(Schmidt hypothesis), in astronomy, a cosmogonic hypothesis the main part of which is the assumption that the planets were formed through the accretion of cold solid bodies of different sizes revolving around the sun. The hypothesis was proposed in 1943 by O. Iu. Shmidt (Schmidt) on the basis of a critical study of the history of planetary cosmogony and an analysis of the regularities underlying planetary motions.
Shmidt was the first to explain the causes of the direct axial rotation of planets (that is, rotation in the same direction as the revolution around the sun) and to pave the way for an explanation of the regularity underlying the distances of the planets from the sun. The assumption that the earth and related planets were formed through the accumulation of solid bodies leads to the conclusion that they originally were in a relatively cold state. This conclusion necessitated a reexamination of many concepts of the geophysical, geological, and geochemical history of the earth. Many aspects of the process of the accumulation and further development of the planets have been studied by Shmidt’s colleagues and proponents on the basis of his hypothesis.
To explain the distribution of angular momentum between the sun and planets, Shmidt advanced the hypothesis that the swarm of bodies from which the planets accumulated was captured by the sun from interstellar space. However, after the 1950 studies of L. E. Gurevich and A. I. Lebedinskii, who showed that the bodies from which the planets accumulated must have been formed in the vicinity of the sun, the idea of the capture of a cluster was replaced by the hypothesis that the sun trapped part of the gas-dust matter of an interstellar nebula.
The part of the Shmidt hypothesis that pertains to the accumulation of planets from cold solid bodies, which has won broad recognition, is often called Shmidt’s theory; in this case, the term “Shmidt hypothesis” is reserved for the assumption that the sun captured matter to construct the planets, an assumption that has yet to be proved and that is rejected by many investigators.
B. IU. LEVIN