2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/89993The time-energy uncertainty relation is discussed for a relativistic massless particle. The Lorentz-invariant uncertainty relation is obtained between the root-mean-square energy deviation and the scatter of registration time. The interconnection between this uncertainty relation and its classical analogue is established.8 pages, no figuresQuantum Physicstext