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GR, gravity and curves

  1. Apr 26, 2010 #1
    I've always admired the way Einstein approached gravity, -which had previously been treated as an a attraction, that is, a determined kinematics that had to be accounted for by a force-,from a completely different point of view, looking at it as the curvature that matter-energy produces in the trajectories of the rest of matter-energy. In a sense he switched kinematic notions by geometrical ones. Now purists are always stressing that since GR one shouldn't even talk about gravity as a force and that trajectories of bodies in gravitation fields are geodesics.
    Now my question, has anybody tried that approach to the expansion of the universe,looking at it as the effect of a curvature of spacetime, that i guess would have to be opposite to the gravity field curvature? Of course the question would remain as to what would produce such a field?
    If it is too wild a speculation, please let me know
    Thanks
     
  2. jcsd
  3. Apr 26, 2010 #2

    Mentz114

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    Gold Member

    These are called cosmological solutions of general relativity. Try looking here for a start

    http://en.wikipedia.org/wiki/Friedmann_equations.

    I don't have time to give a better answer right now ...
     
  4. Apr 26, 2010 #3

    JesseM

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    Yes, the fact that the universe is not static (either expanding or contracting) is a pretty unavoidable prediction of GR, the only way to make it static is to set the cosmological constant to one precise value and even then the solution is unstable to perturbations. The expansion of the universe doesn't require any sort of antigravity or anything (as you seem to suggest by 'opposite to the gravity field curvature), as I understand it it's a consequence of the initial momentum of the matter coming out of the Big Bang singularity, and the mass and energy of all that matter is constantly working to slow down the rate of expansion (though dark energy or the cosmological constant seem to be working in the opposite direction to accelerate the expansion, but this fits into standard GR too if you allow fields with 'negative pressure')
     
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