Hawking radiation is a groundbreaking theoretical prediction made by physicist Stephen Hawking in 1974, which suggests that black holes are not completely black, but instead can emit radiation and lose mass over time—ultimately leading to their slow evaporation.
According to classical general relativity, nothing—not even light—can escape from a black hole. But when quantum mechanics is taken into account, the story changes. Near the event horizon (the boundary of a black hole), quantum fluctuations in the vacuum constantly produce virtual particle-antiparticle pairs. Normally, these pairs annihilate each other almost instantly.
However, near a black hole’s event horizon:
- One particle of the pair may fall into the black hole,
- The other may escape into space as real radiation.
To an outside observer, it appears as though the black hole is emitting particles. This radiation is what we call Hawking radiation. Because energy is carried away by the escaping particles, the black hole loses mass. Over an extremely long time, if no mass is added, the black hole will shrink and eventually evaporate completely.
Key implications of Hawking radiation:
- It bridges quantum mechanics, thermodynamics, and general relativity,
- It gives black holes a temperature and entropy, transforming them into thermodynamic objects,
- It raises the black hole information paradox, a major unresolved question about what happens to information swallowed by black holes,
- It suggests that tiny primordial black holes, if they exist, may have already evaporated or be in their final stages.
Though Hawking radiation has not yet been observed directly due to its faintness, it remains a profound insight into how the laws of physics operate at the intersection of the quantum and the cosmic.