  The cosmic infrared background (CIB) radiation was a long-sought fossil of
energetic processes associated with structure formation and chemical evolution
since the Big Bang. The COBE Diffuse Infrared Background Experiment (DIRBE) and
Far Infrared Absolute Spectrophotometer (FIRAS) were specifically designed to
search for this background from 1.25 microns to millimeter wavelengths. These
two instruments provided high quality, absolutely calibrated all-sky maps which
have enabled the first detections of the CIB, initially at far infrared and
submillimeter wavelengths, and more recently in the near infrared as well. The
aim of this paper is to review the status of determinations of the CIB based
upon COBE measurements. The results show that the energy in the CIB from far
infrared to millimeter wavelengths is comparable to that in the integrated
light of galaxies from UV to near infrared wavelengths: the universe had a
luminous but dusty past. On the assumption that nucleosynthesis in stars is the
energy source for most of this light, the results also imply that 1 to 8
percent of cosmic baryons has been converted to helium and heavier elements in
stars. The integrated background light from UV to millimeter wavelengths is
about 10 percent of that in the cosmic microwave background.
