EDGE: How has your own work influenced science fiction writers?

DAVIES: Several times a year I get sent science fiction manuscripts based upon my work. I just had one last week in fact, which was actually a time travel story by an Australian science fiction writer. He wanted to get the physics right. The best-known science fiction writers who have drawn my work are Gregory Benford and Margaret Atwood. Benford came to see me in the early 70's to discuss time travel, and in his Nebula-winning book Timescape he features me as a character! It's the first time I appeared in somebody's novel. Atwood's book Cat's Eye has some element of physics, which she thanks me for. More recently, I have been helping a film director with a movie about a scientist who is the target of an obsessional admirer.

Although it is a two-way street, I would probably say that professional scientists are more influenced by science fiction than the other way around. You see, a fiction writer can create a purely imaginary world. It's in the nature of fiction that you don't have to stick to the rules. People use the term science fiction as though it refers to a uniform genre, but it's doesn't. It shades from what we might call hard sci-fi — the sort of stuff that Michael Crichton might write, which is my preference — right off into fantasy, fairy stories with scientific overtones. Terry Pratchett, who writes humorous fairy stories with a science basis to them, is a classic example of the latter. I'm afraid I don't like that sort of stuff terribly much personally, though Pratchett's Discworld novels are hugely successful. Anyway, the point is that there's no obligation for him to stick to the usual laws of nature. In fact, there's even a book called The Science of Disc World which invents an imaginary science for Discworld — well and good. While most science fiction writers have some understanding of basic science, they aren't studying very carefully what is going on at the forefront of science. They may pick up some ideas, but they're mostly not going to study the detailed technicalities of the science itself. Very few of them try and get it completely right. Michael Crichton and Arthur C. Clarke are exceptions. But I guess the old adage applies: why let the facts stand in the way of a good story.

EDGE: Let's get back to the science. How and when would time travel ever manifest itself?

DAVIES: Well I've already mentioned that travel into the future is a reality — but of course it's trivial — the sort of leaps into the future you get from traveling in a jet aircraft amounts to a few billionths of a second, so that's not going to excite anybody. And the only place where you see very significant temporal distortions is in particle physics, where the particles are moving very close to the speed of light. But to most people they're not very interesting objects, these subatomic particles. A human being is never going to travel, in the foreseeable future, at an appreciable fraction of the speed of light. So we're not talking about an effect that's of any practical value, or even any curiosity value, it's just too small for us to notice. But if you could achieve speeds close to the speed of light, or find another way to travel into the future, then I guess that would be of great interest because it would then be possible to make space journeys over many light years in a human lifetime. It would be wrong to suppose that if you wanted to travel to a star a hundred light years away that the journey's going to take you a hundred years — in your frame of reference. If you're traveling close to the speed of light, it might take just ten years. In terms of wanting to get there within your lifetime, this is a significant effect. But again, we're talking about something that is so far beyond current technology; it's pretty fanciful.

When it comes to traveling backwards in time, well, you might think that if it is achieved at some stage in the future, we're going to see time travelers coming back to visit us now. This is an argument that is often used against time travel. Where are they? Where are these tempanauts? Shouldn't they be popping up all over New York saying, 'Yeah, time travel is possible, we invented the time machine in the year 3000, and we're coming back to tell you about it.' Now there is a let-out for this argument in the case of the wormhole time machine. According to the physics of the wormhole, you can't use it to travel back to a time before the construction of the wormhole itself. If we managed to build a wormhole time machine this year, we could put it in a warehouse and wait ten years and travel back to 2000, but we couldn't go and see the dinosaurs or anything of that sort. The only way we could do that is if some aliens made a wormhole millions of years ago and lent it to us. So maybe the reason we don't see time travelers from the future is simply because the only type of time machine that you can make is one that can't be used before the manufacture date on the machine. Then we're not going to see these time tourists. It's anybody's guess as to when such a machine might be built. But if the wormhole is the only way to do it, then we're talking about cosmic-scale engineering, something on the outer fringes of the possible.