'Dissident' physicists have postulated various alternative explanations for the alleged cosmic expansion due to the Big-Bang-induced and dark-energy-sustained ever-increasing expansion of space(-time). Among these is the effect of gravity which allegedly 'stretches' light waves (and allegedly also bends them via gravitational lensing) as they pass large masses, such as stars, galaxies or galactic clusters. The stretching phenomenon is an increase in wavelength, and corresponding decrease in frequency, required by the assumption that light speed remains constant (within a medium). If light speed is variable, would there also be a gravitational cosmic redshift, i.e., one that alters light speed without affecting the waveform itself (i.e., no 'stretching')?
