Harrison Ford played lead roles in Blade Runner and Star Wars

The 1982 movie, in which retired cop Harrison Ford hunts four renegade human replicants, came top in a poll of 60 scientists by the Guardian newspaper.

Stanley Kubrick's 2001: A Space Odyssey came second, with Star Wars and The Empire Strikes Back taking third place.

Stephen Minger, a stem cell biologist, said Blade Runner had won because it was "so far ahead of its time".

SCIENTISTS' TOP 10 SCI-FI FILMS 1. Blade Runner (1982) 2. 2001: A Space Odyssey (1968) 3. Star Wars (1977)/Empire Strikes Back (1980) 4. Alien (1979) 5. Solaris (1972) 6. Terminator (1984)/T2: Judgement Day (1991) 7. Day the Earth Stood Still (1951) 8. War of the Worlds (1953) 9. The Matrix (1999) 10. Close Encounters of the Third Kind (1977)

The film was loosely based on the Philip K Dick short story Do Androids Dream of Electric Sheep? and is set in a dystopian futuristic vision of Los Angeles.

Mr Minger, from King's College, London, said: "Blade Runner is the best movie ever made.

"It was so far ahead of its time and the whole premise of the story - what is it to be human and who are we, where we come from? It's the age-old questions."

Chris Frith of the Institute of Cognitive Neuroscience at University College, London, paid tribute to the film's discussion of how to tell a human from a machine.

'Appealing idea'

The empathy test used by the movie's policemen "is not far away from the sort of thing that cognitive neuroscientists are actually doing today," he said.

VOTE RESULTS Which of these is the greatest science fiction film of all time? Blade Runner  61.87%  2001  11.57%  Star Wars  9.92%  Alien  6.38%  Solaris (1972)  10.27%  847 Votes Cast Results are indicative and may not reflect public opinion

Kubrick and author Arthur C Clarke's collaboration, 2001: A Space Odyssey, was rated highly in the poll for special effects which were revolutionary at the time it was filmed in 1968.

Other movies which made it into the scientists' top 10 included Terminator and T2: Judgement Day, The Day the Earth Stood Still and The Matrix.

Seth Shostak, senior astronomer at the Search for Extraterrestrial Intelligence, California, voted for the 1953 classic, War of the Worlds.

He said: "The idea that there could be life that's developed in completely other circumstances in a completely different world which you would never recognise. That's a very appealing idea."

The Matrix came ninth in the science fiction film poll

The scientists were also asked by the Guardian to vote for their favourite authors.

Isaac Asimov headed the list for his collection of short stories I, Robot - which was inspiration for the recent Hollywood film starring Will Smith - and his Foundation Trilogy.

Day of the Triffids by John Wyndham was also a favourite, as was Fred Hoyle's The Black Cloud.

Other writers in the top 10 included Arthur C Clarke, Ursula le Guin, Philip K Dick, Ray Bradbury, Frank Herbert and Stanislaw Lem.