Are humans the only sentient beings in the universe? What is the likelihood that others exist in the cosmos? Can they visit or communicate with earth? Where are they? This seminar examines the last fifty years of the scientific search for intelligent life off the earth. The occurrence of intelligence on a planet depends on astrophysical, biological, and environmental factors. Students investigate these factors and attempt to estimate the number of civilizations within the galaxy. The seminar also examines the view that humans are truly the only intelligent life in the galaxy based on the lack of extraterrestrial artifacts within the solar system. Affiliate department: Physics.