Sir Roger Penrose: Are Singularities Real?

on youtube and we should be ready to go here in just a second let's see if this is live on the internet uh let's see here where are we i think we are live yes let's see here live and i'm gonna go to make sure people can see us out on the internet uh it is a great pleasure to have you today roger sir roger penrose let me just make sure we are broadcasting to all the places we want to be broadcasting to yes i believe that we are i see it we've got already 34 people are watching there we go great okay everybody welcome to this episode a very special episode of the arthur c clarke center for human imaginations into the impossible podcast featuring my friend and a collaborator sir roger penrose roger welcome to you it's a great pleasure thank you and uh has anything happened to you since the last time we spoke any any news in your life uh since the summer it was a little thing i heard a few weeks ago yes yes so first i want to wish you a hearty congratulations for your uh your receiving of the 2020 nobel prize in physics a half of a share of the nobel prize and i do want to talk about that as we as we um as we go live i do put out slides for this that people can find in the youtube chat box so if people are interested in following along i will uh i will show some slides along the way so i'll give you guys a couple of seconds to get to those slides they're in the chat and in the comments and these are regarding the subject of today is not going to be sir rogers nobel prize at first we're going to talk a little bit about that because i think people are curious about it but we're also going to talk about a wonderful book that's made a huge impact on me and many other people and that's his book cycles of time which came out in 2011 when one of the formative books of the early part of the last decade that describes in some detail auditors very curious and provocative conformal cyclic cosmology and to to understand it i think it's helpful to have some preliminaries about the uh the way that the um the model was developed and devised and what made you come up with it essentially uh but first i want to ask uh where were you when you got the phone call that you were a recipient of this uh particular gilded metal here how did you find out well it was a bit curious because it was a bit protracted you see i think the first sort of faint notice was when i was just coming out of the shower so but it was a call from my pa patrona winton and she told me she'd had this strange message uh and she wanted somebody wanted to know my phone number and she said she didn't give my phone number out and uh and then she sort of started to get a little bit suspicious and she said this is about a prize and they said no we're not allowed to say anything so um she phoned me up you said that's when i was just coming out of the show and uh and i thought um well i have no idea what this is about but you it's i don't see any reason why i shouldn't give my phone number so she did give my phone number to them i just waited a long time and then nothing happened and then finally i did get a phone call from somebody from the academy of sciences in sweden so it wasn't getting a little bit more suspicious and she didn't say what it was about but she said that a little while the director would front of the academy or whatever he is was going to phone me up so nothing happened again and so i think i went with something else and then the phone did ring and i said he did introduce himself and started talking to me and then he said oh you would you hang on for a bit so i waited and i waited and i was in my weight and then i just hung up if it's something important you call me back so he did call me back eventually and he said it was a nobel prize yes wow and so did you did you react honestly to feel like it was an overdue occasion for this or did you think that by endorsing my book losing the nobel prize that you are finally out of it i'll remind you what you said you called it a fascinating autobiographical account full of intriguing detail of the passions and inspirations that underlie the scientific quest a highly thoughtful and informative book i i think this for me was the last you're the closest i'll ever get to having a real not chocolate version of these but uh but um did you feel like it was long overdue i mean a lot of people speculated that your good friend stephen hawking who we'll speak a lot about today obviously um that he deserved a nobel prize and that he was um yeah he was unfairly overlooked so to speak what were your reactions it took a long time the the prize says that you must give it to someone in the preceding year uh and you've been making contributions every year but but uh the award uh citation really cites work done perhaps many decades ago so did you feel like it was expected or totally unexpected how did it how did you react to it on a personal level the trouble is various people had told me that that you know it's overdue so i had to believe no i didn't wouldn't have expected this at all um apart from what people you know some people seem to think that i mean the work i did as you say was ages ago it was in actually 1964 when i did the work paper was published in 65 and that was at a time when the quasars had been where they'd been around for a bit and people puzzling about them because they seem to be so bright and yet so small from the variation the timing of variations that they had to be of a size comparable with what's called the schwarzschild radius and people knew that if anything was that kind of size they would collapse i mean there was a paper in in 1949 sorry yes 1939 sorry 1939 by oppenheimer and schneider where they had described the collapse of a dust cloud and this was basically the picture of collapse to a black hole but people didn't take it very seriously most particularly einstein who was in the same institute not even sure einstein even read the paper but um i think what people thought was two things about it one was it a collapsing dust cloud and dust has no pressure so you might think it's nothing to stop it the other thing more important is that it's spherically symmetrical so everything simply falls in towards the center with nothing to stop it and so it's not so surprising that you would get an infinite density in the middle and this would be a catastrophe you didn't know what to do with it but people thought well that's very unrealistic in any realistic situation apart from the pressure which actually works the other way pressure doesn't help you but apart from the pressure issue um you wouldn't expect this thing to be exactly spherically symmetrical so you think it would collapse inwards get very dense and swirl around and come swishing out again this was also sort of confirmed in quotes by a paper by lipschitz and flatnikov two russians who appeared to have proved that in the general case you would not get singularities so this place of infinite density or some catastrophe like that would not happen and so it would swish around and presumably come out again i looked at the paper and i sort of i didn't notice the mistake in it there was a mistake in the paper but i did feel that arguments of that sort were probably not too persuasive to me and so i didn't think it was conclusive and i started thinking about visually analyzing myself being inside a collapsing collection of material matter and i more or less came to the conclusion that you couldn't prove anything just by local argument it had to be something global something more not in one place but in the sort of some surrounding region and this was a key thought that it was something non-local and later on i came to this there's a story which i told people often about when i was talking to ival robinson who was an englishman who worked in relativity theory in dallas texas mostly and he was visiting back home in his home country and talking to me and he was somebody who had the real gift of the gab i mean artistically i mean he was he was a wonderful speaker and he was just talking to me i don't know what about and then we got to this side street where we had to cross the road and the conversation stopped him across the road and then we got to the other side it started up again he told all the and all sorts of exciting things he was telling me about then he went home i went off somewhere and i came away thinking having this strange feeling of elation and i couldn't think why i felt like that so i went through all the things that happened to me during the day what what i had for breakfast and what i did after that and did i have a walk or catch the tube or you know obviously caught the tube but um well it was and then eventually working through all the things that happened i got to this time when we crossed the street now i realized in that time crossing the street i had an idea which was i think the idea of what i call a trapped surface that's what's called a trap surface which is a surface i can actually describe what it is you think of a surface an ordinary two-dimensional surface and it's closed up so it's like a spherical surface it doesn't have to be a sphere but imagine it's closed up and that surface you imagine a flash of light occurs on that surface now normally if you have a flash flood on the surface if the surface is bendy it'll it'll be concave on one side and complex on the other and the concave side the light will be converging on the other side it'll be diverging but in this curious case when you get in this beyond this point of no return it's what we now would call inside the horizon but when you're at that stage you can find surfaces where the flash of light both the inward flash and the outward flash are converging so the light rays are coming together on both sides and i knew that this would be bad news from studies that i'd done previously of looking at future sets you look at the house set in space time you see what region can you reach by um time-like curves that is particles which don't travel faster than light what kind of region do they sweep out and what's the boundary of that region and what's it look like and what is it generated by light rays and what the light rays do and how do they reach their caustic surfaces and crossing regions and so on and i was familiar with that and i realized that when you had this situation you're gonna have trouble you would there's no real way i mean there are various sort of loopholes but no serious loopholes as long as the energy density doesn't go negative or something like that you would definitely have to have a singularity and so this was the paper i wrote this paper and said uh the tune singularities were necessary in it collapse the main point about this is that you don't make any assumption of symmetry is you can break the symmetric case and then wiggle it around as long as you don't wiggle it hugely so it's qualitatively fairly similar but doesn't mean that the matter has to fall in towards the center it can be quite complicated any in any way you like as long as it starts starts in this sort of converging state and then it necessarily has you get a singularity i had a slightly awkward point in the proof which charlie misner improved later on so it was um i want to ask you about that in terms of uh collaboration et cetera but uh but first before we get to that so i'm showing a slide from a picture from cycles of time where you describe this in fall into the singularity this summer you know uh you were you were quite busy this summer maybe in uh anticipation your your uh your your third eye or something knew that you were going to be very busy and and i do want to take the time to to uh to appreciate you and to recognize and express gratitude for being on the show in such a hectic time uh you have to prepare your your nobel lecture etc but i was um inviting you over the summer and it just the timing didn't work out for you to be on our podcast discussing theories of everything with our guests uh we ended up having quite a lovely series of guests this summer and and we were entranced by these ideas about theories of everything and how they could perhaps unify quantum quantum mechanics with gravity and a lot of what i took away from that discussion was kind of a new doubt that singularities exist and not to be offend you in any way but we have no physical evidence of a black hole singularity um and the converse process we'll talk about uh you know you talk about falling into the black hole and what you would see once you pass the event horizon with all the light cones tilting towards the singularity and all paths uh all world lines will terminate on the singularity but um are singularities also a matter of faith that a physicist must have or do we have any evidence of anything in nature that is physically infinite uh in any regard that we have evidence for i think the answer to that question is we have well we have things in aerodynamics where you get shock waves and so on i mean but then you say the physics that you've been using at some point you have to replace by more refined physics and so the idea here and this is what i certainly stated in the paper was that maybe you have to consider quantum gravity that quantum mechanics classical theory of general relativity which is a classical period of gravity um doesn't uh combine with quantum mechanics and so when the densities get enormous you might expect the quantum effects would start to become important density is getting or the curvatures become enormous and so the classical description would become inappropriate no it's quite prepared to accept that but in a sense well you see i i tended not to use the word singularity in most of the discussions i'm not quite sure i remember what i said in that particular paper it was in the title but i don't know whether i'd certainly considered other possibilities like the last people in the chat room can you look up the title of somebody post that in the chat uh for sir roger because i forgotten it too yes i think he's in the title yeah so somebody out there please we have hundreds of people listening right now so somebody will post it in the chat room for us yes gravitational collapse and space-time singularities actually i can't remember because i've written so many pages just 400 by my count roger it's but not on its subject other subjects yes but you see it was more stephen hawking when he started working on the cosmological singularity that he tended to use the word singularity and i think he more or less converted me to using it later it's just a useful term it's a singularity in the classical theory but it doesn't mean that physics gives up it might be that the physics does something probably more where quantum mechanics is playing a more important role so i was quite prepared to believe that in fact that was the sort of view i had but that led to other things you see i've been trying to work on this nobel lecture you see and there are two two sides to it one is what led up to it that that singular that paper basically and what grew out of the paper is the second part and what grew out of it and i mean there's i can sort of go through it if you like um first of all well stephen hawking picked up on the techniques i was using i should say that i i gave the first time i talked about this was a lecture i gave in king's comic college london and in the movie you see stephen hawking sitting in the audience with sparks coming out of his head of inspiration or whatever it is the trouble with this was he wasn't actually there right i mean hollywood got something wrong factually and science it's not quite so bad because denis sharma who was a good colleague and friend of mine who was in cambridge at the time and he uh he he educated me a lot on physics he was a crucial person in my education in physical sciences particularly um rarity and other things too and he uh asked me if i'd give a repeat talk in cambridge and i said sure and in january early january i gave a talk i think it was early january uh and stephen hawking was that talk it was a repeat of the one in london is that when you met him for the first time roger that's what i meant yes it wasn't just the he was president in the audience because i had a special session with him and and george ellis i see probably brandon carter i can't remember but george ellis was certainly there and we talked about the details of the argument i'd used they were looking at something not nearly so general is that what i was doing and then stephen picked up very quickly on these arguments and used the version of my theorem in the opposite direction in time to to prove a result in cosmology but it was not a terribly strong result and he developed the techniques considerably beyond what i had done and eliminated many of the loopholes and applied it to cosmology as well as to black holes and then later on we got together and wrote a paper which more or less encompassed the results which we'd done before um but you see stephen picked up on the sort of black the big bang end of it and an important thing you see about general relativity in most physics is that it's symmetrical in time the theory works one way just as well as it works the other way so if you expect to get singularities when matter is collapsing in the future you would expect to get singularities the other way around when matter is diverging away from a very dense state in the past this is the picture of the big bang and the question is this is generic thing too i mean can you perturb it in some way and maybe get rid of the singularity so you might imagine instead of having a big bang which was the beginning you might have had a previously collapsing phase which somehow swirled around in a complicated way and then came swishing out again now the next stage in the story was when i was you know i think it was i was in princeton again i should say i was in princeton when the quasar things were getting there and so i was worrying about the well i wasn't actually in princeton when i thought of the theorem but it was just a little after that but i was pre in princeton again and they used to have these meetings in stevens institute in hoboken new jersey which was a short drive from princeton and many people used to go there and they would go there from other universities in new york state and they were it was a good place for getting together thinking about things in relativity that was mainly to do with that and one of the cars i i i i noticed that one of the cars that could have taken me up there was was full but in the car was james peebles jim peebles who was the previous physics snowboarder i mean last year but i saw when he was there i took my opportunity i said um you cosmologists i mean there are many many cases where you can get singularities and models and they could expand from singularities and all sorts of different kinds of moles why don't you consider these in cosmology and he looked at me and he said because the universe is not like that i thought gosh i can't i assume he meant by evidence from the cosmic macro background you see this very uniform radiation coming with all very very tiny variations in temperature and this is pretty good indication of how very very uniform the big bang was so i thought my gosh it's very very different and this sort of bugged me for a long time you have the singularities and collapse which are very complicated and hugely diverging i should say something now about the kind of physics or the kind of curvature you get in space-time in four-dimensional space you can have two kinds of curvature one of them is called the ritchie curvature riccci and the other is called the vial curvature w-e-y-l now it it kind of worked hard done earlier in looking at spinners and general relativity which is an important motivational thing in my case you can see very easily that the thing splits into these two parts now the richie curvature is directly what's given by the matter so you have a matter density and that gives you just there where the matter is richie curvature now when you don't have any richie curvature there's the other kind which is the vile curvature now vile curvature describes the gravitational field i mean this is the way it wasn't necessarily the way most people looked at it they tend to think of the metric as giving the gravitational field but the curvature that describes free gravity or gravitational waves or the gravitational field in the same way that as in electromagnetism you have the electromagnetic field and you have the sources which are the charges so the charges are the analog of the richie tensor and the electromagnetic field that's the analog of the vial tensor and it's important to get this distinction now in the early universe you get very very big concentration of matter that's richie curvature but what about the vile curvature now you see i began to realize and this is a big factor in in the whole discussion is this difference between the type of singularity you get in the past that's the big bang or in the future when black holes is um well the curvature is very different but the other point of importance is this very very important principle in physics or the what's called the second law of thermodynamics now the second law of thermodynamics tells you that entropy now entropy is a sort of measure of randomness think of it as just a measure of randomness the entropy increases with time that's the second law of thermodynamics i mean it might have little fluctuations where sometimes it goes down but the general trend is it increases with time now well an important factor in this is the work done by beckenstein and hawking where they showed that there is an entropy assigned to a black hole and this entropy is proportional to the surface area of the horizon of the i think it's important first of all i don't think i just made this point earlier that people got very confused in the early days about the horizon and the singularity because the way that schwarzschild originally wrote it down the solution of einstein's equations which described the spherically symmetrical body the way he wrote it down is you have this place where the things seem to go haywire and this is called the schwarzschild singularity now this singularity if you think of the sun for example and you imagine squashing it down you see the the schwarzschild solution applies to the vacuum outside the sun but within the sun you've got matter and so that particular solution doesn't apply you have another one short she'll have another solution which people don't take very seriously but the main point is that you have a different solution when there is matter so outside you get zero and that's what we normally call the schwarzschild solution is the outside of the sun's body well say yeah say the sun now suppose you imagine that the sun contracted to smaller and smaller without any radiation or anything coming out if it were to contract then you have the great a bigger region of vacuum and a more concentrated region of matter now if you could squash it right down until i forget a couple of kilometers or something i forget well that was directed exactly you get to this structural so-called singularity people thought oh that's just nonsense and you get you can't deal with it but various people realize one of the most important of these was lametra who is a very important cosmologist he was a he was a priest a belgian priest and he um discovered solutions uh on the answer well there was friedman originally but lemaitre um looked at the big bang and he was a big promoter of the big bang and he had was the people person who really i guess persuaded einstein you had to take these things seriously but uh he also realized that if you sort of let mata fall in it could cross through this region which used to be called the schwarzenegger singularity and it's not a singularity it's what we now call a horizon so this is a region where mata can fall in and once it's got through this region it can't get out again so it's a sort of one-way trapdoor or something it gets through the surface and there's no escape and in the spherically structural symmetrical model that friedman and and um rock remembers talking about cosmologies so that um that lametra had you see you you have this picture of a black hole and the oppenheimer and snyder later on had this collapsing dust cloud which was the same sort of picture and you can see in both those models that the horizon that the what's r equals 2n this is the in the sort of units that's used in relativity theory r is the radius m is the mass and when the radius reaches twice the mass in these curious units then you get to this radius but it's not a singularity it's a horizon verizon meaning you can fall through it but you can't get back out again or light can't get out again that's the key point light can fall in light thinks it's going out but it's actually falling in if you like as it goes through the horizon and the pictures you like that i like to draw we have these cones yes i'm showing that on the screen i have the slides and remind people they can download the slides and the link i'm putting in the comments and chat uh you can get these very slides and i'm showing not only the black hole conformal space-time diagram but also the white hole which as you say violently i mean this is as violent as sir roger gets it says violently disobeys the second law of thermodynamics and so i want to understand that so yes keep going i'm showing the picture as you're speaking sir roger yes we see the the black hole by this hawking beckenstein hawking foreign has a sort of general physical argument to show that the surface area of this horizon would be a measure of entropy but he didn't know exactly the formula then stephen hawking had a much more refined argument to show exactly that the entropy was given by this area a quarter of the area in appropriate units and this turns out to be an absolutely stupendous value so if you consider now with the sort of sizes of black holes we know are out there the amount of entropy in the current now and now in the current universe is almost entirely in black holes by an absolutely enormous factor now i was aware of this enormous factor and don page who used to i used to talk to quite a bit he looked after stephen hawking quite a bit when he was i think dawn was a graduate student at that time but dom was very good with the figures you could ask him something like this and we'd come up with a precise figure and he just told me how enormous this entropy was in these black holes and this made it clear that when you get clumping of material and the material clumps more and more and finally it produces black holes this is a you can see this is the second law in action now it's curious the way gravity behaves it's rather you see it's misleading in many ways people think of a gas in the box or something like that and you might have a gas which is in one corner of the box with some kind of compartment and you release the gas and it spreads out through the box now that's an increase in the entropy so you have a an irregular distribution of gas which is a low entropy state and then it spreads out through the box and this is getting to a higher entropy state so as the gas spreads out through the box the entropy is increasing now that's the sort of picture you get with a lot of materials and so on but gravity is the opposite you have things spread out and that is low entropy and then when the material clumps together that represents increasing entropy so the picture is sort of the opposite but nevertheless it's still the second law to get uniformity to clumping and we live off it i mean forget about the black holes the sun's out there and that used to be just a distribution of gas spread out uniformly and as it clumped together you've got this hot spot in the dark sky and that gives us the entropy which we live off life schrodinger wrote a book called what is life and he was the first person ready to point this out this distribution this disparity between the hot spot of the sky which is the sun and the cold dark sky is what we live off yeah so you get photons from the sun which are high frequency and there are relatively small number of those photons and then the infrared photons which escape back out into space carrying essentially the same energy that comes in so we don't get energy from the sun this is a misleading thing people think we don't get energy from the sun because the energy just goes back out again in the night but it goes back out in a high entropy form because there are many many more photons taking the energy out that came in from the sun because the frequency going out is lower and by planck's famous formula you need more of them to cavities carry the same energy and therefore more degrees of freedom and therefore there's more entropy so they that carries the entropy away and we get the sun as a source of low entropy that's the key point that schrodinger made and i want to point out sir roger just uh just to stop you for a second so there is um that you can buy a copy of what is live erwin schrodinger's book and the forward is written by none other than sir roger penrose so you guys are linked together uh both electronically and intellectually and by this prize here that i have to resist eating all the time but go on to roger yeah so we live on the on this differential and entropy and energy uh not the energy and heat from the sun but instead from this different large differential and processing of entropy correct exactly that's right and that was schrodinger i've always been a great admirer of schrodinger he's one of my great i'm a great fan of him i learned general relativity from of all really how did that come about no he has this little book called space-time structure oh i i'm not familiar with it okay i'll have to look at it you can ignore the last chapter where he goes on to some unified view of there but everything else and he just he just described these things in a nice friendly way i was like would you say that that influenced you sorry to interrupt roger but would that influence you in your pursuit of the soft and wet world in other words consciousness that later drove you into learning about consciousness would that be attributable to schrodinger that's a complicated story i would say not so directly no but i mean in a certain way i certainly had been influenced by and that book in particular yeah but so getting back to the white holes and and the black holes analogy how does it violently disobey the second law of thermodynamics to have a white hole after all wouldn't that be analogous to the big bang singularity that uh hawking and you and others have worked on well you see it has a big entropy it still has the same forking entropy um about this entropy is high so you see if it's if it were to evaporate away you see imagine that collapse through a black hole or the white hole would expand out to become a distribution material and that would be a huge reduction in entropy so it goes violently as i said i suppose against the second law because if you simply reverse the collapse to a black hole you have you have a relatively small entropy to begin with on in the material which goes enormously up as soon as it crosses the horizon and the entropy goes absolutely shooting up so you have the opposite behavior which is just dreadfully against the second law now you may say second laws people you often say oh it's just a statistical thing and so it's not so fundamental but well i think i don't i think it is very fundamental it's fundamental because really because what started it off and what started it off was the fact that there were no white holes in the beginning we had no vile curvature you see i put this hypothesis this is just a hypothesis like everybody else at the time i thought you had to describe singularities by quantum gravity and so yeah i was certainly of that view that you think the why you sort of resolve the singularities in black holes or how you resolve it would be through some kind of quantum gravity nobody knows what the correct theory is but that would be how you do it now how would that singular how that theory applies in the big bang well maybe it resolves that singularity and maybe gives you a bounce instead of a explosion but the nature of the singularity since my sort of brief conversation with jim peebles in the back of the car i had to get in another car it was full but that persuaded me that the universe started on this very strange low entropy initial singularity and it's low entropy in gravity not in the matter the matter seemed to be pretty well thermalized as much as you could have as far as one could see that's not where the the low entropy resided low entropy resides in the fact that the gravitational degrees of freedom were not activated and this is what i sort of postulated as what i call the vile curvature hypothesis that is the past type singularities like the big bang for some reason had to be zero vowel curvature the singularities in the future black hole singularities would be wildly diverging infinite biocurvature and the matter might have even been wiped out by them so perhaps it's almost entirely in viral curvature at that point and this is a huge discrepancy between the two types of singularity and at that time i thought well this tells us that quantum gravity whatever it just must be a really really odd theory so all right i thought it was an odd theory but maybe this all tied in with sort of beliefs i had that somehow gravity was responsible for the collapse of the wave function you see and that was a view which i still hold but not in quite the same way because i don't think the the quantum gravity is really what's responsible for the big bang singularity so so that's uh that's provocative as well and that actually connects to this conversation that we had over the summer with er eric weinstein sabian hossenfelder we had lee smallin your friend lee smallin and and uh for a bit we had lisa randall before she cut out but we we had this discussion as to whether or not there really is a need for quantum gravity and to keep beating on a dead horse or even to is there a need for a theory of everything in other words is it if god i know you and i have talked about god on previous podcasts but just stipulate for the time being that which you get by playing around with the schrodinger equation and doing something different from it from evolving the schrodinger equation evolving according to the schrodinger equation so you suddenly throw the schrodinger equation out the window pull in something else gives you probabilities wheel that out the out the door again and bring it up back in through the window to shred your equation and go ahead back again i mean it's completely inconsistent what you do now all sorts of people worry about this some lots of physicists don't they say well we just take the theory as it is when we make a measurement we do what we're told and so on and that's fine it works well people who do quantum mechanics in some practical way always do that people who are more philosophically minded worry more about what really happening they might say well things get so complicated you can't very well use the schrodinger equation and you do something else if you look carefully at what you do when you do something else you see it's cheats at some point it always cheats it has to cheat because schrodinger equation doesn't say you get alternative problems is it says you get this complicated state which involves stupid positions of different alternatives so that's uh that's the the measurement problem the quantum interpretations foundations so but is it true that you know i heard it once said maybe it was uh another one of your um co-laureates who said something like quantum mechanics needs interpretations like birds need ornithologists in other words we love to have you know kind of a neat way of describing but i know for sure that richard feynman a definite co-laureate of yours said something to the effect that uh that you know the word is not the thing and and being able to for us to understand it it just means that there's a lacuna in our uh way of describing it and even if we can describe it satisfactorily that doesn't mean we truly understand it the fact that we can write down classical you know general relativity doesn't necessarily mean that we truly understand it because it would have things in it necessarily so but i think one crisp question for you is what if there was no singularity with that but it was a very dense object extremely dense you know denser than anything that we can imagine but not truly infinitesimal in extent would that affect the observables in any of your theories of black holes or as we'll come to later in triple c well you i mean it doesn't make much difference you see because we're not going to see the singularities and you can travel into i mean it wouldn't be you take one of these really big super massive black holes you could probably take a spaceship go into it i don't know how long probably a year maybe that's where the details are you could have you could play cards or you could try and work out how what the space time is doing out there and you observe things outside you would look at the universe outside you could have a decent time this time of life for a while and then curvatures start to get so big that you get ripped to pieces but still you wouldn't know what happened to singularity because you just run into it you wouldn't see any any other singularities certainly if cosmic censorship is correct in the in the sense i like to see you wouldn't even see any of the other singularities i mean i it's it's wrong to think of it as a point really that that's one of the things when you look at the prophetical structure of things the singularity is really a space-like region which you run into but um that doesn't matter too much it's uh funny because we'll have on a friend of yours hopefully in a little bit uh jenna levin has agreed to come on just to wish you a a hearty congratulations later i'm hoping to patch her in on this phone call but she's written a book that comes out next week called black hole survival guide i'm showing it on the screen here so it could be very practical i'll ask her i will ask her when she comes on how long it will take and what she will do on the way down but please continue well she's been looking at that that's nice yes yeah no you have quite a bit of time you could certainly you could certainly do a lot of observations as you fall you couldn't communicate with your friends yeah you won't you won't publish it but um that wouldn't be much good though but uh um no unless you see there were wormholes and then of course you have to violate energy and all that sort of stuff but um never mind no it doesn't matter that much in a sense except you know as you say you said it before i mean why do we need to know is it just we we like to know what's happening because we like to know what's happening not because it's any use to us well i guess that applies to lots of things in in astrophysics and so on you might see what was it recently a magneton was it yes just the other day somebody had i mean that's good fun and you might work it out and so on but you're not likely to go and see it um no the point is the different one which i hadn't really got down to the argument i'm making is that we need a theory which combines general relativity in quantum mechanics and that we really need if we want coherent description of the world in many ways we need that theory which combines generality and quantities but it won't be what people think of as a quantum gravity theory that it's not quantum mechanics which rules it's it's they both have to rule in in some kind of uh union the thing is that the problem with quantum mechanics is i'm trying to say is this reduction of the state or collapse of wave function whatever you want to call it which seems to go against unitarity they go against the schrodinger equation you have to have something else and either you have to know the sort of routes that people take maybe it's consciousness which has different laws i'm sure that doesn't resolve the measurement problem i mean i've always you could imagine for example some distant planet on which there is an atmosphere something like the earth's atmosphere and we know about things like butterfly effects that the actual atmosphere depends on tiny little effects it's a chaotic system and it depends ultimately probably on quantum effects now you see this space probe is going out to this distance several light years away and it wants to take a photograph of the atmosphere of this planet now there's no life on that planet it's it's an earth-like planet but there's no life on it so there are no butterflies where it doesn't i mean there could be butterflies but there are there are no conscious observers and so according to the consciousness it reduces the state theory the atmosphere will be some complete quantum mess of superpositions of different atmospheres it's a wuge okay the the probe sends this pictures of this whoosh back to the earth and it takes a few light years and then somebody is sitting in front of a computer screen looking at this whoosh as soon as the picture comes on the computer screen because that's a conscious being looking at it suddenly it can reduces into one atmosphere or another this to me is complete absurdity even more absurd than shows of his cat it's telling us that there is something wrong with the view that it's consciousness that reduces the state so i don't think it's that i do however have this crazy view that it could be the other way around that whatever is involved in the state reduction which i believe to be a physical process which is going around all over around us the stage is being reduced all over the place it's reduced when you get enough mass displacement so it's not just a dead cat and a live cat you have two configurations which differ sufficiently it doesn't have very much and you can see how much it is from the calculation it doesn't have to be very much and then it reduces to one or the other so this reduction is a physical process which takes place spontaneously there doesn't have to be any conscious being looking at it or even anywhere close it just does it itself according to some law which involves both gravity and quantum mechanics which we don't have yet although it's possible to make estimates using principles of general relativity mainly the principle of equivalence which is the principle of galileo and einstein that free fall cancels out gravity so the rocks falling from the leaning tower of pisa if they ever were would be fall together as though there were no gravity and galileo gives a wonderful description of fireworks you see a fireworks goes up and you see this beautiful spherical thing falling just as though there was no gravity and he uses this description in his books i i find that really wonderful yeah so you you well appreciated that you could cancel gravity out by falling freely and then einstein takes this further to say yes this is a fundamental principle gravity is not a force it's something more subtle than that you can cancel it out locally what's interesting is how that force varies from place to place and this is where you get into the vial curvature the vinyl curvature tells you one of the ways in which you can vary as you move from place to place so what i'm saying is that this principle is inconsistent with the principles of chronic pain you can do a little calculation and you can see that if you take the principle of equivalence it is inconsistent with the normal principles of quantum field theory but if you see if you can cancel a gravitational field field with with free fall then it gives you a different vacuum than you do if you if you don't free fall and this gives you if you have it different free falls in different places you have a problem with quantum field theory and you can estimate how big that problem is and that gives an estimate of how quickly a quantum state will reduce in terms of how much mass you've displaced between the two states and that while curvature is a purely classical object correct yes and so um how does it play a role maybe we can move to um uh talking about uh well i want to finish uh this discussion of um of black holes and especially of what happens with the so-called hawking radiation that will eventually become important when we talk about uh when we talk about conformal cyclic cosmology can i get from you uh what how did you react when when stephen came to you and when you learned about hawking radiation this was in 1970 so how did you react did you say i wish i thought of that no it was more like this i can tell you the story no i simply heard whether i heard a room over i think i phoned up dennis i can't remember i i i think i've been away somewhere and i called dennis up and and they said what's new i can't remember exactly what it was he said wasn't it so have you heard there's the stephen hawking tells you that black holes actually radiate and so on and i said what and so i phoned stephen up and i phoned him up and he described it to me and it was um i think there were two questions one is i ask what happens to the the black hole because the radius can't get smaller without negative energy so he said well in quantum field theory you can violate the energy conditions which i knew already so i said oh i see it's that okay but then he said um i can't remember in which order but then he said it's very good to have an entropy no to have a temperature attached to black hole because that makes sense of the formula that he well steven and brandon carter and and jim bardeen i think it was just three of them there may be another author they'd written a paper in the analogies between black hole dynamics and thermodynamics and you had one thing corresponds to this thing and the thing that was missing in this analogy was the temperature you see everybody thought black holes didn't have any temperature they have to be absolutely cold and i didn't know if you weren't worried by that so i i think i did think of the entropy who did apply to the black hole but stephen thought it was merely an analogy and then he until he did his calculation to show that there was a temperature and therefore it wasn't just an analogy it could be real and so then he told me this it fits in with the formula and say ah okay that's fine so so no i was convinced already in that phone conversation but i hadn't thought of it no i thought i thought if you make sense of the thermodynamic analogy which i really believed already that that would the temperature had to be there i hadn't predicted this at all so i was surprised about it but in in view of this conversation i was i was happy with it reasonable [Laughter] and what do you make of the connection between black holes and the origin of the universe as we turn towards uh conformal cyclic cosmology now i want to get your opinion about how it is possible that such you know two completely different on the face of it uh events and so forth are a phenomena have at their core potentially interwoven uh aspects and even in the case of both hawking radiation and conformal cyclic cosmology they have uh much to say about not only the beginning of the universe potentially but the end of the universe uh in terms of what will remain uh many eons from now so why why is it that a black hole would play a role in uh in the future of of the entirety of our universe well you see this yeah i mean i was i remember thinking how boring the universe is going to be you see because okay you get these black holes they're pretty exciting for a bit but then you get rather bored with them after a while they swallow entire galactic clusters that's the likely likely thing superclusters will disperse from each other but individual clusters will ultimately be swallowed by well various black holes and they swallow each other you see and then there's some final king of black holes which just sits there and it sits there and it sits there now that's pretty damn boring but what's really boring is you have to wait for well something like i guess don page told me 10 to 103 years or so more than a google year a thousand google years or something you have to wait till the biggest of these black holes finally finally finally decide to evaporate away completely and disappear with a pop something like that and then it's dead boring absolutely dead boring so i thought gosh this is boring and then well who's going to be bored by this mostly photons they're just running around protons running around and it's very hard to bore a photon not simply because photons don't have any experiences but because the time from the creation of any photon until infinity is nothing people often argue it the same way they say times freezes or something it's the wrong way around time flips by enough it's nothing so they're in no time experience at all with for that photon the entire universe flashes by until it gets to infinity and goes through to the other side now why do i say goes through the other side because in the early days when i said the early days in the 1960s where people were playing around with gravitational radiation and trying to work out how you work out the energy carried away in gravitational waves and so on and bondi and sax and people had wonderful formerly for this and i said i thought of a better way of looking at it from my point of view you take a conformal map and you squash infinity down to a sort of boundary now what is a conformal map i think a very good illustration of this is one of these escher pictures there's a famous one called um i think it's circle limit four yes i'm showing that yeah i'm showing that on the screen for our listeners angels in the devil yes yes the angels the devils and the three-dimensional model that you have of it in the book it's real yes i'll show that yes go on sir roger three different geometries you can have uh uh to two-dimensional surface well take the the circle limit that's the angels and devils seeming to crowd themselves more and more together towards the edge of the picture now as far as these angels and devils are concerned you have to imagine that their geometry they're not getting squashed towards the edge they are the same size and shape as the ones in the middle and this is a conformal representation which means angles are correctly depicted right up towards the edge so if you looked at the angle on the devil's wing say that would be exactly the same as closest you could get to the edge or the shape of the devil's eye pretty well is the same right small shapes are correctly represented even though they look smaller the what's called the conformal oh we've run out of time so we can oh no no it's uh i have um just have john 11 on the line uh i'm trying to bring her out janna can you hear us my screen is going blank oh no can you see me i can see you in the corner but okay oh it's okay i still see you um trying to ring john 11 here to get her on uh jenna are you there i can't see you i can't hear you let me uh keep going actually sir roger while i'm working on this can you hear me i can hear you but you're small oh okay yeah don't worry about my size for a second yeah i see here yeah okay so janna's here now there's a question that i find really interesting uh from a listener named church of entropy the question is is it possible i'll read you the question how is it possible to have a universe with singularities that also has conformal the ability to make conformal mappings don't they exclude you know doesn't uh the existence of it even a singularity preclude the existence of conformal mappings no let me i i don't know if i can get your picture back because it's somehow it's just let me see hold on does this work um can you see me now no roger do you see me at all if you click on the picture do you hear me if i click on the little picture yeah if you click on the little picture it should make it bigger nothing got bigger but then it went small again yeah um let's see okay i can still hear you and i can see you so i think that's yeah i think that's the important thing if as long as you can see me i can see you uh even if it's small don't worry about it being small roger it's not that's not important yes i think you're looking awfully small that's what it is yeah okay yeah don't worry about that yes um oh singularity when you see conformal geometry is actually something i used to be interested i think i played around with it when i was an undergraduate even before maybe you can think of it in the plane you see it's you see in the plane you think of uh projective geometry if the straight line is the dominant thing and if you you know think of a picture you project a figure onto a plane and straight lines remain straight lines that's projective geometry like a formal geometry is something where angles are preserved and you can have conformal geometry oh jana i think i lost sir roger let me see everybody please bear with us as we're trying to get sir roger connected with jen 11 hopefully he will pick up the phone the skype call now for now just to remind you to download the slides in the link in the comment section i left the link there uh let's see if i can get him back on try to get too complicated here it'll probably just be a minute he's quite good at uh technology especially for a theorist let's see if he'll come back on uh so we will continue because i want to get to the con to the conformal cyclic cosmology and hopefully that will work let me switch back oh all right now it's saying call him when he gets back let me try to reconnect him i know he's still there i do know he has to reconnect let's see if that will work hopefully his computer is still working roger past the event horizon hopefully not because that would mean he wouldn't come back if he uh doesn't pick up i'll try him by email one more time some reason i think he's gotten kicked off let me try one more time here see if this works yes hopefully he'll cyclically return to the magic of skype all right i'm trying to text him now bear with me here okay i'm ringing him should be there try one more chance here see now i'm frozen that's not good uh can people hear me still out in the stream can people still hear me let me know if you can hear me out there in the stream could be a quantum fluctuation very good one he's cycled out of the universe that's a good question can you guys hear me on the stream if not let me know yes you guys can hear me okay good let's see if i can get him back on oh maybe there we go ah roger yes can you hear me i can hear you all right and jen are you there too yeah wow i'm here roger and i can see roger i can't see you anymore brian you can't see me okay don't worry i'm not so important [Laughter] hi guys it's great to have you here so yeah now now we can all hear it do you guys hear us on the internet still on on youtube this is just for a youtube question do you guys have it on youtube you see the important thing is that if you have full relativity you have clocks to measure times and therefore distances like to send a light signal back and forth and you can measure distance that way so you have accurate clocks and this comes about because you have mass now the the opposite side to this is if you have a state of the world where you don't have mass and in the very very remote future all the black holes have evaporated away and you've just got photons basically photons you've got some other things too but let's forget them essentially photons running around they don't have any mass and therefore the geometry that they respect is conformal geometry where you can stretch and squash as long as the stretch is uniform you have to stretch as much the swiss that way and you have to stretch the time by the same answers you stretch the space so the light cones remain there just as they were now this kind of geometry is the geometry of the physics of masslessness and in the very remote future the argument how so the argument goes you have massless physics maxwell's equations which describe electromagnetism and photons if you like they are completely invariant under squashing and stretching you can squash in one place stretch in another place maximum locations don't even know anything's happened this applies to massless things now what about the big bang it's just the same but for the opposite reason there you have enormous energies things swishing around an enormous speed and there the kinetic energy of particles completely dominates the mass so although they do have mass the particles in the in the very early universe the mass the closer you get to the big bang the more and more irrelevant the mass becomes and you have a massless physics right as you go in the limit back into the big brand again you have massless physics so my argument is that in those two regions the dominant physics of the universe or the dominant geometry of the universe is conformal geometry con physics of of massless things so the remote future is masses because it's got all that rarified and basically photons and the big bang where you have basically massless entities again the physics is very very similar it looks completely different because in one case the big bang you've got enormous densities and enormous temperatures in the remote future you have ridiculously small densities and very very cold very hearts of the big bang very cold in the remote future but if you do the squashing the geometric squashing in the future and the geometric stretching of the big bang the temperature goes up when you squash the future the temperature goes down when you stretch the big bang and there is a match it looks as though they could easily match and the argument here is that they do match so it's a hypothesis that if you squash down the remote future you get something looking like another big bang so the picture i have is one where you think it more like a cylinder you have the big bangs stretched out and this infinity is squashed down and then you can join that cylinder onto another one let's have another one before so that our big bang was the conformal continuation of the remote future of a previous eon i'm calling it so i say our eon is big bang to a remote future the next eon will have our remote future is its big bang our big bang was the remote future of one eon it's big bang was a remote feature of another one and so on now i used to go around giving lectures on this feeling fairly satisfied nobody will ever be able to disprove it so i can go on forever giving these talks and then irritatingly i had an idea the idea was when you consider the black holes before they've evaporated away particularly ones which cohabit a cluster of galaxies our own black hole which just dropped the nobel prize as well for the the uh two other people who shared the nobel prize for amazing observations which i was most impressed with when i saw them but you see these stars going around this invisible central object you see they're going these wonderful orbits i thought gosh kepler was right well almost because you see these elliptical orbits going around and around although in different different planes and so on and there's this thing in the middle pulling them around in these orbits wonderful and so there's evidence for something like a four million solar mass black hole in the center both the nobel prize which it got but anyway um these black holes gradually gulp down pretty well i don't know what proportion of the stars in the galaxy in the galaxy they swallowed but probably most of the stars and millions right jenna what's the uh mass at the center is it four million yeah it's four million for sagittarius a star and uh but the one that we took the picture of in m87 is uh more in the billions of times the massive sun much much bigger but because it's 55 million light years away um it actually subtends about the same size on the sky for the telescope as our smaller black hole does that's 26 000 light years away which is to say much closer ah so it's bigger and further but uh but was the only other target for the event horizon telescope project and and i think that that was the only big surprise at the reveal i was actually went to the national press club to see the reveal i was so excited oh wow and uh yeah i was and i they had three badges scientists journalists and like friends and i think i took all three and um and so for me that was the big surprise was that it was m87 that they took the picture of not sagittarius a star right so we're still in pursuit of our of an image of our own black hole now when we look at showing the cover of your book now uh the black hole survival guide coming out on tuesday i'm excited to uh to be described discussing that with you this coming tuesday um yeah looking forward to that so we had a question for you earlier uh the astronaut who's on the cover i presume that's you right um uh that uh that person who is falling in on the cover uh the question is what is the nature of the of the time and the experience for such a person obviously i don't well they might survive where they're pictured just on the outside of the iran horizon but how long will it take for this astronaut this comely astronaut to to get to his or her ultimate doom right so the the trick of surviving a black hole for as long as possible is to fall into as big a black hole as possible which seems counterintuitive to people you would imagine a bigger black hole is stronger gravitational field but it would be worse but actually you notice the curvature less so imagine you're standing on a basketball your two feet are very aware that you're struggling because they're in different points on the curvature of the black hole of the of the basketball but if you're standing on the earth you don't really notice right your feet feel like they're leveled like they're flat and so the same concept with a very big black hole you could sail across the event horizon very comfortably uh you could still be vigorous with youth when you cross the event horizon you would hardly notice that you had done so there wouldn't really be an obvious experience that would let you know that you had crossed the event horizon so that's one of the beautiful ideas that einstein came up with which was the equivalence principle and it has to do with but the fact that if space time is gently curved it should look like space time and empty in in flat empty space but once you cross the event horizon then you have a very short order before you hit the singularity and i'm sorry i missed some of the previous conversations so i'm not sure if sir roger talked about this but uh but part of uh the nobel prize winning work was to prove that at least in the context of general relativity the formation of the singularity was inevitable and not only that and i sh i saw you showed some of those light crown pictures it's in your future right so the singularity is unavoidable once you've crossed you can no more avoid it then you can avoid a future moment in time and in a black hole around the size of our sun which would be a very very small black hole um you have much less than a second to survive before you get into real trouble if you make the black hole as big as m87 like six billion times the mass of the sun something like that um you you have that much longer to live six million times longer to live you might even be able to eke out a year if you made the black hole tens of billions of times the mass of the sun um so you would have a very existentially fraught year as you as you encount you know knew inevitably that the singularity was was in your future and there might even be some trajectories you could rig where you you got a little bit longer out of it but um but destruction is inevitable and janna i want to thank you so much for uh the discussion we're joined now by another special guest uh sir eric weinstein is joining us from uh somewhere in the ethernet uh eric you're looking sharp say hello to jana levin your friend jenna levin and mine uh and uh jenna i'm gonna uh yes you can jump off jenna i wanna just say tune in tuesday we're gonna have two live streams with janna one at nine in the morning or so or ten in the morning pacific at one pm eastern we're going to discuss the entirety of this wonderful new book black hole survival guide thank you jana have a wonderful weekend brian thanks for doing this eric great to see you if bravely and sir roger i miss you already the last time i saw you was last december and it was lovely so be well everyone thanks for having me on bye janna bye bye-bye so eric let me get you included here you are on live on screen with sir roger penrose uh i can't hear you eric can you uh is your are you muted i think i think you're muted eric i can i can't hear you i can hear let me see okay there we are hello eric roger great to see you again wanted to first of all just say mazel tov on uh getting the recognition um it's great to see first level top-level theory back in the game um and uh just wanted to wish you all the best in muzzleload i appreciate that thank you so eric we're going to be talking in a minute about uh roger's conformal cyclic cosmology we just had a very riveting discussion about the while curvature hypothesis and whether or not we even need a theory of everything whether or not we even have reason to believe that there are singularities in space-time um uh i said to roger the only instances they appear uh are forever shrouded from our view either in the deep ancient past of the universe at the at the origin of the universe our current uh cycle of the universe if you will or perhaps hidden at the core of black holes forever inaccessible as janna points out in her book what say you are singularity's real or are we just kind of fooling ourselves and if they're not real uh why do we need a theory of quantum gravity well the first thing i would say is why waste that question on me with roger around so let's let's spin it towards right i want to hear you guys converse about it yeah so so i asked roger i got his opinion but i'm not going to let i'm not going to tell you what it was because i don't want to prejudice your opinion i know how i know how influential roger is on you and i know how how susceptible you are to peer pressure this is like going into a dojo and finding anderson silva wants to spar something like that okay so here we go um i guess what my read on it and in part your work sir is um that this is the key to understanding that einstein is really only an effective theory because i don't believe that those singularities will be there in an ultimate theory and the fact that they're shrouded by mystery and that they're sort of protected so that we sort of can prove that they have to be there at this level of theory but on the other hand we can't really get at them because they are in fact screened from us in one way or the other for these two different types of singularities is this cert the indication that einstein must be effective or could it be in some sense an ultimate theory in that sector with these singularities essential features of space time itself is this an artifact of our description or is this in fact how the underlying structure likely is in your opinion and if i need to rephrase the question and i'd love to get back to the vile tensor but that would be the opening yeah so do you want me to say something yeah i mean i guess it's you see when i first wrote my papers on this i don't think i tended to use the word singularity it's just we don't know what happens at that point stephen hawking was more um bold about using the word singularity i think he meant okay as far as the classical theory is concerned we have a singularity so it gives up at that point i mean like with the shock wave you might say the the theory of laminar flow or whatever it is and aerodynamics gives up and you have to have another theory which describes a shock wave um so it's the argument would be something like that so general relativity as we know it would not apply to what happens but whether there's any useful future to to the situation you see you might say the very notion of your spacetime and what it means to say talk about the future makes no sense at that point so in the absence of any theory it's telling us that our theory of space time general relativity gives up at that point it doesn't tell us if anything happens i mean what does it mean anything you took into that region might get destroyed and then it doesn't mean anything to say it continues you see this was an argument stephen made uh which i would have agreed with you see here's he's an irony you see i would have agreed with this argument the big bang you see was the beginning you may say what was before the big bang well it's meaningless to talk about what was before because the very notion of before is a space by space-time notion and therefore it doesn't make any sense to talk about before the big bang and i would have said yeah yeah i agree with that and here am i contradicting myself see if you've got a theory then you can maybe go beyond what you had before so i i don't agree with the agreement which means to talk about before the big bang i better not because i'm talking about it so eric both of you guys have had uh you know controversial but provocative new theories that push the boundaries of the accepted uh dogma i think in many circles uh you know sir roger is sort of a hero or precursor to some of the work that you're trying to do now uh certainly he has for me i want to turn to his to his conformal cyclic cosmology which is my uh area of expertise such as it is and and talk about well first uh first of all what's it like to be on the avant-garde of physics in a good way to work without a tightrope to pursue things that may not have answers uh what does that feel like for for you and what kind of inspiration do you take personally from someone like sir roger well i mean first of all roger is oddly of course uh singular in our in our pantheon of living physics heroes as being i would say almost everyone would say the most generative of our first rank of physicists so that is he is less constrained um because in some sense we're in such a late stage of physics that almost every interesting idea is dead on arrival and so having any ideas at all that aren't immediately dead on arrival is very very difficult and i think that one of the things that this nobel prize is going to do is to send a message to future generations that um it's okay to be highly generative you just have to do it in a radical and conservative fashion simultaneously so the math is extremely um you know it's impeccable stuff and on the other hand uh it's also wild stuff i remember seeing the um the newsletters from the twister group back before the internet and this was like sama's dot we weren't sure whether people were taking drugs in oxford or what was going on but it was florid and it was in its own language and it was clearly shared by a group of people and i i just think you have to think about roger penrose as like son raw the great jazz artist who had a cult and a commune in his house but also produced some of the best music around this is really a throwback to that tradition it says that it's possible that roger could have done this if he wasn't at oxford as well i would say the one thing that i want to be really clear about is also bringing back hardcore geometry rather than always coming back to the quantum as the source of weirdness i think one of the things roger has done through his artistry and his ability to depict what can barely be seen is to show us the wonder of geometry that is now underneath all fundamental physics as post jim simon's work with cn yang and so right now we're living in a world that's purely geometric in which most of the public discussion of physical weirdness is about the quantum and so i think roger renewed that einsteinian connection and the sort of simon's yang connection um by making this relevant but i would like to get off a technical question as well of course go for it you talk a lot about the vile curvature tensor which is the part that gets killed when we write down the einstein field equations it's the part of the curvature that's sort of thrown away with the bones in the skin when we formulate the einstein field equation on the other hand it's also weirdly the part of the curvature as per the churn theory that contains most of the topological information about the nature of the space on which it resides what do you make of the fact that we throw away the portion of curvature that tells us about the the holed-ness and the doughnutedness of potentially space-time but we retain the portion that is complementary to that when we write down the einstein field equations is that a coincidence does it have greater significance well i'm not sure i'm answering your question but the way i would look at it is not in this respect different from electromagnetism because there one has the maximal field and you have the charged sources so in general relativity the an analogy according to me it wasn't perhaps the way other people would look at it but according to the way i look at it you see that the vile curvature is very analogous to the maxwell field and when you write it in spinners it's almost you know just the same equation you write down so it's the vial curvature is an analog of the electromagnetic field and the richie curvature is the analog of the charge so you see you you have matter with charged matter and you that gives you the source for the maxwell field and here we have the the richie tensor which gives you the source to the vowel field so it's not so different in that respect and i think i'm looking at a bit differently from the way you are well that's interesting because i wouldn't have because the maxwell theory doesn't break into pieces whereas the rimani and or einstein theory does break the curvature into pieces i don't know i don't think i've ever heard that expression of order of differentiation you see yeah i mean there is a different order of differentiation because when you write down the maxwell field and the charge there is a different level but the in the mac in the einstein theory the ritchie and vile curvature at the same level you see people think of them as the as the curvature tensor i think was when i wrote these things in terms of a spinner form which made these things look more different see the vowel curvature is looks you know just four indices rather than two but it looks awfully like natural things i quite agree with you about putting these curvatures together while brian is distracted i can actually take over his podcast and ask you a few more questions if you don't mind one question i was curious about is that in low dimensions close to where we are and close to the signature in which we're in which is one dimension of time and three of space yeah um there are lots of weird coincidences we have a mass possibility in two spatial and one temporal dimensions called topological mass that's not available anywhere else again partially due to jim simons but this time with churn we've got this cotton tensor that replaces the vial tensor in some ways in dimension three we've got self dual equations in dimension four but you'd have to have two dimensions of time and two of space so we have all of these weird just miss um opportunities for our four dimensions three of space and one of time and we're surrounded by exotica there are platypus and uh an echidna everywhere and weirdly we're always just out of reach of their weirdness to power our universe we could have used topological mass maybe rather than the higgs mechanism if we were one spatial dimension lower do these practical jokes suggest to you that they are of any real importance or are they merely sort of distractions uh in a perverse creator's sense of humor meant to waste our time and get our hopes up only to dash them to the ground i think it's a very subtle question you see you have these okay man by the way i'm gonna take a victory lap like that yeah that's you got a platypus in there you got you got a whole host of oddities in the orey of eric weinstein go on sir roger sorry for the plural of a platypus is this or is it that's hard if you could figure that out you'll win the nobel prize in physiology this turns out to be octopodes topic well i think an octopuses i thought it was perfectly legitimate to call them octopuses yeah i think it is legitimate but the the top drawer way of pissing everyone off is to say oh properties i was pronouncing as octopodes for years but please sir continue and this is a this isn't a kidney okay nikki no i don't know i have no idea but anyway these i i was told that if you if you don't know enough latin or greek or whatever it is you can always use the english way put s on the end um anyway so uh yeah i mean you've got these strange creatures and you have strange creatures in different dimensions and the trouble is if you're a mathematician as i accompany a lot of people who are doing the mathematics twisted theory is a good example you see you do you do it on the wrong signature inside of you and you get all sorts of beautiful things and they prove wonderful theorems and all sorts of stuff and you can take more dimensions too and you could do things like this and you can play around with this or you can do what ed whitton did just change the signature the other way around to take two pluses and two minuses and then your twisted theory becomes real and so on okay it might be a nice trick to play around with for a bit but it's not physics physics is the lawrence in signature and i've always tried to gear what i've done to what physics is doing more and try to not get too pulled away by mathematical things which may be very beautiful and elegant and they do amazing things in all sorts of different ways but are they connected with physics deeply not necessarily there are a lot of traps you see you can go guide it off in all sorts of different directions mathematically and how connected with the physical world are they i don't know i mean they might be in some way i mean spinners you take spinners and if it's in louisiana they have this particular personality when you lorenzo in space time when you go to 26 dimensions they're horrendous so where do you go and do you study well they study things they have a beauty of in dimensions but it's not well same thing but there's certain things in 24 dimensions or seven like there's a vector cross product in seven dimensions it doesn't feel like we're very close to it so i don't think it tempts us it's a very weird thing to know about why seven dimensions would have a vector cross product but the fact that we're so close to these three and four dimensional coincidences is feels very different to me than let's say the leech lattice or particular results in 26 dimensions which are really dimensions 24 results having to do with super symmetry and things like this well i don't know i mean mathematics is full of coincidences and they may not may or may not have anything to do with physics so you're agnostic in some sense yes yes definitely i would say most of them don't seem to have messages and they may some deeper remote physics that we come to eventually we'll see oh that's what that's for you see and then one of the things that i find fascinating about your work is is that you really come across to me as someone trained as a mathematician who actually has accepted the yoke of physics which in some sense is a very weird thing because most people who appreciate the beauty of mathematics find the idea that one particular physical world should draw our attention to be kind of coercive imprisoning it feels artificially small whereas from the physics side most people who really want to keep themselves wedded to the world in which we live train themselves to resist the siren song of beautiful mathematics yeah why are so few people in this interesting little overlap between them who are really concerned about the physical world and the most beautiful mathematics which oddly the physical world seems to know very well i don't know that i can answer that question but but you're right it is it is a puzzling thing well when i was doing my mathematics course i did an undergraduate in mathematics of course in the uk that includes a bit of applied mathematics so i did know about lagrange equations and and that sort of stuff it's been funny sir roger to see the response on the on the internet uh reminds me of a quote by again your fellow laureate albert einstein who said that if my theory of relativity proves to be correct germany will claim me as a german and france and france will claim me as a citizen of the world however if it proves wrong france will say i'm german and german germany will say i'm a jew and it reminded me of you made a quote the other day that said something like to the mathematicians i'm a physicist into the physicist i'm a mathematician uh it was kind of uh rhyming with that and and i wonder if an alien wakes sir roger up at three in the morning you've done all this different work in math and physics in quantum mechanics and consciousness and black holes and singularities and what's that art and yep absolutely if this alien comes from another planet and first of all do you believe aliens exist and second of all what do you define yourself to that alien aliens oh i see do i believe first do you believe in aliens and second if if they do exist and they wake you up what are you a mathematician a physicist an artist a scientist yes oh right i mean i get away with it by saying a mathematical physicist but that's cheating um where it where is my soul i suppose you might ask is that sort of what is closest to your heart very difficult question because of beauty in the mathematics but you see it's a hard question no i was going to say when i was an undergraduate um i would a thing that completely bowed me over was complex analysis you know it's the way they teach it they first teach real analysis and they go oh no c naught function c one functions three seventeen functions c infinity c omega functions the infinity functions and they're all different and then you do complex analysis once there is differentiable and the whole lot there in front of your face complex analysis your contour integral is amazing all that stuff and i thought before i knew much physics i thought gosh wouldn't it be amazing if the physical world was really driven by this wonderful structure and i had a lot of kind of internal conflict between complex numbers and combinatorial physics because i used to be equally direct attracted by both ideas but i think the complex analysis one in the end it's just the magic in it what about higher spaces complex if a complex appeals to you i've got these things called quaternions if quaternions appeal to you i've got these octonians and then eric always loves to go on about uh clifford algebras etc what is there a limit is there some place where the fascination stops for you uh when it comes to the bewitching power of mathematics in the physical world we swear these two two sides to me um having their battle and the physics side probably wins because i mean the beauty lies on the mathematics side but the and the um what would i say the uh the drive comes from when eric was on my show we talked about uh how how physics classical you know not classical physics but classical approach to solving theoretical uh problems seems to have uh stalled in some sense with breakthroughs like yours uh coming you know before either eric or i were born in the in the 60s that this are we are we stagnating in theoretical i should say are you guys stagnating and theoretically i'm just a simple experimentalist so i take no blame from uptonians i think the split octones probably do it fundamentally oh really split ah what are the split octonians uh can you describe that either one of you well you see octonians you've got you've got eight generators and you don't have a positive you have a well the same thing of quaternions first you've got a norm which is the sum of the squares and it's not a similar thing for octonions is split quaternions you would have two pluses and two minuses uh let me just think split octonians it basically it's like you you have um quaternion you have quit you have proper quaternions in them you can find subsystems which are genuine quaternions but this is all to do with twisted theory and palatial twisted theory you've got these algebras and you've got the sub-algebras which looks to me as though they're going to be things like these certainly the quaternions i think these octonians have a role to play it is it's to do with the signature you get on twitter's you see you've got this form which is hermitian form which has two pluses and two minuses when you write that as a real form you've got four pluses and four minuses and you can think of that as an eight-dimensional vector space and uh the i think the split optonians have a role to play there but it's something i i i might change my mind so i have a question from a listener uh miguel uh goes by yeti tears good friend eric's in mine eric uh and miguel is wondering uh sir roger penrose what is the initial inspiration for your drawings your tilings your your mercurial sketches that are so um mesmerizing what what question do you ask yourself before you sit down to do art what do you ask yourself well there's all sorts of things i think if you look at my old notebooks you find it's full of these drawings and mostly they are where i couldn't think i could i got stuck you see and so i just drop draw wide wild things yeah they're very wild so i came from a see my grandfather on the my father's side was a professional uh yes he was a very good artist and my father was one of four brothers all of them who were distinguished they were very good artists my father was a very good artist but his younger brother roland became a big figure in the surrealist movement so he was in with all the uh picasso and accents and various people and he uh also was one of the originators of the institute for contemporary arts in britain and started it and uh you know but my father's interest in art was much more um what would you say conservative he liked to draw realistic views and things um so my i departed from that myself i would draw one thing sometimes i draw realistic things but it's not not technically that very interesting so eric go ahead you come from a family sir of uh eccentrics and geniuses and incredibly interesting tree do you believe that that tree um really is intrinsically in some sense tied to the uk with its toleration for tolerance for people who weirdly either conform or wildly not don't conform that there's a sort of a weird way in which you can be british and be respectable and totally non-respectable at the same time there's some special sauce i think you're right there is something there that's right no certain britain you know there is a sort of kind of snobbish very uh conservative whatever the world is um but then the respect for uh being outrageous in one way or another yes i think i think there is and and and being uh there's an obvious word just just slipped out of my mind here uh i think outrageous is pretty good brian he said i was gonna go with iconoclastic and uh courageous but yes i mean there is a respect for that in britain which you know this is i don't think you get so much of that in the states at least i don't know if it's true now but it hasn't been perhaps so much of the past we're trying to get elon musk to behave so he'll stop getting those rockets so sir roger i can't help but ask you know from the personal side um how do you think of of stephen now how how do you think his legacy is affected by your nobel prizes eric my friend always says there are nobel prizes that give prestige to the to the victor to the one who wins it and then there's there are victors who give prestige to the nobel prize i think eric you would agree with me that the latter is true for sir roger um dude you can't do that he's right here i know that that's right well he will indulge me i i told him you know he endorsed my book losing the nobel prize and it could have cost him his nobel prize you know if they were smart they they wouldn't have pushed you down and you he ascended in the same motion so sir roger what would how would steven have reacted uh first of all do you think that he should have shared in this prize i mean this this rule that only three people can win it is so antiquated and and ridiculous and and clearly you know he he deserved it in a large sense according to a lot of people where do you come down on that it's a difficult one you see he always thought that if they had if the walking evaporation for small little tiny black holes had been observed then he would have got the nobel prize which maybe he would have but the thing is i was always doubtful that little tiny black holes would be there because i thought the big bang had to be very smooth and i didn't see how they could have come about that's not really the point here um i didn't see that i mean it as you say you need to get it for something which is observed and that seems to be one of the rules um and since those black hole what does he call them the uh black hole explosions have been seen but you see maybe they are seen this is a sort of irony because this is getting back to ccc well it's not that yet yeah the hawking of aberration yes that that is the that what you might call it the hawking they're hooking uh we'll have to wait 10 to 165 years though to observe it that's the whole point that's the point we're seeing them already actually oh yes okay so let's turn there uh eric you're welcome to stay in this i want to talk about conformal cyclic cosmology and hawking points of course yeah go ahead eric absolutely i had the um bizarre fortune to have uh jim watson in my office years ago oh gosh yes and um and he was talking about his uh his relationship with francis who francis crick would pass and i happened to be able to bring up on my screen a clip of sir francis talking from beyond the grave as it were about their collaboration and i watched jim just get misty that there was the sense of something wondrous had had half past and that he was still in the world to tell the tale but francis had gone on and then i said i accused him i said you know i read your book very carefully and it really felt to me like you worked out the hydrogen bonds as soon as you found out that the hydrogen atoms on the nucleotides were in the wrong place in the textbooks and from jerry donahue can you admit that you really did the double helix and he said something that i just i'll never forget and shocked me to my core he said oh no he said i did the inside i did the hydrogen bonds francis did the sugar phosphate backbone on the outside and then it was suddenly clear to me that the greatest collaboration in the history of science potentially was a pure collaboration in that you could see the work of both individuals in the structure my question to you is is there any echo of that in your work with stephen hawking and i would say that just since we're talking about the nobel prize it's interesting that neither of you needed the nobel prize to win universal respect among your peers and that that is itself a signature of um of how profound this work is in your collaboration with stephen hawking is there a parallel to saying that you can see the intertwining of the two sets of ideas coming together as one that's a difficult one i mean it's certainly he carried the arguments that i had originally a good deal further and you could say get rid of the kosher surface assumption i had in my in my theorem and so on and then we wrote a paper together on this so certainly there was a big influence in what he was doing some of the techniques developed the idea of koshi horizon which he introduced and things he did afterwards to do with the black holes well these were more or less done with other people like the work on on the uh well it was brandon carter i guess who well you you have to go back to to to to um israel then israel who showed that the um stationary solutions with horizons had to be spherically symmetrical it's quite curious abe astakar reminded me of this that there was a lot of many people held the view that black holes couldn't exist at that stage because they there would be so many which were especially symmetrical so why could they exist but it seemed to me that they could simply radiate away the multiples and they would end up certainly symmetrical but then the work done by started by brandon carter and then robinson um not like the other one um david robinson that's right was there another one i can't keep forgetting the names here but they basically showed that the the cursed solution was the but there was a contribution from stephen hawking which which showed that if they weren't actually symmetric you see the all the work they did was assuming oxy symmetry um and then stephen showed more or less that they had to be axismetric if they were going to be stationary which is a reasonable good argument so he did some at that time i thought that he was doing the best work of anybody in general relativity but that sort of we kind of diverged in our views later on and he went off and started getting too influenced in my view by string theory and things like that and also thinking that black holes and that wasn't yeah we're going to the story there but he tend to argue that uh black holes and white holes were the same in some sense which seemed to me to be absurd if you had a classical object somehow he thought that the space-time was somehow observer-dependent concept which was not the view i had and so we we did diverge well i will say that when you have people like in let's say in mathematics uh jean-pierre ser and alexander grothendig who came together and diverged one of the things that i value the most is the letters that they would write back and forth arguing their points not only is the collaboration valuable but the fact that you have people up at that level yeah who find things on which they can disagree and do so productively i have to say that it's both the confluence and the conflict that animate these partnerships and we've seen this from gilbert and sullivan to lenin mccartney wherever it is you know there is an aspect of tension that actually seems to be very generative well certainly our disagreements did were valuable to me in a sense it did drive me a certain direction so i had to think more deeply about things i was thinking about but we didn't bring us together in any way because he um i don't know but the last and i did you want i haven't really talked about ccc properly yes yes we'll get to that yeah i want to know what did he think about we'll get into the details of it in a minute but what did steven think about ccc well i'll come to that you see because and the answer is going to be i don't know i can guess what he said you see um you know the story i'd more or less explained about you know about coverage hypothesis and all that and then i sort of thought it can't be that it's got to be um that you continue the conformal infinity to to the stretching out the big bang and and paul todd my graduate student i think he was still a graduate student of mine at that time and he more or less formulated the condition on the big bang that it should be continuable as a conformal manifold so it's the boundary of a smooth a smooth boundary thus doesn't quite give you the var curvature hypothesis it gives you it's finite but not zero he didn't want it zero because it led it to trouble you into trouble with the equations and so when i said i wanted zero because i knew from theorems particularly uh um forgetting people's names now helmut friedrich who had shown that with the positive the positive cosmological consequence it was a big factor there and this came from a conversation i mean my own view of it came from a conversation i had with jerry ostriker and i remember i had a wrong reason for thinking it had to be zero which has to do with trista theory and i had a way of i thought solving the googly problem that's not going to all that which required the cosmological constant to be zero and so then i when all this noise about the the red redshifts and the supernovae and seeing well it looks as though there's an exponential expansion or something going on and i think we were going into dinner some college probably warden or something and they were jerry ostriker was there and i said to him um surely all this stuff about the um exponential expansion that could be just dust couldn't be and he looked at me and he said look that's not the point the point is that you put in the cosmological constant it makes so many things fit so much better in cosmology it's not just the the exponential expansion observations from the the reddening of the concealing redshift of the supernova and all that uh so i thought okay you win basically and so i got converted to the cosmological constant and this you see made scry the null infinity not not null anymore but space like and this is absolutely crucial because you need something to fit onto the big bang which is automatically space-like so the fact that the remote future had a i mean you have a conformal future conformal future boundary which was space-like and therefore could be joined onto a under a big bang in a plausible way was was a consequence of this realization but you see paul had the view that that you could describe the via curvature hypothesis in this way but if you actually join it on to a remote future the vowel coverage has to be zero as i said helmut friedrich and the theorem come while i'm showing you this which is expectation anyway for other reasons and if this this causes some problems in what you do after the big bang um and it leads you to actually creation of a very it really makes dark matter come into the picture so you have to have dark matter so i think it was a good thing so anyway let's get back to the story yes i think i'd have described this before in some in this discussion but i thought there was no i had this idea of joining the big bang into a normally which seemed to be a plausible thing to do maybe just a guess speculation nobody would ever prove me wrong and then i had this idea that maybe collisions between supermassive black holes would produce signals which are strong enough that you might see if our curvature would influence if it would be in a derivative i forget how many derivatives you need it's maybe four or four derivatives i think before you see the volatility showing up in the in the next eon but you do get an effect which would affect the the matter and you would see these rings in the sky and uh david spurgle the first person to try to analyze this and he got interested in i think he was trying to disprove it yes and he got amir hajian to look at it and they did various things and the way they were looking at it was a way that as i learned later they would never see anything and they didn't see anything but later on came to me and said he'd been looking at this and he'd been looking at it a different way the difference between the two was do you look at the sky fixing a radius and seeing whether the distribution of temperatures is gaussian over the whole sky and that was what david berger was suggesting and i could see that wasn't going to be any use to me for to the effects that i was going to come to the way value was looking at it was looking fixing the points and then looking at the different radii for each point and you see that do you see i mean the way he was doing is originally wasn't going to convince anybody and didn't and so we got into trouble for that because he was analysis was not uh in various ways i didn't know anything about this at the time but uh he seems to the questions you could see with this given center more of these low various rings if you saw two or three that would be what i'd expect because you have superman if you have a cluster of galaxies then there have been several collisions within that same cluster and they would look like one point in this in the celestial in the cosmic background backgrounds cosmic micro background sky and so you'd see rings which are concentric and so that's what vahe looked for and then we after a lot of fuss and everything we seem to see a signal although nobody seemed to believe us and then simultaneous with us in doing it completely different way the polish group polish group christophe meisner pavel nirovsky and another poll who was doing the numerical analysis and they seem to see evidence for these rings too um with about 99.4 uh i'm going to show up on the screen the analysis for this paper so let me let me take a step back i'm going to show on the screen for listeners and viewers uh what uh what what sir roger is talking about let's see that did not work here let me let me undo that uh so first of all i want to go uh back to uh what this is not so there's a famous picture of the cosmic microwave background with stephen hawking's initials in it s h and these are these are cold spots uh of of significance that's as steven used to say although eric and my mutual friend sabine hosenfelder thinks it also stands for her initials uh but uh yeah yeah i know you've had your encounters with her too and she can be quite quite a quite delightfully uh persnickety but uh but this is not uh looking for stephen hawking's initials at all we're talking about what are what you call hawking points which arise as a natural consequence of the uh the persistence of memory of of black holes surviving in successive eons and so yes i thought about these things before but i didn't face up to them because the one place in the crossover from one e on to the next where you don't get a smooth transition everywhere else you can write down differential equations and see what how would this transition be described but the supermassive black holes all the radiation although you think of it spread out spread out because it takes so long to be spread out it's all completely squashed into a little point so every supermassive black hole all the radiation that comes out of that will be squashed into one point in the crossover surface probably on our side smaller than the prank length i'd have to look at that yeah it doesn't appear the hawking points don't appear in in this book in cycles of time you you were you're not mentioning that uh in this book they don't appear in there so what how did it come about after the publication discussions with christoph meisner you see we were talking about the rings first and then we're talking more generally about what other things might i can't remember all the conversations because i don't completely remember talking about the talking points then but he says we did later on he then looked for little rings and noticed this very strong signal that is you saw you look you compared with a thousand simulations and out of the you for a particular size and this is basically four degrees across in the sky and this is um significant because okay you have here's the crossover surface i have to fill the right here's the crossover surface so walking point you have a black hole evaporating away and all the radiation is concentrating that point all that energy comes through and you and it has to come through because you can do integrals to show that it can't disappear the mass of that object has to come through at this point but roger is that true if it's even if it's not a singularity again we have no evidence for singular what if there are no singularities someone tells you god stephen comes down from shamayim from heaven above and he asks you uh roger my buddy my friend there are no such things as singularities does that hold true do you would you abandon the model it doesn't matter who you do integrals around it you see it's like saying is a charge an infinite density of charge at that point we don't care you do an integral gauss integral and you say you've got the value of the charge from that integral around the surface so when you've got this point it's affect whether it's a singularity or just a huge concentration of mass or what have you or radiation or something makes very little difference i mean maybe it does at some point and that would be very interesting but for the moment all you know is this energy bursts out and it's it bursts out you don't see it because you don't see anything until 380 000 years after the big bang okay now we come back to jim peebles and all that sort of work and last year's nobel prize and the now there are very good calculations to tell you the physics of what goes on from big bang to last scattering or or decoupling or don't you want to call it slightly different places but more or less the same between that is a lot of physics which they calculate this point will spread out a little bit concentration matter but it will spread out to this region which is about four degrees across in the sky eight times the moon's light full moon's diameter and so what you would get is something like an input of enormous input of energy into that little point it jiggles around it has some kind of a gaussian behavior it ends up with a kind of gaussian distribution of temperature and the claim we're making is that you're seeing that gaussian distribution what they do is they look at a temperature drop you take rings the ring and of a certain diameter and see how the temperature drops from outside the ring to inside the rim and then you make a comparison with the of the real sky with thousand simulations and this but this particular just two little slightly different diameters you take you see amongst this 1 000 simulations you don't see any of them which have the strength that you see in the real sky so the real sky stands out above all of those and is that true and oh sorry go ahead i have a follow-up about polarization but i'll get to that when he did 10 000 simulations another nine uh nine thousand and then what used to be a zero became a one in one spot and the other one it became a two that tells you you just do a little bit of statistic tells you the big confidence level this is a real effect in the real sky is 99.98 so this is a much stronger signal than we saw with the win eric i don't know how much you've looked at this uh at this cosmological model but um what what are your impressions about it from uh educated lay person you're shaking i can't hear you you're muted still i think he's shaking his head okay all right so i've seen the international symbol for don't drag me into this i don't want to say uh let's see roger could you move a little closer to the camera or or tilt it down a little bit so i have a paper that i'm showing on the sky on the sky on the screen uh from friends of mine on the plonk team and they show the plots that you're talking about with significant um hawking points plotted and they make a couple of cases uh they talk about how these hawking points would evolve or or behave depending on whether or not you looked at them both statistically through the all the planck data that's available now in 2018 which includes multi-frequency and polarization so the first obvious thing that i would do uh is look at these in polarization because that is more than just doubling the information in some sense it's it's sort of squaring the amount of information or more uh so have you looked at it and does the significance hold up because according to them it goes down but but what have you learned it looks at it with different things and they also looked at the plankton of the wmap data what i found most not most convincing but very convincing is that if you look at you see there's a different analysis that dan and did to look for where these points are you see the analysis that was done in the paper doesn't locate the points at all it's just an overall analysis for the entire sky and this is where these confidence levels come from it doesn't tell you where they are but dan anne looked specifically for points where the intensity increased at this sort of level and he found quite a few points now i'm not sure that i believe all of them what i do tend to believe is that the strongest the five strongest points in the in the planck data if you look in the wmap data they're all there in exactly the same spots there's a sixth one in the w map which is pretty strong when you go back and look at the plant and you see it's there too it's not one of the five strongest or the six strongest but it's there so those six points which you see in both maps i think the case is very strong that they are what we would call hawking points now ab initio if you took us you know a a cosmological model a black hole density these come from supermassive black holes not unlike the ones at the center of the milky way m87 and elsewhere knowing that there are many many of such supermassive black holes perhaps one at the center of every supermassive or massive cluster of galaxies why wouldn't you see more than literally we could count on one hand two reasons one is you see a very small proportion of them you see only the ones which are just at our particle horizon you see where our past light cone goes it hits the surface there all have lots of them in the middle you don't see any of them the only you see with the colliding ones with the rings you do see ones in the middle but here you only see the ones just on the edge so it's a very small proportion of all the black holes these are only the very big ones i think you would see a lot more than the ones we've seen these are only the big ones um i would think a dedicated analysis of some sort you might have to have another satellite i don't know you ought to be able to see a lot more i think we're only seeing the strongest ones which we happen to catch which are just on that little tiny um rim what you little little tiny surface which is uh where are just where our particle horizon happens to be so that's that's the reason you don't see lots more i wouldn't expect i'm lucky probably to see those ones as strong as we do in fact it needs working out exactly how big they are i have a way of doing it which we haven't actually worked out i've tried to get christoph to look at it he tries to get me to be more specific about how to do it well that brings up another question from one of my listeners in india who asks for a young student such as himself or herself uh what what kind of directions in cosmology if you were starting off again as as a young graduate student with a with a bright mind and eager disposition what would you recommend that somebody pursue i think there are a lot of problems a lot of questions to answer here there are questions of particle physics to answer what are the error bombs now when i say erebon that is a dark matter particle now it doesn't matter according to the scheme dark matter should be created at the big bang and then gradually decay away it's created through the equations you see the equations only work at the crossover from eon to eon if you introduce a dark matter the dominant material in the universe then now it has to have a half-life of something like 10 to the 11 years so we're just about seeing the ones decaying now but since the majority of the matter in the universe is dark matter you probably should see quite a lot of these decades do you actually see them what do they decay into now i consider their decay into into gravitational signals so probably these are signals you might pick up in gravitational wave detectors it needs a lot more work to work out what on earth these signals are like i don't know what they're like i just think they should be gravitational signals but another thing that persists you know the the persistence of memory as carl sagan used to say my my friend and miniature here here's uh here's a carl sagan right there um he used to call it the pursuit really related to um things that survive time especially things like your wonderful books and i'm trying to work with our friend uh um let's see i had a little glitch right here but in the the matrix didn't like when i said uh lord eric weinstein or that he is going to write a book but you are going to write a book eric but carl sagan said a book is proof that human beings can work magic i think black holes are kind of magical i also think that magnetic fields are kind of magical and is it not possible is it not possible for for magnetic fields to make it through the simulation yeah so so can you talk about that absolutely no this is in fact i was going to ask you that question very interesting no you see a black magnetic field i mean this is really paul todd again who well he was sitting next to somebody i can't remember it was a question that came up about primordial magnetic fields and things like that which seem to be you get these things in voids and where do they come from themselves yes it's fascinating so paul asked me you say well what about magnetic fuels and electric clusters did they come through and i said yeah sure just electromagnetism they come through like like like a beam of light definitely so you should see them where should you see them you should see them where you used to have a cluster of galaxies presumably that's where they would be strongest where are they they're where their hawking points are so you i would guess you ought to see primordial magnetic fields around talking points and that's something we can test and you and i have talked about collaborating uh as well on this phenomenon um and uh one of my uh actually my post one of my colleagues is a postdoctoral scholar here uh dr grant tepley formerly of caltech and currently of uc san diego works in the simon's observatory he wants to know if you've looked at uh if you've looked at the cold spot there's this anomalous cold spot not a hot spot like a hawking point would be but a cold spot and that's a subject of great interest because it's anomalous at the many many sigma level of significance what do you think about cold spots in the theory of conformal cyclic cosmology this is only a guess so i i'm not i think people have told me where it is but i think it is fairly close to you see one of the most striking pictures you get and i don't know if you've got that one up it's a picture that vahe made of the planck data it's the paper that we wrote together on the fermi paradox can you find that paper yes i'm gonna uh i'll look that up um but keep keep describing it it'll take me a second to what he plotted was in the plaque data centers of low variance rings and you only count them if you see at least three concentric rings these three concentric rings that's right there may be more than three but no less than three and they are color coded now here's where i get confused they're color coded according to the temperature the average temperature now because of two backwardnesses the red ones are actually the very distant ones in the theory the color coding is that the red ones are the hot ones and so you might think of them as blue but they're also in ccc it goes the other way around that say the distance signals are the blue are the blue shifted ones because the signal is coming towards us and therefore it's blue shifted you won't see them if it's going away from us whereas the near ones you see them if it's going away from us that's the way the geometry works so that the there's a big splodge the biggest splodge in the picture if you see if you see have you got the picture up there i'm trying it's a very low resolution the picture that i have but um but keep going there's a picture where you see color-coded multiple significance levels for yes i'll show that yeah and you see on the bottom sort of you see there's a the middle galactic plane is removed so there's a whole region which is cut out but then points which are not in the removed region even if the circles intersect the removed region they are included in this scheme and the color coding is depending on according to me how distant they are so if you see red ones they are blue shifted and therefore distant i always get myself confused though because that's the right way around but the point is the cold spot it could be it could be essentially a sign convention in the way that he's making the plots in other words or cold part well there is a convention which i have to come to as a confused people let me get to that there's a cold spot i think is close to the red splodge well with a huge number of sources outside our particle horizon so we don't directly see the galaxies however we do see according to this the collisions between supermassive black holes in the galaxies and so those that that galactic super duper cluster is only evidenced by the collisions between the black holes in the in that super duper cluster so what i'm claiming is that there is a super or was is the right word i guess a super massive black hole cluster a super massive cluster let's say of of galaxies presumably with large very large numbers of supermassive black holes running into each other and producing this huge red conglomeration now i'm just this is not off the top of my head because i thought of it before but it was on top of the top of my head then too maybe this huge density of galactic and you see this in homogeneity there other people have to explain it somehow anyway it's there in this analysis now what it ex what it indicates is a question for other people but we claim it is evidence of a supermassive a super duper i'll call it cluster of galaxies where you are seeing the collisions of the galaxies the gravitational wave signals from those collisions and they're coming through now that if that was a huge density of material then the material around it would be attracted towards it now that could mean that material that we see within our is to some extent moving away from us and therefore colder so if the cold spot is somewhere around there that's a possible evidence from these signals that the uniform that the universe is not merely so homogeneous and isotropic as people think this not only from i think very strikingly from that picture i'm trying to guide you to in value you see the color very brightly colored one i think it's 1b or something you can't remember numbering yeah i'm showing them all there's several of them and they depend on uh which quadrant of the galaxy one is looking at um but i know you have an appointment coming up soon sir roger so i want to be respectful of your time and thank you you'll be soon picking up uh a special kind of of of coal of hot spot when you journey and make the journey although it's gonna be virtual right you're not gonna be in person for the nobel uh the nobel banquet is not taking place this year they don't even know what's going on let alone me now they want me to be at the swedish embassy see this concert there's a building that's swedish out of sweden in london where i have to go which is i'm not sure if it's the swedish embassy but it's it's part of the swedish embassy complex and uh i think they will the the uh event will take place they're probably everybody with masks on yes and i think they may give me a medal of some sort then i knew it was uh i knew they would find a way to punish you for leaving in comium on my fair book uh somehow and it looks like 2020 has conspired to make that come true i want to uh thank you sir roger and my friend eric eric any final words for our beloved friend uh just congratulations and if you have any thoughts about where you think young people younger than myself should be charging off i hope you will make them known to the field because i think that your voice newly empowered as it were by this shiny disc is going to make a huge difference in renewing the field i hope i want something clarified though before before yes yes i i think i'm working on it there are some thoughts about that absolutely um yes indeed well you may know about this this thing called the penrose institute which has it may have a revival yeah yes we're hoping to establish that here deepen our connections between the arthur c clarke center for human imagination and the penrose institute which will be located here uh let me ask you a question which is very critical to this question i understand from what you've just been saying if i interpret this right that the telescopes or whatever is it chimney or yes we'll have telescopes in chile and at the south paul antarctica oh both oh that's good now presumably you are you're able to pinpoint magnetic fields is that the question well rather than just the issue yeah the issue of primordial magnetic fields is a very rich one because as you mentioned we have evidence for magnetic fields on all scales from the human being scale to the planetary scale to the galaxy to the cluster scale tens of megaparsecs across but we have no evidence for an uncollapsed magnetic field a magnetic field not associated with some gravitationally bound structure one of the goals of the simon's observatory is to do just that to look for primordial magnetic field signatures which will reveal themselves at high resolution with our large aperture telescope the led six meter diameter telescope of the simon's observatory is building where they are it's not just an overall we're gonna survey a very large fraction of the sky tens and tens of percent not as much as plank but with much higher resolution much higher precision and much higher accuracy in terms of calibration for planck was not designed and neither was wmap it could do polarization but in terms of doing it you have to look for very subtle experimental effects that can systematically contaminate but what's so cute roger and you'll appreciate your friend jim simons in mine uh he is convinced that there is a signature of churn simon's birefringence cosmic birefringence that we're also looking for there was actually a claim of evidence for it that just came out uh published by uh scientists in in japan and in uh and in germany and uh but the issue is uh you get it for free if you search for primordial magnetic fields which presumably could confirm or possibly you know this as well as i do refute our own favorite hypotheses it could be true that we discover that there are no hawking points that's a possibility but what's so interesting is we get for free constraints on lorentz violation on parity violation and on things exotic physics scalar fields etc uh called cosmic birefringence and so uh we get it for free we're gonna learn a tremendous amount about this we'll be able to test it and who knows you you and you and jim might get a second one you might be the second person ever to get a a non-chocolate gelt uh nobel prize no no the other people have had to do yes that's true oh yes yes but in physics only one right only on the uh bardeen right oh yeah says yes that's right yes um so i want to thank you i want to remind people in the into the impossible family that we're going to be doing a live stream with adam reese uh uh sir rogers co-laureate we're doing a live stream with adam reese janna levin wendy friedman david spurgle who you mentioned and uh and myself coming up this tuesday night we're doing live star gazing it's the 30th birthday of the hubble telescope sir roger and it's the 20th birthday of the international space station so our partners and friends in wyoming stargazing we're going to use huge telescopes to recreate the 1920s kurdish shapley debate that concerned the size of the universe so that's happening tuesday night this coming tuesday the 10th of november at 6 pm eastern time i hope you guys will join uh in what continues to be a wonderful year of pandemic podcasting sir roger penrose i want to thank you so much uh i'm sorry i kept you so long i i can't resist it's it's too difficult when you have good friends to chat with i wish you all the best congratulations a hardy mazel tov as we say and uh and all the best roger be well be healthy and continue to do great work and inspire billions around the world thank you so much yes bye gentlemen goodbye

Channel: Dr Brian Keating

Views: 31,862

Keywords: Astrophysics, cosmology, Cosmic Microwave Background Radiation, Big Bang, Inflationary Universe, Hawking Points, Ccc cosmology, Conformal cyclic cosmology, Roger Penrose, Sir Roger Penrose, Roger Penrose Stephen hawking, Nobel Prize Winner Sir Roger Penrose, Sir Roger Penrose Nobel Prize, janna levin black hole, Sir Roger Penrose: Conformal Cyclic Cosmology, Black Holes Nobel Prize w/ Eric Weinstein Janna Levin, singularity, theory of everything, eric weinstein geometric unity

Id: 57SMQj3lOm0

Length: 140min 6sec (8406 seconds)

Published: Fri Nov 06 2020

Reddit Comments

[u/Winterflags]

Eric joins the stream at 1h 13m: https://youtu.be/57SMQj3lOm0?t=4376