For centuries, scientists have been preoccupied with the search for a reference frame in the Universe that could unambiguously determine, for example, the Earth revolves around the Sun, or vice versa. Neither the Ptolemy system nor the Copernican system possess such uniqueness. Kepler’s laws also do not clarify this issue. Einstein's theory of relativity suggests the equality of both points of view. But for many researchers, the question remained open. And finally, uniqueness, as if, appeared. Uniqueness is formed by the difference of gravitational potentials