A pi symbol hands on a wall in Nafplio, Greece, July 2021.
| Photo Credit: Taso Katsionis/Unsplash
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.
Pi is also useful in determining the necessary scale of a tank that serves heating and air conditioning systems in buildings of various sizes.
Space agencies like ISRO use pi to calculate orbits, the positions of planets, elements of rocket propulsion, and spacecraft communication.
NASA holds its annual Pi Day Challenge online, offering games and puzzles, such as calculating the orbit of an asteroid or the distance a moon rover would need to travel each day to survey a certain area.
As for Einstein: possibly the world’s best-known scientist, he was born on March 14, 1879, in Germany. The value of pi was used in many of his breakthrough theories and now Pi Day gives the world another reason to celebrate his achievements.
The famed physicist Stephen Hawking also died on March 14, 2018, at age 76. And he once said: “One of the basic rules of the universe is that nothing is perfect. Perfection simply doesn’t exist. Without imperfection, neither you nor I would exist.”
Ironically, pi is the perfect example.
Published – March 17, 2025 08:50 am IST