[Lunatic Fringe]

If a large asteroid is going to his us, it is already on the path to do so.

Perhaps not. An asteroid in the field between Mars and Jupiter can collide with another, sending it on a trajectory with our orbit.

What's scary is that our recent near misses went completely undetected because the asteroid originated from path between Earth and the sun, making it impossible to see until it passed.

[freakboy]

An asteroid in the field between Mars and Jupiter can collide with another, sending it on a trajectory with our orbit.

That is exactly my point. I never said that the path was straight, only that it is governed by the laws of physics and is already determined. If such an asteroid is going to have a collision, sending it to earth, it is already on a path to do so.