Geometry is the science of correct reasoning on incorrect figures.
In Nonplussed! we considered some consequences of tossing a needle, in particular, onto a set of equally spaced parallel lines. The fact, surprising and historically significant, that the probability of the needle landing across a line involved π was first investigated by the eighteenth-century French scientist Georges Louis Leclerc, Comte de Buffon: hence the name Buffon’s Needle. Here we move to the twentieth century to consider a simple question about spinning the needle, which has its own intriguing and important answer.