Pi on a windowsill, or 'it's all Greek to me...'

Hmmm, now for a delicious etymology! The Greek letter pi, like other Greek letters, had a numerical designation when written discretely. For example, rho, kappa, delta, when written together indicate the number 124 since rho=100, kappa=20, and delta=4 (they are linearly additive). Pi was equal to 80, and in contemporary Greece is often used to designate ordinal numbers comparable to the way the rest of Europe tends to use Roman numerals. It was not until Euler, that magical mathematician, adopted William Jones' 1706 definition of pi as 3.1415, that the advent of pi as a description of this irrational constant became common. Pi is often defined as the ratio of a circle's circumference to its radius, but the ubiquitous constant seems to pop up in rather odd areas. For instance, the probability that a pin of a certain length will cross the lines of a lattice of a slightly smaller length tends towards pi (Buffon's Needle).

It is also the inspiration for an aptly titled homage to repetitive (or not!) techno music. It is also the frame for one of my favorite anecdotes. At the 762nd decimal place of the expansion of pi, there is a series of six consecutive 9s. This place is often referred to as the Feynman Point, since the physicist once remarked that if he could recite pi to 762 places, he could then say, 6,6,6,6,6,6, and so forth and so on, implying that pi is rational.