Hawking, Stephen (William) (1942– )

English physicist and cosmologist whose work in general relativity – particularly gravitational field theory – led to a search for a quantum theory of gravity to explain black holes and the Big Bang, singularities that classical relativity theory does not adequately explain. His book A Brief History of Time (1988) gives a popular account of cosmology and became an international best-seller. He later co-wrote (with Roger Penrose) The Nature of Space and Time (1996), and published The Universe in a Nutshell in 2002.

Hawking's objective of producing an overall synthesis of quantum mechanics and relativity theory began around the time of the publication in 1973 of his seminal book The Large Scale Structure of Space-Time, written with G F R Ellis. His most remarkable result, published in 1974, was that black holes could in fact emit particles in the form of thermal radiation – the so-called Hawking radiation.

Hawking was born in Oxford, studied at Oxford and Cambridge, and became professor of mathematics at Cambridge in 1979. He developed motor neurone disease, a rare form of degenerative paralysis, while still a college student, and uses a wheelchair and communication equipment. Hawking's most fruitful work was with black holes, stars that have undergone total gravitational collapse and whose gravity is so great that nothing, not even light, can escape from them. Since 1974, he has studied the behaviour of matter in the immediate vicinity of a black hole. He has proposed a physical explanation for Hawking radiation which relies on the quantum-mechanical concept of ‘virtual particles’ – these exist as particle–antiparticle pairs and fill ‘empty’ space. Hawking suggested that, when such a pair is created near a black hole, one half of the pair might disappear into the black hole, leaving the other half, which could escape to infinity. This would be seen by a distant observer as thermal radiation.