Time Travel. A History

*7 Ralph Milne Farley, “The Man Who Met Himself” (1935). Of course the man is in a ten-year loop, too. He uses the time to make money in the stock market.

*8 Rudy Rucker, a mathematician and, later, an author of science fiction.

*9 The self-description he ultimately settled on: “filmmaker, photographer, traveler.”

TWELVE

What Is Time?

Why is it so difficult—so degradingly difficult—to bring the notion of Time into mental focus and keep it there for inspection? What an effort, what fumbling, what irritating fatigue!

—Vladimir Nabokov (1969)

PEOPLE KEEP ASKING what time is, as if the right combination of words could slip the lock and let in the light. We want a fortune-cookie definition, a perfect epigram. Time is “the landscape of experience,” says Daniel Boorstin. “Time is but memory in the making,” says Nabokov. “Time is what happens when nothing else does”—Dick Feynman. “Time is nature’s way to keep everything from happening all at once,” says Johnny Wheeler or Woody Allen. Martin Heidegger says, “There is no time.”^*1

What is time? Time is a word. The word refers to something, or some things, but surprisingly often the conversation goes off track when people forget whether they’re arguing about the word or the thing(s). Five hundred years of dictionaries have created the assumption that every word must have a definition, so what is time? “A nonspatial continuum in which events occur in apparently irreversible succession from the past through the present to the future” (American Heritage Dictionary of the English Language, fifth edition). A committee of lexicographers labored over those twenty words and must have debated almost every one. Nonspatial? That word is not to be found in this very dictionary, but all right, time is not space. Continuum? Presumably time is a continuum—but is that known for sure? “Apparently irreversible” seems a hedge. You sense they’re trying to tell us something they hope we already know. The challenge is not so much to inform us as to offer some discipline and care.

Other authorities offer entirely different constructions. Not one of them is wrong. What is time? “The general term for the experience of duration,” according to the Encyclopaedia Britannica (many editions). The very first English dictionary, Robert Cawdrey’s in 1604, avoided the problem and skipped right from thwite (“shave”) to timerous (“fearefull, abashed”). Samuel Johnson said “the measure of duration.” (And duration? “Continuance, length of time.”) A 1960 children’s book trimmed the definition to a single word: Time Is When.^*2

The people who compose definitions for dictionaries try to avoid the circularity that comes when they use the very word they are defining. With time it’s unavoidable. The lexicographers of the OED throw up their hands. They divide “time” (only the noun, not the interjection^*3 or the obscure conjunction) into thirty-five distinct senses and almost a hundred subsenses, including: a point in time; an extent of time; a specific period of time; time available…; the amount of time taken up by something; and time viewed as a medium through which travel into the past or future is hypothesized or imagined to be possible. (“Cf. time travel.”) They are covering all the bases. Perhaps their best effort is sense number ten: “The fundamental quantity of which periods or intervals of existence are conceived as consisting, and which is used to quantify their duration.” Even that definition merely postpones the circularity. Duration, period, and interval are defined in terms of time. The lexicographers know very well what time is, until they try to define it.

Like all words, time has boundaries, by which I don’t mean hard and impenetrable shells but porous edges. It maps weirdly between languages. A Londoner might say, “He did it fifty times, at the very least,” while in Paris, where the word for time is temps, fifty times is cinquante fois. Meanwhile, when the weather is good, the Parisian says, C’est beau temps. A New Yorker thinks the time and the weather are different things.^*4 And that is just the beginning. Many languages use a separate word to ask “What is the time?” as opposed to “What is time?”