Sir Roger Penrose: New Cosmological View of Dark Matter, which Strangely and Slowly Decays

welcome to Friday afternoon at the arthur c-- clark center for human imagination which is a space in your imagination because we typically hold our events over in Atkinson Hall or maybe a couple other places but it's the first time we've been in this neck of the woods so glad you were able to to hunt us down and and be here for what seems to be a kind of recurring thing for the Clark center to help to to engage Sir Roger Penrose and a series of recurring things that we're trying to do that also helps get the Penrose Institute going here and and you know today and and and Sir Rogers talked about a number of different things and his different appearances here and today it's a cosmological matter that he's discussing and you know this but what he's done is run the gamut from thinking about issues in cosmology to things and artificial intelligence to things about consciousness and and for me this is really you know such an example that you know that we can point to from the Clark Center's perspective on on how the imagination is able to extend our understanding of what we think reality is into territories of the unknown that we then can explore and test and utilize to then kind of reconstruct our view of what nature of reality is because you know and I think it also points to that most of what we really know our our fragments of this phenomena we call reality and that it's our scent that's that are but we're wired our cognition is wired to kind of try to make sense of those fragments and and I think that sense making is also something that I would attribute to the the phenomena of the imagination as well and you know that you know kind of comes out of this ability to kind of you know anticipate the stuff that might go bump in the night and how we might have to take measures to to you know take guard against that during the day and here I think what we see is a way in which at least some of the things that I think about when I think about how Sir Rodgers work relates to cosmology is to think about how we take these fragmentary ideas that describe the universe like general relativity on one hand and quantum mechanics on the other hand and and but the way that they connect right now is still something that we largely have to imagine that we had that then it kind of can guide us to thinking about how we build the knowledge to bring those two things together and but to further introduce today's program I'm going to I'm going to now introduce dr. Bryan Keating here who's the associate director of the Clark center and a professor of astrophysics here at UCSD well it's a great pleasure to have Sir Roger Penrose back here for the second time in less than a year and I'm happy to announce that we could only get him here if we promise to replicate the weather conditions of Oxford England at this current time so the weather cooperated with us Sir Roger was here last in the summer participating in a program led by dr. Hameroff who runs a yearly conference on the science of consciousness which is a topic that was also engaged with very heartily last night by Sir Roger and members of brain Corporation which I love like anything that is an anagram of my first name but but the brain Corporation is striving to make these autonomous objects that follow laws that were first brought to my attention 1989 when I was in high school by Sir Roger in his epochal book the emperor's new mind that really set me on a path of curiosity and discovery and wanting to imitate one you know milli magnitude of what Rogers accomplished in his career he spend realms from mathematics to physics to cosmology to ontology philosophy consciousness he's as intellectually peripatetic as they come and he's really a role model that exemplifies what we stand for in the arthur c clarke center for human imagination which is bridging these interdisciplinary venues from arts to science to medicine and and and being able to to so astutely walk in all these different fields it's just so impressive to me I'll give you his official bio he's the emeritus professor of mathematical Institute of the University of Oxford he's winner of the Copley medal and the Wolf Prize which he shared with Stephen Hawking who went on to some fame as well he has made it all encompassing predictions models theories that have ranged from both things that we formerly thought were forbidden symmetries in nature that were only recently discovered to have as they say forbidden symmetry fivefold symmetry and actually some of her sir Rogers tilings famous tilings will be shown in the two billion dollar-plus new terminal that's being built now currently for opening believe it's the sales part of the Salesforce Tower in San Francisco and it's going to be covered with Penrose tiling which is quite quite fantastic when when Suraj was here last time we interviewed him as part of our podcast which we call in to the impossible based on a phrase from sir arthur c clarke that the only way that you can understand what's possible is to go a little bit into the impossible so i refer you to that podcast which you can find in the Clark center website imagination UCSD edu and so it's such a treat to have him here he's he's able to speak on so many different topics it's it's it's it's quite astounding to me to be in the presence of such a scholar so very much looking forward to it and now please enjoy this lecture by Sir Roger Penrose well thank you very much Brian and also for the earlier introduction and my apologies for this archaic I give lectures these days and according to procedure which is really up dated and so i annoy people when I go to conferences because they set up all this stuff just for me and it's very irritating but so I apologize for having caused all this I should explain what I'm going to talk about what the CCC mean it's what is a proposal that I've made some years ago over a decade ago I think on cosmology the C stands for a conformal cyclic cosmology I'll explain what the conformal and cyclic are about and I haven't normally I've talked about si si si quite a lot of different places but I've talking about dark matter in this context is a recent one si si si always had something to say what about what dark matter is I should say that people refer to the mysterious things in nature that cosmology is thrown up miss dark energy and the other is that matter which seems to dominate the material universe I the dark energy so-called is a thing which very much drives the theory that I'm going to talk about but dark matter is a sort of offshoot of it which I didn't dare I've mentioned much because I thought well look if it tells you what dark matter is that's too much and so I keep better keep quiet about that but the thing is I will say some what it says about dark matter that's the point of this talk but I think I'll start by just showing you it's giving you a reference usually people do this at the end I thought I'd do this now because this is a paper by colleagues of mine two of them are polish I call him my polish colleagues and the paper that they admittedly really I think submitted for publication about five years ago has finally come out just this Monday it just came out on Monday anyway so this theory tells you I should say the paper is an observational paper and they do an analysis of the cosmic microwave background I'll say a bit more about that later this analysis the theory makes a certain prediction about that and they look for the signals that the theory predicts and they found a signal which had a ninety nine point two percent confidence now they finally this paper after lots and lots of complaints every one of which they dealt with the paper was published and earned on the condition that the author's said in their opening sentences that the effect that they see might be a chance effect we've seen a little strange because it's always you look for things and you see is it's a chance effect the thing about this is they actually give the probability of is chance effect and the probability according to them as accepted in this paper is that it's 1 in 125 so it means that the theory has a good chance of being correct I thought I'd start that way because you might otherwise think that everything I'm saying is a load of cobblers which of course it might be but at least it has a observational consequence which seems to lie on this theory and it's very likely right ok well let me start by showing you what we think the universe is like quite apart from my theory this is a spacetime picture so you have to think of time going up a picture actually well that I think so you have to think of the time as sections through this and this is I'm representing Musa sections as you go up so the time progresses on we're somewhere around here are not sure exactly where you have to think that this is three-dimensional space I can't draw over three dimensions and and time is going this way this is the big bang at the bottom where the universe began and this at the top is the exponential expansion that was observed and got the Nobel Prize a few years ago and people call this dark energy I don't like that term because it's not really energy in any normal sense and it's not really dark it's transparent that's true but nevertheless it's a term which is given to it I should explain all of what this Wiggly stuff at the back is the wiggly stuff at the back it's just that I don't want to prejudice the issue as to whether the universe is closed in which case this would join up at the back or open in which case it keeps on going so it doesn't matter in this scheme it might be open it might be closed either way anyway we have a big bang and then this expansion starts off like that slows down a bit and then it starts to accelerate and this was the the effect that was observed recently and people say it's dark energy I prefer to call it Einstein's cosmological constant lambda Einstein you introduced this term into his equations in 1917 for the wrong reason he wanted a universe that was static and so he tried to retract it afterwards when it was seen that the universe was actually expanding saying he he'd made a huge blunder because he could have predicted the universe was expanding and he didn't recursive static the scheme that I want to tell you has something in common with the idea of a static universe but it's not static I say this picture I'm not monkeying with that that is what we see some people might complain that there is something right on a bottom here right after the Big Bang called inflation no I say a little bit about inflation but in order to say what that looks like I have to bring up my powerful magnifying glass and have a look and what we will see is something like this I should say all that stuff is the handle of a magnifying glass I think that's part of the universe here we have the initial expansion which is another one of these exponential self-similar that is it looks like itself on all scales self-similar expansion and to say that it's a bit like what the universe is doing on a huge scale but this is on a very tiny scale originally originally and then it expanded like that now this is introduced for various reasons many of them don't really work in my view one or two of them are genuine reasons that if you don't have another explanation for them you're in trouble so bear that in mind I want to give you something where see people often talk about inflation because the universe is over a uniform and they wonder why that could be an inflation suppose to stretch out any wrinkles who kind of get stretched out that's a bad reason that's not a good reason I want to explain a little bit why it's a bad reason but in a moment not just yet let's think about first the universal as we seem to know it with possibly you see the inflation could be in this picture because it would have taken place right inside that little black spot on the bottom and you wouldn't even know I haven't drawn it so doesn't matter but let me I want to do something to this picture to make it a little bit more comprehensible in the sense you see this exponential expansion in the future goes on indefinitely according to the standard picture but I want to do something to do it squash it down in a way I'm going to squash down infinity to make it something to look at and I want to stretch out the Big Bang there that's something you look at house a little bit more about that in a minute but in order to do this to make this picture fit in a little bit better off you're a bit smaller that's the same the left-hand thing is the same picture we had before but the squashing down of infinity here is that mixing them to a finite boundary and the stretching out of the Big Bang makes that into a finite bottom so these are true to mathematical tricks and the first one is this is the squashing of infinity the second one is the squashing of Big Bang just to give you an idea of what this stretch sorry this stretching of the Big Bang squashing of Infinity the squashing of infinity is something which many of you have perhaps seen this is an Escher picture which is a similar kind of thing to the squashing down of infinity this is a kind of a universe it's what's called hyperbolic geometry don't worry about that too much but s has drawn these fish I think their fish black ones and white ones and the point about this picture is infinity which is around the edge there is represented as a finite boundary and Escher has done this cleverly earth transformation originally due to Beltrami an Italian mathematician and it's what's called conformal now conformal means that you could squash it down as long as the squashing is isotropic squash it the same amount that way as you do that way so in particular the circles which are the eyes of the fish remain circles in the matter how close to the boundary you get so the squashing is this very special kind which is called conformal and preserves angles it preserves small shapes but the size can be big or small so bear that in mind because it's just that kind of thing which I'm going to be doing in my transformations this one is just like the SU thing is talking about infinity and finished being squashed down into this finite boundary at the end and this is the opposite where the Big Bang is stretched out now I should say something about this idea of conformal because in space-time what that means is that space and time gets squashed by the same amount and I have a picture here of what we call the light cones or the null cones in space-time at any point in space-time its space and time together that means three dimensions of space one of time I can't draw the space dimension so you have to imagine maybe it's true just imagination and but at any point you have one of these cones imaginary imagined to be there what these currents tell you is what what light would do the speed of light it tells you so if you have a flash there as time progresses that flash increases increases increases and that is represented by this cone shape in space-time now the thing is that the conformal transformations leave these cones alone because they squash the space in by just as much as the squash the time done and it's rather remarkable how much of physics is insensitive to this squashing and stretching I see what we would know if you stretched space because physics Noakes knows how big things are but let me say something a bit more about that this is this cone represents most of the local geometry of space-time Einstein's theory requires a thing called the metric the metric has ten numbers to defining so it has ten components so there are ten numbers to define exactly what the metric is one point and basically nine of those numbers well really it's the nine independent ratios of those two numbers define are defined by and define this cone so the cone is really given by these nine numbers so in a certain sense the conformal structure is most of the space time because it's nine out of the ten numbers now those nine numbers the firmly the cone what does the tenth number or the scaling and where do you get that from whether you get that from clocks so I'm imagining here some clocks zipping along at different speeds and they're supposed to be identical clocks and these surfaces here these bowl shaped surfaces represent where the first tick of those clocks would be the next second tick the third take and you imagine the clock coming in this way and that would be ticks is represented here now the thing is if you had different clocks one goes faster than the other then it would change how these cones are but how these surfaces the bowl shaped surfaces are but it wouldn't affect the cones the current would be the same it respected respective of the clocks now you see one of the remarkable things about physics which is what Einstein's theory really depends upon is that space-time has an extremely precise measure of time and if you've got the time you've got the space so it used to be that the measure of distance was the meter rule in Paris but the meter will in Paris's is no good now for the kind of precision one needs but clocks are extraordinarily precise and you don't need the rulers anymore because you just say well if you have a if you know what a clock is then you talk about instead of talking about years you talk about light-years now they're talking about seconds you talk about seconds and so on so the speed of light go neighbors you to get from time to space so you don't need the space if you've got the time measure now here at the top I've got the two most important or most famous equations of 20th century physics one of those has to be of course Einsteins e equals MC squared the other one is Max Planck's e equals H nu nu is the frequency is the energy in each case and Planck's formula is extremely puts the basis of quantum mechanics if you like and what Einstein equation tells you is that energy and mass are equivalent mass and energy equivalent what Planck still for me changes frequency and mass equivalent you put the two together and it tells you that mass and frequency are equivalent another way of saying that is that if you have a stable massive particle so it doesn't decay or something it's a stable massive particle it is a clock of extraordinary precision it has a well-defined mass and mass means that it ticks at a rate which is absolutely very very extraordinary precise and this precision enables you to measure space time to an extraordinary degree for example one of the things in Einstein's theory is that these if you go up or if you have a clock on the ground from another one way up in the air somewhere that they won on the ground ticks a little more slowly than the one up there well the clocks can be measured so precisely that I had a clock here and a clock here you can measure the difference between time rates so that and the precision of these clocks really depends on these fundamental equations here something very fundamental in built into physics now I'm going to undermine which I what I just said in the sense when I say that the measure of space and time depends on clocks if you don't have any mass if you only have things with no mass then you just have the cones and you don't have these services in here you have these nine numbers you don't have the ten and an awful lot of physics doesn't require the mass scale when I say an awful lot the most immediate part of physics which has this property is the behavior of light electromagnet electromagnetism that electricity and magnetism according to the very famous and very wonderful equations of James Clark Maxwell who explained how mass how electric electricity and magnetism interrelate and propagate through space as waves and that they propagate with the speed of light and this was a very much remarkable discovery of the nineteenth century and so this is all to tell you that these cones that's give me the speed of light is something inbuilt into nature but you don't have any mass the photons the particles which is described light if you like quantum particles don't have any mass and therefore they're no good at defining the scale they are only interested in these nine numbers they're interested in the conformal structure and if you do if the world was constructed entirely out of photons you just wouldn't be interested in the scale of things there wouldn't be any meaning to the scale of things now I want to say that a lot of what is going on in physics and what are the important things that I want to talk about are really when the mass goes to zero so let me say a little bit more about that but before doing that let me go to the Maya picture which I just had this one here and I said that there was you could squash infinity Donna it could stretch the BIGBANG out but there's something very different about these two things if you want to stretch out squash down infinity it's an extremely general thing the mass the universe doesn't have to be completely uniform you see all the original cosmological models and still we work with these that were introduced by Friedman and Lemaitre and and robertson-walker and Paris people assume that the universe is exactly symmetrical exactly smooth looks the same in whatever direction you look in and that's a good approximation but the universe isn't quite like that it's got irregularities and those irregularities might spoil this picture where dozens in the future there is a good theorem due to a mathematical physics Fredrick who has shown that as long as you just have things like massless particles like light photons and things which don't have any mass then infinity works just as well whether it's one of these exact models or not it doesn't matter how irregular it is now it's a very different story when you go to the Big Bang the Big Bang is something extraordinarily special and the fact that you can do this stretching out is a very remarkable fact and we don't know that you can if you like but it's a remarkable fact of the universe that it looks as though you can and let me I'll have to say a little bit more about that in a minute but let me first say that this these two things I'm saying these two tricks mathematical tricks are very widely applicable and there's no problem I don't think cosmologists would object to my doing these tricks they they're perfectly good tricks and so I've not said anything particularly outrageous at this point now I'm going to say something outrageous that the universe is can be thought of one of these sort of cylinders but that is just one of a succession of what I'm calling eons so let me bring this picture back Hammond on this very well by messing myself up that's the picture I just showed you what I'm saying is that this on the left is the sort of standard view of what the universe looks like big bang outs of this exponential remote future expansion this is stretched and squashed but this stretched out infinity becomes the Big Bang of the next Eon I'm calling that an eon a eo-n and we have the previously on another one after us and rather than the Big Bang to infinity being a unique event and that's it I'm saying this is something which continues there was one before there was one after and you might say this is a totally outrageous idea but I did say that there is good evidence for it and I gave me this probability of 125 to one let's say there's a hundred twenty-five to one that this is the correct picture well that's a little bit outrageous I'm not sure quite say it like that but it's definitely some good evidence that it might be true at least some of the implications of the theory could seem to be true that's a bit about what those are shortly but that's not the main point of the talk today so that this is stretching out our big bang and squashing doubt in the previous eons infinity they fit perfectly and when I say they fit perfectly that conform or structure that is these light cones will match together now how do I get away with that physically well I get away with it physically near the Big Bang because well that's a normal picture of the Big Bang as you go back into the past things get hotter and hotter and hotter that means more and more energy in the individual particles the energy gets so great that the mass part of that energy becomes totally irrelevant and those particles behave as though they had no mass so as far as the six is concerned there's a big bang it's really these massless entities that can form a structure which is input the important thing what about the remote future well the remote future you have all sorts of things happening well one of the things happening is that we have lots and lots of photons all over the place and photons are massless we have lots of things like stars and all that we have galaxies and what happens to galaxies is well the galaxies that we know about particularly ours and lots of others have in their centers an absolutely supermassive black hole and that black hole will swallow material and swallow material get bigger and bigger as time goes on and what will happen to these black holes eventually they'll be sitting around but according to Stephen Hawking and I'm accepting this after a huge length of time those black holes where they have a temperature now that temperature is ridiculously small however when the universe expands and expands and expands expands the universe cools down and gets so cold that those black holes become the hottest things around and then they start to radiate away their energy and when they radiate away they get smaller and smaller and smaller and disappear with a pot I'm calling it a pop because it's not really very big compared with their sources of energies we're talking right up to the end anyway they disappear now how long does that take where depends how big the black hole is according to the standard calculations if you take the biggest black holes around it'll be something like a googol years that is to say one with a hundred zeros years that's an awful long time but we're talking about in eternity after all the energy is eaten wrong than that so what was it Woody Allen said determinate the change there's not a long time especially at the end where you see this is the black hole so you have to wait around I call that the very I call it the boring era when there's nothing left for black holes but the very boring area with when they've all evaporated away and there's really nothing left practically nothing left except photons now the main radiation out of these black holes will be photons the Starlight which is still hanging around out there almost entirely photons now the photons have no mass I thought maybe we can get away with the idea that there's nothing around but massless things no that doesn't make we're a little bit of imagination in fact you can't really get it all rid of all particles this way it's not just electrons that be hanging around you they won't there be a lot of them don't fall into black holes and they have a lot of particles so they might and get annihilated with but they get separated from each other and then be hanging around so I've introduced a hypothesis they're not too many hypotheses here actually apart from those original one yeah hypotheses that mass after a very very long time I don't know how long time it would take finally fades out so even though mass is such a precise thing now in a long long time that we have available infinite in infinite times that these miss mass will fade away there are there are some plausible reasons for this because I just may be a little bit technical here the way that particle physicists talk start talking about particles the first thing they say well this is about their mass and spin and these are things which are called Casimir operators you don't know whether it means don't worry Casimir operators of the Poincare group if you don't know what that means don't worry but what it means if you have special relativity then in particular mass is an absolute constant thing but the thing is we've got this lambda term in nine science equations and I claim that's what it is that is giving this exponential expansion and that lambda term means that this pranker a group isn't quite the right group you should be doing in a different group which is called the de sitter group and what turns out is that mass is not the Casimir operator but so it doesn't have to be absolutely constant but the rate at which it would change is very very slow indeed probably much longer than the current age of the yes so I always say that is undoubtedly the case we have no evidences yet for any to fade out of mass but I would one of the features of this model is that I'm suggesting is that this does fade out in the remote remote future and that means that you have the conditions of helmet-free grips here I'm satisfied and so at both ends it seems possible thing I'd need to talk more about the Big Bang because I said that something very special now this is important let me say a little bit about entropy what's entropy well it's more or less I'm gonna be very sort of general colloquial about it I'll say it should be it's more or less a measure of randomness more technical than that but measure of randomness and there is a thing called the second law of thermodynamics which says this measure of randomness gets more and more as time increases the entropy increases and so things get more and more random another way of saying the same thing is that you go back in time things get less and less random so as you go back back back to what's the Big Bang you should be seeing something very unrounded with a very very low entropy well what's the best evidence we have for the existence of the Big Bang well there's something called the Cosmic Microwave Background this is radiation coming you've got the Nobel type novella Nobel Prize twice so it's something this radiation coming in all directions it's supposed to be roughly speaking the flash of the Big Bang cool does not quite right it it's really one hundred eighty thousand more or less years after the Big Bang but it's pretty well especially big bang that's pretty close to the bang and that radiation is something we see and is very uniform over the sky and it has another feature if you look at this what's called its spectrum here we have the the the frequency in this direction and the intensity in that direction and we see a curve like this this is a very early measurement that was the first satellites that went up to look for this cosmic cosmic microwave reckon this is the COBE satellite and they found this very close agreement between the shape of the curve representing these frequencies I should say era bars there about 500 times definitely could see them 500 times bigger than they actually are so these error bars fit this curve to a tremendous precision and that precision is telling you What's it telling you this curve is that is the famous plank back blackbody curve and what's that's an indication of it's an indication of randomness of maximum entropy now there's something here which seems to me as this I call it the mammoth in the room you see you go back and back in time the entropy is going down and down and down and down and down until it reaches a maximum now you don't have to be much of a mathematician to realize there's something funny going on there minimum yes but a maximum well that's a pretty good piece of evidence that you get this random effect as this very early indication of the Big Bang but what it's really telling is it's not a paradox it looks like a paradox at first sight well I say see a mammoth in the room it's because although physics from astronomers cosmology is well aware of this they don't try to explain it well they maybe try to introduce inflation but that doesn't do it is ha that's indicated in the minister I've got my slides in the right order now the thing is that this is a very remarkable fact it's a remarkable fact but you have this no it's not before entropy was of the maximum they couldn't have been because that disagrees the second law of thermodynamics it was very low but it was very low in something you don't see in this curve what you see in this curve is the result of a sort of equilibrium between matter and radiation and that's what the Planck curve is telling you there's an equilibrium of a sort or maximum entropy state between matter and radiation what it does not say is anything about gravity now there is something else that says something about gravity I should say that the other part about this Mac this microwave background is it's very very uniform over the sky you measure the temperature in different directions you have to correct for the Earth's motion but once you've corrected for that because the heart of the way we got where we're heading a little Cola where we've come from but if you're correct for that you find that the temperature is to one part in 100,000 pretty well constant over the sky in fact there's not quite constant this is important for lots of kinds of observations but anyway this tells you that the universe was extremely uniform all the way around it was very uniform and that's telling you in a way that this trick which I'm applying in the past it's not such a bad trick because the irregularity is well let me show you with a picture I also going to show you which is a picture which is rather you see I should confess that I'm not a fan of inflation I don't think inflation ever took place so even though it is a standard part of current cosmology and there is our good reasons for it which are one of them I shall come to you in just a minute there are good reasons for it one of those good reasons is well one of the reasons often put forward for inflation is not the good reason and one of you one reason I got in trouble is I can't find the critical slide which I need in order to show you what I'm talking about now what have I done with it's the earliest one I was showing you okay now you see this is the sort of picture of the universe now inflation is supposed to be here and it's supposed to iron out the universe by this enormous and exponential stretching now I'm trying to tell you that that doesn't really work it's also something else let's suppose that the universe was collapsing now it might have been collapsing I mean models certainly can be put forward collapse Einstein's equations work just as well as that ways that way independent of the direction of time but if you have little irregularities here these are the riddler regularities would form black holes they've congeal with each other and form one unholy mess so the picture the much more probable picture would be a thing like that I hope my smiles are working here a great mess and you can put inflation they think will be in photon which is supposed to determine the situation you can put inflation feels in and it doesn't make any difference in this picture they don't really change anything so there's no reason almost all possible universes are like that in fact you can even make an estimate of how many like that as a person like that and you find that the number like this is opposed to this for something like 10 to the power 10 to the power 100 24 times as many like this is there are like that so it's an extraordinary chance event if it was chance that it was like that and this is the sort of thing I said that mammoths in the room cosmologists tend not to worry about that they just think well maybe it was something convenient that maybe inflation could do the rest or something I don't know as far as I'm aware a my own scheme is the only one that really tells you that it's got to be like that the the Big Bang doesn't work with this conformer stretching unless it was a very uniform initial state and that very uniform initial state I spend a lot of time trying to find what that meant and I introduced something called the vile curvature hypothesis you know just know what that meant you'd have to know where the VAR curvature is my colleague in Oxford Paul Todd have a much better way of saying it and his way of saying it is roughly speaking you that you can stretch the BIGBANG out in the conformal way that I was saying so that this trick works so it's really is telling you this trick works according to Paul Todd's hypothesis and that's a way of saying that this universe has this special character that the gravitational degrees of freedom were wiped out and the rest of the matter can behave as randomly as he likes as time goes on then there are literally irregularities in the matter but these come in two worlds galaxies and stars and the stars get hot and the rest of the sky is cold and you have this hot spot in the sky and the coat background and this is what life comes from and all that sort of stuff so the reason that we don't have a completely uninteresting maximum entropy useless universe is because the gravitational degrees of freedom we're not excited in the initial state and they Bick as they become slowly excited then we get all the interesting stuff that we have in the universe life and all that kind of thing so what I'm saying then is that yes we've got to explain that the other theories as far as I can see don't explain that this one does in the sense that the scheme doesn't work unless you could stretch out the Big Bang to make it smooth so that's really the idea now I talked about the second law of thermodynamics let me say something else about this you might say okay if the entropy is going up and up and up and up and I can this a sensible question why is the universe and I and trouble finding things here because it's I put the blame on the small space here but it's really my column yeah here we go here is the the Marvel conformal cyclic cosmology there we are and so I'm saying that the Big Bang was the continuation of a infinite future of the previous eon now how what about entropy now you see surely if second law is right that'll tell us that entropy is going up and up and up and up and up and how can you have a model like this the entropy going up and up and up and how does it make sense like worried million for a long time and I thought of this model let me tell you what I believe is the explanation now there are certain things which I say from time to time which disagree with a lot of what physicists say and I'm going to say something well I have friends on both sides and the fact I have a third friend one friend on both sides and that friend is Stephen Hawking and let me just say I'm not sure I can read all this yet but let you read it but the key thing is well first of all where is most of the entropy in the universe at the moment it's almost entirely in black holes you have this formula do to beckon CERN and Hawking which tells you how much entropy there is in the black hole and as of now it's utterly totally dominated by black holes the entropy in the universe in black holes utterly swamps everything else okay it may not have norway's like that before they were black holes no but black holes the amount of entropy becomes absolutely stupendous so those are the main problem and what happens to black holes well I just said they've back right away by walking of apparition now you say I've got friends on both sides what did Hawking originally say the old Hawking without having about old new the older or the the young Hawking I should say young Hawking's said information is lost in black holes you made a big point of that but then later on here he got caught bullying bike and that shouldn't say that you changed his mind when he changed his mind and said information is not lost in black holes now you see most physicists don't like information to be lost because that disagrees where the fundamental principle of quantum mechanics and this unitarity no no no no no you can't information I don't agree with that because I don't believe that this fundamental principle of quantum mechanics is true main reason I don't is that if you can make a measurement in quantum mechanics that violates its already so there's the unitarity principle of quantum mechanics which tells the information doesn't get lost it's violated already in measurements nothing but cost quantum people have ways of getting around that they talk about many worlds and all that stuff I'm not going to say that I think there's only one world and in that one world you've got to do something about quantum measurement problem and what it tells you to me is the gravitational context and I don't want to go into all of that well that comes back again shortly the gravitational context entropy so the information or the degrees of freedom actually what it is are destroyed but if you like the unitarity principle is not necessarily true so quantum mechanics needs modification and the modification is also it's already there in measurement but it is there particularly because of gravity and what's more gravitational than a black hole well black holes lose information and if you draw appropriate diagrams and survey because it's obvious they lose information how can you possibly not include information lose information but I should say this is a minority view it's a minority view among physicists because they don't like to spoil unitarity when these arguments go on and on and on and on I think that Hawking was originally right the information is vast and to argue that it comes back in some sense is not correct that's not I say a view that's shared by nevertheless I think the reason is not pretty powerful and the argument here is it's a little bit tricky so you see I don't want to violate the second law and I'm not violating the second law but what I am doing is saying that when these black holes disappear they swallow degrees of freedom and these degrees of freedom don't count anymore so you have a definition entropy and that definition depends on the grooves of freedom that you're interested in when some of them get swallowed up by a black hole and get destroyed you have to change your mind and say what I used to call the entropy that's not so good anymore call anymore because they use those degrees of freedom which aren't any use to it and even they've gone so you redefine your entropy you renormalize the entropy and that comes whopping down every time you lose the black hole that entropy that you're interested in is much much lower and as far as I can see that works I'm in detail when we need to check things but it does seem to me that you when the black holes when they people one after the other the useful entropy that you use to define things in the physics that's left there comes down it's never violates the second law of thermodynamics because you've changed the notion of what you mean by entropy as time goes on but that's a little bit of a tricky one I thought I'd better say that because perhaps I could have waited to the questions and somebody would ask them one reasonable question to ask okay now I want to talk about the dark matter and all that and I'm afraid that I probably haven't got time to say all the things I want to say but before even saying that let me just make a little point about the paper that got accepted by the Royal Astronomical Society and the prediction that I've made was that I kept asking myself what is the biggest what's the most violent thing that could happen in one of these Ian were the big bangs pretty violent but next after that and that might have a chance of creating a signal which would get from one Eon to the next and I thought well how about the collision between supermassive black holes we know from the LIGO observations these wonderful observations that black holes of a few maybe 30 times the mass of the Sun have been observed whacking to each other and they send a signal which is so powerful that they can be observed from galaxies which is many many many many light-years away now these are only trivial size just if you know 20 or 30 times this because the Sun this massive as the Sun but what about these supermassive black holes our galaxy has a black hole which is about 4 million times the mass of the Sun we are on a collision course with the Andromeda galaxy which has a much much bigger black hole I forget the figures maybe 2040 time Thank You 40 times bigger than I won we were collide after a few thousand million years not so long really and then the but our galaxies may go through each other and grow a few times I don't know whether the black holes will capture each other the first time or a second at the third time but they will eventually feel each other our spiral around into each other and kaboom well a little bit bigger than that except you weren't here cuz its gravitational waves and okay some of these detectors somewhere might detect them but no that's never be that those gravitational wave signals will reach the crossover surface and get through no it's quite tricky you have to ask yourself in what form do they get through and here's my the equations come in I I think I'll just talk pretty well quickly about the equations without telling you much about them but nice pictures just to show you there are some equations like this you see the vial of curvature which is this thing with the C is to conform a curvature and that's the thing which measures have curved up a conformal spaces we don't have a metric and that measures the intensity of gravity in a certain sense and that has to go through for money on to the next you know what does the fifth spot but the way that you measure the scale of a gravitational wave is by something almost the same except that when you scale it with this Omega thing that Capital thing there is capital Omega it they scale differently and what that tells you is that the wave scaling that gravitational signal fades away and so that you have zero in the viol curvature in the next Eon however the derivative across the surface has a value that you can measure and then you look at the equations and oh yeah I've got questions written yes you can see the sort of thing yeah there's only some of them you look at the equations and they tell you that this disturbance which was originally a gravitational one gets transformed into well it's the fourth derivative of a scalar field which has to be created at the crossover now that's a key thing that you get this creation of a new material now this is the dark matter according to the theory you see if you write down the equations you find it's not so hard to see this because if I size equation has got to work right across from one side of the other when you're when you have the compress state you've got to have something which pulls the universe together where's on the other side that's not there now when you match from one side to the other you have to have this conformal factor which I call Omega and it's you change it to its inverse on the other side I know I'm talking to people who will understand these things and other people who who aren't familiar with these ideas so I just rattle through it a bit but what you find is this factor here which initially is introduced in order to be able to write the equations down so you have the Einstein equations and you find that they go crazy when you get to the boundary so notice for them not to go crazy you Infant introduced as a convenience this Omega thing now this Omega thing is simply a scale factor it's just squash factor and it doesn't mean anything physically and you can see it but then you pretend it has me something physically and you say it's got an energy momentum tensor which is this thing right here then you see Einstein's equations become very easy they're just this funny thing equal to energy momentum tensor of mass well that's just a trick okay writing things down but the thing is that when you go from one side to the other the the what I call they can be reciprocal hypothesis is the conformal factor becomes its inverse its reciprocal on the other side and that is the trick which makes the whole scheme work and that trick has the remarkable fact effect that it changes this Omega thing which is initially not real it's just a way of writing the Einstein equations with an extra factor so that you can have a a system of equations which make mathematical sense they're what's called conformally invariant they don't care whether it's stretch or not and so they work right up to the cross over servants however on the other side this thing suddenly becomes something quite different it becomes an actual field that behaves like a new field which wasn't there before and this new field you need it there to make the equations work I say this is the initial form of dark matter so the thing is it does have a match with what we know about dark matter it's there it's the dominant material in the universe in the early days you're probably still the dominant material in the universe it only interacts with things gravitationally because according to this scheme it's the sort of form of gravity it carries over those degrees of freedom which were entirely in gravity nothing else makes any impact time except in the secondary way it's not it's it's a gravitational thing it's sort of a scalar partner to gravity and that scalar thing is the dark matter now this dark matter does various things in the scheme which is very important now let me just say what do you expect the mass of it would be it starts off effectively massless like everything else but then it picks up a mass now what can that mass V it's only gravity we're talking about what mass is there that's only gravity the thing which is called the Planck mass could be a few factors of pie and eights and things like that but never mind about it essentially the Planck mass now what is the Planck mass how big is that it's about 10 to the minus 5 grams how big is that an ordinary thickness well P I always thought of his imbalance the mass of a flea or small flea I've seen it described more precisely as the mass of the eye hopefully that doesn't seem very big something you need a good lens or a microscope to look at the thing but from particle physicists point is huge ordinary particles in the ordinary standard model of particle nothing like it this is absolutely enormous now I've talked to bearish people Jim Peebles perhaps the most distinguished cosmologists there is around and Josie was also a very distinguished cosmologists independently asked them well what are the limits are there on Darkman observational ii from the cosmological and Astrophysical point of view and people said absolutely huge they could be a little tiny neutrino thing like or they could be the mass of the Sun individual particles I don't think you thought they were that big that Planck mass particles away way within that huge scale I asked Joe silk and he said yes that's a very plausible the observational point of view some people don't like it because then they know more immediately think of black holes that scale and a black hole of a scale that we don't really know what you would do the theory would be a little bit separated way in tiny fractions of scale but that's it there's no reason why it should it could be a stable particle so what I say is is a stable particle but it can't be quite stable because we don't want it there by the next Eon it's got to come again each time you cross over from beyond Eon you create this new dark matter which wasn't there before that means it has to decay away between Big Bang and infinity what's the decay rate well the decay rate would have to be determined by the other thing which is purely gravitational that is the lambda term in Einstein's theory which tells you that the half-life of this thing should be not well estimated this is something like 10 to the 11 years so that's a bit longer than the age of the universe up to now it needs to be something like that if not a bit more for something which I'll say in a minute so these dark matter particles well since I can't talk about them and I got to give him a name so I looked up on Google to say was there a God of Darkness and Google said there wasn't a Greek one but there was an Egyptian once you take Egyptian gods and he was called Erebos so I gave a lecture saying it I couldn't find anything in the Greek gods and then I look back game and Google and is it changed and he turned into a Greek god so I was perfectly happy with math I performed a great Greek god I think because he has more status it's a green card but he was the god of darkness and he's a primordial God - that's fits in very well cause these you came in there before other things so so every boss is the man another man that God and so this suggests that these particles you called Le Bon's so I'm going to call them Mary bombs I might have called Mary bosons I tended not to do that because I didn't see they were very very quantum mechanical but that was a mistake perhaps I'm calling the married ones now anyway these particles have to be very very dominating and they have to decay they have to be scalar particles because these are they don't have any spin no here are the era bonds and mass I think I'm just saying the Morris things know his name but let me say one more thing I did say that I had trouble with the measurement problem in quantum mechanics and the fact that unitarity doesn't really seem to hold when you have measurements in quantum mechanics and I have this proposal that various other people have proposals this nature the gravity the interplay between general relativity and quantum mechanics is what tells you that the quantum state does have this decay if you have its Schrodinger's cat earliest cat according to Schroeder you you could make a cat that was dead and alive it's according to Schrodinger's equation you follow his equation the cat would be superposition of being alive and dead and Schrodinger's moral is saying look this is ridiculous people often say now well you know you could make a Schrodinger cat and Schrodinger said you could well surely was really pointing out the problems with making a cat that was alive and at the same time then people say well you open the box and somebody looked in it and immediately when they look in the box they can't become one or the other that's not what I'm saying what I say is this is already that in the earliest one you have a file of poison and the hammer hits it or something I'm saying as soon as that hammer hits a crash it's already that's become one or the other even before that as the hammer moves it will become already one or the other but that's not the conventional view but it's my view now what about Arab on particles if they have a plank mass they were instantaneously when I say instantaneously in about 10 to the minus 14 forty-three seconds I think it is like time which is instantaneous as far as you and I are concerned so this means you have these particles which try to spread out as a quantum respecting quantity respectable quantum Parton would do according to the Australian Chris and then WHAM they reduce into a particle again so they behave like classical particles how do they decay where I worried about this there's nothing to decay into except gravitons and then I was I was talking to an event the vet Fuentes who has ideas about measuring gravitational waves in ways that go beyond LIGO and so on anything I've lost something anyway I was talking to her and I worried a bit because if you had a detector which could measure a single graviton and it had a Planck mass it would blow the blasted thing to pieces it wouldn't mean any use to have a detector you have me back why I say it would blow it to pieces because the energy and the Planck mass particle is about a sizable artillery shell you wouldn't want it going off in this room it would kill everybody in the room so that's not a nice thing to try to detect so I began thinking well maybe it's not like that well after all if it's a classical particle it will decay into a classical wave now it's still a quantum mechanical thing so it should have a frequency okay maybe Planck frequency but if it's got such a high frequency it will behave in a rather strange way now just to explain this I hope I don't have any time left you all do I I have a few minutes five okay I'll try and do it in five minutes now you see I used to think about these things a lot what is the effect of a gravitational wave well you see imagine you've got these two arms going on right angles and the wave is coming straight down what is it squashes one arm in and stretches the other and then there's stretches that you have this effect which is opposite from the two arms and that makes specifically look for however if you have a high oscillatory wave of that sort and this is you can think about these things by thinking of Len optics and that's the way you should think about it you imagine an optical bench which is a lot of lenses you put like thousand you have positive lenses and you can put it together and see whether they the strength of the length of the lens the power of the lens is the inverse of its focal length now if you put two lenses close together the powers add up but if you pull them apart a bit then there's a correction term due to the distance between them now suppose we have a stigmatic lenses so this is what gravitational waves are like they squash in one direction than they stretch in the other so you have pure astigmatism with no focusing positive or negative now if you have two of these lenses opposite to each other right up against each other they will completely cancel but if you pull on the part the correction term comes in and they behave like a positive lens now suppose you have an oscillation between these two things like this then what you see is the correction term and that's behaving like a positive lens and that is the energy content of this gravitational impulsive wave so if you imagine a higher satori gravitational wave it behaves like an impulse so if that wave came down that's like a witch squash them both at once so you wouldn't see them however if it came along one of the button horizontally along one of their arms then it was squash one way and not do anything the other way so it could see so they're the kind of thing that I imagined that might even be seen by LIGO or something but have not been said to be seen but they would go immediately into the rubbish bin and I'm hope they keep all their rubbish bins because I'm rather than saying that they probably should Ben could be important now I have now you see the error bond decay is important cosmologically for two reasons one of them going back for inflation what is inflation good for now one of the real things that it's good for is to explain something about the variations in temperature over the sky there's a remarkable feature that they have and this is what's called scale invariance so you look at different scales and you see the same kind of pattern and nobody could think of a way of explaining that and this was the reason in my view that inflation didn't die at birth because it has this exponential self-similar behavior so if you have a disturbance in that inflationary phase that will have a scale invariance and so that's the main good thing about inflation there a couple of other good things about correlations between things and distances which are hard to explain if you don't have something either inflationary phase or something going on before the Big Bang now I say I don't like inflation inflation would ruin the picture that's not just in my name it would kill the picture however if you don't have inflation you've got to have something else which explains this self-similar behavior now there is something there I don't have inflation but I have eons and I have the eon prior to ours and I say that that beyond I go back to this picture here here we go all right well it was an exponential expansion it's not after the Big Bang it was before the Big Bang listen this sort of reflects an earlier idea to do to the physicist finis Gianna thank you had a very great physicist and this is a similar sort of idea I'm saying that there is this disturbance and the previous a young and that's what caused this thing temperature variations in the cosmic background but what was it Rishi I used to think maybe it was these black hole encounters well Christoph Meisner my polish colleague said convinced me that didn't work because you get very little uniformity and all sorts of clumping yes in the woods that's not going to all that but I I was persuaded by him it doesn't work you've got to think of something else so I suggested how about the decay of dark matter particles he wasn't so keen when I first told him we had another girl in Warsaw later we worked on it and he say yeah you will get the skeletons and you can see on the model that you will get the scale invariance so what I'm saying is that error bonds do that that's what you're looking at in these temperature scale events now you see in this picture I think you get an idea there is the crossover surface or here it is and you see here are the era bonds in the previous Eon coming and hitting us or hitting our crossover surface and causing this temperature variations which will be scaling in thereand yeah this all depends on the decay is not being too early or too late in this so you have to worry a little bit about that but then you can see them in the same eon maybe and this would be a possible way of seeing effects from different galaxies you might be able to see the Dark Matter itself if we could find detectors which were sensitive enough to the sorts of signals that I'm talking about or maybe you could see close ones in our own galaxy these are two quite different possibilities in the only if I'm girl in our own galaxy they would look like impulsive effects bang just like that maybe you'll see well maybe they have been seen the distant galaxies is their subtle thing and I was a bit worried by this because when you look at the figures and I have some figures here and let me not say too much about them but I say if you look at the figures and I was worrying about how many airlines there would be in a galaxy and where they'd be enough of them were gravitational waves are detected to see them and it got really depressing because you'd need to have a signal you see I was thinking about this for a reason that there was a paper but not a paper it was even submitted to a journal by some Copenhagen is this headed by Andrew Jackson I think and they claim that in the LIGO data the amount of it which has been already released where you see these signals which are the gravitational wave signals and you have two detectors and there is a certain time lag between where one of them receives them the other one because this signal has to get hit one person than the other and that's perfectly consistent this sort of time lag you see but what these people said is if you look at the noise you're not looking at the actual signal but just around the signal and you see things which are considered to be irrelevant and you find the same time delay now there's an argument I don't saying they're right I know that other people have repeated it and find the same effect maybe that's not a real effect it's something spurious I don't know but he did when I first heard about this I just get them to talk about these era bonds in Vienna and it started to worry me because I thought my god maybe they're seeing Arab on signals from the galaxy in which those black holes sit and there will be other examples if you take the Yeun dromeda galaxy and see what about the time delay there do you get the correlation there that's another galaxy that black holes aren't colliding there but nevertheless the signals ought to be there and then I started to do calculations with figures and all that and I got a bit depressed by this and how do you see something which would be just a general whoosh from a galaxy and how do you know it's just different from another one well it was a curious thing because I had a bit of a correspondence with me what's her name Sabine a person who makes rude comments about mysterious from time to time and so she was making a bit of a rude comment about mine and I had a response a well maybe you see not be so you want to have a random signal that you might be able to tell the time delay from a distant galaxy but she said oh you mean hbt do you have no idea what is hbt oh she said oh oh that's Hanbury Brown to it all hammering Brown Twiss that's something I knew about but what does it mean it's an effect you its Hanbury Brown Twiss we're talking about the diameters of stars and they were looking at photons from different parts of the star and lots of physicists complained they were using interference effects and that they shouldn't be able to see anything because you can only see interference between particles and themselves not do another and they said no no you see this effect and eventually it turned out they were right because particles coming from distant parts of the star are automatically entangled because they are bosons now bosons that the state of those pairs of particles are already entangled and I don't want to go into the quantum mechanics what that means that the quantum physicists here will know what I mean when sent insane entangled they're not really independent and even though they're widely separated and you get a certain calmness in the signal due to the fact that these things are automatically entangled with the other particles now there's something very similar happens here because you've got the error bonds from one part of the galaxy and the other pilot you think what does this one know about that one well they're both Airy bones and airy bonds are scalar particles even though they reduce themselves to looking like classical particles they're still bosons so there will be this inter relation between distance decays right very strange effect and I haven't thought through enough about this to see whether I believe it so it's a question mark I think there's a reasonable chance that it's right and that reasonable chance would say maybe you can with a suitable gravitational wave detector see over error bonds from distant galaxies I hope it's true because it was very exciting to see the Dark Matter directly rather than these indirect ways it may be that it's nonsense and the signal would not be nearly intense enough to be able to see it I think you need Hanbury one twist in order to have a chance of seeing anyway that's the end of what I want to say thank you very much I think we'll take just one or two questions we have some refreshments they brought in some error bonbons and we're gonna enjoy those so I'd like to take questions from people under the age of 20 only you asserting my host prerogative so check kids in the audience you can interact with a very eminent scientist sofa have any question remember there are no stupid questions only stupid questionnaires no I'm just kidding please anybody all right I'm gonna turn it over to older people's questions which may be less well now I see who's gonna ask a question I know it's going to be interesting dr. David Britt I refuse to grow up Roger I I was wondering about these things well first off what fraction of radiation in at the end of the Google universe and I pronounce it Google not Google what fraction of the radiation in that future universe would come from the evaporating black holes because there's going to be a lot of of legacy radiation I did wonder about this and you see the although it's ridiculously small the amount of radiation that comes from a black hole you don't have to wait until the temperature of the universe gets lower and that is that's a lot a big part of that Google years good goal yes right however in total if there's quite a lot you see there's the in pretty well the entire mass of that black hole will deposit itself in some way in and make some kind and the rest is all stretched out well it would be very stretched out but then the universe squashes things down and so you have to address that question appropriately but there's and then it's an interesting question which I had wondered about yes all right I'll ask some others later any time for one more question oh and you're gonna make me run to the back of the room serious cold this will be the last question we don't let the food cool off to absolute zero um my son Otto is like Stephen Hawking he can't speak so he types but he wanted to know if you believe in global warming yes yes suddenly 13 my son's 13 by the way okay well I don't know that matters what am I saying for the answers because the evidence is very strong and I certainly believe it's happening yes I see every reason why it should be having I mean should in the bad sense when one knows we're pumping all this these greenhouse gases other than the sky and we have no way of compensating that or nothing significant going in the other direction so yes I can't see why it's not globally globally warming and we see it is so I I'm afraid I'm on the rather depressing side of this argument yes let's thank Sir Roger again and get the food while still aboard [Applause] [Music]

Channel: Arthur C. Clarke Center for Human Imagination

Views: 73,149

Rating: 4.7914891 out of 5

Keywords: Roger Penrose, physics, cosmology, Big Bang, conformal cyclic cosmology, inflation, dark matter, erebons, Arthur C. Clarke, Arthur C. Clarke Center for Human Imagination, Clarke Center

Id: xlSMME-Cl5g

Length: 75min 2sec (4502 seconds)

Published: Thu Feb 01 2018