Scientific American reports on new findings about wormholes. Theoretically, these black hole-related phenomena make a great part of science fiction, giving people the ability to instantaneously move across vast distances of space or even travel across time. In practice… well, that stuff seems like it might be possible:
Einstein and Rosen discovered that, theoretically at least, a black hole’s surface might work as a bridge that connected to a second patch of space. The journey might be as if you went down the drain of your bathtub, and instead of getting stuck in the pipes, you came out into another tub just like the first.
Subsequent work expanded this idea but turned up two persistent challenges that prevent the formation of easily spotted, humanly usable wormholes: fragility and tininess. First, it turns out that in general relativity, the gravitational attraction of any normal matter passing through a wormhole acts to pull the tunnel shut. Making a stable wormhole requires some kind of extra, atypical ingredient that acts to keep the hole open, which researchers call “exotic” matter.
Second, the kinds of wormhole-creating processes that scientists had studied rely on effects that could prevent a macroscopic traveler from entering…. A bigger wormhole seems to require a process or type of matter that is both unusual and believable.
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One easy-to-picture idea comes from a preprint study by [Nabil] Iqbal and his Durham University colleague Simon Ross. The two tried to see if they could make the Gao-Jafferis-Wall method produce a large wormhole. “We thought it would be interesting, from a sci-fi point of view, to push the limits and see whether this thing could exist,” Iqbal says. Their work showed how special disturbances within the magnetic fields surrounding a black hole could, in theory, generate stable wormholes. Unfortunately, the effect still only forms microscopic wormholes, and Iqbal says it is highly unlikely the situation would occur in reality.
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Physicist Juan Maldacena of the Institute for Advanced Study, who had suggested connections between wormholes and entanglement back in 2013, and his collaborator Alexey Milekhin of Princeton University have found a method that could produce large holes. The catch in their approach is that the mysterious dark matter that fills our universe must behave in a particular way, and we may not live in a universe anything like this.
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You can read Iqbal and Ross’ work here, and Maldacena and Milekhin’s work here.