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Thread: Where/when are we in a yo-yo universe?

  1. #1 Where/when are we in a yo-yo universe? 
    New Member
    Join Date
    Apr 2010
    Here's a novice question...

    Assuming we accept the yo-yo model of the continually expanding and contracting universe, can we know whether the universe is currently expanding or contracting?

    Maybe I've missed the point, but I assume that when a contraction occurs, time (along with space) moves backwards?

    Surely if it were contracting, we would only see it contracting by viewing it from the perception of someone moving FORWARD in time? I mean wouldn't we see a contracting universe just as we see one moving forward? Only spacetime would be contracting rather than expanding?

    Maybe I'm talking utter drivel but if someone could enlighten me a bit on this whole affair I'd be very grateful!

    Cheers! :-D

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  3. #2  
    Universal Mind John Galt's Avatar
    Join Date
    Jul 2005
    Hi Dave,
    I don't mess much with cosmology because a) to do it properly you need the math, and b) it is presently overloaded with theory based upon possibly prejudiced interpretations of observation.

    That said the current view is that the universe is not in a yo-yo mode, but is set to expand at an ever increasing rate.

    If it were a yo-yo it is not my understanding that time would reverese when the contraction began.

    I'd caution you that there are members here who have highly singular views of the origin of the universe that they will express as if it were gospel, so take everything you read in these replies with a pinch of salt - except for my own response which should be taken with an entire cellar.

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  4. #3  
    Join Date
    May 2008
    The dogma is that the universe is expanding and that around several billion years ago, dark energy increased the rate of expansion. There is also the point that as things get further apart, gravity would weaken and so expansion increase faster.

    Time is a man-made measure of change. There would be no difference in change between an expanding and a contracting universe (ie: cesium would still have the same number of oscillations per second).

    A problem with a collapsing universe is that you get a black hole which gets ever larger and larger, till everything is inside it. Last year someone theorised that matter (as in a black hole) may break down at 10^-92 tons per cubic meter but if it suddenly became energy and the density as it started expanding went above the magic figure, then you would have matter again, and so it would start collapsing again, so a yo-yo effect, forever.

    A lot is taken on speculation here so no hard facts and there are some other theories. Ultimate proof of expansion would be to see it happening but time scales are such that we live in a 3D photo of the universe so will never see it happen.
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