Pascal's Yahtxxee, or why I don't worry about very improbable things

I understand the impulse to say "nothing's impossible". We've been raised on stories about heroes triumphing over impossible odds. Our scientific understanding of what's possible has greatly expanded in the last couple centuries. Things once thought impossible have become possible at historically unprecedented speed. "Nothing's impossible" is a good heuristic, because if someone tells you something's impossible, especially someone with a lot of power, it's probably because they don't want you to try. But like all good heuristics, this can be harmful when followed dogmatically, or taken to an absurd extreme. Some things really are impossible, or so unlikely they're not worth thinking about. And thinking otherwise can lead us to act against our own self-interest. Say you roll a six-sided die. What are the odds that you'll roll a 17? I can tell you with confidence that the odds are zero. I can bet you a billion dollars that you won't roll a 17. Even if you can roll it hundreds of times a…