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Universe 93 billion light years?

  1. May 27, 2010 #1

    If the universe is 13.7 billion years old, how is the diameter 93 billion light years? Light travels 1 light year for every year. Then if two particles were expanding outwards to form the size of the diameter, it would be approximately 28 billion light years. Can somebody explain this confusion?
  2. jcsd
  3. May 27, 2010 #2
    From the same article:

  4. May 27, 2010 #3
  5. May 28, 2010 #4


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    Basically, the CMB which we see today was emitted from matter that was, at the time, about 44 million light years away. At the time, however, the universe was expanding very rapidly, so that the light has taken a full 13.7 billion light years to get here. In fact, for much of this time it wasn't even approaching us, but the rapid expansion left photons traveling in our direction even more space to travel than they crossed. Eventually the expansion rate slowed enough that the photon started to make headway, and finally arrive after 13.7 billion years.

    In that time, our universe expanded by a factor of about 1100 times. This means that the matter which emitted the CMB we see today at 44 million light years away is currently around 48 billion light years away. But this distance has little to do with the path light traveled to get here.
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