Stephen William Hawking was born in Oxford on January 8, 1942, exactly three hundred years after the death of Galileo, a coincidence he noted with evident satisfaction throughout his life. He was an unremarkable student at St Albans School, where his classmates nicknamed him "Einstein" more as a joke than a prediction, and went to University College, Oxford, where he later admitted to averaging about an hour of study per day. He was diagnosed with amyotrophic lateral sclerosis at twenty-one, shortly after beginning his doctoral work at Cambridge. Doctors gave him two years to live. He lived to seventy-six. The diagnosis, rather than paralyzing his ambition, appears to have concentrated it. His doctoral thesis on the properties of expanding universes established him as a serious theoretical physicist, and his subsequent work on black holes transformed cosmology. In 1974, he demonstrated that black holes are not entirely black but emit radiation through quantum effects near the event horizon, a discovery now called Hawking radiation that unified quantum mechanics and general relativity in a way no one had previously achieved. His body deteriorated steadily: he lost the ability to walk, then to write, then to speak. For the last decades of his life, he communicated through a speech-generating device controlled by a single muscle in his cheek, selecting words from a screen at approximately one word per minute. He wrote A Brief History of Time in this manner; it sold over ten million copies and spent a record 237 weeks on the Sunday Times bestseller list. He said the diagnosis was, in some ways, useful. It focused him.