I think we need a version of the New Battery Technology Checklist[1] for this type of article. (Though I understand that the research itself often just aims solve specific tensions in cosmology, and it is only the reporting that over-hypes it as a full replacement for dark matter.)
Dear alternative dark matter theory claimant,
Thank you for your submission of a proposed revolutionary theory to replace dark matter. Your new theory claims to be superior to dark matter models and will transform our understanding of the universe. Unfortunately, your theory will likely fail, because:
[ ] It cannot explain galaxy rotation curves across all galaxy types.
[ ] It fails to account for gravitational lensing observed in galaxy clusters.
[ ] It cannot explain the Bullet Cluster observations where dark matter appears separated from normal matter.
[ ] It is inconsistent with the cosmic microwave background anisotropies.
[ ] It cannot explain the large-scale structure and formation of the universe.
[ ] It introduces arbitrary parameters without physical justification.
[ ] It lacks a sound theoretical foundation or violates established physics principles.
[ ] It fails to explain the observed velocity dispersions in dwarf spheroidal galaxies.
[ ] It cannot account for empirical relations like the Tully-Fisher relation.
[ ] It cannot be tested or falsified by current or near-future experiments.
Ironically, many of those are also levelled at dark matter theories.
Tully-Fisher - dark matter fails to explain the Tully-Fisher relation naturally, and requires a lot of tweaking and feedback effects (arbitrary parameters).
Rotation curves - recent empirical observations shows galactic rotation curves remain flat far beyond what dark matter can explain [1]
Falsified - we've been trying to find dark matter for a long time and failed. The window of possible candidates for dark matter is now surprisingly small.
I am not claiming that dark matter is wrong. I am claiming that the success of it is by no means proven , and it has many problems of its own (including those you list as problems for alternative theories).
> Falsified - we've been trying to find dark matter for a long time and failed. The window of possible candidates for dark matter is now surprisingly small
It needs to be falsifiable not necessary to be in a direct or easy way. We still currently have a large portion of the dark sector parameter space unexplored. I would not call that surprisingly small [1].
Also there are many models of dark matter that was excluded by experiments already. I would describe falsifability as a problem fpr MOND models.
Yes, I wasn't using the term falsifiable well at all there. It should be possible to falsify a theory, even if it's hard. And we are falsifying dark matter theories, excluding some of them in the process.
I'm not sure MOND is harder to falsify than dark matter. There have been some recent observations looking at wide binary stars. Throw as much money into falsifying MOND as we have into trying to find dark matter particles, and we can compare!
If you have a way of obtaining this money for MOND, that would be great. Until then the scientific community will focus the limited resources on the more sound ideas. And will focus less on a theory that have the potential to evade all observational contradictions by changing the fitting parameters.
And please don't compare that with dark matter because it has very well integrated framework with particle physics. It does not come merely as a way to only explain galaxy rotation curves while having problems with any larger structures.
MOND only has a single constant parameter, so I'm not sure if you are referring to something else here?
Making dark matter fit observation involves halos and cusps and getting the distribution just right so that the Tully Fisher relation (which is about the luminous matter) still holds.
As a layman, I find MOND involves considerably less fitting!
You will need to have a field theory to go beyond what MOND in original form does. It does only modify Newtonian gravity in the non-relativistic regime, and it applies well at the scale of galaxies but does not address relativistic effects like the one we actually see. One example would be gravitational lensing . To be a successful theory of gravity you would need to be consistent with General relativity. That's the reason why you would go to extend MOND to field theory. The most famous framework would be TeVeS and it does have many fitting parameters.
I enjoy reading these kinds of physics / astro-physics debates on HN. They make the neuroscience ones I’m use to seem quaint and manageable in comparison.
Neither can dark matter, unless ad hoc distributions are added, and we have arbitrary speed ups and slow downs of inflation, and if current distance and red shift measurements are valid, which we know they are not.
The problem is that the distance measurements are wrong, and the models have a lot of simplifications due to otherwise being too computationally complex.
Sorry, the conclusion in the paper really underlies how poorly the results fit the evidence: "The resulting almost doubling in the age of the Universe and increasing the formation times by 1 order of magnitude has been a subject of concern and requires that the new model also explain some critical cosmological and astrophysical observations" [0]
It's a double edged sword. On the one hand the model helps to explain the "impossible early galaxy" problem (since the universe is older than we thought).
On the other hand, if the universe is older there are other things that will need more research to figure out.
You should be sceptical, but there is not as yet a reason to entirely reject it. I'm not really a fan of the tired light theories myself, but glad to see different ideas being explored.
A good point. I have heard of primordial black holes as a candidate for (at least some) dark matter. Not heard that dust was ever a candidate (if you have a reference it would be appreciated).
Baryonic (tangible) dark matter exists in the form of MACHOs, which includes small cold planetary-mass dwarf stars. But there's a limited number of these, and the Big Bang hydrogen helium ratio puts limits on the amount of baryonic matter there can be.
I think there are too many unknowns and we are nowhere near close to fully understanding our universe that we should be open minded to new ideas and see if they fit into our understanding. Dark matter is one explanation to the bullet cluster but perhaps there is another we just don't understand. Yes if someone has a perpetual motion machine to the spam folder but I am always open to hear new ideas to our universe.
The whole article just accepts the paper as gospel. I've noticed this as a problem with lots of science reporting, where the latest paper or whatever completely supersedes all previous research. Sometimes even, as in this case, when the latest paper is just written by some rando with an axe to grind.
> The new model is a hybrid model that combines the tired light (TL) theory with a variant of the ΛCDM model in which the cosmological constant is replaced with a covarying coupling constants' (CCC) parameter α.
Are the dark-matter-phobes going to pretend this is "simpler" than dark matter w.r.t Occam's razor? I bet they are. Can't wait.
Dark matter to me seems a lot like the ether. Our understanding is wrong and we don’t know how or why so we invented a fudge factor to explain it. One day people will think we were silly to believe it.
I think we need a version of the New Battery Technology Checklist[1] for this type of article. (Though I understand that the research itself often just aims solve specific tensions in cosmology, and it is only the reporting that over-hypes it as a full replacement for dark matter.)
Dear alternative dark matter theory claimant,
Thank you for your submission of a proposed revolutionary theory to replace dark matter. Your new theory claims to be superior to dark matter models and will transform our understanding of the universe. Unfortunately, your theory will likely fail, because:
[ ] It cannot explain galaxy rotation curves across all galaxy types.
[ ] It fails to account for gravitational lensing observed in galaxy clusters.
[ ] It cannot explain the Bullet Cluster observations where dark matter appears separated from normal matter.
[ ] It is inconsistent with the cosmic microwave background anisotropies.
[ ] It cannot explain the large-scale structure and formation of the universe.
[ ] It introduces arbitrary parameters without physical justification.
[ ] It lacks a sound theoretical foundation or violates established physics principles.
[ ] It fails to explain the observed velocity dispersions in dwarf spheroidal galaxies.
[ ] It cannot account for empirical relations like the Tully-Fisher relation.
[ ] It cannot be tested or falsified by current or near-future experiments.
[ ] Your claims are unfounded or exaggerated.
1. https://news.ycombinator.com/item?id=26633670
Ironically, many of those are also levelled at dark matter theories.
Tully-Fisher - dark matter fails to explain the Tully-Fisher relation naturally, and requires a lot of tweaking and feedback effects (arbitrary parameters).
Rotation curves - recent empirical observations shows galactic rotation curves remain flat far beyond what dark matter can explain [1]
Falsified - we've been trying to find dark matter for a long time and failed. The window of possible candidates for dark matter is now surprisingly small.
I am not claiming that dark matter is wrong. I am claiming that the success of it is by no means proven , and it has many problems of its own (including those you list as problems for alternative theories).
[1] https://tritonstation.com/2024/06/18/rotation-curves-still-f...
> Falsified - we've been trying to find dark matter for a long time and failed. The window of possible candidates for dark matter is now surprisingly small
It needs to be falsifiable not necessary to be in a direct or easy way. We still currently have a large portion of the dark sector parameter space unexplored. I would not call that surprisingly small [1].
Also there are many models of dark matter that was excluded by experiments already. I would describe falsifability as a problem fpr MOND models.
[1] https://pdgweb.lbl.gov/2024/reviews/rpp2024-rev-dark-matter....
Yes, I wasn't using the term falsifiable well at all there. It should be possible to falsify a theory, even if it's hard. And we are falsifying dark matter theories, excluding some of them in the process.
I'm not sure MOND is harder to falsify than dark matter. There have been some recent observations looking at wide binary stars. Throw as much money into falsifying MOND as we have into trying to find dark matter particles, and we can compare!
If you have a way of obtaining this money for MOND, that would be great. Until then the scientific community will focus the limited resources on the more sound ideas. And will focus less on a theory that have the potential to evade all observational contradictions by changing the fitting parameters.
And please don't compare that with dark matter because it has very well integrated framework with particle physics. It does not come merely as a way to only explain galaxy rotation curves while having problems with any larger structures.
MOND only has a single constant parameter, so I'm not sure if you are referring to something else here?
Making dark matter fit observation involves halos and cusps and getting the distribution just right so that the Tully Fisher relation (which is about the luminous matter) still holds.
As a layman, I find MOND involves considerably less fitting!
You will need to have a field theory to go beyond what MOND in original form does. It does only modify Newtonian gravity in the non-relativistic regime, and it applies well at the scale of galaxies but does not address relativistic effects like the one we actually see. One example would be gravitational lensing . To be a successful theory of gravity you would need to be consistent with General relativity. That's the reason why you would go to extend MOND to field theory. The most famous framework would be TeVeS and it does have many fitting parameters.
Thanks, that is helpful. I knew that MOND wasn't relativistic; that a relativistic version might have many more parameters had not occurred to me.
I enjoy reading these kinds of physics / astro-physics debates on HN. They make the neuroscience ones I’m use to seem quaint and manageable in comparison.
One fun aspect of science for me is until it's explained, the explanation still exists, just our awareness and discovery doesn't, yet.
>[ ] It introduces arbitrary parameters without physical justification.
Every fundamental theory does this.
And they come along about once in a century.
Which doesn't make it wrong, but is it perhaps enough to call it an extraordinary claim?
Dark matter is one of the few things that has been studied enough for all of the ordinary explanations to have been ruled out.
Neither can dark matter, unless ad hoc distributions are added, and we have arbitrary speed ups and slow downs of inflation, and if current distance and red shift measurements are valid, which we know they are not.
The problem is that the distance measurements are wrong, and the models have a lot of simplifications due to otherwise being too computationally complex.
I'm doing a sed `s/dark matter/luminiferous ether/g` replacement here and it holds up!
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Sorry, the conclusion in the paper really underlies how poorly the results fit the evidence: "The resulting almost doubling in the age of the Universe and increasing the formation times by 1 order of magnitude has been a subject of concern and requires that the new model also explain some critical cosmological and astrophysical observations" [0]
Call me skeptical of the claims made.
[0] https://iopscience.iop.org/article/10.3847/1538-4357/ad1bc6#...
It's a double edged sword. On the one hand the model helps to explain the "impossible early galaxy" problem (since the universe is older than we thought).
On the other hand, if the universe is older there are other things that will need more research to figure out.
You should be sceptical, but there is not as yet a reason to entirely reject it. I'm not really a fan of the tired light theories myself, but glad to see different ideas being explored.
Any article/paper claiming nonexistence of dark matter that does not mention the bullet cluster should be sent to the spam folder.
The bullet cluster is not the slam dunk proof of dark matter that is commonly supposed. For example, see this: https://tritonstation.com/2024/02/06/clusters-of-galaxies-ru...
>So the unseen mass in clusters could just be ordinary matter that does not happen to be in a form we can readily detect.
That is the same thing as dark matter...
No. Dark matter is a proposed form of matter which does not interact with light.
Normal matter we can't detect isn't dark matter - it's just currently undetected matter. As our observational ability improves we find more of it.
That's WIMPS, early candidates for dark matter included primordial black holes and dust.
A good point. I have heard of primordial black holes as a candidate for (at least some) dark matter. Not heard that dust was ever a candidate (if you have a reference it would be appreciated).
WIMPS are most probably not real. They'll keep searching but it's quite unlikely they'll find any.
https://en.m.wikipedia.org/wiki/LZ_experiment
Baryonic (tangible) dark matter exists in the form of MACHOs, which includes small cold planetary-mass dwarf stars. But there's a limited number of these, and the Big Bang hydrogen helium ratio puts limits on the amount of baryonic matter there can be.
Dark matter is a question, not a theory.
WIMPS, sterile neutrinos, SIDM, primordial blackholes, MACHO, MoND, entropic gravity, &c all seek to answer the black hole question.
I think there are too many unknowns and we are nowhere near close to fully understanding our universe that we should be open minded to new ideas and see if they fit into our understanding. Dark matter is one explanation to the bullet cluster but perhaps there is another we just don't understand. Yes if someone has a perpetual motion machine to the spam folder but I am always open to hear new ideas to our universe.
I assume you are referring to gravitational lensing estimates of total matter versus visible?
"Tired light" has been debunked for decades. Unfortunately, phys.org articles are notorious for not pointing out things like this.
The whole article just accepts the paper as gospel. I've noticed this as a problem with lots of science reporting, where the latest paper or whatever completely supersedes all previous research. Sometimes even, as in this case, when the latest paper is just written by some rando with an axe to grind.
Tired light has been retired ... https://www.science.org/content/article/tired-light-hypothes...
> The new model is a hybrid model that combines the tired light (TL) theory with a variant of the ΛCDM model in which the cosmological constant is replaced with a covarying coupling constants' (CCC) parameter α.
Are the dark-matter-phobes going to pretend this is "simpler" than dark matter w.r.t Occam's razor? I bet they are. Can't wait.
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More comments here (it's the same paper):
https://news.ycombinator.com/item?id=39742010 ("Hypothesis That Universe Has No Dark Matter and Is 27B Years Old"; 71 comments)
Dark matter to me seems a lot like the ether. Our understanding is wrong and we don’t know how or why so we invented a fudge factor to explain it. One day people will think we were silly to believe it.
But today we measure little to fail theories early and fail them loud.Instead endless mathturbation.
Probably not and its just our too primitive understanding and “trying to make the calculations work”
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