Is the CMBR a relic from the big bang or an image from background galaxies?

In summary: The paper discusses how light of the CMB gets influenced by galaxies which formed later - they are in the path of the existing light and can influence it.Thanks MFB.
  • #1
Lino
309
4
Some time ago there was a thread which suggested that there was a logic / papers that demonstrated why the the CMBR could not be the result of ligh from background objects / galaxies. Unfortunately, I have not been able to locate the thread or associated material. Is this correct, and could anyone give me references to related material?

(I apprecialte that I am not / unlikely talking about light or resibual light from visible galaxies.)

Regards,

Noel.
 
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  • #2
It is correct that the CMBR cannot be light from galaxies or similar objects. It could not explain its spectrum and the tiny angular variations of the temperature.
I do not know of any papers discussing this - it is just too far away from observations, I think.
 
  • #3
Thanks MFB. I was reading a paper by Molnar & Birkinshaw on Contributions to the Power Spectrum of Cosmic Microwave Background from Fluctuations Caused by Clusters of Galaxies (ArXiv 0002271) and it reminded me of the thread - I probably just mis-remember!

Regards,

Noel.
 
  • #4
The paper discusses how light of the CMB gets influenced by galaxies which formed later - they are in the path of the existing light and can influence it.
 
  • #5
Thanks MFB.

Regards,

Noel.
 
  • #6
mfb said:
I do not know of any papers discussing this - it is just too far away from observations, I think.

If you go back into the late-1960's and early-1970's you'd find plenty of papers. The idea that CMB was the result of diffuse galaxies was the "last stand" of the steady state model.

http://adsabs.harvard.edu/abs/1968Natur.217..339S

The problem with that explanation of the CMB was that you should see small fluctuations due to the individual galaxies, and you don't...

http://adsabs.harvard.edu/abs/1973ApJ...181..243B
http://adsabs.harvard.edu/abs/1973ApJ...182L..61C

One thing that happens a lot in astrophysics is that people come up with an idea, it gets killed, and then people forget why it got killed. Also looking at astrophysics history is interesting. The way it gets presented in textbooks, was that in 1965 when the CMB was discovered people immediately moved to support the big bang. In fact it took a few years, because the steady state people were able to come up with explanations for CMB, and the first set of measurements from sounding rockets actually went against the BB.

By the early 1970's, it was obvious that there were problems with the sounding rocket data, and that balloon and satellite data pretty clearly confirmed the big bang by showing that the spectrum was extremely smooth, and couldn't come from difuse galaxies.
 
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  • #7
Thanks TwoFish. That makes sense.

Regards,

Noel.
 

1. What is the CMBR and how was it discovered?

The CMBR, or Cosmic Microwave Background Radiation, is a faint glow of light that permeates the entire universe and is believed to be the residual energy from the Big Bang. It was first discovered in 1964 by Arno Penzias and Robert Wilson, who were conducting experiments with a large radio antenna and found a persistent noise that they could not explain.

2. What evidence supports the idea that the CMBR is a relic from the Big Bang?

There are several pieces of evidence that support the idea that the CMBR is a relic from the Big Bang. One of the most significant is the fact that the CMBR has a nearly uniform distribution across the entire sky, with only small variations in temperature. This is consistent with the idea that it originated from a single, highly energetic event. Additionally, the CMBR has been found to have a blackbody spectrum, which is also predicted by Big Bang theory.

3. How do we know that the CMBR is not just radiation from other sources?

Scientists have been able to rule out other sources of radiation as the cause of the CMBR. For example, stars and galaxies emit radiation at different wavelengths than the CMBR, and the CMBR has been found to have a distinct spectral signature that does not match any known sources. Additionally, the CMBR has been found to be isotropic, meaning it has the same intensity and characteristics in all directions, which is not expected from other sources of radiation.

4. How does the CMBR provide evidence for the expanding universe?

The CMBR provides evidence for the expanding universe through a phenomenon called the cosmic microwave background dipole. This refers to the fact that the CMBR appears to be slightly warmer in one direction and cooler in the opposite direction. This is consistent with the idea that the universe is expanding, as the light from the Big Bang would have been stretched and cooled as the universe expanded, resulting in a dipole pattern.

5. Are there any competing theories for the origin of the CMBR?

While the majority of scientific evidence supports the idea that the CMBR is a relic from the Big Bang, there are some alternative theories that have been proposed. One is the steady-state theory, which suggests that the universe has always existed in a steady state and the CMBR is just radiation from distant galaxies. However, this theory does not explain the uniformity and blackbody spectrum of the CMBR, and it has been largely rejected by the scientific community.

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