Eddie Redmayne has led tributes to Professor Stephen Hawking following the physicist's death at 76, describing him as "the funniest man" he has ever met.
Tributes paid across the world as 'genius' Stephen Hawking dies aged 76
The actor, who won an Oscar for his portrayal of Prof Hawking in 2014 film The Theory Of Everything, said in a statement: "We have lost a truly beautiful mind, an astonishing scientist and the funniest man I have ever had the pleasure to meet.
"My love and thoughts are with his extraordinary family."
Prime Minister Theresa May was among others paying tribute to Prof Hawking.
She said: "Professor Stephen Hawking was a brilliant and extraordinary mind - one of the great scientists of his generation.
"His courage, humour and determination to get the most from life was an inspiration. His legacy will not be forgotten."
Scientist and broadcaster Professor Brian Cox told BBC Radio 4's Today programme that Prof Hawking was "one of the greats".
"There are many good theoretical physicists who make a big contribution, but there aren't that many greats," he added.
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"And by that I mean that I think there are physicists in a thousand years' time, they will still be talking about Hawking radiation, they will be using his fundamental results on black holes.
"Actually, the last time I saw him at his 75th birthday party, he was talking about the new gravitational wave experiment where we've seen the collisions of black holes, and speculating that those results might be able to prove some of his theorems once and for all.
"Plus his contributions to the physics of the very early universe, so there are at least three and possibly more areas where his work will be remembered as long as there are cosmologists and that's the best you can hope for as a scientist."
Actress and neuroscientist Mayim Bialik, who met and worked with Prof Hawking when he appeared on US sitcom The Big Bang Theory, tweeted: "As we near Pi day (3.14) I join the global community in mourning the loss of the greatest physicist of our era."
Along with a picture of Prof Hawking with the cast of the programme, she added: "#StephenHawking is free from the physical constraints of this earthly condition we all exist in and he is soaring above us now marveling at it all."
Death of a genius: Professor Stephen Hawking dies aged 76
The Big Bang Theory's Johnny Galecki wrote on Instagram: "RIP #stephenhawking Not only your brilliance, but your sense of humor will be sorely missed by all."
Inventor of the World Wide Web, Sir Tim Berners-Lee, tweeted: "We have lost a colossal mind and a wonderful spirit. Rest in peace, Stephen Hawking."
Physicist James Hartle, whose work with Prof Hawking led to the Hartle-Hawking model of the universe's origins, said his colleague had "inspired a lot of people".
Prof Hartle told BBC Radio 4's Today: "What was unique about him was that he had a marvellous ability to see through all the clutter in physics and to see what the essential points are and that, of course, was a great thing for going forward."
He added: "My memory of him would be on several fronts: first our work together, as a scientist, and second as a human being whose whole story is of triumph over adversity and who inspired a lot of people, including me."
Scottish First Minister Nicola Sturgeon, who was among the politicians sharing tributes, said Prof Hawking had "changed the way we see the universe".
European Council president Donald Tusk tweeted: "'It matters if you just don't give up.' Remembering Stephen Hawking."
Indian prime minister Narendra Modi said Prof Hawking had "made the world a better place" and his death was "anguishing".
"Professor Stephen Hawking was an outstanding scientist and academic. His grit and tenacity inspired people all over the world," a tweet on his page said.
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US astrophysicist Neil deGrasse Tyson was one of the first to pay tribute to Prof Hawking. Sharing a photo of himself and Prof Hawking on Twitter, he said the scientist's death has "left an intellectual vacuum in his wake".
He added: "But it's not empty. Think of it as a kind of vacuum energy permeating the fabric of spacetime that defies measure. Stephen Hawking, RIP 1942-2018."
Nasa described Prof Hawking as an "ambassador of science", adding in a tweet: "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."
Greenpeace USA thanked Prof Hawking for helping people understand their place in the universe and for "leaving us in awe and wonder".