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Comments about an issue in cosmology?

  1. Oct 23, 2008 #1

    tfb

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    Learned Gentlemen,
    My Doctorate is in Medicine, so my questions and comments might be below you. Where can I ask questions and make comments about an issue in cosmology?
    Thanks,
    tfb
     
  2. jcsd
  3. Oct 23, 2008 #2

    cristo

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    Re: questions

    Sure, you can ask them here.

    Note that it is frowned upon to enter another's thread and ask your own, separate question (this is called hijacking). Therefore, I've made you your own thread here.
     
  4. Oct 23, 2008 #3

    tfb

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    Re: questions

    Thanks, cristo!
    So I have a new thread? How can I find it and do further questions and comments. Sorry to be a D.A.
    tfb
     
  5. Oct 23, 2008 #4
    Re: questions

    :)

    I know you will find it. The suspense is building.
     
  6. Oct 24, 2008 #5

    tfb

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    Re: questions

    The Doppler principal leads us to "The Red Shift". We worship the purity and infallability of conclusions born of "The Red Shift". But many of our current, troublesome puzzles can be traced back to "The Red Shift", i.e. The Dark Energy squabble. Wouldn't it be an ironic hoot if we learned that many unsuspected factors are skewing Red Shift data? When masses are separated by growing distances, is there no loss of gravitational force between them? Could that contribute to universal expansion?
    tfb
     
  7. Oct 24, 2008 #6
    Re: questions

    Well, I see you found the thread. You know, that question is not an unusual one for people who are interested in cosmology. Actually there are many factors that skew red shift data, but there are many ways to confirm expansion as well.

    How much do you know about expansion or as it is sometimes called inflation of the universe? The outcome of the expansion depends on the energy density of the universe and based on current understanding the expansion is accelerating so the indication is that the universe will expand forever unless some other factors are operative.

    Many cosmologies exist in addition to Big Bang Theory which is the one I was referring too. Eternal inflation, the Arrow of Time, de Sitter universe, the Big Rip and my favorite, Quantum Wave Cosmology are all alternative theories and/or ideas.

    The only one of that group that defeats entropy is QWC but is not theory, it is protoscience because it cannot be tested but is consistent and compatible with science, doesn't invoke unreasonable speculation and has no supernatural dogma.

    I'm out of power and on vacation so I have to recharge. Let me know if you look in to any of the alternative cosmologies.

    One more thing, gravity. The inverse square rule applies to the separation of galaxies so yes the gravitational attraction declines at the inverse of the square of the distance. And yes, that accounts for the expansion after an early period during expansion where gravity still allows clumping of matter, and star and galaxy formation. After expansion reaches the point where it exceeds the ability of gravity to cause further grouping on a large scale, then expansion is in control. The average energy density will determine if expansion or gravity ultimately wins?
     
  8. Oct 25, 2008 #7

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    Re: questions

    Thanks, Force 1. Inflation was almost instantaneous, and "done" unless it restarts or continues. My interest is in the acceleration of expansion. Isn't that dependant on what we believe to be Red Shift?
    Gravity-wise, I guess we're S.O.L.
    tfb
     
  9. Oct 25, 2008 #8
    Re: questions

    You are correct about the inflation in Big Bang Theory. It is referred to as exponential inflation in the first picoseconds. There are alternative cosmologies that consider inflation on-going, like Eternal Inflation, The Arrow of Time, and others.

    In eternal inflation, there are patches of the universe that experience inflation at different rates, and the rate experienced by a patch can vary depending on the proximity to other patches. The thing is though that entropy is always progressing and so the final outcome of Eternal Inflation is complete entropy.

    A simple question is, why isn't entropy complete yet? The obvious answer is that our patch of space has experienced low entropy relative to the greater universe. Of course that could be true but with very similar preconditions, the universe could be perpetual and entropy could be defeated as in the ideas expressed in QWC.

    Given the choice and the similar preconditions, a cosmology that predicts the defeat of entropy seems more likely simply because "here we are still" :).
     
  10. Oct 28, 2008 #9
    Re: questions

    I take this to mean the more rapid expansion of the universe that appears to be taking place over the past few billion years. Nobody knows just exactly what is causing this, but the red shift is an effect, not a cause. It's a leftover relic signature that requires a lot of interpretation but as far as is known is a good indicator.

    It is hypothesized that dark energy may be the source of the more rapid expansion we observe, and perhaps this is "vacuum energy" but I don't believe anyone understands why the expansion rate has begun to increase.
     
  11. Oct 28, 2008 #10

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    Re: questions

    Red-shift not a cause? If our assumptions on red-shift interpretations are false, then it is a cause. If we abandoned red-shift data, then we'd have no reason to invent "dark energy". What am I missing? Thanks,
    tfb
     
  12. Oct 28, 2008 #11

    DrChinese

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    Re: questions

    As best as can be determined, expansion of the universe continued past the very early inflation. It is not clear what the rate of expansion is, nor is it clear exactly how it is changing. You are correct that the red shift is used to study this, and the results are dependent on the specific sample used. Clearly, if your sample is unintentionally biased in some way, the conclusion may not be accurate.

    The smoking gun (perhaps a slight exaggeration) for continued inflation/expansion of the universe is the discovery of so-called "high z" celestial objects. These have such high red shift, they are receding from us at speeds much greater than c. The highest of these have z > 6.5 and that corresponds to recession speeds of over 3c.

    You may be interested in the following references:

    Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe, by Tamara M. Davis, Charles H. Lineweaver

    A galaxy at a redshift z = 6.96
     
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