An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 86 Search : action
packing fraction
  برخه‌ی ِ انباشتگی   
barxe-ye anbâštegi (#)

Fr.: coefficient de tassement   

The difference between the isotopic mass of a nuclide and its mass number divided by its mass number. The packing fraction is a measure of the stability of the nucleus.

Packing, from the verb pack "to put together in a pack," from the noun pack, from M.E. pak, packe, from M.D. pac or perhaps M.L.G. pak; → fraction.

Barxé, → fraction; anbâštegi quality noun of anbâštan, anbârdan "to fill, to replete;" Mid.Pers. hambāridan "to fill;" from Proto-Iranian *ham-par-, from prefix ham- + par- "to fill;" cf. Av. par- "to fill," parav-, pauru-, pouru- "full, much, many;" O.Pers. paru- "much, many;" Mid.Pers. purr "full;" Mod.Pers. por "full, much, very;" PIE base *pelu- "full," from *pel- "to be full;" cf. Skt. puru- "much, abundant;" Gk. polus "many," plethos "great number, multitude;" O.E. full.

polarization fraction
  برخه‌ی ِ قطبش   
barxe-ye qotbeš

Fr.: fraction de polarisation   

The ratio expressed by P = (Ipar - Iper) / (Ipar + Iper), where Ipar and Iper are the light intensities with the electric field vector respectively parallel and perpendicular to the incident beam.

polarization; → fraction.

principle of action and reaction
  پَروز ِ ژیرش و واژیرش، ~ کنش و واکنش   
parvaz-e žireš va vâžireš, ~ koneš va vâkoneš

Fr.: principe d'action et de réaction   

Newton's third law of motion, which states that for every action there must be an equal and opposite reaction.

principle; → action; → reaction.

principle of least action
  پَروز ِ کمترین ژیرش، ~ ~ کنش   
parvaz-e kamtarin žireš, ~ ~ koneš

Fr.: principe de moindre action   

The principle that, for a system whose total mechanical energy is conserved, the path to be taken for the system from one configuration to another is the one whose action has the least value relative to all other possible paths and from the same configurations. Also called Maupertuis' principle, least-action principle.

principle; → least; → action.

proton-proton reaction
  واژیرش ِ پروتون-پروتون   
vâžireš-e-e proton-proton

Fr.: réaction proton-proton   

A → thermonuclear reaction in which two protons collide at very high velocities and combine to form a → deuterium. See also → proton-proton chain.

proton; → reaction.

pycnonuclear reaction
  واژیرش ِ چگال‌هسته‌ای   
vâžireš-e cagâl-hasteyi

Fr.: réaction pycnonucléaire   

A nuclear reaction that takes place at high densities and relatively low temperatures. Pycnonuclear reactions are almost temperature independent and occur even at zero temperature. These reactions are extremely slow at densities typical for normal stars but intensify with increasing density. For example, carbon burns into heavier elements at densities over 1010 g cm-3.

Pycnonuclear, from pycno- a combining form meaning "dense, thick," from Gk. pyknos "dense, solid" + → nuclear; → reaction.

Vâžireš, → reaction; cagâl-hasteyi, from cagâl, → dense, + hasteyi, → nuclear.

quantum of action
  کو‌آنتوم ِ ژیرش   
kuântom-e žireš

Fr.: quantum d'action   

Since → Planck's constant has the dimension of → energy × → time, its sometimes called the quantum of → action.

quantum; → action.


Fr.: raréfaction   

The state of being rarefied, less dense.
An instantaneous reduction in density of a gas resulting from passage a sound wave; opposite of → compression.

M.E. rarefien, from M.Fr. rarefier, from L. rarefacere "make rare," from rarus "loose, wide apart, thin, infrequent."

Verbal noun from âlar present stem of âlaridanrarefy + , a suffix.

rarefaction wave
  موج ِ آلرش   
mowj-e âlareš

Fr.: onde de raréfaction   

A pressure wave in a fluid generated by rarefaction. It travels in the opposite direction to that of a shock wave in the medium.

rarefaction; → wave.

  واژیرش، واکنش   
vâžireš, vâkoneš

Fr.: réaction   

1) General: Action in response to some influence, event, stimulus.
2) An equal and opposite force exerted by a body against a force acting upon it. → principle of action and reaction.
3) A → nuclear reaction; → chain reaction.
4) → chemical reaction.

Verbal noun of → react.

reaction rate
  نرخ ِ واژیرش   
nerx-e vâžireš

Fr.: taux de réaction   

The speed with which a → chemical reaction takes place. In other words, the change in → concentration of a → substance divided by the → time interval during which the change is observed.

reaction; → rate.

šekast (#)

Fr.: réfraction   

1) Optics: The change of direction which a beam of light undergoes as it enters a medium of different → refractive index.
2) Acoustics: The change in direction in sound waves on reaching the boundary between two media.
3) Seismology: The bending of a seismic wave as it enters a material of different density.

From L.L. refractionem (nominative refractio) "a breaking up," from L. refractus, p.p. of refringere "to break up," from re- "back" + combining form of frangere "to break," from PIE base *bhreg- "to break" (cf. Goth. brikan, O.E. brecan "to break;" Lith. brasketi "crash, crack").

Šekast, past stem of šekastan "to break, split;" Mid.Pers. škastan "to break;" Av. scind-, scand "to beak, cleave;" Proto-Iranian *skand- "to break, cleave;" PIE sken- "to cut off."

resonant reaction
  واژیرش ِ باز‌آوا   
vâžireš-e bâzâvâ

Fr.: réaction résonnante   

A nuclear reaction whose probability is enhanced at an energy corresponding to an energy level of one of the nuclei. → resonance capture.

Resonant, verbal adj. of → resonate; → reaction.

screened Coulomb interaction
  اندرژیرش ِ باپرده‌ی ِ کولن   
andaržireš-e bâparde-ye Coulomb

Fr.: interaction de Coulomb écrantée   

The → Coulomb interaction reduced owing to the presence of other electrons. See → shielding effect.

screen; → coulomb; → interaction.

simple fraction
  برخه‌ی ِ ساده   
barxe-ye sâdé

Fr.: fraction simple   

A fraction in which the → numerator and → denominator are positive → integer numbers. Compare → compound fraction.

simple; → fraction.

sky subtraction
  زیرکرشش ِ آسمان   
zirkaršeš-e âsmân

Fr.: soustraction de ciel   

The act or instance of removing the contribution of non-related, intervening foreground light to the object.

sky; → subtraction.

strong interaction
  اندرژیرش ِ سترگ   
andaržireš-e sotorg

Fr.: interaction forte   

The interaction between quarks that is transmitted by gluons. The characteristic range of the strong interaction is 10-13 cm, and the time scale over which it operates is on the order of 10-23 second. Also called → strong force.

strong; → interaction.


Fr.: soustraction   

The operation of finding the difference between two numbers or quantities.

Verbal noun of → subtract.

tensor contraction
  ترنگش ِ تانسور   
terengeš-e tânsor

Fr.: contraction de tenseur   

An operation of tensor algebra that is obtained by setting unlike indices equal and summing according to a summation convention.

contraction; → tensor.

thermonuclear reaction
  واژیرش ِ گرماهسته‌ای   
vâžireš-e garmâhaste-yi (#)

Fr.: réaction thermonucléaire   

A nuclear reaction in which two or more atomic nuclei fuse into a single heavier nucleus by a collision of the interacting particles at extremely high temperatures. Chains of thermonuclear reactions, such as the → proton-proton chain and the → CNO cycle, account for the energy radiated from the Sun and more massive stars.

thermo- + → nuclear; → reaction.

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