A few days ago we interviewed a time traveller on our C4 show. Not literally - at least not yet. He is a highly respected American Professor of Physics at the University of Connecticut - one of the first black Americans to ever receive a doctorate in this subject.

He is a fascinating man, a mesmerising talker. He is also convinced he has cracked the theory of time travel.

For Ronald Mallett his obsession with time began when he was just 10. He was one of four young children living in the Bronx in New York City. His father Boyd was a gadget freak, a talented electronic technician, and young Ronald and his dad spent many hours in the evenings experimenting with capacitors and circuits, building crystal radios and other gadgets.

Then, without warning, his father died of a heart attack.

Ronald was devastated. As far as he was concerned the sun rose and set on his father. In his grief, this bright and inquisitive little boy happened to read HG Wells's The Time Machine. Already hooked on science fiction, he fastened on time travel as a way he could go back to before his father's death to warn him about his unhealthy lifestyle - Boyd was a workaholic and a very heavy smoker.

So Ronald's path was set. In his early teens he read Einstein's theory of relativity, which introduced the concept of spacetime - space and time were essentially different aspects of the same thing, and if it is possible for us to move backwards and forwards in space, which it is, it should equally be possible to do the same in time.

Ronald grew up, saved money and got into university. All the time he was researching the theoretical possibility of using gravity to reverse the passage of time. And as I write, a time machine is being designed at Connecticut using Ronald's theories and equations. Essentially the mechanism depends on circulating light that twists space and time, creating a time loop. It works in a similar way to stirring milk into a cup of coffee, creating a vortex through which a person could travel.

His theories are firmly based on Einstein's theory of relativity, and other scientists say there is nothing in physics to disprove his ideas. The sad thing is that his time traveller could only travel backwards until the minute the machine is switched on. Therefore Ronald will never be able to talk to his dad again because time travel was not invented when Boyd died.

The science is all beyond me but it's amazing that a powerful human love could lead to us all living in a world where time travel will be commonplace.