It's time to abandon Earth, warned the world's most famous theoretical physicist. In an interview with website Big Think, Stephen Hawking warned that the long-term future of the planet is in outer space.

"It will be difficult enough to avoid disaster on planet Earth in the next hundred years, let alone the next thousand, or million. The human race shouldn't have all its eggs in one basket, or on one planet," he said.

"I see great dangers for the human race," Hawking said. "There have been a number of times in the past when its survival has been a question of touch and go. The Cuban missile crisis in 1963 was one of these. The frequency of such occasions is likely to increase in the future."  But I'm an optimist. If we can avoid disaster for the next two centuries, our species should be safe, as we spread into space," he said.

Still, we need to act and act fast, Hawking stated. "It will be difficult enough to avoid disaster in the next hundred years, let alone the next thousand or million. Our only chance of long-term survival is not to remain inward looking on planet Earth but to spread out into space. We have made remarkable progress in the last hundred years. But if we want to continue beyond the next hundred years, our future is in space."

In April, he warned of the dangers of communicating with aliens, telling the Discovery Channel that extra-terrestrials are almost certain to exist -- and humanity should avoid contact with them at all cost. The answer, he suggests, is that most of alien life will be the equivalent of microbes or simple animals -- the sort of life that has dominated Earth for most of its history -- and they could pose a serious threat to us.