Photos: Partying it up for Pi Day

A poster at San Francisco's Exploratorium welcomes visitors to Pi Day celebrations on March 14. Pi is defined as the ratio between a circle's diameter and its circumference. It is commonly known as 3.14159, or 22/7. But the current record for determining pi, an infinite number, is 1.2 trillion digits.

Photo by Daniel Terdiman/CNET News.com