The source of cosmic background radiation

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Cosmic background radiation (CMB) is primarily considered to be leftover radiation from the Big Bang rather than radiation from visible matter, as the number of CMB photons vastly exceeds that of photons from light matter. Observations of the CMB show it to be extremely uniform, contrary to claims of a filamentary nature. The average temperature of the CMB is 2.7K, with temperature variations being minuscule compared to the average. The energy per photon from light matter is significantly higher than that of CMB photons, further supporting the distinction between the two. Overall, the characteristics of CMB reinforce its origin as a remnant of the early universe.
Lesnick
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All stars and Galaxies appear to give off the whole spectrum of electromagnetic radiation.
If one views images of the distribution of background radiation in detail it appears to be filimetary in nature. Also if one views the distribution of visible matter in the universe it also appears filimetary in nature, it looks as though one could super impose one on top of the other.
Why do we think that background radiation is radiation left over from the big bang and not just the radiation from all of the visible matter in the universe.
 
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The number of photons created by light matter (which by the way were generated after the CMB was aleady in existence) is several orders of magnitude less than the number of CMB photons. Thus, these light matter photons cannot account for the observed number of CMB photons.
 
Lesnick said:
If one views images of the distribution of background radiation in detail it appears to be filimetary in nature.
No, it's not filimentary at all. And it's even worse for this view than a naive glance at the picture Nabeshin posted would imply: that image is not the temperature, but the difference in temperature from the average. The average temperature is 2.7K. Those little differences are 100,000 times smaller than the average. The CMB isn't filimentary: it's extremely uniform.
 
It would not be a perfect black body spectrum.
 
That's another point: the average energy per photon from light matter (locally) is several tens of eV (about 1000x that of the CMB, and CMB photons are in fact local), yet the number density of light photons is lower than the CMB number density.
 

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