2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/196678The effective metric is introduced by means of two examples (non-linear electromagnetism and hydrodynamics),along with applications in Astrophysics. A sketch of the generality of the effect is also given.9 pages, contributions for the proceedings of the First International Workshop on Astronomy and Relativistic Astrophysics (IWARA 2003), Olinda (Brazil)Astrophysicstext