Answer to Question #46141 in Astronomy | Astrophysics for deepu singh
What is cosmic background radiation? Explain why it is so important to the debate between evolving and a steady-state universe.
Cosmic background radiation is an almost isotropic (same in any point in the sky) radiation that can be observed in radiowaves band that correspond to black body radiation at temperature approximately 3K. This is the thermal radiation assumed to be left over from the "Big Bang" of cosmology. Steady-state universe stated that Universe was always as cold in the past as it is now. Contrarily, Big Bang theory, or theory of hot-and-dense-universe-in-the-past tells us that in the past all the matter was closer and hence, hotter. It was moment in the past, when it was so dense, that it does not allow the light to spread (because ionized matter absorbed it). After expanding universe became transparent, and we now see light from that last scattering after recombination of ions as cosmic background radiation. Thus, discovery of cosmic background radiation proved the Big Bang theory.