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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.
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the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center.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.
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 ...
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 Sun-centered positions displayed a cyclical motion with respect to time but without retrograde loops in the case of the outer planets. [dubious – discuss] In principle, the heliocentric motion was simpler but with new subtleties due to the yet-to-be-discovered elliptical shape of the orbits. Another complication was caused by a problem ...
The technique of drawing apparent polar wander was first developed by Creer et al. (1954), and was a major step taken towards the acceptance of the plate tectonics theory. Since then many discoveries have been made in that field, and apparent polar wander has become better understood with the evolution of the theory and of the geocentric axial ...
It is the most accurate technique currently available to determine the geocentric position of an Earth satellite, allowing for the precise calibration of radar altimeters and separation of long-term instrumentation drift from secular changes in ocean surface topography. Satellite laser ranging contributes to the definition of the international ...
However, despite the work's geocentric approach, the Aryabhatiya presents many ideas that are foundational to modern astronomy and mathematics. Aryabhata asserted that the Moon, planets, and asterisms shine by reflected sunlight, [ 10 ] [ 11 ] correctly explained the causes of eclipses of the Sun and the Moon, and calculated values for π and ...