At Rest with our Hubble view

Discussion in 'Pseudoscience' started by quantum_wave, May 26, 2013.

  1. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    In that Inflation paragraph above, NASA contributors addressed the CMB homogeneity as being problematic in regard to the standard cosmological view at that time. They call it a "cosmological problem", but it wasn't; it was simply a scientific observation supported by huge amounts of data.

    The problem was with the standard view of cosmology at that time. Either the standard cosmology had to be abandoned, or amended by adding faster-than-light expansion, dubbed Inflation, so that the background temperature could be causally connected to the Big Bang. One alternative considered must have been the existence of some external greater universe as the source of the inflowing thermalized background. The problem was that would require preconditions to the big bang, and corresponding changes to the infinitely dense zero volume nature of the singularity.
     
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  3. PhysBang Valued Senior Member

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    Or the flatness was merely an initial condition of the universe.
     
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  5. AlexG Like nailing Jello to a tree Valued Senior Member

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    The problem with that is that any deviation from flatness,no matter how small, with omega either greater or less than 1, would rapidly increase.
     
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  7. PhysBang Valued Senior Member

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    Sure. But this doesn't prevent there from being a very, very flat initial condition to the universe.
     
  8. AlexG Like nailing Jello to a tree Valued Senior Member

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    If omega, at 1 second after the initial BB was 0.9999999999999995, then today it would be just a little over .25.
    If omega was 1.0000000000000005 initially, today it would be about 1.75.

    In the first case, the density would have dropped so quickly that galaxies would never have formed.
    In the second case, the universe would have already collapsed.

    (The Inflationary Universe Alan Guth, pp 24-25.)
     
  9. PhysBang Valued Senior Member

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    That's great.

    But irrelevant.

    It doesn't influence the probability that the initial density of the universe was 1 because there is no basis on which to calculate that probability.
     
  10. AlexG Like nailing Jello to a tree Valued Senior Member

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    It shows that unless it was exactly one, to over 16 decimal places, it would be way off by now. Given the huge range of possible values, the probability that it was exactly one is vanishingly small. So it's not at all irrelevant.

    Whereas with Inflationary theory, omega would be driven to 1, no matter what it's initial value.
     
  11. brucep Valued Senior Member

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    WMAP measures Omega to be 1 with a very small error bar. Guth's inflation can start at any Omega but will go to 1 very quickly. That's one of the theoretical prediction that the WMAP experiment confirms. A list of some important results from the WMAP experiment. Probably the 'least accessed' important experiment of modern times.

    http://map.gsfc.nasa.gov/
     
  12. PhysBang Valued Senior Member

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    What is the probability that a universe will start with a specific set of initial conditions?

    This is not exactly true. There are many different kinds of inflationary scenarios, some of which produce a total energy density of 1, some of which do not. These should be evaluated on the evidence that they are correct, not on their ability to match a single parameter measurement.
     
  13. AlexG Like nailing Jello to a tree Valued Senior Member

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    Oh, that's certainly not the only piece of evidence, just the one we were discussing. And all inflationary scenarios drive omega towards one.
     
  14. brucep Valued Senior Member

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    All inflation models don't require Omega to be 1. The correct model does.
     
  15. PhysBang Valued Senior Member

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    You certainly do read the PR of the inflationary theorists! Yes, there is some evidence for particular inflationary hypotheses, but no, not all inflationary scenarios produce flatness.
     
  16. brucep Valued Senior Member

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    The PR? Some evidence? Every prediction was confirmed. You need to do some reading. Or not depending whether you give a crap about the accuracy of comments you make on the subject of this science.
     
  17. AlexG Like nailing Jello to a tree Valued Senior Member

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    Can you point me to an Inflationary hypothesis which does not drive omega to 1?
     
  18. brucep Valued Senior Member

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    Chaotic models.
     
  19. PhysBang Valued Senior Member

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    What predictions are you talking about? As far as I can tell, the only solid evidence for inflationary theory is some of the features of the anisotropies of the CMB. And that this is something that is very dependent on a number of assumptions.
    Given that the evidence is not conclusive about the overall density, those who support the theory better hope that inflation doesn't always produce flatness.

    Madsen & Ellis 1998 showed how inflationary theories could produce essentially any value for the overall mass-energy density. Madsen, M. S. and G. F. R. Ellis (1988), "The evolution of [Omega] in inflationary universes", Monthly Notices of the Royal Astronomical Society 234: 67-77.

    http://adsabs.harvard.edu/abs/1988MNRAS.234...67M
     
  20. AlexG Like nailing Jello to a tree Valued Senior Member

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  21. brucep Valued Senior Member

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    Read some paper on the subject that isn't 25 years old. Read the WMAP papers and the detailed predictions from Guth's inflation. Read how the CMBR was empirically evaluated during this experiment. The flatness is THIS universe. There's no requirement that any other universe have Omega 1. This universe is Omega 1 as Guth's Inflation predicts. The empirical evidence confirms this to within an error bar of .004. It's fascinating that most folks who proclaim an interest in modern physics and Cosmology are thirty years behind on how our universe came into being. Based on Carl Sagan's comment, in 'Contact', that 95% of the human race believes in a creation event initiated by some diety they believe in. The evidence on the density IS conclusive. Maybe you think the science isn't conclusive. Read Hawking's comment on the occasion of the WMAP team getting that award. I've been following this stuff since I read the first edition of Hawking's book and he talked about his cosmological model 'The No Boundary Proposal'.
     
  22. brucep Valued Senior Member

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    They can't rule out an Omega of 1. Omega 1 is the obvious outcome of inflation so models with Omega's < 1 had to be considered to account for this physics. Linde was formulating his initial inflation model 'incommunicado' behind the iron curtain. A major issue in the beginning was finding a way for the inflation model to describe the evolution of a universe whose known observable matter was only a very small percentage of Omega 1. Thats the same paper Physbang linked. What I just described was the Omega Problem. The empirical study done by WMAP confirmed Guth's model. The Omega problem was eliminated for this universe.
     
  23. PhysBang Valued Senior Member

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    You are now contradicting yourself. Guth's inflation is quite old and has been replaced by newer hypotheses.

    But, yes, the modern WMAP papers are the source of evidence for inflationary theories. But what else is there?

    For some WMAP papers, perhaps, with a host of assumptions that WMAP adds. Supernovae observations tend to skew to a density higher than critical. There are still some challenges to be addressed in this work.
    I only know what I read in the actual scientific papers.
     

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