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: 663
methanol maser
  میزر ِ متانول   
meyzer-e metânol

Fr.: maser méthanol   

A maser source in which excited methanol molecules (CH3OH) 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.

methanol; → maser.

method
  روش   
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
  روش ِ کمترین چاروش‌ها   
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
  روش ِ پرتورش‌های ِ کوچک   
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
  روش ِ نزدینش‌های ِ پیاپی   
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
  متیس   
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 × 1016 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
  چرخه‌ی ِ متون   
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
  ۱، ۲) متریک؛ ۳) متری   
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.
2) In → general relativity the metric describes the → space-time geometry and gives the interval between two neighboring → events.
3) Pertaining to the meter or to the → metric system.

From → meter + → -ic.

metric prefix
  پیشوند ِ متری   
pišvand-e metri

Fr.: préfixe du système international d'unités   

Any of the suffixes adopted by the International System of Units (→ SI units).
For numbers larger than 1: → deca- (101), → hecto- (102), → kilo- (103), → mega- (106), → giga- (109), → tera- (1012), → peta- (1015), → exa- (1018), → zetta- (1021), and → yotta- (1024) .
For numbers smaller than 1: → deci- (10-1), → centi- (10-2), → milli- (10-3), → micro- (10-6), → nano- (10-9), → pico- (10-12), → femto- (10-15), → atto- (10-18), → zepto- (10-21), and → yocto- (10-24).

metric; → prefix.

metric space
  فضای ِ متریک   
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.
In mathematical language, the properties, for a nonempty set X, can be expressed as:
1) d(x,y)≥ 0 and d(x,y) = 0 if and only if x = y.
2) d(x, y) = d(y,x) for all x, y ∈ X.
3) d(x,z)d(x,y) + d(y,z) for all x, y, and z ∈ X. Also called → triangle inequality.

metric; → space.

metric system
  راژمان ِ متری   
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; → system.

metric tensor
  تانسور ِ متریک   
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; → tensor.

metric unit
  یکای ِ متری   
yekâ-ye metri (#)

Fr.: unité métrique   

A physical → measurement unit in the → metric system.

metric; → unit.

metrology
  اندازه‌شناسی   
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.

Andâze-šenâsi, from andâzé, → measure, + -šenâsi, → -logy.

MeV
   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
  بوتار ِ MHD   
butâr-e MHD

Fr.: condition MHD   

ideal MHD condition.

magnetohydrodynamics (MHD); → condition.

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
  اندرزنش‌سنج ِ مایکلسون   
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
  آزمایش ِ مایکلسون-مورلی   
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
  ریز ماه   
riz mâh

Fr.: pleine lune d'apogée   

Same as → apogee full Moon.

micro-; → Moon.

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