gas cannot be used to distinguish between the two initial states, and therefore information has been lost. It is now widely believed that the reasoning leading to the paradox above is flawed. Several solutions have been put forward that are reviewed below. Popular culture The information paradox has received coverage in the popular media and has been described in popular-science books. Some of this coverage resulted from a widely publicized bet made in 1997 between John Preskill on the one hand and Hawking and Kip Thorne that information was not lost in black holes. The scientific debate on the paradox was described in a popular book published in 2008 by Leonard Susskind called The Black Hole War. (The book carefully notes that the 'war' was purely a scientific one, and that at a personal level, the participants remained friends.) The book states that Hawking was eventually persuaded that black-hole evaporation was unitary by the holographic principle, which was first proposed by 't Hooft, further developed by Susskind and later given a precise string theory interpretation by the AdS/CFT correspondence. In 2004, Hawking also conceded the 1997 bet, paying Preskill with a baseball encyclopedia "from which information can be retrieved at will" although Thorne refused to concede. Solutions Since the 1997 proposal of the AdS/CFT correspondence, the predominant belief among physicists is that information is indeed preserved in black hole evaporation. However, there are broadly two main streams of thought about how this happens. Within, what might broadly be termed, the "string theory community", the dominant idea is that Hawking radiation is not precisely thermal but receives quantum correlations that encode information about the black hole's interior. This viewpoint has been the subject of extensive recent research and received further support in 2019 when researchers amended the computation of the entropy of the Hawking radiation in certain models, and showed that the radiation is in fact dual to the black hole interior at late times. Hawking himself was influenced by this view and in 2004, published a paper that assumed the AdS/CFT correspondence and argued that quantum perturbations of the event horizon could allow information to escape from a black hole, which would resolve the information paradox. In this perspective, it is the event horizon of the black hole that is important and not the black-hole singularity. On the other hand, within, what might broadly be termed, the "loop quantum gravity