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Articles: A black hole theory zapped

Posted by admin on Thursday, July 22, 2004 - 01:22 AM

Renowned physicist Stephen Hawking yesterday conceded he was wrong about a long-held idea about black holes, backing off a theory that had raised the tantalizing possibility that the collapsed stars were swallowing information and sending it to alternate universes.
Hawking, who became a household name and cultural icon for his groundbreaking contributions to the understanding of the cosmos, announced at a Dublin research conference that he had reworked a theory that he proposed in 1975, and which had split physics for years: the notion that a black hole is so powerful that it not only swallows up light and matter, but also destroys all information about those things. That idea contradicts a fundamental tenet of modern physics, which says information cannot be destroyed. It also raised speculations that the information that seemed to be gone might be sent to another universe. The conflict energized physics, and the surprise addition of Hawking to the conference's list of speakers sparked buzz last week throughout the science world. ''I am sorry to disappoint science fiction fans," he said. ''But if you jump into a black hole, your mass energy will be returned to our universe, but in a mangled form. ''There is no baby universe branching off [inside a black hole], as I once thought," said Hawking, who speaks through a computerized device and uses a wheelchair. He has Lou Gehrig's disease. His announcement also settled a bet made a few years ago with physicist John Preskill of the California Institute of Technology, who wagered an encyclopedia that Hawking's theory was wrong. ''I'm now ready to concede the bet," Hawking said yesterday. ''I will give John Preskill the encyclopedia he has requested. John is all-American, so naturally he wants an encyclopedia of baseball." Since Hawking proposed the theory in 1975, mainstream thought in physics has moved away from his idea that black holes can destroy information. Preskill, who has had more than one wager with Hawking, made the bet in 1997, as the more recent school of physics called string theory emerged with arguments that black holes released the information they sucked in. ''I would view [Hawking's concession] as kind of a natural step in the evolution of the way the entire physics community has been thinking," said physicist and cosmologist Alan Guth, of the Massachusetts Institute of Technology. Many physicists yesterday said they were interested that the father of the black hole problem had joined the mainstream. ''Hawking was perhaps among the very few holdouts," said physicist Samir Mathur, of Ohio State University. ''It was high time to give up on the bet because of all the things that have happened in string theory over the past 10 years." Hawking's charismatic public persona and fame as best-selling author of ''A Brief History of Time" drew an unusual amount of attention to the 17th International Conference on General Relativity and Gravitation, which otherwise would have been a low-profile event. After Hawking submitted a terse request to appear at the conference, a buzz built up among physicists and the popular press about what he might say. Yesterday about 700 physicists, and dozens of journalists were on hand for his presentation. Hawking will lay out his retraction in fuller form in a research paper, to be published next month. In his talk, Hawking said that in fact, information can escape a black hole, suggesting it leaked out of irregularities on the surface -- although that information would be transformed from its original state. If a person were to jump into a black hole, Hawking said yesterday, he or she eventually would be returned to the universe ''in a mangled form, which contains the information about what you were like, but in an unrecognizable state." This dismisses speculation about the possibility of using black holes as a portal to other universes. But for some physicists who have been watching from afar, the presentation was unsatisfying because Hawking has not explained why his original, elegant argument was wrong. Earlier this week, when Hawking's retraction was still only rumor, string theorist Andrew Strominger of Harvard University suggested that continued study of the original problem would be worth the time: ''This puzzle that Hawking raised is going to be one of the things that drives us on to the next revolution of the understanding of the laws of nature." The announcement yesterday did not change Strominger's mind. ''I wouldn't have accepted the encyclopedia because I don't think the issue is closed," he said.

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