Full disclosure: I have the first 51 digits of pi tattooed on my left calf and foot, so I am personally and permanently attached to the traditional definition of pi. My left legPi is a fundamental constant of the universe, and it is defined to be a circle's circumference divided by its diameter, or the distance around a circle divided by the distance across it. The number pi shows up in math and physics on a regular basis, even when we are not talking about circles, and it is safe to say that...