An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1965 Search : ion
  ۱، ۲، ۳) ایوش؛ ۳) گداز   
1, 2, 3) iveš; 3) godâz (#)

Fr.: fusion   

1) The act or process of fusing; the state of being → fused; that which is fused; the result of fusing.
2) A → nuclear reaction between atomic nuclei (→ nucleus) as a result of which a heavier nucleus is formed and a large quantity of → nuclear energy is released. → proton-proton chain, → CNO cycle, → nucleosynthesis.
3) Change of the → state of a → substance from → solid to → liquid which occurs at a definite → temperature at a given applied → pressure. Same as melting.

From M.Fr. fusion, from L. fusionem, from fusus, p.p. of fundere "to pour, melt."

Verbal noun form of → fuse.


Fr.: fuzzification   

The first step carried out in a → fuzzy logic system during which a → crisp set of → input data are gathered and converted to a → fuzzy set using fuzzy → linguistic variables, fuzzy linguistic terms, and → membership functions.

Verbal noun of → fuzzify; → -tion.

galactic rotation
  چرخش ِ کهکشان   
carxeš-e kahkešân

Fr.: rotation galactique   

The revolving of the gaseous and stellar content of a galaxy around its central nucleus. The rotation is not uniform, but differential. One revolution of the Sun within our own Galaxy takes about 220 million years, or one cosmic year.

galactic; → rotation.

galactic rotation problem
  پراسه‌ی ِ چرخش ِ کهکشانی   
parâse-ye carxeš-e kahkešâni

Fr.: problème de la rotation galactique   

The discrepancy between observed galaxy → rotation curves and the theoretical prediction, assuming a centrally dominated mass associated with the observed luminous material.

galactic; → rotation; → problem.

galaxy formation
  دیسش ِ کهکشان   
diseš-e kahkešân

Fr.: formation de galaxies   

The study dealing with the processes that gave rise to galaxies in a remarkably → early Universe. See also → structure formation, → protogalaxy

galaxy; → formation.

Galilean transformation
  ترادیس ِ گالیله‌ای   
tarâdis-e Gâlile-yi (#)

Fr.: transformation galiléenne   

The method of relating a measurement in one → reference frame to another moving with a constant velocity with respect to the first within the → Newtonian mechanics. The Galilean transformation between the coordinate systems (x,y,z,t) and (x',y',z',t') is expressed by the relations: x' = x - vt, y' = y, z' = z. Galilean transformations break down at high velocities and for electromagnetic phenomena and is superseded by the → Lorentz transformations.

Galilean; → transformation.


Fr.: galvanisation   

The coating of steel or iron with → zinc, either by immersion in a bath of molten zinc or by electrolytic deposition from a solution of zinc sulfate, to give protection against corrosion.

Verbal noun of → galvanize.

Gamow condition
  بوتار ِ گاموف   
butâr-e Gamow

Fr.: condition de Gamow   

The constraint on the → baryon number density at T ~ 109 K in the early → expanding Universe. Gamow recognized that a key to the element buildup is the reaction n + p ↔ d + γ. Deuterium needs to be produced in sufficient abundance for higher elements to form, but if all → neutrons are immediately locked up into → deuterium, no higher elements can form either. The Gamow condition is expressed by nb<σv>t ~ 1, where nb is the baryon number density, σ is the cross section for the reaction at relative → velocity v, and t the expansion time-scale for the → Universe. This means that the time-scale for the above reaction is comparable to the expansion time. From this condition the baryon number density at the start of element buildup is found to be nb ~ (σvt)-1 ~ 1018 cm-3 at T = 109 K (P. J. E. Peebles, 2013, Discovery of the Hot Big Bang: What happened in 1948, arXiv.1310.2146).

Gamow barrier; → condition.

gas equation
  هموگش ِ گاز   
hamugeš-e gâz

Fr.: équation des gaz   

An equation that links the pressure and volume of a quantity of gas with the absolute temperature. For a gram-molecule of a perfect gas, PV = RT, where P = pressure, V = volume, T = absolute temperature, and R = the gas constant.

gas; → equation.

gaseous diffusion
  پخش ِ گازی   
paxš-e gâzi

Fr.: diffusion gazeuse   

An → isotope separation process using the different diffusion speeds of → atoms or → molecules for separation. This process is used to divide → uranium hexafluoride (UF6) into two separate streams of U-235 and U-238. Before processing by gaseous diffusion, uranium is first converted from → uranium oxide (U3O8) to UF6. The UF6 is heated and converted from a solid to a gas. The gas is then forced through a series of compressors and converters that contain porous barriers. Because uranium-235 has a slightly lighter isotopic mass than uranium-238, UF6 molecules made with uranium-235 diffuse through the barriers at a slightly higher rate than the molecules containing uranium-238. At the end of the process, there are two UF6 streams, with one stream having a higher concentration of uranium-235 than the other (EVS, a Division of Argonne National Laboratory).

gaseous; → diffusion.

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.

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.

general precession
  پیشایان ِ هروین   
pišâyân-e harvin

Fr.: précession générale   

The secular motions of the → celestial equator and → ecliptic. In other words, the sum of → lunisolar precession, → planetary precession, and → geodesic precession.

general; → precession

general precession in longitude
  پیشایان ِ هروینِ درژنا   
pišâyân-e harvin-e derežnâ

Fr.: précession générale en longitude   

The secular displacement of the → equinox on the → ecliptic of date.

general; → precession; → longitude.

general precession in right ascension
  پیشایان ِ هروین ِ راست‌افراز   
pišâyân-e harvin-e râst afrâz

Fr.: précession générale en ascension droite   

The secular motion of the → equinox along the → celestial equator.

general; → precession; → right ascension.

  هروین‌کرد، هروینش   
harvinkard, harvineš

Fr.: généralisation   

The act or process of generalizing; → generalize.
A result of this process; a general statement, proposition, or principle.

Verbal noun of → generalize.


Fr.: génération   

1) A coming into being.
2) The → production of → energy (→ heat or → electricity).

Verbal noun of → generate.

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