How to build a time machine
How to Build a Time Machine
When the seemingly unimaginable—at least to certain people—happened and Hillary Clinton lost the 2016 Presidential election, many of her supporters suddenly started asking questions about what went wrong: Could something have been done differently? What if her strategy had been more aggressive? What if she’d campaigned more in Wisconsin? What if she'd added Bernie Sanders to her ticket—or what if Sanders had won the nomination to begin with? What if the media had covered Donald Trump differently? What if? What if? When we think back and try to answer those questions, we’re thinking about building alternate histories based on the notion that we can somehow, miraculously, go back in time and do it all over.Thinking about time travel may seem like something humans have been doing since the first caveman dropped the first rock on his foot. But, even to begin to imagine the possibility of time travel, your mind must be able to wrap itself around the notion of a past and a future. Otherwise, where would you be travelling, exactly? In his new book, “Time Travel,” James Gleick argues that before the invention of the printing press, less than six hundred years ago, notions of any sort of temporal dislocation were next to impossible; people saw the future as relatively similar to the past—large changes over time simply weren’t visible or accessible. We could travel over geographical distances, exploring unknown lands, but the exploration of time wasn’t on anyone’s mind. The furthest people went was to seek a personal prophecy. But that didn’t involve a vision of time travel so much as a desire to know what lay in store for you, personally; for the world at large, well, what you saw was what you got, now and forever.After Gutenberg’s invention, the world changed: “Saving our cultural memory in something visible, tangible, and shareable,” Gleick writes. Now that the past could be recorded and accessed at will, it became much easier to understand that some sort of forward trajectory was possible. That view was cemented by the Industrial Revolution—when people could see just how different the world looked from how it had a decade earlier. “Before futurism could be born, people had to believe in progress,” Gleick writes. The first real time traveller, as we understand the notion today, H. G. Wells’s creatively named Time Traveller, appeared in 1895. (Gleick dismisses examples like Rip Van Winkle as mere precursors: they didn’t travel, actively; they slept, and time passed.)Before long, it was difficult to imagine an existence in which the idea of travelling through time didn’t exist. It quickly permeated science, with Einstein’s theory of relativity and notions of how to surpass the speed of light; found its way into literature, with Virginia Woolf’s “stretching and warping” of time; and seeped into popular culture, with vanity exercises in building time capsules. Why did time travel become so central, so quickly? Part of the answer is surely that the most central part of time travel is the one we carry with us, always: our memory. For what is remembering something but travelling through time? Once the notion of time travel starts to come naturally to the human mind, it is supremely easy to assimilate it into our mode of thinking. We don’t have to do any mental calisthenics to fathom how it could come to pass. Memory enables personal time travel immediately. If you have no notion of the passage of time, you cannot project yourself to a future point in it. In recent years, it has become clear that the centrality of memory is even more extreme: the very way our memory works allows us to imagine different futures, not just recall what has taken place. Memory is the very stuff of time travel.Time travel is as much a cultural staple now as it has ever been. It’s fodder for countless movies—as many people noted, “Back to the Future Part II” predicted the World Series victory of the Cubs and the rise of Trump. And it has become increasingly incorporated into research areas that are far removed from the physics where it originated. As psychologists study the workings of the human mind and memory, time travel has become a common element.For some time, scientists have known that memory is anything but precise. It doesn’t record the past accurately, and it plays tricks on us. For decades, this was seen as a kind of design flaw. Now some researchers suspect that the fallibility of memory isn’t necessarily a quirk or negative side effect of neural wiring but a necessity for being able to imagine the future. At Harvard, Daniel Schacter, a psychologist who studies memory, proposes that thinking about the past is absolutely necessary for imagining the future. “Imagining the future depends on much of the same neural machinery that is needed for remembering the past,” he writes. What’s more, the fact that the past is flexible—that our memory “sins,” to borrow a word from Schacter’s writing—is what allows us to imagine things that have never happened. We recombine elements from what we recall into memories that have never taken place. The future is based on a realignment of what we know, not a straightforward recapitulation of it. Schacter calls this the constructive episodic simulation hypothesis. If our memory is too fixed, we cannot flexibly recombine elements. “Think of the brain as a fundamentally prospective organ that is designed to use information from the past and the present to generate predictions about the future,” he explains.Indeed, Schacter’s own work and contributions from other laboratories suggest that people with amnesia aren’t able to do the most rudimentary exercises in future projection. One early patient, K.C., was found to be incapable of coming up with a single thing that might possibly happen to him in the future. Absent the ability to recollect episodes from his own life, he lost the ability to imagine future episodes that might take place. Not only is the past of a person with no memory inaccessible; his ability to think about the future is imperilled. Time travel, then, is ultimately—and paradoxically—an exercise in remembering. And without that capacity it simply cannot exist.Clive Wearing was a prominent musician who, in 1985, lost his ability to remember. As far as he was concerned, only the last few seconds of any given day had actually happened. “It was as if every waking moment was the first waking moment,” his wife wrote. His journal forms a poignant narrative of his condition—variations of “I am awake” written every few minutes, and then just as assiduously crossed out and replaced by “this time properly awake” or “awoke for the first time, despite my previous claims.” It’s as profound a testament as ever to the power—and terror—of the present moment, amplified by the absence of memory. This is it: right now is forever. The feeling is pressing enough that it must be noted and catalogued. “To imagine the future was no more possible for Clive than to remember the past,” Oliver Sacks wrote in his Profile of Wearing for this magazine, in 2007.Wearing’s amnesia came with benefits: he truly lived in the present moment. As Sacks points out, every moment was to him a new gift; every meeting with his wife, a revelation; every piece of good news, a source of incomparable joy. But he was forever stuck in the pre-time-travel era—and for him even the time travel of imagination was not possible. And that is a tragedy in its own right. Early in his book, Gleick explores one of the earliest conceptions of time travel, the Universe Rigid—a four-dimensional construct thought up by Wells. It’s a model of the world with time already built in, and so it is unchanging: past, present, and future all exist at once. “The Universe Rigid is a prison,” Gleick writes. “Only the Time Traveller can call himself free.” Without mental time travel, without a conception of the past, we remain, like Wearing, prisoners.Gleick is not a believer in the feasibility of actual time travel, now or ever. “It does not exist. It cannot,” he writes. We cannot go back in time and change how Clinton approached the election. All we can do is learn from what happened, and wait for the chance to do it better. As the author Israel Zangwill put it, “There is no getting into the future, except by waiting.” Our memory is and always will be as good as time travel gets, and in the meantime time will do the travelling for us. Perhaps that’s not altogether a bad thing. Wells, the original time-travel creator, was disappointed by the future when it came, “as a child finding lumps of coal in the Christmas stocking.” It couldn’t compete with what he had imagined. Reality is no match for imagination—and our current reality has made that point all too clearly.