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The edge of the universe

  1. Nov 11, 2004 #1
    And what will we find there? Maybe us.

    What would be wrong with considering that we ARE on the edge of the universe!

    After all every where we look we can only see into the past where thinks get smaller and older the further away they are until reaches the very small BIG BANG space.

    The light we see say just 10 light from a place on the edge 10 years ago. It has just followed the Edge to visit us for just a moment. As we move on the edge further into where and when ever. The light must pass us by visiting other places in space as the only way it can stay on the edge. (Maybe it can visit us again if it finds a mirror on the way.) But always staying on the edge following what ever Gravity wells and bumps it may find along the way.

    Like having trouble finding the forest for all the trees in the way.
    The harder we look for the edge may, have us missing the idea that we are already on the edge of it.

    Light even gravity waves travel on the edge, while we exist on the edge.

    RB
     
  2. jcsd
  3. Nov 11, 2004 #2

    Chronos

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    Nothing wrong with thinking of us as being at the 'edge' of the universe. This is the oldest part of it we can observe. On the other hand, the fact we are uniformly surrounded by galaxies at all distances and no evidence of mirroring has been found to date [some folks have already analyzed WMAP data for that and came up empty] pretty strongly suggests there is no physical 'edge' [or center] of the universe.
     
  4. Nov 11, 2004 #3
    The Universe is not uniform, except for vibration which is 2-5 kelvin. There is no 'Great Attractor' or edge.
     
  5. Nov 11, 2004 #4
    The edge of the universe, from our perspective, is the big bang singularity inverted.
     
  6. Nov 11, 2004 #5
    Big bang :uhh: dear lord.

    pls don't get offended.
     
  7. Nov 12, 2004 #6
    Eh? I'm a Biology dude, and don't know much cosmology, but is the Big Bang now passe?
     
  8. Nov 12, 2004 #7
    Only to those who don't get enough. :wink:
     
  9. Nov 12, 2004 #8

    marcus

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    I do think the picture cosmologists have of the (start of expansion or) big bang is changing.

    But the general idea is pretty durable and I dont see how it can change in its broad outlines: we see all this expansion and we extrapolate it back to an epoch when it began.

    the theoretical models that cosmologists depend on are General Relativity and the simplified Friedmann model that derives from it. these are used to describe how space can expand (and under different condtions also contract) and be curved by matter etc.

    until recently they didnt have a quantized version of Gen. Rel., they only had the classical 1915 version. When you extrapolate back the classical model reaches a breakdown point where it blows up
    and predicts infinite curvature, infinite density
    a breakdown like that is called a singularity
    it means there is something wrong with the theory

    In 2001 the classical singularity was removed by Martin Bojowald, then at Penn State. He used a quantized version of Gen Rel called "loop quantum gravity".

    In was not entirely unexpected. People had known for a long time that Gen Rel had this breakdown and had been expecting that quantizing would fix it. that has happened in other theories, quantizing has fixed other classical theories that had infinities or predicted other unnatural behavior.

    Since 2001 one sometimes hears big bang called "big bounce" because
    now the equations dont just go back to a certain moment and blow up, they keep on extrapolating back into a prior contracting phase.

    In the quantized Gen Rel model the contraction reaches a maximum density and temperature and then expansion starts. The model automatically creates the conditions need for an episode of "inflation" followed by the slower less-radical expansion which we now observe.

    for a current review with bibliography, this was posted on the online archive earlier this year
    http://arxiv.org/gr-qc/0402053
    Loop Quantum Cosmology: Recent Progress

    if you want to take a look at it, the 2001 landmark paper is also on the archive
    http://arxiv.org/gr-qc/0102069
    Absence of Singularity in Loop Quantum Cosmology

    In a certain sense a singularity, which defines a sharp boundary to the applicability of a mathematical model, is an edge.
    So one can say that the universe described by classical 1915 Gen Rel had an edge.

    Qualitatively the moment of the Big Bang has not changed, it is still inferred to be very hot and very dense. What one infers about particles and radiation is pretty much unchanged.
    But it has changed because it no longer needs to be seen as a boundary to inference.

    The same can be said about the central singularities of black holes.

    By now a lot of other researchers are engaged in removing cosmological and big bang singularities and studying what should replace them. people are beginning to come up with ideas of what traces might be visible in the texture of the microwave background that could be used to test aspects of the big bounce. If you look at the bibliography you will see it has become a rather active area of research with lots of papers published.

    there is more to the story (they do cosmology with Strings and Branes too, but that is a separate department, which I dont follow) but that's a brief sketch of some of it.

    No, BB is not passé
    but possibly getting re-styled
     
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