Preliminary Aspects of Classical Physics.- A Simple Approach to Einstein's Special Relativity.- Introducing Einstein's General Relativity.- Testing Einstein's General Relativity.- Gravitational Waves and Energy-Momentum.- The Universe According to Relativity.- Spacetime Diagrams for General Relativity.- The Motion of the Stars in the Galaxies.- The Motion of Galaxies in Galaxy Clusters.- Dark Energy.- Time Machines, the Multiverse and Other Fantasies.