An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < abe Ein phy > >>

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.

Planck; → constant.

precession constant
  پایای ِ پیشایان   
pâyâ-ye pišâyân

Fr.: 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 barpârešigi

Fr.: 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.

proportionality + → constant.

propositional constant
  پایای ِ گزاره‌ای   
pâyâ-ye gozaare#ay

Fr.: constante propositionnelle   

Logic: A → propositional symbol that represents a → specific → proposition.

propositional; → constant.

radiation constant
  پایای ِ تابش   
pâypa-ye tâbeš

Fr.: constante de rayonnement   

Same as → radiation density constant.

radiation; → constant.

radiation density constant
  پایای ِ چگالی ِ تابش   
pâypa-ye cagâli-ye tâbeš

Fr.: 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 bâzhâzidé

Fr.: 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 bâzhâzidé

Fr.: constante de Planck réduite   

reduced Planck constant.

reduced Planck constant.

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-markazi

Fr.: 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 fanar

Fr.: 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-Boltzmann

Fr.: 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 zamini

Fr.: 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 zamâni

Fr.: 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 gâzhâ

Fr.: constante universelle des gaz   

Same as → gas constant.

universal; → gas; → constant.

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