2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/106760This is a pedagogical review of the recent observational data obtained from type Ia supernova surveys that support the accelerating expansion of the universe. The methods for the analysis of the data are reviewed and some of the theoretical implications obtained from their analysis are discussed.References added. 35 pages, 17 figures. Invited Review at the Third Aegean Summer School: `The Invisible Universe Dark Matter and Dark Energy' (see http://www.physics.ntua.gr/cosmo05/sci_prog.html). PPT file of talk available at http://leandros.physics.uoi.gr/home/AstrophysicsGeneral Relativity and Quantum CosmologyHigh Energy Physics - PhenomenologyHigh Energy Physics - Theorytext