An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 654
mâtris (#)

Fr.: matrice   

1) An orderly array of numbers, algebraic symbols, or mathematical functions, especially when such arrays are added and multiplied according to certain rule; e.g. → Jordan matrix.
2) The fine grained material found in between the → chondrules, fragments and metal grains found inside → stony meteorites.

From O.Fr. matrice, from L. matrix "female animal kept for breeding," in L.L. "womb, source, origin," from mater, → mother.

Mâtris, loan from Fr., as above.

matrix calculus
  افماریک ِ ماتریس‌ها   
afmârik-e mâtrishâ

Fr.: calcul matriciel   

The treatment of matrices whose entries are functions.

matrix; → calculus.

matrix inverse
  ماتریس ِ وارون   
mâtris-e vârun

Fr.: matrice inverse   

For a → square matrix whose → determinant is not zero, the unique matrix A-1 satisfying the relation AA-1 = A-1A = I, where I is the → identity matrix.

matrix; → inverse.

mâddé (#)

Fr.: matière   

1) Physical or corporeal substance in general, whether solid, liquid, or gaseous, especially as distinguished from incorporeal substance, as spirit or mind, or from qualities, actions, and the like.
2) Whatever has size and shape, is solid and tangible, takes up space.
3) Anything that contains mass. → material.

M.E. mater(e), materie, from O.Fr. mat(i)ere, materie, from L. materia "substance from which something is made," also "hard inner wood of a tree," from mater, → mother, PIE base *mater-, see below.

Mâddé, variant mâyé "substance, essence; quantity, amount;" Mid.Pers. mâtak/mâdak "substance, the essential element of anything; materials" (Sogd. patmâδé "matter, substance"), from mât, mâd "mother; substance" (see E. matter, as above), from O.Pers./Av. mātar- "mother;" cf. Ossetic mad/madae "mother;" Khotanese mâta "mother;" Skt. mātár- "mother;" Gk. meter, mater; L. mater (Fr. mère, Sp. madre); O.E. môdor from P.Gmc. *mothær (O.S. modar, Dan. moder, Du. moeder, Ger. Mutter); Lith. mote "wife."
Note: Ar. mâddat is borrowed from Mid.Pers. mâdak, as above, and Arabicized through association with madda "to extend."

matter era
  دوران ِ مادّه   
dowrân-e mâddé (#)

Fr.: ère dominée par la matière   

A critical change in the history of the Universe, which occurred after the radiation era, when the density of energy contained within matter exceeded the density of energy contained within radiation. This transition started about 5000 years after the Big Bang, when the temperature had fallen to 3 x 104 K. Later, 380 000 years after the Big Bang, when the temperature was 3000 K, matter and radiation were no longer coupled together and the Universe became transparent.

matter; → era.

matter-dominated Universe
  گیتی ِ مادّه‌چیره   
giti-ye mâdde-ciré

Fr.: Univers dominé par la matière   

A Universe in which the matter energy density (Ωm ≈ 1) provides most of the total energy density. According to the → Big Bang model, in the early history of the → Universe a → radiation-dominated phase preceded the matter-dominated phase. This phase is characterized by R/R0 ∝ t2/3, where R is the → cosmic scale factor and t is time.

matter; → dominate; → Universe.

Maunder minimum
  کمینه‌ی ِ ماؤندر   
kamine-ye Maunder

Fr.: minimum de Maunder   

A period from about 1645 to 1715 when the number of → sunspots was unusually low. This → solar activity minimum is attested also through the increased content of carbon 14 in tree rings in that period. The reason is that the cosmic rays which produce 14C reach the Earth in a greater number when there is weak solar activity (see also → radiocarbon dating). The Maunder minimum occurred during a period of cooling of the Earth, called the → Little Ice Age. The Maunder minimum is one of a number of periods of low solar activity, including the → Dalton minimum, the → Sporer minimum, the → Wolf minimum , and the → Oort minimum.

After the British astronomer Edward Walter Maunder (1851-1928) who, along with Gustav Spörer of Germany, first called attention to this phenomenon; → minimum.

bišiné (#)

Fr.: maximum   

The greatest value attained (or attainable) by a function; the opposite of minimum.

From L. maximum, neuter of maximus "greatest," superlative of magnus "great, large" cognate with Pers. meh "great, large" (Mid.Pers. mah, mas; Av. maz-, masan-, mazant- "great, important," mazan- "greatness, majesty," mazišta- "greatest;" cf. Skt. mah-, mahant-; Gk. megas; PIE *meg- "great").

Bišiné, from biš "much, more; great" (from Mid.Pers. veš "more, longer; more frequently," related to vas "many, much" (Mod.Pers. bas); O.Pers. vasiy "at will, greatly, utterly;" Av. varəmi "I wish," vasô, vasə "at one's pleasure or will," from vas- "to will, desire, wish") + -in superlative suffix + nuance suffix.

maximum density of water
  چگالی ِ بیشینه‌ی ِ آب   
cagâli-ye bišine-ye âb

Fr.: densité maximale de l'eau   

The density of pure water occurring at 3.98 °C, which is 1.0000 g cm-3, or 1000 kg m-3. Water when cooled down contracts normally until the temperature is 3.98 °C, after which it expands. Because the maximum density of water occurs at about 4 °C, water becomes increasingly lighter at 3 °C, 2 °C, 1 °C, and 0 °C (→ freezing point). The density of liquid water at 0 °C is greater than the density of frozen water at the same temperature. Thus water is heavier as a liquid than as a solid, and this is why ice floats on water. When a mass of water cools below 4 °C, the density decreases and allows water to rise to the surface, where freezing occurs. The layer of ice formed on the surface does not sink and it acts as a thermal isolator, thus protecting the biological environment beneath it. This property of water liquid is very unusual; molecules pack more closely than in the crystal structure of ice. The reason is that → hydrogen bonds between liquid water are not stable, they are continuously broken and new bonds are created. In the crystal structure of ice molecules have a fixed pattern creating empty space between molecules.

maximum; → density; → water.

maximum entropy method (MEM)
  روش ِ درگاشت ِ بیشینه   
raveš-e dargâšt-e bišiné

Fr.: méthode d'entropie maximum   

A deconvolution algorithm which functions by minimizing a smoothness function in an image. The MEM seeks to extract as much information from a measurement as is justified by the data's signal-to-noise ratio.

maximum; → entropy; → method.

maximum likelihood
  شدواری ِ بیشینه   
šodvâri-ye bišiné

Fr.: maximum de vraisemblance   

A statistical procedure based on choosing the value of the unknown parameter under which the probability of obtaining an observed sample is highest.

maximum; → likelihood.

maxwell (Mx)
maxwell (#)

Fr.: maxwell   

The unit of → magnetic flux. The flux through 1 square cm normal to a magnetic field of 1 → gauss. It is equal to 10-8 → weber (Wb)s.

After James Clerk Maxwell (1831-1879), British outstanding physicist, who made fundamental contributions to electromagnetic theory and the kinetic theory of gases.

Maxwell bridge
  پل ِ ماکسول   
pol-e Maxwell

Fr.: pont de Maxwell   

A type of → Wheatstone bridge used for measuring → inductance in terms of → resistance and → capacitance.

maxwell; → bridge.

Maxwell gap
  گاف ِ ماکسول   
gâf-e Mawxell

Fr.: division de Maxwell   

A division in Saturn's ring in the outer part of the C ring. It is about 87500 km from Saturn's center and is 500 km wide. The gap was discovered in 1980 by Voyager 1.

Not discovered by J. C. Maxwell, but named in his honor; → maxwell; → gap.

Maxwell's demon
  پری ِ ماکسول   
pari-ye Maxwell

Fr.: 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 Maxwell

Fr.: équations de Maxwell   

A set of four vector equations that describe the electric and magnetic fields arising from varying distributions of electric charges and currents, and how those fields change in time. In their 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 + μ0ε0E/∂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). Einstein referred to them as Maxwell-Heaviside-Hertz equations; → equation.

Maxwell's rule
  رزن ِ ماکسول   
razan-e Maxwell

Fr.: règle de Maxwell   

Every part of a deformable electric circuit tends to move in such a direction as to enclose the maximum magnetic flux.

maxwell; → rule.

Maxwell-Boltzmann distribution
  واباژش ِ ماکسول-بولتسمان   
vibâžš-e Maxwell-Boltzmann

Fr.: 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.

Maya calendar
  گاهشمار ِ مایا   
gâhšomâr-e Mâyâ

Fr.: calendrier Maya   

A complex calendar created by the ancient central American Mayas which uses three different dating systems in parallel: Long Count, Tzolkin, and Haab. Only Haab has a direct relationship with the length of the year. It is a solar → vague year consisting of 18 months of 20 days each, and an additional period of 5 → epagomenal days. Tzolkin is a calendar of 13 x 20 = 260 days running within Haab and is used for ritual purposes. A date is usually described by specifying its position in both the Tzolkin and Haab calendars. The least common multiple of the two calendars, called the Calendar Round, has 18,980 days, representing a cycle of 73 sacred years, or 52 vague years. The Long Count is the number of days since the start of the Maya era. There is disagreement about the beginning date of the Long Count. Most authorities agree, however, that the Long Count started in 3114 B.C., with several possible dates.

Maya, proper name; → calendar.

Möbius band
  باند ِ موی‌بیوس   
bând-e Möbius

Fr.: ruban de Möbius   

A surface with only one side, made by putting a simple twist in a long, rectangular strip of paper, then pasting the ends together.

After the German astronomer and geometer August Ferdinand Möbius (1790-1868); → band.

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