Franco Selleri and the rotating disk

I concentrate on the \emph{pars destruens}, rather than the \emph{pars construens}, of Selleri's work on the Sagnac effect. He speaks (2003) of the ``impossibilita di spiegare la fisica sulla piattaforma ruotante con la TRS,'' and may have a point. By confining our attention to the world-cylinder above a circle on the disk we avoid broader integrability issues that just cause confusion. A rate of rotation foliates the cylinder into timelike spirals, and also into the simultaneity spirals hyperbolically orthogonal to them; together the two foliations give rise to all sorts of temporal absurdities.