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( music ) the eight traits successful people have in common . number one : passion . successful people love what they do . when i asked russell crowe what led to his academy award for best actor , he said , `` the bottom line is i love the actual job of acting . i have a great passion for it . '' successful people in all fields love what they do , whether it 's astrophysicist jaymie matthews , author j.k. rowling or athlete michael phelps . and not just big names -- margaret macmillan , a history professor , says , `` i spent my life doing what i loved . '' carlos , a bus driver i sit with at starbucks , says , `` i love what i do . i 've only missed three days in four years . '' and believe it or not , even successful dentists love what they do . izzy novak says , `` i love dentistry . i ca n't imagine being anything else . '' but what about business ? many of you are in business , and we tend to think that business is more about cold numbers than hot passion , more about logic than love , so what surprised me was how often successful business people actually use the words `` passion '' or `` love '' when they talk about their work . when jack welch was ceo of general electric , he was asked if he liked his job . he said , `` no , i do n't like this job . i love this job . '' we can have passion for a profession . kathleen lane , chief strategist at workcar , says , `` i 've found a profession i love . '' she also says , `` stress is n't working 15 hours at a job you like , stress is working 15 minutes at a job you dislike . '' we can have a passion for people . nez hallett iii , ceo of smart wireless , says , `` i used to be in sales . now i 'm a ceo . i just love being around people . '' we can have passion for a product . james dyson , the vacuum cleaner guy , says , `` i love vacuum cleaners , and i will love them until the day i die . '' ( laughter ) yup , when he dies , they 're just going to cremate him and suck up those ashes with a dyson vacuum , and place it on the shelf . ( laughter ) we can have passion for a particular field . anita roddick , the great founder of the body shop , once said , `` i love retailing . i love buying and selling and making connections . '' she also said , `` i do n't like systems , financial sheets or plans . '' yes , no matter how much we love what we do , there 's always going to be stuff we do n't love . the trick is to make sure the stuff you do n't love only takes up 20 percent of your time , and the stuff you do love takes up 80 . if it 's the other way around , we 're in the wrong job . passion is sometimes mistaken for ambition . people call donald trump ambitious , but he says , `` i 'm not ambitious . i just love what i do . and if you love what you do , you do a lot of stuff . and then people say , 'oh , you 're ambitious . ' '' the cool thing about passion is it turns underachievers into superachievers . i have a long list of famous underachievers -- like albert einstein -- who people said would go nowhere when they were young . for instance , who said this , besides me ? `` i was sitting in my room being a depressed guy , trying to figure out what i was doing with my life . '' turns out it was bill gates . bill was such an underachiever , his parents actually sent him to counseling . yeah , i can just hear the neighbors back then saying , `` jeez , that gates kid . what a loser . he 's never going to go anywhere . '' and he did n't , until he discovered his passion for software . the big problem is finding your passion . sure , there 's the kid that knows they want to be an accountant or an architect or an astronaut from the time they 're 10 , but i found a much bigger group of successful people who , when they were young , and even when they were older , did n't have a clue what their passion was , and it took them a long time to find it or to fall into it . dawn lepore , chief information officer at charles schwab , said to me , `` i fell into what i do , and i did n't know i loved it until i fell into it . '' and i hear that a lot . so how do people find their passion ? well they just get out there and try a lot of stuff and explore many paths . robert munsch explored many paths . he said to me , `` i studied to be a priest and that turned out to be a disaster . i tried working on a farm . they did n't like me . i worked on a boat . it sank . i tried a lot of things that did n't work , but i kept trying and then i tried something that did work . '' and i 'd say it worked ; as a children 's author , he 's sold over 40 million books . yes , finding a job we love is like finding a person we love . sometimes we 've just got to go on a lot of really bad dates before we find the right one . now , i read a survey of 18- to 25-year-olds , and 81 percent said their first or second life goal was to get rich . and i thought , boy , they 've got it all wrong . because i 've interviewed many millionaires and billionaires , and guess how many of them said their life goal was to get rich ? zero ! they did n't do it for money , they did it for love . they went for the zing , not the ka-ching ka-ching . when bill gates and paul allen started microsoft , they did n't do it for the money . bill says , `` paul and i never thought we 'd make much money . we just loved writing software . '' and with that attitude , he became the richest man in the world . j.k. rowling did n't write harry potter books for the money . she said , `` i love writing these books . i just wanted to make enough money to continue to write . '' and with that attitude , she became a billionaire . i became a millionaire by following my heart , not my wallet , and a number of times i walked away from great-paying jobs to do poor-paying jobs i loved better . once was when i had a great job , traveling the world , making a lot of money , but i was n't doing the one thing i loved at the time , which was photography . so i said , i think i 'll leave and start my own little photo company . my heart said , yeah ! go for it . my wallet , and all my friends , i might add , said , are you crazy ? you ca n't walk away from all the money ! you 'll starve . i did n't listen to them . i walked away , and yeah , at first there was n't much money , but it did n't matter , because i was having fun doing what i loved . and eventually , the money came , and much more than if i 'd stayed in my old job . so i learned it 's true , what they say : if you do what you love , the money comes anyway . so i 'd say if you really want to get rich , put money at the bottom of your goals list and passion at the top . and why does it work that way ? because if you love what you do , you automatically do the other seven things that lead to success and wealth . you will work hard , you will push yourself , you will persist . and what if you 're in a job you do n't love ? well , just follow your passion on the side . remember , albert einstein was a patent clerk . that was his job , but his passion was physics . and he wrote four of his most important papers in his spare time as a hobby , and became one of the world 's greatest scientists . so it 's amazing what you can do if you love what you do . ( applause )

he said , `` no , i do n't like this job . i love this job . '' we can have passion for a profession .

the video shows there are many possible career passions . you can have passion for an industry , a profession , a product , working with people , etc . 1 ) what is your passion ? describe what you love to do . 2 ) now use those words to help you write your own perfect job description . if you saw an ad for the job you would really love , what would it say ?

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

and later studies have confirmed that our emotional well-being , how often and how intensely we feel things like joy , sorrow , anxiety , or anger , do n't seem to improve with wealth or status beyond a certain point . this has to do with a phenomenon known as hedonic adaptation , or the hedonic treadmill . it describes our tendency to adapt to new situations to maintain a stable emotional equilibrium .

the hedonic treadmill :

many of the inanimate objects around you probably seem perfectly still . but look deep into the atomic structure of any of them , and you 'll see a world in constant flux . stretching , contracting , springing , jittering , drifting atoms everywhere . and though that movement may seem chaotic , it 's not random . atoms that are bonded together , and that describes almost all substances , move according to a set of principles . for example , take molecules , atoms held together by covalent bonds . there are three basic ways molecules can move : rotation , translation , and vibration . rotation and translation move a molecule in space while its atoms stay the same distance apart . vibration , on the other hand , changes those distances , actually altering the molecule 's shape . for any molecule , you can count up the number of different ways it can move . that corresponds to its degrees of freedom , which in the context of mechanics basically means the number of variables we need to take into account to understand the full system . three-dimensional space is defined by x , y , and z axes . translation allows the molecule to move in the direction of any of them . that 's three degrees of freedom . it can also rotate around any of these three axes . that 's three more , unless it 's a linear molecule , like carbon dioxide . there , one of the rotations just spins the molecule around its own axis , which does n't count because it does n't change the position of the atoms . vibration is where it gets a bit tricky . let 's take a simple molecule , like hydrogen . the length of the bond that holds the two atoms together is constantly changing as if the atoms were connected by a spring . that change in distance is tiny , less than a billionth of a meter . the more atoms and bonds a molecule has , the more vibrational modes . for example , a water molecule has three atoms : one oxygen and two hydrogens , and two bonds . that gives it three modes of vibration : symmetric stretching , asymmetric stretching , and bending . more complicated molecules have even fancier vibrational modes , like rocking , wagging , and twisting . if you know how many atoms a molecule has , you can count its vibrational modes . start with the total degrees of freedom , which is three times the number of atoms in the molecule . that 's because each atom can move in three different directions . three of the total correspond to translation when all the atoms are going in the same direction . and three , or two for linear molecules , correspond to rotations . all the rest , 3n-6 or 3n-5 for linear molecules , are vibrations . so what 's causing all this motion ? molecules move because they absorb energy from their surroundings , mainly in the form of heat or electromagnetic radiation . when this energy gets transferred to the molecules , they vibrate , rotate , or translate faster . faster motion increases the kinetic energy of the molecules and atoms . we define this as an increase in temperature and thermal energy . this is the phenomenon your microwave oven uses to heat your food . the oven emits microwave radiation , which is absorbed by the molecules , especially those of water . they move around faster and faster , bumping into each other and increasing the food 's temperature and thermal energy . the greenhouse effect is another example . some of the solar radiation that hits the earth 's surface is reflected back to the atmosphere . greenhouse gases , like water vapor and carbon dioxide absorb this radiation and speed up . these hotter , faster-moving molecules emit infrared radiation in all directions , including back to earth , warming it . does all this molecular motion ever stop ? you might think that would happen at absolute zero , the coldest possible temperature . no one 's ever managed to cool anything down that much , but even if we could , molecules would still move due to a quantum mechanical principle called zero-point energy . in other words , everything has been moving since the universe 's very first moments , and will keep going long , long after we 're gone .

translation allows the molecule to move in the direction of any of them . that 's three degrees of freedom . it can also rotate around any of these three axes .

how many rotational ‘ degrees of freedom ’ does a non-linear molecule have ?

( piano playing ) steven : we 're looking at one of the single canvases from a series of canvases of the campbell soup cans by andy warhol from 1962 at the museum of modern art . and one of the really important questions that comes up about , especially modern art , is well , why is this art ? sal : when you ask me that a bunch of things kind of surface in my brain . it does evoke something in me so i 'm inclined to say yes , but then there 's a bunch of other things that say well , if i did n't see this in a museum and if i just saw this in the marketing department of campbell 's soup , would you be viewing it differently ? steven : because it 's advertising then . sal : yes . steven : but in the context of the museum or in the context of andy warhol 's studio , it 's not quite advertising , right ? sal : even if it 's the exact same thing . steven : yeah . sal : and the idea here is by putting it in the museum it 's saying look at this in a different way . steven : well that 's right , it really does relocate it , it does change the meaning , it does transform it , and that 's really one of the central ideas of modern art is that you can take something that 's not necessarily based in technical skill , because i do n't think you would say that this is beautifully rendered . sal : right . steven : but it relocates it and makes us think about it in a different way . sal : and so , i guess he would get credit for taking something that was very , almost mundane , something you see in everyone 's cupboard , and making it a focal point like you should pay attention to this thing . steven : i think that 's exactly right and i think that he 's doing it about a subject that was about as low a subject as one could go . i mean cheap advertising art was something that was so far away from fine art from the great masters and then to focus on something as lowly as a can of soup , and cream of chicken no less , right ? ( laughs ) sal : a lot of it is , if he did it 50 years earlier , people would have thought this guy 's a quack and if he did it now they 'd think he was just derivative and ... it was really just that time where people happened to think this was art . steven : i think that that 's right . in 1962 , what warhol is doing is he 's saying what is it about our culture that is really authentic and important ? and it was about mass production , it was about factories . he in a sense said let 's not be looking at nature as if we were still an agrarian culture , we 're now an industrial culture . what is the stuff of our visual world now ? sal : i think i 'm 80 percent there . i remember in college there was a student run art exhibit and as a prank a student actually put a little podium there and put his lunch tray . he put a little placard next to it , you know , lunch tray on saturday or something is what he called it . so he did it as a prank and everyone thought it was really funny but to some degree it 's kind of a sign that maybe what he did was art . steven : well i think that 's why it was funny because it was so close , right ? sal : and to some degree when someone took a lunch tray and gave it the proper lighting and gave it a podium to look at it and wrote a whole description about it , i did view the lunch tray in a different way . that 's kind of the same idea , that something that 's such a mundane thing but you use it everyday . i mean , what would you say to that ? was that a prank or was that art ? steven : i think it is a prank but it 's also very close to some important art that had been made earlier in the century . he had license to do that because of somebody named marcel duchamp . in fact , warhol had in a sense the same kind of license to not focus on the making of something , not focus on the brushwork , not focus on the composition , not focus on the color , but focus on the refocusing of ideas . sal : and the reason why we talk about warhol or duchamp or any of these people is that , as you said , it 's not that they did something technically profound . obviously campbell soup 's marketing department had already done something as equally as profound , it 's more that they were the people who looked at the world in a slightly different way and highlighted that . steven : well i think that that 's right . warhol is also very consciously working towards asking the same questions that the prankster at your school was asking . he 's saying can this be art ? and in fact he 's really pushing it . look at the painting closely for a moment . this is one of the last paintings that he 's actually painted . he 's really defined the calligraphy of this campbell 's , he 's really sort of rendered the reflection of the tin at the top . but then he stopped and he said , i do n't want to paint the fleur de lis . you see those little fleur de lis down at the bottom . i do n't want to paint those . so he actually had a little rubber stamp made of them and actually sort of placed them down mechanically . what does that mean for an artist then , to say i do n't even want to bother to paint these ? i 'm just going to find a mechanical process to make this easier . warhol is doing something i think which is important which is reflecting the way that we manufacture , the way that we construct our world . think about the things that we surround ourselves with , almost everything was made in a factory . almost nothing is singular in the world anymore . it 's not a world that we would normally find beautiful . sal : i do n't know , sometimes i feel and correct me if i 'm wrong , that a decision was made that warhol was interesting or great and then people will interpret his stuff to justify his greatness . that oh look , he used a printer instead of drawing it which shows that he was reflecting the industrial or whatever , but if he had done it the other way , if he had hand drawn it or hand drawn it with his elbow you know , or finger painted it or something people would say oh is n't this tremendous because we normally would see this thing printed by a machine and now he did it with his hands . how much do you think that is the case or am i just being cynical ? steven : well no , i think that there 's value in a certain degree of cynicism and i think that in some ways what we 're really talking about here is what does it mean to be an avant-garde artist ? what does it mean to sort of change the language of art and to try to find ways that art relates to our historical moment in some really direct and authentic way ? sal : and maybe it 's easy for me to say this because i remember looking at this when i took 5th grade art class , andy warhol and all of that , so now it seems almost not that unique but in '62 what i 'm hearing is that warhol was really noteworthy because he really did push people 's thinking . steven : i think that warhol was looking for , in 1962 , a kind of subject matter that was completely outside of the scope of that we could consider fine art . one of his contemporaries , roy lichtenstein , was asked what pop art was and he said , `` well we were looking for subject matter that was so despicable , `` that was so low , that nobody could possibly believe that it was really art . '' and i think you 're right , i think now we look at it and it 's so much a part of our visual culture that we immediately accept it . but i think that it 's really interesting to retrieve just how shocking and radical that was . sal : this is fascinating . it seems like there 's a lot of potential there , that stuff that 's pseudo-art made for other purposes , for commercial purposes but if you kind of shine a light on it , in the way that a light has been shone on this , that it does ... in your mind would that cross the barrier into being art ? steven : well i think that , you mentioned before , that if somebody was doing this now it would feel really derivative . and i think that that 's right . i think it underscores just how hard it is to find in our culture now , ways of making us see the world in new ways . sal : fascinating . ( piano playing )

( piano playing ) steven : we 're looking at one of the single canvases from a series of canvases of the campbell soup cans by andy warhol from 1962 at the museum of modern art . and one of the really important questions that comes up about , especially modern art , is well , why is this art ? sal : when you ask me that a bunch of things kind of surface in my brain .

what do you think art is ? are there limitations - can anything be art ?

there 's a man by the name of captain william swenson who recently was awarded the congressional medal of honor for his actions on september 8 , 2009 . on that day , a column of american and afghan troops were making their way through a part of afghanistan to help protect a group of government officials , a group of afghan government officials , who would be meeting with some local village elders . the column came under ambush , and was surrounded on three sides , and amongst many other things , captain swenson was recognized for running into live fire to rescue the wounded and pull out the dead . one of the people he rescued was a sergeant , and he and a comrade were making their way to a medevac helicopter . and what was remarkable about this day is , by sheer coincidence , one of the medevac medics happened to have a gopro camera on his helmet and captured the whole scene on camera . it shows captain swenson and his comrade bringing this wounded soldier who had received a gunshot to the neck . they put him in the helicopter , and then you see captain swenson bend over and give him a kiss before he turns around to rescue more . i saw this , and i thought to myself , where do people like that come from ? what is that ? that is some deep , deep emotion , when you would want to do that . there 's a love there , and i wanted to know why is it that i do n't have people that i work with like that ? you know , in the military , they give medals to people who are willing to sacrifice themselves so that others may gain . in business , we give bonuses to people who are willing to sacrifice others so that we may gain . we have it backwards . right ? so i asked myself , where do people like this come from ? and my initial conclusion was that they 're just better people . that 's why they 're attracted to the military . these better people are attracted to this concept of service . but that 's completely wrong . what i learned was that it 's the environment , and if you get the environment right , every single one of us has the capacity to do these remarkable things , and more importantly , others have that capacity too . i 've had the great honor of getting to meet some of these , who we would call heroes , who have put themselves and put their lives at risk to save others , and i asked them , `` why would you do it ? why did you do it ? '' and they all say the same thing : `` because they would have done it for me . '' it 's this deep sense of trust and cooperation . so trust and cooperation are really important here . the problem with concepts of trust and cooperation is that they are feelings , they are not instructions . i ca n't simply say to you , `` trust me , '' and you will . i ca n't simply instruct two people to cooperate , and they will . it 's not how it works . it 's a feeling . so where does that feeling come from ? if you go back 50,000 years to the paleolithic era , to the early days of homo sapiens , what we find is that the world was filled with danger , all of these forces working very , very hard to kill us . nothing personal . whether it was the weather , lack of resources , maybe a saber-toothed tiger , all of these things working to reduce our lifespan . and so we evolved into social animals , where we lived together and worked together in what i call a circle of safety , inside the tribe , where we felt like we belonged . and when we felt safe amongst our own , the natural reaction was trust and cooperation . there are inherent benefits to this . it means i can fall asleep at night and trust that someone from within my tribe will watch for danger . if we do n't trust each other , if i do n't trust you , that means you wo n't watch for danger . bad system of survival . the modern day is exactly the same thing . the world is filled with danger , things that are trying to frustrate our lives or reduce our success , reduce our opportunity for success . it could be the ups and downs in the economy , the uncertainty of the stock market . it could be a new technology that renders your business model obsolete overnight . or it could be your competition that is sometimes trying to kill you . it 's sometimes trying to put you out of business , but at the very minimum is working hard to frustrate your growth and steal your business from you . we have no control over these forces . these are a constant , and they 're not going away . the only variable are the conditions inside the organization , and that 's where leadership matters , because it 's the leader that sets the tone . when a leader makes the choice to put the safety and lives of the people inside the organization first , to sacrifice their comforts and sacrifice the tangible results , so that the people remain and feel safe and feel like they belong , remarkable things happen . i was flying on a trip , and i was witness to an incident where a passenger attempted to board before their number was called , and i watched the gate agent treat this man like he had broken the law , like a criminal . he was yelled at for attempting to board one group too soon . so i said something . i said , `` why do you have treat us like cattle ? why ca n't you treat us like human beings ? '' and this is exactly what she said to me . she said , `` sir , if i do n't follow the rules , i could get in trouble or lose my job . '' all she was telling me is that she does n't feel safe . all she was telling me is that she does n't trust her leaders . the reason we like flying southwest airlines is not because they necessarily hire better people . it 's because they do n't fear their leaders . you see , if the conditions are wrong , we are forced to expend our own time and energy to protect ourselves from each other , and that inherently weakens the organization . when we feel safe inside the organization , we will naturally combine our talents and our strengths and work tirelessly to face the dangers outside and seize the opportunities . the closest analogy i can give to what a great leader is , is like being a parent . if you think about what being a great parent is , what do you want ? what makes a great parent ? we want to give our child opportunities , education , discipline them when necessary , all so that they can grow up and achieve more than we could for ourselves . great leaders want exactly the same thing . they want to provide their people opportunity , education , discipline when necessary , build their self-confidence , give them the opportunity to try and fail , all so that they could achieve more than we could ever imagine for ourselves . charlie kim , who 's the ceo of a company called next jump in new york city , a tech company , he makes the point that if you had hard times in your family , would you ever consider laying off one of your children ? we would never do it . then why do we consider laying off people inside our organization ? charlie implemented a policy of lifetime employment . if you get a job at next jump , you can not get fired for performance issues . in fact , if you have issues , they will coach you and they will give you support , just like we would with one of our children who happens to come home with a c from school . it 's the complete opposite . this is the reason so many people have such a visceral hatred , anger , at some of these banking ceos with their disproportionate salaries and bonus structures . it 's not the numbers . it 's that they have violated the very definition of leadership . they have violated this deep-seated social contract . we know that they allowed their people to be sacrificed so they could protect their own interests , or worse , they sacrificed their people to protect their own interests . this is what so offends us , not the numbers . would anybody be offended if we gave a $ 150 million bonus to gandhi ? how about a $ 250 million bonus to mother teresa ? do we have an issue with that ? none at all . none at all . great leaders would never sacrifice the people to save the numbers . they would sooner sacrifice the numbers to save the people . bob chapman , who runs a large manufacturing company in the midwest called barry-wehmiller , in 2008 was hit very hard by the recession , and they lost 30 percent of their orders overnight . now in a large manufacturing company , this is a big deal , and they could no longer afford their labor pool . they needed to save 10 million dollars , so , like so many companies today , the board got together and discussed layoffs . and bob refused . you see , bob does n't believe in head counts . bob believes in heart counts , and it 's much more difficult to simply reduce the heart count . and so they came up with a furlough program . every employee , from secretary to ceo , was required to take four weeks of unpaid vacation . they could take it any time they wanted , and they did not have to take it consecutively . but it was how bob announced the program that mattered so much . he said , it 's better that we should all suffer a little than any of us should have to suffer a lot , and morale went up . they saved 20 million dollars , and most importantly , as would be expected , when the people feel safe and protected by the leadership in the organization , the natural reaction is to trust and cooperate . and quite spontaneously , nobody expected , people started trading with each other . those who could afford it more would trade with those who could afford it less . people would take five weeks so that somebody else only had to take three . leadership is a choice . it is not a rank . i know many people at the seniormost levels of organizations who are absolutely not leaders . they are authorities , and we do what they say because they have authority over us , but we would not follow them . and i know many people who are at the bottoms of organizations who have no authority and they are absolutely leaders , and this is because they have chosen to look after the person to the left of them , and they have chosen to look after the person to the right of them . this is what a leader is . i heard a story of some marines who were out in theater , and as is the marine custom , the officer ate last , and he let his men eat first , and when they were done , there was no food left for him . and when they went back out in the field , his men brought him some of their food so that he may eat , because that 's what happens . we call them leaders because they go first . we call them leaders because they take the risk before anybody else does . we call them leaders because they will choose to sacrifice so that their people may be safe and protected and so their people may gain , and when we do , the natural response is that our people will sacrifice for us . they will give us their blood and sweat and tears to see that their leader 's vision comes to life , and when we ask them , `` why would you do that ? why would you give your blood and sweat and tears for that person ? '' they all say the same thing : `` because they would have done it for me . '' and is n't that the organization we would all like to work in ? thank you very much . thank you . ( applause ) thank you . ( applause )

we would never do it . then why do we consider laying off people inside our organization ? charlie implemented a policy of lifetime employment .

what does sinek say matters most inside an organization ?

translator : andrea mcdonough reviewer : bedirhan cinar what do harry potter , katniss everdeen , and frodo all have in common with the heroes of ancient myths ? ( roar ) what if i told you they are all variants of the same hero ? do you believe that ? joseph campbell did . he studied myths from all over the world and published a book called `` the hero with a thousand faces , '' retelling dozens of stories and explaining how each represents the mono-myth , or hero 's journey . so , what is the `` hero 's journey '' ? think of it as a cycle . the journey begins and ends in a hero 's ordinary world , but the quest passes through an unfamiliar , special world . along the way , there are some key events . think about your favorite book or movie . does it follow this pattern ? status quo , that 's where we start . 1:00 : call to adventure . the hero receives a mysterious message . an invitation , a challenge ? 2:00 : assistance the hero needs some help , probably from someone older , wiser . 3:00 : departure the hero crosses the threshold from his normal , safe home , and enters the special world and adventure . we 're not in kansas anymore . 4:00 : trials being a hero is hard work : our hero solves a riddle , slays a monster , escapes from a trap . 5:00 : approach it 's time to face the biggest ordeal , the hero 's worst fear . ( roar ) 6:00 : crisis this is the hero 's darkest hour . he faces death and possibly even dies , only to be reborn . 7:00 : treasure ( roar ) as a result , the hero claims some treasure , special recognition , or power . 8:00 : result this can vary between stories . do the monsters bow down before the hero , or do they chase him as he flees from the special world ? 9:00 : return after all that adventure , the hero returns to his ordinary world . 10:00 : new life this quest has changed the hero ; he has outgrown his old life . 11:00 : resolution all the tangled plot lines get straightened out . 12:00 : status quo , but upgraded to a new level . nothing is quite the same once you are a hero . many popular books and movies follow this ancient formula pretty closely . but let 's see how well `` the hunger games '' fits the hero 's journey template . when does katniss everdeen hear her call to adventure that gets the story moving ? when her sister 's name is called from the lottery . how about assistance ? is anyone going to help her on her adventure ? haymitch . what about departure ? does she leave her ordinary world ? she gets on a train to the capital . ok , so you get the idea . what do you have in common with harry potter , katniss everdeen , and frodo ? well , you 're human , just like them . the hero 's journey myth exists in all human cultures and keeps getting updated , because we humans reflect on our world through symbolic stories of our own lives . you leave your comfort zone , have an experience that transforms you , and then you recover and do it again . you do n't literally slay dragons or fight voldemort , but you face problems just as scary . joseph campbell said , `` in the cave you fear to enter lies the treasure you seek . '' what is the symbolic cave you fear to enter ? auditions for the school play ? baseball tryouts ? love ? watch for this formula in books , movies , and tv shows you come across . you will certainly see it again . but also be sensitive to it in your own life . listen for your call to adventure . accept the challenge . conquer your fear and claim the treasure you seek . and then , do it all over again .

9:00 : return after all that adventure , the hero returns to his ordinary world . 10:00 : new life this quest has changed the hero ; he has outgrown his old life . 11:00 : resolution all the tangled plot lines get straightened out .

when does the hero realize that he/she is changed ( or has outgrown his/her old life ) ?

each year in the united states , players of sports and recreational activities receive between 2.5 and 4 million concussions . how dangerous are all those concussions ? the answer is complicated , and lies in how the brain responds when something strikes it . the brain is made of soft fatty tissue , with a consistency something like jello . inside its protective membranes and the skull 's hard casing , this delicate organ is usually well-shielded . but a sudden jolt can make the brain shift and bump against the skull 's hard interior , and unlike jello , the brain 's tissue is n't uniform . it 's made of a vast network of 90 billion neurons , which relay signals through their long axons to communicate throughout the brain and control our bodies . this spindly structure makes them very fragile so that when impacted , neurons will stretch and even tear . that not only disrupts their ability to communicate but as destroyed axons begin to degenerate , they also release toxins causing the death of other neurons , too . this combination of events causes a concussion . the damage can manifest in many different ways including blackout , headache , blurry vision , balance problems , altered mood and behavior , problems with memory , thinking , and sleeping , and the onset of anxiety and depression . every brain is different , which explains why people 's experiences of concussions vary so widely . luckily , the majority of concussions fully heal and symptoms disappear within a matter of days or weeks . lots of rest and a gradual return to activity allows the brain to heal itself . on the subject of rest , many people have heard that you 're not supposed to sleep shortly after receiving a concussion because you might slip into a coma . that 's a myth . so long as doctors are n't concerned there may also be a more severe brain injury , like a brain bleed , there 's no documented problem with going to sleep after a concussion . sometimes , victims of concussion can experience something called post-concussion syndrome , or pcs . people with pcs may experience constant headaches , learning difficulties , and behavioral symptoms that even affect their personal relationships for months or years after the injury . trying to play through a concussion , even for only a few minutes , or returning to sports too soon after a concussion , makes it more likely to develop pcs . in some cases , a concussion can be hard to diagnose because the symptoms unfold slowly over time . that 's often true of subconcussive impacts which result from lower impact jolts to the head than those that cause concussions . this category of injury does n't cause noticable symptoms right away , but can lead to severe degenerative brain diseases over time if it happens repeatedly . take soccer players , who are known for repeatedly heading soccer balls . using a technique called diffusion tensor imaging , we 're beginning to find out what effect that has on the brain . this method allows scientists to find large axon bundles and see how milder blows might alter them structurally . in 2013 , researchers using this technique discovered that athletes who had headed the ball most , about 1,800 times a year , had damaged the structural integrity of their axon bundles . the damage was similar to how a rope will fail when the individual fibers start to fray . those players also performed worse on short-term memory tests , so even though no one suffered full-blown concussions , these subconcussive hits added up to measurable damage over time . in fact , researchers know that an overload of subconcussive hits is linked to a degenerative brain disease known as chronic traumatic encephalopathy , or cte . people with cte suffer from changes in their mood and behavior that begin appearing in their 30s or 40s followed by problems with thinking and memory that can , in some cases , even result in dementia . the culprit is a protein called tau . usually , tau proteins support tiny tubes inside our axons called microtubules . it 's thought that repeated subconcussive hits damage the microtubules , causing the tau proteins to dislodge and clump together . the clumps disrupt transport and communication along the neuron and drive the breakdown of connections within the brain . once the tau proteins start clumping together , they cause more clumps to form and continue to spread throughout the brain , even after head impacts have stopped . the data show that at least among football players , between 50 and 80 % of concussions go unreported and untreated . sometimes that 's because it 's hard to tell a concussion has occurred in the first place . but it 's also often due to pressure or a desire to keep going despite the fact that something 's wrong . this does n't just undermine recovery . it 's also dangerous . our brains are n't invincible . they still need us to shield them from harm and help them undo damage once it 's been done .

so long as doctors are n't concerned there may also be a more severe brain injury , like a brain bleed , there 's no documented problem with going to sleep after a concussion . sometimes , victims of concussion can experience something called post-concussion syndrome , or pcs . people with pcs may experience constant headaches , learning difficulties , and behavioral symptoms that even affect their personal relationships for months or years after the injury .

which of the following could be a concussion symptom ?

translator : andrea mcdonough reviewer : bedirhan cinar you 've probably heard of pavlov 's dogs , the phrase that often summarizes dr. ivan pavlov 's early 20th century research , in which he demonstrated that we can alter what stimuli elicit a reflective response in canines . he showed this by sounding a bell just before he presented his group of dogs with meat powder . after many presentations of the bell , followed by tasty meat powder , the dogs eventually began to salivate at just the sound of the bell . they salivated even when there was no meat powder present . this phenomenon is n't limited to dogs . consider the placebo effect , in which a pill with no active substances brings about a response similar to a pill with a substance present . what changes here is our reaction to our ailment , such as perceiving less pain and not the ailment itself . or , consider the love humans have for a parent . some would argue that this love is instinctual , and they may be partially right . but , the argument fails to account for the equal amount of love that children adopted later in life hold for their adoptive parents . but the behaviorist argument can account for both accounts of love . a parent , biological or not , is constantly paired with things like food , smiles , toys , affection , games , protection , and entertainment . and a parent 's constant association with these wonderful or crucial aspects of a child 's life has a similar , albeit more complicated , effect that meat powder had on pavlov 's salivating dogs . in other words , if one 's parent is predictive of really good or really important things , then one 's parent becomes a really good and important thing , too . and there is also romantic advice to be gained from pavlov 's observations . we all need food to survive , right ? and someone who can provide such things in a delicious , saliva-producing manner stands to become our human equivalent of a ringing bell . in other words , if you can cook one or more scrumptious meals for a potential love interest , there 's a good chance that you 'll be viewed more favorably in the future , even if you did n't prepare the delicious food . and who would n't want the love of their life drooling over them ? but life is not just bell rings and salivation . there 's also a dark side to this type of learning , called `` taste aversion '' . taste aversion occurs when we ingest some food that eventually makes us sick , and , as a result , we avoid that food , sometimes for the rest of our lives . taste aversion is so powerful that the effect can be seen even if the illness is experienced hours later and even if the food itself did not actually make us sick . such is the case when we have the flu , and , by accident , we ingest some food moments prior to vomiting . in this case , we know that the food did not cause the vomiting , but our bodies do n't know that . and the next time we encounter that food , we are likely to refuse eating it . now , imagine the potential consequences of undercooking a meal on a first date . if the food makes your date sick , it is possible for them to associate that bad feeling with not just the food , but with < i > your < /i > food in particular . if the episode was traumatizing enough , or if it also happens on a subsequent date , they may come to relate you with the consequences , just like pavlov 's dogs related the bell with the meat powder . in other words , the sight of you showing up at the next dinner date might actually make your date nauseous ! as the old saying goes , the fastest way to someone 's heart is through their stomach , assuming you do n't make them sick in the process .

what changes here is our reaction to our ailment , such as perceiving less pain and not the ailment itself . or , consider the love humans have for a parent . some would argue that this love is instinctual , and they may be partially right .

to build rapport with a young child , one might consider pairing oneself with :

if you live on the east coast of the united states , you 've spent the last 17 years of your life walking , eating and sleeping above a dormant army of insects . these are the cicadas . every 17 years , billions of them emerge from the ground to do three things : molt , mate and die . there are 15 different broods of cicadas out there , grouped by when they 'll emerge from the ground . some of these broods are on a 13-year cycle , others are on a 17-year clock . either way , the cicadas live underground for most of their lives , feeding on the juices of plant roots . when it 's time to emerge , the adults begin to burrow their way out of the ground and up to the surface , where they 'll live for just a few weeks . during these weeks , though , everybody will know the cicadas have arrived . there will be billions of them . and they 're loud . male cicadas band together to call for female mates , and their collective chorus can reach up to 100 decibels -- as loud as a chain saw . in fact , if you happen to be using a chain saw or a lawn mower , male cicadas will flock to you , thinking that you 're one of them . now , like most things in nature , the cicadas do n't arrive without a posse . there are all sort of awesome and gross predators and parasites that come along with the buzzing bugs . take the fungus massospora for example . this little white fungus buries itself in the cicada 's abdomen and eats the bug alive , leaving behind its spores . when those spores rupture , they burst out of the still-alive cicada , turning the bug into a flying saltshaker of death , raining spores down upon its unsuspecting cicada neighbors . but while we know pretty precisely when the cicadas will arrive and fade away , we 're still not totally certain of why . there are certain advantages to having your entire species emerge at once , of course . the sheer number of cicadas coming out of the ground is so overwhelming to predators , it is essentially guaranteed that a few bugs will survive and reproduce . and since cicadas emerge every 13 or 17 years , longer than the lifespan of many of their predators , the animals that eat them do n't learn to depend on their availability . but why 13 and 17 years , instead of 16 or 18 or 12 ? well , that part no one really knows . it 's possible the number just happened by chance , or , perhaps , cicadas really love prime numbers . eventually , the cicadas will mate and slowly die off , their call fading into the distance . the eggs they lay will begin the cycle again , their cicada babies burrowing into the earth , feeding on plant juice , and waiting for their turn to darken the skies and fill the air with their songs . in 17 years , they 'll be ready . will you ?

if you live on the east coast of the united states , you 've spent the last 17 years of your life walking , eating and sleeping above a dormant army of insects . these are the cicadas . every 17 years , billions of them emerge from the ground to do three things : molt , mate and die .

are cicadas still part of the food chain ? if so , how ?

translator : andrea mcdonough reviewer : jessica ruby enough mutations can bypass these fail-safes , driving these cells to divide recklessly . that one rogue cell becomes two , then four , then eight . `` how do you animate real materials , like brains and nerves and stuff like that ? how do you take something that does n't move and then make it move ? '' `` so , that 's actually , we used a method called stop-motion animation , in which you are moving the objects underneath the camera , each frame , one at a time , and you take a picture for each picture that you 've created . so , for this , we were watching a lot of videos on how cell division works , and from that , i created a line-drawn animation that was my reference animation . and , using the software that we use for stop-motion , i was actually able to look at that reference material while shooting so i could kind of arrange underneath the camera in order to match my animation as i would follow along . and we actually shot all of this on a green screen , and the purpose of using the green screen was , for example , in the scene where you see many cells dividing at one time , for me to have actually have to animate each of those cells unanimously dividing at the same time would have been a lot of work that we would n't have had time for . so , the green screen allowed me to do a couple of cell divisions that i could then duplicate in order to show cell division : two , then four , then eight . '' `` so , you only have to basically actually record it once and then you can just duplicate it on the computer . '' `` exactly . '' `` so , it sounds really painstaking . how long did it take to , like , record one cell division ? '' `` i think i did in a day , i did a couple of cell divisions . so , sort of a full work day , so , probably a couple of hours for one . i think , actually , the stuff that took longer was the text . we were animating the word , 'growth ' . we were animating it getting smaller and taller and wider . and for this , i was literally adding one single seed at a time in order to create that animation . '' `` so , how did you animate the word cancer ? '' `` i actually started with the word cancer written and moved backwards and was surgically removing one seed at a time , and then we played that photage backwards to make it look like it was appearing . we use that trick a lot of times in stop-motion because if you want things to really conform , any time that you 're having things come together or fall apart , it usually makes more sense to start with that together frame and work from there , and do the scatter from there , and then , just play that in reverse . it 's a little too painstaking . stop-motion is painstaking , it 's a labor of love , but you have to also be practical when you have a deadline . '' `` so , there 's this technique that you guys use to make the cells look like they 're alive so they 're not just sitting there . that 's called shimmering . how does that work exactly ? '' `` so , in animation , shimmering is usually when you are , if you 're doing drawn animation , you 're drawing that same drawing multiple times but with slight variations so that way , you do n't have a stagnant , still frame under the camera . with the cells , using the seeds and the nerds , we had the opportunity to really have a look , like they were kind of vibrating and pulsating in a way . and so , those are actually , depending on the cell , three to five pictures . with the candy nerds , i would rearrange their position each time so there 's actually removing all the colorful nerds , leaving the purple ones in the center and moving the colorful ones back in into a different position . but with the seeds , when the seeds were shimmering , for that , i would actually just very , very , very lightly , like , roll my hand over it very slightly and then make sure none of them fell out of the constraints of the cell , fix the edges , and take that picture , and just slightly do that again . so , it just slightly changes their position or rustles them up a little bit so that would cycle over and over . and those would play on what animators call threes . and threes means that each picture is on screen for three frames at twenty-four frames per second . so , for the shimmers , you were seeing eight different pictures each second of footage . '' `` how much of your sweat and tears are on these nerds ? '' `` i think , actually , to be honest , the part that was the most perspirational of using the nerds for animation was the place where we had to separate them into colors in order to use them to animate . every time i would put them on the screen to animate , on the tabletop to animate , i would have to separate them out at the end of the day again . and that was the most frustrating part . and , honestly , up until , like , three weeks ago , i dropped my purse on the ground and , like , lentils came out of my purse and onto the floor . like , there 's , this video will stay with me forever . '' `` in your bag . '' `` in my bag . it goes wherever i go . ''

`` so , there 's this technique that you guys use to make the cells look like they 're alive so they 're not just sitting there . that 's called shimmering . how does that work exactly ? ''

lisa describes the animation effect known as shimmering . in your own words , how does it work ?

so here we have a sample of cobalt . now i have got lots and lots of different samples of cobalt in my drawer , so this is cobalt sponge . cobalt is , in many ways , similar to iron . it can form magnets . so this cobalt has been generated from a solution and it ’ s been made in very , very finely dispersed so it has a very large surface area . it ’ s very good for doing catalytic reactions . the magnets that you use in colour televisions , for the loud speakers , contain cobalt . you need to use cobalt in the magnets in the colour television or the old sort of colour television not the ones with lcd screens because the magnetic fields from larger magnets could affect the electron guns and so spoil the colours so you need a very small magnet on your loud speaker or the colours all go funny . cobalt sponge absorbs lots and lots of gas for perhaps hydrogenation . many years ago , in the 1970s , when there was a civil war in africa in the region katanga where cobalt is mined , there was a shortage of cobalt and the production of colour televisions stopped for some considerable time until the production restarted . so you can see it flows in the bottle . so i have another sample of cobalt and that is simply a foil . so again that is a very nice malleable tin-type foil ; very , very good structures .

so here we have a sample of cobalt . now i have got lots and lots of different samples of cobalt in my drawer , so this is cobalt sponge . cobalt is , in many ways , similar to iron . it can form magnets .

cobalt compounds have been used for millennia as a pigment for glass and ceramics . what is the color of these pigments ?

think about all the things that need to happen for a human settlement to thrive : obtaining food , building shelter , raising children and more . there needs to be a way to divide resources , organize major efforts and distribute labor efficiently . now imagine having to do this without any sort of planning or higher level communication . welcome to the ant colony . ants have some of the most complex social organization in the animal kingdom , living in structured colonies containing different types of members who perform specific roles . but although this may sound similar to some human societies , this organization does n't arise from any higher level decisions , but is part of a biologically programmed cycle . in many species , all the winged males and winged virgin queens from all the nearby colonies in the population each leave from their different nests and meet at a central place to mate , using pheromones to guide each other to a breeding ground . after mating , the males die off , while females try to establish a new colony . the few that are successful settle down in a suitable spot , lose their wings , and begin laying eggs , selectively fertilizing some using stored sperm they 've saved up from mating . fertilized eggs grow into female workers who care for the queen and her eggs . they will then defend the colony and forage for food , while unfertilized eggs grow into males whose only job is to wait until they are ready to leave the nest and reproduce , beginning the cycle again . so how do worker ants decide what to do and when ? well , they do n't really . although they have no methods of intentional communication , individual ants do interact with one another through touch , sound and chemical signals . these stimuli accomplish many things from serving as an alarm to other ants if one is killed , to signaling when a queen is nearing the end of her reproductive life . but one of the most impressive collective capabilities of an ant colony is to thoroughly and efficiently explore large areas without any predetermined plan . most species of ants have little or no sense of sight and can only smell things in their vicinity . combined with their lack of high level coordination , this would seem to make them terrible explorers , but there is an amazingly simple way that ants maximize their searching efficiency ; by changing their movement patterns based on individual interactions . when two ants meet , they sense each other by touching antennae . if there are many ants in a small area this will happen more often causing them to respond by moving in more convoluted , random paths in order to search more thoroughly . but in a larger area , with less ants , where such meetings happen less often , they can walk in straight lines to cover more ground . while exploring their environment in this way , an ant may come across any number of things , from threats or enemies , to alternate nesting sites . and some species have another capability known as recruitment . when one of these ants happens to find food , it will return with it , marking its path with a chemical scent . other ants will then follow this pheromone trail , renewing it each time they manage to find food and return . once the food in that spot is depleted , the ants stop marking their return . the scent dissipates and ants are no longer attracted to that path . these seemingly crude methods of search and retrieval are , in fact , so useful that they are applied in computer models to obtain optimal solutions from decentralized elements , working randomly and exchanging simple information . this has many theoretical and practical applications , from solving the famous traveling salesman problem , to scheduling computing tasks and optimizing internet searches , to enabling groups of robots to search a minefield or a burning building collectively , without any central control . but you can observe these fascinatingly simple , yet effective , processes directly through some simple experiments , by allowing ants to enter empty spaces of various sizes and paying attention to their behavior . ants may not be able to vote , hold meetings or even make any plans , but we humans may still be able to learn something from the way that such simple creatures are able to function so effectively in such complex ways .

these seemingly crude methods of search and retrieval are , in fact , so useful that they are applied in computer models to obtain optimal solutions from decentralized elements , working randomly and exchanging simple information . this has many theoretical and practical applications , from solving the famous traveling salesman problem , to scheduling computing tasks and optimizing internet searches , to enabling groups of robots to search a minefield or a burning building collectively , without any central control . but you can observe these fascinatingly simple , yet effective , processes directly through some simple experiments , by allowing ants to enter empty spaces of various sizes and paying attention to their behavior .

for what kinds of tasks is it necessary to have a plan , or central control , and for what kinds of tasks is it better to work collectively , with each individual using only what it can detect nearby ?

you know , back in the '40s and '50s , the original standard television had a 4 to 3 width to height ratio . that shape was chosen to be a slight rectangle , but still mostly square , thus having the maximal screen area for the given dimensions . and that 's still the ratio on many tvs and computer monitors in today 's homes . the problem is , hardly anybody today treats video content in a 4 to 3 ratio . see , this whole problem started when people wanted to watch movies from the theater in the comfort of their own homes . movie screens are considerably larger than our home television . more important , the screen is completely different rectangle and ca n't mathematically fit on our tv screens without manipulation . a typical tv is one and a third times wider than it is tall some movie screens could be up to three times as wide as it is tall . so what 're we going to do to make it fit ? well , we have all kinds of options . well , we could squeeze and stretch and mangle everything onto the screen , to make it all fill up , and everyone would look ridiculously thin and compressed . the good news is the sound would be just fine , although i do n't think people would be too happy about that option , particularly the actors in the movie . we could just cut a chunk of the original movie like a cookie cutter and just see that frame of the movie . the problem with that would be people and objects would be speaking from off the screen , or , even worse , they might be cut in half . some movie editors use what 's called the `` pan and scan '' technique to allow the full height of the tv screen to be used , but pick and choose what section of the original movie should be shown on your screen thus eliminating the annoying cutting of people . imagine that job : staring at a 4 to 3 hole watching movies all day , deciding for everyone which piece of the screen is the most important part for people to see . now let 's do a little quick math . if we compare a major cinematic film produced on a 2.35 to 1 aspect frame with my standard 4 to 3 tv screen , we find out that only 55 % of the movie can actually fit on the screen at any one time . just over half ! you 've seen the disclaimer at the beginning of the movie on tv or dvd that says , `` this film has been modified from its original format to fit on your tv screen . '' well , what it should say is , `` we are only displaying 55 % of the movie of our choosing . '' now for all the full-screen tv lovers , this is your dilemma : do you want to see all the movie , or is 55 % good enough ? how about new tvs ? around the start of the century , some widescreen tvs emerged in a 16 to 9 , or 1.78 times wider than it is tall . well , this screen fits the movie a little better , but still only shows 75 % of the original movie at one time . suppose someone made a tv for your living room that was actually 2.35 to 1 to show those full movies ? well , the tv with the same height as the most current 50-inch tvs - that tv would be close to six feet long . and on top of that , you 'd only use the full screen when you watched movies . most of the other content would have to be stretched , or have empty space on the sides of the screen . of course , there is one more option . we can just shrink the movie screen proportionally , to fit the width of your home television . we can mathematically scale the original to fit exactly the width of the screen and this 'll preserve the entire movie screen , but show the infamous black bars along the top and bottom that so many television watchers abhor . of course , now you can argue that we 're only using 75 % of that screen . and that is where the real question is : do you want your full screen , or do you want to see the entire movie ? most likely , you just need a bigger tv .

of course , now you can argue that we 're only using 75 % of that screen . and that is where the real question is : do you want your full screen , or do you want to see the entire movie ? most likely , you just need a bigger tv .

do you want your full screen , or do you want to see the entire movie ? do you consider yourself an avid tv watcher or a movie buff ? do the notorious black bars necessary on typical televisions bother you , or is it a welcome compromise ? explain how you would ideally watch a movie on your television .

so you 're going to the museum and it 's great . the guards check your bag so you , i do n't know , shoot a painting ; you go up some fancy escalators , you see naked statues . and then it happens . you see a super ugly medieval baby . why do medieval babies look like ugly middle aged men ? this baby looks like he wants to tell you to that 'a boat is just a money pit ' . it might seem like medieval artists were just bad at drawing . but it turns out that babies in medieval art are actually ugly for a reason . while there were breakthroughs in anatomy and perspective that happened later in the renaissance , ugly medieval babies were an intentional choice before that time . if somebody told you to paint like pablo picasso and you gave them norman rockwell , you would have screwed up . and it 's the same way for artists working in churches in italy . it 's because most of these babies were depictions of jesus and mary . they were influenced by the idea of the homunculus , which is latin for little man . these babies looked like benjamin button because philosophers believed jesus was born perfectly formed and unchanged . the adult jesus was represented in the baby jesus . until the renaissance , when everything changed . generally , we think of the middle ages lasting from around the 5th to 15th century , and it kind of overlapped the beginning of the renaissance in the 14th century . the renaissance probably began in florence italy , but it 's important to note that it unfolded over centuries and countries in a time when everything moved slowly . so , it was n't instant beautiful babies everywhere . still , the change in style did happen , and it happened for a couple of reasons . places like florence were getting richer and churches were n't the only places that could afford paintings . people could get their own babies painted , and they wanted them to look like cute chubby babies , not homunculi . and because the renaissance was all about classics , they looked at greek and roman art , which was all about idealized forms that ditched the medieval abstraction for beauty . anyway , the point is that after the renaissance cherubs did n't seem out of place , and neither did cuter pictures of baby jesus as the renaissance spread through europe . and it 's kinda stayed that way since . we want babies who look like they need their cheeks pinched , not their prostates checked . we want them chubby and cute , and we want babies that fit our ideals . because those medieval babies ? they have a face that only a mother can love .

it 's because most of these babies were depictions of jesus and mary . they were influenced by the idea of the homunculus , which is latin for little man . these babies looked like benjamin button because philosophers believed jesus was born perfectly formed and unchanged .

what does ‘ homunculus ’ mean ?

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 .

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 .

if you wanted to make circe into a kind-hearted sorceress , what sorts of effects on the body would you expect the drugs in her food to have ?

[ go project films ] i think that facing death changes people ... which is what happened with me . before this experience , i was a completely different person with a completely different dream . my last dream which was to treat cancer and right now my dream of changing the world in another way . [ welcome to canada ] [ over 4.8 million syrians are refugees living in neighboring countries . ] [ 6.5 million more are displaced within syria . ] [ in november 2015 , the government of canada promised ] [ to resettle 25,000 syrian refugees within 6 months . ] [ the 2400 court motel in vancouver is one of 9 temporary housing sites ] [ for the newly arrived refugees . ] [ may 2016 , vancouver , canada ] staying at the motel is this hard transitional stage . you are homesick and you 're also thinking about remaining family members overseas living under horrendous circumstances . i try my best to introduce the new reality . i try my best to ease the impact of their resettlement process as refugees , as someone who did n't choose to come here , as someone who had to come here . hi , my name is mohammed from immigrant services society of british columbia , iss of bc contacting you regarding your place on craigslist . [ tell me we have three children . ] you 're looking at the two bedroom or the three bedroom ? - two bedroom , two bedroom . - two bedroom ? okay . - oh , two bedroom ? - the two bedroom , yeah . how many people you have ? a family of five people with three small kids . - yeah , that too many . - that is too many ? [ she 's telling you that 's too many people . ] [ okay , tell her thank you ... they are young . ] thank you . i 'm with my clients right now . so i 'm helping him . he wants to share with you , the kids are so small and the ages are ... the place is too small for five people . oh , oh , i see . [ - she 's saying the house is too small to fit five people . ] [ - what about the 3 bedroom ... what 's the rental cost ? ] okay , what about the three bedroom that you have ? $ 3,500 a month . that will be expensive for a new immigrant family . is it possible for you to see the kids and ... i can not accommodate five people in that place . yeah , thank you so much . i 'm sorry . [ the two bedroom house , it 's too small to accommodate five people . ] [ the other house with 3 bedrooms , it 's too expensive , it 's $ 3,500 a month . ] moving to canada is not easy at all . my job is all about providing first language services [ oh my god . ] to the newly arrived refugees . [ we 're going to try and find you another house . ] i 'm the person who welcomes them and i will help them with everything that they will need in their resettlement process . it 's really hard to explain the reality on the ground in syria . it keeps on changing on a daily basis . syrians are just caught up in the middle of this non-sense chaos . many of them have spent many years in refugee camps in neighboring countries trying to just wait for this crazy war to finish . when they realized it 's going to be much longer , this syrian refugee crisis started . [ this is a transitional stage and it 's very difficult . ] [ i was just like you when i came here . ] [ the same reception center , same counselor ] [ and even signed the same papers . ] [ attended the same orientation , and was looking for a house . ] [ so you have been through this before . ] [ the exact same thing . ] [ -i would not encourage you to work right away ] [ -of course not , i need to learn the language first . ] [ excellent thinking . focus on english . ] [ your life starts tomorrow . ] [ god willing , we will start a new life tomorrow . ] before 2011 , before everything has started , we were living a happy life . i was born in al-hasakah , syria , a very peaceful city , a city of so many languages , ethnic components , and religious components with the idea and the notion of accepting others . i was in my fourth year of my medical studies in syria , i was trying my best to become a doctor , and my dream was to treat cancer . my generation was dreaming of having freedom , having some basic things that the average canadian would not think about . [ filmed by mohammed in homs , syria ] we never thought we could have faced such a brutal , barbaric response from your own government , just for gathering in the street and shouting the word `` freedom . '' we were just standing there and surprisingly they started shooting and people started falling ... at that point everyone started running , everyone who had survived it , started running , and some people were just on the ground covered with blood . i 'm calling you regarding clients of mine who are moving to your place tomorrow morning . [ -what 's happening in aleppo is breaking my heart . ] [ -a lot of problems are happening there . ] yeah , because we 're in the middle of , you know , arranging all the transportation needed for all of these families . all righty . thank you so much . [ this boy is dying . ] [ i want my brother . where is my mother and father ? ] [ where is my mom ? ] [ say , `` there is no god but god . '' ] for syrians , it is so normal to open your facebook and see the death of your friend on social media . it is something that is really hard and that is really difficult to accept , to observe , and to even think about . [ there is no power except what lies in god 's hands . ] i 'm about to turn 27 next month . in this small lifetime , i have been arrested three times . i have been in five different detention places . the first thing that they did in the detention center was hanging me from the ceiling . they had handcuffs on my hands like this and they had a chain coming down from the ceiling , and they have hooked that chain to my hands like this , and they kept me like this for three days . after spending three days like this , the actual torture started . they spent so many days practicing all kinds of torture on me , and on other syrian people , in that detention center . i can never forget this old man who was sleeping next to me ... he used to say , `` you see all of this ... one day , all of this will be just a story that you will be telling to other people . '' after 120 days of torture , i was finally released ... i was finally able to see sunlight again . the only thing that i wanted to do is talk to my family . i just wanted to see them but also say goodbye to them ... get the hell out of there and never look back . i took a taxi from damascus to beirut where there was no shelling , no explosions , just a normal life ... three hours away from where i was , from where i was tortured , it was unbelievable for me . iss of bc kingsway . good morning . syrians in lebanon are not allowed to work , are not allowed to go to school . syrians in lebanon are simply not welcomed . the best job that i could find was washing cars from 9 am to 9 pm for $ 20 a day . i was just struggling to have a life . my whole life changed with a single phone call . i pick up the phone , it was this same phone . so i pick up and i was told that , `` this is the canadian embassy calling for mohammed alsaleh , '' i was like , `` yes , speaking . '' so they told me , `` we have an application on your behalf to come to canada , are you interested ? '' and i was like , `` yes , i 'm . '' [ in november 2014 mohammed was granted asylum in canada and arrived in vancouver . ] [ to date thousands of syrian families have arrived in canada . ] each syrian family is thinking about someone who 's left behind ... if it was a brother , if it was a mother , or if it was a father . this is something that i can see among the people that i 'm helping , and this is something that i can relate to on a personal level because of the situation of my family . my family had to illegally cross the border between syria and turkey . they had to crawl in the mud in order to make it to safety . come on , pick up . [ hello . ] [ hello ... hello . ] [ hello , mama . ] [ how are you , mother ? ] [ i swear we miss you . we miss you so much . ] [ me too . i miss you so so much . ] [ shahad , what is this beautiful hair ? ] [ this is the new style , with these bangs . ] [ wow , look , look your hair is so long now . ] when i last saw my family , my youngest sister was seven , right now she is ten , and i do n't know how old would she be when i meet her . it 's really hard to know that you might not be able to meet them . [ look at how my hair looks . ] [ güzel ! güzel like the turkish say . ] [ are you learning turkish ? ] [ a little bit , not much yet . ] [ we try a little bit when we go out , things like that . ] [ -great . ] [ even though we are in turkey , the situation is tough here . ] [ we are always stressed and tired . life is hard here . ] [ what 's important is that you guys are safe and sound ] [ and you are not in danger , ] [ and we do n't have to worry about your life being in danger . ] [ and that 's the most important thing right now , ] [ to let these few months pass while everything is processed and you get here . ] [ god willing , because the situation here is n't comfortable and one does n't feel at home . ] [ -yes , yes . -you always feel like something is missing . ] [ god willing , we will all be together soon here in canada . ] [ that 's what we hope for . hopefully everything will work out . ] [ i miss you so so so much . ] in order for people to get settled and to feel like home , i think the only missing part is time . they just need time . [ speaking foreign language ] [ welcome , welcome to our new house . ] [ a hundred congratulations on the new house , it 's a lovely home . ] [ god bless you , it 's lovely having you all here . ] my first client was a family of 13 people who have just came to canada . [ the best thing you did was to get this property . ] [ here you can play , whatever you want is here . ] i was telling them , `` you 're safe now . one year ago , i was standing exactly where you are and right now i 'm helping you , so do n't worry everything 's going to be fine . '' i want everyone to realize how tremendous , how beautiful it is to offer people a place to call home ... which is something priceless that i really , really appreciate having right now . it 's heart breaking to see the country that you grew up in get destroyed . i 'm one of the ones lucky enough to come back from the dead , to tell their stories , to share their suffering with the rest of the world , which is something that i think is part of my obligation toward syrians and toward canadians . [ mohammed continues to support his family as he works to bring them safely to canada . ] [ according to the un , approximately 250,000 people ] [ have been killed in syria and 13.5 million people are in urgent need of humanitarian assistance . ] [ to date , 29,817 syrian refugees have been welcomed to canada . ] [ 2016 go project films ]

[ 6.5 million more are displaced within syria . ] [ in november 2015 , the government of canada promised ] [ to resettle 25,000 syrian refugees within 6 months . ] [ the 2400 court motel in vancouver is one of 9 temporary housing sites ] [ for the newly arrived refugees . ]

the prime minister of canada , justin trudeau , when asked about welcoming syrian refugees to canada said in a 2015 interview , `` this is something that we are able to do in this country because we define a canadian not by a skin color or a language or a religion or a background , but by a shared set of values , aspirations , hopes and dreams that not just canadians but people around the world share . '' what do you think trudeau means by a `` shared set of values '' ? how does mohammed live by a set of values ? do you think that we , as humans , have a moral responsibility to respond to other humans in need during a humanitarian crisis ? why or why not ?

we already know that the world is made of things , things like cats and macaroni salad , and macaroni salad is made of things like mayo and mustard and celery , which are all made of molecules . as we 'll see , these molecules are made of the same stuff , just mixed together in different ways . let 's go back to our macaroni salad . we 've already unmixed things physically as much as we can . now , we 'll go further and unmix things chemically by breaking some bonds . many larger , complex molecules are just a bunch of smaller molecules bonded together like building blocks . here , again , macaroni salad provides a nice example . if you look at the pasta , you 'll notice it 's made of a lot of this stuff , starch , which is this molecule , otherwise known as amylose . turns out , if you break some bonds , amylose is made up of smaller molecules of glucose , a simple sugar . if you take a bunch of these same glucose molecules and rearrange them in a different way , you get cellulose , which is what plants are made of . so , while this piece of pasta made of amylose and this wooden spoon made of cellulose look vastly different , they 're both essentially made of the same molecules , just stuck together differently . this type of breaking apart and recombining is what goes on when you digest food . the complex proteins found in the foods we eat , like carrots and eggs , ca n't be used by our bodies because we are not carrots or chickens . what we can use are the smaller molecules that make up these proteins , the amino acids . during digestion , our bodies break these proteins up into their amino acids so they can be rearranged and put back together to make human proteins . but let 's keep breaking bonds . all molecules are made up of atoms bonded together . if some molecules are building blocks , atoms are the building blocks of the building blocks . and you 'll notice that with the molecules from macaroni salad , the same six types of atoms keep showing up : carbon , hydrogen , oxygen , nitrogen , phosphorus , and sulfur , or chonps . there 's a few others , but the big six is what macaroni salad is made of . if we went a step further , we could use these same atoms , recombine them , and make other stuff like gasoline or sulfuric acid , methane , and nylon . it 's all made from the same elements that make up macaroni salad . so , to recap , everything is made of atoms . they are the stuff that things are made of . atoms are grouped together in different ways to form molecules . these molecules are constantly being combined , broken apart , and recombined . they get thrown into mixtures , separated , remixed over and over and over again . the stuff that things are made of is always in flux ; it 's always changing . macaroni salad is only macaroni salad for a short time . you eat it , some of it becomes part of you , the rest eventually goes into the ocean and gets eaten by other animals that die , and after millions of years , they turn into oil , which is where gasoline comes from . and that 's why gasoline and macaroni salad are not that different - they 're both made of the same stuff , just one tastes better .

the complex proteins found in the foods we eat , like carrots and eggs , ca n't be used by our bodies because we are not carrots or chickens . what we can use are the smaller molecules that make up these proteins , the amino acids . during digestion , our bodies break these proteins up into their amino acids so they can be rearranged and put back together to make human proteins .

humans ca n't use the large molecules in proteins but can use _________ .

translator : marcia de brito reviewer : ariana bleau lugo ( guitar music throughout ) music is a language . both music and verbal languages serve the same purpose . they are both forms of expression . they can be used as a way to communicate with others . they can be read and written . they can make you laugh or cry , think or question , and can speak to one or many . and both can definitely make you move . in some instances , music works better than the spoken word , because it does n't have to be understood to be effective . although many musicians agree that music is a language , it is rarely treated as such . many of us treat it as something that can only be learned by following a strict regimen , under the tutelage of a skilled teacher . this approach has been followed for hundreds of years with proven success , but it takes a long time . too long . think about the first language you learn as a child . more importantly , think about how you learned it . you were a baby when you first started speaking , and even though you spoke the language incorrectly you were allowed to make mistakes . and the more mistakes you made , the more your parents smiled . learning to speak was not something you were sent somewhere to do only a few times a week . and the majority of the people you spoke to were not beginners . they were already proficient speakers . imagine your parents forcing you to only speak to other babies until you were good enough to speak to them . you would probably be an adult before you could carry on a proper conversation . to use a musical term , as a baby , you were allowed to jam with professionals . if we approach music in the same natural way we approached our first language , we will learn to speak it in the same short time it took to speak our first language . proof of this could be seen in almost any family where a child grows up with other musicians in the family . here are a few keys to follow in learning or teaching music . in the beginning , embrace mistakes , instead of correcting them . like a child playing air guitar , there are no wrong notes . allow young musicians to play and perform with accomplished musicians on a daily basis . encourage young musicians to play more than they practice . the more they play the more they will practice on their own . music comes from the musician , not the instrument . and most importantly , remember that a language works best when we have something interesting to say . many music teachers never find out what their students have to say . we only tell them what they are supposed to say . a child speaks a language for years before they even learn the alphabet . too many rules at the onset , will actually slow them down . in my eyes , the approach to music should be the same . after all , music is a language too .

and both can definitely make you move . in some instances , music works better than the spoken word , because it does n't have to be understood to be effective . although many musicians agree that music is a language , it is rarely treated as such .

in some instances , music works better than the spoken word . why ?

since the dawn of humanity , an estimated 100.8 billion people have lived and died , a number that increases by about .8 % of the world 's population each year . what happens to all of those people 's bodies after they die and will the planet eventually run out of burial space ? when a person 's heart stops beating , the body passes through several stages before it begins decomposing . within minutes after death , the blood begins settling in the lower-most parts of the body . usually eight to twelve hours later , the skin in those areas is discolored by livor mortis , or post-mortem stain . and while at the moment of death the body 's muscles relax completely in a condition called primary flaccidity , they stiffen about two to six hours later in what 's known as rigor mortis . this stiffening spreads through the muscles , and its speed can be affected by age , gender , and the surrounding environment . the body also changes temperature , usually cooling off to match its environment . next comes decomposition , the process by which bacteria and insects break apart the body . many factors affect the rate of decomposition . there is , however , a basic guide of the effect of the environment on decompositon called casper 's law . it says that if all other factors are equal , a body exposed to air decomposes twice as fast as one immersed in water and eight times as fast as one buried in earth . soil acidity also greatly affects bone preservation . high-acidity soils with a ph of less than 5.3 will rapidly decompose bone , whereas in a neutral or basic soil with a ph of 7 or more , a skeleton can remain in relatively good condition for centuries . different cultures throughout history have developed unique approaches to burials . as far back as the first neanderthal burials , death was accompanied by rituals , like the positioning , coloring , or decorating of corpses . traditional christian burials decorate the body in dress , while in traditional islam , a body is wrapped in a piece of ritual fabric with the face oriented toward mecca . traditional hindus ceremonially burn the body , and zoroastrians , followers of one of the oldest monotheistic religions , traditionally place bodies atop a tower to expose them to the sun and scavenging birds.` before the industrial revolution , burials were simple and accessible . these days , with suitable burial land running out in high-population areas , purchasing private gravesites can be costly , and many people ca n't afford simple burials . even cremation , the second most common burial practice in the world , comes with a high cost . as for the question of running out of space , the issue is n't so much about total land in the world as it is that large populations cluster together within cities . most of the big cities in the world may run out of suitable burial grounds within a century . for london , it 's even sooner . that may happen by 2035 . so are there alternatives to traditional burials that might help with the space issue ? in some countries , skyscraper cemeteries enable vertical burials . some options focus on the body 's relationship with the environment . promession , for example , freeze-dries and pulverizes the body , creating a powder that can turn into compost when mixed with oxygen and water . there are also green burials that use special materials , such as biodegradable caskets , urns that sprout trees , and burial suits that grow mushrooms . eternal reefs take that concept to the depths of the ocean using a mixture of ashes and cement to create marine habitats for sea life . death is an inevitable part of the human condition , but how we treat bodies and burials continues to evolve . we may each have different spiritual , religious , or practical approaches to dying , but the ever-increasing demand for burial space might give us a push to be creative about where our bodies go after the final stages of life .

high-acidity soils with a ph of less than 5.3 will rapidly decompose bone , whereas in a neutral or basic soil with a ph of 7 or more , a skeleton can remain in relatively good condition for centuries . different cultures throughout history have developed unique approaches to burials . as far back as the first neanderthal burials , death was accompanied by rituals , like the positioning , coloring , or decorating of corpses .

when was the first burial observed in the human history timeline ?

translator : andrea mcdonough reviewer : jessica ruby worst case scenario : zombie apocalypse . how will you survive ? you might be surprised to find out how much geography skills can help you fend off doom . by geography , i mean analyzing the world around you . one geographic concept that could really help you out in a zombie apocalypse is movement . so , first , what moves ? people move , animals move , and , while sometimes slowly , zombies move as well . but that 's not all . goods move , too . goods can be resources , such as food supplies and weapons . people or zombies tend to move these . so , if you see a big pile of zombie supplies where there was n't one before , you 're probably on the trail . ideas also move . ideas can include entertainment , zombie movies , news and information about zombie attacks , and architecture , or how to build a safe shelter . and , second , why do people or zombies move ? when people , animals , or zombies move , it 's called migration . two concepts that affect migration are push and pull factors . push factors will make you want to leave somewhere . pull factors make you want to go to a place . a lack of resources , unstable economy , or high crime rate might be push factors making people want to move . nice weather , a good economy , or lots of resources would be pull factors for lots of people , enticing them to move . while zombies are definitely a push factor for humans , a city full of people would be a pull factor for hungry zombies who want to eat humans . there are some things that make movement easier for people or zombies . waterways and highways can make traveling faster . moving across clear , open space is easier than a tough terrain . and just as land forms can create boundaries that affect movement , so can political boundaries , like a border gate , for example . so , how can you analyze these movement factors to help your chance of survival ? there are three basic steps . one - identify the points or locations to analyze . what are your options ? two - find what connects them . are there highways , waterways , or open land ? and three - find the patterns of movement that happen over that connection . do people or goods move across it ? by comparing relationships between different places , you can see what connections they have . for example , pick two cities . look at the highway connecting them . if people use that highway to commute to work , those cities have a strong relationship . but this other city over here does n't have a direct connection to the other cities . there 's even a river in the way . it does n't have as strong of a relationship . if a zombie outbreak started here , which city would you rather start out in ? where would you flee to ? so , how do you decide where to go in a zombie apocalypse ? do you just run in a random direction ? or do you use your geographic skills to lead your camp of survivors to safety ? if you want to stay alive , it helps to understand how and why we move .

when people , animals , or zombies move , it 's called migration . two concepts that affect migration are push and pull factors . push factors will make you want to leave somewhere .

what are examples of pull factors ?

have you ever been floating in a swimming pool , all comfy and warm , thinking , `` man , it 'd be cool to be an astronaut ! you could float out in outer space , look down at the earth and everything . it 'd be so neat ! '' only that 's not how it is at all . if you are in outer space , you are orbiting the earth : it 's called free fall . you 're actually falling towards the earth . think about this for a moment : that 's the feeling you get if you 're going over the top of a roller coaster , going , like , `` whoa ! '' only you 're doing this the whole time you 're orbiting the earth , for two , three , four hours , days . whatever it takes , right ? so , how does orbiting work ? let 's take a page from isaac newton . he had this idea , a little mental experiment : you take a cannon , you put it on top of a hill . if you shoot the cannonball , it goes a little bit away . but if you shoot it harder , it goes far enough so that it lands a little bit past the curvature of earth . well , you can imagine if you shot it really , really , hard , it would go all the way around the earth and come back -- boom ! -- and hit you in the backside or something . let 's zoom way back and put you in a little satellite over the north pole of the earth and consider north to be up . you 're going to fall down and hit the earth . but you are actually moving sideways really fast . so when you fall down , you 're going to miss . you 're going to end up on the side of the earth , falling down , and now the earth is pulling you back in sideways . so it 's pulling you back in and you fall down , and so you miss the earth again , and now you 're under the earth . the earth is going to pull you up , but you 're moving sideways still . so you 're going to miss the earth again . now you 're on the other side of the earth , moving upward , and the earth 's pulling you sideways . so you 're going to fall sideways , but you 're going to be moving up and so you 'll miss . now you 're back on top of the earth again , over the north pole , going sideways and falling down , and yep -- you guessed it . you 'll keep missing because you 're moving so fast . in this way , astronauts orbit the earth . they 're always falling towards the earth , but they 're always missing , and therefore , they 're falling all the time . they feel like they 're falling , so you just have to get over it . so technically , if you ran fast enough and tripped , you could miss the earth . but there 's a big problem . first , you have to be going eight kilometers a second . that 's 18,000 miles an hour , just over mach 23 ! the second problem : if you 're going that fast , yes , you would orbit the earth and come back where you came from , but there 's a lot of air in the way , much less people and things . so you would burn up due to atmospheric friction . so , i do not recommend this .

that 's 18,000 miles an hour , just over mach 23 ! the second problem : if you 're going that fast , yes , you would orbit the earth and come back where you came from , but there 's a lot of air in the way , much less people and things . so you would burn up due to atmospheric friction .

if a ball is tossed up in the air , when does it not experience the force of gravity ?

maybe you 've recently seen the phrase `` gluten-free '' on food packaging , or take-out menus , shampoo bottles , apartment listings , the tag of your shirt , on a hammer , as a lower back tattoo , or in your friend 's resume . next time someone starts telling you about their newfound freedom from gluten , here are some questions you can ask , and the well-informed answers that your friend , being a reasonable individual making educated dietary choices , and by no means just following the latest diet craze , will tell you . what is gluten ? gluten is an insoluble protein composite made up of two proteins named gliadin and glutenin . where might you encounter gluten ? gluten is found in certain grains , particularly wheat , rye and barley . what has gluten been doing for the previous entirety of human history , and why do you suddenly care about it ? gluten is responsible for the elastic consistency of dough and the chewiness of foods made from wheat flour , like bread and pasta . for some people , these foods cause problems , namely wheat allergy , celiac disease , and non-celiac gluten sensitivity . wheat allergy is an uncommon condition that occurs when a person 's immune system mounts an allergic response to wheat proteins , leading to mild problems , and in rare cases , a potential dangerous reaction called anaphylaxis . celiac disease is an inherited disease , in which eating foods with gluten leads to inflammation and damage of the lining of the small intestine . this impairs intestinal function , leading to problems like belly pain , bloating , gas , diarrhea , weight loss , skin rash , bone problems like osteoporosis , iron deficiency , small stature , infertility , fatigue and depression . untreated , celiac disease increases the risk of developing certain types of cancer . celiac disease is present in one in every 100 to 200 persons in the u.s . when blood tests suggest the possibility of celiac , the diagnosis is confirmed with a biopsy . the most effective treatment is a gluten-free diet , which helps heal intestinal damage and improve symptoms . some people do n't have celiac disease or a wheat allergy , but still experience symptoms when they eat foods with gluten . these people have non-celiac gluten sensitivity . they experience painful gut symptoms and suffer from fatigue , brain fog , joint pain or skin rash . a gluten-free diet typically helps with these symptoms . so how many people actually have this gluten sensitivity you speak of ? gluten sensitivity 's occurrence in the general population is unclear , but likely much more common than wheat allergy or celiac disease . diagnosis is based on the development of symptoms , the absence of wheat allergy and celiac disease , and subsequent improvement on a gluten-free diet . there 's no reliable blood or tissue test , partly because gluten sensitivity is n't a single disease , and has a number of different possible causes . for example , it may be the case that gluten can activate the immune system in the small intestine , or cause it to become leaky . but sometimes , people claiming gluten sensitivity are actually sensitive not to wheat proteins , but sugars found in wheat and other foods , called fructans . the human intestine ca n't break down or absorb fructans , so they make their way to the large intestine or colon , where they 're fermented by bacteria , producing short-chain fatty acids and gases . this leads to unpleasant symptoms in some people with bowel problems . another possible explanation behind gluten sensitivity is the nocebo effect . this occurs when a person believes something will cause problems , and because of that belief , it does . it 's the opposite of the more well-known and much more fortuitous placebo effect . given how much bad press gluten is getting in the media , the nocebo response may play a role for some people who think they 're sensitive to gluten . for all these reasons , it 's clear that the problems people develop when they eat wheat and other grains are n't exclusively due to gluten . so a better name than non-celiac gluten sensitivty might be wheat intolerance .

some people do n't have celiac disease or a wheat allergy , but still experience symptoms when they eat foods with gluten . these people have non-celiac gluten sensitivity . they experience painful gut symptoms and suffer from fatigue , brain fog , joint pain or skin rash .

explain why gluten sensitivity is difficult to diagnose .

language is an essential part of our lives that we often take for granted . with it , we can communicate our thoughts and feelings , lose ourselves in novels , send text messages , and greet friends . it 's hard to imagine being unable to turn thoughts into words . but if the delicate web of language networks in your brain became disrupted by stroke , illness , or trauma , you could find yourself truly at a loss for words . this disorder , called aphasia , can impair all aspects of communication . people who have aphasia remain as intelligent as ever . they know what they want to say , but ca n't always get their words to come out correctly . they may unintentionally use substitutions called paraphasias , switching related words , like saying `` dog '' for `` cat , '' or words that sound similar , such as `` house '' for `` horse . '' sometimes , their words may even be unrecognizable . there are several types of aphasia grouped into two categories : fluent , or receptive , aphasia and non-fluent , or expressive , aphasia . people with fluent aphasia may have normal vocal inflection but use words that lack meaning . they have difficulty comprehending the speech of others and are frequently unable to recognize their own speech errors . people with non-fluent aphasia , on the other hand , may have good comprehension but will experience long hesitations between words and make grammatical errors . we all have that tip-of-the-tongue feeling from time to time when we ca n't think of a word , but having aphasia can make it hard to name simple , everyday objects . even reading and writing can be difficult and frustrating . so how does this language loss happen ? the human brain has two hemispheres . in most people , the left hemisphere governs language . we know this because in 1861 , the physician paul broca studied a patient who lost the ability to use all but a single word , `` tan . '' during a postmortem study of that patient 's brain , broca discovered a large lesion in the left hemisphere now known as broca 's area . scientists today believe that broca 's area is responsible in part for naming objects and coordinating the muscles involved in speech . behind broca 's area is wernicke 's area near the auditory cortex . that 's where the brain attaches meaning to speech sounds . damage to wernicke 's area impairs the brain 's ability to comprehend language . aphasia is caused by injury to one or both of these specialized language areas . fortunately , there are other areas of the brain which support these language centers and can assist with communication . even brain areas that control movement are connected to language . fmri studies found that when we hear action words , like `` run '' or `` dance , '' parts of the brain responsible for movement light up as if the body was actually running or dancing . our other hemisphere contributes to language , too , enhancing the rhythm and intonation of our speech . these non-language areas sometimes assist people with aphasia when communication is difficult . so how common is aphasia ? approximately 1 million people in the u.s. alone have it , with an estimated 80,000 new cases per year . about one-third of stroke survivors suffer from aphasia making it more prevalent than parkinson 's disease or multiple sclerosis , yet less widely known . there is one rare form of aphasia called primary progressive aphasia , or ppa , which is not caused by stroke or brain injury , but is actually a form of dementia in which language loss is the first symptom . the goal in treating ppa is to maintain language function for as long as possible before other symptoms of dementia eventually occur . however , when aphasia is acquired from a stroke or brain trauma , language improvement may be achieved through speech therapy . our brain 's ability to repair itself , known as brain plasticity , permits areas surrounding a brain lesion to take over some functions during the recovery process . scientists have been conducting experiments using new forms of technology , which they believe may encourage brain plasticity in people with aphasia . meanwhile , many people with aphasia remain isolated , afraid that others wo n't understand them or give them extra time to speak . by offering them the time and flexibility to communicate in whatever way they can , you can help open the door to language again , moving beyond the limitations of aphasia .

there is one rare form of aphasia called primary progressive aphasia , or ppa , which is not caused by stroke or brain injury , but is actually a form of dementia in which language loss is the first symptom . the goal in treating ppa is to maintain language function for as long as possible before other symptoms of dementia eventually occur . however , when aphasia is acquired from a stroke or brain trauma , language improvement may be achieved through speech therapy .

ppa is a type of :

what causes , say , heroin addiction ? this is a really stupid question , right ? it ’ s obvious ; we all know it ; heroin causes heroin addiction . here ’ s how it works : if you use heroin for 20 days , by day 21 , your body would physically crave the drug ferociously because there are chemical hooks in the drug . that ’ s what addiction means . but there ’ s a catch . almost everything we think we know about addiction is wrong . if you , for example , break your hip , you ’ ll be taken to a hospital and you ’ ll be given loads of diamorphine for weeks or even months . diamorphine is heroin . it ’ s , in fact , much stronger heroin than any addict can get on the street because it ’ s not contaminated by all the stuff drug dealers dilute it with . there are people near you being given loads of deluxe heroin in hospitals right now . so at least some of them should become addicts ? but this has been closely studied ; it doesn ’ t happen . your grandmother wasn ’ t turned into a junkie by her hip replacement . why is that ? our current theory of addiction comes in part from a series of experiments that were carried out earlier in the 20th century . the experiment is simple : you take a rat and put it in a cage with two water bottles . one is just water , the other is water laced with heroin or cocaine . almost every time you run this experiment , the rat will become obsessed with the drugged water and keep coming back for more and more , until it kills itself . but in the 1970s , bruce alexander , a professor of psychology , noticed something odd about this experiment : the rat is put in the cage all alone . it has nothing to do but take the drugs . what would happen , he wondered , if we tried this differently ? so he built rat park , which is basically heaven for rats ; it ’ s a lush cage where the rats would have colored balls , tunnels to scamper down , plenty of friends to play with , and they could have loads of sex— everything a rat about town could want . and they would have the drugged water and the normal water bottles . but here ’ s the fascinating thing : in rat park , rats hardly ever use the drugged water ; none of them ever use it compulsively ; none of them ever overdose . but maybe this is a quirk of rats , right ? well , helpfully , there was a human experiment along the same lines : the vietnam war . 20 % of american troops in vietnam were using a lot of heroin . people back home were really panicked , because they thought there would be hundreds of thousands of junkies on the streets of the united states when the war was over . but a study followed the soliders home and found something striking : they didn ’ t go to rehab ; they didn ’ t even go into withdrawal ; 95 % of them just stopped after they got home . if you believe the old theory of addiction , that makes no sense . but if you believe prof. alexander ’ s theory , it makes perfect sense , because if you ’ re put into a horrific jungle in a foreign country where you don ’ t want to be , and you could be forced to kill or die at any moment , doing heroin is a great way to spend your time ; but if you go back to your nice home with your friends and your family , it ’ s the equivalent of being taken out of that first cage and put into a human rat park ; it ’ s not the chemicals , it ’ s your cage . we need to think about addiction differently . human beings have an innate need to bond and connect . when we are happy and healthy , we will bond with the people around us . but when we can ’ t , because we ’ re traumatized , isolated , or beaten down by life , we will bond with something that gives us some sense of relief . it might be endlessly checking a smartphone ; it might be pornography , video games , reddit , gambling , or it might be cocaine . but we will bond with something , because that is our human nature . the path out of unhealthy bonds is to form healthy bonds , to be connected to people you want to be present with . addiction is just one symptom of the crisis of disconnection that ’ s happening all around us . we all feel it . since the 1950s , the average number of close friends an american has has been steadily declining . at the same time , the amount of floor space in their homes has been steadily increasing . to choose floor space over friends , to choose stuff over connection . the war on drugs we ’ ve been fighting for almost a century now has made everything worse . instead of helping people heal and getting their life together , we have cast them out from society , we have made it harder for them to get jobs and become stable , we take benefits and support away from them if we catch them with drugs , we throw them in prison cells , which are literally cages , we put people who are not well in a situation which makes them feel worse and hate them for not recovering . for too long , we ’ ve talked only about individual recovery from addiction . but we need now to talk about social recovery . because something has gone wrong with us as a group . we have to build a society that looks a lot more like rat park and a lot less like those isolated cages . we are going to have to change the unnatural way we live and rediscover each other . the opposite of addiction is not sobriety ; the opposite of addiction is connection . this video is a collaboration with johann hari , the author of the book “ chasing the scream : the first and last days of the war on drugs ” . he was very kind to work with us on this video to spread the word . we recommend that you give the book a try . our videos are made thanks to your support on patreon.com . if you want to help us make more of them , we really appreciate your support . we made an interactive version of this video together with some friends . see the link in the description . subtitles by the amara.org community

the experiment is simple : you take a rat and put it in a cage with two water bottles . one is just water , the other is water laced with heroin or cocaine . almost every time you run this experiment , the rat will become obsessed with the drugged water and keep coming back for more and more , until it kills itself .

what were the results of putting the drug-laced water bottle in `` rat park '' ?

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 .

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 .

what does the hubble deep field image teach us about the big bang and the universe as a whole ?

one of the most amazing facts in physics is this : everything in the universe , from light to electrons to atoms , behaves like both a particle and a wave at the same time . all of the other weird stuff you might have heard about quantum physics , schrodinger 's cat , god playing dice , spooky action at a distance , all of it follows directly from the fact that everything has both particle and wave nature . this might sound crazy . if you look around , you 'll see waves in water and particles of rock , and they 're nothing alike . so why would you think to combine them ? physicists did n't just decide to mash these things together out of no where . rather , they were led to the dual nature of the universe through a process of small steps , fitting together lots of bits of evidence , like pieces in a puzzle . the first person to seriously suggest the dual nature of light was albert einstein in 1905 , but he was picking up an earlier idea from max planck . planck explained the colors of light emitted by hot objects , like the filament in a light bulb , but to do it , he needed a desperate trick : he said the object was made up of oscillators that could only emit light in discrete chunks , units of energy that depend on the frequency of the light . planck was never really happy with this , but einstein picked it up and ran with it . he applied planck 's idea to light itself , saying that light , which everybody knew was a wave , is really a stream of photons , each with a discrete amount of energy . einstein himself called this the only truly revolutionary thing he did , but it explains the way light shining on a metal surface knocks loose electrons . even people who hated the idea had to agree that it works brilliantly . the next puzzle piece came from ernest rutherford in england . in 1909 , ernest marsden and hans geiger , working for rutherford , shot alpha particles at gold atoms and were stunned to find that some bounced straight backwards . this showed that most of the mass of the atom is concentrated in a tiny nucleus . the cartoon atom you learn in grade school , with electrons orbiting like a miniature solar system , that 's rutherford 's . there 's one little problem with rutherford 's atom : it ca n't work . classical physics tells us that an electron whipping around in a circle emits light , and we use this all the time to generate radio waves and x-rays . rutherford 's atoms should spray x-rays in all directions for a brief instant before the electron spirals in to crash into the nucleus . but niels bohr , a danish theoretical physicist working with rutherford , pointed out that atoms obviously exist , so maybe the rules of physics needed to change . bohr proposed that an electron in certain special orbits does n't emit any light at all . atoms absorb and emit light only when electrons change orbits , and the frequency of the light depends on the energy difference in just the way planck and einstein introduced . bohr 's atom fixes rutherford 's problem and explains why atoms emit only very specific colors of light . each element has its own special orbits , and thus its own unique set of frequencies . the bohr model has one tiny problem : there 's no reason for those orbits to be special . but louis de broglie , a french phd student , brought everything full circle . he pointed out that if light , which everyone knew is a wave , behaves like a particle , maybe the electron , which everyone knew is a particle , behaves like a wave . and if electrons are waves , it 's easy to explain bohr 's rule for picking out the special orbits . once you have the idea that electrons behave like waves , you can go look for it . and within a few years , scientists in the us and uk had observed wave behavior from electrons . these days we have a wonderfully clear demonstration of this : shooting single electrons at a barrier with slits cut in it . each electron is detected at a specific place at a specific time , like a particle . but when you repeat the experiment many times , all the individual electrons trace out a pattern of stripes , characteristic of wave behavior . the idea that particles behave like waves , and vice versa , is one of the strangest and most powerful in physics . richard feynman famously said that this illustrates the central mystery of quantum mechanics . everything else follows from this , like pieces of a puzzle falling into place .

rather , they were led to the dual nature of the universe through a process of small steps , fitting together lots of bits of evidence , like pieces in a puzzle . the first person to seriously suggest the dual nature of light was albert einstein in 1905 , but he was picking up an earlier idea from max planck . planck explained the colors of light emitted by hot objects , like the filament in a light bulb , but to do it , he needed a desperate trick : he said the object was made up of oscillators that could only emit light in discrete chunks , units of energy that depend on the frequency of the light . planck was never really happy with this , but einstein picked it up and ran with it .

what did max planck use to explain the spectrum of light emitted by a hot object ?

between 2008 and 2012 , archeologists excavated the rubble of an ancient hospital in england . in the process , they uncovered a number of skeletons . one in particular belonged to a wealthy male who lived in the 11th or 12th century and died of leprosy between the ages of 18 and 25 . how do we know all this ? simply by examining some old , soil-caked bones ? even centuries after death , skeletons carry unique features that tell us about their identities . and using modern tools and techniques , we can read those features as clues . this is a branch of science known as biological anthropology . it allows researchers to piece together details about ancient individuals and identify historical events that affected whole populations . when researchers uncover a skeleton , some of the first clues they gather , like age and gender , lie in its morphology , which is the structure , appearance , and size of a skeleton . bones , like the clavicle , stop growing at age 25 , so a skeleton with a clavicle that has n't fully formed must be younger than that . similarly , the plates in the cranium can continue fusing up to age 40 , and sometimes beyond . by combining these with some microscopic skeletal clues , physical anthropologists can estimate an approximate age of death . meanwhile , pelvic bones reveal gender . biologically , female pelvises are wider , allowing women to give birth , where as males are narrower . bones also betray the signs of ancient disease . disorders like anemia leave their traces on the bones . and the condition of teeth can reveal clues to factors like diet and malnutrition , which sometimes correlate with wealth or poverty . a protein called collagen can give us even more profound details . the air we breathe , water we drink , and food we eat leaves permanent traces in our bones and teeth in the form of chemical compounds . these compounds contain measurable quantities called isotopes . stable isotopes in bone collagen and tooth enamel varies among mammals dependent on where they lived and what they ate . so by analyzing these isotopes , we can draw direct inferences regarding the diet and location of historic people . not only that , but during life , bones undergo a constant cycle of remodeling . so if someone moves from one place to another , bones synthesized after that move will also reflect the new isotopic signatures of the surrounding environment . that means that skeletons can be used like migratory maps . for instance , between 1-650 ad , the great city of teotihuacan in mexico bustled with thousands of people . researchers examined the isotope ratios in skeletons ' tooth enamel , which held details of their diets when they were young . they found evidence for significant migration into the city . a majority of the individuals were born elsewhere . with further geological and skeletal analysis , they may be able to map where those people came from . that work in teotihuacan is also an example of how bio-anthropologists study skeletons in cemeteries and mass graves , then analyze their similarities and differences . from that information , they can learn about cultural beliefs , social norms , wars , and what caused their deaths . today , we use these tools to answer big questions about how forces , like migration and disease , shape the modern world . dna analysis is even possible in some relatively well-preserved ancient remains . that 's helping us understand how diseases like tuberculosis have evolved over the centuries so we can build better treatments for people today . ancient skeletons can tell us a surprisingly great deal about the past . so if your remains are someday buried intact , what might archeologists of the distant future learn from them ?

biologically , female pelvises are wider , allowing women to give birth , where as males are narrower . bones also betray the signs of ancient disease . disorders like anemia leave their traces on the bones .

cribra crani , which affects the cranial vault and causes the outer surface of spongy bone to become thinner and more porous , is a result of which disease ?

earthquakes have always been a terrifying phenomenon , and they 've become more deadly as our cities have grown , with collapsing buildings posing one of the largest risks . why do buildings collapse in an earthquake , and how can it be prevented ? if you 've watched a lot of disaster films , you might have the idea that building collapse is caused directly by the ground beneath them shaking violently , or even splitting apart . but that 's not really how it works . for one thing , most buildings are not located right on a fault line , and the shifting tectonic plates go much deeper than building foundations . so what 's actually going on ? in fact , the reality of earthquakes and their effect on buildings is a bit more complicated . to make sense of it , architects and engineers use models , like a two-dimensional array of lines representing columns and beams , or a single line lollipop with circles representing the building 's mass . even when simplified to this degree , these models can be quite useful , as predicting a building 's response to an earthquake is primarily a matter of physics . most collapses that occur during earthquakes are n't actually caused by the earthquake itself . instead , when the ground moves beneath a building , it displaces the foundation and lower levels , sending shock waves through the rest of the structure and causing it to vibrate back and forth . the strength of this oscillation depends on two main factors : the building 's mass , which is concentrated at the bottom , and its stiffness , which is the force required to cause a certain amount of displacement . along with the building 's material type and the shape of its columns , stiffness is largely a matter of height . shorter buildings tend to be stiffer and shift less , while taller buildings are more flexible . you might think that the solution is to build shorter buildlings so that they shift as little as possible . but the 1985 mexico city earthquake is a good example of why that 's not the case . durng the quake , many buildings between six and fifteen stories tall collapsed . what 's strange is that while shorter buildings nearby did keep standing , buildings taller than fifteen stories were also less damaged , and the midsized buildings that collapsed were observed shaking far more violently than the earthquake itself . how is that possible ? the answer has to do with something known as natural frequency . in an oscillating system , the frequency is how many back and forth movement cycles occur within a second . this is the inverse of the period , which is how many seconds it takes to complete one cycle . and a building 's natural frequency , determined by its mass and stiffness , is the frequency that its vibrations will tend to cluster around . increasing a building 's mass slows down the rate at which it naturally vibrates , while increasing stiffness makes it vibrate faster . so in the equation representing their relationship , stiffness and natural frequency are proportional to one another , while mass and natural frequency are inversely proportional . what happened in mexico city was an effect called resonance , where the frequency of the earthquake 's seismic waves happen to match the natural frequency of the midsized buildings . like a well-timed push on a swingset , each additional seismic wave amplified the building 's vibration in its current direction , causing it to swing even further back , and so on , eventually reaching a far greater extent than the initial displacement . today , engineers work with geologists and seismologists to predict the frequency of earthquake motions at building sites in order to prevent resonance-induced collapses , taking into account factors such as soil type and fault type , as well as data from previous quakes . low frequencies of motion will cause more damage to taller and more flexible buildings , while high frequencies of motion pose more threat to structures that are shorter and stiffer . engineers have also devised ways to abosrb shocks and limit deformation using innovative systems . base isolation uses flexible layers to isolate the foundation 's displacement from the rest of the building , while tuned mass damper systems cancel out resonance by oscillating out of phase with the natural frequency to reduce vibrations . in the end , it 's not the sturdiest buildings that will remain standing but the smartest ones .

you might think that the solution is to build shorter buildlings so that they shift as little as possible . but the 1985 mexico city earthquake is a good example of why that 's not the case . durng the quake , many buildings between six and fifteen stories tall collapsed . what 's strange is that while shorter buildings nearby did keep standing , buildings taller than fifteen stories were also less damaged , and the midsized buildings that collapsed were observed shaking far more violently than the earthquake itself . how is that possible ?

during the mexico city earthquake of 1985 certain buildings collapsed , while others remained standing . what was the issue with the buildings that collapsed ? how could these collapses have been avoided ?

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 .

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 .

why do you decide on ‘ odd or even ’ for the ‘ secret meaning ’ of the first person ’ s guess ?

we already know that the world is made of things , things like cats and macaroni salad , and macaroni salad is made of things like mayo and mustard and celery , which are all made of molecules . as we 'll see , these molecules are made of the same stuff , just mixed together in different ways . let 's go back to our macaroni salad . we 've already unmixed things physically as much as we can . now , we 'll go further and unmix things chemically by breaking some bonds . many larger , complex molecules are just a bunch of smaller molecules bonded together like building blocks . here , again , macaroni salad provides a nice example . if you look at the pasta , you 'll notice it 's made of a lot of this stuff , starch , which is this molecule , otherwise known as amylose . turns out , if you break some bonds , amylose is made up of smaller molecules of glucose , a simple sugar . if you take a bunch of these same glucose molecules and rearrange them in a different way , you get cellulose , which is what plants are made of . so , while this piece of pasta made of amylose and this wooden spoon made of cellulose look vastly different , they 're both essentially made of the same molecules , just stuck together differently . this type of breaking apart and recombining is what goes on when you digest food . the complex proteins found in the foods we eat , like carrots and eggs , ca n't be used by our bodies because we are not carrots or chickens . what we can use are the smaller molecules that make up these proteins , the amino acids . during digestion , our bodies break these proteins up into their amino acids so they can be rearranged and put back together to make human proteins . but let 's keep breaking bonds . all molecules are made up of atoms bonded together . if some molecules are building blocks , atoms are the building blocks of the building blocks . and you 'll notice that with the molecules from macaroni salad , the same six types of atoms keep showing up : carbon , hydrogen , oxygen , nitrogen , phosphorus , and sulfur , or chonps . there 's a few others , but the big six is what macaroni salad is made of . if we went a step further , we could use these same atoms , recombine them , and make other stuff like gasoline or sulfuric acid , methane , and nylon . it 's all made from the same elements that make up macaroni salad . so , to recap , everything is made of atoms . they are the stuff that things are made of . atoms are grouped together in different ways to form molecules . these molecules are constantly being combined , broken apart , and recombined . they get thrown into mixtures , separated , remixed over and over and over again . the stuff that things are made of is always in flux ; it 's always changing . macaroni salad is only macaroni salad for a short time . you eat it , some of it becomes part of you , the rest eventually goes into the ocean and gets eaten by other animals that die , and after millions of years , they turn into oil , which is where gasoline comes from . and that 's why gasoline and macaroni salad are not that different - they 're both made of the same stuff , just one tastes better .

it 's all made from the same elements that make up macaroni salad . so , to recap , everything is made of atoms . they are the stuff that things are made of . atoms are grouped together in different ways to form molecules .

explain , in a nutshell , how everything is made out of the same stuff .

( music ) eight to be great : the eight traits successful people have in common . number two : work . when i was interviewing all these successful people , they kept telling me how hard they worked . and i remember standing there thinking , `` ah , jeez , another comment about work ? why do n't they tell me the real secret to their success ? '' then finally i realized , hard work is a real secret to their success . all successful people work very hard . martha stewart said to me , `` i 'm a real hard worker . i work and work and work all the time . '' media tycoon rupert murdoch said , `` it 's all hard work . nothing comes easily . but i have a lot of fun . '' did he say fun ? yes . successful people have fun working . that 's why i say they 're not really workaholics . they 're workafrolics . jim pattison , chairman of the jim pattison group , is a workafrolic . he says , `` business is my recreation . i 'd rather go to our factories and meet with our people than go to the beach , i can tell you that . '' dave lavery , the nasa whiz who builds those robots for mars , said to me , `` we work our fingers to the bone . but it does n't seem like work . it 's fun . it 's what we want to do . we do n't want to put things down and go home . '' bill gates is a workafrolic . even after he was a multimillionaire , he worked most nights until 10 p.m. , and only took two weeks off in seven years . and he probably spent them on his computer . oprah is a workafrolic . she says , `` i never see daylight . i 'd come into work at 5:30 in the morning when it was dark , and leave at 7 or 8 when it was dark . '' i 'm a workafrolic . and over the years , i 've gone through many days and even weeks without much sleep , just because i was having so much fun . and i got ta admit , at times like that you say to yourself , `` am i the only one working this hard ? '' because there 's a myth it comes easy to some people . you turn on the tv , nobody 's working that hard . a guy like chris rock stands up on stage , tells a few jokes . what 's hard about that ? but even chris says , `` i was n't the funniest guy growing up , but i was the guy who worked on being funny the hardest . '' trust me . i 've interviewed over 500 successful people , not one of them said it came easy , even though they were doing what they loved . we tend to underestimate work and overestimate talent . but in the end , work tops talent . arthur benjamin , america 's best math whiz , said to me , `` i think numbers and i have always gotten along . but i 'm sure my 'talent ' is just due to the time and hours and work that i 've put into it . '' many talented people do n't achieve as much success as they could , unfortunately , because they sit back on their talent and never learn to work hard . that 's what happened to michael jordan when he first started playing basketball . he had the talent , but he was n't putting in the work , and the coach actually cut him from the high school basketball team . boy , that was a wake-up call . he says , `` i was very disappointed . i started working on my game the day after i was cut . '' and he soon became the hardest working player in basketball , who made fun of the other players who were n't working hard . and that hard work is what made him the greatest basketball player of all time . so i 'd say the real gift is n't talent , it 's the ability to work hard . and we tend to underestimate work and overestimate smarts . but in the end , work wins over smarts . in fact , many successful people are n't the smartest , they just work the hardest . francois parenteau , who business week called the top independent analyst on wall street , said to me , `` i 'm certainly not that smart . i ca n't even remember my own zip code . '' but he also says , `` work is a big part of my life . i think about investments pretty much 24 hours a day , seven days a week . '' nez hallett iii is ceo of smart wireless , and i thought , that 's ironic because he told me he 's not that smart . he says , `` i graduated from high school with a c average , and college with a c-minus average . '' but now the smart phd 's are reporting to him . how did he do it ? he said , `` if you 're going to be successful at anything , the key thing is to work hard . '' i 'm not smart . as proof , here 's my actual 12th grade report card . it was the only one my parents ever kept . do n't ask me why they kept it ; it 's nothing to brag about . as you can see , i was a c student , not an a student . i do n't think i 'd even make it into college these days . so how did i achieve some success and wealth ? i just worked hard , many 60- to 80-hour weeks . and now i know i 'm not alone . thomas stanley studied hundreds of millionaires , and he discovered most millionaires were n't a students , did n't score high on tests and teachers did n't think they 'd ever succeed . but they did succeed , because they worked hard . so the good news is if you 're not the smartest , if you 're a c student , not an a student , the really good news is you can still succeed . because the word `` success '' has two c 's and no a 's . ( laughter ) you can still succeed as long as you work hard . and what if you are smart ? well , i 'm sorry , there 's absolutely no hope for you . because many smart people do n't achieve as much success as they could , unfortunately , because they rest on their smarts and never learn to work hard . jeong kim , president of lucent technologies , says , `` people who are the smartest sometimes do n't realize their full potential , because things get too easy , so they do n't push themselves hard . '' after a talk i gave at one of the world 's top 10 business schools , a man came up to me and said , `` you know , when i got my mba here a few years ago , i was one of the smartest people in the class . i thought i had it made . so after i graduated , i sat back and i did n't work hard . and i went downhill . and now , at this point in my life , i 've gone nowhere . i have n't achieved any success at all . '' he said , `` thanks for the wake-up call . now i know what i need to do . i need to work . '' so the bottom line is , whether you 're smart or not , whether you 're talented or not , just keep working . ( applause )

yes . successful people have fun working . that 's why i say they 're not really workaholics .

people who have fun working are ?

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 .

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 .

what disadvantage did our sun-adapted ancestors have when they moved to northern latitudes ?

translator : andrea mcdonough reviewer : jessica ruby there are still lots of things about space that we may never be able to answer , like is time travel possible ? or are aliens living somewhere else in the milky way ? but there is one thing i believe about space : space is trying to kill me . space is n't out to get me personally . it 's also trying to kill you and everybody else . think about it . space does n't naturally have what we need to survive when we travel there : no air , it 's too hot or too cold , no ozone to protect us from those nasty uv rays , either . this all sounds bad , but what can space really do to me if i stay on earth ? what we need to understand is that objects in space can cause people to think their days are numbered , even when there are events on earth that can hurt or kill us before something from space does . so , what are the odds that one of these objects will really affect earth and you and me in our lifetime ? well , we can take what we know about the universe to try and figure that out . you might have heard stories about asteroids hitting the earth . that would be pretty bad . scientists think asteroids might have killed off most of the dinosaurs . sounds like something we should worry about , right ? well , astronomers can now watch asteroids in space and see them coming using complex computer models to predict the deadly rock 's path . for a while , the reported odds that asteroid apophis would strike earth in 2036 were once 1 in 625 . but , after updating their data , astronomers now say the chances are extremely low . okay , what about the sun ? hollywood movies like to pick on our sun by showing earth destroyed by solar flares or the sun dying out , which would cause earth to freeze . astronomers predict our sun contains enough gas to make energy for another 3 to 5 billion years . so , in 3 to 5 billion years , if people still exist on earth , they 'll have to deal with that . but today , well , we 're safe . sometimes the sun does shoot flares at earth , but the magnetic fields surrounding our planet blocks most of that radiation . the radiation that does get through creates things like the aurora borealis . gigantic solar flares can mess with our satellites and electrical equipment , but the chances of it killing you are pretty slim . okay , what about that supermassive black hole in the middle of our galaxy ? what happens to earth , and us , when it pulls us in ? after all , it is supermassive . nope , not going to happen . that 's one big object that ca n't bother us . how can we be so sure ? our solar system is on the edge of the milky way while the nearest supermassive black hole is about 26,000 light years from earth . that means we are n't on that black hole 's menu . so , you still think space objects are trying to kill you even after what i 've told you so far ? i think i 've even convinced myself that odds are really good that space and the objects up there wo n't kill me after all . but i 'll probably keep looking up just to make sure nothing is headed my way .

okay , what about the sun ? hollywood movies like to pick on our sun by showing earth destroyed by solar flares or the sun dying out , which would cause earth to freeze . astronomers predict our sun contains enough gas to make energy for another 3 to 5 billion years .

what helps protect earth from radiation caused by solar flares ?

approximately 7 million people around the world die from heart attacks every year , and cardiovascular disease , which causes heart attacks and other problems like strokes , is the world 's leading killer . so what causes a heart attack ? like all muscles , the heart needs oxygen , and during a heart attack , it ca n't get enough . fatty deposits , or plaques , develop on the walls of our coronary arteries . those are the vessels that supply oxygenated blood to the heart . these plaques grow as we age , sometimes getting chunky , hardened , or enflamed . eventually , the plaques can turn into blockages . if one of the plaques ruptures or cracks , a blood clot will form around it in minutes , and a partially closed artery can become completely blocked . blood flow is cut off to the cardiac muscle and the oxygen-starved cells start to die within several minutes . this is a myocardial infarction , or heart attack . things can rapidly deteriorate in the absence of treatment . the injured muscle may not be able to pump blood as well , and its rhythm might be thrown off . in the worst case scenario , a heart attack can cause sudden death . and how do you know that someone is having a heart attack ? the most common symptom is chest pain caused by the oxygen-deprived heart muscle . patients describe it as crushing or vice-like . it can radiate to the left arm , jaw , back , or abdomen . but it 's not always as sudden and dramatic as it is in the movies . some people experience nausea or shortness of breath . symptoms may be less prominent in women and the elderly . for them , weakness and tiredness may be the main signal . and surprisingly , in many people , especially those with diabetes , which affects the nerves that carry pain , a heart attack may be silent . if you think that someone might be having a heart attack , the most important thing is to respond quickly . if you have access to emergency medical services , call them . they 're the fastest way to get to a hospital . taking aspirin , which thins the blood , and nitroglycerin , which opens up the artery , can help keep the heart attack from getting worse . in the emergency room , doctors can diagnose a heart attack . they commonly use an electrocardiogram to measure the heart 's electrical activity and a blood test to assess heart muscle damage . the patient is then taken to a high-tech cardiac suite where tests are done to locate the blockages . cardiologists can reopen the blocked artery by inflating it with a balloon in a procedure called an angioplasty . frequently , they also insert a metal or polymer stent that will hold the artery open . more extensive blockages might require coronary artery bypass surgery . using a piece of vein or artery from another part of the body , heart surgeons can reroute blood flow around the blockage . these procedures reestablish circulation to the cardiac muscle , restoring heart function . heart attack treatment is advancing , but prevention is vital . genetics and lifestyle factors both affect your risk . and the good news is that you can change your lifestyle . exercise , a healthy diet , and weight loss all lower the risk of heart attacks , whether you 've had one before or not . doctors recommend exercising a few times a week , doing both aerobic activity and strength training . a heart-healthy diet is low in sugar and saturated fats , which are both linked to heart disease . so what should you eat ? lots of fiber from vegetables , chicken and fish instead of red meat , whole grains and nuts like walnuts and almonds all seem to be beneficial . a good diet and exercise plan can also keep your weight in a healthy range , which will lower your heart attack risk as well . and of course , medications can also help prevent heart attacks . doctors often prescribe low-dose aspirin , for example , particularly for patients who 've already had a heart attack and for those known to be at high risk . and drugs that help manage risk factors , like high blood pressure , cholesterol , and diabetes , will make heart attacks less likely , too . heart attacks may be common , but they do n't have to be inevitable . a healthy diet , avoiding tobacco use , staying fit , and enjoying plenty of sleep and lots of laughter all go a long way in making sure your body 's most important muscle keeps on beating .

fatty deposits , or plaques , develop on the walls of our coronary arteries . those are the vessels that supply oxygenated blood to the heart . these plaques grow as we age , sometimes getting chunky , hardened , or enflamed .

what are the blood vessels that supply oxygenated blood to the heart called ?

translator : andrea mcdonough reviewer : bedirhan cinar at birth , our bodies are roughly 75 % water . we remain mostly water for the rest of our lives . we can not survive even a week without fresh water . there 's no life without it for ecosystems , societies , and individuals . so , how much usable water is there on earth ? most of the water on earth is ocean , a salty 97.5 % , to be precise , and the remaining 2.5 % is fresh water . that little sliver of liquid sustains human life on earth , it literally holds up civilizations . 2.5 % is a small proportion to be sure , and even that is broken down into smaller parts : surface water , water in ice caps and polar regions , and ground water . first , surface water . all the liquid water above ground is surface water and it is a tiny blip of an amount . 0.3 % of all fresh water is surface water . it may seem counterintuitive , but it accounts for little streams all over the planet . all rivers , including the nile , the jordan , and the mississippi , and lakes , large to small , like victoria , the great lakes , and baikal . second , ice caps and polar regions freeze up to 70 % of the planet 's fresh water . this water is significant , but it is n't available for human use in a regular way . finally , nearly 30 % of all water on earth is ground water . as the name suggests , that 's water in the ground . it can rest still and deep in huge caverns , or it can snuggle in the little crevices of rock and pebble . the upshot - thank goodness for ground water ! it 's invisible to us , but it is much more plentiful than surface water . it is much more reliable and easier to obtain than frozen water . without ground water , our societies would be parched . so , how are we using that water ? as a result of industrialization and population growth , demand for fresh water skyrocketed in the last century . where is all that water going ? first , we have to remember that fresh water is a global concern , but it is always local . context matters . the sahara is not seattle . still , some general information can help us get a handle on major trends . who consumes the most fresh water ? and , what sectors consume the most fresh water ? first , who . well , the united states consumes the most water per capita of any country in the entire world , followed by parts of europe and large industrializing nations like china . but , this does n't tell us what water is being used for . so let 's look at it another way . if we ask what kinds of uses water is going towards , we see a different picture . agriculture accounts for roughly 70 % of global fresh water consumption . again , remember the numbers vary by region , but still , it 's a staggering amount . and , this makes a certain kind of sense : we need to eat , we need water to grow food ; the bigger the population , the more food we need ; and , the wealthier we get , the more meat we eat , and the more water is required to produce our food . furthermore , 22 % of all fresh water worldwide goes to industrial uses . this includes the production of electricity , the extraction of fossil fuels , and the manufacturing of all manner of goods , from microchips , to paper , to blimps . 70 % to agriculture , 22 % to industrial uses , what 's left ? 8 % all those domestic uses - cooking , cleaning , bathing , drinking - it 's a drop in the bucket of overall water use .

still , some general information can help us get a handle on major trends . who consumes the most fresh water ? and , what sectors consume the most fresh water ? first , who .

what are the main ways you consume fresh water ? where can you cut back usage to help conserve ?

so our reaction ’ s ready . now all we need again is a little bit of water just to start it off . so we ’ re here today and we ’ ve come back after hours because we need to use this room for a long period of time because we ’ re going to do something quite exciting . because brady ’ s bought another camera which you can see he ’ s setup over there and we ’ re going to use that second camera to capture one second of film every minute for maybe two or three hours and we ’ re going to do some time lapse . something i ’ ve seen on tv with like flowers opening or plants growing but never with chemistry developing . silver is one of the few metallic elements that occurs naturally as the metal in nature . so that if you ’ re lucky you can wander around and find lumps of silver lying around on the ground . and this is how , in ancient times , silver was discovered so it has been known for thousands if not tens of thousands of years . gold is somewhat similar and also copper . but most other metals combine too easily with oxygen or other elements so you don ’ t find them naturally . so i thought what we ’ d do today is through a competition reaction and that competition reaction is based on something called the reactivity series of metals . so we ’ re going to compare the reactivity of two metals . it ’ s a bit like a game of football . we ’ re going to give one of those metals the football and in this case it ’ s another component or another salt component , nitrate . so the two metals that are going to be competing for the nitrate are silver and copper . and really these are related by something called the reactivity series . one of these metals is going to win , i know that and i hope we ’ ll find it during this video . silver had a particular use in photography and in the old days when people used photographic film the black colour that you saw on developed negatives is in fact silver . a photographic film consists of a layer of silver bromide or sometimes silver iodide and when the light shines on it the light just starts a tiny amount of reaction making silver and then when you put it in the developing solution the catalytic amount of silver that you ’ ve produced causes a big reaction and you make a large amount of silver . and so you get this black colour which then you can print as pictures . so on the bench i ’ ve got a small beaker or an erlenmeyer flask , as we chemists call it , which is full of deionised water . so we ’ ve passed the water through a machine which has taken out all of the other ions so that they can ’ t play around with the competition reaction that we want to start today . firstly , i ’ m going to start off by giving the prize of the competition to silver . so here i ’ ve got a sample of silver nitrate . it ’ s sensitive to light so i can ’ t leave it out on the bench very often . so now what i want to do , i ’ m going to put some into the water to make a silver nitrate solution . so i want to make sure that there ’ s plenty in there so that it ’ s saturated . now we ’ ve got to put in the competitor . so what we ’ re going to do , we ’ re going to take some copper , copper metal . and this is just a sample of wire which i ’ ve rubbed with some wire wool just to make it sort of nice and shiny . and now all i ’ m going to do is dangle it into the silver nitrate . then it ’ s going to start to compete for the nitrate and we ’ ll see what happens . so brady ’ s started the recording and i think the best thing for us to do is to go away and do something a little bit more exciting and come back and have a look in an hour . silver has become quite popular recently as a potential new way of making things anti-bacterial : killing bacteria . so now we ’ re going to make some flash powder and the flash powder we ’ re going to make today is a two component mixture . it ’ s very finely ground magnesium and the second component is ground silver nitrate , solid ok . so we take these two components and we mix the two together very intimately and neil ’ s just weighing the materials out right now . so we ’ re going to put the magnesium and the silver nitrate , the two powders , together into a small plastic container here . we ’ re going to mix them very , very carefully and then we ’ re going to see what happens when we initiate a chemical reaction . for hundreds of years people have used silver spoons . partly , i think , because silver is quite easy to make but also because the silver does have properties that kill bacteria so a silver spoon is less likely to get harmful bacteria on it than if you have one that ’ s made out of wood or horn of a cow or something like that . so we ’ re mixing these very carefully , in the fume hood , just in case the chemistry starts before we want it to . and in recent times people have started making very , very fine particles of silver , so called nanoparticles , which can exist in solutions . so here i ’ ve got a solution of silver nanoparticles . you can see it doesn ’ t look silver it looks a bit yellow actually and you can tell that it ’ s got particles in it because , if i can find a torch… so here we ’ ve got particles and you can see the particles better if we shine a light through it and if you look at the light you can see that there is a cone of light that looks rather like the headlights of a car in fog . and this is an effect that ’ s called the tyndall cone which indicates that there are very , very tiny particles suspended in the solution . so this is not silver dissolved in the water but actually very tiny particles . so let ’ s start the reaction , just with a little bit of water . wow ! i think we should do it again though . yeah ! laughter people are now using the silver nanoparticles for all sorts of purposes . here you can see that they ’ ve been put onto some sort of plastic and you can now buy socks which have silver nanoparticles on them which are claimed to kill the bacteria that make your feet smell . so we ’ re going to repeat the reaction . b-b-b-b… squawcks that ’ s going to come out somewhere isn ’ t it ? silver will conduct electricity , it will also conduct heat . if you ’ ve ever tried stirring tea with a silver spoon it gets very hot , you tend to drop it . it also conducts electricity well . so we ’ re going to repeat the reaction so that you can see it again , because that was really fast . this time we ’ re going to do it on a glass dish so you can see it a bit better . we ’ ll pour out a small amount . laughter so our reaction ’ s ready . now all we need again is a little bit of water just to start it off . did you catch that ? i managed to close my eyes this time ( ! ) during the second world war , when the us government was involved in enriching uranium as part of the manhattan project they needed an enormous amount of wire to make magnets . and so a huge amount of silver was taken from the us treasury where it was stored as silver to give value to the us dollar and was turned into wires to make magnets . and i believe that the silver was never returned or at least it wasn ’ t returned at the end of the war as was promised . well , i ’ ve managed to fill maybe one minute ’ s worth of time by now maybe two because we ’ ve been away about two hours . so we ’ re going to go back and have a look at the flask to see if there are any changes . if you remember when we left it was a nice clear solution of silver nitrate with some copper wire which was just immersed inside . so let ’ s go and have a look . there ’ s been big changes in our flask ! so if you look carefully you can see now that the copper wire itself is covered in very , very sharp crystals of silver which have basically become deposited on the surface . copper has now won this chemical reaction . it ’ s now going into the solution ; it ’ s taking the salt element and precipitating solid silver crystals . so if you look carefully , you can see that the colour of the solution has changed . it was colourless , now it ’ s blue which tells me there is another ion , copper , in the solution .

there ’ s been big changes in our flask ! so if you look carefully you can see now that the copper wire itself is covered in very , very sharp crystals of silver which have basically become deposited on the surface . copper has now won this chemical reaction .

in the beautiful experiment pete performed , which was then converted into an amazing time-lapse by brady , we saw silver crystals precipitated on the surface of copper wire . but why does the solution turn blue ?

energy is all around us , a physical quantity that follows precise natural laws . our universe has a finite amount of it ; it 's neither created nor destroyed but can take different forms , such as kinetic or potential energy , with different properties and formulas to remember . for instance , an led desk lamp 's 6 watt bulb transfers 6 joules of light energy per second . but let 's jump back up into space to look at our planet , its systems , and their energy flow . earth 's physical systems include the atmosphere , hydrosphere , lithosphere , and biosphere . energy moves in and out of these systems , and during any energy transfer between them , some is lost to the surroundings , as heat , light , sound , vibration , or movement . our planet 's energy comes from internal and external sources . geothermal energy from radioactive isotopes and rotational energy from the spinning of the earth are internal sources of energy , while the sun is the major external source , driving certain systems , like our weather and climate . sunlight warms the surface and atmosphere in varying amounts , and this causes convection , producing winds and influencing ocean currents . infrared radiation , radiating out from the warmed surface of the earth , gets trapped by greenhouse gases and further affects the energy flow . the sun is also the major source of energy for organisms . plants , algae , and cyanobacteria use sunlight to produce organic matter from carbon dioxide and water , powering the biosphere 's food chains . we release this food energy using chemical reactions , like combustion and respiration . at each level in a food chain , some energy is stored in newly made chemical structures , but most is lost to the surroundings , as heat , like your body heat , released by your digestion of food . now , as plants are eaten by primary consumers , only about 10 % of their total energy is passed on to the next level . since energy can only flow in one direction in a food chain , from producers on to consumers and decomposers , an organism that eats lower on the food chain , is more efficient than one higher up . so eating producers is the most efficient level at which an animal can get its energy , but without continual input of energy to those producers , mostly from sunlight , life on earth as we know it would cease to exist . we humans , of course , spend our energy doing a lot of things besides eating . we travel , we build , we power all sorts of technology . to do all this , we use sources like fossil fuels : coal , oil , and natural gas , which contain energy that plants captured from sunlight long ago and stored in the form of carbon . when we burn fossil fuels in power plants , we release this stored energy to generate electricity . to generate electricity , heat from burning fossil fuels is used to power turbines that rotate magnets , which , in turn , create magnetic field changes relative to a coil of wire , causing electrons to be induced to flow in the wire . modern civilization depends on our ability to keep powering that flow of electrons . fortunately , we are n't limited to burning non-renewable fossil fuels to generate electricity . electrons can also be induced to flow by direct interaction with light particles , which is how a solar cell operates . other renewable energy sources , such as wind , water , geothermal , and biofuels can also be used to generate electricity . global demand for energy is increasing , but the planet has limited energy resources to access through a complex energy infrastructure . as populations rise , alongside rates of industrialization and development , our energy decisions grow more and more important . access to energy impacts health , education , political power , and socioeconomic status . if we improve our energy efficiency , we can use our natural resources more responsibly and improve quality of life for everyone .

electrons can also be induced to flow by direct interaction with light particles , which is how a solar cell operates . other renewable energy sources , such as wind , water , geothermal , and biofuels can also be used to generate electricity . global demand for energy is increasing , but the planet has limited energy resources to access through a complex energy infrastructure . as populations rise , alongside rates of industrialization and development , our energy decisions grow more and more important .

think about your school and its use of energy . what are your school ’ s primary and secondary sources of energy ?

( music ) on a typical day at school , endless hours are spent learning the answers to questions . but right now , we 'll do the opposite . we 're going to focus on questions where you ca n't learn the answers , because they 're unknown . i used to puzzle about a lot of things as a boy . for example , what would it feel like to be a dog ? do fish feel pain ? how about insects ? was the big bang just an accident ? and is there a god ? and if so , how are we so sure that it 's a he and not a she ? why do so may innocent people and animals suffer terrible things ? is there really a plan for my life ? is the future yet to be written , or is it already written and we just ca n't see it ? but then , do i have free will ? who am i , anyway ? am i just a biological machine ? but then , why am i conscious ? what is consciousness ? will robots become conscious one day ? i mean , i kind of assumed that some day i would be told the answers to all these questions . i mean , someone must know , right ? huh . guess what ? no one knows . most of those questions puzzle me more now than ever . but diving into them is exciting because it takes you to the edge of knowledge , and you never know what you 'll find there . so , two questions to kick off this series , questions that no one on earth knows the answer to ... text : how many universes are there ? why ca n't we see evidence of alien life ?

but diving into them is exciting because it takes you to the edge of knowledge , and you never know what you 'll find there . so , two questions to kick off this series , questions that no one on earth knows the answer to ... text : how many universes are there ?

how does anderson feel about the idea that there are questions we can ’ t answer ?

one day the universe will die . but why ? and how ? and will the universe be dead forever ? and how do we know that ? first of all , the universe is expanding . and not only that , the rate of its expansion is accelerating . the reason : dark energy . dark energy is a strange phenomenon that scientists believe permeates the universe . until 1998 we thought that the universe must work a bit like a ball that you throw into the sky . the ball moves up , but at some point it has to come down again . but the expansion of the universe is actually speeding up . that ’ s like throwing a ball up and watching it fly away faster and faster and faster . where is this acceleration coming from ? well , we don ’ t know , but we call it “ dark energy ” . einstein thought of it first and then decided it was stupid . now , astrophysicists have decided it is plausible . trouble is , this is all very theoretical , and we don ’ t actually know what the properties of dark energy are . but there are various theories and they lead us to three scenarios for the end of the universe . one : the big rip . since its birth , the universe has been expanding . for unknown reasons new spaces created everywhere equally . the space between galaxies expands , so they move apart . the space inside galaxies also expands , but here , gravity is strong enough to keep them together . in the big rip scenario , the expansion accelerates up to a point where space expands so fast that gravity can ’ t compensate for this effect anymore . the result is a big rip . at first , only large structures like galaxies are torn apart , since space between the single objects expands very fast . next , big bodies like black holes , stars , and planets die . their gravity isn ’ t strong enough to keep them together , so they dissolve into their components . in the end , space would expand faster than the speed of light . atoms would now be affected , and they would just disband . once space is expanding faster than light , no particle in the universe can interact with any other particle anymore . the universe would dissolve into countless lonely particles that won ’ t be able to touch anything else in a strange , timeless universe . hmm , and you thought you felt lonely ! two : heat death or a big freeze . in a nutshell , the difference between the big rip and heat death is that in a heat death scenario matter stays intact and is converted over an incredibly long but finite period of time into radiation , while the universe expands forever . but how does this work ? let ’ s talk about entropy . every system tends towards the state of highest entropy , like when we have a latte macchiato . initially , it has different regions , but over time , they will cool down and disintegrate , until it ’ s uniform . and this also applies to the universe . so , while the universe gets bigger and bigger , matters slowly decays and spreads out . at some point , after lots of generations of stars , all the gas clouds necessary to form stars will be exhausted , so the universe will turn dark . the remaining suns will die ; black holes will slowly degenerate and evaporate over trillions of years due to what ’ s known as hawking radiation . when this process is complete , only a dilute gas of photons and light particles remains , until even this decays . all activity in the universe ceases at this point ; entropy is at its maximum and the universe is dead forever . unless… theoretically , it might be possible that after an incredibly long amount of time , there might be a spontaneous entropy decrease as a result of something called “ quantum tunneling ” , leading to a new big bang . three : big crunch and big bounce . this is the most uplifting scenario . if there is less dark energy than we think or it decreases over time , gravity will be the dominating force in the universe one day . in a few trillion years , the rate of expansion of the universe will slow down and stop . after that , it reverses . galaxies will race at each other , merging as the universe becomes smaller and smaller . since a smaller universe also means a hotter universe , temperatures rise everywhere all at once . one hundred thousand years before the big crunch , background radiation would be hotter than the surfaces of the most stars , which means that they would be cooked from the outside . minutes before the big crunch happens , atom cores are ripped apart , before supermassive black holes devour everything . finally , all black holes would emerge into a supermassive mega-black hole that contains the entire mass of the universe , and in the last moment before the big crunch it would devour the universe , including itself . the big bounce theory states that this has happened a lot of times and that the universe goes through an infinite cycle of expansion and contraction . well , wouldn ’ t that be nice ? so what will actually happen to the universe in the end ? at the moment , heat death seems the most likely , but we at kurzgesagt hope that this “ dead forever ” stuff is wrong and the universe will start over and over again . we do n't know for sure either way , so let ’ s just assume the most uplifting theory is true . by the way , we have a twitter account . subtitles by the amara.org community

and how do we know that ? first of all , the universe is expanding . and not only that , the rate of its expansion is accelerating .

this video claims that the universe is expanding . what is the cause of its expansion ?

there are a lot of ways this marvelous language of ours , english , does n't make sense . for example , most of the time when we talk about more than one of something , we put an s on the end . one cat , two cats . but then , there 's that handful of words where things work differently . alone you have a man ; if he has company , then you 've got men , or probably better for him , women too . although if there were only one of them , it would be a woman . or if there 's more than one goose , they 're geese , but why not lots of mooses , meese ? or if you have two feet , then why do n't you read two beek instead of books . the fact is that if you were speaking english before about a thousand years ago , beek is exactly what you would have said for more than one book . if modern english is strange , old english needed therapy . believe it or not , english used to be an even harder language to learn than it is today . twenty-five hundred years ago , english and german were the same language . they drifted apart slowly , little by little becoming more and more different . that meant that in early english , just like in german , inanimate objects had gender . a fork , gafol , was a woman ; a spoon , laefel , was a man ; and the table they were on , bord , was neither , also called neuter . go figure ! being able to use words meant not just knowing their meaning but what gender they were , too . and while today there are only about a dozen plurals that do n't make sense , like men and geese , in old english , it was perfectly normal for countless plurals to be like that . you think it 's odd that more than one goose is geese ? well , imagine if more than one goat was a bunch of gat , or if more than one oak tree was a field of ack . to be able to talk about any of these , you just had to know the exact word for their plural rather than just adding the handy s on the end . and it was n't always an s at the end either . in merry old english , they could add other sounds to the end . just like more than one child is children , more than one lamb was lambru , you fried up your eggru , and people talked not about breads , but breadru . sometimes it was like sheep is today - where , to make a plural , you do n't do anything . one sheep , two sheep . in old english , one house , two house . and just like today , we have oxen instead of oxes . old english people had toungen instead of tongues , namen instead of names , and if things stayed the way they were , today we would have eyen instead of eyes . so , why did n't things stay the way they were ? in a word , vikings . in the 8th century , scandinavian marauders started taking over much of england . they did n't speak english , they spoke norse . plus , they were grown-ups , and grown-ups are n't as good at learning languages as children . after the age of roughly 15 , it 's almost impossible to learn a new language without an accent and without slipping up here and there as we all know from what language classes are like . the vikings were no different , so they had a way of smoothing away the harder parts of how english worked . part of that was those crazy plurals . imagine running up against a language with eggru and gat on the one hand , and then with other words , all you have to do is add 's ' and get days and stones . would n't it make things easier to just use the 's ' for everything ? that 's how the vikings felt too . and there were so many of them , and they married so many of the english women , that pretty soon , if you grew up in england , you heard streamlined english as much as the real kind . after a while nobody remembered the real kind any more . nobody remembered that once you said doora instead of doors and handa instead of hands . plurals made a lot more sense now , except for a few hold-outs like children and teeth that get used so much that it was hard to break the habit . the lesson is that english makes a lot more sense than you think . thank the ancestors of people in copenhagen and oslo for the fact that today we do n't ask for a handful of pea-night instead of peanuts . although , would n't it be fun , if for just a week or two , we could ?

the fact is that if you were speaking english before about a thousand years ago , beek is exactly what you would have said for more than one book . if modern english is strange , old english needed therapy . believe it or not , english used to be an even harder language to learn than it is today .

have you noticed evolution in the english language ? explain your observations ( including reasons you think they happened ) .

translator : andrea mcdonough reviewer : jessica ruby what 's an algorithm ? in computer science , an algorithm is a set of instructions for solving some problem , step-by-step . typically , algorithms are executed by computers , but we humans have algorithms as well . for instance , how would you go about counting the number of people in a room ? well , if you 're like me , you probably point at each person , one at a time , and count up from 0 : 1 , 2 , 3 , 4 and so forth . well , that 's an algorithm . in fact , let 's try to express it a bit more formally in pseudocode , english-like syntax that resembles a programming language . let n equal 0 . for each person in room , set n = n + 1 . how to interpret this pseudocode ? well , line 1 declares , so to speak , a variable called n and initializes its value to zero . this just means that at the beginning of our algorithm , the thing with which we 're counting has a value of zero . after all , before we start counting , we have n't counted anything yet . calling this variable n is just a convention . i could have called it almost anything . now , line 2 demarks the start of loop , a sequence of steps that will repeat some number of times . so , in our example , the step we 're taking is counting people in the room . beneath line 2 is line 3 , which describes exactly how we 'll go about counting . the indentation implies that it 's line 3 that will repeat . so , what the pseudocode is saying is that after starting at zero , for each person in the room , we 'll increase n by 1 . now , is this algorithm correct ? well , let 's bang on it a bit . does it work if there are 2 people in the room ? let 's see . in line 1 , we initialize n to zero . for each of these two people , we then increment n by 1 . so , in the first trip through the loop , we update n from zero to 1 , on the second trip through that same loop , we update n from 1 to 2 . and so , by this algorithm 's end , n is 2 , which indeed matches the number of people in the room . so far , so good . how about a corner case , though ? suppose that there are zero people in the room , besides me , who 's doing the counting . in line 1 , we again initialize n to zero . this time , though , line 3 does n't execute at all since there is n't a person in the room , and so , n remains zero , which indeed matches the number of people in the room . pretty simple , right ? but counting people one a time is pretty inefficient , too , no ? surely , we can do better ! why not count two people at a time ? instead of counting 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , and so forth , why not count 2 , 4 , 6 , 8 , and so on ? it even sounds faster , and it surely is . let 's express this optimization in pseudocode . let n equal zero . for each pair of people in room , set n = n + 2 . pretty simple change , right ? rather than count people one at a time , we instead count them two at a time . this algorithm 's thus twice as fast as the last . but is it correct ? let 's see . does it work if there are 2 people in the room ? in line 1 , we initialize n to zero . for that one pair of people , we then increment n by 2 . and so , by this algorithm 's end , n is 2 , which indeed matches the number of people in the room . suppose next that there are zero people in the room . in line 1 , we initialize n to zero . as before , line 3 does n't execute at all since there are n't any pairs of people in the room , and so , n remains zero , which indeed matches the number of people in the room . but what if there are 3 people in the room ? how does this algorithm fair ? let 's see . in line 1 , we initialize n to zero . for a pair of those people , we then increment n by 2 , but then what ? there is n't another full pair of people in the room , so line 2 no longer applies . and so , by this algorithm 's end , n is still 2 , which is n't correct . indeed this algorithm is said to be buggy because it has a mistake . let 's redress with some new pseudocode . let n equal zero . for each pair of people in room , set n = n + 2 . if 1 person remains unpaired , set n = n + 1 . to solve this particular problem , we 've introduced in line 4 a condition , otherwise known as a branch , that only executes if there is one person we could not pair with another . so now , whether there 's 1 or 3 or any odd number of people in the room , this algorithm will now count them . can we do even better ? well , we could count in 3 's or 4 's or even 5 's and 10 's , but beyond that it 's going to get a little bit difficult to point . at the end of the day , whether executed by computers or humans , algorithms are just a set of instructions with which to solve problems . these were just three . what problem would you solve with an algorithm ?

surely , we can do better ! why not count two people at a time ? instead of counting 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , and so forth , why not count 2 , 4 , 6 , 8 , and so on ?

in real life , why do you think people tend to count by 1s and 2s but not by 3s ?

they say that if walls could talk , each building would have a story to tell , but few would tell so many fascinating stories in so many different voices as the hagia sophia , or holy wisdom . perched at the crossroads of continents and cultures , it has seen massive changes from the name of the city where it stands , to its own structure and purpose . and today , the elements from each era stand ready to tell their tales to any visitor who will listen . even before you arrive at the hagia sophia , the ancient fortifications hint at the strategic importance of the surrounding city , founded as byzantium by greek colonists in 657 bce . and successfully renamed as augusta antonia , new rome and constantinople as it was conquered , reconquered , destroyed and rebuilt by various greek , persian and roman rulers over the following centuries . and it was within these walls that the first megale ekklesia , or great church , was built in the fourth century . though it was soon burned to the ground in riots , it established the location for the region 's main religious structure for centuries to come . near the entrance , the marble stones with reliefs are the last reminders of the second church . built in 415 ce , it was destroyed during the nika riots of 532 when angry crowds at a chariot race nearly overthrew the emperor , justinian the first . having barely managed to retain power , he resolved to rebuild the church on a grander scale , and five years later , the edifice you see before you was completed . as you step inside , the stones of the foundation and walls murmur tales from their homelands of egypt and syria , while columns taken from the temple of artemis recall a more ancient past . runic inscriptions carved by the vikings of the emperor 's elite guard carry the lore of distant northern lands . but your attention is caught by the grand dome , representing the heavens . reaching over 50 meters high and over 30 meters in diameter and ringed by windows around its base , the golden dome appears suspended from heaven , light reflecting through its interior . beneath its grandiose symbolism , the sturdy reinforcing corinthian columns , brought from lebanon after the original dome was partially destroyed by an earthquake in 558 ce , quietly remind you of its fragility and the engineering skills such a marvel requires . if a picture is worth a thousand words , the mosaics from the next several centuries have the most to say not only about their biblical themes , but also the byzantine emperors who commissioned them , often depicted along with christ . but beneath their loud and clear voices , one hears the haunting echoes of the damaged and missing mosaics and icons , desecrated and looted during the latin occupation in the fourth crusade . within the floor , the tomb inscription of enrico dandolo , the venetian ruler who commanded the campaign , is a stark reminder of those 57 years that hagia sophia spent as a roman catholic church before returning to its orthodox roots upon the byzantine reconquest . but it would not remain a church for long . weakened by the crusades , constantinople fell to the ottomans in 1453 and would be known as istanbul thereafter . after allowing his soldiers three days of pillage , sultan mehmed the second entered the building . though heavily damaged , its grandeur was not lost on the young sultan who immediately rededicated it to allah , proclaiming that it would be the new imperial mosque . the four minarets built over the next century are the most obvious sign of this era , serving as architectural supports in addition to their religious purpose . but there are many others . ornate candle holders relate suleiman 's conquest of hungary , while giant caligraphy discs hung from the ceiling remind visitors for the first four caliphs who followed muhammad . though the building you see today still looks like a mosque , it is now a museum , a decision made in 1935 by kemal ataturk , the modernizing first president of turkey following the ottoman empire 's collapse . it was this secularization that allowed for removal of the carpets hiding the marble floor decorations and the plaster covering the christian mosaics . ongoing restoration work has allowed the multiplicity of voices in hagia sophia 's long history to be heard again after centuries of silence . but conflict remains . hidden mosaics cry out from beneath islamic calligraphy , valuable pieces of history that can not be uncovered without destroying others . meanwhile , calls sound from both muslim and christian communities to return the building to its former religious purposes . the story of the divine wisdom may be far from over , but one can only hope that the many voices residing there will be able to tell their part for years to come .

it was this secularization that allowed for removal of the carpets hiding the marble floor decorations and the plaster covering the christian mosaics . ongoing restoration work has allowed the multiplicity of voices in hagia sophia 's long history to be heard again after centuries of silence . but conflict remains .

restoration is a costly and difficult process of evaluating the character of the past and how it will relate to the future . imagine that you had to undergo the task of restoring the hagia sophia . research the process , develop a plan to “ restore ” the building and be prepared to defend your changes .

so element 96 was curium which named after marie curie and pierre curie who were the discoverers of radium . because of its high levels of radioactivity curium can be used in thermoelectric generators to produce electricity and you ’ ll get about 120 watts per hour out of one of these . however , because it is so radioactive no-one ’ s really interested in using it in commercial processes . well , past uranium everything is synthetically made , you need access to nuclear power stations or nuclear bombs or big colliders to be able to make these elements . they are extremely radioactive , very hard to handle , and only a handful of places in the uk have got the sort of facilities you need to deal with these types of compounds . so even somebody such as myself , it ’ s not really what i do , it ’ s a little bit beyond where my area is . i ’ d pretty much stop at uranium . that ’ s the limit of normal laboratory chemistry .

so element 96 was curium which named after marie curie and pierre curie who were the discoverers of radium . because of its high levels of radioactivity curium can be used in thermoelectric generators to produce electricity and you ’ ll get about 120 watts per hour out of one of these . however , because it is so radioactive no-one ’ s really interested in using it in commercial processes .

what is the application of curium steve mentioned in the video ?

translator : andrea mcdonough reviewer : bedirhan cinar about 100 days ago , we landed a two-ton suv on the surface of another planet , on the surface of mars . this is one of the first pictures we took there with our rover , looking out at mount sharp . i kind of cry a little bit , choke up , when i see this picture . why mars and why do we look at these other planets ? part of it is to understand our own planet -- what 's the context for us ? we live on this amazing planet , but mars is a lot like earth . it 's similar in size . during the daytime , it can get up to 70 degrees fahrenheit . so , it 's so like earth , but at the same time , this is a barren landscape . you do n't see any trees , you do n't see any cactuses growing , anything like that . today i 'm going to tell you about how we got from earth to mars and why it 's so cool . so one of the things we start with is a blank sheet of paper . we knew from the previous missions in 2004 , spirit and opportunity , there was water on mars in the past . but what 's the next step ? we 're looking for an even more fundamental level of , what does it take to have life survive ? and so , to have that kind of knowledge and understanding , we have to carry a mass amount of instruments . we have to carry the kind of labs that people have whole rooms devoted to on earth inside of , essentially , a small car . and we shrunk it all down to something that weighs about as much as i do , and then put it inside of this rover that weighs as much as your car does . and that rover is now on the surface of mars , but it 's so heavy , and so it kind of takes a special challenge for us to make it all work and come together . so we look at our tool of , what do we have to land stuff on mars ? and one of the options is airbags . we 've done it before . airbags are pretty cool , they bounce around a lot . you could never put a human inside of an airbag , because they would get squashed . but the problem with airbags is , the airbags you see here , which landed the smaller rover -- it 's like 400 pounds , the entire rover -- were about the size of this room . so you can imagine the size of airbags it would take to land a two-ton rover on mars . and they 'd have to be made out of materials that do n't even exist today , so it 'd be some kind of exotic material that we 'd have to develop and it may or may not work . so , what about rockets ? you know , you see all the rocket ships landing in old movies , all rockets on the bottom -- it 's a cool idea . it works when they 're pretty light still , but the problem is , these rockets have to be pretty strong to actually softly land you on mars . and so they would be so powerful they could dig holes into the ground and then you would just end up inside of a hole and not be able to drive out of it . so , not the best design . but what if i could take the rockets and move them up ? and that 's what we came up with . it 's a rocket-powered jet pack ; we call it the sky crane . basically , this big rocket sits on top of our rover and when we 're ready to land , the rocket hovers in place and we slowly lower the rover to the ground . and then we touch down , we 're actually on the wheels , we 're ready to drive , day one . but in addition to that , the scientists were like , `` we actually want to go somewhere interesting . '' the last two missions were cool , but they basically landed in what was like landing in the plains or desert . not very exciting . we all know from the exciting places on earth like the grand canyon , those are , for the scientists , the most interesting , because you see that whole layer , you see years and years of history all in one place . the same thing is true for where we landed . we wanted to land somewhere that was unique , that had this crater wall where things had been dug up for us , where mountains were pushing things up . but the problem is , if you landed with the older systems , you could 've landed on the side of that mountain and just tumbled off , could 've been the side of a cliff , the crater wall or a large boulder . so we needed a kind of technology to help us land in a very small area , and that was this little guided entry from apollo . we took it from the 1960s . we flew over like the manned vehicle , because they have to pick up men , you ca n't just land all over the place . and then we landed , like , spot-on in the middle . and in fact , it was so spot-on that when we did it , it was basically like a quarterback launching towards mars -- like a quarterback , though , that was in seattle , throwing at a receiver that was moving here in giants stadium . that 's how accurate we were . kind of awesome . but you only get one shot , and so we actually have to design a system that we can build and test and operate , and so it 's not just about can we get it to mars , but , if it 's only one chance , how do you make sure that one chance goes well ? so there 's all these processes to make sure things are built properly . then we go out to the desert and drive around and test it . we fly things in f-18s to make sure the radar systems work in high speeds . then , most importantly , we test the team to make sure they know how to operate it . we do n't want to miss it because we sent the wrong command and now it 's going to be rebooting forever . so , that guy fred there , he did a lot of that . and then we launched it on this rocket to mars . we landed 2,000 pounds on mars , but the entire thing was about 10,000 pounds when we lifted off from earth , all the fuel and the solar arrays and everything else that we needed . and , again , we were so accurate that we landed in this , like , little pin-point on mars . in the meantime , though , we had to design a landing system that worked . and i told you about the actual physics of it , but here 's the catch : mars is about 14 minutes away from earth in light speed , which means if i try to control it with a joystick , i would be always controlling to 14 minutes in advance , so it would n't work . so we had to give it all the smarts and knowledge it needed to make it happen . so we built in all these smarts and algorithms and told it here 's what you 're going to have to do , and it goes from basically five times the speed of a speeding bullet to about a baby 's crawl , all within about seven minutes , which are called the seven minutes of terror , because i was about to throw up . ( laughter ) but today we 're on the surface of mars , and this was one of the panoramas we took a couple days after we landed , and it 's amazing to me , because you look at this , and can see the grand canyon , you can see your own planet , you can imagine walking on the surface . and so what we 're going to do and continue to do is to understand what makes mars so special and what makes earth even more special that we 're all here together today . so we 'll see where curiosity takes us -- not just our rover , but our sense of exploration . thank you . ( applause )

it 's a rocket-powered jet pack ; we call it the sky crane . basically , this big rocket sits on top of our rover and when we 're ready to land , the rocket hovers in place and we slowly lower the rover to the ground . and then we touch down , we 're actually on the wheels , we 're ready to drive , day one .

though the actual curiosity rover weighed much less , how much did the entire rocket ( which included the rover ) weigh at the time of take off ?

it was a night like any other night , except here i was climbing the platonic peaks like romeo on a second date . ( ugh ) i was there for the dame . she had eyes like imaginary numbers and curves that went on forever . said she wanted to go home . said i could help . said the pay was good . did n't say anything about climbing a ... voice : `` who 's there ? '' manny brot : `` manny brot , private eye . '' voice : `` what are you doing here ? '' `` a pretty number sent me to find a stolen dingus . '' voice : `` well , to enter the cave , you must answer my riddles three . '' what was it with riddles , and why do they always come in threes ? `` is it an egg ? '' `` no . why would it be an egg ? '' `` it 's usually an egg . '' `` what can i hold in my hand , but has zero area ? '' `` is it a dodo egg ? '' `` it 's not an egg ! '' i took out the rock that had nearly brained me before and gave it a hard ponder . the size of the rising bump on my conk said to me that this thing had area , and a lot of it . but what if i carved out a triangle from this side here ? as any mook could see , this triangle had a quarter of the area of the full triangle . i did the same thing again with each of the smaller triangles . again , a quarter of the remaining area -- gone . and i just kept going . after an infinite number of cuts , i was satisfied that my triangle had zero area . a bounded shape with zero area . now , it 's not often that i surprise myself , but my own two mitts had created something crazy , and new . `` very good . ( ahem ) now , show me a shape with finite area , but an infinitely long perimeter . '' `` let me get this straight . if i want to make a snip in the border of this shape , smooth it out , and lay it on the ground ... `` `` it would go on for ... `` `` wait 'til i 'm through , and then you can talk . it would go on forever . '' `` are you through ? '' `` yeah . '' `` so show me that shape then . '' mmm ... i had n't been this stuck since the rubik 's cube fiasco of '58 . all the shapes i knew had perimeters . circles : 2πr . triangles : sum of their sides . what 's this ? an angle . an angle from heaven . what if i were to pinch each side , like so . a third of the way through , just so . and do it again , and again , and again . after each pinch , the perimeter got a third longer because where there had been three line segments , now there were four . as for the area , every pinch made more triangles , that 's true . but those triangles were getting smaller and smaller . you could say that the area was converging , approaching a fixed number , while the perimeter was just getting bigger and bigger , uncontrollably ballooning like an overindulgent birthday clown . after infinity pinches , flimflam , there it was : finite area , but infinite perimeter . now that is a piece of work . `` oh , you 're good . ( ahem ) riddle three : show me a picture that if i magnify it under my microscope , i 'll keep seeing the original picture , no matter how much i zoom in . '' `` you 're a strange little man . '' `` thank you . '' i was out of ideas , so i looked at my muse , my complex dora . voice : `` who 's the dame ? '' and then it hit me . `` she 's a heart breaker , my fractal femme fatale . will she do ? '' `` yes , she 'll do just fine . '' ( lightning ) it was dark , and at first i thought the cave was empty , but then i noticed : the box . the dame had played me like a triangle . she had told me she wanted to go home . ( lightning ) what she really wanted was to bring her home here . the fractals spread everywhere . most of them the same no matter how deep you looked at them , like dora 's mugshot . some had infinitely long perimeters , others were objects with no area or volume , all of them created through infinite repetition . so , you wanted to know what fractals are ? well , kid , they 're the stuff that dreams are made of . ( music )

and then it hit me . `` she 's a heart breaker , my fractal femme fatale . will she do ? ''

try inventing your own fractal .

ok , today we 're going to talk about the mole . now , i know what you 're thinking : `` i know what a mole is , it 's a small furry creature that digs holes in the ground and destroys gardens . '' and some of you might be thinking that it 's a growth on your aunt 's face with hairs sticking out of it . well , in this case , a mole is a concept that we use in chemistry to count molecules , atoms , just about anything extremely small . have you ever wondered how many atoms there are in the universe ? or in your body ? or even in a grain of sand ? scientists have wanted to answer that question , but how do you count something as small as an atom ? well , in 1811 , someone had an idea that if you had equal volumes of gases , at the same temperature and pressure , they would contain an equal number of particles . his name was lorenzo romano amedeo carlo avogadro . i wonder how long it took him to sign autographs . unfortunately for avogadro , most scientists did n't accept the idea of the atom , and there was no way to prove he was right . there was no clear difference between atoms and molecules . most scientists looked at avogadro 's work as purely hypothetical , and did n't give it much thought . but it turned out he was right ! by late 1860 , avogadro was proven correct , and his work helped lay the foundation for the atomic theory . unfortunately , avogadro died in 1856 . now the thing is that the amount of particles in even small samples is tremendous . for example , if you have a balloon of any gas at zero degrees celcius , and at a pressure of one atmosphere , then you have precisely six hundred and two sextillion gas particles . that is , you have six with 23 zeros after it particles of gas in the container . or in scientific notation , 6.02 times 10 to the 23rd particles . this example is a little misleading , because gases take up a lot of space due to the high kinetic energy of the gas particles , and it leaves you thinking atoms are bigger than they really are . instead , think of water molecules . if you pour 18.01 grams of water into a glass , which is 18.01 milliliters , which is like three and a half teaspoons of water , you 'll have 602 sextillion molecules of water . since lorenzo romano - uh , never mind - avogadro was the first one to come up with this idea , scientists named the number 6.02 times 10 to the 23rd after him . it is simply known as avogadros 's number . now , back to the mole . not that mole . this mole . yep , this number has a second name . the mole . chemists use the term mole to refer to the quantities that are at the magnitude of 602 sextillion . this is known as a molar quantity . atoms and molecules are so small , that chemists have bundled them into groups called moles . moles are hard for students to understand because they have a hard time picturing the size of a mole , or of 602 sextillion . it 's just too big to wrap our brains around . remember our 18.01 milliliters of water ? well , that 's a mole of water . but how much is that ? exactly what does 602 sextillion look like ? maybe this 'll help . exchange the water particles for donuts . if you had a mole of donuts , they would cover the entire earth to a depth of eight kilometers , which is about five miles . you really need a lot of coffee for that . if you had a mole of basketballs , you could create a new planet the size of the earth . if you received a mole of pennies on the day you were born and spent a million dollars a second until the day you died at the age of 100 , you would still have more than 99.99 % of your money in the bank . ok. now we sort of have an idea how large the mole is . so how do we use it ? you might be surprised to know that chemists use it the same way you use pounds to buy grapes , deli meat , or eggs . when you go to the grocery store , you do n't go to the deli counter and ask for 43 slices of salami , you buy your salami by the pound . when you buy your eggs , you buy a dozen eggs . when we hear the word dozen , we probably think of the number 12 . we also know that a pair is two , a baker 's dozen is 13 , a gross is 144 , and a ream of paper is - anybody ? a ream is 500 . well , a mole is really the same thing . for a chemist , a mole conjures up the number 6.02 times 10 to the 23rd , not a fuzzy little animal . the only difference is that the other quantities are more familiar to us . so there you have it - the story of the mole , avogadro , basketballs , and how to buy salami at the grocery store .

well , in 1811 , someone had an idea that if you had equal volumes of gases , at the same temperature and pressure , they would contain an equal number of particles . his name was lorenzo romano amedeo carlo avogadro . i wonder how long it took him to sign autographs .

what did lorenzo romano amedeo carlo avogadro theorize in 1811 ?

translator : andrea mcdonough reviewer : jessica ruby imagine a world in which you see numbers and letters as colored even though they 're printed in black , in which music or voices trigger a swirl of moving , colored shapes , in which words and names fill your mouth with unusual flavors . jail tastes like cold , hard bacon while derek tastes like earwax . welcome to synesthesia , the neurological phenomenon that couples two or more senses in 4 % of the population . a synesthete might not only hear my voice , but also see it , taste it , or feel it as a physical touch . sharing the same root with anesthesia , meaning no sensation , synesthesia means joined sensation . having one type , such as colored hearing , gives you a 50 % chance of having a second , third , or fourth type . one in 90 among us experience graphemes , the written elements of language , like letters , numerals , and punctuation marks , as saturated with color . some even have gender or personality . for gail , 3 is athletic and sporty , 9 is a vain , elitist girl . by contrast , the sound units of language , or phonemes , trigger synestetic tastes . for james , college tastes like sausage , as does message and similar words with the -age ending . synesthesia is a trait , like having blue eyes , rather than a disorder because there 's nothing wrong . in fact , all the extra hooks endow synesthetes with superior memories . for example , a girl runs into someone she met long ago . `` let 's see , she had a green name . d 's are green : debra , darby , dorothy , denise . yes ! her name is denise ! '' once established in childhood , pairings remain fixed for life . synesthetes inherit a biological propensity for hyperconnecting brain neurons , but then must be exposed to cultural artifacts , such as calendars , food names , and alphabets . the amazing thing is that a single nucleotide change in the sequence of one 's dna alters perception . in this way , synesthesia provides a path to understanding subjective differences , how two people can see the same thing differently . take sean , who prefers blue tasting food , such as milk , oranges , and spinach . the gene heightens normally occurring connections between the taste area in his frontal lobe and the color area further back . but suppose in someone else that the gene acted in non-sensory areas . you would then have the ability to link seemingly unrelated things , which is the definition of metaphor , seeing the similar in the dissimilar . not surprisingly , synesthesia is more common in artists who excel at making metaphors , like novelist vladimir nabokov , painter david hockney , and composers billy joel and lady gaga . but why do the rest of us non-synesthetes understand metaphors like `` sharp cheese '' or `` sweet person '' ? it so happens that sight , sound , and movement already map to one another so closely , that even bad ventriloquists convince us that the dummy is talking . movies , likewise , can convince us that the sound is coming from the actors ' mouths rather than surrounding speakers . so , inwardly , we 're all synesthetes , outwardly unaware of the perceptual couplings happening all the time . cross-talk in the brain is the rule , not the exception . and that sounds like a sweet deal to me !

welcome to synesthesia , the neurological phenomenon that couples two or more senses in 4 % of the population . a synesthete might not only hear my voice , but also see it , taste it , or feel it as a physical touch . sharing the same root with anesthesia , meaning no sensation , synesthesia means joined sensation .

why might a synesthete be advantaged ?

cerium is one of only two elements which , if you strike it , will make sparks . one of them is iron and the other one is cerium . and so i bought this when i was on holiday a year ago . i haven ’ t had the chance to use it . it contains , it consists of a rod here which claims to have several metals including cerium . let ’ s see if it sparks . ok so cerium , element number 58 , has some bizarre uses , would you believe it ’ s used in self-cleaning ovens . so it ’ s not very easy to do but , once you get the hang of it , it does go quite well . cerium also has uses such for staining glass . so if you want to stain your glass yellow then you could use cerium in that . what is happening is that tiny pieces of cerium are being knocked off and , in the air , they just burst into flames . so , i think , the property is , not so much that it forms a spark , but that you can knock off the right size lumps to make them burn . these things that are being knocked off are probably just a few nanometres , that ’ s a thousandth-millionth of a metre across so they ’ re very tiny size . so then the surface area is high because it ’ s small so it has a large surface compared to its volume . and so it reacts with oxygen very rapidly and heats up and bursts into flame . the point about cerium is that very small particles of cerium oxide are now becoming quite important in various areas of technology . there ’ s a company , or several companies , that are using nano particles of cerium oxide as an additive for fuels to make a particular diesel fuel to try and make it burn better and give more power when you are driving diesel cars . and here in nottingham we are trying to develop new ways of making these nano particles by reacting cerium with high temperature water and it ’ s been quite successful . it ’ s also used in organic synthesis by chemists for making organic molecules because it can be very reactive under certain circumstances . cerium is also used in permanent magnets for obvious applications in magnetism .

there ’ s a company , or several companies , that are using nano particles of cerium oxide as an additive for fuels to make a particular diesel fuel to try and make it burn better and give more power when you are driving diesel cars . and here in nottingham we are trying to develop new ways of making these nano particles by reacting cerium with high temperature water and it ’ s been quite successful . it ’ s also used in organic synthesis by chemists for making organic molecules because it can be very reactive under certain circumstances .

as the professor explained , his research has involved making nanoparticles by reacting cerium with ...

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

before we get into how to save the frogs , let 's start by taking a look at why they 're disappearing and why it 's important to keep them around . habitat destruction is the number one problem for frog populations around the world . there are seven billion humans on the planet , and we compete with frogs for habitat .

what are some of the primary environmental problems in your part of the world . are there any that are likely to affect frogs ? can you think of ways to educate your fellow citizens about the problem and possibly even come up with solutions ?

for most of history , humans had no idea what purpose the heart served . in fact , the organ so confused leonardo da vinci , that he gave up studying it . although everyone could feel their own heart beating , it was n't always clear what each thump was achieving . now we know that the heart pumps blood . but that fact was n't always obvious , because if a heart was exposed or taken out , the body would perish quickly . it 's also impossible to see through the blood vessels , and even if that were possible , the blood itself is opaque , making it difficult to see the heart valves working . even in the 21st century , only a few people in surgery teams have actually seen a working heart . internet searches for heart function , point to crude models , diagrams or animations that do n't really show how it works . it 's as if there has been a centuries old conspiracy amongst teachers and students to accept that heart function can not be demonstrated . meaning that the next best thing is simply to cut it open and label the parts . that way students might not fully grasp the way it works , but can superficially understand it , learning such concepts as the heart is a four-chambered organ , or potentially misleading statements like , mammals have a dual-circulation : one with blood going to the lungs and back , and another to the body and back . in reality , mammals have a figure-eight circulation . blood goes from one heart pump to the lungs , back to the second heart pump , which sends it to the body , and then back to the first pump . that 's an important difference because it marks two completely different morphologies . this confusion makes many students wary of the heart in biology lessons , thinking it signals an intimidating subject full of complicated names and diagrams . only those who end up studying medicine compeltely understand how it all actually works . that 's when its functions become apparent as medics get to observe the motion of the heart 's valves . so , let 's imagine you 're a medic for a day . what you 'll need to get started is a whole fresh heart , like one from a sheep or pig . immerse this heart in water and you 'll see that it does n't pump when squeezed by hand . that 's because water does n't enter the heart cleanly enough for the pumping mechanism to work . we can solve this problem in an extraordinarly simple way . simply identify the two atria and cut them off , trimming them down to the tops of the ventricles . this makes the heart look less complicated because the atria have several incoming veins attached . so without them there , the only vessels remaining are the two major heart arteries : the aorta and pulmonary artery , which rise like white columns from between the ventricles . it looks -- and really is -- very simple . if you run water into the right ventricle from a tap ( the left also works , but less spectacularly ) , you 'll see that the ventricular valve tries to close against the incoming stream . and then ventricle inflates with water . squeeze the ventricle and a stream of water squirts out of the pulmonary artery . the ventricular valves , called the tricuspid in the right ventricle and the mitral in the left , can be seen through the clear water opening and closing like parachutes as the ventricle is rhythmically squeezed . this flow of water mimics the flow of blood in life . the valves are completely efficient . you 'll notice they do n't leak at all when the ventricles are squeezed . over time , they also close against each other with very little wear and tear , which explains how this mechanism continues to work seamlessly for more than 2 billion beats a heart gives in its lifetime . now , anyone studying the heart can hold one in their hands , make it pump for real and watch the action unfold . so place your hand above your own and feel its rhymic beat . understanding how this dependable inner pump works gives new resonance to the feeling you get when you run a race , drink too much caffeine or catch the eye of the one you love .

simply identify the two atria and cut them off , trimming them down to the tops of the ventricles . this makes the heart look less complicated because the atria have several incoming veins attached . so without them there , the only vessels remaining are the two major heart arteries : the aorta and pulmonary artery , which rise like white columns from between the ventricles .

when the heart is working inside the body , the job of the atria is to ________ .

you can think of your cells as the kitchen in a busy restaurant . sometimes your body orders chicken . other times , it orders steak . your cells have to be able to crank out whatever the body needs and quickly . when an order comes in , the chef looks to the cookbook , your dna , for the recipe . she then transcribes that message onto a piece of paper called rna and brings it back to her countertop , the ribosome . there , she can translate the recipe into a meal , or for your cells , a protein , by following the directions that she 's copied down . but rna does more for the cell than just act as a messenger between a cook and her cookbook . it can move in reverse and create dna , it can direct amino acids to their targets , or it can take part in rna interference , or rnai . but wait ! why would rna want to interfere with itself ? well , sometimes a cell does n't want to turn all of the messenger rna it creates into protein , or it may need to destroy rna injected into the cell by an attacking virus . say , for example , in our cellular kitchen , that someone wanted to cancel their order or decided they wanted chips instead of fries . that 's where rnai comes in . thankfully , your cells have the perfect knives for just this kind of job . when the cell finds or produces long , double-stranded rna molecules , it chops these molecules up with a protein actually named dicer . now , these short snippets of rna are floating around in the cell , and they 're picked up by something called risc , the rna silencing complex . it 's composed of a few different proteins , the most important being slicer . this is another aptly named protein , and we 'll get to why in just a second . risc strips these small chunks of double-stranded rna in half , using the single strand to target matching mrna , looking for pieces that fit together like two halves of a sandwich . when it finds the matching piece of mrna , risc 's slicer protein slices it up . the cell then realizes there are odd , strangely sized pieces of rna floating around and destroys them , preventing the mrna from being turned into protein . so , you have double-stranded rna , you dice it up , it targets mrna , and then that gets sliced up , too . voila ! you 've prevented expression and saved yourself some unhappy diners . so , how did anybody ever figure this out ? well , the process was first discovered in petunias when botanists trying to create deep purple blooms introduced a pigment-producing gene into the flowers . but instead of darker flowers , they found flowers with white patches and no pigment at all . instead of using the rna produced by the new gene to create more pigment , the flowers were actually using it to knock down the pigment-producing pathway , destroying rna from the plant 's original genes with rnai , and leaving them with pigment-free white flowers . scientists saw a similar phenomena in tiny worms called c. elegans , and once they figured out what was happening , they realized they could use rnai to their advantage . want to see what happens when a certain gene is knocked out of a worm or a fly ? introduce an rnai construct for that gene , and bam ! no more protein expression . you can even get creative and target that effect to certain systems , knocking down genes in just the brain , or just the liver , or just the heart . figuring out what happens when you knock down a gene in a certain system can be an important step in figuring out what that gene does . but rnai is n't just for understanding how things happen . it can also be a powerful , therapeutic tool and could be a way for us to manipulate what is happening within own cells . researchers have been experimenting with using it to their advantage in medicine , including targeting rna and tumor cells in the hopes of turning off cancer-causing genes . in theory , our cellular kitchens could serve up an order of cells , hold the cancer .

but wait ! why would rna want to interfere with itself ? well , sometimes a cell does n't want to turn all of the messenger rna it creates into protein , or it may need to destroy rna injected into the cell by an attacking virus .

scientists hope to use rnai to help treat conditions caused by single gene mutations . these mutations would create incorrect rna , which would in turn create malformed proteins . explain how introducing long , double-stranded rna that matches the gene into a cell could help knock down the effects of these malformed proteins .

one of the great things about science is that when scientists make a discovery , it 's not always in a prescribed manner , as in , only in a laboratory under strict settings , with white lab coats and all sorts of neat science gizmos that go , `` beep ! '' in reality , the events and people involved in some of the major scientific discoveries are as weird and varied as they get . my case in point : the weird history of the cell theory . there are three parts to the cell theory . one : all organisms are composed of one or more cells . two : the cell is the basic unit of structure and organization in organisms . and three : all cells come from preexisting cells . to be honest , this all sounds incredibly boring until you dig a little deeper into how the world of microscopic organisms , and this theory came to be . it all started in the early 1600s in the netherlands , where a spectacle maker named zacharias janssen is said to have come up with the first compound microscope , along with the first telescope . both claims are often disputed , as apparently he was n't the only bored guy with a ton of glass lenses to play with at the time . despite this , the microscope soon became a hot item that every naturalist or scientist at the time wanted to play with , making it much like the ipad of its day . one such person was a fellow dutchman by the name of anton van leeuwenhoek , who heard about these microscope doohickeys , and instead of going out and buying one , he decided to make his own . and it was a strange little contraption indeed , as it looked more like a tiny paddle the size of a sunglass lens . if he had stuck two together , it probably would have made a wicked set of sunglasses that you could n't see much out of . anyhoo , once leeuwenhoek had his microscope ready , he went to town , looking at anything and everything he could with them , including the gunk on his teeth . yes , you heard right . he actually discovered bacteria by looking at dental scrapings , which , when you keep in mind that people did n't brush their teeth much -- if at all -- back then , he must have had a lovely bunch of bacteria to look at . when he wrote about his discovery , he did n't call them bacteria , as we know them today . but he called them `` animalcules , '' because they looked like little animals to him . while leeuwenhoek was staring at his teeth gunk , he was also sending letters to a scientific colleague in england , by the name of robert hooke . hooke was a guy who really loved all aspects of science , so he dabbled in a little bit of everything , including physics , chemistry and biology . thus it is hooke who we can thank for the term `` the cell , '' as he was looking at a piece of cork under his microscope , and the little chambers he saw reminded him of cells , or the rooms monks slept in in their monasteries . think college dorm rooms , but without the tvs , computers and really annoying roommates . hooke was something of an underappreciated scientist of his day -- something he brought upon himself , as he made the mistake of locking horns with one of the most famous scientists ever , sir isaac newton . remember when i said hooke dabbled in many different fields ? well , after newton published a groundbreaking book on how planets move due to gravity , hooke made the claim that newton had been inspired by hooke 's work in physics . newton , to say the least , did not like that , which sparked a tense relationship between the two that lasted even after hooke died , as quite a bit of hooke 's research -- as well as his only portrait -- was ... misplaced , due to newton . much of it was rediscovered , thankfully , after newton 's time , but not his portrait , as , sadly , no one knows what robert hooke looked like . fast-forward to the 1800s , where two german scientists discovered something that today we might find rather obvious , but helped tie together what we now know as the cell theory . the first scientist was matthias schleiden , a botanist who liked to study plants under a microscope . from his years of studying different plant species , it finally dawned on him that every single plant he had looked at were all made of cells . at the same time , on the other end of germany was theodor schwann , a scientist who not only studied slides of animal cells under the microscope and got a special type of nerve cell named after him , but also invented rebreathers for firefighters , and had a kickin ' pair of sideburns . after studying animal cells for a while , he , too , came to the conclusion that all animals were made of cells . immediately , he reached out via snail mail , as twitter had yet to be invented , to other scientists working in the same field with schleiden , who got back to him , and the two started working on the beginnings of the cell theory . a bone of contention arose between them . as for the last part of the cell theory -- that cells come from preexisting cells -- schleiden did n't exactly subscribe to that thought , as he swore cells came from free-cell formation , where they just kind of spontaneously crystallized into existence . that 's when another scientist named rudolph virchow , stepped in with research showing that cells did come from other cells , research that was actually -- hmm ... how to put it ? -- `` borrowed without permission '' from a jewish scientist by the name of robert remak , which led to two more feuding scientists . thus , from teeth gunk to torquing off newton , crystallization to schwann cells , the cell theory came to be an important part of biology today . some things we know about science today may seem boring , but how we came to know them is incredibly fascinating . so if something bores you , dig deeper . it 's probably got a really weird story behind it somewhere .

and it was a strange little contraption indeed , as it looked more like a tiny paddle the size of a sunglass lens . if he had stuck two together , it probably would have made a wicked set of sunglasses that you could n't see much out of . anyhoo , once leeuwenhoek had his microscope ready , he went to town , looking at anything and everything he could with them , including the gunk on his teeth .

if you could invent one `` science gizmo , '' what would it be ? do you think your invention would lead to any discoveries that would change our understanding of science ?

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 .

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 .

how many people can the bridge hold at a time ?

ok , today we 're going to talk about the mole . now , i know what you 're thinking : `` i know what a mole is , it 's a small furry creature that digs holes in the ground and destroys gardens . '' and some of you might be thinking that it 's a growth on your aunt 's face with hairs sticking out of it . well , in this case , a mole is a concept that we use in chemistry to count molecules , atoms , just about anything extremely small . have you ever wondered how many atoms there are in the universe ? or in your body ? or even in a grain of sand ? scientists have wanted to answer that question , but how do you count something as small as an atom ? well , in 1811 , someone had an idea that if you had equal volumes of gases , at the same temperature and pressure , they would contain an equal number of particles . his name was lorenzo romano amedeo carlo avogadro . i wonder how long it took him to sign autographs . unfortunately for avogadro , most scientists did n't accept the idea of the atom , and there was no way to prove he was right . there was no clear difference between atoms and molecules . most scientists looked at avogadro 's work as purely hypothetical , and did n't give it much thought . but it turned out he was right ! by late 1860 , avogadro was proven correct , and his work helped lay the foundation for the atomic theory . unfortunately , avogadro died in 1856 . now the thing is that the amount of particles in even small samples is tremendous . for example , if you have a balloon of any gas at zero degrees celcius , and at a pressure of one atmosphere , then you have precisely six hundred and two sextillion gas particles . that is , you have six with 23 zeros after it particles of gas in the container . or in scientific notation , 6.02 times 10 to the 23rd particles . this example is a little misleading , because gases take up a lot of space due to the high kinetic energy of the gas particles , and it leaves you thinking atoms are bigger than they really are . instead , think of water molecules . if you pour 18.01 grams of water into a glass , which is 18.01 milliliters , which is like three and a half teaspoons of water , you 'll have 602 sextillion molecules of water . since lorenzo romano - uh , never mind - avogadro was the first one to come up with this idea , scientists named the number 6.02 times 10 to the 23rd after him . it is simply known as avogadros 's number . now , back to the mole . not that mole . this mole . yep , this number has a second name . the mole . chemists use the term mole to refer to the quantities that are at the magnitude of 602 sextillion . this is known as a molar quantity . atoms and molecules are so small , that chemists have bundled them into groups called moles . moles are hard for students to understand because they have a hard time picturing the size of a mole , or of 602 sextillion . it 's just too big to wrap our brains around . remember our 18.01 milliliters of water ? well , that 's a mole of water . but how much is that ? exactly what does 602 sextillion look like ? maybe this 'll help . exchange the water particles for donuts . if you had a mole of donuts , they would cover the entire earth to a depth of eight kilometers , which is about five miles . you really need a lot of coffee for that . if you had a mole of basketballs , you could create a new planet the size of the earth . if you received a mole of pennies on the day you were born and spent a million dollars a second until the day you died at the age of 100 , you would still have more than 99.99 % of your money in the bank . ok. now we sort of have an idea how large the mole is . so how do we use it ? you might be surprised to know that chemists use it the same way you use pounds to buy grapes , deli meat , or eggs . when you go to the grocery store , you do n't go to the deli counter and ask for 43 slices of salami , you buy your salami by the pound . when you buy your eggs , you buy a dozen eggs . when we hear the word dozen , we probably think of the number 12 . we also know that a pair is two , a baker 's dozen is 13 , a gross is 144 , and a ream of paper is - anybody ? a ream is 500 . well , a mole is really the same thing . for a chemist , a mole conjures up the number 6.02 times 10 to the 23rd , not a fuzzy little animal . the only difference is that the other quantities are more familiar to us . so there you have it - the story of the mole , avogadro , basketballs , and how to buy salami at the grocery store .

now , back to the mole . not that mole . this mole . yep , this number has a second name . the mole . chemists use the term mole to refer to the quantities that are at the magnitude of 602 sextillion .

what 's another name for the mole ?

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

that makes our bodies go into a decline , which eventually results in disease and death . but if that 's consistently true , why the huge variance in aging patterns and lifespan within the animal kingdom ? the answer lies in several factors , including environment and body size . these can place powerful evolutionary pressures on animals to adapt , which in turn makes the aging process different across species .

which of the following factors is thought to contribute to the short lifespan of roundworms ?

in the mid-1970 ’ s , erno rubik invented the rubik ’ s cube . but that doesn ’ t mean knew how to solve it . it took him a few moths to figure it out . by the time the first world rubik ’ s cube championships were held in 1982 , the winner -- he could solve the cube in a little less than 23 seconds . and these days ? [ news montage of collin ’ s record ] this is world record holder collin burns , and today , we find out how he did it . [ titles ] “ it could last another day ; it could last another few years . the previous record lasted for just over 2 years . but with single solve , especially , you just need to get lucky . or at least that ’ s a big part of it. ” collin tends to downplay his skills but it ’ s worth noting there are two types of world records . the way speedcubing competitions work is that volunteers scramble the cubes according to instructions that are generated by a computer , so competitors all get the same scramble . they do 5 solves and their three middle scores are averaged . so collin holds the world record for a single solve . but the world record for an average score is held by a 19-year-old in australia . still , collin ’ s record is a huge deal . at the competition where we met up with him , kids were asking him for his autograph . he ’ s now being sponsored by a cube company and by a cube retailer , which are paying for him to travel internationally . and he wants people to know , you could do this too . “ the biggest misconception about cubing is that it ’ s difficult , which it really isn ’ t. ” pop culture treats the rubik ’ s cube like some sort of iq test , but it ’ s not . at least not anymore . “ generally average is much more impressive because you have to be consistently fast. ” still , collin ’ s record is a huge deal . at the competition where we met up with him , other kids were asking him for autographs . “ are you that famous cube guy ? ” i recently bought a cube online and it came with instructions for beginners . and if you memorize those , you can solve the cube in a couple minutes . it helps to understand the design of the puzzle . at first glance , it looks like a cube made out of cubes — right , three layers of nine . but if you look closer , you ’ ll see there aren ’ t actually any cubes here . so that tells you that the corners will always be corners , the edges will always be edges , and the middle pieces determine the color of that face . speedcubers will buy special cubes . they can lubricate them and adjust the tension . but the real key to their speed is efficiency - they ’ re looking several moves ahead , and they use fewer moves to get the same result . so there are 43 quintillion possible arrangements for the cube . a few years back , some researchers borrowed computing power from google to find out that any scramble can be solved in 20 moves or less . they call it god ’ s number . but humans just aren ’ t that good . the beginners ’ method that i learned uses 100 to 200 moves . speedcubers use more around 50 to 60 moves . and they can do that , in part , because of the knowledge gained by the previous generation of speedcubers . when the cube first spread around the world back in the 80s , people had to learn through trial and error . this was happening in a lot of math departments and campus clubs . people were discovering the cube at the same time , and they were sharing what they learned . the method collin uses was developed by jessica fridrich , an engineering professor who was a college student at the time . it starts with a cross on one of the faces . and that face becomes the bottom layer . then what they do is solve the corners of the bottom layer and the middle layer simultaneously . “ so , now you can see that all of this is solved. ” and for the final layer , they ’ re choosing from dozens of algorithms that they ’ ve memorized . and those are sequences of moves that mess up the cube temporarily to move certain pieces into place . and then put the rest of the cube back where it was . the rubik ’ s cube has made a comeback in recent years along with that same ethic of sharing tips and strategies . so all the resources you need are there , there ’ s just one other thing . practice ! this is collin nearly 5 years ago . world records are not built in a day .

it took him a few moths to figure it out . by the time the first world rubik ’ s cube championships were held in 1982 , the winner -- he could solve the cube in a little less than 23 seconds . and these days ?

at the first rubik 's cube championship in 1982 , how fast did the winner solve the cube ?

here at scishow hq we have a little food area for the employees - sometimes there are donuts . sometimes there are nuts . sometimes dried mango . but the one thing that never sticks around and is gone as soon as we can buy it is the wonderful , beautiful , noble banana . unfortunately for us , they may not be around forever . [ intro music ] first , the good : bananas are healthy , packed with nutrition and energy , they fit in your hand and give nice little cues when they 're perfectly ripe , and are easy to peel and eat ; shocking statistic , the banana is wal-mart 's number one selling item . not the potato chip , not coca-cola , not fifty shades of grey , bananas . they appear to be so perfect for human consumption that kirk cameron attempted to use them to prove the existence of god . of course this banana was not created by god , or really even nature . bananas , at least the ones that you see at the store , were created by people . do n't get me wrong , there are wild banana plants - lots of them - they 're native to south and southeast asia , and there are dozens of species and thousands of varieties . they 're just not the ones we eat . some those species , as you might suspect , have seeds , 'cause that 's what fruits are , they 're fleshy bodies containing seeds . so you might wonder , why have you never eaten a banana seed ? well , you have ... kinda . in cultivated bananas the seeds have pretty much stopped existing . if you look closely you can see tiny black specks . those are all that 's left , and they 're not fertile seeds . if you plant them , nothing grows . today 's bananas are sterile mutants . i 'm not trying to be mean , that 's just the truth . unless you were alive in the 1960 's ( hats off to all those older scishow viewers out there ) every banana you have ever eaten was pretty much genetically identical . this is a cavendish , the virtually seedless variety that we all eat today , but it was n't always our banana of choice . until the 1960s , everyone was eating the same banana , it was just a different banana - the gros michel , a bigger , sweeter fruit with thicker skin . you might notice that banana flavored things do n't really taste like bananas . well they do - they taste like the gros michel . the genetic monotony of the gros michel crop was its undoing . a fungicide resistant pathogen called the panama disease began infecting gros michel crop . by the time growers understood how vulnerable their crops were , the gros michel variety was all but extinct . the entire banana industry had to be retooled for the cavendish . since they 're seedless , the only way to reproduce them is to transplant part of the plant stem , and for the last 50 years we 've been good with the cavendish , 'cause it 's more resistant to the panama disease . however somewhat terrifyingly a strain of panama disease that affects the cavendish strain that we all eat has been identified . a global monoculture of genetically identical individuals is a beautiful sight to a pathogen . the fungus only has to figure out how to infect and destroy a single individual , and suddenly there is no diversity to stop it , or even slow it down . that 's led to a lot of scientists worrying about or even predicting the outright demise of the cavendish . this wonderful most popular of fruits might completely cease existence . the good news is we now have a much better understanding of genetics , epidemics , fungi , and pathology . scientists and growers have already taken steps to protect the cavendish . some growers are creating genetically different bananas that might replace the cavendish crop if it fails , while scientists are attempting to genetically engineer cavendish plants with immunity to panama disease . plus we learned a lot from the gros michel debacle . infected fields are quickly being destroyed and new crops are grown from pathogen-free lab-grown plant stock . so thanks to the people who work tirelessly to grow and harvest bananas and bring them to us so that we can offer them inexpensively to our employees , and thanks to the growers and scientists working tirelessly to make sure that they do n't go the way of the gros michel . thanks for watching this episode of scishow , if you have any questions , comments or suggestions for us , you can find us on facebook , twitter or in the comments below , and if you want to continue getting smarter this year at scishow , you can go to youtube.com/scishow and subscribe . [ banana eating noises ] [ music ]

bananas , at least the ones that you see at the store , were created by people . do n't get me wrong , there are wild banana plants - lots of them - they 're native to south and southeast asia , and there are dozens of species and thousands of varieties . they 're just not the ones we eat .

1. wild banana plants are native to_____ ?

one of the most remarkable aspects of the human brain is its ability to recognize patterns and describe them . among the hardest patterns we 've tried to understand is the concept of turbulent flow in fluid dynamics . the german physicist werner heisenberg said , `` when i meet god , i 'm going to ask him two questions : why relativity and why turbulence ? i really believe he will have an answer for the first . '' as difficult as turbulence is to understand mathematically , we can use art to depict the way it looks . in june 1889 , vincent van gogh painted the view just before sunrise from the window of his room at the saint-paul-de-mausole asylum in saint-rémy-de-provence , where he 'd admitted himself after mutilating his own ear in a psychotic episode . in `` the starry night , '' his circular brushstrokes create a night sky filled with swirling clouds and eddies of stars . van gogh and other impressionists represented light in a different way than their predecessors , seeming to capture its motion , for instance , across sun-dappled waters , or here in star light that twinkles and melts through milky waves of blue night sky . the effect is caused by luminance , the intensity of the light in the colors on the canvas . the more primitive part of our visual cortex , which sees light contrast and motion , but not color , will blend two differently colored areas together if they have the same luminance . but our brains ' primate subdivision will see the contrasting colors without blending . with these two interpretations happening at once , the light in many impressionist works seems to pulse , flicker and radiate oddly . that 's how this and other impressionist works use quickly executed prominent brushstrokes to capture something strikingly real about how light moves . 60 years later , russian mathematician andrey kolmogorov furthered our mathematical understanding of turbulence when he proposed that energy in a turbulent fluid at length r varies in proportion to the 5/3rds power of r. experimental measurements show kolmogorov was remarkably close to the way turbulent flow works , although a complete description of turbulence remains one of the unsolved problems in physics . a turbulent flow is self-similar if there is an energy cascade . in other words , big eddies transfer their energy to smaller eddies , which do likewise at other scales . examples of this include jupiter 's great red spot , cloud formations and interstellar dust particles . in 2004 , using the hubble space telescope , scientists saw the eddies of a distant cloud of dust and gas around a star , and it reminded them of van gogh 's `` starry night . '' this motivated scientists from mexico , spain and england to study the luminance in van gogh 's paintings in detail . they discovered that there is a distinct pattern of turbulent fluid structures close to kolmogorov 's equation hidden in many of van gogh 's paintings . the researchers digitized the paintings , and measured how brightness varies between any two pixels . from the curves measured for pixel separations , they concluded that paintings from van gogh 's period of psychotic agitation behave remarkably similar to fluid turbulence . his self-portrait with a pipe , from a calmer period in van gogh 's life , showed no sign of this correspondence . and neither did other artists ' work that seemed equally turbulent at first glance , like munch 's `` the scream . '' while it 's too easy to say van gogh 's turbulent genius enabled him to depict turbulence , it 's also far too difficult to accurately express the rousing beauty of the fact that in a period of intense suffering , van gogh was somehow able to perceive and represent one of the most supremely difficult concepts nature has ever brought before mankind , and to unite his unique mind 's eye with the deepest mysteries of movement , fluid and light .

that 's how this and other impressionist works use quickly executed prominent brushstrokes to capture something strikingly real about how light moves . 60 years later , russian mathematician andrey kolmogorov furthered our mathematical understanding of turbulence when he proposed that energy in a turbulent fluid at length r varies in proportion to the 5/3rds power of r. experimental measurements show kolmogorov was remarkably close to the way turbulent flow works , although a complete description of turbulence remains one of the unsolved problems in physics . a turbulent flow is self-similar if there is an energy cascade .

true or false : a complete description of turbulence is to this day an unsolved problem in physics .

probability is an area of mathematics that is everywhere . we hear about it in weather forecasts , like there 's an 80 % chance of snow tomorrow . it 's used in making predictions in sports , such as determining the odds for who will win the super bowl . probability is also used in helping to set auto insurance rates and it 's what keeps casinos and lotteries in business . how can probability affect you ? let 's look at a simple probability problem . does it pay to randomly guess on all 10 questions on a true/ false quiz ? in other words , if you were to toss a fair coin 10 times , and use it to choose the answers , what is the probability you would get a perfect score ? it seems simple enough . there are only two possible outcomes for each question . but with a 10-question true/ false quiz , there are lots of possible ways to write down different combinations of ts and fs . to understand how many different combinations , let 's think about a much smaller true/ false quiz with only two questions . you could answer `` true true , '' or `` false false , '' or one of each . first `` false '' then `` true , '' or first `` true '' then `` false . '' so that 's four different ways to write the answers for a two-question quiz . what about a 10-question quiz ? well , this time , there are too many to count and list by hand . in order to answer this question , we need to know the fundamental counting principle . the fundamental counting principle states that if there are a possible outcomes for one event , and b possible outcomes for another event , then there are a times b ways to pair the outcomes . clearly this works for a two-question true/ false quiz . there are two different answers you could write for the first question , and two different answers you could write for the second question . that makes 2 times 2 , or , 4 different ways to write the answers for a two-question quiz . now let 's consider the 10-question quiz . to do this , we just need to extend the fundamental counting principle a bit . we need to realize that there are two possible answers for each of the 10 questions . so the number of possible outcomes is 2 , times 2 , times 2 , times 2 , times 2 , times 2 , times 2 , times 2 , times 2 , times 2 . or , a shorter way to say that is 2 to the 10th power , which is equal to 1,024 . that means of all the ways you could write down your ts and fs , only one of the 1,024 ways would match the teacher 's answer key perfectly . so the probability of you getting a perfect score by guessing is only 1 out of 1,024 , or about a 10th of a percent . clearly , guessing is n't a good idea . in fact , what would be the most common score if you and all your friends were to always randomly guess at every question on a 10-question true/ false quiz ? well , not everyone would get exactly 5 out of 10 . but the average score , in the long run , would be 5 . in a situation like this , there are two possible outcomes : a question is right or wrong , and the probability of being right by guessing is always the same : 1/2 . to find the average number you would get right by guessing , you multiply the number of questions by the probability of getting the question right . here , that is 10 times 1/2 , or 5 . hopefully you study for quizzes , since it clearly does n't pay to guess . but at one point , you probably took a standardized test like the sat , and most people have to guess on a few questions . if there are 20 questions and five possible answers for each question , what is the probability you would get all 20 right by randomly guessing ? and what should you expect your score to be ? let 's use the ideas from before . first , since the probability of getting a question right by guessing is 1/5 , we would expect to get 1/5 of the 20 questions right . yikes - that 's only four questions ! are you thinking that the probability of getting all 20 questions correct is pretty small ? let 's find out just how small . do you recall the fundamental counting principle that was stated before ? with five possible outcomes for each question , we would multiply 5 times 5 times 5 times 5 times ... well , we would just use 5 as a factor 20 times , and 5 to the 20th power is 95 trillion , 365 billion , 431 million , 648 thousand , 625 . wow - that 's huge ! so the probability of getting all questions correct by randomly guessing is about 1 in 95 trillion .

in order to answer this question , we need to know the fundamental counting principle . the fundamental counting principle states that if there are a possible outcomes for one event , and b possible outcomes for another event , then there are a times b ways to pair the outcomes . clearly this works for a two-question true/ false quiz .

if there are a possible outcomes for one event and b possible outcomes for another event , then there are a times b ways to pair the outcomes . what is this known as ?

translator : andrea mcdonough reviewer : jessica ruby is it possible to create something out of nothing ? or , more precisely , can energy be made into matter ? yes , but only when it comes together with its twin , antimatter . and there 's something pretty mysterious about antimatter : there 's way less of it out there than there should be . let 's start with the most famous physics formula ever : e equals m c squared . it basically says that mass is concentrated energy , and mass and energy are exchangeable , like two currencies with a huge exchange rate . 90 trillion joules of energy are equivalent to 1 gram of mass . but how do i actually transform energy into matter ? the magic word is < i > energy density < /i > . if you concentrate a huge amount of energy in a tiny space , new particles will come into existence . if we look closer , we see that these particles always come in pairs , like twins . that 's because particles always have a counterpart , an antiparticle , and these are always produced in exactly equal amounts : 50/50 . this might sound like science fiction , but it 's the daily life of particle accelerators . in the collisions between two protons at cern 's large hadron collider , billions of particles and antiparticles are produced every second . consider , for example , the electron . it has a very small mass and negative electric charge . it 's antiparticle , the positron , has exactly the same mass , but a positive electric charge . but , apart from the opposite charges , both particles are identical and perfectly stable . and the same is true for their heavy cousins , the proton and the antiproton . therefore , scientists are convinced that a world made of antimatter would look , feel , and smell just like our world . in this antiworld , we may find antiwater , antigold , and , for example , an antimarble . now imagine that a marble and an antimarble are brought together . these two apparently solid objects would completely disappear into a big flash of energy , equivalent to an atomic bomb . because combining matter and antimatter would create so much energy , science fiction is full of ideas about harnessing the energy stored in antimatter , for example , to fuel spaceships like star trek . after all , the energy content of antimatter is a billion times higher than conventional fuel . the energy of one gram of antimatter would be enough for driving a car 1,000 times around the earth , or to bring the space shuttle into orbit . so why do n't we use antimatter for energy production ? well , antimatter is n't just sitting around , ready for us to harvest . we have to make antimatter before we can combust antimatter , and it takes a billion times more energy to make antimatter than you get back . but , what if there was some antimatter in outer space and we could dig it out one day from an antiplanet somewhere . a few decades ago , many scientists believed that this could actually be possible . today , observations have shown that there is no significant amount of antimatter anywhere in the visible universe , which is weird because , like we said before , there should be just as much antimatter as there is matter in the universe . since antiparticles and particles should exist in equal numbers , this missing antimatter ? now that is a real mystery . to understand what might be happening , we must go back to the big bang . in the instant the universe was created , a huge amount of energy was transformed into mass , and our initial universe contained equal amounts of matter and antimatter . but just a second later , most matter and all of the antimatter had destroyed one another , producing an enormous amount of radiation that can still be observed today . just about 100 millionths of the original amount of matter stuck around and no antimatter whatsoever . `` now , wait ! '' you might say , `` why did all the antimatter disappear and only matter was left ? '' it seems that we were somehow lucky that a tiny asymmetry exists between matter and antimatter . otherwise , there would be no particles at all anywhere in the universe and also no human beings . but what causes this asymmetry ? experiments at cern are trying to find out the reason why something exists and why we do n't live in a universe filled with radiation only ? but , so far , we just do n't know the answer .

consider , for example , the electron . it has a very small mass and negative electric charge . it 's antiparticle , the positron , has exactly the same mass , but a positive electric charge .

the main difference between particles and antiparticles is their opposite electric charge . discuss the effect on the spectrum of anti-atoms , and hence the optical appearance of an anti-star .

translator : andrea mcdonough reviewer : bedirhan cinar people often think the word `` doubt '' spelling is a little crazy because of the letter `` b '' . since it does n't spell a sound , most folks ca n't figure out what it 's doing there . but in spite of what most of us learn in school , sound is < i > never < /i > the most important aspect of spelling an english word . a word 's meaning and history need to come first . to doubt means to question , to waver , to hesitate . as a noun , it means uncertainty or confusion . the present-day english word `` doubt '' started as a latin word , `` dubitare '' . it first moved from latin into french where it lost both its `` buh '' sound and its letter `` b '' . and then it came into english in the 13th century . about 100 years later , scribes who wrote english but also knew latin , started to reinsert the `` b '' into the word 's spelling , even though no one pronounced it that way . but why would they do this ? why would anyone in their right mind reinsert a silent letter into a spelling ? well , because they knew latin , the scribes understood that the root of `` doubt '' had a `` b '' in it . over time , even as fewer literate people knew latin , the `` b '' was kept because it marked important , meaningful connections to other related words , like `` dubious '' and `` indubitalbly , '' which were subsequently borrowed into english from the same latin root , `` dubitare '' . understanding these historical connections not only helped us to spell `` doubt , '' but also to understand the meaning of these more sophisticated words . but the story does n't end there . if we look even deeper , we can see beyond the shadow of a doubt , just how revealing that `` b '' can be . there are only two base words in all of english that have the letters `` d-o-u-b '' : one is doubt , and the other is double . we can build lots of other words on each of these bases , like doubtful and doubtless , or doublet , and redouble , and doubloon . it turns out that if we look into their history , we can see that they both derive from the same latin forms . the meaning of double , two , is reflected in a deep understanding of doubt . see , when we doubt , when we hesitate , we second guess ourselves . when we have doubts about something , when we have questions or confusion , we are of two minds . historically , before english began to borrow words from french , it already had a word for doubt . that old english word was `` tweogan , '' a word whose relationship to `` two '' is clear in its spelling as well . so the next time you are in doubt about why english spelling works the way it does , take a second look . what you find just might make you do a double-take .

over time , even as fewer literate people knew latin , the `` b '' was kept because it marked important , meaningful connections to other related words , like `` dubious '' and `` indubitalbly , '' which were subsequently borrowed into english from the same latin root , `` dubitare '' . understanding these historical connections not only helped us to spell `` doubt , '' but also to understand the meaning of these more sophisticated words . but the story does n't end there .

explain the method you used to learn to spell words . would you consider yourself a good speller ? do you think the way you learned to spell had something to do with your ability to spell words ?

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

every chicken was once an egg , every oak tree an acorn , every frog a tadpole . the patch of mold on that old piece of bread in the back of your fridge , not so long ago that was one , solitary cell .

which of the following statements is true :

a handful of species on earth share a seemingly mysterious trait : a menstrual cycle . we 're one of the select few . monkeys , apes , bats , humans , and possibly elephant shrews are the only mammals on earth that menstruate . we also do it more than any other animal , even though its a waste of nutrients and can be a physical inconvenience . so where 's the sense in this uncommon biological process ? the answer begins with pregnancy . during this process , the body 's resources are cleverly used to shape a suitable environment for a fetus , creating an internal haven for a mother to nurture her growing child . in this respect , pregnancy is awe-inspiring , but that 's only half the story . the other half reveals that pregnancy places a mother and her child at odds . as for all living creatures , the human body evolved to promote the spread of its genes . for the mother , that means she should try to provide equally for all her offspring . but a mother and her fetus do n't share exactly the same genes . the fetus inherits genes from its father , as well , and those genes can promote their own survival by extracting more than their fair share of resources from the mother . this evolutionary conflict of interests places a woman and her unborn child in a biological tug-of-war that plays out inside the womb . one factor contributing to this internal tussle is the placenta , the fetal organ that connects to the mother 's blood supply and nourishes the fetus while it grows . in most mammals , the placenta is confined behind a barrier of maternal cells . this barrier lets the mother control the supply of nutrients to the fetus . but in humans and a few other species , the placenta actually penetrates right into the mother 's circulatory system to directly access her blood stream . through its placenta , the fetus pumps the mother 's arteries with hormones that keep them open to provide a permanent flow of nutrient-rich blood . a fetus with such unrestricted access can manufacture hormones to increase the mother 's blood sugar , dilate her arteries , and inflate her blood pressure . most mammal mothers can expel or reabsorb embryos if required , but in humans , once the fetus is connected to the blood supply , severing that connection can result in hemorrhage . if the fetus develops poorly or dies , the mother 's health is endangered . as it grows , a fetus 's ongoing need for resources can cause intense fatigue , high blood pressure , and conditions like diabetes and preeclampsia . because of these risks , pregnancy is always a huge , and sometimes dangerous , investment . so it makes sense that the body should screen embryos carefully to find out which ones are worth the challenge . this is where menstruation fits in . pregnancy starts with a process called implantation , where the embryo embeds itself in the endometrium that lines the uterus . the endometrium evolved to make implantation difficult so that only the healthy embryos could survive . but in doing so , it also selected for the most vigorously invasive embryos , creating an evolutionary feedback loop . the embryo engages in a complex , exquisitely timed hormonal dialogue that transforms the endometrium to allow implantation . what happens when an embryo fails the test ? it might still manage to attach , or even get partly through the endometrium . as it slowly dies , it could leave its mother vulnerable to infection , and all the time , it may be emitting hormonal signals that disrupt her tissues . the body avoids this problem by simply removing every possible risk . each time ovulation does n't result in a healthy pregnancy , the womb gets rid of its endometrial lining , along with any unfertilized eggs , sick , dying , or dead embryos . that protective process is known as menstruation , leading to the period . this biological trait , bizarre as it may be , sets us on course for the continuation of the human race .

but in humans and a few other species , the placenta actually penetrates right into the mother 's circulatory system to directly access her blood stream . through its placenta , the fetus pumps the mother 's arteries with hormones that keep them open to provide a permanent flow of nutrient-rich blood . a fetus with such unrestricted access can manufacture hormones to increase the mother 's blood sugar , dilate her arteries , and inflate her blood pressure . most mammal mothers can expel or reabsorb embryos if required , but in humans , once the fetus is connected to the blood supply , severing that connection can result in hemorrhage .

the hormones the fetus pumps into the mother 's blood can :

[ go project films ] i think that facing death changes people ... which is what happened with me . before this experience , i was a completely different person with a completely different dream . my last dream which was to treat cancer and right now my dream of changing the world in another way . [ welcome to canada ] [ over 4.8 million syrians are refugees living in neighboring countries . ] [ 6.5 million more are displaced within syria . ] [ in november 2015 , the government of canada promised ] [ to resettle 25,000 syrian refugees within 6 months . ] [ the 2400 court motel in vancouver is one of 9 temporary housing sites ] [ for the newly arrived refugees . ] [ may 2016 , vancouver , canada ] staying at the motel is this hard transitional stage . you are homesick and you 're also thinking about remaining family members overseas living under horrendous circumstances . i try my best to introduce the new reality . i try my best to ease the impact of their resettlement process as refugees , as someone who did n't choose to come here , as someone who had to come here . hi , my name is mohammed from immigrant services society of british columbia , iss of bc contacting you regarding your place on craigslist . [ tell me we have three children . ] you 're looking at the two bedroom or the three bedroom ? - two bedroom , two bedroom . - two bedroom ? okay . - oh , two bedroom ? - the two bedroom , yeah . how many people you have ? a family of five people with three small kids . - yeah , that too many . - that is too many ? [ she 's telling you that 's too many people . ] [ okay , tell her thank you ... they are young . ] thank you . i 'm with my clients right now . so i 'm helping him . he wants to share with you , the kids are so small and the ages are ... the place is too small for five people . oh , oh , i see . [ - she 's saying the house is too small to fit five people . ] [ - what about the 3 bedroom ... what 's the rental cost ? ] okay , what about the three bedroom that you have ? $ 3,500 a month . that will be expensive for a new immigrant family . is it possible for you to see the kids and ... i can not accommodate five people in that place . yeah , thank you so much . i 'm sorry . [ the two bedroom house , it 's too small to accommodate five people . ] [ the other house with 3 bedrooms , it 's too expensive , it 's $ 3,500 a month . ] moving to canada is not easy at all . my job is all about providing first language services [ oh my god . ] to the newly arrived refugees . [ we 're going to try and find you another house . ] i 'm the person who welcomes them and i will help them with everything that they will need in their resettlement process . it 's really hard to explain the reality on the ground in syria . it keeps on changing on a daily basis . syrians are just caught up in the middle of this non-sense chaos . many of them have spent many years in refugee camps in neighboring countries trying to just wait for this crazy war to finish . when they realized it 's going to be much longer , this syrian refugee crisis started . [ this is a transitional stage and it 's very difficult . ] [ i was just like you when i came here . ] [ the same reception center , same counselor ] [ and even signed the same papers . ] [ attended the same orientation , and was looking for a house . ] [ so you have been through this before . ] [ the exact same thing . ] [ -i would not encourage you to work right away ] [ -of course not , i need to learn the language first . ] [ excellent thinking . focus on english . ] [ your life starts tomorrow . ] [ god willing , we will start a new life tomorrow . ] before 2011 , before everything has started , we were living a happy life . i was born in al-hasakah , syria , a very peaceful city , a city of so many languages , ethnic components , and religious components with the idea and the notion of accepting others . i was in my fourth year of my medical studies in syria , i was trying my best to become a doctor , and my dream was to treat cancer . my generation was dreaming of having freedom , having some basic things that the average canadian would not think about . [ filmed by mohammed in homs , syria ] we never thought we could have faced such a brutal , barbaric response from your own government , just for gathering in the street and shouting the word `` freedom . '' we were just standing there and surprisingly they started shooting and people started falling ... at that point everyone started running , everyone who had survived it , started running , and some people were just on the ground covered with blood . i 'm calling you regarding clients of mine who are moving to your place tomorrow morning . [ -what 's happening in aleppo is breaking my heart . ] [ -a lot of problems are happening there . ] yeah , because we 're in the middle of , you know , arranging all the transportation needed for all of these families . all righty . thank you so much . [ this boy is dying . ] [ i want my brother . where is my mother and father ? ] [ where is my mom ? ] [ say , `` there is no god but god . '' ] for syrians , it is so normal to open your facebook and see the death of your friend on social media . it is something that is really hard and that is really difficult to accept , to observe , and to even think about . [ there is no power except what lies in god 's hands . ] i 'm about to turn 27 next month . in this small lifetime , i have been arrested three times . i have been in five different detention places . the first thing that they did in the detention center was hanging me from the ceiling . they had handcuffs on my hands like this and they had a chain coming down from the ceiling , and they have hooked that chain to my hands like this , and they kept me like this for three days . after spending three days like this , the actual torture started . they spent so many days practicing all kinds of torture on me , and on other syrian people , in that detention center . i can never forget this old man who was sleeping next to me ... he used to say , `` you see all of this ... one day , all of this will be just a story that you will be telling to other people . '' after 120 days of torture , i was finally released ... i was finally able to see sunlight again . the only thing that i wanted to do is talk to my family . i just wanted to see them but also say goodbye to them ... get the hell out of there and never look back . i took a taxi from damascus to beirut where there was no shelling , no explosions , just a normal life ... three hours away from where i was , from where i was tortured , it was unbelievable for me . iss of bc kingsway . good morning . syrians in lebanon are not allowed to work , are not allowed to go to school . syrians in lebanon are simply not welcomed . the best job that i could find was washing cars from 9 am to 9 pm for $ 20 a day . i was just struggling to have a life . my whole life changed with a single phone call . i pick up the phone , it was this same phone . so i pick up and i was told that , `` this is the canadian embassy calling for mohammed alsaleh , '' i was like , `` yes , speaking . '' so they told me , `` we have an application on your behalf to come to canada , are you interested ? '' and i was like , `` yes , i 'm . '' [ in november 2014 mohammed was granted asylum in canada and arrived in vancouver . ] [ to date thousands of syrian families have arrived in canada . ] each syrian family is thinking about someone who 's left behind ... if it was a brother , if it was a mother , or if it was a father . this is something that i can see among the people that i 'm helping , and this is something that i can relate to on a personal level because of the situation of my family . my family had to illegally cross the border between syria and turkey . they had to crawl in the mud in order to make it to safety . come on , pick up . [ hello . ] [ hello ... hello . ] [ hello , mama . ] [ how are you , mother ? ] [ i swear we miss you . we miss you so much . ] [ me too . i miss you so so much . ] [ shahad , what is this beautiful hair ? ] [ this is the new style , with these bangs . ] [ wow , look , look your hair is so long now . ] when i last saw my family , my youngest sister was seven , right now she is ten , and i do n't know how old would she be when i meet her . it 's really hard to know that you might not be able to meet them . [ look at how my hair looks . ] [ güzel ! güzel like the turkish say . ] [ are you learning turkish ? ] [ a little bit , not much yet . ] [ we try a little bit when we go out , things like that . ] [ -great . ] [ even though we are in turkey , the situation is tough here . ] [ we are always stressed and tired . life is hard here . ] [ what 's important is that you guys are safe and sound ] [ and you are not in danger , ] [ and we do n't have to worry about your life being in danger . ] [ and that 's the most important thing right now , ] [ to let these few months pass while everything is processed and you get here . ] [ god willing , because the situation here is n't comfortable and one does n't feel at home . ] [ -yes , yes . -you always feel like something is missing . ] [ god willing , we will all be together soon here in canada . ] [ that 's what we hope for . hopefully everything will work out . ] [ i miss you so so so much . ] in order for people to get settled and to feel like home , i think the only missing part is time . they just need time . [ speaking foreign language ] [ welcome , welcome to our new house . ] [ a hundred congratulations on the new house , it 's a lovely home . ] [ god bless you , it 's lovely having you all here . ] my first client was a family of 13 people who have just came to canada . [ the best thing you did was to get this property . ] [ here you can play , whatever you want is here . ] i was telling them , `` you 're safe now . one year ago , i was standing exactly where you are and right now i 'm helping you , so do n't worry everything 's going to be fine . '' i want everyone to realize how tremendous , how beautiful it is to offer people a place to call home ... which is something priceless that i really , really appreciate having right now . it 's heart breaking to see the country that you grew up in get destroyed . i 'm one of the ones lucky enough to come back from the dead , to tell their stories , to share their suffering with the rest of the world , which is something that i think is part of my obligation toward syrians and toward canadians . [ mohammed continues to support his family as he works to bring them safely to canada . ] [ according to the un , approximately 250,000 people ] [ have been killed in syria and 13.5 million people are in urgent need of humanitarian assistance . ] [ to date , 29,817 syrian refugees have been welcomed to canada . ] [ 2016 go project films ]

[ 6.5 million more are displaced within syria . ] [ in november 2015 , the government of canada promised ] [ to resettle 25,000 syrian refugees within 6 months . ] [ the 2400 court motel in vancouver is one of 9 temporary housing sites ] [ for the newly arrived refugees . ]

in november 2015 , the government of canada promised to resettle 25,000 syrian refugees within how many months ?

language is an essential part of our lives that we often take for granted . with it , we can communicate our thoughts and feelings , lose ourselves in novels , send text messages , and greet friends . it 's hard to imagine being unable to turn thoughts into words . but if the delicate web of language networks in your brain became disrupted by stroke , illness , or trauma , you could find yourself truly at a loss for words . this disorder , called aphasia , can impair all aspects of communication . people who have aphasia remain as intelligent as ever . they know what they want to say , but ca n't always get their words to come out correctly . they may unintentionally use substitutions called paraphasias , switching related words , like saying `` dog '' for `` cat , '' or words that sound similar , such as `` house '' for `` horse . '' sometimes , their words may even be unrecognizable . there are several types of aphasia grouped into two categories : fluent , or receptive , aphasia and non-fluent , or expressive , aphasia . people with fluent aphasia may have normal vocal inflection but use words that lack meaning . they have difficulty comprehending the speech of others and are frequently unable to recognize their own speech errors . people with non-fluent aphasia , on the other hand , may have good comprehension but will experience long hesitations between words and make grammatical errors . we all have that tip-of-the-tongue feeling from time to time when we ca n't think of a word , but having aphasia can make it hard to name simple , everyday objects . even reading and writing can be difficult and frustrating . so how does this language loss happen ? the human brain has two hemispheres . in most people , the left hemisphere governs language . we know this because in 1861 , the physician paul broca studied a patient who lost the ability to use all but a single word , `` tan . '' during a postmortem study of that patient 's brain , broca discovered a large lesion in the left hemisphere now known as broca 's area . scientists today believe that broca 's area is responsible in part for naming objects and coordinating the muscles involved in speech . behind broca 's area is wernicke 's area near the auditory cortex . that 's where the brain attaches meaning to speech sounds . damage to wernicke 's area impairs the brain 's ability to comprehend language . aphasia is caused by injury to one or both of these specialized language areas . fortunately , there are other areas of the brain which support these language centers and can assist with communication . even brain areas that control movement are connected to language . fmri studies found that when we hear action words , like `` run '' or `` dance , '' parts of the brain responsible for movement light up as if the body was actually running or dancing . our other hemisphere contributes to language , too , enhancing the rhythm and intonation of our speech . these non-language areas sometimes assist people with aphasia when communication is difficult . so how common is aphasia ? approximately 1 million people in the u.s. alone have it , with an estimated 80,000 new cases per year . about one-third of stroke survivors suffer from aphasia making it more prevalent than parkinson 's disease or multiple sclerosis , yet less widely known . there is one rare form of aphasia called primary progressive aphasia , or ppa , which is not caused by stroke or brain injury , but is actually a form of dementia in which language loss is the first symptom . the goal in treating ppa is to maintain language function for as long as possible before other symptoms of dementia eventually occur . however , when aphasia is acquired from a stroke or brain trauma , language improvement may be achieved through speech therapy . our brain 's ability to repair itself , known as brain plasticity , permits areas surrounding a brain lesion to take over some functions during the recovery process . scientists have been conducting experiments using new forms of technology , which they believe may encourage brain plasticity in people with aphasia . meanwhile , many people with aphasia remain isolated , afraid that others wo n't understand them or give them extra time to speak . by offering them the time and flexibility to communicate in whatever way they can , you can help open the door to language again , moving beyond the limitations of aphasia .

language is an essential part of our lives that we often take for granted . with it , we can communicate our thoughts and feelings , lose ourselves in novels , send text messages , and greet friends .

a paraphasia is :

most people recognize his name and know that he is famous for having said something , but considering the long-lasting impact his teachings have had on the world , very few people know who confucius really was , what he really said , and why . amid the chaos of 6th century bce china , where warring states fought endlessly among themselves for supremacy , and rulers were frequently assassinated , sometimes by their own relatives , confucius exemplified benevolence and integrity , and through his teaching , became one of china 's greatest philosophers . born to a nobleman but raised in poverty from a very young age following the untimely death of his father , confucius developed what would become a lifelong sympathy for the suffering of the common people . barely supporting his mother and disabled brother as a herder and account keeper at a granary , and with other odd jobs , it was only with the help of a wealthy friend that confucius was able to study at the royal archives , where his world view would be formed . though the ancient texts there were regarded by some as irrelevant relics of the past , confucius was inspired by them . through study and reflection , confucius came to believe that human character is formed in the family and by education in ritual , literature , and history . a person cultivated in this way works to help others , guiding them by moral inspiration rather than brute force . to put his philosophy into practice , confucius became an advisor to the ruler of his home state of lu . but after another state sent lu 's ruler a troop of dancing girls as a present and the ruler ignored his duties while enjoying the girls in private , confucius resigned in disgust . he then spent the next few years traveling from state to state , trying to find a worthy ruler to serve , while holding fast to his principles . it was n't easy . in accordance with his philosophy , and contrary to the practice of the time , confucius dissuaded rulers from relying on harsh punishments and military power to govern their lands because he believed that a good ruler inspires others to spontaneously follow him by virtue of his ethical charisma . confucius also believed that because the love and respect we learn in the family are fundamental to all other virtues , personal duties to family sometimes supersede obligations to the state . so when one duke bragged that his subjects were so upright that a son testified against his own father when his father stole a sheep , confucius informed the duke that genuinely upright fathers and sons protected one another . during his travels , confucius almost starved , he was briefly imprisoned , and his life was threatened at several points . but he was not bitter . confucius had faith that heaven had a plan for the world , and he taught that a virtuous person could always find joy in learning and music . failing to find the ruler he sought , confucius returned to lu and became a teacher and philosopher so influential , that he helped shaped chinese culture and we recognize his name worldwide , even today . for the disciples of confucius , he was the living embodiment of a sage who leads others through his virtue , and they recorded his sayings , which eventually were edited into a book we know in english as `` the analects . '' today , millions of people worldwide adhere to the principles of confucianism , and though the precise meaning of his words has been debated for millennia , when asked to summarize his teachings in a single phrase , confucius himself said , `` do not inflict upon others that which you yourself would not want . '' 2,500 years later , it 's still sage advice .

a person cultivated in this way works to help others , guiding them by moral inspiration rather than brute force . to put his philosophy into practice , confucius became an advisor to the ruler of his home state of lu . but after another state sent lu 's ruler a troop of dancing girls as a present and the ruler ignored his duties while enjoying the girls in private , confucius resigned in disgust . he then spent the next few years traveling from state to state , trying to find a worthy ruler to serve , while holding fast to his principles .

what did confucius think was the most important role of the ruler ?

translator : andrea mcdonough reviewer : bedirhan cinar mysteries of vernacular miniature , something distinctively smaller than other members of its type or class . miniature traces its roots to the latin , < i > minium < /i > , which meant , `` red lead '' . minium referred , in particular , to a compound of lead used as a pigment in medieval times . in those days , because there were no printing presses , groups of scribes were tasked with painstakingly copying all books by hand . whenever they needed to denote a chapter break or a division of text , scribes would switch from standard black to the red pigment , minium . another important visual device used to increase the prominence of certain portions of text was to set them off with large , ornate , and colorful capital letters , often surrounded by tiny , detailed paintings . the italians began to refer to these elaborate and diminutive paintings as < i > miniatura < /i > , illuminations . because of the necessarily small size of the paintings , miniatura began to be associated with all things wee and spawned to other words with the same base , like the latin < i > minimum < /i > , for least . miniatura was transmuted into english in the 16th century as the word , < i > miniature < /i > , and since that time , it has had the exact same meaning we use today .

another important visual device used to increase the prominence of certain portions of text was to set them off with large , ornate , and colorful capital letters , often surrounded by tiny , detailed paintings . the italians began to refer to these elaborate and diminutive paintings as < i > miniatura < /i > , illuminations . because of the necessarily small size of the paintings , miniatura began to be associated with all things wee and spawned to other words with the same base , like the latin < i > minimum < /i > , for least . miniatura was transmuted into english in the 16th century as the word , < i > miniature < /i > , and since that time , it has had the exact same meaning we use today .

what are some of the modern english words that came from miniatura ?

so in the bottom we see neon and this is a small glass discharge tube which has got a very low pressure of neon inside it . it ’ s generally used for lots of signs and things like that . you might see ‘ fish and chips ’ or perhaps a ‘ disco ’ or something like that . so neon is an inert gas like helium and it doesn ’ t really form any compounds at all . most of you have probably seen neon because it ’ s used in these so-called neon signs where you take a glass tube and put a high voltage and it produces a red light . so you can see that , again , a discharge , a high potential discharge is going across this tube and it ’ s exciting all of the neon molecules inside , such that we get this exciting , really vivid red colouration . and skilled glass-blowers can blow this into glass shapes of signs saying ‘ pizza ’ or whatever on shops . you can freeze neon at very low temperatures about 10 degrees absolute and early on in my scientific career i did do an experiment in solid neon . it produced a great result with an iron compound and i ’ m still quite proud of it several years on . but it ’ s not really very important in terms of absolute chemistry . so this is just a simple pocket spectroscope and it allows us to analyse the wavelengths of light that each of these individual light sources is giving off . so each individual atom as it ’ s excited in its emission zone can give rise to different lines or different frequencies of radiation or light and we can use this little device to analyse which elements are in each of these different elements of light . so we put it up to our eyes and we look through , and we look at the different colours of the lines in the different gases .

so in the bottom we see neon and this is a small glass discharge tube which has got a very low pressure of neon inside it . it ’ s generally used for lots of signs and things like that .

neon was discovered in 1898 by sir william ramsay and morris w. travers in london . from where did they isolate it ?

how did adolf hitler , a tyrant who orchestrated one of the largest genocides in human history , rise to power in a democratic country ? the story begins at the end of world war i . with the successful allied advance in 1918 , germany realized the war was unwinnable and signed an armistice ending the fighting . as its imperial government collapsed , civil unrest and worker strikes spread across the nation . fearing a communist revolution , major parties joined to suppress the uprisings , establishing the parliamentary weimar republic . one of the new government 's first tasks was implementing the peace treaty imposed by the allies . in addition to losing over a tenth of its territory and dismantling its army , germany had to accept full responsibility for the war and pay reparations , debilitating its already weakened economy . all this was seen as a humiliation by many nationalists and veterans . they wrongly believed the war could have been won if the army had n't been betrayed by politicians and protesters . for hitler , these views became obsession , and his bigotry and paranoid delusions led him to pin the blame on jews . his words found resonance in a society with many anti-semitic people . by this time , hundreds of thousands of jews had integrated into german society , but many germans continued to perceive them as outsiders . after world war i , jewish success led to ungrounded accusations of subversion and war profiteering . it can not be stressed enough that these conspiracy theories were born out of fear , anger , and bigotry , not fact . nonetheless , hitler found success with them . when he joined a small nationalist political party , his manipulative public speaking launched him into its leadership and drew increasingly larger crowds . combining anti-semitism with populist resentment , the nazis denounced both communism and capitalism as international jewish conspiracies to destroy germany . the nazi party was not initially popular . after they made an unsuccessful attempt at overthrowing the government , the party was banned , and hitler jailed for treason . but upon his release about a year later , he immediately began to rebuild the movement . and then , in 1929 , the great depression happened . it led to american banks withdrawing their loans from germany , and the already struggling german economy collapsed overnight . hitler took advantage of the people 's anger , offering them convenient scapegoats and a promise to restore germany 's former greatness . mainstream parties proved unable to handle the crisis while left-wing opposition was too fragmented by internal squabbles . and so some of the frustrated public flocked to the nazis , increasing their parliamentary votes from under 3 % to over 18 % in just two years . in 1932 , hitler ran for president , losing the election to decorated war hero general von hindenburg . but with 36 % of the vote , hitler had demonstrated the extent of his support . the following year , advisors and business leaders convinced hindenburg to appoint hitler as chancellor , hoping to channel his popularity for their own goals . though the chancellor was only the administrative head of parliament , hitler steadily expanded the power of his position . while his supporters formed paramilitary groups and fought protestors in streets . hitler raised fears of a communist uprising and argued that only he could restore law and order . then in 1933 , a young worker was convicted of setting fire to the parliament building . hitler used the event to convince the government to grant him emergency powers . within a matter of months , freedom of the press was abolished , other parties were disbanded , and anti-jewish laws were passed . many of hitler 's early radical supporters were arrested and executed , along with potential rivals , and when president hindenburg died in august 1934 , it was clear there would be no new election . disturbingly , many of hitler 's early measures did n't require mass repression . his speeches exploited people 's fear and ire to drive their support behind him and the nazi party . meanwhile , businessmen and intellectuals , wanting to be on the right side of public opinion , endorsed hitler . they assured themselves and each other that his more extreme rhetoric was only for show . decades later , hitler 's rise remains a warning of how fragile democratic institutions can be in the face of angry crowds and a leader willing to feed their anger and exploit their fears .

but upon his release about a year later , he immediately began to rebuild the movement . and then , in 1929 , the great depression happened . it led to american banks withdrawing their loans from germany , and the already struggling german economy collapsed overnight .

what role did the great depression of 1929 play in making the nazi party a force in german politics ?

gravity . it controls the universe . everything attracts everything else . ouch ! including you . ow ! in this final lesson , we 'll explore what gravity means for space-time , or rather what space-time means for gravity . until now , we 've been dealing with things moving at constant speeds , with straight world lines in space-time . but once you add gravity , if you measure a speed at one moment , then again a bit later , the speed may have changed . in other words , as i discovered , gravity causes acceleration , so we need the world line to look different from one moment to the next . as we saw in the last lesson , the correct way to tilt an object 's world line is using a lorentz transformation : einstein 's stretch and squash trick . so , to map out what gravity is doing to tom 's motion , we need to create a whole load of little patches of space-time , each transformed by different amounts . so that my world line is at a different angle in each one . and then , we 're ready to stitch everything together . we assemble a cozy quilt of space-time where world lines look curved . where the world lines join , the objects collide . by making these connections between the patches , a curvature gets built into space-time itself . but einstein 's true genius was to describe precisely how each patch is stretched and squashed according to nearby mass and energy . the mere presence of stuff curves the space-time , and curving space-time moves the stuff around . this is gravity , according to einstein . previously , isaac newton had explained gravity using the ideas of force and acceleration , without any wibbily wobbly space-time , and that did pretty well . but einstein 's theory does just slightly better at predicting , for example , the orbit of mercury around the sun , or the way that light rays are deflected by massive objects . more importantly , einstein 's theory predicts things that simply do n't exist in older theories where space , time and gravity were separate . the stitching can leave wrinkles in the space-time material . these are called gravitational waves , which should be detectable as tiny , repetitive , subtle squashes and stretches in space . so we 're building experiments to check if they are there . in the meantime , indirect evidence , most recently in the polarization patterns of light left over from the big bang , strongly suggest that they are . but despite einstein 's successes , when too much stuff gets concentrated in too small a space , like in a black hole , the curvature of space-time becomes so large , that his equations collapse . we need a new picture of space-time that incorporates quantum mechanics to unlock the secret at the heart of black holes . which means there 's plenty more to be discovered about space , time , and space-time in the future .

gravity . it controls the universe .

quantum gravity – the union of quantum mechanics and einstein ’ s theory of gravity – has so far proved impossibly hard to construct . if we could work it out , it would be significant because :

in 1898 , marie and pierre curie discovered radium . claimed to have restorative properties , radium was added to toothpaste , medicine , water , and food . a glowing , luminous green , it was also used in beauty products and jewelry . it was n't until the mid-20th century we realized that radium 's harmful effects as a radioactive element outweighed its visual benefits . unfortunately , radium is n't the only pigment that historically seemed harmless or useful but turned out to be deadly . that lamentable distinction includes a trio of colors and pigments that we 've long used to decorate ourselves and the things we make : white , green , and orange . our story begins with white . as far back as the 4th century bce , the ancient greeks treated lead to make the brilliant white pigment we know today . the problem ? in humans , lead is directly absorbed into the body and distributed to the blood , soft tissues , and mineralized tissues . once in the nervous system , lead mimics and disrupts the normal functions of calcium , causing damages ranging from learning disabilities to high blood pressure . yet the practice of using this toxic pigment continued across time and cultures . lead white was the only practical choice for white oil or tempera paint until the 19th century . to make their paint , artists would grind a block of lead into powder , exposing highly toxic dust particles . the pigment 's liberal use resulted in what was known as painter 's colic , or what we 'd now call lead poisoning . artists who worked with lead complained of palseys , melancholy , coughing , enlarged retinas , and even blindness . but lead white 's density , opacity , and warm tone were irresistible to artists like vermeer , and later , the impressionists . its glow could n't be matched , and the pigment continued to be widely used until it was banned in the 1970s . as bad as all that sounds , white 's dangerous effects pale in comparison to another , more wide-spread pigment , green . two synthetic greens called scheele 's green and paris green were first introduced in the 18th century . they were far more vibrant and flashy than the relatively dull greens made from natural pigments , so they quickly became popular choices for paint as well as dye for textiles , wallpaper , soaps , cake decorations , toys , candy , and clothing . these green pigments were made from a compound called cupric hydrogen arsenic . in humans , exposure to arsenic can damage the way cells communicate and function . and high levels of arsenic have been directly linked to cancer and heart disease . as a result , 18th century fabric factory workers were often poisoned , and women in green dresses reportedly collapsed from exposure to arsenic on their skin . bed bugs were rumored not to live in green rooms , and it 's even been speculated that napoleon died from slow arsenic poisoning from sleeping in his green wallpapered bedroom . the intense toxicity of these green stayed under wraps until the arsenic recipe was published in 1822 . and a century later , it was repurposed as an insecticide . synthetic green was probably the most dangerous color in widespread use , but at least it did n't share radium 's property of radioactivity . another color did , though - orange . before world war ii , it was common for manufacturers of ceramic dinnerware to use uranium oxide in colored glazes . the compound produced brilliant reds and oranges , which were appealing attributes , if not for the radiation they emitted . of course , radiation was something we were unaware of until the late 1800s , let alone the associated cancer risks , which we discovered much later . during world war ii , the u.s. government confiscated all uranium for use in bomb development . however , the atomic energy commission relaxed these restrictions in 1959 , and depleted uranium returned to ceramics and glass factory floors . orange dishes made during the next decade may still have some hazardous qualities on their surfaces to this day . most notably , vintage fiestaware reads positive for radioactivity . and while the levels are low enough that they do n't officially pose a health risk if they 're on a shelf , the u.s. epa warns against eating food off of them . though we still occasionally run into issues with synthetic food dyes , our scientific understanding has helped us prune hazardous colors out of our lives .

as bad as all that sounds , white 's dangerous effects pale in comparison to another , more wide-spread pigment , green . two synthetic greens called scheele 's green and paris green were first introduced in the 18th century . they were far more vibrant and flashy than the relatively dull greens made from natural pigments , so they quickly became popular choices for paint as well as dye for textiles , wallpaper , soaps , cake decorations , toys , candy , and clothing .

the bright green pigments found in scheele ’ s and paris green were later found to contain :

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

but after billions of dollars in research , we have n't found a solution for a disease that affects more than 14 million people and their families at any given time . cancer arises as normal cells accumulate mutations . most of the time , cells can detect mutations or dna damage and either fix them or self destruct .

how can we detect heterogeneity of cancer cells ?

flatulence , or passing gas , is a normal daily phenomenon . most individuals , yes , that includes you , will make anywhere from 500-1500 milliliters of gas and can pass gas ten to twenty times a day . but where does this bodily gas come from ? a small proportion may come from ingesting air during sleep , or at other times , but the majority of gas is produced by bacteria in our intestines as they digest parts of food which we can not . our intestine is home to trillions of bacteria living in a symbiotic relationship with us . we provide them with a safe place to stay and food to eat . in exchange , they help us extract energy from our food , make vitamins for us , like vitamin b and k , boost our immune system , and play an important role in gastrointestinal barrier function , motility and the development of various organ systems . clearly , it 's in our best interest to keep these bacteria happy . gut bacteria get their nutrition primarily from undigested food , such as carbohydrates and proteins , which come to the large intestine . they ferment this undigested food to produce a wide range of compounds , such as short-chain fatty acids and , of course , gases . hydrogen and carbon dioxide are the most common gaseous products of bacterial fermentation , and are odorless . some people also produce methane due to specific microbes present in their gut . but methane is actually odorless , too . well then , what stinks ? the foul smell is usually due to volatile sulfur compounds , such as hydrogen sulfide and methanethiol , or methyl mercaptan . these gases , however , constitute less than 1 % of volume , and are often seen with ingestion of amino acids containing sulfur , which may explain the foul smell of gas from certain high protein diets . increased passage of gas is commonly noticed after eating foods with high amounts of indigestible carbohydrates , like beans , lentils , dairy products , onions , garlic , leeks , radishes , potatoes , oats , wheat , cauliflower , broccoli , cabbage , and brussel sprouts . humans lack the enzymes , so the bacteria able to ferment complex carbohydrates take over , and this naturally leads to more gas than usual . but if you feel uncomfortable , bloated or visibly distended , this may indicate impaired movement of gas along the gastrointestinal track . it 's important not to just blame certain foods for gas and bloating and then avoid them . you do n't want to starve the bacteria that digest these complex carbohydrates , or they 'll have to start eating the sugars in the mucus lining of your intestines . your personal gas will vary based on what you eat , and what bacteria are in your gut . for example , from the same starting sugar , the bacteria clostridium produces carbon dioxide , butyrate and hydrogen , while propionibacterium can produce carbon dioxide , propionate and acetate . at the same time , methanogens can use hydrogen and carbon dioxide produced by other bacteria to generate methane , which can reduce the total volume of gas by using up hydrogen and carbon dioxide . so there 's a complex web among intestinal bacteria allowing them to flourish by either directly consuming undigested food , or using what other bacteria produce . this interaction largely determines the amount and type of gas produced , so gas production is a sign that your gut bacteria are at work . but in some instances , people may develop abnormal increased flatulence . a common example is lactose intolerance . most individuals have the enzyme for breaking down lactose , a sugar present in milk and milk-derived products . but some people either lack it entirely , or have a reduced amount , such as after a gastrointestinal infection , so they 're unable to digest lactose products and may experience cramping , along with increased flatulence due to bacterial fermentation . but remember , most gas is produced as a natural result of bacterial fermentation in the intestine , and indicates healthy functioning of the gut . the amount and type can vary based on your diet and the bacteria in your intestine . exercise social courtesy while passing gas , and do try to forgive your bacteria . they 're only trying to be helpful .

a small proportion may come from ingesting air during sleep , or at other times , but the majority of gas is produced by bacteria in our intestines as they digest parts of food which we can not . our intestine is home to trillions of bacteria living in a symbiotic relationship with us . we provide them with a safe place to stay and food to eat .

a symbiotic relationship such as the one between the billions of bacteria in a human ’ s intestines and a human is considered to be mutualism . list several ways both species benefit from one another by maintaining this relationship .

oh , excuse me ! have you ever yawned because somebody else yawned ? you are n't especially tired , yet suddenly your mouth opens wide and a big yawn comes out . this phenomenon is known as contagious yawning . and while scientists still do n't fully understand why it happens , there are many hypotheses currently being researched . let 's take a look at a few of the most prevalent ones , beginning with two physiological hypotheses before moving to a psychological one . our first physiological hypothesis states that contagious yawning is triggered by a specific stimulus , an initial yawn . this is called fixed action pattern . think of fixed action pattern like a reflex . your yawn makes me yawn . similar to a domino effect , one person 's yawn triggers a yawn in a person nearby that has observed the act . once this reflex is triggered , it must run its course . have you ever tried to stop a yawn once it has begun ? basically impossible ! another physiological hypothesis is known as non-conscious mimicry , or the chameleon effect . this occurs when you imitate someone 's behavior without knowing it , a subtle and unintentional copycat maneuver . people tend to mimic each other 's postures . if you are seated across from someone that has their legs crossed , you might cross your own legs . this hypothesis suggests that we yawn when we see someone else yawn because we are unconsciously copying his or her behavior . scientists believe that this chameleon effect is possible because of a special set of neurons known as mirror neurons . mirror neurons are a type of brain cell that responds equally when we perform an action as when we see someone else perform the same action . these neurons are important for learning and self-awareness . for example , watching someone do something physical , like knitting or putting on lipstick , can help you do those same actions more accurately . neuroimaging studies using fmri , functional magnetic resonance imaging , show us that when we seem someone yawn or even hear their yawn , a specific area of the brain housing these mirror neurons tends to light up , which , in turn , causes us to respond with the same action : a yawn ! our psychological hypothesis also involves the work of these mirror neurons . we will call it the empathy yawn . empathy is the ability to understand what someone else is feeling and partake in their emotion , a crucial ability for social animals like us . recently , neuroscientists have found that a subset of mirror neurons allows us to empathize with others ' feelings at a deeper level . ( yawn ) scientists discovered this empathetic response to yawning while testing the first hypothesis we mentioned , fixed action pattern . this study was set up to show that dogs would enact a yawn reflex at the mere sound of a human yawn . while their study showed this to be true , they found something else interesting . dogs yawned more frequently at familiar yawns , such as from their owners , than at unfamiliar yawns from strangers . following this research , other studies on humans and primates have also shown that contagious yawning occurs more frequently among friends than strangers . in fact , contagious yawning starts occurring when we are about four or five years old , at the point when children develop the ability to identify others ' emotions properly . still , while newer scientific studies aim to prove that contagious yawning is based on this capacity for empathy , more research is needed to shed light on what exactly is going on . it 's possible that the answer lies in another hypothesis altogether . the next time you get caught in a yawn , take a second to think about what just happened . were you thinking about a yawn ? did someone near you yawn ? was that person a stranger or someone close ? and are you yawning right now ? ( yawn ) ( lip smacking )

we will call it the empathy yawn . empathy is the ability to understand what someone else is feeling and partake in their emotion , a crucial ability for social animals like us . recently , neuroscientists have found that a subset of mirror neurons allows us to empathize with others ' feelings at a deeper level .

_______ is the ability to understand what someone else is feeling and partake in their emotion .

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

and indeed , the skeletal remains of black death victims found in london show telltale signs of malnutrition and prior illness . the destruction caused by the black death changed humanity in two important ways . on a societal level , the rapid loss of population led to important changes in europe 's economic conditions .

what caused the black death ?

♪ a treasure trove of planets found astronomers are celebrating a new discovery . sean carey , manager , spitzer science center , caltech ipac the big news is that around a very nearby cold , small star we found seven rocky , earth-sized planets , all of which could potentially have liquid water . three of them orbit in the habitable zone around the star . and liquid water could exist on any of the seven planets given the right conditions . nikole lewis , james webb telescope project scientist , space telescope science institute for me it 's mind-blowing . the first time i saw what the system had in it , i was just like , `` you got to be kidding me ! '' then i looked at the data myself . i 'm like , `` yup , there they all are . '' it 's just , i would have never predicted this . it 's beyond , you know , anything i could 've ever dreamt of . the planetary system is called trappist-1 after the belgian-operated telescope in chile . trappist found two planets in 2016 . nasa 's spitzer space telescope , with the help of ground-based telescopes , discovered five more . michael gillon , principal investigator , trappist , university of liege , belgium i felt super-excited . amazed by the very existence of this system ... was kind of ... of yeah ... of shock . the trappist-1 planets are extremely close to one another . from a planet 's surface you could easily see other trappist-1 planets in the sky . if you were standing on one of these planets you 'd actually see a lot of them sort of in the sky whipping by on these very short orbital periods . nasa 's james webb telescope , launching in 2018 , could teach us even more about the trappist-1 system . it will be able to detect the chemical fingerprints of water , methane and oxygen of potential atmospheres , key ingredients in assessing habitability . it is an excellent , fantastic discovery . all images of planets are artist 's conceptions . jet propulsion laboratory california institute of technology

♪ a treasure trove of planets found astronomers are celebrating a new discovery . sean carey , manager , spitzer science center , caltech ipac the big news is that around a very nearby cold , small star we found seven rocky , earth-sized planets , all of which could potentially have liquid water . three of them orbit in the habitable zone around the star .

how many rocky , earth-sized planets did the spitzer space telescope find around a nearby star ?

so , the apocalypse has happened . the zombies have come and gone , and all plant life on earth has died somehow . all you have are some basic supplies and some seeds of a few types of essential plants . so , what should you do to make absolutely sure they grow , seeing how rebuilding human civilization absolutely depends on it ? well , you 'd probably think the last thing you should do with these crucially important seeds is something like poking holes in them , or grinding them with sandpaper , or throwing them in acid or hot water . but , in fact , all of these are methods that are commonly used to help seeds start growing . a typical seed consists of a plant embryo encased in a hard seed coat . to start growing , it needs to emerge or sprout from inside this shell . this process is called germination . but just as it would be hard for you to get out of a jail cell with no windows and no doors , the embryo might need a little help escaping from its seed prison , and any process that makes this easier by wearing down the seed coat is called scarification . this lets moisture and nutrients get through the seed coat , making the embryo start growing until it breaks through . now , you might be wondering why it is that plants would need humans to do all these weird things to their seeds in order to grow , and , in fact , they do n't . in natural environments , seed coats are worn down by cold temperatures , bacteria , or even animal digestion . our scarification methods just mimick and accelerate these natural processes to increase the chances of successful germination . one technique we can use is called nicking . to do this , we make a small cut or scratch into the seed coat . be careful not to cut too deep ! you do n't want to damage the plant embryo inside . another way is to file down the seed coat using sandpaper or a nail file . once again , you do n't want to file too much , just enough to wear down some of the seed coat . after applying either of these methods , you 'll want to spray the seeds with bleach to prevent mold . seeds can also be soaked in water to soften the coat . one way to do this is to place the seeds in a nylon bag , then place the bag into hot water . turn off the heat immediately and allow the water to cool to room temperature before removing the seeds . it 's important not to heat the seed for too long as this will kill the embryo . again , you 'll want to spray them with bleach afterwards . finally , you can try immersing the seeds in a sulfuric acid solution . make sure you 're wearing protective goggles and gloves any time you work with such a dangerous substance . place the seeds into a wire mesh pouch and immerse the pouch in the solution for ten minutes . then take out the pouch and rinse it with clean water . take out the seeds and , as before , spray them with bleach so they do n't get moldy . if you try all of these methods , you will see that some of them are more effective than others , and some work best for different types of plants that have harder or thicker coats . so , knowing what seed scarification techniques work best will be useful if you ever need to survive a cataclysm , start a farm , or just want to plant in your own garden .

but , in fact , all of these are methods that are commonly used to help seeds start growing . a typical seed consists of a plant embryo encased in a hard seed coat . to start growing , it needs to emerge or sprout from inside this shell .

what do we call any method that breaks down the hard seed coat ?

i ’ ve invited you all here today because i wanted to talk to you about some ugly stereotypes that are going around . i ’ ve been hearing a lot of unfair , unseemly , and unscientific generalizations being made lately . and they mostly have to do with sex . and your hormones . people have a nasty habit of equating “ hormones ” with a particular set of behaviors and conditions , most of which have to do with reproduction , or sexual development , or acts that include what my brother john has referred to as “ skoodilypooping. ” for example , people will say that “ hormones ” are why kevin has zits , and is being all moody , or why hannah , who ’ s three months pregnant , just cried watching a commercial for car insurance -- which , let ’ s be honest , i do that too . now , i ’ m not saying that hormones aren ’ t at the root of sexual attraction , or zits , or occasional bouts of extreme emotion , because they are . that ’ s just not all that they do . not even close . when people talk about “ hormones ” in the contexts that i just mentioned , what really they mean is `` sex hormones . '' but sex hormones are just one kind of hormone that you have coursing through your body right now . in fact , there are at least 50 different types of these chemical messengers at work in your body at this very minute , but only a very few of them have anything at all to do with sex . the truth is , from birth to death , just about every cell and function in your body is under your hormones ’ constant influence . they ’ re floating through your blood , regulating your metabolism , your sleep cycle , your response to stress , and the general and incredibly important overall homeostasis that keeps you not dead . some hormones are just there to make other hormones trigger even more hormones -- in a kind of chemical relay race that biologists refer to , rather elegantly , as “ cascades. ” these hormones run through you no matter what your mood is , or whether you have zits . so the reality is : we ’ re all hormonal ... all of the time . ok , to begin to understand our hormones -- and the endocrine system that produces , releases , and re-absorbs them -- we have to step back and take a broad view . not just by emphasizing that sex hormones aren ’ t the only hormones you have -- but also by looking at how your hormones interact with your other organ systems . because , if anything , your body has two bosses -- two complementary systems that are constantly shouting instructions over each other , to all of your bits and pieces . both your endocrine system and your nervous system are constantly trafficking information around your corpus , gathering intel , making demands , controlling your every move . they just have totally different ways of doing it . your nervous system uses lightning-fast electrochemical action potentials , delivered by an expressway made of neurons to specific cells and organs . but your endocrine system prefers a slower , wider stream of data . it secretes hormones that travel through your blood -- not through neurons -- so they move more slowly , but they also produce widespread effects that last a whole lot longer than an action potential . now , compared to your heart or brain or other , arguably more glamorous organs , your endocrine system ’ s organs and glands are kinda small and lumpy . they ’ re also rogues -- instead of being all nestled together like in your other organ systems , these guys are scattered all over the place , from your brain to your throat , to your kidneys , to your genitals . a gland is a just any structure that makes and secretes a hormone . and the master gland in your body is the pituitary , which produces many hormones that signal other glands -- like the thyroid , parathyroid , adrenal , and pineal glands -- to make their own hormones . the endocrine system also includes a few organs -- like the gonads , the pancreas , and the placenta in pregnant women -- all of which have some other non-hormonal functions and are made up of multiple tissue types . and technically the hypothalamus in your brain is in the endocrine club too , since in addition to all of its busy brain duties , it does produce and release hormones . so , thanks to these glands and organs , you ’ ve got all these hormones diffusing through your blood , doing all sorts of different things , but the thing to remember about them is that a hormone can only trigger a reaction in specific cells -- their so-called target cells -- that have the right receptors for it . so , just like some keys can open many locks , while others only work with one , so too can the hormone-target-cell relationship either be widespread or localized . you ’ re probably gon na want an example of that . so , your thyroid -- at the bottom of your throat -- produces the hormone thyroxine , which stimulates metabolism and binds to receptors in most of the cells in your body . but your pituitary -- which is nestled all comfy under your brain -- produces follicle-stimulating hormone , which helps regulate growth and triggers sexual maturity , and it only targets specific cells in the ovaries and testes . so how do hormones bind to their target cells ? well , chemically , most hormones are either made of amino acids -- including their more complex structures like peptides or proteins -- or they ’ re derived from lipids , like cholesterol . and this is key , because a hormone ’ s chemical structure determines if it ’ s water soluble , like most amino acid-based ones are , or lipid soluble , like steroids are . solubility is important because your cell membranes are made of lipids . that means that water soluble ones can ’ t get across them . so target cells for those kinds of hormones have receptors for them on the outside of their membranes . lipid-soluble hormones , on the other hand , can just basically glide right through that cell membrane , so their receptor sites are inside their target cells . either way , when a target cell is activated , the hormone alters its activity , by either increasing or decreasing some of its functions -- usually with the goal of maintaining your body ’ s homeostasis in one way or another . so , if hormones are keeping your body in balance , what ’ s putting your body out of balance ? i don ’ t know -- could i interest you in some pie ? if you have a couple of nice , generous helpings of strawberry-rhubarb pie -- and just to make things interesting , let ’ s say they ’ re a la mode -- your blood glucose level is gon na go through the roof . and the pancreas regulates your blood sugar by releasing two different hormones -- insulin and glucagon . once you have a belly full of that pie , beta cells in your pancreas release insulin , which helps lower your blood sugar by increasing the rate at which your cells store the sugar either as glycogen or as fat for later use . now , let ’ s say you ’ ve done the opposite : you ’ ve eaten no pie -- you ’ re pie-less -- in fact , you ’ ve eaten nothing for hours . if your blood sugar drops too low , then alpha cells in the pancreas will instead send out glucagon , which helps raise your blood sugar levels , in part by decreasing the storage of sugar in your cells , and triggering their release of glucose back into the blood . lots of different endocrine-related illnesses -- like diabetes or hyperthyroidism -- tend to be the result of either hyper ( too much ) or hypo ( too little ) secretion of certain hormones , which throw your homeostasis off balance . but there are lots of more common -- and less obvious -- ways your hormones can get out of balance , not because of some disorder , but because these signaling chemicals are just caught up in a chain reaction , which can take a while to subside . some hormones just exist to control other hormones , which in turn control still more hormones . so as soon as one starts to trickle out , you can pretty quickly wind up with a cascade on your hands . you ’ ve got a few different hormone cascades going on at any given moment , but one of the big ones -- one that ’ s really worth understanding -- is the hypothalamic-pituitary-adrenal axis , or the hpa axis , because you don ’ t want to have to say that every time . this is a complex series of interactions between three glands that ultimately regulates lots of your body ’ s daily processes , like digestion , sexuality , immune response , and how you handle stress . and it ’ s complex not just because of all the glands involved -- it ’ s also one of the more crucial instances of your endocrine system coordinating with your nervous system . specifically , it ’ s behind that fight-or-flight response that everybody keeps talking about . the hpa axis is essentially the endocrine system ’ s companion to the sympathetic nervous system . the sympathetic system , in times of high stress , does things like speed up your heart rate and direct blood away from the digestive organs and to the muscles . but many of the other effects of the stress response are carried out by your endocrine system . and getting your nervous and endocrine systems to work together in times of crisis is where the hypothalamus comes in . it ’ s the hub of where the two systems meet -- it keeps tabs on what ’ s going on all over your body , analyzing your blood for signs that something might be off . so , let ’ s revisit our fight-or-flight scene from a few lessons ago -- the old burning house scenario . so you ’ re sleeping , dreaming about petting pandas with emma watson or whatever , when the smoke alarm goes off . well , action potentials in your brain trigger neurons in your hypothalamus to release the peptide hormone crh , or corticotropin releasing hormone . the crh makes the very short trip through the bloodstream to the anterior pituitary gland , where , because it ’ s water soluble , it binds to receptors on the outside of its target cells . there , it triggers the release of adrenocorticotropic hormone , or acth . the acth travels -- again through the bloodstream -- to the adrenal cortices of the adrenal glands on top of your kidneys . when the acth binds to receptors on cells in an adrenal cortex , it triggers the release of a frenzy of different freak-out compounds known as glucocorticoid and mineralcorticoid hormones . typically these guys help us deal with day-to-day stress by keeping our blood sugar and blood pressure balanced . but under major stress -- like waking up in a burning building stress -- these hormones , like cortisol , cause the classic fight-or-flight response : ramping up your blood pressure , dumping glucose into your bloodstream , shutting down non-emergency services like your immune system and sperm and egg development . and guess what ? now that all these stress hormones are pulsing through your blood , the hypothalamus back in the brain senses them . and because its job is to monitor and maintain balance whenever possible , it then stops secreting crh , which -- eventually -- causes the other glands to stop secreting their panic hormones . now , because this element of the stress response is hormonal rather than electrical , it comes on more slowly than the nervous system part , and it takes longer to subside , too , as those stress hormones linger in the blood before being broken down by enzymes . so . we ’ re a long way from teenage crushes and zits and crying over commercials at this point , aren ’ t we ? as a life-long owner of hormones , i hope you ’ ll join me in dispelling the stereotypes that surround these powerful and important chemicals , and give them the respect they rightly deserve . today we looked at the endocrine system , and how it uses glands to produce hormones . these hormones are either amino-acid based and water soluble , or steroidal and lipid-soluble , and may target many types of cells or just turn on specific ones . we also touched on hormone cascades , and how the hpa axis effects your stress response . thank you to our headmaster of learning , thomas frank , and to all of our patreon patrons who help make crash course possible through their monthly contributions . if you like crash course and you want to help us keep making free educational content for the whole world , you can go to patreon.com/crashcourse . crash course is filmed in the doctor cheryl c. kinney crash course studio . this episode was written by kathleen yale , edited by blake de pastino , and our consultant is dr. brandon jackson . it was directed by nicholas jenkins , the editor is nicole sweeney , the script supervisor was stefan chin , our sound designer is michael aranda and the graphics team is thought café .

but there are lots of more common -- and less obvious -- ways your hormones can get out of balance , not because of some disorder , but because these signaling chemicals are just caught up in a chain reaction , which can take a while to subside . some hormones just exist to control other hormones , which in turn control still more hormones . so as soon as one starts to trickle out , you can pretty quickly wind up with a cascade on your hands .

which hormones does the pituitary produce and what function do those hormones serve ?

translator : andrea mcdonough reviewer : jessica ruby today , we 're going to look at the world of rome through the eyes of a young girl . here she is , drawing a picture of herself in the atrium of her father 's enormous house . her name is domitia , and she is just 5 years old . she has an older brother who is fourteen , lucius domitius ahenobarbus , named after her dad . girls do n't get these long names that boys have . what is worse is that dad insists on calling all his daughters domitia . `` domitia ! '' his call to domitia drawing on the column , domitia iii . she has an older sister , domitia ii , who is 7 years old . and then there 's domitia i , who is ten . there would have been a domitia iv , but mom died trying to give birth to her three years ago . confused ? the romans were too . they could work out ancestry through the male line with the nice , tripartite names such as lucius domitius ahenobarbus . but they got in a real mess over which domitia was married to whom and was either the great aunt or the great stepmother and so on to whom when they came to write it down . domitia iii is not just drawing on the pillar , she 's also watching the action . you see , it 's early , in the time of day when all her dad 's clients and friends come to see him at home to pay their respects . lucius popidius secundus , a 17 year old , he wants to marry domitia ii within the next five to seven years , has come as well . he seems to be wooing not his future wife , but her dad . poor lucius , he does not know that domitia 's dad thinks he and his family are wealthy but still scumbags from the subura . afterall , it is the part of rome full of barbers and prostitutes . suddenly , all the men are leaving with dad . it 's the second hour and time for him to be in court with a sturdy audience of clients to applaud his rhetoric and hiss at his opponent . the house is now quieter . the men wo n't return for seven hours , not until dinner time . but what happens in the house for those seven hours ? what do domitia , domitia , and domitia do all day ? not an easy question ! everything written down by the romans that we have today was written by men . this makes constructing the lives of women difficult . however , we ca n't have a history of just roman men , so here it goes . we can begin in the atrium . there is a massive loom , on which dad 's latest wife is working on a new toga . domitia , domitia , and domitia are tasked with spinning the wool that will be used to weave this mighty garment , 30 or more feet long and elliptical in shape . romans loved the idea that their wives work wool . we know that because it 's written on the gravestones of so many roman women . unlike women in greece , roman women go out the house and move about the city . they go to the baths in the morning to avoid the men or to separate baths that are for women only . some do go in for the latest fad of the ad 70s : nude bathing with men present . where they have no place is where the men are : in the forum , in the law court , or in the senate house . their place in public is in the porticos with gardens , with sculpture , and with pathways for walking in . when domitia , domitia , and domitia want to leave the house to go somewhere , like the portico of livia , they must get ready . domitia ii and domitia iii are ready , but domitia i , who is betrothed to be married in two years to darling philatus , is n't ready . she 's not slow , she just has more to do . being betrothed means she wears the insignia of betrothal : engagement rings and all the gifts pilatus has given her - jewels , earrings , necklaces , and the pendants . she may even wear her myrtle crown . all this bling shouts , `` i 'm getting married to that 19 year old who gave me all this stuff i 'm wearing ! '' while as they wait , domitia ii and domitia iii play with their dolls that mirror the image of their sister decked out to be married . one day , these dolls will be dedicated to the household gods on the day of their wedding . okay , we 're ready . the girls step into litters carried by some burly slaves . they also have a chaperone with them and will be meeting an aunt at the porticus of livia . carried high on the shoulders of these slaves , the girls look out through the curtains to see the crowded streets below them . they traverse the city , pass the coliseum , but then turn off to climb up the hill to the porticus of livia . it was built by livia , the wife of the first emperor augustus , on the site of the house of vedius pollio . he was n't such a great guy . he once tried to feed a slave to the eels in his fish pond for simply dropping a dish . luckily , the emperor was at the dinner and tamed his temper . the litters are placed on the ground and the girls get out and arm in arm , two by two , they ascend the steps into the enclosed garden with many columns . domitia iii shot off and is drawing on a column . domitia ii joins her but seeks to read the graffiti higher up on the column . she spots a drawing of gladiators and tries to imagine seeing them fighting , something she will never be permitted to do , except from the very rear of the coliseum . from there , she will have a good view of the 50,000 spectators but will see little by way of blood and gore . if she really wanted a decent view , she could become a vestal virgin and would sit right down the front . but a career tending the sacred flame of vesta is not to everybody 's taste . domitia i has met another ten year old also decked out in the insignia of betrothal . home time . when they get there after the eighth hour , something is up . a smashed dish lies on the floor . all the slaves are being gathered together in the atrium and await the arrival of their master . dad is going to go mad . he will not hit his children , but like many other romans , he believes that slaves have to be punished . the whip lies ready for his arrival . no one knows who smashed the dish , but dad will call the undertaker to torture it out of them , if he must . the doorkeeper opens the front door to the house . a hush comes over the anxious slaves . in walks not their master but , instead , a pregnant teenager . it is the master 's eldest daughter , age 15 , who is already a veteran of marriage and child birth . guess what her name is . there is a five to ten percent chance she wo n't survive giving birth to her child , but , for now , she has come to dinner with her family . as a teenage mother , she has proved that she is a successful wife by bringing children and descendants for her husband , who will carry on his name in the future . the family head off to the dining room and are served dinner . it would seem dad has had an invite to dinner elsewhere . with dinner concluded , the girls crossed the atrium to bid farewell to their older sister who is carried home in a litter , escorted by some of dad 's bodyguards . returning to the house , the girls cross the atrium . the slaves , young and old , male and female , await the return of their owner . when he returns , he may exact vengeance , ensuring his power over the slaves is maintained through violence and terror , to which any slave could be subjected . but , for the girls , they head upstairs for the night , ready for bed .

what is worse is that dad insists on calling all his daughters domitia . `` domitia ! '' his call to domitia drawing on the column , domitia iii .

what peculiar thing did domitia 's father do ?

light is the fastest thing we know . it 's so fast that we measure enormous distances by how long it takes for light to travel them . in one year , light travels about 6,000,000,000,000 miles , a distance we call one light year . to give you an idea of just how far this is , the moon , which took the apollo astronauts four days to reach , is only one light-second from earth . meanwhile , the nearest star beyond our own sun is proxima centauri , 4.24 light years away . our milky way is on the order of 100,000 light years across . the nearest galaxy to our own , andromeda , is about 2.5 million light years away space is mind-blowingly vast . but wait , how do we know how far away stars and galaxies are ? after all , when we look at the sky , we have a flat , two-dimensional view . if you point you finger to one star , you ca n't tell how far the star is , so how do astrophysicists figure that out ? for objects that are very close by , we can use a concept called trigonometric parallax . the idea is pretty simple . let 's do an experiment . stick out your thumb and close your left eye . now , open your left eye and close your right eye . it will look like your thumb has moved , while more distant background objects have remained in place . the same concept applies when we look at the stars , but distant stars are much , much farther away than the length of your arm , and the earth is n't very large , so even if you had different telescopes across the equator , you 'd not see much of a shift in position . instead , we look at the change in the star 's apparent location over six months , the halfway point of the earth 's yearlong orbit around the sun . when we measure the relative positions of the stars in summer , and then again in winter , it 's like looking with your other eye . nearby stars seem to have moved against the background of the more distant stars and galaxies . but this method only works for objects no more than a few thousand light years away . beyond our own galaxy , the distances are so great that the parallax is too small to detect with even our most sensitive instruments . so at this point we have to rely on a different method using indicators we call standard candles . standard candles are objects whose intrinsic brightness , or luminosity , we know really well . for example , if you know how bright your light bulb is , and you ask your friend to hold the light bulb and walk away from you , you know that the amount of light you receive from your friend will decrease by the distance squared . so by comparing the amount of light you receive to the intrinsic brightness of the light bulb , you can then tell how far away your friend is . in astronomy , our light bulb turns out to be a special type of star called a cepheid variable . these stars are internally unstable , like a constantly inflating and deflating balloon . and because the expansion and contraction causes their brightness to vary , we can calculate their luminosity by measuring the period of this cycle , with more luminous stars changing more slowly . by comparing the light we observe from these stars to the intrinsic brightness we 've calculated this way , we can tell how far away they are . unfortunately , this is still not the end of the story . we can only observe individual stars up to about 40,000,000 light years away , after which they become too blurry to resolve . but luckily we have another type of standard candle : the famous type 1a supernova . supernovae , giant stellar explosions are one of the ways that stars die . these explosions are so bright , that they outshine the galaxies where they occur . so even when we ca n't see individual stars in a galaxy , we can still see supernovae when they happen . and type 1a supernovae turn out to be usable as standard candles because intrinsically bright ones fade slower than fainter ones . through our understanding of this relationship between brightness and decline rate , we can use these supernovae to probe distances up to several billions of light years away . but why is it important to see such distant objects anyway ? well , remember how fast light travels . for example , the light emitted by the sun will take eight minutes to reach us , which means that the light we see now is a picture of the sun eight minutes ago . when you look at the big dipper , you 're seeing what it looked like 80 years ago . and those smudgy galaxies ? they 're millions of light years away . it has taken millions of years for that light to reach us . so the universe itself is in some sense an inbuilt time machine . the further we can look back , the younger the universe we are probing . astrophysicists try to read the history of the universe , and understand how and where we come from . the universe is constantly sending us information in the form of light . all that remains if for us to decode it .

our milky way is on the order of 100,000 light years across . the nearest galaxy to our own , andromeda , is about 2.5 million light years away space is mind-blowingly vast . but wait , how do we know how far away stars and galaxies are ?

if a galaxy is 1 million light years away , the image that we take today is a picture of the galaxy when it was _______ younger .

you 're telling a friend an amazing story , and you just get to the best part when suddenly he interrupts , `` the alien and i , '' not `` me and the alien . '' most of us would probably be annoyed , but aside from the rude interruption , does your friend have a point ? was your sentence actually grammatically incorrect ? and if he still understood it , why does it even matter ? from the point of view of linguistics , grammar is a set of patterns for how words are put together to form phrases or clauses , whether spoken or in writing . different languages have different patterns . in english , the subject normally comes first , followed by the verb , and then the object , while in japanese and many other languages , the order is subject , object , verb . some scholars have tried to identify patterns common to all languages , but apart from some basic features , like having nouns or verbs , few of these so-called linguistic universals have been found . and while any language needs consistent patterns to function , the study of these patterns opens up an ongoing debate between two positions known as prescriptivism and descriptivism . grossly simplified , prescriptivists think a given language should follow consistent rules , while descriptivists see variation and adaptation as a natural and necessary part of language . for much of history , the vast majority of language was spoken . but as people became more interconnected and writing gained importance , written language was standardized to allow broader communication and ensure that people in different parts of a realm could understand each other . in many languages , this standard form came to be considered the only proper one , despite being derived from just one of many spoken varieties , usually that of the people in power . language purists worked to establish and propagate this standard by detailing a set of rules that reflected the established grammar of their times . and rules for written grammar were applied to spoken language , as well . speech patterns that deviated from the written rules were considered corruptions , or signs of low social status , and many people who had grown up speaking in these ways were forced to adopt the standardized form . more recently , however , linguists have understood that speech is a separate phenomenon from writing with its own regularities and patterns . most of us learn to speak at such an early age that we do n't even remember it . we form our spoken repertoire through unconscious habits , not memorized rules . and because speech also uses mood and intonation for meaning , its structure is often more flexible , adapting to the needs of speakers and listeners . this could mean avoiding complex clauses that are hard to parse in real time , making changes to avoid awkward pronounciation , or removing sounds to make speech faster . the linguistic approach that tries to understand and map such differences without dictating correct ones is known as descriptivism . rather than deciding how language should be used , it describes how people actually use it , and tracks the innovations they come up with in the process . but while the debate between prescriptivism and descriptivism continues , the two are not mutually exclusive . at its best , prescriptivism is useful for informing people about the most common established patterns at a given point in time . this is important , not only for formal contexts , but it also makes communication easier between non-native speakers from different backgrounds . descriptivism , on the other hand , gives us insight into how our minds work and the instinctive ways in which we structure our view of the world . ultimately , grammar is best thought of as a set of linguistic habits that are constantly being negotiated and reinvented by the entire group of language users . like language itself , it 's a wonderful and complex fabric woven through the contributions of speakers and listeners , writers and readers , prescriptivists and descriptivists , from both near and far .

and while any language needs consistent patterns to function , the study of these patterns opens up an ongoing debate between two positions known as prescriptivism and descriptivism . grossly simplified , prescriptivists think a given language should follow consistent rules , while descriptivists see variation and adaptation as a natural and necessary part of language . for much of history , the vast majority of language was spoken .

a dialect of a given language may become the standard variety of that language…

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

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

which diseases kill more people than ebola ?

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

the identity of an atom is determined only by the number of protons in its nucleus . hydrogen is hydrogen because it has just one proton , carbon is carbon because it has six , gold is gold because it has 79 , and so on . indulge me in a momentary tangent .

why did we choose gold for the last element in the video ?

translator : andrea mcdonough reviewer : bedirhan cinar every cell in your body is separated from those around it by its outermost layer , its membrane . a cell membrane must be both sturdy and flexible . imagine a membrane made of metal - great at keeping the cell 's guts inside , but horrible at letting materials flow in and out . but a membrane made of fishnet stocking would go too far in the opposite direction - leaky , but easily torn . so , the ideal membrane falls somewhere in the middle . over the past few centuries , we 've learned a lot about the way membranes work . the tale starts in the late 1800 's when , according to legend , a german woman named agnes pockels was doing dishes . her observation , that not all detergents dissolve grease in the same way , piqued her curiosity , so she made careful measurements of the size of soapy films that formed on the surface of a metal tray filled with water . later , in the 1920 's , ge scientists irving langmuir and katharine blodgett reexamined the problem with a more elaborate contraption and found that those tiny slicks were in fact a single layer of oil molecules . each oil molecule has one side that loves water and floats on the surface , and one side that loathes water and protrudes into the air . so what does it have to do with cell membranes ? well , at the turn of the 20th century , chemists charles overton and hans meyer demonstrated that the cell membrane is composed of substances that , like oil , have a water-loving part and a water-loathing part . we now call these substances lipids . in 1925 , two scientists , evert gorter and francois grendel , pushed our understanding further . they designed an experiment meant to test whether cell membranes are made of only one layer of lipids , a monolayer , or two layers stacked on top of one another , called a bilayer . gorter and grendel drew blood from a dog , a sheep , a rabbit , a goat , a guinea pig , and human volunteers . from each of these samples , they extracted all the lipids from all the red blood cells and placed a few drops of this extract on a tray of water . true to form , the lipids , like oil , spread out into a monolayer , whose size gorter and grendel could measure . if they compared the surface area of that monolayer to the surface area to the intact red blood cells , they 'd be able to tell whether the red blood cell membrane is one or two layers thick . to understand the design of their experiment , imagine looking down at a sandwich . if you measure the surface area of what you see , you 'll get the dimensions of a single slice of bread even though there are two slices , one stacked perfectly atop the other . but , if you open the sandwich and place the two slices side by side , you get twice the surface area . the gorter and grendel experiment is basically the same idea . the open sandwich is the monolayer formed by extracted cellular lipids spreading out into a sheet . the closed sandwich is the intact red blood cell membrane . low and behold , they observed a two-to-one ratio , proving beyond the shadow of a doubt that a cell membrane is a bilayer , which when unstacked , yields a monolayer twice its size . so almost 30 years before the double-helix structure of dna was elucidated , a single experiment involving fancy versions of household materials enabled deep insight into the basic architecture of the cell .

from each of these samples , they extracted all the lipids from all the red blood cells and placed a few drops of this extract on a tray of water . true to form , the lipids , like oil , spread out into a monolayer , whose size gorter and grendel could measure . if they compared the surface area of that monolayer to the surface area to the intact red blood cells , they 'd be able to tell whether the red blood cell membrane is one or two layers thick .

if you could be known for any discovery , what would it be and why ?

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

that 's why these methods require a prescription from a doctor . the choice of contraceptive method is a personal one , and what works best for you now may change later . scientists also continue to research new methods , such as a male pill that would prevent sperm production .

once a person chooses a type of contraceptive :

few individuals have influenced the world and many of today 's thinkers like plato . one 20th century philosopher even went so far as to describe all of western philosophy as a series of footnotes to plato . he created the first western university and was teacher to ancient greece 's greatest minds , including aristotle . but even one of the founders of philosophy was n't perfect . along with his great ideas , plato had a few that have n't exactly stood the test of time . so here are brief rundowns of a few of his best and worst ideas . plato argued that beyond our imperfect world was a perfect unchanging world of forms . forms are the ideal versions of the things and concepts we see around us . they serve as a sort of instruction manual to our own world . floating around the world of forms is the ideal tree , and the ideal youtube channel , and even the ideal justice , or ideal love . our own reality is comprised of imperfect copies of ideal forms . plato argued that philosophers should strive to contemplate and understand these perfect forms so that they may better navigate our misleading reality . while it may seem silly , the disconnect between the world as it appears and the greater truth behind it is one of philosophy 's most vexing problems . it 's been the subject of thousands of pages by theologians , philosophers , and screenwriters alike . it raises questions like should we trust our senses to come to the truth or our own reason ? for plato , the answer is reason . it alone provides us with at least the potential to contemplate the forms . but reason did n't always pan out for plato himself . when he sought to situate humankind amongst the animals , he lumped us in with birds . `` featherless bipeds '' was his official designation . diogenes the cynic , annoyed by this definition , stormed into plato 's class with a plucked chicken , announcing , `` behold . plato 's man . '' but back to a few good ideas . plato is one of the earliest political theorists on record , and with aristotle , is seen as one of the founders of political science . he reasoned that being a ruler was no different than any other craft , whether a potter or doctor , and that only those who had mastered the craft were fit to lead . ruling was the craft of contemplating the forms . in his republic , plato imagined a utopia where justice is the ultimate goal . plato 's ideal city seeks a harmonious balance between its individual parts and should be lead by a philosopher king . millennia before his time , plato also reasoned that women were equally able to rule in this model city . unfortunately , plato was inconsistent with women , elsewhere likening them to children . he also believed that a woman 's womb was a live animal that could wander around in her body and cause illness . this bad idea , also espoused by other contemporaries of plato , was sadly influential for hundreds of years in european medicine . furthermore , he thought that society should be divided into three groups : producers , the military , and the rulers , and that a great noble lie should convince everyone to follow this structure . the noble lie he proposed was that we 're all born with gold , silver , or a mixture of brass and iron in our souls , which determine our roles in life . some thinkers have gone on to credit the idea of the noble lie as a prototype for 20th century propaganda , and the philosopher king as inspiration for the dictators that used them . should a few bad ideas tarnish plato 's status as one of the greatest philosophers in history ? no ! plato gave the leaders and thinkers who came after him a place to start . through the centuries , we 've had the chance to test those ideas through writing and experience , and have accepted some while rejecting others . we are continuing to refine , amend , and edit his ideas which have become foundations of the modern world .

diogenes the cynic , annoyed by this definition , stormed into plato 's class with a plucked chicken , announcing , `` behold . plato 's man . '' but back to a few good ideas .

there are three groups in plato ’ s ideal society . these are :

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

in short , people tend to prefer things they 've been exposed to before . for example , a song comes on the radio that we do n't particularly like , but then we hear the song at the grocery store , at the movie theater and again on the street corner . soon , we are tapping to the beat , singing the words , even downloading the track .

have you ever disliked a song at first , and then come to like it ? why might that be ?

so here , this is a really quite unusual sample from goodfellow and you see this is samarium , so this is one of the lanthanides . ok so samarium is a beautiful element to work with as it can change what we refer to as oxidation states very easily which gives it many more things it can do in chemistry . it ’ s also a fascinating element in the sense that we can use it to date samples from the moon . so this is a sample of samarium and there ’ s is a very small amount of it here , perhaps half of a gram . but you know there 's some interesting things we can see about this package because we can see on this label it says “ packed in argon – handle with care. ” now it ’ s packed in argon because argon is very , very inert , it doesn ’ t react with anything , so it ’ s used to store , safely , this sample so that we can get it to carry out research . but i think that this sample has perhaps become damaged because , i think , the packets maybe broken because the samarium is gone and all you can see there inside is this white powder which , i suspect , is samarium oxide , so unfortunately not elemental samarium , but close . samarium is also very important because it ’ s a neutron absorber , which means it ’ s got a lot of use in nuclear power stations . basically to stop them going ‘ boom ’ .

it ’ s also a fascinating element in the sense that we can use it to date samples from the moon . so this is a sample of samarium and there ’ s is a very small amount of it here , perhaps half of a gram . but you know there 's some interesting things we can see about this package because we can see on this label it says “ packed in argon – handle with care. ” now it ’ s packed in argon because argon is very , very inert , it doesn ’ t react with anything , so it ’ s used to store , safely , this sample so that we can get it to carry out research . but i think that this sample has perhaps become damaged because , i think , the packets maybe broken because the samarium is gone and all you can see there inside is this white powder which , i suspect , is samarium oxide , so unfortunately not elemental samarium , but close . samarium is also very important because it ’ s a neutron absorber , which means it ’ s got a lot of use in nuclear power stations .

why was the sample of samarium that pete showed us packed in argon ?

what if i told you there were trillions of tiny bacteria all around you ? it 's true . microorganisms called bacteria were some of the first life forms to appear on earth . though they consist of only a single cell , their total biomass is greater than that of all plants and animals combined . and they live virtually everywhere : on the ground , in the water , on your kitchen table , on your skin , even inside you . do n't reach for the panic button just yet . although you have 10 times more bacterial cells inside you than your body has human cells , many of these bacteria are harmless or even beneficial , helping digestion and immunity . but there are a few bad apples that can cause harmful infections , from minor inconveniences to deadly epidemics . fortunately , there are amazing medicines designed to fight bacterial infections . synthesized from chemicals or occurring naturally in things like mold , these antibiotics kill or neutralize bacteria by interrupting cell wall synthesis or interfering with vital processes like protein synthesis , all while leaving human cells unharmed . the deployment of antibiotics over the course of the 20th century has rendered many previously dangerous diseases easily treatable . but today , more and more of our antibiotics are becoming less effective . did something go wrong to make them stop working ? the problem is not with the antibiotics but the bacteria they were made to fight , and the reason lies in darwin 's theory of natural selection . just like any other organisms , individual bacteria can undergo random mutations . many of these mutations are harmful or useless , but every now and then , one comes along that gives its organism an edge in survival . and for a bacterium , a mutation making it resistant to a certain antibiotic gives quite the edge . as the non-resistant bacteria are killed off , which happens especially quickly in antibiotic-rich environments , like hospitals , there is more room and resources for the resistant ones to thrive , passing along only the mutated genes that help them do so . reproduction is n't the only way to do this . some can release their dna upon death to be picked up by other bacteria , while others use a method called conjugation , connecting through pili to share their genes . over time , the resistant genes proliferate , creating entire strains of resistant super bacteria . so how much time do we have before these superbugs take over ? well , in some bacteria , it 's already happened . for instance , some strands of staphylococcus aureus , which causes everything from skin infections to pneumonia and sepsis , have developed into mrsa , becoming resistant to beta-lactam antibiotics , like penicillin , methicillin , and oxacillin . thanks to a gene that replaces the protein beta-lactams normally target and bind to , mrsa can keep making its cell walls unimpeded . other super bacteria , like salmonella , even sometimes produce enzymes like beta-lactams that break down antibiotic attackers before they can do any damage , and e. coli , a diverse group of bacteria that contains strains that cause diarrhea and kidney failure , can prevent the function of antibiotics , like quinolones , by actively booting any invaders that manage to enter the cell . but there is good news . scientists are working to stay one step ahead of the bacteria , and although development of new antibiotics has slowed in recent years , the world health organization has made it a priority to develop novel treatments . other scientists are investigating alternate solutions , such as phage therapy or using vaccines to prevent infections . most importantly , curbing the excessive and unnecessary use of antibiotics , such as for minor infections that can resolve on their own , as well as changing medical practice to prevent hospital infections , can have a major impact by keeping more non-resistant bacteria alive as competition for resistant strains . in the war against super bacteria , deescalation may sometimes work better than an evolutionary arms race .

some can release their dna upon death to be picked up by other bacteria , while others use a method called conjugation , connecting through pili to share their genes . over time , the resistant genes proliferate , creating entire strains of resistant super bacteria . so how much time do we have before these superbugs take over ?

a lack of antibiotics reduces overall bacterial death . how does this decrease the likelihood that antibiotic-resistant bacteria will outcompete non-resistant bacteria ?

the city sky is , frankly , rather boring . if you look up at the patches of murk between buildings , you might be able to pick out the big dipper , or perhaps , orion 's belt . but hold on . look at that murky patch again and hold our your thumb . how many stars do you think are behind it ? ten , twenty ? guess again . if you looked at that thumbnail-sized patch of sky with the hubble space telescope , instead of points of light , you 'd see smudges . these are n't stars . they 're galaxies , just like our milky way . cities of billions of stars , and more than 1,000 of them are hidden behind your thumb . the universe is bigger than you can see from the city , and even bigger than the starry sky you can see from the countryside . this is the universe as astrophysicists see it , with more stars than all the grains of sand on earth . by staring up at the stars at night , you 've taken part in the oldest science in human history . the study of the heavens is older than navigation , agriculture , perhaps even language itself . yet unlike other sciences , astronomy is purely observational . we can not control the parameters of our experiments from lab benches . our best technology can send man to the moon , and probes to the edge of the solar system . but these distances are vanishingly small compared to the yawning gulfs between stars . so how can we know so much about other galaxies , what they 're made of , how many there are , or that they 're even there at all ? well , we can start with the first thing we see when we look up at night : the stars . what we are trying to learn is their properties . what are they made of ? how hot are they ? how massive ? how old ? how far are they from earth ? and believe it or not , we can learn all of these things simply from the light shining in the sky . we can decipher one kind of stellar message by turning starlight into rainbows . when you look at a rainbow on earth , you 're really looking at light from our sun being scattered through water droplets in the atmosphere into all the different wavelengths that make it up . and we study the light from other stars , we can create rainbows on demand using not water droplets , but other specific instruments that disperse light . when we look at the scattered light from our sun , we see something strange : dark lines in our rainbow . these lines are the characteristic fingerprints of atoms . each type of atom in the solar atmosphere soaks up light at specific wavelengths , and the amount of absorption depends on how many of these atoms there are . so by observing how much light is missing at these characteristic wavelengths , we can tell not only what elements are in the sun 's atmosphere , but even their concentrations . and the same idea can be applied to study other stars . make a spectral rainbow , see what 's missing , and figure out which elements are present . bingo . now you know what stars are made of . but we are n't restricted to just the wavelengths that our eyes perceive . consider radio waves . yes , they can bring the billboard top 100 to your car , but they can also travel almost unimpeded through space . because they 've come so far , radio waves can tell us the very early history of the universe , from just a few thousand years after the big bang . we can also study the infrared light , emitted by colder objects , like the gas and dust clouds in space , and the ultraviolet light from the hot stars recently born from those clouds . studying different wavelengths not only gives us a more complete picture of any single object but also different views of the universe . for this reason , astrophysicists use several different kinds of telescopes covering the spectrum from the infrared to the ultraviolet to the x-ray , from giant radio dishes to giant silver mirrors to space satellites , detecting light that would be otherwise blocked by the earth 's atmosphere . astrophysicists do n't just see the billions of stars among the billions of galaxies in the universe . they hear , feel and sense them through many channels , each revealing a different story . but it all begins with light , the kind we can see and the kind we ca n't . want to know the secrets of the universe ? just follow the light .

if you looked at that thumbnail-sized patch of sky with the hubble space telescope , instead of points of light , you 'd see smudges . these are n't stars . they 're galaxies , just like our milky way .

it is impossible to send astronauts to other stars with the current technology , yet astronomers have been actively looking for lives on exoplanets ( i.e . planets orbiting other stars ) . from what we have learned about stars , how could scientists find other life out in space even though they can not send anybody there to investigate ?

this might seem hard to believe , but right now , 300 million women across the planet are experiencing the same thing : a period . the monthly menstrual cycle that leads to the period is a reality most women on earth will go through in their lives . but why is this cycle so universal ? and what makes it a cycle in the first place ? periods last anywhere between two and seven days , arising once within in a 28-day rotation . that whole system occurs on repeat , happening approximately 450 times during a woman 's life . behind the scenes are a series of hormonal controls that fine tune the body 's internal workings to make menstruation start or stop during those 28 days . this inner machinery includes two ovaries stocked with thousands of tiny sacks called follicles that each contain one oocyte , an unfertilized egg cell . at puberty , ovaries hold over 400 thousand egg cells , but release only one each month , which results in pregnancy or a period . here 's how this cycle unfolds . each month beginning around puberty , the hormone-producing pituitary gland in the brain starts releasing two substances into the blood : follicle stimulating hormone and luteinizing hormone . when they reach the ovaries , they encourage the internal egg cells to grow and mature . the follicles respond by pumping out estrogen . the egg cells grow and estrogen levels peak , inhibiting the production of fsh , and telling the pituitary to pump out more lh . that causes only the most mature egg cell from one of the ovaries to burst out of the follicle and through the ovary wall . this is called ovulation , and it usually happens ten to sixteen days before the start of a period . the tiny oocyte moves along the fallopian tube . a pregnancy can only occur if the egg is fertilized by a sperm cell within the next 24 hours . otherwise , the egg 's escapade ends , and the window for pregnancy closes for that month . meanwhile , the now empty follicle begins to release progesterone , another hormone that tells the womb 's lining to plump up with blood and nutrients in preparation for a fertilized egg that may embed there and grow . if it does n't embed , a few days later , the body 's progesterone and estrogen levels plummet , meaning the womb stops padding out and starts to degenerate , eventually falling away . blood and tissue leave the body , forming the period . the womb can take up to a week to clear out its unused contents , after which , the cycle begins anew . soon afterwards , the ovaries begin to secrete estrogen again , and the womb lining thickens , getting ready to accommodate a fertilized egg or be shed . hormones continually control these activities by circulating in ideal amounts delivered at just the right time . the cycle keeps on turning , transforming each day and each week into a milestone along its course towards pregnancy or a period . although this cycle appears to move by clockwork , there 's room for variation . women and their bodies are unique , after all . menstrual cycles occur at diffferent times in the month , ovulation comes at various points in the cycle , and some periods last longer than others . menstruation even begins and ends at different times in life for different women , too . in other words , variations between periods are normal . appreciating these differences and learning about this monthly process can empower women , giving them the tools to understand and take charge of their own bodies . that way , they 're able to factor this small cycle into a much larger cycle of life .

the tiny oocyte moves along the fallopian tube . a pregnancy can only occur if the egg is fertilized by a sperm cell within the next 24 hours . otherwise , the egg 's escapade ends , and the window for pregnancy closes for that month .

an egg has _____ to be fertilized .

every spring , hundreds of adventure-seekers dream of climbing qomolangma , also known as mount everest . at base camp , they hunker down for months waiting for the chance to scale the mountain 's lofty , lethal peak . but why do people risk life and limb to climb everest ? is it the challenge ? the view ? the chance to touch the sky ? for many , the draw is everest 's status as the highest mountain on earth . there 's an important distinction to make here . mauna kea is actually the tallest from base to summit , but at 8850 meters above sea level , everest has the highest altitude on the planet . to understand how this towering formation was born , we have to peer deep into our planet 's crust , where continental plates collide . the earth 's surface is like an armadillo 's armor . pieces of crust constantly move over , under , and around each other . for such huge continental plates , the motion is relatively quick . they move two to four centimeters per year , about as fast as fingernails grow . when two plates collide , one pushes into or underneath the other , buckling at the margins , and causing what 's known as uplift to accomodate the extra crust . that 's how everest came about . 50 million years ago , the earth 's indian plate drifted north , bumped into the bigger eurasian plate , and the crust crumpled , creating huge uplift . mountain everest lies at the heart of this action , on the edge of the indian-eurasian collision zone . but mountains are shaped by forces other than uplift . as the land is pushed up , air masses are forced to rise as well . rising air cools , causing any water vapor within it to condense and form rain or snow . as that falls , it wears down the landscape , dissolving rocks or breaking them down in a process known as weathering . water moving downhill carries the weathered material and erodes the landscape , carving out deep valleys and jagged peaks . this balance between uplift and erosion gives a mountain its shape . but compare the celestial peaks of the himalayas to the comforting hills of appalachia . clearly , all mountains are not alike . that 's because time comes into the equation , too . when continental plates first collide , uplift happens fast . the peaks grow tall with steep slopes . over time , however , gravity and water wear them down . eventually , erosion overtakes uplift , wearing down peaks faster than they 're pushed up . a third factor shapes mountains : climate . in subzero temperatures , some snowfall does n't completely melt away , instead slowly compacting until it becomes ice . that forms the snowline , which occurs at different heights around the planet depending on climate . at the freezing poles , the snowline is at sea level . near the equator , you have to climb five kilometers before it gets cold enough for ice to form . gathered ice starts flowing under its own immense weight forming a slow-moving frozen river known as a glacier , which grinds the rocks below . the steeper the mountains , the faster ice flows , and the quicker it carves the underlying rock . glaciers can erode landscapes swifter than rain and rivers . where glaciers cling to mountain peaks , they sand them down so fast , they lop the tops off like giant snowy buzzsaws . so then , how did the icy mount everest come to be so tall ? the cataclysmic continental clash from which it arose made it huge to begin with . secondly , the mountain lies near the tropics , so the snowline is high , and the glaciers relatively small , barely big enough to widdle it down . the mountain exists in a perfect storm of conditions that maintain its impressive stature . but that wo n't always be the case . we live in a changing world where the continental plates , earth 's climate , and the planet 's erosive power might one day conspire to cut mount everest down to size . for now , at least , it remains legendary in the minds of hikers , adventurers , and dreamers alike .

clearly , all mountains are not alike . that 's because time comes into the equation , too . when continental plates first collide , uplift happens fast .

describe the steps of mountain formation over time .

welcome to the ted-ed beta website tour . i 'm logan smalley , i 'm bedirhan cinar , i 'm jordan reeves , and i 'm stephanie lo . we represent the ted-ed team . we 're going to tell you about how the website is organized , about the lessons that surround each video , how you can customize or flip your own lesson , and how you can measure the lesson 's effect on your class or the world . towards the end of the tour , we 'll reveal one more major feature that directly affects every person viewing this video . let 's get started with the home page . on the home page , you 'll find original ted-ed videos , each is a lesson recorded by an actual educator that 's visualized by a professional animator . you can nominate educators and animators in the `` get involved '' section of the site . the ted-ed library can be browsed through two different lenses . learners can use the `` series '' view to browse videos thematically and based on their own curiosity . and teachers can use the browse by `` subject '' view to find the perfect short video to show in class or to assign as homework . every video on ted-ed is accompanied by a lesson . these lessons do n't replace good teaching , but they can be supplementary resources for students and teachers around the world . let 's look at this one , created by a teacher in the us and an animator in the uk . when you arrive on the lesson page , simply click play ; the video will continue to play as you navigate the lesson 's sections that surround it . in the `` quick quiz '' section , you 'll find multiple-choice questions that check for basic comprehension of the video . you get real-time feedback on your answers and if you get one wrong , you can use the video hint . you 'll find open-answer questions in the `` think '' section . and in the `` dig deeper '' section , you 'll find additional resources for exploring the topic . you can complete the lessons anonymously , but if you log in , you can track your own learning across the site . just visit the `` recent activity '' feed , and you 'll find answers you 've saved to lessons that you 've already started or completed . and now to one of the most powerful features of the ted-ed website : flipping a lesson . flipping a featured lesson allows you to edit each of the lesson 's sections . you can edit the title as it relates to your class . you can use the `` let 's begin '' section to provide instructions or context for the lesson . you can select or deselect any `` quick quiz '' question . in the `` think '' section , you can add your own open-answer questions . and in the `` dig deeper '' section , you can use the resources provided or add your own . when you finish flipping a lesson , it 'll publish to a new and unique url . and because the link is unique , it can measure the progress of any learner you share it with . you can use it to measure participation and accuracy of any individual student 's answers . so that 's how you flip a featured ted-ed video , we 've got one more major feature to tell you about . using the ted-ed platform , you can flip any video from youtube . that means you can create a lesson around any ted talk , any tedx talk , but also any of the other thousands of great educational videos on youtube , including the ones that you yourself could record , upload and flip . and through flipping these lessons , together we 'll create a free and remarkable library of lessons worth sharing .

let 's get started with the home page . on the home page , you 'll find original ted-ed videos , each is a lesson recorded by an actual educator that 's visualized by a professional animator . you can nominate educators and animators in the `` get involved '' section of the site .

how do you nominate an educator or animator ?

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

`` and what were these crimes ? '' `` your honor , the watergate scandal was one of the grossest abuses of presidential power in history . nixon 's men broke into the democratic national committee headquarters to wiretap the offices and dig up dirt on opponents for the reelection campaign . ''

what did the watergate scandal involve ?

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 !

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 ?

what is tyler writing about ?

there 's a prevailing attitude that art does n't matter in the real world . but the study of art can enhance our perception and our ability to translate to others what we see . those skills are useful . those skills can save lives . doctors , nurses , and law enforcement agents can use painting , sculpture , and photography as tools to improve their visual acuity and communication skills , which are critical during investigations and emergencies . if you 're treating an injury , investigating a crime scene , or trying to describe either of those things to a colleague , art can make you better at it . here , imagine you 're a seasoned cop or a dedicated doctor , but also imagine you are at a museum and let 's look at a painting . rene magritte 's `` time transfixed '' of 1938 depicts a mysterious and complex interior that invites analysis not unlike that required of a patient 's symptoms or the scene of a crime . a miniature train whose origin and destination are unknown is emerging from a fireplace , and the smoke from the locomotive appears to flow up the chimney as if from the fire that is conspicuously absent below . the eeriness of the scene is echoed in the empty living room , enhanced by wood-grain floors and decorative wall moldings to the right of the fireplace . perched atop the mantelpiece are two candlesticks and a clock . behind these objects is a large mirror that reveals an empty interior and only a partial reflection of the objects before it . the juxtaposition of the objects surrounding the moving train raises numerous questions for which there seem to be no apparent answers . did i summarize the painting accurately or leave any details out ? it 's no big deal if you see something else in a painting , but what if we 're both seasoned cops ? i call you for back-up . you show up only to realize the two bank robbing ninjas i 'd mentioned were actually six bank robbing ninjas with lasers . close study of art can train viewers to study thoroughly , analyze the elements observed , articulate them succinctly , and formulate questions to address the seeming inconsistencies . scrutinizing the details of an unfamiliar scene , in this case the work of art , and accurately conveying any observable contradictions is a critically important skill for both people who look at x-rays and those who interrogate suspects . let 's interrogate this painting , shall we ? okay , magritte , that 's quite a little picture you 've painted . but why are n't there any train tracks ? why no fire ? what happened to the candles ? why does n't the fireplace have a little tunnel for the train ? it just comes straight through the wall . and the clock says it 's about quarter to one , but i 'm not sure the light that comes through the window at an angle says it 's just past noontime . what 's this painting all about , anyway ? that 's when you , my trusty partner , hold me back , then i leave . you give magritte a cup of coffee and keep grilling him to see if this painting would hold up in court . viewers can provide a more detailed and accurate description of a situation by articulating what is seen and what is not seen . this is particularly important in medicine . if an illness is evidenced by three symptoms and only two are present in a patient , a medical professional must explicitly state the absence of that third symptom , signifying that the patient may not have the condition suspected . articulating the absence of a specific detail or behavior known as the pertinent negative is as critical as stating the details and behaviors that are present in order to treat the patient . and conspicuous absences are only conspicuous to eyes trained to look for them . art teaches professionals across a wide spectrum of fields not only how to ask more effective questions about what can not be readily answered , but also , and more importantly , how to analyze complex , real world situations from a new and different perspective , ultimately solving difficult problems . intense attention to detail , the ability to take a step back and look differently , we want first responders to have the analytical skills of master art historians at least . art trains us to investigate , and that 's a real world skill if there ever was one .

there 's a prevailing attitude that art does n't matter in the real world . but the study of art can enhance our perception and our ability to translate to others what we see . those skills are useful . those skills can save lives . doctors , nurses , and law enforcement agents can use painting , sculpture , and photography as tools to improve their visual acuity and communication skills , which are critical during investigations and emergencies .

art can be used in which of the following professions to enhance observation and perception skills :

so here we have tin , but this is a different sample of tin from what people might be used to because most people see tin in foil , or they think it is tin foil that they use to wrap up the chicken , mostly that is aluminium foil . tin has the symbol sn because it comes from the latin word stannum which means tin and in fact if you go to devon in the southwest of england you will find that some of the towns there are called stannary towns because that ’ s where they used to mine and trade in tin . tin has a very old role in trade and in technology . bronze which people used in the old days was an alloy of tin and copper which gave better swords than copper , so if you were fighting with somebody who had a copper sword and you had a bronze one , you won , at least if you were quick . here we see a beautiful sample of tin metal and you can see it is a really beautiful rod and it is packaged in glass to stop oxidation , but you can see a beautiful silvery shiny metal . tin has also been used very widely for coating the insides of iron and steel containers for food , that ’ s why they are called tin even though they were made from iron but they had a thin coating of tin on the surface , and tin is also used very widely for solder , for putting together metal components or electronic components . lovely sample of tin , so we will pop that back in and back into the drawer .

here we see a beautiful sample of tin metal and you can see it is a really beautiful rod and it is packaged in glass to stop oxidation , but you can see a beautiful silvery shiny metal . tin has also been used very widely for coating the insides of iron and steel containers for food , that ’ s why they are called tin even though they were made from iron but they had a thin coating of tin on the surface , and tin is also used very widely for solder , for putting together metal components or electronic components . lovely sample of tin , so we will pop that back in and back into the drawer .

tin soldiers were almost never made of pure tin . which alloys were used to make these soldiers for children ?

we already know that the world is made of things , things like cats and macaroni salad , and macaroni salad is made of things like mayo and mustard and celery , which are all made of molecules . as we 'll see , these molecules are made of the same stuff , just mixed together in different ways . let 's go back to our macaroni salad . we 've already unmixed things physically as much as we can . now , we 'll go further and unmix things chemically by breaking some bonds . many larger , complex molecules are just a bunch of smaller molecules bonded together like building blocks . here , again , macaroni salad provides a nice example . if you look at the pasta , you 'll notice it 's made of a lot of this stuff , starch , which is this molecule , otherwise known as amylose . turns out , if you break some bonds , amylose is made up of smaller molecules of glucose , a simple sugar . if you take a bunch of these same glucose molecules and rearrange them in a different way , you get cellulose , which is what plants are made of . so , while this piece of pasta made of amylose and this wooden spoon made of cellulose look vastly different , they 're both essentially made of the same molecules , just stuck together differently . this type of breaking apart and recombining is what goes on when you digest food . the complex proteins found in the foods we eat , like carrots and eggs , ca n't be used by our bodies because we are not carrots or chickens . what we can use are the smaller molecules that make up these proteins , the amino acids . during digestion , our bodies break these proteins up into their amino acids so they can be rearranged and put back together to make human proteins . but let 's keep breaking bonds . all molecules are made up of atoms bonded together . if some molecules are building blocks , atoms are the building blocks of the building blocks . and you 'll notice that with the molecules from macaroni salad , the same six types of atoms keep showing up : carbon , hydrogen , oxygen , nitrogen , phosphorus , and sulfur , or chonps . there 's a few others , but the big six is what macaroni salad is made of . if we went a step further , we could use these same atoms , recombine them , and make other stuff like gasoline or sulfuric acid , methane , and nylon . it 's all made from the same elements that make up macaroni salad . so , to recap , everything is made of atoms . they are the stuff that things are made of . atoms are grouped together in different ways to form molecules . these molecules are constantly being combined , broken apart , and recombined . they get thrown into mixtures , separated , remixed over and over and over again . the stuff that things are made of is always in flux ; it 's always changing . macaroni salad is only macaroni salad for a short time . you eat it , some of it becomes part of you , the rest eventually goes into the ocean and gets eaten by other animals that die , and after millions of years , they turn into oil , which is where gasoline comes from . and that 's why gasoline and macaroni salad are not that different - they 're both made of the same stuff , just one tastes better .

here , again , macaroni salad provides a nice example . if you look at the pasta , you 'll notice it 's made of a lot of this stuff , starch , which is this molecule , otherwise known as amylose . turns out , if you break some bonds , amylose is made up of smaller molecules of glucose , a simple sugar .

which is the starch molecule ?

translator : andrea mcdonough reviewer : morton bast i 'm a mechanical engineering professor at the university of pennsylvania , and my favorite hobby is photography . and as i travel around the world , i love taking photographs like these , so i can remember all the beautiful and interesting things that i 've seen . but what i ca n't do is record and share how these objects feel to touch . and that 's kind of surprising , because your sense of touch is really important . it 's involved in every physical interaction you do every day , every manipulation task , anything you do in the world . so the sense of touch is actually pretty interesting . it has two main components . the first is tactile sensations , things you feel in your skin . and the second is kinesthetic sensations . this has to do with the position of your body and how it 's moving , and the forces you encounter . and you 're really good at incorporating both of these types of sensations together to understand the physical interactions you have with the world and understand as you touch a surface : is it a rock , is it a cat , is it a bunny , what is it ? and so , as an engineer , i 'm really fascinated and i have a lot of respect for how good people are with their hands . and i 'm intrigued and curious about whether we could make technology better by doing a better job at leveraging the human capability with the sense of touch . could i improve the interfaces to computers and machines by letting you take advantage of your hands ? and indeed , i think we can , and that 's at the core of a field called haptics , and this is the area that i work in . it 's all about interactive touch technology . and the way it works is , as you move your body through the world , if , as an engineer , i can make a system that can measure that motion , and then present to you sensations over time that kind of make sense , that match up with what you might feel in the real world , i can fool you into thinking you 're touching something even though there 's nothing there . so here are three examples and these are all done from research in my lab at penn . the first one is all about that same problem that i was showing you : how can we capture how objects feel and recreate those experiences ? so the way we solve this problem is by creating a hand-held tool that has many different sensors inside . it has a force sensor , so we can tell how hard you 're pushing ; it has motion tracking , so we can tell exactly where you 've moved it ; and it has a vibration sensor , an accelerometer , inside , that detects the shaking back and forth of the tool that lets you know that 's a piece of canvas and not a piece of silk or something else . then we take the data we record from these interactions . here 's ten seconds of data . you can see how the vibrations get larger and smaller , depending on how you move . and we make a mathematical model of those relationships and program them into a tablet computer so that when you take the stylus and go and touch the screen , that voice-coil actuator in the white bracket plays vibrations to give you the illusion that you 're touching the real surface , just like if you touched , dragged back and forth , on the real canvas . we can create very compelling illusions . we can do this for all kinds of surfaces and it 's really a lot of fun . we call it haptography -- haptic photography . and i think it has potential benefits in all sorts of areas like online shopping , maybe interactive museum exhibits , where you 're not supposed to touch the precious artifacts , but you always want to . the second example i want to tell you about comes from a collaboration i have with dr. margrit maggio at the penn dental school . part of her job is to teach dental students how to tell where in a patient 's mouth there are cavities . of course they look at x-rays , but a large part of this clinical judgment comes from what they feel when they touch your teeth with a dental explorer . you 've all had this happen , they go across . what they 're feeling for is if the tooth is really hard , then it 's healthy , but if it 's kind of soft and sticky , that 's a signal that the enamel is starting to decay . these types of judgments are hard for a new dental student to make , because they have n't touched a lot of teeth yet . and you want them to learn this before they start practicing on real human patients . so what we do is add an accelerometer on to the dental explorer , and then we record what dr. maggio feels as she touches different extracted teeth . and we can play it back for you as a video with a touch track -- not just a sound track , but also a touch track , that you can feel by holding that repeating tool . you feel the same things the dentist felt when they did the recording , and practice making judgments . so here 's a sample one . here 's a tooth that looks kind of suspicious , right ? it has all those brown stains . you might be thinking , `` we should definitely put a filling in this tooth . '' but if you pay attention to how it feels , all the surfaces of this tooth are hard and healthy , so this patient does not need a filling . and these are exactly the kind of judgments doctors make every day and i think this technology we 've invented has a lot of potential for many different things in medical training , because it 's really simple and it does a great job at recreating what people feel through tools . i think it could also help make games more interactive and fun and more realistic in the sensations that you feel . the last example i want to tell you about is again about human movement . so if any of you have ever learned sports , how do you get good at something like surfing ? you practice . you practice some more and more , right ? making small corrections , maybe getting some input from a coach , learning how to improve your motions . i think we could use computers to help make that process more efficient and more fun . and so here , for example , if i have six different arm movements that i want you to learn , you come into my lab at penn and try out our system . we use a kinect to measure your motions , we show graphics on the screen , and then we also give you touch cues , haptic feedback on your arm , delivered by these haptic arm bands which have motors inside , and guide you as you move . so , if we put it together , as you 're trying to track this motion , if you deviate -- say , maybe , your arm is a little too high -- we turn on the motors right there on the skin to let you know you should move down , almost like a coach gently guiding you and helping you master these movements more quickly and make more precise corrections . we developed this system for use in stroke rehabilitation , but i think there are a lot of applications , like maybe dance training or all sorts of sports training as well . so now you know a little bit about the field of haptics , which i think you 'll hear more about in the coming years . i 've shown you three examples . i just want to take a moment to acknowledge the great students who work with me in my lab at penn and my collaborators . they 're a great group . i also want to thank you for your kind attention . ( applause )

and indeed , i think we can , and that 's at the core of a field called haptics , and this is the area that i work in . it 's all about interactive touch technology . and the way it works is , as you move your body through the world , if , as an engineer , i can make a system that can measure that motion , and then present to you sensations over time that kind of make sense , that match up with what you might feel in the real world , i can fool you into thinking you 're touching something even though there 's nothing there .

what is the word used to describe interactive touch technology ?

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

what is the shape of a molecule ? well , a molecule is mostly empty space . almost all of its mass is concentrated in the extremely dense nuclei of its atoms .

by volume , a molecule is mostly ________ .