There's a lot of background mess in our mental pictures of the world. We try and be accurate on important issues, but a whole lot of the less important stuff we pick up from the media, the movies, and random impressions. And once these impressions are in our mental pictures, they just don't go away - until we find a fact that causes us to say "huh", and reassess.
Here are three facts that have caused that "huh" in me, recently, and completely rearranged minor parts of my mental map. I'm sharing them here, because that experience is a valuable one.
- Think terrorist attack on Israel - did the phrase "suicide bombing" spring to mind? If so, you're so out of fashion: the last suicide bombing in Israel was in 2008 - a year where dedicated suicide bombers managed the feat of killing a grand total of 1 victim. Suicide bombings haven't happened in Israel for over half a decade.
- Large scale plane crashes seem to happen all the time, all over the world. They must happen at least a few times a year, in every major country, right? Well, if I'm reading this page right, the last time there was an airline crash in the USA that killed more that 50 people was... in 2001 (2 months after 9/11). Nothing on that scale since then. And though there has been crashes on route to/from Spain and France since then, it seems that major air crashes in western countries is something that essentially never happens.
- The major cost of a rocket isn't the fuel, as I'd always thought. It seems that the Falcon 9 rocket costs $54 million per launch, of which fuel is only $0.2 million (or, as I prefer to think of it - I could sell my house to get enough fuel to fly to space). In the difference between those two prices, lies the potential for private spaceflight to low-Earth orbit.
What's interesting about the Fermi Estimate post is that its examples encourage you look for predictors that are unexpectedly reliable, rather than those that first jump to mind.
That I haven't heard of many plane crashes in the past decade, this sounds like something I might hear on a post arguing an opposite point. "Sure, you've haven't heard of plane crashes in a decade, but why suspect that reliable predictors are in the neighborhood of your daily activities rather than your knowledge about the world? And now I will eye you knowingly until you learn something of your cognitive biases!"
Although, perhaps there aren't any estimated-statistics approaches that would be any good here, that wouldn't rely on other more incidental bits of information you happen to possess. Sure, you could try to list the top causes of flight disasters (human error and mechanical malfunction?) and estimate the likelihood these things occur, and also estimate how many of these flights result in large scale deaths. But there may be too many variables; either that, or I have ways to go in making Fermi estimates. In any case, it would be hard to incorporate the time variation of flight disaster outcomes. For all I know, flight safety has skyrocketed in the past decade due to widespread process improvement resulting from studying past disasters. And how could I ever predict that effectiveness, or predict how long it would take to come about?
Please see my sibling comment on why the availability heuristic delivers in spades about jumbo jet crashes.