Into the Impossible With Brian Keating - Julian Barbour: The Janus Point and the Arrow of Time (#180)

Episode Date: September 9, 2021

Julian Barbour is the author of the highly regarded The Discovery of Dynamics and the bestseller The End of Time and now, The Janus Point. He received his PhD in physics from the University of Cologne in 1968. He is a past visiting professor of physics at the University of Oxford and lives on the edge of the scenic Cotswolds, UK. A major new work of physics, The Janus Point will transform our understanding of the nature of existence. In a universe filled by chaos and disorder, Julian Barbour makes the radical argument that the growth of order drives the passage of time — and shapes the destiny of the universe. Time is among the universe's greatest mysteries. Why, when most laws of physics allow for it to flow forward and backward, does it only go forward? Physicists have long appealed to the second law of thermodynamics, held to predict the increase of disorder in the universe, to explain this. In The Janus Point, physicist Julian Barbour argues that the second law has been misapplied and that the growth of order determines how we experience time. In his view, the big bang becomes the "Janus point," a moment of minimal order from which time could flow, and order increase, in two directions. Julian Barbour on "The Janus Point: A New Theory of Time" | Videos: https://youtube.com/watch?v=FMD8B7VRX0w&feature=share https://www.youtube.com/watch?v=0E0NmHQ0WLc 00:00:00 Intro 00:02:57 The story of the book cover. 00:04:33 What does time mean to you? 00:05:36 The influence of Ernst Mach. 00:09:11 About the "Royal" Zero. 00:28:30 Entaxy, thermodynamics and statistcal mechanics. 00:35:57 The cyclic universe. 00:41:28 The theoretical virtues of the Janus Point. 00:55:05 Is there a necessity for a theory of quantum gravity? 01:07:00 What is the failure of the "singularity" theory of cosmogenesis? 01:09:00 The essence of the Janus Point theory. 01:17:58 The Borde-Guth-Vilenkin Theorem 01:21:25 How do you reconcile the Janus Point Paradigm with current observations? 01:38:00 What would you put on a timeless monolith? 01:43:00 What is now possible that you once thought was not as a younger man? LinkedIn Jobs is the best platform for finding the right candidate to join your business this fall. It’s the largest marketplace for job seekers in the world, and it has great search features so that you can find candidates with any hard or soft skills that you need. And now, you can post a job for free. Just visit linkedin.com/impossible to post a job for free.  Audible is hands-down my favorite platform for consuming podcasts, fiction and nonfiction books! With an Audible membership, you can download titles and listen offline, anytime, anywhere. The Audible app is free and can be installed on all smartphones and tablets. You can listen across devices without losing your spot. Audible members don’t have to worry about using their credits right away.  Start your free 30-day trial today:  Audible.com/impossible or text “impossible” to 500-500 📺 Watch my most popular videos:📺 A New Contender is Here! https://www.youtube.com/watch?v=-6A6myur--c Frank Wilczek https://youtu.be/3z8RqKMQHe0?sub_confirmation=1 Weinstein and Wolfram https://www.youtube.com/watch?v=OI0AZ4Y4Ip4?sub_confirmation=1 Sheldon Glashow: https://youtu.be/a0_iaWgxQtA?sub_confirmation=1 Michael Saylor The Physics of Bitcoin https://youtu.be/CaN_CDKqXOg?sub_confirmation=1 Sir Roger Penrose, Nobel Prize winner: https://www.youtube.com/watch?v=AMuqyAvX7Wo?sub_confirmation=1 🏄‍♂️ Find me on Twitter at https://twitter.com/DrBrianKeating 🔔 Subscribe for more great content https://www.youtube.com/DrBrianKeating?sub_confirmation=1 ✍️Detailed Blog posts here: https://briankeating.com/blog.php 🎙️Listen on audio only platforms: https://briankeating.com/podcast.php A production of http://imagination.ucsd.edu/ Learn more about your ad choices. Visit megaphone.fm/adchoices

The Janus point is 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 physics could be solved with a revolutionary new proposal from Julian Barboor, who's today's guest on Into the Impossible. Come along and experience this journey in what Lee's Mullen called a rare combination of humanity and a perspective coming from a lifetime of the study of history and philosophy of cosmology. Julian Barboor 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 Barboor. Any sufficiently advanced technology is indistinguishable from magic. Hello, everybody, and welcome to a very special episode of the Into the Impossible podcast, featuring renowned physicist Julian Barboor, 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 Jeremy England, who is not English, but he was on to speak about his book. Every Life is on Fire. We have Carlo Rovelli, who's written many books on Time. And we'll have Craig Callender'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 such a treat for me. Julian Barboor 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 been a very mixed year weather-wise, but it's very pleasant today. I even took this news for an hour in the garden. Oh, that's lovely. Yeah, we are experiencing what is known as June Gloom. Even though it's July, we should be frying in July. But in San Diego, right now we've got May Gray and June Gloom,

and 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, various activities and I wanted to give it the depth and attention that it deserved.

And Julian Barber was the author of highly regarded the discovery of dynamics and the bestseller 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 life and the university. and time. But before we do that, Julian, 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, and that will come out in our discussion, I think. The cover is entirely the work of basic books and the UK edition. Perhaps I can show you the UK edition, which is also quite striking. There's the cover of the UK edition. 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. So Roger, publishers have done me proud. No question of it. Yes, it is a lovely work. and it's a work of art as well, and I recognize many names in here, including T.J. Kelleher, who I guess was your editor, one of your editors. I've known him for several years myself,

but I wanted to begin by discussing the notion of time and where does it come from? Because I've had on Carl Over Valley, I've had on many Frank Wilczek, and I always have these solipsistic or tautological definitions that I am forced to use. 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 Carlo, 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 Dirac 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 the primary thing is change.

What Mach 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 relativity 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? And I'm still working on that. And I've got a wonderful group of collaborators now, somewhere in their early 20s.

then I've got some in their 40s and another very good mathematician who's about 60 I guess. So it's actually speeding up now these things. Let me make one comment, though, about Einstein, if I may. When Ernst Muck died in 1916, Einstein wrote a very handsome obituary of him. And among other things, 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 when he was asked what his time, I think his answer was very much like

what Frank Wilczek 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 he never did that. But in fact, I think one of the things in Chapter 7 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 proximate to that point in time, if it is indeed even a point, with a question I've posed to all of my guests, including Sir Roger, after he won his Nobel Prize, and that was 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 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? Well, we would really have to go into 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, when I went to state,

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 saying that there's 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 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 all illustrating things with triangles.

So if I had just three points, three bodies in the universe, and there are the apex of the three vertices of the triangle, it's meaningless to say what the size of the triangle is because there's nothing 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 Iran'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. I think it probably should be two pi, shouldn't it? Four pi is the area. So the thing that I'm saying is that if you just look at what the shape does, I don't think, I suspect there are no singularities at all. Hmm. And is that a fundamental aspect of an error or problem in relativity or in our concept? Because 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 infinities should be taken as seriously as they are. and yet they're 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 falsification later on. But this notion that something infinite can go to become something finite has kind of been resolved or at least addressed since the time of Zeno and his famous paragraph. So, you know, what extent is if infinity, if zero is real, I guess the question would be, one over infinity, why is that not real? Well, one over zero, sir. 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, 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 altogether at their common center of mass. And this is called a total collision. 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. When they collide together, the shape must tend to be an equilateral triangle. Now, if you say that the 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, 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. 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 a completely different way, potentially, on thinking about the singularities

at 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 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 Bang. where the universe is in its most uniform shape that it can possibly have.

That's in, and 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, in fact, 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 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 the reason why we always imagine there's always a size to something

is because of the image that's projected onto our retina. So the size of the object is the fraction of the area compared with our complete retina. And that's just the same if you think about looking at the sky at Orion, the nebula of Orion, sorry, the constellation of Orion, 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 one of my listeners was eager to discuss with you is whether or not, if time is emergent, you know, and space time are somehow equivalent that, you know, shouldn't space be emergent in some sense. And Lee Smallen, our mutual friend, who you kindly asked a question of when he appeared on the podcast about two months ago, sat to say he has not reciprocated yet.

I'll be waiting and 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 basically fundamental constraints on causality. And so what about space would be privileged? In other words, would space pre-exist time? 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 a wonderful saying. And I just don't think you can do without geometry. In fact, I would retain the continuum. And all I would retain is angles. And this is actually 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 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 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 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 really, I would say,

of lengths, that's all I think you need. You could probably just get by or you'd 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 upend 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, you know, what has been the reaction to that statement? That is a very provocative statement.

And you admit as such in the book that 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 treated with a lower priority, perhaps than position? Well, let me say, first of all, there is a mathematical way of dealing with a phase space

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 Marx ideas seriously that really what happens locally is somehow rather is governed by the whole universe.

So Mach 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, time really in that classical picture, before we attempt to get to quantum mechanics, 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 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 all the others but the totality will make a sort of 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 the measure of how much it has changed its position compared with how much all the others have changed their relative positions. I see. Right. And so that then takes us back to this ratio or gauge-free description. But I also think, Julian, I often say mathematics is highly abstract in that you never seen a triangle. 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 weigh?

And that's a nonsensical question, because triangles are, you know, collections of three non-colonere, co-connected points, which are themselves of zero dimension, which is kind of mind-boggling for humans to envision. So it's curious to me that you can build up shake dynamics and the reality of dynamics 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 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 all of the great concepts in mathematics are suggested by our experience, and they're idealized from that. And I think the real numbers are a human creation, but I would say let us work with them. I had a few years ago, I had a discussion with Gerhard Toft, 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. His ideal is to build up everything from zero and the positive integers. Nothing else, he said. So I said, you're then like Dedekind, who said, you know, 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, why don't you accept the real numbers? Because the real numbers are a creation of man. Man is part of nature. And he smiled and I think he accepted that that was not an unreasonable point of view. We have to start with somewhere. And I think there's that, there's a wonderful saying of Popper, the philosopher, about there is no really sound empirical foundation of what we do in theory. 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 attitude. So I will happily for the moment accept the real numbers, and Euclidean and Riemannian 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 Entaxi.

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 systems to convert energy into labor or work, et cetera? So what is Entaxi, what does it do for us that entropy does not do? Well, 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 Sardicano 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 Klausius' is 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 hour of time, what entropy is and so forth. And do you 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. 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 in a given interval of energies how many quantum states there are 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 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, 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 uses it as a ruler to make it. 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 what I call a state function which grows. And then if you look in these Janus point solutions, you find that the number of microstates 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 Flavia 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 goes on increasing. forever in a Newtonian system which is unbounded. And 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 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... The other particles, if they're single particles, are moving in accordance with Newton's first law. So this is actually exactly showing what Einstein wanted to understand where do inertial frames of reference come from 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 Machian treatment of a universe requires. everything falls together into place beautifully.

Wonderful. So the next topic I want to talk about is the notion of 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 cosmogynese and other concepts, 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,

if I say, 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 life cycle. Your summer starts now with Memorial Day deals at the Home Depot. It's time to fire up summer cookouts with the next grill for burner gas grill on special buy for only $199. And entertain all season with the Hampton Bay West Grove seven-piece outdoor dining set for only $49. This Memorial Day get low prices guaranteed at the Home Depot. While supplies, price in valid May 14th or May 27th, U.S. only exclusions apply. See homedepot.com slash price match for details.

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 universe would compile more and more entropy. Does the Janice 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 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 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. Virtually, certainly every solution that is not, doesn't have negative energy, has that behavior. 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, lots of micro-states being bundled up together so that you can't see what's happening. And it's just, I think the, one of the main things I feel really confident about 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, the 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 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. Maybe people are just blind to this. I think one of the reasons, so the point about thermodynamics, it seemed to rest on such wonderfully secure foundations, the impossibility of making perpetual motion machines. But it's still all of its concrete results, all of the solid results rely on that box. You read Willard Ibs's great book published just before he died. He essentially

requires, he's talking about 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 Janus point. But if you have these total explosions, which come out. 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 arrow 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 you 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. Just look. You take what they look like. It's the heavens proclaim the glory of God or something.

They proclaim my idea that the universe is more interesting. So let's discuss what I've 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 Paparian falsification rubric. It's much more thorough. He does involve certain things that I find controversial, such as your theory should strike scientist 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 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 sine qua 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 if employed and taken seriously, would have led to the falsification of his ideas because he believed in vortices and gears and ether and all sorts of things. So imagine if experiment, if Carl Popper were around back then, I don't know, no, no, there's no little gears. There's no little whirls and vortices.

So your theory must be wrong. No, so that's not fair. And to be fair to Popper, he said things like he appreciated the steady state and he appreciated other models staying around longer, perhaps, than history might judge them to be valid because it impels people to make observations and you want to crack your test. Some of the other theoretical virtues I want to confront you with, and you mentioned 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'm going 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 it will be inescapable. It will be, you know, the dominant future of existence in the universe will be that we will be aware of an arrow of time. So I think 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, which actually by Fiat, which we physicists, you know, find abhorrent, but nevertheless, 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 disprove that? Because obviously it's consistent. If I was putting on a critics hat, I would say, well, that's a retradiction, Julian.

You're trying to come up with a theory that provides an hour of time. But what new, like what can we tell my future grad students and your grandchildren, et cetera? what can they look forward to doing to providing evidence or falsification of that scenario, given that we all believe there is an hour of time that we experience, is there a consequence of the data, you know, some limit on black hole masses, some limit on minimum number of generations of leptons, is there some piece of data of evidence that could substantiate it beyond the retradictive nature of the existence of an arrow of time? The best hope I have is not for those Januspoit 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 really, 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, 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 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 Sloan, they make the first progress to showing that something similar like that can be expected in general relativity. It's related to the BKL scenario when it's quiescent, if you're familiar with that, Brian. So the great triumph of inflation was to give these fluctuations, the Harrison Zeldovich fluctuations out of which 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's very difficult to see how it gets started. And my understanding is there's some uncertainty about how it ends and whether there's internal inflation and things like that. Now, if these ideas are right, 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 will surely be, I think you have to admit, for all the triumphs of inflation, 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 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 it may be decades, if we're on the right track, I think it could be decades before we've vindicated. But if we do come to vindication,

it will be a clean sweep. We will start with a very uniform universe. Of necessity, it will start very uniform and then it would 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 theory of structure formation than a theory of the initial conditions of the universe. And that avoids having to think about both its lacunae in terms of inability to explain itself without the existence of the multiverse,

which I find personally more to the unpalatable side, as my viewers will undoubtedly recognize, and sort of almost tantamount for a replacement of a godlike fiat instantiation of the universe with an infinite number of creative forces like mini 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 it makes a concrete prediction. It may not be observable. The waves may be too feeble to leave an 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.

In the Janus point, I assume there are no gravitational primordial tensor perturbations. In the, well, in the Newtonian model, certainly not, that's for sure. There may well be in general relativity when, but there are really a lot of work 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 that could be gravitational waves. And as opposed to the present situation where a magnitude is unknown, it's the R parameter, isn't it? 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 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, there's nothing outside it, then you, 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 Tico Brahe had made, he thought that that implied that the comet must have gone clean through. the crystal spheres that carried the planets. So nothing was carrying the planets. And 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 bogeyman, it's causing its potential. 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, Dr. Stephen Meyer, who supports intelligent design and we had a lively department. about that, but nevertheless, was this board Gooth Valen theorem that posits that any expanding space time had necessarily a beginning or ultimate boundary, sometimes misidentified, according to Belenkin, as a singularity, but more properly, I think identified by Carol and others,

including Valenkin afterwards, as sort of the breakdown of classical general relativity. So one of the virtues I think of your scenario is that it doesn't require quantum mechanics 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, there has to be a quantum description of relativity that's commensurate with all of our other classical and quantum theories of electromagnetism and quantum electrodynamics, the only two regions where it seems to be relevant are, near singularities, which are unobservable. So we have this kind of uroboros, 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 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? What I feel definitely is we have to have a quantum theory of the whole universe, because, I mean, otherwise, I mean, 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.

Yes, absolutely. what I do I mean everybody thinks 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 black holes

and for a long time now my collaborators and I have been saying no quantum gravity will 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 damnably interesting now. And they seem to be interesting in black. The evidence from black holes is that they're interesting by then, I mean, with the work of Beckenstein and Hawking. So that's how I would put it. And well, that's all I can say, I think, that we're looking to turn this upside down. There's an interesting thing.

I know Kala very, very well, and I've also talked quite often with Abiyashdaka. And quite a number of years ago, this might be 20 years ago or more, I said to them, do you think quantum gravity will require, 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 Abbe and Carlo unhesitatingly said, no, we can start with quantum gravity in a part of the universe. We don't have to have a quantum theory of the whole universe. Now, with my Machian convictions that you have to talk about the whole universe, I disagreed on that one there. So that would be where I would disagree with Carlo and Abbe. I think Lee has more sympathy.

Lee is, of those three founders of Loop Quantum Gravity, Lee is closer to my position, I think, than the other two. Yeah, I agree. I think the thing that perplexes people and is sometimes used by proponents of intelligent design and proponent religious practitioners is to use this board, Goof-Lankan theorem and use it to basically motivate a beginning which would then be in harmony with the Torah or Old Testament 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 Blanken himself says things that he doesn't actually believe it. leads to a singularity, but he does say that this, the entropy, 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 spacetime geodesics terminate on going backwards, must be lower still. So the universe must have originated in a very special, non-random, standard. of extremely low entropy. In your mind, I mean, what is the lacuna, the gap, the problem with Lankan's claimant 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 Valen and Goof 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 and you'll achieve lower and lower entropy. And the question, of course, is that, you know, who ordered it to be zero in the beginning? But that's, you know. So I guess I'm asking, what are the failings of that theorem, the singularity theorem, which is a misnomer, of board gluth and the blanken that your theory rectifies?

Is it that that it's purely geometric? It's scale-free. It's gauge-invariant. Is it that it's more an interpretation, 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 the approach that you've taken over there, succinctly as possible? Well, I come back again.

I'm going to get verging on religious now. It's okay. We've had on rabbis and the Christian scientists. I am very, very struck by this idea that the universe does have a beginning, 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? creation, the word in Latin? What is the etymology of creation?

Isn't it to emerge from or something like that, to emerge? You're quite close. It actually comes from an Indo-Germanic word, which means to grow. It's nothing to me, it's not Creatio X. Nihilo. It's to grow. Now, if you think about my idea that the universe starts very, 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 point particle model, the quantity that measures that is this complexity. It does everything. It does everything at once. It's the size of the universe, it's the intrinsic size of the universe, measured by rods within it. It's the potential energy made scale invariant. I think it's a very good chance it's got it, that it's time. 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 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. I want to turn to a different epoch in the universe when it's matter-dominated, far away from the radiation domination of the extremely early universe.

Now it's matter-dominated, and it's growing at a certain rate, but the rate of change 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 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. 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 very significant in the history of the universe is as it gets more clumped and matter gets more concentrated 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 in homogeneous.

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. Now that's been ruled out. However, I don't rule out a connection between the increasing clustering, the growth of black holes, the increasing number of black holes, with the rate of clocks, that these could somehow be, that could be some effect there, and that the apparent acceleration of the universe is an artifact of that. Now, that's very speculative, but I don't think it can be ruled out. And when we look at the features of the Janus Point model, I think what would be very interesting for me to get is your thoughts on, you know, the inspiration that you talked about from Leibniz is monid oligy. So, you know, how did you come up with this as an influence?

What is 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, who wrote, you know, the calculus as well as, you know, what Feynman, who plays a role in your book, he called the language that God speaks. So in one hand, we have, you know, scale-free things. You're talking about gauge invariant 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 Bigner 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 dimension less. So how do we reconcile Leibniz versus Einstein or maybe even Euclid versus Newton as mathematical kind of, protagonist's set of post. Well, you put quite a lot for me. Let me say there have been two sort of philosophically speaking

there have been two huge influences in my life. The first was Ernst Mark when I read him. That was back in 63. It wasn't until 1977, so 14 years later that I read Leibniz for the first time. And just a few of his

philosophical papers, and they made a huge impact on me. 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 Leibniz just raise 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 rely on differences. And then his idea was that to have a world that is more perfect than any other one, it should be maximal variety. The variety. So in the

monodology, he says that the universe is more, 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 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 Leibniz Papers. It's a colossal project. They got to volume 50 when I had lunch with him in Hanover. And I told him 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. You said this place was steps from the water. We just haven't found the steps yet. How much did we save? Enough. Enough to get lost. Or you could book a stay with Hilton. Welcome to your oceanfront room. Just steps from the water.

The Hilton sale is on now. Book on Hilton.com or the Hilton app and save up to 20% to get the stay you expected. When you want savings, not surprises. It matters where you stay. Hilton for the stay. We talked a lot about 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 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, 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 hold 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, a 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 cyst of 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, bidirectional 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 elliptical orbits. And so I would say this is an indication. that we've got a completely different story when we think about the whole universe

not being in a box because it is just quite different. That Janus point is not there for some past 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 the main claim I make in the book, and I don't necessarily tie it to that specific Janus point model as a second one where it's only half of that Janus point, 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 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

concision and austerity, parsimony, etc. But primarily, not necessarily due to falsification, 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 it and is there anything that could falsify it, this notion of the fundamental nature of dimensionless objects 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. 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 measure the measure of the clustering grows it fluctuate 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 a great triumph if it could be done. We spoke earlier about the Bored Goose-Velan theorem and whether or not that could be leading cosmologists to a low-entropy state of the universe. What are your feelings about the Borg-Guth-Velan theorem, which, sometimes improperly is called a singularity theorem, as Lincoln himself has said, it doesn't really predict the 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 classical general relativity. But I wonder, can you, you know, steal man your opponents and say, what are the arguments that you believe are valid that motivate a quantum theory of gravity? Well, I think it's, in the first place, I would say it's a quantum theory of the whole universe. 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 it's.

things behave. That's for absolutely sure. There's 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. 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 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 starts very uniform and it just goes on growing, getting more structured. 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? while the relative deceleration of the universe, if not a contraction, still the arrow of time and so forth, how does that behave in a universe with multiple components, just taking matter and dark energy, which we know to exist? How do we, how does that reconcile with the Janus Point

paradigm? Well, let me say I have to call it it the half Janus point paradigm. Yes. The theory starting with a total explosion in the Newtonia, in the standard picture with size, it's where it's the size is zero. But I would say size is a gauge degree of freedom. 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 come into existence later on as the universe evolves. If the universe is all tightly interconnected as a Machian relational picture of the universe says it should be, then I think it's quite possible that the apparent, 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 pace 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 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, it's hard not understanding the way clocks work. 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 they don't, the quantum mechanics of the universe doesn't look like the quantum mechanics of the objects, the things we study 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. don't hold in bland absolute space and time as Newton imagined sort of a translucent block of ice and a clock ticking away, 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 Brunabertotti back in the late 70s, early 80s.

And I think that is the definitive implementation of Marx's principle, Marx idea. And I think it's entirely possible that something happens with quantum mechanics, that the local quantum mechanics we see with Hilbert's space and operators and all that is an emergent effect from a rather, the different quantum mechanics of the entire universe. I see. And I think the last kind of topic that I want to get into is this very provocative statement that you made 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 Barbar, a renowned cosmologist, a true remote men.

mentor to me and many people. I'm sorry to tell you, Julian, you have influenced me to the good, hopefully. So I'm going to ask you about the primacy of space over time in just a second. You've got to call a stop at some stage. I can talk to you to the end of time, which could be a long period of time. So Julian, now what I would love to do with you, if you will indulge me, is go into the impossible. This is when I ask 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 the word science in Latin,

sciencia 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 guest now in the Into the Impossible segment? Yeah, that's fine by me. Yes, I'll do my best. Okay, here we go. So the first one has to do with sort of a concept in Judaism or in the philosophy of my religion, which has to do with what? it's known as an ethical will. So 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, 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 errors of the ideological kind, which I count myself as one. Yeah. Well, I did, let me just, I did make just a few notes because it's quite a challenge. Yes. 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 at the oracle at Delphi. And certainly I think I have, I've certainly done, I think, quite well in all things moderation.

You know, I never smoked. I never drank excessively and things like that. It makes one of us. And so forth. Know yourself, know thyself is harder. I'm not sure quite how well. I knew myself. Perhaps I could say that I was, I used to be, 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 was put on medication back in 2004 after I had been psychotic, which has completely eliminated all traces of me being bipolar. You might not have thought it at times in my thing, But it's a miracle.

It's the medication they used to give to epileptics called Valprite. They don't understand why it works for epilept. It's an anti-convulsin. But it has definitely stabilized me. Once I went on to it through a trial, I joined a trial and it cured me. So now I think I can say I more or less know myself. So the other thing that I did, I was very, lucky in going independent 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 I would say don't be afraid of being going independent I when I got really interested in the nature of time and motion I decided not I decided not to go into academia. I decided to go independent. Felix Birrani, 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 learned 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 top 20. I think you do. Yeah, I think you do. It was desperately boring, but I opted for that against trying to set up, because a lot of people say they'll, they'll make a business, make their fortune and retire at 35. And I said to myself, if I try 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 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 published his autobiography a few years ago. And I heard him interviewed on radio because when I 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 in the interview on the radio, he was asked,

Didn't that feel risky? And Paul said, it didn't feel risky. It felt necessary. 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 I've never regretted it. So then one other thing I will say, you asked what,

What was the best job I had? So I was the best job I had for four and a half months. I was a weather observer in the Canadian Arctic. By some chance I got a job of 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 all I had to do, every three hours, I had to do five minutes work, which was make a weather observation. Well, at least there's consistency there. It's like San Diego. You know, it's very easy.

I absolutely loved it there. I mean, there were about a dozen innuit. There was a Hudson Bay Company, a man with 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, and this is the thing which I do think we should really try and preserve the world. It is so amazing. And the worry of wars and climate change. 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 is a scary thought. Yeah. So that brings me on to what I would say is, you know, well, yes, you ask me about, I mean, you suggested I read the at the end of Genesis, but I'm very impressed by another Jew, that is Jesus, and 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 neighbor as thyself. Of these two commandments hang all the law on the profits. Now, I'm agnostic. I've 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 are valuable. So I rate happiness very highly.

So as regards Jesus's second commandment, I accept it totally. I say try to treat your neighbor as yourself, but make sure that you're happy yourself. Otherwise, it's just going to be a down, right, miserable person. Right. 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 the commandments are very, 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, Kolva-Homer, do you have to love yourself like yourself? But, but, you know, if you have to treat people with weightiness, with heart 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. The second question, though, is reminiscent of one of the characters in this book, Richard Feynman, who has many, many appearances in the Janus point.

And he said, if asked to summarize the greatest amount of information in the shortest sentence, he said that he would sort of 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 here they are. Now, 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 define, 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 three particles will move in a straight line. And Leibniz said this is nonsense. All that happens is there are separation 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?

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. Congerence 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 what I can do 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, Bertotti 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 there's quite a nice, I used to travel to all the conferences with my triangles. They were two big cardboard. plywood triangles and hold them up and do that. And on Google images, you can find a nice color picture of me and Krak off in Poland doing it. Yes, we'll include that. My monolith.

As long as the universe is something self-contained, I'm very confident about that. It meets a lot of criteria. Maybe what we'll do is make your monolith 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. Clark's third law. Did you ever know Sir Arthur, Julian? No, I've read one or two of his books. When I was younger, I did read a bit of science fiction, The War of the Worlds and things like that. But I don't read any science fiction now. But yeah, I certainly know of the man.

Right, right. That's for sure, yes. So he had many, many great aphorisms, including my favorite from time to time to use and my colleagues is 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 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 father was earning good news. money at the BBC. He'd inherited some money. I was very lucky. I grew, I had a very stable upbringing. At school, I was, 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. 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 was lucky. I wasn't. 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 the courage, the brilliance, the insight to go two hours plus with me in total. And I think, again, this could be just the logarithm or 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, Brian. Thanks very much. Any sufficiently advanced technology is indistinguishable from magic. Please support the show by rating, commenting, sharing, and leaving reviews. We appreciate hearing from you, and it really helps keep our universe expanding. Watch our YouTube channel at Dr. Brian Keating. That's DR. Brian Keating, and join our premieres Tuesdays at 8 a.m. Pacific Time. Follow Brian on Twitter and Medium and support us on Patreon at Dr. Brian Keating.

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