[HN Gopher] New Hubble data suggests an ingredient missing from ...
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New Hubble data suggests an ingredient missing from current dark
matter theories
Author : dnetesn
Score : 48 points
Date : 2020-09-11 10:04 UTC (1 days ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| Hickfang wrote:
| Yea, the missing ingredient is darker dark matter :]
| andrewflnr wrote:
| The current top-level comments are infuriating. You demand that
| scientists be honest, then accuse then 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 wrote:
| 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.
|
| I also still fully stand by my previous comment on this
| subject: https://news.ycombinator.com/item?id=23666620
| andrewflnr wrote:
| 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.
| dnautics wrote:
| > 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 wrote:
| 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.
| dnautics wrote:
| 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.
| anoncareer0212 wrote:
| sir this is a thread about Hubble data
| OpticalWindows wrote:
| Will the James Webb telescope help detail such phenomenon better
| than the hubble?
| noizejoy wrote:
| I'm not sure I understand the difference between "additional
| ingredient" and "a higher concentration of"
| T-A wrote:
| Dark matter models predict how the stuff is supposed to be
| distributed.
| cozzyd wrote:
| Here's the arXiv preprint: 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.
| lachlan-sneff wrote:
| 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.
| ChrisClark wrote:
| > 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.
| yongjik wrote:
| 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."
| daxfohl wrote:
| 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.
| duutfhhh wrote:
| 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."
| daxfohl wrote:
| 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.
| dnautics wrote:
| 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.
| lisper wrote:
| "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
| DennisP wrote:
| I don't really have an opinion but in fairness, the article
| is about a discrepancy between the data and current dark
| matter models.
| lisper wrote:
| 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.
| mehrdadn wrote:
| 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...
| jjoonathan wrote:
| 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.
| dnautics wrote:
| Disclaimer, 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 wrote:
| > There's no evidence for it
|
| [citation needed]
| tiborsaas wrote:
| If 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 wrote:
| 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).
| joshocar wrote:
| There is a LOT of evidence for the existence of dark matter.
|
| https://en.m.wikipedia.org/wiki/Dark_matter#Observational_ev...
| dnautics wrote:
| 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".
| lachlan-sneff wrote:
| What you've linked to is evidence that our understanding of
| gravity is wrong OR there is dark matter.
| magicalhippo wrote:
| 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.
| T-A wrote:
| https://en.wikipedia.org/wiki/Dark_matter#Observational_evid...
| lachlan-sneff wrote:
| Those are evidence for our physics not actually matching
| reality, not evidence for dark matter specifically.
| T-A wrote:
| If 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_relat
| i...
| leeoniya wrote:
| to add to this, the Higgs boson was predicted in 1964 and
| not detected till 2012:
|
| https://en.m.wikipedia.org/wiki/Higgs_boson
| dnautics wrote:
| 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.
| leeoniya wrote:
| > 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.
| dnautics wrote:
| > plenty of eventually-proven math conjectures
|
| 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.
| heavenlyblue wrote:
| You are arguing semantics
| morelisp wrote:
| 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.
| ajkjk wrote:
| Are you a physicist? What possibly makes you think you have
| enough background to disregard the (tremendous) evidence for
| it?
| mellosouls wrote:
| 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...
| freeone3000 wrote:
| 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.
| morelisp wrote:
| > 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.
| yes_man wrote:
| 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
| mountainboy wrote:
| common sense?
|
| rational thought?
|
| logic?
|
| reason?
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