In order to outline possible future directions in galaxy research, this book wants to be a short stopover, a moment of self-reflection of the past century of achievements in this area. Since the pioneering years of galaxy research in the early 20th century, the research on galaxies has seen a relentless advance directly connected to the parallel exponential growth of new technologies. Through a series of interviews with distinguished astronomers the editors provide a snapshot of the achievements obtained in understanding galaxies. While many initial questions about their nature have been addressed, many are still open and require new efforts to achieve a solution. The discussions may reveal paradigms worthwhile revisiting. With the help of some of those scientists who have contributed to it, the editors sketch the history of this scientific journey and ask them for inspirations for future directions of galaxy research.

Dynamics of Stellar Systems focuses on the theoretical problems in stellar dynamics. The book first offers information on stellar dynamics, including historical development, fundamentals of synthetic method, and value of stellar dynamics. The text discusses the fundamental concepts of stellar statistics. Properties of univariate distribution functions; multivariate distribution functions; and statistical properties of stars are explained. The text then describes the elementary theory of galactic rotation and irregular forces in stellar systems. The text also tackles statistical stellar dynamics of neglecting encounters. Considerations include Boltzmann equation in curvilinear coordinates; importance of using one-valued integrals of the motion; and fundamental differential equation of stellar dynamics. The book also underscores the regular orbit of stars and dynamics of centroids. The text describes the dynamics of spherical stellar and rotating stellar systems. The theory of polytropic spheres; basic equations for spherical systems; masses and rotation of galaxies; and boundaries of galaxies are discussed. The text is highly recommended for readers interested in stellar dynamics.

Paul describes the rise of statistical cosmology and how it has set the stage for many of the most significant developments of twentieth-century astronomy.