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Some of the strongest evidence for dark matter to date has been discovered – and ironically, that's thanks to its absence. In a pair of studies published this week, astronomers have shed new light on dark matter through close observation of a galaxy previously found to have very little of the stuff, while the same team found a new example of a similar oddball galaxy.
It's generally believed that galaxies are held together through the gravitational influence of clumps of dark matter, so to find a galaxy with little to no dark matter was a surprise. And while it might sound like a strike against the theory, it actually ends up supporting it.
A Second Galaxy Missing Dark Matter in the NGC 1052 Group (DOI: 10.3847/2041-8213/ab0d92) (DX)
Still Missing Dark Matter: KCWI High-resolution Stellar Kinematics of NGC1052-DF2 (DOI: 10.3847/2041-8213/ab0e8c) (DX)
(Score: 0) by Anonymous Coward on Monday April 01 2019, @10:02PM (39 children)
Interestingly, the rotation rates are still consistent with non-dark matter theories.
(Score: 0) by Anonymous Coward on Monday April 01 2019, @10:19PM
https://tritonstation.wordpress.com/2018/04/04/the-dwarf-galaxy-ngc1052-df2/ [wordpress.com]
(Score: 2) by melikamp on Monday April 01 2019, @11:16PM (33 children)
(Score: 0) by Anonymous Coward on Monday April 01 2019, @11:37PM (32 children)
And? The results are pretty much the same, still consistent.
(Score: 2) by melikamp on Tuesday April 02 2019, @02:24AM (31 children)
No I mean, would it hurt the submitters to post links to full text? Here's the other one:
https://arxiv.org/pdf/1901.05973.pdf [arxiv.org]
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @02:39AM
Have to wait for one of the MOND guys to work out a value for that one. I am no expert.
But it is another "ultra-diffuse galaxy", which (afaik) means there is less deviation between MOND and Newtonian predictions: https://physics.stackexchange.com/questions/373555/mass-discrepancy-acceleration-relation-in-%CE%9Bcdm-paradigm [stackexchange.com]
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @03:08AM (29 children)
Someone already published a mond prediction for this one:
From Table 2:
https://arxiv.org/abs/1901.02679 [arxiv.org]
In your paper they say:
So it is on the low end but keep in mind what these intervals mean. If you check the MOND predictions for 100 galaxies you would expect about 10 to be outside the 90% CI if MOND was correct.
(Score: 1) by khallow on Tuesday April 02 2019, @04:31AM (28 children)
it's a classic epicycle theory even more so than the dark matter hack.
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @04:41AM (22 children)
It's not even a theory, think about it more like Keplers laws.
MOND is a quantitative relationship with amazing predictive skill (and thus usefulness) that needs to be explained. It seems very unlikely "dark matter" (arbitrary sized and shaped spheriods of some exotic substance surrounding each galaxy) can explain why MOND works. This is precisely because the deviations from newtonian dynamics should not be so lawlike in that case.
(Score: 1) by khallow on Tuesday April 02 2019, @08:46AM (21 children)
Except of course, that would explain it. That's why the dark matter is proposed in the first place.
Predictive? Like what? None of the things mentioned so far have been predicted by MOND.
We already know general relativity is a massive deviation from Newtonian dynamics at cosmological scales.
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @09:22AM (3 children)
Sorry, I thought you had some idea of what you are talking about. MOND has predicted every galactic rotation curve discovered since 1983. Dark matter has been post hoc fit to every single one, just exactly enough to match the MOND prediction.
(Score: 1) by khallow on Tuesday April 02 2019, @10:14AM (2 children)
So has dark matter based theories. Epicycles are a wonderful thing, until you get too many of them.
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @10:23AM (1 child)
No they have not. They have never predicted a single one because it is impossible. All black matter explanations are post-hoc. Every single one.
And MOND doesn't have epicycles. It is a simple relationship where you plug in values for the surrounding mass. The only trouble is getting good estimates of those values. There is nothing similar to epicycles that are added ad hoc.
Dark matter on the other hand, is literally 3D epicycles. It is invisible spheroids of stuff added in after the fact to make the predictions work.
(Score: 1) by khallow on Tuesday April 02 2019, @10:44AM
To the contrary, small object near a large object (where the weakly interacting matter can be drawn off by gravitation interference) is one such place. It predicts the existence of galaxies without much in the way of dark matter. The mechanism of creation conveniently falls under the external field effect (EFE) assumption.
Two have already been mentioned. The initial weak gravity deviation from Newtonian mechanics. And the EFE assumption. Neither has physical explanation. It just fits data, just like the dark matter assumption does.
In other words, "simple relationship where you plug in values for the surrounding mass". We already know the universe has priors since distribution of matter follows no simple relation on any scale we can observe. So dark matter priors is not even a little bit of a stretch.
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @09:24AM (12 children)
I mean you are responding in a thread discussing how MOND predicted one of these galaxies curves too. Someone worked out the prediction before this paper came out (+ a dozen more). Are you even comprehending any of this?
(Score: 1) by khallow on Tuesday April 02 2019, @10:35AM (11 children)
The data preceded the prediction (keep in mind that the theory had to be modified in the first place to explain the sort of system which is adjacent to a large mass, and hence, would be mostly likely to be stripped of dark matter in the dark matter theories). And you still neglect the big issue. MOND has all sorts of adaptations to fit observation. But we continue to find things it needs to adapt to. For a short list:
Seriously, why is the presence of dark matter considered a big problem even though we still have much we don't understand about such things, but the presence of aphysical characteristics not considered a problem? My view is that dark matter is simply stuff that we haven't seen yet - sorry, that's not that big a stretch despite all that has gone on, and MOND is a massive ad hoc with a number of justifications based only on explaining incomplete data.
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @10:56AM (3 children)
You seem incapable of even recognizing that in this very case someone published a MOND-based prediction, then later another group published rotation curve data that matched the prediction.
There is no room for ad hoc adjustments to MOND, it is set in stone since 1983. The only thing is getting good estimates of the parameters to plug in. So every time you repeat that it is false. You can go look at the original papers to see it (but I know you won't).
It is pointless to discuss something with someone who just repeats falsehoods that are easily disproved by just reading a few sentences in a journal article they refuse to look at. That is messed up dude.
(Score: 1) by khallow on Tuesday April 02 2019, @12:56PM (2 children)
Open cluster data predates 1983. And I don't buy that current MOND-based predictions are based on that theory.
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @01:12PM (1 child)
You just "don't buy it", because data mentioned in a paper existed before the paper was written. That is your argument now...
This is so sad, on other topics you seemed to have an actual thought process.
(Score: 1) by khallow on Tuesday April 02 2019, @01:51PM
Yes. That's correct. Please recall the key problem. There is no physical explanation for any part of MOND, then or now. It's instead an adjustment to existing theory to explain discrepancies. That's exactly the role of dark matter as well. Both are epicycles.
Further, we have the problem of the gravity environment. Somehow MOND claims that these disperse galaxies are close enough higher mass to have these mechanics, but not the galaxy, NGC 1052 which is generating the external gravitational field in question. NGC 1052, instead has a dark matter halo [hawaii.edu] (possibly with two axes, "Some galaxies (e.g.NGC 1052, M32)are well-fit by two-integral models"). Think about that. Something outside of a galaxy has no MOND effect allegedly due to the external gravitational field of the galaxy, but the galaxy itself does. How did the gravitational field grow that much stronger outside NGC 1052 that it eliminated the MOND effect?
(Score: 2) by Gaaark on Tuesday April 02 2019, @02:02PM (6 children)
"Seriously, why is the presence of dark matter considered a big problem even though we still have much we don't understand about such things,"
And yet you have big problem with QI, even though it is a better, more scientific model.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 1) by khallow on Wednesday April 03 2019, @04:16AM (5 children)
The catch is that MOND at least explains most galaxies with "no" dark matter effects as being embedded in a stronger gravitational field. QI seems to predict that dark matter effects should be stronger because of the weak internal gravitational field of the galaxy rather than the opposite which is actually observed.
(Score: 2) by Gaaark on Wednesday April 03 2019, @10:21AM (4 children)
Uhhhh,...QI seems to predict there IS NO dark matter.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 1) by khallow on Wednesday April 03 2019, @12:51PM (3 children)
(Score: 2) by Gaaark on Wednesday April 03 2019, @10:45PM (2 children)
Okay, I guess I don't understand where you are going.
QI only deals with motion and speed: galaxies don't fly apart due to inertia.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 1) by khallow on Wednesday April 03 2019, @11:12PM (1 child)
The problem here was motion and speed of rare sorts of galaxies that the other two theories have figured out how to shoehorn explanations for. The QI explanation is lacking since the galaxies in question are low density satellite galaxies, most of their mass got robbed by NGC 1052 in some long ago collisions. So they're precisely the sort of low local gravity objects that QI should be describing. Unless QI has the MOND issue where external gravitation fields (here from NGC 1052) cause the physics to somehow change.
(Score: 2) by Gaaark on Thursday April 04 2019, @01:37AM
run the numbers against his formula.
I'm betting you get the numbers you're looking for.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 2) by FatPhil on Tuesday April 02 2019, @07:35PM (3 children)
> We already know general relativity is a massive deviation from Newtonian dynamics at cosmological scales.
The bulk of what we can see out there that is interacting gravitationally with each other isn't travelling anything like relativistic speeds in any of their reference frames, so the deviations from Newton are pretty tiny - smaller than the error bars around any measurements we make. The things receding from us with enormous relative velocities are not interacting with us gravitationally at all, so the deviations are effectively zero.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 1) by khallow on Wednesday April 03 2019, @12:54PM (2 children)
(Score: 2) by FatPhil on Wednesday April 03 2019, @08:44PM (1 child)
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 1) by khallow on Wednesday April 03 2019, @11:16PM
Sorry, not with respect to mass that's far away. Newtonian dynamics, for example, would have instantaneous interactions between widely separated superclusters of galaxies not billions of years of lag. Cosmological inflation and the current observation of "negative energy" (which really is just observed current stretching of the universe).
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @04:50AM
And look how the dark matter proponents are misusing statistics. What they did is something like publish 100 different papers about one galaxy each, wherein they compare 90% confidence intervals to MOND predicted values for every galaxy.
So they made 100 different comparisons and didn't adjust their significance level for that. It is actually very likely a few will be outside the 90% CI if MOND is correct. In fact, we would predict 10% of the predictions are outside the interval.
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @05:10AM (3 children)
Also, the external field effect is crucial to MOND, it isn't something added on later. It is just negligible in most cases so they ignore it.
https://arxiv.org/abs/1010.1349 [arxiv.org]
(Score: 1) by khallow on Tuesday April 02 2019, @10:45AM (2 children)
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @11:00AM (1 child)
Very first paper about MOND, section III, # 2.
http://adsabs.harvard.edu/doi/10.1086/161130 [harvard.edu]
There is nothing ad hoc about this.
(Score: 1) by khallow on Tuesday April 02 2019, @12:54PM
(Score: 2) by FatPhil on Tuesday April 02 2019, @05:37AM (3 children)
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: -1, Flamebait) by Anonymous Coward on Tuesday April 02 2019, @05:44AM (2 children)
You are beyond hope sir. I mean really, you have lost touch with reality. Once you start denying that a priori predictions that turn out consistent with the data are support for the theory they came from, it is over. You have your religion and aren't giving it up.
(Score: 2) by FatPhil on Tuesday April 02 2019, @07:37PM (1 child)
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: -1, Troll) by Anonymous Coward on Wednesday April 03 2019, @02:00AM
What in the world are you responding to?
This is hilarious.
(Score: 2, Funny) by Anonymous Coward on Monday April 01 2019, @10:07PM (15 children)
GAAAAARRRKKK!!!! [youtube.com]
(Score: 1) by RandomFactor on Monday April 01 2019, @10:12PM (2 children)
It's so wrong when an AC wins a thread this early.
В «Правде» нет известий, в «Известиях» нет правды
(Score: 0) by Anonymous Coward on Monday April 01 2019, @10:36PM (1 child)
I could have posted as logged in, but where's the fun in that?
(Score: 2) by aristarchus on Tuesday April 02 2019, @08:47AM
At least Gaaaaark is happy, now that Dark Matter has been banished to the wastebin of history . . . oh, what? It hasn't? Oh, crap, Gaaark is not going to be happy about this.
Science, it is just too damned uncertain and hard! I mean, what are we to believe? Will not someone just tell us what to believe? Oh, thank you, Alex Jones!
(Score: 2) by Gaaark on Tuesday April 02 2019, @03:26AM (11 children)
Yeah, here we go again...
..."It has none...which is PROOF the thing that doesn't exist DOES exist! Just like My ass DOESN'T have whip cream all over it, so whip cream on asses exists! PROOF!
God exists BECAUSE we have no proof he exists! PROOF!"
More pseudo-scientific garbage...
AAAAACCCC!
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @03:41AM (9 children)
See the thread above. Not only do these fail to contradict MOND, a MOND prediction for this new "no dark matter" galaxy was published beforehand.
This dark matter propaganda is really stretching credulity at this point. I am beginning to doubt that they are being intellectually honest, and thinking instead there is some scam going on.
(Score: 2) by Gaaark on Tuesday April 02 2019, @03:52AM (8 children)
Yup: QI too.
The scam is that they get loads of funding for DM, just like how they (used to?) get loads of funding for string theory.
Follow the money, find the reason for crap.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @04:29AM (2 children)
Why can't they get loads of funding for MOND/QI? Just because dark matter is so vague?
(Score: 2) by Gaaark on Tuesday April 02 2019, @04:02PM (1 child)
Dark matter is 'established' science while QI and MOND are 'pseudo' science.....so say we all.....all except those that realise that dark matter was JUST created out of thin air to save General Relativity.
Instead of realising that GR has faults, the DM magicians waved their hands around and said Abra-cadaver enough to get noticed.
QI just got some DARPA funding, though. Good news for REAL science.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @06:00PM
I dunno man, reading what people say not just here and elsewhere it looks like blindly repeating mantras. I couldn't even get khallow to recognize the publication date of a prediction is before the publication date of the rotation curve data for the second "missing dark matter" galaxy. All it requires is looking at the dates on two documents.
He has apparently been rendered incapable of making a simple comparison between two published dates, that is some pretty strong mental gymnastics. Think about it.
Then he "just doesn't buy it" that the equations for MOND published in 1983 are the same ones used today. He provides no source or reason for this, just intuits it I guess. It is like their minds reject actual science making consistently accurate predictions without post-hoc fiddling as impossible.
So I suspect shilling/trolling.
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @10:30AM (4 children)
People in this thread seem very opinionated but totally ignorant of the topic (eg, Mr Khallow above). They just string together a bunch of blatantly false things about MOND, and then conclude therefore dark matter is a great idea. Is that normal? Or are they trolling?
(Score: 1) by khallow on Tuesday April 02 2019, @01:56PM (3 children)
Explain why MOND works, then we'll have something to go on. In the mean time, we already know that there is dark matter, but what we know of isn't enough at present to explain the observed discrepancies. Finding more dark matter is not that big a stretch. A theory of gravity that can't be observed anywhere near Earth should already be tripping alarms for you.
(Score: 2) by Gaaark on Tuesday April 02 2019, @04:06PM
MOND is not the droid you are looking for...QI is.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @05:49PM (1 child)
"Gravity," per se, does not exist. It's an artifact of the distortion of spacetime by mass.
How does that old saw go again? Spacetime tells matter how to move; matter tells spacetime how to curve.
(Score: 1) by khallow on Wednesday April 03 2019, @02:18AM
An observable artifact. That makes it just as real as anything else you can observe.
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @04:34AM
GAAAARRRRKKKK! [youtube.com]
(Score: 5, Funny) by All Your Lawn Are Belong To Us on Monday April 01 2019, @10:27PM (8 children)
If the galaxy in question is light on dark matter (and Wikipedia seems to have doubt about that FWIW and it might not be much), does that mean that a galaxy that has too little detectable matter and too much undetectable matter a galaxy that is dark on light matter?
This sig for rent.
(Score: 2, Funny) by RandomFactor on Monday April 01 2019, @11:00PM
TFA does mention "galaxy Dragonfly 44 [keckobservatory.org], which has the exact opposite problem of being composed of 99.99 percent dark matter" but they were light on details of the dark galaxy.
В «Правде» нет известий, в «Известиях» нет правды
(Score: 2) by Gaaark on Tuesday April 02 2019, @03:28AM (6 children)
If dark matter shits in the woods, will it make a smell?
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @05:50PM (5 children)
I don't know. But you appear to believe that yours does not. Self-deception is the worst kind of lie.
(Score: 2) by Gaaark on Tuesday April 02 2019, @07:49PM (4 children)
Hahaha.... GOOD COME-BACK!
You. are. the. MASTER!
*Golf clap*
SO....what are you? 12...13 years old?
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @09:14PM (3 children)
Old enough that I could be your father. In fact, I (or a cast of thousands) might well be, given what a whore your mom is.
(Score: 2) by Gaaark on Tuesday April 02 2019, @09:36PM (2 children)
Hoh SHIT! You are SOOOO good at come-backs.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Wednesday April 03 2019, @12:25AM (1 child)
That's so sweet! Kissy kissy, baby!
(Score: 2) by Gaaark on Wednesday April 03 2019, @02:15AM
Yup: you're 12.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 2) by FatPhil on Tuesday April 02 2019, @12:07AM (2 children)
NOOOOOO!!!!
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @12:26AM (1 child)
Got somewhere you gotta be? Any way you slice it our current tech will have you dead before getting there, even if you weigh 7 tennis balls.
(Score: 1, Funny) by Anonymous Coward on Tuesday April 02 2019, @01:02AM
Why would I weigh seven tennis balls? Why can't I just weigh one and multiply the result by seven?
(Score: -1, Offtopic) by Anonymous Coward on Tuesday April 02 2019, @01:38AM
I love you. I love you.
(Score: 0) by mpc755 on Tuesday April 02 2019, @12:28PM (7 children)
Dark matter is a supersolid that fills 'empty' space, strongly interacts with ordinary matter and is displaced by ordinary matter. What is referred to geometrically as curved spacetime physically exists in nature as the state of displacement of the supersolid dark matter. The state of displacement of the supersolid dark matter is gravity.
The supersolid dark matter displaced by a galaxy pushes back, causing the stars in the outer arms of the galaxy to orbit the galactic center at the rate in which they do.
Displaced supersolid dark matter is curved spacetime.
In the Bullet Cluster collision the dark matter has not separated from the ordinary matter. The collision is analogous to two boats that collide, the boats slow down and their bow waves continue to propagate. The water has not separated from the boats, the bow waves have. In the Bullet Cluster collision the galaxy's associated dark matter displacement waves have separated from the colliding galaxies, causing the light to lense as it passes through the waves.
(Score: 0) by mpc755 on Tuesday April 02 2019, @12:30PM (1 child)
The reason for the mistaken notion the galaxy is missing dark matter is that the galaxy is so diffuse that it doesn't displace the supersolid dark matter outward and away from it to the degree that the dark matter is able to push back and cause the stars far away from the galactic center to speed up.
It's not that there is no dark matter connected to and neighboring the visible matter. It's that the galaxy has not coalesced enough to displace the supersolid dark matter to such an extent that it forms a halo around the galaxy.
A galaxy's halo is not a clump of dark matter traveling with the galaxy. A galaxy's halo is displaced supersolid dark matter.
(Score: 1, Insightful) by Anonymous Coward on Tuesday April 02 2019, @05:53PM
And which candidate [xkcd.com] fits your description of "supersolid dark matter?"
(Score: 2) by Gaaark on Tuesday April 02 2019, @04:09PM (4 children)
Or, dark matter DOES NOT EXIST...go with Occam's razor and choose the scientific, simple QI.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @05:55PM (3 children)
Or you don't exist. There's about the same amount of evidence for that as there is for dark matter: Both have only been indirectly observed.
(Score: 2) by Gaaark on Tuesday April 02 2019, @07:55PM (2 children)
Ooooooo.....SO Scientific, just like dark matter!
Hmmm... except DM HASN'T even been INDIRECTLY observed, only IMAGINED to be observed, while my wife has observed me many times.
Try again, bright eyes.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @09:10PM (1 child)
What is this "wife" of which you speak?
Some sort of fleshlight?
(Score: 2) by Gaaark on Tuesday April 02 2019, @09:38PM
GOOD. ONE!
No wonder you believe in dark matter.
--- Please remind me if I haven't been civil to you: I'm channeling MDC. ---Gaaark 2.0 ---
(Score: 0) by Anonymous Coward on Tuesday April 02 2019, @05:52PM
Sounds like a new art style, like Oil on Canvas.
Though it'd end up a bit more energetic ...