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Thread: Galaxy rotation

  1. #1 Galaxy rotation 
    Forum Cosmic Wizard icewendigo's Avatar
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    Do galaxies rotate all at the same time? (where outer stars follow inner stars instead of going more slowly like outer planets of our solar system)

    Isnt this strange that the relatively faster outer stars dont exit the galaxy and that the relatively slower inner stars dont(or do they) spin closer to the center?

    What is the current theory to explain this observation?


    Could their be metagravitational forces acting beyond gravity, such that at a range greater than a solar system (ex a few light years) there would be a weak repulsive force (anti-gravity) and that at greater range there would be another weak gravitational-like force?
    Each of these two super scallar forces would be too faint to be measured in our own solar system but might be observable in inter stellar space?


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  3. #2  
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    they invented dark matter to explain this.


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  4. #3  
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    Quote Originally Posted by Jeremyhfht
    they invented dark matter to explain this.
    No Jeremy, they Hypothesised the existence of dark matter, they may have invented a theory, but dark matter? that was either God or the big bang....
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  5. #4  
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    Or just plain nothing. Haha, funny ey?
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  6. #5  
    Forum Cosmic Wizard icewendigo's Avatar
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    Dark Matter
    how can any kind of matter explain this? Even if it generates gravity would it not still cause inner stars to rotate faster than outer ones?
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    Quote Originally Posted by icewendigo
    Dark Matter
    how can any kind of matter explain this? Even if it generates gravity would it not still cause inner stars to rotate faster than outer ones?
    Only the mass inside the star's orbit influences the orbit. The mass outside the orbit has no effect. This is Gauss' law as applied to gravity (the same one for E&M but with different constants and terms). Does this help?

    Cheers
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  8. #7 rotation 
    Forum Professor leohopkins's Avatar
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    Galaxy rotation.

    Could it be that at the heart of every galaxy; whether active or inactive that lies at the very centre a black hole. And that our and every other galaxy's spin is induced by the feeding of the black hole; and as the matter is "sucked down the plughole" of the blackhole (event horizon) a vortex occurs, spinning the matter; and as the entire galaxy is in the grip of the black holes gravitational range, we spin with it. And if fact our galaxy is being eaten at the centre; and slowly but surely we are receeding into it.

    There are forces out there so strong, so huge that they are incomprehensible. No wonder our tiny little planet seems do wondereous and inpredictable and weird; for to those forces which grip an entire galaxy, we as beings and as observers are nothing but quantum.
    The hand of time rested on the half-hour mark, and all along that old front line of the English there came a whistling and a crying. The men of the first wave climbed up the parapets, in tumult, darkness, and the presence of death, and having done with all pleasant things, advanced across No Man's Land to begin the Battle of the Somme. - Poet John Masefield.

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  9. #8 Re: rotation 
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    Quote Originally Posted by leohopkins
    Galaxy rotation.

    Could it be that at the heart of every galaxy; whether active or inactive that lies at the very centre a black hole.
    Psst....how the #$%& can a black hole be *inactive*?! It's not a bloody volcano!
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  10. #9  
    Forum Cosmic Wizard icewendigo's Avatar
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    Only the mass inside the star's orbit influences the orbit. The mass outside the orbit has no effect. This is Gauss' law as applied to gravity (the same one for E&M but with different constants and terms). Does this help?
    I m sorry but I dont understand, maybe if you rephrase and give an example it could help.

    A mass outside the orbit should imo affect the orbit, the sun for example is not straight onto the earth's orbital path (far in the center) and surely affects the earths orbit, and sufficent mass if close enough can affect orbit no matter which direction it is?

    Could it be that at the heart of every galaxy; whether active or inactive that lies at the very centre a black hole.
    According to observations there are super black holes in virtually every galaxy, but this does not explain the unusual rotation, whether a large black hole or 10 stars of equivalent mass should not make a difference that I can explain at this time.

    vortex occurs, spinning the matter
    Yes but although stars that come close to he galactic black hole have been observed to be accelerated when doing a fly by, the way I understand it most stars near the center move not too fast but too slowly compared to the respectively very fast moving outer stars. Stars in a section appear to keep pace like a solid wheel where inner matter will have made one rotation at the same time as the outer matter If thats true Im blown away until I understand something else (maybe that Guass law thing)

    how the #$%& can a black hole be *inactive*?! It's not a bloody volcano!
    I agree but it can be used figuratively to refer to a black hole that is not in the process of ripping matter in. Our own galactic black hole is currently 'innactive' for lack of a better term and we should be glad, cause when it sucks in large mass of matter (stars, large clouds) it also creates polar matter projections that are the equivalent of a galactic particle projection cannon that can sterilize whole sections of a galaxy that happens to be in the path of the gargantuan stream of massive radiation (very bad).
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  11. #10 Because Jeremy.......... 
    Forum Professor leohopkins's Avatar
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    Because Jeremy...........

    Black holes do not feed all of the time !!
    The hand of time rested on the half-hour mark, and all along that old front line of the English there came a whistling and a crying. The men of the first wave climbed up the parapets, in tumult, darkness, and the presence of death, and having done with all pleasant things, advanced across No Man's Land to begin the Battle of the Somme. - Poet John Masefield.

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  12. #11 Re: Because Jeremy.......... 
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    Quote Originally Posted by leohopkins
    Because Jeremy...........

    Black holes do not feed all of the time !!
    I can't see that truly renders them 'inactive' though. They [may] exist and if they do, the forces they exert on surrounding space time, is effectively constant irrespective of whether or not some poor planet or star has strayed into it's clutches.
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  13. #12 Re: Because Jeremy.......... 
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    Quote Originally Posted by leohopkins
    Because Jeremy...........

    Black holes do not feed all of the time !!
    correct they don't feed all the time---but they do spin at a very fast rate, all the time.

    in my OPINION; there may be at least two things called BH, or at least there are two or more overall effects of BH involvement.

    if this thing spinning at a rate of 300 to 1000 times per second has a gravity effect, it would have to be in some form of relay. this might explain why larger stars are seen toward the center and indirectly why there are bulges in most spirals.
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    have you heard about MOND?
    http://en.wikipedia.org/wiki/MOND
    thats one theory to explain the acceleration of universes.

    http://cosmicvariance.com/2006/08/21...matter-exists/
    btw, there supposedly a lot more dark energy, than theres dark matter in the universe.

    scientists has basically said that dark matter and dark energy just proves how little we know about our universe.
    when you have eliminated the impossible, whatever remains, however improbable, must be the truth
    A.C Doyle
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    I've just had a thought, when we look at a another galaxy we are seeing it over a period of time, that is the light from the closest part to us arrives perhaps several hundred thousand years in advance of the light from the furthest part! - this means it's not quite the shape we see ...

    Ok it's only distorted by perhaps a fraction of a percent which makes no real difference but I like the thought.

    On the actual rotation of the galaxy, I have heard it suggested that gravity exerted by a black hole may differ from normal gravity and that if so this could account for the outer stars, - I have tried to google it but can't find it, anybody else recall this, something to do with the laws of physics within the event horizon being different to those outside.
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  16. #15  
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    Quote Originally Posted by Megabrain
    I've just had a thought, when we look at a another galaxy we are seeing it over a period of time, that is the light from the closest part to us arrives perhaps several hundred thousand years in advance of the light from the furthest part! - this means it's not quite the shape we see ...
    I've pondered this before. I for one don't know why scientists waste their time looking for other forms of life on other planets when it probably hasn't even evolved yet (according to the light we see). And lets assume we did find signs of life, they'd be long extinct by now :? (possibly anyway)

    On the actual rotation of the galaxy, I have heard it suggested that gravity exerted by a black hole may differ from normal gravity and that if so this could account for the outer stars, - I have tried to google it but can't find it, anybody else recall this, something to do with the laws of physics within the event horizon being different to those outside.
    I've had this thought as well, and I can't find the idea on google either. Quite frankly, the larger (mass wise) and closer you get to a black hole, the more things become a leetle screwy. Gravity wise, the fact that stars seem to mass together into galaxies only when said supermassive black hole is present, seems to say something.

    Sure, there are smaller galaxies without black holes (note: smaller), but these normally also have insanely dense cores that will soon become a black hole.
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  17. #16  
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    "Read all about it " - "Science Forum gets it's first ever Nobel prize"..
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  18. #17  
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    Quote Originally Posted by Megabrain
    "Read all about it " - "Science Forum gets it's first ever Nobel prize"..
    The problem with that is even if we could put it in physics...it's guesswork. Good luck defeating the people that believe in something never proven (dark matter) with something never proven.
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  19. #18  
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    There are Nasa photo's claiming proof of dark matter [or energy] - I say claiming as I am not 100% convinced - I'm sort of 'open minded' as it were....
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  20. #19  
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    Quote Originally Posted by Megabrain
    There are Nasa photo's claiming proof of dark matter [or energy] - I say claiming as I am not 100% convinced - I'm sort of 'open minded' as it were....
    that's like photo's claiming to see people's auras and ghost anomalies. Tweak the photo's until you get what you want and whammo.

    However, I want to see that nasa article concerning those photo's.
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  21. #20  
    Forum Ph.D. william's Avatar
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    For a discussion of dark matter, you might refer back to a previous thread;
    http://www.thescienceforum.com/Dark-...1%21-3662t.php

    In there is a link to an article by an astrophysicist named Clowe.
    http://xxx.lanl.gov/abs/astro-ph/0608407
    Since that time, he and collaborators have another article on the same subject. Here it is;
    http://xxx.lanl.gov/abs/astro-ph/0611496

    I summarized the first paper in the dark matter thread, and I haven't read the second yet.

    There seems to be evidence that dark matter exists, or else gravity as we know it needs modification. But Clowe et al. state that their observations are 'independent of assumptions regarding the nature of the gravitational force law,' implying that dark matter is real....

    Cheers
    wm
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  22. #21  
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    Found it!

    http://antwrp.gsfc.nasa.gov/apod/ap060824.html
    Quote " the blue hues show the distribution of dark matter in the cluster."

    N.B These are not neccessarily the views of Megabrain - so if you are gonna shoot it down, don't point the gun my way!
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  23. #22  
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    Quote Originally Posted by Megabrain
    Found it!

    http://antwrp.gsfc.nasa.gov/apod/ap060824.html
    Quote " the blue hues show the distribution of dark matter in the cluster."
    That is the same cluster that Clowe et al. studied.
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  24. #23  
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    Well I got it from NASA! - so sucks to you

    Anyway the second article you show I have just read the first page and a half and found it very interesting [I'll have a longer look when time allows.].
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  25. #24  
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    Actually, that photo gives credit to Clowe. See the caption.
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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  26. #25  
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    You know, I would have written something discrediting the supposed "evidence" for the third link, but a commenter did it already for me.

    I won't state that "dark matter" hasn't been discovered. However I disagree that empirical evidence for it is demonstrated in this collision. Other phenomena that could explain the images include excitation of preexisting gases or imaging artifacts. Nowhere in the article does it state that the mass of "dark matter" was actually observed passing unimpeded through the normal matter or other "dark matter."
    http://www.sciencenews.org/articles/20060826/fob1.asp

    Dark matter isn't a science investigation. So far it's faith, with a lot of fancy mathematics. Most of what the "It's dark matter!" people sound like remind me of evangelists. :?
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  27. #26  
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    Quote Originally Posted by william
    Actually, that photo gives credit to Clowe. See the caption.
    No, it acknowledges a contribution to the compilation to Clowe et al.

    I don't think Mr Clowe can see that part of the sky from his yard..

    Jeremy
    The {2nd} article does not claim [if I remember correctly] that the composite is proof, it argues that the photo is support for.
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  28. #27  
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    Quote Originally Posted by Jeremyhfht
    You know, I would have written something discrediting the supposed "evidence" for the third link, but a commenter did it already for me.

    I won't state that "dark matter" hasn't been discovered. However I disagree that empirical evidence for it is demonstrated in this collision. Other phenomena that could explain the images include excitation of preexisting gases or imaging artifacts. Nowhere in the article does it state that the mass of "dark matter" was actually observed passing unimpeded through the normal matter or other "dark matter."
    http://www.sciencenews.org/articles/20060826/fob1.asp

    I think the reader's comment is unjustified. He gives two alternatives; excitation of preexisting gas and imaging artifacts.

    The first cannot be because lithium 7 and deuterium sets upper and lower limits, respectively, on the baryonic density of the universe by the way they are created and destroyed. This limit is around 4%. But gravitational evidence shows that there is 'stuff' that accounts for about 26% of the density of the universe, 22% being dark matter. In short, dark matter (with the exception of WIMPs and MACHOs) must be nonbaryonic. Preexisting gas is baryonic. That argument fails.

    The second argument of imaging artifacts sounds more like denial. That must fall under some facet of logical fallacy - discredit one of the premises. I'm pretty sure that the observers know what they are doing when it comes to imaging - especially since it has been used for quite some time....

    The last thing the commenter states is;
    'Nowhere in the article does it state that the mass of "dark matter" was actually observed passing unimpeded through the normal matter or other "dark matter."'
    Well, I got news for him - neither were the clusters! That type of collision takes on the order of millions of years if not more. Our own sun takes around 240 million years just to complete one orbit around the Milky Way!

    Dark matter isn't a science investigation. So far it's faith, with a lot of fancy mathematics. Most of what the "It's dark matter!" people sound like remind me of evangelists. :?
    The study of dark matter is indeed a scientific investigation. I'm not sure why you think it's not. And I'm not sure why you are so resistant to it.... :? Gravitational lensing, rotation curves, and the Li 7 and 2H limits of baryonic matter are strong evidence in support of it.
    "... the polhode rolls without slipping on the herpolhode lying in the invariable plane."
    ~Footnote in Goldstein's Mechanics, 3rd ed. p. 202
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