Dark Matter Galaxies?

[astroron (Ron)]

An astronomer as proposed that the Milky Galaxy has a "Dark Matter Dwarf Galaxy" companion
http://www.bbc.co.uk/news/world-us-canada-12188642
It should be very interesting to see where this goes, if the theory is right what does this say for the Mass of the Universe
Cheers

[Robh (Rob)]

Ron, Most interesting.

How liberally is the word "galaxy" being used here? There is no suggestion that a dark matter galaxy would consist of something analagous to stars.
The implications of the existence of a small dark matter galaxy are enormous.
It is assumed that dark matter interacts only weakly with other matter and primarily through gravitational forces due to mass. So does dark matter exhibit similar gravitational organisation (e.g. core and disk or elliptical shape) to a normal rotating galaxy? How much influence would several of these dark matter galaxies have on the structure of a "hosting" normal galaxy in proximity?
If there is so much dark matter then one would think that there would have to be dark matter super-sized galaxies far bigger than the Milky Way.

Regards, Rob

[xelasnave]

Originally Posted by Robh

Ron, Most interesting.

How liberally is the word "galaxy" being used here? There is no suggestion that a dark matter galaxy would consist of something analagous to stars.
The implications of the existence of a small dark matter galaxy are enormous.
It is assumed that dark matter interacts only weakly with other matter and primarily through gravitational forces due to mass. So does dark matter exhibit similar gravitational organisation (e.g. core and disk or elliptical shape) to a normal rotating galaxy? How much influence would several of these dark matter galaxies have on the structure of a "hosting" normal galaxy in proximity?
If there is so much dark matter then one would think that there would have to be dark matter super-sized galaxies far bigger than the Milky Way.

Regards, Rob

Rob my limited ability to manage sums still leaves me with the view raised in your last sentence. It would seem that the more dark matter you enlist to solve the anomalies the greater the problem becomes.

I do feel that the reliance on the prospect that dark matter exists and to settle upon such a conclusion as valid prevents consideration of alternatives or adjustment to our current understanding of gravity.

I am not at odds with GR per se but when we have to introduce dark matter as the only possible answer I feel we may be denying the opportunity of other ideas.

In my view the Pioneer anomaly must announce we have something wrong in our current understanding of gravity yet still they seek answers that must fit current science rather than accepting there is something we have not got right....the last time I checked there were many folk occupied in finding an explanation but the commonality is they all seek to fit the anomaly into current understanding which clearly has betrayed us.

alex

[GeoffW1 (Geoff)]

Hi,

Well Brian Cox is back to examine gravity tonight on SBS2. These programs have been on before but are still interesting, if a bit shallow.

Cheers

[Robh (Rob)]

Originally Posted by xelasnave

I do feel that the reliance on the prospect that dark matter exists and to settle upon such a conclusion as valid prevents consideration of alternatives or adjustment to our current understanding of gravity.

I am not at odds with GR per se but when we have to introduce dark matter as the only possible answer I feel we may be denying the opportunity of other ideas.

alex

The pre-occupation with the dark matter proposal results from our inability to formulate an alternative model that will explain all the current observations. As you say, most of the current research and modeling hinges on the existence of dark matter to simplify explanations of gravitational anomalies. I feel that eventually a convergence of discoveries and ideas from various fields (dynamic physics, GR and quantum physics) will lead to the correct interpretation.
If evidence for dark matter increases (e.g. discovery of its particle nature) then we can all applaud the time and effort spent looking for it.

Regards, Rob

[astroron (Ron)]

Originally Posted by xelasnave

Rob my limited ability to manage sums still leaves me with the view raised in your last sentence. It would seem that the more dark matter you enlist to solve the anomalies the greater the problem becomes.

I do feel that the reliance on the prospect that dark matter exists and to settle upon such a conclusion as valid prevents consideration of alternatives or adjustment to our current understanding of gravity.

I am not at odds with GR per se but when we have to introduce dark matter as the only possible answer I feel we may be denying the opportunity of other ideas.

In my view the Pioneer anomaly must announce we have something wrong in our current understanding of gravity yet still they seek answers that must fit current science rather than accepting there is something we have not got right....the last time I checked there were many folk occupied in finding an explanation but the commonality is they all seek to fit the anomaly into current understanding which clearly has betrayed us.

alex

Alex I am sure there Astro physicist out there grappelling with the problem of Dark Matter I am sure everyone is not 100% sure of dark Matter, but untill further evidence comes along, it is the best they can come up with
I am sure there is no head in the sand as far as Dark matter is concerned, there seems an awefull amount of evidence for the Hipothosis.
Cheers

[xelasnave]

Yes dark matter is on the minds of those who believe it and equally on the minds of those who dont accept it...mind you most are happy to accept it as reasonable given the observations enlisted in support.

I simply feel uncomfortable with the prospect of there being something we can not observe other than by its projected gravitational influence.
I ask what could it be if it is indeed there?

Maybe it is concentrations of HB particles..maybe it is the mass of concentrations of neutrinos ..mind you their mass means the concentration must be extreme.

However if there is as much as the sums require one would think there must be a way of observing it other than by gravitational influence.
I am cautious to accept it with no alternative considered possible to the current understanding of gravity.

I have said it many times but a push universe would not need dark matter but again the particles that make up a push universe may have the mass and therefore be "dark matter"...

Notwithstanding the observations in support of the concept I do think we have much to understand to explain the things dark matter seeks to explain.

alex

[CraigS]

Y'know Alex;

I have come to the conclusion that it really doesn't make a difference what I believe .. which is great because I can believe whatever I like, and these beliefs are completely independent of the evidence at hand and where theory leads me.

I think you have mentioned before you are a man who believes nothing .. and yet you also say …

I simply feel uncomfortable with the prospect of there being something we can not observe other than by its projected gravitational influence. I ask what could it be if it is indeed there?

Am I to take it that your discomfort comes from some belief lurking deep down in your soul ??

Cheers

[xelasnave]

[QUOTE=CraigS;679319]Y'know Alex;

I have come to the conclusion that it really doesn't make a difference what I believe .. which is great because I can believe whatever I like, and these beliefs are completely independent of the evidence at hand and where theory leads me.

The ultimate freedom is abandoning all beliefs...or so I believe.

Evidence is a loose term unfortunately.

A christian will point to a passage in the bible as evidence and be entirely happy that his duty of providing evidence has been adequately discharged for the argument he is supporting.

A big banger will enlist evidence contained within anothers research which although impressive still is "their" evidence" and so often evidence goes to support the side we have chosen to be on... for a big banger their evidence is rarely of personal experience but gained from anothers research and data.

Finally we can only conclude although there is evidence in support of the big bang theory as for the individual one must conclude it is belief that the big bang evidence is valid ..just as does the christian say their biblical evidence is valid...my point is both finally have beliefs in the story they support as opposed to first hand observation that makes their story valid..so I say belief is what most of us are really working with irrespective of who one calls upon in support...

EG...I know black holes exist because I have read all Steven Hawking has written and I "believe" him. I have no idea as to the science or the sums and I am in effect saying I believe him rather than I believe the science as such....

I think you have mentioned before you are a man who believes nothing .. yes I state such and try to remember that that is what I believe.


Am I to take it that your discomfort comes from some belief lurking deep down in your soul ??

No Craig ..the term soul relates only to what is on the bottom of my feet.

If there is any problem with what I believe in I contend it is simply this...I dont know what to believe anymore.... I wont go into why I dont believe in religion but I suspect many would question why I wont simply accept the current cold dark matter standard model of particle physics..it seems to me to have many aspects that I could accept if my mate the tarot card reader had put forward (because many concepts of the standard model are really "out there" ) but when the leaders in science lend support to some of the aspects of the model I am left wondering if the world is not in the hands of folk who are just as happy to entertain the prospect of unicorns ...really where is the support or evidence for string theory...it has assumed massive following and yet what are its foundations in observation. and so how can I believe the current science when there are aspects that confound reasonable thinking (in my view) and this is not a comment that they are right or wrong but only upon their believability... and so I dont believe and yet I can not cut myself off from learning more about their approach..I read all I can..I listen to the wonderful input given to me here..not to prove it right or wrong but simply to hear their side of things... I dont need to be convinced to listen..be it religion tarot cards or particle physics....and the more I learn the more I can accept as reasonable but also the more I feel they (everyone) really dont know as much as their posturing would lead us to conclude.

AND even if someone believes they are correct it does not mean I have to accept their belief irrespective of how conclusive they believe their evidence to be.... just because most believe the big bang does not mean I have to believe it or offer an alternative... I can simply not believe anything anymore nor do I have to....and such a stand works well because you can hear what someone has to say and simply nod and not respond with a reason why their way cant work...peace at last.
Have you not noticed I dont buy into arguments these days...mmm maybe that is not obvious but more my view of myself.

I do like the push universe concept but that does not mean I believe it is the "way"....

alex

[mswhin63 (Malcolm)]

There is a factor that is binding Galxies together and this was stated as dark matter and it is still only a term to define something that can't be seen or currently unable to measure only provide a mathematical conclusion something else exist.

I think the post on trillions of earth's located more objects that have been found in galaxies and this on it own will change the mathematical outcome of dark matter.

Personally I dont know and I dont want to come to a conclusion yet until more tests are done and find this elusive matter, but while it is commonly talk about the term "Dark Matter" has changed to a physical mass that has been detected which is unfortunate.

I am considering another option away from an invisiable matter in that in the spiral arms there is a uniform motion of solar system rotation mostly in one direction creating a gravitational swirling that is pulling external arms closer back into the centre and establishing an equalibrium. It may be a load of rubbish but I am not going to conclude this as fact but would be interested in its outcome.

The problems is that we would need massive amount of exopanetary data to determin the rotation of exo-solar systems.

[astroron (Ron)]

Originally Posted by mswhin63

There is a factor that is binding Galxies together and this was stated as dark matter and it is still only a term to define something that can't be seen or currently unable to measure only provide a mathematical conclusion something else exist.

I think the post on trillions of earth's located more objects that have been found in galaxies and this on it own will change the mathematical outcome of dark matter.

Personally I dont know and I dont want to come to a conclusion yet until more tests are done and find this elusive matter, but while it is commonly talk about the term "Dark Matter" has changed to a physical mass that has been detected which is unfortunate.

I am considering another option away from an invisiable matter in that in the spiral arms there is a uniform motion of solar system rotation mostly in one direction creating a gravitational swirling that is pulling external arms closer back into the centre and establishing an equalibrium. It may be a load of rubbish but I am not going to conclude this as fact but would be interested in its outcome.

The problems is that we would need massive amount of exopanetary data to determin the rotation of exo-solar systems.

Malcolm
Today's APOD may be of interest for your theory
http://antwrp.gsfc.nasa.gov/apod/astropix.html
Cheers

[mswhin63 (Malcolm)]

That is a good photo, haven't had a chance today to see this one thanks.

Actually it was yesterdays one - http://antwrp.gsfc.nasa.gov/apod/ap110120.html that spurred my thought. Noticed all the external objects around the galaxy something you dont see with normal vision. I can't imagine how many colder objects are circulating around.

I have thought about this for a while since your original thread on the trillions of earths. That was a real eye opener.

[CraigS]

A squashed beach ball dark matter halo around the Milky Way eh, Ron ?
I'm not sure the modellers have considered such a shape yet in their calculations for rotation curves. (At least I haven't seen any such model shapes, yet).

Hi Malcolm:
The calculated mass attributable to Dark Matter absolutely swamps and vastly outweighs normal matter. The 'Trillions of Earths' discovery is still miniscule compared with the required mass.


Cheers

[astroron (Ron)]

Hi Malcolm I actually made a post with that image in it on the 05/01/11
http://www.iceinspace.com.au/forum/s...ad.php?t=70204
But you can't beat APOD when it comes to grabbing peoples attention
Cheers

[astroron (Ron)]

Originally Posted by CraigS

A squashed beach ball dark matter halo around the Milky Way eh, Ron ?
I'm not sure the modellers have considered such a shape yet in their calculations for rotation curves. (At least I haven't seen any such model shapes, yet).

Hi Malcolm:
The calculated mass attributable to Dark Matter absolutely swamps and vastly outweighs normal matter. The 'Trillions of Earths' discovery is still miniscule compared with the required mass.


Cheers

Hi Craig ,I thought that there should be some strange shapes in the spiral arms of the Galaxy with this massive halo around it
Cheers

[CraigS]

Originally Posted by astroron

Hi Craig ,I thought that there should be some strange shapes in the spiral arms of the Galaxy with this massive halo around it
Cheers

Hmmm … why so, Ron ?

Cheers

[astroron (Ron)]

Originally Posted by CraigS

Hmmm … why so, Ron ?

Cheers

Craig I should have said this massive object near it
It should have some effect just like the Magallenic clouds but much more so as Dark matter is supposed to weigh more than normal matter
Cheers

[mswhin63 (Malcolm)]

Originally Posted by CraigS

Hi Malcolm:
The calculated mass attributable to Dark Matter absolutely swamps and vastly outweighs normal matter. The 'Trillions of Earths' discovery is still miniscule compared with the required mass.


Cheers

I understand that but the matter is that some matter has been found, the main thing is gravity working differently in the out arms toward the inner arms. Consider a rotating solar system in a way that it attraction to a neighbour solar system and so on toward the inner arms are holding the orbit in.

I am not much for putting things into words but I was only considering the possibility of that aspect and whether it has been considered. Trying to consider an example, but was considering setting up a smoke test creating a vortex in the middle and them mini vortex's spirling outside. all in a symmetrical spin or a natural spin that work with each other to keep the outer edge pulling in.

I must admit this is mostly the reason for going back to school to express myself more clearly.

[xelasnave]

Originally Posted by mswhin63

I understand that but the matter is that some matter has been found, the main thing is gravity working differently in the out arms toward the inner arms. Consider a rotating solar system in a way that it attraction to a neighbour solar system and so on toward the inner arms are holding the orbit in.

I am not much for putting things into words but I was only considering the possibility of that aspect and whether it has been considered. Trying to consider an example, but was considering setting up a smoke test creating a vortex in the middle and them mini vortex's spirling outside. all in a symmetrical spin or a natural spin that work with each other to keep the outer edge pulling in.

I must admit this is mostly the reason for going back to school to express myself more clearly.

I am driven to comment on your last sentence Malcolm.

Your expression is great if someone does not understand they can ask you to put it another way

Thank you for your input.

alex

[snas (Stuart)]

Re the use of the word "belief":

Yes dark matter is on the minds of those who believe it and equally on the minds of those who dont accept it...mind you most are happy to accept it as reasonable given the observations enlisted in support.

Alex, I quite enjoy reading your often "contrary" views. When reading the views of, say, an astrologer or a homeopath, I would definitely not enjoy their contrary views because their views are based on total and utter ignorance and delusion. Your contrary views however display thought and insight. Not saying that I necessarily always agree with your views, but I can at least see that you have put some fair thought into them.

Without someone like yourself here, this forum would be much less interesting.

EG...I know black holes exist because I have read all Steven Hawking has written and I "believe" him. I have no idea as to the science or the sums and I am in effect saying I believe him rather than I believe the science as such....

My thoughts re belief are that belief is what christians do. Someone who professes to know tells them, "This is how it is because the good book says!" and they believe it simply because the good book or the church said it is so.

So to say that "theory x" is true simply because Stephen Hawking said so is just as silly a thing to do if you have not examined the actual evidence behind the theory he has proposed. This would then put you on a par with christians (or muslims, hindus etc).

On the other hand, it is not for me to argue with Stephen Hawking. If he says it is so, then it is not unreasonable to expect that what he professes to be is, at the very least, a reasonable hypothesis.

Based on the religious model, belief can then be described as blind faith based not on valid evidence but on ignorance and self righteousness.

The scientific approach is to examine evidence etc (don't need to expound the scientific process to almost all of those on this forum). Accepting a theory as valid on the basis that it is elegant, as simple as possible, agrees with observations and is falsifiable is a fair thing to do.

At this point, accepting the theory is not "belief", rather it is an acceptance of observed evidence, although with the rider that future observations may require an adjustment to the theory.

Re: Dark matter

At this point in time, DM is a hypothesis put forward to explain an observation. A pseudo-scientist will say, "This is the theory!" and then search for, or invent evidence to fit the hypothesis and will discard evidence that fails to support the hypothesis. Just google homeopathy for multiple excellent examples of this.

Those who are researching not dark matter but rather the cause of the observation that there appears to be too little observable mass in the universe to explain the speed of rotation (excuse me if I have that wrong) of galaxies will, if they are good scientists, have their minds open to the possibility that the hypothesis of DM is wrong. Those who are not open to this possibility can only be described as not good scientists.

As I feel you are a "good" scientist, I am sure that you have your mind open to DM being real (and also to push gravity being not real) while still exploring other options.

Proving the existence of something we cannot see is always going to be a problem. That said, there would be few (rational) scientific thinkers who would discount the existence of atoms, electrons etc, even though their sheer lack of size makes it impossible for us to ever actually see them. Despite this inability to see these particles, the massive weight of evidence says that they must exist. Black holes and DM are slightly larger scale versions of things we cannot see and so are very difficult to prove. It appears that the weight of evidence in favour of the existence of black holes makes it extremely likely that they do in fact exist. DM, being a somewhat newer theory has less evidence to back it. Time will tell. Further evidence in favour of DM or against DM will mount and the hypothesis will either move on, with adjustments, to become theory or will need to be totally discarded in favour of a new hypothesis.

Regards

Stuart