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Setting Aside All Authority: Giovanni Battista Riccioli and the Science against Copernicus in the Age of Galileo
Setting Aside All Authority is an important account and analysis of seventeenth-century scientific arguments against the Copernican system. Christopher M. Graney challenges the long-standing ideas that opponents of the heliocentric ideas of Copernicus and Galileo were primarily motivated by religion or devotion to an outdated intellectual tradition, and that they were in continual retreat in the face of telescopic discoveries. Graney calls on newly translated works by anti-Copernican writers of the time to demonstrate that science, not religion, played an important, and arguably predominant, role in the opposition to the Copernican system. Anti-Copernicans, building on the work of the Danish astronomer Tycho Brahe, were in fact able to build an increasingly strong scientific case against the heliocentric system at least through the middle of the seventeenth century, several decades after the advent of the telescope. The scientific case reached its apogee, Graney argues, in the 1651 New Almagest of the Italian Jesuit astronomer Giovanni Battista Riccioli, who used detailed telescopic observations of stars to construct a powerful scientific argument against Copernicus. Setting Aside All Authority includes the first English translation of Monsignor Francesco Ingoli’s essay to Galileo (disputing the Copernican system on the eve of the Inquisition’s condemnation of it in 1616) and excerpts from Riccioli's reports regarding his experiments with falling bodies.
288 pages, Paperback
First published January 1, 2015
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June 26, 2021
The popular story of the debate over Copernicanism is usually told as one of religious dogma vs. science. This book presents an opposed viewpoint. In fact, there were serious scientific challenges to the Copernican theory, and in favor of a hybrid geocentric model (Tycho’s), through the time of Galileo.
Christopher Graney focuses his book on Giovanni Battista Riccioli’s New Almagest, published in 1651. The book is in part a defense of Riccioli against misrepresentations of his treatment of Copernicanism, misrepresentations that support the popular story. But Riccioli painstakingly examined the arguments for and against Copericanism, taking as the leading alternative not the Ptolemaic system, but Tycho’s hybrid system, with the sun, moon, and stars orbiting the earth, and the remaining planets orbiting the sun.
The strongest argument against the Copernican system that is discussed by Riccioli is far from a religious argument. It concerns annual parallax and the sizes of stars, and is drawn from Tycho.
Here is an outline of the argument. If Copernicus’s model were true, and the stars sufficiently close, we should be able to measure changes in the positions of stars as seen from the earth at 6 month intervals. When we are on one side of the sun, looking at a star against the background of other stars, its position with respect to those stars (and other points of reference) should differ from its position when we are looking at the same star from the opposite side of the sun. The difference in the star’s position would be a measure of annual parallax, its change in position at opposite sides of the earth’s orbit around the sun.
In fact, measurements taken at the time, including especially those of Tycho, the greatest observational astronomer of the time, revealed no such parallax. Given the lack of measurable annual parallax, the stars must be at a greater distance than previously thought for the Copernican picture to be valid.
Revised distances to the stars wouldn’t make Copernicanism untenable. But many if not most leading observers of the time, including Tycho, Galileo, and Marius, saw, when they looked at the stars, either with the naked eye or with a telescope in the case of Galileo and Marius, a spherical image of discernible size. Estimates of the sizes of stars differed with different observers. But all estimates of the stars’ apparent sizes, coupled with the distance for the stars required to produce no measurable annual parallax, led to a conclusion that the stars must be unbelievably large, on the order of hundreds, thousands, or even millions of times the size of the sun. As astronomer Peter Cruger wrote:
Indeed, if a tiny star had a visible breadth even of a mere 60th of a minute [one second], then according to the above hypothesis its true thickness would be more than nine times that of the Sun, and its volume 730 times greater. I therefore do not understand how the Pythagorean or Copernican Systema Mundi can survive.
In fact, the observations of stars’ sizes were illusory, and some observers suggested so. But no theory of light and optics at the time could explain them as illusory. So, at the time, Tycho’s theory had a distinct advantage in not implying annual parallax, with the earth maintaining a constant position with respect to the orbit of the stars around it.
Another point of contention was what we now call Coriolis effects. The physics of the time did support a notion of “common motion” by which objects on the earth retained the rotational motion of the earth (assuming such a motion) when launched or dropped from objects fixed to the earth. Thus an object dropped from a tower would fall at the foot of the tower rather than some distance from it, as the earth moved between the time it was dropped and the time it landed.
But if in fact the earth does rotate, points on the earth’s surface should rotate at different speeds depending on their latitude. The effect is now well-known, but at Ricciolli’s time, it was not. In fact, for reasons detailed in Graney’s book, it was not detectable, given the measuring instruments and other limitations of the time. Detectable Coriolis effects would have provided strong evidence for earth’s rotation, but were lacking.
None of this is to say that there were no scientific arguments favoring Copernicanism. Galileo countered some of the anti-Copernican arguments, although the star size problem itself was persistent until it could be demonstrated that apparent stellar diameters were illusory.
Some defenders of Copernicanism themselves appealed to religious argument, Phlips Lansbergen in particular appealing to the majesty of God to argue that the seemingly incredible sizes of the stars following from the anti-Copernican argument were in fact quite acceptable.
Many of the participants in the arguments were of course priests — Ricciolli himself was a Jesuit priest. They could well be motivated by defense of religious dogma, but the weightier arguments themselves are not religious ones.
I’m not an expert and have not read competing arguments against Graney’s. I’ve certainly grumbled at the popular accounts that cast the players in black and white terms, as pure-hearted scientists vs. religious dogmatists. Graney’s book certainly goes a long way to show why that picture may be seriously off-kilter.
It also provides some good fodder for thinking about how scientific theories succeed and fail. Here is a good case where there appear to have been good observational reasons for rejecting a theory that we now fully accept. To suppose that scientific observers and theorists of the time were "wrong" in supporting Tycho's theory is at least a bit ingenuous. By the same token, to suppose those observers and theorists, like Galileo, who supported Copernicanism at the time to have been "wrong" for persisting despite contrary evidence would also be ingenuous.
Christopher Graney focuses his book on Giovanni Battista Riccioli’s New Almagest, published in 1651. The book is in part a defense of Riccioli against misrepresentations of his treatment of Copernicanism, misrepresentations that support the popular story. But Riccioli painstakingly examined the arguments for and against Copericanism, taking as the leading alternative not the Ptolemaic system, but Tycho’s hybrid system, with the sun, moon, and stars orbiting the earth, and the remaining planets orbiting the sun.
The strongest argument against the Copernican system that is discussed by Riccioli is far from a religious argument. It concerns annual parallax and the sizes of stars, and is drawn from Tycho.
Here is an outline of the argument. If Copernicus’s model were true, and the stars sufficiently close, we should be able to measure changes in the positions of stars as seen from the earth at 6 month intervals. When we are on one side of the sun, looking at a star against the background of other stars, its position with respect to those stars (and other points of reference) should differ from its position when we are looking at the same star from the opposite side of the sun. The difference in the star’s position would be a measure of annual parallax, its change in position at opposite sides of the earth’s orbit around the sun.
In fact, measurements taken at the time, including especially those of Tycho, the greatest observational astronomer of the time, revealed no such parallax. Given the lack of measurable annual parallax, the stars must be at a greater distance than previously thought for the Copernican picture to be valid.
Revised distances to the stars wouldn’t make Copernicanism untenable. But many if not most leading observers of the time, including Tycho, Galileo, and Marius, saw, when they looked at the stars, either with the naked eye or with a telescope in the case of Galileo and Marius, a spherical image of discernible size. Estimates of the sizes of stars differed with different observers. But all estimates of the stars’ apparent sizes, coupled with the distance for the stars required to produce no measurable annual parallax, led to a conclusion that the stars must be unbelievably large, on the order of hundreds, thousands, or even millions of times the size of the sun. As astronomer Peter Cruger wrote:
Indeed, if a tiny star had a visible breadth even of a mere 60th of a minute [one second], then according to the above hypothesis its true thickness would be more than nine times that of the Sun, and its volume 730 times greater. I therefore do not understand how the Pythagorean or Copernican Systema Mundi can survive.
In fact, the observations of stars’ sizes were illusory, and some observers suggested so. But no theory of light and optics at the time could explain them as illusory. So, at the time, Tycho’s theory had a distinct advantage in not implying annual parallax, with the earth maintaining a constant position with respect to the orbit of the stars around it.
Another point of contention was what we now call Coriolis effects. The physics of the time did support a notion of “common motion” by which objects on the earth retained the rotational motion of the earth (assuming such a motion) when launched or dropped from objects fixed to the earth. Thus an object dropped from a tower would fall at the foot of the tower rather than some distance from it, as the earth moved between the time it was dropped and the time it landed.
But if in fact the earth does rotate, points on the earth’s surface should rotate at different speeds depending on their latitude. The effect is now well-known, but at Ricciolli’s time, it was not. In fact, for reasons detailed in Graney’s book, it was not detectable, given the measuring instruments and other limitations of the time. Detectable Coriolis effects would have provided strong evidence for earth’s rotation, but were lacking.
None of this is to say that there were no scientific arguments favoring Copernicanism. Galileo countered some of the anti-Copernican arguments, although the star size problem itself was persistent until it could be demonstrated that apparent stellar diameters were illusory.
Some defenders of Copernicanism themselves appealed to religious argument, Phlips Lansbergen in particular appealing to the majesty of God to argue that the seemingly incredible sizes of the stars following from the anti-Copernican argument were in fact quite acceptable.
Many of the participants in the arguments were of course priests — Ricciolli himself was a Jesuit priest. They could well be motivated by defense of religious dogma, but the weightier arguments themselves are not religious ones.
I’m not an expert and have not read competing arguments against Graney’s. I’ve certainly grumbled at the popular accounts that cast the players in black and white terms, as pure-hearted scientists vs. religious dogmatists. Graney’s book certainly goes a long way to show why that picture may be seriously off-kilter.
It also provides some good fodder for thinking about how scientific theories succeed and fail. Here is a good case where there appear to have been good observational reasons for rejecting a theory that we now fully accept. To suppose that scientific observers and theorists of the time were "wrong" in supporting Tycho's theory is at least a bit ingenuous. By the same token, to suppose those observers and theorists, like Galileo, who supported Copernicanism at the time to have been "wrong" for persisting despite contrary evidence would also be ingenuous.
October 20, 2022
One of the most enjoyable and interesting recent books on the history of the transition to heliocentricity. Chris Graney has retranslated and reexamined the "Almagestum Novum", a 1651 encyclopedic compendium on the then "state of the art" of astronomy and physical sciences, written by Jesuit Giovan Battista Riccioli. The core of the book is 126 carefully stated "propositions" pro or against Copernicus's planetary system. For each of these Riccioli lays out both sides of the argument in a very neutral manner, before giving his own opinion.
The most surprising thing for anyone used to the commonly held view that all Copernicus's enemies in the XVII century were either religious zealots or reactionary Aristotelians is that of these 126 arguments, only two are religious (and are not even those we usually hear when Galileo's process is discussed). For Riccioli the "silver bullets" making Tycho Brahe0s geo-heliocentric system preferable to Copernicus are the detection of the so-called Airy disks (the apparent disk size of stars when seen with XVI century telescopes) and the lack of detection of the Coriolis effect due to earth rotation.
Both arguments were due to the lack of technology sensitive enough to resolve stars as points and detect Coriolis, but taken in the context of XVI-century technology they are perfectly reasonable!
Another amazing insight is how Copernicans at the time resorted in their turn to arguments about religion or aesthetics to justify their views. So it was not science vs superstition, but a two-way match between different scientific and philosophical views where religion was just one of the elements used by both sides.
It's a great read for anyone interested in the history of science.
The most surprising thing for anyone used to the commonly held view that all Copernicus's enemies in the XVII century were either religious zealots or reactionary Aristotelians is that of these 126 arguments, only two are religious (and are not even those we usually hear when Galileo's process is discussed). For Riccioli the "silver bullets" making Tycho Brahe0s geo-heliocentric system preferable to Copernicus are the detection of the so-called Airy disks (the apparent disk size of stars when seen with XVI century telescopes) and the lack of detection of the Coriolis effect due to earth rotation.
Both arguments were due to the lack of technology sensitive enough to resolve stars as points and detect Coriolis, but taken in the context of XVI-century technology they are perfectly reasonable!
Another amazing insight is how Copernicans at the time resorted in their turn to arguments about religion or aesthetics to justify their views. So it was not science vs superstition, but a two-way match between different scientific and philosophical views where religion was just one of the elements used by both sides.
It's a great read for anyone interested in the history of science.
September 27, 2021
I read this book cover-to-cover in basically 24 hours, I loved it that much.
The author reexaminess the debates regarding universal models - Ptolemiac, Copernican, Galilean, Tychonic, etc. Contrary to popular opinion, this was not science v. religion, it was science v. science - and up until the 1700s, science actually seemed to be on the non-heliocentric side. This was a really interesting exploration of how the scientific debate actually existed historically, rather than as it was imagined to be. I highly recommend this for anyone interested in the history of science in general or in this astronomical model debate in particular.
The author reexaminess the debates regarding universal models - Ptolemiac, Copernican, Galilean, Tychonic, etc. Contrary to popular opinion, this was not science v. religion, it was science v. science - and up until the 1700s, science actually seemed to be on the non-heliocentric side. This was a really interesting exploration of how the scientific debate actually existed historically, rather than as it was imagined to be. I highly recommend this for anyone interested in the history of science in general or in this astronomical model debate in particular.
August 9, 2021
Yes! This is the book that anyone who is trying to understand the renaissance helio/geo-centric debate needs to read. Not only is it the most accessible guide to the science around Galileo's trial, it also neatly describes the time scales for actually solving the problems described by both the Copernicans and Tychoneans.
I couldn't recommend this read more.
I couldn't recommend this read more.
February 9, 2021
I guess I'm tired of old dry science books. This one was ok. I found myself just reading the words to get through it. Comparing it to History of Warfare made it more interesting. To compare and contrast these books helps one learn better how science works. The struggle to align what is observed with what is true.
Displaying 1 - 5 of 5 reviews