2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/1944I review the assumptions and observations that motivate the concept of the extragalactic cosmic background radiation, and the issues of energy accounts and star formation history as a function of galaxy morphological type that figure in the interpretation of the measurements of the extragalactic infrared background.8 pages; in IAU Conference 204, the Extragalactic Infrared Background and its Cosmological Implications, Manchester, August 2000, eds M. Harwit and M. G. HauserAstrophysicstext