March 14, 2015

**3,141592653589793238462643383279502884197169399375105820974944592307816406286 20899862803482534211706798214808651328230664709384460955058223 – this is Pi to 138 decimal places so you can put it on Twitter.**

Pi is an irrational number, which means it cannot be expressed as a ratio of integers. Therefore, it has a never ending representation in decimals, which are commonly used today. Despite this fact, Pi is an absolute superstar among mathematical symbols and it has millions of fans around the world who celebrate its existence on the occasion of Pi Day, on March 14th (3.14).

Or maybe its irrationality helps it to gain more attention? Over the years of mathematical learning, an entire discipline of “Piphilology” has emerged, which consists of inventing poems, songs and mnemonics to help to remember more Pi digits. But these mnemonics are just a small part of Pi culture. There are plenty of Pi limericks, written just for fun.

Like this one:

*Now there is an ancient Greek letter,
And I think no other is better.
It isn’t too tall,
It might look very small,
But its digits, they go on forever.*

Why does Pi enjoy such a wonderful career? We asked Mauro Carfora, Professor of Mathematical Physics at University of Pavia, and Journal Editor of Geometric flows, the open access serial by De Gruyter Open to tell us a bit about it. And he started by answering: “Asking about it is like asking: can you provide me with some information about God?”.

Anyway, his whole answer seems like a nice attempt at solving this complicated task. Thus, I am pleased to present it here:

*Pi marks the earliest activities involving mathematics in all ancient societies (say Egypt, Babylon, China, Maya). We should search for reasons for computing it in the need, of ancient people, for rules for calculating the measure of a piece of land, in the astronomy for calendar making, and in the fascinatingly regular shape of the circle: ancient men must have been certainly pleased by the infinite symmetry of this geometrical figure present everywhere, from the bounding disk of the Sun to the beautiful eyes of their beloved.*

*A well-known problem intimately connected with pi, “squaring the circle”, viz. constructing a square equal in area to a given circle by using, in a finite number of steps, only ruler and compass, has accompanied mathematics from Euclid times to the end of the nineteenth century, and has shaped in many subtle ways the development of modern mathematics. From the wonderful Archimedes’ method of calculating pi to the proof of the transcendence of pi by von Lindemann, and culminating in the most beautiful relation ever in Mathematics, Euler’s identity:*

*relating among themselves the five mathematical symbols that rule Mathematics. Pi is the Joy of Mathematics.*

Pi is shows up everywhere – adds prof. Anna Fino, Journal Editor of Complex Manifolds – In chemistry, physics, mathematics, whether you’re talking circles or cycles or anything to do with a curve, you’re going to find Pi in there somewhere.