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New Hubble data suggests an ingredient missing from current dark matter theories
- Hickfang 6y agoYea, the missing ingredient is darker dark matter :]
- noizejoy 6y agoI’m not sure I understand the difference between “additional ingredient” and “a higher concentration of”
- T-A 6y agoDark matter models predict how the stuff is supposed to be distributed.
- dogma1138 6y agoNot 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).
- nynx 6y agoHonestly, 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.
- T-A 6y agohttps://en.wikipedia.org/wiki/Dark_matter#Observational_evidence https://en.wikipedia.org/wiki/Dark_matter#Observational_evid...
- nynx 6y agoThose are evidence for our physics not actually matching reality, not evidence for dark matter specifically.
- T-A 6y agoIf by "evidence" you mean "direct detection", presumably in an Earth-based experiment, then fine, there is none. 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_relativity#Results_of_testing_theories https://en.wikipedia.org/wiki/Alternatives_to_general_relati...
- leeoniya 6y agoto add to this, the Higgs boson was predicted in 1964 and not detected till 2012: https://en.m.wikipedia.org/wiki/Higgs_boson https://en.m.wikipedia.org/wiki/Higgs_boson
- dnautics 6y agoHuge 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.
- leeoniya 6y ago> 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.
- lisper 6y ago"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..." https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics
- DennisP 6y agoI don't really have an opinion but in fairness, the article is about a discrepancy between the data and current dark matter models.
- lisper 6y agoSure. 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.
- dogma1138 6y agoIf 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.
- dogma1138 6y agoMOND 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.
- jjoonathan 6y agoIf 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.
- dnautics 6y agoDisclaimer, I'm not an astronomer. 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.
- gbrown 6y ago> There's no evidence for it [citation needed]
- tiborsaas 6y agoIf it's tireing for you imagine the scientists who dedicated significant amount of their lives to figure out what explains this baffling observation. Another problem with MOND is that no matter how you tune it, it can't explain the Bullet cluster for example.
- dnautics 6y agoSure, 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).
- joshocar 6y agoThere is a LOT of evidence for the existence of dark matter. https://en.m.wikipedia.org/wiki/Dark_matter#Observational_evidence https://en.m.wikipedia.org/wiki/Dark_matter#Observational_ev...
- nynx 6y agoWhat you've linked to is evidence that our understanding of gravity is wrong OR there is dark matter.
- magicalhippo 6y agoAnd 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.
- kmm 6y agoBut 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.
- ashildr 6y ago> That's what makes dark matter so attractive to physicists. I _really_ like what you did here :-)
- dnautics 6y agoMOND 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".
- ajkjk 6y agoAre you a physicist? What possibly makes you think you have enough background to disregard the (tremendous) evidence for it?
- mellosouls 6y agoTo 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...
- freeone3000 6y agoSo 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.
- morelisp 6y ago> as yet zero detection of actual matter that fits it's properties. Except for all the ways we have to detect actual matter (i.e. gravitation) that fits its properties.
- dbsmith83 6y agoYou 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
- yes_man 6y agoI 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
- morelisp 6y agoOK 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.
- yongjik 6y agoHonestly 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."
- daxfohl 6y agoI 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.
- duutfhhh 6y agoOr 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."
- ifdefdebug 6y ago> Honestly I'm not sure why some people oppose "dark matter" so much 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.
- StanislavPetrov 6y agoIts 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.
- daxfohl 6y agoIt 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.
- dnautics 6y agoI 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.
- matthewdgreen 6y agoI’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.
- dnautics 6y agoYes 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.
- mehrdadn 6y agoThere'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...
- ChrisClark 6y ago> I am not a physicist, I am simply a concerned citizen. I don't think you can even be a 'concerned citizen' on this topic without some introductory knowledge of dark matter.
- mountainboy 6y agocommon sense? rational thought? logic? reason?
- andrewflnr 6y agoThe 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.
- exmadscientist 6y agoFor 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. I also still fully stand by my previous comment on this subject: https://news.ycombinator.com/item?id=23666620 https://news.ycombinator.com/item?id=23666620
- dnautics 6y ago> 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.
- SubiculumCode 6y agoOh 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.
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- OpticalWindows 6y agoWill the James Webb telescope help detail such phenomenon better than the hubble?
- Already__Taken 6y agoIf you can do it with infrared then yes is the JWT rule of thumb.
- cozzyd 6y agoHere's the arXiv preprint: https://arxiv.org/abs/2009.04471 https://arxiv.org/abs/2009.04471 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.
- jdey56 6y agoThere'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.
- dylan604 6y agoI'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?
- koheripbal 6y agoI have a pet theory that repulsive and attractive forces exist at infinity at ever increasing scales.
- WealthVsSurvive 6y agoI 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.