Bending Time and Space with Light

Time twister: New Scientist reports that a professor of theoretical physics, Ronald Mallett, thinks he has found a practical way to make a time machine. Unlike other "time travel" solutions, such as wormholes, Mallett's solution relies heavily on light, a much more down to earth ingredient when compared to the "negative energy" matter used to open wormholes. Even though light doesn't have mass, it does have the quirky ability to bend space-time. Last year, Mallett published a paper describing how a circulating beam of laser light would create a vortex in space within its circle (Physics Letters A, vol 269, p 214).
To twist time into a loop, Mallett worked out that he would have to add a second light beam, circulating in the opposite direction. Then if you increase the intensity of the light enough, space and time swap roles: inside the circulating light beam, time runs round and round, while what to an outsider looks like time becomes like an ordinary dimension of space.
The energy needed to twist time into a loop is enormous, but Mallet saw that the effect of circulating light depends on its velocity: the slower the light, the stronger the distortion in space-time. Light gains inertia as it is slowed down, so "Increasing its inertia increases its energy, and this increases the effect," Mallett says. There is still a lot of work to do to make this process a reality, and it probably won't happen for some "time", but the concept of plausible time travel in our time is intriguing, if only because of the moral and paradoxical issues it raises. The most famous paradox, of course, is going back in time to kill your grandparents, effectively negating your very own existence - but then you wouldn't be able to go back in time, would you? My favourite solution to said paradoxes is the Terminator or Bill and Ted version of time travel in which what you've done in the past has already influenced your present (and future). [via ArsTechnica]