QUANTUM-MECHANICAL THEORY
The physical theory, which describes phenomena in the world of elementary particles and systems, consisting of them, are called quantum mechanics. The vital difference of the quantum-mechanical way of describing of a state of a system from the method of the classical mechanics is: quantum mechanics helps the find only probability of discovery of the object in the given spatial region. To define simultaneously coordinates and velocity (or kinetic moment) of a particle in any moment of time is impossible in principle. Quantum mechanics gives a statistical description of states of microsystems, without using the notion of motion path, without definition of coordinates as time functions.