Dialogue Concerning the Two Chief World Systems

It's not the most alluring of titles, I admit, and even though most people have heard of Galileo and many know enough of his achievements to admire him, I suspect few people would consider reading a book by him. However, I urge you very strongly to buy this book and at least give it a try. It's a wonderful work, full of fascinating and brilliant insights and Stillman Drake's superlative translation makes it extremely readable. It gives a fascinating insight into what Galileo *really* did to annoy the Inquisition and shows his often brilliantly witty and occasionally dangerously sarcastic style. Even to dip into, this book is a monumental pleasure. Try this, the first few lines of the Introduction - To The Discerning Reader: "Several years ago there was published in Rome a salutary edict which, in order to obviate the dangerous tendencies of our present age, imposed a seasonable silence upon the Pythagorean opinion that the Earth moves. There were those who impudently asserted that this decree had its origin not in judicious inquiry, but in passion none too well informed. Complaints were to be heard that advisers who were totally unskilled in astronomical observations ought not to clip the wings of reflective intellects by means of rash prohibitions. Upon hearing such carping insolence, my zeal could not be contained..." I first read that while studying History of Science over thirty years ago, laughed out loud, and read the rest of the book with immense pleasure. It is written in the form of dialogues presided over by Sagredo ("wise man") and conducted between Salviati (really Galileo himself) and the person representing the Church's orthodoxy, whom Galileo christened Simplicio. Tactful, he wasn't, but he was a brilliant physicist and a brilliant author, filling the book with witty and amazingly ingenious arguments resulting in poor Simplicio being confounded at every turn. I cannot say strongly enough what a pleasure this book is. It really isn't just a tome which will sit on your shelf looking impressive, or which you ought to plough through because it will Do You Good. It's wonderfully enjoyable and hugely rewarding, and I recommend it very highly indeed.

This is the famous book that got Galileo in trouble with the Inquisition. Galileo Galilei was one of the greatest scientists of all time. In Galileo's time the all powerful Catholic Church had decreed that the Earth was at the center of the Universe and that all celestial bodies orbited the Earth. The reasons given for this were Theological in nature, not scientific. According to the Church the Earth was a special place in the Universe, because God had chosen the Earth to be Man's home. By the sixteenth century Science had progressed to the point where this view of the Universe became increasingly untenable as it did not agree with observations about planetary motion. To resolve the difficulties created by these observations Copernicus had published from his deathbed a new theory proposing that the planets moved around the Sun in nearly circular orbits. Copernicus theory seemed to agree much better with what was known at the time about planetary motion. Galileo being perhaps the greatest scientist of his time immediately saw that the Copernican theory must be right, and debated the matter with people holding the opposite view at the University where he was a renowned professor, Mathematician and Scientist. For a while debates, arguments and counterarguments followed, until in July 1609 Galileo found the definitive proof that the Copernican theory was right. The story has been recounted in the "Starry Messenger" by Galileo. He had seen a toy sold by a Flemish spectacle maker in Venice which made distant objects look like they were near. Galileo bought the toy and did not rest until he had figured out how it worked. He then turned the toy into a scientific instrument, and the first telescope was born. Galileo soon turned his invention towards the heavens, and he almost immediately made a number of groundbreaking discoveries. When he observed Jupiter he noticed that Jupiter had Moons just like the Earth had, and by observing the Moons of Jupiter and Jupiter on successive nights he soon discovered that the Moons of Jupiter clearly orbited Jupiter, not the Earth, as they were supposed to by the Ptolomaic theory taught by the Church. This was the definitive proof that the Ptolomaic theory was just plain wrong. He started to teach this but trouble soon ensued. Galileo had been ordered by the Church that he could not discuss the Copernican theory except as a Hypothesis. When Pope Urban VIII became the Pope Galileo was greatly encouraged, because as Cardinal Maffeo Barberini prior to being elected Pope Urban VIII, he had been a great admirer of Galileo. When the new Pope was elected, Galileo had an interview with him and was told that he could teach the Copernican theory, but only as a Hypothesis, and he was not allowed to teach it as the "objective truth". In 1632 Galileo published this great book in which he debated the two systems between three protagonists. One of them called Simplicio (roughly simple-minded) was defending the Ptolomaic

During the [in]famous controversy of Galileo and the Church, the actual point of contention was this very work which Galileo published. In the Dialogue, he was supposed to set forth arguments for and agains the Ptolemaic worldview (the unmoving earth in the centre of the universe) and the Copernican (the earth and other planets going around the sun). This book does that, and brilliantly, showing Galileo's resourcefulness as a scientist, philosopher (at least to an extent!) and writer. The charge against him was that rather than being even-handed, the book was clear support of Copernicanism. This is a non-obvious topic but what is obvious is the importance and magnificence of the work in terms of both the subject matter (the importance of the structure of the universe) and method (a colourful dialogue containing heated debate which spans literally dozens of arguments for and against each system). The work has 3 characters: Salviati who is a Copernican, Simplicio who is an Aristotelian and follower of the Ptolemaic system, and Sagredo, a non-affiliated but intelligent person. They meet and debate over 4 days. The first deals with the question of whether the substance of the heavens is fundamentally different to the earth as well as some other fundamental assertions of Aristotelianism. The second deals with the earth's daily rotation. The third is about the alleged yearly orbit of the earth around the sun. The fourth (considered by Galileo to be the crown of his argument - which is all the more endearing as it is wrong) is about the cause of the tides. Reading this is especially interesting because [almost!] all of us believe that the earth goes around the sun, so it's easy to just approach this simplistically. But the reality is, it was an actual matter of debate, as the book shows. And no, Galileo does not *prove* the earth moves (contrary to the blurb at the back of the book), rather he proposes some very good arguments. Reading them critically was great at making me question things I consider fundamental. As per the edition, it contains a very good, readable translation along with Galileo's margin notes and good footnotes which unfortunately aren't matched to the body text so you have to flip forward and back. The only other disappointment was Einstein's simplistic yay-Galileo-boo-obviously-stupid-Church-and-Aristotelianism introduction. Other than that, it's great great great! An absolute milestone in human thought.

The book is well done, I like the type, the notes are informative, the preface by Einstein is by Einstein, and Drake inserts the Italian phrase at the right moments. The book itself is not read as much as it should be--it is an excellent introduction to the history of science and cosmological thought, and an informative specimen of the rhetoric of science at the very moment that rhetoric is derogated by Galileo. For instance, Galileo borrows the valorization of circular motion from Plato and Aristotle (Galileo sides with Plato against Aristotle) and argues that all motion is circular, even freefall, but not circular precisely, but spiral. He is relying in part on the geometry of spirals by--Apollonius?--a good example, to my mind, of the "geometrization of space." The equation of freefall is also demonstrated geometrically in a way that is very elegant. It should also be noted that Simplicio is hardly the fool that he is made out to be--his objections are far more acute than this reader could come up with on his own. The enormous prestige of physics and science is in my opinion one of the greatest obstacles to thinking, and reading Galileo goes a long way towards an appreciation of what mathematical physics is not.

This book clears up a universe. Galileo had hundreds of problems with the Inquisition,even though he had written his masterpiece based on his observation of the cosmo, in a period that technological devices were rare. The book is not only a scientific work but also a piece of good literature, a historical lesson of how to write and how to defend a great idea. The dialogues remind Plato works and make the book really update.