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

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 equant   فلک ِ معدل (المسیر)   falak-e mo'adel (al-masir) (#)Fr.: équant   In Ptolemy's → geocentric system, an imaginary point near the center of the → deferent but at a position opposite to that of the Earth from the center of the deferent. Ptolemy further supposed that the distance from the Earth to the center of the deferent was equal to the distance from the center of the deferent to the equant. He also claimed that the planet's deferent and the → epicycle described uniform circular motion around the equant.L. aequant-, s. of aequans, pr.p. of aequare "to make equal."Falak-e mo'adel (al-masir), literally "the sphere that equalizes (the path)," from Ar. falak "celestial orbit; sphere; heaven," from Babylonian pulluku + mo'adel "equalizing" (+ masir "path"). equate   هموگیدن   hamugidanFr.: mettre en équation   To put in the form of an equation; to state the equality of or between.L. æquatus, p.p. of æquare "to make equal," from æquus "equal, level, even."Infinitive form of hamug, → equal. equation   هموگش   hamugešFr.: équation   A statement asserting the equality of two numbers or two expressions. It consists of two parts, called sides or members of the equation, separated by the Same as → equality sign.From L. æquation- "an equalizing," noun of → equate.Verbal noun of hamugidan, → equate. equation of motion   هموگش ِ جنبش   hamugeš-e jonbešFr.: équation de mouvement   1) Any equation that describes the motion of objects, i.e., variation of velocity, distance covered, acceleration, etc., as a function of time; e.g., V = V0 + at, S = Vt + (1/2)at2. 2) For a fluid, a relation, in its most fundamental form, equating the rate of change of momentum of a selected portion of fluid and the sum of all forces acting on that portion of fluid. 3) In quantum mechanics, an equation that governs the time variation of the → state of the system. → Schrodinger equation. However, in the Heisenberg formulation of quantum mechanics the equation of motion does not involve the states, which in this case is time independent, but rather the → observables of the system.→ equation; → motion. equation of state   هموگش ِ حالت   hamugeš-e hâlatFr.: équation d'état   In physics and thermodynamics, the equation that describes the relationship between pressure, density, and temperature, e.g. → ideal gas law, → van der Waals equation, → polytropic process, → virial equation of state.→ equation; → state. equation of state parameter   پارامون ِ هموگش ِ حالت   pârâmun-e hamugeš-e hâlatFr.: paramètre de l'équation d'état   In cosmology, a → dimensionless parameter introduced by the → equation of state representing the ratio of the pressure to the energy density of a fluid, such as the → dark energy: w = p/ρ. The → deceleration or → acceleration of an → expanding Universe depends on this parameter (→ accelerating Universe). A number of numerical values of this parameter are as follows: for the → cosmological constant: w = -1, for → non-relativistic matter (present-day → baryons): w = 0, and for → relativistic matter (photons, neutrinos): w = +1/3. Together with Ω(dark energy) and Ω(matter), w provides a three-parameter description of the dark energy. The simplest parametrization of the dark energy is w = constant, although w might depend on → redshift.→ equation; → state; → parameter. equation of the equinoxes   هموگش ِ هموگانها   hamugeš-e hamugânhâFr.: équation des équinoxes   The difference between → apparent sidereal time and → mean sidereal time. It is due to the nutation of the Earth's polar axis of rotation about its precessional motion. It ranges from +0.8 to +1.2 seconds. Also known as → nutation in right ascension.→ equation; → equinox. equation of time   هموگش ِ زمان   hamugeš-e zamânFr.: équation du temps   The difference, due to Earth's elliptical orbit and variable orbital velocity, between apparent solar time and mean solar time. It varies throughout the year, and slightly from year to year. At present, it reaches extremes of about -14 minutes in February, and about +16 minutes in November. The equation of time is visually illustrated by an → analemma.→ equation; → time. equator   هموگار، استوا   hamugâr, estevâ (#)Fr.: équateur   The great circle on the surface of a body formed by the intersection of the surface with the plane passing through the center of the body perpendicular to the axis of rotation. → celestial equator.From M.L. æquator "equalizer" (of day and night, as when the sun crosses the equator), from æquare "to make equal, equate" + -tor.Hamugâr, from hamug, → equal + -âr suffix forming agent nous (as in parastâr) or contracted present stem of âvardan "to bring; to cause, to produce." equator plane   هامن ِ هموگاری   hâmon-e hamugâriFr.: plan équatorial   An imaginary plane → perpendicular to the → axis of a → sphere dividing the sphere into two congruent parts.→ equator; → plane. equator system   راژمان ِ هموگاری   râžmân-e hamugâriFr.: système équatorial   A set of celestial coordinates based on the celestial equator as the primary great circle. The coordinates are → declination and → right ascension.→ equator; → system. equatorial   هموگاری   hamugâriFr.: équatorial   Of, pertaining to, or near an equator, especially the equator of the Earth.From → equator + -ial, variant of → -al.Hamugâri, from hamugâr, → equator, + adj. suffix -i. equatorial bulge   بر‌آمدگی ِ هموگاری   barâmadegi-ye hamugâriFr.: bourrelet équatorial   The excess of the equatorial diameter over the polar diameter of a celestial object, such as the Earth or the Moon.→ equatorial; bulge, from O.Fr. bouge "leather bag," from L. bulga "leather bag," of Gaulish origin.Barâmadegi, from barâmadan "to grow out; to emerge," from bar- "on, upon, up" (Mid.Pers. abar, O.Pers. upariy "above; over, upon, according to," Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + âmadan "to come" (Mid.Pers. âmadan; O.Pers. gam- "to come; to go;" Av. gam- "to come; to go," jamaiti "goes;" cf. Skt. gamati "goes;" Gk. bainein "to go, walk, step;" L. venire "to come;" Tocharian A käm- "to come;" O.H.G. queman "to come;" E. come; PIE root *gwem- "to go, come"). equatorial coordinate system   راژمان ِ هماراهای ِ هموگاری   râžmân-e hamârâhâ-ye hamugâriFr.: système de coordonnées équatoriales   An astronomical → coordinate system for indicating the positions of → celestial objects on the → celestial sphere. The system consists of two components, → right ascension and → declination. Right ascension is the angle between the → vernal equinox and the point where the → hour circle intersects the → celestial equator. The right ascension is always measured eastward from the vernal equinox, in the units of hours, minutes, and seconds. Declination is the angle between the celestial equator and the position of the star measured along the star's hour circle. It is measured in degrees, minutes, and seconds north or south of the celestial equator. By definition, the vernal equinox is located at right ascension 0h and declination 0°. Equatorial coordinates change with time due to the → precession of the Earth's → rotation axis.→ equatorial; → coordinate; → system. equatorial coordinates   هماراها‌ی ِ هموگاری   hamârâhâ-ye hamugâriFr.: coordonnées équatoriales   Celestial coordinates in the → equator system.→ equatorial, → coordinate. equatorial mounting   برنشاند ِ هموگاری   barnešând-e hamugâriFr.: monture équatoriale   A telescope mounting consisting of a polar axis pointed toward the celestial pole, and a declination axis supporting the instrument at right angles to the polar axis.→ equatorial; → mounting. equatorial plane   هامن ِ هموگاری   hâmon-e hamugâriFr.: plan équatorial   The plane containing a celestial object's equator.→ equatorial; → plane. equatorial radius   شعاع ِ هموگاری   šo'â'-e hamugâriFr.: rayon équatorial   Of a planet, the distance from the center to the equator. For Earth it is 6,378.1370 km. Jupiter has an equatorial radius 11.2 times Earth's value.→ equatorial; → radius. equatorial wind   باد ِ هموگاری   bâd-e hamugâriFr.: vent équatorial   A slow, dense → stellar wind (high → mass loss rate) emanating from equatorial regions of a → B[e] star. The equatorial and → polar winds are the two main wind components in B[e] stars. The mechanism suggested to explain this wind morphology is the rotationally induced → bistability mechanism.→ equatorial; → wind. equi-   هموگ-   hamug-Fr.: équi-   A prefix meaning "equal," as in → equinox, → equilibrium, → equipartition.M.E., from L. aequi-, combining form representing aequus, → equal.Hamug-, → equal.