The first step? Completing a space telescope called Sentinel, equipped with optics to search the skies for threatening objects, scheduled for launch in 2018. Funded largely by private donors like Googler Peter Norvig and Reddit CEO Yishan Wong, the setup has a pretty light budget—just a few hundred million dollars to save whole cities from destruction.

What got you so interested 
in asteroids? I spent six months aboard the International Space Station. From there, you notice a stark difference between the moon and the Earth: The moon is covered in craters. But Earth has craters too—you just can’t see them, because they’re underneath the oceans. So anybody who knows anything about space and probability knows that this is something you have to solve. Nothing else matters at all if you’re going to get wiped out. Since 2000, there have been eight impacts roughly the size of Hiroshima or larger, and the fact that asteroids hit Earth somewhat randomly means you’re basically on borrowed time. You don’t know when the next one’s gonna happen.