The Cosmos

An article in the New York Times by Dennis Overbye gives the latest chapter in Stephen Hawking’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 ‘eternal prisons’ but could leak radiation. There ensued 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 always possible, in theory, to reverse time. This became known as the ‘information paradox’ and was the subject of a famous bet between Hawking and Caltech professor John Preskill. (Hawking conceded defeat 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, Hawking and his colleagues Andrew Strominger (Harvard) and Malcolm Perry (Cambridge) announce they have found a clue pointing the way out of black holes. They new results undermine John Wheeler’s famous notion that black holes have “no hair” — that they are shorn of the essential properties of the things they have consumed.

Looked at from the right vantage point — from a far distance in time, technically known as “null infinity” — 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. This has been dubbed in their paper a “soft hair” theory.

For a more complete description of this story, see the full NYT article.

In a subsequent article, Dennis Overbye answers questions on black holes submitted by his readers.