The Exploratorium in San Francisco holds an annual Pi Procession of pi's digits.

Story highlights

Math geeks and others celebrate Pi Day every March 14

Pi, or roughly 3.14, is the ratio of circumference to diameter of a circle

The Pi Day holiday idea started at the Exploratorium museum in San Francisco

Albert Einstein was also born on March 14

CNN  — 

March 14 is my favorite day to be a nerd.

Across the country, math geeks in museums, schools, private groups and elsewhere gather to celebrate the number pi, approximately 3.14. That’s why March 14 – 3-14 – is Pi Day. What’s more, Albert Einstein was born on this day.

A quick refresher: Pi is defined as the distance around a perfect circle, or the circumference, divided by the distance across it, or the diameter. It is also involved in calculating the area of a circle, the volume of a sphere, and many other mathematical formulas you might need in the sciences.

Throughout history, people have been captivated by this number because there is no way to calculate it exactly by a simple division on your calculator. What’s more, its digits go on infinitely, without any pattern in the numbers. 3.1415926535897932 … etc. Even that many digits are more than most people would need for everyday use, but some folks have been inspired to memorize thousands of digits of pi, or even use the digits to create poetry or music.

On Pi Day, one number ‘reeks of mystery’

Math may be scary, but pi is not – as evidenced by the widespread revelry on Pi Day. One might even say – gasp! – it’s cool to like pi these days. Even the House of Representatives supported the designation of March 14 as National Pi Day in 2009.

In countries where the day is written before the month, Friday is 14-3, which looks less like pi. “And so Pi Day is an acquired taste,” mathematician Jonathan Borwein, at the University of Newcastle in Australia, said in an e-mail.

Conveniently, “pi” sounds like “pie,” and pies are round. You could celebrate Pi Day in a casual way by grabbing a slice of pastry, or pizza. If you’re in enrolled in school, your math class or math department might be doing something special already.

Social Media

Follow CNN Science News

  • Facebook: CNNScience
  • Twitter: @CNNLightYears

    But if you happen to live in a particularly pi-happy place, you might be able to take part in some larger-scale, pi-inspired activities.

    Where Pi Day began

    If you want to go where the day is said to be “invented,” look no further than San Francisco’s Exploratorium. Larry Shaw, who worked in the electronics group at the museum, began the tradition in 1988. Last year was Pi Day’s 25th anniversary there.

    Pi Day began as a small gathering with mostly museum staff. Now it’s a public pi extravaganza featuring a “Pi procession,” whose attendees get a number – 0 to 9 – and line up in the order of pi’s digits: 3.14159265 … you get the idea.

    The parade ends at the “pi shrine” – a pi symbol with digits spiraling around it embedded in the sidewalk, which was unveiled last year.

    The Exploratorium installed this "pi shrine" in the sidewalk in front of its new location in 2013.

    For those who can’t attend in person, the Exploratorium has a Second Life Pi Day event that includes “irrational exhibits, fireworks, cheerleaders, music, and dancing.” The museum also lists a bunch of educational activities to teach about the concept of pi.

    On Pi