The geological revolution revealed that the Earth is of great antiquity
and yet has a history we can read in the land. We will discuss ideas
of cyclic and linear time, historical versus physical age estimates,
the discovery of geological time, and
radiometric dating methods that give us our present estimate of
4.54+/-0.05 Gyr for the age of the Earth. Recorded live on 2009 Sep 30
in Room 1005 Smith Laboratory on the Columbus campus of The Ohio State
University.