When was the geocentric model made

The centers of the epicycles of Mercury and Venus must lie on the line joining the Earth and the Sun. Stars are fixed on an outermost sphere. This model gives predictions on the positions of the planets within a few degrees from the actual positions. This was generally accepted and the Ptolemaic model dominated the western world for years. The deferent is a circle whose center point is removed from the Earth, which was used to account for the differences in the lengths of the seasons. The purpose of he epicycle was to account for retrograde motion, where planets in the sky appear to be slowing down, moving backwards, and then moving forward again.

Unfortunately, these explanations did not account for all the observed behaviors of the planets. While this system remained the accepted cosmological model within the Roman, Medieval European and Islamic worlds for over a thousand years, it was unwieldy by modern standards. Granted, it did manage to predict planetary motions with a fair degree of accuracy, and was used to prepare astrological and astronomical charts until replaced by the heliocentric model of the Universe.

At the same time, however, every planet in the model required an epicycle revolving on a deferent and offset by an equant, which were also different for each planet. In time, these complexities would come to be challenged. During the Middle Ages, the geocentric model gained new power and as it became synthesized with Christian theology to become an essential canon. As part of a general trend whereby classical knowledge was being rediscovered by the 13th century and after, the adoption of the Aristotelian-Ptolemiac model of the Universe was part of a marriage between Faith and Reason champion by scholars like St.

Thomas Aquinas. As a result of this, challenging the view that the heavens revolved around the Earth was not merely a scientific matter, but a matter of heresy.

It is also why support for the heliocentric model of the Universe was also carefully tempered and its adoption gradual. The geocentric view of the Universe was also the accepted cosmological model in the Islamic world during the Middle Ages. In the early 11th century, Egyptian-Arab astronomer Alhazen wrote a critique entitled Doubts on Ptolemy ca.

Around the same time, Iranian philosopher Abu Rayhan Biruni — discussed the possibility of Earth rotating about its own axis and around the Sun — though he considered this a philosophical issue and not a mathematical one.

In the 11th and 12th centuries several Andalusian astronomers, centered in the Almohad Moorish territory of Spain, challenged the geocentric model of the Universe as well. For instance, 11th century astronomer Abu Ishaq Ibrahim al-Zarqali aka. Arzachel departed from the ancient Greek idea of uniform circular motions by hypothesizing that the planet Mercury moves in an elliptic orbit.

In the 12th century, fellow Andalusian Nur ad-Din al-Bitruji aka. Alpetragius proposed a planetary model that abandoned the equant, epicycle and eccentric mechanisms. Though these were largely philosophical in nature and did not result in the adoption of heliocentrism, many of the arguments and evidence put forward resembled those used later by Copernicus. In the 16th century, Nicolaus Copernicus began devising his version of the heliocentric model, which represented the culmination of years worth of research.

Like others before him, Copernicus built on the work of a number classical astronomers who did not support the geocentric view, as well as paying homage to the Maragha school and several notable philosophers from the Islamic world. This forty-page manuscript described his ideas about the heliocentric hypothesis, which was based on seven general principles.

These principles stated that:. Thereafter he continued gathering data for a more detailed work, and by , he had come close to completing the manuscript of his magnum opus — De revolutionibus orbium coelestium On the Revolutions of the Heavenly Spheres.

In it, he advanced his seven major arguments, but in more detailed form and with detailed computations to back them up. By placing the orbits of Mercury and Venus between the Earth and the Sun, Copernicus was able to account for changes in their appearances.

In essence, they are significantly closer to Earth when at opposition than when they are at conjunction. However, due to fears that the publication of his theories would lead to condemnation from the church as well as, perhaps, worries that his theory presented some scientific flaws he withheld his research until a year before he died. It was only in , when he was near death, that he sent his treatise to Nuremberg to be published.

As already noted, Copernicus was not the first to advocate a heliocentric view of the universe, and his model was based on the work of several previous astronomers. The first recorded examples of this are traced to classical antiquity, when Aristarchus of Samos ca.

In his treatise The Sand Reckoner, Archimedes described another work by Aristarchus in which he advanced an alternative hypothesis of the heliocentric model. As he explained:. Now you are aware that 'universe' is the name given by most astronomers to the sphere whose center is the center of the earth and whose 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 of Samos brought out a book consisting of some hypotheses, in which the premises lead to the result that the universe is many times greater than that now so called. His hypotheses are that the fixed stars and the sun remain unmoved, that the earth revolves about the sun in 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 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.

This gave rise to the notion that there should be an observable parallax with the "fixed stars" i. According to Archimedes, Aristarchus claimed that the stars were much farther away than commonly believed, and this was the reason for no discernible parallax. The only other philosopher from antiquity who's writings on heliocentrism have survived is Seleucis of Seleucia ca.

A Hellenistic astronomer who lived in the Near-Eastern Seleucid empire, Seleucus was a proponent of the heliocentric system of Aristarchus, and is said to have proved the heliocentric theory. According to contemporary sources, Seleucus may have done this by determining the constants of the geocentric model and applying them to a heliocentric theory, as well as computing planetary positions possibly using trigonometric methods. Alternatively, his explanation may have involved the phenomenon of tides, which he supposedly theorized to be related to the influence of the moon and the revolution of the Earth around the Earth-moon 'center of mass'.

In the 5th century CE, Roman philosopher Martianus Capella of Carthage expressed an opinion that the planets Venus and Mercury revolved around the sun, as a way of explaining the discrepancies in their appearances.

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. In his treatise De Docta Ignorantia On Learned Ignorance Cardinal Nicholas of Cusa — CE asked whether there was any reason to assert that the sun or any other point was the center of the universe.

Indian astronomers and cosmologists also hinted at the possibility of a heliocentric universe during late antiquity and the Middle Ages. In CE, Indian astronomer Aaryabhata published his magnum opus Aryabhatiya, in which he proposed a model where the Earth was spinning on its axis and the periods of the planets were given with respect to the sun.

He also accurately calculated the periods of the planets, times of the solar and lunar eclipses, and the motion of the moon. In the 15th century, Nilakantha Somayaji published the Aryabhatiyabhasya, which was a commentary on Aryabhata's Aryabhatiya.

In it, he developed a computational system for a partially heliocentric planetary model, in which the planets orbit the sun, which in turn orbits the Earth. In the Tantrasangraha , he revised the mathematics of his planetary system further and incorporated the Earth's rotation on its axis. Also, the heliocentric model of the universe had proponents in the medieval Islamic world, many of whom would go on to inspire Copernicus. Prior to the 10th century, the Ptolemaic model of the universe was the accepted standard to astronomers in the West and Central Asia.

However, in time, manuscripts began to appear that questioned several of its precepts. For instance, the 10th-century Iranian astronomer Abu Sa'id al-Sijzi contradicted the Ptolemaic model by asserting that the Earth revolved on its axis, thus explaining the apparent diurnal cycle and the rotation of the stars relative to Earth.

In the early 11th century, Egyptian-Arab astronomer Alhazen wrote a critique entitled Doubts on Ptolemy ca. Around the same time, Iranian philosopher Abu Rayhan Biruni — discussed the possibility of Earth rotating about its own axis and around the sun — though he considered this a philosophical issue and not a mathematical one. At the Maragha and the Ulugh Beg aka. Samarkand Observatory, the Earth's rotation was discussed by several generations of astronomers between the 13th and 15th centuries, and many of the arguments and evidence put forward resembled those used by Copernicus.

Despite his fears about his arguments producing scorn and controversy, the publication of Copernicu's theories resulted in only mild condemnation from religious authorities. Over time, many religious scholars tried to argue against his model. But within a few generation's time, Copernicus' theory became more widespread and accepted, and gained many influential defenders in the meantime.

These included Galileo Galilei , who's investigations of the heavens using the telescope allowed him to resolve what were seen as flaws in the heliocentric model, as well as discovering aspects about the heavens that supported heliocentrism.

For example, Galileo discovered moons orbiting Jupiter, sunspots, and the imperfections on the moon's surface — all of which helped to undermine the notion that the planets were perfect orbs, rather than planets similar to Earth. While Galileo's advocacy of Copernicus' theories resulted in his house arrest, others soon followed. German mathematician and astronomer Johannes Kepler also helped to refine the heliocentric model with his introduction of elliptical orbits.

Prior to this, the heliocentric model still made use of circular orbits, which did not explain why planets orbited the sun at different speeds at different times. By showing how the planet's sped up while at certain points in their orbits, and slowed down in others, Kepler resolved this. In addition, Copernicus' theory about the Earth being capable of motion would go on to inspire a rethinking of the entire field of physics.

Whereas previous ideas of motion depended on an outside force to instigate and maintain it i. These ideas would be articulated by Sir Isaac Newton, who's Principia formed the basis of modern physics and astronomy. Although its progress was slow, the heliocentric model eventually replaced the geocentric model. In the end, the impact of its introduction was nothing short of a revolutionary. Henceforth, humanity's understanding of the universe and our place in it would be forever changed.

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