2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/83906It is shown that the "twin paradox" arises from comparing unlike entities, namely perceived intervals with eigenintervals. When this lacuna is closed, it is seen that there is no twin paradox and that eigentime can serve as the independent variable for mechanics in Special Relativity.4 pages LaTeX2e with 1 eps figureGeneral PhysicsPopular Physicstext