"Are we Seeing Signals from Before the Big Bang?" - Professor Sir Roger Penrose OM FRS

tonight in this equation a number written several including in bursaries at one the cycle time that won numerous awards to grow commander the 1988 will track the business which he share the Stephen Hawking or enjoyed contribution to our standing on the universe Japan's workers talks life has always been signal before Big Bang thank you for coming to a cutter and people to join me tonight well thank you very much is this working by the way can you hear me at the back but is it just my voice or is it just the voice let me switch something on how about that any different no how about that good okay I'm voices might give out on me so to worry about that but this is another title for my talk which I think you just saw so okay now first of all I should say this talk is about cosmology and it's about an idea which I used to refer to as a crazy idea because I want to get in there first before other people said so it's actually let me give you first of all a picture of some of the earlier ideas about what the universe is like these are all after Einstein's general theory of relativity and in who when he started to suggest his equations I might apply to cosmology the first solutions were by russian mathematical physicist called friedman and as are most of my other pictures time is going up the page so you have think of space as sections through and the time is progressing this way and among Friedman solutions were one that looked like this in space-time terms you imagine that the space is closed up it's really a three-dimensional version of a sphere surface of a sphere and I've only drawn this as a circle because I can't draw all the dimensions in there start it started with a big bang expanded and then collapse back to what's called a Big Crunch and that bounce and then did it again and again like that so that was the solution and people used to call this an oscillating universe mainly because the radius as a function of time is given by cycloids who have imagined a hoop circular hoop with a point and it's rolling along this line and the point traitor's art this cycloid so you see it keeps on going so the idea was perhaps there were cycles in the sense now there are various problems with this one of them being the second law of thermodynamics because if you have a second law of thermodynamics the thing called entropy which is a measure of randomness in some sense should be increasing all the time and Talman one of the few cosmologists who really worried about this issue it would be important when what I want to say the second law of thermodynamics and he had a model which was a modification the Friedman's original one in which these cycles sort of got bigger and bigger and he did accommodate the second law in a way which which made sense certainly in those days when they didn't know about black holes because black holes are the major contributor to the second law and that again also will be important in what I want to say now various people in particular wheeler worried about where the constants of nature might get changed each time and so on that's not been a featuring what I want to say but something to think about Smolin had a version where you had new phases of the universe budding out of black holes and so on and I have some problem with the geometry not fitting very well that won't be important also what I want to say there are other models which are based on ideas from string theory you'll be happy to hear may be or depends whether your string theories are not happy if you're not a string theorist to hear that I won't be mentioning anything about string theory apart from what I'm saying here that these two depending on string theory Steinhardt and Tarak have a model which does resemble mine in some respects venice Yano has a model which certainly my scheme does involve in an important way okay so most of those things I won't have much to say about but what is the universe like as far as we know well it's like this now this whereas it's like this again it's a space-time picture time going up the picture and here you notice this funny stuff going on the back these are supposed to be the space sections going up here time progressing this way big bang there I'm only putting that in the back because I don't want to prejudice the issue as to whether the universe is closed or open it might be one or the other doesn't actually feature in what I want to say what is perhaps useful is to see the different spatial geometries that you can have if you have a uniform universe this is when the curvature is positive these I should say our asha pictures and models which illustrate very nicely the different kinds of geometry of uniform geometry you can have of course these are two-dimensional and you have to think of a three-dimensional version but that works fine could either be closed up like the case of the Friedmann model which I was just showing you many years ago maybe you must imagine that these are special sections are spheres here you have a sphere here we have the Euclidian case and here we have the hyperbolic case people these days seem to be saying that it's flat in this sense on on the whole in a sense that's the worst possible case because it means we don't really know it is certainly very close to being that it might be one of these on the models it might be something quite different too but these are as long as it's reasonably uniform on a large scale it has to be one of these possibilities inertia has Illustrated these things with these nice tessellations of angels and devils I want to concentrate on this one not because I think the universe is is this hyperbolic case with negative curvature but because this picture illustrates certain things I'll come back to that later the main point it illustrates is that infinity here is represented as a finite boundary so your entire model of the universe is represented as a finite picture with infinity as that boundary and it's what's called a conformal representation so that means that angles are correctly represented or put another way if you take a small feature like say the eyes of the Devils those the shape of that I will be correctly represented right down to the edge okay it'll be slightly deform the smaller shape the less the defamation is but it's just get smaller as you get to the edge but the shape is preserved or angles are preserved infinitesimally preserved that's what conformal means you'll come back to that some important concept which will have some relevance okay let's go back to what we think the universe is like now we have you might want to know where we are in this picture where we're sort of roundabout there I'm not sure but somewhere where the accelerated expansion which is this part here this is the conventional an stein expansion universe expands out here from the Big Bang the expansion slows down and then it's supposed to be accelerating in its expansion this is actually what Einstein's equations will tell you if you incorporate the term that Einstein introduced in 1917 which is he referred to as the cosmological constant people nowadays give it other names like dark energy and so on but it's well described by the equations that I understand introduced the slight modification of his initial equations in fact it's the only thing you can do through his initial equations without ruining them you can put this extra term in and this extra term Einstein initially put in for the wrong reason because he wanted the universe that was uniform closed up like the Friedman models with here but not actually oscillating so it would be static like a in the picture it would look like a like a cylinder going up here so it was static and to make it static he needed this cosmological term now shortly after that it was convincingly demonstrated by Hubble and others that the universe is actually expanding and so that's not a good model and Einstein was kicking himself and saying well if I hadn't put this term in I might have predicted that the universe is actually expanding I don't know if he said that but he did say that he thought his cosmological constant was his greatest mistake well it turns out that and stay in Einsteins mistakes turned out to be true and it seems that there is this term and that term very beautifully describes the accelerated expansion that we do happen to see okay now there's another feature of this picture that I want to talk about you might say where is it inflation now inflation is supposed to have taken part taking taking place very early in the universe and it might be that it is there in this picture because it would be tucked into this little black spot at the beginning and you wouldn't know whether it was there on and the point of view of this picture so if you want to have a better picture of inflation you have to get a very very powerful microscope well magnifying glass here and here I have a picture of what you might see which is the inflationary phase now the main point I want to make about inflation apart from the fact that the other reason I haven't budged in this picture which is that I don't really believe it if you don't believe it you have to have some other explanation for what is explained by inflation well as some of the things that explain why inflation aren't really explained by inflation in fact the main reasons for introducing is in the first place though most of those don't actually explain things that well I won't really go into that because it's not important for what I want to say it does explain certain things which you do need an explanation for and I'll have to come to those things briefly later so you need something like inflation take notice that it's very much like the exponential expansion that we do see on a large scale completely different scale we do see this exponential expansion taking over in the universe now as I say we're up here somewhere where it's just beginning to make its mark and the claim of inflation is that something very like that was happening in the early stages but what's different in the model that I'm presenting you with is that well in a sense inflation was there but it was not there after the Big Bang it was in a certain sense there before the Big Bang but how do you make sense of that well first of all you make sense of it by adopting two mathematical tricks and I'm going to try explain this mathematically well actually the universe would be it would be handy if it was a bit smaller than that for this transparency so let me make it a little bit smaller and I'll show you the tricks the tricks are the following first of all you squash down the future infinity to get a finite boundary now that is just the same trick that done to space-time rather than to the space as Asha was employing this is actually a done first by the mathematician belt Rami people tend to in mathematics they tend to call it the Poincare a representation it's actually due to Beltrami a good Dale do perform from Cairo but never mind Hungary we discovered it so that's reasonable it's about that anyway so you can sort of squash infinity down and that same way as in that picture but now to space-time I'm squashing infinity down to this boundary it's just a trick what's the other trick the other trick is to stretch out the Big Bang also to get a finite boundary that's the opposite trick to the one that Asher was showing you in this picture now there's a little bit of a difference in status between these things in a logical status the difference is explained here one is the future trick works very very generally it's it's really no restriction on the universe at all if you've got this positive cosmological constant this exponential expansion and the universe thins out and there's nothing much left except photons and things which don't have any mass and so on then this will always work this trick there's a theorem due to Helmut Friedrich who has demonstrated this pretty convincingly now that requires positive cosmological constant which is what we seem to have however the other trick the stretching out of the Big Bang is a huge restriction on the nature of the Big Bang so here is he an extremely strong restriction which corresponds to suppressing gravitational degrees of freedom and the generality of that or lack of it is exploited by my colleague Paul Todd and I'll come back to that and say why it's important now these two tricks I should say are nice things you like to do whether they have any physical content is another question who certainly nice ways of looking at the universe as a whole you can sort of draw it on one piece of paper if you like which is rather nice but I want to use it in a more dramatic way I say that this thing that I'm doing here let's forget the right one Hut here we go the two tricks which I am applying here in a certain sense real and not only that but they are part of a progression of universe what I'm calling these eons so each one of these is an eon and each eon starts with its Big Bang and ends with this infinite exponential expansion but the idea is that when you squash down infinity it looks very much like a stretched arc Big Bang and that's rather remarkable but I'm asserting more than that but it is actually the stretched art Big Bang is a squash down infinity if this is us here and we're sitting here somewhere then there was an eon prior to ours whose remote future became our Big Bang our remote future will become the Big Bang of the next Eon and so on and this may be extended indefinitely in both directions now I want to try and justify first of all Todd's trick here why is it that we can get away with making that infinite expansion well the point is really to do with the second law of thermodynamics as I mentioned briefly before but I want to say more about it in fact I want to talk about two things about the second law of thermodynamics which well two things which have to do I should say with the microwave background you see talk about the Big Bang very glibly and they say there's lots of evidence that it was there but what is the strongest piece of evidence that the Big Bang was there well the stronger piece of evidence basically it was the piece of evidence which was main one in in disproving the older steady state theory which I grew up with rather in my young student days and the point is that there is this radiation coming out in space from all directions which is basically photons and well they are photons it's electromagnetic radiation coming from all directions of indicating a temperature of something like two point seven degrees above absolute zero so it's very cold it was seen I say it's won the Nobel Prize twice and two separate occasions first for the original discovery by Penzias and Wilson who discovered it by mistake in a sense although it was there it was predicted that it should be there by Dickey and gamma off people the idea was that in Lee the flash of the Big Bang would produce this radiation and as the universe expanded so here we have this flash the Big Bang as the universe expanded it would have cooled the very very hot radiation that it was originally to this two point seven degrees above absolute zero and the two features about this first of all the thermal spectrum for some reason I don't seem to have nice slide that I would have shown you here I didn't find that one I didn't realize it was missing but there is a if you look at the temperature the intensity of the radiation for various different frequencies then you find a very nice curve which is the Planck radiation curve and the Planck radiation curve is telling you that what you're looking at is thermal equilibrium now there's a bit of a paradox here I was talking about the second law of thermodynamics the second law tells you that randomness or entropy if you like is increasing with time now another way of saying that you see if entropy is increasing the time then lo is saying it is if you go back in time and should be is decreasing so that means that the entropy must be very very small at the Big Bang and it has to be just for very very basic reasons the fact that we have a second law of thermodynamics and that we believe that that second law was still holding way way back into the Big Bang now if that's the case then the initial Big Bang must have been very very special very low entropy at least in some particular respect and what we see the evidence for that Big Bang we see this beautiful Planck curve the most perfect plank curve ever seen in any observation what does that tell us tells us that what we're looking at was thermal equilibrium what's thermal equilibrium it's maximum entropy now that might seem to be a puzzle but for some reason cosmologists hardly ever worried about it work Tolman I did mention did he's one of the few who really did worry about this question but for some reason when you see what the problems of cosmology are and there could be a list of them the second law is never mentioned I never understand that because it is a huge mystery but the mystery isn't quite what the way I'm putting it you see you might say how could it be that this maximum entropy state which we seem to see in the Big Bang that's what the Planck spectrum is telling you it's a maximum entropy state maximum disorder how can that be the very small entropy that started the second law it's not a contradiction is just as 'el and I want to tell you what that puzzle is why is it not a contradiction well I think some people used to argue without thinking that it's got something to do with the universe expanding and maybe they were and you couldn't wasn't room for much entropy in this mode that's just a little wrong answer and Tolman certainly appreciated that but I'll give you another better reason for why it's there well not better but another reason why it's the wrong answer now okay if that's not the right answer what is the right answer well you have to address the question of what you're looking at you're looking at photons and those photons are coming from their interaction with matter so you've got matter and radiation apart from the expansion which is basically adiabatic that's what Talman pointed out so the fact that the expansion is there is neither here nor there it really is modulo the expansion if you like a maximum entropy state but what's the other feature of the back away background the fact that it's thermal it's a thermal spectrum is one thing but the other thing is that it's almost exactly uniform of the whole sky now almost exactly uniform it's not quite uniform but the major way in which it's not uniform is due to the Earth's motion so the earth is moving through it and when you correct for that you'll get something which is extremely uniform its uniform the temperature is the same in different parts of the sky to a few parts perhaps in 100,000 so a few parts in in 10 to the fifth very very uniform now I'm going to be saying something about the little ways in which it's not uniform later on but but that's completely swamped by Vera Lee's uniform now what's that telling us well again you might says telling us you're looking at high entropy well you see when we talk about the second law of thermodynamics the sort of thing you might talk about is a gas in a box and you might imagine that if you had a little compartment here and all the gas was in that compartment with some malls you remove the walls and then the gas will spread out through the box so uniformity certainly is an aspect of large entropy so as the the uniformity increases the entropy also increases so that's consistent with high entropy you're back where you started but suppose these were not molecules in a gas but suppose you had a galactic scale box if you like and you're looking at stars and those stars are gravitating now if they were uniform originally there would be a strong tendency for them to clump and become less uniform simply because gravity is a universally attractive force and now entropy is increasing with the increasing clumpiness now what do we see we see uniformity that is consistent with this picture and with this picture so you're seeing a combination of high entropy in everything except gravity gravity which was the thing that was not thermalized it somehow room louf from everything that was going on it was stuck at a very low value in the initial state now the thing is people didn't kind of think about that much because the models such as Friedman's for example they assumed uniformity in order to solve the equations if you're going to solve Einstein's equations that quite difficult you good thing to assume it's a very uniform universe turns out the universe is very uniform but two people have forgotten how to big an assumption that is then I come back to that issue too it's a huge assumption and that is the thing but here's the mystery the mystery is why was it that everything was high entropy in other words all thermalized except for gravity it's not a contradiction it's a mystery and it seems to me that is one of the biggest mysteries of cosmology nobody ever mentioned what I do but nobody ever seems to mention it now this clumping is a feature which is what we all depend upon and just to make that clear why are we all here well good reason why we're all here has to do with the fact that the Sun is here and the Sun is the source of low entropy and you can think of that as the fact that well you see people think what's the Sun for what do we get from it really where we get energy from the Sun that's not really correct because the earth as a whole throws away just about the same amount of energy as it gets from the Sun if it didn't the earth would just get hotter and how it was getting a bit harder than of global warming but that's relatively small on the scale I'm talking about here if it wasn't the fact that the energy from the Sun didn't go out again into into empty space we would just be all frazzled away so that we have to lose that energy but what the key point is that entropy you see the Sun is hot the but the background sky is cold that means the photons from the Sun are high energy the photons which go back these are solar yellow photons and the photons going back are reading for read these are much less individually less energetic so therefore there are many many more photons to carry the same amount of energy coming in this means more organization or if you go to the definition of entropy fewer degrees of freedom here many many more degrees of freedom here and so the enter energy is thrown away in a high entropy form so what we get from the Sun is the source of low entropy that's the key and well why is the Sun there at all well why is it hot it's hot for all sorts of reasons because of thermonuclear reactions and all sorts of things but the key point is it's there at all and it's there at all because of gravitational clumping it's the previously uniform gas was clumped into the Sun and that heated up just the mere fact that it was clumping in fact if there weren't any thermonuclear reactions the Sun would have got much hotter much quicker and then it would have cooled off it wouldn't be much use to us but it would still have got very hot so the point is the thermonuclear reactions actually could slow it down so the Sun can stay there for a long time and keep us warm but not at the main point is that they keep the entropy down plants make use of that I photosynthesis and then ultimately we eat plants or animals that eat plants and so on that's how it all works okay let's just indicate that this gravitational clumping is an important feature now I want to go back and talk about the what's the sort of maximum entropy state well it's a black hole so the black hole is where the entropy finally ends up and in the present universe as we know it by far the major contribution to the entropy of the universe is in black holes is in the supermassive black holes such as we have in our galactic center and other galaxies also have black holes in their center which having a huge absolutely enormous amount of entropy contained in them now I want therefore to say something about black holes so let me give you a picture of a black hole and my picture of a black hole like my other pictures most of them will be a spacetime picture here we have time going up a picture and here we have some collapsing material to make a black hole and this is the horizon of the black hole now the main thing about this picture but two things which are important one is if you like The Horizon or that is a feature of the light cones so the important thing is to know what the cones are the light cones well you can you can think of at each point in space-time there is a one of these double cones drawn on it of course you could have them n right number of dimensions here I've thrown one a way to draw on the draw of the cone this is a special picture if you imagine the flash of light taking place here then the history of that will be described by this future cone especially it will be a point and then the section correspond to there and the section consequence is fear of getting out there expanding with the speed of light there's also a pass cone which represent what light would do you have to imagine every point there's one of these cones there isn't necessarily light there it's just telling what light would do if it were there and to understand special relativity you just imagine these cones uniformly distributed throughout the four-dimensional space-time general relativity they're not uniform they're kind of oh Piggly Piggly in each case you have well the cone is the future part in the past part a photon has a world line that's the history of that photon thought of as a particle which will be tangential to the cones all the way along and then there are massive particles which are always within the cones telling us that the massive particles have to have a world line which represents a speed which is less than the speed of light if these cones are tipped over in various ways the light the particles have to be constrained to have their world lines within the cones however they are tipped and again the photons along the cones the massive particles within the cones so we need that and now that just shows us a bit more about what's going on here and the horizon has this rather uncomfortable feature that it carried when you see the light cones roll to throw it tilted over this way pointing inwards and if you were unfortunate enough or foolish enough to happen to be in the neighborhood of this like this horizon you would then find yourself trapped inside and you can't get out because any world line that draws itself outwards would have to violate the because of causality condition because has to be can train to be within the cone the other even more unpleasant feature is that you will shortly encounter the singularity in the middle where the space-time curvature becomes infinite densities become infinite or hell breaks loose the equations find themselves giving up somewhere down in the middle there so because curvatures become infinite densities become infinite and so you're stuck okay that's the black hole with its singularities in the middle well at least this is just a picture it mainly got from the spherically symmetrical case in general there will be irregularities those irregularities we know from theorems that they will still result in singularities even though the picture won't be exactly like that okay our picture of the universe now has to be modified here we have the singularity the Big Bang where these space-time curvature is also were infinite and we have these singularities now in the black holes which will be in various places now the point here about second law is that the singularities in black holes are of a character where you could say the entropy is enormous and in that's true in black holes from the famous bekenstein Hawking formula for the entropy in a black hole is an absolutely enormous figure and that is in a sense telling us that when you get to the singularity you will have a very very gravitationally random State so it's very very high entropy quite unlike what you see at the Big Bang in fact it's the singularity structures which drive the whole thing it's the bank of the Big Bang happened to be a singularity of a very special kind which is not shared by the singularities in black holes now you see I can kind of make the reason why if you like inflation and any of these other arguments don't give an explanation of why the backhoe is special it's really just the second law I want to imagine just theoretically that the universe was collapsing let's suppose it was but with a second law which is still going in the same direction upwards now black holes will then form and these black holes will meet each other swallow each other up congeal and form one incredible mess at the end of congealing singularities so that will be the picture something like this with entropy going up and up and up and up to some ridiculously enormous value when all these black holes can deal with each other now if you put inflation in which is supposed to be due to with some special field called the inflaton field which is supposed to you smooth the uniform at you universe out well you can see it can't do that because what would happen if you reverse this when you just get this mess and that means that would have been a much more likely initial state for the universe where it started out very very general and in photon fields don't do anything for you so that's the whole big problem is why was the universe initially like this and not like that where the likelihood of it being like this is absolutely enormous in fact let me give you some idea of how absolutely enormous it would have been okay the Big Bang must have been subject to an absolutely huge constraint due to the suppression of gravitational degrees of freedom and you can work out from the bekenstein hawking formula for the entropy in a black hole how special that state was let me not go into that details of that it's not a difficult calculation or anything it's just it's the answer the answer is that the in probability of finding the universe anything like the way we did find it is about one part in 10 to the power 10 to the power 124 you may see this figure 123 somewhere not that makes much difference to the art it's like happily stupendous difference for the actual number but hardly any difference of the argument whatsoever this is because the if you include dark matter then the number goes up to 124 you may see 123 quotas in some places that's without the dark matter that's the only difference okay the reason for the double exponent has to do with the definition of entropy which involves a logarithm I won't go into that here but this is giving you how unlikely if it was just chosen randomly how unlikely anything like the universe that we actually encountered and had in at the bit nature of the Big Bang that sort of unlikeliness now let's not worry for the moment about how that could have come about let's just address the question of what was it like how would you describe geometrically what that universe was like specialized in that way well there was a thing I used to I used to phrase it in this way the viol curvature hypothesis trouble with that is you need to know what the viol curvature is and I haven't got time to explain that too so let's not do it that way fortunately there's a better way of doing it it's awkward condition to state just in terms of curvatures but Paul Tom my colleague in Oxford in 2003 came up with another way of saying at a very mathematical elegant mathematical proposal well I've cut the piece of transparency off here so I'm going to show that to you only in a little while let me worry for the moment not about what the Big Bang was like but the other end so we'll think about not just why the universe was like this not like this but what about the remote future well the remote future first of all things will fall into black holes black holes get bigger galaxies collide with each other and then black holes get bigger still and a lot of matter war well this this exponential expansion will thin the universe down you'll have black holes and the matter thinning them thinning it down in the remote future what happens to the black holes well according to Stephen Hawking and I certainly agree with him when the universe you see black holes are not entirely cold they're pretty cold in fact well I think Steven wrote an article calling black holes are hot how hot are they but the mins are big they are the bigger they are the colder they are the smallest black holes therefore will be the hottest ones one of the smallest ones we have any reason to believe in those are a few solar masses a few times the mass of the Sun what is the Hawking temperature of those black holes well you have to think to get the right sort of ballpark figure you have to think of the coldest temperature ever produced artificially on the earth and that's the sort of scale very very very cold but these are the hot ones the really cold ones are the supermassive black holes like the million to 4 million solar mass black hole in our galactic center or the far bigger ones that people are detecting in other galaxies and the thing is that when the universe expands by this exponential expansion it will get colder and colder and the microwave background will come colder and colder until it gets colder than any black hole we have any reason to come about the really huge supermassive black holes and you have to think of a timescale of something like ten to the hundred years or a googol years is sometimes called one followed by 100 zeros and in that kind of time scale it may be longer or even really bigger once the black holes will evaporate away because they will be the hottest things around and when the husband things around there will be thermal radiation coming from the black hole very very cold long wave meant like protons mainly what long long wavelength photons will be carrying away the matter very very slowly to something like a googol years and as they carry away energy they must therefore carry where mass and therefore the black hole will get smaller and smaller and smaller until it goes off with a pop well I've called you the pop here because although it's quite a sizable explosion it will not be anything of significance on the Astrophysical scale so even if well the final pop is only about not Hilary shell but I guess you have a fairly big explosion before that when you lose something like a nuclear explosion but that's chicken feed with regard to things on a cosmological scale so I'm calling it a pop okay so what's our picture look like now here is our universe this before and now I'm putting the new black holes in and they're going off pop now this I should say is grossly not to scale I mean it's way up there somewhere the other point I want to stress here is what I have rather written here this is the when they've all gone this is what I call the very boring error now you see it's pretty boring already when there's nothing much going on except black holes and I can't think of much more anything that's more boring that's sitting around waiting for you maybe a Google years waiting for that black hole to go off pop seems to me rather boring but that's nothing compared with how boring is going to be after that now I use an emotional argument at this point okay I admit it's an emotional argument I think that somehow that's not a very satisfying picture you know universe is over exciting though wherever we are up here and justice imagine that that is the fate of the whole thing seems to me to be pretty miserable but then I began to think well who's going to be around to be bored by this not us the main things going around by far the main things will be photons it is incredibly hard to bore a photon there are two reasons why one is probably doesn't have any experiences but the other is the basic thing about relativity see here we have I shall join the light cones I've talked about light cones up to this point but what I haven't talked about is the rest of the structure which gives you the metric which Einstein needs to describe his space-time geometry the metric component the metric is the thing that sometimes when G a B or G mu nu or G for beta or something like that and it has ten independent components for points ten numbers characterize it at each point nine of those numbers well is the ratios of these ten numbers simply just telling you where the cone is exactly how it sits and how fat it looks in your representation and so on it's just telling what light does so nine of the components are telling you the light cones the tenth is the scale now you see if you want the metric suppose you want to describe how big things are in relativity well you might say where you want to measure distances and distance is the ruiers and you say might measure ruler ruler distances by taking what you say meters and how big as a meter well then you go to the meter rule in Paris the trouble is that's not much use anymore because it's not very accurate by a kind of standards that we have nowadays a much better way is to use a clock and the speed of light clocks other things which determine the scale now clocks I've put them in here in this picture I've got two identical clocks going through this point and these are this is represents the first tick that's the second tick and the third tick so you need to add to your light-cone these sort of surfaces here and the crowding of them is the tenth component now you see we have very good clocks in physics it's one of these amazing things that the two most important simple equations of the 20th century physics Einsteins e equals mc-squared and Max Planck's a equals H nu nu being the frequency even the energy M the mass M H and C being constants Planck ice I told you that energy and mass are interchangeable Planck tells you that energy and frequency interchange will put them together tells you that mass and frequency are interchangeable so if you have a particle whose mass or rest masses M that determines quite uniquely through these formally a frequency M times C squared over H and so it's an oscillator very very well defined in terms of its mass and that is basically how ultimately it's the mass which tells you how wonderful clocks are atomic and nuclear clocks are depend ultimately on on this very fundamental concept of time which comes from those very fundamental equations which come from the mass so if you have if you have mass then you have a time scale but if you don't have mass as its represented by this Photon there is no measurement of time the photon doesn't know the progression of time at all so as far as the photon photon is concerned well one way of putting is energy is infinity is no big deal see the photons doesn't even know the passage of time I can go right up to in turn eternity and as far as its concerned nothing much has happened so if we imagine photons they're not bored at all if they are allowed to have feelings they wouldn't be born another way of saying all this is I go back to the picture I had before and what I want to do to it is make it a little bit more complete because if we take the representation here it's only the light cone structure that's actually the conformal structure remember the angels and devils in the azure picture this is the space time version of it is just to know the light cones that's conformal geometry it doesn't know the scale if you want to know the scale you put your clocks in here we have them at the top here there's a clock and this gives you these surfaces have these parabolic so hyperbolic surfaces here and the crowding of them is giving you the full metric now now a lot of physics you might even say most of physics doesn't need the scaling if you don't have rest mass you just need the conformal structure this most dramatically applies to Maxwell's equations for the electromagnetic field they are completely invariant under change of scale you can change the scale arbitrary in different places by different amounts and the Maxwell equations come out completely unscathed so they don't know they don't even care about the scale it's also true of the yang-mills equations which have to do with strong and weak interactions the only total difference there is that mass comes in an important way it's the mass which knows the scale and you're in when mass is there you have to know the scale the mass is not there this is the kind of geometry want if mass it is there you need the whole geometry well mass in another way also features as the source of gravity and as the source of gravity it's important in general relativity so you need to know the mass you need to know the scale for general relativity but then gravity it's again mass because it's not the source of gravity which is involved okay now if you just have the conformal structure I sing in there a very remote future it's mainly photons of their around and so it's the conformal geometry which will be important and if it's the conformal geometry that's important then you can go back to this picture and say okay infinity can be squashed down and what the physics doesn't really know and this is physics with mass in it just without any mass in it it doesn't really care that this is a boundary it's just like anywhere else so that's the philosophy and so one can think of the very remote future as being and this is a trick that we used for a long time is to squash infinity down if you want to talk about radiation in general relativity and so on is there's been a useful trick to squash infinity down and talk about the Maxwell field what it's doing on this boundary and that's sort of asymptotic properties the next one or and this trick will work here okay it's just a trick you treat the extremely remote future squash it down and it's handy okay now I'm trying to say with only massless things conformal geography support important well there is a little bit of an issue here because although there most of the particles lying around will be photons there will be massive particles to some of the might decay may be protons decay but you can't very well get rid of the electrons because there's nowhere for them to go electrons and positrons will be will be stuck with they'll be pretty scarce but they're still there so that will spoil this picture so I'm going to propose and this is an unconventional proposal that mass will gradually mass itself will gradually fade out in the very very remote future it's a sort of reverse of a Higgs mechanism that in that when the temperature gets very very cold then the mass for that the the mass will fade away as I said it's not the front cannot conventional but it's there's no evidence against it and then the conformal geometry would be what's important I tell your future boundary then you might say well what's on the other side of that boundary or the question is what was there go back to what Todd's proposal was what is Todd's proposal well it's this that the space-time can be represented informally so if you forget about the scaling so that the big bang or the smooth surface and in fact that does kill off all the gravitational degrees-of-freedom that's technical point which I can't go into but he was regarding this is basically a mathematical trick a way of formulating the condition on the big bang that corresponds to the low entropy in gravitational degrees of freedom can be high entropy never ething else there's lots of things running around here but it was just a mathematical trick what I'm saying is that these tricks are real that there was something before the Big Bang it couldn't have been a collapsing universe which might be the most obvious thing to think of because then you're in trouble with the second law because the great mess which I showed you for the collapsing models will give you something which doesn't stretch out to become smooth that's very basically what starred is saying that if you want to get rid of at a gravitational degrees of freedom you have this smooth boundary and so anything where the gravitation degrees of freedom are piling up and producing this great congealing of black hole singularities isn't going to be any use for back here it doesn't explain this this state I mean you could say well heads for this in some sense on maybe the second law went in the opposite direction back this way it does while there was this very special state however if it was the continuation of the remote future of something before it then you look at the equations and you see yes the gravitational field is cooled off and it just comes from the way things transform under these conformal Maps and I won't really go into that here so that's the picture and then globally this picture is the one I showed you here that our Big Bang was the continuation of the remote future of something before and in the way this enables you to get away with not having inflation well why does it do that well you see you have the exponential expansion of the previous phase and that looks rather like inflation so inflation does explain certain things there is I think one of the the scale invariance of the fluctuations in the microwave background is the sort of thing that you need inflation for or else something else which does it also and I would say all those a lot to be checked in this that the exponential expansion of the previous eon does in that respect what inflation would do in the more conventional picture so that's the idea one question you might well ask is the Tollman question what's happened to the second law of thermodynamics if entropy is increasing and increasing increasing how can you have a cyclic model like this well here is where you have to bear in mind where most of the entropy was or is I should say already in the universe as we know it it's in black holes what happens the black holes they evaporate away well does that violate the second law of thermodynamics no it doesn't but you have to be careful and what I'm saying is you have to be very careful and it goes back to something Stephen Hawking said in if I've got the date down here but it was a long time when he first put forward these ideas and he said information or phase space volume is really what it is gets lost in the singularities in black holes and then he changed his mind a much later he said no no somehow I feel he got browbeaten by other people who wanted the interim somehow information not to be lost and so he changed his mind I think he's right originally the original thing and you look at some of these diagrams and you could say yes information does get lost it gets swallowed into the singularity and there's no way around as far as I can see now what does this mean this means that when you define your entropy you have to worry do you take into account those degrees of freedom which are swallowed by the black hole or don't you when the black hole is gone there's hardly any point in taking them into consideration and so you change your mind about what you don't your definition of entropy is it's sort of Leary normalization of the definition you subtract a huge number from the entropy which corresponds to the loss of degrees of freedom in that black hole and if you do that you get a consistent picture that the entropy the second law is never violated it's sort of transcended in a sense but the second law drives in fact most of what you say about black holes is not it's not violated Morris you don't even need to know much of the physics the second law almost all you need to know it tells you that what the black hole does it has a huge entropy it disappears because it has a temperature temperature goes up as the black hole gets smaller and what happens to it well if it disappears it will carry away from our universe those degrees of freedom which it's swallowed and then you say I'm not interested in those degrees of freedom anymore I'm going to define my entropy without taking them into consideration and that brings the definition of the entropy down so that by the time all the black holes have gone it's silly to use the old definition because those black holes have swallowed all those degrees of freedom the definition you now use is blue back down to the value you need to have the low value that we get for the next Eon all these things need more detailed examination but it seems to me that they are consistent as far as I can tell what about observational consequences well I try to think you know what could possibly be a signal which gets from before us this is the crossover surface between the previous Aeon and us it's really a three-dimensional surface but I've drawn it as a plane here this is up here us up here we look back to the microwave background which is just a little bit over the crafter the crossover surface here and what was going on before that we might possibly see well what's the most violent thing I could think of apart from the Big Bang itself if you like the most violent thing in the previous Eon would have been collisions between supermassive black holes I mentioned before we have a black hole in the center of our galaxy which is about 4 million times the mass of the Sun we are on a collision course with Andromeda and a even bigger galaxy than us with a black hole in its center which is about 20 times as big as ours when they collide it won't be anywhere soon white had said thank goodness it won't be anyway since some of you said well that's a pity it would have been rather dramatic to see this collision I can figure yeah it would be rather dramatic you can see simulations on the web incidentally what it might have looked like might look like this in the future when we hit Andromeda when you see this lot of empty space in the Andromeda so we're not likely to hit anything but for maybe some dust or something but the black holes are quite likely to capture each other they'll spiral around and spiral around and finally swallow each other up with one stupendous explosion that explosion will be mainly in the form of gravitational waves that is the gravitational version of light ripples in space-time and I've drawn in this picture these are the black holes coming spiraling into each other whoof bang well know how to call it walloping bang and there is the sum a few percent of the rest mass of the black holes will be carried away which is pretty huge and that will be carried away in on the sort of scales we're talking about here almost instantaneously and this explosion will come up hit this crossover surface well then you want to look at the equations and see what it does it transfers itself from a gravitational effect into a kick given to the initial form of dark matter there has to be some creation of some scalar substance in order for the equations to make sense I'm calling that the initial form of dark matter we don't really know if it behaves like dark matter but that is since nobody else knows what it is I can more or less suggest that that it is something which automatically comes about to accompany the gravitational fields it has to be there otherwise the equations inconsistent it will acquire a mass due to some form of higgs process I presume and then it becomes like the dark matter we see well by the time you see it's in the microwave background this impulse will be rather deadened but in the form of giving that initial dark matter of a kick of velocity and what you would see something like looking at ripples on a pond so this is the microwave sky and I claim that each one of these black hole encounters will be like a ripple in the pond where a drop of rain had hit and it gives you a circular ripple and you imagine the rain stops after a while that's when all the black holes have gone here and then you just look like a pond which is Ripley all over the place and that's the microwave background so I say but then you ought to be able to see if you do some clever enough statistical analysis that these ripples were still the circular patterns are still hiding there and can be extracted if you look at the right look at them in the right way and do the right analysis well one point I had tried to get people to do this and it was very hard to get people look at it but my Armenian colleague waha Gossage on did look for these things he looked in a slightly different way from what I was expecting he looked for regions where the variation of the temperature is very anomalous lilo round circles but in order to get a significant effect you have to look for concentric sets now you see why would you expect to see concentric sets but because if you have one of these supermassive black holes it's liable to swallow others another one in another one another one and then each time you might get these supermassive black hole encounters which will produce these explosions which would look like concentric rings so the idea is do you see concentric rings well he was looking for low variance or do you see a temperature which is either slightly warmer than the average that would be from a distant source when the signal is coming towards us and then the initial dark matter is a velocity in our direction or those are the wrong warm ones which are from very distant sources or the near sources the signal will be cooler because it's giving their rid the microwave background material a kick in the opposite direction now we finally after lots of arguments with referees and so on it's on this way of looking at things this is a way of testing whether the thing is real or not that you look at the sky and see how many of these circles you see which have this particular criterion of low variance and then you look again at a slightly twisted sky so I imagine you twist the sky the twist goes more and more as you get down to the bottom and that twist makes the circles into slightly elliptical shapes and then you apply the same analysis so basically you're now looking for elliptical shapes in the real sky and you can make the twist bigger and bigger and bigger if this twist value s is 2 or 5 something like that you're looking for Lipsey's which are almost circles the ratio of the major to minor axis differs from 1 by 1 or 2 percent right down to when s is 80 which is the biggest we looked at where you are really looking at ellipses which look like a lips as' with the major to minor axis ratio is about two so that's the kind of thing we're looking at and I hope I can get thee before I go to that let me since I may not easily go backwards and forwards this was after we did this analysis some people in Poland chap called Meisner who with some other people did a different kind of analysis much more like what I had originally suggested and he looks for signals which I have a sort of front you see it has a sharp edge on the front and then it tails off one way or the other and so you see the sharp edge on the front see this is the gravitational wave coming up here here is crossover it's become a kick in the original material when it acquires a mass it starts to the viscosity comes in and getting acquires a tail and so you see a sharp front here and tailing off so you have a spike that was the idea and this is the picture here which is trying to indicate that and so you will see certain profiles that you might be able to see in the microwave background I'll come to that in these pictures here what people actually see well originally now I want to get this working do i press something to make it working now let's see do I need the screen or is it you better help me because I'm not quite sure yes just that one yeah that would be yes I think so is that the first one it probably is yes yes that's right that's right yes that's fine okay that's on the screen yes that's fine okay good okay well this is what the he goes Oh John found in the actual sky you have to bear in mind this is the entire sky the fit in the middle is the Galactic plane you just said we don't count these signals which come to us from within this region but we can't them if they're outside the region you do count circles if a major part of them is outside the region as long as the center is outside the region the galactic center is there and this is the entire skies of unwrapped it's a standard sort of projection now initially this is he was looking for concentric sets of circles which are of low variation so he's not looking for warm or cool particularly he's looking for circles where the variation in temperatures you go around is smaller than on the average and significantly smaller that's the idea and that would be the kind of thing you would expect in this picture but not looking for the average temperature rather than when they're ready it tends to be ones which are warmer and therefore in my picture would be sources which are further away if they're blue that means they're cooler it's the wrong way around redshift did you see is the blue is there is the blue ones and the blue shifted one to the red ones but that's the way I'm afraid the color scheme works okay here we see 352 I think it is circles in the sky in the true sky now to see whether this is a real effect first of all you can look at a simulation ah this isn't the one I was expecting to see that's a general simulation you see far fewer in simulation but that was not the way we were doing it so let me see I guess I have to press something to go back do I yes you better help me because I have no expert at this thing I'm afraid as you can tell how do I go to one of the other place I'm not sure this is the first picture is it can I do the first one sure yeah that's right yeah it is the same as that picture actually but the top one that's it it is the same as the right hand run at the top okay that's fine like I can move it I think okay the left hand one just shows where the center's are the first thing which is rather prominent about that is that it's very non-uniform and the conventional explanations you see the conventional explanation for the fluctuations of temperature in the microwave background that it's some kind of quantum effect expanded out by the inflation but if it's a quantum effect sort of random why do you get this crowding in certain regions I was not expecting to see crowding at all but seeing it I can give you an explanation it's just that in the previous Eon there were regions where there were huge concentrations of extremely large galaxies and with very very big black holes in their centers and those were the ones that caught cause the signals that we actually see here and this represents a very crowded region here there's another quadric region there and then some other ones would this would be a distant one on my scheme because it means because you see red ones so it's the they are blue shifted the signals are coming towards us this is a closer region here which is redshift in other words blue in the picture that's the interpretation that would give okay now we start to we start to twist and you see Ron the two 352 the number at the top they see is the number of centers we see of the at least three circles with the same centers three Lovera circles with the same sentence 352 of them you twist and remember that this is a twist where you're only looking at one or two percent away from a circle it drops by a factor of three as the twist goes up the numbers drop and they drop quite consistently right the way down do when you get to the bottom it's the sort of numbers that you would see from a random sky so these numbers are probably mean nothing you see they're the ones that you're seeing at the top we claim our are real on the whole most of them are real but the ones at the bottom are not okay now to move myself to the next slide i do i if i press something I'll press the wrong thing so is it this arrow here no so that's what you want you oh I piss on that it's on that's on the mouse no on yeah that one yes that one that's fine yeah okay good that's it now this is for four concentric circles centers with at least four no variance rings and we still see 56 start to twist the numbers drop dramatically in fact they disappear altogether when you get down to well you see they've gone completely here and they're pretty well gone here - these ones are probably they're all on the edge so they probably shouldn't really be counted but never mind they're certainly gone by when you get to the two-two-one if you're honest ellipses that really look like ellipses there aren't any or virtually none okay now I have to find my next picture ah yes sorry I have to I'm not familiar with their procedures here can I just find the next move those steps if you hang around here my accepted on yes let's have that one yes this is just nice seeing it on honor this is again the three circle that the real sky looking at these three circles that's the South Pole where you see more going on than in the North Pole and do you see let's have a look at the next one that's the North Pole this is a different projection so here let's go on yeah that's the South Pole just go on I think well that's a whole W map that is the data produced by the ah no I want the first one that we were looking at can we do that I'm not sure the order of the must have got mixed no that's it yes that's it good fine okay I don't know this now that's a simulation you'll notice they look extremely different not just that there are far fewer of them the colors are not extruder randomly looking they're also the greenish all the way over you don't see any particular big ones notice that we find quite a few quite large ones like these ones here quite big ones you don't see any of those in the simulation um but that's not where we're depending on now this is the more recent Planck satellite the others were the old W of that one which has been going on for decades or so I'm not sure how long the Planck data was only released less than a year ago and the same analysis has been done here this is now looking for and looks like at least for now this must I think that's only three I don't quite know this is for this is looking for centers with at least three you notice that it's rather than disappearing with this more precise data it's it's more and more defined but it defined I can't quite remember what the number is there never mind yeah this is this is the three or more centers this is the four or more centers that's right and you still see these very concentrated regions like here and so on and you could they're very similar to what we had before but in a way more pronounced except that I'm saying it wrong am i a little confused yes this is this is the thrill more in the Planck data that's three or more circles in the black data this is four or more and the W in that data this is Forum on the Planck data and you see these huge concentrations in certain regions this would be a dairy distant source and the other ones got smaller for some reason I mean obviously these things will have to be looked at by other people more carefully the Polish group oh no this is this is the still Iowa a lot this is just showing you the Centers and what's very striking is that although the criterion for looking for them was simply nothing to do with the average temperature it was just choosing them because then you're looking for the low variance circles with a variation in the temperature is particularly low and what you find is that is extremely correlated with the temperature so you have some regions where they're very warm other regions with their cool the explanation would be on my scheme that this is a very distant source in the previous Eon that is a relatively close source in the previous Eon and that is why you see the temperature clumping in this way we nice to see an explanation from the point of view of inflation or something I can't see how you would get things like this okay now I'm going to go on to the next one I stirred it can I move it to the left huh ah yes I want the Polish one that's the next picture what I should be doing something here and capture but I don't yeah before yes it's the next one else yeah no it's that one yeah that's right okay this is Planck data again and this is the Polish group so you see they use a completely different card here and they don't look for concentric sets they look for things with a sharp edge either on the outside of the inside and you notice that they're very clumped also now I can't think of any other explanation than something along the line you see if you see some red ones you see not to them doesn't mean this means the temperature goes up sharply now if it goes up sharply it doesn't mean that the average temperature is big or not so why did you find lots of red ones all in the same region where something goes up and then it tails off up and tails off oh and the blue ones also seem to be crowded no that's where it goes down and tells us downs and tells off so you get that clumping of these regions and that would be explained on the kind of scheme that I've been describing I don't know of any way of explaining it in any other way he'll be interesting to see and there have been very very one well done there the pictures here and the analysis as far as I can see there's nothing to complain about of course other people should look at it very carefully but what's going on well I can give you an explanation of what's going wrong going on but maybe that's not the right one and maybe it's something else but it would be very interesting to see what and I think I stopped at that point thank you very much what's been worth well that was you yes the original idea was it was just a mathematical tool I mean it was really it was an idea that I put forward in in the 70s I think it was 80s contract remember now just to try and get nice ways of looking at the energy carried by gravitational waves so you want it to rather than doing a complicated limits this is what people tended to do you just have this geometrical way you squash infinity down and you could see that that's for infinity it's quite a general technique and then you can see the values that are at infinity gives you the radiation field for electromagnetic field or for gravitational field and then the formula for energy carriage is something you can do on a fairly local basis such as infinity it's much easier than taking a limit so that was just as you say a mathematical device now here because we were doing it for without worrying about the cosmological term so you're looking at asymptotically flat spaces and there you have an infinity which is now and it has its own problems it's easier in some ways and harder in others but with the cosmological constant it's space like and that you can quite easily see from the mathematics and if it's space like then you can contemplate this scheme of mine because the singularities are likely due to space like - if you didn't have the cosmological constant this scheme wouldn't work but well I mean so are you things that will be a physical process which is because I'm trying too hard to visualize how you were attached a small point which I think one of the troubles is that people tend to think of the big bang as a point and you always see the square you know when the universe was the size of a grapefruit and then when it was the size of a pea and so on but that's misleading when you think about the causal structure which in fact is what you're always looking at so you're looking at light rays it's much better to think of it as a surface and in fact it's related to the problem people always have that how are these fact you see if it was a point you see the light cones are kind of pointing right out like that how can there be a causal influence between them because as soon as they've left that point they're completely out of course or contact now you can see that in space like picture because they're light cones are like that and they become in causal connector but they're simply space like separated then nothing to do with each other which is a problem if you think of a big bang as a point event but you see causally it's a surface and we've got used to that idea just from the mathematical tricks you see it's a matter of getting used to it I think but once you got used to it and it's much closer to the physics because the physics is pretty well like like things is photons or things are very high energy that you're still talking about there and the cause all nature is crucial so you can understand it's really a lot of separated points what is it that connected them well it was the previous Eon if you've got a previous Eon sitting there then it all becomes nice and causal and you're looking at pretty well classical differential equations one of the beauties of this except that all my I'm I lose a lot of friends one way or the other you see my cosmologists friends are ready to inflation hate me and then I quantum gravity friends who are wedded to the Big Bang is that it is the place where quantum gravity makes its mark you see now I'm saying no you can treat all these things with classical equations quantum gravity hasn't got much to do with it which is the great shame I used to say this anything this is the great laboratory for testing quantum gravity but on this scheme no you just need to have a way of handling having infinity and putting it into the equations of the equations work and become finite equations and that requires a bit of reorganizing phrasing things in ways where where they you just get ordinary differential equations and it makes mathematical sense I mean there are some questions which still needs sorting out but but at least the framework looks as though it makes sense well yes well it has to be I mean something like a Higgs mechanism you see I actually didn't make this point here but but when you get close to the Big Bang you go back in time then you get to a time very early on where the temperature was higher than the Higgs mass temperature and before that you effectively haven't just massless physics so that's just that's conventional that's not nothing outrageous there when you go closer as a Big Bang the dominating physics becomes more and more massless physics and so conformal geometry is is the right geometry for the physics okay there might be things you know anomalies and all sorts of things you got to worry about to what extent is this completely true but the general feeling is certainly that's not where the thing is unconventional the general feeling is that you have massless physics going on in the very early stages now what's not so conventional is why you have lastest physics in the remote future but that's why I'm saying that I need a sort of inverse Higgs where the mass when the temperature gets very very cold you need a reverse process something like that that means these things need to be worked out I'm not saying that it's all sorted out you had a beginning question which I'm not sure I dress oh that considerate yes well of course we did look for circles and not squares originally ah but we look for ellipses and that's okay we didn't bother to look for squares I did suggest my colleague why don't you look for squares and he wouldn't do it too much trouble but the looking for ellipses is rosy and easy because you just twist the sky that's an easy transformation use the same algorithm exactly the same one you looked at the old sky that's the same the sky is twisted but it's the same as twisting your circles so you're looking for elliptical shapes in the real sky and you see the numbers drop dramatically so okay we're looking for circles originally of course because that was what the theory said but we now after that look for elliptical shapes and the poles I should say insa also completely independently have looked at their data and they find a dramatic drop-off when they look for ellipses so certainly it circles over ellipses there's no reason to believe that squares are there of course somebody wants to look for them I'm quite happy for that equilateral triangles things like that but it's just a nuisance but ellipses are easy to look for they're not even quite ellipses they're the slightly distorted almost ellipses all these various scissors going though yes of the other I'm just interested sort of how you get from one to the other you trouble get like an infinite time you actually don't get they're all okay you actually get over the yes yes well I mean how you do it is with mathematics but that's not what you want to know and you have to have a mathematics which carries you across sensibly but the idea is well the whole question is you know who's measuring time out there you see well especially if mass fades away if mass fades out then the clocks I was talking about actually are not very good for the very remote future particularly because it's likely that if the mass fades out it will do so in different rates for different kinds of particles now if all of the particles uniformly wears out then you might have a big question about which metric do you choose but I choose the metric for which the Einstein equations remain true now if you use a metric in which the mass fades out and you use that metric that is to say clocks defined by the particles then you will find a violation of the Einstein equations because it'll look as though the universe is contracting with no source to it in a sense which but but if you let the basically what I say you let the cosmological constants determine the metric because the cosmological constant is another place where the scale is broken that's not much good for building a clock in practice but on the cosmological scale it does determine the scale and I say that is in fact I try to suggest this is a crazy idea I try to suggest that you could use units see people are used to using Planck units the Planck units to say take Planck's constant to be one the speed of light to be one or Planck's constant over 2pi to be one speed of light to be one the gravitational constant to be one Boltzmann's constant to be one and then you've got all your units fixed they're a bit absurd but they're fixed now I'm saying something a little bit more absurd I don't make the gravitational constant equal to what equal to one I say make the cosmological constant equal to three the reason for three is a technical point but if you make it three the equations are much neater when you're talking about what happens at infinity and it's just choice of units but that is sort of saying that the cosmological constant is fixed and it determines ultimately the scale of the metric so there is a fixed scale which tells you how to keep things under control as you go from money on to the next but it I'm afraid it does depend on the mathematics and and there are also some questions in the mathematics which are some slightly different things you might do not completely obvious which is the best some of my colleagues have different ways of doing it but but they are perfectly well defined equations and you have to say well the physics follows that although it's infinity there's nobody around to think of it as infinity because it's only massless things and as far as they're concerned it's infinities like anywhere else it's an idea you get used to like earlier question you see one gets used to playing around with squashing infinity around when you're talking about massless fields gravity and electromagnetism you can look at infinity and see what they're doing out there and since they don't have any mass they don't they're quite happy out there the equations are quite happy when you describe them it's a slightly difficult idea because we're used to thinking in very metric terms in our physics normally but when you don't have mass around it's not such a natural thing to do in the conformal geometry becomes a more relevant type of geometry yeah okay to the next isn't it let everything slow start up yeah well you see the way yeah okay less what doesn't forget well the idea I mean you need to have a I have a thing well check all the reciprocal hypothesis the idea is that the conformal factor you use post Big Bang is the inverse of the one pre-big bang so it's as though changing the scale factor from to its inverse 0 goes to infinity infinity to 0 that that well you the way I think about it is the following you can think of you can use the old metric if you like the universe gets thinner and thinner and thinner and thinner right out to infinity you cross infinity and then you have on the other side a collapsing universe coming from it and from any infinity infinity coming in what you find from the equations is that the collapsing version of your universe has a negative gravitational constant and the idea is that that becomes awkward for the universe it doesn't like that version it prefers the other version it prefers the gravitational constant be positive and you have a different interpretation which uses the inverse conformal factor and then that creates a whole lot of scalar matter which is the initial dark matter I'm claiming which is necessarily there and then to the dominant form of matter in the initial state it has to decay away in some way or another or else it would build up and be there at the next Aeon you don't want that there is some I believe indirect evidence that it does decay but I wouldn't take that too seriously but the point is that you need to make some interpretations and I do I say that first of all that there is a decay of rest mass to make sure it's conformally works with the crossover and that there is this knew that the inverse conformal factor is the one to use in the next Eon it's the more physical one because your gravitational constant has become positive and and there is then a big bang and you have the dominant matter is this scalar material and then matter the rest mass other kinds of matter require rest mass through some Higgs type mechanism and you go with the next ear on this the idea but there are some guesses and speculations involved on that I fully admit but it does seem to present an overall picture which seems to be consistent not too much freedom in how you write your equations still a certain amount not too much freedom and seems to be consistent with observations like this if it's some other theory you want you've got to explain these things you've got to explain why they effects are very clumpy which don't seem to be consistent with the inflation picture maybe there's another way of getting that out I'm sure people will think of somewhere why is the entropy so low well you see in this scheme just simply the way the conformal factors work gravitation is killed off dead if the information is not it goes into this initial dark matter so it goes from the gravitational degrees of freedom and the gravitational waves into this initial dark material and so that picks up the information that was there in the gravitational field but it's not there as gravitational field and this gives you the very special initial state that we seem to see I'm not so it has to be like that but I'm saying that at least it does give you a way of looking at many of the puzzles which are not even addressed in most cosmological schemes such as why the entropy was so low in this very particular way it gives you that today we do have a freshman about five so please do stick around

Channel: Oxford University Scientific Society

Views: 98,497

Rating: 4.7422323 out of 5

Keywords: Roger Penrose (Author), Science (Literary Genre), Physics (Idea), Big Bang (Idea), Time (Dimension), Space (Literature Subject)

Id: npmDbbGbSoE

Length: 89min 45sec (5385 seconds)

Published: Wed Jan 29 2014

Reddit Comments

[u/iofprovidents]

This is certainly a mind fuck. I feel insignificant