Hawking radiation is the faint thermal glow that black holes emit because of quantum effects near the event horizon, predicted by Stephen Hawking in 1974. Pairs of virtual particles constantly appear in empty space; near a horizon, one can fall in while the other escapes, carrying away energy. Over unimaginable spans of time this slowly drains the black hole's mass until it evaporates entirely. The radiation is far too cold to detect from real astrophysical black holes, but laboratory analogs using sound waves and ultracold atoms have observed the effect's signature.