this post was submitted on 17 Mar 2024
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A cosmology without dark matter (lemmy.world)
submitted 7 months ago by DelightfullyDivisive@lemmy.world to c/science@lemmy.world
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I haven't found anything calling this crank science, although it does make some rather sweeping claims. One is that dark matter does not exist, and another is that the universe is 27 billion years old.

https://phys.org/news/2024-03-universe-dark.html

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[–] mumblerfish@lemmy.world 15 points 7 months ago* (last edited 7 months ago) (1 children)

Just some superquick thoughts...

Regarding "TL" from wikipedia:

Despite periodic re-examination of the concept, tired light has not been supported by observational tests and remains a fringe topic in astrophysics.[4]

It is not very reliable to use a component to build a model that has "no support from observations". This is a theoretical result, I don't mind them doing this work, one needs to do these things to understand the various aspects of a problem.

From one of Gutas papers, re. "CCC" (I think they are referencing the "CCC" here at least):

A scalar-tensor theory of gravity is considered [...]

Yeah, it is not generally a good idea to just throw in more components, like here a scalar. I'm guessing it cannot be the inflaton, since it is has to matter for late-time cosmology, so they either have to explain why this scalar has not been found by the LHC or that it is the Higgs. Maybe they do?

The paper linked in the article is also about fitting some cosmological data. Does it still explain galaxy rotations? What about other cosmological data, like equation of state parameter and such?

I'd say this is very teoretical work, on some quite unstable legs. I would not throw out the ΛCDM+dark matter just yet.

[–] Sodis@feddit.de 4 points 7 months ago (1 children)

It is not very reliable to use a component to build a model that has “no support from observations”.

But it has support from observations? It's an alternative explanation for the red shifts we observe from far away sources.

ΛCDM has also problems. For example that two different methods of calculating the Hubble constant do not agree, or that the James Webb telescope found galaxies, that are too old. The latter was the motivation for the paper and gives an explanation for it, contrary to current models.

Yeah, it is not generally a good idea to just throw in more components, like here a scalar.

Well, guess what the Λ in ΛCDM is? They just put it in there to be able to fit the theory to the observation. And it's absurd to say, that they would've found that in the LHC, when they also did not find dark matter particles, even though they are actively looking for those.

Does it still explain galaxy rotations? What about other cosmological data, like equation of state parameter and such?

They are aware of this and mention it already in the abstract:

It remains to be seen if the new model is consistent with the CMB power spectrum, the Big Bang nucleosynthesis of light elements, and other critical observations.

It's quite common for research groups to do this, because their work is quite complex and takes time. They proved that their approach might have some merit and now other groups can help them going forward with it.

[–] mumblerfish@lemmy.world 2 points 7 months ago (1 children)

Well, guess what the Λ in ΛCDM is? They just put it in there to be able to fit the theory to the observation. And it's absurd to say, that they would've found that in the LHC, when they also did not find dark matter particles, even though they are actively looking for those.

Kind of, but also not really. It is a bit different to add a CC which we can implicitly measure the size and equation of state of instead of adding a scalar which we observationally only have a lower bound on the mass on (from not being found in LHC). If their fit makes the mass very high, then they are fine is all I'm saying. The CC and dark matter are different, so yeah, it... would be strange to ask to find the CC att LHC because it did not find dark matter...? What?

It's quite common for research groups to do this, because their work is quite complex and takes time. They proved that their approach might have some merit and now other groups can help them going forward with it.

Absolutely. This is perfectly fine. I'm just saying with how far this direction has come right now, I'm not convinced, but that shouldn't mean much :-)

[–] Sodis@feddit.de 2 points 7 months ago (1 children)

The point with the LHC is, that it is very hard to find something, that you are not actively looking for. You have to at least have a certain understanding of the decay channels of the proposed particle to be able to scan the data for it. It's the same problem they have for discovering dark matter particles.

[–] mumblerfish@lemmy.world 2 points 7 months ago (1 children)

Sure. In model building like this I would assume that you'd make the particle heavy to explain absence from experiments, or you'd make it couple in strange ways. Do the authors here do either? Higgs was hard to find because a little bit of both, dark matter is from the couplings entirely (no coupling to the SM). The scalar, I assume, is not dark matter (that is the claim here), so it must couple to SM so unless heavy it most likely should have shown up at LHC. It is a similar problem, but not the same. If it is the couplings and not the mass that should explain the absence then is there anything in the model that would give a hint to how it couples to anything in the SM? I doubt it, because this is basically pure GR work from what I understand, and not QFT. But, I don't know, I'm just being sceptical here.

[–] Sodis@feddit.de 1 points 7 months ago (1 children)

I mean, it doesn't have to relate to a particle. Lambda is also associated with a property of space itself.

[–] mumblerfish@lemmy.world 2 points 7 months ago

Well... And so can scalars, sure, like in string theory where scalar fields represent various kinds of aspects of geometry of the extra dimensions. But they are, also this scalar, dynamical fields (which the CC is not) and these fields would correspond to "particles". You couple this field to all the other fields of the SM and you get interactions, you have particles. Its a particle.

This is why I know this is generally a problem, in string theory you have all these scalars that comes from compactification, you need to explain why they are not seen by experiments = make them heavy. Otherwise you get new particles, new forces, lots of physics that is not real.

[–] Carrolade@lemmy.world 11 points 7 months ago (1 children)

Dark matter theories have had competitors for a long time. MOND is a pretty significant one.

A helpful thing to keep in mind is astrophysicists are well aware that theories of the "age of the universe" are closer to that interesting thought experiment phase than a more concrete sort of harder theory. This stuff is still many years from being nailed down even a little bit.

[–] Sodis@feddit.de 3 points 7 months ago (1 children)

Yeah, but somehow mainstream science gaslit everyone into thinking, that the current model is definitely right, even though there are relevant observations, that are not explained by it. But I guess we just need a new even bigger particle accelerator and then we will definitely find dark matter particles!

[–] DelightfullyDivisive@lemmy.world 1 points 7 months ago (1 children)

I don't know that scientists gaslit anyone. I think it's more the state of journalism driven by the way it is monetized. Chasing SEO drives clickbait headlines and sensational claims to the top of everyone's feed.

I really appreciate the discussion on Lemmy.

[–] Sodis@feddit.de 3 points 7 months ago

Oh with mainstream science I meant the journalism, probably bad wording.

[–] Krudler@lemmy.world 2 points 7 months ago* (last edited 7 months ago)

It's crank science, it relies on the tired light theory which is the flat earth of cosmology.

Edit

The results are a "smashing success" if you are willing to accept that the universe is substantially younger than we already know it to be.

Edit2

https://iopscience.iop.org/article/10.3847/1538-4357/ad1bc6#apjad1bc6s3

I recommend you read the Discussion and Conclusions parts if not anything else. It's pretty grim and contains a series of bald-faced "admissions" that this is shenanigans.

[–] m3t00@lemmy.world 0 points 7 months ago

reminds me of early reports of the Colorado river. deeper than it looks