The Missing Third Question

Abstract

This is about a question that could have been put logically by Einstein or anyone that has followed his way of reasoning,
following two other guided or heuristic questions. In the literature that analyses Einstein’s scientific work, it is said that in his
analysis of so-called mechanical principle of relativity, he was trying to understand if there was something in the laws of nature
that was justifying it. Logically, a question comes up: Did something exist in laws of nature that conditioned discrimination in
identification possibilities of the difference between mechanical experiments from one side and optical, magnetic etc. ones on
the other? Why in principle was impossible for mechanical experiments to identify this difference, but it was not for, say, optical
experiments? Einstein by his principle of restricted relativity gives an answer to this question. He did the same for “Why”-s of
principal impossibility to differentiate the rest from the straight-lined uniformed motion by any physical experiment carried within
a system of reference. Now is the time to ask the third “Why” which logically follows the two mentioned and to propose an
answer. That is the “Why”-s of principal impossibility to differentiate the immobility (or the rest) from the any mechanical motion
by any physical experiment carried within a system of reference.