Accelerating galaxies?

  • #26
malawi_glenn
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In my opinion, WMAP results have 'sealed the fate' of the way General Relativity has been applied to cosmology. In short -- it is not much needed.


Nice title -- but the article doesn't 'prove' a thing. Exotic dark matter won't be proved until it is no longer 'dark'. All that is shown here is that some results can be made consistent with someones preconceived ideas. There are far too many other possibilities in this situation to say it 'must' be 'dark matter'.

(Specifically, yes I have read the article -- and been through it more than once -- does not convince me.)

Can't you refer to peer-reviewed articles instead? Claim that DM is completely unknown is not consensus so you must back it up with something more than just your own opinions..

The article was published in Astrophysical Journal Letters, we know that the anomalies in galaxy rotations, gravitational lensing etc are due to matter, but what exactly this matter is composed of is yet left to be discovered.

Which forum paragraph prohibits you to post in full length? The crackpot paragraph?

You are only against the proposed explanation that the Dark Matter is "non-baryonic" i.e. you think Supersymmetric particles etc. is crap?
 
  • #27
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Can't you refer to peer-reviewed articles instead? Claim that DM is completely unknown is not consensus so you must back it up with something more than just your own opinions..

The article was published in Astrophysical Journal Letters, we know that the anomalies in galaxy rotations, gravitational lensing etc are due to matter, but what exactly this matter is composed of is yet left to be discovered.

Which forum paragraph prohibits you to post in full length? The crackpot paragraph?

You are only against the proposed explanation that the Dark Matter is "non-baryonic" i.e. you think Supersymmetric particles etc. is crap?
I can have opinions that are not on your approved list. I hope we haven't dropped to that level.

Specifically on this article, what is being reported:

1) There appear to be two regions that contain unseen matter.

2) By their calculations this matter is likely associated with the clusters in collision.

3) They are apparently NOT gas clouds -- (like the others which showed collision)

4) IF their assumptions and calculations are correct these two regions are on the continuing
course for the clusters.

5) In short they are non-visible matter. In a sense that makes them 'dark'.

Try reading the article and replacing the word 'dark' with 'unseen' or 'not-visible'. Exactly what do you know about this matter? I see nothing that says anything particularly in support of non-baryonic matter. First thing that came to my mind was highly compact matter objects from the cores of the clusters. Highly compacted matter would be little effected by this collision (assuming no direct hit).

Normal 'exotic' -- nothing new.
 
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  • #28
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You are only against the proposed explanation that the Dark Matter is "non-baryonic" i.e. you think Supersymmetric particles etc. is crap?
I have no opinion on 'Supersymmetric particles'. I do have some questions about how they would 'clump' into clouds. How does that work?
 
  • #29
malawi_glenn
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I have no opinion on 'Supersymmetric particles'. I do have some questions about how they would 'clump' into clouds. How does that work?
I certainty have no clue what you are against or what your quest is.

How does "ordinary" matter "clump"?... gravity perhaps?
 
  • #30
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I certainty have no clue what you are against or what your quest is.

How does "ordinary" matter "clump"?... gravity perhaps?
Yes, of course. I guess I was assuming that you were referring to the 'new neutrinos'. My understanding was that while not truly 'massless' they had very little mass -- likely to move rather easily.

And by their nature no other forces -- that I'm aware of -- would hold them together as a group.

Further, I have no idea what might make them 'clump up' completely separately from normal matter.
First glance at them one would expect to find some 'hanging around' -- that is if they are capable of hanging around due to gravity alone.

Why are you assuming I have some 'agenda' beyond asking for information?

(Note: ordinary matter has a 'stickyness' created by the electromagnetic fields from the atoms and electrons. What might this new matter have?)
 
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  • #31
malawi_glenn
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what is a 'new' neutrino? I am phd student in theoretical particle physics and never heard that term before, maybe you are referring to neutralinos? Or just the good old Standard Model neutrinos with mass? Their mass is too small to account for the missing energy density. I can give you some good reading advices, try the textbook by Grupen "Astroparticle Physics".

I don't know why electromagnetic effects should be vital for making up gas clouds, never seen such fine tuning in the simulations I've seen...

Are you a student of physics or similar?

I asked for your agenda regarding this quest of keep saying that dark matter is unknown, does not explain anything and so on, but in the meantime saying that modified gravity theories are crap as well. What do you want?
 
  • #32
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what is a 'new' neutrino? I am phd student in theoretical particle physics and never heard that term before, maybe you are referring to neutralinos? Or just the good old Standard Model neutrinos with mass? Their mass is too small to account for the missing energy density. I can give you some good reading advices, try the textbook by Grupen "Astroparticle Physics".

I don't know why electromagnetic effects should be vital for making up gas clouds, never seen such fine tuning in the simulations I've seen...

Are you a student of physics or similar?

I asked for your agenda regarding this quest of keep saying that dark matter is unknown, does not explain anything and so on, but in the meantime saying that modified gravity theories are crap as well. What do you want?
I want to know more. The reason for questions -- my only reason.

I have a MSc in Engineering Physics -- obtained over 35 year ago. It did include several courses in astrophysics and cosmology of the time. I am now retired and wanting to learn all that I have missed while having to make a living.

In my life experience I have learned not to accept reports at face value -- always question. Just the process of questioning often brings forth new information. It nearly always helps put matters in better context. The article writers and people in the field use many assumptions that are not always obvious to ones outside the field. Its very hard to determine what they are from the outside.
 
  • #33
malawi_glenn
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Well asking questions are ok, but you sometimes make very bold statements etc.

You then might want to pick up the book I referred to, it contains both modern particle physics and cosmology/astrophysics suitable for master students and contain many references.
 
  • #34
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Well asking questions are ok, but you sometimes make very bold statements etc.

You then might want to pick up the book I referred to, it contains both modern particle physics and cosmology/astrophysics suitable for master students and contain many references.
Planning on it -- as soon as I can afford it. Thanks.
 
  • #35
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...mispost
 
  • #36
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If the rate of expansion of the universe is speeding up how could the expansion be caused by an explosion (Big Bang)? I know of no explanation for an explosion that gains energy over time.
 
  • #37
DaveC426913
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how could the expansion be caused by an explosion (Big Bang)?
It wasn't. The Big Bang was not an explosion. It was a rapid inflation. "Big Bang" was actually a term coined by its critics as a way to ridicule it.
 
  • #38


New to the forum. Could the gravitational time dilation (as opposed to dark matter) explain why the outer stars of a galaxy are able to travel at the high speeds. Essentially, they travel slower but have more time to make up the distance.

On a side note, how much empirical evidence is there for dark energy? If dark matter was proved to be an incorrect hypothesis, would dark energy be necessary? Could local gravitational fields at the more distant clusters be causing the changes in velocity?
 
  • #39
DaveC426913
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New to the forum. Could the gravitational time dilation (as opposed to dark matter) explain why the outer stars of a galaxy are able to travel at the high speeds. Essentially, they travel slower but have more time to make up the distance.
They have factored in relativistic effects, yes.
 

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