# 3/14 is Pi Day!

February 25, 2022

The date of March 14 is quite special to some, especially to mathematicians. Used in almost everything involving circles, you may have heard it at least once before, and may have confused it with pies instead. The mathematical constant, Pi (π) has been useful to not just mathematics, but also architecture, particle physics, and astrophysics.

The date 3/14 is the first three digits of Pi, 3.14, which is what makes it known as Pi Day to some. If you’re particularly interested in math, keep reading! This will explain many things about this famous number, and maybe facts you’ve never heard of before.

**The Number**

Pi! That weird symbol you keep seeing in complex, confusing equations and expressions! Pi is the ratio between a circle’s circumference to its diameter. Great! What does that mean? Simply put, it’s how many times the length of the diameter appears in the circle’s circumference. No matter how small or large the circle is, the ratio will always be the same.

Pi is an irrational number, which means it cannot be written as a simple fraction. Approximations such as 22/7 only get you to a few decimal places. The first six digits are 3.14159, and the decimal places continue on forever.

As a result, Pi has become one famous number to many people, even to people who don’t know what it is! Pi has transcended throughout modern human history for quite some time, speaking of which, Pi is a transcendental number, which means it cannot be explained algebraically. But over the course of centuries, humans have been trying to get to the end of this never-ending number.

**The History**

Humans have been trying to calculate pi for quite a long time, for 4,000 years in fact, and its earliest records appeared from China all the way to Greece. Trying to estimate Pi without calculators was a real challenge. One way of calculating Pi was using regular polygons, circumscribing and inscribing a polygon around and inside a circle, and you can get an estimation of Pi.

The more sides the polygons had, the more of an accurate estimation you can get. This method however was no easy task, people would sometimes spend years calculating with polygons of thousands of sides, only for a few several correct decimal places. That is, until Issac Newton, who just invented calculus, discovered a new method of calculating Pi which was much faster.

Today, we have specialized computers that can count well into the billions of digits, with the latest record having over 60 trillion digits!

There are multiple other methods and equations by other people that try to calculate Pi, however for common uses you only need the first few digits.

It’s uniqueness has made it famous all over the world, and this has evolved into interesting subjects about it.

**The Culture**

It’s influence over the world has spread into various topics among math communities and in popular culture.

You may have heard of Pi memorization, it might be obvious, but it’s where you try to memorize as many correct digits of Pi as possible. Some people have this as a hobby, however there are actual competitions to see who has the most digits memorized. The current world record is 70,000 digits, verified by the Guinness World Records.

Pi has also been represented in some buildings and places, a science museum in France known as the Palais de la Découverte has a circular room containing 707 wooden digits of Pi. A Pi symbol mosaic is featured outside the Technical University of Berlin.

Of course, pies are closely associated with Pi and pies are usually eaten on Pi Day.

There’s usually something called the “Pi minute” which is at 1:59 on Pi Day which is when the date contains the first six digits of Pi, 3/14 1:59. Pi day 2015 was special in that the year also lined up with the digits, for one second during the morning and night, the date represented 3/14/15 9:26:53, the first 10 digits of Pi.

Two times Pi, which is approximately 6.283, also has a special name, Tau. Instead of the circumference over the diameter, it’s divided by the radius. If you know more about circles, you know the radius is half the length of the diameter. Although more obscure, Tau Day or Two Pi Day on June 28 is celebrated by some.

For people who write the day before the month in dates, Pi Approximation Day on July 22 (22/7) can be another date to celebrate the famous constant.

Dates and celebrations aside, the number has even more purpose than just being a number to be happy about, it’s useful for pretty much anything that involves curves and circles.

**Final Facts**

This can’t be facts about Pi without elaborating more on circles, the equation to the area of a circle is πr^2, which is Pi times the radius squared. Think about a circle with radius 1 sliced up into extremely thin pizza slices, and arranging the slices into a rectangle with the pointy vertices facing inwards in the rectangle. The width of the rectangle should be the radius, and the length of the rectangle should be Pi times the radius. Multiplying π*r* by *r* is the same as πr^2. If the radius is 1, then the equation turns into π*1*1, which is π. So the area of a circle with radius 1 is Pi.

That explanation was probably not clear enough, but just to remind you, there’s a lot more to Pi than just this.

Apart from just normal geometry like ellipses, spheres, cylinders, and sine waves, Pi helps in calculating normal distributions, and as I mentioned before in astrophysics, Pi is used to study orbits and gravitational effects on objects in space. Pi is also found in Non-Euclidean geometry, and there’s many more complicated things involving it.

Yes, the number is special to some and less relevant for others, but if you’ve read all the way to the end, you may have learned something new! Once again, it is quite special to some, and you can find a small hint of it in every circle.