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How dominant is gravity stated in general relativity.?

  1. Jun 8, 2012 #1
    Is gravity strong enough to attract 2 galaxies togeather in Gr..I mean is gravity present everywhere in the universe or are there places in universe filled with vacuum and has no gravity waves through it.?
     
  2. jcsd
  3. Jun 9, 2012 #2

    PeterDonis

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    Gravity is present everywhere in the universe. Much of the universe is vacuum, but that doesn't mean there's no gravity there. Whether gravity will make two particular objects, like two particular galaxies, move towards each other depends on the specific details of the situation.

    "Gravity waves" are probably present everywhere in the universe, but they may be too weak to be detectable in lots of places.
     
  4. Jun 9, 2012 #3
    Can this be true,that gravity even though present is very weak such that it can be ignored in MOST of the vacuum of the universe.consider a place between 2 galaxies where gravity is minimum.can this minimum be zero/negligible.?
     
  5. Jun 9, 2012 #4
    yes, depending on what you are considering. A rocketship would not experience any particluar gravitational effects 'between 2 galaxies'. But galaxy formation itself depends on gravity and cannot be ignored. And a good cosmological model of the universe cannot ignore gravity: you can see some effects of the changing matter density [hence gravity] and changing energy density in illustrations here:


    http://en.wikipedia.org/wiki/Metric_expansion_of_space#What_space_is_the_universe_expanding_into.3F

    and further down the page..

    Another way to say this is that cosmological spacetime distances are curved.
     
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