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Big Crunch in an Open Universe

  1. Jul 2, 2010 #1
    I have read from online sites and in books about the FLRW model which provides curvature to the universe via math problems. In the three models, there is a flat universe which is equal to zero and will have the same fate as an open universe, a spherical universe which is greater than one and will have the same fate as a closed universe and a negatively curved universe which is less than one and will have the same fate as an open universe.

    My question is, since a big crunch is more than likely to occur in a closed universe, can it still occur in an open universe if the right conditions occur?
  2. jcsd
  3. Jul 3, 2010 #2


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    Your information is out of date, JC.

    A universe which is spatially closed, for instance space being a hypersphere---being spherical, as you said---does not have to undergo a crunch. It can expand forever at an increasing rate.

    The mainstream view changed in 1998. Before that, people would talk in terms of those three types you mentioned. The "open", the "flat", and the "closed". In those old, pre-1998 discussions, the "closed" model always ended in a crunch.

    You should probably trash any books that give that outdated view, and get rid of any online material that presents those three types like that. Cosmology has changed a lot since 1998. The obsolete books and articles can confuse people.

    First learn cosmology in the standard case assuming a small constant positive Lambda (which the data suggests) and then if you want speculate about what would happen if Lambda was gradually changing (but so far no clear evidence of this.)

    Yes, if Lambda changed very radically it could make an "open" universe eventually crunch. But that is very speculative and iffy. The current value of Lambda was only measured for the first time in 1998 and people are still studying it and taking more data to pin it down. Too early to consider it anything but a small positive constant.
    Last edited: Jul 3, 2010
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