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
primordial abundance
  فراوانی ِ بن‌آغازین   
farâvâni-ye bonâqâzin

Fr.: abondance primordiale   

The relative amount of a light element (e.g. deuterium, lithium, helium) synthesized in the early Universe.

primordial; → abundance.

primordial black hole
  سیه‌چال ِ بن‌آغازین   
siyahcâl-e bonâqâzin

Fr.: trou noir primordial   

A black hole formed following the Big Bang event due to incredibly violent turbulence that squeezed concentrations of matter to high densities. These black holes, first suggested by Stephen Hawking, are expected to have a mass comparable to that of a mountain and a size as small as an atom. Same as → mini black hole.

primordial; → black hole.

primordial curvature perturbation
  پرتورش ِ خمیدگی ِ بن‌آغازین   
partureš-e xamidegi-ye bonâqâzin

Fr.: perturbation de courbure primordiale   

In cosmological models, the phenomenon that is supposed to seed the → cosmic microwave background anisotropies and the structure formation of the Universe.

primordial; → curvature; → perturbation.

primordial galaxy
  کهکشان ِ بن‌آغازین   
kahkešân-e bonâqâzin

Fr.: galaxie primordiale   

A high redshift, metal-deficient galaxy that formed very early in the history of the Universe.

primordial; → galaxy.

primordial helium
  هلیوم ِ بن‌آغازین   
heliom-e bonâqâzin

Fr.: hélium primordial   

The helium element created in the → early Universe, around 3 minutes after the → Big Bang, when the temperature dropped to 109 degrees; in contrast to the helium being synthesized in stars. Based on observations of helium → emission lines in → H II regions of metal-poor dwarf galaxies (→ metal-deficient galaxy), the primordial 4He → chemical abundance (by mass) is estimated to be YP = 0.24672 ± 0.00017. Moreover, using observations of a near-pristine → intergalactic cloud, a value of 0.250 +0.033-0.025 has been reached (Cooke & Fumagalli, 2018, Nature Astronomy, 2, 657). The theoretical He abundance predicted by → Big Bang nucleosynthesis is 0.24709 ± 0.00017 (Pitrou et al., 2018, arXiv:1801.08023).

primordial; → helium.

primordial nucleosynthesis
  هسته‌هندایش ِ بن‌آغازین   
haste-handâyeš-e bonâqâzin

Fr.: nucléosynthèse primordiale   

The formation of → chemical elements in the → early Universe, between about 0.01 seconds and 3 minutes after the → Big Bang, when the nuclei of primordial matter collided and fused with one another. Most of the → helium in the → Universe was created by this process. Same as → Big Bang nucleosynthesis

primordial; → nucleosynthesis.

principal
  فرین   
farin

Fr.: principal   

First or highest in rank, importance, value, etc. See also → main.

M.E., from O.Fr. principal, from L. principalis "first in importance," from princeps "first, chief, prince," literally "that takes first," from primus "first" + root of capere "to take."

Farin literally "foremost," from far-, Mid.Pers. fra-; O.Pers. fra- "forward, forth;" Av. frā "forth," pouruua- "first;" cf. Skt. pūrva- "first," pra- "before, formerly;" Gk. pro; L. pro; O.E. fyrst "foremost," superlative of fore, E. fore + -in superlative suffix.

principal axis
  آسه‌یِ فرین   
âse-ye farin (#)

Fr.: axe principal   

1) Optics: Any imaginary line passing through the center of curvature of a → spherical mirror or → lens and the corresponding geometrical center. Principal axis is perpendicular to the mirror or lens at the pole. Rays of light parallel to the principal axis of a → concave mirror will appear to converge on a point in front of the mirror somewhere between the mirror's pole and its center of curvature. Same as → optical axis.
2) Mechanics: One of three mutually perpendicular axes of an object about which the → moment of inertia is maximum or minimum. More specifically, an object has an infinite number of moments of inertia. If an object is not symmetrical about all planes through its → center of mass, then there will be one → axis of rotation about which the moment of inertia is largest, and there will be one axis of rotation about which the moment of inertia is smallest. These two axes will always be perpendicular to each other and are the principal axes of the object. The third principal axis of an object is the axis perpendicular to these two axes. In general the → angular momentum (L) of a body spinning about a point O is not in the same direction as the axis of rotation, or that of the → angular velocity angular velocity (ω); that is L is not parallel to ω. For certain bodies, however, there can be certain axes for which L and ω are parallel. In that case L = , where I is the moment of inertia about the axis in question. In a symmetric rigid body, the axes of symmetry coincide with the principal axes of the moment of inertia

principal; → axis.

principal quantum number
  عدد ِ کو‌آنتومی ِ فرین   
adad-e kuântomi-ye farin

Fr.: nombre quantique principal   

In atomic physics, the first of a set of quantum numbers which describe an atomic orbital. Symbolized as n, it characterizes the size and energy of an orbital.

principal; → quantum; → number.

principle
  پَروَز   
parvaz (#)

Fr.: principe   

A fundamental, primary assumption, or general law from which others are derived.

From M.E., from O.Fr. principe, from L. principium "a beginning, first part," from princeps "first, chief, prince," literally "that takes first," from primus "first" + root of capere "to take."

Parvaz "origin, root, stock" (as used in particular by Ferdowsi); cf. Av. fra-vāza- "drawing from; leading onward," from Av. fra-, frā- "before; forward, forth" (fratəma- "first, front," pouruua- "first," fra-cara- "preceding;" O.Pers. fra- "forward, forth;" Mid.Pers. fra-; cf. Skt. pra- "before, formerly," prathama- "earliest, initial," pūrva- "first;" Gk. pro; L. pro; O.E. fyrst "foremost," superlative of fore) + vaz- "to draw, guide; bring; possess; fly; float," vazaiti "guides, leads" (cf. Skt. vah- "to carry, drive, convey," vahati "carries," pravaha- "bearing along, carrying," pravāha- "running water, stream, river;" L. vehere "to carry;" O.E. wegan "to carry;" O.N. vegr; O.H.G. weg "way," wegan "to move," wagan "cart;" M.Du. wagen "wagon;" PIE base *wegh- "to drive;" see also → flight).

principle of action and reaction
  پَروز ِ ژیرش و واژیرش، ~ کنش و واکنش   
parvaz-e žireš va vâžireš, ~ koneš va vâkoneš

Fr.: principe d'action et de réaction   

Newton's third law of motion, which states that for every action there must be an equal and opposite reaction.

principle; → action; → reaction.

principle of constancy
  پروز ِ پایایی ِ تندی ِ نور   
parvaz-e pâyâyi tondi-ye nur

Fr.: principe de la constance de la vitesse de la lumière   

The second postulate in Einstein's theory of → special relativity whereby the → velocity of light in → vacuum has the same absolute value in all → inertial reference frames irrespective of the direction and speed of propagation of the light source. It should be emphasized that this constancy of the speed of light holds among → reference frames moving uniformly with respect to each other. An observer accelerated with respect to a light source will measure a speed of light that is smaller than the speed of light measured in a → rest frame. See also → principle of relativity.

principle; constancy, noun related to → constant.

principle of covariance
  پَروز ِ هم‌ورتایی   
parvaz-e hamvartâyi

Fr.: principe de covariance   

In special relativity, the principle that the laws of physics take the same mathematical form in all inertial frames of reference.

principle; → covariance.

principle of equivalence
  پَروز ِ هموگ‌ارزی   
parvaz-e hamug-arzi

Fr.: principe d'équivalence   

In → general relativity the principle which states that in the immediate proximity of an → accelerating system the acceleration is physically equivalent to → gravitational force. This principle also implies the equivalence of → gravitational mass and → inertial mass. Same as the → equivalence principle. See also → Einstein's elevator.

principle; → equivalence.

principle of excluded middle
  پروز ِ میانی سکلانده   
parvaz-e miyâni sokalândé

Fr.: principe du milieu exclu, ~ ~ tiers ~   

The second principle of → formal logic introduced in Aristotle's theory of the → syllogism: A statement is either → true or → false. In other words, two → contradictory → propositions cannot both be true. The truth of one implies the falsehood of the other. Also called law of excluded middle and → principle of excluded third.

principle; → exclude; → middle.

principle of excluded third
  پروز ِ سومی سکلانده   
parvaz-e sevomi sokalândé

Fr.: principe du tiers exclu   

Same as → principle of excluded middle.

principle; → exclude; → third.

principle of identity
  پروز ِ ایدانی   
parvaz-e idâni

Fr.: principe d'identité   

The first principle of → formal logic introduced in Aristotle's theory of the → syllogism: If a statement is true then it is true. Also called → law of identity.

principle; → identity.

principle of least action
  پَروز ِ کمترین ژیرش، ~ ~ کنش   
parvaz-e kamtarin žireš, ~ ~ koneš

Fr.: principe de moindre action   

The principle that, for a system whose total mechanical energy is conserved, the path to be taken for the system from one configuration to another is the one whose action has the least value relative to all other possible paths and from the same configurations. Also called Maupertuis' principle, least-action principle.

principle; → least; → action.

principle of non-contradiction
  پروز ِ ناپادگویی   
parvaz-e nâpâdguyi

Fr.: principe de non-contradiction   

The third principle of → formal logic introduced in Aristotle's theory of the → syllogism: No statement can be both → true and → false at the same time. Also called → law of non-contradiction.

principle; → non-; → contradiction.

principle of relativistic causality
  پروز ِ بنارمندی ِ باز‌آنیگی‌مند   
parvaz-e bonârmandi-ye bâzânigi-mand

Fr.: principe de la causalité relativiste   

One consequence of the theory of → special relativity, according to which no two events separated by a distance greater than their separation in time multiplied by the → speed of light may have a → causal influence on each other. Violation of this principle leads to → paradoxes, such as that of an → effect preceding its → cause.

principle; → relativistic; → causality.

<< < -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 > >>