Concept
Quantum Mechanics
The physics of the very small, where particles behave as probabilities and empty space is never truly empty. The theory Hawking forced to meet gravity.
Last updated 23 May 2026 · How we research
Quantum mechanics is the branch of physics that describes the world at its smallest scales: atoms, electrons, photons and the like. At that level, nature behaves very differently from the everyday world. Particles do not have definite positions and speeds until measured; instead they are described by probabilities. Energy comes in discrete packets, or "quanta." And, crucially for Hawking's work, even empty space is never truly empty: it seethes with pairs of "virtual" particles flickering in and out of existence.
Quantum mechanics is extraordinarily well tested and underpins almost all modern technology, from transistors to lasers. Its one great failure is that it has never been successfully combined with general relativity, Einstein's theory of gravity. The two theories work beautifully in their own domains but contradict each other when both should apply at once.
Why it mattered to Hawking
That unresolved clash is where Hawking did his defining work. His discovery of Hawking radiation came from applying quantum mechanics to the empty space at the edge of a black hole, somewhere general relativity says nothing should ever escape. The result, that black holes glow faintly and slowly evaporate, was the first concrete bridge between the quantum world and gravity, and it created the information paradox, a puzzle that turns precisely on the quantum rule that information can never be destroyed.