Question

State the special theory of relativity given by Einstein.

Answer 1

Step 1: Introduction

1. In 1905 Einstein proposed the theory of special relativity.
2. This theory gave an explanation of how speed affects space, mass, and time.
3. This theory treats problems that involve an inertial frame of reference.
4. The laws of physics are the same in all inertial frames of reference. This postulate follows from the absence of a universal frame of reference.
5. The speed of light in free space has the same value in all inertial frames of reference i.e., $3\times {10}^8\mathrm{m}/\mathrm{s}$.

Step 2. Postulates of the special theory of relativity

The two postulates of the special theory of relativity are as follows:

1. Principle of relativity: The states of changed physical systems are not affected, whether these changes of state be referred to the one or the other of two systems in uniform translatory motion relative to each other, i.e., the laws of physics are invariant.

2. Principle of invariant light speed: Light always travels at a constant velocity c in empty space, regardless of the state of motion of the emitting entity, i.e., the speed of the light in a vacuum is the same in any other space irrespective of the light source.

In the theory of relativity, reference frames play a vital role. It is used to measure a time of events by using a clock.