ON 28 June 2009, at 1200 UTC, Stephen Hawking hosted a party for time travellers at the University of Cambridge. Among the careful preparations, the most important was to invite guests only after the event had taken place. Much to Hawking鈥檚 disappointment, nobody showed up.
Travelling through time may never be feasible, but it remains a perennially popular topic in science fiction, philosophy and theoretical physics. In Time Travel, James Gleick provides an absorbing history of the idea, eloquently elucidating the reasons for its enduring appeal.
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The concept of time travel is surprisingly recent. 鈥淭hough the ancients imagined immortality and rebirth and lands of the dead,鈥� Gleick observes, 鈥渢ime machines were beyond their ken.鈥� In fact, he traces the trope back to a single work of fiction: The Time Machine, written by H. G. Wells between 1888 and 1895.
It tells of an unnamed time traveller who rides into the future on an apparatus resembling a bicycle. His voyage is made possible by the fact 鈥渢here is no difference between Time and any of the three dimensions of Space except that our consciousness moves along it鈥� (as the Traveller helpfully explains to his temporally challenged friends).
His reasoning (and Wells鈥檚 story) were inspired by the investigations of 19th-century mathematicians such as Bernhard Riemann. But as Gleick observes, Wells鈥檚 vision was equally driven by technology: 鈥淭ime became vivid, concrete, and spatial to anyone who saw the railroad smashing across distances on a coordinated schedule.鈥�
If the literary roots of time travel are The Time Machine, then scientific interest originated with Einstein鈥檚 special theory of relativity, published in 1905. In Gleick鈥檚 account, these two foundations were mutually reinforcing. Science gave credibility to the fiction, which made the science more accessible. The combination was so potent, and expanded so quickly, that time travel began to seem like a truly timeless principle.
鈥淭oday the time machine is no longer obligatory to the game of altering the past 鈥� it has been internalised鈥�
Gleick traces its literary pedigree, sometimes to the point of tedium, from Wells to writers such as Robert Heinlein and Jorge Luis Borges. He also delves into pop culture, ranging from Star Trek to Woody Allen.
Then there鈥檚 the science. While Einstein remained sceptical of voyaging through the space-time continuum, his close friend Kurt G枚del mathematically described an alternate universe in which time warped to loop back on itself. G枚del gave the calculation to Einstein for his 70th birthday, often checking later whether his theory had been proven.
It wasn鈥檛, but G枚del鈥檚 鈥渃losed time-like curves鈥� continued to bedevil physics long after his death, ultimately inspiring a rebuttal by Hawking, who claimed that time loops violated established laws of physics. Hawking organised his Cambridge party as experimental evidence.
Whether or not Hawking has the final say, the concept of time travel has proven phenomenally productive. Within physics, Gleick captures some of the intellectual ferment in his account of the debate about whether time is an illusion. Within literature, he鈥檚 particularly incisive in his account of alternative histories, which originated as an accident of time travel. 鈥淭ravel to the past begins as tourism in the extreme,鈥� he writes. But the sightseers 鈥渟tart tinkering鈥�. Eventually they aim at history鈥檚 greatest villains, and murder Hitler, or slay his mother.
Beyond the adrenaline, what makes this compelling is the chance to imagine what might have been. Counterfactual narratives let us examine the past more speculatively, and explore how things can go awry in the present. Is despotism a function of personal charisma or socio-economic conditions? How do we prevent a holocaust? 鈥淣odal points must exist,鈥� says Gleick, 鈥渏ust not鈥� where we think.鈥�
Today the time machine is no longer obligatory. The game of altering the past has been so internalised that Gleick suggests the notion of time travel has fundamentally changed the way we think.
To illustrate, he cites our habit of burying time capsules. Only since the 20th century have we sought ways to communicate with the future. Now we tend to interpret any box of coins found under a cornerstone as an effort by ancestors to send us a message. In fact, those old cornerstone caches were votive offerings, not meant to be discovered.
In contrast to his enthusiasm for SF, Gleick finds a time capsule 鈥渁 tragicomic time machine鈥�, moving through time at a rate of one second per second. Few capsules survive, he notes, and why should the future care about us in the first place?
But here Gleick neglects the wisdom of his book, forgetting that time travel is experienced in the traveller鈥檚 present. Time machines are instruments for exploring the past and future, to augment our current knowledge or enrich our lived experience. Placing items in a time capsule is an opportunity for self-appraisal. Considering how we would like to be perceived by the future is a way of examining what we most cherish.
Random House
This article appeared in print under the headline 鈥淔ast forward鈥�
