During the first celebration, the Exploratorium's employees marched around one of the circular spaces of the museum because Pi is the ratio of a circle's circumference to its diameter.

During the first celebration, the Exploratorium's employees marched around one of the circular spaces of the museum because Pi is the ratio of a circle's circumference to its diameter.

During the first celebration, the Exploratorium's employees marched around one of the circular spaces of the museum because Pi is the ratio of a circle's circumference to its diameter.

During the first celebration, the Exploratorium's employees marched around one of the circular spaces of the museum because Pi is the ratio of a circle's circumference to its diameter.

SAN FRANCISCO -- Every March 14, mathematicians, scientists and math lovers around the world celebrate Pi Day, a commemoration of the mathematical sign Pi. That's because the date written numerically ...