Since the 1970’s when Stephen Hawking pioneered black hole theory, he has maintained that when an object falls into a black hole, no information can escape, it is lost forever. Hawking's view at that time and up to recently (2004) follows Einstein’s general theory of relativity.
Relativity predicts that at certain locations in space, matter collapses into an infinitely small and dense point, called a singularity. The force of gravity at this point is so great that nothing, not even light can escape, the reason for the name ‘black hole’.
Because the singularity is so small (infinitely small), it cannot have any structure, therefore it cannot hold information. Any data about particles entering a black hole will be lost forever.
Unfortunately quantum physics does not agree with this prediction of general relativity. Quantum theory says that any process can be run in reverse, therefore starting conditions can in theory be inferred from the end products alone. The implication is obvious – a black hole must somehow store information about the objects that fell into it – even if we can never access that information.
In 2004 Hawking changed his position, he now believes that information is stored and can escape a black hole. This reversal of position is the result of Hawking’s attempt to combine quantum theory with general relativity, in a powerful theory of quantum gravity. He used a mathematical technique called the “Euclidean path integral”. This is a very complex technique that lumps all the possible histories of a system into one equation. This mathematical technique was first used by Richard Feynman (one of my favorite physicists) and is generally applied to subatomic particles. Hawking has been steadily working for years on applying it to black holes. "The view seems to be forming in his mind that there isn't a black hole in the absolute sense, there's just a region where things take a very long time to escape," says Hawking's Cambridge University colleague Gary Gibbons. This implies that black holes do not actually narrow to a singularity at all.
This means that an object entering a black hole is not completely destroyed. Instead, the black hole is altered as it absorbs the object. Even though it would almost certainly be impossible to access and information about the object, the data is still there – inside the black hole.
One may ask how information can possibly ever escape a black hole. To answer that we need to look at one of Hawking’s greatest discoveries – black holes slowly evaporate into space by losing particles at the edge of the event horizon, this is called Hawking radiation. Eventually the black hole will shrink to the size of a tiny kernel, at which point a growing torrent of radiation starts to leak out, possibly carrying the lost information with it.
It is unlikely that this change in position will be embraced by the scientific community, Preskill says that Hawking’s new position on quantum gravity rests on shaky mathematical foundations, “I am skeptical about whether he has found a fully satisfactory resolution to the problem,” he says. Only time will tell.
This about face by Hawking means he loses a long-standing bet with John Preskill, a theoretical physicist at the California Institute of Technology. In the bet Hawking maintained that anything gobbled up by a black hole was forever hidden from the outside universe. Preskill bet that the information carried by an object was not destroyed when it falls into a black hole; the information could actually be recovered. "Stephen has changed his position, and I am expecting him to concede the bet," Preskill says. His prize is to be an encyclopedia, "from which information can be recovered at will". After Hawking admitted he had been wrong, his original offer of a cricket encyclopedia was turned down in favor of “Total Baseball: The Ultimate Baseball Encyclopedia”. Preskill told the assembled media he had always hoped there would be witnesses when Hawking conceded, but “this really exceeds my expectations.”
Relativity predicts that at certain locations in space, matter collapses into an infinitely small and dense point, called a singularity. The force of gravity at this point is so great that nothing, not even light can escape, the reason for the name ‘black hole’.
Because the singularity is so small (infinitely small), it cannot have any structure, therefore it cannot hold information. Any data about particles entering a black hole will be lost forever.
Unfortunately quantum physics does not agree with this prediction of general relativity. Quantum theory says that any process can be run in reverse, therefore starting conditions can in theory be inferred from the end products alone. The implication is obvious – a black hole must somehow store information about the objects that fell into it – even if we can never access that information.
In 2004 Hawking changed his position, he now believes that information is stored and can escape a black hole. This reversal of position is the result of Hawking’s attempt to combine quantum theory with general relativity, in a powerful theory of quantum gravity. He used a mathematical technique called the “Euclidean path integral”. This is a very complex technique that lumps all the possible histories of a system into one equation. This mathematical technique was first used by Richard Feynman (one of my favorite physicists) and is generally applied to subatomic particles. Hawking has been steadily working for years on applying it to black holes. "The view seems to be forming in his mind that there isn't a black hole in the absolute sense, there's just a region where things take a very long time to escape," says Hawking's Cambridge University colleague Gary Gibbons. This implies that black holes do not actually narrow to a singularity at all.
This means that an object entering a black hole is not completely destroyed. Instead, the black hole is altered as it absorbs the object. Even though it would almost certainly be impossible to access and information about the object, the data is still there – inside the black hole.
One may ask how information can possibly ever escape a black hole. To answer that we need to look at one of Hawking’s greatest discoveries – black holes slowly evaporate into space by losing particles at the edge of the event horizon, this is called Hawking radiation. Eventually the black hole will shrink to the size of a tiny kernel, at which point a growing torrent of radiation starts to leak out, possibly carrying the lost information with it.
It is unlikely that this change in position will be embraced by the scientific community, Preskill says that Hawking’s new position on quantum gravity rests on shaky mathematical foundations, “I am skeptical about whether he has found a fully satisfactory resolution to the problem,” he says. Only time will tell.
This about face by Hawking means he loses a long-standing bet with John Preskill, a theoretical physicist at the California Institute of Technology. In the bet Hawking maintained that anything gobbled up by a black hole was forever hidden from the outside universe. Preskill bet that the information carried by an object was not destroyed when it falls into a black hole; the information could actually be recovered. "Stephen has changed his position, and I am expecting him to concede the bet," Preskill says. His prize is to be an encyclopedia, "from which information can be recovered at will". After Hawking admitted he had been wrong, his original offer of a cricket encyclopedia was turned down in favor of “Total Baseball: The Ultimate Baseball Encyclopedia”. Preskill told the assembled media he had always hoped there would be witnesses when Hawking conceded, but “this really exceeds my expectations.”
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