Pi Day was on March 14. Why is it celebrated?

Celebrate Pi Day on March 14 with math enthusiasts worldwide, honoring the infinite and practical uses of the mathematical constant.

Mathematics enthusiasts around the world, from college students to rocket scientists, celebrate Pi Day, which is on March 14 every year. The date was chosen because it can be written 3/14 — the first three digits of an infinite number with many practical uses.

Simply put, pi is a mathematical constant that expresses the ratio of a circle’s circumference to its diameter. It figures into numerous formulas used in physics, astronomy, engineering, and other fields, dating back thousands of years to ancient Egypt, Babylon, and China.

Pi Day itself dates to 1988, when physicist Larry Shaw began celebrations at a science museum in San Francisco. The holiday didn’t really gain national recognition until, in 2009, the US Congress officially designated every March 14 to be the big day in the hopes of spurring more interest in math and science. Fittingly, the day is also Albert Einstein’s birthday.

Pi is considered a constant number. It is also mathematically irrational. Long before computers, scientists such as Isaac Newton spent hours calculating decimal places by hand. The first algorithms that calculated pi up to record-setting lengths of several million digits were based on formulae published by Indian mathematician Srinivasa Ramanujan in 1914.

Today, using sophisticated computers, researchers have come up with trillions of digits for pi after the decimal point, but there is no end.

The number didn’t get its name until 1706, when Welsh mathematician William Jones began using the Greek symbol for the number. It’s the first Greek letter in the words “periphery” and “perimeter,” and pi is the ratio of a circle’s periphery, or circumference, to its diameter.

The number is key to accurately pointing an antenna towards a satellite. It helps figure out everything from the size of a massive cylinder needed in refinery equipment to the size of paper rolls used in printers.