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Expanding of the universe

  1. Nov 2, 2003 #1
    the universe is expanding, ok. but what is causing this? the big bang? in that case, what causes the expansion to accelerate or decelerate? and what is beyond the boundaries of the universe?
  2. jcsd
  3. Nov 2, 2003 #2
    Yes, the Big Bang is responsible for the expansion. The gravitational attraction of all the matter in the universe causes the expansion to decelerate. However, it is now believed that there is some special kind of matter or radiation, called "dark energy", which has negative pressure and causes a gravitational repulsion. Right now, that repulsion appears to be winning out over the gravitational attraction of the normal matter, so there is a net acceleration.

    There is a boundary to the observable universe; beyond it is just more universe that we can't see, because light from it hasn't reached us. But the entire universe as a whole is not thought to have a boundary.
  4. Nov 2, 2003 #3
    It's possible that this dark energy can be related with the scalar field that caused inflation?
  5. Nov 2, 2003 #4
    What is powering the exspansion? the fact that E=1.17XT (according to GR, if E is more than "1" the cosmos will collapse. My class calculated the age of the cosmos, based on this eq. at 13.989 BY. Not bad for college kids in a sophmore astrophysics class!

    Just be glad it does not collapse. Then..who knows? Effect preceeds cause? what a mess.


  6. Nov 2, 2003 #5
    It's been proposed before, for instance in


    but in general it's hard to come up with a field that correctly does double-duty as both inflaton and dark energy.
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