Menachem Shmei,
“scientists themselves acknowledge that it is impossible for them to prove one way or the other (according to Einstein’s theory of relativity)”
I don’t think the issue is that they cannot prove one or the other – but rather either can be chosen as a valid frame of reference. Also, you and ujm are bringing in Einstein, but this form of relativity is older and applicable in Newtonian physics. Einstein’s special relativity showed that our observations of time and mass are also dependent on the frame of reference, and general relativity addresses gravity.