A fantastic think-outside-the-box idea from a student at MIT.
Sung wool paek suggests we fire paintballs at any asteroid on a crash collision with Earth. The combined effects of multiple hits will knock the asteroid slightly off course. Then the white paint will increase the asteroid’s reflectivity, moving the asteroid more and more off course. The only catch it that we need about 20 years warning, and we’ll need to fire the paintballs from space. Nevermind the naysaying though, this is a great piece of thinking way outside the box.