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Stephen Hawking recently said that black holes do not exist. According to Wikipedia, black holes are predicted by General Relativity. So it would seem to follow that Stephen Hawking believes that General Relativity is wrong.

Am I missing something?

Craig Feinstein
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    When I see a question like this my first instinct is to ask "Did you read the paper? Or even the abstract?" – dmckee --- ex-moderator kitten Jan 29 '14 at 16:37
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    Yes, I read the paper, but I'm not an expert on physics. – Craig Feinstein Jan 29 '14 at 16:40
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    @CraigFeinstein I think you did not read the academic paper published by Hawking. A careful examination will show you that he never asserts that black holes don't exist. – Danu Jan 29 '14 at 16:41
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    He said, "The absence of event horizons mean that there are no black holes." He also says, "A different resolution of the paradox is proposed, namely that gravitational collapse produces apparent horizons but no event horizons behind which information is lost." These two statements together imply that he believes that black holes don't exist. – Craig Feinstein Jan 29 '14 at 16:47
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    The continuation of the first quote is, in the sense of regimes from which light can't escape to infinity. That is, there are no event horizons (what your 2nd quote says) which is different from the black hole itself. – Kyle Kanos Jan 29 '14 at 16:53
  • The 2nd sentence after your selective first quote also says, This suggests that black holes should be redefined as metastable bound states of the gravitational field. Is that unambiguous enough an assertion that he believes BHs do exist? – Kyle Kanos Jan 29 '14 at 16:54
  • But you can't have a black hole without an event horizon in the sense of regimes from which light can't escape to infinity. Otherwise, the hole can't be black since light can escape. But I thought GR predicts black holes. – Craig Feinstein Jan 29 '14 at 16:56
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    All the news outlets are reporting that he said that black holes don't exist. – Craig Feinstein Jan 29 '14 at 16:58
  • I think when he says, "This suggests that black holes should be redefined as metastable bound states of the gravitational field", he means that black holes don't exist, so you have to redefine the phenemonon that was once assumed to be explained by a black hole as something else. – Craig Feinstein Jan 29 '14 at 17:07
  • Isn't the point of his paper to show that you can't have an event horizon due to the information problem? – Kyle Kanos Jan 29 '14 at 18:15

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No, he does not think that GR is wrong. Actually, in his article on arxiv, he gives some ideas in order to (try to) solve a problem associated to the information paradox for evaporating black holes. That would mean that the usual idea of black hole we have would not longer be accurate. It does not imply that GR is wrong (at least on the domain of validity where we believe it provides a pretty good description of physics).

LoveU
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  • So then we have a contradiction. If he doesn't believe in BHs but believes in GR, this contradicts the conventional wisdom that GR implies BHs, as is stated in the Wikipedia article on BHs. – Craig Feinstein Jan 29 '14 at 18:21
  • Someone should update the Wikipedia article. – Craig Feinstein Jan 29 '14 at 18:21
  • Not really. Because what Hawking is talking about is actually on the wedge of validity of GR. It does involve quantum effects ; something that GR is not able to take into account. To be accurate, nobody believes in GR because we know there should be another theory to describe quantum gravity. But, as long as some assumptions are verified, GR is a theory that describe the physics of gravitation in a very convincing way. And if you have even more restricting assumptions, you don't need GR ; you can use Newtonian theory. It will gives you very good results, as long as used in a correct framework. – LoveU Jan 29 '14 at 22:55