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Thread: Cmb

  1. #1
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    Cmb

    Is there an energy density to the CMB?
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  2. #2
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    ? Wouldn't it be the same as the energy density of the Universe at the time it was emitted?

  3. #3
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    Well, the photon count of the Universe has stayed approximately the same but the energy per photon has gone down with the cosmological red shift. And the volume of the universe has increased in proportion to the scale factor cubed. So the energy density of the CMB varies inversely with scale factor to the power four.

    Grant Hutchison

  4. #4
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    I would say yes, there is energy density in the CMB. We know from observation how may photons are passing through any given volume of space, and how much energy they are carrying.

  5. #5
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    Since the CMB is black body radiation, the energy density can be calculated from (4*sigma/c)T4 = 4 x 10-14 J/m3.

    Grant Hutchison

  6. #6
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    Thank you all!
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  7. #7
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    Quote Originally Posted by Copernicus View Post
    Thank you all!
    You know you could have googled that much faster?

    Grant Hutchison

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