Scientists, politicians and actors have paid tribute to world renowned physicist Stephen Hawking, who has been called an "inspiration to millions".
The British scientist, famed for his work on black holes, died peacefully at his home in Cambridge aged 76.
Astronomer Royal Lord Rees, one of the world's most eminent scientists, described his life as a "triumph".
Others described him as a "unique individual" whose death "has left an intellectual vacuum in his wake".
Prof Hawking was diagnosed with a rare form of motor neurone disease at the age of 21 and was told he had only a few years to live.
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He was known for his theories on black holes and relativity and went on to publish several popular science books including A Brief History of Time.
The University of Cambridge, where Prof Hawking completed his PhD and went on to become Lucasian Professor of Mathematics - a role once held by Sir Isaac Newton - described him as "an inspiration to millions".
Queues have formed at Gonville and Caius College - where Prof Hawking was a fellow for more than 50 years - to sign a book of condolence.
Buckingham Palace said the Queen will be sending a message of condolence to Prof Hawking's family.
Prof Hawking's children, Lucy, Robert and Tim, said in a statement: "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."
Stephen Hawking, who was born in 1942, studied physics in Oxford and later went on to Cambridge for his postgraduate research in cosmology
Speaking to BBC Radio 4's Today programme, broadcaster Prof Brian Cox called him "one of the greats" and said physicists in 1,000 years' time "will still be talking about Hawking radiation", his theory about black holes.
British astronaut Tim Peake, who flew in space in 2016, said Prof Hawking "inspired generations to look beyond our own blue planet and expand our understanding of the universe".
And the inventor of the World Wide Web, Sir Tim Berners-Lee, praised Prof Hawking's "colossal mind and wonderful spirit".
Many friends and fans have also hailed his humour, with actor Eddie Redmayne, who portrayed Prof Hawking in 2014 film biopic The Theory of Everything, calling him "the funniest man I have ever met".
Fellow actor Benedict Cumberbatch, who also played the physicist in a 2004 BBC TV film, remembered his "wickedly funny sense of humour".
"He virtually created the publishing genre of popular science. I will miss our margaritas but will raise one to the stars to celebrate your life," he added.
Benedict Cumberbatch said Prof Hawking was a "true inspiration for me and for millions around the world"
Meanwhile, Lord Rees - who holds the most prestigious post in astronomy in the UK - recalled meeting Prof Hawking at Cambridge University in 1964, describing him as "unsteady on his feet and speaking with great difficulty" following his diagnosis with the degenerative disease.
"Even mere survival would have been a medical marvel, but of course he didn't just survive. He became one of the most famous scientists in the world," Lord Rees said
"He was diagnosed with a deadly disease, and his expectations dropped to zero. He himself said that everything that happened since then was a bonus."
"And what a triumph his life has been," Lord Rees added.
Factfile: Stephen Hawking
Born 8 January 1942 in Oxford, England
Earned place at Oxford University to read natural science in 1959, before studying for his PhD at Cambridge
By 1963, was diagnosed with motor neurone disease and given two years to live
Outlined his theory that black holes emit "Hawking radiation" in 1974
In 1979, he became the Lucasian Professor of Mathematics at Cambridge - a post once held by Sir Isaac Newton
Published his book A Brief History of Time in 1988, which has sold more than 10 million copies
In the late 1990s, he was reportedly offered a knighthood, but 10 years later revealed he had turned it down over issues with the government's funding for science
Prime Minister Theresa May opened PMQs with a nod to Prof Hawking's "exceptional contributions to science and our knowledge of the universe speak for themselves".
"As his children have said, his courage and persistence with his brilliance and humour inspired people across the world," she said.
Labour leader Jeremy Corbyn also paid tribute to the physicist - who was a Labour supporter - and said he "inspired the world with his determination to explain the mysteries of the cosmos" and "showed breathtaking courage to overcome life's adversities".
Former US President Barack Obama, who Prof Hawking met in 2009 to receive the Presidential Medal of Freedom, tweeted a photo of them both alongside the words: "Have fun out there among the stars".
Barack Obama
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@BarackObama
Have fun out there among the stars.
10:58 AM - Mar 14, 2018
Meanwhile, from the worlds of science, technology and space, Nasa said Prof Hawking's theories "unlocked a universe of possibilities".
NASA
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@NASA
Remembering Stephen Hawking, a renowned physicist and ambassador of science. His theories unlocked a universe of possibilities that we & the world are exploring. May you keep flying like superman in microgravity, as you said to astronauts on @Space_Station in 2014
1:06 AM - Mar 14, 2018
American astrophysicist Neil deGrasse Tyson tweeted: "His passing has left an intellectual vacuum in his wake" while George Smoot, who won the Nobel Prize in Physics, described Prof Hawking as "very competitive".
The European Space Agency shared a photo of Prof Hawking in 2007 experiencing zero gravity aboard a plane, alongside a caption which said he "showed us there are no limits to achieving our dreams".
Figures from the worlds of science and technology praised Prof Hawking's "colossal" mind
Meanwhile, Professor Stephen Toope, vice-chancellor of the University of Cambridge said Prof Hawking has left "an indelible legacy".
"Prof Hawking was a unique individual who will be remembered with warmth and affection not only in Cambridge but all over the world," he said. "He will be much missed."
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Celebrities including Sam Smith, Nancy Sinatra and Janelle Monáe also shared tributes.
Cher recalled meeting Prof Hawking for lunch and discussing history while Katy Perry said: "There's a big black hole in my heart".
Comedian Dara O'Briain, who has a degree in mathematics and theoretical physics and is also the presenter of the BBC's Stargazing Live, called Prof Hawking "a hero of mine".
He said: "What a privilege it was to know Stephen Hawking. He was a triumph of what we, as humans, can achieve."
Dara Ó Briain
Replying to
I asked him once “How have you lived so long?” And he said “How can I die, when I have so much of the Universe left to explore?”
3:53 AM - Mar 14, 2018
His life story was made into a 2014 film, The Theory of Everything, starring Eddie Redmayne as the scientist
He also went on to meet Queen Elizabeth in 2014 during a charity event at St James' Palace
Meanwhile, neuroscientist and The Big Bang Theory actress Mayim Bialik, who met with Prof Hawking when he starred in the series, shared a photo of him and the cast.
She described him as "the greatest physicist of our era" while the show itself thanked him "for inspiring us and the world".
The Big Bang Theory
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In loving memory of Stephen Hawking. It was an honor to have him on The #BigBangTheory. Thank you for inspiring us and the world.
1:13 AM - Mar 14, 2018
Many people have praised Prof Hawking's contribution to popular culture, with Oxford University biologist Sally Le Page remarking he was "as much as a cultural icon as a scientific one".
According to online retailer Amazon, Prof Hawking's book A Brief History of Time has risen to the top of its best sellers list following the announcement of his death on Wednesday.
Hawking's discoveries
With the Oxford mathematician Roger Penrose, he showed that if there was a Big Bang, it must have started from an infinitely small point - a singularity
Black holes radiate energy known as Hawking radiation, while gradually losing mass. This is due to quantum effects near the edge of the black hole, a region called the event horizon
He predicted the existence of mini-black holes at the time of the Big Bang. These black holes would have shed mass until they vanished, potentially ending their lives in an explosion that would release vast amounts of energy
In the 1970s, Hawking considered whether the particles and light that enter a black hole were ultimately destroyed if the black hole evaporated. Hawking initially thought that this "information" was lost from the Universe. But the US physicist Leonard Susskind disagreed. These ideas became known as the information paradox. In 2004, Hawking conceded that the information must be conserved
The Royal Albert Hall said the "genius" Prof Hawking was the second physicist, after Albert Einstein in 1933, to ever sell out the venue with his lecture in 1995.
The Motor Neurone Disease Association said Prof Hawking "played a vital role" in raising awareness of the disease, which kills more than half of people within two years of diagnosis.
MND Association
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The 
Our thoughts are with Professor Hawking’s family. Throughout his inspirational life Professor Hawking played a vital role in raising awareness of motor neurone disease around the world.
3:48 AM - Mar 14, 2018
The charity said it had seen such an "influx of donations" following the announcement of Prof Hawking's death that its website had crashed.