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Expansion of the universe

  1. Mar 5, 2013 #1
    As I understand it, the rate at which the universe is expanding is increasing. Can the rate of expansion ever exceed the speed of light? If/when it does exceed the speed of light, Does that mean that we would look up into the night sky and see nothing? Does that mean that it is taking longer and longer for light to reach us from distant galaxies? What other implications does this have?
  2. jcsd
  3. Mar 5, 2013 #2


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    It is already far in excess of the speed of light. This is a recession velocity however, so nothing is MOVING at FTL, it's just receeding at FTL. Currently the objects at the edge of our observable universe are receeding at about 3c.

    Eventually, according to current theory, the local cluster, and perhaps only the Milky Way, will eventually be all that is left in our own observable universe. That means that from earth you would see almost exactly what you seen now with the naked eye, but with telescopes it would be a different story.

    If the "big rip" scenario (unlikely) happens, then EVERYTHING will spread apart.
  4. Mar 6, 2013 #3


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    Total dark energy energy is increasing, since it is proportional to the volume of the universe. Another way of putting it is the dark energy density is constant, so that locally it doesn't get any stronger. This means that things held together (such as galaxies and galactic clusters) by gravity will stay together.


    See section on "Implications". There are alternate scenarios to the description I gave.
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