March 14 (3/14) marks the 22nd annual Pi Day, which celebrates the mathematical constant Pi (π), whose first three digits are 3.14.
In mathematics, Pi represents the ratio of a circle's circumference to its diameter. Though scientists, aided by computers, have recently calculated up to the 5 trillionth digit of Pi, the number itself is irrational, meaning its decimal representation will repeat infinitely. Thus, π has come to symbolize the unknown in popular culture.
To get you in the 3/14 spirit, we've collected some videos about Pi, including songs, fun facts and a movie trailer. View the slideshow (below) and vote for your favorite Pi Day video.