Assuming it is feasible to accelerate a ship to relativistic speeds, they could well decide to exterminate us in self-defense. A relativistic bomb delivers enor

Assuming it is feasible to accelerate a ship to relativistic speeds, they could well decide to exterminate us in self-defense. A relativistic bomb delivers enormous destructive power, and by definition, it is never where you see it when you see it, and is probably unstoppable. http://www.projectrho.com/rocket/rocket3aa.html#killingstar http://www.projectrho.com/rocket/rocket3aa.html#killingstar has a very good writeup on the subject.