Watch Live: Defending Earth from Asteroids with Neil Tyson

Asteroids orbit the Sun between Mars and Jupiter in the asteroid belt. But near-Earth asteroids come much closer to our planet. Major collisions are exceedingly rare, but there are about a million near-Earth asteroids that are large enough to substantially damage or destroy a major city. » 10/25/13 6:06am 10/25/13 6:06am