Today is Pi Day, a celebration of one of the most fascinating mathematical constants: π (3.14159265358979…). Defined as the ratio of a circle’s circumference to its diameter, pi has intrigued mathematicians and scientists for thousands of years.

Pi Day is observed on March 14 (the 3rd month) since 3, 1, and 4 are the first three significant figures of π.

Ten Fascinating Facts About Pi:

1. The first recorded estimate of pi dates back to around 1650 BC, when the ancient Egyptians approximated it as 3.16. The Babylonians had a similar value, while the Greek mathematician Archimedes (c. 250 BC) was the first to accurately calculate pi using a geometric method.

2. Pi plays a crucial role in physics, astronomy, and mathematics. It is also essential in architecture and construction, influencing designs from bridges and arches to the Pyramids of Giza.

3. Welsh mathematician William Jones introduced the π symbol in 1706, though it wasn’t widely adopted until Swiss mathematician Leonhard Euler popularized it in the 18th century.

4. Albert Einstein, one of history’s greatest physicists, was born on March 14, 1879—making Pi Day even more special!

5. Physicist Larry Shaw organized the first official Pi Day in 1988 at the San Francisco Exploratorium, where it has been celebrated ever since. The holiday has since gained worldwide popularity among math enthusiasts.

6. During World War II, the Allies used pi to encode secret messages between the U.S. and the U.K., replacing letters and numbers with digits from pi.

7. The world record for reciting pi’s decimal places belongs to Rajveer Meena of India, who recited 70,000 digits on March 21, 2015. Wearing a blindfold, he maintained perfect recall for 10 hours!

8. Givenchy sells a men’s cologne called “Pi,” marketing it as a fragrance for intelligent and visionary men.

9. In 2014, 589 students at a German elementary school formed the largest human pi symbol. In 2017, 520 teachers and students in Todi, Italy, created the longest human representation of pi’s digits, with the city’s mayor holding up the number three at the start.

10. Eating pie on Pi Day is a beloved tradition! Whether it’s pizza pie, pot pie, shepherd’s pie, or a classic dessert pie, the key is to keep it round—just like pi itself.