(Glazba)
One of the funny things about owning a brain is that you have no control over the things that it gathers and holds onto, the facts and the stories. And as you get older, it only gets worse. Things stick around for years sometimes before you understand why you're interested in them, before you understand their import to you. Here's three of mine. When Richard Feynman was a young boy in Queens, he went for a walk with his dad and his wagon and a ball. He noticed that when he pulled the wagon, the ball went to the back of the wagon. He asked his dad, "Why does the ball go to the back of the wagon?" And his dad said, "That's inertia." He said, "What's inertia?" And his dad said, "Ah. Inertia is the name that scientists give to the phenomenon of the ball going to the back of the wagon." (Laughter) "But in truth, nobody really knows." Feynman went on to earn degrees at MIT, Princeton, he solved the Challenger disaster, he ended up winning the Nobel Prize in Physics for his Feynman diagrams, describing the movement of subatomic particles. And he credits that conversation with his father as giving him a sense that the simplest questions could carry you out to the edge of human knowledge, and that that's where he wanted to play. And play he did. Eratosthenes was the third librarian at the great Library of Alexandria, and he made many contributions to science. But the one he is most remembered for began in a letter that he received as the librarian, from the town of Swenet, which was south of Alexandria. The letter included this fact that stuck in Eratosthenes' mind, and the fact was that the writer said, at noon on the solstice, when he looked down this deep well, he could see his reflection at the bottom, and he could also see that his head was blocking the sun. I should tell you -- the idea that Christopher Columbus discovered that the world is spherical is total bull. It's not true at all. In fact, everyone who was educated understood that the world was spherical since Aristotle's time. Aristotle had proved it with a simple observation. He noticed that every time you saw the Earth's shadow on the Moon, it was circular, and the only shape that constantly creates a circular shadow is a sphere, Q.E.D. the Earth is round. But nobody knew how big it was until Eratosthenes got this letter with this fact. So he understood that the sun was directly above the city of Swenet, because looking down a well, it was a straight line all the way down the well, right past the guy's head up to the sun. Eratosthenes knew another fact. He knew that a stick stuck in the ground in Alexandria at the same time and the same day, at noon, the sun's zenith, on the solstice, the sun cast a shadow that showed that it was 7.2 degrees off-axis. If you know the circumference of a circle, and you have two points on it, all you need to know is the distance between those two points, and you can extrapolate the circumference. 360 degrees divided by 7.2 equals 50. I know it's a little bit of a round number, and it makes me suspicious of this story too, but it's a good story, so we'll continue with it. He needed to know the distance between Swenet and Alexandria, which is good because Eratosthenes was good at geography. In fact, he invented the word geography. (Laughter) The road between Swenet and Alexandria was a road of commerce, and commerce needed to know how long it took to get there. It needed to know the exact distance, so he knew very precisely that the distance between the two cities was 500 miles. Multiply that times 50, you get 25,000, which is within one percent of the actual diameter of the Earth. He did this 2,200 years ago. Now, we live in an age where multi-billion-dollar pieces of machinery are looking for the Higgs boson. We're discovering particles that may travel faster than the speed of light, and all of these discoveries are made possible by technology that's been developed in the last few decades. But for most of human history, we had to discover these things using our eyes and our ears and our minds. Armand Fizeau was an experimental physicist in Paris. His specialty was actually refining and confirming other people's results, and this might sound like a bit of an also-ran, but in fact, this is the soul of science, because there is no such thing as a fact that cannot be independently corroborated. And he was familiar with Galileo's experiments in trying to determine whether or not light had a speed. Galileo had worked out this really wonderful experiment where he and his assistant had a lamp, each one of them was holding a lamp. Galileo would open his lamp, and his assistant would open his. They got the timing down really good. They just knew their timing. And then they stood at two hilltops, two miles distant, and they did the same thing, on the assumption from Galileo that if light had a discernible speed, he'd notice a delay in the light coming back from his assistant's lamp. But light was too fast for Galileo. He was off by several orders of magnitude when he assumed that light was roughly ten times as fast as the speed of sound. Fizeau was aware of this experiment. He lived in Paris, and he set up two experimental stations, roughly 5.5 miles distant, in Paris. And he solved this problem of Galileo's, and he did it with a really relatively trivial piece of equipment. He did it with one of these. I'm going to put away the clicker for a second because I want to engage your brains in this. So this is a toothed wheel. It's got a bunch of notches and it's got a bunch of teeth. This was Fizeau's solution to sending discrete pulses of light. He put a beam behind one of these notches. If I point a beam through this notch at a mirror, five miles away, that beam is bouncing off the mirror and coming back to me through this notch. But something interesting happens as he spins the wheel faster. He notices that it seems like a door is starting to close on the light beam that's coming back to his eye. Why is that? It's because the pulse of light is not coming back through the same notch. It's actually hitting a tooth. And he spins the wheel fast enough and he fully occludes the light. And then, based on the distance between the two stations and the speed of his wheel and the number of notches in the wheel, he calculates the speed of light to within two percent of its actual value. And he does this in 1849. This is what really gets me going about science. Whenever I'm having trouble understanding a concept, I go back and I research the people that discovered that concept. I look at the story of how they came to understand it. What happens when you look at what the discoverers were thinking about when they made their discoveries, is you understand that they are not so different from us. We are all bags of meat and water. We all start with the same tools. I love the idea that different branches of science are called fields of study. Most people think of science as a closed, black box, when in fact it is an open field. And we are all explorers. The people that made these discoveries just thought a little bit harder about what they were looking at, and they were a little bit more curious. And their curiosity changed the way people thought about the world, and thus it changed the world. They changed the world, and so can you. Thank you. (Applause)
Jedna od čudnih stvari kada posjedujete mozak je da nemate nikakvu kontrolu nad stvarima koje skuplja i zadržava, činjenice i priče. I što postajete stariji, to postaje gore. Stvari ostaju godinama dok ne shvatite zašto ste zainteresirani za njih, prije nego svhatite njihovu važnost za vas. Ovdje su tri moje. Kada je Richard Feynman bio mladi dječak u Queensu, otišao je u šetnju sa svojim ocem, svojim kolicima i loptom. I primjetio je da kada vuče kolica, lopta ide prema stražnjem kraju. I pitao je svog oca, "Zašto lopta ide prema stražnjem kraju kolica?" I njegov otac je rekao, "To je inercija." Rekao je, "Što je inercija?" I njegov otac je rekao: "Ah, inercija je ime koje su znanstvenici dali fenomenu lopte koja ide prema stražnjem dijelu kolica. Ali zapravo, nitko ne zna." Feynman je prikupio diplome na MIT-u, Princetonu, riješio je katastrofu Challengera, i na kraju je dobio Nobelovu nagradu iz Fizike zbog Feynmanovih dijagrama koji opisuju kretanje subatomskih čestica. I on pripisuje zasluge razgovoru sa svojim ocem jer su mu dali osjećaj da ga najednostavnija pitanja mogu odnijeti do ruba ljudskog znanja, i da je to mjesto gdje se on želi igrati. I igrao se. Eratosten je bio treći knjižničar velike knjižnice u Aleksandriji i dao je mnoge doprinose znanosti. Ali ono po čemu se najviše pamti započelo je u pismu koje je primio kao knjižničar iz grada Sweneta, koji je bio južno od Aleksandrije. Pismo je uključivalo činjenicu koja se zaglavila u Eratostenovu umu, i činjenica je bila da je pisac rekao da u podne na solsticiji, kad pogleda u svoj duboki bunar, može vidjeti svoj odraz na dnu, i da također može vidjeti da je njegova glava blokirala sunce. Sad, moram vam reći -- ideja da je Christopher Columbus otkrio da je svijet sferičan je potpuno netočna. Uopće nije istina. Zapravo, svatko tko je bi educiran shvaćao je da je svijet sferičan od Aristotelovog vremena, i Aristotel je to dokazao sa jednostavnom opservacijom. Primjetio je da svakog puta kada je vidio Zemljinu sjenu na Mjesecu, ona je bila kružna, i jedini oblik koji uvijek stvara okruglu sjenu je sfera, dakle Zemlja je okrugla. Ali nitko nije znao kako je velika dok Eratostenes nije dobio pismo s ovom činjenicom. Tako da je shvaćao da je sunce direktno iznad grada Sweneta, jer gledajući niz bunar, to je bila ravna crta dolje niz bunar, ravno pored glave tog tipa do sunca. Eratostenes je znao još jednu činjenicu. Znao je da štap zabijen u zemlju u Aleksandriji u isto vrijeme i istog dana, u podne, u sunčev zenit, na solsticij, sunce bi bacalo sjenu koja je pokazivala da je 7,2 stupnja izvan osi. Sada, ako znate obujam kruga, i imate dvije točke na njemu, sve što trebate je udaljenost između ove dvije točke, kako biste izračunali obujam. Tristo šezdeset stupnjeva podijeljeno sa 7,2 jednako je 50. Znam da je poprilično okrugao broj, i čini i mene sumnjičavim u svezi ove priče, ali to je dobra priča, pa ćemo nastaviti s njom. Trebao je znati udaljenost između Sweneta i Aleksandrije, što je dobro jer je Eratosten bio dobar u geografiji. Zapravo, izmislio je riječ geografija. Cesta između Sweneta i Aleksandrije bila je cesta trgovanja, i trgovci su morali znati koliko im dugo treba da tamo dođu, trabali su znati točnu udaljenost, tako da je znao vrlo precizno da je udaljenost između dva grada 500 milja. Pomnožite to sa 50 i dobijete 25000, što je unutar jedan posto stvarnog promjera Zemlje. Ovo je učinio prije 2200 godina. Sad živimo u dobu gdje multi-milijarderski uređaji traže Higgsov boson. Otkrivamo čestice koje možda putuju brže od brzine svjetlosti, i sva ova otkrića su moguća zbog tehnologije koja je razvijena u posljednjih nekoliko desetljeća. Ali za većinu ljudske povijesti, morali smo otkriti te stvari koristeći naše oči i uši i naše umove. Armand Fizeau je eksperimentalni fizičar u Parizu. Njegova specijalnost je zapravo pročišćavanje i potvrđivanje rezultata drugih, i ovo će se možda činiti malo kao pirovo istraživanje, ali zapravo ovo je duša znanosti, jer nema činjenice koja ne može biti neovisno potkrijepljena. I on je bio upoznat sa Galileovim eksperimentima u kojima je pokušao utvrditi ima li ili ne svjetlo brzinu. Dakle, Galileo je smislio jedan zaista divan eksperiment gdje su on i njegov asistent imali lampu, i svatko od njih je držao lampu. I Galileo je otvorio svoju lampu, i asistent bi otvorio svoju. I stvarno su dobro svladali tempiranje. Znali su tempiranje. I onda su stali na dva vrha brda, udaljenih oko dvije milje, i učinili istu stvar pod pretpostavkom Galilea da ako svjetlo ima primjetnu brzinu, on će primjetiti zaostajanje u povratku svjetlosti iz asistentove lampe. Ali svjetlost je bila prebrza za Galilea. Promašio je za nekoliko redova veličine kada je pretpostavio da je svjetlost otprilike 10 puta brža od brzine zvuka. Fizeau je bio svjestan ovog eksperimenta. Živio je u Parizu, i postavio je dvije eksperimentalne stanice, udaljene optilike pet i pol milja u Parizu. I riješio je Galileov problem, i učinio je to sa prilično trivijalnim komadom opreme. Učinio je to s ovime. Maknut ću kliker na sekundu jer želim da uključite vaš mozak u ovo. Ovo je nazubljeni kotač. Ima puno zareza i ima hrpu zubaca. Ovo je bilo Fizeauovo rješenje za slanje diskretnih pulsova svjetlosti. Postavio bi zraku iza jednog od ovih zareza. Ako usmjerim zraku kroz ovaj zarez prema zrcalu, pet milja udaljenom, zraka se odbija od zrcala i dolazi natrag kroz ovaj zarez. Ali nešto interesantno događa se kako okreće kotač brže. Primjećuje da se ponaša kao da se vrata zatvaraju iznad zrake koja se vraća njegovom oku. Zašto je to tako? Zato što puls svjetlosti ne stiže natrag kroz isti zarez, već pogađa zubac. I vrti kotač dovoljno brzo i u potpunosti zaklanja svjetlost. I onda, na osnovu udaljenosti dvaju stanica i brzine kojom se njegov kotač kreće i broja zareza na kotaču, računa brzinu svjetlosti unutar dva posto njene stvarne vrijednosti. I to čini 1849. To me stvarno pokreće u znanosti. Kad god imam problema sa shvaćanjem koncepta, vratim se i istražujem ljude koji su otkrili taj koncept. Gledam priču kako su došli do toga da to shvaćaju. I ono što se dogodi kada gledate što su oni koji su otkrili razmišljali kada su došli do svojih otkrića, je da shvaćate da nisu tako različiti od nas. Svi smo mi vreće mesa i vode. I svi počinjemo s istim alatima. Volim ideju da se grane znanosti zovu polja istraživanja. Većina ljudi gleda na znanost kao zatvorenu, crnu kutiju, kad je zapravo otvoreno polje. I mi smo svi istraživači. Ljudi koji su napravili ova otkrića su samo malo više razmišljali o tome što su gledali, i bili su malo znatiželjniji. I njihova znatiželja promijenila je način na koji ljudi gledaju svijet, i zato je promijenila svijet. Oni su promijenili svijet, i možete i vi. Hvala vam. (Pljesak)