About a week ago I finished reading Bob Westman's monumental book The Copernican Question. The book is jam-packed with scholarship and was very thought-provoking. I could write a lot about it, but I don't have time. I just want to jot down the two major takeaways I got from reading Westman's book.
The first has to do with how important astrology was in the development of Copernican astronomy. These days we tend to think of astronomy as the supremely UNpractical science. Astronomy is the poster child of "fundamental science". Modern astronomy is all about understanding the cosmos, not building a better mousetrap (although NASA will always claim that the space program helps us develop new technologies, and some folks still dream of human colonies on Mars, etc). But back in the 16th century there was a practical side to astronomy. Partly this had to do with basic issues of seasonal change, which has to do with the apparent motions of the Sun and can be well understood with the good old Celestial Sphere model. But another practical aspect to astronomy in that age was astrological prognostication, which intimately involved the motion and ORDER of the planets.
Westman points out that Copernicus' work came at a time when astrology was under attack, particularly by Pico de Mirandola. Pico's criticisms were many, but among them he noted that astronomical predictions were not of sufficient accuracy to allow for accurate astrological prognostication. He also noted that astronomers weren't even certain of the ordering of the planets, or how far they lay from Earth. Westman suggests that Copernicus' De Revolutionibus can be seen as a response to these ASTRONOMICAL aspects of Pico's attack on astrology. So it may be the case that Copernican astronomy was an attempt to put astrology on surer footing.
The subsequent development of Copernican astronomy was also closely tied to astrology. Some astronomers who favored Copernicus' ideas disavowed astrology (Maestlin), some practiced astrology but did not really write much about it (Galileo), and some saw Copernican astronomy as the foundation for a reform of astrological practice (Kepler). But any attempt to reform astronomy could not, in that day, completely ignore the practical applications of astronomy in the form of astrology.
The other major thing I learned from Westman's book is just how divergent the early "Copernicans" were in their views. So much so that Westman claims the term "Copernican" doesn't even make sense if applied to these people as a group. Although these people may have shared a commitment to a model of the solar system in which the Sun was stationary near the center, they diverged on nearly every other question about astronomy. Some believed in a finite universe (Kepler) some believed in an infinite universe filled with populated worlds (Bruno). Some thought physics should form the basis of a reformed astronomy (Kepler), some thought astronomy could be used to motivate a reformation of physics (Galileo), and some thought physics and astronomy should be kept entirely separate (Maestlin). Some never even clearly stated whether they thought the Earth orbited the Sun or not (Gilbert).
This second lesson speaks to me because of some recent experiences I have had in trying to reform something. The opponents of reform have a unity of vision that is lacking in the proponents of reform. Those who oppose reform are armed not only with criticisms of the reform effort, but also with a solidarity in support of the existing situation. What we have is good, and here is why your suggested change is bad. On the other hand, the proponents of reform often want reform for a host of divergent reasons. They may have completely different criticisms of the status quo. They may be excited about totally different parts of the proposal for reform. In short, they are much less unified than the supporters of the status quo. I think this is a big reason why change is so hard. And maybe that's the way it should be.
Thankfully, though, it is possible for divergent views to coalesce behind a a really strong proposal for reform. And so Copernican astronomy (as reconceived by Kepler and again by Newton) ultimately prevailed.
This is from Swerdlow's review in Perspectives on Science: Beneath the appearance of erudition, the gravity of rumination, the plethora of citation, errors of fact and of understanding, of translation and of paraphrase, of commission and of omission, only touched upon here, are so innumerable that it could take as many pages as Professor Westman has written to explain and correct them. His word, his snippets of sources, cannot be taken on trust; it is necessary to read every original source to determine whether he is correct or incorrect, whether he has understood or read what he cites. No one but the author can be expected to do that, and it does not appear that he has done so or can do so. Trust once lost is difªcult to recover."
ReplyDeleteThanks for the comment. I'll have to read Swerdlow's full review. He is certainly much more of an expert than am I! But it may be that the two themes I mentioned in my post would still hold up under scrutiny. One of them, the fact that the early Copernicans did not all agree with each other, was something I really already knew. I just had never really thought about it. But I'm familiar enough with the work of Copernicus, Rheticus, Bruno, Digges, Kepler, and Galileo to know that they had some very different ideas about certain topics. I don't know as much about Maestlin or Gilbert or some of the others, but I doubt that changes the overall idea: those who argue for major change do so for a host of different reasons, while those who argue for the status quo often present a more unified front.
DeleteThe role of astrology may very well be exaggerated by Westman. I'm in no position to judge that. But there is no denying the importance of astrology generally in that culture, nor the fact that astrology was of importance to a few of the major players (Kepler is an obvious example). In claiming that Copernicus was motivated to reform astronomy to answer Pico's criticism of astrology, Westman uses lots of plausibility arguments, which are a bit weak. But if one expands out from Copernicus (even only as far as Rheticus) then there is solid evidence of an important role for astrology in the "Copernican Revolution".