I'm not sure if either Einstein or Newton said that all frame of reference are equally valid. That from my point of view, the laws of physics is the same from your point of view. All frame reference can be put on an equal footing. I was wondering, can one consider the geocentric view that the earth as the center of the universe to be equally valid as the sun as the center? That the astronomical model that Ptolemy with epicycles can be viewed on a equal footing as the commonly accepted model where the sun is in the center of the solar system. I know that it's tempting to say that because the sun center model is simpler and hence more elegant and "better". But I think that it is possible to construct an entire astronomical paradigm having the earth as the origin of reference point. Please let me know what you think.