Hubble finds first galaxy in the local universe without dark matter

[1] http://norbert-winter.com/wp-content/uploads/2018/02/2017-03...

Its my opinion that there is something about the black hole at the center of these galaxies that's causing discrepancies that we attribute to "dark matter". The fact that this new galaxy is so sparse and distributed and shows no sign of dark matter seems to re-affirm this. I'd be curious to know if it even has a central black hole.

Even if you remove dark matter from the picture, there's still the acceleration of expansion (increase of the Hubble term over time), for which there is pretty solid data, namely the discrepancy of brightness and redshift of distant supernovae.

https://en.wikipedia.org/wiki/Accelerating_expansion_of_the_...

By far the "cosmological constant" sort of outweighs all the other terms in the Universe's stress energy tensor.

Known in science as Occaam's razor.

> maybe we just didn't understand gravity very well

We definitely don't understand it when it comes to quantum scales. And maybe we don't understand it properly at macro scales.

But know that the universe is in no way obligated to be simple to the layman.

E.g. Speed of light seems to be constant, so we're going to make up all this bizarre stuff about time dilation and space faring twins.

you miss my point entirely, your explanation is around an assumption of dark matter. You are not saying this galaxy behaves in such a way that MOND cannot explain, you are saying the galaxy behaves in such a way that based on believing in dark matter, this galaxy moves as if it doesnt have it thus MOND is wrong.

I seem to have to qualify my statements with this but I am not attacking the idea of dark matter (nor am I defending MOND) I am just questioning the logic of this one point.

----Edit------ I think it could be confusing what i mean by saying there is no mechanism explaining why dark matter exists. I just mean specifically why. It is a theory that postulates the existence of something but does not give a mechanism to how it gets there. This is not my field of research though so I could be terribly wrong about that.

Secondly, I know for absolute certainty that most models we believe in, are wrong if you take the combined perceptive into account. There are nutjobs out there how actually believe there is a difference between physics, chemistry and astrophysics. Every model that has paradoxes must have errors.

So, please, falsify it for me, I take logical or mathematical arguments as well as publicly accepted measurements interpreted under this model. Everything else is just bullshit. Just because many people believe something does not make it right, in fact history has shown the opposite (if it concerns natural sciences).

https://www.amazon.com/Basic-Structures-Matter-Supergravitat...

This is the only more or less complete description of the model, if you think it's to expensive, and still want to falsify it (please do), I can give you a pdf. Take into account that you will need a year or so to really grasp it, it's a thick book with quite dense content.

https://www.researchgate.net/profile/Stoyan_Sargoytchev

It triggered my curiosity, but I did not understand the model from it. I understood that the perspective is quite different, but I got many things wrong (my fault). Then I started to read the main book I linked in the other comment.

One advise: Start at the beginning and read linear. After some weeks/months it will start to click and things start to make much more sense then. After that you can jump in the book and it will not be confused. If you just jump into the middle because you are looking for an easy answer for something of your interest, it will just be confusing. One of the reviewer on amazon seem to have done that, that's the 1 star opinion without any quality argument.

There are two possibilities to explain the physical world: complicated or complex (sorry easy answers will not work). This model takes the complex way, nothing is really complicated in this model, but the level of detail is enormous compared to the default perspective. We normally thing the neutrino is small, in this model it's huge.

The problem I see is that it just takes to much time for most people to really dig into this to a point where write something as deep as the original theory is possible. As always, working with fringe sciences will bring you no luck in the scientific community.

Don't get me wrong, I would also take one page that seriously falsifies the theory so I can move on. Would have been nice but isn't, that's OK. I will be sad, but letting theories go is part of development.

I have talked to countless people in person and usually I can quickly answer their questions and it works much better then mediums like this one. Unfortunately, there seem not much coming out of this except getting some fans. I have spent surely months writing emails to physicists, asking them about their opinion. Not a single good answer, some show interest but that's it.

As I also follow more critical views on climate change then IPCC, from my perspective an open mind and theories like this are the last hope for human survival. And don't come me with renewable energies like solar - we increased CO2 output by 2% in 2017 and this is without melting permafrost and other feedback loops we triggered. Most people just don't get it that we are in free fall now, the blue ocean event is right in front of our doorsteps.

To be honest, my perspective is quite dark, especially consider our track record of f*ing things up :(

From what I understand of MOND, the less attraction to visible mass (as you would expect from a "ultra diffuse" galaxy like this), the smaller the effect should be. So MOND predicts the effect should be relatively small for this galaxy.

Further, in the paper that the OP references they do a calculation and get odds of something around 1/20 that a galaxy like this will exist if MOND is correct.

The interesting part is that for some reason they interpret that as ruling out MOND, while meanwhile saying "no one has any idea how this thing can exist if the dark matter theory is right". I would think "no idea how it can exist" should correspond to odds less than 1/20.

Now, one possible alternative to dark matter is that gravity itself doesn't behave the way we think it does. There is a group of theories that we generally call MOND (MOdified Newtonian Mechanics), which propose that gravity is stronger than we think at very low levels of acceleration. When is acceleration very low? Well, it's low when an object is very far away from any other sources of gravity, and this actually describes most stars in galaxies. If a star isn't too near the center of a galaxy, the gravitational force on it is extremely small -- much smaller, for example, than the pull of the sun on the earth. Most stars are traveling in nearly a straight line, bending only ever so slightly on an enormous circular path. That bending is caused by a teeny tiny acceleration -- a gravitational pull -- toward the center of the galaxy's mass. Which is always more or less right in the middle.

MOND theories propose that as objects get farther away from each other and experience less gravity, the gravity still remains stronger than is predicted by classical newtonian mechanics. Thus, the gravity experienced by most stars in a galaxy is greater than we think, and therefore they must rotate faster for the galaxy to maintain a stable shape.

These are attractive theories IMO, and they explain some things that dark matter has difficulty explaining. However, the galaxy described in the article is a serious problem for MOND, because MOND says that it should be rotating as fast as all other galaxies of its size. But it isn't. It is rotating at the rate predicted by the classic newtonian model of gravity, which would naturally seem to rule out any other modified model of gravity.

"Intuitive" means two different things in this context. One is that, over time, theoreticians certainly gain a lot of intuition about how the relevant math works. That's no substitute for doing the work, but it does cut down on the number of mistakes you make, you often have a decent sense of what's definitely not going to work, etc.

The other meaning is what people usually imply - that some combination of analogies with everyday phenomena finally "clicks" and you "understand" the physics all of a sudden. That's just nonsense. Past the natural limits of our everyday intuitions (which are very narrow indeed, consider how something as trivial as terminal velocity is often unintuitive to students in basic mechanics) physics is applied math, everything else is a crude approximation at best.

They click about as much as a well designed but strange piece of code suddenly start to make sense.

The problem is that detection relies upon the details of the recoil of atomic nuclei, and the recoil is much smaller for cold neutrinos than relativistic neutrinos, so we have detected pretty much exactly zero Cosmic Neutrino Background neutrinos directly, although there is plenty of indirect evidence from astrophysical observation. The interaction cross section of a "heavy neutrino"-like particle might be smaller than that of a neutrino of the same temperature (it might not feel the weak force at all, so caeteris paribus it might be many orders of magnitude less detectable just because the common interaction is purely gravitational), so not only is such a Cold Dark Matter candidate harder to detect (because cold ~ low recoil) but the interaction cross-section might be even smaller than that between the neutrino and a big atomic nucleus.

> how much low hanging fruit is actually left

There's no real way to answer that rigorously, as it really depends on what one means by "low hanging". Above neutrino floor? Below detector volumes in low numbers of cubic metres? Somewhere within the reach of existing technology at budgets less than the LHC? Somewhere within the reach of technology likely available in twenty years at budgets (adjusted for inflation and economic conditions) less than Super-Kamiokande?

> someone ... created [a theory] that assumed ... dark matter

Yes, that's what theorists do. Then their theories must confront evidence from direct experiment and astrophysical observation. Most theories fail very hard and very quickly; there are an awful lot of different lines of evidence from modern experimental physics and astronomy, and all of them have to be met in a concordance cosmology.

Indeed, the article at the top highlights that a "hm, that's odd, I can't explain it if the observations hold up" will disfavour a family of serious alternatives to \Lambda-CDM. \Lambda-CDM is just fine with galaxies having substantial underdensities and overdensities of dark matter, since the coupling between CDM and luminous matter is very weak. More galaxies like the one in the article, and indeed their opposites where there is a lensing event with surprisingly little luminous matter, would be more evidence supporting CDM.

On the other hand, a cosmology which does not postulate General Relativity and instead proposes a modified theory of gravitation wherein gravitational interactions are sourced exclusively by luminous matter (and the six non-luminous matter particles already in the Standard Model) cannot be a concordance cosmology in the face of a zoo of galaxies like the one in the article.

> a theory that predicts dark matter from some other set of assumptions

Cold Dark Matter was driven by a set of large scale observations starting in the 1960s. Other lines of evidence, starting in the 1990s (BOOMERaNG experiment) also began to demand it at wholly different scales. What was not demanded was any particular microscropic description -- CDM was an "in the large" matter field with some particular characteristics in the Friedmann-Lemaître-Robertson-Walker model, and could in principle be a large mix of types of non-luminous matter including a large fraction of merely hard-to-see isolated Jupiter-esque objects made of ordinary Standard Model particles.

Entirely separately, the application of gauge theory to solve problems in the Standard Model -- wholly unconnected to the gravitational sector -- suggested the addition of extra particles, several of which could in large number fulfil the large-scale requirements of Cold Dark Matter. "Oh, neat, our proposal for a sterile neutrino or a lowest-mass superpartner, or an axion can behave like Cold Dark Matter, let's look for astrophysical evidence of our proposed particle, as well as evidence from laboratory experiments".

One can consider the reverse: neutrinos were proposed before much was known about galaxies (and even directly detected years before galaxy rotation curves were studied by Rubin et al.). Lots and lots and lots of them are produced in common astrophysical processes like stellar nucleosynthesis, and thus would have to enter into the total energy density of a cosmological model (and they do, as Hot Dark Matter, as a component of the \Lambda-CDM parameter \Omega_rad). Lots and lots and lots of them are also expected in cosmological nucleosynthesis (baryogenesis), and so also have to enter into the total energy density (and they do, as relic neutrinos of the Cosmic Neutrino Background, parameterized as \Omega_\nu). As we discover more about the microscopic details of the total energy-density, more components of the total \Omega are likely to be added. We are in serious trouble if we have to remove an existing component, however, or if we cannot resolve conflicting evidence for the total energy density \Omega_tot.

A modified gravity theory that produces a cosmology without \Omega_c h^2 ~ 0.12 (the parameter and value representing dark matter density) will tend to struggle with the lines of evidence other than galaxy rotation curves that support the current value.

I would phrase it as "There's something happening that we see only indirectly—by its diffuse gravitational influence. Let's give it a name."

That's happened many times before in science. For example, the measurable perturbation of Mercury's orbit due to special relativity—it was measured before it was explained, and there were multiple competing explanations.

Or, long before that, the causes of disease. What we believe now (invisibly small germs) was laughed at.

>The first accurate measurement of the gravitational redshift of a white dwarf was done by Popper in 1954, measuring a 21 km/sec gravitational redshift of 40 Eridani B.

The effect has been seen in experiments. (See the section on experimental verification.)

Basically “dark matter” just means “something that makes the observations work” and the choice of words “dark matter” is because it would work to have some kind of yet-unexplained matter that doesn’t interact with the matter we know about. It looked like it might also work to change the theory of gravity, in which case that was a bad choice of placeholder name — but now this is a counterexample to that idea.

We know that every particle we've been able to track down and verify the existence of responds to the gravitational force. We also know that some particles (like neutrinos) have virtually no interaction with anything other than gravitational force, to the point where the vast majority of them will pass through the entire earth undetected and having virtually no effect on anything or anyone.

The notion of particles that are even harder to detect than neutrinos doesn't seem that absurd. It's kind of anthropocentric to assume that most of the mass in the universe is going to be the same kind of mass that we are, or that we are at least capable of easily observing.

And think about what it would imply if there were no dark matter. It would almost imply that, as of the late 20th century, humanity finally had a basic comprehension of all of material existence.

The universe that humanity understood before Copernicus and Galileo is less than 1% of what we can see now. If our math is right and there really is enough dark matter and dark energy to throw off our models, then the universe we can see now is about 5% of everything that exists. That seems pretty plausible for a civilization that can barely get out of its own atmosphere.

The longer answer is that dark matter isn't particularly special or unique in this. We make observations, and where they don't match our expectations, we hypothesize new things to fill the gaps. Sometimes they're borne out by later observations, sometimes not.

We've hypothesized the existence of planets to explain deviations in planets' orbits. Sometimes the hypothesized planets existed, sometimes they didn't. In the early days of chemistry, we came up with a whole bunch of elements; sometimes they turned out to be compounds that were particularly difficult to break down. We came up a whole host of particles and subparticles, and the ones that we still think are real aren't necessarily the ones you would have guessed at the time they were proposed. If you pick up an old text book on quantum mechanics, you'll find they keep referring to it as "the new quantum mechanics", not just because it was being nailed down at the same time the text books were written but to distinguish it from "the old quantum mechanics" from twenty years earlier that it was replacing.

Sometimes the hacky models are the best we have to offer; most people will call the Standard Model of particle physics just a hacky description of the observed phenomenon, but all the elegant models to replace it haven't really paid off.

It's possible that dark matter will go the way of luminiferous aether, but so far all the observations astrophysicists are making really jive well with the idea of dark matter, so for now it gets to stay in the "weird things about the universe many people don't like" category instead of the "stupid ideas no one can believe that people used to believe" category. I mean, it makes me angry that a neutron isn't just an electron and proton mashed together, but them's the breaks.

Microlensing involves gravity. The difference is that normal matter that could be dark matter would be relatively things massive but compact things like black holes and brown dwarfs as opposed to a diffuse halo. The compactness would make them detectable by lensing.

"They behave similarly to neutrinos except are much more massive..." And yet we can build neutrino detectors and "see" neutrinos. So far similar detectors for dark matters have failed to detect anything:

https://en.wikipedia.org/wiki/Large_Underground_Xenon_experi...

Lack of detection, plus this sparse galaxy with no sign of dark matter, is starting to slowly rule out the simpler explanations by virtue of outliers that don't fit any model.

You yourself mentioned it, but I always remind detractors that the standard model IS WRONG.

The sparseness of this galaxy is what intrigues me. What if the lack singularity at the center is the key?

You've mixed this up a bit.

Because neutrinos have such a low invariant mass, they have little inertia, so are readily accelerated to speeds comparable to the speed of light at production time or when scattering off an atomic nucleus. A heavy neutrino has a higher invariant mass by definition, and thus more inertia, and thus are likely to move less than a lower-inertia regular neutrino when encountering an an atomic nucleus.

Since there is a lot of gas and dust around at the start of structure formation, you need some mechanism to keep energy-momentum localized around the matter that will become luminous matter like stars and hot gas. Adding inertia to a particle that is otherwise highly comparable to a neutrino would do the job. Normal neutrinos approaching close enough ("scattering") to an atomic nucleus would tend to get a large kick, which can be considered as a substantial Lorentz boost. Heavy neutrinos suffer a smaller kick.

There are is an additionally point worth considering here: there are almost certainly cold regular neutrinos in a relic field called the cosmic neutrino background, which is analogous to the cosmic microwave background. These neutrinos rarely interact with atomic nuclei, but when they do they are liable to get a big kick. They also are so low-energy that there would have to be an enormous amount of them if they were a major component of Cold Dark Matter; enough that there would be visible nuclear-reaction signatures in our sky as they get heated up by collision with hot gas and the like in the galaxies around which the standard cosmology expects there to be lots of Cold Dark Matter. The heating up of such huge densities of cold standard neutrinos (by weak interactions with hot baryons) would also kick many of the neutrinos out of galaxies over time, which produces a smearing out of visible matter as an observable.

Those galaxy-scale observables and the peaks in the CMB power spectrum (plotting the fluctuations in the CMB temperature spectrum at different angular scales) preclude primordial cold standard neutrinos as an important component of Cold Dark Matter operating since the formation of the earliest galaxies.

The canonical example of how tweaking your model to fit observed data doesn’t necessarily results in a good theory.