March 14th is a day for celebrating the mathematical constant known as “Pi.” The significance of the date chosen for this celebration is simple if you look at the date in the month/day format of 3/14, and realize that those three digits match the first three digits of pi. But Pi is anything but simple for some of us to understand.

Pi, or π (3.14159265359…), is a mathematical constant that we have all had to work with, starting in 10th-grade geometry. Many students are simply taught that π is equal to 3.14, but there is a much more interesting history to this mathematical constant, that your math teacher didn’t tell you about!

The first documented inquiries into the value of π were in Babylonia and Egypt, about 4,000 years ago. Rope was used to measure the circumference of a large circle, such as a cylindrical pillar, and compare it to the diameter of the circle. It was found that the ratio of the circumference to the diameter of the circle (π) was slightly greater than 3. The Rhind Papyrus, written in 1650 B.C. by an Egyptian scribe named Ahmes, gave an approximation of π ( 3.16049) which was surprisingly accurate!

The next group in the ancient world to study Pi were the Greeks. Archimedes of Syracuse used a novel method to approximate the value of pi. He started with a polygon inside of a circle and increased the number of sides of the polygon until it had so many sides that it was essentially a circle. In this way, Archimedes could accurately (for the times) estimate the perimeter of the polygons, which estimated the circumference of the circle. He approximated that π is less than 3.140845 but greater than 3.142857.

After the work of Archimedes of Syracuse, not much occurred in regards to finding the most approximate of π until the late 16th century, in France. Improving upon Archimedes’ method, Franḉois Viete found that pi was greater than 3.145926535 but less than 3.1465926537.

The next few hundred years yielded more and more accurate approximations of π. The next large surge in approximated digits of π came from the use of early computers in 1961 when John Wrench and Daniel Shanks found the first 100,000 digits of π. By 1973, 1 million digits of π were found, and today we know the first 6 billion digits of π!

Pi Day was first celebrated by staff at the San Francisco Exploratorium in 1988, and the phenomenon has grown to have worldwide exposure. Pies and puns are shared widely, and the day is given extra significance in the scientific community as it is also the birthday of Albert Einstein. In 2009, The United States House of Representatives passed a non-binding resolution recognizing March 14 as National Pi Day.

Happy Pi Day to all!