What is a planet? Is Pluto a planet? This lecture traces the debate on

the nature of what it means to be a planet by taking an historical approach,

looking at how the question has arisen with the discovery of the asteroids and

later Pluto and the Kuiper Belt. Many of the issued raised at the 2006

IAU General Assembly meeting were raised two centuries before after the

discovery of Ceres and Pallas. We will end with the new definition of a

planet, and why Pluto is better understood as a Dwarf Planet, among the

two largest objects of the class of small icy bodies of the outer solar

system, than as the smallest of the planets. Recorded 2006 Nov 30 in

100 Stillman Hall on the Columbus campus of The Ohio State University.