The Copernican Revolution: Planetary Astronomy in the Development of Western Thought

A Flawed MasterpieceThis masterpiece was a 1956 case study for Thomas Kuhn. It was on a road that led him to his magnificent theory of scientific revolutions in 1962. All the important conceptions are here, anomaly, crisis, scientific community, and paradigm.The fatal flaw is in Kuhn’s claim about the nature of the crisis faced by the scientific community in the Renaissance. Crisis is an important conception for Kuhn. It meant that scientists could no longer accept the errors between observed locations of the planets and the predictions made by Ptolemy’s theory. For example, the Viennese astronomers Regiomontanus and Peurbach observed an error of 2 degrees for Mars in 1458. They also found the predicted eclipse of the moon happened one hour later than predicted. They found these errors grotesque.Kuhn thinks the increasing complexity of the Ptolemaic system sapped its accuracy. This does not fit the facts. Owen Gingerich in “Crisis versus Aesthetic in the Copernican Revolution” tested the claim. The predictions used to test it were in printed tabular form called ephemerides issued by various astronomers. These were compared with the actual positions of the planet Mars. Mars is the most difficult planet to predict for the Ptolemaics. The time span was 1270 to 1585. The tables were virtually identical theoretically. The degree of error was also uniform between them. Complexity did not cause inaccuracy. The errors came from something else.Ptolemy was wrong; Earth did indeed move and was not the center of the universe. It was a premise of Copernicus’ theory that it revolved about the sun and spun on its axis. To predict the location of the planet Mars in the sky, one had to not only know its orbit, but the Earth’s as well. Kuhn claims that this led to no improvement in predicting the planets’ locations in space and time. See page 169 of his text. This is curious, since it mathematically increases the quantitative power of the planetary theory. Was Kuhn correct or not?Gingerich’s article shows error data for Ptolemaic and Copernican ephemerides. The data sets are in powerful graphical form. They overlap one another in time for comparability. I found the Ptolemaics had a very similar variance in error of about 2.15 with a characteristic lobate error pattern. The Copernicans had a much lower variance of about 0.90 with an interesting dentate pattern. The range of error was much lower for them, too.Clearly, the astronomers of the Renaissance read Copernicus’ innovative textbook, found that it led to dramatically better results in prediction and adopted it, whether they agreed with its premises or not. One of its early readers was Michael Maestlin. Astronomy at that time was a required course for undergraduates. Tellingly, he used Ptolemaic theory for those classes. He used Copernicus’ text for the graduate program. History knows him as the mentor to Kepler. Their letters are precious.Finally, Kuhn is mistaken about the complexity of the mathematics of Copernicus. I can tell you it is no more difficult than a class in second year algebra and I encourage all to read it. There are very many insights in it not found in the secondary literature. Read it, know it, and love it. A full English translation by A. M. Duncan is available and recommended.Charles Pierce Wikman

It is a pity that the Amazon rating system is limited to only 5-stars. This book is, in my opinion, worth many more. I must admit that I hesitated getting this book for many years as I was misled by the sub-title "Planetary Astronomy in the Development of Western Thought". I believed this to be a thick and imponderable philosophical tome - it is not. The book is clearly written, and does not require that the reader have a mathematical, philosophical or astronomical background. The book describes the paradigm shift from an earth-centered universe to a sun-centered one. It thus begins with the astronomical beliefs of the ancient Greeks and shows the evolution of astronomy from this to that of Copernicus and then to Newton's explanation using his equations of gravity.I learned a lot from this book. For instance,1. I learned a bit about solar and celestial navigation.2. I never even realized that the seasons are of unequal length, now I do and I understand why.3. I now have a reasonable idea of the complexity of the Ptolemaic (earth-center) view of the cosmos and why it was believed for 2000 years. Kuhn does a great job of explaining and describing the essence of this very complex system.4. I now understand some of the influences that led Copernicus to believe that the Ptolemaic paradigm needed to be replaced. The reasons for this shift were many and complex, but are clearly stated.5. I always thought that the system developed by Copernicus was what we believe today, but now I realize that it was much more complex, but that while it was as complex as that of Ptolemy it was not more accurate in its predictions. I also see why some of the incorrect assumptions made by Copernicus led to this complexity and lack of accuracy.6. I clearly see why in spite of its complexity and lack of increased accuracy the Copernican paradigm gradually replaced the Ptolemaic paradigm, but not without overcoming a considerable amount of resistance.7. I understand the importance of the contributions of Tycho Brahe and Johannes Kepler to the ultimate dominance of the Copernican system.8. I learned how Johannes Kepler, Rene Descartes and Robert Hooke influenced the work of Isaac Newton and that Newton's laws of gravity were not a unique creation of his alone, although its complete mathematical formulation certainly was.These ideas in this book are presented in a very clear and very accessible manner. I now have to add this book to my short list of those that I think anyone who considers himself/herself well educated should be acquainted with.

I just started reading the book. It's in decent condition for a used book. Looks like it will be a good experience reading it.

This is a great review of astronomy prior to Copernicus and how astronomy then changed. The old Aristotle/Ptolemaic constructions were much more thoughtful than I had learned in secondary school and their predictive power was much better too. So in both a qualitative and quantitative way these theories were hard to dispute even with Copernicus' new sun centered universe, which did not do any better quantitatively. Gradually, as the telescope came into existence (Galileo) so that the observational data pushed the astronomers away from the circles and epicycles to the ellipses, did astronomy advance to predictions quantitatively better. This book shows how that all came to be and how it affected the world outside astronomy. It shows how the old cosmology had come to be adopted as a world view in religion and why they clung to it so. Anyone reading this book will gain a greater respect for what the ancients accomplished and how brilliant they were in building the cosmology that was replaced by Copernicus, Brahe, Kepler, Galileo, and Newton. It also showed how these built on others who are not so well known. It is a fascinating read.

Before, I was not really convinced that the heliocentric revolution was the fact of Copernicus. I always considered Galileo the real person who made the revolution. Thomas Kuhn made a point and showed how Copernicus brought a real change in the vision of the world. I always enjoyed reading Thomas Kuhn and recommend all his writings.

I thought this book was interesting, but a bit slow. It worked very well for class, though, and it came in great condition.

A hard and worthwhile read

Este es un libro apasionante, desde el inicio el propósito es expresado con claridad: mostrar como la ciencia desborda sus propias fronteras para influir y transformar el pensamiento y modificar, revolucionar, las concepciones y prejuicios de las demás disciplinas humanas. El ejemplo de la Revolución Copernicana es presentado de forma crítica y clsra