# The principle of relativity

entered Galileo relativity principle is primarily distributed in the mechanical system.He stated that no mechanical experiments not possible to determine whether the system is at rest or is moving uniformly.In other words, when performing a different inertial coordinate systems (with existing inertial forces) of the same mechanical tests, the results will be similar.

Galileo noticed that the mechanics of movement, but rather collision, bumps, flying shells and other phenomena gives the same results: in uniform rectilinear motion laboratories, and at rest.

Explain the mechanical principle of relativity is possible in the following example.Let us assume that one vehicle drives near the other, without any shocks, that is, at a constant rate, evenly.And everything is shrouded in dense fog so thick that a number can not see anything at all.The question is this: can the passengers in the vehicle to determine which of them moves?Can you help them, making experiments on the mechanics?

It turns out that in this case, passengers can observe only relative motion.Despite the fact that all traffic laws and rules of vector addition developed by moving laboratories, they are not detected, "do not feel" on his no influence of this movement.The principle of relativity also indicates that no mechanical experiments failed to detect the rectilinear uniform motion of the reference frame relative to the stars and the sun.However, the accelerated motion of the reference system relative to the stars and the sun has an effect on the results of experiments.

Galilean relativity principle in mechanics, deserves special attention.None of the Galilean system can not give preference in principle, despite the fact that in practical terms it is advisable to consider a particular reference frame preferred depending on the situation.

So, for passengers traveling in the vehicle coordinate system, which is connected to the machine frame of reference will be more natural than that, which is connected to the road.And the latter system, in turn, will be more convenient for a person to observe the movement of the car, standing beside the road.Various systems have Galilean equivalence principle, which is expressed in the fact that the transition between the systems are essentially the same formula, and variable serves only the relative speed.

This principle of relativity is considered from the point of view of kinematics, but such equivalence of the various systems is also characteristic of the speakers.This is a classic principle of relativity.

There is also a special principle, which applies to any physical phenomenon, not only in mechanical movement.Its essence lies in the fact that for all coordinate systems which move relative to each other uniformly and straight, all physical phenomena occur equally, and any physical tests give similar results.

This provision is defined as a special principle of relativity, as it relates to special cases of rectilinear uniform motion.In this case, all the laws look the same for both coordinate systems related to the stars, and for any other systems that move uniformly in a straight line relative to the stars.

There is also a more general principle, which covers cases of coordinate systems with rapid movement.He is known as the general principle of relativity.