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Redshift as a distance indicator

  1. Nov 26, 2009 #1
    Surely it is possible to take a spectrum, deduce the redshift, then use this as a definitive distance indicator for all distances.

    Why is it we use the distance ladder???
     
  2. jcsd
  3. Nov 26, 2009 #2

    mgb_phys

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    The distance ladder was used to get the conversion factor between redshift and distance - Hubble's constant.

    Also for nearer objects hubble's law isn't necessarily true if enough of their velocity is due to relative motion rather than the universe expanding.
     
  4. Nov 26, 2009 #3

    Chronos

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    We need independent corroborations to test distance indicators. We must be doing something right as all are pretty consistent one to the other.
     
  5. Nov 27, 2009 #4
    So for long distances, do we only use other methods (e.g SN) because of the uncertainty in Hubble's constant?
     
  6. Nov 27, 2009 #5

    mgb_phys

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    No we use SN to get Hubble's constant.
     
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