On March 14, NASA will join people across the U.S. as they celebrate an icon of nerd culture: the number pi. So well known and beloved is pi, also written π or 3.14, that it has a national holiday named in its honor. And it’s not just for mathematicians and rocket scientists. National Pi Day is widely celebrated among students, teachers and science fans, too. Read on to find out what makes pi so special, how it’s used to explore space and how you can join the celebration with resources from NASA.