About Those Fearsome Black Holes? Never Mind
Published:
r. Stephen W. Hawking threw in the towel
yesterday, or at least an encyclopedia.
Dr. Hawking, the celebrated
As atonement he presented Dr. John Preskill, a
physicist from the California Institute of Technology, with a baseball encyclopedia.
The encyclopedia was the stake in a famous bet Dr. Hawking and another
Caltech physicist, Dr. Kip Thorne, made with Dr. Preskill
in 1997. Dr. Hawking and Dr. Thorne said information about what had been
swallowed by a black hole could never be retrieved from it; Dr. Preskill and many other physicists said it could. The
winner was to get an encyclopedia, from which information could be freely
retrieved.
This esoteric sounding debate is of great consequence to science, because if
Dr. Hawking had been right, it would have violated a basic tenet of modern
physics: that it is always possible to reverse time, run the proverbial film
backward and reconstruct what happened in, say, the collision of two cars or
the collapse of a dead star into a black hole.
Now, on the basis of a new calculation, Dr. Hawking has concluded that
physics is safe and information can escape from a black hole. "I want to
report that I think that I have solved a major problem in theoretical
physics," he told his colleagues, according to a transcript of his
remarks.
Standing in front of television cameras, as well as an auditorium full of
physicists, Dr. Preskill said he had always dreamed
that there would be witnesses when Dr. Hawking conceded, but "this really
exceeds my expectations," according to an account by The Associated Press.
Dr. Hawking's new calculation was received by
other physicists with reserve. They cautioned that it would take time to
understand it. Some of them emphasized that a long line of work by various
theorists in recent years suggested that information could escape from black
holes.
"Until Stephen's recent reversal, he was about the only person still
getting it wrong," said Dr. Leonard Susskind, a
theorist at Stanford.
Dr. Hawking spoke yesterday at the 17th International Conference of General
Relativity and Gravitation. He was added to the program at the last minute,
only two weeks ago, after sending a note to the organizers that he had solved
the problem.
His dramatic timing seems sure to add to his legend. Dr. Hawking, 62, has
been confined to a wheelchair for decades by amyotrophic lateral sclerosis, or
Lou Gehrig's disease, and speaks through a voice
synthesizer hooked to a computer on which he types one letter at a time.
Nevertheless, he has been one of the world's leading experts on gravity,
traveling the world constantly, training generations of graduate students at
Theorists have worried about the fate of information in black holes since
the 1960's. In 1974, Dr. Hawking stunned the world by showing that when the
paradoxical quantum laws that describe subatomic behavior were taken into
account, black holes should leak and eventually explode in a shower of
particles and radiation.
The work was, and remains, hailed as a breakthrough in understanding the
connection between gravity and quantum mechanics, the large and the small in
the universe.
But there was a hitch, as Dr. Hawking pointed out. The radiation coming out
of the black hole would be random. As a result, all information about what had
fallen in - whether it be elephants or donkeys - would be erased. In a riposte
to Einstein's famous remark that God does not play dice, rejecting quantum
uncertainty, Dr. Hawking said in 1976, "God not only plays dice with the
universe, but sometimes throws them where they can't be seen."
That was a violation of quantum theory, which says that information is
preserved, and quantum theory is a foundation of all modern physics.