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Evidence of Cosmic Backround Radiation cooling

  1. Oct 17, 2012 #1
    What experiments have been conducted to confirm that the Cosmic Background Radiation (CBR) is indeed cooling over time and at any specified rate? The time requirement for obtaining separate points for measuring change seems preclusive.
     
  2. jcsd
  3. Oct 17, 2012 #2

    bcrowell

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    If it hadn't been cooling over time, then we would be detecting it now in the sky as visible light rather than microwaves.

    Ratios of helium to deuterium are also sensitive to the gravitational effects of radiation in the early, radiation-dominated universe (minutes or hours after the big bang). These ratios are consistent with the rate of cooling predicted by GR:
    Steigman, Ann. Rev. Nucl. Part. Sci. 57 (2007) 463.
     
  4. Oct 17, 2012 #3

    Chronos

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    Evidence the universe was cooler in the past, which is precisely what is expected in an expanding universe, has been confirmed several ways. One of the more compelling cases is reported in http://arxiv.org/abs/1012.3164, and http://www.das.uchile.cl/das_ingles/...asurements.php [Broken].
     
    Last edited by a moderator: May 6, 2017
  5. Oct 17, 2012 #4

    bcrowell

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    Cool! The second link is broken, through.
     
    Last edited by a moderator: May 6, 2017
  6. Oct 18, 2012 #5

    Garth

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    Don't you mean 'hotter in the past'?
    I'm doing that all the time!!

    Garth
     
    Last edited by a moderator: May 6, 2017
  7. Oct 18, 2012 #6

    Chronos

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    Yep, another bout of dyslexia. trying to fix link to second article http://www.das.uchile.cl/das_ingles/new_temp_measurements.php [Broken]
     
    Last edited by a moderator: May 6, 2017
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