2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/93335It is always stated that the position operator for massless particles has non-comutting components. It is shown that the reason is that the commutation relations between coordinates and momenta differs for massive and massless particles. The correct one for massless particles and a position operator with commuting components are derived.16 pages, Latex, no figureQuantum Physicstext