Recent discoveries in astronomy, especially those made with data collected by satellites such as the Cosmic Background Explorer and the Hubble Space Telescope, have brought the science of cosmology to the forefront of public interest. These new observations suggest the tantalizing possibility that the solutions to some of history's most elusive mysteries might be found in the near future, making modern cosmology a topic that holds special interest for scientists and nonscientists alike. Foundations of Modern Cosmology provides a highly accessible, thorough, and descriptive introduction to the historical development of and the physical basis for the modern big bang theory. This new textbook is ideal for electives that follow traditional introductory astronomy courses. It is intended to fill the gap between the many popular-level books, which can generally provide only a superficial treatment of the subject, and the advanced texts intended for students with strong backgrounds in physics and mathematics. The text is self-contained, appropriate for a one-semester course, and designed to be understandable to students with a grasp of elementary algebra. Emphasis is given to the scientific framework for cosmology, particularly the basic concepts of physics that underlie modern theories of relativity and cosmology; the importance of data and observations is stressed throughout. The text is divided into five major sections: historical background, a review of basic physics and astronomy, relativity, fundamental big bang theory, and current research areas, including structure formation, inflation, and quantum cosmology. Review questions, key terms, and an extensive glossary provide students with helpful study aids. In addition, the authors' website (http://astsun.astro.virginia.edu/~jh8h/Foundations) offers a wealth of supplemental information, including additional questions, references to other sources, and color NASA photographs.