Time Travel. A History

The revelation is that we can share no now—no universal present moment. But was that altogether a surprise? Before Einstein was born, John Henry Newman, poet and priest, wrote that “time is not a common property; / But what is long is short, and swift is slow/And near is distant, as received and grasped / By this mind and by that, / And every one is standard of his own chronology.” For him it was intuitive.

“Your now is not my now,” wrote Charles Lamb in England to his friend Barron Field in Australia, the far side of the earth, in 1817, “your then is not my then; but my now may be your then, and vice versa. Whose head is competent to these things?”

Nowadays we are all competent to these things. We have time zones. We can contemplate the International Date Line, where an imaginary boundary divides Tuesday from Wednesday.^*3 Even when we suffer from jet lag—the quintessential disease of time travel—we are shrewd in our suffering and can nod wisely at William Gibson’s account of “soul delay”:

Her mortal soul is leagues behind her, being reeled in on some ghostly umbilical down the vanished wake of the plane that brought her here, hundreds of thousands of feet above the Atlantic. Souls can’t move that quickly, and are left behind, and must be awaited, upon arrival, like lost luggage.

We know that the light of the stars is ancient light, that distant galaxies reveal themselves to us only as they once were, not as they now are. As John Banville reminds us in his novel of that name, ancient light is all we have: “Even here, at this table, the light that is the image of my eyes takes time, a tiny time, infinitesimal, yet time, to reach your eyes, and so it is that everywhere we look, everywhere, we are looking into the past.”^*4 (Can we peer into the future as well? That clever time traveler Joyce Carol Oates says via Twitter, “As minutes are required for the sun’s light to reach us, we are living always in a sunlit past. Just the reverse, reading bound galleys.”)

When everything reaching our senses comes from the past, when no observer lives in the now of any other observer, the distinction between past and future begins to decay. Events in our universe can be connected, such that one is the cause of the other, but, alternatively, they can be close enough in time and far enough apart that they cannot be connected and no one can even say which came first. (Outside the light cone, says the physicist.) We are more isolated, then, than we may have imagined, alone in our corners of spacetime. You know how fortune-tellers pretend to know the future? It turns out, said Richard Feynman, that no fortune-teller can even know the present.

Einstein’s powerful ideas spread in the public press as rapidly as in the physics journals and disrupted the placid course of philosophy. The philosophers were surprised and outgunned. Bergson and Einstein clashed publicly in Paris and privately by post and seemed to be speaking different languages: one scientific, measured, practical; the other psychological, flowing, untrustworthy. “ ‘The time of the universe’ discovered by Einstein and ‘the time of our lives’ associated with Bergson spiraled down dangerously conflicting paths, splitting the century into two cultures,” notes the science historian Jimena Canales. We are Einsteinian when we search for simplicity and truth, Bergsonian when we embrace uncertainty and flux. Bergson continued to place human consciousness at the center of time, while Einstein saw no place for spirit in a science that relied on clocks and light. “Time is for me that which is most real and necessary,” wrote Bergson; “it is the necessary condition of action. What am I saying? It is action itself.” Before an audience of intellectuals at the Société Française de Philosophie in April 1922, Einstein was adamant: “The time of the philosophers does not exist.” Einstein, it seems, prevailed.

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.