Time Travel. James Gleick

witty. People of the nineteenth century sometimes asked, as people will, “What is time?” The question arises in many different contexts. Say you want to explain the Bible to children. The Educational Magazine, 1835:

      Ver. 1. In the beginning God created the heaven and the earth.

      What do you mean by the beginning? The beginning of time.—What is time? A measured portion of eternity.

      But everyone knows what time is. It was true then and it’s true now. Also no one knows what time is. Augustine stated this pseudoparadox in the fourth century and people have been quoting him, wittingly and unwittingly, ever since:

      What then is time? If no one asks me, I know. If I wish to explain it to one that asks, I know not.^fn2

      Isaac Newton said at the outset of the Principia that everyone knew what time was, but he proceeded to alter what everyone knew. Sean Carroll, a modern physicist, says (tongue in cheek), “Everybody knows what time is. It’s what you find out by looking at a clock.” He also says, “Time is the label we stick on different moments in the life of the world.” Physicists like this bumper-sticker game. John Archibald Wheeler is supposed to have said, “Time is nature’s way to keep everything from happening all at once,” but Woody Allen said that, too, and Wheeler admitted having found it scrawled in a Texas men’s room.^fn3

      Richard Feynman said, “Time is what happens when nothing else happens,” which he knew was a wisecrack. “Maybe it is just as well if we face the fact that time is one of the things we probably cannot define (in the dictionary sense), and just say that it is what we already know it to be: it is how long we wait.”

      When Augustine contemplated time, one thing he knew was that it was not space—“and yet, Lord, we perceive intervals of times, and compare them, and say some are shorter, and others longer.” We measure time, he said, though he had no clocks. “We measure times as they are passing, by perceiving them; but past, which now are not, or the future, which are not yet, who can measure?” You cannot measure what does not yet exist, Augustine felt, nor what has passed away.

      In many cultures—but not all—people speak of the past as being behind them, while the future lies ahead. They visualize it that way, too. “Forgetting what is behind and straining toward what is ahead, I press on,” says Paul. To imagine the future or the past as a “place” is already to engage in analogy. Are there “places” in time, as there are in space? To say so is to assert that time is like space. The past is a foreign country: they do things differently there. The future, too. If time is a fourth dimension, that is because it is like the first three: visualizable as a line; measurable in extent. Still, in other ways time is unlike space. The fourth dimension differs from the other three. They do things differently there.

      It seems natural to sense time as a spacelike thing. Accidents of language encourage that. We have only so many words; before and after have to do double duty as prepositions of space as well as time. “Time is a phantasm of motion,” said Thomas Hobbes in 1655. To count time, to compute time, “we make use of some motion or other, as of the sun, of a clock, of the sand in an hourglass.” Newton considered time to be absolutely different from space—after all, space remains always immovable, whereas time flows equably without regard to anything external, and by another name is called duration—but his mathematics created an inevitable analogy between time and space. You could plot them as axes on a graph. By the nineteenth century German philosophers in particular were groping toward some amalgam of time and space. Arthur Schopenhauer wrote in 1813, “In mere Time, all things follow one another, and in mere Space all things are side by side; it is accordingly only by the combination of Time and Space that the representation of coexistence arises.” Time as a dimension begins to emerge from the mists. Mathematicians could see it. Technology helped in another way. Time became vivid, concrete, and spatial to anyone who saw the railroad smashing across distances on a coordinated schedule—coordinated by the electric telegraph, which was pinning time to the mat. “It may seem strange to ‘fuse’ time and space,” explained the Dublin Review, but look—here is a “quite ordinary” space-time diagram:

      So Wells’s Time Traveller can speak with conviction: “Scientific people know very well that Time is only a kind of Space. Here is a popular scientific diagram, a weather record. This line I trace with my finger shows the movement of the barometer … Surely the mercury did not trace this line in any of the dimensions of Space … but certainly it traced such a line, and that line, therefore, we must conclude was along the Time-Dimension.”

      In the new century everything felt new; physicists and philosophers gazed upon Time, so often capitalized, with new eyes. Twenty-five years after The Time Machine the “new realist” philosopher Samuel Alexander put it this way:

      If I were asked to name the most characteristic feature of the thought of the last twenty-five years I should answer: the discovery of Time. I do not mean that we have waited till to-day to become familiar with Time. I mean that we have only just begun in our speculation to take Time seriously and to realize that in some way or other Time is an essential ingredient in the constitution of things.

      What is time? Time machines may help us understand.

      WELLS WAS NOT READING Schopenhauer, and philosophical introspection was not his style. His ideas about time were informed by Lyell and Darwin, who read the buried strata that frame the ages of the earth and the ages of life. He studied zoology and geology as a scholarship student at the Normal School of Science and Royal School of Mines, and these subjects encouraged him to view the world’s history as if from a great height—its lost epochs, a panorama unfolding, “the small-scale horse-foot, hand-industry civilizations that culminated in the seventeenth and eighteenth centuries, by the change of pace and scale due to mechanical invention.” Geological time, so vastly extended, disrupted the earlier sense of historical time, in which the world was plausibly considered to be six thousand years old. The scales were so different; human history was dwarfed.

      “O earth, what changes has thou seen!” wrote Tennyson. “The hills are shadows, and they flow/From form to form, and nothing stands.” Lately, too, there was a science called archeology—grave robbers and treasure hunters in the service of knowledge. Archeologists, digging, were exposing buried history. At Nineveh, at Pompeii, at Troy, vaults were opened; past civilizations appeared, frozen in stone, but lifelike. Archeological digs exposed diagrams ready-made, with time a visible dimension.

      Less obviously, people could see layers of time all around. Travelers riding in steam-driven railroad trains looked out their windows onto a landscape where oxen plowed the fields as they had done in medieval times, horses still hauled and harrowed, yet telegraph wires split the sky. This caused a new kind of confusion or dissociation. Call it temporal dissonance.

      Above all, modern time was irreversible, inexorable, and unrepeatable. Progress marched onward—a good thing, if you were a technological optimist. Cyclical time, crosswinds of time, eternal return, the wheel of life: these were romantic notions now, for poets and nostalgic philosophers.

      The Normal School, later renamed the Royal College of Science, was a lucky place for H. G., the youngest son of a shopkeeper and a former housemaid. As a teenager he had spent three unhappy years serving as a draper’s apprentice. Now, in the college’s new five-story elevator-equipped building, he studied elementary biology with (“under the shadow of”) Thomas H. Huxley, the famous Darwinian—a mighty intellectual liberator, Wells thought, bravely battling the priests and know nothings, establishing the facts of evolution from painstakingly assembled fossil evidence and embryological material, filling up the “great jig-saw puzzle,” the confirmation of the tree of life. It was the most educational year of his life: “a grammar of form and a criticism of fact.” He had less use for the course in physics, of which he later remembered little but his own ineptitude in trying to contrive a barometer from some bits of brass and wood and glass tubing.