BREAKING: This Newfound Wormhole Allows Information to Escape Black Holes

In 1985, when the great Carl Sagan was writing the novel Contact, he needed to quickly transport his protagonist Dr. Ellie Arroway from Earth to the star Vega. He had her enter a black hole and exit light- years away, but he did not know if this made any sense.

 A wormhole split in two with swirls of blue on one side and swirls of pink on the other with a ringed planet in the background.

The Cornell University (CU) astrophysicist and television star consulted his friend Kip Thorne, a black hole expert at the California Institute of Technology (who won a Nobel Prize earlier this month). Thorne knew that Arroway couldn’t get to Vega via a black hole, which is thought to trap and destroy anything that falls in. But it occurred to him that she might make use of another kind of hole consistent with Albert Einstein’s general theory of relativity: a tunnel or “wormhole” connecting distant locations in space-time.

While the simplest theoretical wormholes immediately collapse and disappear before anything can get through, Thorne wondered whether it might be possible for an “infinitely advanced” sci-fi civilization to stabilize a wormhole long enough for something or someone to traverse it. He figured out that such a civilization could in fact line the throat of a wormhole with “exotic material” that counteracts its tendency to collapse. The material would possess negative energy, which would deflect radiation and repulse space-time apart from itself. Sagan used the trick in Contact, attributing the invention of the exotic material to an earlier, lost civilization to avoid getting into particulars. Meanwhile, those particulars enthralled Thorne, his students and many other physicists, who spent years exploring traversable wormholes and their theoretical implications. They discovered that these wormholes can serve as time machines, invoking time-travel paradoxes — evidence that exotic material is forbidden in nature.

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.

 A wormhole connects distant locations in space. Illustration shows 2 Wormhole mouths in space connected by a tunnel, called a throat The simplest theoretical wormholes immediately close off because the throat is attracted to itself. Showng the tunnel collapsed, leaving just the two mouths, which are now called black holes. A quantum connection between the mouths could thwart a throat collapse, allowing something to travel through the wormhole. Showing a Quantum connection as a glow around the mouths, which has Stabilizing effects on the wormhole tunnel

Lucy Reading-Ikkanda/Quanta Magazine

The new wormhole work began in 2013, when Jafferis attended an intriguing talk at the Strings conference in South Korea. The speaker, Juan Maldacena, a professor of physics at the Institute for Advanced Study in Princeton, New Jersey, had recently concluded, based on various hints and arguments, that “ER = EPR.” That is, wormholes between distant points in space-time, the simplest of which are called Einstein-Rosen or “ER” bridges, are equivalent (albeit in some ill-defined way) to entangled quantum particles, also known as Einstein-Podolsky-Rosen or “EPR” pairs. The ER = EPR conjecture, posed by Maldacena and Leonard Susskind of Stanford, was an attempt to solve the modern incarnation of the infamous black hole information paradox by tying space-time geometry, governed by general relativity, to the instantaneous quantum connections between far-apart particles that Einstein called “spooky action at a distance.”

The paradox has loomed since 1974, when the British physicist Stephen Hawking determined that black holes evaporate — slowly giving off heat in the form of particles now known as “Hawking radiation.” Hawking calculated that this heat is completely random; it contains no information about the black hole’s contents. As the black hole blinks out of existence, so does the universe’s record of everything that went inside. This violates a principle called “unitarity,” the backbone of quantum theory, which holds that as particles interact, information about them is never lost, only scrambled, so that if you reversed the arrow of time in the universe’s quantum evolution, you’d see things unscramble into an exact re-creation of the past.

Almost everyone believes in unitarity, which means information must escape black holes — but how? In the last five years, some theorists, most notably Joseph Polchinski of the University of California, Santa Barbara, have argued that black holes are empty shells with no interiors at all — that Ellie Arroway, upon hitting a black hole’s event horizon, would fizzle on a “firewall” and radiate out again.

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