I just got back from a visit to the Carnegie Institution of Washington where I gave a talk and saw some old friends. I was a postdoc at the Department of Terrestrial Magnetism (DTM) in the ’90s. DTM is so-named because in their early days they literally traveled the world mapping the magnetic field. When I was there, DTM+ had a small extragalactic astronomy group including Vera Rubin*, Francois Schweizer, and John Graham. Working there as a Carnegie Fellow gave me great latitude to pursue whatever science I wanted, with the benefit of discussions with these great astronomers. After my initial work on low surface brightness galaxies had brought MOND to my attention, much of the follow-up work checking all (and I do mean all) the other constraints was done there, ultimately resulting in the triptych of papers showing that the bulk of the evidence available at that time favored MOND over the dark matter interpretation.
When I joined the faculty at the University of Maryland in 1998, I saw the need to develop a graduate course on cosmology, which did not exist there at that time. I began to consider how cosmic structure might form in MOND, but was taken aback when Simon White asked me to referee a paper on the subject by Bob Sanders. He had found much what I was finding, that there was no way to avoid an early burst of speedy galaxy formation. I had been scooped!
It has taken a quarter century to test our predictions, so any concern about who said what first seems silly now. Indeed, the bigger problem is informing people that these predictions were made at all. I had a huge eye roll last month when Physics Magazine came out with
February 12, 2024
Physics Magazine
NEWS FEATURE
JWST Sees More Galaxies than Expected
February 9, 2024
The new JWST observatory is revealing far more bright galaxies in the early Universe than anyone predicted, and astrophysicists have more than one explanation for the puzzle.
Far more bright galaxies in the early Universe than anyone predicted! Who could have predicted it? I guess I am anyone.
Joking aside, this is a great illustration of the inefficiency of scientific communication. I wrote a series of papers on the subject. I wasn’t alone; so did others. I gave talks about it. I’ve emphasized it in scientific reviews. My papers are frequently cited, ranking in the top 2% among the top 2% across all sciences. They’re cited by prominent cosmologists. Heck, I’ve even blogged about it. And yet, it comes as such a surprise that it couldn’t have possibly happened, to the extent that no one bothers to check what is in the literature. (There was a similar sociology around the prediction of the CMB second peak. It didn’t happen if we don’t look.)
So what did the Physics Magazine article talk about? More than one explanation, most of which are the conventionalist approaches we’ve talked about before – make star formation more efficient, or adjust the IMF (the mass spectrum with which stars form) to squeeze more UV photons out of fewer baryons. But there is also a paper by Sabti et al. that basically asserts “this can’t be happening!” which is exactly the point.
Sabti et al. ask whether the can boost the amplitude of structure formation in a way that satisfies both the new JWST observations and previous Hubble data. The answer is no:
We consider beyond-ΛCDM power-spectrum enhancements and show that any departure large enough to reproduce the abundance of ultramassive JWST candidates is in conflict with the HST data.
Sabti et al.
At first, this struck me as some form of reality denial, like an assertion that the luminosity density could not possible exceed LCDM predictions, even though that is exactly what it is observed to do:
On a closer read, I realized my initial impression was wrong; they are making a much better argument. The star formation rate is what is really constrained by the UV luminosity, but if that is attributed to stellar mass, you can’t get there from here – even with some jiggering of structure formation. That appears to be correct, within the framework of their considerations. Yet an alteration of structure formation is exactly what led to the now-corroborated prediction of Sanders (1998), so something still seemed odd. Just how were they altering it?
It took a close read, but the issue is in their equation 3. They allow for more structure formation by increasing the amplitude. However, they maintain the usual linear growth rate. In effect, they boost the amplitude of the linear dashed line in the left panel below, while maintaining its shape:
This is strongly constrain at both higher and lower redshifts, so only a little boost in amplitude is possible, assuming linear growth. So what they’ve correctly shown is that the usual linear growth rate of LCDM cannot do what needs to be done. That just emphasizes my point: to get the rapid growth we observe in the narrow time range available above redshift ten, the rate of growth needs to be nonlinear.
Nonlinearity is unavoidable in MOND – hence the prediction of big galaxies at high redshift. Nonlinearity is a bear to calculate, which is part of the reason nobody wants to go there. Tough nougies. They teach us in grad school that the early universe is simple. It is a mantra to many who work in the field. I’m sorry, did God promise this? I understand the reasons why the early universe should be simple in standard FLRW cosmology, but what if the universe we live in isn’t that? No one has standing to promise that the early universe is as simple as expected. That’s just a fairy tale cosmologists tell their young so they can sleep at night.
+DTM has since been merged with the Geophysical Laboratory to become the Earth and Planets Laboratory. These departments shared the Broad Branch Road campus but maintained a friendly rivalry in the soccer Mud Cup, so named because the first Mud Cup was played on a field that was a such a quagmire that we all became completely covered in mud. It was great fun.
*Vera was always adamant that she was not a physicist, and yet a search returns the thumbnail
even though the Wikipedia article itself does not (at present) make this spurious “and physicist” assertion.
Triton Station 
Nice post 🌹
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“this is a great illustration of the inefficiency of scientific communication”
Actually this is a great illustration of how orthodoxy ignores dissent considering dissenters as nobody, typical in any aspect of society.
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There is that.
I recently saw a quote about Bohm’s interpretation of quantum mechanics attributed to Oppenheimer that dismisses it by saying something to the effect that “we should all agree not to talk about it.” That is clearly intended to mean “it isn’t worth our time to think about” but it is also not a refutation of the idea. In the present context, it seems more like a declaration that we are too lazy to re-think fundamental issues, and the orthodox never need to do so.
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Thinking is indeed at the core of the problems that beset theoretical physics. As you suggest there is a rigid unwillingness to reconsider the foundational assumptions that underlie the standard models. The expanding universe assumption is as inviolable as if it had been handed down on stone tablets by some great god of mathematicism. But there is more to it than that.
There is also a profound unwillingness or perhaps inability to think about physical systems on their own terms, rather than in terms of some preferred mathematical model of the system under consideration. Here the situation with Bohmian mechanics is illustrative of the problem.
In the standard interpretation of QM the wavefunction is all that is considered and its statistical outcomes are treated as the only necessary and complete description of quantum systems. In fact however the wavefunction is an inadequate and incomplete description of quantum reality.
The wavefunction itself has no physical correlate and it does not describe a physical process that produces the observed statistical distribution. Theorists make up for this shortcoming by positing the metaphysical nonsense of wavefunction collapse, superposition of states and wave-particle duality.
Bohmian mechanics, in contrast, provides a qualitative description of the interaction between a particle and a wave that is continuous with the rest of physical reality where we find distinct particles and waves (matter and energy) interacting. Bohmian mechanics produces the same statistical results as the standard wavefunction-only interpretation while also providing a physically plausible mechanism for producing the observed statistical results.
In addition to that, the proposed mechanism and its statistical results have been replicated on the classical laboratory scale. Similarly scaled waves and particles in the laboratory behave as they do on the quantum scale.
Lastly, Bohmian mechanics requires a chaotic sub-field and empirical reality provides one in the ambient electromagnetic energy that permeates physical reality – everywhere there is no matter (mass) there is omnidirectionally sourced electromagnetic energy.
So why is Bohmian mechanics, well supported by physical observations, disfavored among quantum theorists? I would suggest because it requires physical as well as mathematical considerations and it is difficult for modern theorists to think about physics directly – they have not been trained to do that. They have only been trained to think in terms of certain preferred mathematical models. In that cloistered system physical reality is at best an afterthought. As a consequence we get superposition of states, wave-particle duality and the absurd Big Bang model. That’s no way to do science.
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Challenging mainstream (official) narratives is “misinformation” according to the gatekeepers, and exactly like in totalitarian societies challenging the party line is an economic and sometimes even a legal liability. Obviously totalitarian tendencies are trending and the signs are everywhere.
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Too many skeletons in the closet.
Too many unasked and unanswered questions.
Any interested teenager can come up with the following questions:
what are they made of?
Charge, mass, and spin=1/2 are transformed into no charge, no mass, and spin=1.
What properties must the components of electrons, positrons, and light have?
Or is it random and meaningless?
According to De Broglie, its appearance changes depending on how fast you move towards the electron…
How does this happen?
I don’t see how you can answer this with Bohm mechanics,
no matter how skillfully you glue particles and waves together.
Wasted time.
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If there’s a logical thread in this comment it eludes me. Are you suggesting that the wavefunction-only interpretation answers those questions? Do those answers, to the extent you think they exist, rely on metaphysical nonsense like superposition of states?
What we have here is not a good faith argument but a form of argumentation by non sequitur. None of the points raised in my original comment are addressed. You certainly don’t address the central point that Bohmian mechanics correctly predicts quantum behavior using the empirically established (on classical scales) physical concepts of waves and particles.
I don’t know which interpretation of QM you favor but all of them other than Bohmian mechanics are heavily reliant on metaphysical conceits that have no empirical correlates. Like much of the rest of modern theoretical physics the model(s) are heavily reliant on a convenient cloak of invisibility to shield their bizarre metaphysics from direct detection.
In short Bohmian mechanics is a qualitative and quantitative model of QM that relies on standard physics while the other “interpretations” rely on imaginary metaphysics. That was the point of my comment and you provided a text book example of the “we’d rather not think about physics” attitude that is central to the mathematicist posturing that has made an incoherent mess of modern theoretical physics.
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Hello Budrap,
I think quantum mechanics is wrong. The results are excellent. But its premises are wrong. (*)
We calculate with a continuous space. But I don’t think that makes any sense at all for entangled objects.
It would be great fun for me to destroy quantum mechanics. To do this, however, I would have to answer many questions in one stroke:
What does our space consist of?!
(My ether must fulfill relativistic symmetry, for example).
and then, what is everything else we know made of…
My idea of the double-slit experiment: What if everything behaves like a shock wave? An object hits the double slit on one side and on the other side components come off the double slit to form the object again, including the transformation that the double slit forces…
In the Terminator 2 movie there is a scene where the T1000 goes through a prison grid. More precisely, he merges with the grid and passes through it. This analogy is not perfect, but it frees me from the contradictions I usually read…
(*) I had logic for half a year in high school. It was boring as hell. Only one point was interesting:
You can start with something false and arrive at something true with correct mathematical transformations.
In one sentence:
I consider quantum mechanics to be false – in the above sense.
Accordingly, I consider all interpretations to be nonsense.
That probably doesn’t answer all your questions,
but it says how I think.
Best regards Stefan
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any one comment
arXiv:2403.09555 Testing MOND on small bodies in the remote solar system by David Vokrouhlický, David Nesvorný, Scott Tremaine
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Yes, thank you. The authors asked my opinion about this, and I saw no problems with it, but neither have I absorbed it enough to comment in detail. I hope to get around to talking about this when I have had the chance to form an opinion.
In general I ask people not to post entire abstracts/pdfs/videos, especially when they are off topic. Links are fine, as are off-topic questions, but let’s start by trying to stay on topic for a while.
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its about MOND and I’ve posted abstracts specific about MOND in the past. I would like to hear from you, since I regularly see MOND papers.
I only post MOND-observational papers here, sometimes MOND theoretical papers.
So MOND can exist in the outer edges of our solar system, in the area of trans-neptune object?
would the hypothetical planet 9 follow MOND given its extremely far orbit?
Wouldn’t such objects be subject to the external field effect from our galaxy?
could the trans-neptune objects orbits in our solars ystem distinguish between MOND and dark matter?
could you do a wide binary type test in our solar system, at extreme outer edges in AU units?
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Yes – you (and others) have posted abstract here before. I’m asking you not to. A query and a link to the abstract suffice. We don’t need the whole thing; people can follow the link if they want it.
By on-topic, I mean the topic of this post, not just anything to do with MOND, which at some level is everything in the universe. The comments always seem to wander away over time, sometimes to strange places, which is fine, BUT let’s try sticking with the prompt for at least a little while.
I have, for a long time, been hoping to do a post on planet 9, whose existence may be inferred because of MOND – see https://arxiv.org/abs/2304.00576. The paper you note by Vokrouhlický et al. would seem to contradict that claim. I don’t know that we can have enough information yet to decide either way.
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okay as this is the first time i won’t post abstracts as you wish
so objects orbiting greater than 250 astronomical units in our solar system is in the MOND regime in terms of acceleration.
could this be used to distinguish dark matter vs MOND, or is there too little dark matter to tell?
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To get to the MOND regime, you need to go much further out – about 7000 AU from the sun. Even there, the Galactic field is about 1.8*a0, so the primary MOND effects is just starting to become perceptible. However, there are subtle effects that could be detectable much closer in with sufficiently high precision data.
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astronomers can’t find hypothetical planet 9 at 250AU are telescopes able to see out to 7000AU?
Do telescopes have the required sufficiently high precision to test MOND effects out to 250 AU?
does the solar system have a dark matter halo ?
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@neo
“astronomers can’t find hypothetical planet 9 at 250AU are telescopes able to see out to 7000AU?”
“Do telescopes have the required sufficiently high precision to test MOND effects out to 250 AU?”
I think you misunderstand the difficulty of finding the hypothetical planet 9. If you go back and look at the discovery of Neptune, the perturbations of Uranus’ orbit used to calculate the predicted position of Neptune were based on less than a single orbit. R A Lyttleton in his 1968 book “Mysteries of the Solar System”, re-analysed both Adams’ and Le Verrier’s calculations and showed that the discovery was not as straightforward as it is usually presented. Tombaugh’s discovery of Pluto was pure luck as the corresponding calculations had assumed a mass comparable with the mass of the Earth.
Finding a new planet is essentially about detecting its change in position with respect to the background stars. It is not about whether the planet is bright enough to detect it; Pluto was discovered using a 13″ astrographic camera; but more about the number of background stars against which it is projected and must be separated from. Proper motion scales linearly with time so positional precision can be traded off against the length of time over which observations are made.
7000 AU is around the saddle point for the Milky Way-Sun system, so we would expect any MOND effects to be strongest there, but the disadvantage is from our location we are looking straight towards the Galactic centre where the density of stars is highest. The wide binary search where the stars are around the same distance from the Galactic Centre as the Sun is, gives a rather cleaner background.
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Hoping you are able to find the time for the Planet 9 post! That said I have no idea how you can be so productive…
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Neither do I. Seriously – it is getting impossible to find the time.
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@Laurence Cox
thanks
is arXiv:2403.09555 robust to disadvantage is from our location we are looking straight towards the Galactic centre where the density of stars is highest
is dark matter make a difference @7000AU?
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I would be cautious in using long-period comet orbits in modelling. Although, in theory there should be no outgassing from them when they are near aphelion, that really only applies to thermal outgassing; impacts by other bodies would still cause outgassing and orbital changes. I think that I would wait for the new survey telescopes to find more TNOs and enough time for their orbits to be determined accurately. As far as dark matter is concerned; it’s the same issue as for wide binaries which Stacy wrote about last May.
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I have a point for the discussion on the sociology of the belief in dark matter, which sometimes excludes other evidence in a blinkered way. There’s an extra motivation to add to the causes, I don’t know if you see it the same way, any thoughts would be of interest. In the podcast last month, you mention that we know from the abundances in the early universe that the density of baryons is about 5% of the critical mass.
It seems to me they want to find DM to prop up GR in a much more serious way than just to make it correct at low accelerations. They need it because we know space is flat at a large scale, from the CMB. In flat space theories that’s to be expected, and is not a problem (also the refractive medium interpretation for GR, originally from Eddington). But curvature predicts that if space is flat, there must be an exceptional reason. And one is, the universe is at the critical density. So they need DM, to help curvature avoid being falsified – that is, GR in its present form, with curvature.
The other thing that can save it is inflation – you’ve mentioned how in the history of cosmology, changes were made to accommodate inflation. It can prop up GR over the same issue, because it flattens space by pushing it out early on. So even though inflation has major problems (and Penrose says it has been falsified), it is defended determinedly. Big theories need small theories to prop them up, just as string theory needed supersymmetry. And although it may be a taboo, GR is obliged to explain why space is flat at a large scale. Both ways out are looking a bit shaky, and I’d say people might have faced up to the RAR far more than they have without that element in there.
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Yes, I think that’s right. Space doesn’t have to be flat in GR; it could be a wide range of things with flat being a special case. Inflation gave a good reason for why it would be flat… but it originally achieved that by driving the mass density parameter to exactly one. Consequently, all through the ’80s and well into the ’90s, every time we observers found Omega_m < 1, the Inflationary theorists would scream at us to look harder you idiots it has to be Omega_m = 1. Eventually the evidence prevailed that Omega_m < 1, so then they moved the goalposts and said well, Omega_m + Omega_Lambda = 1 is OK which is technically true but also an abandonment of the original prediction and motivation for Inflation.
So, yes, there is a big circle of self-reinforcing circular reasoning.
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Dear Stacy,
Dark matter and energy are so ingenious, with little or no ingenuity.
Putting the sun at the center of the planetary system was ingenious.
It was ingenious because the epicycles then arise as the apparent movement of Mars.
And the movement of Earth and Mars is then much simpler.
(If you want to explain the movement of Earth and Mars with the help of angels,
then the angels have it much easier).
Relativistic symmetry is ingenious because it explains the view of two very different observers.
Unfortunately, the only thing that needs to be added here is a substantial idea of the ether…
Dark matter is not sophisticated; it is like an engineering tool.
However, it also has the advantage that you can organize research.
You can show a student what is available and then tell him to vary this or that.
He learns to calculate and program, and after a while, he gets his master’s or doctorate.
You can’t do that if you want to derive the MOND formula.
One simply doesn’t know where to start.
All ideas are falsified faster than a student could present any result.
It reminds me a little of the movie “Hidden Figures” about three black women,
who work at NASA in the 1960s.
One of them is assigned to carry out calculations (under time pressure).
As soon as she finished, her boss told her that she could put everything in the bin
because the parameters had changed…
This goes on week after week…
This may be just about acceptable for an employee,
but you can’t explain to a student in training week after week
that everything was useless…
Thank you for all the blog posts
Stefan
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could any one comment on the mechanism for MOND in GR
3 recent 2024 papers on the mechanism for MOND in GR and no abstract
arXiv:2403.03227 [pdf, other]On GR dragging and effective galactic dark matterFederico Re, Marco GaloppoComments: 28 pages, 4 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc)
Anomalous contribution to galactic rotation curves due to stochastic spacetime
Jonathan Oppenheim, Andrea Russo
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics – Theory (hep-th)
arXiv:2402.19459 [pdf, other]
arXiv:2403.13019 [pdf, ps, other]Many body gravity and the galaxy rotation curvesS GaneshComments: 13 pages, 6 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics of Galaxies (astro-ph.GA); High Energy Physics – Phenomenology (hep-ph); High Energy Physics – Theory (hep-th); Mathematical Physics (math-ph)
may be considered combining MOND in GR
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I’ve never believed in the existence of Dark Matter. It’s “Brazil Nut” like behavior as a basis for structure formation seems too contrived. Instead, l think there needs to be a more comprehensive understanding of Spacetime.
Do a “Scholar Search” for H. Sato and K. Maeda and you’ll find a whole series of open access papers they published in the eighties (a time when the Large Scale Structure was just beginning to be realized) on the physical effects of expanding Voids and how they actually expel baryons from their interiors. The result being that baryons are actually confined to the strip-like volumes between the expanding Voids.
It also seems reasonable to investigate the idea of “gravitational solitons” that may exhibit at the interface between the expanding Spacetime of the Voids and the stationary Spacetime of gravitationally bound matter structures. It would not surprise me if that interaction resulted in “curved Spacetime”; something that looked and acted like a gravitational field. It would also not surprise me if Dark Matter haloes were, in fact, gravitational solitons.
I note that Hossenfelder did a talk a few years back on the subject (Is Dark Matter Real?) About halfway through it she describes a mathematical object that she refers to as pseudo gravity. She dismisses it, but maybe there’s something there.
I believe that MOND is a tool showing that some physical effect is occurring, in a similar sense to the way temperature provides proof that atoms or molecules are in motion. I find it difficult to understand how gravity could have a “minimum value”, unless Spacetime has a minimum energy value it can impart to matter. But, that might be noticeable in the Late Time Sachs-Wolfe Effect.
I note that the shapes of galaxy clusters appear to be prolate. This observation implies a universal physical process that hasn’t been explained. Does MOND provide some insight?
so, yes, I like to see work like the three papers you’ve referenced, especially the first one.
And, lastly, isn’t GR non linear?
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It’s not as if ‘gravity has a minimum value’ – the slope roughly halves its steepness. There are different ways of taking the puzzle, but one is – why does the descending slope of acceleration values basically halve its steepness at a certain point? Another is – why does the Newtonian pattern continue, but get increasingly compressed radially beyond a certain point, by r/rM. A general question is – why does the outer pattern refer to the what the inner pattern would otherwise have been out there beyond the limit, if the outer pattern hadn’t for some reason appeared? These may or may not be on the right track, but of all the different ways of seeing it, one (or more) will be the right question, and when you have that, there’s a better chance of getting to the right answer.
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