2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/200392After pointing out the historical avatar at the origin of a would be twin or clock paradox, we argue that, at least on a local scale, the (re-qualified) paradox is but a necessary consequence of the sole principle of causality.17 pages, no figures, submitted to Am. J. PhysGeneral Relativity and Quantum Cosmologytext