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But traveling faster than light would require infinite energy; it is possible on paper, not in practice. More recently, physicists have theorized other ways that physical travel into the past could be achieved, but they are still exotic and expensive. A technological civilization thousands or more years in advance of our own, one able to harness the energy of its whole galaxy, could create a wormhole linking different points in the fabric of spacetime and send a spaceship through it.8 It is an idea explored widely in science fiction and depicted vividly in Christopher Nolan’s 2014 film Interstellar. But all this is academic for our purposes. For Gleick, what we are really talking about with time travel is a thought experiment about the experiencer—the passenger—in a novel, disjointed relationship to the external world. We can readily perform feats of “mental time travel,” or at least simulate such feats, as well as experience a dissociation between our internal subjective sense of time and the flux of things around us and even our own bodies.9 According to Gleick, part of what suddenly facilitated four-dimensional thinking in both popular writing and the sciences was the changing experience of time in an accelerating society. The Victorian age, with its steam engines and bewildering pace of urban living, increased these experiences of dissociation, and they have only intensified since then. Time travel, Gleick argues, is basically just a metaphor for modernity, and a nifty premise upon which to base literary and cinematic fantasies that repair modernity’s traumas. It also shines a light on how confused we all are about time. The most commonly voiced objection to time travel—and with it, precognition—is that any interaction between the future and past would change the past, and thus create a different future. The familiar term is the grandfather paradox: You can’t go back in time and kill your grandfather because then you wouldn’t have been born to go back in time and kill your grandfather (leaving aside for the moment the assumed inevitability of wanting to kill your grandfather, which is an odd assumption). The technical term for meddling in the past this way is “bilking,” on the analogy of failing to pay a promised debt.10 Whatever you call it, it is the kind of thing that, in Star Trek, would make the Enterprise’s computer start to stutter and smoke and go haywire—the same reaction, in fact, that greets scientific claims of precognition. (As Dean Radin puts it, laboratory precognition results like those cited in the past two chapters “cause faces to turn red and sputtering noises to be issued from upset lips.”11) Information somehow sent backward in time from an event cannot lead to a future that no longer includes that event—and we naturally intuit that it would be very hard not to have such an effect if we meddled in the timeline. Our very presence in the past would change things.
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