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Can expansion be due to large-scale curvature?

  1. Jan 16, 2012 #1
    I wanted to say I love the posts on this Cosmology forum - very good reads.

    My question is whether there is enough to large-scale curvature alone to cause the expansion of the universe as we measure it? Why can't galaxies accelerating away from us be moving in curved space?

    I agree with the idea of infinite matter-energy density at some time in the past and also with inflation. I believe I understand homogeneity and isotropy.

    The question in part is whether large-scale curvature satisfactory to move galaxies in ever increasing velocities with further distances would be consistent with observations like COBE data and also would it be symmetrical.

    Clay Cravens
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  3. Jan 16, 2012 #2
    Expansion isn't due to 'curvature', per se. Curvature is defined at a point (or region) of spacetime, while expansion is the behavior of curvature over time---the 'velocity' of the curvature, if you will.
    Accelerated expansion is a level further away from curvature itself, its like the 'acceleration' of the curvature (again, a loose metaphor) and requires a driving force beyond the curvature itself.
    But galaxies certainly are moving in curved space.
  4. Jan 17, 2012 #3


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    Actually, it's entirely the other way around. The expansion of space is quite precisely and accurately described as space-time curvature. It is not, however, spatial curvature. The spatial curvature of our observable universe is very close to zero. But it does have space-time curvature, and that manifests itself as expansion.
  5. Jan 17, 2012 #4
    Yeah, @Chalnoth is definitely correct; not sure what I was thinking on that one...
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