What is the composition and structure of the Earth's atmosphere? Why is\nit as warm as it is, and how did it form? These are the questions for\ntoday's lecture. The Earth's atmosphere is a complex, dynamic, and\nevolving system. We will discuss the composition and structure of the\natomsphere, the nature of the different thermal layers, the Greenhouse\nEffect, and the Primordial Atmosphere and atmospheric evolution. This\nwill give us a basis for comparison when we begin to examine other\nplanetary atmospheres in future lectures. Recorded 2006 Nov 1 in 100\nStillman Hall on the Columbus campus of The Ohio State University.