6. Special theory of relativity. Introduction

Already in Newton's dynamics, the selection of inertial motion among all other motions is clearly formulated. The direct logical consequence of Newton's first law is the assertion that all inertial observers are equal in rights to the extent that Newton's first law is valid. Einstein, on the other hand, extended this equality to all phenomena in general, having formulated the famous postulates:

1. All physical laws are invariant with respect to the transition from one inertial reference system to another.

2. The speed of light in vacuum is equal to the same value in all reference systems and does not depend on the speed of movement of the source, nor on the speed of movement of the receiver.