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A brief history of time travel

In his brisk and entertaining perspective, time travel, or at least backwards
CONVERSATION

new book, Time Travel: time travel, seems to preclude the possibility
A History, James Gleick of free will.
serves as an enthusiastic In the 1980s, the Russian physicist
guide through the fourth Igor Novikov put forth what is now known
dimension as seen in as the ‘self-consistency conjecture’, which
literature and popular posited, in short, that the probability of

COURTESY OF THE AUTHOR / PANTHEON BOOKS

culture. I spoke with Gleick inconsistent histories in closed time-like
to discuss his book, the curves was exactly zero. Quantum events
interface between science should play themselves out the same way the
and science fiction and what second time around. Gleick notes that “this
makes genuinely compelling time travel. was why writing the book was so much fun.
Gleick begins his story around the Watching first the science fiction writers
turn of the twentieth century, which saw and then the physicists grapple with these
both H. G. Wells’s publication of The Time questions. What we love about science is the
Machine and, not entirely coincidentally, very way it undermines our common sense
Albert Einstein’s annus mirabilis papers. Wells and it’s a great joy whenever it happens.” He
wasn’t a scientist, and nobody — least of all cites classic sci-fi movies like The Terminator,
Gleick — would make the argument that 12 Monkeys (itself a remake of La Jetée, a
The Time Machine presaged special relativity, film he lovingly describes in detail in his
but he argues that language itself made But Twain’s Connecticut Yankee is more book) and, in a particularly neat resolution,
spacetime almost an inevitable concept; we of a tourist than what we now consider a ‘Blink’ (an episode of the classic sci-fi series
use the same word for the flow of time and time traveller. Doctor Who).
the flow of a river, for example. “Physicists Gleick makes the pitch that the precursors The ‘trick’ in great time travel literature
didn’t invent that analogy; it was partly of modern time travel include many ideas becomes the way in which the author closes
built into the language because we don’t that we wouldn’t call time travel at all: the loop. As Gleick puts it, “the job of a good
have words for everything. But the words sleeping into the future, for example, in the time travel writer is to explore the paradox by
connecting space and time became more tradition of Rip Van Winkle or in prophecies taking it seriously … but when you go back
powerful over time.” going back to the ancients. In the early and think about it, you can see the trick”.
The nineteenth century was a golden decades of the twentieth century, the time What distinguishes Time Travel: A
age of geology and Wells in particular was capsule fad represented a way of speaking History from other books more focused
fascinated by it. There is a very literal sense in directly to the future — albeit only in on the philosophy or physics of time
which the physical strata of Earth represent one dimension. travel is that Gleick allows himself into
movement through time. That, along with Wells’s time traveller, however, wasn’t the realm of the aesthetic. It is irrelevant
the synchronization of clocks required for simply a passive observer. He could affect whether the physical mechanism for time
successful railroads, started many thinkers the future (and Wells seemed to be uniquely travel is driven by a steampunk bicycle or
on the path of considering what time interested in travelling into the future), a wormhole — you have to believe in the
really is. Gleick notes, “Wells’s hero, the prompting Gleick to propose a parlour game dramatic stakes.
time traveller, makes a speech explaining similar to the ‘flight or invisibility?’ litmus As to the practical possibility of time
why time travel is possible in a way that to test for superpowers: “if you had one shot travel, Gleick is something of a sceptic.
modern ears is almost comically pedantic. with a time machine, would you go into the Common sense, he argues, suggests that
We can see that his vision of the Universe is future or the past, provided you could go and the past really is immutable, no matter
almost standard — it’s Einstein’s version of return safely?” how clever the theoretical models that
the Universe”. The future is full of promise, but in the past imply otherwise. And despite the apparent
But time as a river, or a dimension or you could — perhaps — fix your mistakes. symmetry of the microscopic laws of physics,
any of the familiar analogies is more than Gleick’s tour of the development of what there really is, he argues, something different
simple language at play. We know, and are by now are familiar paradoxes brings about the future and the past. “The future
Einstein showed, that space and time really into focus the giants of early science fiction. hasn’t been written yet. When did that
can be rotated into one another with a One example is Ray Bradbury’s A Sound of become controversial?” ❐
suitable choice of frame. Wells’s innovation Thunder, which showed that changes in the
was to consider seriously the premise of past (in the story, the crushing of a butterfly DAVE GOLDBERG
freely traversing time as we would any in the Jurassic) can lead inexorably to Dave Goldberg is in the Department of Physics,
other dimension. dramatic changes in the present. Drexel University, Philadelphia, Pennsylvania
Wells is a seminal figure in the Temporal manipulations can create 19104, USA.
development of fictional time travel, but he paradoxes, the most famous of which e-mail: goldberg@drexel.edu
wasn’t the first. Mark Twain’s A Connecticut amounts to the fact that you can’t kill
Yankee in King Arthur’s Court, for example, your grandfather and prevent your own ■■Time Travel: A History by James Gleick is
predated The Time Machine by six years. birth — or can you? From a storytelling available through Pantheon Books.

892 NATURE PHYSICS | VOL 12 | OCTOBER 2016 | www.nature.com/naturephysics

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