Why can't the universe be infinite big?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by pluto2, Dec 17, 2011.

  1. pluto2 Registered Senior Member

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    Lawrence Krauss says that the Universe cannot be infinitely big because then this means that we could not have evolved. But fact is, we evolved.

    Olbers' paradox basically says the same thing. Olbers' paradox says that the night sky could not have been dark if there were an infinite number of stars.

    But what are the other reasons that the universe cannot be infinitely big besides of these reasons?
     
    Last edited: Dec 17, 2011
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  3. mathman Valued Senior Member

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    Olber's paradox is not relevant, since we cannot see light more than 13.7 billion years old.

    Krauss's assertion (as you stated it) looks like a non sequitor.
     
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  5. Aqueous Id flat Earth skeptic Valued Senior Member

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    If expansion contradicts the definition of "infinitely big" then, no.
     
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  7. Fraggle Rocker Staff Member

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    The Big Bang hypothesis says that the universe started out as a point (or perhaps it was the size of one elementary particle) and expanded from there. It also says that the universe is roughly 13,000,000,000 years old. If the universe were infinite it would mean that the outer portions of it have traveled an infinite distance in a finite time. That would be a velocity equal to infinity, and that's impossible according to the Laws of Thermodynamics--and I think also according to a few other laws as well.

    Lately we have discovered things "moving" faster than the speed of light, for example, stars being farther away from each other than they should be, but that's explained away by the claim that empty space is expanding. Nonetheless, this travel/expansion/magic/whatever you call it, is still taking place at a finite speed, even though this pokes some holes in our model of the universe.

    There is no evidence that anything can travel/expand/whiz along on a witch's magic broom/whatever you call it, at infinite speed. That would not just poke holes in our model of the universe. It would tear it into tiny pieces, roll it into a ball, douse it in kerosene, set it on fire, and flush it down the toilet.
     
  8. Aqueous Id flat Earth skeptic Valued Senior Member

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    Well said.
     
  9. Robittybob1 Banned Banned

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    "There is no evidence that anything can travel/expand/whiz along on a witch's magic broom/whatever you call it, at infinite speed. That would not just poke holes in our model of the universe. It would tear it into tiny pieces, roll it into a ball, douse it in kerosene, set it on fire, and flush it down the toilet. "
    Plenty have suffered this very fate. Each era thinks their knowledge to be perfect, only to see it later smashed and flushed.
     
  10. Big Chiller Registered Senior Member

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    How is it that matter and energy both of which are finite in measurement exist in an universe of infinite volume?
     
  11. ughaibu Registered Senior Member

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    If measurements are made using natural numbers, finite measurements are no more of an objection to an infinitely extensive universe than is arithmetic an objection to the infinitude of natural numbers.
     
  12. Big Chiller Registered Senior Member

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    I understand that but measurements aren't made using rational integers, rational integers are abstractions that are assigned to measurements. When one measures an inch of something one can compare it to a different measurement, so infinitude of arithmetics does not apply to reality. At least no infinite number has ever been shown to be applicable to reality the infiniteness of arithmetics seem to be purely abstractions.
     
  13. ughaibu Registered Senior Member

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    I dont see how any of that is relevant to my point. Please explain what problem you think is incurred by finite subsets of the infinite.
     
  14. Big Chiller Registered Senior Member

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    I thought you were talking about measurements and not sets.
     
  15. ughaibu Registered Senior Member

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    If there is a space which can be measured in finite sub-sections, then that space constitutes a set of finitely and regularly separated points. If you have nothing interesting to say about this, please stop replying to me.
     
  16. Big Chiller Registered Senior Member

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    Where have you seen me deny that space constitutes of finitely separated points? :shrug:
    I don't see how your statement is a reply to mine.
     
  17. ughaibu Registered Senior Member

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    Last chance; what is the problem with finite measurements, in an infinite universe?
     
  18. Big Chiller Registered Senior Member

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    The problem is you're claiming the abstractions such as rational integers and sets represent the measurements themselves but I've already said they don't represent the measurements they are assigned to the measurements so they remain abstractions.
     
  19. Rav Valued Senior Member

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    People have started to think about Singularities differently these days. While the initial state of the universe as we know it was certainly unimaginably hot and dense, there's no particular reason why it couldn't have been an infinite volume that was unimaginably hot and dense at every point. The metric expansion of such a 'singularity' would be consistent with what we observe.

    Edward L Wright has a simple illustration here.
     
  20. ughaibu Registered Senior Member

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    I know you said this, and I pointed out that it's irrelevant, as far as I can tell, however, I suspect it's actually gibberish. Can you express it in the skeletonised form of an argument with clearly stated premises and conclusion, please.
     
  21. Big Chiller Registered Senior Member

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    How is it irrelevant if you want to support your premise which is finite measurements can be made in an universe of infinite volume, you claimed in your original response as support that infinite sets can represent the volume of the universe but that could only be if arithmetic abstractions can represent measurements. You did say rational numbers are used to measure things.
     
    Last edited: Dec 18, 2011
  22. ughaibu Registered Senior Member

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    I've had enough. You have not supported your claim, so I reject it. Finite measurements do not conflict with an infinite universe.
     
  23. Big Chiller Registered Senior Member

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    I did not make a claim I was asking a question and you however haven't provided any support for your refutation of my question.
     
    Last edited: Dec 18, 2011

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