As you may know, it is my firm and unflinching belief that our math & science “holidays” should be scheduled so that they actually teach something about the number being celebrated. Sure, 3.14 is a reasonable estimate of π, and March 14th does represent that number in typical US calendar notation (which has no respect for the hierarchical organization of dates).
But, that says nothing about what π represents. It represents the relationship between the radius (r) of a circle and both its circumference (C=2πr) and area (A=πr2). When it comes to expressing this relationship using dates, I prefer circumference because both the radius and circumference are lengths. Also, expressing the year as a circle makes sense to me (and, based on their mythologies, a large number of human cultures).
If C is 365.25 days and π is π, then 2r is approximately 116 days, which makes r approximately 58 days.
Which is why, at The Finch & Pea, 27 February is Pi Day.
It may officially be Pi Day, but that doesn’t make it right1. The 14th of March is perhaps the least educational date we could pick for Pi Day. True, π=3.14; and, true, today’s date is 3-14 (using nonsensical American notation). That tells us what π is, approximately, it does not teach us what π means. Continue reading
Traditionally, Pi Day is 14 March, because that is 3-14 and π~3.14 (except in Indiana where it was 3 for a short time – also mythically in Alabama and Tennessee). That tells you the approximate number as our calendar does not handle irrational numbers well. It also does not work in Europe where they sensibly order their dates hierarchically day-month-year.
It also does not describe at all is how we get to that value. π describes the relationship between the radius of circle (r) and its area (A) or circumference (C): A=πr2 and C=2πr. If we set the length of the year (365.25 days) as the area, the radius of our year circle is 11 days. The 11th day of the year is, not surprisingly, 11 January.
I personally prefer to celebrate Pi Day as recognized by the circumference tradition on 27 February (r=58), but to each their own.
If you would like to know how to make an actual pie, check out Ben’s recipe for Pumpkin Pie.