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Black holes and dark matter holding galaxies together?

  1. Jul 17, 2004 #1
    This is just an idea but if galaxies have or develop a black hole in their center couldnt it be possible that darkmatter uses the electromagnetic field of the black hole to keep the galaxy in place and also keeps it from colliding with another galaxy. I cant really explain what i am thinking but im trying to explain why a large number of galaxies have black holes in their centers and the expasion of the universe. please correct me if this i am completely uninformed and if this makes no sense at all.
     
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  3. Jul 18, 2004 #2
    I am mot an expert here!

    Recently, scientist have discovered a force that overcome the force of gravity. Stars are found to be circulating or in other mode about a black hole.
    The expansion of the universe is resulted due to this special kind of force.
    Every thing in the universe is in motion. We togther with our planet and our star(sun) and other stars and also galaxies are in motion. A collection of stars represent a galaxy. Two stars expreiance a force on each other. This force which the stars experiance on each other is known to be action and reaction force. One star pull the other towards it self and the other also pull the star toward it self.
    However, the stars don't collide.

    Possible reason,
    The two stars are in continious motion. And they will create magnetic property. So this magnetic property will overcome the force which this stars expreiance on each other. If the stars were not moving they would have collided with each other. In such a way the total force on the system is balanced.
     
    Last edited: Jul 19, 2004
  4. Jul 18, 2004 #3

    -- Well, the Black Hole is what keeps the galaxy together, and dark matter is what pulls things towards each other (on the large scale). Dark matter WOULD be the reason why galaxies collide with each other in the first place. It works just like gravity, but instead of repeling, it attracts everything. I hope this answers your question, :approve:
     
  5. Jul 19, 2004 #4
    WTF?
    Gravity is suppose to be what attracts, it doesn’t repel... dark matter/energy is what is suppose to be pushing everything at an accelerated rate.
     
  6. Jul 20, 2004 #5

    Chronos

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    Black holes in the center of galaxies appear to be the rule, not the exception. Gravity is attractive, but, not at cosmological distances. I think [that is usually my first mistake] there is a fifth force at work in the universe... the cosmological constant. We have the known forces... strong nuclear, weak nuclear, electromagnetic and gravity... I boldly propose the cosmological constant is a fifth constant. Gravity is the weak sister in current theory, but, it doesn't hold a candle to the cosmological constant: who's effect is so weak it can only be measured in mega parsecs. Yet, it drives the large scale structure of the universe. I would not propose this had I not derived it from the field equations of GR [sounds good, but I am really hoping no one will ask me to prove it].
     
    Last edited: Jul 20, 2004
  7. Jul 20, 2004 #6
    And how is conservation of energy maintained with these new forces and potentials from dark matter and dark energy?
     
  8. Jul 23, 2004 #7
    sorry about that, i just read my own post again, like Arctic Fox said, gravity attracts, and Dark Matter Repels.
     
  9. Jul 23, 2004 #8
    dark energy is the expansion force, if there is such a thing
    dark matter has normal gravity, like any other matter,
    if there is dark matter
     
  10. Jul 24, 2004 #9
    What electromagnetic field of a black hole??? I've never heard of anything of that sort. Of course, that is not to say there isn't one, but I see no reason that there should be one.

    Edit: as for galaxies colliding, our own gallaxy has an appointment with our nearest neighbor, the Andromeda galaxy, scheduled for about 3-6 billion years from now.

    Actually, all galaxies have a super-massive black hole in their center. And the reason for that is that the BH are instrumental in the process of the very formation of a galaxy.

    The expansion of the univesre is thought to be caused by the big bang, but also assisted by the cosmological constant.
    AFAIK, a star has a net electrical charge of 0. So the motion of a star cannot produce a magnetic field. That said, stars do in fact have magnetic fields, but these arise from different effects, mostly the motion of plasma *within* a star.
    I think the stars' magnetic fields are much weaker than their gravitational pull.
    Actually, the reverse is true. If they were not moving, they could not collide, since a collision requires movement. The reason they do not collide, is because their orbits around the gallactic center do not intersect (at least not usually... which raises an interesting question - I will start a new thread).
     
    Last edited: Jul 24, 2004
  11. Jul 26, 2004 #10
    In my thoughts; a black hole should have an extremely powerful EM field around it. Yet, at the same time I think that the intense gravity may compress or suppress the field... sounds like something to brainstorm about - anyone want to start a new thread on it?
     
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