Your Mileage May Vary

Today, July the 17th, is Yellow Pig Day, a day for mathematicians to celebrate Yellow Pigs and the number 17.

The holiday was started by Princeton math students David C. Kelly and Mike Spivak in the late 60s while drinking at a local pub. The origins beyond that, and the relevance of yellow pigs or the number seventeen, are difficult to come by. Some say that the two were drinking so hard that instead of seeing pink elephants, they saw yellow pigs.

The number 17, according to Kelly, is the most random number, that is, there are more random numbers divisible by 17 than not. The Parthenon is 17 columns long; there are 17 steps from the landing to the door in Sherlock Holmes’ house at 221b (13 x 17b) Baker Street; the last mission to the Moon was on Apollo 17 in 1972 (17×116); the biblical flood started on the 17th, and Noah’s Ark landed on the Mount Ararat (alt. 17,000 feet) on the 17th. [more seventeens]

After Princeton David Kelly started the Hampshire College Summer Studies Program, a six week program for high school students interested in math. It was here at Hampshire College in Amherst, Massachusetts that Kelly turned yellow pigs and the number 17 into a holiday.

Each year the program has a three day Yellow Pig Math Days celebration where students attend lectures, make yellow pig t-shirts, sing songs about yellow pigs, and visit the home of Kelly, who boasts the largest collection of yellow pigs. Hampshire College alumni come back every year to take part in the festivities and hear Kelly read his annual list of random seventeens.

As for Mike Spivak, he has written several math texts, all of which include references to yellow pigs. His text, Calculus is “Dedicated to the Memory of Y.P.” and an index entry for “Pig, Yellow” refers the reader to a page with the sentence: In this case we will go whole hog. Other texts feature yellow pigs on the cover, and references to cowering cops.

• Photos from Yellow Pig Math Days 2006
• Jargon File reference to Yellow Pigs
• 1982 article in The Harvard Crimson about Yellow Pig Day