The Black Hole Information Paradox is a profound conflict between the principles of quantum mechanics and general relativity regarding the fate of information that enters a black hole. According to general relativity, a black hole is defined essentially by its mass, charge, and spin (the "no-hair theorem"), and information about the matter that formed it is hidden behind the event horizon. However, Stephen Hawking discovered in 1974 that black holes emit thermal radiation—now known as Hawking radiation—due to quantum effects, causing them to lose mass and eventually evaporate completely.

The paradox arises because Hawking's original calculation indicated this radiation is thermal and random, carrying no information about the black hole's contents. If the black hole evaporates entirely, the information appears to be irretrievably lost. This  ...