Tributes have been paid to British science fiction writer Sir Arthur C Clarke - whose short story was turned into the film 2001: A Space Odyssey - who has died in Sri Lanka at the age of 90.
SIR PATRICK MOORE, ASTRONOMER
He was ahead of his time in so many ways. Quite apart from artificial satellites there were other things too. A great science fiction writer, a very good scientist, a great prophet and a very dear friend, I'm very, very sad that he's gone.
TERRY PRATCHETT, AUTHOR
It is very hard to hear [the news of his death], I must say. He was one of a generation of remarkably good science fiction writers, but I think he was one of the best known and, indeed, the best in the world.
He made things seem real. I think the reason that 2001 will be remembered for a very long time, both the book and the movie, was that before then spaceships, you could see the string. It wasn't really taken seriously.
So much hard work went into 2001 and it became real for lots of people...
He saw the things that he had forecast come to pass - not all of them, but certainly the artificial satellite in synchronous orbit, was one of his ideas and so he's perhaps, quite well known, as - if you like - one of the founding fathers of the space age.
ALAN STERN, NASA ADMINISTRATOR
Arthur Clarke was a gifted writer of science and science fiction, and an unparalleled visionary of the future, inspiring countless young people throughout the middle and later 20th century with his hopeful vision of how spaceflight would transform societies, economies, and humankind itself.
Although his personal odyssey here on Earth is now over, his vision lives on through his writing; he will be sorely missed.
GEORGE WHITESIDES, NATIONAL SPACE SOCIETY
That particular enthusiasm of his was what I think made him so popular in many ways, that he was always thinking about what could come next but also about how life could be improved in the future. It's a vision that I think we could use more of today.