The topic of many movies and books, the time machine is one that, if ever realised, would probably be seen as the biggest technology breakthrough of all time.
It might seem impossible, but Ronald Mallett, a theoretical physicist at the University of Conneticut in the United States, has been working on his idea for a time machine since early 2007, after declaring in 2006 that time travel would be possible within the 21st century, and possibly within less than a decade.
Although previous ideas for time travel have been proposed, based on black holes or cosmic strings, Mallett’s theory, known as the Space-time Twisting by Light (STL) project is the first to be seriously considered, with funding for the project progressing slowly but steadily.
Mallett has explained that his time machine will use circulating laser beams, and is based on Einstein’s Theory of Relativity:
"For the strong gravitational field of a circulating cylinder of light, I have found new exact solutions of the Einstein field equations for the exterior and interior gravitational fields of the light cylinder. The exterior gravitational field is shown to contain closed timelike lines.
The presence of closed timelike lines indicates the possibility of time travel into the past. This creates the foundation for a time machine based on a circulating cylinder of light.”
We’re still nowhere near being able to hop a train into the past, but the fact that the idea is being seriously considered is pretty exciting.