Heliocentrism[a] is the astronomical model in which the Earth and planets revolve around the Sun at the center of the Solar System. Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center. The notion that the Earth revolves around the Sun had been proposed as early as the 3rd century BC by Aristarchus of Samos, but at least in the medieval world, Aristarchus's heliocentrism attracted little attention—possibly because of the loss of scientific works of the Hellenistic Era.[b]
It was not until the 16th century that a mathematical model of a heliocentric system was presented, by the Renaissance mathematician, astronomer, and Catholic cleric Nicolaus Copernicus, leading to the Copernican Revolution. In the following century, Johannes Kepler introduced elliptical orbits, and Galileo Galilei presented supporting observations made using a telescope.
While the sphericity of the Earth was widely recognized in Greco-Roman astronomy from at least the 4th century BC, the Earth's daily rotation and yearly orbit around the Sun was never universally accepted until the Copernican Revolution.
While a moving Earth was proposed at least from the 4th century BC in Pythagoreanism, and a fully developed heliocentric model was developed by Aristarchus of Samos in the 3rd century BC, these ideas were not successful in replacing the view of a static spherical Earth, and from the 2nd century AD the predominant model, which would be inherited by medieval astronomy, was the geocentric model described in Ptolemy's Almagest.
The Ptolemaic system was a sophisticated astronomical system that managed to calculate the positions for the planets to a fair degree of accuracy. 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. However, he rejected the idea of a spinning Earth as absurd as he believed it would create huge winds. His planetary hypotheses were sufficiently real that the distances of the Moon, Sun, planets and stars could be determined by treating orbits' celestial spheres as contiguous realities. This made the stars' distance less than 20 Astronomical Units, a regression, since Aristarchus of Samos's heliocentric scheme had centuries earlier necessarily placed the stars at least two orders of magnitude more distant.
Problems with Ptolemy's system were well recognized in medieval astronomy, and an increasing effort to criticize and improve it in the late medieval period eventually led to the Copernican heliocentrism developed in Renaissance astronomy.
The non-geocentric model of the Universe was proposed by the Pythagorean philosopher Philolaus (d. 390 BC), who taught that at the center of the Universe was a "central fire", around which the Earth, Sun, Moon and planets revolved in uniform circular motion. This system postulated the existence of a counter-earth collinear with the Earth and central fire, with the same period of revolution around the central fire as the Earth. The Sun revolved around the central fire once a year, and the stars were stationary. The Earth maintained the same hidden face towards the central fire, rendering both it and the "counter-earth" invisible from Earth. The Pythagorean concept of uniform circular motion remained unchallenged for approximately the next 2000 years, and it was to the Pythagoreans that Copernicus referred to show that the notion of a moving Earth was neither new nor revolutionary. Kepler gave an alternative explanation of the Pythagoreans' "central fire" as the Sun, "as most sects purposely hid[e] their teachings".
Heraclides of Pontus (4th century BC) said that the rotation of the Earth explained the apparent daily motion of the celestial sphere. It used to be thought that he believed Mercury and Venus to revolve around the Sun, which in turn (along with the other planets) revolves around the Earth. Macrobius Ambrosius Theodosius (AD 395–423) later described this as the "Egyptian System," stating that "it did not escape the skill of the Egyptians," though there is no other evidence it was known in ancient Egypt.
The first person known to have proposed a heliocentric system, however, was Aristarchus of Samos (c. 270 BC). Like Eratosthenes, Aristarchus calculated the size of the Earth, and measured the sizes and distances of the Sun and Moon. From his estimates, he concluded that the Sun was six to seven times wider than the Earth, and thought the larger object would have the most attractive force.
His writings on the heliocentric system are lost, but some information about them is known from a brief description by his contemporary, Archimedes, and from scattered references by later writers. Archimedes' description of Aristarchus's theory is given in the former's book, The Sand Reckoner. The entire description comprises just three sentences, which Thomas Heath translates as follows:
You are aware ['you' being King Gelon] that "universe" is the name given by most astronomers to the sphere, the centre of which is the centre of the earth, while its radius is equal to the straight line between the centre of the sun and the centre of the earth. This is the common account (τά γραφόμενα), as you have heard from astronomers. But Aristarchus 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 the fixed stars, situated about the same centre 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 centre of the sphere bears to its surface.— The Sand Reckoner (Arenarius I, 4-7)
Aristarchus presumably took the stars to be very far away because he was aware that their parallax would otherwise be observed over the course of a year. The stars are in fact so far away that stellar parallax only became detectable when sufficiently powerful telescopes had been developed.
No references to Aristarchus's heliocentrism are known in any other writings from before the common era. The earliest of the handful of other ancient references occur in two passages from the writings of Plutarch. These mention one detail not stated explicitly in Archimedes's account— namely, that Aristarchus's theory had the Earth rotating on an axis. The first of these reference occurs in On the Face in the Orb of the Moon:
Only do not, my good fellow, enter an action against me for impiety in the style of Cleanthes, who thought it was the duty of Greeks to indict Aristarchus of Samos on the charge of impiety for putting in motion the Hearth of the Universe, this being the effect of his attempt to save the phenomena by supposing the heaven to remain at rest and the earth to revolve in an oblique circle, while it rotates, at the same time, about its own axis.— On the Face in the Orb of the Moon (De facie in orbe lunae, c. 6, pp. 922 F - 923 A.)
Only scattered fragments of Cleanthes's writings have survived in quotations by other writers, but in Lives and Opinions of Eminent Philosophers, Diogenes Laërtius lists A reply to Aristarchus (Πρὸς Ἀρίσταρχον) as one of Cleanthes's works, and some scholars have suggested that this might have been where Cleanthes had accused Aristarchus of impiety.
The second of the references by Plutarch is in his Platonic Questions:
Did Plato put the earth in motion, as he did the sun, the moon, and the five planets, which he called the instruments of time on account of their turnings, and was it necessary to conceive that the earth "which is globed about the axis stretched from pole to pole through the whole universe" was not represented as being held together and at rest, but as turning and revolving (στρεφομένην καὶ ἀνειλουμένην), as Aristarchus and Seleucus afterwards maintained that it did, the former stating this as only a hypothesis (ὑποτιθέμενος μόνον), the latter as a definite opinion (καὶ ἀποφαινόμενος) ?— Platonic Questions (Platonicae Quaestiones viii. I, 1006 C)
The remaining references to Aristarchus's heliocentrism are extremely brief, and provide no more information beyond what can be gleaned from those already cited. Ones which mention Aristarchus explicitly by name occur in Aëtius's Opinions of the Philosophers, Sextus Empiricus's Against the Mathematicians, and an anonymous scholiast to Aristotle. Another passage in Aëtius's Opinions of the Philosophers reports that Seleucus the astronomer had affirmed the Earth's motion, but does not mention Aristarchus.
Since Plutarch mentions the "followers of Aristarchus" in passing, it is likely that there were other astronomers in the Classical period who also espoused heliocentrism, but whose work was lost. The only other astronomer from antiquity known by name who is known to have supported Aristarchus' heliocentric model was Seleucus of Seleucia (b. 190 BC), a Hellenistic astronomer who flourished a century after Aristarchus in the Seleucid empire. Seleucus was a proponent of the heliocentric system of Aristarchus. Seleucus may have proved the heliocentric theory by determining the constants of a geometric model for the heliocentric theory and developing methods to compute planetary positions using this model. He may have used early trigonometric methods that were available in his time, as he was a contemporary of Hipparchus. A fragment of a work by Seleucus has survived in Arabic translation, which was referred to by Rhazes (b. 865).
Alternatively, his explanation may have involved the phenomenon of tides, which he supposedly theorized to be caused by the attraction to the Moon and by the revolution of the Earth around the Earth and Moon's center of mass.
There were occasional speculations about heliocentrism in Europe before Copernicus. In Roman Carthage, the pagan 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. Capella's model was discussed in the Early Middle Ages by various anonymous 9th-century commentators and Copernicus mentions him as an influence on his own work.
The Ptolemaic system was also received in Indian astronomy. Aryabhata (476–550), in his magnum opus Aryabhatiya (499), propounded a planetary model in which the Earth was taken to be spinning on its axis and the periods of the planets were given with respect to the Sun. His immediate commentators, such as Lalla, and other later authors, rejected his innovative view about the turning Earth. He also made many astronomical calculations, such as the times of the solar and lunar eclipses, and the instantaneous motion of the Moon. Early followers of Aryabhata's model included Varahamihira, Brahmagupta, and Bhaskara II.
For a time, Muslim astronomers accepted the Ptolemaic system and the geocentric model, which were used by al-Battani to show that the distance between the Sun and the Earth varies. In the 10th century, al-Sijzi accepted that the Earth rotates around its axis. According to later astronomer al-Biruni, al-Sijzi invented an astrolabe called al-zūraqī based on a belief held by some of his contemporaries that the apparent motion of the stars was due to the Earth's movement, and not that of the firmament. Islamic astronomers began to criticize the Ptolemaic model, including Ibn al-Haytham in his Al-Shukūk 'alā Baṭalamiyūs ("Doubts Concerning Ptolemy", c. 1028), who branded it an impossibility.
Al-Biruni discussed the possibility of whether the Earth rotated about its own axis and orbited the Sun, but in his Masudic Canon (1031), he expressed his faith in a geocentric and stationary Earth. He was aware that if the Earth rotated on its axis, it would be consistent with his astronomical observations, but considered it a problem of natural philosophy rather than one of mathematics.
In the 12th century, non-heliocentric alternatives to the Ptolemaic system were developed by some Islamic astronomers, such as Nur ad-Din al-Bitruji, who considered the Ptolemaic model mathematical, and not physical. His system spread throughout most of Europe in the 13th century, with debates and refutations of his ideas continued to the 16th century.
The Maragha school of astronomy in Ilkhanid-era Persia further developed "non-Ptolemaic" planetary models involving Earth's rotation. Notable astronomers of this school are Al-Urdi (d. 1266) Al-Katibi (d. 1277), and Al-Tusi (d. 1274).
The arguments and evidence used resemble those used by Copernicus to support the Earth's motion. The criticism of Ptolemy as developed by Averroes and by the Maragha school explicitly address the Earth's rotation but it did not arrive at explicit heliocentrism. The observations of the Maragha school were further improved at the Timurid-era Samarkand observatory under Qushji (1403–1474).
European scholarship in the later medieval period actively received astronomical models developed in the Islamic world and by the 13th century was well aware of the problems of the Ptolemaic model. In the 14th century, bishop Nicole Oresme discussed the possibility that the Earth rotated on its axis, while Cardinal Nicholas of Cusa in his 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," recalling Hermes Trismegistus.
In India, Nilakantha Somayaji (1444–1544), in his Aryabhatiyabhasya, a commentary on Aryabhata's Aryabhatiya, developed a computational system for a geo-heliocentric planetary model, in which the planets orbit the Sun, which in turn orbits the Earth, similar to the system later proposed by Tycho Brahe. In the Tantrasamgraha (1501), Somayaji further revised his planetary system, which was mathematically more accurate at predicting the heliocentric orbits of the interior planets than both the Tychonic and Copernican models, but did not propose any specific models of the universe. Nilakantha's planetary system also incorporated the Earth's rotation on its axis. Most astronomers of the Kerala school of astronomy and mathematics seem to have accepted his planetary model.
Some historians maintain that the thought of the Maragheh observatory, in particular the mathematical devices known as the Urdi lemma and the Tusi couple, influenced Renaissance-era European astronomy, and thus was indirectly received by Renaissance-era European astronomy and thus by Copernicus. Copernicus used such devices in the same planetary models as found in Arabic sources. Furthermore, the exact replacement of the equant by two epicycles used by Copernicus in the Commentariolus was found in an earlier work by Ibn al-Shatir (d. c. 1375) of Damascus. Copernicus' lunar and Mercury models are also identical to Ibn al-Shatir's.
The state of knowledge on planetary theory received by Copernicus is summarized in Georg von Peuerbach's Theoricae Novae Planetarum (printed in 1472 by Regiomontanus). By 1470, the accuracy of observations by the Vienna school of astronomy, of which Peuerbach and Regiomontanus were members, was high enough to make the eventual development of heliocentrism inevitable, and indeed it is possible that Regiomontanus did arrive at an explicit theory of heliocentrism before his death in 1476, some 30 years before Copernicus. While the influence of the criticism of Ptolemy by Averroes on Renaissance thought is clear and explicit, the claim of direct influence of the Maragha school, postulated by Otto E. Neugebauer in 1957, remains an open question.Since the Tusi couple was used by Copernicus in his reformulation of mathematical astronomy, there is a growing consensus that he became aware of this idea in some way. It has been suggested that the idea of the Tusi couple may have arrived in Europe leaving few manuscript traces, since it could have occurred without the translation of any Arabic text into Latin. One possible route of transmission may have been through Byzantine science, which translated some of al-Tusi's works from Arabic into Byzantine Greek. Several Byzantine Greek manuscripts containing the Tusi-couple are still extant in Italy. Other scholars have argued that Copernicus could well have developed these ideas independently of the late Islamic tradition. Copernicus explicitly references several astronomers of the "Islamic Golden Age" (10th to 12th centuries) in De Revolutionibus: Albategnius (Al-Battani), Averroes (Ibn Rushd), Thebit (Thabit Ibn Qurra), Arzachel (Al-Zarqali), and Alpetragius (Al-Bitruji), but he does not show awareness of the existence of any of the later astronomers of the Maragha school.
It has been argued that Copernicus could have independently discovered the Tusi couple or took the idea from Proclus's Commentary on the First Book of Euclid, which Copernicus cited. Another possible source for Copernicus's knowledge of this mathematical device is the Questiones de Spera of Nicole Oresme, who described how a reciprocating linear motion of a celestial body could be produced by a combination of circular motions similar to those proposed by al-Tusi.
Nicolaus Copernicus in his De revolutionibus orbium coelestium ("On the revolution of heavenly spheres", first printed in 1543 in Nuremberg), presented a discussion of a heliocentric model of the universe in much the same way as Ptolemy in the 2nd century had presented his geocentric model in his Almagest. Copernicus discussed the philosophical implications of his proposed system, elaborated it in 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. In reality, Copernicus's system did not predict the planets' positions any better than the Ptolemaic system. This theory resolved the issue of planetary retrograde motion by arguing that such motion was only perceived and apparent, rather than real: it was a parallax effect, as an object 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 epicycles, retained as a physical reality the irregular back-and-forth motion of the planets, which Kepler characterized as a "pretzel".
Copernicus cited Aristarchus in an early (unpublished) manuscript of De Revolutionibus (which still survives), stating: "Philolaus believed in the mobility of the earth, and some even say that Aristarchus of Samos was of that opinion." 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
The first information about the heliocentric views of Nicolaus Copernicus was circulated in manuscript completed some time before May 1, 1514. Although only in manuscript, Copernicus' ideas were well known among astronomers and others. His ideas contradicted the then-prevailing understanding of the Bible. In the King James Bible (first published in 1611), First Chronicles 16:30 states 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 cardinals. On November 1, 1536, Archbishop of Capua Nikolaus von Schönberg wrote a letter to Copernicus from Rome encouraging him to publish a full version of his theory.
However, in 1539, Martin Luther said:
"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."
Nicolaus Copernicus published the definitive statement of his system in 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 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 heretical during the next 60 years. There was an early suggestion among Dominicans 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 order of nature" by saying that "the sun does not move and that it is the earth that revolves and that it turns".
On the other hand, Calvin is not responsible for another famous quotation which has often been misattributed to him: "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. It has been suggested that the quotation was originally sourced from the works of Lutheran theologian Abraham Calovius.
Prior to the publication of De Revolutionibus, the most widely accepted system had been proposed by Ptolemy, in which the Earth was the center of the universe and all celestial bodies orbited it. Tycho Brahe, arguably the most accomplished astronomer of his time, advocated against Copernicus's heliocentric system and for 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.
Tycho appreciated the Copernican system, but objected to the idea of a moving Earth on the basis of physics, astronomy, and religion. The Aristotelian physics of the time (modern Newtonian physics was still a century away) offered no physical explanation for the motion of a massive body like Earth, whereas it could easily explain the motion of heavenly bodies by postulating that they were made of a different sort substance called aether that moved naturally. So Tycho said that the Copernican system "... expertly and completely circumvents all that is superfluous or discordant in the system of Ptolemy. On no point does it offend the principle of mathematics. Yet it ascribes to the Earth, that hulking, lazy body, unfit for motion, a motion as quick as that of the aethereal torches, and a triple motion at that." Likewise, Tycho took issue with the vast distances to the stars that Aristarchus and Copernicus had assumed in order to explain the lack of any visible parallax. Tycho had measured the apparent sizes of stars (now known to be illusory – see stellar magnitude), and used geometry to calculate that in order to both have those apparent sizes and be as far away as heliocentrism required, stars would have to be huge (much larger than the sun; the size of Earth's orbit or larger). Regarding this Tycho wrote, "Deduce these things geometrically if you like, and you will see how many absurdities (not to mention others) accompany this assumption [of the motion of the earth] by inference." He also cited the Copernican system's "opposition to the authority of Sacred Scripture in more than one place" as a reason why one might wish to reject it, and observed that his own geo-heliocentric alternative "offended neither the principles of physics nor Holy Scripture".
The Jesuit astronomers in Rome were at first unreceptive to Tycho's system; the most prominent, Clavius, commented that Tycho was "confusing all of astronomy, because he wants to have Mars lower than the Sun." However, after the advent of the telescope showed problems with some geocentric models (by demonstrating that Venus circles the Sun, for example), the Tychonic system and variations on that system became popular among geocentrists, and the Jesuit astronomer Giovanni Battista Riccioli would continue Tycho's use of physics, stellar astronomy (now with a telescope), and religion to argue against heliocentrism and for Tycho's system well into the seventeenth century (see Riccioli).
Galileo was able to look at the night sky with the newly invented telescope. He published his discoveries that the Sun rotated and that Venus exhibited a full range of phases in his Letters on Sunspots (1613). 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.
In his 1615 "Letter to the Grand Duchess Christina", Galileo defended heliocentrism, and claimed it was not contrary to Holy Scripture. He took Augustine's position on Scripture: not to take every passage literally when the scripture in question is in a Bible 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.
In February 1615, prominent Dominicans including Thomaso Caccini and Niccolò Lorini brought Galileo's writings on heliocentrism to the attention of the Inquisition, because they appeared to violate Holy Scripture and the decrees of the Council of Trent. Cardinal and Inquisitor Robert Bellarmine was called upon to adjudicate, and wrote in April that treating heliocentrism as a real phenomenon would be "a very dangerous thing," irritating philosophers and theologians, and harming "the Holy Faith by rendering Holy Scripture as false."
In January 1616 Msgr. Francesco Ingoli addressed an essay to Galileo disputing the Copernican system. Galileo later stated that he believed this essay to have been instrumental in the ban against Copernicanism that followed in February. According to Maurice Finocchiaro, Ingoli had probably been commissioned by the Inquisition to write an expert opinion on the controversy, and the essay provided the "chief direct basis" for the ban. The essay focused on eighteen physical and mathematical arguments against heliocentrism. It borrowed primarily from the arguments of Tycho Brahe, and it notedly mentioned the problem that heliocentrism requires the stars to be much larger than the Sun. Ingoli wrote that the great distance to the stars in the heliocentric theory "clearly proves ... the fixed stars to be of such size, as they may surpass or equal the size of the orbit circle of the Earth itself." Ingoli included four theological arguments in the essay, but suggested to Galileo that he focus on the physical and mathematical arguments. Galileo did not write a response to Ingoli until 1624.
In February 1616, the Inquisition assembled a committee of theologians, known as qualifiers, who delivered their unanimous report condemning heliocentrism as "foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture." The Inquisition also determined that the Earth's motion "receives the same judgement in philosophy and ... in regard to theological truth it is at least erroneous in faith." Bellarmine personally ordered Galileo
to abstain completely from teaching or defending this doctrine and opinion or from discussing it... to abandon completely... the opinion that the sun stands still at the center of the world and the earth moves, and henceforth not to hold, teach, or defend it in any way whatever, either orally or in writing.— Bellarmine and the Inquisition's injunction against Galileo, 1616
In March, after the Inquisition's injunction against Galileo, the papal Master of the Sacred Palace, Congregation of the Index, and Pope banned all books and letters advocating the Copernican system, which they called "the false Pythagorean doctrine, altogether contrary to Holy Scripture." In 1618 the Holy Office recommended that a modified version of Copernicus' De Revolutionibus be allowed for use in calendric calculations, though the original publication remained forbidden until 1758.
In Astronomia nova (1609), Johannes Kepler had used an elliptical orbit to explain the motion of Mars. In Epitome astronomiae Copernicanae (1617–1621) 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.
Pope Urban VIII encouraged Galileo to publish the pros and cons of heliocentrism. Galileo's response, Dialogue concerning the two chief world systems (1632), clearly advocated heliocentrism, despite his declaration in the preface that,
I will endeavour to show that all experiments that can be made upon the Earth are insufficient means to conclude for its mobility but are indifferently applicable to the Earth, movable or immovable...
and his straightforward statement,
I might very rationally put it in dispute, whether there be any such centre in nature, or no; being that neither you nor any one else hath ever proved, whether the World be finite and figurate, or else infinite and interminate; yet nevertheless granting you, for the present, that it is finite, and of a terminate Spherical Figure, and that thereupon it hath its centre...
Some ecclesiastics also interpreted the book as characterizing the Pope as a simpleton, since his viewpoint in the dialogue was advocated by the character Simplicio. Urban VIII became hostile to Galileo and he was again summoned to Rome. Galileo's trial in 1633 involved making fine distinctions between "teaching" and "holding and defending as true". For advancing heliocentric theory Galileo was forced to recant Copernicanism and was put under house arrest for the last few years of his life.
According to J. L. Heilbron, informed contemporaries of Galileo's "appreciated that the reference to heresy in connection with Galileo or Copernicus had no general or theological significance."
René Descartes postponed, and ultimately never finished, his treatise The World, which included a heliocentric model, but the Galileo affair did little to slow the spread of heliocentrism across Europe, as Kepler's Epitome of Copernican Astronomy became increasingly influential in the coming decades. By 1686 the model was well enough established that the general public was reading about it in Conversations on the Plurality of Worlds, published in France by Bernard le Bovier de Fontenelle and translated into English and other languages in the coming years. It has been called "one of the first great popularizations of science."
In 1687, Isaac Newton published Philosophiæ Naturalis Principia Mathematica, which provided an explanation for Kepler's laws in terms of universal gravitation and what came to be known as Newton's laws of motion. This placed heliocentrism on a firm theoretical foundation, although Newton's heliocentrism was of a somewhat modern kind. Already in the mid-1680s he recognized the "deviation of the Sun" from the centre of gravity of the Solar System. 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.
Meanwhile, the Catholic Church remained opposed to heliocentrism as a literal description, but this 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 meridiane; i.e., they were turned into "reverse sundials", or gigantic pinhole cameras, 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, P.M.) which included all previous condemnations of heliocentric books.
In the mid-eighteenth century the Catholic Church's opposition began to fade. An annotated copy of Newton's Principia 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. In 1758 the Catholic Church dropped the general prohibition of books advocating heliocentrism from the Index of Forbidden Books. The Observatory of the Roman College was established by Pope Clement XIV in 1774 (nationalized in 1878, but re-founded by Pope Leo XIII as the Vatican Observatory in 1891). In spite of dropping its active resistance to heliocentrism, the Catholic Church did not lift the prohibition of uncensored versions of Copernicus's De Revolutionibus or Galileo's Dialogue. The affair was revived in 1820, when the Master of the Sacred Palace (the Catholic Church's chief censor), Filippo Anfossi, refused to license a book by a Catholic canon, Giuseppe Settele, because it openly treated heliocentrism as a physical fact. Settele appealed to pope Pius VII. After the matter had been reconsidered by the Congregation of the Index and the Holy Office, Anfossi's decision was overturned. Pius VII approved a decree in 1822 by the Sacred Congregation of the Inquisition to allow the printing of heliocentric books in Rome. Copernicus's De Revolutionibus and Galileo's Dialogue were then subsequently omitted from the next edition of the Index when it appeared in 1835.
Already in the Talmud, Greek philosophy and science under general name "Greek wisdom" were considered dangerous. They were put under ban then and later for some periods.
The first Jewish scholar to describe the Copernican system, albeit without mentioning Copernicus by name, was Maharal of Prague, his book "Be'er ha-Golah" (1593). Maharal makes an argument of radical skepticism, arguing that no scientific theory can be reliable, which he illustrates by the new-fangled theory of heliocentrism upsetting even the most fundamental views on the cosmos.
Copernicus is mentioned in the books of David Gans (1541–1613), who worked with Tycho Brahe and Johannes Kepler. Gans wrote two books on astronomy in Hebrew: a short one "Magen David" (1612) and a full one "Nehmad veNaim" (published only in 1743). He described objectively three systems: Ptolemy, Copernicus and of Tycho Brahe without taking sides. Joseph Solomon Delmedigo (1591–1655) in his "Elim" (1629) says that the arguments of Copernicus are so strong, that only an imbecile will not accept them. Delmedigo studied at Padua and was acquainted with Galileo.
An actual controversy on the Copernican model within Judaism arises only in the early 18th century. Most authors in this period accept Copernican heliocentrism, with opposition from David Nieto and Tobias Cohn. Both of these authors argued against heliocentrism on grounds of contradictions to scripture. Nieto merely rejected the new system on those grounds without much passion, whereas Cohn went so far as to call Copernicus "a first-born of Satan", though he also acknowledged that he would have found it difficult to counter one particular objection based on a passage from the Talmud.
In the 19th century two students of the Hatam sofer wrote books that were given approbations by him even though one supported heliocentrism and the other geocentrism. The one, a commentary on Genesis Yafe’ah le-Ketz written by R. Israel David Schlesinger resisted a heliocentric model and supported geocentrism. The other, Mei Menuchot written by R. Eliezer Lipmann Neusatz encouraged acceptance of the heliocentric model and other modern scientific thinking.
Since the 20th century most Jews have not questioned the science of heliocentrism. Exceptions include Shlomo Benizri and R. M.M. Schneerson of Chabad who argued that the question of heliocentrism vs. geocentrism is obsolete because of the relativity of motion. Schneerson's followers in Chabad continue to deny the heliocentric model.
Kepler's laws of planetary motion were used as arguments in favor of the heliocentric hypothesis. Three apparent proofs of the heliocentric hypothesis were provided in 1727 by James Bradley, in 1838 by Friedrich Wilhelm Bessel and in 1851 by Foucault. Bradley discovered the stellar aberration, proving the relative motion of the Earth. Bessel proved that the parallax of a star was greater than zero by measuring the parallax of 0.314 arcseconds of a star named 61 Cygni. In the same year Friedrich Georg Wilhelm Struve and Thomas Henderson measured the parallaxes of other stars, Vega and Alpha Centauri.
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.
The concept of an absolute velocity, including being "at rest" as a particular case, is ruled out by the principle of relativity, also eliminating any obvious "center" of the universe as a natural origin of coordinates. Some forms of Mach's principle consider the frame at rest with respect to the distant masses in the universe to have special properties.
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 approximately at one focus of the 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. (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 small "wobble" in the Sun's motion.
In modern calculations, the terms "geocentric" and "heliocentric" are often used to refer to reference frames. In such systems the origin in the center of mass of the Earth, of the Earth–Moon system, of the Sun, of the Sun plus the major planets, or of the entire Solar System, can be selected. Right ascension and declination are examples of geocentric coordinates, used in Earth-based observations, while the heliocentric latitude and longitude are used for orbital calculations. This leads to such terms as "heliocentric velocity" and "heliocentric angular momentum". In this heliocentric picture, any planet of the Solar System can be used as a source of mechanical energy because it moves relatively to the Sun. A smaller body (either artificial or natural) may gain heliocentric velocity due to gravity assist – this effect can change the body's mechanical energy in heliocentric reference frame (although it will not changed in the planetary one). However, such selection of "geocentric" or "heliocentric" frames is merely a matter of computation. It does not have philosophical implications and does not constitute a distinct physical or scientific model. From the point of view of general relativity, inertial reference frames do not exist at all, and any practical reference frame is only an approximation to the actual space-time, which can have higher or lower precision.
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.
Greek astronomy is astronomy written in the Greek language in classical antiquity. Greek astronomy is understood to include the ancient Greek, Hellenistic, Greco-Roman, and Late Antiquity eras. It is not limited geographically to Greece or to ethnic Greeks, as the Greek language had become the language of scholarship throughout the Hellenistic world following the conquests of Alexander. This phase of Greek astronomy is also known as Hellenistic astronomy, while the pre-Hellenistic phase is known as Classical Greek astronomy. During the Hellenistic and Roman periods, much of the Greek and non-Greek astronomers working in the Greek tradition studied at the Musaeum and the Library of Alexandria in Ptolemaic Egypt.
The development of astronomy by the Greek and Hellenistic astronomers is considered, by historians, to be a major phase in the history of astronomy. Greek astronomy is characterized from the start by seeking a rational, physical explanation for celestial phenomena. Most of the constellations of the northern hemisphere derive from Greek astronomy, as are the names of many stars, asteroids, and planets. It was influenced by Egyptian and especially Babylonian astronomy; in turn, it influenced Indian, Arabic-Islamic and Western European astronomy.Aristarchus of Samos
Aristarchus of Samos (; Greek: Ἀρίσταρχος ὁ Σάμιος, Aristarkhos ho Samios; c. 310 – c. 230 BC) was an ancient Greek astronomer and mathematician who presented the first known heliocentric model that placed the Sun at the center of the known universe with the Earth revolving around it. He was influenced by Philolaus of Croton, but Aristarchus identified the "central fire" with the Sun, and he put the other planets in their correct order of distance around the Sun. Like Anaxagoras before him, he suspected that the stars were just other bodies like the Sun, albeit further away from Earth. His astronomical ideas were often rejected in favor of the geocentric theories of Aristotle and Ptolemy. Nicolaus Copernicus attributed the heliocentric theory to Aristarchus.Aryabhata
Aryabhata, आर्यभट (IAST: Āryabhaṭa) or Aryabhata I (476–550 CE) was the first of the major mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy. His works include the Āryabhaṭīya (which mentions that in 3600 Kaliyuga, 499 CE, he was 23 years old) and the Arya-siddhanta.
For his explicit mention of the relativity of motion, he also qualifies as a major early physicist.Copernican
Copernican means of or pertaining to the astronomer Nicolaus Copernicus
For the Copernican system of astronomy, see heliocentrism
For the philosophical principle, see Copernican principle
For the lunar geological period, see Copernician
Copernican federalism explains use in politics
Copernican paradigm explains use in Australian republicanismCopernican Revolution
The Copernican Revolution was the paradigm shift from the Ptolemaic model of the heavens, which described the cosmos as having Earth stationary at the center of the universe, to the heliocentric model with the Sun at the center of the Solar System. Beginning with the publication of Nicolaus Copernicus’s De revolutionibus orbium coelestium, contributions to the “revolution” continued until finally ending with Isaac Newton’s work over a century later.Copernican heliocentrism
Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. It positioned the Sun near the center of the Universe, motionless, with Earth and the other planets orbiting around it in circular paths modified by epicycles and at uniform speeds. The Copernican model displaced the geocentric model of Ptolemy that had prevailed for centuries, placing Earth at the center of the Universe. It is often regarded as the launching point to modern astronomy and the Scientific Revolution.
Copernicus was aware that the ancient Greek Aristarchus had already proposed a heliocentric theory, and cited him as a proponent of it in a reference that was deleted before publication, but there is no evidence that Copernicus had knowledge of, or access to, the specific details of Aristarchus' theory. Although he had circulated an outline of his own heliocentric theory to colleagues sometime before 1514, he did not decide to publish it until he was urged to do so late in his life by his pupil Rheticus. Copernicus's challenge was to present a practical alternative to the Ptolemaic model by more elegantly and accurately determining the length of a solar year while preserving the metaphysical implications of a mathematically ordered cosmos. Thus, his heliocentric model retained several of the Ptolemaic elements causing the inaccuracies, such as the planets' circular orbits, epicycles, and uniform speeds, while at the same time introducing such innovative ideas as:
Earth is one of several planets revolving around a stationary Sun in a determined order
Earth has three motions: daily rotation, annual revolution, and annual tilting of its axis
Retrograde motion of the planets is explained by Earth's motion
Distance from Earth to the Sun is small compared to the distance from the Sun to the stars.Earth's orbit
Earth orbits the Sun at an average distance of 149.60 million km (92.96 million mi), and one complete orbit takes 365.256 days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi). Earth's orbit has an eccentricity of 0.0167. Since the Sun constitutes 99.76% of the mass of the Sun–Earth system, the center of the orbit is extremely close to the center of the Sun.
As seen from Earth, the planet's orbital prograde motion makes the Sun appear to move with respect to other stars at a rate of about 1° eastward per solar day (or a Sun or Moon diameter every 12 hours). Earth's orbital speed averages about 30 km/s (109044 km/h; 67756 mph), which is fast enough to cover the planet's diameter in 7 minutes and the distance to the Moon in 4 hours.From a vantage point above the north pole of either the Sun or Earth, Earth would appear to revolve in a counterclockwise direction around the Sun. From the same vantage point, both the Earth and the Sun would appear to rotate also in a counterclockwise direction about their respective axes.Emil Gustav Lisco
Emil Gustav Lisco (January 13, 1819 – February 8, 1887) was a German Protestant Christian pastor.
Lisco was born in Berlin, the son of Friedrich Gustav Lisco, a pastor and theologian. From 1845 Emil became a pastor as well, also in Berlin. Among his more notable public positions was strident opposition to Copernican heliocentrism, against which he argued in an 1868 letter and in an 1872 lecture.Galactocentrism
In astronomy, Galactocentrism is the theory that the Milky Way Galaxy, home of Earth's Solar System, is at or near the center of the Universe.Observations by William Herschel in 1785 suggested that the Milky Way was a disk-shaped galaxy with the sun in a central position. Although heliocentric, Herschel's observations were the first attempt at an observational cosmology.Herschel's heliocentric theory was overthrown by astronomer Harlow Shapley's work on globular clusters in 1918. Shapley's research marked the transition from heliocentrism to galactocentrism, placing the Galactic Center of the Milky Way Galaxy far away from the sun, towards Sagittarius. Heber Doust Curtis and Edwin Hubble further refuted the heliocentric view of the universe by showing that spirals are themselves far-flung galactic systems. By 1925, the galactocentric model was established.The theory of Galactocentrism was an important step in the development of cosmological models as speculation on the existence of other galaxies, comparable in size and structure to our own, placed the earth in its proper perspective with respect to the rest of the universe. Shifts from heliocentrism to galactocentrism and later acentrism have been compared in significance to the Copernican Revolution.Galileo's Daughter
Galileo's Daughter: A Historical Memoir of Science, Faith, and Love is a book by Dava Sobel. It is based on the surviving letters of Galileo Galilei's daughter, the nun Suor Maria Celeste, and explores the relationship between Galileo and his daughter. It was nominated for the 2000 Pulitzer Prize for Biography or Autobiography.Galileo Galilei
Galileo Galilei (Italian: [ɡaliˈlɛːo ɡaliˈlɛi]; 15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Galileo has been called the "father of observational astronomy", the "father of modern physics", the "father of the scientific method", and the "father of modern science".Galileo studied speed and velocity, gravity and free fall, the principle of relativity, inertia, projectile motion and also worked in applied science and technology, describing the properties of pendulums and "hydrostatic balances", inventing the thermoscope and various military compasses, and using the telescope for scientific observations of celestial objects. His contributions to observational astronomy include the telescopic confirmation of the phases of Venus, the observation of the four largest satellites of Jupiter, the observation of Saturn and the analysis of sunspots.
Galileo's championing of heliocentrism and Copernicanism was controversial during his lifetime, when most subscribed to geocentric models such as the Tychonic system. He met with opposition from astronomers, who doubted heliocentrism because of the absence of an observed stellar parallax. The matter was investigated by the Roman Inquisition in 1615, which concluded that heliocentrism was "foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture". Galileo later defended his views in Dialogue Concerning the Two Chief World Systems (1632), which appeared to attack Pope Urban VIII and thus alienated him and the Jesuits, who had both supported Galileo up until this point. He was tried by the Inquisition, found "vehemently suspect of heresy", and forced to recant. He spent the rest of his life under house arrest. While under house arrest, he wrote Two New Sciences, in which he summarized work he had done some forty years earlier on the two sciences now called kinematics and strength of materials.Galileo affair
The Galileo affair (Italian: il processo a Galileo Galilei) was a sequence of events, beginning around 1610, culminating with the trial and condemnation of Galileo Galilei by the Roman Catholic Inquisition in 1633 for his support of heliocentrism.In 1610, Galileo published his Sidereus Nuncius (Starry Messenger), describing the surprising observations that he had made with the new telescope, namely the phases of Venus and the Galilean moons of Jupiter. With these observations he promoted the heliocentric theory of Nicolaus Copernicus (published in De revolutionibus orbium coelestium in 1543). Galileo's initial discoveries were met with opposition within the Catholic Church, and in 1616 the Inquisition declared heliocentrism to be formally heretical. Heliocentric books were banned and Galileo was ordered to refrain from holding, teaching or defending heliocentric ideas.Galileo went on to propose a theory of tides in 1616, and of comets in 1619; he argued that the tides were evidence for the motion of the Earth. In 1632 Galileo published his Dialogue Concerning the Two Chief World Systems, which implicitly defended heliocentrism, and was immensely popular. Responding to mounting controversy over theology, astronomy and philosophy, the Roman Inquisition tried Galileo in 1633 and found him "vehemently suspect of heresy", sentencing him to indefinite imprisonment. Galileo was kept under house arrest until his death in 1642.Index Librorum Prohibitorum
The Index librorum prohibitorum (Latin, "List of Prohibited Books") was a list of publications deemed heretical, or contrary to morality by the Sacred Congregation of the Index (a former Dicastery of the Roman Curia) and thus Catholics were forbidden to read them without permission.There were scattered attempts to censor individual books before the sixteenth century, notably the ninth-century Decretum Glasianum, but none of these were either official or widespread. Much later, a first version (the Pauline Index) was promulgated by Pope Paul IV in 1559, which Paul F. Grendler believed marked "the turning-point for the freedom of enquiry in the Catholic world", and which lasted less than a year, being then replaced by what was called the Tridentine Index (because it was authorized at the Council of Trent), which relaxed aspects of the Pauline Index that had been criticized and had prevented its acceptance.The 20th and final edition appeared in 1948, and the Index was formally abolished on 14 June 1966 by Pope Paul VI.The aim of the list was to protect the faith and morals of the faithful by preventing the reading of theologically, culturally, and politically disruptive books. Books thought to contain such errors included works by astronomers such as Johannes Kepler's Epitome astronomiae Copernicanae, which was on the Index from 1621 to 1835, and by philosophers, like Immanuel Kant's Critique of Pure Reason. The various editions of the Index also contained the rules of the Church relating to the reading, selling and pre-emptive censorship of books—editions and translations of the Bible that had not been approved by the Church could be banned.Latin Church canon law still recommends that works concerning sacred Scripture, theology, canon law, church history, and any writings which specially concern religion or morals, be submitted to the judgment of the local ordinary. The local ordinary consults someone whom he considers competent to give a judgment and, if that person gives the nihil obstat ("nothing forbids") the local ordinary grants the imprimatur ("let it be printed"). Members of religious institutes require the imprimi potest (it can be printed) of their major superior to publish books on matters of religion or morals.Some of the scientific theories in works that were on early editions of the Index have long been routinely taught at Catholic universities worldwide; for example, the general prohibition of books advocating heliocentrism was only removed from the Index in 1758, but already in 1742 two Minims mathematicians had published an edition of Isaac Newton's Principia Mathematica (1687) with commentaries and a preface stating that the work assumed heliocentrism and could not be explained without it. The burning at the stake of Giordano Bruno, whose entire works were placed on the Index in 1603, was because of teaching the heresy of pantheism, not for heliocentrism or other scientific views. Antonio Rosmini-Serbati, one of whose works was on the Index, was beatified in 2007. Some have argued that the developments since the abolition of the Index signify "the loss of relevance of the Index in the 21st century."A complete list of the authors and writings present in the successive editions of the Index is given in J. Martínez de Bujanda, Index Librorum Prohibitorum, 1600–1966. A list of the books that were on the Index can be found on the World Wide Web.Lucio Russo
Lucio Russo (born 22 November 1944) is an Italian physicist, mathematician and historian of science. Born in Venice, he teaches at the Mathematics Department of the University of Rome Tor Vergata.
Among his main areas of interest are Gibbs measure of the Ising model, percolation theory, and finite Bernoulli schemes, within which he proved an approximate version of the classical Kolmogorov's zero–one law.In the history of science, he has reconstructed some contributions of the Hellenistic astronomer Hipparchus, through the analysis of his surviving works, and the proof of heliocentrism attributed by Plutarch to Seleucus of Seleucia and studied the history of theories of tides, from the Hellenistic to modern age.Mysterium Cosmographicum
Mysterium Cosmographicum (lit. The Cosmographic Mystery, alternately translated as Cosmic Mystery, The Secret of the World, or some variation) is an astronomy book by the German astronomer Johannes Kepler, published at Tübingen in 1597 and in a second edition in 1621. Kepler proposed that the distance relationships between the six planets known at that time could be understood in terms of the five Platonic solids, enclosed within a sphere that represented the orbit of Saturn.
This book explains Kepler's cosmological theory, based on the Copernican system, in which the five Pythagorean regular polyhedra dictate the structure of the universe and reflect God's plan through geometry. This was the first attempt since Copernicus to say that the theory of heliocentrism is physically true. According to Kepler's account, he accidentally discovered the basis of the model while demonstrating the geometrical relationship between two circles. From this he realized that he had stumbled on a similar ratio to the one between the orbits of Saturn and Jupiter. He wrote, "I believe it was by divine ordinance that I obtained by chance that which previously I could not reach by any pains." But after doing further calculations he realized he could not use the two-dimensional polygons to represent all the planets, and instead had to use the five Platonic solids.Pope Urban VIII
Pope Urban VIII (Latin: Urbanus VIII; baptised 5 April 1568 – 29 July 1644) reigned as Pope from 6 August 1623 to his death in 1644. He expanded the papal territory by force of arms and advantageous politicking, and was also a prominent patron of the arts and a reformer of Church missions.
However, the massive debts incurred during his pontificate greatly weakened his successors, who were unable to maintain the papacy's longstanding political and military influence in Europe. He was also involved in a controversy with Galileo and his theory on heliocentrism.Regiomontanus
Johannes Müller von Königsberg (6 June 1436 – 6 July 1476), better known as Regiomontanus (), was a mathematician and astronomer of the German Renaissance, active in Vienna, Buda and Nuremberg. His contributions were instrumental in the development of Copernican heliocentrism in the decades following his death.
Regiomontanus wrote under the Latinized name of Ioannes de Monteregio (or Monte Regio; Regio Monte); the adjectival Regiomontanus was first used by Philipp Melanchthon in 1534. He is named after Königsberg in Lower Franconia, not the larger Königsberg (modern Kaliningrad) in Prussia.Seleucus of Seleucia
Seleucus of Seleucia (Greek: Σέλευκος Seleukos; born c. 190 BC; fl. c. 150 BC) was a Hellenistic astronomer and philosopher. Coming from Seleucia on the Tigris, Mesopotamia, the capital of the Seleucid Empire, or, alternatively, Seleukia on the Erythraean Sea, he is best known as a proponent of heliocentrism and for his theory of the origin of tides.Tychonic system
The Tychonic system (or Tychonian system) is a model of the Solar System published by Tycho Brahe in the late 16th century, which combines what he saw as the mathematical benefits of the Copernican system with the philosophical and "physical" benefits of the Ptolemaic system. The model may have been inspired by Valentin Naboth and Paul Wittich, a Silesian mathematician and astronomer. A similar model was implicit in the calculations a century earlier by Nilakantha Somayaji of the Kerala school of astronomy and mathematics.It is conceptually a geocentric model: the Earth is at the centre of the universe, the Sun and Moon and the stars revolve around the Earth, and the other five planets revolve around the Sun.
At the same time, the motions of the planets are mathematically equivalent to the motions in Copernicus' heliocentric system under a simple coordinate transformation, so that, as long as no force law is postulated to explain why the planets move as described, there is no mathematical reason to prefer either the Tychonic or the Copernican system.