Wormholes are theoretical tunnels through the fabric of space-time that could potentially allow rapid travel between widely separated points — from one galaxy to another, for example, as depicted in Christopher Nolan's "Interstellar," which opened in theaters around the world earlier this month.
While wormholes are possible according to Einstein's theory of general relativity, such exotic voyages will likely remain in the realm of science fiction, said renowned astrophysicist Kip Thorne of the California Institute of Technology in Pasadena, who served as an adviser and executive producer on "Interstellar."
"The jury is not in, so we just don't know," Thorne, one of the world's leading authorities on relativity, black holes and wormholes, told Space.com. "But there are very strong indications that wormholes that a human could travel through are forbidden by the laws of physics. That's sad, that's unfortunate, but that's the direction in which things are pointing."
The major barrier has to do with a wormhole's instability, he said.
"Wormholes — if you don't have something threading through them to hold them open — the walls will basically collapse so fast that nothing can go through them," Thorne said.
Holding wormholes open would require the insertion of something that anti-gravitates — namely, negative energy. Negative energy has been created in the lab via quantum effects, Thorne said: One region of space borrows energy from another region that didn't have any to begin with, creating a deficit.
"So it does happen in physics," he said. "But we have very strong, but not firm, indications that you can never get enough negative energy that repels and keeps the wormhole's walls open; you can never get enough to do that."
Furthermore, traversable wormholes — if they can exist at all — almost certainly cannot occur naturally, Thorne added. That is, they must be created by an advanced civilization.