This introductory astronomy text has become a new standard for full-year courses. The unifying theme is evolution--of astronomical bodies and of the universe as a whole. The opening chapters survey cosmologies from ancient times forward. Succeeding chapters in the Second Edition have been rearranged to follow the popular order of topics covering, respectively, the nature and evolution of the planets, the stars, galaxies and the universe. There is a new chapter on gravitation and energy. The chapter on Einstein and relativity appears later in the text to conform to the standard syllabus. Physical phenomena are described using algebraic, trigonometric and geometric arguments.