I don't have access to the paper, but it seems to make zero testable predictions and is therefore just mathematical fiction. If it's not falsifiable, it's not science.
EDIT: the last sentence is "Given sufficient redshift (or, equivalently, time) resolution effected by the redshift slicing, one might just find that the Hubble diagram exhibits jumps in the redshift distance relation, which would be very revealing."
So they say it's testable. However, we see the effects of "dark matter" (or whatever it really is) today affecting the spin of galaxies, so I don't see how that's compatible with the explanation of these events being "rare".
mr_mitm 6 hours ago [-]
He wants to look for discontinuities in the Hubble relation. Quoting from the article:
> Looking to the future of his research, Lieu says the next step to validating his model of the cosmos could come through observations using earthbound instruments rather than something like the James Webb Space Telescope.
>"The best way to look for the proposed effect is actually to use a large ground-based telescope—like the Keck Observatory [Waimea, Hawaii], or the Isaac Newton Group of Telescopes in La Palma, Spain—to perform deep field observations, the data of which would be 'sliced' according to redshift," the researcher notes.
>"Given sufficient redshift (or, equivalently, time) resolution effected by the redshift slicing, one might just find that the Hubble diagram exhibits jumps in the redshift distance relation, which would be very revealing."
Not sure how feasible this is though.
nodfyr 5 hours ago [-]
All these papers miss the fact that our main evidence for dark matter (or something like it) is the cosmic microwave background. I see no mention on how this very convoluted model can reproduce it.
The evidence is in the oscillations of the primordial plasma seen directly in the CMB. These come from the gravity pulling the plasma and pressure pushing back. Without DM they would be too shallow, DM helps by pulling the plasma gravitationally without opposing the fall with pressure of its own.
nobody9999 10 minutes ago [-]
>All these papers miss the fact that our main evidence for dark matter (or something like it) is the cosmic microwave background. I see no mention on how this very convoluted model can reproduce it.
I am not an astronomer, but IIUC (and I may not), the first evidence for dark matter was posited by Fritz Zwicky[0] in 1933 based on the rotational velocities of galaxies, work by Vera Rubin[1] confirmed in more detail decades later, confirming Zwicky's hypothesis.
Since then Rubin's work has been repeatedly confirmed.
And while Penzius and Wilson "discovered" the Cosmic Microwave Background (CMB) a few years before Rubin published her data, (again, IIUC) the CMB was not used as a reliable tool to look for dark matter until better quality data was gathered in the 1980s and 1990s.
I’ve never really understood how just adding extra invisible stuff to make the equations work is justified either? It seems more likely there is simply something wrong with the equations.
fxj 5 hours ago [-]
The neutrino was also a particle that nobody could observe at the time when Pauli proposed it. It was just a manifestation of the energy and spin conservation.
The Higgs is the same. It is not needed, but it solves the mass problem of the weak force. It is the only scalar field so far that we have observed and it was not clear whether it would exist at all.
Quintessence and sterile neutrinos are also just pieces that make the equations of the world look prettier, but they are also candidates for dark energy and dark matter.
Pauli wrote in his famous letter:
"I agree that my remedy could seem incredible because one should have seen those neutrons very earlier if they really exist. But only the one who dare can win and the difficult situation, due to the continuous structure of the beta spectrum, is lighted by a remark of my honoured predecessor, Mr Debye, who told me recently in Bruxelles: “Oh, It’s well better not to think to this at all, like new taxes”. From now on, every solution to the issue must be discussed. Thus, dear radioactive people, look and judge."
It doesn't, and the problems have only become more problematic over time, but it's the least bad hypothesis that's broadly accepted. I suspect a generational succession is required for new paradigms to be contemplated.
There are many researchers proposing simpler, novel, and testable solutions that seem to go unnoticed. For example, I'm a fan of Alexandre Deur's work. He has some simple and elegant solutions that I've never seen discussed even though they appear "obvious". For example, from 21 years ago: https://arxiv.org/pdf/2004.05905
That paper is suggesting that one of the reasons why galaxies are spinning faster than some calculations expect is because they're failing to account for the gravitational lensing of gravity itself, which bends gravity down towards the disk.
teamonkey 22 minutes ago [-]
> I suspect a generational succession is required for new paradigms to be contemplated.
There are a constant stream of new paradigms contemplated (including this one!)
The problem is that they’re contemplated, tested and found wanting.
The notion of dark matter (and dark energy, which is a completely different animal) isn’t hanging around because of stubborn professors or a lack of imagination, it’s because nothing better has come along yet.
The good thing about this theory is that it seems easily testable. Maybe it’ll be different.
mr_mitm 4 hours ago [-]
That paper focuses on rotation curves, like all DM skeptics. I can only assume because this problem is understandable with high school level math. But that's neither the only nor the best evidence for DM. If your new hypothesis doesn't even mention the CMB power spectrum, it's not really worth listening, sorry. And to be taken seriously, it has to explain at least most of the data. DM does that, everything else does not.
magicalhippo 2 hours ago [-]
I'm just a layman, but in this[1] paper from 2023 Deur and his collaborators took his model[2] and applied it to the Hubble Tension problem. This paper does mention fitting the CMB well (as I understand it), and the model having no Hubble Tension.
I know his work has been contentious in the past, and that his past work has used multiple models that are not entirely compatible for different problems, weakening his claims.
That said, at least from my armchair it seems like a worthwhile direction to pursue.
The phrase "Dark Matter" literally means we don't know and therefore until something testable is postulated and tested (to be fair i believe some candidates have fallen by the wayside over the years as measurement has improved), it's principally equivalent to plugging in a giant X and giving it properties not unlike Fermi's famous elephant curve fitting comment.
mr_mitm 3 hours ago [-]
Just FYI I have a PhD in cosmology, so no need to explain to me what "Dark Matter" does or doesn't mean, but thanks anyway. It sounds like you saw that video by Angela Collier about how Dark Matter is a set of observations, and while I think it's a good video, it's a bit disingenuous to pretend that working scientists put theories of dark matter and theories of modified gravity in the same category. I know Collier literally says that MOND is a DM theory, but I respectfully disagree, as this does not reflect the reality of the language researchers use. Even if you didn't see that video, my point still stands.
Basically, our equation isn't working, and roughly speaking the equation has gravity on the left hand side and matter content on the right hand side. Matter tells spacetime how to curve and spacetime tells matter how to move, is the old motto. Because the equation isn't working, we have two options: modifying the left hand side or modifying the right hand side (or both). In my perception, researchers refer to the first option as theories of modified gravity, and the other option as theories of dark matter.
Putting both options into one category is over simplifying the situation and isn't helpful.
tekla 1 hours ago [-]
Hey I'm sure a bunch of Youtube videos from Collier and Sabine makes you an expert in the field of physics because they make you feel smart.
mnky9800n 5 hours ago [-]
Change happens in physics one funeral at a time.
DrNosferatu 43 minutes ago [-]
Very true - but the CMB has outlived quite some funerals.
tsimionescu 4 hours ago [-]
Well, the point is actually pretty simple. You start with an equation that works for some galaxies. Then you find a galaxy where it doesn't work - you adjust the equation and now it works again. But then you find a new galaxy where it still doesn't work, you adjust again. You try this for 5, 10, 20 galaxies, just adjust the equation - but at some point there is a limit where the equation doesn't bare any more adjustment, and you still have hundreds of other galaxies that don't work.
So, the alternative that starts being simpler is a single simple equation that works for all galaxies, but allow each galaxy to have varying amounts of stuff in it with mass, but that doesn't interact electromagnetically. Right now, this is the simplest solution we have that fits all observations well.
Is it the right answer? We won't be sure unless we can detect particles that fit the necessary characteristics, and a theory that explains the distribution of these particles in different kinds of galaxies. Unfortunately, the models we have allow these particles to be arbitrarily hard to detect, at the level that we can't really rule them out even if we had a particle accelerator the size of the Earth that didn't find them.
Now, in principle a different equation could exist that has the same solutions as the current equations where they work, and different solutions where they don't work, without adding O(number of galaxies) extra parameters. But just like the dark matter particles, unless we stumble upon it, we can't know if it exists or not.
ldunn 1 hours ago [-]
It bears mentioning that the situation is even more constraining than this, because you're not just looking at galactic dynamics - you're looking at galaxy _cluster_ dynamics, and gravitational lensing measurements, and the CMB, and large-scale structure formation, and whatever else.
Dark matter is not Fermi's elephant, as invoked elsewhere in the thread. It's more like the story of the blind men and the elephant - except that the blind men recognise that their individual observations, taken together, admit a coherent explanation.
mprime1 3 hours ago [-]
> never really understood how just adding extra invisible stuff to make the equations work is justified
IANAP but here’s my understanding.
At the end of the month you spent $2000, you’re not sure how so you track down your expenses:
That ‘unknown’ is dark matter. It’s a placeholder. It’s there and makes your total but you can’t explain it yet.
mr_mitm 5 hours ago [-]
This is basically the first and most common objection laypeople have. (In fact, this comes up in every single thread on HN about DM, not exaggerating.) Believe it or not, scientists have thought of that as well. They tried, and nothing fits the data as well as the standard model.
The trope is so common that there even is an xkcd for it:
A common objection, and for good reason: just because you do not know the right model does not make your bad model somehow true
I mean, when you miss 85% of the stuff, you gotta admit that, perhaps, your stuff is wrong
And yes, it can work even if it is wrong
mr_mitm 4 hours ago [-]
Nobody said it's "true", whatever that even means for a model. The claim is that it's the best anyone has been able to come up with. And not for a lack of trying.
Everybody also acknowledges that there are issue with DM, it's just that every other known model has bigger issues.
JackSlateur 3 hours ago [-]
Ha, my bad
When you write "this is the [..] most common objection laypeople have", I understood "In contrast with the experts who know better"
Of course, if as you say, everybody knows that this is a wrong, specifying "laypeople" seems unnecessary
mr_mitm 3 hours ago [-]
You seem to have a concept that a scientific model is either "true" or "wrong", but that's not case. All models are wrong, but some are more useful than others. It's better to judge models by their ability to describe reality, and that is not a binary property, but a continuous one.
king_magic 2 hours ago [-]
It’s not a good objection. It conveniently ignores the actual data.
francois14 4 hours ago [-]
I wonder what the motto was before Einstein suggested a new model.
nonrandomstring 5 hours ago [-]
Or maybe there's nothing wrong with the equations, they're just the
wrong equations. Or based on a fundamentally wrong assumption.
fxj 4 hours ago [-]
The equations that we already have are sufficient to describe the universe to 99.9999999% but they are a hodge podge of several different theories that all work very very well in their respective regime. QM + GR + Lambda CMD + ...
But this just doesnt look nice to eye and the mind. The laws of nature "must" be shorter, more symmetric. Thats why we invented Superstrings which solves everything, but can never be tested...
my 2 ct
tsimionescu 4 hours ago [-]
QM and GR are mutually exclusive: if one is right, the other must be wrong (of course, it's very much still possible that both are wrong). If you use GR to predict the movement and interactions of photons in a medium, it's just wrong. If you use QM to predict the movement of light around a huge body, especially a black hole, it's just wrong. And what's worse, there is no limit or term you can add such that you could say "QM works only for objects up to size X, GR works for objects larger than size Y".
Also, we're nowhere near explaining 99.99999999% of the behaviors we see in the universe. In fact, we're not even able to explain 6% of the things we see in cosmology - as is often explained, dark matter accounts for 27% of all energy in the universe, and dark energy for 68% - and we have no ideas what these actually are, if they exist at all.
fxj 4 hours ago [-]
Well, actually we have developed a very good feeling when to apply which theory. From subatomic particles to the large scale structure of the universe the right theories applied give us excellent results. lambda CDM models very well fit to the observed structures and the standard model describes all the particles that have been observed so far. We are desparately looking for effects that are unexplained by the standard model in particle physics so far. That is the reason why it is so difficult to justify yet another particle accelerator at CERN.
my 2 cent
nonrandomstring 4 hours ago [-]
> laws of nature "must" be shorter
Coming at this from philosophy of science rather than as a physicist,
I feel those quotes around "must".
I think you also recognise how that might be a sort of "fundamentally
wrong assumption".
Imagine your words replayed 50 years in the future, not on physics but
applied tp the problem of general AI/sentience.
"The equations that we already have are sufficient to describe human
thought to 99.9999999% but they are a hodge podge of several
different theories...."
Whereupon a psychologist/neuroscientist in any epoch would say:
"Why on Earth are you looking for a *singular*, unified explanation
of human experience?"
What you can have is a set of "best they can be", internally
self-consistent and well evidenced theories, none of which can ever
fully explain the system - and that is the nature/feature of the
system. Isn't that what Godel and Russell showed us?
TheOtherHobbes 1 hours ago [-]
It may be - probably is - a feature of the limits of our mental processes so far.
But there's no good reason to assume the system itself just happens to mirror those limits. It would be very strange if the entire universe worked in inconsistent ways that matched the naive reasoning of some not very interesting animals on an ordinary star in the middle of nowhere.
ForOldHack 6 hours ago [-]
I would argue that it is falsifiable. What I think you are looking for is verifiable and repeatable. It took almost 30 years to verify Einstien. He said about the collection of a hundred papers trying to prove he is wrong, "you only need one paper to prove it wrong."
It's a therotical paper. Leave it to the expermentaliats to design a test to prove it right. Diffraction gratings prove QED. Right. Feynman's biographer said that.
TL;DR - replace one big singularity with multiple singularities.
As in last sentence there is "The only difference between this work and the standard model is that the temporal singularity occurred only once in the latter, but more than once in the former."
tldr
baxtr 3 hours ago [-]
Not sure why you’re being downvoted.
If a theory doesn’t generate at least one falsifiable prediction it’s not a scientific theory.
Only managed a first read, but it seems there's no explanation for the CMB.
Let alone any explanation for the CMB power spectrum peaks...
...therefore I won't bother further ;)
DrNosferatu 31 minutes ago [-]
If you ask me, Inflation is far more problematic than the Dark Stuff. Nevertheless, so far it remains the best explanation we have for observed phenomena ¯\_(ツ)_/¯
throwaway81523 5 hours ago [-]
phys.org used to be less of a gosh wow outlet.
fhars 4 hours ago [-]
Really? Since I first noticed links to pyhs.org on HN, I have always wondered why it is not permanently banned as a link target.
uninformed-me00 5 hours ago [-]
phys.org as a domain feels reliable, I guess that's how they make money doing "non-profit" (by having negative effects on humanity) stuff.
scotty79 4 hours ago [-]
The amount of ads I see there in Chrome is stunning.
> The origin of these temporal singularities is unknown—safe to say that the same is true of the moment of the Big Bang itself
If you still want to assume that weird things you mathematically need happen whenever you need them for no reason then why not stick with cosmic inflation?
3 hours ago [-]
Rendered at 14:05:47 GMT+0000 (Coordinated Universal Time) with Vercel.
EDIT: the last sentence is "Given sufficient redshift (or, equivalently, time) resolution effected by the redshift slicing, one might just find that the Hubble diagram exhibits jumps in the redshift distance relation, which would be very revealing." So they say it's testable. However, we see the effects of "dark matter" (or whatever it really is) today affecting the spin of galaxies, so I don't see how that's compatible with the explanation of these events being "rare".
> Looking to the future of his research, Lieu says the next step to validating his model of the cosmos could come through observations using earthbound instruments rather than something like the James Webb Space Telescope.
>"The best way to look for the proposed effect is actually to use a large ground-based telescope—like the Keck Observatory [Waimea, Hawaii], or the Isaac Newton Group of Telescopes in La Palma, Spain—to perform deep field observations, the data of which would be 'sliced' according to redshift," the researcher notes.
>"Given sufficient redshift (or, equivalently, time) resolution effected by the redshift slicing, one might just find that the Hubble diagram exhibits jumps in the redshift distance relation, which would be very revealing."
Not sure how feasible this is though.
The evidence is in the oscillations of the primordial plasma seen directly in the CMB. These come from the gravity pulling the plasma and pressure pushing back. Without DM they would be too shallow, DM helps by pulling the plasma gravitationally without opposing the fall with pressure of its own.
I am not an astronomer, but IIUC (and I may not), the first evidence for dark matter was posited by Fritz Zwicky[0] in 1933 based on the rotational velocities of galaxies, work by Vera Rubin[1] confirmed in more detail decades later, confirming Zwicky's hypothesis.
Since then Rubin's work has been repeatedly confirmed.
And while Penzius and Wilson "discovered" the Cosmic Microwave Background (CMB) a few years before Rubin published her data, (again, IIUC) the CMB was not used as a reliable tool to look for dark matter until better quality data was gathered in the 1980s and 1990s.
[0] https://en.wikipedia.org/wiki/Fritz_Zwicky#Dark_matter
[1] https://en.wikipedia.org/wiki/Vera_Rubin#Rotational_curves
The Higgs is the same. It is not needed, but it solves the mass problem of the weak force. It is the only scalar field so far that we have observed and it was not clear whether it would exist at all.
Quintessence and sterile neutrinos are also just pieces that make the equations of the world look prettier, but they are also candidates for dark energy and dark matter.
Pauli wrote in his famous letter:
"I agree that my remedy could seem incredible because one should have seen those neutrons very earlier if they really exist. But only the one who dare can win and the difficult situation, due to the continuous structure of the beta spectrum, is lighted by a remark of my honoured predecessor, Mr Debye, who told me recently in Bruxelles: “Oh, It’s well better not to think to this at all, like new taxes”. From now on, every solution to the issue must be discussed. Thus, dear radioactive people, look and judge."
https://icecube.wisc.edu/neutrino-history/1931/01/1931-pauli...
There are many researchers proposing simpler, novel, and testable solutions that seem to go unnoticed. For example, I'm a fan of Alexandre Deur's work. He has some simple and elegant solutions that I've never seen discussed even though they appear "obvious". For example, from 21 years ago: https://arxiv.org/pdf/2004.05905
That paper is suggesting that one of the reasons why galaxies are spinning faster than some calculations expect is because they're failing to account for the gravitational lensing of gravity itself, which bends gravity down towards the disk.
There are a constant stream of new paradigms contemplated (including this one!)
The problem is that they’re contemplated, tested and found wanting.
The notion of dark matter (and dark energy, which is a completely different animal) isn’t hanging around because of stubborn professors or a lack of imagination, it’s because nothing better has come along yet.
The good thing about this theory is that it seems easily testable. Maybe it’ll be different.
I know his work has been contentious in the past, and that his past work has used multiple models that are not entirely compatible for different problems, weakening his claims.
That said, at least from my armchair it seems like a worthwhile direction to pursue.
[1]: https://arxiv.org/abs/2301.10861
[2]: https://arxiv.org/abs/1709.02481
Basically, our equation isn't working, and roughly speaking the equation has gravity on the left hand side and matter content on the right hand side. Matter tells spacetime how to curve and spacetime tells matter how to move, is the old motto. Because the equation isn't working, we have two options: modifying the left hand side or modifying the right hand side (or both). In my perception, researchers refer to the first option as theories of modified gravity, and the other option as theories of dark matter.
Putting both options into one category is over simplifying the situation and isn't helpful.
So, the alternative that starts being simpler is a single simple equation that works for all galaxies, but allow each galaxy to have varying amounts of stuff in it with mass, but that doesn't interact electromagnetically. Right now, this is the simplest solution we have that fits all observations well.
Is it the right answer? We won't be sure unless we can detect particles that fit the necessary characteristics, and a theory that explains the distribution of these particles in different kinds of galaxies. Unfortunately, the models we have allow these particles to be arbitrarily hard to detect, at the level that we can't really rule them out even if we had a particle accelerator the size of the Earth that didn't find them.
Now, in principle a different equation could exist that has the same solutions as the current equations where they work, and different solutions where they don't work, without adding O(number of galaxies) extra parameters. But just like the dark matter particles, unless we stumble upon it, we can't know if it exists or not.
Dark matter is not Fermi's elephant, as invoked elsewhere in the thread. It's more like the story of the blind men and the elephant - except that the blind men recognise that their individual observations, taken together, admit a coherent explanation.
IANAP but here’s my understanding.
At the end of the month you spent $2000, you’re not sure how so you track down your expenses:
That ‘unknown’ is dark matter. It’s a placeholder. It’s there and makes your total but you can’t explain it yet.The trope is so common that there even is an xkcd for it:
https://www.xkcd.com/1758/
I mean, when you miss 85% of the stuff, you gotta admit that, perhaps, your stuff is wrong
And yes, it can work even if it is wrong
Everybody also acknowledges that there are issue with DM, it's just that every other known model has bigger issues.
When you write "this is the [..] most common objection laypeople have", I understood "In contrast with the experts who know better"
Of course, if as you say, everybody knows that this is a wrong, specifying "laypeople" seems unnecessary
But this just doesnt look nice to eye and the mind. The laws of nature "must" be shorter, more symmetric. Thats why we invented Superstrings which solves everything, but can never be tested...
my 2 ct
Also, we're nowhere near explaining 99.99999999% of the behaviors we see in the universe. In fact, we're not even able to explain 6% of the things we see in cosmology - as is often explained, dark matter accounts for 27% of all energy in the universe, and dark energy for 68% - and we have no ideas what these actually are, if they exist at all.
my 2 cent
Coming at this from philosophy of science rather than as a physicist, I feel those quotes around "must".
I think you also recognise how that might be a sort of "fundamentally wrong assumption".
Imagine your words replayed 50 years in the future, not on physics but applied tp the problem of general AI/sentience.
Whereupon a psychologist/neuroscientist in any epoch would say: What you can have is a set of "best they can be", internally self-consistent and well evidenced theories, none of which can ever fully explain the system - and that is the nature/feature of the system. Isn't that what Godel and Russell showed us?But there's no good reason to assume the system itself just happens to mirror those limits. It would be very strange if the entire universe worked in inconsistent ways that matched the naive reasoning of some not very interesting animals on an ordinary star in the middle of nowhere.
It's a therotical paper. Leave it to the expermentaliats to design a test to prove it right. Diffraction gratings prove QED. Right. Feynman's biographer said that.
https://arxiv.org/abs/2503.08733
> it seems to make zero testable predictions and is therefore just mathematical fiction
I'll have a look when I get the time, but the reference to his previous paper really doesn't bode well.
TL;DR - replace one big singularity with multiple singularities.
As in last sentence there is "The only difference between this work and the standard model is that the temporal singularity occurred only once in the latter, but more than once in the former."
tldr
If a theory doesn’t generate at least one falsifiable prediction it’s not a scientific theory.
Only managed a first read, but it seems there's no explanation for the CMB.
Let alone any explanation for the CMB power spectrum peaks...
...therefore I won't bother further ;)
If you still want to assume that weird things you mathematically need happen whenever you need them for no reason then why not stick with cosmic inflation?