Nothing can escape a black hole\’s event horizon — yet new research suggests it can secretly leak information. The study authors say this leaking would show up in subtle signals in gravitational waves, and now we know how to look for them.
In 1976, Stephen Hawking rocked the astrophysics world with his discovery that black holes aren\’t completely black. Instead, they emit tiny amounts of radiation and, given enough time, can emit so much radiation that they disappear completely. But this created a big problem.
Information flows into black holes as they consume matter, and that information can\’t escape. But Hawking radiation doesn\’t take any information with it. So what happens to a black hole when it disappears?
This \”black hole information paradox\” has puzzled researchers for decades, and they\’ve developed several possible solutions. One is known as nonlocal nonlocality. In this scenario, the interiors of black holes are connected to their exteriors through \”quantum nonlocality\” — in which correlated particles share the same quantum state — an effect that Einstein called \”spooky action at a distance.\”
This nonlocality is \”nonviolent\” because there\’s no energetic thing like an explosion or merger that\’s causing the incoming gravitational waves — ripples in space-time outside the black hole. Rather, they\’re being caused by quantum connections between the inside and outside of the black hole.
If this hypothesis is true, there are tiny disturbances in space-time around black holes that aren\’t completely random. Instead, the variations would be correlated with information inside the black hole. Then, when the black hole disappears, information is preserved outside of it, thus resolving the paradox.
In a recent preprint paper that has not yet been peer-reviewed, researchers at Caltech examined this intriguing hypothesis to find out how we might test it.
The researchers found that these non-local quantum correlations don\’t just leave an imprint in the space-time surrounding black holes; they also leave a signature in the gravitational waves emitted when black holes merge. These signatures exist as tiny fluctuations above the main gravitational wave signal, but they have a unique spectrum that clearly distinguishes them from normal waves.
The researchers outlined a program to isolate this special signal. They found that existing gravitational wave detectors, such as the Laser Interferometer Gravitational-Wave Observatory and the Virgo Interferometer, don\’t have the sensitivity to comprehensively determine whether non-locality is an accurate solution to the black hole information paradox.
But next-generation instruments that are currently being designed and built might be able to do just that. The next step in the research is to create even more accurate models of how non-violent non-locality affects the space-time around realistic black holes. This would allow accurate predictions of changes in the gravitational wave signal – and could also resolve the infamous paradox.