Time Travel

by James Gleick

  Wells himself did not approve. He assured Dunne that “prevision” was claptrap and that time traveling was make-believe—“that I [Dunne] have taken something which he never intended to be treated seriously…and have brooded too much upon it.” But Eliot and other literary searchers absorbed Dunne’s provocative ideas and imagery, including the prospect of a kind of immortality. The future is a faded song, Eliot writes. The way up is the way down (another fragment from Heraclitus), and the way forward is the way back. He has sensed that all time is eternally present, but he is not sure.*3 If all time is eternally present / All time is unredeemable.

  The Universe Rigid? Eliot in Four Quartets is not trying to persuade us of a system of the world. He suffers paradox and self-doubt. “I can only say, there we have been: but I cannot say where. / And I cannot say, how long, for that is to place it in time.” He speaks through masks. Not only are words slippery; the problem with using words to describe time is that words themselves are in time. A string of words has a beginning, a middle, and an end. “Words move, music moves / Only in time.” Is eternity a place of motion or of stillness? Movement or pattern? Can these coexist? At the still point of the turning world? When he says a Chinese jar moves perpetually in its stillness, you know that’s a metonym. What moves perpetually in its stillness is a poem.*4

  You shall not think “the past is finished” or “the future is before us.” Time does not belong to us; we cannot grasp it or define it. We can barely count it. The tolling bell, Eliot tells us,

  Measures time not our time, run by the unhurried

  Ground swell, a time

  Older than the time of chronometers, older

  Than time counted by anxious worried women

  Lying awake, calculating the future,

  Trying to unweave, unwind, unravel

  And piece together the past and the future,

  Between midnight and dawn, when the past is all deception,

  The future futureless.

  —

  WHEN BORGES, the philosopher poet, wrote that time is a river, he meant approximately the opposite. Time is not a river, nor is it a tiger, nor a fire. Borges, the critic, used a bit less paradox, a bit less misdirection. His language regarding time is apparently plain. In 1940 he, too, wrote about Dunne and his Experiment with Time, declaring it absurd, in a mild way. Part of Dunne’s argument was a reflection on consciousness—how it cannot be contemplated without falling into recursive loops (“a conscious subject is conscious not only of what it observes, but of a subject A that also observes and therefore, of another subject B that is conscious of A, and…” on and on). He was onto something important, recursion as an essential feature of consciousness, but then he concluded that “these innumerable intimate observers do not fit into the three dimensions of space, but they do in the no less numerous dimensions of time.” Borges knew this was nonsense, and it was his kind of nonsense. He saw something in it, a way to think about how the perception of time must be built on memory: “successive (or imaginary) states of the initial subject.” He recalled an observation made by Gottfried Wilhelm Leibniz: “If the spirit had to reflect on each thought, the mere perception of a sensation would cause it to think of the sensation and then to think of the thought and then of the thought of the thought, and so to infinity.” We create memories or our memories create themselves. Consulting a memory converts it into a memory of a memory. The memories of memories, the thoughts of thoughts, blend into one another until we cannot tease them apart. Memory is recursive and self-referential. Mirrors. Mazes.*5

  Dunne’s precognitive dreams and involuted logic led him to a belief in a preexisting future, an eternity within human reach. Borges said Dunne was making the mistake “those absentminded poets” make when they start to believe their own metaphors. By absentminded poets he seemed to mean physicists. By 1940 the new physics took the fourth dimension and the space-time continuum as real, but Borges emphatically did not:

  Dunne is an illustrious victim of that bad intellectual habit—denounced by Bergson—of conceiving time as a fourth dimension of space. He postulates that the future toward which we must move already exists (also conceived in spatial form, in the form of a line or a river).*6

  Borges had more to say than most about the problem of time in the twentieth century. For him paradox was not a problem but a strategy. He believed in time—its reality, its centrality—yet he titled his crucial essay “A New Refutation of Time.” Of eternity he was not so fond. In another essay, “A History of Eternity,” he declared: “For us, time is a jarring, urgent problem, perhaps the most vital problem of metaphysics, while eternity is a game or a spent hope.” Everyone “knows” (said Borges) that eternity is the archetype and our time merely its fleeting image. He proposed the opposite: Time comes first; eternity is created in our minds. Time is the substance, eternity the effigy. Contrary to Plato—contrary to the Church—eternity is “more impoverished than the world.” If you are a scientist, you may substitute infinity. That is your creation, after all.

  As for his new refutation of time, its essence is an argument he has “glimpsed” or “foreseen” and in which he himself does not believe. Or does he? It comes to him in the night. In the Proustian hours. What is time when you awaken, between dreams, register the rustling sounds, the shadowy walls—or, let’s say you’re Huckleberry Finn, rafting down the river…

  Negligently he opens his eye: he sees an indefinite number of stars, a nebulous line of trees. Then he sinks into a sleep without memories, as into dark waters.

  Borges notes that this is “a literary, not a historical” case. The doubting reader is invited to substitute a personal memory. Think of an incident in your past. When is that memory? Not at any time—not at any precise time. It is an instant on its own, suspended, apart from any supposed space-time continuum. Spacetime? “I tend to be always thinking of time, not of space,” Borges writes. “When I hear the words ‘time’ and ‘space’ used together, I feel as Nietzsche felt when he heard people talking about Goethe and Schiller—a kind of blasphemy.”

  He denies simultaneity, just as Einstein did, only Borges does not care about the signal velocity (light speed) because our natural state is alone and autonomous, our signals are fewer and less reliable than the physicist’s.

  The lover who thinks, “While I was so happy, thinking about the faithfulness of my beloved, she was busy deceiving me,” is deceiving himself. If every state in which we live is absolute, that happiness was not concurrent with that betrayal.

  The lover’s knowledge cannot modify the past, though it can modify the recollection. Having dispensed with simultaneity, Borges also denies succession. The continuity of time—the whole of time—another illusion. Furthermore, this illusion, or this problem, the never-ending effort to assemble a whole from a succession of instants, is also the problem of identity. Are you the same person you used to be? How would you know? Events stand alone; the totality of all events is an idealization as false as the sum of all the horses: “The universe, the sum total of all events, is no less ideal than the sum of all the horses—one, many, none?—Shakespeare dreamed between 1592 and 1594.” Oh, Marquis de Laplace.

  We have a tendency to take our words too seriously, which happens (paradoxically) when we are unconscious of them. Language offers a woefully meager set of choices for expressing what we need to express. Consider this sentence: “I haven’t seen you for a [?] time.” Must the missing word be long?*7 Then time is like a line or a distance—a measurable space. The language forces this upon us. Who was the first person to say that time “passes” or time “flows”? We are seldom conscious of the effect of language on our choice of metaphors, the effect of our metaphors on our sense of reality. Usually we give the words no thought at all. When we do, we may well wonder what we’re really saying. “I’m terrified of the thought of time passing (or whatever is meant by that phrase) whether I ‘do’ anything or not,” Philip Larkin wrote to his lover Monica Jones. The words lead
us in a certain direction.

  In English and most Western languages, the future lies ahead. In front of us. Forward. The past is behind us, and when we are running late we say we have fallen behind. Yet this forward-backward orientation is neither obvious nor universal. Even in English, it seems we can’t agree on what it means to move a meeting back one day. Some people are certain that back means earlier. Others are equally certain that it means later. On Tuesday, Wednesday lies before us, though Tuesday is before Wednesday. Other cultures have different geometries. Aymara speakers, in the Andes, point forward (where they can see) when talking about the past and gesture behind their backs when talking about the future. In other languages, too, yesterday is the day ahead and tomorrow is the day behind. The cognitive scientist Lera Boroditsky, a student of spatiotemporal metaphors and conceptual schemas, notes that some Australian aboriginal communities orient themselves by cardinal direction (north, south, east, west) rather than relative direction (left, right) and think of time as running east to west. (They have a strongly developed sense of direction, compared to more urban and indoor cultures.) Mandarin speakers often use vertical metaphors for time: 上 (shàng) means both above and earlier; 下 (xià) means below and next. The up month is the one that just ended. The down month is on its way.

  Or are we on our way? Boroditsky and others speak in terms of “ego-moving” versus “time-moving” metaphors. One person may feel the deadline approaching. Another may feel herself approaching the deadline. These may be the same person. You may swim onward, or the river may bear you.

  If time is a river, are we standing on the bank or bobbing along? “To say time passes more quickly, or that time flows, is to imagine something flowing,” wrote Wittgenstein.

  We then extend the simile and talk about the direction of time. When people talk of the direction of time, precisely the analogy of a river is before them. Of course a river can change its direction of flow, but one has a feeling of giddiness when one talks of time being reversed.

  That is the giddiness of the time traveler—like looking at an Escher staircase. Time passes. “The hours pass slowly.” “The hours pass quickly.” And without contradicting ourselves, we pass the time. We say these words, and we understand them perfectly.

  Time is not a river. Where does that leave time travel?

  —

  A MAN LIES supine on an iron cot in a locked room, pondering his own imminent death. Through the window he can see roofs and the sun, shaded by clouds. He is aware of the time: it is a “six o’clock sun.” His name may or may not be Yu Tsun. We gather that he is a German spy. He is in possession of the Secret. The Secret is a single word, a name, “the exact location of the British artillery park on the River Ancre.” But he has been discovered and marked for assassination. He turns out to be something of a philosopher.

  It seemed incredible to me that that day without premonitions or symbols should be the one of my inexorable death….Then I reflected that everything happens to a man precisely, precisely now. Centuries of centuries and only in the present do things happen; countless men in the air, on the face of the earth and the sea, and all that really is happening is happening to me.

  This is a fiction by Borges, “El jardín de senderos que se bifurcan,” the title story of his first collection—eight stories, sixty pages—published in 1941 by the modernist journal Sur in Buenos Aires. Borges, who read The Time Machine with excitement when he was young, had published some poetry and some criticism. He was a prolific translator from English, French, and German, including Poe, Kafka, Whitman, and Woolf. To support himself he worked as an assistant at a small, down-at-the-heels branch library, cataloguing and cleaning the books.

  Seven years later, “The Garden of Forking Paths” became Borges’s first story to appear in English translation. His American publisher was not a literary establishment or journal but Ellery Queen’s Mystery Magazine, August 1948. He did appreciate mystery. Now his reputation is large, but he did not gain much fame in English-speaking countries until the sixties, when he shared the first Prix International with Samuel Beckett. By then he was an old man, and blind.

  Ellery Queen (joint pseudonym for two cousins from Brooklyn) was happy to publish what could barely be called a detective story. It has no detective, but it does have a struggle among spies, a pursuit, a revolver chambering a single bullet, a confrontation, and a murder. There is not just a mystery but a philosophical mystery—so we are told. Yu Tsun is informed, “Philosophic controversy usurps a good part of the novel.” To what does the controversy pertain?

  I know that of all problems, none disturbed him so much as the abysmal problem of time. Now then, the latter is the only problem that does not figure in the pages of the Garden…

  The Garden of Forking Paths is an enormous riddle, or parable, whose theme is time; this recondite cause prohibits its mention.

  The story folds in upon itself: The Garden of Forking Paths is a book inside a book. (And now inside a pulp magazine.) The Garden is a meandering novel by “the oblique Ts’ui Pên.” It is a book that is also a maze. It is a set of chaotic manuscripts, “an indeterminate heap of contradictory drafts.” It is a labyrinth of symbols. It is a labyrinth of time. It is infinite—but how can a book, or a maze, be infinite? The book says, “I leave to the various futures (not to all) my garden of forking paths.”

  The paths fork in time, not in space.

  The Garden of Forking Paths is an incomplete, but not false, image of the universe as Ts’ui Pên conceived it. In contrast to Newton and Schopenhauer, your ancestor did not believe in a uniform, absolute time. He believed in an infinite series of times, in a growing, dizzying net of divergent, convergent and parallel times. This network of times which approached one another, forked, broke off, or were unaware of one another for centuries, embraces all possibilities of time.

  In this, as in so many things, Borges seemed to be peering over the horizon.*8 Later the literature of time travel expanded to encompass alternative histories, parallel universes, and branching time lines. A parallel adventure was under way in physics. Having drilled far down inside the atom, to a place where particles are inconceivably small and behave sometimes like particles and sometimes like waves, physicists encountered what appears to be an inescapable randomness at the heart of things. They were continuing the project of computing future states from specified initial conditions at time t = 0. Only now they were using wave functions. They were solving the Schrödinger equation. Calculations of wave functions via the Schrödinger equation produce not specific results but probability distributions. You may remember Schrödinger’s cat: either alive or dead, or neither alive nor dead, or, if one prefers (it’s something of a matter of taste), simultaneously alive and dead. Its fate is a probability distribution.

  When Borges was forty years old and writing “The Garden of Forking Paths,” a boy named Hugh Everett III was growing up in Washington, D.C., where he read voraciously in science fiction—Astounding Science Fiction and other magazines. Fifteen years later he was at Princeton, a graduate student in physics, working with a new thesis advisor: that same John Archibald Wheeler, who must continually reappear, Zelig-like, in the history of time travel. Now it is 1955. Everett is uncomfortable with the idea that simply making a measurement must alter the destiny of a physical system. He makes note of a talk at Princeton in which Einstein says he “could not believe that a mouse could bring about drastic changes in the universe simply by looking at it.”*9 He is also hearing all kinds of dissatisfaction with the various interpretations of quantum theory. Niels Bohr’s, he feels, is “overcautious.” It works, but it doesn’t answer the hard questions. “We do not believe that the primary purpose of theoretical physics is to construct ‘safe’ theories.”

  So what if, he asks—encouraged by Wheeler, who is open as always to the weird and paradoxical—what if every measurement is actually a branching? If a quantum state can be either A or B, then neither possibility is privileged: now there are two copies of th
e universe, each with its own observers. The world really is a garden of forking paths. Rather than one universe, we have an ensemble of many universes. The cat is definitely alive, in one universe. In another, the cat is dead. “From the viewpoint of the theory,” he writes, “all elements of a superposition (all ‘branches’) are ‘actual,’ none any more ‘real’ than the rest.” Protective quotation marks run rampant. For Everett, the word real is thin ice atop a dark pond:

  When one is using a theory, one naturally pretends that the constructs of the theory are “real” or “exist.” If the theory is highly successful (i.e. correctly predicts the sense perceptions of the user of the theory) then the confidence in the theory is built up and its constructs tend to be identified with “elements of the real physical world.” This is however a purely psychological matter.

  Nonetheless, Everett had a theory, and the theory made a claim: everything that can happen does happen, in one universe or another. New universes are created on demand, as it were. When a radioactive particle may or may not decay, the Geiger counter may or may not register a click, the universe forks again. His dissertation itself followed a difficult path. It exists in several versions. One draft went to Copenhagen, where Bohr did not like it at all. Another, shortened and revised with help from Wheeler, became a paper that could be published in Reviews of Modern Physics—despite the obvious objections. “Some correspondents,” Everett wrote in a postscript, complained that “our experience testifies” that there is no branching, because we only have one reality. “The argument fails when it is shown that the theory itself predicts that our experience will be what it in fact is,” he said—namely, that in our own little universe we remain unaware of any branching. When Copernicus theorized that the earth moves, critics objected that we feel no such motion, and they were wrong for precisely the same reason.