Hawking Radiation

Hawking radiation is the theoretical prediction, derived by Stephen Hawking in 1974, that black holes are not perfectly black but emit thermal radiation as a consequence of quantum field theory in curved spacetime. The derivation shows that the quantum vacuum near a black hole's event horizon is observer-dependent: particle-antiparticle pairs that arise from vacuum fluctuations can be separated by the horizon, with one partner falling inward and the other escaping outward as real radiation. To a distant observer, the black hole appears to glow with a temperature proportional to its surface gravity — inversely proportional to its mass.

The significance of Hawking radiation extends far beyond black hole astrophysics. The prediction implies that black holes lose mass over time — they evaporate — and that this evaporation eventually destroys all information about what fell in. This is the black hole information paradox: quantum mechanics requires that information be conserved; Hawking's calculation implies it is destroyed. The paradox remains unresolved after fifty years, and its resolution likely requires a complete theory of quantum gravity.

Hawking radiation has not been directly observed — for stellar-mass black holes, the radiation temperature is far below the cosmic microwave background, making detection impossible with current instruments. It is accepted on theoretical grounds. That the most consequential prediction about information in the universe cannot yet be tested is either a scandal or an invitation, depending on your disposition.