Sir Bernard, best known for his pioneering work with the Jodrell Bank radio telescope, near Manchester, surprised a gathering of Fellows of the Royal Society recently by telling them that while the Hale-Bopp comet has raised the public's interest in astronomy, the dangers that the Earth faces from such floating pieces of interplanetary rock were less widely realised.
He also warned that while some people are in favour of trying to detect and divert asteroids which endanger us, "others say that the risk of an impact is so small that it would be cheaper to let it happen and then rebuild London, or whatever city was destroyed".
But Sir Bernard told the Independent on Sunday that "to calculate on that sort of basis, that it's cheaper to let people die and then rebuild, is not the way I would want to live at all. I would do everything I could do divert a threatening asteroid, of course."
Such measures might include launching nuclear missiles at the object before it hit the Earth, aiming to divert or destroy it.
Scientists differ on whether that would reduce the risk, or create more objects that would endanger us. They agree that wandering asteroids pose a very real threat to life on Earth, but there is no co-ordinated government response.
A US programme called Spaceguard, that used radio telescopes to detect and monitor potentially hazardous celestial bodies, ran out of funding last year. The British National Space Centre hosted a meeting on the subject last November, but last week a spokesman said: "There are various moves within governments around the world to reinforce the watch, but I am not aware of any developments here."
Sir Bernard said: "The whole of our modern society cares only what's going to happen tomorrow. Nobody's going to produce money to protect our remote descendants. People will say that the risk is so small that we can't worry about it - but I say, a chance of 1 in 100,000 is not zero."
Comet Hale-Bopp is about 40 kilometres across, but never came nearer to Earth than 100 million miles.
In the past five years archaeologists have agreed that the dinosaurs were finally wiped out 65 million years ago by an asteroid 100 miles wide which hit the Yucatan peninsula in Mexico, travelling at 20,000 mph.
End of World, Sunday ReviewReuse content