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Question about the Universe (Urgent)

  1. May 21, 2004 #1
    Please I know that this question has ben asked many times, but I really need to get an answer on it. It's urgent.

    Is the universe finite or infinite ?

    If there is another thread discussing the question, please post the link.
    Also any other link poiting to a relevant website is appreciated.

    Thank you all for your time.
     
  2. jcsd
  3. May 21, 2004 #2
    In order for the universe to be infinite in extent, it would either have to be created that way in which case it cannot be traced to a cause and so causality is broken. Or it must have been expanding forever in which case we cannot trace it back to a cause. In either case, an infinite universe violates causality.
     
  4. May 21, 2004 #3

    marcus

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    you might enjoy these two websites which have
    cosmology FAQ

    Ned Wright (teaches graduate and undergrad cosmology courses at UCLA)
    http://www.astro.ucla.edu/~wright/cosmology_faq.html

    Eric Linder (similar standing at Berkeley, college textbook on cosmology)
    http://supernova.lbl.gov/~evlinder/umass/faq.html

    At Linder's site, see his answer to the frequently asked question
    "How could an infinite universe have been, say, the size of a golf ball?"

    At Wright's site, he answers the FAQ
    "How can the Universe be infinite if it was all concentrated into a point at the Big Bang?"

    the main scientific observation is that the U does not appear curved at large scale
    measurements using the microwave background indicate that the curvature is either exactly zero or very close to zero
    it is so surprisingly flat that the simplest thing to assume is that it is exactly flat (but there is no way of being sure at present which is true, flat or within a percent or so)

    if the U is flat (i.e. zero curvature) then by far the simplest model with that property is that it is infinite in spatial extent

    this is consistent with the observations made so far, no reputable cosmologist will exclude the possibility and in fact it is the prevailing notion
    (which is why Linder and Wright take care to explain it) BUT
    it has not been proven

    it is very difficult to distinguish, with telescopes and suchlike gear, between the case of an infinite uncurved universe and
    the case of a very enormous universe with a very small positive curvature
    where it goes out way way beyond the farthest we can see, so to us it looks flat, but then curves around and closes with itself so it is after all finite.

    however you cant go wrong if you assume PROVISIONALLY that it is infinite because that agrees with the observations and is overall the simplest model

    you are right, we have had several threads about this at PF
    maybe you could find them by using the keyword search option at the top
     
  5. May 24, 2004 #4
    Check out an article on Space.com that attempts to answer that very question.
     
    Last edited: May 24, 2004
  6. May 24, 2004 #5
    Thx a lot, I am grateful to all of you
     
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