2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/86797An orbiting `photon clock' is proposed to test directly the relativity of simultaneity of special relativity. This is done by comparison of the arrival times at a ground station of three microwave signals transmitted by two satellites following the same low Earth orbit.5 pages, 1 figureGeneral Physicstext