The universe is really big. We live in a galaxy, the Milky Way Galaxy. There are about a hundred billion stars in the Milky Way Galaxy. And if you take a camera and you point it at a random part of the sky, and you just keep the shutter open, as long as your camera is attached to the Hubble Space Telescope, it will see something like this. Every one of these little blobs is a galaxy roughly the size of our Milky Way -- a hundred billion stars in each of those blobs. There are approximately a hundred billion galaxies in the observable universe. 100 billion is the only number you need to know. The age of the universe, between now and the Big Bang, is a hundred billion in dog years. (Laughter) Which tells you something about our place in the universe.
Vesolje je res veliko. Živimo v galaksiji, v Galaksiji Rimska cesta. Tu je približno sto milijard zvezd. In če vzamemo kamero in jo usmerimo v naključno točko na nebu, in pustimo odprto zaslonko, seveda, če je naša kamera pripeta na vesoljski teleskop Hubble, bomo videli nekaj takega. In v vsaki teh lis je galaksija približno velikosti naše Rimske ceste -- sto milijard zvezd v vsaki taki lisi. V vidnem vesolju je približno sto milijard galaksij. 100 milijard je edino število, ki si ga moramo zapomniti. Starost vesolja, med zdaj in Velikim Pokom je sto milijard v pasjih letih. (Smeh) Kar nam pove nekaj o našem mestu v vesolju.
One thing you can do with a picture like this is simply admire it. It's extremely beautiful. I've often wondered, what is the evolutionary pressure that made our ancestors in the Veldt adapt and evolve to really enjoy pictures of galaxies when they didn't have any. But we would also like to understand it. As a cosmologist, I want to ask, why is the universe like this? One big clue we have is that the universe is changing with time. If you looked at one of these galaxies and measured its velocity, it would be moving away from you. And if you look at a galaxy even farther away, it would be moving away faster. So we say the universe is expanding.
Nekaj, kar naredimo s tako sliko, je preprosto občudovanje. To je izjemna lepota. Pogosto sem se spraševal, kakšen je pritisk evolucije ki je naše prednike izoblikoval do te mere da so uživali v slikah galaksij čeprav jih niso imeli. Toda mi bi jih radi tudi razumeli. Kot kosmolog, želim vprašati: Zakaj je vesolje takšno? Velik namig, ki ga imamo, je da se vesolje spreminja skozi čas. Če bi gledali v eno teh galaksij in izmerili njeno hitrost, bi se odmikala od nas. In če se zazremo še v bolj oddaljeno galaksijo, se le-ta odmika še hitreje. Zato pravimo, da se vesolje širi.
What that means, of course, is that, in the past, things were closer together. In the past, the universe was more dense, and it was also hotter. If you squeeze things together, the temperature goes up. That kind of makes sense to us. The thing that doesn't make sense to us as much is that the universe, at early times, near the Big Bang, was also very, very smooth. You might think that that's not a surprise. The air in this room is very smooth. You might say, "Well, maybe things just smoothed themselves out." But the conditions near the Big Bang are very, very different than the conditions of the air in this room. In particular, things were a lot denser. The gravitational pull of things was a lot stronger near the Big Bang.
In to seveda pomeni, da so bile v preteklosti, vse stvari bližje skupaj. V preteklosti je bilo vesolje gostejše, in bilo je bolj vroče. Če stisnemo stvari skupaj, temperatura naraste. To se nam zdi smiselno. Kar se nam ne zdi tako smiselno je, da je bilo vesolje, v zgodnji dobi, skoraj ob Velikem Poku, tudi zelo gladko, enakomerno. Morda boste pomislili, da to ni presenetljivo. Tudi zrak v tem prostoru je zelo enakomeren. Lahko rečete: "No, morda se stvari same uredijo". Toda razmere ob Velikem Poku, so bile zelo, zelo drugačne kot so razmere zraka v tem prostoru. Še posebej, stvari so bile zelo gostejše. Gravitacijske sile stvari so bile močnejše ob Velikem Poku.
What you have to think about is we have a universe with a hundred billion galaxies, a hundred billion stars each. At early times, those hundred billion galaxies were squeezed into a region about this big -- literally -- at early times. And you have to imagine doing that squeezing without any imperfections, without any little spots where there were a few more atoms than somewhere else. Because if there had been, they would have collapsed under the gravitational pull into a huge black hole. Keeping the universe very, very smooth at early times is not easy; it's a delicate arrangement. It's a clue that the early universe is not chosen randomly. There is something that made it that way. We would like to know what.
Kar lahko razmislimo je, da imamo vesolje z sto milijardami galaksij in v vsaki sto milijard zvezd. V zgodnjih časih, so bile te milijarde galaksij stisnjene v območje približno te velikosti -- dobesedno, v zgodnjih časih. In predstavljajte si tako stiskanje brez kakršnih koli nepopolnosti, brez nobenih malih točk kjer bi bilo nekaj manj atomov, kot nekje drugje. Kajti, če bi bile, bi se zrušile pod gravitacijsko silo v ogromno črno luknjo. Ohranjanje zelo enakomernega vesolja v zgodnjih časih ni preprosto, je občutljiva ureditev. To je namig, da zgodnje vesolje ni izbrano naključno. Tu je nekaj, kar ga je ustvarilo na ta način. In mi bi radi vedeli kaj.
So part of our understanding of this was given to us by Ludwig Boltzmann, an Austrian physicist in the 19th century. And Boltzmann's contribution was that he helped us understand entropy. You've heard of entropy. It's the randomness, the disorder, the chaoticness of some systems. Boltzmann gave us a formula -- engraved on his tombstone now -- that really quantifies what entropy is. And it's basically just saying that entropy is the number of ways we can rearrange the constituents of a system so that you don't notice, so that macroscopically it looks the same. If you have the air in this room, you don't notice each individual atom. A low entropy configuration is one in which there's only a few arrangements that look that way. A high entropy arrangement is one that there are many arrangements that look that way. This is a crucially important insight because it helps us explain the second law of thermodynamics -- the law that says that entropy increases in the universe, or in some isolated bit of the universe.
Torej del našega razumevanja nam je podal Ludwig Boltzmann, austrijski fizik v 19. stoletju. In Boltzmannov prispevek nam je pomagal razumeti entropijo. Slišali ste za entropijo. To je naključje, nered, kaotičnost nekih sistemov. Boltzmann nam je podal formulo -- danes vklesano na njegov nagrobnik -- ki količinsko določa kaj je entropija. In v bistvu pravi le, da je entropija število načinov, s katerimi lahko prerazporedimo sestavine sistema, tako da se ne opazi, tako, da makroskopsko zgleda enako. Če vzamemo zrak v tej sobi, ne opazimo vsakega posameznega atoma. Nizka konfiguracija entropije je taka, v kateri je samo nekaj postavitev, ki zgledajo tako. Visoka ureditev entropije je taka, kjer je več možnih postavitev, ki zgledajo tako. To je ključnega pomena, ker nam pomaga razložiti drugi zakon termodinamike -- zakon, ki pravi, da entropija v vesolju narašča. ali v omejenem delčku vesolja.
The reason why entropy increases is simply because there are many more ways to be high entropy than to be low entropy. That's a wonderful insight, but it leaves something out. This insight that entropy increases, by the way, is what's behind what we call the arrow of time, the difference between the past and the future. Every difference that there is between the past and the future is because entropy is increasing -- the fact that you can remember the past, but not the future. The fact that you are born, and then you live, and then you die, always in that order, that's because entropy is increasing. Boltzmann explained that if you start with low entropy, it's very natural for it to increase because there's more ways to be high entropy. What he didn't explain was why the entropy was ever low in the first place.
Razlog za naraščanje entropije je preprost, ker je veliko več načinov za doseganje visoke entropije, kot nizke entropije. To je čudovito razumevanje, vendar nekaj manjka. Razumevanje, da entropija narašča, mimogrede, kar je za nami imenujemo časovni vektor, razlika med preteklostjo in prihodnjostjo. Vsaka razlika med preteklostjo in prihodnjostjo je zaradi naraščanja entropije -- dejstvo, da se lahko spomnimo preteklosti, toda ne prihodnosti. Dejstvo, da se rodimo, živimo in umremo, vedno v tem vrstnem redu, to je zaradi naraščanja entropije. Boltzmann je razložil tudi, da če začnemo z nizko entropijo, je zelo naravno, da se poveča, ker je veliko več načinov za stanja z visoko entropijo. Kar pa ni razložil, je zakaj je bila entropija vedno nizka v izhodišču.
The fact that the entropy of the universe was low was a reflection of the fact that the early universe was very, very smooth. We'd like to understand that. That's our job as cosmologists. Unfortunately, it's actually not a problem that we've been giving enough attention to. It's not one of the first things people would say, if you asked a modern cosmologist, "What are the problems we're trying to address?" One of the people who did understand that this was a problem was Richard Feynman. 50 years ago, he gave a series of a bunch of different lectures. He gave the popular lectures that became "The Character of Physical Law." He gave lectures to Caltech undergrads that became "The Feynman Lectures on Physics." He gave lectures to Caltech graduate students that became "The Feynman Lectures on Gravitation." In every one of these books, every one of these sets of lectures, he emphasized this puzzle: Why did the early universe have such a small entropy?
Dejstvo, da je bila entropija vesolja nizka je odsev dejstva da je bilo prvotno vesolje zelo enakomerno. To bi radi razumeli. To je naloga nas kozmologov. Nažalost, to ni problem, ki smo mu namenili dovolj pozornosti. To ni en izmed prvih odgovorov, ki ga slišiš, če vprašaš sodobnega kozmologa: "Katere probleme poskušate rešiti?" Nekdo, ki je razumel, da je to problem je bil Richard Feynman. Pred 50 leti, je imel serijo rezličnih predavanj. Predaval je na priljubljenih predavanjih ki so postali "Karakter fizikalnih zakonov". Predaval je študentom na Caltechu, danes znanimi kot "Feynmanova predavanja o fiziki". Predaval je Caltech-ovim podiplomantom, kar poznamo kot "Feynmanova predavanja o gravitaciji". V vsaki izmed teh knjig, vsaki zbirki predavanj, je povdarjal vprašanje: Zakaj je imelo zgodnje vesolje tako majhno entropijo?
So he says -- I'm not going to do the accent -- he says, "For some reason, the universe, at one time, had a very low entropy for its energy content, and since then the entropy has increased. The arrow of time cannot be completely understood until the mystery of the beginnings of the history of the universe are reduced still further from speculation to understanding." So that's our job. We want to know -- this is 50 years ago, "Surely," you're thinking, "we've figured it out by now." It's not true that we've figured it out by now.
Tako pravi -- In ne bom naglaševal -- pravi: "Zaradi nekega vzroka, je vesolje, v nekem času, imelo zelo nizko entropijo za svojo energijsko vsebnost, in odtlej je entropija naraščala. Časovnega vektorja ne moremo povsem razumeti dokler skrivnost začetka zgodovine vesolja ni dokončno zmanjšana iz špekulacije v razumevanje". To je naša naloga. Želimo vedeti -- to je bilo pred 50 leti in razmišljate: "Seveda do danes smo to rezrešili". Ni res, da smo do danes to rezrešili.
The reason the problem has gotten worse, rather than better, is because in 1998 we learned something crucial about the universe that we didn't know before. We learned that it's accelerating. The universe is not only expanding. If you look at the galaxy, it's moving away. If you come back a billion years later and look at it again, it will be moving away faster. Individual galaxies are speeding away from us faster and faster so we say the universe is accelerating. Unlike the low entropy of the early universe, even though we don't know the answer for this, we at least have a good theory that can explain it, if that theory is right, and that's the theory of dark energy. It's just the idea that empty space itself has energy.
Problem je postal še večji namesto lažji, ker smo v letu 1998 spoznali nekaj ključnega o vesolju, česar doslej nismo vedeli. Spoznali smo, da vesolje pospešuje. Vesolje se ne samo širi. Če pogledate galaksije, se oddaljujejo. Če se vrnemo čez milijard let in spet pogledamo, se galaksije oddaljujejo še hitreje. Posamezne galaksije drvijo stran od nas hitreje in hitreje. Tako pravimo, da vesolje pospešuje. Za razliko od nizke entropije zgodnjega vesolja, čeprav ne poznamo odgovora na to, imamo vsaj dobro terorijo, ki nam to lahko razloži, in če je teorija pravilna, je to teorija temne energije. Je le ideja, da ima tudi prazen prostor energijo.
In every little cubic centimeter of space, whether or not there's stuff, whether or not there's particles, matter, radiation or whatever, there's still energy, even in the space itself. And this energy, according to Einstein, exerts a push on the universe. It is a perpetual impulse that pushes galaxies apart from each other. Because dark energy, unlike matter or radiation, does not dilute away as the universe expands. The amount of energy in each cubic centimeter remains the same, even as the universe gets bigger and bigger. This has crucial implications for what the universe is going to do in the future. For one thing, the universe will expand forever.
V vsakem malem kubičnem centimetru prostora, neglede na to kaj vsebuje, neglede ali so ali ni delcev, materije, sevanja ali česarkoli, še vedno je prisotna energija v samem prostoru. In ta energija, po Einsteinu izvaja potisk na vesolje. To je ponavljajoč impulz, ki potiska galaksije narazen eno od druge. Ker se temna energija, za razliko od snovi ali sevanja, ne razredči medtem, ko se vesolje širi. Količina energije v vsakem kubičnem centimetru ostaja enaka, tudi, ko se vesolje veča in veča. To ima ključne posledice na obnašanje vesolja v prihodnjosti. Ena stvar: vesolje se bo večno širilo.
Back when I was your age, we didn't know what the universe was going to do. Some people thought that the universe would recollapse in the future. Einstein was fond of this idea. But if there's dark energy, and the dark energy does not go away, the universe is just going to keep expanding forever and ever and ever. 14 billion years in the past, 100 billion dog years, but an infinite number of years into the future. Meanwhile, for all intents and purposes, space looks finite to us. Space may be finite or infinite, but because the universe is accelerating, there are parts of it we cannot see and never will see. There's a finite region of space that we have access to, surrounded by a horizon. So even though time goes on forever, space is limited to us. Finally, empty space has a temperature.
Ko sem bil vaše starosti, nismo vedeli, kaj se bo zgodilo z vesoljem. Nekateri so mislili, da se bo vesolje v prihodnosti sesedlo. Einsteinu je bila ta ideja všeč. Toda če je temna energija, in če temna energija ne gre stran, se bo vesolje le širilo in širilo za vse večne čase. 14 milijard let nazaj, 100 milijard pasjih let, toda neskončno število let v prihodnjost. Medtem, za vse namene in namere, prostor vidimo kot končen. Prostor je lahko končen ali neskončen, vendar, ker vesolje pospešuje, so predeli, ki jih ne moremo videti in jih nikoli ne bomo videli. Imamo dostop le do končnega območja vesolja, ki ga obkroža obzorje. Tudi če je čas neskončen, je prostor za nas omejen. Končno, prazen prostor ima temperaturo.
In the 1970s, Stephen Hawking told us that a black hole, even though you think it's black, it actually emits radiation when you take into account quantum mechanics. The curvature of space-time around the black hole brings to life the quantum mechanical fluctuation, and the black hole radiates. A precisely similar calculation by Hawking and Gary Gibbons showed that if you have dark energy in empty space, then the whole universe radiates. The energy of empty space brings to life quantum fluctuations. And so even though the universe will last forever, and ordinary matter and radiation will dilute away, there will always be some radiation, some thermal fluctuations, even in empty space. So what this means is that the universe is like a box of gas that lasts forever. Well what is the implication of that?
1970 nam je Stephen Hawking povedal, da črna luknja, čeprav mislimo, da je črna, pravzaprav oddaja sevanje, če upoštevamo kvantno mehaniko. Ukrivljenost prostora-časa okrog črne luknje oživi kvantno mehanično fluktuacijo, in tako črna luknja seva. Natančno podoben izračun Hawkinga and Gary Gibbonsa je pokazal, da če imamo temno energijo v praznem prostoru, potem celotno vesolje seva. Energija praznega prostora oživi kvantno fluktuacijo. Tudi če bo vesolje trajalo večno, in se bo običajna snov in sevanje redčilo, bo vedno ostalo nekaj sevanja, nekaj termične fluktuacije, tudi v praznem prostoru. To pomeni, da je vesolje kot škatla plina, ki traja večno. In kaj je posledica tega?
That implication was studied by Boltzmann back in the 19th century. He said, well, entropy increases because there are many, many more ways for the universe to be high entropy, rather than low entropy. But that's a probabilistic statement. It will probably increase, and the probability is enormously huge. It's not something you have to worry about -- the air in this room all gathering over one part of the room and suffocating us. It's very, very unlikely. Except if they locked the doors and kept us here literally forever, that would happen. Everything that is allowed, every configuration that is allowed to be obtained by the molecules in this room, would eventually be obtained.
Posledice je proučeval Boltzmann v 19. stoletju. Rekel je, no, entropija narašča ker obstaja veliko, veliko več načinov, da je vesolje z visoko entropijo, kot z nizko entropijo. Toda to je verjetnostna izjava. Verjetno bo naraščala, in ta verjetnost je ogromna. Zagotovo nam ni treba skrbeti, da se ves zrak v tej sobi zbere v eni sami točki in nas tako zaduši. To je zelo, zelo neverjetno. Razen, če bi kdo zaklenil vrata in nas zadrževal tu dobesedno za vedno, bi se to zgodilo. Vse kar je dovoljeno, vsaka postavitev, ki se lahko pripeti molekulam v tej sobi, je lahko dosežena pod pravimi pogoji.
So Boltzmann says, look, you could start with a universe that was in thermal equilibrium. He didn't know about the Big Bang. He didn't know about the expansion of the universe. He thought that space and time were explained by Isaac Newton -- they were absolute; they just stuck there forever. So his idea of a natural universe was one in which the air molecules were just spread out evenly everywhere -- the everything molecules. But if you're Boltzmann, you know that if you wait long enough, the random fluctuations of those molecules will occasionally bring them into lower entropy configurations. And then, of course, in the natural course of things, they will expand back. So it's not that entropy must always increase -- you can get fluctuations into lower entropy, more organized situations.
Boltzmann pravi: poglej, lahko začnemo vesolje ki je v termičnem ravnovesju. Ni vedel za Veliki Pok. Ni vedel za širjenje vesolja. Mislil je, da sta prostor in čas razložena po Isaacu Newtonu -- bila sta absolutna in večna. Njegova ideja naravnega vesolja je bila taka, kjer se molekule zraka širijo vsepovsod enakomerno -- vse molekule. Toda če ste vi Boltzmann, veste, da če čakaš dovolj časa, naključna fluktuacija teh molekul občasno pripelje molekule v konfiguracije nizke entropije. In tedaj, seveda, se v naravnem toku, ponovno razširijo. Torej ni nujno, da entropija vedno narašča -- lahko dobimo fluktuacije v nižjo entropijo, bolj urejene razmere.
Well if that's true, Boltzmann then goes onto invent two very modern-sounding ideas -- the multiverse and the anthropic principle. He says, the problem with thermal equilibrium is that we can't live there. Remember, life itself depends on the arrow of time. We would not be able to process information, metabolize, walk and talk, if we lived in thermal equilibrium. So if you imagine a very, very big universe, an infinitely big universe, with randomly bumping into each other particles, there will occasionally be small fluctuations in the lower entropy states, and then they relax back. But there will also be large fluctuations. Occasionally, you will make a planet or a star or a galaxy or a hundred billion galaxies. So Boltzmann says, we will only live in the part of the multiverse, in the part of this infinitely big set of fluctuating particles, where life is possible. That's the region where entropy is low. Maybe our universe is just one of those things that happens from time to time.
Če je to res, Boltzmann izumlja dve zelo sodobni ideji -- mnogovesolje in antropično načelo. Govori nam, da je problem s termičnim ravnovesjem, da ne moremo živeti tam. Pomnite, življenje samo je odvisno od časovnega vektorja. Nebi mogli obdelovati informacij, prebavljati, hoditi in govoriti, če bi živeli v termičnem ravnovesju. Tako, če si predstavljate veliko, zelo veliko vesolje, neskončno veliko vesolje, z delci, ki se naključno zaletajo eden v drugega, bo prišlo do občasnih majhnih nihanj v nizkem stanju entropije, ki se nato zopet sprostijo. Toda prihajalo bo tudi do večjih nihanj. Občasno, bo ustvarjen planet ali zvezda ali galaksija ali sto milijard galaksij. Torej Boltzmann govori, da bomo živeli samo v delu mnogovesolja, v delu tega neskončnega nabora nihajočih delcev, kjer je možno življenje. To je področje, kjer je entropija nizka. Morda je naše vesolje le ena izmed stvari, ki se zgodijo občasno.
Now your homework assignment is to really think about this, to contemplate what it means. Carl Sagan once famously said that "in order to make an apple pie, you must first invent the universe." But he was not right. In Boltzmann's scenario, if you want to make an apple pie, you just wait for the random motion of atoms to make you an apple pie. That will happen much more frequently than the random motions of atoms making you an apple orchard and some sugar and an oven, and then making you an apple pie. So this scenario makes predictions. And the predictions are that the fluctuations that make us are minimal. Even if you imagine that this room we are in now exists and is real and here we are, and we have, not only our memories, but our impression that outside there's something called Caltech and the United States and the Milky Way Galaxy, it's much easier for all those impressions to randomly fluctuate into your brain than for them actually to randomly fluctuate into Caltech, the United States and the galaxy.
Zdaj je vaša domača naloga, da razmišljate o tem, kaj to pomeni. Carl Sagan je nekoč izjavil, da "če želimo speči jabolčno pito, moramo najprej izumiti vesolje". Toda ni imel prav. Po Boltzmannu, če želimo speči jabolčno pito, le počakamo na naključno gibanje atomov, ki nam speče pito. To se bo dogajalo bolj pogosto kot naključno gibanje atomov, ki pripelje do sadovnjaka in nekaj sladkorja in pečice, in nam nato speče pito. Ta scenarij daje napovedi. In napovedi so, da so nihanja, ki nas ustvarjajo minimalna. Tudi, če si predstavljate, da ta soba obstaja in je resnična, da smo tukaj, imamo svoje spomine in vtis, da je tam zunaj nekaj imenovanega Caltech in ZDA in galaksija Rimska cesta, je enostavnejše, da se vsi ti vtisi naključno zanihajo v vaših možganih, kot za pravo naključno nihanje v Caltech, ZDA in galaksijo.
The good news is that, therefore, this scenario does not work; it is not right. This scenario predicts that we should be a minimal fluctuation. Even if you left our galaxy out, you would not get a hundred billion other galaxies. And Feynman also understood this. Feynman says, "From the hypothesis that the world is a fluctuation, all the predictions are that if we look at a part of the world we've never seen before, we will find it mixed up, and not like the piece we've just looked at -- high entropy. If our order were due to a fluctuation, we would not expect order anywhere but where we have just noticed it. We therefore conclude the universe is not a fluctuation." So that's good. The question is then what is the right answer? If the universe is not a fluctuation, why did the early universe have a low entropy? And I would love to tell you the answer, but I'm running out of time.
Dobra stvar je, da ta scenarij ne deluje, ni pravi. Ta scenarij predvideva, da smo minimalno nihanje. Tudi če izpustimo našo galaksijo, ne bi dobili sto milijard drugih galaksij. In tudi Feynman je razumel to. Feynman govori: "Od hipoteze da je svet nihanje, in vse napoveduje, da če pogledamo del sveta, ki ga še nismo doslej, bo ta zmešan, nič kot predel, ki smo ga gledali -- visoka entropija. Če je naš red zaradi nihanja, nebi pričakovali reda nikjer drugje razen, kjer smo ga pravkar zaznali. Zatorej zaključujemo, da vesolje ni nihanje". To je dobro. Vprašanje je kaj je pravi odgovor? Če vesolje ni nihanje, zakaj je zgodnje vesolje imelo nizko entropijo? In rad bi vam povedal odgovor, a moj čas se izteka.
(Laughter)
(Smeh)
Here is the universe that we tell you about, versus the universe that really exists. I just showed you this picture. The universe is expanding for the last 10 billion years or so. It's cooling off. But we now know enough about the future of the universe to say a lot more. If the dark energy remains around, the stars around us will use up their nuclear fuel, they will stop burning. They will fall into black holes. We will live in a universe with nothing in it but black holes. That universe will last 10 to the 100 years -- a lot longer than our little universe has lived. The future is much longer than the past. But even black holes don't last forever. They will evaporate, and we will be left with nothing but empty space. That empty space lasts essentially forever. However, you notice, since empty space gives off radiation, there's actually thermal fluctuations, and it cycles around all the different possible combinations of the degrees of freedom that exist in empty space. So even though the universe lasts forever, there's only a finite number of things that can possibly happen in the universe. They all happen over a period of time equal to 10 to the 10 to the 120 years.
Tu je vesolje o katerem govorimo, nasproti vesolji, ki zares obstaja. Pravkar sem vam pokazal to sliko. Vesolje se širi že vsaj zadnjih 10 milijard let. Ohlaja se. Toda zdaj vemo dovolj o prihodnosti vesolja, da rečemo veliko več. Če temna energija ostaja okrog, bodo zvezde okrog nas porabile svojo jedrsko gorivo in ugasnile. Padle bodo v črne luknje. Živeli bomo v vesolju brez ničesar v njem, razen črnih lukenj. To vesolje bo trajalo 10 do 100 let -- veliko dlje, kot je živelo naše malo vesolje. Prihodnost je veliko daljša od preteklosti. Tudi če črne luknje ne trajajo večno. Bodo izhlapele, in ostal nam bo le prazen prostor. Tak prazen prostor v bistvu traja večno. Kakorkoli, če opazite, ker prazen prostor oddaja sevanje, so tam pravzaprav termična nihanja, in ciklično prehajajo vse različne možne kombinacije stopenj svobode, ki obstajajo v praznem prostoru. Tako tudi, če je vesolje večno, je le končno mnogo stvari, ki se lahko zgodijo v vesolju. Vse se zgodijo v časovnem obdobju enakem 10 na 10 na 120 let.
So here's two questions for you. Number one: If the universe lasts for 10 to the 10 to the 120 years, why are we born in the first 14 billion years of it, in the warm, comfortable afterglow of the Big Bang? Why aren't we in empty space? You might say, "Well there's nothing there to be living," but that's not right. You could be a random fluctuation out of the nothingness. Why aren't you? More homework assignment for you.
Tu sta dve vprašanji za vas. Prvo: Če vesolje traja 10 na 10 na 120 let, zakaj se rodimo v prvih 14 milijard let vesolja, v toplem, udobnem siju Velikega Poka? Zakaj nismo v praznem prostoru? Lahko rečete: "No, tam ni ničesar za življenje". Toda to ni pravilno. Lahko bi bili naključno nihanje iz ničesar. Zakaj niste? Še nekaj domačih nalog za vas.
So like I said, I don't actually know the answer. I'm going to give you my favorite scenario. Either it's just like that. There is no explanation. This is a brute fact about the universe that you should learn to accept and stop asking questions. Or maybe the Big Bang is not the beginning of the universe. An egg, an unbroken egg, is a low entropy configuration, and yet, when we open our refrigerator, we do not go, "Hah, how surprising to find this low entropy configuration in our refrigerator." That's because an egg is not a closed system; it comes out of a chicken. Maybe the universe comes out of a universal chicken. Maybe there is something that naturally, through the growth of the laws of physics, gives rise to universe like ours in low entropy configurations. If that's true, it would happen more than once; we would be part of a much bigger multiverse. That's my favorite scenario.
Kot sem rekel, pravzaprav ne vem odgovora. Podal vam bom moj najljubši scenarij. Bodisi da je tako. Ni razlage. To je surovo dejstvo o vesolju, ki ga morate spoznati in sprejeti ter nehati postavljati vprašanja. Ali morda Veliki Pok ni začetek vesolja. Jajce, ne-razbito jajce, je konfiguracija z nizko entropijo, in ko odpremo hladilnik ne rečemo, "Ha, kako presenetljivo najti to nizko stopnjo entropije v našem hladilniku". To je ker jajce ni zaprt sistem; pride iz kokoši. Morda vesolje pride iz vesoljne kokoši. Morda je tam nekaj, kar naravno skozi razvoj zakonov fizike, daje porast vesolju, kot je naše z nizko entropijo. Če je to res, bi se zgodilo več kot enkrat; bi bili del veliko večjega mnogovesolja. To je moj najljubši scenarij.
So the organizers asked me to end with a bold speculation. My bold speculation is that I will be absolutely vindicated by history. And 50 years from now, all of my current wild ideas will be accepted as truths by the scientific and external communities. We will all believe that our little universe is just a small part of a much larger multiverse. And even better, we will understand what happened at the Big Bang in terms of a theory that we will be able to compare to observations. This is a prediction. I might be wrong. But we've been thinking as a human race about what the universe was like, why it came to be in the way it did for many, many years. It's exciting to think we may finally know the answer someday.
Organizatorji so me prosili naj zaključim z drzno špekulacijo. Moja drzna špekulacija je da me bo zgodovina popolnoma upravičila. In čez 50 let, bodo vse moje trenutno divje ideje sprejete kot resnične tako znanstveniki kot druge skupnosti. Vsi bomo verjeli, da je naše malo vesolje le majhen delček veliko večjega mnogovesolja. In še več, razumeli bomo kaj se je zgodilo ob Velikem Poku v teoretičnem smislu, ker bomo lahko primerjali opazovanja. To je moja napoved. Lahko se motim. Toda kot človeštvo razmišljamo o tem, kakšno je bilo vesolje in zakaj je nastalo in je takšno kot je, že mnogo, mnogo let. Razburljivo je, če pomislimo, da bomo morda nekoč le vedeli odgovor.
Thank you.
Hvala vam.
(Applause)
(Aplavz)