Origins: 3.14159265…

How do you find the holy grail of mathematics?

You start with a circle, which is the easiest geometric shape to draw (just fix one end of a string in place and swing the other end around it, inscribing a circle). Then measure the circle’s perimeter (also known as the circumference) and the distance across its widest point (the diameter). Divide the circumference by the diameter—and you have that well-known but eternally daunting number, p, or pi, which has a value of 3.14159265…

That is part of the mystique of p: Whatever the size of the circle, the value remains the same (what mathematicians call a “constant”). Unfortunately, p is also “irrational,” meaning that it is impossible to calculate its value completely; the decimals go on forever without regular repetition.

Calculating the value of p has been a puzzle for millennia. One of the earliest implied values is given in a biblical passage describing the construction of a huge basin for Solomon’s Temple: “Then [Hiram of Tyre] made the molten sea; it was round, ten cubits from brim to brim, and five cubits high. A line of thirty cubits would encircle it completely” (I Kings 7:23). In other words, p = 30÷10 or 3.