We’re only 7 days away from Pi day! Coincidentally, that is also the 11th, 27th, 35th… digits in the never-ending and non-repeating circle (bad pun) of numbers called “pi”. But what exactly is pi? How does it work? And most importantly, what is Pi day?

The earliest records of pi come from Ancient Egypt and present day Iraq in the year 1900 BC. Slowly, mathematicians from almost all corners of the globe began to discover pi as well. India, Greece, Rome, and China all developed ways of calculating pi, resulting in the approximate value of seven digits of pi by 480CE. Today, computers have calculated pi to five trillion decimal digits, a pretty amazing feat as 1600 years ago, the greatest mathematicians only knew seven. In simple terms, pi is the ratio of a circle’s diameter to its circumference. For example, if the circle’s diameter was one unit, the circumference would be π units. A visual demonstration is shown here.

Use of pi in mathematics, science, and engineering is universal. From probability to geometry, architectural design to aerodynamics, pi plays a huge part in our lives. Pi day was created to in 1988 by Larry Shaw in San Francisco. A fun idea at first, the holiday was officially recognized by the US House of Representatives 29 years later. Today, pi day involves people eating pie, discussing pi, and celebrating the birthday of Albert Einstein. Officially, the celebration starts at 1:59pm to add to the approximate 3.14159 when combined with the date.

So get ready for pi day; Fire up the ovens, bring out the compasses, and whip out those cone-shaped party hats because we’re going on a mathematical adventure.