Talk:Dark energy/Archive 5

dark energy the result of a systematic measurement error?

• https://phys.org/news/2020-01-evidence-key-assumption-discovery-dark.html
• https://www.mnn.com/earth-matters/space/stories/everything-we-thought-we-knew-about-dark-energy-might-be-wrong

So they assumed a standard candle stayed the same luminosity throughout its life, when empirical observation appears it fades overtime. This results in a miscalculation of distance, which, when corrected, makes dark energy disappear. How to integrate into the article? Kevin Baas^talk 19:33, 7 January 2020 (UTC)

FWIW - @Kevin Baas: & others -  Done - already integrated in the main article - as follows:

A study published in 2020 questioned the validity of an essential assumption which supports the existence of dark energy, and suggests that dark energy may not actually exist. Lead researcher of the new study, Young-Wook Lee of Yonsei University, said, "Quoting Carl Sagan, extraordinary claims require extraordinary evidence, but I am not sure we have such extraordinary evidence for dark energy. Our result illustrates that dark energy from SN cosmology, which led to the 2011 Nobel Prize in Physics, might be an artifact of a fragile and false assumption."

References

seems to be ok - please post if otherwise of course - in any case - Enjoy! :) Drbogdan (talk) 20:03, 7 January 2020 (UTC)

Standard candles are not the only cosmological measurement that provides evidence for dark energy. There are many other precise cosmological measurements including the cosmic microwave background, baryon acoustic oscillations, large-scale structure measurements, etc. Bringing all of these measurements together is how experts continue to conclude that there exists another form of energy. We should be careful not to amplify sensationalized articles as compared to what is happening within the cosmological research community. Cosmojellyfish (talk) 02:59, 22 January 2020 (UTC)

I disagree with the basic premise and tone of the above statement. Joseph Silk and co have shown that the concordance of other datasets that make up the evidence for Dark Energy no longer exists.

https://arxiv.org/abs/1911.02087 https://arxiv.org/abs/2003.04935

In any case it's widely acknowledged that other than type 1a supernova Hubble diagram, all other evidence for dark energy is indirect.

https://arxiv.org/abs/1506.05478

Incidentally, it has been discussed back in 1987 itself (by George Ellis and co) that because the Universe is quite inhomogeneous, it can only be represented by an FLRW metric, and that the process requires the making of a lot of choices w.r.t. how peculiar velocities are treated etc. https://iopscience.iop.org/article/10.1088/0264-9381/4/6/025

This is also the core of the Green and Wald vs Buchert, Ellis ..... debate. https://arxiv.org/abs/1505.07800

Incidentally Sarkar's recent paper (1808.04597) was attacked by Rubin (Saul Perlmutters former PhD student) & Heitlauf: https://arxiv.org/abs/1912.02191

And Sarkar and co seem to now be waiting for their response to get reviewed: https://arxiv.org/abs/1912.04257

The gist of it seems to be that SN1a data shows an acceleration only when about 70% of the data have been corrected towards the 'cosmic rest frame' using a model of the local peculiar velocities that already assumes concordance cosmology, and in the process inserts an arbitrary discontinuity within the data of about 0.07 magnitudes (when the evidence for acceleration in Perlmutter 1999 was stated as the high redshift supernovae were dimmer by about 0.15 mag compared to low redshift ones). Of course, general relativity is based on the idea that there are no preferred frames (inertial or non inertial).

Sarkar also seems to have found a lot of issues with the SN1a data itself:

https://arxiv.org/abs/1911.06456

and in a recent interview has described the data as 'doctored'.

http://backreaction.blogspot.com/2020/03/how-good-is-evidence-for-dark-energy.html

I think the mainstream of cosmology is George Ellis, and ignoring the 1987 'fitting problem in cosmology' to use sparse directionally skewed data to claim dark energy with bad statistical methods makes Riess, Perlmutter etc the ones who do sensationalized research.

Given these nuances and the recent crisis in cosmology, I would suggest that this article be expanded to also include the possibility that dark energy is pseudoscience. I will make an attempt myself once the above Silk and Sarkar papers are in print.

BattleOrc (talk) 13:52, 23 April 2020 (UTC)

Completely disagree. The Valentino, Melchiorri & Silk paper doesn't refute the existence of dark energy, it just shows (at most, since it's controversial) that Planck CMB data favors a closed universe. Evidence for dark energy comes from not just SN1a, the article itself gives several other methods. It's true the evidence is indirect, but that doesn't mean dark energy is not well-founded, since it's based on well-established theories like GR. Sarkar's paper is already in the text and it's viewed as rather fringe by other cosmologists, see names in e.g. [1]. I will oppose any attempt to treat dark energy as pseudoscientific. Banedon (talk) 20:17, 23 April 2020 (UTC)

Hahaha. You seem to have ignored the second Silk paper which literally calls for a 'drastically different model'. In addition, you may note that:

The debate that concluded in 2015, between Robert Wald and collaborators on one side and Rocky Kolb, George Ellis etc on the other hand ( https://arxiv.org/abs/1505.07800 ) is something without parallels in other fields of science. If this happened in particle physics, it would be like Michael Peskin and Francis Halzen debating if quarks are real. And this is because you cant just use GR at 'cosmological scales' (weasel words), when its geometric effects have been verified at solar system scales, and the Field equations connect the local metric with the local stress energy tensor, which means that any dynamical model that describes the whole (clearly inhomogeneous) Universe is a coarse grained average of physics that is happening at solar system scales. There is no reason to believe that the averaged out model is FLRW. Go read some George Ellis papers. FLRW is not the same as GR. It's a toy model. You may find table 1 of https://arxiv.org/abs/2002.10831 useful. Also, https://arxiv.org/abs/1109.2314

So once the above eprints are published, I will be attempting to rewrite this article to point out that DE should be treated as pseudoscience. BattleOrc (talk)

The second Silk paper doesn't disprove dark energy at all. Read the abstract carefully. It says the data "...simultaneously excludes a flat universe and a cosmological constant at 99% C.L." So we can have dark energy (in the form of a cosmological constant) if we don't have a flat universe. Further, the abstract says "either LCDM needs to be replaced by a drastically different model, or else there are significant but still undetected systematics". Excluding Lambda-CDM doesn't mean dark energy is disproved, in the same way that any model that disproves Lambda-CDM doesn't disprove the existence of matter. Or there might be significant but still undetected systematics.

You can try to rewrite the article, but I'll say that I will almost surely find it a contentious change and you will have to demonstrate consensus (here used in the Wikipedia sense of the word). Banedon (talk) 21:43, 27 April 2020 (UTC)

I think your notion of burden of proof is a bit misplaced.. dark energy was never proven in the first place. that other evidence you mention, the indirect evidence that supported the dark energy model, by itself (without the SN1a evidence) does not lead to dark energy as a conclusion: it supported the model in that it is data that would be expected to be seen if the model were correct. But none of it requires the existence of dark energy. all of the observational data that required an explanation for which dark energy was favoured relied on SN1a as standard candles. without that, then there's no longer a need for that hypothesis. Firejuggler86 (talk) 16:12, 16 April 2021 (UTC)

wimps, machos.. are proposited particles, with little experimental checking. we know little to nothing about black holes, their mass their age. and their evolution. we imaged just one. they could harbour more mass than we know. something else on our known theories can say light is wave or particle, but a theory says it is not either something 'we cant imagine'. what cant we imagine? how can we make any assumptions on anything if we can´t explain light and electromagnetism? dark matter and energy was proposed, it is magical and aesthetical. found the higgs boson at great cost. why not find the supposedly darkwhatever matter or energy which would be the most abundant? — Preceding unsigned comment added by Abestrobi (talk • contribs) 02:06, 22 February 2021 (UTC)

Dark Matter

From the introductory paragraph : "Prior to these observations, the only forms of matter–energy known to exist were ordinary matter, antimatter, dark matter, and radiation." I find this language problematic. Dark matter is not "known" to exist, unlike the other items mentioned. It is hypothesized or inferred to exist but has never been observed directly or discovered (a la the Higgs boson, e.g.). Indeed, when one clicks the link to dark matter, it quickly becomes clear that its existence is the currently favored hypothesis but is not settled science. Also, the language used implies that dark energy is also "known" to exist, which is false for the same reasons I listed for dark matter, and of course farther down the page competing ideas are discussed. That sentence of the introduction needs an overhaul. I'm hoping someone else will do it but will do it myself eventually if not. 2601:41:200:5260:7901:2F51:EBEF:946E (talk) 21:42, 29 May 2021 (UTC)

I think that's a good point. I am not qualified to rewrite the lead, but I changed "known" to "thought", as I think that addresses the immediate problem with the sentence. It's also, to a general reader, more accurate: We thought these things were everything, now we think there's something else too. More knowledgeable editors can fine-tune from there. Schazjmd (talk) 21:59, 29 May 2021 (UTC)

It’s an odd statement even before considering what forms are “known” vs “thought” vs “hypothesized” to exist. The terms “ordinary matter” and “radiation” can have different meanings in different contexts, and it’s clear from the edit history that this sentence has been edited based on several different understandings of what “ordinary matter” might include. I suggest deleting this sentence altogether. —Amble (talk) 22:50, 30 May 2021 (UTC)

I’ve made an edit to refocus the sentence in question. —Amble (talk) 22:56, 30 May 2021 (UTC)

Is the FAQ correct?

Currently there's a FAQ for the question "The total amount of dark energy increases as space expands. Doesn't that violate conservation of energy?". The answer given is "Conservation of energy is not well-defined in curved spacetime, since the stress-energy tensor does not transform cleanly under change of coordinates. In the Newtonian interpretation of the FRW metric, the extra dark energy created by the expansion of space is balanced out by the decrease in gravitational energy."

Are we sure this is correct? I'm under the impression that energy is not expected to be conserved because the metric of the universe is not time-invariant (in turn because the universe is expanding). Ping LaundryPizza03. Banedon (talk) 08:57, 16 December 2021 (UTC)

It is essential to notice that dark energy is associated with a very intense tension (negative pressure). In general relativity, the gravitational attraction is caused by both energy and pressure. The tension is so strong that it overwhelms the dark energy itself and results in a net gravitational repulsion. This is why the expansion of the universe is accelerating. When things move away from the normal gravitational attraction, this reduces their kinetic energy and converts it into gravitational potential energy. Similarly, when an object moves away from this universal gravitational repulsion, its kinetic energy increases and gravitational potential energy is reduced (becomes more negative). In the case of dark energy, the work done by the expansion just creates more dark energy in the newly created space rather than making "kinetic" energy. JRSpriggs (talk) 15:24, 16 December 2021 (UTC)

I expect the FAQ is roughly correct if one assumes interpretation that is not given in the response, as may be seen from JRSpriggs' response. Without a reference for Newtonian interpretation, perhaps the FAQ should be reduced to the GR answer only: "The total amount of dark energy would seem to increase as space expands. Doesn't that violate conservation of energy?", answered as "Energy is ill-defined in curved spacetime, since the stress–energy tensor cannot be integrated in a coordinate-independent manner over a region of such a space." 172.82.46.56 (talk) 16:23, 16 December 2021 (UTC)

 Done, until you can find a ref that supports an interpretation similar to that of JRSpriggs. –LaundryPizza03 (dc̄) 04:23, 17 December 2021 (UTC)

Double figure on estimated distribution of matter and energy in the universe

Currently (29 May 2022) the article contains two almost identical figures about the estimated distribution of matter and energy in the universe. The numbers used are not identical - the second figure use more recent numbers. I propose to consolidate both figures and use the same numbers in the article. — Preceding unsigned comment added by Steffeler (talk • contribs) 20:09, 29 May 2022 (UTC)

Si units please

I came here looking for the density of dark energy in SI units (joules per cubic metre) and could not find it. Can this be corrected please ? It seems like a simple thing to ask for and a serious omission. 84.66.21.64 (talk) 09:51, 14 December 2022 (UTC)

The article does quote the cosmological constant in the lead as mass density. Multiply by the speed of light squared (E=mc²) to get the equivalent energy density, which is 6×10⁻¹⁰ J/m³. –LaundryPizza03 (dc̄) 10:44, 14 December 2022 (UTC)

The value of the SI system is that there is no need to calculate conversions between one unit and another. The SI unit of energy is the Joule; that is what is needed. I will copy the figure you give into the main text Andrewg4oep (talk) 09:44, 18 December 2022 (UTC)

David Merritt

Actually, I think that this entire section should be removed. Merritt claims to evaluate things objectively, but actually pushes MOND as an alternative (actually, false dichotomy) to conventional cosmology. He is neither a well respected philosopher of science and, as his writings show, as noted in the referenced article, seems to know little about cosmology. Certainly his ideas are not consensus. Does one have to prove that they are not consensus? That is like a court asking a defendant to prove their innocence. With regard to dark energy, he makes many claims which are demonstrably false, hence the added reference which has a large number of references to back up its rebuttal of Merritt. This is not the place to repeat the rebuttal; those interested can read the article (freely available). — Preceding unsigned comment added by 2001:9E8:239D:EB00:B09D:197F:F6D0:C2B1 (talk) 08:14, 4 January 2023 (UTC)

Wiki Education assignment: PHY 381 History of Modern Physics

This article was the subject of a Wiki Education Foundation-supported course assignment, between 7 September 2022 and 24 December 2022. Further details are available on the course page. Student editor(s): Jeffrey Sucuzhanay (article contribs).

— Assignment last updated by Janyahmercedes (talk) 02:52, 26 January 2023 (UTC)

Observational Evidence for Cosmological Coupling of Black Holes and its Implications for an Astrophysical Source of Dark Energy

Hi, just heard this news. I'm not sure how best to edit this article, but thought someone better than me could use this

• https://iopscience.iop.org/article/10.3847/2041-8213/acb704
• https://www.ralspace.stfc.ac.uk/Pages/first-evidence-black-holes-source-of-dark-energy.aspx
• https://www.youtube.com/watch?v=gjwxnoPoEHQ&t=240s

Chupon (talk) 18:49, 16 February 2023 (UTC)

Article issues and classification

The article has a large amount of unsourced content. It is marked as having unsourced statements (July 2021 and June 2022) and weasel-worded phrases, January 2023. 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. The article fails the criteria, reassess classification to C-class. It is also tagged as "needing clarification" from January 2023 which is not indicative of "well written" per criteria #4.

There are nineteen entries in the "External links". Three seems to be an acceptable number and of course, everyone has their favorite to add for four. The problem is that none is needed for article promotion.

• ELpoints #3) states: Links in the "External links" section should be kept to a minimum. A lack of external links or a small number of external links is not a reason to add external links.
• LINKFARM states: There is nothing wrong with adding one or more useful content-relevant links to the external links section of an article; however, excessive lists can dwarf articles and detract from the purpose of Wikipedia. On articles about topics with many fansites, for example, including a link to one major fansite may be appropriate.
• WP:ELMIN: Minimize the number of links. I will trim all but the first three and article regulars can review them. -- Otr500 (talk) 15:08, 28 February 2023 (UTC)
• Note: Had to pick three random links. Blog and surveys were not a good choice. Wikipedia:External links#External links section states: Do not use {{cite web}} or other citation templates in the External links section. Citation templates are permitted in the Further reading section. -- Otr500 (talk) 15:22, 28 February 2023 (UTC)

Extended-confirmed-protected edit request on 31 August 2023

Hello,

The first papers that collected data from supernovae which originated the idea for dark matter are this one by Riess Et al. and this other one by Perlmutter Et al., both from the late 1990s.The references could be added to the beginning of the article Mexican Physicist (talk) 17:09, 31 August 2023 (UTC)

 Not done: The papers are already referenced in "Inflationary dark energy". Per WP:LEADCITE, citations are generally not needed in the lead if already cited in the body. ARandomName123 (talk)^{Ping me!} 18:18, 31 August 2023 (UTC)

Extended-confirmed-protected edit request on 9 September 2023

The second sentence of the introduction currently reads:

> The first observational evidence for its existence came from measurements of supernovas, which showed that the universe does not expand at a constant rate; rather, the universe's expansion is accelerating.

Instead, it should say something like:

> The first observational evidence for its existence came from measurements of supernovas, which showed that despite the gravitational attraction of the universe's matter, the expansion of the universe is not slowing down; rather, the universe's expansion is accelerating.

Or more simply, since the expectation of deceleration is mentioned later in the paragraph:

> The first observational evidence for its existence came from measurements of supernovas, which showed that the universe's expansion is accelerating.

The reason for either change is that there was never any reasonable expectation (at least since the 1930s) that the universe would expand at a constant rate. Aseyhe (talk) 18:51, 9 September 2023 (UTC)

Good suggestion: I've implemented your final sentence. - Parejkoj (talk) 23:59, 9 September 2023 (UTC)

Impact on structure growth

Currently missing from the article is any mention that dark energy suppresses the growth of structure. astro-ph/0305286 and astro-ph/0604485 are early theory papers on the idea, particularly pointing out that it can distinguish dark energy from modified gravity. There's also a recent review at 2212.05003. For example, the WiggleZ survey mentioned in the large-scale structure section used measurements of both the expansion rate and the growth rate to constrain dark energy (per their article, which may be different from the one the cited news stories are referring to, but I can't actually figure out which article the stories are referring to).

Aseyhe (talk) 19:24, 9 September 2023 (UTC)

I'm not an expert in this corner of cosmology, but I'm not sure what we would write here. "Dark matter suppresses the growth of structure", and then? We can't exactly write "it can distinguish dark energy from modified gravity", given that it's in a section on observational evidence, "Dark matter suppresses the growth of structure" is not observational evidence. Banedon (talk) 07:41, 11 September 2023 (UTC)