20-2 The postulates of special relativity 1. Einstein offered two postulates that form the basis of his special theory of relativity o The principle of relativity: The laws of phys are the same in all inertial reference frames. sics (D The principle of the constancy of the speed of light The speed of light in free space has the same value c in all inertial reference frames 2. The first postulate declares that the laws of physics are absolute, universal, and same for all inertial observers20-2 The postulates of special relativity 1. Einstein offered two postulates that form the basis of his special theory of relativity. (I) The principle of relativity: “The laws of physics are the same in all inertial reference frames.” (II) The principle of the constancy of the speed of light : “ The speed of light in free space has the same value c in all inertial reference frames.” 2. The first postulate declares that the laws of physics are absolute, universal, and same for all inertial observers