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Dark matter, entropy and gravity

  1. Sep 9, 2014 #1
    If dark matter affects normal matter (by gravity), does that mean that normal matter also affects dark matter? I think it does...

    In which case;

    Black holes could attract BOTH dark and normal matter?

    Does this give any opportunity to "information loss"?
    What if some information in normal matter does not "disappear", but it becomes dark matter?

    Also, in thermodynamics, in all isolated systems, entropy level increases?

    A black hole is not an isolated system, since matter that is outside goes into it (also, light).
    Does that mean that the more a black hole devours, it becomes bigger, but also decreases in entropy?


    Entropy becomes so BIG that it evaporates?

    And if dark matter can be sucked in by black holes, that means it follows the rules of thermodynamics? Specifically, entropy?

    I am sorry if I have some logical failures in this, I am learning about awesome, exciting, and to me new physics :P.
    Last edited: Sep 9, 2014
  2. jcsd
  3. Sep 9, 2014 #2


    Staff: Mentor

  4. Sep 9, 2014 #3


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    Why do you think dark matter has negative mass and would decrease the mass of the black hole? This is not at all true but I'm wondering where you ever heard such a thing.
  5. Sep 9, 2014 #4
    I don't think it does. Why do You think I think that?
  6. Sep 9, 2014 #5


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    Guess I misunderstood what you said. Probably read it too quickly.
  7. Sep 9, 2014 #6


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    yes and yes.

    I would say that the information is transferred to dark matter, not that it becomes dark matter, in the same way that kinetic energy might be transferred from normal matter to dark matter. Indeed, information might reside in kinetic energy.

    In all dark matter theories of which I am aware, dark matter follows the rules of thermodynamics and entropy.

    Operationally, dark matter is defined as not emitting photons, not interacting via QCD color charge, and being nearly collisionless. The main distinctions between dark matter particles involve self-interaction (or the lack thereof) via some new force that acts between dark matter particles, the number of kinds of dark matter particles, the mass of these particles and their mean velocity (related to their origin as thermal relics or otherwise), their status as fermions or bosons, and their cross-sections of interaction with ordinary matter (if any). Otherwise, it is just like any other kind of matter.
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