Read here: http://milesmathis.com/pi2.html
Abstract: I show that in kinematic situations, π is 4. For all those going ballistic over my title, I repeat and stress that this paper applies to kinematic situations, not to static situations. I am analyzing an orbit, which is caused by motion and includes the time variable. In that situation, π becomes 4. When measuring your waistline, you are not creating an orbit, and you can keep π for that. So quit writing me nasty, uninformed letters.