asteroids

i think we should be fairly concerned because if we know that an asteroid is comming, we can evacuate the people it is going to affect.
take tanguska for example, if we would have known that a huge bomb thing was going to hit, we could have gotton the people to saftey. we could completly avoid the affects of a shoemaker levy 9 asteroid because if we know it's coming, we could possibly destroy it or evacuate the people.
On the other hand, they say once every million years a football field or larger sized asteroid threatens earth. and if we can't fix that problem like they did on armageddon, then we are screwed.