Physicist: Time machine is within grasp

Since he was ten years old, Ronald Mallett has longed to travel back in time. Forty-seven years ago, his father died young from a heart attack brought on by heavy smoking and, ever since, Mallett has yearned to visit the past and warn him about the dangers of cigarettes.

Nearly half a century later, the professor of physics believes he can make a time machine - and he's deadly serious. By the end of the summer, he will have begun building a device he reckons will be capable of sending physical objects into the past.

The idea of time travel has fired the imaginations of science-fiction writers for decades, but Mallett's machine will not involve reaching 88mph in a DeLorean kitted with a flux capacitor, as in Back To The Future.

Instead, it uses a circulating beam of light, created with a laser, which will bend space and time. By applying Einstein's theory of gravity, the University Of Connecticut professor will fire rotating laser beams through crystals to twist time into loops and enable objects to travel in time.

Initially, Mallett intends only to transport minute particles into the immediate past but he believes the potential for sending larger objects, and even ourselves, is there. He said: 'Getting a large-scale object to go through time would take a greater amount of energy, but if you can show it's happening on a sub-atomic level, then it becomes an engineering problem to get bigger things through.'

According to Mallett, anything could be transported if sufficient energy were available.

But there is scepticism among the scientific world as to whether time travel is even theoretically possible. The idea throws up endless paradoxes, including the obvious question: if a time machine has been created in the future, why hasn't someone come back to show us how to do it?

Mallett counters this by pointing out that a person coming back in time would create a parallel universe, of which modern physics dictates there could be an infinite number. And anyway, his device would not allow us to travel to any period in history. 'On a practical level, my device would only be able to take you back as far as when the machine was first turned on,' said Mallett. 'For example, if I switched one on now, by Christmas you would only be able to come back to any time from now.'

This is unfortunate for Mallet as it would not enable him to visit his father. But while his machine will not get him back, he suggests interstellar travel may open the doors to the past. He said: 'The universe is probably teeming with life and there are likely to be civilisations who developed time travel before us. Imagine one did 10,000 years ago - we could use their machine to travel into our past.'

It may be a long wait until we find these machines, but in time-travel terms, we have probably already found them in the future.