Stephen Hawking tells mankind: leave Earth or die

Superbrain scientist Stephen Hawking has said that humankind must colonise new planets within the next 200 years, or face extinction.

The world-renowned astrophysicist, who came close to mowing down this writer as a young whippersnapper, told web site Big Think he was an "optimist", but said that spreading out into space was humanity's only hope of survival in the long term.

"I see great dangers for the human race," Hawking said. "There have been a number of times in the past when survival has been a question of touch and go. The Cuban missile crisis in 1963 is one of these.

"The frequency of such occasions is likely to increase in the future. We shall need great care and judgment to negotiate them all successfully."

Hawking delivered a stark warning over the rise in global population and issues such as global warming:

"Our population and use of the finite resources of planet Earth are growing exponentially, along with our technical ability to change the environment for good or ill," he said.

"But our genetic code carries selfish and aggressive instincts that were a survival advantage in the past. It will be difficult enough to avoid disaster in the next 100 years let alone the next thousand or a million."

"If we can avoid disaster for the next two centuries our species should be safe as we spread into space."

This is why, he said, he was in favour of manned - "or should I say personned?" - space flight. The wag.

If some of Hawking's earlier pronouncements are to be believed, exploring our galaxy won't be entirely without risk either. In a BBC documentary in April, the academic cautioned against trying to make contact with alien lifeforms, saying that we could not guarantee they would be friendly.

You can hear Hawking's worries here.