Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Proof of Universe Expansion

  1. Apr 7, 2007 #1
    Where can we find the prove of universe expansion from the equations of General Relativity?
  2. jcsd
  3. Apr 8, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    First you need to make some assumptions - that the universe is homogeneous and isotropic.

    Then the solution of Einstein's equations is a FRW metric, see for instance http://en.wikipedia.org/wiki/Friedmann-Lemaître-Robertson-Walker_metric

    The expansion or contraction is governed by Friedman's equations


    If you add a cosmological constant to these equations, there is a static solution (the Einstein static universe), but it is unstable, and also requires some very special parameter values.

    So you can't quite "prove" that the universe must be expanding or contracting (as there is the static Einstein solution), but it would require a lot of coincidences to have this happen if GR is correct.

    Of course, observation strongly suggests that the universe is expanding.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Proof of Universe Expansion
  1. Universe expansion (Replies: 6)

  2. Universal expansion (Replies: 37)