Engineering Physics Annotation << Back Mechanical Structure of Universe. Spin Aphonin V.V. The electron spin has no rational explanation in modern physics. The proposed paper provides an explanation of spin experiments, which is based on the idea of an electron as a vortex ring in the world medium (ether). The most surprising is the Stern-Gerlach experiment, which can only be explained on the basis of the radical statement that the spin of a free electron is zero. Another statement is based on this conclusion: a particle called a "neutrino" does not exist. Most of the work is devoted to outlining the basics of the theory, since explanations are incomprehensible without understanding the basics. Keywords: spin, electron, experiment, theories. DOI: 10.25791/infizik.8.2025.1498 Pp. 37-62.