Pi Day — π ≈ 3.14159…

π is the ratio of any circle's circumference to its diameter — a constant that appears throughout mathematics, physics, and engineering, far beyond its geometric origins. It is irrational (cannot be written as a fraction) and transcendental (not the root of any polynomial with integer coefficients). Archimedes proved 3 + 10/71 < π < 3 + 1/7 using 96-sided polygons. Today π has been computed to over 100 trillion decimal digits, yet no pattern ever repeats — every digit sequence you can imagine appears somewhere in its expansion.