ABSTRACT
Fine-structure constant α = e2/ћc ≈ 1/137 (e-electron charge, ћ-Planck constant, c-speed of light) characterizes intensity of electromagnetic interaction of elementary particles. In quantum electrodynamics, electrically charged particles interact due to exchange of virtual photons. Fine-structure constant arises as a nondimensional parameter, which characterizes intensity of this interaction. Fine-structure constant is one of values, which physicists have been measuring with increasing accuracy for many decades. This constant determines energy levels of electrons in atoms exactly. The fi ne structure of these levels emerges due to electric attraction of electrons to the nucleus and electromagnetic interactions between electrons.
