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A Talk With Julian Barbour

JULIAN BARBOUR: The question I'm always asking myself is, what is the universe and how does it work? I come at it from the point of view of fundamental physics, basic questions of quantum mechanics and its relationship to classical mechanics. Quantum mechanics was discovered in 1925 — 1926, and it gave a completely new picture of physics which was extraordinarily surprising, and it's still very difficult to understand. It suggests the world is not at all like we see it. That has remained a really big problem, and it's getting more and more discussion, more and more interest from people. This is what I'm really thinking about; how to reconcile the fact that the world seems to be classical, we seem to have unique past, things seem to be in definite positions, and have a definite future — that's what it seems to be like, but quantum mechanics tells us that it is different — not like that at all. The aim is to try and find a description of the entire universe that is quantum mechanical and understand how it nevertheless it can look like the classical world that we actually see and experience.

I came into it quite by chance by reading a newspaper article about the attempts that the great Paul Dirac, one of the discoverers of quantum mechanics, was making about 40 years ago to bring it together with Einstein's general theory of relativity. He'd come across a rather surprising fact and this led him to question whether the picture of space — time that was the whole basis of Einstein's theory really was as fundamental as people had thought. This prompted me to think about time itself. For nearly 36 years now, I've been thinking about time and trying to understand it at the most fundamental level. If you look at the history of physics, surprisingly few people have really thought about time and what it truly is. Even Einstein only thought about certain aspects about time; he never asked what it means to say that a second today is the same as a second tomorrow. This is a very fundamental question. Einstein somehow assumed that it is meaningful, but he never actually asked how does that come about and how can that be? He never defined the notion of duration. So there are aspects of time that haven't been fully studied, in my opinion.

JB: Can you give me another example besides duration?

BARBOUR: Certainly. One of the great questions in physics is whether there's some sort of invisible framework in which everything unfolds. Newton introduced the notions of absolute space and absolute time. Absolute space is like a translucent glass block that stretches from infinity to infinity; it's a fixed frame of reference in which everything happens. Newtonian time is like some invisible river that flows uniformly for ever. The trouble with this is that we can't see this invisible framework, all we see are things moving relative to each other. This is the relational viewpoint, as opposed to the absolute viewpoint of Newton. The challenge has been to create a theory containing genuine relationships between genuine things, and not relationships between real things and unobservable things. That's what I've spent a lot of my time working on. It's given me the ideas which I'm trying now to develop into a complete cosmology, a complete explanation of what the universe is.