Stephen Hawking has reduced the timeframe humanity has to find a new planet from 10,000 years, to 1000, to now just 100.
In a new documentary for the BBC, Expedition New Earth, the famed cosmologist said "climate change, overdue asteroid strikes, epidemics and population growth" were making life on Earth "increasingly precarious".
A statement released by the BBC about the programme says Prof Hawking's latest research shows "science fact is closer to science fiction than we ever thought".
Last year, Prof Hawking said the end of life as we know it on Earth was "a near certainty in the next thousand or ten thousand years".
"Hawking thinks the human species will have to populate a new planet within 100 years if it is to survive," the BBC statement reads.
Prof Hawking has long argued in favour of finding a new planet.
"We must… continue to go into space for the future of humanity," he told Oxford University students in November. "I don't think we will survive another 1,000 years without escaping beyond our fragile planet."
While science is the key to getting off Earth, Prof Hawking has also warned it brings "new ways things can go wrong".
Especially if we meet aliens, which he suspects won't be as friendly as any of the races in Star Trek, having had perhaps billions of years of evolution more than us.
"They will be vastly more powerful and may not see us as any more valuable than we see bacteria," he said last year.