New Problems I have with Dark Matter

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If for any given segment of the sky there are twice as many elliptical galaxies as there are spiral galaxies and if light to mass ratio of these elliptical galaxies (M/LH ratio is about 1.8, independent of RE/R1/2).

https://arxiv.org/pdf/1303.6896.pdf

It would seem that 2/3 of the universe does not require dark matter. Indeed, whatever mass is not observed for ellipticals could be explained with discrepancies and black holes. Regardless of the fact that dark matter do explain spiral galaxies well, it would seem reckless to postulate its existence if 2/3 of the universe does not require it. Just as reckless, perhaps, all or most universe density assessments. But then you are left with explaining the rotation curve of the Milky Way and other spiral galaxies.

But still, in my thinking, if you have multiple merges (at least 4), you have overpowered Newtonian Physics; that is the energy of motion of merging elliptical galaxies would eventually trump Newtonian gravity whereby the rotation curve tells more the story of merge motion than it does of gravity. And what about the part of the rotation curve that flattens; because Newtonian gravity is overruled by motion, it is essentially a halo of gas thus explaining why the rotation curve flattens.

So its not that our calculation of the mass of the Milky Way is wrong, it is simply very deceiving. If you have trouble imagining what I am saying, it takes enormous energy to take an elliptical galaxy and flatten it to a spiral galaxy; that energy cannot be lost and I believe that the bulk of the rotation curve that is observed reflects that energy while still accurately weighing the galaxy.
 
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  • #2
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That only considers one specific type of elliptic galaxies and it doesn't rule out the presence of significant dark matter in them.
Unrelated to that: I wonder what happened to the publication. "submitted to ApJ Letters" in 2010 - where is the publication?
Regardless of the fact that dark matter do explain spiral galaxies well, it would seem reckless to postulate its existence if 2/3 of the universe does not require it.
99.99% of the universe doesn't need plutonium to exist but yet we postulate its existence because we have clear evidence for it in the remaining 0.01%.
But still, in my thinking, if you have multiple merges (at least 4), you have overpowered Newtonian Physics; that is the energy of motion of merging elliptical galaxies would eventually trump Newtonian gravity whereby the rotation curve tells more the story of merge motion than it does of gravity. And what about the part of the rotation curve that flattens; because Newtonian gravity is overruled by motion, it is essentially a halo of gas thus explaining why the rotation curve flattens.
That makes no sense at all.
 
  • #3
Drakkith
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Indeed, whatever mass is not observed for ellipticals could be explained with discrepancies and black holes.
The available evidence does not support this claim. In fact, observations have ruled out most models that attempt to use large numbers of black holes to explain dark matter if I remember correctly.

Regardless of the fact that dark matter do explain spiral galaxies well, it would seem reckless to postulate its existence if 2/3 of the universe does not require it.
It makes perfect sense if that 1/3 requires it and the other 2/3 doesn't rule it out. That's not ideal perhaps, as there should be an explanation as to why 2/3 of galaxies do not appear to require dark matter, but it is certainly not the death knell of dark matter. Of course, this assumes that the paper you provided is accurate.

Just as reckless, perhaps, all or most universe density assessments.
Please provide valid references supporting your claim that the majority of density assessments are incorrect.

But still, in my thinking, if you have multiple merges (at least 4), you have overpowered Newtonian Physics; that is the energy of motion of merging elliptical galaxies would eventually trump Newtonian gravity whereby the rotation curve tells more the story of merge motion than it does of gravity. And what about the part of the rotation curve that flattens; because Newtonian gravity is overruled by motion, it is essentially a halo of gas thus explaining why the rotation curve flattens.
This makes no sense. You've just strung some science words together without understanding them. You might as well say that the expansion of momentum during the mergers causes a temperature flux in the rotation of moving objects.
.
If you have trouble imagining what I am saying, it takes enormous energy to take an elliptical galaxy and flatten it to a spiral galaxy; that energy cannot be lost and I believe that the bulk of the rotation curve that is observed reflects that energy while still accurately weighing the galaxy.
That's not how gravity, or physics, works. Your appear to be missing a great deal of understanding of the basic concepts of gravity, energy, and other things, and I am unsure how I could begin to address this.
 
  • #4
PeterDonis
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Newtonian gravity is overruled by motion
I don't know where you are getting this from, but it's wrong. As @Drakkith says, you appear to have some very basic misunderstandings about how gravity works.
 
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Thanks for your feedback guys. Sorry for the gravity diarrhoea. I looked at various rotation curves for various galaxies, and there is enough variation to outright refute MOND or any modification thereof as you would continuously have to modify the formula to accommodate each galaxy which is ridiculous much more ridiculous then postulating something based on 1/3 of the universe. Has a study been done on dark matter density to show any correlation such as heavier galaxies have more, wider have more, wider + heavier have more, or somewhat proportional size of black hole at the centre? Black holes would be especially useful for pooling dark matter due to time dilation + supreme gravity. Interestingly however, it is more likely that dark matter is not massive at all because you would think that mass MUST strongly interact with other mass, so this weakly interactive dark matter I think is a load of crap. More likely it is a field particle extending gravity's range. Any theories proposing something like this?
 
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Drakkith
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Has a study been done on dark matter density to show any correlation such as heavier galaxies have more, wider have more, wider + heavier have more, or somewhat proportional size of black hole at the centre? Black holes would be especially useful for pooling dark matter due to time dilation + supreme gravity.
No they wouldn't. Black holes (even supermassive ones) are so incredibly small compared with the size of their host galaxy that they chances of any dark matter particles getting close enough to experience severe gravitational effects is very small.

Interestingly however, it is more likely that dark matter is not massive at all because you would think that mass MUST strongly interact with other mass, so this weakly interactive dark matter I think is a load of crap.
I don't know what you mean by 'massive' in this context. It must be massive in the sense that it has mass and interacts through gravity. That much is clear. The 'weak' in weakly interacting massive particles (WIMPs) refers to the fact that they don't interact strongly with the EM force, explaining why they are invisible to our telescopes and why they don't clump together very well like normal matter does. It has little to do with gravity or mass.

. More likely it is a field particle extending gravity's range. Any theories proposing something like this?
I don't even know what a 'field particle' is supposed to be and I've never head of anything theorizing that a particle can extend gravity's range. So no, I'm pretty sure there aren't any mainstream theories along this line of thought.
 
  • #7
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so this weakly interactive dark matter I think is a load of crap.
Based on what you have written so far, you don't have enough knowledge and understaing to have an opinion like that.
 
  • #8
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The galactic halo is the dark matter (plus smaller contributions from visible matter).
 
  • #10
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a massive rotating Galactic Halo can explain at least some of the need for dark matter?
If you fill it with material that acts only gravitationally, not electromagnetically, I suppose you could avoid the need for dark matter. :wink:
 
  • #11
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If you fill it with material that acts only gravitationally, not electromagnetically, I suppose you could avoid the need for dark matter. :wink:
"Dark matter, by any other name, would pull as strong"?
 
  • #12
I have often wondered if for spiral galaxies, a massive rotating Galactic Halo can explain at least some of the need for dark matter?
https://en.wikipedia.org/wiki/Galactic_halo
The galactic halo is the dark matter (plus smaller contributions from visible matter).
The "Galactic Halo" is a collection of low metallicity stars whose collective mass is insufficient to account for the motions of disk stars required by dark matter, hence the hypothesis of a dark matter "halo".
 
  • #13
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That is part of the smaller contributions I mentioned.
 
  • #14
That is part of the smaller contributions I mentioned.
I wasn't being critical of you - I was trying to help Tanelorn understand the difference between dark matter, and galactic, halo…
neonred said:
If for any given segment of the sky there are twice as many elliptical galaxies as there are spiral galaxies...it would seem that 2/3 of the universe does not require dark matter.
I'm afraid you're a little confused there, it's quite the opposite - elliptical galaxies make up only 20%, the rest are spirals...As mfb eluded to at the top of post #2, the galaxies in the study you provided are a special class of elliptical galaxies known as cD galaxies. These galaxies are found at the centers of galaxy clusters and are known to be very massive - which makes them ideal candidates for examination through gravitational lensing, which is what the study did. They calculated these galaxies masses using gravitational lensing and compared that to their masses determined by the amount of light they gave off and found the two different estimates to agree with each other and so found that there was no evidence or need for there being any dark matter in or around them. There's no evidence for dark matter in normal elliptical galaxies, either.
The energy of motion of merging elliptical galaxies...whereby the rotation curve tells more the story of merge motion...thus explaining why the rotation curve flattens.
So you're saying that spiral galaxies are the result of mergers between elliptical galaxies, and their rapid motion due to the merger results in a flat rotation curve? Well that's an interesting idea...the only thing is, elliptical galaxies consist of very old stars and have no interstellar gas, while spiral galaxies have copious amounts of gas and are forming massive young stars to this day. So if spirals result from the collision of ellipticals, where would the gas to form the massive stars come from?...In the article they talk about the reverse problem; If these giant elliptical galaxies are formed from the merger of spiral galaxies, which consist of ordinary with dark matter, how come they don't find any evidence for the dark matter in the merged product? A clue to a possible solution to this dilemma lies with:
Drakkith said:
The "weak" in weakly interacting massive particles(WIMPs) refers to the fact that they don't interact strongly with the EM force, explaining why they are invisible to our telescopes and why they don't clump together very well like normal matter does.
So if spiral galaxies were colliding within the cluster but not right at the cluster center, the gas would collide inelastically, losing angular momentum and falling to the cluster center while the stars and dark matter stay where they are, thus forming these giant elliptical galaxies without any dark matter.
 

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