IF YOU want to time-travel through wormholes 鈥� theoretical space-time 鈥渢unnels鈥� that could act as short cuts through the universe 鈥� be prepared to choose between not knowing where you鈥檒l arrive or not arriving at all.
In theory, wormholes work when they are coated with a mysterious form of matter that exerts negative pressure. If a balloon were filled with the stuff, it would deflate. Physicists Roman Buniy and Stephen Hsu at the University of Oregon in Eugene calculated the properties of two types of wormholes with this exotic matter: one that follows the laws of classical physics and another that follows the laws of quantum mechanics. It turns out that with quantum-mechanical wormholes there is no guarantee about where exactly in space and time you will pop out. 鈥淭he end point of the wormhole might be in a wall or under the Pacific Ocean,鈥� Hsu says. 鈥淎lternatively, you might exit a year before or after you thought you would.鈥�
Researchers had believed that classical wormholes, which are less uncertain, could serve as more practical portals through space-time. But Buniy and Hsu have found that these wormholes are inherently unstable (). 鈥淚f someone nudged the [wormhole] a little, it would cause the system to fall apart, the way a bridge would collapse,鈥� says Hsu. 鈥淚t would probably not last long enough for you to get through to the other side.鈥�
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That puts hopeful wormhole travellers between a rock and a hard place, says Hsu.
