Gravity of Earth or (). Gravitational acceleration contributes to the total gravity acceleration, but other factors, such as the rotation of Earth, also contribute, and, therefore, affect the weight of the object. Gravity does not normally include the gravitational pull of the Moon and Sun, which are accounted for in terms of tidal effects. It is a vector (physics) quantity, whose direction coincides with a plumb bob. A non-rotating perfect sphere of uniform mass density, or whose density varies solely with distance from the centre (spherical symmetry), would produce a gravitational field of uniform magnitude at all points on its surface. The Earth
Chinese sun and moon mirrors "fangzhu" mirrors "jiàn" 見 "seeing" the sun and moon. The Way of Heaven is called the Round; the Way of Earth is called the Square. The square governs the obscure; the circular governs the bright. The bright emits "qi", and for this reason fire is the external brilliance of the sun. The obscure sucks in "qi", and for this reason water is the internal luminosity of the moon. Emitted "qi" endows; retained "qi" transforms. Thus yang endows and yin transforms. The unbalanced "qi" of Heaven and Earth, becoming perturbed, causes wind; the harmonious "qi" of Heaven and Earth, becoming calm,