Julian Barbour: The Janus Point & the Arrow of Time

the janus point it's a startling new glimpse into an alternative theory of not only the origin of the universe but of the origin of the arrow of time itself suggesting that one of the greatest mysteries in all of physics could be solved with a revolutionary new proposal from julian barbour who's today's guest on into the impossible come along and experience this journey in what lisa mullen called a rare combination of humanity and a perspective coming from a lifetime of the study of history and philosophy of cosmology julian barbour writes a book that is both a work of literature and a masterpiece of scientific thought come along on this journey into the impossible with me and author julian barbour any sufficiently advanced technology is indistinguishable from magic [Music] hello everybody and welcome to a very special episode of the into the impossible podcast featuring renowned physicist julian barbour who is reaching us all the way from the united kingdom and this is entropy month and time month on the into the impossible podcast we had on uh jeremy england who is not english but he was on to speak about his book every license life is on fire and we have carlo rivelli who's written many books on time and we'll have craig calendar's wonderful book who wrote a graphic novel about time but today we're talking about a very provocative and new theory of time and the origin of our wonderful universe with a real legend this is this is such a treat for me uh julian barbour is joining us how are you doing today sir oh very well thank you and for a change we've got lovely weather here it's uh it's been a very mixed year weather-wise but it's very pleasant today i even took snooze for an hour in the garden oh that's lovely yeah we are experiencing what is known as june gloom uh even though it's july uh we should be frying in july but in san diego right now we've got may gray and june gloom and uh it's very it's very disruptive but we will make it do you guys deal with it 300 days of the year we can take a couple days of the year so i'm just going to read your bio from the book which you kindly sent to me about six months ago and i keep postponing it because of uh various activities and i wanted to give it the depths and depth and attention that it deserved and julian barbour is the author of highly regarded the discovery of dynamics and the best-seller end-of-time phenomenal book he received his phd in physics from university of cologne in 1968 he's a past visiting professor in physics at the university of oxford and lives on the edge of the cotswolds i've never been to the cotswolds i hear it's lovely and i'd love to see your garden someday and we're going to talk about um life and the universe and time but before we do that uh julian uh you're so gracious i want to do what i do with all of my guests who write books and that's to do what you're told never to do which is to judge a book by its cover but what else do you have to judge a book by when you see it for the first time unless you know the author i want to ask you how did you come up with the title and the cover design of this wonderful new book i didn't i came up with the title uh and that will come out in our discussion i think the cover is entirely the work of basic books uh and the uk edition perhaps i can show you the uk edition which is also quite striking yes there's there's the cover of the uk edition um oh wow and there's the back of it roger penrose saw that cover and said he thought it was a very clever cover yes yes it is a lovely work and it's a work of art as well and i recognize many names in here including uh tj kelleher who i guess was your editor one of your editors i've known him for several years myself but i wanted to um to begin by by discussing the the notion of time and and where does it come from because i've had on carl aurora valley i've had on many frank wilcheck and i always have these solipsistic or tautological definitions that i am forced to use such as time is what clocks measure according to frank time is what increases entropy or is associated with the increase of entropy according to carlow clausius and others what does time mean to you what is is time fundamental is time emergent and what do those two terms mean in the context of time well i've been thinking about time now for close on 60 years and my ideas have been evolving i have to say but i certainly started off quite by chance in the autumn of 1963. quite by chance i read an article about what dirac had said about the structure of einstein's great theory of general relativity in which he questioned whether four-dimensional symmetry was a fundamental feature of the physical world and sometime after i read that i said well if iraq is saying that shouldn't we start thinking about what time is and then i very soon came to the conclusion that if nothing changed we couldn't say that time passed so so the primary thing is change what mark said was it's utterly impossible to measure the changes of things by time quite the contrary time is an abstraction at which we arrive from the changes of things and also in mach it was from mach i learned the insistence he had on the relative activity of motion or position that you define position relative to other objects and really ever since then i've been thinking my question has been what is time what is motion uh and and i'm still working on that and i've got a wonderful group of collaborators now some are in their early twenties uh then i've got some in their forties and another very good mathematician who's about sixty i guess uh so it's it's actually speeding up now these these things let me make one comment though about einstein if i may of course well against mark died in 1916 einstein wrote a very handsome uh obituary of him and among other things he's he quoted that passage about time that i've just given and described it as a gem but if you look through all of his works everything he did and what he wrote i don't think you'll find any attempt by einstein to put that into reality in his work wow and what he when he was asked what his time i think his answer was very much like what frank wilczyk said it's what a clock tells but he didn't but then which i think is very significant in his autobiographical notes in 1948 he said when he'd created general relativity he'd committed a sin in that he'd introduced two quite distinct things one was the space-time manifold with the metric on it and then completely independently he admitted that he was bringing in from outside rods and clocks that measured it and he said that's inconsistent the rods and the clocks should emerge out of the fundamental equations of the theory and and he never did that but in fact i think one of the things in chapter seven of my book i do explain how at least within einstein's theory rods and clocks do emerge and that indicates strongly that they don't exist near the big bang so i think we have to rethink very radically how we think about the conditions of the big bang because there aren't any rods and clocks there right and i'm wondering if there's anything there there or equivalently at the singularity of a black hole i want to start maybe even more more approximate to that to that point in time if it is indeed even a point with a question i've posed to all of my guests uh including sir roger after he won his nobel prize uh and that was you know whether or not singularities should be taken seriously because we know of no process in nature that is infinite that is has unbounded size magnitude density temperature energy infinitesimal length scale et cetera et cetera and yet we talk about things like singularities somebody said you know singularity black hole is where god is dividing by zero or something like that but we don't really know um the you know the correspondence of things that are infinite but we do know things that are zero and i want to ask you first you make a large discussion of what you call the royal zero is that somehow going to play a role in a new conception of how we should think about singularities how does the royal zero figure in it's the most unique number because it's a number that is scale free it doesn't need a rod as you say it doesn't need a clock as you say there's something special about zero what role does it play in the janus point concept in well we would really have to go into uh where the title of the janus point comes from so this goes back to the first qualitative result in dynamics discovered by lagrange in 1772 when he was studying the three-body problem that gave newton such terrible headaches the earth's sun and the moon and what he showed was that if the energy of the system is not negative so it's either zero or positive then in the distant past the size of the system is infinitely great it comes down to a finite value and then it rises up again to an infinite value in the future that's in the standard sort of newtonian idea of time going from past to future but you could reverse it because time reversal symmetry and that point of zero size in the newtonian representation is what i call the royal zero but basically i would say i when i went to study mathematics at cambridge they said what is the equal sign in an equation mean it means that the two things on the two sides of that equal sign are exactly the same it's equality so in some senses it's it's saying that this identity now in fact i would say rather more than the size i now think shape is the really fundamental thing and one should think more about in fact i would even say that size is is a gauge degree of freedom it's something we've put into physics which shouldn't be there so i'm going to start with my famous triangles i'm always illustrating things with triangles so if if i had just three points three mater three bodies in the universe and they're at the apex of of the sorry the three vertices of the triangle it's meaningless to say what the size of the triangle is because there's nothing outside the side outside the triangle to measure its size so all you can speak about is the ratio of the lengths of the sides or the angles and if you think about it we don't see lengths we see angles because when we look at the sky when we look at orion's belt we see that it subtends about a few degrees but that's a fraction of four pi the whole way around the sky and i think it should probably should be two pi shouldn't it for bias area so um the thing that i'm saying is that if you just look at what the shape does i don't think that i suspect there are no singularities at all hmm and is that is that a fundamental aspect of an error or problem in relativity or in our concept because i as i know and i want to talk about artificial intelligence the problem julian is that i have about 10 hours worth of questions to ask you and i only have about an hour and a half scheduled with you so we'll try to be brief but we'll also try to come back to it but i don't know that infinity should be taken as seriously as they are and yet they're tr sort of treated as sacrosanct in physics and we talk about the big bang singularity we talk about a black hole's singularity these are unobservable and we'll get into you know falsification later on but um but this notion that that something infinite can go to become something finite has you know kind of been resolved or at least addressed since the time of zeno and his famous paradox so you know what extent is in if infinity uh if zero is real i guess the question would be one over infinity why is that not real well or one over zero yeah one of the problems i'm facing in talking with you now brian is that my thoughts have developed quite a lot because writing that book was tremendously stimulating and you may have noticed that at the end of chapter 8 i hesitated a new idea about what time is so let me let me to help me get into it let me talk about these very remarkable solutions in newton's theory because i think they illustrate how perhaps cosmology the way we think about the big bang should be completely changed now in newtonian theory it's been known for over a hundred years that if you have point particles interacting in accordance with newton's laws it is possible that they collide all together at their common center of mass and this is called a total collision [Music] and in the three-body problem whatever the masses of those particles they can either do it on a line and that was discovered by euler or they can do it uh when they collide together the shape must tend to be an equilateral triangle now if you say that this highs has no meaning it's a gauge degree of freedom then if the shape stays sensible and even becomes very sensible and uniform and becomes an equilateral triangle when they all collide that if you say that the only physical degrees of freedom are the ones that describe the shape the angles if they stay well behaved there's no singularity so let me hold up this triangle and move it ever further away from the camera you see the size change but not the shape this to me suggests very strongly that the shape is the only thing that counts and this puts this puts a completely different way potentially on thinking about the singularities of the big bang i won't hazard anything about black holes because i'm more interested and haven't i haven't really thought much about black holes but i certainly have about the big bang and i think that's a very interesting possibility and if you have uh if you have lots of particles there are many many possibilities for these total collisions or total explosions if you reverse them the other way then you get a newtonian big bang and in that case you can start off one of these total explosions these newtonian big bangs where the universe is in its most uniform shape that it can possibly have that's in and it it has the shape of what is called a central configuration it's a scale invariant quantity you blow it up as much as you like but the ratios between the particles just stays the same and basically if you think about the history of the universe let's just forget about inflation what we know as a fact is that a split second after the big bang the universe was extraordinarily uniform and it has got more structured in homogeneous ever since and i would think maybe these newtonian big bangs are a model of the universe when you if you shall we say you you you put on spectacles and all you can see is the shape and not the size of course we can't avoid putting in a shape as well i think we're very i think the reason why we always imagine there's always a size to something is because of the image that's projected onto our retina and that is a so the size of the object is the fraction of the area compared with our complete retina and that's just um if you think about looking at the sky at orion the nebula of orion i'm sorry the constellation of orion it it has a certain size relative to the total area of the sky so i think the bedrock of physics should be ratios and at all stages it should be ratios and if we're talking about a triangle representing the complete universe it should just be the ratios of the sides or the angles yes and that brings up a concept that uh one of my listeners was eager to discuss with you is whether or not if time is emergent you know and space time or somehow equivalent uh that you know shouldn't space be emergent in some sense and lee smallin our mutual friend uh who you kindly asked a question of when he appeared on the podcast about two months ago uh sad to say he has not reciprocated yet i'll be waiting and i'll ping him again and see if he can if he can give us a comment but he's quite busy but you know he kind of has this belief as i understand it that you know that space time itself can emerge from uh basically fundamental constraints on causality uh and so what about space would be privileged in other words would space pre-exist time i well all science starts with certain hypotheses and mine is that geometry is fundamental and actually my favorite saying is one of galileo's he that attempts natural philosophy without geometry is lost it's it's it's a wonderful saying and i just don't think you can do without geometry uh in fact i would i would retain the continuum and all i would retain is angles and this is actually when you when you try i mean if you set about taking out everything in the way we think about physics and do physics and say what can what redundant things can i take out and get down to what if i go any further i will destroy everything and i can't i can no longer walk because i've chopped off my legs what i want to know is what is the essential things and my belief is that it is actually geometrical relationships and they can be illustrated in the first place i think with particles in space you can do an incredible amount with particles in space with where you have separations between the particles and some separations are greater than others but the ratio is well defined it's a pure number that's another of my fundamental principles the whole of cosmology and physics should be expressed in terms of pure numbers now you can say newton's the rot set in with newton when he introduced time and distance so uh the greeks always said ratios must be of the same things so you can take ratios of two lengths and then you've got a pure number but newton introduced time as well as length in in his things so the velocity is a distance divided by time dx by dt and that's an improper ratio so i want to build up what i call shape dynamics using only ratios of of really i would save lengths that's all i think you need you could probably just get by or you can get a very long way with a very interesting theory just using points in euclidean space and another controversial statement that you make in the janus point is that momentum should not be treated as equal to position this if true and if accepted would up end our notion of everything from classical hamiltonian dynamics to the quantum quantum dynamics that are predicated on such kinds of conjugation relationships so i want to ask you um you know what has been the reaction to that statement that is a very provocative statement and you admit as such in the book uh that your your your courage is undaunted by the arrows that you might take but maybe they won't do any damage because they only carry momentum after all and momentum is not real so what do you mean by this that momentum should be kind of a um you know treated with a lower priority perhaps than position well let me say first of all there is a a mathematical way of dealing with a phase space with which has an odd number of dimensions it's called i think a contact structure so there is a mathematical way of dealing with these things and i think the whole problem with this is that people haven't taken mark's ideas seriously that really what happens locally is somehow rather is governed by the whole universe so so mark conjectured that the local inertial frame of reference in which newton's laws are formulated is determined by the whole universe by the masses in the whole universe and when you do that um time really in that classical picture before we attempt to get to quantum mechanics time time in that classical picture is just somehow an average of how all of the quantities have all of the separations have changed so you can have a separation of all of the things so it just put out objects on the table and move them all a little bit then each of them will have moved a certain amount relative to the all the others but the totality will make a sort of a background quantity and then each of them will have a proportion of how much it's moved compared with the others so you can always ascribe to an individual particle what proportion of the change of the universe it has done compared with all the others so its momentum is a fraction of all the others so that's again coming back to the ratio so i would say in classical mechanics if you really want to have something that locally looks like a momentum you've got to say it's it's the measure of how much it has changed its position compared with how much all the others have changed their relative positions um i see so um right and so that then takes us back to this ratio or gauge free description um but i also think julian i often say you know mathematics is highly uh as highly abstract in that you've never seen a triangle um we can't we can only visualize a triangle you know i always say if somebody says no triangles are real i say what is a triangle way and that's a nonsensical question because triangles are you know collections of three non-uh co-linear connected uh points which are themselves of zero dimension which is kind of mind-boggling uh for humans to envision so um it's curious to me that uh you can build up shake dynamics and the reality of dynamics and and even concepts like the janus point from something that's purely imaginary that you would have to admit doesn't exist in reality i mean you can't hand me a triangle you can ask me to visualize it but can a computer really handle it no because a computer has only an approximation a quantized level to approximate a point as one over the small the largest number in its memory bank right so to what extent can we build up reality on things that are purely fictional or created by the human mind perhaps well two comments about that first of all i think i think all of the great concepts in mathematics are suggested by our experience and they're idealized from from that and i think the the real numbers are a human creation but i would say let us work with them i had a few years ago i i had a discussion with gerhardt tuft the nobel prize winner i've met him a few times we had actually about an hour long discussion and he was telling me about his ideas he he his ideal is to build up everything from zero and the positive integers nothing else he said so i said you're then like dedicated who said you know the god created the integers and the rest is the work of man mention work so then i said yes so then i said yes but the what is why don't you accept the real numbers because the real numbers are a creation of man man is part of nature [Laughter] and he smiled and i think he accepted that that was not an unreasonable point of view so we have to start with somewhere and uh i think there's that there's a wonderful saying of of poppa the the um philosopher about there is no really sound empirical foundation of what we do in syria we just drive down piles into the swamp until they make a reasonably secure platform and we work on that until we have to drive the piles further down so that's very much my my attitude so um i will happily for the moment of moment except the real numbers and euclidean and romanian geometry and let's see how far we get with that now a new concept for me at least you may have written about it elsewhere is this concept of end taxi can you explain that and how that is an improvement because it must be an improvement upon what we think about as entropy and the ability for um for systems to convert energy into labor or work et cetera so what is what is end taxi what does it do for us that entropy does not do well let me let me go back a bit into the essence of the book i mean a major part of the book thermodynamics and statistical mechanics was born out of the study of steam engines this absolutely wonderful book that sadi kano published in 1824 his aim was to make a steam engine with maximal efficiency what was the maximal efficiency that could be obtained and the key thing about steam engines is the steam has to stay in the cylinder essentially in a box now you read any of the papers of clausius who first formulated the second law of thermodynamics of maxwell of boltzmann even up to willard gibbs they all start off by saying we imagine things like billiard balls or atoms or molecules that are bouncing off each other but they are in a box and they bounce elastically off the walls of the box and the whole of statistical mechanics is based on this concept of a box and klaus is his wonderful definition of entropy in the second law that requires very careful passage from reversible passages from one equilibrium state to another in a box it's absolutely crucial he couldn't have defined entropy without that box and i have read quite a lot of the literature on the problem of the origin of the era of time what entropy is and so forth and you know i have not seen one single place where anybody has said does it make a difference if the box isn't there it's quite extraordinary but when you start thinking about trying to define entropy when the box isn't there you're in a completely different ballpark if you say that the energy of the universe is conserved and i think that's a reasonable assumption then you can't do all of the wonderful things you can do in thermodynamics and statistical mechanics is change the entropy by compressing the box and things like that so you've got to look for some other quantity which defines a state function the so the key state function in statistical mechanics is the energy and then you see you count how many microstates there are for a given energy and that's not that much difference when you've got a quantum system you count the in a given interval of energies how many quantum states there are in in that interval but in all of those cases you've got some system which is either in a box or it's self-confined so what do you do if you've got a system which can expand freely like we think the universe is doing so i've there is a quantity which i call the complexity which is an extraordinarily interesting quantity it's the ratio of the mean square length of all the separations between the particles divided by the mean harmonic length so essentially you take the average of the long distances in the numerator and then you take the average of the short distances in the denominator and that gives you what i call the complexity and it's a measure of how clustered a system of particles is it's also very remarkably the newton potential the newton gravitational potential made scale invariant by multiplying by the center of mass moment of inertia which is half the trace of the inertia tensor and this is a very very interesting quantity and it is something you can call it the intrinsic size of that universe of those particles so we've got a finite number of particles because the distances between the small particles you can regard them as little rulers which are measuring the whole size so if i come to my triangle again i can take its shortest side and use this as a ruler to measure the longest one so the triangle has its own size it has an intrinsic size and that same thing i think could actually serve as a notion of time and all of this would be in terms of pure numbers and that complexity in the newtonian classical theory when you go from that janus point of mind or from a total explosion that complexity in the classical newtonian theory fluctuates but it grows and that's that's what i call a state function which grows and then if you look in these janus point solutions you find that the number of micro states in the volume of what i call shape space actually decreases it does not increase so i define a quantity which i call in taxi well it was coined by my collaborator flavio mccarty which behaves in exactly the opposite way to entropy so when you take the box away everything is turned upside down you have to as kepler said in a different context we must philosophize about these things differently and so that complexity gets goes on increasing forever in the newtonian system which is unbounded and as it as it does that the universe does not get more disordered it gets more ordered because you find that kepler pairs form for example kepler pairs form and when a kepler pair forms this is i'm going back to when einstein didn't say what a clock is when you're at that janus point the particles are uniformly distributed and they're moving more or less randomly with respect to each other but then in both directions away from the janus point the particles cluster and very often they will form a kep form kepler pairs and as that kepler pair forms its rotation period becomes the period of a clock its major axis becomes a rod and the direction of the major axis becomes a compass so you've got a kepler pair which is a rod clock and compass all in one and relative to it you can see that the other particles if they're single particles are moving in accordance with newton's first law so this is actually exactly showing what new what einstein wanted to understand where do inertial frames of reference come from and and what are rods and clocks they emerge out of a dynamics and this can all be done with systems which have zero energy and zero angular momentum which is what a machine treatment of a universe requires everything falls together into pace placed beautifully wonderful so the next topic i want to talk about is the notion of a a cyclic universe or a cycling universe a collapsing universe these are literally as old as time much older than the big bang concept dating back to egyptian cosmogenies and other concepts um which date you know thousands of years before the common era i want to ask you the classical objection if i tell a normal person on the street who happens to have an advanced degree in general relativity i say um i'm talking with a renowned scientist today about his theory that predicts that time can go in two directions at a single point and the universe's uh life cycle they'll say well tommy gold explored these back in the 50s 60s and 70s and ruled them out in some sense or they were ruled out because of the problem of dissipation of entropy and the unbounded nature that every cycle in universe would compile more and more entropy does the janus point share anything in common with a cyclical bouncing aeon does it have anything in common or is it fundamentally different from those conceptions of cosmogenesis i would say it's fundamentally different and i would say the main significance of that janus point idea which i'm increasingly thinking serves its main purpose is to sh to undermine the idea that the arrow of time is due to increase of entropy and also to undermine the idea undermine the idea that you have to impose some special condition in the past a past hypothesis as david albert calls it to explain the growth of entropy so when i showed that example of of how the three-body problem behaves and it's exactly the same however many particles you have that is nothing whatever that special point that special janus point is not there because of some extra condition that i've had to put in on top of newton's laws it's a direct consequence of newton's laws uh virtually certainly every every solution that is not doesn't have negative energy has that behavior and it and moreover as you go away from the janus point the universe gets more clustered in both directions there's a precise way to characterize that clustering by a pure number and those defines directions of time those are arrows of time that are nothing whatever to do with statistical arguments it's nothing whatever to do with things all lots of microstates being bundled up together so that you can't see what's happening and and it's it's just i think the one of the main things i feel really confident about uh what i put in the janus point is that it undermines the standard story about the arrow of time needing some special condition in the past and moreover that that increase of entropy is what's going on in the universe i argue that what is going on in the universe is increase of structure it's getting more interesting and if you just look at me now as i'm pumped pontificating brian compared with what the universe was like just after the big bang i think i've got a point it's got a lot more interesting and a lot more structured and maybe people are just blind to this i think i think one of the reasons so the the point about thermodynamics it res it seemed to rest on such wonderfully secure foundations the impossibility of making perpetual motion machines but but it's still all of its concrete results all of the solid results rely on that box you read willard gibbs's great book published just before he died he essentially requires he's talking about a hamiltonian dynamics and the system must have the phase space of the system must have a bounded measure that's essentially putting a box in and if you take that away it's just everything is different but then i think now increasingly i'm coming to think that much more interesting than the janus point solutions is the ones where it's really so that's when in the newtonian representation the size remains finite at the at the janus point but if you have these total explosions which come out of in the newtonian picture out of zero size and if you take out the size story it comes out of the most uniform shape that the universe can have i think that's much more interesting but it still defines an error of time the arrow of time is just the universe is going from being extraordinarily uniform to getting ever more varied and that's actually what look around at the universe and the evidence from what the astronomers find and this wonderful telescope i think you're involved with well all of those ones down in chile um just look you take what they look like it's the heavens proclaim the glory of god or something proclaim my idea that the universe is more interesting so let's discuss uh what have been called the theoretical virtues by michael keyes no relationship to me but he has a paper called systematizing the theoretical virtues and he talks about what makes a good theory and what differentiates it from an inadequate or a subpar theory and it goes a lot deeper than the palparian falsification rubric it's much more thorough he does involve certain things that i find controversial such as uh your theory should strike scientists as beautiful as that's a virtue as your countryman paul dirac said it is more important to have beauty in one's equations than to have them fit experiment i i wish i was with you know as an experimentalist i take personal umbrage at that statement i don't believe it i also don't believe that experiments should be held up as the cinequa non of whether a theory should be should be at least grappled with and i use the example lately of maxwell in 1860s when he was coming up with the unified theory of electromagnetism and his famous equations he wanted a mental model which uh if employed and taken seriously would have led to the falsification of his ideas because he believed in vortices and gears and and ether and all sorts of things so imagine if experiment if carl popper were around back then oh no no that's there's no little gears there's no little whirls and vortices so your theory must be wrong no so that's not that's not fair and to be fair to popper he said things like he appreciated the steady state and he appreciated uh other models staying around longer perhaps than the history might judge them to be valid because it impels people to make observations and you want to correctly test some of the other theoretical virtues i want to confront you with and you mentioned you know observation and we're going to get to that the first one of the virtues is explanatory depth your theory should apply to a wide range of scenarios if it is correct it should also explain data and the final kind of virtue that i'm going to talk about is adequacy your theory posits causes that account for the effects of the data and of course that relies on evidentiary data being available so i want to ask you what are the observable or evidentiary consequences of the janus point scenario whether or not regardless of whether or not we can currently detect them as you say well it certainly it says that there will be an arrow of time a very profound one that that the it will be inescapable it will be you know that the dominant future of of existence in the universe will be that we will be aware of an arrow of time so i think that's that's a that's a that's a good start and when we look at data in the universe of course you know we want to be cognizant that that could also be applicable to the past hypothesis uh which actually by fiat which we physicists you know find abhorrent but nevertheless uh we uh you could also say that that hypothesis gives us an arrow of time it doesn't give us two hours of time and so my question to you is are there pieces of evidence now respecting popper that could um disprove that because obviously it's consistent it's it's it if i was putting on a critic's hat i would say well that's a retrodiction julian you're you're trying to come up with a theory that provides an hour of time but what new express like what can we tell my future grad students and your grandchildren etc what can they look forward to doing to providing evidence or falsification of that scenario given that we all believe there is an arrow of time that we experience uh is there another um is there a consequence of the data you know some limit on black hole masses uh some limit on minimum number of of generations of of leptons is there some piece of data of evidence that could substantiate it beyond the retrodictive nature of the existence of an arrow of time the the best hope i have is not for those janus point ones where there's two sides but where i have these total explosion ones where in the newtonian picture it starts with zero size but the way i think about it it starts in its most uniform shape and i think this is where we have the best chance of really making some progress because if this idea is right i think it should provide a clear alternative to inflation that at some stage should be testable because it would show up in the cmb in the data in the cmb because what is out of that theory it all that we've got at the moment is the newtonian theory but we can see a good chance that something like it will happen in general relativity that the that we're using that newtonian model of a total explosion starting with great uniformity to try and get some idea of what might happen in general relativity because there's great uncertainty about the big bang at the moment and in a paper by my collaborators koslovsky mccarty and david sloane they makes the first progress to showing that something similar like that can be expected in in general relativity it's related to the bkl scenario when it's quiet if you're familiar with that uh brian so and so the the the greek the great triumph of inflation was to give these uh fluctuations the harrison zeldovich fluctuations out of which uh then all of structure in the universe developed and the key thing about the early universe was that it was very uniform but there were small fluctuations with a very definite structure the scale invariant spectrum and the reason why we've come my collaborators and i to this picture of this total explosion in the newtonian theory was a challenge by a cosmologist at oxford pedro ferreira to see if in newtonian theory we could find hints of an alternative to inflation because inflation has its triumphs and they're well deserved but it it's very difficult to see how it gets started and my understanding is this some uncertainty about how it ends and whether there's internal inflation things like that now if these ideas are right when if and when we get to applying them to general relativity i would suggest there will be absolutely no shadow of doubt how the universe starts and it should make very precise predictions that could be verified in the cmb so there's definitely hope there and it would surely be i think you have to admit for all the triumphs of inflation it's it's it's a bit shaky on its foundations there's a lot of argument about how you get from this very symmetric bunch davis vacuum to astronomers actually seeing a a a real universe which breaks the symmetry there's a lot of question marks over inflation now if and it's a big if of course and and it may be decades if i'm if we're on the right track i think it could be decades before we've indicated but if we if we do come to vindication it will be a clean sweep we we will start with a a very uniform universe of necessity it will start very uniform and then it will get more varied in a very definite way and that would be of course quite a nice triumph indeed yeah i think of inflation more as a uh as a theory of structure formation than a theory of the initial conditions of the universe and that avoids you know having to think about both its lacunae in terms of inability to explain itself without the existence of the multiverse which i find you know personally uh more to the unpalatable side as my viewers will undoubtedly recognize um and sort of a almost tantamount for a replacement of a god-like fiat instantiation of the universe uh with that you know an infinite number of creative uh you know forces like many bubble universes but nevertheless it is very successful and one of the things it does predict is that there should be a stochastic background of primordial tensor perturbations or gravitational waves which are obviously one of the key targets for experiments such as our simon's observatory and other projects around the world and the hope is that you know these could be measured and that would somehow lead to confirmation of inflation although which inflationary model and which multiverse kind of scenario that is not specified but um it makes a concrete prediction it may not be observable the waves may be too feeble to leave an imprint the inflation may have occurred at a low enough energy scale that even though it did occur it won't produce anything that we could see uh nevertheless what does in the janus point i assume there are no gravitational primordial tensor perturbations in in in well in the in the newtonian model certainly not that's for sure uh there may well be uh in in general relativity when but there are really a lot of work has got to be done on the general relativity side of this to really begin to make progress but i think it's i think it is definitely possible there could be gravitational waves and as opposed to the present situation where it that magnitude is unknown the it's the r parameter isn't it um this should this should make a definite prediction i think but this would require understanding of all the forces of nature i mean there is talk of this new fifth force i mean it probably would be a complete package but um [Music] there's hope there's hope and all i will say is it's a completely different way of thinking about these things and it's a very simple one it's just a very clear straightforward idea to say that if the universe is i should say if the universe is spatially closed it's it's there's nothing outside it then you shouldn't talk about the scale of the universe and everything should be expressed in terms of ratios i don't think you can have a simpler more secure foundation for conceptualizing about the universe than that and on that basis once you do that things change dramatically let me go back to kepler so when kepler thought about the observations of the comet that tycho brahe had made he thought that that implied that the comet must have gone clean through the celeste the crystal spheres that carried the planets so nothing was carrying the planets and he said he said henceforth the planets must find their way through the void like the birds through the air we must philosophize about these things differently so i see this claim that get rid of size it's a it's it's a bogeyman it's causing it's potentially causing all these problems with singularities and things and if you stop and think about it if i may say so it's blindingly obvious at least it should be questioned at the most fundamental level i think it's i will go as far as saying it stinks so one concept that's gotten a lot of attention lately and even i spoke with a gentleman uh dr steven meyer who supports intelligent design and we had a lively debate about that but nevertheless uh was this board uh guthvalenkin theorem that posits that any expanding spacetime had necessarily a beginning or ultimate boundary um sometimes misidentified according to the lincoln as a singularity uh but more properly i think identified by carol and others uh including the lincoln afterwards as a sort of um the breakdown of classical general relativity so one of the virtues i think of your scenario is that it doesn't require quantum mechanics uh to be reconciled with gravity and i always say that until you hand me a letter from god and it says you have to marry quan there has to be a quantum description of of relativity with uh that's commensurate with all of our other classical and quantum theories of electromagnetism and quantum quantum electrodynamics um the only two regions where it seems to be relevant are near singularities which are unobservable so we have this kind of uh uroburus the snake eating its tail that we need quantum gravity to explain singularities but singularities only exist in regions that are in practice and in principle unobservable so i wonder if you can take the other side julian do you think you know argue against your position in other words a steel man what do you think are the best arguments that we need that we have to have a theory of quantum gravity do you think it's uh there are arguments to be made that support the necessity of a quantum theory of gravity or is it just kind of part of the appeal that human beings have to make everything classical quantum uh what i feel definitely is we have to have a quantum theory of the whole universe because i mean otherwise i mean the fact the the facts of quantum mechanics around us i mean you and i couldn't be talking like this if it weren't for quantum mechanics that's absolutely correct yeah what i what i do i mean everybody thinks uh i think virtually everybody in the field thinks that the problems of quantum gravity are at their most extreme at the big bang and also in in black holes and for a long time now my collaborators and i have been saying no quantum gravity will the the quantum theory of the universe will take its simplest form at the big bang because their its shape is at its most uniform and the quantum issues will become interesting later on and we know they're we know they're damnably interesting now and they seem to be interesting in black of the evidence from black holes is that that they're interesting by by then i mean with the hawk of work of beckenstein and hawking um so that's how i would put it um and well that that's all i can say i think that we're looking to turn this upside down there's an interesting thing i know uh color very very very well and i've also talked quite often with abby ashtakar and quite a number of years ago this might be 20 years ago or more i said to them [Music] do you think quantum gravity will require a first of all to be in the first place a quantum theory of the whole universe or only of a part of it and both abbey and carlo unhesitatingly said no we can start with quantum gravity in in a part of the universe we don't have to have a quantum theory of the whole universe now with my machian uh convictions that you have to talk about the whole universe i i disagreed on that one there so that that would be where i would disagree with with carlo and um uh abbey um i think lee has more sympathy of those three founders of loop quantum gravity lee is closer to my position i think than the other two yeah i agree uh i think the thing that you know perplexes people and is sometimes used by proponents of intelligent design and and proponent religious uh you know practitioners is is to use this board uh guth lincoln theorem um and uh and use it to basically motivate a beginning which would then you know be in harmony with the torah or old testament uh description in genesis 1 1 interestingly enough that fred hoyle used to criticize cosmologists who supported the big bang as being overly concerned with genesis which i think is laughable nowadays people don't associate cosmologists with being fervent bible beaters but nevertheless people do use this theorem and vlankan himself says things that the uh he doesn't actually believe it leads to a singularity but he does say that this uh the entropy uh according to the behavior of entropy in the observable part of the universe is many orders of magnitude lower than its maximum state and the second law of thermodynamics says that the initial entropy of our co-moving region on this boundary not the singularity but the eventual boundary that all space-time geodesics terminate on going backwards must be lower still so the universe must have originated in a very special non-random state of extremely low entropy in your mind i mean what is uh what is the lacuna the gap the the the problem with with lincoln's claiming that necessitates a new interpretation of time itself in other words armed with gr armed with an expanding space time you don't even need to say it's inflation although obviously the lankan and guth are huge supporters of that but nevertheless if you just have an expanding space time you'll go back to some point in the past uh and you'll achieve lower and lower entropy and the question of course is that uh you know who who ordered it to be zero in the beginning but that's that's you know uh so i guess i'm asking what are the what are the failings of that theorem the singularity theorem which is a misnomer of bored bluth and lincoln that that your theory rectifies is it is it that that it's purely uh geometric it's scale free it's gauge invariant is it that it's more an interpretation a a difference rather than an actual physical prediction obviously they would predict inflationary gravitational waves because they support inflation but you believe inflation is not necessarily mandatory so what are the virtues of of the approach that you've taken over there succinctly as possible well i i come back again i'm going to get a verging on on religious now um okay it's okay we've had on rabbis and and christian scientists i uh i am very very struck by this idea that the universe does have a beginning but it's but it's a very uniform beginning and out of that then structure grows now i recently checked out the etymology of the word creation do you know what it is as a matter of interest uh creation the word in in latin or yeah where what what is the etymology of creation well i'll emerge from or something like that to emerge uh you're quite close it actually comes from an indo-germanic word which means to grow it's nothing to to me it's not creatio x nihilo it's to grow now if you think about my idea that the universe starts very uniform it's like a flat field with soil just a little bit of variety in the soil and then out of that the grass and the bushes and the trees grow and the quantity that measures that growth is i come back to this extraordinary in the newtonian theory in the in the point particle model the quantity that measures that is this complexity it does everything at once it's the size of the unit it's the intrinsic size of the universe measured by rods within it it's the it's the potential energy made scale invariant i think there's a very good chance it's got it that it's time so so in fact i would say time is creation because the amount of creation is literally the time it's the potential energy made scale invariant it is really actually rather if i may say so an attractive theory it'll be a pity if it's wrong well at least you're not saying what uh einstein said on the occasion of the 1919 eclipse saying that he would feel sorry for god if the data didn't bear him out um i want to turn to a different epoch in the universe when it's married matter dominated far away from the radiation domination of the extremely early universe now it's matter dominated and uh and it's growing at a certain rate but the rate of changes is not accelerating yet because dark energy is subdominant how does that fit in how do you have periods of contraction or relative deceleration of rods and clocks in in your model how can that accommodate the observations that we know the universe was much less rapidly differentially relatively speaking to today accelerating compared to what it is doing now and will do into the far future i'll be very speculative here and just suggest that perhaps the acceleration of the universe might be an artifact of not treating scale properly so the all i will say is that first of all it's clear to me that clocks come into existence later on in the universe it's quite interesting and and very significant in this dude the universe is as it gets more clumped and mata gets more concentrated in into galaxies and stars and things like that and i think it's quite interesting that the acceleration seems to have set in more or less at the time broadly speaking when the universe really started to become significantly uh inhomogeneous so maybe i mean dirac and others conjectured that the gravitational constant was not constant and in fact when i was first collaborating with my italian collaborator bertotti back in the 70s it was still experimentally an open question whether the gravitational constant was time dependent as dirac had argued uh now that's been ruled out however i don't rule out a connection between the increasing clustering the the growth of black holes the increasing number of black holes with the rate of clocks that these could somehow be uh that could be some effect there and that the apparent acceleration of the universe is an artifact of that now that that's that's very speculative but i think it's i don't think it can be ruled out and when we look at um the the features of uh of the janus point model i think what's would be very interesting for me to get is your thoughts on uh you know the inspiration that you talked about from leibniz is uh moanid ology uh so you know how how did you come up with this uh as an influence what was the role that leibniz plays in this besides you know kind of being thought of as a counterweight if i'm not mistaken to newton uh who wrote you know the calculus as as well as you know what feynman who plays a role in your book he called the language that god speaks so in the one hand we have you know scale free things you're talking about gauge and variant objects like shapes being a primary fundamental monad of the universe perhaps but then you have calculus playing the actual role in differential geometry and relativity and so forth so how do you reconcile these two aspects of mathematics and their usefulness in physics and as vigner said so unreasonably so that on one hand we need that calculus which is inherently dimension full but then these other objects are more fundamental in your estimation because they're dimensional less so how do we reconcile leibniz versus einstein or or maybe even you know euclid versus versus newton as mathematical kind of uh protagonists said opposed to that you put quite a lot for me here yeah let me let me say there have been two uh sort of philosophically speaking uh there have been two huge influences in my life the first was aunts mark when i read him that was back in 63 it wasn't until uh 1977 so 14 years later that i read leibniz for the first time and he uh just a few of his philosophical papers and they made a huge impact on me they the thing that he said was that what he was really attacking was newton's idea of space being something like a perfect translucent block of ice where there was no marks in it nothing like that and and leibniz just raised his hand in horror and says if there's no variety in the world we can't see anything we can't begin without variety so right at the heart of leibniz's whole feeling is that we rely on variety we we rely on differences and then his idea was that to have a a world that is more perfect than any other one it should be maximal variety that the variety so in the monadology he says that the the universe is more ver we live in a universe that is more varied than any other possible universe but subject to the simplest possible laws and i found that a very attractive idea and i uh lee smolin took it over very enthusiastically and between us we developed an idea called maximal variety which still lives on now interestingly about seven years ago i had an introduction to the man who had just retired as the editor of the liveness papers it's a colossal project they got to volume 50 when i had lunch with him in hanover and he said and i told him of my enthusiasm for that idea of leibniz and as i recall he said to me well leibniz actually had two ideas one was that the universe is eternally more varied than any other possible universe and the second one is that it's striving to become ever more varied we talked a lot about uh some of the novel concepts in the book i wonder if you could just briefly recapitulate the two that are most significant to me are really in contrast to the so-called past hypothesis which in uh in in essence inserts by fiat the low entropy state of the early universe what is the replacement of such a phenomenon in the janus point concept the first thing to say is that the whole notion of entropy developed with thermodynamics out of the study of steam engines and in a steam engine the steam must stay in the cylinder which is effectively in a box and the main starting point i have to completely rethink the whole story of the entropy of the universe as opposed to systems within it i mean the laws of thermodynamics certainly held in my kitchen where i'm sitting now but do they apply unchanged to the whole universe which i don't think is in a box so that's my starting point to rethink the concept of entropy so if i start with the simplest model i can which is the newtonian theory of point particles interacting through universal gravitation and right back in 1772 the great mathematician lagrange was studying the three-body problem earth sun and moon and he found a very important result which was it was the first qualitative result in dynamics it was in the infinite past as you think of it in newtonian terms the size of the system that's its moment of inertia is infinitely great as time passes it gets smaller and smaller it comes down to a minimum value of minimum finite value and then it increases again to an infinite value and i call that minimum point the janus point now if you have lots of particles at that janus point the system the particles are more uniformly distributed than on either side of the janus point and in addition as you go away from and they're moving more or less like a swarm of bees in a random way so you would say there that their entropy is maximal it's very much like a lot of atoms in a box or a free gas in a box but as you go away from the janus point in both directions of time the system breaks up into clusters and becomes much more ordered and those that degree of clustering can be measured precisely by a quantity a scale invariant quantity it's a pure number that i call the complexity that defines direction of time bi-directional arrows of time away from the janus point and rather than the universe getting more disordered as you go away from that disordered state at the janus point it gets ever more better ordered clusters formed kepler pairs form and go around each other in beautiful uh elliptical orbits and so i would say this is an indication that we we've got a completely different story when we think about the whole universe not being in a box because the it is just quite different that janus point is not there for some path hypothesis it hasn't been had to nobody's had to add it to newton's equations to put it there it's there as a direct consequence of newton's equations as long as the energy is not negative and even if it's negative you'll get something like a janus region in virtually all the solutions so this for the main claim i make in the book and i don't necessarily tie it to that specific janus point model is a second one where it's only half of that javascript so to speak is that this just puts a really fundamental question over the whole idea that the arrow of time corresponds to the growth of an entropy of the whole universe and that to explain it you have to say that the universe started in a very special way and some of the um notions that i've talked about on this channel have to do with not popper's version of falsification which i always point out popper actually thought that the steady state model or the quasi-steady state model had some virtues but actually the virtue of you know epistemological uh concision and austerity parsimony etc but primarily not necessarily due to falsification but um but nevertheless due to the ability for current day evidence to shed some light or some bayesian you know confidence on our models are there predictions of the janus point paradigm that would lead us to have more faith in it and is there anything that could uh falsify it this notion of the um the the fundamental nature of of dimensionless objects and and sort of gauge free objects is there anything that could lead more evidence to it that exists currently or could exist in the future or is there anything that could prove it wrong in your opinion i think there is real hope uh and this relies on not taking that particular model that i showed where the size in the newtonian picture remains finite but it is actually zero and now there are these very so the basic idea that my collaborators and i have been following for some time is to use newtonian theory to get some idea of what might be happening in general relativity at the big bang because remarkably in newtonian theory and it's been known for over a century that there are situations in newtonian theory if you have a whole lot of particles that are interacting with newtonian gravity they can all collide instantaneously at their center of mass at the common center of mass and that's called a total collision and by time reversal symmetry you can reverse the direction and then it becomes what i call a total explosion and the very interesting thing about such a total explosion is that it has to start in a very very special way it has to start when the particles are in what is called a central configuration the shape is very special and there's one of those possible shapes which is extremely special which is the most uniform state that the universe can possibly have it's not exactly uniform but it's very uniform indeed and then as you go away from that total explosion this quantity that i call complexity the measuring the measure of the clustering grows it flu in the classical theory it fluctuates and it grows and now if something like this happens in general relativity in in a quantum form of general relativity i think this could indicate that the universe of necessity the law that governs the whole universe starts in the most uniform way it possibly can but with certain small fluctuations which then grow and if you leave out all the fine details this is broadly what we know about the universe so i think there is a hope that if these ideas could be developed further in the context of general relativity it would lead to precise predictions about fine details in the microwave background and that would be be a great triumph if it could be done uh we spoke earlier about the board guth philenkin theorem and whether or not that could um you know be leading cosmologists to a low entropy state of the universe what are your feelings about the board guth blanken theorem which sometimes improperly is called a singularity theorem as the lincoln himself has said it doesn't really predict a singularity and as sean carroll has pointed out you know there are alternatives to thinking about it and perhaps the best way to think about it is when classical gr breaks down one of the virtues of the janus point paradigm is that you only need newtonian mechanics essentially it's very generative and and classical general relativity but i wonder can you you know steel man your opponents and say what are the arguments that you believe are valid that motivate a quantum theory of gravity uh well i i think it's it's in the first place i would say it's a quantum theory of the whole universe uh that's uh that's what's that's what we need i mean certainly you and i couldn't be talking to each other if quantum mechanics wasn't governing the way things behave right uh that's that's for absolutely sure this photons coming off my laptop screen showing your smiling face in california that's an absolute miracle so i do believe we need a quantum description of the whole universe um but the point i keep on making is that the idea that the universe has a size which is somehow measured by something outside the universe is just for me that stinks i think it's just not tenable if the universe is a self-contained object in newton in einstein's theory if it's spatially closed then any size it has must be some intrinsic size that's from measuring rods within it and therefore the only thing that one should look at is the shape of the universe and i don't think anybody is thinking about that well sometimes roger penrose is talking a little bit along those lines but certainly not in the way that we are so if you actually look at what the shape of the universe is doing when you have these total explosions that start from a very uniform shape this suggests a completely different way of thinking about cosmology that the universe starts uniform you don't need inflation to make it uniform because it must start uniform that's the nature of the law of the universe and it's a time asymmetric law in this case where we have a total explosion it it it's it starts very uniform and it just goes on growing getting more structured the the structures increase and that matches exactly what we see if you look through any telescope that's the story the telescopes tell you and when we look back in cosmic history we see after an early period very brief period of radiation domination the universe became matter dominated and there it stood until you know five billion years ago or so when it started to accelerate how does entropy behave and how does the janus point reconcile the you know the relative deceleration of the universe if not a contraction still the um the arrow of time and and so forth how does that behave in a universe with um with multiple components just taking matter and dark energy which we know to exist how do we how does that reckon how is that reconciled with the janus point um paradigm well uh let me say i uh i have to call it it's the half janus point paradigm yes the theory starting with the total explosion in the newtonia in the in the standard picture with size it's where it's the size of zero but i would say size is a gauge degree of freedom that what you should think of is the universe starts in the most uniform with the most uniform shape it can possibly have now rods and clocks don't exist anywhere near the big bang they only they come into existence later on as the universe evolves if the universe is all tightly interconnected as a machine relational picture of the universe as it should be then i think it's quite possible that the apparent except that the accelerated expansion of the universe is actually not really there it's because we don't realize that the rates of clocks are affected by how clustered the universe is and it is interesting that the accelerated expansion seems to have begun more or less at the phase at the epoch when the universe was becoming significantly clustered clumpy in homogeneous so that's a very tentative idea but i think it's not impossible we we do know that dirac thought that the gravitational constant was time dependent now we know that's not that's ruled out but i think it could be that there's an overall effect of the um it's it's our not understanding the way clocks work and um and also i mean i do think there must be a quantum description of the universe but the rules of quantum mechanics that we find about us i believe are emergent so that they don't the the universe the quantum mechanics of the universe doesn't look like the quantum mechanics of the objects the things we study in in in the universe in the laboratory and that is matched with the origin of inertial frames of reference and mark said the law of inertia the inertial frames of reference they don't hold in bland absolute space and time as newton imagined sort of a translucent block of ice and a clock ticking away it independently of anything that's happening in the universe mark said somehow rather the fact that the law of inertia is something due to the action of all the masses of the universe on each individual body and that is the theory that i elaborated with my italian collaborator bruno bertotti back in the late 70s early 80s and i think that is the definitive implementation of mark's principle mark's idea and i think it's entirely possible that something happens with quantum mechanics that the local quantum mechanics we see with hilbert space and operators and all that is an emergent uh effect from a rather different quantum mechanics of the entire universe um i see and uh i think the last uh kind of topic that i want to get into is uh this very provocative statement that you made that that position is fundamental but momentum isn't and i wonder if you can answer that in just one second i want to remind people we're talking to julian barbour a renowned uh cosmologist a true remote mentor to me and many people i'm sorry to tell you julian you're uh you have influenced me to the good hopefully uh so i'm going to ask you about the primacy of space over time in just a second office yeah you've got to call it stop at some stage i could talk to you till the end of time which uh which could could be a long a long period of time um so julian now what i would love to do with you if you will uh indulge me is go into the impossible this is when i asked my guest to honor me by coming on this podcast with kind of the big picture topics we discussed a lot about your knowledge which is with the word science in latin cientia means knowledge but now i want to talk to you about your wisdom your sapienza and if we could do that i would be quite a great thrill to me so would you mind talking about the so-called big picture questions that i always love to ask my guests now in the into the impossible segment yeah that's fine by me yes i'll do my best okay here we go uh so the first one has to do with uh with sort of a concept in in judaism or in uh the philosophy of my religion which has to do with what's known as an ethical will so um many many decades from now when you reach the biblical age of 120 years old and as shakespeare said and you quote many times from shakespeare in this wonderful book the janus point uh you depart again not for 50 years please god or nature or janus if you will i want to ask you what do you want to put in your ethical will not your not your knowledge but your wisdom to leave for future future heirs of the ideological kind which i count myself as one yeah well i did i did uh let me just i did make just a few notes because it's quite a challenge so first of all when i was in my late teens i got very enthusiastic about antiquity and the above all the greek authors and i picked up from them two greek sayings in all things moderation and know thyself know thyself is that the oracle at delphi uh and certainly i think i have i've certainly done i think quite well in in all things moderation uh you know i never smoked i never drank excessively and things like that i had one of us and so forth um know yourself know thyself is is harder i'm not sure quite how well i knew myself um perhaps i could say that i was i used to be uh not terribly seriously i used to be bipolar and didn't know about it you didn't read about those things when i had it but by great good luck i i was put on medication uh back in 2004 after i had been psychotic which has completely eliminated all traces of me being a bipolar you might not have thought it at times in my thing but it's a it's a miracle it's the it's the medication they used to give to epileptics called valproate they don't understand why it works for epilep it's an anti-convulsant but it is it is definitely stabilized me once i went on to it through a trial i joined a trial and it it cured me so now i think i do can say i more or less know myself [Music] so a thing the other thing that i i did i was very lucky in going independent um and i think i was lucky in my father he'd been an independent arabic scholar he actually became deputy head of the arabic service of the bbc and he may have been a bit of a role model for me so um i would say don't be afraid of being going independent um [Music] i when i got really interested in the nature of time and motion uh i decided not to go into academia i decided to go independent um felix birani a noticed relative noted relativist i asked him what it's like being in academia he said if you can do the administration give the lectures and write one or two good research papers a year yes if you have doubts about any of those three no and i immediately it was clear to me it wasn't for me because i wanted to study the nature of time and motion and there was no way i was going to produce one of two good research papers a year so i went independent and i deliberately took up the most boring job imaginable which was translating russian scientific journals into english i got into it by chance i'd learnt russian as a hobby and would you believe it for 28 years i translated those journals but it gave me a salary at least as good as a professor and i had a third of my time to do exactly what i wanted wow and i reckon an interesting thing is i reckon i generated about 70 million words in english now and those are all on library shelves around the world now if you ranked humanity in order of how many words they generated which are library shelves where would i come i think i've got a sporting chance to be in the first top 20. i think you do yeah i think yeah it was it was desperately boring but i opted for that against trying to set up a because a lot of people say they'll they'll go and they'll make a business make their fortune and retire at 35 and i said to myself if i tried that it won't i'll get so hooked by the business better to have a boring job where i'm desperate to get away from it and think about the physics and it worked and then in 1996 on the 19th of may i said i'm not translating anymore and i've been free now for 25 years and i've had 25 years with really good collaborators top class collaborators and the ideas are still coming the the the they're great and i'll say one more thing perhaps one there's a wonderful stand-up comedian paul merton in this country and he publishes autobiography a few years ago and i heard him interviewed on radio because when i went decided to go independent my family and my wife's family from germany said you're taking a huge risk julian and paul merton decided to become a stand-up comedian when he was 16 and the in the interview on the radio he was asked didn't that feel risky and paul said it didn't feel risky it felt and i suddenly realized that was exactly what had happened with me so my ethical will would be if you really feel something is necessary perhaps have the courage to go for it and certainly i've never regretted it and um so then one other thing i will say you asked what what was the best job i had somewhere the best job i had for for four and a half months i was a weather observer in the canadian arctic by some chance i got a job up just exactly just a quarter of a mile inside the arctic circle at bathurst or bathurst bathurst inlet it's one of the beauty spots in the arctic i was there for four and a half months and the all i had to do every three hours i had to do five minutes work which was make a weather observation at least there's consistency there it's like san diego you know it's it's very easy i absolutely loved it there i mean there were about a dozen inuit there was a hudson bay company a man with a hudson bay and just one canadian i was with and i took two suitcases full of books and read them by the midnight sun and for years afterwards i would say i've got to go back to the arctic it was so beautiful but amazingly uh and this is the thing which i do think we should really try and preserve the world it is so amazing and the the worry of wars and and climate change i so far as i know the average temperature at bathurst inlet where i was for the summer of 1958 is now four or five degrees centigrade warmer wow yeah that is just staggering in you know when i've gone from early 20s now to 84 that that is a scary thought so that brings me on to what i would say is you know uh well yes you asked me about i mean you you suggested i read the uh at the end of genesis but um i'm very impressed by another jew that is jesus and he he summed up it in two commandments love the lord thy god with all thy heart and with all thy soul and with all thy mind this is the first and great commandment and the second is like unto it thou shalt love thy neighbors thyself of these two commandments hang all the law on the prophets now i'm agnostic i have no idea where the universe comes from why i'm here but i do think it is precious and you know i think it would be an appalling tragedy if intelligent life disappears from the universe we might be the only place in the universe where it exists so i think that's very important and i do think the preservation of intelligent life and happiness uh are valuable so i i i rate happiness very highly so as regards jesus's second commandment i i accept it totally i say try to treat your neighbor as yourself but make sure that you're happy yourself otherwise you're just going to be a down right miserable person right and that's the people and and i will say of myself luckily i've basically been a pretty happy person i've been blessed with a cheerful personality it seems yes yes you certainly have and you are very influential on me and literally thousands around the world yes it is true that uh the commandments are very uh to be taken seriously means that if you have to love your neighbor as yourself you know all the more so we say in hebrew culver homer do you have to love yourself like yourself uh but but you know if you have to treat people with with um with weightiness with hot with with importance as your parents and so you should treat yourself and that's great that you mentioned self-care and taking care of your mental health as you did and i imagine that will play into your advice to your former self which will be the final question uh the second question though is reminiscent of one of the characters in this book richard feynman who has many many um appearances in the janus point and he said if asked to summarize the greatest uh amount of information in the shortest sentence he said that he would sort of uh put forth the atomic hypothesis that everything is made of atoms and they have electrons and structure and so forth i want to ask you if you had a monolith a time capsule like arthur c clark sentinel and you could be guaranteed julian it would last for a billion years what would you put on it or in it besides a northern canadian weather forecast i would put my two triangles yes let me see them hold them up so so here they are now the the the fundamental question that goes back to newton and leibniz is how do you define motion what is motion so newton invented absolute space and time so that he could defy so that he could give a mathematical definition of the law of inertia so for him there is an absolute space like a block of ice and in it you can draw lines and free particles will move in a straight line and leibnitz said this is nonsense all that happens is there are separations between particles and they change so if this is if at this triangle at the vertices of the triangle there are three particles they can move according to newton they can move in two ways they can change the separations between the particles and at the same time the whole triangle can be moving in absolute space and leibniz says no that's no good all that is real is the changes in the separations now i do take very seriously the principle of least action how do you define action what is the action when i go from a triangle that has this size and shape and a triangle that has that size and shape slightly different and i'm going to say what is the difference between those two triangles without using the position that they are in my kitchen i'm just going to use the two triangles so i'm going to say i take this is my reference triangle and then i take the second triangle and i lay it on top of the other one and try and bring it to overlap to congruence congruence is the fundamental principle for making proofs in geometry so i'm going to try and bring it to congruence but i can't do it exactly because they're not the same size and shape but but what i can do is is move them into different positions and then i can take the separation where particle one is in this triangle and in this triangle so there's a separation i'm going to square that separation i'm going to multiply it by the mass of that particle i'm going to do it at each of those three vertices and then i'm going to add that up and then i'm going to move it until i get it into the position that minimizes that quantity and i say that that is the process of best matching that was what my collaborator betty and i developed in our paper published in the proceedings of the royal society in 1982 and i think i am very confident that that actually solves the problem of how you define motion provided the universe is a self-contained thing so that's what's going to go in my monolith out in there and this there's quite a nice i used to travel to all the conferences with my triangles they were two big cardboard um plywood uh triangles and hold them up and do that and on google images you can find a nice color picture of me and crack off in in poland doing it so yes we'll include that monolith in the background as long as the universe is something self-contained i'm very confident about that yeah it meets a lot of criteria maybe what we'll do is make your monolith uh have a triangular cross section or multiple triangular cross sections like some kind of penrose staircase and the final question that we ask all of our guests has to do with sir arthur c clarke's third law did you ever know sir arthur julian no i've i've read one or two of his books i when i was younger i i did read a bit of science fiction the war of the worlds and things like that but um i don't read any science fiction now but yeah i know i certainly know of the man anyway right that's for sure yes so he had many uh many great aphorisms including uh my favorite uh from time to time to use with my colleagues is uh he would say for every expert there's an equal and opposite expert but for now his third law gave me the name of this podcast his third law states the only way of discovering the limits of the possible is to venture a little way past them into the impossible so i want to ask you what was the aspect of life that was most mysterious or most foreboding intimidating as a 20 year old but now it makes perfect sense to you because you had the courage to go into the impossible what worried me i tell you what i don't think i was ever seriously worried by anything brian well i was dead lucky i mean my my my father was earning good money at the bbc he'd inherited some money i was very lucky i grew i had a very stable upbringing i at school i was re i could high jump i was reasonably athletic i now you ask me i don't think i ever worried about anything i just i wanted to become an astronomer i got absolutely hooked on astronomy at about the age of 10 and until i started asking myself what is time and what is motion uh i still wanted to be an astrophysicist like you or a cosmologist but then suddenly these questions came so i said i'm just going to try and answer these questions so i i was lucky i wasn't [Laughter] is that a satisfactory answer yeah you knew early on well that's great and you also gave wonderful advice earlier in this segment but julian for now i want to thank you for having uh the courage the brilliance the insight to go uh two hours plus with me in total and uh and i think again this could be just the logarithm or the of the amount of time i wish i could spend with you and i hope i get to meet you someday soon all right great good to talk to you bro thanks very much any sufficiently advanced technology is indistinguishable from magic [Music] you

Channel: Dr Brian Keating

Views: 11,515

Keywords: Dr Brian Keating, brian keating into the impossible, into the impossible, lex fridman, sabine hossenfelder, eric weinstein, brian keating, cosmology, michio kaku, big bang, arrowoftime, entaxy, Royal Zero, Ernst Mach, Janus Point, Borde Guth Vilenkin, thermodynamics, closer to truth, julian barbour, is time real, julian barbour time, how does time work, time is an illusion, barbour end of time, closer to truth full episodes, theory of time, janus point theory of time

Id: nojc3iXpFxw

Length: 105min 42sec (6342 seconds)

Published: Thu Sep 09 2021