Today is Pi Day: 3.14. It's also the birthday of Albert Einstein. Pi is the distance around a perfect circle or the circumference, divided by the distance across it, or the diameter. It's involved in calculating the area of a circle, the volume of a sphere, and many other mathematical formulas you might need in science. In fact, there's no way to calculate it exactly. Its digits go on infinitely (3.1415926535...). Pi is one of those things that is drilled into you in High School.