An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < -me mac mag mag mag mag mai Mal mar mas mas mat Max mea mec mel mer mes met met met mic mid mil min mis mne mod mol mon Mor mou mul muo > >>

Number of Results: 679
Maxwell's equations
  هموگش‌های ِ ماکسول   
hamugešhâ-ye Maxwell

Fr.: équations de Maxwell   

A set of four vector equations that describe the electric and magnetic fields arising from varying distributions of electric charges and currents, and how those fields change in time. In their differential form, these equations are:
i) ∇.E = ρ/ε0 (→ Gauss's law for electricity),
ii) ∇.B = 0 (→ Gauss's law for magnetism),
iii) x E = -∂B/∂t (→ Faraday's law of induction),
iv) x B = μ0J + μ0ε0E/∂t (→ Ampere's law), with c2 = 1/(μ0ε0), where E is → electric intensity, B is → magnetic flux density, ρ is → charge density, ε0 is → permittivity, μ0 is → permeability, J is → current density, and c is → speed of light.

maxwell. It should be emphasized that the equations originally published by James Clerk Maxwell in 1873 (in A Treatise on Electricity and Magnetism) were 20 in number, had 20 variables, and were in scalar form. The German physicist Heinrich Rudolf Hertz (1857-1894) reduced them to 12 scalar equations (1884). It was the English mathematician/physicist Oliver Heaviside (1850-1925) who expressed Maxwell's equations in vector form using the notations of → gradient, → divergence, and → curl of a vector, thus simplifying them to the present 4 equations (1886). Einstein referred to them as Maxwell-Heaviside-Hertz equations; → equation.

Maxwell's rule
  رزن ِ ماکسول   
razan-e Maxwell

Fr.: règle de Maxwell   

Every part of a deformable electric circuit tends to move in such a direction as to enclose the maximum magnetic flux.

maxwell; → rule.

Maxwell-Boltzmann distribution
  واباژش ِ ماکسول-بولتسمان   
vibâžš-e Maxwell-Boltzmann

Fr.: distribution de Maxwell-Boltzmann   

The distribution law for kinetic energies (or, equivalently, speeds) of molecules of an ideal gas in equilibrium at a given temperature.

maxwell; → Boltzmann's constant; → distribution.

Maya calendar
  گاهشمار ِ مایا   
gâhšomâr-e Mâyâ

Fr.: calendrier Maya   

A complex calendar created by the ancient central American Mayas which uses three different dating systems in parallel: Long Count, Tzolkin, and Haab. Only Haab has a direct relationship with the length of the year. It is a solar → vague year consisting of 18 months of 20 days each, and an additional period of 5 → epagomenal days. Tzolkin is a calendar of 13 x 20 = 260 days running within Haab and is used for ritual purposes. A date is usually described by specifying its position in both the Tzolkin and Haab calendars. The least common multiple of the two calendars, called the Calendar Round, has 18,980 days, representing a cycle of 73 sacred years, or 52 vague years. The Long Count is the number of days since the start of the Maya era. There is disagreement about the beginning date of the Long Count. Most authorities agree, however, that the Long Count started in 3114 B.C., with several possible dates.

Maya, proper name; → calendar.

Möbius band
  باند ِ موی‌بیوس   
bând-e Möbius

Fr.: ruban de Möbius   

A surface with only one side, made by putting a simple twist in a long, rectangular strip of paper, then pasting the ends together.

After the German astronomer and geometer August Ferdinand Möbius (1790-1868); → band.

Mössbauer effect
  ا ُسکر ِ موسباؤر   
oskar-e Mössbauer

Fr.: effet Mössbauer   

The resonant and recoil-free emission and absorption of gamma rays by atoms bound in a solid form.

Named after Rudolf Mößbauer (1929-), a German physicist who studied gamma rays from nuclear transitions, and discovered this phenomenon in 1957; → effect.

  ۱) میانگین؛ ۲) چماردن   
1) miyângin (#); 2) cemârdan

Fr.: 1) moyenne; 2) signifier, vouloir dire   

1a) General: A quantity having a value intermediate between the values of other quantities; an average.
1b) → arithmetic mean.
1c) → geometric mean.
1d) → harmonic mean.
1e) → weighted mean.
1f) → root mean square.
2) To have as its sense or signification; signify.

1) From O.Fr. meien, from L. medianus "of or that is in the middle," → median.
2) Verb of → meaning.

1) Miyângin "the middle; middle-sized; the middle pearl in a string," from miyân, → middle, + -gin a suffix forming adjectives of possession.
2) → meaning.

mean anomaly
  ناسانی ِ میانگین   
nâsâni-ye miyângin

Fr.: anomalie moyenne   

The angle between the periapsis of an orbit and the position of a hypothetical body that orbits in the same period as the real one but at a constant mean angular velocity.

mean; → anomaly.

mean catalog place
  جای ِ میانگین ِ کاتالوگی   
jâ-ye miyângin-e kâtâlogi

Fr.: position catalogue moyenne   

That point on the → celestial sphere at which an object would be seen from the solar system → barycenter affected by the → e-terms → aberration.

catalog; → mean; → place.

mean daily motion
  جنبش ِ روزانه‌ی ِ میانگین   
jenbeš-e ruzâne-ye miyângin (#)

Fr.: mouvement diurne moyen   

The average movement of a body along its orbit in one day, usually expressed in degrees.

mean; → diurnal; → motion.

mean element
  بن‌پار ِ میانگین   
bonpâr-e miyângin

Fr.: élément moyen   

An element of an adopted reference orbit that approximates the actual, perturbed orbit. Mean elements may serve as the basis for calculating perturbations.

mean; → element.

mean equator
  هموگار ِ میانگین   
hamugâr-e miyângin

Fr.: équateur moyen   

The orientation the Earth's equator would have if the nutation was subtracted.

mean; → equator.

mean equinox
  هموگان ِ میانگین   
hamugân-e miyângin

Fr.: équinoxe moyen   

A fictitious equinox whose position is that of the vernal equinox at a particular epoch with the effect of nutation removed.

mean; → equinox.

mean free path
  پویش ِ آزاد ِ میانگین   
puyeš-e âzâd-e miyângin (#)

Fr.: libre parcours moyen   

The mean distance which a particle moves between two successive collisions with other particles of the medium. Mean free path is inversely proportional to the number of particles per cm3 (n), and the collision → cross section (σ). In the case of a gas with molecules having a diameter of d, the cross section is equal to the area of a circle of radius d, i.e. σ = πd2, and the mean free path is given by: l = 1/(nσ). Taking into account the relative velocity distribution of the colliding molecules, l = 1/(√2 . nσ). For a gas at one atmosphere pressure and room temperature, the average distance between molecules is roughly 3.5 × 10-7 cm, that is some 35 times the diameter of a molecule. Taking the gas density n = 2.4 × 1014 molecules cm-3, and a typical diameter d = 2 × 10-8 cm for a molecule, the mean free path is 3.3 × 10-5 cm. This means that the average distance between collisions is about 95 times the average distance between molecules.

mean; → free; → path.

Puyeš, verbal noun of puyidan "to run, trot; wander," from Mid.Pers. pôy-, pwd- "to run;" cf. Gk. speudein "to hasten;" Lith. spudinti; âzâd, → free; miyângin, → mean.

mean life
  زیست ِ میانگین   
zist-e miyângin

Fr.: vie moyenne   

The average amount of time an unstable radioisotope exists before it decays, It is equal to 1.44 times the half-life.

mean; → life.

mean molecular weight
  وزن ِ مولکولی ِ میانگین   
vazn-e molekuli-ye miyângin (#)

Fr.: poids moléculaire moyen   

The total atomic or molecular weight divided by the total number of particles. For instance, the mean molecular weight of a plasma of pure ionized 4He would be 4 (the atomic mass number) divided by 3, the total number of particles (1 nucleus plus 2 electrons), i.e. 4/3.

mean; → molecular; → weight.

mean moon
  ماه ِ میانگین   
mâh-e miyângin (#)

Fr.: lune moyenne   

A fictitious Moon that has the same average motion as the true Moon but that is not subject to any gravitational perturbations by other bodies.

mean; → moon.

mean motion
  جنبش ِ میانگین   
jonbeš-e miyângin (#)

Fr.: mouvement moyen   

The average angular velocity of a satellite in an elliptical orbit.

mean; → motion.

mean parallax
  دیدگشت ِ میانگین   
didgašt-e miyângin

Fr.: parallaxe moyenne   

The parallax, derived by means of statistical studies of brightness and motions, for a large group of stars whose individual parallaxes cannot be measured.

mean; → parallax.

mean place
  جای ِ میانگین   
jâ-ye miyângin

Fr.: position moyenne   

An object's celestial position as determined for a given mean equator and equinox. → mean position.

mean; → place.

<< < -me mac mag mag mag mag mai Mal mar mas mas mat Max mea mec mel mer mes met met met mic mid mil min mis mne mod mol mon Mor mou mul muo > >>