Gravity Tractor

Scientists have finally come up with a way to keep the earth from being utterly decimated by giant asteroids other than blowing the shit out of them. It's called a "gravity tractor". The theory is that just by having a huge 20 ton ship flying along side of the asteroid, they could alter the path of the asteroid. How? The 20 ton space ship would basically use it's own mass to pull the asteroid off course. That's how I understood it anyway.

From ctv.ca:

The authors, Edward Lu and Stanley Love, believe a gravity tractor could safely deflect a 200 metre-wide asteroid in about a year.

Such a strategy has advantages over other proposals:

* Blowing up an asteroid could still leave the Earth vulnerable to incoming fragments, as was dramatized in the Hollywood movie Deep Impact.
* Deflecting an asteroid with the dramatic impact of a heavy spacecraft, "would only result in a minuscule modification of the object's orbit," NASA reports.