Comment author: lightpurpledye 17 July 2011 11:51:01AM 0 points [-]

What about the aliens who landed on earth, murdered Fred and then went away again? Or the infinite number of other possibilities, each of which has a very small probability?

What confuses me about this is that, if we do accept that there are an infinite number of possibilities, most of the possibilities must have an infinitesimal probability in order for everything to sum to 1. And I don't really understand the concept of an infinitesimal probability -- after all, even my example above must have some finite probability attached?

Comment author: abstractnonsense 17 July 2011 10:35:38PM -1 points [-]

Being as, at any one time, the universe only has a finite space about any point that can be reached at sub-speed of light times. As a result there is only a finite amount of matter and, furthermore, possibility that can happen at the point where Fred died. This limits us to finite probabilities of discrete events.

Were your case possible and we were talking about continuous probabilities it would be the case that any one event is impossible; an "area" in probability space between two limiting values (events in probability space) would give you a discrete probability. You're issue is one that I had issues with until I really sat and thought about how integrals work.

FYI: everything I have said is essentially based on my understanding of special relativity, probability and calculus and are more than open to criticism.