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Expansion question

  1. Feb 25, 2016 #1
    I know expansion explains the size of the space/time framework. Is the "expansion" we see between objects relative to each other (objects seem to be getting farther away in all directions) due to continued expansion of space/time or is there also an inter-framework explosive (for lack of a better word) expansion going on. I know I'm not being too clear so let me ask this.

    I am not sure about the status of 'the big crunch' as a theory anymore but let's talk about that since it helps me to explain the above. When people talk about the big crunch I believe they were talking about an eventual universal gravitational attraction between objects bringing them together into a single point. To me that would mean that the gravitational attraction going on there would be working within the entire space/time framework in its expanded state...not the framework itself. In other words the big crunch would not be a deflation of space/time (opposite to what happened originally with expansion) but rather a simple gravitational attraction of the objects with the expanded space/time. But then the possible resulting big REBANG would be contained within the already expanded space/time from the previous big bang.

    So this means to my weak analysis that the only way to get to a REBANG and have it be a true repeat of the previous big bang space/time would have to deflate somehow thus requiring a new expansion with the rebang.

    I know it appears now that none of this will happen since it is still accelerating which brings me back to the question. Is this expansion an expansion of space/time only or objects that are truly moving away from each other as a result of an explosive component to the big bang sans the expansion component.

    In other words if the apparent expansion is due to space/time expansion then is there any actual motion of the objects within the framework or is everything stationary within the framework and just the framework is expanding.

    Using the balloon analogy...the dots on the balloon move away from each other as a result of the expansion of the framework (surface of the balloon) but are the dots themselves also moving within the framework along the surface away from each other? This would be measured positionally as the relative position of an object to its proper position within space/time as if expansion was not occuring.

    Wow. I hope someone can understand what I'm asking.

    tex
     
  2. jcsd
  3. Feb 25, 2016 #2

    QuantumQuest

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    Gold Member

    As far as the currently widely accepted cosmological model is concerned (ΛCDM + inflation), it is the metric space that expands.

    This is not scientifically justified.

    There is actual motion of the objects, but the recession of galaxies is due to expansion.

    I recommend this

    http://www.phinds.com/balloonanalogy/

    I also recommend reading the Wikipedia page about current cosmological model

    https://en.wikipedia.org/wiki/Lambda-CDM_model
     
  4. Feb 25, 2016 #3
    It's closer to the second, the framework is expanding.
    https://en.wikipedia.org/wiki/Metric_expansion_of_space
    However objects can also have 'proper motion', relative to each other, but that's not really relavent on the scale of the universe as a whole.
    It's relavent for nearby objects though, the Andromeda galaxy is actually getting closer to the milky way despite the overall cosmic expansion.
     
    Last edited: Feb 25, 2016
  5. Feb 25, 2016 #4
    Is the space/time framework dependent on mass inside of it for its existence? If, in a thought experiment, we could snap our fingers and all matter disappears, is the framework still there? In other words is the space/time independent of the matter it contains or is it the matter that establishes the framework. The reason I ask is this...how could you have a big crunch followed by a rebang unless the framework deflates also during the big crunch bringing us back to a similar starting point.

    I guess I'm confused on this point...I think of space/time as it expanded as an expanding container in which matter coalesced...the two being different, one a container and the other the stuff in the container. As the container expanded the stuff in the container also expanded.

    tex
     
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