You will remember pi, of course. It is the mathematical constant whose value is the ratio of any circle’s circumference to its diameter. Pi also is the ratio of a circle’s area to the square of its radius. Simply by writing those two sentences I have caused most readers to grit their teeth, remember their high school geometry and higher math courses with a grim shudder, and thank their lucky stars that they never have to use such concepts in their jobs.
Pi is probably the most important mathematical constant, and it is also the point at which math begins to reveal its dark, kinky soul. Pi is an irrational number that starts as 3.14 and then trails off into an endless series of numbers that do not repeat. Some friendless, misguided people celebrate March 14 — that is, 3.14 — as pi day and do things like bake pies with the value of pi to a certain number of decimal places along the rim of the pie crust.
Given the celebration of pi, and its weird irrationality, in the math community, who would have suspected that there is an anti-pi contingent? But there is, and yesterday was their day. These friendless, misguided math enthusiasts propound tau as the preferred alternative to pi. Tau is a mathematical constant that is twice as large as pi; hence tau is 6.28 and change, and tau day is June 28. Why do the tau proponents dis pi and tout tau? They say that tau is a more natural, convenient way to express the mystical qualities of circles, because circles really are about radii — that is, the distance from a circle’s center to the points along the circle — not diameters.
Now that tau day is over, we can gratefully return to our daily lives.