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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 722
Riemann problem
  پراسه‌ی ِ ریمان   
parâse-ye Riemann

Fr.: problème de Riemann   

The combination of a → partial differential equation and a → piecewise constant → initial condition. The Riemann problem is a basic tool in a number of numerical methods for wave propagation problems. The canonical form of the Riemann problem is: ∂u/∂t + ∂f(u)/∂x = 0, x ∈ R, t > 0, u(x,0) = ul if x < 0, and u(x,0) = ur if x > 0 .

Riemann's geometry; → problem.

Riemann's geometry
  هندسه‌ی ِ ریمان   
hendese-ye Riemann

Fr.: géométrie de Riemann   

Same as → Riemannian geometry.

Riemannian; → geometry.

Riemannian
  ریمانی   
Riemanni (#)

Fr.: riemannien   

Of or pertaining to Georg Friedrich Bernhard Riemann (1826-1866) or his mathematics findings. → Riemannian geometry, → Riemannian manifold, → Riemannian metric, → Riemann problem, → Riemann curvature tensor.

After the German mathematician Georg Friedrich Bernhard Riemann (1826-1866), the inventor of the elliptic form of → non-Euclidean geometry, who made important contributions to analysis and differential geometry, some of them paving the way for the later development of → general relativity.

Riemannian geometry
  هندسه‌ی ِ ریمانی   
hendese-ye Riemanni

Fr.: géométrie riemannienne   

A → non-Euclidean geometry in which there are no → parallel lines, and the sum of the → angles of a → triangle is always greater than 180°. Riemannian figures can be thought of as figures constructed on a curved surface. The geometry is called elliptic because the section formed by a plane that cuts the curved surface is an ellipse.

Riemannian; → geometry.

Riemannian manifold
  بسلای ِ ریمانی   
baslâ-ye Riemanni

Fr.: variété riemannienne   

A → manifold on which there is a defined → Riemannian metric (Douglas N. Clark, 2000, Dictionary of Analysis, Calculus, and Differential Equations).

Riemannian; → metric.

Riemannian metric
  متریک ِ ریمانی   
metrik-e Riemanni

Fr.: métrique riemannienne   

A positive-definite inner product, (.,.)x, on Tx(M), the tangent space to a manifold M at x, for each x  ∈ M, which varies continually with x (Douglas N. Clark, Dictionary of Analysis, Calculus, and Differential Equations).

Riemannian; → metric.

rift
  چاک، گسل‌دره   
câk, gosal-darré

Fr.: rift; fissure, crevasse   

1) General: a gap or break made by splitting, cleaving, etc.; fissure; cleft.
2) Geology: A narrow cleft, fissure, or other opening in rock, made by cracking or splitting.
3) Geology: An elongated trough in the Earth's crust bounded by → faults.

M.E., from a Scandinavian source; cf. Dan., Norw. rift "a cleft."

1) Câk "fissure, rupture, cleft, crack," related to caqidan "to drive a nail, strike together, fix a spike;" caxidan "to quarrel, strive;" diatectal Shughni cuγ, Roshani coγ "breaking, tearing, ripping up;" Malâyeri ceqidan "cracking of a cold porcelain bowl when receiving hot water;" Yazghulami cok-, coxt "to pound, to stamp;" Wakhi cuk-, cukt "to strike;" Ossetic cædyn "to shake, strike iron;" Lori cok "a mark fixed to separate two grounds;" Sogd. cax "to battel, fight;" Mid.Pers. (prefixed) pacên "copy" (see also Cheung 2007). Gosal-darré, from gosal, → fault, + darré, → valley.

rift valley
  گسل‌دره   
gosal-darré

Fr.: fossé d'effondrement, ~ tectonique   

A long, narrow valley formed by the lowering of land between two → faults. Also called → graben.

rift; → valley.

Rigel (β Ori)
  رجل   
Rejl (#)

Fr.: Rigel   

The brightest star in the constellation → Orion (visual magnitude 0.18). A → blue supergiant of type B8 Iab with an initial mass of 17 solar masses, Rigel is 773 light-years away, and actually shines with the light of 40,000 Suns. It is accompanied by a fairly bright, seventh magnitude companion nine seconds of arc apart. The companion is itself double, the components much fainter and much less massive → main sequence stars of type B.

Rigel "foot," short for Ar. rijl al-jauza' (رجل‌الجوزاء) "the foot of jauza'." The latter word means "the manifest one," initially "black sheep with white middle." The Gk. figure was translated as such because of its conspicuousness among other constellations.

Rejl, from Ar., as above.

Rigel Kentaurus
  پای ِ کنتاؤروس   
Pâ-ye Kentawros

Fr.: Rigil Kentaurus   

Same as the star → Alpha Centauri.

From Ar. Rijl al-Qanturis "foot of Centaurus," from rijl "foot," + Qanturis Arabicized → Centaurus.

Pâ-ye Kantawros, "foot of Centaurus," from , → foot, + Kentawros, → Centaurus.

right
  ۱) راست؛ ۲) درست؛ ۳) راشن   
1) râst (#); 2) dorost; 3) râšan

Fr.: droit   

1a) Straight, free from curves, angles, or irregularities. → right ascension.
1b) Opposite of → left. → right-hand rule, → right-hand screw rule.
2) In accordance with fact, reason, or truth; correct or true.
3) Something that a person is or should be morally or legally allowed to have, get, or do (Merriam-Webster).

M.E.; O.E. reht, riht; cf. O.H.G. reht, Ger. recht, O.N. rettr, Goth. raihts; P.Gmc. *rekhtaz, cognate with Pers. râst, as below.

1) Râst "right, true; just, upright, straight;" Mid.Pers. râst "true, straight, direct;" Soghdian rəšt "right;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Av. rāz- "to direct, put in line, set," razan- "order;" related to Mid.Pers. rây-, râyênitan "to arrange;" Mod.Pers. raj "line, row," variants raž, rak, râk, rezg (Lori), radé, râdé "line, rule, row," rasté, râsté "row, a market with regular ranges of shops;" ris, risé "straight;" 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;" PIE base *reg- "move in a straight line," hence, "to direct, rule;"
2) Dorost "correct, whole, complete, healthy," → integral.
3) Râšan, related to râst, as above; cf. Mid.Pers. Rašn "Justice deity; calendar 18th day;" Av. rašnu- "the Zoroastrian Justice deity, orientation."

right angle
  زاویه‌ی ِ راست   
zâviye-ye râst

Fr.: angle droit   

An angle of 90°.

right; → angle.

right ascension
  راست‌افراز   
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.

right; ascension, M.E. ascencioun, from O.Fr., from L. ascendere "to climb up," from → ad- "to" + scandere "to climb."

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."

right triangle
  سه‌بر ِ راست   
sebar-e râst (#)

Fr.: triangle droit   

A triangle one of whose angles is a → right angle.

right; → triangle.

right-hand rule
  رزن ِ دست ِ راست   
razan-e dast-e râst

Fr.: règle de la main droite   

See → Fleming's rules.

right; → hand; → rule.

right-hand screw rule
  رزن ِ پیچ ِ راست‌گرد   
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.

right; → hand; → screw; → rule.

right-handed
  راستال، راستدست   
râstâl, râstdast (#)

Fr.: droitier   

Using the right hand with greater skill or ease than the left.

right; → hand + -ed.

Râstâl, from râst, → right, + -al-al. Râstdast, with dast, → hand.

rigid
  سخت‌پای   
saxtpây (#)

Fr.: rigide   

1) General: Stiff or unyielding; inflexible, strict, severe.
2) Physics: → rigid body; → rigidity.

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."

rigid body
  جسم ِ سخت‌پای   
jesm-e saxtpây

Fr.: corps rigide   

Mechanics: A system of many particles whose positions relative to one another remain fixed.

rigid; → body.

rigidity
  سخت‌پایی   
saxtpâyi

Fr.: rigidité   

1) The quality or state of being → rigid. See also → modulus of rigidity.
2) → magnetic rigidity.

rigid + → -ity.

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