For all of you nerds, pie-in-the-sky dreamers and circular reasoners (and anyone who's been accused of being, or wants to be, any of those), your day has come. Pi Day. On March 14. And in 2013, Pi Day turns 25.
A quick refresher: Pi, the ratio of a circle's circumference to its diameter, is 3.14159.... It's an irrational, infinite number; it has been calculated to 10 trillion decimal places so far, and each digit appears as often as any other digit. There are no patterns or repeating sequences among the digits, so pi seems to be statistically random.
San Francisco has a unique claim to Pi Day--it was born in our very own Exploratorium, the brainchild of physicist Larry Shaw. In 1988, Shaw got his Exploratorium colleagues to help build a pi shrine, circle around it and eat pie. The U.S. House of Representatives in 2009 passed a non-binding resolution recognizing March 14 as National Pi Day. The reasoning was simple: "Whereas since 1995 the United States has shown only minimal improvement in math and science test scores" and "America needs to reinforce mathematics and science education...to compete in a 21st-century economy," our reps figured that designating and promoting Pi Day might nudge those scores up. It's a nice coincidence that March 14 is Albert Einstein's birthday.
Pi Day is now an international phenomenon. In San Francisco, here are some 2013 public celebrations of the homegrown holiday, including the writing of pi in the sky above the Exploratorium. And you can read or watch Life of Pi, watch Pi, memorize as many pi digits as you can, walk, spin and think in circles, eat pie, and be irrational for the day.
25th Annual Pi Day
March 14, at 1-3 pm
Come to the birthplace of Pi Day. Starting with the installation of the Pi Shrine at 1 pm, the homage includes a pi parade, demos about pi and sampling of pie. Look up to see pi in the sky, literally: Synchronized skywriters will scrawl pi's digits in the air, starting at 1:59 pm. Sing “Happy Birthday” to Albert Einstein, too.
Outside the Exploratorium (outdoors), Pier 15, San Francisco 94111. Free.
Pi NightLife
March 14, at 6-10 pm
An evening of pi, pi puns and pi riffs. There are hula hoops to gyrate and their dimensions to calculate; Sudoku and other fun math (not an oxymoron here) puzzlers offered by the Mathematical Sciences Research Institute; and pie samples from Whole Foods and Peasant Pies. A baker shows you how to make a pie, and a rep from Pie Ranch, a sustainable farm and education center on a pie-wedge-shaped plot near Pescadero, talks about food systems. Learn about pi in the sky, i.e., its role in the search for exoplanets. Morrison Planetarium director Ryann Wyatt gives a special presentation, “Music of the Spheres,” about theories dating back to ancient times about the unheard music from planets’ motion. Hear live music from electronic musicians, and roam around the many exhibits and creatures of the sprawling Cal Academy.
At the California Academy of Sciences, 55 Music Concourse Dr., Golden Gate Park, San Francisco 94118. Ages 21+. Tickets $10, 12.
Pi Day Puzzle Party
March 14, at 7 pm
Exercise your gray matter in a fun and boisterous competition to solve math and logic puzzles. You can fly solo or with a crew of up to six people; come with crew mates or form a team once you arrive. Bring pencils and scratch paper, and for brain power, chomp on food truck offerings. Hosted by math guy Wes Carroll and organized by Ask a Scientist.
At the SoMa StrEat Food Park, 428 11th St., San Francisco. Free.


