Pi, the mathematical constant, has infinite digits and has been approximated by many civilizations for thousands of years. Pi Day, celebrated annually on March 14, is significant to space exploration as it is the birthday of many important people linked to space exploration. Pi is used in man-made objects like sports equipment, household appliances, and in space exploration. Engineers use pi to calculate parachute size, safely land spacecraft on Mars, study tremors, capture planetary maps, and search for exoplanets.