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Simulate Into Future?

  1. May 20, 2007 #1
    I looked briefly at the thread herein regarding "Simulating the universe" but it did not appear to involve the future -- just evaluating validity of different theories leading to present.

    Has anyone run any simulation into the future, say 100 billion years? To see for example what happens involving Great Attractor ?

    -Harry Wertmuller
  2. jcsd
  3. May 20, 2007 #2


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    Unless you have a model of spacetime geometry which works to bring you up to the present---and can be confirmed by observational tests, then there is no way to project into the future.

    What model are you proposing to use? Newtonian gravity? That is obviously unrealistic.

    the prevailing model of the expanding universe is called LCDM.

    according to this model we do NOT get swallowed by the "Great Attractor".
    eventually we get farther and farther away from concentrations of mass like Great Attractor and Virgo Cluster.

    this does not make anybody happy AFAIK
    it might be fun to be swallowed by the Great Attractor
    but according to the best model we have at present it's existence is irrelevant to us in the long run.

    computer sims have been run to study the collision between Milky and Andromeda, and the subsequent predicted merger. That IS likely to occur in our future. So there will be some excitement. And yes, some computer simulations have been run.

    Abraham Loeb is one of the top astronomers in the US, I think this paper is pretty credible.

    The Collision Between The Milky Way And Andromeda
    T.J. Cox, Abraham Loeb (Harvard/CfA)
    submitted to MNRAS

    "We use a N-body/hydrodynamic simulation to forecast the future encounter between the Milky Way and the Andromeda galaxies, given current observational constraints on their relative distance, relative velocity, and masses. Allowing for a comparable amount of diffuse mass to fill the volume of the Local Group, we find that the two galaxies are likely to collide in a few billion years - within the Sun's lifetime. During the first close encounter of the two galaxies, there is a 12% chance that the Sun will be pulled from its present position and reside in the extended tidal material. After the second close encounter, there is a 30% chance that the Sun will reside in the extended tidal material, and a 2.7% chance that our Sun will be more tightly bound to Andromeda than to the Milky Way. Eventually, after the merger has completed, the Sun is likely to be scattered to the outer halo and reside at much larger radii (>30 kpc). The density profiles of the stars, gas and dark matter in the merger product resemble those of elliptical galaxies. Our Local Group model therefore provides a prototype progenitor of late--forming elliptical galaxies."

    I started a thread about this in General Astronomy, but since you bring it up here maybe we should discuss it here.
    The issue of what galaxies we can expect to merge with in the future and which we can expect NOT to depends very much on "dark energy" or the cosmological constant. So this is to that extent a Cosmology issue. It involves the consensus LCDM model.

    Last edited: May 20, 2007
  4. May 20, 2007 #3
    Since the galactic collision simulation answers my question, your post regarding it definitely belongs here.

    Regarding your comments about being swallowed by great attractor: I did not ask. I was wondering whether an ultra-ultra- black hole might be created, or what; irrespective of whether we were included in it. Well?
  5. May 20, 2007 #4


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    Heh heh. Most of the questions you are capable of asking I (for one) am incapable of answering.
    AFAIK the Great Attractor has never been mapped. AFAIK we don't have a clue what it looks like, only that it is a concentration of mass (like a very large cluster or supercluster) which is off somewhere in the Hydra-Centaurus direction. I don't think we can see it, what with all the dust and crud and intervening stuff. But I could be wrong.

    I imagine the Great Attractor to be simply something like the Virgo Cluster only much bigger.

    I suspect the Virgo Cluster (which is easier to speak definitely about) is destined to form a big black hole. But I could be wrong.

    Unfortunately by the time Virgo Cluster clumps, it will probably be too far away for us to see.

    About the future. Larry Krauss (who is top notch) posted a very beautiful essay about the cosmological future recently. You should read it
    Really. This is professional astrophysics but it speaks to the soul.
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