Is it really science, if a theory cannot be falsified?
For instance, with the Big Bang theory, whenever observation doesn’t match prediction, some enormous force of nature can be inserted and no one gives it a second thought. What if accountants could just write in a figure and call it Dark Money, whenever they find a gap in the books?
Long before Inflation, Dark Matter, or Dark Energy, the first patch was when it was observed the redshift increases proportional to distance in all directions, creating the effect that we appear to be at the center of this expansion. So it was changed from an expansion in space, to an expansion of space, because “spacetime!”
Which totally ignores the central premise of General Relativity, that the speed of light is always measured as a Constant. If the light is being redshifted, because it is taking longe to cross the space, obviously then, intergalactic light is not Constant to intergalactic space. Two metrics are being derived from the same light. One based on its speed and one based on its spectrum.
Given the effect is described as “expanding space,” then it is necessarily expanding relative to the speed, which would mean the speed is still the denominator.
The fact is that we are at the center of our point of view and so an optical effect would be the reasonable solution. Multispectrum light does redshift over distance, as the higher spectrums dissipate faster, but that would raise the question of whether individual photons travel billions of lightyears, or are we sampling a wave front? Which gets to the even more sacrosanct question of whether photons are truly discrete, or simply the smallest measureable quanta of light.
While this line of questioning is most easily ignored, I suspect the James Webb Space Telescope will find the cosmic background radiation to be the light of ever more distant sources, shifted off the visible spectrum, not the afterglow of some particular event. The solution to Olber’s Paradox.