(Music) Sometimes when I'm on a long plane flight, I gaze out at all those mountains and deserts and try to get my head around how vast our Earth is. And then I remember that there's an object we see every day that would literally fit one million Earths inside it. The sun seems impossibly big, but in the great scheme of things, it's a pinprick, one of about 400 billion stars in the Milky Way galaxy, which you can see on a clear night as a pale, white mist stretched across the sky. And it gets worse. There are maybe 100 billion galaxies detectable by our telescopes, so if each star was the size of a single grain of sand, just the Milky Way has enough stars to fill a 30 foot by 30 foot stretch of beach three feet deep with sand. And the entire Earth doesn't have enough beaches to represent the stars in the overall universe. Such a beach would continue for literally hundreds of millions of miles. Holy Stephen Hawking, that is a lot of stars. But he and other physicists now believe in a reality that is unimaginably bigger still. I mean, first of all, the 100 billion galaxies within range of our telescopes are probably a minuscule fraction of the total. Space itself is expanding at an accelerating pace. The vast majority of the galaxies are separating from us so fast that light from them may never reach us. Still, our physical reality here on Earth is intimately connected to those distant, invisible galaxies. We can think of them as part of our universe. They make up a single, giant edifice, obeying the same physical laws and all made from the same types of atoms, electrons, protons, quarks, neutrinos that make up you and me. However, recent theories in physics, including one called string theory, are now telling us there could be countless other universes, built on different types of particles, with different properties, obeying different laws. Most of these universes could never support life, and might flash in and out of existence in a nanosecond, but nonetheless, combined they make up a vast multiverse of possible universes. in up to 11 dimensions, featuring wonders beyond our wildest imagination. And the leading version of string theory predicts a multiverse made of up to 10 to the 500 universes. That's a one followed by 500 zeroes, a number so vast that if every atom in our observable universe had its own universe and all of the atoms in all of those universes each had their own universe, and you repeated that for two more cycles, you'd still be at a tiny fraction of the total -- namely, one trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillionth. But even that number is minuscule compared to another number: infinity. Some physicists think the space-time continuum is literally infinite, and that it contains an infinite number of so-called pocket universes with varying properties. How's your brain doing? But quantum theory adds a whole new wrinkle. I mean, the theory's been proven true beyond all doubt, but interpreting it is baffling. And some physicists think you can only un-baffle it if you imagine that huge numbers of parallel universes are being spawned every moment, and many of these universes would actually be very like the world we're in, would include multiple copies of you. In one such universe, you'd graduate with honors and marry the person of your dreams. In another, not so much. There are still some scientists who would say, hogwash. The only meaningful answer to the question of how many universes there are is one, only one universe. And a few philosophers and mystics might argue that even our own universe is an illusion. So, as you can see, right now there is no agreement on this question, not even close. All we know is, the answer is somewhere between zero and infinity. Well, I guess we know one other thing: This is a pretty cool time to be studying physics. We just might be undergoing the biggest paradigm shift in knowledge that humanity has ever seen.
(Muzika) Ponekad, kada sam na dugačkom letu, posmatram sve te planine i pustinje i pokušavam da shvatim koliko je zapravo velika naša Zemlja. Onda se setim da je tu predmet koji vidimo svakoga dana u koji bi, bukvalno, stalo milion Zemalja. Sunce deluje nemoguće veliko, ali u celom funkcionisanju stvari, to je samo delić, jedna od oko 400 milijardi zvezda u galaksiji Mlečni puti, koju možete videti po vedroj noći kao bledu, belu izmaglicu, rastegljenu preko neba. Stvar se pogoršava. Postoji možda 100 milijardi galaksija vidljivih našim teleskopom, tako da kada bi svaka zvezda bila veličine zrna peska, samo Mlečni put bi imao dovoljno zvezda da ispuni plažu širine 9 sa 9 metara i 90 cm dubine u pesku. Cela Zemlja nema dovoljno plaža da prikaže zvezde u celom univerzumu. Takva plaža bi se bukvalno protezala stotinama miliona kilometara. Stivena Hokinga mu, to je mnogo zvezda. Ali on i drugi fizičari sada veruju u realnost koja je nezamislivo još veća. Mislim, najpre, 100 milijardi galaksija u okvirima našeg teleskopa su verovatno minijaturan razlomak sveukupnog. Sam svemir se širi ubrzanim korakom. Velika većina galaksija se od nas toliko brzo udaljava da svetlo od njih možda nikada ne dođe do nas. Ali ipak, naša fizička realnost ovde na Zemlji je blisko povezana sa onim udaljenim, nevidljivim galaksijama. Možemo da mislimo o njima kao o delu našeg univerzuma. Oni sačinjavaju jedno, ogromno zdanje, pokoravajući se istim fizičkim zakonima i svi su sačinjeni iz istih vrsta atoma, elektrona, protona, kvarkova, neutrona koji sačinjavaju tebe i mene. Međutim, skorašnje teorije u fizici, kao i teorija struna, govore nam da bi moglo da postoji još nebrojivo mnogo drugih univerzuma, koji su sagrađeni od drugačijih vrsta čestica, sa drugačijim svojstvima i pokoravaju se drugačijim zakonima. Većina ovih univerzuma nikada ne bi mogla da podrži život i mogli bi da se pojave ili nestanu za nanosekundu, ali ipak, kombinovani čine veliku različitost mogućih univerzuma u 11 dimenzija, uz čuda koja su izvan naše najluđe mašte. Vodeća verzija teorije struna predviđa multiverzum koji sačinjava od 10 na 500 univerzuma. To je jedan praćen sa 500 nula, brojem koji je toliko veliki da kada bi svaki atom u našem vidljivom univerzumu imao svoj sopstevni univerzum i kada bi svi atomi u svim univerzumima svaki imali svoj univerzum, i kada biste to ponovili sa još dva kruga, i dalje biste bili kod malog razlomka celine --- što znači jedan bilion biliona biliona biliona biliona biliona biliona biliona biliona biliona biliona biliona biliona biliona biliona. Čak je i taj broj minijaturan kada ga uporedimo sa drugim brojem: beskonačnošću. Neki fizičari misle da je kontinuum prostor-vreme bukvalno beskrajan i da se sastoji iz beskonačnog broja, takozvanih džepnih univerzuma sa osobinama koje se menjaju. Kako je vaš mozak? Kvantna teorija dodaje potpuno novu boru. Mislim, teorija je dokazana istinitom izvan svake sumnje, ali je njeno tumačenje je zbunjujuće. Neki fizičari misle da je jedino možete pojasniti ako zamislite da se taj veliki broj paralelnih univerzuma razmnožava svakog trenutka i mnogi od ovih univerzuma bi zapravo bili upravo kao svet u kome živimo, sastojali bi se iz više kopija vas. U jednom takvom univerzumu, diplomirali biste sa najboljim ocenama i udali biste se za osobu iz snova. U nekom drugom, ne bi baš bilo tako. I dalje postoje naučnici koji bi rekli da su to budalaštine. Jedini značajan odgovor na pitanje koliko ima univerzuma je ovaj: postoji samo jedan univerzum. Nekoliko filozofa i mističara bi mogli da kažu da je čak i naš univerzum iluzija. Kao što možete da vidite, trenutno ne postoji slaganje u vezi sa ovim pitanjem, ni izbliza. Sve što znamo je da je odgovor negde između nule i beskonačnosti. Pretpostavljam da znamo još jednu stvar: ovo je odličan trenutak za učenje fizike. Moguće je da upravo proživljavamo najveću promenu paradigme u znanju koju je čovečanstvo ikada videlo.