4 ms·

I'd love to get an informed answer to this too. Is it more accurate to interpret inferred distances derived from redshift as an average estimate? If so it woul

• pdonis 4y ago
  > Is it more accurate to interpret inferred distances derived from redshift as an average estimate? We don't estimate distances just based on redshift. We use all three of the observables I mentioned--redshift, apparent luminosity, and angular size--as inputs to estimate parameters in our cosmological models, and one of those parameters is the scale factor--the "size" of the universe, which is what is used in the model to ultimately get actual distances--as a function of time. The models of course have error bars--no model is ever exact--and some of those error bars are due to variations of the motions of individual galaxies from the idealized cosmological expansion in the models. So in that sense distances given by the models are a sort of estimate, yes, based on the average motion.
• mr_mitm 4y ago
  The effect you are talking about is real, but it's generally small. The cause is called peculiar velocity, and it could introduce uncertainties of a few percent, which is relatively small for cosmological standards. We know how velocities are distributed inside galaxy clusters. It leads to the "finger of god" effect, which makes it appear as if objects would be distributed such that they tend to align along our line of sight. See: https://en.wikipedia.org/wiki/Peculiar_velocity https://en.wikipedia.org/wiki/Peculiar_velocity