If you travel in certain circles, which you likely do, you’ve probably heard that Pi Day this year is special. This year it aligns not just with 3.14 but with 3.1415, a feat of the Gregorian calendar that will not happen again for a century. At which point most of us will not be around. Which was not intended to be a pun. As we countdown to the big day, here’s a random assortment of things to know about our friend pi: • pi is the ratio of a circle's circumference to its diame