Geocentric model

geocentricPtolemaic systemPtolemaicgeocentrismPtolemaic modelPtolemaic astronomyPtolemaic cosmologycenter of the universeEarth's centralityEarth-centered universe
In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center.wikipedia
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Universe

physical worldThe Universeuniverses
In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center.
The earliest cosmological models of the Universe were developed by ancient Greek and Indian philosophers and were geocentric, placing Earth at the center.

Astronomy

astronomicalastronomerastronomers
In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center.
This is known as the geocentric model of the Universe, or the Ptolemaic system, named after Ptolemy.

Orbit

orbitsorbital motionplanetary motion
Under the geocentric model, the Sun, Moon, stars, and planets all orbited Earth.
Originally geocentric, it was modified by Copernicus to place the Sun at the centre to help simplify the model.

Aristarchus of Samos

AristarchusAristarchos of Samos
However, the Greek astronomer and mathematician Aristarchus of Samos (c.
His astronomical ideas were often rejected in favor of the geocentric theories of Aristotle and Ptolemy.

Classical planet

classical planetsplanetsnaked eye planets
Under the geocentric model, the Sun, Moon, stars, and planets all orbited Earth.
The Ptolemaic system used in Greek astronomy placed the planets in order, closest to Earth to furthest, as the Moon, Mercury, Venus, Sun, Mars, Jupiter, and Saturn.

Celestial sphere

celestialcelestial hemispherehemisphere
The celestial sphere, still used for teaching purposes and sometimes for navigation, is also based on a geocentric system which in effect ignores parallax.
All objects in the sky can be conceived as being projected upon the inner surface of the celestial sphere, which may be centered on Earth or the observer.

Ptolemy

Claudius PtolemyClaudius PtolemaeusPtolemaic
The geocentric model was the predominant description of the cosmos in many ancient civilizations, such as those of Aristotle in Classical Greece and Ptolemy in Roman Egypt.
Ptolemy's model, like those of his predecessors, was geocentric and was almost universally accepted until the appearance of simpler heliocentric models during the scientific revolution.

Johannes Kepler

KeplerDioptriceJohan Kepler
The ancient Greeks believed that the motions of the planets were circular and not elliptical, a view that was not challenged in Western culture until the 17th century, when Johannes Kepler postulated that orbits were heliocentric and elliptical (Kepler's first law of planetary motion). The geocentric model held sway into the early modern age, but from the late 16th century onward, it was gradually superseded by the heliocentric model of Copernicus (1473-1543), Galileo (1564-1642), and Kepler (1571-1630).
Under the instruction of Michael Maestlin, Tübingen's professor of mathematics from 1583 to 1631, he learned both the Ptolemaic system and the Copernican system of planetary motion.

Superseded theories in science

obsolete scientific theorysupersededSuperseded scientific theories
In astronomy, 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. The geocentric model held sway into the early modern age, but from the late 16th century onward, it was gradually superseded by the heliocentric model of Copernicus (1473-1543), Galileo (1564-1642), and Kepler (1571-1630).

Spherical Earth

spherical shape of the Earthspheresphericity of the Earth
Ancient Greek, ancient Roman, and medieval philosophers usually combined the geocentric model with a spherical Earth, in contrast to the older flat-Earth model implied in some mythology.
In this geocentric model, the structure of the universe was believed to be a series of perfect spheres.

Almagest

cataloghis book on astronomyMagna Syntaxis
His main astronomical work, the Almagest, was the culmination of centuries of work by Hellenic, Hellenistic and Babylonian astronomers.
170). One of the most influential scientific texts of all time, it canonized a geocentric model of the Universe that was accepted for more than 1200 years from its origin in Hellenistic Alexandria, in the medieval Byzantine and Islamic worlds, and in Western Europe through the Middle Ages and early Renaissance until Copernicus.

Heliocentrism

heliocentricheliocentric modelheliocentric theory
The geocentric model held sway into the early modern age, but from the late 16th century onward, it was gradually superseded by the heliocentric model of Copernicus (1473-1543), Galileo (1564-1642), and Kepler (1571-1630).
Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center.

Tychonic system

geoheliocentricTychonicalternative geocentric (or "geo-heliocentric") model
It has been determined, in fact, that the Copernican, Ptolemaic and even the Tychonic models provided identical results to identical inputs. 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 Tycho Brahe's Tychonic system (in which the Earth was still at the center of the universe, and around it revolved the Sun, but all other planets revolved around the Sun in one massive set of epicycles), or variations on the Copernican 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.

Copernican heliocentrism

Copernican systemCopernican theoryCopernican model
The earliest heliocentric model, Copernican heliocentrism, could remove Ptolemy's epicycles because the retrograde motion could be seen to be the result of the combination of Earth and planet movement and speeds.
The Copernican model displaced the geocentric model of Ptolemy that had prevailed for centuries, which had placed Earth at the center of the Universe.

Ancient Greek astronomy

Greek astronomyGreek astronomerastronomy
The geocentric model entered Greek astronomy and philosophy at an early point; it can be found in pre-Socratic philosophy.
The two-sphere model is a geocentric model that divides the cosmos into two regions, a spherical Earth, central and motionless (the sublunary sphere) and a spherical heavenly realm centered on the Earth, which may contain multiple rotating spheres made of aether.

Primum Mobile

dodecatemorymovedoutermost moving sphere
In classical, medieval, and Renaissance astronomy, the Primum Mobile (or "first moved") was the outermost moving sphere in the geocentric model of the universe.

Babylonian astronomy

Babylonian astronomersBabylonianastronomer
His main astronomical work, the Almagest, was the culmination of centuries of work by Hellenic, Hellenistic and Babylonian astronomers.
Their worldview was not exactly geocentric either.

Astronomy in the medieval Islamic world

astronomerastronomyIslamic astronomy
For over a millennium European and Islamic astronomers assumed it was the correct cosmological model.
From this time, independent investigation into the Ptolemaic system became possible.

Flat Earth

flatEarth is flatEarth was flat
Ancient Greek, ancient Roman, and medieval philosophers usually combined the geocentric model with a spherical Earth, in contrast to the older flat-Earth model implied in some mythology.

Earth

Earth's surfaceterrestrialworld
In astronomy, 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.
Earth was generally believed to be the center of the universe until the 16th century, when scientists first conclusively demonstrated that it was a moving object, comparable to the other planets in the Solar System.

Early modern period

early moderncolonial eraearly modern era
The geocentric model held sway into the early modern age, but from the late 16th century onward, it was gradually superseded by the heliocentric model of Copernicus (1473-1543), Galileo (1564-1642), and Kepler (1571-1630).

De revolutionibus orbium coelestium

De revolutionibusOn the Revolutions of the Heavenly SpheresDe revolutionibus orbium cœlestium
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.
The book, first printed in 1543 in Nuremberg, Holy Roman Empire, offered an alternative model of the universe to Ptolemy's geocentric system, which had been widely accepted since ancient times.

Deferent and epicycle

epicyclesdeferentdeferents and epicycles
However, while providing for similar explanations, the later deferent and epicycle model was flexible enough to accommodate observations for many centuries.
In the Hipparchian, Ptolemaic, and Copernican systems of astronomy, the epicycle (from, literally upon the circle, meaning circle moving on another circle ) was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets.

Apparent retrograde motion

retrograde motionretrograderetrogradation
These combined movements cause the given planet to move closer to and further away from the Earth at different points in its orbit, and explained the observation that planets slowed down, stopped, and moved backward in retrograde motion, and then again reversed to resume normal, or prograde, motion.
In the geocentric model of the Solar System proposed by Apollonius in the third century BCE, retrograde motion was explained by having the planets travel in deferents and epicycles.

Tycho Brahe

BraheTychoTyge Brahe
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 Tycho Brahe's Tychonic system (in which the Earth was still at the center of the universe, and around it revolved the Sun, but all other planets revolved around the Sun in one massive set of epicycles), or variations on the Copernican system.
As an astronomer, Tycho worked to combine what he saw as the geometrical benefits of the Copernican system with the philosophical benefits of the Ptolemaic system into his own model of the universe, the Tychonic system.