Black hole information paradox

The black hole information paradox is the apparent contradiction between quantum mechanics, which requires that information be conserved, and Stephen Hawking's 1974 prediction that Hawking radiation is purely thermal and carries no information about the matter that fell into the black hole. If a black hole evaporates completely, the information describing the quantum state of infalling matter seems to be destroyed — a violation of the unitary evolution that underlies all quantum physics. The paradox has driven decades of research in quantum gravity, producing proposals from black hole complementarity to the firewall argument, and remains unresolved. Its resolution will likely require a fundamental revision of how we understand spacetime, information, and the relationship between them.