[Iscool]

NASA can and does do things that no one else on earth can do and better then anyone else can do for now.

It is mind boggling that they can shoot a comet scores of millions of miles away travelling at such a great speed, no less...And how do they know it's there...What radar screen tracks this thing???

But in view of this, what's also mind boggling is how can the 'star wars project' MISS an incoming missle from just a few thousand miles away travelling at a mere thousand or two miles per hour???

Do you believe in UFO's???

[RightWhale]

how do they know it's there

Good question. Either the spaceship or the target. Consider this your assignment: bone up on celestial navigation and report back.

[RightWhale]

a mere thousand or two miles per hour

Numbers are important to engineers.

[El Gato]

And how do they know it's there...What radar screen tracks this thing???

They see it with telescopes and determine it's orbit from multiple measurements over time. Once you know the orbit, you know where it will be for quite some time in the future, and where it's been for quite some time in the past. That's actually less true with comets than say for asteroids or planets because comets "outgas" which can effect their orbits slightly.