By sort of combining the research of a lot of smart people, I came up with an equation for dread [dread=uncontrollability+unfamiliarity+imaginability+suffering+scale of destruction+unfairness]. The dread equation is a simplification, but it's a way to explain why we fear something so much when it is so unlikely. Part of it is the lack of control. That's why we're more scared of plane crashes than car crashes even though we know rationally which is more dangerous.