(Glasba)
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)
Ena od zanimivih stvari o možganih je ta, da nimamo nadzora nad tem, kar možgani sprejemajo in obdržijo; to so zgodbe in dejstva. Ko se staramo, postane še hujše. Stvari včasih ždijo leta in leta, preden razumemo, zakaj nas zanimajo in kaj nam prinaša njihov vnos. Podal vam bom tri zgodbe. Ko je bil Richard Feynman še fantek, živeč v Queensu je bil na sprehodu s svojim očetom, s sabo pa je imel še voziček in žogo. Opazil je, da ko je vlekel voziček za seboj, se je žoga zakotalila proti koncu vozička. Očeta je vprašal: "Zakaj se je žoga premaknila proti koncu?" Oče pa mu je odvrnil: "Temu se reče vztrajnost." Richard je vprašal: "Kaj pa je to?" Oče mu je odgovoril: "Vztrajnost je ime, ki so ga dali znastveniki pojavu, ko se žoga zakotali proti koncu vozička. V resnici pa noben ne ve, kaj je to." Feynman je diplomiral na MIT-u, Princetonu, razložil je nesrečo raketoplana Challenger, dobil je Nobelovo nagrado za fiziko za lastne Feynmanove diagrame, ki so opisovali premikanje osnovnih delcev. Zasluge pripisuje temu pogovoru z očetom. Dal mu je občutek, da nas lahko preprosta vprašanja popeljejo na kraj človeškega védenja in tam se je hotel malce poigrati. In se je. Eratosten je bil tretji knjižničar v veliki knjižnici v Aleksandriji in je veliko pripomogel k znanosti. Zgodba o dosežku, po katerem je najbolj znan se je začela s pismom, ki ga je prejel kot knjižničar, iz mesta Swenet, južno od Aleksandrije. V pismu je bilo navedeno dejstvo o katerem je premišljeval Eratosten. Pošiljatelj je zapisal, da ko je opoldne na sončev solsticij pogledal v globok vodnjak, je lahko videl svoj odsev na dnu in da je njegova glava delala senco. Naj vam kar zdaj povem. Ideja, da je Krištof Kolumb odkril, da je svet okrogel je neumnost. To sploh ni res. Pravzaprav, že od časa Aristotla je vsak izobraženec s preprostim opazovanjem razumel, in to je Aristotel tudi dokazal, da je svet okrogel. Opazili so, da vsakič, ko se je videla Zemljina senca na površju Lune je bila senca okrogla. Edina oblika, ki meče tako senco je krogla, kar dokazuje, da je Zemlja okrogla. Nihče pa ni vedel, kako velika je, dokler ni Eratosten dobil tistega pisma. Razumel je, da je sonce direktno nad mestom Swenet, kajti če gledaš v vodnjak, je bilo tako kot da bi ravna črta, potekala mimo glave v vodnjak. Eratosten je vedel še nekaj. Palica je, zapičena v tla v Aleksandriji ob istem dnevu, ob istem času, opoldne, ko je sonce v zenitu, ob solsticiju metala senco pod kotom 7,2 stopinji. Če poznate obseg kroga in imate dve točki na njem, potem morate samo vedeti razdaljo med tistima točkama, da ekstrapolirate obseg. 360 stopinj, deljeno z 7,2 je enako 50. Vem, da je okrogla številka in celo jaz sem sumničav do te zgodbe ampak je dobra, zato bom nadaljeval. Erastoten je rabil vedeti, koliko je razdalja med Swenetom in Aleksandrijo. To je dobro, kajti geografija mu je šla od rok. Pravzaprav je ustvaril besedo "geografija". Pot med Swenetom in Aleksandrijo je bila trgovska pot in trgovci so morali vedeti, koliko časa je trajala pot. Morali so vedeti natančno razdaljo in on je točno vedel, da je razdalja med mestoma 500 milj (približno 805 km). Pomnožite s 50 in dobite 25.000 milj (40.233 km), kar odstopa za približno 1 odstotek od dejanskega premera Zemlje. To je izračunal 2.200 let nazaj. Živimo v dobi, ko oprema, vredna več milijard dolarjev išče Higgsov bozon. Odkrivamo delce, ki lahko potujejo hitreje od svetlobe in takšna odkritja so možna s tehnologijo, ki so jo razvili v zadnjih desetletjih. Toda večino časa v naši zgodovini smo morali odkriti take stvari z očmi, ušesi in umom. Armand Fizeau je bil eksperimentalni fizik v Parizu. Njegova posebnost je bila, da je dodeloval in potrjeval rezultate drugih ljudi in morda zveni kot pobiranje zaslug toda to je pravzaprav bistvo znanosti, ker nobeden ne more kar sam potrditi nekega dejstva. Poznal je Galilejeve poskuse, ko je skušal določiti svetlobi njeno hitrost. Galileo je izvedel čudovit poskus. On in njegov pomočnik sta imela vsak svojo svetilko. Galileo je posvetil s svojo, isto je storil tudi pomočnik. Bila sta res dobro usklajena. Preprosto sta to vedela. Potem sta stala na dveh hribih, približno 3,2 km narazen in ponovila poskus. Galileo je domneval, da če ima svetloba razpoznavno hitrost, bi opazil zakasnitev, ko bi pomočnik posvetil s svojo svetilko. Ampak svetloba je bila prehitra za Galileja. Za kar nekajkrat je napačno domneval, da je svetloba približno desetkrat hitrejša od zvoka. Fizeau je poznal ta poskus. Živel je v Parizu in je postavil dve eksperimentalni postaji, oddaljeni med seboj približno 8,6 km. Rešil je Galilejevo zagato tako, da je uporabil relativno vsakdanjo opremo. Uporabil je eno od teh. Za nekaj časa bom pospravil daljinec, ker hočem, da malce razmišljate zraven. Tole je zobato kolesce. Ima zareze in zobce. Tako je Fizeau lahko pošiljal ločene curke svetlobe. Za eno od teh zarez je posvetil z žarkom. Če posvetimo s takim žarkom v ogledalo oddaljeno 8 km stran, se žarek odbija od ogledala in vrača skozi zarezo. Ko pa je kolesce zavrtel hitreje, se je zgodilo nekaj zanimivega. Zdelo se mu je, kot da bi se žarku svetlobe, ki se vrača v njegovo oko zapirala vrata. Čemu je tako? Vzrok je v curku svetlobe, ki se ni vračal nazaj skozi isto zarezo. Pravzaprav je zadeval v zobec. Dovolj hitro je vrtel kolesce in prekril svetlobo. Potem pa je sodeč po razdalji med postajama, hitrosti kolesca in številom zarez izračunal hitrost svetlobe, ki je odstopala za približno 2 odstotka od dejanske količine. To je storil leta 1849. To me res privlači pri znanosti. Ko imam težave z razumevanjem neke zamisli, grem raziskovat, kako so ljudje to odkrili. Pogledam njihovo pot spoznanja. Ko pogledate, o čem so razmišljali izumitelji ob svojih odkritjih boste razumeli, da niso tako različni od nas. Vsi smo vreče mesa in vode. Začnemo z istimi pripomočki. Všeč mi je to, da se različne veje znanosti imenujejo študijska področja. Večina ljudi meni, da je znanost zaprta, črna škatla, ampak v bistvu je odprto področje. Vsi smo raziskovalci. Osebe, o katerih odkritjih sem govoril so le malce bolj pomislile, kaj v bistvu gledajo, bile so malo bolj radovedne. Njihova radovednost je spremenila način, kako ljudje razmišljajo o svetu in tako je tudi prišlo do sprememb v svetu. Spremenili so svet in lahko ga tudi vi. Hvala. (Aplavz)