The celestial horizon, also called the rational horizon, is a great circle parallel to the horizon, the center of which is the center of the Earth. For the Brisbane bus routes known collectively as the Great Circle Line (598 & 599), see the following list of Brisbane Transport routes A great circle on a sphere A great circle is a circle on the surface of a sphere that has the same diameter as the sphere, dividing the... Parallel is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. ... Horizon The horizon is the line that separates earth from sky. ... Earth is the current Good Article Collaboration of the week! Please help to improve this article to the highest of standards. ...

See also

• Celestial sphere