So I might perceive a stream of photons as radio waves from our current inertial frame, but if I were on a ship approaching the speed of light head-on towards that same stream of photons, I might perceive them as visible light? Or ultraviolet or gamma ray.
Wait… that doesn’t sound right, for some reason.
It took billions of years of universe-stretching for the CMB to redshift to microwave, I don’t think me pushing pedal to the metal for a few seconds on a rocket ship is going to counteract all those years.
Then also those CMB photons are more diffuse, spread out.
Doesn’t Coloumb play into this?