Stephen Hawking

Stephen Hawking was a bright but unremarkable student at Oxford who, by his own account, did about an hour of work a day. Shortly after starting his doctorate at Cambridge he was diagnosed with amyotrophic lateral sclerosis, a form of motor neurone disease. He was 21 and doctors expected him to live about two years.

The diagnosis, he later said, made him focus. He got engaged, finished his PhD and started the work that would make his name: showing that the equations of general relativity imply the universe began in a singularity, and then, in 1974, that black holes are not completely black but leak radiation and eventually evaporate. "Hawking radiation" linked gravity, quantum theory and thermodynamics for the first time.

The disease slowly took away his ability to walk, write and finally speak. After a tracheotomy in 1985 he communicated through a speech synthesiser, selecting words with a hand-clicker and later with a cheek muscle, at a few words a minute. He held the Lucasian Chair of Mathematics at Cambridge, once held by Newton, for 30 years.

A Brief History of Time, published in 1988, sold more than 25 million copies. He appeared on The Simpsons and Star Trek, experienced weightlessness on a zero-gravity flight at 65, and remained a public voice on science and disability until he died at 76, more than half a century past his original prognosis.