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.
CreditYou can learn more from the tauists
here.
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!
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.
More reading:
http://www.scientificamerican.com/article/let-s-use-tau-it-s-easier-than-pi/http://www.livescience.com/34132-what-makes-pi-special.html