Doppler shift is an astronomical observation which could come under any number of different interpretations. For example, if someone sees a blue star it's not a given that the star is accelerating towards the earth, or anywhere. The star may just be blue.
No, it's not, because we see emmision spectra blueshifted, and i hope that you're not saying that all chemists are in conspiracy.
Nothing's at the center. It's a shared center of attraction, like that which occurs in a binary star system or a multiple system. As for what causes the stars to attract, that is of course, unknown.
in RE it's called gravity, and it's caused by mass, not 'nothing'
ronomy is a matter of observation and interpretation. There can never be an experiment with the cosmos to come to the absolute truth of the matter like there can in Chemistry. Astronomy is an observing science. Astronomy can never follow the Scientific Method. The Astronomer cannot conduct an experiment on the cosmos. He can only observe and interpret.
Chemistry is not only an observation, it's also explanation, calculation, deductive and inductive reasoning, as Astronomy is.
If there is any interpretation of some phenomena, it MUST be confirmed in all situations, and if there is any situation that proves interpretation to be wrong, in must be updated or changed.
If there are 2 correct interpretations of phenomena, te cannot say what is the good one until we will conduct any experiment(or observation for astrophysics) that will give different results in different interpretations.