2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/34763After some remarks about the history and the mystery of the vacuum energy I shall review the current evidence for a cosmologically significant nearly homogeneous exotic energy density with negative pressure (`Dark Energy'). Special emphasis will be put on the recent polarization measurements by WMAP and their implications. I shall conclude by addressing the question: Do the current observations really imply the existence of a dominant dark energy component?16 pages, Invited talk at the Seventh Hungarian Relativity Workshop, 10-15 August, 2003, Sarospatak, HungaryGeneral Relativity and Quantum Cosmologytext