Special relativity to a first observer O, and frame S′ (pronounced "S prime") belongs to a second observer O′. Since there is no absolute reference frame in relativity theory, a concept of 'moving' doesn't strictly exist, as everything is always moving with respect to some other reference frame. Instead, any two frames that move at the same speed in the same direction are said to be "comoving". Therefore, "S" and "S"′ are not "comoving". The principle of relativity, which states that physical laws have the same form in each inertial reference frame, dates back to Galileo, and was incorporated into Newtonian physics.
Criticism of the theory of relativity Leiden in 1920, shortly after the Bad Nauheim debates, Einstein himself acknowledged that according to his general theory of relativity, so-called "empty space" possesses physical properties that influence matter and "vice versa". Lenard also argued that Einstein's general theory of relativity admits the existence of superluminal velocities, in contradiction to the principles of special relativity; for example, in a rotating coordinate system in which the Earth is at rest, the distant points of the whole universe are rotating around Earth with superluminal velocities. However, as been pointed out by Weyl, it's not possible to handle a rotating extended system as