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Cosmological and doppler redshift

  1. Apr 28, 2015 #1
    cosmological redshifts are caused by the metric expansion of space, whereas doppler shift is a result of relative velocities through space. So before the development of the modern cosmological models, how did astronomers originally distinguish these two causes of redshifts (e.g. when they tried to verify the Hubble's law) ? Even with the use of Hubble's law and the standard cosmological model, can we tell how exactly these two mechanisms contribute to these redshifts?
  2. jcsd
  3. Apr 28, 2015 #2


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    It was a question of appearances. It would be very strange if distant galaxies were all moving away from us at random.
  4. Apr 28, 2015 #3
    doesn't that only imply the existence of the Hubble flow? I mean how did astronomers ascertain how much of the redshift of a single object is caused by the Hubble flow and how much by doppler shift?
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