Talk:Dialogue Concerning the Two Chief World Systems

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"Some of this is to show what Galileo considered good science, such as the discussion of William Gilbert's work on magnetism." The point of the section on magnetism is to show that there are bodies in nature that have two natural motions -- in the case of the magnet, weight and magnetism. This is a refutation of the Aristotelian argument that bodies can only have one natural motion (such as downwards, or circular), which would disallow the double motion of the Earth (rotation and revolution). Thus, this section is by no means a digression from astronomy. (I think this was pointed out by Finocchiaro, but I don't have the reference handy.) 02:19, 20 July 2006 (UTC)

It is not clear to me why the popularity of Tycho's system in the Church is especially relevant. The Church, after all, was not the only group with a vested interest in non-Copernican ideas.

It is relevant because it makes the story of Galileo versus the Church less good and evil than the popular rendition.

It's fine for the fight not to be Martyr Galileo versus the Evil Church Empire; but if the idea is that Galileo was attacking the Church and being dishonest with the issues, I've already argued against that point. Those points. The concept that Galileo was not launching an assault on the Church deserves a better hearing than it has got from either "side" since White's time; the possibility that he meant what he said can explain a lot. Dandrake 21:07 25 Jul 2003 (UTC) Gack! Did I fail to sign my original posting? Mea culpa,

BTW I've heard many times the statement that the Church had moved from Ptolemy to Tycho by that time, but it seems always to have been people citing each other or giving no citation at all. I wouldn't mind seeing a development of this claim based on primary sources, or a citation of a good secondary source as distinct from all the tertiary and n-ary sources. And null-ary source, if I may say so.

In any case, I don't know of any strong Tychonic tendencies among the academic philosophers. Theories that Simplicio was a taunt at the Pope should not distract us from the fact that his role in the Dialogue is that of a conservative philosopher, follower of Simplicius, and not a churchman at all. Colombe and Cremonini, the real-life models for Simplicio, appear to have been much concerned with the Aristotelean perfection of the Heavens, which the Tychonian system tends to disrupt. In fact, Simplicio quotes many times, with approval, a philosopher who was no fan of Tycho: Scipio Chiaramonte, author of the Anti-Tycho.

Galileo's directing no arguments directly at Tycho's system can be thought a sort of intellectual dishonesty, a straw-man approach, if his purpose was to attack the Church. It's another matter if, as the text pretty clearly indicates, he was aiming at fuddy-duddy philosophers who insisted on the inerrancy of Aristotle. (And see the paragraph I'm about to add to the main entry.)

By the way, during the entire difficulty process of negotiating a license for publication of the book, did any Church authority whatever raise any problem about its supposedly treating the Church unfairly by omitting Tycho's system? I've never run into evidence of that, but I could be wrong.

If not, then the whole idea that G omitted T's system in order to make the Church look bad (I think that's the idea) looks like a red herring. It's not as if the problem, if it were one, could have been overlooked because nobody thought of Tycho; the "T" section of an index to the Dialogue will confirm this.
Dandrake 21:19 25 Jul 2003 (UTC)

Adding the pointer to on-line text was a well-intentioned idea, but that page appears to be a copyright violation; specifically, it's lifted from Dartmouth, which I think has a license to use the text privately, but not to post it or let it be posted publicly. Zapped it pending clarification. Dandrake 22:45, Jul 24, 2004 (UTC)

Does it state how long it took Galileo to write it? VLCMSTNHXXXC 10:26, Nov 26, 2006

Written in Italian, not Latin[edit]

Shouldn't there be a mention that the book was written in Italian, which the general population could read? Had it been written in Latin, the norm for scholarly work of the period, I believe , the general population would not have been able to read it. This was supposed to have been a particular irritation to the Church. SagredoDiscussione? 18:22, 24 December 2007 (UTC)

Who did the supposing? —Preceding unsigned comment added by (talk) 13:25, 21 March 2009 (UTC)
I believe I have seen something like this claim made in print, but—as far as I can recall—not in any source I would regard as authoritative. In all the surviving documents from Galileo's trial, there is only one brief comment about his having written the Dialogue in Italian. This was in the report of Melchior Inchofer, one of the theologians tasked with providing an opinion on the orthodoxy of its contents. Inchofer argued that by using Italian Galileo showed that he had written the Dialogue not to appeal either to foreigners, as he had stated in his preface, nor to other learned men, but to induce the common people to adopt the Copernican opinion.
I agree that the article should mention the fact that the Dialogue was written in Italian. Just at the moment, though, I can't see any obviously natural place to slot it in. I'll therefore put off doing it until either someone else beats me to it, or I can come up with a wording that will smoothly fit somewhere into the article.
David Wilson (talk · cont) 15:00, 21 March 2009 (UTC)

Note 6[edit]

The site given in Note 6 omits anything that puts Galileo or Einstein in a poor light. The original Preface should be consulted. —Preceding unsigned comment added by (talk) 13:16, 21 March 2009 (UTC)

Note 6 has now become Note 14.

Full text?[edit]

Sorry, I know Wikipedia is not a forum but still, where can I find the full text of the Dialogue? "Acceptable" languages for me would be German, English or Russian.-- (talk) 11:22, 24 April 2009 (UTC)

The reference desks—either humanities or science in this case—are the proper places to ask questions like this. I have copied your question to a new section at the humanities reference desk and answered it there.
David Wilson (talk · cont) 15:45, 24 April 2009 (UTC)
The full text would be appropriate content for Wikisource, at which point, an infobox template could be added to this article which links to it. That'd be rather nice actually. -Verdatum (talk) 20:08, 24 April 2009 (UTC)
A copy of the original Italian text is available on the Italian wikisource. Please feel free to add an infobox with a link to it.
David Wilson (talk · cont) 09:48, 25 April 2009 (UTC)


A recent edit added text which maintained that Galileo's argument in favour of Copernicus's system from the apparent motion of sunspots "is wrong, as the relative motions of sunspots are the same whether in both the Ptolemaic and Copernican system". No source was provided for this assertion, and it is contradicted by numerous modern reliable sources. I have therefore provided three such sources and rewritten the relevant passage to conform to what is contained in those sources.

It does seem to me to be true—if I may be permitted to peddle a modest piece of original reseach of my own—that the explanation of the apparent motion of sunspots in geostatic systems doesn't need to be quite as complicated as the cited sources appear to make out. It could be accounted for by having the Sun's axis of rotation precess uniformly about another axis, parallel to the Earth's, with a period of precisely one sidereal day. However, this is still rather more implausible than the simple explanation available in Copernicus's system, and, in any case, I don't see how it can be included in the article until someone has found a reliable source which contains it.
David Wilson (talk · cont) 18:19, 22 June 2010 (UTC)

Galileo was convicted of "grave suspicion of heresy" based on the book[edit]

If I remember it well, what was concerned was not the conclusions of Galileo himself (as at the time, and because nobody had thought about the yet to come Foucault pendulum experiment, both systems could be seen as functionally identical, one of them allowing just much easier computations as Copernic had signalled it), but the fact that he explained the reasons to consider geocentrism as superior were "irrelevant". They were, but that statement seemed at the time an insult towards Aristotes and the university teachers (as well as a blasphemy, for the Church). Galileo, overestimating the intelligence of his peers, has already irritated most university professors at the time by showing Aristote's affirmation that heaviest objects always fell faster was incorrect (by dropping weights from the tower of Pisa). (talk) 16:17, 26 August 2011 (UTC)

Origin of the Name "Simplicio"[edit]

The origin given in the article for the "Simplicio" character appears to be contrary to the one Galileo gave in the prologue of the Dialogue itself.

The Dialogue's prologue (I'm using the English translation by Stillman Drake, which can be found at various places on the Net) has this to say:

I often talked with these two [Sagredo & Salviati] of such matters in the presence of a certain Peripatetic philosopher whose greatest obstacle in apprehending the truth seemed to be the reputation he had acquired by his interpretations of Aristotle.

A little further on it adds (parenthetically):

Nor shall the good Peripatetic lack a place; because of his excessive affection toward the Commentaries of Simplicius, I have thought fit to leave him under the name of the author he so much revered, without mentioning his own.

In other words ALL THREE characters derive from real individuals, not just Sagredo & Salviati. In the case of "Simplicio", however, Galileo chose to conceal the name of the real individual behind a nom-de-guerre, doubtless for good reason!

So what does the article have to say? First of all it does not state that the origin of all of three names (let alone Simplicio's) is given by Galileo himself in the Dialogue.

Bearing that failure in mind, it makes the following claims:

He is supposedly named after Simplicius of Cilicia, a sixth-century commentator on Aristotle, but it was suspected the name was a double entendre, as the Italian for "simple" (as in "simple minded") is "semplice".

That word "supposedly" conveys doubt as to the truth of the origin of that name. Had Galileo been cited as the origin of the name, that word would have conveyed doubt as to the truth of Galileo's account. However, since Galileo has not been mentioned in that context it instead carries the imputation that the Simplicius origin is a mere hypothesis by some OTHER individual trying to work out where Galileo got these names from--which in turn would make the double entendre alternative a competing hypothesis by yet another individual.

All of which is kind of weird given that the statement in the article which follows would appear to itself be an hypothesis despite being presented as undisputed fact:

Simplicio is modeled on two contemporary conservative philosophers, Ludovico delle Colombe (1565-1616?), Galileo's fiercest detractor, and Cesare Cremonini (1550–1631), a Paduan colleague who had refused to look through the telescope. Colombe was the leader of a group of Florentine opponents of Galileo's, which some of the latter's friends referred to as "the pigeon league".

So instead of Galileo's one anonymous individual masquerading as "Simplicio" we now have an amalgam of two!

So who do we believe? Galileo or the hypothesizers?

I have no idea and the article is itself short on details as to why Colombe and Cremonini are suspected to be Simplicio.

For my own part I can't argue one way or the other, nor do I want to. I merely point out that on such matters the article would seem to be deficient and misleading and needs to be modified. -- (talk) 11:19, 29 September 2011 (UTC)


About four passages have been omitted from Einstein's remarks. — Preceding unsigned comment added by (talk) 15:07, 19 July 2013 (UTC)

There is no actual deception, as the word "condensed" is used. — Preceding unsigned comment added by (talk) 15:15, 19 July 2013 (UTC)
Even the word "condensed" is deceptive, as it gives the impression that the effort was to save time only, when it is actually for ideological reasons. The omissions are made to put Einstein and Galileo in a good light. — Preceding unsigned comment added by (talk) 10:38, 24 July 2013 (UTC)


Prince Cesi's letter to Galileo was written in 1612. This mentioned Kepler's two laws of 1609 as common knowledge, at that time. — Preceding unsigned comment added by (talk) 10:46, 20 August 2014 (UTC)

This is not quite accurate. The letter in which Cesi mentions Kepler's elliptical orbits is this one of July 21, 1612. Neither Kepler's second law nor the location of the Sun at one of the foci of a planet's elliptical orbit is mentioned anywhere in the letter. Nor does it appear to me that Cesi's choice of language gives much of a clue as to whether he thought Kepler's proposal for elliptical orbits was "common knowledge at that time". Here's my own translation of the relevant passage:
" ... and because, just like Your Lordship, I knew of motions concentric with neither the Sun nor the Earth, of some [concentric] with the Earth, and of some—or perhaps all, if the paths of the planets are elliptical, as Kepler would have it—[concentric] with the Sun."
Whether the expression enclosed in square brackets should be "concentric" or "not concentric" is not entirely clear, because the expression is not repeated in Cesi's Italian, and has to be inferred from its first occurrence. But, as is the standard practice in Italian, Cesi uses a double negative, in which the first occurrence of the expression is actually "not concentric", and this makes the Italian ambiguous. My reading agrees with that of Shea and Artigas (also adopted by Edward Rosen), which seems to me to make more sense. But there are at least two scholars (James Voelkel and Erwin Panofsky) who adopt the alternative interpretation.
The view that Cesi's letter shows Kepler's first two laws to have been "common knowledge" doesn't appear to be widely held by respected authorites in the history of science. While I have found two such authorities who have held that view (James Voelkel, in the reference linked to above, is one; Max Caspar, in his biography of Kepler, is another), most I have seen discuss Cesi's letter say merely that it mentions elliptical orbits. According to this paper, Kepler's ideas were "rather slow in establishing themselves, and until about 1630 there are few references to them in the literature of the time." I therefore don't believe Wikipedia should be stating as fact that Cesi's letter mentions either of Kepler's laws as being "common knowledge" at the time.
David Wilson (talk · cont) 16:25, 11 April 2015 (UTC)
Galileo might have heard about Kepler's laws by a variety of methods. A group of supporters of Kepler formed in England, including William Crabtree, Jeremiah Horrocks and William Gascoigne. This was in 1636. — Preceding unsigned comment added by (talkcontribs) 09:47, April 15, 2015‎
Caspar, in his biography of Kepler, implies the Galileo might have read Kepler's 1609 book. See pages 192-197. — Preceding unsigned comment added by (talkcontribs) 10:09, April 15, 2015‎.
In general, Galileo and Kepler were on good terms with one another from 1610. — Preceding unsigned comment added by (talkcontribs) 10:11, April 15, 2015‎
Galileo and Kepler could be said to have been on good terms from August 1597 when the former wrote to the latter complimenting him on his Mysterium Cosmographicum. Kepler replied enthusiastically the following October.
As far as I can tell, most respected authorities on Galileo consider it very likely that Kepler's proposal of elliptical orbits was known to him. However, if he ever made any comments on any of Kepler's laws, no record of them seems to have survived. Thus, all the evidence of what Galileo knew about Kepler's laws, of which Cesi's letter of 1612 is apparently one of the most important pieces, is indirect, and there is apparently none to indicate that his knowledge went any further than the mere proposal of elliptic orbits.
I can't find any implication on pp.192–97 of Caspar's Kepler that "Galileo might have read" Kepler's Astronomia nova of 1609. All Caspar says (p.195) is that Kepler longed for Galileo's acknowledgement of what he had achieved in Astronomia nova—an acknowledgement which he never got. Nevertheless, It is true that Galileo might have read it, especially since he is known to have owned a copy. By all accounts, however, it was very obscure and difficult to read, even by experts, and no hint of the conclusion that Mars's orbit is elliptical appears before the end of chapter 58. In this article (p.105) Stillman Drake says "Galileo's familiarity with Kepler's tidal explanation suggests that he had read the Astronomia nova". But Kepler's tidal theory appears in the introduction. I have seen at least one other scholar assert that that's probably the only part of the book that Galileo might have read, and here, Hans Blumenthal Blumenberg asserts that Galileo had not read the book at all before he made his telescopic discoveries (how Blumenthal Blumenberg thinks he knows this is anybody's guess).
David Wilson (talk · cont) 12:13, 17 April 2015 (UTC)
Hans Blumenberg's name seems to have been Blumenberg, not Blumenthal. Hans might have thought that his claim put Galileo in a good light, as independent of Kepler.
How far Seleucus of Seleucia had come to the notice of Galileo is hard to ascertain.

Ship Argument[edit]

I should point out that the "Ship" thought experiment for frame of reference did not originate with Galileo as the text suggests, it appears centuries earlier in Oresme's "Livre du ciel et du monde" and also in Cusa's "Learned Ignorance". — Preceding unsigned comment added by (talk) 00:02, 31 March 2015 (UTC)

Nicholas of Cusa made several remarks that are close to modern ideas. Kepler might have mentioned him. — Preceding unsigned comment added by (talk) 09:38, 28 April 2015 (UTC)
Kepler mentioned Nicholas of Cusa in 1597. — Preceding unsigned comment added by (talk) 09:44, 28 April 2015 (UTC)
Nicholas of Cusa might have come to the notice of Galileo in 1597. — Preceding unsigned comment added by (talk) 13:29, 11 May 2015 (UTC)