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Thread: Universe Expansion

  1. #1 Universe Expansion 
    Forum Sophomore oceanwave's Avatar
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    Not really sure where to locate this thread but figured that physicists should be well poised to answer this:

    Is it true that the only reason why the whole universe is not covered in light (blindingly so) is that the universe is expanding? If im not mistaken, there seems to be a paradox related to this issue. For example: if we look up into the night sky, with so many sources of light (stars and our sun) its rather strange that it isnt all bright in the same way how a dark room is lit up with a bright bulb (excluding objects which block out the light.)


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    Well no I don't think it has to do with expansion (i could be wrong). I will give an analogy. That bulb you speak of - take it outside. It won't light up the entirity of its surroundings. How could it? It has a limited number of photons.


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    Moderator Moderator Dishmaster's Avatar
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    This is "Olbers' paradox". In simple words it goes: "If the universe was infinite, why is the night sky not as bright as the day? In an infinite universe, there should be a source of light in every single direction; in fact even an infinite number of them. This means that every patch of the sky should be illuminated." The main argument against this paradox is that the universe is not infinite, neither in space nor in time. All the more detailed arguments (also the expansion, i.e. redshift) are mostly a consequence of that.
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    Quote Originally Posted by Dishmaster
    This is "Olbers' paradox". In simple words it goes: "If the universe was infinite, why is the night sky not as bright as the day? In an infinite universe, there should be a source of light in every single direction; in fact even an infinite number of them. This means that every patch of the sky should be illuminated." The main argument against this paradox is that the universe is not infinite, neither in space nor in time. All the more detailed arguments (also the expansion, i.e. redshift) are mostly a consequence of that.
    Oh I see. I don't think I properly understood the question. Nice link.
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    Forum Sophomore Tharghana's Avatar
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    That Paradox is quite interesting, but I think the distances between stars dims the light, as the light leaves the source in every direction, the further it travels the father apart the light gets, so that its not noticeable even thought its everywhere.
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    Quote Originally Posted by Tharghana
    That Paradox is quite interesting, but I think the distances between stars dims the light, as the light leaves the source in every direction, the further it travels the father apart the light gets, so that its not noticeable even thought its everywhere.
    In an infinite universe, distances don't matter. Yes, you are right: The intensity of the light scales with the square of the distance. That's for one light source. But as soon you have an infinite number of light sources in a row, you still get practically a sum of infinite brightness.
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    Forum Sophomore Tharghana's Avatar
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    But as soon you have an infinite number of light sources in a row, you still get practically a sum of infinite brightness.
    :? but thats only if the Universe is infinite right? Guessing that I don't see an infinitely bright night sky i'm guessing it inst..
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  9. #8  
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    If five things held, then even the single photon arriving from the most distant stars would add up to a blindingly bright universe:
    - There were infinitely many stars, which would necessarily require a universe of infinite size.
    - There had already been infinitely long for the light from the most distant stars to reach us.
    - There was nothing absorbing that light.
    - Stars lasted forever.
    - Photons lasted forever.

    If all of those were true, we should see (a lot of) light coming from every direction all the time. Since we obviously don't, at least one of these must be untrue. Various observations have actually ruled out at least the first four, and I'm pretty sure the last one as well.
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  10. #9  
    Forum Sophomore oceanwave's Avatar
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    wow...ok, yea, the paradox was something like that...erm actually, i got the idea from a sf novel long ago...just forgot the actual terms...thanks all for the help...so, is the paradox still valid today? (meaning that does it stand alone as a theory and prove the expansion of the universe?)
    What do you do when the last day of your life is approaching...........?
    Me?
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  11. #10  
    Moderator Moderator Dishmaster's Avatar
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    Quote Originally Posted by Tharghana
    But as soon you have an infinite number of light sources in a row, you still get practically a sum of infinite brightness.
    :? but thats only if the Universe is infinite right? Guessing that I don see an infinitely bright night sky i'm guessing it inst..
    Indeed. That is the actual meaning of a paradox. It is an "apparent" contradiction. In this case, the assumption does not hold (infinity), so the paradox is resolved.
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  12. #11  
    Forum Sophomore Tharghana's Avatar
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    So this Paradox proves the Universe is not Infinate?
    www.periodicvideos.com - A Great Site

    "Well, good chemists shouldn't lick their fingers, anyways." - Martyn Poliakoff

    "You have lived to die, and your running out of life."

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  13. #12  
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    It more or less proves that at least one of the things I listed isn't true. Other observations have shown none of them to be.
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  14. #13  
    Forum Sophomore Total Science's Avatar
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    Everything in the universe is expanding (growing) including the Earth.
    "The most likely site for error is in the most fundamental of our beliefs." -- Samuel Warren Carey, geologist, 1988
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  15. #14  
    Forum Radioactive Isotope MagiMaster's Avatar
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    Oh great. Another one.
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  16. #15  
    Forum Sophomore Tharghana's Avatar
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    Oh great. Another one.
    That made my day .
    www.periodicvideos.com - A Great Site

    "Well, good chemists shouldn't lick their fingers, anyways." - Martyn Poliakoff

    "You have lived to die, and your running out of life."

    "Once and a while, I go out of my way... to kill you... a little"
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  17. #16  
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    The Universe isn't expanding all theories claiming such are false and misleading.

    "What would the Universe expand into?"

    It would expand into itself, and therefore there is no expansion. And besides what energy would fuel this expansion? The infinite energy Himself stopped creating after the Big Bang. Science used the Book Of GOD to learn about the cosmos, about the Sun, the Moon, and so much more. But also the theory of the Big Bang.


    2Enoch.25:[1]I commanded in the very lowest parts, that visible things should come down from invisible, and Adoil came down very great, and I beheld him, and lo! He had a belly of great light. [2]And I said to him: Become undone, Adoil, and let the visible come out of you. [3]And he came undone, and a great light came out. And I was in the midst of the great light, and as there is born light from light, there came forth a great age, and showed all creation, which I had thought to create. BANG!!!!!!!!!!!!

    and visible things from invisible.
    and visible things from invisible.

    GOD created this very Universe with a Big Bang.
    HOUSE OF THE GREAT KING.
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  18. #17  
    Forum Sophomore Tharghana's Avatar
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    And another...
    www.periodicvideos.com - A Great Site

    "Well, good chemists shouldn't lick their fingers, anyways." - Martyn Poliakoff

    "You have lived to die, and your running out of life."

    "Once and a while, I go out of my way... to kill you... a little"
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  19. #18  
    Moderator Moderator Dishmaster's Avatar
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    Quote Originally Posted by Tharghana
    And another...

    Ignoring those individuals is already too much attention.
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