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

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 mass function   کریای ِ جرم   karyâ-ye jermFr.: fonction de masse   1) The number of a class of objects as a function of their mass. → initial mass function (IMF); → present-day mass function (PDMF). 2) A numerical relation between the masses of the two components of a → spectroscopic binary that provides information on the relative masses of the two stars when the spectral lines of only one component can be seen. If Mp is the mass of primary (whose spectrum is known), Ms is the mass of secondary, and i the → angle of inclination of the orbit, the mass function is given by: (Ms3. sin3i) / (Mp + Ms)2.→ mass; → function. mass segregation   سوایش ِ جرم   savâyeš-e jermFr.: ségrégation de masse   A consequence of the → dynamical relaxation process in a gravitationally → bound system, such as a → star cluster or a → globular cluster, where massive and low-mass members occupy different volumes. Massive members sink toward the center, while less massive members tend to move farther away from the center.→ mass; → segregation. mass-energy relation   باز‌آنش ِ جرم-کاروژ   bâzâneš-e jerm-kâružFr.: relation masse-énergie   The famous equation proposed by Einstein as a consequence of his special theory of relativity describing the equivalence of mass and energy: E = mc2, where E is energy, m is the equivalent amount of mass, and c is the velocity of light.→ mass; → energy; → relation. mass-luminosity relation   باز‌آنش ِ جرم-تابندگی   bâzâneš-e jerm-tâbandegiFr.: relation masse-luminosité   A relationship between luminosity and mass for stars that are on the main sequence, specifying how bright a star of a given mass will be. Averaged over the whole main sequence, it has been found that L = M3.5, where both L and M are in solar units. This means, for example, that if the mass is doubled, the luminosity increases more than 10-fold.→ mass; → luminosity; → relation. mass-metallicity relation (MZR)   بازانش ِ جرم-فلزیگی   bâzâneš-e jerm-felezigiFr.: relation masse-métallicité   A correlation between the → stellar mass (or → luminosity) and the → gas metallicity of → star-forming galaxies (Lequeux et al. 1979) according to which massive galaxies have higher gas metallicities. Several large galaxy surveys, such as the → Sloan Digital Sky Survey (SDSS), have confirmed that galaxies at all → redshifts with higher stellar masses retain more metals than galaxies with lower stellar masses. Besides the dependence on stellar mass, other studies have found further dependences of gas metallicity on other physical properties at a given mass, such as → specific star formation rate, → star formation rate, and stellar age. These higher dimensional relations could provide additional constraints to the processes that regulate the metal enrichment in galaxies. In addition to gas metallicity, also the → stellar metallicity of galaxies is found to correlate with the stellar mass, suggesting the mass-metallicity relation already existed at early epochs of galaxy evolution (Lian et al., 2017, MNRAS 474, 1143, and references therein).→ mass; → metallicity; → relation. mass-size relation   بازانش ِ جرم-اندازه   bâzâneš-e jerm-andâzeFr.: relation masse-taille   The relation between the → stellar mass and the physical size of a galaxy. Studies show that the sizes increase with stellar mass, but that the relation weakens with increasing → redshift. Separating galaxies by their → star formation rate, model simulations show that → passive galaxies are typically smaller than → active galaxies at a fixed stellar mass. These trends are consistent with those found in observations; the level of agreement between the predicted and observed size-mass relations is of the order of 0.1 dex for redshifts < 1 and 0.2-0.3 dex from redshift 1 to 2. Known also as the → luminosity-size relation (Furlong et al., 2016, MNRAS 465, 722, and references therein).→ mass; → size; → relation. materialization   ۱) مادیگش؛ ۲) مادیگانش   1) mâdigeš 2) mâdigânešFr.: matérialisation   The act or process of materializing.Verbal noun of → materialize. mathematical conjecture   هاشن ِ مزداهیک   hâšan-e mazdâhikFr.: conjecture mathématique   A statement that one expects to be true, but for which one does not yet know a proof. Once the → proof is found, the conjecture becomes a → theorem. mathematical expectation   امید ِ مزداهیک، بیوسش ِ ~، ~ ِ ریاضی   omid-e mazdâhik, bayuseš-e ~, ~ riyâziFr.: espérance mathématique   In probability and statistics, of a random variable, the summation or integration, over all values of the random variable, of the product of the value and its probability of occurrence. Also called → expectation, → expected value. Maxwell's demon   پری ِ ماکسول   pari-ye MaxwellFr.: démon de Maxwell   A → thought experiment meant to raise questions about the possibility of violating the → second law of thermodynamics. A wall separates two compartments filled with gas. A little "demon" sits by a tiny trap door in the wall. He is able to sort hot (faster) molecules from cold molecules without expending energy, thus bringing about a general decrease in → entropy and violating the second law of thermodynamics. The → paradox is explained by the fact that such a demon would still need to use energy to observe and sort the molecules. Thus the total entropy of the system still increases.Named after James Clerk Maxwell (→ maxwell), who first thought of this experiment; → demon. Maxwell's equations   هموگش‌های ِ ماکسول   hamugešhâ-ye MaxwellFr.: équations de Maxwell   A set of four fundamental equations that describe the electric and magnetic fields arising from varying electric charges and magnetic fields, electric currents, charge distributions, and how those fields change in time. In their vector differential form, these equations are: i) ∇.E = ρ/ε0 (→ Gauss's law for electricity), ii) ∇.B = 0 (→ Gauss's law for magnetism), iii) ∇ x E = -∂B/∂t (→ Faraday's law of induction), iv) ∇ x B = μ0J + μ0ε0∂E/∂t (→ Ampere's law), with c2 = 1/(μ0ε0), where E is → electric intensity, B is → magnetic flux density, ρ is → charge density, ε0 is → permittivity, μ0 is → permeability, J is → current density, and c is → speed of light.→ maxwell. It should be emphasized that the equations originally published by James Clerk Maxwell in 1873 (in A Treatise on Electricity and Magnetism) were 20 in number, had 20 variables, and were in scalar form. The German physicist Heinrich Rudolf Hertz (1857-1894) reduced them to 12 scalar equations (1884). It was the English mathematician/physicist Oliver Heaviside (1850-1925) who expressed Maxwell's equations in vector form using the notations of → gradient, → divergence, and → curl of a vector, thus simplifying them to the present 4 equations (1886). Before Einstein these equations were known as Maxwell-Heaviside-Hertz equations, Einstein (1940) popularized the name "Maxwell's Equations;" → equation. Maxwell-Boltzmann distribution   واباژش ِ ماکسول-بولتسمان   vibâžš-e Maxwell-BoltzmannFr.: distribution de Maxwell-Boltzmann   The distribution law for kinetic energies (or, equivalently, speeds) of molecules of an ideal gas in equilibrium at a given temperature.→ maxwell; → Boltzmann's constant; → distribution. mean daily motion   جنبش ِ روزانه‌ی ِ میانگین   jenbeš-e ruzâne-ye miyângin (#)Fr.: mouvement diurne moyen   The average movement of a body along its orbit in one day, usually expressed in degrees.→ mean; → diurnal; → motion. mean moon   ماه ِ میانگین   mâh-e miyângin (#)Fr.: lune moyenne   A fictitious Moon that has the same average motion as the true Moon but that is not subject to any gravitational perturbations by other bodies.→ mean; → moon. mean motion   جنبش ِ میانگین   jonbeš-e miyângin (#)Fr.: mouvement moyen   The average angular velocity of a satellite in an elliptical orbit.→ mean; → motion. mean position   نهش ِ میانگین   neheš-e miyânginFr.: position moyenne   Same as → mean place.→ mean; → position. meditation   سگالش   segâleš (#)Fr.: méditation   The act of meditating. → consideration.From L. meditatatus p.p. of meditari "to think over, reflect, consider," from PIE root *med- "to measure, limit, consider, advise," → mode.Verbal noun of → meditate. megatons of TNT   مگاتن ِ TNT   megâton-e TNT (#)Fr.: megatonnes de TNT   A unit of explosive force equal to one million metric tons of → T.N.T.. 1 megaton = 4.2 × 1022 → ergs = 4.2 × 1015 → joules.→ mega-; → ton. membership function   کریای ِ هموندی   karyâ-ye hamvandiFr.: fonction d'adhésion   One of several functions used in the → fuzzification and → defuzzification steps of a → fuzzy logic system to map the → nonfuzzy input values to → fuzzy linguistic terms and vice versa. A membership function is used to quantify a linguistic term.→ membership; → function. mention   ۱) ایات؛ ۲) ایاتیدن   1) ayât; 2) ayâtidanFr.: 1) mentionner; 2) mention   1) To refer briefly to; name, specify, or speak of (Dictionary.com). 2) A direct or incidental reference; a mentioning (Dictionary.com).M.E. mencioun, from O.Fr. mencion "mention, memory, speech," from L. mentionem "a calling to mind, a speaking of," from root of Old L. minisci "to think," related to mens "mind," from PIE root *men- "to think;" cf. Pers. man, mân "thought, to think," → mind.Ayât, from Mid.Pers. ayât, ayâd "remembrance, recollection, memory;" Mod.Pers. yâd.