Modern cosmology is a topic that holds special interest for the scientist and nonscientist alike. This textbook covers the historical development and physical basis for the modern big bang theory of cosmology, and is intended to fill the gap between the many popular-level books which present cosmology in a superficial manner, or which emphasize the esoteric at the expense of the basic, and the advanced texts intended for readers with strong backgrounds in physics and mathematics. The book is self-contained, appropriate for an ancillary course, and designed to be easily accessible to anyone with a grasp of elementary algebra. Sufficient qualitative and quantitative information is presented to provide the student with a firm understanding of the basic physics that makes up the foundations of the framework for cosmology and the importance of data and observations. The text is divided into five major sections, covering the historical background, a review of the basic physics and astronomy, relativity, basic big bang theory, and current research areas including structure formation, inflation, and quantum cosmology. Review questions, key terms and an extensive glossary should make this an excellent study aid for students.