Editing Geocentric model (section)

==Ptolemaic and rival systems==
{{too few opinions|date=June 2015}}<!--Missing [[Mu’ayyad al-Din al-’Urdi]] and [[Ibn al-Shatir]]-->
Not all Greeks agreed with the geocentric model. The [[Pythagoreanism|Pythagorean]] system has already been mentioned; some Pythagoreans believed the Earth to be one of several planets going around a central fire.<ref name= "JohansenRosenmeier1998"/> [[Hicetas]] and [[Ecphantus]], two Pythagoreans of the 5th century BC, and [[Heraclides Ponticus]] in the 4th century BC, believed that the Earth rotated on its axis but remained at the center of the universe.<ref name= "Sarton1953"/> Such a system still qualifies as geocentric. It was revived in the [[Middle Ages]] by [[Jean Buridan]]. Heraclides Ponticus was once thought to have proposed that both Venus and Mercury went around the Sun rather than the Earth, but it is now known that he did not.<ref name= "Eastwood1992"/> [[Martianus Capella]] definitely put Mercury and Venus in orbit around the Sun.<ref name="Lindberg2010"/> [[Aristarchus of Samos]] wrote a work, which has not survived, on [[heliocentrism]], saying that the Sun was at the center of the universe, while the Earth and other planets revolved around it.<ref name= "Lawson2004">{{cite book |last= Lawson |first= Russell M. |date= 2004 |title= Science in the Ancient World: An Encyclopedia |publisher= [[ABC-CLIO]] |isbn= 1851095349 |page=19}}</ref> His theory was not popular, and he had one named follower, [[Seleucus of Seleucia]].<ref name= "Russell1945"/>
[[Epicurus]] was the most radical. He correctly realized in the 4th century BC that the universe does not have any single center. This theory was widely accepted by the later Epicureans and was notably defended by [[Lucretius]] in his poem [[De rerum natura]].<ref>Line 1067 onwards.</ref>

===Copernican system===
{{Main|Copernican heliocentrism}}
In 1543, the geocentric system met its first serious challenge with the publication of [[Copernicus]]' ''[[De revolutionibus orbium coelestium]]'' (''On the Revolutions of the Heavenly Spheres''), which posited that the Earth and the other planets instead revolved around the Sun. The geocentric system was still held for many years afterwards, as at the time the Copernican system did not offer better predictions than the geocentric system, and it posed problems for both [[natural philosophy]] and scripture. The Copernican system was no more accurate than Ptolemy's system, because it still used circular orbits. This was not altered until [[Johannes Kepler]] postulated that they were elliptical (Kepler's [[Kepler's laws of planetary motion#First law|first law of planetary motion]]).

===Tychonic system===
{{Main|Tychonic system}}
[[Image:Tychonian system.svg|thumb|upright=1.2|In this depiction of the Tychonic system, the objects on blue orbits (the Moon and the Sun) revolve around the Earth. The objects on orange orbits (Mercury, Venus, Mars, Jupiter, and Saturn) revolve around the Sun. Around all is a sphere of stars, which rotates.]]
[[Tycho Brahe]] (1545-1601), made more accurate determinations of the positions of planets and stars. He sought the effect of stellar parallax, which would have been empirically verifiable proof of the Earth's motion around the Sun predicted by the Copernican model. Having observed no effect, he rejected the idea of the Earth's motion.{{sfnp|Kuhn|1957|pages=200–201}}  

Consequently, he introduced a new system, the Tychonic system, in which the Earth was still at the center of the universe, and around it revolved the Sun, but all the other planets revolved around the Sun in a set of epicycles. His model considered both the benefits of the Copernican model and the lack of evidence for the Earth's motion.{{sfnp|Kuhn|1957|pages=201–206}}

===Observation by Galileo and abandonment of the Ptolemaic model===
With the invention of the [[telescope]] in 1609, observations made by [[Galileo Galilei]] (such as that [[Jupiter]] has moons) called into question some of the tenets of geocentrism but did not seriously threaten it. Because he observed dark "spots" on the Moon, craters, he remarked that the moon was not a perfect celestial body as had been previously conceived. This was the first detailed observation by telescope of the Moon's imperfections, which had previously been explained by Aristotle as the Moon being [[Contamination|contaminated]] by Earth and its heavier elements, in contrast to the [[aether (classical element)|aether]] of the higher spheres. Galileo could also see the moons of Jupiter, which he dedicated to [[Cosimo II de' Medici, Grand Duke of Tuscany|Cosimo II de' Medici]], and stated that they orbited around Jupiter, not Earth.<ref name= "Finocchiaro2008"/> This was a significant claim as it would mean not only that not everything revolved around Earth as stated in the Ptolemaic model, but also showed a secondary celestial body could orbit a moving celestial body, strengthening the heliocentric argument that a moving Earth could retain the Moon.<ref>{{cite web|url=http://www.atnf.csiro.au/outreach/education/senior/astrophysics/galileo.html|title=Galileo and the Telescope|work=Commonwealth Scientific and Industrial Research Organisation|access-date=17 October 2014}}</ref> Galileo's observations were verified by other astronomers of the time period who quickly adopted use of the telescope, including [[Christoph Scheiner]], [[Johannes Kepler]], and Giovan Paulo Lembo.<ref>Lattis, James L. (1995). Between Copernicus and Galileo: Christoph Clavius and the Collapse of Ptolemaic Cosmology, University of Chicago Press, pgs 186-190</ref>

{{multiple image
|footer=In 1610 [[Galileo Galilei]] observed with his telescope that [[Phases of Venus|Venus showed phases]], despite remaining near the Sun in Earth's sky (first image). This proved that it orbits the [[Sun]] and not [[Earth]], as predicted by [[Copernican heliocentrism|Copernican]] and [[Tychonic system|Tychonic]] models, and disproved the Ptolemaic one (second image). 
|align=right
|image1 = Phases-of-Venus2.svg|
|image2 = Phases-of-Venus-Geocentric.svg|}}
In December 1610, [[Galileo Galilei]] used his telescope to observe that [[Venus]] showed all [[Phases of Venus|phases]], just [[lunar phase|like the Moon]]. He thought that while this observation was incompatible with the Ptolemaic system, it was a natural consequence of the heliocentric system.

However, Ptolemy placed Venus' [[deferent]] and [[epicycle]] entirely inside the sphere of the Sun (between the Sun and Mercury), but this was arbitrary; he could just as easily have swapped Venus and Mercury and put them on the other side of the Sun, or made any other arrangement of Venus and Mercury, as long as they were always near a line running from the Earth through the Sun, such as placing the center of the Venus epicycle near the Sun. In this case, if the Sun is the source of all the light, under the Ptolemaic system:
{{Blockquote|If Venus is between Earth and the Sun, the phase of Venus must always be [[crescent]] or all dark.

If Venus is beyond the Sun, the phase of Venus must always be [[gibbous]] or full.}}
But Galileo saw Venus at first small and full, and later large and crescent.
This showed that with a Ptolemaic cosmology, the Venus epicycle can be neither completely inside nor completely outside of the orbit of the Sun. As a result, Ptolemaics abandoned the idea that the epicycle of Venus was completely inside the Sun, and later 17th-century competition between astronomical cosmologies focused on variations of the Tychonic or Copernican systems.
===Historical positions of the Roman Catholic hierarchy===
The famous [[Galileo affair]] pitted the geocentric model against the claims of [[Galileo]]. In regards to the theological basis for such an argument, two Popes addressed the question of whether the use of phenomenological language would compel one to admit an error in Scripture. Both taught that it would not. [[Pope Leo XIII]] wrote:
{{Blockquote|we have to contend against those who, making an evil use of physical science, minutely scrutinize the Sacred Book in order to detect the writers in a mistake, and to take occasion to vilify its contents. ... There can never, indeed, be any real discrepancy between the theologian and the physicist, as long as each confines himself within his own lines, and both are careful, as St. Augustine warns us, "not to make rash assertions, or to assert what is not known as known". If dissension should arise between them, here is the rule also laid down by St. Augustine, for the theologian: "Whatever they can really demonstrate to be true of physical nature, we must show to be capable of reconciliation with our Scriptures; and whatever they assert in their treatises which is contrary to these Scriptures of ours, that is to Catholic faith, we must either prove it as well as we can to be entirely false, or at all events we must, without the smallest hesitation, believe it to be so." To understand how just is the rule here formulated we must remember, first, that the sacred writers, or to speak more accurately, the Holy Ghost "Who spoke by them, did not intend to teach men these things (that is to say, the essential nature of the things of the visible universe), things in no way profitable unto salvation." Hence they did not seek to penetrate the secrets of nature, but rather described and dealt with things in more or less figurative language, or in terms which were commonly used at the time, and which in many instances are in daily use at this day, even by the most eminent men of science. Ordinary speech primarily and properly describes what comes under the senses; and somewhat in the same way the sacred writers-as the Angelic Doctor also reminds us – "went by what sensibly appeared", or put down what God, speaking to men, signified, in the way men could understand and were accustomed to.|[[Providentissimus Deus]] 18}}

Maurice Finocchiaro, author of a book on the Galileo affair, notes that this is "a view of the relationship between biblical interpretation and scientific investigation that corresponds to the one advanced by Galileo in the "[[Letter to the Grand Duchess Christina]]".<ref name="Finocchiaro1989"/> [[Pope Pius XII]] repeated his predecessor's teaching:
{{Blockquote|The first and greatest care of Leo XIII was to set forth the teaching on the truth of the Sacred Books and to defend it from attack. Hence with grave words did he proclaim that there is no error whatsoever if the sacred writer, speaking of things of the physical order "went by what sensibly appeared" as the Angelic Doctor says, speaking either "in figurative language, or in terms which were commonly used at the time, and which in many instances are in daily use at this day, even among the most eminent men of science". For "the sacred writers, or to speak more accurately – the words are St. Augustine's – the Holy Spirit, Who spoke by them, did not intend to teach men these things – that is the essential nature of the things of the universe – things in no way profitable to salvation"; which principle "will apply to cognate sciences, and especially to history", that is, by refuting, "in a somewhat similar way the fallacies of the adversaries and defending the historical truth of Sacred Scripture from their attacks".|''[[Divino afflante Spiritu]]'', 3}}

In 1664, [[Pope Alexander VII]] republished the ''[[Index Librorum Prohibitorum]]'' (''List of Prohibited Books'') and attached the various decrees connected with those books, including those concerned with heliocentrism. He stated in a [[papal bull]] that his purpose in doing so was that "the succession of things done from the beginning might be made known [''quo rei ab initio gestae series innotescat'']".<ref name= "Alexandri VII1664"/>

The position of the curia evolved slowly over the centuries towards permitting the heliocentric view. In 1757, during the papacy of Benedict XIV, the Congregation of the Index withdrew the decree that prohibited ''all'' books teaching the Earth's motion, although the ''Dialogue'' and a few other books continued to be explicitly included. In 1820, the Congregation of the Holy Office, with the pope's approval, decreed that Catholic astronomer [[Giuseppe Settele]] was allowed to treat the Earth's motion as an established fact and removed any obstacle for Catholics to hold to the motion of the Earth:
{{Blockquote|The Assessor of the Holy Office has referred the request of Giuseppe Settele, Professor of Optics and Astronomy at La Sapienza University, regarding permission to publish his work Elements of Astronomy in which he espouses the common opinion of the astronomers of our time regarding the Earth’s daily and yearly motions, to His Holiness through Divine Providence, Pope Pius VII. Previously, His Holiness had referred this request to the Supreme Sacred Congregation and concurrently to the consideration of the Most Eminent and Most Reverend General Cardinal Inquisitor. His Holiness has decreed that no obstacles exist for those who sustain Copernicus' affirmation regarding the Earth's movement in the manner in which it is affirmed today, even by Catholic authors. He has, moreover, suggested the insertion of several notations into this work, aimed at demonstrating that the above mentioned affirmation [of Copernicus], as it has come to be understood, does not present any difficulties; difficulties that existed in times past, prior to the subsequent astronomical observations that have now occurred. [Pope Pius VII] has also recommended that the implementation [of these decisions] be given to the Cardinal Secretary of the Supreme Sacred Congregation and Master of the Sacred Apostolic Palace. He is now appointed the task of bringing to an end any concerns and criticisms regarding the printing of this book, and, at the same time, ensuring that in the future, regarding the publication of such works, permission is sought from the Cardinal Vicar whose signature will not be given without the authorization of the Superior of his Order.<ref>{{Cite web|url=https://inters.org/approval-Settele-heliocentric|title=Decree of Approval for the Work "Elements of Astronomy" by Giuseppe Settele, in support of the Heliocentric System &#124; Inters.org|website=inters.org}}</ref>}}

In 1822, the Congregation of the Holy Office removed the prohibition on the publication of books treating of the Earth's motion in accordance with modern astronomy and Pope Pius VII ratified the decision:
{{Blockquote|The most excellent [cardinals] have decreed that there must be no denial, by the present or by future Masters of the Sacred Apostolic Palace, of permission to print and to publish works which treat of the mobility of the Earth and of the immobility of the sun, according to the common opinion of modern astronomers, as long as there are no other contrary indications, on the basis of the decrees of the Sacred Congregation of the Index of 1757 and of this Supreme [Holy Office] of 1820; and that those who would show themselves to be reluctant or would disobey, should be forced under punishments at the choice of [this] Sacred Congregation, with derogation of [their] claimed privileges, where necessary.<ref>{{cite book|last=Fantoli|first=Annibale|title=Galileo: For Copernicanism and For the Church|date=1996|publisher=University of Notre Dame|isbn=0268010323|page=475}}</ref>}}

The 1835 edition of the Catholic ''List of Prohibited Books'' for the first time omits the ''Dialogue'' from the list.<ref name="Finocchiaro1989"/> In his 1921 [[papal encyclical]], ''[[In praeclara summorum]]'', [[Pope Benedict XV]] stated that, "though this Earth on which we live may not be the center of the universe as at one time was thought, it was the scene of the original happiness of our first ancestors, witness of their unhappy fall, as too of the Redemption of mankind through the Passion and Death of Jesus Christ".<ref name= "BenedictXV1921"/> In 1965 the [[Second Vatican Council]] stated that, "Consequently, we cannot but deplore certain habits of mind, which are sometimes found too among Christians, which do not sufficiently attend to the rightful independence of science and which, from the arguments and controversies they spark, lead many minds to conclude that faith and science are mutually opposed."<ref name= "PaulIV19665"/> The footnote on this statement is to Msgr. Pio Paschini's, ''Vita e opere di Galileo Galilei'', 2 volumes, Vatican Press (1964). [[Pope John Paul II]] regretted the treatment that Galileo received, in a speech to the [[Pontifical Academy of Sciences]] in 1992. The Pope declared the incident to be based on a "tragic mutual miscomprehension". He further stated:
{{Blockquote|Cardinal Poupard has also reminded us that the sentence of 1633 was not irreformable, and that the debate which had not ceased to evolve thereafter, was closed in 1820 with the imprimatur given to the work of Canon Settele. ... The error of the theologians of the time, when they maintained the centrality of the Earth, was to think that our understanding of the physical world's structure was, in some way, imposed by the literal sense of Sacred Scripture. Let us recall the celebrated saying attributed to Baronius "Spiritui Sancto mentem fuisse nos docere quomodo ad coelum eatur, non quomodo coelum gradiatur". In fact, the Bible does not concern itself with the details of the physical world, the understanding of which is the competence of human experience and reasoning. There exist two realms of knowledge, one which has its source in Revelation and one which reason can discover by its own power. To the latter belong especially the experimental sciences and philosophy. The distinction between the two realms of knowledge ought not to be understood as opposition.<ref name= "John PaulII1992"/>}}