People get cranky when you burst their bubble. Over time, advances in astronomy have relentlessly reinforced the utter insignificance of Earth on a celestial scale. Fortunately, political and religious leaders stopped barbecuing astronomers for saying so, turning their spits with human-rights activists instead.
Nathan MyhrvoldMost estimates of the mortality risk posed by asteroid impacts put it at about the same risk as flying in a commercial airliner. However, you have to remember that this is like the entire human race riding the plane - it is one of the few risks that really could wipe us all out.
Nathan MyhrvoldCrazy ideas sometimes work, and the technological society that we have is built on a foundation of those crazy ideas that work.
Nathan Myhrvold