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

The science of dating, of ordering time, of arranging in periods, and of determining temporal distances between past events.

Chronology, from Gk. khronos "time" + → -logy.

Gâhšenâsi, from gâh "time" + -šenâsi, → -logy. Gâhrâik, from gâh + rây, ârâ "order, arrangement" stem of ârâstan "to arrange, to set in order, adorn" (Mid.Pers. ârây-, ârâstan "to arrange, adorn," O.Pers. râs- "to be right, straight, true," râsta- "straight, true" (Mod.Pers. râst "straight, true"), râd- "to prepare," Av. râz- "to direct, put in line, set," Av. razan- "order," Gk. oregein "to stretch out," L. regere "to lead straight, guide, rule," p.p. rectus "right, straight," Skt. rji- "to make straight or right, arrange, decorate," PIE base *reg- "move in a straight line") + -ik, → -ics.

A highly precise timepiece.

Chronometer, from from Gk. khronos "time" + → -meter.

Gâhsanj, zamânsanj, from gâh or zamân "time" + -sanj→ -meter.

1) A container or machine in which cream or milk is agitated to make butter.
2) To shake or agitate with violence or continued motion (Dictionary.com).

M.E. chirne, O.E. cyrne cyr(i)n; cognate with M.L.G. kerne, O.N. kjarni, kirna, may be related to → kernel because of the "grainy" appearance of churned cream.

Gavis "churn," of unknown origin.

In → galactic dynamics models, the process of gaining or losing → angular momentum by stars mostly at the → Lindblad resonances without gaining random motion. Figuratively, transient → spiral waves in → galactic disks churn the stars and gas in a manner that largely preserves the overall angular momentum distribution and leads to little increase in random motion. Churning is the main reason for → radial migration of stars. See also → blurring (J. A. Sellwood & J. J. Binney, 2002, astro-ph/0203510 and references therein).

Verbal noun of → churn.

A group of very rare → carbonaceous chondrites which are unusual because they do not have → chondrules. They are thought to be the most primitive of all meteorites. As a result of alteration, they lack chondrules and → CAIs, but contain up to 20% water, as well as various alteration minerals. Only five CI chondrite falls are known, and of these, only four are massive enough for multiple chemical analyses. The Orgueil meteorite is the most massive of CI chondrites.

C for → carbon, I stands for Ivuna meteorite that fell in Tanzania in 1938; → chondrite.

A mineral, mercuric sulphide, HgS, which is the primary → ore for the production of → mercury. It is a → crystalline solid with a bright → red color. Cinnabar is highly toxic.

From O.Fr. cinabre, from L. cinnabaris, from Gk. kinnabari, maybe ultimately from Pers. šangarf "red lead, cinnabar," of unknown origin.

Being, having, characterized by, or occurring in approximately 24-hour periods or cycles, as of biological activity or function (Merriam-Webster.com).

From L. circa "about," → circum-, + diem, accusative singular of dies "day," → diurnal.

Any of several physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness in an organism's environment. Circadian rhythms are found in most living things, including animals, plants and many tiny microbes.

→ circadian; → rhythm.

The Compasses. A small, faint → constellation in the southern hemisphere near → Musca and → Triangulum Australe, at about 15h right ascension and 60° south declination. Abbreviation: Cir; genitive Circini.

L. circinus "pair of compasses," from circus "circle, ring," from or akin to Gk. kirkos "a circle," from PIE *kirk- from base *(s)ker- "to turn, bend" (from which derives also Pers. carx "wheel, cycle," → cycle).

Pargâr, → compasses.

A closed curve lying in a plane and so constructed that all its points are equally distant from a fixed point in the plane.

From O.Fr. cercle, from L. circulus "small ring," dim. of circus "ring," from or akin to Gk. kirkos "a circle," from PIE *kirk- from base *(s)ker- "to turn, bend," related to Pers. carx "wheel, everything revolving in an orbit, circular motion, chariot."

Parhun "circle" in Mod.Pers. classical texts, from Proto-Iranian *pari-iâhana- "girdle, belt," from pari-, variant pirâ-, → circum-, + iâhana- "to girdle," cf. Av. yâh- "to girdle." The Pers. word pirâhan "shirt" is a variant of parhun. Gk. cognate zone "girdle."
Dâyeré, from Ar.

A small circle on the celestial sphere parallel to the horizon. The locus of all points of a given altitude. Also called → almucantar, → altitude circle, → parallel of altitude.

→ circle; → altitude.

1) A circle of the celestial sphere, parallel to the ecliptic.
2) A circle on the terrestrial surface parallel to the equator, along which longitude is measured.

→ circle; → latitude.

1) A great circle of the celestial sphere, from the pole to the ecliptic at right angles to the plane of the ecliptic.
2) A great circle on the terrestrial surface that meets the North and South poles and connects all places of the same longitude.

→ circle; → longitude.

1) General: A closed, usually circular line that goes around an object or area.
2) Physics: → electric circuit.

From O.Fr. circuit, from L. circuitus "a going around," from stem of circuire, circumire "go around," from circum "around," → circum- + -ire "to go" (cf. Gk. ienai "to go," Skt. eti "goes," O.Pers. aitiy "goes," Av. aeiti "goes," Mod.Pers. âyad "comes," PIE *ei- "to go, to walk."

Gardrâh, from gard "turning round, revolving," from gardidan "to turn, to change" (Mid.Pers. vartitan, Av. varət- "to turn, revolve," Skt. vartati, L. vertere, O.H.G. werden "to become;" PIE *werto, *wer-) + râh "way, path," from Mid.Pers. râh, râs "way, street" (Mid.Pers. 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 *roto- "to run, to turn, to roll").
Barqrâh, from barq, → electricity, + râh, as above.

1) Having the form of a circle.
2) Moving in or forming a circle or a circuit.

M.E. circuler, O.Fr. circuler, from L. circularis, from circulus, → circle, + -aris "-ar," variant of → -al, joined to words in which an l precedes the suffix (circular; lunar; singular).

Dâyere-yi, parhuni, from dâyeré or parhun→ circle + -i adj. suffix.

A → magnetic field whose lines of force (→ line of force) run around the perimeter of the magnet.

→ circular; → magnetic; → field.

Motion in which an object moves in a circle at a constant speed. The velocity, however, changes not because the magnitude of the velocity changes, but because its direction changes. The changing velocity creates an acceleration, called → centripetal acceleration. This acceleration results from the → centripetal force.

→ circular; → motion.

The path of a object in → circular motion.

→ circular; → orbit.

The → polarization of an → electromagnetic radiation in which the electric field vector describes a circle about the direction of propagation at any point in the path of the radiation. Circular polarization is a combination of two perpendicular → linearly polarized waves that are 90 degrees out of phase with each other. Circular polarization may be referred to as "right-hand" or "left-hand," depending on the rotation direction as viewed by the observer.

→ circular; → polarization.

Circular band-pass interference filter whose thickness and central wavelength vary along the perimeter. They are used in low-resolution spectrophotometers mainly in the infra-red.

→ circular; → variable; → filter.