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. 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. For those who ca n'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