Comment by LorenPechtel

And nature doesn't have infinite risk events?!

We are reasonably confident that no likely gamma ray bursters are pointed at us and within lethal range. We know dinosaur killers are out there--a failure to map every such object in the solar system is a small probability of an infinite risk. Why are there no ICBMs fitted for point defense against a city killer asteroid? You have the rocket, you have the boom. You need a seeker that can guide it to impact (there are other radars that could illuminate, it just needs to home on the reflection) and a standoff fuse that will fire it at the last possible millisecond.