Time Travel

Despite his objections Zangwill couldn’t help but admire Wells’s “brilliant little romance.” He shrewdly noticed that The Arabian Nights had employed a sort of time-machine precursor: a magic carpet that traverses space. Meanwhile, even in 1895, Zangwill seemed to understand certain peculiar implications of time travel—the paradoxes, we will soon say—better than Wells himself.

The Time Machine looks one way: forward. Ostensibly Wells’s time machine could travel to the past with a reverse throw of the lever, but the Time Traveller had no interest in going there. And a good thing too, says Zangwill. Just think what difficulties would be entailed. Our past had no Time Traveller barging through. A past that included a Time Traveller would be a different past, a new past. None of this was easy to put into words:

Had he travelled backwards, he would have reproduced a Past which, in so far as his own appearance in it with his newly invented machine was concerned, would have been ex hypothesi unveracious.

Then there’s the problem of meeting oneself. Zangwill becomes the first to notice this, and he will not be the last:

Had he recurred to his own earlier life, he would have had to exist in two forms simultaneously, of varying ages—a feat which even Sir Boyle Roche would have found difficult.

(His readers would recognize Roche as the Irish politician who said, “Mr. Speaker, it is impossible I could have been in two places at once, unless I were a bird.”)

The book reviewers came and went, and before long philosophers got into the game. When they first took notice of time travel it was with a certain embarrassment, like a symphony conductor unable to look away from an organ grinder. “A frivolous example drawn from contemporary fiction,” said Professor Walter Pitkin at Columbia University, writing in the Journal of Philosophy in 1914. Something was stirring in science—the realm in which time was a measurable and absolute quantity known familiarly as t—and philosophers were uneasy. In the first years of the new century, when they turned to the subject of time, they had one thinker above all to contend with: the young Frenchman Henri Bergson. In the United States, William James, who might otherwise have been resting on his laurels as the “father of psychology,” found new vitality in Bergson. “Reading his works is what has made me bold,” James said in 1909. “If I had not read Bergson, I should probably still be blackening endless pages of paper privately, in the hope of making ends meet that were never meant to meet.” (He added, “I have to confess that Bergson’s originality is so profuse that many of his ideas baffle me entirely.”)

Bergson asks us to remember how artificial is the notion of space as an empty homogenous medium—the absolute space announced by Newton. It is a creation of human intellect, he notes: “We may as well say that men have a special faculty of perceiving or conceiving a space without quality.” Scientists may find this abstract empty space to be useful for calculating, but let’s not make the mistake of confusing it with reality. Even more so with time. When we measure time with mechanical clocks, when we draw diagrams where time is an axis on a graph, we may fall into the trap of imagining time to be merely another version of space. To Bergson, time t, the time of the physicists, sliced into hours, minutes, and seconds, turned philosophy into a prison. He rejected the immutable, the absolute, the eternal. He embraced flux, process, becoming. For Bergson, the philosophical analysis of time could not be divorced from our human experience of it: the overlapping of mental states, the segue from one to the next that we experience as duration—la durée.

He held time apart from space rather than commingling the two: “Time and space begin to interweave only when both become fictional.” He saw time, not space, as the essence of consciousness; duration, the heterogeneous tide of moments, as the key to freedom. Philosophers were about to follow physics down a new path, and Bergson would be left behind, but for now he was hugely popular. Crowds thronged his lectures at the Collège de France, Proust attended his wedding, and James called him a magician. “Dive back into the flux then,” cried James. “Turn your face toward sensation, that flesh-bound thing which rationalism has always loaded with abuse.” Here he parted company with physics.

What really exists is not things made but things in the making. Once made, they are dead … Philosophy should seek this kind of living understanding of the movement of reality, not follow science in vainly patching together fragments of its dead results.

Pitkin seems to have felt that he needed to rescue the poor scientists from Bergson’s onslaught. Described by Time magazine in a brief moment of fame as “a man of many ideas, some of them large,” he was a founding member of a short-lived movement that called itself new realism. In his 1914 essay he declared that he liked some of Bergson’s “conclusions” but despised his “entire method,” particularly the rejection of scientific process in favor of psychological introspection. Pitkin proposed to clear up the space-time conundrum by means of logical proof. He would embrace the physicists’ t and t′ and t′′ and yet he would prove once and for all that time is different from space. To wit: we can move hither and yon in space, but not in time. Or rather, we do move in time, but not freely: “a thing moves in time only by moving with all other things.” And how would he prove this? In a most unexpected way:

To make the proof as simple as possible, I shall present it in the form of a sober criticism of one of the wildest flights of literary fancy which that specialist in wild flights, H. G. Wells, has indulged in. I refer, of course, to his amusing skit, The Time Machine.

It was the first but not the last time that Mr. Wells’s amusing skit would impose itself upon the attention of this august journal.

“You cannot leap back into the thirteenth century, nor can a man of that period hop into our own,” wrote Pitkin. “Mr. Wells would have us imagine a man at rest in the space dimensions, but moving with respect to the time of that space field. Very well! Let us do our noblest to play the game. What do we find? Something very disconcerting indeed. Something which, I fear, will make time-touring very unpopular among sedate people.”

The traveler flies, not through abstract time (like the “pure space” of the geometer). He flies through real time. But real time is history: and history is the course of physical events. It is the sequence of activities, physical, physiological, political, and otherwise.

Do we really want to go down this road? Must we look for errors of logic in a piece of fantastic fiction?

Yes, we must. The practitioners of time travel, even in “pulp” magazines, were soon to work out rules and justifications that would make a Talmudist proud. What is allowed, what is possible, what is plausible—the rules evolved and varied, but logic must be honored. We may as well begin with Professor Pitkin, man of many ideas, some of them large, in the Journal of Philosophy.

His argument would not seem very sophisticated to a typical teenage sci-fi aficionado circa 1970. In fairness, he recognizes that common human intuition about the world often fails to comprehend the strangeness of reality. Science keeps surprising us. Which way is up, for example? “It was held impossible ‘by the very nature of things,’” he notes, “that the earth should be a sphere, with people on the other side walking, heads downward.” (He might have added that Aristotle’s common sense revealed three and no more than three spatial dimensions: “the line has magnitude in one way, the plane in two ways, and the solid in three ways, and beyond these there is no other magnitude because the three are all.”) Could it be, he asks, that time travel merely strikes us as impossible “because of certain prejudices we entertain or certain facts and tricks of which we are still hopelessly ignorant?” Let us be open-minded. “[The] answer, whatever that may be, carries immeasurable consequences for metaphysics.”

So Pitkin applies the tools of logic. These are his chief points:

• As the time machine rushes through the years, everything ages rapidly, so the man in the machine should, too. “Nations rise and fall, tempests leap up, destroy, and subside, houses are built with toil and burned in the frenzy of sudden war, and so on.” As for the tourist, his clothes are unruffled and he scarcely ages a day. “How is this possible? If he has passed through a hundred thousand generations, why isn’t he a hundred thousand generations old?” Here is an obvious contradiction: “the first contradiction in the whole proceeding.”

• Time goes at a certain rate, and this rate must be the same for everyone, everywhere. “Two objects or systems” cannot have “different rates of displacement or change in time”—obviously. Pitkin scarcely knew what devilishness Albert Einstein was conjuring in Berlin.

• Traveling through time must obey rules of arithmetic, just like traveling through space. Do the math: “To traverse a million years in a few days is exactly like traveling a thousand miles in one inch.” A thousand miles does not equal one inch; ergo, a million years cannot equal a few days. “Now is not this a pure self-contradiction, on a par with the proposition that you or I can go from New York to Pekin without moving farther than our own front door?”

• The time traveler would surely bump into things. Example: Let’s say he leaves his workshop for a future date, January 1, 1920. While he’s gone, his abandoned wife sells the house. It is torn down. Bricks are heaped where the workshop stood. “But where, oh where, is the traveler? If he remains in the same place, he is surely beneath the ton of bricks and so is his precious machine … This, we aver, is most uncomfortable for the tourist. He is fairly interpenetrated with bricks.”

• Looked at from an astronomical point of view, celestial motion must be considered as well. “The traveler who moves only in time and not at all in space would suddenly find himself strangling in the empty ether, while the earth went hurtling away from beneath him.”

Impossible, concludes the philosopher. No one can travel into the future or the past on Mr. Wells’s time machine. We must find other ways of dealing with past and future, every day of our lives.

WE NEED NOT DEFEND Mr. Wells, because he never meant to promulgate a new theory of physics. He didn’t believe in time travel. The time machine was the handwaving—the pixie dust that helps the willing reader suspend disbelief and get through the story. (See handwavium, n.) It was sheer coincidence that the Time Traveller’s mumbo-jumbo tracked so well with a revolutionary view of spacetime that emerged in physics a decade later. Except, of course, that it was no coincidence at all.

Wells worked hard to make the handwaving plausible. This first technology of time travel ended up being fairly robust. In fact, he anticipated Pitkin’s semiscientific objections and some others as well. For example, it is the Medical Man who says that space differs from time in that we move freely through one but not the other.

“Are you so sure we can move freely in space?” the Time Traveller retorts. “Right and left we can go, backward and forward freely enough … But how about up and down? Gravitation limits us there.” That was more true, of course, in the nineteenth century than in the twenty-first. Now we’re used to whizzing about in all three of our dimensions, but space travel (as we might call it) used to be more constrained. Railroads and bicycles were new. So were elevators and balloons. “Before the balloon,” says the Time Traveller, “save for spasmodic jumping and the inequalities of the surface, man had no freedom of vertical movement.” What the balloon does for the third dimension, the time machine might do for the fourth.

Our hero presents his miniature prototype time machine as an amalgam of science and magic: “You will notice that it looks singularly askew, and that there is an odd twinkling appearance about this bar, as though it was in some way unreal.” A turn of the tiny lever sends the gizmo into the void with a puff of wind. Now Wells anticipates the next objection from the realists. If the time machine has gone back to the past, why had they not seen it en route (as it were) when they were in the room last Thursday? And if into the future, why is it not still visible, passing through each successive moment? The explanation comes in ersatz psychological jargon. “It’s presentation below the threshold,” says the Time Traveller, nodding to the Psychologist. “You know, diluted presentation.” The same reason you can’t see the spokes of a spinning bicycle wheel or a bullet whizzing through the air. (“Of course,” the Psychologist replies. “I should have thought of it.”)

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.

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.

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.”

As for Wells himself, he continued to disappoint his believers.

“The reader got a fine confused sense of immense and different things,” he said in 1938. “The effect of reality is easily produced. One jerks in one or two little unexpected gadgets or so, and the trick is done. It is a trick.” (He was just back in London after a seven-city American lecture tour titled “Organization of the World Brain,” and he felt a need to deny special futuristic powers. “It is not a bit of good pretending I am a prophet. I have no crystal into which I gaze, and no clairvoyance.”)

LET’S LOOK one more time at how the trick was done:

… the dance of the shadows, how we all followed him, puzzled but incredulous, and how there in the laboratory we beheld a larger edition of the little mechanism which we had seen vanish from before our eyes. Parts were of nickel, parts of ivory, parts had certainly been filed or sawn out of rock crystal. The thing was generally complete, but the twisted crystalline bars lay unfinished upon the bench beside some sheets of drawings, and I took one up for a better look at it. Quartz it seemed to be.

“Look here,” said the Medical Man, “are you perfectly serious? Or is this a trick …?”

For Wells’s first readers, technology had a special persuasive power. This vague machine put a claim on the readers’ belief in a way that magic never could. Magic might include clouts on the head, as in Connecticut Yankee, as well as the talismanic act of turning back the hands on a clock. The cartoon “Felix the Cat Trifles with Time” employs both devices: Old Father Time unwinds his clock past “Year of 1” and “Stone Age” and whacks poor Felix with a club.

Before that, in 1881, a newspaperman, Edward Page Mitchell, published “The Clock That Went Backward” anonymously in the New York Sun. Old Aunt Gertrude, spectral in her white nightgown and white nightcap, has a mysterious bond with her eight-foot-tall Dutch clock. It seems defunct—until one night, when she winds it up in the flickering light of a candle, the hands begin to turn backward, and she falls dead. This becomes the occasion for a philosophical disquisition by one Professor Van Stopp:

Well, and why should not a clock go backward? Why should not Time itself turn and retrace its course? … Viewed from the Absolute, the sequence by which future follows present and present follows past is purely arbitrary. Yesterday, today, tomorrow; there is no reason in the nature of things why the order should not be tomorrow, today, yesterday.