009: bye, bye, miss american pi
The history of π is an illustrious one, to be sure. It begins almost 4,000 years ago, with the likes of the Babylonian and Egyptian geometers, and continues to the piphilologists of today. I myself can only claim to know the first twenty or so digits, but it is rather fascinating, the lengths some go to remember, and the tricks they use to do so. For example: "How I want a drink, alcoholic of course, after the heavy lectures involving quantum mechanics!" etc.

Nevertheless, the history of π includes such illustrious figures as Archimedes and Isaac Newton himself, who in fact used infinitesimal calculus to develop his own series and calculated the constant to what he admitted were embarrassing digits. I believe he claimed he had no other business to which he might have attended at the time, though I remain under the impression that he had been lonely. π even warrants a mention in the Bible, specifically 1 Kings 7:23. Of all the sources of its age, the Bible was likely the least accurate about the value of π, approximating it as 3, as in the following quotation: "And he made a molten sea, ten cubits from the one brim to the other... and a line of thirty cubits did compass it round about."

In any event, though its precise calculation took thousands of years, π is a simple concept, one that many cover in the early years of elementary school. C = 2πr; we all learn it. People of all levels of experience with math may bond over it, due to their shared understanding. The same should be true for other things.