Talk:Cosmic microwave background/Archive 3

Pictures showing the removed foreground elements, as well as highlighting the anomalies?
I think pictures like that would help improve the article, not to mention the readers' understanding of what is being described. --TiagoTiago (talk) 05:01, 27 September 2014 (UTC)

Lede needs edit.
The lede states: "(Alternatively if spectral radiance is defined as dEλ/dλ then...". This is just wrong. That is, dE/dλ is NOT spectral radiance. The implied claim is also made that dE/dv can be called 'spectral radiance', which if I understand the terminology correctly is also wrong. It is technically correct, I think, to state "spectral radiance dE/dv peaks at ..." but dE/dv qualifies (clarifies) the term 'spectral radiance' - since it could be, for instance, photon count rather than energy which is 'peaking'. This is just slightly sloppy. Why not make it correct by describing the spectral radiance function which peaks? Alternatively, you could speak about the differential (or incremental) change in energy with frequency or wavelength having a maximum.Abitslow (talk) 18:41, 30 December 2014 (UTC)

Flux
I would like to see a sentence on the flux in photons per second per area, and watts per square meter. 10 trillion photons per second per squared centimeter is stated at  but figure is rough. But most of what I look at so far are problems for students to solve and not a reliable source. Also is energy density more like 4.178×10-14? Graeme Bartlett (talk) 22:46, 18 January 2015 (UTC)

1964 discovery? APS says 1963; Wilson says 1965...?
The American Physical Society says: June 1963: Discovery of the Cosmic Microwave Background, at http://www.aps.org/publications/apsnews/200207/history.cfm I assume the main article is correct. There are also claims that the discovery was made in 1965. It's obvious that there's widespread confusion about the date that the big bang theory was proposed (not on WP, but all over the web on "authoritative" sites), and when was, and by whom was, the expanding universe proposed: http://scitation.aip.org/content/aip/magazine/physicstoday/article/64/8/10.1063/PT.3.1194 But seems like the date of the discovery of the CMB should be more clear. In Wilson's Nobel lecture at http://www.nobelprize.org/nobel_prizes/physics/laureates/1978/wilson-lecture.pdf he gives dates of 1963 and 1965, and for 1964 only references the work of Doroshkevich and Novikov. So, is there a correct year of the discovery of the CMB? Bob Enyart, Denver KGOV radio host (talk) 05:03, 26 February 2015 (UTC)


 * Just found this in Penzias' lecture http://www.nobelprize.org/nobel_prizes/physics/laureates/1978/penzias-lecture.pdf "The year 1964 also marked a reawakened interest in the "Gamow Theory” by Hoyle and Taylor (1964) as well as the first unambiguous detection of the relict radiation." So, "unambiguous". That seems to settle it in favor of the main article's date. Bob Enyart, Denver KGOV radio host (talk) 05:14, 26 February 2015 (UTC)


 * They started working on the project in 1963, detected the signal in 1964, took data 1964-65, and understood the nature of the signal and published in 1965. It comes down (as often happens) to the question of whether you have to know what you've discovered before you can say you've discovered it.  --Amble (talk) 06:03, 26 February 2015 (UTC)

Dust and not dust
These two edits by Wdanwatts, suggest that galactic dust emission is responsible for large-scale features in the CMB. The second edit does have a more suitable source than the first edit did. However, the basic problem is that the article text and the sources are talking about two different things. The article is talking about the CMB temperature anisotropies, which have been measured to very high signal-to-noise on a wide range of angular scales and at many frequencies. The foreground (such as dust) contributions here are small away from the galactic plane, and are well understood. The temperature anisotropies are generated by primordial scalar density perturbations which evolve in a simple way to create the "acoustic peaks" in the CMB power spectrum. Where galactic dust becomes relevant is in looking for a different, much fainter signal in the CMB polarization. The pure-curl or "B-mode" component of the polarization is used to search for a possible signal of inflationary gravitational waves or "tensor perturbations". The very faint B-mode polarization signal has only recently been detected at all, and is now beginning to be measured with high signal to noise at multiple frequencies. It appears that dust does contribute most or all of the detected B-mode polarization signal, so there is no clear evidence for a detection of IGW. However, this simply isn't relevant to this section of the article, which is describing the much larger and very precisely measured temperature anisotropy signal. --Amble (talk) 01:57, 13 May 2015 (UTC)
 * That said, the reference to BICEP (actually BICEP1, not BICEP2 which detected the B-mode signal) also seems to be a bit out of place. A very large number of experiments have measured large-scale CMB anisotropies.  Perhaps BICEP1 is mentioned for its measurement of E-mode polarization (which is well measured apart from dust), but I'm not really sure.  It would perhaps be better not to single out any particular experiments here. --Amble (talk) 02:02, 13 May 2015 (UTC)

Subjective Worldview Claim
The next-to-last paragraph of the lede begins with this: "Precise measurements of the CMB are critical to cosmology, since any proposed model of the universe must explain this radiation."

I would like to humbly point out that this is a subjective worldview claim. There's no such thing as a model which adequately "explains" every observed phenomenon; each model has its strengths and weaknesses. So the author is showing favoritism toward CMB and any model which explains it (at the expense of explaining certain other phenomena).

Admittedly this favoritism may reflect the Scientific Consensus on the subject, which is surely Wikipedia's intent. But at least we need not be dishonest that it's favoritism. The Scientific Consensus can be selective about which phenomena it says "must" be explained and which it does not.

QuartzMMN (talk) 04:11, 29 June 2015 (UTC)


 * Any proposed model needs to explain it because if it doesn't, the model is clearly wrong. That's hardly 'subjective'. Headbomb {talk / contribs / physics / books} 22:19, 29 June 2015 (UTC)


 * Apologies ... you seem not to have understood my comment. By your reasoning, every model ever conceived should be "clearly wrong," because none of them are perfect.


 * E.g., one might consider life on earth a more conspicuous phenomenon than the CMB - and more deserving of an explanation. Yet decades of research has brought the Scientific Consensus no closer to explaining it than "reasonable conjecture".


 * Intelligent people must live with speculation when faced with no alternative. Our choice of model is not whether to speculate, but on what to speculate.


 * In light of this, I hope you see how ridiculous it is to stake a claim on one observed phenomenon and say it "must be explained" above more obvious phenomena. It merely reflects a preference about what sort of speculation one can live with.


 * QuartzMMN (talk) 16:47, 11 August 2015 (UTC)

Etymology

 * paleos + photons = old thermal radiation [旧光子 paleophoton]
 * protos + photons = first thermal radiation
 * archo- /archaeo- + photons [introduced by experimental physicist Giorgos Grammatikakis] = first thermal radiation — Preceding unsigned comment added by 2.84.220.197 (talk) 17:11, 26 September 2015 (UTC)

rare term but used among students

proto-photons has a second meaning - it is a theoretical not yet discovered particle supposedly contributing to gravity - this is a totally separate - not connected meaning — Preceding unsigned comment added by 2.84.220.197 (talk • contribs)

[ask for more]
 * Students may have made this up, but we need to see this used in reliable writings. I did a Google scholar search and found nothing at all. Graeme Bartlett (talk) 00:12, 24 September 2015 (UTC)


 * I totally agree! Cosmic microwave background is easier to pronounce than protophotons or paleophotons. We must stick to the old name. Students aren't wise enough to be listened. — Preceding unsigned comment added by 2.84.220.197 (talk • contribs)


 * Students have done all kinds of valuable work on the CMB, including making major contributions to things that are mentioned in the article. They published their work in scientific journals, which are reflected in secondary sources, and Wikipedia uses those.  When students try to put things they've made up directly into the article, we welcome them to Wikipedia and invite them to help build the encyclopedia (but remove the made-up stuff).  If you'd like to help improve CMB articles, I'd be happy to suggest some tasks that would be really helpful. --Amble (talk) 15:21, 24 September 2015 (UTC)
 * 旧光子 translates to "old photons". But our Chinese article on the topic is called zh:宇宙微波背景辐射, and does not make a mention of 旧光子.  This 旧光子 name gives a hint of tired light. Graeme Bartlett (talk) 04:53, 8 October 2015 (UTC)

"tired light" is not lectically [as a word] the same as "tired photon" as you claimed, it would have been in Chinese: 累光子 - tired photon/not tired light. Also "tired" doesn't mean old, but yes Fritz Zwicky claimed that time plays a crucial role. By the way tired light is hypothetical, and the CMB - cosmic microwave background experimental fact.

旧 means old but also paleo-, a prefix in Japanese and Chinese - same character. Paleo- means that the photon was emitted in the past. Tired light means that hypothetically a photon emitted in the past, has been affected by the expansion of space-time. So these terms focus on different issues.

Timeline
The timeline section appears to have been merged with this article by a single editor without discussion. To me it badly disrupts the flow of the article and should be moved back to the original location. What do you think? Praemonitus (talk) 22:11, 1 April 2016 (UTC)
 * As a test, I moved the timeline down to the bottom. Is that better? Isambard Kingdom (talk) 22:20, 1 April 2016 (UTC)
 * Yes, I think that would be an improvement. Praemonitus (talk) 15:20, 2 April 2016 (UTC)
 * Is the timeline even necessary? Isambard Kingdom (talk) 15:21, 2 April 2016 (UTC)
 * It may depend on who you ask. Among editors there seems to be an audience for creating timelines, outlines, lists, and the like; possibly because they are easier to build than proper articles. But to me they don't provide a very engaging read. Praemonitus (talk) 17:27, 2 April 2016 (UTC)

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My edits
Someone has undone my edits twice today without adequately explaining why. Regarding the quote that they restored to the introduction, there were several problems with it. Firstly, it was not made clear that it was text taken from an external source. Second, that source is a non-free source. Third, it did not say anything that was not better expressed elsewhere in the introduction. Fourth, it did not fit in at all with the text surrounding it. Thus, it added nothing to the article, but was a copyright violation. This is supposed to be a free encyclopaedia, so using non-free text can only be done in certain situations. One key justification is that a free alternative is not available. That's clearly not the case here.

As for the other two edits the user objected to, they haven't yet indicated why. Perhaps they would do so here. 128.40.9.164 (talk) 21:05, 29 November 2016 (UTC)
 * I think that we can certainly do without that multiline quote. There seems to be no reason to have it.  Its not as if it is something irreplaceable such as the first words spoken after the CMB was found. Graeme Bartlett (talk) 21:20, 29 November 2016 (UTC)


 * Thank you for your input. It is disappointing that the user who was undoing the edits never bothered to justify his actions.  128.40.9.164 (talk) 16:18, 6 December 2016 (UTC)

Misleading Introduction
The first line of this article: "The cosmic microwave background (CMB) is the thermal radiation left over from the 'Big Bang' of cosmology." I think it's misleading. CMB is from the time of recombination, 300,000 years after the Big Bang, not from the Big Bang itself. How about changing it to "...thermal radiation left over from the time of recombination." 220.244.178.10 (talk) 11:56, 6 April 2015 (UTC)


 * flaws? this article is one of best Ive seen on wiki, describes what subject is understandable. quantities might need clarification. Juror1 (talk) 09:58, 7 December 2017 (UTC)

Source for value of photon energy of CMB photons
The article currently states in the third paragraph of the introduction

"The photon energy of CMB photons is about 6.626534 × 10−4 eV."

Where does this value come from? I searched via both Google and Google Scholar but was unable to locate a source for this claim. --  Toshio   Yamaguchi  10:13, 27 August 2017 (UTC)


 * This comes from computing the energy of a photon at the stated frequency. Back of the envelope computation: Energy is given by $$E = hf$$, where $$h$$ is Planck's constant and $$f$$ the frequency of light. The article states that the peak frequency is at 160.23 GHz. Then, computing $$E$$ yieds 1.0616952 × 10-22 J. Convert from Joules to electron Volts and you get that answer. — Preceding unsigned comment added by 142.197.11.70 (talk) 21:03, 31 December 2017 (UTC)

A Commons file used on this page has been nominated for speedy deletion
The following Wikimedia Commons file used on this page has been nominated for speedy deletion: You can see the reason for deletion at the file description page linked above. —Community Tech bot (talk) 03:51, 7 August 2018 (UTC)
 * ESA Planck CMB.jpg

Should mention water vapour blocks the microwaves
In the Cosmic microwave background this article mentions that the radiation is observed from satellites and telescopes in the Atacama desert in Chile and at the South Pole. However it does not explain to the reader why this is.

I think the section should have an intro paragraph briefly summarizing the reasons. I'm quoting here from the South Pole Telescope article - this text could be edited and trimmed down a little as an introductory motivational paragraph


 * "The South Pole is the premier observing site in the world for millimeter-wavelength observations. The Pole's high altitude (2.8 km/1.7 mi above sea level) means the atmosphere is thin, and the extreme cold keeps the amount of water vapor in the air low. This is particularly important for observing at millimeter wavelengths, where incoming signals can be absorbed by water vapor, and where water vapor emits radiation that can be confused with astronomical signals. Because the sun does not rise and set daily, the atmosphere at the pole is particularly stable.  Further, there is no interference from the sun in the millimeter range during the months of polar night."

It is easily adapted to include the reasons for observing in the dry Atacama desert and from above the atmosphere in satellites. If you have any thoughts do say - otherwise if there is no response after a few days, I will be WP:BOLD and add the para myself. Robert Walker (talk) 16:09, 16 August 2018 (UTC)

Not too technical
The section --2600:1700:BFC2:A3E0:9DED:3F05:1D3E:333E (talk) 15:37, 12 August 2019 (UTC)Relationship to the Big Bang has a sidebar that says it is ( or may be ) too technical for the average reader; It is nothing of the sort and I find it lacking some features of what may be correct only for an entire volume of work yet me — with no formal training in the subject — only what I can find on the internet — see only significant prior work by the reader is to be expected before it is an easy read; This subject is rapidly developing due to machines which have never here-to-fore existed yet archaic convention continues to rule and dominate efforts 2600:1700:BFC2:A3E0:9DED:3F05:1D3E:333E (talk) 15:37, 12 August 2019 (UTC) there is nothing complex that needs to be kept from view as the work is not such that just anybody with no prior work raises their hand while professionals are working

nicholas_jordan456 ••• I am not familiar with how to do wikki; I believe I am on a talk page and not making any edits
 * I agree, I have removed the tag. Tags such as this should (unless it is really obvious) always say what exactly is too technical in the reason parameter or make a comment on the talk page. Bellowhead678 (talk) 19:13, 12 August 2019 (UTC)

Untitled
cmb has not proven to be evidence of a big bang... its hypothesized... and very far from proven. in fact its unlikely it is evidence of a big bang. in fact its unlikely the universe was ever created... it simply is. no beginning no end — Preceding unsigned comment added by Majorheadrush (talk • contribs) 13:37, 30 August 2019 (UTC)

Can there be a clear statement: for the CMB, z = ____?
The article already has this: "Since decoupling, the temperature of the background radiation has dropped by a factor of roughly 1100[52] due to the expansion of the universe. As the universe expands, the CMB photons are redshifted, causing them to decrease in energy. The temperature of this radiation stays inversely proportional to a parameter that describes the relative expansion of the universe over time, known as the scale length. The temperature Tr of the CMB as a function of redshift, z, can be shown to be proportional to the temperature of the CMB as observed in the present day (2.725 K or 0.2348 meV):[53] Tr = 2.725 ⋅ (1 + z) For details about the reasoning that the radiation is evidence for the Big Bang, see Cosmic background radiation of the Big Bang." So might it be helpful to add to the article a succinct statement, something to the effect of: "The cosmic microwave background has a redshift of z = 1089", or something like that? Thanks for your consideration! Bob Enyart, Denver KGOV radio host (talk) 02:34, 27 December 2019 (UTC)

Thanks!
In my humble opinion, this is a very well written article. Chapeau! — Preceding unsigned comment added by Koitus~nlwiki (talk • contribs) 13:10, 15 February 2020 (UTC)

CMB Peak Frequencies
I came to the article attempting to find the peak frequencies of the cosmic microwave background but have been unable to locate that information. I know that the peak frequency is 160.4 but do not know what the other three peak frequencies are. Does anyone here know?

CWatchman (talk) 17:48, 16 September 2020 (UTC)

The main peak has a thermal 2.725 kelvin black body spectrum which peaks in the microwave range at a frequency of 160.4 GHz, corresponding to a wavelength of 1.9 mm.

CWatchman (talk) 17:50, 16 September 2020 (UTC)

Nagging Shortfall
If the observer is close to the edge of the Universe, the CMB from that side should be blue shifted vs the CMB from the far side.

The graph of CMB we have puts the observer smack dab in the center of the Universe. It is more likely that all points in the Universe observe the same CMB. That means that CMB does not delineate the beginning of the Universe.GuildCompounder (talk) 20:18, 31 October 2020 (UTC)
 * Your comment suggests you think the Universe is finite in extent. The Copernican principle would suggest that we do not occupy a special position at the "center", but instead just see the view shared by all other locations. That would suggest there is no center and no edge, or at least none within the observable Universe. Praemonitus (talk) 16:54, 12 April 2021 (UTC)

Decoupling complete
"The maximum of the PVF (the time when it is most likely that a given CMB photon last scattered) is known quite precisely. The first-year WMAP results put the time at which P(t) has a maximum as 372,000 years.[58] This is often taken as the "time" at which the CMB formed. However, to figure out how long it took the photons and baryons to decouple, we need a measure of the width of the PVF. The WMAP team finds that the PVF is greater than half of its maximal value (the "full width at half maximum", or FWHM) over an interval of 115,000 years. By this measure, decoupling took place over roughly 115,000 years, and when it was complete, the universe was roughly 487,000 years old."

Perhaps my understanding is faulty, but wouldn't it be (mostly) complete after: 372,000 + (115,000/2) = 429,500 years? Praemonitus (talk) 20:04, 22 October 2021 (UTC)

B-Mode section out of date
We are now at Keck/BICEP3, which is returning r < 0.036. The current section looks 7 years out of date.

Also, r is never defined.

2600:1700:C280:3FD0:F92F:79DA:1665:C1DF (talk) 21:42, 6 December 2021 (UTC)

Missing Responses and Criticism
This article is missing a responses and criticism section 185.107.13.110 (talk) 09:00, 24 April 2022 (UTC)


 * See Criticism for some reasons not to have a separate section for criticism. The article does have a lot of material on the history and study of the CMB and why people regard it as very important. It’s not obvious what would go in a criticism section (too isotopic? Not polarized enough?). Could you give some specific examples of what you think is missing? —Amble (talk) 16:53, 24 April 2022 (UTC)

Frequency on Graph should be labeled Wavenumber
The graph of cosmic microwave background spectrum measured by the FIRAS instrument on the COBE labels the x-axis to be in terms of frequency, but it should be labeled in terms of wavenumber, since the units are 1/cm.

I edited the Image to reflect the changes as this also bothers me. In general I think it would be better to have a plot with the frequency but I don't have the data. I just have one question, how do I upload / reference correctly the changed image? — Preceding unsigned comment added by SourBitter (talk • contribs) 07:14, 16 November 2022 (UTC)

Image is gone
The map of the Cosmic Microwave Background from Planck was recently deleted from Commons due to "no permission". Is this image available under CC BY-SA (likely in a paper), or does it need to be uploaded locally as fair use? SevenSpheres (talk) 23:02, 28 October 2022 (UTC)
 * I put the WMAP image in in place of Planck, since WMAP images are public domain. Planck results are published in Astronomy & Astrophysics, which is not CC BY but copyright ESO. (The Astrophysical Journal and The Astronomical Journal are now CC-BY, but not the other two major astronomy journals.) If someone can find a suitably-licensed Planck image, that would be nice, but I don't think WMAP vs Planck makes much of a difference for the purposes of a gorgeous picture in this article. —Alex (Ashill &#124; talk &#124; contribs) 20:55, 7 December 2022 (UTC)

Proposed merge of "Timeline of prediction, discovery and interpretation" into "Timeline of cosmological theories"
The article section titled "Timeline of prediction, discovery and interpretation" would seem to be somewhat redundant with the "History" section. I'm proposing that we merge it into the related Timeline of cosmological theories article where it likely would be more useful and relevant. Do you concur? Praemonitus (talk) 16:49, 12 April 2021 (UTC)
 * Oppose; the topics are overlapping, but Timeline of cosmological theories is broader; suggest leaving the structure as it is, but adding a see also template in Talk:Cosmic microwave background. Klbrain (talk) 14:03, 22 May 2022 (UTC)
 * Why have separate History and Timeline sections in this article? Their purposes are redundant. Praemonitus (talk) 16:03, 22 May 2022 (UTC)
 * It is very common to have a separate timeline (see, for example, the descendants of Category:Historical timelines), primarily because for important topics it is worth having a narrative history covering major events, and more comprehensive listing covering (also) more minor event. Hence, this is a conventional form of WP:SUMMARY. Klbrain (talk) 16:50, 4 June 2022 (UTC)
 * It is common to have a separate timeline in separate articles, yes. This article is already quite long, so a reasonable compromise would be to do a content fork. "Timeline of cosmic microwave background knowledge", perhaps? Praemonitus (talk) 19:02, 4 June 2022 (UTC)
 * My view remains that the current structure works for readers, with a history section proving a narrative of key events, the timeline providing a list of events (not all of which are important enough to be covered in the narrative, and the separate Timeline of cosmological theories being a list for a broader topic. I might be misunderstanding the compromise position proposed, but I don't think that we need a new separate page. Klbrain (talk) 07:51, 22 October 2022 (UTC)
 * Oppose As per Klbrain. 2001:8003:913E:5D01:651B:2954:55BA:4C8 (talk) 14:31, 13 December 2022 (UTC)

Informing the reader this is a theory under the theorized model of the Big Bang Theory
The article mentions in the 1st line that the CMB "is" something in the Big Bang "Big Bang cosmology". While this is not technically wrong. It hides the fact that this is a theory. For a common reader, this is given as a fact. The citation made to support this, "Sunyaev, R. A. (1974)." uses the words "model" and "theory".

So I propose that the words "is theorized" be included in the 1st line of the article.

I understand that all of you have to "fight" flat-earthers all day trying to change significant articles. But this is not about that. I'm trying to explain to you, and the user, that you are over extending your theories to facts.

On the absolute, all understanding of reality is a theory. So the question is, when does the understanding stop being a "theory" and start being accepted as a fact.

I agree with:


 * It is an objective truth that the observed universe is moving away from a specific point.
 * It is an objective truth that the big bang happened on that specific point.
 * It is an objective truth that the events described in the 1st instances of Planck time happened.

And I even agree that the CMB characteristics correlate with the emissions at the 1st instances of the big bang.

Where I disagree with the most is that nothing else in the known or unknown universe can generate emissions that can correlate with the big bang. While the big bang existence is an objective truth, the idea that the entirety of the universe started with it is not an objective truth. It is a theory.

It is an objective truth that everything we can observe was created with the Big Bang. But we could just be "too small" to realize what is very far away. To my understanding, the idea that there was nothing "before" the Big Bang is the part that is not "objective truth". By all chance, It can be a localized thing in a very, very vast universe.

This idea that the CMB is a result of the Big Bang is a loop of self-supporting theories. For the CMB to be a result of the Big Bang, Space needs to be "limited" and fully created in the Big Bang. But then the CMB is used to prove that the Big bang created everything.

And again. I'm not saying that it's "probably" right. But it's not an objective truth on the same level of "the Big Bang happened".

As such, this is "theorized" and the user should read it on the 1st line in concordance with the 1st citation. Joao.cordeiro (talk) 17:04, 7 January 2023 (UTC)


 * No. The point is not to be "in concordance with the 1st citation", but to accurately summarize the entire article, which is built not upon one citation but upon many &mdash; indeed, directly or indirectly, upon the entire literature. Moreover, your statements of "objective truth" are themselves garbled. The universe is not "moving away from a specific point"; that's not how metric expansion works. There is no circular reasoning or "loop of self-supporting theories". XOR&#39;easter (talk) 18:08, 7 January 2023 (UTC)


 * I'm afraid you are confused about terminology. There's no such opposition between "theory" and "objective truth". All we have are theories. Some of them are speculative, and some of them are accepted. And an accepted scientific theory is the best knowledge we can have, the closest thing we have to "objective truth". Note, for example, that in the first sentence of Big Bang it is referred to as a theory (although you call it "objective truth"). Ditto for general relativity and quantum mechanics. This is not to cast doubt on them.
 * Now if there is doubt about the validity of the theory, of course we have to state that in the article prominently. Not by using the "theory" adjective, but by mentioning that it is speculative, or controversial, explaining its shortcomings and alternative theories. Most importantly, though, this is not about whether you doubt the theory. It's about whether there exists controversy in the scientific literature. And in the case of the CMB, there isn't. Tercer (talk) 18:41, 7 January 2023 (UTC)
 * The theory adjective should be used when the entirety of it cannot be considered objective truth.
 * Let's say that Theory T1 explains mechanisms M1, M2 and M3.
 * If M1 and M2 are considered objective truths while M3 is not fully understood, then the adjective "theory" should be used.
 * I'm not saying that 99% of what is said here is not objective truth. But some of it can, in the future, be explained by more complex models. This is not "certain" in the common sense of the word.
 * "but to accurately summarize the entire article, which is built not upon one citation but upon many"
 * But That's not how Wikipedia works. A statement needs a citation. And that citation needs to prove the statement.
 * The citation used of the 1st sentence explains a possible model on a theory. It fails to prove the 1st line. Joao.cordeiro (talk) 19:58, 7 January 2023 (UTC)
 * Yes, that is how Wikipedia works. XOR&#39;easter (talk) 21:10, 7 January 2023 (UTC)
 * This reply has no value if you cannot quote the article that contradicts what I said. Joao.cordeiro (talk) 21:16, 7 January 2023 (UTC)
 * "The verifiability policy advises that material that is challenged or likely to be challenged, and direct quotations, should be supported by an inline citation"
 * I am challenging that this very well framed on the "theory" status and should have the word or expression "theory" or "theorized" in that sentence. While the current version states is as a fact.
 * That line is supported by a single inline citation. That supports my view instead of yours.
 * The way that Wikipedia works is that inline citations confirm statements on those lines. Joao.cordeiro (talk) 21:22, 7 January 2023 (UTC)
 * Complex, current, or controversial subjects may require many citations; others, few or none. There is no scientific controversy here. Moreover, the given source does support the sentence to which it is attached; it is not a reference full of speculation, but one that describes how predictions are made that agree with observations. XOR&#39;easter (talk) 13:20, 8 January 2023 (UTC)
 * Complex, current, or controversial subjects Joao.cordeiro (talk) 14:34, 8 January 2023 (UTC)
 * It's been established for decades. So, "current" doesn't really apply. And the entire rest of the article is there to explain the complexities. And the existing citation does, in fact, support the sentence as written. XOR&#39;easter (talk) 14:47, 8 January 2023 (UTC)
 * So you are saying that we should do a complex statement and 10 paragraphs later place its citation? Joao.cordeiro (talk) 15:02, 8 January 2023 (UTC)
 * No, I'm saying that the existing citation does, in fact, support the sentence as written. XOR&#39;easter (talk) 15:05, 8 January 2023 (UTC)
 * I think this line of argument as ended, since we both agree that statements need inline citations. For the need of "theory" or "model" in the 1st line, there are other open talks below. Joao.cordeiro (talk) 15:08, 8 January 2023 (UTC)
 * I don't actually think that the opening line here needs its own inline citation. But it has one, which when read in its entirety &mdash; rather than just skimming the abstract for words like "model" and "theory" &mdash; makes this entire section beside the point. XOR&#39;easter (talk) 15:24, 8 January 2023 (UTC)
 * I think I wasted my time trying to teach anything. These categories of "theory" versus "objective truth" only exist in your head. How hard is that to understand? Tercer (talk) 22:38, 7 January 2023 (UTC)
 * Then can you please separate in some kind of category a spectrum between a morning thought before breakfast and a postulate?
 * I don't mind adapting my argument to however expressions you like to use, in order for you to understand my point. Joao.cordeiro (talk) 14:44, 8 January 2023 (UTC)


 * The first element of the lead that is theorized (as in a scientific theory) is that the recombination epoch is the source of the CMB. The existence of this radiation and its relative age is well established through observation. Hence, mention of a "theory" is not needed in the first sentence. Praemonitus (talk) 19:07, 7 January 2023 (UTC)
 * But how do you explain that the word theory is mentioned on the 1st line of the big bang article, while in this article it's not used on the entire introduction? Joao.cordeiro (talk) 20:02, 7 January 2023 (UTC)
 * The Big Bang is a theory; the CMB is an observation. The Big Bang is used to explain the known existence and properties of the CMB, as well as other well-observed aspects of the Universe. This is comparable to how the theory of stellar fusion is used to explain the observation that stars shine. Praemonitus (talk) 21:04, 7 January 2023 (UTC)
 * Is this article, and in particular the 1st paragraph about the observation or about its connection to the theory? Joao.cordeiro (talk) 21:14, 7 January 2023 (UTC)
 * I already answered this in my first post. Praemonitus (talk) 21:52, 7 January 2023 (UTC)
 * My point is that this article appears to hide the word "theory" and replace it with "cosmology".
 * This could have happened without intent. But I don't believe it.
 * And as so, I believe that the word theory should appear on that 1st line as long as it appears on the 1st line of the "Big Bang" article.
 * Removing the word theory on one side and not on the other looks to me as a disguised attempt to elevate this to fact. Like a 2-step attempt to make both articles as facts. Joao.cordeiro (talk) 22:05, 7 January 2023 (UTC)
 * I would have no problem with removing "In Big Bang cosmology" from the first sentence and moving it down to the recombination line, if that is the consensus. Praemonitus (talk) 22:10, 7 January 2023 (UTC)
 * In that direction, maybe the article could focus its introduction (or at least the 1st paragraph) about the observation instead of the theorized explaination. Joao.cordeiro (talk) 22:14, 7 January 2023 (UTC)
 * With the exception of a sentence segment, the first paragraph is focused on the observation. Praemonitus (talk) 02:48, 8 January 2023 (UTC)
 * The "In Big Bang cosmology" phrase was probably just the typical context-setting with which articles habitually begin (like "In physics, ..." or "In mathematics, ..."). I don't think that kind of context-setting is necessary here, so removing that phrase is fine. XOR&#39;easter (talk) 13:28, 8 January 2023 (UTC)
 * Does anyone have any issue with removing it? And starting the article with "The CMB is faint cosmic background radiation filling all space..." Joao.cordeiro (talk) 14:38, 8 January 2023 (UTC)
 * Starting the article that way would push an important fact about what the CMB is until later than it ought to be said. The opening sentences, as adjusted today by Praemonitus, are fine. XOR&#39;easter (talk) 14:49, 8 January 2023 (UTC)
 * It would push it to the 2nd paragraph. Allowing the 1st to be about the observation.
 * Quite in line on what we expect of wikipedia to be. Joao.cordeiro (talk) 14:52, 8 January 2023 (UTC)
 * If a police officer asks you in the middle of the street: "What is the cosmic microwave background" should your 1st sentence of the answer be "a faint cosmic background radiation filling all space" or "a remnant from a primordial stage of the universe" ? Joao.cordeiro (talk) 14:56, 8 January 2023 (UTC)
 * Why is a police officer asking me about the CMB? Why, more generally, should a conversational answer &mdash; e.g., "It's leftover energy from the early universe that you can pick up with an old-school rabbit-ear TV antenna" &mdash; be the same as the opening lines of an encyclopedia article? XOR&#39;easter (talk) 15:08, 8 January 2023 (UTC)
 * Because this is Wikipedia and not "the exclusive Wikipedia that only scientists read"
 * A police officer is the correct public audience to be making that question here.
 * Then let's look at the article "Wheel". The 1st sentence says "A wheel is a circular component that is intended to rotate on an axle bearing"
 * According to you, this is secondary information because the importance of the wheel would be the primary information, right? (and we know how the wheel is quite important)
 * If now, how is the description of the CMB not on 1st line on this article like it is on the wheel? Joao.cordeiro (talk) 15:13, 8 January 2023 (UTC)
 * "if not"* Joao.cordeiro (talk) 15:14, 8 January 2023 (UTC)
 * If a police officer asked you what a wheel is, would you say that it is "a circular component that is intended to rotate on an axle bearing"? The current opening line is a description of what the CMB is, not a statement about its importance. XOR&#39;easter (talk) 15:27, 8 January 2023 (UTC)
 * Yes I would. How would you answer it instead? Joao.cordeiro (talk) 16:12, 8 January 2023 (UTC)
 * Per MOS:LEADSENTENCE, it should be a definition of what the subject is, rather than how it got there. I think I'd be okay with moving a suitably adjusted second sentence to the first. I.e. essentially flipping the first and second sentences. Praemonitus (talk) 19:23, 8 January 2023 (UTC)
 * I would go further and move it to the 2nd paragraph. But if we have to compromise here, sure. Joao.cordeiro (talk) 19:35, 8 January 2023 (UTC)
 * As I read it, the current first sentence is already saying what the subject is; pushing off "remnant" and "primordial" seems wrong. If there is a problem with the opening, it's a slight choppiness, like the repetition of "cosmic". XOR&#39;easter (talk) 20:20, 8 January 2023 (UTC)
 * To me, starting an article of something that is visible with how it is explained in theory is wrong.
 * An article should start with what something is. And in this case, it is what we observe.
 * Then, after, we can try explaining how it was created.
 * On the example of the wheel, again, what we have right now is similar to starting with: "The place and time of the invention of the wheel remains unclear, because the oldest hints......" Joao.cordeiro (talk) 01:55, 9 January 2023 (UTC)
 * The CMB is relic radiation &mdash; echoes from the past, if you want to be poetic about it. Your invented example of a bizarre way to start the article wheel is simply not analogous. And even a statement like "the CMB fills space" is theory-laden, as the philosophers say: we infer that it is present everywhere, even though we have not measured everywhere and never will. Likewise, a statement such as "the CMB is electromagnetic radiation" itself depends upon our theory of electromagnetism to have any meaning. Your standard, if taken at face value and implemented consistently, would leave us with no way to begin the article at all. XOR&#39;easter (talk) 04:18, 9 January 2023 (UTC)
 * I will give you that my argument by itself started in a confusing manner even in my head. Thankfully, Praemonitus was able to guide me into understanding my concerns better.
 * I have no concern at all that this article shows how the Big Bang is responsible for the CMB and all the math/logic behind it.
 * My issue was and still is with how this article starts. The way the start is written appears to be intended to with only one objective, to confirm with absolute language the Big Bang Theory.
 * And in the process of doing that it even goes away from Wikipedia guidelines to introduction as stated by Praemonitus.
 * But unlike the introduction. The rest of the article does not share this intent. The word "theory" appears very early on, connected to the explaining of its origins. And with that i have no issue at all.
 * So I would propose that this intent is removed from the article. Note that I'm not talking about the information itself, but where it is located and how it is expressed.
 * The article should start with what is not theoretical, the observation, and the history of its finding, in the 1st paragraph.
 * And continue with the importance of it to the theory of the Big Bang on the 2nd paragraph. Joao.cordeiro (talk) 13:51, 9 January 2023 (UTC)
 * Both the observation and the history are theory-laden. XOR&#39;easter (talk) 15:44, 9 January 2023 (UTC)
 * No, the observation can be detected with the correct equipment and is independent from the theory 2001:8A0:5EE9:4F00:17A:D1C4:62B2:43D1 (talk) 16:22, 9 January 2023 (UTC)
 * Understanding what your equipment is telling you requires theory &mdash; well-established theory, like Maxwell's equations and the blackbody radiation law, but theory nonetheless. XOR&#39;easter (talk) 16:35, 9 January 2023 (UTC)

Sorry but this is starting to read like a bunny trail argument. I think the main point should be that we're not 100% sure about what happened before the CMB appeared; but we're pretty certain that the CMB is there. At present, everything that happened beyond that apparent radiation shell is subject to modelling, whereas afterward we can observe it more directly. That's probably the main point we need to get across to most readers. The argument about what is theory and what is fact gets a bit circular. Praemonitus (talk) 23:03, 9 January 2023 (UTC)


 * I really, really disagree with mentioning the Nobel Prize before the Big Bang. The latter is vastly more important than the former; prizes are given in recognition of the significance of a discovery, and the discovery is what we ought to stress. The article on quantum electrodynamics doesn't mention the 1965 Nobel for Feynman, Schwinger, and Tomonaga in its lede. Radium doesn't mention the 1911 prize to Curie. The lede of photoelectric effect mentions Einstein but not the 1921 prize. Bose–Einstein condensate doesn't get around to mentioning the Prize until the History section. On the one hand, we have a fact about the origin of the entire observable universe, and on the other, we have a Jeopardy clue. XOR&#39;easter (talk) 23:13, 9 January 2023 (UTC)
 * In that case I'm okay with removing mention of the prize, but we should definitely keep the discovery information. Praemonitus (talk) 01:02, 10 January 2023 (UTC)
 * I also think that dropping a mention of the more general cosmic background radiation topic into the intro without following up on it is, itself, a violation of the style manual. Explaining the relation between the two in the intro is a lesser wrong. XOR&#39;easter (talk) 23:21, 9 January 2023 (UTC)
 * Okay. The current lede is actually a poor summary of the article. The second paragraph could be chopped down, and more coverage can be given to sections 5 and 7. Praemonitus (talk) 01:02, 10 January 2023 (UTC)
 * That sounds reasonable. XOR&#39;easter (talk) 01:35, 10 January 2023 (UTC)
 * Sorry about how far this went, but read a better "summary" of my issue with the article, search "I will give you that my argument by itself" Joao.cordeiro (talk) 02:00, 10 January 2023 (UTC)
 * Also, please understand that the article as been changed many times between the comments on this topic. You may need to look at history to understand my 1st complain Joao.cordeiro (talk) 02:03, 10 January 2023 (UTC)
 * No worries. I appreciate that you were willing to take this to the talk page to hash it out, rather than edit warring. Praemonitus (talk) 06:18, 10 January 2023 (UTC)
 * There was no ill intent. Just pure ignorance about how the edit process works. I was unaware that this talk page existed. Thankfully, Tercer was kind to post the link on a private msg. Joao.cordeiro (talk) 15:00, 10 January 2023 (UTC)

Vertical axis on graph should be radiance, not intensity
The Jasnky is a unit of spectral irradiance equivalent to 10−26 watts per square metre per Hertz. Thus the units MJy/sr on the vertical axis of the graph is a measure of spectral radiance, not intensity.
 * Unfortunately, it appears that "Intensity" is the label used for the vertical axis on the original source diagrams. Praemonitus (talk) 15:46, 16 February 2023 (UTC)

Article issues and classification

 * The "Primary anisotropy" subsection has three unsourced paragraphs. The "Adiabatic density perturbations" section is unsourced. All but one sentence of the "Isocurvature density perturbations" subsection is unsourced and has a "citation needed" tag. The "Late time anisotropy" is unsourced with "clarification needed" tags. Other paragraphs are also unsourced.
 * The B-class criteria #1 states; The article is suitably referenced, with inline citations. It has reliable sources, and any important or controversial material which is likely to be challenged is cited. At present the article does not meet the criteria for B-class assessment. -- Otr500 (talk) 03:15, 28 February 2023 (UTC)
 * I'm not sure it fully satisfies criteria 6 either: "The article presents its content in an appropriately understandable way". In particular, the "Data reduction and analysis" section may not be useful to a lay reader. It's probably at a B− rating, rather than a C rating. Praemonitus (talk) 04:26, 28 February 2023 (UTC)

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., --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)