126 Arguments

Today’s birthday boy unites two of the main themes of this blog. On the one side I have often written about the unfair judgement of Catholic, and in particular Jesuit, contributions to science in the Early Modern Period, fighting against the widely held opinion that they contributed nothing and only tried to block scientific progress on religious grounds. On the other hand I have posted prominently on the mistaken belief that the choice of astronomical systems in the Early Modern Period was a straight two-way fight between Ptolemaic geocentrism and Copernican heliocentrism. The Jesuit scientist Giovanni Battista Riccioli who was born on 17^th April 1598 amongst his diverse scientific activities provided one of the best contemporary discussions of the cosmological /astronomical situations in his Almagestum novum from 1651.

Frontispiece of Riccioli’s 1651 New Almagest. Source: Wikimedia Commons

In this landmark publication in the history of astronomy he provides a list of 126 arguments pro and contra heliocentricity. Unfortunately this major work has been cruelly neglected in the earlier Whig history version of the history of science and never translated into English or any other modern language. My Internet friend Professor Christopher Graney who is an expert on the technical aspects of the early use of the telescope in astronomy has translated Riccioli’s list into English. I will let Chris introduce his own paper, which can be read here:

126 Arguments Concerning the Motion of the Earth, as presented by Giovanni Battista Riccioli in his 1651 Almagestum Novum

Abstract: In 1651 the Italian astronomer Giovanni Battista Riccioli published within his Almagestum Novum, a massive 1500 page treatise on astronomy, a discussion of 126 arguments for and against the Copernican hypothesis (49 for, 77 against). A synopsis of each argument is presented here, with discussion and analysis. Seen through Riccioli’s 126 arguments, the debate over the Copernican hypothesis appears dynamic and indeed similar to more modern scientific debates. Both sides present good arguments as point and counter-point. Religious arguments play a minor role in the debate; careful, reproducible experiments a major role. To Riccioli, the anti-Copernican arguments carry the greater weight, on the basis of a few key arguments against which the Copernicans have no good response. These include arguments based on telescopic observations of stars, and on the apparent absence of what today would be called “Coriolis Effect” phenomena; both have been overlooked by the historica!
 l record (which paints a picture of the 126 arguments that little resembles them). Given the available scientific knowledge in 1651, a geo-heliocentric hypothesis clearly had real strength, but Riccioli presents it as merely the “least absurd” available model – perhaps comparable to the Standard Model in particle physics today – and not as a fully coherent theory. Riccioli’s work sheds light on a fascinating piece of the history of astronomy, and highlights the competence of scientists of his time.