<ol>
<li><p>Are there any observations that more distant galaxies appear to rotate more slowly than closer galaxies? </p></li>
<li><p>What methods are used to measure the rotational speed of galaxies? (both orbital speed profiles and/or bulk average rotation speed) </p></li>
<li><p>What is the current limit for how far away a galaxy can be to make such measurements? </p></li>
</ol>

<p>I greatly appreciate any answer or links to info on this topic.  I am not an astronomer by profession or education, just deeply fascinated with cosmology. </p>

CC BY-SA 4.0
2018-10-19T06:00:05.273Z
Regarding #1, that is very specific - suggesting you have a hypothesis. Please see https://physics.stackexchange.com/questions/156611/the-doppler-shift-and-the-apparent-speed-of-galactic-rotation-with-distance/301560#301560
ProfRob
CC BY-SA 4.0
2018-10-21T02:58:48.103Z
Thank you.  Your description in the link answers question #2 very well. Any idea about the greatest distance over which these types of measurements have been made?  My guess is that no discernible correlation between rotation speed and distance has been detected, since it would probably be widely discussed, but has it been ruled out?  I imagine estimating inclination is inexact, making such measurements quite fuzzy.
Blundervan
<galaxy><galactic-dynamics>
Galactic rotation speeds - questions from a non-astronomer
Blundervan
# Galactic rotation speeds - questions from a non-astronomer

(Asked by: username_0 on 2018-10-19)

1. Are there any observations that more distant galaxies appear to rotate more slowly than closer galaxies?
2. What methods are used to measure the rotational speed of galaxies? (both orbital speed profiles and/or bulk average rotation speed)
3. What is the current limit for how far away a galaxy can be to make such measurements?

I greatly appreciate any answer or links to info on this topic. I am not an astronomer by profession or education, just deeply fascinated with cosmology.

**Tags:** galaxy, galactic-dynamics
> **Comments:**
> **username_1**: Regarding #1, that is very specific - suggesting you have a hypothesis. Please see https://physics.stackexchange.com/questions/156611/the-doppler-shift-and-the-apparent-speed-of-galactic-rotation-with-distance/301560#301560  
> **username_0**: Thank you.  Your description in the link answers question #2 very well. Any idea about the greatest distance over which these types of measurements have been made?  My guess is that no discernible correlation between rotation speed and distance has been detected, since it would probably be widely discussed, but has it been ruled out?  I imagine estimating inclination is inexact, making such measurements quite fuzzy.  

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