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

A prefix which means being at or near the middle point of; being or occupying a middle place or position.

M.E., from O.E. midd-, cognate with O.H.G. mitti, O.N. mithr, Gothic midjis, O.Ir. mide, L. medius, Gk. mesos, Skt. mádhya-, Av. maidiia- "middle, the middle," Pers. miyân, as below.

Miyâni, from 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."
nim-, nimé, → half.

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.