All we really know is that light appears to lose energy over distance (lower wavelength = lower energy).
We needed a mechanism to explain how light could possibly lose energy without interacting with anything. The easiest assumption was that galaxies were accelerating away from us because light being emitted by accelerating bodies gets sort of stretched out to a longer wavelength. (or that the bodies arenâ(TM)t technically accelerating away, but rather space is being stretched between us and the other galaxies which likewise stretches out light in those regions?)
If the above is not the case, what else can explain EMR (light) losing energy without interacting with anything? Can it be hidden interactions with dark matter gravity? Can it be that light naturally decays? Can it be something else cooler than those? I donâ(TM)t know. iâ(TM)m just an uneducated dweeb. No one should listen to me about anything.