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In Cosmology , the cosmic microwave background radiation (most often abbreviated '''CMB''' but occasionally '''CMBR''', '''CBR''' or '''MBR''', also referred as '''relic radiation''') is a form of Electromagnetic Radiation discovered in 1965 that fills the entire universe A.A. Penzias and R.W. Wilson, "A Measurement of Excess Antenna Temperature at 4080 Mc/s", ''Astrophysical Journal'' '''142''',419-421 (1965). It has a thermal 2.725 Kelvin Black Body spectrum which peaks in the Microwave range at a frequency of 160.2 GHz , corresponding to a wavelength of 1.9 mm. Most cosmologists consider this radiation to be the best evidence for the Big Bang model of the universe. FEATURES is the most precisely measured Black Body spectrum in nature. The Data Point s and Error Bar s on this graph are obscured by the theoretical curve.]] The cosmic microwave background is variations are only 18 µK.This ignores the Dipole anisotropy, which is due to the Doppler Shift of the microwave background radiation due to our Peculiar Velocity relative to the Comoving cosmic rest frame. This feature is consistent with the Earth moving at some 380 km/s towards the constellation Virgo . ''The Far-Infrared Absolute Spectrophotometer '' (''FIRAS'') instrument on the NASA Cosmic Background Explorer (COBE) satellite has carefully measured the spectrum of the cosmic microwave background. FIRAS compared the CMB with a reference Black Body and no difference could be seen in their spectra. Any deviations from the black body form that might still remain undetected in the CMB spectrum over the wavelength range from 0.5 to 5 mm must have a weighted Rms value of at most 50 parts per million (0.005%) of the CMB peak brightness.D. J. Fixsen ''et al.'', "The Cosmic Microwave Background Spectrum from the full COBE FIRAS data set", ''Astrophysical Journal'' 473, 576–587 (1996). This made the CMB spectrum the most precisely measured black body spectrum in nature. The cosmic microwave background is a prediction of or Decoupling (referring to electrons combining with nuclei and to the decoupling of matter and radiation respectively). The photons have continued cooling ever since; they have now reached 2.725 K and their temperature will continue to drop as long as the universe continues expanding. Accordingly, the radiation from the sky we measure today comes from a spherical surface, called the surface of last scattering, from which the photons that decoupled from interaction with matter in the early universe, 13.7 billion years (13.7 G yr) ago, are just now reaching observers on Earth. The big bang suggests that the cosmic microwave background fills all of observable space, and that most of the radiation energy in the universe is in the cosmic microwave background, which makes up a fraction of roughly 5×10-5 of the total density of the universe.The Energy Density Of A Black-body Spectrum is , where ''T'' is the temperature, is the Boltzmann constant, is the Planck constant and ''c'' is the speed of light. This can be related to the critical density of the universe using the parameters of the Lambda-CDM Model . Two of the greatest successes of the big bang theory are its prediction of its almost perfect of the big bang. Some information, such as the Shape Of The Universe , can be obtained straightforwardly from the cosmic microwave background, while others, such as the Hubble Constant , are not constrained and must be inferred from other measurements.D. N. Spergel ''et al.'', "First-year Wilkinson Microwave Anisotropy Probe (WMAP) observations: determination of cosmological parameters", ''Astrophysical Journal Supplement'' 148, 175–194 (2003). HISTORY See Also: Discovery of cosmic microwave background radiation Timeline of cosmic microwave background astronomy The cosmic microwave background was predicted in 1948 by George Gamow and Ralph Alpher , and by Alpher and Robert Herman . Moreover, Alpher and Herman were able to estimate the temperature of the cosmic microwave background to be 5 K, though two years later, they re-estimated it at 28 K.G. Gamow, "The Origin of Elements and the Separation of Galaxies," ''Physical Review'' 74 (1948), 505. G. Gamow, "The evolution of the universe", ''Nature'' '''162''' (1948), 680. R. A. Alpher and R. Herman, "On the Relative Abundance of the Elements," ''Physical Review'' 74 (1948), 1577.. Although there were several |
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