British physicist Stephen Hawking, who dedicated his life to explaining some of the most complex questions about life and the universe, has died age 76.
Hawking died peacefully at his home in Cambridge, UK, in the early hours of Wednesday, said a family spokesman.
"We are deeply saddened that our beloved father passed away today," his children Lucy, Robert, and Tim said in a statement.
Hawking's work ranged from the origins of the universe itself to the mysteries of black holes in space and relativity. One of his popular science books, 'A Brief History of Time', stayed on the Sunday Times best-sellers list for no fewer than 237 weeks. The sub-molecular world of quantum theory can predict what happens at the beginning and end of time, he once said.
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“He was a great scientist and an extraordinary man whose work and legacy will live on for many years,” his family said. “His courage and persistence with his brilliance and humor inspired people across the world.”
Hawking was confined most of his life to a wheelchair as his body was ravaged by the wasting motor neurone disease he contracted at age 21. As his physical worsened, he had to resort to speaking through a voice synthesizer and communicating through small gestures.
Some of Hawking's best quotes
The famous physicist was also known for his inspirational quotes. Here's a selection of a few of them:
— “One, remember to look up at the stars and not down at your feet. Two, never give up work. Work gives you meaning and purpose and life is empty without it. Three, if you are lucky enough to find love, remember it is there and don't throw it away.”
— “We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the Universe. That makes us something very special.”
— “Quiet people have the loudest minds.”
— “Life would be tragic if it weren't funny.”
— “My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all.”
— "I believe the simplest explanation is, there is no God. No one created the universe and no one directs our fate. This leads me to a profound realization that there probably is no heaven and no afterlife either. We have this one life to appreciate the grand design of the universe and for that, I am extremely grateful."
— "Although I cannot move and I have to speak through a computer, in my mind I am free."
— "We are in danger of destroying ourselves by our greed and stupidity. We cannot remain looking inwards at ourselves on a small and increasingly polluted and overcrowded planet."
— "My disabilities have not been a significant handicap in my field, which is theoretical physics. Indeed, they have helped me in a way by shielding me from lecturing and administrative work that I would otherwise have been involved in. I have managed, however, only because of the large amount of help I have received from my wife, children, colleagues and students. I find that people in general are very ready to help, but you should encourage them to feel that their efforts to aid you are worthwhile by doing as well as you possibly can."
The physicist and author of A Brief History of Time has died at his home in Cambridge. His children said: ‘We will miss him for ever’
Stephen Hawking, the brightest star in the firmament of science, whose insights shaped modern cosmology and inspired global audiences in the millions, has died aged 76.
A brief history of Stephen Hawking's Brief History of Time Read more
His family released a statement in the early hours of Wednesday morning confirming his death at his home in Cambridge.
Hawking’s children, Lucy, Robert and Tim, said in a statement: “We are deeply saddened that our beloved father passed away today. He was a great scientist and an extraordinary man whose work and legacy will live on for many years. His courage and persistence with his brilliance and humour inspired people across the world.
“He once said: ‘It would not be much of a universe if it wasn’t home to the people you love.’ We will miss him for ever.”
For fellow scientists and loved ones, it was Hawking’s intuition and wicked sense of humour that marked him out as much as the fierce intellect that, coupled with his illness, came to symbolise the unbounded possibilities of the human mind.
I’m not afraid of death, but I’m in no hurry to die. I have so much I want to do first Stephen Hawking
Hawking was driven to Wagner, but not the bottle, when he was diagnosed with motor neurone disease in 1963 at the age of 21. Doctors expected him to live for only two more years. But Hawking had a form of the disease that progressed more slowly than usual. He survived for more than half a century.
Hawking once estimated he worked only 1,000 hours during his three undergraduate years at Oxford. In his finals, he came borderline between a first- and second-class degree. Convinced that he was seen as a difficult student, he told his viva examiners that if they gave him a first he would move to Cambridge to pursue his PhD. Award a second and he threatened to stay. They opted for a first.
Those who live in the shadow of death are often those who live most. For Hawking, the early diagnosis of his terminal disease, and witnessing the death from leukaemia of a boy he knew in hospital, ignited a fresh sense of purpose. “Although there was a cloud hanging over my future, I found, to my surprise, that I was enjoying life in the present more than before. I began to make progress with my research,” he once said. Embarking on his career in earnest, he declared: “My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all.”
He began to use crutches in the 1960s, but long fought the use of a wheelchair. When he finally relented, he became notorious for his wild driving along the streets of Cambridge, not to mention the intentional running over of students’ toes and the occasional spin on the dance floor at college parties.
The life of Stephen Hawking – in pictures Read more
Hawking’s first major breakthrough came in 1970, when he and Roger Penrose applied the mathematics of black holes to the universe and showed that a singularity, a region of infinite curvature in spacetime, lay in our distant past: the point from which came the big bang.
Penrose found he was able to talk with Hawking even as the latter’s speech failed. Hawking, he said, had an absolute determination not to let anything get in his way. “He thought he didn’t have long to live, and he really wanted to get as much as he could done at that time.”
There is no heaven or afterlife for broken-down computers; that is a fairy story for people afraid of the dark Stephen Hawking
In 1974 Hawking drew on quantum theory to declare that black holes should emit heat and eventually pop out of existence. For normal-sized black holes, the process is extremely slow, but miniature black holes would release heat at a spectacular rate, eventually exploding with the energy of a million one-megaton hydrogen bombs.
His proposal that black holes radiate heat stirred up one of the most passionate debates in modern cosmology. Hawking argued that if a black hole could evaporate, all the information that fell inside over its lifetime would be lost forever. It contradicted one of the most basic laws of quantum mechanics, and plenty of physicists disagreed. Hawking came round to believing the more common, if no less baffling, explanation that information is stored at a black hole’s event horizon, and encoded back into radiation as the black hole radiates.
Marika Taylor, a former student of Hawking’s and now professor of theoretical physics at Southampton University, remembers how Hawking announced his U-turn on the information paradox to his students. He was discussing their work with them in the pub when Taylor noticed he was turning his speech synthesiser up to the max. “I’m coming out!” he bellowed. The whole pub turned around and looked at the group before Hawking turned the volume down and clarified the statement: “I’m coming out and admitting that maybe information loss doesn’t occur.” He had, Taylor said, “a wicked sense of humour.”
Hawking’s run of radical discoveries led to his election in 1974 to the Royal Society at the young age of 32. Five years later, he became the Lucasian professor of mathematics at Cambridge, arguably Britain’s most distinguished chair, and a post formerly held by Isaac Newton, Charles Babbage and Paul Dirac, one of the founding fathers of quantum mechanics.
Hawking’s seminal contributions continued through the 1980s. The theory of cosmic inflation holds that the fledgling universe went through a period of terrific expansion. In 1982, Hawking was among the first to show how quantum fluctuations – tiny variations in the distribution of matter – might give rise through inflation to the spread of galaxies in the universe. In these tiny ripples lay the seeds of stars, planets and life as we know it.
But it was A Brief History of Time that rocketed Hawking to stardom. Published for the first time in 1988, the title made the Guinness Book of Records after it stayed on the Sunday Times bestsellers list for an unprecedented 237 weeks. It sold 10m copies and was translated into 40 different languages. Nevertheless, wags called it the greatest unread book in history.
Hawking married his college sweetheart, Jane Wilde, in 1965, two years after his diagnosis. She first set eyes on him in 1962, lolloping down the street in St Albans, his face down, covered by an unruly mass of brown hair. A friend warned her she was marrying into “a mad, mad family”. With all the innocence of her 21 years, she trusted that Stephen would cherish her, she wrote in her 2013 book, Travelling to Infinity: My Life With Stephen.
In 1985, during a trip to Cern, Hawking was taken to hospital with an infection. He was so ill that doctors asked Jane if they should withdraw life support. She refused, and Hawking was flown back to Addenbrooke’s Hospital in Cambridge for a lifesaving tracheotomy. The operation saved his life but destroyed his voice. The couple had three children, but the marriage broke down in 1991. Hawking’s progressive condition, his demands on Jane, and his refusal to discuss his illness, were destructive forces the relationship could not endure, she said. Jane wrote of him being “a child possessed of a massive and fractious ego,” and how husband and wife became “master” and “slave”.
My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all Stephen Hawking
Four years later, Hawking married Elaine Mason, one of the nurses employed to give him round-the-clock care. The marriage lasted 11 years, during which Cambridgeshire police investigated a series of alleged assaults on Hawking. The physicist denied that Elaine was involved, and refused to cooperate with police, who dropped the investigation.
Hawking was not, perhaps, the greatest physicist of his time, but in cosmology he was a towering figure. There is no perfect proxy for scientific worth, but Hawking won the Albert Einstein award, the Wolf prize, the Copley medal, and the Fundamental Physics prize. The Nobel prize, however, eluded him.
He was fond of scientific wagers, despite a knack for losing them. In 1975, he bet the US physicist Kip Thorne a subscription to Penthouse that the cosmic x-ray source Cygnus X-1 was not a black hole. He lost in 1990. In 1997, Hawking and Thorne bet John Preskill an encyclopaedia that information must be lost in black holes. Hawking conceded in 2004. In 2012, Hawking lost $100 to Gordon Kane for betting that the Higgs boson would not be discovered.
He lectured at the White House during the Clinton administration – his oblique references to the Monica Lewinsky episode were evidently lost on those who screened his speech – and returned in 2009 to receive the presidential medal of freedom from Barack Obama. His life was played out in biographies and documentaries, most recently The Theory of Everything, in which Eddie Redmayne played him. He appeared on The Simpsons and played poker with Einstein and Newton on Star Trek: The Next Generation. He delivered gorgeous put-downs on The Big Bang Theory. “What do Sheldon Cooper and a black hole have in common?” Hawking asked the fictional Caltech physicist whose IQ comfortably outstrips his social skills. After a pause, the answer came: “They both suck.”
Hawking has argued that for humanity to survive it must spread out into space, and has warned against the worst applications of artificial intelligence, including autonomous weapons.
Stephen Hawking – obituary by Roger Penrose Read more
Hawking was happy to court controversy and was accused of being sexist and misogynist. He turned up at Stringfellows lap dancing club in 2003, and years later declared women “a complete mystery”. In 2013, he boycotted a major conference in Israel on the advice of Palestinian academics.
Some of his most outspoken comments offended the religious. In his 2010 book, Grand Design, he declared that God was not needed to set the universe going, and in an interview with the Guardian a year later, dismissed the comforts of religious belief.
“I regard the brain as a computer which will stop working when its components fail,” he said. “There is no heaven or afterlife for broken-down computers; that is a fairy story for people afraid of the dark.”
He spoke also of death, an eventuality that sat on a more distant horizon than doctors thought. “I’m not afraid of death, but I’m in no hurry to die,” he said. “I have so much I want to do first.”
What astounded those around him was how much he did achieve. He leaves his three children, from his first marriage to Jane Wilde, and three grandchildren.
Using the Hubble Space Telescope and other sophisticated tools of observation and analysis, however, astronomers have identified hundreds of objects that are too massive and dark to be anything but black holes, including a supermassive one at the center of the Milky Way. According to current theory, the universe should contain billions more.
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As part of his Ph.D. thesis in 1966, Dr. Hawking showed that when you ran the film of the expanding universe backward, you would find that such a singularity had to have existed sometime in cosmic history; space and time, that is, must have had a beginning. He, Dr. Penrose and a rotating cast of colleagues went on to publish a series of theorems about the behavior of black holes and the dire fate of anything caught in them.
Dr. Hawking’s signature breakthrough resulted from a feud with the Israeli theoretical physicist Jacob Bekenstein, then a Princeton graduate student, about whether black holes could be said to have entropy, a thermodynamic measure of disorder. Dr. Bekenstein said they could, pointing out a close analogy between the laws that Dr. Hawking and his colleagues had derived for black holes and the laws of thermodynamics.
Dr. Hawking said no. To have entropy, a black hole would have to have a temperature. But warm objects, from a forehead to a star, radiate a mixture of electromagnetic radiation, depending on their exact temperatures. Nothing could escape a black hole, and so its temperature had to be zero. “I was very down on Bekenstein,” Dr. Hawking recalled.
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To settle the question, Dr. Hawking decided to investigate the properties of atom-size black holes. This, however, required adding quantum mechanics, the paradoxical rules of the atomic and subatomic world, to gravity, a feat that had never been accomplished. Friends turned the pages of quantum theory textbooks as Dr. Hawking sat motionless staring at them for months. They wondered if he was finally in over his head.
When he eventually succeeded in doing the calculation in his head, it indicated to his surprise that particles and radiation were spewing out of black holes. Dr. Hawking became convinced that his calculation was correct when he realized that the outgoing radiation would have a thermal spectrum characteristic of the heat radiated by any warm body, from a star to a fevered forehead. Dr. Bekenstein had been right.
Dr. Hawking even figured out a way to explain how particles might escape a black hole. According to quantum principles, the space near a black hole would be teeming with “virtual” particles that would flash into existence in matched particle-and-antiparticle pairs — like electrons and their evil twin opposites, positrons — out of energy borrowed from the hole’s intense gravitational field.
They would then meet and annihilate each other in a flash of energy, repaying the debt for their brief existence. But if one of the pair fell into the black hole, the other one would be free to wander away and become real. It would appear to be coming from the black hole and taking energy away from it.
But those, he cautioned, were just words. The truth was in the math.
“The most important thing about Hawking radiation is that it shows that the black hole is not cut off from the rest of the universe,” Dr. Hawking said.
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It also meant that black holes had a temperature and had entropy. In thermodynamics, entropy is a measure of wasted heat. But it is also a measure of the amount of information — the number of bits — needed to describe what is in a black hole. Curiously, the number of bits is proportional to the black hole’s surface area, not its volume, meaning that the amount of information you could stuff into a black hole is limited by its area, not, as one might naïvely think, its volume.
That result has become a litmus test for string theory and other pretenders to a theory of quantum gravity. It has also led to speculations that we live in a holographic universe, in which three-dimensional space is some kind of illusion.
Andrew Strominger, a Harvard string theorist, said of the holographic theory, “If it’s really true, it’s a deep and beautiful property of our universe — but not an obvious one.”
The discovery of black hole radiation also led to a 30-year controversy over the fate of things that had fallen into a black hole.
Dr. Hawking initially said that detailed information about whatever had fallen in would be lost forever because the particles coming out would be completely random, erasing whatever patterns had been present when they first fell in. Paraphrasing Einstein’s complaint about the randomness inherent in quantum mechanics, Dr. Hawking said, “God not only plays dice with the universe, but sometimes throws them where they can’t be seen.”
Many particle physicists protested that this violated a tenet of quantum physics, which says that knowledge is always preserved and can be retrieved. Leonard Susskind, a Stanford physicist who carried on the argument for decades, said, “Stephen correctly understood that if this was true, it would lead to the downfall of much of 20th-century physics.”
On another occasion, he characterized Dr. Hawking to his face as “one of the most obstinate people in the world; no, he is the most infuriating person in the universe.” Dr. Hawking grinned.
Dr. Hawking admitted defeat in 2004. Whatever information goes into a black hole will come back out when it explodes. One consequence, he noted sadly, was that one could not use black holes to escape to another universe. “I’m sorry to disappoint science fiction fans,” he said.
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Despite his concession, however, the information paradox, as it is known, has become one of the hottest and deepest topics in theoretical physics. Physicists say they still do not know how information gets in or out of black holes.
Raphael Bousso of the University of California, Berkeley, and a former student of Dr. Hawking’s, said the present debate had raised “by another few notches” his estimation of the “stupendous magnitude” of Dr. Hawking’s original discovery.
In 1974, Dr. Hawking was elected a Fellow of the Royal Society, the world’s oldest scientific organization; in 1979, he was appointed to the Lucasian chair of mathematics at Cambridge, a post once held by Isaac Newton. “They say it’s Newton’s chair, but obviously it’s been changed,” he liked to quip.
Dr. Hawking also made yearly visits to the California Institute of Technology in Pasadena, which became like a second home. In 2008, he joined the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, as a visiting researcher.
Having conquered black holes, Dr. Hawking set his sights on the origin of the universe and on eliminating that pesky singularity at the beginning of time from models of cosmology. If the laws of physics could break down there, they could break down everywhere.
In a meeting at the Vatican in 1982, he suggested that in the final theory there should be no place or time when the laws broke down, even at the beginning. He called the notion the “no boundary” proposal.
With James Hartle of the Institute for Theoretical Physics in Santa Barbara, Calif., Dr. Hawking envisioned the history of the universe as a sphere like the Earth. Cosmic time corresponds to latitude, starting with zero at the North Pole and progressing southward.
Although time started there, the North Pole was nothing special; the same laws applied there as everywhere else. Asking what happened before the Big Bang, Dr. Hawking said, was like asking what was a mile north of the North Pole — it was not any place, or any time.
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By then string theory, which claimed finally to explain both gravity and the other forces and particles of nature as tiny microscopically vibrating strings, like notes on a violin, was the leading candidate for a “theory of everything.”
In “A Brief History of Time,” Dr. Hawking concluded that “if we do discover a complete theory” of the universe, “it should in time be understandable in broad principle by everyone, not just a few scientists.”
He added, “Then we shall all, philosophers, scientists and just ordinary people, be able to take part in the discussion of why it is that we and the universe exist.”
“If we find the answer to that,” he continued, “it would be the ultimate triumph of human reason — for then we would know the mind of God.”
Until 1974, Dr. Hawking was still able to feed himself and to get in and out of bed. At Jane’s insistence, he would drag himself, hand over hand, up the stairs to the bedroom in his Cambridge home every night, in an effort to preserve his remaining muscle tone. After 1980, care was supplemented by nurses.
Dr. Hawking retained some control over his speech up to 1985. But on a trip to Switzerland, he came down with pneumonia. The doctors asked Jane if she wanted his life support turned off, but she said no. To save his life, doctors inserted a breathing tube. He survived, but his voice was permanently silenced.
It appeared for a time that he would be able to communicate only by pointing at individual letters on an alphabet board. But when a computer expert, Walter Woltosz, heard about Dr. Hawking’s condition, he offered him a program he had written called Equalizer. By clicking a switch with his still-functioning fingers, Dr. Hawking was able to browse through menus that contained all the letters and more than 2,500 words.
Word by word — and when necessary, letter by letter — he could build up sentences on the computer screen and send them to a speech synthesizer that vocalized for him. The entire apparatus was fitted to his motorized wheelchair.
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Even when too weak to move a finger, he communicated through the computer by way of an infrared beam, which he activated by twitching his right cheek or blinking his eye. The system was expanded to allow him to open and close the doors in his office and to use the telephone and internet without aid.
Although he averaged fewer than 15 words per minute, Dr. Hawking found he could speak through the computer better than he had before losing his voice. His only complaint, he confided, was that the speech synthesizer, manufactured in California, had given him an American accent.
His decision to write “A Brief History of Time” was prompted, he said, by a desire to share his excitement about “the discoveries that have been made about the universe” with “the public that paid for the research.” He wanted to make the ideas so accessible that the book would be sold in airports.
He also hoped to earn enough money to pay for his children’s education. He did. The book’s extraordinary success made him wealthy, a hero to disabled people everywhere and even more famous.
The news media followed his movements and activities over the years, from visiting the White House to meeting the Dallas Cowboys cheerleaders, and reported his opinions on everything from national health care (socialized medicine in England had kept him alive) to communicating with extraterrestrials (maybe not a good idea, he said), as if he were a rolling Delphic Oracle.
Asked by New Scientist magazine what he thought about most, Dr. Hawking answered: “Women. They are a complete mystery.”
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In 1990, Dr. Hawking and his wife separated after 25 years of marriage; Jane Hawking wrote about their years together in two books, “Music to Move the Stars: A Life With Stephen Hawking” and “Traveling to Infinity: My Life With Stephen.” The latter became the basis of the 2014 movie “The Theory of Everything.”
In 1995, he married Elaine Mason, a nurse who had cared for him since his bout of pneumonia. She had been married to David Mason, the engineer who had attached Dr. Hawking’s speech synthesizer to his wheelchair.
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In 2004, British newspapers reported that the Cambridge police were investigating allegations that Elaine had abused Dr. Hawking, but no charges were filed, and Dr. Hawking denied the accusations. They agreed to divorce in 2006.
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A complete list of survivors was not immediately available, but on Wednesday morning, his children, Robert, Lucy and Tim, released the following statement:
“We are deeply saddened that our beloved father passed away today. He was a great scientist and an extraordinary man whose work and legacy will live on for many years. His courage and persistence with his brilliance and humour inspired people across the world. He once said, ‘It would not be much of a universe if it wasn’t home to the people you love.’ We will miss him forever.”
Among his many honors, Dr. Hawking was named a commander of the British Empire in 1982. In the summer of 2012, he had a star role in the opening of the Paralympics Games in London. The only thing lacking was the Nobel Prize, and his explanation for this was characteristically pithy: “The Nobel is given only for theoretical work that has been confirmed by observation. It is very, very difficult to observe the things I have worked on.”
Dr. Hawking was a strong advocate of space exploration, saying it was essential to the long-term survival of the human race. “Life on Earth is at the ever-increasing risk of being wiped out by a disaster, such as sudden global nuclear war, a genetically engineered virus or other dangers we have not yet thought of,” he told an audience in Hong Kong in 2007.
Image copyright AFP
Stephen Hawking - who died aged 76 - battled motor neurone disease to become one of the most respected and best-known scientists of his age.
A man of great humour, he became a popular ambassador for science and was always careful to ensure that the general public had ready access to his work.
His book A Brief History of Time became an unlikely best-seller although it is unclear how many people actually managed to get to the end of it.
He appeared in a number of popular TV shows and lent his synthesised voice to various recordings.
Stephen William Hawking was born in Oxford on 8 January 1942. His father, a research biologist, had moved with his mother from London to escape German bombing.
Hawking grew up in London and St Albans and, after gaining a first-class degree in physics from Oxford, went on to Cambridge for postgraduate research in cosmology.
Image copyright Rex Features Image caption He was diagnosed with motor neurone disease while at university
As a teenager he had enjoyed horse-riding and rowing but while at Cambridge he was diagnosed with a form of motor neurone disease which was to leave him almost completely paralysed.
As he was preparing to marry his first wife, Jane, in 1964 his doctors gave him no more than two or three years of life.
But the disease progressed more slowly than expected. The couple had three children, and in 1988 - although Hawking was by now only able to speak with a voice synthesiser following a tracheotomy - he had completed A Brief History of Time - a layman's guide to cosmology.
It sold more than 10 million copies, although its author was aware that it was dubbed "the most popular book never read".
He received honorary degrees, medals, prizes and awards throughout his career and was honoured with a CBE in 1982. He was reportedly offered a knighthood in the 1990s but later revealed he had turned it down over issues with the government's funding for science.
Media playback is unsupported on your device Media caption Scientist in the public eye
Celebrity
Hawking discovered the phenomenon which became known as Hawking radiation, where black holes leak energy and fade to nothing. He was renowned for his extraordinary capacity to visualise scientific solutions without calculation or experiment.
But it was perhaps his "theory of everything", suggesting that the universe evolves according to well-defined laws, that attracted most attention.
"This complete set of laws can give us the answers to questions like how did the universe begin," he said. "Where is it going and will it have an end? If so, how will it end? If we find the answers to these questions, we really shall know the mind of God."
Image copyright PA Image caption He believed the universe evolves according to well-defined laws
Hawking's celebrity status was acknowledged even by The Simpsons - he was depicted drinking at a bar with Homer, suggesting he might steal Homer's idea that the universe is shaped like a doughnut.
He appeared in a special documentary about BBC comedy series Red Dwarf during which he spoke about why he enjoyed the show and also starred in Star Trek: The Next Generation as a hologram of his image.
The rock group Pink Floyd used his distinctive synthesised voice for the introduction to Keep Talking, on their 1994 album The Division Bell.
Undeterred by his condition, he continued his work as Lucasian Professor of Mathematics at Cambridge University, and in 2001, his second book - Universe in a Nutshell - was published.
Erratic
He believed his illness brought some benefits; he said before he developed the disease he had been bored with life.
But his condition inevitably made him dependent on others. He often paid tribute to his wife, who had looked after him for more than 20 years, and friends and relatives were shocked when he left her for one of his nurses, Elaine Mason, whom he married in 1995. The couple later divorced in 2006.
Image copyright Reuters Image caption Hawking later went on to marry one of his nurses, Elaine Mason, in 1995. They were married for 11 years before they divorced
By 2000, Hawking was a frequent visitor to the emergency department of Addenbrooke's Hospital in Cambridge, seeking treatment for a variety of injuries. Police questioned several people about allegations that he had been subjected to verbal and physical abuse over a period of years.
He was known to be an erratic, almost reckless driver of his electric wheelchair, and Hawking insisted his injuries were not caused by abuse. No action was taken.
In 2007, he became the first quadriplegic to experience weightlessness on board the so-called "vomit comet", a modified plane specially designed to simulate zero gravity. He said he did it to encourage interest in space travel and booked a seat on Sir Richard Branson's Virgin Galactic sub-orbital space plane.
"I believe that life on Earth is at an ever-increasing risk of being wiped out by a disaster such as sudden nuclear war, a genetically engineered virus, or other dangers. I think the human race has no future if it doesn't go into space. I therefore want to encourage public interest in space."
Image copyright PA Image caption Eddie Redmayne played Hawking in The Theory of Everything
In 2014, the film The Theory of Everything was released, based on Jane Hawking's account of their courtship and marriage. Hawking himself met Eddie Redmayne as part of the actor's preparation for taking on the role of the scientist.
In a series for the Discovery Channel, he said it was perfectly rational to assume there was intelligent life elsewhere but warned that aliens might just raid earth of its resources and then move on.
Hawking also predicted the end of humanity from global warming, a large comet or a new virus.
He collaborated with Russian investor Yuri Milner in 2015 to work on projects to find evidence of alien life.
He once wrote that he had motor neurone disease for practically all his adult life but said that it had not stopped him having an attractive family and being successful in his work.
"It shows," he said, "that one need not lose hope."
