Ref: http://physicsweb.org/article/news/8/7/11
Hawking loses black hole bet
22 July 2004
Stephen Hawking revealed his eagerly awaited solution to the black
hole information paradox at a conference in Dublin yesterday. In
doing so he conceded that he had lost a bet that he and Caltech
theorist Kip Thorne had made with John Preskill, also of Caltech,
about black holes. However, Thorne has yet to be convinced by
Hawking's arguments.
Classical black holes are regions of space where gravity is so strong
that nothing, not even light, can escape from them. The region beyond
which nothing can escape is known as the event horizon. All the
information in the light and matter that falls through the event
horizon is lost forever because the black hole can be described by
just three numbers: its mass, electric charge and angular momentum.
In the 1970s, however, building on earlier work by Jacob Bekenstein
and applying quantum theory to black holes, Hawking showed that these
mysterious objects also have a temperature, which means that they
give off thermal radiation. The black holes should therefore
eventually disappear. The problem is that this thermal radiation does
not contain any information, which means that the information that
originally fell into the black hole disappears. However, this is not
allowed by quantum theory.
In their bet, which was made in 1997, Hawking -- who is based at
Cambridge University -- and Thorne argued that information was lost
in a black hole, whereas Preskill said that it was not. The winner or
winners of the bet had to provide the loser or losers with an
encyclopaedia of their choice "from which information can be
recovered with ease".
Now Hawking has conceded defeat by saying that information can escape
from a black hole and therefore is not lost. If he is right, making a
such a significant breakthrough in the search for a quantum theory of
gravity should overcome the disappointment of losing the bet and
having to hand over an encyclopaedia of baseball to Preskill. "It is
great to solve a problem that has been troubling me for 30 years,"
said Hawking, "even though the answer is less exciting than the
alternative I suggested."
Hawking presented his solution to the 17th International Conference
on General Relativity and Gravitation in Dublin. His solution relies
on a black hole being able to have more than one topology at the same
time, and when he performs a quantum mechanical "path integral" over
all the topologies, he finds that information is not lost. "The way
the information gets out [of a black hole] seems to be that a true
event horizon never forms," said Hawking, "just an apparent
horizon."
Hawking also dismisses his previous suggestion that the information
might have leaked into a different "Baby" universe. "The information
remains firmly in our universe," he told the conference. "I am 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 the
information about what you were like, but in an unrecognisable
state."
.
|
