By John Novitsky of Woodside, an engineer and businessman in Silicon Valley for 33 years.
Congratulations Almanac readers. As you read this article, there won't be another "Pi Day" like this for 1,000 years. It's a celebration of one of the most famous irrational numbers in history.
Pi is a constant, defined as the circumference of a circle divided by its diameter. This year is special; the first 10 digits of Pi are 3.141592653. Expressed as a date and time, that's this Saturday, 3/14, year 2015, at 9:26:53 in the morning (though some quibble that it should be at 9:26:54 a.m. due to rounding).
The earliest known written representations of Pi appeared on clay tablets from Babylon (circa 1900 B.C. to 1600 B.C.), and on a papyrus scroll from Egypt (1850 B.C.).
The Greek mathematician Archimedes defined Pi more accurately back in 250 B.C. It took 1,000 years before mathematicians developed better tools to improve Archimedes' calculation.
Today, supercomputers have calculated Pi out to 13.3 trillion digits; no pattern repeats. People try to memorize Pi; the record is over 67,000 digits.
Most people consider the first well known "Pi Day" celebration to have been organized at the San Francisco Exploratorium in 1988.
Here in Silicon Valley, and around the world, many engineers and mathematicians celebrate Pi day by eating pie, and telling math jokes with their scientific friends.
Generally, the more bad jokes you can squeeze into your pie recipe, the better. (Slice up 3.14 apples, bake till a golden mean, and so forth.) Could be a fruit pie, a meat pie, a pizza pie, an ice cream pie, an insect pie: it's all good.
MIT notifies its students of acceptance of admission on Pi day (3/14), at Tau time (6:28 p.m.) to honor both rival numbers. (Tau day celebrations are already being planned for 6/28 2031. Most Tau Day celebrations won't be as "tasteful," since eating a Tau is ... well ... less well defined.) 3/14 is also Albert Einsten's birthday.
Whether you are a high school student eagerly awaiting your MIT admission notification this Saturday evening, or hanging out with your slide rule carrying friends groaning over bad puns but eating good pies, Happy Pi Day.