[extropy-chat] Hawking says information *can* escape black holes

[Damien Broderick]

 From New Scientist:

Hawking cracks black hole paradox

19:00 14 July 04

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After nearly 30 years of arguing that a black hole destroys everything that 
falls into it, Stephen Hawking is saying he was wrong. It seems that black 
holes may after all allow information within them to escape. Hawking will 
present his latest finding at a conference in Ireland next week.

The about-turn might cost Hawking, a physicist at the University of 
Cambridge, an encyclopaedia because of a bet he made in 1997. More 
importantly, it might solve one of the long-standing puzzles in modern 
physics, known as the black hole information paradox.

It was Hawking's own work that created the paradox. In 1976, he calculated 
that once a black hole forms, it starts losing mass by radiating energy. 
This "Hawking radiation" contains no information about the matter inside 
the black hole and once the black hole evaporates, all information is lost.

But this conflicts with the laws of quantum physics, which say that such 
information can never be completely wiped out. Hawking's argument was that 
the intense gravitational fields of black holes somehow unravel the laws of 
quantum physics.

Other physicists have tried to chip away at this paradox. Earlier in 2004, 
Samir Mathur of Ohio State University in Columbus and his colleagues showed 
that 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 - then the black hole becomes a giant tangle of strings. And the 
Hawking radiation emitted by this "fuzzball" does contain information about 
the insides of a black hole (New Scientist print edition, 13 March).


Big reputation

Now, it seems that Hawking too has an answer to the conundrum and the 
physics community is abuzz with the news. Hawking requested at the last 
minute that he be allowed to present his findings at the 17th International 
Conference on General Relativity and Gravitation in Dublin, Ireland.

"He sent a note saying 'I have solved the black hole information paradox 
and I want to talk about it'," says Curt Cutler, a physicist at the Albert 
Einstein Institute in Golm, Germany, who is chairing the conference's 
scientific committee. "I haven't seen a preprint [of the paper]. To be 
quite honest, I went on Hawking's reputation."

Though Hawking has not yet revealed the detailed maths behind his finding, 
sketchy details have emerged from a seminar Hawking gave at Cambridge. 
According to Cambridge colleague Gary Gibbons, an expert on the physics of 
black holes who was at the seminar, Hawking's black holes, unlike classic 
black holes, do not have a well-defined event horizon that hides everything 
within them from the outside world.

In essence, his new black holes now never quite become the kind that gobble 
up everything. Instead, they keep emitting radiation for a long time, and 
eventually open up to reveal the information within. "It's possible that 
what he presented in the seminar is a solution," says Gibbons. "But I think 
you have to say the jury is still out."


Forever hidden

At the conference, Hawking will have an hour on 21 July to make his case. 
If he succeeds, then, ironically, he will lose a bet that he and 
theoretical physicist Kip Thorne of the California Institute of Technology 
(Caltech) in Pasadena made with John Preskill, also of Caltech.

They argued that "information swallowed by a black hole is forever hidden, 
and can never be revealed".

"Since Stephen has changed his view and now believes that black holes do 
not destroy information, I expect him [and Kip] to concede the bet," 
Preskill told New Scientist. The duo are expected to present Preskill with 
an encyclopaedia of his choice "from which information can be recovered at 
will".


Jenny Hogan