An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

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.
2) → geodetic.

From Fr. géodésique, → geodesy; → -ic.

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").

The shortest line between two points on a surface. Also called → geodesic.

→ geodesic; → line.

→ geodesic precession.

→ geodesic; → precession

1) The path taken by a light ray in a curved → space-time just as a → timelike geodesic describes the path of a material particle.
2) A → geodesic of length zero.

→ null; → geodesic.