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Does space expansion theory obey relativity laws?

  1. Jul 26, 2008 #1
    Does space expansion theory obey relativity laws??

    I've been wondering about the idea of space expansion that's been used to explain red shift effects in most of our universe, which forgive me if i am wrong is nothing(space) propelling matter.

    Please could someone tell me if i am misunderstanding space expansion and give a correct explanation of it for me.

    Or if i have understood it correctly, surely it goes against relativistic principals?
  2. jcsd
  3. Jul 26, 2008 #2
    Re: Does space expansion theory obey relativity laws??

    What you call space expansion, which I find an inaccurate and confusing phrase, is in full agreement with general relativity. And in the absence of a cosmological constant it is also locally in agreement with special relativity.
  4. Jul 26, 2008 #3


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    Re: Does space expansion theory obey relativity laws??

    I think the really inaccurate phrase is "propelling". Azzikika, you shouldn't think of it as space moving matter. It's more accurate to think of it as matter staying in the same place (at approximately constant spatial coordinates) while space grows. I'm not sure why Jennifer doesn't like the term "space expansion", but I'm guessing that it has something to do with the fact that GR is a theory about spacetime, not space, and spacetime doesn't change. It just "is".
  5. Jul 27, 2008 #4
    Re: Does space expansion theory obey relativity laws??

    but if 'space grows', as it were, then 2 seperate objects are moving relative to each other in this process, with no causal force. i personally cannot get my head around this concept.

    i probably need to learn alot more, but for now i choose to believe the motion is caused by a substantive force, probably massive external gravity beyond our current horizons. i think space expansion is a result, not a cause of whatever is occurring in our universe.

    i also thought that gravity distorts space time, thus it isn't constant.
    Last edited: Jul 27, 2008
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