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CA 10.03 CMB Uniform Distribution


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CMB analysis confirms the uniform temperature throughout the known Universe with only negligible anisotrophy.

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CA 10.03 CMB Uniform Distribution

  1. 1. © ABCC Australia 2015 DISTRIBUTION OF LIGHT IN CMB Cosmic Adventure 10.03
  2. 2. © ABCC Australia 2015 Blank Plot When CMB was discovered in the 1960s by Penzias and Wilson, the CMB panorama was found to be remarkably uniform across the sky - it is nothing more than a blank plot. Scientists could not find anything more from the CMB anything other than assuming this this is the relic radiation left behind from the earlier universe.
  3. 3. © ABCC Australia 2015 Satellites to look for More Details Nearly thirty years after the discovery of the cosmic microwave background (CMB), a series of satellite probes had been launched to measure it in better details. It started with the satellite COBE in 1992, then WMAP in 2003, and finally Planck in 2009. PLANCK WMAP COBE 1989-1993 2003-2012 2009-2013 Ongoing
  4. 4. © ABCC Australia 2015 Evenness found by Cosmic Background Explorer (COBE) In 1992, the Cosmic Background Explorer (COBE) satellite confirmed the CMB temperature 𝑇0 to be: 2.725° Kelvin The ripples which represent temperature variations were only delineated at the level of 1 part in 100,000. COBE 1989-1993
  5. 5. © ABCC Australia 2015 The WMAP results In 2003, the WMAP satellite obtained a more detailed map of the sky. It also showed fluctuation departures from 2.725 Kelvin. But these fluctuations were very small - only a few micro Kelvins, or millionths of a degree as previously found. In the words of the scientists, the universe as a whole is spatially homogeneous and isotropic. -200 T (𝜇K) +200 WMAP 2003-2012
  6. 6. © ABCC Australia 2015 Small Deviations The variations are so tiny that units of millionths of a degree are used. The variations average from -200 millionth of a degree Kelvin (blue) to +200 millionth of a degree Kelvin (red). False colours are used to show the variation 1° 1,000,000
  7. 7. © ABCC Australia 2015 Planck Observations Planck was launched in 2009, and the recent data represent the product of the spacecraft's first 15.5 months of observations, further confirming the previous findings and providing more details for astronomical analysis.
  8. 8. © ABCC Australia 2015 Isotropic & Homogeneous Since the distribution of cosmic photons is entirely the same everywhere and in all directions, the present universe is isotropic, i.e. it looks the same in all directions, rotationally symmetric; and homogeneous looking the same at all points in the Universe, symmetric under translations.
  9. 9. © ABCC Australia 2015 Different from Present Day Homogeneity It is unlike the present day approximation of the universe where the idea of homogeneity and isotropy only apply to the part of the universe in a large scale over 100 million parsec (1 parsec =31 trillion km). In a small scale the uneven distribution of material bodies like stars, galaxies, and groups of galaxies make the approximation invalid. This is not an approximation. It is a real situation true to all scales, from the distance universe to the space around the earth.
  10. 10. © ABCC Australia 2015 Incredible Evenness Present Universe in Large Scale On the cosmic map of the universe the cosmic radiation is incredibly uniform. The distribution is so perfectly even that not a single hump or spot of unevenness can be found. This means that it is impossible to mark out the temperature map clearly in the normal scale of one degree difference. If we stretch out the entire sky sphere onto a flat table and try to draw a temperature map with different colours, it is a monochromatic one.
  11. 11. © ABCC Australia 2015 Contribution of CMB Scientists who worked on the analysis of CMB and subsequent experiments came up with various useful information such as polarization fluctuations, noise, power spectrum, temperature, etc. . . All these greatly helped the scientists to determine the nature and kinds of material that made up the universe. The DASI & the Martin A Pomerantz Observatory, South Pole Owens Valley Radio Observatory
  12. 12. © ABCC Australia 2015 In Collaboration with Cosmic Redshift However, none these attributes of CMB can compared with the theory of Big Bang – the supposedly most significant cosmological at the time. This was done by various scientists by associating it with another great discovery of the last century – the Cosmic Redshift discovered In 1927.
  13. 13. © ABCC Australia 2015 To be continued on Cosmic Adventure 10.04 THE COSMIC REDSHIFT