# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 axial inclination   درکیل ِ آسه   darkil-e âséFr.: inclinaison de l'axe   The angle at which a planet's axis of rotation is tilted, with respect to that of the planet's orbit.→ axial; → inclination. axial precession   پیشایان ِ آسه‌ای   pišâyân-e âse-yiFr.: précession axiale   1) A change in the orientation of the → rotation axis of a non-spherical, spinning body caused by → gravity. A rotating top will precess in a direction determined by the → torque exerted by its → weight. The precession → angular velocity is inversely proportional to the spin angular velocity, so that the precession is faster and more pronounced as the top slows down. 2) In particular, the gradual shift in the orientation of Earth's rotation axis which traces out a conical path once every ~ 26,000 years. The cause of the Earth's precession is the → equatorial bulge of the Earth, brought about by the → centrifugal force of the → rotation, which has changed the Earth from a perfect sphere to a slightly flattened one, thicker across the equator. The attraction of the Moon and Sun on the bulge is the reason which makes the Earth precess.→ axial; → precession. axial symmetry   همامونی ِ آسه‌ای   hamâmuni-ye âse-yiFr.: symmétrie axiale   A symmetry with respect to a line. A geometric configuration is said to have axial symmetry if it remains unchanged when rotated about a given line.→ axial; → symmetry. axial tilt   گرای ِ آسه   gerâ-ye âséFr.: inclinaison de l'axe   The angle between an object's → rotation axis and its → orbital axis. In other words, the angle between its → equatorial plane and → orbital plane. Same as → axial inclination and → obliquity, but not to be confounded with → orbital inclination.→ axial; → tilt. axiom   بنداشت، ارز‌آغازه   bondâšt (#), arzâqâzé (#)Fr.: axiome   In any system of mathematics or logic, a statement or proposition from which secondary statements or propositions are derived. The truth of an axiom is either taken for granted or assumed. In modern practice, axiom and → postulate have the same meaning.M.Fr. axiome, from L. axioma, from Gk. axioma "authority," literally "something worthy," from axioun "to think worthy," from axios "worthy," from PIE adj. *ag-ty-o- "weighty," from base *ag- "to drive, draw, move."Bondâšt, literally "taking as the base," from bon "root, origin, base" + dâšt "held," from dâštan "to have, to hold, to maintain, to consider." Arzâqâzé, from arz "value" + âqâzé "beginning, principle," from âqâz "beginning." axiom of constraints   بنداشت ِ پاوندها   bondâšt-e pâvandhâFr.: axiome des contraintes   An axiom in → statics, stating that any → constrained body can be treated as a → free body detached from its → constraints, provided the latter are represented by their → reactions.→ axiom; → constraint. axiomatic   بنداشتی   bondâštiFr.: axiomatique   Of, relating to, or resembling an → axiom.→ axiom; → -ic. axiomatic system   راژمان ِ بنداشتی   râžmân-e bondâštiFr.: système axiomatique   Any system of → logic which explicitly states → axioms from which → theorems can be → deduced.→ axiomatic; → system. axion   اکسیون   aksion (#)Fr.: axion   A hypothetical weakly-interacting → boson of small mass required by models of → particle physics in order to solve the strong CP problem and explain a number of observed astrophysical/cosmological phenomena, including → dark matter, and the dimming of → type Ia → supernovae (→ accelerating Universe). Photons traveling in the → intergalactic medium would in part turn into axions in the presence of magnetic fields. The transformed photons are not detected on Earth and therefore supernovae would appear fainter even if the Universe is not accelerating.Axion, first coined by Frank Wilczek (2004 Nobel Prize in Physics) apparently after a brand of washing detergent! The reason seems to be the idea that the particle will iron out a wrinkle in the → standard model of fundamental particles and forces while solving the problem of the Universe's → missing mass. axis   آسه   âsé (#)Fr.: axe   1) One of the principal lines through the center of a figure or a solid, especially, the line which divides the figure or solid symmetrically. 2) A fixed line along which distances are measured or to which position are referred.L. axis "axle, pivot," akin to O.E. eax "axis, axle," Gk. axon "axle," Skt. aksa- "axle, axis, beam of a balance;" PIE base *aks- "axis."Âsé, from Pers. dialects: Qâyeni asak "the shaft connecting the plough to the yoke," Lori esi "a pillar (used to put up a tribal tent)," variants hosi, hosin, Tabari âssen "the foot of a door on which it turns," cf. Skt. ISA- "pole or shafts of a carriage or plough," Av. aêša "the two shafts," Mod.Pers. xiš "plough(share)," Gk. oiax "handle of rudder, tiller, helm," PIE base *ei-, *oi- "pole, thill." axis of rotation   آسه‌ی ِ چرخش   âse-ye carxešFr.: axe de rotation   Same as → rotation axis and → rotational axis.→ axis; → rotation. axisymmetric   همامون ِ آسه‌ای، آسه-همامون   hamâmun-e âse-yi, âse-hamâmunFr.: axisymétrique   Having → axisymmetry. axisymmetry   همامونی ِ آسه‌ای، آسه-همامونی   hamâmuni-ye âse-yi, âse-hamâmuniFr.: axisymétrie   Same as → axial symmetry. azimuth   سوگان، سمت   sugân, samtFr.: azimut   The → angular distance from the → North point eastward to the intersection of the → horizon with the → vertical circle passing through the object. Azimuth is 0° for an object due north, 90° due east, 180° due south, and 270° due west. → Altitude and azimuth constitute the → horizon coordinate system.From O.Fr. azimut, from Ar. as-sumut (السمت) "the directions, ways," pl. of as-samt "the direction, way."Sugân, from su "direction" + -gân direction suffix. azimuth circle   پرهون ِ سوگان، دایره‌ی ِ ~   parhun-e sugân, dâyere-ye ~Fr.: cercle d'azimut   One of great circles of the → celestial sphere which passes through the → zenith, → nadir, and the star, cutting the horizon at right angles. Same as → vertical circle.→ azimuth; → circle. azimuthal   سوگانی   sugâniFr.: azimutal   Or, or pertaining to an → azimuth.→ azimuth + → -al. azimuthal angle   زاویه‌ی ِ سوگانی   zâviye-ye sugâniFr.: angle azimutal   In → spherical coordinates, an angle measured from the x-axis in the xy-plane.Azimuthal, adj. from azimuth; → angle. azimuthal magnetic field   میدان ِ مغناتیسی ِ سوگانی   meydân-e meqnâtisi-ye sugâniFr.: champ magnétiquue azimutal   In the → solar dynamo model, a magnetic field that points from east to west or vice-versa.→ azimuthal; → magnetic; → field. azimuthal projection   فراشانش ِ سوگانی   farâšâneš-e sugâniFr.: projection azimutale   A map projection on which the → azimuths of all points are shown correctly with respect to the center. A plane tangent to one of the Earth's poles is the basis for polar azimuthal projection.→ azimuthal; → projection. azimuthal quantum number   عدد ِ کو‌آنتومی ِ سوگانی   adad-e kuântomi-ye sugâniFr.: nombre quantique azimutal   In quantum mechanics, a quantum number that distinguishes the different shapes of the orbitals.Azimuthal, adj. from → azimuth; → quantum number.