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I would like to know more about the beginning of time in terms of

  1. Sep 14, 2011 #1
    I would like to know more about the beginning of time in terms of entropy. How can we explain the formation of a more ordered universe from a more ordered condensed structure that exploded and evolved to what the universe is right now? Where did the gravity come from and what is it's effect in the maintenance of a more ordered universe?
  2. jcsd
  3. Sep 14, 2011 #2

    Ken G

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    Gold Member

    Re: Entropy

    Entropy did not go down when the universe expanded, even though gravity did clump stuff together. To understand the entropy of a system, you have to look at everything that happened-- when galaxies and stars form, they do so by sending a significant amount of energy outward into the reaches of space, often in the form of light. That energy experiences large regions where it can enter into a great many number of states, even though the material left behind gets access to fewer states. So the net is more states, not fewer-- entropy increases.
    There are entropic models of where gravity (and spacetime itself) comes from, they are kind of new and I don't know how well fleshed-out they are. But you are right that the expansion of the universe is crucial-- creating all that extra space is what provides the potential for more states, so that's what allows the ordered structures to form even when the universe at large is obeying the cosmological principle. The key point is, there is no rule that says the number of possible states cannot increase, the rule simply says that the universe will find ways to access the new possibilities for more states as they appear. If you don't notice that is happening, you might think order is increasing when in fact the universe becomes more disordered as it accesses this larger number of possible states.
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