Irrational number

So it turns out that it's unknown whether pi + e is irrational. Crazy eh?

For those not in the mathematical loop, pi is the ratio of a circle's circumference to its diameter.

e is a little trickier to explain. Perhaps the easiest way of learning about e is to look at the Wikipedia page, which gives some explanation and a great number of equivalent definitions.

A number is said to be rational if it can be written as fraction of two whole numbers. For instance 12 = 12/1, -1.5 = (-3)/2 etc... It turns out that neither pi nor e can't be written as a fraction, but it's certainly not obvious (indeed unknown) whether their sum can or can't.

Proofs on a postcard to...