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Earth's rotation. Earth's rotation or Earth's spin is the rotation of planet Earth around its own axis, as well as changes in the orientation of the rotation axis in space. Earth rotates eastward, in prograde motion. As viewed from the northern polar star Polaris, Earth turns counterclockwise . The North Pole, also known as the Geographic North ...
Animation showing the difference between a sidereal day and a solar day. Sidereal time ("sidereal" pronounced / saɪˈdɪəriəl, sə -/ sy-DEER-ee-əl, sə-) is a system of timekeeping used especially by astronomers. Using sidereal time and the celestial coordinate system, it is easy to locate the positions of celestial objects in the night sky.
The prime meridian is the centre of the near side of the Moon. A planetary coordinate system (also referred to as planetographic, planetodetic, or planetocentric) [ 1][ 2] is a generalization of the geographic, geodetic, and the geocentric coordinate systems for planets other than Earth. Similar coordinate systems are defined for other solid ...
Antikythera mechanism. The Antikythera mechanism (fragment A – front and rear); visible is the largest gear in the mechanism, about 13 cm (5 in) in diameter. The Antikythera mechanism ( / ˌæntɪkɪˈθɪərə / AN-tik-ih-THEER-ə, US also / ˌæntaɪkɪˈ -/ AN-ty-kih-) [1] [2] is an Ancient Greek hand-powered orrery (model of the Solar ...
Foucault's pendulum in the Panthéon, Paris. The Foucault pendulum or Foucault's pendulum is a simple device named after French physicist Léon Foucault, conceived as an experiment to demonstrate the Earth's rotation. A long and heavy pendulum suspended from the high roof above a circular area was monitored over an extended time period, showing ...
Earth orbits the Sun at an average distance of 149.60 million km (92.96 million mi), or 8.317 light-minutes, [ 1] in a counterclockwise direction as viewed from above the Northern Hemisphere. One complete orbit takes 365.256 days (1 sidereal year ), during which time Earth has traveled 940 million km (584 million mi). [ 2] Ignoring the ...
Right ascension (abbreviated RA; symbol α) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the ( hour circle of the) point in question above the Earth. [1] When paired with declination, these astronomical coordinates specify the location of a point on the ...
Clockwise. Two-dimensional rotation can occur in two possible directions or senses of rotation. Clockwise motion (abbreviated CW) proceeds in the same direction as a clock 's hands relative to the observer: from the top to the right, then down and then to the left, and back up to the top. The opposite sense of rotation or revolution is (in ...