Today is pi day! Before we delve into that 3.14 slices of pie and many nerd jokes (even the US Congress designated today with a resolution to officially recognize pi), let’s talk about the one of the most significant symbols in mathematics.

We know π as a specific ratio of the circumference to the diameter of a circle. π as a number is irrational with no patterns in its calculation.  While computer scientists have calculated π to billions of places, but it’s always a mystery as to the next number.

Even though we simply refer to π and its relationship to C/d, π appears all over nature: The double helix, concentric rings of a pebble splashing, waves, the Heisenberg principle.

But π also has problems.  While true π =C/d, π is more commonly used as 2π, which is tau (τ). And τ is the ratio of circumference to radius (τ = C/r).

The famous web comic, xkcd trying to rectify π and τ.

Credit

Until tau gets its own day, we have pi. And lots of it.

To ensure we’re making proper use of this day, here is a little pi humor for you:

What do you get when you cut a jack-o’-lantern by its diameter?… Pumpkin Pi!

What do you get when you take the sun and divide its circumference by its diameter?…Pi in the sky.

3.14% of Sailors are PIrates!

What is the official animal of Pi Day?… the PIthon!

You should never talk to pi, he goes on forever…

When an octopus eats pi … octopi!

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I will love you until π runs out of decimal places.

Beware, the ides of Pi, March.

Credit: Craig Snodgrass

A self portrait of π.

Magnum Pi

Be rational. Get real.