A Physicist Who Denies That Dark Matter Exists
cosmos.nautil.us
cosmos.nautil.us
I've always felt this way about dark matter, but as a lay person with no background in physics, it's an opinion I'm hesitant to express.
if you have a model that predicts something, but the prediction is off by several orders of magnitude, the model is wrong. no other field would invent invisible stuff to explain that the model is still right. (well, maybe finance)
I have always had the same inclination. It seems like a classic candidate for using Occam's razor. Would love to hear someone who knows more about physics weigh in with a more nuanced viewpoint.
Particle physics has a long history of noticing gaps in the experimental data that don’t match up with current theories and positing that maybe a new particle would solve the problem. This goes right back to things like the neutrino (which was posited to preserve momentum in certain particle interactions IIRC) and even the neutron.
Sometimes the suggestion pans out, sometimes it doesn’t. You can see this kind of thing in action - when there was that anomaly in the CERN data a year or two ago there were a flurry of papers suggesting possible particles, none of which panned out because the anomaly turned out to be statistical noise. The various particulate explanations for the observed discrepancy between the spiral galaxy rotation curves and the observed distribution of matter are very similar: Take a gap in the data & speculate about what kind of particle would fill the hole.
When you combine the fact that, historically, speculating about whether new particles could explain anomalies in the observed data has been very productive for C20th physics with the reality that physicists are also loath to toss aside general relativity (which has been spectacularly successful) just because of one observed anomaly that has yet to be explained, it’s entirely unsurprising that physicists are keen on new particles as explanations for the galactic rotation curves.
At the same time, every physicist will happily admit that there’s a great big hole in the standard model - i.e. that it doesn’t include gravity at all - and that any unifying theory might also explain away the galaxy rotation curves in a way that doesn’t require new particles. Indeed, if a unifying theory could pull off that trick it would be evidence that the theory has a good chance of being true. Sadly, to date, no one has managed to come up with such a unification, and we have no real idea what such a theory would look like beyond the obvious: that it should explain the observed facts & match QFT & GR in the regimes where those theories are accurate.
Here's a couple of examples of quantum theories of gravity.
http://www.phys.lsu.edu/faculty/pullin/talks/pire1.pdf
http://www.staff.science.uu.nl/~hooft101/lectures/erice02.pd...
http://einrichtungen.ph.tum.de/T31/seminars-past/seminar-tal...
http://www.damtp.cam.ac.uk/research/gr/public/qg_ss.html
The extent to which these are complete, consistent, natural (in the fine-tuning sense), and so forth is debatable but these are certainly existing examples of quantum theories of gravity, and indeed the first is a perfectly reasonable Effective Field Theory that people work in regularly.
> QFT doesn’t include gravity at all
I think you mean "The Standard Model of Particle Physics", which is a quantum field theory (as is e.g. perturbative quantum gravity).
> the things you might analyse with the full QFT
Atoms and molecules have gravitational fields; when you send one through a double slit, which way does their gravitational field go?
http://www.nature.com/nnano/journal/v7/n5/abs/nnano.2012.34....
A quantum theory of gravity is needed to answer that.
Assemble a huge number of particles in superposition with 1/(sqrt 2) (|M @ a> + |M @ b>), with a & b separated. A quantum theory of gravity is needed to describe the gravitational influence of M on a small test object (General Relativity's answer is just wrong :( ).
But perhaps that’s me being picky :)
> I think you mean "The Standard Model of Particle Physics", which is a quantum field theory (as is e.g. perturbative quantum gravity).
Sure: I was just quoting the parent comment & using the term informally to stand in for the mouthful that is TSMoPP.
(I’d love to see an experimental setup that was capable of detecting the gravitational field of a single molecule: that would be impressive!)
On the contrary, the ones I listed are all completely in accord with General Relativity up to strong gravity and absent superposed sources, which is found from studying the renormalization group flow of perturbative quantum gravity and is four loops of gravitons in a 3+1 dimensional spacetime. Strong gravity can only be found very close to the singularity of black holes (and well inside event horizons, except at the final evaporation), or in the very early universe. So we're good for neutron stars, and have no problems studying things around the event horizons of astrophysical black holes.
The only new mathematical formalism in perturbative quantum gravity is renormalization, and that goes back to the 1980s. Perturbative quantum gravity itself comes from the 1990s.
Sean Carroll has a good explanation of renormalization and effective field theory here:
http://www.preposterousuniverse.com/blog/2013/06/20/how-quan...
Asymptotically safe gravity posits an ultraviolet fixed point at which one can take a finite number of measurements, producing a strong gravity completion that perturbative renormalzation cannot; this is prompted by asymptotic safety in QCD. Below that limit, ASG completely matches perturbative quantum gravity, and so in the EFT limit it's the same as General Relativity.
There are five or six of other viable families of quantum theories of gravity, where viability means they accord exactly with perturbatively quantized General Relativity in its effective field limit, and thus agree completely with GR in the classical limit and weak gravity, and additionally are candidates as fundamental theories because they do not rely on perturbative renormalization by power counting and thus are expected to be useful to arbitrarily high energies.
Additionally it is not wildly irresponsible to think that mathematical research (perhaps not driven by physics!) will produce a tractable renormalization that does not require nature to select a convenient effect to suppress the explosion of parameters at high energies.
> I’d love to see an experimental setup that was capable of detecting the gravitational field of a single molecule: that would be impressive!
Everyone would. We're down below milligrams and yoctoNewtons:
https://arxiv.org/abs/1602.07539
http://newscenter.lbl.gov/2014/06/26/smallest-force-ever-mea...
I'm not as au fait about how the other side of the tunnel is approaching the ultimate meeting point, but it's not unreasonable to think of nanogram masses in superposition. Experiments were only at thousands of atomic mass units a few years ago, though: https://arxiv.org/abs/1310.8343
Unfortunately General Relativity can only have the whole gravitational influence of these molecules go through one or the other slits. However all of the quantum theories in my previous message have the distribution of the gravitational influence follow distribution of the matter, as one would expect.
But I’ll chase up some of the ASG references. Thanks for those.
(yoctoNewtons! We live in amazing times...)
Annoyingly, experimental evidence can be hard to come by because any viable mathematical formalism has to reproduce the successes of GR, and it is shockingly easy to depart from GR in a serious way even in very weak gravity.
ASG's main anti-features are that it's not in itself a fundamental ToE; what it would accomplish (if it holds up) is getting the gravity part right to Planck scales and avoiding the incompatibility with QFT. Who knows what beyond-the-Standard-Model physics outside the gravitational sector will look like at those scales?
ASG is not alone in this, though.
String theory, on the other hand, would let gravity and matter emerge from something like a field of strings resembling dark energy, where cooling increases the apparent volume of the cosmological frame at a given scale factor. Slow thermalization in turn produces everything else, like dark matter, baryons, light, and so on.
There are other less popular theories from which matter and spacetime geometry emerge, too.
And of course it goes the other way around too, where matter theories can arise from geometry (Cartan torsion is still viable, and Poplawski still tries to get people to pick up Riemann-Cartan geometry; and quantum geometrodynamics remains viable too).
> We live in amazing times
The amazing thing is that collaboration, simulation, and publication is hugely improved upon even a couple of decades ago. If in the early 1900s people had WWW and message boards, email and message boards, LaTeX, ArXiv, and so forth, who knows what might have been different given the big brains around at the time !
In richer countries we have relative peace, antibiotics and sanitation. Feynman's wife died of TB while he was working on the Manhattan project; that's the trifecta there, just once removed from a theoretical physicist. Henry Moseley was shot through the head on the battlefield at Gallipoli. Many other scientists had their work seriously disrupted during both world wars and during cold war repressions (Sakharov on the one hand, Condon on the other; the former got it much worse of course).
That’s fair. I wasn’t aware that anyone had managed to make any potentially observable predictions at this point, so thanks for updating me on that.
(As an observer from the sidelines of physics I’ve always had a fondness for Loop Quantum Gravity / Spin Foams over String Theory(ies) personally, but not for any particularly deep reason that I can point to as justification.)
I recommend the introduction to
Class.Quant.Grav.27:245026,2010 DOI: 10.1088/0264-9381/27/24/245026
https://arxiv.org/abs/1008.3621
which is reasonably accessible and high-level in a way that's hard to find for asymptotically safe gravity (which is unsurprising given that renormalization group flow is a bit abstruse).
The Higgs boson took a long time to be discovered, but people thought it would be there because the alternative was the Standard Model being wrong. And so they looked, and there it was. Perfectly compatible with the Standard Model.
If two things that are observably exactly the same behave differently, then what should one conclude is the simplest explanation?
If you look in a telescope for a year, and notice that an apparently free-floating star out in the galaxy with no neighbors is taking a sharply curved path and everything else in the sky is going basically straight, you have two choices: 1) either something you can't see yet is there and acting on the star, 2) conservation of momentum, and the law of equal and opposite reactions need to be thrown out because they're wrong, and we need to start from scratch with physics.
Which of those two would Occam say is more likely?
Scientific theories are generally not just amalgamations of tweaks. General relativity is internally consistent, explains so much, and just got a huge boost last year with the first detection of gravity waves... which BTW are invisible stuff that was invented based on theory. It is not lightly cast aside.
In my opinion Verlinde's theory is a better candidate as a replacement of dark matter, since it doesn't require changing the theory of gravity as drastically as MOND does. That said, his theory does require a combination of general relativity with quantum physics, which is tricky. Compared to both just adding a bit of dark (not necessarily invisible) matter is a lot simpler.
Physics also has an unfruitful history of invisible stuff: ether, strings (string theory), etc.
Personally I'm glad something other than dark matter is being considered. I was only told that the rotational velocities of galaxies did not match the predictions. IME simple explanations tend to work better for mechanics in physics (until quantum mechanics...)
Right, and there is also evidence for dark matter.
In this case we have a theoretical mode, but we later notice our empirical data doesn't match this. Both MOND and dark matter are an attempt to patch up our existing theory to explain what we have seen. This is less compelling, because it is post-hoc and these theories might just work because we force it to work by over fitting. To use an analogy to machine learning, it is like training on your test set; no on is impressed when you then have good performance on your test set.
With that said, I think that point of view would apply to both theories equally.
There have been several independent observations that are explained by dark matter, and it's not like the theory for dark matter was specifically changed to accommodate those observations. The most well-known is around gravitational lensing, as the amount of observable mass in clusters of galaxies does not match the amount of distortion that we observe. There are however several others. This kind of independent validation of a theory from other angles is a textbook case of how theories are validated - they are proposed to explain one thing, but turn out to also explain other things.
MOND meanwhile has a much tougher time explaining the other observational evidence. It has had to be extensively patched to fit the other cases. Additionally, as noted elsewhere in the comments, neutrinos are not dissimilar to dark matter. Both are forms of matter that it do not interact electromagnetically, making them all but impossible to detect directly. Theorizing that there is more than one such type of particle is not very much of a stretch. Taking that into account, MOND seems to be a much more complex solution than just having another type of matter with properties similar to those we have already seen.
Almost all of the skepticism around dark matter comes from outside of the scientific community, and I think both the name and it being lumped in with dark energy (which is just a placeholder, not an actual validated theory) are part of what contributes to this. While obviously the consequences of this skepticism are significantly less dire, the reasons for it seem pretty similar to those of climate change skeptics - primarily tied to human intuition.
General relativity might be wrong, but it's probably not over-fitted because it's quite simple as far as theoretical constructs go.
And it has a pretty good track record. Both black holes and gravity waves were "invented" because the theory seemed to indicate that they should exist, even though there was no evidence yet. Both were spectacularly confirmed last year.
That said, we know there is some shortcoming in either GR or quantum mechanics (or both), because they don't agree under certain conditions. Dark matter, being a gravitational phenomena that seems like it might be a new kind of particle, is potentially in that same area.
Inventing and then testing, though. As you said, GR got a huge boost last year, still being tested a century after being proposed. That's how science should be!
We know the darkX behaviour and we have some ideas as to explanation, but far from being proved in the way GR has been.
Dark energy, dark matter, string theory. Lots of IQ being poured into them, with a reasonable chance they're not the answer.
And like dark matter, black holes point out shortcomings in our theories--they are ground zero for the incompatibility between general relativity and quantum mechanics.
And yet, even though we don't fully understand them, there is not much public doubt that black holes really exist. To the contrary: they are quite popular!
I'm not arguing that just because we think black holes exist, therefore dark matter must also exist. That's bad logic. I'm just pointing out that a lot of the popular concerns with dark matter are not unique to dark matter.
> "But if it does turn out that a new theory of gravity is needed, what kind of theory would it be? How could it correctly describe the motion of the bodies in the Solar System, as Einstein's theory is known to do, and still give us the different prediction for the universe that we need?"
https://science.nasa.gov/astrophysics/focus-areas/what-is-da...
As other commenters said, physics has a history of "adding unobservable objects", and then finding a way to observe them.
This is the "silver bullet" if you will for a lot of these theories: https://en.wikipedia.org/wiki/Bullet_Cluster
It would be great if "just" modifying the equations works. But it has an uphill climb against observed data.
And yes, as Cozzyd points out, matter is actually part of these equations. The simplest changes involve adding an extra term to the equation with such-and-such properties that disappear in the normal cases - that is dark matter.
But that's not the case. We have petabytes of data from space (if not more). Your theory needs to match all of them, give or take noise. The common example of the Bullet Cluster [1] comes up a lot, but it's just one particularly exciting example of the problem. I've seen people create variants of MOND that try to address the Bullet Cluster problem, but you start having to have some sort of really weird gravity memory effect in space or something, where space itself "remembers" that it used to have a lot of matter in it and still has a small amount of gravitation in it despite no longer containing the corresponding mass. Which I suppose isn't necessarily out of the question given that we're intrinsically discussing a non-linearity in gravity, but it's still a bit strange.
By the time you work out what MOND is going to need to look like in order to explain everything we see in space, it ends up losing its "Oh, it's just one more simple term on gravity" nature and starts looking pretty weird itself. It's constrained by the real data to be at least as weird as dark matter itself, because the data itself is weird. Given the history physics has had with "calling its shots" and identifying the necessity of particles years or decades before they are detected, dark matter is something that I consider at least not out of the question.
I also am sympathetic to MOND solutions as well. After all, "the math looked awfully weird by the time we finished working out the theory" also has a long and illustrious history in physics too! What's true is true, regardless of how we feel about how beautiful it is. We also have a Standard Model of particle physics that, whatever its known flaws may be, doesn't immediately obviously have a hole for dark matter in it, so perhaps the "we've called our shots before" argument doesn't apply so well here. There is something to be said for not trying to push a new particle in there. But if MOND is the answer, you're likely to find the final result to have non-trivial weirdness in it, too.
[1]: https://en.wikipedia.org/wiki/Bullet_Cluster#Significance_to...
That's honestly not so "weird" at all. There are TONS of examples of objects and substances having that kind of behavior in nature. If I crash my car into something, the metal "remembers" what happened to it. If I run electricity through an inductor, the magnetic field "remembers" that electricity was being run through that space and doesn't just disappear the moment the electricity is turned off. Momentum is the same thing. Humans remember what happened to them because consciousness records everything that happens to us. What prevents gravity from being something similar? Gravity itself may mean exactly the same thing as space having a kind of memory and operating fundamentally by the law of cause and effect. Things may seem weird only in the absence of such a clear principle.
That there's stuff that has a mass but doesn't interact well with light, or that space is able to curve itself without mass, thus also rendering Einstein false.
This immediately raises further questions: How long does space remember? How's the exact mechanism? Where and how does empty space store that information? What happens to E=mc2?
Clearly, Occam's Razor can only be applied correctly if you can distinguish what you really know from what are actually your assumptions. Not only do people hear what they want - but those who don't know don't know they don't know.
However, I get suspicious when someone argues by analogy. Your "my car remembers a crash, furthermore humans do remember, therefore space could also remember gravity" does not seem reasonable to me.
I am also not sure why my post got downvoted.
Edit: As I think about it, "but Einstein showed that you can bend space without mass" again is an argument by analogy. It doesn't matter what analogies exist. The theory should be tested according to empiric evidence. Pulling your analogies together judt for the sake of abandoning a different theory - where's the point in that?
Did you mean the metric tensor g_{\mu\nu} or the Ricci curvature tensor R_{\mu\nu}?
"Gravitational field" is one of those shifty things in GR that makes one sympathetic to MTW's refusal to identify the term with any particular mathematical object.
You're right though; there are plenty of exact solutions to the Einstein Field Equation which are vacuum solutions -- no matter, just gravity.
Recall the operant definition of "weird" here is something that fits into the sentence "I find the idea of 23% of the universe being invisible particles that we are completely incapable of detecting is weirder than the idea that we have gravity slightly wrong."
Mathematically, if we add non-linear terms to gravity, it isn't that weird that you might get a memory-like effect, among other things. But would someone who agrees with the previous sentence agree that this is still less "weird" than 23% of the universe being so invisible that we still can't pick it up, even in 2017?
I think that's, in a certain sense, not really correct. Without some form of Occam's Razor, you can't do science — or at least, you can't come to any definite conclusions, because there are always infinitely many models that would explain any observation.
Turning that around, it means that for any fixed amount N of data in support of your hypothesis, there's an ugliness/arbitrariness threshold H_0 such that if your hypothesis is more ugly/arbitrary/possessed of entia multiplicata than H_0 you shouldn't accept it yet.
I'm afraid that's a category error. I wasn't talking about science. I was talking about truth.
Many truths are literally incomprehensible. There are many systems out there in the world that may even consist entirely of atomic parts that we fully understand but we still can not understand the totality of all the parts, that simply consist of too many bits (in the information theoretic sense) for us to ever understand. The truths are true nevertheless.
I'm a bit old fashioned that way. The idea that there is no objective reality, or that if we can't understand it it can't exist, may be very exciting philosophies among the word-loving crowd, but I do not find them useful models of reality.
It actually wouldn't surprise me that much to discover that we can't quite nail down the laws of physics the universe operates on even in principle for some reason. (And I don't mean with any sort of copouts like "it might be a simulation" or anything; I mean the laws of physics that appear to govern the universe we appear to live in, regardless of whether that is itself sitting on top of something else.) Based on our progress in understanding the universe, I'd still guess that it's reasonably likely that we can find all the basic, atomic principles. But I wouldn't be stunned to be wrong.
The Bullet Cluster isn’t the incontrovertible
evidence for particle dark matter that you have
been told it is
As an astronomer in the field of clusters, I don't know anyone who takes MOND-like theories seriously. Any non dark matter explanation for the bullet cluster would have to be extremely contrived.
the probabilities and number of clusters imply we'd expect
a bullet cluster
Hayashi & White 2006 -- BC is apparently consistent with LCDM.
Farrar & Rosen 2007 -- BC is apparently not consistent with LCDM.
Nusser 2008 -- BC possibly not consistent with LCDM.
Angus & McGaugh 2008 -- BC is more consistent with MOND cosmology than LCDM.
Llinares et al. 2009 -- BC is more consistent with MOND cosmology than LCDM.
Lee & Komatsu 2010 -- BC is apparently not consistent with LCDM.
Forero-Romano et al. 2010 -- BC is apparently consistent with LCDM.
Thompson & Nagamine 2012 -- BC is apparently not consistent with LCDM.
Watson et al. 2014 -- BC is apparently consistent with LCDM.
Krajlic & Sarkar 2015 -- BC is apparently consistent with LCDM.
Bouillot et al. 2015 -- BC is apparently consistent with LCDM.
Thompson et al. 2015 -- BC is apparently consistent with LCDM.
However, there's lots of scope for taking an unphysical and even incomplete theory seriously [this supergravity researcher puts it well: https://arstechnica.com/science/2013/05/earning-a-phd-by-stu... ]
Relativistic approaches to MOND might eventually raise interesting questions about the EFT, and those are what a QG phenomenologist lives for. So it's easy to see why she'd take MOND seriously without taking it too seriously.
(As an example, Verlinde's recent work is partly provoked by MOND, and it's also nice to see a string theorist step outside of the AdS comfort zone and confront what we see in our sky).
Which variants are these?
cf. section 8.3, https://arxiv.org/abs/1112.3960
Several of the relativstic MOND theories (see chapter 7 of the same review) are detailed, and I don't see how any of the 8.3 set matches the quote above.
It's already a few years old, though, so maybe you've seen something newer.
> We also have a Standard Model of particle physics that, whatever its known flaws may be, doesn't immediately obviously have a hole for dark matter in it
There's a hole in chirality, which was part of the motivation for WIMPs as CDM.
There's a hole in the Strong-CP problem, which was part of the motivation for axions as CDM.
There's a hole in the hierarchy problem, also part of the motivation for WIMPs but also the motivation for Little-Higgs-like CDM.
Those particle dark matter candidates came from BTSM gauge theorists, not relativists.
> I also am sympathetic to MOND solutions as well.
If you make MOND relativistic you wind up adding a field to G = T; which side it's on doesn't really matter - it'd mostly be either down to an aesthetic choice based on coupling strength, or social considerations (this goes back to at least 1918! [1]).
[1] https://arxiv.org/abs/1211.6338 (and sure enough even in 2017 you will not be arrested by the EFE police if you put the cosmological constant onto the T side as a source, and you might even want to, e.g. in quintessence modelling, or in the cosmological frame; also cf. the choice between the Einstein frame and the Jordan frame for scalar-tensor gravity)
Today of course, this sounds ridiculous. But my physics teacher was always keen to point out that the people involved weren't stupid and that it was an important theory because it was a good starting mental model of how things actually worked and led to our better understanding today.
I wonder if dark matter is similar. It's not flat wrong, it's the best explanation that we have so far and in it will lead us into another breakthrough of understanding.
It doesn't quite work that way, because charges can be positive and negative, whereas oxygen can only be positive or zero. But until you're able to do some pretty careful measurements, or create a good vacuum, it's hard to tell.
It's a great analogy. Phlogiston theorized that combustion involved an undetectable (with the technology of the day) substance. That substance was investigated over time and the theory was refined until eventually people figured out that the sign was inverted. If you think of "the opposite of oxygen" as still being a pretty solid theory, not absurd, it comes out looking pretty good.
Your fuel is exhausted by gaining something. Your fuel may even still be there, but you can't keep burning it because there is too much of an extra thing, which is also necessary for burning.
A pretty sofisticated setup (at the time) was preparated to prove the fairly established idea that light propagated through Aether.
Well, the failure of the experiment motivated a lot of scientists to improve and test other models.
I can't exactly recall right now, but Einstein's work was supported by the work of many other scientists.
It's not the case that at the time an alternative theory of gravity, space and time was unpopular, as you can see in the works of Lorentz and Minkowski for example.
Not to degrade Einstein's contribution, but to shed light on how the actual scientific process diverges from the popular perception (even among fairly educated people).
In quantum mechanics and analyzing the history of it's development this is much more evident. E.G. Max Planck on his solution to the Ultraviolet Catastrophe[1]: "My unavailing attempts to somehow reintegrate the action quantum into classical theory extended over several years and caused me much trouble."
0: https://simple.wikipedia.org/wiki/Michelson%E2%80%93Morley_e...
The comment by Mordehai Milgrom, " the emperor has no clothes, that dark matter is our generation’s ether." rings true to me. So far no dark matter has been found by LHC.
They used to say 95% of the universe was dark matter. Now they say 68% is dark energy and 27% dark matter. Still only 5% normal matter. Could it be that there is 100% normal matter, 95% of which are transient and temporal in vacuum? If we were to follow Milgrom, and not invent substances, it seems plausible that we still have more math work to do.
AIUI, assuming that gravity tends to 1/r at galactic distances "solves" the dark matter problem, for galactic rotation at least. The problem is that there are other phenomena that involve invoking dark matter that aren't explained by MOND. In short, changing gravity sounds appealing, but the math doesn't quite work out, just as xkcd commented about it (see https://xkcd.com/1758/ ).
Why? I think I can use simple force formula such as F=k/r without any idea of extra dimensions or topology.
A)has infinite density
B)drops off as 1/r^2
We know that gravity drops off as 1/r^2 for all cases except galaxy rotation curves so for it become 1/r for just this specific scale requires that from gravity's perspective the surface area of a sphere usually but doesn't always increase as r^2. Which in turn means it doesn't move through the 3 spacial dimensions that everything else does.
How did you arrive at this? Which force has infinite density and where? k/r is finite except at the point where the source is, the formula is invalid there.
That's a nice example of a prediction being wrong, inventing an as-yet-unobserved chunk of matter to fix it, and that invention then being correct.
Of course, there's a counter-example in the inner solar system in the form of Vulcan. It was invented to explain Mercury's orbit, but the solution ended up being Relativity. So it's not always the right answer.
If you want examples involving entirely new classes of matter, I believe neutrons and neutrinos would fit the bill. Both were invented to explain discrepancies in theories well before they were directly observed.
Remember that coming up with a new type of matter is a form of fixing the model. The model is, essentially, "what does the universe actually look like?" If adding a new type of matter gets you closer, then that's fine. If changing the equations works better, then that's fine too.
Remember that dark matter isn't just some arbitrary fudge factor that gets inserted into the observations to make the numbers come out right. It is a comprehensive theory that allows for observations and predictions. No, nobody knows just what it actually is, but there's a great deal of evidence that there is a lot of "stuff" in the universe which interacts gravitationally but not in other ways.
I see this sentiment a lot, and I'm not sure that dark matter skeptics understand just how much supporting evidence there is for dark matter, or just how difficult it is to "fix Newton." People have been trying real hard for a long time, and nobody has been able to come up with anything like a coherent modification of gravitation that explains the observations.
Correct me if I'm wrong, which is quite likely, but isn't it one of the qualities ascribed to dark matter that it doesn't interact with 'ordinary' matter or photons in any way other than gravity, and therefore can't be directly observed?
Or to turn the question around, is the dark matter hypothesis actually falsifiable?
Neutrinos were actually an early candidate for dark matter. The numbers didn't work out, but it's an example of something that would interact weakly.
And sure, dark matter is falsifiable. If observations are made where gravity appears to deviate from what's visible and can't be explained by adding invisible mass, that would falsify it. Or if someone finally comes up with a change to the known laws of physics which explains the observations better than dark matter does, that would do it.
Remember, nothing is truly "directly observed." All we can do to observe stuff is to see how it affects other stuff. Whether it's with photons or with gravity, it's all ultimately indirect.
Two dark matter particles headed directly at each other would pass through each other and be only slightly deflected by their gravitational interaction.
Based on observed dimming events while monitoring many stars, we have ruled out brown dwarfs as more than 20% of the total. Other possibilities still remain, but none have shown evidence of being sufficient to explain dark matter. However we have not ruled out the possibility of it being something that we haven't thought of yet.
Whats to stop us from "adding epicycles" when that happens?
The spacetime curvature, mass/energy, and gravity have quite a few interesting interactions as in gravity as a force, vs gravity as a feature of spacetime, vs potential other forms of gravity. We aren't even sure at this point if a curved spacetime without mass/energy that would generate that curve, would actually produce gravity or not since we aren't able to observe this nor do we have a complete theory of gravity.
A hypothesis that there's local unexplained curvature...Well that's really what dark matter is all about. What's curving it?
(for posterity) My understanding is that spacetime being flat is akin to it being the surface of the universe's curves. Explain, expand, or correct me if that's wrong; I'm certainly no physicist.
Except space isn't perfectly smooth. It does curve, and that curvature is gravity. That's what general relativity is all about. If you want to postulate some way for the universe to curve absent observable mass, go ahead: you're doing nothing but restating the dark matter problem in a (minimally) different way.
The de Sitter vacuum is an exact solution to the Einstein Field Equations of General Relativity that does exactly that.
Our expanding universe will very likely closely approximate de Sitter space in the extreme far future.
There are many other vacuum solutions; it's normal in General Relativity to think of curvature as being a background laid down by hand (ideally approximating nature) and then perturbing that background with matter or probing it with test particles.
> Except space isn't perfectly smooth.
General Relativity is defined on a smooth (infinitely differentiable) manifold.
This is very important! https://en.wikipedia.org/wiki/Smoothness
There can be arbitrary curvature in the manifold, however, and unfortunately with the Einstein Field Equations you can pretty easily produce manifolds with curvature singularities, and those are manifestly not smooth (and that is one driver for research aiming to extend General Relativity).
But to the first order, your experience of gravitation near the surface of the Earth emerges from the very weak manifold curvature the planet and its microscopic components and their motions source. The nearest strong curvature is a couple of kiloparsecs away.
But then again there are multiple contenders for dark matter.
> Remember that dark matter isn't just some arbitrary fudge factor that gets inserted into the observations to make the numbers come out right.
I look at dark matter/energy as a measurement of what we don't know - it is not necessarily matter or energy (although it could be). It is an effect or the sum of effects that we are not aware of. It's almost like the predictions that Mendeleev made with the periodic table.
Personally, I don't like dark matter because my "hack" alarm bells start ringing. That being said, I also don't know what I don't know.
> nobody has been able to come up with anything like a coherent modification of gravitation that explains the observations.
There have been promising "non-matter" dark matter hypotheses[1], though these hypotheses seem to be quickly relegated to the disinterested bucket. In that way, it wouldn't hurt if slightly fewer eyes were looking at particle dark matter and slightly more at "non-matter" dark matter.
Dark matter is called matter because it has mass, i.e. it experiences gravitational attraction to itself and to other forms of matter.
Dark energy is called energy because it acts like radiation, i.e. it has negative pressure.
> Personally, I don't like dark matter because my "hack" alarm bells start ringing. That being said, I also don't know what I don't know.
Your second sentence is far closer to the mark than your first. Dark matter was indeed seen as a hack in the 1930s when it was first proposed, but there is now a large and remarkably consistent body of observations that show its presence. Here's one lay-friendly blog post that briefly describes some of the evidence: https://medium.com/starts-with-a-bang/why-dark-matter-9252bf...
> In that way, it wouldn't hurt if slightly fewer eyes were looking at particle dark matter and slightly more at "non-matter" dark matter.
It's kind of like quantum mechanics at this point. The only reason there aren't more eyes looking at alternatives to dark matter is because we already did that over the last few decades, and the evidence in favor of dark matter kind of became ridiculously overwhelming.
If you want to float an alternative to dark matter at this point, you have to, at the very least, come up with a theory that explains all the things that dark matter explains. (Presumably you would also come up with something that dark matter doesn't explain that your theory does, but one thing at a time.)
> Dark energy is called energy because it acts like radiation, i.e. it has negative pressure.
I was going to post something similar, but tempered a little, since some participants in this discussion are skeptical of the existence of these things. I think the dark energy statement is fine, but would weaken the dark matter one to say, e.g., it's called matter because we can observe effects (lensing, rotation curves, etc.) which can be explained by the presence of matter.
In this way, dark matter and dark energy definitely exist, in the same way that centrifugal and coriolis forces definitely exist: they explain concrete observations, and by squinting at the formulae we see that the terms we've introduced have units of mass (dark matter), energy (dark energy) and force (centrifugal and centripetal).
The effects explained by centrifugal and coriolis forces can also be explained in a different way, by taking into account the rotation of our frame of reference. Articles like this one show that the jury's still out on whether the effects of dark matter and dark energy can be explained in a different way.
AFAIK dark matter is quite widely accepted as a fundamental explanation, rather than a "fictitious" one like centrifugal/coriolis forces, while it's common to treat dark energy as a "placeholder" at the moment: it may be a form of energy which permeates space, or it may be an effect of something else (e.g. some unexpected behaviour of spacetime, like discretisation or some other change of metric).
While we're still some way from understanding dark energy, I have no problem with models of dark matter (although SUSY's looking less likely every day); after all, why should we demand that all matter interact elecromagnetically?
On the other hand, when theorising about what dark energy might be, I think it's fine if that explanation encompasses the effects of dark matter too. Just because we discovered the dark matter effects first, it doesn't mean they must be explained first.
That said, I think you're wrong about alternate hypotheses being quickly dismissed. Alternatives are regularly proposed and evaluated. Many are eventually found to be lacking in the face of the evidence collected, but some remain viable candidates (for example: https://arstechnica.com/science/2017/01/new-ideas-on-gravity...).
There are multiple "contenders" for dark matter, none of them actually explain observations and measurements.
Dark Energy is also in that same category especially in it's purest form as a "universal constant" that was added then removed then added back again to GR when we were sure if the universe is static, expanding at a constant pace or expanding under acceleration.
As far as MOND goes the biggest "curiosity" people have with it is that it works at all, because it shouldn't, you shouldn't be able to just fudge so many factors and have a theory that works, is stable, and predictive (even tho it has various issues especially with regards to cosmology like star and cluster formations).
Which might hint that there is actually something there. That gravity might not work in the same manner over distances, that maybe there is more than one gravity (there are hints that quantum gravity and what we call gravity might be different things already).
If we were to hollow out an asteroid, would there still be a blob of intangible dark matter inside of it?
Matter forms big balls because it collides with other matter and turns kinetic energy into heat. If dark matter is weakly interacting, it won't collide, so after falling into a star it will just shoot right back out the other side. It might form a stable orbit, but it also might just fly away and fall through some other gravity well.
You can probably expect some bulk gravitational effects (e.g. Dark matter might tend to cluster along large matter distributions like galaxies), but in general it wouldn't be amenable to staying in one place.
Dark matter may be some field or interaction of existing fields that we don't understand yet.
What you are saying is the exact same thing.
Particles aren't exactly the same idea because they don't explain the coupling between fields, or things like 'virtual particles' which don't "count" as real particles but have important real behaviors of the field itself.
The latter two are awfully hard to distinguish from relativistic approaches to MOND; indeed you could quantize most of the approaches in Chapter 7 of https://arxiv.org/abs/1112.3960 .
More generally, you can put a scalar or other degree of freedom on either side of the usual write-down of the Einstein Field Equations - on the R side it's "modified gravity", but on the T side it's "modified matter". There's no strong reason to choose one side over the other (Einstein and Schrödinger had a couple of letters to each other about "which side" as early as 1918![1]).
Either way you're adding a field to General Relativity -- and you'd see that in a Langrangian formulation like an expansion of the Einstein-Hilbert action[2]. There is no real reason that you couldn't quantize a field on either side of G = T (consider how g is quantized in perturbative quantum gravity, for example), and if they couple at all non-gravitationally to standard model particles, you'd very much want to.
Finally, historically, particle CDM was strongly motivated by QFT considerations in the first place, with the expectation that they would be lightest MSSM sparticles or mass-explaining sterile neutrinos on the WIMP hand, or alternatively strong-CP resolving axions. So your "lens" is standard, so I agree with your parent comment.
Lastly, you wrote essentially the same comment several days ago https://news.ycombinator.com/item?id=13600085 .
[1] https://arxiv.org/abs/1211.6338
[2] e.g. S = \int \left[ 1/2 R + \mathcal{L}_{baryons} + \mathcal{L}_{photons} + \mathcal{L}_{neutrinos} + \mathcal{L}_{CDM} + ... \right] \sqrt{-g} {d}^{4}x.
.. on the same topic regarding dark matter. Is there a "no duplicate comments" rule? Topics are often cyclic on HN, I don't see why an answer has to change for the same recurring topic.
I'm afraid I don't know much about CDM or sparticles or Ricci scalars.
My comment isn't intended to be a self-contained proof of my inclination here. It is simply intended as a "this is my feeling or belief on this matter absent any further exploration " e.g. I am not an expert.
I agree my statement doesn't contain much information, again it's just an uneducated feeling/guess.
So sure, I get that there's more to the story regarding the nuance between particles and fields than I hinted at. Your clarification of the differences shows that.
I also suspect you have a deeper understanding on the relationship between the two perspectives than most.. so comments like mine aren't as such addressed to folks with your background but rather to folks who don't have such a background and seem to omit the "field picture" in lay discussions.
Wherever you have a quantum field, you have particles, at least for some set of observers in a relativistic quantum field theory. You were right that there are lots of subtleties in a complicated QFT like an extension of the Standard Model that includes CDM, but this generic property of relativistic QFTs is behind the term "particle dark matter".
CDM is "cold dark matter". Matter because it's a source of gravitation; cold because it moves very slowly compared to the speed of light (otherwise it would run away from galaxies rather than hanging around keeping them heavy); dark because it doesn't feel electromagnetism.
From the perspective of a relativist, CDM need not be particle dark matter. However, we can treat General Relativity as a field theory and can even quantize it (with some caveats) and the result gives us particles (gravitons in perturbative quantum gravity). New degrees of freedom that are "gravitational" are probably only "gravitational" in terms of the strength of interactions with other particles (i.e., very weak) but will still be representable as e.g. a gauge boson.
In a quantum field theory like the Standard Model, the fields' local contents are invariant under a set of transformations. When a configuration (like a proton) looks the same under various transformations, there is a symmetry at work preserving that invariant "look", much like when you rotate a circle around its centre in the Euclidean plane, it looks the same whatever angle you turn it.
The Standard Model has a number of parameters whose values are only known empirically, mostly by experiment, with little clue about why the values are the way they are. A common approach to reducing the number of such parameters involves expanding the symmetry group. Supersymmetry is one such approach, and creates a bunch of "superpartner" particles -- sparticles -- for each of the particles in the Standard Model. In minimalist supersymmetry theories, the lowest-mass sparticle tends to have the characteristics of Cold Dark Matter listed above. Other sparticles appear and can (via a new symmetry) explain apparent problems in the Standard Model.
The Ricci scalar is a value at each point in spacetime that describes the curviness of a shell of all points at the same distance from that point or equivalently the internal volume of such a shell. When the scalar increases at a point, the surface of the ball is locally flatter or equivalently the internal volume is smaller. If you move a ball through a region of spacetime where the Ricci scalar takes on various values, an observer at the centre of the shell will think the shell is more or less cramped as the value changes up and down, while a small observer standing on the outside of the shell will see the "ground" curve away (or the horizon move closer, equivalently) as the Ricci scalar decreases. If you seriously increase the Ricci scalar inside the Earth you would still measure a diameter of about 12 700 km, but from eye-level you could see to the other side of your continent. Likewise, if you seriously decrease the Ricci curvature below zero, you'd measure the same diameter of 12 700 km, but from eye-level your next door neighbour's house would be over the horizon.
The Ricci scalar appears on the gravity side of the Einstein Field Equations along with other quantities describing how lengths, durations and angles are calculated at each point.
Instead of postulating endless world-splitting or whatever.
If anything, the Vulcan hypothesis was not bold enough. It was a much greater leap of faith to assume that Newton's mechanics was just a low energy approximation, hence the twist in Mercury's orbit.
Anyway, we don't really know what this whole dark matter business is, but for now the prevailing hypothesis is the dark-matter-as-a-new-type-of-particle. Of course, you're welcome to pursue a different line of thought, and let the truest hypothesis win. This is how science works.
Now, the picture is only mostly as neat now than it was a few years ago, since there is now quite a bit strain with particle physics, but still everywhere in astrophysics it looks like there is some component missing. If that component is dark-matter or a modification of gravity or a remnant of something else is a question about which story journalists want to tell. The thing is, nature does not have to adhere to how we name the left or right hand side of an equation, and that is on a phenomenological level really the difference between mond and dark matter, you either write the term on the gravity side or on the matter side of Newton's law.
It is not that physicists invent an invisible component to make a model work, physicists look at the universe and find hints of a missing matter component everywhere. It is just that journalists love to claim that scientists are puzzled.
This is a great line! But, it's not fair.
The inventing of invisible stuff is an attempt to fix the model. The current model is known to be wrong, because the experimental data isn't matching the model. We have evidence of motion we can't explain... ok, something must be causing it. Right?
Black holes and gravity are invisible things predicted by physics.
That said, I believe the main reason that many physicists prefer some kind of dark matter "particle" is that it's extremely difficult to modify general relativity (GR) without breaking the theory. GR provides such accurate predictions that modifying it just the slightest is almost guaranteed to break something somewhere else (e.g. at some other scale), which forces you to introduce nasty (if you ask me) scale dependent effects.
This does not mean that we shouldn't modify GR, it just means that it's very difficult to make it work. And physicists tend to like simple theories that work (for reasons such as https://en.wikipedia.org/wiki/Occam's_razor).
And yet physics has done this continuously with many discoveries happening in theory first before being verified by reality.
In fact, this is also part of making a model that works. There's no rule that models must be bound by what you only know right now.
The problem with MOND is that it straight-up isn't compatible with relativity. The core of relativity is that the laws of physics from all reference frames are the same. Sure, you can make a MOND that gels with alot of the math resulting from general relativity, but saying "MOND is correct at the large scale and Newtonian mechanics is correct at smaller scales" is gibberish if you actually want to keep relativity itself.
> In 2004, Bekenstein proposed his TeVeS, or Relativistic Gravitational Theory for MOND. Since then, several different relativistic MOND formulations have been put forth, including one by me, called Bimetric MOND, or BIMOND.
> So, no, incorporating MOND into Einsteinian physics is no longer a challenge. I hear this statement still made, but only from people who parrot others, who themselves are not abreast with the developments of the last 10 years. There are several relativistic versions of MOND. What remains a challenge is demonstrating that MOND can account for the mass anomalies in cosmology.
I'm not a physicist and definitely not qualified to evaluate those claims, but it doesn't seem to be a concern to Milgrom.
addendum: If you're going to throw away relativity, step up, stop being a coward: straight up throw away relativity and say Einstein was wrong. Again, you need to come up with some very compelling evidence and a seriously strong theory, but don't weasel around the fact that you're saying that just as Newtonian mechanics accurately models a subset of relativity's domain, relativity accurately models a subset of your theory. Present that new theory or acknowledge you're a mad man that accepts variable physics; don't do neither.
This was during the early days of Quantitative Easing, the Federal Reserve and many other nations (notably from the lesson I'm thinking of, Japan's National Bank) were flooding money into the market, so QE wasn't working properly.
There is a serious problem with economics on the larger scales, and I've yet to hear anyone talk about it.
The problem with this is that we already know Newtonian physics is wrong. It makes incorrect predictions for planetary orbits in the solar system (the original wrong prediction was the motion of Mercury, but the perihelion shift that is not predicted by Newtonian physics but is predicted by general relativity has now been verified, AFAIK, for all the inner planets). So the way to "fix Newton" is to adopt general relativity instead.
And once you adopt general relativity, you can't just arbitrarily change the equation for "acceleration due to gravity" the way MOND does. That equation is not a free parameter in GR; it's derived from the Einstein Field Equation. So you would have to change the Einstein Field Equation, and that would change all of the predictions of GR, not just the prediction for galaxy rotation curves.
What I've just stated is the standard objection to MOND among physicists. Milgrom mentions relativistic formulations of MOND and says that this issue is "no longer a problem", but I think that's much too optimistic.
If you choose to rather adjust Newtonian physics, we have to go all in and the new problem becomes not only how to "fix" it but also how to explain away the clumping of the Cosmic Microwave Background that is thought to be due to dark matter, the graviational lensing in the Bullet Cluster, the large-scale "web" structure of galaxies in the Universe. Structures and effects that actually fit a dark matter universe pretty well.
But yes, maybe there _is_ something else going on, and as a software developer sometimes working on the most terrible things of all: combinations of bugs interacting, and where you keep hunting down a futile rabbit hole assuming a single bug.
Maybe this is a combination of bugs in our theories interacting. It could be that this is part flaws in the Newtonian model, part about faults in some other model? That might explain why we've been bashing our heads on the dark matter wall for so long now.
They include some non-luminous matter, but only require 1/5th to 1/10th as much as would be required by Dark Matter theories. So I think saying they require 'Dark Matter' is confusing. They don't really require a new class of matter and could easily be explained by the presence of some amount of non-luminous baryonic matter in some cases which hardly seems outrageous.
Because even though it reduces the amount of dark matter required it still has missing matter.
I also found this quote very relative to this age.
"Why not? What’s the big deal? If something doesn't work, fix it. I wasn't trying to be bold. I was very naïve at the time. I didn't understand that scientists are just as swayed as other people by conventions and interests."
That does not sound like a coincidence.
Did the constant change when the universe was smaller? Or does the light speed depend on the size of the universe?
Of course, the radius of the universe has clearly changed with time- this could mean that a0 did or that c did.
His life's work: we had fun doing the math :)
Dr. Stone said that "no quest for the truth is wasted." (that's a quote from my advisor, not Dr. Stone) And he's right! Even if we've got a far more nuanced view of marriage and the family now, he turned over new stones and raised questions that people had to address. His methodology made further research possible. Even if he was wrong (and he thought that he had gotten it wrong), he still made it possible for later historians to do great things.
All that's to say: I totally respect the attitude of having fun doing the math. (as I think parent does as well) This kind of effort is never wasted.
Don't mistake it with scientific topics like e.g. Climate science "Denial".
This is key because people (IMO particularly engineers like myself) think when stuff is added it is less likely to be correct which in some cases true but others not so much.
The thing is MOND actually adds a bunch of stuff and doesn't explain a whole bunch of other stuff (yet). What sell me on dark matter is the clustering of galaxies and the universe itself (like how did we get these massive super black holes in the galaxy with MOND?).
On a rather tangental note... do you remember when maverick scientist were shunned and if you go back far enough in some cases heretics? Now days it seems to pay nicely to be contrarian in terms of media coverage (at the cost of being revolted by your peers. There was a SA article on this a while back (famous scientist being hated).
Why don't they ever fix that?
Just would loved more current criticism on his theories.
The way they proved the fact that DNA is the genetic molecule.
Good philosophers, mostly eastern ones, tried very hard to establish a distinction between products of imagination and adequate representations of what is.
The classic example is how the brain conditioned by hundreds of thousands of years by Mother Nature readily mistakes a rope for a snake. Notice, that there is nothing arbitrary here - just wrong interpretation of an appearance.
Modern, based on statistics hipster's science could be compared to a bundle of snakes.)
Nothing exist unless experimentally proven and replicated.
Since you continue to evade the question, I will only ask once more time: Describe the experiment that demonstrates the existence of consciousness in a manner which is "experimentally proven and replicated".
I'm forced to interpret failure to describe the experiment as your admission that you don't actually require "experimentally proven and replicated" to believe things, or at least that you cherry pick some propositions to require that standard.
That's OK too, no one is demanding that you be intellectually honest or self-consistent. But you should not be surprised if people call you out on it though.
In every neurology department which deals with brain injures and pathology one could see the evidences that the states of consciousness and even its pretense or absence are bound by particular parts of the brain, which, in turn, is an artifact conditioned by the evolutionary forces and constraints of this particular universe and its physical laws.
The way medical science went from Phineas Gage to modern maps of the brain centers, insights into how the vision sub-system works, etc. constitutes the experimental proofs you are asked for.
The proof could be considered still incomplete (but nevertheless it is valid because there is not a single contradiction in what is experimentally confirmed), because there is no way to describe step-by-step the whole development from a single fertilized egg to you, but there is no doubt that there is nothing extra to that mere "mechanical" process, and that the mind is what the brain does and that conscious, which some people would call primordial awareness, is mere a product of the brain activity, which can be affected by chemical compounds and even switched on and off, which, BTW, happens every time you fall asleep (because it is not required) and wake up.
I asked you to describe the experiment which proves that consciousness exists.
Merely saying that consciousness is a product of the brain is like proving dark matter by saying it's a product of the universe. I hope you can understand why that is not a convincing argument.
This statement is nonsense. The presence or absence of consciousness could be empirically verified and experimentally tested. The presence or absence of dark matter could not be empirically verified because the concept which is referenced by this pair of words belongs to the category of abstract ideas.
Notice, that consciousness is not an abstract idea, it belong to the category of biological processes. You have here a logical error of assuming existence of an abstract concept, which neither could be empirically verified nor experimentally tested.
There is a subtle difference between a product of the physical brain and a product of group-thinking or sectarian beliefs. While the concepts which form the basis of this or that system of beliefs are certainly exist inside the consciousness of the individual believers and certainly are presented in their shared vocabulary, the phenomena which these concepts presumably accurately and completely capture does not exist anywhere in the universe.
No, it can't; there are various behavioral traits that are conjectured to be indicative of consciousness that can be tested, but consciousness itself can either be tested nor observed in anyone except the observer.
> Notice, that consciousness is not an abstract idea, it belong to the category of biological processes.
No, consciousness is not a biological process, it's a phenomenon which is assumed to occur as a product of biological processes, though it's often conjectured that it could also occur as a product of other processes as well.
Some limited artificial consciousness is obviously possible, even artificial self-consciousness, at least in theory. But possibility does not imply existence.
How?
> consciousness is not an abstract idea, it belong to the category of biological processes.
Okay, describe the experiment which can prove that you are justified in making such statements.
Electric force is many orders of magnitude stronger than gravity. So, if the objects in the universe are charged, the repelling force between them could account for the expansion acceleration in a very simple way.
Lets suppose the Earth and the Sun were both positively charged sufficiently that their repulsive force was enough to noticeably affect the orbit of the Earth. For that to be true, the repulsive forces due to the positive charge on earth itself would have to be so great that it would blast the planet to fragments.
We've measured the charge of base particles, we know their charge to 8 decimal places. (e.g. for electrons).
There is simply no way for the force of electromagnetism to be different at the scale of solar systems.
Even MOND is a tiny modification to Newtons laws, and only a modification in extreme circumstances.
Of course, as I wrote, both laws follow the same power-law, so this can not solve the dark matter problem. Indeed you can absorb it in the gravitational constant.
I also did not suggest that electromagnetism should be different at the scale of solar systems.
A test of the charge equivalence of protons and electrons to 8 digits is by far not good enough to rule this out. You have to probe the proton charge to ~1E-20 for a 1% change of the gravitational effect. This is beyond the reach even for atomic level measurements. More interesting are the bounds on charge conservation.
> starting from the 1980s, the new cosmological dogma was that dark matter constituted a staggering 95 percent of all matter in the universe. That lasted, well, right until the bomb hit us in 1998. It turned out that the expansion of the universe is accelerating, not decelerating like all of us originally thought. Any form of genuine matter, dark or not, should have slowed down acceleration. And so a whole new type of entity was invented: Dark energy. Now the accepted cosmology is that the universe is made up of 70 percent dark energy, 25 percent dark matter, and 5 percent regular matter. But dark energy is just a quick fix, the same as dark matter is.
That makes it sound like dark energy is an offshoot of dark matter, a different type of dark matter that explains an accelerating expansion instead of the extra gravitational effects.
The electromagnetic force still follows the inverse square law. So if objects in the universe are charged, the effects end up being similar to the force of gravity.
i.e. it's still an inverse square law, and it's still linearly related to the observable mass.
The only way something else is happening is if you use either the dark matter / energy theories, or MOND.
The shorter explanation is that it's naive to think that "off the cuff" ideas from amateurs are better than ideas from experts in the field who have devoted decades of their life to the subject.