On May 22, 1955, Ronald Mallett's father, a 33-year-old TV repairman from the Bronx, died of a sudden heart attack. Mallett (pronounced M'lette) was 10 years old and the trauma of the event, not unnaturally, knocked him for six. A year later, he read H.G. Wells's classic novel The Time Machine, which gave him the idea to build a device that would allow him to return to 1955 and save his father's life.

So far the story is fabulous, painful and babyish, the stuff of Hollywood - but fast-forward 47 years to June 2002 and the same Ronald Mallett, now professor of theoretical physics at the University of Connecticut, is delivering a paper in Washington to about 50 physicists at an International Association for Relativistic Dynamics conference, in which he explains how a machine involving a circuit of lasers could, in theory, send a particle backwards in time.

It has long been known that Einstein's relativity allows for certain forms of theoretical time travel. If you whizz off into outer space at the speed of light, you will find upon your return that time passed much quicker for those on Earth than it did for you in your rocket. The unsolved practical problem is how to get a human body to move at such a speed. Einstein tells us this cannot be done.