Pound & Rebka Experiment: Earth's Spin Rotation Speed

[PeterDonis]

In the OP it does not say "the relative velocity between the source and the emitter"

It says "speed difference", yes. That's just a quibble over terminology. You can go back and make that substitution in all of my posts; it won't change anything of substance.

In the ECI, you can calculate invariant quantities

Sure, but the "speed difference" is not one of them.

 

[PeterDonis]

Except Dale.

As far as I can tell, @Dale agrees with me. If I'm mistaken about that, he can correct me.