The Earth's eccentricity in Kepler's refutation of the Tychonic approach to the problem of Mars

Abstract

In this paper I explain Kepler's procedure for refuting the Ptolemaic-Tychonic approach to the problem of Mars, by using latitudinal observations at Mars's opposition, from Chapter 19 of the Astronomia Nova. This critique is fundamental to his reformation of the foundations of astronomy with his first two laws. Moreover, as I argue, the strategy he follows is deeply rooted in certain rhetorical considerations that he employed during the composition of his work.