The postulates of special theory of Relativity
The postulates of special theory of Relativity:
Einstein in 1905, formulated this special theory of relativity on the basis of following postulates:
- The laws of physics are same in all inertial frames. This is the principle of relativity.
- The speed of light in vacuum is constant and same as observed from all inertial frames. This is known as the principle of constant of speed of light.
The first postulate implies that not only the laws of mechanics but also that of electrodynamics and optics should be same for all inertial reference systems. There is no privileged frame like ether or absolute space.
The second postulate is really a consequence of the first, because if Maxwell’s equations hold in all inertial frames, then the only possible value for the speed of light is c. These postulates embody Einstein’s Special Theory of Relativity, first published in 1905 in a paper titled On the Electrodynamics of Moving Bodies. Later he would incorporate gravity and acceleration in his General Theory of Relativity. As in Newtonian Relativity, there is no way to detect absolute motion. Only the relative velocities between two inertial reference frames matters. These seemingly simple postulates have extraordinary consequences. For example, when you turn on the headlights of a car, the light beam leaves the car at a relative velocity of c = (3.0* 108)m/s. However, someone standing on the sidewalk also measures the speed of the light beam as c independent of the velocity of the car! How can this be? As we shall see, our concepts of space and time must be modified.