Stephen Hawking, then still a physics student at Oxford University, discovered in 1963 that black holes emit radiation (Bekenstein-Hawking radiation). These supermassive objects, from which nothing can escape once the event horizon is crossed, not even light, emit weak radiation, and can eventually disappear. This discovery is a real revolution since it calls into question the very definition of the black hole, which, releasing particles into space, would not have an infinite gravitational force.