Three and a Bit — Why is pi 3.14, and what is pi actually measuring?

Pi is 3.14 because every circle, whatever size it is, rolls exactly 3.14 of its own widths in one full turn — so the distance around a circle is always about 3.14 times the distance across it. Pi is a measurement, not a magic number to memorise. Roll a wheel one turn along a line and find it with your own hands, work out how much padding a round trampoline needs, get it wrong by 63 centimetres, and find out why a rope around the whole Earth would only need six more metres to lift it a metre off the ground.