Chelyabinsk Meteor Explosion Equaled 500 Kilotons of TNT

What's great about astronomy is it doesn't just answer some of the biggest questions (How old is the universe? Can life exist on other planets? What's the prettiest planet in the solar system?) -- it also has a few practical applications, too. As the residents of Chelyabinsk, Russia, found out last Feb. 15 when a large space rock exploded overhead, not knowing what's going on in the skies can be pretty harmful. And, thanks to that very rock, we now have an even better understanding of what ha