In the generation following Copernicus, the question of planetary

motions was picked up by two remarkable astronomers: Tycho Brahe, the

brilliant Danish astronomer whose precise measurements of the planets

represented the highest expression of pre-telescope astronomy, and

Johannes Kepler, the brilliant and tormented German mathematician who

used Tycho's data to derive his three laws of planetary motion. These

laws were to sweep away the vast complex machinery of epicycles, and

provide a geometric description of planetary motions that set the stage

for their eventual physical explanation by Isaac Newton a generation

later. Recorded 2006 Oct 11 in 100 Stillman Hall on the Columbus campus

of The Ohio State University.