From Eternity to Here (5 page)
But when we examine carefully the notion that time itself somehow “flows,” we hit a snag. The flow of the river was a change with time—but what is it supposed to mean to say that time changes with time? A literal flow is a change of location over time—but time doesn’t have a “location.” So what is it supposed to be changing with respect to?
Think of it this way: If time does flow, how would we describe its speed? It would have to be something like “
x
hours per hour”—an interval of time per unit time. And I can tell you what
x
is going to be—it’s 1, all the time. The speed of time is 1 hour per hour, no matter what else might be going on in the universe.
The lesson to draw from all this is that it’s not quite right to think of time as something that flows. It’s a seductive metaphor, but not one that holds up under closer scrutiny. To extract ourselves from that way of thinking, it’s helpful to stop picturing ourselves as positioned within the universe, with time flowing around us. Instead, let’s think of the universe—all of the four-dimensional spacetime around us—as somehow a distinct entity, as if we were observing it from an external perspective. Only then can we appreciate time for what it truly is, rather than privileging our position right here in the middle of it.
The view from nowhen
We can’t literally stand outside the universe. The universe is not some object that sits embedded in a larger space (as far as we know); it’s the collection of everything that exists, space and time included. So we’re not wondering what the universe would really look like from the point of view of someone outside it; no such being could possibly exist. Rather, we’re trying to grasp the entirety of space and time as a single entity. Philosopher Huw Price calls this “the view from nowhen,” a perspective separate from any particular moment in time.
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We are all overly familiar with time, having dealt with it every day of our lives. But we can’t help but situate ourselves within time, and it’s useful to contemplate all of space and time in a single picture.
And what do we see, when looking down from nowhen? We don’t see anything changing with time, because we are outside of time ourselves. Instead, we see all of history at once—past, present, and future. It’s like thinking of space and time as a book, which we could in principle open to any passage, or even cut apart and spread out all the pages before us, rather than as a movie, where we are forced to watch events in sequence at specific times. We could also call this the Tralfamadorian perspective, after the aliens in Kurt Vonnegut’s
Slaughterhouse-Five
. According to protagonist Billy Pilgrim,
The Tralfamadorians can look at all the different moments just the way we can look at a stretch of the Rocky Mountains, for instance. They can see how permanent all the moments are, and they can look at any moment that interests them. It is just an illusion we have here on earth that one moment follows another like beads on a string, and that once a moment is gone it is gone forever.
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How do we reconstruct our conventional understanding of flowing time from this lofty timeless Tralfamadorian perch? What we see are correlated events, arranged in a sequence. There is a clock reading 6:45, and a person standing in their kitchen with a glass of water in one hand and an ice cube in the other. In another scene, the clock reads 6:46 and the person is again holding the glass of water, now with the ice cube inside. In yet another one, the clock reads 6:50 and the person is holding a slightly colder glass of water, now with the ice cube somewhat melted.
In the philosophical literature, this is sometimes called the “block time” or “block universe” perspective, thinking of all space and time as a single existing block of spacetime. For our present purposes, the important point is that we
can
think about time in this way. Rather than carrying a picture in the back of our minds in which time is a substance that flows around us or through which we move, we can think of an ordered sequence of correlated events, together constituting the entire universe. Time is then something we reconstruct from the correlations in these events. “This ice cube melted over the course of ten minutes” is equivalent to “the clock reads ten minutes later when the ice cube has melted than it does when the ice cube is put into the glass.” We’re not committing ourselves to some dramatic conceptual stance to the effect that it’s
wrong
to think of ourselves as embedded within time; it just turns out to be more
useful
, when we get around to asking why time and the universe are the way they are, to be able to step outside and view the whole ball of wax from the perspective of nowhen.
Opinions differ, of course. The struggle to understand time is a puzzle of long standing, and what is “real” and what is “useful” have been very much up for debate. One of the most influential thinkers on the nature of time was St. Augustine, the fifth-century North African theologian and Father of the Church. Augustine is perhaps best known for developing the doctrine of original sin, but he was interdisciplinary enough to occasionally turn his hand to metaphysical issues. In Book XI of his
Confessions
, he discusses the nature of time.
What is by now evident and clear is that neither future nor past exists, and it is inexact language to speak of three times—past, present, and future. Perhaps it would be exact to say: there are three times, a present of things past, a present of things present, a present of things to come. In the soul there are these three aspects of time, and I do not see them anywhere else. The present considering the past is memory, the present considering the present is immediate awareness, the present considering the future is expectation.
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Augustine doesn’t like this block-universe business. He is what is known as a “presentist,” someone who thinks that only the present moment is real—the past and future are things that we here in the present simply try to reconstruct, given the data and knowledge available to us. The viewpoint we’ve been describing, on the other hand, is (sensibly enough) known as “eternalism,” which holds that past, present, and future are all equally real.
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Concerning the debate between eternalism and presentism, a typical physicist would say: “Who cares?” Perhaps surprisingly, physicists are not overly concerned with adjudicating which particular concepts are “real” or not. They care very much about how the real world works, but to them it’s a matter of constructing comprehensive theoretical models and comparing them with empirical data. It’s not the individual concepts characteristic of each model (“past,” “future,” “time”) that matter; it’s the structure as a whole. Indeed, it often turns out to be the case that one specific model can be described in two completely different ways, using an entirely different set of concepts.
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So, as scientists, our goal is to construct a model of reality that successfully accounts for all of these different notions of time—time is measured by clocks, time is a coordinate on spacetime, and our subjective feeling that time flows. The first two are actually very well understood in terms of Einstein’s theory of relativity, as we will cover in Part Two of the book. But the third remains a bit mysterious. The reason why I am belaboring the notion of standing outside time to behold the entire universe as a single entity is because we need to distinguish the notion of time in and of itself from the perception of time as experienced from our parochial view within the present moment. The challenge before us is to reconcile these two perspectives.
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THE HEAVY HAND OF ENTROPY
Eating is unattractive too . . . Various items get gulped into my mouth, and after skillful massage with tongue and teeth I transfer them to the plate for additional sculpture with knife and fork and spoon. That bit’s quite therapeutic at least, unless you’re having soup or something, which can be a real sentence. Next you face the laborious business of cooling, of reassembly, of storage, before the return of these foodstuffs to the Super ette, where, admittedly, I am promptly and generously reimbursed for my pains. Then you tool down the aisles, with trolley or basket, returning each can and packet to its rightful place.
—Martin Amis, Time’s Arrow
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Forget about spaceships, rocket guns, clashes with extraterrestrial civilizations. If you want to tell a story that powerfully evokes the feeling of being in an alien environment, you have to reverse the direction of time.
You could, of course, simply take an ordinary story and tell it backward, from the conclusion to the beginning. This is a literary device known as “reverse chronology” and appears at least as early as Virgil’s
Aeneid
. But to really jar readers out of their temporal complacency, you want to have some of your characters experience time backward. The reason it’s jarring, of course, is that all of us nonfictional characters experience time in the same way; that’s due to the consistent increase of entropy throughout the universe, which defines the arrow of time.
THROUGH THE LOOKING GLASS
F. Scott Fitzgerald’s short story “The Curious Case of Benjamin Button”—more recently made into a film starring Brad Pitt—features a protagonist who is born as an old man and gradually grows younger as time passes. The nurses of the hospital at which Benjamin is born are, understandably, somewhat at a loss.
Wrapped in a voluminous white blanket, and partly crammed into one of the cribs, there sat an old man apparently about seventy years of age. His sparse hair was almost white, and from his chin dripped a long smoke-coloured beard, which waved absurdly back and forth, fanned by the breeze coming in at the window. He looked up at Mr. Button with dim, faded eyes in which lurked a puzzled question.
“Am I mad?” thundered Mr. Button, his terror resolving into rage. “Is this some ghastly hospital joke?”
“It doesn’t seem like a joke to us,” replied the nurse severely. “And I don’t know whether you’re mad or not—but that is most certainly your child.”
The cool perspiration redoubled on Mr. Button’s forehead. He closed his eyes, and then, opening them, looked again. There was no mistake—he was gazing at a man of threescore and ten—a
baby
of threescore and ten, a baby whose feet hung over the sides of the crib in which it was reposing.
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No mention is made in the story of what poor Mrs. Button must have been feeling around this time. (In the movie version, at least the newborn Benjamin is baby-sized, albeit old and wrinkled.)
Because it is so bizarre, having time run backward for some characters in a story is often played for comic effect. In Lewis Carroll’s
Through the Looking-Glass
, Alice is astonished upon first meeting the White Queen, who lives in both directions of time. The Queen is shouting and shaking her finger in pain:
“What IS the matter?” [Alice] said, as soon as there was a chance of making herself heard. “Have you pricked your finger?”
“I haven’t pricked it YET,” the Queen said, “but I soon shall—oh, oh, oh!”
“When do you expect to do it?” Alice asked, feeling very much inclined to laugh.
“When I fasten my shawl again,” the poor Queen groaned out: “the brooch will come undone directly. Oh, oh!” As she said the words the brooch flew open, and the Queen clutched wildly at it, and tried to clasp it again.
“Take care!” cried Alice. “You’re holding it all crooked!” And she caught at the brooch; but it was too late: the pin had slipped, and the Queen had pricked her finger.
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Carroll (no relation
21
) is playing with a deep feature of the nature of time—the fact that causes precede effects. The scene makes us smile, while serving as a reminder of how central the arrow of time is to the way we experience the world.
Time can be reversed in the service of tragedy, as well as comedy. Martin Amis’s novel
Time’s Arrow
is a classic of the reversing-time genre, even accounting for the fact that it’s a pretty small genre.
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Its narrator is a disembodied consciousness who lives inside another person, Odilo Unverdorben. The host lives life in the ordinary sense, forward in time, but the homunculus narrator experiences everything backward—his first memory is Unverdorben’s death. He has no control over Unverdorben’s actions, nor access to his memories, but passively travels through life in reverse order. At first Unverdorben appears to us as a doctor, which strikes the narrator as quite a morbid occupation—patients shuffle into the emergency room, where staff suck medicines out of their bodies and rip off their bandages, sending them out into the night bleeding and screaming. But near the end of the book, we learn that Unverdorben was an assistant at Auschwitz, where he created life where none had been before—turning chemicals and electricity and corpses into living persons. Only now, thinks the narrator, does the world finally make sense.
