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Cosmic Background Radiation

Fossil Radiation

Since its discovery in 1965, the radiation has been carefully studied and found to be a perfect blackbody as expected from theory. Since, this radiation represents fossil radiation from the initial big bang, any additional motion of Earth around the Sun, the Sun around the galactic center, and the galaxy through space should be reflected in a slight asymmetry in the background radiation. The net motion of Earth in some specific direction should be reflected by a slight Doppler shift of the background radiation coming from that direction toward shorter wavelengths.

Doppler shift is the same effect that the police use to ascertain the velocity of approaching vehicles. Of course there will be a similar shift toward longer wavelengths for light coming from the direction from which we are receding. This effect has been observed indicating a combined peculiar motion of Earth, Sun, and galaxy on the order of 600 km/sec.

Finally, small fluctuations in the background radiation are predicted which eventually led to the formation galaxies, clusters of galaxies. Such fluctuations have been found by the CO(smic) B(ackground) E(xplorer) Satellite, launched by NASA in 1989. COBE detected these fluctuations at about 1 part in 105 which was right near the detection limit of the satellite. The details of these fluctuations are crucial to deciding between more refined models of the expanding universe. COBE was decommissioned in 1993, but scientists are still unraveling the information contained in its data.

It is perhaps not too much of an exaggeration to suggest that cosmic background radiation has elevated cosmology from enlightened speculative metaphysics to an actual science. We may expect developments of this emerging science to lead to a definitive description of the evolutionary history of the universe in the near future.

George W. Collins, II

KEY TERMS

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Blackbody

—A blackbody (not to be confused with a black hole) is any object which absorbs all radiant energy which falls upon it and subsequently re-radiates that energy. The radiated energy can be characterized by a single dependent variable, the temperature. That temperature is known as the blackbody temperature.

Doppler shift

—The change in frequency or wavelength resulting from the relative motion of the source of radiation and the observer. A motion of approach between the two will result in a compression of the waves as they pass the observer and a rise in "pitch" in the frequency of the wave and a shortening of the relative wavelength called a "blue shift." A relative motion of recession leads to a lowering of the "pitch" and a shift to longer "redder" wavelengths.

Microwave radiation

—Electromagnetic radiation that occurs in the wavelength region of about 0.4 in to 3.3 f (1 cm to 1 m).

Additional topics

Science EncyclopediaScience & Philosophy: Cosine to Cyano groupCosmic Background Radiation - Fossil radiation