Mansuripur's Paradox

A recent article claims that the Lorentz force law is incompatible with special relativity. We discuss the "paradox" on which this claim is based. The resolution depends on whether one assumes a "Gilbert" model for the magnetic dipole (separated monopoles) or the standard "Ampere" model (current loop). The former was presented in these pages many years ago; the latter requires the inclusion of "hidden momentum."