I have become despondent for the progress of science.

Despite enormous progress both observational and computational, we have made little progress in solving the missing mass problem. The issue is not one of technical progress. It is psychological.

Words matter. We are hung up on missing mass as literal dark matter. As Bekenstein pointed out, a less misleading name would have been the acceleration discrepancy, because the problem only appears at low accelerations. But that sounds awkward. We humans like our simple catchphrases, and often cling to them no matter what. We called it dark matter, so it must be dark matter!

Vera Rubin succinctly stated the appropriately conservative attitude of most scientists in 1982 during the discussion at IAU 100:

To highlight the end of her quote:

I believe most of us would rather alter Newtonian gravitational theory only as a last resort.

Rubin, V.C. 1983, in the proceedings of IAU Symposium 100: Internal Kinematics and Dynamics of Galaxies, p. 10.

Exactly.

In 1982, this was exactly the right attitude. It had been clearly established that there was a discrepancy between what you see and what you get. But that was about it. So, we could add a little mass that’s hard to see, or we could change a fundamental law of nature. Easy call.

By this time, the evidence for a discrepancy was clear, but the hypothesized solutions were still in development. This was before the publication of the suggestion of Peebles and separately by Steigman & Turner of cold dark matter. This was before the publication of Milgrom’s first papers on MOND. (Note that these ideas took years to develop, so much of this work was simultaneous and not done in a vacuum.) All that was clear was that something extra was needed. It wasn’t even clear how much – a factor of two in mass sufficed for many of the early observations. At that time, it was easy to imagine that amount to be lurking in low mass stars. No need for new physics, either gravitational or particle.

The situation quickly snowballed. From a factor of two, we soon needed a factor of ten. Whatever was doing the gravitating, it exceeded the mass density allowed in normal matter by big bang nucleosynthesis. By the time I was a grad student in the late ’80s, it was obvious that there had to be some kind of dark mass, and it had to be non-baryonic. That meant new particle physics (e.g., a WIMP). The cold dark matter paradigm took root.

Like a fifty year mortgage, we are basically still stuck with this decision we made in the ’80s. It made sense then, given what was then known. Does it still? At what point have we reached the last resort? More importantly, apparently, how do we persuade ourselves that we have reached this point?

Peebles provides a nice recent summary of all the ways in which LCDM is a good approximation to cosmologically relevant observations. There are a lot, and I don’t disagree with him. The basic argument is that it is very unlikely that these things all agree unless LCDM is basically correct.

Trouble is, the exact same argument applies for MOND. I’m not going to justify this here – it should be obvious. If it isn’t, you haven’t been paying attention. It is unlikely to the point of absurdity that a wholly false theory should succeed in making so many predictions of such diversity and precision as MOND has.

These are both examples of what philosophers of science call a No Miracles Argument. The problem is that it cuts both ways. I will refrain from editorializing here on which would be the bigger miracle, and simply note that the obvious thing to do is try to combine the successes of both, especially given that they don’t overlap much. And yet, the Venn diagram of scientists working to satisfy both ends is vanishingly small. Not zero, but the vast majority of the community remains stuck in the ’80s: it has to be cold dark matter. I remember having this attitude, and how hard it was to realize that it might be wrong. The intellectual blinders imposed by this attitude are more opaque than a brick wall. This psychological hangup is the primary barrier to real scientific progress (as opposed to incremental progress in the sense used by Kuhn).

Unfortunately, both CDM and MOND rely on a tooth fairy. In CDM, it is the conceit that non-baryonic dark matter actually exists. This requires new physics beyond the Standard Model of particle physics. All the successes of LCDM follow if and only if dark matter actually exists. This we do not know (contrary to many assertions to this effect); all we really know is that there are discrepancies. Whether the discrepancies are due to literal dark matter or a change in the force law is maddeningly ambiguous. Of course, the conceit in MOND is not just that there is a modified force law, but that there must be a physical mechanism by which it occurs. The first part is the well-established discrepancy. The last part remains wanting.

When we think we know, we cease to learn.

Dr. Radhakrishnan

The best scientists are always in doubt. As well as enumerating its successes, Peebles also discusses some of the ways in which LCDM might be better. Should massive galaxies appear as they do? (Not really.) Should the voids really be so empty? (MOND predicted that one.) I seldom hear these concerns from other cosmologists. That’s because they’re not in doubt. The attitude is that dark matter has to exist, and any contrary evidence is simply a square peg that can be made to fit the round hole if we pound hard enough.

And so, we’re stuck still pounding the ideas of the ’80s into the heads of innocent students, creating a closed ecosystem of stagnant ideas self-perpetuated by the echo chamber effect. I see no good way out of this; indeed, the quality of debate is palpably lower now than it was in the previous century.

So I have become despondent for the progress of science.

Stacy McGaugh is an astrophysicist and cosmologist who studies galaxies, dark matter, and theories of modified gravity. He is an expert on low surface brightness galaxies, a class of objects in which the stars are spread thin compared to bright galaxies like our own Milky Way. He demonstrated that these dim galaxies appear to be dark matter dominated, providing unique tests of theories of galaxy formation and modified gravity. Professor McGaugh is currently the chair of the Department of Astronomy at Case Western Reserve University in Cleveland, Ohio, and director of the Warner and Swasey Observatory. Previously he was a member of the faculty at the University of Maryland, having also held research fellowships at Rutgers, the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, and the Institute of Astronomy at the University of Cambridge after earning his Ph.D. from the University of Michigan.

110 thoughts on “Despondency”

  1. I’m going to turn comments back on. I reserve the right to turn them off again if things get out of hand, up to and including the deletion of comments that I deem inappropriate for whatever arbitrary and capricious reason I feel like. Which is to say: behave. Don’t use this as an advertising spot for your pet ideas. Try searching to see if I have already answered a question previously before asking it again. Don’t be a jerk. ETC.

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    1. Yeah, my feeling (mostly made by readings here, B. Ryden’s, “Intro to Cosmology” is good. ) is there’s some truth in both, and we need a young Einstein to help us find the right model. The ‘catch-22’ is there is no funding for ‘crack-pot’ mond theories and so no young Einstein in their right mind is going to go near it. I think S. Hossenfelder is doing work on some super-fluid like gravity phase transition… but I know nothing of details.
      IMHO science funding is broken, and I don’t know how to fix it either.

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  2. I identified two major problems with the review by Peebles, one of which Stacy points out:

    1) The data agree very well with LCDM, so it must be right.
    This logic is obviously flawed. I never begin my papers with MOND fits rotation curves very well, so it must be right. Instead, I often begin with problems for LCDM, and then see if maybe MOND can address them. Even if it could, saying it must be right makes little sense normally – the tests are usually not so specific, and allow other possible interpretations. Similarly, evidence like the CMB can be explained in both LCDM and MOND, and in a rather similar way.

    2) Peebles argues that MOND without dark matter of some sort faces serious difficulties. But in a previous work (MNRAS, 499, 2845) – described in a previous TritonStation blog called “Big trouble in a deep void” – I argued that MOND likely does need hot dark matter in the form of 11 eV/c^2 sterile neutrinos to explain galaxy clusters and the CMB. Ultimately, even if there are undiscovered particles that don’t interact with light, they could well follow Milgrom’s rather than Newton’s law of gravity – as could we all. The differences are not that big in everyday circumstances.

    These are indeed very serious logical fallacies, which undermine the whole review. A more honest way to put it would be that both theories work very well in some circumstances, but these are generally distinct – only a few observables like the CMB work very well in both theories. Due to the distinct regions of success, we need to come up with a hybrid model that gets the best of both LCDM and MOND. We know this is needed because changing the gravity law or adding dark matter are not individually sufficient to explain the observations, so some combination is required.

    As an advocate of MOND, I don’t say that since LCDM fails this or that test, all aspects of it are wrong. Similarly, if advocating LCDM, one should not say that MOND is wrong because it fails this or that test, but try and identify what aspect of MOND is wrong. Very rarely do I hear something like: Gravity from an isolated mass distribution declines as inverse square in the low acceleration regime, so MOND is wrong. That would be a good argument, but I have never heard that. Instead, I have heard logically fatally flawed arguments about what is wrong with MOND along this line: Dark matter is needed on large scales. So? Use hot rather than cold dark matter, then galaxies are unaffected by it and are purely baryonic, meaning MOND is still a great idea. Or use cold dark matter if you prefer, but don’t pretend it’s the only possibility.

    All theories fit some data, and have problems with other aspects. If the problems are in theoretically unclear areas, maybe they are not serious problems & will be solved. If the problems are in theoretically clear areas and the observations are secure, there is a deeper problem with the theory, but some aspects of it might still be correct. This is why I am happy to borrow some aspects of LCDM, while hoping areas currently considered problematic for MOND will eventually prove not to be.

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    1. Yeah, (You know more than I do, so take this with a grain of salt.) My hope is some theory that predicts a_0 in mond (phase transition?) has a particle (lowest level excitation) associated with it that explains the long range interactions. Your ~10 eV neutrino, maybe?

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  3. Well, I hope I can meet the high bar that Dr. McGaugh has set for acceptable comments. Seriously. My first logical argument to Stacy and the readers/commenters is that the scientific method has failed you. The scientific method has not provided a means for you to go back and correct the priors that were incorrect. To be totally frank, nature (personified for fun) is a trickster. Nature has fooled scientists in so many ways. It is difficult to even begin this argument, because scientists are so strident about the scientific method, and yet it is their version of the scientific method that has held them (you) back from discovering reality. I’m not all that bright, but if you stumble across the basic bone structure of nature, everything becomes entirely clear. Look, I’ll minimize mentioning here how science screwed up by throwing point charges on the discard pile, instead of giving them volumetric immutability, but had someone had that thought between 1870 and 1920, nature would have been solved easily within a fortnight. It is really that simple. I’m a fricking idiot, but I got lucky, and I can see how simple it is. So set aside everything you think you know for now. Look, everything is local. Forget these idiotic fields with no field generators. Astrophysicists are in the best position for solving nature, but they are at the wrong scale. Drop down some 40-60 orders of magnitude. Everything is about orbiting point charges, which are Planck length order of magnitude, and the fields they generate and their influence on other point charges in spacetime aether or standard model particles. Actually that is redundant. You have no idea how mass works. You have no idea about energy shielding. You are deluded by incorrect priors. No wonder you are despondent. It is not possible to reach the solution building upon your faulty foundation.

    You really must let go of your priors. General relativity is great at its scales of applicability, but it doesn’t work at the smallest local scales where it becomes evident that spacetime is an aether of standard model particles. Likewise, the inflationary big bang and expansion are ill-conceived. Yes, you will get all those back, but transformed. The inflationary bangs must be realized to be processes that may happen in any galaxy with the right conditions in a fashion distributed in time and possibly periodically. It is steady state at large time scales. Therefore expansion is galaxy-local and in opposition to other galaxies. I know it is strange to contemplate, but that is the reality, and pair production and other processes precipitate traditional standard matter which then gravitates back towards the dominant local galaxy. Now that we have eliminated the 13.8 billion year old universe idea, in favor of steady state, it seems logical that spactime is composed of tired photons and neutrinos that have redshifted so far that they become massy and drop velocity until they are captured by the last galaxy on their path. These tired photons and neutrinos and other detritus of decomposed particles that form the spacetime aether (curvy per Einstein) are typically at such low energy that they barely interact with low energy standard model matter. I suppose it is possible that they may even combine into other low energy stable particles. We know nothing about this realm. Seriously, contemplate that. We know nothing, because it is at scales many orders of magnitude below our observability technology.

    Ok, this is getting long. It’s not me that is the problem. It is you. Physicists are so stuck their ways and unwilling to question the scientific method, that they are despondent. I am offering the bone structure of the new paradigm. Suspend disbelief and take it out for a spin. Everything will make so much more sense. You can keep all your observations. Your ‘accepted’ math needs only scales of applicability. Sadly, there are many prior interpretations that you will need to discard if you want to move beyond despondency into productivity.

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  4. On seeing the text by Peebles yesterday on the arXiv discussed by Stacy in the post above I became disoriented and unsure in which century we are in. Collecting my memories and senses, the question emerged why so many celebrated people seem to have missed the recent past ten years worth of development in the field.

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    1. Another point where Peebles ignores 40 years of advances in theory regards the lack of the flatness problem in cosmology. That is even more obvious than MOND phenomenology yet is ignored in textbooks even more than MOND. Unless the MOND community come out as critics of those who continue to believe in the flatness problem, you cannot expect others to come out in support of MOND. Most don’t because they don’t understand it well enough. And most non-MOND astrophysicists don’t work on ΛCDM.

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  5. As someone genuinely interested in MOND but with stakes neither in &LambdaCDM; nor in MOND, my view is that the main reason that MOND isn‘t taken more seriously is because of over-the-top, exaggerated, and factually wrong rhetoric by the likes of David Merritt. He‘s one of the worst offenders, but other (by no means all) MOND aficionados make the same mistakes. (Yes, one can argue that some supporters of ΛCDM make misguided comments about MOND. So? The question is how to get MOND to be taken more seriously, a problem which ΛCDM doesn‘t have.)

    Also, dark matter does not imply WIMPs. There are other candidates which have not been ruled out. So arguing that dark matter is improbable because WIMPs haven‘t been detected (a dubious claim in any case; how long did it take until neutrinos were detected, and we knew how many were coming from where) is a non-starter. Other candidates are not expected to be detected in the laboratory (and, no, they weren‘t constructed that way). For that matter, the prospects of detecting MOND effects in the lab are small.

    Most ΛCDM aficionados do not assume that all is hunky dory. Entire conferences are devoted to problems of ΛCDM. But there is a catch-22 here: say all works extremely well and one is accused of smugly ignoring problems; say that not all is understood and one is accused of clinging to an obsolete paradigm.

    I‘ve written extensively on why I think that Merritt‘s approach is really bad, and bad for MOND. If the MOND community thinks that I have made a mistake, publish a rebuttal. If not, then come out and say that you disagree with Merritt‘s straw-man attacks. Don‘t make the the-enemy-of-my-enemy-must-be-my-friend fallacy.

    As far as I can tell, if MOND effects are not detected in wide-binary systems where they are expected, then there would be no credible way to explain that failure. It is an acid test for MOND. If MOND fails it, it is dead.
    If I am wrong here, let me know how. The MOND community should be promoting this test loudly and clearly.

    MOND still needs to explain the CMB—all 7 detected peaks. I’ll have to check whether the paper mentioned here a while back which claimed a significant advance in that direction has been accepted in the meantime.

    Back in 1015, I published two papers in MNRAS which make the point that the supernova magnitude—redshift relation seems to indicate that, even though we know that the universe is very inhomogeneous on the scales of a supernova beam, at least with regard to visible matter, nevertheless observations support a form of the magnitude—redshift relation which is the same as if matter (and I mean Ω=0.3) were distributed homogeneously. It seems that the average effect is the same in the case of a light beam crossing a succession of voids and concentrations of matter of much higher than average density. Does this follow naturally from MOND? Can one even say one way or the other without a credible relativistic theory?
    Inquiring minds want to know.

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    1. I had a feeling you were alive before the Norman conquest of England. (Only joking! I realise the year should read 2015)

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      1. [This really fits more with my comment in the other thread above, but the typo was here]. Well, it does seem like my efforts to convince the community (don’t take it from me; take it from the many people much better known that I am whom I cite in my review) that the flatness problem is bogus have been going on for that long!

        Anyone interested in the sociology of science should investigate this. Almost all cosmology textbooks mention the flatness problem as a real problem. And yet, as my review demonstrates, many of the most important people in the fields of cosmology and general relativity have written many articles, published in the leading journals in the field, which point out that the problem is based on a misunderstanding. Yet this is ignored by writers of textbooks. Relevance to MOND: don’t blame on evil what you can blame on ignorance.

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        1. My bias comes from having a earth sciences educational background and from reading books like “Revolution in the Earth Sciences: From Continental Drift to Plate Tectonics” by A. Hallam. The bottom up data from experimental and observational scientists willing to get their hands dirty tends to win out in the end in the earth sciences. e.g. literately in the case of Marie Curie’s work on radioactive decay, leading to the invalidation of Lord Kelvin’s widely accepted estimate for the maximum age of the earth based on the then theory of thermodynamics (ignoring the energy released by radioactive decay of certain uranium and thorium isotopes found in the earths crust). Cosmology is really a currently immature continuation of the earths science project in many ways. Working our way back in time slowly and methodically is a legitimate and valuable scientific technique, rather than focusing too much on the big bang at this stage. I suppose its a competition between the particle physics mentality and a earth’s science mentality.

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    2. > As far as I can tell, if MOND effects are not detected in wide-binary systems where they are expected, then there would be no credible way to explain that failure. It is an acid test for MOND. If MOND fails it, it is dead. If I am wrong here, let me know how.

      As long as the external field effect of the large scale structure, Andromeda and the satellite galaxies are taken into account, starting from the field equation, there is no escape afaik. I’m skeptical that the full Gaia DR3 will have enough power to detect the effect. The EFE due to extragalactic sources is quite strong in the outer galaxy which is precisely where the hope for wide binaries is focused right now. Hopefully Gaia eventually accumulates enough sources. It’d be a real shame if only a next generation IR successor to Gaia could give the final say.

      > MOND still needs to explain the CMB—all 7 detected peaks. I’ll have to check whether the paper mentioned here a while back which claimed a significant advance in that direction has been accepted in the meantime.

      You mean the Skordis and Złosnik one? Hasn’t been according to ADS. Not too surprising. Publishing and peer review is slower than a snail.

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    3. how long did it take until neutrinos were detected

      22 years, 1934 – 1956. Twice that length of time has passed since the identification of ‘dark matter’ (1978).

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      1. Yes, but with neutrinos, we knew their properties, knew how many were coming from where, knew their energies, and it still took 22 years. As other comments here show, I would bet that dark matter, if it exists, is not some sort of particle. However, someone deciding that something is ruled out just because they subjectively have waited long enough doesn’t cut it.

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    4. “As far as I can tell, if MOND effects are not detected in wide-binary systems where they are expected, then there would be no credible way to explain that failure. It is an acid test for MOND. If MOND fails it, it is dead.”
      I have to admit that I heard repeatedly of testing MoND using the wide binaries but for me it seem virtually impossible to do. I may be wrong, for sure, but I don’t know how you can extract precise orbital parameters for the stars from what it is just basically only one sample point (given the involved orbital periods, in the order of tens of thousands, if not hundreds of thousands years, the Gaia data, even if it spreads over multiple years, represents virtually only a single point in the orbit).
      How do you confirm that two stars are really bounded gravitationally in a wide binary configuration and not just a chance association?
      How do you determine the current orbital configuration (i.e. the shape of the orbit) based on just one sample point?
      How do you determine the masses of the stars with enough precision? Typically, in binaries, you use orbital dynamics. Here – you need to show that orbital dynamics are not governed by ND so you need another way to determine them. But based on luminosity / color and models, how can you assure the needed accuracy?
      (Of course, I use “you” as a general appellative and I’m not referring specifically at you, Phillip…)
      All in all, I’m not really sure that the wide binary test would be the conclusive test that would settle the debate around MoND. My bets are that the results will be regarded as inconclusive – given their errors bars, they will be compatible with both ND and MoND.
      Even though, normally, I would hardly believe that MoND would be dead if it fails this test, I’m sure that in the eyes of some of the LCDM community members (in the likes of Ethan Siegel), such a failure in a specific test condition will be regarded as a complete failure. They would be more than happy to have yet another reason to just ignore the “noise” produced by MoND.

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    5. And this, Phillip, is an example of asking questions I’ve answered before. This particular rant is basically a repeat of a post of yours that provoked me to close comments previously. It wasn’t the only thing, but yours was the precipitating event. I don’t see the point in responding again if the same questions keep coming up. So – short version:
      – Please stop making ad hominem attacks on Merritt. You are welcome to your opinion, but there is nothing straw-man about his entire book on the topic. You are simply wrong about that. To complain that he is the one being over the top contradicts every experience I’ve had trying to discussing this issue over the past quarter century. People were agressively dismissive of MOND long before Merritt wrote his book. Whether you consider him to be over the top has absolutely nothing to do with their reaction, and everything to do with their insecurities at having invested their entire world view in something completely different. You want over the top? See http://astroweb.case.edu/ssm/mond/fanmail2015.html
      – Dark matter does imply new physics, and the overwhelming majority of the community seems convinced that it has to be a new particle. For practically forever, that was a WIMP. So it is a form of gaslighting to pretend that the failure of WIMP searches isn’t a problem for the standard cosmology, which for all that time has been tied to it by the hip.
      – Wide binaries are a hard test to apply, and like so many things, I think it is not at all clear which way it is going to go. Nevertheless, there are people who are promoting this test loud and clear – some of them in these comments! Yet you say this like it isn’t happening.
      – Yes, we need an explanation for the CMB in any theory. LCDM fits it because it has enough free parameters to do so. I’m less impressed by the fit that than I am with the fact that it gives almost the same answer as independent probes, all of which point to something in the neighborhood of LCDM – as I’ve written here before. This apparent agreement is less good than advertised, as seen in the growing tensions: not just H0, but BBN, sigma_8, and the optical depth to reionization. In MOND, the problem is much harder. Rather than the mother of all free parameters provided by non-baryonic dark matter, one has to invent a relativistic theory and do the calculation which involves writing a code that it took many bright people years and years to do in GR. So a much high bar. RMOND claims to fit the entire CMB spectrum. Whether it is “right” as a deeper theory, I don’t know. But it is a demonstration that it is possible to construct such a theory, which many cosmologists have long asserted would be impossible.
      – MOND is non-linear, so large scale inhomogeneities arise naturally. Whether this explains the SN observations, I don’t know. It does naturally explain the large bulk velocity flows (e.g., https://arxiv.org/abs/1305.3651) that *might* lead to such an effect. I imagine the Hubble flow gets distorted on scales larger than expected conventionally. What we need is to do measure the SN Hubble diagram in directions all over the sky to map out any distortions. A map of the universe in phase space extending out to much higher z that so far obtained.
      – Inquiring minds can find most these answers already in the literature or somewhere on this blog. You seem less interested in answers than in debate for the sake of debate. I’m bored by it.

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      1. I‘ve also become convinced that the comments here are not the right place for the discussions I want to have. I’ll return to the refereed literature.

        A final, very important point: The term “ad hominem” has a very specific meaning: it means criticizing the person rather than the argument. If I did that in the case of Merritt, please point out exactly where (here or via email). I detest ad-hominem arguments and it is a serious charge to be accused of them. (Of course, it is arguably a matter of opinion whether Merritt’s arguments are exaggerated, but the fact that some of his opponents are unnecessarily dismissive of MOND is irrelevant to the quality of Merritt’s arguments.)

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  6. Stacy,
    Since the James Webb Telescope is currently scheduled to launch in October of this year, with the observing time available some time in 2022. can you provide us with (or encourage a guest poster to or thoughts from a wider spectrum of researchers) some thoughts on the question; what are likely to be the key differences between galaxy formation in the very early universe compared with later on, for MOND and the latest snapshot of LCDM, that the James Webb Telescope might observe in the forthcoming decade. Hopefully to help counter balance the dark matter (over) hype that is likely to begin soon.

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  7. As an interested but unqualified layman, all I want to say is that I greatly appreciate Dr. McGaugh’s work and his posts here. Let’s face it, humanity is a mess, and takes many steps backward for a few steps forward, and we really shouldn’t expect much of it; but a few people, such as Dr. McGaugh, do give me some hope. (Right or wrong, they are doing our best work.)

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  8. What if it’s the other way around, that mass is an effect of gravity, rather than gravity a property of mass?
    For one thing the problem isn’t really missing mass, but excess gravity.
    Its seems logical that any information, whether it’s as waves or particles, amounts to some form of consolidation, in order that it can be measured. Geometrically, this “inward curvature.”
    Galaxies are energy radiating out, as mass coalesces in, so if they balance out, then the initial inward curvature starts where quantification begins.
    What really is “mass,” other than tightly bound energy?

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  9. Reading Peebles’ paper I was struck by a few things. Two of the biggest:

    He isn’t familiar with how pervasive and serious the problems with the DM paradigm are and the extent to which they are problems not only at the galactic scale but at the cosmology scale (depending upon how you count, I probably have twenty serious, serious problems on my running list, about two-thirds at galaxy scale or below and a third at cosmology scale).

    And, he isn’t aware that there is more to modified gravity than non-relativistic toy model MOND. In particular, Deur, Moffat, Bekenstein, and other relativistic extensions or variants on MOND. Also conformal gravity and various f(R), f(R,T), etc. modified gravity theories.

    Peebles isn’t the only offender, of course. I don’t know how many new DM particle papers I see a month that propose some new DM candidate that is already ruled out by other published work that the proposer doesn’t consider. I don’t know how many papers I’ve read that make the dubious claim that SUGRA or SUSY or axions are “well motivated” when after the LHC (and in the case of the “strong CP problem” at the outset), this isn’t really true. I don’t know how many people mistakenly think that the Bullet Cluster killed modified gravity theories. There have been dozens of observational studies strongly disfavoring NFW shaped inferred halos, and yet, time and time again, new papers continue to rely upon them as if they were well established empirical facts.

    Part of the problem is that is seems like there is no one doing for DM particle parameter space and modified gravity theory what the Particle Data Group does for fundamental particle properties and hadron properties, that is, systemically, in a subject-matter organized systemic manner, synthesize the global bounds imposed on various theories from observational limits and analysis. It is done very narrowly (e.g. compiling dark dark matter detection search results from different experiments in a single chart), but there aren’t similar compilations for DM annihilation searchers, for galaxy dynamics searches, for implications from inferred DM halo shapes.

    Ultimately, however, I am not despondent. One of the reasons that few people are up to speed on the literature is that we are drinking from a firehose of new, well collected, increasingly precise data on multiple fronts (better telescopes in all EM wave lengths 9e.g. new 21cm data), neutrino astronomy, gravitational wave astronomy, cosmic ray analysis, direct DM detection experiments, particle accelerator searches, muon g-2 measurements, and theory and analysis work too). Astronomy and cosmology aren’t quite as overcome by the Big Science monopoly of group think as HEP since the personnel and resources per experiment are smaller allowing for more diversity. Everybody acknowledges that the phenomena attributed to DM is the biggest unsolved problem in all of physics and there is a massive effort by everyone in any potentially relevant subfield of science to address it. This is a huge constants with HEP where only a handful of inbred collaborations are doling out new data sparingly and are heavily influences by a small number of senior managers who set priorities for benchmark theories and analysis heavily influenced by SUSY. False positives for DM are still being quickly shot down. Little by little the DM particle parameter space is being whittled down. In truth, it is probably already constrained to zero or close to zero if you know all of the literature. Only a few proclaim it, but truly sterile DM is pretty much ruled out by observational evidence (which at a minimum puts modified gravity on a level playing field with interacting DM theories in Occam’s Razor). We will get there. I give it 20-30 years, but it will happen.

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    1. What are the problems at the cosmology scale? Hopefully not “we don’t know what dark matter is”.

      Bekenstein? TeVeS has been ruled out (among others in a paper by MOND enthusiast Bob Sanders).

      Yes, there are other modified-gravity theories. I remember George Efstathiou issuing the challenge to have an alternative theory of which nothing more is required than explaining current data better than ΛCDM. Does that theory exist?

      Once again, don’t harp on dark matter. It also doesn’t make sense to accuse the standard-cosmology crowd of spending too much time thinking about particle dark matter, then oneself criticizing only particle dark matter. Maybe it is primordial black holes, self-interacting, superfluid, etc.

      DM as the biggest unsolved problem in physics? What about quantum gravity? Since we know a) that neutrinos have mass and b) that they have no mass in the standard model, then c) the standard model must be incomplete, so dark matter from some extension to the standard model wouldn’t be surprising at all.

      Since there is good evidence that there is dark matter on cosmological scales, it is not out of the question that dark matter can explain MOND phenomenology. I appreciate the elegance of MOND. But some things are complicated. Think of the weather, many types of physics at different spatial and temporal scales. Could anyone who didn’t know the Earth have predicted, from first principles, the different types of clouds or the shape of a tornado funnel?

      If MOND is the explanation for galaxy-scale stuff, one also has to explain why dark matter avoids galaxies if one accepts that it exists on cosmological scales.

      I think that more collaboration would bring more progress. Get people interested in MOND by stressing the phenomenology, which cries out for explanation whatever it is. Most people don’t know about most MOND phenomenology. Not everyone on the other side is a victim of group think and trapped within.a Kuhnian paradigm.

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      1. “What are the problems at the cosmology scale?”

        The current state of the art is EDGES which has revealed that primordial radio wave backgrounds from around 228 million years after the Big Bang (redshift z=17) contradict the LambdaCDM prediction, while being consistent with a no DM hypothesis. See Bowman, J., Rogers, A., Monsalve, R. et al. An absorption profile centred at 78 megahertz in the sky-averaged spectrum. Nature 555, 67–70 (2018).

        The KIDS telescope observation of very large scale structure which shows it to be 8.3% smoother (i.e. less clumpy) than predicted by LambdaCDM. See, e.g., http://kids.strw.leidenuniv.nl/pr_jul2020.php

        The aggregate statistical distribution of galaxy types and shapes, called the “halo mass function” is wrong. https://tritonstation.com/2020/01/26/the-halo-mass-function/

        The “impossible early galaxy” problem (i.e. galaxies are observed sooner after the Big Bang than predicted). See, e.g.Pavel Kroupa, Ladislav Subr, Tereza Jerabkova, Long Wang “Very high redshift quasars and the rapid emergence of super-massive black holes” arXiv (July 28, 2020) (MNRAS, in press) and Manoj K. Yennapureddy, Fulvio Melia, “A Cosmological Solution to the Impossibly Early Galaxy Problem” (March 19, 2018).The problem persists in warm DM and self-interacting DM cases. arxiv:2002.11129 and arxiv:1506.01377.

        The Hubble tension. See, e.g. arxiv:2010.12164

        Deviations from the cosmological principle (i.e. the observed Universe is not quite isotropic; it is also manifestly inhomogeneous). See, e.g, Roya Mohayaee, Mohamed Rameez, Subir Sarkar, “Do supernovae indicate an accelerating universe?” arXiv:2106.03119 (June 6, 2021) and arxiv:2106.05284

        It predicts too few galaxy clusters. See, e.g., arXiv:1902.10837.

        It gets globular cluster formation wrong. See, e.g., Peter Creasey, et al., “Globular Clusters Formed within Dark Halos I: present-day abundance, distribution and kinematics” (June 28, 2018); Scarpa et al., “Globular Clusters as a Test for Gravity in the Weak Acceleration Regime” (2006) arxiv:0601581

        There are too many galaxy clusters colliding at speeds that are too high relative to each other. See, e.g., Jounghun Lee, Eiichiro Komatsu, “Bullet Cluster: A Challenge to LCDM Cosmology” (May 22, 2010). Later published in Astrophysical Journal 718 (2010) 60-65.

        There are alternative modified gravity theories to toy model MOND that explain pretty much everything that dark matter particle theories do (including, e.g., the cosmic coincidence problem, clusters, the Bullet Cluster, galaxy formation, the 21cm signal, and the cosmic microwave background radiation pattern observed). See, e.g., Constantinos Skordis, Tom Złosnik, “A new relativistic theory for Modified Newtonian Dynamics” arXiv (June 30, 2020).

        SMALLER SCALE PROBLEMS

        A summary of the galaxy scale issues can be found, e.g., at James S. Bullock, Michael Boylan-Kolchin, “Small-Scale Challenges to the ΛCDM Paradigm” (July 13, 2017, last updated September 2, 2019) arXiv 1707.04256. Some of the more notable ones:

        Wide binaries don’t match Newtonian gravity. Hernandez et al., “Wide binaries as a critical test for Gravity theories” (2012) arxiv:1205.5767 and arXiv:1611.08635

        Satellite galaxies are consistently located in a two dimensional plane relative to the core galaxy. Marcel S. Pawlowski, Pavel Kroupa “The Milky Way’s Disk of Classical Satellite Galaxies in Light of Gaia DR2” arXiv (November 12, 2019) (Accepted for publication in MNRAS).

        Not as many satellite galaxies are observed as predicted, and the number of satellite galaxies is related to budge mass in spiral galaxies despite ΛCDM not predicting this effect. See, e.g., B. Javanmardi, M. Raouf, H. G. Khosroshahi, S. Tavasoli, O. Müller, A. Molaeinezhad, “The number of dwarf satellites of disk galaxies versus their bulge mass in the standard model of cosmology” (November 21, 2018) (accepted in The Astrophysical Journal). and arxiv:1707.04256

        It doesn’t explain systemic variation in the amount of apparent dark matter in elliptical galaxies, or why spiral galaxies have smaller proportions of ordinary matter than elliptical galaxies in same sized inferred dark matter halos, or why thick spiral galaxies have more inferred dark matter than thin ones. See, e.g., arXiv:2010.06692 and arXiv:2010.01186 and arXiv:2004.05905.

        It doesn’t explain strong statistical evidence of an external field effect that violates the strong equivalence principle. See arXiv:2009.11525

        It doesn’t do a good job of explaining the rare dwarf galaxies (that are usually dark matter dominated) that seem to have no dark matter. Isabel M.E. Santos-Santos, et al., “Baryonic clues to the puzzling diversity of dwarf galaxy rotation curves” (November 20, 2019) (submitted to MNRAS).

        It doesn’t explain deficits of X-ray emissions in low surface brightness galaxies. See arXiv:1906.05867.

        The halo shapes are usually wrong (too cuspy and not in the NFW distribution predicted by the theory). See, e.g., arXiv:1701.02698

        The gravitational lensing of subhalos in galactic clusters recently observed to be much more compact and less “puffy” than LambdaCDM would predict. Massimo Meneghetti, et al., “An excess of small-scale gravitational lenses observed in galaxy clusters” 369 (6509) Science 147-1351 (September 11, 2020).

        The correspondence between the distribution of ordinary matter and inferred dark matter in galaxies is too tight; truly collisionless dark matter should have less of a tight fit in its distribution to ordinary matter distributions than is observed. See, e.g, Paolo Salucci, “The distribution of dark matter in galaxies” (November 21, 2018) (Invited review for The Astronomy and Astrophysics Review) and arXiv:2008.04052. This is also the case in galaxy clusters. Antonino Del Popolo et al., “Correlations between the Dark Matter and Baryonic Properties of CLASH Galaxy Clusters” (August 6, 2018).

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        1. Hmm – I was also about to ask for dr. McGaugh’s opinion on the smoothness of the universe according to the Dark Energy Survey results. It seems the DES results point in the same direction as the KiDS results.
          Since a MoNDian universe forms structure earlier, I would assume that a smoother universe is also something a MoND type theory would struggle with. Am I wrong?

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          1. Whatever the proper theory of structure formation turns out to be, your comment make is it clear that problems (which might be resolved, much as the lack of a viable relativistic theory is a problem for MOND) with ΛCDM do not necessarily imply that there is thus more evidence for MOND.

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            1. Everybody agrees that toy model MOND is not the correct theory. It is a phenomenological approximation with a significant but not complete range of applicability (that nonetheless performs impressively there. Moffat’s MOG, Deur’s quantum gravity inspired approach, f(R), f(T), Conformal gravity, and other options for modified gravity that largely replicate MOND where it works but works better elsewhere.

              ΛCDM has serious flaws. The flaws in the cosmology area are quite generic to all CDM particle theories. The issues at the galaxy scale pretty much rule out all forms of truly sterile,collisionless DM particles. Self-interacting DM or some sort of 5th forth interaction with regular matter could conceivable fit the data (with a new force as well as a new particle). But the forces in those cases are quite constrained.

              Also, if modified gravity can look like DM particle theories at galaxy scales, it is hardly surprising that it might be quite similar at cosmology scales as well.

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        2. Many of your problems (those I am not commenting on explicitly) have to do with ΛCDM, not dark matter per se. Just like MOND phenomenology can be true if neither non-relativistic MOND or TeVeS is true, DM can be true even if a specific model of structure formation involving ΛCDM is wrong. (And keep in mind that the EDGES result needs to be confirmed.). Think baby and bathwater.

          It is not clear how the Hubble tension, even if real, somehow invalidates dark matter. As far as I know, no-one predicted it, which should have happened if it is an obvious consequence of other theories.

          No-one has ever claimed that the universe is completely homogeneous. The question is whether the inhomogeneity has significant effects. The result you mention is far from confirmed.

          I’m still waiting for the Skordis and Zlosnik paper to be accepted. I think that if one publishes a preprint, then, if the paper is accepted, one should be obliged to publish the rejection letter, whether or not one agrees with it.

          As for wide binaries, experts in the field read and comment here and they agree with me that the jury is still out.

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  10. Hi Stacy, Thank you for this post on despondency.
    Although MOND has a better record of predictions than LCDM, I tend to agree with Sabine Hossenfelder that, in the long run, explanatory power is a better measure of a hypothesis than either pre-dictions or post-dictions (Backreaction “Predictions are overrated” 04-May-2020). As your “LCDM and MOND compared” table shows (The MOND Pages), MOND provides better explanations in some areas and LCDM better explanations in other areas; it is unfortunate that there is little overlap. To me the way forward is to find areas where both MOND and LCDM have serious problems (there are none in your table), and then to pursue these.
    Separately, I am not convinced that the missing matter problem is a simple binary choice between some new form of matter (e.g. LCDM) and some new form of gravity (e.g. MOND). I’m pretty sure there must be other sensible options out there waiting to be put forward by sensible & capable scientists. So I’m not despondent; I’m just desperate for something new.

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  11. I am not an expert on the history of science, but it is one of my favorite reading topics.

    That said, I am of the opinion that the longer an explanation for a mysterious phenomena is unable to be proven, and especially if the explanation itself is such that it cannot be falsified, the more likely it is that a major paradigm change is needed. The longer it takes, the more significant (and subtle) the paradigm change will likely be.

    The fact that LCDM and MOND are incompatible, and both seem to be incomplete in different ways, but both are needed to explain all observables, screams (to me) of a need for a new paradigm.

    Since almost 50 years have already passed, I think we can expect some major new paradigm. Looking at the history books, 50 years is maybe not that long a time for a change of the scope that seems to be needed.

    What I am saying is: Do not despair, whatever it is will come, in its own time.

    Liked by 1 person

  12. It definitely feels as if physics has gotten stuck. In some ways it reminds me of the slow, steady drip of observations that increased in tempo through the 19th century and led to quantum theory in the 20th. One big difference is that the general 19th century attitude was I-dunno, but the modern attitude is we-do-know-even-if-it-is-wrong. Despite that, it was over 20 years between Boltzmann suggesting quantization and Planck’s hypothesis, and Planck’s work was just a start. I’m sure a lot of people felt despondent back then despite the prevailing optimism in the field.

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  13. Dear Stacy,
    It is always a pleasure to run into your posts every now and again. I fully understand your despondency, but I do not share it, perhaps I am an optimist. In my opinion, we loose in terms of scientific debate when we frame the question as DM vs MOND. I would argue that a more productive question to ask is ” Is Newtonian/GR gravity the final answer at all scales or not ? ” Notice that the failure of the above proposition does not in any way imply the correctness of MOND as such. In my opinion, we have found sufficient and sufficiently tight scalings around gravitational annomalies to justify ditching standard gravity as an absolute answer at all scales (how on earth is it that this is considered subersive or quakery, which other physics of even more boradly, scientific theory that we know is presented as a universal absolute answer ?!) This does not imply DM does not exist in absolute terms, only that it is not the driving causal entity behind the many gravitational annomalies we are dealing with. It does however, land us in the need for a modified gravity theory, whatever that ends up meaning.

    In this sense, if wide binaries dissprove MOND as such, that in no way becomes a validation of the DM hypothesis. It is remarkable that MOND as such has succeeded in making so many a priori successfull predictions, but we still lack a definitive covariant version of it, notice for example that most attempts in that sense focus on the “deep MOND” regime, and introduce the transition between GR and modified GR, entirely by hand. But yet, even if wide binaries do not prove MOND right, they might well dissprove standard gravity.

    At present there is no way of excluding an option where in a succesfull modified gravity theory the EFE becomes position/density/whatever dependent. Clinging to standard gravity is going to become very difficult if wide binaries dissprove keplerian expectations, we must keep an open mind and not try to force all new data into the MOND framework, GAIA will soon enough yield very interesting answers.

    I am hopefull we will all live to see the end of the dark ages.

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    1. “Is Newtonian/GR gravity the final answer at all scales or not ?”

      The only reasonable answer to this question is “no”. The Newtonian/GR formalisms were constructed in the context of the solar system and that is the only scale where they have worked well. From the galaxy scale on up, they only work with the ad hoc additions of DM & DE.

      That requires us to believe that 95% of the matter-energy content of the LCDM model “universe” consists of some undetectable stuff, the only salient purpose of which is to make the underlying “expanding universe” model fit observations. Given that the “expanding universe” is an assumption of the standard model, and this assumption was made at the dawn of modern observational-cosmology era, the inability of the theoretical community to give any thought to reconsidering that assumption is a scientific scandal.

      The “expanding universe” model has effectively been axiomized – it is held true by definition. Axioms are perfectly acceptable in deriving abstract mathematical formalisms. But nothing can be held true by definition in science.

      It hardly needs mentioning that not even a well established researcher like Dr McGaugh could get funding to investigate the viability of non-expanding cosmological models. Not only would he not get funding, he would likely find his career jeopardized. Halton Arp’s fate as a working astronomer was a cautionary tale for anyone considering a challenge to the Big Bang orthodoxy.

      Like you, I would hope to soon see an end to this new Dark Age, but the guild-like system that pervades and scientifically compromises the theoretical physics community, presents a serious impediment to any such hope.

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        1. Lol.
          Philip,
          I have an analogy for the difference between faith and probabilities you can harrumph at.
          If you are an antelope, running with the herd, you have to be one with the hive mind. It’s not like you can just stop and scratch your ear, or grab a bite of grass.
          Now if you are some little squirrel running through the underbrush, you have to listen for every rustle of the leaves, or consider every flash in the peripheral vision.
          The fact is that at some quantity of effort, science does become a herd and herds are sociological. Occasionally they will run off a cliff.
          Cosmology has gone post-empirical and all future generations of theorists will not spend their careers chasing untestable theories. Multiverses come to mind. At which point, the reaction sets in and everything goes back to being on the table.

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          1. Oh brodix, don’t waste your keystrokes on Phillip. When I was in the corporate world we had engineers who we said were in charge of sales prevention, throwing flak into the air about why things wouldn’t work rather than figuring out how to make them work. You might have noticed that my idea has two particle types and two parameters. That’s it. And I even picked up the idea from the physics discard pile and repaired it. Yet Phillip never engages on the idea. He only defends the failed present conditions of particle and astro physics. I have been astonished that scientists aren’t willing to consider new ideas that change the paradigm. My idea has zero woo, where the state of the art physics is chock full of woo. Even when I offer that I am only ideating in the scales and territories between GR and QM it doesn’t stop the vitriol from the likes of Phillip. I’ve even gone back and identified the specific decisions where the wrong narrative interpretation was chosen like a physics historian would do, and still no engagement. I have pretty much given up hope that physicists will ever engage. They are in an enormous crisis, yet like a caged animal, just roar and bite at the zoo tourists that fund them and want to help. It is all so tragic.

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            1. I don’t want start a discussion so this would be my only response to you here.
              If you brought up the corporate world, note that in the same corporate environment, team members that repeatedly ignore directives and bring repercussions over the entire team, are usually marginalized by the rest of the team.
              And repeated offenders are usually let go from the company.

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              2. That is simply wrong. They will be published if good. Just because they are rejected doesn’t mean that it is because they were from an outsider, but probably because they were not good.

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            3. Mark,
              I grew up in the world of horse racing, so I have a fairly good sense of the social dynamics. It’s always going to cycle between expansion and consolidation. What the specialists can’t see are the underlaying cultural influences on which they build their castles.
              Ask yourself, is time the point of the present, moving past to future, codified as measures of duration, that we experience as mobile organisms navigating our environment, or is it change, turning future to past?
              As in tomorrow becomes yesterday, because the earth turns. In which case, there is no physical dimension of time, because the past is consumed by the present, to inform and drive it. Applied physics refers to this as causality and conservation of energy. Cause becomes effect.
              Consequently time is an effect, like temperature, pressure, color, sound. Time is frequency, events are amplitude.
              It’s a fairly common occurrence that tools become gods over time. Money being a prime example. The medium becomes the message. With theoretical physics, math has gone from being the tool, emergent with the processes and patterns it models, to being the god, platonic forms, above and beyond all.
              So it’s not like that is going to change, but the larger society, from which academia is not actually separate, is going through some fairly significant cataclysms and the resulting reality check will likely reduce funding for some of the more off the wall ideas.

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            4. Hi J Mark,

              I don’t know you, and from all I know you may be a very nice person who is a lot of fun to talk with. I don’t presume to judge you, nor do I have that right. But I can still observe behavior and draw conclusions from that.

              To make my point more clear I’ll present a “theory” and make up a story around it — all purely tongue-in-cheek, not at all serious — which I’ll call the Axle Grease Theory. I “claim” to have come up with this theory while musing long hours about tooth decay, how people keep getting cavities in spite of all the advances in dental care and health science. I had the “epiphany” — accompanied by the euphoria and rush of blood to the head that told me I must be on the right track — that dental science has been missing something very basic. Dental science has failed to see the obvious, i.e., that people need a more robust protection for their teeth to guard against teeth-destroying bacteria. Axle grease!! If only everyone would coat their teeth regularly with it, the axle grease would keep all those buggers away from the teeth or choke them out if they managed to get through it. I’ll call this my Axle Grease Theory, or AGT (because giving it an acronym makes it sound more impressive). And because I want people to know I was the one who came up with the idea I’ll call it Marty’s Axle Grease Theory (MAGT).

              Now I just need to convince the medical science practitioners about the obvious thing they’ve been missing all these years, and how I have solved the problem. But they resist! What??! Clearly the Dental Association has a vested interest in protecting their steady income from evaporating if my theory were to gain traction, so they fight it every step of the way. And the medical journals? They’re run by hide-bound scientists who wouldn’t recognize a brilliant, paradigm-changing idea if it hit them in the face. I haven’t made much headway talking to scientists and dentists in their offices either. They all demand Proof that my idea is medically sound, and they point to “little problems” like toxicity of axle grease (which is a detail that I have no doubt will be solved in the final MAGT, or FMAGT), but I’m pretty sure that’s all a smokescreen to hide their closed-mindedness and their need to preserve the current paradigm and funding stream. I’ve tried talking about my idea on a number of medical blogs too, but they’re just as closed minded and accuse me of “inappropriate comments” or scold me for spamming their blog with my “pet theory.” My experience with all this just proves that medical science is a closed club that is bound to the past, and for an outsider to break through that barrier is hopeless, even if they have a revolutionary, game-changing idea.

              End of fictitious story, and back to the matter at hand…

              I expect the above “story” is ridiculous enough that some key points are obvious. First is the total lack of concern for the bigger picture. There are obvious problems (obvious to anyone who knows anything about toxicity, and anyone who knows human nature enough to know people aren’t going to regularly use something foul tasting and “yucky” like axle grease), but the “theory” ignores them. There is no connection at all to data — the idea is “pulled out of a hat,” and all discussion of it is based on intuitive arguments rather than showing any quantitative connection to reality. The “theory” goes against a huge amount of accumulated research and experience by competent people. Why should anyone take it seriously? The fictitious “me” certainly didn’t meet the burden of proof required of someone who seeks meaningful change.

              Maybe (hopefully) you can see some of your own behavior in this illustration. I’m not saying that your idea is automatically wrong, nor that it’s ridiculous like my MAGT. But I think you are going about it the wrong way. You are taking what I’ll call a lazy approach: you aren’t doing the hard work of developing your idea into a quantitative theory that is concrete enough to be tested rigorously against observations, and then showing it is demonstrably better (using data!) at predicting those observations than the theories that already have empirical support. It’s important to not just focus narrowly on data that agree with your idea, but to look for, and take into account, what it doesn’t explain or gets wrong. Otherwise it’s just cherry-picking, and few people you want to reach will take it (or you) seriously.

              It’s also important to genuinely have respect (not just for show!) for all the knowledge that has accrued in physics/astronomy/cosmology over time, and why people have arrived at the current theoretical framework rather than something else like your own ideas. Part of that is doing a lot of learning (ideally with a PhD or similar course of intensive study); that alone will get you more respect because it demonstrates seriousness. It also means understanding the standards that most scientists expect of each other, such as a certain level of rigor, communicating in peer-reviewed journals, and so on. Those standards evolved for good reasons, and if you don’t know why then you should find out.

              Finally, do you see a contrast between Stacy’s blog posts and your own comments that mention your ideas and/or diatribes? Stacy is very specific in his claims, and backs up his statements with observational data, strong reasoning and personal experience. From my perspective at least, much of your commentary hints at arrogance — i.e., like you’ve got some things All Figured Out and physics/astronomy/cosmology practitioners are unwilling/unable to See what you See. If only you knew how many other people (and there are a lot!) also think they’ve got things All Figured Out, but what they’ve “figured out” doesn’t agree with what you’ve figured out. Why should anyone in science take your (or their) ideas seriously if you haven’t shown enough respect toward scientists and science to follow some basic rules?

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              1. Hi Marty, My number one principle is to reciprocally honor the dignity of each individual. The issue here is the word reciprocally. For a number of reasons many physicists have developed antagonistic behaviour towards any outsider bearing ideas and even to insiders with out of the mainstream ideas. This is a huge problem for many reasons, but the biggest is that if it is true that major interpretive errors have caused the current crisis In particle and astro physics, then how will physicists get back on track. I hope you have noticed that I focus on the interpretive errors. Observations are what they are (though even faulty priors could lead to confusion) and I have explained carefully where the math is suspect due to confusion around ranges of applicability, continuous vs quantum, and so forth. These are highly technical observations about the foundational assumptions of the physics math. I’ve also given a physical implementation which physics sorely lacks and shown that implementation to be parsimonious and a simple repair to a prior physics theory. It seems to me that there is a tremendous amount of intellectual dishonesty if physicists won’t engage on this set of ideas, particularly because these are many of the same issues brought up by physics luminaries and authors. Anyway, I’m continuing to make strong progress and maybe someday I’ll encounter a physicist who is truly interested on collaborating on ideas that have zero woo instead of banging their noggin on the same issues for decades with little progress. At some point I would think they must come to realize they made some major errors in the prior interpretations. That would be what I would do if I were despondent.

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        2. Philip,
          I haven’t studied Mark’s idea, but my prediction is that the background radiation will eventually resolve to be the light of ever further sources, shifted off the visible spectrum, as I see redshift as an optical effect.

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          1. In re: brodix’s prediction “that the background radiation will eventually resolve to be the light of ever further sources, shifted off the visible spectrum”

            This is why the JWST is incredibly exciting to me. As I understand it, the JWST will be capable of observing farther away in time and distance than previous instruments. If it sees what I predict it will see, that will be the end of LCDM in its current form. As before, I think a lot of LCDM will be recoverable, but simply turned inside out and transformed to a hypothesis of galaxy local inflationary mini-bangs (GLIM?) in an ~steady-state cosmology.

            Nobel winner Brian Schmidt mentioned in a 2012 lecture that the Hubble deep field images each cover about one 32 millionth of the sky and that each image shows around 5000 galaxies.

            That is about 160 billion galaxies near the surface of the observable sphere at a range of ~10B years ago. What is the proportion of galaxies that have jetting SMBH or AGN at any one time? What fraction of the galaxies mini-banging in the even more distant Planck CMB observations would be required to account for the Planck photon observations? And in particular the power spectrum — keeping in mind it is basically the banging process but distributed in locality and time (intermittenet).

            Could a professional astrophysicist please explain whether CMB observations are merely consistent with a Big Bang or actual evidence of a Big Bang? Could the CMB observations also be consistent with galaxy local inflationary mini-bangs?

            Thanks and I tried to be extra respectful and I really do simply want to help get the fields beyond their current major issues.

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            1. Mark,
              I have to agree that your style does stir up the hornets nest.
              Personally my interest in cosmology is only of the most basic curiosity, yet it is from that very plain jane approach that I keep stumbling across various conceptual issues that resist resolution.
              My doubt first arose in reading A Brief History of Time, back in 89, where Hawking made what is apparently a well established point, that universal expansion is in inverse proportion to gravity, resulting in what is referred to as “flat space.” Omega =1, as he put it. Which struck my own feeble thought processes as logically invalidating the overall expansion. If what is expanding between galaxies, is equal to what is collapsing into them, the effect would seem to be more of some sort of cosmic convection cycle.
              In the mid 90’s, on the old NYTimes Mysteries of the Universe forum, I happened to raise this issue, in terms of some spatial effect, aka, spacetime. To which another respondent, who said he’d studied Cosmology at U of Chicago, said it was much simpler to explain it in terms of the relationship of light to mass. That he’d set out to do a thesis paper on it and his adviser commented that if he wanted to pursue it, he might better consider another field. Which he did.
              In the course of this running through my head, it also occurred to me that the notion of time as moving past to future overlooks its basic relativism, in that it is also the events going future to past, if we use the present as the reference, not the events. Since there only seems to be this present state, it seemed worth consideration. Given that energy is conserved, it would seem to mean it only exists as the present, manifesting it, since lost energy would be left in the past, as an increase of energy would arrive with the future, so it would seem energy creates time, as well as temperature, pressure, color and sound. Time is frequency, events are amplitude.
              Now consider this in terms of a basic wave; The energy drives it, as it passes through the medium, while the resulting fluctuations rise and fall. So while the energy goes to the future, any form it expresses goes to the past. Now consider that pretty much all of physics is premised on information as foundational. In classical physics, water drops form from feedback of wave action. Doe this apply to the quantum level?
              We in the West have this atomistic view of physics, that there is some elemental level of objects, atoms, then quanta, now strings, of which everything else is emergent. Along with faith in math as platonically real, as opposed to emergent with he patterns it models.
              So lets just say that energy and the forms expressed go opposite directions of time. Much as consciousness goes to the future, while thoughts go to the past.
              Which leads to my above point, that quantization and gravity are just opposite ends of the spectrum, of this process of “inward curvature.” A feedback loop of ever increasing consolidation of energy. Then the excess gravity would be due to the curvature further up the spectrum. Until it reaches the eye of the storm, that are black holes and all energy goes out.
              I have to say that I’m just putting this idea out there, whether its ignored or considered is beyond my control and so beyond my worry. I am not in the business of jumping through the necessary hoops, nor do I readily butt my head against walls. At this point in life, it’s like talking sports.

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            2. > “Could the CMB observations also be consistent with galaxy local inflationary mini-bangs?”

              If you mean, “Does red-shifted starlight average out to look like the CMB?” Then the answer is no. See here for an old (1997) understandable explanation:

              http://www.astro.ucla.edu/~wright/stars_vs_cmb.html

              If you mean, “Do active galactic nuclei spectra look like the CMB?” Then the answer is no, there are broad categories of AGN but generally their spectra all look different and nothing like a black-body. See here for a few old examples:

              https://astronomy.swin.edu.au/cosmos/a/Active+Galactic+Nuclei
              https://pages.astronomy.ua.edu/keel/agn/spectra.html

              Note that adding millions of different random spectra together won’t average to give a perfect black-body. Also adding multiple different perfect black-body spectra together doesn’t give you a perfect black-body spectrum in total, it just gives you a smeared out curve. The CMB has been measured to be such a perfect fit to a black-body curve that it is a stringent test of predictions from cosmological models.

              Liked by 1 person

  14. I haven’t read Peebles’ review paper yet, but I am nearly half-way through his “Cosmology’s Century”, published last year. Jumping ahead to Chapter 6, which deals with subluminal mass, he does spend two pages discussing Milgrom’s MOND and does reference Lelli, McGaugh and Schombert (2017). Near the bottom of page 264 he says “But community opinion is that the wonderfully simple flat rotation curves of many spiral galaxies have to be transient accidents of the way matter of the various kinds was spun up as it settled into the inner parts of galaxies. I accept this as a useful working hypothesis, with reservations mostly kept to myself.” [I would have to type out about half a page of text properly to put these statements in context.]

    Although I’ve only just reached Chapter 5 of the book, I have found it very useful in understanding how we got to where we are in cosmology. In particular Peebles doesn’t hide all the false starts and dead ends, so one gets a much better feeling for how community opinion developed over time (even if it happens to be wrong in some respects).

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      1. Thanks, I thought that both your and Virginia Trimble’s reviews were very fair. If I am going to make any criticism of Peeble’s book (and it is only a minor criticism), it comes at the end. Although he completes chapter 9 with a section on the future of physical cosmology and mentions Kelvin’s ‘clouds’ in it; he doesn’t really look at any experimental data after 2003, except that which completes an earlier picture. So while we get Planck and BAO data on one side of the scales, we only have SN1a on the other. There is no mention of H0 from LIGO, or from gravitational lensing of quasars (H0LiCOW) for example. To include a short discussion of what measurements of these properties could give us in the future would put the ‘clouds’ comments into perspective.

        In chapter 10, among other points, he asks the counterfactual question: what happens if Einstein becomes a musician? Would we have still ended up with General Relativity (or something very much like it)? You can trace a direct line from Einstein through Friedmann (who, but for his untimely death, would have been Gamov’s dissertation supervisor) through Gamov to Alpher and the Big Bang and BBNS. Without this would Dicke been looking for the CMB and in a position to interpret Penzias & Wilson’s results so promptly? Even then, the original proposals for what later became COBE were losing applicants in the NASA competition for an Explorer-class mission that was won by IRAS. With far more good scientific satellite/probe projects than could be funded by NASA even then, COBE could very easily have been delayed by a decade or more than it was. Counterfactuals are very difficult to scope and I am not criticising Peebles’ assessment, just pointing out some additional factors.

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  15. I’ll be candid., and I honestly don’t mean to offend. But as an outsider, the MOND CDM battle appear to me like two medieval theologists debating whether it is 27 or 28 – angels on the head of a pin. How can anyone seriously claim to know from astronomical observations what had happened 14 billions years ago?! One can certainly refute a given model with such observations, but since the space of all possible models is infinitely large, this gets us not an inch closer to the answer.
    The only way to make real progress, and further justify the exponentially increasing spending of public money in this field, is to view astronomy as yet another `laboratory’ for testing terrestrial physics. And for this to be possible one has to constrain physics by the (natural) requirement of scale covariance. Without this requirement, Maxwell’s extrapolation of Faraday’s findings would have been groundless; without this extremely restrictive requirement, infinitely many modes of interaction between ordinary matter could potentially dominate on astronomical scales, and infinitely many small scale extensions of SM could be contemplated, giving rise to DM with virtually any required properties. This is in line with Einstein’s view: constrain you theory sufficiently and naturally until a unique one emerges (for a beautiful demonstration of this procedure see https://www.physics.utah.edu/~lebohec/P5110/Material/levy-leblond_ajp_44_271_76.pdf )

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  16. This is a great post in the sense that it may reinvigorate professionals and amateurs alike to think outside the ‘boxes’ they may be trapped in. That is the effect it had on me. I’m particularly wanting to fully read the papers authored, or co-authored by Stacy under the links: “succeed”, “so many predictions”, “diversity and precision”, before continuing work on a rather amateur concept titled: “Speculations Regarding Matter Waves and MONDian Astrophysics”. The paper co-written by Benoit Famaey and Stacy McGaugh titled: “Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions” is 164 pages long, so will take some time to digest and hopefully understand. For sure, anyone (particularly amateurs) trying to contribute to a resolution of the current impasse in cosmology need to have their feet firmly on the ground with respect to current empirical data in observational astronomy and constraints imposed by established physics.

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  17. When I turned off comments, it also turned off notifications. The latter seems to have remained off, so I have to explicitly come check what people have had to say. I may try to answer some questions, but there are a lot, and I plan to vacation next week (formally starting yesterday).

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  18. Stacy

    can you comment

    Christopher Conselice
    @conselice
    Merging galaxies in the early universe are a problem for non-dark matter theories

    Merging galaxies throw shade on alternative dark matter theory

    Galaxies in the early universe were merging up to 10 times more than is predicted by theories of “modified Newtonian dynamics”, known as MOND. This rate of mergers is in line with theories that take into account dark matter, the invisible and as yet undetected stuff thought to make up about 85 per cent of all matter.

    https://www.newscientist.com/article/2280746-merging-galaxies-throw-shade-on-alternative-dark-matter-theory/

    Christopher Conselice at the University of Manchester in the UK, and his colleagues analysed observations of half a million galaxies from the local …

    Christopher Conselice –
    Christopher J. Conselice (born 1974/5) is an American astrophysicist who is currently a Professor of Astrophysics at the University of Manchester.

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  19. I thank you for banning personal non-peer-reviewed pet theories, although it doesn’t seem to have actually totally worked.
    Please don’t despair. Eventually, likely someone will come up with a theory that resolves the issues that MOND-like theories and DM (or mixtures of the two) face and, with luck, give some novel predictions as well, and this resolution will cause many to switch camps to whatever side it may be; unpopular ideas that make lots of successful predictions and have no obvious failures become more popular ones. If the idea is deep enough, it may even have the mathematical beauty to be conceptually appealing and popular right away. Although it is perhaps a terrible reason to ignore it, there are those who surely find MOND ‘ugly’ for its lack of deeper explanation, just as simply positing some vague form of DM by itself is unappealing. A deeper idea could go a long way.
    When we consider the time between Newton and Einstein, a long wait between revolutions doesn’t seem that unreasonable. If few people working in the right direction seems terrifying, it’s helpful to think about the fact that there used to be a lot less physicists (and humans) in general and yet we still got by. Although it is true that the mathematics has gotten much steeper, it continually developing gives physics more tools to work with. I personally think (and believe this is generic and common enough to not count as a pet theory, but I apologize if I am wrong) that more mathematics is needed to tackle the deep questions and that this needs to be tackled before we can really make progress; the difficulty in making QFT mathematically vigorous points to this. Current physics (and tweaks on old math) is simply not ambitious enough. In that light, yes, I suppose we are in a rut. But there is no reason to think it will stay that way as long as there are at least some people interested in such things!

    In the meantime, I would enjoy it if you continued to tackle the articles that pop up from time to time claiming to ‘kill’ or throw doubt on MOND, such as the one linked by Daniel Hwang.

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    1. Kirk,
      Consider this a question, more so than a theory, but doesn’t math itself pose the same issue you raise of MOND, that there is no deeper explanation, then this is pattern matching that works?
      Wouldn’t it be interesting to have a broad debate as to whether math is emergent with the processes and patterns it models, or is it somehow Platonic? Is there math in the void, or does it also emerge with the primal fluctuations?
      My own sense is that math is reductionism. That patterns are distilled down to their most stable relations, configurations, tautologies, etc. Yet the result is descriptive, not explanatory. Epicycles worked because they described the view of the cosmos from earth, but they failed because they didn’t go deep enough into causes. Which is what you are saying about MOND. That it effectively models what is seen, without giving any deeper explanation.

      Liked by 1 person

      1. So, it is quite easy to point at things like epicycles. But if you look at the history of physics, it has always been new math that has lead to the biggest shifts in our understanding of gravity: Newton came up with calculus, and Riemann and Gauss made Einstein’s work possible. Without this new mathematics, their work would not have, well, worked. And I don’t think most people would deny that Newton and Einstein’s works are far more explanatory than epicycles.
        Certainly, mathematics can be used to reduce things to simpler forms (although it does not have to, which I believe is part of where your confusion lies). But it can also highlight entirely new ways of seeing the world, or point out areas that were previously incoherent and vague. To me, math is just the art of being non-vague and non-contradictory. If you could state what a void is in highly technical enough language, then you could also say why exactly a void must necessarily have quantum phenomena or change in entropy – why these things are actually one in the same, and thus, why the universe must come to exist. Or alternatively, you could prove that ‘voids’ as we popularly think of them could never exist, and that the most basal, zerolike state isn’t voidlike and has certain dynamics, depending on your definition again of ‘void’. Whatever the language of the ultimate theory, it will have to be in math. That one can also try to model things with epicycles and this also happens to have math in it is irrelevant: epicycles were not new math, they were old math at the time. What I am saying is that we need new mathematics that lights up our understanding the same way calculus or Riemannian geometry let us understand and see a whole new world of possibilities. Without math/geometry, there is really no way of properly conveying what a ‘intrinsically curved space’ is or why this should have anything to do with gravity.
        What I am trying to say about MOND and DM is that the math is simply not ambitious enough. Whether this math is ‘Platonic’ and somehow exists outside the universe does not make sense to me as a question, as I don’t believe in an ‘outside’ of the Universe, and I don’t really think it’s actually relevant to the question of whether we can get deeper more explanatory math that clarifies, say, ‘what a void geometry is and must necessarily do’, since that is clearly talking about a physical system, and we can always slap a label on a physical system and make statements about how it is not another physical system. So to answer your question, yes, there is math in the void, in a trivial sense, provided a void is not inherently contradictory.

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        1. Kirk,
          Thanks for the reply.
          I would assume a void to be a state of absolute zero, or an equilibrium, where all the positives and negative cancel out. It would seem implicit in Special Relativity, as the frame with the fastest clock and longest ruler would be closest to the equilibrium of the vacuum. As opposed to a frame moving at the speed of light, presumably in relation to this void, where the clock and ruler shrink to zero.
          The main problem I have with the concept of spacetime, as anything more than a mapping device, is with time being treated as a singular dimension, codified as measures of duration.
          Yes, we are mobile organisms, so our experience is as a sequence of perceptions, logically based on the need to navigate, thus the sense of time as the point of the present, moving past to future, but the reality is that change turns future to past. Tomorrow becomes yesterday, because the earth turns. Duration is the present, as the events come and go.
          So there is no literal dimension of time, because the past is consumed by the present, to inform and drive it. Aka, causality and conservation of energy, in applied physics. Cause becomes effect.
          Different clocks can run at different rates simply because they are separate actions. Think metabolism.
          Time is asymmetric because it is a measure of action and action is inertial. The earth only turns one direction.
          Energy is conserved, because it creates time, as well as temperature, pressure, color and sound. Time is frequency, events are amplitude.
          So energy, as process and present, goes past to future, while the patterns it generates go future to past. In terms of a wave, the energy drives it, while the fluctuations rise and fall. So energy and any information derived from it go opposite directions of time. Like consciousness goes past to future, while thoughts go future to past.
          Which gets back to the void as equilibrium. If we delete all activity and information from space, the two qualities remaining would be equilibrium and infinity. While energy radiates out, toward infinity, information coalesces in, toward equilibrium. The effect of the feedback being these cosmic convection cycles called galaxies.
          So yes, math is a very useful tool, but it’s not a magic wand. We are never going to be time traveling through wormholes in the fabric of spacetime, if we just conjure up enough mathematical faerie dust.
          The field where math is most common and basic is accounting and in accounting, they understand the complexities can obscure as easily as they can enlighten, so simply writing in a figure and calling it dark money, rather than going back and tearing apart all the previous figures, is frowned on.

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        2. Kirk: But if you look at the history of physics, it has always been new math that has lead to the biggest shifts in our understanding of gravity: Newton came up with calculus, and Riemann and Gauss made Einstein’s work possible.

          Well no actually, that completely misrepresents the historic development of our cosmological understanding. Until Ptolemy’s geocentrism was jettisoned in favor of Copernicus’ solar-centric model, no progress in understanding the nature of the Cosmos was possible. Without Copernicus, Kepler, Newton, and Einstein would not have been able to make their contributions.

          The problem wasn’t with Ptolemy’s math; it was his misunderstanding of the physical system he was attempting to model, that lead him, out of necessity, to epicycles. Ptolemy had a bad qualitative model to work with. Nonetheless, he successfully mathematicised that completely erroneous physical model into a useful calculational device. There could not be a more clear cautionary tale against the primacy of math in physics. It doesn’t matter if your calculations work; if the underlying model misrepresents the nature of physical reality, it is scientifically speaking, wrong.

          The analogy to modern cosmology is also quite clear. Where Ptolemy had geocentrism and perfect circles constraining his model, we now have the “expanding universe” constraint. That “expanding universe” constraint rests on the two foundational assumptions of all modern cosmological models:

          1) The Cosmos is a unified, coherent, simultaneous entity – a “universe”.
          2) The cause of the observed cosmological redshift is some form of recessional velocity.

          Neither of those assumptions has any direct empirical evidence to support it, far less evidence, in fact, than Ptolemy had for geocentrism. Can a math model derived on the basis of those assumptions, be massaged to agree with actual observations? Sure. Again this is exactly analogous to the Ptolemaic model.

          What you are espousing is mathematicism, the scientifically unjustified belief that math models somehow underlie and determine the nature of physical reality. They do not. And while many, though certainly not all members of the scientific academy, would explicitly deny that they hold that view, it is, functionally, the default paradigm of the modern scientific academy.

          It is because of the mathematicist error that we continue the Snipe Hunt for dark matter. The results of a 40 year search are clear – there is no direct empirical evidence for the existence of dark matter. The search must be continued, however, because the gravitational models derived in the context of the solar system must scale to galaxies and beyond or, they will have failed. But they can’t fail because they are Universal Laws – it says so in all the textbooks!

          We don’t, at this time, need new math. We need a new qualitative model of the Cosmos to replace the naive, century-old “expanding universe” version we are currently stuck with. You can’t fix the problem by tinkering with the existing math, you need to discard the erroneous assumptions. Until then, it’s dark (undetectable) stuff all the way down.

          Liked by 1 person

          1. Kirk’s point was that in order to get that qualitative new model, you may very well need new math.
            Of course, it is not a necessary precondition, but the point was that the history of physics indicates this is usually the case.

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            1. And my point was that Kirk’s pseudo-historical claim “…it has always been new math that has lead to the biggest shifts in our understanding of gravity… “ ignored the actual fact that the “new math” he cited needed the fertile solar-centric model for development, and that necessary paradigm shift to solar-centrism did not arise as a consequence of “new math”, the math that made the model work had to be subsequently developed over time.

              You claim that “…to get that qualitative new model, you may very well need new math… the point was that the history of physics indicates this is usually the case.” So, you changed the argument from “always” to “usually the case” and offered only a vague handwaving assertion that such was historically true.

              I gave a specific example of a monumental paradigm shift, one that directly contradicted Kirk’s ahistorical account, where Newton and Einstein’s math evolved in a qualitative vacuum, rather than being consequent on a specific qualitative shift. Got any specific counter-examples, of similar significance, you’d like to offer in support of your “usually the case” argument, particularly with regard to cosmology?

              Ultimately, my point here is that modern cosmology is at exactly the type of dead-end that geocentrism represented – a scientifically inert, zombie model is kept lumbering along with clever math. But math is not physics, and confusing the two (as mathematicism is wont to do) leads to infelicitous scientific results – the physically absurd LCDM model being a case in point.

              Liked by 1 person

              1. It is interesting that so many people can’t process that the insight has to occur, before it can be formalized and clarified. I suppose the more people involved, the more it becomes about the system, than any real sense of how it came to be.
                We easily come to see stability as the norm and change as incremental, as the earthquakes recede into myth.

                Liked by 1 person

              2. I’ll have to say that Kirk’s words were carefully chosen and he is basically correct in what he says here and I misread them. You even quoted him exactly but you also misread him.
                He did not say that you need new math to get a new model. The key point for new math is a deeper understanding of the model / theory. Yes, you had Copernicus or Kepler before Newton (and also Galilei and Tycho Brahe, both equally important to the development of solarcentric models), but that wasn’t his point. The point was that only after we got calculus, we got a deeper understanding of why the things are like they are in the solar system (i.e. why the Kepler’s laws are like that).

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            2. Math is a tool, like a computer. When the results seem to be going off into the wild blue yonder, it can be the wise thing to consider if the premises might be flawed. Garbage in, garbage out.

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  20. As regards the latest challenge to MOND – galaxies merging 10 times more than MOND can account for in the early universe – it’s hard to find more info on it. I couldn’t read beyond the beginning of the 2nd paragraph in the New Scientist article, as it was behind a paywall. Searching the net also came up empty on this presumably new information. I did find a paper from Caltech, where it is pointed out that galactic mergers take several times longer in MOND than in the Standard cosmological model. I’ll have to keep searching the net to find the actual paper on this.

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  21. I become despondent as well when I see things like this repeated: (Standard Model):

    “It can explain at a fundamental level literally every single experiment that we’ve ever done,” said David Tong, a physicist at the University of Cambridge.

    https://www.quantamagazine.org/the-mystery-at-the-heart-of-physics-that-only-math-can-solve-20210610/

    The SM explains ~5% of all the stuff we know about and its explanation has 40+ parameters and dippy renormalization.

    The problems in Physics are deep. I am hopeful that the non ‘me too’ hiring will result in some sort of breakthrough. We have had 50 years of professors promoting and hiring their clones. It has not worked out.

    Liked by 1 person

    2. About two-dozen parameters and it explains everything but gravitational phenomena (at the fundamental level). Renormalization has also been theoretically validated long after it was invented and used widely.

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  22. btw d

    “But what about the smallest scales? Together with my postdoc Mohammad Safarzadeh, I studied recently the latest data available from the Gaia survey of ultrafaint dwarf galaxies that are satellites of the Milky Way. We showed that their behavior deviates from MOND’s expectations. Just like clusters of galaxies, dwarf galaxies appear to argue against the universality of MOND on all scales.

    Does the success of MOND on Milky Way scales and its failures on both smaller and larger scales offer new insights about the nature of dark matter?”

    reference https://www.scientificamerican.com/article/maybe-dark-matter-is-more-than-one-thing/

    apparently Mond fails to get ultrafaint dwarf galaxies that are satellites of the Milky Way correct

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    1. I’d say I have two gripes with the paper:
      1) “However, these orbital motion estimates are based on cold dark matter potential for the MW and whether the same orbital dynamics would be inferred in MOND remains to be verified with detailed orbital motion simulation.”
      2) “We did not investigate correlations with other estimators such as ellipticity of the UFD as projected on the sky, or adiabaticity (which is a measure of the number of internal orbits of stars over the number of orbits of the satellite around its host). Ellipticity, adiabaticity, and other estimators have been used in McGaugh & Wolf (2010) and shown to be a proxy to tidal features and we do not investigate these in this work”
      If you want to investigate MoND effects in limit cases, you’d better be laying the problem correctly for those limit cases.
      On the other hand, I have to give them credit for not concluding that MoND fails but to more data is needed.
      But their title is indeed conducive to the apparent conclusion that MoND fails.
      I too am curious about dr. McGaugh opinion, especially since, as per the paper, he already provided comments to the authors.

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  23. I agree with David Carnochan, “the way forward is to find areas where both MOND and LCDM have serious problems […], and then to pursue these.”

    We’ve gone down so many blind alleys in the last 40 years, yet Zwicky’s dark matter problem is still not resolved. It’s the inconsistencies in decisions made way before the ’80s that are haunting us. Like a seventy-year mortgage, we are still stuck with the decisions we made in the ’50s!

    Nobody said a real paradigm shift was going to be easy, especially with “intellectual blinders that are more opaque than a brick wall.” But get your hopes up because some people are working hard to expose the problems in cosmology: Pavel Kroupa, Fulvio Melia, Martín López-Corredoira, Subir Sarkar, … Stacy McGaugh.

    Liked by 2 people

  24. Daniel, thanks for the reference to the Scientific American article by Avi Loeb. This one is fully accessible, though I’ve been meaning to re-subscribe to Scientific American magazine. Having just gotten home from a visit to a local casino, I’ll read it in the morning. I’ve got quite a bit of reading on my plate with the 3 papers authored, or co-authored, by Stacy that I’m currently reading, one of which I was reading on the way to the casino, while my brother was driving.

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  25. Just for the fun factor, sorry for being off-topic – I can’t help but laugh at the top image and the word count. For (80’s) computer geeks, to see “Stuck in the 80s” with 1024 words count… that really resonates.
    The 80s, i8080, Z80, ZX80…. just so many references in that words combination!

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  26. Stacy, after exploring the issue for many years, here is my opinion.

    I agree that there is no data in favor of dark matter.
    I agree that many repeat what others say.
    I agree that some other mechanism is at work in nature at large distances.

    But I do not know what the mechanism it is.
    Inventing a new law of physics without connection to the rest of physics is not a way out.
    This missing link is the issue.

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    1. Gina,
      Thoughts; What are the conceptually cultural issues, that might serve as bottlenecks in current physics?
      For example, is quantization fundamental, or is it measurement?If it’s a function of measurement, then there would be some sort of condensation, which would resemble a very faint, but very broad gravitational effect.

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  27. If DM is the correct paradigm, how is it that the halo, which is five times as massive as the host galaxy, isn’t disrupting its shape? The only environmental clue is flat rotation curves. Interacting galaxies disrupt one another and settle into a new stable configuration. But DM haloes only envelope their hosts. And if MoND theories are correct why are dwarf galaxies positioned in polar orbits. Clearly, the polar orbits of satellite galaxies hint at unexplained environmental pressures. An environment illuminated by the halo. It seems there must be another answer.

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  28. New study today “Dark matter is slowing the spin of the Milky Way’s galactic bar”. Regardless of the merit or otherwise of this new study, it is significant that they take the trouble to add that “”Our finding also poses a major problem for alternative gravity theories—as they lack dark matter in the halo, they predict no or significantly too little slowing of the bar.”
    My point is that this seems to indicate that MOND etc is not being ignored by mainstream science, but rather that they are attempting to engage with its arguments.

    Like

    1. I don’t know what to make out of that paper. In their conclusion section they state: “Adding to our previous arguments for a slowing Galactic bar purely based on kinematics, this work provides further evidence using photometry. Hence, our works support the existence of a standard dark-matter halo that has taken up angular momentum from the slowing bar. Alternative theories of gravity are disfavoured since they cannot explain the missing angular momentum (Ghafourianet al.2020)”, with a citation to another paper.
      That another paper is “Does Modified Gravity Predict Fast Stellar Bars in Spiral Galaxies?” and here it is what it says in the introduction: “Therefore we may conclude that simulations in the particle DM paradigm predict slow bars. On the other hand, it is well known in the literature that almost all of the observed pattern speeds are fast (Corsini2011;Garma-Oehmichen et al.2020). Furthermore, it seems that bars are formed fast and remain as fast rotators during the cosmological timescale (Pérez et al.2012). This fact is considered to be a challenge to the standard cosmological model”.
      Then, in their conclusion: “As the main result of this paper, we confirm that the modified gravity models predict fast bars in contrast to the DM models. Of course, this means that modified gravity is in better agreement with observation.”
      Now you tell me who should we believe in the end? On the one hand, we have a paper that claims that bars are slowing down in agreement with DM models, and, on the other hand, we have another paper that claims that observations show that the bars form fast and remain fast, in accordance to modified gravity models.

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    2. I got distracted and hit post too soon.
      To a certain degree, you are right that MoND-like theories are not being ignored (for, instance, the second paper that I quoted). On the other hand – I would not say they are attempting to engage with its arguments, at least not in this paper. The claim that modified gravity models are disfavored came only in the conclusions section and only as a citation to a paper authored by others.

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  29. Stacy says that the “best scientists are always in doubt” and despairs because, with regards to dark matter, he seems to fear that is no longer the case. I think he under estimates the beneficial effect that he and other proponents of MOND have had on mainstream science. Whatever the final verdict, LCDM or MOND or some other, keeping the current debate ongoing is the right thing to do.
    The UCL / Oxford study claims to be the first to measure the slowdown of the Milky Way’s galactic bar, so prima facie it is capable of deriving reliable conclusions, but it would be good to get independent confirmation.

    Liked by 1 person

    1. It does seem as if the ‘world’ is fixated on a dark matter particle. And to those proponents I would ask them to calculate the Lagrangian that must induce different shaped galaxies and different shapes within galaxies. And, then the polar orbits of dwarfs. On the other hand Mondian dynamics (potentially) resolves those issues (ignoring the dwarfs). But how? MoND seems more like a kind of galactic DNA. It builds a bulge here and a disc there, but sometimes neither. And here I’m only discussing galaxies. You encounter a whole new ballgame when you have to consider clusters and super clusters. There must be some natural process that hasn’t been discovered. Something that doesn’t require modified gravity or exotic particles.

      Liked by 1 person

  30. Dear Stacy and Crew:

    I’ve been really impressed with the level of creative thought here recently and the willingness of some to talk about the big issues facing astrophysics (and particle physics – they are more related than most realize). I made a new post with pictures to show my hypothesis. https://johnmarkmorris.com/2021/06/15/new-physics-in-pictures/

    The real key, whether you grok my illustrations or not, is : to realize that electric and magnetic fields have a maximum scalar value and this gives spherical volumetric immutability to the field generators (I call them point charges) that make the structures, that make all the ‘fields’ of particle physics (QED, QFT, QCD, inflaton, etc.).

    The really cool thing about this model is what it means to the mathematics, so I will list a few of those here along with their implications. This does require that I talk a bit about my ‘pet theory’ but since there is some new open-ness here, perhaps Stacy will allow it. Or not. Whatever.

    0) spherical volumetrically immutable field generators are incredibly symmetric mathematically. That is a good thing, because we need a lot of symmetry to understand why nature has been so hard to solve.

    1) volumetric immutability means there is no singularity, anywhere. Therefore, physicists should perform the due diligence of rethinking the theory of black holes, especially SMBH. This also means say goodbye to wormholes which is probably ok with most physicists. It also means that SMBH could possibly develop a core of these immutable objects. And it would keep growing. My instinct tells me that the interior particles of that core would not be detectable beyond a few layers deep from the surface of the core which would be packed FCC or HCP (math).

    2) volumetric immutability of the fundamental field generators also means that general relativity, as well as it works, is not correct in several respects. First, discard that portion of the integral that goes from the smallest field generator to zero. That causes a lot of problems, including the UV catastrophe. Next, realize that when you approach the scale at which these field generators exist, which is I think around the Planck length in radius, that there would be effects that are not accounted for in general relativity (which has no physical implementation.)

    3) Next, let’s imagine that those field generators in ‘Planck cores’ can somehow escape the SMBH. They would present as an inflationary mini-bang. The field generators would do basically what the big bang theory says, which is to form structures. Take a look at my pictures of the standard model particles. Although I haven’t yet drawn the charts for W, Z, gluon, or Higgs boson, I did depict the photon. Each of these structures has its own unique pattern of electromagnetic fields that physicists call by different names as our higher level structure ‘fields’. I hypothesize that those behaviours lead directly to the math of QFT, QED, QCD, etc.

    4) You can now determine what is continuous and what is quantized. Certainly the two fundamental electromagnetic field generators are quantized due to volumetric immutability. Oppositely charge field generators can form an orbiting circuit that can transact energy in h-bar units of angular momentum. This provides a physical implementation for so many of our formulas that talk about spin, frequency, and wavelength (except wavelength is not yet understood to be related to the velocity of the orbiting dipole). Background space is continuous. Field generators move continuously through space. Fundamental quantization is the two field generators. Higher order quantization is due to structure behaviour.

    5) Renormalization was a clue, not a thing to work around! Sigh. Enough said.

    Ok, I could go on and on and that would be too much. Also, it is a lot more fun, if you do the thinking yourself. Even if you want to call this a toy model, it is amazingly powerful. Explore it.

    Lastly, please watch at least the Particles section of this recent Frank Wilczek interview. https://youtu.be/LDTe8uFqbws starting at 1:21:56 through 1:55:58. If you watch the whole interview and pay very close attention I think you will realize that Frank, who is in my estimation the closest physicist to the solution of nature, is talking about things which map directly to the pictures which I have posted, or something very close. If you want to solve nature, examine my pictures, listen to Frank, repeat until you get it. Eventually it should click and then you can never go back to the confused state of physics today. Asymptotic freedom is essentially saying that there are limits to the fields. So as two attrracting opposite point charge generators approach, this limit is repelling them!

    Best to all of you and especially Stacy for stimulating the wonderful discussion.

    p.s. Sincere apologies to anyone who is offended by my confidence in this solution or my clap-back on disrespectful naysayers. I think once you jump this hurdle to the layer below the standard model, everything will make sense. Again I appeal to you to look at my pictures with an intellectually honest open mind and collaborate on linking this model into particle and astro physics, even if it means rearranging prior interpretations. Since many of you have highly honed mathematical skills, you could probably turn these ideas into something the journals would publish far faster than I can. Please do.

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    1. Honestly – I care more about comments not being closed here than your model.
      I think most of the commentators here care more about being able to discuss on the subject matter than to review pet theories.

      Liked by 1 person

      1. This puts me in an awkward position. Opening comments here was something of a test. Many of you passed, but a lot did not. I have no interest in weeding out troublesome individual comments (or difficult individuals), so I am inclined to close the comments entirely.

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        1. I can understand your position, but if there were no comments I would visit your blog only very rarely (perhaps a few times a year, because I would only need to catch up on the new posts) so I might have missed your Golden Webinar. The existence of comments means that I come here several times a week to check for new comments – I only need to look at the ‘recent comments’ in the top left corner.- and sometimes a posting, leads to a useful conversation, for example with Philip Helbig in this thread.

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  31. If I understand correctly, your main reason for despondency is your assessment that there is not enough doubt in the scientific community. I agree with this assessment, and I agree it is a reason for despondency. But doubt is like entropy – it increases. Or at least, I think it does, but now I’m not so sure.

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    1. If as I hypothesize, the fundamental charged field generators make structures that emit the higher level fields of the standard model particles AND those charged field generators have a limit to their packing density, THEN if nature generates such a clump of charged field generators it would have one microstate. S = k log (w). Therefore entropy would be zero, which would blow the minds of physicists today. Also the particles in the clump would have maximum possible energy yet zero kinetic energy relative to one another, or zero relative temperature. Does this ring any bells for anyone? It should. Explains major open problems parsimoniously. Love to all.

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      1. If the entropy is zero, I suppose the doubt must be zero as well. As observation seems to confirm. On the other hand, my doubt seems to have become infinite, so I suppose it needs to be re-normalized.

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  32. I had a sense of déjà vu from reading an April 2007 article in Sky and Telescope titled: “Battlefield Galactica: Dark Matter vs. MOND” authored by Govert Schilling. Towards the end of the article cosmologist Joel Primack expresses his confidence that WIMPs will show up at CERN “…within 10 years or so”. He then mentions another promising dark matter candidate, the axion, which “..should also show up within 10 to 15 years”. But he adds the cautionary concern that if no dark matter particle shows up in the laboratory within two decades it will be “one of my worst nightmares”. Just over 14 years have passed since that article was written and dark matter particles are as elusive as ever.

    One particular aspect of MOND that really clinched this phenomenological theory in my mind, with regard to pointing us in the right direction for solving the non-Newtonian behavior in galaxies, is its unerring ability to replicate the fine details in galactic rotation curves as enshrined in Renzo’s Rule. Because putative dark matter is spread out in a vast halo its gravitational effect in simulations is to wash out the finer details in the rotation curves of galactic discs. MOND’s success at duplicating Renzo’s Rule strikes me as an extremely important clue as to the physical mechanism that underlies MOND’s mathematical framework.

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    1. I’m not sure that MOND can be called a theory. It’s more like a law. It reminds me of the conflict between Wien’s Law and the Rayleigh/Jeans Law that was finally resolved with Planck’s Constant. IMO MOND is more an indication that something else needs to be recognized. Something that recognizes the validity of Newton/Einstein in all cases, while still explaining why MOND works here, but not there.

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      1. Using the geocentric versus heliocentric conflict as a template, it’s worth considering the geocentric perspective is far more evident and measurable, from our point of view.
        So rather than digging ever further into the details of the current paradigm, how might we step back and try to figure out what is the current mote, or beam, in our eye, this time around.
        I think the most evident one is the issue of time. As mobile organisms, our experience is as a sequence of perceptions, logically an evolutionary adaptation to navigation. Yet it means time is currently enshrined in physics as the point of the present, moving past to future, codified as measures of duration, when the evident reality is that change turns future to past. Potential, actual, residual.
        There are lots of interesting consequences of this, since it makes time an effect, similar to temperature, pressure, color and sound, rather than space. Time is frequency, events are amplitude.
        Though it’s just not how the centuries and millennia of educational evolution have come to see it, so there is just no breaking through the shell. Meanwhile some fantasy land of post empirical physics is considered necessary, as the institutional inertia is just too great.

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      2. I have some doubt as to whether it is reasonable to expect “the validity of Newton/Einstein in all cases”, since no-one has ever proposed a plausible physical mechanism for these laws of gravity either. But I agree the analogy with Planck’s constant is telling: we need to quantise gravity, and until that is done in a plausible *physical*, not mathematical, way, the required breakthrough will not come.

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        1. It can’t be the other way around, we can’t “curve” quantization?
          It seems, from a conceptual point of view, that the nodes are presumed to precede the network, that there has to be some baseline unit, rather than feedback between the processes and the units.
          I may be an amateur, but it seems quantization requires some inward contraction, some “collapse of the wave function.”

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          1. I have a feeling we may be saying the same thing in different words. But I don’t want to abuse the hospitality of this blog by discussing any of my pet theories, so I invite you to continue the discussion on my blog.

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        2. And I fear that a quantized gravity solution will only verify the current observational results that point to MOND here and Newton/Einstein there. Because, at heart it will be a Spacetime theory. And gravity is only a type of configuration of Spacetime. And, so far, gravitational results are all we’re focusing on regardless the model we use. Which won’t put an end to the Dark Matter paradigm. And won’t clarify the MOND results.

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          1. I’m not sure I agree. It depends on the type of quantum gravity that emerges. I don’t think we can predict that. Certainly your conclusions apply to the kind of mathematical theories of quantum gravity that people talk about. That is why I emphasise that we need a physical theory first. Forget the mathematics of quantum field theory and general relativity, and start again with a real physical insight. An insight, moreover, that does not obviously contradict a century or so of experiment and observation. But it is allowed to contradict a century of theory, provided it is consistent with that theory being a suitable approximation in suitable circumstances. Very tough, but very necessary.

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  33. I’ve been wondering if the higher than anticipated approach velocity (for LCDM) of the two galaxies in the Bullet Cluster is measured by the recessional velocity of the individual galaxies departing from the collision zone, or the joint approach speed of the gas clouds, or both. This info undoubtedly is somewhere on Tritonstation, so I will need to search for it. That MOND accommodates this high velocity is certainly another feather in that phenomenological theory’s cap.

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    1. Often we can only observe line of sight velocities via the Doppler shift. In the case of the two clusters that make up the bullet cluster system, the collision velocity is inferred from the hydrodynamics of the observed bow shock in the X-ray emitting gas. This seems to be almost entirely transverse motion in the plane of the sky.

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      1. Thank you, Stacy, for this information on the Bullet Cluster. I finally came across the paper “The collision velocity of the bullet cluster in conventional and modified dynamics”, which you co-authored with G. W. Angus. Between that paper and several others I should be able to find all the data on this iconic system needed to see if it’s compatible with a toy model I had that posits an underlying mechanism for MONDian behavior.

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  34. Interesting result in “A Tip of the Red Giant Branch Distance of 22.1 ± 1.2 Mpc to the Dark Matter Deficient Galaxy NGC 1052–DF2 from 40 Orbits of Hubble Space Telescope Imaging”
    I guess this is not exactly what the DM community hoped for.

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    1. Interesting that the reports I saw about the paper say nothing about MoND, while the paper mentions it in the abstract, and probably also in the body (it’s behind a paywall so I cannot access it)

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  35. I found a really nice, graphic of the Bullet Cluster at astro.ucla.edu called “Blinking the Bullet”. The components individually blink on sequentially with the last image being a composite of all the components of this system – the galaxies in the two clusters, lensing from the assumed Dark Matter, and hot X-ray emitting gas. I have a pile of papers to read on astrophysics, and bring them along every time I go someplace. Since the bullet cluster is of great interest to me I’ll be bringing papers on it from Stacy’s Tritonstation website, and other sources, in an upcoming trip. My twin and I will be staying several days at our older brother’s house in a rural area. Best of all he has a large roof deck with horizon to horizon views in most directions; ideal for observing the night sky.

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