Giovanni Battista Ricciolis Seventy-Seven Arguments Against the Motion of the Earth: An English Rendition of Almagestum Novum Part II, Book 9, Section 4, Chapter 34, Pages 472-7

In 1651 the Italian Jesuit Giovanni Battista Riccioli (1598-1671) published in his encyclopedic work on astronomy, the Almagestum Novum, 77 arguments against the Copernican movement of the Earth. These arguments are often mentioned in secondary sources, but a complete listing has not been readily available - thus one is provided here, in English. The 77 include interesting arguments from physics and astronomy that went on to become subjects of further investigation after the advent of Newtonian physics.

💡 Research Summary

This paper presents an English translation and analysis of the “Seventy-Seven Arguments Against the Motion of the Earth” compiled by the Italian Jesuit astronomer Giovanni Battista Riccioli in his 1651 monumental work, Almagestum Novum. While these arguments are frequently mentioned in historical scholarship, a complete listing has been largely inaccessible to modern readers. This work aims to fill that gap by providing a concise, tabular English rendition of the arguments from Part II, Book 9, Section 4, Chapter 34 of Riccioli’s text, along with the Copernican responses he recorded and the author’s own commentary.

The introduction contextualizes Riccioli’s work, noting that he was a respected astronomer of his time who produced what is considered the most comprehensive 17th-century analysis of the Earth’s mobility. The paper then addresses the contradictory perceptions of his 77 arguments: some historians dismiss them as religiously motivated, Aristotelian, and tedious, while others acknowledge Riccioli’s scientific rigor. The author challenges the former view by systematically presenting the arguments’ content.

The arguments are categorized into several types: those based on physical experiments with falling bodies (arguments #1-6), those concerning the effects of Earth’s rotation on projectile motion and falling bodies—anticipating the Coriolis effect (#6, etc.), philosophical arguments about the simplicity and economy of motion in the universe (#7, etc.), arguments from telescopic observations of stars, and others drawn from natural phenomena like wind and bird flight. Crucially, the author notes that only two of the 77 arguments are explicitly religious, and even these are minor.

Riccioli himself highlighted three categories as particularly powerful and unanswered by Copernicans: 1) arguments from simplicity and economy of motion, 2) arguments from the predicted effects of a rotating Earth on artillery and falling bodies, and 3) arguments from stellar observations (which forced Copernicans to invoke Divine Omnipotence to explain the stars’ telescopic disks). The paper emphasizes that the latter two were genuinely insoluble in the 17th century. Experimental confirmation of the Coriolis effect and a proper understanding of stellar images through telescopes were not achieved until the 19th century. This supports historian Owen Gingerich’s thesis that the acceptance of Copernicanism was driven not by contemporary observational “proofs” but by the coherent theoretical framework later provided by Newtonian physics.

In conclusion, the paper argues that Riccioli’s 77 arguments represent a serious scientific critique of Copernican theory from a pre-Newtonian perspective. Far from being a sterile or purely religious exercise, they identified genuine physical and astronomical puzzles that would later become subjects of fruitful scientific investigation. The translation makes this significant episode in the history of science more accessible and encourages a reevaluation of Riccioli’s role as a sophisticated participant in the scientific debates of his era.