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| Hawking: Black holes store information | Hawking: Black holes store information |
| (35 minutes later) | |
| Black holes preserve information about the stuff that falls into them, according to Prof Stephen Hawking. | Black holes preserve information about the stuff that falls into them, according to Prof Stephen Hawking. |
| Physicists have long argued about what happens to information about the physical state of things that are swallowed up by black holes. | Physicists have long argued about what happens to information about the physical state of things that are swallowed up by black holes. |
| It was thought that this information was destroyed, but it turned out that this violated laws of quantum physics. | It was thought that this information was destroyed, but it turned out that this violated laws of quantum physics. |
| Prof Hawking now says the information may not make it into the black hole at all, but is held on its boundary. | Prof Hawking now says the information may not make it into the black hole at all, but is held on its boundary. |
| "The information is not stored in the interior of the black hole as one might expect, but in its boundary - the event horizon," he told a conference at the KTH Royal Institute of Technology in Stockholm, Sweden. | "The information is not stored in the interior of the black hole as one might expect, but in its boundary - the event horizon," he told a conference at the KTH Royal Institute of Technology in Stockholm, Sweden. |
| In broad terms, black holes are a region in space where the gravity is so strong that nothing that gets pulled in - even light - can escape. | In broad terms, black holes are a region in space where the gravity is so strong that nothing that gets pulled in - even light - can escape. |
| At the same time, the laws of quantum mechanics dictate that everything in our world can be broken down into information, for example, a string of 1s and 0s. And according to those laws, this information should never disappear, not even if it gets sucked into a black hole. | At the same time, the laws of quantum mechanics dictate that everything in our world can be broken down into information, for example, a string of 1s and 0s. And according to those laws, this information should never disappear, not even if it gets sucked into a black hole. |
| But according to Einstein's theory of general relativity, the information must be destroyed. This quandary is known as the information paradox. | |
| Prof Hawking believes the information doesn't make it inside the black hole at all. Instead, it is transformed into a 2D hologram at the surface of the black hole's event horizon. This is a boundary, or point of no return, where escape from the gravitational pull of the black hole becomes impossible. | |
| Working with Cambridge colleague Prof Malcolm Perry and Harvard professor Andrew Strominger, Hawking believes that information is stored in the form of what are known as super translations. | Working with Cambridge colleague Prof Malcolm Perry and Harvard professor Andrew Strominger, Hawking believes that information is stored in the form of what are known as super translations. |
| "The idea is the super translations are a hologram of the ingoing particles," Hawking explained. | "The idea is the super translations are a hologram of the ingoing particles," Hawking explained. |
| "Thus, they contain all the information that would otherwise be lost." | "Thus, they contain all the information that would otherwise be lost." |
| Prof Marika Taylor, a theoretical physicist at the University of Southampton, told BBC News: "Einstein's theory says that matter gets sucked into the black hole, falling behind its event horizon. | Prof Marika Taylor, a theoretical physicist at the University of Southampton, told BBC News: "Einstein's theory says that matter gets sucked into the black hole, falling behind its event horizon. |
| "Holography seems to suggest that Einstein's picture of black holes isn't right. In particular, it's not clear that there is actually an 'inside' to black holes at all - matter which gets sucked in might get stuck at the event horizon and hang around as a hologram there." | "Holography seems to suggest that Einstein's picture of black holes isn't right. In particular, it's not clear that there is actually an 'inside' to black holes at all - matter which gets sucked in might get stuck at the event horizon and hang around as a hologram there." |
| But she added that there was no consensus on this. | But she added that there was no consensus on this. |
| On the question of matter getting stuck at the event horizon, she said: "Nobody really understands the details of how this happens - this is what Hawking is trying to work out and what other related ideas 'fuzzball' and 'firewall' explore too." | On the question of matter getting stuck at the event horizon, she said: "Nobody really understands the details of how this happens - this is what Hawking is trying to work out and what other related ideas 'fuzzball' and 'firewall' explore too." |
| There's currently little additional detail on the maths behind Prof Hawking's talk, but he and his collaborators plan to publish a scientific paper in coming weeks. | There's currently little additional detail on the maths behind Prof Hawking's talk, but he and his collaborators plan to publish a scientific paper in coming weeks. |
| Light particles - or photons - can be emitted from black holes due to quantum fluctuations, a concept known as Hawking radiation. Information from the black hole might be able to escape via this route. | Light particles - or photons - can be emitted from black holes due to quantum fluctuations, a concept known as Hawking radiation. Information from the black hole might be able to escape via this route. |
| But, Prof Hawking says it would be in "chaotic, useless form," adding: "For all practical purposes the information is lost." | But, Prof Hawking says it would be in "chaotic, useless form," adding: "For all practical purposes the information is lost." |
| If the information was not in this chaotic form, an observer might be able to reconstruct everything that had fallen into the black hole over a vast amount of time. | |
| Follow Paul on Twitter. | Follow Paul on Twitter. |