system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can we measure the velocities of the redshift of stars?

Are they measured assuming the earth itself isn't moving or is this somehow taken into account?
gpt
You are basing this on a false assumption, movement requires two things, an object and a point of reference, however the most important part is that **these are interchangeable**. It is not a matter of "is the star moving or is Earth moving," because according to physics, both principles are exactly the same.