Time Travel. A History

Wells likewise foresaw the objection of the Philosopher that the traveler risked crashing through piles of bricks and other unexpected alterations in the landscape. “So long as I travelled at a high velocity through time, this scarcely mattered; I was, so to speak, attenuated—was slipping like a vapour through the interstices of intervening substances!” Simple, when you put it that way. Halting in the wrong place, however, would still be dangerous. And exciting.

To come to a stop involved the jamming of myself, molecule by molecule, into whatever lay in my way; meant bringing my atoms into such intimate contact with those of the obstacle that a profound chemical reaction—possibly a far-reaching explosion—would result, and blow myself and my apparatus out of all possible dimensions—into the Unknown.

Wells laid down the rules, and from then on all the world’s time travelers would have to obey. Or if not obey, at least explain. Jack Finney put it this way in a time-travel story in the Saturday Evening Post, 1962: “There’s a danger a man might appear in a time and place already occupied….He’d be all mixed in with the other molecules, which would be unpleasant and confining.” Explosions are ever popular. Philip K. Dick in 1974: “…the hazard in re-entry of being out of phase spatially and colliding right down to the molecular level with two tangent objects….You know, ‘No two objects can occupy the same space at the same time.’ ” At last, the perfect corollary of “Nobody can be in two places at once.”

Wells never did justify treating the earth as a fixed point of the cosmos. Nor for that matter did he worry about where the Time Machine gets the energy to power its voyages. Here, too, he established a tradition. Even a bicycle needs someone to pedal, but time machines have unlimited free fuel, by the universe’s grace.

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WE’VE HAD A CENTURY to think about it, and we still need to remind ourselves every so often that time travel is not real. It’s an impossibility, just as William Gibson suspected—a magic on the order of kissing one’s own elbow. But when I say that to a certain well-known theoretical physicist, he gives me a pitying look. Time travel is no problem, he says. At least if you want to travel to the future.

Oh, well, sure—you mean we’re all traveling forward in time anyway?

No, says the physicist, not just that. Time travel is easy! Einstein showed us how to do it. All we have to do is approach a black hole and accelerate to near the speed of light. Then, welcome to the future.

His point is that acceleration and gravitation both slow the clocks, relativistically, so you could age a year or two on a spaceship and return home a century hence to marry your great-grandniece (as Tom Bartlett does in Robert Heinlein’s 1956 novel Time for the Stars). This is proven. GPS satellites have to compensate for relativistic effects in their very exact calculations. It’s hardly time travel, though. It is time dilation (per Einstein, Zeitdilatation). It’s an antiaging device.^*2 And it’s a one-way street. There’s no going back to the past. Unless you can find a wormhole.

“Wormhole” is John Archibald Wheeler’s word for a shortcut through the warped fabric of spacetime—a “handle” of multiply connected space. Every few years someone makes headlines by hailing the possibility of time travel through a wormhole—a traversable wormhole, or maybe even a “macroscopic ultrastatic spherically-symmetric long-throated traversable wormhole.” I believe that these physicists have been unwittingly conditioned by a century of science fiction. They’ve read the same stories, grown up in the same culture as the rest of us. Time travel is in their bones.

We have arrived at a moment of cultural history when the doubters and naysayers are the real practitioners of time travel, the science-fiction writers themselves. “Totally impossible on theoretical grounds,” declared Isaac Asimov in 1986. He didn’t even bother to hedge his bets.

It can’t and won’t be done. (If you’re one of those romantics who thinks nothing is impossible, I won’t argue the case, but I trust you won’t decide to hold your breath until such a machine is built.)

Kingsley Amis, assessing the literary culture of science fiction in 1960, felt he was stating the obvious when he said, “Time travel, for instance, is inconceivable.” Thus practitioners of the genre resort to some version of Wells’s hand-waving explanation—“an apparatus of pseudo-logic”—or, as time goes on, simply trust their readers to suspend disbelief. And so it’s the science-fiction writers who remain willing to treat the future as open, while all around them physicists and philosophers surrender to determinism. “One is grateful that we have a form of writing which is interested in the future,” said Amis, “which is ready to treat as variables what are usually taken to be constants.”