Postulates of Special Relativity

Relativity is based on two very simple ideas; everything else follows from these. These are:

  1. The relativity postulate : the laws of physics apply in every inertial reference frame.
  2. The speed of light postulate : The speed of light in vacuum is the same for any inertial reference frame (c = 3.00 x 108 m/s). This is true no matter how fast a light source is moving relative to an observer.