An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 90 Search : meter
-sanj (#)

Fr.: -mètre   

A combining form meaning "measure," used in the names of instruments measuring quantity, extent, degree.

From Fr. -mètre; → meter.

Suffix -sanj, present stem of sanjidan "to measure; to compare," from Mid.Pers. sanjidan "to weigh," from present tense stem sanj-, Av. θanj- "to draw, pull;" Proto-Iranian *θanj-. Other terms from this base in Pers.: lanjidan "to pull up," hanjidan, âhanjidan "to draw out," farhang "education, culture."

21-centimeter line
  خط ِ ۲۱ س.م.   
xatt-e 21-sântimetr (#)

Fr.: raie 21-cm   

The → emission line of → neutral hydrogen in interstellar clouds. It lies in the radio spectrum at wavelength of about 21 cm, frequency 1420 MHz. Its existence was predicted by Hendrik van de Hulst in 1944 and discovered by Harold Ewen and Edward Purcell in 1951.

Twenty-one (21); → twenty + → one; → centimeter; → line.

acceleration parameter
  پارامون ِ شتاب   
pârâmun-e šetâb

Fr.: paramètre d'accéleration   

A measure of the departure from a constant rate of the acceleration of the Universe, expressed by: q(t) = R(t)R ..(t)/R .2(t), where R(t) represents the size of the Universe at time t. Traditionally, a negative sign is inserted in the above equation for the → deceleration parameter.

acceleration; → parameter.


Fr.: actinomètre   

Any instrument for measuring the intensity of radiation, especially that of the Sun, in its thermal, chemical, and luminous aspects.

Actinometer, from actino- combining form with the meaning "ray, beam," from Gk. aktis, aktin "ray," + → -meter.

Partow, → ray; + -sanj, → -meter.

  فرازسنج، فرازیاب   
farâzsanj (#), farâzyâb (#)

Fr.: altimètre   

An instrument which determines the altitude of an object with respect to a fixed level, such as sea level.

L. altus "high" + → -meter.

Farâzsanj, from farâz "above, over, aloft" + -sanj, → -meter; farâzyâb, from farâz + yâb "finder," from yâbidan "to find, discover, obtain."

bâdsanj (#)

Fr.: anémomètre   

An instrument for measuring and indicating the force or speed of the wind.

From Gk. anemos "wind" + → -meter.

Bâdsanj, from bâd "wind" + -sanj, → -meter.

angular diameter
  ترامون ِ زاویه‌ای، قطر ِ ~   
tarâmun-e zâviye-yi, qotr-e ~

Fr.: diamètre angulaire   

The apparent diameter of an object in angular measure.

angular; → diameter.

angular diameter distance
  اپست ِ زاویه‌ای   
apest-e zâviye-yi

Fr.: distance angulaire   

1) The ratio of an object's → linear size (l) to its → angular size (δθ, in → radians), that is DA = l/δθ. It is used to convert observed angular separations into proper separations at the source.

2) In cosmology, a distance defined as the ratio of an object's physical transverse size (l) to its angular size (δθ). It is used to convert angular separations in telescope images into proper separations at the source. The angular diameter distance is defined by: DA = l / δθ. Consider a light source of size l at r = r1 and t = t1 subtending an angle δθ at the origin (r = 0, t = t0). The proper distance between the two ends of the object is related to δθ by: δθ = l / [a(t1). r1], where a(t1) is the → scale factor at the present epoch. Therefore, DA = r1 / (1 + z). The angular diameter distance has the particularity that it does not increase infinitely with z→ ∞. It gets its maximum value at a → redshift of ~ 1 and then decreases for higher z. Therefore, more distant objects appear larger in angular size. This is explained by considering the size of the Universe when the light of the object was emitted. At that time the Universe was smaller and therefore the object occupied a larger fraction of the size of the Universe. In other words, objects appear larger because the entire Universe acts as a → gravitational lense.

angular; → diameter; → distance.

angular momentum parameter
  پارامون ِ جنباک ِ زاویه‌ای   
pârâmun-e jonbâk-e zâviye-yi

Fr.: paramètre de moment angulaire   

The ratio J/M, where J is the → angular momentum of a → rotating black hole and M the mass of the black hole.

angular; → momentum; → parameter.

apparent diameter
  ترامون ِ پدیدار، قطر ِ ~   
tarâmun-e padidâr, qotr-e ~

Fr.: diamètre apparent   

The angular diameter of a celestial body expressed in degrees, minutes, and seconds of arc, or in radians.

apparent; → diameter.

Atacama Large Millimeter Array (ALMA)
  آرست ِ بزرگ ِ میلیمتری ِ آتاکاما   
ârast-e bozorg-e milimetri-ye âtâkâmâ (ALMA)

Fr.: Grand réseau millimétrique Atacama   

One of the largest ground-based astronomy projects and a major new facility for world astronomy located on the plain of the → Chajnantor Chilean Andes, San Pedro de Atacama, some 5000 m above sea level. ALMA will initially comprise 66 high precision antennas, with the option to expand in the future. There will be an array of fifty 12 m antennas, acting together as an → interferometer to capture → millimeter and → submillimeter wavelengths of 0.3 to 9.6 mm. It will have reconfigurable baselines ranging from 15 m to 18 km. A compact array of 7 m antenna and few 12 m diameter antennas (ACA) will be used to measure the diffuse emission. Resolutions as fine as 0''.005 will be achieved at the highest frequencies. Construction of ALMA started in 2003 and will be completed in 2012. The ALMA project is an international collaboration between Europe, Japan, and North America in cooperation with the Republic of Chile. ALMA is funded in Europe by the → European Southern Observatory (ESO). The first 12 m diameter antenna, built by Mitsubishi Electric Corporation for the National Astronomical Observatory of Japan, was handed over to ESO in 2008. It will shortly be joined by North American and European antennas. ALMA will allow astronomers to study the cool Universe, i.e. the molecular gas and tiny dust grains from which stars, planetary systems, galaxies, and even life are formed.

Atacama the name of a desert, west of the Andes mountains in Chile, covering a 1,000 km strip of land on the Pacific coast of South America; → large; → millimeter; → submillimeter; → array.

fešârsanj (#)

Fr.: baromètre   

Instrument for measuring the atmospheric pressure. It is used in determining height above sea level and predicting changes in weather.

baro- + → -meter.


Fr.: bolomètre   

1) An instrument for measuring the intensity of radiant energy in amounts as small as one millionth of an erg. It uses the change in resistance of a thin conductor caused by the heating effect of the radiation. → actinometer, → photometer, → pyrheliometer, → pyrometer, radiometer.
2) In astronomy, an instrument that measures the amount of radiant energy received from a celestial object.

From Gk. bole "stroke, beam of light," from ballein "to throw" + middle suffix -o- + → -meter..

Tafsanj, from taf "heat, warmth; light, brightness," from tâbidan, "→ radiate," + sanj, → -meter.

centimeter (cm)
sântimetr (#)

Fr.: centimètre   

A unit of length in the → metric system, equal to one-hundredth of a meter, which is the current unit of length in the → International System of Units (SI).

centi-; → meter.

  گاه‌سنج، زمان‌سنج   
gâhsanj (#), zamânsanj (#)

Fr.: chronomètre   

A highly precise timepiece.

Chronometer, from from Gk. khronos "time" + → -meter.

Gâhsanj, zamânsanj, from gâh or zamân "time" + -sanj-meter.

Couette viscometer
  وشک‌سنج ِ کویءت   
vošksanj-e Couette

Fr.: viscosimètre de Couette   

A device consisting of two vertical coaxial cylinders and a fluid filling the volume between the cylinders and used for measuring the viscosity of the fluid. The inner cylinder is stationary while the outer cylinder rotates. The amount of shear stress produced owing to rotation is directly proportional to the viscosity of the fluid.

Couette flow; → viscometer.

deceleration parameter
  پارامون ِ واشتاب   
pârâmun-e vâšetâb

Fr.: paramètre de décéleration   

A parameter designating the rate at which the expansion of the Universe would slow down owing to the braking gravitational effect of the matter content of the Universe. It is expressed by: q(t) = -R(t)R ..(t)/R .2(t), where R(t) represents the size of the Universe at time t. See also → expansion parameter; compare with → acceleration parameter.

deceleration; → parameter.

density parameter
  پارامون ِ چگالی   
pârâmun-e cagâli

Fr.: paramètre de densité   

One of the four terms that describe an arranged version of the → Friedmann equations. They are all time dependent.
1) For matter: Ωm = 8πGρm/(3H2), where G is the → gravitational constant, ρm is the mean matter density, and H the → Hubble parameter. The matter density parameter is also expressed as Ωm = ρmcrit, where ρcrit is the → critical density.
2) For radiation: Ωr = 8πGρr/(3H2), where ρr is the radiation equivalent of matter density. This parameter is also expressed as Ωr = ρrcrit.
3) For the → cosmological constant: ΩΛ = Λc2/(3H2). Similarly, ΩΛ = ρΛcrit, where &rhoΛ = Λc2/(8πG) is sometimes referred to as the density of → dark energy.
4) For the → curvature of space-timeΩk = -kc2/(R2H2), where k is the → curvature constant and R the → cosmic scale factor.
Note that: Ωm + Ωr + ΩΛ + Ωk = 1, and Ωtotal = Ωm + Ωr + ΩΛ = 1 - Ωk.

density; → parameter.

tarâmun (#)

Fr.: diamètre   

Any chord passing through the center of a figure. The length of this chord.

O.Fr. diamètre, from L. diametrus, from Gk. diametros "diagonal of a circle," from dia- "across, through" + metron "a measure" → meter.

Tarâmun, from tarâ- "across, through," → trans- + mun/mân "measure," as in Pers. terms pirâmun "perimeter," âzmun "test, trial," peymân "measuring, agreement," peymâné "a measure; a cup, bowl," from O.Pers./Av. mā(y)- "to measure," cf. Skt. mati "measures," matra- "measure," Gk. metron "measure," L. metrum; PIE base *me- "to measure."

  توان سنج   
tavânsanj (#)

Fr.: dynamomètre   

A device for measuring mechanical force; specifically, one that measures the output or driving torque of a rotating machine.

Dynamometer, from → dynamo + → -meter.

Tavânsanj, from tavân "power," → dynamics + -sanj, → -meter.

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