Interview with Julian Barbour

By Mitzi Haslinger –  Copyright 2002-2010

The End Of TimeJulian Barbour is an English theorist on astrophysics and time. He proposes that the quantum universe is static, existing as a set of states independent of time, governed only by their probability. Our notion of time arises from observation of these states. Barbour says, “. . . time is an illusion. The phenomena from which we deduce its existence are real, but we interpret them wrongly. My arguments are presented in The End of Time.”

Mitzi: Could you tell us how you got interested in the study on time and a little about your background.
Julian: Well, I was hooked by astronomy when I was about nine. I went to Cambridge and studied mathematics, and I took a year out and went to Germany and learned Russian and German. While I was there, I started seriously to think about doing a Ph.D. in astronomy at the observatory.

Quite by chance I read an article about the attempts to give a unified description of the universe, a quantum description, which also took into account Einstein’s general theory of relativity. That is how I came to think about the foundations of physics and – particularly – time. As you may have realized, I have come to the conclusion that ultimately time is an illusion. It is an inappropriate concept to describe the universe.

Mitzi: What do you think about Bohm’s description of the universe in which he describes the implicate and explicate order.
Julian: I am not sure I would necessarily agree that that is the way the world works. My view is that there is something real out there, that it has a structure, and that when we describe that structure in terms of physics, it is not appropriate to put time or motion into that description.

What I might conjecture is that it is consciousness that gives us the impression of motion and gives us other data, which we interpret in the first place by means of the concepts of time. We have a notion of time as something linear, so that is a very common belief of people. It is my belief that there is a timeless structure out there in the world, but we perceive the appearance of motion. I think it is widely accepted that the senses and our conscious impressions may not be an immediately accurate guide to how we should think about the world.

Mitzi: What led you to write your book, The End of Time?
Julian: There is a thing called the problem of time that when you try to put together quantum mechanics and Einstein’s general theory of relativity, you get an equation, which is called the Wheeler-DeWitt equation. It seems to describe a static universe in which nothing happens. It is like a frozen universe. About ten years ago when I was thinking about these things very intensively, I came to what I felt was the correct interpretation of this equation, which gives you an overall picture of how you should think about the world and also a conjecture about why the world has the structure that we find around us.

I thought about it for five years and couldn’t find anything wrong with it. In fact, I found quite a lot of supporting evidence. I was well aware that I had quite a lot of ideas, some of which were very different from the way most people thought about physics, about what is motion, what is time, and what is space. If I am right and there is no time, and I have managed to get some sort of idea about why we nevertheless think there is time, that is potentially very interesting. So I thought I would write a book about it; set out my ideas as clearly as I could for a wide audience. I have got a very fruitful collaboration with a few people, which is actually giving very encouraging results.

Mitzi: What is your definition of time?
Julian: We have to be very careful because there are two quite different forms of physics. In classical physics, time is something a bit like an invisible washing line. At each point along that washing line, the universe has some arrangement of its parts, some particular structure. You could imagine taking a snapshot of that particular configuration of what the universe looks like and then you could hang it on the washing line at the time corresponding to it. A minute later you could take another snapshot and a lot of things in the universe would have moved somewhat. So you will have a slightly different snapshot, and you would hang that on the washing line at one minute later. So you would have a lot of snapshots hanging on the washing line, all of them with their correct spacing. That is essentially how Isaac Newton thought about time and is still the way many people think about time to this day.

Now in classical physics, the starting point of my work is just very simply to say, well, look, actually the washing line is completely useless. The universe doesn’t have any external framework like that. I set out to describe in classical physics how things change their positions in the world, getting rid of that washing line. That I have succeeded in doing, and I think people are increasingly recognizing that that is an interesting and possible way of looking at things. In classical physics, I am not changing the idea that there is a unique sequence of events. I am just saying you don’t need a washing line to hang them on.

Suppose we had a universe that was just three particles. We could take snapshots of those three particles which create a history of this universe. There would be a whole succession of these three particles, which would form triangles. You could imagine triangles hanging on the washing line. The Newtonian universe of three particles would be just one succession of triangles.

Now quantum mechanics is a very different story altogether. It suggests there isn’t one single succession of states. There is every conceivable succession of states. Quantum mechanics suggests that in some senses all the triangles are there at once and it is quite wrong to think of the triangles being arranged on a line. They sort of form a multidimensional space. You could also imagine them in a huge heap.

Getting back to the Newtonian picture, because I have got rid of the washing line, you could call each individual triangle in this toy model I am describing an instant of time. There isn’t a washing line, there isn’t any line of time, but there are individual instants of time and they are like snapshots of the universe. They are just what the shape of the universe is in any given instant.

To get the picture that is appropriate for quantum mechanics, you have to enlarge your vision and think that all possible instants of time, all possible shapes of the universe are all present at once. Quantum mechanics is very, very different and my ideas don’t really start having exciting implications until you take on board the possibility that they are all there at once. That is a big change. Quantum mechanics is very mysterious. There seem to be probabilities. Now we are getting into very deep water. Quantum mechanics, when you try to interpret it, is very deep.

Somehow or other there are probabilities for these different possible instants of time – triangles in my model or snapshots of the entire universe, if we are going to be realistic. Somehow each of them has a probability, which is determined in accordance with a definite rule. That is the mathematical picture that emerges, or at least has emerged from what I am doing and proposing. It is very, very different from the orthodox way in which one thinks about time.

Mitzi: What is the broad implication to quantum mechanics of your changing the definition of time?
Julian: The really interesting thing is the law that determines what probabilities each instant of time – each possible configuration of the universe – has and how that works out. This has big potential implications for causality, predetermination, and all sorts of things because it suggests the universe works in a quite different way.

In the old picture – and it is the way virtually all of my physics colleagues still think; I see this every time I read a physics paper – there are initial conditions and then there are laws of how the universe evolves. For some reason or other, initial conditions get created, either by God or spontaneously, and then the laws take over and the universe evolves from that. What we find around us now is the consequence of what was set up in some very distant past or in the big bang.

I don’t think the law works like that at all. I think it is a law that works all at once and picks out probabilities all in one holistic way. In a way, I say the instants of time are competing or possibly collaborating with each other to get as much probability as they can. It all sounds very abstract and difficult. It is a conjecture on my part, but I think there is something going for it.

Mitzi: Change becomes something much more real to the moment than in the previous view, which even though scientists are describing something in terms of quantum physics, it is still with a linear way of thinking.
Julian: What really counts now is not so much change as difference. Two things which are nearly the same, but not exactly the same, can get very different probabilities. That is all determined in my view by one huge big law, which somehow determines all the probabilities at once. They are all somehow resonating with each other. If things are strongly in sympathy with each other, then that helps them to get a higher probability.

It is quite a nice, holistic way of thinking about things. It wasn’t planned that way, but it does go down well with people with religious and philosophical inclinations because one can see all of creation at once. I haven’t come from any particular religious drive on my part. I think it is more to do with the fact that science works with laws, and in some sense laws are something eternal. That sort of brings in the God’s-eye view of things.

Mitzi: Most conventional scientists outside of physics still think very much in terms of classical physics, in terms of the linear, materialistic view. You are saying that actually a lot of physicists still think that way.
Julian: Yes, I think that is true.

Mitzi: How can a change in thinking be brought about?
Julian: First of all, it is not easy to change the way people think about the world. This is a long-term process, to use conventional language. It took something like 150 years for Copernicus’ proposal to get accepted generally.

Quantum mechanics has a very radical, very remarkable interpretation, which is called the many-worlds interpretation. Initially very few people took it seriously. About ten years ago a small group of people who were trying to make sense of cosmology and quantum mechanics were trying to create what you would call quantum cosmology. A majority of these people favored the many-worlds interpretation because they found it completely impossible to make any sense of quantum mechanics any other way.

If you want to know the biggest problem of the day in physics, ultimately I think it has got to be: what does quantum mechanics really mean? What does it really tell us about the world? The amazing thing is that it is very hard to work out what it says about the world.

There is one extremely strange interpretation, which goes back to the original founding fathers, called the Copenhagen interpretation. Then there is the idea that David Bohm put forward and then there is the many-worlds interpretation.

I think there is clear evidence that more people are now taking the many-worlds interpretation seriously. If it becomes the majority opinion among physicists, then the ideas I put forward in my book will be much easier for people to accept.

The best thing that could happen to me would be if scientists seriously started trying to disprove my theory, because it is always good when people can’t disprove a theory. If they fail, then it looks better.

Mitzi: Are you planning on writing another book?
Julian: I think it is quite likely. The next one would be a more technical book. The End of Time has only one equation in it and it leaves out a lot of technical details. Quite a lot of people who do have physics training have said to me that they were a bit disappointed there weren’t more equations. I will also include new exciting results we have.

Mitzi: Amit Goswami thinks that consciousness creates our physical reality.
Julian: That is not a position I am advocating, but for a long time I was very attracted to that possibility. There is a difficulty for me with the views that start with saying consciousness is primary and is creating everything. It solves some philosophical problems, there is no doubt about it, and that is why I was very attracted to it.

The problem is that it is extremely difficult to say, well, why does the world seem to be material? Why do theories like quantum mechanics and Einstein’s general theory of relativity work so extraordinarily well? That is very, very difficult to explain. Either way you have an extremely difficult problem, so I have a conservative approach to consciousness. I just accept that it exists. At the moment, I say that it is somehow correlated with the material world in a way which is completely baffling.

I don’t ascribe any active role to consciousness at all, but I do say consciousness is very important because everything we know about the world – whether it be conscious or unconscious – comes to us through consciousness.

Consciousness is our only source of information, and I believe it is ultimately a true source of information. You have to make that assumption. This is essentially what Descartes said, “If there is a malignant God creating us and deliberately deceiving us, then we are just lost.” We can’t accept that assumption. We have got to assume that God is playing reasonably fair with us. I think this is very much the lesson which comes out of the whole history of science and physics. We have to be careful about the way we interpret what we get. First impressions might not be the correct ones.

Mitzi: Does your theory on time have a specific effect on string or superstring theory?
Julian: My main aim is to create a theory of the universe in which you don’t start off by assuming some structure, some framework, in which things fit. This is widely recognized as a problem with string theory. They have not succeeded in formulating it in a way in which it does without some external framework. The underlying concept of string theory assumes that there is a string moving around in space and that space has properties. My feeling is that if they ever do get a satisfactory theory, it will be one that doesn’t have a background structure and it will be a timeless theory like I am proposing.

String theory has had a huge number of people working on it for nearly 20 years now. They still, to be quite honest, have not got anything definite that shows that it is working and that they are on the right track. They have got some important stuff, but there is a huge gap between the hype and what is really there, and there is an even bigger gap between what is there and what needs to be there.

Mitzi: You started thinking about time 38 years ago in terms of your human time frame, so what kinds of questions are you asking yourself these days? What is on your mind?
Julian: I have new results with my collaborators that I am trying to push forward. I am working on pretty technical issues at the moment. My thoughts at the moment are very practical. How can I persuade scientists – that are better at the technical issues and equations than myself – to take my ideas seriously and work on them? I have got a whole host of ideas. I think what I will do is to write them all out in a book and present copies to selected victims and see if they will take the bait.

Mitzi: What are your thoughts about time and space only existing between two points in consciousness?
Julian: Fifteen or twenty years ago I gave a lot of thought to trying to put consciousness first. This is idealistic philosophy. I am particularly interested in Leibniz’s approach to it. Leibniz postulated that conscious beings are the ultimate reality and the whole world is nothing but the relationships between conscious beings. He called them monads and said that the monads are the ultimate atoms of existence.

This has had a big influence on the way I think about things. In this view, you and I would be just different views of the universe seen from a particular point of view among the ultimate atoms. In the end I came to feel that that couldn’t quite be made to work, although I still find it very attractive. What I have really done is import a whole host of Leibniz’s ideas into the way I think about physics in slightly more conventional terms.

For me now the ultimate atoms of existence are the instants of time, and we are somehow imbedded in them. I wouldn’t rule out some major change. I think it is entirely possible that there will be some huge insight about consciousness. I think it could happen totally out of the blue at any time. This could then totally change the way we think about things. Maybe a view like you advocate might then – and I was very attracted to it 15 to 20 years ago – might be justified.

Mitzi: Now in Leibniz’s view, is a monad equal to the Observer in quantum theory?
Julian: Could be. It might be. I think that is a distinct possibility.

Mitzi: Thanks very much, Julian.

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