Astronomical Images : System of the World according to Copernicus and Galileo

Pierre Gassendi

Astronomical Images

<p style='text-align: justify;'>Pierre Gassendi (1592-1655) was educated at Aix and Avignon, and became a priest in 1616. He learnt astronomy from Gaultier de la Valette, observed the transit of Mercury in 1631 (<i>Mercurius in sole visus</i>), and taught astronomy at the Collège Royal in Paris. He was fascinated by atomism as an alternative to Aristotelianism (<i>Syntagma philosophicum</i>), knew Nicolas Claude Fabri de Peiresc, Marin Mersenne and Isaac Beeckman, and was familiar with the works of Kepler, Galileo and Descartes. The <i>Institutio astronomica</i> is a textbook on astronomy in three books: the first book teaches elements of the spheres, the second the models (or '<i>theoria</i>') of the planets, and the third book discusses the 'systems' of Copernicus and Tycho Brahe. This image comes from the third book. Here, Gassendi presents the Ptolemaic, Copernican and Tychonic world systems in the context of a comprehensive history of astronomy in which, whilst praising Copernicus, he eventually defers to Holy Scripture and accepts the Tychonic system. Gassendi's portrayal of the planetary spheres of the Copernican system is close to that in Galileo's <i>Dialogo sopra i due massimi sistemi del mondo</i> (1632), though unlike Galileo he encloses them safely within the sphere of the fixed stars.</p>