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A Cosmological Pot Sticker

  1. Feb 19, 2006 #1

    Chronos

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    I was thinking about posting this in the cosmology forum, but, concluded the more philosophically inclined souls would have more fun with it:

    http://www.arxiv.org/abs/astro-ph/0602280
    Issues in the Philosophy of Cosmology

    A thought provoking paper, IMHO.
     
  2. jcsd
  3. Mar 23, 2006 #2
    Indeed thought provoking. The statement that the Universe must be older than the oldest star was interesting. I was wondering if this implies that if, in the future, using more powerful space telescopes, we should locate something more distant than, say 20 billion light-years out, would we then say the Big Bang model was wrong or just change the variable and say the Universe is not 13.7 billion years old, it is now 20+ billion years old.
     
    Last edited: Mar 23, 2006
  4. Mar 23, 2006 #3

    chroot

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    The age of the universe is 13.7 billion years. However, the particle horizon, the greatest distance we can theoretically see, is not 13.7 billion light-years, but instead about 47 billion light-years. The universe was not always as big as it is today, so early light did not take as long to cross it as it would today.

    - Warren
     
  5. Mar 23, 2006 #4
    Thank you for the response. To ask the question another way: If an energy source should be detected 100 billion light years away, would the Big Bang theory require that the age of the Universe be increased to 100+ billion years or would the energy source be thought of as originating in another universe (a different big bang universe)? Or is the question so unreasonable to even consider in an abstract mode? (I realize that the probability of detecting this speculative energy source would be extremely small, but 'what if'?)
     
  6. Mar 23, 2006 #5

    chroot

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    If we detected something 100 billion light-years away, two things are possible:

    1) Our understanding of cosmology is entirely wrong, and the universe is much older than previously thought.

    2) Our understanding of cosmological distance indicators is wrong, and the objects are not really 100 billion light-years away.

    Keep in mind that our measurements of distances are themselves based on a model of cosmological expansion, which could be wrong.

    Either way, there's no "other universe" involved because, by definition, anything we can see exists in this universe.

    - Warren
     
  7. Mar 24, 2006 #6
    I agree that anything we can detect exists in this universe, but it does not necessarily mean that it originated in our Big Bang event. I have no problem with 'science' being limited to one Big Bang event, but philosophically I can see no reason that if nature produced one event we should not expect to find more than one. In the cosmology section of the science department I would not suggest such a thing, but I would hope that in the philosophy department it is OK.
     
  8. Apr 8, 2006 #7
    Hi Warren,
    You failed to bring attention to a very simple fact. Your boundary is set via the phrase, "the greatest distance we can theoretically see". By the common theory, that boundary occurs when light begins to propagate as an independent entity (I'll let others clarify that statement). The issue you should have raised to sd01g is the fact that the "Big Bang" starts with a point universe and that, if we could see through that impenetrable boundary which light cannot penetrate (which of course we can, in our minds eye), the boundary to which we could see would recede to infinity. :biggrin:

    Personally, I think there is a lot of confusion about that issue and it bears directly on the inflation issues often talked about. That is to say, a layout of the universe presuming special relativity is sufficient is logically inconsistent at such distances. :yuck:

    Have fun -- Dick
     
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