An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 683
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.


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.


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.


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.

  ۱) ریز-؛ ۲) میکرو-   
1) riz-; 2) mikro-

Fr.: micro-   

1) A combining form for "small."
2) A prefix meaning one millionth (10-6).

From Gk. mikros "small."

Riz-, from riz "very small."


Fr.: microinformatique   

The area of computer science dealing with the use and development of microcomputers, and related peripheral devices and softwares. Also microinformatics.

micro-; → compute.

Riz-, → micro-; azdâyik, → informatics.


Fr.: microcosme   

Anything that is regarded as a world in miniature.
A unity that is an epitome of a larger unity; opposed to macrocosm.

micro-; → cosmos.


Fr.: microgravité   

The state or condition where the force of → gravity is very weak, e.g. the → weightlessness experienced inside an orbiting spacecraft.

micro-; → gravity.


Fr.: effet de microlentille   

A type of → gravitational lens, where the foreground → lensing object is of low mass, and the multiple images produced are too close together on the sky to be observed as separate images. Gravitational microlensing occurs when a foreground star happens to lie very close to our line of sight to a more distant background star. The foreground star acts as a lens, splitting the light from the background source star into two or more images, which are typically unresolved. However, these images of the source are magnified, by an amount that depends on the angular separation between the lens and source. If with the passage of time the lens moves across the Earth-source, the amount of brightening changes. Typically the source will appear to brighten, reach a maximum and then fade symmetrically back to normal over the course of a few weeks or months; this is called a → microlensing event. If the foreground star happens to host a planet with projected separation near the paths of these images, the planet will also act as a lens, further perturbing the images and resulting in a characteristic, short-lived signature of the planet. Microlensing is used in the search for → dark matter in the → Milky Way galaxy and its nearest neighbours, as well as for → extrasolar planets (e.g. B. S. Gaudi, 2010, arXiv:1002.0332).

micro-; → lensing.

microlensing degeneracy
  واگنی ِ ریز‌لنزش   
vâgeni-ye riz-lenzeš

Fr.: dégénérescence des paramètres de l'effet de microlentille   

Determining the three various parameters of a microlensing event (the lens-source relative parallax and proper motion, and the mass of the lens) from only one physical parameter (the event time scale). Currently the microlensing degeneracy affects the vast majority of events and makes any individual event impossible to interpret with certainty.

microlensing; → degeneracy.

microlensing event
  رویداد ِ ریزلنزش   
ruydâd-e rizlenzeš

Fr.: événement de microlentille   

The effect arising whenever a source star and lens star pass each other at an angular separation involving the → Einstein radius (RE) of the lens. The time-scale for such an event is defined as tE = RE/v, where v is the magnitude of the relative transverse velocity between source and lens projected onto the lens plane.

microlensing; → event.


Fr.: micrométéorite   

A small grain sized meteorite which can only be positively identified under the microscope.

micro-; → meteorite.


Fr.: micromètre   

1) A screw thread device used to make accurate physical linear measurements.
2) Same as → micron.

micro-; → -meter.

mikron (#)

Fr.: micron   

A unit of length in the metric system equal to one millionth of a meter (10-6 m); symbol μ. Also called micrometer.

Coined 1880 in Fr. from Gk. mikron, neutral of mikros "small."


Fr.: microorganisme   

Any organism too small to be seen by the naked eye, e.g. bacteria, viruses, and protozoa.

micro-; → organism.

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