The idea of an asteroid slamming into Earth may sound like science fiction. But astrophysicists say that with hundreds of thousands of asteroids crossing our planet's orbit,  the threat is very real.

Host Stephanie Martin talks with Stanford Professor Scott Hubbard. He's overseeing the development a new telescope that -- if all goes as planned -- will launch into space five or six years from now and begin mapping the asteroids around us. In a perfect world, that would help us know exactly which ones are headed our way, so scientists can get to work on trying to head them off.