Physicists have worked out a way that it might be feasible to send someone through a wormhole. Wormholes are tunnels between two black holes that connect distant regions of space-time, and normally it would be impossible to pass something through them, but factoring in an extra dimension might make it possible.
Under Albert Einstein’s theory of general relativity, which describes the behaviour of gravity and space-time, most wormholes would either close whenever something falls in or be extremely small and disappear immediately. Juan Maldacena at the Institute for Advanced Study in New Jersey and Alexey Milekhin at Princeton University have figured out how a traversable wormhole could exist while following all of the laws of physics as we know them.
They calculated that if there were an additional dimension of space-time, it would allow for a large number of quantum fields. Fluctuations in quantum fields can produce negative energy, which could keep the wormhole from collapsing.
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There is no evidence that all these extra fields exist, but they theoretically could, says Maldacena. “There are two questions here, which are: whether you would expect this to occur naturally – and there the answer is almost certainly no – and also if you could expect a sufficiently advanced civilisation to be able to make it,” says Aron Wall at the University of Cambridge. “It could in theory be made with mostly ordinary matter and quantum effects,” he says. Whether that would be worth the effort is another question entirely, he adds.
In order to be physically possible, travelling through a wormhole to a distant location would have to take longer than flying there directly through space at the speed of light. However, because of the effects of general relativity, time would pass differently for the person inside the wormhole. “It wouldn’t take very long from the perspective of the person inside, while everyone they knew on the outside gets old and dies,” says Wall.
Falling through the wormhole wouldn’t be all that unpleasant, though; you would just slowly accelerate to extraordinarily high speeds, and then decelerate again when you emerge. “It’d be just like being in free fall – like there is a hole in the ground and you step in and just fall, and then three seconds later you’d emerge on the other side,” says Don Marolf at the University of California, Santa Barbara. Anything else that falls into the wormhole will also accelerate to nearly the speed of light.
Unless the wormhole was thoroughly cleaned out and everything else blocked from entering it, falling in would mean certain death. “Whenever you travel close to the speed of light, any particle or dust grain or anything that you hit will be problematic. Even a photon would cause you trouble,” says Maldacena. “So that’s a word of caution.”
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