Most physicists labour in obscurity. Stephen Hawking attained cult status, partly because of his scientific insights and partly because of his devastating disability and instantly recognisable synthesised voice.
Hawking's most famous scientific insight concerned the arcane physics of black holes. He discovered the phenomenon which has become known as Hawking radiation, in which black holes leak energy and fade to nothing. But Hawking radiation was not what he was famous for in a popular context. His illness gave him a pre-eminence in the public eye that he would never have enjoyed had he been in perfect health. He was feted by Hollywood stars, invited to the White House by president Bill Clinton and appeared in advertisements as well as cameo roles in Star Trek, Futurama and The Simpsons - in one episode of which his cartoon doppelganger told Homer Simpson: "Your theory of a doughnut-shaped universe is interesting. I may have to steal it."Making sense of everything
Another factor in Hawking's fame was his idea that scientists would one day discover the single "unified theory of everything". In 1988, he explored this issue in A Brief History of Time, which sold more than 25million copies. It was a bold attempt to explain to the layman current thinking on the origins of the universe and the properties of space-time. He concluded the book with the thought that if we discover a complete theory of physics, we may be able to find the answer to the question of why we and the universe exist. "If we find the answer to that, it would be the ultimate triumph of human reason - for then we would know the mind of God."Hawking's life was dominated, positively as well as negatively, by a rare form of motor neurone disease that left him increasingly helpless. He was confined to a wheelchair by the time he was 30, and in 1986, aged 44, his voice was removed to save his life after an attack of pneumonia. From then on, he spoke through a computer synthesiser on the arm of his wheelchair. It was remarkable that he survived at all. When the disease was diagnosed in 1963, doctors gave him 14 months to live.
Hawking was born on January 8 1942 in Oxford, the eldest son of Dr Frank Hawking, a prominent research biologist. He was brought up in St Albans, where the routines of middle-class life were tempered by parental bohemianism. The family car was a London taxi and holidays were spent in a gipsy caravan.
Surprisingly slow to learn to read, young Hawking was skinny and unco-ordinated. He was seen by his peers as the stereotypical boffin type - useless at games except cross-country running, but good at mathematics and enthusiastic (and chaotic) in chemistry.
He was never top of his class, but a close friend at school recalled his "incredible instinctive insight". Faced with a complex mathematical problem, he "just knew the answer - he didn't have to think about it".He went to University College, Oxford, in 1959 and studied mathematics for a year before switching to physics. His mind, according to his tutor, was "completely different from all of his contemporaries", but he did "positively make an effort to come down to their level and be one of the boys".
After graduating in 1962, he decided to go to Cambridge for postgraduate work in cosmology, which he said excited him because it concerned "the big question: where did the universe come from?"
Hardly had Hawking arrived in Cambridge than symptoms he had first noticed at Oxford - slurred speech and trouble tying his shoelaces among them - became worse. (At Oxford he had also seemed to others angry and frustrated at nothing in particular, and his movements had become jerky.)
In 1963 he was diagnosed as suffering from amyotrophic lateral sclerosis, an incurable progressive deterioration of the motor nerves that prevents muscle function, affecting speech, swallowing and the limbs, and usually ends in a fatal paralysis of the chest muscles.
For the next two years, Hawking did little research work. He stayed in his room, listening to Wagner, reading science fiction and drinking. Then the disease seemed to stabilise and his prospects seemed brighter. He found fresh enthusiasm and returned to work on his doctorate. He also fell in love with a language student named Jane Wilde, and they were married in 1965. Hawking described the marriage as a turning point.
Black holes and singularities
In his PhD thesis, Properties of the Expanding Universe, in 1966, Hawking suggested that the cosmic clock could be run backwards to the Big Bang, the beginning of the universe. He stayed at Cambridge after receiving his doctorate, working on black holes and singularities with mathematician Roger Penrose.
Hawking delivered his mathematical evidence for Hawking radiation at a symposium in Oxford in February 1974, to the consternation and disbelief of most of his colleagues. Although it was later confirmed by others, it still represented one of the greatest challenges ever to confront theoretical physics.General relativity suggested that black holes could only get bigger and bigger. But by bringing quantum theory into play, Hawking showed they could "evaporate" and explode. It was a dramatic demonstration that black holes, while severed from the space-time continuum, have important effects on it. The revelation that black holes emit matter and energy also strengthened their link with the Big Bang theory.
Hawking's paper on the radiation from black holes was a significant step for another reason - it combined features of quantum physics with classical general relativity, theories that are still widely regarded as almost incompatible, the former dealing with the very small and the latter with the very big.
Hawking now turned to the challenge of uniting them to form a grand unified theory - a new single theory, encompassing gravity at the large scale, and the strong nuclear, weak nuclear and electromagnetic forces at the small scale - which would describe the behaviour of all the matter in the universe.
In spite of his efforts, his prediction that the answer would emerge by the end of the 20th century proved wide of the mark.
For most of his life, Hawking managed to escape many of the trappings of fame - such as tabloid fascination with his private life. But this all changed in 1990 when he announced he was leaving his wife Jane after 25 years to move in with Elaine Mason, one of his nurses, whose former husband, David, had created his voice box. The pair married in 1995.
The end of his first marriage was messy and difficult. Hawking was accused of selfishness and Mason of marrying him so that she could bask in the reflected glory of his celebrity.
In 1999, his former wife published an angry memoir, Music to Move the Stars: My Life with Stephen, in which she described the daily grind of struggling to meet the demands of her three children as well as her increasingly dependent and demanding husband.Her portrait of Hawking and his new wife was not flattering. An "all-powerful emperor", he "had not liked being treated as but one member of the family when he considered his rightful place to be on a pedestal at the centre". In Mason, he had found someone who "was prepared to worship at his feet".
No sooner had the book appeared than reports began to circulate that all was not well in Hawking's new household. By 2000 he had become a frequent visitor to Addenbrooke's Hospital casualty department, suffering from a series of mysterious injuries - broken bones, gashes and severe bruising.
In 2004, after Hawking had once again been taken to hospital, reports appeared in the media alleging that his new wife had systematically beaten, bullied, humiliated and degraded him over several years. No fewer than 10 nurses who had worked with Hawking were said to have come forward to allege numerous acts of cruelty.
Hawking, though, consistently refused to say how he came by his injuries, or to be interviewed by police. When officers turned up at his house offering to interview him and his wife in separate rooms, he threatened to sue them for harassment.
"My wife and I love each other very much," he maintained. "It is only because of her that I am alive today." In 2006, however, the couple filed for divorce.Sense of fun
Despite all these problems, Hawking's mind remained razor sharp and his career flourished. In 2002 he was awarded the Aventis Prize for Science Books for The Universe in a Nutshell. Some colleagues found in him a self-righteous streak, and he gave few references to the work of others in his field.
Others found him difficult to work with. But he never seemed to lose his sense of fun, and the mischievous glint in his eyes. In 2007 he enjoyed zero gravity on a specially organised flight in the US, allowing him to float free of his wheelchair. "It was amazing," he said. "I could have gone on and on. Space here I come."
Indeed, in 2009 Hawking was offered a place aboard a proposed commercial space flight operated by Sir Richard Branson. "I would love to go to the moon, or go into space," he said in 2015, "but I fear the doctors won't allow it."
With his first wife, Jane, he had two sons and a daughter. After the end of his marriage to Mason, Hawking resumed closer relationships with his first family and in 2007 Jane revised her 1999 memoir into the less angry Travelling to Infinity: My Life with Stephen, which was adapted into the film The Theory of Everything, starring Eddie Redmayne and Felicity Jones, in 2014.My computer
By STEPHEN HAWKING
Since 1997, my computer-based communication system has been sponsored and provided by Intel® Corporation. A tablet computer mounted on the arm of my wheelchair is powered by my wheelchair batteries, although the tablet’s internal battery will keep the computer running if necessary.
My main interface to the computer is through an open-source program calledACAT, written by Intel. This provides a software keyboard on the screen. A cursor automatically scans across this keyboard by row or by column. I can select a character by moving my cheek to stop the cursor. My cheek movement is detected by an infrared switch that is mounted on my spectacles.
This switch is my only interface with the computer. ACAT includes a word prediction algorithm provided by SwiftKey, trained on my books and lectures, so I usually only have to type the first couple of characters before I can select the whole word. When I have built up a sentence, I can send it to my speech synthesiser.
I use a separate hardware synthesiser, made by Speech Plus. It is the best I have heard, although it gives me an accent that has been described variously as Scandinavian, American or Scottish.
Through ACAT I can also control the mouse in Windows. This allows me to operate my whole computer. I can check my e-mail using Microsoft Outlook, surf the internet using Firefox, or write lectures using Microsoft Word. My latest computer from Intel also contains a webcam which I use with Skype to keep in touch with my friends.
I can express a lot through my facial expressions to those who know me well. I can also give lectures. I write the lecture beforehand, then save it to disk. I can then use a part of the ACAT software called Lecture Manager to send it to the speech synthesiser a paragraph at a time.
It works quite well and I can try out the lecture and polish it before I give it.I keep looking into new assistive technologies, and I have experimented with eye-tracking and brain-controlled interfaces to communicate with my computer. However, although they work well for other people, I still find my cheek-operated switch easier and less fatiguing to use. - hawking.org.uk..