Humans should evacuate Earth within 100 years if we want to survive, Stephen Hawking has warned.
The world famous theoretical physicist says that life on Earth is at too high of a risk of being destroyed by a disaster - such as asteroid strikes, over-population or climate change - to carry on into the 22nd century.
Hawking plans to expand on this declaration in a new documentary seeking to help future generations.
In BBC's Expedition New Earth, Professor Hawking travels the globe to get a greater understanding of how we can ditch Earth and head into space.
It's a stark contrast from his shouts last November, when he estimated humans could not survive another 1,000 years.
He said: "Most recent advances in cosmology have been achieved from space where there are uninterrupted views of our Universe but we must also continue to go into space for the future of humanity.
"I don't think we will survive another 1,000 years without escaping our fragile planet.
"I therefore want to encourage public interest in space, and I have been getting my training in early."
Professor Hawking added: "It has been a glorious time to be alive and doing research in theoretical physics."
"Our picture of the universe has changed a great deal in the last 50 years and I am happy if I have made a small contribution.
"The fact that we humans who are ourselves mere collections of fundamental particles of nature have been able to come so close to understanding the laws that are governing us and our universe is a great achievement."
In the afterword to the book How to Make a Spaceship, Hawking said: "I believe that life on Earth is at an ever-increasing risk of being wiped out by a disaster, such as a sudden nuclear war, a genetically engineered virus, or other dangers,' he said.
"I think the human race has no future if it doesn't go to space."
At a speech he gave to students from Oxford University, Hawkings said: "Remember to look up to the stars and not down at your feet.
"Try to make sense of what you see and wonder about what makes the universe exist.
"Be curious and however life may seem there's always something you can do and succeed at - it matters that you don't just give up."
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