Why it's not explained just by Doppler redshift caused by faster movement of those galaxies billions of years ago when that light was emitted? Would the speeds of the galaxies necessary for Doppler redshift to explain all of the observed galaxies redshift be unreasonable or is there something else that prevents such explanation to be sufficient? I noticed that distance to far galaxies are given in terms of their redshift rather than lightyears. Do we have any other way to tell how far these galaxies are? What is the farthest data point of distance and redshift that we can use to verify how they should correlate? Could you point me to some experimental data of this kind?