râst afrâz (#)
Fr.: ascension droite
A coordinate in the → equatorial system measured from the → vernal equinox eastward to the point where the object → hour circle intersects the → celestial equator. Right ascension (symbol α) is expressed in hours, minutes, and seconds. See also: → declination.
Râst, → right; afrâz present stem of afrâzidan, afrâštan "to raise, exalt, extole," from Mid.Pers. abrâstan, abrâz- "to lift, raise," from ab-, from O.Pers./Av. abiy-/aiwi- "to, upon, against;" cf. Skt. abhi-, Gk. amphi- + râst "straight, direct, true;" from O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Av. rāz- "to direct, put in line, set," razan- "order;" cf. Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" Ger. recht; E. right; PIE base *reg- "move in a straight line," hence, "to direct, rule."
sebar-e râst (#)
Fr.: triangle droit
A triangle one of whose angles is a → right angle.
razan-e dast-e râst
Fr.: règle de la main droite
See → Fleming's rules.
right-hand screw rule
razan-e pic-e rast-gard
Fr.: règle de la vis droite
A rule that gives the direction of the resultant vector in a → vector product: A x B = C. It is the direction of advance of a right-hand screw whose axis, held perpendicular to the plane of A and B, is rotated in the same sense that rotates the first-named vector (A) into the second-named vector B through the smaller angle.
râstâl, râstdast (#)
Using the right hand with greater skill or ease than the left.
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.