Big Bang Creation Myths | Roger Penrose, Sean Carroll, Laura Mersini-Hougton

so the theme of the debate is whether the universe began as all our children are taught in school with a big bang to discuss this um we're very fortunate to have on my left Roger Penrose and now Rogers an Oxford mathematician philosopher of science pioneered the mathematics of black holes you were Hawking's mentor weren't him he worked with you you should never believe am i right Sean Carroll cosmologists and physicists California Institute of Technology writes regularly for the New York Times wire New Scientist and if flora turns up I shall introduce her might the big bang theory be mistaken Sean would you like to just start right so to answer that we first have to say what we mean by the big bang theory because this phrase is meant in two very different contexts right we all know the universe is expanding so if you run the clock backwards if you run the film to the past 14 billion years ago it was in a hot dense state and we have something called the Big Bang model of cosmology which is simply the statement that fourteen billion years ago the universe was in a hot dense state it expanded and cooled and went from being very smooth to relatively lumpy which it is right now with all these stars and galaxies and so forth that's the Big Bang model it is true there's no point in doubting the Big Bang model okay we don't let people up here on stage if they doubt that part of the Big Bang model but if you take seriously general relativity and you say well what happened at the very beginning what happens so we know exactly what the universe was doing one minute after the very beginning of the Big Bang okay from one minute after 214 billion years after we understand that first minute is a little bit up for grabs so classical general relativity the theory that Einstein gave us for space and time would say according to Roger and Stephen Hawking that at that moment T equals zero at the very beginning there was a singularity but there's also this thing called mechanics which gets in the way which is not part of general relativity so if you want to say the big bang event the Big Bang moment the beginning of everything we don't know whether that is right or not we have room as theoretical physicists and cosmologists to invent new scenarios and debate over which is right which is wrong and so that's where our disagreement comes in I'm pretty agnostic to be honest about whether or not that moment because it's a moment in time the Big Bang not a place in space it's not an explosion in a pre-existing space it's the beginning of everything it's the moment before which there were no other moments and that's the model and the question is is that model right so I I have two favorite theories and neither one of them is Rogers favorite theory so that gives us something to talk about one theory that I think is very at least on the table as plausible is yes that is the beginning of the universe and it's because time and space themselves are not fundamental that when you get deep into the guts of quantum mechanics you realize that all the stuff around us the tables the chairs space itself time itself are emergent approximate phenomena they're like talking about the air as a fluid with the temperature and a pressure rather than talking about the molecules maybe even time is just a good approximation and it started 14 billion years ago that's one possibility that I think is very plausible the other if time is truly fundamental if time is real and they're an inextricable from the fundamental equations then I think it's very likely that the Big Bang was not the beginning in that case but I also think that as Roger has emphasized better than anyone there's something very profound about the nature of time in our observable universe namely that it has a direction right that the past is different from the future and if we can get into this I hope the reason why the past is different from the future in your everyday life the reason why you remember yesterday and not tomorrow is ultimately because of what conditions were like at the Big Bang that's what set up the arrow of time and that's the fundamental mystery of cosmology why was it like so my favorite view of that is that there is a much larger universe that we don't see that our little universe is a tiny little part of the whole picture and the whole picture is actually symmetric that there are people in our past who think that we are in their past the time runs in the opposite direction for them as it does for us this is not by any means set in stone we don't know it for sure but these are the kinds of scenarios that we're talking about as professional cosmologists to understand why the universe that we do live in looks the way it does marvelous so that's all clear time may not be fundamental it may be people in your future looking at you in their past or something the way around marvelous okay Roger and are you gonna make it worse or better and that's a good question well you see Shaun didn't mention the thing that I was really going to disagree about according to conventional theory okay the Big Bang this is big mystery and what was it and did quantum mechanics have an important role to play and what was going on well the dress that question in the moment but there was supposed to be something within the first ten to the minus thirty two seconds now what does that mean you think of a number one fraction the bottom the denominator is a number which has 32 digits and that fraction ridiculously small fraction of a second the universe was supposed to have expanded far more rapidly than anything that we're aware of now it's called an exponential expansion which is supposed to taking place and that's called inflation and it is very much part of conventional cosmology now to me that's the weak point of conventional cosmology because you have to introduce ideas which there's no other reason for apart from making it do this but apart from that if you go one blip after that I completely agree with what Sean soon so the argument has to be what from before that and I'm claiming that although there was this idea of a steady state model which grew up with I may say when I was in Cambridge as a graduate student this was all going on and Denis Sharma was a good friend of mine and Bondi and gold and people I used to know fred hoyle and they were all dead keen on this idea that the universe went on expanding expanding and it didn't change much because new matter was created all the time okay I like that theory because philosophically it meant there was no beginning and you could talk about the universe in that kind of way now I'm picking up on that in a different way though I'm not disagreeing with a Big Bang there was a big bang I am rather disagreeing that quantum mechanics was important there and that's a big point of difference really the reason that you're allowed to continue before the Big Bang which was what I'm trying to claim is because in a certain sense I'm agreeing is shown that you don't have time how do we measure time we have extraordinarily accurate clocks today because a particle of mass is really a clock and this based on the two basic most famous formula of 20th century physics namely Einsteins equals MC squared which tells you energy and mass equivalent and Max Planck's equals H nu or F whatever call it which tells you of energy and frequency equivalent put the two together that tells you that mass and frequency are equivalent that tells you that if you have a massive particle it is a clock of extraordinary precision now the point is when you don't have massive particles and this would apply to the remote future when basically the universe is dominated by photons running around either from stars or from black holes you see Stephen Hawking his most famous discovery if you like or a theoretical discovery was that black holes are not completely black or they're not completely cold that they have a temperature that temperature is so low that it's much lower than anything who built in the lab certainly with the big biggest black holes sun galaxy has a black hole in its center which is about 4 million times the mass of the Sun that's so cold that it puts everything else in the shade now the thing is the record of Hawking the things eventually will evaporate away because the universe gets colder than the black holes they evaporate away and disappear so when those have disappeared there's nothing left but things which don't have any mass there's the photons basically that's true and that they're the only way of you don't have clocks anymore because you don't have mass and so the remote future you have no way of keeping time and the idea is that this remote future where you have this expansion of the universe which is becoming exponential expansion which is what we currently observe continues forever now I found that a really depressing picture it seems to me you know the universe is pretty exciting now but then you eternity of boredom but then I thought who's gonna be born I'll not ask her we won't be around the main things will be out there photons and it's very hard to borrow photon I'll tell you because photons the main reason is probably they don't experience anything but that's not the point the main point is that they don't measure time photons right up to infinity and they're still there and they said what what what you've got to do with the universe they're still there the idea is that the universe continues with what I call another Eon hour Eon started with a big bang and ends with this exponential expansion that then becomes the big bang of another Eon and there was an eon before I could go and talk for endlessly this if you allow me but the beginning there was an and now that Rogers got that clear for you Lara has turned out so now it will get what right so laura mercier Houston cosmologists professor of physics and focuses on the multiverse so we had a universe we've got a long line of them one out of the other and now we're gonna have more universes and you can shake a stick out might the Big Bang Theory be mistaken it's a shame to ask you such as more question before you put your breath but please it is not wrong and by Big Bang I mean cosmic inflation it is not wrong it's incomplete it tells us all we want to know from the moment the universe comes into existence the present day it agrees exquisitely well with observations but it creates its own problem of the origin what it came from this is your first split that tiny moment yeah exactly well I mean maybe we didn't really talk about inflation will get seems like a very short introduction do you want to say so yeah cosmic inflation gives us this beautiful picture were the large-scale structure in the universe and the Cosmic Microwave Background basically everything we observe around us he seeded from those primordial quantum fluctuations and how the whole universe started small and stretched all its non-uniformities as cosmic inflation made that universe to accelerate and grow big very quickly so we have a set of observations our precision cosmologies is a very advanced field by now so all our observations will agree perfectly well with this picture of cosmic inflation it does not mean they prove cosmic inflation it's conceivable that someone else might come along with a different picture that also agrees with this set of observations however we are happy because here is a theory that tells us everything from the first fraction of a second to present-day and we know our universe started small and it's growing but that picture does not tell us what gave that first energy and what was there before and not lies beyond our universe is about 10 to the power 27 centimeters the visible universe and it's only 13.8 billion years old these are big numbers but they are not in conceivably big so we all of us have the right to ask what was there thirteen point nine billion years ago or what was there at what's beyond 10 to the power 27 centimeters okay so um we've got a great story but we're missing the first paragraph in this story it says that that bit got torn off so you've got a great story from then on but you don't know what happened right at the beginning the first page um well then our our first question really is do we have to have a beginning I mean it's nice to have one all stories start with once upon a time and do we need one do we need a first cause or are some scientists happy that we don't have one and it is our preference for having a beginning because you lot have inherited that that sort of myth structure from from Christianity I mean I don't think the engines are too worried about this yes Oh Jeff do you think we we we have to have a beginning or is it just a an article of faith well currently my scheme does not have a beginning but the beginning that we think of as the Big Bang was the continuation of something which didn't look like a Big Bang but wasn't it previously expanding what I call an eon and these went on as far as the theory goes indefinitely so there was no beginning in this scheme of course that might not be right but I think there are some observations very recent observations which I don't see how you can explain on the basis of current inflationary theory and I rather disagree about inflation being a nice beautiful theory it's a very artificial theory well you have to introduce concepts which are invented just before we get on to that when you say an eon have I got the right picture that basically is saying before our universe our current what there was before it yes and it sort of came to an end and then there's another one it's an old idea that the universe expanded and then collapsed again so we're just sensing with beginnings and endings well let me just go back to the old idea see this was one of the very old originally right after Einstein produced his theory three months of the equations and one of the solutions was which expanded and collapse like this and it went through these phases no this is very different because it never collapses and that's what people have trouble swallowing you see how can this universe which is expanding getting rarefied cold and all that become this Big Bang which is very hot and compressed and they look completely different but they're not completely different if you don't have mass because it's a funny idea but in this model when you don't have clocks around which you don't when you don't have mass then they've in small become equivalent it's what you call conformal equivalent large things and small things you can't tell them apart if you don't have a scale which tells the difference and the scale gets lost when you don't have particles with mass and so when that scale is lost this expanding indefinitely expanding universe becomes a big bang of the next even though it was very large one spot yes when you see lose track of what large means when you've only got photons running around there's no meaning to saying it's larger small the equations become identical I agree it's a hard idea to swallow and it's lanky Roger of YouTube willing to swallow this ID or would you rather look like you you want to say something in terms of your question can we do with universe that didn't have a beginning certainly we can but we observe that that's not the case with our universe we know our universe at the beginning so we don't get to have a choice on that and in terms of the theory of cosmic inflation explaining many of the features we observe in our universe I did state before that it's a beautiful and natural theory that's true except that it has a very very unnatural feature which is the one that Roger pointed out in the 70s I believe that the chance of starting the universe with high energy inflation is incredibly small it's 1 to the power 10 and we've had this discussion and and in that sense yes I completely agree with Roger that that's a very unnatural beginning to have a very special beginning to have but that argument is a consequence of the second law of thermodynamics we can turn it around and say our universe study started at an incredibly small entropy or at an exquisitely ordered state at a very special state so always give the problem of the origin of the universe whether it's via cosmic inflation or via some other mechanism or some other theory that problem will always be tied up with the issue of the second law of thermodynamics by which entropy always grows so whatever beginning we can conceive of in the future the entropy of that state would have grown so that beginning would will always be special relative to some final state and and that is the part where I'm not sure I agree with Roger any further I I like his his theory of eons and and cycles in the universe but I have not thought carefully on how that evades the second law of thermodynamics whether you can have such a theory whether you don't lose information in each cycle I think it's an absolutely key point yeah absolutely right the answer to it according to my scheme goes lands us in another one of these big controversies it has to do with black holes see the entropy in our universe right now is almost uh turley dominated by black holes and so what happens to us black holes well they evaporate away by hawking of aberration and then you have to take a view which is not so normal see people tend to think that somehow the information is going to come back black holes but I say no this is there were two Hawking's the Hawking you put forward this theory first about her black hole evaporation who said information was lost there's the second Hawking who changed his mind and said no information somehow got to backing it back again I think he was right the first time he was right the first time information is lost and it's because the information is lost that you allow all that information and the entropy does is involved in that and you start again by with what's left and that's how you satisfy the second law so it does make sense as far as I know the scheme I'm proposing is the only one I know of at least which you get this very uniform gravitation free as degrees of freedom in the gravity gravitational field not there in the next Eon so it starts clean all over again and it makes sense with a second law and I don't know of any other scheme which does that well let's ask Sean I actually do have a scheme talk about that or we could back up a little bit cuz you still have this well I'm just do you think we need the beginning well yeah I mean you sort of like opened a little bit of a door to saying you know does the University to creator to make this something right so well it's early in the morning we muscle push some hot buttons just to get people wait right so we have a whole bunch of different scenarios for the very very long scale evolution of the universe some of which are eternal time goes from minus infinity to plus infinity some of which are finite the universe has not only a beginning but an end and some of which are halfway right the universe has a beginning but not an end in fact that last one even though it's the weirdest is kind of the running working model for most respectable cosmologists today and so you can ask in the context of any of these what else is there to be explained other than what the universe is doing right there's a sense in which there's a philosophy which I don't necessarily agree with but you can say science says what the universe does it doesn't say why the universe does those so in particular you might think that there's a very big difference in the explanatory burden if the universe has a beginning versus when it doesn't if you were Isaac Newton if you believed in classical mechanics the universe just lasts forever right time is absolute and it just goes on forever Newton actually was a little bit worried about the implications of that Newton thought that God would come in and rearrange the planets occasionally because otherwise they would they would run off and later Pierre Simone applause made fun of him for that loss of courage and just believing the universe could run all by itself but then once general relativity comes along with Einstein you can show that if the universe is full of stuff it's either expanding or contracting so there was probably a crunch or a bang right there was a beginning or an end and one of the first people who take this seriously was a a priest George lameta and he developed his theory of the primeval atom which we would now call the Big Bang and he said you know several billion years ago everything was on top of everything else maybe the universe contra Newton had a start right and you know who loved this idea was the Pope the Pope said all right good I'm gonna put you on a commission then you can write a paper that science is proven that God created the universe now right and lumetri said no I do not want to do that I don't want to cuz let Metra was a smart cookie you know he knew this is the 1920s he knew like you know we don't have the final answer now we can't write a document that says prove that God created the universe because it had a beginning because some smart cosmologists is gonna come along as head it doesn't have a beginning right someday in the future so but nevertheless there's this thought that if the universe is eternal it could be self-sustaining they could just be self-contained and all by itself whereas if it had a beginning there needs to be a cause for its creation and I would say that even then that's not right this is one of the wonderful consequences of this way of thinking about the intersection of quantum mechanics and gravity that Stephen Hawking others have pursued is that even a universe with the beginning can be fully self-contained that's a description of the universe just because it has a first moment in time does not require anything outside to push the button and get it started you shouldn't think of even if the Big Bang is the beginning let me just say parenthetically all these different scenarios we're talking about are unlikely to be true okay cuz we don't know the right answer but Roger scenario my scenario Laura's scenario none of these have a better than 10% chance each a being final answer right so if it does turn out to be true that the universe had a beginning you shouldn't think of it as there was nothing necessar it's very hard to not think of that way cuz the flow of time is embedded in how we think about the world and you think about well if there was the Big Bang then it came from nothingness but there wasn't a nothingness that turned into the Big Bang that's the wrong way of thinking think about it from the other side there was a first moment of time in the history of the universe and just because there was that doesn't mean there was some reason why it happened so it's reasonable that's right you know I would I would sadly I would have you know Roger mentioned the disappointing idea that the universe will last for infinity years in the future and we'll all be dead it's also kind of disappointing to say well why did the universe exist at all and the answer is it just did stop asking questions like that yeah see you're disappointed not addicted yeah I am disappointed um how there are alternatives to the Big Bang we should consider I mean does the multiverse help and does eons help or we just left with the same problem picking up words on death the origin of the universe question whether it at the beginning or or not is very closely related to another fundamental problem and one that's even harder and that's the nature of time because we were so deliberately waiting our hands and speaking of time before the Big Bang and time after this and after and before that but we don't know whether time is fundamental or it emerged with the universe itself so unless we have a better understanding of that issue probably what was there before the Big Bang does not make sense do we need a multiverse I I believe so for many reasons the first one we know by observations that our local universities have a beginning so that that immediately implies that there is something else beyond detergent and before that particular beginning if with the caveat that that time exists before our universe did so in that case of course I did it's hard to believe in a cosmos with with an eternal time with the fundamental time parameter that the only thing that ever happened for eternity was just one pop our universe and nothing else so it's quite natural that one would expect many structures to twigs is beyond the structure of our universe and that is a extension of the Copernican principle we're simply saying not long ago we thought planet Earth is the center of the universe and then the solar system and now we are saying even our local universe is not the center of the cosmos were just one humble member somewhere in in a vast beautiful and complex cosmos so that that to me makes sense the other reason why I over a decade ago took this idea of the multiverse seriously is because whenever you you probe these questions of the origins why did we start with this universe the kind of question that Roger asked when I calculated the probability to start with such a universe that question does not make sense if you don't have an ensemble a pool of possibilities from which to choose from if all I all I have in my pocket is I don't know ten pounds then it does not make sense for me to ask what's the probability that if I put my hand in my pocket I'll pull some other note that is not 10 pounds of course there is a hundred percent probability that the only thing that will come out is 10 pounds and nothing else and and the same with the universe if you insist that we must have only one universe then I I do not see how the question why did we start with this universe can make sense and and that if you dig deeper that that really boils down to two very fundamentally different approaches to to the nature of our universe in theoretical physics one is the approach of the theory of everything a single universe and underlying theory were that of course ideal you can write on a t-shirt but an underlying theory that tells you absolutely everything you need to know about this universe alternative approach is the multiverse the possibility that the cosmos is more complex more there are more structures we besides our universe and and depending and and the second that the latter also allows for an indeterminate ik universe one that is based on own probabilities and the first one is based on a deterministic universe so these two very different tastes to physics also determine the kind of one universe versus many universes approach but whichever way people coming eventually will all be forced as we solve one problem after another after another we'll all be forced to merge into one point of view and and and hopefully that will happen soon Roger isn't the multiverse enough why do we need eons as well well let me make clear about the distinction here you see when people say multiverse you're thinking in what you might call parallel you think of a more stacked up next to each other but the point of view that I'm pulling for was a sequential so they're one after the other and they were really very different now there are reasons that some people put forward which are worth taking seriously that there might be parallel universes and these have to do with apparently coincidental constants of nature and so on which allow life as we know it to come about now I think these are arguments one is look at and take seriously I don't get completely persuaded by them because it more or less tells you that life as we know it couldn't come about unless these numbers were right but if these numbers have different values may be a different completely different kind of life that we have no experience of and here's where science fiction is very useful I mean there's a lovely book by Robert forward which describes life on a neutron star and their processes go on millions and millions of times faster than ours it's a wonderful story because you have to relate human timescales to them to the timescales of the Chi these creatures I think it's a wonderful exploration of how life could be so very different for those arguments it's an interesting question I think I'm confused but even if the universities have I don't have the arguments about the existence of life and and fine-tuning of the constants of nature life arises as we know it in our universe even that argument is not correct there there's a lot of work tons I've looked at some of those with collaborators Fred Adams and Stephon Alexander where we show that you can vary the fine-structure constant responsible for electromagnetic interactions and a Newton's constant by six orders of magnitude and still get life as we know it in fact and I still get life as we know it I mean in fact [Laughter] this constant stake in our universe make our universe not right at the center of the most favorable region for life to arise we're somewhere in the corner so the arguments that that we have fine-tuning and there there is one universe or or there is a new trend known as the multiverse research has taken off there is a new trend of anthropic dressing of the multiverse saying oh well if you have so many possible universes in this multiverse then the the one we really care about is the one that allows life and that's because then we can witness it but now that we know that you don't need to fine-tune the constants of nature life can arise in many but you would still need a beginning in the multiverse I mean the multiverse now well each of those universes have have a beginning yeah each of them but you have an infinite number of them right and they are not parallel parallel universes refer specifically to something that that song writes a lot about that's the interpretation the many-worlds of quantum mechanics so that that's a very specific do we do you agree that we don't need a beginning with the universe because you admitted there was a little you know the man's it's the conventional story is that there's a man on the floor and he's dead but we didn't actually see what happened right we don't need the beginning me being the operative word there it may be that the Big Bang was the beginning as Roger has emphasized for many years now the observed fact is that our early universe is very very special if you took all the different ways you could arrange all the photons and particles of matter in the universe the one that we actually have for the our observed Big Bang is extraordinarily unlikely that's these ten to the ten to the hundred and twenty something unlikely and so either that was a tremendous accident and we got lucky nobody believes that or there's a reason why that's something that does seem to demand a reason why maybe it's because it was the best it was the simplest right Roger has the idea of the cycles and the eons is another one so let me let me actually try to defend this idea of inflation that has been remarked upon a couple times inflation seems like a cheat visa fee this particular problem because the problem is why is universe so unlikely inflation is a theory where you start in a particular kind of state and then it expands and cools and very naturally becomes the universe that we see but that place you started as Laura already said is even more unlikely so that doesn't seem to help the reason why it might help is because even though it's unlikely in this sort of sense of all the possible ways the universe could start it is maybe makeable in a way that the ordinary universe is not if you see the universe that is all around us with two trillion galaxies in the observable universe and you wind that clock backwards until you hit the point at which quantum gravity is unavoidable right the the closest thing we can come to the beginning of the universe and you don't believe in inflation everything we see around us was this big it was about one centimeter across you might think if you're not a highly trained professional cosmologists that's very small yep but if you are like that's huge because you're comparing it to sub atomic scales the size of atoms and particles so you needed a universe that was perfectly smooth and regular across a centimeter when all the particles that we know about are much much much smaller than that what inflation lets you do is start the universe much much much smaller than that so if you have a theory for how universes are created such as my favorite theory of baby universes where you start with a big empty universe and there's a quantum fluctuation that bubbles off a little bubble of space that grows into our universe the little bubble of space that you make is much more likely to be small than to be big and if you want to start with a small universe and make a big one like ours inflation does a very good job so I think there can be a role for inflation whether or not it's true I'm not sure ten percent right but nevertheless it does serve eight an obvious purpose that we might like to take advantage of in understanding why we started from someplace very special and got the verse we see we are fundamentally out of time and we can't run it backwards or get it from any other universe I'm afraid and so really all it remains is for me to ask you to join me in thanking our panelists [Applause]

Channel: The Institute of Art and Ideas

Views: 166,070

Rating: 4.7523222 out of 5

Keywords: roger penrose, penrose, roger, big bang, sean carroll, carroll, laura mersini-haughton, big bang theory, how did the universe begin, big bang explained, did the universe have a beginning, sir roger penrose, orignin of life, einstein, gravity, cosmological constant, physics, problems with the big bang, big band wrong, quantum, quantum theory, quantum mechanics, classical physics, cosmology, hawkins, laura mersini-houghton, theoretical physics, penrose nobel prize

Id: 7HES3bPNAsA

Length: 38min 11sec (2291 seconds)

Published: Fri Dec 21 2018