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The above equation describes the Earth's gravitational potential, not the geoid itself, at location ,,, the co-ordinate being the geocentric radius, i.e., distance from the Earth's centre. The geoid is a particular equipotential surface, [27] and is somewhat involved to compute. The gradient of this potential also provides a model of the ...
A view of the Earth's geoid, as provided by EGM96. The Earth Gravitational Models (EGM) are a series of geopotential models of the Earth published by the National Geospatial-Intelligence Agency (NGA). They are used as the geoid reference in the World Geodetic System.
Consequently, he introduced a new system, the Tychonic system, in which the Earth was still at the center of the universe, and around it revolved the Sun, but all the other planets revolved around the Sun in a set of epicycles. His model considered both the benefits of the Copernican model and the lack of evidence for the Earth's motion. [33]
Shift of the world's economic center of gravity since 1980 and projected until 2050 [7] Various definitions of geographical centres exists. The definitions used by the references in this article refer to calculations within the 2 dimensions of a surface, mainly as the surface of Earth is the domain of human cultural existence.
In such a system, the Sun, Moon, and stars circle a central Earth, while the five planets orbit the Sun. [16] The essential difference between the heavens (including the planets) and the Earth remained: Motion stayed in the aethereal heavens; immobility stayed with the heavy sluggish Earth. It was a system that Tycho said violated neither the ...
If Earth's shape were perfectly known together with the exact mass density ρ = ρ(x, y, z), it could be integrated numerically (when combined with a reciprocal distance kernel) to find an accurate model for Earth's gravitational field. However, the situation is in fact the opposite: by observing the orbits of spacecraft and the Moon, Earth's ...
Aristotle proposed a geocentric model of the universe in De Caelo. The Earth is the center of motion of the universe, with circular motion being perfect because Earth was at the center of it. There can be only one center of the universe, and as a result there are no other inhabited worlds within it besides Earth. As such the Earth is unique and ...
The simplest model for the shape of the entire Earth is a sphere. The Earth's radius is the distance from Earth's center to its surface, about 6,371 km (3,959 mi). While "radius" normally is a characteristic of perfect spheres, the Earth deviates from spherical by only a third of a percent, sufficiently close to treat it as a sphere in many ...