Science

Prof Hawking cracks riddle of black holes – which may be portals to other universes

Top boffin reckons he's made a Quantum Leap of science

Professor Stephen Hawking thinks he has solved the 40-year-old information paradox – a conundrum of what happens to matter in black holes.

Matter that gets sucked into a black hole was thought to be destroyed by the immense forces involved, as per the theory of general relativity. However, that's a problem from a quantum mechanics point of view, because matter's information about its physical state is supposed to be permanent – so throwing it all away when it enters a black hole would create a paradox.

Forty years ago, Professor Hawking wrote a highly controversial paper suggesting that black holes emit radiation. Initially, he thought that this Hawking radiation, as it is now known, couldn't account for the information paradox, although he amended his theory to state that some information may escape.

Now Prof Hawking proposes that the information about matter sucked into a black hole is preserved albeit in a 2D format. In a lecture on Tuesday at the Swedish KTH Royal Institute of Technology, Prof Hawking explained that in April he'd been inspired by a talk given by Harvard's Professor Andrew Strominger, and now thinks that the sucked-in matter's information is stored in the black hole – in a "super translation."

"The information is not stored in the interior of the black hole as one might expect, but in its boundary – the event horizon," Prof Hawking said. "The idea is the super translations are a hologram of the ingoing particles, thus they contain all the information that would otherwise be lost."

While the information is stored, the translation into hologramatic mode renders it into a "chaotic, useless form," the professor added. "For all practical purposes the information is lost."

Prof Hawking theorizes that as a black hole runs out of matter to consume, its radiation output will cause it to shrink and evaporate. The information stored in the event horizon would be transmitted back to our universe via Hawking radiation, and possibly down the hole and into other universes.

"The existence of alternative histories with black holes suggests this might be possible," Prof Hawking said. "The hole would need to be large, and if it was rotating it might have a passage to another universe. But you couldn't come back to our universe. So although I'm keen on space flight, I'm not going to try that."

The idea about information being stored in the event horizon is not new – Professor Gerard 't Hooft and others proposed this two decades ago, but Prof Hawking's view carries a lot of weight in the scientific community. More details on the proposal will be shared later in the week.

"I claim he is now where I was 20 years ago," 't Hooft told the Wall Street Journal today. "If he announces this as a new idea, I won't be thrilled." ®

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