Famed theoretical physicist Stephen Hawking has spent his life pondering big questions about the wider universe. In recent years, he’s turned his attention closer to home, talking about AI, climate change, alien invasion, and other threats to the future of humanity. Now, he’s put an expiration date on our species if we don’t get into space. He’s giving us just 1,000 years.Hawking’s latest warning came in a speech delivered at Britain’s Oxford University Union. He noted that Earth is fragile, as is any single planet. The odds of a catastrophic global event wiping out humanity in any given year is slim, but over the course of years the chance becomes quite high. Human activity is only increasing those odds as well.

Hawking noted in the speech that some of the most pressing concerns for the future of humanity could come in the next century, as artificial intelligence is perfected and global climate change continues to affect civilization. When something happens on Earth, we don’t want all of humanity to be here, according to Hawking. The best way to keep the species going is to make sure we’ve got a backup — humans on other planets and maybe even in other star systems.

But where could we go? The easiest way to get humans off of Earth is to colonize Mars, and there are some ambitious plans to make that a reality within our lifetimes. The SpaceX Interplanetary Transport System is designed to shuttle as many as 200 people to Mars in each three month trip. Launches would only happen when the orbit of Mars put it close enough to Earth for such a quick journey. It’s certainly feasible to move people to Mars, but creating a functional society is still an unknown. Mars has no magnetic field to protect people from radiation and its thin atmosphere isn’t breathable.

ITS Mars

Mars is a good start, but being in a completely different solar system would be the ultimate backup for humanity. Astronomers are constantly finding potentially habitable exoplanets, but we can’t get to any of them with current technology. The most likely target for further examination is Proxima Centauri, which harbors an exoplanet that may be Earth-like. First, we need to get a closer look at it, which the upcoming James Webb Space Telescope can manage. A few centuries ago, wooden sailing ships were the fastest way to travel, so who know what we’ll have in another couple generations? Proxima Centauri might not seem that distant.

A whole millennium might sound like a lot of time, but humanity has existed in more or less its current form for about 100,000 years. It’d be an awful shame if all this progress we’ve made was for naught in just 1% of that time. We should probably get on this.