# Geocentric model

The geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center. Under most geocentric models, the Sun, Moon, stars, and planets all orbit Earth. 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.

## Quotes

* Both ancient and medieval observers had noted that in many respects nature appeared to be governed by the principle of simplicity, and they had recorded the substance of their observations to this effect in the form of proverbial axioms which had become currently accepted bits of man's conception of the world. That falling bodies moved perpendicularly towards the earth, that light travelled in straight lines, that projectiles did not vary from the direction in which they were impelled, and countless other familiar facts of experience, had given rise to such common proverbs as: 'Natura semper agit per vias brevissimas'; 'natura nihil facit frustra'; 'natura neque redundat in superfluis neque deficit in necessariis' [Nature always acts by the shortest path; nature does nothing in vain; nature never overflows into the unnecessary, nor is she deficient in what is necessary]. This notion, that nature performs her duties in the most commodious fashion, without extra labour, would have tended to decrease somewhat the repulsion which most minds must have felt at Copernicus; the cumbrous epicycles had been decreased in number, various irregularities in the Ptolemaic scheme were eliminated... That such a tremendous shift in the point of reference could be legitimate was a suggestion quite beyond the grasp of people trained for centuries to think in terms of a homocentric philosophy and a geocentric physics. ...Copernicus could take the step because... he had definitely placed himself in... [the] dissenting Platonic movement. ...It was no accident that he became familiar with the remains of the early Pythagoreans, who almost alone among the ancients had ventured to suggest a non-geocentric astronomy.
** Edwin Arthur Burtt, The Metaphysical Foundations of Modern Physical Science Ch. 2 Copernicus and Kepler (A) The Problem of the New Astronomy, pp. 26-44.
* Ptolemy... against the champions of this or that cosmology of the heavens... had dared to claim that it is legitimate to interpret the facts of astronomy by the simplest geometrical scheme which will 'save the phenomena,' no matter whose metaphysics might be upset. His conception of the physical structure of the earth, however, prevented him from carrying through in earnest this principle of relativity, as his objections to the hypothesis that the earth moves amply show.
** Edwin Arthur Burtt, in The Metaphysical Foundations of Modern Physical Science (1924) p. 35.
* Galileo had the experience of beholding the heavens as they actually are for perhaps the first time, and wherever he looked he found evidence to support the Copernican system against the Ptolemaic, or at least weaken the authority of the ancients. This shattering experience—of observing the depths of the universe, of being the first mortal to know what the heavens are actually like—made so deep an impression... that it is only by considering the events of 1609... that one can understand the subsequent direction of his life.
** I. Bernard Cohen, The Birth of a New Physics (1959) pp. 57-58.
* The Greek philosopher, Plato, in the fourth century B.C. asked his students if they could devise a theory or explanation to explain this erratic planetary motion using some form of circular motion. Being keen observers, the Greeks came up with the most logical and obvious conclusions; namely, that the earth was the center about which the sun, the moon, planets, and the stars rotated. This model of the universe is called a geocentric or earth-centered model. It satisfactorily explained the daily motion of the stars and sun by assuming that they were attached to invisible crystalline spheres that rotated about the earth. The axis of the sphere of the sun was tilted with respect to that of the stars to account for the variation of the sun's height at zenith with the various seasons. Since the sun appears to move through the stars and was brighter, it was assumed to be nearer to the earth than the stars. The spheres of the Moon, Mercury, and Venus were placed within the sphere of the sun while those of Mars, Jupiter, and Saturn were placed outside the sphere of the sun but within the sphere of the stars.
** Cooperative General Science Project (CGSP) Staff, O. P. Puri (Director), "Concepts in Physical Science" Ch. 1 Concepts in Motion, p. 7.
* The fundamental core of contemporary Darwinism, the theory of DNA-based reproduction and evolution, is now beyond dispute among scientists. It demonstrates its power every day, contributing crucially to the explanation of planet-sized facts of geology and meteorology, through middle-sized facts of ecology and agronomy, down to the latest microscopic facts of genetic engineering. It unifies all of biology and the history of our planet into a single grand story. Like Gulliver tied down in Lilliput, it is unbudgable, not because of some one or two huge chains of argument that might — hope against hope — have weak links in them, but because it is securely tied by thousands of threads of evidence anchoring it to virtually every other area of human knowledge. New discoveries may conceivably lead to dramatic, even "revolutionary" shifts in the Darwinian theory, but the hope that it will be "refuted" by some shattering breakthrough is about as reasonable as the hope that we will return to a geocentric vision and discard Copernicus.
** Daniel Dennett, Darwin's Dangerous Idea (1995)
* The present revolution of scientific thought follows in natural sequence on the great revolutions at earlier epochs in the history of science. Einstein's special theory of relativity, which explains the indeterminateness of the frame of space and time, crowns the work of Copernicus who first led us to give up our insistence on a geocentric outlook on nature; Einstein's general theory of relativity, which reveals the curvature or non-Euclidean geometry of space and time, carries forward the rudimentary thought of those earlier astronomers who first contemplated the possibility that their existence lay on something which was not flat. These earlier revolutions are still a source of perplexity in childhood, which we soon outgrow; and a time will come when Einstein's amazing revelations have likewise sunk into the commonplaces of educated thought.
** Arthur Eddington, The Theory of Relativity and its Influence on Scientific Thought (1922), p. 31-32.
* Fundamental changes in science have always been accompanied by deeper digging toward the philosophical foundations. Changes like the transition from the Ptolemaic to the Copernican system, from Euclidean to non-Euclidean geometry, from Newtonian to relativistic mechanics... have brought about a radical change in our common-sense explanation of the world. From all these considerations everyone who is to get a satisfactory understanding of twentieth century science will have to absorb a good deal of philosophical thought. But he will soon feel the same thing holds for a thorough understanding of the science which originated in any period of history.
** Philipp Frank, Philosophy of Science: The Link Between Science and Philosophy (1957)
* Persisting in their original resolve to destroy me and everything mine by any means they can think of, these men are aware of my views in astronomy and philosophy. They know that as to the arrangement of the parts of the universe, I hold the sun to be situated motionless in the center of the revolution of the celestial orbs while the earth revolves about the sun. They know also that I support this position not only by refuting the arguments of Ptolemy and Aristotle, but by producing many counter-arguments; in particular, some which relate to physical effects whose causes can perhaps be assigned in no other way. In addition there are astronomical arguments derived from many things in my new celestial discoveries that plainly confute the Ptolemaic system while admirably agreeing with and confirming the contrary hypothesis.
** Galileo Galilei, Letter to the Grand Duchess Christina (1615) Essay published in 1615, in response to enquiries of Christina of Tuscany, as quoted in Aspects of Western Civilization : Problems and Sources in History (1988) by Perry McAdow Rogers, p. 53
* It may be true that scientism and evolutionism (not science and evolution) are among the causes of atheism and materialism. It is at least equally true that biblical literalism, from its earlier flat-earth and geocentric forms to its recent young-earth and flood-geology forms, is one of the major causes of atheism and materialism. Many scientists and intellectuals have simply taken the literalists at their word and rejected biblical materials as being superseded or contradicted by modern science. Without having in hand a clear and persuasive alternative, they have concluded that it is nobler to be damned by the literalists than to dismiss the best testimony of research and reason. Intellectual honesty and integrity demand it.
** Conrad Hyers, The Meaning of Creation: Genesis and Modern Science (1984)
* The odd thing about this story is that the heliocentric view was known in Europe long before Copernicus but, for various reasons, was totally ignored by the "established" dogma... All this time all kinds of absurdities were written about the heavens, the celestial spheres, the Empyrean and so on, which constituted the “established” view. And all the time the real knowledge was there and all those schoolmen, could, with some practical observation and sensible application of Mathematics, have found out that the Ptolemaic system was not true. But they did not: they preferred to argue about such weighty matters as how many angles could sit on the point of a pin. And when the proofs were presented to them in black and white, hard and irrefutable mathematical demonstrations, they still rejected them preferring the comforts of the ‘‘established” dogma. Theology (and Church interests) decided what was acceptable, not Mathematics.
** "ESTABLISHMENT" OF A VIEW Author(s): N. Kazanas Source: Annals of the Bhandarkar Oriental Research Institute, Vol. 83 (2002), pp. 179-182
* I shall try to sum up the main obstacles which arrested the progress of science for such an immeasurable time. The first was the splitting of the world into two spheres, and the mental split which resulted from it. The second was the geocentric dogma, the blind eye turned on the promising line of thought which had started with the Pythagoreans and stopped abruptly with Aristarchus of Samos. The third was the dogma of uniform motion in perfect circles. The fourth was the divorcement of science from mathematics. The fifth was the inability to realize that a body at rest tended to stay at rest, a body in motion tended to stay in motion. The main achievement of the first part of the scientific revolution was the removal of these five cardinal obstacles. This was done chiefly by three men: Copernicus, Kepler and Galileo. After that, the road was open to the Newtonian synthesis; from there on the journey led with rapidly gaining speed to the atomic age.
** Arthur Koestler, The Sleepwalkers: A History of Man's Changing Vision of the Universe (1959)
* Joseph Ratzinger has stood still because as a Bavarian Catholic in the Hellenistic tradition, interpreted in Roman terms, he wanted to stand still. To this degree he represented and represents a different basic model of theology and church, as different from mine as in astronomy Ptolemy's geocentric picture of the world is different from Copernicus' heliocentric picture.
** Hans Küng, Disputed Truth: Memoirs (2008) Vol. 2, p. 329.
* Let us... examine the point on which Newton, apparently with sound reasons, rests his distinction of absolute and relative motion. If the earth is affected with an absolute rotation about its axis, centrifugal forces are set up in the earth: it assumes an oblate form, the acceleration of gravity is diminished at the equator, the plane of Foucault's pendulum rotates, and so on. All these phenomena disappear if the earth is at rest and the other heavenly bodies are affected with absolute motion round it, such that the same relative rotation is produced. This is, indeed, the case, if we start ab initio from the idea of absolute space. But if we take our stand on the basis of facts, we shall find we have knowledge only of relative spaces and motions. Relatively, not considering the unknown and neglected medium of space, the motions of the universe are the same whether we adopt the Ptolemaic or the Copernican mode of view. Both views are, indeed, equally correct; only the latter is more simple and more practical. The universe is not twice given, with an earth at rest and an earth in motion; but only once, with its relative motions, alone determinable. It is, accordingly, not permitted us to say how things would be if the earth did not rotate. We may interpret the one case that is given us, in different ways. If, however, we so interpret it that we come into conflict with experience, our interpretation is simply wrong. The principles of mechanics can, indeed, be so conceived, that even for relative rotations centrifugal forces arise.
** Ernst Mach, The Science of Mechanics (1893) pp. 231-232, a Thomas J. McCormick translation of Die Mechanik in ihrer Entwickelung [Mechanics and Its Evolution] (1883)
* Talk of the sublime, the exalted, the eternal, the passionate, of glory, challenge, or majesty fills some of us with bewilderment, discomfort, and embarrassment; others with sour resentment or scornful disbelief. To reinstate such values seems to us like trying to reinstate Ptolemaic astronomy—equally misguided, incomprehensible, and inimical to our perceived interests.
** R. W. K. Paterson, The New Patricians (1998), p. 45.
* It became clear that our Galaxy is only one system among many, and that the universe is far vaster than the particular stellar system to which the Sun and planets belong. Since then developments have been more rapid than at any time since the days of Copernicus, Digges and Bruno when the geocentric hypothesis of the cosmos received its death-blow.
** Gerald James Whitrow, "Theories of the Universe" (Apr 10, 1958) The New Scientist
* These seven bodies were the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn, all of which were documented by the Babylonians over three thousand years ago. Until the sixteenth century, the most commonly held view was that the Earth was at the centre of the Universe and that the seven bodies revolved around the Earth.
** Peter Wothers, Antimony, Gold, And Jupiter’s Wolf How The Elements Were Named (2019) p. 2.

## See also

* Aristarchus of Samos
* Galileo Galilei
* Copernican heliocentrism
* Nicolaus Copernicus
* Cosmology
* History of science
* Johannes Kepler
* Ptolemy
* Scientific Revolution

## External links

* Dialogue Concerning the Two Chief World Systems (1632) by Galileo Galilei
* Ptolemaic System, from The Galileo Project, Rice University.