What paradox arises from the conflict between quantum mechanics and black hole physics?

The paradox arising from the conflict between quantum mechanics and black-hole physics is the information paradox.

More fully called the black hole information paradox, it centers on what happens to the detailed information describing matter that falls into a black hole. Quantum mechanics requires physical evolution to be reversible in principle: a complete final state should retain enough information to reconstruct the initial state. Classical general relativity, however, makes the black hole appear to hide everything behind its event horizon.

The tension became acute after Stephen Hawking’s work in the 1970s showed that black holes should emit thermal Hawking radiation. His calculation suggested that this radiation depends only on broad properties such as mass, electric charge, and angular momentum, not on the microscopic details of what formed the black hole. If the black hole eventually evaporates, the original information seems to disappear, violating quantum unitarity.

“Information paradox” is the standard short form, not a reference to a lack of ordinary data. Most modern theoretical work favors information preservation, but the precise mechanism remains an active problem in quantum gravity. The Page curve, holography, and black-hole complementarity are among the ideas used to study it.