An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 657
Mid-Atlantic Ridge
  روک ِ میان-اتلسی   
ruk-e miyân Atlasi

Fr.: dorsale médio-atlantique   

An immense chain of underwater mountains that runs down the middle of the Atlantic Ocean. The MAR, approximately 500-1000 km wide, extends 16,000 km from Iceland to the Antarctic Circle. The MAR is so high that it actually rises above sea level in many places, forming volcanic islands. The Azores, Ascension, St. Helena, and Iceland all arise from this great Atlantic range. The chain results from the movement of the continental plates. As these plates slowly separate, they leave gaps in the → Earth's crust. This allows molten rock from beneath the Earth's crust to reach the surface and forms a ridge. The MAR is a part of the global → mid-ocean ridge system.

mid-; → Atlantic; → ridge.

mid-infrared
  فروسرخ ِ میانی   
forusorx-e miyâni (#)

Fr.: infrarouge moyen   

The portion of the → electromagnetic radiation lying between the → near-infrared and the → far-infrared. This covers the wavelength range approximately from 8 to 30 → microns. See also: → infrared radiation, → submillimeter radiation.

mid-; → infrared.

mid-ocean ridge
  روک ِ میان-اقیانوسی   
ruk-e miyân-oqyânusi

Fr.: dorsale médio-océanique   

Any of submarine mountain ranges that stretch around the world through the Atlantic Ocean and across the Pacific and Indian Oceans. Such ridges generally stand about 1000 m to 3000 m above the adjacent ocean floor and are about 500-1000 km in width.

mid-; → ocean; → ridge.

midday
  نیمروز   
nimruz (#)

Fr.: midi   

The middle of the day; noon or the time centering around noon.

mid-; → day.

middle
  ۱) میان؛ ۲) میانی   
1) (n.) miyân; 2) (adj.) miyâni

Fr.: 1) milieu; 2) du milieu   

The point, part, position, etc., equidistant from extremes or limits.

M.E., O.E. middel; cf. M.L.G., Du. middel, Ger. mittel, variant mid; cognate with Pers. miyân, as below; from PIE *medhyo-.

1) Miyân "within, between, center," from Mid.Pers. mayân "middle; among, between," Av. maidiia- "middle, the middle," maiδiiāna- "middle, center," maδəma- [adj.] "middle, being in the middle; middling, of a middling size or quality," maiδim "in the midst of," cf. Skt. mádhya- "middle, located in the middle;" O.H.G. mitti "located in the middle."
2) From miyân + suffix -i.

middle atmosphere
  هواسپهر ِ میانی، جو ِ ~   
havâsepehr-e miyâni, javv-e ~

Fr.: atmosphère moyenne   

The region lying between the → troposphere and the → thermosphere comprising the → stratosphere and the → mesosphere (Meteorology Glossary, American Meteorological Society).

middle; → atmosphere.

middle infrared
  فروسرخ ِ میانی   
forusorx-e miyâni (#)

Fr.: infrarouge moyen   

Same as → mid-infrared.

middle; → infrared.

middle latitudes
  وَروناهای ِ میانی   
varunâhâ-ye miyâni

Fr.: latitudes moyennes   

The latitude belt roughly between 35 and 65 degrees North and South. Also referred to as the temperate region.

middle; → latitude.

middle term
  ترم ِ میانی   
tarm-e miyâni

Fr.: moyen terme   

Logic: In a → syllogism, the categorical term occurring in both the → major term and the → minor term.

middle; → term.

midnight
  نیمشب   
nimšab (#)

Fr.: minuit   

Generally, the middle of the night as indicated by twelve o'clock at night.
True midnight: The time when the Sun is closest to nadir and the night is equi-distant from dusk and dawn. The opposite of noon.

From mid- an E. combining form related to → middle; → night.

Nimšab, from nim "mid-, half" (Mid.Pers. nêm, nêmag "half;" Av. naēma- "half;" cf. Skt. néma- "half") + šab, → night

midnight Sun
  خورشید ِ نیمشب   
xoršid-e nimšab (#)

Fr.: Soleil de minuit   

The phenomenon occurring when the Sun is visible above the horizon at midnight. This phenomenon can be seen at positions north of the Arctic Circle and south of the Antarctic Circle when the Sun is circumpolar (around the summer solstice in the northern hemisphere and the winter solstice in the southern hemisphere respectively).

midnight, → sun.

Mie scattering
  پراکنش ِ می   
parâkaneš-e Mie

Fr.: diffusion de Mie   

The scattering of → electromagnetic waves by → particles of → size comparable to the radiation → wavelength. Mie scattering depends weakly upon the wavelength, hence the → scattered light spectrum is similar to that of the → incident light. Mie scattering explains the → white color of clouds when scattering is due to → water droplets having a size of few microns. Cloud → droplets with a diameter of around 20 microns or so are large enough to scatter all visible wavelengths more or less equally. Because all wavelengths are scattered, clouds appear to be white. When clouds become very deep, less and less of the incoming solar radiation makes it through to the bottom of the cloud, which gives these clouds a darker appearance.

Named after Gustav Adolf Mie (1868-1957), a German physicist, whose theory of 1908 explains the process; → scattering.

Mie theory
  نگره‌ی ِ می   
negare-ye Mie

Fr.: théorie de Mie   

The explanation of the → scattering of → electromagnetic waves by → homogeneous spheres of arbitrary → size and → composition using analytical solutions of → Maxwell's equations. See also: → Mie scattering, → Rayleigh scattering.

Mie scattering; → theory.

migrate
  موژیدن   
mužidan

Fr.: émigrer, immigrer   

1) To go from one country, region, or place to another.
2) To pass periodically from one region or climate to another, as certain birds, fishes, and animals.
3) Chem.: To move toward an electrode during electrolysis; (of atoms within a molecule) to change position (Dictionary.com).

From L. migratus p.p. of migrare "to move from one place to another," ultimately from PIE *meigh- "to move, go;" cf. Gk. ameibein "to change," Iranian muž-, as below.

Mužidan, ultimately from Proto-Ir. *maij- "to move (to places);" cf. Parachi muž-, muš-, Yazghulami mûž- "to go," mexw-/maxwt- "to move, shake," Gilaki maxtan "to stroll," Gonâbâdi mejon "ague, shivering, shaking chills," Sangesari moj; cognate with L. migrare "to move, go," as below, Skt. niméghanāna- "moving down;" PIE *meigh- "to move, go."

migration
  موژش، کوچ   
mužeš, kuc (#)

Fr.: migration   

1) The process or act of migrating; a migratory movement.
2) For an astronomical body, the process or act of changing its place over considerably large distances under the effect of certain physical forces. See, for example, → orbital migration; → Type I migration; → Type II migration.
3) Chem.: A movement or change of position of atoms within a molecule (Dictionary.com).

migrate; → -tion. Kuc "the act of moving from a dwelling, a place to another, decamping, migration."

migratory
  موژشی   
mužeši

Fr.: migratoire   

Migrating; periodically migrating; pertaining to migration.

migrate + -ory, an adj.-forming suffix.

Milankovich cycles
  چرخه‌های ِ میلانکوویچ   
carxehâ-ye Milankovich

Fr.: cycles de Milankovitch   

The theory according to which variations in the elements of Earth-Sun geometry are responsible for the sequence of ice ages during the Pleistocene era. The main elements are the varying tilt of the Earth's rotational axis, and the varying eccentricity of the Earth's orbit.

Named after the Serbian mathematician Milutin Milankovitch (1879-1958), who introduced the concept during the first half of the twentieth century.

milk
  شیر   
Šir (#)

Fr.: lait   

An opaque white fluid secreted by female mammals for the nourishment of their young.

M.E.; O.E. meol(o)c, (Anglian) milc; cf. Gr. Milch, Goth. miluks; akin to L. mulgere, Gk amelgein "to milk;" PIE base *melg- "wiping, stroking;"

Šir "milk;" Mid.Pers. šir; cf. Skt. ksira- "milk."

Milky Way
  راه ِ شیری   
Râh-e Širi (#)

Fr.: Voie lactée   

The diffuse glowing band of light seen on dark nights spanning the sky as a great circle. It is produced by light from stars and nebulae in the → Galactic plane. The apparent form of the Milky Way in the sky results from a geometrical effect created by our location in the outlying regions of a huge, flattened disk of stars. → Milky Way galaxy.

From L.L. galaxias "Milky Way," from Gk. galaxis kyklos "emilky circle," from gala (gen. galaktos) "milk."
In Gk. mythology, Jupiter, hoping to immortalize his infant son Hercules (who was born to a mortal woman), placed the baby on Juno's breast. Her milk spilled up, forming the Milky Way.
Milky, from milk; M.E.; O.E. meol(o)c, (Anglian) milc; cf. Gr. Milch, Goth. miluks; akin to L. mulgere, Gk amelgein "to milk;" PIE base *melg- "wiping, stroking;" → way.

Râh, → way; širi, adj. of šir "milk;" Mid.Pers. šir; cf. Skt. ksira- "milk."

Milky Way galaxy
  کهکشان ِ راه ِ شیری   
kahkešân-e râh-e širi (#)

Fr.: Voie lactée   

A → spiral galaxy, of which the → solar system is a small part. It is the second largest in our → Local Group of galaxies. The Milky Way is a disk-shaped system, with a diameter of between 80,000 and 100,000 → light-years and a thickness of about 2,000 light-years, containing more than 1011 stars. The stars are divided into two main categories, → Population II stars and → Population I stars.
The core, or nucleus, of the Galaxy is surrounded by an ellipsoidal central → bulge that measures some 15,000 light-years in diameter and about 6,000 light-years in the direction perpendicular to the plane of the disk. Surrounding the bulge and extending in a near spherical distribution above and below the → Galactic plane is the → Galactic halo. The halo contains about 200 → globular clusters and an extremely thinly scattered population of individual stars.
The Sun is located just over half way out from the center to the edge of the disk at a distance of about 25,000 light-years. In common with other stars, the Sun revolves around the → Galactic Center. Its → orbital velocity is about 220 km s-1 and its → orbital period is about 225 million years. Overall, the Galaxy exhibits → differential rotation, that is stars and gas clouds closer to the center have shorter orbital periods than those that are located further out.
The → spiral arms of the Milky Way lie within its disk, where bright → young stars, → H II regions, and → molecular clouds of gas and dust are concentrated into curved "arms" that appear to radiate from the central bulge in a spiral pattern. The Galaxy's spiral pattern consists of several major arms and a number of shorter segments, one of which, the → Orion arm, contains the Sun and the Orion star-forming region.
Near-infrared observations have shown that the stars in the central bulge are arranged in an elongated → galactic bar, about twice as long as it is wide, that is seen nearly end on from the present location of the solar system. The exact center, or nucleus, of the Galaxy coincides with a strong source of radio emission, called → Sagittarius A, that is less than 15 astronomical units in diameter. Observations of the speeds at which clouds of ionized gas are revolving round the → Galactic center imply that several million solar masses of material are concentrated within a region of about one light-year in radius. Since only about half of this mass can be accounted for by stars, it seems likely that the balance (about 2.5 million solar masses) is contained in a central black hole and that accretion onto this black hole is the underlying source of the energy radiated by Sagittarius A.
The Milky Way also has a → dark matter component. The Galactic → rotation curve indicates that there is a large amount of invisible → non-baryonic surrounding the whole Galaxy.

Milky Way; → galaxy.

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