73. A composition for iai: Dark matter doesn’t exist! Yearly, a three quarter billion USDollars are wasted on an illusion.

After attending the “HowTheLightGetsIn” Festival in Hay on Wye in Wales, June 2nd-5th, 2022, I was asked by the Institute for Art and Ideas (iai) to draft a text capturing the current state of the dark matter science. It was published on July 12th, 2022. Here it is:

Dark matter doesnt exist

A straight pdf version for download is available here:

For a version in Spanish see “Einstein estaba equivocado: necesitamos una nueva teoría del cosmos“. A critique appeared as “Kroupa on Dark Matter vs MOND“.

Related to the above iai publication is the piece that appeared on Nov.25th, 2016, in aeon: “Has dogma derailed the scientific search for dark matter?“. Presentations are available on YouTube: Heidelberg Colloquium (November 2013), “The Vast Polar Structures around the Milky Way and Andromeda“, Golden Webinar (April 2021), “On the Non-Existence of Dark Matter“, and Astronomy on Tap Koeln (March 2022), “Dark Matter Kindergarten Stuff“. In May, 2021, Sabine Hossenfelder explained “Dark Matter, The Situation has Changed“.

While composing the iai text the question returned about how much money is being spent each year on a) salaries of all dark matter people, b) dark matter searches. The draft I had sent to iai (the above text) was immediately accepted and I did not have the opportunity to include the following updated estimate into it. But here it is:

My estimate: There are 12131 IAU members.

If half work on dark matter and if the average salary is 40000 USDollars per year, we have 242 million dollar per year being spent on dark matter research.

If there are currently ten dark matter searches, each costing on average 50 million per year, we have 500 million dollars per year (much of it on salaries for engineers, equipment, astronauts).

That is, the tax-payer is expending something like three-quarter of a billion dollars each year on largely useless “research”. A large fraction of scientific funding thus meanwhile goes into an activity which is based on pure belief contrary to evidence. One might interject that some of the experiments lead to the development of new technology. This would be equivalent to the situation where a state organises, using tax-payer money, a job-programme which employs people to dig many holes. The useful aspect of this would be that the unemployment rate would decrease, but the measure would leave no lasting benefit. In terms of the dark matter problem, it would be advisable to support research projects on non-falsified theories which lead to innovative technologies. Another way to express the above is to say that our modern, 21st century technological civilisation is essentially actively funding religion camouflaged as science with the above amount.

The dark-matter based models were clearly ruled out already in 2010 (read “Local-Group tests of dark-matter concordance cosmology . Towards a new paradigm for structure formation“) and definitely falsified in 2012 (read “The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology“). Today, ten years later, ample time has passed even for the dimmest scientist to be able to catch up. Given that the arguments against dark matter have not been shown to be invalid, and have in fact multiplied manyfold (see the iai piece above), it is simply not to be understood from a rational point of view why we keep expending so many valuable resources into a falsified theory while, at the same time, suppressing a highly interesting and successful alternative. The scientists who continue pushing for this falsified dark-matter theory are hurting the sciences and are, by ignoring the falsifications, being unscientific. They appear to behave more like ancient Egyptian priests who fervently guard their particular god(s) to thrive on the citizens by faking the ability for communicating with these imaginary deities.

What keeps this system going? The LCDM model is a gold of mine for those, the “LCDM priests”, who are able to sell the dark matter and dark energy stories to the funding agencies. An impression of how this works can be gleaned by watching the Golden Webinars in Astrophysics (see e.g. Post 65). An excellent example of the process is evident the time following 1:13:18 in the Golden Webinars in Astrophysics by Martin Rees as a consequence of Martin Rees suggesting that the non-detection of dark matter is trouble.

Furthermore, the LCDM model is guarded by suppressing fundamental empirical evidence: David Merritt eloquently documents how virtually all important modern textbooks fail to report essential information on galaxies (see Table 1 in Merritt 2017). From my own personal experience I know of significant mobbing within universities and general massive discouragement of young researchers against touching MOND. More than one student working with me have told me that it was recommended by other very senior researcher that they not work with me. When I was younger, I was too told that one may publish on MOND, but only to show it is wrong. It appears that this “guiding” by senior researchers of younger ones may have contributed to the long list of flawed such claims (“The List of Messups” or “The List of Shame”, Post 70). A classical example of continued mis-representation of MOND is the repeated claim that the Bullet Cluster falsifies MOND (this was shown to be wrong already by Angus, Famaey & Zhao 2006, MNRAS ), and a present-day example can be found in the Introduction of a MNRAS publication which dismisses MOND altogether but ends up discovering a trivial MOND result.

It has thus become a perpetually repeating cycle: young scientists are, in nearly all research institutions, not confronted with the essential information, and at best learn about it in the context of fringe science, something better not to touch if a career is desired. They need a post-doctoral or better position, or the one or other prize. To ensure success they do what is needed. In this way the scientific system appears to have become corrupt: despite being ruled out by the evidence (see the iai composition above), dark matter has come to be seen as a non-exotic and established part of physics. For the benefit of ones own career one sticks with dark matter rather than following the “fringe evidence”.

This text is my (Pavel Kroupa’s) responsibility only.

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.

64. Youtube playlist full of MOND talks, debates and more

(Guest post by Mark Huisjes, December 8th, 2021)

In the following guest post by Mark Huisjes (GIS Analyst and master student at Utrecht University) we would like to promote a Youtube playlist, which includes talks, debates, Q&A’s, and more videos related to MilgrOmiaN Dynamics (MOND). This playlist is aimed for anyone who is interested in this research field.

Over the past year I’ve built a Youtube playlist of videos related to MOND, which is available online here.

Youtube playlist of talks, debates, interviews, Q&A sessions, and much more hosted by Mark Huisjes.

It contains more than 70 hours of talks, debates, interviews, Q&A sessions, and much more. Most of the listed videos are in English, but videos in French, Spanish, German, and Czech are also available at the end of the playlist. Subjects covered include fundamental MOND phenomenology such as rotation curves, the baryonic Tully-Fisher relation, the central density relation, and the radial acceleration relation, but also more advanced topics such as the external field effect, satellite galaxy planes, wide binaries, TeVeS, superfluid dark matter, and νHDM cosmology, and scientific tests of the hypothesis that dark matter exists.

This way people can easily find a talk if it is available online and delve deeper into the theory of MOND!

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

63. Hybrid models may solve mystery of dark matter

(Guest post by Tobias Mistele, December 1st, 2021)

Tobias Mistele is a PhD student at the Frankfurt Institute for Advanced Studies studying hybrid MOND-dark-matter models. Besides his physics research he also works on Scimeter.

Hybrid models, which combine dark matter and modified gravity, were long neglected. In this post, I explain why such models are now attracting attention as a path out of a stalemate.

There is observational evidence for missing baryonic mass on both cosmological and galactic scales. Most notably, the fluctuations in the cosmological microwave background (CMB) on cosmological scales and rotation curves on galactic scales. Traditionally, this is explained by non-relativistic dark matter particles (cold dark matter, CDM) that do not interact much except gravitationally. These CDM particles form a pressureless fluid on cosmological scales and later accumulate around galaxies, forming a dark matter halo. The pressureless fluid explains the fluctuations in the CMB. The mass of the halo around galaxies explains galactic rotation curves. An alternative paradigm is modified gravity. Instead of postulating particles that produce additional mass, modified gravity postulates a different gravitational force. Modified Newtonian Dynamics (MOND) is a modified gravity model that is quite successful on galactic scales. For example, consider the so-called Radial Acceleration Relation (RAR) shown in Figure 1. This is a relation between the standard Newtonian gravitational acceleration due to the stars and gas in a galaxy, gbar = GMb/r2, and the total acceleration gobs we infer from observed rotation curves. In a world without dark matter and without modified gravity, these two are the same, gbar = gobs. In the real world they are not. This is the missing mass problem in galaxies. More importantly, this relation between gobs and gbar has little scatter. Thus, the total acceleration gobs can be predicted just from the baryonic mass distribution, i.e. from gbar.

Figure 1: The Radial Acceleration Relation (RAR). Credits: One Law to Rule Them All: The Radial Acceleration Relation of Galaxies (Lelli et al. 2017). With kind permission by Federico Lelli.

This is non-trivial in DM models. In principle, two galaxies with the same baryonic mass distribution (the same gbar) can have different dark matter halos and thus a different gobs, but this doesn’t happen. In contrast, MOND naturally explains this. In fact, the RAR shows precisely what MOND postulates. At Newtonian accelerations gbar larger than a0 ≈ 10-10 m/s2 nothing new happens. Newton’s gravitational force law remains. But at accelerations gbar smaller than a0, the total acceleration changes to (a0 gbar)1/2.

Unfortunately, both CDM and MOND remain unsatisfactory when considered individually. MOND, for example, cannot explain all the missing mass on galaxy cluster scales. And, so far, no MOND-based models have been able to explain the fluctuations in the CMB, at least not without introducing some type of dark matter after all. CDM, on the other hand, has its own problems. For example, there is so far no convincing explanation for MOND-like scaling relations like the RAR. There’s just no reason why the dominant dark matter halo should be predictable from the visible baryonic mass in such a simple way. Another problem is that observed galactic bars tend to rotate faster than what CDM predicts. The dynamical friction of a CDM fluid slows down galactic bars. Then there’s the plane-of-satellites problem. Satellites of the Milky Way co-orbit in thin, planar structures. A natural explanation would be that these satellites were created from the tidal tails of interacting galaxies. But then they would not have their own dark matter halo which contradicts their high internal velocity dispersion. Also, CDM seems to be too slow to grow large structures. Massive clusters at high redshift like El Gordo are very unlikely to form so early in CDM.

So if not MOND or CDM – then what? One answer is both! That’s what hybrid MOND-dark-matter models are about. These are models that have both a pressureless fluid on cosmological scales (to explain the CMB) and a MOND-like force in galaxies (to explain e.g. the RAR).

Let me illustrate the general ideas behind hybrid models with an example – a model called superfluid dark matter (SFDM) proposed by Berezhiani & Khoury. This model has various problems, but it serves as a good illustration of the general features of hybrid models. SFDM postulates a specific new type of particle that behaves like standard CDM on cosmological scales and therefore explains the CMB in the standard way. But around galaxies, these particles condense to form a superfluid. The collective excitations of this superfluid, called phonons, then mediate a MOND-like force in galaxies. This MOND-like force is an emergent property of these particles in the superfluid phase. This is how this model explains MOND-like scaling relations like the RAR.

Of course, the superfluid itself has a mass. This produces a standard gravitational force that affects stars and gas. That is to say the superfluid also acts as dark matter in galaxies. So then we have both a MOND-like force and dark matter around galaxies. But does this not solve the missing mass problem twice? So that rotation velocities end up even larger than what we observe?

Figure 2: The Milky Way rotation curve in superfluid dark matter. The dark matter contribution is small, but becomes more important at larger radii. Credits: Tobias Mistele

The answer to that is that the superfluid DM component is usually subdominant within galaxies because the superfluid halo is very cored. Its mass becomes relevant only at larger radii. This is illustrated in Figure 2 for the Milky Way rotation curve.

One might be tempted to adjust one’s models so that the DM contribution becomes even smaller. Just to reproduce the MOND-like scaling relations even more cleanly. But one must be careful with this. Some amount of dark matter is needed in hybrid models to explain the missing mass on galaxy cluster scales for which MOND cannot fully account and, in some models, also to explain gravitational lensing.

Superfluid dark matter is not the only hybrid model. For example, recently Skordis and Złosnik proposed a model that reproduces MOND in galaxies (SZ model). This is also a hybrid model and has, deservedly, received a lot of attention since it is fully-relativistic and it was demonstrated explicitly that this model fits the CMB. Like in SFDM, the MOND and DM components are related to each other in the SZ model.

Such a common origin for the cosmological and galactic phenomena is theoretically appealing. But not all hybrid models have such a common origin. For example, the so-called νHDM model does not. Moreover, such a common origin often brings about internal tensions that must be carefully avoided.

In SFDM, for example, this common origin means that the phonon field is involved both in providing the DM and the MOND components. One technical consequence is that the usual U(1) symmetry of the superfluid must be explicitly broken which has various non-technical implications. For example, the superfluid equilibrium state might not be valid on timescales longer than galactic timescales.

The common origin for the DM and MOND components complicates things also for the SZ model. In this model, there is a kind of mass term for the static gravitational field in galaxies. Mass terms generally make forces short-range. To keep the gravitational force in galaxies long-range, the mass term must be chosen small. But a smaller mass term in galaxies means a larger pressure of the DM-like fluid in cosmology. Observations indicate a very small pressure of the DM fluid. So the galactic and cosmological phenomena push the model in different directions. This has forced the authors to include certain non-linearities as a counter.

Besides these model-specific constraints, there is also a new type of phenomenon that quite generally constrains models with a common origin for the MOND and DM components. Namely, stars often lose energy just by moving through a galaxy. Let me explain.

Accelerated charges produce electromagnetic waves. Accelerated masses produce gravitational waves. In general, whenever matter is coupled to a force carrier (e.g. the electromagnetic or the gravitational field), matter that accelerates produces waves corresponding to that force carrier. But even non-accelerated matter objects can produce waves. Namely if they move faster than the speed with which these waves propagate. For example, in a medium, electromagnetic waves propagate slower than the vacuum speed of light. Charged particles in such a medium emit electromagnetic waves if they move faster than this reduced speed of light. These waves are then called Cherenkov radiation. Such charged particles lose energy and slow down. A similar phenomenon occurs frequently in modified gravity theories whenever gravitational waves propagate at less than the vacuum speed of light. This is called gravitational Cherenkov radiation. Usually, only highly relativistic matter objects emit Cherenkov radiation, both in modified gravity theories and in electromagnetism. This is because the propagation speed of waves is usually relativistic, so that only relativistic particles are fast enough.

But this is different in hybrid MOND-DM models with a common origin for the MOND and DM components. Such models usually contain a force carrier (for the MOND-like force) whose associated waves propagate with non-relativistic speed (because this force is related to the non-relativistic dark matter fluid). Thus, even non-relativistic objects like stars might move faster than the wave propagation speed associated with the MOND force. Such stars will then lose energy and slow down, because they emit a special type of gravitational Cherenkov radiation. For example, in SFDM stars that move faster than the superfluid’s speed of sound will lose energy by emitting sound waves and slow down until they are slower than the superfluid’s speed of sound. This is illustrated in Figure 3. A star may be on a standard circular orbit when it is sufficiently slow, but will otherwise lose energy and circle towards the center of a galaxy.

Figure 3: The orbit of a star in the plane Z = 0 of a galaxy with (dotted orange line) and without (straight blue line) the Cherenkov radiation typical of hybrid MOND-DM models with a common origin for the MOND and DM components. The two cases are labeled as “With friction” and “Without friction” because in the specific approximation used, the Cherenkov radiation acts like an effective friction force on the star. Credits: Tobias Mistele

This reasoning applies only to models with a common origin for the DM and MOND components. So it does apply to SFDM and the SZ model, but not to the νHDM model. When actually doing the calculation one needs to be careful because of the non-linearities that are inherent in any MOND model. Still, it is possible to rule out part of the parameter space of SFDM using the observed Milky Way rotation curve. Basically, one requires that stars that orbit around the Milky Way with the rotation curve velocity do not lose much of their energy during the Milky Way’s lifetime. The SZ model avoids such constraints due to a special property. The coupling to matter is much larger in the static limit than in dynamical situations, which suppresses the energy emitted by Cherenkov radiation. Though I should say that the calculation for this model was done in a simplified setup so that the result should be taken with a grain of salt.

To sum up, the observational evidence for both MOND-like scaling relations on galactic scales and a DM-like fluid on cosmological scales has only become more convincing in recent years. This motivates hybrid MOND-DM models. We may not yet have a completely satisfactory model and much remains to be explored. Still, this general type of model will likely become ever more relevant in the future.

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

62. Mailing list for the MOND community

(Guest post by Indranil Banik, November 22nd, 2021)

In the following guest post by Dr. Indranil Banik (past AvH Fellow in the SPODYR group at Bonn University and now at the St.Andrews University), we would like to promote a mailing list for the MOND community and anybody who is interested in this research field.

Following a request, I have set up a mailing list for the MOND community and anybody who wants to stay updated about our work. The idea is that if someone wants to advertise an upcoming talk or an article they have recently posted but they are at an early career stage and do not know everyone in the MOND community, they can just send an email to the mailing list. Also if some discussions between more senior researchers take place through this list, then any early career researchers signed up to it will be included in the conversation even if nobody thought explicitly to include them in the conversation. Regardless of whether you are signed up, you can send an email to the mailing list and everyone on it should receive the message.

The email address is: mondworkers@gmail.com

Please contact Elena Asencio if you want to sign up to this mailing list and thus receive the emails sent to it, she will be in charge of sending an invitation link which you need to accept in order to complete the sign up: s6elena@uni-bonn.de

We think it is not appropriate to send such invitation links to people who have not requested it, as such a request would take only a little time and we would not ask for any reasons for why you want to sign up.
At the moment, only a very small number of emails have been sent to the mailing list because I have only recently set it up. I envisage that it would not be used all that often for a while, and slowly catch on as more people know about it. Obviously it is not suitable for a great many emails as the sender might only want specific people to see it rather than the whole mailing list. But there are times when people want their email to gain extra visibility, and that is what this is about.

Please advertise this to especially early career researchers, it is intended for sharing adverts for upcoming talks, notifying others of articles and blogs, and discussing research ideas you want to share. In general, it is for anything you want to share with everyone on the list, including I suppose asking for advice. It is important that the more senior researchers working on MOND are signed up to it so that early career researchers who want to e.g. advertise a talk or get advice about a project manage to contact everyone on the list without knowing all their names and email addresses. In principle, a fair amount of customisation is possible with the filters that are used, and different filters can be used for different people on the list. At the moment, the only filtering in place is to prevent administrative emails being sent to everyone on the list. Requests to modify filters can be considered, and of course you can be removed from the mailing list if you ask. Thank you to those of you who have already signed up.

61. The crisis in the dark matter problem becomes a historically unparalleled failure in the scientific method

This year, Pavel Kroupa was asked to hold a Golden Webinar in Astrophysics on the dark matter problem. This contribution provides the link to the recording of this presentation which has now become available on YouTube. In this presentation, Pavel Kroupa argues that the dark matter problem has developed to become the greatest crisis in the history of science, ever. This contribution also provides links to recordings available on YouTube of previous related talks by the same speaker from 2010 (the Dark Matter Debate with Simon White in Bonn) and 2013 (in Heidelberg). This might allow some insight into how the debate and the research field have developed over the past dozen or more years.

1) Golden Webinar: “From Belief to Realism and Beauty: Given the Non-Existence of Dark Matter, how do I navigate amongst the Stars and between Galaxies?”

On April 9th, 2021, Prof. Pavel Kroupa presented a talk in the Golden Webinars in Astrophysics series on “From Belief to Realism and Beauty: Given the Non-Existence of Dark Matter, how do I navigate amongst the Stars and between Galaxies?”. The talk is now available on Youtube:

The slides to the talk without the fictitious story can be downloaded here:

If you are interested in other talks presented during The Golden Webinars in Astrophysics series, you can find the record of those already presented on their Youtube Channel, and here is a list of upcoming talks. The Golden Webinars are provided as a free public service and have no registration fees.

2) The vast polar structures around the Milky Way and Andromeda

In November 2013, Prof. Pavel Kroupa presented “The vast polar structures around the Milky Way and Andromeda” in the Heidelberg Joint Astronomical Colloquium. In the talk he discussed the failures of the Standard model of cosmology and the implications for fundamental physics.

A blog entry from 2012 on the vast polar structure (VPOS) of satellite objects around the Milky Way can be found here.

3) Bethe-Kolloquium “Dark Matter: A Debate”

In November 2010, Prof. Simon White (Max Planck Institute of Astrophysics, Garching) and Prof. Pavel Kroupa (University of Bonn) debated on the concept and existence of dark matter during the Bethe Colloquium in Bonn. Their presentations and the subsequent debate are available here:

a) Presentations by Prof. White and Prof. Kroupa

Summary of both presentations:

b) The Debate

The German-language television channel 3sat produced a TV report on the Bethe Colloquium, which can be also found on Youtube (available only in German):

Part I

Part II

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

58. The tidal stability of Fornax cluster dwarf galaxies in Newtonian and Milgromian dynamics

(Guest post by Indranil Banik and Elena Asencio, August 2nd, 2021)

A directly-related presentation by Elena Asencio is available here:

The tidal stability of Fornax cluster dwarf galaxies in Newtonian and Milgromian gravity

The slides of the presentation can be downloaded here:

A large number of dwarf galaxies in the Fornax cluster (Figure 1) appear to be disturbed, most likely due to tides from the cluster gravity. In the standard cosmological model (ΛCDM) , the observable structure of the dwarfs is barely susceptible to gravitational effects of the cluster environment, as the dwarfs are surrounded by a dark matter halo. Because of this, it is very hard to explain the observations of the perturbed Fornax dwarfs in this theory. However, these observations can be easily explained in MOND, where dwarfs are much more susceptible to tides due to their lack of protective dark matter halos and the fact that they become quasi-Newtonian as they approach the cluster center due to the external field effect.

Figure 1: Fornax galaxy cluster. The yellow crosses mark all the objects identified in the Fornax deep survey (FDS) for this region of the sky, the black circles are masks for the spikes and reflection haloes, and the red crosses mark the objects that pass the selection criteria to be included in the FDS catalog. Image taken from Venhola et al. 2018.

The impact of tides on what the dwarfs look like is illustrated in Figure 2, which shows the fraction of disturbed galaxies as a function of tidal susceptibility η in ΛCDM and MOND, with η = 1 being the theoretical limit above which the dwarf would be unstable to cluster tides. Moreover, there is a lack of diffuse galaxies (large size and low mass) towards the cluster center. This is illustrated in Figure 3, which shows how at low projected separation from the cluster center, dwarfs of any given mass cannot be too large, but larger sizes are allowed further away. Figure 3 thus shows a clear tidal edge that cannot be explained by selection effects, since the survey detection limit would be a horizontal line at 1 on this plot such that dwarfs above it cannot be detected. Diffuse dwarf galaxies are clearly detectable, but are missing close to the cluster center. Another crucial detail in Figure 3 is that dwarfs close to the tidal edge are much more likely to appear disturbed, which is better quantified in Figure 2 in the rising fraction of disturbed galaxies with tidal stability η. The tidal edge is also evident in Figure 2 in that the dwarfs only go up to some maximum value of η, which should be close to the theoretical stability limit of 1. This is roughly correct in MOND, but not in ΛCDM.

Figure 2: Fraction of disturbed galaxies for each tidal susceptibility bin in MOND (red) and ΛCDM (blue). Larger error bars in a bin indicate that it has fewer dwarfs. The bin width of the tidal susceptibility η is 0.5 in MOND and 0.1 in ΛCDM (each data point is plotted at the center of the bin). Notice the rising trend and the maximum η that arises in each theory.

Figure 3: Projected distances of Fornax dwarfs to the cluster center against the ratio Re/rmax, where Re is the dwarf radius containing half of its total stellar mass, and rmax is the maximum Re at fixed stellar mass above which the dwarf would not be detectable given the survey sensitivity. The dwarfs are classified as “disturbed” (red) “undisturbed” (blue). The black dashed line shows a clear tidal edge – at any given mass, large (diffuse) dwarfs are present only far from the cluster center. This is not a selection effect, as the survey limit is a horizontal line at 1 (though e.g. some nights could be particularly clear and allow us to discover a dwarf slightly above this).

We therefore conclude that MOND and its corresponding cosmological model νHDM (see blog post “Solving both crises in cosmology: the KBC-void and the Hubble-Tension” by Moritz Haslbauer) is capable of explaining not only the appearance of dwarf galaxies in the Fornax cluster, but also other ΛCDM problems related to clusters such as the early formation of El Gordo, a massive pair of interacting galaxy clusters. νHDM also better addresses larger scale problems such as the Hubble tension and the large local supervoid (KBC void) that probably causes it by means of enhanced structure formation in the non-local universe. These larger scale successes build on the long-standing success of MOND with galaxy rotation curves (“Hypothesis testing with gas rich galaxies”). MOND also offers a natural explanation for the Local Group satellite planes as tidal dwarf galaxies (“Modified gravity in plane sight”), and has achieved many other successes too numerous to list here (see other posts). Given all these results, the MOND framework appears better suited than the current cosmological model (ΛCDM) to solve the new astrophysical challenges that keep arising with the increase and improvement of the available astronomical data, which far surpass what was known in 1983 when MOND was first proposed.

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.

43. Pavel Kroupa on ” The vast polar structures around the Milky Way and Andromeda “

In case you, like me, have missed Pavel Kroups’s recent talk at the Joint Astronomical Colloquium in Heidelberg, you now have the opportunity to watch a movie of the event and download the slides. The movie is quite long (more than an hour), but it is worth watching it to the end. While the talk is titled “The vast polar structures around the Milky Way and Andromeda”, Pavel talks about much more, starting with tidal dwarf galaxies and ending with a discussion of indications for an alternative model of gravity.

This presentation is very similar and in most parts identical to Pavel’s presentations held at Monterey at the conference “Probes of Dark Matter on Galaxy Scales” and in Durham at the “Ripples in the Cosmos” conference. The latter talk resulted in quite a discussion on Peter Coles’ (aka Telescoper) blog “In the Dark”, following his criticism of Pavel’s talk as being “poorly argued and full of grossly exaggerated claims”. The video of a very similar presentation now offers everybody the opportunity to develop their own opinion on the issue. Given the numerous questions Pavel got during his talk and afterwards, people must have thought that it was worth the effort to argue with him, in contrast to Peter’s opinion.


See the overview of topics in The Dark Matter Crisis.

39. Question E: The Dark Matter Crisis continues: on the difficulties of communicating controversial science

(Continuation of the series A-E)

There has been an unsuccessful attempt to close down The Dark Matter Crisis. Here is the story (and an email by Jim Peebles): UPDATE: The guest post is now online.

As regular readers of our blog know, and first-time readers may be able to guess from this blog name, Pavel and I mostly write about the problems and shortcomings of the dark matter hypothesis. One aspect of our research is to test dark matter models on cosmologically small scales such as the Local Group of galaxies. Over the past years, our research and those of others has revealed that numerous model expectations of the dark matter hypothesis are not met by observations. This led us to the conclusion that we should consider a paradigm shift in how we understand the dark matter phenomenon. Maybe, we thought, a modification of the laws of gravity, one possible approach being Mordehai Milgrom’s MOdified Newtonian Gravity (MOND), could solve these issues.

Doing research that identifies shortcomings in a widely-held assumption and that is skeptical of a mainstream hypothesis is certainly a very interesting and rewarding endeavor for a scientist. It is closely connected to the fundamental scientific method of falsification and holds potential for groundbreaking discoveries. However, working on a controversial scientific topic also has its downsides. For one, papers criticizing basic assumptions are less attractive to be cited in mainstream publications. And before publication, controversial science already faces a more challenging peer-review process. For example Ashutosh Jogalekar explains in his blog The Curious Wavefunction:

“[…] reviewers under the convenient cloak of anonymity can use the system to settle scores, old boys’ clubs can conspire to prevent research from seeing the light of day, and established orthodox reviewers and editors can potentially squelch speculative, groundbreaking work.”

In addition to these ‘formal’ scientific interactions via academic publishers, there is also communication amongst scientists. For instance, early PhD students, who are still in the process of learning about the business of doing science, may be looking for advice from mentors and other more experienced scientists. Unfortunately, when the talk comes to controversial areas of science, students are often discouraged from getting involved in non-mainstream research (note, however, Avi Loeb‘s opposite advice). This begins with the commonly expressed belief that such research might “hurt your career”, but sometimes even more direct warnings are made. For example, a few years ago a professor told me that he would never hire someone who has published even a paper on MOND. A fellow PhD student got a similar piece of “advice” while visiting a different university, where one scientist advised him that he should only publish results which are negative for MOND, but nothing in support of it.

For people who are just starting in science, especially, such comments may be alarming. Graduate students do not yet know much about the job market. They therefore tend to believe what the ‘old boys’ tell them. To researchers who have a bit more experience, such warnings are often incomprehensible since they know by then (if they didn’t already initially) that it is entirely unscientific to withhold research results that do not fit a pre-determined picture.

The difficulties of working in a controversial field of research do not stop here. Communicating such science to a wider audience can also result in problems. While the public is generally very interested in the challenges faced by prevailing theories, there are difficulties to overcome. One of them is the question of how to differentiate completely unscientific things (the paranormal, creationism, …), from actual, albeit controversial, science.

A promising approach to overcome this difficulty is to discuss controversial science publicly. This way, the public can follow and be part of the debate, learn that arguments are backed by references to peer-reviewed research and see that hypotheses need to be tested through comparison with observational data—essentially the public gets to view the scientific process as it is applied in any branch of research. By demonstrating that scientists stick to facts, respond to opposing arguments and do not resort to emotionally driven rhetoric, we can adequately demonstrate the strengths of science.

The strength of the scientific method over dogmatic beliefs should always prevail in order to be able to contemplate the possibility of paradigm shifts. This is indeed a complex idea to explain, and presenting research results as absolute truth is something scientists should be prepared not to do. Unfortunately, this is not always the case. Sometimes, some people profess the ideas they subscribe to as the scientific or absolute truth. Such claims of absolute truth completely contort the nature of science. It is certainly going too far when science bloggers, in an attempt to protect their preferred mainstream theory, demand that a scientists’ blog be closed because their views differ. Scientists who publish their research in scientific journals, who go through the peer-review process and who in the end publish slightly unorthodox but nonetheless valuable ideas, should not be censored from the science blogosphere.

Unfortunately, this is what happened to our blog, The Dark Matter Crisis.

A popular science blogger demanded that SciLogs.com discontinue our blog and has, for a short time, succeeded. We would like to use this occurrence as an example of the reactions and difficulties faced when doing online communication of controversial science topics. The incident demonstrates why debate in science must be based on objective facts and not be driven by personal opinions. It illustrates the dangers of mixing scientific convictions with personal goals and emotions.

Why we started the Dark Matter Crisis blog

In late 2009, Pavel and I wrote an invited article for the German popular science magazine Spektrum der Wissenschaft about dwarf galaxies as tests of cosmology. During the process, Spektrum asked us to also start an accompanying science blog on SciLogs.eu, to provide a place for discussions that might arise due to the controversial nature of our work. We were very hesitant initially, but after talking to students and colleagues we agreed to start a blog. What convinced us to blog was the possibility to get in touch with readers, which would allow immediate feedback and discussions, and the ability to continuously provide current information about our active field of research. When the Spektrum article was published in July 2010, the blog The Dark Matter Crisis went online, too. We blogged on it for about two years, and then agreed to move The Dark Matter Crisis to the new SciLogs.com network. The first article on the SciLogs.com blog was published on January 3, 2013.

The discontinuation of The Dark Matter Crisis

On January 28, we received an email from the SciLogs.com community manager. The email informed us that our blog had been discontinued and that we would no longer be able to update it, although the blog’s archive would remain on the site. The short explanation provided was that the “thesis pushed by The Dark Matter Crisis is now overwhelmingly considered incorrect by the scientific community and as such cannot be considered sound enough to be promulgated by SciLogs.com”.

As we blog mostly about our own and related research, such a justification not only attacks our blogging but also hits at the very heart of our scientific work. Consequently, the first reaction to this email was shock, quickly followed by many questions. Which “theses pushed” by our blog “is now overwhelmingly considered incorrect”? That the currently prevailing hypothesis of cold dark matter has serious problems? This certainly is not considered overwhelmingly incorrect, as there are many scientists working on addressing these problems, both within the framework of standard cosmology (e.g. Mutch et al. 2013, Fouquet et al. 2012), as well as by modifying it (e.g. Lovell et al. 2012, Macció et al. 2012) or even by taking a completely different approach (e.g. Famaey & McGaugh 2012). Also, we were invited to start the blog because of the controversial nature of this topic.

Furthermore, at the time of discontinuation, the SciLogs.com version of The Dark Matter Crisis had only one blog post thus far. The sole post presents the recent discovery of a co-rotating plane of satellite galaxies around Andromeda reported in Ibata et al. (2013, Nature). It discusses possible implications which are right now actively debated among scientists. In fact, that blog post was, as far as I can tell, the only one on the web to provide a detailed explanation as to why the Nature paper might be a threat to Einstein’s theory of gravitation, which was explicitly alluded to by numerous publications, but explained by none (most articles in classical media focussed on the 15-year-old co-author of the study). Surely, it is not the aim of SciLogs.com, as a service to provide information to the public, to censor a blog that was communicating science to the public. Therefore, we concluded that this blog post could not have been the reason for the discontinuation.

But even expanding the scope to the old SciLogs.eu blog, we cannot see where we push a thesis which is not scientifically sound. Our blog posts are full of references to peer-reviewed publications. While we often discuss non-mainstream interpretations, we always remain within the realm of science and discuss an active field of research. For example, we frequently mention alternatives to dark matter which try to explain the missing mass phenomenon by non-Newtonian gravity laws. As an active scientist in this field, one can certainly not say that this is not scientifically sound and “overwhelmingly considered incorrect”. Just looking at the number of citations to the first paper about MOND by Milgrom, shows a citation count that has been constantly rising over the last few years and is currently at 1066.

So, what might have triggered the decision to discontinue our blog?

What Who has triggered our blog’s discontinuation?

Digging around on Twitter revealed several interesting discussions which were obviously related to the discontinuation of The Dark Matter Crisis. It turns out that a former-scientist-turned-blogger, who had spent a few years doing research in cosmology (publishing 5 first-author papers with now 88 citations), demanded the discontinuation.

The blogger (@StartsWithABang) contacted @scilogscom on January 24 by replying to a 15-day old tweet that announced our blog’s move to the new domain. He tweeted “Bummed that @scilogscom is in the business of promoting contrarian scientist viewpoints.”, and asks the SciLogs.com community manager (@notscientific) “[Why] are you allowing @scilogscom to promote contrarian voices that undermine public understanding of [science]?”, adding “You have taken on “Dark Matter Crisis” blog, whose mission is to undermine all of physical cosmology & promote MOND.”

The two agreed to discuss the issue via email, with the blogger adding that he was “*personally* worried that you are promoting clicks & false controversy over quality science content”, and states that he is “very, VERY disappointed about this move that @scilogscom has made”.

By now the SciLogs.com community manager has explained to us what happened after these tweets. He and the publishing director responsible for SciLogs.com unfortunately assumed that the blogger’s criticism was justified. They decided to close our blog without conferring with others or asking us for a statement. After we complained about the discontinuation, they performed an internal investigation, which involved reaching out to astrophysicists and other people, and have realized that discontinuing our blog was a big mistake. We attribute SciLogs.com’s poor judgement to two factors: neither the community manager nor the publishing director has an (astro)physical background, it was the first time that SciLogs.com had experienced an attack against one of its blogs.

So, the result was that four days after the tweets about The Dark Matter Crisis were posted, our blog was discontinued. Interestingly, only a few hours later the blogger who complained about our blog tweeted: “Shout out to the @SciLogscom  team, esp. @notscientific  and @laurawheelers, for stepping up & vetting their #science blogs for quality!”. (@laurawheelers was not involved in the decision to discontinue our blog. She only referred @StartsWithABang to SciLogs.com’s community manager.) @StartsWithABang added “They are storing the archives, but the blog is inactive and will not be continued”. While until then this situation was only an example of one blogger attacking our blog and our research with contorted accusations, the reactions of a few other Twitter users  were disheartening.  Some of them, science communicators and even an active astronomer, welcomed the blog’s discontinuation. One would have hoped that they would see the value of our science blog, regardless of their own opinions on the controversial topic we blog about.

Some slightly earlier attacks

The incident seems to be related to a recently published paper by us: Kroupa, Pawlowski & Milgrom (2012). When the paper appeared on the preprint server arXiv on January 18, this lead to a short discussion on Twitter, during which the same blogger who would later led to the short-timed discontinuation of our blog, made some pretty harsh accusations against “the MOND zealots”, whom he seems to call a mix of skeptics and liars and deniers who trot out misinformation and undermine confidence in science. In reaction to our paper, he published a blog post in which he claims to rule out MOND with one graph. Unfortunately, his blog post does not address any of the issues discussed in our recent paper, nor does it address those discussed in many other papers over the recent years.

In reaction to the accusations and contorted depiction of our research, I submitted a comment to the blog post. It asks for a clarification of the accusations and tries to start an objective discussion. There was no reason to censor it. Nevertheless, the comment was not published the first time, so I submitted it again the following day. Again, it was not published. I then decided to ignore the issue and the blogger in the future, as a factual debate seemed to be undesired and emotion-laden quarreling on the web is a waste of time. However, as our blog was actively attacked only a few days later by that very same blogger, the comment is being published here for transparency:

“When I understand your Twitter tweets from yesterday correctly, you think that “Kroupa and some of the other MOND zealots” are, at least to a certain extend, liars and deniers who “trot out misinformation & undermine confidence in science”. Is this what you were saying or did I misunderstand something? My honest opinion is that this would be unnecessarily aggressive, insulting, unprofessional and unscientific as it does not help to establish a well-founded discussion of the scientific issues.

The fact that you do not address the numerous problems of LCDM, many of which are mentioned in the recent paper, does not help shaping a discussion. In your blog post, you base your argumentation on only one problem of MOND: the the strong oscillations in the matter power spectrum. However, according to e.g. Famaey & McGaugh (2012), this problem is not as clear-cut as you claim. They write: “the non-linearity of MOND can lead to mode mixing that washes out the initially strong signal by z = 0”, and even suggests a more robust test.

More fundamentally, basic logic tells us that falsifying one hypothesis does not provide information about the validity of an opposing one. Just to give an example: Disproving that the world is a disk does not prove that the guy who is claiming that the earth is donut-shaped is right. As it turns out, the earth is neither a disk nor a donut, but essentially a sphere. Nevertheless, you jump from this graph to a conclusion about “MOND, MOG, TeVeS, or any other dark-matter-free alternative”. In addition, if you would consider the numerous failures of the LCDM model in a similar way like those of MOND, according to your argumentation we would have to give up on both, modified gravity theories and dark matter.

As a last note, I’d like to point out that in our recent paper we do not present MOND as the final answer. The fact that there is not a single “MOND”, but many different attempts to construct a full theory of modified gravity (see Sect. 6) already demonstrates that more work needs to be done. But in order to search for a solution of the many problems LCDM has on scales of many Mpc and below (where MOND is very successful), scientists should be encouraged to investigate this possibility. That is what a paradigm shift is, in my opinion: acknowledging that there are problems and being open-minded for new or alternative explanations, without hiding the problems that these alternatives may themselves face. As we acknowledge in the paper, mass discrepancies in galaxy clusters and building a consistent cosmology are real challenges for MOND, but there exist more or less convincing answers to these problems in the various effective covariant theories that have been proposed to date (see e.g. the list of theories in Famaey & McGaugh 2012 and their Section 9.2). Even if most of these tentative new explanations will turn out to be unsuccessful, I am sure there still is much to learn about the Universe. We have made this clear in the final sentences of our paper, too: “Understanding the deeper physical meaning of MOND remains a challenging aim. It involves the realistic likelihood that a major new insight into gravitation will emerge, which would have significant implications for our understanding of space, time and matter.”

So, I don’t think there is any lying, denying or misinformation involved on part of us as active scientists. It is just that the Universe is a hard nut to crack. Having the strength to admit that none of the current models are the final answer should in fact increase our confidence in science.”

It is ironic that in a comment on this very blog post, the blogger suggests to a critical reader that if he does not like his way of blogging, the reader could get his own blog. Only a few days later the blogger seems to have worked towards the discontinuation of our blog …

The aftermath and an upcoming guest post

After being informed about the discontinuation and after having discovered the background story on Twitter, we got in touch with the staff responsible for SciLogs.com. As mentioned before, they quickly realized that the discontinuation of The Dark Matter Crisis was a mistake. After discussing the issue with Richard Zinken, the publishing director of Spektrum der Wissenschaft (who is also responsible for the SciLogs.com blog network), he and the community manager apologized for the incident. We have accepted the apology and understand that mistakes can happen. During the last weeks, we worked together with the SciLogs.com team, thinking about what would be the best way to re-open the blog and how to handle the recent events in a constructive way. Together with Richard and the community manager we developed this blog post on the difficulties faced when communicating controversial research.

Together, we also decided to invite a guest blogger to The Dark Matter Crisis, preferably a cosmologist who is skeptical about our views. We hope that this helps to shape the debate and keep it at a scientific level, in contrast to the seemingly emotionally driven attacks which misshape the public’s view of how science handles controversial research. We have asked a few colleagues for such posts, and are content that one experienced scientist has agreed to act as our guest blogger. We know that he is well-respected in the field. His guest post will go online tomorrow.

UPDATE (March 09 2013): In a recent blog post, supposedly trying to shut off people working on dark matter alternatives forever, the blogger attacking us wrote: “Courtesy of Scott Dodelson, I present to you the one graph that incontrovertibly settles the matter.” We now rather offer you a guest blog post on that matter by … Scott Dodelson.

In the meantime, Jim Peebles, Albert Einstein Professor Emeritus of Science at Princeton University, gave us his explicit permission to publish the full, unedited email in which he explains that he would not like to be our guest blogger. We would like to thank him for this and, given our recent experience, fully understand that he prefers to not start blogging:

“Hello Pavel

Sorry for the delay. I have been thinking about your email, and have decided that I will not contribute a commentary on your situation.

I agree with many of your points. The behavior of [SciLogs.com] is silly; this is not the way of science. As you indicate, the community is remarkably optimistic about galaxy formation within the standard LCDM cosmology. I consider this an example of the human herd instinct. With you I distrust talk of precision cosmology; we are still seeking an accurate cosmology. But I think we differ on the weight of evidence for LCDM. I am deeply impressed by the variety of independent lines of evidence that point to LCDM, and conclude that the case for LCDM as a useful approximation to reality on the scale of the Hubble length is about a good as one gets in physical science. No one can prove that there is not another cosmology without dark matter that fits the data as well as LCDM, and no one can prove that there is not another theory that works as well as quantum mechanics. I expect we both put the odds on the latter as too low to matter. I feel close to the same about the former.

You are entirely entitled to take the approach I see in your blog, but I do not want to state my opinion on your blog. I don’t want to take up [blogging] anywhere!

Regards, Jim”

In addition, you can have a look at a recent article in New Scientist: “Dark matter rival boosted by dwarf galaxies”. The article mentions James Binney, from the University of Oxford, who says that he “believes that some sort of MOND-like behaviour may manifest itself on small scales”, while Avi Loeb, of Harvard University, being skeptical about MOND, nevertheless states that: “The theory deserves a lot of respect.”

We believe that all astronomers, whether skeptical or not of our controversial research, are able to agree with Loeb’s statement, and it is in this spirit that we would like to continue our endeavours in online science communication.

By Marcel S. Pawlowski and Pavel Kroupa  (08.03.2013): “The Dark Matter Crisis continues: on the difficulties of communicating controversial science” on SciLogs. See the overview of topics in The Dark Matter Crisis.