Scientists discover a 'dark' Milky Way: Massive galaxy consists almost entirely of dark matter

The abstract says 98 % DM.

This one is gonna bring out the "Theorists"...:-)

Almost certain to be caused by a high level of chocolate

This one is gonna bring out the "Theorists"...:-)

Oh, you mean that zany Zwicky Astrologer from the 1930's giving us his latest Horoscope Readings? Next we'll be hearing about Tired Light Theory from the same bunch who continue following this guy's zany ideas.

If a population III galaxy existed and was found nearby, wouldn't it look very similar? The metal poor stars would have been huge and fast lived. Even pulsars would stop as the aging star remnants slowed and cooled. Younger population 1 and 2 stars would still be active, but they wouldn't have formed until after the first round of supernovas started flashing through that galaxy.

They say nothing of the CCM mass

so for comparison what percentage off the milky way is in the form of stars and "normal" matter?

"We have no idea how galaxies like Dragonfly 44 could have formed,"

And still the merger maniacs hold out hope for dark matter. Obviously the interpretation of the observation is wrong. Dark matter is simply a place-holder for misinterpreted observations. But such a conclusion is heresy in the minds of committed merger maniacs.

And still the merger maniacs hold out hope for dark matter. Obviously the interpretation of the observation is wrong. Dark matter is simply a place-holder for misinterpreted observations. .

How so?
How on earth do you explain the observations without it?
Currently, it is the only credible theory that explains the way we see the motion of visible mater in galaxies short of assuming we have got the law of gravity wrong and with the law of gravity operating differently over some completely arbitrary 'long' distances thus making the law much more complex.
https://en.wikipe...k_matter
"... its (dark matter ) existence and properties are inferred from its gravitational effects such as the motions of visible matter,..."
It is no good just asserting a seemingly perfectly reasonable scientific theory is wrong despite it explaining the observations if you fail to explain an alternative that seems better; so what alternative theory do you propose?...

humy,

How on earth do you explain the observations without it? [dark matter]

Creating imaginary matter does not explain the observations. Rather than creating imaginary matter because our observations do not match our models of gravity, we should try to determine why our models fail.

That dark matter is simply imaginary is evident from one simple aspect, that there is always just enough dark matter in just the right places to account for whatever we observe. There is never too much or too little and it is always in just the right places.

Note that we don't find dark matter in our solar system. Our models of gravity do not require imaginary matter in our solar system to perfectly model the movements of the planets, etc. But our galaxy outside our solar system is supposed to be full of the stuff.

When an idea doesn't make sense, it is reasonable to conclude that the idea is nonsense.

There is never too much or too little and it is always in just the right places.

I think you fail to grasp something pretty fundamental:
Of course will the calcs come out to exactly the amount/place needed because the calcs are based on "how much and where is DM needed to account for the observable effects"

Since we have no direct observation of DM how else do you think scientists come up with these figures? Magic?

antialias_physorg,

I think you fail to grasp something pretty fundamental:
Of course will the calcs come out to exactly the amount/place needed because the calcs are based on "how much and where is DM needed to account for the observable effects"

No, that was exactly my point. It is simply created [imagined] in just the right amounts and in just the right places to normalize our observation to our models of gravity. It started out as a kludge and remains a kludge to make our models match what we see.

Generally, when a model fails, we try to discover why it fails, which often leads to new discoveries and/or a better model. When we say "We will just create some imaginary stuff and we can make our model work", we close the door to finding out why our model failed.

The number of people that visit this site and yet don't understand the scientific method is quite disappointing.

It started out as a kludge and remains a kludge to make our models match what we see.

You fail to grasp the significance of such calcs. They show us where to look to verify (or falsify) the current crop of hypotheses.

No one knows what DM is. There are theories and they need to be tested. A kludge would just be something that was put in there "just because". This is not the case with DM research.

Generally, when a model fails, we try to discover why it fails, which often leads to new discoveries and/or a better model.

Gee whiz...what do you think DM is?
Hint: It is an attempt to quantify why the current model fails and therefore is aimed to lead to new discoveries and a better model. Bravo. You've just 'discovered' the blindingly obvious.

antialias_physorg,

Gee whiz...what do you think DM is?

I thought I was quite clear. Dark Matter is simply Imaginary Matter. It was simply 'made up' out of nothing when we saw that our models of gravity did not explain the movements of stars in the galaxy.

No one knows what DM is.

That is precisely the problem with a kludge. You begin to believe that your kludge is real and try to determine what your imagined matter is composed of.

Everyone is looking for dark matter instead of looking for a solution to the gravitational anomalies we observe. Daily we are informed that someone has 'found' dark matter like in this article where we have a 'dark matter' galaxy.

I thought I was quite clear. Dark Matter is simply Imaginary Matter.

You might want to read up what DM is before making such statements. Obvioulsy it is not 'quite clear' to you. DM is a placeholder label for an observed effect. Nothing more. Nothing less. NOTHIN in this says it must be matter.
Currently the only thing we know of that produces effects like the ones observed is (ordinary) matter. Therefore looking for some form of matter is the best way to start the search of what is causing this. But DM explanations aren't limited to matter.

Dark : because we can't see it
Matter: because it behaves like matter does.

That's the long and short of it. That it must be matter is your (erroneous) assumption which no one in the world shares (least of all scientists).

1. The universe is older than we think.
2. There are more dead stars than we think.
3. Apparently, there are more dead galaxies than we think.
4. Dark matter is matter we can't see, right?

Creating imaginary matter does not explain the observations. Rather than creating imaginary matter because our observations do not match our models...

If we follow this line of thinking, then we might as well revert back to considering everything as just a mix of air, water, earth and fire

3. Apparently, there are more dead galaxies than we think.

That doesn't grok with the distribution of DM.

it is the only credible theory that explains the way we see the motion of visible mater in galaxies

What "motion" are you talking about? Give just one example of this so-called "motion" within our own Spiral Galaxy that has unexplained anomalous "motion".

Are you aware of the fact that Zwicky originally theorized DM was to be found in Envelopes completely enshrouding ONLY Spiral Galaxies?

assuming we have got the law of gravity wrong and with the law of gravity operating differently over some completely arbitrary 'long' distances thus making the law much more complex.

Before you & your ANONYMOUS EXPERTS at Wikipedia post unscientific tripe like this, take up an actual study of Einstein's General Relativity & knock it off with this business of quoting one another about things you IMAGINE is written in the document versus what is REALLY in the document. Copy & Paste the relevant sections of GR about which you are referencing so we have no doubt.

What "motion" are you talking about?

One example is right in the article (did you even read it)? Here, lemme help:

"Very soon after its discovery, we realized this galaxy had to be more than meets the eye. It has so few stars that it would quickly be ripped apart unless something was holding it together,"

Obvioulsy it is not 'quite clear' to you. DM is a placeholder label for an observed effect. Nothing more. Nothing less. NOTHIN in this says it must be matter.

Oh just knock it off with this "placeholder" crap.........your degree in Human Biology qualifies you ONLY to be an Undertaker, it gets you no points when it comes to a basic comprehension of Nuclear Physics. Stick to your studies of human cadavers & stop imagining "placeholder" is a somehow a clever obfuscation for the fact that Zwicky was serious about this Cosmic Fairy Dust completely enshrouding Spiral galaxies.

If you think Zwicky was so dead-on right, then where is the DM Halo enshrouding the Milky Way? Describe the so-called gravitational anomalies. What we find circling the MW are vast halos of Visible Matter stretching halfway to Andromeda & vice versa, exactly in the locations where Zwicky said we'd find his DM that supposedly prevents the 2 galaxies from imploding, but instead we simply find more VM.

@Benni the difficulty with detecting dark matter in the Milky Way is that we are in the middle of it and so much of the contents are obscured from view. This makes working out precisely the distribution and velocity of the matter within it a very hard job indeed. This is unlike with other spiral galaxies that we can see in their entirety: without fail we can see that our laws of gravity are failing to accurately describe the dynamics. Hence, scientists have hypothesised that either there is some unseen (dark) matter within the galaxies or that Einstein's theory needs tweaking. To claim otherwise is just plain wrong and willful ignorance of scientific fact: things don't move as we expect on the largest scales.

Also this: http://www.nature...237.html

When observation does not agree with theory we have to modify theory or look for new phenomena. I this case, the best explanation for velocities of galaxies exceeding Newtonian values was to postulate the existence of matter that does not interact with the EM force. Other models of gravity did not match the observations. When someone comes up with a model that does, let them publish it instead coming here to attack anyone who does not agree with their hillbilly physics.

This logic is how neutrinos and other particles were found. Its how Pluto was found. Its how the...you get the idea.

Benni, and pretty much every other nonsense person here: Science did not stop when the first person said something was a certain way or not. Attacking the first person to have an idea is ludicrous in the field of science, in the same way it's ludicrous to deify the first person to have one. Who gives a flying F if Zwicky thought whatever you claim he thought? The fact is that much research has supported the hypothesis since then, even if it hasn't resolved which hypothesis best describes the material itself.

It's the same BS as creationists attacking "Darwin" as if biology began and ended with the Origin of the Species.

It's the same BS I see here constantly about how Einstein didn't come up with black holes, therefore they can't exist because he didn't say so.

Science grows over time and learns new things.

You should try the same.

Benni the difficulty with detecting dark matter in the Milky Way is that we are in the middle of it

If this were true, then being "in the middle of it" should make it easier, not harder, so what do we find when we place DM Detectors out in the middle of where you think we should find DM, we find zip.

When Einstein calculated Photon Deflection in GR, he first calculated the exact mass of the Sun at the point of the peripheral disc of its Visible Matter. This alone proves there is no DM component anywhere within the entire solar system & you can't prove Einstein was wrong about his gravity calculations. So if we're so "right in the middle of it", Einstein would have included such additional gravity in his Field Equations, but he didn't.

Have you ever studied the actual text of GR? Or are you just one of the many who read the Wiki stuff & become overnight geniuses about what you think the contents of GR is compared to what is really there?

.your degree in Human Biology qualifies you ONLY to be an Undertaker, it gets you no points when it comes to a basic comprehension of Nuclear Physics.
I have an university degree in EE. No, I am not a particle physicists or a cosmologist but I do like to read the papers that they put out (and have been reading stuff on these subjects since I was a kid)

It's just completely perplexing that there are people who come on here, write pages of pages about how dark matter can't be this or that (spending hours and probably entire days of their time doing so)...without even bothering to invest the 5 minutes to look up what the definition of dark matter even is.

It seems that some people just want to write stuff without caring whether its right or wrong or even makes sense. (On second thought...now I get why Trump actually has even a single supporter. If there are enough of such people then that explains a lot of things.)

When someone comes up with a model that does, let them publish it instead coming here to attack anyone who does not agree with their hillbilly physics.

Ah, the reasonable proposal of a science fairy dreaming of a perfect fantasyland. The problem with the fantasy is that the system of science has built it constraints that limit any proposed model to that that only fits within those already established limits. This is the result of a irrationally rational system of science. Nature need not fit within the bounds of science principals formulated by the limited intellect of humans.

Dark matter is likely simply an observational phenomenon of light being refracted by the underlying unobservable diffusive medium present everywhere being itself distorted in concentration due to the nearby presence of concentrated matter like a galaxy. Hard to prove within the bounds of science, but nonetheless very likely true. Quick, maniacs attack!

I assume they've tested and discarded conventional explanations. Could it just be neutral (non-ionized molecular) hydrogen? Is it possible some galaxies are 'failed' galaxies, so to speak? Perhaps consisting of a primordial blob of H₂ so evenly distributed that the greater part of it has never yet coalesced into regional dense volumes, thence proto-stars; finally, stars.

@Benni I find your desperate pleas for attention both aggravating and a little sad. Wasting away your lonely life masturbating into a sock in a darkened room, followed by unending trolling on phys.org to get the attention from humans that you so crave. It's okay to be alone Benni, you just need to use that lonely energy in a positive way for yourself: go out into the real world, talk to a stranger, immerse yourself in nature. Don't spend your days getting angry and worked up about things you don't understand, live your life! Best of luck, I'm rooting for you.

I assume they've tested and discarded conventional explanations

It should be clarified that that is meant in this particular (and perhaps similar) instance. In general, neutral hydrogen has been falsified as a general explanation for DM.

Almost certain to be caused by a high level of chocolate

99.99% DARK chocolate.

Science grows over time and learns new things.

But the difference is that Einstein was a lot smarter than those who explicitly makes statements in other threads on this site that Mass & Energy are not EQUIVALENT. Then when I confront you with explicit corrections from Special Relativity that they are EQUIVALENT, you go try to back track your error with long windy explanations in phony attempts to convince readers that you were MISUNDERSTOOD. No, you weren't misunderstood, you are an Astro-physics Aficionado attempting to convolute credible theses by a Nuclear Physicist (Einstein) into your personal versions of fantasyland science.

Nuclear Physics is not beyond my grasp, I'm immersed in it professionally on a daily basis. It's when you Perpetual Motion DM & BH Enthusiasts get so serious about your obvious Perpetual Motion Math that things become so entertaining on a site about Science. Those of us who can actually do the Math see how thinly veiled your arguments are.

That dark matter is simply imaginary is evident from one simple aspect, that there is always just enough dark matter in just the right places to account for whatever we observe. There is never too much or too little and it is always in just the right places.

This is a mischaracterisation of the model. Dark matter is not simply simply sprinkled in quantiles wherever needed. From simulation it is known that cold dark matter forms self similar halos with a very particular profile, in a universe with only cold dark matter if you know the density at some radius from the center you know the parameters of the halo you are in, because it only has one parameter and one measurement is enough to determine it. That's very powerful. Those profiles can be tested in observation by measuring the dynamics of galaxies, NFW profiles are very good fits to galaxy cluster lensing. ...

Wasting away your lonely life masturbating into a sock in a darkened room, followed by unending trolling on phys.org to get the attention from humans that you so crave.

........I challenge you DM Enthusiasts to put up quotes from Einstein's GR to prove your claims, and this is what comes back. If clowns like you are so serious about what you claim is Proven Science, then why do you need to huddle under an umbrella together & become such foul mouthed groupies?

You can go further too and make a simple connection between dark matter halos and galaxies in the real world by matching them by abundance (density in space). What you find is that at high mass the dark matter massively outstrips the normal matter, (because of the Schechter function's exponential decay). Also at low mass where the luminosity function is flatter than the dark matter halo abundance you find that in order to match by abundance dwarf galaxies must be dominated by dark matter. From just simply simulations done in the late 80's and 90's and some simple logic we have rationed out that very small galaxies like this one should be dominated by dark matter, as observed here.

Cold Dark Matter is not some infinitely flexible model that can fit any galaxy, their are dwarf galaxies where some people claim they cannot be fit by NFW profiles and are evidence against CDM and that is a very active field of research both in simulation and observation.

make a simple connection between dark matter halos and galaxies in the real world by matching them by abundance (density in space). What you find is that at high mass the dark matter massively outstrips the normal matter, (because of the Schechter function's exponential decay). Also at low mass where the luminosity function is flatter than the dark matter halo abundance you find that in order to match by abundance dwarf galaxies must be dominated by dark matter

.........total nonsense, but not surprising coming from someone who has already unequivocally stated in past threads that "gravity is not conserved" when Mass/Energy are transformed. If you actually knew anything about Nuclear Physics you would not find yourself in the continuing conundrums of such contradictions as compared to what OBSERVATIONS have already PROVEN.

@Benni Science moves on, so should you. I challenge you to quote the part that explains general relativity in Principia Mathematica, otherwise relativity is wrong. While you're at it, show me where Darwin talked about DNA in the Origin of Species - not gemmules please.

We can, and have, shown you a whole host of current valid scientific papers verifying the dark matter problem. But you don't care, you don't read it, you just go stick your fingers in your ears (and who knows where else) and go on with your lonely dark day.

Note that we don't find dark matter in our solar system. Our models of gravity do not require imaginary matter in our solar system to perfectly model the movements of the planets, etc. But our galaxy outside our solar system is supposed to be full of the stuff.

Note one can calculate the mass of dark matter enclosed by the solar system if we assume a smooth NFW profile normalised by the estimates of the local density. If you integrate all the mass enclosed in a 100 AU sphere its about 1x10^19 kg, about the mass of a medium sized asteroid or Saturn's moon Phoebe. If you calculate the acceleration on a probe at this radius it's 9 order of magnitude small than the Pioneer anomaly. This is far bellow the precision needed to calculate the trajectories of spacecraft.

@IMP-5 lovely stuff, prepare for the response: I assume those so called facts were made by so called experts on so called physics

but not surprising coming from someone who has already unequivocally stated in past threads that "gravity is not conserved" when Mass/Energy are transformed.

I never said that, please fabricate quotes.

Benni: please define the phrase "gravity is (not) conserved." There's literally no meaning to such a phrase in physics. It's not even a statement to get right or wrong. It is devoid of meaning.

What you may be thinking of is 'conservation of energy' and 'gravitational potential energy.' Which, while they're useful placeholder concepts in freshman physics classes, they take on very specific meaning in the context of relativity (since gravity isn't an explicit force, and since conservation of energy is dependent upon how one measures time, which changes under relativity).

But there's no such thing as "conservation of gravity."

The only thing I'll say about mass energy equivalence is that you've been shown to be, at the very least, imprecise in your wording, if not outright wrong. The phrase is literally "rest-mass energy equivalence," because it only holds true in systems at rest. But you can't be bothered with details like actual science, I understand.

marcush 5 / 5 (6) 6 hours ago
The number of people that visit this site and yet don't understand the scientific method is quite disappointing.

I'm thinking that the troll/crank olympics is held in 2016 as well. The judges seem to have their hands full. Personally, I've never seen the entertainment value in dwarf tossing and shin kicking. The Modulated Flatulence trials seem to be particularly popular.

Has Dragonfly 44 been mapped at 21 cm? I can't find a reference. Suppose its mass is due simply to cold molecular hydrogen? Not all DM need be mysterious.

Before you & your ANONYMOUS EXPERTS at Wikipedia

1- anybody is an expert compared to you.
2- you can check the history of any wikipedia article and find the author(s)

Glad to teach you something.
Oh I forgot, I can't teach anything to a posing pagiarising psycho.

If this were true, then being "in the middle of it" should make it easier, not harder,

Not necessarily. DM has very low density.
A person in the middle of a very light fog will only observe the fog at some distance.

........I challenge you DM Enthusiasts to put up quotes from Einstein's GR to prove your claims,

Why would it take a quote from Einstein to prove anything?
A quote from the charming Zwicky would do equally well.

Note that we don't find dark matter in our solar system. Our models of gravity do not require imaginary matter in our solar system to perfectly model the movements of the planets, etc. But our galaxy outside our solar system is supposed to be full of the stuff.

Note one can calculate the mass of dark matter enclosed by the solar system if we assume a smooth NFW profile normalised by the estimates of the local density. If you integrate all the mass enclosed in a 100 AU sphere its about 1x10^19 kg, about the mass of a medium sized asteroid or Saturn's moon Phoebe. If you calculate the acceleration on a probe at this radius it's 9 order of magnitude small than the Pioneer anomaly. This is far bellow the precision needed to calculate the trajectories of spacecraft.

Let's settle this once and for all, Benni.
High noon. What is your answer ?

But there's no such thing as "conservation of gravity."

.....so why then are YOU making up such a terminology? I never stated there was.

Next thing for you is demonstrate an OBSERVATION or MEASUREMENT proving gravity IS NOT MASS/ENERGY DEPENDENT. Can you do that & be bothered with details of actual science? There is no Einstein Field Equation for such a concept, but maybe you have one of Schneibo's pictures of a BH?

Hi everyone, I have been too busy with my own work to do more than read-through-only since my last post. Still busy, so can only post briefly the following REMINDERS in the next few posts, and then leave again.

Firstly to:

@Benni: Please get it straight; Zwicky postulated ONLY ORDINARY, but unseeable then, EM-interacting type matter. The later NON-EM-interacting 'exotic matter' fantasies was NOT Zwicky's fault! And we ARE recently/constantly finding his postulated ORDINARY EM-interacting type matter everywher we look through our NEW telescopes that can see the radiating matter that was previously too 'low brightness' to see. So please stop slagging off Zwicky. OK?

Anyway, the observed motions can NOW be explained adequately by (1) formerly unseen ordinary stuff being found; and (2) by correct GR application to regions with observed NON-Keplerian distribution/mass parameters that make orbital profiles appear NON-Keplerian if we don't apply correct parameters. OK?

(cont)

So please stop slagging off Zwicky. OK?

..........NO, the crackpot Astrophysicist has just way too much entertainment value attached to his zany ideas.....next up-Tired Light.....more Zwicky for ya.

(cont)

@IMP-9: Please update your data base before repeating now-obsolete 'interpretations/explanations'. Be aware our MW galaxy's size/shape/mass parameters has been EXTENDED to include MUCH ORDINARY EM type stuff that was ALWAYS OUT THERE but only recently 'seen' for the first time! Same applies to galaxy CLUSTERS and SUPERCLUSTER environs/parameters.

So 'NON-EM DM' interpretations like "it went through collision unscathed" etc are NOW OBVIOUSLY OBSOLETE interpretations/explanations. As that EXTENSIVELY distributed ORDINARY but unseen stuff was ALWAYS OUT THERE even BEFORE the collisions/interactions between galaxies! So IF we could see that low brightness EXTENDED regions it would be ORDINARY dust, gas (hydrogen/Helium), subatomic (electrons, pions, quark-gluon etc) stuff; and NOT the NON-EM-interacting 'exotic/unknown' stuff of latter-day DM speculations.

Moreover, experts who simulated Cold DM have since simulated HOT DM; with similar 'results'. Useless. OK?

(cont)

"99.99% is in the form of dark matter—a hypothesized material that remains unseen but may make up more than 90% of the universe."

Oy vey, not much of cosmology know how in here. Dark matter is often seen, so not "hypothesized". [See the Planck Legacy Archive, or the massive galaxy surveys which observe it in many independent experiments.]

But the observations, such as here, doesn't reveal much of its properties.

(cont)

@antialias_physorg: It's great to hear you like reading papers. But unless you bring to that reading impartial scrutiny and objectivity, you will just be like many of those you castigate, because you will fall into believing stuff that is based on flawed science or pseudoscience 'exercises' and 'interpretations' etc. You know this is possible; even in people with degree or whatever 'qualification/reputation' etc. Remember?

May I suggest you consider your own ideas about what's been going on; from initial EM-interacting (Zwicky hypothesis/interpretation), to later NON-EM-interacting hypotheses from others who came after him and made a mess of it all with their fantasies and ill-informed speculations bearing NO resemblance to reality/scientific method (by interpreting 'evidence' to suit heir predisposed biases based on severely limited, but arrogantly professed as 'scientific' nonetheless, understanding of what was actually 'out there' (pls see post to IMP-9).

Bye. :)

"So 'NON-EM DM' interpretations like "it went through collision unscathed" etc are NOW OBVIOUSLY OBSOLETE interpretations/explanations."

They obviously aren't, since EM interacting matter can't predict what is seen. Even spurious finds can't do it- If you do the math you will see why. (Notably you just spew CAPS comments, with neither own calculations or references to any.)

This has long been known, and is why DM physics was discovered. "Multiple lines of evidence suggest the majority of dark matter is not made of baryons:" [ https://en.wikipe...c_matter ] An alternate theory has to predict all those multiple lines of evidence, _quantitatively_. Good luck!

Hi Benni. :)

Ok, I will answer this but then have to go. So brief as I can...

So please stop slagging off Zwicky. OK?

..........NO, the crackpot Astrophysicist has just way too much entertainment value attached to his zany ideas.....next up-Tired Light.....more Zwicky for ya.

Mate, what exactly is it about WE ARE FINDING THE ORDINARY STUFF HE POSTULATED that you don't understand?

As for 'tired light' etc, it may be that all that stuff we are finding in supposedly 'empty space' may have something to do with that as well (at least to some degree worth investigating further as to exact effects on light signals from such long space distances which have A LOT OF ORDINARY EM-interacting stuff in it.

Benni, seriously, as a fellow skeptic of some stuff that issues from 'mainstream' sources/claims, I suggest that it is best NOT to be as pigheaded and biased as some of that mainstream seems to be. Don't you think? Else 'one' is no better than 'they' are.

Bye. :)

Dark matter is often seen, so not "hypothesized".

So, now, you have pics of DM, Schneibo has pics of BHs...........who else has pics you refuse to share?

Benni, seriously, as a fellow skeptic of some stuff that issues from 'mainstream' sources/claims, I suggest that it is best NOT to be as pigheaded and biased as some of that mainstream seems to be. Don't you think? Else 'one' is no better than 'they' are.

Maybe, but my lifestyle demands I take Science seriously, not something to be trifled with. Airbrushed photos of DM & artistic renderings of a BH vortex is so far beyond reality as to become "a catch me if you can" Confidence Game. You can always tell when you've caught up with someone's Con Game & called them on it, they react with vicious foul mouth innuendo such as this:

Wasting away your lonely life masturbating into a sock in a darkened room, followed by unending trolling on phys.org to get the attention from humans that you so crave

.........and gets 5 Star votes from Shavo for that post, a lot of "science" there would you say?

Has Dragonfly 44 been mapped at 21 cm? I can't find a reference. Suppose its mass is due simply to cold molecular hydrogen?

The whole Coma cluster has been mapped at 21 cm – neutral hydrogen amount was 3.7 x 10^21/cm², which works out to about 0.8 x 10^14 solar masses (see p. 661 here).

Not all DM need be mysterious.

They found 47 total UDGs in the Coma cluster, Dragonfly 44 was the second largest, but I don't think that makes much of a dent in the amount of dark matter.

@Benni. :)

No argument re most of that other stuff (except, I already reminded you/everyone that BHs involve hybrid dynamics/forces which DO create an 'event horizon'; so you have to be more specific re you argument about re BH properties etc. I have to leave you/others to work through those matters between yourselves, as I have little time at present.

Anyhow, my earlier comment to you was ONLY about a pigheaded insistence. You keep attacking Zwicky about the (back then) undetectable ORDINARY EM-interacting matter he postulated, EVEN THOUGH HE IS BEING PROVED CORRECT by all that ordinary stuff we've been finding out there!

Hence my polite request you STOP attacking him. It's the LATER 'exotic' NON-EM-interacting DM speculators you should direct your ire at, not Zwicky; because we ARE finding the REAL EM-interacting DM that Zwicky postulated! So it's not fair to keep badmouthing him. OK?

PS: Please ADDRESS/IDENTIFY posts/quotes; especially replying to multiple posters. :)

Hi torbjorn_b_g_larsson. :)

Mate, please leave out prior assumptions/reading bias when reading what I pointed out to IMP-9 earlier.

The point was that IF that ordinary stuff was ALREADY OUT THERE but undetectable, (as indicated by discovery that our MW and nearer galaxies have extended mass distrubutionb far beyond what was assumed previously from purely visible indicators), then all those other interpretations/assumptions (about DM distribution/dynamics round galaxy clusters/collisions far away) must ALSO BE REVISED to reflect the likelihood that what we have been 'observing' is also involving MUCH EXTENDED ORDINARY MASS distributions already out there WHICH THE GALAXIES are moving though/colliding.

Do you see the subtle point? If it was ALREADY out there, then it's wrong to assume it 'got out there' due to NON- EM-interaction during galaxy collisions etc.

And that DM can be ORDINARY (from electrons, pions etc to Hydrogen/Helium/dust etc); so NOT 'exotic'. OK?

Bye. :)

Late edit –

What if many of the 47 UDGs in the Coma cluster are similarly composed predominantly of dark matter? Does that mean there's more dark matter than previously thought? I don't think so, since the simulations are already pretty close at the large scales.

........total nonsense, but not surprising coming from someone who has already unequivocally stated in past threads that "gravity is not conserved" when Mass/Energy are transformed. If you actually knew anything about Nuclear Physics you would not find yourself in the continuing conundrums of such contradictions as compared to what OBSERVATIONS have already PROVEN.

Please provide an instance of when Shav has stated this.

@Benni

But there's no such thing as "conservation of gravity."

I never stated there was.

Yes you did. I quote from your earlier post on this article:

"..............total nonsense, but not surprising coming from someone who has already unequivocally stated in past threads that "gravity is not conserved".

Note that we don't find dark matter in our solar system. Our models of gravity do not require imaginary matter in our solar system to perfectly model the movements of the planets, etc. But our galaxy outside our solar system is supposed to be full of the stuff.

Note one can calculate the mass of dark matter enclosed by the solar system if we assume a smooth NFW profile normalised by the estimates of the local density. If you integrate all the mass enclosed in a 100 AU sphere its about 1x10^19 kg, about the mass of a medium sized asteroid or Saturn's moon Phoebe. If you calculate the acceleration on a probe at this radius it's 9 order of magnitude small than the Pioneer anomaly. This is far bellow the precision needed to calculate the trajectories of spacecraft.

Let's settle this once and for all, Benni.
High noon. What is your answer ?

You did not defend yourself. You're dead now.

@Benni

But there's no such thing as "conservation of gravity."

I never stated there was.

Yes you did. I quote from your earlier post on this article:

"..............total nonsense, but not surprising coming from someone who has already unequivocally stated in past threads that "gravity is not conserved".

Now Benni will lay low for a while, using other sock puppets.
Then the psycho comes back as if nothing happened.

I still find the arguments for dark matter being real matter with mass unconvincing. So far investigators have "found" DM in the halo's of each galaxy in exact amounts to allow spirals to rotate the way they do, in the bullet cluster in some form of association which allows huge amounts of it to pass directly through another cluster unaffected by the target's gravity (???) but supposedly leaving the galaxies with the DM they depend on intact (else why do we not see a lot of messed up galaxies resulting from other cluster collisions stripping the DM from the galaxies?). Several other problems and inconsistencies.

@Benni

But there's no such thing as "conservation of gravity."

I never stated there was.

Yes you did. I quote from your earlier post on this article:

"..............total nonsense, but not surprising coming from someone who has already unequivocally stated in past threads that "gravity is not conserved".

"gravity is not conserved"

versus

But there's no such thing as "conservation of gravity."

Shavo makes up a new terminology & I get the credit for it. No wonder you can believe in Schwarzschild's Black Hole Math.

OK smart guy trying to be a semanticist, you be the one to explain how Infinite Gravity Wells can exist on the surface of a Finite Stellar Mass? By what concept of physics can you demonstrate that when the volume of a GIVEN MASS is reduced in size that GRAVITY is increased in magnitude creating greater attraction to another body?

I still find the arguments for dark matter being real matter with mass unconvincing.

That's only because you don't understand them. For example,

... in the bullet cluster in some form of association ...

The "forms of association" are gravity (associated with all the matter) and electromagnetic interactions (which are only associated with the visible [baryonic] matter).

... which allows huge amounts of it to pass directly through another cluster unaffected by the target's gravity (???)

Which is the part you don't understand – everything's affected by gravity. The dark matter wasn't directly affected by electromagnetism, but the visible matter was and it formed the bullet shaped shock wave. The observation of the Bullet Cluster is also very strong evidence against the MoND theories (mentioned by tinitus wrt Dragonfly 44), in addition to being very convincing evidence for the "realness" of dark mater.

The dark matter wasn't directly affected by electromagnetism,

.........oh knock it off with the semantics, you don't know this, and you don't know this because you've never isolated any DM to prove it.

Look, VM matter halos extend from galaxy to galaxy, yet we don't observe odd behavior exhibited by them that would indicate unexplained orbital patterns in the way those halos & loose clusters orbit their gravitationally bound hosts.

@Benni

Schwarzschild's Black Hole Math.

The Schwarzschild metric is a direct implication of GRT
BUT it requires a basic understanding of mathematics to understand that.
You however are a math illiterate.
Why do you then make such statements?
Attention whoring, I suppose

The Schwarzschild metric is a direct implication of GRT BUT it requires a basic understanding of mathematics to understand that

Schwarzschild metric is https://www.resea...gularity just by formally thinking physicists.

Whatever. It is a mathematically correct solution of GRT, which is beyond your comprehension.

It's worth to note in this respect, that Einstein dismissed it too.

That is grossly untrue. Schwarzschild's solution showed that Einstein's theory predicted Mercury's perihelion advance and the both scientists were exhilarated about this.

Would you call him illiterate attention whore?

You are the illiterate attention whore and Einstein is the great scientist.

@tinitus
I meant of course that Benni is the illiterate attention whore.
Why do you defend that psycho anyway.

This idea that R#r in Schwarzschild's original paper has been around.
Check out Antoci on arxiv.org.

Why do you defend that psycho anyway

You should argue the written text, not the posters here.

You can't argue content with Benni. Many have tried and failed.
It was not Einstein's solution. Einstein was happy that the _exact solution_ by Schwarzschild confirmed his prediction. Einstein did not reject Schwarzschild's solution as far as I know. Please provide a link if he did exactly that.

I meant of course that Benni is the illiterate attention whore.
Why do you defend that psycho anyway.

Beacuse Zephyr (tinitus in his umpteenth incarnation after having been re-re-re...-rebanned and re-re-re...-reregisted) will defend anything that is wrong. He's just wired that way. It doesn't even matter that Benni and he are mutually exclusive wrong.

@Benni
Schwarzschild's Black Hole Math.

The Schwarzschild metric is a direct implication of GRT
BUT it requires a basic understanding of mathematics to understand that.
You however are a math illiterate.
Why do you then make such statements?
Attention whoring, I suppose

......Oh but the Schwarzschild metric for Radii is extraordinarily simple to follow, it's the leap you Astrophysics Aficionados create when you defy Einstein Field Equations & try spoonfeeding to the casual reader that Infinite Wells of Gravity can exist on the surface of a Given Finite Stellar Mass by simply shrinking it's volume.

When it is beyond your limited comprehension of the laws of Physics that GRAVITY is MASS DEPENDENT, then we get this kind of stuff:

Wasting away your lonely life masturbating into a sock in a darkened room, followed by unending trolling on phys.org to get the attention from humans that you so crave

.......yeah, what you call OUT OF IDEAS.

:

The Schwarzchild's BH solution suffers with problems both from intrinsic, both extrinsic perspective... third problem is related to time definition in relativity: once time effectively stops at the event horizon, the collapse of matter into black hole should stop there too. All these paradoxes point to the entropic and informational paradox of black holes too..

This statement seems based on poor understanding of the significance of the choice for where to locate the origin of the coordinate system that's used for doing the maths. With proper understanding, your trouble at r = r_s is just a coordinate singularity and there are both interior (0 < r < r_s) and exterior (r > r_s) solutions. See Schwarzchild metric > Singularities and black holes

I agree that the comparison of GRT to the difference between observation and Newtonic simulation should be based on the latest observations, including data from the Messenger mission and the latest simulation capabilities. It is astonishing that the wikipedia article is based on Clemence (1947), who based himself on analysis from 1912 (!) and observation of LeVerrier(1800's). The Mercury orbit deserves the highest scrutiny but in practice hardly anyone studies it.
Note: I disagree with your statements on DM and on Solar flattening/rotation, whichever you mean. Convince me with hard evidence if you can.

@Benni
Since 1916 gravity is energy dependent.

Maybe we finally have the answer to Fermi's 'where are they' paradox. The Universe may be strewn with completely dark matter galaxies, with dark technologies and dark intelligent beings who have been walking amongst us and through us, but not interacting with us.

Has it not occurred to everyone looking for mystical dark matter and black holes, that it does not exist. The theories of gravity may be wrong. We have space being stretched by planets explaining what we see in our solar system, another type of gravity exists at the centre of rotating galaxies analogous to a whirl pool, again stretching space. The standard model of physics might actually cover more than 4% of everything, if einstein was wrong and there was a proper understanding of how gravity really works. etc etc blah blah I could go on but I wont. Relativity must be correct and the laws of thermodynamics are correct and no energy escapes from an atom except in the form of a photon. some small adjustments to those theories and you have the theory of everything, blah total crap dont you think. Darkmatter exists ha ha and so do black holes and fairies at the bottom of the garden.

The Universe may be strewn with completely dark matter galaxies, with dark technologies and dark intelligent beings who have been walking amongst us and through us, but not interacting with us.

DM doesn't work that way. If DM is massive particles then they don't interact with one another strongly, If they did then their distribution would be different.

etc etc blah blah I could go on but I wont.

Good. Because you'd be noticing that you'd be running into a whole lot of self contradictions. Ignorance is bliss.

......Oh but the Schwarzschild metric for Radii is extraordinarily simple to follow ...

I doubt that you can follow it.
Was it so hard to admit that the Schwarzschild metric (for Radii, wtf?) is a consequence of GRT?
It took you a year or so.

The statement "dark matter—a hypothesized material that remains unseen but may make up more than 90% of the universe." is wrong. Our current knowledge says that 4% of the universe is standard matter, 23% dark matter and 73% dark energy. So, dark matter makes up 23% of the universe, or if we count only matter and not dark energy, it makes up for (23/27=0.85) 85% of all matter.

Yes, the Schwarzschild metric is a consequence of GR,

.......No it isn't, it's a total fabrication & you can't prove differently.

If there were all this excess GRAVITY everywhere in the Universe, supposedly creating all kinds of unusual motions of stellar mass, then how was Einstein able to calculate Photon Deflection within 0.02% of accuracy at the peripheral disc of the SUN if 80-95% of the mass of the Sun were actually MISSING? When Einstein did this in 1915, no one was even thinking about the possibility of the existence of DM GRAVITY, so how did he get it SO right?

You Astrophysics Aficionados & your Schwarzschild Perpetual Motion Math need to spend some time sitting in a classroom & learn the difference between Reality & Fantasy. This FEEL GOOD math you have concocted for yourselves only gets you laughed at by those of us who are professionally engaged in using SR & GR on a daily basis.

Most of the Universe is not MISSING & you can't prove differently.

@Benni

Yes, the Schwarzschild metric is a consequence of GR,

.......No it isn't, it's a total fabrication & you can't prove differently.

He does not have to . Schwarzschild has already done it! So the proof is there if you could be bothered to read and understand it.

@Benni That would be because 80-95% of the Sun's mass isn't missing... If you read up the thread, within a 100ly ball around the sun there is only the equivalent of an asteroid's mass worth of Dark Matter. It is only when we start looking at large (millions of light years) scales that we begin to see the cumulative effect of all this diffuse dark matter dominating dynamics. Not on the local scale where the Sun dominates as the mass of dark matter is minuscule in relation.

According to those that actually study general relativity (1000's of clever scientists with PhD's and published papers and other such accolades) most of the Universe is, in fact, missing. I fail to see what your problem is with dark matter? What are you advocating as an explanation to observed failings of GR on large scales? We would all love general relativity to be perfect, for a while we thought it was, but the facts of the universe tell us otherwise, much to our bemusement.

Yes, the Schwarzschild metric is a consequence of GR, but it also leads into a coordinate inversion at the event horizon. Which means, the singularity for photons exist there and the space-time gets inverted.

Zeph, you're aware of the importance of covariance and you appear to understand various metrics and coordinate systems. But you seem to be saying that there's some kind of mirror symmetry at the event horizon and you should know already that is not the case, because:

"...over a sufficiently small region around r = 2m the spacetime manifold is (locally) indistinguishable from flat spacetime, and the line element is approximately given by the Minkowski metric in terms of suitable coordinates. (This is implied by the equivalence principle.)" Quoted from Swarzschild Coordinate Time
And see also Spacetime Inversion

late edit, Also Zeph you're aware that photons detected from distant gamma ray bursts show no hint of what would be expected had they traveled through a kind of spacetime having a quantum mechanical foam-like structure – ...scientists find "spacetime foam" not slowing down photons... (you commented under the name "Dethe" there, and Fleetfoot handed you your hindquarters, like repeatedly. Good ol' days, huh?)

Yes, the Schwarzschild metric is a consequence of GR,

.......No it isn't, it's a total fabrication & you can't prove differently.

You have a relapse. The proof is all over the internet and in all textbooks on the subject.

If there were all this excess GRAVITY everywhere in the Universe,

You completely change the subject from one sentence to another. It is called incoherence.

supposedly

Observedly.

creating all kinds of unusual motions of stellar mass, then how was Einstein able to calculate Photon Deflection within 0.02% of accuracy

He knew physics.

if 80-95% of the mass of the Sun were actually MISSING?

It isn't. No one ever said that.

When Einstein did this in 1915, no one was even thinking about the possibility of the existence of DM GRAVITY

They did not even know about galaxies back then.

so how did he get it SO right?

Because the amount of DM in the solar system is utterly insignificant.

Insane.

The group of isometries of the Schwarzschild metric is the subgroup of the Poincaré group ...

Zeph, that's a copy/paste straight from the Wiki link I gave you. What you originally said was,

the interior solution is inverted to exterior one, which would imply, that the gravitational force should act/point towards outside the black hole, not into it (and this is also what the dark matter does in limited extent).

And that's not even correct, quoting from the Wiki link:

For r < r_s the Schwarzschild radial coordinate r becomes timelike and the time coordinate t becomes spacelike. A curve at constant r is no longer a possible worldline of a particle or observer, not even if a force is exerted to try to keep it there; this occurs because spacetime has been curved so much that the direction of cause and effect (the particle's future light cone) points into the singularity

The event horizon just the limit of what a far away external observer can see.

The general relativity has nothing to say about event horizon interior:

In the context of the most general, spherically symmetric, vacuum solution for the Einstein field equations (that is, in the context of Schwarzschild geometry), general relativity has everything to say about it because it's the only thing being considered – the other interesting solutions and theories come from considering additional things like electric charge, angular momentum, quantum mechanics, and extensions to the Standard Model.

The Universe may be strewn with completely dark matter galaxies, with dark technologies and dark intelligent beings who have been walking amongst us and through us, but not interacting with us.

DM doesn't work that way. If DM is massive particles then they don't interact with one another strongly, If they did then their distribution would be different.

Have you had a sense of humour transplant?

The event horizon just the limit of what a far away external observer can see

The time will stop at the event horizon, which implies the http://casa.color...st0.gif.

Only as seen by an observer at very large distance.

Have you had a sense of humour transplant?

When you've been around here for some time you'll find that the site is chock full of people who post similar stuff in all earnestness all the time. Just go look at the posts of tinitus in this very thread. Crazies abound.

It pays to mark sarcasm in your posts. There is nothing too ludicrous not to be defended seriously by some on here. Nothing.

@antialias_physorg, I am mystified as to why creationist posts are not simply and instantly removed from this site. Why does a respectable site like this virtually encourage trolling?

I am mystified as to why creationist posts are not simply and instantly removed from this site.

You and me both. Crank/pseudoscience and religion are epxressly stated in the forum guidelines as grounds for a ban. Not that that keeps the crazies away long. I mean look at tinitus (Zephyr). the guy has ben banned and reregistered so often he must be running close to triple digits by now...and the collection of his sockpuppet accounts spans pages.

I do remember that the site used to be moderated quite heavily (you would get told off for simply typing "WTF"). But I guess physorg doesn't have the manpower for this anymore.
(and clicks create cash..there's always that)

antialias_physorg,

I am mystified as to why creationist posts are not simply and instantly removed from this site.

You and me both.

Even the Vatican allows the discussion of alternate viewpoints.

Science is supposed to be about keeping an open mind. Of course, when you make science a religion, you tend to develop the blasphemy/heretic mindset.

This article and discussion is about dark matter or the lack thereof. I fail to see why you have to discuss religion at all unless you are using this forum to proselytize.