The role of Einstein's theory of relativity in science

When natural science dominated the mechanistic picture of the world and there was a tendency to reduce the explanation of all phenomena of nature to the laws of mechanics, the principle of relativity was beyond doubt. The situation changed dramatically when physicists began to study electrical, magnetic and optical phenomena. Maxwell combined all these phenomena within a single electromagnetic theory. With the creation of this theory for physicists became apparent lack of classical mechanics to describe the phenomena of nature. In this connection, the question naturally arises: is the principle of relativity also valid for electromagnetic phenomena?

Describing the course of his reasoning, the creator of the theory of relativity Albert Einstein points to two arguments that testify to the generality of the principle of relativity.

This principle is implemented with great precision in mechanics, and therefore it was hoped that it would prove correct in electrodynamics.

If inertial systems are inequitable to describe the phenomena of nature, then it is reasonable to assume that the laws of nature are most simply described in only one inertial system. For example, in a reference system related to a moving wagon, mechanical processes would be described more complicated than in a system related to the railway track. Even more striking is the Earth's motion around the Sun at a speed of 30 kilometers per second. If the principle of relativity were not fulfilled in this case, then the laws of motion of bodies would depend on the direction and spatial orientation of the Earth. Nothing similar, ie physical inequality of different directions, was found. However, there is a supposed incompatibility of the principle of relativity with the well-established principle of the constancy of the speed of light in the void (300,000 km / s).

The dilemma arises: the rejection of either the principle of the constancy of the speed of light or the principle of relativity. The first principle is set so precisely and unequivocally that the refusal of it would be clearly unjustified and, moreover, connected with the excessive complication of the description of the processes of nature. Equally difficult are the challenges to the principle of relativity in the field of electromagnetic processes.

Let's turn to the imaginary experiment. Suppose that a rail car with velocity v is moving along the rails, in the direction of motion of which a light beam with velocity s is sent. The process of the propagation of light, like any physical process, is determined by some reference system. In our example, such a system would be expensive. The question is, what will be the speed of light relative to the moving car? It is easy to calculate that it is equal to w = c-v, ie the difference in the speed of light in relation to the lane of the road and to the wagon. It turns out that it is less than its constant value, which contradicts the principle of relativity, according to which physical processes occur equally in all inertial frames of reference, such as a railway web and a uniformly straight, moving wagon. However, this contradiction is supposed, because in fact the speed of light does not depend on whether the light source is moving or resting. In fact, as A. Einstein showed:

The law of propagation of light and the principle of relativity are compatible. And this position forms the basis of a special theory of relativity.

The supposed contradiction of the principle of relativity of the law of constancy of the speed of light arises because classical mechanics, according to Einstein, relied "on two unjustified hypotheses":

- the length of time between two events does not depend on the state of motion of the body of the reference.