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Humble tokamak physicist owns generations of cosmological wankers
- williamscales 6y agoWhat is going on with the incredibly hostile tone in the article? As far as I’m aware, cosmologists are working hard to actually find answers and would be happy about any result that holds up.
- ravar 6y agoIf you spend enough time in physics grad school its very easy to end up feeling that way. I personally loved the tone of the article.
- goostavos 6y agoDitto. The tone is what keeps me subscribed to his site. I don't know anything about physics, but I still enjoy reading his rantings.
- happytoexplain 6y agoIt's really unfortunate. People hate elitism so much they will frame any achievement by somebody "humble" or in any way outside a perceived circle of experts as a triumph against assholes
- bjornsing 6y agoNa... I’m pretty elitist but I like this kind of tone. It depends on who you see as the elite.
- floatingatoll 6y agoCosmologists would be rationally happy once the result holds up, but as with most science fields, the folks within the field will be irrationally hostile to an outsider showing them an insight they’ve overlooked, and may spend the next ten or twenty years aggressively fighting against it regardless of its merits. To provide an IT analogy, imagine being tech support for a bunch of alpha-cowboy engineers. They’ll tell you they did all the obvious things, they’ll object to being asked to perform simple diagnostic tests (“does the problem go away if you create a temporary new user account on your system?”), they’ll resent you for not having an immediate solution, and they’ll resent you when you find the basic step they missed. Yes, they’ll accept the solution you offer, but they’ll fight you tooth and nail until it’s unarguably proven that you’re right. That’s often what cross-domain innovation in science is like. EDIT: per comment below, this is a much better explanation: https://www.smbc-comics.com/comic/how-math-works https://www.smbc-comics.com/comic/how-math-works
- bbatha 6y agoTokamak plasma physics is a cousin of cosmology anyway — at the end of the day they’re studying balls of plasma it just depends on if they’re natural and giant or man made and small. I worked in a plasma physics department and people did both reactor physics and cosmology all of the time. So thisnt really an outsider perspective.
- naringas 6y ago> and may spend the next ten or twenty years aggressively fighting against it regardless of its merits. it seems more accurate to say that they retire and the new generation of physics professors are more open to those ideas because they encountered them as students before building a career on some sub-sub field which migh have ended up as a dead end...
- BalinKing 6y ago(Possibly) obligatory SMBC: https://www.smbc-comics.com/comic/how-math-works https://www.smbc-comics.com/comic/how-math-works
- floatingatoll 6y agoI’m going to edit this into my post now because it’s so much better than what I said! Thanks!
- ncmncm 6y agoAs Max Planck is quoted, "Science progresses one funeral at a time". (He probably said it in German.) I just wonder how many biochemists will need to retire and get Alzheimer's before work on suppressing amyloids is finally abandoned, and something that could possibly work gets a grant. In the meantime, take your valacyclovir!
- willis936 6y agoAlfvein cosmology was largely abandoned after the discovery of CMB. It’s too bad really, since it holds up quite well in many regards. The hostile tone when discussed is frustration that it is no longer even discussed by mainstream cosmologists. We teach kids about plum pudding but not the career cosmologists about MHD?
- smsm42 6y agoI've read the headline and thought to myself "sounds like something from Locklin". And surely enough... It's just how he writes (sometimes), I think. Doesn't bother me too much but I see how it could be off-putting to some.
- jamesgreenleaf 6y agoIt's the author's style: https://scottlocklin.wordpress.com/about/ https://scottlocklin.wordpress.com/about/ I bet it gets more clicks than a moderate tone would. "Cosmologists hate him! See how he solved dark matter with this one weird trick..."
- dylan604 6y agoBut I already know what happens next. We've seen it before
- amelius 6y agoI don't think such a great finding deserves an article in this tone. Posting the original paper instead would be more appropriate.
- mieses 6y agoThanks for adding a much needed air of self-importance and sanctimony to the discussion.
- happytoexplain 6y agoI don't detect either of those in the parent post. What are you referring to?
- lumost 6y agoIn fairness, I think many physics students assumed that someone had done the GR to show that DM wasn't just a GR effect. I recall a near identical situation as the author when it came to someone presenting galaxy rotation curves based on newtonian gravity and thinking "that's odd, but someone has surely done the math by now".
- exabrial 6y agoIt's humor. Lighten up.
- dan-robertson 6y agoEven cringe humour requires good delivery
- happytoexplain 6y agoThe command, "lighten up", is a double edged sword.
- exabrial 6y agoIt's a play on words since the topic is dark matter, but I also think that humor was lost...
- deleted 6y ago[deleted]
- slibhb 6y agoLooks like the author got banned from HN for that tone: https://news.ycombinator.com/threads?id=scottlocklin https://news.ycombinator.com/threads?id=scottlocklin I find him hilarious but I suppose it's a cultural thing and I understand that lots of people find it degrading.
- narag 6y agoWhat is going on with the incredibly hostile tone in the article? No idea. But the question that bothers me is: is he right? I mean, is this idea something obvious? I'm not even asking if it's true, just if this is one of the first explanations you should come up with when facing this particular problem. Because, in that case, it's puzzling.
- protastus 6y agoI don't think we should shoot the messenger. There are too many academics with huge egos. Too many papers obfuscate simple results behind unnecessarily complex and brittle mathematical models, because huge formulas and proofs make the authors look smart, and impressing the reviewers is a requirement for publication. Everyone who has a PhD in engineering knows professors who make careers out of solving made up problems with tenuous connection with the real world, and thus highly questionable utility. Maybe I'm old fashioned, but I think engineering is about solving practical problems and building shit. And then in physics, it's apparently now mainstream to produce theories that aren't testable. Of course, the math has to be very sophisticated and specialized -- dead-end work with simple math wouldn't get funded, much less become an entire field of study. Which is to say: explaining reality is hard, and all the linear problems have solutions. Today, some find it more convenient to invent another universe that still has open problems, and solve those. To obfuscate, in comes a ton of math with weird notation invented with colleagues who also play this game. It would be awesome if 3 generations of researchers got scooped by an applied physicist from a different field because nobody bothered to model galaxy rotation curves with general relativity. GR would be too boring, entirely lacking in crazy math.
- lend000 6y agoI'm no physicist but it seems like large things like galaxies should tend to rotate simply by the universal expansion analog to the Coriolis effect. Is there a pattern to the rotation that could confirm or reject that?
- db48x 6y agoNo, the expansion of the universe doesn't create any forces at all. The expansion happens not because galaxies are being pushed apart, or because galaxies are moving apart, but because new distance is being created between the galaxies.
- rbanffy 6y agoIt helps if you think of our 3D space as the Flatland on a party balloon being inflated. If all you perceive is the surface, everything seems to be moving away from you.
- AtlasBarfed 6y agoIt addresses the rate of galactic spin, but does that explain the bullet cluster?
- AnimalMuppet 6y agoIt... might. But if moving masses can create moving "magnetic like" gravitational fields, then one could plausibly come up with some history of motion of conventional matter that could create the configuration of gravitational fields that we see in the bullet cluster. Can any such history result in the observed current configuration of conventional matter? I don't know. Note well: I have only a BS in physics, and have not stayed in the field. Take all opinions with a train of salt. (Yes, I stole that typo from someone here on HN. Don't remember who, but it was worth doing deliberately.)
- tilt_error 6y agoIf there are currents, there ought to be eddies as well. Where there are eddies, you usually find flotsam. Is it too far fetched that there could be regions with seemingly strange behavior, if observed individually and isolated?
- dnautics 6y agoIirc Lambda cdm fails to explain how two galaxies could wind up colliding like that in the first place, since under lambda cdm the likelihood of such collisions is vanishingly low.
- segfaultbuserr 6y agoContext: Factoring in gravitomagnetism could do away with dark matter https://phys.org/news/2021-03-factoring-gravitomagnetism-dark.html https://phys.org/news/2021-03-factoring-gravitomagnetism-dar... > Current assessments of galactic rotation curves are based upon a framework of Newtonian accounts of gravity, a new paper published in EPJ C, by Gerson Otto Ludwig, suggests that if this is substituted with a general relativity-based model, the need to recourse to dark matter is relieved, replaced by the effects of gravitomagnetism. > In this paper, Ludwig presents a new model for the rotational curves of galaxies which is in agreement with previous efforts involving general relativity. [...] eliminating the need for dark matter. The theory still needs some development before it is widely accepted, with the author particularly pointing out that the time evolution of galaxies modelled with this framework is a complex problem [...]
- jonplackett 6y agoHow long until someone verifies if this is actually right? I’ve never liked dark matter. I hope it doesn’t exist.
- de6u99er 6y agoTo me Dark Matter was always just another term for Aether, a mysterious something made up to name the unexplainable.
- irjustin 6y agoIt is because there needed to be a name for something that was unexplainable.
- jonplackett 6y agoBut I didn’t like the way it was named as if it was something specific. ‘Matter’ makes it seem like a specific thing when it was just a made up thing because we didn’t know some other thing. (I like talking in past tense about dark matter) In general I don’t like the way science is taught as if we already know everything. It would be much better to make more of the things we don’t know. That would be a lot more inspiring.
- torrance 6y agoThere are examples of observed galaxies that have apparently separated from their associated dark matter halos - and which rotate like Newtonian gravity would predict. These class of galaxies have always been a thorn in MOND theories, and I think would be an issue here too.
- whatshisface 6y agoThose are just MOND galaxies with undark matter.
- devoutsalsa 6y agoI liked Dr. Becky’s video in the topic of a galaxy that appears to have no dark matter: https://youtu.be/gMDKDs9C4lo https://youtu.be/gMDKDs9C4lo
- Sniffnoy 6y agoMy understanding is that, though commonly repeated, this is not actually true. The thing is that modified gravity (MOND) theories modify gravity by introducing a new field(s); this means that, as with dark matter, it is possible for this new field to be concentrated away from the normal matter. Quoting from here: https://backreaction.blogspot.com/2017/01/the-bullet-cluster-as-evidence-against.html https://backreaction.blogspot.com/2017/01/the-bullet-cluster... > Isn’t it obvious the visible stuff is separated from the center of the gravitational pull? But modifying gravity works by introducing additional fields that are coupled to gravity. There’s no reason that, in a dynamical system, these fields have to be focused at the same place where the normal matter is. Indeed, one would expect that modified gravity too should have a path dependence that leads to such a delocalization as is observed in this, and other, cluster collisions. Indeed since any new dark matter particle would also be a new field, dark matter theories vs modified gravity theories are actually not that different -- both add new fields, the difference is just what kind. I mean OK obviously what kind matters a lot, but the point is that the difference isn't quite as large as it's currently made out to be, and things like the Bullet Cluster that show a matter-vs-gravity distinction aren't the slam-dunk evidence against modified gravity that they're commonly claimed to be.
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- rdw 6y agoDr. Hossenfelder has been on the beat of searching for mathematical ways of eliminating dark matter for some years. I hope she writes something about this paper. https://backreaction.blogspot.com/2019/10/dark-matter-nightmare-what-if-we-just.html https://backreaction.blogspot.com/2019/10/dark-matter-nightm... https://backreaction.blogspot.com/2018/07/evidence-for-modified-gravity-is-now.html https://backreaction.blogspot.com/2018/07/evidence-for-modif... https://backreaction.blogspot.com/2018/04/no-that-galaxy-without-dark-matter-has.html https://backreaction.blogspot.com/2018/04/no-that-galaxy-wit... https://backreaction.blogspot.com/2018/03/modified-gravity-and-radial.html https://backreaction.blogspot.com/2018/03/modified-gravity-a... https://backreaction.blogspot.com/2016/10/modified-gravity-vs-particle-dark.html https://backreaction.blogspot.com/2016/10/modified-gravity-v... As a counter, there's this article which lists a daunting number of phenomena that dark matter explains which competing theories have to also explain, and why that's very difficult: https://medium.com/starts-with-a-bang/only-dark-matter-and-not-modified-gravity-can-explain-the-universe-e272e5f64707 https://medium.com/starts-with-a-bang/only-dark-matter-and-n...
- dnautics 6y ago"a daunting number of phenomena" Well, yeah, when your model is a fudge factor that is independently parametrizable at every cubic parsec of space, you'd expect it to be able to explain a ton of things.
- deleted 6y ago[deleted]
- User23 6y agoThis is also my answer for the “why don’t you like dark matter?” question.
- mhh__ 6y agoI find it really hard to judge her - on the one hand I have read papers of hers that I enjoyed but equally she seems to be courting this weird populist movement by positioning herself as an outsider despite being a professional researcher in physics.
- wrnr 6y agoSo you are saying that if you have a mass moving in space this space acquires extra mass?
- naringas 6y agoso empty space on a galactic scale might have measurable weight?? emtpy space does have energy and energy equals mass
- ChuckMcM 6y agoBasically, yes. But what it is really doing is "dragging" the space time frame of reference around. An analogy that might be applicable; Let's say you were pulling on a rope, and someone else was providing a counter pull. You would feel a force F pulling against you on the rope. Now if someone started pulling on the rug that the other person was standing on away from you, you would feel a force F' which felt stronger than the force you felt when no one was pulling the rug. If I understand the concept of graviomagnetism as presented in the paper correctly (and there is certainly a big possibility that I do not!) then the motion of mass through spacetime creates a gravity field like the wake of a boat through water. And presumably this is a source of gravity waves when two black holes are orbiting each other.
- tra3 6y agoCan someone dumb this down for me? Were we using some sort of a model that explained extra mass away by using "dark matter" and now this guy is suggesting that we use a different model that fits the observations neatly?
- ChuckMcM 6y agoHere's my take on it, I don't have a doctorate in physics so its really just my understanding having read the linked paper. If you're a galaxy spinning around, as one does, and you use simple Newtownian physics to calculate the orbits, then there is a problem because at the velocity things are moving, they should be moving apart. And yet they are what appears to be otherwise stable orbits around the galactic center. So to solve that conundrum, one postulation has been that there is more mass in the galaxy than we can see. Since we can only see things that either emit light, or occlude things that are emitting light, that missing matter has been dubbed "dark." The paper, on the other hand, says "No, the force holding this thing together is the result of graviomagnetic forces generated by the masses moving around." (not something Newton ever considered, and really only comes into play at very large scales and very large velocities) If you accept the mathematics and the model in the paper, then it means you don't need dark matter to explain galaxy shape, which would mean that a number of physics Phds work is incorrect in describing what is going on.
- johncolanduoni 6y agoYes, the author appears to have overcome some limitations in existing models of galaxy rotation that incorporate gravitomagnetic effects (yes, others have thought of this before unlike Scott Locklin suggests and the paper even cites them). The claim is that these existing models were over-simplified to make them solvable: the less-simplified model proposed in this paper is much harder to solve but the author is an expert in mathematically similar effects in magnetohydrodynamics and appears to have found a solution. There are other astronomical observations that we still don’t have as good an explanation for (e.g. certain gravitational lensing observations) but this is a step in the direction of being able to dismiss the need for dark matter from our cosmological theories.
- sbahsva 6y ago
- headmelted 6y ago“You can see where this is going” Uuuuummmmmmmmm..
- ajg4 6y agoOk, it maybe describes the galaxies rotational curves, actually a few other theories about modified newtonian dynamics are capable of doing that too.. However it doesnt explain the bullet cluster, structure formation or the power spectrum of the CMB
- bjornsing 6y agoBut the explanation is just general relativity... I mean, what does it matter if some other ad hoc theory can explain it too? In my book, if GR explains it that’s the end of it. Sure there may still be a ton of stuff that requires explanation and where dark matter may be a possible explanation, but what can be attributed to GR shall not be attributed to some ad hoc fudge factor.
- ajg4 6y agoYoure right, that doesnt matter I am just wondering: if GR explains the rotation curve, how can GR still explain the shapiro delay or lensing?
- hertzrat 6y agoAm I the only one who thinks this is a an awful title? Or have we moved on to insulting entire classes of people?
- Ericson2314 6y agoI always like to mention the existence of gravitomagnitism as a pleasing example of symmetries being preserved. Would be neat if this worked out.
- jjkleid 6y agoI wonder how this new paper differs from this, from 16 years ago: https://arxiv.org/abs/astro-ph/0507619 https://arxiv.org/abs/astro-ph/0507619
- catlifeonmars 6y agoThe new paper cites the old paper, in fact.
- rarefied_tomato 6y agoAfter referencing that paper and a couple others, the new work says "... practically all the galactic rotation models so far are based on potential theory and the circular orbit concept in the Newtonian framework" "In the present article a new model for the rotation curve of galaxies is developed including the effects associated with mass currents... ... It is shown that the inclusion of the gravitomagnetic field clarifies some inconsistencies of the standard potential theory."
- cygx 6y agoThat's the wrong paragraph to cite. The parts relevant to Cooperstock's (and similar) work is this: > Although filled with controversy, the studies of the galactic rotation via general relativity [16,17,18] reach the same basic conclusion of the present paper. Namely, the dragging effect of a gravitomagnetic component (time-space component of the metric) explains the flat rotation curve at large distances, without the recourse to dark matter. The main problem with the general relativistic models is the very limited number of exact solutions of the Einstein field equations [...] > The calculated motion in the general relativistic approach corresponds to the free-fall of test particles in the assumed metric, without consistently considering the effect of the large galactic mass density distribution on the metric. Actually, this is the same objection that can be made to the classical approach [...] > Fluid models, as used in the present paper, consider the mean motion of particles in the Vlasov-like collective gravitational field. The gravitoelectromagnetic weak field approximation to general relativity, used in the present paper, leads to a tractable self-consistent solution of the galactic rotation problem. Citation [16] in particular is a reference to https://arxiv.org/abs/astro-ph/0610370 https://arxiv.org/abs/astro-ph/0610370
- exabrial 6y agoThis is way over my head, but essentially one guy decided to include magnetic fields (in addition to gravity) into account when calculating why galaxies don't fling themselves to bits? Eli5
- tobmlt 6y agoNot magnetism. In full on GR you get gravitomagnetism - a gravitational analogue to magnetism. The author made use Of full on GR instead of a Newtonian approximation. I thought this was already known to be helpful?
- blake1 6y agoThis is about gravitomagnetism. It would be beautiful if someone who studies electromagnetism in a turbulent plasma explain dark matter away. But these efforts always flounder on the bullet cluster results. I’m not going to get excited until I can see how those data are disposed of.
- auntienomen 6y agoAlso: gravitomagnetism is taught in pretty much every textbook on GR. It'd be a bit surprising if the people who wrote those textbooks (e.g. Steve Weinberg) didn't notice that elementary topics in their own textbooks could solve major problems in their fields.
- DetroitThrow 6y agoI don't think people working with GR did ignore it like the author suggest, the paper seems to cite older attempts to reconcile the phenomena using more simplified models. Also another comment further down seeming to observe the same thing: https://news.ycombinator.com/item?id=26442664 https://news.ycombinator.com/item?id=26442664
- amelius 6y agoIt seems that the phenomenon is already part of cosmological simulations. https://sciencenode.org/feature/toward-a-realistic-cosmic-evolution.php https://sciencenode.org/feature/toward-a-realistic-cosmic-ev... (Note: frame-dragging is another term for gravitomagnetism)
- ncmncm 6y agoThere is absolutely no need for gravitomagnetism to explain the bullet cluster. If it accounts for rotation curves, or even just a substantial fraction of rotation curves, that's a box checked: GR and (those) galaxies' rotation turn out consistent after all. Then it will be DM's problem to explain why DM shows up only where a fudge is needed. My expectation is that the universe will not cease to mystify for a long time. We can live with the Bullet Cluster losing its (maybe too-) convenient explanation.
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- ThalesX 6y agoI can't help but think about the Memristor[0] and the symmetry on which it its theoretization was based on: > Chua in his 1971 paper identified a theoretical symmetry between the non-linear resistor (voltage vs. current), non-linear capacitor (voltage vs. charge), and non-linear inductor (magnetic flux linkage vs. current). From this symmetry he inferred the characteristics of a fourth fundamental non-linear circuit element, linking magnetic flux and charge, which he called the memristor. In contrast to a linear (or non-linear) resistor the memristor has a dynamic relationship between current and voltage including a memory of past voltages or currents. Other scientists had proposed dynamic memory resistors such as the memistor of Bernard Widrow, but Chua introduced a mathematical generality. How amazing would it be to identify a quirk allowing us to manipulate gravity using flux and charge! I'm probably misunderstanding this as I'm not even grasping the fields these concepts involve, but, one can dream. [0] https://en.wikipedia.org/wiki/Memristor#The_memristor_as_a_fundamental_electrical_component https://en.wikipedia.org/wiki/Memristor#The_memristor_as_a_f...
- de6u99er 6y agoIf confirmed, looks very much like it tbh., then he's a safe bet for the next Nobel Price in Physics.
- floxy 6y agoSo what implications might this have for dark energy?
- 8bitsrule 6y agoBut then, in the plus column: 1) In 50 years, the formalists got really good at formalism; 2) 50 years of paychecks.
- sega_sai 6y ago(Astrophysist here). This is complete BS. (I can't comment on the theoretical aspects of gravitomagnetism, not my area of expertise) but the data part is a joke. They "fitted" the rotation curves of three galaxies with their very obscure model with a bunch of parameters. What does it prove -- nothing. Plus, if I understand their model correctly, their model will not work for systems without any rotation, i.e. dwarf spheroidals galaxies which do not rotate, but still have ~ 1000 more dark matter than visible matter (based on stellar velocity dispersion measurements). And the evidence for dark matter is there is not only in flat rotation curves, but in cosmic microwave background for example; as to explain the cosmic microwave background you must have a large fraction of DM in early universe.
- frongpik 6y agoRe: those dwarf galaxies. Their core (massive black hole?) still spins, right?
- ncmncm 6y agoNot having even tried out applying relativistic gravitation to any galaxy at all, when the numbers seem to show a significant effect, is an enormous omission. Even if this doesn't wholly pan out, you and your colleagues have all failed at your job. Their failing in no way absolves you. It is not necessary for the result to match observations in any but a sampling of galaxies. In particular, they don't need to explain any other phenomena than rotation curves. With those matched, it will be your and your colleagues' responsibility to show why those galaxies lack the dark matter all galaxies are supposed to have, and to explain how your cosmic background curves accommodate the painfully clear lack of sufficient expected dark matter. The number of galaxies found to have no room for dark matter will only increase. If your theory accommodates any random amount of dark matter equally well, that removes dark matter from the list of reasons to believe it, and makes having promoted that as a reason a fib.
- auntienomen 6y agoMaybe you shouldn't assume that the scientists are all stupid, just because some rando wrote a blog post. This 'result' isn't going to hold up.
- mikewarot 6y agoGravitomagnetism [1] a new thing I hadn't heard of until reading this. I played with the math a while, and it seems that a fast spinning object in the lab would generate a field 2.5E-12 times that of the earth, if my math is right. A 2" trailer hitch spinning at 10,000 RPM, should generate a field of 2.5E-26 Hz That's an incredibly small effect. I doubt it will get measured on the ground in a lab. 1 - https://en.wikipedia.org/wiki/Gravitoelectromagnetism#Gravitomagnetic_fields_of_astronomical_objects https://en.wikipedia.org/wiki/Gravitoelectromagnetism#Gravit...
- mdip 6y ago:: The tone sounds like I'm being harsh (i.e. "stupid scientists!"), that is not intended. Any developer understands that the "actual fix/solution" often looks "really obvious/simple". It doesn't mean the developer who spent weeks to get to that elegant, perfect, implementation is stupid for not having thought of it in the first few hours of development... Something's been bothering me and for whatever reason, the term "Gravitomagnetism" has come up, oddly, several times in the last two days. Oddly because this paper was the start of it. Two days ago I was repairing a brushed DC motor and started thinking about magnetism more generally, which made me realize I've "forgotten" what little fundamental knowledge I used to have about magnetism. My first search was to search the relationship between gravity and electricity[0]. And after a mess of reading, I happened onto a pretty poor set of explanations about what the term "Gravitomagnetism" meant and after a lot of reading, I wasn't entirely clear if that gravitomagnetism was mainstream or crackpot (partly due to fascination reading those Air Force patent articles reducing the amount of time spent actually learning something). I'm guessing there's an obvious answer and my ignorance of the subject is at fault, but as I read about Dark Matter, it feels like an "excuse". Going simply from Wikipedia[1], "Observational Evidence", the evidence for its existence starts off with something that can be casually paraphrased as "Given our best understanding of how things should work, when we actually measure how things are working, we find the numbers don't work, so 'Dark Matter'." And as you get further down the evidence list, you start to find things like "why there's so much of it" (except where in the heck is it all?) and why Galaxies are important for observing it. I know my mind is probably polluted with outdated (and, let's face it, probably often bad) information from various reporters covering a subject they know less about than I do (and that's not saying much), but as I read that over, I kept thinking "it really sounds like an idea that is better explained by something else". Am I completely off, here? [0] Which led to a bizarre hoax called the Hutchison Effect, several Quara articles of various quality, and all of those weird Air Force patents (due to another questionable 'effect' named after its supposed identifier). [1] https://en.wikipedia.org/wiki/Dark_matter https://en.wikipedia.org/wiki/Dark_matter - no, I'm not expecting this is the best explanation, but it's the best I've got!
- jgalt212 6y agoCan we use the same math to disprove the existence of structural racism? Obviously, racism exists, I just don't like the hand washy application of "structural racism." i.e. we're all guilty, or it's not me it's society's fault.
- geeB 6y agoI am (as many here it seems) on the side of wishing that all the phenomena currently ascribed to dark matter will be all explained away by some more elegant and less "tunable" theory. However, imo the chances of the specific idea from the article being the case are very low, and it's more likely that there is a problem with the new way of calculating the gravitomagnetic contribution, either in theory or with the code/computation. I've had the same idea a few years ago. It's nice because the effect is that the moving matter in a certain orbit causes an increase in the centripetal acceleration (i.e. higher velocity) for orbits further out, and a reduction for orbits further in, which is in the right direction to flatten the rotation curves. Being a procrastinating amateur and not knowing/being able to invent sophisticated techniques such as the one in the article, I didn't fully go though with the calculations, because after some unsuccessful attempts I convinced myself that the effects involved are way too small to matter. Consider two equal electric charges a certain distance from each other. If they move perpendicularly to the line between them at constant velocity, there will be an attractive force due to the magnetic field that opposes the electric repulsion. However, the ratio of the magnetic to electric force is the familiar (v/c)^2, at least for non-relativistic speeds, and in any case the magnetic force can never exceed the electric force, because perpendicular distances are preserved in the Lorentz transformation. Hence the most the magnetic force can do is slow down the repulsion between the charges, exactly in the amount consistent with time dilation in the moving frame (where the charges are stationary so there is no magnetic field). Transposing that to gravitomagnetism, I think that within that approximation the situation is the same. At the very best the gravtomagnetic force can equal the gravitoelectric force when masses move close to the speed of light, making it mathematically impossible to account for the DM mass being greater than the baryonic mass. On top of that, at typical velocities in galaxies the magnetic effect is ~1M times smaller. Together with the facts that 1. there are other unexplained phenomena that won't be explained by this, and 2. it's trivial in retrospect so probably some truly smart person thought of it already and discarded it a minute later without even thinking it's worth publication, I just abandoned it, always wanting to get back to it eventually just for fun when I have the time (sadly this seems to always mean never). Fast forward a few years, and I see this article on HN, and really regretted having been lazy with my dismissal, maybe I missed something along with everyone else, and should have really done the calculations. So I found a few hours this weekend, learned julia for the Nth time, and finally did what I should have done years ago... and as expected the gravitomagnetic effects have zero material impact on the rotation curves. Now, admittedly my calculations are not fully correct, but I think my approximations are reasonable enough that they wouldn't be many orders of magnitude off, validating the intuition about relative strength of electric vs magnetic force. So I'd be very surprised if the results in the article turn out to be right. I don't think it's fair to attack scientists for not having simulated galaxies with full GR. They realized with much less work than me that it does not matter. At the sizes, masses, and velocities of galaxies, the effects are minuscole, and using Newtonian gravity is sufficient, especially if the phenomenon to explain is so large. It's like in the solar system: GR can explain Mercury's precession, but it wouldn't help if we had orbital anomalies equivalent to effect of 5 solar masses scattered throughout the orbital plane. Anyway, another thing I've put off forever is making an HN account after a long time reading. So since I saw this story here and it made me finally get that idea out of my system, what better occasion to also create an account and get that out of my system too :)