This comment as part of a response to the question, “how would a person from 1940 transplanted to 2010 react?” puts the question of relative expertise into focus for me: “Our cars are not much different from the 1940 cars, except for price (they are cheaper with respect to salary). Maybe they are a bit faster, but not significantly.”
And I think…”what? WHAT? Have you even *seen* a new car? In 2003 I got to drive my ’54 Chevy pickup back-to-back with a 2003 Chevy pickup, and the difference in the two vehicles was staggering–it was a gibbons-to-humans comparison.
But that’s the difference between knowing a lot about a thing, and only having a surface knowledge. When I see the things that people have no concept about regarding cars, it reminds me of the many things that I probably have no concept of regarding things that I’m not hugely interested in: politics, cooking, candles, electronics, horses…et cetera.
Which is why, I suppose, research is such an important part of writing and world-building.