Black holes may have soft hair (say Stephen Hawking and colleagues)
| By The Cosmos
An article in the New York Times by Dennis Overbye gives the latest chapter in Stephen Hawkingâ€™s saga concerning whether the properties of matter that has fallen into a black hole are lost forever, or whether there is a way out. Forty years ago, Hawking showed theoretically that black holes were not â€˜eternal prisonsâ€™ but could leak radiation. There ensuedÂ a long-running debate about whether this radiation retained any information or attributes of the original matter. If it does not, this violates a tenet of modern physics, that it is alwaysÂ possible, in theory, to reverse time. This became known as the â€˜information paradoxâ€™ and was the subject of a famous bet between Hawking and Caltech professor John Preskill.Â (Hawking conceded defeatÂ 10 years ago, admitting that advances in string theory, had left no room in the universe for information loss.) In a paper published to be published this week in Physical Review Letters,Â Hawking and his colleagues Andrew StromingerÂ (Harvard) and Malcolm PerryÂ (Cambridge) announce they have found a clue pointing the way out of black holes. They new results undermineÂ John Wheelerâ€™s famous notion that black holes have â€œno hairâ€ â€” that they are shorn of the essential properties of the things they have consumed. Looked at from the right vantage pointÂ â€” from a far distance in time,Â technically known as â€œnull infinityâ€ â€” black holes might not be not be bald at all. A tell-tale pattern of light rays bordering the event horizon contains information about what has passed through.Â This has been dubbed in their paper a â€œsoft hairâ€ theory. For a more complete description of this story, see the full NYT article. In a subsequent article, Dennis Overbye answers questionsÂ on black holes submitted by hisÂ readers.