Expansion of the Universe

Discussion in 'Astronomy, Exobiology, & Cosmology' started by christie66, Jan 6, 2005.

  1. christie66 Registered Member

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    If the universe is expanding, what is it expanding into?
     
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  3. Xko Registered Senior Member

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    I love that question, and i don't understand it either.

    Can't wait to see answers to this one...
     
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  5. christie66 Registered Member

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    Let me clarify the best I can.

    You cannot - to the point of our own perception anyways - get something from nothing. It is not possible to move one object into a place that does not exist. To imagine something being infintesimal, to imagine something lasting literally forever is impossible. Again, to the point of our own perception of that which is time and dimension. If we were able to manufacture a craft - using the term craft loosely - that could travel to the end of the universe - if such a thing exists at all - what would see?

    Is our own universe - we perceive as being the only universe - destroying something in order to expand into it. Is the universe even expanding at all. What we perceive as truth may in turn be nothing but far from it. After all, everything we know and believe is based on a theory, a sorta, maybe, coulda happened but we really don't know. If one theory was proved wrong, every thing else based on that theory in turn would be wrong also. But how would you even prove the theory wrong, with another assumption. Let's all face it, we know nothing, everything is based on a guess that sounds like it could be right.

    Our own perception of things is very limited. We are three dimensional bodies living in a four dimensional world. What we perceive as time is the fourth dimension, we can only experience the whole of things one frame at a time as our own experiencing can only be preceived on a three dimensional level. Which is why to imagine something being infinite is not possible, it is not within the same dimension that our minds are capable of understanding.

    So thats where my question lies, if the universe is expanding what is it expanding into?
     
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  7. Blandnuts Registered Senior Member

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    Insufficient data/unable to comprehend.
     
  8. Boris2 Valued Senior Member

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  9. zanket Human Valued Senior Member

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    Start with a universe infinite in extent. Let the distance between any 2 chunks of it increase. That's all there is to it. An infinite thing doesn't need to expand into something to expand.
     
  10. Just_Not_There Do I Look Like I Care?! Registered Senior Member

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    I always thought the universe is only apparently infinite because it is expanding at the speed of light. According to the big bang theory it started as a ball of energy. What was outside the ball of energy?
     
  11. zanket Human Valued Senior Member

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    It is generally accepted that the "ball of energy" was not a ball but rather energy (the same as matter) infinite in extent and infinitely dense (no spaces). Then the distance between any 2 chunks of it began increasing (that is, spaces formed to create chunks) and the distance continues to increase to this moment. The big bang was an explosion of space within infinitely dense matter/energy that was and continues to be infinite in extent.
     
  12. marv Just a dumb hillbilly... Registered Senior Member

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    Try this:

    The universe is infinite in both duration and dimension. All matter is finite being a subset of an infinite universe. The universe is not expanding since there is no "outside" to expand into. There was no Big Bang to "kick" everything off. Matter is continously being re-arranged through physical laws that we are still learning. There is a constant exchange between "space" and matter that is not yet understood.

    Of course, few people accept this senario, but then people once thought the Earth to be flat. But this theory is much more eloquent than the Big Bang or any religious concept. Unfortunately, it's not as much fun, nor does it create as many jobs as the Big Bang theory and religion do.
     
  13. mercurio 9th dan seppuku sensei Registered Senior Member

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    No, I believe spacetime is expanding, or whatever it does that we experience as expanding. Could even be a side-effect of time, or entropy, forcing change. Also there is this theorem of Whitehead that states that a sphere can only be infinitely connected if it's contractible. I think that's correct, and I also believe the universe to be infinitely connected, so that would sort of add up.
     
  14. Maddad Time is a Weighty Problem Registered Senior Member

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    In the currently accepted theory (which I am dubious of accepting), the universe does not expand into anything. Space itself increases, taking matter with it as it does.
     
  15. superluminal I am MalcomR Valued Senior Member

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    Things need to exist within a context. When something comes into being, like a universe, what context is it arising in? If a statistically improbable fluctuation in the vacuum energy caused our universe to pop out (a theory I've heard) how could there be a fluctuation in the vacuum if there was no space to begin with?!?!?
     
  16. Maddad Time is a Weighty Problem Registered Senior Member

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    The universe is the context in which things come into being.
     
  17. eburacum45 Valued Senior Member

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    Some theories which suggest that the Big Bang was a random fluctuation also suggest that there have been a (perhaps) infinite number of big bangs and expansions previous to our own.
    It seems likely (according to current theories) that the Big Bang will not reverse iself into a big crunch; rather the universe will continue to expand and become less dense until space becomes almost empty; once all the black holes and even massive particles have eventually evaporated, the universe will become a blank stage waiting for the next random fluctuation to produce a new expansion. Smaller fluctuations will occur all the time; perhaps some will be big enough to create shortlived expansions, many of which will (apparently) collapse into black holes. A very few will become long lived cosmoi like the one we live in.

    As I said, this is just one theory among many contenders.
     
  18. mercurio 9th dan seppuku sensei Registered Senior Member

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    As noted in another thread, that is not possible: a cycle of big bangs/big crunches would lead to an ever increasing entropy. This is not borne out by observation, as they say. Meaning it's not true.
     
  19. zanket Human Valued Senior Member

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    I've read that too but don't understand it. Theory says that a big bang is the beginning of space and time. Then there is no "before" the big bang. Even a "cycle" is meaningless. Seems like the physicists behind the entropy theory want their cake and to eat it too.
     
  20. mercurio 9th dan seppuku sensei Registered Senior Member

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    As to the theory:

    http://www.physlink.com/Education/AskExperts/ae181.cfm

    I think the essential problem is one of context. Everything has a context, except the Universe. Neither in time, or space. It very much looks like a one-off thing. Very hard to accept, I agree.

    Some, like Lee Smolin see a cycle in the way of Universes giving birth to black holes giving birth to new Universes. That's turning the problem neatly into one of those Escher paintings without beginning or end, but they do not explain very much, and give you the idea you've been tricked somehow.

    But maybe it's simpler than that, like Tipler says: one culmination into something unspeakably superiour at the end of time, and the whole shebang just uncoils all its true dimensions, rewinds time, picks up all information and transcends into never-neverland.

    But a big crunch/big bang cycle has a real problem, agreed upon I think by many who disagree on just about anything else: you cannot recycle entropy. I don't see it happen either.

    Maybe one of the math bigshots like lethe could gives us a good rundown on entropy, although that's probably a bit too advanced for use simple folk to really grasp anyway...
     
  21. eburacum45 Valued Senior Member

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    As I pointed out before, entropy is an observed quality of our universe as it exists now; it cannot reliably be applied to the universe before the big bang.
     
    Last edited: Jan 14, 2005
  22. blobrana Registered Senior Member

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    Indeed,
    In a `previous` <i>parental</i> universe the entropy may have run `backwards`.
    (I discount the big-crunch scenario, but a <b>big-rip</b> is still a hot favourite)

    (helpful link) http://en.wikipedia.org/wiki/Big_Rip
     
  23. mercurio 9th dan seppuku sensei Registered Senior Member

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    Maybe, but if you have no mechanism by which it recycles, no explanation of how it resets itself, aren't you handwaving the whole problem away, and simply favouring a neat model?

    http://lbl.confex.com/lbl/2001/program/abstract_1584.htm

    If it started with a statistical fluctuation, you should at least end up in a situation that would allow for a new 'chance' to restart the whole thing. Failure to do so, makes the model invalid, however neat it looks.

    In simple terms, a looping movie does not make sense if you skip logically necessary frames at any point. 'Circular eggfrying' needs a believable way of 'unclutching' the eggs at a certain point.
     

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