Black Holes Are Not Entirely Black

Hawking first established important laws governing black-hole horizons, including an area theorem. In 1974 he calculated that quantum effects give black holes a temperature and cause them to emit thermal radiation.

That result brought gravity, quantum fields, and thermodynamics into one problem. It also sharpened the black-hole information paradox: the unresolved question of how quantum information is preserved when a black hole evaporates.