Astrophysicist here.
This is the same shtick from from a known anti-DM guy.
A few points.
* DM particle haven't yet been found.
* The current best theory of the structure formation and galaxy evolution involves dark matter and critically depend on it to reproduce observations.
* There is a broad variety of Dark matter models that are consistent with simulations.
* It is possible there is some theory that somehow explains everything without the need of dark matter, but it doesn't exist (now), and very likely it would work effectively like dark matter. Without such theory, claiming DM doesn't exist is simply stupid IMO.
* There are a few cases where you can find tensions with the existing DM based paradigm. I.e. the is test pointed in the article involving galactic bar in the paper "Fast galaxy bars continue to challenge standard cosmology". Note the toned down title. In this paper they just compared one specific feature of galactic disks in the simulations to the data and show that it doesn't match. I'd argue there are many reasons that could be the case that doesnt' involve killing DM. The same applies to other tensions.
* A final point. Even Modified Newtonian Dynamics theories require DM, because without it you cannot form enough structure early in the universe (as dark matter start to collapse earlier) and is essential to reproduce the amount of structure we see in the cosmic microwave background.
> * The current best theory of the structure formation and galaxy evolution involves dark matter and critically depend on it to reproduce observations.
Dark matter models are fine-tuned to reproduce certain observations. These don't really count as evidence in favour of DM.
> * It is possible there is some theory that somehow explains everything without the need of dark matter, but it doesn't exist (now), and very likely it would work effectively like dark matter. Without such theory, claiming DM doesn't exist is simply stupid IMO.
MOND has more points in favour for it as a preferred theory than DM models. See [1].
> Even Modified Newtonian Dynamics theories require DM, because without it you cannot form enough structure early in the universe (as dark matter start to collapse earlier) and is essential to reproduce the amount of structure we see in the cosmic microwave background.
I'm not sure why I should find your claim that DM is "essential" as persuasive given MOND has received orders of magnitude less attention and less development than DM models. I would certainly not bet any money on MOND being incapable of reproducing these observations.
> This is the same shtick from from a known anti-DM guy.
Whether it's a "shtick" or not, his basic point seems like one that is worthy of some kind of substantive counter argument, if one exists. His basic point is that small galaxies orbiting larger galaxies should experience Chandrasekhar dynamical friction if dark matter exists, but no such thing is observed. Therefore dark matter cannot exist.
Has any astrophysicist who supports the dark matter hypothesis published a counter argument to this?
Edit: A published paper of Kroupa's that gives much more detail about his point is here:
We cannot simulate evolution of galaxies using equations of General Relativity. So at best the simulations are done using Newton mechanics with minimal corrections like accounting for finite speed of light. And often it is not even done using Newton mechanics per see, but numerical models use artificial constrains like a minimal distance between stars to avoid dealing with numerical instabilities.
Yet there is no proof that such simplifications or constrains are valid on the scale of a typical galaxy. Moreover, when people managed to use full equations of General Relativity, then it was possible to account the effects previously thought to require the dark matter hypothesis.
So until it is mathematically proven that the current simulations are valid approximations, I will remain very skeptical about the dark matter.
I don't understand this: "Without such theory, claiming DM doesn't exist is simply stupid IMO."
You are saying that without another theory to explain something, the current theory must be true because ... How does this logic work exactly?
In the middle ages, there wasn't a theory that explained headaches, so dismissing the idea that we should cut hole in people's skulls to let out the evil spirits is "stupid"?
Dismissing the idea that lighting is caused by Zeus being angry is "stupid" because there is no other theory yet?
My general relativity professor claimed the need to postulate the existence of dark matter disappears when using basis vectors for derivations. To be honest, as the only undergraduate in the class, it was mostly way over my head.
Hopefully I'm not misrepresenting his views, I think the paper is DOI:10.1140/epjp/i2011-11032-x
This Pavel Kroupa guy is popping up a lot across the futurist and credulous science fandom forums. To cut to the chase, his theory only applies to galactic dynamics and it doesn't even do a very good job at it. There are many other aspects that MOND doesn't address. Kroupa doesn't even bring interesting critiques of DM to the table, just claims about his theories and then concluding DM doesn't exist.
May I get your thoughts on this idea of mine:
We all know the marbles on a rubber sheet experiment. Masses produce "dents" in spacetime that "pull" on other objects.
Couldn't it be that that these dents are balanced out by bulges between the masses, that would additionally "push" smaller masses (like solar systems) towards larger masses (like the centers of galaxies)?
In an experiment it would look like this: the rubber sheet seals the top of a container filled with water. Now if you push down at some point, the increasing water pressure will push up all around that point.
If you now added a marble onto that bulge, it would roll down a steeper angle than it would in the normal experiment ... just like if there was extra mass ("dark matter").
Has anyone in the MoND world looked into the James Webb observations that seem to contradict our current theories of galaxy formation in the early universe?
ie the observations seem to show more mature structures than predicted, we're finding.
I've been wondering if some MoND / non-DM kind of theory may better explain these new JWST observations.
- I'm not anything close to an astrophysicist, so give me some rope :-)
I would like to toss my own idea into this discussion. This idea incorporates a mechanism that would explain why gravity might slightly deviate from Newtonian and/or GR in some circumstances.
This paper also adapts GR in such a way that it is consistent with galactic rotation rates, the anisotropies of the CMB, and cosmological expansion -- while showing that the simple operation of gravity is the cause of each of these phenomena.
Cyclic Gravity and Cosmology (CGC) predicts that there are discrete specific sizes allowable for macro-objects. The instability of Bennu and the fact that it behaves more like loosely held scree rather than a compact mass -- is an example of a mass that is not exactly at one of the discrete allowable sizes. Please also refer to the link I included wherein I uploaded a video simulation of the formation of a solar system using this type of force law. (This is in section 18 of the paper)
I would greatly appreciate any comments on this idea. Copies may be downloaded here:
I feel like scientists today have forgotten a fundamental truth about science and understanding: We can never _know_ when we are right about our theories. We can only ever _know_ when we are wrong about them. New evidence can arrive at any time, and that evidence will either bolster our theories, or prove one or more theories incorrect. New evidence is always arriving.
I mean do we really believe that we know everything about this? Somehow, we A) know we have large knowledge gaps, AND B) believe that we understand things we have unanswered questions about.
We have a LOT of confidence about dark matter and exactly zero direct evidence.
It seems much more likely to me (I am not a scientist) that we are wrong about things that we assume to be hard facts and those error(s) have artificially produced the need for dark matter in order for things to make sense.
It’s not shtick, it makes perfect sense to me - unlike your post which has no substance.
Group-think does not equal truth.
Just because there is no compelling alternative theory does not make the Dark Matter Theory correct.
It’s probably nonsense, like many theories in Physics such as the Big Bang. Our level of intelligence and understanding, at the moment, is simply too small to comprehend the mysteries of the Universe that we live in.
Does this guy also reject DM models based on MACHOs?
I think they expect particles to be thrown out and result with slowdown but dark objects as massive as stars wouldn't be thrown at such a huge rate to observe slowdown, am I right?
QI (quantized inertia) is a theory created by Mike McCulloch in the UK. It predicts galaxy rotations, including wide binaries extremely well, amongst other things. It is well worth a look.
> * The current best theory of the structure formation and galaxy evolution involves dark matter and critically depend on it to reproduce observations.
The stories we like to tell require dark matter. Otherwise our stories are wrong
> * There is a broad variety of Dark matter models that are consistent with simulations.
We have a lot of stories using dark matter. We really like it
> * It is possible there is some theory that somehow explains everything without the need of dark matter, but it doesn't exist (now), and very likely it would work effectively like dark matter. Without such theory, claiming DM doesn't exist is simply stupid IMO.
Our stories are just stories but it is all we have
> * There are a few cases where you can find tensions with the existing DM based paradigm.
Our stories are not internally consistent.
> * A final point. Even Modified Newtonian Dynamics theories require DM, because without it you cannot form enough structure early in the universe (as dark matter start to collapse earlier) and is essential to reproduce the amount of structure we see in the cosmic microwave background.
We really like stories with dark matter
I love Astrophysics! Pure math with constraints. Do not confuse it with reality
What if the "dark matter" is actually ions not observable from our telescopes? Plasma Physics hold ions permeating the Universe as a premise & has physical experiments reproducable in the lab to back up their claims...And can use classical EM equations explain how the stars & galaxies work instead of some novel Physics which needs constructs such as "Dark Matter" to balance the equations...
Last I understood (I am not an expert) MOND and related theories fails to explain certain observed phenomena, and goes against other experimentally verified laws/phenomena.
PBS Spacetime covers this topic in several videos, a good one being [1]. Matt (the host, an astrophysicist), describes what MOND (and other alternative theories, like relativistic-MOND) needs to do but haven't done yet:
1. Give the right answer in more than one special case. MOND may describe a few situations accurately, but it does not describe all situations where we have evidence for dark matter. Only some.
2. Consistent with other known laws and theories that are experimentally verified. According to Matt and others, MOND is not consistent with existing laws such as conservation of energy or angular momentum.
3. Make testable predictions beyond what it was tuned for.
Am I missing out on some extraordinary development in MOND and/or MOND-like theories that occurred recently?
The article is not about MOND, it is about the falsification of Dark Matter. They do advocate MOND, but the main takeaway is right up front:
> The current cosmological model only works by postulating the existence of dark matter – a substance that has never been detected, but that is supposed to constitute approximately 25% of all the universe. But a simple test suggests that dark matter does not in fact exist. If it did, we would expect lighter galaxies orbiting heavier ones to be slowed down by dark matter particles, but we detect no such slow-down. A host of other observational tests support the conclusion: dark matter is not there.
> 1. Give the right answer in more than one special case. MOND may describe a few situations accurately, but it does not describe all situations where we have evidence for dark matter. Only some.
DM also fails numerous observations, like the one described in this article, external field effects, and more. It failed numerous previous observations as well until more parameters were added to DM theories to account for actual observations.
> 3. Make testable predictions beyond what it was tuned for.
This is backwards. DM has been tuned to match certain predictions, where MOND's predictions are free of parameters and yet fit observations. That's actually strong evidence in favour of MOND.
See my other comments here for a reference to a paper that reviews the evidence for/against both.
If someone were to ask me I'd say I embraced the scientific consensus that dark matter is real, but in my heart of hearts I have to admit that it smells like phlogiston and aether to me, and its lack of falsifiability is not something I can ignore.
Can someone with the appropriate background please confirm or refute?
"But a simple test suggests that dark matter does not in fact exist. If it did, we would expect lighter galaxies orbiting heavier ones to be slowed down by dark matter particles, but we detect no such slow-down."
Is that hypothesis correct? (i.e. would we expect lighter galaxies orbiting heavier ones to slow down if dark matter exists)
If it is correct, and we don't observe that effect, would it not be a very strong argument refuting the existence of dark matter?
For folks mentioning this as a "crackpot" or "anti-dm" theory, is the strong claim that the hypothesis is incorrect?
As a complete physics layperson, I can’t comment with any authority on the subject matter.
What I do have is a metric fuckton of experience with incentives and mechanism design in technical fields: and mainstream physicists have been talking like people who have bonuses linked to specific outcomes for decades.
The moving goalposts around falsifiability, the too-coincidental synergies between supersymmetric-style (and there for string world) stuff and missing mass (dark matter), the growing group of highly-qualified skeptics, the curt public dismissals everything from LQG to constructor stuff to MOND as beneath refutation, the popularizers who go on PBS and don’t even acknowledge a debate.
And the alternative explanation, that it takes so long to learn this stuff that your career is over if Dark Matter or String Theory turns out to be hokum? Yeah, that scans.
Not so different from Alzheimer's researchers continuing to give one another federal grants for ways to block production of amyloids decades after it has been shown to be a dead end. One wonders what all those amyloid biochemists can do with themselves once amyloid grants finally go away.
I'm an astrophysicist. I love the idea of shaking up how we do science, but MOND models really aren't that compelling for a practicing scientist (I would love to be wrong). I periodically consider working a modified gravity project, but it never seems that interesting. Maybe I can lay out my personal impressions for you in a software analogy.
There are simple situations where physics can be reasonably distinguished from the noise. Think Newton watching an apple fall from a tree -- these are test harnesses with a debugger and careful control of the environment. There are also astrophysical situations where it's very hard to squeeze insight out of the chaos. Instead of looking at an apple to derive Newtonian gravity, imagine instead trying to figure gravity out by looking at a flock of birds. There are tricky things in the way of our understanding, like lift, turbulence, and biomechanics. We hope to understand the bad situations someday, but right now it's tough. Instead of the nice test harness, these situations are like debugging through cryptic, un-reproducible user complaints. What's their OS? Do they have the right drivers installed? Do they have all of their ports blocked for some reason?
In astrophysics, one nice system is the Universe at very large scales: echos of the big bang, the clustering of matter, and the formation of structure. We have great data these days about the large scales, and general relativity (GR) + dark matter (DM) is a very predictive model here. To our chagrin, the data always matches the theory. It takes 5 or 6 parameters, but the model has withstood huge improvements in data quality without really changing since the 90s. The other nice situation is the small scales like our own solar system: we can measure things extremely precisely at home, and again GR works remarkably well. There are a few other good situations involving objects like pulsars. Finally there are the hard situations: intermediate scales that involve the messy physics of star and galaxy formation. We don't really know how these processes work, but we can cobble together simple models with DM that sort of match the data.
Modified gravities in the literature always seem to act exactly like general relativity + dark matter in the clean, understandable situations, although it takes various contortions (screening) for these models to do this. Modified gravity models seem to only act differently in the bad arenas that are hard to understand, when there trickier issues like galaxy and star formation. That's deeply suspicious, and really weakens the value proposition of these alternatives. It's like introducing a software feature to fix something that never happens on the dev machine, based on mysterious user reports that you can only half decipher.
To me, this is the cost of discovery. Just like a game of chess, you have to spend a lot of energy/cost thinking about lines that will not come to fruition to find the correct path.
Poor Alzheimer's research was/is stunted for a few people at the top pushing the wrong path. We'll see if that's the case for DM vs MOND vs something else.
Money will always be distributed to the wrong areas, but as long as you believe the human race to exist far into the future, it will eventually work itself out.
This is very cynical but there's some truth to it. I also believe that it's less conscious. Once people accept an idea they're conditioned to think of it as true, and then when jobs and institutions revolved around that it amplifies aberrations. Maybe String Theory is total bupkiss, a lot of people are going to have a hard time with it.
But with this subject we're at least working with observable data ...
I know nothing of astrophysics and my opinion counts for shithole.
But DM has always reminded me of aether (https://en.m.wikipedia.org/wiki/Aether_(classical_element)) - a magical element that we add to current understanding of physics to correct for errors caused by missing knowledge. DM sounds so magical that it feels like an unknown force akeen to gravitation.
But once again, I don't know anything about this, so, who cares.
I will start by saying that I know very little about theoretical physics so I could be totally off here. But to me the idea of dark matter feels a little like the theory of ether[1]. Basically we observed a behavior we couldn’t explain, so we create a new invisible substance that permeates the cosmos to fill the hole in our scientific world view. It turned out that we just didn’t understand the science well enough, and there was no ether out there in the first place. Dark matter feels like too convenient of an explanation given that we have never detected it.
To people saying the Dark Matter sounds like aether, phlogiston, or miasma, I have to wonder. Dark Matter is simply something that isn't affected by electromagnetic fields. We already have particles that don't interact with one or more forces. The weak interaction only affects fermions and antifermions. The strong force only affects quarks, photos are massless, etc. What's so hard to accept about a particle that doesn't interact with electromagnetism, and thus neither absorbs nor emits light?
The issue is not whether it acts like regular matter.
At issue is, rather, whether observations consistent with DM as formulated should be privileged over others that are not. Current behavior of cosmologists is that inconvenient observations should not count, and need not be paid any attention.
That is why the authors bring up sociological explanations for cosmologists' behavior. It is not scrupulous science.
It's not hard to accept existence of dark matter, but it is an extremely flexible, hard to prove answer. If you see a galaxy that rotates differently, you say it has more or less dark matter. It sounds like an easy answer.
> a model universe in which the normal matter we see around us in the form of atoms makes up only 5% of all the energy in it. About 20% is made up of exotic dark matter particles
> for each gram of normal matter there are 25 grams of the exotic dark matter
20% is four times 5%, yet there is 25x difference in mass? How does that work?
At this point, I consider "Dark Matter" to be a substitute for "Shit We Don't Know About". We know, roughly, how gravity and all these forces are supposed to behave.
Certain celestial bodies don't follow those rules according to what we know about both the rules and those bodies.
So there's something we don't know about there. Either the body or the rule is missing something. If it's the body, then there's a whole mess of matter that's just imperceptible to our current methods. It is "dark" to our observation.
(Disclaimer: am particle physicist, but not a cosmologist) For a bit of context, see Sec. III.6 of https://arxiv.org/abs/2105.05208 ("Challenges for ΛCDM: An update", where ΛCDM is the "standard model of cosmology"). The linked article refers to _known_ problems that this model has describing small scale structures. That dark matter doesn't exists seems like a non-sequitur to me.
Can someone with an actual physics background clarify my understanding:
My interpretation of "dark matter" isn't that it's literally "matter" that is invisible and we are trying to find a way to detect it and interact with it.
Rather it's just a shorthand term that explains our math. We detect gravity. The only thing that we know that makes gravity is matter. We detect more gravity for the amount of matter we see. Therefore we call what we cannot detect "dark matter". But that's it. We have no other semblance that it is somehow "matter". We might as well call it "Unknown Gravity Generator".
Is that right or am I off base?
If I'm right, then could it just be as simple that gravity Works Differently at galactic scales much the same way that everything works differently at quantum scales and relativistic (ie high velocity) scales? And as such, we don't really need to "find" dark matter, but rather we just need to find out exactly under what circumstances the equations change - much as Einstein did for relativity? And it's a super hard problem because while we can make things move at the speed of light in a lab, we can't really give something galactic mass in a lab, and observing galactic-masses in the real world on a human scale is very hard as any relevant measurements would require multiple lifetimes to observe (hypothetically)
If I'm wrong, in what other ways is dark matter "matter-y" that makes it a useful term? And do scientists believe there is a chance we could actually be able to "generate" it an experimental environment?
Only 30 years ago we had never seen a brown dwarf, even though its existence had been theorized much earlier. There are not enough brown dwarfs to account for the missing mass in the universe, but is it at all possible that some other type of body that we have not yet seen could account for it? Or is the requirement that dark matter be non-baryonic a fundamental requirement of the theory?
How do the recently discovered rare galaxies that look like they have no dark matter fit in with the idea that instead of clumpy stuff that can end up distributed oddly, we're dealing with a universal physical law? Shouldn't the physical law be the same for all galaxies?
All the celestial bodies that make up the system are in free fall (acceleration) toward the center of the system.
Gravity is the action that tries to maintain a defined acceleration towards the gravity source according to the distance from the gravity source.
Therefore, if the gravity source accelerates, the gravitational action should be considered different from when the gravity source is stationary.
Sciama named this action "inertial induction" and proposed it.
All the stars that make up the galaxy are in free fall (acceleration) toward the center of the galaxy. Current calculation methods do not take this fact into account at all.
There is no way that the observation can be explained by a calculation method that ignores the facts.
I have written a paper* on how the inertial induction of stars works in galaxies.
*N. Namba, "Stellar movement in the galaxy explained by inertial induction", Phys. Essays 15, 156(2002)
In addition, I mentioned the essence of gravity and inertia in a 2014 paper, showing that the existing theory of gravity is incomplete.
The full text of this paper is now available on GALE ACADEMIC ONE FILE.
Please see attached.
The thing to me, why do we assume kepler's law applies to galaxies? It has only been proven in relation to the solar system. Perhaps it has been proven to work for the exoplanets in other systems?
Also what exactly is dark matter? Is it some exotic unproven god or is it just dust, hydrogen that just doesnt glow or light up?
What about our observations are just wrong? What if we haven't adjusted our observations for https://en.wikipedia.org/wiki/Local_Interstellar_Cloud and thusly we are slightly off because of some latent glow from the local cloud? Or perhaps even going further and being in some transition to the neighbour cloud is throwing observations off.
What if most of the dark matter surrounding an object is moving in more or less the same direction at the same velocity, being in the same neighborhood?
The Chandrasekhar-friction-based objection to dark matter seems to assume that dark matter must be a kind of soup that is standing still, while only the galaxies (or whatever objects) wade through it.
[+] [-] sega_sai|3 years ago|reply
* DM particle haven't yet been found.
* The current best theory of the structure formation and galaxy evolution involves dark matter and critically depend on it to reproduce observations.
* There is a broad variety of Dark matter models that are consistent with simulations.
* It is possible there is some theory that somehow explains everything without the need of dark matter, but it doesn't exist (now), and very likely it would work effectively like dark matter. Without such theory, claiming DM doesn't exist is simply stupid IMO.
* There are a few cases where you can find tensions with the existing DM based paradigm. I.e. the is test pointed in the article involving galactic bar in the paper "Fast galaxy bars continue to challenge standard cosmology". Note the toned down title. In this paper they just compared one specific feature of galactic disks in the simulations to the data and show that it doesn't match. I'd argue there are many reasons that could be the case that doesnt' involve killing DM. The same applies to other tensions.
* A final point. Even Modified Newtonian Dynamics theories require DM, because without it you cannot form enough structure early in the universe (as dark matter start to collapse earlier) and is essential to reproduce the amount of structure we see in the cosmic microwave background.
[+] [-] naasking|3 years ago|reply
Dark matter models are fine-tuned to reproduce certain observations. These don't really count as evidence in favour of DM.
> * It is possible there is some theory that somehow explains everything without the need of dark matter, but it doesn't exist (now), and very likely it would work effectively like dark matter. Without such theory, claiming DM doesn't exist is simply stupid IMO.
MOND has more points in favour for it as a preferred theory than DM models. See [1].
> Even Modified Newtonian Dynamics theories require DM, because without it you cannot form enough structure early in the universe (as dark matter start to collapse earlier) and is essential to reproduce the amount of structure we see in the cosmic microwave background.
I'm not sure why I should find your claim that DM is "essential" as persuasive given MOND has received orders of magnitude less attention and less development than DM models. I would certainly not bet any money on MOND being incapable of reproducing these observations.
[1] From Galactic Bars to the Hubble Tension: Weighing Up the Astrophysical Evidence for Milgromian Gravity, https://www.mdpi.com/2073-8994/14/7/1331/htm
[+] [-] pdonis|3 years ago|reply
Whether it's a "shtick" or not, his basic point seems like one that is worthy of some kind of substantive counter argument, if one exists. His basic point is that small galaxies orbiting larger galaxies should experience Chandrasekhar dynamical friction if dark matter exists, but no such thing is observed. Therefore dark matter cannot exist.
Has any astrophysicist who supports the dark matter hypothesis published a counter argument to this?
Edit: A published paper of Kroupa's that gives much more detail about his point is here:
https://arxiv.org/pdf/1406.4860.pdf
[+] [-] _0w8t|3 years ago|reply
Yet there is no proof that such simplifications or constrains are valid on the scale of a typical galaxy. Moreover, when people managed to use full equations of General Relativity, then it was possible to account the effects previously thought to require the dark matter hypothesis.
So until it is mathematically proven that the current simulations are valid approximations, I will remain very skeptical about the dark matter.
[+] [-] spfzero|3 years ago|reply
You are saying that without another theory to explain something, the current theory must be true because ... How does this logic work exactly?
In the middle ages, there wasn't a theory that explained headaches, so dismissing the idea that we should cut hole in people's skulls to let out the evil spirits is "stupid"?
Dismissing the idea that lighting is caused by Zeus being angry is "stupid" because there is no other theory yet?
[+] [-] sbussard|3 years ago|reply
Hopefully I'm not misrepresenting his views, I think the paper is DOI:10.1140/epjp/i2011-11032-x
[+] [-] cratermoon|3 years ago|reply
[+] [-] xnoreq|3 years ago|reply
Couldn't it be that that these dents are balanced out by bulges between the masses, that would additionally "push" smaller masses (like solar systems) towards larger masses (like the centers of galaxies)?
In an experiment it would look like this: the rubber sheet seals the top of a container filled with water. Now if you push down at some point, the increasing water pressure will push up all around that point. If you now added a marble onto that bulge, it would roll down a steeper angle than it would in the normal experiment ... just like if there was extra mass ("dark matter").
[+] [-] nickpinkston|3 years ago|reply
ie the observations seem to show more mature structures than predicted, we're finding.
I've been wondering if some MoND / non-DM kind of theory may better explain these new JWST observations.
- I'm not anything close to an astrophysicist, so give me some rope :-)
[+] [-] jbakhos|3 years ago|reply
This paper also adapts GR in such a way that it is consistent with galactic rotation rates, the anisotropies of the CMB, and cosmological expansion -- while showing that the simple operation of gravity is the cause of each of these phenomena.
Cyclic Gravity and Cosmology (CGC) predicts that there are discrete specific sizes allowable for macro-objects. The instability of Bennu and the fact that it behaves more like loosely held scree rather than a compact mass -- is an example of a mass that is not exactly at one of the discrete allowable sizes. Please also refer to the link I included wherein I uploaded a video simulation of the formation of a solar system using this type of force law. (This is in section 18 of the paper)
I would greatly appreciate any comments on this idea. Copies may be downloaded here:
https://vixra.org/pdf/2203.0032v3.pdf
[+] [-] replygirl|3 years ago|reply
[+] [-] naikrovek|3 years ago|reply
I mean do we really believe that we know everything about this? Somehow, we A) know we have large knowledge gaps, AND B) believe that we understand things we have unanswered questions about.
We have a LOT of confidence about dark matter and exactly zero direct evidence.
It seems much more likely to me (I am not a scientist) that we are wrong about things that we assume to be hard facts and those error(s) have artificially produced the need for dark matter in order for things to make sense.
[+] [-] garyclarke27|3 years ago|reply
[+] [-] scotty79|3 years ago|reply
I think they expect particles to be thrown out and result with slowdown but dark objects as massive as stars wouldn't be thrown at such a huge rate to observe slowdown, am I right?
[+] [-] mynegation|3 years ago|reply
[+] [-] onlyrealcuzzo|3 years ago|reply
[+] [-] unknown|3 years ago|reply
[deleted]
[+] [-] taylorius|3 years ago|reply
[+] [-] worik|3 years ago|reply
We do not know that dark matter exists
> * The current best theory of the structure formation and galaxy evolution involves dark matter and critically depend on it to reproduce observations.
The stories we like to tell require dark matter. Otherwise our stories are wrong
> * There is a broad variety of Dark matter models that are consistent with simulations.
We have a lot of stories using dark matter. We really like it
> * It is possible there is some theory that somehow explains everything without the need of dark matter, but it doesn't exist (now), and very likely it would work effectively like dark matter. Without such theory, claiming DM doesn't exist is simply stupid IMO.
Our stories are just stories but it is all we have
> * There are a few cases where you can find tensions with the existing DM based paradigm.
Our stories are not internally consistent.
> * A final point. Even Modified Newtonian Dynamics theories require DM, because without it you cannot form enough structure early in the universe (as dark matter start to collapse earlier) and is essential to reproduce the amount of structure we see in the cosmic microwave background.
We really like stories with dark matter
I love Astrophysics! Pure math with constraints. Do not confuse it with reality
[+] [-] mixmastamyk|3 years ago|reply
> Without such theory, claiming DM doesn't exist is simply stupid IMO.
Expressing flaws in an idea does not require a better one in any way. The search continues.
[+] [-] briantakita|3 years ago|reply
[+] [-] ziddoap|3 years ago|reply
PBS Spacetime covers this topic in several videos, a good one being [1]. Matt (the host, an astrophysicist), describes what MOND (and other alternative theories, like relativistic-MOND) needs to do but haven't done yet:
1. Give the right answer in more than one special case. MOND may describe a few situations accurately, but it does not describe all situations where we have evidence for dark matter. Only some.
2. Consistent with other known laws and theories that are experimentally verified. According to Matt and others, MOND is not consistent with existing laws such as conservation of energy or angular momentum.
3. Make testable predictions beyond what it was tuned for.
Am I missing out on some extraordinary development in MOND and/or MOND-like theories that occurred recently?
[1] https://www.youtube.com/watch?v=0sTBZ2G4vow
[+] [-] jvanderbot|3 years ago|reply
> The current cosmological model only works by postulating the existence of dark matter – a substance that has never been detected, but that is supposed to constitute approximately 25% of all the universe. But a simple test suggests that dark matter does not in fact exist. If it did, we would expect lighter galaxies orbiting heavier ones to be slowed down by dark matter particles, but we detect no such slow-down. A host of other observational tests support the conclusion: dark matter is not there.
[+] [-] naasking|3 years ago|reply
DM also fails numerous observations, like the one described in this article, external field effects, and more. It failed numerous previous observations as well until more parameters were added to DM theories to account for actual observations.
> 3. Make testable predictions beyond what it was tuned for.
This is backwards. DM has been tuned to match certain predictions, where MOND's predictions are free of parameters and yet fit observations. That's actually strong evidence in favour of MOND.
See my other comments here for a reference to a paper that reviews the evidence for/against both.
[+] [-] causi|3 years ago|reply
[+] [-] neosat|3 years ago|reply
Is that hypothesis correct? (i.e. would we expect lighter galaxies orbiting heavier ones to slow down if dark matter exists)
If it is correct, and we don't observe that effect, would it not be a very strong argument refuting the existence of dark matter?
For folks mentioning this as a "crackpot" or "anti-dm" theory, is the strong claim that the hypothesis is incorrect?
[+] [-] benreesman|3 years ago|reply
What I do have is a metric fuckton of experience with incentives and mechanism design in technical fields: and mainstream physicists have been talking like people who have bonuses linked to specific outcomes for decades.
The moving goalposts around falsifiability, the too-coincidental synergies between supersymmetric-style (and there for string world) stuff and missing mass (dark matter), the growing group of highly-qualified skeptics, the curt public dismissals everything from LQG to constructor stuff to MOND as beneath refutation, the popularizers who go on PBS and don’t even acknowledge a debate.
And the alternative explanation, that it takes so long to learn this stuff that your career is over if Dark Matter or String Theory turns out to be hokum? Yeah, that scans.
[+] [-] ncmncm|3 years ago|reply
[+] [-] find|3 years ago|reply
There are simple situations where physics can be reasonably distinguished from the noise. Think Newton watching an apple fall from a tree -- these are test harnesses with a debugger and careful control of the environment. There are also astrophysical situations where it's very hard to squeeze insight out of the chaos. Instead of looking at an apple to derive Newtonian gravity, imagine instead trying to figure gravity out by looking at a flock of birds. There are tricky things in the way of our understanding, like lift, turbulence, and biomechanics. We hope to understand the bad situations someday, but right now it's tough. Instead of the nice test harness, these situations are like debugging through cryptic, un-reproducible user complaints. What's their OS? Do they have the right drivers installed? Do they have all of their ports blocked for some reason?
In astrophysics, one nice system is the Universe at very large scales: echos of the big bang, the clustering of matter, and the formation of structure. We have great data these days about the large scales, and general relativity (GR) + dark matter (DM) is a very predictive model here. To our chagrin, the data always matches the theory. It takes 5 or 6 parameters, but the model has withstood huge improvements in data quality without really changing since the 90s. The other nice situation is the small scales like our own solar system: we can measure things extremely precisely at home, and again GR works remarkably well. There are a few other good situations involving objects like pulsars. Finally there are the hard situations: intermediate scales that involve the messy physics of star and galaxy formation. We don't really know how these processes work, but we can cobble together simple models with DM that sort of match the data.
Modified gravities in the literature always seem to act exactly like general relativity + dark matter in the clean, understandable situations, although it takes various contortions (screening) for these models to do this. Modified gravity models seem to only act differently in the bad arenas that are hard to understand, when there trickier issues like galaxy and star formation. That's deeply suspicious, and really weakens the value proposition of these alternatives. It's like introducing a software feature to fix something that never happens on the dev machine, based on mysterious user reports that you can only half decipher.
[+] [-] irjustin|3 years ago|reply
Poor Alzheimer's research was/is stunted for a few people at the top pushing the wrong path. We'll see if that's the case for DM vs MOND vs something else.
Money will always be distributed to the wrong areas, but as long as you believe the human race to exist far into the future, it will eventually work itself out.
[+] [-] jollybean|3 years ago|reply
But with this subject we're at least working with observable data ...
[+] [-] ape4|3 years ago|reply
[+] [-] charles_f|3 years ago|reply
But DM has always reminded me of aether (https://en.m.wikipedia.org/wiki/Aether_(classical_element)) - a magical element that we add to current understanding of physics to correct for errors caused by missing knowledge. DM sounds so magical that it feels like an unknown force akeen to gravitation.
But once again, I don't know anything about this, so, who cares.
[+] [-] celeritascelery|3 years ago|reply
[1] https://en.m.wikipedia.org/wiki/Aether_theories
[+] [-] oniony|3 years ago|reply
And this wikipedia article, <https://phys.org/news/2022-07-dark-ditch-favor-theory-gravit...>, seems to give a more balanced appraisal.
[+] [-] lief79|3 years ago|reply
[+] [-] cratermoon|3 years ago|reply
[+] [-] ncmncm|3 years ago|reply
At issue is, rather, whether observations consistent with DM as formulated should be privileged over others that are not. Current behavior of cosmologists is that inconvenient observations should not count, and need not be paid any attention.
That is why the authors bring up sociological explanations for cosmologists' behavior. It is not scrupulous science.
[+] [-] saberdancer|3 years ago|reply
[+] [-] davrosthedalek|3 years ago|reply
[+] [-] munchler|3 years ago|reply
> for each gram of normal matter there are 25 grams of the exotic dark matter
20% is four times 5%, yet there is 25x difference in mass? How does that work?
[+] [-] bena|3 years ago|reply
Certain celestial bodies don't follow those rules according to what we know about both the rules and those bodies.
So there's something we don't know about there. Either the body or the rule is missing something. If it's the body, then there's a whole mess of matter that's just imperceptible to our current methods. It is "dark" to our observation.
[+] [-] untilted|3 years ago|reply
[+] [-] deanCommie|3 years ago|reply
My interpretation of "dark matter" isn't that it's literally "matter" that is invisible and we are trying to find a way to detect it and interact with it.
Rather it's just a shorthand term that explains our math. We detect gravity. The only thing that we know that makes gravity is matter. We detect more gravity for the amount of matter we see. Therefore we call what we cannot detect "dark matter". But that's it. We have no other semblance that it is somehow "matter". We might as well call it "Unknown Gravity Generator".
Is that right or am I off base?
If I'm right, then could it just be as simple that gravity Works Differently at galactic scales much the same way that everything works differently at quantum scales and relativistic (ie high velocity) scales? And as such, we don't really need to "find" dark matter, but rather we just need to find out exactly under what circumstances the equations change - much as Einstein did for relativity? And it's a super hard problem because while we can make things move at the speed of light in a lab, we can't really give something galactic mass in a lab, and observing galactic-masses in the real world on a human scale is very hard as any relevant measurements would require multiple lifetimes to observe (hypothetically)
If I'm wrong, in what other ways is dark matter "matter-y" that makes it a useful term? And do scientists believe there is a chance we could actually be able to "generate" it an experimental environment?
[+] [-] isolli|3 years ago|reply
[+] [-] rsaarelm|3 years ago|reply
[+] [-] NoriakiNamba|3 years ago|reply
*N. Namba, "Stellar movement in the galaxy explained by inertial induction", Phys. Essays 15, 156(2002)
In addition, I mentioned the essence of gravity and inertia in a 2014 paper, showing that the existing theory of gravity is incomplete. The full text of this paper is now available on GALE ACADEMIC ONE FILE. Please see attached.
https://go.gale.com/ps/i.do?p=AONE&u=googlescholar&id=GALE|A...
[+] [-] incomingpain|3 years ago|reply
However, we have observations which break the rules. https://en.wikipedia.org/wiki/Galaxy_rotation_curve
The thing to me, why do we assume kepler's law applies to galaxies? It has only been proven in relation to the solar system. Perhaps it has been proven to work for the exoplanets in other systems?
Also what exactly is dark matter? Is it some exotic unproven god or is it just dust, hydrogen that just doesnt glow or light up?
What about our observations are just wrong? What if we haven't adjusted our observations for https://en.wikipedia.org/wiki/Local_Interstellar_Cloud and thusly we are slightly off because of some latent glow from the local cloud? Or perhaps even going further and being in some transition to the neighbour cloud is throwing observations off.
[+] [-] greenthrow|3 years ago|reply
[+] [-] kazinator|3 years ago|reply
The Chandrasekhar-friction-based objection to dark matter seems to assume that dark matter must be a kind of soup that is standing still, while only the galaxies (or whatever objects) wade through it.