Tim O'Reilly tweeted about this proposal to deflect pesky asteroids on a collision course with earth. I'm reading The Last Policeman so this is even more interesting to me than usual.
Paintballs may deflect an incoming asteroid
In the event that a giant asteroid is headed toward Earth, you'd better hope that it's blindingly white. A brightly colored asteroid would reflect sunlight — and over time, this bouncing of photons off its surface could create enough of a force to push the asteroid off its course.
How might one encourage such a deflection? The answer, according to an MIT graduate student: with a volley or two of space-launched paintballs.