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Session 24 - HAD II.
Oral session, Monday, January 13
The paper discusses the historical background to Johann Kepler's 1609 magnum opus, the Astronomia Nova, in which the astronomer introduces his first two laws of planetary motion; and his 1627 Rudolphine Tables, wherein he presents a system for computing ephemerides based on the new Keplerian physical astronomy. Since the predictions of the latter work buttress the veracity of the former, a comparison of the tabular prophecies with recorded observations of Kepler's successors allows us to investigate the seventeenth-century reception of his ideas.
The paper analyzes the Rudolphine Tables' algorithm for the computation of planetary positions and then applies the method to the determination of the position of Mercury on 7 November 1631 and the position of Venus on 24 November 1639, when Pierre Gassendi and Jeremiah Horrox, respectively, witnessed the solar transits of these planets. The paper then contrasts the computed results with Gassendi's and Horrox's observations and with the planetary positions deduced by a modern routine, and describes how the success of Kepler's predictions provided a powerful impetus for the adoption of Keplerian ellipses and the law of areas.
Program listing for Monday