An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 639
equalizer
  هموگ ساز   
hamugsâz

Fr.: équaliseur   

Electronics: A device, usually an electric network, designed to correct for unequal attenuation of phase shift in the transmission of signals.

Agent noun from → equalize.

equals sign
  نشانه‌ی ِ هموگ   
nešâne-ye hamug

Fr.: signe égal   

A mathematical symbol (=) that indicates equality of two expressions on each side of the sign. Same as → equality sign. The equals sign appears for the first time in Robert Recorde's book The Whetstone of Witte published in 1557. He was a Welsh physician and mathematician.

equal; → sign.

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   
hamugidan

Fr.: 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   
hamugeš

Fr.: 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 jonbeš

Fr.: 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 hâlat

Fr.: 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 hâlat

Fr.: 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 hamugânhâ

Fr.: 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 zamân

Fr.: 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 hamugâri

Fr.: 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 hamugâri

Fr.: 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   
hamugâri

Fr.: 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 hamugâri

Fr.: bourrelet équatorial   

The excess of the Earth's equatorial diameter over the polar diameter.

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 hamugâri

Fr.: 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 hamugâri

Fr.: coordonnées équatoriales   

Celestial coordinates in the → equator system.

equatorial, → coordinate.

equatorial mounting
  برنشاند ِ هموگاری   
barnešând-e hamugâri

Fr.: 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 hamugâri

Fr.: plan équatorial   

The plane containing a celestial object's equator.

equatorial; → plane.

equatorial radius
  شعاع ِ هموگاری   
šo'â'-e hamugâri

Fr.: 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.

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