TABLE OF CONTENTS This is the name of a science that became part of the physics at the beginning of the 20th century. Quantum mechanics is understood here as a theory for investigating the laws of motion of microparticles at velocities much lower than the velocity of light. These laws work basically on atomic scales of distances, but in some cases they also hold in the macroworld. We can mention several quantum phenomena besides superconductivity that can be observed without any magnifying devices, namely, laser light, magnetic ordering of atoms in a ferromagnetic material, etc. Although this science is now completely developed, its laws have not yet become customary for people. It is perhaps for this reason that they are almost ignored in school. And, conversely, the laws remain unwanted perhaps because they are not studied in school.
But an account of superconductivity should necessarily start in the realm of quantum mechanics. It is indispensable because the phenomenon of superconductivity itself is essentially quantum and it could not be understood until the construction of quantum mechanics was accomplished.
To make the mechanism of superconductivity visual, we shall consider the behavior of electrons in crystals. If the particles obey the laws of classical mechanics, it would be convenient to treat them like billiard balls. A billiard ball on a billiard table moves with a certain velocity. We are accustomed to the fact that its position, velocity, and energy can be arbitrary and, at any rate, they do not depend on the size...
