My favorite proposed method of asteroid deflection: http://www.planetary.org/explore/projects/laser-bees/ http://www.planetary.org/explore/projects/laser-bees/

My favorite proposed method of asteroid deflection: http://www.planetary.org/explore/projects/laser-bees/ http://www.planetary.org/explore/projects/laser-bees/ The idea is to ablate material off of one side of the asteroid using lasers and/or mirroring sunlight to redirect its trajectory. This is better than using a nuclear bomb which risks fragmenting the asteroid. If you intercept early enough it doesn't take much of a change in trajectory to miss Earth.