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Dark Energy as a Gravitational Field?

  1. Sep 15, 2007 #1
    I've been wondering, is it possible to model both the Hubble redshift and dark energy as a gravitational field which gets strong the further away you look? For example, we know that light from distant galaxies is red-shifted, which is equivalent to a photon having climbed out of a gravitational potential well. At the same time, since the light coming to us from these distant objects is all from the past, we could treat the past as a gravitational well. So, increasing distance and increasing past having higher gravitational attraction. If everything sits in a gravitational well which always increases as you look further out, and if the cause of this gravitational well is the fact that the universe was smaller before, then it would appear that everything would always be attracted to the edge of the universe, and that this attraction would increase over time because there would be more past behind us.

    So, I guess, the question is, can dark energy be modeled as a gravitational field coming from the "edges" of the universe, causing objects to accelerate ever faster away from each other?

    Another example is take a black hole. Things are attracted to the event horizon, but suppose we turn it inside out. The objects are inside the black hole now, but they are repelled from the singularity and attracted to the event horizon.
  2. jcsd
  3. Sep 15, 2007 #2
    This would seem to conflict with the homogenuity of the universe - there would be more matter at great distance from the hubble center.

    There is however an interesting aspect to uniform radial dilation of a spherical volume - both the surface area and the volume must accelerate
  4. Sep 16, 2007 #3
    Isn't greater matter at great distance from the hubble center what we see? We find far more galaxies at the edge of Hubble radius than we do in the local vicinity.
  5. Sep 16, 2007 #4


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    If you mean the limits of the Hubble sphere, any field coming from there would have no effect because of the spherical symmetry.
  6. Sep 16, 2007 #5
    But we are looking back in time - when the universe was smaller - more galaxies per unit volume
  7. Sep 16, 2007 #6
    Right, there would be no accelerative effects, but the calculations have to be made using relativistic methods. There would definitely be red-shift, which again could be perceived as galaxies receding from each other.

    That's my point, kind of. The more to the past we look, the greater red-shift we see. So can it not be construed that the universe is climbing out of a gravitational potential well as it goes from past to future? And by virtue of the fact that it takes time for information to travel across space, the farther out we look, the deeper we see this gravitational well to be (the greater the red-shift), so the gravitational well could also be seen as increasing with increasing distance in space.

    Now, I think, actual acceleration may not be important. What is needed is that the red-shifting of the galaxies we see increases, not just with distance from us, but also with the passage of time.
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