149 | Lee Smolin on Time, Philosophy, and the Nature of Reality

The challenge to a theoretical physicist pushing beyond our best current theories is that there are too many ways to go. What parts of the existing paradigm do you keep, which do you discard, and why make those choices? Among today’s theorists, Lee Smolin is unusually reflective about what principles should guide us in the construction of new theories. And he is happy to suggest radical revisions to well-established ideas, in areas from the nature of time to the workings of quantum mechanics. We talk about time, the universe, the role of philosophy, a new picture of spacetime, and the future of physics.

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Lee Smolin received his Ph.D. in physics from Harvard University. He is currently on the faculty of the Perimeter Institute in Waterloo, Canada, where he was a founding member. Among his awards are the Majorana Prize, the Klopsteg Memorial Award, and the Buchalter Cosmology Prize. He is the author of several books, most recently Einstein’s Unfinished Revolution: The Search for What Lies Beyond the Quantum.

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0:00:01.0 Sean: Hello everyone, and welcome to the Mindscape podcast. I’m your host, Sean Carroll. One of the interesting things about science is that people within science, the working scientists, can get really quite emotional and tied up in their favourite ideas even if we don’t yet know which idea is right. Even if we’re convinced that eventually the experiments are gonna have the last word, and they’re gonna tell us which ideas are right along the way, we get very attached. We care about one idea being right or the other one, which is very different than the stereotype of the cold and analytical science type. Part of that is, of course, that the interesting part of being a theoretical physicist, the kind of scientist that I am, is proposing new ideas for what the fundamental laws of nature might be.

0:00:42.9 Sean: A lot of theoretical physics is taking the known laws of nature and working out what their consequences are. So how do stars form, how do you make a high-temperature superconductor, how does DNA split, and things like that, but another part of it is proposing entirely better, newer novel ideas for what the fundamental laws are supposed to be. And when it comes to that, how in the world are we supposed to know how to best invent new laws or if someone proposes some new laws, how in the world are we supposed to say, “Yeah, that seems plausible to me,” or, “No, no, no. That’s completely crazy.” This is a judgment call. This is something people, who are completely working in good faith, will have different ideas about.

0:01:25.1 Sean: So today’s guest is Lee Smolin. He probably needs no introduction, very well known to any of you who are interested in theoretical physics. Lee is one of the pioneers of loop quantum gravity. He is one of the founding members of the Perimeter Institute for Theoretical Physics in Waterloo, Canada. And one of the interesting things about Lee is that not only is he working in quantum gravity and related fields, but he thinks very carefully about how to be a theoretical physicist. And the other interesting thing is, his answer to that question is different than most theoretical physicists’ answer is. To be honest, a lot of theoretical physicists have some feelings about what works and what doesn’t, but they don’t reflect on it that much. They just march forward, “I think this idea is good. Let’s look at that,” whereas, Lee really thinks about the philosophical underpinnings of what he’s doing, tries to build a coherent story based on principles that one should follow to say, “Here is what should come next.”

0:02:23.8 Sean: And the reason I like it is because I love that way of working. And yet, Lee and I come to completely different answers about almost all of the interesting issues in theoretical physics. So I think that this is a very interesting conversation to listen to both because of the substance of the theoretical physics ideas we talk about and also for the stylistic questions of how physicists or scholars and intellectuals more broadly should proceed in developing new ideas. Anyway, let me remind you that we love it here at Mindscape when you do things like leave reviews of the podcast on iTunes, etcetera, or you can support Mindscape by going to Patreon. Go to patreon.com/seanmcarroll, and you can become a patron that lets you ask me anything questions, get ad-free episodes of the podcast, and generally feel good about yourself. With all that, let’s go.

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0:03:31.5 Sean: Lee Smolin, welcome to Mindscape podcast.

0:03:34.1 Lee Smolin: Thank you very much.

0:03:35.7 Sean: So it’s great to have you on. You’ve clearly written a lot about different topics in physics, many of which overlap with things that I’ve written about. So before we get to specifics of your recent work, I thought for the audience members out there, for the one or two who are not familiar with your work, it’ll be fun just to go through and give some of the positions, some of the basic ideas that you’ve been thinking about over the years. So why don’t we start with the most obvious one, which is quantum gravity. You have spent a lot of your physics career thinking about quantum gravity. I bet that most listeners of Mindscape understand that quantum gravity is a thing that we need to understand, but let’s put those people aside, and for the ones who are not familiar with the problem, how do you even say what the issue is when it comes to reconciling quantum mechanics and gravity?

0:04:21.8 LS: So the way that I say it is that Einstein started this revolution in physics in 1905. And there were two parts to the revolution, quantum theory, which Einstein really got started on, got it started on, and the revolution of thinking about space and time and gravity and cosmology, which came as general relativity. And my sense is that we’re still in the midst of this revolution. And there are… Particularly challenging are two aspects of it. Well, I’ll say three aspects, which I think are all connected. One is to make sense of quantum mechanics. And of course, you and I both have a lot to say about that. But another one is to get a description of the gravitational field and spacetime in the same terms as the other physical fields.

0:05:21.9 LS: And I say this because I tend to agree with Einstein, that bringing together gravity and the other forces will change our description of the other forces as much as gravity so whether we’ll relativise the quantum or quantise relativity. Certainly, I’ve thought about both of those things. And then there’s another set of problems which I think are deeply related to those, which is how the universe chose the laws that it seems to have chosen. And not just what are the laws, but why are they the laws? How were they chosen?

0:06:01.1 Sean: Right. You, of course, famously have been working… Were a pioneer of loop quantum gravity in particular. What is your current state of thinking about how loop quantum gravity is doing? Was it a step in the right direction? Is it still on the table or do we not know yet?

0:06:18.3 LS: Good. So can I tell a little bit about that story the way that I tell it…

0:06:25.1 Sean: Please.

0:06:25.1 LS: Which is I think different from how some other people tell it. So I wanted to do quantum gravity coming into undergraduate school and graduate school. But I went to graduate school at Harvard during a period when the standard model had just a few years ago been invented. And it was full of all that wonderful physics. And I particularly got captivated by the physics of Ken Wilson and Sasha Polyakov, Sasha Migdal, and a number of other people who were interested in the idea, analogous to the quantisation of magnetic flux and superconductor, that you could have something like the electromagnetic field, namely these gauge fields, where the electric fields flux got quantised. And that would lead to observe a picture of the electric flux being carried along strings that had quarks at the ends of them. And that heuristic picture, as it developed with QCD, had a powerful influence on me.

0:07:30.2 LS: And I thought, I think I was just in the right place at the right time, that how natural it would be to apply those same methods and those same ideas to the gravitational field. So that’s what I started off doing. My first paper was the version of lattice quantum gravity, in which the loops of quantised electric flux on the lattice were the main actors. Now, we would call this confoma.

0:07:57.5 Sean: So sorry. Just to be clear for the people who are not… This is great stuff ’cause I’m very interested in what you’re saying, but it might not be familiar to everyone. So there is this technique for understanding the strong interactions, like you said, the glue on fields that hold quarks together that thinks not just about the field at every point in space, but what happens when you go around a loop. So that’s an existing thing in the study of the strong interactions. And you’re saying, so your inspiration was, to do that for gravity.

0:08:27.1 LS: Right. And it was pure stuff. [chuckle] And so, what was needed was a good formulation of general relativity that made the analog of the gauge fields that tells you how to move things around what we called parallel transport around space that those are the variables in the Yang-Mills theory. And we needed a formulation of general relativity that focused on the same kinds of variables in general relativity. And I’ll be condescending about if I ask the current provider though in late 1985. And then it was just like snapping little toys together, so to speak. And so why I wanna emphasize that is, for me, it’s an idea and it’s a powerful idea. And at the kinematical level, it gave us very interesting insights in itself. String theory, which had been developing and had started to get interested in quantum gravity in a big way two or three years before that, so it was not different in my mind. It was also the development of his quantised loops of electric flux. And…

0:09:48.4 Sean: The… Sorry. Let me just butt in to say, the very first person that I interviewed… Not the first episode I published, but the first person I interviewed for the Mindscape Podcast was Carlo Rovelli. And at the end, I said, “So do you think that there is some hope for string theory and loop quantum gravity to come together and merge in some common understanding?” And he said, “No.” [chuckle] So you might wanna put your opinion about that also?

0:10:14.5 LS: Well, Carlo and I are dear, dear old friends. And we disagree about many, many things, but, and I don’t know how probably it will be, but just my mind says, and the way that I looked at the problem of quantum gravity, was those were different versions of the same idea. And I certainly try to bring them closer. And Carlo would be right to say without much success, but the thing that didn’t happen, sort of, sociologically, in which there were these two communities of people who didn’t understand each other, I was very much against some at both sides. So I don’t see them really… Certainly, they have different… They’ve taken away different shapes. But I think the following things I would defend saying at the following ways. Each of them, and a number of other approaches as well, have some brilliant successes, and that makes us really interested.

0:11:21.4 LS: Each of them has roadblocks, which have been there for at least 20 years and longer. And I think it’s ridiculous that we continue, and in fact, we’re not continuing very much if you look at what the new people coming into the field are doing. There is very little here… I would say nobody is doing what we were doing 25 years ago, thankfully, or just a handful. The last time I saw a paper or talking with somebody, I actually calculated a string amplitude. So it’s a long time ago.

0:11:57.9 Sean: Long time though, yeah.

0:12:00.3 LS: One of what the really interesting young people are doing are as hard to classify. It’s some of this, and some of this, and they walk between the communities, and they don’t notice that there are barriers. And somebody like Sabrina Gonzalez Pasterski and Laura De… So that’s what I’m hopeful for.

0:12:23.7 Sean: I think that’s right. I’ve had a few string theorists on the show also, and I always like to ask them, “Do you call yourself a string theorist?” And they always say, “No.” [chuckle] All the modern string theorists, even Lenny Susskind who is modern in the sense of pushing the field forward, but not modern in the sense of when he appeared on the scene, yeah, doesn’t think of himself under that label because like you say, the boundaries are falling between them. But let me just go in one further step in that direction because back in the day, at least one of the arguments between people who were on the loop quantum gravity side and people on the string theory side was whether or not you could really make progress by thinking about gravity in and of itself, apart from the other forces of nature. And one of the string theory arguments was you can’t. I mean, they only made up that argument because they seem to have a way of doing them all at the same time. What is your feeling about that now? I mean, does it make sense to think about quantum gravity as a field apart from everything else or do you have to just dive right in and get a theory of everything?

0:13:28.7 LS: I think it happens to make sense to think about quantising the gravitational field without matter, but it’s much better to try to include matter, I mean, that the world is full of matter. When you include matter, there are some questions right away that are really compelling to think about. One of them is that matters becomes chiral, which maybe not everybody knows the words, but looking at the particles in the standard model, especially the neutrinos in a mirror, they’re not the same. There’s not a symmetry under looking at nature than they are. And that seems tempting to think of that as fundamental.

0:14:16.4 LS: And there’s some reasons we’ve talked about that. And then… But then, we’re supposed to connect that up with gravity, which at the classical level is completely left, right symmetry. And that seems odd. And one of the attractions of the original Ashtekar way of thinking about the gravitational field was that it is also chiral. And is this sort of hidden chirality, which is if you look at it in the right, twisted way, it looks simpler. And that’s true of a number of other developments in spacetime theory like twistor theory, Roger Penrose’s invention. So I certainly think there’s matter in the world. And I’m very interested in the question of why this matter. It’s not just they’re gauge theories, but why is this sensitive quasi-one?

0:15:16.1 Sean: Good. And then the other thing I wanted to get on the table was one outgrowth of string theory in the late ’90s was the idea of the multiverse and the anthropic principle. I mean, it was a pre existing idea, but it became very, very popular with the string theory landscape of different possibilities. You were a critic of the way that that was approached in the string theory community with the anthropic principle, but you have your own ideas about cosmological natural selection and so forth, which to some outsiders seemed similar, even though you were criticizing the string theory version. So can you tell the people who don’t know anything about these ongoing debates where you come down there?

0:15:51.5 LS: Well, again, let me start if it’s not too self-referential…

0:15:56.4 Sean: Please.

0:15:56.8 LS: With how I started on this. So Andrew Strominger who is a friend, called me one day… This is the way I remember it. And there was… So string theory at first, in 1984, there were five versions of string theory in 10 dimensions. And then they were if you found out you could curl up the extra six dimensions and listen, beautiful, elegant, complex geometry, you could classify some of the different ways to curl them up. And there was supposed to be 700,000 variants according to Yau who we all admire but nobody understood the argument. And there was a sort of idea that we would look and pick among the 100,000 or so and find the one MSP that looks just like the standard model at one. And Andy had realized that there were uncountably many more. That was just the tip of the iceberg. And he wrote a paper about that. And when he called me, he was very despairing about that. He says, “We’ll never get any phenomenology out of this because how are we going to search this vast, huge space to find the standard model?”

0:17:11.9 LS: And so at that point, just the serendipitous things, I was reading a lot of theoretical evolutionary theory just for fun, and you must know the attractiveness of reading Stephen Jay Gould at his prime or Lynn Margulis. It was wonderful stuff so I kind of had it on the brain. And I started to think, could you attach… Biology solves that problem as a huge landscape. And the word comes from there. It comes from population biology. It was a huge landscape that population biologists talk about, and they have basically a mechanism to search, to think about it like a mathematical geneticist. They have a mechanism to search this landscape and find optimal creatures, find creatures that are… Whose fitness is optimized. So I started thinking along those lines and just ask, can I invent a scenario where there will be something that will be extremised?

0:18:17.1 LS: And one of the things I thought about which was the thing that I published under cosmological natural selection was that what the universe wanted to do was reproduce itself and reproduce itself through black holes that led to baby universes. That was an old idea, and that was due to Johnny Wheeler and other people at that time. Also, due to the charming was the idea that the constants of nature changed when you went through that transition to new baby universe. He called it reprocessing universe and he imagined that everything was just changing randomly. And all I had to add was a constraint that said, “No. On the average, per dimension list constants to change per generation is small.” And then you have a search procedure that will discover those regions of parameter space and elite universes that have a lot of black holes. So that was the idea. And I then had to learn a lot of astronomy and astrophysics which was great and put together some sense of whether that was plausible.

0:19:27.3 LS: So I published that idea. It makes a very small number of predictions that I… I’m following those predictions. I don’t think it’s likely right. And I deeply dislike the fact that to work, it depends on multiple versions of the universe. Although they are rather differently organized than in the internal inflation picture, I’m still certainly, well not me, but that idea is guilty of propagating many universe to explain their own. And I deeply despise that. [chuckle] But I will point to the fact that it makes predictions as a kind of proof of concept.

0:20:14.3 Sean: Okay so both the string theory landscape and your version of cosmological natural selection involve many, many different universes with different features, but you’re saying that, if I understood correctly, because your universe is changed slowly, and you can look for the solution that maximizes their reproductive fitness and that makes more predictions than the string theory landscape does?

0:20:39.1 LS: Yes, but it’s zero versus two.

0:20:41.4 Sean: Okay. [laughter] I mean, I think that…

0:20:44.5 LS: You go ahead.

0:20:46.5 Sean: Any of them would make predictions like the cosmological constant allows for the existence of life, right?

0:20:51.0 LS: Yeah. Yes, but what… To be a real prediction, it has to be a feature of the universe that’s decoupled from orthogonal to whether there’s life or not.

0:21:06.2 Sean: Okay.

0:21:06.4 LS: Though one of those predictions is about the value of the strange quark mass and the relation that it has to the upper limit of masses of neutrons stars. And, as far as I can tell, that’s not coupled to whether we exist or not.

0:21:23.4 Sean: Okay, that makes sense. And then the final thing to get on the ground, because it’s very related to this multiverse question, is the many-worlds interpretation of quantum mechanics, one of my favorite ideas. And you’ve written a book recently, Einstein’s Unfinished Revolution, where you talk a lot quantum mechanics and you make it clear that many worlds is not on your list of viable alternatives. So maybe you wanna share with the audience why you think that’s the case.

0:21:50.1 LS: Let me practice that. And I’m not just saying that because this is your program. If you look at that book, you’ll see that the many worlds to the Everett approach has two chapters and has the longest chapters in the book. So I take you guys seriously.

0:22:10.4 Sean: Good.

0:22:11.2 LS: And I spent a lot… In fact, that was an agony for me [chuckle] because I do not believe for various reasons that I hope we’ll talk about, but that’s the way nature is organised. But I think that there’s been the… There’s a world of things that have happened since the original Everett tries to it, kind of sense of it. And there’s a number of people in Oxford who you know who they are, and yourself and your collaborators, and a number of other people, who have worked really seriously to make sense of that interpretation or the original claims to that interpretation. And it was really challenging for me to try to understand what was going on because it’s pretty subtle, at least for a dumb guy or whatever like me. [chuckle] It’s pretty subtle, and I wanted to present this to… When we were writing these books, some of it is to promote our own ideas, but some of it is the responsibility of presenting it to the public so they can choose. So they can get it right.

0:23:24.9 Sean: Sure.

0:23:25.8 LS: And so we can talk about the ins and outs of that, but that’s my preface.

0:23:31.9 Sean: Yup. And with that preface on the table, why don’t you like many worlds, having done all this agonizing work? [chuckle]

0:23:39.5 LS: What level of personal explanation would you like? So let me start with… It cuts off my hopes. So my hopes are and have always been, that quantum mechanics was incomplete. And there was a physical theory that is physical discoveries to be made, which would be enlightening about the nature of space and time. And that’s always been the goal of the work that I’ve been trying to do in quantum foundation. So the minimal thing to say is that, if you’re right, then I have nothing to… There’s nothing to do in the direction I’ve been working and I don’t… It’s not that I feel like I have a great stake, but it’s taken a lot of time and effort and I still believe that that’s a life or to me it’s a very possible direction for science.

0:24:40.2 Sean: Good. So let me actually… Let me just sort of reiterate that in my own words so you can tell me if I’m understanding correctly. One of the things about Everett, the many-worlds interpretation is, it says that we basically do understand quantum mechanics. We understand what the sort of space of quantum states is, how it evolves. There’s a tremendous amount of work to be done “to interpret it,” to figure out how that simple underlying description matches on to the world that we see, but the basic physics is somehow there. And what you’re saying is that you have either a hope or desire or intuition or a thought that we don’t understand the basic quantum dynamics and that trying different versions of that might help us understand other problems in physics, so you don’t wanna shut that off in the way that Everett might see appear to do.

0:25:30.0 LS: Yes. At least I wanna go ahead in my little corner and develop that because I think that that’s tied to the question about how the universe chose its laws. I think it’s tied to quantum gravity. And especially what ties it to quantum gravity is the hypothesis that space is not fundamental, and that space is there for emergent out of something more fundamental and that nonlocality… That something being emergent, the property that we call locality, the things talk with other things nearby them would be disordered. That’s not what physicist say. To have nonlocality appearing in the universe and that nonlocality could play a role in the nonlocality that we discover in the quantum phenomenon. And that’s an interesting question. So that is part of the picture I have, the math I have in my head of where I’m going.

0:26:42.5 Sean: Well that makes sense. And in fact, it’s a perfect segue because I did wanna get into now the specific ideas, so thank you for indulging me with that little set of background questions. But I thought it might be fun to start, because in your book, you’re very interested in philosophy as well as science, and you’ve taken seriously a lot of philosophers, not just the most modern philosophers doing quantum foundations or whatever, but the history of philosophy and a lot of thoughts from that. And one of the perspectives you put forward is that you would like whatever our physical theory that we develop to be to come from some well-articulated principles, and you say that Einstein did this with relativity, for example, we should at least give it a try. And then you list in your book in Einstein’s Unfinished Revolution, you have five principles that you want a theory to follow. Now, I don’t wanna put you on the spot. Do you wanna tell us what the five principles are or do you want me to mention them and then you can comment?

0:27:41.1 LS: Well, [laughter] I have different versions of this, so let’s see if it’s the same. I’ll start off and we’ll see if its the same file.

0:27:49.0 Sean: Good.

0:27:49.4 LS: All the lists that have been done start with the idea of relationalism. That’s the first one. That is the principles that Leibniz laid out in his writings about how to make a background independent to the final gravity in final cosmology, which is what Leibniz was doing [laughter] in my opinion.

0:28:12.2 Sean: So by the way, in your book, that’s principal number two. That’s not principle number one. [laughter]

0:28:17.1 LS: Principle number one is probably realism then.

0:28:20.6 Sean: Nope, it’s background independence.

0:28:21.8 LS: I missed that. I’m sorry. [laughter] Background independence is a clear consequence of riding this. Anyway…

0:28:30.6 Sean: Exactly. I actually… I’m only drawing this out because as a fellow book writer, and we know better than the people who are reading the books that they evolve in time, right? Like the book that you actually read is just a snapshot of what it was when you had to hand it in, but if you were given more time, you’d probably keep tweaking it along the way.

0:28:50.5 LS: Oh, of course, of course.

0:28:52.5 Sean: So what is relationalism then? What does that mean in down-to-earth terms.

0:28:56.6 LS: In down-to-earth terms, that means that there’s no such thing as absolutely where you are in space because where you are relative to some landmarks, which you have to pick up. It is the same thing as true of time. There’s no absolute time, which goes on with it, is any change or motion in the world. The principles of life, let’s say you have to describe time in terms of change and use some actual… We would say a physical clock. We don’t believe the way Newton believed that there’s some view of God, which is absolutely where things are and when things are. That they all… It all comes down to relationship. One of the ways that Leibniz put it is the principle that is called, I will say in other words, and it’ll come to me.

0:29:56.9 Sean: Okay.

0:29:58.1 LS: The principal is that there can be no two events in the world that are identical, described by the relational properties so… Or no two objects. So if you have an event and you look around you and you see a certain deal around you, and you have another event which sees exactly the same view around it, then they must be the same event.

0:30:25.1 Sean: This is the identity of indiscernibles.

0:30:27.0 LS: This is the identity of indiscernibles, thank you, principle of identity of indiscernibles. And I find this a very useful principle for constructing theories.

0:30:36.9 Sean: And I get the impression from reading those principles in particular, but the whole thing that, part of your intuition is that we make progress by stripping away given elements. The less the ultimate theory of physics says, “Well, this is just fixed once and for all, and we can’t change it,” the happier you are. And so we went from there from Newtonian absolute space to Einstein and quantum mechanics, and it’s a series of stripping away of absolutes.

0:31:06.2 LS: Yes, and I think more specifically, the way that I like to say this, is that we live inside this universe, this one universe, for purposes of discussion give me that for the moment, this one universe, and we’re trying to understand its properties. Now, what we do most days is this, is we look at a small part of it, a ball rolling down an inclined plane, a rocket shooting off the solar system, a phone, whatever, and we treat the physics of that in isolation, that is, we pretend it’s isolated from other things in the universe but not completely because we have to… We’d like to use big, solid, stable things in the rest of the universe, like the whole solar system itself to give meaning to measurements that we make on these small things.

0:32:03.1 LS: So the way that we actually test the theory implicitly assumes that we’re discussing a small part of the universe, which is only weakly interacting with the rest of the universe. So that’s fine and that works very well. But if you’re cognizant of that, and it’s like you and I both want to make a theory of the whole universe and understand the universe as something that stands alone and is in some sense a whole closed system, then you’ve gotta find a different starting point and that’s one of the lessons of the… Thinking through these idea. Trying to get good principles to start.

0:32:49.7 Sean: Did you wanna say anything specific about background independence as a principle? What does that mean?

0:32:54.6 LS: Sure. Well, that’s basically… Background independence says that in your mathematical description of the system that you’re describing, there’s no fixed mathematical structures which don’t have a back and forth relation with other things. In other words, if this thing, whatever it is, influences the behaviour or the evolution of some degree of freedom, there’s a reciprocal interaction by which this thing also changes. So there’s not anything which we just use for reference, for coordinates, for landmarks, that’s not also dynamic and not also involved in the analysis of the dynamics. And then this of course came from Leibniz. Mach enunciated as what Einstein called Mach’s principle. So that’s an example, so let’s just say it.

0:34:01.7 LS: Newton liked to say that one way he could prove that absolute space was there is take a bucket half-filled with water and hold it up by some strings and rotate it, and the water would be pushed up on the side of the bucket when it was rotating and not when it was not. And Newton said, “You see that proves that when it’s rotating, it’s rotating relative to something, which I’m gonna call absolute space.” And Mach said, “No, you’re actually rotating not in a significant way relative to you standing and doing the experiment, but you’re rotating relative to all the stars and stuff in the galaxy, and the group of galaxies, and so forth. And the way you could tell experimentally is that you should just keep the bucket fixed and rotate the whole universe around it.” [chuckle] And you would see in that second case, the water go up on the sides the same way. And that Einstein called Mach’s principle. And in general relativity, it’s true.

0:35:07.7 Sean: Is it? [chuckle]

0:35:10.1 LS: I knew you are gonna ask that. Yes. So let me finish the sentence. General relativity describes different kinds of systems with different, what we call boundary conditions, conditions far away from the systems we’re describing. And if we put on what are called asymptotic conditions, so we insist that the universe is… Just goes to flat spacetime or some other known spacetime far away, then this principle is not realised because we’re anchoring… We’re like tying everything down. It’s like tying down the circus tent far away, but if the universe is conceptualised as closed, then it is satisfied.

0:35:57.1 Sean: Okay, fair enough. So let me see, on my list, we have background independence… Oh wait, I have a sub-question sparked by what you just said. When you talk about background independence and relationalism for that matter, this philosophy that things are not given, things are sort of constructed with respect to other things going on in the world, does that go so far as to include constants of nature, the fine-structure constant, the mass of the electron, things like that is part of your set of principles that we should expect these things that conventional physics says are just data that are given once and for all in the universe to be more alive and more dynamical?

0:36:40.2 LS: Yes, absolutely. And that’s what cosmological natural selection was aimed at. And I’m surprised that more particle physicists aren’t interested in that idea because that… Let me… Philosophers are only good when they’re good; they’re only useful when they’re useful, so to speak. I don’t think we should just put up a paper mache versions of all the philosophers and bow down to them. But I was shocked when I had had those ideas. And then a friend of mine, who was a philosopher, sent me some pages from Peirce, Charles Sanders Peirce, who was a very influential American philosopher, who in the 1890s, said that it’s not enough to explain nature in terms of laws. The most important thing is to explain why are those the laws. And he goes on to say that within science, the only way of explaining why the laws are the laws is if they’re the result of some evolution, analogous to biology. So much for originality.

[laughter]

0:37:51.8 Sean: You can always find things. That’s why you shouldn’t read things written by other people because it makes you sad about your own contributions. So let me see. So what I have here then is background independence, space and time are relational, causal completeness was another principle that you mentioned.

0:38:06.0 LS: Yes.

0:38:06.0 Sean: So what does that mean?

0:38:07.0 LS: That means there ain’t nothing outside the universe. That means that every explanation in terms of causes going back in time has to stay within this one universe.

0:38:19.1 Sean: Are there people who don’t believe that or does it depend on how we define the word universe?

0:38:24.9 LS: Sure.

0:38:25.8 Sean: Okay. [chuckle] I mean, does cosmological natural selection fit in with causal completeness?

0:38:31.7 LS: Yes. If you define all that as… Because there’s one causal future.

0:38:37.3 Sean: Okay. And then I have reciprocity, which I guess is related to background independence. So what is reciprocity?

0:38:43.7 LS: That was the word for what I was saying about, if A influences B and B influences A. And it comes from one of Einstein’s papers on general relativity.

0:38:55.1 Sean: And this is just for, again, for the people who are not experts here. It always bothered me about hidden variable approaches to quantum mechanics: Pilot-wave, Bohmian mechanics ideas. In these ideas, you have a wave function that does the ordinary thing that wave functions do in everyone else’s version of quantum mechanics. You also have some more variables that tell you the positions of the particles, and the wave function influences the particles, but the particles do not influence the wave function. So is it correct to conclude that this bothers you also? [chuckle]

0:39:26.4 LS: Yes. Oh yes, my God.

0:39:28.3 Sean: That’s good. [chuckle]

0:39:29.4 LS: No, that bothers me a lot. And I mean the things that I have come up with are not as elegant as Bohm, de Broglie, possibly because I’m trying to really… I tend not to have hidden variables in that sense, but use nonlocality to introduce nonlocal interactions between the degrees of feeling that already are there.

0:40:00.7 Sean: So I wanna ask how we should think about these principles. Here’s a list of five principles. They’ll evolve over time as we tweak them. Look, even the Ten Commandments aren’t exactly the same in the Bible every time they appear, so we’re in good company there, but do you take these principles as kind of non-negotiable? You’re so committed to them that you’re only gonna consider physics that satisfies them or is it more like you’re starting with some hypotheses, hypothetical principles, and we’ll see whether they take us to the right place or not?

0:40:30.6 LS: Surely more the second.

0:40:32.2 Sean: Okay.

0:40:32.7 LS: I… Background independence or relationalism, and we didn’t mention realism. But realism, it’s not a principle of physics, but it’s a principle of doing science, are very important to me. And if you showed me a film from 200 years in the future and it was a great success for physics, which violates every one of the things I deeply hold dear to me, I guess I’d like to know what else is coming on in 200 years. [chuckle] I’d be surprised, but it could… Sure. I mean one of the things for me, being this kind of scientist is I’m trying to get somewhere, I’m trying to discover something. And David Finkelstein who was somebody else who very much worked with principles said once to me that the reason why I think about philosophy and principles is it gives me a running start. So when I’m sitting here in 2021 and I’m trying to move forward, if I come with a running start, I have a chance of getting somewhere.

0:41:47.4 Sean: Right. It gives you a little bit of a guide post. You’re not just flailing around randomly. At least you’re trying to adhere to your principles. That’s something.

0:41:54.3 LS: Right. But they’re certainly… I mean, you’re somebody else who’s studying seriously the philosophical relations of that, but I would certainly say, I’m not a scholar. You don’t trust me for what’s the right interpretation of any of these people. Don’t trust me for the history. It’s all inspiring. And if it fails to be inspiring, if I don’t get anywhere, then I would certainly be looking to… One of the things I would question would be these principles.

0:42:31.4 Sean: And one of the potential worries that I had while reading that section of the book was, you put right there, space and time are relational as one of the principles, and that sort of begs the question, are there things called space and time in our philosophy? Like, certainly, I know that you don’t even think that space is fundamental, nor do I, so is it presuming too much to have the word space and time right there in one of our foundational principles?

0:43:00.2 LS: What’s the alternative?

0:43:01.0 Sean: Well, you could just have a wave function. [chuckle]

0:43:02.8 LS: Oh, you mean not have… Whoa, so what seems to me or at least I’m told is the least popular of the different positions I’ve adopted is the one that says that time is fundamental and goes all the way down below space, below laws.

0:43:27.3 Sean: Right.

0:43:27.9 LS: But risk causations, so. And I’ve developed this with different collaborators in the context of a series… Several series of models, the energetic causal sets, the causal theory I’ve used, etcetera. And I like to work with models because they’re very concrete. You’re not working with it. You’re not deriving abstract things from abstract things.

0:43:54.1 Sean: I mean, sorry, maybe even explain to the non-scientists out there what you mean by the word “model”, like that model has a specific identity to the mind of a physicist. [chuckle]

0:44:06.8 LS: So we start by stating some principles, of course, loosely and then we make models of them, and I wanna distinguish this from a theory. A model is something that can be defined by a small list of rules. You can imagine playing it the way that somebody would play a game. But a model means that you try to capture, in the simplest way, the implications of some assumption or some phenomena, but you don’t try to get all the details in each model. You try to… And as I’ve been a physicist over time, I’ve learned to really admire the people who are good at this, which I don’t know that I’m basically good at. But for example, Per Bak, if you knew him, he unfortunately died a long time ago, was a master at making the simplest model that illustrated some idea he had about statistical physics. And so a good model demonstrates or exhibits some idea clearly and you can either solve it on a piece of paper or put it in a little computer program and code it up. And it’s not any more complicated than Minecraft.

0:45:33.3 Sean: So Per Bak famously considered sand dripping onto sand piles and causing little avalanches. So that’s a model. The simple harmonic oscillator is a model, these simple idealized systems that get at some of the principles we’re talking about and you can hopefully learn something by studying them in detail, even if no one pretends they’re the whole universe.

0:45:53.3 LS: Right.

0:45:54.1 Sean: Good. And I wanna get on to this time being real and having some real causal power, but before we do that, I need to ask some questions about the principle of sufficient reason because you say in the book, in some sense, I forget which way it goes, either all of your principles arise from the principle of sufficient reason, or taken together, they imply the principle of sufficient reason. So what is the principle of sufficient reason and why are you such a big fan?

0:46:22.6 LS: The principle of sufficient reason is… States that for every fact about the universe, such that it’s possible to ask, “Why is it this way and not that way?” So an example would be, if you’re talking about space, why is the universe here and not 10 feet to the left? If you’re talking about time, why did the whole universe start when it did 13 point whatever billion years ago and not 10 minutes later? And this principle of sufficient reason says, either there’s a reasonable explanation for that, that is an explanation. In law, they have the reasonable person standard. So a sort of reasonably judicious person would agree that that was an explanation. Or, and this is the sort of back edge of it, which is its most important use, or you’re asking a question that really has no meaning. So in the case of those two questions I named, the issue is not, “Is there a reason why the universe was not created 10 feet to the left?” But can you construct a cosmological theory in which there’s meaning to how far Los Angeles is from Toronto but there’s no meaning to where the whole universe is right now?

0:47:49.2 Sean: Right, okay. But I’m not a fan of the principle of sufficient reason, and I know you are. So that’s why I wanna dig into this. Probably, you and I care more about whether or not this is true than most of the listeners, but we’re gonna indulge ourselves.

0:48:00.9 LS: Okay.

0:48:02.2 Sean: I think it all depends on what you mean by a reason and you try to invoke a reasonable person standard, but I’m not quite sure that that qualifies ’cause we’re very far away from what the reasonable people are familiar with. If I ask a question like, “Why are there eight planets in the solar system?” It’s mostly an accident. I could trace it back to the whole initial conditions for the universe and the laws of evolution and so forth, but that doesn’t strike me as what someone would call a reason. There’s different numbers of planets around different stars and we happen to get eight. How does that fit in to the principle of sufficient reason?

0:48:39.5 LS: I think you show it how it fits then. It’s the result of the history of the bunch of gas and dust that became our solar system.

0:48:49.3 Sean: Okay. So in that sense, it’s a way of saying that, the behaviour is law-like. The behaviour follows some rules and you can find the current situation given the earlier situation, plus the laws.

0:49:02.0 LS: Let me give a harder case. These are some things that I’ve been thinking about recently with some collaborators over the last few years. We’re trying to write something about these kind of things. Supposing you get interested in biology, which I know you are and you have been, and you… We get interested in how proteins get made and the whole story of the RNA, DNA and RNA, and messenger RNA and that whole complicated thing. And we want to know, why is there a particular protein that’s prevalent in the biosphere? And we imagine several kinds of explanations. There’s the brute force deterministic explanation of, there were some initial conditions in the universe, the laws are deterministic, and you compute and you compute, and it just happened that way. Then there is the functional explanation that a biologist might wanna give, which says, and let me… I forgot to say the most important thing. There are something like 20 to the thousandth different possible proteins, and those that are found in the biosphere are many fewer, maybe 10 to the seventh or 10 to the ninth or something. So what distinguishes those that are found in the biosphere? And the answer is, if you allow functional explanation, it is not very complicated. This molecule makes something, which performs a function for the beings that isn’t, that make it, that make them more viable, have better fitness, and so forth.

0:50:56.4 LS: So there are functional explanations. And what the interesting challenge… Let me start from the… There’s a certain amount of argument, which much of which to me is not to the point of, well, we believe in the determinism of the laws of physics, so that’s already a complete explanation. So the functional bit of the explanation must be not relevant or not enlightening, but in fact, it is enlightening. And what I would say is that we are blessed by having both, that is, we can make a functional explanation for why those proteins exist. And we can also check, do they satisfy the laws of physics and the laws of chemistry at every stage in that explanation? But we can’t hope with current technology to just compute from the way it functions in universe, whether they would be prevalent or not. You see where I’m going?

0:51:57.4 Sean: I do, yeah. Okay, I’m gonna bite my tongue because I think that’ll get us down a rabbit hole, but we both put our positions on the table there. And I do wanna talk about the reality of time, which I think is very important. You’ve written a whole book with a subtitle, the Reality of Time. But it means different things when you say that time is real. So there’s one sense in which time could be real in which you’re just distinguishing fundamental from emergent, right? There’s a lot of approaches to quantum gravity, for example, the Wheeler-DeWitt equation, where time is emergent rather than fundamental, but in my mind, I would still call it real in either case. But you’re attaching…

0:52:37.4 LS: Of course.

0:52:38.4 Sean: Sorry?

0:52:39.3 LS: Of course.

0:52:40.1 Sean: Yes. And you’re attaching something a little bit more significant to your notion of real that I would not want to attach. I mean, I think that time is real, but it’s just a label on different things, much like space is, whereas you’re giving time some role as exerting a causal oomph in the universe. And why don’t you give us the sales pitch for that point of view?

0:53:02.3 LS: Well, thank you. It’s been changing over the course of my career in recent years.

0:53:10.4 Sean: Over time.

0:53:11.5 LS: Over time. What I want to say is that what I believe to be the case is that when we’re arguing or we’re discussing what is fundamental… And let me just reiterate to make sure we mean the same thing, but that the question is not whether it’s real. There’s lots of emergent, manufactured, inventive things which are not in the laws of physics which are real, which are all around me and you and so forth. But the question, we… I think it is something that we know how to do pretty well, to go down in levels of dependence, that is, in science, there’s a certain level where we use biological explanation, biological concepts. And then we can explain those in terms of molecules and the chemistry of molecules.

0:54:13.7 LS: And we go down a level and certain concepts at this level are reduced to concepts which hold because of the laws of chemistry and physics. And we can go down a series of levels like this. And it’s interesting that as we go down levels, concepts get stripped away because they’re reduced to concepts at the lower level. And I don’t… As a side story, we can talk about is… What the different kinds of causation, whether causation can go up and down, both, and… But let me not say that now. Let me just talk about the kind of ontology of it.

0:54:56.9 LS: There is… You assert a level or maybe several levels, where there’s no longer a concept that relates to our experience of time. And my hope is that your belief is that that’s not the case and that as low as you go, there will always be time and in a particular sense. And the particular sense is that the world at that level will be a process of events, which are created and which then disappear. And the events have causes which are prior events, that is, you can talk about who the cause… The immediate causes of one event are or some other events, and that each of them have prior causes. And the events and that structure of who is the prior cause to who is part of what goes all the way down. I’m not done, but that’s part of the structure.

0:56:08.5 LS: Then very anachronistically, I believe that there is that… The correct level, the correct description involves a notion of, now these are the events which are in existence now, which are in the process of being created and about to be in the process of creating future events. And that it’s not only possible, but absolutely fundamental to ultimately talk about the world in terms of what is real now and that that is the two things make up the meaning of time when I say that time is fundamental, the process of the continual creation of events and the fact that I believe there is something objective and universal in the notion of now it is some time. And in the past, some other things happened, they’re no longer happening, and some other things may happen in the future.

0:57:16.0 Sean: So, a variety of presentism, is it safe to say?

0:57:18.8 LS: It’s a variety of presentism.

0:57:20.6 Sean: And in particular, you would say, I think that what we call the “arrow of time” is something that’s built-in to the fundamental nature of reality.

0:57:27.6 LS: Absolutely, yes.

0:57:28.7 Sean: Right. And so, this is very interesting to me, both physically and philosophically, so let me just ask about it in more detail. A point of view of someone like me, and I’m not alone, is that, of course, there’s an arrow of time in our everyday experience of the world, ice cubes melt in glasses of water, they don’t un-melt, etcetera, etcetera. But we do more and more understanding of physics. We boil these things down into something like Newton’s laws, or Schrodinger’s equation, or Maxwell’s equations, and suddenly there is no arrow of time there. And that’s okay because we can still explain the macroscopic arrow of time as an emergent collective phenomenon. And somehow you want to put the arrow of time back in at an even deeper level than Newton’s laws, Einstein’s equations, etcetera.

0:58:14.7 LS: Yes.

0:58:16.6 Sean: So, to someone like me, that sounds like a step backwards. We have explained the arrow of time as this emergent phenomenon and now you wanna put it back in. I always have questions about this for myself because as we make progress in physics, and we learn that something that was brute and fundamental can now be explained in more fundamental terms. That always seems like progress and we’re reluctant to let it go, but sometimes, we have to let it go. Sometimes we have to take a step backwards to make progress. I guess I’m simultaneously asking you why you think it’s necessary to undo that progress we made and how you in general feel about this move of sometimes admitting that you have to take a step back to take two steps forward?

0:59:04.0 LS: Good. So let me mention some of the things that we owe, some of the homework we have to do if we take the stance. One of them is, we have to explain what was your starting point, which is explain why there are errors in the history of the universe that results from our assumptions, in which to a good approximation, the laws look time symmetric. And we have a story about that, which has to do with the formation of limit cycles and so forth, and we have some words and we studied this in various models. And we by the ways, this work is with Marina Cortes. Another thing we have… So we have a story about that, that I’d be happy to expound if you want.

1:00:05.9 LS: The second thing we have to do is ask looking at it from the other way which is like going backwards from the present, through the years as it was is, as… Are there extensions of the physical theories that we used in this particularly general relativity and quantum field theory? Do they have modifications or extensions where we see the symmetry in time we were still failing? So that, is there… A lot of people who are cosmologists we work with study modifications of general relativity. It’s a big activity. Are there any sensible modifications that use the time symmetry when you turn the mind? And if we therefore see a smooth transition described by these theories, maybe muck around and make some cosmological predictions, and with Andrew Liddle and Marina, we have some papers on that. So…

1:01:01.7 Sean: And did you wanna say something about the general idea of abandoning progress we think we’ve made for a greater purpose?

1:01:10.1 LS: I don’t know that I have… Sometimes it’s necessary.

1:01:16.1 Sean: Good. Okay.

1:01:16.8 LS: I don’t know that I have in general… What you get, many of the most taught of physicists have been concerned about the apparent disappearance of the notion of what they sometimes they call them “the now”, or “the present moment.” You can find Einstein worrying about that and trying to put back in the distinction of this thing, past, present and future, as a fundamental distinction. There’s a paper that a collaborator and I just posted, hopefully it will appear tonight, in which we mull over some very interesting quotes of Freeman Dyson, Heisenberg and Schrodinger, in which they said, “Quantum mechanics is really a description of the future, and the reason why people get confused about these issues like the measurement problem is they don’t understand that the quantum description is only a description of the field.”

[chuckle]

1:02:20.5 Sean: Okay. I hate to leave that out there, but I’ll link to the paper when it comes out, when we publish this episode, so people can look for it themselves because…

1:02:27.5 LS: Right, right. But in other words, these very thoughtful people have worried about the absence of the notion of the now in our physical theory, and my collaborator, by the way, is Clelia Verde. And so we’re trying to address this quite. This people and Einstein had over the absence of the now.

1:02:56.8 Sean: Well, and it goes… I do wanna give you a chance to say a little bit about the specifics of this theoretical structure you’ve been developing. I boiled it down to a statement that the universe should be thought of as a series of events, not things, and each event has a view of the universe. That’s probably too simplistic, but maybe you can elaborate on it.

1:03:19.2 LS: So imagine that the universe consists of a number of events which are created by some just previous events. Each event has a number of progenitors or parent events, and each event gives rise to a number of, we can just call them “children events”, and that this is the basic dynamics of the universe. This is how the universe really runs under everything.

1:03:54.5 Sean: Is it fundamentally discrete then?

1:03:56.8 LS: Yes, yes, it’s fundamentally discrete.

1:03:57.7 Sean: Okay.

1:04:02.1 LS: I’m not yet using the language of quantum theory because one of our results is that in several of these models we can show the emergence of quantum theory. At the moment, what is real is these events because of processes that continually create them, and we insist on keeping in the description, energy and momentum, whereas a lot of people at that level, see those as things that go out the door and come back as emergent. There is a notion of the view of such an event. The view is basically just to find now as an event, and look around you and what do you see. What’s coming at you is a whole lot of photons and hopefully not too many other stuff, [chuckle] which has ranges of energies, which impinge on you. And I’m using this as a kind of metaphor, but see yourself right now as an event, and your view is all these things that are coming to you, that inform you of the world in your neighborhood, or equivalently in your causal path. And what we do… So this world has no space so there’s no forces that can fall off at one over distance squared or any other factor.

1:05:31.2 LS: There’s no functions of space, there’s no derivatives, so we can’t write any field equations, so how are we gonna do dynamics? And one of the ideas is that these views are the stuff that dynamics acts upon, in particular, the fundamental laws exist that can give a measure to how different the views of two events are. And the fundamental dynamics is expressed as a certain function of differences between views of different events averaged over the universe as it exists now. And we have an operational meaning of now. Basically, an event is part of now if it has been created but it hasn’t yet made all the children it’s going to make. And… Anyway, that gives us a notion of a present, and that’s the fundamentals of this.

1:06:40.7 Sean: So it does seem… Compared to my own more Everettian views, it does seem, even if you can in some limit recover quantum mechanics, it seems pretty classical to me in that there’s a set of events. And that’s it. That’s the set. It’s not like the sum over every possible set of events. But maybe that is just in concord with your feeling that there is only one universe, and if you really went completely, to superimpose all the different universes, that would not be what you’re looking for.

1:07:12.1 LS: Well, there’s a view that Clelia Verde and I are trying to make work in this new paper, which brings in some parts of quantum theory. What we say is that the fundamental distinction is not the difference between the past, present, and future. The fundamental distinction is between some properties that are incompletely known or indefinite, and some quantities that are definite, and that when an event is, is a moment of transition of some indefinite quantity becoming definite. And we then try to make a very simple picture of the world in which everything stems from that.

1:08:01.3 Sean: And you do have a principle in there or at least, I don’t know, a law or whatever you wanna call it, that you maximize the diversity of these things?

1:08:08.7 LS: Yes. Yeah.

1:08:09.6 Sean: Which sounds like a social justice statement from the university, but you have definite physical definitions for diversity in view here. They’re a little bit different.

1:08:18.8 LS: Yes. And that’s, of course, getting a little bit of satire again, [chuckle] which given the present crazy world, we thought was useful. But let me give that definition because it’s not very difficult. And this actually was invented with Julian Barbour way back in the ’80s. Julian was… I don’t know if everybody knows who… Julian is a historian of physics and the philosophy of physics, and a physicist as well. And he was the mentor for myself and for other people of my generation, to teach us these ideas about relationalism. The first time I met him, he asked me if I knew Leibniz and I said, “Leibniz who?”

1:09:08.7 Sean: Yeah.

1:09:10.6 LS: So this is something that Julian and I just invented. And the idea is basically that we take all pairs of views in the universe, compare them, give a numerical measure of how different they are, and some that’s put an end and some that are all pairs. And that’s what we call the variety of a system.

1:09:38.3 Sean: And this is maximized either by assumption or do you show that it’s true?

1:09:43.3 LS: No, we put it… I’ll use a technical term and then I’ll explain it. We put it in the action, particularly. Its absolute value is the potential energy.

1:09:57.9 Sean: Okay.

1:10:00.0 LS: And its rate of change between events and events just causally prior to them is the kinetic energy.

1:10:09.2 Sean: And so the idea is that we have a bunch of events, and they all have their views. I mean, counting the variety, the diversity amongst the different views. But in a very down-to-earth physical sense, we maximize that. And the hope is our universe comes out. Can I ask how much our universe has come out so far? Do we recover Einstein’s equation for general relativity?

1:10:30.1 LS: No, here’s what we recovered. We recover space and actually spacetime. So what becomes emergent… Originally, in the theory, there’s momentum, but there’s no positions. But what emerges is a Minkowski spacetime with an embedding that takes these events to points of Minkowski space, one. Two, motion of particles, of relativistic particles in that Minkowski space. Three, and these are as… There’s a quantity, which I’ll just call one over N, and I think you can come back and I can tell you more about what it is. For one over N goes to zero or N goes to infinity, we get the classical trajectory. For… At leading order in the correction, so that’s one over square root of N and taking a non-relativistic limit and making certain assumptions about the initial conditions, we drive a version of quantum mechanics. We drive distorted equation acting on a complex wave function, with corrections that would look like non-linear functions of the way it functions.

1:11:53.3 Sean: Okay.

1:11:53.9 LS: We can compute. Let me stop there. That’s rather the things that are in progress but that’s what’s been published.

1:12:03.4 Sean: Okay. But then the hope is to keep going and show that you do get curved spacetime and Einstein’s equation and maybe even the standard model of particle physics.

1:12:12.2 LS: Yes, it would be great. We’ll see.

1:12:16.0 Sean: But with the caveat that you want to imagine that the laws of physics themselves change over time or can change over time?

1:12:22.0 LS: Yes.

1:12:22.9 Sean: So does that have an experimental consequence? Do we expect to see slight variations and defined structure constant or something like that?

1:12:29.6 LS: That’s a very, very, very interesting question. The cosmological natural selection, which, just to go way back, as we said makes two predictions. The idea that the constants of nature change in cosmology, in modern cosmology, goes back to João, as I’m sure you know. And he looked to changes in this constant, and they’ve been looked for repeatedly and not been found. I don’t remember what the level is now, but it’s several hours’ magnitude past G over G. Didn’t have the units. I don’t know. There’s so many things about this, which… Let me cut this thing. There are a few things about this stuff which I feel I have under control, and there are a lot of things which I don’t know the answer.

1:13:24.9 Sean: Okay. Well, that’s fair. That’s how science goes so we can’t blame you for that. I’m just asking because I was wondering how things were going. Good. So to finish up, I have two questions. One is, you mentioned as we were chatting before we actually came on, that I made an off-hand remark that caused you to do a U-turn, and you didn’t say what the remark was or what the U-turn was, so maybe let’s hear that.

1:13:47.3 LS: Goes later. Yes. And this time, I very much thank you for, although I don’t think you like it all. [chuckle] So, something that we haven’t touched on yet is the whole issue of the mind, the brain, the qualia, and all that, which most of my career, I felt was too hard to mess with, so I stayed away from that.

1:14:11.9 Sean: Consciousness, yeah.

1:14:13.1 LS: Yeah, all that. But I have published one paper… When I published one paper, and it’s a result of a remark he made. So ever since college, I was a naive panpsychist, or the sophisticated, the fancy word for this is Russellian monist.

1:14:39.3 Sean: Yup.

1:14:40.2 LS: And that is, I believe that qualia and conscious experiences are real, and they other aspects of the matter which makes up our brain, and therefore, you get to have the determinism of the laws of physics, making, explaining everything that happens in the brain, so you know you’re not a dualist functionally or causally. But you get to be a dualist as to the kinds of properties that things have, and there are external relational properties by which things move around that physics describes. And there are quite a few other inner or intrinsic qualities, which are like the experience of colors and sound, and which we know what they’re like for our brain because we inhabit our brain. But why not just say that the whole world has that dual aspect? I think now that’s a really dumb idea. [chuckle] I respect the people who had it, but what we said… It’s funny how this sounds. This was a momentary conversation going into a talk, and you said, “That doesn’t make any sense because why would nature, whatever qualia and consciousness are, if they have no causal influence in the world because the causes are already explained by physics, why should nature be part of them? What are they doing in the world?”

1:16:17.6 LS: And several years later, I find myself thinking about that. And the conclusion I came to, and this I’m very changeable on because this is very current stuff, but I said, “Gee, Sean must be right. Therefore, consciousness must actually have causal power in the world,” which is not the conclusion you drew from it, but it is the natural conclusion to draw. And therefore… So I made that hypothesis about correlation or representative, which is with, people in this consciousness business are saying they’re looking for neural correlates of quality or consciousness. So given the situation I just described with you is another aspect of the theory of views, which is that not every view has fixed consequences. And you’re gonna have to give me a little time to justify this, but most views have fixed consequences, which are the same as what have happened to similar views in the past. But in order to believe that the laws can change, I have to believe that some very small minority of views are not… Don’t have precedent or the laws of nature don’t know what to do with them.

1:17:57.2 LS: And they have to somehow discover novel behaviour, a novel response to their situation and so the hypothesis that it’s those that correspond to events, which have to do with quality of consciousness. And so I wrote a paper about that. I was very excited about that. I wrote a paper about it. And I’m glad that paper’s out there. [laughter] And I did not… I’m basically, I’m very confused. I don’t know how you feel. I feel that we have, as scientists, our descendants, that is the scientists of 200 or 300 or 500 years in the future are gonna have to grapple with this. I feel like I grappled with it and I got an idea and put it out there, but I don’t wake up in the mornings feeling excited about, “Now I’m gonna go to work on that idea.” I feel like it’s beyond where science can be. We can imagine things, but we don’t know how to reason about them.

1:19:08.2 Sean: Well, Philip Goff was a previous guest on the podcast, a big advocate for panpsychism. Am I correct in thinking that you, like myself, were invited to contribute to this Journal of Consciousness Studies Special issue about his work?

1:19:23.3 LS: Yes.

1:19:24.1 Sean: So it made me think of it because I just handed in my paper in which I precisely say that, look, you can either modify the laws of physics to allow consciousness to poke things around and have a causal influence or you don’t. And if you don’t, you can say, “Well, there’s still something mental that is an aspect of the world that just has no influence on how things behave or consciousness is just an emergent property from the true physical behaviour of things. And my attitude was, if you wanna modify the laws of physics, if you wanna have real mental aspects that have a causal influence, then be my guest. That’s hard. There’s a large barrier to entry ’cause we know a lot about the laws of physics, but at least it’s respectable. But this idea that mental aspects are there and somehow utterly important yet have zero causal influence, that’s what I said, I don’t even quite consider to be respectable. That’s my own personal view. I’m a physicalist myself. I think it can emerge, but the idea that you’re not going to have any effect on the standard model of particle physics and yet there’s this crucial aspect of the universe, I’m not quite sure how that’s supposed to work.

1:20:32.8 LS: Yes, so thank you. I got to that place and yeah, it’s… Let me say something generally because we both had the experience of being physicists and getting interested in and opening up to discourse with philosophers. And sometimes it’s certainly been very useful to me, very helpful. I mean, we didn’t mention it all, but you started to mention my books on time. And one of them was with Roberto Mangabeira Unger, who has been a very, very important person and is, I think, really an important philosopher that people should pay more attention. And then there’s kind of all the people we know, the people in Oxford, in New York, where they are both faced with really excellent philosophies of physics. And I find it very, very, both inspiring and humbling to interact with them. Their life is to know what’s going on, what all the arguments are against any view you bring to them.

1:21:53.3 Sean: [chuckle] It’s frustrating, yes, but it is very helpful to talk to them for exactly that reason. So which leads me very nicely into the very last question I have. You’ve been very indulgent with me with your time here, so one of the ways in which I think that you and I are a little bit different, but is, I’m glad that there is diversity of use, in the usual sense, not in the physics sense, is that when we have a puzzle in physics, when there’s something we don’t fully understand, whether it’s consciousness or the arrow of time, or the foundations of quantum mechanics, there’s various ways one can go in hypothesising how to do better. And my first impulse is always, I think what Wheeler called Radical Conservatism, like keep the basic ingredients as solidly as you can, the Schrödinger equation, the physical nature of matter, Boltzmann’s statistical mechanic, etcetera, and try to see how, from those simple ingredients we can reach this, a better understanding of the thing that we’re trying to get to.

1:22:56.3 Sean: Whereas I get the impression that you and people who are on a similar path are just much more willing to say, “Nope, let’s just throw out everything. Let’s throw out the Schrödinger equation, let’s just change the fundamental nature of matter because these are big problems and we’re not gonna solve them without big solutions.” So do you have any words of wisdom, short or long, about the differences between these two philosophies? Do you think that one is sort of generally better or do you think that it’s just good that different people are trying different things?

1:23:29.2 LS: I think they’re both necessary. And one thing that would be very interesting at some point is to have a conversation with you and Carlo if I may and maybe a few other people. I put Carlo more and more in that same category, although he’s in… He didn’t start out there. [chuckle] But one of the interesting things about this profession is we get to watch each other evolve over the last time.

1:24:00.8 Sean: Sure.

1:24:01.3 LS: There were a couple of things that were really formative to me. I would… First, I did part of an undergraduate degree in philosophy, but as I said, I wrote a paper in philosophy of mind, which took this view that we both criticize. And I was… They said I thought about consciousness at all. I was satisfied with that. It was the problem of the last date of string theory or any other kind of theory, and how are we gonna explain where the choice of laws come from. It had a very destabilising effect on me. It got me thinking about things that most of my friends and colleagues were not thinking about. Something that was also destabilising and it’s hard… In my life, it seems like people play a big role, and friends and people who are not friends who I talk with, as illustrated by history, take a big role… The first person who argued with me when I was irregular… After we found that Wheeler-DeWitt equation, so how could I not love it.

[laughter]

1:25:20.7 Sean: Be in love with that. Yeah.

1:25:22.8 LS: But then we found out what was hard. It happens in that approach. You can, almost by inspection, find solutions of the Wheeler-DeWitt equation but quantum mechanics is more than just the wave functions. It’s specially a theory with a lot of vision then. It’s the observables and the inner product. And what we never did in conventional loop quantum gravity was find quantum mechanical observables that were honestly derived from mechanical observables, and that was… Nor did we ever construct the physical inner product. And so that programme was very frustrating to me, and that had a big influencer. And then I was about to say Fotini Markopoulou was the first person who just came and sat me down and said, “Look, you’re wasting your time. That will never work. You have to think about time maybe being fundamental and space not.”

1:26:26.2 LS: She was the first person who articulated that idea in our community, and she articulated it to me very powerfully. Now, of course, I have… She’s somebody who was very important to me generally, and I have enormous respect for her. But that intervention played a role. And a few years after that, I started working with Roberto Mangabeira Unger and he basically took me to task and said, “What kind of… ” He wouldn’t quite say it like that, but “What kind of fool are you? Here you are, talking about the laws changing and the landscape, and here you’re working on getting time to emerge from the Wheeler-DeWitt equation. Doesn’t that bother you?”

1:27:13.8 LS: So it’s been very important who I talk to and listen to. And I feel like over the last 10 years or so, and it took that long, so there were always these elements, but I was working on hidden variable theories every three years and so forth. But all of this really coalesce into this research programme over the last 10 years.

1:27:39.2 Sean: Yeah, well, whether or not the laws of physics change with time, I’m glad that our views of the laws of physics are changing over time because we don’t know them yet and we have to be a little bit flexible about it. So Lee Smolin, thanks very much for being on the Mindscape Podcast.

1:27:51.9 LS: Oh, thank you very much, Sean. Great.

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