Talk:Cosmic microwave background

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Former good article Cosmic microwave background was one of the Natural sciences good articles, but it has been removed from the list. There are suggestions below for improving the article to meet the good article criteria. Once these issues have been addressed, the article can be renominated. Editors may also seek a reassessment of the decision if they believe there was a mistake.
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January 29, 2006 Good article nominee Listed
July 13, 2009 Good article reassessment Delisted
Current status: Delisted good article
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Evolution of CMB radiation (decrease in temperature)[edit]

In the most widely recognized fate of the universe - heat death when entropy is maximum and everything is torn apart and stretched out, the temperature of the universe (and of CMB radiation too) will eventually reach zero, right? If that's the case, is there a formulation to calculate the temperature of CMB radiation with regards to time?Mastertek (talk) 10:29, 25 October 2011 (UTC)

Content problems[edit]

Items 3-33 are currently duplicated as 35-65, but I don't know how to delete the duplicate set! EqualMusic (talk) 18:31, 23 January 2009 (UTC)

Unfortunately I'm not seeing what you describe. After checking through the list, I only found one unexpected duplicate, and that has just been merged. Perhaps it was a result of vandalism that has since been corrected?—RJH (talk) 20:34, 24 January 2009 (UTC)

Inverted Logic[edit]

The last line of the introduction section has inverted logic: "As a result, most cosmologists consider this radiation to be the best evidence for the Big Bang model of the universe."

This item is about the CMBR, not the 'Big Bang' theory, thus the line should say, "As a result, most cosmologists consider the Big Bang theory of the universe to be the best explanation for the CMBR."
Makuabob (talk) 09:37, 11 February 2009 (UTC)

That works for me. I very much doubt you'd have been reverted if you just made the change yourself, per WP:BOLD. Thanks for the suggestion.—RJH (talk) 17:34, 11 February 2009 (UTC)

Difficult Sentences[edit]

The final two sentences in the 2nd paragraph of the Features section read: "At this point, the photons scattered off the now neutral atoms and began to travel freely through space. This process is called recombination or decoupling, which refers to electrons combining with nuclei and to the decoupling of matter and radiation respectively."

The first impression is that photons traveling freely through space is called recombination or decoupling. Linking these to terms together makes for difficulty. "Recombination" (ummm,... these nuclei and electrons were 'brand new,' NEVER been combined before,... in THIS universe, anyway!) allows "decoupling" of the photons from matter. Can these two lines be combined into one that makes this relationship clearer?
Makuabob (talk) 15:08, 11 February 2009 (UTC)

I made a few tweaks to the paragraph. Did that help any? I agree in that the use of 'recombination' seemed a bit odd to me as well, but that appears to be the jargon used. Thanks.—RJH (talk) 17:46, 11 February 2009 (UTC)
Reads much better! Thanks.
Makuabob (talk) 01:30, 12 February 2009 (UTC)

This is true, recombination is the term used, but it does in fact not make sense as the protons and electrons are forming atoms for the first time. Another case of annoying science terminology. — Preceding unsigned comment added by (talk) 20:24, 13 December 2011 (UTC)

Needs a re-write[edit]

The following paragraph has a number of significant problems:

Measurements of the CMB have made the inflationary Big Bang theory the standard model of the earliest eras of the universe. This theory predicts that the initial conditions for the universe are originally random in nature, and follow a roughly Gaussian distribution. The power spectrum of these fluctuations has been calculated, and agrees startlingly well with the observations, although certain observables, for example the overall amplitude of the fluctuations, are more or less free parameters of the cosmic inflation model. Therefore, meaningful statements about the inhomogeneities in the universe need to be statistical in nature. This leads to cosmic variance in which the uncertainties in the variance of the largest scale fluctuations observed in the universe are difficult to accurately compare to theory. The model uses a Gaussian random field with a nearly scale invariant or Harrison-Zel'dovich spectrum to represent the primeval inhomogeneities.

First, it is assuming reader knowledge that they may not possess. E.g. jargon like power spectrum, Gaussian distribution, scale invariant and Harrison-Zel'dovich spectrum. (See WP:MTAA and WP:Jargon.) Second, it is employing a vague, PoV remark, "agrees startlingly well". (See WP:PoV and Wikipedia:MoS#Unnecessary_vagueness.) Third, the text has been tortured until I'm not sure what it is trying to say.

I think it needs a complete re-write in order to be accessible to the general public. Does anybody have a suggestion on how to proceed? Thanks.—RJH (talk) 19:19, 22 February 2009 (UTC)

Here's a link to a fairly readable version that might serve as an inspiration Sci. Am article. LouScheffer (talk) 21:09, 25 February 2009 (UTC)

Is Lopsided[edit]

[1] Yes, the CMB is lopsided. At least, so the data says. Zazaban (talk) 20:19, 25 February 2009 (UTC)

Recent changes and big bang theory[edit]

Recently, various editors have been removing paragraphs discussing why the big bang is believed to be the best explanation for the CMBR. In particular, the paragraph on non-isotropy is critical here, and should not be removed. It describes a feature of the CMBR that is very well measured, is explained by the big bang, and not by any other theory so far. It's perfectly OK to not like the big-bang theory, but this is science and not politics. You can't simply delete the opposing evidence and hope no-one notices.

There are several references included that point out cases where the non-isotropies do not exactly match the predictions of the big-bang model. If you read them, they are not questioning the big bang itself, but instead details of the expansion process. So they support the big bang in general (expansion and inflation occurred). Note that no other theory (to my knowledge) has predicted the non-isotropies at all, much less got all the details right. LouScheffer (talk) 07:12, 22 May 2009 (UTC)

Changes to the Late Time Anisotropy[edit]

The proton was added (and then deleted, for now) to the particles which cause Thompson Scattering. It is a charged particle when stripped of its only electron and also is a source of Thompson Scattering. However, according to, the scattering cross-section varies by q^4/m^2 so a proton is much harder to "hit." It seems that a mention of this other 'particle' would be an informative addition. If there are no reasonable objections, I will add it later with a mention that protons produced a small part the Thompson Scattering that occurred.
Makuabob (talk) 22:34, 26 May 2009 (UTC)

GA Reassessment[edit]

This discussion is transcluded from Talk:Cosmic microwave background radiation/GA1. The edit link for this section can be used to add comments to the reassessment.

GA review – see WP:WIAGA for criteria

This review is part of Wikipedia:WikiProject Good articles/Project quality task force/Sweeps, a project devoted to re-reviewing Good Articles listed before August 26, 2007.

  1. Is it reasonably well written?
    A. Prose quality:
    Prose is generally ok for a Good Article, a little technical at times, but that is to be expected. There was a {{technical}} template on the talk page, but I removed it because it belongs on the article page. However I disagreed with the assessment that this article is too technical for a general audience and presents just enough technical detail for those who are knowledgeable.
    B. MoS compliance:
    Introduction is a good length (WP:LEAD).
  2. Is it factually accurate and verifiable?
    A. References to sources:
    B. Citation of reliable sources where necessary:
    I started out with such high hopes. Everything was well-referenced at first, but then there were whole sections without one citation. A large number of the links are also dead.
    C. No original research:
    Unsourced statements may contain original research.
  3. Is it broad in its coverage?
    A. Major aspects:
    B. Focused:
  4. Is it neutral?
    Fair representation without bias:
  5. Is it stable?
    No edit wars, etc:
  6. Does it contain images to illustrate the topic?
    A. Images are copyright tagged, and non-free images have fair use rationales:
    B. Images are provided where possible and appropriate, with suitable captions:
  7. Overall:
    Pass or Fail:
    Article will be placed on hold until the references issue can be addressed. If an editor does not express interest in addressing these issues within seven days, the article will be delisted and reassessed as B class. --ErgoSumtalktrib 22:19, 5 July 2009 (UTC)
I fixed the deadlink, updated one, and standardized references. That being said, this is about the extent of what I can do. Asking the Astronomy project directly would probably yield editors who can reference the unreferenced sections.Headbomb {ταλκκοντριβς – WP Physics} 19:21, 7 July 2009 (UTC)
Article has been delisted and reassessed as B-class. Feel free to renominate once these issues have been addressed. --ErgoSumtalktrib 20:48, 13 July 2009 (UTC)

are there implications of the redshifted peak of of the spectrum?[edit]

Would the redshifting of the peak of the cosmic background do anything interesting at various ages of the universe if it matched an absorption line in some material like hydrogen or helium (or would the peak be so weak that it would not make so large a difference?) I mean that running recent history backwards the peak would reach into the infrared at sometime and cause things to be baked, no? I've never seen reference to the idea as we explored distant galaxies. But the time of transparency of the original plasma would correspond to the limit of the Lyman series, no(or from the transition of just the alpha or last state so that hydrogen didn't keep absorbing some of it)? So from the ultra-violet through the current microwave peak the universe has been bathed by energy, most of the time ignoring it, but occasionally in tune with it and absorbing and re-emitting some of it. Like echoes, no? Of course the peak isn't really totally sharp so there would be a region (and thus a period) or likely interaction. But that has to be matched against the power of the signal which is decreasing.... The only comment I've seen on the power of the signal as of today is something like 10% of the tv noise (no channel) is from the background. Scaling it back up the spectrum and the other limit when the background first escaped would be quite hot- when the plasma finally condensed to gas and then became un-excited.I don't have the math background to track this but it seems to me there could have been a time when the signal was strong enough to have a measurable effect when it crossed some threshold of interest - like say when the main absorption line of sodium was matched so all the sodium in the universe would start getting excited though this specific example may be thrown off by occurring at a time when there was little or no sodium available in the universe (sometime after the first stars.) Smkolins (talk) 15:17, 13 July 2009 (UTC)

The current models of the early universe include what is called the Boltzmann equations that model all the interactions between the CMB and matter. After decoupling, there was basically only hydrogen and helium in the universe, which did not interact. Galaxies (and heavier elements) did not start forming until the CMB had cooled to ~30K, and thus the CMB did not affect them much. --Kiyo.masui (talk) 20:01, 20 July 2009 (UTC)

Follow up: The absorption lines you mentioned are observable. Cosmologist often talk about the optical depth. Also the following source talks about the 21cm absorption line in neutral hydrogen. --Kiyo.masui (talk) 21:21, 20 July 2009 (UTC)

Inhomogenaities could be quantum fluctuations, not thermal[edit]

In the inflationary paradime, the fluctuations are of quantum nature, not thermal. This should probably be at least mentioned givin the mounting evidence for inflation. --Kiyo.masui (talk) 20:06, 20 July 2009 (UTC)

Data Reduction and analysis[edit]

I revised the Data reduction and analysis subsection to add detail. The largest change was to move the paragraph on the CMBR dipole to the data analysis section because it really belongs there. It's a foreground effect that must be subtracted out before the fine-scale structure of the CMBR becomes apparent. --Virgil H. Soule (talk) 19:10, 7 September 2009 (UTC)

are we the centre of the universe?[edit]

our universe evolved from the 'big bang'when 'quantum fluctuations'were playing their role but surprisingly penzius and wilson in 1965 found exactly what friedmann predicted that universe is same in whichever direction we look in the form of cosmic background radiation how then we get such a 'symmetric' universe from such an uncertain one?does that mean that we are at centre of universe?if yes did dimensions existed even at the time of big bang? that too mean that there was no singularity at the time of big bang and thus there must be a reason for the big 'bang'! that must be explained by laws of physics. —Preceding unsigned comment added by (talk) 15:01, 15 December 2009 (UTC)

The big bang was not an event localized in space. The entire early evolution of the universe happened everywhere and in very similar fashion. Thus, wherever you look, you see more or less the same. This is not unique for our position in the universe, but would (most likely) be true regardless of your point of observation. Blennow (talk) 09:15, 23 December 2009 (UTC)

Pardon my ignorance: Did we measure the cosmic background radiation in other parts of the universe? Orphadeus (talk) 05:27, 14 May 2011 (UTC)

No, I believe that astronomers are measuring the CBR emission along the surface of a sphere centered at the Earth. But see the Copernican principle.—RJH (talk) 14:45, 27 May 2011 (UTC)
The current measurements cover the whole sky from where we are. Unless you have means to travel to another galaxy, we cannot do the same from another location. We have however measured the temperature of very distant clouds of hydrogen which are in equilibrium with the CMBR as it was billions of years ago and it was hotter then as we expect. George Dishman (talk) 22:37, 3 March 2014 (UTC)

A typo?[edit]

4000 K is not 0.25 eV, rather it is 0.35 eV. Am I wrong or is there a typo? —Preceding unsigned comment added by (talk) 03:32, 22 April 2010 (UTC)

0.25eV is 3000K, about the temperature of the plasma when the CMBR was released. RockSolidCosmo (talk) 21:16, 25 October 2010 (UTC)

New image from Planck telescope[edit]

The newly released image from the Planck telescope's one-year sky survey (viewable here) needs to be incorporated into the article pronto. -- (talk) 16:43, 5 July 2010 (UTC)

Also, here is some new information on the new data:
But feel free to add the information yourself. That is what wikipedia is. :) Andrew Colvin • Talk 04:40, 6 July 2010 (UTC)

I'm of the opinion that the image should be reverted back to the WMAP image. The new Plank image isn't really showing the CMBR. Until the Milky Way can be digitally subtracted, it pretty much dominates the image.--Sfazzio (talk) 20:55, 6 July 2010 (UTC)

I agree with Sfazzio, in addition, for the current Planck press-released images, the color map is not linear with the temperature fluctuations. RockSolidCosmo (talk) 21:14, 25 October 2010 (UTC)

A note for future reference, as the Planck images are from ESA they are most likely going to be copyright and not public domain and thus unusable without a fair-use rationale. ChiZeroOne (talk) 22:47, 5 September 2011 (UTC)

Dark flow[edit]

As a way to expand the article, perhaps a mention of Dark flow could be summarized in this article somewhere as it seems to be a related topic. -- œ 07:24, 23 October 2010 (UTC)

RELIKT-1 1992 results are not generally believed.[edit]

I was surprised to see the RELIKT-1 result claims given precedence here over COBE as the discovery of the primary CMB anisotropy, and a clear implication made that the Nobel Prize was given to the COBE workers only because of a delay in publication of RELIKT-1's results. However, it is clear from the astrophysical literature that the 1992 RELIKT-1 claim of primary anisotropy (Strukov et al. 1992, is not generally accepted. The RELIKT detectors were not multi-frequency, and thus could not remove the (dominant) galactic foreground. The quadrupole structure Strukov et al. reported is not seen in more detailed COBE maps (see e.g.,, and thus is widely judged to be incorrect. Therefore I think it is extremely inappropriate to claim that RELIKT-1 discovered the primary anisotropy in the CMB, and I am cutting these claims out of this article.Craigheinke (talk) 00:39, 24 October 2010 (UTC)

Popular culture section[edit]

While the present other stuff exists defence for inclusion isn't particularly impressive and just makes me want to delete it more, thinking about it, in this case maybe it should be kept. As far as I'm aware this is the first piece of TV fiction (if not all popular fiction) to have the CMBR as the major plot line. Can we find evidence of that? I think that would make it a notable comment.

Don't get me wrong, I love to expunge irrelevant trivia that seems to breed like rabbits as much as the next dedicated Wikipedian but in this case I think there is an argument for inclusion in the article. It's a small reference (not undue weight) and at present I'm not sure can easily be worked into the main text just yet. ChiZeroOne (talk) 15:49, 3 December 2010 (UTC)

I'm actually pretty sure there will be more TV stuff about CMBR soon. We should keep the section and add more things gradually. --Novis-M (talk) 18:18, 3 December 2010 (UTC)

Another perspective on CMBR[edit]

One of the questions that might be addressed for those of us less informed is how radiation emitted that long ago can still be around today. For example, a person could naively assume 380,000 years after the big bang that the radius of the universe would be at most 380,000 light years. Then any radiation emitted within this sphere and directed towards any internally selected location, assuming in accord with special relativity a velocity of c relative to the selected location, should have passed it when the universe was less than 760,000 years old. Obviously this is wrong.

The following argument, somehow simplified and condensed, might help. In accord with general relativity, we make the speed of radiation not c relative to some point far away both in time and space, but only c relative only to the objects in that region of space through which it is currently traveling. Place the earth at the origin of a coordinate system, and imagine radiation now reaching the earth having originated from a region at a distance of D light years and with a velocity of v relative to the origin of the coordinate system. Placing the earth at the center of the observed universe is in accord with how we see things. Placing it in the center of the actual universe is far too bold of an assumption. For the purposes of the current argument, however, it simplifies the discussion without diminishing the validity of the conclusion. Placing the earth, and our earth-bound observer, at the center of the coordinate system maximizes the time of reception of light in all directions.

Divide the path taken by the light into n small segments of equal length, dx. I will use dx to denote the initial length of each segment and dxi to denote the length of the ith segment when the radiation first enters it. Dxi must be a function of time as well as n if we are to accommodate an expanding universe. If the most distant segment was moving away from us at the speed of v, then closer segments should have a recessional velocity approximately proportional to their relative distance. With n segments, assign the recessional velocity of segment dxi so as to be (i/n)v. [i = 0 corresponds to the center of the coordinate system.] Thus, a segment halfway to the outer edge would be receding at half the speed of v; one a quarter of the way, at v/4, etc. Within each segment, a photon travels at velocity c relative to that segment, crossing it in time dxi/c. However, during that time of transit, each segment would have increased somewhat in size as well as moved further from earth. During the transit time of dxi /c the outer edge of the universe (still moving away from us at a velocity v) is now (dxi) (v/c) further away. Dividing this expansion equally among all n segments, each would be dxi (v/(cn)) wider. Since the total increase in the length of all j segments, j = 0 to j = i-1, would be given by ivdxi /(cn), the ith segment is also ivdxi /(cn) further away.

In general the following expressions apply to the ith segment.

segment length at time of photon’s entrance to segment: dx(1+ v/(cn))n-i.

transite time across segment: (dx/c)(1+ v/(cn)) ))n-i.

speed of recession of segment: iv/n

increase in distance of segment from center during transit of photon: (iv/c)(dx/n)(1+ v/(cn))n-i.

expansion of each segment, j = 0 to (i-1), during transit of ith segment: (v/c)(dx/n)(1+ v/(cn)) n-i.

Since dx = D/n, the total time for a photon to move from an initial distance D to the earth is given by the sum [i = o to n] of the transit times across each segment, i.e.

(D/c)∑(1/n)(1 + v/(cn))n-i.

The limit value of this expression as n approaches infinity is (D/v)(ev/c - 1) where e is the base of the natural logarithms. Based on this argument, if D = 380,000 and v = c, the radiation would have arrived at the center in less than 700,000 years. Obviously, in order to fit observations, either D must be much greater than 380,000 light years or v much greater than c, or some combination of both. How much bigger? If we keep v = c and force the entire expression to have a value of about 15.5 billion years, then D equals a distance of slightly over 9 billion light years. How big can D be and have the cosmos still be in thermal equilibrium during the time CMB radiation was emitted?

If we let v vary but hold D at 380,000, then in order to be received some 15.5 billion years later, the factor (ev/c - 1)/v must equal approximately 40789, implying a recessional velocity v of about 13.196c. It would seem that velocities greater than that of light must have been a feature of the early cosmos. Obviously with a v value this high there is little need to limit the 380,000 year old universe to a radius of 380,000 light years. How can such enormous velocities be achieved from a single explosion?

This result points out the dilemma posed by the CMBR for those of us less versed in the technical details. Is it sufficiently accurate to have a place, greatly condensed, in the article? Samdhatte (talk) 16:30, 21 July 2011 (UTC)

Isotropy vs. Anisotropy[edit]

Need a little clarification for laymen: despite the fact that scientists are still studying the anisotropies of CMB radiation, it is supposed to be isotropic. Am I wrong? Mastertek (talk) 10:30, 25 October 2011 (UTC)

It's a question of scale. The CMBR is not perfectly isotropic, but, as the article says, it is isotropic to roughly one part in 100,000. A simile may help - a billiard ball is smooth and round (i.e. isotropic) at millimetre scales, but at sub-micrometre scales it looks quite rough. The two interesting questions that are triggered by the close-but-not-quiote-perfect isotropy of the CMBR are (i) what does it's near-perfect isotropy tell us about conditions shortly after the Big Bang and (ii) what do its very small anisoptropies tell us about the subsequent development of the early universe. We think that the answer to question (i) is cosmic inflation; question (ii) is still being actively studied. Gandalf61 (talk) 07:04, 26 October 2011 (UTC)

Other Theories[edit]

Just as the Big Bang theory is not the only theory of ultimate beginnings, the CMB has explanations other than the one presented in the article. For the sake of objectivity, I suggest that you present more than the biased point of view. cf. CREATION'S TINY MYSTERY by Robert Gentry. (talk) 20:35, 29 December 2011 (UTC)

Wikipedia:Fringe theories. Simply put, no. Self-published pseudo-scientific ramblings are not required, and to present such views as a credible alternative would give them undue weight in an article not centered on creationism. ChiZeroOne (talk) 21:02, 29 December 2011 (UTC)

Incorrent definition of isocurvature perturbations[edit]

The article defines isocurvature perturbations as ones where "the sum of the fractional overdensities is zero" - but actually it should be the sum of the overdensities themselves, not the fractional ones. If you take 1% extra matter and 1% less radiation you won't end up with the same overall density (and hence curvature) because matter and energy have different densities to start with. So, we should re-word it to take that into account. I'm not immediately sure how to do so and still keep it as clear though - any suggestions? Olaf Davis (talk) 13:35, 27 April 2012 (UTC)

Strange dimensions[edit]

Frequency is normally indicated in Hz which is 1/sec. 1/cm is wavelength.

Also the intensity looks strange. Who can clarify? --Hans Eo (talk) 13:04, 18 May 2012 (UTC)

It's a slightly odd unit, the wavenumber. You can convert to frequency by multiplying by the speed of light. It's common in some fields to give the frequency in wavenumbers, leaving the constant c implied. --Amble (talk) 07:42, 2 June 2012 (UTC)

Temperature - details?[edit]

Hi, folks! (Pushing down the thread in hope for an answer after almost a year...)

I'd like to find a diagram that tells me in detail about the (probable) development of the universe's temperature on a time line from the big bang until today. Couldn't find anything like that myself :(

In the article it reads, "some 380,000 years after the Big Bang [...] the temperature of the universe was about 3000 K", and in the following paragraph: "Since [that time], the temperature of the background radiation has dropped by a factor of roughly 1,100 due to the expansion of the universe [...] The temperature of the CMB as observed in the present day [is] 2.725 K".

How did the temperature develop between the time of 3000 K and the 2.7 K of today? Was that drop linear, exponential, etc.?

I am especially interested in how high the temperature was between 5 and 2 billion years ago.

If you happen to have (or find) a diagram it might also be a nice addition to the article. I'm not much of a mathematician, so having a neat visual representation would be nice.

Greetings - Th. A., Cologne Univ. - (talk) —Preceding undated comment added 15:30, 26 May 2011 (UTC).

Paris Herouni[edit]

"Among his many experiments are his Projected, built, and adjusted which was used for the First Radio-Optical Telescope (ROT-54/2.6) – the “Herouni Mirror Radio telescope” – the large antenna of which with a diameter 54 m has one of the best parameters among all Large Antennas in the world. He concluded and built an Antenna Parameters and Phase Shift Angle, being the first 11, based on the World National Primary Standards. The “AREV” Project, which is a new type of powerful and ecologically pure Solar Power Plant. He was the first to come across the powerful radio-flare on Etta Gemini star, a red giant and the powerful flares associated with that type of star. He also was the first to measure an aperture of an antenna, in the World Radio Hologram. Using this, he designed and built many highly, effective Automatic Complexes of equipment for NF –FF Antenna Measuremen[3]. The state of the art 50m radio-telescope antenna showed that there is no CMB present in the universe, thus big bang never happened. This is perfectly consistent with Penrose-Gurzadyan new theory that Big-Bang never happened and that the Universe oscillates infinitely Bold text[4]."
The above is from the following Wiki: — Preceding unsigned comment added by (talk) 11:49, 5 June 2011 (UTC)

What the heck is this? No nutcase answers, please. Thanks. Greetings. Th. A., (talk) 01:25, 7 June 2011 (UTC)

Hi, folks! I'm sad there hasn't been a serious answer yet, but I'm not giving up hope. Still waiting ... (talk) 22:21, 5 September 2011 (UTC)

It's been months now. But I'm still tuned in and waiting ... (talk) 16:04, 17 October 2011 (UTC)

Hi! The question is still open. Moreover, the article might profit from such a table => thus pushing this thread down the list. Greetings, (talk) 23:18, 21 May 2012 (UTC)

To the 141.20 user: Thanks for pointing this out. The claims in the Paris Herouni article are indeed implausible and completely unsupported by the Economist article that had been used as a source. I have removed it and made a note at Talk:Paris Herouni. In the future, you are invited to BOLDly edit articles. It's especially valuable to improve articles by finding sources to support the text, and by flagging or removing claims that are not supported. --Amble (talk) 01:48, 2 June 2012 (UTC)

Look-back time[edit]

Any particular reason why the look-back time to the CMBR (~13.4B years) should not be mentioned in the article? (talk) 13:51, 13 June 2012 (UTC)

I agree, the lookback time would be valuable. Would you care to add it, along with a source? This is Wikipedia, so you are welcome to edit the article. --Amble (talk) 15:26, 13 June 2012 (UTC)


I believe Hinshaw et al. 2009, ApJS, 180, 255 is a good citation for the measurement of the doppler shift relative to the CMB rest frame DJ Fixsen — Preceding unsigned comment added by (talk) 19:05, 2 July 2012 (UTC)

Article gets progressively worse.[edit]

It starts well, then has some unclear writing.

Later, it seems to be taken over by someone with a list of obscure technical details, involving technical vocabulary, presented in a disconnected manner. The story of the discovery of the CMB is repeated near the end.

This is definitely not an "encyclopedia entry". It is just garbled collection of details in vocabulary unfamiliar to non-specialists. 77Mike77 (talk) 18:41, 13 November 2012 (UTC)

good point. So, have you fixed it yet? ;) (talk) 10:54, 28 December 2012 (UTC)

Are you joking? It would just be reverted back.77Mike77 (talk) 06:31, 19 May 2013 (UTC)

Cold Spot[edit]

There seems to be no mention to the CMB cold spot in this article. Shouldn't it be somewhere in there? Dauto (talk) 19:19, 23 April 2013 (UTC)

Off-topic comment for removal.[edit]

Towards the end of the article on the CMBR, there is this comment about Cosmology itself: "More generally, at least some astronomers and cosmologists take a far more skeptical approach to all cosmological inferences in general. For example, Michael Disney questions whether cosmology is a real physical science, or only a human narrative constructed to fit patterns we find in cosmological data." First, this is not related to the CMBR, the existence of which is not disputed by any professional scientist. Second, M. J. Disney's 2007 article in American Scientist is not an "example" of a skeptical movement among "some scientists", it is just a personal opinion piece reflecting his own misgivings. Cosmology is a speculative science In which theories change as new observations come in. I cannot find even one other article arguing the view that Cosmology is not a science. I have seen a few comments to the effect that Disney was being tongue-in-cheek and trying to stir up discussion with his magazine article; he is well-respected in his field, and made some good points about the tenuous nature of cosmological data, and the inferences drawn, but he is a "lone rogue" in his controversial view that Cosmology is not a science. The existence of one magazine article from 2007 is not significant enough to warrant the quoted comment in an article on the CMBR, and I would like to delete it.77Mike77 (talk) 04:25, 19 May 2013 (UTC)

I agree and will remove it Pmokeefe (talk) 13:08, 31 July 2013 (UTC)

--- Hi. The article is supposed to be about CMBR. While references and links to the 'Big Bang' theory obviously aren't out of place, I seem to be reading something of a piece whose subject is justifying that theory based on CMBR, not an article on CMBR itself. Shouldn't that be in "Big Bang Theory" article? Not that I'm not finding some good info, but major sections would seem to me to be "off topic". (talk) 05:26, 20 September 2013 (UTC)--Craig

Axis of Evil supposedly aligned with the Solar system[edit]

The following web page suggests alignments that are so precise they couldn't arise by chance, The solar system seems to line up with the largest cosmic features. Is this mere coincidence or a signpost to deeper insightts?

This is a personal blog by a physicist who knows the subject, none the less it's a personal blog from someone who may have his own agenda and it's certainly not good enough to cite in Wikipedia. Chief scientist from WMAP, Charles L. Bennett suggested coincidence and human psychology were involved, "I do think there is a bit of a psychological effect, people want to find unusual things." Bennett merits a Wikipedia article and is cited in the New Scientist. Found: Hawking's initials written into the universe Dragan Huterer seems to have done significant work involving Dark energy though. [2]

I personally think Bennett is much more likely to be correct than Huterer, the Copernican principle is well established and vast bodies of evidence support the CP. In the very unlikely event that further research shows the Solar system is specially aligned with the early universe what will that mean? It will increase the probability that the universe was made for us or for us and for an unknown number of planetary systems with similar alignment. It won't prove that any single designer is the god of any specific human monotheistic religion or that any design team are gods/goddesses of any specific human polytheistic religion. Similarly even if it is assumed that the universe is designed for life this says nothing about the hypothetical designer or design team. Proxima Centauri (talk) 17:44, 14 December 2013 (UTC)

Could the magnetic or electric field of the Sun or the Solar system as a whole, influence the measurements? --TiagoTiago (talk) 04:59, 27 September 2014 (UTC)

The CMB cold spot is also called the axis of evil. Are they different names for the same object? I'm not sure enough to put it into the article. Proxima Centauri (talk) 13:29, 25 February 2014 (UTC)

18 µK RMS figure incorrect[edit]

The article says the RMS of the CMB fluctuations after subtracting the dipole is 18µK. However, in the source it cites, 18 µK only appears as the RMS of the quadrupole spherical harmonics coefficients. The total CMB RMS (after removing the dipole) is about 0.1 mK, more than 5 times higher. Amaurea (talk) 01:00, 26 March 2014 (UTC)

Caption for microscope image at top of page[edit]

The caption for the first image on the page now reads "Evidence of gravitational waves in the infant universe may have been uncovered by the microscopic examination of the focal plane of the BICEP2 radio telescope". This does not make any sense. The evidence was uncovered from the images BICEP2 took, not from using a microscope to look at the detector wafers. It's a nice image, but it doesn't seem to have anything to do with the article. Amaurea (talk) 15:37, 7 April 2014 (UTC)

Mismatch frequency / wavelenght?[edit]

Dear, In the introduction of that article, I can read: The CMB has a thermal black body spectrum at a temperature of 2.72548±0.00057 K.[4] The spectral radiance dEν/dν peaks at 160.2 GHz, in the microwave range of frequencies. (Alternatively if spectral radiance is defined as dEλ/dλ then the peak wavelength is 1.063 mm.) I believe there is a mistake in that statement (?) since the frequeny and wavelengh are linked through the following: λ=c/Freq therefore, if dEν/dν peaks at 160.2 GHz, the corresponding wavelengh should be 1.87 mm (conversely, if the correct wavelenght was 1.063 mm, the matching frequency should be 282 GHz ). this assume that the propagation is equal to the speed of light in vacuum at 299 792 458 m/sec — Preceding unsigned comment added by Pierretw (talkcontribs) 07:19, 15 June 2014 (UTC)

The peak wavelength and peak frequency are physically different. It's not simply a unit conversion. This is because you're taking a derivative with respect to a different quantity, so you have to apply the chain rule to convert dEν/dν to dEλ/dλ. --Amble (talk) 08:59, 15 June 2014 (UTC)

Pictures showing the removed foreground elements, as well as highlighting the anomalies?[edit]

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.[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)


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 [3] 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?[4] Graeme Bartlett (talk) 22:46, 18 January 2015 (UTC)

1964 discovery? APS says 1963; Wilson says 1965...?[edit]

The American Physical Society says: June 1963: Discovery of the Cosmic Microwave Background, at 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: But seems like the date of the discovery of the CMB should be more clear. In Wilson's Nobel lecture at 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 "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. [5] --Amble (talk) 06:03, 26 February 2015 (UTC)