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B Did we just discover the Milky Way is in middle of nowhere?

  1. Jun 8, 2017 #1
  2. jcsd
  3. Jun 8, 2017 #2
    Some more detailed reading here, it explains the Homogeneous/Under-Density pretty well.
  4. Jun 8, 2017 #3


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    The universe is approximately homogeneous on its largest scales, but at smaller scales it is highly inhomogeneous.
  5. Jun 8, 2017 #4
    It may well be that the Milky way is in a region where galaxies are less dense than other regions, but it doesn't seem like a 'void'
    The Milky way has several smaller satellite galaxies, and Andromeda is nearby on a cosmic scale, also with satellite galaxies,
    then there is the local group of a dozen or so galaxies which we are bound with.
  6. Jun 8, 2017 #5


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    Voids, in the context of cosmology, are large regions of space which have less density (hence, far fewer galaxies) than average. It's not about being a perfect vacuum. See here: https://en.wikipedia.org/wiki/Void_(astronomy)
  7. Jun 8, 2017 #6


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    Given the length scale of the void according to the paper (about 300 Mpc), the entire "Local supercluster" of galaxies (the Virgo cluster and other clusters that orbit it, including our Local Group) is within the void. So "void" certainly doesn't mean "practically empty of galaxies". The difference in average density does not look to be all that great in absolute terms.
  8. Jun 13, 2017 #7
    Visual help: "HD - Cosmography Local Universe - subtitles in english, french, italian"

    I've watched that video about 10 times now, never get tired of it. *I* live there! That's amazing.

    The part at the end where they animate the map ("fanciful" as the narrator says, but still)
  9. Jun 14, 2017 #8
    It's as if the Universe were composed of living Galaxies, and Galactic Families, which 'feed' on the matter around them, travelling ro places where there is more food, and leaving the locales where the nourishment has been exhausted. What an image, and fanciful story!
  10. Jun 16, 2017 #9
    Thanks for the videos, they are very interesting. I can see the local void is really quite small, I missed that in the original article.
    So it seems the great attractor is a very important feature. Are there other examples of this magnitude around the Universe?
    What is going to happen when all these galaxies end up in that same place? A multitude of galaxy collisions presumably which probably means it is not a nice place for life to exist?
  11. Jun 16, 2017 #10
  12. Jun 16, 2017 #11
    1oldman, thanks and that is just 2 galaxies colliding, it seems like 1000s or more heading towards the great attractor!
  13. Jun 16, 2017 #12
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