New Hitchhiker's Guide Entry: Measurement.
It is well known and widely accepted that behind everyday reality
there is one driving force that keeps the whole thing together and
stops the universe flying apart and ensures that computers, space
travel and calorie controlled diets are possible. It's called
mathematics.
But in order for maths to work there first has to be a lot of
grubbing about under the sofa until certain basic numbers are
discovered.
The ratio of the circumference of a circle to its radius is one
such number, known universally as “that bloody annoying thing that
goes on for ever but is really just three and a bit”, helps nascent
societies to work out how much grain goes in a tin, how much a log of
wood weighs and answer the question “How big is that gigantic alien
space probe anyway?”
http://guideentries.blogspot.com/2011/09/measurement.html
Enjoy!