Pi Day took place on March 14, 2024. Our friendly neighborhood constant is used in engineering to determine the dimensions of gears, wheels, and pipes. Pi is also used in computer science to generate random numbers for cryptography, simulation, and gaming. With a tip of the cap to math enthusiasts, we offer a quick cheat sheet to pi and its fascinating history.

Pi has been known since ancient times The first recorded approximation of pi was done by the ancient Egyptians around 1650 BC. They estimated the value of pi to be around 3.16. The ancient Babylonians also had a similar approximation, as did the ancient Greeks. The Greek mathematician Archimedes is credited with being the first to accurately calculate pi using a geometric method around 250 BC.

The symbol for pi (π) was first used by Welsh mathematician William Jones in 1706. However, it was not widely adopted until the 1730s when Swiss mathematician Johann Lambert started using it. The symbol was chosen because it is the first letter of the Greek word for perimeter (περιμετρος).

Pi is an irrational number, which means that it cannot be expressed as a finite decimal or fraction. Its decimal representation goes on forever, without repeating. This property has intrigued mathematicians for centuries, and many have attempted to calculate pi to as many digits as possible. As of 2021, the most accurate calculation has been done up to 62.8 trillion digits!

Filmmaker Darren Aronofsky (Requiem for a Dream, The Fountain, Black Swan) made his feature film debut in 1998 with Pi, a psychological thriller following an obsessed mathematician who believes everything in nature can be understood through numbers.

Pi Day began in 1988 when Larry Shaw, a physicist at the Exploratorium in San Franscico celebrated the calculation on March 14 (3.14). Fittingly, it’s also Albert Einstein’s birthday. Shaw originally celebrated “Pi Day” by simply eating pies and discussing mathematical constants. It would evolve to include a parade, a pi shrine, the eating of pies (pizza and desserts), and more.

Pi Day was recognized as a national holiday in 2009 and is internationally celebrated.

Not only is pi irrational, but it is also a transcendental number. This means that pi is not a root of any nonzero polynomial equation with rational coefficients. In simpler terms, it cannot be expressed as the solution to any algebraic equation with rational coefficients. This property makes pi even more mysterious and intriguing.

Nathan Mihm, a Mathnasium lead instructor in Eagan, MN, has memorized over 500 digits of pi and continues to learn more for each Pi Day. Nathan developed a passion for mathematics in 9th grade as a participant in the Eagan High School mathematics team.

Practical uses for pi include determining tank sizes for heating and air conditioning systems, calculating the Earth’s circumference (take that flat earthers), accurately pointing an antenna toward a satellite, and determining the size of paper rolls to print this very magazine!

My personal favorites include pi helping NASA engineers design the parachute for Mars landings, searching for exoplanets outside our solar system and peering below Jupiter’s clouds to estimate the volume of materials in the planet’s atmosphere.

In World War II, the Allies used pi to encode messages sent between the US and the UK. They would use pi digits to represent letters, numbers, and other characters.

If March 14th truly represented pi, it would never end. Many would be stuck in a cold, gray-clouded void between winter and spring filling out endless NCAA tournament brackets and consuming far too many Shamrock Shakes.

(facts provided by mathnasium.com, nasa.com, exploratorium.edu)