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

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 58 Search : constant
 physical constant   پایای ِ فیزیکی   pâyâ-ye fiziki (#)Fr.: constante physique   A fundamental → physical quantity that is generally believed to be both universal in nature and constant in time.→ physical; → constant. Planck constant   پایای ِ پلانک   pâyâ-ye Planck (#)Fr.: constante de Planck   A physical constant that determines the energy of quantum as a function of its frequency; symbol h. Also called → Planck's constant. On 16 November 2018, the International Bureau of Weights and Measures (BIPM) voted to redefine the kilogram by fixing the value of the Planck constant, thereby defining the kilogram in terms of the second and the speed of light. Starting 20 May 2019, the new value is exactly 6.626 070 15 × 10-34 J s. The → reduced Planck constant, ħ = h / 2π, is also called the → Dirac constant.→ Planck; → constant. Planck's constant   پایای ِ پلانک   pâyâ-ye Planck (#)Fr.: constante de Planck   → Planck; → constant. precession constant   پایای ِ پیشایان   pâyâ-ye pišâyânFr.: constante de précession   The amount by which the equinoctial points drift westward annually due to precession. Its value for epoch J2000.0 is 50''.26, resulting from the westward → precession of the equator (50".38), and the eastward → precession of the ecliptic (0".12).→ precession; → constant. proportionality constant   پایای ِ برپارشیگی   pâyâ-ye barpârešigiFr.: constante de proportionalité   Math.: A → constant that converts a proportionality into an → equation. Thus the proportionality constant k converts the proportionality y ∝ x into the equation y = kx. propositional constant   پایای ِ گزاره‌ای   pâyâ-ye gozaare#ayFr.: constante propositionnelle   Logic: A → propositional symbol that represents a → specific → proposition. radiation constant   پایای ِ تابش   pâypa-ye tâbešFr.: constante de rayonnement   Same as → radiation density constant.→ radiation; → constant. radiation density constant   پایای ِ چگالی ِ تابش   pâypa-ye cagâli-ye tâbešFr.: constante de rayonnement   The constant related to the total energy radiated by a → blackbody and defined as: a = 4σ/c, where σ is the → Stefan-Boltzmann constant and c the → speed of light. Its value is a = 7.5657 x 10-15 erg cm-3 K-4. Same as → radiation constant.→ radiation; → density; → constant. reduced Planck constant   پایای ِ پلانک ِ باز‌هازیده   pâyâ-ye Planck-e bâzhâzidéFr.: constante de Planck réduite   The → Planck constant divided by 2π and denoted ħ, pronounced h-bar. Also called the → Dirac constant.Reduced, p.p. of → reduce; → Planck's constant. reduced Planck's constant   پایای ِ پلانک ِ باز‌هازیده   pâyâ-ye Planck-e bâzhâzidéFr.: constante de Planck réduite Rydberg constant   پایای ِ رودبَری   pâyâ-ye Rydberg (#)Fr.: constante de Rydberg   A fundamental constant of atomic physics appearing in the → Rydberg formula. The Rydberg constant for hydrogen is 109,739 cm-1.→ rydberg; → constant. selenocentric gravitational constant   پایای ِ گرانشی ماه‌مرکزی   pâyâ-ye gerâneši-ye mâh-markaziFr.: constante gravitationnelle sélénocentrique   A parameter representing the product of the → gravitational constant by the → lunar mass. It is 49.03 x 1011 m3 s-2.→ selenocentric; → gravitational; → constant. solar constant   پایای ِ خورشیدی   pâypa-ye xoršidi (#)Fr.: constante solaire   The amount of solar radiation in all wavelengths received per unit of time per unit of area on a theoretical surface perpendicular to the Sun's rays and at Earth's mean distance from the Sun. Its mean value is 1367.7 W m-2 or 1.37 × 106 erg sec-1 cm-2. In other words, the solar constant is the mean → solar irradiance on the outer atmosphere when the Sun and Earth are spaced at 1 → astronomical unit. See also: → solar luminosity.→ solar; → constant. spring constant   پایای ِ فنر   pâpâ-ye fanarFr.: constante de rappel du ressort   A characteristic of a spring which is defined as the ratio of the force affecting the spring to the displacement caused by the force. In other words, the spring constant is the force applied if the displacement in the spring is unity. It is expressed by the equation k = -F/x (from → Hooke's law), where F = force applied, x = displacement by the spring. The spring constant is usually expressed in Newton per meter (N/m).→ spring; → force. Stefan-Boltzmann constant   پایای ِ اشتفان-بولتسمن   pâyâ-ye Stefan-BoltzmannFr.: constante de Stefan-Boltzmann   The constant of proportionality present in the → Stefan-Boltzmann law. It is equal to σ = 5.670 × 10-8 W m-2 K-4 or 5.670 × 10-5 erg cm-2 s-1 K-4.→ Stefan-Boltzmann law; → constant. terrestrial gravitational constant   پایای ِ گرانشی زمینی   pâyâ-ye gerâneši-ye zaminiFr.: constante gravitationnelle terrestre   A parameter representing the product of the → gravitational constant by the Earth's mass. It is 3.987 x 1014 m3s-2 or 3.987 x 105 km3s-2.→ terrestrial; → gravitational; → constant. time constant   پایای ِ زمانی   pâyâ-ye zamâniFr.: constante de temps   Th speed of response of a detector, usually measured as 1/(2πν), where ν is the chopping frequency at which the responsivity fails to 1/√2 of its maximum value.→ time; → constant. universal gas constant   پایای ِ هرگانی ِ گاز‌ها   pâyâ-ye hargâni-ye gâzhâFr.: constante universelle des gaz   Same as → gas constant.→ universal; → gas; → constant.

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