You’ve probably heard of pi—a number between 3 and 4 that harbors infinite decimal places, although often truncated to 3.14. Here’s pi with enough digits to see all ten numerals 0 through 9: 3.14159265358979323846264338327950 … You get pi simply by dividing the circumference of a circle by its diameter. That same ratio prevails no matter the size of the circle. The very existence of pi is a profound truth of Euclidean geometry, celebrated each year by all card-carrying geeks of the world on March 14—a date that can be written as 3.14. Math can be beautiful.
