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Question about relation between galaxies

  1. Mar 26, 2006 #1
    why is it that galaxies are placed the way they are in our observable universe? as spirals of solar systems with empty space between them?

    isn't it a concept of the big bang theory that, the universe was created from a point of singularity? And at an instant, all matter was ejected from that point? if so, then why does our universe appear the way it does? Should it not look more like scattered planets and stars exploding from a single point? which then eventually collapse back to that point?

    to me it seams more reasonable that each galaxy is it's own, and not created relative to other galaxies. something like a big bang to create each galaxy.

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  3. Mar 26, 2006 #2


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    I'm not sure I understand your question, but remember that stars, planet, galaxies, etc. were not formed during the Big Bang, but well after. The basic picture is that you start with a universe that's nearly, but not completely uniform (mostly hydrogen gas). As time goes on, those parts of the universe that are slightly more dense than the others (overdensities) will start to collapse. In the current cosmological model, the first things to collapse will be tiny galaxies and star clusters. As time goes on, bigger and bigger objects collapse to form larger galaxies (like the spiral in your picture) and, eventually, galaxy clusters.

    The relationship between the positions of galaxies is roughly described by the power spectrum. Think of the distribution of matter in the universe like a foam, with overdensities appearing randomly in space and the distribution of overdensities given by the power spectrum. Today, this distribution is a combination of the initial randomness in the nearly uniform hydrogen gas and the effects of gravitational collapse that occurred afterwards.
  4. Mar 26, 2006 #3


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    You have a naive concept of the universe, jon pan. ST took you through the basics.
  5. Mar 28, 2006 #4

    i know, that's why i'm here asking question. thankx for the input
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