The End of Time: The Next Revolution in
Physics [A Review]

In a twist of the old question about a tree falling in the forest with no one around to hear it, theoretical physicist Julian Barbour asks: ''If nothing changed, would time pass?'' His startling answer, contained in his new book ''The End of Time: The Next Revolution in Physics'' (Oxford University Press), is no. ''If nothing happened, if nothing changed, time would stop,'' he writes. ''For time is nothing but change. It is change that we perceive as occurring all around us, not time. In fact, time doesn't exist.''

He talked recently about this provocative notion and the book with Health & Science Editor Doug Bailey.

Q. How can a layperson grasp the concept that time doesn't exist?

A. Imagine taking a snapshot of the universe at one moment. You'd get one snapshot or picture. One ''now.'' That's the fundamental concept of how it works. In classical physics if we put the snapshots together we perceive the passage of time, much like if we put real pictures together to form a movie. But of course, the motion produced by running pictures together is an illusion, just as it's an illusion to say our series of snapshots of the universe represents time.

Q. This idea has been around for a while, but it hasn't been widely accepted. Why is that?

A. It's actually an old idea. The suggestion was made by Isaac Newton. Can we construct a theory of the universe where you don't presuppose this invisible framework we call time exists, and still work out the laws of motion for the universe? Initially Einstein took it seriously but eventually gave up when he couldn't change it. But when you look at Einstein's structure, he did achieve it.

You can understand the universe in terms of pictures of individual snapshots without the existence of time. Then [American physicists John Wheeler and Bryce De Witt] found the equation in 1967 that's been almost forgotten that may actually govern the universe and yet it doesn't mention time - yet explains what time does.

Q. So why do you think this might catch on now?

A. Science is looking for a unifying theory between relativity and quantum mechanics. This could be the embryonic bond. It just can't be dismissed. People have wanted to take it seriously for years but it's difficult to make a mathematical formula that will stay with it. Yet it has an inner coherence to it that makes it interesting. I'm not saying that I'm absolutely correct. In fact if this inspires someone to examine it and prove I'm wrong, that's fine.

Q. If time didn't exist, wouldn't everything happen at once?

A. What exists are just ''nows.'' Our experience in any instant is within any snapshot. It's a contradiction to say you can experience them together. They're like fossils, not only containing now, but our memories of what happened in other nows. Obviously there is a feeling of the passage of time. We just could interpret it in a different way. Change is the primary thing.

Q. Your theory fits quite nicely into the other worlds theory that parallel universes exist and that time travel could be possible. But you write that discussing time travel is boring. Why?

A. I don't want to sound arrogant but there's a saying by some French philosopher that says, ''Superficial people find the extraordinary fascinating and profound people find the ordinary riveting.'' Sitting on the bank of the river watching it flow past is marvelous and I don't need any more. We are studying the Big Bang, for example, and for a theoretical physicist, the Big Bang is as close to us as the house across the street. They're both in our head so they're here. What's wonderful about the universe is we can already travel through our intellect, and maybe to other nows. Intellectually I'm attracted to the many worlds interpretation. It's hard to imagine that I'm bifurcating many times into copies of myself, but that's what it says.

Q. What would change if your theory was widely accepted?

A. At the scientific level it would be hard to foresee. When Copernicus made his proposal that the Earth orbited around the sun it was a relatively modest idea. It was impossible to see what the implications were. Keppler and Galileo changed things a bit, then Newton completely changed the picture of the world. It's hard for us to visualize the picture of the world prior to Newton. He got ahold of many great truths. Now Einstein's theory, and quantum mechanics...it all came from the Copernican revolution.

If I'm correct that the ''now'' is not only in the physical but also in the subconscious world, there would be huge implications. It does have the potential to turn what we think about the world inside out. As of now, the world we see around us seems impossible because it seems so ordered.

Q. Is this really science, or philosophy?

A. It's on the borderline, I would say. But many questions about the universe start off philosophical, then become mathematical, and then physics. It may take decades to convert the equation into real physics. It hasn't caught the public attention or the eye of working scientists. I'm playing the role of the gadfly, getting people to take a look at this.

'The End of Time' is scheduled for publication later this month.