Did you know if you mesure the length of your arm and divide by the length of your elbow to your finger you will get 
As of today in 2008, nobody in the world has found the sum of
all they know is that it converges because of the p-serie theorem but they cannot find the sum.
One of my teachers, as been working on that sum for about 5 years now, he found a concret answer (he ended up creating an instrument of that serie called ''tritare'' its pretty cool) but he has not found a mathematical expression to express it.
My pic is the instrument called Tritare.