The world's top scientists have paid tribute to Stephen Hawking who has died aged 76.
US astrophysicist Neil deGrasse Tyson says Stephen Hawking's passing will leave an "intellectual vacuum".
"But it's not empty. Think of it as a kind of vacuum energy permeating the fabric of spacetime that defies measure," he said in a tribute following the news of Professor Hawking's dead on Wednesday.
Last year, Mr Tyson, who is best known for his television series Cosmos: A Spacetime Odyssey, received the prestigious Stephen Hawking Medal for Science Communication.
Celebrity scientist Lawrence Krauss tweeted "a star just went out in the cosmos" following the news.
Astronaut Scott Kelly described Mr Hawking's death "as a loss for all humanity".
The United State's space agency NASA also remembered the renowned physicist, tweeting "may you keep flying like superman in microgravity".
Queen Elizabeth II sent a message of condolence to Hawking's family, Buckingham Palace said.
Prime Minister Theresa May praised the scientist as "a brilliant and extraordinary mind" on Twitter, adding he was " 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," she said.
Tearful well-wishers lined up at the University of Cambridge's Gonville and Caius College, where Hawking was a fellow for more than five decades, to sign a book of condolence.
"So many people have come to pay tribute to #StephenHawking we've increased the books of condolence to four. Many beautiful and moving messages," the college wrote on Twitter.
Professor Didier Queloz, an astrophysicist and colleague of Hawking's, told AFP that he was "an extraordinary person to meet".
Australian scientists inspired by 'near-superhuman' Hawking
The renowned cosmologist and astrophysicist inspired many Australian scientists.
Dr Brad Tucker, a research fellow and manager at Mount Stromlo Observatory at the Australian National University, said Professor Hawking pushed fellow scientists to challenge themselves and the unknown.
"He leaves having inspired many of us and having helped us to tackle the big questions that humans have asked for centuries," Dr Tucker said in a statement.
Associate Professor Alan Duffy, a research fellow in the Centre for Astrophysics and Supercomputing, said Mr Hawking's discoveries in black hole physics were legendary.
"He was also wonderfully funny with a fantastic media savviness that propelled him into A-list celebrity stardom as few other scientists before."
Professor Duffy said Professor Hawking's illness made his achievements "near-superhuman".
World leaders have also paid tribute, including Indian President Ram Nath Kovind, who said Mr Hawking's courage and resilience would continue to inspire for generations.