Time Travel: A History (10 page)

What does his framework mean for our understanding of the true nature of things? His biographer Jürgen Neffe sums up the situation judiciously. “Einstein provided no explanations for these phenomena,” he says. “No one knows what light and time really are. We are not told
what
something is. The special theory of relativity merely provides a new rule for measuring the world—a perfectly logical construct that surmounts earlier contradictions.”

—

HERMANN MINKOWSKI READ
Einstein’s 1905 paper on special relativity with special interest. He had been Einstein’s mathematics teacher in Zurich. He was forty-four years old and Einstein was twenty-nine. Minkowski saw that Einstein had knocked the concept of time “from its high seat,” had shown, indeed, that there is no
time,
but only
times.
But he thought that his former student had left the big job unfinished—had stopped short of stating the new truth about the nature of all reality. So Minkowski prepared a lecture. He delivered it at a scientific meeting in Cologne on September 21, 1908, and it is famous.

“Raum und Zeit”
was his title, “Space and Time,” and his mission was to declare both concepts null and void. “The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength,” he began grandly. “They are radical.
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.
”

Credit 4.1

He reminded his listeners that space is denoted by three orthogonal coordinates,
x, y, z,
for length, breadth, and thickness. Let
t
denote time. With a piece of chalk, he said, he could draw four axes on the blackboard: “the somewhat greater abstraction associated with the number 4 does not hurt the mathematician.” And so on. He was excited. This was “a new conception of space and time,” he declared; “the first of all laws of nature.” He called this conception the “principle of the absolute world.”

Four numbers,
x, y, z, t,
define a “world point.” Together, all the world points that trace an object’s existence from birth to death form a “world line.” And what shall we call the whole shebang?

The multiplicity of all thinkable
x, y, z, t
systems of values we will christen the
world.

Die Welt!
Good name. But we just call it spacetime now. (The continuum.) If we resist (“Because I know that time is always time / And place is always and only place,” said T. S. Eliot), we do so in vain.

It was a bit of misdirection for Minkowski to begin by saying his lecture was grounded in experimental physics. His true subject was the power of abstract mathematics to reshape our understanding of the universe. He was a geometer above all. The physicist and historian Peter Galison puts it this way: “Where Einstein manipulated clocks, rods, light beams, and trains, Minkowski played with grids, surfaces, curves, and projections.” He thought in terms of the most profound visual abstraction.

“Mere shadows,” Minkowski said. That was not mere poetry. He meant it almost literally. Our perceived reality is a projection, like the shadows projected by the fire in Plato’s cave. If the world—the absolute world—is a four-dimensional continuum, then all that we perceive at any instant is a slice of the whole. Our sense of time: an illusion. Nothing passes; nothing changes. The universe—the real universe, hidden from our blinkered sight—comprises the totality of these timeless, eternal world lines. “I would fain anticipate myself,” said Minkowski in Cologne, “by saying that in my opinion physical laws might find their most perfect expression as reciprocal relations between these world lines.” Three months later he was dead of a ruptured appendix.

Thus the idea of time as a fourth dimension crept forward. It did not happen all at once. In 1908
Scientific American
“simply explained” the fourth dimension as a hypothetical space analogous to the first three: “For passing into the fourth dimension, we should pass out of our present world.” The next year the magazine sponsored an essay contest on the topic “The Fourth Dimension,” and not one of the winners or runners-up considered it to be time—notwithstanding the German physicists and the English writer of fantastic fiction. The space-time continuum was radical indeed. Max Wien, an experimental physicist, described his initial reaction as “a slight brain-shiver—now space and time appear conglomerated together in a gray, miserable chaos.”
^*5
It offends common sense. “The texture of Space is not that of Time,” cries Vladimir Nabokov, “and the piebald four-dimensional sport bred by relativists is a quadruped with one leg replaced by the ghost of a leg.” If these critics sound Filbyish, even Einstein did not immediately embrace Minkowski’s vision:
“überflüssige Gelehrsamkeit,”
he called it—superfluous learnedness. But Einstein came around. When his friend Besso died in 1955, Einstein consoled his family with words that have been quoted many times:

Now he has departed from this strange world a little ahead of me. That means nothing. People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion.

Einstein died three weeks later.

—

FUNNY IRONY,
though.

A century after Einstein discovered that perfect simultaneity is a chimera, the technology of our interconnected world relies on simultaneity as never before. When telephone-network switches get out of sync, they drop calls. While no physicist “believes in” absolute time, humanity has established a collective official timescale, preached by a choir of atomic clocks maintained at a temperature near absolute zero in vaults at the United States Naval Observatory in Washington, the Bureau International des Poids et Mesures near Paris, and elsewhere. They bounce their networked light-speed signals to one another, make the necessary relativistic corrections, and thus the world sets its myriad clocks. Confusion about past and future cannot be tolerated.

To Newton this would make perfect sense. International atomic time has the effect of codifying the absolute time that he created, and for the same reason: it lets the equations work out and the trains run on time. A century
before
Einstein, this technical achievement in simultaneity would have been almost impossible to conceive. The very notion of simultaneity scarcely existed. It was a rare philosopher who considered the question of what time it might be in a faraway place. One could hardly even hope to know, said the doctor and philosopher Thomas Browne in 1646,

It being no ordinary or Almanack business, but a probleme Mathematical, to finde out the difference of hours in different places; nor do the wisest exactly satisfy themselves in all. For the hours of several places anticipate each other, according to their Longitudes; which are not exactly discovered of every place.

All time was local. “Standard time” had no use before the railroad came and could not be established before the telegraph. England began
synchronizing its clocks
(new expression) to railway time in the mid-nineteenth century, when telegraph signals went out from the new electromagnetic clock at the Royal Observatory in Greenwich and the Electric Time Company in London. Also to the newly coordinated clock towers and electric street clocks of Bern.
^*6
These were technologies on which the ideas of Einstein depended, and also the ideas of H. G. Wells.

So now, on a hilltop near the Potomac River, the United States maintains a Directorate of Time, a subdepartment of the navy and by law the country’s official timekeeper. Likewise in Paris is the BIPM, which also owns the international prototype of the kilogram. These are the keepers of
temps universel coordonné,
or coordinated universal time, or UTC—which I think we can admit is arrogantly named. Let’s just call it Earth time.

All the chronometric paraphernalia of modernity: scientific, and yet arbitrary. Railroads made time zones inevitable, and in hindsight we can see that time zones already entailed a sense of time travel. They were not organized all at once, by fiat. They had many beginnings. For example, on November 18, 1883, a Sunday, known afterward as “the Day of Two Noons,” James Hamblet, general superintendent of the Time Telegraph Company in New York City, reached out his hand and stopped the pendulum of the standard clock in the Western Union Telegraph Building. He waited for a signal and then restarted it. “His clock is adjusted to hundredth parts of a second,” reported the
New York Times,
“a space of time so infinitesimal as to be almost beyond human perception.” Around the city, tickers announced the new time and jewelers’ shops adjusted their clocks. The newspaper explained the new setup in science-fictional terms:

When the reader of The Times consults his paper at 8 o’clock this morning at his breakfast table it will be 9 o’clock in St. John, New-Brunswick, 7 o’clock in Chicago, or rather in St. Louis—for Chicago authorities have refused to adopt the standard time, perhaps because the Chicago meridian was not selected as the one on which all time must be based—6 o’clock in Denver, Col., and 5 o’clock in San Francisco. That is the whole story in a nut-shell.

Of course, that was nothing like the whole story. Arbitrary as they were, the railroads’ time zones did not please everyone, and a new oddity followed: Daylight Saving Time, as it was known in North America, or, as Europeans called it, Summer Time. Even now, after a century of experience, some people find this twice-yearly time jump disturbing, and even physically uncomfortable. (And philosophically unsettling. Where does the hour go?) Germany was the first to impose
Sommerzeit,
during World War I, hoping to save coal. Soon after, the United States adopted it, then repealed it, then reimposed it. In England, seeking evening light for hunting, King Edward VII had the clocks on the royal estate set to “Sandringham Time,” a half hour ahead of Greenwich. When the Nazis occupied France, they ordered all the clocks moved an hour forward, to Berlin time.

It was not just a matter of minutes and hours. The days and the years, too, confounded a world whose farthest parts were now in close communication. When, finally, would humanity agree on a uniform calendar? The new League of Nations took up the question after World War I. Its Committee on Intellectual Cooperation chose the philosopher Bergson as its president; another member, briefly, was Einstein. The League tried to impose the Gregorian calendar, itself the product of centuries of strife and revision, on nations less concerned with computing the proper dates of Easter feasts. The prospect of leaping forward or back in time created anxiety. Those nations did not fall in line. Bulgarians and Russians complained that their citizens could not be made suddenly to age by thirteen days, to surrender thirteen days of their lives in the name of globalization. Conversely, when France condescended to join Greenwich time, the Parisian astronomer Charles Nordmann said, “Some people may have consoled themselves with the reflection that to grow younger by 9 minutes and 21 seconds, on the authority of the law, was a pleasure worth having.”

Had time become a thing over which dictators and kings could exercise power? “The Problem of Summer Time” is the English title of a new sort of time-travel story, published in 1943 by a darkly satirical Parisian writer, Marcel Aymé. In French it is
“Le décret”
—The Decree—issued after scientists and philosophers discover how easy it is to advance the time an hour forward each summer and back again each winter. “Little by little,” says the narrator, “the realization spread that time was under man’s control.” Humans are time’s dynamic masters: they may hurry up or slow down to suit themselves. Anyway “the old, stately pace was over.”

There was much talk of relative time, physiological time, subjective time and even compressible time. It became obvious that the notion of time, as our ancestors had transmitted it down the millennia, was in fact absurd claptrap.

With time now seemingly at their command, the authorities see a way to escape the nightmare of a war that seemed endless. They decide to advance the years by seventeen: 1942 leaps forward to 1959. (In the same spirit, moviemakers in Hollywood began to tear pages from calendars and spin the hands of clocks so as to move time along for their viewers.) The decree makes the world and all its people seventeen years older. The war has come to an end. Some have died, others have been born, and everyone has some catching up to do. It’s all rather disorienting.

Aymé’s narrator travels from Paris by railroad into the countryside. A surprise awaits him there. Apparently the decree has not spread everywhere. A storm, some wine, a troubled sleep, and in a distant village he encounters active German soldiers, and, sure enough, the mirror now shows him the thirty-nine-year-old he was, not the fifty-six-year-old he had become. On the other hand, he still has his newly acquired memories of those seventeen years. This is disturbing—indeed, impossible. “To be from an era, I thought, is to behold the world and oneself in a certain way that belongs to that era.” Is he fated to relive the same life, burdened with memories of times to come?