The book of the famous Soviet astronomer Professor N.I. Idelson consists of separate historical and scientific essays-sketches, which in a fascinating form tell about the classical theories of celestial mechanics, the theory of gravity, the theory of the figure of the Earth, the theory of movements of celestial bodies, as well as about the creators of science. The combination of a fascinating form of presentation with deep penetration into the essence of the question makes the book interesting both to specialists - mechanics and astronomers, and to a wide range of readers.