by James Gleick
ALSO BY JAMES GLEICK
Chaos: Making a New Science
Genius: The Life and Science of Richard Feynman
Faster: The Acceleration of Just About Everything
What Just Happened: A Chronicle from the Information Frontier
Isaac Newton
The Information: A History, a Theory, a Flood
Copyright © 2016 by James Gleick
All rights reserved. Published in the United States by Pantheon Books, a division of Penguin Random House LLC, New York, and distributed in Canada by Random House of Canada, a division of Penguin Random House Canada Limited, Toronto.
Pantheon Books and colophon are registered trademarks of Penguin Random House LLC.
Grateful acknowledgment is made to Houghton Mifflin Harcourt Publishing Company for permission to reprint excerpts from “Burnt Norton” and “The Dry Salvages” from Four Quartets by T. S. Eliot, copyright © 1936 by Houghton Mifflin Harcourt Publishing Company, renewed 1964 by T. S. Eliot, and renewed 1969 by Esme Valerie Eliot. Reprinted by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Library of Congress Cataloging-in-Publication Data
Name: Gleick, James.
Title: Time travel / James Gleick.
Description: New York : Pantheon Books [2016]
Identifiers: LCCN 2016002323. ISBN 9780307908797 (hardcover). ISBN 9780307908803 (ebook). ISBN 9780375715204 (open market).
Subjects: LCSH: Space and time—Popular works. Time travel—Popular works.
Classification: LCC QC173.59.S65 G54 2016. DDC 530.11—dc23. LC record available at lccn.loc.gov/2016002323
Ebook ISBN 9780307908803
www.pantheonbooks.com
Jacket by Peter Mendelsund
v4.1_r1
ep
To Beth, Donen,
and Harry
Your now is not my now; and again, your then is not my then; but my now may be your then, and vice versa. Whose head is competent to these things?
—Charles Lamb (1817)
The fact that we occupy an ever larger place in Time is something that everybody feels.
—Marcel Proust (1927?)
And tomorrow
Comes. It’s a world. It’s a way.
—W. H. Auden (1936)
Contents
Cover
Also by James Gleick
Title Page
Copyright
Dedication
Epigraph
Chapter One: Machine
Chapter Two: Fin de Siècle
Chapter Three: Philosophers and Pulps
Chapter Four: Ancient Light
Chapter Five: By Your Bootstraps
Chapter Six: Arrow of Time
Chapter Seven: A River, a Path, a Maze
Chapter Eight: Eternity
Chapter Nine: Buried Time
Chapter Ten: Backward
Chapter Eleven: The Paradoxes
Chapter Twelve: What Is Time?
Chapter Thirteen: Our Only Boat
Chapter Fourteen: Presently
Acknowledgments
Sources and Further Reading
Illustration Credits
About the Author
ONE
* * *
Machine
Being young, I was skeptical of the future, and saw it as a matter of potential only, a state of things that might or might not arise and probably never would.
—John Banville (2012)
A MAN STANDS AT the end of a drafty corridor, a.k.a. the nineteenth century, and in the flickering light of an oil lamp examines a machine made of nickel and ivory, with brass rails and quartz rods—a squat, ugly contraption, somehow out of focus, not easy for the poor reader to visualize, despite the listing of parts and materials. Our hero fiddles with some screws, adds a drop of oil, and plants himself on the saddle. He grasps a lever with both hands. He is going on a journey. And by the way so are we. When he throws that lever, time breaks from its moorings.
The man is nondescript, almost devoid of features—“grey eyes” and a “pale face” and not much else. He lacks even a name. He is just the Time Traveller: “for so it will be convenient to speak of him.” Time and travel: no one had thought to join those words before now. And that machine? With its saddle and bars, it’s a fantasticated bicycle. The whole thing is the invention of a young enthusiast named Wells, who goes by his initials, H. G., because he thinks that sounds more serious than Herbert. His family calls him Bertie. He is trying to be a writer. He is a thoroughly modern man, a believer in socialism, free love, and bicycles.*1 A proud member of the Cyclists’ Touring Club, he rides up and down the Thames valley on a forty-pounder with tubular frame and pneumatic tires, savoring the thrill of riding his machine: “A memory of motion lingers in the muscles of your legs, and round and round they seem to go.” At some point he sees a printed advertisement for a contraption called Hacker’s Home Bicycle: a stationary stand with rubber wheels to let a person pedal for exercise without going anywhere. Anywhere through space, that is. The wheels go round and time goes by.
The turn of the twentieth century loomed—a calendar date with apocalyptic resonance. Albert Einstein was a boy at gymnasium in Munich. Not till 1908 would the Polish-German mathematician Hermann Minkowski announce his radical idea: “Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.” H. G. Wells was there first, but unlike Minkowski, Wells was not trying to explain the universe. He was just trying to gin up a plausible-sounding plot device for a piece of fantastic storytelling.
Nowadays we voyage through time so easily and so well, in our dreams and in our art. Time travel feels like an ancient tradition, rooted in old mythologies, old as gods and dragons. It isn’t. Though the ancients imagined immortality and rebirth and lands of the dead time machines were beyond their ken. Time travel is a fantasy of the modern era. When Wells in his lamp-lit room imagined a time machine, he also invented a new mode of thought.
Why not before? And why now?
—
THE TIME TRAVELLER BEGINS with a science lesson. Or is it just flummery? He gathers his friends around the drawing-room fire to explain that everything they know about time is wrong. They are stock characters from central casting: the Medical Man, the Psychologist, the Editor, the Journalist, the Silent Man, the Very Young Man, and the Provincial Mayor, plus everyone’s favorite straight man, “an argumentative person with red hair” named Filby.
“You must follow me carefully,” the Time Traveller instructs these stick figures. “I shall have to controvert one or two ideas that are almost universally accepted. The geometry, for instance, that they taught you at school is founded on a misconception.” School geometry—Euclid’s geometry—had three dimensions, the ones we can see: length, width, and height.
Naturally they are dubious. The Time Traveller proceeds Socratically. He batters them with logic. They put up feeble resistance.
“You know of course that a mathematical line, a line of thickness nil, has no real existence. They taught you that? Neither has a mathematical plane. These things are mere abstractions.”
“That is all right,” said the Psychologist.
“Nor, having only length, breadth, and thickness, can a cube have a real existence.”
“There I object,” said Filby. “Of course a solid body may exist. All real things—”
“So most people think. But wait a moment. Can an instantaneous cube exist?”
“Don’t follow you,” said Filby [the poor sap].
“Can a cube that does not last for any time at all, have a real existence?”
Filby became pensive. “Clearly,” the Time Travelle
r proceeded, “any real body must have extension in four directions: it must have Length, Breadth, Thickness, and—Duration.”
Aha! The fourth dimension. A few clever Continental mathematicians were already talking as though Euclid’s three dimensions were not the be-all and end-all. There was August Möbius, whose famous “strip” was a two-dimensional surface making a twist through the third dimension, and Felix Klein, whose loopy “bottle” implied a fourth; there were Gauss and Riemann and Lobachevsky, all thinking, as it were, outside the box. For geometers the fourth dimension was an unknown direction at right angles to all our known directions. Can anyone visualize that? What direction is it? Even in the seventeenth century, the English mathematician John Wallis, recognizing the algebraic possibility of higher dimensions, called them “a Monster in Nature, less possible than a Chimaera or Centaure.” More and more, though, mathematics found use for concepts that lacked physical meaning. They could play their parts in an abstract world without necessarily describing features of reality.
Under the influence of these geometers, a schoolmaster named Edwin Abbott Abbott published his whimsical little novel Flatland: A Romance of Many Dimensions in 1884, in which two-dimensional creatures try to wrap their minds around the possibility of a third; and in 1888 Charles Howard Hinton, a son-in-law of the logician George Boole, invented the word tesseract for the four-dimensional analogue of the cube. The four-dimensional space this object encloses he called hypervolume. He populated it with hypercones, hyperpyramids, and hyperspheres. Hinton titled his book, not very modestly, A New Era of Thought. He suggested that this mysterious, not-quite-visible fourth dimension might provide an answer to the mystery of consciousness. “We must be really four-dimensional creatures, or we could not think about four dimensions,” he reasoned. To make mental models of the world and of ourselves, we must have special brain molecules: “It may be that these brain molecules have the power of four-dimensional movement, and that they can go through four-dimensional movements and form four-dimensional structures.”
For a while in Victorian England the fourth dimension served as a catchall, a hideaway for the mysterious, the unseen, the spiritual—anything that seemed to be lurking just out of sight. Heaven might be in the fourth dimension; after all, astronomers with their telescopes were not finding it overhead. The fourth dimension was a secret compartment for fantasists and occultists. “We are on the eve of the Fourth Dimension; that is what it is!” declared William T. Stead, a muckraking journalist who had been editor of the Pall Mall Gazette, in 1893. He explained that this could be expressed by mathematical formulas and could be imagined (“if you have a vivid imagination”) but could not actually be seen—anyway not “by mortal man.” It was a place “of which we catch glimpses now and then in those phenomena which are entirely unaccountable for by any law of three-dimensional space.” For example, clairvoyance. Also telepathy. He submitted his report to the Psychical Research Society for their further investigation. Nineteen years later he embarked on the Titanic and drowned at sea.
By comparison Wells is so sober, so simple. No mysticism for him—the fourth dimension is not a ghost world. It is not heaven, nor is it hell. It is time.
What is time? Time is nothing but one more direction, orthogonal to the rest. As simple as that. It’s just that no one has been able to see it till now—till the Time Traveller. “Through a natural infirmity of the flesh…we incline to overlook this fact,” he coolly explains. “There is no difference between Time and any of the three dimensions of Space except that our consciousness moves along it.”
In surprisingly short order this notion would become part of the orthodoxy of theoretical physics.
—
WHERE DID THE IDEA come from? There was something in the air. Much later Wells tried to remember:
In the universe in which my brain was living in 1879, there was no nonsense about time being space or anything of that sort. There were three dimensions, up and down, fore and aft and right and left, and I never heard of a fourth dimension until 1884 or thereabout. Then I thought it was a witticism.
Very 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.*2
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.*3
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 coordi
nated 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:
Credit 1.1
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.