Last Saturday (March 14, aka National π Day), when I randomly pulled a pair of socks out of my sock drawer, I was astonished at the coincidence that it was my “π Day” pair. I suspect that not all of our readers are sufficiently esoteric to celebrate this popular holiday, so I will briefly bring you up to date. In 1988 an eccentric physicist (Larry Shaw) at the Exploratorium, a science museum in San Francisco, initiated a celebration honoring π, the Greek letter representing the ratio between the circumference of a circle and its diameter.
We amateur mathematicians know that π is an irrational number, a number that cannot be expressed as the ratio of two integers, and that its decimal expansion is infinite. π equals 3.14159265358979232….., which slide rule precision quickly approximated with 3.14. If we express the date (March 14) numerically as 3/14, the transition to 3.14 is an easy one, so Shaw called it π Day. In 2009, in one of its rational moves, the United States House of Representatives passed a resolution designating March 14 as National π Day. In 2019 the United Nations Educational, Scientific, and Cultural Organization (UNESCO) designated National π Day as the International Day of Mathematics. The climax occurred in 2015 when the combination of the 3/14/15 date and the 9:26:53 time involved the first ten digits in proper sequence. Mathematicians and scientists across the world celebrated “π Instant”, the infinitesimal time interval when all the digits were represented. I suppose they deserve the right to behave weirdly now and then!
My son’s Alma Mater, the Massachusetts Institute of Technology (MIT), has no shortage of such uninhibited people. They post, on-line, the names of the successful applicants for admission on National π Day at 6:28 (π times two) pm. Albert Einstein’s birthday was on March 14, so Princeton University has a double celebration, with both pie-eating and Einstein Look-alike” contests.
I thought I was onto something unique when I remembered that we slide rule pushers used the ratio 22/7, which equals 3.14 to three significant figures; perhaps July 22 could be an alternate National π Day. Turns out lots of folks were ahead of me on that one; trivial buffs know that July 22 is “π Approximation Day”.
I suspect my infatuation with the whole idea of National π Day is the fact that it merges two of my niche favorites – mathematics and pie. I come by my love of pie naturally; it was a staple in the diet of my father’s family. They served pie at all three meals in the day. My father preferred to have his pie at the beginning of a meal, as an appetizer rather than as dessert. The first time I saw a bumper sticker saying “Life is short, eat dessert first!”, I thought of him. Fortunately for me, my daughter Beth has inherited the baking genes from both sides of her family; she is easily the best pie baker I know. Choosing between apple, pecan, and pumpkin pie at one of her holiday meals is always a challenge.
As I write this, we are in the middle of Iditarod Week and I am busy following its action. Fortunately, there is a plethora of information available on the Internet, making up for the dearth of news about it on conventional media. One of the human-interest stories that appeals to me is the reputation that checkpoint Takotna has built as the preferred spot for mushers to take an extended rest stop so they can enjoy the pies that the villagers prepare for them each year. Sadly, this year the last mushers had left Takotna on Friday, too soon to celebrate National π Day there.
Mathematically π is far too interesting to cover adequately in a short column like this one. Perhaps a subject for a future one.
In 250 BC Archimedes came up with a reasonable approximation of the value of π by the method of polygons. He determined the length of the smallest ninety-six sided polygon that could enclose a circle and the largest one that could be enclosed by a circle, determining that the value for π had to be greater than 223/71 (3.1408..) and less than 22/7 (3.1429…). Around 256 AD Chinese mathematician Lui Hui used a polygon with 3,072 sides to derive a value of 3.1416. The development of infinite series technology in the sixteenth and seventeenth centuries provided a more effective way to extend the precision to hundreds of decimal points. In 1844 a German savant named Zacharias Dase used it to calculate the value to two hundred decimal places in his head.
Welsh mathematician William Jones is credited with the first use of the symbol π to represent the circle to diameter ratio in 1706. Leonhard Euler’s widely read 1748 work “Introductio in analysin infinitorium” introduced it to popular usage by mathematicians.
Leave it to the mathematicians to find fault with even a centuries-old concept like π! There is a growing faction within the current mathematical community to boycott National π Day and replace it with June 28, National Tau (τ) Day. It is their contention that the ratio of the circumference of a circle to its radius, which they call Tau (τ) is much more useful than π. For example, the angle at the tip of a pizza slice (assuming the pizza is sliced into eight equal pieces) is π/4, not π/8. If that doesn’t convince you how about the fact that trigonometric functions cycle every 2 π radians. And if that doesn’t work, I welcome you into the club of non-mathematicians who consider the entire argument balderdash. After all, what does National Tau (τ) Day offer to compete with apple pie?
I suspect National π Day’s celebration should be tongue-n-cheek, a celebration of us square pegs trying to find round holes. We would be happy if were celebrated. every day.