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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the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center. Under most geocentric models, the Sun, Moon, stars, and planets all orbit Earth.
Motion of the Sun (yellow), Earth (blue), and Mars (red). At left, Copernicus's heliocentric motion. At right, traditional geocentric motion, including the retrograde motion of Mars. For simplicity, Mars's period of revolution is depicted as 2 years instead of 1.88, and orbits are depicted as perfectly circular or epitrochoid.
The Earth-centered, Earth-fixed coordinate system (acronym ECEF), also known as the geocentric coordinate system, is a cartesian spatial reference system that represents locations in the vicinity of the Earth (including its surface, interior, atmosphere, and surrounding outer space) as X, Y, and Z measurements from its center of mass.
Created Date: 8/30/2012 4:52:52 PM
Epicyclic theory, in part, sought to explain this behavior. The inferior planets were always observed to be near the Sun, appearing only shortly before sunrise or shortly after sunset. Their apparent retrograde motion occurs during the transition between evening star into morning star, as they pass between the Earth and the Sun.
On no point does it offend the principle of mathematics. Yet it ascribes to the Earth, that hulking, lazy body, unfit for motion, a motion as quick as that of the aethereal torches, and a triple motion at that. [6] (The "triple motion" refers to its daily rotation, yearly revolution, and axial precession.)
The first motion is a uniform revolution, with a period of one year, from west to east along a circular orbit whose centre is offset from the Sun by 1/25 of the orbit's radius. The second motion is the daily rotation about an axis which passes through the Earth's centre and is inclined at an angle of about 23 1 ⁄ 2 ° to the perpendicular to ...
Galileo's tidal theory entailed the actual, physical movement of the Earth; that is, if true, it would have provided the kind of proof that Foucault's pendulum apparently provided two centuries later. Without reference to Galileo's tidal theory, there would be no difference between the Copernican and Tychonic systems.