Dialogue Concerning the Two Chief World Systems: Ptolemaic and Copernican

Enjoyed learning about the logic of the Copernican system and how it was supported by Galileo.It was interesting to see just how much science DID NOT know in the early 1600s and how much Galileo got wrong. Yet they still got to the (mostly) right conclusions.You can also see how he pissed off the pope (his friend) with his many insulting and condescending comments included in the dialog.I found out that Galileo wasn't treated nearly as badly by the church as is presented. Being consigned to a villa within a mile or two of his daughters, supported by wealthy benefactors and continuing his work and writing, is a lot better than is represented. The church actually went relatively easy on him (for the day).Some of the logical arguments did get a bit long and tedious. But, it is a great history lesson and I learned a little science.

This substantial 1632 work by Galileo was about much more than just the "two motions" of the Earth, namely the rotation on its axis and its orbit around the Sun. Galileo used the 3-person dialogue form to present his theories on many other physics and astronomy subjects too.This  Modern Library edition  of Galileo's "Dialogue concerning the two chief world systems" is well edited and well bound. The look-and-feel of the book is very pleasing, especially the unusually pleasant color scheme of the front cover, the light but strong paper, and the good choice of font. The introductions and end-notes give excellent context and explanation of aspects of the book which are difficult for the modern reader. The translation is of good quality, an excellent compromise between precision and comprehensibility.However, there is one thing which must be criticised in the style of this book. That is the lack of pointers to end-notes. There are no asterisks or superscript numbers to tell you where end-notes are provided. My solution was to pencil in the missing end-note references wherever required in the book. So not only did I need to use two book-marks while reading this book. I also had to mark the end-note locations in pencil in advance. Personally, I prefer foot-notes, so that I don't have to use two book-marks and flip back and forth to read the end-notes. In this book, the end-notes are really essential. Much of the book makes little sense without them. On the positive side, the end-notes are very well written.Concerning the content, at first I was very worried by the medieval argumentation in the first 100 pages or so. It seemed to be a catalog of medieval-style bad logic, almost a parody of medieval thinking. Then I started to notice that many of the arguments against the mobile Earth were pretty strong. Faced with some of these arguments, even in the 21st century it would be difficult for a physicist to counter them. I tried some examples on some well educated friends, and they could not think of counter-arguments. For example, why is that we don't experience an 800 kilometre per hour wind if the Earth is rotating that fast? Galileo doesn't answer this very well, and no one in the 21st century has been able to explain this to me either!I can see from this book why the mobile Earth was so strongly resisted by religious authorities. Galileo was proposing that the laws of physics in the heavens are the same as on Earth. That was challenging the idea that heaven and Earth are different. The heaven is perfect and eternal, while the Earth is corruptible and ephemeral. If heaven obeys the Earthly laws of physics, where do good pious people go after they die? So there was much more at stake here (if you'll forgive the unintentional pun) than just the double mobility of the whirling Earth.I won't list the areas of physics and astronomy which are discussed in this book. There are too many. However, you should be aware that this book discusses new ideas in a very wide range of astronomical and physical subjects. This book is also a summary of the wide range of literature at that time with implications both for and against the Copernican theory. We tend to think of Galileo in his role as a contributor to the progress of knowledge. However, this book is also a "State of the Art" summary which documents the entire way of scientific thinking in his time, the controversies, the technological achievements, and the intellectual ferment that was clearly gaining momentum, which we now know led to the rapid explosion of science in the following decades.

The book was disappointing in many aspects. There was too much philosophical discussion and too little experimental results to support points. There were too many insults to the supporters of the Ptolemaic theory. Galileo couldn't resist mocking their lack of understanding. This approach is very surprising since the best way to convince people who are confused is not by giving more detailed arguments or make them feel silly. It is best to show the results of experiments and then explain why they might have been confused.Let me give an example: The supporters of the Ptolemaic theory believed that the Earth could not be moving. Because if it did, a vertically falling object would fall behind as the Earth moves under. They claimed this could be verified by dropping a stone from the top of the mast of a moving ship. As the stone drops, the ship would have moved forward away from the falling rock, and the rock would have hit the ship's deck some distance behind the mast. This is claimed on page 146. But until page 168 there is no mention that if this experiment is actually done, the stone will hit right at the bottom of the mast! And when Simplicio says he can't believe something so unnatural, instead of listing the experiments done, Salviati admits he has not done the experiments! He says it should be so, and goes onto more discussion! Why not do this experiment, in front of witnesses, publish results? Why not do all the experiments mentioned in the book with arrows, objects falling, combination of initially horizontal speed with the vertical acceleration, and show the path is a parabole? (As Galileo does in his last book.) Wouldn't this clear all the confusion better than too many abstract experiments?Aristotle is quoted as saying he would change his own theories and beliefs if experimental results didn't agree with them. So, it is especially ironic that Galileo, famous for the scientific approach, neglects actual experiments and tries too much arguing.In many places, Galileo can't resist insults. The Third Day debate starts with "very childish, not to say ridiculous, reasons in maintaining the opinion which appears to them to be true." Later he goes on with "vanity of his enterprise," "imbeciles," "fooleries," "too stupid to realize their own limitations."The Pope was Galileo's very good friend and admirer, but I can see how he got upset reading this book. It is not just because Galileo discussed the Copernican system but how he did it. Not well done!p.s. Wrong theory of the tides, no mention of Kepler's elliptical orbit theory which was published long before this book, quite a few other places with wrong arguments,...

It's amazing that a modern English translation of this classic wasn't attempted until 1952, so it's not generally available as an e-book (except for excerpts). But the full version is well worth reading. Given that his main experience of tides was in Venice (whose tides are mainly diurnal), and that gravitation wasn't properly understood at the time, his theory of the tides wasn't as rubbishy as most people have assumed since the 18th C. But it's the delightful way he knocks Aristotle off his perch that is the best part, starting with his tongue in cheek preface.

A very special book, taking me a little time to read and digest.

Brilliant book, just finished first day dialogue, can't believe this book was written in 1632.

Good book

Can be hard going at times but fascinating use of logic and thought experiments to demonstrate proofs. Aimed at those with a keen interest in science and space.