Stephen Hawking (1943–), a British physicist and mathematician, is considered to be the greatest theoretical physicist of the late twentieth century. In spite of being severely handicapped by amyotrophic lateral sclerosis (ALS), he has made major contributions to scientific knowledge about black holes and the origin and evolution of the universe though his research into the nature of space-time and its anomalies. For instance, Hawking proposed that a black hole could emit thermal radiation, and he predicted that a black hole would disappear after all its mass has been converted into radiation (called “Hawking’s radiation”). A current objective of Hawking is to synthesize quantum mechanics and relativity theory into a theory of quantum gravity. He is also the author of several books, including the popular best-selling work A Brief History of Time.