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Is expansion of space relative?

  1. Aug 2, 2007 #1
    Could it be that some spaces are expanding more than others?

    What about the reverse? Could it be that some parts of space are contracting more than others? Is it relative?

    Could GR support the notion that space where matter exists is shrinking faster than space far away from matter?

    Would this still conserve the cosmic background radiation? Would it still lead to its redshift?
  2. jcsd
  3. Aug 8, 2007 #2


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    On the scale that needs to be considered the universe, to use a non-technical term, is so samey that you'd expect any variation will be negligible.
  4. Aug 9, 2007 #3
    I carn't see why not - area's of space with a high density of matter would be highly curved and so 'resist' spacetime expansion. Space is defined by the distance between objects, its not an independent entity, so the relative space between two exploding stars is expanding, whereas the space around a collapsing neutron star is collapsing. I'm not sure if this applies for the Universe as a whole, since its expansion derives from the energy of the big-bang.
    There does seem to be a contradiction though, because spacetime is not a permanent background, it is defined by the properties of matter - at the same time the Universe is expanding. What is doing the expanding?
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