Redshift and Blueshift are not entirely due to the Doppler's Effect but also to the Medium Composition. A Suggested Experiment with Different Medium Compositions

The General Theory of Relativity asserts that the redshift and blueshift are entirely due to the \textit{Doppler's Effect}, which is caused by the motion of light source: if the source is moving away from the observer the frequency received is lower [redshift], but if the source is moving towards the observer the frequency received is higher [blueshift]. But Doppler's Effect itself is actually an appearance to a \underline {Subjective Observer}, because the frequency is the same all over (if one considers the \underline {Absolute Observer}). We believe that the redshift and blueshift are not entirely due to the Doppler's Effect, but also due (as in the light bending) to the medium composition (medium that could be formed by waves, particles, plasma, dust, gaseous, fluids, solids, etc.), to the medium density, to the medium heterogeneity, to the medium structure, and to the electromagnetic and gravitational fields contained in that medium that may interfere with the light that passes through. We suggest an \textbf{Experiment {\#} 2} should be done by changing the medium's composition elements (particles, fields, etc.), structures, densities, heterogeneities, etc. (but keeping the other data fixed, i.e. the relative speeds of the wave and the observer as well as the wave's traveling distance stay the same). By changing the medium the light passes through, one should get different \underline {degrees of redshifts/blushifts}.