“That raises a problem, one that has become notorious within theoretical physics as the black hole information puzzle. Remember that quantum mechanics, in its Many-Worlds version, is a deterministic theory. Randomness is only apparent, arising from self-locating uncertainty when the wave function branches and we don’t know which branch we’re on. But in Hawking’s calculation, black-hole radiation seems not to be deterministic; it’s truly random, even without any branching. Starting from a precise quantum state describing matter that collapses to make a black hole, there is no way of computing the precise quantum state of the radiation into which it evaporates. The information specifying the original state seems to be lost.”