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Thread: Expanding Universe?

  1. #1 Expanding Universe? 
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    The further away into the distance one looks, the further back in time one sees and the faster things appear to be travelling away from the observer. However, surely the perceived rate of expansion should increase over time, not decrease. Also, if everything is expanding and moving away from everything else then is not the observer expanding too? And aren't the particles (photons etc) we see moving away also expanding? If they are, then how can the expansion be accurately measured when the metrics themselves are changing?

    I've asked my Physics teacher but he couldn't explain it so I could understand it so any help is appreciated.

    Thanks


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  3. #2  
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    Hi Paul:

    I don't understand the expansion well enough to explain it. Here is an article that covers some of the issues you brought up:


    http://arxiv.org/abs/0707.0380

    Best,

    Dedo


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  4. #3  
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    Thanks for that.

    Further to my original post, while it's perceived that the universe is expanding could not the same observations be made with the universe contracting. This could explain why the further away (distance & time) objects are the faster they are retreating.

    I'm getting more and more confused and frustrated as the more I think about it the more it makes sense and it appears that science is either inventing unknowns to fit into the current models or just ignore it.
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  5. #4  
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    http://ca.geocities.com/Samsade@roge...exp.index.html

    I'm not really sure what your asking, the universe is expanding, in the same way a balloon expands when you blow air into it. the theory is the big bang sort of shot everything out at a very high speed and because there is no constant gravitational or frictional force in space it has just kept going.

    there is an additional theory that says the universal expansion is speeding up due to dark matter or somesuch theoretical partical (or god farting) I would imagine this is a result of intergalactic gravity, different galaxies will pull smaller ones into a faster speed, a faster expansion from our point of view, eventually enough smaller galaxies will be going faster and move past the larger ones to influence the larger one and move it faster
    It's not how many questions you ask, but the answers you get - Booms

    This is the Acadamy of Science! we don't need to 'prove' anything!
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  6. #5  
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    Quote Originally Posted by Paul D

    Further to my original post, while it's perceived that the universe is expanding could not the same observations be made with the universe contracting. This could explain why the further away (distance & time) objects are the faster they are retreating.
    Paul

    I don't know if this will help but it might...

    1. The expansion of the universe is considered to be the expansion of space, not the matter within it. So no, the galaxies and photons etc are not considered to be expanding.

    2. Indeed it might be possible to model the situation as space staying the same but every item in the universe shrinking, with a concomitant reduction in the gravitational forces between them and a rise in apparent distance between them, but this would outrageously violate our conservation laws and would need a heck of a lot of additional mathematics to cope with it. Following Occam's Razor, therefore, we tend not to multiply entities unnecessarily.

    3. Indeed there is a lot that appears to be arbitrary in modern cosmology (why do we use Guth's 'Inflationary Universe' for instance?) but a lot of it comes from attempting to make sense, within the models we follow, of the data we collect. It may indeed be that a time will come when the jury-rigging of the system is overthrown by one of Kuhn's famous paradigm shifts - perhaps a Theory of Everything that integrates gravity with the other forces and explains in principle, and less arbitrarily, the data we find. ut until then we would be advised to stick with what we have - it has been shown to work better than any other models we have. Who knows, though? Perhaps if these questions spark your interest enough, you could be the person to make that revolutionary discovery or two..

    cheer

    shanks
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  7. #6  
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    Paul D. The idea is that the redshift of most galaxies, etc shows that they are speeding away from us but the big bang idea has many, many problems which have not been explained or have poor explanations.

    We know that gravity redshifts photons in the same way and we know that the universe is full of gravitational sources. Why should a photon not redshift just by travelling long distances with gravitation pulling on it from so many places over often billions of years. We know gravity is homogeneous over distances when it is at it's weakest or when there are counter pulls. The redshifting is just a measure of galactic distances.
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