An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 399
gauge theory
  نگره‌ی ِ گز   
negare-ye gaz (#)

Fr.: théorie de jauge   

A field theory in which it is possible to perform a transformation without altering any measurable physical quantity.

gauge; → theory.

gauge transformation
  ترادیس ِ گز   
tarâdis-e gaz (#)

Fr.: transformation de jauge   

A change of the fields of a gauge theory that does not change the value of any measurable quantity.

gauge; → transformation.



A technique in which the thickness, density, or quantity of a material is determined by the amount of radiation it absorbs.

Gauging, from → gauge + → -ing, suffix of nouns formed from verbs, expressing the action of the verb or its result.

Gazkard, from gaz, → gauge, + kard past stem of kardan "to do, make," → gauge.

Gaunt factor
  کروند ِ گاؤنت   
karvand-e Gaunt

Fr.: facteur de Gaunt   

In the atomic theory of spectral line formation, a quantum mechanical correction factor applied to the absorption coefficient in the transition of an electron from a bound or free state to a free state.

Gaunt, after John Arthur Gaunt (1904-1944), English physicist born in China, who significantly contributed to the calculation of continuous absorption using quantum mechanics; → factor

gauss (#)

Fr.: gauss   

The c.s.g. unit of magnetic flux density (or magnetic induction), equal to 1 maxwell per square centimeter, or 10-4 tesla.

Named after the German mathematician and physicist Carl Friedrich Gauss (1777-1855).

Gauss's law for electricity
  قانون ِ گاؤس در برق   
qânun-e Gauss dar barq

Fr.: loi de Gauss en électricité   

The total electric flux ψ out of an arbitrary closed surface in free space is equal to the net charge within the surface divided by the → permittivity. In differential form: ∇ . E = ρ/ε0, where ρ is the → charge density and ε0 the permittivity. The integral form of the law: ∫E . dS = Q0 (closed surface integral). This is one of the four → Maxwell's equations.

gauss; → law; → electricity.

Gauss's law for magnetism
  قانون ِ گاؤس در مغنات‌مندی   
qânun-e Gauss dar meqnâtmandi

Fr.: loi de Gauss en magnétisme   

The → magnetic flux through an arbitrary closed surface equals zero. Mathematically, in differential form: ∇ . B = 0 and in integral form: ΦB = ∫B.dS = 0 (closed surface integral). This is one of the four → Maxwell's equations. This law expresses the fact that there are no free magnetic poles (→ monopoles) in nature and that all the lines of force of a magnetic field are closed curves.

gauss; → law; → magnetism.

Gauss's lemma
  نهک ِ گاؤس   
nehak-e Gauss

Fr.: lemme de Gauss   

If a → polynomial with → integer coefficients can be → factorized into polynomials with → rational number coefficients, it can be factorized using only integers.

Gaussian; → lemma.

Gauss's theorem
  فربین ِ گاؤس   
farbin-e Gauss

Fr.: théorème de Gauss   

The total normal induction over any closed surface drawn in an electric field is equal to 4π times the total charge of electricity inside the closed surface. Gauss's theorem applies also to other vector fields such as magnetic, gravitational, and fluid velocity fields. The theorem can more generally be stated as: the total flux of a vector field through a closed surface is equal to the volume → integral of the vector taken over the enclosed volume. Also known as → divergence theorem, Ostrogradsky's theorem, and Gauss-Ostrogradsky theorem.

gauss; → theorem.

Gaussi (#)

Fr.: gaussien   

Of or relating to Carl Friedrich Gauss or his mathematical theories of magnetism, electricity, astronomy, or probability. → Gaussian distribution; → Gaussian profile.


Gaussian distribution
  واباژش ِ گاؤسی   
vâbâžeš-e Gaussi (#)

Fr.: distribution gaussienne   

A theoretical frequency distribution for a set of variable data, usually represented by a bell-shaped curve with a mean at the center of the curve and tail widths proportional to the standard deviation of the data about the mean.

Gaussian; → distribution.

Gaussian elimination
  اسانش ِ گاؤسی   
osâneš-e Gaussi

Fr.: élimination de Gauss   

A method of solving a matrix equation of the form A x = b, where A is a matrix and x and b are vectors. The process consists of two steps, first reducing the elements below the diagonal to 0 and second, back substituting to find the solutions.

Gaussian; → elimination.

Gaussian function
  کریای ِ گاؤس   
karyâ-ye Gauss

Fr.: fonction de Gauss   

The function e-x2, whose integral in the interval -∞ to +∞ gives the → square root of the → number pi: ∫e-x2dx = √π. It is the function that describes the → normal distribution.

Gaussian; → function.

Gaussian gravitational constant
  پایای ِ گرانشی ِ گاؤس   
pâyâ-ye gerâneši-ye Gauss

Fr.: constante gravitationnelle de Gauss   

The constant, denoted k, defining the astronomical system of units of length (→ astronomical unit), mass (→ solar mass), and time (→ day), by means of → Kepler's third law. The dimensions of k2 are those of Newton's constant of gravitation: L 3M -1T -2. Its value is: k = 0.01720209895.

Gaussian; → gravitational; → constant.

Gaussian integer
  درست ِ گاؤس   
dorost-e Gauss

Fr.: entier de Gauss   

A → complex number whose → real and → imaginary parts are both integers.

Gaussian; → integer.

Gaussian profile
  فراپال ِ گاؤسی   
farâpâl-e Gaussi

Fr.: profile gaussien   

The shape of a curve representing a normal distribution.

Gaussian; → profile.


Fr.: gaussienité   

Math.: The condition of having → Gaussian distribution. The extent to which something is Gaussian.

Gaussian + → -ity.

Gay-Lussac's law
  قانون ِ گی-لوساک   
qânun-e Gay-Lussac (#)

Fr.: loi de Gay-Lussac   

1) Law of combining volumes. The volumes of gases used and produced in a chemical reaction, are in the ratio of small whole numbers when measured at constant temperature and pressure.
2) For a gas held at constant volume, there is a direct correlation between temperature and pressure: P1/T1 = P2/T2. Gay-Lussac's law, → Boyle-Mariotte law, and → Charles' law were later unified into the → ideal gas law.

Named after Joseph Louis Gay-Lussac (1778-1850), a French chemist and physicist; → law.

GD 165B
GD 165B

Fr.: GD 165B   

The prototype of the → L dwarf class. It has a spectral type of L4 V. This object was discovered by Becklin & Zuckerman (1988, Nature 336, 656) as the red companion to a → white dwarf (DA4) lying 104 → light-years away. Its true nature was however recognized several years later (Kirkpatrick et al. 1993, ApJ 406, 701). It has an → effective temperature of 1900 K and a luminosity about 10-4 times that of the Sun (→ solar luminosity).

GD, referring to Giclas Dwarf, a catalog of white dwarf stars compiled at the Lowell Observatory (Giclas et al. 1980, LowOB 8, 157).


Fr.: gegenschein, lueur anti-solaire   

A faint glow of light in the night sky seen exactly opposite the Sun. The gegenschein is sunlight back-scattered off millimeter-sized dust particles along the ecliptic. In comparison with zodiacal light (forward-scattered sunlight), which is triangular in shape and found near the horizon, the gegenschein is roughly circular. Same as counterglow.

Gegenschein, from Ger. gegen "counter, opposed to" (O.H.G. gegin, gagan, M.Du. jeghen, E. against, again) + Schein "glow, shine" (M.H.G. schinen, O.H.G. skinan, P.Gmc. *skinanan; E. shine; cf. Mod.Pers. sâyé "shadow;" Mid.Pers. sâyak "shadow;" Av. a-saya- "throwing no shadow;" Skt. chāya- "shadow;" Gk. skia "shade;" Rus. sijat' "to shine;" PIE base *skai- "bright").

Pâdfrouq "counterglow," from pâd- "agaist, contrary to" (from Mid.Pers. pât-; O.Pers. paity "agaist, back, opposite to, toward, face to face, in front of;" Av. paiti; cf. Skt. práti "toward, against, again, back, in return, opposite;" Pali pati-; Gk. proti, pros "face to face with, toward, in addition to, near;" PIE *proti) + foruq "light, brightness" (related to rôšan "light; bright, luminous;" ruz "day," afruxtan "to light, kindle;" Mid.Pers. payrog "light, brightness," rošn light; bright," rôc "day;" O.Pers. raucah-; Av. raocana- "bright, shining, radiant," raocah- "light, luminous; daylight;" cf. Skt. rocaná- "bright, shining, roka- "brightness, light;" Gk. leukos "white, clear;" L. lux "light" (also lumen, luna; E. light, Ger. Licht, and Fr. lumière; PIE base *leuk- "light, brightness").

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