Pi Day reveals origins of pi symbol

Everyone with a basic understanding of mathematics knows about pi, the world’s most famous irrational number. And just as recognizable is the pi symbol: 𝝅. But where did it come from? How did a symbol resembling a Stonehenge formation after one too many drinks become a worldwide icon? 

It’s easy to take for granted how much work, human intuition, and experimentation went into developing mathematical concepts that underpin our elementary knowledge today. The mathematicians of antiquity in Babylon and Egypt, for instance, worked out a ratio of a circle’s circumference to its diameter accurate to two decimal places, with Chinese mathematicians improving accuracy to seven decimal places by around 500 BCE. In fact, thanks to invaluable artifacts like the Rhind Papyri, historians have a solid understanding of antiquity’s mathematical understanding dating back to 1650 BCE.

With over 3,500 years of work behind the mathematical constant, designating March 14, or 3.14, as Pi Day seems like the least we modern beneficiaries can do.

Recognition of 𝝅 as the universal pi symbol, on the other hand, is a much more recent invention barely older than the United States of America. According to Britannica, the earliest known use dates back to 1706 by the British mathematician William Jones, with some scholars speculating that he may have taken inspiration from an earlier mathematician named John Machin. The symbol itself is taken from the Greek alphabet, pi being the 16th of 24 total letters. Prior to Machin, mathematicians used inconsistent representations of the constant, with History Today writing that other symbols and approximations like 22/7 and 355/113 were used instead.

“Though he did not prove it, Jones believed that π was an irrational number: an infinite, non-repeating sequence of digits that could never totally be expressed in numerical form,” Patricia Rothman wrote for History Today in 2009. “In Synopsis he wrote: ‘… the exact proportion between the diameter and the circumference can never be expressed in numbers…’. Consequently, a symbol was required to represent an ideal that can be approached but never reached. For this Jones recognised that only a pure platonic symbol would suffice.”  

Despite its murky origins, scholars generally agree that it was Swiss mathemetician Leonhard Euler who popularized the symbol. In 1727, Euler published Essay Explaining the Properties of Air with the Greek letter making its proud debut — although the ratio itself was expressed as 6.28. It wasn’t until 1736, with Euler’s Mechanica, that he introduced the 3.14 figure we know and love today.

Nearly 300 years later, we all benefit from the work of curious minds like Jones and Euler, with Honeywell writing that engineers use pi to talk to satellites, drive electric motors, size up refinery vessels, measure paper rolls, determine tank capacities, and much more. So whether you celebrate Pi Day with a nice, hot slice of pie, a rewatch of your favorite math-themed movie, or doing nothing special at all, it’s always worth sparing a moment to remember the individuals who laid the foundations of the modern world.

Cameron Rasmusson
Cameron Rasmusson is a writer and journalist. His first job out of the University of Montana School of Journalism took him to Sandpoint, Idaho as a staff writer for the Bonner County Daily Bee. Since 2010, he's honed his skills as a writer and reporter, joining the MultiLingual staff in 2021.

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