To dispel any doubt that a meteor striking in one place can have an impact around the world, Bryson describes the domino effect that would follow from an asteroid impact. An impact would trigger natural disasters and debris, and it would fill the entire atmosphere with dark clouds. This means that little, if any, life would be able to survive worldwide. Thus, even a small asteroid impact has the potential to completely wipe out life as we know it. With this in mind, Bryson wants to emphasize how close humans come to being wiped out on a daily basis.