The human race must colonise space within the next two centuries or it will become extinct, Stephen Hawking has warned.
The renowned astrophysicist said he fears mankind is in great danger and its future "must be in space" if it is to survive.
In an interview with website Big Think he said threats to the existence of the human race, such as the 1963 Cuban missile crisis, are likely to increase in the future and plans to handle them must be put in place now.
"We shall need great care and judgment to negotiate them all successfully," he told Big Think.
"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."
Professor Hawking also warned that population rise and finite resources on Earth meant life was becoming increasingly dangerous and the only way to build upon the progress made over the last century was to look out to the rest of the galaxy.
He added: "That is why I'm in favour of manned, or should I say 'personed', space flight."
Earlier this year, Professor Hawking warned that exploring space may not be entirely without risk.
In a series for the Discovery Channel, he said humans should be wary about making contact with alien life forms as they may not be friendly.