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'[[Image:Heliocentric.jpg|thumb|250px|right|Heliocentric Universe]] [[Image:geoz wb en.svg|thumb|250px|Heliocentrism (lower panel) in comparison to the geocentric model (upper panel)]] '''Heliocentrism''', or '''heliocentricism''',<ref>''Teaching about Evolution and the Nature of Science'' (National Academy of Sciences, 1998), p.27; also, Don O' Leary, ''Roman Catholicism and Modern Science: A History'' (Continuum Books, 2006), p.5.</ref> is the [[astronomy|astronomical]] theory that the [[Earth]] and planets revolve around the [[Sun]] and that the Sun is stationary and at the center of the [[universe]]. The word comes from the [[Ancient Greek|Greek]] ({{lang|el|[[wikt:ἥλιος|ἥλιος]]}} ''[[helios]]'' "sun" and {{lang|el|[[wikt:κέντρον|κέντρον]]}} ''kentron'' "center"). Historically, heliocentrism was opposed to [[geocentrism]], which placed the Earth at the center. The notion that the Earth revolves around the Sun was first proposed in the [[3rd century BC]] by [[Aristarchus of Samos]]. However, it was not until the 16th century that a fully predictive mathematical model of a heliocentric system was presented, by<!-- do not add a nationality claim --> mathematician and astronomer [[Nicolaus Copernicus]]. In the following century, this model was elaborated and expanded by [[Johannes Kepler]] and supporting observations made using a [[telescope]] were presented by [[Galileo Galilei]]. ==Development of heliocentrism== To anyone who stands and looks at the sky, it seems clear that the Earth stays in one place while everything in the sky rises and sets once a day. Observing over a longer time, one sees more complicated movements. The Sun makes a slower circle over the course of a year; the [[planet]]s have similar motions, but they sometimes move in the reverse direction for a while ([[apparent retrograde motion|retrograde motion]]). As these motions became better understood, more elaborate descriptions were required, the most famous of which was the geocentric [[Ptolemaic system]], formulated in the 2nd century. Though incorrect, the Ptolemaic system manages to calculate the correct positions for the planets to a moderate degree of accuracy, though [[Ptolemy]]'s demand that [[Deferent and epicycle|epicycles]] not be eccentric caused needless problems for the motions of [[Mars]] and especially [[Mercury (planet)|Mercury]]. Ptolemy himself, in his ''[[Almagest]]'', points out that any model for describing the motions of the planets is merely a mathematical device, and since there is no actual way to know which is true, the simplest model that gets the right numbers should be used;{{Citation needed|date=August 2009}} however, he himself chose the epicyclic geocentric model and in his ultimate work, [[Ptolemy#Astronomy|Planetary Hypotheses]], treated his models as sufficiently real that the distances of moon, sun, planets and stars could be determined by treating orbits' [[Celestial spheres#Antiquity|celestial spheres]] as contiguous realities. This made the stars' distance less than 20 [[Astronomical Units]]<ref>Dennis Duke, [http://people.scs.fsu.edu/~dduke/ptolemy.html Ptolemy's Universe]</ref>—a clear regression, since Aristarchus's heliocentric scheme had centuries earlier [[#Ancient Greece|necessarily]] placed the stars at least two orders of magnitude more distant. ===Philosophical discussions=== Philosophical arguments on heliocentrism involve general statements that the Sun is at the center of the universe or that some or all of the planets revolve around the Sun, and arguments supporting these claims. These ideas can be found in a range of [[Greek language|Greek]], [[Arabic]] and [[Latin]] texts. These early sources, however, do not provide techniques to compute any observational consequences of their proposed heliocentric ideas. ====Ancient Greece==== {{See|Greek astronomy}} In the 4th century BC, [[Aristotle]] wrote that: {{quote|"At the center, they [the [[Pythagoreans]]] say, is [[fire (classical element)|fire]], and the Earth is one of the stars, creating night and day by its circular motion about the center."|[[Aristotle]]|''[[On the Heavens]]'', [http://etext.library.adelaide.edu.au/a/aristotle/heavens/book2.html Book Two], Chapter 13}} [[Image:Aristarchus working.jpg|thumb|right|[[Aristarchus of Samos|Aristarchus's]] 3rd century BC calculations on the relative sizes of the Earth, Sun and Moon, from a 10th century AD Greek copy]] The reasons for this placement were [[Greek philosophy|philosophic]], based on the [[classical element]]s, rather than scientific; fire was more precious than earth in the opinion of the Pythagoreans, and for this reason the fire should be central. However, the central fire is not the Sun. The Pythagoreans believed the Sun orbited the central fire along with everything else. Aristotle dismissed this argument and advocated geocentrism. [[Heraclides Ponticus|Heraclides of Pontus]] (4th century BC) explained the apparent daily motion of the celestial sphere through the rotation of the Earth. The first person to present an argument for a heliocentric system, however, was [[Aristarchus of Samos]] (''c''. 270 BC). Like [[Eratosthenes]], [[Aristarchus]] calculated the size of the Earth, and measured the [[Aristarchus On the Sizes and Distances|size and distance of the Moon and Sun]], in a treatise which has survived. From his estimates, he concluded that the Sun was six to seven times wider than the Earth and thus hundreds of times more voluminous. His writings on the heliocentric system are lost, but some information is known from surviving descriptions and critical commentary by his contemporaries, such as [[Archimedes]]. Some have suggested that his calculation of the relative size of the Earth and Sun led Aristarchus to conclude that it made more sense for the Earth to be moving than for the huge Sun to be moving around it. Though the original text has been lost, a reference in [[Archimedes]]' book ''[[The Sand Reckoner]]'' describes another work by Aristarchus in which he advanced an alternative [[hypothesis]] of the heliocentric model. Archimedes wrote: {{quote|You King Gelon are aware the 'universe' is the name given by most astronomers to the sphere the center of which is the center of the Earth, while its radius is equal to the straight line between the center of the Sun and the center of the Earth. This is the common account as you have heard from astronomers. But Aristarchus has brought out a book consisting of certain hypotheses, wherein it appears, as a consequence of the assumptions made, that the universe is many times greater than the 'universe' just mentioned. His hypotheses are that the fixed stars and the Sun remain unmoved, that the Earth revolves about the Sun on the circumference of a circle, the Sun lying in the middle of the orbit, and that the sphere of fixed [[star]]s, situated about the same center as the Sun, is so great that the circle in which he supposes the Earth to revolve bears such a proportion to the distance of the fixed stars as the center of the sphere bears to its surface.<ref>Arenarius, I., 4–7</ref>}} Aristarchus thus believed the stars to be very far away, and saw this as the reason why there was no visible [[parallax]], that is, an observed movement of the stars relative to each other as the Earth moved around the Sun. The stars are in fact much farther away than the distance that was generally assumed in ancient times, which is why stellar parallax is only detectable with [[telescope]]s. [[Archimedes]] says that Aristarchus made the stars' distance larger, suggesting that he was answering the natural objection that heliocentrism requires stellar parallactic oscillations. He apparently agreed to the point but placed the stars so distant as to make the parallactic motion invisibly minuscule. Thus heliocentrism opened the way for realization that the universe was larger than the geocentrists taught.<ref><cite id="rawlinsnote">D.Rawlins, [http://www.dioi.org/vols/we0.pdf Aristarchus's vast universe: ancient vision], contends that all of Aristarchus's huge astronomical estimates of distance were based upon his gauging the limit of human visual discrimination to be approximately a ten thousandth of a radian which is about right.</cite></ref> It should be noted that [[Plutarch]] mentions the 'followers of Aristarchus' in passing, so it is likely that there are other astronomers in the Classical period who also espoused heliocentrism whose work is now lost to us. However, the only other astronomer from antiquity who is known by name and who is known to have supported Aristarchus' heliocentric model was [[Seleucus of Seleucia]], a [[Babylonian astronomy|Mesopotamian astronomer]] who lived a century after Aristarchus. [[Seleucus of Seleucia]] (b. 190 BC)<ref>{{cite web|url=http://adsabs.harvard.edu/abs/2000eaa..bookE3998 |title=Seleucus of Seleucia (c. 190 BC-?) |doi=10.1888/0333750888 |publisher=Adsabs.harvard.edu |date= |accessdate=2009-08-08}}</ref> adopted the heliocentric system of [[Aristarchus of Samos]], and is said to have proved the heliocentric theory.<ref>{{cite web|url=http://www.ics.forth.gr/~vsiris/ancient_greeks/hellinistic_period.html |title=Index of Ancient Greek Philosophers-Scientists |publisher=Ics.forth.gr |date= |accessdate=2009-08-08}}</ref> According to [[Bartel Leendert van der Waerden]], Seleucus may have proved the heliocentric theory by determining the constants of a [[geometry|geometric]] model for the heliocentric theory and by developing methods to compute planetary positions using this model. He may have used [[trigonometry|trigonometric]] methods that were available in his time, as he was a contemporary of [[Hipparchus]].<ref>[[Bartel Leendert van der Waerden]] (1987). "The Heliocentric System in Greek, Persian and Hindu Astronomy", ''Annals of the New York Academy of Sciences'' '''500''' (1), 525–545 [527–529].</ref> ====Medieval Europe==== [[Image:Nicholas of Cusa.jpg|right|thumb|[[Nicholas of Cusa]], 15th century, asked whether there was any reason to assert heliocentrism]] There were occasional speculations about heliocentrism in Europe before Copernicus. In [[Carthage#Roman Carthage|Roman Carthage]], [[Martianus Capella]] (5th century A.D.) expressed the opinion that the planets Venus and Mercury did not go about the Earth but instead circled the Sun.<ref>William Stahl, trans., ''Martianus Capella and the Seven Liberal Arts'', vol. 2, ''The Marriage of Philology and Mercury'', 854, 857, New York: Columbia Univ. Pr, 1977, pp. 332–3</ref> Capella's model was discussed in the [[Early Middle Ages]] by various anonymous [[ninth-century]] commentators<ref>{{cite book | last = Eastwood | first = Bruce S. | title = Ordering the Heavens: Roman Astronomy and Cosmology in the Carolingian Renaissance | publisher = Brill | date = 2007 | location = Leiden | pages = 244–259 | isbn = 978-90-04-16186-3}}</ref> and Copernicus mentions him as an influence on his own work.<ref>Bruce S. Eastwood, "Kepler as Historian of Science: Precursors of Copernican Heliocentrism according to ''De revolutionibus'' I, 10", ''Proceedings of the American Philosophical Society'', 126 (1982): 367–394.</ref> During the [[Late Middle Ages]], Bishop [[Nicole Oresme]] discussed the possibility that the Earth rotated on its axis, while Cardinal [[Nicholas of Cusa]] in his ''[[De Docta Ignorantia|Learned Ignorance]]'' asked whether there was any reason to assert that the Sun (or any other point) was the center of the universe. In parallel to a mystical definition of God, Cusa wrote that "Thus the fabric of the world (''machina mundi'') will ''quasi'' have its center everywhere and circumference nowhere."<ref>Nicholas of Cusa, ''De docta ignorantia'', 2.12, p. 103, cited in Koyré (1957), p. 17.</ref> ===Mathematical astronomy=== In [[Mathematics|mathematical]] astronomy, models of heliocentrism involve mathematical computational systems that are tied to a heliocentric model and where positions of the planets can be derived. The first computational system explicitly tied to a heliocentric model was the [[Copernican heliocentrism|Copernican model]] described by [[Copernicus]], but there were earlier computational systems that may have implied some form of heliocentricity, notably [[Aryabhata]]'s model, which has astronomical parameters which some have interpreted to imply a form of heliocentricity. Several [[Islamic astronomy|Muslim astronomers]] also developed computational systems with astronomical parameters compatible with heliocentricity, as stated by [[Abū al-Rayhān al-Bīrūnī|Biruni]], but the concept of heliocentrism was considered a philosophical problem rather than a mathematical problem. Their astronomical parameters were later adapted in the Copernican model in a heliocentric context. ====Medieval India==== [[Image:2064 aryabhata-crp.jpg|thumb|right|[[Aryabhata]], 5th century, developed a computational planetary model which has been interpreted as heliocentric]] {{See|Indian astronomy}} [[Aryabhata]] (476–550), in his ''magnum opus'' ''[[Aryabhatiya]]'', propounded a computational system based on a planetary model in which the Earth was taken to be [[Earth's rotation|spinning on its axis]] and the periods of the planets were given with respect to the Sun. Some have interpreted this to be a heliocentric model,<ref>[[Bartel Leendert van der Waerden|B. L. van der Waerden]] (1970), ''Das heliozentrische System in der griechischen,persischen und indischen Astronomie,'' Naturforschenden Gesellschaft in Zürich, Zürich: Kommissionsverlag Leeman AG. ([[cf.]] Noel Swerdlow (June 1973), "Review: A Lost Monument of Indian Astronomy", ''Isis'' '''64''' (2), p. 239–243.) <br />[[Bartel Leendert van der Waerden|B. L. van der Waerden]] (1987), "The heliocentric system in Greek, Persian, and Indian astronomy", in "From deferent to equant: a volume of studies in the history of science in the ancient and medieval near east in honor of E. S. Kennedy", ''[[New York Academy of Sciences]]'' '''500''', p. 525–546. ([[cf.]] Dennis Duke (2005), "The Equant in India: The Mathematical Basis of Ancient Indian Planetary Models", ''Archive for History of Exact Sciences'' '''59''', p. 563–576.).</ref><ref>Thurston (1994), p. 188. {{quote|"Not only did Aryabhata believe that the earth rotates, but there are glimmerings in his system (and other similar systems) of a possible underlying theory in which the earth (and the planets) orbits the sun, rather than the sun orbiting the earth. The evidence is that the basic planetary periods are relative to the sun."}}</ref><ref>[[Lucio Russo]] (2004), ''The Forgotten Revolution: How Science Was Born in 300 BC and Why It Had To Be Reborn'', [[Springer Science+Business Media|Springer]], Berlin, ISBN 978-3-540-20396-4. ([[cf.]] Dennis Duke (2005), "The Equant in India: The Mathematical Basis of Ancient Indian Planetary Models", ''Archive for History of Exact Sciences'' '''59''', p. 563–576.)</ref> but this view has been disputed by others.<ref>Noel Swerdlow (June 1973), "Review: A Lost Monument of Indian Astronomy" [review of [[Bartel Leendert van der Waerden|B. L. van der Waerden]], ''Das heliozentrische System in der griechischen, persischen und indischen Astronomie''], ''Isis'' '''64''' (2), p. 239–243. {{quote|"Such an interpretation, however, shows a complete misunderstanding of Indian planetary theory and is flatly contradicted by every word of Aryabhata's description."}}</ref><ref>David Pingree (1973), "The Greek Influence on Early Islamic Mathematical Astronomy", ''Journal of the American Oriental Society'' '''93''' (1), p. 32. {{quote|"The reader should note that, in writing this survey, I have disregarded the rather divergent views of [[Bartel Leendert van der Waerden|B. L. van der Waerden]]; these have been most recently expounded in his ''Das heliozentrische System in der griechischen, persischen und indischen Astronomie'', Zürich 1970."}}</ref><ref>Dennis Duke (2005), "The Equant in India: The Mathematical Basis of Ancient Indian Planetary Models", ''Archive for History of Exact Sciences'' '''59''', p. 563–576 [http://people.scs.fsu.edu/~dduke/india8.pdf]. {{quote|"Thus for both outer and inner planets, the mean motion given is the heliocentric mean motion of the planet. There is no textual evidence that the Indians knew anything about this, and there is an overwhelming amount of textual evidence confirming their geocentric point of view. Some commentators, most notably van der Waerden, have however argued in favor of an underlying ancient Greek heliocentric basis, of which the Indians were unaware. See, e.g. B. L. van der Waerden, “The heliocentric system in Greek, Persian, and Indian astronomy”, in ''From deferent to equant: a volume of studies in the history of science in the ancient and medieval near east in honor of E. S. Kennedy'', Annals of the new york academy of sciences, 500 (1987), 525–546. More recently this idea is developed in about as much detail as the scant evidence allows in L. Russo, ''The Forgotten Revolution'' (2004)."}}</ref> He was also the first to discover that the planets follow [[ellipse|elliptical]] orbits, on which he accurately calculated many astronomical constants, such as the periods of the planets, times of the [[solar eclipse|solar]] and [[lunar eclipse|lunar]] [[eclipse]]s, and the instantaneous motion of the Moon.<ref name=Joseph>Joseph (2000).</ref><ref>Thurston (1994).</ref> Early followers of Aryabhata's model included [[Varahamihira]], [[Brahmagupta]], and [[Bhaskara II]].<br /><br /> [[Nilakantha Somayaji]] (1444–1544), in his ''Aryabhatiyabhasya'', a commentary on Aryabhata's ''Aryabhatiya'', developed a computational system for a partially heliocentric planetary model, in which the planets orbit the Sun, which in turn orbits the Earth, similar to the [[Tychonic system]] later proposed by [[Tycho Brahe]] in the late 16th century. Nilakantha's system, however, was mathematically more efficient than the Tychonic system, due to correctly taking into account the equation of the center and [[latitude|latitudinal]] motion of Mercury and Venus. Most astronomers of the [[Kerala school of astronomy and mathematics]] who followed him accepted his planetary model.<ref>George G. Joseph (2000), p. 408.</ref><ref>K. Ramasubramanian, M. D. Srinivas, M. S. Sriram (1994). "Modification of the earlier Indian planetary theory by the Kerala astronomers (c. 1500 AD) and the implied heliocentric picture of planetary motion", ''[[Current Science]]'' '''66''', p. 784–790.</ref> ====Middle East==== [[Image:Ghotb2.jpg|thumb|[[Qutb al-Din al-Shirazi|Qutb al-Din]], 13th century AD, discussed whether heliocentrism was a possibility]] {{See|Islamic astronomy}} In the medieval [[Islamic Golden Age|Islamic civilization]], due to the scientific dominance of the [[Geocentric model#Claudius Ptolemy|Ptolemaic system]] in early [[Islamic astronomy]], most [[List of Muslim astronomers|Muslim astronomers]] accepted the geocentric model.<ref>"All Islamic astronomers from Thabit ibn Qurra in the ninth century to Ibn al-Shatir in the fourteenth, and all natural philosophers from al-Kindi to Averroes and later, are known to have accepted ... the Greek picture of the world as consisting of two spheres of which one, the celestial sphere ... concentrically envelops the other." A. I. Sabra, "Configuring the Universe: Aporetic, Problem Solving, and Kinematic Modeling as Themes of Arabic Astronomy," ''Perspectives on Science'' 6.3 (1998): 288–330, at pp. 317–18</ref> However, several Muslim scholars had discussions on whether the Earth moved and tried to explain how this might be possible. In the 9th century, the Persian astronomer [[Ja'far ibn Muhammad Abu Ma'shar al-Balkhi]] developed a planetary model which can be interpreted as a heliocentric model. This is due to his [[Orbit (disambiguation)|orbital revolutions]] of the planets being given as heliocentric revolutions rather than geocentric revolutions, and the only known planetary theory in which this occurs is in the heliocentric theory. His work on planetary theory has not survived, but his astronomical data were later recorded by al-Hashimi and [[Abū Rayhān al-Bīrūnī]].<ref>[[Bartel Leendert van der Waerden]] (1987). "The Heliocentric System in Greek, Persian and Hindu Astronomy", ''Annals of the New York Academy of Sciences'' '''500''' (1), 525–545 [534–537].</ref> [[Ibn al-Haytham|Alhacen]] (Ibn al-Haytham) wrote a scathing critique of [[Ptolemy]]'s model in his ''Doubts on Ptolemy'' (c. 1028), which some interpret to imply he was criticizing Ptolemy's geocentrism,<ref name=Qadir>Qadir (1989), p. 5–10.</ref> but many agree that he was actually criticizing the details of Ptolemy's model rather than his geocentrism.<ref>[http://setis.library.usyd.edu.au/stanford/entries/copernicus/index.html Nicolaus Copernicus], [[Stanford Encyclopedia of Philosophy]] (2004).</ref> Alhacen did, however, later propose the [[Earth's rotation]] on its axis in ''The Model of the Motions'' (c. 1038).<ref>Roshdi Rashed (2007). "The Celestial Kinematics of Ibn al-Haytham", ''Arabic Sciences and Philosophy'' '''17''', p. 7–55. [[Cambridge University Press]].</ref> In 1030, the Persian scientist and astronomer [[Abū Rayhān Bīrūnī|Biruni]] discussed the Indian astronomical theories of [[Aryabhata]], [[Brahmagupta]] and [[Varahamihira]] in his ''Indica''. (Al-)Biruni agreed with the [[Earth's rotation]] about its own axis, and while he was initially neutral regarding the heliocentric and [[geocentric model]]s,<ref>Michael E. Marmura (1965). "''An Introduction to Islamic Cosmological Doctrines. Conceptions of Nature and Methods Used for Its Study by the Ikhwan Al- lmfao -Safa'an, Al-Biruni, and Ibn Sina'' by Seyyed [[Hossein Nasr]]", ''Speculum'' '''40''' (4), p. 744–746.</ref> he noted that heliocentrism was a philosophical problem, rather than a mathematical problem.<ref name=Saliba>Saliba (1999).</ref> Abu Said [[al-Sijzi]], a contemporary of Biruni, suggested the possible movement of the Earth around the Sun, which Biruni did not reject. [[Qutb al-Din al-Shirazi|Qutb al-Din]] (b. 1236), in his ''The Limit of Accomplishment concerning Knowledge of the Heavens'', also discussed whether heliocentrism was a possibility.<ref name=Baker>A. Baker, L. Chapter (2002).</ref> [[Image:Al-Biruni Afghan stamp.jpg|thumb|right|11th-century Persian scientist, [[Abū al-Rayhān al-Bīrūnī|Biruni]], suggested that if the [[Earth's rotation|Earth rotated]] on its axis this would be consistent with astronomical theory. He discussed heliocentrism but considered it was a philosophical problem.]] [[Abū Rayhān Bīrūnī|Biruni]] discussed the possibility of whether the Earth rotated about its own axis and around the Sun, but in his ''Masudic Canon'', he set forth the principles that the Earth is at the center of the universe and that it has no motion of its own.<ref>E. S. Kennedy, "Al-Bīrūnī's Masudic Canon", ''Al-Abhath'', 24 (1971): 59–81; reprinted in David A. King and Mary Helen Kennedy, ed., ''Studies in the Islamic Exact Sciences,'' Beirut, 1983, pp. 573–595.</ref> He was aware that if the Earth rotated on its axis and around the Sun, this would be consistent with his astronomical parameters,<ref name=Khwarizm>[http://muslimheritage.com/topics/default.cfm?ArticleID=482 Khwarizm], Foundation for Science Technology and Civilisation.</ref><ref>G. Wiet, V. Elisseeff, P. Wolff, J. Naudu (1975). ''History of Mankind, Vol 3: The Great medieval Civilisations'', p. 649. George Allen & Unwin Ltd, [[UNESCO]].</ref> but he considered this a philosophical problem rather than a mathematical one.<ref name=Saliba/> [[Nasīr al-Dīn al-Tūsī|Nasir al-Din al-Tusi]] (b. 1201) resolved significant problems in the [[Geocentric model#Claudius Ptolemy|Ptolemaic system]] by developing the [[Tusi-couple]] as an alternative to the physically problematic [[equant]] introduced by [[Ptolemy]].<ref name=Gill>M. Gill (2005).</ref> 'Umar al-Katibi al-[[Qazwini]] (d. 1277), who also worked at the [[Maragheh observatory]], in his ''Hikmat al-'Ain'', wrote an argument for a heliocentric model, but later abandoned the model.<ref name=Baker/> [[Ibn al-Shatir]] (b. 1304) eliminated the need for an equant, proposing a system that was only approximately geocentric, rather than exactly so, having demonstrated [[trigonometry|trigonometrically]] that the Earth was not the exact center of the universe. His rectification was later used in the Copernican model, along with the earlier [[Tusi-couple]] and the Urdi lemma of [[Mo'ayyeduddin Urdi]]. Their theorems played an important role in the [[Copernican heliocentrism|Copernican model of heliocentrism]],<ref name=Gill/> which was achieved by reversing the direction of the last vector connecting the Earth to the Sun.<ref name=Saliba/> In the published version of his masterwork, Copernicus also cites the theories of [[Muhammad ibn Jābir al-Harrānī al-Battānī|Albategni]], [[Arzachel]] and [[Averroes]] as influences,<ref name=Covington>Covington (2007).</ref> while the works of [[Ibn al-Haytham|Alhacen]] and [[Abū al-Rayhān al-Bīrūnī|Biruni]] were also known in Europe at the time.<ref name=Qadir/> ====Renaissance Europe==== {{Main|Copernican heliocentrism}} [[Image:Mikolaj Kopernik.jpg|thumb|right|[[Nicolaus Copernicus]], 16th century, described the first computational system explicitly tied to a heliocentric model]] In the 16th century, [[Nicolaus Copernicus]]'s ''[[De revolutionibus]]'' presented a full discussion of a heliocentric model of the universe in much the same way as [[Ptolemy]]'s ''[[Almagest]]'' had presented his geocentric model in the 2nd century. Copernicus discussed the philosophical implications of his proposed system, elaborated it in full geometrical detail, used selected astronomical observations to derive the parameters of his model, and wrote astronomical tables which enabled one to compute the past and future positions of the stars and planets. In doing so, Copernicus moved heliocentrism from philosophical speculation to predictive geometrical astronomy. This theory resolved the issue of planetary retrograde motion by arguing that such motion was only perceived and apparent, rather than [[reality|real]]: it was a [[parallax]] effect, as a car that one is passing seems to move backwards against the horizon. This issue was also resolved in the geocentric [[Tychonic system]]; the latter, however, while eliminating the major [[epicycle]]s, retained as a physical reality the irregular back-and-forth motion of the planets, which [[Kepler]] characterized as a "[[pretzel]]."<ref>Owen Gingerich, ''The Book Nobody Read'' (Heinman, 2004, p. 51)</ref> Copernicus cited Aristarchus in an early (unpublished) manuscript of ''De Revolutionibus'' (which still survives) so he was clearly aware of at least one previous proponent of the heliocentric thesis. However, in the published version he restricts himself to noting that in works by [[Cicero]] he had found an account of the theories of [[Hicetas]] and that [[Plutarch]] had provided him with an account of the [[Pythagoreans]] [[Heraclides Ponticus]], [[Philolaus]], and [[Ecphantus]]. These authors had proposed a moving earth, which did not, however, revolve around a central sun. ==Religious attitudes to heliocentrism== Heliocentrism had been in conflict with religion before Copernicus. One of the few pieces of information we have about the reception of Aristarchus's heliocentric system comes from a passage in [[Plutarch]]'s dialogue, ''Concerning the Face which Appears in the Orb of the Moon''. According to one of Plutarch's characters in the dialogue, the philosopher [[Cleanthes]] had held that Aristarchus should be charged with impiety for "moving the hearth of the world".<ref>Dreyer [[#Reference-Dreyer-1953|(1953,]] [http://www.us.archive.org/GnuBook/?id=historyofplaneta00dreyuoft#151 p.138)]; Plutarch [[#Reference-Plutarch-1957|(1957, p.55)]] [http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Plutarch/Moralia/The_Face_in_the_Moon*/A.html#T923 (on-line copy available)]. According to [http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Plutarch/Moralia/The_Face_in_the_Moon*/A.html#note36 a footnote] in the latter reference, [[Diogenes Laertius]] listed a work of Cleanthes' (apparently now lost) with the title ''Against Aristarchus'' [[#Reference-Plutarch-1957|(Plutarch, 1957, p.54)]].</ref> In fact, however, Aristarchus's heliocentrism appears to have attracted little attention, religious or otherwise, until Copernicus revived and elaborated it.<ref>Dreyer [[#Reference-Dreyer-1953|(1953,]] [http://books.google.com.au/books?id=fL-P-UQtg5EC&pg=PA139 pp.139ff)].</ref> ===Circulation of Commentariolus (before 1533)=== The first information about the heliocentric views of [[Nicolaus Copernicus]] were circulated in manuscript. Although only in manuscript, Copernicus' ideas were well known among astronomers and others. His ideas appeared to contradict the bible. In the [[King James Bible]] Chronicles 16:30 state that "the world also shall be stable, that it be not moved." Psalm 104:5 says, "[the Lord] Who laid the foundations of the earth, that it should not be removed for ever." Ecclesiastes 1:5 states that "The sun also ariseth, and the sun goeth down, and hasteth to his place where he arose." Nonetheless, in 1533, [[Johann Albrecht Widmannstetter]] delivered in [[Rome]] a series of lectures outlining Copernicus' theory. The lectures were heard with interest by [[Pope Clement VII]] and several Catholic [[Cardinal (Catholicism)|cardinals]]. On 1 November 1536, [[Archbishop of Capua]] [[Nikolaus Cardinal von Schönberg|Nicholas Schönberg]] wrote a letter to Copernicus from Rome encouraging him to publish a full version of his theory. However, in 1539, [[Martin Luther]] said: {{quote|"There is talk of a new astrologer who wants to prove that the earth moves and goes around instead of the sky, the sun, the moon, just as if somebody were moving in a carriage or ship might hold that he was sitting still and at rest while the earth and the trees walked and moved. But that is how things are nowadays: when a man wishes to be clever he must . . . invent something special, and the way he does it must needs be the best! The fool wants to turn the whole art of astronomy upside-down. However, as Holy Scripture tells us, so did Joshua bid the sun to stand still and not the earth."}} This was reported in the context of a conversation at the dinner table and not a formal statement of faith. [[Melanchthon]], however, opposed the doctrine over a period of years. ===Publication of de Revolutionibus (1543)=== [[Nicolaus Copernicus]] published the definitive statement of his system in [[De Revolutionibus Orbium Coelestium|''De Revolutionibus'']] in 1543. Copernicus began to write it in 1506 and finished it in 1530, but did not publish it until the year of his death. Although he was in good standing with the Church and had dedicated the book to [[Pope Paul III]], the published form contained an unsigned preface by [[Andreas Osiander|Osiander]] defending the system and arguing that it was useful for computation even if its hypotheses were not necessarily true. Possibly because of that preface, the work of Copernicus inspired very little debate on whether it might be [[heresy|heretical]] during the next 60 years. There was an early suggestion among [[Dominican Order|Dominican]]s that the teaching of heliocentrism should be banned, but nothing came of it at the time. Some years after the publication of ''De Revolutionibus'' [[John Calvin]] preached a sermon in which he denounced those who "pervert the course of nature" by saying that "the sun does not move and that it is the earth that revolves and that it turns".<ref>[[#Reference-Rosen-1995|Rosen (1995, p.159).]] Rosen disputes the earlier conclusion of another scholar that this was referring specifically to Copernicus's theory. According to Rosen, Calvin had very likely never heard of Copernicus and was referring instead to "the traditional geokinetic cosmology".</ref> On the other hand, Calvin is not responsible for another famous quotation which has often been misattributed to him: {{quote|"Who will venture to place the authority of Copernicus above that of the Holy Spirit?"}} It has long been established that this line cannot be found in any of Calvin's works.<ref>Rosen, Edward (1960), ''Calvin’s attitude toward Copernicus'' in ''Journal of the History of Ideas'', volume 21, no. 3, July, pp.431–441. Reprinted in [[#Reference-Rosen-1995|Rosen (1995, pp.161–171)]].</ref><ref>Gingerich, Owen (2004), ''The Book Nobody Read''. New York: Walker and Co.</ref><ref>Hooykaas, R. (1973). ''Religion and the rise of modern science''. Reprint, Edinburgh: Scottish Academic Press, 1977.</ref> It has been suggested<ref>Bye, Dan J. (2007). ''McGrath vs Russell on Calvin vs Copernicus: a case of the pot calling the kettle black?'' in ''[[The Freethinker (journal)|The Freethinker]]'', volume 127, no. 6, June, pp.8–10. [http://homepages.shu.ac.uk/~llrdjb/potkettleblack.htm Available online here.]</ref> that the quotation was originally sourced from the works of [[Lutheran]] theologian [[Abraham Calovius]]. ===Tycho Brahe's geo-heliocentric system c. 1587=== Prior to the publication of ''De Revolutionibus'', the widely accepted system had been that of [[Ptolemy]], in which the [[Earth]] was the center of the universe and all celestial bodies orbited it. [[Tycho Brahe]] advocated an alternative to the Ptolemaic geocentric system, a geo-heliocentric system now known as the [[Tychonic system]] in which the five then known planets orbit the sun, while the sun and the moon orbit the earth. The Jesuit astronomers in Rome were at first unreceptive to Tycho's system; the most prominent, [[Christopher Clavius|Clavius]], commented that Tycho was "confusing all of astronomy, because he wants to have Mars lower than the Sun." <ref>Fantoli, 2003, p.&nbsp;109</ref> ===Publication of Starry messenger (1610)=== [[Image:Galileo.arp.300pix.jpg|thumb|right|In the 17th century AD [[Galileo Galilei]] opposed the [[Roman Catholic Church]] by his strong support for heliocentrism]]Galileo was able to look at the night sky with the newly invented telescope. He published his discoveries in [[Sidereus Nuncius]] including (among other things) the moons of Jupiter and that Venus exhibited a full range of phases. These discoveries were not consistent with the Ptolemeic model of the solar system. As the Jesuit astronomers confirmed Galileo's observations, the Jesuits moved toward Tycho's teachings.<ref>Arthur Koestler, ''The Sleepwalkers (Penguin Arkana, 1989 p. 433)</ref> ===Publication of Letter to the Grand Duchess (1615)=== In a [[Letter to the Grand Duchess Christina]], Galileo defended heliocentrism, and claimed it was not contrary to Scriptures (see [[Galileo affair]]). He took [[Augustine of Hippo|Augustine]]'s position on Scripture: not to take every passage literally when the scripture in question is a book of poetry and songs, not a book of instructions or history. The writers of the Scripture wrote from the perspective of the terrestrial world, and from that vantage point the sun does rise and set. In fact, it is the Earth's rotation which gives the impression of the sun in motion across the sky. ===The decree of 1616=== The Letter to the ''Grand Duchess Christina'' prompted the papal authorities to decide whether heliocentrism was acceptable. Galileo was summoned to Rome to defend his position. The Church accepted the use of heliocentrism as a calculating device, but opposed it as a literal description of the solar system. Cardinal [[Robert Bellarmine]] himself considered that Galileo's model made "excellent good sense" on the ground of mathematical simplicity; that is, as a ''hypothesis'' (see above). And he said: {{quote|"If there were a real proof that the Sun is in the center of the universe, that the Earth is in the third sphere, and that the Sun does not go round the Earth but the Earth round the Sun, then we should have to proceed with great circumspection in explaining passages of Scripture which appear to teach the contrary, and we should rather have to say that we did not understand them than declare an opinion false which has been proved to be true. But I do not think there is any such proof since none has been shown to me."|Koestler (1959), p. 447–448}} Bellarmine supported a ban on the teaching of the idea as anything but hypothesis. In 1616 he delivered to Galileo the papal command not to "hold or defend" the heliocentric idea.<ref>Arthur Koestler, ''The Sleepwalkers'' (Penguin Arkana, 1989 p. 468)</ref> The Vatican files suggest that Galileo was forbidden to teach heliocentrism in any way whatsoever, but whether this ban was known to Galileo is a matter of dispute.<ref>Arthur Koestler, ''The Sleepwalkers'' (Penguin Arkana, 1989 p. 469)</ref> ===Publication of Epitome astronomia Copernicanae (1617-1621)=== In [[Astronomia nova]] (1609), [[Johannes Kepler]] had used an elliptical orbit to explain the motion of Mars. In ''Epitome astronomia Copernicanae'' he developed a heliocentric model of the solar system in which all the planets have elliptical orbits. This provided significantly increased accuracy in predicting the position of the planets. Kepler's ideas were not immediately accepted. Galileo for example completely ignored Kepler's work. Kepler proposed heliocentrism as a physical description of the solar system and ''Epitome astronomia Copernicanae'' was placed on the index of prohibited books despite Kepler being a Protestant. ===Publication of Dialogue concerning the two chief world systems=== [[Pope Urban VIII]] encouraged Galileo to publish the pros and cons of Heliocentrism. In the event, Galileo's ''[[Dialogue concerning the two chief world systems]]'' clearly advocated heliocentrism and appeared to make fun of the Pope. Urban VIII became hostile to Galileo and he was again summoned to Rome.<ref>Arthur Koestler, ''The Sleepwalkers'' (Penguin Arkana, 1989 p. 491)</ref> Galileo's trial in 1633 involved making fine distinctions between "teaching" and "holding and defending as true". For advancing heliocentric theory Galileo was put under house arrest for the last few years of his life. Theologian and pastor [[Thomas Schirrmacher]], however, has argued: {{quote|"Contrary to legend, Galileo and the Copernican system were well regarded by church officials. Galileo was the victim of his own arrogance, the envy of his colleagues, and the politics of Pope Urban VIII. He was not accused of criticizing the Bible, but disobeying a papal decree."<ref>{{cite web|last=Schirrmacher |first=Thomas |url=http://www.answersingenesis.org/tj/v14/i1/galileo.asp |title=The Galileo affair: history or heroic hagiography? |publisher=Answersingenesis.org |date= |accessdate=2009-08-08}}</ref>}} According to J. L. Heilbron, Catholic scientists have also: {{quote|"appreciated that the reference to heresy in connection with Galileo or Copernicus had no general or theological significance."|Heilbron (1999)}} ===Subsequent developments=== The Church's opposition to heliocentrism as a literal description did not by any means imply opposition to all astronomy; indeed, it needed observational data to maintain its calendar. In support of this effort it allowed the cathedrals themselves to be used as solar observatories called ''[[Sundial#Precision noonmarks|meridiane]]''; i.e., they were turned into "reverse [[sundial]]s", or gigantic [[pinhole camera]]s, where the Sun's image was projected from a hole in a window in the cathedral's lantern onto a meridian line. In 1664, [[Pope Alexander VII]] published his ''[[Index Librorum Prohibitorum]] Alexandri VII Pontificis Maximi jussu editus'' (Index of Prohibited Books, published by order of Alexander VII, [[Pontifex Maximus|P.M.]]) which included all previous condemnations of heliocentric books.<ref>"The Pontifical Decrees Against the Doctrine of the Earth's Movement, and the Ultramontane Defence of Them", Rev. William Roberts, 1885, London</ref> An annotated copy of [[Philosophiae Naturalis Principia Mathematica]] by [[Isaac Newton]] was published in 1742 by Fathers le Seur and Jacquier of the Franciscan Minims, two [[Catholic]] mathematicians with a preface stating that the author's work assumed heliocentrism and could not be explained without the theory.<ref name=newt-hc>Newton's heliocentrism was of a somewhat modern kind, since already in the mid-1680s he recognized the "deviation of the Sun" from the centre of gravity of the solar system (see Curtis Wilson, "The Newtonian achievement in astronomy", pages 233-274 in [[#refGHA2A|R Taton & C Wilson (eds) (1989)]], ''The General History of Astronomy'', Volume 2A, [http://books.google.com/books?id=rkQKU-wfPYMC&pg=PA233 at page 233]). For Newton it was not precisely the centre of the Sun or any other body that could be considered at rest, but "the common centre of gravity of the Earth, the Sun and all the Planets is to be esteem'd the Centre of the World", and this centre of gravity "either is at rest or moves uniformly forward in a right line" (Newton adopted the "at rest" alternative in view of common consent that the centre, wherever it was, was at rest) (text quotations from 1729 translation of Newton ''Principia'', Book 3 (1729 vol.2) [http://books.google.com/books?id=6EqxPav3vIsC&pg=PA233 at pages 232-233]).</ref> In 1758 the Catholic Church dropped the general prohibition of books advocating heliocentrism from the ''Index of Forbidden Books''.<ref>John L.Heilbron, ''Censorship of Astronomy in Italy after Galileo'' (in McMullin, Ernan ed., ''The Church and Galileo'', University of Notre Dame Press, Notre Dame, 2005, p. 307, IN. ISBN 0-268-03483-4)</ref> [[Pope Pius VII]] approved a decree in 1822 by the [[Sacred Congregation of the Inquisition]] to allow the printing of heliocentric books in [[Rome]]. ==The view of modern science== The thinking that the heliocentric view was also not true in a strict sense was achieved in steps. That the Sun was not the center of the universe, but one of innumerable stars, was strongly advocated by the mystic [[Giordano Bruno]]. Over the course of the 18th and 19th centuries, the status of the Sun as merely one star among many became increasingly obvious. By the 20th century, even before the discovery that there are many galaxies, it was no longer an issue. Even if the discussion is limited to the [[solar system]], the sun is not at the geometric center of any planet's orbit, but rather at one [[focus (geometry)|focus]] of the [[ellipse|elliptical]] orbit. Furthermore, to the extent that a planet's mass cannot be neglected in comparison to the Sun's mass, the center of gravity of the solar system is displaced slightly away from the center of the Sun.<ref name=newt-hc /> (The masses of the planets, mostly [[Jupiter]], amount to 0.14% of that of the Sun.) Therefore a hypothetical astronomer on an [[extrasolar planet]] would observe a "wobble" in his perception of the Sun's motion. Giving up the whole concept of being "at rest" is related to the [[principle of relativity]]. While, assuming an unbounded universe, it was clear there is no privileged ''position'' in space, until postulation of the [[special theory of relativity]] by [[Albert Einstein]], at least the existence of a privileged class of inertial systems absolutely ''at rest'' was assumed, in particular in the form of the hypothesis of the [[luminiferous aether]]. Some forms of [[Mach's principle]] consider the frame at rest with respect to the masses in the universe to have special properties. ===Modern use of ''geocentric'' and ''heliocentric''=== In modern calculations, the origin and orientation of a coordinate system often are selected for practical reasons, and in such systems the origin in the [[Center of mass#Barycenter in astrophysics and astronomy|center of mass]] of the Earth, of the Earth-Moon system, of the Sun, of the Sun and the major planets, or of the entire solar system can be selected. However, such selection of "geocentric" or "heliocentric" coordinates has only practical implications and not philosophical or physical ones. ==See also== * [[Geocentrism]] * [[History of astronomy]] * [[Aristarchus of Samos]] * [[Kant]] ==External Links== * [http://scienceray.com/astronomy/does-heliocentrism-means-that-the-sun-is-stationary/ Does Heliocentrism Means That the Sun is Stationary?] * [http://bldgblog.blogspot.com/2007/04/heliocentric-pantheon-interview-with.html Heliocentric Pantheon] ==Notes== {{reflist|2}} ==References== <div class="references-small"> {{col-begin}} {{col-2}} * Ajram, K. (1992). ''Miracle of Islamic Science'', Appendix B. Knowledge House Publishers. ISBN 0911119434. * Baker, A. and Chapter, L. (2002), "Part 4: The Sciences". In M. M. Sharif, "A History of Muslim Philosophy", ''Philosophia Islamica''. * [[Madame Blavatsky|Blavatsky, Helena P.]] (1877). ''[[Isis Unveiled]]''. [[Theosophical Society in America|Theosophical University Press]]. ISBN 0-911500-03-0. * Covington, Richard (May-June 2007). "Rediscovering Arabic science", ''[[Saudi Aramco World]]'', p.&nbsp;2–16. *{{cite book | title= A History of Astronomy from Thales to Kepler | author= [[J. L. E. Dreyer|Dreyer, J.L.E.]] | publisher= Dover Publications | year= 1953 | url=http://www.archive.org/details/historyofplaneta00dreyuoft | location= New York, NY | ref=Reference-Dreyer-1953}} * Fantoli, Annibale (2003). ''Galileo&nbsp;— For Copernicanism and the Church'', 3rd English edition, ''tr.'' George V. Coyne, SJ. Vatican Observatory Publications, Notre Dame, IN. ISBN 88-209-7427-4. * Gill, M. (2005). [http://www.chowk.com/show_article.cgi?aid=00005502&channel=university%20ave Was Muslim Astronomy the Harbinger of Copernicanism?] * [[Martin Haug|Haug, Martin]] (1863). ''The Aitareya Brahmanam of the Rigveda, Containing the Earliest Speculations of the Brahmans on the Meaning of the Sacrificial Prayers''. ISBN 0-404-57848-9. * Heath, T.L. (1913). ''Aristarchus of Samos, the ancient Copernicus: a history of Greek astronomy to Aristarchus'', Oxford, Clarendon. ISBN 0-486-24188-2 (1981 Dover reprint). * Heilbron, J. L. (1999). ''The Sun in the Church: Cathedrals as Solar Observatories''. Harvard University Press, Cambridge, MA. ISBN 0-674-85433-0. * [[Sir Fred Hoyle|Hoyle, Sir Fred]] (1973). ''[[Nicolaus Copernicus]]''. Heinemann Educational Books Ltd., London. ISBN 0-435-54425-X. * Joseph, George G. (2000). ''The Crest of the Peacock: Non-European Roots of Mathematics'', 2nd edition. Penguin Books, London. ISBN 0691006598. * [[Arthur Koestler|Koestler, Arthur]], (1959) ''The Sleepwalkers: A History of Man's Changing Vision of the Universe'', Penguin Books; 1986 edition: ISBN 0-14-055212-X, 1990 reprint: ISBN 0-14-019246-8 * [[Alexandre Koyré|Koyré, Alexandre]] (1957). ''From the Closed World to the Infinite Universe''. Baltimore: Johns Hopkins Univ. Pr. {{col-2}} * [[Thomas S. Kuhn|Kuhn, Thomas S.]] (1957). ''The Copernican Revolution''. Cambridge: Harvard Univ. Pr. ISBN 0-674-17103-9 * [[Subhash Kak|Kak, Subhash C.]] (2000). 'Birth and Early Development of Indian Astronomy'. In Selin, Helaine (2000). ''Astronomy Across Cultures: The History of Non-Western Astronomy'' (303–340). Boston: Kluwer. ISBN 0-7923-6363-9. *{{cite book | title= Plutarch's Moralia in Fifteen Volumes, XII | author= [[Plutarch]] | publisher= William Heinemann | others= Loeb Classical Library edition, translated by Harold Cherniss and William C. Helmbold | year= 1957 | location= London | ref=Reference-Plutarch-1957}} * Qadir, Asghar (1989). ''Relativity: An Introduction to the Special Theory''. World Scientific. ISBN 9971506122. * [[A. I. Sabra|Sabra, A. I.]] (1998). "Configuring the Universe: Aporetic, Problem Solving, and Kinematic Modeling as Themes of Arabic Astronomy," ''Perspectives on Science'' '''6''', p.&nbsp;288–330. *{{cite book | title = Copernicus and his Successors | author= Rosen, Edward | publisher= Hambledon Press | year= 1995 | isbn= 1 85285 071 X | location= London | ref= Reference-Rosen-1995}} * [[George Saliba|Saliba, George]] (1999). [http://www.columbia.edu/~gas1/project/visions/case1/sci.1.html Whose Science is Arabic Science in Renaissance Europe?] [[Columbia University]]. *<cite id=refGHA2A>{{cite book | title= Planetary astronomy from the Renaissance to the rise of astrophysics Part A: Tycho Brahe to Newton | editor1-first= René | editor1-last= Taton | editor2-first= Curtis | editor2-last= Wilson | publisher= Cambridge University Press | year= 1989 | location= Cambridge | isbn= 0-521-24254-1 | url=http://books.google.com/books?id=rkQKU-wfPYMC | accessdate = 2009-11-06 | ref=Reference-Taton&Wilson-1989}} * Teresi, Dick (2002). ''Lost Discoveries: The Ancient Roots of Modern Science&nbsp;— from the Babylonians to the Maya''. [[Simon & Schuster, Inc.|Simon & Schuster]], New York. ISBN 0-684-83718-8. * Roger Hart, Jamil Ragep, Dick Teresi (2002). [http://www.npr.org/templates/story/story.php?storyId=885213 "Ancient Roots of Modern Science"], ''[[Talk of the Nation]]'' (NPR discussion of intercultural scientific contacts; astronomy is discussed in the first fifteen-minute segment). * Thurston, Hugh (1994). ''Early Astronomy''. Springer-Verlag, New York. ISBN 0-387-94107-X. * Walker, Christopher, ed. (1996). ''Astronomy before the telescope''. London: British Museum Press. 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