i was watching an interview with micho kaku (who wrote physics of the impossible wich is one of my favorite books) talking about "city buster" and "planet buster" asteroids and while im not really worried (big surprise i know) i was wondering how far ahead we can predict these deadly asteroids cause getting hit on the head with a rock the size of an apartment building isnt exactly high on my list of ways to die (its down there with "ebola virus" and "zombie outbreak")