The Thorne–Hawking–Preskill bet was a public bet on the outcome of the black hole information paradox made in 1997 by physics theorists Kip Thorne and Stephen Hawking on the one side, and John Preskill on the other, according to the document they signed 6 February 1997,[1] as shown in Hawking's 2001 book The Universe in a Nutshell.
Thorne and Hawking argued that since general relativity made it impossible for black holes to radiate, and lose information, the mass-energy and information carried by Hawking radiation must be "new", and must not originate from inside the black hole event horizon.
Hawking had earlier speculated that the singularity at the centre of a black hole could form a bridge to a "baby universe", into which the lost information could pass; such theories have been very popular in science fiction.
But according to Hawking's new idea, presented at the 17th International Conference on General Relativity and Gravitation, on 21 July 2004 in Dublin, black holes eventually transmit, in a garbled form, information about all matter they swallow: The Euclidean path integral over all topologically trivial metrics can be done by time slicing and so is unitary when analytically continued to the Lorentzian.
On the other hand, the path integral over all topologically non-trivial metrics is asymptotically independent of the initial state.