What is one of the main contributing reasons that the largest "look-back" times we have observed are between 8 and 9 billion years, whereas the universe is thought on the basis of its Hubble expansion to be roughly 15 billion years old?

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    Light can last only about 8 to 9 billion years before decaying to invisibility due to age.
     Severe clouds and dust interfere with our ability to look any further away than we have at present.
     All older galaxies have already used up their supply of fuel and faded away.
     When the first galaxies formed, the universe was effectively much smaller, but their current appearance took several billion years to reach us.
     The first galaxies formed no earlier than about 8 billion years ago and have been expanding and moving away ever since.
asked Sep 20, 2012 in Astronomy by anonymous
    

1 Answer

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When the first galaxies formed, the universe was effectively much smaller, but their current appearance took several billion years to reach us.
answered Sep 22, 2012 by SkyStar ~Expert~ (2,855 points)

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