About Those Fearsome Black Holes? Never Mind


Published: July 22, 2004

Dr. Stephen W. Hawking threw in the towel yesterday, or at least an encyclopedia.

Dr. Hawking, the celebrated Cambridge University cosmologist and best-selling author, declared at a scientific conference in Dublin that he had been wrong in a controversial assertion he made 30 years ago about black holes, the fearsome gravitational abysses that can swallow matter and energy, even light.

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 Cambridge and writing books like the popular "Brief History of Time." He has also married twice and fathered three children, and appeared on "The Simpsons" and "Star Trek: The Next Generation."

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.