In this article, a bijective research methodology is applied where every element in the model corresponds to exactly one element in physical reality. An element in the physical reality X and the corresponding element in the model Y are related by the bijective function. A bijective research methodology confirms that the Lorentz factor has its origin in the variable density of universal space. A lower value of the space density corresponds to the higher value of the Lorentz factor. Universal space is not “empty”; space is the primordial energy of the universe. Universal space is the absolute frame of reference for all observers as confirmed experimentally by the GPS system, which demonstrates that the relative rate of clocks is valid for all observers. A planet's perihelion precession and the Sagnac effect are the results of the space rotation.