Since pi-day, March 14, is coming up, let’s prepare by pondering the number that has obsessed and tortured minds for centuries. This Greek letter, of course, represents the relationship between a circle and its diameter. It’s certainly known by smart alien civilizations throughout the universe. Other universe-wide numbers probably memorized by tattooed Andromeda school-kids no doubt include the four-to-one mass ratio of helium to hydrogen and the speed of light.