Not all, LCDM does or can at least predict distribution, primordial/micro black holes, MACHO's CBM etc. don't but then most of them rely on the same distribution as normal matter (because for the most part they are just that, as anything that falls within the existing standard model is well normal matter).
Honestly, I'm a little tired of the whole dark matter thing. There's no evidence for it, and physicists keep coming up with more and more complex models to fit the data when they don't actually understand what's going on there.
Why haven't MOND or other theories become more popular?
Edit: MOND isn't great either - it just has a parameter that they tune until it matches the observation.
Edit 2: I am not a physicist, I am simply a concerned citizen.
Huge difference: when Higgs was predicted there was a clear path to how to find it. We do not currently have a theory that describes a way to find LCDM that is not begging the question of its existence (not circular reasoning), although we do have several shots-in-the-dark that are ongoing (and a handful that have concluded with no observation).
Also IIRC, Rubin's seminal observations on dark matter were in the 60s too, and dark matter was postulated in 1930.
> Huge difference: when Higgs was predicted there was a clear path to how to find it.
is that really a huge difference? plenty of eventually-proven math conjectures were initially posed with no knowledge of how a proof will be found.
perhaps with the higgs it was easier because it was conceivable that we could produce the necessary collision energies here on earth, while other problems remain at unattainable scales for a clear path to exist today.
As a theoretical math major and a practicing scientist, I'm just going to have to say that these are not comparable, neither in process, nor ontologically.
> conceivable
that's a very weak way of saying the scaling factor of collision energies was known, and the technology to build the required machine right around the corner (we could have found the higgs with technology proposed for the hole in texas, only 20-or-so years after the prediction of the higgs; at the time higgs was postulated superconductors were already known for 10 years and the first superconducting NMR was 10 years away).
Anyways, my point is that there is a categorical difference. At the time of its postulation, building an experiment that could say yay or nay about the existence of the higgs was largely an engineering problem.
True. But f.e. search for Higgs on Tevatron pretty much started after top quark discovery, ca 1995. And Tevatron was covering one energy range after another in search for Higgs, and would have found it if not being closed, around today date. We knew what to look for.
With DMwe're shooting in the dark, so to speak, in hope something will turn up
I'm not sure why this is being downvoted, it's technically correct (tho I'm not sure if it was in good faith) the observations don't explicitly require Dark Matter, it's just currently the most likely answer given the theoretical frameworks and observational evidence we have.
There are essentially 3 (or 2.5) explanations, that we have (a lot of) missing mass, that we don't understand gravity or that we don't understand spacetime.
Most theories revolve around the missing mass part this includes all possible theoretical candidates for Dark Matter from both within and beyond the standard model, overall a single candidate or a combination of a few likely ones seems to fit our observations the most.
Modified Gravity; these theories actually have gotten plenty of attention in the 80's and 90's but the problem is that most of them don't fit observations especially modern ones like the bullet cluster and gravitational waves, most of them aren't relativistic (or don't have a relativistic formulation) and they overall suck at predicting everything else including the formation of galaxies and stars in the first place.
"Modified Spacetime"; mostly relegated to the dark corners of the web and to pseudo scientific forums technically possible but I haven't seen anything that comes close to being an actual theory as in having an actual mathematical basis.
They basically revolve around various possible ways of affecting spacetime curvature, basically if you could curve spacetime without out mass to the same extent as say the earth's mass does you'll technically will end up with the same gravity well. The more "serious" of these tend to revolve around various attempts at gauge gravity.
I usually consider the "Modified Spacetime" as being an offshoot of Modified Gravity theories.
"The most serious problem facing [MOND] is that it cannot completely eliminate the need for dark matter in all astrophysical systems: galaxy clusters show a residual mass discrepancy even when analysed using MOND. The fact that some form of unseen mass must exist in these systems detracts from the elegance of MOND as a solution to the missing mass problem..."
Sure. But the question was: why doesn't MOND get more love? And the answer is: because it doesn't actually solve the problem. Nothing solves the problem at the moment. That's what makes this such a juicy mystery.
If we are being completely frank here MOND doesn't gets as much love because it goes against GR, besides the fact that General Relativity is one of the most observationally validated theories we have there is quite a bit of dogma revolving around it as well.
MOND isn't a career ender as much as say cold fusion is, but it's pretty close.
And in all honesty if we look at Modified Gravity theories as a whole they shouldn't be anymore more offensive to one's career than say string theory and despite string theory being essentially a dead end for decades now it doesn't get anywhere near that level of stigma that MOND does and that's more for a cultural / dogmatic reason than purely scientific ones.
MOND brings it down to levels that could potentially be explained with missing baryonic matter and other Dark Matter candidates that fall within the standard model.
There are however other issues with MOND including that gravity is still instantaneous (in most variations) which we know with gravitational waves it isn't, as well as that most of them don't lend to the formation of stars and galaxies.
If we take vanilla MOND then the universe as we know it shouldn't have been formed matter wouldn't clump up to form the formations we can see around us and the one we live on.
If MOND and Dark Matter both fit the data and MOND did it with few parameters while DM did it with a field of parameters, everyone would prefer MOND and it wouldn't be the slightest bit controversial. The problem is that MOND doesn't fit the data. Some galaxies behave one way, some behave the other way, and it isn't very inspiring when a MOND model fails to fit observations and its advocates try to hand-wave the problem away.
DM: we see complexity, let's treat it as fundamental.
MOND: we see complexity, let's ignore the inconvenient parts.
I think that is a mischaracterization; IIRC, MOND fits the overwhelming balance of galaxies with a single parameter, and there are only a handful of exceptions (probably around in the hundreds or so?) out of all of the galaxies.
also:
MOND doesn't explain intergalactic movement, or the clumpiness of the universe. But there's ALSO no good reason to believe that that "LCDM dark matter" does either, because by the "curve-fitting nature" of LCDM it could literally explain anything. If all of the oxygen in my room went to the northeast corner of my room and suffocated me, you could come up with a dark matter field that explained that phenomenon. As a scientist, that worries me. Also doesn't mean that LCDM is wrong.
Sure, but a counterexample of one or two could be literally anything. After all, conventional dark matter theories don't do a good job of explaining why there just so happens to be galaxies with highly-deviant clumps of dark matter.
If the bullet cluster is a great counter example for MOND, then conventional dark matter is highly opportunistic curve fitting (which doesn't mean it's not correct).
And that's why there's groups working on both dark matter and modified/new theories of gravity.
It seems quite difficult to modify GR or make a new theory of gravity which explains the new observations while matching GR in the old ones, where GR has been verified. But if someone manages, then you'll see scientists flock to it.
But the hypothesis of dark matter fits all of the evidence, while no alternative theory of gravity comes close. That's what makes dark matter so attractive to physicists.
I'm not shunning the idea, I've worked on alternative explanations myself (with no concrete result), but for the moment we remain convinced that dark matter is the better theory.
MOND does not reject the observational evidence for Dark Matter theory, it just postulates that it primary cause is not a "non-baryonic particle that interacts only via the gravitational field".
To be fair, there is a lot of evidence for the phenomena described as "dark matter", but as yet zero detection of actual matter that fits it's properties.
Perhaps that is the complaint here - and asking for academic background is an argument from authority...
So the name of dark matter might be misleading, but there is some mass/pressure/something that's causing gravitational lensing but itself doesn't interact with light.
You are assuming this thing exists because it has properties to fit your observations, and then using that as evidence that said thing exists. I'm not saying DM doesn't exist..it probably does, but your logic is flawed
I am just another armchair physicist but saying there is no detection of dark matter sounds a bit like circular reasoning. You detect matter like your phone in your hand through electromagnetic interaction. We have detected that there is something in space that completely disregards electromagnetic force, but exerts gravitational force. Hence the idea that we have not detected it is simultaneously false in 2 ways:
- it cannot be detected the way you detect your phone in your hand or see light so your definition of detection seems to escape the basic premise of dark matter: its ability to avoid electromagnetic force, and also,
- we have detected it through gravitational anomalies
But to be fair, you can detect the phone in your hands many many many ways.
With the DM effect, we ONLY see gravitational anomalies as you said. Though DM may very well be the reason, it does not automatically mean it MUST be some matter we cannot see
and asking for academic background is an argument from authority...
No it isn't. It isn't even an argument of any sort. I think most reasonable people would interpret that as an attempt to gather evidence to support applying a heuristic filter to the question of "is it worth my time to continue engaging with this person or not?"
I admit that I haven't been reading about dark matter lately. Last I checked, it had not been verified via experimental evidence. Is that still the case?
There is a difference between observations and _experimental_ evidence, which I think the GP was referring to.
It is heavily verified by experimental evidence, and has been since it was first proposed. That's why people have spent so much time studying it. It's not like it was just a random hair-brained idea someone had.
The only thing we haven't done is figured out what it is in terms of other concepts we know, such as elementary particles.
Sure, the anomolous observations are verified, but there is no experiment that has been conducted to directly detect it as far as I know. What you said about what we don't know is precisely my point. Given that this article mentions the discrepancy between models and observations, I'd say we know hardly much at all about it--whatever it may be given that we can't directly detect it and we can't even make a good model to predict its behavior
Healthy skepticism is a good thing for science. Until DM is proven, it is worth exploring other avenues--may the best experiment win. If you don't understand this, you are a zealot rather than a scientist.
Everyone here agrees that healthy skepticism is good for science. The GP's post was not healthy skepticism:
> Honestly, I'm a little tired of the whole dark matter thing. There's no evidence for it, and physicists keep coming up with more and more complex models to fit the data when they don't actually understand what's going on there.
Reads as:
"I know nothing, but I assume that there's no evidence for this because I haven't done any research, and I assume that physicists are foolishly sticking to the theory because they're desperate".
This couldn't be further from the truth, and it could be dispelled with 5 minutes of googling.
You're being downvoted for the same dismissive cluelessness:
> Last I checked, it had not been verified via experimental evidence. Is that still the case?
In reality, there has been mountains of experimental evidence ever since the theory was first proposed, which is why it has been taken seriously for decades. That's why the "Observational evidence" section on Wikipedia has 11 sections in it, reflecting thousands of papers. We still don't know what it is at an _atomic_ level but we know where it is, what it weighs, how it moves, and what it interacts with.
OK honestly this shit is equivalent to global warming denialism and should be tolerated just as much i.e. much less than HN let alone mainstream media allows.
Honestly I'm not sure why some people oppose "dark matter" so much. We know there's something out of ordinary, it behaves like matter, and it doesn't interact with light (hence "dark"). Given that, "dark matter" is as inoffensive a name as possible. People are acting like we named it "quasiflavored eleven-dimensional supersymmetry carriers."
I think it's a natural reaction after Einstein. The whole physics world was certain about this Aether thing, and it turned out to be wrong and much more beautifully solved by plain geometry. "Dark matter", taken at surface level, sounds like going down the exact same rabbit hole.
There's a fundamental difference though. With dark matter, the evidence of the stuff is much more direct and precise. We can determine the shape and concentration of it. Aether on the other hand was a hand-wavy metaphysical concept from the beginning. There was never any experimental evidence that aether was a real thing; it was just a concept invented to patch up the inherent inconsistencies in electromagnetic theory near the speed of light.
Or spacetime is that aether. This is like some dusty books have been claiming that there's an invisible fluid substance around us that supports life, then when science discovers oxygen, it says "See? There is no invisible ether or anything like that around us, only atoms."
Its not the name "dark matter" have an objection too, its misleading and/or confused attitudes like the one you yourself exhibit in your comment!
> We know there's something out of ordinary, it behaves like matter, and it doesn't interact with light
That's wrong, and presupposes the existence of dark matter, rather than treating it as a possibility. What we know is that our formulas don't match up with our observations. We don't know why that is. One suggestion is that there is some sort of invisible stuff out there that we cannot detect, but would make our formulas add up, so it could exist. Its perfectly legitimate to speculate about the existence of dark matter, and to set up different experiments to try to detect it, but its not fine to pretend that its "settled science" that dark matter is out there and its only a matter of finding it. Unless and until someone detects "dark matter" or figures out another reason why our calculations don't add up its existence will remain an open question.
Years ago, vaguely describing it as “formulas not adding up” would have been fair enough but there are quite a few studies now giving a much more detailed picture than that. Some galaxies seem to have quite a lot of it, some galaxies not much at all, so it’s harder and harder to just tweak formulas for the visible matter in a way that explains all the evidence.
It accumulates in blobs, around some galaxies, trailing others, and not in some galaxies at all. So the appearance and behavior of it matches the model that there's "stuff" there, not that there's some parameter missing from our gravitational model. With the latter you'd presumably get some less arbitrary accumulations of it.
I think the point of MOND is that it explains a higher proportion of galaxies with a single parameter than something where you have to pick a parameter for each galaxy strictly from observation.
Key to note that this doesn't mean it's right. But one wonders why there isn't more skepticism about conventional dark matter theories.
Like what if I said "there isn't global warming, there's just a mysterious unobservable dark thermal input adjustment that we have to apply to every month's reading to make our models work out". You'd say that I was crazy.
I’m not a physicist but this seems like an arbitrary metric. One theory claims that there are fundamental rules that the physical forces obey, but they don’t seem to obey them in certain places we can observe. The other theory also says there are certain physical rules that govern matter, and those rules hold everywhere, but merely posits that the matter is distributed unequally. Since the latter condition is obviously true of normal baryonic matter, this doesn’t seem like a parameter explosion.
Yes but we have independent observation of that baryonic matter. Suppose we hadn't discovered the theory of relativity. The rules for gravity hold everywhere except for the orbit of Mercury. For several decades it is reasonable to guess there is "mystery meat" planet somewhere that we can't see. Possibly even a hamburger sized black hole orbiting the sun. But to think that the field equations for gravity are wrong is nonsense. Fast forward a few decades and Eventually we can't find this mystery planet and it's decided that an interpretation that the gravity field equations are wrong is more sensible.
I’m not objecting to the idea of alternative theories. I’m objecting to the parent commenter’s idea that “explains more galaxies with a single parameter” should be an argument in favor of it. By that metric your Mercury example is a great illustration: oddities in several of the outer planets’ orbits were caused by unknown planets, but only Mercury’s unusual orbit requires new theories of gravity. So clearly the Newtonian theory explains more instances with a single parameter, and is thus better. (Obviously in the real world this is not how theories should be evaluated.)
The appropriate MOND/DM analogy here would be to propose general relativity as an explanation for Mercury but then find another planet(oid) in the system where GR suggests an effect, but to notice that the effect is measurably not present. You can’t just say “got most of them right” when you propose such a theory. You need to revise your theory until it explains the observations.
There's a lot of evidence for it, just not direct detection on it. It's like if you came into your room and saw writing on the wall, your carpets removed, your computer taken apart, etc. and then claimed there's no evidence anyone has been in your room just because you didn't physically find anyone in your room.
There are things to be frustrated about with the dark matter hypothesis (and I am too), but lack of evidence isn't one. Dark energy seems to be another beast though...
The current top-level comments are infuriating. You demand that scientists be honest, then accuse them of all-out fraud when they admit they have questions, secure in your ignorance of the things they actually have figured out and tried to tell you over and over again. You are more concerned with feeling smart and skeptical than actually learning. You are the reason we can't have nice things.
For some reason, dark matter brings out the crazies. It was true when I worked in physics, and it's still true now.
People need to understand that physicists do NOT consider dark matter to be settled, in any sense! The experiments are not done to polish up any theory... they're done because all of the theories are awful, and guidance from observations is necessary for further progress.
> physicists do NOT consider dark matter to be settled, in any sense
Almost every honest physicist will say that. But not all physicists are honest, and I don't trust that there is a positive correlation between honest scientists and loudness in the scientific community, especially where it interfaces with the general public. And if you want an explanation of why dark matter brings out the crazies, I think that's as good a reason as any.
Oh bullshit. Know nothing's of the intricacies of the field love to pretend that the experts are dishonest or idiots. It is so tiring. I'm a neuroscientist, I know nothing of this field, so I keep my damn mouth shut about it. People who've read a few pop physics books should also shut their damn mouths.
nobody's saying they're idiots. But it's not like the structure of how contemporary scientific discovery gets done isn't ridden with questionable processes that should make you doubt that the system is aligned with producing good science. There is nothing fundamentally different about how physics gets funded (TLAs like NSF, NIH giving out grants via committee), and how physics professors get promoted (H-factors and hiring committees, playing politics at conferences, choosing strategically to work for certain PIs, the truly smart grad students and postdocs burning out and quitting).
Most of my peers from high school went into high energy physics (one works at JLab, another is a professor at an east coast college; the others quit or went into... other fields, like finance). Although I am no longer a practicing biochemist, when we got together we complained about the exact same things. So yeah, I don't know about the intricacies of what happens in physics. But that doesn't mean I don't have real insight about what's going on.
I believe GP is trying to say that the people you hear the most from are not necessarily the real experts. The phenomenon of experts being silent while idiots make noise is damn near a human universal, so it's a hypothesis worth taking seriously regardless of the field. The problem is when people use that as an excuse to loudly substitute their own nonsense rather than try to find the actual experts.
For example, throughout my career, whatever the commercial domain, there is almost always a noisy competitor whose product is an amateur hour shit-show, usually a superficial clone of the market leader, that still picks up market share from naive customers by sheer volume of message.
When you’re trying to focus on making something that actually creates value for others this can be an irritating distraction. “Pay attention to competitors, but obsess over customers” isn’t always a comfortable mantra to fulfil.
I suspect the fact that you can't observe dark matter directly, but physicists all seem to promote it, enables a combination of (at least superficially) reasonable empirical skepticism and conspiracy-minded contrarianism to work together. You have to expend a little bit of actual effort to see through the logic, and if you have any inclination to believe Big Physics is lying to you, then it's easy to just not bother. People forget that the universe does not owe us comprehensibility.
Contrary to your linked comment, to this non-physicist, nearly all physicists in public seem to say that, while the details are unknown, dark matter is pretty much definitely a thing. AFAICT they're not wrong about there being multiple lines of evidence for it. But if you mean "no one worth listening to" says even that much, then I don't know any physicists worth listening to.
It does not seem like it to me (non physicist with some physicist friends from other fields who try to dumb down stuff to me).
In my world (SE) it seems like a proprietary binary that must be included for the rest of an open source product describing the observable universe to work very well. Everyone seems to hate it, but nobody wrote something better, yet.
Every competing implementation fails to work in other areas that we already are using in production, extensively.
And when some professional, who read and understood the source code, starts talking about it, a lot of people voice stupid ideas that they would not have if they passed some lectures on the subject.
Edit to add: I envy physicists a little - the best thing for “them” to happen seems to be if something does not work in a very peculiar way.
Ok, but do any of them take seriously the idea that it doesn't exist at all? It was my impression that even theories that try to modify gravity in ways that also explain stuff like the CMB spectrum sort of end up inventing dark matter anyway (IIRC TeVeS was the big one like that).
The attitude you’re describing is an epidemic right now. Maybe it’s always been like this, and it’s just a part of human nature, but it seems more prevalent than ever.
> You demand that scientists be honest, then accuse them of all-out fraud when they admit they have questions, secure in your ignorance of the things they actually have figured out and tried to tell you over and over again.
Because everybody thinks they can "intuit" their way to knowledge.
No. No you can't. We KNOW you can't. We have experiments and statistics and double-blind trials for exactly this reason.
"Intuition" only works when coupled with huge amounts of knowledge and effort.
Part of the problem is that too many people never suffer the consequences of "truth" in modern society. Consequently, far too many people get the idea that "truth" is negotiable.
But, this is not new:
“There is a cult of ignorance in the United States, and there has always been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.”
If you've been raised on a intellectual diet of breakfast television, lip-service superstition, patriotic exceptionalism, and checkbox pedagogy, then you may not inwardly digest that knowledge progresses by incrementally pushing back the boundaries of ignorance, or its key corollary, that leading-edge discovery is driven by people with the most nuanced understanding of their own ignorance.
The existential confrontation of research processes and discourse is such anathema to a prevailing mindset of certainty and explanation that a psychosis may develop.
So bring your kids up to be comfortable with doubt, to inoculate them against becoming conspiracy nuts.
For every one of those here, there are 1,000X more out there like them. We’ve managed through this before, but social media has made anti-intellectualism the dominant strain of public expression. It is only natural for public leaders to follow. It’s where the action is.
It was nearly a millenia between the sacking of Rome and the Renaissance. Intellectuals seem to have the idea that we can’t have that type of reset again. As populations options narrow with climate change and vaunted scientists fail to provide solutions, those populations will turn elsewhere.
All my life the public has had an anti-intellectual bend to it. Which is fine, disagreement and conflict has it's place. People come with their preferred worldview. The issue is when luddites try to break printing presses, burn down labs and ignore true results when they appear.
As I understand, they see a discrepancy between simulation and observation of some lensing observables. Could be something wrong with the calculation of the observables, something wrong with the implementation of the simulations, or (the exciting bit) with the physics put into the simulations. As a complete non-expert on lensing observables and cosmological simulations, I'd guess it's one of the first two. As mentioned in the text, there are many other discrepancies between observations and simulations that are still unresolved. This adds to that list.
There's a good candidate for the dark matter role. You're going to laugh (and then downvote fiercely): it's ether.
However this time science knows what this ether is and already performs some experiments on it, although doesn't recognize it as a valid state of matter.
Ether is multiquarks essentially. Protons and neutrons are the densest or biggest form of ether. A tetraquark sporadically appearing in experiments is a particle of thinner ether. Individual quarks are very thin ether. So far so good and it's just a matter of terminology.
There are a few interesting claims made with respect to ether that science can actually verify. One claim is that ether is a legit state of matter and everything is packed with it. This doesn't contradict observations because most of the ether forms compounds with no electric charge, so there's no electron cloud around them that we could detect. Second claim is that ether forms very complex compounds with very sophisticated structure. The most complex compounds are atomic nucleus, the simplest ones are the basic multiquarks, but there's a whole zoo in between. Ether isn't just 6 quarks with an occasional tetraquark, it's a whole periodic table. What do you think the atomic nucleus consists of? Ball shaped protons and neutrons? Is it because thats what you've seen on a textbook picture or because nucleus tends to spit out individual protons and neutrons on collisions? Take a look at the competing theories explaining the structure of nucleus and ask yourself if they look convincing.
If this guess is right, dark matter is huge clouds of mostly neutral ether that can't possibly interact with light, as photons have nothing to bounce of (unless an occasional photon hits a quark directly). Ether could form a ring of "asteroids" around Earth: it would affect trajectories of spacecrafts, but otherwise would be completely undetectable. We would see it as a mysterious deviation from the computed trajectory.
And don't confuse ether with aether. The latter is literally space and particles of aether are electrons, neutrinos and all that quantum zoo.
I'm waiting for the missing ingredient to be STRIIIINGS!!! Dark matter is carried on strings that pop in and out, but only when you observe them. As soon as you stop observing, it pops back in to keep things in equilibrium. Next theory?
I think the physicists are touchy about our layman's thoughts on this, and they are correct in that there is little to no evidence to support claims like this. However, I too, look at incompleteness, entropy, things like prime number distribution, and chaos, and I can't help but think: it (everything) really does seem to be destroying things only to bring them back again in a novel form.
It's intuitive, it's not suggested by evidence, it's based in imagination rather than reason, but I imagine the universe as a matter / energy creation machine in which the forces that tear everything apart seem to be generative. I think perhaps over time we will observe a correlation between the entropic forces at the edge of the universe and the gravitational forces of dark matter in the center of galaxies. I think dark matter is dark because its light hasn't reached us as its trapped by gravity, yet its gravity is there. It's new matter, and we don't know how it got there. I think we'll find the bridge by looking into quantum mechanics, and how particles behave in relation to one another when they're in conditions similar to those described at the point of heat death of the universe, everything broken down, even time. When that happens, what's the difference between any one thing and another? I'm not entirely convinced: "well, nothing at all" is the answer. Do we know nothing at all is stable? The big bang seems to suggest that nothing at all is extremely unstable.
I think the physicists are touchy because imagination has replaced reasoning in key areas. Whereas you and I would probably love to be told exactly why we might be wrong about our crackpot musings in a field we upfront claim to know little about.
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[ 3.7 ms ] story [ 148 ms ] threadWhy haven't MOND or other theories become more popular?
Edit: MOND isn't great either - it just has a parameter that they tune until it matches the observation.
Edit 2: I am not a physicist, I am simply a concerned citizen.
However, that leads to your follow-up question why MOND and other modified models of gravity are not more popular. It's not for lack of trying:
https://en.wikipedia.org/wiki/Alternatives_to_general_relati...
https://en.m.wikipedia.org/wiki/Higgs_boson
Also IIRC, Rubin's seminal observations on dark matter were in the 60s too, and dark matter was postulated in 1930.
is that really a huge difference? plenty of eventually-proven math conjectures were initially posed with no knowledge of how a proof will be found.
perhaps with the higgs it was easier because it was conceivable that we could produce the necessary collision energies here on earth, while other problems remain at unattainable scales for a clear path to exist today.
As a theoretical math major and a practicing scientist, I'm just going to have to say that these are not comparable, neither in process, nor ontologically.
> conceivable
that's a very weak way of saying the scaling factor of collision energies was known, and the technology to build the required machine right around the corner (we could have found the higgs with technology proposed for the hole in texas, only 20-or-so years after the prediction of the higgs; at the time higgs was postulated superconductors were already known for 10 years and the first superconducting NMR was 10 years away).
Anyways, my point is that there is a categorical difference. At the time of its postulation, building an experiment that could say yay or nay about the existence of the higgs was largely an engineering problem.
With DMwe're shooting in the dark, so to speak, in hope something will turn up
There are essentially 3 (or 2.5) explanations, that we have (a lot of) missing mass, that we don't understand gravity or that we don't understand spacetime.
Most theories revolve around the missing mass part this includes all possible theoretical candidates for Dark Matter from both within and beyond the standard model, overall a single candidate or a combination of a few likely ones seems to fit our observations the most.
Modified Gravity; these theories actually have gotten plenty of attention in the 80's and 90's but the problem is that most of them don't fit observations especially modern ones like the bullet cluster and gravitational waves, most of them aren't relativistic (or don't have a relativistic formulation) and they overall suck at predicting everything else including the formation of galaxies and stars in the first place.
"Modified Spacetime"; mostly relegated to the dark corners of the web and to pseudo scientific forums technically possible but I haven't seen anything that comes close to being an actual theory as in having an actual mathematical basis. They basically revolve around various possible ways of affecting spacetime curvature, basically if you could curve spacetime without out mass to the same extent as say the earth's mass does you'll technically will end up with the same gravity well. The more "serious" of these tend to revolve around various attempts at gauge gravity.
I usually consider the "Modified Spacetime" as being an offshoot of Modified Gravity theories.
https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics
MOND isn't a career ender as much as say cold fusion is, but it's pretty close.
And in all honesty if we look at Modified Gravity theories as a whole they shouldn't be anymore more offensive to one's career than say string theory and despite string theory being essentially a dead end for decades now it doesn't get anywhere near that level of stigma that MOND does and that's more for a cultural / dogmatic reason than purely scientific ones.
There are however other issues with MOND including that gravity is still instantaneous (in most variations) which we know with gravitational waves it isn't, as well as that most of them don't lend to the formation of stars and galaxies. If we take vanilla MOND then the universe as we know it shouldn't have been formed matter wouldn't clump up to form the formations we can see around us and the one we live on.
DM: we see complexity, let's treat it as fundamental.
MOND: we see complexity, let's ignore the inconvenient parts.
I think that is a mischaracterization; IIRC, MOND fits the overwhelming balance of galaxies with a single parameter, and there are only a handful of exceptions (probably around in the hundreds or so?) out of all of the galaxies.
also: MOND doesn't explain intergalactic movement, or the clumpiness of the universe. But there's ALSO no good reason to believe that that "LCDM dark matter" does either, because by the "curve-fitting nature" of LCDM it could literally explain anything. If all of the oxygen in my room went to the northeast corner of my room and suffocated me, you could come up with a dark matter field that explained that phenomenon. As a scientist, that worries me. Also doesn't mean that LCDM is wrong.
[citation needed]
Another problem with MOND is that no matter how you tune it, it can't explain the Bullet cluster for example.
If the bullet cluster is a great counter example for MOND, then conventional dark matter is highly opportunistic curve fitting (which doesn't mean it's not correct).
https://en.m.wikipedia.org/wiki/Dark_matter#Observational_ev...
It seems quite difficult to modify GR or make a new theory of gravity which explains the new observations while matching GR in the old ones, where GR has been verified. But if someone manages, then you'll see scientists flock to it.
I'm not shunning the idea, I've worked on alternative explanations myself (with no concrete result), but for the moment we remain convinced that dark matter is the better theory.
I _really_ like what you did here :-)
Perhaps that is the complaint here - and asking for academic background is an argument from authority...
Except for all the ways we have to detect actual matter (i.e. gravitation) that fits its properties.
- it cannot be detected the way you detect your phone in your hand or see light so your definition of detection seems to escape the basic premise of dark matter: its ability to avoid electromagnetic force, and also,
- we have detected it through gravitational anomalies
With the DM effect, we ONLY see gravitational anomalies as you said. Though DM may very well be the reason, it does not automatically mean it MUST be some matter we cannot see
No it isn't. It isn't even an argument of any sort. I think most reasonable people would interpret that as an attempt to gather evidence to support applying a heuristic filter to the question of "is it worth my time to continue engaging with this person or not?"
There is a difference between observations and _experimental_ evidence, which I think the GP was referring to.
The only thing we haven't done is figured out what it is in terms of other concepts we know, such as elementary particles.
Healthy skepticism is a good thing for science. Until DM is proven, it is worth exploring other avenues--may the best experiment win. If you don't understand this, you are a zealot rather than a scientist.
> Honestly, I'm a little tired of the whole dark matter thing. There's no evidence for it, and physicists keep coming up with more and more complex models to fit the data when they don't actually understand what's going on there.
Reads as:
"I know nothing, but I assume that there's no evidence for this because I haven't done any research, and I assume that physicists are foolishly sticking to the theory because they're desperate".
This couldn't be further from the truth, and it could be dispelled with 5 minutes of googling.
You're being downvoted for the same dismissive cluelessness:
> Last I checked, it had not been verified via experimental evidence. Is that still the case?
In reality, there has been mountains of experimental evidence ever since the theory was first proposed, which is why it has been taken seriously for decades. That's why the "Observational evidence" section on Wikipedia has 11 sections in it, reflecting thousands of papers. We still don't know what it is at an _atomic_ level but we know where it is, what it weighs, how it moves, and what it interacts with.
There's a fundamental difference though. With dark matter, the evidence of the stuff is much more direct and precise. We can determine the shape and concentration of it. Aether on the other hand was a hand-wavy metaphysical concept from the beginning. There was never any experimental evidence that aether was a real thing; it was just a concept invented to patch up the inherent inconsistencies in electromagnetic theory near the speed of light.
But I think you might be after something:
> Given that, "dark matter" is as inoffensive a name as possible.
Precisely. Dark matter is boring. People want Klingons.
> We know there's something out of ordinary, it behaves like matter, and it doesn't interact with light
That's wrong, and presupposes the existence of dark matter, rather than treating it as a possibility. What we know is that our formulas don't match up with our observations. We don't know why that is. One suggestion is that there is some sort of invisible stuff out there that we cannot detect, but would make our formulas add up, so it could exist. Its perfectly legitimate to speculate about the existence of dark matter, and to set up different experiments to try to detect it, but its not fine to pretend that its "settled science" that dark matter is out there and its only a matter of finding it. Unless and until someone detects "dark matter" or figures out another reason why our calculations don't add up its existence will remain an open question.
Key to note that this doesn't mean it's right. But one wonders why there isn't more skepticism about conventional dark matter theories.
Like what if I said "there isn't global warming, there's just a mysterious unobservable dark thermal input adjustment that we have to apply to every month's reading to make our models work out". You'd say that I was crazy.
The appropriate MOND/DM analogy here would be to propose general relativity as an explanation for Mercury but then find another planet(oid) in the system where GR suggests an effect, but to notice that the effect is measurably not present. You can’t just say “got most of them right” when you propose such a theory. You need to revise your theory until it explains the observations.
There are things to be frustrated about with the dark matter hypothesis (and I am too), but lack of evidence isn't one. Dark energy seems to be another beast though...
I don't think you can even be a 'concerned citizen' on this topic without some introductory knowledge of dark matter.
rational thought?
logic?
reason?
People need to understand that physicists do NOT consider dark matter to be settled, in any sense! The experiments are not done to polish up any theory... they're done because all of the theories are awful, and guidance from observations is necessary for further progress.
I also still fully stand by my previous comment on this subject: https://news.ycombinator.com/item?id=23666620
Almost every honest physicist will say that. But not all physicists are honest, and I don't trust that there is a positive correlation between honest scientists and loudness in the scientific community, especially where it interfaces with the general public. And if you want an explanation of why dark matter brings out the crazies, I think that's as good a reason as any.
Most of my peers from high school went into high energy physics (one works at JLab, another is a professor at an east coast college; the others quit or went into... other fields, like finance). Although I am no longer a practicing biochemist, when we got together we complained about the exact same things. So yeah, I don't know about the intricacies of what happens in physics. But that doesn't mean I don't have real insight about what's going on.
For example, throughout my career, whatever the commercial domain, there is almost always a noisy competitor whose product is an amateur hour shit-show, usually a superficial clone of the market leader, that still picks up market share from naive customers by sheer volume of message.
When you’re trying to focus on making something that actually creates value for others this can be an irritating distraction. “Pay attention to competitors, but obsess over customers” isn’t always a comfortable mantra to fulfil.
Contrary to your linked comment, to this non-physicist, nearly all physicists in public seem to say that, while the details are unknown, dark matter is pretty much definitely a thing. AFAICT they're not wrong about there being multiple lines of evidence for it. But if you mean "no one worth listening to" says even that much, then I don't know any physicists worth listening to.
It does not seem like it to me (non physicist with some physicist friends from other fields who try to dumb down stuff to me).
In my world (SE) it seems like a proprietary binary that must be included for the rest of an open source product describing the observable universe to work very well. Everyone seems to hate it, but nobody wrote something better, yet. Every competing implementation fails to work in other areas that we already are using in production, extensively.
And when some professional, who read and understood the source code, starts talking about it, a lot of people voice stupid ideas that they would not have if they passed some lectures on the subject.
Edit to add: I envy physicists a little - the best thing for “them” to happen seems to be if something does not work in a very peculiar way.
Because everybody thinks they can "intuit" their way to knowledge.
No. No you can't. We KNOW you can't. We have experiments and statistics and double-blind trials for exactly this reason.
"Intuition" only works when coupled with huge amounts of knowledge and effort.
Part of the problem is that too many people never suffer the consequences of "truth" in modern society. Consequently, far too many people get the idea that "truth" is negotiable.
But, this is not new:
“There is a cult of ignorance in the United States, and there has always been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge.”
― Issac Asimov
The existential confrontation of research processes and discourse is such anathema to a prevailing mindset of certainty and explanation that a psychosis may develop.
So bring your kids up to be comfortable with doubt, to inoculate them against becoming conspiracy nuts.
It was nearly a millenia between the sacking of Rome and the Renaissance. Intellectuals seem to have the idea that we can’t have that type of reset again. As populations options narrow with climate change and vaunted scientists fail to provide solutions, those populations will turn elsewhere.
As I understand, they see a discrepancy between simulation and observation of some lensing observables. Could be something wrong with the calculation of the observables, something wrong with the implementation of the simulations, or (the exciting bit) with the physics put into the simulations. As a complete non-expert on lensing observables and cosmological simulations, I'd guess it's one of the first two. As mentioned in the text, there are many other discrepancies between observations and simulations that are still unresolved. This adds to that list.
However this time science knows what this ether is and already performs some experiments on it, although doesn't recognize it as a valid state of matter.
Ether is multiquarks essentially. Protons and neutrons are the densest or biggest form of ether. A tetraquark sporadically appearing in experiments is a particle of thinner ether. Individual quarks are very thin ether. So far so good and it's just a matter of terminology.
There are a few interesting claims made with respect to ether that science can actually verify. One claim is that ether is a legit state of matter and everything is packed with it. This doesn't contradict observations because most of the ether forms compounds with no electric charge, so there's no electron cloud around them that we could detect. Second claim is that ether forms very complex compounds with very sophisticated structure. The most complex compounds are atomic nucleus, the simplest ones are the basic multiquarks, but there's a whole zoo in between. Ether isn't just 6 quarks with an occasional tetraquark, it's a whole periodic table. What do you think the atomic nucleus consists of? Ball shaped protons and neutrons? Is it because thats what you've seen on a textbook picture or because nucleus tends to spit out individual protons and neutrons on collisions? Take a look at the competing theories explaining the structure of nucleus and ask yourself if they look convincing.
If this guess is right, dark matter is huge clouds of mostly neutral ether that can't possibly interact with light, as photons have nothing to bounce of (unless an occasional photon hits a quark directly). Ether could form a ring of "asteroids" around Earth: it would affect trajectories of spacecrafts, but otherwise would be completely undetectable. We would see it as a mysterious deviation from the computed trajectory.
And don't confuse ether with aether. The latter is literally space and particles of aether are electrons, neutrinos and all that quantum zoo.
It's intuitive, it's not suggested by evidence, it's based in imagination rather than reason, but I imagine the universe as a matter / energy creation machine in which the forces that tear everything apart seem to be generative. I think perhaps over time we will observe a correlation between the entropic forces at the edge of the universe and the gravitational forces of dark matter in the center of galaxies. I think dark matter is dark because its light hasn't reached us as its trapped by gravity, yet its gravity is there. It's new matter, and we don't know how it got there. I think we'll find the bridge by looking into quantum mechanics, and how particles behave in relation to one another when they're in conditions similar to those described at the point of heat death of the universe, everything broken down, even time. When that happens, what's the difference between any one thing and another? I'm not entirely convinced: "well, nothing at all" is the answer. Do we know nothing at all is stable? The big bang seems to suggest that nothing at all is extremely unstable.
I think the physicists are touchy because imagination has replaced reasoning in key areas. Whereas you and I would probably love to be told exactly why we might be wrong about our crackpot musings in a field we upfront claim to know little about.