Lyceum & Book Club - Week 11 - Article- Transition from Medieval Geocentrism to Heliocentrism

From universe today:

Medieval Geocentrism:

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.

For starters, the separation of the Universe into the “heavens” and the Earth, with the Earth at the center of creation and the heavens beyond, agreed with the Christian view of mankind being the pinnacle of God’s creation. Second, the Prime Mover of Aristotle’s cosmos was interpreted as being the God of Christian theology, and the outermost sphere of the Prime Mover was equated with the Christian Heaven.

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. Hence why it did not come to be challenged until the 16th century with the publication of Nicolaus Copernicus‘ De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres), which he only published posthumously to avoid controversy. 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. However, beginning in the 10th century CE, there were several Muslim astronomers who challenged one or more aspects of Ptolemy’s work. For instance, Iranian astronomer Abu Sa’id al-Sijzi (ca. 945 – ca. 1020) 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. 1028) in which he criticized many aspects of his model. Around the same time, Iranian philosopher Abu Rayhan Biruni (973 – 1048) 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. This was followed by Fakhr al-Din al-Razi’s (1149–1209) publication of his treatise Matalib, which dealt with conceptual physics. In it, he rejected the notion of the Earth’s centrality within the universe and instead proposed a cosmology in which there were a “thousand thousand worlds beyond this world…”

And at the Maragha Observatory in eastern Iran, the Damascus mosque, and the Ulugh Beg (aka. Samarkand) Observatory in modern-day Kazakhstan, the Earth’s rotation was discussed by several generations of astronomers between the 13th and 15th centuries. 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.

The Heliocentric Model:

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.

By 1514 century, Copernicus summarized his ideas in a short treatise titled Commentariolus (“Little Commentary”), which he began circulating to friends.