As I understand it, a black hole is supposed to evaporate through Hawking radiation after a long but finite amount of time. Also, the radiation encodes in some sense the information of the matter that fell into the black hole. This according to an observer ("Alice") outside the event horizon.(adsbygoogle = window.adsbygoogle || []).push({});

But according to Alice, when matter ("Bob") does fall into a black hole, time slows down for him so that the amount of time that it takes for him to actually cross the event horizon tends to infinity. (Or is it infinity?)

So how does the Hawking radiation encode Bob's information? Whenever it starts, it can't encode information about matter that hasn't yet crossed the event horizon - that would be info duplication, wouldn't it? So when does information about Bob start to reappear? Billions of years after what?

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# When does Hawking radiation start?

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