2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/231463We propose a parallel introduction to Galilean and Einsteinian relativity based on the causal structure and inertial motions. Galilean and Poincare transformations, as objects secondary to the geometrical structure, are left aside.36 pages (26 pages text, 29 figures)Classical PhysicsGeneral Physicstext