The fictional Dr Who famously travelled through time in an emergency phone box. Sadly no one performed the same trick for this month's conference. Credit: © BBC

If there are any time travellers out there, they're certainly keeping quiet about it. Despite a storm of publicity, a time travellers' convention on 7 May attracted not a single visitor from anywhen other than the present.

The event was dreamed up by Amal Dorai, a graduate student in electrical engineering and computer science at the Massachusetts Institute of Technology (MIT), Cambridge. He hoped that an open invitation to the bash would be read by distant descendants who, presumably having mastered the mysteries of time and space, would drop in to say 'hi' from the future.

Promotional e-mails asked students to slip invites into little-used library books, or add them to time capsules, so that they could be discovered in years to come. The instructions included precise coordinates for the campus volleyball court, which was reserved as a landing pad for time machines, just in case. Dorai asked any visitors from the future to bring proof, such as a cure for cancer or a cold-fusion machine (presumably branded as the popular household appliance, 'Mr Fusion').

The convention attracted 450 guests, about a third of them from MIT, some from as far away as California. A DeLorean car, as used in the film Back to the Future, was helpfully provided by Hank Eskin, a Massachusetts-based member of the DeLorean Owners Club. And speakers at the convention included MIT professors such as physicist Alan Guth, who kindly said he'd take the credit for any futuristic visitors.

"But we didn't get anyone claiming to be a time traveller," says the disappointed host. Still, that doesn't prove that time travel is impossible.

Stranger than fiction

I think the real reason no-one came is that time travel to the past is impossible. Amal Dorai , time travel convention organiser

According to Einstein, travelling into the future is quite feasible. As objects approach the speed of light, the flow of time they experience slows to a crawl, while the rest of the Universe carries on as normal. This means that when an astronaut in a speeding spaceship returns to Earth, they have aged less than their friends back home. In a sense, this puts them further into the future than they would have been if they had remained on terra firma.

But travelling back in time is a bit more complicated, requiring wormholes, exotic matter and some pretty speculative physics. In theory, wormholes are tunnels through space-time that connect distant parts of the Universe. Travelling through them zips you across the cosmos so fast that you effectively travel faster than the speed of light, and you may find yourself in a place where time has not yet caught up.

Discussions about wormholes aren't limited to Star Trek conventions; some physicists claim they could exist ('Making a wormhole just got easier...').

No show

So why no visitors? Was it simply that the invite didn't wind up in the right hands? "The publicity was so extensive, I don't think that was the problem," says Dorai. It took just five days to make it from a mention on the news website Slashdot to the front page of The New York Times. "I could barely keep up," says Dorai.

Time travellers may have been reluctant to make themselves known because of the risk of altering their own future, of course. As Marty McFly found to his cost in Back to the Future, there's nothing as dangerous as meddling with your past. Or having your mother fall in love with you.

The risks of precipitating a temporal calamity might actually make time travel illegal, rather than impossible, adds Dorai. Anyone wishing to attend the event could have fallen foul of a time cop keen to keep the space-time continuum free of meddling tourists.

Drop in time

Maybe they were put off by the 'bring your own bottle' policy of the convention, I suggest. Planning an alcoholic event for 500 people was just too difficult for Dorai. "If that's what kept them away, it's very unfortunate," he says. He proposes that any time traveller who would still like to pay a visit should hook up with him next week. "We'll buy a ton of booze and then go back to the convention," he laughs.

Several physicists have pointed out that it may only be possible to go back in time to the point at which a time machine was first invented. "But I think the real reason no one came is that time travel to the past is impossible," Dorai says. "It would destroy our concept of cause and effect."

So this was just an excuse for a party, right? Kind of, admits Dorai, although he insists that the event was genuinely testing an interesting idea. Fortunately, his tutors were supportive, and it proved an interesting study of the power of the Internet to spread information rapidly around the world.

Even though his studies have nothing to do with time travel, his professors granted him an extension on his deadlines, because he was so busy with the conference. Of course if time travellers had actually shown up he could have got his work in ahead of time... or at any time, really.