From L. rigidus "hard, stiff, rough," from rigere "to be stiff;" related to L. frigus "cold," Gk. rhigos "frost, cold."
Saxtpây, from saxt, → hard, + pây present stem of pâyidan "to stand firm, to be constant, steady, fixed;" Mid.Pers. pâyitan, pâtan, pây- "to protect; wait, stand," Sogdian p'y "to protect, watch over;" O.Pers./Av. pâ(y)- "to protect, keep" pâtar- "protector, watcher," cf. Skt. pâ- "to protect, keep," pâti "protects;" Gk. poimen "shepherd," poma "lid, cover;" L. pastor "shepherd," panis "bread;" PIE base *pa- "to protect, guard, pasture, feed."
Fr.: corps rigide
Mechanics: A system of many particles whose positions relative to one another remain fixed.
Rigil Kentaurus (α Centauri)
Fr.: Alpha du Centaure
Another name of → Alpha Centauri.
Rigel, from Ar. rijl (
Pâ "foot, step" (from Mid.Pers. pâd, pây; Av. pad- "foot;" cf. Skt. pat; Gk. pos, genitive podos; L. pes, genitive pedis; P.Gmc. *fot; E. foot; Ger. Fuss; Fr. pied; PIE *pod-/*ped-); Kentâwros→ Centaurus.
M.E., from M.L. rigorosus, from rigor "stiffness, rigor," from rigere "to be stiff."
Farsaxt, from far- intensive prefix "much, abundant; elegantly" (Mid.Pers. fra- "forward, before; much; around;" O.Pers. fra- "forward, forth;" Av. frā, fərā-, fra- "forward, forth; excessive;" cf. Skt. prá- "before; forward, in fron;" Gk. pro "before, in front of;" L. pro "on behalf of, in place of, before, for;" PIE *pro-) + saxt "hard, strong, firm, secure, solid, vehement, intense" (Mid.Pers. saxt "hard, strong, severe;" Av. sak- "to understand or know a thing, to mark;" cf. Skt. śakta- "able, strong," śaknoti "he is strong," śiksati "he learns").
rigorous selection rule
razan-e gozineš-e farsaxt
Fr.: règle de sélection rigoureuse
A → selection rule obeyed by → discrete transitions. Among them are: rigorous selection rules for → electric dipole transitions (→ permitted) requiring: 1) ΔJ must be 0 or ± 1 with J = 0 ↔ 0 forbidden. 2) ΔMJ = 0, ± 1. 3) → Parity change, i.e. even ↔ odd.
A long, narrow, straight or sinuous trench or valley with steep walls and roughly parallel sides on the surface of the Moon.
From Ger. Rille "a small rivulet or brook."
Borrowed from E., as above.
The outer edge, border, margin, or brink of something, especially of a circular object.
M.E., from O.E. -rima (in compounds, as in særima "seashore"); cognate with O.Norse rimi "raised strip of land, ridge"
Labé "limb, edge," from lab "lip;" Mid.Pers. lap; cognate with L. labium, E. lip; Ger. Lefze.
A long fissure on the surface of a planet or Moon; plural form rimae.
From L. rima "fissure, slit."
Loan from E., as above.
Fr.: coordonnées de Rindler
The coordinates that describe the → Minkowski space-time in a → hyperbolic version of → polar coordinates. If the coordinates in an → inertial frame is denoted by (t,x), the Rindler coordinates (η,ξ) are defined by: t = (1/α) eαξ sinh (αη) and x = (1/α) eαξ cosh (αη), where α is some positive constant.
Named after Wolfgang Rindler (1924-), Austrian physicist; → coordinates.
Fr.: coin de Rindler
1) halqé (#); 2) zang (#)
Fr.: 1) anneau; 2) sonnerie
1) A circular band of something. → gossamer ring.
O.E. hring "circular band" (cf. O.N. hringr, Ger. Ring), literally "something curved," from PIE base *(s)ker- "to turn, bend."
1) Halqé, loan from Ar. Halqat "ring, hoop, circle."
Fr.: galaxie en anneau
A galaxy with a ring-like appearance around the central luminous center. The ring consists of massive, relatively young bright stars. It is believed that ring galaxies result from the head-on collision of two different galaxies.
Fr.: longitude de l'anneau
Of → Saturn, the angle measured with respect to the sub-observer point (a line connecting the observer to Saturn) in the direction of the orbital motion.
Fr.: Nébuleuse de l'Anneau
A bright → planetary nebula in the constellation → Lyra, also called M57 or NGC 6720. In small telescopes it has the appearance of a slightly elliptical luminous ring around a central hot star (15th magnitude). The radius is one-third of a → light-year, and the nebula is about 2,000 light-years away.
ring opening angle
zâviye-ye gošâyeš-e halqé
Fr.: angle d'ouverture des anneaux
Of → Saturn, the angle between the line of sight and the ring plane. Also known as elevation angle, tilt angle.
Zâviyé, → angle; gošâyeš "opening," verbal noun from gošudan, gošâdan "to open up, loose, let free;" gošâd "opened; ample, broad;" Mid.Pers. wišâdan "to let free;" Khotanese hīyā "bound;" O.Pers. višta "untied, loosened," vištāspa- "with loosened horses" (personal name); Av. višta "untied," ā-hišāiiā "holds fettered," hita- "fastened, tied on, put to;" cf. Skt. sā- "to bind, fasten, fetter," sitá- "bound," ví-sita- "untied;" halqé, → ring.
Fr.: système d'anneaux
Fr.: desexcitation finale
The last stage of → merger between two → black holes undergoing → inspiral. At the end of the evolution of a → binary black hole system, the black holes get close enough to → merge together into a single, larger black hole (→ black hole merger). The resulting black hole is at first distorted and asymmetric, but in the ringdown process the black hole's vibrations decay due to → gravitational radiation leaving finally a quiescent, spinning black hole.
M.E. ring, from O.E. hringan; akin to O.Norse hringja "to ring;" → down.
1) A small ring.
Fr.: ondulation, ride
A wave on a fluid surface, of sufficiently short wavelength, in which gravity is the dominant influence.
Of unknown origin, perhaps frequentative of rip (v.) "to tear apart."
Cinâv, literally "water wrinkle," from cin "fold, plait, wrinkle" + âv, variant of âb, → water.