Geocentric Coordinate Time (TCG)
zamân-e hamârâ-ye zamin-markazi
Fr.: Temps coordonné géocentrique
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).
keyhân-šenâsi-ye zamin-markazi (#)
Fr.: cosmologie géocentrique
A model of the Universe in which the Earth is centrally located and the Sun, planets, and stars revolve around the Earth.
Fr.: latitude géocentrique
The angle between the geocentric location vector and the → geodetic equator.
Fr.: longitude géocentrique
The same as → geodetic longitude.
Fr.: parallaxe géocentrique
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.
Fr.: système géocentrique
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.
The outermost part of Earth's atmosphere, a tenuous halo of hydrogen and some helium extending out to perhaps 15 Earth radii, which emits Lyman-alpha radiation when it is bombarded by sunlight.
1) The shortest distance between two points in space (or
→ space-time). A
geodesic on a sphere is an → arc of a
→ great circle. In the theory of
→ general relativity,
freely falling bodies follow geodesic paths in space-time.
Kehinrah "shortest path," from kehin, superlative of keh "small, little, slender" (related to kâstan, kâhidan "to decrease, lessen, diminish," from Mid.Pers. kâhitan, kâstan, kâhênitan "to decrease, diminish, lessen;" Av. kasu- "small, little;" Proto-Iranian *kas- "to be small, diminish, lessen") + râh "path, way, road" (from Mid.Pers. râh, râs "way, street," also rah, ras "chariot;" from Proto-Iranian *rāθa-; cf. Av. raθa- "chariot;" Skt. rátha- "car, chariot," rathyā- "road;" L. rota "wheel," rotare "to revolve, roll;" Lith. ratas "wheel;" O.H.G. rad; Ger. Rad; Du. rad; O.Ir. roth; PIE base *roto- "to run, to turn, to roll").
Fr.: ligne géodésique
The shortest line between two points on a surface. Also called → geodesic.
Fr.: précession géodésique
The study and measurement of the shape, size, and curvature of the Earth.
From Fr. géodésie, from Gk. geodaisia, from → geo- + dai(ein) "to divide" + -sia, variant of -ia a noun suffix.
Zamin-sanji, from zamin, → geo-, + sanji, from sanjidan "to measure; to compare," from Mid.Pers. sanjidan "to weigh," from present tense stem sanj-, Av. θanj- "to draw, pull;" Proto-Iranian *θanj-. Other terms from this base in Pers.: lanjidan "to pull up," hanjidan, âhanjidan "to draw out," farhang "education, culture."
mâhvâre-ye zamin-sanji, ~ zamin-sanjik
Fr.: satellite géodésique
A type of Earth observing satellite used to measure the location of points on Earth's surface with great accuracy. Their observations help determine the exact size and shape of Earth, act as references for mapping, and track movements of Earth's crust.
Of, relating to, or determined by → geodesy.
Fr.: coordonnées géodésiques
Fr.: donnée géodésique
Fr.: équateur géodésique
The plane swept out as the generating ellipse of the → reference ellipsoid rotates about its minor axis.
Fr.: latitude géodésique
Fr.: longitude géodésique
Fr.: méridien géodésique
Fr.: parallèle géodésique