What would happen if you fell into a black hole? For a long time, the only acceptable answer was that you would die.
That is, unless a theoretical wormhole—a portal in spacetime between two black holes—were to save you. But according to physicists’ calculations, most wormholes immediately collapse. And attempts to prove the viability of a stabilizing “exotic material,” inserted along the lining of the wormhole tunnel by an advanced civilization, have failed.
Now, a new theory is percolating among physicists that presupposes the existence of a type of wormhole that would not depend on “exotic material” to keep it intact.
Here’s Natalie Wolchover, reporting for Quanta Magazine:
The flurry of findings started last year with a paper that reported the first traversable wormhole that doesn’t require the insertion of exotic material to stay open. Instead, according to Ping Gao and Daniel Jafferis of Harvard University and Aron Wall of Stanford University, the repulsive negative energy in the wormhole’s throat can be generated from the outside by a special quantum connection between the pair of black holes that form the wormhole’s two mouths. When the black holes are connected in the right way, something tossed into one will shimmy along the wormhole and, following certain events in the outside universe, exit the second. Remarkably, Gao, Jafferis and Wall noticed that their scenario is mathematically equivalent to a process called quantum teleportation, which is key to quantum cryptography and can be demonstrated in laboratory experiments.
John Preskill, a black hole and quantum gravity expert at Caltech, says the new traversable wormhole comes as a surprise, with implications for the black hole information paradox and black hole interiors. “What I really like,” he said, “is that an observer can enter the black hole and then escape to tell about what she saw.” This suggests that black hole interiors really exist, he explained, and that what goes in must come out.
The quantum connection is significant not just because it provides a lifeline to anyone at risk of death by black hole. Most physicists are constantly struggling with how reconcile space-time geometry, governed by general relativity, with the new science of quantum mechanics. The so-called ER = EPR conjecture, originally posed by Juan Maldacena of the Institute for Advanced Study in Princeton and Leonard Susskind of Stanford University, showed in 2013 that wormholes are mathematically equivalent to entangled quantum particles—a great step in the direction of a unified theory of physics.
The new traversable wormhole concept, proposed by Ping Gao and Daniel Jafferis of Harvard University and Aron Wall of Stanford University, is an extension of Maldacena’s and Susskind’s work; it implies that a traversable wormhole is, in fact, possible. Their paper equates a traversable wormhole (as opposed to a standard one) to quantum teleportation (as opposed to a pair of entangled particles).
Another problem this theory might solve is the black hole information paradox, first introduced by Stephen Hawking in 1974. He determined that black holes evaporate by slowly giving off heat in the form of particles, called “Hawking radiation.” This heat contains no information about the black hole’s contents; thus, information cannot and does not escape from a black hole. This violates a main principle of quantum theory known as “unitarity” that some people have tried to work around by making the black hole’s event horizon into a kind of firewall—something that burns matter immediately upon contact. But that scenario would mean that there’s no such thing as the interior of a black hole. A wormhole protects unitarity (the idea that information is never lost)—whatever falls into one black hole leaves the other black hole as Hawking radiation.
Wolchover’s article goes into some detail as to what this means for entangled black holes, quantum gravity, and more. Suffice it to say that black holes are some of the most fertile locales in our universe for the study of what makes the cosmos tick.