Dialogue Concerning the Two Chief World Systems: Ptolemaic and Copernican

by Galileo Galilei, Stephen Jay Gould (Editor), Stillman Drake (Translator)

Galileo’s Dialogue Concerning the Two Chief World Systems, published in Florence in 1632, was the most proximate cause of his being brought to trial before the Inquisition. Using the dialogue form, a genre common in classical philosophical works, Galileo masterfully demonstrates the truth of the Copernican system over the Ptolemaic one, proving, for the first time, that the earth revolves around the sun. Its influence is incalculable. The Dialogue is not only one of the most important scientific treatises ever written, but a work of supreme clarity and accessibility, remaining as readable now as when it was first published. This edition uses the definitive text established by the University of California Press, in Stillman Drake’s translation, and includes a Foreword by Albert Einstein and a new Introduction by J. L. Heilbron.

Genres: Science, Philosophy, Nonfiction, Classics, Physics, History, Astronomy

586 pages, Paperback

First published February 21, 1632

About the author

Galileo Galilei was a Tuscan (Italian) physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations, and support for Copernicanism. Galileo has been called the "father of modern observational astronomy", the "father of modern physics", the "father of science", and "the Father of Modern Science." The motion of uniformly accelerated objects, taught in nearly all high school and introductory college physics courses, was studied by Galileo as the subject of kinematics. His contributions to observational astronomy include the telescopic confirmation of the phases of Venus, the discovery of the four largest satellites of Jupiter, named the Galilean moons in his honour, and the observation and analysis of sunspots. Galileo also worked in applied science and technology, improving compass design.

Galileo's championing of Copernicanism was controversial within his lifetime. The geocentric view had been dominant since the time of Aristotle, and the controversy engendered by Galileo's presentation of heliocentrism as proven fact resulted in the Catholic Church's prohibiting its advocacy as empirically proven fact, because it was not empirically proven at the time and was contrary to the literal meaning of Scripture. Galileo was eventually forced to recant his heliocentrism and spent the last years of his life under house arrest on orders of the Roman Inquisition.

Reviews

[Roy Lotz · Rating 4 out of 5]

I should think that anyone who considered it more reasonable for the whole universe to move in order to let the earth remain fixed would be more irrational than one who should climb to the top of your cupola just to get a view of the city and its environs, and then demand that the whole countryside should revolve around him so that he would not have to take the trouble to turn his head.

It often seems hard to justify reading old works of science. After all, science continually advances; pioneering works today will be obsolete tomorrow. As a friend of mine said when he saw me reading this, “That shit’s outdated.” And it’s true: this shit is outdated.

Well, for one thing, understanding the history of the development of a theory often aids in the understanding of the theory. Look at any given technical discipline today, and it’s overwhelming; you are presented with such an imposing edifice of knowledge that it seems impossible. Yet even the largest oak was once an acorn, and even the most frightening equation was once an idle speculation. Case in point: Achieving a modern understanding of planetary orbits would require mastery of Einstein’s theories—no mean feat. Flip back the pages in history, however, and you will end up here, at this delightful dialogue by a nettlesome Italian scientist, as accessible a book as ever you could hope for.

This book is rich and rewarding, but for some unexpected reasons. What will strike most moderns readers, I suspect, is how plausible the Ptolemaic worldview appears in this dialogue. To us alive today, who have seen the earth in photographs, the notion that the earth is the center of the universe seems absurd. But back then, it was plain common sense, and for good reason. Galileo’s fictional Aristotelian philosopher, Simplicio, puts forward many arguments for the immobility of the earth, some merely silly, but many very sensible and convincing. Indeed, I often felt like I had to take Simplicio’s side, as Galileo subjects the good Ptolemaic philosopher to much abuse.

I’d like to think that I would have sensed the force of the Copernican system if I were alive back then. But really, I doubt it. If the earth were moving, why wouldn’t things you throw into the air land to the west of you? Wouldn’t we feel ourselves in motion? Wouldn’t canon balls travel much further one way than another? Wouldn’t we be thrown off into space? Galileo's answer to all of these questions is the principal of inertia: all inertial (non-accelerating) frames of reference are equivalent. That is, an experiment will look the same whether it's performed on a ship at constant velocity or on dry land.

(In reality, the surface of the earth is non-inertial, since it is undergoing acceleration due to its constant spinning motion. Indeed the only reason we don’t fly off is because of gravity, not because of inertia as Galileo argues. But for practical purposes the earth’s surface can be treated as an inertial reference frame.)

Because this simple principle is the key to so many of Galileo’s arguments, the final section of this book is trebly strange. In the last few pages of this dialogue, Galileo triumphantly puts forward his erroneous theory of the tides as if it were the final nail in Ptolemy’s coffin. Galileo’s theory was that the tides were caused by the movement of the earth, like water sloshing around a bowl on a spinning Lazy Susan. But if this was what really caused the tides, then Galileo’s principle of inertia would fall apart; since if the earth’s movements could move the oceans, couldn’t it also push us humans around? It’s amazing that Galileo didn’t mind this inconsistency. It’s as if Darwin ended On the Origin of Species with an argument that ducks were the direct descendants of daffodils.

Yet for all the many quirks and flaws in this work, for all the many digressions—and there are quite a few—it still shines. Galileo is a strong writer and a superlative thinker; following along the train of his thoughts is an adventure in itself. But of course this work, like all works of science, is not ultimately about the mind of one man; it is about the natural world. And if you are like me, this book will make you think of the sun, the moon, the planets, and the stars in the sky; will remind you that your world is spinning like a top, and that the very ground we stand on is flying through the dark of space, shielded by a wisp of clouds; and that the firmament up above, something we often forget, is a window into the cosmos itself—you will think about all this, and decide that maybe this shit isn’t so outdated after all.

[Orhan Pelinkovic · Rating 4 out of 5]

It must have been unnerving and exhausting to write a book with the Inquisition watching over your shoulder. Under such conditions, an Italian inventor and astronomer, Galileo Galilei (1564-1642), an individual of unwavering determination, courage, and intelligence wrote the Dialogue Concerning the Two Chief World Systems (1632).

The book is structured as a four day discussion, where each day represents one chapter. The story is narrated through a trialogue between: (i) Salviati, a friend and follower of Galileo, and a strong proponent of Copernicus's and Aristarchus’s heliocentric model (planets orbit the Sun), (ii) Sagredo, who is also Galileo's friend and maintains a neutral but open-minded stance to new ideas, and (iii) Simplicio, who is an advocate of Aristotle's and Ptolemy's teachings and a missionary of the geocentric model (Sun and other planets orbit the Earth).

I imagined these characters as an embodiment of Galileo's personal journey through knowledge, moments of doubt, and discoveries. I saw, Simplicio, as a metaphor for Galileo in his youth, who studied Aristotle's, Euclid's, and Ptolemy's teachings when he began his science education. Sagredo, as a metaphor for Galileo during his process of learning new ideas while questioning and doubting the old. Lastly, Salviati, the main character, as a metaphor for the older Galileo that has formulated his own revolutionary ideas, discoveries, and redefined the scientific method by introducing experimental and measurement-based testing with rigorous skepticism of what is observed. As Salviati says "what has a beginning, a middle, and an end can and must be called perfect".

The book reads like the Socratic dialogues, and at times it feels like you're in an ancient comedy play. Many branches of science are discussed, with an emphasis on celestial bodies and their characteristics, positions, and movements. The books discusses and proves that objects fall at the same acceleration regardless of their mass and that Earth and its atmosphere rotate simultaneously. We also see how Galileo's lens and magnification improvements to the already existing telescope aided him to first discover the moon craters, sun's sunspots, and the four moons of Jupiter. Galileo's work would have at least earned him a Nobel Prize today, but in his time, the Inquisition found him guilty of heresy and sentenced him to life imprisonment for writing this book. The only “reward” he received was to serve his imprisonment under house arrest.

Why the missing star? Galileo is brilliant, but the narrative was a bit unvaried and repetitive, and I think that only those interested in geometry and astronomy could truly enjoy the read, as I did! The book did leave me curious why Johannes Kepler's three laws of planetary motion, that were publish 13 years prior to this book, were not presented, even though Kepler was mentioned a couple of times in the book, although, not related to his elliptical orbits and equations.

This was a relaxing read for me and I am going to stick around this period for a while researching it through other books. I am fascinated being able to visit the past and personally witnessing a new approach to reasoning and method of acquiring knowledge.

[Manny · Rating 4 out of 5]

[A pleasant Venetian villa; through the open window, we see tourists photographing each other with their iPads while gondolas traverse a canal in the background. SALVIATI effusively greets his guests, SAGREDO and SIMPLICIO]

SALVIATI: Welcome, dear friends, and many thanks for answering my urgent convocation! It is my earnest wish that we now devote some hours to mutual discussion, as we have so often done before, but this time on a different topic: to wit, that book written by Galileo in 1629, which has excited so much controversy in the nearly four centuries since it first appeared to an astonished world.

SAGREDO: Indeed, there is nothing that could afford me more pleasure, for I know that no man has greater power than you, Salviati, to penetrate to the heart of things and make the difficult appear simple. I am yours to command, and what little wit I have is entirely at your disposal.

SALVIATI: If my discourse has merit, it is as much due to the keen testing it has received at your hands as to any small ability I may myself possess. And naturally I must also thank Simplicio, who will in his usual way propound the contrary hypotheses, and take it in good part that he is continually refuted and humiliated at our hands. I hope he will understand that it is not done in any spirit of malice, but merely that the truth may be the more plainly seen.

SIMPLICIO: To be honest, I do not know what you are talking about; I feel that, on the whole, I have acquitted myself well in our verbal jousts. But I wonder if we may not proceed to the matters on which we intended to converse; for we have now spent many minutes on these polite exchanges, pleasant as they may be, and I cannot but help that I fear we may be in danger of losing our audience. Indeed, if there were one criticism I feel tempted to level against our Linceian friend's book, it is that it is overlong, and contains too much that is at best of marginal relevance to the subjects it purportedly seeks to treat, and rather tends to divagate into side-channels which with time have lost their urgency and interest.

SALVIATI: You are mistaken, Simplicio, and I will lead you to deduce that from facts that you already know full well. Now tell me, is it not true that a book in many respects is like to a house?

SIMPLICIO: I fail to grasp your meaning. The one is made of words, and the other of bricks and mortar; how could these be the same?

SALVIATI: You are correct, my dear Simplicio, but you do not go far enough in your reasoning. A heap of bricks is no house, just as a list of words is no book. To build a house, you must skillfully arrange the bricks, to form the foundation, then the first storey, then the second, and so on; and similarly, to make a book, the words must be arranged to create the introduction, then the first chapter, then the second, until one reaches the end.

SIMPLICIO: This I grant you.

SALVIATI: Now one may look at a house, and feel that it is overlarge; but if one should remove some of the bricks from a lower storey, what will happen?

SIMPLICIO: It will collapse, of course.

SALVIATI: Exactly so! And in the same way, were we to remove some of the words from this book, the argument would fall of its own accord; for just as the higher bricks in a house are balanced on the lower, so the later words of a book rest on the earlier. Now do you see?

SIMPLICIO: But--

SAGREDO: I, for my part, am quite overcome by the elegance of Salviati's reasoning; truly, if this be the only thing I learn today, I shall count myself well rewarded already. And now I think we must heed Simplicio's warning, and move on to weightier matters, namely the content of the book and the question of how well it has withstood the test of the years.

SALVIATI: An excellent plan. Simplicio, lest you again tax us with losing time in overlong and prolix explanations, I beg you to do us the honour of guiding our conversation in an appropriate direction. What is your opinion here?

SIMPLICIO: Well, surely all the world is now in agreement on this point. Galileo, the revered author of this book, is universally acknowledged as a martyr, maybe even the foremost martyr, of science in its age-old war with religion; time has given him right on each and every point he brought up, and has long covered his ecclesiastical opponents in shame and ignominy. Indeed, his words, Eppur si muove, have become a veritable rallying-cry for scientists in their fight against base religious superstition.

SALVIATI: Though this phrase does not in fact appear anywhere in the book, and there is some doubt as to whether Galileo ever said it.

SIMPLICIO: This is of little matter. The important thing is Galileo's scientific arguments, which eloquently speak for themselves.

SALVIATI: By his scientific arguments, you mean his proofs that the Earth rotates on its axis and circles the sun, rather than standing still in the center of the universe, as argued by Aristotle and the Peripatetic school?

SIMPLICIO: Quite so, that is exactly what I refer to.

SALVIATI: Now tell me, which of Galileo's several arguments did he consider weightiest and of most significance?

SIMPLICIO: It is some time since I read the Dialogue; I fear I do not recall it in sufficient detail to be able to answer.

SALVIATI: Then I shall ask you quickly to read the final chapter, so that you can remind yourself of its content. Here, I have brought a copy with me. Well?

SIMPLICIO: It is true, he does consider his argument from the nature of the tides to be the most convincing; and with the advance of scientific knowledge, it would appear that it is not correct in every detail.

SAGREDO: My dear Simplicio, you are too kind to your revered author! To say that it is not correct in every detail is the grossest of understatements; say rather, that it is utterly fallacious from start to finish, and can be readily refuted by arguments which Galileo himself adduces in earlier parts of the book. That he should obstinately have clung to it over the course of two decades and regarded it as the crowning jewel in his life's work is one of the great mysteries of science.

SALVIATI: To make a bad matter worse, Galileo even goes so far as to pour scorn on what later turned out to be the correct hypothesis, namely that tides are caused by the gravitational influence of the moon and sun, as argued by the Catholic priest Marcantonio de Dominis in his 1624 pamphlet Euripus sive sententio de fluxu et refluxu maris, and he moreover castigates the author as dealing in occult speculations.

SIMPLICIO: I do not know what to say; I find it hard to believe that the great Galileo could have mistaken himself to this extent, and I am sure that a closer reading of the passage will reveal much in his favour. But even if your accusations have substance, which I do not concede, a single slip is hardly of great consequence. The rest of the book is still sound. Otherwise, I doubt that so many great scientists would speak as warmly as they do in Galileo's favour. For example, Bertrand Russell in Science and Religion refers to him as "the greatest man of his age", while A.D. White in A History of the Warfare of Science with Theology in Christendom says--

SALVIATI: Let us for the moment leave to one side the opinions of these learned men, and continue with those of Galileo. For example, please tell me a little more about his observations on the paradox of the rotating Earth?

SIMPLICIO: With pleasure. Galileo confronted arguments that the Earth could not rotate, and utterly refuted them. He showed that all motion was relative, in contradiction to the then-established principles of Aristotle; and with his celebrated experiment of dropping an object from the mast of a moving boat--

SALVIATI: Was this experiment ever performed?

SIMPLICIO: I am not sure. But the result is so obvious that this is hardly necessary. A moment's reflection suffices to show that--

SALVIATI: Surely this is not a trivial matter. Galileo repeatedly argues that all points of disagreement must be resolved by experiment; yet, on a point crucial to his theory, he either did not perform the experiment, or gives no details of what was done.

SIMPLICIO: In that case, I am convinced that Galileo did perform the experiment. And since the rest of the argument is clearly sound, this small point of doubt is no more than an academic quibble.

SAGREDO: Steady on, Simplicio! You are sure that the argument is sound?

SIMPLICIO: Quite sure. Though, as I said, I have not read the book recently.

SALVIATI: I think our friend touches here on the question of whether a rotating Earth would throw off all loose objects due to the action of a centrifugal force. Can you tell us how Galileo answered this objection? You may wish to read this passage first.

SIMPLICIO: I am somewhat confused. It appears, on a superficial reading, that Galileo believes himself to have proved that no rotating planet, no matter how quickly it turns, can ever throw off an object into space. But surely it is impossible that Galileo could have meant this; I fear the translator has somehow garbled his words, or given them an unintended meaning.

SALVIATI: And why do you suspect that the translation is at fault?

SIMPLICIO: It is surely obvious! All the world knows that, when Galileo was confronted by the Inquisition, he was utterly in the right, and the the Inquisition in the wrong; why, I have recently read as much in books by Richard Dawkins and the late Christopher Hitchens, peace be upon his memory. Were there such gaps and lacunae in Galileo's reasoning as you suggest, once could well believe that matters were quite unclear, and that the Inquisition were not entirely unreasonable in their methods of proceeding.

SALVIATI: What I am asking is the following: does a close study of the text lead you to this conclusion?

SIMPLICIO: It is hardly important: I am sure that these great thinkers could not be mistaken on such an important matter.

SALVIATI: But my dear Simplicio, Galileo would not wish you to quote authorities in his defence: the entire burden of his argumentation is that one should examine the facts for oneself and ignore the opinions of authorities, be they ever so weighty. I fear it was exactly this obstinacy, which falls dangerously close to the opinions of Luther and Calvin, which prompted the ire of the Holy See, in the person of Pope Urban VIII.

SAGREDO: I am once again struck by the extraordinary insight which Salviati brings to bear on all matters: we are truly fortunate to be in the presence of a man who can render the most difficult matters simple. I feel that I have been stumbling about in the dark all through this discussion, and only now am able to see things in the clear light of day. I will make haste to reread Galileo's book, paying the closest attention to all the matters of which Salviati speaks, so that I can form my own opinion of them. And now, I fear that we have been overtaxing our aimiable friend's hospitality, and we are all wearied by our discussion; so I move that we adjourn the day's proceedings, and continue again tomorrow when our spirits have been refreshed.

[Belinda · Rating 5 out of 5]

4,75 sterren - Nederlandse paperback 🐳🐳🐳
Dit boek moet inzinken. Recensie volgt later. 🌹🌹🌹

[Alp Turgut · Rating 4 out of 5]

Copernicus’in "Göksel Kürelerin Devinimleri Üzerine" adlı eserindeki Güneş sistemini kanıtlarla gerçeğe dönüştüren Gelileo’nun "İki Büyük Dünya Sistemi Hakkında Diyalog / Dialogues Concerning Two New Sciences / Dialogo sopra i due massimi sistemi del mondo" kitabı her açıdan Copernicus’un eserinin çok ötesinde. Öncelikle fikirlerini Sokratik diyalogları andıran diyaloglarla okuyucuya sunan Galileo, Copernicus aksine eseri sadece teknik bir eser olmaktan uzaklaştırarak tüm okuyucu kitlesinin yararlanabileceği bir eser ortaya çıkarmış. Bu sebeple yazarın sadece bilim alanında değil aynı zamanda edebi alanda da ne kadar yetenekli olduğunu görmek hiç de zor değil. Buna rağmen kitabı okumanın zaman zaman oldukça zor olduğunu söylemekte fayda var. Herkesin rahatlıkla okuyacağı bir kitap olmamakla beraber teknik açıklamalar içeren sayfaların da çok keyifli olduğu söylenemez. İşte bu yüzden Galileo’nun değerini okuyucuya sunarak her kütüphanede olması gereken bir eser olduğunu düşündüğüm "İki Büyük Dünya Sistemi Hakkında Diyalog", 1600’lü yılların başında Aristoteles felsefesini benimsemiş Skolastik Dünya’da neler yaşandığını öğrenmek adına fazlasıyla değerli bir kitap.

03.10.2018
İstanbul, Türkiye

Alp Turgut

http://www.filmdoktoru.com/kitap-labo...

[Aurelia · Rating 4 out of 5]

Pour plus d’un millénaire, le géocentrisme d’Aristote et de Ptolémée a été tout ce que les hommes avaient en tant que connaissance des objets célestes. La terre est fixe, au centre de l’univers, autour de laquelle tournent les planètes chacune attachée à sa sphère, pour trouver ensuite, la sphère des étoiles fixes. Une fois la sphère de la lune dépassée, c’est le règne des objets inchangeables et incorruptibles, contraire à tout ce qui fait notre terre, le destructible et l’éphémère. Mais ces cieux si tranquilles ont été perturbés au XVIème siècle par l’apparition d’étoiles nouvelles observables à l’œil nu. Encore plus, un télescope plus performant a ouvert aux humains ces territoires si inaccessibles, et soudainement la lune montre ses cratères et montagnes, Jupiter dévoile ses satellites.

Ces nouvelles observations ont mis en échec tout le système Ptoléméen, et dérangeaient également toute une classe d’hommes savants de filiation péripatéticienne. Il fallait un homme d’inégale audace et confiance pour briser ces idoles scientifiques. Avancer et défendre ce qu’on appelait à cette époque la position copernicienne était un tabou dans le monde scientifique. Mais Galilée invite à un changement de méthode et d’esprit. Au lieu de l’exégèse interminable des textes d’Aristote pour en tirer du savoir, il faut lire le livre de la Nature directement, associer l’expérimentation avec le raisonnement mathématique, dont la rigueur est capable de dépasser les impasses de la rhétorique scolastique. En adoptant la maïeutique socratique, il tire les vraies conclusions des âmes, parce qu’après avoir effectué la bonne observation et le raisonnement qu’il faut, le savoir est déjà présent, il ne reste qu’à l’extraire de la profondeur des idées ancrées et adulées des anciens.

Pour nous, les lecteurs modernes, il s’agit en premier lieu d’une leçon de courage et de pensée critique. Un rappel que le savoir, est après tout, un effort collectif, personne ne peut prétendre l’avoir atteint en totalité. La remise en question par tous est nécessaire pour le perfectionnement de ce que construisent les hommes. En deuxième lieu, c’est un exercice d’empathie scientifique, vivant dans un monde post-Newtonien on ne peut qu’essayer de s’identifier avec ces humains pratiquant une Physique et une Mécanique presque embryonnaire, discutant des problèmes que nous avons traité au lycée avec évidence, mais chez eux tout est beaucoup plus compliqué vu l’état rudimentaire de leur outils mathématiques. Il s’agit d’apprendre à observer, à transposer, à raisonner. Dans ces débuts, la science se faisait par des arguments et des observations de la vie quotidienne, pas de laboratoires ou d’appareils sophistiqués. A mainte fois, La réponse peut être devant nos yeux mais nous est invisible.

Une autre merveille de ce livre est qu’on peut clairement voir les fragments de ce que deviendra le calcul intégral et les lois de la gravité avec Newton, même la Relativité d’Einstein. C’est un enchainement de la curiosité et de la persévérance qui lie les humains à travers les siècles et les époques, pour déchiffrer la Nature.

Plus que son génie scientifique et esprit courageux, Galilée est aussi un auteur éloquent, simple et habile. Il a l’art d’enseigner et d’expliquer de différentes manières, d’anticiper les arguments des adversaires et d’attaquer leur fondement. Malgré les parties des preuves de géométrie et de calculs un peu longs, comme on les faisait au XVIIème siècle, en somme son dialogue n’est pas du tout la lecture fastidieuse à laquelle en s’attendait, au contraire, il est écrit en un style plein de beauté, d’humour et d’intelligence.

[Beauregard Bottomley · Rating 5 out of 5]

The end of Scholasticism starts with this book. The Aristotelian thought (or as the book usually calls them The Peripatetics) and its appeal to authority and the appearance of the phenomena as truth are overturned. Sometimes what we see (such as the sun rising in the east) is not what is.

I loved the way Galileo uses the Aristotelian logic to poke holes in the Ptolemaic science (particularly, using proof by contradiction). Often in the other books I've read they'll make a statement such that Galileo purposely kept his argument to the Ptolemaic versus the Copernican system and ignored the Tycho system because he couldn't refute that as easily. After having read this book, I don't see that at all. The argument on the movement of the sunspots moving across the sun are best explained by a moving earth (or otherwise would lead to bizarre motions of the sun) and would work against the Tycho system as well.

Except for the bible, I don't think any single book from all the books I've read over the last five years has been mentioned or quoted more frequently then this book has.

There are multiple reasons to really enjoy this book. It's a great peek into the mindset of the very beginnings of modernity countermanding the pernicious influence of religious thought by permeating reason and rational thought. Proof by authority is never sufficient. The narrative we use to explain the world is as important as the phenomena. Relativity is cool. Even a brilliant person gets things wrong such as Galileo does with his tide hypothesis (now I finally understand what that was).

Often the book would read exactly like the morons who today argue against Climate Change. Particularly, the section were Galileo was trying to show the super nova of 1574 was in the firmament and not below the moon. The argumentation that they were using sounded just like what the morons who say that the weather stations on earth (or the satellites) aren't recording accurately because of blah, blah, blah.

Science has multiple values and none of them are absolute. One of it's values is how the story your telling fits into the current web of knowledge that's available. The moving earth around the sun upsets everything that was thought to be known as true in 1610 Europe and shakes it to its core, but, in the end, good argumentation with the proper narrative will end out. Fortunately, simplicity, accuracy, explanation, and prediction are some of the other values of science.

Relative thought is hard to grasp and Galileo makes it easy. I would spend multiple days on two or three pages trying to digest what was being said. It's always good to learn how other people think before gravity was a force and calculus wasn't yet discovered.

This version of the book I thought was very good. It had necessary footnotes (I didn't know Etiopico was Ethiopia and often referred to all of Africa below Egypt, e.g.). The least self-aware statement I've seen is in the forward by Albert Einstein which he wrote in June 1952 while criticizing Galileo for ignoring Keplers' elliptical orbits: "a grotesque illustration of the fact that creative individuals are often not receptive". Gee, Einstein maybe should have been receptive to quantum theory, don't you think?

[Manuel Alfonseca · Rating 4 out of 5]

ITALIANO: Già dalla dedica al Gran Duca di Toscana, Galileo dimostra la sua capacità di offendere gli altri, che alla fine lo portò a processo da parte dell'Inquisizione. Infatti, nella dedica dice che le differenze tra uomo e animali non sono nulla rispetto alle differenze tra alcuni uomini e altri. In primo luogo mette i filosofi (compreso se stesso), davanti al resto degli uomini. E soprattutto colloca i filosofi che studiano la cosmologia, rappresentati da Tolomeo e Copernico. Non lo dice, ma forse pensava anche a se stesso. Vale a dire che le prime parole della sua dedizione servono a disprezzare quasi tutti gli uomini del suo tempo, che non erano dediti alla cosmologia. Può sorprendere che si sia fatto dei nemici con questo libro?

Salviani esordisce affermando che gli argomenti scientifici sono migliori di quelli filosofici di Aristotele. Invece di dire che ci sono tre dimensioni perché il numero tre è perfetto, è meglio dire che non possono esserci più di tre rette perpendicolari tra loro (in tre dimensioni, ovviamente, in quattro dimensioni potrebbero esserci quattro rette perpendicolari tra loro, ma quel Galileo non lo sapevo).

In seguito afferma che ogni corpo che parte da fermo, si muove accelerando in linea retta, e quando ha raggiunto la posizione che vuole raggiungere, adotta un movimento circolare. Qui Galileo sbaglia. Invece, ha ragione nella sua analisi del moto accelerato da piani inclinati senza attrito.

Il quarto giorno cerca di mostrare che la Terra si muove perché ci sono le maree. Qui commette un grave errore: respinge l'influenza della luna, perché non trova spiegazione che l'alta marea si ripeta due volte al giorno, una sotto la luna, e l'altra quando la luna si trova dalla parte opposta. Deve essersi reso conto che il giorno lunare (due passaggi successivi della luna attraverso lo stesso meridiano) è esattamente uguale al doppio del ciclo delle maree. Ciò implica che entrambi i fenomeni sono correlati, che uno è probabilmente la causa dell'altro, e resta solo da spiegare perché il ciclo delle maree si verifica due volte per giorno lunare. Newton lo ha spiegato. Dal momento che Galileo non sapeva come spiegarlo, avrebbe dovuto lasciare la questione in sospeso, fino a quando altre scoperte o teorie non la risolvessero. Invece, poiché desiderava avere un argomento decisivo a favore della teoria di Copernico, rifiutò il rapporto tra le maree e la luna, con un atteggiamento poco scientifico. Invece, inventa un'altra teoria basata sulla combinazione dei due movimenti della Terra (rotazione attorno al suo asse e rivoluzione attorno al sole), illustrata dal movimento dell'acqua in un bicchiere. L'effetto esiste, in effetti, ma è molto più piccolo di quanto Galileo sospettasse, non era evidente all'epoca (se non come esperimento mentale) e non prova che la Terra ruoti attorno al sole, come intendeva Galileo.

Più opportuni sono altri argomenti, come le fasi di Venere, i satelliti di Giove, le macchie solari, le montagne della luna; gli ultimi due come argomenti contro la perfezione dei cieli, difesi dagli antichi filosofi.

ENGLISH: In his dedication of this book to the Grand Duke of Tuscany, Galileo shows his ability to offend almost everyone, which ultimately led to his trial by the Inquisition. Indeed, in the dedication he says that the differences between man and animals are nothing compared to the differences between some men and other men. In the first place he puts the philosophers (himself included), against every other man. And above all, he places those philosophers who study cosmology, represented by Ptolemy and Copernicus. He does not say so, perhaps he was also thinking of himself. In other words, the first words of his dedication serve to despise almost all other men of his time. No wonder that he made many enemies with this book!

Salviani begins by stating that scientific arguments are better than Aristotle's philosophical ones. Rather than saying that there are three dimensions because three is a perfect number, it's better to say that there can be no more than three lines perpendicular to each other (in three dimensions, of course; in four dimensions there could be four lines perpendicular to each other, but that Galileo didn't know).

He later affirms that every body that starts from rest moves accelerating in a straight line, and when it has reached the position it wants to reach, it adopts a circular motion. Here Galileo is wrong. But he is correct in his analysis of accelerated motion along frictionless inclined planes.

On the fourth day of the debate he tries to show that the Earth moves, because there are tides. Here he makes a serious mistake: he dismisses the influence of the moon, because he has no explanation for the fact that high tides take place twice a day, below the moon, and once again when the moon is at the opposite side of the Earth. He should have realized that the lunar day (two successive passages of the moon through the same meridian) is exactly equal to twice the tidal cycle. This implies that both phenomena are correlated, that one is probably the cause of the other, and it only remains to explain why the tidal cycle occurs twice on each lunar day. Newton explained this. Since Galileo did not know how to explain it, he should have left the question pending, until further discoveries or theories would explain it. Instead, because he desperately wanted to have a decisive argument in favor of the Copernican theory, he rejected the relationship between the tides and the moon, with an unscientific attitude. Instead, he invents another theory based on the combination of the two movements of the Earth (rotation around its axis and revolution around the sun), illustrated by the movement of water in a tumbler. The effect does exist, indeed, but it is much smaller than Galileo suspected, was not noticeable at his time (except as a thought experiment), and does not prove that the Earth revolves around the sun, as Galileo intended.

More opportune are other arguments, such as the phases of Venus, the satellites of Jupiter, sunspots, the mountains of the moon; the last two as arguments against the perfection of the heavens, defended by the ancient philosophers.

ESPAÑOL: Ya desde la dedicatoria al Gran Duque de Toscana, Galileo demuestra su habilidad para ofender a otros, que al final le llevó a juicio por la Inquisición. En efecto, en la dedicatoria dice que las diferencias entre el hombre y los animales no son nada comparadas con las diferencias entre unos hombres y otros. En primer lugar pone a los filósofos (incluido él mismo), frente al resto de los hombres. Y por encima de todos, coloca a los filósofos que se dedican a estudiar cosmología, representados por Ptolomeo y Copérnico. No lo dice, pero quizá pensaba también en sí mismo. O sea, que aprovecha su dedicatoria para despreciar a casi todos los hombres de su época, que no se dedicaban a la cosmología. ¿Puede extrañar que se ganara enemigos con este libro?

Salviani empieza afirmando que los argumentos científicos son mejores que los filosóficos de Aristóteles. En vez de decir que hay tres dimensiones porque el número tres es perfecto, es mejor decir que no puede haber más de tres rectas perpendiculares entre sí (en tres dimensiones, claro; en cuatro dimensiones podría haber cuatro rectas perpendiculares entre sí, pero eso Galileo no lo sabía).

Más tarde afirma que todo cuerpo que parte del reposo, se mueve acelerando en línea recta, y cuando ha alcanzado la posición a donde quiere llegar adopta un movimiento circular. Aquí Galileo se equivoca. En cambio, acierta en su análisis del movimiento acelerado por planos inclinados sin rozamiento.

En la cuarta jornada trata de demostrar que la Tierra se mueve basándose en las mareas. Aquí comete un grave error: desestima la influencia de la luna, porque no encuentra explicación a que la marea alta se repita dos veces al día, una vez debajo de la luna, y la otra cuando la luna está en la parte opuesta de la Tierra. Debió haberse dado cuenta de que el día lunar (dos pasos sucesivos de la luna por el mismo meridiano) es exactamente igual al doble del ciclo de las mareas. Esto implica que ambos fenómenos están relacionados, que uno es probablemente causa del otro, y sólo falta explicar por qué el ciclo de las mareas ocurre dos veces en cada día lunar, cosa que explicó Newton. Puesto que Galileo no sabía explicarlo, debería haber dejado la cuestión pendiente hasta que otros descubrimientos o teorías la resolvieran. En lugar de ello, porque quería a toda costa tener un argumento decisivo en favor de la teoría de Copérnico, rechazó la relación entre las mareas y la luna, con una actitud poco científica. En su lugar, inventa otra teoría basada en la combinación de los dos movimientos de la Tierra (rotación alrededor de su eje y revolución alrededor del sol), ilustrada por el movimiento del agua en un vaso. El efecto existe, en verdad, pero es mucho más pequeño de lo que Galileo sospechaba, en su época no era perceptible (salvo como experimento mental) y no demuestra que la Tierra gire alrededor del sol, como Galileo pretendía.

Más oportunos son otros argumentos, como las fases de Venus, los satélites de Júpiter, las manchas solares, las montañas de la luna; los dos últimos como argumentos en contra de la perfección de los cielos, defendida por los antiguos filósofos.

[Jonathan · Rating 5 out of 5]

Why hadn't I read this book before? Not just one of the greatest texts in the history of science but fabulously written and entertaining as a dialogue. We hear about Galileo in high school, but that isn't like getting it right from the source.

[Hunter · Rating 2 out of 5]

I was rooting for the Inquisition throughout this one. So much of modern scientific ideology is already present here in seed form.

Some scattered notes:

-On page 16, Salviati (Galileo's stand-in) makes a strange comment critical of Aristotle, accusing him of pulling tricks, and says that ideally science should start with general theories and then proceed to empirical observation or experimentation. What's going on here? Does this theory-first view even comport with what Salviati says elsewhere?

-Salviati is at pains to continuously set "rhetoric" against "rigorous demonstrations," saying that science in its truest form partakes of the latter and not at all of the former. Yet the whole book is one long, bloated work of Rhetoric (capital R). Simplicio (the Aristotelian stand-in, literally "idiot") gives the Aristotelian worldview in its absolute worst light, and Salviati constantly adopts a high tone—by no means is he just giving the data, "trusting the science."

-On p. 35, Salviati calls logic, "as it is generally understood, the organ with which we philosophize." Right after, he subtly overturns in one fell swoop the primacy of philosophy, saying that authority in any given field ought to belong to its practitioners, implying in a way that Science is above Philosophy.

-Salviati, on page 10, says (ostensibly against Aristotle in the Physics) that three is not a perfect number. Is this a veiled attack on the Trinity? Take note of his very Straussian interpretation of why Pythagoreans articulated a mystical numerology: to hide the power of math away from the masses, keeping it for themselves.

-Salviati is sowing the seeds for the emergence of the cult of scientific-technical experrtise. Recall the pandemic: Remember how, on the advice of experts, we removed children from schools, causing an unprecedented crisis in education, all for spurious "public health" ends? And remember when, in the midst of lockdowns, layoffs, and school/church closures, scientists gave their rubber stamp to massive riots and protests on the grounds of racial injustice being a public health crisis greater than the pandemic itself? Whatever side one falls on as regards these questions, they are clearly questions to be resolved in a communal forum. They are moral and political questions, bound up with what a community desires and what it sets as its ends, questions that must be worked out in a public conversation, not decided upon the basis of a mythic Objective Expertise. They are value-laden questions! Already, we see this rule of the expert set in motion in Galileo.

-This advent of technical expertise is evident most clearly in the fact that the telescope is constantly brought up. On page 56, and again at 67, Salviati effectively communicates that science "proceeds" on the basis of technical advancement (and he's not wrong). But this marks a huge shift: Formerly science was an activity anyone could undertake with just their eyes, reason, and a strong enough will. But now, the technical instrument mediates my investigation, and I have to trust in the craft of the lenscrafter. What's more, such expensive instruments lead to the advent of Scientists as a professional class, whose need of funding places them in close relation with interested financiers, the greatest of whom is the state.

-Finally, note well how Salviati claims that, in his doctrine, he ennobles the Earth, rather than corrupting the heavens. But is this just cope? Imagine: Christ is God, becomes one of us, and in so doing opens up the possibility that we can become gods ourselves. What could possibly be more ennobling than divine adoption and theosis? “We are stardust, we are golden, we are billion-year-old carbon,” in Joni Mitchell’s words? Nonsense. This can in no way match the ennoblement of man that Abrahamic faith offers. What is more, we are at the center of an ordered universe. Our cosmic importance, on the basis of the Christian account, is clear. To then disrupt this would be deeply, unspeakably frightening. Given such reasonable horror, would it not make sense to develop a new "religion" which exalts change, mutation, and impermanence?

Here I am reminded of T. S. Eliot's great quote: "Humankind cannot bear very much reality." Human beings must find a way to live with the things they uncover and think to be "true," lest they go mad. They NEED myth; myth is a constitutive part of truth. If Salviati just took the straight nihilist route, not only would it be a horrible "pitch" for the heliocentric model, but what is more important, it would be crippling to the soul, life-denying, something truly spiritually unacceptable.

[Belinda Vlasbaard · Rating 5 out of 5]

4,5 sterren - Nederlandse paperback

Draait de aarde om de zon, of de zon om de aarde? Dat was een van de kernvragen aan het begin van de wetenschappelijke revolutie die vanaf de zestiende eeuw in Europa plaatsvond.

Copernicus koos voor het eerste, en Galilei werkte het idee later uit in zijn toentertijd revolutionaire werk Dialoog over de twee voornaamste wereldsystemen. Het was een frontale aanval op de tot dan toe gangbare wetenschapsopvattingen van de natuurfilosofen.

De Kerk verbood Galilei in 1616 om de leer van Copernicus nog langer te verkondigen. Toen er een nieuwe Paus aantrad, Urbanus VIII, vriend en bewonderaar van Galilei, leek er een meer liberale wind te gaan waaien.

Na uitgebreide gesprekken met de paus begon Galilei in 1624 aan zijn fameuze boek. Hoewel Galilei op last van de Kerk passages aanpaste, ontbrandde er direct na de publicatie een felle strijd rond dit boek, uitmondend in het beruchte proces, waarbij Galilei zijn opvattingen moest afzweren.

Nu, bijna 400 jaar na verschijnen, is dit baanbrekende werk voor het eerst in het Nederlands beschikbaar.

Galileo Galilei (1564-1642), revolutionair natuuronderzoeker, verwierf in 1610 wereldfaam met de publicatie van zijn telescoopwaarnemingen aan de hemel.

Hij gaf de mechanica een volledig nieuwe grondslag. Vanwege zijn alom als meesterwerk erkende Dialoog over de twee voornaamste wereldsystemen werd hij door de inquisitie bestraft met levenslange gevangenisstraf, later omgezet in huisarrest.

Zeer interessant. Verbaasd wat er allemaal ontdekt en bestudeerd is zo lang geleden.
En wat een verschrukking dat je gevangenisstraf of huisarrest krijgt voor je mening.

[Daria Cantini · Rating 5 out of 5]

“S’io guardo alcuna statua delle eccellenti, dico a me medesimo: «E quando sapresti levare il soverchio da un pezzo di marmo, e scoprire sì bella figura che vi era nascosa? quando mescolare e distendere sopra una tela o parete colori diversi, e con essi rappresentare tutti gli oggetti visibili, come un Michelagnolo, un Raffaello, un Tiziano?». S’io guardo quel che hanno ritrovato gli uomini nel compartir gl’intervalli musici, nello stabilir precetti e regole per potergli maneggiar con diletto mirabile dell’udito, quando potrò io finir di stupire? Che dirò de i tanti e sì diversi strumenti? [...] Che diremo dell’architettura? che dell’arte navigatoria? Ma sopra tutte le invenzioni stupende, qual eminenza di mente fu quella di colui che s’immaginò di trovar modo di comunicare i suoi più reconditi pensieri a qualsivoglia altra persona, benché distante per lunghissimo intervallo di luogo e di tempo? parlare con quelli che son nell’Indie, parlare a quelli che non sono ancora nati né saranno se non di qua a mille e dieci mila anni? e con qual facilità? con i vari accozzamenti di venti caratteruzzi sopra una carta”.

[Xander · Rating 3 out of 5]

I read parts of this book in 2016, when I was self-studying physics. I used a textbook that often referred to the main historical works of figures like Copernicus, Kepler and Galilei, and I thought it interesting to read (parts of) these references as well.

I found Galilei's books surprisingly accessible and fun to read. Works of Copernicus and Kepler are hard to read for modern day readers due to the heavy use of outdated and complex mathematics. Galileo uses the form of a dialogue to bring his point across - a world of difference!

In his first Dialogue, on the two main world systems (Ptolemaic and Copernican, or geocentric and heliocentric respectively), Galileo uses three characters to explain the two different systems. Salviati is the modern (by Galilei's standards) view of Copernicus, which set the Sun at the centre of the cosmos and the Earth and the five planets in circular motions around the Sun. Simplicio represents the old system, based on the astronomical model of Ptolemy and the philosophy of Aristotle - this is the system that was guiding in Christian theology at the time (due to Thomas Aquinas who combined the philosophy of Aristotle with the Christian doctrines).

Salviati starts to explain the practical consequences of the Copernican view, while Simplicio keeps using Aristotelean objections to his views. Sagredo, the third character, is a neutral listener and is persuaded, during the conversation, to adopt more and more of the new Copernican world system and drop more and more of the Christian/Aristotelean world system. This takes place during (a fictional) four days, in which different topics are discusses between the three characters.

From what I remember, Salviati uses the Aristotelean style of arguing, leading to the defeat - time and time again - of Simplicio. In other words, Salviati adopts Simplicio's way of arguing and hence defeats Simplicio with his own rules.

It is easy to see which character represents Galileo - Salviati - and it is not strange that this book led Galilei to be arrested by the Inquisition. Galilei had written Siderius Nuncius some years before, in which he explained his discoveries with the telescope. This was ground breaking science at the time, especially the discovery of the phases of Venus, which was the decisive observation that vindicated the Copernican world system. The phases are the product of the motion of the Earth around the Sun and the orbit of Venus around the Sun. The position of Venus relative to the Earth changes, hence the different sizes and shapes of Venus.

This led Galilei to conclude that the 'retrograde motion' in the old system of Ptolemy was falsified, hence the Ptolemaic system should be dropped in the trash can and the Copernican system should be adopted. In a time (the Counter Reformation) when the Catholic Church felt the need to regain and strengthen its orthodoxy, it's not strange that Galilei was warned not to publish anything anymore on the topic of Copernican astronomy.

His first Dialogue was Galilei's refusal to accept this restriction. Instead of explaining on the basis of observational evidence (as in Siderius Nuncius) the falsehood of the Ptolemaic world system, he now went head-on and destroyed the whole Aristotelean/Christian worldview philosophically. In other words, he denied the Church warning not to publish and hence was arrested, tried and convicted to lifelong house arrest. Galilei was old enough at the time of his trial, so lifelong house arrest wasn't that bad. The worst thing for him was that he was not allowed to publish anymore.

(Still, he managed to write a second dialogue in his dying days and sneak it out of his house to let it be published in Leyden.)

The whole context of the Dialogue on the Two Chief World System makes this a remarkable book. It is important as a historical document, culturally as well as scientifically. As a bonus, it's written very well. I can definitely recommend reading this book! I, for one, plan to read this book again in the future (as a whole instead of loose parts).

[Tyler Faulkner · Rating 4 out of 5]

Book Review of Galileo Galilei's Dialogue Concerning the Two Chief World Systems

Galileo Galilei’s Dialogue Concerning the Two Chief World Systems is a fictional account of a debate Galileo had with two of his peers, himself represented in the character Salviati, who in the narrative intends to weaken arguments relative to conventional astronomy and cosmology. Through various examples, Salviati attempts to reconstruct the universe mathematically and provides illustrations and geometrical proofs to support his argument.

Salviati’s chief interlocutor is Simplicio, a staunch supporter of Aristotelian philosophy, and the cosmological implications that derive from it. Whereas his opponent, Salviati, is presented as a fiery intellectual, Simplicio comes across as more of a dunce, a man stuck in his ways and fatally attached to a philosophy that he hasn’t examined scrupulously enough to fashion new ideas and concepts out of, but rather regurgitates imbibed knowledge.

The third interlocutor is Sagredo, whom Galileo attempts to present as a neutral listener, but as the narrative progresses, it is apparent that his bias heavily favors Salviati’s worldview, so much so that it often appears that he and Salviati are on the same team. Indeed, Sagredo’s neutrality is highly questionable at best, and the derision that he and Salviati direct at Simplicio does more to credit Simplicio’s fortitude than to discredit his argument.

Indeed, I found much of Simplicio’s arguments to be philosophically sound and succinct, whereas practically every idea Salviati introduced required graphs, complex mathematical equations, or geometric models to gather anything from it. Though I admit to an elementary comprehension of advanced mathematics, I am inclined to believe that what I experience tangibly better reflects reality than abstraction, in whatever form.

Salviati’s verbosity and arrogance throughout the novel increasingly endeared me to Simplicio, who at all times is calm and reflective, and frequently admits that his knowledge of a subject or concept is insufficient and declines to comment. In contrast, Salviati is combative and arrogant in argumentation—not to mention demeaning. Though he exclaims his inability to prove that the earth is in motion rather than stationary, his speech suggests that he believes otherwise.

Though technically fictional, Galileo reveals in the introduction that the narrative is based off of his experience. It is curious how little Tycho Brahe was discussed, given his renown as an accurate astronomer, not to mention the Imperial Mathematician before his death, as well as the creator the Tychonic cosmological model, the predominant contemporary cosmological understanding. That Galileo sidestepped the Tychonian model so egregiously, is to his discredit.

Though I am suspect of Galileo as an astrological demigod, I admit that I enjoyed it from a literary perspective. There is a liveliness to his style that impressed me, though I am dubious about his ability to create multidimensional characters. Nevertheless, the dialogue format was easy to read and contains much unexpected wit and flair from the astronomer, who appears to have had quite the imagination and a mastery of language. If you can endure thirty-plus pages filled with geometric equations and graphs, the writing alone makes it worth the read.

[James Violand · Rating 5 out of 5]

Believe it or not, I found this to be one of the most interesting books I have ever read. Easily understood, it is a seminal work in the history of science. Excellent.

[Recensioni in tre parole · Rating 4 out of 5]

Rivoluzionario. Scientifico. Argomentativo.

[laila · Rating 3 out of 5]

Kind of a page turner but too long.

[Selçuk Altıntav · Rating 5 out of 5]

Bu kitap çok özel bir kitap. Bu kitabi özel yapan nedir peki? Bu kitabi özel yapan bir degil bir çok sebep var ve bu sebeplerin bir kismini kendimce belirtmeye calisacagim sizlere. Ancak şunu söyleyebilirim ki, çok rahat okuyabileceğiniz bir kitap degil. Bunun sebebi ise bugün kolayca bildigimiz şeylerin, bu kitapta modern bilimin anlaşilir ispata dayali stiline uygun olarak ortaya atilmamis, daha çok dogmatik bicimde var olmus teorilerin, Galileo'nun belirledigi 3 karakter arasinda tartismalarla curutulmesi seklinde ilerliyor olmasi. Bunda okumayi zorlastiracak ne var diyebilirsiniz fakat, bir cumle kurarak soyleyebildigimiz, Dunyanin kendi etrafinda saat yonu tersine donusu ve ayni sekilde saat yonu tersinde gunes cevresindeki yillik hareketini, size sayfalarca suren diyaloglarda dogmatik dusuncelere karsi sayfalarca savunuldugunda sikilmaya basliyorsunuz. Ve burada can sikici olan seylerden biri de peripatetikcilerin gercekten asiri derecede sinir bozucu olmasi. Peki bu kitapta guzel olan ne var sorusunun cevabina gelecek olursak eger: Benim ilgimi ceken ve bir cirpida yazabildiklerim sunlar olurdu. Modern bilimin bugunku stiline temel teskil etmesi (bu sebeple Galileo modern bilmin babasi kabul ediliyor). Teleskopun astroniomi uzerindeki etkisinin gozlemlendigi ilk eser olusu(ve tek bir icadin ne kadar cok kitabi ve ideolojiyi yok ettigini gormek). Kilisenin bilim uzerindeki kisitlayici etkilerinin eserde sikca kendini gostermesi. Eski bilim ve yeni bilim arasindaki gecis surecini gozlemleyebilmek imkanini veriyor olusu ve aklima gelmeyen mutlaka bir suru guzel sey var... Kitabi okumak icin bazi konularda bilgi sahibi olmak gerekiyor. Ozellikle astronomi, matematik, geometri ve bu kitapta savunulan dusuncenin karsisindaki, peripatetikci bakisin beslendigi temel. Ve son olarak Galileo'nun ne kadar efsane bir karakter oldugunu goreceksiniz. Beklediginizden fazlasi olacagini goreceginizden eminim.

[Mark Woodland · Rating 4 out of 5]

This is still a fascinating read over 400 years later. They don't write them like this anymore; the classic "dialogue" format that one finds in classic writings such as those by Plato was not in general use. However, given the clash between the two dominant models of the order of the universe at the time, it was a perfect choice, and well "argued" on each side. Of course, the Copernican system was proved out, but the process by which it was done is an excellent example of the use of logic, and the demonstration of facts, observation and data as the trump cards over the "thought experiment" mindset behind the Ptolemaic system. In that respect, the Dialogue is an important forerunner of the modern scientific paper; it's written in such a way that it not only proves itself right, but explains how the data was gathered and analyzed, and invites others to duplicate the experiments that led to the proof. This was what gave it such lasting power, despite the Catholic Church's attempts to suppress it. Fortunately, Galileo had many powerful friends in Europe who made sure that it continued to circulate. Amusingly, well over 400 years later, the best that the Church can come up with is that they may have been a little hasty when it came to Galileo; they have yet to come out and say that they were wrong. I recommend this book to anyone interested in astronomy, logic, mathematics or scientific inquiry. The quality of the translation is impressive as well.

[Kevin Orrman-Rossiter · Rating 5 out of 5]

A magnificent example of lucid writing. Surely one of the finest pieces of dialogue form of exposition. In addition a beautifully constructed argument and example of renaissance natural philosophy. In reading it I could not help but compare the stolid reasoning of Simplicio with the climate denialists of present day. Galileo's wit and argument are to be admired as a writer and his science intuition and reasoning would put many great scientists today to shame - a true pleasure to read.

[Khalil · Rating 5 out of 5]

According to Socrates Everybody can grasp philosophical truths if they just use their innate reason , and that is what Galileo " tried " to do with Simplicio , he ( Galileo ) worked exactly like Socrates ( and his mother before him ) as a midwife , and tried to give birth to Simplicio`s reason in time which scriptures was sacred and reason was forbidden .

[Petra Hermans · Rating 5 out of 5]

I believe in a new kind of science, every time an old religion
has been overcome.

[Dan · Rating 2 out of 5]

Welp, I'm convinced.

[Linda Arnoldus · Rating 4 out of 5]

Galileo famously contested the geocentric model in favor of the heliocentric model and was placed on house arrest (where he eventually died) by the church. It seems that opposition from the church was the sign of a groundbreaking scientific discovery at the time, and although this may seem trivial to us contemporaries, this discovery did literally change the way humanity saw the world.

I recommend reading this book in the modern day because we are still fighting the fight against ignorance. Science is being constantly opposed by the status quo and even backwards-thinking backlash. In the US we are facing book bans, censorship, misinformation about vaccines, and flat-Earthers. The rejection of science in preference of ignorance is still happening, and one only needs to read this book to understand how long this has been going on.

Galileo chooses to present his findings as a dialogue for many reasons. Firstly, his argument is not only scientific but philosophical. For example, he argues that the heliocentric model is simpler and can be justified more easily. Secondly, he was facing opposition from the church and needed to weave in statements in favor of the church to placate the officials. Thirdly, he uses intelligent characters as a means of conveying information but has another character (Simplicio, analogous to simpleton) who agrees with the status quo. This “Devil’s advocate” of sorts allows Galileo to respond to counter arguments. The second and third points are reinforced when Galileo identifies Simplicio as a firm Peripatetic (follower of Aristotle). Simplicio refuses to waiver from Aristotle’s teachings and takes this to a ridiculous extent where he refuses to believe direct, empirical, scientific evidence. This is to show people how ridiculous it is to adhere to tradition, old texts, and even the church’s advice when presented with irrefutable evidence (this reminded me of evolution deniers). He says that Aristotle would want us to question him, because that’s what philosophers do. He claims that philosophers think and historians repeat, and if you want to simply repeat what has already been said you cannot call yourself a philosopher. This has parallel with Galileo’s situation: people at the time saw heliocentrism and anthropocentrism as Christian since the Bible tells the story of creation in relation to humans, but Galileo is implicitly arguing that the Bible isn’t meant to be taken literally in this way and that these long-standing beliefs need to be challenged. He claims you can’t derive all truth from a single text in relation to Aristotle, which is a sly way of refuting overreliance on the Bible. It should be noted that Galileo didn’t actually say anything sacreligious in this text. If he had explicitly said anything about how religion hinders scientific and social progress he would have been burned at the stake. Rather, he tries to appeal to the church, which only half worked. If he didn’t have to convince people that his writing was not sacrilege his ideas definitely would have been communicated better by a scientific research paper.

To keep raving about how much I love this book, Galileo even shows that he doesn’t believe in astrology or alchemy, which was forward thinking for the time. It is interesting to me to read about astrology being debunked as a pseudoscience knowing about its modern resurgence in popularity.

I only read Chapter 8 for a class and I can say that I don’t recommend reading too much more. It is extremely detailed. However, if you are interested in doing a deep-dive into the artful way Galileo presented his argument, this book is for you. Two of my favorite quotes from Chapter 8:
“Only the blind need a guide.”
“Our discussions are about the sensible world and not about a world on paper.”

Before I conclude, I want to say that my opinions are influenced by how much I love and admire Galileo. He is responsible for claiming that mathematics is the language with which the universe was written. I deeply admire his commitment to science, understanding of mathematics, and philosophical musings about the nature of our reality.

In conclusion, Galileo shows us that the truth is often inconvenient. Sometimes it dismantles entire worldviews, entire paradigms about how the universe works. The truth is often hard to accept, and very difficult to understand. But it is still the truth.

[Christopher Byram · Rating 3 out of 5]

I first discovered this book when it was referenced on Khan Academy, in the article 'READ: Galileo Galilei', in Unit 5, in the course 'World History Project - Origins to the Present'. The article states that, in 1623, a Florentine who admired the author became Pope Urban VIII. The author had six audiences (meetings) with the Pope in 1624 and received permission to publish his theory on the causes of tides, provided he did not take sides on the cosmological debate. For the next six years, the author worked on this book, which turned into a dialogue concerning the relative merits of the Ptolemaic and the Copernican conceptions of the Universe, without reaching a conclusion of one over the other. To carry out the discussion, the author invented three characters: Salviati, who gave Copernicus’s views; Simplicio, who presented Aristotelian/Ptolemaic views; and Sagredo, an interested layman. Simplicio was named for an ancient Greek commentator on Aristotle.

The publisher of the book received a license to print, and the book appeared in Florence in March 1632. An outbreak of the plague delayed copies being sent to Rome. In August of the same year, an order came from the Roman Inquisition to stop all sales.

The author's student and friend, the Grand Duke Cosimo II, had died in 1621. The new Grand Duke of Tuscany, Ferdinand, protested the book, which seemed to him, and to many of the Church leaders, to portray Simplicio as a simpleton and fool, and thus to take sides in the debate. The Pope considered the character of Simplicio an insult, as did the other Church leaders. In September 1632, The author was charged with "vehement suspicion of heresy" and ordered to come to Rome for a trial. Ill, he did not appear until February 1633.

The author denied that he was defending heliocentrism, but he finally admitted that one could get that impression from the book. He was threatened with torture, forced to recant the heliocentric model, and, in June of that year, sentenced to indefinite imprisonment in Rome. His book was put on the Index of Prohibited Books. Three of the 10 judges disagreed with the verdict. Legend has it that as the author left the courtroom he whispered, “Eppur si muove [Still it (Earth) moves],” but this was most likely invented later.

The author was crushed by the harsh verdict. The archbishop of Siena, who had disagreed with the verdict, got permission to take the author into his home and helped him through his depression. Two years before his trial, the author had taken a villa on the outskirts of Florence, to be next to the convent where his daughters were nuns. After a few months in Rome, the author received permission to return to his own villa, to be guarded by representatives of the Inquisition, a house arrest. He was ill with a hernia, heart palpitations, and insomnia. A few months after his return home, his older daughter, Maria Celeste, with whom he was very close, died in April 1634.

The following year, this book was published in Latin in Strasburg, Alsace (France), outside the grasp of the Catholic Inquisition, thereby reaching a much more cosmopolitan audience than the suppressed Italian text.

[Marcos Augusto · Rating 4 out of 5]

In the Dialogue’s witty conversation between Salviati (representing Galileo), Sagredo (the intelligent layman), and Simplicio (the dyed-in-the-wool Aristotelian), Galileo gathered together all the arguments (mostly based on his own telescopic discoveries) for the Copernican theory and against the traditional geocentric cosmology. As opposed to Aristotle’s, Galileo’s approach to cosmology is fundamentally spatial and geometric: Earth’s axis retains its orientation in space as Earth circles the Sun, and bodies not under a force retain their velocity (although this inertia is ultimately circular). But in giving Simplicio the final word, that God could have made the universe any way he wanted to and still made it appear to us the way it does, he put Pope Urban VIII’s favourite argument in the mouth of the person who had been ridiculed throughout the dialogue. The reaction against the book was swift. The pope convened a special commission to examine the book and make recommendations; the commission found that Galileo had not really treated the Copernican theory hypothetically and recommended that a case be brought against him by the Inquisition. Galileo was summoned to Rome in 1633. During his first appearance before the Inquisition, he was confronted with the 1616 edict recording that he was forbidden to discuss the Copernican theory. In his defense Galileo produced a letter from Cardinal Bellarmine, by then dead, stating that he was admonished only not to hold or defend the theory. The case was at somewhat of an impasse, and, in what can only be called a plea bargain, Galileo confessed to having overstated his case. He was pronounced to be vehemently suspect of heresy and was condemned to life imprisonment and was made to abjure formally. There is no evidence that at this time he whispered, “Eppur si muove” (“And yet it moves”). It should be noted that Galileo was never in a dungeon or tortured; during the Inquisition process he stayed mostly at the house of the Tuscan ambassador to the Vatican and for a short time in a comfortable apartment in the Inquisition building. (For a note on actions taken by Galileo’s defenders and by the church in the centuries since the trial, see BTW: Galileo’s condemnation.) After the process he spent six months at the palace of Ascanio Piccolomini (c. 1590–1671), the archbishop of Siena and a friend and patron, and then moved into a villa near Arcetri, in the hills above Florence. He spent the rest of his life there. Galileo’s daughter Sister Maria Celeste, who was in a nearby nunnery, was a great comfort to her father until her untimely death in 1634.

[Andy · Rating 4 out of 5]

This is sometimes a difficult read in the manner that old books are, especially old math and science books, where the manner of discussion can feel sharply out of step with modern language and methodology. Nevertheless, I found it an interesting look into history, a snapshot of shifting attitudes at the start of the Enlightenment that captures both the old and new ways of thinking.

As the well-written preface by translator Stillman Drake points out, it was intended for a wide, popular audience. It’s in the style of a fictional dialogue that’s mostly gone now from scientific writing, and features three friends, Salviati, Simplicio, and Sagredo, arguing “hypothetically” about a variety of physical subjects, but primarily the heliocentric vs. geocentric models of the solar system. “Hypothetically” is in quotes, as the book is nominally supposed to depict a neutral, armchair-intellectual discussion to deflect accusations of heresy. But it’s clear that the more empirical, rational arguments of Salviati carry the day over the Aristotlean beliefs of Simplicio, and that Galileo considers Salviati’s arguments to be the truth.

The first day (the chapters are arranged as days in which the friends meet and discuss) is a little challenging because it works on refuting ideas that we’ve long relegated to “history of philosophy,” in particular arguments rooted in the “perfection” of celestial objects. The second and third days are easier for the modern reader, with some real-world scenarios that aren’t too far off of those bandied today in introductory physics classes, and some mathematics that are tantalizingly close to the then-not-quite-invented calculus. More significantly for us, though, we see the emergence of an empirical attitude and the rejection of established old thinkers when it conflicts with observation (perhaps boosted by technology, like the telescope, that did not exist during the old thinkers’ times). The fourth day is short, and covers a theory of the tides that is now known to be incorrect.

The translator Drake’s footnotes are solid, providing not only historical context but some examinations of where Galileo was actually wrong, although Drake sometimes comes off as deferent, even obsequious, to Galileo the historical figure. (Somewhat in contrast to Galileo’s own position on the ancient greats!)

[Renato Renato · Rating 5 out of 5]

What can I say about this book ? Surprisingly, a lot more readable and pleasant than one could expect! I mix of philosophy, logic, geometry and of course astronomy arranged in the very attractive format of an eloquent dialogue between three friends during four days. It is definitely not just a science book but a real piece of literature meant to be informative as much as to be enjoyed.

Here are two small excerpts from the ones I loved in this book. Both from the character Sagredo at different moments:

"It always seems to me extreme rashness on the part of some when they want to make human abilities the measure of what nature can do. On the contrary, there is not a single effect in nature, even the least that exists, such that the most ingenious theorists can arrive at a complete understanding of it. This vain presumption of understanding everything can have no other basis than never understanding anything. For anyone who had experienced just once the perfect understanding of one single thing, and had truly tasted how knowledge is accomplished, would recognize that of the infinity of other truths he understands nothing."

"Besides, what does it mean to say that the space between Saturn and the fixed stars, which these men call too vast and useless, is empty of world bodies? That we do not see them, perhaps? Then did the four satellites of Jupiter and the companions of Saturn come into the heavens when we began seeing them, and not before? Were there not innumerable other fixed stars before men began to see them? The nebulae were once only little white patches; have we with our telescopes made them become clusters of many bright and beautiful stars? Oh, the presumptuous, rash ignorance of mankind!"

[Michal Paszkiewicz · Rating 5 out of 5]

A very interesting read, although not as easy as one would expect, given the knowledge that this was probably the most 'popular' scientific work of its era.

The book gives a pretty comprehensive account of Galileo's thoughts at the time, so is the most excellent historical record of his weltanschauung. I am slightly disappointed at the introduction by Einstein, whom I considered to be more informed, but I guess he was a scientist and not a historian.

The thing that was the most interesting to me was that the supposed slur of 'Simplicio' as being simple is not so pronounced - he is given a great deal of respect by the other two characters, unlike, for example various authors referenced or hinted at, such as Chiaramonti or Seleucus (who both had slightly theories of tides).

The culmination in a tidal theory is most interesting - Galileo must have thought that this was his trumping argument, yet it was faced with scepticism even at the point of publishing, with him being forced to change the title to not include the tides in it. Nonetheless, while he did not get the theory right, it was interesting to discover how much information he had available to him on the tides - including a fairly decent account of how tidal sizes change across the coast of the mediterranean.

I think this work is worth reading for anyone interested in the history of science, as it is more approachable than most other books of its period, and it does give an account of multiple different conflicting theories, even if the author is obviously biased.

[Hiéroglyphe · Rating 4 out of 5]

Pour un ouvrage scientifique majeur vieux de quatre siècles, je m'attendais à une lecture ardue, mais la forme du dialogue et le style plaisants le rende très facile d'accès. Les démonstrations physiques et astronomiques se comprennent sans trop de difficulté avec un niveau scientifique de collège/lycée. Par contre l'ensemble est long et dense; Les plus de 600 pages comprennent de nombreuses redondances, qui sont parfois bienvenues pour mieux expliquer les milles et un détails de cette bataille cosmique mais on se perd souvent… D'autant que rien n'est réellement tranché ! Galilée déroule ses démonstrations mais, inquisition oblige, doit systématiquement les équilibrer avec celles du système géocentrique. Sans oublier qu'une partie de ces théories (toute la quatrième "journée", sur l'origine des marées) est faux.

Outre son intérêt historique, la valeur de livre tient surtout dans le fait qu'il décrit à merveille le raisonnement scientifique à travers le dialogue entre différents points de vues qui, loin de s'insulter comme le ferait des trolls à l'heure d'internet, explique pas à pas leurs idées, en s'aidant d'expériences et de théories pour avancer sur le chemin de la vérité. Le cœur du livre étant le danger qu'il y a à se reposer sur une figure d'autorité (Aristote, Dieu...) au lieu de tester soi-même une théorie.