cosmic background radiation

Diffuse electromagnetic radiation that appears to pervade the whole of the universe. Its discovery in 1964 by Arno Penzias and Robert Wilson (publicly announced in 1965) was of immense importance in cosmology because it provided strong evidence in favour of the Big Bang theory. It is believed to be the relic of the radiation generated in the event that marked the origin of the universe. The spectrum of the background radiation is characteristic of a black body at a temperature of 2.73 degrees above absolute zero (2.73 K) and is most intense in the microwave region. The Milky Way Galaxy is travelling through space at 600 km/s relative to the background radiation. Measurements made by the Cosmic Background Explorer satellite (COBE) in 1992 showed for the first time that the radiation is not completely smooth in its distribution across the sky when corrections have been made for expected causes of variation in the basic data. Ripple-like variations amounting to about ten millionths of a degree were discovered. They are believed to be the first signs of structure emerging in the early universe.