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methanol maser meyzer-e metânol Fr.: maser méthanol A maser source in which excited methanol molecules (CH_{3}OH) produce → maser emission. Methanol masers are signposts of the early stages of star formation, many being associated with sources that have not developed an → H II region. There are more than 20 different methanol transitions that have been observed. They are divided into two categories: Class I, excited by collisions, and class II, excited by infrared radiation. The most important class I masers are at a frequency of 44.1 GHz, while he most important class II masers are at a frequency of 6.7 GHz. |
method raveš (#) Fr.: méthode A manner or mode of procedure, especially an orderly, logical, or systematic way of instruction, inquiry, investigation, experiment, and so on. From M.Fr. méthode, from L. methodus "way of teaching or going," from Gk. methodus "scientific inquiry, method of inquiry," originally "following after," from → meta- "after" + hodos "way." Raveš "mthod," originally "going, walking," from row "going," present stem of raftan "to go, walk;" Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack" + -eš a suffix of verbal nouns. |
method of least squares raveš-e kamtarin cârušhâ Fr.: méthode des moindres carrés A method of fitting a curve to data points so as to minimize the sum of the squares of the distances of the points from the curve. → method; → least squares. |
method of small perturbations raveš-e parturešhâ-ye kucak Fr.: méthode des petites perturbations The linearization of the appropriate equations governing a system by the assumption of a steady state, with departures from that steady state limited to small perturbations. Also called perturbation method. → method; → small; → perturbation. |
method of successive approximations raveš-e nazdinešhâ-ye payâpey Fr.: méthode d'approximations successives The solution of an equation or by proceeding from an initial approximation to a series of repeated trial solutions, each depending upon the immediately preceding approximation, in such a manner that the discrepancy between the newest estimated solution and the true solution is systematically reduced. → method; → successive; → approximation. |
Metis Metis Fr.: Métis The innermost moon of → Jupiter. Also known as Jupiter XVI. It was discovered in 1979 in images taken by Voyager 1. Its mass is about 3.6 × 10^{16} kg and its dimensions 60 × 40 × 34 km. Its mean distance from Jupiter is 128 000 km and its → orbital period is 0.29 Earth days, which is faster than Jupiter's rotation period. Metis is one of the → Shepherd moons of Jupiter. Named in 1983 after the first wife of Zeus. |
Metonic cycle carxe-ye Meton Fr.: cycle de Méton A time interval lasting 235 → lunations, or about 19 → tropical years (235 = 19 x 12 + 7), after which → lunar phases recur on the same days of the year. Named after Meton of Athens, a Gk. mathematician, astronomer, geometer, and engineer who used it in 432 B.C., but it was known to the Babylonians by around 500 B.C. and to the Chinese around 600 B.C.; → cycle. |
metric 1), 2) metrik (#); 3) metri (#) Fr.: métrique 1) A mathematical → expression consisting of an
→ array of → components which are needed
for calculating → infinitesimally small
→ distances between two → points
in some geometrical → space.
More simply put, the → function
used to define a distance between two points in a
→ metric space.
Also called → distance function. |
metric prefix pišvand-e metri Fr.: préfixe du système international d'unités Any of the suffixes adopted by the International System of Units
(→ SI units). |
metric space fazâ-ye metrik Fr.: espace métrique An set of points such that the distance between every pair of points is defined
by a → distance function with
the following properties: 1) the distance from
the first point to the second equals zero if and only if the points
are the same, 2) the distance from the first point to the second
equals the distance from the second to the first, and 3) the sum of
the distance from the first point to the second and the distance from
the second point to a third exceeds or equals the distance from the
first to the third. |
metric system râšmân-e metri Fr.: système métrique A standard system of measurement using decimal units, in which the units of length, time, and mass are meter, second, and kilogram respectively. |
metric tensor tânsor-e metrik Fr.: tenseur métrique The abstract tensor operation which is computed in a particular → reference frame using the → metric components. The metric tensor defines magnitude and direction of vectors about a point. |
metric unit yekâ-ye metri (#) Fr.: unité métrique A physical → measurement unit in the → metric system. |
metrology andâze-šenâsi Fr.: métrologie The science of measurement, embracing both experimental and theoretical determinations at any level of uncertainty in any field of science and technology. From metro-, a combining form meaning "measure," → meter, + → -logy. |
MeV MeV Fr.: MeV Mega (million) → electron volt. A unit of → energy used to describe the total energy carried by a → particle or → photon. → mega- + → electron volt. |
MHD condition butâr-e MHD Fr.: condition MHD |
mho mho Fr.: mho An older name for the unit of electrical → conductance, which is defined to be the reciprocal of the → ohm. It is now replaced by the → siemens. Ohm spelt backward. |
Michelson interferometer andarzanešsanj-e Michelson Fr.: Interféromètre de Michelson An apparatus that produces interference fringes by splitting a beam of monochromatic light so that one beam strikes a fixed mirror and the other a movable mirror. When the reflected beams are brought back together, an interference pattern results. It is used to measure very precise lengths, such as the wavelength of light, and for high-resolution spectroscopy. Named after Albert Abraham Michelson (1852-1931), German-American physicist, who built the interferometer for the → Michelson-Morley experiment of 1887; → interferometer. Andarzanešsanj, → interferometer. |
Michelson-Morley experiment âzmâyeš-e Michelson-Morley (#) Fr.: expérience de Michelson-Morley An experiment performed in 1887 to establish the presence or absence of an → ether, a medium through which light was supposed to travel. The experiment aimed to measure the speed of light coming from different directions. However no → ether drift was found. The null results obtained showed that the ether hypothesis was incorrect. Consequently, the theory of → special relativity, with its hypothesis that the speed of light is the same in all → inertial frames, reconciled the results of the Michelson-Morley experiment with the rest of physics. → Michelson interferometer; Michelson received the Nobel Prize in 1907 for his work, the first American to receive the Prize in science. Edward Williams Morley (1838-1923), an American chemist; → experiment. |
micro Moon riz mâh Fr.: pleine lune d'apogée Same as → apogee full Moon. |
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