Talk:Cosmic microwave background

Addition of Explanation of the impact the temperature of the CMB's quantum fluctuations has on the Density of matter in the Universe

The article should include an explanation of how high temperatures after the Big Bang due to quantum fluctuations resulted in higher mass densities of localities throughout the Universe. Something explaining that warmer areas are denser and cooler areas are more void-like would be good to include. ScientistBuilder (talk) 19:21, 12 October 2021 (UTC)ScientistBuilderScientistBuilder (talk) 19:21, 12 October 2021 (UTC)

It's actually the other way around! Areas where the CMB temperature is higher are less dense, and areas where the CMB temperature is lower are more dense. [1], [2] --Amble (talk) 19:10, 22 October 2021 (UTC)

This topic is briefly mentioned in the Multipole section but could be expanded upon. Praemonitus (talk) 19:25, 22 October 2021 (UTC)

Regarding the correspondence between temperature and overdensities, it is actually a scale dependent phenomenon. As the user above points out, at large scales (l<100 ish) overdensities correspond to cool spots due to the integrated Sachs Wolfe effect, and vice versa for underdensities. However, at small scales the anisotropies are generated by acoustic physics in the primordial plasma. There, compression during baryon-acoustic oscillations heats up the plasma and overdensities can correspond to hot spots. Fireballs619 (talk) 04:09, 28 January 2024 (UTC)

Polarization section reorg.

The "Polarization" section had at least four copies of the same material mixed around. I've edit it down to two duplicates now.

The B-mode polarization is contaminated by E-mode polarization seen through gravitational lensing. This is per Hanson et al. and I believe this is the way astrophysics looks at B-mode. So I changed the text from discussion of two types of B-mode to a more layered 1-2 form.

The last two subsections of the Polarization section again repeat the same material with more (primary) references and details. These section should be merged with B-mode above it or possibly made sub-subsections of B-mode. Johnjbarton (talk) 18:33, 8 May 2024 (UTC)

This Annual Review is exceptionally clear and comprehensive:

• Kamionkowski, Marc, and Ely D. Kovetz. "The quest for B modes from inflationary gravitational waves." Annual Review of Astronomy and Astrophysics 54 (2016): 227-269.

Johnjbarton (talk) 18:05, 10 May 2024 (UTC)

Redundant, repetitious material that repeats in different places.

The article has roughly the same material in different places. Needs to be cleaned up. Thus my reorganization and deletion edits. Johnjbarton (talk) 18:38, 10 May 2024 (UTC)

"Predictions prior to the Big Bang interpretation"

The section "Predictions prior to the Big Bang interpretation" was re-added by @David Highfield. It has numerous problems.

1. The section title implies that the content relates to historic prediction, but in fact the topic is alternatives to Big Bang models.
2. The first sentence is ambiguous. "There are challenges to the standard CMB intepretation within the big bang framework." I think it means "There are challenges to the standard Big Bang interpretation of CMB."
3. The third sentence repeats content in the timeline and does not cite a secondary source for a claim on history. "Earliest known" is a fact that needs to be supported by published historical analysis.
4. The second paragraph reads "This [paper] documents the history of predictions." That's not encyclopedic.
5. The third paragraph is a long quote from "Assis, Andre KT, and Marcos CD Neves. "History of the 2.7 K temperature prior to Penzias and Wilson." Apeiron 2.3 (1995): 79-84." The quoted passage and the article itself is about the background radiation temperature. I will return to this point.
6. The last two paragraphs describe a fringe theory. See WP:FRINGE. The only way to include this work would be to have reliable secondary references per WP:PSTS or build WP:CONSENSUS.
7. Overall it's a jumble.

The Assis paper is discussed in

• Narlikar, Jayant V., and Thanu Padmanabhan. "Standard cosmology and alternatives: A critical appraisal." Annual Review of Astronomy and Astrophysics 39.1 (2001): 211-248. The Assis paper ia minor point in the overall picture of alternative cosmology.

I think we could have a section on alternative theories for CMB. It should be based on a broad review similar to the Narlikar/Thanu work. Johnjbarton (talk) 01:26, 14 May 2024 (UTC)

I moved the above named section into Theories section and rewrote it based on the review paper. The Assis paper is included, but Lerner and that theory is not included (it is not mention in the review).

Lerner's work is cited in

• López-Corredoira, Martín. "Tests and problems of the standard model in Cosmology." Foundations of Physics 47.6 (2017): 711-768.

(with both negative and positive comments) but that review also concludes:

• We must also admit that alternative theories are not at present as competitive as the standard model in cosmology in terms of giving better explanations.

Johnjbarton (talk) 02:27, 14 May 2024 (UTC)

The article non-standard cosmology covers alternatives to the Big Bang theory. If there is a section added on alternatives, I would think it belongs on the Big Bang article, rather than here. Praemonitus (talk) 05:33, 14 May 2024 (UTC)

In response to points 1-7 above. Science proceeds by a process of conjecture and refutation. It is not set in stone. As the paper I linked clearly outlines, there were a number of predictions relating to the background temperature of space prior to the measurement that was commandeered by Big Bang advocates. These earlier predictions were more accurate, and this fact is well documented. Point by point.

1. These are historic predictions. They are historical fact. They may also be used to support alternatives to the Big Bang, but they stand alone regardless. The paper makes no claims about alternative cosmologies. To suggest as much is disingenuous.
2. My original sentence is just fine, typo aside.
3. See the paper. See 5.
4. It's a peer reviewed paper.
5. See point 2, hence the wording of my original sentence. Alternative views do not necessarily interpret the CMB as a remnant heat signature, but radiation, possibly from plasmas.
6. 'Fringe' is a matter of opinion. Eric Lerner and Anthony Peratt are respected, credentialled scientists. What is your expertise in this field, may I ask?
7. Overall, your response has an air of superior cynicism about it. Furthermore, it represents historical revisionism. Little wonder that so many people utter the words "Yes, I know," after they mention Wikipedia.

David Highfield (talk) 09:48, 14 May 2024 (UTC)