In fact, all of these combined do not equal 3E22, so if the world's top infallible physicist agreed the LHC would destroy the world and was certified sane by an infallible psychiatrist, AND an asteroid struck Geneva the last time you planned to turn the LHC on, AND you know the world will end the day the LHC is activated, then if your real probability was 3E22 you should now (by my calculations) think that, on balance, there's about a one in three chance the LHC would destroy the world.

This is why I don't like using numbers like 3E22 as probabilities.

Brilliant. Is there any chance I could persuade you to present this as a top level post on the front page? This is a comment I expect to reference when related subjects come up in the future.