Black holes do not obliterate information about things which fall into them, but mangle information instead. So says Stephen Hawking, backtracking on his own theory about black holes after 30 years.

The physicist was forced to concede a bet he made with American theoretical physicist John Preskill in 1997 as he unveiled his new theory on Wednesday. Preskill had doubted Hawking’s theory that black holes destroy everything that falls into them. Hawking now says information can escape from within them.

He revealed his new theory to a packed auditorium at a conference in Dublin, Ireland on Wednesday. New Scientist broke the news on 14 July that Hawking, at the University of Cambridge, had changed his mind about black holes after solving a long-standing paradox in physics.

“I want to report that I think I have solved a major problem in theoretical physics,” announced Hawking as he described his solution to the black hole information paradox.


This paradox, ironically, stems from Hawking’s own work. In the 1970s he proved that black holes lose mass by emitting radiation and eventually evaporate altogether.

Science fiction

But this conflicted with the laws of quantum physics, which state that information about what fell into the black hole can never be completely wiped out. Hawking previously argued that the intense gravitational fields inside the black hole were unravelling the laws of quantum mechanics, possibly sending the information shooting off into other universes. Now he thinks the information simply leaks out back into our own Universe.

Hawking explains the implications. “I’m sorry to disappoint science fiction fans, but if information is preserved, there is no possibility of using black holes to travel to other universes.

“If you jump into a black hole, your mass energy will be returned to our Universe, but in a mangled form, which contains information about what you were like, but in an unrecognisable state.”

In concluding that information escapes, Hawking’s views have come into line with ideas that other theorists have been pushing for years.

For example, if a black hole is modelled according to string theory – in which the universe is made of tiny, vibrating strings rather than point-like particles – there are pretty convincing arguments that say information can get out, according to Joseph Polchinski from the University of California in Santa Barbara, US.

Cricket alternative

“We’re getting the same conclusions using some of the same tools,” says Polchinski.

Hawking reached his solution by considering what happened to black holes of all different shapes and sizes after an infinite amount of time. He showed that the amount of information at the end was equal to the amount of information at the beginning, but said nothing about what happened to it in the middle.

Hawking also failed to completely convince Kip Thorne, a physicist from the California Institute of Technology, and his betting partner, that he had resolved the paradox.

But Hawking was ready to concede the bet that he and Thorne had made with Preskill. “John is all American, so naturally he wants an encyclopaedia of baseball,” said Hawking. “I had great difficulty in finding one over here, so I offered him an encyclopaedia of cricket, as an alternative, but John wouldn’t be persuaded of the superiority of cricket.”