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.

To Shaw, pi seemed like an ideal subject of scientific celebration. It also had a lucky homophone in “pie,” which offered up a tasty way to entice children and adults to learn about math. (Conveniently, pies are typically shaped like circles, too.)

The Exploratorium hosted its first Pi Day on March 14, 1988, with fruit pie for everyone at the museum to enjoy at 1:59 p.m. (Those are the next three digits after 3.14.)

Eventually, the Exploratorium added a celebration of Albert Einstein’s birthday to its annual festivities (he was born on March 14, 1879). Each year, Shaw would lead a parade through the museum with a boombox blaring the digits of pi to the tune of “Pomp and Circumstance,” culminating in walking 3.14 times around a “Pi Shrine” — a brass plaque inscribed with the first 100 digits of pi — while singing “Happy Birthday” to Einstein.

Shaw told SFGate in 2009 that he and other participants regarded the Pi Shrine with the reverence of worshipers at a religious site. “Ours is a mystery religion,” said Shaw, whom the museum staff fondly called the “Prince of Pi.”

“Just like others, we circumambulate the things we respect,” he told the news outlet. Shaw died in 2017.

Though the museum still goes all out to celebrate each year. Pi Day has long since outgrown its association with the Exploratorium. But that’s not something to be lamented, Sharkland told me.

“It just blossomed,” he said. “It’s something we’re proud of.”

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And before you go, some good news

After another wet winter, California state park officials expect an impressive bloom of wildflowers this spring, USA Today reports.

A number of climate conditions — including rain, sunlight and humidity — affect when and how plentifully the flowers bloom. When these factors come together in just the right proportions, California’s ordinarily dry hillsides become carpeted with lupines, poppies, desert sunflowers and lilies that draw visitors to the state parks.

Though it’s a challenge to forecast the scale of the bloom each spring, state park officials believe that this year will be better than average. Parks across the state experienced a spectacular bloom last year.

Wildflowers are already popping up in some areas of the state, including parts of Anza-Borrego Desert State Park, and more are expected elsewhere from mid-March through May. The parks department has created a guide to the areas that are already blooming. Get ready for some rainbow flora.

Thanks for reading. I’ll be back tomorrow. — Soumya

P.S. Here’s today’s Mini Crossword.

Maia Coleman and Briana Scalia contributed to California Today. You can reach the team at CAtoday@nytimes.com.

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