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

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.

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.

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.

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

→ mid-; → day.

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.

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

→ middle; → atmosphere.

Same as → mid-infrared.

→ middle; → infrared.

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

→ middle; → latitude.

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

→ middle; → term.

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

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.

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.

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.

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 *meig^h- "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," mex^w-/max^wt- "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 *meig^h- "to move, go."

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."

Migrating; periodically migrating; pertaining to migration.

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

A → NASA funded project to support and provide to the astronomical community a variety of astronomical data archives, with the primary focus on scientifically related data sets in the optical, ultraviolet, and near-infrared parts of the spectrum. MAST is a huge database that contains astronomical observations of stars, planets and galaxies from 16 separate NASA space science missions, including the Hubble Space Telescope. It is located at the Space Telescope Science Institute (STScI).

In honor of senator Barbara A. Mikulski for her active support for science, NASA, and the astrophysics community; → archive; → space; → telescope.

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.

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; (Parth. šyft); Khotanese švida; Sogd. xšiβd (Yaghnobi xšift; Yadgha xšira); Av. xšvid-, xšvipta-; cf. Skt. ksira- "milk."

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."