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 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 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.
Back formation from Fr. méthylène, → methylene.
Fr.: chlorure de méthyle
A → chemical compound (CH3Cl), which is the most abundant → organohalogen in the Earth's atmosphere. It has both natural and synthetic origins. Also called chloromethane. Low levels of methyl chloride occur naturally in the environment. Methyl chloride is formed in the oceans by natural processes (e.g., marine phytoplankton) and from biomass burning in grasslands and forested areas (e.g., forest fires); it has been detected at low levels in air all over the world. Other sources of exposure to methyl chloride include cigarette smoke, polystyrene insulation, and aerosol propellants; home burning of wood, coal, or certain plastics. High levels may occur at chemical plants where it is made or used. Acute (short-term) exposure to high concentrations of methyl chloride in humans has caused severe neurological effects. Methyl chloride has also caused effects on the heart rate, blood pressure, liver, and kidneys in humans (United States Environmental Agency, EPA).
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.
Fr.: cycle de Méton
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.
1), 2) metrik (#); 3) metri (#)
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.
Fr.: préfixe du système international d'unités
Any of the suffixes adopted by the International System of Units
(→ SI units).
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.
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.
Fr.: tenseur métrique
yekâ-ye metri (#)
Fr.: unité métrique
The science of measurement, embracing both experimental and theoretical determinations at any level of uncertainty in any field of science and technology.
Fr.: condition MHD
Ohm spelt backward.
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.
Andarzanešsanj, → interferometer.
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.
Fr.: pleine lune d'apogée
Same as → apogee full Moon.