Astronomers say time travel is just science fiction
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Your support makes all the difference.Astronomers are concerned that the public is getting Star Trek-style science fiction dressed up as science fact, following reports that Professor Stephen Hawking believed that travelling in time is possible.
Dr Simon Mitton, an astronomer at Cambridge University, said: "It has been known for the past 20 years that if you can come up with a mechanism for severely distorting spacetime and creating a "wormhole", then it would be possible at the level of equations for single particles to travel from the present into the past."
But, he added: "It worries me that in describing circumstances in which time-travel and faster-than-light travel are a possibility within theoretical physics, popular reports often fail to distinguish what you can do for a single particle from many-particle systems - people or space-ships - which cannot participate in this phenomenon."
Professor Hawking had previously doubted the idea of time travel, but in the foreword to a new book, The Physics of Star Trek, by US astronomer Lawrence Krauss, which is due to be published next month, he writes: "One of the consequences of rapid interstellar travel would be that one could also travel back in time."
Professor Hawking, Lucasian Professor of Mathematics at Cambridge, said: "There is a two-way trade between science fiction and science. We may not yet be able to boldly go where no man or woman has gone before, but at least we can do it in the mind."
He emphasised that while he believed time-travel was theoretically possible, it would probably never be practically possible.
The first "proof" that Einstein's theory of general relativity allowed time travel was published by the mathematical logician Kurt Godel in 1949. He derived from the theory a cosmological model of a rotating universe in which journeys backwards in time were possible. However, Godel's model universe bears no resemblance to the one we inhabit.
In 1988, stimulated by Carl Sagan's 1986 science fiction novel Contact, the US cosmologist Kip Thorne and two of his colleagues examined the idea of quantum-mechanical wormholes in space as time-tunnels into the past.
Professor Thorne discussed the idea extensively in the last chapter of his book Black Holes and Time Warps: Einstein's Outrageous Legacy, published last year. He concluded: "We cannot know for sure until physicists have fathomed in depth the laws of quantum gravity."
For the moment, time machines have still not got further than the pages of HG Wells.
Building a Tardis, page 17
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