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Earth's rotation axis moves with respect to the fixed stars (inertial space); the components of this motion are precession and nutation. It also moves with respect to Earth's crust; this is called polar motion. Precession is a rotation of Earth's rotation axis, caused primarily by external torques from the gravity of the Sun, Moon and other bodies.
Universal time tracks the Earth's rotation in time, which performs one revolution in about 24 hours. The Earth's rotation is uneven, so UT is not linear with respect to atomic time. It is practically proportional to the sidereal time, which is also a direct measure of Earth rotation. The excess revolution time is called length of day (LOD).
A medieval depiction of the Ecumene (1482, Johannes Schnitzer, engraver), constructed after the coordinates in Ptolemy's Geography and using his second map projection. In cartography, a map projection is any of a broad set of transformations employed to represent the curved two-dimensional surface of a globe on a plane.
Models representing the ever-changing orientation of the Earth in space are available from the International Earth Rotation and Reference Systems Service. Examples include: J2000: One commonly used ECI frame is defined with the Earth's Mean Equator and Mean Equinox (MEME) at 12:00 Terrestrial Time on 1 January 2000.
Sidereal time is a "time scale that is based on Earth's rate of rotation measured relative to the fixed stars". [ 1 ] Viewed from the same location , a star seen at one position in the sky will be seen at the same position on another night at the same time of day (or night), if the day is defined as a sidereal day (also known as the sidereal ...
The transcontinental country, which spans Asia and Europe, has a total surface area of 17.1 million square kilometers – Russia consists of land area for the most part, only about 4% of total ...
Political map of Europe, showing south at the top. Research suggests that north-south positions on maps have psychological consequences. In general, north is associated with richer people, more expensive real estate, and higher altitude, while south is associated with poorer people, cheaper prices, and lower altitude (the "north-south bias").
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