Hot on the heels of square root day, a loosely conceived mathematical celebration that fell on March 3 (3/3/09), comes today's pi day. The present "holiday" celebrates the yearly agreement between the calendar (3/14) and the first three digits of pi (3.14...), the ratio of circumference to diameter for a circle. (Europeans, we're terribly sorry: your preference for day/month notation precludes the celebration of pi day, as there is no 31/4—April has just 30 days.)

A follower of SciAm on Twitter,firesignth, clued us in to pi day and its culmination, pi second, which arrives at 1:59:26 today. At that moment, one numerical representation of the date and time, 3.1415926, aligns with pi out to seven decimal places (a creative display of pi several decimal places further than that is at left).

Whereas square root day enthusiasts were encouraged to eat radishes and other roots cut into squares (or, three-dimensionally speaking, cubes, as one astute commenter pointed out), pi day enthusiasts should indulge in pie, of course, which brings the double benefit of being both a homophone of the word pi and a circle. (Just how closely your pie's circumference/diameter ratio comes to pi depends on the precision of your baking.)

While celebrations such as square root day and pi day may seem contrived, one could argue that any way to generate excitement around math is a good thing. In a survey of 11- to 13-year-olds spearheaded by the Raytheon Company, 84 percent of children reported a preference for cleaning their rooms, eating their vegetables or going to the dentist when the alternative was doing math homework. And just this week, in a lecture at Columbia University, 1979 physics Nobelist Sheldon Glashow lamented the mathematical illiteracy of American youth. "If you have not taught a course in physics for poets"—as Glashow has—"you cannot believe the level of mathematical incompetence of the average college graduate," he said.

But if general mathematical cheerleading or feting the famous ratio isn't enough to get you in a celebratory mood, feel free to observe Talk Like a Physicist day instead, an amalgamation of pi day and Albert Einstein's birthday—the great physicist was born 130 years ago today.