Geocentric model

The geocentric model was the predominant description of the cosmos in many European ancient civilizations, such as those of Aristotle in Classical Greece and Ptolemy in Roman Egypt, as well as during the Islamic Golden Age.

However, the Greek astronomer and mathematician Aristarchus of Samos (c. 310 – c. 230 BC) developed a heliocentric model placing all of the then-known planets in their correct order around the Sun.

Aristotle believed that the Moon was in the innermost sphere and therefore touches the realm of Earth, causing the dark spots (maculae) and the ability to go through lunar phases.

Further, barring the opportunity to fall closer the center, terrestrial bodies tend not to move unless forced by an outside object, or transformed to a different element by heat or moisture.

The original purpose of the eccentric was to account for the difference in length of the seasons (northern autumn was about five days shorter than spring during this time period) by placing the Earth away from the center of rotation of the rest of the universe.

Muslim astronomers generally accepted the Ptolemaic system and the geocentric model,[6] but by the 10th century, texts appeared regularly whose subject matter expressed doubts concerning Ptolemy (shukūk).

[11][12] According to al-Biruni, Sijzi invented an astrolabe called al-zūraqī, based upon a belief held by some of his contemporaries "that the motion we see is due to the Earth's movement and not to that of the sky".

[15] In the 12th century, Arzachel departed from the ancient Greek idea of uniform circular motions by hypothesizing that the planet Mercury moves in an elliptic orbit,[16][17] while Alpetragius proposed a planetary model that abandoned the equant, epicycle and eccentric mechanisms,[18] though this resulted in a system that was mathematically less accurate.

Like their Andalusian predecessors, the Maragha astronomers attempted to solve the equant problem (the circle around whose circumference a planet or the center of an epicycle was conceived to move uniformly) and produce alternative configurations to the Ptolemaic model without abandoning geocentrism.

They were more successful than their Andalusian predecessors in producing non-Ptolemaic configurations which eliminated the equant and eccentrics, were more accurate than the Ptolemaic model in numerically predicting planetary positions, and were in better agreement with empirical observations.

[31] In 1543, the geocentric system met its first serious challenge with the publication of Copernicus' De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres), which posited that the Earth and the other planets instead revolved around the Sun.

[35] Galileo's observations were verified by other astronomers of the time period who quickly adopted use of the telescope, including Christoph Scheiner, Johannes Kepler, and Giovan Paulo Lembo.

As a result, Ptolemaics abandoned the idea that the epicycle of Venus was completely inside the Sun, and later 17th-century competition between astronomical cosmologies focused on variations of the Tychonic or Copernican systems.

Johannes Kepler analysed Tycho Brahe's famously accurate observations, and afterwards constructed his three laws in 1609 and 1619, based upon a heliocentric model wherein the planets move in elliptical paths.

In his Principia, Newton explained his theory of how gravity, previously thought to be a mysterious, unexplained occult force, directed the movements of celestial bodies, and kept our Solar System in working order.

Several empirical tests of Newton's theory, explaining the longer period of oscillation of a pendulum at the equator and the differing size of a degree of latitude, would gradually become available between 1673 and 1738.

This finally confirmed the assumptions made by Copernicus, providing accurate, dependable scientific observations, and conclusively displaying how distant stars are from Earth.

Rather, relativity states that the Sun, the Earth, the Moon, Jupiter, or any other point for that matter could be chosen as a center of the Solar System with equal validity.

[citation needed] What the principle of relativity points out is that correct mathematical calculations can be made regardless of the reference frame chosen, and these will all agree with each other as to the predictions of actual motions of bodies with respect to each other.

[48] A study conducted in 2005 by Jon D. Miller of Northwestern University, an expert in the public understanding of science and technology,[49] found that about 20%, or one in five, of American adults believe that the Sun orbits the Earth.

Pope Leo XIII (1878–1903) wrote: we have to contend against those who, making an evil use of physical science, minutely scrutinize the Sacred Book in order to detect the writers in a mistake, and to take occasion to vilify its contents.

Hence they did not seek to penetrate the secrets of nature, but rather described and dealt with things in more or less figurative language, or in terms which were commonly used at the time, and which in many instances are in daily use at this day, even by the most eminent men of science.

Ordinary speech primarily and properly describes what comes under the senses; and somewhat in the same way the sacred writers-as the Angelic Doctor also reminds us – "went by what sensibly appeared", or put down what God, speaking to men, signified, in the way men could understand and were accustomed to.Maurice Finocchiaro, author of a book on the Galileo affair, notes that this is "a view of the relationship between biblical interpretation and scientific investigation that corresponds to the one advanced by Galileo in the "Letter to the Grand Duchess Christina".

He stated in a papal bull that his purpose in doing so was that "the succession of things done from the beginning might be made known [quo rei ab initio gestae series innotescat]".

He is now appointed the task of bringing to an end any concerns and criticisms regarding the printing of this book, and, at the same time, ensuring that in the future, regarding the publication of such works, permission is sought from the Cardinal Vicar whose signature will not be given without the authorization of the Superior of his Order.

[54]In 1822, the Congregation of the Holy Office removed the prohibition on the publication of books treating of the Earth's motion in accordance with modern astronomy and Pope Pius VII ratified the decision: The most excellent [cardinals] have decreed that there must be no denial, by the present or by future Masters of the Sacred Apostolic Palace, of permission to print and to publish works which treat of the mobility of the Earth and of the immobility of the sun, according to the common opinion of modern astronomers, as long as there are no other contrary indications, on the basis of the decrees of the Sacred Congregation of the Index of 1757 and of this Supreme [Holy Office] of 1820; and that those who would show themselves to be reluctant or would disobey, should be forced under punishments at the choice of [this] Sacred Congregation, with derogation of [their] claimed privileges, where necessary.

[52] In his 1921 papal encyclical, In praeclara summorum, Pope Benedict XV stated that, "though this Earth on which we live may not be the center of the universe as at one time was thought, it was the scene of the original happiness of our first ancestors, witness of their unhappy fall, as too of the Redemption of mankind through the Passion and Death of Jesus Christ".

The error of the theologians of the time, when they maintained the centrality of the Earth, was to think that our understanding of the physical world's structure was, in some way, imposed by the literal sense of Sacred Scripture.

[58]A few Orthodox Jewish leaders maintain a geocentric model of the universe based on the aforementioned Biblical verses and an interpretation of Maimonides to the effect that he ruled that the Earth is orbited by the Sun.

[59][60] The Lubavitcher Rebbe also explained that geocentrism is defensible based on the theory of relativity, which establishes that "when two bodies in space are in motion relative to one another, ... science declares with absolute certainty that from the scientific point of view both possibilities are equally valid, namely that the Earth revolves around the sun, or the sun revolves around the Earth", although he also went on to refer to people who believed in geocentrism as "remaining in the world of Copernicus".