One of the most important numbers in our universe is the number Pi or π. Explore humankind’s odyssey—attempts throughout the ages that truly transcend cultures—to compute, approximate, and understand this enigmatic number. The constant π helps us understand our universe with greater clarity. The definition of π inspired a new notion of the measurement of angles, a new unit of measurement. This important angle measure is known as “radian measure” and gave rise to many important insights in our physical world.