On the Meaning of Relativity in Contemporary Physics

The paper examines the evolution of the concept of relativity from origins, in the 17th century, to this day. Doubtless the concept of relativity has undergone a substantial change that misrepresents the concept that instead expresses in its essence the fact that laws and equations of physics do not depend on the inertial reference frame and on the inertial observer. The principle of relativity hence is valid only for inertial reference frames and observers who move with constant relative motion. For all inertial observers the same laws of physics and the same equations are valid, it doesn’t mean nevertheless for them also the same mathematical solutions are valid when these solutions depend on inertial velocity of a second reference frame with respect to the reference frame supposed at rest.