For my social circle it's not remotely in the obscure category. I suspect that none of my friends or coworkers would have to look it up on Google...
This is what a liberal arts education is for.
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Of course I realize that not everybody is lucky enough/even wants to get a liberal arts education, but the social/educational structure of America is not something I'm looking to attack this comment.
I also have a liberal arts education, but those fruitful years were reserved for prevaricating on and dissecting various obscure and convoluted logical arguments related to phenomenology.
If you assume everybody on HN is an American, maybe.
I also attended a French school, where it was covered, and I've had at least one conversation with my Norwegian family in which it came up.
Thus, what passes for a "standard high school education" in the United States varies wildly -- in some schools, you can graduate without even being able to read and comprehend a magazine article. In others, the top graduates often find Harvard less intellectually rigorous than their high school (because Harvard has to help their students from worse high schools catch up).