This article appears in the Witness section of the Summer 2017 issue of the New Humanist. Subscribe today.

Can human beings survive on Earth? Stephen Hawking doesn’t think so. The astrophysicist argues that we must colonise another planet within the next 100 years if humanity is to survive climate change, asteroid strikes, epidemics and overpopulation.

Hawking, who is now 74, has warned numerous times about existential threats to the human race, focusing specifically on climate change and nuclear war and saying that we have just 1,000 years before extinction. He has also warned that the development of artificial intelligence could spell the end for humanity. Some commentators have suggested that it is ironic that a leading scientist should issue such dire warnings about the potential risks of technological and scientific progress.

“Although the chance of a disaster to planet Earth in a given year may be quite low, it adds up over time, and becomes a near certainty in the next thousand or ten thousand years,” Hawking said in 2016. “By that time we should have spread out into space, and to other stars, so a disaster on Earth would not mean the end of the human race. However, we will not establish self-sustaining colonies in space for at least the next hundred years, so we have to be very careful in this period.”

This might sound fantastical, but in a two-part documentary, Expedition New Earth, Hawking and two other scientists will explore the practical possibility of humans setting up away from Earth. He is not alone in considering this a distinct possibility. In 2009, NASA launched its Kepler spacecraft, with the mission of searching the nearby region of our galaxy for Earth-sized planets orbiting in the habitable zone of stars similar to our sun. This zone is called the “Goldilocks zone” because it is the range where pressure and temperature are “just right” for liquid water to exist on a planet’s surface.

Hawking’s documentary, which will air later this year, is part of the BBC’s new science season, named “Tomorrow’s World”, after the popular science and technology programme that ran from 1965 to 2003.

The original Tomorrow’s World made some accurate predictions about inventions we now take for granted – such as the mobile phone, cash machines and computers. It also featured some less successful predictions – like water-borne bicycles, paper underwear and the imminent discovery of life on Mars.

Those who want to see a long future for humanity on Earth will hope that Hawking’s prediction falls into the latter category.