FASTEN your seatbelts and hold on tight-intergalactic space travel is back on the agenda. Sceptics who dismiss the idea of faster-than-light travel through "wormholes" in space may have to think again, because new calculations based on Einstein's general theory of relativity suggest that wormholes large and stable enough to allow intergalactic travel really can exist.
The possibility that the cosmos is peppered with short cuts through space and time has intrigued people ever since 1915 when German theorist Ludwig Flamm found hints of their existence in Einstein's equations. While attempts to unify the fundamental forces of nature suggest that tiny quantum wormholes may exist, most experts suspect that some fundamental law of physics prevents the formation of large wormholes-not least because these would theoretically allow time travellers to go back in time and, say, prevent their own birth by accidentally killing one of their parents.
Now a Russian theorist has found a new type of wormhole that is compatible with the known laws of physics, yet can be as big and stable as you like. According to Sergei Krasnikov, a relativity expert at the Pulkovo Observatory in St Petersburg, the standard arguments against large wormholes assume that they all have the same basic shape, and need to be crammed with "exotic matter" to keep them open (New Scientist, 6 September 1997, p 49).
Such exotic matter has never been seen, but theory suggests it can be created literally out of nothing when space and time are curved in the right way. What Krasnikov has found is a new type of wormhole that can create its own supply of exotic matter-and in sufficient quantities to make it big enough and keep it open long enough for people to use.
"This new wormhole, like every other, needs exotic matter for it to form, and like some others can produce it by itself," Krasnikov told New Scientist. "What's new is that this wormhole actually generates enough to make it arbitrarily large." Other theorists admit to being intrigued by the new work, but remain cautious.
"It's worth taking seriously," says Ian Moss, a relativity expert at the University of Newcastle upon Tyne. "The main worry is that it could fall down on some technical detail." Paul Davies of Imperial College, London, adds that proving something is theoretically possible does not prove it actually exists: "My feeling is that the matter is still open," he says.
Krasnikov accepts that testing his claims by building a wormhole is far beyond present technology. Even so, such wormholes may have been left over from the big bang, he says-and finding one would have a dramatic effect on interstellar travel: "If there is a wormhole connecting the vicinities of the Earth and the star Vega, one can take a short cut by flying through it."
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