Time and time again:
Colleague: I can bet you mathematicians have never thought of <trivial observation>!
Me: I don't want to dampen your enthusiasm, but they've been at this for *thousands of years*. Let's see, that's Sumer/ancient China/India/Greece/13th century Italy/...

It's odd to me that educated technical types will have a decent intuitive grasp of the highlights of 20th century physics, but 19th century mathematics is an undiscovered country - even the major landmarks are unheard of.

Note this is NOT in any way a criticism. I'm just struck by the fact mathematics general knowledge is only held by mathematics specialists - this is not the case for other fields.