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The classical physics has following troubles:
(i) Classical physics does not put any limit on the speed of light.
(ii) The classical physics assumes space and time to be absolute.
(iii) Classical theory considers mass to be constant. However, it can be variable.
(iv) The classical physics is valid when the speed of the considered object is much less than the speed of light in vacuum.
The Postulates of Special Theory of Relativity: The postulates of special theory of relativity are as follows:
(i) All of the laws of physics must be the same in all inertial reference frames.
(ii) The speed of light in vacuum has the same value c = 3.00 × 108 m/s, in all inertial frames, regardless of the velocity of the observer or the velocity of the source emitting the light.
Consequences of Einstein’s Postulates:Due to the establishment of the postulates of special theory of relativity, following are the consequences:
(i) In relativistic mechanics, there is no such thing as absolute length or absolute time.
(ii) Events at different locations that are observed to occur simultaneously in one frame are not observed to be simultaneous in another frame moving uniformly past the first. That is simultaneity is not an absolute concept but rather one that depends on the state of motion of the observer.
(iii) When we measure the length of an object in another frame moving with a constant speed relative to the first one the length contraction occurs along the direction of motion.
(iv) Due to relativistic Doppler effect red shift occurs.
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Relativity