An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 13116 Search : far
rivalry
  هماوردی   
hamâvardi (#)

Fr.: rivalité   

1) The action, position, or relation of a rival or rivals; competition.
2) An instance of this (Dictionary.com).

Noun from → rival.

river
  رود   
rud (#)

Fr.: rivière   

A large natural stream of water flowing in a definite course.

M.E., from O.Fr. rivere, riviere, from V.L. *riparia "riverbank, seashore, river," noun use of feminine of L. riparius "of a riverbank."

Rud, from Mid.Pers. rôd "river," O.Pers. rautah- "river;" cf. Skt. srotas- "river," sru- "to flow;" Pali sota- "stream, flood;" Gk. rhoos "a stream, a flowing," from rhein "to flow;" O.E. stream; Ger. Strom; PIE base *sreu- "to flow."

roAp star
  ستاره‌ی Apی ِ تند نونده   
setâre-ye Ap-ye tond navandé

Fr.: étoile Ap à oscillation rapide   

Same as → rapidly oscillating Ap star

rapidly oscillating Ap star

Robertson-Walker metric
  متریک ِ روبرتسون-واکر   
metrik-e Robertson-Walker (#)

Fr.: métrique de Robertson-Walker   

The mathematical description of the interval (→ space-time separation) between → events ("points" in space-time) in a → homogeneous and → isotropic → Universe. It results from an exact solution of → Einstein's field equations of → general relativity. Under the assumptions, the Robertson-Walker interval is expressed by:
ds2 = c2dt2 - R2(t) [dr2/(1 - kr2) + r22 + r2sin2θ dθ2)].
Same as Friedmann-Lemaître-Robertson-Walker metric. Compare → Minkowski metric.

Named after Howard Percy Robertson (1903-1961), American mathematician and physicist, and Arthur Geoffrey Walker (1909-2001), British mathematician and physicist, for their contributions to physics and physical cosmology; → metric.

robot
  روبوت   
robot (#)

Fr.: robot   

A machine that does mechanical, routine tasks on command.

From Czech, coined by Karel Čapek in the play R.U.R. (1920), from the base robot-, as in robota "compulsory labor," robotník "peasant owing such labor," from robotiti "to work, drudge."

Robot, loan from E., as above.

robust
  تناور   
tanâvar (#)

Fr.: robuste   

The quality of a model when it is insensitive to small discrepancies in assumptions.

From L. robustus "strong and hardy," literally "as strong as oak," from robur, robus "hard timber, strength," also "a special kind of oak," named for its reddish heartwood, from L. ruber, → red.

Tanâvar "robust, stout, corpulent," from tan "corpus, body," → if and only if + âvar contraction of âvarandé agent noun of âvardan "to bring; to cause, produce," → collect.

Roche limit
  حد ِ رُش   
hadd-e Roche

Fr.: rayon de Roche   

The smallest distance at which a → satellite under the influence of its own → gravitation and that of a central mass about which it is describing a → Keplerian orbit can be in equilibrium. This does not, however, apply to a body held together by the stronger forces between atoms and molecules. At a lesser distance the → tidal forces of the → primary body would break up the → secondary body. The Roche limit is given by the formula d = 1.26 RMMm)1/3, where RM is the radius of the → primary body, ρM is the → density of the primary, and ρm is the density of the secondary body. This formula can also be expressed as: d = 1.26 Rm (MM/Mm)1/3, where Rm is the radius of the secondary. As an example, for the Earth-Moon system, where RM = 6,378 km, ρM = 5.5 g cm-3, and ρm = 2.5 g cm-3 is 1.68 Earth radii.

Named after Edouard Albert Roche (1820-1883), the French astronomer who first calculated this theoretical limit in 1848; → limit.

Roche lobe
  لپ ِ رُش   
lap-e Roche

Fr.: lobe de Roche   

The region around a star in a → binary system within which orbiting material is gravitationally bound to that star. The point at which the Roche lobes of the two stars touch is called the → inner Lagrangian point. → equipotential surface.

Roche limit; → lobe.

Roche lobe overflow (RLOF)
  سرریز ِ لپ ِ رُش   
sarriz-e lap-e Roche

Fr.: débordement du lobe de Roche   

A process in a → binary system when a star fills its → Roche lobe, often by becoming a → giant or → supergiant during the later stages of → stellar evolution. When the star expands, any material that passes beyond the Roche lobe will flow onto the binary → companion, often by way of an → accretion disk. This occurs through the → inner Lagrangian point where the gravity of the two stars cancels. The RLOF is responsible for a number of phenomena including → cataclysmic variables, → Type Ia supernovae, and many → X-ray binary systems.

Roche lobe; → overflow.

rock
  برد، سنگ   
bard (#), sang (#)

Fr.: roche   

1) A large mass of → stone forming a hill, cliff, promontory, or the like.
2) Geology: Mineral matter of variable composition, consolidated or unconsolidated, assembled in masses or considerable quantities in nature, as by the action of heat or water (Dictionary.com).

M.E. rokk(e), from O.Fr. ro(c)que, roche (cf. Sp., Provençal roca, It. rocca, M.L. rocca, V.L. *rocca, of uncertain origin.

Bard (Dehxodâ) "rock, stone," used in a large part of Western Iran, specifically in Lori and Kurd., related to Kurd. pal "rock, stone;" cf. Gk. poros "rock." Sang, → stone.

rock crystal
  بلور ِ سنگی، برد-بلور   
bolur-e sangi, bard-bolur

Fr.: cristal de roche   

Pure natural crystalline form of → silica, SiO2, which is transparent and colorless.

rock; → crystal.

rocket
  روکت   
roket

Fr.: fusée   

A projectile driven by reaction propulsion that carries its own propellants. → missile = mušak (موشک).

From It. rocchetto "a rocket," literally "a bobbin," diminutive of rocca "a distaff," with reference to its shape.

rocket astronomy
  اخترشناسی با روکت   
axtaršenâsi bâ roket

Fr.: astronomie par fusée   

The study of celestial bodies in the wavelengths that are almost completely absorbed by the atmosphere, by using a rocket to carry instruments above 250 km to measure the searched for phenomena.

rocket; → astronomy.

rocketry
  روکت‌شناسی، روکت‌گری   
roket šenâsi, roketgari

Fr.: fuséologie   

The science of rocket design, development, and flight.

rocket + -ry a noun suffix.

Roket šenâsi, from roket, → rocket, + šenâsi, → -logy; roketgari with suffix -gari, from -gar, → -or.

rockoon
  روکلون   
roklon

Fr.: fusée-sonde lancée à partir d'un ballon   

A rocket launched from a balloon at a pre-determined height and fired by a ground-controlled radio relay when some particular event, e.g. a solar flare, occurs.

From rocket + balloon.

From roket + lon, → ballon astronomy.

Roemer delay
  درنگ ِ رؤمر   
derang-e Rømer

Fr.: retard de Rømer   

A time delay caused by the light travel across a → dynamical system. The finite → speed of light causes a delay, for example, between the → primary eclipse and the → secondary eclipse in → binary systems.

Named after Ole Rømer (1664-1710), who discovered the finite speed of light, → Roemer's measurement; → delay.

Roemer's measurement
  اندازه‌گیری ِ رؤمر   
andâzegiri-ye Rømer

Fr.: mesure de Rømer   

The first successful measurement of the → speed of light carried out by the Danish astronomer Ole Rømer in 1675 at Paris Observatory. Astronomers knew that the mean period of revolution for Jupiter's innermost satellite → Io (Jupiter I) was 42.5 hours. During this period Io was sometimes eclipsed by Jupiter. Astronomers expected that if Io was visible at some time it must be visible 42.5 hours later. But Ole Rømer discovered that there were many irregularities in Io's orbital period. Sometimes Io appeared too early and other times too late in relation to the expected times. The irregularities repeated themselves precisely at a one-year interval, which meant that they must be connected to the Earth's rotation around the Sun. Rømer attributed this difference in time to the additional distance the light from Io had to travel at different times, and used this information to calculate the speed of light. He found that it takes light 22 minutes to traverse the Earth's orbital diameter; the correct figure was later determined to be 16 minutes and 40 seconds. Rømer was able to measure the speed of light to be 230,000 km s-1. Although this figure was very close to the currently accepted value of 300,000 km s-1, it was rejected by the scientific community of the time, who assumed it to be much too high a figure.

Ole Rømer (1664-1710); → measurement.

roentgen
  رونتگن   
rontgen (#)

Fr.: roentgen   

A unit of radiation exposure defined as a charge release rate of 258 micro-coulombs per kilogram of air.

Named after the German physicist Wilhelm Konrad Röntgen (1845-1923), one of the early investigators of radioactivity.

roentgenium
  رونتگنیوم   
rontgeniom (#)

Fr.: roentgenium   

An artificially produced radioactive chemical element; symbol Rg. Atomic number 111; mass number of most stable isotope 272; melting point, boiling point, specific gravity, and valence unknown.

Named after the German physicist Wilhelm Konrad Röntgen (1845-1923), one of the early investigators of radioactivity.

rogue
  ولگرد   
velgard (#)

Fr.: vagabond   

A vagabond or tramp. A dishonest or unprincipled person.

Perhaps short for obsolete roger "begging vagabond."

Velgard "vagabond, roamer, tramp."

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc coh col col col Com com com com com com com com Com con con con con con con con con con con con con coo Cor Cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg ura uti val var vec Vel ver Ver vie Vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>