Roger Penrose: Black Holes, Art and Science, and the Beginning and End of Time.

[Music] hi i'm lawrence krauss and welcome to the origins podcast roger penrose is known to the public as the winner of the 2020 nobel prize in physics which he shared with several astronomers who who discovered a black hole at the center of our galaxy or at least demonstrate its existence by looking at the motion of stars and we've talked to one of them andre guez roger shared the nobel prize for showing 50 years earlier that black holes in fact were an inevitable consequence of general tutti something which really hadn't been accepted at the time because black holes are so weird but roger's known to physicists for many other things as a remarkable mathematician who's developed techniques that have been that have really changed the way we think of general relativity so-called penrose diagrams he's also discovered a fascinating aspect of nature called penrose tiles which he and i talked a lot about which in some ways was sparked or sparked his interest in in the art of escher and we had a wonderful discussion about very early experience he had as a young man talking to escher and and actually helping him in some sense with some of his images some of his impossible images roger has recently uh promoted an idea in cosmology called conformal cyclic cosmology which frankly as i discussed in the in our dialogue is a controversial idea which really hasn't hasn't been widely accepted uh in the community beyond himself and his colleagues and i have um several concerns and questions about it he and i had a had a discussion we talked about his early life and science his experiences having to do with general relativity and what led him to his current work uh which which uh which we discuss at length in the latter part of the podcast i hope that this will provide a new glimpse into the way scientists can debate ideas uh hopefully respectfully and fruitfully and how ideas at the forefront of science can remain controversial and how most important as we discussed at the end how scientists should uh be not happy to be wrong but certainly willing to be wrong and proclaim they're wrong and change their minds because that's what differentiates science from say religion in any case it was a true pleasure to talk to uh roger and i hope you will enjoy this in-depth discussion of physics and mathematics with roger penrose this is a very special edition of the origins podcast as well because the origins podcast video no ad video is moving today from patreon to sub stack to our new to my new substract page and it will be freely these this video will be freely available as all things will be on the substract page but i hope and the origins project foundations hopes that you will subscribe to substack because the funds that that of subscribers that to the substance site will go to help the foundation to help make this podcast possible hope you enjoy it if you don't watch it on on sub stack you can always listen to it uh a link through substance at any of the standard listening sites itunes etc uh or you can watch it on as always on the youtube channel and we hope you'll subscribe to that if you if you watch it on youtube so once again roger penrose [Music] well roger thank you very very much for for taking the time out to talk to me i really appreciate it it's really good to see you again and uh and and and i know i think i emailed you but now i can personally say also congratulations on the prize uh well thank you and uh i was trying to remember the last time we were together and i think i don't know if you remember this but i i think it was at oxford at a debate with philosophers where you and i were partners and i don't even remember what the context of the debate was except that i remember that you and i won i'm afraid i don't even remember it yeah all i remember is a bunch of oxford philosophers and we were i think it was about physics versus philosophy in some way and and where we are physics or philosophy we were on the yeah i think we were on the physics side i'm pretty sure philosophy is science versus versus physics and and um and i i remember um yeah i just remember you were my debating partner on that and and it was fun to do it and i actually mostly just remember the drinks afterwards but in any case um it was that i think that was the last time we're together i wanted to um uh talk about many aspects of your science here and and which we'll get to um including ideas about cosmology which is an area we both have worked in among other things but i but this is an origins podcast and i wanna i wanna um begin with your origins which are quite interesting to me in a variety of ways um you come from a scientific family in a sense at least at least your father and your stepfather and i guess uh in some sense uh at least uh grandparents as well father my mother's father certainly he was he was a scientist physiologist yes yes well now i'm just wondering where the um you know in the context of growing up in that household where i i where the influence was for you to want to learn about science or mathematics um did it come from discussions with your grandparents or which of your parents would sort of encourage that father mainly my father also i should say my older brother oliver who he was very precocious much more i mean i wasn't at all he was um and he knew a lot of physics and i learned quite a bit from him but mainly it was my father from whom i learned yeah quite a lot of mathematics actually he was he worked in human genetics was his topic yeah but he he did quite a lot of mathematics he certainly was interested and excited by mathematics as as quite a lot of other scientific matters and i learned a lot from him yeah that's true i i've i i well i knew you your father was the kind of worked in genetics i don't know was your mother um was she educating science at all or or yes indeed she was medically trained well i i don't know i want to go into this particularly she was trained as a doctor but my father had lots of lots of positive qualities but he had one big negative quality which was some for some psychological reason which i could never get the hang of he wouldn't let her realize herself in her in a medical profession or in almost anything strange we have a lot of good qualities but i have to strike that one as a bad quality i'm afraid yeah yeah no it's it was it's unfortunate i think it happened a lot especially in an earlier generation but that's that's unfortunate here but did she um play a role also in encouraging your interest i think she did in a slightly um well how would i put it she couldn't express herself in such an independent way but there was her she had a way of relating to me which was slightly kind of not quite direct i kind of know how to say it exactly okay i think i learned a lot of how to express myself from her she was very um the use of language i think she was had had a skill in the mind it's interesting to me that often happens in in um in my experience with uh with mothers in fact in terms of language um the did did you read a lot uh did books influence you about yours and science did you pick up books by the you know the standard well-known you know james jeans or whoever else would they not some of these things but i would say i was not much of a reader i was a very slow reader i think and i did not read a great deal but i there were some things i did read some bert and russell and yeah there is yeah i i read it but yeah well i mean you know it's interesting to see that again the differences in people and in both i love the fact that that that that almost any stereotype of a scientist is wrong and um and and yeah and uh and that that it takes all types and i think it's encouraging for young people to realize that and you know in so many ways not just uh you know some people read a lot some people don't read but people often assume especially young people that they're not good enough or capable enough because they don't have x quality and and it's really important to realize that people that who have been quite successful sometimes also don't have that quality whether they're not the mathematical prodigy or they're not they don't read or whatever it's science when it's healthy takes all all kinds and i think that's really nice i think i sort of read second hand you see oliver was a great reader and somehow i got from him but certainly he read to me sometimes and he read to me the the uh mr tompkins books oh okay yes i don't remember that and various other things to do with science which he did so i think he had a big influence on on my he was you know how much older how much older two years yes yeah my older bride one brother was older and i think certainly strongly influenced me when i was younger although he wasn't he became a lawyer but but uh my interest in a variety of fields was certainly didn't become a scientist and he yeah he's a physicist in fact he became a uh a member of the royal society and so on hell of the royal society yeah no it well i want to get to your your siblings because you have a really interesting there's something interesting about your background that that seemed to encourage all of you to do to both have be very gifted in your own fields but also to be interested in them i think it's uh um uh um but you know i was gonna so when it comes to reading i was gonna say in some sense that one of the good things about science mathematics and physics in particular is that if you're good enough you don't have to read at all as feynman used to kind of i think unfortunately epitomize in some sense uh that's true yeah and um i wanna there are two aspects of your childhood i wanna i wanna ask about your your father was a math a geneticist interested in mathematics i you have a stepfather who was a mathematician i don't know what's whether there was any influence there too or not that came much later you see that was after my father died in the 70s oh okay so that was when my mother married max newman who had been a good friend of my father's way way back oh interesting apparently he'd had a crush on my mother even way back there after my father died he sort of made the beeline for her okay in the 70s no but that was okay that was much later then okay now and the other thing i can't help sing because behind me is is is is a a wonderful river i'm i'm now moved back to canada where i grew up i haven't been back here yeah that's a real background that's that's my beautiful and prince edward island but it's a beautiful background but it's um and i'm very happy to be here but you have a canadian background that i didn't know of you spent some of the war years i think in in in canada in london ontario what what was your father doing there well i was there from well i was in 19 1939 i guess we went there years of getting confused 1939 that's right i i 1939 i was seven years old when we went and i had my eighth birthday in canada yes we went first to the us to philadelphia and then my father got his job um at the ontario hospital that's just near just outside london ontario and so he spent the war years there but that was a big influence on me in what way well um i went to ryerson school and then to central collegiate for my final year uh it was curious now my first year there i had a teacher i couldn't get on with it at all she had what was called high grade two in low grade three i was in low grade three okay now she considered because i was very bad at doing mental arithmets she used to have these things were able to add a number and then multiple myself and it was done too quickly for me i just got lost i always got lost and she thought i was too stupid for low grade three it moved me down into high grade two wow i was too good for high grade two so she couldn't place me between you know high grade two and low grade three however later on she got rid of me i think by just as a way of getting rid of me i got moved up with some other people into high grade through i i don't think she thought i was good enough for high grade three but but since we never got on i think she probably thought this was a way of getting rid of me ah i did have a i forget whether it was in high grade three or later but i did have a very insightful teacher mr mr stanette and i he used to have these mathematics tests and i never did very well in these tests but he noticed that the reason i didn't do well as i simply didn't finish the tests and so he decided to let me have as long as i liked so i could just go on and go on and the people were playing in the playground and i could watch them out in windows and i would just be slogging away through the test and then i would do very well i'd get into the in the 90s you see and he realized that it was simply that i was too slow oh wow this is fascinating because again i mean i've known of you as a brilliant mathematician since since i started doing physics and and and it's it's fascinating that that um in a sense you were um people didn't realize it wasn't it wasn't as if you they recognized you as a mathematical prodigy or anything like that early on and no well i used to make models and things with my father so this this was a separate thing we did at home yes well now when did you so did that um did that i was going to ask you man maybe this is relevant i mean good teachers are really from some again it's not universal that it's important for people i know some people who said teachers never impacted on them their whole lives but but having good teachers certainly for me and many people i know has been a a particularly good teacher has can have a huge impact on a young person and that's why i guess i'm i give so much respect especially for teachers of young children because they can really really change a person's trajectory and and this teacher had an impact did you i was going to ask you what got you interested in mathematics your father of course talked about mathematics but when did you kind of get the sense or or did you get the sense that you wanted to be a mathematician early on or did that just kind of happen ah it's a good question too actually i remember i mean there's a story i often tell you see my older brother was clearly going to be a physicist my younger brother was only interested in chess but that's not quite true he was interested in all games and of course part of my background i don't know do you have this down but my younger brother jonathan became in the record compliance yeah but in record time how old was he when he became a chess man grand master well he never he did become a grand master but that's a slightly complicated story okay um he didn't eventually become a grand master but but his uh i can't remember he first won the british chess championship i think in his early twenties ah okay he was in this 20s but he entered for the british boys championship that he won i remember but he was good at almost all games and i remember this is a curious story i remember he beat me at this game you know stone paper scissors yeah sure and he would completely walk me regularly i thought surely this is a game of chance how can he beat me at this game of chance and i said i mean is this sort of some um jinx or something like that so what i did was i got a table of logarithms opened it in the middle a huge nerve it sort of took people's random figures and translated the numbers into stone paper and scissors and i made a long strip of this and i would follow this and then i broke even so that was a good relief to me [Laughter] he was actually using psychology or something i mean he had an extraordinarily good memory he used to play this game what people call pears or pillman and you see the backs of the cars and you turn two over and when you push them back you see all i see is the backs of the cards but everything he still sees the fronts of the card another way and he oh absolutely hit that game there's no question about that one well go on sorry but anyway the fact that he was so much better obviously than me at chess i've never played chess well that's not quite true either i i hated chess and tried not to ever to play chess there was an occasion when i was at school in london university college school when uh my younger brother jonathan was the first board of chess and my three jewish friends were the board two three and four and occasionally they needed the board five and they put me on board five i think just to scare the opposition that there were two penroses in the team i'd never won a game i have to say i never played chess apart from that um he sort of he sort of immunized me against playing chess which i think was important i don't know whether i would have ever got interested in chess but i certainly didn't because of because he was much too good oh that's you mean you think you might have gone to the dark side if he hadn't become it's quite possible oliver did play chess and he was four years four four years and four months older and so he was able to keep by by really working very hard at it he was able to keep ahead for quite a while until they both played in the british chess championship and jonathan came out ahead of him oliver was good enough to be cambridge university champion so you've got some feelings oh wow okay well look let's let's let's um it's it's interesting and glad to see that you're you know this is another stereotype that you're not at well maybe you could have been a chess uh wonderful chess but you weren't but i'm i'm happy to hear that although it is a game of people who like well the memory part is i think really and uh obviously important to be a good it was very good he could remember certainly up to the scale i even knew in that when growing up i think that's right he could remember every game he'd ever played but in a sense you would like games and we'll get to that i think or i'll i like puzzles be is perhaps a better way of putting it because we'll get to that what i think are some beautiful obviously beautiful puzzles that you've been involved in um and and so that natural interest but let's let's since you mentioned two of them you're you have this amazing siblings are just amazing as you say oliver a physicist um your sister shirley hodgson's a geneticist right yes yes one who followed in my you see i was supposed to be the doctor and family this is well i mean my mother i was you know a jewish mother i was she wanted me to be a doctor my brother to be a lawyer and he became a lawyer both parents being medically trained of course obviously he was going to do physics he was a dead last jonathan was only interested in games and chess and stuff he was a dead last roger he's the one who's going to follow up in there and i used to take these vocational guidance tests from canada and you sort of line these things up this way in that way and my camera was a doctor and i i was going to be the doctor in the family and they were very relieved that they you know i was going to carry on the tradition and the moment came when i was entering my last two years at school university college school in london and each one of us had to walk up to see the headmaster and see what they were going to do in their final two years so i walked up and i was going to be a doctor as i walked up to see him and he said well what do you want to do in your final two years and i said i think i have this right biology chemistry and mathematics and he said no you can't do that combination if you want to do mathematics you can't do biology if you want to do biology you can't do mathematics make your choice so i said mathematics physics and chemistry oh wow and there was my medical degree down the tubes that moment oh it's fat uh this is fat this is again fascinating for me personally because i i i want to be a doctor my vocational test had me be a doctor in canada when i grew up but you know my cuz my mother had convinced me and i convinced myself i wanted to be a doctor and then for me it was in the final years of high school when um yeah when when i i guess my problem was that my mother had sort of convinced me doctors were scientists and i got fascinated with science and at some point i kind of had the realization that they weren't necessarily the same thing that and the fact and it may have been different in britain and well maybe it wouldn't it wasn't but i i actually did take a biology class and at that point it was just memorization it was just memorizing the parts of a frog and that and i just said this doesn't interest me at all at that time of course biology has changed a lot yes but you say i think i mean my mother thought i would have had a good bedside manner or something i don't know about that but i would have been a complete disaster with drugs because i would never remember any of these names and so on so i shouldn't have been let loose on these things at all well it's so it's so it's interesting that you did it sort of was a choice to do you know but you know but mathematics but it was math biology or mathematics so by then you kind of knew you wanted to do mathematics and of course you did do mathematics and and i want to ask you it's jumping ahead a little bit do you think of yourself as a mathematician or a physicist first and foremost often when i talk to people i say well i'm amongst physicists i'm a mathematician i don't like mathematicians i'm a physicist um that's an intriguing question i think you see i'm very interested in the mathematics but it's got more and more focus as uh in the physics i mean the physics is the driving force but the mathematics is is the way you go okay so but so okay but the physics be was the driving force but it wasn't all i mean was it but initially i mean your phd was on tensor methods and algebraic geometry was it was it mo was it motivated by physics or was it motivated by interest in new mathematics that was mathematics yeah sure you see all these stories i have to tell you all your stories man that's fine it was one of the stories i have to backtrack a little bit here i think when i was at university college london doing mathematics i should say my father was not keen on my doing mathematics and not something else he thought if you could do other things you should do mathematics and on the side like he did in some sense yes that's right and he was not keen on my just doing a mathematics course but he got one of the lecturers a man called castleman who made up tests i have a lot of respect for the castleman he made up a special test i can't remember whether it was six or twelve problems and he said look you can do these problems take the whole day if you like do as many or as few as you like if you only do two or three that's fine i i did the lot um but these were all tests with sort of a twist to them they were not sort of straightforward he must have worked very hard on working but anyway since i did so well on those tests my father sort of relented and said okay oh that's going back a little further but let's not go back quite so far there were some radio talks how by the way how how when was this uh what stage was this when you're an undergraduate or younger i when i was a in my an undergraduate okay to the university college uh for lectures and things there i can't remember exactly which year it was it doesn't matter i just wondered if it was before university or not anyway i'm sorry i interrupted but you were going you were going to move on to one could check this out because the fred hoyle radio talks were key and i remember racing home to hear these radio talks there were five of them i think they started with the earth and the atmosphere and then they worked their way out and solar systems yeah sure galaxies and then he talked about cosmology and when he talked about cosmic this was the steady state the days of the steady state model sure and he talked about the galaxy which was seen faster and faster at a certain point they would reach reach the speed of light and when they exceeded the speed of light they would disappear and you wouldn't see them and i had drawn little pictures and things and i couldn't quite get my mind around this and i was visiting cambridge and i did see my brother oliver for some reason which i have not forgotten but i remember having this lunch with him in the kingswood restaurant and we were talking away and i said i didn't quite understand was giving these very nice talks but quite understand about these galaxies disappearing and so on and he said well look i don't understand much about cosmology but sitting on the table over there is one of my good colleagues his sharma and he knows all about cosmology he'll tell you so i went and sat down next to dennis and explained my little problems and do my probably like clones and things and surely they will just fade away they don't let's disappear like that so he said well if i don't really know about this i go and ask fred [Laughter] anyway i didn't hear what came out of that but when i did go to cambridge eventually as a as a research student no yeah a research student doing algebraic geometries algebraic yeah working on the hodge yeah and um then this sort of took me under his wing and he uh we wanted went on long drives to to to plays in stratfor with shakespeare and often stopping off in oxford just one reason or another and driving at great speed around corners and things like that look that's forced that's the action of the distant stars like mars principle and things like that and they'll be discussing what happens we'll suppose the earth disappeared but you still feel the acceleration and what about so on suppose the stars were removed so we had these sort of conversations a lot and it was very influential on me so i learned from dennis a great deal of physics so i would say that my early education in physics largely came from venice dennis dennis sharma sure i would say there are also three courses i went to in my first second i can't remember exactly which years at cambridge three courses which had nothing whatsoever to do to do with my research the three courses were one um herman bondi oh wow on general relativity one was a man known steen on mathematical logic one was paul durack one quantum mechanic and they were all extremely influentially influential on me in many ways the steam one because i learned about girls here ah magnetic logic and that sort of thing yeah and the big effect really my point of view that i later formulated more strongly came from steve's lectures and understanding about turing machines and girdle serum and he was very clear on those topics wow this is uh fascinating because i knew of course xiaomi had an impact but i'd assumed it was after you're finished your phd and uh uh okay now it's interesting that shyama took you under your wing his wing when you were doing a student in mathematics but i guess um was it because of the introduction you had with your brother or how did you or or is it just that form yes that's how i knew him but i think it was my just the fact that i seem to have some insights into cosmology which which he hadn't seen before i think he was really just drawing light currents which is not much of an insight really but that's well we'll get to that and well it is it changes it changed the world in many ways i want to i want to get to that we'll get there eventually in the next five or six hours no and but um but this is fascinating well but i want to i still want to focus on this sort of transition from mathematics physics so you knew you did your phd in algebraic geometry and tensors of course are highly relevant to physics but it was really the the algebraic geometry that fascinated you at the time and one of the reasons i'm asking is a personal one i did a degree in mathematics and one in physics um and and what kind of surprised me is you know i was always very good in mathematics but but there were some really excellent mathematicians young mathematicians who who were uh who i was with in my mathematics classes and i just assumed that you know since since mathematics since physics was really mathematics to me i mean it was really you know was the basis of physics that these mathematicians would would breeze through the physics classes that if when that some of them did take with me and what shocked me is that they were much better mathematicians me but they could didn't have but they had a heck of a hard time in the physics classes which i shocked me because i thought it would should be trivial to them and at the same time to me what kind of i was trying to decide and i saw that when i was in physics classes i could see where we were going in math classes i could always kind of do everything but i could never kind of see beyond the horizon if you want to call it that i couldn't see where things were going and that's when i kind of realized i wasn't a mathematician and i'm wondering if that kind of but you you well what if that impact on you at all but i mean i guess it didn't because you kind of knew you were a mathematician but i wanted to sort of ask in that sense um about your experience as a mathematician who obviously obviously had insights about physics i think there's something in what you say in me also but it's a little bit different um well i should also i'll keep telling you these little stories because they're very influential no i think it's it really not only just interesting to me but interesting for people who are listening the stories are wonderful way to understand things when i went to work with hodge i was one of four graduate students one of them gave up after a little while i don't remember how long so then when they were three one of them did go through get a phd and he gave up mathematics at that point and became interested in history and philosophy of of physics i guess that was michael hoskin oh okay and he became a historian a lot of i don't know of physics primarily and the two of the remaining people were left i was a little bit i chose a topic i tried a list of topics and i chose one of these and i i just decided that i looked as i wasn't all together happy with this topic and he said well perhaps you'd like to sit in on the other graduate students class and just see what what you what you make of it so i sat in on this undergraduate students class and i did not understand a single word of what's going on and i thought my god if they're all like this what am i doing here that was michael atea oh my god okay we've got to respect each other in our different ways yes that was michael wow okay well that's a high bar though yeah there was something a bit special about magnets who by the way one should say you had a huge influence on physics and i used i got to know him too and and he was uh he was wonderful to talk to as a physicist to talk about mathematics yes he was yes but he knew all the mathematics he had an extraordinarily broad group but not just his knowing it was understanding what was wanted yeah exactly in a different sort of way yes and there was a thing i remember this occasion i had a problem i was just beginning to see the importance of certain things to do with twisted theory and how to how it got developed a certain way and i talked to his singer who was this great collaborator oh yeah another person i had that i talked to how do i solve this problem he said oh that's not right i'll tell you just solve these equations here and then that tells you the answer [Music] okay then when i got back to cambridge this is the mistakes i got back to cambridge and i talked to michael i said because i wasn't quite happy couldn't see quite and saw this equation and then i asked him the same question and he said oh you're doing like this he drew a little picture he said just listen this and this and then he said well you have to show that this thing is the number of degrees of freedom this and so on and then you do it like this and then you kind of you just take a line in the number line there's your answer wow you know you should take this and let's bring these subjects together and that pops your answer and that was my problem see yes michael is here and it's interesting to see both singer and atiyah the atiyah singer index theorem is incredible exactly this wasn't an instance yet wow well okay so so it was clear to you that there were um how can i put it better mathematicians maybe around you um but those people were much better at handling the amount of americans i felt i had some quality that was different in a way which is true yeah but well i don't know what it was but it was not the same as michael's you see he had this great grasp and there were people talking about new ideas that were coming in using um as as max newman's who became my stepfather used to say in in his younger days in topology we're talking about triangles now they talk about square squares and soon there'll be pentagons you see and this is going on the people were talking about this abstract very abstract ideas and i could never get my feeling the proper feeling for those abstract things that people were going on with and had such fluency with and i couldn't pick up on it so much i was much better at fiddling with the kinds of geometrical ideas well speaking of see think of geometrical ideas i wonder what you know i tend to think pictorially and it seems to me you you do too in many ways in particular around around the same time i think i was i was amazed i didn't realize that escher's influence on you and your influence on escher which i should have known about i guess um uh so i apologize for not but um the the the geometric i mean you're obviously interested in geometry but the but it seemed to me that this fascination about impossible pictures combined in interesting puzzles and kind of games with an interest in in geometry in a very pictorial way i do and and then we'll get to like cones but but but um you would you say you think about mathematics pictorially and and yes very much i would say i'm much more visual than i would always see when i was at school i remember thinking you know that i maybe thought rather differently about mathematics and other people and when i went to university i would find people who thought like myself it wasn't like that at all i found people felt more differently from me than i had experienced before and i would talk to somebody and i didn't understand much about what they were saying and he didn't understand what's mine but in the end i could see what what what it was and it was somehow i think they were out of our class i can't remember there were maybe about 14 people there were three i would judge who could think visually one of them could but was not specifically visual one of them was more visual and there was me that is particularly visual but on the other hand most of the others were not visual and i always thought that somehow i don't know that there's a kind of selection advantage not to be visual in mathematics yeah i had this experience when i at university college school no university college when i did my undergraduate degree that the way they did it in ucs in the ucl was to have the first two years you would take your main exam at the end of the first two years and then your specialist topics at the end of the third year now that's so i've done my first two years and then in the third year i was doing the two geometrical papers you see now as it turned out as i found out later my best papers were not on the geometry they were on algebra and the thing is in algebra you you just you don't have to you see your reports equation then you go over to there with the geometry you read the problem you translate it into a picture you solve the problem and then you translate it back into words and write it down in a lot of words and this sort of flipping backwards and forwards i was i didn't finish the papers and it was like that and then my slowness began to show itself oh interesting so it was but i rather felt that there is a selective advantage in not being the visual type in mathematics yeah hardly just because if in examinations it's selected against but if you are if you think about the mathematics in a geometrical way you can't get it out so easily as if you're directly yeah yeah you go off and then come back and and and i thought there was very much of that double translation in in what i had to do and this was slowing oh me down particularly true in in the classes too that the people i taught i remember lecturing that i tended to be a bit visual in the way i taught and often they didn't like it very much so they wanted me to write down equations all the time and not draw pictures and that somehow it's only a rather small proportion of them who come through who do have these visual skills and the best ones can do both of course i mean michael j was very much yeah sure he could do both it's interesting when you say that it's interesting to me i just thought of the history of physics it was probably galileo was probably lucky that they didn't have algebra at the time or at least because he thought he thought in terms of pictures and much of his you know which is now much of what he did which seems convoluted could be done in an instant algebraically but he was but he didn't have to do that translation he was a good artist too yeah he's a good artist as well in fact that you know it's you just hit me back to where i wanted to go which is i mean i'm i one of my big points throughout much of my career especially my popularization of science is that is this connection between science and culture and this this unfortunate um uh branching uh of of of science as a separate area when it's not it's a part of our culture in in every way and and as is art and and and and the and uh and often say that that uh you know that the purpose of of the two is the same this change our perspective of our place in the cosmos and when you see a piece of art it does that or a piece of music and listen to a piece of music and and same with science but the actually the the the conjoining of art and science i can't think of a better example in some ways than your experience with escher and i and i and i i want to have a number of questions about that and we will get to cosmology eventually but this is fascinating and i think i hope it's fascinating for others but but i don't care it's fascinating for me um and uh uh were you interested in art or how did how did your uh how did you the thing with escher come about and maybe you could talk about that a little bit well it had already been interesting of the three brothers i mean my sister shirley came along later she hadn't just enough but the two brothers were not at all i was the artistic one amongst those people um and so i did i certainly could relate to my father he was he was a very good artist but he came from an artistic family his father was a professional painter extraordinarily skilled yes i mean very traditional in what he did but they were extremely skilled artistic james doyle penrose oh okay i didn't know that okay so that's interesting this background you have it's it's fascinating and my all all three brothers of him so that he was one of four brothers they were all good artists the one who became most distinguished an artist was his younger brother roland who became part of the surrealist movement he was a great friend of picasso and oh wow like danced and the artistic and he became a big figure in in the surrealist movement in britain wow that's uh well that's a whole other subject i wrote a book about once about impressionism and extra dimensions and and and and and um and and picasso and and others and and you know those his seeing many faces a face from many different perspectives is the way it would look if you were four dimensional looking down at a three-dimensional object and and there was a lot of fascination at that time with mathematics in that in that particular art world but that's a a separate thing but so you were the artist can you i mean uh can you draw well as well or no i'm not because my vision is god's pieces but no i used to do that in fact if you look at if you look at most of my books you'll see the drawings are done by me okay okay books you have to look at the the earlier ones were not i got brown beaten and letting me office yeah but eventually it was like this and i would sketch it out for you for the professional artist and that would be going look that's wrong this line shouldn't even find that i'm not in front of it i'd correct it come back and it would still be wrong and i get look this is ridiculous why did i just do it myself so so in the new book for example i i i want to focus because i i thought i should focus on one thing i the new book which is largely on on your new ideas in cosmology there are lots of pictures you did all those pictures all the ones which were not directly taken from wow okay all of the ones going back to the certainly the empress new mind that we're all about okay wow road to reality yes nightism wow and then i mean okay so there's there's this wonderful penrose triangle and and um and which i guess you know well withdrawn i don't know if you had drew it originally in with with the straight lines or or not but um originally yes well i put a little bit of no almost nobody copies notices the perspective in the drawing there is a perspective in the drawing in uh in the paper i had with my father ah oh really okay was that so does the penrose triangle was with your father or no yes oh i didn't know that now that the story was well i wrote i think three papers of my father was it three or four wow one two i think it's fourth i can't vote but the puzzles for christmas yes that's pretty much oh wow wonderful i'm just trying to have a losing card but um but yes the paper on the impossible objects was by my father my father and me you see that wonderful i've been to this exhibition this was when i was in my second year as a graduate student and i went with a colleague of mine to amsterdam to see the uh this was the congress the international congress of mathematicians taking place in epstein and at one point i think i was just getting on a tram and my lecturer in topology sean wiley was just getting off and he held this book in his hand which was a catalogue one earth is that and there was this picture of eschers of night and day and the birds going back and on what's that and he said you'd be interested there's this artist called esha who's like an exhibition in the van gogh museum so i went and i saw it and it absolutely stunned me and i went away thinking let me try and do something impossible not quite as the court thought i saw in the in his exhibition because at that time he didn't have one and then i drew this triangle with bridges and roads and things going off in different directions and i simplified it to the triangle then i showed my father and he then started to draw buildings which were impossible and then came up with a staircase so we decided we'd like to write a paper on that we couldn't think what subject it was so where do we send it and then my father said oh i happen to know the editor of the british journal of psychology so we'll decide it's psychology and so he got him to accept the article for the british journal of psychology oh interesting oh wow and we gave credit to escher in this way the exhibition and we sent a copy to aisha and it was through that that ezra and my father had a correspondence and when i was driving in in the netherlands for some other reason and i was somewhere near to um where she lived and i phoned him up and he invited me and my then wife and we had tea and and i talked to asha for a bit and we sat at the end of a long i was at one end of a long table he was at the other end on two sides at one side he had his pile he said i don't have many of these left but he pushed the other pile towards me said choose one wow wow this was a real challenge to choose one yeah holy mackerel what wow you still have it i assume uh-huh yes well it's i don't have it in there i have it in my own house it's i i now have a record i don't know if it's a record or not but i have nine dashes wow wow it's quite a puzzle how i actually have mine i know how i have two of them but i know i haven't why it happened but i know how it happened but why it happened by no more it's strange but i two of them were one that those he actually gave to my father which was the staircase the ascending and descending you you wow you have that i don't know and the other one was to pick one i picked out of this pile which he was rather pleased that i chose because he said people don't normally appreciate that one it's called fishing scales fishes and scales and it's the sort of um violation of theory of types kind of yeah you have this fish and it's got scales and the tails get bigger and bigger and then they become a fish and then its scales becomes the original fish so it has this paradoxical nature and it's a very striking picture this is one of my favorites yeah well wow we're on the ashmolean museum that can be seen anybody wants to see them i can say i can now you well this is wow well that's a very fortunate experience but uh and and um but you actually as i'm right that you influenced escher right the ascending staircase was motivated by the impossible triangle or am i wrong about that case oh you had the staircase on paper and but his pain his piece of art was done after that motivated by that am i wrong that's right yes no you see he did in the meantime yeah i have to give him credit there's a picture he drew called belvedere belvedere does use a similar idea so he had he had that independence but the idea actually people point out to me that it was done by oscar wright's father the swedish artist and he had a thing very much similar to my possible tribe which is actually dealing with cubes all stacked up but it's the same thing basically i hadn't known about actually well well it's often the case that lots of people come up with good ideas at the same time yeah well this is somewhat early i have to admit but but it was not not known to me or to actually at that stage but as you did know some of the um i mean there's a boy girl picture of the gallows yeah things that joined up in an impossible that clearly delivered i mean people make out oh he made a mistake what he was doing now again this was this was relatively early right this was when you were still an undergraduate or was it a graduate student or when you were first a graduate student when and that fascination with that the art i think is just as i say it's just a beautiful way of combining the fascination with some aspects of mathematics and i and and the art and the fact that similar things can attract different people it's a yes but it was curious because i didn't realize it was chromology until later see this there was a television crew and i can't remember what it was for it was some b i'm not sure if it was bbc or not it was a it was a television crew making a film and it was it was about twisters strange much before anybody was physics was interested twisters we'll get it at one point it was very strange because they were doing this thing with twisters at one point they said what are they actually for and i said well actually you can use them to solve maxwell's equations that's for electromagnetism yes sure on four equations and they said oh how does that how does that work oh i said well it was an idea i couldn't possibly explain what's that idea well it's the thing called cause it chromology i couldn't explain whether to say i'm afraid it's not it's not something but then i went away and then i remember lying in bed that that night i think my god yes i can explain it's just this possible triangle this realization of chromology yeah i probably they never use it of course but did you ever write that up or anything in that uh yes it was written up i have an article because another conference i was at this was a conference in rome or something it's in rome because yes you spent a lot of time in italy and there was a big thing about azure conference and i was supposed to give a talk the next day about well i was going to talk about the triangle and chromology and i was talking to a mathematician i wish i could remember his name the the night before the evening before and i was saying that i wanted to talk about this driver which is an example of curl margie and he said oh what group well it's really the which depends when you put perspective and it is a multiplicative group if you're multiplying difficult with the real positive reals really if you're looking at uh um with perspective otherwise you just anyway but anyway he said whatever you do any other group of the genesis i don't know how about that too mine's possible well yes my gosh you can't do it with that too so i in the lecture i gave an example of is that two examples and then i produce other ones better ones later on and i have an article which has got it's got all these things i should send you the references yeah i'd like to i'd like to see that okay that's that then years later we're by the way we're we're almost getting to cosmology just so you know or at least at least well we are well we yeah anyway but we're in the we're on that yes pinnacle there of talking about that but is part of the connection yes they're going yes yeah but um but you came i want i can't resist coming back to penrose tiles which in some sense is revisiting once again another impossible it's not quite the same kind of impossible puzzle but something that seems impossible on the surface and and and you came back to it years later that was in the 1970s right um yes there was a slightly different train of thought and there we go back to steam and company because i have been interested in computability i had this sort of parallel interest in computability issues and i think i remembered looking at the mathematical reviews and seeing that there was an example of a tiling problem which was known which was came from the study of computability and i think that was robert berger was it can't remember i get the name straight here no that was that was not problem robert berger was the one who first yeah i don't know which part of the story i should tell you in one order um but i had this pattern it came that came separately from that i had i had a way of usually my procrastination was the source of these things because i was supposed to write a letter to an invitation to give a seminar for one of the london colleges and i hadn't responded for ages and i was trying to get down to write this lesson like the fact that it was so late it was a sort of blockage against my writing it and i looked at the logo on the the university and it was this pentagon subdivided into six small one in the middle and then five going around said that's a simple logo and so it's funny what happens if you iterate that you put the big one into the little ones and you blow it up and put that in and it blows up well you have lots of gaps and holes and then you fill these and i had a way of filling the gaps and there was a bit of a choice there could you do would you do it this way or that way a or b way i did it the a way which was very lucky or maybe instinctive i'm not sure what because a japanese person had earlier done it the b way and it didn't need anywhere anyway you get this iteration and it produces these lots of pictures so i did it that way and i produced a pattern i rather like the pattern and i have a friend of mine was ill in hospital and i sent her a copy of this she was interested in mathematical things and i thought this would cheer her heart perhaps so that was just that pattern that's what it was later on i remember looking at this pattern and just having this i suppose it's what people call inspiration i'm not quite sure what i wonder whether you could force that pattern as a jigsaw puzzle and i thought probably you could and this is one of these things you know some people say oh they have this idea and it's a hundred percent they believe it's true what percentage did i get 50 probably i think it's always about fifty percent it could easily be wrong but it has a good chance of being right so i played around with it and i realized you needed five versions you needed three different versions of the pentagon because they occurred in a slightly different arrangement either they had five others around it three others or two others and this meant that you had a different dealing with them and so you had six different shapes which will tile the plane only period on non-periodically yeah i was going to for listeners who don't know about the tiling the whole point is that tile you can tie this plane non-periodically with in a way that seemed to defy many much intuition about how you could build things i knew you could pick top here theoretically because i think i had been playing around with certain shapes which you could tie with smaller versions of the same shape yeah and iterate that yeah and that gives you a non-period of time but it's you you take the shape and you could tell them appearing incredibly easily so it's not yeah there's no way of forcing it to be non-periodic so the key point here is that it forces the long period of the only way of tiling with using these matching rules and the matching rules can be forced by jigsaw arrangements and i was visiting cambridge oxford oxford sorry i was visiting oxford for a conference it was in honor of coulson who i think had just died i was going to be his replacement as rice ball professor although he moved previously into chem professor he become professor of chemistry i hadn't taken up my position as yet but i think it was the year before or during the academic year prior to my taking up my position there but i did visit the institute mass institute and i talked to simon cochran who was a princeton mathematics professor good friend of john conways and silent coaching was telling me about these six tiles of now i've got their names confused that wasn't robert burger was it there was a it was a student of te hao wong who had found the first non-periodic enforcement which you use several thousand different shapes you need seven these are squares i think with colored edges or something and you needed in his version about get confused by who the other chap was now but somebody who had gotten the number down to six this this was right from from the number that robert berger had originally of thousands and then he i think he had got it down to about 109 or something and the number had got worked its way down to six and that was the smallest one that had been found at that level and i was told by signing coaches that this mathematician whose name is slipped my mind now um like to get the numbers down to their minimum you see and then here he done it with six and i said well i know i can do it with five because i had my six styles you see and one of the which wasn't quite so elegant with the five that i knew you could do so i said i know i know i can do it with five so i went home and chilled around for a bit i think this must have been when i was in visiting cumberton you said my mother lived with max newman she married max newman who had a house in cumberland near cambridge but he during the week he tended to live still in manchester where he was he'd do this research there and then the weekends he came out with i really can't remember very much clearly but i think i must have been incompetent when i realized that you could get the number down from the five i had to four no quite proud of that yeah and i thought after a little while i thought i wonder if i could do any better than that i fiddled around and they got it down to two and people asked me what my reaction was i got dance too and when i say my reaction they get a little puzzled by this disappointment why was i disappointed i don't know you see i think it's just too easy surely this is known this must be you're looking at the golden um [Music] mosaics of the people surely you see you'll see this thing here i don't know if that was the reason i thought i just thought it was you said yeah you thought you solved a really hard problem and it must have been an easy problem but it turned out to be an even harder problem yes i just thought it was too easy yeah that's why i was disappointed you said too easy this is stupid like some darts and then i realized with the rhombuses a little later the rhombuses came came second afterwards well were you what was your reaction when you kind of learned that nature um nature incorporated some of these ideas was that was that a shock a complete shock or did you expect that well yes well there is a curious story which is still a glorious story i think people often ask me i would give a lecture on instance and somebody would ask me put up my headset please um doesn't this mean there's a whole area of crystallography this is way before shetland i should say okay is there isn't there a whole new area of crystallography opening and my response would be yes in principle you're absolutely right but how on earth would nature do it because you need to have a non-local knowledge you can't do it simply locally yeah now give an example where you have this correct tiling and then there are two type alternatives of each and either a kite or a dart you can put the the kite here and then you can put kai to a dot there or a dot here oh no you can only do it with a dart here and a kite here not two whatever it is yeah and you can't tell it only goes wrong way over here you see yeah so how would nature if crystal assembly as i was mistakenly believing at the time it's like you've got this little ridge and then it's joined up in rhythm and then next ridge and they build up so you can't do it that way so how would nature do it and then paul steinhardt and i were both at a conference in israel on something completely different from cosmology i think harmonically it was and we were both giving talks on something different i was talking about energy and relativity or something and he was talking about something about cosmology inflation probably and and he said i want to write you something something else he showed me these pictures that shetland has shown and my reaction was okay nature has found some way to do it it wasn't a complete shock it was a pleasant surprise i would say i would say yes nature has found some non-local way of assembling these things or else maybe it's not quite as accurate as they think oh you could see these pictures were pretty good and and the destruction patterns were amazing yeah i wondered whether you know you nature could build up locally find an obstruction but then some due to some fluctuation overcome that obstruction and it just came and and and with enough random trials you'd you'd you'd appear to have something that's not local but i don't see i think when i say it's a mystery i think it's a mystery still not resolved because i think it has to do with the collapse of the wave function okay well that's okay when you go from like my dog didn't like that [Laughter] fluid or gas to a rigid thing like a crystal it's got to have collapsed because the crystal really does know where its atoms are whereas the fluid or the gas these states is going to be some thing where the atoms are not localized and so there is a reduction of the state involved in making a muscle okay well that's that's an interesting idea it's it's i i was gonna i've tried to think of the subjects i want to avoid and collapse the wave function was one um that in our discussion today from now on yeah no no no no because we could go on about it but i i wanted to think about things i guess that i think are a little more concrete or at least well maybe we'll get there in a different context because it may be relevant when we come to the cosmology aspects coming back let's get to i you know as i say i find this fascinating and i kind of wanted to divide this two hours or so into into into two parts and so i want to move now generally from this fascination with puzzles and mathematics and and and i knew of your sort of emerging interest in in cosmology although i didn't realize it had begun so early i thought maybe it began when you're you know later and when shama had begun and it was so i didn't realize it was so early yeah but what but what brought you into and i was going to ask about twisters but i think i'm going to leave it there i'm going to because we're going on maybe we'll come back to it but i was going to ask where twitter's because i was i think the first lecture by the way i ever heard from you as a student when i was in boston at mit or maybe when i was at harvard was on twisters and i didn't i admit i didn't understand most of it at the time um but any and i do remember vividly wondering whether uh i i was very interested in mathematical physics at that time i i i just removed out of that later on but always i was fascinated but well what new mathematics when every time you discover some new mathematics what can it relate to physics and i think that's why i was fascinated by twisters but but um when you got involved in physics your focus went to general relativity and i'm wondering you know you obviously had the quantum mechanics experience with dirac but whether whether there was it was the peculiar aspect of the sort of geometry geometrics and and ultimately topology of general relativity that attracted you your interest right off the off the bat was that it or was it physics problems that attracted your interest well it was the easiest route into physics in the sense that the geometry was directly there yeah okay but let me give you you see unfortunately all these things are little stories which are quite com well let me give you this story because it's fine look believe me that i want to hear the stories no more no apologies would be interested in algebraic geometry and all that stuff and hodges lectures and why they were all over the place and could i make sense of them and i developed this notation which was a this geometrical notation for tensors basically so i draw rather than trying to find where this little a was the same as the little a down there and you need micro see them you just draw a line joining them you see so i said no these are just pictures these are where you have diagrams and pictures and i had this way of representing symmetries and skew symmetries and i learned a lot about that and the problem that hardships suggested which incidentally i never solved except showing that it had no solution well that's that's pretty hard to believe when i told him at first there was no solution in terms of polynomials you have to take rational functions or something no that was that that was a big he didn't believe me for a long time it was quite striking but anyway now that's probably why he moved me over to todd after the first year ah because he didn't i think he didn't believe me and i only i knew i learned she didn't believe me only in my third years third year because he eventually come around yes because he repeated the calculation i remember the expression on his face and he said you were right all the time this is why he moved me on to try i don't know if it made much difference to me because i didn't click with tom any more than i did with hodge really but it was important to me because in order to cope with this problem which was very complicated when you translate it it had to be tensors that's the way you look at it and the and the way you do it it tends to be very complicated but so you had to have this complicated notation that senses and so a lot of what i did in that thesis of mine which is really not so much to do with that it was a horrible notation i learned the right notation later on i should have done it that way it was a horrible way of doing it so my thesis is not to be recommended anybody's breathe but um but i did this this problem of hardships where you could solve it in a certain way but i'm sure there was no polynomial solution which was a bit of a shame because it looks efficient it's playing with the indices enjoying them so on but in order to play with these things i developed this graphical notation and i realized this was sort of an abstract idea you could develop tensor ideas which were not realizable in terms of components so the i had these abstract tenses and the one i liked the best was the minus two dimensional tenses they had the nicest in the tree and they were beautiful and you could relate them to the four color problem and things like that which one but anyway the it wasn't so much about the minus two dimensions but the idea that you could have them to use abstract things and then i learned about physics i was interested in physics and i talked to dennis about them and the dirac equation this wonderful equation for the electron how do these things work well they involve spinners what about the spinners i mean how can you have a spinner which seems to be a square root of a vector that means you take one of these lines and you take a razor blade and split it down and cure there is a curious story here which i don't know the answer to the iraq's lectures had two parts there was this quantum mechanics one quantum mechanics two i went to quantum mechanics one where when i was undergraduate and by trying to fit things together later on i think it must have been in my first year as a research fellow did i say undergraduate when i was a graduate yeah you did say graduate when i was a research fellow and that must have been when i went to dirac's quantum mechanics too oh okay in his course he gave he deviated from his normal course and he gave a week's lecture on two component spinners i had struggling been struggling with the book that dennis had recommended to me which was courson's book totally unreadable full of information absolutely full of information but utterly unreadable i couldn't make sense of it at all i couldn't understand what spinners were for to offer that the iraq's course beautiful made it absolutely clear to me i could see what they were doing and what they were and the two components minutes and the rack had a beautiful paper on two spinners where he looked at all the different spins rather than going to all the different cases one after the other you do the whole thing all at once it was it was a beautiful paper which influenced me very much and so i thought two components spinners my gosh that's that's something i think i understand that then there was the lecture given by david finkelstein in london when we were both in cambridge i was my first sec second year i think as a as a research fellow as a research fellow at cambridge and dennis said there's this lecture given by david finkelstein in london uh i think it would be interesting to go to it so he went to this lecture this was on how you could go through the schwarzschil so-called singularity yeah and using these coordinates that i think we'll find we now call them the eddington tinklestone coordinates because you're getting to use them unknowingly at some early time but i've learned you could go through this so-called horizon i mean so-called singularity and it was really only horizon so i learned about that and i was amazed by this and i remember having discussion with david finkelsten afterwards where he pointed out we swapped subjects i went into general relative general relativity and he went into combinatorial physics i got the big better deal out of that i think yeah well it worked it was it turned out to be good for you let's put it that way anyway he i talked to him about spin networks you see which would you i see and then he taught me about um like the singularities being not not at r equals 2m at all so i came away from this and seeing there's still a singularity at the middle and i'd wondered look you got rid of a singularity seeming at one place but you can't you've got it pushed into the middle now is there a general theorem which would tell you you can't you know the singularities i had no idea how you i said how on earth would i prove it i have the foggiest idea what would i know that most people don't know about general relativity i've got an idea how about two component spinners i try and see whether two component spin is any use in general relativity so i did i looked at that and i think it's amazing this very complicated conformal tensor which is the evolve answer becomes this very beautiful totally symmetrical object which i understood perfectly because it was only in two dimensions and it's complex dimensions you can factorize every polynomial in homogeneous modern area and this is a wonderful subject and it was that that took me into general relativity in a serious way oh okay now although okay that's actually heard of that before the i want to put in perspective especially for younger people don't realize it i mean this fickleston result was part of an emerging people don't understand how misunderstood black holes were at the time i mean that people thought indeed that this that what was now we think of as event horizon which isn't if you pass through it you wouldn't know you passed through it to some extent and and and but it was something singular and represented some some real issue wasn't there but people also of course partly what amazed me partly until you were there before me because i was alive then but not a physicist but didn't really appreciate that black holes were inevitable at all and and i had heard that wheeler sort of got you interested and i think wheeler's wheeler is a i who i happen to meet when i was young and had influence on me but he he had a remarkable influence on a lot of people but but it was uh almost ironic i had heard that wheeler got you interested in this question um and it and again for historical perspective as i've heard you point out but people should know that this question of whether black holes were inevitable not mathematically but physically was an open question that had been dealt with and people had constantly especially einstein had constantly felt it couldn't be because there was something pathological about them and even when and einstein constantly uh didn't believe the results that were showing the opposite for right sort of beginning with chandrasekhar but then with oppenheimer and snyder in 1939 which in some sense should have convinced people um it was and that was 1939 but my understanding was wheeler wasn't was a hold out right through till perhaps it was your work that trained turned him around but he was a hold out right till the mid 60s although ironically he was the person who we is often credited with giving the name black hole to black holes he came around the opposite way and became a a cheerleader for black holes and so i wonder if you could talk about a little bit about whaler's influence on your thinking at the time or maybe maybe you'd already well there's two things i want to address one was his influence versus sort of what you just talked about finkelstein and then the other one which is so important to real for people to realize not just that our picture of black holes as being inevitable was not at all the conventional wisdom in the 50s and right up until the 60s but then also to do to do you justice the the significance of of of penrose diagrams which in in general relativity at least are as ubiquitous as feynman diagrams are in my opinion in quantum field theory namely they just change the way people picture things allowing you to picture things in a way you couldn't before and i wanted to ask you you said that they were there but you know these conformal diagrams were always in your head so those are two questions i've con you know i've convoluted them but what was wheeler's influence on you in terms of thinking about what would eventually lead to the singularity theorems and were the the pictures that ultimately gave you you you thought about things globally in a way that people hadn't been thinking about general relativity before you in in terms of these conformal diagrams or or penrose diagrams and had you been thinking about them a long time before as well so if we can go to those two questions i'd love to follow up on that okay let's talk about the conformal diagrams okay you see it takes us back to syracuse you see i go and i was in princeton you talked about wheel and he also influenced me distinctly i went to i think i was i gave up my third year of a fellowship in cambridge to to go to the us primarily princeton to work with wheeler on a nato fellowship the nato fellowship was a two-year fellowship and i went we see it was partly i guess there was some complication about my wife being my wife to be being american and all that yeah okay which i think i won't go to that all that but it was a big mistake too whatever because they have too many implications and if you change one of them it changes everything yeah yeah it doesn't make any sense yeah but anyway one of the reasons for going there was because uh my wife to be at that point was america but that i don't know how important that was i also was interested in working with wheeler because he was interested in crazy ideas yes that wheeler was definitely interested in crazy ideas and i wrote to him a letter full of my crazy ideas probably very stupid for wheeler was all right but he apparently was as i learned later received this letter and he couldn't make a tale of it and you gave it to charles misner charlie misner to see is this chapter completely natural doesn't make any sense and i think charlie business said look this makes a lot of sense i can't i can't i don't know if that's fabrication if the story was correct or not but there was something of that was whether it was i think it must have been childhood um martial was an influence on me in interesting ways but uh but uh yeah there were crazy things in that paper which was something that was still crazy but uh well you still like crazy ideas and we'll get to some of them that i think are kind of crazy but we'll get there yeah that's true now i have to give up on some of this but some of them turned out to be right he's just curious yeah yeah but anyway um the wheel of part of it was to get interested in gravitational collapse and uh mistakes of matter which you could have which were very concentrated there was a limit to what you could do and seiko and all these things uh and the open house did you did you know about oppenheimer snyder or i think my master's learnt it during that period in princeton exactly when i picked up on it i'm not totally sure but i think again let me let me just step back for listeners uh so the the point was that you know the people had wondered whether these this ultimate you know stars can collapse to white dwarfs but then after a certain level they can't they appear nothing appears to be able to stop them and in some sense that's what chandrasekhar had shown but there were big ques but everyone felt something had to stop him physics couldn't be that crazy and uh what oppenheimer and schneider showed in 39 just before the the war when oppenheimer got involved with other things um was that if you took a a very special case spherically symmetric collapse that under reasonable conditions which they thought were reasonable if the matter had a certain kind of form which was called pressureless and that it would that a black what we would now call a black hole was inevitable and um and then the question was was it only inevitable because of the simplifications they had made and it took a long time i mean it took i guess 25 years before anyone namely you ultimately resolved that problem and so that problem had been around for a while one people wondered whether that's nice and that's cute but maybe there's a way out of it because things aren't really spherically symmetric and there'll be all sorts of complexity and i'm sure that that led wheeler to not believe in the oppenheimer snyder thing and i don't and maybe he he he expressed those concerns to you when you were talking to him i don't know yes now let's just think you see the time we're talking about is is 1964. 64. i was back in in england and i was in burkback college now you wanted to talk about the the conformal diagrams but that didn't have much of a role at this stage except it did in a certain sense which i could explain perhaps but it's true what was more important in all this was the discovery of quasars there will be signals coming in from the deep universe radio signals which seem to indicate there are objects out there which were extremely energetic producing enormous amounts of energy more much more than the entire output of a galaxy you would need to have more than but yet these objects the variations in the intensity or whatever it was were of such abruptness let's say they varied in such a small time scale that if these were coherent bodies and since it was the whole thing that was varying somehow they had to be no larger than the solar system because you had to think of how long would light take to propagate from one side to the other exactly they couldn't be that big and still be coherent to the level of getting these these variations which were seen so there was a lot of discussion and people were very excited about this and fred hoyle i remember fred hoyle and and uh and uh what's this oh what was this collaboration i should remember his name there was a famous famous paper by burbee at the one who actually got the nobel prize oh yeah yeah okay i was going to say was what's his name yeah yeah yeah yeah yeah um i would just in my time i was going to say the guy who actually won the nobel prize and for some reason the other guys especially hoyle missed out which it seemed kind of crazy but um oh what's his name isn't that awful i know him but anyway i know that forgetting somebody's name is infectious yeah yeah absolutely okay in any case the unknown nobel prize winner follow willie fowler thank you got it before me okay anyway yes that's right and um was i going to try to say here we have we both got distracted they were worrying about what else could could there be structures so big that they were down at their fortunate radius saw the size that's what they seemed to be and there was a lot of confusion about what that meant and there was also a lot of confusion about whether the redshift was real was it really the distance they were was this because these bodies were taking part in the expansion of the universe and therefore extraordinarily distant and therefore these signals really were as strong as people thought or were they a lot closer and it was really a gravitational redshift instead or something else some other feature and there was a lot of discussion about that but anyway it was sort of in the air that bodies could be out there of this sort of science getting down to their schwarzschild's radius scale which was i suppose what got me interested what got what got wheeler interested he was very excited about this and what would happen and i think as you say there was this belief that the the oppenheimer schneider model was unrealistic for the two reasons you mentioned one is everything was falling exactly focused at the center secondly they were what was called dust there was no pressure and therefore the nothing to stop them so why if there's nothing to stop them focus at the center obviously you are going to get an infinite density and therefore a singularity but it's clearly artificial because they went the closer they got to the middle they're more slight more that slight deviations would mean they weren't all focused towards each other they would swish around and maybe pressure would do make them swish more and they would swish around and come back swirling out again this point of view picture was confirmed in quotes by the paper by liscious and kalanicos these two russians who had apparently shown that in the generic case you would not get singularities so this was the background i had to think about now for some reason i wasn't very convinced by oppenheimer schneider i looked at the paper i did not notice that there was a mistake in the paper which there which was a it was corrected later i suppose by belinsky i hadn't noticed a mistake i didn't look like oh no you're not talking about yourself you mean you mean uh lift shifts and which i did not find convincing i thought the techniques they were using were taking too much making too too many assumptions which might not be right there was something that was not right but that was different from what i was worrying about it wasn't that they were let me just ask it wasn't that they were thinking locally and you were thinking globally in any way i mean it wasn't they were focusing on yeah but the question is the one question is whether you're allowed to think locally in this problem oh okay and i think that one of the things that worried me whether locally thinking was and i'd certainly was like when i said walking in the woods so we had a nice woods live live right where i lived and i used to walk in the woods to try and get inspiration i remember trying to think what it was like falling inside this entity and could a local infinite divergence produce a problem if there was going to be a problem it had to be a non-local problem that was the sort of view i'd formulated okay i didn't know what it was but then i'd had this paper you see there is a relevance to the conformal boundaries uh which was sort of incidental because i had been writing a paper which involved that idea which i'd probably put into the royal society more or less simultaneously i think i put it a little earlier than the other paper but in this paper i had to use the fact that infinity had to have a spherical structure it had to be like a sphere like the sphere you see when you look at it or could it be something more complicated and part of the argument depended on it being spherical so i thought well and any sensible person would assume this and who cares just write the paper and send it in i worried about it i thought can one show that it had to be spherical for some reason and so i worked out what do i know about general structures i didn't say i don't know much but i looked about i looked at the boundary of of the future at a point i think that was what i was looking at and so i began to get a little bit used to what the boundaries of futures looked like and they had certain properties and so i had this at the background of my mind i knew certain properties that boundaries of futures have grown when i say a future i mean you'll look at the all take some regions in space time look at all the points that can be reached not going faster than light from that initial region and look at the boundary of that region what is its structure what curious features does it have so i got a bit of an understanding of that for this separate reason which was purely purely incidental accidental too okay now one time this is a little bit later i was walking with ivor robinson like i told this story to many people before but let me tell you it again he was visiting he was an englishman very english but the americans loved him because he had this wonderful english way of speaking which is so different from the way they spoken it was poetic and musical and he really really did have a way with works with nobody else that i knew did have we had away with words and we were walking along like in malet street or something near where i worked college and he was talking to me about this he had away with words as i say and also um didn't want to be interrupted normally okay so he was talking to me we come to this side road which we have to cross as we cross the road the conversation stops we get to the other side the conversation resumes after after a while he has to go off somewhere and i go to my office in birkbeck college and i have this strange feeling of elation why on earth do i have this feeling of relation so i go through all the things that happened to me during the day what i have for breakfast when i've got walking through the woods and i'll decide where to get in the past and i get on the right bus and so forth and then i get to crossing the street and the idea comes back to me which was evidently the idea of a trapped surface this was how you would use the knowledge i had of boundaries of futures and see that there was something odd about the boundary of this notion of what i called a trapped surface the boundary of this trapped surface would have to be compact because of the things i knew about i'm not quite sure how many of them i didn't know about at that time but i realized that this was something i should follow up on when i got back into my office i sketched out the argument which became the argument in in the paper which got the nobel prize yeah yeah yeah the trap surfaces which is which is a global way of thinking about what's inevitable but it was the idea don't don't write down equations you see what did people do about generative universities either they would look at exact solutions and iva was a real expert you know you have the little tricks to show you how exact and roy kerr yeah sure in the cursed solution and ken newman in looking at various tricks like this you know experts finding exact solutions now i wasn't um i was certainly not an expert on computers and that's the other thing people they put it on a computer in those days there's no hope in any case you might say there's no hope because when things parameters start to get very large you don't know why they're diverging maybe it's a computer problem and something to do with the code or what those and who knows if it's really singular yeah anyway i don't believe anybody has computed very far into a black hole that would be an interesting question well i'm dealing with those divergence i mean that's been a large part of the work and trying to understand gravitational waves is really is how to deal with those divergences near event horizons a lot of progress has been made of course but there's the gravitational waves you're looking at weak fields yeah yeah yeah without worry about the thing but the exact nature of the signal and the ringing you have to worry about you're taking your computer you have to go over many scales and that and and and looking and that's been a without that i think that that progress could have been made without those thoughts that's true well their computers have come extremely yeah no i completely agree with that that's right but in it for the actual singularity situation is not so clear yeah okay and uh but what you could show with these global arguments and yes it had to be singular although i've always kicked myself for not using in my paper what charlie misner pointed out to me later that there's a much the most complicated part of the art which i sort of skirted over in in the paper um can be replaced by a much simpler argument which was i mean i knew it i should have used it already but charlie pointed out to me later well did you did the but the the the traps but already thinking of these cones of the of of the sort of uh critical yes yeah were critical for trapped terrorism but you had been thinking about them for a while or did that or uh or did that just come in the context of the trap surfaces now they have to back up a bit to the conformal diagrams yeah yeah yeah you see in my two-year nato fellowship i decided that okay there was a lot going on in princeton and i learned a lot of gr stuff but it was one particular perspective and there was also a lot going on syracuse and i felt that i really needed to be president of what was going on in syracuse and so for half my last year i went actually to syracuse actually i spent on cornell as well at first syracuse and there uh i got to know ted newman much better i had known him a bit before but that's we collaborated together and started working on the spin coefficient notation and things like that but also as an important uh angie troutman visited there from poland another well-known and he gave a talk on the asymptotic properties of gravitational fields and i think in particular the fact that the leading term had to be null which was i think he was the first i think to show that and he gave a lecture which was an interesting lecture but it was full of complicated calculations and i thought oh i can't cope with this maybe there's another way of doing all this stuff and i thought how about inversions i don't quite know what made me think of that and i knew that you could turn the well the riemann sphere you get out of the complex plane and things like that and can you make infinity and define that by inverting and i started talking to engelbert shooking with who was my roommate in syracuse he was a big influence on me in two distinct facts practiced one was i tried to talk about conformal transmitting i did think about you know inversions for schweinsteiger and i got put off because you invert and the point is insanity is singular it doesn't work oh dear what a pity but i did in the meantime talk to engelbert about conformal transformations and he told me that maxwell's equations would conform the invariant i think he referred me to a paper which did it only in this special case where you were tweaking versions and things like that but i did it a different way and i realized that it's confronting event in the strong way that you can have a conformal factor which is variable yeah again for the listeners conformal advances some sense allows you to scale scale lengths arbitrarily in different ways uh over space and and things look the same i mean to to be very crude about it to be more precise have a look at airships circle nets okay yeah okay very beautiful examples of conformal maps yeah yeah he's got a lot of other ones which you can form but the circle limits are the most clear you just look at the age and there you can see infinity has been into a form into a finite boundary i was trying to do that with in in the space-like sense looking at special sections um one of the visitors at syracuse if i have it right was ray sax at the time he was in the army i think he had to join the army the us army i suppose i can't remember i think he he learned how to play go out there i remember he must have been critical he beat he was able to beat me a girl impressed me [Laughter] what was the other thing he did was he had this wonderful result but you didn't just have the leading term was now according to trump but if you look at not the one over r but the one over r squared then you have three principles you see this is something i'd learnt from my understanding with spinners and that you could look at the vile curvature that's that part of your curvature which describes gravity you remove the richie part which is the mass part the pure part is represented by the vile conformal collision and it's got four principal null directions they're pointing on the right so you can classify them by how they join how they coincide in general they're separate in the now part when what 12 had shown was the leading term out of infinity they all come together what ray sax had shown is if you come in from infinity they peel off one after the other that's to say one over r one over r squared went over our cube one over after the fourth uh went right to the fifth and it was a very beautiful result yeah very striking and beautiful about that that's racist his work with bondi you see bondi had bondi had looked at the axisymmetric case of radiating spaces and had an inklings as to how the energy was described and how it could be the radiation could carry energy away trauma had some understanding of this but not in the full way that bonding described but it was axi-symmetric you had to assume that there was a symmetry around an axis sax generalizes so you could remove the symmetry altogether and he had this result about the curvature the peeling off prophet t used corner i was very impressed with this i remember being at home back in england in stanmore and where i used to live in the basement where i had my private uh used to be meant to be a garage but it was badly designed nobody could get into the garage so but i use it as my study having drilled through the uh through the um attic through the ceiling which was made of this poisonous substance asbestos knowledge that this was that very dangerous that you should nowhere drool through it or hacksaw through it which i did and i made a little trapdoor up into the house with my way of isolating myself from what was going on there which was a good thing to do um [Music] anyway thinking i had my nice big blackboard down there and if the thought came to me i've been going the wrong way i've been going out in a spatial direction if you go in a null direction other than the like cone it doesn't go infinity well you see what it the thing is that things go as a different power of of the radius one over r and one over one over r squared and whenever there are and i hadn't realized it was this different power and that made everything finite instead of instrument and if your viral curvatures finalizes the tendency and you look at the different components and they peel off that's exactly the premium property it's just saying that the curvature is finite on the boundary and so i began to realize looking at these conformal boundaries was a fruitful thing to do and then it's just it's funny how you know and well i guess it's the way it is yeah the right tools randomly from different places just happened to come together at the right time that's right and and ultimately produced something which changed changed and and and by the way and by the way to be fair though wasn't just that they did just not just change that paper as i said before they changed things i i like the quote from kip thorne who said that you know you revolutionize the tools of and i i certainly you know thinking in terms of what i call penrose diagrams and what most people do now um do change the way you think i mean you know feynman pointed out you can think about thing the same thing many different ways and sometimes for certain problems thinking about it one way is more fruitful and for other problems thinking about it one way is is more fruitful and and in the case of thinking about general principles that don't rely on specific things like spherical symmetry thinking and these conformal pictures gives you well certainly either way both for black holes and and and we'll now finally get to the other aspect of cosmology thinking about far future and far past conformal tools are very useful and and obviously they drive your thinking right now before i i do get i want to get to your the modern thinking of the far future and far past that you're thinking about which i will say in advance i i find i don't think are right but but but but at least they don't smell right to me but in any case i i do i want to leave that to near the end because i'm fascinated by these things and i didn't want this to be sort of back and forth about whether we agree or disagree about certain things but before we get there i'm intrigued by the fact that of course the the the penrose singularity theorem late very shortly afterwards and i don't want to spend a lot of time because people focus on stephen hawking a lot but um but you know it was it's sort of almost obvious that what that there's another important singularity in in in the world and and it's not just in black holes it's in principle at the beginning of the universe and i was surprised in a way that you didn't um think or at least incorporate that in the original paper if unless i'm maybe there was an offhand remark about it um but i'm wondering what why you didn't and what uh and it was just you were so focused on that particular problem or or hadn't started to think about other aspects of cosmology yet at that point i think there was the feeling i had that once having shown that the singularities were general were generic in collapse they would clearly be generic in a big bang universe so you just saw it was so obvious it wasn't worth mentioning is that maybe i'm a that's a way of putting it i'm not quite sure i thought my thought processes were quite like that he's sort of like that but you see stephen hawking picked up on this in a serious way i had the i the story of course the movie is his claims that i gave this talk and uh movies are movies he was present at this talk which he wasn't the the lecturer i gave in london i did give a lecture at king's college this was in late in 1964 when i had the argument i i hadn't got the publication i don't know whether i'd written the paper at that point yet i'm not sure i would remember being very pleased not that stephen hawking was there because he wasn't i didn't know anything about steven but but jl singh was there john yeah the general relativist which book i first learned general relativity from i was so pleased he was there because he looked at jim dean relatively in this geometrical way and i that's i i loved it so he was the person from whom i learnt a lot from gr absolutely yes and anyway that's not very relevant but stephen had picked up on this and and eventually pushed it dennis persuaded me to give a repeat so i did give her a repeat early in 1965 and stephen hawking was present at that lecture and more importantly i had a private session with him and george ellis see stephen and george were trying to do something much less general in thinking and i'm not sure whether brandon carter was there he said it was part of the story but um steve picked up on it very quickly and applied actually my actual theorem two cosmological situations so his first paper was a piece red letters paper which reversed about the time and you had to the point was that i needed an assumption that the initial surface was non-compact there was this conflict between the non-compact initial surface and the compactness of the boundary of the future of the trapped surface and that that's where the singularity theorem comes in you need that conflict and if you don't have the compactness the non-compactness of the initial state then you you can't prove the theorem so if you had a universe that was closed then how do you do it but stephen used it in a way in reverse time direction in a way i hadn't thought of that this was looking at the microwave background early stages of the universe it did become the basis of our much much later joint paper that we wrote where the he he then developed the ideas well with discussions with me from time to time but they were primarily with people in cambridge brandon i think was a big factor correcting mistakes and things like that even was a little bit sloppy in his arguments but these were mistakes of the first kind rather than mistakes of the second kind by the first kind i mean those that you just changed the argument a little bit and it comes correct those are the second kind of ones that completely wreck the whole thing fortunately there were mistakes of the first kind but they were corrected and and this this story sort of went on even i was actually his thesis which had mistakes and i think i found about five of them in the thesis and i was going to point them out and he'd found them all by the time he was attention uh examination yep no okay my comments were fun i mean he he certainly developed these things very much i just didn't bother i thought i was probably working on twister theory so i wonder i want to work with ideas and i'll twist it there and okay singularity's a generic we know that okay it would be nice to have a proper theorem for big bang but um which is eventually this paper we had yeah so stephen pushed it but you your interest was as you say a little bit elsewhere in fact it's interesting because right after this i have the question about twisters but i but that's the question i'm not going to talk about because i want to get i want to get yeah uh um uh because it was clear that you were interested in them at the time but any case but but but i wanna so so stephen had taken it and pushed it back to the to the key question of of uh of uh of the existence of a singularity yes in the big bang and the anon of non-avoidance of such the fact that that classic the fact that classically you there was a thing there is no way of avoiding a singularity uh classically in in a big bang and and of course the question many of us have in some sense the same question people might have had about a black hole was well you know can quantum mechanics get around that and and and i think there are different viewpoints on that um i'm of the type that prop i suspect that the answer is yes and that quantum gravity will allow us to get around it but but this leads to your fascination with cosmology both in the far future and the far past which brings us more to the present and you have been one of the most um well most of one of the most well-known and to some extent vocal holdouts against what has been for become for most people the standard picture of cosmology which involves this thing called inflation which which um which says which you know again i'm not going to we don't have neither the time nor the probably incarnation to do a whole show on inflation right now but but which basically says that the standard big bank model has a bunch of paradoxes and there are and what is fascinating for me about inflation and always has been um is that is that um it involves physics well below the plank scale involves the kind of physics that you don't have to speculate about oh well maybe maybe this miracle happens or that miracle happens in particle physics it's a natural phenomenon that there are phase transitions as we would call them now in the universe and under certain fairly general conditions a phase transition will will inevitably happen that will cause the universe to expand dramatically and and exponentially in general and that if that happens for some short period it will resolve a number of the paradoxes in fact of of uh of the standard model cosmology and moreover it was later understood after alan guth had first recognized that from the three mer what were then the three miracles of inflation but people don't often talk about monopoles anymore but there were there are a bunch of paradoxes why the universe appeared to be so flat um uh why in some sense there was so much entropy and and and also why um these objects called magnetic monopoles didn't exist but but later on there was a another result which in some ways has almost become more important is that it allowed you a meth a a calculational mechanism to say that the fluctuations we see in the universe a which are very small back in could were calculable and could be due to nothing other than quantum mechanics so a really in my opinion a beautiful result um not in your opinion i think but but um and so the but the great thing is it doesn't rely on going all the way back to t equals zero in some sense and i don't want to play up the analogy too greatly but i remember actually when alan was talking to you in the program i was watching he pointed out that inflation isn't a theory for the origin of the universe it's a theory for what happened after the universal origin it reminded me of the statement that darwin once made you know or that people that evolution is not a theory of the origin of life it's the theory of what happens after life the hard part is what gets life going and the easy part is natural selection in a sense but um and and i tend to think of that way too inflation happily obviates that that burning question about what happens at t equals zero which is a question that obviously is intrigued you more and you've you'd and and your argument against inflation which is really what i want to get to there are a few of them is that somehow it requires very special conditions in the early universe that it's not as generic as it seems um i think you would say to be fair to and and that it requires and you focus on this on on what's on entropy which is a a subtle and beautiful concept so subtle that the person who developed entropy killed himself because we wouldn't believe it in some sense boltzmann um but uh but um and then later on um um uh uh paul um earnfest killed himself also who was a who was a who was a um a disciple of boltzmann so it's had a long history yeah in fact one of my favorite lines in a book i think by um goldstein uh uh is a book and i forget who but it who it's a book on on on condensed matter physics and it talks about entropy and it says so noble history boltzmann did this he killed himself aaron fess thought about this he killed himself now it's our turn to think about it and it's i love that line but um uh but you're you you know your point is that somehow it requires extremely low entropy low low a and entropy in some sense one can think of as as um disorder it requires a very low disorder in the gravitational field early on or another way of saying it is it requires some smooth some smoothness in the universe that everything that you think about when you think about collapse um defies your in understanding of what collapse of what the early universe should look like which you think should be incredibly messy because if you think of the final stage of collapse it's it's incredibly messy there's curvature there's all sorts of garbage and and how can an early universe be smooth enough to have inflation happen so if i have i capitalized your your concern accurately that's accurate it's not put us quite as forcefully well i wouldn't expect as i would put it yeah okay you see it's been a conundrum which has worried me for a long time and for some reason i look around and nobody else seems to be worried about it but yet to me it's been the huge conundrum i remember this is i don't know i shouldn't tell that story okay well let's let's okay let's skip that one then um unless you really want to it's your it's your it's one of my fondment stories oh well then since i wrote a book on feinman i'm always happy to hear about fyman's story so send me my book on fineman sometimes i'm very happy with that okay now i have about four finalists sorry i won't tell you all of them but this one i have to tell backwards because i learnt later i was giving a talk in caltech about the second law of thermodynamics and cosmology and i can't remember what the title was or something was bringing those topics together and i learned later but feynman had seen the notice about this lecture and he had told some colleague of his oh i'm going to go to this lecture and i'm going to heckle i'm going to heckle this guy okay if you like to do yeah absolutely so this is the beginning of the story okay i start giving my talk and i come to what talks about in a minute it's not getting my talk and i come to a certain point where somebody this room is not all that full but there's firemen over here and someone way behind him with somebody else this person behind fire i assume is some nobel prize winner because think it's full of them and he started hector not finement he's done heckle fireman turned around you said you shut up listen to what the guys say perfect the point i was making which i haven't really appreciated up to that point see people talk about the microwave background curve and there's a beautiful curve and they put the error bars for the temperature being yeah and they're magnified by a factor of five hundred thousand yeah they're really hugging the curve within the incline let me point out i think it's still true that the best black body curve in nature is it's never been reproduced on earth as as as um as faithfully as the universe does i don't think we've ever produced a black body which is the canonical picture of an object at a finite temperature in quantum mechanics and i don't think it's ever been reproduced in the laboratory on earth as as effectively as the universe did it that's interesting yes i see i haven't quite realized that but anyway you see this absolutely beautiful plant curve what does that tell you it tells you you're looking at thermal equilibrium yes somebody called it there you go back and back and back in time and back and back and back into the earliest thing you actually see maximum entropy surely the second law of thermodynamics says it should be small and it's such an obvious obvious obvious point why don't people talk about it and stress it well you know what let me let me give you the count well okay let me give you my counter argument coming at it relatively late first of all um why would one expect otherwise this time i sent my my i if i come thinking about it as a particle physicist which is originally my training although my thesis could probably well maybe the problem although my thesis relates to something that i want to get to in a second which i think is another argument about why the early universe it's not a problem at all about generating entropy but i mean reaction rates are fast compared to the expansion rate you would expect to be in thermal equilibrium it's the natural oh the it's the rare violations from thermal equilibrium that have caused interesting things to happen in the universe which is why you and i are here having this conversation is those rare violations that have allowed us to happen but thermal equilibrium should be the norm in a sense if as long as interactions are fast compared to expansion yes but our universe is not the norm we've got we've got an entropy which is not as it's maximum well so where does it go it starts from the top you know what was it i've reached the top and yeah oh there's a line yes well it's but yeah but we you know we're just going to go to another maximum that's larger and you see there's a mistake in thinking that the expansion of the universe is going to make it bigger there's more entropy room financially as the universe gets bigger that's the theory no as as gravity begins to be partly because of negative specific heat as gravity begins to operate effectively i mean and become black holes so i mean we're already both on the same wave okay go on i won't interrupt no it's gravity that's right i mean gravity was not thermalized yeah gravity wasn't thermal but again okay but why would you expect it to be gravity is the weakest force in nature why should it be thermalized until late in the universe why should you expect it it's it's irrelevant no no no no it has to start off low yeah it has to start off a little bit but but the point is there be a universe in which the gregories of freedom and gravity were not excited yeah but but but okay look let but let's say let's get to inflation i mean the point is that you don't need it can be you can have a crazy universe but as long as isn't as long as there's some small enough region where it isn't that crazy which is kind of inevitable in in in ultimately um you're going to get inflation and one point that i didn't see you emphasize in in when i saw you talk with alan which i think is really important when it comes to calculating probabilities because i know you've calculated how improbable it is to to get such a small reason but exponentials are wonderful and the point about inflation is not that it'll just inflate long enough to create a universe that we see and why isn't it half as big and or a quarter of a big but it doesn't go away the hard part about inflation is getting it to stop and therefore if you have a small region that's going to inflate inevitably because of that exponential expansion which is in general eternal because it can't percolate if you find yourself no matter how small it is because exponentials are exponentials you're inevitably if you look at space space is going to be dominated by regions that have inflated because of the fact that that event that's the argument i don't understand why alan didn't bring up with you inevitably like it doesn't work why well i mean i just might and it doesn't work i mean i don't know why i i usually i think i the strongest argument is probably in fashion faith and fantasy reality and i do talk about this and i can't see why you don't have an inflation which maybe okay give us our galaxy if you like why do we need all those other ones way over there i mean we don't need them do we i mean maybe they what's what's the use of the of the andromeda galaxy to us well it could it could it many things i suppose it could be that we might be an outlier and therefore you need lots of them in order to get in order to get one that that that that varies enough to be us i mean that you know there's a hundred billion of them and that allows for this god has made all these useless universes out there not doing anything for the natural selection which evolves on the earth okay give the whole galaxy if you like i don't really think we need most of it it has to be fairly calm probably you need most of it in order to get the stars initially in order to get the iron up in order to get the heavy elements up enough to have enough supernovae to get past the ticket to get enough stuff for you and me inflation is is terribly wasteful you see it's trying to produce all this entire universe it's really an anti-anthropic argument so maybe i shouldn't go in trying to try well i mean but i mean but the point is that wasteful is in the eye the beholder in some sense because you might say that about the human genome too there's a lot of events but but the point is that the universe doesn't care whether what's wasteful or not and it's not trying the purpose of the universe isn't to have life there's no purpose and and so it's so if if it's wasteful related to the things that you care about who cares that's what you care about but the universe doesn't give a damn that's misrepresenting what i'm trying to say okay sorry good probably because i misrepresented this oh okay good because i purposely don't want to misrepresent you okay now i think it's it's somehow using an argument of this sort to i mean you say that that with the reason uh from where we started now the reason that the entropy was low or that the lens of the entropy is low in gravity was because it needed to be in a place where for us to be around you needed to have a part of the universe of that nature well i guess i guess i guess i don't think of it i think that too teleological i guess i'm thinking the point is phys things will anything that can happen that can happen will happen that's a really important property in physics right anything that can especially in a universe that's old enough but but in general anything that can happen that isn't impossible is going to happen okay and so there will be a region that will inflate because inflation is kind of generic when it comes to thinking about the physics of the early universe and once it does space and i mean space well beyond our universe the multiverse if you want to call that if you ask where where is it likely to put your finger down it's going to be in a place that's inflated and maybe still inflating because once it happens everything else goes by the wayside it just becomes as cancer that if you want to think about it that that that goes on forever exponentially increasing regions of the universe in this false vacuum state and no matter what you do you can't get rid of it but why does it do it all globally in the whole universe rather than just locally because because of the uniform way it has to know exactly when to turn off well no no but that's the point it doesn't have to know exactly in terms of it in principle it never turns off locally it turns off locally it turns off but inflation's already done its business by that point and locally you get this hot big bang after inflation but inflation is still happening in most of what you would call the multiverse and it's kind of you can't get rid of it it's not a matter of of why is it there in some sense it's if once it happens it's it's like a cancer in a sense if you maybe maybe that's a good analogy for you because you probably think it's a cancerous idea but but uh but once it happens you're stuck but it shouldn't happen so uniformly global i think you see let's not i i don't know perhaps i shouldn't go into all this you see i'm worrying about the dissimilar dissimilarity between this picture and what happens in collapse yes i understand gravitational is absolutely different yeah and i've read it discussed i should say in your new book i mean i've read your new book in anticipation of this so and you talk about that in great detail um and and it's i work through your new book and so if people are interested they can look at that anyway go on so when you say my new book you mean fashion faith and fantasy well i don't know what the new book the one i forget the name of it now um is that what it is no i thought it was the one where you the somewhere you describe your new picture right cycles of time yes cycles of time isn't that the newest is there another one is it's not the newest i think you could be right yeah yeah yeah and that's i mean i wanted to look at the way you because i've always i try to do people justice especially when i'm going to talk to them on this and so i'd kind of dismissed ccc for some time because it just didn't smell right to me and i thought it's not fair so i wanted to read your book to to learn about it i went through in detail anyway good no no i'm glad to hear that because most people have never looked at the book well i i think you can't criticize well i mean i can criticize ideas offhand in my office without having without knowing what i'm talking about but generally i like to think that if i'm going to do it in a form like this i should at least i respect that point of view very much and i i appreciate that no i i think i mean it shouldn't the book needs rewriting yeah i think so but that's that's one of the three books i have to be writing now and how am i going to write three books all at once i i kind of sensed that you was core dump for you you wanted to get the ideas out and also because you were you the editors were afraid to say no no you really need to you really need to just say it another way and that's what my inception was but i well clearly it was it was not i don't think even these observations of the circles was present there was it no because that's right no i must there must have been something because they were in the little story there's the boy looking at the rings yeah yeah yeah there's there's discussion of the circles there must be some indication but the fact about them no nobody was believing a word of it at that time yeah and i think for some reason because because i don't think mahe had you couldn't trust well it's not quite clear what you could trust me you couldn't there's a lot of stuff i can't you know it's still true i think yes that's absolutely true and and have been ignored and still being ignored but then you see the polish group got in and they're found completely independently and doing a different method and all that and they see these things yeah and the question whether you see them and the weather i i don't want to get partly i don't want to get broiled in that debate you know whether you see these things you may think are remnants which i'm still not are con i'm still not convinced or generic for maybe what reasons we'll get to or and but even if they're there whether they're significant and they really differ from inflation there's debates about that and and it's i don't i'd rather avoid it right now i want to i want to go to the heart of the argument which is why one is driven to this you're right but the heart of the argument is not addressed foundation and the heart of the argument is that the singularities in collapse are utterly different from the big bang okay well let's go back and look at another argument i i gave one argument for why i think inflation is is so not only so generic but so overwhelming that you can't get away from it and it and it does what you need to do in a calf way but let's go back to another one which is you know classical singularities are nice but many of us well i'll speak for myself but i think it's fairly fairly common think that quantum effects you know you can't go all the way back to the singularity and and i'm actually i i actually i don't know if i said this in pub but i remember when i was a graduate when i was just got moved to harvard after being graduate student i actually did a calculation which i found out my alex for lincoln was doing at the same time um and i never published it at the time i was working with a friend in affleck and i thought okay well it's not worth publishing but but the idea that quantum mechanics can allow creation of universes in principle um is something of course i've written about i've written a whole book that you never saw nothing about this and i find it i find it inevitable and fascinating but um it's a way to create to avoid that question and obviate that question and say we don't have to go back to singularity quantum mechanics can create a universe with properties that are not that are that are not surprisingly um perhaps appropriate for the initial what you might call the initial state of our universe and and yeah i think you've gone back to a state you say that you haven't really quite gone back to the big bang you've gone up to some early stage before inflation has even started yeah you've i've gone back from literally what i would call nothing and the philosophers have debated whether it's really nothing but i think that's just semantics but no no universe no space time to suddenly creating a space time and if quantum if gravity is a quantum theory you will have space times that come spontaneously into existence that's should be since the since the variable the quantum variables are space and time if you're going to fluctuations you should have a fluctuation that creates a space time an unlikely one was that why is it such an unlikely one because you see in the big in the collapse you have these singularities and they seem to represent some kind of ends now and sure quantum gravity and i used to think like everybody else if quantum gravity comes in where it probably does what good does it do you i mean it doesn't let me let let me tell you what good it does you and i and i will allow you this is a chance for me to talk about my thesis and the physical review of letters that i've written on which may have a citation i'm not sure but um but i asked the same question and i here's an example i thought well look if you're going to spontaneously create stuff then it seems to me what you're going to spontaneously create is is a system that's much more likely and if i have small regions this and i'm going to spontaneously pop into that i'm not going to create something that's uniform i'm going to create a black hole surrounded by radiation because in fact the entropy is much larger right and and so therefore i suggested that if if if you created all these regions you'd have all these primordial black holes and they'd evaporate it was actually just before inflation was my way of creating a lot of entropy in the universe the white house well well no they can be black holes which will evaporate because because it turns out in a re interestingly enough if you know this if the region is small enough then a black hole will be in thermal equilibrium with the region it once it expands beyond a certain size the black hole will suddenly become unstable because if the volume is less i think if the black hole is more than two-thirds the size the volume i forget the number it turns out that specific heat being what it is the black hole more and as the black hole radiates more energy will go back in than out and so as the region expands only after it's a certain size will the black hole become unstable but anyway my point was it was a way to generate entropy and i and the inflation generates entropy beautifully so i don't see that you want to get rid of it the point is the entropy is so low no you want to drain you want to create entropy and huge amounts of entropy and matter so whatever is there in gravity seems irrelevant i mean the whole point about our universe is it's hot right and why is it hot and not cold that was the problem that particle physicists asked why do we live in universe with a billion photons for every every proton that seemed like a strange and crazy the media wasn't strange and crazy but it was a strange and crazy question i think that led most particle physicists to start thinking about cosmology why are we in a hot universe which from your point of view is saying so the puzzle for us is why is the entropy of matter so great not why is the entropy of gravity so low it's a different way that's a different argument yeah and that but but but but quantum mechanics seems to do that very well it ju and and it autumn and and and it automatically in some sense does it in a way that that that ensures that curvature is small where's the timeless imagery in any of this i don't see it i mean you've got this these horrible things which come up in black holes and we don't of course know detail what happens but it's so different from what our universe is like i mean to me it's just that we haven't got the right theory we're talking about the early universe in ways that we could talk about the remote universe where we get the wrong answer because the remote universe in the remote future is completely different it isn't like this at all there you do have the gravitational waves gravitational degrees of freedom dominating they run right ahead of everything else they dominate completely well it's interesting to hear you say that because oh sorry i don't want to uh because because in some sense the whole point of of of conformal cyclical cosmology i think i got it right ccc um is that is it ultimately the late universe does look like the early universe in your picture they're one in the same you know in a sense and and and so in a sense it seems to me you're trying to do with a picture which relies on physics we don't yet know in some sense the only tiny little spots only in the hawking points yeah well i don't know there's a whole if i list you know some my old friend mike turner mike turner i think said you're allowed to have one tooth fairy in your cosmological model and i tried to write down what i thought were the tooth fairies which i counted five in in in ccc one was um um in some sense that quantum gravity is not relevant at the beginning but but also the black holes destroy all that entropy um by you know that's a that's another i mean that's a supposition but it's just tooth fairy i mean it's you you require in order for your late universe to look like uh uh you know you get rid of all that gravitational entropy in the in the final stages of a black hole singularity so you require that you require it seems to me also that particle masses might decay without any evidence of that um in some sense you require um that lamb to be fine-tuned for reason you so you require a large number and you know a large number that allows lambda to be a small number today uh you know this n to 10 to the 20th which you say lambda can be that to the fourth sixth power or something like that um and you require don't you require a massive scale or field at some very massive which you later on you put to be dark matter so you kind of require and you require there's no tooth fairy there that's that's that's necessary but it's necessary what i'm saying is you you have what i mean it's not it's a question that's not that's not a truth oh okay okay okay i'll give you that one but in some sense you require avoiding i it's it's uh i guess what i'm thinking is you kind of say quantum gravity solves the problems in the late universe of gravitational entropy and and it can do it because of your of black holes can do strange things but if you say that why don't you just say quantum gravity solves the problems in our universe and quantum gravity for reasons we don't know produces a beginning a universe that has low entropy i mean it's almost the same thing you're just pushing the problem to the end of one universe instead of saying it happens at the beginning of another i don't think that's at all fair okay maybe and i i'm glad and i'd like to hear why almost the entire crossover from one to the next is is not okay you do need a mass fade out which is a big assumption and i always said that however it is based on something which is part of mathematics namely that the first thing that you do in quantum in particle physics more or less is look for the casimir operators of the funct group yeah now one of these are mass and spin so you say these absolutely conserve quantities now what i'm saying is that this is only approximately correct because the right group is not the conquering group it's a city group the one that we normally refer to not one in the information or something yeah the real one the real world i think the one that einstein mistakenly introduced into it yeah the one that i'd say the one that comes automatically from quantum field theory but again it's my thinking that you know you can't get away from it you can't get away from the vacuum having energy maybe it has to be there for some other reason but it's certainly observed to be fair so yeah so it's not a truth theory the fairness yeah oh absolutely it's there it's a big it's it's so i'm trying to say that there is that term and if you take the view that the group actually at which could be relevant in cosmological scales is the disito group rather than the funkare group it's not so surprising that mass is not absolutely conserved it's not saying it is decays in this exactly this way or that way i agree that's missing and i said i've always said that's missing but on the other hand it's not such a tooth theory because it's already said that you've got to have something if you're going to accommodate the cosmological constant into your particle physics it's just not shown up in most yeah okay i mean it's well it's well motivated in the context of what you want to do i'm not arguing it isn't i'm just saying it's something you kind of have to introduce well i think that the one two three that bothers me the most i think well i don't i mean it may be true is this insistence that all of that extra entropy that's genera the gravitational entropy that's generated in the late universe disappears because it falls into black holes and then black holes destroy it and and it does they don't emit it it doesn't come out of the black hole and and that's required right that's really required otherwise the late universe your late universe doesn't look like the low entropy universe you really need to be the beginning of the next universe well it does yes now you see most look at the conformal picture it's almost entirely the the junction to the next eon is almost entirely smooth that is the the all the the effect of of a taking galactic cluster what happens it gets swallowed probably mostly anyway by a supermassive black hole that thing stays around for maybe 10 to 100 years it depends how big it is finally evaporates away by hawking evaporation now you look at the conformal picture that's tiny it's less than the black scale on the other side yeah which which it's less than plain scale so you were automatically driven to transplant in physics which means you're already in some sense you're already making assumptions about a theory we don't kind of know about it what was that you know a lot about it you know how much you know how much mass that i shouldn't go into this because i'm still in the middle of trying to write just take okay running two papers with kristoff and it's really interesting because it does use twister theory so we can avoid that it uses a bit of twister theory to show how you can work out what the mass how much energy comes out of the spot so the hawking point and you can work out there should be a certain amount of energy which will spread out to a certain size by the time you see last scattering there is an interesting thing from the discussion with alan grouse which is developed in a certain very interesting direction which i think i certainly should talk about here okay well no no no no yeah we'll wait till you publish that but i mean i i i do i still don't quite understand why the why this tr these high energy stuff that's transplanting comes and just manifests itself in the causing microwave background when in fact i would have thought that would mean you'd have anisotropies in the energy early on in the history of the universe which would then auto i mean you you one of the things that inflation overcomes is the fact that any small fluctuations in the early history of the universe will magnify due to gravity and therefore well we've got an inflation given for free which is the cosmological inflation and that is the universe yeah i guess it seems to me what you're saying is i don't like this inflation in the early universe even though it happens naturally in every particle physics model so i'm going to invent i'm going to i'm going to invent some aspects of of general relativity and quantum gravity in the late universe that allow me to produce exactly the same thing without having the with without having the natural consequence of the evolution of the general universe well let me ask you let me and you know i i'm bringing these up as questions not to attack because i'm i'm trying to understand it i mean i i i have problems with it but i'm also realizing i probably don't understand things here's another question i have obviously conformal conformal transformations have been very good to you and yeah and and it's something that's focused a lot of your thinking about and and and that drives your thinking about this conformal cyclic cosmology but conformal but the universe but quantum mechanics breaks conformant variants and and masses break conformal and variants and and and both in the early history of the universe i mean there's there's dimensional transmutation there's always scales put in there's a scale of qcd what do you mean by that well it introduces quantum quantum mechanics and relativity automatically introduce scales that are like the qcd scale the scale at which and so and when you when you do that yeah where normalization group automatically produces dimensional parameters which which which which which violate conformal invariance unless you have string theory but i know you're not depending on string theory either so we'll avoid that okay i see what you're talking about but i think one has to be careful about these things and also it plays a role in what i'm trying to say too but i can't talk about it because it's not okay okay no no worries but that doesn't bother me but here's another here's another i'll just throw out some of the things i've been thinking about because i as i say i don't want to just have a back and forth i i i i think i made it clear that i find in inflation kind of inevitable and natural and automatically overwhelming but but aside from that bias here's another thing the late universe i thought a lot about the late universe i did eschatology i didn't even know that was the word until freeman died until freeman dyson told me that's what i was doing and because we and i had a lot of fun okay eschatology eschatology the far future of the universe is what you're doing too but now you know and and and so and and freeman and i had a bunch of debates and it comes back to the beginning it was actually hardly due to good old fred hoyle again who was not only just a wonderful scientist but a wonderful science fiction writer oh absolutely wrote the black cloud which i'm sure is oh yeah it's not i completely agree and and freeman when i were thinking about life in the future history of the universe and what fluctuations could do and other things and if you're going to wait 10 to the 100 years for the black holes for everything then you might expect other then then other extremely rare fluctuations can produce things like maybe even galaxies and so why are you so certain that the universe is just pure radiation and not only that but more largely low energy low frequency radiation a little bit of hydrogen running around in this well it could be more than hydrogen it could be i mean if you have 10 to 100 years quantum fluctuations are wonderful things and and you could imagine a very improbable fluctuate not even a boltzmann brain but uh but a but a problem fluctuations but i don't believe it yes i think these arguments a lot of arguments which are all sort of philanthropic to some of them where you you somehow if the universe lives long enough then anything can happen sort of arguments i i think that's not right now you see it's when i'm saying that it's probably more a kind of feeling that has grown up since since coming across ccc and the argument is when it's from a conformal perspective it's not that long i'm in the end the end of the universe what i mean is infinity but that's not such a long time if you've got if you've got a mass fader depends on how quickly it happens then then it's you can't think of that as there's a huge difference between infinity and long time and and and my favorite quote of that is woody allen's who says eternity is a long time especially near the end but uh yeah the argument i know and you're going to say in some sense it's not too long because sometimes it is not that long yes yeah of course 10 to 100 years is a long time but in a certain sense compared with any kind of infinity any mathematician who plays with infinities knows that's true real time and mathematicians love infinities physicists tend to not like them and um and that's another the question of of probabilities of things happening do those problems stay the same or do they start going down when the universe becomes more rarified and that's the problem i should say about not just anthropic principle but to some extent any time we start imagining probabilities when we don't have a fundamental theory when you don't know the phase space of probabilities then you can almost prove anything right and and i think it's a problem that's often you yeah the ccc picture gives you a perspective on the world which makes you not scared of infinity okay okay and and and okay and and i and well then yeah i agree in principle inflation does too because it gives me a potentially eternally future universe of inflating that's an interesting thing i mean the way that kristoff has been playing with it and i'm sure i may be revealing too much classes the interest the question about inflation has come up in this you see i've always dismissed the whole thing it said well it doesn't play a role but he's taking it more seriously being a particle physicist and he knows the reasons that people put these things in and and there is a role for some of these things it's not quite what i had the picture we have at the moment is not quite well any good theory evolves hopefully as especially you know and that's the whole point i think for people who may view the discussion you are having as as me being a contrarian physics evolves by discussions like this and i think it's really important for people to realize that and i think the other and i want to i guess i want to somehow i've because it's been fascinating and i hope it's equally fascinating for others and i as i say the purpose is wasn't to say hey i don't you know i have problems with ccc was to explore your ideas because you've been they're so fascinating and your history of ideas is fascinating to me but i think what i wanted what it does also illustrate is that when you're at the edge of physics when you're the region where we really don't know what's happening there can be these vastly different views and that's a good thing and ultimately ultimately nature's going to determine what works and what doesn't and it's important for people to try and poke holes in other people's work and as well as in their own now the hardest part is to poke it in your own that's why other having discussions with others is often useful because you realize that what and and i so therefore you know i think it's it you know we have different views of what's likely and what's not likely and that's because at this point we're at the edge of knowledge and i think um and that's fine and right now opinions and views and biases come in eventually that'll all wash away like yesterday's newspaper because nature will tell us which way it works and doesn't i certainly hope anyway and whether it'll be in our lifetime or or in a thousand years i don't know but but uh let me just get to the end of this and say what what do you think remains to be done what what are the key challenges without revealing your papers where do you think the future of cosmology lies and i'm not talking about the future of the universe i'm talking about the future of the field well i'm hoping that people will start to take us seriously i haven't seen it happening it happens much more likely with people who aren't cosmologists and people who aren't wedded to inflation for example and all these ideas which has become part of their thinking and certainly i remember this conference i was at was one of the most awful experiences i remember having in a lecture which i had given it was a an invitation to go to the 50th anniversary event in princeton 50th anniversary of the discovery of the microwave background and jim peebles whom i have a lot of respect for and liking for ask me one has to absolutely absolutely completely and he asked me would i take part in one of the uh discussion sessions that they had and they had several of them and although each one of them they before the discussion session they would each one would present a paper they give their own point of view and then they have the discussion each one now our mom is the last one this one um what's his name green my michael grip brian green or or or michael green the the string theorist no not michael green brown green brian green okay yeah he's also string theorists but anyway a different one yeah okay he was more of a popular yeah and he was going to be the chairman and he's and he said we're going to do this differently i'm going to ask all the questions we won't have any initials giving your official point of view and so on i said look i went to see one of the organizat everybody else up to this point you had a chance of giving presenting their own point of view why am i not allowed to do that and then i said well look i have a few transparencies i really wanted to show and he said how many would you like to show and i thought how about three he said how about two so the moment came i said well look none of the questions that uh ryan green was asking had anything to do with what i was going to say except the one was slightly close to it i took here's my chance you see i said i've been given the opportunity to show a few slides two two actually didn't grumble to say but i was hoping it was going to be three or four so i started showing these things and it was basically one of them was on the uh the circles and that when you twist the sky they just get less and less and less so it is a circular feature and that was the thing that the baha'i done on my suggestion because i there was another way of doing it which i won't go into that complicated story because it needs to be resolved sometime but never mind um i think it was i can't remember what the other one was but it was mostly about that and then at the end somebody and i made the point about the fact that um that uh oh i guess i'm gonna remember forget people's names again it doesn't matter for the most the public won't know the names anyway anyway this big princeton very distinguished princeton cosmologist who got to look and repeat by his things do they see these things and i was going to say and then we never found anything this was a voice shouting out from the audience and i said they never found anything that's because they were looking at them i bet it's david spurgle you're talking about prayer miss david smith you're absolutely right he was david's father but then other from the audience started catcalling and saying we thought penrose had done good work about all the singularities and black holes and all this stuff and what's he talking about before the big bang now all this advances and i thought this was not a very un improper way of dealing with the speaker and you know they were just cat calls yeah sure it was very strange and i i said it was the most unpleasant experience i had in alexa i think well i hope that you haven't felt that way over our talk because i have great respect for you no no i mean i think i i you know we've the last part of this has been contentious and it should be because nothing isn't contentious but it's just somehow being disregarded yeah i know it's better to be oh yeah it's better to be argued with and disregarded i think that's always we're going to get regarded and though nobody's looking at us well look i i i hope we've now gone on a little over two and a half hours and i hope and i hope it didn't seem like that for you it didn't seem like that for me and i i and i think it's you know it's been more than worth every second and i have really enjoyed learning try and finish answering your question where is cosmology going so i hope people will take me seriously and they realize that the evidence that we have for the hawking points which the confidence level is 99.98 percent you can't throw that away it means something curiously it doesn't quite mean what we say in the paper because there was something slightly true i would have to say which came out of alan grouf's discussion and it's interesting but i'm not going to go into that because yeah and i presume that is that that you know that the correlations introduced by uh adiabatic random gaussian fluctuations also produce something that doesn't look that different well there is something else which no okay well i'll wait it'll be it'll be fun to learn it might be important which isn't very intriguing and i think it gives a different angle on that so when i say where is kelsey melody going i'm hoping that some of these things will be picked up because it's much more exciting to me than playing around with things that we don't know much about and these are observational facts yeah sure well that's what i mean the universe is ultimately going to be the arbiter of this it isn't going to be a gang in princeton or or me or you it's going to be the universe and that's what makes it so exciting we will ultimately we'll ultimately hopefully if we're lucky the universe will give us signals that'll allow us to to adjudicate debates between prejudices or beauty or other things that may or may not be relevant and also the wonderful thing about science one of the wonderful things is finding out you're wrong and and learning and i think i like to think i hope both in you and you and i feel that way i i would love to be wrong about my bias i think it makes it much more interesting and now let me tell you a story about somebody saying you see i learned my cosmology a lot from dennis sharma sure and he was very dedicated to the steady state model yeah comes the microwave background observations first of all he struggles with it and says it could be some effect and so then he gives up he goes around giving talks saying i was wrong the steady state model is wrong and he i have always had a tremendous respect for him i don't know many scientists who go so emphatically to say that something they had been arguing for such strength and simply saying it was wrong it's a mark of a great scientist and feyman said that too the but the hardest person the easiest person to fool is yourself and the hardest thing to do if you're a scientist especially if you love something dearly is to look at it and say what's wrong with it and it's a great it's a great and and and uh look i i i think this has been has many lessons for young scientists and members of the public and i'll give you another a little coder to this too absolutely keep go i'm enjoying it go on so dennis sharma said he was wrong he then built up a group of people studying quantum gravity he says what we need to learn is quantum gravity that's the important part of of course the big bang that's sure understand the alien universe and it gets along with all this and i agree with all that stuff now i'm saying he was wrong then because it's not quantum gravity it's the ccc model because quantum gravity is i don't think we've of written a resolution to this because i'm saying that quantum gravity yes you seem to be led to something like that in the big bang singularities they're a mess they're probably belinda koletnikov bko model mizuno bklm models sure they probably are but that is not going to answer the problem for big bang it's completely different well well let me let me let me oh sorry so let me let me put a different code on this then what would it take for you to say to go around giving lectures saying i was wrong well the ccc model is shown to be wrong but how what would it what would do it for you wouldn't be hard look i mean if one could see that uh well nobody has accepted the apart from them i haven't seen anybody outside our group when i say our group i mean people who've become into our group through not having been in it before um i mean the polish people for example you see i mean alan good keeps thinking your group and i said my group what these are people who came completely outside yeah yeah sure well the group expands and people look at these things so i'm hoping that people will take these things which have a strong evidence for them not just the talking points there these signals are stronger but the rings and the rings are consistent there's also the thing which we well done but that's not the answer to my question that's you're saying you're hoping they'll be proved right i i want the ant the question i want to know is what well if they're not if they're not seen that would be signific evidence against me that's the trouble you see so i think proven wrong would have to be something else okay and we don't but is there any smoking gun that would i just out of interest that would you say look this convinces me it's the wrong that i'm barking up the wrong tree well there are places where the numbers come back could come out wrong okay you've got to have for example as far as i can see it you've got to have the decay not the yes the decay of dark matter particles you see this is we haven't stressed this particularly yeah i mean i have written it in the paper yeah well i was going to it was one of my tooth fairies you got to have the decay of dark matter particles has to take part in about the la the half-life has to be about 10 to the 11 years yeah this has to give you the in the uh it has to give you the what is it called spectral index the spectral index doesn't come from some fancy quantum oil it comes just from the fact that you're thinning out in the dark matter particles yeah and that's another and my bad that was on my tooth fairy list i think in this so you require it it's something you add to the theory didn't come out naturally but you require it to be there on the one hand it's a tooth fairy which is regarded as bad and now you're putting it to the good side but it's yeah but you know yeah but if it makes a prediction that can be ruled out then it's good so so so let's bottom line is let's wait and see and i hope um i hope this is not theoretical you want to see does the implication of introducing the the cosmological constant into the particle physics picture give you a decay of dark matter we don't know that that could be shown to be completely wrong does it if your decay rate which would agree with the spectral index that could be that could be wrong i mean that that could be these are observational things i don't know how much decay of the dark matter particles observation at this stage well i hope we don't have to wait 10 to the 11 years before we resolve this question uh because because uh well i i can't see why there's any real problem about proving it wrong the colossal places you could prove it wrong well i don't i'm you know i have i'm going to be in this way agnostic to some extent i have my prejudices but but it's fascinating to learn i i'm the story of of where we how we got here which i think has been for me fascinating is is just i'm glad we got to focus on on so much interesting science and the and and the way of thinking about the world i think some people regard ccs actually having been proved wrong oh yeah i realized that and that's why i wanted to read what you said because i i i kind of felt like if it had been you might have you might have agreed and and obviously you don't think so and um um i'll bet against it you bet ford and one of us uh can have a nice bottle of wine if it if we find out that which i might regards just proved wrong you see but now we skipped sideways which is the the size of the hooking points you see aaron guthrie told me from standard calculations of when the if you put in all this particle stuff apparently and you try to work out in conformal time when would the um last scattering surface be and according to his calculation it would be half a conformal time than we actually see it so that could be regarded as proving it's wrong so if you'd like it is proving that version theory wrong i think that's true well you know i i i'm glad there's that back and forth discussion um and and i'm glad we're having one and i hope to have another one if we have an opportunity but i'm really glad we had this chance to have this one i hope you enjoyed it and um and and i hope we got to tell i mean you know you've done a lot obviously anytime one wins a nobel prize when it comes it's lots of inevitable interviews and discussions but i hope that this is i tried i wanted to make this a little bit different it has been a bit different and it's been much more interesting for me thank you well thank you thank you so very much uh what points about inflation which as i say these are very relevant to what kristoff has been doing i've never taken it seriously probably for a bad reason not partly because i hadn't known enough about quantum field theory and particle physics and knowing where all these condensates and whatever they are to produce inflationary phases and things like that and i've never taken it seriously because mainly because it doesn't smooth the universe out it may it may do things certain things of importance and that could be looked at in the right way which which is in a sense proving me wrong to a certain degree because i've never i've never taken any of it seriously i'm glad that my the my at least the discussion not mine but the ones i emphasize that matter to me about about the inevitability of these phase transitions is an issue that you're thinking about it's something that i have swept to one side without looking at and it really i have become persuaded that they are important in this picture and that is in a certain sense showing me wrong well that's a good thing and let me put it conversely one of the reasons i wanted to have the discussion besides the fact that i want to have a chance to chat with you again was that i knew unless i did had it i probably wouldn't have the patience to work through your book and your ideas because i would tend to just dismiss them and so for me it's been a learning experience and caused a lot of thinking which i particularly appreciate as well so i hope we both benefited and and every time i'm with you i'm sure i do so thank you again and i know the public will i convince the public will benefit from this discussion so thanks so much thank you very much i think i've missed out on my walk but apart from that [Music] [Laughter] [Music] i hope you enjoyed today's conversation this podcast is produced by the origins project foundation a non-profit organization whose goal is to enrich your perspective of your place in the cosmos by providing access to the people who are driving the future of society in the 21st century and to the ideas that are changing our understanding of ourselves and our world to learn more please visit originsprojectfoundation.org

Channel: The Origins Podcast

Views: 178,471

Keywords: The Origins Podcast, Lawrence Krauss, The Origins Podcast with Lawrence Krauss, The Origins Project, Science, Podcast, Culture, Physicist, Video Podcast, Physics

Id: kE81mlArUs0

Length: 170min 29sec (10229 seconds)

Published: Thu Mar 24 2022