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# Hologram Within a Hologram Hints at Fate of Black Holes

Lucy Reading-Ikkanda/Quanta Magazine

Nov 19 2019

Categories:

Hard Problems, Students

Like cosmic hard drives, black holes pack troves of data into compact spaces. But ever since Stephen Hawking calculated in 1974 that these dense spheres of extreme gravity give off heat and fade away, the fate of their stored information has haunted physicists.

The problem is this: The laws of quantum mechanics insist that information about the past is never lost, including the record of whatever fell into a black hole. But Hawking’s calculation contradicted this. He applied both quantum mechanics and Albert Einstein’s theory of gravity to the space around a black hole and found that quantum jitters cause the black hole to emit radiation that’s perfectly random, carrying no information. As this happens the black hole shrinks and eventually disappears.

But does its information disappear with it, meaning quantum mechanics is wrong? Or does the problem lie with Einstein’s theory? When forced to choose, many physicists back the quantum rule and suspect that information somehow escapes in the black hole’s radiation, which in that case isn’t random after all. Figuring out how the information gets out should point the way past Einstein’s theory to a more complete quantum theory of gravity. Yet after 45 years of grappling with this “black hole information paradox,” no one has pinpointed the alleged misstep in Hawking’s calculation. [Read more.]