The Webcomic XKCD makes the point that given the birth rate of the United States, for each thing that "everyone knows" when they are adults, every day there are 10000 people who hear it for the first time.
There's an XKCD for everything.


So let's not mock people who do not know things, even common things, if they are willing to learn. They're one of today's lucky ten thousand, because one can only experience the wonders of learning something for the first time once.
If this journey has taught me anything, it is the importance─and difficulty─of holding to one's convictions in the face of failure...of striving always to replace one's ignorance with knowledge.
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Despite having seeing it many times, and know what to do when the markers appear, yesterday I had to ask in Novice Network what "limit cut" refers to. And I'm a Battle Mentor.