Happy Pi Day, Earth! Celebrate the Math Holiday with Countries Across the World

We all know what Pi is. It's that funny little symbol (π) on our calculator that's equal to 3.14. Despite its two-letter length and relatively small value, Pi has an enormous and lengthy history dating back to ancient times.

So what's so special about Pi? You don't hear any other numbers, fractions, or ratios getting their own special name. Well in case you didn't know, Pi is the ratio of a circle's circumference to its diameter.  Archimedes, the ancient Greek mathematician, determined that Pi was 22/7 when he began using polygons to approximate circles. But until 1706, it was merely known as Pi, or 3.14159.

Then, in 1706, William Jones began using the Greek letter (π) to symbolize Pi because the letter 'p' was used to represent the perimeter of circles. The Greek letter became even more popular when Swiss mathematician Leonhard Euler began using it in 1737. And since then, Pi has been a celebrity in the world of mathematics.

Pi's usefulness can be as expansive as calculating the spherical volume of our universe or as simple as solving a geometric equation. On 39 digits beyond Pi's decimal are needed to accurately calculate the spherical volume of the universe, which is significant because in recent years Pi has been calculated to over one trillion digits past its decimal. Its symbol is most famously represented in the area of a circle equation, A = πr², and the volume of a cylinder equation, V = πr²h.

You can learn more fun facts and even purchase some gear on the Pi Day website.

Pi has a fairly notable achievement dating back to 2500 B.C. The Great Pyramid at Giza in Egypt is believed to have been designed based on Pi. This belief was proposed by John Taylor, a publisher and writer, who discovered that dividing the perimeter of the pyramid of its base by its height produces a number that is close to 2*π. However, the construction of the pyramid, which took place from 2589 to 2566 B.C., has shown no evidence of the intentional use of Pi.

More interesting facts and bits about Pi can be found in this Live Science article. Happy Pi Day everyone!