Schools, math fans celebrate Pi Day -- Celebrate with pi, not cake

Monday is Pi Day — a day to celebrate a number with desserts, numerical recitations and hot-dog throwing.

Pi, the number that expresses the ratio of a circle's circumference to its diameter, was first calculated in ancient times. Though it's a number with no endpoint, its digits start with 3.14159. Thus, March 14, or 3/14, for Pi Day.

The first Pi Day was celebrated in 1989 at the San Francisco Exploratorium.

Now the celebration has spread around the world, and math teachers, students and other self-proclaimed math fans amused or intrigued by pi celebrate the number.

At Morgan Park Academy on the Southwest Side, teachers will focus on pi in class, said Morgan Park's math team leader, James Kowalsky. In his geometry class, Kowalsky in the past has had students take cardboard squares and cut them multiple times to fit them into circles, which allows students to calculate the area of the circles without using pi.

In an after-school pi event at Walter Payton College Prep, students will throw hot dogs on a floor marked with evenly spaced parallel lines. Why? Because the proportion of hot dogs that cross the lines when they fall works out to be approximately one over pi, said Payton mathematics chairman Paul Karafiol.

One highlight of many Pi Day events is a competitive recitation of the numerous digits of pi, which modern computers have calculated to a trillion decimal places. At Morgan Park, the record is 312 digits, while the DuPage Science Fiction and Fantasy Society has had someone recite more than 100 digits, and a Payton student who's now at Yale University remembered a mind-blowing 500 digits.