Stephen Hawking says the only way humankind can escape mass extinction is to find another planet. And the clock is ticking. From a report on USA Today:During a speech at Britain's Oxford University Union, Hawking detailed the history of man's understanding of the universe and reiterated that the future of humankind lies in space. "We must also continue to go into space for the future of humanity," he said. "I don't think we will survive another 1000 years without escaping beyond our fragile planet."