This book is written to bring out the physical content behind the mathematical formulae.This text describes the gravitational interactions and evolution of astronomical systems on all scales, from small groups of stars through galaxies and clusters of galaxies to the Universe itself. It is written to bring out the physical content behind the mathematical formulae, and contains a number of exercises and suggestions for research topics.This text describes the gravitational interactions and evolution of astronomical systems on all scales, from small groups of stars through galaxies and clusters of galaxies to the Universe itself. It is written to bring out the physical content behind the mathematical formulae, and contains a number of exercises and suggestions for research topics.This text describes the gravitational interactions and evolution of astronomical systems on all scales, from small groups of stars through galaxies and clusters of galaxies to the Universe itself. In a rapidly developing area of astronomy, it is the first comprehensive treatise on the subject to be published since the early 1960s. Concentrating on the basic physics, at a graduate student level, it also develops many astronomical applications in considerable detail. The book is self-contained. Most results are derived from preceding ones in a straightforward way. It is written to bring out the physical content behind the mathematical formulae, and contains a number of exercises and suggestions for research topics. Bibliographies with nearly 300 selected references provide gateways into the literature.Preface; Introduction; 1. Idealized homogeneous systems - basic ideas and gentle relaxation; 2. Infnite inhomogeneous systems - galaxy clustering; 3. Finite spherical systems - cluster of galaxies, galactic nuclei, globular clusters; 4. Finite flattered systems - galaxies; Index.' & the author achieves a ery nice balance between mathematics, physics and astronomy as well as between the reality and lC%