Information, Please

Betting on whether data disappear down black holes

Ron Cowen

Can the universe keep a secret? Suppose you realize there's incriminating evidence in your diary. You could shred the diary to bits, but a tenacious detective could reassemble them into the original document. You could burn your diary, but physicists will tell you that—at least in theory—the ash, carbon dioxide, and other products of the combustion provide all the information needed to reconstruct every page. Desperate, you resort to the ultimate solution: Drop the diary into a black hole. Surely, your secret will be safe there.

Until recently, the celebrated University of Cambridge cosmologist Stephen J. Hawking would have agreed with you. But after nearly 30 years, Hawking has reversed his opinion. Even black holes can't destroy information, he announced in July at the International Conference on General Relativity and Gravitation in Dublin.

This change of heart aligns Hawking with most physicists, who long ago adopted as a sacred and an immutable law the concept that information, like energy, is never destroyed. But mind-bending paradoxes emerge when scientists try to figure out what happens when information falls into a black hole.

According to one perspective, information seems to be in two places at once.

Understanding these paradoxes isn't merely an esoteric undertaking, says theorist Andrew Strominger of Harvard University. With the answer to the black hole riddle, scientists will be better equipped to solve one of the most challenging problems in all of physics: tying together quantum theory, which rules the domain of the very small, and general relativity, the highly successful theory of gravity developed by Albert Einstein in 1915….

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“Information, Please: Betting on whether data disappear Joe Stud Student down black holes” Physical Science

Science News Oct. 11, 2004

Sept. 25, 2004 ( Vol. 166, No. 13)

p. 202

Since Steven Hawking came up with his theory of black holes about 30 years ago, he thought that anything that was pulled into one was completely destroyed and lost forever. However many physicists didn’t think that was true, and even Hawking has recently changed his mind about black holes.

At a conference in Dublin in July, 2004, Hawking announced “even black holes can't destroy information.” This is an idea that many physicists think is similar to the law of conservation of energy—that, like energy, information can never be destroyed (though, personally, I think it can be created…unlike energy).

Though this is all theoretical, scientists hope to be able to use the ideas from this black holes research into uniting the quantum theory and general relativity.