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.
Principle of relativity the Lorentz transformations from the principle of relativity "alone" and obtain the constancy of the speed of light as a "consequence". Using only the isotropy of space and the symmetry implied by the principle of special relativity, one can show that the space-time transformations between inertial frames are either Galilean or Lorentzian. In the Lorentzian case, one can then obtain relativistic interval conservation and the constancy of the speed of light. The general principle of relativity states: That is, physical laws are the same in "all" reference frames—inertial or non-inertial. An accelerated charged particle might emit synchrotron radiation, though a