where it remains today . in the orderly , quiet environment of the museum , alongside numerous half-finished michelangelo sculptures , overt religious and political interpretations fall away , giving way to detached contemplation of michelangelo 's artistic and technical skill . but even here , the astute viewer may notice that david 's head and hand appear disproportionately large , a reminder that they were made to be viewed from below . so , not only does context change the meaning and interpretation of an artwork throughout its history , sometimes it can make that history resurface in the most unexpected ways .
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ultimately voting to place it in front of the palazzo della signoria , the town hall and home of the new republican government . this new location transformed the statue 's meaning . the medici family , who for generations had ruled the city through their control of banking , had recently been exiled , and florence now saw itself as a free city , threatened on all sides by wealthy and powerful rivals .
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this video explains how location gives meaning . can understanding the time period be as important ? how can understanding the time period also contribute to our understanding of art ?
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the heisenberg uncertainty principle is one of a handful of ideas from quantum physics to expand into general pop culture . it says that you can never simultaneously know the exact position and the exact speed of an object and shows up as a metaphor in everything from literary criticism to sports commentary . uncertainty is often explained as a result of measurement , that the act of measuring an object 's position changes its speed , or vice versa . the real origin is much deeper and more amazing . the uncertainty principle exists because everything in the universe behaves like both a particle and a wave at the same time . in quantum mechanics , the exact position and exact speed of an object have no meaning . to understand this , we need to think about what it means to behave like a particle or a wave . particles , by definition , exist in a single place at any instant in time . we can represent this by a graph showing the probability of finding the object at a particular place , which looks like a spike , 100 % at one specific position , and zero everywhere else . waves , on the other hand , are disturbances spread out in space , like ripples covering the surface of a pond . we can clearly identify features of the wave pattern as a whole , most importantly , its wavelength , which is the distance between two neighboring peaks , or two neighboring valleys . but we ca n't assign it a single position . it has a good probability of being in lots of different places . wavelength is essential for quantum physics because an object 's wavelength is related to its momentum , mass times velocity . a fast-moving object has lots of momentum , which corresponds to a very short wavelength . a heavy object has lots of momentum even if it 's not moving very fast , which again means a very short wavelength . this is why we do n't notice the wave nature of everyday objects . if you toss a baseball up in the air , its wavelength is a billionth of a trillionth of a trillionth of a meter , far too tiny to ever detect . small things , like atoms or electrons though , can have wavelengths big enough to measure in physics experiments . so , if we have a pure wave , we can measure its wavelength , and thus its momentum , but it has no position . we can know a particles position very well , but it does n't have a wavelength , so we do n't know its momentum . to get a particle with both position and momentum , we need to mix the two pictures to make a graph that has waves , but only in a small area . how can we do this ? by combining waves with different wavelengths , which means giving our quantum object some possibility of having different momenta . when we add two waves , we find that there are places where the peaks line up , making a bigger wave , and other places where the peaks of one fill in the valleys of the other . the result has regions where we see waves separated by regions of nothing at all . if we add a third wave , the regions where the waves cancel out get bigger , a fourth and they get bigger still , with the wavier regions becoming narrower . if we keep adding waves , we can make a wave packet with a clear wavelength in one small region . that 's a quantum object with both wave and particle nature , but to accomplish this , we had to lose certainty about both position and momentum . the positions is n't restricted to a single point . there 's a good probability of finding it within some range of the center of the wave packet , and we made the wave packet by adding lots of waves , which means there 's some probability of finding it with the momentum corresponding to any one of those . both position and momentum are now uncertain , and the uncertainties are connected . if you want to reduce the position uncertainty by making a smaller wave packet , you need to add more waves , which means a bigger momentum uncertainty . if you want to know the momentum better , you need a bigger wave packet , which means a bigger position uncertainty . that 's the heisenberg uncertainty principle , first stated by german physicist werner heisenberg back in 1927 . this uncertainty is n't a matter of measuring well or badly , but an inevitable result of combining particle and wave nature . the uncertainty principle is n't just a practical limit on measurment . it 's a limit on what properties an object can have , built into the fundamental structure of the universe itself .
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it has a good probability of being in lots of different places . wavelength is essential for quantum physics because an object 's wavelength is related to its momentum , mass times velocity . a fast-moving object has lots of momentum , which corresponds to a very short wavelength .
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for a quantum particle to have a long wavelength , it should have :
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the elephant is a creature of epic proportions , and yet it owes its enormity to more than 1,000 trillion microscopic cells , and on the epically small end of things , there are likely millions of unicellular species , yet there are very few we can see with the naked eye . why is that ? why do n't we get unicellular elephants , or blue whales , or brown bears ? to find out , we have to peer into a cell 's guts . this is where most of the cell 's functions occur , enclosed by a cellular membrane that acts as the doorway into and out of the cell . any resources the cell needs to consume , or waste products it needs to expel , first have to pass through this membrane . but there 's a biological quirk in this set up . a cell 's surface and volume increase at different rates . cells come in many shapes , but imagining them as cubes will make the math easy to calculate . a cube has six faces . these represent the cell membrane , and make up its surface area . a cube measuring one micrometer on each side , that 's one millionth of a meter , would have a total surface area of six square micrometers . and its volume would be one cubic micrometer . this would give us six units of surface area for every single unit of volume , a six to one ratio . but things change dramatically if we make the cube ten times bigger , measuring ten micrometers on each side . this cell would have a surface area of 600 square micrometers and a volume of one thousand cubic micrometers , a ratio of only .6 to one . that 's less than one unit of surface area to service each unit of volume . as the cube grows , its volume increases much faster than its surface area . the interior would overtake the membrane , leaving too little surface area for things to quickly move in and out of the cell . a huge cell would back up with waste and eventually die and disintegrate . there 's another plus to having multitudes of smaller cells , too . it 's hardly a tragedy if one gets punctured , infected , or destroyed . now , there are some exceptionally large cells that have adapted to cheat the system , like the body 's longest cell , a neuron that stretches from the base of the spine to the foot . to compensate for its length , it 's really thin , just a few micrometers in diameter . another example can be found in your small intestine , where structures called villi fold up into little fingers . each villus is made of cells with highly folded membranes that have tiny bumps called microvilli to increase their surface area . but what about single-celled organisms ? caulerpa taxifolia , a green algae that can reach 30 centimeters long , is believed to be the largest single-celled organism in the world thanks to its unique biological hacks . its surface area is enhanced with a frond-like structure . it uses photosynthesis to assemble its own food molecules and it 's coenocytic . that means it 's a single cell with multiple nuclei , making it like a multicellular organism but without the divisions between cells . yet even the biggest unicellular organisms have limits , and none grows nearly as large as the elephant , whale , or bear . but within every big creature are trillions of minuscule cells perfectly suited in all their tininess to keeping the earth 's giants lumbering along .
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why do n't we get unicellular elephants , or blue whales , or brown bears ? to find out , we have to peer into a cell 's guts . this is where most of the cell 's functions occur , enclosed by a cellular membrane that acts as the doorway into and out of the cell . any resources the cell needs to consume , or waste products it needs to expel , first have to pass through this membrane .
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what part of the cell serves as the doorway into and out of the cell ?
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this is the story of three plastic bottles , empty and discarded . their journeys are about to diverge with outcomes that impact nothing less than the fate of the planet . but they were n't always this way . to understand where these bottles end up , we must first explore their origins . the heroes of our story were conceived in this oil refinery . the plastic in their bodies was formed by chemically bonding oil and gas molecules together to make monomers . in turn , these monomers were bonded into long polymer chains to make plastic in the form of millions of pellets . those were melted at manufacturing plants and reformed in molds to create the resilient material that makes up the triplets ' bodies . machines filled the bottles with sweet bubbily liquid and they were then wrapped , shipped , bought , opened , consumed and unceremoniously discarded . and now here they lie , poised at the edge of the unknown . bottle one , like hundreds of millions of tons of his plastic brethren , ends up in a landfill . this huge dump expands each day as more trash comes in and continues to take up space . as plastics sit there being compressed amongst layers of other junk , rainwater flows through the waste and absorbs the water-soluble compounds it contains , and some of those are highly toxic . together , they create a harmful stew called leachate , which can move into groundwater , soil and streams , poisoning ecosystems and harming wildlife . it can take bottle one an agonizing 1,000 years to decompose . bottle two 's journey is stranger but , unfortunately , no happier . he floats on a trickle that reaches a stream , a stream that flows into a river , and a river that reaches the ocean . after months lost at sea , he 's slowly drawn into a massive vortex , where trash accumulates , a place known as the great pacific garbage patch . here the ocean 's currents have trapped millions of pieces of plastic debris . this is one of five plastic-filled gyres in the world 's seas . places where the pollutants turn the water into a cloudy plastic soup . some animals , like seabirds , get entangled in the mess . they , and others , mistake the brightly colored plastic bits for food . plastic makes them feel full when they 're not , so they starve to death and pass the toxins from the plastic up the food chain . for example , it 's eaten by lanternfish , the lanternfish are eaten by squid , the squid are eaten by tuna , and the tuna are eaten by us . and most plastics do n't biodegrade , which means they 're destined to break down into smaller and smaller pieces called micro plastics , which might rotate in the sea eternally . but bottle three is spared the cruel purgatories of his brothers . a truck brings him to a plant where he and his companions are squeezed flat and compressed into a block . okay , this sounds pretty bad , too , but hang in there . it gets better . the blocks are shredded into tiny pieces , which are washed and melted , so they become the raw materials that can be used again . as if by magic , bottle three is now ready to be reborn as something completely new . for this bit of plastic with such humble origins , suddenly the sky is the limit .
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as plastics sit there being compressed amongst layers of other junk , rainwater flows through the waste and absorbs the water-soluble compounds it contains , and some of those are highly toxic . together , they create a harmful stew called leachate , which can move into groundwater , soil and streams , poisoning ecosystems and harming wildlife . it can take bottle one an agonizing 1,000 years to decompose .
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leachate is produced as :
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so you just strained a muscle and the inflammation is unbearable . you wish you had something ice-cold to dull the pain , but to use an ice pack , you would have had to put it in the freezer hours ago . fortunately , there 's another option . a cold pack can be left at room temperature until the moment you need it , then just snap it as instructed and within seconds you 'll feel the chill . but how can something go from room temperature to near freezing in such a short time ? the answer lies in chemistry . your cold pack contains water and a solid compound , usually ammonium nitrate , in different compartments separated by a barrier . when the barrier is broken , the solid dissolves causing what 's known as an endothermic reaction , one that absorbs heat from its surroundings . to understand how this works , we need to look at the two driving forces behind chemical processes : energetics and entropy . these determine whether a change occurs in a system and how energy flows if it does . in chemistry , energetics deals with the attractive and repulsive forces between particles at the molecular level . this scale is so small that there are more water molecules in a single glass than there are known stars in the universe . and all of these trillions of molecules are constantly moving , vibrating and rotating at different rates . we can think of temperature as a measurement of the average motion , or kinetic energy , of all these particles , with an increase in movement meaning an increase in temperature , and vice versa . the flow of heat in any chemical transformation depends on the relative strength of particle interactions in each of a substance 's chemical states . when particles have a strong mutual attractive force , they move rapidly towards one another , until they get so close , that repulsive forces push them away . if the initial attraction was strong enough , the particles will keep vibrating back and forth in this way . the stronger the attraction , the faster their movement , and since heat is essentially motion , when a substance changes to a state in which these interactions are stronger , the system heats up . but our cold packs do the opposite , which means that when the solid dissolves in the water , the new interactions of solid particles and water molecules with each other are weaker than the separate interactions that existed before . this makes both types of particles slow down on average , cooling the whole solution . but why would a substance change to a state where the interactions were weaker ? would n't the stronger preexisting interactions keep the solid from dissolving ? this is where entropy comes in . entropy basically describes how objects and energy are distributed based on random motion . if you think of the air in a room , there are many different possible arrangements for the trillions of particles that compose it . some of these will have all the oxygen molecules in one area , and all the nitrogen molecules in another . but far more will have them mixed together , which is why air is always found in this state . now , if there are strong attractive forces between particles , the probability of some configurations can change even to the point where the odds do n't favor certain substances mixing . oil and water not mixing is an example . but in the case of the ammonium nitrate , or other substance in your cold pack , the attractive forces are not strong enough to change the odds , and random motion makes the particles composing the solid separate by dissolving into the water and never returning to their solid state . to put it simply , your cold pack gets cold because random motion creates more configurations where the solid and water mix together and all of these have even weaker particle interaction , less overall particle movement , and less heat than there was inside the unused pack . so while the disorder that can result from entropy may have caused your injury in the first place , its also responsible for that comforting cold that soothes your pain .
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in chemistry , energetics deals with the attractive and repulsive forces between particles at the molecular level . this scale is so small that there are more water molecules in a single glass than there are known stars in the universe . and all of these trillions of molecules are constantly moving , vibrating and rotating at different rates .
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which best illustrates how many water molecules exist in a glass of water ?
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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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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 .
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which is not a routine treatment recommended to cancer treatments ?
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i just came back from a community that holds the secret to human survival . it 's a place where women run the show , have sex to say hello , and play rules the day -- where fun is serious business . and no , this is n't burning man or san francisco . ( laughter ) ladies and gentlemen , meet your cousins . this is the world of wild bonobos in the jungles of congo . bonobos are , together with chimpanzees , your living closest relative . that means we all share a common ancestor , an evolutionary grandmother , who lived around six million years ago . now , chimpanzees are well-known for their aggression . ( laughter ) but unfortunately , we have made too much of an emphasis of this aspect in our narratives of human evolution . but bonobos show us the other side of the coin . while chimpanzees are dominated by big , scary guys , bonobo society is run by empowered females . these guys have really worked something out , since this leads to a highly tolerant society where fatal violence has not been observed yet . but unfortunately , bonobos are the least understood of the great apes . they live in the depths of the congolese jungle , and it has been very difficult to study them . the congo is a paradox -- a land of extraordinary biodiversity and beauty , but also the heart of darkness itself -- the scene of a violent conflict that has raged for decades and claimed nearly as many lives as the first world war . not surprisingly , this destruction also endangers bonobo survival . bushmeat trades and forest loss means we could n't fill a small stadium with all the bonobos that are left in the world -- and we 're not even sure of that to be honest . yet , in this land of violence and chaos , you can hear hidden laughter swaying the trees . who are these cousins ? we know them as the `` make love , not war '' apes since they have frequent , promiscuous and bisexual sex to manage conflict and solve social issues . now , i 'm not saying this is the solution to all of humanity 's problems -- since there 's more to bonobo life than the kama sutra . bonobos , like humans , love to play throughout their entire lives . play is not just child 's games . for us and them , play is foundational for bonding relationships and fostering tolerance . it 's where we learn to trust and where we learn about the rules of the game . play increases creativity and resilience , and it 's all about the generation of diversity -- diversity of interactions , diversity of behaviors , diversity of connections . and when you watch bonobo play , you 're seeing the very evolutionary roots of human laughter , dance and ritual . play is the glue that binds us together . now , i do n't know how you play , but i want to show you a couple of unique clips fresh from the wild . first , it 's a ball game bonobo-style -- and i do not mean football . so here , we have a young female and a male engaged in a chase game . have a look what she 's doing . it might be the evolutionary origin of the phrase , `` she 's got him by the balls . '' ( laughter ) only i think that he 's rather loving it here , right ? yeah . ( laughter ) so sex play is common in both bonobos and humans . and this video is really interesting because it shows -- this video 's really interesting because it shows the inventiveness of bringing unusual elements into play -- such as testicles -- and also how play both requires trust and fosters trust -- while at the same time being tremendous fun . but play 's a shapeshifter . ( laughter ) play 's a shapeshifter , and it can take many forms , some of which are more quiet , imaginative , curious -- maybe where wonder is discovered anew . and i want you to see , this is fuku , a young female , and she is quietly playing with water . i think , like her , we sometimes play alone , and we explore the boundaries of our inner and our outer worlds . and it 's that playful curiosity that drives us to explore , drives us to interact , and then the unexpected connections we form are the real hotbed for creativity . so these are just small tasters into the insights that bonobo give us to our past and present . but they also hold a secret for our future , a future where we need to adapt to an increasingly challenging world through greater creativity and greater cooperation . the secret is that play is the key to these capacities . in other words , play is our adaptive wildcard . in order to adapt successfully to a changing world , we need to play . but will we make the most of our playfulness ? play is not frivolous . play 's essential . for bonobos and humans alike , life is not just red in tooth and claw . in times when it seems least appropriate to play , it might be the times when it is most urgent . and so , my fellow primates , let us embrace this gift from evolution and play together , as we rediscover creativity , fellowship and wonder . thank you . ( applause )
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now , i 'm not saying this is the solution to all of humanity 's problems -- since there 's more to bonobo life than the kama sutra . bonobos , like humans , love to play throughout their entire lives . play is not just child 's games .
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what do you think cognitively separates humans from bonobos and chimps , our primate cousins .
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imagine you 're at a football game when this obnoxious guy sits next to you . he 's loud , he spills his drink on you , and he makes fun of your team . days later , you 're walking in the park when suddenly it starts to pour rain . who should show up at your side to offer you an umbrella ? the same guy from the football game . do you change your mind about him based on this second encounter , or do you go with your first impression and write him off ? research in social psychology suggests that we 're quick to form lasting impressions of others based on their behaviors . we manage to do this with little effort , inferring stable character traits from a single behavior , like a harsh word or a clumsy step . using our impressions as guides , we can accurately predict how people are going to behave in the future . armed with the knowledge the guy from the football game was a jerk the first time you met him , you might expect more of the same down the road . if so , you might choose to avoid him the next time you see him . that said , we can change our impressions in light of new information . behavioral researchers have identified consistent patterns that seem to guide this process of impression updating . on one hand , learning very negative , highly immoral information about someone typically has a stronger impact than learning very positive , highly moral information . so , unfortunately for our new friend from the football game , his bad behavior at the game might outweigh his good behavior at the park . research suggests that this bias occurs because immoral behaviors are more diagnostic , or revealing , of a person 's true character . okay , so by this logic , bad is always stronger than good when it comes to updating . well , not necessarily . certain types of learning do n't seem to lead to this sort of negativity bias . when learning about another person 's abilities and competencies , for instance , this bias flips . it 's actually the positive information that gets weighted more heavily . let 's go back to that football game . if a player scores a goal , it ultimately has a stronger impact on your impression of their skills than if they miss the net . the two sides of the updating story are ultimately quite consistent . overall , behaviors that are perceived as being less frequent are also the ones that people tend to weigh more heavily when forming and updating impressions , highly immoral actions and highly competent actions . so , what 's happening at the level of the brain when we 're updating our impressions ? using fmri , or functional magnetic resonance imaging , researchers have identified an extended network of brain regions that respond to new information that 's inconsistent with initial impressions . these include areas typically associated with social cognition , attention , and cognitive control . moreover , when updating impressions based on people 's behaviors , activity in the ventrolateral prefrontal cortex and the superior temporal sulcus correlates with perceptions of how frequently those behaviors occur in daily life . in other words , the brain seems to be tracking low-level , statistical properties of behavior in order to make complex decisions regarding other people 's character . it needs to decide is this person 's behavior typical or is it out of the ordinary ? in the situation with the obnoxious-football-fan-turned-good-samaritan , your brain says , `` well , in my experience , pretty much anyone would lend someone their umbrella , but the way this guy acted at the football game , that was unusual . '' and so , you decide to go with your first impression . there 's a good moral in this data : your brain , and by extension you , might care more about the very negative , immoral things another person has done compared to the very positive , moral things , but it 's a direct result of the comparative rarity of those bad behaviors . we 're more used to people being basically good , like taking time to help a stranger in need . in this context , bad might be stronger than good , but only because good is more plentiful . think about the last time you judged someone based on their behavior , especially a time when you really feel like you changed your mind about someone . was the behavior that caused you to update your impression something you 'd expect anyone to do , or was it something totally out of the ordinary ?
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behavioral researchers have identified consistent patterns that seem to guide this process of impression updating . on one hand , learning very negative , highly immoral information about someone typically has a stronger impact than learning very positive , highly moral information . so , unfortunately for our new friend from the football game , his bad behavior at the game might outweigh his good behavior at the park .
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research suggests that when learning about someone ’ s abilities , positive information is ______ , compared to negative information .
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some superheros can move faster than the wind . the men in apollo 10 reached a record-breaking speed of around 25,000 miles per hour when the shuttle re-entered the earth 's atmosphere in 1969 . would n't we save a lot of time to be able to move that fast ? but what 's the catch ? air is not empty . elements like oxygen and nitrogen , even countless dust particles , make up the air around us . when we move past these things in the air , we 're rubbing against them and creating a lot of friction , which results in heat . just like rubbing your hands together warms them up or rubbing two sticks together makes fire , the faster objects rub together , the more heat is generated . so , if we 're running at 25,000 miles per hour , the heat from friction would burn our faces off . even if we somehow withstood the heat , the sand and dirt in the air would still scrape us up with millions of tiny cuts all happening at the same time . ever seen the front bumper or grill of a truck ? what do you think all the birds and bugs would do to your open eyes or exposed skin ? okay , so you 'll wear a mask to avoid destroying your face . but what about people in buildings between you and your destination ? it takes us approximately one-fifth of a second to react to what we see . by the time we see what is ahead of us and react to it - time times velocity equals distance equals one-fifth of a second times 25,000 miles per hour equals 1.4 miles - we would have gone past it or through it by over a mile . we 're either going to kill ourselves by crashing into the nearest wall at super speed or , worse , if we 're indestructible , we 've essentially turned our bodies into missiles that destroy everything in our path . so , long distance travel at 25,000 miles per hour would leave us burning up , covered in bugs , and leaves no time to react . what about short bursts to a location we can see with no obstacles in between ? okay , let 's say a bullet is about to hit a beautiful damsel in distress . so , our hero swoops in at super speed , grabs her , and carries her to safety . that sounds very romantic , but , in reality , that girl will probably suffer more damage from the hero than the bullet if he moved her at super speed . newton 's first law of motion deals with inertia , which is the resistance to a change in its state of motion . so , an object will continue moving or staying at the same place unless something changes it . acceleration is the rate the velocity changes over time . when the girl at rest , velocity equals zero miles per hour , begins accelerating to reach the speed within seconds , velocity increases rapidly to 25,000 miles per hour , her brain would crash into the side of her skull . and , when she stops suddenly , velocity decreases rapidly back to zero miles per hour , her brain would crash into the other side of her skull , turning her brain into mush . the brain is too fragile to handle the sudden movement . so is every part of her body , for that matter . remember , it 's not the speed that causes the damage because the astronauts survived apollo 10 , it 's the acceleration or sudden stop that causes our internal organs to crash into the front of our bodies the way we move forward in a bus when the driver slams on the brakes . what the hero did to the girl is mathematically the same as running her over with a space shuttle at maximum speed . she probably died instantly at the point of impact . he 's going to owe this poor girl 's family an apology and a big fat compensation check . oh , and possibly face jail time . doctors have to carry liability insurance just in case they make a mistake and hurt their patients . i wonder how much superhero insurance policy would cost . now , which superpower physics lesson will you explore next ? shifting body size and content , super speed , flight , super strength , immortality , and invisibility .
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we 're either going to kill ourselves by crashing into the nearest wall at super speed or , worse , if we 're indestructible , we 've essentially turned our bodies into missiles that destroy everything in our path . so , long distance travel at 25,000 miles per hour would leave us burning up , covered in bugs , and leaves no time to react . what about short bursts to a location we can see with no obstacles in between ?
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why wouldn ’ t a superhero have time to react to things or situations when traveling at 25,000 miles per hour ?
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what 's your sign ? in western astrology , it 's a constellation determined by when your birthday falls in the calendar . but according to the chinese zodiac , or shēngxiào , it 's your shǔxiàng , meaning the animal assigned to your birth year . and of the many myths explaining these animal signs and their arrangement , the most enduring one is that of the great race . as the story goes , yù dì , or jade emperor , ruler of the heavens , wanted to devise a way to measure time , so he organized a race . the first twelve animals to make it across the river would earn a spot on the zodiac calendar in the order they arrived . the rat rose with the sun to get an early start , but on the way to the river , he met the horse , the tiger , and the ox . because the rat was small and could n't swim very well , he asked the bigger animals for help . while the tiger and horse refused , the kind-hearted ox agreed to carry the rat across . yet , just as they were about to reach the other side , the rat jumped off the ox 's head and secured first place . the ox came in second , with the powerful tiger right behind him . the rabbit , too small to battle the current , nimbly hopped across stones and logs to come in fourth . next came the dragon , who could have flown directly across , but stopped to help some creatures she had encountered on the way . after her came the horse , galloping across the river . but just as she got across , the snake slithered by . the startled horse reared back , letting the snake sneak into sixth place . the jade emperor looked out at the river and spotted the sheep , the monkey , and the rooster all atop a raft , working together to push it through the weeds . when they made it across , the trio agreed to give eighth place to the sheep , who had been the most comforting and harmonious of them , followed by the monkey and the rooster . next came the dog , scrambling onto the shore . he was a great swimmer , but frolicked in the water for so long that he only managed to come in eleventh . the final spot was claimed by the pig , who had gotten hungry and stopped to eat and nap before finally waddling across the finish line . and so , each year is associated with one of the animals in this order , with the cycle starting over every 60 years . why 60 and not twelve ? well , the traditional chinese calendar is made up of two overlapping systems . the animals of the zodiac are associated with what 's called the twelve earthly branches , or shí'èrzhī . another system , the ten heavenly stems , or tiāngān , is linked with the five classical elements of metal , xīn , wood , mù , water , shuǐ , fire , huǒ , and earth , tǔ . each element is assigned yīn or yáng , creating a ten-year cycle . when the twelve animals of the earthly branches are matched with the five elements plus the yīn or the yáng of the heavenly stems , it creates 60 years of different combinations , known as a sexagenary cycle , or gānzhī . so someone born in 1980 would have the sign of yáng metal monkey , while someone born in 2007 would be yīn fire pig . in fact , you can also have an inner animal based on your birth month , a true animal based on your birth date , and a secret animal based on your birth hour . it was the great race that supposedly determined which animals were enshrined in the chinese zodiac , but as the system spread through asia , other cultures made changes to reflect their communities . so if you consult the vietnamese zodiac , you may discover that you 're a cat , not a rabbit , and if you 're in thailand , a mythical snake called a naga replaces the dragon . so whether or not you place stock in what the zodiac says about you as an individual , it certainly reveals much about the culture it comes from .
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in fact , you can also have an inner animal based on your birth month , a true animal based on your birth date , and a secret animal based on your birth hour . it was the great race that supposedly determined which animals were enshrined in the chinese zodiac , but as the system spread through asia , other cultures made changes to reflect their communities . so if you consult the vietnamese zodiac , you may discover that you 're a cat , not a rabbit , and if you 're in thailand , a mythical snake called a naga replaces the dragon .
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compare and contrast the chinese zodiac with another system , such as western astrology . how are they similar ? how are they different ?
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why does salt dissolve in water but oil does n't ? well , in a word , chemistry , but that 's not very satisfying , is it ? well , the reason salt dissolves and oil does not comes down to the two big reasons why anything happens at all : energetics and entropy . energetics deals primarily with the attractive forces between things . when we look at oil or salt in water , we focus on the forces between particles on a very , very , very small scale , the molecular level . to give you a sense of this scale , in one glass of water , there are more molecules than known stars in the universe . now , all of these molecules are in constant motion , moving , vibrating , and rotating . what prevents almost all of those molecules from just flying out of the glass are the attractive interactions between molecules . the strength of the interactions between water , itself , and other substances is what we mean when we say energetics . you can think of the water molecules engaging in a constant dance , sort of like a square dance where they constantly and randomly exchange partners . put simply , the ability for substances to interact with water , balanced with how they disrupt how water interacts with itself , plays an important role in explaining why certain things mix well into water and others do n't . entropy basically describes the way things and energy can be arranged based on random motion . for example , think of the air in a room . imagine all the different possible arrangements in space for the trillions of particles that make up the air . some of those arrangments might have all the oxygen molecules over here and all the nitrogen molecules over there , separated . but far more of the possible arrangements have those molecules mixed up with one another . so , entropy favors mixing . energetics deals with attractive forces . and so , if attractive forces are present , the probability of some arrangements can be enhanced , the ones where things are attracted to each other . so , it is always the balance of these two things that determines what happens . on the molecular level , water is comprised of water molecules , made up of two hydrogen atoms and an oxygen atom . as liquid water , these molecules are engaged in a constant and random square dance that is called the hydrogen bonding network . entropy favors keeping the square dance going at all times . there are always more ways that all the water molecules can arrange in a square dance , as compared to if the water molecules did a line dance . so , the square dance constantly goes on . so , what happens when you put salt in the water ? well , on the molecular level , salt is actually made up of two different ions , chlorine and sodium , that are organized like a brick wall . they show up to the dance as a big group in formation and sit on the side at first , shy and a bit reluctant to break apart into individual ions to join the dance . but secretly , those shy dancers just want someone to ask them to join . so , when a water randomly bumps into one of them and pulls them into the dance away from their group , they go . and once they go into the dance , they do n't come back out . and in fact , the addition of the salt ions adds more possible dance positions in the square dance , so it is favored for them to stay dancing with water . now , let 's take oil . with oil , the molecules are sort of interested in dancing with water , so entropy favors them joining the dance . the problem is that oil molecules are wearing gigantic ballgowns , and they 're way bigger than water molecules . so , when an oil molecule gets pulled in , their size is really disruptive to the dance and the random exchange of partners that the waters engage in , a very important part of the dance . in addition , they are not great dancers . the water molecules try to engage the oil molecules in the dance , but they just keep bumping into their dresses and taking up all the room on the dance floor . there are way more ways the waters can dance when the oil gets off the floor , so the waters squeeze out the oil , pushing it back to the bench with the others . pretty soon , when a large number of oils have been squeezed over to the side , they band together to commiserate about how unfair the waters are being and stick together as a group . so , it is this combination of the interactions between molecules and the configurations available to them when they 're moving randomly that dictates whether they mix . in other words , water and oil do n't mix because they just do n't make great dance partners .
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and in fact , the addition of the salt ions adds more possible dance positions in the square dance , so it is favored for them to stay dancing with water . now , let 's take oil . with oil , the molecules are sort of interested in dancing with water , so entropy favors them joining the dance . the problem is that oil molecules are wearing gigantic ballgowns , and they 're way bigger than water molecules . so , when an oil molecule gets pulled in , their size is really disruptive to the dance and the random exchange of partners that the waters engage in , a very important part of the dance .
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a surfactant is a molecule that can dissolve in both oil and water and can be added to an oil spill to help facilitate the mixing of the oil and water ( which can make it easier to disperse an oil spill ) . can you build an explanation using the dance analogy for how a surfactant might work on mixing oil and water ? then try to build an explanation without using analogies or personifying the molecules . ( remember , by avoiding personification of molecules you can not say that they “ like ” or “ want ” things . just focus on energetics and entropy ! )
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i 'm going to try to shine a historical light on our language , and tell you a story about the electric vocabulary . it all begins over 2,600 years ago . an ancient greek , called thales of miletus , is thought to be the first person to observe what we would today call electrical phenomena . he discovered that a piece of amber , when rubbed with fur , could pick up small pieces of straw . in thales 's language , amber was called `` electron . '' for a long time , that was pretty much all anybody knew about the subject . and nature had to wait around 2,200 years before any new investigations were made into amber 's properties . william gilbert , a 17th-century english scientist , discovered that with a careful experimentation , a number of other materials could display the attractive properties of amber . he also found that they could attract objects besides straw . gilbert named these amberlike objects after the greek for amber . he called them `` electrics . '' about 40 years later , in nearby norwich , sir thomas browne carried out similar experiments . he did n't figure out anything different from william gilbert , yet the way he described the experiments coined the word we use all the time . the way he saw it , when you rub , say , a crystal with a cloth , it becomes an electric object . and just as we speak of elastic objects , and say they possess the property of elasticity , electric objects possess the property of electricity . the 18th-century french physicist charles du fay was the next person to make an important new discovery . he found that almost any object , except for metals and fluids , could be turned electric after subjecting them to a combination of heating and rubbing . in addition , he found that when two electrics are place near each other , they sometimes attract , and sometimes repel . with this extra knowledge , du fay found that there were two distinct groups of electrics . any two objects from the same group will always repel , while a pair of one from each group will always attract . despite these new discoveries , du fay 's descriptions of the physics are all lost to history . instead , it is the vocabulary of a charismatic young american that we still remember and use to this day . benjamin franklin heard of the work going on in europe , and started his own playful experiments . he quickly learned how to make electric devices that would de-electrify by producing very large sparks . keen on mischievous pranks , franklin would often shock his friends with these machines . as he built more effective devices , he likened the act of electrifying and de-electrifying to charging and discharging weaponry . it did n't take long for franklin and others to realize that it was possible to link these weapons of mischief together . franklin , continuing with the metaphor , likened this grouping to cannons on a ship . the gun deck on a military vessel fired their cannons simultaneously , in a battery . similarly , this electric battery , would discharge all at the same time , causing large sparks . this new technology raised an interesting question : was a lightning cloud just a large electrical battery ? franklin 's description of all this was as follows : he supposed that there is a substance he called the electrical fluid , that is common to all things . if , say , a person rubs a glass tube , this rubbing , or charging , causes a flow of this fluid , or an electrical current , to move from the person to the glass . both the person and the tube become electrics as a result . normally , if the person was standing on the ground , their electrical fluid would return to normal , with an exchange from the common stock of the earth , as franklin called it . standing on something like a wax block can cut off this supply . franklin said that an object with an excess of this fluid was positively charged , and something lacking this fluid was negatively charged . when objects touch , or are near each other , the electrical fluid can flow between them until they reach a balance . the bigger the difference in the fluid between the two objects , the larger the distance the fluid can jump , causing sparks in the air . and , it is the material of the object that determines if it gains or loses electrical fluid during charging . these are du fay 's two groups of electrics . you might have heard the phrase : `` opposite charges attract , like charges repel . '' that 's why . for the next 150 years , franklin 's theory was used to develop many more ideas and discoveries , all using the vocabulary he invented . this scientific inquiry brought forth technological advances and eventually , scientists were able to take a closer look at the electric fluid itself . in 1897 , j.j. thomson , working in cambridge , england , discovered that the electrical fluid is actually made up of small particles named by the physicist george stoney as `` electrons . '' and so we return to the ancient greek word for amber , where our story began . however , there 's an epilogue to this tale . it was discovered that these electrons flow in the opposite direction to what franklin supposed . therefore , objects that are positively charged do n't have an excess of electrical fluid , they actually lack electrons . yet , instead of relabeling everything the other way around , people have decided to hold on to franklin 's vocabulary as a matter of habit and convention . while acknowledging the discovery of electrons , they kept franklin 's flow of electrical fluid , renaming it : conventional current . the electron has become the salmon of electricity , swimming upstream in a ghostly river of conventional current . this can be , understandably , confusing for many people who are n't familiar with the history of these ideas . and so i hope , with this short story about the electric vocabulary , you will be able to see through the accident and whimsy of this subject and can gain a clearer understanding of the physics of electrical phenomena .
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that 's why . for the next 150 years , franklin 's theory was used to develop many more ideas and discoveries , all using the vocabulary he invented . this scientific inquiry brought forth technological advances and eventually , scientists were able to take a closer look at the electric fluid itself .
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in the lesson , you saw how benjamin franklin used analogies to describe parts of his theory and the equipment he used . can you think of any other analogies ( or metaphors , or similes ) used in scientific vocabulary ?
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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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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 .
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how much has earth 's average surface temperature increased since 1750 ?
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deep inside yale university 's beinecke rare book and manuscript library lies the only copy of a 240-page tome . recently carbon dated to around 1420 , its vellum pages features looping handwriting and hand-drawn images seemingly stolen from a dream . real and imaginary plants , floating castles , bathing women , astrology diagrams , zodiac rings , and suns and moons with faces accompany the text . this 24x16 centimeter book is called the voynich manuscript , and its one of history 's biggest unsolved mysteries . the reason why ? no one can figure out what it says . the name comes from wilfrid voynich , a polish bookseller who came across the document at a jesuit college in italy in 1912 . he was puzzled . who wrote it ? where was it made ? what do these bizarre words and vibrant drawings represent ? what secrets do its pages contain ? he purchased the manuscript from the cash-strapped priest at the college , and eventually brought it to the u.s. , where experts have continued to puzzle over it for more than a century . cryptologists say the writing has all the characteristics of a real language , just one that no one 's ever seen before . what makes it seem real is that in actual languages , letters and groups of letters appear with consistent frequencies , and the language in the voynich manuscript has patterns you would n't find from a random letter generator . other than that , we know little more than what we can see . the letters are varied in style and height . some are borrowed from other scripts , but many are unique . the taller letters have been named gallows characters . the manuscript is highly decorated throughout with scroll-like embellishments . it appears to be written by two or more hands , with the painting done by yet another party . over the years , three main theories about the manuscript 's text have emerged . the first is that it 's written in cypher , a secret code deliberately designed to hide secret meaning . the second is that the document is a hoax written in gibberish to make money off a gullible buyer . some speculate the author was a medieval con man . others , that it was voynich himself . the third theory is that the manuscript is written in an actual language , but in an unknown script . perhaps medieval scholars were attempting to create an alphabet for a language that was spoken but not yet written . in that case , the voynich manuscript might be like the rongorongo script invented on easter island , now unreadable after the culture that made it collapsed . though no one can read the voynich manuscript , that has n't stopped people from guessing what it might say . those who believe the manuscript was an attempt to create a new form of written language speculate that it might be an encyclopedia containing the knowledge of the culture that produced it . others believe it was written by the 13th century philosopher roger bacon , who attempted to understand the universal laws of grammar , or in the 16th century by the elizabethan mystic john dee , who practiced alchemy and divination . more fringe theories that the book was written by a coven of italian witches , or even by martians . after 100 years of frustration , scientists have recently shed a little light on the mystery . the first breakthrough was the carbon dating . also , contemporary historians have traced the provenance of the manuscript back through rome and prague to as early as 1612 , when it was perhaps passed from holy roman emperor rudolf ii to his physician , jacobus sinapius . in addition to these historical breakthroughs , linguistic researchers recently proposed the provisional identification of a few of the manuscript 's words . could the letters beside these seven stars spell tauran , a name for taurus , a constellation that includes the seven stars called the pleiades ? could this word be centaurun for the centaurea plant in the picture ? perhaps , but progress is slow . if we can crack its code , what might we find ? the dream journal of a 15th-century illustrator ? a bunch of nonsense ? or the lost knowledge of a forgotten culture ? what do you think it is ?
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real and imaginary plants , floating castles , bathing women , astrology diagrams , zodiac rings , and suns and moons with faces accompany the text . this 24x16 centimeter book is called the voynich manuscript , and its one of history 's biggest unsolved mysteries . the reason why ?
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what would be a good way to try to decode the voynich manuscript ?
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how do nerves work ? are nerves simply the wires in the body that conduct electricity , like the wires in the walls of your home or in your computer ? this is an analogy often made , but the reality is that nerves have a much more complex job in the body . they are not just the wires , but the cells that are the sensors , detectors of the external and internal world , the transducers that convert information to electrical impulses , the wires that transmit these impulses , the transistors that gate the information and turn up or down the volume- and finally , the activators that take that information and cause it to have an effect on other organs . consider this . your mother gently strokes your forearm and you react with pleasure . or a spider crawls on your forearm and you startle and slap it off . or you brush your forearm against a hot rack while removing a cake from the oven and you immediately recoil . light touch produced pleasure , fear , or pain . how can one kind of cell have so many functions ? nerves are in fact bundles of cells called neurons and each of these neurons is highly specialized to carry nerve impulses , their form of electricity , in response to only one kind of stimulus , and in only one direction . the nerve impulse starts with a receptor , a specialized part of each nerve , where the electrical impulse begins . one nerve 's receptor might be a thermal receptor , designed only to respond to a rapid increase in temperature . another receptor type is attached to the hairs of the forearm , detecting movement of those hairs , such as when a spider crawls on your skin . yet another kind of neuron is low-threshold mechanoreceptor , activated by light touch . each of these neurons then carry their specific information : pain , warning , pleasure . and that information is projected to specific areas of the brain and that is the electrical impulse . the inside of a nerve is a fluid that is very rich in the ion potassium . it is 20 times higher than in the fluid outside the nerve while that outside fluid has 10 times more sodium than the inside of a nerve . this imbalance between sodium outside and potassium inside the cell results in the inside of the nerve having a negative electrical charge relative to the outside of the nerve , about equal to -70 or -80 millivolts . this is called the nerve 's resting potential . but in response to that stimulus the nerve is designed to detect , pores in the cell wall near the receptor of the cell open . these pores are specialized protein channels that are designed to let sodium rush into the nerve . the sodium ions rush down their concentration gradient , and when they do , the inside of the nerve becomes more positively charged- about +40 millivolts . while this happens , initially in the nerve right around the receptor , if the change in the nerve 's electrical charge is great enough , if it reaches what is called threshold , the nearby sodium ion channels open , and then the ones nearby those , and so on , and so forth , so that the positivity spreads along the nerve 's membrane to the nerve 's cell body and then along the nerve 's long , thread-like extension , the axon . meanwhile , potassium ion channels open , potassium rushes out of the nerve , and the membrane voltage returns to normal . actually , overshooting it a bit . and during this overshoot , the nerve is resistant to further depolarization-it is refractory , which prevents the nerve electrical impulse from traveling backwards . then , ion pumps pump the sodium back back out of the nerve , and the potassium back into the nerve , restoring the nerve to its normal resting state . the end of the nerve , the end of the axon , communicates with the nerve 's target . this target will be other nerves in a specialized area of the spinal cord , to be processed and then transmitted up to the brain . or the nerve 's target may be another organ , such as a muscle . when the electrical impulse reaches the end of the nerve , small vesicles , or packets , containing chemical neurotransmitters , are released by the nerve and rapidly interact with the nerve 's target . this process is called synaptic transmission , because the connection between the nerve and the next object in the chain is called a synapse . and it is here , in this synapse , that the neuron 's electrical information can be modulated , amplified , blocked altogether or translated to another informational process .
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it is 20 times higher than in the fluid outside the nerve while that outside fluid has 10 times more sodium than the inside of a nerve . this imbalance between sodium outside and potassium inside the cell results in the inside of the nerve having a negative electrical charge relative to the outside of the nerve , about equal to -70 or -80 millivolts . this is called the nerve 's resting potential . but in response to that stimulus the nerve is designed to detect , pores in the cell wall near the receptor of the cell open .
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there is an imbalance in the ions on the inside of the nerve and the outside of the nerve resulting in a negative electrical charge of approximately -70 millivolts . this is called the nerve ’ s :
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translator : andrea mcdonough reviewer : bedirhan cinar miss gayle 's 5 steps to slam poetry , a lesson of transformation . step 1 : write it all down . `` take one memory , explore it like a new land , '' the visiting poet tells the class . `` do n't leave anything out . '' tyler sits in this high school workshop , dizzy with where to start . memories wander in and out of his heart like vagrants searching for home . he bends to his desk , he writes , `` the snow goes black when the moon turns its eyes away , all paper is yellow , all letters spell eviction note , mama 's lies are footsteps too many to count . making excuses on black snow . 'i paid the rent , this is your room forever , baby . i love you . ' but , she would n't even look at me . '' step 2 : read out loud . as he writes , his lips try on words then toss them out like bad tenants . he pushes his desk back , stands . `` aunt jocelyn 's rice pudding was sweet , but that 's not what i want to write . have you ever been so cold your hair becomes an icicle ? your little sister 's fear of the dark freezes on her lips like she 's kissed the ice tray ? how hungry have you been ? '' step 3 : cut the fat . abandon extra words . his pen becomes a machete , slashing ands , thens , becauses . step 4 : read out loud , again . the 11th grade boy makes sure step 3 's cuts were n't too deep . step 5 : add flava . juice , power , movement , emotion . `` vanilla flavoring is the secret to my aunt 's pudding . i kick out a few raisins but leave one or two . life needs some bitter to man up the sweet . '' his hands reach out like shells to hold our disbelief . is this tyler speaking ? the one who keeps his eyes on the floor like they 're carrying something heavy ? voice rattles windows . `` i am free now . '' body quivers with the pulse of each word . `` the sun 's joy melts snow . '' fingers trace the curve of his jaw . `` my aunt 's face was warm as a water heater when she let us in that night . '' our boy is done , his transformation complete . step 1 : write it all down . step 2 : read out loud . step 3 : cut the fat . step 4 : read out loud . step 5 : add flava . tyler 's first poem takes residence in his heart . he flings his arms wide like an open door . welcome home !
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`` vanilla flavoring is the secret to my aunt 's pudding . i kick out a few raisins but leave one or two . life needs some bitter to man up the sweet . ''
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which one of the steps is repeated ?
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have you ever been gazing at a starry sky when suddenly a bright dot glided into view ? if it was n't blinking , then you 've had the distinct pleasure of seeing one of mankind 's greatest collaborative feats with your own eyes : the international space station . roughly the size of six-bedroom house , and weighing more than 320 cars , the international space station is so large that no single rocket could have lifted it into orbit . instead , it was assembled piece by piece while hurtling through space at 28,000 kilometers per hour , lapping the earth once every 90 minutes . it all started when sixteen nations signed the space station intergovernmental agreement , laying out each partner 's expected contributions to the iss , from modules and maintenance to sharing information and finances . at an estimated 100 billion u.s. dollars , the space station would be the most expensive object ever built . the whole world watched as a russian rocket launched the first module of the iss into the sky . zarya , meaning sunrise , was equipped with two solar panels and a propulsion system that had the important task of keeping the young station from crashing into the earth by staying a safe 400 kilometers away . the u.s. space shuttle endeavour followed two weeks later carrying unity , a node module to which other modules could be connected , and an international six-person assembly crew . then came zvezda , which brought communications and living accommodations . ever since the international space station 's first tenants arrived , it 's been continually occupied with more than 200 visitors spending an average of six months on board . astronaut samantha cristoforetti holds the record for the longest single space flight by a woman at 199 days on the iss . 2001 saw the arrival of destiny , the first of four research modules , where astronauts spend approximately 36 hours a week conducting extraordinary experiments in microgravity . their schedules are packed with exercise , two hours a day to fend off muscle atrophy , station maintenance and repair , and connecting with family or awe-inspired minds around the world . but they still find time for fun , with regular movie nights and even shooting the first music video in space . destiny also controls the seven-jointed robotic canadarm2 . capable of moving more than 100,000 kilograms , it 's perfect for unloading new arrivals from shuttles . 2001 was a busy year for the space station with the addition of quest , the main airlock for strolls outside , and pirs , a pier for russian spacecrafts to dock including the ever-ready emergency escape vehicle , soyuz . then , on february 1st , 2003 , after delivering research modules to the iss , the space shuttle columbia exploded during reentry tragically killing the seven-member crew on board . after a four-year hiatus , work quickly picked up pace with the addition of more hubs , airlocks , docks , and an observation cupola for stunning 360-degree views of our world and beyond . other critical components included platforms and trusses to support radiators that direct all the heat generated by the station 's electronics into space and solar panels that are efficient enough to power 55 homes . it took ten years and over 30 missions , but finally , the international space station was complete , coinciding with the u.s. space shuttle program 's retirement . the space station continues to serve as an incredible model for international collaboration . this year , two people began a one-year stay on the iss , allowing scientists to study the long-term physical and psychological effects of being in space , which would prove useful for increasingly ambitious space travel , like trips to mars . over its lifetime , we 've learned an immense amount scientifically , but also about our capacity to work together and accomplish truly remarkable acts .
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other critical components included platforms and trusses to support radiators that direct all the heat generated by the station 's electronics into space and solar panels that are efficient enough to power 55 homes . it took ten years and over 30 missions , but finally , the international space station was complete , coinciding with the u.s. space shuttle program 's retirement . the space station continues to serve as an incredible model for international collaboration . this year , two people began a one-year stay on the iss , allowing scientists to study the long-term physical and psychological effects of being in space , which would prove useful for increasingly ambitious space travel , like trips to mars .
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about how big is the international space station ?
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how does your smartphone know exactly where you are ? the answer lies 12,000 miles over your head in an orbiting satellite that keeps time to the beat of an atomic clock powered by quantum mechanics . phew . let 's break that down . first of all , why is it so important to know what time it is on a satellite when location is what we 're concerned about ? the first thing your phone needs to determine is how far it is from a satellite . each satellite constantly broadcasts radio signals that travel from space to your phone at the speed of light . your phone records the signal arrival time and uses it to calculate the distance to the satellite using the simple formula , distance = c x time , where c is the speed of light and time is how long the signal traveled . but there 's a problem . light is incredibly fast . if we were only able to calculate time to the nearest second , every location on earth , and far beyond , would seem to be the same distance from the satellite . so in order to calculate that distance to within a few dozen feet , we need the best clock ever invented . enter atomic clocks , some of which are so precise that they would not gain or lose a second even if they ran for the next 300 million years . atomic clocks work because of quantum physics . all clocks must have a constant frequency . in other words , a clock must carry out some repetitive action to mark off equivalent increments of time . just as a grandfather clock relies on the constant swinging back and forth of a pendulum under gravity , the tick tock of an atomic clock is maintained by the transition between two energy levels of an atom . this is where quantum physics comes into play . quantum mechanics says that atoms carry energy , but they ca n't take on just any arbitrary amount . instead , atomic energy is constrained to a precise set of levels . we call these quanta . as a simple analogy , think about driving a car onto a freeway . as you increase your speed , you would normally continuously go from , say , 20 miles/hour up to 70 miles/hour . now , if you had a quantum atomic car , you would n't accelerate in a linear fashion . instead , you would instantaneously jump , or transition , from one speed to the next . for an atom , when a transition occurs from one energy level to another , quantum mechanics says that the energy difference is equal to a characteristic frequency , multiplied by a constant , where the change in energy is equal to a number , called planck 's constant , times the frequency . that characteristic frequency is what we need to make our clock . gps satellites rely on cesium and rubidium atoms as frequency standards . in the case of cesium 133 , the characteristic clock frequency is 9,192,631,770 hz . that 's 9 billion cycles per second . that 's a really fast clock . no matter how skilled a clockmaker may be , every pendulum , wind-up mechanism and quartz crystal resonates at a slightly different frequency . however , every cesium 133 atom in the universe oscillates at the same exact frequency . so thanks to the atomic clock , we get a time reading accurate to within 1 billionth of a second , and a very precise measurement of the distance from that satellite . let 's ignore the fact that you 're almost definitely on earth . we now know that you 're at a fixed distance from the satellite . in other words , you 're somewhere on the surface of a sphere centered around the satellite . measure your distance from a second satellite and you get another overlapping sphere . keep doing that , and with just four measurements , and a little correction using einstein 's theory of relativity , you can pinpoint your location to exactly one point in space . so that 's all it takes : a multibillion-dollar network of satellites , oscillating cesium atoms , quantum mechanics , relativity , a smartphone , and you . no problem .
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let 's break that down . first of all , why is it so important to know what time it is on a satellite when location is what we 're concerned about ? the first thing your phone needs to determine is how far it is from a satellite .
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which of the following equations were discussed as important for smartphone location ?
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we all know about the dinosaurs that once roamed the planet , but long after they went extinct , great beasts we call the megafauna lived on every continent . in the americas , ground sloths the size of elephants pulled down trees with their claws . saber-toothed cats the size of brown bears hunted in packs , but they were no match for short-faced bears , which stood thirteen feet on their hind legs , and are likely to have driven these cats away from their prey . there were armadillos as big as small cars , an eight foot beaver , and a bird with a 26 foot wingspan . almost everywhere , the world 's megafauna were driven to extinction , often by human hunters . some species still survive in parts of africa and asia . in other places , you can still see the legacy of these great beasts . most trees are able to resprout where their trunk is broken to withstand the loss of much of their bark and to survive splitting , twisting and trampling , partly because they evolved to survive attacks by elephants . the american pronghorn can run so fast because it evolved to escape the american cheetah . the surviving animals live in ghost ecosystems adapted to threats from species that no longer exist . today , it may be possible to resurrect those ghosts , to bring back lost species using genetic material . for instance , there 's been research in to cloning woolly mammoths from frozen remains . but even if it 's not possible , we can still restore many of the ecosystems the world has lost . how ? by making use of abandoned farms . as the market for food is globalized , infertile land becomes uncompetitive . farmers in barren places ca n't compete with people growing crops on better land elsewhere . as a result , farming has started to retreat from many regions , and trees have started to return . one estimate claims that two-thirds of land in the us that was once forested but was cleared for farming has become forested again . another estimate suggests that by 2030 , an area in europe the size of poland will be vaccated by farmers . so even if we ca n't use dna to bring back ground sloths and giant armadillos , we can restore bears , wolves , pumas lynx , moose and bison to the places where they used to live . some of these animals can reshape their surroundings , creating conditions that allow other species to thrive . when wolves were reintroduced to the yellowstone national park in 1995 , they quickly transformed the ecosystem . where they reduced the numbers of overpopulated deer , vegetation began to recover . the height of some trees quintupled in just six years . as forests returned , so did songbirds . beavers , which eat trees , multiplied in the rivers , and their dams provided homes for otters , muskrats , ducks , frogs and fish . the wolves killed coyotes , allowing rabbits and mice to increase , providing more food for hawks , weasels , foxes and badgers . bald eagles and ravens fed on the carrion that the wolves abandoned . so did bears , which also ate the berries on the returning shrubs . bison numbers rose as they browsed the revitalized forests . the wolves changed almost everything . this is an example of a trophic cascade , a change at the top of the food chain that tumbles all the way to the bottom , affecting every level . the discovery of widespread trophic cascades may be one of the most exciting scientific findings of the past half century . they tell us that ecosystems that have lost just one or two species of large animals can behave in radically different ways from those that retain them . all over the world , new movements are trying to catalyze the restoration of nature in a process called rewilding . this means undoing some of the damage we 've caused , reestablishing species which have been driven out , and then stepping back . there is no attempt to create an ideal ecosystem , to produce a heath , a rainforest or a coral reef . rewilding is about bringing back the species that drive dynamic processes and then letting nature take its course . but it 's essential that rewilding must never be used as an excuse to push people off the land . it should happen only with the consent and enthusiasm of the people who work there . imagine standing on a cliff in england , watching sperm whales attacking shoals of herring as they did within sight of the shore until the 18th century . by creating marine reserves in which no commerical fishing takes place , that can happen again . imagine a european serengeti full of the animals that used to live there : hippos , rhinos , elephants , hyenas and lions . what rewilding reintroduces , alongside the missing animals and plants , is that rare species called hope . it tells us that ecological change need not always proceed in the same direction . the silent spring could be followed by a wild summer .
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what rewilding reintroduces , alongside the missing animals and plants , is that rare species called hope . it tells us that ecological change need not always proceed in the same direction . the silent spring could be followed by a wild summer .
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the process by which predators drive ecological change throughout the natural system is called :
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his face is recognized all over the world . the young medical student who became a revolutionary icon . but was che guevara a heroic champion of the poor or a ruthless warlord who left a legacy of repression ? order , order . hey , where have i seen that guy before ? ahem , your honor , this is ernesto che guevara . in the early 1950s , he left behind a privileged life as a medical student in argentina to travel through rural latin america . the poverty and misery he witnessed convinced him that saving lives required more than medicine . so he became a terrorist seeking to violently overthrow the region 's governments . what ? the region 's governments were brutal oligarchies . colonialism may have formally ended , but elites still controlled all the wealth . american corporations bought up land originally seized from indigenous people and used it for profit and export , even keeping most of it uncultivated while locals starved . could n't they vote to change that ? oh , they tried , your honor . in 1953 , che came to guatemala under the democratically-elected government of president árbenz . árbenz passed reforms to redistribute some of this uncultivated land back to the people while compensating the landowners . but he was overthrown in a cia-sponsored coup . the military was protecting against the seizure of private property and communist takeover . they were protecting corporate profits and che saw that they would use the fear of communism to overthrow any government that threatened those profits . so he took the lessons of guatemala with him to mexico . there , he met exiled cuban revolutionaries and decided to help them liberate their country . you mean help fidel castro turn a vibrant cuba into a dictatorship . dictatorship was what cuba had before the revolution . fulgencio batista was a tyrant who came to power in a military coup . he turned havana into a luxury playground for foreigners while keeping cubans mired in poverty and killing thousands in police crackdowns . even president kennedy called it the worst example of `` economic colonization , humiliation , and exploitation in the world . '' whatever batista 's faults , it ca n't compare to the totalitarian nightmare castro would create . forced labor camps , torture of prisoners , no freedom to speak or to leave . but this is n't the trial of fidel castro , is it ? che guevara was instrumental in helping castro seize power . as a commander in his guerilla army , he unleashed a reign of terror across the countryside , killing any suspected spies or dissenters . he also helped peasants build health clinics and schools , taught them to read , and even recited poetry to them . his harsh discipline was necessary against a much stronger enemy who did n't hesitate to burn entire villages suspected of aiding the rebels . let 's not forget that the new regime held mass executions and killed hundreds of people without trial as soon as they took power in 1959 . the executed were officials and collaborators who had tormented the masses under batista . the people supported this revolutionary justice . which people ? an angry mob crying for blood does not a democracy make . and that 's not even mentioning the forced labor camps , arbitrary arrests , and repression of lgbt people that continued long after the revolution . there 's a reason people kept risking their lives to flee , often with nothing but the clothes on their backs . so was that all this che brought to cuba ? just another violent dictatorship ? not at all . he oversaw land redistribution , helped established universal education , and organized volunteer literacy brigades that raised cuba 's literacy rate to 96 % , still one of the highest in the world . which allowed the government to control what information everyone received . guevara 's idealistic incompetence as finance minister caused massive drops in productivity when he replaced worker pay raises with moral certificates . he suppressed all press freedom , declaring that newspapers were instruments of the oligarchy . and it was he who urged castro to host soviet nuclear weapons , leading to the cuban missile crisis that brought the world to the brink of destruction . he was a leader , not a bureaucrat . that 's why he eventually left to spread the revolution abroad . which did n't go well . he failed to rally rebels in the congo and went to bolivia even when the soviets disapproved . the bolivian government , with the help of the cia , was able to capture and neutralize this terrorist in 1967 , before he could do much damage . while doing plenty of damage themselves in the process . so that was the end of it ? not at all . as che said , the revolution is immortal . he was publicly mourned in cities all over the world . not by the cubans who managed to escape . and his story would inspire young activists for generations to come . ha . a trendy symbol of rebellion for those who never had to live under his regime . symbols of revolution may become commodified , but the idea of a more just world remains . maybe , but i 'm not sharing my coffee . che guevara was captured and executed by government forces in bolivia . his remains would not be found for another 30 years . but did he die a hero or had he already become a villain ? and should revolutions be judged by their ideals or their outcomes ? these are the questions we face when we put history on trial .
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you mean help fidel castro turn a vibrant cuba into a dictatorship . dictatorship was what cuba had before the revolution . fulgencio batista was a tyrant who came to power in a military coup .
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in which of the following areas did the revolution not improve cuba ?
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translator : andrea mcdonough reviewer : bedirhan cinar picture this : your friend and you are watching a sitcom and a sassy sidekick walks into a room , carrying a four-tiered wedding cake . he trips , falls , and face-plants into the cake . your friend doubles over with laughter and says , `` it 's so ridiculous ! so ironic ! '' well , quick , what do you do ? do you laugh along with the laugh track and let this grievous misinterpretation of irony go ? or , do you throw caution to the wind and explain the true meaning of irony ? if you 're me , you choose the latter . unfortunately , irony has been completely misunderstood . we tend to throw out that term whenever we see something funny or coincidental . and while many examples of true irony can be funny , that is not the driving factor of being ironic . a situation is only ironic if what happens is the exact opposite of what was expected . if you expect a , but get b , then you have irony . let 's take the slap-stick cake situation as an example . when someone walks in precariously balancing something that should n't be carried alone , trips , falls , and makes a mess , it is funny , but it 's not ironic . in fact , you probably expect someone who is single-handedly carrying a huge cake to trip . when he does , reality aligns with expectations , and so that is not irony . but what if the sassy sidekick walked in wearing a gold medal that he 'd won at the cake walking event at the atlanta olympics in 1996 ? what if that sidekick was a professional cake carrier ? then , maybe there would have been a reasonable expectation that he would have been more skilled when carrying a ridiculously large cake . then , when that reasonable expectation was not met by the tripping sidekick , irony would have been exemplified . another example . a senior citizen texting and blogging . the common and reasonable expectation of more mature men and women is that they do n't like or know technology , that they have a hard time turning on a computer , or that they have the old brick cell phones from the 1980s . one should not expect them to be connected , high-tech , or savvy enough to text or to be blogging , which must seem like some sort of newfangled thing that `` back in my day , '' they never had . so when granny pulls out her smart phone to post pictures of her dentures or her grandkids , irony ensues . reasonable expectations of the situation are not met . that is irony . so while the cake dropper might not be ironic , there are all kinds of situations in life that are . go out , and find those true examples of irony .
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your friend doubles over with laughter and says , `` it 's so ridiculous ! so ironic ! '' well , quick , what do you do ?
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an example of an ironic popular song is `` when i 'm 64 '' by the beatles . it 's ironic for several reasons . one , only two of the four beatles actually made it to 64. two , paul mccartney had a pretty difficult 64th year of life ( that 's the year he divorced his wife , heather mills ) . what about alanis morissette 's song `` ironic '' ? are any of her examples actually irony ? pick another song that you think is ironic and explain why .
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imagine two people are listening to music . what are the odds that they are listening to the exact same playlist ? probably pretty low . after all , everyone has very different tastes in music . now , what are the odds that your body will need the exact same medical care and treatment as another person 's body ? even lower . as we go through our lives , each of us will have very different needs for our own healthcare . scientists and doctors are constantly researching ways to make medicine more personalized . one way they are doing this is by researching stem cells . stem cells are cells that are undifferentiated , meaning they do not have a specific job or function . while skin cells protect your body , muscle cells contract , and nerve cells send signals , stem cells do not have any specific structures or functions . stem cells do have the potential to become all other kinds of cells in your body . your body uses stem cells to replace worn-out cells when they die . for example , you completely replace the lining of your intestines every four days . stem cells beneath the lining of your intestines replace these cells as they wear out . scientists hope that stem cells could be used to create a very special kind of personalized medicine in which we could replace your own body parts with , well , your own body parts . stem cell researchers are working hard to find ways in which to use stem cells to create new tissue to replace the parts of organs that are damaged by injury or disease . using stem cells to replace damaged bodily tissue is called regenerative medicine . for example , scientists currently use stem cells to treat patients with blood diseases such as leukemia . leukemia is a form of cancer that affects your bone marrow . bone marrow is the spongy tissue inside your bones where your blood cells are created . in leukemia , some of the cells inside your bone marrow grow uncontrollably , crowding out the healthy stem cells that form your blood cells . some leukemia patients can receive a stem cell transplant . these new stem cells will create the blood cells needed by the patient 's body . there are actually multiple kinds of stem cells that scientists can use for medical treatments and research . adult stem cells or tissue-specific stem cells are found in small numbers in most of your body 's tissues . tissue-specific stem cells replace the existing cells in your organs as they wear out and die . embryonic stem cells are created from leftover embryos that are willingly donated by patients from fertility clinics . unlike tissue-specific stem cells , embryonic stem cells are pluripotent . this means that they can be grown into any kind of tissue in the body . a third kind of stem cells is called induced pluripotent stem cells . these are regular skin , fat , liver , or other cells that scientists have changed to behave like embryonic stem cells . like embryonic stem cells , they , too , can become any kind of cell in the body . while scientists and doctors hope to use all of these kinds of stem cells to create new tissue to heal your body , they can also use stem cells to help understand how the body works . scientists can watch stem cells develop into tissue to understand the mechnanisms that the body uses to create new tissue in a controlled and regulated way . scientists hope that with more research , they can not only develop specialized medicine that is specific to your body but also better understand how your body functions , both when it 's healthy and when it 's not .
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in leukemia , some of the cells inside your bone marrow grow uncontrollably , crowding out the healthy stem cells that form your blood cells . some leukemia patients can receive a stem cell transplant . these new stem cells will create the blood cells needed by the patient 's body .
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an undifferentiated cell is…
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conventional wisdom about diets , including government health recommendations , seems to change all the time . and yet , ads routinely come about claiming to have the answer about what we should eat . so how do we distinguish what 's actually healthy from what advertisers just want us to believe is good for us ? marketing takes advantage of the desire to drop weight fast , and be stronger , slimmer , and brighter . and in the big picture , diet plans promising dramatic results , known as fad diets , are just what they seem : too good to be true . so where do diet fads even come from ? while the ancient greeks and romans rallied behind large-scale health regimens centuries earlier , this phenomenon began in earnest in the victorian era with crazes like the vinegar diet and the banting diet . since then , diets have advised us all sorts of things : to excessively chew , to not chew at all , to swallow a grapefruit per meal , non-stop cabbage soup , even consumption of arsenic , or tapeworms . if the idea of diet crazes has withstood history , could this mean that they work ? in the short term , the answer is often yes . low-carbohydrate plans , like the popular atkins or south beach diets , have an initial diuretic effect . sodium is lost until the body can balance itself out , and temporary fluid weight loss may occur . with other high-protein diets , you might lose weight at first since by restricting your food choices , you are dropping your overall calorie intake . but your body then lowers its metabolic rate to adjust to the shift , lessening the diet 's effect over time and resulting in a quick reversal if the diet is abandoned . so while these diets may be alluring early on , they do n't guarantee long-term benefits for your health and weight . a few simple guidelines , though , can help differentiate between a diet that is beneficial in maintaining long-term health , and one that only offers temporary weight changes . here 's the first tipoff : if a diet focuses on intensely cutting back calories or on cutting out entire food groups , like fat , sugar , or carbohydrates , chances are it 's a fad diet . and another red flag is ritual , when the diet in question instructs you to only eat specific foods , prescribed combinations , or to opt for particular food substitutes , like drinks , bars , or powders . the truth is shedding pounds in the long run simply does n't have a quick-fix solution . not all diet crazes tout weight loss . what about claims of superfoods , cleanses , and other body-boosting solutions ? marketing emphasizes the allure of products associated with ancient and remote cultures to create a sense of mysticism for consumers . while so-called superfoods , like blueberries or açaí , do add a powerful punch of nutrients , their super transformative qualities are largely exaggeration . they are healthy additions to a balanced diet , yet often , they 're marketed as part of sugary drinks or cereals , in which case the negative properties outweight the benefits . cleanses , too , may be great in moderation since they can assist with jumpstarting weight loss and can increase the number of fresh fruits and vegetables consumed daily . scientifically speaking , though , they 've not yet been shown to have either a long-term benefit or to detox the body any better than the natural mechanisms already in place . everywhere we look , we 're offered solutions to how we can look better , feel fitter , and generally get ahead . food is no exception , but advice on what we should eat is best left to the doctors and nutritionists who are aware of our individual circumstances . diets and food fads are n't inherently wrong . circumstantially , they might even be right , just not for everyone all of the time .
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food is no exception , but advice on what we should eat is best left to the doctors and nutritionists who are aware of our individual circumstances . diets and food fads are n't inherently wrong . circumstantially , they might even be right , just not for everyone all of the time .
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how does your body adjust to the caloric decrease in some diets ?
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beneath your ribs , you 'll find , among other things , the pancreas , an organ that works a lot like a personal health coach . this organ controls your sugar levels and produces a special juice that releases the nutrients from your food to help keep you in the best possible shape . the pancreas sits just behind your stomach , an appropriate home , as one of its jobs is to break down the food you eat . it aids digestion by producing a special tonic made of water , sodium bicarbonate , and digestive enzymes . sodium bicarbonate neutralizes the stomach 's natural acidity , so these digestive enzymes can perform their jobs . lipase breaks down fatty substances , protease splits up proteins , and amylase divides carbohydrates to create energy-rich sugars . most of those nutrients then get absorbed into the blood stream , and go on to enrich the body . while all this is happening , the pancreas works on another critical task , controlling the amount of sugar in your blood . it achieves this with the hormones insulin and glucagon , which are produced in special cells called the islets of langerhans . having too much or too little sugar can be life threatening , so the pancreas must stay on constant alert . after a big meal , the blood often becomes flushed with sugar . to bring us back to normal , the pancreas releases insulin , which makes the excess sugar move into cells , where it 's either used as an energy source , or stored for later . insulin also tells the liver to shut down sugar production . on the other hand , if blood sugar is low , the pancreas releases a hormone called glucagon that tells the body 's cells and liver to release stored sugars back into the bloodstream . the interplay between insulin and glucagon is what keeps our sugar levels balanced . but a faulty pancreas can no longer coach us like this , meaning that this healthy balance is destroyed . if it 's weakened by disease , the organ 's ability to produce insulin may be reduced , or even extinguished , which can trigger the condition known as diabetes . without regular insulin release , sugar steadily builds up in the blood , eventually hardening the blood vessels and causing heart attacks , kidney failure , and strokes . the same lack of insulin deprives cells of the energy-rich sugar they need to grow and function . people with diabetes also tend to have higher levels of glucagon , which makes even more sugar circulate . without this internal health coach , our sugar levels would go haywire , and we would n't be able to digest important nutrients . but like any coach , it 's not the pancreas ' job alone to keep us healthy . it needs our conscious participation , too .
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the pancreas sits just behind your stomach , an appropriate home , as one of its jobs is to break down the food you eat . it aids digestion by producing a special tonic made of water , sodium bicarbonate , and digestive enzymes . sodium bicarbonate neutralizes the stomach 's natural acidity , so these digestive enzymes can perform their jobs . lipase breaks down fatty substances , protease splits up proteins , and amylase divides carbohydrates to create energy-rich sugars .
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by imagining you are a morsel of food entering the digestive system , explain why pancreatic enzymes are so important for helping you achieve your goal of infiltrating the bloodstream with nutrients .
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throughout the history of mankind , three little words have sent poets to the blank page , philosophers to the agora , and seekers to the oracles : `` who am i ? '' from the ancient greek aphorism inscribed on the temple of apollo , `` know thyself , '' to the who 's rock anthem , `` who are you ? '' philosophers , psychologists , academics , scientists , artists , theologians and politicians have all tackled the subject of identity . their hypotheses are widely varied and lack significant consensus . these are smart , creative people , so what 's so hard about coming up with the right answer ? one challenge certainly lies with the complex concept of the persistence of identity . which you is who ? the person you are today ? five years ago ? who you 'll be in 50 years ? and when is `` am '' ? this week ? today ? this hour ? this second ? and which aspect of you is `` i '' ? are you your physical body ? your thoughts and feelings ? your actions ? these murky waters of abstract logic are tricky to navigate , and so it 's probably fitting that to demonstrate the complexity , the greek historian plutarch used the story of a ship . how are you `` i '' ? as the tale goes , theseus , the mythical founder king of athens , single-handedly slayed the evil minotaur at crete , then returned home on a ship . to honor this heroic feat , for 1000 years athenians painstakingly maintained his ship in the harbor , and annually reenacted his voyage . whenever a part of the ship was worn or damaged , it was replaced with an identical piece of the same material until , at some point , no original parts remained . plutarch noted the ship of theseus was an example of the philosophical paradox revolving around the persistence of identity . how can every single part of something be replaced , yet it still remains the same thing ? let 's imagine there are two ships : the ship that theseus docked in athens , ship a , and the ship sailed by the athenians 1000 years later , ship b . very simply , our question is this : does a equal b ? some would say that for 1000 years there has been only one ship of theseus , and because the changes made to it happened gradually , it never at any point in time stopped being the legendary ship . though they have absolutely no parts in common , the two ships are numerically identical , meaning one and the same , so a equals b . however , others could argue that theseus never set foot on ship b , and his presence on the ship is an essential qualitative property of the ship of theseus . it can not survive without him . so , though the two ships are numerically identical , they are not qualitatively identical . thus , a does not equal b . but what happens when we consider this twist ? what if , as each piece of the original ship was cast off , somebody collected them all , and rebuilt the entire original ship ? when it was finished , undeniably two physical ships would exist : the one that 's docked in athens , and the one in some guy 's backyard . each could lay claim to the title , `` the ship of theseus , '' but only would could actually be the real thing . so which one is it , and more importantly , what does this have to do with you ? like the ship of theseus , you are a collection of constantly changing parts : your physical body , mind , emotions , circumstances , and even your quirks , always changing , but still in an amazing and sometimes illogical way , you stay the same , too . this is one of the reasons that the question , `` who am i ? '' is so complex . and in order to answer it , like so many great minds before you , you must be willing to dive into the bottomless ocean of philosophical paradox . or maybe you could just answer , `` i am a legendary hero sailing a powerful ship on an epic journey . '' that could work , too .
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let 's imagine there are two ships : the ship that theseus docked in athens , ship a , and the ship sailed by the athenians 1000 years later , ship b . very simply , our question is this : does a equal b ? some would say that for 1000 years there has been only one ship of theseus , and because the changes made to it happened gradually , it never at any point in time stopped being the legendary ship .
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why is the question `` who am i '' so difficult to answer ?
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we 've decided to make a new video about aluminium because it 's a long time over five years since we made the first one and ... we did n't say very much . aluminium is a surprisingly abundand element . if you look at this periodic table here , where the area of the different elements gives you a rough idea of the abundance you can see that aluminium is one of the most abundant metals up there with sodium , magnesium and calcium . more aluminum than potassium ; about the same or perhaps even more than iron . we 're never going to run out of aluminium . the problem with aluminium is that you do n't find aluminium metal in nature as a metal . it 's always tied up with other compounds ; mostly with oxygen , in clays . you know what clays are , the sort of muddy stuff that you get stuck on your shoes when it 's raining . to get the aluminium out of the clay , that is , to break the aluminium/oxygen bonds , which are very strong ; requires a lot of energy , which comes from electricity . so , making aluminium is very energy intensive . that 's why people like to recycle aluminium because once you 've got it , it 's worth preserving ; but it 's fantastically important because aluminium is a very light metal . and it 's often used as an alloy because the aluminium alloys are stronger than the aluminium itself , so , if you 're using it for aircraft or some other use like that where you want to combine lightness with strength then the stronger you can make it , the better . but when it was first made , in the 19th century , isolated as a metal it was terrifically valuable and there are stories of the french emperor serving his honored guests with aluminium plates or aluminium cutlery while the less important people had silver or gold ; but those times have passed and now you can get cupcakes and things like that surrounded by foil of aluminium . aluminium is a very good metal for making things because it has a very thin coating of aluminium oxide on the surface which prevents it [ from ] reacting with things . but as soon as that coating goes it becomes very reactive . alfred worden : hadley base , do you read houston ? david scott : yeah . now , 5 by , joe . worden : okay . worden : and i guess we 're standing by for your high-gain alignment per the checklist . scott : okay , stand by . you may have seen our video where we put copper chloride in one of these cupcake holders ... [ first of all i 'm going to dissolve some up and make a fairly concentrated solution . i 'm going to place this here . ] ... and what came out was this , or rather the copper chloride came out through the hole . [ it starts boiling really quite nicely . now , imagine i was doing this for my children who were quite small at that time , and ... voosh ! ] and the aluminium was completely dissolved up forming aluminium chloride and copper metal . in my own research , aluminium is quite important ; quite a lot of our equipment uses aluminium . not so much for the high pressure tubing that we use because quite a lot of my reaserch involves high pressures but we use it for the metal blocks that we put round the tubing so that we can heat it up . aluminium has a good electrical conductivity , and it 's also easy to machine . this is a piece of equipment here where we have a tube going down the middle . you can see the diameter of the tube here . around it is an aluminium block and an electrical heater . now , this particular case there was an accident , or a mishap , because the thermocouple that was controlling the temperature of this fell out . so , the heater got hotter and hotter , and eventually , the aluminium melted and poured down here . and i think this is really beautiful . well , fortunately , i was not in the lab or i would 've got very angry with my students but i think when it happened it was quite exciting ; this would have been glowing almost red because the melting point of aluminium is around 500 degrees centigrade . but then once it formed originally it was very shiny but quickly , it again developed the surface layer of aluminium oxide . if you have fine particles of aluminium and blow them into a flame ... ... then they will burn quite spectacularly and you form aluminium oxide . now , on the face of it , aluminium oxide sounds a rather boring compound but it 's really very useful and we use it quite a lot in our research in all sorts of different ways . it looks like a white powder . not very exciting . but in our group this aluminium oxide has been a fantastic catalyst all sorts of reactions that we did n't expect have gone with this material . my students keep it in a bottle almost like a magic catalyst and i 've only been given a little to show you . it acts as a solid acid which can be used at very high temperature and will get various acid-catalyzed reactions of organic compounds . it will make ethers , we have made various alkynes and a whole series of different compounds and my students still use it very much . if you melt the aluminium oxide , which we ca n't do here but can be done industrially , you can make single crystals which are transparent like glass and then you can grow a single crystal tube , like this one , which because it 's a single crystal , it 's terrifically strong . it 's the defects that make something weak and so if you have just one crystal there are no defects and so it 's very strong . so you can put a very high pressure inside this tube without it blowing up . brady : but you could make that tube out of metal , professor . professor : but , if you have a metal then you ca n't see what 's going on inside , and we 're using these tubes for photochemical reactions . so , we take a light like this , and shine it on the chemicals going through the tube under high pressure and we can convert one chemical into another . we can do this very efficiently because the light is absorbed by the molecules that we want to react and so we dont waste the energy on everything else . and using leds , which are a very efficient light source , you can get a process that is very energy efficient and it all depends on having this sapphire tube . this is synthetic sapphire . the real sapphire , the gems , have impurities in them , of other metals , which give them the nice colors , particularly the blue . princess kate has a blue sapphire ring which belonged to her husband 's mother , princess di , before her . and so , these are very valuable ones . but synthetic sapphire is also expensive but not in the same class as a natural gem . brady : what can nature do that the guys at the sapphire factory ca n't do ? professor : nature has time . the people who grow this will take hours or days or perhaps weeks to grow it . nature can spend thousands or millions of years growing a particular gem and therefore they can heat it up and cool it down in natural surroundings , in volcanoes ... or whatever far more slowly than people can afford to do industrially . there 's a lot of argument whether you should call it aluminum or aluminium now , there is n't a totally correct one because both forms are acceptable . but , all or nearly all chemists use aluminium because it 's very important to use a standardized nomenclature right across the world . and i think aluminium sounds nicer . student : hi professor , my question is is it aluminum or aluminium ? 'cause i want to know what to call my aluminium model . apparantly , there was a decision in 1990 by iupac the international union of pure and applied chemistry that it should definately be called a l u m i n i u m but then they relented three years later and said you could use aluminum as well . but if you 're a serious chemist you really need to say aluminium , because otherwise people wo n't find your papers , your publications , when they search because they 'll almost certainly put an `` i '' ' in the name . aluminium is frequently used or used [ to be ] frequently used kkfor sauce pans , for cooking in because it 's easy to make , easy to machine and particularly when people used electric stoves it was easy to make a flat bottom so that you got good contact between the electric element and the sauce pan . the problem with aluminium sauce pans is that if you 're cooking some fairly acidic food , for example boiling lemons or rhubarb something like that which is quite acidic you can dissolve some of the aluminium and people got quite worried about getting aluminium in their food . also , if you cook red cabbage , which is an indicator ; blue for alkali , red for acid , then if you boil it in an aluminium sauce pan it goes blue . and earlier in my carreer i used a red cabbage together with a white one to make a union jack , a u.k. flag with a mixture of red and blue-red cabbage and the white from the white cabbage . unfortionately , i 've lost the photo ; brady is very cross with me . but it was quite fun cooking it in the kitchen . i did it once myself , but it was such a lot of work that the second time a got one of my students to do it .
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it will make ethers , we have made various alkynes and a whole series of different compounds and my students still use it very much . if you melt the aluminium oxide , which we ca n't do here but can be done industrially , you can make single crystals which are transparent like glass and then you can grow a single crystal tube , like this one , which because it 's a single crystal , it 's terrifically strong . it 's the defects that make something weak and so if you have just one crystal there are no defects and so it 's very strong .
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a single crystal sapphire tube is very strong , mainly because :
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hi , i ’ m john green , and this is crash course world history . let ’ s begin today with a question . why am i alive ? also , why don ’ t i have any eyes ? ah , that ’ s better . the way we answer that question ends up organizing all kinds of other thoughts , like what we should value , and how we should behave , and if we should eat meat , and whether we should dump that boy who is very nice , but insanely clingy , in a way that he can not possibly think is attractive . all of which adds up- uh , mr. green , mr. green , uh , are you talking about me ? yes , i ’ m talking about you , me from the past . i ’ m telling you that one of the reasons we study history is so that you can be a less terrible boyfriend , but more on that momentarily . [ theme music ] today we ’ re going to talk about civilizations , but in order to do that , we have to talk about talking about civilizations , because it ’ s a problematic word . so problematic , in fact , that i have to turn to camera 2 to discuss it . certain conglomerations of humans are seen as civilizations , whereas , say , nomadic cultures generally aren ’ t , unless , you are -- say it with me -- the mongols by calling some groups civilizations , you imply that all other social orders are uncivilized , which is basically just another way of saying that they ’ re savages or barbarians . side note : originally greek , the word barbarian denoted anyone who did not speak ancient greek , because to the greeks , all other languages sounded like bar bar bar bar bar bar . so , that is to say that we are all essentially barbarians , except for the classics majors , which is worth remembering when we ’ re discussing civilizations . civilizations are like most of the things we like to study , they ’ re intellectual constructs . no one woke up in the city of thebe ’ s in egypt one morning and said , “ what a beautiful morning , i sure am living at the height of egyptian civilization. ” still , they ’ re useful constructs , particularly when you ’ re comparing one civilization to another . they ’ re less useful when you ’ re comparing a civilization to a non-civilization type social order , which is why we will try to avoid that . and yes , i am getting to the good boyfriend stuff . patience , grasshopper . so what is a civilization ? well , diagnosing a civilization is a little like like diagnosing an illness . if you have four or more of the following symptoms , you might be a civilization . surplus production . once one person can make enough food to feed several people , it becomes possible to build a city , another symptom of civilization . it also leads to the specialization of labor , which in turn leads to trade . like , if everybody picks berries for a living , there ’ s no reason to trade , because i have berries , and you have berries , but if i pick berries for a living and you make hammers , suddenly , we have cause to trade . civilizations are also usually associated with social stratification , centralized government , shared values , generally in the form of religion , and writing . and at least in the early days , they were almost always associated with rivers . these days you can just bisect a segment of land horizontally and vertically , and boom , build a city . but 5000 years ago , civilizations were almost always associated with rivers . whether that ’ s the tigris and euphrates , the yellow river , the nile , the amazon basin , the coatzacoalcos - gaaah ! i was doing so good until i got to coatzacoalcos ! ( computer says : coatzacoalcos ) coatzacoalcos . maybe . why river valleys ? they ’ re flat , they ’ re well watered , and when they flood , they deposit nutrient-rich silt . we ’ ll have more to say about most of these civilizations later , but let ’ s talk about this guy , the indus valley civilization , ‘ cause it ’ s my all time favorite . the indus valley civilization was located in the flood plain of the indus and sarawati rivers , and it was about the best place in the world to have an ancient civilization because the rivers flooded very reliably twice a year , which meant that it had the most available calories per acre of pretty much anywhere on the planet . we know the indus valley civilization flourished a long time ago . probably around 3000 bce . why is that question literally hanging over my head ? but people of the indus valley were trading with mesopotamians as early as 3500 bce . we also know that it was the largest of the ancient civilizations . archaeologists have discovered more than 1500 sites . so what do we know about this civilization ? let ’ s go to the thought bubble . everything we know about the indus valley civilization comes from archaeology , because while they did use written language , we don ’ t know how to read it , and no rosetta stone has thus appeared to help us learn it . i meant the other rosetta stone , thought bubble , yeah . although , come to think of it , either would be acceptable . so here ’ s what we know , they had amazing cities . harappa and mohenjo daro are the best known , with dense , multi-story homes constructed out of uniformly sized bricks along perpendicular streets . i mean this wasn ’ t some ancient world version of houston , more like chicago . this means they must have had some form of government and zoning , but we don ’ t know what gave this government its authority . cities were oriented to catch the wind and provide a natural form of air conditioning . and they were clean . most homes were connected to a centralized drainage system that used gravity to carry waste and water out of the city in big sewer ditches that ran under the main avenues , a plumbing system that would have been the envy of many 18th century european cities . also , in mohenjo daro , the largest public building was not a temple or a palace , but a public bath , which historians call the great bath . we don ’ t know what the great bath was used for , but since later indian culture placed a huge emphasis on ritual purity , which is the basis for the caste system , some historians have speculated that the bath might have been like a giant baptismal pool . also , they traded . one of the coolest things that the indus valley civilization produced were seals used as identification markers on goods and clay tablets . these seals contained the writing that we still can ’ t decipher , and a number of fantastic designs , many featuring animals and monsters . one of the most famous and frightening is of a man with what looks like water buffalo horns on his head , sitting cross-legged between a tiger and a bull . we don ’ t know what ’ s really going on here , but it ’ s safe to say that this was a powerful dude , because he seems to be able to control the tiger . how do these seals let us know that they traded ? well , because we found them in mesopotamia , not the indus valley . plus , archaeologists have found stuff like bronze in the indus valley that is not native to the region . so what did they trade ? cotton cloth . still such a fascinating export , incidentally that it will be the subject of the 40th and final video in this very series . but here ’ s the most amazing thing about the indus valley people . they were peaceful . despite archaeologists finding 1500 sites , they have found very little evidence of warfare , almost no weapons . thanks thought bubble . ok , before we talk about the fascinating demise of the indus valley civilization . it ’ s time for the open letter . magic ! i wonder what the secret compartment has for me today ? oh ! fancy clothes . i guess the secret compartment didn ’ t think i was dressed up enough for the occasion . an open letter to historians . dear historians , the great bath ? really ? the great bath ? i ’ m trying to make history fascinating , and you give me a term that evokes scented candles , bath salts and frederic fekkai hair products ? i know sometimes the crushingly boring names of history aren ’ t your fault . you didn ’ t name the federalist papers or the austro-hungarian empire or adam smith . but when you do get a chance to name something , you go with the great bath ? not the epic bath of mohenjo daro , or the bath to end all baths , or the pool that ruled , or the moist mystery of mohenjo daro or the wet wonder ? the great bath ? really ? you can do better . best wishes , john green . so what happened to these people ? well , here ’ s what didn ’ t happen to them . they didn ’ t morph into the current residents of that area of the world , hindu indians or muslim pakistanis . those people probably came from the caucasus . instead , sometime around 1750 bce , the indus valley civilization declined until it faded into obscurity . why ? historians have three theories . one : conquest ! turns out to be a terrible military strategy not to have any weapons , and it ’ s possible people from the indus valley were completely overrun by people from the caucasus . two : environmental disaster ! it ’ s possible they brought about their own end by destroying their environment . three : earthquake ! the most interesting theory is that a massive earthquake changed the course of the rivers so much that a lot of the tributaries dried up . without adequate water supplies for irrigation , the cities couldn ’ t sustain themselves , so people literally picked up and headed for greener pastures . well , probably not pastures , it ’ s unlikely they became nomads . they probably just moved to a different plain an continued their agricultural ways . i am already boring you and i haven ’ t even told you yet how to be a better boyfriend and/or girlfriend . i ’ m going to do that now . so we don ’ t know why the indus valley civilization ended , but we also don ’ t really know why it started . why did these people build cities , and dig swimming pools , and make unnecessarily ornate seals ? were they motivated by hunger , fear , a desire for companionship , the need to be near their sacred spaces , or a general feeling that city life was just more awesome than foraging ? thinking about what motivated them to structure their life as they did helps us to think about how we structure our own lives . in short , you ’ re clingy because you ’ re motivated by fear and a need for companionship , and she finds it annoying because it ’ s enough work having to be responsible for herself without having to also be responsible for you . also , you ’ re not really helping her by clinging , and from the indus valley in the bronze age , to school life today , human life is all about collaboration . trading cloth for bronze , building cities together , and collaborating to make sure that human lives are tilted to catch the wind . next week we will travel here to discuss the hot mess o ’ potamia , but in the meantime , if you have any questions , leave them in comments , and our team of semi-trained semi-professionals will do their best to answer them . also , you ’ ll find some suggested resources in the video info below , he said , pointing at his pants . thanks for watching , and we ’ ll see you next week !
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so , that is to say that we are all essentially barbarians , except for the classics majors , which is worth remembering when we ’ re discussing civilizations . civilizations are like most of the things we like to study , they ’ re intellectual constructs . no one woke up in the city of thebe ’ s in egypt one morning and said , “ what a beautiful morning , i sure am living at the height of egyptian civilization. ” still , they ’ re useful constructs , particularly when you ’ re comparing one civilization to another .
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what would you like to learn more about ?
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they call me the tornado chaser . when the wind is up and conditions are right , i get in my car and follow violent storms . `` crazy , '' you say ? perhaps , but really i chase these sky beasts to learn about them . i want to share with you what i know . tornadoes are rapidly rotating columns of air that form inside storms that connect with the ground via a funnel of cloud . when that happens , they tear across the earth , posing a huge threat to life and property . because of this , there 's a great deal of research into these phenomena , but the truth is , there 's still a lot we do n't know about how tornadoes form . the conditions that may give rise to one tornado wo n't necessarily cause another . but we have learned a lot since people first started recording tornadoes , like how to recognize the signs when one is brewing in the sky . are you coming along for the ride ? tornadoes begin with a thunderstorm but not just any thunderstorm . these are especially powerful , towering thunderstorms called supercells . reaching up to over 50,000 feet , they bring high force winds , giant hailstones , sometimes flooding and great flashes of lightning , too . these are the kinds of storms that breed tornadoes , but only if there are also very specific conditions in place , clues that we can measure and look out for when we 're trying to forecast a storm . rising air is the first ingredient needed for a tornado to develop . any storm is formed when condensation occurs , the byproducts of the clouds . condensation releases heat , and heat becomes the energy that drives huge upward drafts of air . the more condensation and the bigger the storm clouds grow , the more powerful those updrafts become . in supercells , this rising airmass is particularly strong . as the air climbs , it can change direction and start to move more quickly . finally , at the storm 's base , if there is a lot of moisture , a huge cloud base develops , giving the tornado something to feed off later , if it gets that far . when all these things are in place , a vortex can develop enclosed by the storm , and forming a wide , tall tube of spinning air that then gets pulled upwards . we call this a mesocyclone . outside , cool , dry , sinking air starts to wrap around the back of this mesocyclone , forming what 's known as a rear flank downdraft . this unusual scenario creates a stark temperature difference between the air inside the mesocyclone , and the air outside , building up a level of instability that allows a tornado to thrive . then , the mesocyclone 's lower part becomes tighter , increasing the speed of the wind . if , and that 's a big if , this funnel of air moves down into that large , moist cloud base at the bottom of the parent storm , it sucks it in and turns it into a rotating wall of cloud , forming a link between the storm that created it and the earth . the second that tube of spinning cloud touches the ground , it becomes a tornado . most are small and short-lived , producing winds of 65-110 miles per hour , but others can last for over an hour , producing 200 mile per hour winds . they are beautiful but terrifying , especially if you or your town is in its path . in that case , no one , not even tornado chasers like me , enjoy watching thing unfold . just like everything , however , tornadoes do come to an end . when the temperature difference disappears and conditions grow more stable , or the moisture in the air dries up , the once fierce parent storm loses momentum and draws its tornado back inside . even so , meteorologists and storm chasers like me will remain on the lookout , watching , always watching to see if the storm releases its long rope again .
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rising air is the first ingredient needed for a tornado to develop . any storm is formed when condensation occurs , the byproducts of the clouds . condensation releases heat , and heat becomes the energy that drives huge upward drafts of air .
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more condensation means :
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this is the story of three plastic bottles , empty and discarded . their journeys are about to diverge with outcomes that impact nothing less than the fate of the planet . but they were n't always this way . to understand where these bottles end up , we must first explore their origins . the heroes of our story were conceived in this oil refinery . the plastic in their bodies was formed by chemically bonding oil and gas molecules together to make monomers . in turn , these monomers were bonded into long polymer chains to make plastic in the form of millions of pellets . those were melted at manufacturing plants and reformed in molds to create the resilient material that makes up the triplets ' bodies . machines filled the bottles with sweet bubbily liquid and they were then wrapped , shipped , bought , opened , consumed and unceremoniously discarded . and now here they lie , poised at the edge of the unknown . bottle one , like hundreds of millions of tons of his plastic brethren , ends up in a landfill . this huge dump expands each day as more trash comes in and continues to take up space . as plastics sit there being compressed amongst layers of other junk , rainwater flows through the waste and absorbs the water-soluble compounds it contains , and some of those are highly toxic . together , they create a harmful stew called leachate , which can move into groundwater , soil and streams , poisoning ecosystems and harming wildlife . it can take bottle one an agonizing 1,000 years to decompose . bottle two 's journey is stranger but , unfortunately , no happier . he floats on a trickle that reaches a stream , a stream that flows into a river , and a river that reaches the ocean . after months lost at sea , he 's slowly drawn into a massive vortex , where trash accumulates , a place known as the great pacific garbage patch . here the ocean 's currents have trapped millions of pieces of plastic debris . this is one of five plastic-filled gyres in the world 's seas . places where the pollutants turn the water into a cloudy plastic soup . some animals , like seabirds , get entangled in the mess . they , and others , mistake the brightly colored plastic bits for food . plastic makes them feel full when they 're not , so they starve to death and pass the toxins from the plastic up the food chain . for example , it 's eaten by lanternfish , the lanternfish are eaten by squid , the squid are eaten by tuna , and the tuna are eaten by us . and most plastics do n't biodegrade , which means they 're destined to break down into smaller and smaller pieces called micro plastics , which might rotate in the sea eternally . but bottle three is spared the cruel purgatories of his brothers . a truck brings him to a plant where he and his companions are squeezed flat and compressed into a block . okay , this sounds pretty bad , too , but hang in there . it gets better . the blocks are shredded into tiny pieces , which are washed and melted , so they become the raw materials that can be used again . as if by magic , bottle three is now ready to be reborn as something completely new . for this bit of plastic with such humble origins , suddenly the sky is the limit .
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here the ocean 's currents have trapped millions of pieces of plastic debris . this is one of five plastic-filled gyres in the world 's seas . places where the pollutants turn the water into a cloudy plastic soup .
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what 's one way we can reduce plastic 's impact on the environment ?
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translator : andrea mcdonough reviewer : bedirhan cinar once upon a time in the magical and very round land of pi , there lived six swashbuckling musketeers . there names were parentheses , exponents , multiplication , division , addition , and subtraction . but each was known best by his or her mark : the two hands ready to catch a fly of parentheses , the small and raised digits of exponents , the mighty x of multiplication , slash of division , plus of addition , and , well , you can guess the symbol by which little subtraction was best known . the land of pi was not necessarily the most peaceful place , and that 's why the numbers of the kingdom needed the musketeers . the land of pi had been ruled by the numbers as anarcho-syndicalist commune , each number with a vote , but , one powerful number from what we 'll call the imperial senate , engineered a war between some robot things and the knights of the kingdom , and then installed himself as supreme emperor , and then puff the magic digit dragon ate him , and a princess or two , and , well , all the other numbers in the land of pi actually . it was kind of a big day . anyway , the musketeers were called to action to save the land of pi from the voracious dragon . they rode towards him on their valiant steeds and attacked . first multiplication , then parentheses , but that did n't work . the dragon continued eating people . so addition tried , but was thrown aside . exponents leaped at the beast and was quickly squashed . nothing was working . the musketeers huddled and formulated a plan . they would attack in sequence , but who should go first ? they bickered for a while , the dragon ate a few more princesses , and then they finally agreed . they jumped into the first , smallest parentheses inside the great puff the digit dragon . parentheses pointed out where to work first and protected exponents , multiplication , division , addition , and subtraction while they diced and sliced . first here , then , move over there , then there . look out ! there 's another set ! parentheses pointed and exponents took the lead . then , it was multiplication , division , addition , and subtraction , each in turn , always the same order . p-e-m-d-a-s when they finished that set , they went to another , and another , always working inside the parentheses in pemdas order . pop ! pop ! pop ! pop ! pop ! pemdas , there is another spot ! do n't forget , there can be parentheses inside parentheses . there 's one ! and that tricky exponent . there we go ! finally , the pemdas musketeers had whittled puff down to his last fearsome roar . but , having vanquished puff the magic digit dragon , all the empire 's numbers sprang again from this tiny little number one , and they all lived happily ever after . except for the emperor number , which they threw into the mouth of an ancient nesting creature in the desert . the end .
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finally , the pemdas musketeers had whittled puff down to his last fearsome roar . but , having vanquished puff the magic digit dragon , all the empire 's numbers sprang again from this tiny little number one , and they all lived happily ever after . except for the emperor number , which they threw into the mouth of an ancient nesting creature in the desert .
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what were all the numbers so afraid of ?
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taking that internship in a remote mountain lab might not have been the best idea . pulling that lever with the skull symbol just to see what it did probably was n't so smart , either , but now is not the time for regrets because you need to get away from these mutant zombies fast . with you are the janitor , the lab assistant , and the old professor . you 've gotten a headstart , but there 's only one way to safety : across an old rope bridge spanning a massive gorge . you can dash across in a minute , while the lab assistant takes two minutes . the janitor is a bit slower and needs five minutes , and the professor takes a whole ten minutes , holding onto the ropes every step of the way . by the professor 's calculations , the zombies will catch up to you in just over 17 minutes , so you only have that much time to get everyone across and cut the ropes . unfortunately , the bridge can only hold two people at a time . to make matters worse , it 's so dark out that you can barely see , and the old lantern you grabbed on your way only illuminates a tiny area . can you figure out a way to have everyone escape in time ? remember : no more than two people can cross the bridge together , anyone crossing must either hold the lantern or stay right next to it , and any of you can safely wait in the dark on either side of the gorge . most importantly , everyone must be safely across before the zombies arrive . otherwise , the first zombie could step on the bridge while people are still on it . finally , there are no tricks to use here . you ca n't swing across , use the bridge as a raft , or befriend the zombies . pause the video now if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 at first it might seem like no matter what you do , you 're just a minute or two short of time , but there is a way . the key is to minimize the time wasted by the two slowest people by having them cross together . and because you 'll need to make a couple of return trips with the lantern , you 'll want to have the fastest people available to do so . so , you and the lab assistant quickly run across with the lantern , though you have to slow down a bit to match her pace . after two minutes , both of you are across , and you , as the quickest , run back with the lantern . only three minutes have passed . so far , so good . now comes the hard part . the professor and the janitor take the lantern and cross together . this takes them ten minutes since the janitor has to slow down for the old professor who keeps muttering that he probably should n't have given the zombies night vision . by the time they 're across , there are only four minutes left , and you 're still stuck on the wrong side of the bridge . but remember , the lab assistant has been waiting on the other side , and she 's the second fastest of the group . so she grabs the lantern from the professor and runs back across to you . now with only two minutes left , the two of you make the final crossing . as you step on the far side of the gorge , you cut the ropes and collapse the bridge behind you , just in the nick of time . maybe next summer , you 'll just stick to the library .
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to make matters worse , it 's so dark out that you can barely see , and the old lantern you grabbed on your way only illuminates a tiny area . can you figure out a way to have everyone escape in time ? remember : no more than two people can cross the bridge together , anyone crossing must either hold the lantern or stay right next to it , and any of you can safely wait in the dark on either side of the gorge . most importantly , everyone must be safely across before the zombies arrive .
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why does everyone crossing the bridge have to stay together ?
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the human brain is one of the most sophisticated organs in the world , a supercomputer made of billions of neurons that processes and controls all of our senses , thoughts , and actions . but there was something charles darwin found even more impressive : the brain of an ant , which he called one of the most marvelous atoms of matter in the world . if you find it hard to believe that something so tiny could have a complex brain , you 're not alone . in his project to classify and describe all living things , swedish naturalist carl linnaeus assumed insects had no brains at all . he was wrong , but understandably so . insect brains are not only miniscule , but in many respects , they function differently than our own . one of the most noticeable differences is that an insect that loses its head can still walk , scratch itself , breathe , and even fly . this is because while our nervous system works like a monarchy , with the brain calling the shots , the insect nervous system works more like a decentralized federation . many insect activities , like walking or breathing , are coordinated by clusters of neurons , also known as ganglia , along their bodies . together with the brain , these local ganglia form the insect nervous system . while an insect can do a lot with just its local ganglia , the brain is still crucial for its survival . an insect 's brain lets it perceive the world through sight and smell . it also chooses suitable mates , remembers locations of food sources and hives , regulates communication , and even coordinates navigation over huge distances . and this vast diversity of behaviors is controlled by an organ the size of the head of a pin , with less than one million neurons , compared to our 86 billion . but even though the insect brain is organized very differently from ours , there are some striking similarities . for example , most insects have smell detectors on their antennae , similar to those found in human noses . and our primary olfactory brain regions look and function rather similarly , with clusters of neurons activated and deactivated in precise timing to code for specific scents . scientists have been astonished by these similarities because insects and humans are not very closely related . in fact , our last common ancestor was a simple worm-like creature that lived more than 500 million years ago . so how did we end up with such similar brain structures when our evolution took almost entirely different paths ? scientists call this phenomenon convergent evolution . it 's the same principle behind birds , bats , and bees separately evolving wings . similar selective pressures can cause natural selection to favor the same evolutionary strategy in species with vastly different evolutionary pasts . by studying the comparison between insect and human brains , scientists can thus understand which of our brain functions are unique , and which are general solutions to evolutionary problems . but this is not the only reason scientists are fascinated by insect brains . their small size and simplicity makes it easier to understand exactly how neurons work together in the brain . this is also valuable for engineers , who study the insect brain to help design control systems for everything from self-flying airplanes to tiny search-and-rescue roach bots . so , size and complexity are not always the most impressive things . the next time you try to swat a fly , take a moment to marvel at the efficiency of its tiny nervous system as it outsmarts your fancy brain .
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many insect activities , like walking or breathing , are coordinated by clusters of neurons , also known as ganglia , along their bodies . together with the brain , these local ganglia form the insect nervous system . while an insect can do a lot with just its local ganglia , the brain is still crucial for its survival .
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in the insect nervous system :
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you and nine other individuals have been captured by super intelligent alien overlords . the aliens think humans look quite tasty , but their civilization forbids eating highly logical and cooperative beings . unfortunately , they 're not sure whether you qualify , so they decide to give you all a test . through its universal translator , the alien guarding you tells you the following : you will be placed in a single-file line facing forward in size order so that each of you can see everyone lined up ahead of you . you will not be able to look behind you or step out of line . each of you will have either a black or a white hat on your head assigned randomly , and i wo n't tell you how many of each color there are . when i say to begin , each of you must guess the color of your hat starting with the person in the back and moving up the line . and do n't even try saying words other than black or white or signaling some other way , like intonation or volume ; you 'll all be eaten immediately . if at least nine of you guess correctly , you 'll all be spared . you have five minutes to discuss and come up with a plan , and then i 'll line you up , assign your hats , and we 'll begin . can you think of a strategy guaranteed to save everyone ? pause the video now to figure it out for yourself . answer in : 3 answer in : 2 answer in : 1 the key is that the person at the back of the line who can see everyone else 's hats can use the words `` black '' or `` white '' to communicate some coded information . so what meaning can be assigned to those words that will allow everyone else to deduce their hat colors ? it ca n't be the total number of black or white hats . there are more than two possible values , but what does have two possible values is that number 's parity , that is whether it 's odd or even . so the solution is to agree that whoever goes first will , for example , say `` black '' if he sees an odd number of black hats and `` white '' if he sees an even number of black hats . let 's see how it would play out if the hats were distributed like this . the tallest captive sees three black hats in front of him , so he says `` black , '' telling everyone else he sees an odd number of black hats . he gets his own hat color wrong , but that 's okay since you 're collectively allowed to have one wrong answer . prisoner two also sees an odd number of black hats , so she knows hers is white , and answers correctly . prisoner three sees an even number of black hats , so he knows that his must be one of the black hats the first two prisoners saw . prisoner four hears that and knows that she should be looking for an even number of black hats since one was behind her . but she only sees one , so she deduces that her hat is also black . prisoners five through nine are each looking for an odd number of black hats , which they see , so they figure out that their hats are white . now it all comes down to you at the front of the line . if the ninth prisoner saw an odd number of black hats , that can only mean one thing . you 'll find that this strategy works for any possible arrangement of the hats . the first prisoner has a 50 % chance of giving a wrong answer about his own hat , but the parity information he conveys allows everyone else to guess theirs with absolute certainty . each begins by expecting to see an odd or even number of hats of the specified color . if what they count does n't match , that means their own hat is that color . and everytime this happens , the next person in line will switch the parity they expect to see . so that 's it , you 're free to go . it looks like these aliens will have to go hungry , or find some less logical organisms to abduct .
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you 'll find that this strategy works for any possible arrangement of the hats . the first prisoner has a 50 % chance of giving a wrong answer about his own hat , but the parity information he conveys allows everyone else to guess theirs with absolute certainty . each begins by expecting to see an odd or even number of hats of the specified color . if what they count does n't match , that means their own hat is that color . and everytime this happens , the next person in line will switch the parity they expect to see .
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why can ’ t the first person be sure of their hat color ?
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if you 're ever walking down the street and come across an oddly stretched out image , like this , you 'll have an opportunity to see something remarkable , but only if you stand in exactly the right spot . that happens because these works employ a technique called anamorphosis . anamorphosis is a special case of perspective art , where artists represent realistic three-dimensional views on two-dimensional surfaces . though it 's common today , this kind of perspective drawing has only been around since the italian renaissance . ancient art often showed all figures on the same plane , varying in size by symbolic importance . classical greek and roman artists realized they could make objects seem further by drawing them smaller , but many early attempts at perspective were inconsistent or incorrect . in 15th century florence , artists realized the illusion of perspective could be achieved with higher degrees of sophistication by applying mathematical principles . in 1485 , leonardo da vinci manipulated the mathematics to create the first known anamorphic drawing . a number of other artists later picked up the technique , including hans holbein in `` the ambassadors . '' this painting features a distorted shape that forms into a skull as the viewer approaches from the side . in order to understand how artists achieve that effect , we first have to understand how perspective drawings work in general . imagine looking out a window . light bounces off objects and into your eye , intersecting the window along the way . now , imagine you could paint the image you see directly onto the window while standing still and keeping only one eye open . the result would be nearly indistinguishable from the actual view with your brain adding depth to the 2-d picture , but only from that one spot . standing even just a bit off to the side would make the drawing lose its 3-d effect . artists understand that a perspective drawing is just a projection onto a 2-d plane . this allows them to use math to come up with basic rules of perspective that allow them to draw without a window . one is that parallel lines , like these , can only be drawn as parallel if they 're parallel to the plane of the canvas . otherwise , they need to be drawn converging to a common point known as the vanishing point . so that 's a standard perspective drawing . with an anamorphic drawing , like `` the ambassadors , '' directly facing the canvas makes the image look stretched and distorted , but put your eye in exactly the right spot way off to the side , and the skull materializes . going back to the window analogy , it 's as if the artist painted onto a window positioned at an angle instead of straight on , though that 's not how renaissance artists actually created anamorphic drawings . typically , they draw a normal image onto one surface , then use a light , a grid , or even strings to project it onto a canvas at an angle . now let 's say you want to make an anamorphic sidewalk drawing . in this case , you want to create the illusion that a 3-d image has been added seamlessly into an existing scene . you can first put a window in front of the sidewalk and draw what you want to add onto the window . it should be in the same perspective as the rest of the scene , which might require the use of those basic rules of perspective . once the drawing 's complete , you can use a projector placed where your eye was to project your drawing down onto the sidewalk , then chalk over it . the sidewalk drawing and the drawing on the window will be nearly indistinguishable from that point of view , so viewers ' brains will again be tricked into believing that the drawing on the ground is three-dimensional . and you do n't have to project onto a flat surface to create this illusion . you can project onto multiple surfaces , or assemble a jumble of objects , that from the right point of view , appears to be something else entirely . all over the planet , you can find solid surfaces giving way to strange , wonderful , or terrifying visions . from your sidewalk to your computer screen , these are just some of the ways that math and perspective can open up whole new worlds .
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though it 's common today , this kind of perspective drawing has only been around since the italian renaissance . ancient art often showed all figures on the same plane , varying in size by symbolic importance . classical greek and roman artists realized they could make objects seem further by drawing them smaller , but many early attempts at perspective were inconsistent or incorrect .
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give some examples of how creativity and problem solving is used in both mathematics and art .
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the year was 1816 . europe and north america had just been through a devastating series of wars , and a slow recovery seemed to be underway , but nature had other plans . after two years of poor harvests , the spring brought heavy rains and cold , flooding the rivers and causing crop failures from the british isles to switzerland . while odd-colored snow fell in italy and hungary , famine , food riots and disease epidemics ensued . meanwhile , new england was blanketed by a strange fog that would not disperse as the ground remained frozen well into june . in what came to be known as `` the year without a summer , '' some thought the apocalypse had begun . a mood captured in lord byron 's poem `` darkness '' : `` i had a dream which was not all a dream . the bright sun was extinguish 'd , and the stars did wander darkling in the eternal space , rayless , and pathless , and the icy earth swung blind and blackening in the moonless air ; morn came and went -- and came , and brought no day . '' they had no way of knowing that the real source of their misfortunes had occurred a year ago thousands of miles away . the 1815 eruption of mount tambora on the indonesian island of sumbawa was what is known as a supervolcano , characterized by a volume of erupted material , many times greater than that of ordinary volcanoes . and while the popular image of volcanic destruction is molten rock engulfing the surrounding land , far greater devastation is caused by what remains in the air . volcanic ash , dispersed by wind , can blanket the sky for days , while toxic gases , such as sulfur dioxide , react in the stratosphere , blocking out solar radiation and drastically cooling the atmosphere below . the resulting volcanic winter , along with other effects such as acid rain , can effect multiple continents , disrupting natural cycles and annihilating the plant life on which other organisms , including humans , depend . releasing nearly 160 cubic kilometers of rock , ash and gas , the mount tambora eruption was the largest in recorded history , causing as many as 90,000 deaths . but previous eruptions have been even more deadly . the 1600 eruption of peru 's huaynaputina is likely to have triggered the russian famine , that killed nearly two million , while more ancient eruptions have been blamed for major world events , such as the fall of the chinese xia dynasty , the disappearance of the minoan civilization , and even a genetic bottleneck in human evolution that may have resulted from all but a few thousand human beings being wiped out 70,000 years ago . one of the most dangerous types of supervolcano is an explosive caldera , formed when a volcanic mountain collapses after an eruption so large that the now-empty magma chamber can no longer support its weight . but though the above-ground volcano is gone , the underground volcanic activity continues . with no method of release , magma and volcanic gases continue to accumulate and expand underground , building up pressure until a massive and violent explosion becomes inevitable . and one of the largest active volcanic calderas lies right under yellowstone national park . the last time it erupted , 650,000 years ago , it covered much of north america in nearly two meters of ash and rock . scientists are currently monitoring the world 's active volcanoes , and procedures for predicting eruptions , conducting evacuations and diverting lava flows have improved over the years . but the massive scale and global reach of a supervolcano means that for many people there would be nowhere to run . fortunately , the current data shows no evidence of such an eruption occurring in the next few thousand years . but the idea of a sudden and unavoidable civilization-destroying apocalypse caused by events half a globe away will remain a powerful and terrifying vision . less fictional than we would like to believe . `` the winds were withered in the stagnant air , and the clouds perish 'd ; darkness had no need of aid from them -- she was the universe . '' - lord byron
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the year was 1816 . europe and north america had just been through a devastating series of wars , and a slow recovery seemed to be underway , but nature had other plans .
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what do you think were the main aspects of the events of 1816 that made people suspect a supernatural apocalypse ?
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we 've decided to make a new video about aluminium because it 's a long time over five years since we made the first one and ... we did n't say very much . aluminium is a surprisingly abundand element . if you look at this periodic table here , where the area of the different elements gives you a rough idea of the abundance you can see that aluminium is one of the most abundant metals up there with sodium , magnesium and calcium . more aluminum than potassium ; about the same or perhaps even more than iron . we 're never going to run out of aluminium . the problem with aluminium is that you do n't find aluminium metal in nature as a metal . it 's always tied up with other compounds ; mostly with oxygen , in clays . you know what clays are , the sort of muddy stuff that you get stuck on your shoes when it 's raining . to get the aluminium out of the clay , that is , to break the aluminium/oxygen bonds , which are very strong ; requires a lot of energy , which comes from electricity . so , making aluminium is very energy intensive . that 's why people like to recycle aluminium because once you 've got it , it 's worth preserving ; but it 's fantastically important because aluminium is a very light metal . and it 's often used as an alloy because the aluminium alloys are stronger than the aluminium itself , so , if you 're using it for aircraft or some other use like that where you want to combine lightness with strength then the stronger you can make it , the better . but when it was first made , in the 19th century , isolated as a metal it was terrifically valuable and there are stories of the french emperor serving his honored guests with aluminium plates or aluminium cutlery while the less important people had silver or gold ; but those times have passed and now you can get cupcakes and things like that surrounded by foil of aluminium . aluminium is a very good metal for making things because it has a very thin coating of aluminium oxide on the surface which prevents it [ from ] reacting with things . but as soon as that coating goes it becomes very reactive . alfred worden : hadley base , do you read houston ? david scott : yeah . now , 5 by , joe . worden : okay . worden : and i guess we 're standing by for your high-gain alignment per the checklist . scott : okay , stand by . you may have seen our video where we put copper chloride in one of these cupcake holders ... [ first of all i 'm going to dissolve some up and make a fairly concentrated solution . i 'm going to place this here . ] ... and what came out was this , or rather the copper chloride came out through the hole . [ it starts boiling really quite nicely . now , imagine i was doing this for my children who were quite small at that time , and ... voosh ! ] and the aluminium was completely dissolved up forming aluminium chloride and copper metal . in my own research , aluminium is quite important ; quite a lot of our equipment uses aluminium . not so much for the high pressure tubing that we use because quite a lot of my reaserch involves high pressures but we use it for the metal blocks that we put round the tubing so that we can heat it up . aluminium has a good electrical conductivity , and it 's also easy to machine . this is a piece of equipment here where we have a tube going down the middle . you can see the diameter of the tube here . around it is an aluminium block and an electrical heater . now , this particular case there was an accident , or a mishap , because the thermocouple that was controlling the temperature of this fell out . so , the heater got hotter and hotter , and eventually , the aluminium melted and poured down here . and i think this is really beautiful . well , fortunately , i was not in the lab or i would 've got very angry with my students but i think when it happened it was quite exciting ; this would have been glowing almost red because the melting point of aluminium is around 500 degrees centigrade . but then once it formed originally it was very shiny but quickly , it again developed the surface layer of aluminium oxide . if you have fine particles of aluminium and blow them into a flame ... ... then they will burn quite spectacularly and you form aluminium oxide . now , on the face of it , aluminium oxide sounds a rather boring compound but it 's really very useful and we use it quite a lot in our research in all sorts of different ways . it looks like a white powder . not very exciting . but in our group this aluminium oxide has been a fantastic catalyst all sorts of reactions that we did n't expect have gone with this material . my students keep it in a bottle almost like a magic catalyst and i 've only been given a little to show you . it acts as a solid acid which can be used at very high temperature and will get various acid-catalyzed reactions of organic compounds . it will make ethers , we have made various alkynes and a whole series of different compounds and my students still use it very much . if you melt the aluminium oxide , which we ca n't do here but can be done industrially , you can make single crystals which are transparent like glass and then you can grow a single crystal tube , like this one , which because it 's a single crystal , it 's terrifically strong . it 's the defects that make something weak and so if you have just one crystal there are no defects and so it 's very strong . so you can put a very high pressure inside this tube without it blowing up . brady : but you could make that tube out of metal , professor . professor : but , if you have a metal then you ca n't see what 's going on inside , and we 're using these tubes for photochemical reactions . so , we take a light like this , and shine it on the chemicals going through the tube under high pressure and we can convert one chemical into another . we can do this very efficiently because the light is absorbed by the molecules that we want to react and so we dont waste the energy on everything else . and using leds , which are a very efficient light source , you can get a process that is very energy efficient and it all depends on having this sapphire tube . this is synthetic sapphire . the real sapphire , the gems , have impurities in them , of other metals , which give them the nice colors , particularly the blue . princess kate has a blue sapphire ring which belonged to her husband 's mother , princess di , before her . and so , these are very valuable ones . but synthetic sapphire is also expensive but not in the same class as a natural gem . brady : what can nature do that the guys at the sapphire factory ca n't do ? professor : nature has time . the people who grow this will take hours or days or perhaps weeks to grow it . nature can spend thousands or millions of years growing a particular gem and therefore they can heat it up and cool it down in natural surroundings , in volcanoes ... or whatever far more slowly than people can afford to do industrially . there 's a lot of argument whether you should call it aluminum or aluminium now , there is n't a totally correct one because both forms are acceptable . but , all or nearly all chemists use aluminium because it 's very important to use a standardized nomenclature right across the world . and i think aluminium sounds nicer . student : hi professor , my question is is it aluminum or aluminium ? 'cause i want to know what to call my aluminium model . apparantly , there was a decision in 1990 by iupac the international union of pure and applied chemistry that it should definately be called a l u m i n i u m but then they relented three years later and said you could use aluminum as well . but if you 're a serious chemist you really need to say aluminium , because otherwise people wo n't find your papers , your publications , when they search because they 'll almost certainly put an `` i '' ' in the name . aluminium is frequently used or used [ to be ] frequently used kkfor sauce pans , for cooking in because it 's easy to make , easy to machine and particularly when people used electric stoves it was easy to make a flat bottom so that you got good contact between the electric element and the sauce pan . the problem with aluminium sauce pans is that if you 're cooking some fairly acidic food , for example boiling lemons or rhubarb something like that which is quite acidic you can dissolve some of the aluminium and people got quite worried about getting aluminium in their food . also , if you cook red cabbage , which is an indicator ; blue for alkali , red for acid , then if you boil it in an aluminium sauce pan it goes blue . and earlier in my carreer i used a red cabbage together with a white one to make a union jack , a u.k. flag with a mixture of red and blue-red cabbage and the white from the white cabbage . unfortionately , i 've lost the photo ; brady is very cross with me . but it was quite fun cooking it in the kitchen . i did it once myself , but it was such a lot of work that the second time a got one of my students to do it .
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we 've decided to make a new video about aluminium because it 's a long time over five years since we made the first one and ... we did n't say very much . aluminium is a surprisingly abundand element . if you look at this periodic table here , where the area of the different elements gives you a rough idea of the abundance you can see that aluminium is one of the most abundant metals up there with sodium , magnesium and calcium .
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in nature , aluminium is most frequently found bonded to which element ?
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translator : andrea mcdonough reviewer : bedirhan cinar these days scientists know how you inherit characteristics from your parents . they 're able to calculate probabilities of having a specific trait or getting a genetic disease according to the information from the parents and the family history . but how is this possible ? to understand how traits pass from one living being to its descendants , we need to go back in time to the 19th century and a man named gregor mendel . mendel was an austrian monk and biologist who loved to work with plants . by breeding the pea plants he was growing in the monastery 's garden , he discovered the principles that rule heredity . in one of most classic examples , mendel combined a purebred yellow-seeded plant with a purebred green-seeded plant , and he got only yellow seeds . he called the yellow-colored trait the dominant one , because it was expressed in all the new seeds . then he let the new yellow-seeded hybrid plants self-fertilize . and in this second generation , he got both yellow and green seeds , which meant the green trait had been hidden by the dominant yellow . he called this hidden trait the recessive trait . from those results , mendel inferred that each trait depends on a pair of factors , one of them coming from the mother and the other from the father . now we know that these factors are called alleles and represent the different variations of a gene . depending on which type of allele mendel found in each seed , we can have what we call a homozygous pea , where both alleles are identical , and what we call a heterozygous pea , when the two alleles are different . this combination of alleles is known as genotype and its result , being yellow or green , is called phenotype . to clearly visualize how alleles are distributed amongst descendants , we can a diagram called the punnett square . you place the different alleles on both axes and then figure out the possible combinations . let 's look at mendel 's peas , for example . let 's write the dominant yellow allele as an uppercase `` y '' and the recessive green allele as a lowercase `` y . '' the uppercase y always overpowers his lowercase friend , so the only time you get green babies is if you have lowercase y 's . in mendel 's first generation , the yellow homozygous pea mom will give each pea kid a yellow-dominant allele , and the green homozygous pea dad will give a green-recessive allele . so all the pea kids will be yellow heterozygous . then , in the second generation , where the two heterozygous kids marry , their babies could have any of the three possible genotypes , showing the two possible phenotypes in a three-to-one proportion . but even peas have a lot of characteristics . for example , besides being yellow or green , peas may be round or wrinkled . so we could have all these possible combinations : round yellow peas , round green peas , wrinkled yellow peas , wrinkled green peas . to calculate the proportions for each genotype and phenotype , we can use a punnett square too . of course , this will make it a little more complex . and lots of things are more complicated than peas , like , say , people . these days , scientists know a lot more about genetics and heredity . and there are many other ways in which some characteristics are inherited . but , it all started with mendel and his peas .
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so we could have all these possible combinations : round yellow peas , round green peas , wrinkled yellow peas , wrinkled green peas . to calculate the proportions for each genotype and phenotype , we can use a punnett square too . of course , this will make it a little more complex .
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in a few words , describe the differences in a recessive phenotype and a dominant genotype .
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when ultraviolet sunlight hits our skin , it affects each of us a little differently . depending on skin color , it will take only minutes of exposure to turn one person beetroot-pink , while another requires hours to experience the slightest change . so what 's to account for that difference and how did our skin come to take on so many different hues to begin with ? whatever the color , our skin tells an epic tale of human intrepidness and adaptability , revealing its variance to be a function of biology . it all centers around melanin , the pigment that gives skin and hair its color . this ingredient comes from skin cells called melanocytes and takes two basic forms . there 's eumelanin , which gives rise to a range of brown skin tones , as well as black , brown , and blond hair , and pheomelanin , which causes the reddish browns of freckles and red hair . but humans were n't always like this . our varying skin tones were formed by an evolutionary process driven by the sun . in began some 50,000 years ago when our ancestors migrated north from africa and into europe and asia . these ancient humans lived between the equator and the tropic of capricorn , a region saturated by the sun 's uv-carrying rays . when skin is exposed to uv for long periods of time , the uv light damages the dna within our cells , and skin starts to burn . if that damage is severe enough , the cells mutations can lead to melanoma , a deadly cancer that forms in the skin 's melanocytes . sunscreen as we know it today did n't exist 50,000 years ago . so how did our ancestors cope with this onslaught of uv ? the key to survival lay in their own personal sunscreen manufactured beneath the skin : melanin . the type and amount of melanin in your skin determines whether you 'll be more or less protected from the sun . this comes down to the skin 's response as sunlight strikes it . when it 's exposed to uv light , that triggers special light-sensitive receptors called rhodopsin , which stimulate the production of melanin to shield cells from damage . for light-skin people , that extra melanin darkens their skin and produces a tan . over the course of generations , humans living at the sun-saturated latitudes in africa adapted to have a higher melanin production threshold and more eumelanin , giving skin a darker tone . this built-in sun shield helped protect them from melanoma , likely making them evolutionarily fitter and capable of passing this useful trait on to new generations . but soon , some of our sun-adapted ancestors migrated northward out of the tropical zone , spreading far and wide across the earth . the further north they traveled , the less direct sunshine they saw . this was a problem because although uv light can damage skin , it also has an important parallel benefit . uv helps our bodies produce vitamin d , an ingredient that strengthens bones and lets us absorb vital minerals , like calcium , iron , magnesium , phosphate , and zinc . without it , humans experience serious fatigue and weakened bones that can cause a condition known as rickets . for humans whose dark skin effectively blocked whatever sunlight there was , vitamin d deficiency would have posed a serious threat in the north . but some of them happened to produce less melanin . they were exposed to small enough amounts of light that melanoma was less likely , and their lighter skin better absorbed the uv light . so they benefited from vitamin d , developed strong bones , and survived well enough to produce healthy offspring . over many generations of selection , skin color in those regions gradually lightened . as a result of our ancestor 's adaptability , today the planet is full of people with a vast palette of skin colors , typically , darker eumelanin-rich skin in the hot , sunny band around the equator , and increasingly lighter pheomelanin-rich skin shades fanning outwards as the sunshine dwindles . therefore , skin color is little more than an adaptive trait for living on a rock that orbits the sun . it may absorb light , but it certainly does not reflect character .
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whatever the color , our skin tells an epic tale of human intrepidness and adaptability , revealing its variance to be a function of biology . it all centers around melanin , the pigment that gives skin and hair its color . this ingredient comes from skin cells called melanocytes and takes two basic forms . there 's eumelanin , which gives rise to a range of brown skin tones , as well as black , brown , and blond hair , and pheomelanin , which causes the reddish browns of freckles and red hair .
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the ingredient that gives skin its color and a version of its own sunscreen is known as :
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imagine that one day , you 're summoned before a government panel . even though you have n't committed any crime , or been formally charged with one , you are repeatedly questioned about your political views , accused of disloyalty , and asked to incriminate your friends and associates . if you do n't cooperate , you risk jail or losing your job . this is exactly what happened in the united states in the 1950s as part of a campaign to expose suspected communists . named after its most notorious practitioner , the phenomenon known as mccarthyism destroyed thousands of lives and careers . for over a decade , american political leaders trampled democratic freedoms in the name of protecting them . during the 1930s and 1940s , there had been an active but small communist party in the united states . its record was mixed . while it played crucial roles in wider progressive struggles for labor and civil rights , it also supported the soviet union . from the start , the american communist party faced attacks from conservatives and business leaders , as well as from liberals who criticized its ties to the oppressive soviet regime . during world war ii , when the usa and ussr were allied against hitler , some american communists actually spied for the russians . when the cold war escalated and this espionage became known , domestic communism came to be seen as a threat to national security . but the attempt to eliminate that threat soon turned into the longest lasting and most widespread episode of political repression in american history . spurred on by a network of bureaucrats , politicians , journalists , and businessmen , the campaign wildly exaggerated the danger of communist subversion . the people behind it harassed anyone suspected of holding left-of-center political views or associating with those who did . if you hung modern art on your walls , had a multiracial social circle , or signed petitions against nuclear weapons , you might just have been a communist . starting in the late 1940s , fbi director j. edgar hoover used the resources of his agency to hunt down such supposed communists and eliminate them from any position of influence within american society . and the narrow criteria that hoover and his allies used to screen federal employees spread to the rest of the country . soon , hollywood studios , universities , car manufacturers , and thousands of other public and private employers were imposing the same political tests on the men and women who worked for them . meanwhile , congress conducted its own witchhunt subpoenaing hundreds of people to testify before investigative bodies like the house un-american activities committee . if they refused to cooperate , they could be jailed for contempt , or more commonly , fired and blacklisted . ambitious politicians , like richard nixon and joseph mccarthy , used such hearings as a partisan weapon accusing democrats of being soft on communism and deliberately losing china to the communist bloc . mccarthy , a republican senator from wisconsin became notorious by flaunting ever-changing lists of alleged communists within the state department . egged on by other politicians , he continued to make outrageous accusations while distorting or fabricating evidence . many citizens reviled mccarthy while others praised him . and when the korean war broke out , mccarthy seemed vindicated . once he became chair of the senate 's permanent subcommittee on investigations in 1953 , mccarthy recklessness increased . it was his investigation of the army that finally turned public opinion against him and diminished his power . mccarthy 's colleagues in the senate censured him and he died less than three years later , probably from alcoholism . mccarthyism ended as well . it had ruined hundreds , if not thousands , of lives and drastically narrowed the american political spectrum . its damage to democratic institutions would be long lasting . in all likelihood , there were both democrats and republicans who knew that the anti-communist purges were deeply unjust but feared that directly opposing them would hurt their careers . even the supreme court failed to stop the witchhunt , condoning serious violations of constitutional rights in the name of national security . was domestic communism an actual threat to the american government ? perhaps , though a small one . but the reaction to it was so extreme that it caused far more damage than the threat itself . and if new demagogues appeared in uncertain times to attack unpopular minorities in the name of patriotism , could it all happen again ?
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mccarthy 's colleagues in the senate censured him and he died less than three years later , probably from alcoholism . mccarthyism ended as well . it had ruined hundreds , if not thousands , of lives and drastically narrowed the american political spectrum .
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how long did the era of mccarthyism last ?
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i 've always collected baseball cards . i first started playing baseball when i was eight years old , and when my hometown , red sox won the world series in 2004 , i began meeting many of the players at autograph signings and events around boston . but i noticed a few things in common . these players were n't very friendly , they were all quite overpaid and they acted more like celebrities . in middle school , a friend introduced me to a new way to collect autographs : writing the players through the mail . in doing so , i would write a letter , send a self-addressed stamped envelope , and send a few baseball cards . within a few weeks , i 'd often get a response . but it was never the modern players that would send back . it was always the players from the 50s and 60s , who were much friendlier , and much less recognized during their career . so , i continued to write letters to these retired ball players , and in 2007 , topps baseball cards came out with a set where they included a few negro league baseball player cards . negro league was a period from 1920 to the 1960s where blacks who were segregated from playing in the major leagues played in their own baseball league , often busing around the country , playing two to three games a day , under much less glamorous conditions . but over time , due to the lack of glamorization and public interest , everything just kind of faded away , leaving the history of the negro leagues behind . so , i ended up writing to these players in this set and within a few weeks , they signed my cards . from here , i began writing to negro leaguers who did n't have baseball cards . guys that were , you know , even less recognized . and in my letters , i 'd often include my phone number , and a few of them began reaching out to me . when i started speaking with them , i noticed they all had a few things in common . none of them had baseball cards , none of them had any documentation , no newspaper articles , no sorts of photos from their career , just nothing tying them to the game . and lastly , they had just left all their teammates behind . they had n't stayed in touch with any of their teammates . so , i tried to change this , and i started off by making baseball cards on my home computer . printing them out , designing them and sending them to ball players . and what i also did is i began signing up for newspaper archive websites where i 'd find old newspaper articles that would give these guys the recognition that , you know , tied them to the game . and lastly , i began becoming kind of like a private investigator , tracking down their former teammates and trying to get these guys back in touch . from here , i went on and i just spoke to these players . it got to the point where i actually had players calling me up , asking me for information . and by the time i was a freshman in high school , it was no longer a hobby at all . i had gone from an autograph collector to this negro league research obsession . i even asked for negro league autographs and stamps for christmas . so , going on through high school , i began to take this work in the negro league much more seriously . i started working with adult negro league researchers where i began working on a few different programs . the first being the negro league annual reunion in birmingham , alabama . at the reunion , we 'd have about 50 to 60 negro league ball players from around the country , and they 'd all come together , and these players would just , you know , sit in the hotel lobby for me from 8am until the late hours of the night just catching up , telling stories , and here we just had a week of events and these guys got some of this recognition and honor that they never really had before . the second program that i began working on was the negro league pension program . and the pension program was a program that was offered by major league baseball , and if you played four years in the negro league , and you can document it , these players would be entitled to 10,000 dollars a year . this meant a lot for these players . many of these guys never really did much after baseball , they did n't make much money . so , when i was able to get these players pensions , it really made a difference . when i started doing this , i encountered a lot of difficulty . i had to go through hundreds and hundreds of newspaper articles trying to find this documentation to prove they played , and in many cases i did . also i want to mention , when i was speaking with these players on the phone , tracking them down , it was n't easy either . i would go through hundreds of articles trying to look for names , find information , and i encountered quite a lot of failure . i would call people up , it would be the wrong person . it would be really awkward . i 'd also have a lot of times where i 'd call players up , and they did n't want to speak at all to me . they would hang up . when i said the word baseball , they would just refuse to talk altogether . this was because they faced a lot of segregation during their careers . along with the lack of glamorization that they faced , they also dealt with a lot of racism on and off the baseball field , which just lasted with them throughout their whole lives . these guys , you know , it was very emotional for them to talk about baseball , and it was really hard to kind of get these guys back , you know , talking about this game that they had kind of left behind . lastly though , i encountered , you know , quite a lot of success as well . some of these guys i 'd call up , i 'd talk to them for two to three hours , and these guys would just go on and on about their stories , telling me , like , exact baseball games and memories that they had . nowadays , i 've attended four negro league reunions , three of which i 've actually roomed with former negro league ball player russell `` crazy legs '' patterson of the indianapolis clowns . he actually snores at night , in case you all were wondering . i 've worked on about a dozen pensions and i 've tracked down over a hundred negro league ball players , constantly finding new ball players , getting them in touch with their former teammates , bringing baseball back into these players ' lives and bringing these guys back into the game . ( music ) thank you ! ( applause )
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i 've always collected baseball cards . i first started playing baseball when i was eight years old , and when my hometown , red sox won the world series in 2004 , i began meeting many of the players at autograph signings and events around boston . but i noticed a few things in common .
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when did cam mention the red sox winning the world series ?
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in the winter of 1995 , scientists pointed the hubble telescope at an area of the sky near the big dipper , a spot that was dark and out of the way of light pollution from surrounding stars . the location was apparently empty , and the whole endeavor was risky . what , if anything , was going to show up ? over ten consecutive days , the telescope took close to 150 hours of exposure of that same area . and what came back was nothing short of spectacular : an image of over 1,500 distinct galaxies glimmering in a tiny sliver of the universe . now , let 's take a step back to understand the scale of this image . if you were to take a ballpoint pen and hold it at arm 's length in front of the night sky , focusing on its very tip , that is what the hubble telescope captured in its first deep field image . in other words , those 3,000 galaxies were seen in just a tiny speck of the universe , approximately one two-millionth of the night sky . to put all this in perspective , the average human measures about 1.7 meters . with earth 's diameter at 12,700 kilometers , that 's nearly 7.5 million humans lined up head to toe . the apollo 8 astronauts flew a distance of 380,000 kilometers to the moon . and our relatively small sun has a diameter of about 1.4 million kilometers , or 110 times the earth 's diameter . a step further , the milky way holds somewhere between 100 to 400 billion stars , including our sun . and each glowing dot of a galaxy captured in the deep field image contains billions of stars at the very least . almost a decade after taking the deep field image , scientists adjusted the optics on the hubble telescope and took another long exposure over a period of about four months . this time , they observed 10,000 galaxies . half of these galaxies have since been analyzed more clearly in what 's known as the extreme deep field image , or xdf . by combining over ten years of photographs , the xdf shows galaxies so distant that they 're only one ten-billionth the brightness that the human eye can perceive . so , what can we learn about the universe from the deep field images ? in a study of the universe , space and time are inextricably linked . that 's because of the finite speed of light . so the deep field images are like time machines to the ancient universe . they reach so far into space and time that we can observe galaxies that existed over 13 billion years ago . this means we 're looking at the universe as it was less than a billion years after the big bang , and it allows scientists to research galaxies in their infancy . the deep field images have also shown that the universe is homogeneous . that is , images taken at different spots in the sky look similar . that 's incredible when we think about how vast the universe is . why would we expect it to be the same across such huge distances ? on the scale of a galaxy , let alone the universe , we 're smaller than we can readily comprehend , but we do have the capacity to wonder , to question , to explore , to investigate , and to imagine . so the next time you stand gazing up at the night sky , take a moment to think about the enormity of what is beyond your vision , out in the dark spaces between the stars .
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almost a decade after taking the deep field image , scientists adjusted the optics on the hubble telescope and took another long exposure over a period of about four months . this time , they observed 10,000 galaxies . half of these galaxies have since been analyzed more clearly in what 's known as the extreme deep field image , or xdf .
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it is thought that there are 200,000,000,000 galaxies in the universe today . all of them are made of the same elements , follow the same laws of physics , and are made up of the same structures as our galaxies , solar system , and you . can this knowledge change how we think of ourselves in relation to other things in the universe ?
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so neil ’ s got a sample of sodium . sodium is a very reactive metal , it is stored under an oil to stop air or moisture getting on it - stop it oxidising , stop it reacting - and as you can see it is a very soft metal , so he is going to put his knife in and withdraw the lump of sodium , so there is about 2 kilos of sodium here , it 's a really quite large rod . so we are going to cut a small sample of the sodium and we are going to see if we can explore some of its chemistry . sodium is again a light metal , rather like lithium and it has a , a melting point about 96 degrees . so the sodium is a very , very shiny metal and as you can see as neil cuts some off , you can see the quite nice shiny material . it ’ s really quite beautiful . reacts very , very quickly with air and also with water , you form the oxide layer which is the white , or the hydroxide is the white crust on the outside . and many of you will know that if you drop sodium into water it reacts almost explosively . so we are going to go outside now , go get some even bigger reactions , with the alkali metals . this is a dog bowl which is stoneware , it is very hard , not likely to break , unless i drop it on my toes . this is sodium , the metal that we cut a minute ago and you can see there is quite a substantial amount of the sodium , and we are going to pop it into the water and see what we can do with the reaction . ok ? so here we have a bowl full of water and maybe , oh , a gram of sodium ? so let ’ s see what happens , see what this reaction ’ s like . so it is reacting really , really quite quickly and really violently with the water , and you can see it is fizzing around and it is generating lots and lots of hydrogen gas . and see now the heat from the reaction is burning away all of that hydrogen which is generating and you can see the orange sodium flame . that was um ? that was good that is a bit of , a chunk of molten sodium has come out of there mate . so , let ’ s burn that . oh , it ’ s on your camera . oh it is too ! sodium chloride is transparent through infrared light and so here we have got a sheet of sodium chloride that has been stuck on to a glass vessel so that you can have infrared light going through it . now this is a broken one , which my students have broken . is that bit , have you got a , we need a needle neil , or a pair of tweezers . so you can see here that these windows have been broken but you can see an interesting aspect of sodium chloride that when it breaks it forms cracks that form at right angles . why is that ? this is related to the structure of the atoms inside the crystal which are arranged in a sort of cubic arrangement . i have also got quite a nice crystal of sodium chloride over here which i don ’ t know if you can see has been turned into a table lamp . and if you switch it on it lights up . so this is just a mass of natural sodium chloride from under the ground somewhere , probably in cheshire or somewhere else like this where they have large underground salt mines , deposits . ok so we have got another lump of sodium , and you can see it ’ s really nice and shiny . ok ? so we are going to pop that into that big bucket of water . see what the chemical reaction is , ok ? so here we go ! so you can see again , see the orange sodium spectrum as the sodium is getting excited as the hydrogen is burning all that heat . whoa ! exciting ! that is brilliant . that is much better . so sodium and water , excellent reaction . that was great . i like sodium , because its symbol na was the nickname that my mother whose name was ena used to use when she was a child , she was known as na , so whenever i see sodium in the formula , i sort of feel a sort of warm motherly feeling from this .
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that is much better . so sodium and water , excellent reaction . that was great .
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what is the flammable gas produced when sodium reacts with water ?
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mysteries of vernacular : ukulele , a small , four-stringed guitar . oddly enough , the word ukulele , in its native hawaiian , literally translates to jumping flea . even more surprising , the instrument itself did not originate in hawaii . so , how did a hawaiian word come to describe a non-hawaiian instrument ? back in the late 1800s , king kalākaua was the last reigning king of the kingdom of hawaii . he was nicknamed `` the merry monarch '' because of his joy for life and , in particular , his love of music . in the king 's court , there was a former british army officer named edward purvis . though a small man , he was quite lively , and his nickname was `` jumping flea , '' `` ukulele '' in hawaiian . like the king , he was a great lover of music . in 1879 , a group of portuguese immigrants arrived on the islands of hawaii , bringing with them a small , four-stringed guitar known as a braguinha . purvis was immediately taken with the instrument and helped spread its popularity throughout the king 's court . as the story goes , it was not long before his nickname , ukulele , jumped from the man to his favorite instrument . as demand grew , several portuguese families began to manufacture the minuscule guitar on the islands , making small modifications until it became the same ukulele we recognize today .
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so , how did a hawaiian word come to describe a non-hawaiian instrument ? back in the late 1800s , king kalākaua was the last reigning king of the kingdom of hawaii . he was nicknamed `` the merry monarch '' because of his joy for life and , in particular , his love of music .
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king kalākaua ’ s sister , liliʻuokalani , inherited the throne when he died and was the last monarch of the kingdom of hawaii . when and why did her reign end ?
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if you wake up one morning with 1,000 times the strength you had the night before , how will you handle delicate day-to-day tasks ? everything must seem so fragile to you since the scale of your strength has expanded one thousand times . you 'd have to be very careful when you 're shaking someone 's hand so you do n't end up breaking their bones or crushing everyone you hug . and using a fork to pick up a piece of broccoli from a styrofoam plate without driving the fork through the plate is going to be as difficult as brain surgery . say the day comes and you get the chance to save a damsel in distress falling from a helicopter . so , you hold out your arms , hoping to catch her . seconds later , you will find yourself holding her lifeless body . what happened ? well , pressure is force divided by area . the smaller the area , the bigger the pressure . this is why we can lift heavy objects without breaking our skin , but a tiny needle can make us bleed with just a little poke . the pressure that will be exerted on her body can be calculated by force divided by the area on the top of your arms that comes in contact with her . it does n't matter if your arms are strong enough to catch her body without breaking your bones . her spine is not strong enough to be caught by you without being damaged . even if you rip off the nearest door to provide a bigger area to catch her with , you still would n't be able to save her anyway . remember , it 's not the fall that kills her , but the sudden stop at the bottom . let 's say she 's falling from a 32 story building , about 300 feet , and you are 6 feet tall , maybe 10 feet on your tippy-toes , with your arms above your head holding a door , in hopes of distributing the pressure across a larger surface area , but all you 're doing is essentially moving the ground up by 10 feet . so , she 's now falling from 290 feet , instead of 300 feet , reaching the speed of 173 feet per second just before impact , not counting air resistance . it 's the equivalent of crashing at 94 miles per hour into a wall with a door in front of it . the only thing that could save her is flying . but that power comes with its own host of scientific issues . if you could fly , what you must do is fly up to her , start flying down at the speed she is falling , hold on to her , then gradually slow down until you come to a complete stop . this process requires a lot of cushion space between the point she starts falling and the ground . every second you waste on changing into your superhero costume and flying up to her height , her head is getting that much closer to the pavement ! if she 's falling from a high place , and you ca n't get to her until she 's only a few feet above the ground , there 's really nothing you can do other than magically turn the pavement into marshmellow to allow her enough time to slowly come to a stop . then , break out the chocolate and graham crackers and you 've got s'mores . mmmm , delicious ! now , which superpower physics lesson will you explore next ? shifting body size and content , super speed , flight , super strength , immortality , and invisibility .
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and using a fork to pick up a piece of broccoli from a styrofoam plate without driving the fork through the plate is going to be as difficult as brain surgery . say the day comes and you get the chance to save a damsel in distress falling from a helicopter . so , you hold out your arms , hoping to catch her .
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what is one way to save the girl falling from a 30-story building ?
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have you ever helped set a table and found yourself wondering where to place the forks ? or sat down to eat a restaurant and wondered which utensils to use ? well , here 's some simple , traditional etiquette tips on how to set a table . what would happen if you set a table like this ? it does n't look good , and you have to clean up the mess before you can even start . let 's try another way . to start , use a placemat or tablecloth , but not both , so the dishes are n't directly on the table . this is more about looks than etiquette , but it 's rare to see nothing under a plate unless you 're eating at a picnic table . set out any flowers , candlesticks , or other decorations you like . candles are usually only lit at night . start with utensils for the main course , putting your dinner fork on the left and your dinner knife on the right-hand side since these are the hands we use them with . here 's a helpful tip : you always eat outside-in , so to set for salad , we 'll put the salad fork to the outside of the dinner fork and the salad knife to the outside of the dinner knife . we 'll have salad first , then our main course . notice , too , that the knife blades are both pointed toward the plate . this is an old tradition from a time when dinner knives were quite sharp , and it was a sign of politeness and nonaggression to keep them pointed away from other diners . we might have some soup , and since soup usually comes first , the soup spoon goes outside the knives since we use our right hand to hold it . here 's another tip : only set the table with what you 'll need . if you 're not eating soup , do n't set a soup spoon . now , for dessert , we 'll have ice cream so we 'll place the dessert up top since we do n't need it for a little while . notice that the bowl of the spool is pointing to the left . this way , when it 's time to eat , you just slide it down and it 's in the right spot . if you were having cake , you 'd set a fork and flip it 180 degrees so it would be right side-up on the left instead . next we 'll anchor our setting with the plate . you can also serve from the kitchen then bring them to the table . the bread plate goes up and to the left of the setting , and the butter knife goes on the plate at an angle , again , with the blade pointing in . there 's only one spot left , and that 's for the drinks . set the wine glass to the upper right , and then place the water glass to the left of it at an angle . if you 're like me and can never remember which goes where , think water , wine , w-a , w-i ; a , i ; they go left to right in alphabetical order . another tip : to remember left and right with the bread and the drinks , think b-m-w like the car . b , your bread plate , is on the left ; m , your meal , is in the middle , and w , your water , is on the right . lastly , the napkin traditionally goes to the left of the forks , though it 's okay to put it underneath them , too . for a fancier meal like this one that takes up a lot of space , we 'll put it in the middle . now we 're ready to eat . hopefully these tips will be helpful the next time you 're asked to help set the table or sit down at a fancy meal . enjoy !
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there 's only one spot left , and that 's for the drinks . set the wine glass to the upper right , and then place the water glass to the left of it at an angle . if you 're like me and can never remember which goes where , think water , wine , w-a , w-i ; a , i ; they go left to right in alphabetical order . another tip : to remember left and right with the bread and the drinks , think b-m-w like the car .
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water , wine ( `` wa '' and `` wi '' ) . a , i. they go in order alphabetically from left to right . the water is always placed to the left of the wine . what 's another good acronym ?
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translator : tom carter reviewer : bedirhan cinar the most important walls in western history are n't even in the west . they surround the modern city of istanbul , constantinople as the romans called it . and for a thousand years , the fate of europe depended on them . constantinople was designed to be the center of the world . when the frontiers of the roman empire began to crumble in the 4th century , the capital was moved to the cultured , wealthy , and still stable east . there , at the crossroads between europe and asia , the hub of the major trade routes of the ancient world , the emperor constantine built his city . this was the city of libraries and universities , 20 times the size of london or paris at the time . it contained the priceless knowledge of the classical world which was fading in the west . to protect this masterpiece from its many enemies , constantine 's successors built the finest defensive fortifications ever made . the first line of protection was a moat 60 feet wide and 22 feet deep , stretching all four miles from coast to coast . pipes from inside the city could fill it at the first sight of the enemy , and a short wall protected archers who could fire at the soaked soldiers trying to swim across . those who were lucky enough to clear the moat had to contend with an unceasing barrage from the 27 foot outer wall above . arrows , spears , or far worse , greek fire -- an ancient form of napalm that would ignite on contact and could n't be extinguished by water -- would rain down on them . squads of roman defenders would carry portable flame throwers , spraying anyone trying to climb out of the moat . the terrified victims would leap back , only to find that they still burned underwater . at times , the romans would also mount siphons onto the ramparts , and launch clay pots full of greek fire from catapults at an invading army . the front lines would turn into an inferno , making it appear as if the earth itself was on fire . if , by some miracle , the outer wall was compromised , attackers would be faced with the final defense : the great inner wall . these walls were wide enough to have four men ride side by side , allowing troops to be rushed wherever they were needed . attilla the hun , destroyer of civilizations , who named himself the scourge of god , took one look at them and turned around . the avars battled the walls uselessly til their catapults ran out of rocks . the turks tried to tunnel under them , but found the foundations too solid . the arabs tried to starve the city into submission , but ran out of food themselves and had to resort to cannibalism . it took the guns of the modern world to finally bring them down . in 1453 , the turks brought their super weapon : a monster cannon that could fire a 15 hundred pound stone ball over a mile . together with more than a hundred smaller guns , they kept up a steady bombardment day and night . a section of the old walls collapsed , but even in their death throes they proved formidable . the rubble absorbed the shock of the cannonballs better than the solid wall . it took a month and a half of continuous blasting to finally open a breach . the last roman emperor , constantine the 11th , drew his sword and jumped into the gap to stop the onrushing horde , disappearing into legend . the city was taken , and the roman empire finally disappeared . but those broken walls had one last gift . as the survivors fled the doomed city , they brought with them their precious books and their ancient traditions . they traveled west to italy , reintroduced the greek language and learning to western europe , and ignited the renaissance . thanks to constantinople 's walls , that pile of brick and marble that guarded them for so long , we still have our classical past .
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they traveled west to italy , reintroduced the greek language and learning to western europe , and ignited the renaissance . thanks to constantinople 's walls , that pile of brick and marble that guarded them for so long , we still have our classical past .
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brownworth concludes with “ thanks to that pile of brick and marble , we still have our classical past. ” why do you think it needed saving ? why do you think ancient greek and roman learning disappeared from the west ?
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translator : andrea mcdonough reviewer : jessica ruby mysteries of vernacular : sarcophagus , a stone coffin typically adorned with decorative carvings or inscriptions . the history of the word sarcophagus is so skin-crawlingly grotesque , it seems to come right out of a low-budget horror film . rather than having a b-movie origin , however , its roots can be traced back to the early roman empire where the greek word sarkophagus was used to describe the limestone that a coffin was made of , not the coffin itself . according to the roman scholar pliny the elder , citizens of the empire believed that limestone from a quarry near troy would dissolve flesh . for this reason , it was quite desireable in the construction of coffins . though it 's unclear if the belief was widespread or even accurately reported by pliny , what is certain is that sarkophagus came from the greek words sark , meaning flesh , and phagein , a verb meaning to eat . from flesh-eating stone to stone coffin , it 's a fitting etymology for the final resting place of the deceased .
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for this reason , it was quite desireable in the construction of coffins . though it 's unclear if the belief was widespread or even accurately reported by pliny , what is certain is that sarkophagus came from the greek words sark , meaning flesh , and phagein , a verb meaning to eat . from flesh-eating stone to stone coffin , it 's a fitting etymology for the final resting place of the deceased .
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what does the greek word sark mean ?
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i want to tell you all about a piece of american history that is so secret , that nobody has done anything about it for 167 years , until right now . and the way that we 're going to uncover this vestigial organ of america past is by asking this question : why ? as we all know -- ( laughter ) we are in the middle of another presidential election , hotly contested , as you can see . ( laughter ) but what you may not know is that american voter turnout ranks near the bottom of all countries in the entire world , 138th of 172 nations . this is the world 's most famous democracy . so ... why do we vote on tuesday ? does anybody know ? and as a matter of fact , michigan and arizona are voting today . here 's the answer : absolutely no good reason whatsoever . ( laughter ) i 'm not joking . you will not find the answer in the declaration of independence , nor will you find it in the constitution . it is just a stupid law from 1845 . ( laughter ) in 1845 , americans traveled by horse and buggy . as did i , evidently . it took a day to get to the county seat to vote , a day to get back , and you could n't travel on the sabbath , so , tuesday it was . i do n't often travel by horse and buggy , i would imagine most of you do n't , so when i found out about this , i was fascinated . i linked up with a group called , what else -- `` why tuesday ? '' to go and ask our nation 's most prominent elected leaders if they knew the answer to the question , `` why do we vote on tuesday ? '' ( video ) rick santorum : anybody knows ? ok , i 'm going to be stumped on this . anybody knows why we vote on tuesdays ? jacob soboroff : do you happen to know ? ron paul : on tuesdays ? js : the day after the first monday in november . rp : i do n't know how that originated . js : do you know why we do vote on tuesday ? newt gingrich : no . dick lugar : no , i do n't . ( laughter ) dianne feinstein : i do n't . darrell issa : no . john kerry : in truth , really , i 'm not sure why . js : ok , thanks very much . ( laughter ) js : these are people that live for election day , yet they do n't know why we vote on that very day . ( laughter ) chris rock said , `` they do n't want you to vote . if they did , we would n't vote on a tuesday in november . have you ever thrown a party on a tuesday ? ( laughter ) no , of course not . nobody would show up . '' ( laughter ) here 's the cool part . because we asked this question , `` why tuesday ? '' there is now this bill , the weekend voting act in the congress of the united states of america . it would move election day from tuesday to the weekend , so that -- duh -- more people can vote . ( applause ) it has only taken 167 years , but finally , we are on the verge of changing american history . thank you very much . ( applause ) thanks a lot . ( applause )
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as we all know -- ( laughter ) we are in the middle of another presidential election , hotly contested , as you can see . ( laughter ) but what you may not know is that american voter turnout ranks near the bottom of all countries in the entire world , 138th of 172 nations . this is the world 's most famous democracy .
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out of 172 nations , what does america rank for voter turnout ?
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behold the human brain , it 's lumpy landscape visibly split into a left and right side . this structure has inspired one of the most pervasive ideas about the brain , that the left side controls logic and the right , creativity . and yet , this is a myth unsupported by scientific evidence . so how did this misleading idea come about , and what does it get wrong ? it 's true that the brain has a right and a left side . this is most apparent with the outer layer , or the cortex . internal regions , like the striatum , hypothalamus , thalamus , and brain stem appear to be made from continuous tissue , but in fact , they 're also organized with left and right sides . the left and the right sides of the brain do control different body functions , such as movement and sight . the brain 's right side controls the motion of the left arm and leg and vice versa . the visual system is even more complex . each eye has a left and right visual field . both left visual fields are sent to the right side of the brain , and both right fields are sent to the left side . so the brain uses both sides to make a complete image of the world . scientists do n't know for sure why we have that crossing over . one theory is it began soon after animals developed more complex nervous systems because it gave the survival advantage of quicker reflexes . if an animal sees a predator coming from its left side , it 's best off escaping to the right . so we can say that vision and movement control are two systems that rely on this left-right structure , but problems arise when we over-extend that idea to logic and creativity . this misconception began in the mid-1800s when two neurologists , broca and wernicke , examined patients who had problems communicating due to injuries . the researchers found damage to the patients ' left temporal lobes , so they suggested that language is controlled by the left side of the brain . that captured the popular imagination . author robert louis stevenson then introduced the idea of a logical left hemisphere competing with an emotional right hemisphere represented by his characters dr. jekyll and mr. hyde . but this idea did n't hold up when doctors and scientists examined patients who were missing a hemisphere or had their two hemispheres separated . these patients showed a complete range of behaviors , both logical and creative . later research showed that one side of the brain is more active than the other for some functions . language is more localized to the left and attention to the right . so one side of the brain may do more work , but this varies by system rather than by person . there is n't any evidence to suggest that individuals have dominant sides of the brain , or to support the idea of a left-right split between logic and creativity . some people may be particularly logical or creative , but that has nothing to do with the sides of their brains . and even the idea of logic and creativity being at odds with each other does n't hold up well . solving complex math problems requires inspired creativity and many vibrant works of art have intricate logical frameworks . almost every feat of creativity and logic carries the mark of the whole brain functioning as one .
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this is most apparent with the outer layer , or the cortex . internal regions , like the striatum , hypothalamus , thalamus , and brain stem appear to be made from continuous tissue , but in fact , they 're also organized with left and right sides . the left and the right sides of the brain do control different body functions , such as movement and sight .
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which four brain structures appear to be made from continuous tissue but are still organized with right and left sides ?
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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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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 .
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what are some other things that might cause a pregnancy test to give the wrong result ?
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in 1796 , the scientist edward jenner injected material from a cowpox virus into an eight-year-old boy with a hunch that this would provide the protection needed to save people from deadly outbreaks of the related smallpox virus . it was a success . the eight-year-old was inoculated against the disease and this became the first ever vaccine . but why did it work ? to understand how vaccines function , we need to know how the immune system defends us against contagious diseases in the first place . when foreign microbes invade us , the immune system triggers a series of responses in an attempt to identify and remove them from our bodies . the signs that this immune response is working are the coughing , sneezing , inflammation and fever we experience , which work to trap , deter and rid the body of threatening things , like bacteria . these innate immune responses also trigger our second line of defense , called adaptive immunity . special cells called b cells and t cells are recruited to fight microbes , and also record information about them , creating a memory of what the invaders look like , and how best to fight them . this know-how becomes handy if the same pathogen invades the body again . but despite this smart response , there 's still a risk involved . the body takes time to learn how to respond to pathogens and to build up these defenses . and even then , if a body is too weak or young to fight back when it 's invaded , it might face very serious risk if the pathogen is particularly severe . but what if we could prepare the body 's immune response , readying it before someone even got ill ? this is where vaccines come in . using the same principles that the body uses to defend itself , scientists use vaccines to trigger the body 's adaptive immune system , without exposing humans to the full strength disease . this has resulted in many vaccines , which each work uniquely , separated into many different types . first , we have live attenuated vaccines . these are made of the pathogen itself but a much weaker and tamer version . next , we have inactive vaccines , in which the pathogens have been killed . the weakening and inactivation in both types of vaccine ensures that pathogens do n't develop into the full blown disease . but just like a disease , they trigger an immune response , teaching the body to recognize an attack by making a profile of pathogens in preparation . the downside is that live attenuated vaccines can be difficult to make , and because they 're live and quite powerful , people with weaker immune systems ca n't have them , while inactive vaccines do n't create long-lasting immunity . another type , the subunit vaccine , is only made from one part of the pathogen , called an antigen , the ingredient that actually triggers the immune response . by even further isolating specific components of antigens , like proteins or polysaccharides , these vaccines can prompt specific responses . scientists are now building a whole new range of vaccines called dna vaccines . for this variety , they isolate the very genes that make the specific antigens the body needs to trigger its immune response to specific pathogens . when injected into the human body , those genes instruct cells in the body to make the antigens . this causes a stronger immune response , and prepares the body for any future threats , and because the vaccine only includes specific genetic material , it does n't contain any other ingredients from the rest of the pathogen that could develop into the disease and harm the patient . if these vaccines become a success , we might be able to build more effective treatments for invasive pathogens in years to come . just like edward jenner 's amazing discovery spurred on modern medicine all those decades ago , continuing the development of vaccines might even allow us to treat diseases like hiv , malaria , or ebola , one day .
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but why did it work ? to understand how vaccines function , we need to know how the immune system defends us against contagious diseases in the first place . when foreign microbes invade us , the immune system triggers a series of responses in an attempt to identify and remove them from our bodies . the signs that this immune response is working are the coughing , sneezing , inflammation and fever we experience , which work to trap , deter and rid the body of threatening things , like bacteria .
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since we have our immune system to protect us from disease , why do we still need a vaccine ?
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translator : andrea mcdonough reviewer : bedirhan cinar one of the grandest scientific tools ever made by mankind is called an atom smasher . and i mean literally grand . the biggest one ever built , the large hadron collider , or lhc , is a ring with a circumference of about 18 miles . that 's more than the entire length of manhattan . so what is an atom smasher ? it is a device that collides atomic nuclei together at extremely high energy . the most powerful one scientists have ever built can heat matter to the hottest temperatures ever achieved , temperatures last seen at a trillionth of second after the universe began . our accelerators are full of engineering superlatives . the beam-containing region of the lhc is a vacuum , with lower pressure than what surrounds the international space station , and is 456 degrees fahrenheit below zero , colder than the temperature of deepest space . a previous accelerator sitting in the lhc tunnel holds the world record for velocity , accelerating an electron to a speed so fast that if it were to race a photon of light , it would take about 14 minutes for the photon to get a lead of about 10 feet . if that does n't impress you , remember the photon is fastest thing in the universe , it goes about 186,000 miles per second . so how do these subatomic particle accelerators work ? well , they use electric fields . electric fields make charged particles move in the same way that gravity will pull a dropped baseball . the force from the electric field will pull a particle to make it move . the speed will continue to increase until the charged particle is moving incredibly fast . a simple particle accelerator can be made by hooking two parallel metal plates to a battery . the charge from the battery moves on to the two metal plates and makes an electric field that pulls the particle along . and that 's it , you got a particle accelerator . the problem is that an accelerator built this way is very weak . building a modern accelerator like the lhc this way would take over five trillion standard d-cell batteries . so scientists use much stronger batteries and put them one after another . an earlier accelerator used this method and was about a mile long and was equivalent to 30 billion batteries . however , to make an accelerator that is equivalent to five trillion batteries would require an accelerator 150 miles long . scientists needed another way . while electric fields would make a particle go faster , magnetic fields make them move in a circular path . if you put an electric field along the circle , you do n't need to use miles of electric fields , you can use a single electric field over and over again . the beams go around the circle , and each time they gain more energy . so very high-energy accelerators consist of a short region with accelerating electric fields , combined with long series of magnets that guide the particles in a circle . the strength of the magnets and the radius of the circular path determines the maximum energy of the beam . once the beam is zooming along , then the real fun begins , the smashing . the reason physicists want to get those particles moving so fast is so that they can slam them into one another . these collisions can teach us about the fundamental rules that govern matter , but they 'd be impossible without the feat of engineering that is the particle accelerator .
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the charge from the battery moves on to the two metal plates and makes an electric field that pulls the particle along . and that 's it , you got a particle accelerator . the problem is that an accelerator built this way is very weak .
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what causes particles in a particle accelerator to move more quickly ?
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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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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 .
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dog owners know the “ guilty look ” when a pet has pooped on the carpet or violated some other rule . but how much is due to what the dog knows versus what the owner knows ? that is , we project out own mental states onto others , both human and not . what might be some downsides to having brains as smart as ours , that seek out patterns even where none exist ?
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pick a card , any card . actually , just pick up all of them and take a look . this standard 52-card deck has been used for centuries . everyday , thousands just like it are shuffled in casinos all over the world , the order rearranged each time . and yet , every time you pick up a well-shuffled deck like this one , you are almost certainly holding an arrangement of cards that has never before existed in all of history . how can this be ? the answer lies in how many different arrangements of 52 cards , or any objects , are possible . now , 52 may not seem like such a high number , but let 's start with an even smaller one . say we have four people trying to sit in four numbered chairs . how many ways can they be seated ? to start off , any of the four people can sit in the first chair . one this choice is made , only three people remain standing . after the second person sits down , only two people are left as candidates for the third chair . and after the third person has sat down , the last person standing has no choice but to sit in the fourth chair . if we manually write out all the possible arrangements , or permutations , it turns out that there are 24 ways that four people can be seated into four chairs , but when dealing with larger numbers , this can take quite a while . so let 's see if there 's a quicker way . going from the beginning again , you can see that each of the four initial choices for the first chair leads to three more possible choices for the second chair , and each of those choices leads to two more for the third chair . so instead of counting each final scenario individually , we can multiply the number of choices for each chair : four times three times two times one to achieve the same result of 24 . an interesting pattern emerges . we start with the number of objects we 're arranging , four in this case , and multiply it by consecutively smaller integers until we reach one . this is an exciting discovery . so exciting that mathematicians have chosen to symbolize this kind of calculation , known as a factorial , with an exclamation mark . as a general rule , the factorial of any positive integer is calculated as the product of that same integer and all smaller integers down to one . in our simple example , the number of ways four people can be arranged into chairs is written as four factorial , which equals 24 . so let 's go back to our deck . just as there were four factorial ways of arranging four people , there are 52 factorial ways of arranging 52 cards . fortunately , we do n't have to calculate this by hand . just enter the function into a calculator , and it will show you that the number of possible arrangements is 8.07 x 10^67 , or roughly eight followed by 67 zeros . just how big is this number ? well , if a new permutation of 52 cards were written out every second starting 13.8 billion years ago , when the big bang is thought to have occurred , the writing would still be continuing today and for millions of years to come . in fact , there are more possible ways to arrange this simple deck of cards than there are atoms on earth . so the next time it 's your turn to shuffle , take a moment to remember that you 're holding something that may have never before existed and may never exist again .
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pick a card , any card . actually , just pick up all of them and take a look .
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the symbol “ ! ” in math is usually _________ .
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everybody loves fireworks -- the lights , the colors , and , of course , the big boom . but the history of fireworks is n't all hugs and celebrations . long before epic fireworks displays , chemists in china invented the key ingredient that propels those bright lights into the sky . that invention was what we now call gunpowder . our story begins back in ancient china in the mid-ninth century where early chinese alchemists were trying to create a potion for immortality . instead , what they created was a flammable powder that burned down many of their homes . they quickly realized that this black powder , which they called fire medicine , was precisely the opposite of something that would make you live forever . in these early days , the chinese had n't yet figured out how to make the powder explode ; it was simply very flammable , and their armies used it to make flaming arrows and even a flamethrower . but once they figured out the right proportions of ingredients to create a blast , they began using the powder even more , creating fireworks to keep evil spirits away and bombs to defend themselves against mongol invaders . it was these mongols , most likely , who spread the invention of gunpowder across the world . after fielding chinese attacks , they learned how to produce the powder themselves and brought it with them on their conquests in persia and india . william of rubruck , a european ambassador to the mongols , was likely responsible for bringing gunpowder back to europe around 1254 . from there , engineers and military inventors created all kinds of destructive weapons . from bombs to guns to cannons , gunpowder left its mark on the world in some pretty terrible ways , in contrast to the beautiful marks it can leave in the air . so , how does black powder propel fireworks into the sky ? you might have seen old westerns or cartoons where a trail of gunpowder is lit and it leads to a large and obviously explosive barrel . once the fire gets to the barrel , a large boom occurs . but why does n't the trail itself explode ? the reason is that burning the powder releases energy and gases . while the trail is burning , these are easily released into the surrounding air . but when the gunpowder is contained within the barrel , the energy and gases can not easily escape and build up until boom ! firework canisters provide a single , upward-facing outlet to channel this explosive energy . the wick ignites the gunpowder and the energy takes the easiest exit from the canister , launching the firework high into the sky . the flame then makes its way through the firework 's encasing and the same reaction occurs high above our heads . so , while the chinese alchemists never found the compound for eternal life , they did find something that would go on to shape all of civilization , something that has caused many tragic moments in human history , and yet still gives us hope when we look up in celebration at the colorful night sky .
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long before epic fireworks displays , chemists in china invented the key ingredient that propels those bright lights into the sky . that invention was what we now call gunpowder . our story begins back in ancient china in the mid-ninth century where early chinese alchemists were trying to create a potion for immortality .
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we now understand that gunpowder needs oxygen to combust . do you think gunpowder can combust in outer space ? explain .
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if humans could fly , without tools and machines , how fast do you think we would go ? as of 2012 , the world record for fastest short-distance sprint speed is roughly 27 miles per hour . running speed depends on how much force is exerted by the runner 's legs , and according to newton 's second law of motion , force is the product of mass times acceleration . and newton 's third law states that for every action , there is an equal and opposite reaction . so , that means running requires having a ground to push off from , and the ground pushes back against the runner 's foot . so , flying would actually be more similar to swimming . michael phelps is currently the fastest human in water and the most decorated olympian of all time . guess how fast he swims ? the answer may surprise you . his fastest recorded speed is less than 5 miles per hour . a child on the ground can easily outrun michael phelps in water , but why is that ? well , let 's go back to newton 's third law of motion . when we run , we move forward by pushing against the ground with our feet and the ground pushes back , propelling us forward . the ground is solid . by definition , it means the particles are essentially locked into place and must push back instead of getting out of the way , but water is liquid and flows easily . when we move our limbs to push back against the water , a part of the water molecules can just slide past one another instead of pushing back . now , let 's think about flying . air has a lot more free space for particles to move past one another , so even more of our energy would be wasted . we would need to push a lot of air backwards in order to move forward . astronauts move around in shuttles in zero gravity when they 're in outer space by pulling on handles installed on the ceiling walls and floors of the shuttle . now , imagine you were given the ability to float . how would you move around in the middle of the street ? well , you would n't get very far by swimming in air , would you ? nah , i do n't think so ! now , assuming you were granted the ability to float and the speed to move around efficiently , let 's discuss the height of your flight . according to the ideal gas law , p-v n-r-t , pressure and temperature has a positive correlation , meaning they increase and decrease together . this is because the air expands in volume with less pressure , so the molecules have more room to wander around without colliding into each other and creating heat . since the atmospheric pressure is a lot lower in high altitudes , it would be freezing cold if you were flying above the clouds . you 'd need to wrap yourself up to keep your core body temperature above 95 degrees fahrenheit , otherwise you 'd start shivering violently , gradually becoming mentally confused and eventually drop out of the sky due to loss of muscle control from hypothermia ! now , the ideal gas law implies that as the pressure decreases , gas volume increases . so , if you were to fly straight up too quickly , the inert gas in your body would rapidly expand the way soda fizzes up when shaken . the phenomenon is called `` the bends , '' decompression sickness , or `` divers disease '' since deep sea scuba divers experience this when they come up too quickly . this results in pain , paralysis , or death , depending on how foamy your blood becomes . okay , well , let 's say you want to fly just a few meters above the ground where you can still see the road signs and breath oxygen with ease . you 'll still need goggles and a helmet to protect you from birds , insects , street signs , electrical wires , and other flying humans , including flying cops ready to hand you a ticket if you do n't follow the flying rules , buddy . now remember , if you have a collision mid-air that knocks you unconscious , you would experience free fall until you hit the ground . without society or the laws of physics , flying would be a totally awesome ability to have . but , even if we could all just float around a few feet above the ground and only moving at a snail 's pace , i 'm telling you , it 's still a cool ability that i 'd want , would n't you ? yeah , i thought so . now , which superpower physics lesson will you explore next ? shifting body size and content , super speed , flight , super strength , immortality , and invisibility .
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as of 2012 , the world record for fastest short-distance sprint speed is roughly 27 miles per hour . running speed depends on how much force is exerted by the runner 's legs , and according to newton 's second law of motion , force is the product of mass times acceleration . and newton 's third law states that for every action , there is an equal and opposite reaction .
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how is newton ’ s third law of motion demonstrated when a person is running ? please draw a picture and label the direction and magnitude of the action force and the reaction force .
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how do you get what you want using just your words ? aristotle set out to answer exactly that question over 2,000 years ago with the treatise on rhetoric . rhetoric , according to aristotle , is the art of seeing the available means of persuasion . and today we apply it to any form of communication . aristotle focused on oration , though , and he described three types of persuasive speech . forensic , or judicial , rhetoric establishes facts and judgements about the past , similar to detectives at a crime scene . epideictic , or demonstrative , rhetoric makes a proclamation about the present situation , as in wedding speeches . but the way to accomplish change is through deliberative rhetoric , or symbouleutikon . rather than the past or the present , deliberative rhetoric focuses on the future . it 's the rhetoric of politicians debating a new law by imagining what effect it might have , like when ronald regan warned that the introduction of medicare would lead to a socialist future spent telling our children and our children 's children what it once was like in america when men were free . but it 's also the rhetoric of activists urging change , such as martin luther king jr 's dream that his children will one day live in a nation where they will not be judged by the color of their skin , but by the content of their character . in both cases , the speaker 's present their audience with a possible future and try to enlist their help in avoiding or achieving it . but what makes for good deliberative rhetoric , besides the future tense ? according to aristotle , there are three persuasive appeals : ethos , logos , and pathos . ethos is how you convince an audience of your credibility . winston churchill began his 1941 address to the u.s. congress by declaring , `` i have been in full harmony all my life with the tides which have flowed on both sides of the atlantic against privilege and monopoly , '' thus highlighting his virtue as someone committed to democracy . much earlier , in his defense of the poet archias , roman consul cicero appealed to his own practical wisdom and expertise as a politician : `` drawn from my study of the liberal sciences and from that careful training to which i admit that at no part of my life i have ever been disinclined . '' and finally , you can demonstrate disinterest , or that you 're not motivated by personal gain . logos is the use of logic and reason . this method can employ rhetorical devices such as analogies , examples , and citations of research or statistics . but it 's not just facts and figures . it 's also the structure and content of the speech itself . the point is to use factual knowledge to convince the audience , as in sojourner truth 's argument for women 's rights : `` i have as much muscle as any man and can do as much work as any man . i have plowed and reaped and husked and chopped and mowed and can any man do more than that ? '' unfortunately , speakers can also manipulate people with false information that the audience thinks is true , such as the debunked but still widely believed claim that vaccines cause autism . and finally , pathos appeals to emotion , and in our age of mass media , it 's often the most effective mode . pathos is neither inherently good nor bad , but it may be irrational and unpredictable . it can just as easily rally people for peace as incite them to war . most advertising , from beauty products that promise to relieve our physical insecurities to cars that make us feel powerful , relies on pathos . aristotle 's rhetorical appeals still remain powerful tools today , but deciding which of them to use is a matter of knowing your audience and purpose , as well as the right place and time . and perhaps just as important is being able to notice when these same methods of persuasion are being used on you .
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but what makes for good deliberative rhetoric , besides the future tense ? according to aristotle , there are three persuasive appeals : ethos , logos , and pathos . ethos is how you convince an audience of your credibility .
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according to aristotle , to build your credibility ( or ethos ) you should focus on your :
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most of us think of the sun as our friend . it helps plants grow , keeps us warm , and who does n't love to lie on the beach on a sunny day ? but for all of it 's good qualities , the sun can also be harmful in large amounts . that 's why we invented sunscreen . the purpose of sunscreen is to shield the body from the sun 's ultraviolet rays , which have several harmful effects , including sunburn , aging , and skin cancer promotion . these rays are separated by their different wave lengths , into types such as uva and uvb , which exert a variety of effects in the skin due to the absorption patterns of chromophores , the parts of the molecules responsible for their color . the primary two chromophores are hemoglobin , found in our red blood cells , and melanin , which gives our skin its pigment . we know that uvb rays cause the skin to burn . the role of uva rays is less well understood and appears to have an effect on our tanning response , carcinogenesis , and aging . so , how does the sunscreen protect us from these rays ? there are two basic types of sunscreen , physical and chemical blockers . physical blockers , like zinc oxide or titanium dioxide , reflect the sun 's rays by acting as a physical barrier . if you 've seen lifeguards with noses covered in white , then you know what this looks like . the same ingredients are primary components of diaper creams , where the goal is also to create a physical barrier . historically , they have n't always been easy to apply and were conspicuously visible on the skin , but new formulations have made this less of an issue . chemical blockers , on the other hand , absorb the sun 's rays . they deteriorate more quickly than physical sunscreens because their ability to absorb the sun diminishes . generally , these are more transparent when rubbed on the skin , but some people develop allergric reactions to some of the chemicals . regardless of the type of sunscreen , all are subjected to testing to determine their sunburn protection factor , or spf . this is essentially a measure of the protection that the sunscreen will provide from uvb rays before one begins to burn . but even if you do n't burn , you still need to use sunscreen because unless you live in a cave , you 're not immune to the effects of the sun . it is true that darker skinned people and those who tan easily have more built-in protection from sunburns , but they are still vulnerable to the effects of uva . children under the age of six months , on the other hand , should have almost no sun exposure as their protective mechanisms are not fully functioning , and their skin is more likely to absorb any sunscreen that is applied . wearing sunscreen helps protect against the development of all three types of skin cancer : basal cell carcinoma , squamous cell carcinoma , and melanoma . on a daily basis , the dna in your cells is developing mutations and errors that are generally handled by machinery within your cells , but ultraviolet rays from the sun lead to mutations that the cell may not be able to overcome , leading to uncontrolled growth and eventual skin cancer . the scariest thing about this is that usually you ca n't even see it happening until its too late . but if these concrete risks to your health are not enough to convince you to use sunscreen , there are aesthetic reasons as well . along with cigarette smoking , sun damage is the leading cause of premature aging . photoaging from chronic sun exposure leads to a loss of elasticity in the skin , in other words , making it look saggy . take a look at this truck driver who 's left side was chronically exposed to the sun and notice the difference . this is an important point . car windows block uvb , the burn rays , but not uva , the aging rays . it is recommended to use sunscreen daily , but you should pay special attention before prolonged sun exposure or when at the beach or among snow since the reflectivity of water and ice amplifies the sun 's rays . for these cases , apply about an ounce fifteen to thirty minutes before you go out and once again soon after you get outside . after that , you should reapply it every two to three hours , especially after swimming or sweating . otherwise you should wear protective clothing with ultraviolet protection factor , or upf . stay in shaded areas , such as under trees or an umbrella , and avoid the sun at the peak hours of 10 a.m. to 4 p.m. and what 's the best kind of sunscreen ? everyone will have their preference , but look for the following things : broad spectra , spf of at least 30 , and water-resistant . a light moisturizer with spf 30 should be good for daily use . take note if you decide to use a spray . they take several coats to effectively cover your skin , like painting a wall with a spray can versus a paint brush . so , enjoy the sun , but enjoy it with sunscreen .
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children under the age of six months , on the other hand , should have almost no sun exposure as their protective mechanisms are not fully functioning , and their skin is more likely to absorb any sunscreen that is applied . wearing sunscreen helps protect against the development of all three types of skin cancer : basal cell carcinoma , squamous cell carcinoma , and melanoma . on a daily basis , the dna in your cells is developing mutations and errors that are generally handled by machinery within your cells , but ultraviolet rays from the sun lead to mutations that the cell may not be able to overcome , leading to uncontrolled growth and eventual skin cancer .
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melanoma is the deadliest of the three types of skin cancer but is often found in areas with little to no sun exposure . why might this be ?
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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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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 .
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before cyanobacteria , oxygen on earth was :
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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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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 .
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on which planet or moon is nasa ’ s curiosity rover currently roving ?
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the onset of cancer usually begins as a solitary tumor in a specific area of the body . if the tumor is not removed , cancer has the ability to spread to nearby organs , as well as places far away from the origin , such as the brain . so how does cancer move to new areas , and why are some organs more likely to get infected than others ? the process of cancer spreading across the body is known as metastasis . it begins when cancer cells from an initial tumor invade nearby normal tissue . as the cells proliferate , they spread via one of the three common routes of metastasis : transcoelomic , lymphatic , or hematogenous spread . in transcoelomic spread , malignant cells penetrate the covering surfaces of cavities in our body . these surfaces are known as peritoneum and serve as walls to segment the body cavity . malignant cells in ovarian cancer , for example , spread through peritoneum , which connects the ovary to the liver , resulting in metastasis on the liver surface . next , cancerous cells invade blood vessels when they undergo hematogenous spread . as there are blood vessels almost everywhere in the body , malignant cells utilize this to reach more distant parts of the body . finally , lymphatic spread occurs when the cancer invades the lymph nodes , and travels to other parts of the body via the lymphatic system . as this system drains many parts of the body , it also provides a large network for the cancer . in addition , the lymphatic vessels empty into the blood circulation , allowing the malignant cells to undergo hematogenous spread . once at a new site , the cells once again undergo proliferation , and form small tumors known as micrometastases . these small tumors then grow into full-fledged tumors , and complete the metastatic process . different cancers have been known to have specific sites of metastasis . for example , prostate cancer commonly metastasizes to the bone , while colon cancer metastasizes to the liver . various theories have been proposed to explain the migration pattern of malignant cells . of particular interest are two conflicting theories . stephen paget , an english surgeon , came up with the seed and soil theory of metastasis . the seed and soil theory stated that cancer cells die easily in the wrong microenvironment , hence they only metastasize to a location with similar characteristics . however , james ewing , the first professor of pathology at cornell university , challenged the seed and soil theory , and proposed that the site of metastasis was determined by the location of the vascular and lymphatic channels which drain the primary tumor . patients with primary tumors that were drained by vessels leading to the lung would eventually develop lung metastases . today , we know that both theories contain valuable truths . yet the full stories of metastasis is much more complicated than either of the two proposed theories . factors like the cancer cell 's properties , and the effectiveness of the immune system in eliminating the cancer cells , also play a role in determining the success of metastasis . unfortunately , many questions about metastasis remain unanswered until today . understanding the exact mechanism holds an important key to finding a cure for advanced stage cancers . by studying both the genetic and environmental factors , which contribute to successful metastasis , we can pinpoint ways to shut down the process . the war against cancer is a constant struggle , and scientists are hard at work developing new methods against metastasis . of recent interest is immunotherapy , a modality which involves harnessing the power of the immune system to destroy the migrating cells . this can be done in different ways , such as training immune cells to recognize cancerous cells via vaccines . the growth and activity of the immune cells can also be stimulated by injecting man-made interleukins , chemicals which are usually secreted by the immune cells of the body . these two treatments are only the tip of the iceberg . with the collaborated research efforts of governments , companies and scientists , perhaps the process of metastasis will be stopped for good .
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patients with primary tumors that were drained by vessels leading to the lung would eventually develop lung metastases . today , we know that both theories contain valuable truths . yet the full stories of metastasis is much more complicated than either of the two proposed theories . factors like the cancer cell 's properties , and the effectiveness of the immune system in eliminating the cancer cells , also play a role in determining the success of metastasis .
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which of the following theories explains metastasis completely ?
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studies have shown that taking vitamins is good for your health and bad for your health . that newly discovered herb can improve your memory or destroy your liver . headlines proclaim a promising new cancer treatment and never mention it again . on a daily basis , we are bombarded with attention-grabbing news , backed up by scientific studies , but what are these studies ? how are they performed ? and how do we know whether they 're reliable ? when it comes to dietary or medical information , the first thing to remember is that while studies on animals or individual cells can point the way towards further research , the only way to know how something will affect humans is through a study involving human subjects . and when it comes to human studies , the scientific gold standard is the randomized clinical trial , or rct . the key to rcts is that the subjects are randomly assigned to their study groups . they are often blinded to make them more rigorous . this process attempts to ensure that the only difference between the groups is the one the researchers are attempting to study . for example , when testing a new headache medication , a large pool of people with headaches would be randomly divided into two groups , one receiving the medication and another receiving a placebo . with proper randomization , the only significant overall difference between the two groups will be whether or not they received the medication , rather than other differences that could affect results . randomized clinical trials are incredible tools , and , in fact , the us food and drug administration often requires at least two to be conducted before a new drug can be marketed . but the problem is that an rct is not possible in many cases , either because it 's not practical or would require too many volunteers . in such cases , scientists use an epidemiological study , which simply observes people going about their usual behavior , rather than randomly assigning active participants to control invariable groups . let 's say we wanted to study whether an herbal ingredient on the market causes nausea . rather than deliberately giving people something that might make them nauseated , we would find those who already take the ingredient in their everyday lives . this group is called the cohort . we would also need a comparison group of people who do not have exposure to the ingredient . and we would then compare statistics . if the rate of nausea is higher in the herbal cohort , it suggests an association between the herbal supplement and nausea . epidemiological studies are great tools to study the health effects of almost anything , without directly interfering in people 's lives or assigning them to potentially dangerous exposures . so , why ca n't we rely on these studies to establish causal relationships between substances and their effects on health ? the problem is that even the best conducted epidemiological studies have inherent flaws . precisely because the test subjects are not randomly assigned to their groups . for example , if the cohort in our herbal study consisted of people who took the supplement for health reasons , they may have already had higher rates of nausea than the other people in the sample . or the cohort group could 've been composed of people who shop at health food stores and have different diets or better access to healthcare . these factors that can affect results , in addition to the factor being studied , are known as confounding variables . these two major pitfalls , combined with more general dangers , such as conflicts of interest or selective use of data , can make the findings of any particular epidemiological study suspect , and a good study must go out of its way to prove that its authors have taken steps to eliminate these types of errors . but even when this has been done , the very nature of epidemiological studies , which examine differences between preexisting groups , rather than deliberately inducing changes within the same individuals , means that a single study can only demonstrate a correlation between a substance and a health outcome , rather than a true cause and effect relationship . at the end of the day , epidemiological studies have served as excellent guides to public health , alerting us to critical health hazards , such as smoking , asbestos , lead , and many more . but these were demonstrated through multiple , well-conducted epidemiological studies , all pointing in the same direction . so , the next time you see a headline about a new miracle cure or the terrible danger posed by an everyday substance , try to learn more about the original study and the limitations inherent in any epidemiological study or clinical trial before jumping to conclusions .
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but even when this has been done , the very nature of epidemiological studies , which examine differences between preexisting groups , rather than deliberately inducing changes within the same individuals , means that a single study can only demonstrate a correlation between a substance and a health outcome , rather than a true cause and effect relationship . at the end of the day , epidemiological studies have served as excellent guides to public health , alerting us to critical health hazards , such as smoking , asbestos , lead , and many more . but these were demonstrated through multiple , well-conducted epidemiological studies , all pointing in the same direction .
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studies conducted in animals can provide us with definitive information about human health risks .
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in 1879 , amateur archaeologist marcelino sanz de sautuola and his young daughter maria explored a dark cave in northern spain . when maria wondered off by herself , she made an amazing discovery . they were standing inside a site of ancient art , the walls and roofs decorated with prehistoric paintings and engravings , ranging from 19,000 to 35,000 years old . similar marks of our ancestors have been preserved in caves all over the world . the oldest we 've found were made up to 40,000 years ago . what do these images tell us about the ancient human mind and the lives of their creators ? these early artists mixed minerals , clay , charcoal , and ochre with spit or animal fat to create paint . they drew with their hands and tools , like pads of moss , twigs , bones , and hair . in many instances , their images follow the contours of the cave to create depth and shade . the most common depictions are of geometric shapes , followed by large mammals , like bison , horses , mammoths , deer , and boars . human figures appear rarely , as well as occasional hand prints . some have theorized that these artworks are the creation of hunters , or of holy men in trance-like states . and we 've found examples created by men , women , and even children . and why did they create this art ? perhaps they were documenting what they knew about the natural world , like modern scientists , or marking their tribal territory . maybe the images were the culmination of sacred hunting rituals or spiritual journeys . or could they be art for art 's sake , the sheer joy and fulfillment of creation ? as with many unsolved mysteries of the ancient world , we may never know for sure , barring the invention of a time machine , that is . but while the answers remain elusive , these images are our earliest proof of human communication , testifying to the human capacity for creativity thousands of years before writing . they are a distinct visual language that imagines the world outside the self , just like modern art forms , from graffiti and painting to animated virtual-reality caves .
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these early artists mixed minerals , clay , charcoal , and ochre with spit or animal fat to create paint . they drew with their hands and tools , like pads of moss , twigs , bones , and hair . in many instances , their images follow the contours of the cave to create depth and shade .
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cave painters commonly drew on cave walls with what tools ?
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one foggy morning in 1884 , the british steamer `` rumney '' crashed into the french ship `` frigorifique . '' seeing their ship filling with water , the french crew climbed aboard the `` rumney . '' but as they sailed towards the nearest port , a silent form suddenly emerged from the fog : the abandoned `` frigorifique . '' it was too late to turn , and the impact was enough to sink the `` rumney . '' as the sailors scrambled into the lifeboats , the empty `` frigorifique '' sailed back into the fog , having seemingly taken its revenge . in reality , the french sailors had left the engines running , and the `` frigorifique '' sailed in a circle before striking the `` rumney '' and finally sinking . but its story became one of the many tales of ghost ships , unmanned vessels that apparently sail themselves . and although they 've influenced works like `` dracula '' and `` pirates of the caribbean , '' crewless ships are n't the product of ghostly spirits , just physics at work . one of the most famous ghost ships was the `` mary celeste '' found sailing the atlantic in 1872 with no one aboard , water in its hold , and lifeboats missing . the discovery of its intact cargo and a captain 's log that ended abruptly led to wild rumors and speculation . but the real culprits were two scientific phenomena : buoyancy and fluid dynamics . here 's how buoyancy works . an object placed in a liquid displaces a certain volume of fluid . the liquid in turn exerts an upward buoyant force equal to the weight of the fluid that 's been displaced . this phenomenon is called archimedes 's principle . objects that are less dense than water , such as balsa wood , icebergs , and inflatable rafts always float . that 's because the upward buoyant force is always stronger than the downward force of gravity . but for objects or ships to float when they 're made of materials , like steel , that are denser than water , they must displace a volume of water larger than their weight . normally , the water filling a ship 's hull would increase its weight and cause it to sink - just what the `` mary celeste 's '' crew feared when they abandoned ship . but the sailors did n't account for fluid dynamics . the water stopped flowing at the point of equilibrium , when it reached the same level as the hull . as it turned out , the weight of the water was n't enough to sink the ship and the `` mary celeste '' was found a few days later while the unfortunate crew never made it to shore . far stranger is the tale of `` a. ernest mills , '' a schooner transporting salt , whose crew watched it sink to the sea floor following a collision . yet four days later , it was spotted floating on the surface . the key to the mystery lay in the ship 's heavy cargo of salt . the added weight of the water in the hull made the vessel sink , but as the salt dissolved in the water , the weight decreased enough that the force of gravity became less than the buoyant force and the ship floated back to the surface . but how do we explain the most enduring aspect of ghost ship legends : multiple sightings of the same ships hundreds of miles and several years apart ? the answer lies in ocean currents , which are like invisible rivers flowing through the ocean . factors , like temperature , salinity , wind , gravity , and the coriolis effect from the earth 's rotation create a complex system of water movement . that applies both at the ocean 's surface and deep below . sailors have always known about currents , but their patterns were n't well known until recently . in fact , tracking abandoned ships was how scientists determined the shape and speed of the atlantic gyre , the gulf stream , and related currents in the first place . beginning in 1883 , the u.s. hydrographic office began collecting monthly data that included navigation hazards , like derelict ships , whose locations were reported by passing vessels . so abandoned ships may not be moved by ghost crews or supernatural curses , but they are a real and fascinating phenomenon born through the ocean and kept afloat by powerful , invisible , scientifically studied forces .
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as it turned out , the weight of the water was n't enough to sink the ship and the `` mary celeste '' was found a few days later while the unfortunate crew never made it to shore . far stranger is the tale of `` a. ernest mills , '' a schooner transporting salt , whose crew watched it sink to the sea floor following a collision . yet four days later , it was spotted floating on the surface .
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the sunken `` a. ernest mills '' rose from the seafloor when :
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where does all this stuff come from ? this rock ? that cow ? your heart ? not the things themselves , mind you , but what they 're made of : the atoms that are the fabric of all things . to answer that question , we look to the law of conservation of mass . this law says take an isolated system defined by a boundary that matter and energy can not cross . inside this system , mass , a.k.a . matter and energy , can neither be created nor destroyed . the universe , to the best of our knowledge , is an isolated system . but before we get to that , let 's look at a much smaller and simpler one . here we have six carbon atoms , 12 hydrogen atoms , and 18 oxygen atoms . with a little energy , our molecules can really get moving . these atoms can bond together to form familiar molecules . here 's water , and here 's carbon dioxide . we ca n't create or destroy mass . we 're stuck with what we 've got , so what can we do ? ah , they have a mind of their own . let 's see . they 've formed more carbon dioxide and water , six of each . add a little energy , and we can get them to reshuffle themselves to a simple sugar , and some oxygen gas . our atoms are all accounted for : 6 carbon , 12 hydrogen , and 18 oxygen . the energy we applied is now stored in the bonds between atoms . we can rerelease that energy by breaking that sugar back into water and carbon dioxide , and still , same atoms . let 's put a few of our atoms aside and try something a little more explosive . this here is methane , most commonly associated with cow flatulence , but also used for rocket fuel . if we add some oxygen and a little bit of energy , like you might get from a lit match , it combusts into carbon dioxide , water and even more energy . notice our methane started with four hydrogen , and at the end we still have four hydrogen captured in two water molecules . for a grand finale , here 's propane , another combustible gas . we add oxygen , light it up , and boom . more water and carbon dioxide . this time we get three co2s because the propane molecule started with three carbon atoms , and they have nowhere else to go . there are many other reactions we can model with this small set of atoms , and the law of conservation of mass always holds true . whatever matter and energy go into a chemical reaction are present and accounted for when it 's complete . so if mass ca n't be created or destroyed , where did these atoms come from in the first place ? let 's turn back the clock and see . further , further , further , too far . okay , there it is . the big bang . our hydrogen formed from a high-energy soup of particles in the three minutes that followed the birth of our universe . eventually , clusters of atoms accumulated and formed stars . within these stars , nuclear reactions fused light elements , such as hydrogen and helium , to form heavier elements , such as carbon and oxygen . at first glance , these reactions may look like they 're breaking the law because they release an astounding amount of energy , seemingly out of nowhere . however , thanks to einstein 's famous equation , we know that energy is equivalent to mass . it turns out that the total mass of the starting atoms is very slightly more than the mass of the products , and that loss of mass perfectly corresponds to the gain in energy , which radiates out from the star as light , heat and energetic particles . eventually , this star went supernova and scattered its elements across space . long story short , they found each other and atoms from other supernovas , formed the earth , and 4.6 billion years later got scooped up to play their parts in our little isolated system . but they 're not nearly as interesting as the atoms that came together to form you , or that cow , or this rock . and that is why , as carl sagan famously told us , we are all made of star stuff .
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not the things themselves , mind you , but what they 're made of : the atoms that are the fabric of all things . to answer that question , we look to the law of conservation of mass . this law says take an isolated system defined by a boundary that matter and energy can not cross .
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why is it difficult to prove the law of conservation of mass when a gas is produced ?
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translator : andrea mcdonough reviewer : jessica ruby in all times and places in our history , human beings have wondered , `` where did we come from ? what 's our place in the world ? what happens to us after we die ? '' religions are systems of belief that have developed and evolved over time in response to these and other eternal mysteries , driven by the feeling that some questions can only be answered by faith and based on an intuition that there is something greater than ourselves , a higher power we must answer to , or some source we all spring from and to which we must return . hinduism means the religions of india . it 's not a single religion but rather a variety of related beliefs and spiritual practices . it dates back five millennia to the time of krishna , a man of such virtue that he became known as an avatar of vishnu , an incarnation of the god in human form . he taught that all life follows karma , the law of cause and effect , and our job is to do our duty , or dharma , according to our place in society without worrying how things turn out . when we die , we are reincarnated into a new body . if we followed our dharma and did our proper duty in our past life , we get good karma , which sends our soul upward in the social scale . our rebirth into the next life is thus determined by what we do in this one . the wheel of rebirths is called samsara . it 's possible for a very holy person to lead a life with enough good karma to escape the wheel . this escape is called moksha . hinduism teaches that everything is one . the whole universe is one transcendent reality called brahman , and there 's just one brahman but many gods within it , and their roles , aspects , and forms differ according to various traditions . brahma is the creator , vishnu is the preserver who sometimes takes on human form , and shiva is the transformer , or lord of the dance . durga is the fiercely protective divine mother . ganesha has an elephant head and is the wise patron of success . hinduism is the third largest religion in the world . and although most hindus live in india , they can be found on every continent , one billion strong . now , let 's travel west , across deserts and mountains to the fertile crescent about 4,000 years ago . judaism began with god calling abraham and sarah to leave mesopotamia and migrate to the land of canaan . in return for their faith in the one true god , a revolutionary concept in the polytheistic world of that time , they would have land and many descendants . from this promise came the land of israel and the chosen people , but staying in that land and keeping those people together was going to be very difficult . the israelites were enslaved in egypt , but god freed them with the help of the prophet moses , who received the ten commandments and later hundreds more . they conquered the promised land , but could only keep it for a few hundred years . israel sits at a crossroads through which many armies marched over the centuries . and in the year 70 , the romans destroyed the temple in their capital , jerusalem . so , the religion transformed itself from a temple religion with sacrifices and priests to a religion of the book . because of this , judaism is a faith of symbolism , reverence , and deep meanings tied to the literature of its history . the many sacred scriptures make up the hebrew bible , or tanakh , and hundreds of written discussions and interpretations are contained in an expansive compendium of deeper meanings , called the talmud . jews find rich , symbolic meaning in daily life . at the passover meal , every item on the menu symbolizes an aspect of the escape from slavery . the importance of growing up is emphasized when young people reach the age of bar and bat mitzvah , ceremonies during which they assume responsibility for their actions and celebrate the weaving of their own lives into the faith , history , and texts of the jewish people . there are 14 million jews in the world today , 6 million in israel , which became independent following the horrors of genocide in world war ii , and 5 million in the united states . but now let 's go back 2500 years and return to india where buddhism began with a young prince named siddhartha . on the night he was conceived , his mother , queen maya , is said to have been visited in her sleep by a white elephant who entered her side . ten months later , prince siddartha was born into a life of luxury . venturing forth from his sheltered existence as a young man , he witnessed the human suffering that had been hidden from him and immediately set out to investigate its sources . why must people endure suffering ? must we reincarnate through hundreds of lives ? at first he thought the problem was attachment to material things , so he gave up his possessions . he became a wandering beggar , which he discovered certainly made him no happier . then he overheard a music teacher telling a student , `` do n't tighten the string too much , it will break . but do n't let it go too slack , or it will not sound . '' in a flash , he realized that looking for answers at the extremes was a mistake . the middle way between luxury and poverty seemed wisest . and while meditating under a bodhi tree , the rest of the answer came to him . all of life abounds with suffering . it 's caused by selfish craving for one 's own fulfillment at the expense of others . following an eight-step plan can teach us to reduce that craving , and thus reduce the suffering . on that day , siddhartha became the buddha , the enlightened one . not the only one , but the first one . the buddhist plan is called the eightfold path , and though it is not easy to follow , it has pointed the way for millions to enlightenment , which is what buddhahood means , a state of compassion , insight , peace , and steadfastness . from the time he got up from under that tree to the moment of his death as an old man , the buddha taught people how to become enlightened : right speech , right goals , a mind focused on what is real , and a heart focused on loving others . many buddhists believe in god or gods , but actions are more important than beliefs . there are nearly a billion buddhists in the world today , mostly in east , southeast , and south asia . 2,000 years ago in judaism 's promised land , christianity was born . just as hindus called krishna `` god in human form , '' christians say the same thing about jesus , and christianity grew out of judaism just as buddhism grew out of hinduism . the angel gabriel was sent by the god of abraham to ask a young woman named mary to become the mother of his son . the son was jesus , raised as a carpenter by mary and her husband joseph , until he turned 30 , when he began his public career as the living word of god . less interested in religiousness than in justice and mercy , jesus healed the sick in order to draw crowds and then taught them about his heavenly father -- affectionate , forgiving , and attentive . then , he would invite everyone to a common table to illustrate his kingdom of god , outcasts , sinners , and saints all eating together . he had only three years before his unconventional wisdom got him into trouble . his enemies had him arrested , and he was executed by rome in the standard means by which rabble-rousers were put to death , crucifixion . but shortly after he was buried , women found his tomb empty and quickly spread word , convinced that he had been raised from the dead . the first christians described his resurrected appearances , inspiring confidence that his message was true . the message : love one another as i have loved you . christians celebrate the birth of jesus in december at christmas , and his suffering , death , and resurrection during holy week in the spring . in the ceremony of baptism , a washing away of sin and welcoming into the christian community , recall jesus 's own baptism when he left his life as a carpenter . in the rite of communion , christians eat the bread and drink the wine blessed as the body and blood of jesus , recalling jesus 's last supper . there are two billion christians worldwide , representing almost a third of the world 's people . islam began 1400 years ago with a man of great virtue , meditating in a mountain cave in the arabian desert . the man was muhammad . he was visited by a divine messenger , again the angel gabriel , in arabic , jibril , delivering to him the words of allah , the one god of abraham . in the next few years , more and more messages came , and he memorized and taught them . the verses he recited were full of wise sayings , beautiful rhymes , and mysterious metaphors . but muhammad was a merchant , not a poet . many agreed the verses were indeed the words of god , and these believers became the first muslims . the word muslim means one who surrenders , meaning a person who submits to the will of god . a muslim 's five most important duties are called the five pillars : shahada , muslims declare publicly , there is no other god but allah , and muhammad is his final prophet ; salat , they pray five times a day facing mecca ; zakat , every muslim is required to give 2 or 3 % of their net worth to the poor ; sawm , they fast during daylight hours for the lunar month of ramadan to strengthen their willpower and their reliance on god ; and hajj , once in a lifetime , every muslim who is able must make a pilgrimage to the holy city of mecca , rehearsing for the time when they will stand before god to be judged worthy or unworthy of eternal life with him . the words of god , revealed to the prophet over 23 years , are collected in the quran , which literally translates into `` the recitation . '' muslims believe it to be the only holy book free of human corruption . it 's also considered by many to be the finest work of literature in the arabic language . islam is the world 's second largest religion , practiced by over one and a half billion muslims around the globe . religion has been an aspect of culture for as long as it has existed , and there are countless variations of its practice . but common to all religions is an appeal for meaning beyond the empty vanities and lowly realities of existence , beyond sin , suffering , and death , beyond fear , and beyond ourselves .
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the word muslim means one who surrenders , meaning a person who submits to the will of god . a muslim 's five most important duties are called the five pillars : shahada , muslims declare publicly , there is no other god but allah , and muhammad is his final prophet ; salat , they pray five times a day facing mecca ; zakat , every muslim is required to give 2 or 3 % of their net worth to the poor ; sawm , they fast during daylight hours for the lunar month of ramadan to strengthen their willpower and their reliance on god ; and hajj , once in a lifetime , every muslim who is able must make a pilgrimage to the holy city of mecca , rehearsing for the time when they will stand before god to be judged worthy or unworthy of eternal life with him . the words of god , revealed to the prophet over 23 years , are collected in the quran , which literally translates into `` the recitation . ''
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the five pillars ( fasting , declaration of belief , pilgrimage , alms , and daily prayer ) are the principle religious duties in ________ .
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everyone knows that stories are made up of words , from short poems to epic novels . but did you know that a single word itself can tell an entire story ? you see , just as we can look at a story 's plot , setting , and characters , we can also study the history of an individual word , where it developed , and the cultures and people who helped shape it . looking into the story of a word is like counting the rings of a tree . newer words , like google or cyborg , have shorter stories . but the older the word , the longer the story and the more it stands to reveal to us not only about itself , but about ourselves and our history . the oldest words in present-day english are those that come from old english , the ancestor of our modern language whose first seeds were planted about 1500 years ago . compared to languages like greek or chinese that date back thousands of years , english is just a sapling in the lexical forest . but the stories of its words often start long before english itself took root . one such word is the familiar word true , as in true stories . let 's take a look . true usually means factual , correct , or faithful to reality . it can also mean exact , properly positioned , upright , or straight . a true friend is loyal , reliable , faithful , and steadfast . the word true is a simple word , and we can add some affixes to grow its family tree with words like truer , truest , truly , truth , and untruth . but if we go in the other direction to look at the roots of true itself , we find even more relatives further up the family tree . the words trust , bethroth , and truce all derive from the same source as true , and these words all denote faithfulness or confidence . a thousand years ago , the word true looked and sounded different than it does today . in several old english dialects , the word treow was a noun that meant good faith or trust , a pledge or a promise . but it also had another definition , tree , and that 's no coincidence . if we trace the roots back even farther , we find that both meanings derive from a common origin , where some of the earliest expressions of the concept of truth were associated with the uprightness of an oak , the steadiness of a silver birch , and the fidelity of an orchard baring fruit year after year . this may sound like a stretch at first , but trees are the oldest living organisms on this planet . some that would have been called treow long ago still stand today . the fortingall yew in scotland is more than 2,000 years old . a californian bristlecone pine is more than 5,000 . and utah 's pando-quaking aspen grove has a single root system that dates back more than 80 millennia . trees have also held a sacred place in many cultures throughout history . the celtic peoples who first inhabited the british isles believed that trees housed deities . and , in fact , the ancient druids take their name from the same ancient root as tree . planting a tree is itself an act of faith and commitment . not only are trees upright and prototypically straight , but they are actual , solid , and real , something you can see and touch . and they are as reliable and steadfast to us today as they were a millennium ago , nurturing us , sheltering us , and providing the pages of our books . philosophers and poets , people in search of the truth , have often sought it in trees . `` what did the tree learn from the earth to be able to talk with the sky ? '' asked pablo neruda . `` a tree falls the way it leans , '' says an old proverb . just as trees mark our landscapes and witness our histories , the stories of words landscape our language , capturing the rains and sunshine of generations and sending roots and branches far and wide . as there is a whole orchard in a single seed , there is a whole story in a single word , and that 's the truth .
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but the older the word , the longer the story and the more it stands to reveal to us not only about itself , but about ourselves and our history . the oldest words in present-day english are those that come from old english , the ancestor of our modern language whose first seeds were planted about 1500 years ago . compared to languages like greek or chinese that date back thousands of years , english is just a sapling in the lexical forest .
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the oldest words in present-day english come from what earlier language ?
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how high can you count on your fingers ? it seems like a question with an obvious answer . after all , most of us have ten fingers , or to be more precise , eight fingers and two thumbs . this gives us a total of ten digits on our two hands , which we use to count to ten . it 's no coincidence that the ten symbols we use in our modern numbering system are called digits as well . but that 's not the only way to count . in some places , it 's customary to go up to twelve on just one hand . how ? well , each finger is divided into three sections , and we have a natural pointer to indicate each one , the thumb . that gives us an easy to way to count to twelve on one hand . and if we want to count higher , we can use the digits on our other hand to keep track of each time we get to twelve , up to five groups of twelve , or 60 . better yet , let 's use the sections on the second hand to count twelve groups of twelve , up to 144 . that 's a pretty big improvement , but we can go higher by finding more countable parts on each hand . for example , each finger has three sections and three creases for a total of six things to count . now we 're up to 24 on each hand , and using our other hand to mark groups of 24 gets us all the way to 576 . can we go any higher ? it looks like we 've reached the limit of how many different finger parts we can count with any precision . so let 's think of something different . one of our greatest mathematical inventions is the system of positional notation , where the placement of symbols allows for different magnitudes of value , as in the number 999 . even though the same symbol is used three times , each position indicates a different order of magnitude . so we can use positional value on our fingers to beat our previous record . let 's forget about finger sections for a moment and look at the simplest case of having just two options per finger , up and down . this wo n't allow us to represent powers of ten , but it 's perfect for the counting system that uses powers of two , otherwise known as binary . in binary , each position has double the value of the previous one , so we can assign our fingers values of one , two , four , eight , all the way up to 512 . and any positive integer , up to a certain limit , can be expressed as a sum of these numbers . for example , the number seven is 4+2+1 . so we can represent it by having just these three fingers raised . meanwhile , 250 is 128+64+32+16+8+2 . how high an we go now ? that would be the number with all ten fingers raised , or 1,023 . is it possible to go even higher ? it depends on how dexterous you feel . if you can bend each finger just halfway , that gives us three different states - down , half bent , and raised . now , we can count using a base-three positional system , up to 59,048 . and if you can bend your fingers into four different states or more , you can get even higher . that limit is up to you , and your own flexibility and ingenuity . even with our fingers in just two possible states , we 're already working pretty efficiently . in fact , our computers are based on the same principle . each microchip consists of tiny electrical switches that can be either on or off , meaning that base-two is the default way they represent numbers . and just as we can use this system to count past 1,000 using only our fingers , computers can perform billions of operations just by counting off 1 's and 0 's .
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how high can you count on your fingers ? it seems like a question with an obvious answer .
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in the english language , the word digit refers to :
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translator : andrea mcdonough reviewer : bedirhan cinar the development and spread of railroads across the united states brought a wave of changes to american life . during the railroad boom , thousands of jobs were created , new towns were born , trade increased , transportation was faster , and the overall landscape of the nation transformed . but , perhaps the most interesting change of all is the least known : the establishment of standard time . today , we know if it is 6:28 a.m. in los angeles , it is 9:28 a.m. in new york , 2:28 p.m. in london , 5:28 p.m. in moscow , and 10:28 p.m in tokyo . no matter where you are , the minute and second are the exact same . but , before the railroads , there was no need for a national or global clock , and each town kept its own local time . so when it was 12 noon in chicago , it was 12:07 p.m. in indianapolis , 11:50 a.m. in st. louis , and 11:27 a.m. in omaha . this worked just fine when the only modes of travel were horses or steamboats , but it became incredibly problematic when railroads came along . how can you keep a train schedule when each town has its own time ? and how do you prevent collisions or accidents on the tracks if train conductors are using different clocks ? it does n't really make sense to leave a station at 12:14 p.m. , travel for 22 minutes , and arrive at 12:31 p.m . in order to eliminate that confusion , the railroads of the united states and canada instituted standard time zones on november 18 , 1883 at noon . it allowed the railroad companies to operate more effectively and reduce deadly accidents . the american public , however , was not so quick to embrace this new change , as many cities continued to use their own local time . resistance was so strong that , in some towns , clocks would show both the local time and the railway time . imagine this conversation : `` pardon me , sir . do you have the time ? '' `` why yes , which do you need ? it 's 12:13 local time and 12:16 railway time . '' ultimately , the logic of keeping a standard time prevailed , and the united states government made time zones a matter of law with the standard time act of march 19 , 1918 . since then , there have been numerous changes to the time zones , but the concept of standard time has remained . but , the united states was actually not the first to develop standard time . the first company to implement the use of standard time was the great western railway in 1840 in britain , and by 1847 , most british railways were using greenwich mean time , or g.m.t . the british government made it official on august 2 , 1880 with the statutes , or definition of time , act . but , while britain may have been the first to establish standard time , it is asia and the islands of the south pacific that enjoyed the first hour of each new day . the international date line passes through the pacific ocean on the opposite side of the earth from the prime meridian in greenwich where , thanks to trains , standard time was first used . trains have evolved over the years and remain a prominent form of transportation and trade throughout the world . and , from the new york city subways to the freight trains traveling across the great plains , to the trolleys in san francisco , they all know exactly what time it is . and , thanks to them , we do too !
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`` why yes , which do you need ? it 's 12:13 local time and 12:16 railway time . '' ultimately , the logic of keeping a standard time prevailed , and the united states government made time zones a matter of law with the standard time act of march 19 , 1918 . since then , there have been numerous changes to the time zones , but the concept of standard time has remained . but , the united states was actually not the first to develop standard time . the first company to implement the use of standard time was the great western railway in 1840 in britain , and by 1847 , most british railways were using greenwich mean time , or g.m.t . the british government made it official on august 2 , 1880 with the statutes , or definition of time , act .
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what was the first company to institute standard time ?
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in the winter of 1995 , scientists pointed the hubble telescope at an area of the sky near the big dipper , a spot that was dark and out of the way of light pollution from surrounding stars . the location was apparently empty , and the whole endeavor was risky . what , if anything , was going to show up ? over ten consecutive days , the telescope took close to 150 hours of exposure of that same area . and what came back was nothing short of spectacular : an image of over 1,500 distinct galaxies glimmering in a tiny sliver of the universe . now , let 's take a step back to understand the scale of this image . if you were to take a ballpoint pen and hold it at arm 's length in front of the night sky , focusing on its very tip , that is what the hubble telescope captured in its first deep field image . in other words , those 3,000 galaxies were seen in just a tiny speck of the universe , approximately one two-millionth of the night sky . to put all this in perspective , the average human measures about 1.7 meters . with earth 's diameter at 12,700 kilometers , that 's nearly 7.5 million humans lined up head to toe . the apollo 8 astronauts flew a distance of 380,000 kilometers to the moon . and our relatively small sun has a diameter of about 1.4 million kilometers , or 110 times the earth 's diameter . a step further , the milky way holds somewhere between 100 to 400 billion stars , including our sun . and each glowing dot of a galaxy captured in the deep field image contains billions of stars at the very least . almost a decade after taking the deep field image , scientists adjusted the optics on the hubble telescope and took another long exposure over a period of about four months . this time , they observed 10,000 galaxies . half of these galaxies have since been analyzed more clearly in what 's known as the extreme deep field image , or xdf . by combining over ten years of photographs , the xdf shows galaxies so distant that they 're only one ten-billionth the brightness that the human eye can perceive . so , what can we learn about the universe from the deep field images ? in a study of the universe , space and time are inextricably linked . that 's because of the finite speed of light . so the deep field images are like time machines to the ancient universe . they reach so far into space and time that we can observe galaxies that existed over 13 billion years ago . this means we 're looking at the universe as it was less than a billion years after the big bang , and it allows scientists to research galaxies in their infancy . the deep field images have also shown that the universe is homogeneous . that is , images taken at different spots in the sky look similar . that 's incredible when we think about how vast the universe is . why would we expect it to be the same across such huge distances ? on the scale of a galaxy , let alone the universe , we 're smaller than we can readily comprehend , but we do have the capacity to wonder , to question , to explore , to investigate , and to imagine . so the next time you stand gazing up at the night sky , take a moment to think about the enormity of what is beyond your vision , out in the dark spaces between the stars .
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this means we 're looking at the universe as it was less than a billion years after the big bang , and it allows scientists to research galaxies in their infancy . the deep field images have also shown that the universe is homogeneous . that is , images taken at different spots in the sky look similar .
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why were the scientist so shocked by the hubble deep field and the extreme deep field images ? discuss all that the images can teach us .
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long before descartes famously declared , `` i think , therefore i am , '' and long after that , scientists and philosophers alike have puzzled over what they call the mind-body problem . is the mind some separate , non-material entity piloting a machine of flesh ? or if it 's just a particularly elusive part of our physical body , how can it translate the input of our animal senses into the seemingly non-physical experiences that we call thoughts ? but though the answers have been debated endlessly , new research suggests that part of the problem lies in how we pose the question in the first place , assuming a distinction between our sensory perception and our ideas that may not really be there . the traditional model of our mental function has been that the senses provide separate data to our brain which are then translated into the appropriate mental phenomena : visual images into trees , auditory experiences into bird songs , and so on . but occasionally , we have come across people whose senses seem to mingle together , allowing them to hear colors , or taste sounds . until recently , the common understanding was that this phenomenon , called synesthesia , was a direct connection between the parts of the brain responsible for sensory stimuli such as seeing the color yellow immediately upon hearing the tone of b flat . but newer studies have shown that synesthesia is actually mediated through our understanding of the shapes , colors and sounds that our senses apprehend . in order for the cross-sensory experiences to occur , the higher level ideas and concepts that our minds associate with the sensory input must be activated . for example , this shape can be seen as either the letter `` s '' or the number `` 5 , '' and synesthetes associate each with different colors or sounds based on how they interpret it despite the purely visual stimulus remaining identical . in another study , synesthetes created novel color associations for unfamiliar letters after learning what the letters were . so because it relies on a connection between ideas and senses , this mental phenomenon underlying synesthesia is known as ideasthesia . synesthesia only occurs in some people , although it may be more common than previously thought . but ideasthesia itself is a fundamental part of our lives . virtually all of us recognize the color red as warm and blue as cold . many would agree that bright colors , italic letters and thin lines are high-pitched , while earth tones are low-pitched . and while many of these associations are acquired through cultural exposure , others have been demonstrated even in infants and apes , suggesting that at least some associations are inborn . when asked to choose between two possible names for these shapes , people from entirely different cultural and language backgrounds overwhelmingly agree that `` kiki '' is the spiky star , while `` bouba '' is the rounded blob , both because of the sounds themselves and the shapes our mouths make to produce them . and this leads to even more associations within a rich semantic network . kiki is described as nervous and clever , while bouba is perceived as lazy and slow . what all of this suggests is that our everyday experiences of colors , sounds and other stimuli do not live on separate sensory islands but are organized in a network of associations similar to our language network . this is what enables us to understand metaphors even though they make no logical sense , such as the comparison of snow to a white blanket , based on the shared sensations of softness and lightness . ideasthesia may even be crucial to art , which relies on a synthesis of the conceptual and the emotional . in great art , idea and aesthesia enhance each other , whether it 's song lyrics combining perfectly with a melody , the thematic content of a painting heightened by its use of colors and brushstrokes , or the well constructed plot of a novel conveyed through perfectly crafted sentences . most importantly , the network of associations formed by ideasethesia may not only be similar to our linguistic network but may , in fact , be an integral part of it . rather than the traditional view , where our senses first capture a collection of colors and shapes , or some vibrations in the air , and our mind then classifies them as a tree or a siren , ideasthesia suggests that the two processes occur simultaneously . our sensory perceptions are shaped by our conceptual understanding of the world . and the two are so connected that one can not exist without the other . if this model suggested by ideasthesia is accurate , it may have major implications for some of the biggest scientific and philosophical issues surrounding the study of mind . without a preexisting concept of self , descartes would not have had an `` i '' to attribute the thinking to . and without a preexisting network of interrelated and distinct concepts , our sensory experience of the world would be an undifferentiated mass rather than the discrete objects we actually apprehend . for science , the task is to find where this network lies , how it is formed , and how it interacts with external stimuli . for philosophy , the challenge is to rethink what this new model of consciousness means for our understanding of our selves and our relation to the world around us .
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synesthesia only occurs in some people , although it may be more common than previously thought . but ideasthesia itself is a fundamental part of our lives . virtually all of us recognize the color red as warm and blue as cold .
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should we strive to maximize ideasthesia in our lives ? or are we fine separating sensation and meaning , enjoying sensations that do n't have meaning and finding meaning without experiencing sensation ?
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we all know about the dinosaurs that once roamed the planet , but long after they went extinct , great beasts we call the megafauna lived on every continent . in the americas , ground sloths the size of elephants pulled down trees with their claws . saber-toothed cats the size of brown bears hunted in packs , but they were no match for short-faced bears , which stood thirteen feet on their hind legs , and are likely to have driven these cats away from their prey . there were armadillos as big as small cars , an eight foot beaver , and a bird with a 26 foot wingspan . almost everywhere , the world 's megafauna were driven to extinction , often by human hunters . some species still survive in parts of africa and asia . in other places , you can still see the legacy of these great beasts . most trees are able to resprout where their trunk is broken to withstand the loss of much of their bark and to survive splitting , twisting and trampling , partly because they evolved to survive attacks by elephants . the american pronghorn can run so fast because it evolved to escape the american cheetah . the surviving animals live in ghost ecosystems adapted to threats from species that no longer exist . today , it may be possible to resurrect those ghosts , to bring back lost species using genetic material . for instance , there 's been research in to cloning woolly mammoths from frozen remains . but even if it 's not possible , we can still restore many of the ecosystems the world has lost . how ? by making use of abandoned farms . as the market for food is globalized , infertile land becomes uncompetitive . farmers in barren places ca n't compete with people growing crops on better land elsewhere . as a result , farming has started to retreat from many regions , and trees have started to return . one estimate claims that two-thirds of land in the us that was once forested but was cleared for farming has become forested again . another estimate suggests that by 2030 , an area in europe the size of poland will be vaccated by farmers . so even if we ca n't use dna to bring back ground sloths and giant armadillos , we can restore bears , wolves , pumas lynx , moose and bison to the places where they used to live . some of these animals can reshape their surroundings , creating conditions that allow other species to thrive . when wolves were reintroduced to the yellowstone national park in 1995 , they quickly transformed the ecosystem . where they reduced the numbers of overpopulated deer , vegetation began to recover . the height of some trees quintupled in just six years . as forests returned , so did songbirds . beavers , which eat trees , multiplied in the rivers , and their dams provided homes for otters , muskrats , ducks , frogs and fish . the wolves killed coyotes , allowing rabbits and mice to increase , providing more food for hawks , weasels , foxes and badgers . bald eagles and ravens fed on the carrion that the wolves abandoned . so did bears , which also ate the berries on the returning shrubs . bison numbers rose as they browsed the revitalized forests . the wolves changed almost everything . this is an example of a trophic cascade , a change at the top of the food chain that tumbles all the way to the bottom , affecting every level . the discovery of widespread trophic cascades may be one of the most exciting scientific findings of the past half century . they tell us that ecosystems that have lost just one or two species of large animals can behave in radically different ways from those that retain them . all over the world , new movements are trying to catalyze the restoration of nature in a process called rewilding . this means undoing some of the damage we 've caused , reestablishing species which have been driven out , and then stepping back . there is no attempt to create an ideal ecosystem , to produce a heath , a rainforest or a coral reef . rewilding is about bringing back the species that drive dynamic processes and then letting nature take its course . but it 's essential that rewilding must never be used as an excuse to push people off the land . it should happen only with the consent and enthusiasm of the people who work there . imagine standing on a cliff in england , watching sperm whales attacking shoals of herring as they did within sight of the shore until the 18th century . by creating marine reserves in which no commerical fishing takes place , that can happen again . imagine a european serengeti full of the animals that used to live there : hippos , rhinos , elephants , hyenas and lions . what rewilding reintroduces , alongside the missing animals and plants , is that rare species called hope . it tells us that ecological change need not always proceed in the same direction . the silent spring could be followed by a wild summer .
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they tell us that ecosystems that have lost just one or two species of large animals can behave in radically different ways from those that retain them . all over the world , new movements are trying to catalyze the restoration of nature in a process called rewilding . this means undoing some of the damage we 've caused , reestablishing species which have been driven out , and then stepping back .
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the mass restoration of the natural world is widely known as :
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chat with a friend about an established scientific theory and she might reply , `` well , that 's just a theory . '' but a conversation about an established scientific law rarely ends with , `` well , that 's just a law . '' why is that ? what is the difference between a theory and a law , and is one better ? scientific laws and theories have different jobs to do . a scientific law predicts the results of certain initial conditions . it might predict your unborn child 's possible hair colors , or how far a baseball travels when launched at a certain angle . in contrast , a theory tries to provide the most logical explanation about why things happen as they do . a theory might invoke dominant and recessive genes to explain how brown-haired parents ended up with a red-headed child , or use gravity to shed light on the parabolic trajectory of a baseball . in simplest terms , a law predicts what happens while a theory proposes why . a theory will never grow up into a law , though the development of one often triggers progress on the other . in the 17th century , johannes kepler theorized cosmic musical harmonies to explain the nature of planetary orbits . he developed three brilliant laws of planetary motion while he was studying decades of precise astronomical data in an effort to find support for his theory . while his three laws are still in use today , gravity replaced his theory of harmonics to explain the planets ' motions . how did kepler get part of it wrong ? well , we were n't handed a universal instruction manual . instead , we continually propose , challenge , revise , or even replace our scientific ideas as a work in progress . laws usually resist change since they would n't have been adopted if they did n't fit the data , though we occasionally revise laws in the face of new unexpected information . a theory 's acceptance , however , is often gladiatorial . multiple theories may compete to supply the best explanation of a new scientific discovery . upon further research , scientists tend to favor the theory that can explain most of the data , though there may still be gaps in our understanding . scientists also like when a new theory successfully predicts previously unobserved phenomena , like when dmitri mendeleev 's theory about the periodic table predicted several undiscovered elements . the term scientific theory covers a broad swath . some theories are new ideas with little experimental evidence that scientists eye with suspicion , or even ridicule . other theories , like those involving the big bang , evolution , and climate change , have endured years of experimental confirmation before earning acceptance by the majority of the scientific community . you would need to learn more about a specific explanation before you 'd know how well scientists perceive it . the word theory alone does n't tell you . in full disclosure , the scientific community has bet on the wrong horse before : alchemy , the geocentric model , spontaneous generation , and the interstellar aether are just a few of many theories discarded in favor of better ones . but even incorrect theories have their value . discredited alchemy was the birthplace of modern chemistry , and medicine made great strides long before we understood the roles of bacteria and viruses . that said , better theories often lead to exciting new discoveries that were unimaginable under the old way of thinking . nor should we assume all of our current scientific theories will stand the test of time . a single unexpected result is enough to challenge the status quo . however , vulnerability to some potentially better explanation does n't weaken a current scientific theory . instead , it shields science from becoming unchallenged dogma . a good scientific law is a finely-tuned machine , accomplishing its task brilliantly but ignorant of why it works as well as it does . a good scientific theory is a bruised , but unbowed , fighter who risks defeat if unable to overpower or adapt to the next challenger . though different , science needs both laws and theories to understand the whole picture . so next time someone comments that it 's just a theory , challenge them to go nine rounds with the champ and see if they can do any better .
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laws usually resist change since they would n't have been adopted if they did n't fit the data , though we occasionally revise laws in the face of new unexpected information . a theory 's acceptance , however , is often gladiatorial . multiple theories may compete to supply the best explanation of a new scientific discovery . upon further research , scientists tend to favor the theory that can explain most of the data , though there may still be gaps in our understanding . scientists also like when a new theory successfully predicts previously unobserved phenomena , like when dmitri mendeleev 's theory about the periodic table predicted several undiscovered elements .
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before louis pasteur , people did not seriously think that tiny microbes could have much of an effect on the 'big-sized ' world of people . louis pasteur challenged the theories of his time when he used microbes to explain how food was spoiling in factories . research at least one new advance that was possible once people accepted that his theory was correct .
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somewhere right now , people are lining up to scare themselves , maybe with a thrill ride or horror movie . in fact , in october of 2015 alone , about 28 million people visited a haunted house in the u.s . but many consider this behavior perplexing , asking the question , `` what could possibly be fun about being scared ? '' fear has a bad rap , but it 's not all bad . for starters , fear can actually feel pretty good . when a threat triggers our fight or flight response , our bodies prepare for danger by releasing chemicals that change how our brains and bodies function . this automatic response jumpstarts systems that can aid in survival . they do this by making sure we have enough energy and are protected from feeling pain , while shutting down nonessential systems , like critical thought . feeling pain-free and energized , while not getting caught up in worrisome thoughts that normally occupy our brains , that all sounds great , and it can be because this response is similar , though not exactly the same to what we experience in positive , high-arousal states , like excitement , happiness , and even during sex . the difference lays in the context . if we 're in real danger , we 're focused on survival , not fun . but when we trigger this high arousal response in a safe place , we can switch over to enjoying the natural high of being scared . it 's why people on roller coasters can go from screaming to laughing within moments . your body is already in a euphoric state . you 're just relabeling the experience . and though the threat response is universal , research shows differences between individuals in how the chemicals associated with the threat response work . this explains why some are more prone to thrill-seeking than others . other normal physical differences explain why some may love the dizziness associated with a loop-de-loop , while loathing the stomach-drop sensation of a steep roller coaster , or why some squeal with delight inside a haunted house , but retreat in terror if taken to an actual cemetery . fear brings more than just a fun , natural high . doing things that we 're afraid of can give us a nice boost of self-esteem . like any personal challenge , whether it 's running a race or finishing a long book , when we make it through to the end , we feel a sense of accomplishment . this is true even if we know we 're not really in any danger . our thinking brains may know the zombies are n't real , but our bodies tell us otherwise . the fear feels real , so when we make it through alive , the satisfaction and sense of accomplishment also feel real . this is a great evolutionary adaptation . those who had the right balance of bravery and wit to know when to push through the fear and when to retreat were rewarded with survival , new food , and new lands . finally , fear can bring people together . emotions can be contagious , and when you see your friend scream and laugh , you feel compelled to do the same . this is because we make sense of what our friends are experiencing by recreating the experience ourselves . in fact , the parts of the brain that are active when our friend screams are active in us when we watch them . this not only intensifies our own emotional experience , but makes us feel closer to those we 're with . the feeling of closeness during times of fear is aided by the hormone oxytocin released during fight or flight . fear is a powerful emotional experience , and anything that triggers a strong reaction is going to be stored in our memory really well . you do n't want to forget what can hurt you . so if your memory of watching a horror film with your friends is positive and left you with a sense of satisfaction , then you 'll want to do it over and over again .
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it 's why people on roller coasters can go from screaming to laughing within moments . your body is already in a euphoric state . you 're just relabeling the experience .
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during fight or flight , our body prioritizes all the following types of brain and body functioning except for :
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it 's so obvious that it 's practically proverbial . you ca n't unboil an egg . well , it turns out you can , sort of . what thermal energy does to the eggs ' molecules , mechanical energy can undo . eggs are mostly made of water and proteins . the proteins start off folded up into intricate shapes , held together by weak chemical bonds . adding heat disrupts those bonds , allowing the proteins to unfold , uncoil , unwind and wiggle freely . this process is called denaturing . the newly liberated proteins bump up against their neighbors and start to form new bonds with each other , more and more as the heat increases , until finally , they 're so entangled that they gel into a solid mass , a boiled egg . that entanglement might look permanent , but it 's not . according to a chemical idea called the principle of microscopic reversibility , anything that happens , like egg proteins seizing up , can theoretically unhappen if you retrace your steps . but adding more heat will tangle the proteins further , and cooling them down will only freeze them , so here 's the trick : spin them around ridiculously fast . i 'm not kidding . here 's how it works . first , scientists dissolve boiled egg whites in water with a chemical called urea , a small molecule that acts as a lubricant , coating the proteins ' long strands and making it easier for them to glide past each other . then , they spin that solution in a glass tube at a breakneck 5000 rotations per minute , making the solution spread out into a thin film . here 's the key part . the solution nearest the wall spins faster than the solution closer to the middle . that difference in velocity creates sheer stresses that repeatedly stretch and contract the proteins until eventually they snap back into their native shapes and stay there . by the time the centrifuge stops spinning , the egg white is back in its original unboiled state . this technique works with all sorts of proteins . bigger , messier proteins can be more resistant to being pulled apart , so scientists attach a plastic bead to one end that adds extra stress and encourages it to fold up first . this unboiling method wo n't work with a whole egg in its shell since the solution has to spread throughout a cylindrical chamber . but the applications go way beyond uncooking your breakfast , anyhow . many pharmaceuticals consist of proteins that are extremely expensive to produce , partly because they get stuck in tangled up aggregates , just like cooked egg whites and have to be untangled and refolded before they can do their jobs . this spinning technique has the potential to be an easier , cheaper and quicker method than other ways to refold proteins , so it may allow new drugs to be made available to more people faster . and there 's one more thing you need to keep in mind before trying to uncook all of your food . boiling an egg is actually an unusual cooking process because even though it changes the way proteins are shaped and bound together , it does n't actually change their chemical identity . most types of cooking are more like the famous maillard reaction , which makes chemical changes that turn sugars and proteins into delicious caramel crunchiness and are a lot harder to undo . so you might be able to unboil your egg , but i 'm sorry to say you ca n't unfry it ... yet .
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that difference in velocity creates sheer stresses that repeatedly stretch and contract the proteins until eventually they snap back into their native shapes and stay there . by the time the centrifuge stops spinning , the egg white is back in its original unboiled state . this technique works with all sorts of proteins .
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given what you know about the structure of the proteins in raw vs. boiled egg white , explain why raw egg white is runny while boiled egg white is solid and bouncy .
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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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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 . ''
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the lewis and clark expedition took place in the early 1800s . how would this journey be different if it had taken place in the early 1900s ? how would it be different if it had taken place in the early 2000s ? how would the group travel ? would they eat the same things ? how might modern technology make things different ?
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what lights up the screen that you 're looking at right now ? trace back the battery chargers and power cords and you 'll end up at an electrical outlet , providing easy , safe access to reliable electricity . but beyond that outlet , the picture gets messier . it takes a lot of fuel to heat our homes , preserve our food , and our power our gadgets around the clock . and for 40 % of the world , that fuel is cheap , plentiful , and it 's called coal . but coal also releases pollutants into the air , like sulfur dioxide , nitrogen oxides , soot , and toxic metals , like mercury . these cause environmental damage , like acid rain , and serious health problems . in fact , in 1952 , coal burning caused such heavy smog in london that pedestrians could n't even see their feet , and thousands of people died from ill health . since then , many countries have deployed technology to remove most of these pollutants before they reach the air . but now we have a new air pollution problem on our hands , one that does n't show up in a cloud of dark smog , but in rising seas , floods , and heat waves . it 's global climate change , and again , the main culprit is coal . it 's responsible for 44 % of global carbon dioxide emissions , which trap the sun 's heat in the earth 's atmosphere , instead of letting it escape . so now the question is how do we remove that bad stuff as well ? that 's the idea behind cleaner coal . creating cleaner coal is really about trying to contain its ill effects with the help of special technologies that make the end product more acceptable . just like the most intriguing superheroes often have their own dark powers to overcome , so we can try and keep coal 's negative forces in check . but why do n't we just exterminate coal if it takes that much effort to clean it up ? simply , coal is extremely valuable to us , and it 's easy to come by . compressed underground for ages , coal holds chemical energy from plants that were fed from by the sun hundreds of millions of years ago , long before humans evolved . that makes coal energy dense , meaning it can be burned 'round the clock . it 's also cheap , if you ignore the pollution costs , and should last us through the end of the 21st century . we 've already got all the infrastructure in place for harnessing its power , and globally , although countries are making a move towards energy from cleaner and more renewable sources , there 's no sign yet that coal use is slowing down . in fact , as of 2012 , over 1000 new coal plants have been proposed , mostly in china and india . since for the time being coal is here to stay , experts say that if we want to reduce its emissions ' impact on the atmosphere , and slow down climate change , we 'll have to think of creative ways of reducing coal 's destructive power . to do that , we need to strip it of its foul forces , all that toxic carbon dioxide that causes havoc in the atmosphere . then , we need to store the co2 somewhere else . this mission is called carbon capture and sequestration , or ccs . and as if carbon dioxide were some evil genie we did n't want to escape , once it has been separated from coal , we 've devised ways to banish it underground . we can do this by injecting it deep into the earth , or by placing it deep under the ocean 's surface . stripping away coal 's negative elements can happen in three ways . first , and most commonly , as coal burns , the exhaust gas can be mixed with a compound called monoethanolamine . like a forceful power-stripping magnet , this compound bonds to the co2 , yanking it out of the gas stream so it can be stored separately underground . another method is to relieve coal of its co2 before it even has a chance to be released as exhaust . in this process , steam and oxygen swoop in to the rescue to convert coal into a special product called syngas , made up of carbon monoxide and hydrogen and some co2 . zap that with some water vapor , and the carbon monoxide gets converted into carbon dioxide , which can be isolated . the leftover hydrogen gas is then used as energy to generate electricity , so there 's an added bonus . a third technique exposes coal to pure oxygen , instead of burning it in air . this creates exhaust gas with higher concentrations of carbon dioxide , which makes it easy to isolate and to banish to the chasms below . all this can reduce emissions at a power plant by up to 90 % , but as with any superhero struggling with their destructive powers , it takes a lot of effort to switch over from the dark side . so these positive pollution-busting forces , although they 're available , have barely been used in commercial power plants because they cost a lot . but ultimately , the bigger problem is that in most parts of the world , it 's still too easy and much cheaper to keep emitting carbon dioxide , and that makes it tempting to completely ignore coal 's dark side . in this case , the most powerful force for good is regulation , the rules that can restrict the amount of carbon dioxide emitted from power plants , and make energy companies around the world wary of what they put into the air . until then , every time you turn on a screen or flick a light switch , coal is lurking in the background , carrying its dark powers with it wherever it goes .
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so now the question is how do we remove that bad stuff as well ? that 's the idea behind cleaner coal . creating cleaner coal is really about trying to contain its ill effects with the help of special technologies that make the end product more acceptable .
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true or false : our use of coal is currently declining
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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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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 .
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which animals are typical deep sea animals ?
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in the 18th century , swedish botanist carolus linnaeus designed the flower clock , a timepiece made of flowering plants that bloom and close at specific times of day . linnaeus 's plan was n't perfect , but the idea behind it was correct . flowers can indeed sense time , after a fashion . mornings glories unfurl their petals like clockwork in the early morning . a closing white water lily signals that it 's late afternoon , and moon flowers , as the name suggests , only bloom under the night sky . but what gives plants this innate sense of time ? it 's not just plants , in fact . many organisms on earth have a seemingly inherent awareness of where they are in the day 's cycle . that 's because of circadian rhythms , the internal timekeepers that tick away inside many living things . these biological clocks allow organisms to keep track of time and pick up on environmental cues that help them adapt . that 's important , because the planet 's rotations and revolutions put us in a state of constant flux , although it plays out in a repetitive , predictable way . circadian rhythms incorporate various cues to regulate when an organism should wake and sleep , and perform certain activities . for plants , light and temperature are the cues which trigger reactions that play out at a molecular scale . the cells in stems , leaves , and flowers contain phytochromes , tiny molecules that detect light . when that happens , phytochromes initiate a chain of chemical reactions , passing the message down into the cellular nuclei . there , transcription factors trigger the manufacture of proteins required to carry out light-dependent processes , like photosynthesis . these phytochromes not only sense the amount of light the plant receives , but can also detect tiny differences in the distribution of wavelengths the plant takes in . with this fine-tuned sensing , phytochromes allow the plant to discern both time , the difference between the middle of the day and the evening , and place , whether it is in direct sunlight or shade , enabling the plant to match its chemical reactions to its environment . this makes for early risers . a few hours before sunrise , a typical plant is already active , creating mrna templates for its photosynthesizing machinery . as the phytochromes detect increasing sunlight , the plant readies its light-capturing molecules so it can photosynthesize and grow throughout the morning . after harvesting their morning light , plants use the rest of the day to build long chains of energy in the form of glucose polymers , like starch . the sun sets , and the day 's work is done , though a plant is anything but inactive at night . in the absence of sunlight , they metabolize and grow , breaking down the starch from the previous day 's energy harvest . many plants have seasonal rhythms as well . as spring melts the winter frost , phytochromes sense the longer days and increasing light , and a currently unknown mechanism detects the temperature change . these systems pass the news throughout the plant and make it produce blooming flowers in preparation for the pollinators brought out by warmer weather . circadian rhythms act as a link between a plant and its environment . these oscillations come from the plants themselves . each one has a default rhythm . even so , these clocks can adapt their oscillations to environmental changes and cues . on a planet that 's in constant flux , it 's the circadian rhythms that enable a plant to stay true to its schedule and to keep its own time .
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for plants , light and temperature are the cues which trigger reactions that play out at a molecular scale . the cells in stems , leaves , and flowers contain phytochromes , tiny molecules that detect light . when that happens , phytochromes initiate a chain of chemical reactions , passing the message down into the cellular nuclei .
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circadian rhythms are especially important in the beginning of a plant 's life . until their phytochromes perceive the presence of light , seed sprouts grow tall and long , and do not produce any green pigment . as soon as they reach light , they begin to produce green pigment and broader leaves . what are the advantages of producing green pigment only after the presence of light ?
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so , you 're thinking of moving to mars . have you picked out a spot for your new home ? no ? well , i 'm here to help . first things first , here are some of the things you 'll need to bring to the red planet : a high tolerance for cold , loneliness , and radiation ; a lifetime supply of breathable air and food ; a multibillion dollar spaceship ; a desire to just get away from it all ; and water . you 're definitely going to need water . so what sort of real estate are you looking for ? how about a mansion in the maze-like noctis labyrinthus ? a hideaway in the happy face crater ? a fortress on the face mesa ? an oceanview ? uh , bad news on the last one . you 're about 4 billion years late . we 're pretty sure that mars used to have oceans , lakes , rivers , the whole package . but over time , almost all of it froze beneath the surface , or evaporated off into space . there 's probably still some trapped beneath the seasonally expanding and contracting carbon dioxide ice caps , though . so what might mars look like today if it had surface water ? that , of course , depends on how much we 're talking about , but maybe something like this . the relatively flat northern hemisphere is below the average elevation , so it would become one giant ocean , while the crater-ridden southern hemisphere would stay mostly high and dry . that difference between hemispheres is a bit bizarre , and we do n't know why it 's like that . the southern half is probably much older , judging by features like the number of craters , and the evidence of increased volcanic activity in the north . okay , so who knows ? maybe one day mars will have oceans again , but for now , what we 've got is essentially one giant dusty desert . in fact , it 's similar enough to deserts on earth , that we 've been able to learn a great deal about mars on our home planet . for instance , martian sand dunes form and behave similarly to our sand dunes , though the martian versions often grow twice as large thanks to a gravitational pull that 's about a third as strong as ours . and mars has some features you wo n't see on earth , like tars , which are crestless sand dunes up to fifteen meters tall , whose formations we have yet to understand . you 're probably wondering , `` what do you get when you combine a planet-wide desert with an atmosphere that , like ours , is subject to wind-generating pressure differentials , dust storms ? '' these will be your main weather hazards on the red planet . they play a large part in making the planet red by distributing rusted iron particles across the surface and into the air . thanks to the low gravity and lack of moisture , these dust storms can last for months and cover the planet . so , you might want to build your home as high as possible . well , look no further . this is olympus mons , the largest volcano in the solar system . even if mars had a breathable atmosphere , you 'd find the views from the 25 kilometer summit breathtaking . or are volcanos not your thing ? then how about valles marineris , the largest canyon in the solar system ? it 's so wide that from one side , the opposite rim would be below the curve of the horizon . still , you 'll catch some spectacular blue sunsets in the normally red sky , which gets its color from the dust absorbing most of the blue light , and the way sunlight is scattered by the atmosphere . have you got spirit , curiosity , or are you just looking for opportunity ? then stop stalling and make the move to mars today . mars : redder than ever .
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there 's probably still some trapped beneath the seasonally expanding and contracting carbon dioxide ice caps , though . so what might mars look like today if it had surface water ? that , of course , depends on how much we 're talking about , but maybe something like this .
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which part of mars ' surface seems older ?
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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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briefly define and contrast physicalism and the knowledge argument . which one is more strongly supported by the thought experiment ?
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do you remember when you first realized that your computer was more than just a monitor and keyboard ? that between the mouse click and the video playing , there was something that captured your intention , understood it , and made it real ? what is that something ? is it gremlins ? let 's imagine that we can shrink down to the size of an electron and inject ourselves into a click of a mouse . if you took your mouse apart , you 'd see that it 's really a very simple machine . it has a couple buttons and a system for detecting motion and distance . you might have an optical mouse that makes these measurements with lights and sensors , but older ones did this with a hard rubber ball and some plastic wheels . same concept . when you click the button on your mouse , it sends a message to the computer with information about its position . when your mouse click is received , it 's handled by the basic input/output subsystem . this subsystem acts like the eyes and ears and mouth and hands of the computer . basically , it provides a way for the computer to interact with its environment . but it also acts like a buffer to keep the cpu from being overwhelmed by distractions . in this case , the i/o subsystem decides that your mouse click is pretty important so it generates an interrupt to the cpu . `` hey , cpu ! got a click here . '' the cpu , or central processing unit , is the brains of the whole computer . just like your brain does n't take up your whole body , the cpu does n't take up the whole computer , but it runs the show all the same . and the cpu 's job , its whole job , is fetching instructions from memory and executing them . so , while you 're typing , typing , typing , maybe really fast , like 60 words a minute , the cpu is fetching and executing billions of instructions a second . yes , billions every second : instructions to move your mouse around on the screen , to run that clock widget on your desktop , play your internet radio , manage the files you 're editing on the hard drive , and much , much more . your computer 's cpu is one heck of a multitasker ! `` but oh my gosh there 's a very important mouse click coming through now ! let 's drop everything now and deal with that ! '' there are programs for everything that the cpu does . a special program for the mouse , for the clock widget , for the internet radio , and for dealing with letters sent by the keyboard . each program was initially written by a human in a human-readable programming language , like java , c++ , or python . but human programs take up a lot of space and contain a lot of unnecessary information to a computer , so they are compiled and made smaller and stored in bits of ones and zeros in memory . the cpu realizes that it needs instructions for how to deal with this mouse click , so it looks up the address for the mouse program and sends a request to the memory subsystem for instructions stored there . each instruction in the mouse device driver is duly fetched and executed . and that 's not nearly the end of the story ! because the cpu learns that the mouse was clicked when the cursor was over a picture of a button on the monitor screen , and so , the cpu asks memory for the monitor program to find out what that button is . and then the cpu has to ask memory for the program for the button , which means that the cpu needs the monitor program again to show the video associated with the button , and so it goes . and let 's just say there are a lot of programs involved before you even see the button on the screen light up when you clicked it . so , just the simple task of clicking your mouse means visiting all of the critical components of your computer 's architecture : peripherals , the basic input-output system , the cpu , programs , and memory , and not one gremlin .
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in this case , the i/o subsystem decides that your mouse click is pretty important so it generates an interrupt to the cpu . `` hey , cpu ! got a click here . ''
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the cpu ’ s job is
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would mathematics exist if people did n't ? since ancient times , mankind has hotly debated whether mathematics was discovered or invented . did we create mathematical concepts to help us understand the universe around us , or is math the native language of the universe itself , existing whether we find its truths or not ? are numbers , polygons and equations truly real , or merely ethereal representations of some theoretical ideal ? the independent reality of math has some ancient advocates . the pythagoreans of 5th century greece believed numbers were both living entities and universal principles . they called the number one , `` the monad , '' the generator of all other numbers and source of all creation . numbers were active agents in nature . plato argued mathematical concepts were concrete and as real as the universe itself , regardless of our knowledge of them . euclid , the father of geometry , believed nature itself was the physical manifestation of mathematical laws . others argue that while numbers may or may not exist physically , mathematical statements definitely do n't . their truth values are based on rules that humans created . mathematics is thus an invented logic exercise , with no existence outside mankind 's conscious thought , a language of abstract relationships based on patterns discerned by brains , built to use those patterns to invent useful but artificial order from chaos . one proponent of this sort of idea was leopold kronecker , a professor of mathematics in 19th century germany . his belief is summed up in his famous statement : `` god created the natural numbers , all else is the work of man . '' during mathematician david hilbert 's lifetime , there was a push to establish mathematics as a logical construct . hilbert attempted to axiomatize all of mathematics , as euclid had done with geometry . he and others who attempted this saw mathematics as a deeply philosophical game but a game nonetheless . henri poincaré , one of the father 's of non-euclidean geometry , believed that the existence of non-euclidean geometry , dealing with the non-flat surfaces of hyperbolic and elliptical curvatures , proved that euclidean geometry , the long standing geometry of flat surfaces , was not a universal truth , but rather one outcome of using one particular set of game rules . but in 1960 , nobel physics laureate eugene wigner coined the phrase , `` the unreasonable effectiveness of mathematics , '' pushing strongly for the idea that mathematics is real and discovered by people . wigner pointed out that many purely mathematical theories developed in a vacuum , often with no view towards describing any physical phenomena , have proven decades or even centuries later , to be the framework necessary to explain how the universe has been working all along . for instance , the number theory of british mathematician gottfried hardy , who had boasted that none of his work would ever be found useful in describing any phenomena in the real world , helped establish cryptography . another piece of his purely theoretical work became known as the hardy-weinberg law in genetics , and won a nobel prize . and fibonacci stumbled upon his famous sequence while looking at the growth of an idealized rabbit population . mankind later found the sequence everywhere in nature , from sunflower seeds and flower petal arrangements , to the structure of a pineapple , even the branching of bronchi in the lungs . or there 's the non-euclidean work of bernhard riemann in the 1850s , which einstein used in the model for general relativity a century later . here 's an even bigger jump : mathematical knot theory , first developed around 1771 to describe the geometry of position , was used in the late 20th century to explain how dna unravels itself during the replication process . it may even provide key explanations for string theory . some of the most influential mathematicians and scientists of all of human history have chimed in on the issue as well , often in surprising ways . so , is mathematics an invention or a discovery ? artificial construct or universal truth ? human product or natural , possibly divine , creation ? these questions are so deep the debate often becomes spiritual in nature . the answer might depend on the specific concept being looked at , but it can all feel like a distorted zen koan . if there 's a number of trees in a forest , but no one 's there to count them , does that number exist ?
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henri poincaré , one of the father 's of non-euclidean geometry , believed that the existence of non-euclidean geometry , dealing with the non-flat surfaces of hyperbolic and elliptical curvatures , proved that euclidean geometry , the long standing geometry of flat surfaces , was not a universal truth , but rather one outcome of using one particular set of game rules . but in 1960 , nobel physics laureate eugene wigner coined the phrase , `` the unreasonable effectiveness of mathematics , '' pushing strongly for the idea that mathematics is real and discovered by people . wigner pointed out that many purely mathematical theories developed in a vacuum , often with no view towards describing any physical phenomena , have proven decades or even centuries later , to be the framework necessary to explain how the universe has been working all along .
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what famous phrase did eugene wigner coin regarding mathematics ?
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how can you play a rubik 's cube ? not play with it , but play it like a piano ? that question does n't make a lot of sense at first , but an abstract mathematical field called group theory holds the answer , if you 'll bear with me . in math , a group is a particular collection of elements . that might be a set of integers , the face of a rubik 's cube , or anything , so long as they follow four specific rules , or axioms . axiom one : all group operations must be closed or restricted to only group elements . so in our square , for any operation you do , like turn it one way or the other , you 'll still wind up with an element of the group . axiom two : no matter where we put parentheses when we 're doing a single group operation , we still get the same result . in other words , if we turn our square right two times , then right once , that 's the same as once , then twice , or for numbers , one plus two is the same as two plus one . axiom three : for every operation , there 's an element of our group called the identity . when we apply it to any other element in our group , we still get that element . so for both turning the square and adding integers , our identity here is zero , not very exciting . axiom four : every group element has an element called its inverse also in the group . when the two are brought together using the group 's addition operation , they result in the identity element , zero , so they can be thought of as cancelling each other out . so that 's all well and good , but what 's the point of any of it ? well , when we get beyond these basic rules , some interesting properties emerge . for example , let 's expand our square back into a full-fledged rubik 's cube . this is still a group that satisfies all of our axioms , though now with considerably more elements and more operations . we can turn each row and column of each face . each position is called a permutation , and the more elements a group has , the more possible permutations there are . a rubik 's cube has more than 43 quintillion permutations , so trying to solve it randomly is n't going to work so well . however , using group theory we can analyze the cube and determine a sequence of permutations that will result in a solution . and , in fact , that 's exactly what most solvers do , even using a group theory notation indicating turns . and it 's not just good for puzzle solving . group theory is deeply embedded in music , as well . one way to visualize a chord is to write out all twelve musical notes and draw a square within them . we can start on any note , but let 's use c since it 's at the top . the resulting chord is called a diminished seventh chord . now this chord is a group whose elements are these four notes . the operation we can perform on it is to shift the bottom note to the top . in music that 's called an inversion , and it 's the equivalent of addition from earlier . each inversion changes the sound of the chord , but it never stops being a c diminished seventh . in other words , it satisfies axiom one . composers use inversions to manipulate a sequence of chords and avoid a blocky , awkward sounding progression . on a musical staff , an inversion looks like this . but we can also overlay it onto our square and get this . so , if you were to cover your entire rubik 's cube with notes such that every face of the solved cube is a harmonious chord , you could express the solution as a chord progression that gradually moves from discordance to harmony and play the rubik 's cube , if that 's your thing .
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we can start on any note , but let 's use c since it 's at the top . the resulting chord is called a diminished seventh chord . now this chord is a group whose elements are these four notes .
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the diminished seventh chord is a group because of its symmetry and because of following the group axioms . are there any other chords in music that satisfy the same axioms ?
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homer 's `` odyssey '' , one of the oldest works of western literature , recounts the adventures of the greek hero odysseus during his ten-year journey home from the trojan war . though some parts may be based on real events , the encounters with strange monsters , terrifying giants and powerful magicians are considered to be complete fiction . but might there be more to these myths than meets the eye ? let 's look at one famous episode from the poem . in the midst of their long voyage , odysseus and his crew find themselves on the mysterious island of aeaea . starving and exhausted , some of the men stumble upon a palatial home where a stunning woman welcomes them inside for a sumptuous feast . of course , this all turns out to be too good to be true . the woman , in fact , is the nefarious sorceress circe , and as soon as the soldiers have eaten their fill at her table , she turns them all into animals with a wave of her wand . fortunately , one of the men escapes , finds odysseus and tells him of the crew 's plight . but as odysseus rushes to save his men , he meets the messenger god , hermes , who advises him to first consume a magical herb . odysseus follows this advice , and when he finally encounters circe , her spells have no effect on him , allowing him to defeat her and rescue his crew . naturally , this story of witchcraft and animal transformations was dismissed as nothing more than imagination for centuries . but in recent years , the many mentions of herbs and drugs throughout the passage have piqued the interest of scientists , leading some to suggest the myths might have been fictional expressions of real experiences . the earliest versions of homer 's text say that circe mixed baneful drugs into the food such that the crew might utterly forget their native land . as it happens , one of the plants growing in the mediterranean region is an innocent sounding herb known as jimson weed , whose effects include pronounced amnesia . the plant is also loaded with compounds that disrupt the vital neurotransmitter called acetylcholine . such disruption can cause vivid hallucinations , bizarre behaviors , and general difficulty distinguishing fantasy from reality , just the sorts of things which might make people believe they 've been turned into animals , which also suggests that circe was no sorceress , but in fact a chemist who knew how to use local plants to great effect . but jimson weed is only half the story . unlike a lot of material in the odyssey , the text about the herb that hermes gives to odysseus is unusually specific . called moly by the gods , it 's described as being found in a forest glen , black at the root and with a flower as white as milk . like the rest of the circe episode , moly was dismissed as fictional invention for centuries . but in 1951 , russian pharmacologist mikhail mashkovsky discovered that villagers in the ural mountains used a plant with a milk-white flower and a black root to stave off paralysis in children suffering from polio . the plant , called snowdrop , turned out to contain a compound called galantamine that prevented the disruption of the neurotransmitter acetylcholine , making it effective in treating not only polio but other disease , such as alzheimer 's . at the 12th world congress of neurology , doctors andreas plaitakis and roger duvoisin first proposed that snowdrop was , in fact , the plant hermes gave to odysseus . although there is not much direct evidence that people in homer 's day would have known about its anti-hallucinatory effects , we do have a passage from 4th century greek writer theophrastus stating that moly is used as an antidote against poisons . so , does this all mean that odysseus , circe , and other characters in the odyssey were real ? not necessarily . but it does suggest that ancient stories may have more elements of truth to them than we previously thought . and as we learn more about the world around us , we may uncover some of the same knowledge hidden within the myths and legends of ages passed .
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but as odysseus rushes to save his men , he meets the messenger god , hermes , who advises him to first consume a magical herb . odysseus follows this advice , and when he finally encounters circe , her spells have no effect on him , allowing him to defeat her and rescue his crew . naturally , this story of witchcraft and animal transformations was dismissed as nothing more than imagination for centuries .
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why is odysseus 's crew so desperate to enter circe 's palatial home ?
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you probably already know everything is made up of little tiny things called atoms or even that each atom is made up of even smaller particles called protons , neutrons and electrons . and you 've probably heard that atoms are small . but i bet you have n't ever thought about how small atoms really are . well , the answer is that they are really , really small . so you ask , just how small are atoms ? to understand this , let 's ask this question : how many atoms are in a grapefruit ? well , let 's assume that the grapefruit is made up of only nitrogen atoms , which is n't at all true , but there are nitrogen atoms in a grapefruit . to help you visualize this , let 's blow up each of the atoms to the size of a blueberry . and then how big would the grapefruit have to be ? it would have to be the same size of -- well , actually , the earth . that 's crazy ! you mean to say that if i filled the earth with blueberries , i would have the same number of nitrogen atoms as a grapefruit ? that 's right ! so how big is the atom ? well , it 's really , really small ! and you know what ? it gets even more crazy . let 's now look inside of each atom -- and thus the blueberry , right ? -- what do you see there ? in the center of the atom is something called the nucleus , which contains protons and neutrons , and on the outside , you 'd see electrons . so how big is the nucleus ? if atoms are like blueberries in the earth , how big would the nucleus be ? you might remember the old pictures of the atom from science class , where you saw this tiny dot on the page with an arrow pointing to the nucleus . well , those pictures , they 're not drawn to scale , so they 're kind of wrong . so how big is the nucleus ? so if you popped open the blueberry and were searching for the nucleus ... you know what ? it would be invisible . it 's too small to see ! ok. let 's blow up the atom -- the blueberry -- to the size of a house . so imagine a ball that is as tall as a two-story house . let 's look for the nucleus in the center of the atom . and do you know what ? it would just barely be visible . so to get our minds wrapped around how big the nucleus is , we need to blow up the blueberry , up to the size of a football stadium . so imagine a ball the size of a football stadium , and right smack dab in the center of the atom , you would find the nucleus , and you could see it ! and it would be the size of a small marble . and there 's more , if i have n't blown your mind by now . let 's consider the atom some more . it contains protons , neutrons and electrons . the protons and neutrons live inside of the nucleus , and contain almost all of the mass of the atom . way on the edge are the electrons . so if an atom is like a ball the size of a football stadium , with the nucleus in the center , and the electrons on the edge , what is in between the nucleus and the electrons ? surprisingly , the answer is empty space . ( wind noise ) that 's right . empty ! between the nucleus and the electrons , there are vast regions of empty space . now , technically there are some electromagnetic fields , but in terms of stuff , matter , it is empty . remember this vast region of empty space is inside the blueberry , which is inside the earth , which really are the atoms in the grapefruit . ok , one more thing , if i can even get more bizarre . since virtually all the mass of an atom is in the nucleus -- now , there is some amount of mass in the electrons , but most of it is in the nucleus -- how dense is the nucleus ? well , the answer is crazy . the density of a typical nucleus is four times 10 to the 17th kilograms per meter cubed . but that 's hard to visualize . ok , i 'll put it in english units . 2.5 times 10 to the 16th pounds per cubic feet . ok , that 's still kind of hard to figure . ok , here 's what i want you to do . make a box that is one foot by one foot by one foot . now let 's go and grab all of the nuclei from a typical car . now , cars on average weigh two tons . how many cars ' nuclei would you have to put into the box to have your one-foot-box have the same density of the nucleus ? is it one car ? two ? how about 100 ? nope , nope and nope . the answer is much bigger . it is 6.2 billion . that is almost equal to the number of people in the earth . so if everyone in the earth owned their own car -- and they do n't -- ( cars honking ) and we put all of those cars into your box ... that would be about the density of a nucleus . so i 'm saying that if you took every car in the world and put it into your one-foot box , you would have the density of one nucleus . ok , let 's review . the atom is really , really , really small . think atoms in a grapefruit like blueberries in the earth . the nucleus is crazy small . now look inside the blueberry , and blow it up to the size of a football stadium , and now the nucleus is a marble in the middle . the atom is made up of vast regions of empty space . that 's weird . the nucleus has a crazy-high density . think of putting all those cars in your one-foot box . i think i 'm tired .
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so imagine a ball that is as tall as a two-story house . let 's look for the nucleus in the center of the atom . and do you know what ?
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what is contained in the nucleus of an atom ?
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