75. No trace of dark matter in the dwarf galaxies of the Fornax Cluster

(by Pavel Kroupa and Elena Asencio) 

In disagreement with dark-matter-theory, dwarf galaxies in the Fornax Galaxy Cluster are void of dark matter. They behave exactly as expected from MOND. The inequality of gravitating mass and inertial mass of galaxies is indepedently confirmed using rotation curves of field disk galaxies.

Dwarf galaxies are supposed to be the most dark-matter dominated galaxies in the Universe. At least according to the standard Einsteinian/Newtonian-gravitation and dark-matter based LCDM model of galaxy formation (Battaglie & Nipoti 2022). In this LCDM model, the dark-matter-dominated dwarf galaxies must, if they are satellite galaxies,  be distributed spheroidally around their host galaxies.  But several studies focussed on the dwarf galaxies in the nearby Universe (the Local Group and its vicinity) have already shown that the LCDM model fails to explain many of their observed properties, in particular, that most of them are in disk-like configurations around their host galaxies (Pawlowski 2018; Pawlowski & Kroupa 2020; Pawlowski 2021; Pawlowski 2021).

Concentrating only on their dark matter content, such dwarf galaxies will be protected, though their large and massive dark matter halos that surround them, from tidal effects if they orbit through a cluster of galaxies. It is well known since at least 2004 that dwarf galaxies cannot be much affected by tides in LCDM theory. Citing from Kroupa et al. (2010, Sec. 2.8): “… the inner region of a satellite is only affected by tides after significant tidal destruction of its outer parts (Kazantzidis et al. 2004).” Therefore, for the visible part of the galaxy, which is the innermost part of any galaxy’s dark-matter halo in the LCDM model, to be affected/perturbed/distorted by tides, the galaxy must first be rid-of most of its dark matter halo. This takes many orbits such that only a very small fraction of observed dwarf galaxies can show tidal deformation if dark matter halos exist. The window of opportunity for catching a dwarf galaxy in this perturbed-by-tides state is brief: When most of the dark matter halo has been removed, it only takes about one more orbit for the dwarf galaxy to be completely destroyed.

By counting the number of observed dwarf galaxies that show signs of tidal deformation, we can thus test for the existence of dark matter: if too many dwarfs are distorted, then dark matter does not exist

In this recently published work (Elena Asencio, Indranil Banik et al. 2022, MNRAS, in press), we present a new line of evidence for the unsuitability of the standard dark-matter-based models to describe these objects. This study, lead by Elena Asencio, is a very extensive analysis of the statistics of the perturbations of dwarf galaxies in the Fornax Cluster of galaxies, and is a result of a multiple-year collaboration between researchers working at the University of Bonn, the University of St. Andrews, the European Southern Observatory in Chile, the University of Oulu in Finland, the University of Groningen in the Netherlands, and Charles University in Prague.

The dwarf galaxies of the Fornax Cluster are subject to the gravitational effects of the cluster environment. In the standard (Newtonian-gravity) dark-matter models, the dwarf galaxies are surrounded by a dark matter halo, so they should be mostly shielded from these gravitational forces. However, many of the Fornax dwarfs are observed to have distorted morphologies, which highly contradicts the LCDM-model expectation – as the results of this study show.

The above image shows the Fornax galaxy cluster. This is fig.9 in Venhola et al. (2018): “Magnification of Field 5 with the detected objects and masks (black circles) overlaid on the image. The yellow points and red symbols correspond to the initial detections of our detection algorithm, and the objects that pass the A_IMAGE > 2 arcsec selection limit, respectively. Aladin (Bonnarel et al. 2000) was used for generating the image. The image is best viewed in color on-screen.

We performed a similar test assuming a MONDian model (i.e. based on Milgromian gravitation without dark matter), which turned out to be very consistent with observations. In MOND, the dwarf galaxy is surrounded by a “phantom dark matter halo” (e.g. Lueghausen et al. 2013; Oria et al. 2021, ApJ) when it is far away from the centre of the galaxy cluster. This phantom dark matter halo is not real, it is merely Newtonian-speak to describe the true Milgromian potential of the galaxy. This potential is deeper and more extended when the dwarf is nearly isolated. When the dwarf plunges into the cluster, this phantom dark matter halo disappears. This is merely the mathematical consequence of the generalised (Bekenstein/Milgromian) Poisson equation and only means that the true Milgromian potential becomes less deep and shrinks. In other words, the galaxy’s gravitating mass is reduced, while its inertial mass remains the same. In this naked state, every dwarf galaxy is susceptible to tides, and so many dwarf galaxies are expected to show signs of distortion. It can happen that the dwarf is completely destroyed, but this would be a rare event and would remove dwarf galaxies quickly that are on orbits that take them very deep into the inner parts of the galaxy cluster. As the dwarf then orbits out from the central region, its phantom dark matter halo grows back (again this is merely a mathematical consequence) and the dwarf galaxy stabilises, having regained its gravitating mass which is much larger than its inertial mass in Milgromian dynamics. This process of loosing the phantom dark matter halo and regaining it as the satellite galaxy orbits within its galaxy cluster or around its host galaxy has been studied in detail in “The dynamical phase transitions of stellar systems and the corresponding kinematics” by Xufen Wu & Pavel Kroupa in 2013.

We thus have a beautiful convergence of LCDM failures – And at the same time, we also have a beautiful convergence of verifications of MOND:

Dwarf satellite galaxies are in planes around their host galaxies, like planetary systems around their stars, and dwarf galaxies have no dark matter.

Both of these properties show dark matter to not exist (and thus the entire LCDM model to be ruled out), and, at the same time, both are well understood if gravitation is Milgromian (see also DMC Blog 49). Both are well understood (i) because dark matter does not exist but the “dark-matter” content of dwarf galaxies is merely due to their orbit-dependent phantom dark matter halos, and (ii) because the planes of satellite galaxies are completely naturally produced when major gas-containing galaxies interact, like what happened between the Milky Way and Andromeda about 10Gyr ago (Bilek et al. 2018; Bilek et al. 2021; Banik et al. 2022).

Is there independent evidence for the waning and waxing phantom dark matter halo around galaxies predicted by MOND?

Haghi et al. (2016, MNRAS) had suggested that this may be nicely tested using rotation curves of galaxies: As stated above, if isolated, the gravitational mass of the galaxy is much larger than its inertial mass. Mathematically this spells out as it having a logarithmic Milgromian potential, which is synonymous to it having a phantom dark matter halo, the mass of which that is within R increases proportionally with distance, R, in Newton-language [Mphantom(<R) propto R]. This is demonstrated in the figure below (Fig.1 in Haghi et al. 2016).

Fig.1 from Haghi et al. (2016): The rotation speed, V, around the centre of a Milky-Way like galaxy as a function of distance, R, from the centre. An isolated galaxy has a flat rotation curve (uppermost solid line), but when other galaxies are placed in its vicinity they exert an external field across the galaxy leading to the external field effect (EFE) which leads the rotation curve to fall. The lowest thin curve is the pure-Newtonian (i.e. Keplerian) rotation curve when all of the phantom dark matter halo of the galaxy has vanished due to a strong EFE – the galaxy being “naked”. The strength of the EFE is described by the external acceleration ae.

The rotation curve is perfectly flat to very large R. Place this same galaxy into a region where there are other galaxies, then Mphantom will be smaller, and the rotation curve will fall. Thus Haghi et al. (2016, MNRAS) wrote the paper “Declining rotation curves of galaxies as a test of gravitational theory” pointing out that a signal is evident. And, using this approach and much improved data, extremely strong independent evidence for the breaking of the equality between inertial mass and gravitating mass described above and as predicted by MOND has thereafter been published by Chae et al. (2020, ApJ) and Chae et al. (2021, ApJ). Clearly, this constitutes a very major progress in fundamental physics.

Press releases about this publication:

in German from Bonn University,

in English: from the University of Bonn and from the University of St. Andrews,

in Czech from Charles University in Prague.

This post is related to the previous DMC Blog 58.

Talks about this project are available (the criticisms raised in the discussion of the ESO talk have been accounted for in our publication Elena Asencio, Indranil Banik et al. 2022, MNRAS, in press).

Elena explains the results in St. Andrews:

And at ESO (critical questions were raised at 34 minutes into the video – see below):

Jumped to 34m:

In The Dark Matter Crisis by Moritz Haslbauer, Marcel Pawlowski and Pavel Kroupa. A listing of contents of all contributions is available here.

74. Fundamental Ideas in Cosmology: Scientific, philosophical and sociological critical perspectives, by Martin Lopez-Corredoira 

Dr. Martin Lopez-Corredoira from the Instituto Astrofisica de Canarias published the book “Fundemantal Ideas in Cosmology: Scientific, philosophical and sociological critical perspectives“. It constitutes an objective documentation of the various modern ideas that have been generated in order to describe the observed Universe, and stresses how very unclear the picture is.

Jacket Image

This book is particularly useful in view of how the first deep observations of the James Webb Space Telescope are already now impacting non-trivially on cosmological theory. The observations are indicating that the observed Universe has formed massive galaxies, weighing some 1000 million solar masses within merely a few hundred million years from the nominal Big Bang. The standard, dark-matter based cosmological models cannot form such galaxies so rapidly.

These observations also have some exciting implications for cosmological models based on MOND. We are working on these. More on that in future posts.

In The Dark Matter Crisis by Moritz Haslbauer, Marcel Pawlowski and Pavel Kroupa. A listing of contents of all contributions is available here.

72. The first MSc-level lecture course on MilgrOmiaN Dynamics (MOND)


Jan Pflamm-Altenburg (SPODYR group, Bonn) successfully applied for a lecture on MOND to be introduced in the winter semester 2022/2023 (WS22/23) and to be held each WS as part of the MSc-in-Astronomy syllabus in Bonn. The process of having the lecture accepted involved appreciable behind the curtain activity. This is a historic moment because we now have the first-ever lecture course at the MSc level in which the theory of Milgromian dynamics will be taught:

In The Dark Matter Crisis by Moritz Haslbauer, Marcel Pawlowski and Pavel Kroupa. A listing of contents of all contributions is available here.

70. The List of Flawed Falsification Claims about MOND

Modern theories in physics need to be tested and, if they significantly fail a test, discarded. Significant means a prediction that is different from the measurement many times the uncertainty. For example, a calculation in a theory A predicts the space ship to end up at a point which is five million km away from where the astronauts are meant to be, and if the uncertainty is only 100km, then we need to reconsider if this theory A might not pose a threat to the lives of the astronauts. A calculation in theory B might, on the other hand, place the astronauts on target (say only 50km away) and they live. Clearly, theory B is preferred over theory A.

In this sense, the dark-matter based theories (case A above) have been rigorously and robustly falsified to any high degree of standard in the physical sciences (see previous and next post). What about MOND (theory B above)? It too is a physical theory allowing predictions. It too can be ruled out.

Srikanth Togere Nagesh has put a large effort to track down and document the published falsifications of MOND. It turns out that the claimed falsifications of MOND have all been shown, in the published scientific research literature via rebuttals, to be flawed. In every case either wrong calculations were done or some essential physical process that acts within MOND and normal matter has been wrongly applied or even ignored. This is touched upon in the Addendum to post 69, and here we publish the full list of tests of MOND that claim MOND is out. As found by Srikanth, all are erroneous and have published rebuttals:

Why do so many researchers publish such sub-standard results? This is probably a sociological issue: a researcher benefits in the eyes of the “ΛCDM priests” if the researcher shows MOND to be wrong. The “ΛCDM priests” disfavour MOND, because if MOND is the valid approximation to the physical Universe, then the dark-matter based models are invalid. This would put “ΛCDM priests” out of job. A researcher who hopes (i) to get a prize, (ii) to publish in Nature, (iii) to get a raise in salary, (iv) to rise up in the career ladder, will thus like to publish anti-MOND results, and would often get away with it, if there were not brighter scientists who still upkeep the ideals and standards of research in the natural sciences.

Cases in point are the incorrect claims that MOND is ruled out published in Nature and Nature Astronomy (see items 17 and 18 and in The List of MOND-falsification claims).

Doing the work needed to write a rebuttal is costly, and so the here documented largely sub-standard “MOND-falsification” research is pulling down the entire research effort. The bright researchers cannot spend as much of their valuable time on actually advancing our understanding of nature, because they are constantly paralysed by needing to react to some new MOND-falsification claim. While it is necessary to keep testing MOND, this needs to be done at high quality.

In The Dark Matter Crisis by Moritz Haslbauer, Marcel Pawlowski and Pavel Kroupa. A listing of contents of all contributions is available here.

69. The ultradiffuse Galaxy AGC 114905 works in MOND

“One can publish one paper on MOND

as long as it shows MOND to be wrong.”

Many “ΛCDM priests”

The above I heard many times before I was branded a “MOND person” by those in authority. Students working with me also reported that they were told the very same thing. I suppose the “LCDM priests” call me a “MOND person” because I published more than one paper on MOND and each of my MOND-related publications showed MOND to work very well. Below is an account on our just-published paper by Banik et al. who rebuts a recent prominent claim that argues (wrongly again) that MOND is falsified. The account is by co-author Srikanth Togere Nagesh who just finished his MSc thesis at the University of Bonn in the SPODYR group with two first-author research publications. After the guest post I add a brief account of two other claims of falsifying MOND that underline the validity of the above quote.

Pavel Kroupa

(The guest post by Srikanth Togere Nagesh follows below. A press release on our publication was published by St. Andrews University.)

Newton formulated a law of gravitation in 1687 that explained the motion of objects with speeds much smaller than the speed of light c. In fact, this was a first unification theory of physics, since he explained two phenomena that people did not think belonged together: the falling apple and the motion of the moon. Einstein developed a theory of gravitation that explains gravitation at speeds comparable to the speed of light c, and becomes Newtonian at speeds much less than c (Einstein 1916). Both the theories were developed using Solar System observations available at the corresponding times. Many decades later, when observations of galaxy rotation curves (RCs) became available in the late 1970s, Newtonian gravitation was applied to understand the behavior of the RCs. But the observed RCs were flat even at the outskirts of the galaxies (see Figure 1 below), which contradicted the conventional expectation of a Keplerian decline beyond the luminous matter, where the Newtonian inverse square law implies that the circular velocity, Vc, should scale with the distance, R, from the center as Vc proportional to R-1/2. The predicted rotation curve using Newtonian gravity and the observed rotation curve had strong discrepancies, and in order to solve this, it was postulated that galaxies reside in haloes of invisible mass, called cold dark matter (CDM), which boosts the gravity and was thought to reconcile the models with the observations. But the addition of dark matter to fix the RC has many extremely serious problems, addressed in a number of research publications (e.g. Kroupa et al. 2010; Peebles & Nusser 2010; Kroupa 2012; Kroupa 2015; Haslbauer et al. 2020; Asencio et al. 2021, Di Valentino et al. 2021; Haslbauer et al. 2022). The models based on the dark matter paradigm combined with dark energy, called ΛCDM models, constitute the standard model of cosmology (SMoC). Warm dark matter variants are essentially the same, as are fuzzy dark matter models (e.g. Dalal & Kravtsov 2022). The “Λ” stands for dark energy, another addition needed in order to make the Newtonian/Einsteinian cosmological models behave more like the observations.

A gravitational law was formulated by Milgrom in 1983, 1983b, 1983c after taking galaxy observations into account. It has a fundamental acceleration constant, a0 approximately 1.2 x 10-10 m/s2 (Gentile 2011), that we can refer to as Milgrom’s constant. This new theory of dynamics (strictly speaking, this can be a new theory of gravitation or of dynamics, the latter leaving the possibility open that inertial mass depends on acceleration, Milgrom 2011, see an interesting implication of this for space travel by Avi Loeb 2022) accounts for the observation that all systems with accelerations below a0 follow space-time scale-invariance (Milgrom 2009), and systems with acceleration greater than a0 follow the usual Newtonian dynamics. MilgrOmiaN Dynamics (MOND) has been successful in predicting the rotation curves of all galaxies (Sanders & McGaugh 2002; Famaey & McGaugh 2012) using Vf = (GMa0)1/4, where Vf is the asymptotic flat velocity that a galaxy’s RC reaches. MOND has also been successful in explaining other phenomena spanning from parsec to giga parsec scales (Banik & Zhao 2022).

Figure 1: The rotation curves for two very different galaxies. The left and right galaxies are, respectively, a massive and a dwarf disk galaxy. The measurements are shown by the open circles with uncertainties as vertical bars. The stellar plus gas components are given by the blue dashed (stars), the red dot-dashed (bulge) and green dotted (gas) contributions in the top panels. The black line shows the rotation curve the astronomer obtained in Newtonian gravitation without dark matter by adding these three colored contributions. The vertical red arrow shows how wrong this so-calculated rotation curve is. But taking the stars, bulge and gas and applying Milgrom’s gravitational law shows how the so-calculated rotation curve (the blue line in the two bottom panels) is an excellent match to the data, without any free parameters having been adjusted. Note especially how the wiggles of the rotation curve are automatically accounted for, this being impossible in the standard (Newton+dark matter) theory (Credits: Famaey & McGaugh 2012).

A new paper claiming MOND does not work: Now what’s the problem?

MOND thus accounts for all well-constrained observed rotation curves of normal, Milky-Way-like, and even rotating dwarf galaxies as well as elliptical and dwarf elliptical galaxies (e.g. Lelli et al. 2017). But not long, ago ultra-diffuse galaxies have been discovered as a new class. Will they fit this same Milgromian law? In 2021, neutral hydrogen (HI) observations of the ultra diffuse gas-rich galaxy AGC 114905 were used by Mancera Pena et al. (2021). The authors claimed that MOND fails to match the galaxy’s rotation curve. They also claim that ΛCDM fails to fit the RC of AGC 114905, which seems to render the galaxy unexplainable by both the theories. They inferred an asymptotic rotational velocity value, Vf, of 23 km/s using the MOND equation for this galaxy, which is surprisingly low for a galaxy with a mass of 1.42 x 10^9 M. The validity of this claim relies on the correctness of the measured apparent angle of inclination, i, between the disc and the sky plane. For example, a face-on galaxy has an inclination of i=0°, and an edge-on galaxy has an inclination i=90°.

Measuring the angle of inclination is done as follows. Contours of constant surface brightness are drawn on the images on the galaxies, then the contours are fit with ellipses of a given ellipticity. The ratio of minor axis to the major axis, q, is calculated for the best fitting ellipse. Taking the arc cosine of this q gives the apparent inclination, iapp, while the true inclination, i, might be different than the apparent one. The authors measured iapp,1 = 32° between the disc and the sky plane using the method above. They also measured iapp,2 = 11° by fitting another ellipse to the contour of AGC 114905, and adapted the former as the correct value.

Figure 2: The rotation curve obtained assuming MOND to be correct and iapp,2=11° is shown by the green curve assuming the observed distribution of stars and gas in the galaxy. Newtonian gravitation without dark matter gives the dashed magenta line. (Figure 6 in Mancera Pena et al. 2021)

(Figure 7 in Mancera Pena et. al. 2021)

The angle of inclination is important because the a rotation curve requires a correction factor of 1/sin(i). In this case, the ratio of sin(32°)/sin(11°) is 2.8, which is quite significant because the MOND prediction of Vf for AGC 114905 is 69 km/s, and the measured Vf is 23 km/s at iapp,1 = 32, which is a factor 3 less than MOND prediction. If one considers the inclination of 11° instead of 32°, then 23 x 2.8 = 64 km/s is quite close to the MOND predicted value. Hence, the galaxy can be reconciled with MOND if the inclination is much larger than the adopted 11°.

Why would anyone choose 11° when the best-fit shows 32°?

This is exactly what is addressed in our recent publication by Banik et. al. (2022) titled, “Overestimated inclinations of Milgromian disc galaxies: the case of galaxy AGC 114905“. In this article, we perform hydrodynamical simulations of a galaxy, computed by myself, with parameters similar to the properties of AGC 114905, in Milgromian gravity using the Phantom of Ramses (PoR) computer code, developed in Bonn in collaboration with Strasbourg by Lueghausen et. al. (2015). We use the observed parameters of AGC 114905 (Mancera-Pena et. al. 2021 above) as initial conditions and evolve the models for 5 billion years with PoR. The simulations include star formation as well. Simulations of such dwarf galaxies have never been done before. Dwarf galaxy simulations are particularly challenging, especially with stellar feedback, as it has never been tested before in MOND. The Bonn-Strasbourg research group did have experience with Milky-Way mass models (Wittenburg et al. 2020). These models of fairly massive galaxies already suggested, as remembered by co-author Pavel Kroupa in our group meeting, that MOND galaxies are much more alive and can appear elongated as they evolve without the help of a mass-dominating dark matter halo. But we did not know if the ultra-diffuse galaxy model would be disrupted due to violent supernova feedback for example, but it seems that stellar feedback does not disrupt the galaxy. In fact, it has the opposite effect of stabilising the galaxy and it evolves to be consistent with the observed one in terms of its present-day constitution.

We ran two models of the same galaxy. An isolated model without an external field, and another model with an external field (wich would come from some distant matter overdensity, e.g. another galaxy). In both cases, the models reproduce the observations and show that AGC 114905 works in MOND. We performed similar analyses on both the models.

What is the external field? It is the overall gravitational field across the galaxy which is generated by the large-scale matter inhomogeneity around the galaxy. A zero external field means the galaxy is completely isolated. A realistic external field, as used in our model, is as expected from the observationally estimate matter distribution. The external field changes the internal dynamics because Milgromian dynamics is a non-linear theory. The external field effect is a prediction of MOND and does not occur in Newtonian dynamics. It has been observationally evident in rotation curves (Haghi et al. 2016) with an observational verification with more than 5 sigma confidence by Chae et al. (2020). Thus, if two completely isolated stars attract each other with a force F, then the force changes to F’ < F if a third star is placed somewhere in the Universe. In Newtonian gravitation, on the other hand, F’ = F.

Initially, the models we simulated using PoR take about 1.5 – 2 billion years to reach dynamical equilibrium, and only the outputs after 2 billion years are used. Movies (see below) show a very active galaxy which changes it’s shape with time and it’s appearance with supernova explosions blowing bubbles into its interstellar medium. We plotted the gas distribution of the model between 2 and 5 billion years and drew a contour of constant surface brightness over each output image. Then we fitted ellipses to these contours and found the best fitting ellipse. We chose only those images where the fitted ellipse had a q value less than 0.86. We found multiple images (outputs) that had non-circular contours, and q << 0.86.

Why is this so important?

If you remember, the angle of inclination, i, is calculated using q, and a lower value of q, gives a higher apparent inclination iapp.

What is so special about it?

Our models have a true inclination of 0°, i.e. they are perfectly face-on throughout the evolution. In MOND, the galaxies are self-gravitating and can easily become non-circular over a period of time, similarly our models become non-circular and when we try to fit an ellipse and calculate iapp, we arrive at a value iapp >> 32°, even though the true inclination is 0°.

We argue that in MOND the same effect is plausible in the case of AGC 114905, where the authors might have arrived at an apparent inclination iapp,1 = 32°, but the true inclination is 11°. The problem was a clear overestimation by Mancera-Pena et. al. (2021) of the inclination based on ellipse fitting, which in turn is due to the non-circular nature of the galaxy, which is possible in MOND. Therefore, if one considers the inclination iapp,2 = 11°, the galaxy is reconciled with MOND. Therefore, the galaxy does not pose any problem to MOND at all, in fact, it backs-up that observed low surface brightness galaxies are known to have such features in MOND (McGaugh, Schombert & Bothun 1995).

In conclusion, it is generally advisable to exclude nearly face-on galaxies for such tests.

Figure 4: The fully self-consistent simulations of AGC 114905 in MOND. (Figure 1 in Banik et al. 2022)

Links to publication and videos

Videos showing the evolution of the models is available here,

Without the external field effect

With the external field effect

Addendum by Pavel Kroupa:

It is noteworthy that the recent peer-reviewed research literature contains claims that MOND does not agree with data that are wrong. That they are wrong could have been readily assessed by consulting with the appropriate experts, which neither the authors nor the editors deemed to be necessary. It appears there is a general feeling that publishing incorrect scientific results is acceptable, as long as these fake MOND to be wrong. Cases in point:

  • van Dokkum et al. 2018: Here the authors claim MOND is wrong by wrongly calculating the velocity dispersion of a dwarf galaxy. Two rebuttals were published: Kroupa et al. (2018) and Famaey et al. (2018). Two other related papers further clarified these types of galaxies (Haghi et al. 2019a; Haghi et al. 2019b). Note that this Nature paper has 12 authors some from ivy-league institutions, three referees and at least one editor. None of these astrophysicists thought it was necessary to ask an expert on Milgromian dynamics whether their calculation was correct. It seems that this whole group of people were all too enthusiastic of showing MOND to be wrong, something that is apparently accepted in the astronomical society. I take this as clear evidence that journals such as Nature distort scientific progress. The damage was great, since such Nature publications draw the attention of reporters, and the ivy-league status of some of the authors enhance the statements made in the publication.
  • Ogle et al. (2019): Analyse very massive disk galaxies and find them to deviate from the baryonic Tully Fisher relation (BTFR) writing in their abstract “The observed high-mass break in the BTFR is inconsistent with the Modified Newtonian Dynamics theory.” In a subsequent study, the same team (Di Teodoro et al. 2021) find this Ogle et al. (2019) work to have been faulty and show (without explaining the flaws of the previous one) that the same galaxies do lie close to the BTFR. They verify the prediction of MOND that all galaxies, also the massive ones, must be on the BTFR for the theory to hold. But these authors do not mention MOND when MOND fails to fail.
  • Mancera-Pena et. al. 2021 – see post by Srikanth above.

This is empirical evidence supporting the quote at the beginning of this post. This evidence also demonstrates how imbalanced and biased the extragalactic research community is against MOND. This community does not uphold the high standards of the scientific method but is corrupt (=statement by Pavel Kroupa) as the research papers written are apparently designed for career advancement rather than scientific advancement. We would falsify MOND with the same vigour as LCDM has been falsified, which is why we, in Bonn, Prague, Strasbourg and St. Andrews, are performing ever more computations using Milgromian dynamics to test and, if necessary, falsify also this rich theory of dynamics.

In The Dark Matter Crisis by Moritz Haslbauer, Marcel Pawlowski and Pavel Kroupa. A listing of contents of all contributions is available here.

65. The Don’t-Look-Up Syndrome of Cosmology: Chicago Cosmologists at their best; and the Hubble Tension does not exist

(by Pavel Kroupa, Friday 21st January 2022)

We humans are, as any living creature, and by necessity, conservative beings. We need to be, since typically most of us prefer to sustain their comfortable arrangements. The cave person will prefer to stay near their cave if the nearby plains below are full of fodder, and they would kill off threats. The cosmologist prefers to stay with their dark matter that made them big and important. So when a comet/climate crisis is discovered to approach Earth and is calculated, with some margin or uncertainty, that it will extinguish known life, it can be easier for the majority to just ignore this and to trust in everything turning out all right in the end. Keep the high spirits up, don’t worry and keep smiling and do not frown, do not spoil the mood by doomsday blubber, don’t look up to the threat. So let us ignore that the temperature of the oceans has already increased by nearly 2 degrees centigrade and that another increase by three will kill off most plankton as shown by Sekerci & Petrovskii (2018) with Earth’s atmosphere consequently running out of oxygen.

What has this to do with modern cosmology? I would claim: everything. The modern, successful homo cosmologicus vehemently defends their dark matter against all odds, even if it means killing the scientific method (testing and falsification of hypotheses using reproducible logical methods); they resist change to their habitat as long as the vast landscape of rewards, awards, grants and riches remains abundant.

On Friday, January 14th, 2022, I watched the Golden Webinar on the Hubble Tension, and on this same Friday there appeared on the arXiv an Annual Review on cosmology. Both scientists (speaker and author) are from the highbrow Kavli Institute for Cosmological Physics at the University of Chicago, and both contributions I found to be remarkable.

In the Golden Webinar on “Tension in the Hubble Constant – Does it mean new Physics?“, the speaker very nicely explained the measurements of the Hubble constant using different distance ladders and which role the uncertainties play. Three points struck me: (1) The speaker declared that the physical reason for the Hubble Tension remains unknown. (2) The speaker declared there to be no other known major tension between observations and the Standard Model of Cosmology (the SMoC, or LCDM model). (3) During the panel discussion, a long time was spent on Penrose’s Conformal Cyclic Cosmology hypothesis and it was speculated that fading dark matter might account for the Hubble Tension. The panel largely agreed that no one knew what dark matter was – it might have a large number of degrees of freedom, thus allowing the introduction of an arbitrary number of free parameters to fit almost anything.

Concerning the three points above, I wrote into the chat two questions (see Figure 1 below). Essentially, accepting the well-observed Gpc-scale KBC void as being a real structure of the Universe, the Hubble Tension must then arise from it logically (Haslbauer et al. 2020). This is because galaxies are accelerated gravitationally towards the sides of the void, and an observer within the void (as we are) then measures an apparent faster expansion of the local Universe (see figure 2 in 52. Solving both crisis in cosmology: the KBC-void and the Hubble-Tension). The Hubble Tension therefore has a very simple physical explanation.

In fact, a real Hubble Tension does not exist: it is merely an apparent effect caused by the observed KBC void (Haslbauer et al. 2020), and it would have been predicted if Wong, Suyu et al. (2020) and Riess et al. (2021) had not made their observations of expansion. It is the same reason, in essence, why apples fall to the Earth: replace the galaxies by apples, and they will fall to where they are attracted to, which is the side of the underdensity.

It was a wonderfull event and fascinating to see how the panel very happily discussed the entirely speculative fading dark matter concept in the context of the Hubble Tension, but no-one appeared to dare to raise the possibility that it might simply be due to the observed KBC void, as in fact it must be. I tried to help the panel by posting my question into the chat, but it appeared to me that, in the intimidating presence of highbrow scientists, discussing fading dark matter was acceptable, while raising the obvious solution was no-go. After all, who wants to ask a seemingly silly down-to-Earth question (“can the observed Gpc underdensity be responsible for the apparent Hubble Tension?”) in view of such intellectual Mt. Everests.

The second point above by the speaker I also found impressive, given that other independent falsifications of the LCDM model at more than five sigma confidence have been published, see the list A-F below. It seems that these contributions were missed in Chicago, or that Chicago Cosmologists “do not look up”. I guess they do not need to look up, since they are already on Mt. Everest.

I am still trying to digest this, which is why I wrote the above first paragraph.

Figure 1: My chat contribution. It received 7 votes, the highest of all questions, but the panel did not raise this issue with the speaker.

Why was neither the Golden Webinar speaker nor the panel willing to delve into the true physical reason for the Hubble Tension? I think that the problem is that the KBC void, which causes the Hubble Tension, falsifies the SMoC with more than 5sigma confidence (Haslbauer et al. 2020), because the SMoC cannot grow such large and deep under densities within a Hubble time. And furthermore, the Chicago Cosmologists, as represented by the speaker and author (next), seem adamantly to refuse to discuss MOND seriously. But MOND is the only known modern non-relativistic theory of gravitation in which the Universe can grow such a large observed void and observed early very massive interacting galaxy clusters (Asencio et al. 2021). We covered this galaxy-cluster problem on a previous occasion. In MOND, there is no Hubble tension (since the voids form naturally) and very massive interacting galaxy clusters also form naturally in the earlier Universe.

On the same day as the above Webinar, an Annual Review on “The Road to Precision Cosmology” was published on the arXiv: It is to appear in Ann.Rev.Nucl.Part.Sci. 72:1-33, https://arxiv.org/abs/2201.04741v1 .

I was interested, since the author is viewed by many to be an outstanding cosmologist, and I expected a fair, balanced and up-to-date review of cosmology for the community of Nuclear and Particle Physicists. This is an important review: Annual Reviews are corner stones of literature. Often they are the first entry point into a research field. Their role is thus truly important. On contemplating the review, I decided to write the following letter – let it speak for itself:

Letter sent on 17th of January 2022 to those addressed (with minute modifications for this forum):

Dear author,

(CC to Editors, Committee Members and Staff of the Annual Review of Nuclear and Particle Physics, and researchers working on MOND),

Concerning your review article "The Road to Precision Cosmology" which is to appear in Ann.Rev.Nucl.Part.Sci. 72:1-33,     https://arxiv.org/abs/2201.04741v1 :

I kindly ask you to adjust this article to represent the modern state of affairs truthfully: As it stands, the article is not a review but a biased misrepresentation of the state-of-the art in the research field. It misrepresents the entire field of cosmology to the research community in Nuclear and Particle Physics. 

If not-citing highly relevant research literature is considered to be equivalent to plagiarism, then you have provided a major example of such ill conduct: "Papers published in A&A should cite previously published papers that are directly relevant to the results being presented. Improper attribution — i.e., the deliberate refusal to cite prior, corroborating, or contradicting results — represents an ethical breach comparable to plagiarism." (citing from "Ethical issues: the A&A policy concerning plagiarism and improper attribution: https://www.aanda.org/index.php?option=com_content&view=article&id=136#Ethical_issues ).

In your article, we read "Sec. 3.1.2. False starts. In 1983, Milgrom noticed...."

This is an unacceptable representation of an entire highly successful and vibrant research field in which an increasing number of brilliant young physicists are active in.  You claim in this section that MOND cannot be falsified. This is wrong. We are actively working on falsifying this theory. MOND can be falsified by, for example, finding systems that do not obey the non-linear MOND Poisson equation.

Your article is not aware of or purposefully ignores that 

  1. The LCDM standard model of cosmology is in tension with the data on many different scales with significantly more than 5 sigma confidence.
  2. The data which are in tension with LCDM are at the same time naturally (i.e. without adjustment of any parameter) explained in a cosmological model which is based on Milgromian gravitation (MOND) without cold or warm dark matter.

Some of the relevant very recent major peer-reviewed research contributions (ignored by your article) on this are:

A) The existence of LCDM dark matter particles is in more than 5sigma tension with observed bar pattern speeds through the test based on Chandrasekhar dynamical friction published in 2021: Fast galaxy bars continue to challenge standard cosmology.

B) Very massive galaxy clusters form and interact at high redshift being in more than 5sigma tension with LCDM published in 2021: A massive blow for ΛCDM - the high redshift, mass, and collision velocity of the interacting galaxy cluster El Gordo contradicts concordance cosmology.

C) The observed local Gpc scale underdensity causes the Hubble tension and is in more than 5sigma tension with LCDM published in 2020: The KBC void and Hubble tension contradict ΛCDM on a Gpc scale - Milgromian dynamics as a possible solution,

Apart from the above extreme inconsistencies of the LCDM model with the respective data (spanning kpc to Gpc scales), MOND accounts for these naturally and it also naturally accounts for:

D) A planar group of galaxies recedes too rapidly from the Local Group (in >3.96 sigma tension with LCDM) published in 2021: On the absence of backsplash analogues to NGC 3109 in the ΛCDM framework.

E) The lack of a bar in the nearby disk galaxy M33 could not be explained in LCDM published in 2020: The Global Stability of M33 in MOND.

F) The planar (disk-like) distribution of satellite galaxies is inconsistent with LCDM but arises naturally in MOND published in 2018: MOND simulation suggests an origin for some peculiarities in the Local Group and Origin of the Local Group satellite planes.

Your article neither cites nor discusses these, and falsely implies the LCDM model to be consistent with the data at the precision level. Further, the review appears to suggest there to be no other model (without dark matter) that can claim comparable success. Claiming today that the LCDM model is a "triumph of precision cosmology" (Sec. 4.1 in your article) is purposefully propagating outdated misinterpretations to an audience who are non-experts in this research field. 

I will publish the contents of this email as an open letter, and I hope to receive a constructive reaction. 


Pavel Kroupa

(Helmholtz-Institut for Nuclear and Radiation Physics, Bonn;                        Astronomy Institute, Charles University, Prague)

The interested reader might also consult “It’s time for some plane speaking” published by Marcel Pawlowski (2021) in Nature Astronomy. Although Marcel suggests there to be no obvious solution in sight, in MOND, the solution is quite trivial. The planes of satellites come from galaxy-galaxy encounters, as explicitly demonstrated by Bilek et al. (2018, A&A and 2021, Galaxies) and Banik et al. (2018, MNRAS).

In The Dark Matter Crisis by Moritz Haslbauer, Marcel Pawlowski and Pavel Kroupa. A listing of contents of all contributions is available here.

60. Recent review talks about MOND, the Hubble tension and MOND cosmology including major problems of the dark matter models to match data

1) To obtain an introduction to MOND and MOND-cosmology, those interested might like to watch the talk below by Dr. Indranil Banik (past AvH Fellow in the SPODYR group at Bonn University, now at St.Andrews University). It was held on Sept. 30th, 2021 at the University of Southampton.

Indranil Banik


Also, the following two previous talks are relevant:

2) In the recent Newton 1665 physics seminar series on  “MOND, the KBC void and the Hubble tension” by Dr. Indranil Banik and Moritz Haslbauer (SPODYR group):

Moritz Haslbauer

3) And also recently, as a CosmoStat Journal Club seminar on “El Gordo: a massive blow to LCDM cosmology” by Dr. Indranil Banik and Elena Asencio (SPODYR group): 

Elena Asencio

In The Dark Matter Crisis by Moritz Haslbauer, Marcel Pawlowski and Pavel Kroupa. A listing of contents of all contributions is available here.

59. Are “darker psychological mechanisms” at work ?

(by Pavel Kroupa)

Two related essays have been published by aeon :

1) David Merritt wrote an essay for aeon with the title “A non-Standard model”. It is a very short version of his prize-winning Cambridge Universe Press book “A philosophical approach to MOND” and addresses the problem the cosmological scientist is faced with when needing to reach a conclusion as to the merit of a theory, given the data

Note that “true prediction” is used throughout this text to mean a prediction of some phenomenon before observations have been performed. Today, many numerical cosmologists and an increasing number of astrophysicists appear to be using a redefinition of “prediction” as simply being an adjusted calculation. Thus, the modern scientists observes data, then calculates what the cosmological model would give, adjusts the calculation to agree with the data, and then publishes this as a model prediction.

On the one hand side there is the standard dark matter based model which never made a successful true prediction (in the sense of pre-data) but is believed widely in the community to be true,

while on the other hand side Milgromian dynamics has made many successful true predictions of new phenomena but is deplored by the community.

David concludes this essay with “But I hope that scientists and educators can begin creating an environment in which the next generation of cosmologists will feel comfortable exploring alternative theories of cosmology.”

In addition to the performance of a model in terms of true predictions, a model can also be judged in terms of its capability to be consistent with data. This is a line of approach of model-testing followed by me and collaborators, and essentially applies the straight-forward concept that a model is ruled out if it is significantly falsified by data. Rigor of the falsification can be tested for using very different independent tests (e.g. as already applied in Kroupa et al. 2010). We have been covering this extensively in this blog. For example, the existence of dark matter particles is falsified by applying the Chandrasekhar dynamical friction test (as explained in Kroupa 2012 and Kroupa 2015): Satellite galaxies slow down and sink to the centre of their primary galaxy because of dynamical friction on the dark matter haloes. This test has been applied by Angus et al. (2011) demonstrating lack of evidence for the slow down. The motions of the galaxies in the nearby galaxy group M81 likewise show no evidence of dynamical friction (Oehm et al. 2017). Most recently, the detailed investigation of how rapidly galactic bars rotate again disproves their slow-down by dynamical friction on the dark matter halos of their hosting galaxies, in addition to the dark-matter based models having a completely incompatible fraction of disk galaxies with bars in comparison to the observed galaxies (Roshan et al. 2021a; Roshan et al. 2021b). All these tests show dark matter to not exist. Completely unrelated and different tests based on the larger-scale matter distribution and high-redshift galaxy clusters have been performed in great detail by, respectively, Haslbauer et al. (2020) and Asencio et al. (2021). Again, each of these individually falsify the standard dark-matter based models with more than five sigma confidence.

In summary: (a) By applying the formalisms of the philosophy of science to the problem whether the dark-matter-based models or the Milgromian models are the better theories in terms of their track record in true predictions, David Merritt demonstrates the latter to be far superior. (b) By applying the model-falsification approach by calculating the significance of how the models mismatch the data, we have come to the exact same conclusion.

As alluded to by David Merritt, the frightening aspect of our times is that the vast majority of cosmological scientists seem either not capable or willing to understand this. The lectures given by the leaders of cosmological physics, as can be witnessed in the Golden Webinars in Astrophysics series, collate an excellent documentation of the current disastrous state of affairs in this community. In my Golden Webinar in Astrophysics I describe, on April 9th 2021, this situation as

the greatest scientific crisis in history ever,

because never before have there been so many ivy-league educated researchers who en masse are so completely off the track by being convinced that a wrong theory (in this case dark matter cosmology) is correct while at the same time ignoring the success of another theory (in this case Milgromian dynamics). At next-to-all institutions, students appear to be indoctrinated by the “accepted” approach, with not few students in my lectures being surprised that the data appear to tell a different story. Many students even come to class believing that elliptical galaxies are the dominant type of galaxy, thus having an entirely wrong image of the Universe in their heads than what is truly out there. Once before there was a great clash of ideas, famously epitomised by Galileo Galilei‘s struggle with the Church. But this was very different, because traditional religious beliefs collided with modern scientific notions. Today, the Great Crisis is within the scientific community, whereby scientists ought to be following the evidence rather than belief. Belief should not even be a word used by scientists, as it implies a non-factual, not logical approach. Rather than belief, we as scientists need to objectively test hypotheses which need to be clearly stated and the results of the tests must be documented in terms of significance levels.

2) And the reader of this blog would probably also be interested in the very related earlier aeon essay by myself on Has dogma derailed the scientific search for dark matter?.

In The Dark Matter Crisis by Moritz Haslbauer, Marcel Pawlowski and Pavel Kroupa. A listing of contents of all contributions is available here.

56. From Belief to Realism and Beauty: Given the Non-Existence of Dark Matter, how do I navigate amongst the Stars and between Galaxies?

(by Pavel Kroupa, 4th of April, 2021, 11:11)

Update (April 15th): After receiving some queries, the slides to the talk w/o the fictitious story can be downloaded here

On April 9th, 2021, I will give this public talk:

If interested, you can join the public lecture by registering here.

The talk, held via zoom, is on April 9that 11:00 Chilean Time (CLT = UTC-4),  8am Pacific Daylight Time (PDT = UTC-7),11am Eastern Daylight Time (EDT = UTC-4), 17:00 Central European Summer Time (CEST = UTC+2)

The Golden Webinars are provided as a free public service and have no registration fees. They are recorded and made available for later viewing via youtube.

In The Dark Matter Crisis by Moritz Haslbauer, Marcel Pawlowski and Pavel Kroupa. A listing of contents of all contributions is available here.

55. “A Philosophical Approach to MOND” wins prestigious award

It is with delight we learned today that David Merritt’s book on “A Philosophical Approach to MOND” published by Cambridge University Press won the Prose Award for Excellence in Physical Sciences and Mathematics. Other authors also competing for this price were Peebles and Weinberg. 

I had written a review of this book which can be read here.

Note also that in 2013 David published a noteworthy text book on “Dynamics and Evolution of Galactic Nuclei” (with Princeton Series in Astrophysics).

This is an opportunity to recall how I personally stumbled into this whole problem concerning dark matter (see also this article on Aeon): My research up until the mid1990s was based on stellar populations, although in Heidelberg we had also measured, for the first time, the actual space velocity of the Magellanic Clouds (in 1994 and 1997). These were my first endeavours into the extragalactic arena. I had heard a fabulous lecture by Simon White who was visiting Heidelberg, showing movies of structure formation in the LCDM model they had just computed in Garching. I personally congratulated Simon for this most impressive achievement.  One could see how major galaxies were orbited by many dwarf satellite galaxies and how all of that formed as the Universe evolved. I had also noted from photographs that when two gas-rich galaxies interact, they expel tidal arms in which new dwarf galaxies form. These new dwarf galaxies are referred to as tidal dwarf galaxies.

The Tadpole Galaxy recorded with the Hubble Space Telescope’s Advanced Camera for Surveys. Evident are the new dwarf galaxies in the 100 kpc long tidal tail.

In the 1990’s the community had largely discarded satellite dwarf galaxies being tidal dwarfs because it was known that they cannot have dark matter (this goes back to Barnes & Hernquist,1992,  later confirmed by Wetzstein, Naab & Burkert 2007).  So it was thought that tidal dwarfs just dissolve and play no important role.  The observed satellite galaxies of the Milky Way have large dynamical M/L ratios, going up to 1000 or more. This proved they can contain a 1000 times more mass in dark matter than in stars and gas. So obviously they cannot be tidal dwarfs. I very clearly remember Donald Lynden-Bell exclaiming in Cambridge, when I was still visiting regularly, that his suggestion that the satellites came from a broken-up galaxy cannot thus be correct, since they contain dark matter. Then I made my discovery (truly by pure chance) published in Kroupa (1997), which made me think that what the celebrated experts are telling me seemed not to be quite right. After this publication I was told more than once this work made me un-hireable.
I had then noted (Kroupa et al. 2005), that the disk of satellites (DoS, including the newer once which Donald had not known) is in conflict with them being dark-matter substructures, as these ought to be spheroidally distributed around the Milky Way galaxy. 
We  argued (to my knowledge for the first time in print, in Kroupa et al. 2010 and in Kroupa 2012 ) that the disk of satellites can only be understood if they are tidal dwarfs. I had also come to the conclusion that my chance discovery above is unlikely to be able to explain the high M/L values of all the satellite galaxies as they would all need to be quite strongly affected by tidal forces which poses a problem for those further than 100 kpc from the Milky Way because their orbital periods begin to approach a Hubble time. And if they are tidal dwarfs (which they must be given they make a disk of satellites),  then this implies we need non-dark-matter models, i.e. , we need to change the law of gravitation to account for the high M/L values these little galaxies display.  Subsequently I was quite fevering (with PhD student Manuel Metz and later Marcel Pawlowski) each time a new satellite was discovered to see where it lay (I used to run to their offices whenever some survey reported a new satellite), and ultimately what the proper motions are doing: if the satellite galaxies form a pronounced disk of satellites then they must be orbiting only within this disk (Pawlowski & Kroupa 2013). I was (this was already in the 2000s) also interested if  John Moffat’s “modified gravity” (MOG) might explain the large M/L ratios, and John Moffat visited me in Bonn. But it turns out that MOG is falsified while Milgromian gravitation (MOND) is, as far as one can tell, the at the moment only possible gravitational theory we can use which accounts for all data and tests so far performed.  Oliver Mueller, Marcel Pawlowski  et al. (2021) affirm that the Milky Way is not unique in having a disk of satellites system. Observing disks of satellites around larger galaxies is not a “look elsewhere effect” since the very-nearest large galaxies are looked at, rather than finding such DoSs around some host galaxy in a very large ensemble of observed galaxies. I think the disk-of-satellites or satellite-plane problem is the clearest-cut evidence why we do not have dark matter. 
The (negative) test for the existence of dark matter particles (warm, cold, fuzzy) via Chandrasekhar dynamical friction is the other (Kroupa 2015).
Plus, with all the other tests performed in strong collaboration with Indranil Banik (notably Haslbauer et al.  2019a, Haslbauer et al. 2019b,  Haslbauer et al. 2020 and Asencio et al. 2021) it materialises that the tests all lead to mutually highly consistent results – we do not have the situation that one test is positive (for dark matter), the other not. They all turn out to be consistently negative. Indranil Banik concludes correctly (Feb.5th, 2021): “There are so many lines of evidence that no single one is critical any more.”
I am personally deeply impressed how everything seems to fall into place (quite nearly everything) once one uses MOND (which is based on a Lagrangian etc.).  Apart from completely naturally resolving the Hubble Tension and easily accounting for massive high-redshift galaxy clusters like El Gordo (see also this account on Triton Station), the DoSs or satellite planes form naturally (as shown independently by Banik et al. 2018 and by Bilek et al. 2018) and these tidal tail dwarf galaxies have large M/L values due to the correct law of gravitation (e.g. this amazing prediction by McGaugh 2016 of the velocities of stars in one of the satellite galaxies and verification thereof by Caldwell et al. 2017).
But, just like with the standard model of particle physics, there definitely is a deeper layer to MOND which we have not yet discovered; a more fundamental theory, which may well be the quantum vacuum which also explains particle masses. Milgrom had already published seminally on this issue.
The huge success of MOND comes not only in it naturally account for the data on scales of a few 100 pc to a Gpc, but also that it is a “progressive research programme“, with the standard dark-matter based models being “degenerative“.  For details, see David Merritt’s book above. 

In The Dark Matter Crisis by Pavel Kroupa. A listing of contents of all contributions is available here.