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First test of rival to Einstein’s gravity kills off dark matter
- empath75 10y ago'Kills off dark matter" is probably overstating the case, but I love this theory because it ties together a lot of big ideas. Verlinde's paper is here: https://arxiv.org/abs/1611.02269 https://arxiv.org/abs/1611.02269
- noobermin 10y agoWhat about the Bullet Cluster[0]? How does his idea address that? His idea deserves some study but a title will "Kills off dark matter" is very infuriating [0] https://en.wikipedia.org/wiki/Bullet_Cluster https://en.wikipedia.org/wiki/Bullet_Cluster
- greglindahl 10y agoIf you read the Wikipedia article, it points out what MOND advocates say about the Bullet Cluster: they try to handwave it away. It's likely that Verlinde's theory needs a similar solution. Unfortunately for handwaving, over time, the number of weird dark-matter-related observations is growing.
- empath75 10y agoI think the study that this article is about looks at lensing data in particular which should explain the bullet cluster, as well, no?
- jayajay 10y agoI remember reading about this as an undergraduate and thinking how attractive his ideas were -- I think Verlinde's ideas have been around for some time. Back then it seemed like few people were giving these ideas thought. I hope more people decide to explore this avenue. It really is a fascinating take on gravity.
- Jun8 10y agoYou may find the top answer to this SE question helpful (asked 5 years ago, though): http://physics.stackexchange.com/questions/6561/are-modified-theories-of-gravity-credible http://physics.stackexchange.com/questions/6561/are-modified.... Especially I think the following comment is spot on: "Galaxy rotation curves are not very good tests for GR itself, since there are so many parameters about mass distribution in a galaxy which are simply not nearly as precisely understood as GR itself"
- Dylan16807 10y agoThat says MOND is a non-theory, so now I'm even more confused since this theory "builds on" MOND.
- CoryG89 10y agoNow I'm confused. What is a non-theory? O.o Theories by definition, may not be correct. It's still a theory. How does one become a non-theorist? I suppose by non-theorizing.
- Dylan16807 10y agoOne way is to propose something that's mathematically equivalent to existing theory. If you have no testable predictions then you're not really doing science. You're doing philosophy. I'm not sure if that's the objection here. They might also be calling it too vague to be a theory, or something else.
- raattgift 10y agoThe New Scientist article writer is who is confusing you. Verlinde does not build on MOND. An explanation and some extracts from his paper are in an earlier comment of mine: https://news.ycombinator.com/item?id=13198573 https://news.ycombinator.com/item?id=13198573 (specifically at the paragraph half-way along in the comment, starting with "Sure Milgrom", if you want to zoom right in.)
- ievahanordah 10y agoGood . Dark matter is bullshit. There's no proof cause there isn't any "dark matter". Whatever the hell that was supposed to mean anyway.
- pavel_lishin 10y agoI'd be kind of bummed to lose dark matter as a concept. I want to hold onto the idea that it's just as rich as our matter, with its own quantum chromodynamics and an equivalent to the electromagnetic force, leading to a "shadow" universe with their own planets, life, etc. that exists side by side us, trying to figure out why their gravity measurements are just slightly off...
- some_guy_there 10y agoI wouldn't be so worried yet. Verlinde's theory is quite fresh and it will take time to conclusively rule out Standard Cosmological model. As of yet, no one has properly worked out entropic gravity equivalent of various gravitational effects that arise in General Relativity such as gravitational lensing, a part of which was used in the paper discussed in the article. Never the less, Verlinde's ideas are more interesting and reasonable than other proposed modification of gravity, but that's just my opinion.
- mentalpiracy 10y agoI had this thought as well. Time to start subscribing more heavily to a viable multiverse theory, at least to support my tastes in science fiction novels anyway.
- CoryG89 10y agoSounds like Stranger Things to me.
- logfromblammo 10y agoYou can also have the idea that there are one-way interactions between the normal-matter universe and the dark-matter universe. It isn't too difficult to formulate a mathematical system where two subsets are completely identical when considered in isolation, but when interacting, one subset operates as if the other doesn't exist, while the other is easily perturbed by any values in the mirror subset. I'm not sure if you can do it without at least one dimensional basis unit that squares to zero, though. Imagine, if you will, that there are dark-matter people. We have no evidence whatsoever that they exist, any they are constantly annoyed by all the real-matter people that wander between their dark-couches and dark-televisions, and the real-matter bicyclists that pedal through their dark-bedrooms at the worst possible times.
- josefdlange 10y agoJuuuust gonna leave this here... http://xkcd.com/1758/ http://xkcd.com/1758/
- deepnotderp 10y agoThis is different because it's an experiment for this theory.
- jessriedel 10y agoIt's not different because this experiment can't discriminate between Verlinde's ideas and long-known alternatives to dark matter. https://news.ycombinator.com/item?id=13197214 https://news.ycombinator.com/item?id=13197214
- Florin_Andrei 10y ago> Now, a team of astronomers studying the distribution of matter in more than 30,000 galaxies say their observations can be explained by an alternative theory that does away with dark matter. If this “modified gravity” is correct, it would up-end hundreds of years of fundamental physics. No, it would reshape the "top" of these theories. The base would remain the same.
- andrewflnr 10y ago“But then if you mathematically factor in the fact that Verlinde’s prediction doesn’t have any free parameters, whereas the dark matter prediction does, then you find Verlinde’s model is actually performing slightly better.” What? How does this work?
- gabrielgoh 10y agoprinciple of parsimony
- krastanov 10y agoSay that you want to estimate what is the chance that observation 1 fits theory A just by accident (the lower this chance is the higher your confidence can be that theory A is "real"). If theory A has parameters you can adjust, it becomes easier for an observation to fit the theory just by accident (because you can adjust the free parameter). This is a fairly flawed description, but it should be a good enough ELI5.
- fjarlq 10y agoFrom the discussion section of Verlinde's paper[1]: > We have shown that the emergent laws of gravity, when one takes into account the volume law contribution to the entropy, start to deviate from the familiar gravitational laws precisely in those situations where the observations tell us they do. We have only made use of the natural constants of nature, and provided reasonably straightforward arguments and calculations to derive the scales and the behavior of the observed phenomena. [..] > In our view this undercuts the common assumption that the laws of gravity should stay as they are, and hence it removes the rationale of the dark matter hypothesis. Once there is a conceptual reason for a new phase of the gravitational force, which is governed by different laws, and this is combined with a confirmation of its quantitative behavior, the weight of the evidence tips in the other direction. [1]: https://arxiv.org/abs/1611.02269 https://arxiv.org/abs/1611.02269
- andrewflnr 10y agoThat's just Occam's razor, though. The phrasing made it sound like they had a quantitative argument for why fewer free parameters made it "perform" better.
- FeatureRush 10y agoWhat would be the next test? Clusters or that dark matter dwarf galaxy causing ripples in our Milky Way?
- thejollysin 10y agoThe "next test" would be to look at more galaxies. They did not actually try to apply their theory too many real world observations. The goal of this paper is to get funding to try and apply their new theory to a huge number of galactic measurements. Until they do THAT, no one in the physics community is going to listen to them.
- beambot 10y ago> String theorist Lubos Motl savaged Verlinde’s ideas in a recent blog post: “I wouldn’t okay this wrong piece of work as an undergraduate term paper.” I find this rudeness and pedantry in academia infuriating. There's no justification for this level of nastiness -- not in private, public, peer review, or science as a whole. Seeking out the unknown and creative explanations thereof is the hallmark of good science; check your ego at the door. I know nothing about him... but in my book, Lubos Motl can go pound sand.
- jessriedel 10y agoLubos Motl hasn't been in academia for almost a decade. Almost everyone inside and outside it finds him obnoxious.
- magicalist 10y ago> I find this rudeness and pedantry in academia infuriating. vs all those "I just don't believe in being fake and sugar coating things" folks in every other industry? Not much unique to academia on that front.
- astrodust 10y agoLike food critics, some have taken the art of shitting on things to absurd heights. "I find this theory highly disagreeable, it contradicts findings by X and Y et al." Compared with: "I once asked my dog for a theory on the nature of the universe, whereupon which he vomited violently on the floor. This explanation has more truth to it than the one presented in this paper, which I can only presume was written by students who, in their youth, were savagely beaten upside the head by their parents much to the detriment of their intellect."
- bsder 10y ago> I find this rudeness and pedantry in academia infuriating. So you'd rather people quietly knife you in review? Because that's what happens if you penalize people for public rudeness. Personally, I'd rather have a loud critique to my face than a polite one behind my back or, even worse, no engagement at all. I don't need your politeness or friendship when I'm putting forth some new theory. I need accurate, engaged criticism and the number of people who will do that is vanishingly small. And a lot of the ones who will do that have social issues almost by definition.
- jsilence 10y agoTotally OT: I read "Einsteins graffitti" and could watch my own brain trying to make sense of the sentence. And fail.
- jessriedel 10y agoFolks, the observation doesn't test Verlinde's idea, this tests a very general class of models, such as the well-known MOND scheme. > Milgrom, however, supports the work. He also points out that according to his own 2013 analysis of gravitational lensing data in galaxies, MOND produces similarly impressive results as Verlinde’s gravitational model does in Brouwer’s study. (Also: http://motls.blogspot.ca/2016/11/verlindes-de-sitter-mond-is-highly.html http://motls.blogspot.ca/2016/11/verlindes-de-sitter-mond-is... ) This data cannot distinguish between Verlinde and other explanations for MOND-like behavior. We've long known that MOND seems to fit a subset of all observational data better the dark matter, in particular the Tully–Fisher relation https://en.wikipedia.org/wiki/Tully%E2%80%93Fisher_relation https://en.wikipedia.org/wiki/Tully%E2%80%93Fisher_relation However, for the rest of the data (e.g., the CMB, large-scale structure, the bullet cluster), MOND is generally considered to give a worse fit than dark matter, or to be silent (because it's not obvious how to extend MOND to a complete cosmological theory). That's why experts think the totality of evidence supports dark matter. Nothing has changed.
- DennisP 10y agoSeems like it's pretty easy to make dark matter a good fit, because you can just adjust the presumed distribution of dark matter to fit the data.
- sandworm101 10y agoIt does seem unfair to fault one theory for making up terms but to ok the invention of dark matter and its placement wherever needed. Perhaps dark matter will be like vulcan: a big chunk of mass invented and placed so as to confirm an outdated model. The new model described a new force, mooting the need for the mass.
- TTPrograms 10y agoIt's faulting one theory for making up terms to fit one source of data and then those same terms failing on 6+ other experiments. Dark matter's predictions are consistent across totally different experiments with fewer sets of parameters.
- daxfohl 10y agoThe central equation in this paper is 4.40. It doesn't seem to account for some galaxies recently discovered that are almost entirely dark matter.
- Animats 10y agoThe title overstates the results of research work. From the article: "Now, a team of astronomers studying the distribution of matter in more than 30,000 galaxies say their observations can be explained by an alternative theory that does away with dark matter." Suggest "Astronomers studying galaxy mass distribution say their observations can be explained without dark matter."
- bmh100 10y agoPlease change the submission title. It is downright misleading. This test did not "kill off" dark matter. To do so would imply overwhelming evidence against the concept of dark matter as a whole. Instead, this theory, which eliminates the need for dark matter in certain situations, has passed its first test. The sentence "... test ... kills off dark matter" is simply false.
- acqq 10y agoMoreover, it's not even a complete "theory" in the sense that it's still not known if it can even repeat the results of the General Relativity. https://news.ycombinator.com/item?id=13197595 https://news.ycombinator.com/item?id=13197595
- raattgift 10y agoIt's not complete for other reasons, several of which are detailed in Verlinde's paper itself; however, it wholly reproduces GR in the EFT limit by design. Indeed, Verlinde starts with standard dS as his unremovable background on which he puts strings. What in GR we would consider perturbations of dS and IR corrections of GR (at ~ galactic scales) emerge from the behaviour of the strings and how they form long-distance entanglements. However, it's not outrageously wrong, and it is noteworthy that an accomplished string theorist has decided to tackle gravity in a universe like ours rather than leaning on AdS/CFT arguments.
- acqq 10y agoThanks for the correction and clarification. For others who, like me, aren't in the field, the "EFT" mentioned is explained, for example, here: https://arxiv.org/abs/gr-qc/0311082 https://arxiv.org/abs/gr-qc/0311082 "The problems of quantizing gravity within the experimentally accessible situations are similar to those which arise in a host of other non-gravitational applications throughout physics. As such, the size of quantum corrections can be safely estimated and are extremely small. The theoretical framework which allows this quantification is the formalism of effective field theories." dS is "de Sitter space": https://en.wikipedia.org/wiki/De_Sitter_space https://en.wikipedia.org/wiki/De_Sitter_space I'd also appreciate a link to the explanation of "What in GR we would consider perturbations of dS and IR corrections."
- brilliantcode 10y agoCan someone explain in layman's terms what really is dark matter and why there's so much obsession around it? If we can't observe it and we are only relying on inferences to explain it's effects, that seems like pretty weak set of legs. Obviously I'm missing the academic discipline to appreciate this topic but nevertheless, I'm curious about our understanding of the very fabric and mechanisms of our reality and the universe.
- thejollysin 10y ago"Dark Matter" is a phrase we use to describe a hole in our understanding of the universe. To put it simply, when we look out into space, at very large scales like galaxies, everything is just too heavy. It appears as if there is a LOT more matter out there than we can see. Things are orbiting faster than they should be, like galaxies are heavier than makes good sense.. Maybe there is some matter out there that is "dark", so we just can't see it. That would be a solution. Or maybe the laws of gravity we wrote down are bad at large scales. No one knows. Trust no one who tells you they know the answer: if they did they would have a Nobel Prize.
- misnome 10y agoWhere "Dark" literally means: does not interact in any way with light
- Avshalom 10y agoSo basically there are four forces: weak and strong nuclear forces; gravity and EM. EM is mediated by photons and visible matter is constantly absorbing and emitting photons. Some particles don't though. Neutrinos for instance. They're dark, they don't interact with light. So when observation showed that there needs to be more matter laying around than we could see some enterprising young turks said "hey, maybe there's a shit ton of dark matter" and that makes the math come out right. the obsession is mostly because people who aren't astronomers seem to think "dark" is a metaphor and go "aha now that no one cares about the oxford comma this will be my new opinion" Up for debate is what kind of particles make up the dark matter and how much mass is dark vs just poor measurements and/or some tweaks to gravity, but unless some one manages to disprove neutrinos: dark matter exists.
- thejollysin 10y agoPhysicist here. Please do not put too much stock in this paper. Some of the folks on this paper are good scientists, but this appears to be more about looking for funding than good science. Their paper on the Arxiv is about building some math to make gravity look like dark matter. But this has been done 1000 times before with no success. They have no physical basis for their math; there is no reality behind it. I do not expect this to get them the Nobel Prize.