Thursday, April 21, 2011

The Book Galileo Was Supposed to Write

The Renaissance Mathematicus cites a paper by Prof. Christoper Graney:
In his Almagestum novum from 1651, the Jesuit scientist Giovanni Battista Riccioli "provides a list of 126 arguments pro and contra heliocentricity (49 for, 77 against). ... 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 historical record... 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."
Recall that Pope Urban had encouraged Galileo to write a book comparing the systems of the world, listing the strengths and weaknesses of each.  What he got was an advocacy for the Copernican system that ignored some vital objections and a satire of a Ptolemaic model which had already been abandoned by Aristotelians.  The phases of Venus had decisively falsified the basic Ptolemaic model, but were equally well explained by the Copernican and the Tychonic models.  The Tychonic model (and the related Ursine model) were the most popular among scientists by the time Galileo wrote the Dialogue, but he does not so much as mention them, let alone refute them.  As it turned out, it was the Keplerian model, with its elliptical orbits, that turned out to be correct.  Riccioli's book is more like what the Pope had in mind.  Not until there was empirical evidence to choose one model over the other could you say it was fact; and that evidence was not forthcoming until the late 1700s and early 1800s. 

1 comment:

  1. The more I learn of the actual historical facts of the case (and the era), the more I think it fitting that the 'Science!' worshippers have latched upon Galileo as their patron saint.


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