Lecture, three hours; discussion, one hour. Requisites: courses 115, 117. Designed for upper-division Astrophysics and Physics majors. In-depth exploration of Big Bang model for universe. Examination of what expanding universe is, how cosmologists measure its properties, and how universe has changed since Big Bang. Topics include cosmic expansion, dark matter, inflation, cosmic microwave background, Big Bang nucleosynthesis, and structure formation. P/NP or letter grading.