His most original research concerned black holes — concentrations of matter so dense that light cannot escape from their gravitational pull. He showed that black holes are not just a bizarre theoretical concept but play an important role in the development of the universe. Indeed, they are not even quite black; they can emit radiation — known as Hawking radiation — and eventually they can evaporate and disappear.
Hawking emerged as a leading populariser in 1988 with the publication of A Brief History of Time. Although his disability made writing a slow and laborious process, he went on to produce several other popular books, including Black Holes and Baby Universes (1993) and The Universe in a Nutshell (2001).
At the same time, he emerged as an immensely popular lecturer who could fill any auditorium with fans eager to hear his elegant voice-synthesised account of the cosmos. He inspired thousands of young people with enthusiasm for research.
Stephen William Hawking was born in Oxford on January 8 1942 — as he liked to point out, this was 300 years to the day after the death of Galileo. His father was a tropical diseases specialist and his mother a Liberal party activist.
He won a scholarship from St Albans School to read physics at University College, Oxford. Then he moved to do a PhD in cosmology at Cambridge university, where he was to spend the remainder of his professional life.
His motor neurone disease (also known as ALS) was diagnosed in his first year at Cambridge. It kills most people within two years but Hawking proved to be a most remarkable survivor, helped by his first wife Jane Wilde, whom he married in 1965 and by whom he had two sons and a daughter.
Hawking’s condition deteriorated over the years and took a marked turn for the worse in 1985, when he caught pneumonia and had a tracheostomy operation. After that, he lost all power of speech and depended on 24-hour care from teams of devoted nurses.
Fortunately technology had by then reached the point at which Hawking could communicate by computer, using tiny movements of his hand, eye or head to select letters and words. These could be saved to disk or spoken out via a speech synthesiser.
By the 1990s Hawking had become a big-name celebrity and the tabloid newspapers feasted on the acrimonious break-up of his marriage and his wedding in 1995 to Elaine Mason, who had been one of his nurses.
His celebrity status irked some scientists, who mocked A Brief History of Time as the most bought and least read science book of all time. They said that, while he was an imaginative cosmologist, statements by admirers that he was the best scientific mind since Einstein were over the top.
Whether Hawking would have made such an impact with his science if he had not suffered from motor neurone disease is impossible to say — and beside the point. It was the combination of disability and scientific brilliance that made him a great man.