A Blog About the Science and Sociology of Cosmology and Dark Matter

Case Western Reserve University

Stacy McGaugh

This is what I hope will be the final installment in a series of posts describing the results published in McGaugh et al. (2024). I started by discussing the timescale for galaxy formation in LCDM and MOND which leads to different and distinct predictions. I then discussed the observations that constrain the growth of stellar mass over cosmic time and the related observation of stellar populations that are mature for the age of the universe.

Kinematics suggest large masses for high redshift galaxies

This post continues the series summarizing our ApJ paper on high redshift galaxies. To keep it finite, I will focus here on the growth of stellar mass. The earlier post discussed what we expect in theory. This depends both on mass assembly (slow in LCDM, fast in MOND), how the assembled mass is converted into stars, and how those stars shine in light we can detect.

Measuring the growth of the stellar mass of galaxies over cosmic time

Mass is a basic quantity. How much stuff does an astronomical object contain?

Galaxy Stellar and Halo Masses: tension between abundance matching and kinematics

When I wrote about Nobel prizes a little while back, I did not expect to return to the subject.

A Nobel prize in physics for something that is not physics

The time is approaching when Nobel prizes are awarded. This inevitably leads to a lot of speculation and chattering rumor. Last year one publication, I think it was

 Physics Today

, went so far as to publish a list of things various people thought should be recognized. This aspirational list was led, of course, by dark matter.

Nobel prizes that were, that might have been, and others that have not yet come to pass

I have said I wasn’t going to attempt to teach an entire graduate course on galaxy dynamics in this forum, and I’m not. But I can give some pointers for those who want to try it for themselves. It also provides some useful context for fans of Deur’s approach. The go-to textbook for this topic is

 Galactic Dynamics

by Binney &amp; Tremaine. The first edition was published in 1987, conveniently when I switched to grad school in astronomy.

Progressive Approximations in Mass Modeling

Given recent developments in the long-running hunt for dark matter and the difficulty interpreting what this means, it seems like a good juncture to re-up* this:  The history of science is a decision tree. Vertices appear where we must take one or another branching. Sometimes, we take the wrong road for the right reasons. A good example is the geocentric vs. heliocentric cosmology.

Decision Trees &amp; Philosophical Blunders

In the previous post, we discussed how lensing data extend the Radial Acceleration Relation (RAR) seen in galaxy kinematics to very low accelerations. Let’s zoom out now, and look at things at higher accelerations and from a historical perspective.

The Radial Acceleration Relation starting from high accelerations

Flat rotation curves and the Baryonic Tully-Fisher relation (BTFR) both follow from the Radial Acceleration Relation (RAR). In Mistele et al. (2024b) we emphasize the exciting aspects of the former; these follow from the RAR in the Mistele et al. (2024a). It is worth understanding the connection. First, the basic result:  The RAR of weak lensing extends the RAR from kinematics to much lower accelerations.

The Radial Acceleration Relation to very low accelerations

“Galaxies are made of stars.” Bob Schommer, quoted by Dave Silva in his dissertation on stellar populations This tongue-in-cheek quote is a statement of the obvious, at least for the 90+ years since Hubble established that galaxies are stellar systems comparable to and distinct from the Milky Way.

This tongue-in-cheek quote is a statement of the obvious, at least for the 90+ years since Hubble established that galaxies are stellar systems comparable to and distinct from the Milky Way. There’s interstellar gas and dust too, and I suppose for nearly half that time, people have also thought galaxies to be composed of dark matter. But you can’t see that;

A Stellar Population Mystery in a Low Surface Brightness Galaxy

That rotation curves become flat at large radii is one of the most famous results in extragalactic astronomy. This had been established by Vera Rubin and her collaborators by the late 1970s. There were a few earlier anecdotal cases to this effect, but these seemed like mild curiosities until Rubin showed that the same thing was true over and over again for a hundred spiral galaxies.

Rotation curves: still flat after a million light-years

I have been spending a lot of time lately writing up a formal paper on high redshift galaxies, so haven’t had much time to write here. The paper is a lot more involved than I told you so, but yeah, I did. Repeatedly. I do have a start on a post on self-interacting dark matter that I hope eventually to get back to. Today, I want to give a quick note about the MHONGOOSE survey. But first, a non-commercial interruption.

The MHONGOOSE survey of atomic gas in and around galaxies

We will return to our usual programming shortly. But first, a few words on the eclipse experience last Monday.

 
 It. Was. Awesome
 

. That’s a few words, so Mission Accomplished. That’s really all I had planned to say. However, I find I am still giddy from this momentous event, so will share my experience of the day, such as words can humbly convey.

The Eclipse Experience

A common refrain I hear is that MOND works well in galaxies, but not in clusters of galaxies. The oft-unspoken but absolutely intended implication is that we can therefore dismiss MOND and never speak of it again. That’s silly. Even if MOND is wrong, that it works as well as it does is surely telling us something.

Clusters of galaxies ruin everything

To start the new year, I provide a link to a discussion I had with Simon White on Phil Halper’s YouTube channel:  In this post I’ll say little that we don’t talk about, but will add some background and mildly amusing anecdotes. I’ll also try addressing the one point of factual disagreement. For the most part, Simon &amp; I entirely agree about the relevant facts; what we’re discussing is the interpretation of those facts.

Discussion of Dark Matter and Modified Gravity

People often ask me of how “perfect” MOND has to be. The short answer is that it agrees with galaxy data as “perfectly” as we can perceive – i.e., the scatter in the credible data is accounted for entirely by known errors and the expected scatter in stellar mass-to-light ratios. Sometimes it nevertheless looks to go badly wrong. That’s often because we need to know both the mass distribution and the kinematics perfectly.

How things go mostly right or badly wrong

This post is adopted from a web page I wrote in 2008, before starting this blog. It covers some ground that I guess is now historic about things that were known about WIMPs from their beginnings in the 1980s, and experimental searches therefore. In part, I was just trying to keep track of experimental limits, with updates added as noted since the first writing.

A lengthy personal experience with experimental searches for WIMPs

Taking a break from galaxies and cosmology, I’d like to post a little praise of NASA for safely returning a piece of an asteroid to Earth. One of the amazing things to me about astronomy &amp; astrophysics is that we have learned how to decipher the composition of distant stars and gas clouds by observing their spectra. I worked on this early in my career and retain an interest in the cosmic abundance of the elements.

OSIRIS-REx returns safely

Continuing from last time, let’s compare recent rotation curve determinations from Gaia DR3:  These are different analyses of the same dataset. The Gaia data release is immense, with billions of stars. There are gazillions of ways to parse these data. So it is reasonable to have multiple realizations, and we shouldn’t expect them to necessarily agree perfectly: do we look exclusively at K giants? A stars?

Recent Developments Concerning the Gravitational Potential of the Milky Way.&nbsp;II. A Closer Look at the Data

Alert reader Dan Baeckström recently asked about NGC 1277, as apparently some people have been making this out to be some sort of death knell for MOND.  My first reaction was NGC who? There are lots of galaxies in the New General Catalog (new in 1888, even then drawing heavily on earlier work by the Herschels). I’m well acquainted with many individual galaxies, and can recall many dozens by name, but I do not know every single thing in the NGC.

Is NGC 1277 a problem for MOND?

I’m back from the meeting in St. Andrews, and am mostly recovered from the jet lag and the hiking (it was hot and sunny, we did not pack for that!) and the driving on single-track roads like Mr. Toad. The A835 north from Ullapool provides some spectacular mountain views, but the A837 through Rosehall is more perilous carnival attraction than well-planned means of conveyance. As expected, the most contentious issue was that of wide binaries.

The MOND at 40 conference

Last time, I commented on the developing situation with binary stars as a test of MOND. I neglected to enable comments for that post, so have done so now. Indranil Banik has shared his perspective on wide binaries in a talk on the subject that is available on Youtube, included below. Indranil and his collaborators are not seeing a MOND effect in wide binaries. Others have, as I discussed in the previous post.

Commentary on Wide Binaries

In the previous post, I wrote about a candidate parent relativistic theory for MOND that could fit the acoustic power spectrum of the cosmic microwave background (CMB). That has been a long time coming, and probably is not the end of the road. There is a long and largely neglected history behind this, so let’s rewind a bit. I became concerned about the viability of the dark matter paradigm in the mid-1990s.

A pre-history of the prediction of the amplitude of the second peak of the cosmic microwave background

I want to start by thanking those of you who have contributed to maintaining this site. This is not a money making venture, but it does help offset the cost of operations. The title is not related to this, but rather to a flood of papers addressing the questions posed in recent posts. I was asking last time “take it where?” because it is hard to know what cosmology under UT will look like. In particular, how does structure formation work?

Ask and receive

Imagine if you are able that General Relativity (GR) is correct yet incomplete. Just as GR contains Newtonian gravity in the appropriate limit, imagine that GR itself is a limit of some still more general theory that we don’t yet know about. Let’s call it Underlying Theory (UT) for short.

Imagine if you can

Cosmology is challenged at present by two apparently unrelated problems: the apparent formation of large galaxies at unexpectedly high redshift observed by JWST, and the tension between the value of the Hubble constant obtained by traditional methods and that found in multi-parameter fits to the acoustic power spectrum of the cosmic microwave background (CMB).   Maybe they’re not unrelated?

Early Galaxy Formation and the Hubble Constant Tension

Something that Sabine Hossenfelder noted recently on Twitter resonated with me:  This is a very real problem in academia, and I don’t doubt that it is a common feature of many human endeavors. Part of it is just that people don’t know enough to know what they don’t know. That is to say, so much has been written that it can be hard to find the right reference to put any given fever dream promptly to never-ending sleep.

Let’s just ignore it

Kuhn noted that as paradigms reach their breaking point, there is a divergence of opinions between scientists about what the important evidence is, or what even counts as evidence. This has come to pass in the debate over whether dark matter or modified gravity is a better interpretation of the acceleration discrepancy problem. It sometimes feels like we’re speaking about different topics in a different language.

What we have here is a failure to communicate

A Philosophical Approach to MOND

is a new book by David Merritt. This is a major development in the both the science of cosmology and astrophysics, on the one hand, and the philosophy and history of science on the other. It should be required reading for anyone interested in any of these topics.

A Philosophical Approach to MOND

We are visual animals. What we see informs our perception of the world, so it often helps to make a sketch to help conceptualize difficult material. When first confronted with MOND phenomenology in galaxies that I had been sure were dark matter dominated, I made a sketch to help organize my thoughts.

Artistic license with the dark matter tree

The dominant paradigm for dark matter has long been the weakly interacting massive particle (WIMP). WIMPs are hypothetical particles motivated by supersymmetry. This is well-posed scientific hypothesis insofar as it makes a testable prediction: the cold dark matter thought to dominate the cosmic mass budget should be composed of a particle with a mass in the neighborhood of 100 GeV that interacts via the weak nuclear force – hence the name.

The Angel Particle

The distance scale is fundamental to cosmology. How big is the universe? is pretty much the first question we ask when we look at the Big Picture. The primary yardstick we use to describe the scale of the universe is Hubble’s constant: the H

 0

in

 v = H
 
 0
 
 D

that relates the recession velocity (redshift) of a galaxy to its distance. More generally, this is the current expansion rate of the universe.

The Hubble Constant from the Baryonic Tully-Fisher Relation

I am a white American male. As such, I realize that there is no way for me to grasp and viscerally appreciate all the ways in which racism afflicts black Americans. Or, for that matter, all the ways in which sexism afflicts women. But I can acknowledge that these things exist. I can recognize when it happens. I’ve seen it happen to others, both friends and strangers. I can try not to be part of the problem.

The Other

One does not simply form stars from 100% of the available baryons.

There has been a veritable feeding frenzy going on with the first JWST data. This is to be expected. Also to be expected is that some of these early results will ultimately prove to have been premature. So –

 caveat emptor!

That said, I want to highlight one important aspect of these early results, there being too many to do all them all justice.

An early result from JWST

The fine-tuning problem encountered by dark matter models that I talked about last time is generic. The knee-jerk reaction of most workers seems to be “let’s build a more sophisticated model.” That’s reasonable – if there is any hope of recovery. The attitude is that dark matter has to be right so something has to work out. This fails to even contemplate the existential challenge that the fine-tuning problem imposes.

Cosmic whack-a-mole

When we look up at the sky, we see stars. Stars are the building blocks of galaxies; we can see the stellar disk of the galaxy in which we live as the vault of the Milky Way arching across the sky. When we look beyond the Milky Way, we see galaxies. Just as stars are the building blocks of galaxies, galaxies are the building blocks of the universe.

Primer on Galaxy Properties

There is a rule of thumb in scientific publication that if a title is posed a question, the answer is no.  It sucks being so far ahead of the field that I get to watch people repeat the mistakes I made (or almost made) and warned against long ago. There have been persistent claims of deviations of one sort or another from the Baryonic Tully-Fisher relation (BTFR). So far, these have all been obviously wrong, for reasons we’ve discussed before.

Are there credible deviations from the baryonic Tully-Fisher relation?

In science, all new and startling facts must encounter in sequence the responses 1. It is not true! 2. It is contrary to orthodoxy. 3. We knew it all along. Louis Agassiz (circa 1861) This expression exactly depicts the progression of the radial acceleration relation.

This expression exactly depicts the progression of the radial acceleration relation. Some people were ahead of this curve, others are still behind it, but it quite accurately depicts the mass sociology. This is how we react to startling new facts. For quotation purists, I’m not sure exactly what the original phrasing was.

A brief history of the Radial Acceleration Relation

Predictive power in science isn’t everything. It’s the only thing.

This is a wise truth that has often been poorly interpreted. I despise some of the results that this sports quote has had in American culture. It has fostered a culture of bad sportsmanship in some places: an acceptance, even a dictum, that the ends justify the means – up to and including cheating, provided you can get away with it.  Winning every time is an impossible standard.

Predictive Power in Science

It’s early in the new year, so what better time to violate my own resolutions? I prefer to be forward-looking and not argue over petty details, or chase wayward butterflies. But sometimes the devil is in the details, and the occasional butterfly can be entertaining if distracting. Today’s butterfly is the galaxy AGC 114905, which has recently been in the news.

The curious case of AGC 114905: an isolated galaxy devoid of dark matter?

An important issue in science is what’s right and what’s wrong. Another is who gets credit for what. The former issue is scientific while the second is social. It matters little to the progress of science who discovers what. It matters a lot to the people who do it. We like to get credit where due. Nowadays, Fritz Zwicky is often credited with the discovery of dark matter for his work on clusters of galaxies in the 1930s.

A few of Zwicky’s rants

A surprising and ultimately career-altering result that I encountered while in my first postdoc was that low surface brightness galaxies fell precisely on the Tully-Fisher relation. This surprising result led me to test the limits of the relation in every conceivable way. Are there galaxies that fall off it? How far is it applicable?

Super spirals on the Tully-Fisher relation

We have a new paper on the arXiv. This is a straightforward empiricist’s paper that provides a reality check on the calibration of the Baryonic Tully-Fisher relation (BTFR) and the distance scale using well-known Local Group galaxies. It also connects observable velocity measures in rotating and pressure supported dwarf galaxies: the flat rotation speed of disks is basically twice the line-of-sight velocity dispersion of dwarf spheroidals.

Leveling the Playing Field of Dwarf Galaxy Kinematics

I’ve been busy. There is a lot I’d like to say here, but I’ve been writing the actual science papers. Can’t keep up with myself, let alone everything else. I am prompted to write here now because of a small rant by Maury Goodman in the neutrino newsletter he occasionally sends out. It resonated with me.   First, some context. Neutrinos are particles of the Standard Model of particle physics.

The neutrino mass hierarchy and cosmological limits on their mass

Britain and America are two nations divided by a common language. attributed to George Bernard Shaw Physics and Astronomy are two fields divided by a common interest in how the universe works. There is a considerable amount of overlap between some sub-fields of these subjects, and practically none at all in others.

attributed to George Bernard Shaw  Physics and Astronomy are two fields divided by a common interest in how the universe works. There is a considerable amount of overlap between some sub-fields of these subjects, and practically none at all in others. The aims and goals are often in common, but the methods, assumptions, history, and culture are quite distinct.

Two fields divided by a common interest

This Thanksgiving, I’d highlight something positive. Recently, Bob Sanders wrote a paper pointing out that gas rich galaxies are strong tests of MOND. The usual fit parameter, the stellar mass-to-light ratio, is effectively negligible when gas dominates. The MOND prediction follows straight from the gas distribution, for which there is no equivalent freedom.

Hypothesis testing with gas rich galaxies

Like the Milky Way, our nearest giant neighbor, Andromeda (aka M31), has several dozen dwarf satellite galaxies. A few of these were known and had measured velocity dispersions at the time of my work with Joe Wolf, as discussed previously. Also like the Milky Way, the number of known objects has grown rapidly in recent years – thanks in this case largely to the PAndAS survey.

Dwarf Satellite Galaxies. III. The dwarfs of Andromeda

A quick note to put the acceleration discrepancy in perspective. The acceleration discrepancy, as Bekenstein called it, more commonly called the missing mass or dark matter problem, is the deviation of dynamics from those of Newton and Einstein. The quantity D is the amplitude of the discrepancy, basically the ratio of total mass to that which is visible.

Astronomical Acceleration Scales

The Milky Way Galaxy in which we live seems to be a normal spiral galaxy. But it can be hard to tell. Our perspective from within it precludes a “face-on” view like the picture above, which combines some real data with a lot of artistic liberty. Some local details we can measure in extraordinary detail, but the big picture is hard. Just how big is the Milky Way?

A Precise Milky Way

There are two basic approaches to cosmology: start at redshift zero and work outwards in space, or start at the beginning of time and work forward. The latter approach is generally favored by theorists, as much of the physics of the early universe follows a “clean” thermal progression, cooling adiabatically as it expands.

The next cosmic frontier: 21cm absorption at high redshift

As soon as I wrote it, I realized that the title is much more general than anything that can be fit in a blog post. Bekenstein argued long ago that the missing mass problem should instead be called the acceleration discrepancy, because that’s what it is – a discrepancy that occurs in conventional dynamics at a particular acceleration scale. So in that sense, it is the entire history of dark matter.

A brief history of the acceleration discrepancy

Virginia, your little friends are wrong. They have been affected by the skepticism of a skeptical age. They do not believe except they see. They think that nothing can be which is not comprehensible by their little minds. All minds, Virginia, whether they be men’s or children’s, are little.

Yes, Virginia, there is a Dark Matter

It has been proposal season for the Hubble Space Telescope, so many astronomers have been busy with that. I am no exception. Talking to others, it is clear that there remain many more excellent Hubble projects than available observing time. So I haven’t written here for a bit, and I have other tasks to get on with. I did get requests for a report on the last conference I went to, Beyond WIMPs: from Theory to Detection.

Critical Examination of the Impossible

A recent paper in Nature by Genzel et al. reports declining rotation curves for high redshift galaxies. I have been getting a lot of questions about this result, which would be very important if true. So I thought I’d share a few thoughts here. Nature is a highly reputable journal – in most fields of science. In Astronomy, it has a well earned reputation as the place to publish sexy but incorrect results.

Declining Rotation Curves at High Redshift?

In 1984, I heard Hans Bethe give a talk in which he suggested the dark matter might be neutrinos. This sounded outlandish – from what I had just been taught about the Standard Model, neutrinos were massless. Worse, I had been given the clear impression that it would screw everything up if they did have mass. This was the pervasive attitude, even though the solar neutrino problem was known at the time. This did not compute!

Neutrinos got mass!

One Law to rule them all, One Law to guide them, One Law to form them all and in the dark halo bind them. Galaxies appear to obey a single universal effective force law. Early indications of this have been around for some time.

One Law to
 
 rule them all, One Law to guide them,
 
 
 One Law to form them all and in the dark halo bind them.
 

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One Law to Rule Them All

Previously I noted how we teach about Natural Law, but we no longer speak in those terms. All the Great Laws are already know, right? Surely there can’t be such things left to discover! That rotation curves tend towards asymptotic flatness is, for all practical purposes, a law of nature. It is tempting to leap straight to the interpretation (dark matter!), but it is worth appreciating the discovery for itself.

Tully-Fisher: the Second Law

I said I would occasionally talk about scientific papers. Today’s post is about the new paper

 Testing Feedback-Modified Dark Matter Haloes with Galaxy Rotation Curves: Estimation of Halo Parameters and Consistency with ΛCDM

by Harley Katz et al. I’ve spent a fair portion of my career fitting dark matter halos to rotation curves, and trying to make sense of the results.

Dark Matter halo fits – today’s cut

So I’m back from this small, convivial meeting. Many thanks to hosts Priya Natarajan and Doug Finkbeiner for putting the program together. I find it especially useful when scientists working on the same problem from different fields come together in this fashion.  It provides fresh perspective. I had wondered whether we were capable of genuine rethinking.

Some rethinking

Vincent: Want to talk about MOND? Jules: No man, I don’t consider MOND. Vincent: Are you biased? Jules: Nah, I ain’t biased, I just don’t dig MOND, that’s all. Vincent: Why not? Jules: MOND is an ugly theory. I don’t consider ugly theories. Vincent: MOND makes predictions that come true. Fits galaxy data gooood.

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Pulp Science

This clickbait title is inspired by the clickbait title of a recent story about high redshift galaxies observed by JWST. To speak in the same vernacular: LOL! What they mean, as I’ve discussed many times here, is that it is difficult to explain these observations in LCDM. LCDM does not encompass all of science.

 Science

* predicted exactly this.

Can’t be explained by science!

So the radial acceleration relation is a new law of nature. What does it mean? One reason we have posed it as a law of nature is that it is interpretation-free. It is a description of how nature works – in this case, a rule for how galaxies rotate.

 Why

nature behaves thus is another matter.

Four Strikes

I recently traveled to my first international meeting since the Covid pandemic began. It was good to be out in the world again. It also served as an excellent reminder of the importance of in-person interactions. On-line interactions are not an adequate substitute. I’d like to be able to recount all that I learned there, but it is too much. This post will touch on one of the much-discussed topics, our own Milky Way Galaxy.

A few words about the Milky Way

It often happens that data are ambiguous and open to multiple interpretations. The evidence for dark matter is an obvious example. I frequently hear permutations on the statement  This is said in all earnestness by serious scientists who clearly believe what they say.

Bias all the way down

A colleague points out to me a recent preprint by Bertone &amp; Tait titled

 A New Era in the Quest for Dark Matter

. Most of the narrative is a conventionalist response to the failure of experimental dark matter searches, posing a legitimate question in this context. Where do we take it from here?

The arrogance of ignorance

Casertano et al. have used Gaia to provide a small but important update in the debate over the value of the Hubble Constant. The ESA Gaia mission is measuring parallaxes for billions of stars. This is fundamental data that will advance astronomy in many ways, no doubt settling long standing problems but also raising new ones – or complicating existing ones.

Cepheids &amp; Gaia: No Systematic in the Hubble Constant

David Merritt recently published the article “Cosmology and convention” in

 Studies in History and Philosophy of Science

. This article is remarkable in many respects. For starters, it is rare that a practicing scientist reads a paper on the philosophy of science, much less publishes one in a philosophy journal.

LCDM has met the enemy, and it is itself

The arXiv brought an early Xmas gift in the form of a measurement of the velocity dispersion of Crater 2. Crater 2 is an extremely diffuse dwarf satellite of the Milky Way. Upon its discovery, I realized there was an opportunity to predict its velocity dispersion based on the reported photometry. The fact that it is very large (half light radius a bit over 1 kpc) and relatively far from the Milky Way (120 kpc) make it a unique and critical case.

Crater 2: prediction verified.

Last time, I addressed some of the problems posed by the radial acceleration relation for galaxy formation theory in the LCDM cosmogony. Predictably, some have been quick to assert there is no problem at all. The first such claim is by Keller &amp;

La Fin de Quoi?

One of the most interesting and contentious results concerning MOND this year has been the dynamics of wide binaries. When last I wrote on this topic, way back at the end of August, Chae (2023) and Hernandez (2023) both had new papers finding evidence for MONDian behavior in wide binaries. Since that time, they each have written additional papers on the subject.

Wide binary debate heats up again

In the previous post, I related some of the history of the Radial Acceleration Relation (henceforth RAR). Here I’ll discuss some of my efforts to understand it. I’ve spent more time trying to do this in terms of dark matter than pretty much anything else, but I have not published most of those efforts. As I related briefly in this review, that’s because most of the models I’ve considered are obviously wrong.

What should we expect for the radial acceleration relation?

The missing mass problem has been with us many decades now. Going on a century if you start counting from the work of Oort and Zwicky in the 1930s. Not quite a half a century if we date it from the 1970s when most of the relevant scientific community started to take it seriously. Either way, that’s a very long time for a major problem to go unsolved in physics.

A Significant Theoretical Advance

Continuing our discussion of galaxy formation and evolution in the age of JWST, we saw previously that there appears to be a population of galaxies that grew rapidly in the early universe, attaining stellar masses like those expected in a traditional monolithic model for a giant elliptical galaxy rather than a conventional hierarchical model that builds up gradually through many mergers.

Old galaxies in the early universe

Happy new year to those who observe the Gregorian calendar. I will write a post on the observations that test the predictions discussed last time. It has been over a quarter century since Bob Sanders correctly predicted that massive galaxies would form by z = 10, and three years since I reiterated that for what JWST would see on this blog. This is a testament to both the scientific method and the inefficiency of communication.

A few videos for the new year

I’ve been wanting to expand on the previous post ever since I wrote it, which is over a month ago now. It has been a busy end to the semester. Plus, there’s a lot to say – nothing that hasn’t been said before, somewhere, somehow, yet still a lot to cobble together into a coherent story – if that’s even possible. This will be a long post, and there will be more after to narrate the story of our big paper in the ApJ.

On the timescale for galaxy formation

I should perhaps explain a little about the title of the last post. It is perfectly obvious to me. But probably not to anyone else. Our brains work in subtly different ways. One thing that mine does, whether I like it or not, is memorize lines and make obscure links between them.

Plate of Shrimp

Cosmology used to be called the hunt for two numbers. It was simple and elegant. Nowadays we need at least six. It is neither simple nor elegant. So how did we get here? The two Big Numbers are, or at least up till the early-90s were, the Hubble constant H

 0

and the density parameter Ω. These told us Everything. Or so we thought. The Hubble constant is the expansion rate of the universe.

Two Numbers

There has been some debate of late over the role of falsifiability in science. Falsifiability is the philosophical notion advocated by Popper as an acid test to distinguish between ideas that are scientific and those that are not. In short, for a theory to be scientific, it has to be subject to falsification.

Falsifiability and Persuadability in Science

Why does MOND get any predictions right?

That’s the question of the year, and perhaps of the century. I’ve been asking it since before this century began, and I have yet to hear a satisfactory answer.

Question of the Year (and a challenge)

In order to agree on an interpretation, we first have to agree on the facts. Even when we agree on the facts, the available set of facts may admit multiple interpretations.

Common ground

Who we give prizes to is more a matter of sociology than science. Good science is a prerequisite, but after that it is a matter of which results we value in the here and now. Results that are guaranteed to get a Nobel prize, like the detection of dark matter, attract many suitors who pursue them vigorously. Results that come as a surprise can be more important than the expected results, but it takes a lot longer to recognize and appreciate them.

Sociology in the hunt for dark matter

I was raised to believe that it was rude to tell people

 I told you so

. Yet that’s pretty much the essence of the scientific method: we test hypotheses by making predictions, then checking to see which told us the correct result in advance of the experiment. So: I told you so. Our paper on massive galaxies at high redshift is out in the Astrophysical Journal today.

Massive Galaxies at High Redshift: we told you so

Galaxies are gravitationally bound condensations of stars and gas in a mostly empty, expanding universe. The tens of billions of solar masses of baryonic material that comprise the stars and gas of the Milky Way now reside mostly within a radius of 20 kpc. At the average density of the universe, the equivalent mass fills a spherical volume with a comoving radius a bit in excess of 1 Mpc.

Galaxy Formation – a few basics

Last time, we discussed the remarkable result that gravitational lensing extends the original remarkable result of flat rotation curves much farther out, as far as the data credibly probe. This corroborates and extends the result of Brouwer et al. They did a thorough job, but one thing they did not consider was Tully-Fisher.

Tully-Fisher from gravitational lensing

I had written most of the post below the line before an exchange with a senior colleague who accused me of asking us to abandon General Relativity (GR). Anyone who read the last post knows that this is the opposite of true. So how does this happen? Much of the field is mired in bad ideas that seemed like good ideas in the 1980s.

Take it where?

It has been two months since my last post. Sorry for the extended silence, but I do have a real job. It is not coincidental that my last post precedes the start of the semester. It has been the best of semesters, but mostly the worst of semesters. On the positive side, I’m teaching our upper level cosmology course. The students are great, really interested and interactive.

Not quiet on the northern front

I would like to write something positive to close out the year. Apparently, it is not in my nature, as I am finding it difficult to do so. I try not to say anything if I can’t say anything nice, and as a consequence I have said little here for weeks at a time. Still, there are good things that happened this year. JWST launched a year ago. The predictions I made for it at that time have since been realized.

Remain Skeptical

In previous posts, I briefly described some of the results that provoked a crisis of faith in the mid-1990s. Up until that point, I was an ardent believer in the cold dark matter paradigm. But it no longer made sense as an explanation for galaxy dynamics. It didn’t just not make sense, it seemed strewn with self-contradictions, all of which persist to this day.

When you have eliminated the impossible…

Just as I was leaving for a week’s vacation, the dark matter search experiment LZ reported its first results. Now that I’m back, I see that I didn’t miss anything. Here is their figure of merit:  LZ is a merger of two previous experiments compelled to grow still bigger in the never-ending search for dark matter.

LZ: another non-detection

I’ve reached the point in the semester teaching cosmology where we I’ve gone through the details of what we call the three empirical pillars of the hot big bang: Hubble Expansion Primordial [Big Bang] Nucleosynthesis (BBN) Relic Radiation (aka the Cosmic Microwave Background;

Tooth Fairies &amp; Auxiliary Hypotheses

I noted last time that in the rush to analyze the first of the JWST data, that “some of these candidate high redshift galaxies will fall by the wayside.” As Maurice Aabe notes in the comments there, this has already happened. I was concerned because of previous work with Jay Franck in which we found that photometric redshifts were simply not adequately precise to identify the clusters and protoclusters we were looking for.

By the wayside

Dark matter remains undetected in the laboratory. This has been true for forever, so I don’t know what drives the timing of the recent spate of articles encouraging us to keep the faith, that dark matter is still a better idea than anything else. This depends on how we define “better.”  There is a long-standing debate in the philosophy of science about the relative merits of accommodation and prediction.

Define “better”

I went on a bit of a twitter bender yesterday about the early claims about high mass galaxies at high redshift, which went on long enough I thought I should share it here.  For those watching the astro community freak out about bright, high redshift galaxies being detected by JWST, some historical context in an amusing anecdote…  The 1998 October conference was titled “After the dark ages, when galaxies were young (the universe at 2 &lt; z &lt;

JWST Twitter Bender

Avi Loeb has a nice recent post

 Recalculating Academia

, in which he discusses some of the issues confronting modern academia. One of the reasons I haven’t written here for a couple of months is despondency over the same problems. If you’re here reading this, you’ll likely be interested in what he has to say. I am not eager to write at length today, but I do want to amplify some of the examples he gives with my own experience.

Some Outsider Perspective from Insiders

OK, basic review is over. Shit’s gonna get real. Here I give a short recounting of the primary reason I came to doubt the dark matter paradigm. This is entirely conventional – my concern about the viability of dark matter is a contradiction within its own context. It had nothing to do with MOND, which I was blissfully ignorant of when I ran head-long into this problem in 1994.

Two Hypotheses

I have become despondent for the progress of science. Despite enormous progress both observational and computational, we have made little progress in solving the missing mass problem. The issue is not one of technical progress. It is psychological. Words matter. We are hung up on missing mass as literal dark matter.

Triton Station