NASA is working to protect us from a giant asteroid collision. I like the simplicity of the current popular plan: just push the thing enough, while it is very far away. The current plan calls for building a satelitte that will orbit the asteroid and change its course ever so slightly by exerting a small gravitational pull on the asteroid. The plan even has a catchy pop name -- asteroid tractor. One draw back has got to be that starting early is a huge priority.