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State of knowledge of dark matter distribution vs Fermi Paradox:Zoo

  1. Feb 16, 2010 #1
    A question for those of you who know about the distribution of dark matter in the galaxy:

    Do we know how "clumpy" dark matter is? Can we tell yet whether dark matter is distributed about as densly as a gas or whether it's possible that there are the equivalent mass distributions that might contain "dark matter star systems"?

    The reason I ask is that I'm curious if that it's possible that dark matter may end up to be purposely hidden star systems in order to effect the Fermi Paradox "they choose not to interact with us" hypothesis. Granted, we'd be talking about a > type 1 civilization on the Kardashev scale, probably a type II.

    See http://en.wikipedia.org/wiki/Fermi_paradox#They_choose_not_to_interact_with_us

    Dan K
  2. jcsd
  3. Feb 16, 2010 #2
    Given that we are not sure what dark matter is (or if it is all the same substance). As far as density, astrophysicists have successfully predicted density gradients (for instance, most of it is in the halo), but I am not really certain how to apply that to your question.
  4. Feb 17, 2010 #3


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    Dark matter is unlike ordinary matter. The particles virtually ignore one another [they are collisionless], as well as all other matter [i.e., no clumping]. Only gravity binds DM, and only in diffuse collections. Most of the dark matter in our galaxy is believed to reside in the galactic halo, as vociferous noted.
  5. Feb 17, 2010 #4
    Hmm, I guess that helps me organise my thoughts about the whole subject. Perhaps it supports the idea that DM could be cloaked star systems... If the DM was all in the core, that might be an unsuitable location for life due to radiation, I've read that out in the halo, heavier elements are not so common, so perhaps that might be a knock against my hypothesis. Although recently the idea of a "Galactic Habitable Zone" has been challenged, as stars can migrate great distances. So yeah I guess I'm no closer to knowing anything... Thanks for the information though :)

    Dan K
  6. Feb 17, 2010 #5
  7. Feb 17, 2010 #6


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    It is reasonably certain DM particles are collisionless.
  8. Feb 17, 2010 #7
    Explaining dark matter as burned-out stars (or in your case, "cloaked" systems) has been hypothesized, but that hypothesis started loosing ground a long time ago and is pretty much considered disproved, from what I have read. Only a fraction of the Milky Way's dark matter could possibly be explained by that hypothesis. While we do not know what dark matter is, we have some idea what it is not.
  9. Feb 17, 2010 #8


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    Virial theory requires a huge amount of missing matter to explain galactic rotation curves and clustering of galaxies in the universe. Observational studies have virtually ruled out cold baryonic matter as a significant contributor to this missing mass. We have an enormous amount of observational data supporting this assertion. Links available upon request.
  10. Feb 18, 2010 #9
    Here is one...


    Also the notion that dark matter could mostly be clumps of something has been pretty much ruled out. Suppose the dark matter were clumps of something. If you stare at a distant object, then from time to time the dark matter clumps will pass in front of a quasar, and you'll see this dip in brightness as you see the clump bend the light of the quasar as a result of a gravitational field.

    We came, we looked, we didn't see anything. So whatever dark matter is, it doesn't form large clumps.

    Now the cool thing is that we can use this technique to find star systems.
  11. Feb 18, 2010 #10
    One problem with this idea is that dark matter affects the very, very early universe, which presumably evolved long, long before there was any sort of intelligent life (although it would make a really neat exercise in writing science fiction to imagine a situation where this constraint didn't hold, and you have an intelligent civilization form right after the big bang and evolve fast enough so that they could do cosmological stuff.)

    Another possibility is that dark energy does create intelligent life forms, it's just that it's a type of intelligence that doesn't obviously look intelligent to us.
  12. Feb 18, 2010 #11
    In what way? Just gravitationally right? If so then it would have been uncloaked at the start, and then cloaked later with the same effect right?

    Although this point kinda seems moot given that most of the above mentioned points tend to point away from the dark-matter-as-cloaked-star-systems hypothesis.

    Thanks for all the input by the way everyone :)

    Dan K
  13. Mar 21, 2010 #12
    Reality is a dream. However, the dream is incomplete and certain details are missing.
    Aliens don't show up because they have not been included in this dream. It's as simple
    as that. This is the reason for the Fermi Paradox.
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