Across the country, math geeks in museums, schools, private groups and elsewhere gather to celebrate the number pi, approximately 3.14. That's why March 14 -- 3-14 -- is Pi Day. What's more, Albert Einstein was born on this day.
A quick refresher: Pi is defined as the distance around a perfect circle, or the circumference, divided by the distance across it, or the diameter. It is also involved in calculating the area of a circle, the volume of a sphere, and many other mathematical formulas you might need in the sciences.