1 Cosmology/COBE

The results from the COBE * satellite are in close quantitative agreement with the predictions of the standard hot Big Bang model, suggesting that the Universe was once hot, dense and isothermal, giving a background radiation spectrum that is close to a perfect blackbody. The need to preserve this blackbody spectrum to match the spectrum observed by the FIRAS instrument on COBE places strong limits on events and scenarios occurring later than 1 year after the Big Bang. The observation of intrinsic anisotropy of the microwave background by the DMR instrument on COBE provides a measurement of the magnitude of the gravitational potential fluctuations that existed 10 5.5 years after the Big Bang. These potential perturbations were either produced in an inflationary epoch sometime during the first picosecond after the Big Bang, or else they are initial conditions dating from t = 0. The angular power spectrum of the correlations is compatible with the inflationary scenario. The observed amplitude of ∆T can be used to restrict theories of the fundamental structure of matter on micro-physical scales and at energies higher than that of the most energetic cosmic rays. The gravitational forces implied by the observed potential can produce the observed clustering of galaxies, but only if the density of the Universe is dominated by some form of transparent " dark " matter, which interacts weakly with photons. While the FIRAS and DMR instruments have 7 • beams, the third instrument on COBE, DIRBE, has collected data with an 0.7 • beam that will be used to improve our knowledge of the cosmic infrared background, but only after the strong foreground emissions from the interplanetary dust cloud and galactic dust are modeled and removed.