Separate groups of physicists have adopted conflicting explanations for the Doppler shift in starlight, namely the moving source and the moving observer models. Both models predict the same degree of shift, but only one of them can be what is happening in nature. I have studied how this situation developed and which model is the simpler and more useful. Unfortunately, for the clearest understanding of the phenomenon, it is not the one more commonly employed.

My discussion is in the form of 4 Substack posts or combined into a single narrative found here. It’s a short read and I think you will find it interesting.