TIME travel is possible and one physicist is so convinced that he is already building a time travel machine. Ronald Mallett, a theoretical physicist from the University of Connecticut, believes that laser lights are the key to time travel. A machine that Mr Mallett is working on is based around the fact that light can create gravitational fields and Albert Einstein's General Theory of Relativity. The 71-year old has previously explained: "In Einstein's General Theory of Relativity, both matter and energy can create a gravitational field. "This means that the energy of a light beam can produce a gravitational field. "My current research considers both the weak and strong gravitational fields produced by a single continuously circulating unidirectional beam of light. "In the weak gravitational field of an unidirectional ring laser, it is predicted that a spinning neutral particle, when placed in the ring, is dragged around by the resulting gravitational field." In a later study, Mr