Black Hole Bets

The original version of a bet on whether naked singularities exist was established on 24 September 1991. Roughly speaking, a singularity arises when gravitational forces are so strong that quantum fluctuations in the geometry of spacetime become large. Usually, singularities occur only inside black holes where they remain invisible to observers who remain outside. A naked singularity occurs outside a black hole, and so might be safely observed. John Preskill and Kip Thorne took the position that naked singularities are possible, while Stephen Hawking bet that they are impossible. Hawking conceded  "on a technicality" on 5 February 1997, accepting that naked singularities can form under very special "nongeneric" conditions.

A new version of the bet on naked singularitites was then established on 5 February 1997, concerning whether naked singularities can also form under "generic" conditions.

Another bet, established on 6 February 1997, concerns what happens to information that is hidden behind the event horizon of a black hole. The issue is whether the information is destroyed and lost forever or might  in principle be recovered from the radiation that is emitted as the black hole evaporates. This time Preskill bet that the information can be recovered, with Hawking and Thorne betting that the information is destroyed.

Update (24 July 2004): My comments about Stephen Hawking’s recent concession.

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