Love Pi Day? You Can Thank San Francisco for That.

Tomorrow is Pi Day, the annual celebration of the ever-intriguing mathematical constant denoted by the Greek letter π. Children in math classes across America will soon be discussing the magic of a circle’s circumference and, perhaps more memorably, devouring delicious pies.

The nerdy holiday, observed on March 14 because the first three digits of pi are 3, 1 and 4, has been recognized by the U.S. House of Representatives. And in 2019, UNESCO designated March 14 as the International Day of Mathematics.

But years before all that, Pi Day was just a wacky tradition at a science museum in the Bay Area.

The Exploratorium, currently at the Embarcadero along San Francisco’s eastern waterfront, was founded in 1969 by the physicist and professor Frank Oppenheimer, who wanted to create a more hands-on way for children to learn about science. (Oppenheimer was the younger brother of J. Robert Oppenheimer, the “father of the atomic bomb” and the subject of this year’s best picture winner at the Oscars.)

Frank Oppenheimer ran the Exploratorium, originally located in the city’s Palace of the Fine Arts, until his death in 1985. Three years later, museum employees found themselves at a staff retreat in Monterey trying to think up ways to continue developing and growing the museum.

That’s when Larry Shaw, a physicist and media specialist at the Exploratorium, felt inspiration strike.

Pi has fascinated mathematicians for thousands of years, not least because it is an irrational number — its digits seem to go on forever without falling into a repeating pattern, a tantalizing glimpse of infinity. It is the ratio of a circle’s circumference to its diameter, and circles themselves tend to hold some mystery, as perfect shapes with no beginning or end, according to Samuel Sharkland, senior program director at the Exploratorium.