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...