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: 13048 Search : far
homocentric spheres
  سپهرهای ِ هم‌مرکز   
sepehrhâ-ye ham-markaz

Fr.: sphères homocentriques   

Concentric → spheres of Eudoxus.

homo-; → center; → -ic; → sphere.

homodyne
  هومودین   
homodin

Fr.: homodyne   

Of, or pertaining to the process of combining two waves, such as → electromagnetic waves, of the same → frequency. See also: → heterodyne.

Homodyne, from → homo- + -dyne, from Gk. dynamicsdynamics.

homogeneity
  همگنی   
hamgeni (#)

Fr.: homogénéité   

State or quality of having a uniform appearance or composition, being homogeneous

homogeneous + → -ity.

homogeneous
  همگن   
hamgen (#)

Fr.: homogène   

1) Of uniform composition or having a common property throughout.
2) Math.: Of the same kind so as to be commensurable. Of the same degree or dimension. → anisotropic homogeneous cosmological model, → homogeneous fluid, → homogeneous linear differential equation, → homogeneous Universe, → homogeneous turbulence, → inhomogeneous, → nonhomogeneous, → nonhomogeneous linear differential equation.

Homogeneous, from M.L. homogeneus, from Gk. homogenes "of the same kind," from homos "same," → homo-, + genos "race, kind," gonos "birth, offspring," from PIE base *gen-/*gon-/*gn- "to produce, beget, be born," cf. Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born," zana- "race" (in sruuô.zana- "belonging to the race of the horned ones"), O.Pers. zana- "tribe" (in paru-zana- "consisting of many tribes"), Skt. janati "begets, bears," jana- "creature, human being, race, tribe, people;" L. genus "race, stock, kind," gignere "to beget."

Hamgen "of the same kind, like each other; friend, partner," from ham-, → homo-, + gen "kind," O.Pers./Av. zana- "race; tribe," cognate with L. genus, as above). Alternatively, gen may be a variant of Mid./Mod.Pers. gôn/gun "kind, type; manner; color, skin color," from Av. gaona- "hair, hair color, color."

homogeneous fluid
  شارّه‌ی ِ همگن   
šârre-ye hamgen (#)

Fr.: fluide homogène   

A fluid with uniform properties throughout, but meteorologists sometimes designate as homogeneous a fluid with constant density.

homogeneous, → fluid.

homogeneous linear differential equation
  هموگش ِ دگرسانه‌ای ِ خطی همگن   
hamugeš-e degarsâne-yi-ye xatti hamgen

Fr.: équation différentielle linéaire homogène   

A → linear differential equation if the right-hand member is zero, Q(x) = 0, on interval I.

homogeneous; → linear; → differential; → equation.

homogeneous turbulence
  آشوبناکی ِ همگن   
âšubnâki-ye hamgen (#)

Fr.: turbulence homogène   

Turbulence in which spatial derivatives of all mean turbulent quantities are negligible.

homogeneous, → turbulence.

homogeneous Universe
  گیتی ِ همگن   
giti-ye hamgen (#)

Fr.: Univers homogène   

A model Universe which is homogeneous and → isotropic on large scales. It is modeled by a → Robertson-Walker cosmology. A homogeneous Universe is filled with a constant density and negligible pressure. Any small spatial region is characteristic for the whole Universe.

homogeneous; → Universe.

homomorphism
  هم-ریخت‌مندی   
ham-rixtmandi

Fr.: homomorphisme   

A → mapping between two mathematical → objects that preserves the object structure. A general → morphism.

homo-; → morphism.

homonuclear molecule
  مولکول ِ هم‌هسته   
molekul-e ham-hasté

Fr.: molécule homonucléaire   

A molecule that is composed of only one type of → chemical element, e.g. the → molecular hydrogen and → ozone.

homo-; → nuclear; → molecule.

Homunculus Nebula
  میغ ِ آدمک   
miq-e âdamak

Fr.: nébuleuse de l'Homoncule   

A nebula of gas and dust (about 17" x 12" in size), which surrounds the massive star Eta Carinae and lies about 7500 light-years away. The surrounding material was ejected by the massive star in 1843 during its violent eruption, and is now expanding at about 500 km/sec.

Homunculus, "a diminutive human being; little man" (since the nebula resembled a small human to early observers), from L. homin-, homun-, homo "eartly being," humus "the earth" (cf. Pers. zamin "earth, ground," Mid.Pers. zamig "earth;" Av. zam- "the earth;" Skt. ksam; Gk. khthôn, khamai "on the ground;" PIE root *dh(e)ghom "earth") + → -ula, -ule; → nebula.

Miq, → nebula; âdamak "little man."

hook
  قلاب   
qollâb

Fr.: crochet   

1) A curved or bent piece of metal or other hard material for catching, holding, or hanging something.
2) Something curved or bent like a hook.

M.E. hoke, O.E. hoc "hook, angle;" cf. M.Du. hoek, Du. haak, Ger. Haken "hook."

Qollab "a hook, a hooked device," probably ultimately from Proto-Ir. gart- "to turn;" cf. Pers. gard-, gardidan, gaštan "to turn, to wind;" cognate with dialectal qellidan "to roll."

Hooke's law
  قانون ِ هوک   
qânun-e Hooke (#)

Fr.: loi de Hooke   

The law stating that if a body is deformed the → strain produced is directly proportional to the applied → stress. If the elastic limit is not exceeded, the material returns to its original shape and size on the removal of the stress. Hooke's law forms the basis of the theory of → elasticity.
More specifically, within certain limits, the force required to stretch an elastic object such as a metal spring is directly proportional to the extension of the spring. It is commonly written: F = -kx, where F is the force, x is the length of extension/compression and k is a constant of proportionality known as the spring constant.

Named after Robert Hooke (1635-1703), British scientist who described the relationship in 1676; → law.

hop
  کپ   
kop

Fr.: 1) sautiller, sauter; 2) sautillement, saut   

1) To move by a quick springy leap or in a series of leaps. (Of a person) Move by jumping on one foot. (Of a bird or other animal) move by jumping with two or all feet at once.
2) An act of hopping; short leap.

M.E. hoppen; O.E. hoppian; cognate with Ger. hopfen, O.N. hoppa.

Kopidan, from kop; cf. (Bašâgardi) kup, (Lârestâni) komp, (Bardesiri) gopak, (Sistâni) job, (Kermâni) pok, pokidan "jump, leap."

horizon
  افق   
ofoq (#)

Fr.: horizon   

1) An imaginary circle that delimits the sky and the Earth.
2) The fundamental great circle of the → horizon system, defined by the intersection of the → celestial sphere and a level plane passing through the observer. → celestial horizon.
3) In → Robertson-Walker models, the boundary separating objects already observed from those not yet observed, or the boundary separating objects observable from unobservable (J. Plebanski, A. Krasinski, 2006, An Introduction to General Relativity and Cosmology, Cambridge Univ. Press).
4) → cosmic horizon.
5) → event horizon.
See also:
apparent horizon, → artificial horizon, → astronomical horizon, → dip of the horizon, → distance to the horizon, → geometric horizon, → horizon coordinate system, → horizon problem, → horizon system, → particle horizon, → sea horizon, → sensible horizon, → sound horizon, → true horizon, → visible horizon.

From O.Fr. orizon, from orizonte, from L. horizontem (nom. horizon), from Gk. horizon kyklos "bounding circle," from horizein "bound, limit, divide, separate," from horos "boundary."

Ofoq, from Ar.

horizon coordinate system
  راژمان ِ هم‌آراهای ِ افقی   
râžmân-e hamârâhâ-ye ofoqi

Fr.: coordonnées horizontales   

The coordinate system based on the position of the observer. The horizontal plane is the fundamental plane and the coordinates are → altitude and → azimuth.

horizon; → coordinate; → system.

horizon problem
  پراسه‌ی ِ افق   
parâse-ye ofoq

Fr.: problème de l'horizon   

A problem with the standard cosmological model of the Big Bang related to the observational fact that regions of the Universe that are separated by vast distances nevertheless have nearly identical properties such as temperature. This contradicts the fact that light moves with a finite speed and, as a result, certain events which occur in the Universe are completely independent of each other. Inflationary cosmology offers a possible solution.

horizon; → problem.

horizon system
  راژمان ِ افقی   
râžmân-e ofoqi

Fr.: coordonnées horizontales   

Same as → horizon coordinate system.

horizon; → system.

horizontal
  افقی   
ofoqi (#)

Fr.: horizontal   

1) Of or pertaining to the → horizon.
2) At right angles to the → vertical; parallel to level ground.
See also:
blue horizontal branch star, → extreme horizontal branch star, → field horizontal branch star, → horizontal branch, → horizontal branch star, → horizontal eclipse, → horizontal parallax, → horizontal refraction, → red horizontal branch star, → supra-horizontal branch star, → zero age horizontal branch star.

From → horizon + → -al.

horizontal branch (HB)
  شاخه‌ی ِ افقی   
šâxe-ye ofoqi (#)

Fr.: branche horizontale   

A set of roughly horizontal points in the → Hertzsprung-Russell diagram of a typical → globular cluster. It displays a stage of stellar evolution which immediately follows the → red giant branch (RGB) in stars with an initial mass < 1.2 Msun. When the star's ascent of the RGB is terminated by the → helium flash, it moves down to the HB. The star's → effective temperature on the HB is higher than it was on the RGB, but the luminosity is considerably less than at the helium flash. Usually HB stars have two energy sources: in addition to the → helium burning in their cores, they experience → hydrogen fusion in a surrounding shell. The thickness of the shell determines the color of the HB stars. A thin shell, involving low → opacity, makes the star look blue. The HB domain encompasses a very large effective temperature range with several members: → extreme HB, → blue HB, → RR Lyrae, → red HB, and → red clump stars. The locations depend on many parameters, including stellar mass, metallicity, age, helium abundance, and rotation.

horizontal; → branch.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer AGB air Alf Alg all alp alt AM amo ana And ang ani ano Ant Ant apa apo app app Ara Arc ari Arr ash ass ast ast asy atm ato att aut ave axi Bab bal Bal bar bar bea Bek Bes bia Big bin bin bip biv bla bli blu Boh Bol Bos bou bra bri bro buo cal cal can cap car Car cat cat CCD Cen cen CH cha cha che Che chr cir cir cit cla clo clo clu Coa coe 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 Cop Cor cor cor cos cos cou cou Cow cre cri cro cry cur cya Cyg dan dar dat de- deb dec dec ded def deg del dem den dep des det dev dia dif dif dih dio Dir dis dis dis dis dis dis DO don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ esc eth Eur Eve exa exc exe exi exp exp ext ext ext fac fal far fed Fer fer fie fin fir fis fla flo flu fol for for fou fra fre Fre fro fut G-t gal gal gam gas Gau Gem gen geo geo geo gia Gli Gol gra gra gra gra gre gri gui H I Hag hal har hat He- hea hel Hel her Hes hie hig his hom hor hot Hub Hug hur hyd hyd hyg hyp ice ide ima Ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv Io ion iro isl iso iso Jac jet jud jur Kel Kep kil Klo Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Meg Mer Mer met met Met mic Mid Mil min Mir mit mod mod mol mon Mor mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ ocu oft ome Oor ope opp opt opt orb ord ori ort osc out ove oxi pai pan par par par par pas pea pen per per per per Per per pha phi pho pho pho phy pio Pla pla pla pla Pla plu Poi pol pol pol poo pos pos pot pra pre pre pre pre pri pri pro pro pro pro pro Pro pro pse pul pur qua qua qua qua que rac rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot Rus Sac sal sat sca sca Sch sci Scu sec sec Sed sel Sel sen ser Sex Sha she sho sid sig sil sim sin siz sla Sma sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spi spr squ sta sta sta sta ste ste ste Sto Str str str sub sub suc sun sup sup sup sup sur swa syn syn tab tar tek tem ter tes the the the the Tho thr tid tim Tis Too Tor tra tra Tra tra tra tri tri tru Tul tur two Typ ult un- und uni uni unk upp Urc utt val var vec vel ver vib vio vir vis voi vor wan wat wav wax wea Wei whi Wil win WN9 wor X-r yel you zer zod > >>