An MIT student has put forward an interesting theory: paintballs could deflect an asteroid's path enough to avert a collision with Earth. As demonstrated in the video below, a pair of perfectly-timed white paintball rounds should be enough to knock an asteroid off its current trajectory, but the really clever bit happens after. By coating the asteroid's surface in white paint its albedo (reflectivity) would increase. The highly-reflective asteroid would then be taken further off course by the pressure of the sun's photons bouncing off the white surface.
The theory comes from Sung Wook Paek, who yesterday won the 2012 "Move an Asteroid Technical Paper Competition," sponsored by the United Nations' Space Generation Advisory Council for his paper on the subject. The paintball concept is an expansion on last year's winning theory, which proposed firing a barrage of pellets at an asteroid to knock it off course.