Nature of Time — Panel Discussion

0:00 I think there was a balcony, but there is no balcony. I just don't know if that's what I look up about. So, we're going to try to pass this microphone back and forth. We'll see how successful we are. although it's possible um Steve could you try speaking uh see if people can hear you from there is this microphone can people hear you can hear okay that's not on oh we turned that on is there a switch wait a minute that one's on yeah I hope we don't get it's feeding back already I think oh that one's yeah that one's perhaps too much Is there a switch on us? Yeah, I think it might be easiest to just pass this back and forth. We'll try that. Well, I'd like to welcome those of you who have only been able to take part in a few of our sessions, or perhaps this is your first visit to our mini-symposium. Welcome you all here. We deliberated a bit before you arrived to determine what would be appropriate themes to address. We're a bit hampered in this task because we've decided, I think we've come to agreement that we know nothing. But on the other hand, we'll do our best here to try to address some of the themes that we considered in this meeting. I would like to first introduce the members of the panel since I think some of you have not made their acquaintance yet. again here with Alexis de Saint-Dour. He comes from the Department of Philosophy, University of Paris 8th. Steve Weinstein is from Philosophy Department, University of Waterloo in Canada. And Cecile de Witmoret is in Physics at University of Texas at Austin. Wolfgang Lindler, Physics, University of Texas at Dallas. Pala Chandran, physics at Syracuse University, and Van de Juan Ferret is in philosophy at the University of Texas at El Paso. So we have discerned a few central themes that we will try

2:30 to address in our discussion here I think probably the major theme that we addressed in this symposium was something that we called relational approaches or relationalist approaches to the time and it probably would be appropriate to give a brief overview of roughly what we mean by that perhaps I'll attempt that first from a more physical point of view. Maybe I'll pass the mic on to Juan and he can give us a perhaps more philosophical perspective. But relational approaches to me mean, when referred to time, that notion of absolute time does not exist. Of course, there was never any question about that since the beginning of the Einsteinian Revolution in 1905. But nevertheless, it is possible to think of material clocks either made of tangible matter or perhaps fields that one could use as timing devices and that one can actually correlate the values recorded by those clocks with other physical quantities and thereby actually track the evolution of phenomena in the universe. So that's very roughly what we mean by relational time, but it's quite possible that one or others of you have a different interpretation, so maybe I'll pass the mic along here and see how anyone wants to make a contribution. Let me also mention here that we would like to get interaction with the audience, so if any of you have any questions or objections, please let us know and we'll try to have an interchange here. Besides questions and objections? No, only questions and no, anything. In philosophy, the question of time, of course, has been informed, sometimes not as well as it could have been, but it's been pretty well informed by some philosophers, very attentive to the physics, and the realization that time can be absolute and leaves us with some options.

5:00 So one option still has been to try to understand time as an entity, as something out there in the world. And some recent approaches even have suggested that maybe we should conceive of time as an infinite amount of instants. And in every instant, you can have a further infinite amount of instants. So by that view, a non-relational view, tried to describe time as some sort of entity status of some sort. The relational account, instead, doesn't want to treat time as an entity, wants to treat it very seriously, but wants to treat it, like Donald was suggesting today, as an intrinsic part of systems, or maybe better said, as the potential of interactions between systems, something that gives the system the possibility of having this dynamical opportunity. And for philosophers, what we're trying to understand, as well as looking at the physics, some of us, When we use time as a parameter or as an operator or whether we try to get rid of time, we try to see what the implications are. What are we saying about time or are we saying anything specific about the ontology of time or are we just simply using a different strategy, a different method for thinking through this idea of interconnection between systems. Yeah, anyone who would like to mention anything? May I just... I wonder whether this idea of relational time could in some ways be connected with Marx's idea of relational space. Everybody since Newton's time, including Newton himself, was dissatisfied with the concept of absolute space, various ideas of how to get around that. And Marx's idea was that there was no such thing as absolute space, that space was nothing but relations between objects. So if you take the sum total of all the relations between all the objects in the world, then that's what space is. And that's how he came to the conclusion that the stuff in the world should actually determine, for example, the and so on, but quite apart from that, I was just wondering whether the philosophical idea of relational time is in any way analogous to this Machian idea of relational space.

7:30 In other words, there's no such thing as absolute time in the Eutonian sense, and the way to get around that is simply to say, well, there are only relations between events, temporal relations between events, but there's no absolute time background. That may be a very naive comment. This is really just a brief comment of what has special relativity done to time. Very often, lots of complicated discussion are made. To me, what special relativity did to time is only that we've lost simultaneity and from that everything else follows. So we've not made time to be the same as face or whatever. We simply have lost simultaneity and to me that's Yeah, I want to add what are you pointing to? Oh, a question. Okay, good. Sure, sure. Oh, please, yeah. Oh, please, yeah. No, is it an objection or a question? My question is about the concept of relation. Because we have a theory, and there are some relations inside the theory, even the theory, and there is a new world in which we live, a physical world. There are also relations in that world. And there are relationships between the mathematical world and the physical world, what we are talking about. I don't know. Oh, you mean, what's relationalism? Until now, we were looking for all the world of politics. Yeah, I mean, it's a good question. I think relationalism, I mean, this is partly what I was going to address. It's sort of a broad notion, and there's a kind of an epistemological component. This isn't directed so much at the relation between mathematical description and the real world, but even when we're talking about the real world, to say that time is relational, it could be an epistemological claim, just a claim that our access to time, what we know about time and changes in time, has to do with the way that we, as material systems, are coordinated with other material objects, in particular clocks.

10:00 Clocks are very useful for knowing about time, so that time is what clocks measure. This is a kind of slogan. Now, you can say time is what clocks measure. You can take epistemologically our knowledge of the passage of time has to do with our knowledge of changes in the positions of the hands on clocks or ignoring digital clocks. It's a very retrograde conference here. Or it can be a more robust ontological or metaphysical claim about what time really is. And that doesn't entirely address your question. Since I got the microphone out, I want to agree, I think, with Cecile and a little bit against one of the earlier comments that I'm not sure that relativity really, the general relativity, the theory of space, time, and matter, Einstein's theory of gravity, or special relativity for that matter, really tells us that time is not absolute. I think that it depends, of course, what you mean by absolute, but one can have models of the universe or models of space-time in which there is no matter, there are no particular relations, but one would be hard-pressed to say that there is no time. There is no, it's true that simultaneity is relative and that different observers, were they to be in this universe, might disagree on the temporal distance, the lapse of time between a pair of events. But I would say that there is time there, which is why that Machian approaches, which Professor Riddler just mentioned, which to general relativity wind up often changing the theory. In a Machian, so for the people who don't know, Ernst Mach was a physicist and philosopher in the 19th century who tried to take these relationalist ideas seriously, and ideas that Newton was worried about. And when general relativity was developed, people tried to, well, general relativity was motivated in part by Machian ideas, and Einstein ended up rejecting them in the end as inadequate. But I think where they really show up is that in a monkey inversion of general relativity, like the Franz-Dicke theory, I think, is an example of this, there really is no interesting gravity or structure of space-time in the absence of matter, in the absence of things which are related to other things, between which there could be relations, okay?

12:30 Whereas in ordinary general relativity, and this is why, and I'll stop here, one can have a universe with no matter in it. This is, of course, just a mathematical universe. Our universe clearly has matter in it, including us. And in ordinary general relativity, you can have a vacuum universe with a lot of structure in it, and including the passage of some sort of time. All right, let me pass this on to, I don't want to monopolize this discussion to Alexei. Thank you. Well, just again, maybe to go on with the answer to Professor Renler, yes, Mahal also threw a relational theory of time. He didn't only have the relational theory of space, he really thought that time was also relational. And, of course, I mean, in this nice tradition, it comes also from Leitnitz. I mean, Leitnitz complained against Newton's absolute space, but also against Newton's absolute time, Newton's conception of time. So, yes, he has it. Maybe just a few things about the world. What do we mean exactly by relational? be tricky because, of course, we see it comes from a lative. And for example, when Maurice Solovine translated Einstein's paper, he was a bit, he had a problem for translating . So he decided that we should call it not relational, but he said in French . And I think maybe we should make a difference and related and it might mean something a little a little bit different and maybe the third thing I would like to add is well so if we call well we'll see the problem later in those relational approach people have suggested that we might bring new kind of mathematics into that and of course the new kind of

15:00 mathematics that people have in mind is category theory, and Grotendieck's idea about and category theory. This idea is to say that, well, what we have, we have a kind of relational thing built in category theory. For very, very, very quickly, in category theory, one can and say that the interesting thing is the arrow, and not the bonds between the arrow. And so this is very, just a quick thing to say about it, but it is an idea that is actually developed. To do a kind of categorical quantum gravity, people like John Bennett are working on that. Maybe we could, well, I guess we could pass back. Yeah, I have a question, okay, good. All right, I'm bringing up ants. But category theory, I want to make a check. I went to cryptography seminar at the same now. Some guys from Oxford are working on that. I have it on my computer to find out for myself. I'm sorry, I didn't know. Category theory. Yeah, yeah, yeah. Oxford guys are working on that, right? Well, many people are working on that. All right, now it's ants, all right. At the beginning of a very large book that students at the University of Texas at Dawson called The Phone Book. And the rest of us called Ravitation by Elizabeth Warren and Wheeler. There's an ant crawling on the surface of an apple. And I don't imagine an ant has any notion of what relationships are. They just do what the queen does. And they follow ant trails. Feynman didn't experiment, but they went around on the surface. Now, an ant that has no notion of relationships, as we do, as supposedly more conscious, what would the ant's perception of time be? I warn you, and I'm saying, and don't mind my friend, I'm asking you to come out over and over. Yeah, well, I think we'll reveal our knowledge on that subject a little bit later in the morning. But I thought I'd move on to another thing that we received substantial attention over

17:30 these two days. And that... Oh, I see a question. Okay. I have a comment to make. This relational approach seems more of something based on human sensory perception. Because I think if you were to conduct experiments where, say, you put somebody in sensory deprivation where they had no way to observe anything moving around them and no way to tell them not to convey, you could easily pull them into thinking that maybe 24-hour days he might have 12 hours of them. And so I'm thinking maybe time to understand it physically, putting our perception aside, I've always thought entropy 4 was the best way to look at it. And even when you have solutions to Einstein's equations, where you have nothing, no matter in the universe, there's always some sort of entropy you can associate with, whether it's the center entropy or horizon entropy So am I wrong to say that the relational approach is just more human bias or what do you guys think? I can say something. You want to say something because I have actually some useful meaning. Yeah, I mean it's true that as Steven and Alexia pointed out that we have to think very carefully what we mean by relation or relative. And I don't think it implies that we need a conscious observer, even though when you start doing experiments like yours, you know, psychological torture of putting somebody in a chamber, and then we're asking about their psychological perception of time, then of course we enter a different realm which I know very little of, the understanding of psychological time. but speaking at the level of time we would say the logical level at the level of we would like to think of of our physics and it is not just our physics but the logical related to our physics then the question is to try to understand what the different theories not just what different theories may be offering us as a way to conceptualize time and some have proposed conscious of your observers to collapse the wave function but there's many approaches that are relational that don't you know that you don't need a conscious observer at all. Good, I could just say one more thing. Yeah, I want to just follow up on that because I thought that was an excellent

20:00 lead into what we were intending to be our next theme and that is a question of of ontology or existence of time. The suggestion is then that that would be something that could exist independent of human observation. That's my understanding of ontology. But this leads into another broader theme that we addressed here, and that is whether, in fact, we should be concerned about such questions. Does it make sense to devote our energies to addressing these metaphysical questions, which have to do with what's knowable and what's real. And this actually would be an excellent opportunity, I think, for one of our members who hasn't yet contributed, to express his opinions on this score, because I think that would be... He's promised something provocative, so... Actually, actually, he was choosing to keep quiet. But I'm forcing them now to speak. So I'm going to pass the mic to Vajali. Let me confess I feel out of place here. For one thing, regarding time, first I don't consider this relational approach as very deep, it looks to me quite old. But meanwhile, there are people like Raphael Sorkin who have studied this problem of including things like diffeomorphism in variance, coordinate changes, in the context of quantum gravity. And there is rather a simple observation of what time might be for an observer. It is what people call as a total order. We can order the events for one observer, totally, so you know what is to the future and what is to the past. That defines a time. It doesn't define a clock. That is up to the individual who is involved. And he has also pointed out that what is meant by causality is what he calls as a partial order. Partial order means that you can say some events are to the future of some other events. If A is to the future of B, then B can influence A. whereas there are events C which cannot be in any relation to the B.

22:30 So if you have a partial order, then you can also introduce causality. And he keeps quoting all the time Riemann. Riemann had this consistent idea that in the very small, what we mean by things like volume, time and so on, are coming from discrete sets. and this happens also in Raphael's model, where you count, say if you have A to the future of B, how much time has passed, you simply count what are the other things in between. If A is bigger than B and there is C and D between this, so A is larger than C, larger than D, larger than B, then you say that the interval of time that has passed is two, because there are two points in between. That is an intrinsic way of doing it, this is Riemann's idea, and from this you can actually develop a well-articulated understanding of what is happening. So, just in anticipation that Don may ask me this question, I wrote down a few points, since I don't want to get into controversies, I'll just say it. The first thing is, let me say that there is underlying all this of theories. I do not know whether we have a unique understanding of nature. Almost certainly this is dependent on our history, our society and the kind of questions we ask of nature. And they can change from society to society because people will ask different questions and there will be different modes of validation of the theory. That seems to me quite evident in itself. However, when we start with scientific theories, by the way, scientific theories are not the exclusive preserve of what people like to boast as Western civilization, they are very, very old. I can quote the literature going to 1000 BC where things are discussed. Because people have to live, they have to control nature and scientific theories emerge. It is, I think, quite obvious that such theories have been formulated in completely different societies. So here there is a control by nature, so the kind of possibilities which are available to you to formulate an explanation of nature is much more disciplined, it seems to me. And then we keep developing and we come to some coherent view of the world. But what is totally unacceptable to a physicist, most physicists, is that there can be two theories

25:00 for the same phenomenon. For example, we have to have, as Bohr was proposing, I don't know really what Bohr meant, but that there is a classical apparatus and a quantum theory. That doesn't make any sense to much of us. I think what he meant by classical apparatus are simply things with a lot of degrees of freedom. Then the classical approximation emerges from that quantum system. And there are actually mathematical models where this has been demonstrated number of physicists in the last 25 years. So to my mind there is only one, maybe there are totally different theories, I do not know. At this moment quantum theory is pretty all inclusive, and I do not think that our brain is operating by totally different principles than quantum theory. The fact that I cannot explain the brain doesn't mean that it has completely different laws, totally different, nothing to do with what happens in chemistry. This I cannot accept. This cannot be correct. So, in any case, let me also say that there is a collapse of the wave packet, all these ideas. They are not really necessary and will cause troubles. The immediate trouble that you will have is that if I try applying quantum theory to cosmology, Many people have tried it. If you have a collapse of the wave packet, who is collapsing the wave packet of the universe? It doesn't make any sense. So, on the other hand, do I describe cosmological evolution classically? That also makes very little sense. Because we would like, we think that what we see experimentally is some approximation to a quantum phenomenon. I think most physicists have no doubt about this. On the other hand, I do want to say that this business of Hilbert spaces and collapses is not necessary. There are other approaches. One approach which is quite popular is coming from the efforts of people like Jalman and especially I would say Raphael Sorkin, again, who has actually tried to develop a coherent theory where probabilities are attached to histories, the whole event, from A to B. You

27:30 have a possibility of going from A to B by different evolutions and you introduce a probability measure on these evolutions. And from this, quite objectively, without our intervention, one can give interpretation to experiments. Then there is another line which is, to my mind, more mathematically precise, is due to coming from people like Siegel, Gelfandir, Neumark and Siegel, where all that you have are certain algebraic structures and states on that algebra. No Hilbert space. States have a technical meaning. And then classical mechanics as well as quantum mechanics can be encompassed in the same framework and they give corresponding answers with some modification in the two cases. To my mind, then Hilbert space is a derived object. You can get Hilbert space by some mathematical manipulations. So, I think that the future is going to be even more strange. It is not going to be that we will get a classical picture. That looks to me outright. The fact that I cannot explain what is happening in my brain and how I acquire knowledge, this is an issue which is very old. And since I belong to the materialist conception of nature, it comes from things like praxis and society and history and our brain connections, let us say the Marxist traditions. But that also, as of now, is totally disjointed from what we know in quantum theory. So they have to be combined in some way, somehow it has evolved. And I think that it will be even more strange than what we imagine. And simply by idealistic imaginations, I do not think they can be solved. That's all I wanted to say. Well, good. So that's to engender some debate and discussion. I'm anticipating some follow-up from anybody? I take it. All right. I was intrigued in the very beginning and the very end. Two points, all right? So you know there's a time boundary. And what I'm going to say is that support for storytellers to give people. First one, when you want to find a time to mention, first thing you start out with is trichotomy. Something's greater than something else.

30:00 And then that's the most, it seemed to me that you were saying that was the most primitive. And I was also, on the point two, very excited. Gelman, I think he's related to Hartle in some way, maybe his thesis advisor, for myself being poking around. Hartle had decoherent histories, Gelman had something with histories. And that Gelman has that evolutionary plane, and there's a cosmic landscape with Suskind, they're gonna have decoherence history, evolution on what Suskind is talking about. I don't really expect to answer any question here. I'm just making connection with people. Thank you. Good. Well, I would like to try to pursue this conversation just a bit further and follow up on Baal's observation, which I agree with, in fact, that the future is going to be far stranger than anything that I think we're capable of imagining now. But should that dissuade us from asking questions of reality, whether we can, whether, will it forever be premature to ask these fundamental questions? that is about the nature of the reality of time, the relationship between the theories that we construct and whatever that real world is out there that we all admit we're incapable of imagining at this moment. So that's also intended to be a provocative remark. So I hope I get a follow-up from our philosophers and from others. There's some question. Somebody wants to ask somebody else. Oh, yes. in response to your comments. I think during the course of the discussions that have been present at this over the course of this symposium, one thing that struck me, philosophically speaking, not from the technical aspect of physics, but philosophically speaking, is that one, you just mentioned that within GR, or general relativity, especially in quantum mechanics, There's no notion of absolute time. I may be mistaking it, but the aspect of what it seems to me, and it's two comments, and I don't know if you all want to discuss it or not,

32:30 But it seems that in a lot of ways, when I speak with physicists, they seem to treat the mathematics and the mapping of our reality, outside of the empirical aspect of it, more real than the empirical phenomenon that they're observing. They treat the mathematics more real than the real. Yeah, good point. Secondly, in reference to time, I think that in a lot of ways, we, it seems to me like there's no absolute notion of time, but what we are doing is arbitrarily projecting a template of orientation onto a continuum in order to orient ourselves within the system itself. and I was hoping maybe that you all might remark on that if it's possible, I'm not sure, I'm not trying to agree Yeah, I got something to say about that Yeah, I find that the idea of projection is, you know, I talked about that a little bit in my talk on, I guess it was yesterday But hearing you talk about it, I'm reminded of the problems that, because it was a very Kantian idea that Kant had with it. So you said, we project something onto this continuum and that there's some sort of system out there. So, you know, the problem that Kant, you know, stumbled over or struggled with was that his idea was that what was out there was the world of things in themselves, the noumenal world. But by his own model, he wasn't really licensed to talk about that. This was the world, the unconceptualized world. So you can't talk about things that you can't conceptualize. You can't put them into words. So this whole idea that we have of ourselves as projecting onto something is kind of illegitimate in a way, all right? In other words, if you think of ourselves as living in time and doing some sort of projection, then it's very hard to say what you mean by projecting time, okay? Because you're sort of assuming time and giving a description of what it is to project the world. So I think this is something I struggle with when I'm thinking, trying to understand time.

35:00 I mean, I have this sort of personal time, but it's very difficult to avoid describing the world also using that time. And then in order to, it's almost as if space and time especially are the background against which you can describe the process of projection. Right? So to say that they themselves are projected is highly problematic. And I think that this comes up in a slightly different form in many different approaches to quantum gravity. This is something I tried to get at yesterday, is I think lots of, in many respects, our concept of the physical world, in particular the way we construct quantum and classical theories, assumes a kind of spectrum, a manifold of events arranged in some sort of order, which, on the other hand, we're trying to construct. I mean, this is the whole problem. General relativity is a theory of space and time, and to regard it as a projection is, to regard space and time as a projection, it's very hard to make sense of what kind of a projection that is, what the process is. We can't even regard projection as a process because process is temporal. Okay, I'll stop there, but I just wanted to sort of point to this. It's an old issue which is connected with this whole Kantian problematica projection. Any other? We're getting involved. I just want to respond because I'll be quick, I'll try to answer first, Don. Are you allowed to think about this in relation, no of course, I'm not a, what is it, a police person trying to stop you. However, it will be much more interesting. It will be much more interesting if the speculation has a considerably greater fantasy and it is at all the same time continually controlled by experiments. Idealistic thinking I cannot accept as very fruitful. It may succeed, but it will be random. Greeks said there were atoms. I don't know why they said it. That appears to me idealistic speculation, metaphysical speculation, with no basis in experiments. So that, I would say metaphysical. I am using it as a physicist. And not to measure it as this, as something, but as speculation about physical nature, which is historically not possible to check. That is all I mean. Secondly, what was it?

37:30 That we think of theories as more real than... I do not know what you mean by are real. We don't use that phrase. But physicists, at least in the way that we operate, despite the divisional labor between different people, physicists in their practice, except in the extreme reaches of quantum gravity, I should say, the models are made and they are checked by experiments. So speculations are continually controlled by experiments. I don't think thing that, for example, the standard model, which practically any serious physicist will say explains all of chemistry and all the way down to scales for the order of 10 to the power of minus 15 centimetres, no practising physicist will say is, that's it, true, no, of course not, they are trying to change it all the time. And then check with the experiments and the hope is that when the machine in LSE is turned on in CERN, or some other fine data is gathered from one of the satellite experiments about the cosmic microwave background, it'll be changed, we hope. We'll get more insight, and one is only too happy if things are simply smashed. So I don't think that people use words like a theory is real. is something that seems to be coming from outside physicists. Then what is it? Last question, time. Something you asked about time, what is it? Yes, it was the aspect of the... I don't mean to say that time does not exist, that's not what I mean to stick to it. If you ask why time exists, I don't... No, what I'm saying is that the notion of marking time itself is actually created within the mind and projected upon... I don't know about mind. I don't know about the mind projection. It seems to me that all of what we know is a praxis, I think that is the word that people It's an interaction between our brain is formed by our experience and it is capable of certain things by our experience. Then we interpret that experience. I don't know how to separate these things. And there is a collective thing. So why are there commonalities in the collection? I suppose it is because we share certain experiences.

40:00 I don't know the answers to these questions. But I am quite satisfied by saying that an intrinsic definition of time for an observer is a total order, while causality, which plays an extremely important role in things like gravity, is a partial order. That seems to me a very powerful definition, and quite coherent with earlier speculations I wonder if I could just make a very simple remark about the role of time as a coordinate. For example, as a Gaussian coordinate. For example, Gauss stressed that coordinates were completely arbitrary. They didn't have to be rectangular or didn't have to mean anything. For example, if I wanted to put coordinates into this room, I would draw completely arbitrary surfaces and call them X surfaces, Y surfaces, Z surfaces, and I'd have a coordinate system, a Gaussian, completely arbitrary coordinate system, which allowed me to give an address to every point in the room. I can talk about the 0.378, and that would be a definite address of a point in the room. In the same way, one needs one more coordinate to give addresses to events. and the picture that Einstein put forward is and I've always found that a very useful idea in teaching time when you talk in relativity especially about time it sort of sits in the air it's a vague concept but you can make it quite you can make it quite concrete by saying that you know just like Gauss had the idea of destroying arbitrary coordinate surfaces over a space I sent it the idea of filling all space conceptually at least with with little standard clocks So you buy the standard clocks in a shop and they're all identical, and then you fill all space with them. And I don't know, there may or may not be a way, that of course is a big problem. Is it possible to, obviously you can't synchronize them in a unique way, but is it at least possible to arrange these clocks so that at least neighboring clocks take more or less the same time? In other words, can you produce a continuous coordinate system, a continuous time coordinate, say even just across this room. But at least time in that, it is certainly not a conceptual thing, it's nothing that

42:30 depends on the human mind or anything, it's simply something that sits out there like a Gaussian coordinate system for space. You add these clocks and that then allows you to give addresses to anything that happens anywhere. but it now has an X, Y, Z, and it also has a time. The time is indicated by whatever clock reads at that point. I think it's a healthy idea of time. It allows you to think of time as something concrete, rather than something vaguely sitting in the air and then having to be ex post facto determined by experiment. Good, good. Cecile. I'd like to address this question in a minute, less than a minute. May I, Mr. Chair? Let's hold off a moment. Actually, this is a very low-level remark which addresses that we can expect a lot of unexpected things from the future, and also the issue which has been raised is quantum mechanics or quantum physics complete theory or not, or just a rather more phenomenological theory than a fundamental theory. And here it is. I think that in the very near future, in five, ten years, what we're going to learn from nanotechnology is going to tell us a lot about quantum mechanics. And that's in the immediate future, and we'll have it. Recently, I thought nanotechnology was just the world to get money from the university. And I didn't know if it was a nanometer or a nanocentimeter or a nanowhat, what, what, until I heard a very good colloquium by Lynn Williams who works in nanotechnology and brought out why quantum mechanics would look very different. And it's based on the issue as simple, that the ratio of surface to volume goes into a totally different order of magnitude, et cetera. So this is just about the immediate future and the completeness of all the mechanics. Please. Thank you.

45:00 About this idea between, let's say, and metaphysical speculation and experiment. I totally agree with what has been said. The only thing is that sometimes experiments come very much later after the ideas, and maybe hundreds later, even centuries after. What do I mean by that? Well, if you look at Leibniz criticism of Newton's theory, it seemed very metaphysical. but in some way it opened a genealogy that came through Mars and that went to Einstein to understand in what way we should understand space-time and which way we should understand space-time. What do I mean by this? Well if you look at special relativity, at the history between special relativity and general relativity, you realize that there was many people that just attempt to find some way to modify Newton's gravitation law to make it coherent with Lorentz transformation. And Einstein was aware that it was not the only thing to do. Einstein was very sensible to Mach criticism of absolute space. And Mach criticism of absolute space came from like that, came from like that. So I mean, in 19, I don't know, 17, I didn't do an experiment, I don't remember. I mean, I think we could make a bridge between Leibniz criticism and that experiment because it's totally connected. The fact that it came very, very much later. and one more thing when you read Hegel's encyclopedia of nature science there's also criticism of Newton's absolute space and that are very closely related to what absolute space became in general relativity so I totally agree with the experiment but in some ways again they can come very very much later Does anybody else have anything that... I even said something just very quick on continuing that thought. Also, the question of metaphysics, it can be understood as wild metaphysics, as anybody beginning to just throw ideas randomly. And then that, yes, probably being coherent, maybe even lucky once in a while.

47:30 not that it is devoid of being sensitive to experience or experiment, which is the opposite. I think metaphysics is important, but the role of metaphysics is to address some difficult questions. Maybe at this point, at this juncture, the evidence is difficult to interpret or is difficult to find, but they might give us some direction from which to pursue our experiments. And then, of course, experiments are not just physics experiments. They can be psychology experiments, because metaphysics is in a way broader than just addressing questions of physics. So it's in a way difficult for me to see the work of Einstein without thinking that he was doing some metaphysics and Newton and Mach of the great scientists that were involved with these metaphysical questions that at some level they're difficult to differentiate from from the physical the physical questions as well and good good we do have a question in the back uh yeah so um cecile argued from that liberal approach of the quantum mechanics, that time is nothing more than a parameter, a useful parameter, but nothing special. And Don, you argue that from the canonical formalism that there is something very special about a particular time variable and you can choose a very special variable. So I'm wondering is there any way we can get you two to agree? It's the two of them. I don't know whether either of us have had enough wine already Well, no, I don't think I would agree entirely with the way in which it characterized my presentation because what I was arguing was that one could make a choice of time, but there are infinitude of possible choices that one can make. And then having made that choice, then one can establish a unique correlation between that time choice and what's happening in the world. So I think in that sense, we don't entirely disagree because all of those different choices of time are useful in some sense. But the usefulness, I think, would be determined more by the possibility of being able to experimentally measure that particular choice that you made.

50:00 I'll pass just a moment to see, but I wanted to follow up on also Wilking's comment about Einstein's conception of time and this notion of filling the universe with clocks. I would identify that precisely as the first instance of this relational approach to time. Because there was, in fact, establishing a relationship between observed phenomena other than the clocks and correlating that with the hand of the clock. So that is a supreme example, I think, of a relational approach. Can I add something? Cecilia wanted to say something first, then we'll pass on. All right, just very quickly, it occurred to me that many people probably didn't really still understand what this relational idea is, and Professor Rindler's example gives an easy way to express it. I mean, the idea of relational time is that—so you have this universe filled with clocks, and I think Leibniz's idea was that if the clocks—you might ask the question, well, if the clocks all stop and then they start again ten minutes later, did ten minutes really elapse or did nothing happen at all? So the absolute view of time is that, no, that description was coherent, ten minutes elapsed, but there was no change. the relational view is that those clocks really define the reading of the clocks defines the passage of time and so that description whereby ten minutes passed or a million years passed and the clocks all started again is a misdescription and what really happened is no time passed there was no change, no passage of time and then I think the earlier question about the role of the second law comes in when you start to worry about Well, these clocks, they're periodic, right? So they go around once every, I don't know, every 12 hours or something. They come back to the same point. So that's the same thing. Did any time pass, or is that the same moment as the earlier moment? So somebody who thinks that the second law is important would say, well, actually, there's some other process that keeps increasing, say, the development of entropy in the universe.

52:30 But behind this purely periodic clock process that allows us to say that time does pass. Okay, so I just offer that as kind of a clarification, I think, as kind of a basic example for people who are a little bit lost about what this relational idea is. Cecilia, back to you. Thank you. Actually, as far as Don and I, I'm not looking at a high level like him, I'm looking at a very low level of a practitioner get something, but I'd like to say a word about experiment in answer to you, that the idea of no space, we already see it in Leibniz, et cetera, but then it really was the experiment of the observation of the deflection of light by the sun, which made it happen, so that all these ideas which are floating around, they really take root when there is an experiment. And I can't resist telling you at this point that the famous 1919 experiment of Einstein that gave him all his fame, et cetera, is a fluke. If you look at the way he measured the deflection of light by the sun, there was not a chance in a hundred So how we got the right answer, that's a happy nonsense. But it's totally, totally unacceptable from an experimental point of view. Good, good, let's see. Alexis, do you want to say? Yeah, we should probably be closing up soon. Thank you. Thank you. So luckily, we have metaphysics. No, I mean, I totally agree. I don't want to have been misunderstood here. is just to tell that we need both of them, I think. And that there's a nice equilibrium, and that's what we need. Just about again, this idea of, I mean, in the way what Steve said, relational space for Descartes or Leibniz was just contiguity. I mean, we don't need to suppose in a way or another something as a box with infinite boundaries. No, it was just contiguity. And some people, I mean, people like Barbara think, for example, that our relational view of time might get us to the fact that time is not a fundamental entity.

55:00 And just like temperature, I mean, there's no such thing as temperature. What there is is that it's not a fundamental level. It comes from statistical mechanics. I think might be a way to see also those relational issues. Okay, actually, I think we need to be closing soon, but I'm hoping that we can perhaps devote a couple minutes to another theme that has arisen, which is closely related to things we've talked about already and that has to do with the reliability and understanding of intuition and why and how things happen that are counterintuitive, particularly related to the notion of time. Most of us today have an intuition of time that's actually pre-Einsteinian. And I have a suspicion that future generations will perhaps have adjusted to this idea that there is no such thing as universal time. That one has to look, as Bob was suggesting, at the societal context in which our intuition is operating. And of course it would be difficult and perhaps it would be undesirable to try to divorce ourselves from our intuition in attempting this understanding of time. So if anyone wants to make a comment regarding intuition, in particular regarding our intuition of time, I want to ask members of the panel first, but unfortunately we're going to have to close up real soon here, but this would be just a closing volley here. Do you want to say anything in that regard? Yeah, oh, I see. Yeah, thank you. Of course, I totally agree with what has been said. I mean, totally in agreement with what I tried to explain yesterday in my general talk. We even have a pre-Copernician way of talking.

57:30 The sun gets up and rays and gets down and everything. So, of course. And I think that even many scientists still work as if we had in some way absolute time and absolute great frames of reference. So, how do we get rid of bad habits? That's one of the questions, of course. Or is it a bad habit? So, we have to get rid of those bad habits. Maybe not. I see the microphone has made it all the way back to me without anyone intercepting it. But let me see. Sergei, you want to ask a question? Regarding the intuition, in yesterday's talk it was said that physicists work, physics is counterintuitive or whatever, I don't remember, but I would like to remember the statement made by Einstein, when journalists came to him and asked about the result of Heidi Reddington experiment of 1990, if the experiment shows something in disagreement with your theory. And then Einstein said it would be when the experiment is wrong. The intuition, I think, is deeply embedded in physics. And physics is based on good intuition. Good physics is based on good intuition, bad physics on bad intuition. my point was just to say that I think I agree with you I didn't mean to say something that was against that, if you take a simple example in set theory, when you try when you start dealing with infinite sets and show that there's infinite sets that are bigger than others, at the beginning it seems counterintuitive so what I mean is that when you get into sets you're in the machine and working with sets At the end, it begins to be intuitive. So what I mean by this is that intuition is not something given. It is related to a theory.

1:00:00 It is related to a construction. That's what I mean. And when you're, well, you've done set theory and deal with counterintuitive approaches, it's not any more counterintuitive to have sets that are infinite sets that are bigger than others. That was just my point. And it's true also for many parts of physics. The construction of theory is based on the right intuition. If you have the right intuition, you will construct the right theory. What do you mean by right intuition? I have a feeling we're not going to resolve this argument. It's like religion? It's a kind of belief. You don't know what will happen, but you feel that this way is right. You know what, I think this is the perfect context in which to terminate our meeting in disagreement. But I would like to thank our panelists for participating in this conversation. Thanks very much. We thank Don for having put it together. Thanks so much. I wanted to mention, and I should have mentioned this last night, that I did not work alone here. In fact, one of my collaborators, Hank Gorman, is in the back here, and he played an important role. Karen Dillon, she also did a great work, so we have them to thank also. So we are going to break for lunch now, we're going to go over to Wright Campus Center. We do have talks this afternoon. 30 in this room. We have an additional speaker. Chris Beatle has agreed to speak to us. So we'll have four talks this afternoon. I'd like to invite you all to come. Dwight Neunschwander is going to speak to us first. I think we would characterize his talk as being a public audience and also carries, I would imagine, too. But in any case, I think you would benefit if I'm coming and listening more than what they have to say. So thank you for coming, and hope we'll see you later. We'll check it out. Yeah. It was nice to see you. Nice to meet you. Yeah, I mean, also, I have to, I teach this afternoon in Dallas.

1:02:30 I don't know. I think the development of physics is largely the opportunity to see what happens in the manual. Yeah. Good.