# 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: 56 Search : constant
 Einstein's gravitational constant   پایای ِ گرانشی ِ اینشتین   pâyâ-ye gerâneši-ye Einstein (#)Fr.: constante gravitationnelle d'Einstein   The coupling constant appearing in → Einstein's field equations, expressed by: κ = 8πG/c4, where G is the Newtonian → gravitational constant and c the → speed of light.→ einstein; → gravitational; → constant. Fermi constant   پایای ِ فرمی   pâyâ-ye FermiFr.: constante de Fermi   The → coupling constant associated with the → weak interaction, which gives rise to → beta decay. CF = 1.167 x 10-5 GeV-2.→ Fermi; → constant. fine-structure constant   پایای ِ ساختار ِ نازک   pâyâ-ye sâxtâr-e nâzokFr.: constante de la structure fine   A measure of the strength of → interaction between a → charged particle and the → electromagnetic field. It is a → dimensionless number expressed (in → cgs units) by α = e2/ħc, where e is the → electron charge, ħ is the → reduced Planck's constant, and c is the → speed of light. It is approximately equal to 1/137 or 7.3 x 10-3. The smallness of this number is of great importance since it determines the size of → atoms and the → stability of → matter. fundamental constant   پایای ِ بنیادین   pâyâ-ye bonyâdin (#)Fr.: constante fondamentale   A physical constant that cannot be expressed in terms of other constants of nature, such as the charge of the electron.→ fundamental; → constant. gas constant   پایا‌ی ِ گاز‌ها   pâyâ-ye gâzhâ (#)Fr.: constante des gaz parfaits   For a given quantity of an → ideal gas, the product of its → pressure and the → volume divided by the → absolute temperature (R = PV/T).→ gas; → constant. Gaussian gravitational constant   پایای ِ گرانشی ِ گاؤس   pâyâ-ye gerâneši-ye GaussFr.: constante gravitationnelle de Gauss   The constant, denoted k, defining the astronomical system of units of length (→ astronomical unit), mass (→ solar mass), and time (→ day), by means of → Kepler's third law. The dimensions of k2 are those of Newton's constant of gravitation: L 3M -1T -2. Its value is: k = 0.01720209895.→ Gaussian; → gravitational; → constant. gravitational constant   پایای ِ گرانشی   pâyâ-ye gerâneši (#)Fr.: constante gravitationnelle   A fundamental constant that appears in → Newton's law of gravitation. It is the force of attraction between two bodies of unit mass separated by unit distance: G = 6.673 x 10-8 dyn cm2 g-2 or 6.673 x 10-8 cm3s-2g-1, or 6.673 x 10-11 N m2 kg-2 or 6.673 x 10-11 m3s-2kg-1. It was first measured in 1798 by Henry Cavendish (1731-1810), 71 years after Newton's death. Same as the → Newtonian constant of gravitation. heliocentric gravitational constant   پایای ِ گرانشی هورمرکزی   pâyâ-ye gerâneši-ye hur-markaziFr.: constante gravitationnelle héliocentrique   A parameter representing the product of the → gravitational constant by the → solar mass. It is 13.27 x 1019 m3 s-2.→ heliocentric; → gravitational; → constant. Hubble constant   پایا‌ی ِ هابل   pâyâ-ye Hubble (#)Fr.: constante de Hubble   → Hubble; → constant. Hubble-Lemaitre constant   پایا‌ی ِ هابل-لومتر   pâyâ-ye Hubble-LemaîtreFr.: constante de Hubble-Lemaître   The → Hubble parameter for the → present epoch. It is the constant of proportionality between the → recession velocities of galaxies and their distances from each other. The latest determinations using the → Hubble Space Telescope observations of → Cepheids give H0 = 72 ± 8 km s-1 Mpc-1 (W. L. Freedman et al., 2001, ApJ 553, 47, arXiv:astro-ph/0012376), the → WMAP observations yield 70.4 ± 1.3 km s-1 Mpc-1 (N. Jarosik et al., 2011, ApJS 192, 14, arXiv:1001.4744), and the → Planck Satellite observations give 67.3 ± 1.2 km s-1 Mpc-1 (Planck Collaboration, 2014, A&A 571, A16, arXiv:1303.5076). More recently, the Hubble constant was derived by a team of astronomers, using the NASA/ESA Hubble Space Telescope, with a 2.4% accuracy (Adam G. Reiss et al., 2016, arXiv:1604.01424). The new value, 73.2 km s-1 Mpc-1, suggests that the Universe is expanding between five and nine percent faster than previously calculated. The → Hubble law is only applicable for large distances (> 20 Mpc), when the proper motions of galaxies in groups and clusters cannot confuse the recession due to expansion.→ Hubble; → Friedmann-Lemaitre Universe; → constant. individual constant   پایای ِ تکال   pâyâ-ye takâlFr.: constant individuel   In predicate logic: A → word or → expression that represents a → specific  → individual or → object. A single object can be denoted by multiple individual constants, reflecting the fact that objects can have multiple names. On the other hand, any individual constant can only denote one object. Individual constants are represented by lower case letters from the beginning of the alphabet: a, b, c.→ individual; → constant. Joule's constant   پایای ِ ژول   pâyâ-ye Joule (#)Fr.: constante de Joule   The proportional relationship of mechanical energy to thermal energy, equal to 4.184 joules per calorie. Also called mechanical equivalent of heat.→ joule; → constant. Kolmogorov constant   پایای ِ کولموگوروف   pâyâ-ye Kolmogorov (#)Fr.: constante de Kolmogorov   The proportionality constant C in Kolmogorov's mathematical analysis of → turbulence which states that the spectral energy E(k) in the range of turbulent scales is E(k) =C ε2/3 k-5/3, where k represents the → wave number (inversely proportional to the wavelength or → eddy size), and ε is the average energy dissipation per unit mass in the fluid. Experimental measurements give C close to 1.5.Andrei Nikolaevich Kolmogorov (1903-1987), a prominent Soviet mathematician, who made major advances in different scientific fields, mainly probability theory, topology, turbulence, classical mechanics, and computational complexity; → constant. magnetic constant   پایای ِ مغناتیسی   pâyâ-ye meqnâtisi (#)Fr.: constante magnétique   A physical constant relating mechanical and electromagnetic units of measurement. It has the value of 4π × 10-7 henry per meter. Also called the permeability of free space, or → absolute permeability.→ magnetic; → constant. Newton constant   پایای ِ نیوتن   pâyâ-ye NewtonFr.: constante de Newton   Same as the → gravitational constant.→ Newton; → constant. Newton's constant   پایای ِ نیوتون   pâyâ-ye NewtonFr.: constante de Newton   Same as the → gravitational constant.→ Newton; → constant. Newtonian constant of gravitation   پایای ِ گرانش ِ نیوتن   pâyâ-ye gerâneš-e NewtonFr.: constante de la gravitation newtonienne   Same as the → gravitational constant.→ Newtonian; → constant; → gravitation. Oort's constants   پایاهایِ اورت   pâyâhâ-ye OortFr.: constantes de Oort   Two parameters, denoted A and B, that describe the major features of our Galaxy's differential rotation in the Sun's neighbourhood. A is one-half of the shear and equal to +14.4 ± 1.2 km s-1 kpc-1, and B, one-half of the vorticity, equal to -12.0 ± 2.8 km s-1 pc-1.→ Oort cloud; → 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.

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