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Very old galaxies

  1. Oct 22, 2009 #1
    With the Hubble telescope now able to see back in time by as much as 10 billion years, can anyone explain the path of the photons from very old galaxies entering the HST during the last 10 billion years and particulary where they were around 4,500 million years ago?
  2. jcsd
  3. Oct 22, 2009 #2


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    I'm guessing you're wondering how they could be travelling for 10Gy if, 4.5Gy ago the universe was a mere 4.5Gly wide.

    Think about running up a 'down' escalator. If you do it right, you can run for a half mile on an escalator that is only 100 yards long.

    While light from a galaxy 4.5Gy ago may have started out only a few Mly away, the universe has expanded greatly in the time it travelled here, so its jounrey was vastly extended.
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