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Thread: Paradox of light and time?

  1. #1 Paradox of light and time? 
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    Learned Gentlemen,
    How is it possible that we can see the light of a galaxy formed 700,000,000 years after the big bang. Consider that this light has been travelling for 13 billion years. Since we both originally started at the same point of origin, supposedly? Our galaxy travels at a snails pace across the universe compared to light speed. The light from that galaxy at that time, should have passed us eons ago. It seems to me that our view of the universe should be relegated to galaxies in our corner of the quadrant, and no more. I understand redshift as an object that is moving away from us, but does that implicitly tell us that it's age is correspondingly older? Enlighten me on this paradox.
    Thanks in advance
    Chris { I'm just a curious novice}


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  3. #2  
    Moderator Moderator Dishmaster's Avatar
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    This question is as if you would ask why we can see the sun. It was formed about 5 billion years ago, but the light travels only 8 minutes. The answer is, it keeps on shining since then.


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  4. #3 I guess I have stated my quandrum incorrectly 
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    Dishmaster,
    We see the sun as it was eight minutes ago, but not as it was 5 billion years ago. That light from the beginning of the sun's birth is well past us and just now being observed in other parts of the universe. The paradox I am confused about is how we can see a new galaxy from the beginning of the universe, where we originated. We didn't get here by travelling faster than light. The light from that galaxy at that time it formed must have been seen by the precursors of our galaxy early in time because we were supposedly in the general vicinity. It is the same as I look up at the sun and see it as it was 5 billion years ago, even though it is eight minutes away. I hope this is the correct parallel. Thanks for your reply.
    Chris
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  5. #4  
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    You need to look up the Inflationary Big Bang model.

    All of the universe is postulated to have been causally connected moments after the big bang. This means light and information were freely exchanged between all parts of the universe as it was small enough for this to happen, and this accounts for the large scale isotropy of the universe.

    Then inflation set in and the universe expanded exponentially for a brief period of time such that parts of the universe became causally disconnected and we are left in our small corner of the universe where causal connection is only valid for the 'observable' universe.

    In this observable universe the expansion hasn't overcome the speed of light yet and so we see distant objects as distant in time.
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  6. #5  
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    Quote Originally Posted by Dishmaster
    This question is as if you would ask why we can see the sun. It was formed about 5 billion years ago, but the light travels only 8 minutes. The answer is, it keeps on shining since then.
    The simplicity of understanding the Universe. Great work dishmaster!
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