We need to build a thriving space colony within the next 100 years if humans are going to avoid extinction, according to astrophysicist Stephen Hawking.

The Telegraph reported that Hawking makes that argument in his new documentary, Expedition New Earth, for the recently revived BBC series Tomorrow’s World. “In it he will claim that time is running out for Earth and if humanity is to survive … we will need to leave our planet and venture further afield,” the publication explained, adding that the documentary shows Hawking and one of his former students traveling the world “to find out how humans could live in outer space.”

It’s not the first time Hawking has made an extreme claim about the future of humanity and life on Earth. One of his more recent declarations was that a genetically engineered virus — one that has been made or modified at a genetic level — was going to kill us all.

Read: Astronomers Find a Planet Like Earth

Doctors are developing these viruses to treat illnesses because they can be used to target specific cells, like cancer cells, and have the potential to cure many diseases. But while these engineered viruses could be lifesaving on a single patient basis, they could be fatal on a larger scale if they are mishandled. Any offspring they would unintentionally make with their natural counterparts would be unpredictable, and could make a disease stronger or even immune to modern medical treatments. And there is the risk of a virus getting out of laboratory containment and spreading through the population, a situation that has happened before, although on a small scale.

When Hawking previously warned against the dangers of a genetically engineered virus, however, he didn’t give humans such a short amount of time to escape Earth.

“I don’t think we will survive another 1,000 years without escaping beyond our fragile planet,” he said at the time, while calling for stronger space travel and colonization efforts.

Photo: NASA/JPL

On top of the risk of a deadly, engineered virus leaking into public spaces, there are also the environmental dangers of climate change, nuclear war, the potential of an enormous asteroid strike wiping us out, and the problem of humanity’s overpopulation of the planet, just to name a few of the biggest challenges when it comes to remaining on Earth.

See also:

9 Places on Earth That Are A Lot Like Mars

These Countries Want to Land on a Mars Moon