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  2. Equator - Wikipedia

    en.wikipedia.org/wiki/Equator

    The equator is the only line of latitude which is also a great circle—meaning, one whose plane passes through the center of the globe. The plane of Earth's equator, when projected outwards to the celestial sphere, defines the celestial equator.

  3. Circle of latitude - Wikipedia

    en.wikipedia.org/wiki/Circle_of_latitude

    The equator is the circle that is equidistant from the North Pole and South Pole. It divides the Earth into the Northern Hemisphere and the Southern Hemisphere. Of the parallels or circles of latitude, it is the longest, and the only 'great circle' (a circle on the surface of the Earth, centered on Earth's center). All the other parallels are ...

  4. Latitude - Wikipedia

    en.wikipedia.org/wiki/Latitude

    This is the definition assumed when the word latitude is used without qualification. The definition must be accompanied with a specification of the ellipsoid. Geocentric latitude (also known as spherical latitude, after the 3D polar angle): the angle between the radius (from centre to the point on the surface) and the equatorial plane. (Figure ...

  5. Equatorial coordinate system - Wikipedia

    en.wikipedia.org/wiki/Equatorial_coordinate_system

    The right ascension symbol α, (lower case "alpha", abbreviated RA) measures the angular distance of an object eastward along the celestial equator from the March equinox to the hour circle passing through the object. The March equinox point is one of the two points where the ecliptic intersects the celestial equator.

  6. Longitude - Wikipedia

    en.wikipedia.org/wiki/Longitude

    A geographical mile is defined to be the length of one minute of arc along the equator (one equatorial minute of longitude) therefore a degree of longitude along the equator is exactly 60 geographical miles or 111.3 kilometers, as there are 60 minutes in a degree. The length of 1 minute of longitude along the equator is 1 geographical mile or 1 ...

  7. Great circle - Wikipedia

    en.wikipedia.org/wiki/Great_circle

    The equator of the idealized earth is a great circle and any meridian and its opposite meridian form a great circle. Another great circle is the one that divides the land and water hemispheres. A great circle divides the earth into two hemispheres and if a great circle passes through a point it must pass through its antipodal point.

  8. Geographical zone - Wikipedia

    en.wikipedia.org/wiki/Geographical_zone

    Like Parmeneides, thinking that the area near the equator was too hot for habitation, Aristotle dubbed the region around the equator (from 23.5° N to 23.5° S) the "Torrid Zone." Both philosophers reasoned the region from the Arctic Circle to the pole to be permanently frozen. This region thought uninhabitable, was called the "Frigid Zone."

  9. Tropic of Cancer - Wikipedia

    en.wikipedia.org/wiki/Tropic_of_Cancer

    The circle's position was at exactly 23° 27′N in 1917 and will be at 23° 26'N in 2045. [3] The distance between the Antarctic Circle and the Tropic of Cancer is essentially constant as they move in tandem. This is based on an assumption of a constant equator, but the precise location of the equator is not truly fixed.