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Stephen William Hawking, CH, CBE, FRS, FRSA (born 8 January 1942) is a British theoretical physicist. Hawking is the Lucasian Professor of Mathematics at the University of Cambridge, and a Fellow of Gonville and Caius College, Cambridge. He is known for his contributions to the fields of cosmology and quantum gravity, especially in the context of black holes, and his popular works in which he discusses his own theories and cosmology in general. These include the runaway popular science bestseller A Brief History of Time, which stayed on the British Sunday Times bestseller list for a record-breaking 237 weeks. His key scientific works to date have included providing, with Roger Penrose, theorems regarding singularities in the framework of general relativity, and the theoretical prediction that black holes should emit radiation, which is today known as Hawking radiation, or sometimes as Bekenstein-Hawking radiation. His scientific career spans more than 40 years and his books and public appearances have made him an academic celebrity and world-renowned theoretical physicist. He is an Honorary Fellow of the Royal Society of Arts. Hawking is disabled by amyotrophic lateral sclerosis (ALS), commonly known in the United States as Lou Gehrig's Disease. The illness has progressed over the years and he is now almost completely paralysed.Hawking's principal fields of research are theoretical cosmology and quantum gravity. In the late 1960s, he and his Cambridge friend and colleague, Roger Penrose, applied a new, complex mathematical model they had created from Albert Einstein's general theory of relativity. This led, in 1970, to Hawking proving the first of many singularity theorems; such theorems provide a set of sufficient conditions for the existence of a singularity in space-time. This work showed that, far from being mathematical curiosities which appear only in special cases, singularities are a fairly generic feature of general relativity. He supplied a mathematical proof, along with Brandon Carter, Werner Israel and D. Robinson, of John Wheeler's "No-Hair Theorem" - namely, that any black hole is fully described by the three properties of mass, angular momentum, and electric charge. Hawking also suggested that, upon analysis of gamma ray emissions, after the Big Bang, primordial or mini black holes were formed. With Bardeen and Carter, he proposed the four laws of black hole mechanics, drawing an analogy with thermodynamics. In 1974, he calculated that black holes should thermally create and emit subatomic particles, known today as Hawking radiation, until they exhaust their energy and evaporate. In collaboration with Jim Hartle, Hawking developed a model in which the Universe had no boundary in space-time, replacing the initial singularity of the classical Big Bang models with a region akin to the North pole: one cannot travel North of the North pole, there is no boundary there. While originally the no-boundary proposal predicted a closed Universe, discussions with Neil Turok led to the realisation that the no-boundary proposal is consistent with a Universe which is not closed also. Among Hawking's many other scientific investigations, included are the study of: quantum cosmology, cosmic inflation, helium production in anisotropic Big Bang universes, large N cosmology, the density matrix of the universe, topology and structure of the universe, baby universes, Yang-Mills instantons and the S matrix; anti de Sitter space, quantum entanglement and entropy; the nature of space and time, including the arrow of time; spacetime foam, string theory, supergravity, Euclidean quantum gravity, the gravitational Hamiltonian; Brans-Dicke and Hoyle-Narlikar theories of gravitation; gravitational radiation, and wormholes.