An Etymological Dictionary of Astronomy and Astrophysics
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1) Relating to, measured from, or with respect to the center of the Earth.
2) Having the earth as a center. → geocentric coordinate system, → Geocentric Coordinate Time, → geocentric cosmology, → geocentric parallax, → geocentric system.

→ geo- + → center + -ic an adjective-forming suffix.

A coordinate system which has as its origin the center of the Earth.

→ geocentric; → coordinate; → system.

The proper time experienced by a clock at rest in a coordinate frame co-moving with the center of the Earth, i.e. a clock that performs exactly the same movements as the Earth but is outside the Earth's gravity well. TCG was defined in 1991 by the International Astronomical Union as one of the replacements for Barycentric Dynamical Time (TDB).

→ geocentric; → coordinate; → time.

A model of the Universe in which the Earth is centrally located and the Sun, planets, and stars revolve around the Earth.

→ geocentric; → cosmology.

The angle between the geocentric location vector and the → geodetic equator.

→ geocentric; → latitude.

The same as → geodetic longitude.

→ geocentric; → longitude.

The difference between the direction of an object as seen from a point on the surface of the Earth and the direction in which it would be seen from the Earth's center. Also known as → diurnal parallax.

→ geocentric; → parallax.

An ancient model of the Universe whereby all the celestial bodies travel around the Earth in circular orbits. Eudoxus of Cnidus (c. 390- c. 337 BC), one of Plato's pupils, maintained that all objects in the sky are attached to moving crystalline spheres, with the Earth at the centre. This model is often named → Ptolemaic system after its most famous supporter, the Greco-Roman astronomer Ptolemy.

→ geocentric; → system.